article posted april 11, 2013 at 08 : 30 pm gmt • comment ( 1 ) • reads 4267 we ended our sound unit by making recycled instruments. each student was taped while he / she presented their instrument to the class. the students also wrote a paragraph about the instrument and took a photo of it using an ipad. the students created a glog ( an interactive poster ) incorporating all of the components. click on the glogster image below to see all of the recycled instrument glogs. the slideshow gives you a front row seat to the " 3h jam session. " enjoy! article posted march 8, 2013 at 08 : 19 pm gmt • comment • reads 1427 this is it, the last set of clues. the clock is ticking and we need to figure out where these landmarks are! it ' s research time 3h crew! good luck! landmark primary clues 2013 - week 3 ( 1a ) abanskaya school ( world explorers ) aban, russia 1. the head of all landmarks 2. the oldest in the city 3. northern hemisphere 4. named in honor of the builder 5. there is the legend about a thing in it 6. lighting of this place change in december 7. chinese room 8. about 122. 3 longitude 9. opened on the independence day ( 2a ) abanskaya school 3 ( team kazakova ) aban, russia 1. tatar burial mound 2. metal, metal 3. black snow, no grass 4. the leader lies at it 5. 40 - 50 n 6. the bloodiest battle 7. world war ii 8. was the largest when it was built 9. the woman on the top ( 3a ) abanskaya school 3 ( team vinokurova ) aban, russia 1. it was founded in a cave. 2. there is a museum there. 3. there was a big fire in 1718 4. 500 people were killed there by the nazi soldiers. 5. it is one of 7 wonders of its country. 6. it is inscribed as a unesco world heritage site. 7. northern hemisphere 8. you can find this landmark between 29 and 31 degrees east longitude. 9. its area is 2, 533, 825 sq ft ( 4a ) aginskaya secondary 2 ( siberian experts ) krasnoyarsk, russia 1. it is a unique place in the world 2. it is situated in the eastern siberia 3. it was founded in 1925 4. it is a nice place for animals to live, for


mr. gonzalez ' s science classes we have three 6th grade science classes and two 8th grade science classes blogging here from the pacific northwest in chimacum, wa! sixth graders are learning a bit about mt saint helens, environmental science through fresh water ecology, and physical science this year. eighth graders are learning about life science this year. please join us as we learn science by exploring our world. mr. g ' s blog mr. g ' s class facebook page here ' s what the creator of this graph wrote, " i tried to come up with the reason for the daylight saving time change by just looking at the data for sunset and sunrise times. the figure represents sunset and sunrise times thought the year. it shows that the daylight saving time change marked by the lines ( dls ) is keeping the sunrise time pretty much constant throughout the whole year, while making the sunset time change a lot. the spread of sunrise times as measured by the standard deviation is 42 minutes, which means that the sunrise time changes within that range the whole year, while the standard deviation for the sunset times is 1 : 30 hours. whatever the argument for doing this is, it ' s pretty clear that reason is to keep the sunrise time constant. " article posted january 31, 2013 at 07 : 27 am gmt - 8 • comment ( 4 ) • reads 85400 " the acoustic levitator uses two small speakers to generate sound waves at frequencies slightly above the audible range – roughly 22 kilohertz. when the top and bottom speakers are precisely aligned, they create two sets of sound waves that perfectly interfere with each other, setting up a phenomenon known as a standing wave. at certain points along a standing wave, known as nodes, there is no net transfer of energy at all. because the acoustic pressure from the sound waves is sufficient to cancel the effect of gravity, light objects are able to levitate when placed at the nodes. " about the blogger i started my teaching career in south central los angeles teaching in modified to full bilingual 4th and 5th grade classes. then i moved to wa state where i have taught mainly 6th through 8th grade. i have enjoyed the culture clash but notice that kids are the same everywhere : o ) my areas of interest are science and technology but i also love studying ancient cultures and learning about different peoples and cultures.


over the last ten thousand years, virtually every aspect of human culture has changed. the food we eat, the homes and shelters we live in, the clothes we wear, our language, music, stories, science, technology, social organization have all changed in fundamental ways that make modern cultures unrecognizably different from hunter - gatherer cultures. one aspect of human culture has remained unchanged over the last ten thousand years – all humans have retained a basic ability to recognize and interpret footprints on a beach. when you look at footprints on a beach, what you see and the way you interpret them is essentially exactly what a hunter - gatherer would have seen and interpreted a hundred thousand years ago. we still use the same reasoning to understand what we are looking at. the hunter - gatherer may have been a more sophisticated tracker, but looking at human footprints on a beach may be one of the few aspects, perhaps the only aspect, of human culture that links us with hunter - gatherer cultures more than a hundred thousand years ago. the art of tracking is the one aspect of hunter - gatherer culture that can be applied in a modern context. it is also the one aspect of hunter - gatherer culture that all modern humans can identify with. not only can traditional trackers benefit by working as trackers in a modern economy. by sharing their tracking expertise, people from other modern cultures can benefit by learning more about the roots of science. the implications for community participation in science are far - reaching. imagine communities throughout the world gathering data... from remote villages in the kalahari, the congo, australia and mongolia,... to school children in new york ' s central park, to london, paris, tokyo, new delhi and beijing... citizens gathering data on birds, animals, plants... millions of people all over the world sharing their data on the internet ( the cloud ), creating a worldwide network to monitor the global ecosystem in real time. the origin of science looks at practical applications of the art of tracking in a modern context. these examples demonstrate continuity between " indigenous knowledge " and modern western science. it demonstrates the ease with which traditional trackers, who cannot read or write, can adopt and take ownership of modern computer technology. these examples break down barriers between conventional notions of " science " and " indigenous knowledge " and between literate and pre - literate cultures. breaking down these barriers challenges us to redefine the boundaries of science.


mail email @ example. com. copyright 2005, kitsapsun. com. all rights reserved. by larry pynn the shared waters of the strait of georgia and puget sound are home to 63 marine species at risk, with over - harvesting, habitat loss, and pollution rated as the biggest threats, according to a research study being released at an international conference starting today. the study by joseph gaydos and nicholas brown also finds that the four jurisdictions responsible for protecting marine species - - b. c., washington state, and the canadian and u. s. governments - - cannot reach consensus on the level of threat facing all of those 63 species. of the 63 species, washington officially considered 73 per cent of them at risk, b. c. 50 per cent, the canadian government 36 per cent, and the u. s. government 31 per cent. as an example, b. c. lists 12 seabirds that neighbouring washington state does not list, even though it is common for various species to fly back and forth across the international boundary. the high number of species at risk in the region ' s marine waters are evidence of " ecosystem decay, " the report ' s authors conclude, and reflect the need for the various levels of governments to work harder on conservation and to adopt an international ecosystem approach. gaydos and brown are with the seadoc society, a marine ecosystem health program administered through the university of california, davis, wildlife health centre, and based in washington ' s san juan islands. as of september 2004, the 63 species at risk consisted of 27 fish, 23 birds, nine mammals ( including the grey whale, harbour porpoise, humpback whale, and killer whale ), three invertebrates, and one reptile. within the puget sound - georgia basin marine ecosystem, the number of invertebrate species is much greater than vertebrate species, yet only three invertebrates are listed at risk - - newcomb ' s littorine snail, olympic oyster, and northern abalone - - suggesting the category is not receiving as much attention as it should. the results of the study are being presented at the puget sound georgia basin research conference running today through thursday in seattle and co - sponsored by environment canada. commenting on the study, tony pitcher, a professor at the university of b. c. fisheries centre, said in vancouver that governments have been slow to adopt an ecosystem approach to marine management. and while states and provinces can have different mandates, he agreed that the international border poses a political obstacle to good management of


- active driver a device driver that implements advanced power management tasks, such as determining device idleness and performing pre - shutdown tasks. see also passive driver - base class in c + +, the class from which another class ( a subclass ) inherits. it can also be used to specify a class from which all classes in a hierarchy ultimately derive ( also known as a root class ). berkeley software distribution. formerly known as the berkeley version of unix, bsd is now simply called the bsd operating system. the bsd portion of darwin is based on 4. 4bsd lite 2 and freebsd, a flavor of 4. 4bsd. a directory in the file system that typically stores executable code and the software resources related to that code. ( a bundle can store only resources. ) applications, plug - ins, frameworks, and kernel extensions are types of bundles. except for frameworks, bundles are file packages, presented by the finder as a single file instead of a folder. see also kernel extension a transmission path on which signals can be dropped off or picked up by devices attached to it. only devices addressed by the signals pay attention to them ; the others discard the signals. buses both exist within the cpu and connect it to physical memory and peripheral devices. examples of i / o buses on darwin are pci, scsi, usb, and firewire. - bus master a program, usually in a separate i / o controller, that directs traffic on the computer bus or input / output paths. the bus master actually controls the bus paths on which the address and control signals flow. dma is a simple form of bus mastering where the bus master controls i / o transfers between a device and system memory and then signals to the cpu when it has done so. see also dma a driver object that consumes services of some kind supplied by its provider. in a driver stack, the client in a provider / client relationship is farther away from the platform expert. see also provider - command gate a mechanism that controls access to the lock of a work loop, thereby serializing access to the data involved in i / o requests. a command gate does not require a thread context switch to ensure single - threaded access. iocommandgate event - source objects represent command gates in the i / o kit. another name for the os x core operating system, or kernel environment. the darwin kernel environment is equivalent to the os x kernel plus the bsd libraries and commands essential to the bs


event - source objects represent command gates in the i / o kit. another name for the os x core operating system, or kernel environment. the darwin kernel environment is equivalent to the os x kernel plus the bsd libraries and commands essential to the bsd commands environment. darwin is open source technology. ( direct memory access ) a capability of some bus architectures that enables a bus controller to transfer data directly between a device ( such as a disk drive ) and a device with physically addressable memory, such as that on a computer ' s motherboard. the microprocessor is freed from involvement with the data transfer, thus speeding up overall computer operation. see also bus master computer hardware, typically excluding the cpu and system memory, which can be controlled and can send and receive data. examples of devices include monitors, disk drives, buses, and keyboards. - device driver a component of an operating system that deals with getting data to and from a device, as well as the control of that device. a driver written with the i / o kit is an object that implements the appropriate i / o kit abstractions for controlling hardware. - device file in bsd, a device file is a special file located in / devthat represents a block or character device such as a terminal, disk drive, or printer. if a program knows the name of a device file, it can use posix functions to access and control the associated device. the program can obtain the device name ( which is not persistent across reboots or device removal ) from the i / o kit. - device interface in the i / o kit, a mechanism that uses a plug - in architecture to allow a program in user space to communicate with a nub in the kernel that is appropriate to the type of device the program wishes to control. through the nub the program gains access to i / o kit services and to the device itself. from the perspective of the kernel, the device interface appears as a driver object called a user client. - device matching in the i / o kit, a process by which an application finds an appropriate device interface to load. the application calls a special i / o kit function that uses a “ matching dictionary ” to search the i / o registry. the function returns one or more matching driver objects that the application can then use to load an appropriate device interface. also referred to as device discovery. see device driver - driver matching in the i / o kit, a process in which a nub, after discovering a specific hardware device,


driver objects that the application can then use to load an appropriate device interface. also referred to as device discovery. see device driver - driver matching in the i / o kit, a process in which a nub, after discovering a specific hardware device, searches for the driver or drivers most suited to drive that device. matching requires that a driver have one or more personalities that specify whether it is a candidate for a particular device. driver matching is a subtractive process involving three phases : class matching, passive matching, and active matching. see also personality - driver stack in an i / o connection, the series of driver objects ( drivers and nubs ) in client / provider relationships with each other. a driver stack often refers to the entire collection of software between a device and its client application ( or applications ). - event source an i / o object that corresponds to a type of event that a device driver can be expected to handle ; there are currently event sources for hardware interrupts, timer events, and i / o commands. the i / o kit defines a class for each of these event types, respectively iointerrupteventsource, iotimereventsource, and iocommandgate. a collection of software abstractions that are common to all devices of a particular category. families provide functionality and services to drivers. examples of families include protocol families ( such as scsi, usb, and firewire ), storage families ( disk drives ), network families, and families that describe human interface devices ( mouse and keyboard ). in the virtual - memory system, faults are the mechanism for initiating page - in activity. they are interrupts that occur when code tries to access data at a virtual address that is not mapped to physical memory. see also page ; virtual memory a type of bundle that packages a dynamic shared library with the resources that the library requires, including header files and reference documentation. note that the kernel framework ( which contains the i / o kit headers ) contains no dynamic shared library. all library - type linking for the kernel framework is done using the mach _ kernelfile itself and kernel extensions. this linking is actually static ( with vtable patch - ups ) in implementation - idle sleep a sleep state that occurs when there has been no device or system activity for the period of time the user specifies in the energy saver pane of system preferences. see also system sleep - information property list a property list that contains essential configuration information for bundles such as kernel extensions. a file named info.


or system activity for the period of time the user specifies in the energy saver pane of system preferences. see also system sleep - information property list a property list that contains essential configuration information for bundles such as kernel extensions. a file named info. plist ( or a platform - specific variant of that filename ) contains the information property list and is packaged inside the bundle. an asynchronous event that suspends the currently scheduled process and temporarily diverts the flow of control through an interrupt handler routine. interrupts can be caused by both hardware ( i / o, timer, machine check ) and software ( supervisor, system call, or trap instruction ). - interrupt handler a routine executed when an interrupt occurs. interrupt handlers typically deal with low - level events in the hardware of a computer system, such as a character arriving at a serial port or a tick of a real - time clock. - i / o catalog a dynamic database that maintains entries for all available drivers on a darwin system. driver matching searches the i / o catalog to produce an initial list of candidate drivers. - i / o kit a kernel - resident, object - oriented environment in darwin that provides a model of system hardware. each type of service or device is represented by one or more c + + classes in a family ; each available service or device is represented by an instance ( object ) of that class. - i / o kit framework the framework that includes iokitlib and makes the i / o registry, user client plug - ins, and other i / o kit services available from user space. it lets applications and other user processes access common i / o kit object types and services. see also framework - i / o registry a dynamic database that describes a collection of driver objects, each of which represents an i / o kit entity. as hardware is added to or removed from the system, the i / o registry changes to accommodate the addition or removal. the complete os x core operating - system environment, which includes mach, bsd, the i / o kit, drivers, file systems, and networking components. the kernel resides in its own protected memory partition. the kernel includes all code executed in the kernel task, which consists of the file mach _ kernel ( at file - system root ) and all loaded kernel extensions. also called the kernel environment. - kernel extension ( kext ) a dynamically loaded bundle that extends the functionality of the kernel. a kext can contain zero or one kernel modules as well as other ( sub ) kexts


loaded kernel extensions. also called the kernel environment. - kernel extension ( kext ) a dynamically loaded bundle that extends the functionality of the kernel. a kext can contain zero or one kernel modules as well as other ( sub ) kexts, each of which can contain zero or one kernel modules. the i / o kit, file system, and networking components of darwin can be extended by kexts. see also kernel module - kernel module ( kmod ) a binary in mach - o format that is packaged in a kernel extension. a kmod is the minimum unit of code that can be loaded into the kernel. see also kernel extension a data structure used to synchronize access to a shared resource. the most common use for a lock is in multithreaded programs where multiple threads need access to global data. only one thread can hold the lock at a time ; by convention, this thread is the only one that can modify the data during this period. see also mutex a central component of the kernel that provides such basic services and abstractions as threads, tasks, ports, interprocess communication ( ipc ), scheduling, physical and virtual address space management, virtual memory, and timers. to translate a range of memory in one address space ( physical or virtual ) to a range in another address space. the virtual - memory manager accomplishes this by adjusting its vm tables for the kernel and user processes. - memory cursor an object that lays out the buffer ranges in a memory descriptor in physical memory, generating a scatter / gather list suitable for a particular device or dma engine. the object is derived from the iomemorycursor class. see also dma ; memory descriptor - memory descriptor an object that describes how a stream of data, depending on direction, should either be laid into memory or extracted from memory. it represents a segment of memory holding the data involved in an i / o transfer and is specified as one or more physical or virtual address ranges. the object is derived from the iomemorydescriptor class. see also dma ; memory cursor - memory protection a system of memory management in which programs are prevented from being able to modify or corrupt the memory partition of another program. although os x has memory protection, mac os 8 and 9 do not. a mutual - exclusion locking object that allows multiple threads to synchronize access to shared resources. a mutex has two states : locked and unlocked


partition of another program. although os x has memory protection, mac os 8 and 9 do not. a mutual - exclusion locking object that allows multiple threads to synchronize access to shared resources. a mutex has two states : locked and unlocked. once a mutex has been locked by a thread, other threads attempting to lock it will block. when the locking thread unlocks ( releases ) the mutex, one of the blocked threads ( if any ) acquires ( locks ) it and uses the resource. the thread that locks the mutex must be the one that unlocks it. the work - loop lock ( which is used by a command gate ) is based on a mutex. see also lock ; work loop a programmatic mechanism for alerting interested recipients ( sometimes called observers ) that an event has occurred. an i / o kit object that represents a detected, controllable entity such as a device or logical service. a nub may represent a bus, disk, graphics adaptor, or any number of similar entities. a nub supports dynamic configuration by providing a bridge between two drivers ( and, by extension, between two families ). see also device ; driver ( 1 ) the smallest unit ( in bytes ) of information that the virtual memory system can transfer between physical memory and backing store. in darwin, a page is currently 4 kilobytes. ( 2 ) as a verb, page refers to the transfer of pages between physical memory and backing store. refer to kernel. framework / headers / mach / machine / vm _ params. hfor specifics. see also fault ; virtual memory - passive driver a device driver that performs only basic power - management tasks, such as joining the power plane and changing the device ’ s power state. see also active driver a set of properties specifying the kinds of devices a driver can support. this information is stored in an xml matching dictionary defined in the information property list ( info. plist ) file in the driver ’ s kext bundle. a single driver may present one or more personalities for matching ; each personality specifies a class to instantiate. such instances are passed a reference to the personality dictionary at initialization. - physical memory electronic circuitry contained in random - access memory ( ram ) chips, used to temporarily hold information at execution time. addresses in a process ’ s virtual memory are mapped to addresses in physical memory. see also virtual memory ( programmed input / output ) a way to move data between a device and system memory in which each byte


used to temporarily hold information at execution time. addresses in a process ’ s virtual memory are mapped to addresses in physical memory. see also virtual memory ( programmed input / output ) a way to move data between a device and system memory in which each byte is transferred under control of the host processor. see also dma a subset of driver ( or service ) objects in the i / o registry that have a certain type of provider / client relationship connecting them. the most general plane is the service plane, which displays the objects in the same hierarchy in which they are attached during registry construction. there are also the audio, power, device tree, firewire, and usb planes. - platform expert a driver object for a particular motherboard that knows the type of platform the system is running on. the platform expert serves as the root of the i / o registry tree. a module that can be dynamically added to a running system or application. core foundation plug - in services uses the basic code - loading facility of core foundation bundle services to provide a standard plug - in architecture, known as the cfplugin architecture, for mac apps. a kernel extension is a type of kernel plug - in. a heavily overloaded term which in darwin has two particular meanings : ( 1 ) in mach, a secure unidirectional channel for communication between tasks running on a single system ; ( 2 ) in ip transport protocols, an integer identifier used to select a receiver for an incoming packet or to specify the sender of an outgoing packet. the portable operating system interface. an operating - system interface standardization effort supported by iso / iec, ieee, and the open group. - power child - power parent - preemptive multitasking a type of multitasking in which the operating system can interrupt a currently running program in order to run another program, as needed. a phase of active matching in which a candidate driver communicates with a device and verifies whether it can drive it. the driver ’ s probemember function is invoked to kick off this phase. the driver returns a probe score that reflects its ability to drive the device. see also driver matching a bsd abstraction for a running program. a process ’ resources include a virtual address space, threads, and file descriptors. in os x, a process is based on one mach task and one or more mach threads. a driver object that provides services of some kind to its client. in a driver stack, the provider in a provider / client relationship is closer to the


. in os x, a process is based on one mach task and one or more mach threads. a driver object that provides services of some kind to its client. in a driver stack, the provider in a provider / client relationship is closer to the platform expert. see also client decrementing the reference count of an object. when an object ’ s reference count reaches zero, it is freed. when your code no longer needs to reference a retained object, it should release it. some apis automatically execute a release on the caller ’ s behalf, particularly in cases where the object in question is being “ handed off. ” retains and releases must be carefully balanced ; too many releases can cause panics and other unexpected failures due to accesses of freed memory. see also retain incrementing the reference count of an object. an object with a positive reference count is not freed. ( a newly created object has a reference count of one. ) drivers can ensure the persistence of an object beyond the present scope by retaining it. many apis automatically execute a retain on the caller ’ s behalf, particularly apis used to create or gain access to objects. retains and releases must be carefully balanced ; too many retains will result in wired memory leak. see also release a service is an i / o kit entity, based on a subclass of ioservice, that has been published with the registerservicemethod and provides certain capabilities to other i / o kit objects. in the i / o kit ’ s layered architecture, each layer is a client of the layer below it and a provider of services to the layer above it. a service type is identified by a matching dictionary that describes properties of the service. a nub or driver can provide services to other i / o kit objects. in bsd - derived systems such as darwin, a socket refers to different entities in user and kernel operations. for a user process, a socket is a file descriptor that has been allocated using socket ( 2 ). for the kernel, a socket is the data structure that is allocated when the kernel ’ s implementation of the socket ( 2 ) call is made. - system sleep a sleep state that occurs when the user chooses sleep from the apple menu or closes the lid of a laptop computer. see also idle sleep in mach, the unit of cpu utilization. a thread consists of a program counter, a set of registers, and a stack pointer. see also task a kernel resource that triggers an event at a specified interval. the event can occur


see also idle sleep in mach, the unit of cpu utilization. a thread consists of a program counter, a set of registers, and a stack pointer. see also task a kernel resource that triggers an event at a specified interval. the event can occur only once or can be recurring. timers are one of the event sources for work loops. - user client an interface provided by an i / o kit family, that enables a user process ( which can ’ t call a kernel - resident driver or other service directly ) to access hardware. in the kernel, this interface appears as a driver object called a user client ; in user space, it is called a device interface and is implemented as a core foundation plug - in services ( cfplugin ) object. see also device interface - user space virtual memory outside the protected partition in which the kernel resides. applications, plug - ins, and other types of modules typically run in user space. - virtual address a memory address that is usable by software. each task has its own range of virtual addresses, which begins at address zero. the mach operating system makes the cpu hardware map these addresses onto physical memory only when necessary, using disk memory at other times. - virtual memory the use of a disk partition or a file on disk to provide the same facilities usually provided by ram. the virtual - memory manager in os x provides 32 - bit ( minimum ) protected address space for each task and facilitates efficient sharing of that address space. - wired memory a range of memory that the virtual - memory system will not page out or move. the memory involved in an i / o transfer must be wired down to prevent the physical relocation of data being accessed by hardware. in the i / o kit memory is wired when the memory descriptor describing the memory prepares the memory for i / o ( which happens when its preparemethod is invoked ). - work loop a gating mechanism that ensures single - threaded access to the data structures and hardware registers used by a driver. specifically, it is a mutex lock associated with a thread. a work loop typically has several event sources attached to it ; they use the work loop to ensure a protected, gated context for processing events. see also event source © 2001, 2007 apple inc. all rights reserved. ( last updated : 2007 - 05 - 17 )


exceptions are a means of breaking out of the normal flow of control of a code block in order to handle errors or other exceptional conditions. an exception is the python interpreter raises an exception when it detects a run - time error ( such as division by zero ). a python program can also explicitly raise an exception with the raise statement. exception handlers are specified with the try... except statement. the try... finally statement specifies cleanup code which does not handle the exception, but is executed whether an exception occurred or not in the preceding code. python uses the ` ` termination ' ' when an exception is not handled at all, the interpreter terminates execution of the program, or returns to its interactive main loop. in either case, it prints a stack backtrace, except when the exception is exceptions are identified by string objects or class instances. selection of a matching except clause is based on object identity ( i. e., two different string objects with the same value represent different exceptions! ) for string exceptions, the except clause must reference the same string object. for class exceptions, the except clause must reference the same class or a base class of it. when an exception is raised, an object ( maybe none ) is passed as the exception ' s ` ` parameter ' ' or ` ` value ' ' ; this object does not affect the selection of an exception handler, but is passed to the selected exception handler as additional information. for class exceptions, this object must be an instance of the exception class see also the description of the try statement in section 7. 4 and raise statement in section 6. 8.


reading this tutorial has probably reinforced your interest in using python - - you should be eager to apply python to solve your real - world problems. now what should you do? you should read, or at least page through, the python library reference, which gives complete ( though terse ) reference material about types, functions, and modules that can save you a lot of time when writing python programs. the standard python distribution includes a lot of code in both c and python ; there are modules to read unix mailboxes, retrieve documents via http, generate random numbers, parse command - line options, write cgi programs, compress data, and a lot more ; skimming through the library reference will give you an idea of what ' s available. the major python web site is http : / / www. python. org / ; it contains code, documentation, and pointers to python - related pages around the web. this web site is mirrored in various places around the world, such as europe, japan, and australia ; a mirror may be faster than the main site, depending on your geographical location. a more informal site is http : / / starship. python. net /, which contains a bunch of python - related personal home pages ; many people have downloadable software there. many more user - created python modules can be found in the python package index ( pypi ). for python - related questions and problem reports, you can post to the newsgroup comp. lang. python, or send them to the mailing list at firstname. lastname @ example. org. the newsgroup and mailing list are gatewayed, so messages posted to one will automatically be forwarded to the other. there are around 120 postings a day ( with peaks up to several hundred ), asking ( and answering ) questions, suggesting new features, and announcing new modules. before posting, be sure to check the list of frequently asked questions ( also called the faq ), or look for it in the misc / directory of the python source distribution. mailing list archives are available at http : / / www. python. org / pipermail /. the faq answers many of the questions that come up again and again, and may already contain the solution for your problem. see about this document... for information on suggesting changes.


the cerebrum, the largest part of the brain, is separated into the right and left hemispheres. the right hemisphere is in charge of the functions on the left - side of the body, as well as many cognitive functions. a right - side stroke happens when the brain ’ s blood supply is interrupted in this area. without oxygen and nutrients from blood, the brain tissue quickly dies. a stroke is a serious condition. it requires emergency care. there are two main types of stroke : an ischemic stroke ( the more common form ) is caused by a sudden decrease in blood flow to a region of the brain, which may be due to : - a clot that forms in another part of the body ( eg, heart or neck ) breaking off and blocking the flow in a blood vessel supplying the brain ( embolus ) - a clot that forms in an artery that supplies blood to the brain ( thrombus ) - a tear in an artery supplying blood to the brain ( arterial dissection ) a hemorrhagic stroke is caused by a burst blood vessel that results in bleeding in the brain. examples of risk factors that you can control or treat include : certain conditions, such as : - high blood pressure - high cholesterol - high levels of the amino acid homocysteine ( may result in the formation of blood clots ) - atherosclerosis ( narrowing of the arteries due to build - up of plaque ) - atrial fibrillation ( abnormal heart rhythm ) - metabolic syndrome - type 2 diabetes - alcohol or drug abuse - medicines ( eg, long - term use of birth control pills ) - lifestyle factors ( eg, smoking, physical inactivity, diet ) risk factors that you cannot control include : - history of having a stroke, heart attack, or other type of cardiovascular disease - history of having a transient ischemic attack ( tia ) — with a tia, stroke - like symptoms often resolve within minutes ( always in 24 hours ). they may signal a very high risk of having a stroke in the future. - age : 60 or older - family members who have had a stroke - gender : males - race : black, asian, hispanic - blood disorder that increases clotting - heart valve disease ( eg, mitral stenosis ) the immediate symptoms of a right - side stroke come on suddenly and may include : - weakness or numbness of face, arm, or leg, especially on the left side of the body - loss of balance


as a graduate student working for ligo ( the laser interferometer gravitational wave observatory ), one of my responsibilities was maintaining date - time code, including accounting for leap seconds, and calculating dates and time thousands of years in the past. what is a leap second? well, the earth ' s rotation rate is slowing down. so, as time goes on the length of the day is longer. this rate is very slow. every few years, the added length must be taken into account, much like the leap day takes into account that the orbital period of the earth around the sun is not exactly 365 days. when a leap second must be inserted is not predictable. the international earth rotation and reference systems service is tasked with making observations of the earth, and producing a twice - yearly report on whether a leap second is due to be added. this comes out by email, and on their website. the report gives a 6 - month or so lead time before the leap second is inserted, at midnight on jan 1 and on jul 1. so, apparently, a leap second was inserted last night : all standard atomic clocks around the world paused for a second. this caused all sorts of havoc with computers and networking devices, causing lots of sites to go down. notably, google was prepared.


handbook of engaged learning projects subject / content area : science, language arts, math, and social target audience : this multigrade level unit will involve third and sixth grade students. this is an interactive, interdisciplinary, thematic project. this is appropriate for students at all ability levels. program requires hardware / software for internet access. project goal : when posed with the problem of destruction of the rainforest, students will develop interpersonal skills, research skills, content objectives, technical skills, and higher order thinking skills. learner outcomes : through cooperative activities, students will be able to : - demonstrate the ability to collect data using various technologies ( internet, cd rom, computer software / hardware, and e - mail ). - analyze the impact of specific human activities on the destruction of tropical rainforests. - organize and analyze collected information gained through interaction - explain the important biological, social, and aesthetic values of the tropical rainforest to their environment. alignment with standards ( national - science standards : 7, 15, 18 - language arts : 1, 3, 4, 5, 7, 9, 10, 11 - math : 4, 6 - geography : 1, 2, 4, 8, 14, 16, 18 assessment of students : students ' performance will be assessed formatively through teacher observations. students and teachers will cooperatively develop a rubric for the final product. summative evaluation will include self - evaluation and teacher evaluation. author : patti furlano, joyce nelson, teri rakes and amy willis, braceville elementary school, braceville, il. of engaged learning projects sponsored by fermi national accelerator laboratory education office and friends of fermilab. funded by the north central regional technology in education consortium based at the north central regional educational laboratory ( ncrel ). created : august, 1997


at any point in the song. the brain has a certain number of entry nodes in the motor - action plan, so you can only access the information from particular points in the song. " even though it feels like it ' s in your fingers, it ' s not, " levitin said. " it ' s in the finger representation in your head. " music and pleasure music is strongly associated with the brain ' s reward system. it ' s the part of the brain that tells us if things are valuable, or important or relevant to survival, said robert zatorre, professor of neurology and neurosurgery at montreal neurological institute. one brain structure in particular, called the striatum, releases a chemical called dopamine in response to pleasure - related stimuli. imaging of the brain can reveal this process is similar to what happens in your brain in response to food or sex. but unlike those activities, music doesn ' t have a direct biological survival value. " it ' s not obvious that it should engage that same system, " zatorre said. musicians can ' t see inside their own brains, but they ' re aware of moments of tension and release in pieces, and that ' s what arrangers of music do. zatorre and colleagues did an experiment where they used whatever music participants said gave them pleasure to examine this dopamine release. they excluded music with words in order to focus on the music itself rather than lyrics - - the melodic structure, for example. at the point in a piece of music when people experience peak pleasure, part of the brain called the ventral striatum releases dopamine. but here ' s something even more interesting : dopamine is released from a different brain area ( the dorsal striatum ) about 10 to 15 seconds before the moment of peak pleasure. why would we have this reaction before the most pleasurable part of the piece of music? the brain likes to investigate its environment and figure out what ' s coming next, zatorre explains. " as you ' re anticipating a moment of pleasure, you ' re making predictions about what you ' re hearing and what you ' re about to hear, " he said. " part of the pleasure we derive from it is being able to make predictions. " so if you ' re getting such a strong dopamine rush from music - - it could even be comparable to methamphetamines, zatorre said - - why not make drug addicts listen to music? it ' s


s patients remember things better, and that learning new skills such as musical instruments might even stave off dementia. there still needs to be more research in these areas to confirm, but limb is hopeful about the prospect of musical engagement as a way to prevent, or at least delay, dementia. " that ' s a pretty amazing thing that, from sound, you can stimulate the entire brain, " limb said. " if you think about dementia as the opposite trend, of the brain atrophying, i think there ' s a lot of basis to it. " music and emotions you may associate particular songs with events in your life - - green day ' s " good riddance ( time of your life ) " might remind you of your graduation day, if you had a graduation in the 1990s or 2000s, for example. despite variation in any given person ' s life experience, studies have shown that music listeners largely agree with one another when it comes to the emotions presented in a song. this may be independent of lyrics ; musical sounds themselves may carry emotional meaning, writes cornell university psychologist carol krumhansl in current directions in psychological science. educational shows such as " sesame street " have been tapping into the power of music to help youngsters remember things for decades. even babies have been shown to be sensitive to beats and can recognize a piece of music that they ' ve already heard. advertisers exploit music in many commercials to make you excited about products. as a result, you may associate songs with particular cars, for instance. here ' s one way you might not already be using music : making a deliberate effort to use music to alter mood. listen to something that makes you energetic at the beginning of the day, and listen to a soothing song after an argument, levitin says. music as a language victor wooten of bela fleck and the flecktones isn ' t a scientist, but he has thought a lot about the process of learning to play music. for him, introducing a child to music shouldn ' t be different from the way a child begins speaking. " i just approach music as a language, because it is, " wooten said. " it serves the same purpose. it ' s a form of expression. a way for me to express myself, convey feelings, and sometimes it actually works better than a written or verbal language. " traditionally, a child learns to play music by being taught how an instrument works, and learning to play easy pieces that they practice over and over. they might also play music


ece497 project ideas we have both mini projects and projects in ece497. mini projects involved finding something interested in the beagle world and installing it to your beagle and demoing it to the class. you would also create a wiki page documenting what you did to get it installed. often you may find multiple efforts do to something, for example there are a few efforts to port android on the beagle. your task is to figure out which one should be used. generally mini projects won ' t require you to write new code ; however they are the background work that may lead to a full project. you should do a couple mini projects for the class. generally they are done alone, but working in pairs is ok. these will be about 1 / 3 of your grade and should be done in the first 5 weeks or so. only one full project is done for the class and it ' s done with a team of 3 or 4. these projects can take a mini project ( or a whole new idea ) and add to it. the goal is to have your work contribute to the open source world. any code is generated will be kept on github and a bitbake receipt will be created to automatically download and create the object files. what follows are - places to look for project ideas - feel free to add your own suggestions. - mini project ideas - add your own suggestions, and do some of them. mark the ones you ' ve done. - full project ideas sources for project ideas here are some links where you ' ll find ideas for your project. - etechdays community lightning talks, this is a one - day web - based conference where many project ideas are presented. one of our 2009 - 2010 senior design projects was found here. - official list of beagle projects, there are many beagle specific projects listed here. many are inactive. list your project here once it running. - augmented reality project, here ' s an idea that i think we can do on the beagle. rather than using augmented reality glasses, i ' d suggest we use a ti dlp pico projector. here ' s ar running on the beagle. - android, this is one of a couple of efforts to port google ' s android os to the beagle. - beagleboard / ideas - 2009 google summer code ideas 2009. mini project ideas | mark a. yoder | | jack ma | | work up an example of controlling the pwm registers from the shell. | |


the beagle. - beagleboard / ideas - 2009 google summer code ideas 2009. mini project ideas | mark a. yoder | | jack ma | | work up an example of controlling the pwm registers from the shell. | | pwm via the shell | | mark a. yoder | | weather station | | ultrasonic weather | | mark a. yoder | | mike yuhas | | interface the beagleboard with an srf08 ultrasonic ranger over i2c | | ultrasonic ranger | | mark a. yoder | | compile the powervr examples | | powervr insider sdk downloads | | mark a. yoder | | work up some gstreamer ps eye demos | | gstreamer ps eye demos and ridgerun | | mark a. yoder | | douglas selby | | get ti ' embedded speech recognizer installed and demo the examples. | | ti embedded speech recognizer | | mark a. yoder | | david zitnik | | demo last year ' s ti speech project. i have a microphone amplifier and mike you can use. | | ece597 project pywikireader | | mark a. yoder | | stephen mayhew | | find who is doing what with kinect on the beagle and install and run it. | | google - beagleboard kinect | | mark a. yoder | | greg harrison | | i have several sony playstation eye web cams and i have examples of how to pull video from them via v4l2 ( ece497 davinci workshop labs ). the eye also has a 4 microphone array. i don ' t know how to get audio from it. figure out how. this may expand to a full project if there is no solution out there. | | google - beagleboard playstation eye microphone array | | mark a. yoder | | find some examples of how to use cmem. cmem is an api and library for managing one or more blocks of physically contiguous memory. it also provides address translation services ( e. g. virtual to physical translation ) and user - mode cache management apis. it ' s used for managing the shared memory between the arm and the dsp on the processor. i ' ve been unable to find examples of how to use it. | | cmem overview | | mike lester | | connect to your beagleboard using ethernet over usb. this allows your beagleboard to share


dsp on the processor. i ' ve been unable to find examples of how to use it. | | cmem overview | | mike lester | | connect to your beagleboard using ethernet over usb. this allows your beagleboard to share the host computer ' s internet connection and allow you to connect via vnc / ssh without the need for an external router / switch. this should make development much easier. | | vnc | | brian hulette | | experiment with audio synthesis and / or sampling / processing. you could either synthesize and play a few tones to generate a song, or have the beagle sample an audio signal then process and output it to create a sort of effects pedal. | | david mcginnis | | david mcginnis | | look into connecting the beagleboard to a phone or headphones using bluetooth. this could involve either outputting audio and taking in audio from a bluetooth headset, allowing you to have audio i / o with the beagleboard, or could involve connecting with phones automatically as they come into range of the beagleboard, allowing for an automatic attendence registration system, among other things. | | david bliss | | david bliss | | get a video stream from a ps eye, and identify the relevant device files. | | playstation _ eye # cite _ note - linux _ support - 32 | | william gerth | | william gerth | | explore the possibility of implementing openaos on the beagle, to make a portable media player and etc. | | http : / / www. openaos. org / | | joel carlson | | lacking a serial port and don ' t have a usb - serial converter? why not find a way to make the beagleboard boot over a usb console connection? | | beagleboard xm u - boot without serial | | joel carlson | | joel carlson | | depending on what one is working on, it might be useful to mount the beagleboard root filesystem over nfs. the link to the right does that using a usb - ethernet connection, but one that just runs over an ethernet cable would be nice. | | mount beagleboard root filesystem over nfs via usb here ' s an example of mounting dfs / afs on the beagle | lei liu | | lei liu | | build communication with fpga via usb port. | | aaron bamberger | | aaron bamberger | | play around with the beagle


the dsp. it currently runs on the arm. | | mark a. yoder | | kinect | | here and here are some interesting things people are doing with kinects. maybe we could port it to the beagle. | | mike lester | | accelerometer - based auto - leveled projection | | several projects have been started to add accelerometer support to the beagleboard. this project would involve getting an accelerometer installed and working, perhaps using a trainer board, as well the ti pico projector. the orientation data from the accelerometer would be used to rotate, skew, keystone the projected image in order to keep it level and normalized. | | aaron bamberger | | kinect based 3d scanner | | build some sort of motorized gantry that allows the kinect to be rotated around ( and possibly from top to bottom ) of an arbitrary object. the motors would be controlled using the beagleboard ' s i2c or spi interfaces. use libfreenect to capture depth information from every side of the object as the kinect rotates around the object. use this data and opengl to build a 3d model of the scanned object | | mark a. yoder | | port windsk6 to the beagle | | windsk6 is a windows program that talks to a ti ' c6711 dsk and performs many interesting audio effects. this project would implement the code running on the windows side on the arm. the arm could capture a frame of audio and send it to the dsp for processing. the arm could then send the processed audio to the speakers. c6run would be used to interact with the dsp. | | david bliss | | automated die tester | | make a device that can roll a die, and keep statistics on how random the die is. the build can either be very complex, or very simple, depending on how you define " rolling a die ". the software doesn ' t necessarily have to know what the numbers mean, it just has to be able to uniquely identify the sides. | | stephen mayhew | | set - playing system | | set is a relatively simple card game that lends itself nicely to image recognition and computer play. the layout is not very structured, and the game play is pretty simple. this project would incorporate image recognition, projection of possible moves ( using the pico projector ), and maybe even speech synthesis, and recognition. for example,


computer play. the layout is not very structured, and the game play is pretty simple. this project would incorporate image recognition, projection of possible moves ( using the pico projector ), and maybe even speech synthesis, and recognition. for example, if someone didn ' t know how to play set, then the board could take them through a tutorial, asking questions of the user as it went along ( " if i have these 2 cards, what 3rd card would make a set? " ). this would make for an interesting demo at conferences. | | michael fuson | spectrum analyzer | | create a real - time audio spectrum analyzer on the beagleboard. project page | | team members | | project title | | description | | yannick polius | | pywikireader | | this project is mostly software, with the hardware element being the use of the dsp. the idea is to tie together three technologies : speech recognition, speech synthesis, and internet access in order to create an interface capable of orating information to the user based on a vocal command. the implementation i have in mind is to use the pocket sphinx speech recognition engine to first understand what the user wants through speech, such as " rose - hulman ". once the speech is translated, the software can execute a wikipedia search to pull said item ' s page. most of the important info is contained within the introductory paragraph, so the software will take only that chunk and feed it into the flite speech synthesis engine. the end result is a simple machine with " mother box " like usability, that is, no interaction besides what is natural to the user ( speaking ) should be necessary to retrieve the information. | | paul morrison | 3d chess with networking | | this project would simulate a hand - held chess game, and the game would allow two player games using two beagleboards over a network connection. the graphics would use the beagle ' s powervr sgx for hardware accelerated graphics by using opengl. in addition to 3d graphics and networking, a third portion of the project would be to optimize the boot time because a chess computer should start up quickly. | | tom most | sumo robot | | the goal of this project is to create a robot capable of competing in the 3. 0 kg weight class of a sumo competition ( an example ). this would have minor hardware and electronics elements, but would focus on communication with sensors using the beagleboard and the linux kernel. at minimum, this involves sensors


competing in the 3. 0 kg weight class of a sumo competition ( an example ). this would have minor hardware and electronics elements, but would focus on communication with sensors using the beagleboard and the linux kernel. at minimum, this involves sensors to detect the edge of the ring and the opposing robot. this would likely be implemented using sharp ir rangefinders, a ultrasonic rangefinders, and ideally a camera. sumo rules. | | ece597 network based mp3 player | | network based mp3 player. the beagle will be programmed using a custom, protocol for transferring files from a network based server ( x86 pc ) to a beagle. speakers will be attached to the beagle, where the file will be played back. possible extensions are a lcd for displaying id3 tag information, and buttons for user interaction ( next track, previous track, etc. ) on the gpio interface. | | chris routh j. cody collins greg jackson keqiong xin | ece597 : auto hud | | use the beagle board to run image recognition on a camera feed located inside a car, and then signaling to the driver via a pico projector various objects of interest. | | adam jesionowski | adding sense to beagle ( see beagleboard / gsoc / ideas ) | | sensory aware applications are becoming more mainstream with the release of the apple iphone. this project would combine both hw and sw to add sensory awareness to beagle. first, additional modules such as gps, 3 - axis accelerometers, gyroscopes, temperature sensors, humidity sensors, pressure sensors, etc, would be added to beagle to compliment the microphone input in order to allow sensing of the real world environment. then sw apis would need to be layered on top to allow easy access to the sensory data for use by applications. | | mitch garvin | interactive pong | | run classic pong, projecting the screen and using a camera to track user ' s hands for input. |


| | this article needs additional citations for verification. ( march 2011 ) | nuclear meltdown is an informal term for a severe nuclear reactor accident that results in core damage from overheating. the term is not officially defined by the international atomic energy agency or by the u. s. nuclear regulatory commission. however, it has been defined to mean the accidental melting of the core of a nuclear reactor, and is in common usage a reference to the core ' s either complete or partial collapse. " core melt accident " and " partial core melt " are the analogous technical terms for a meltdown. a core melt accident occurs when the heat generated by a nuclear reactor exceeds the heat removed by the cooling systems to the point where at least one nuclear fuel element exceeds its melting point. this differs from a fuel element failure, which is not caused by high temperatures. a meltdown may be caused by a loss of coolant, loss of coolant pressure, or low coolant flow rate or be the result of a criticality excursion in which the reactor is operated at a power level that exceeds its design limits. alternately, in a reactor plant such as the rbmk - 1000, an external fire may endanger the core, leading to a meltdown. once the fuel elements of a reactor begin to melt, the fuel cladding has been breached, and the nuclear fuel ( such as uranium, plutonium, or thorium ) and fission products ( such as cesium - 137, krypton - 88, or iodine - 131 ) within the fuel elements can leach out into the coolant. subsequent failures can permit these radioisotopes to breach further layers of containment. superheated steam and hot metal inside the core can lead to fuel - coolant interactions, hydrogen explosions, or water hammer, any of which could destroy parts of the containment. a meltdown is considered very serious because of the potential, however remote, that radioactive materials could breach all containment and escape ( or be released ) into the environment, resulting in radioactive contamination and fallout, and potentially leading to radiation poisoning of people and animals nearby. nuclear power plants generate electricity by heating fluid via a nuclear reaction to run a generator. if the heat from that reaction is not removed adequately, the fuel assemblies in a reactor core can melt. a core damage incident can occur even after a reactor is shut down because the fuel continues to produce decay heat. a core damage accident is caused by the loss of sufficient cooling for the nuclear fuel within the reactor core. the reason may be one


melt. a core damage incident can occur even after a reactor is shut down because the fuel continues to produce decay heat. a core damage accident is caused by the loss of sufficient cooling for the nuclear fuel within the reactor core. the reason may be one of several factors, including a loss - of - pressure - control accident, a loss - of - coolant accident ( loca ), an uncontrolled power excursion or, in reactors without a pressure vessel, a fire within the reactor core. failures in control systems may cause a series of events resulting in loss of cooling. contemporary safety principles of defense in depth ensure that multiple layers of safety systems are always present to make such accidents unlikely. the containment building is the last of several safeguards that prevent the release of radioactivity to the environment. many commercial reactors are contained within a 1. 2 - to - 2. 4 - metre ( 3. 9 to 7. 9 ft ) thick pre - stressed, steel - reinforced, air - tight concrete structure that can withstand hurricane - force winds and severe earthquakes. - in a loss - of - coolant accident, either the physical loss of coolant ( which is typically deionized water, an inert gas, nak, or liquid sodium ) or the loss of a method to ensure a sufficient flow rate of the coolant occurs. a loss - of - coolant accident and a loss - of - pressure - control accident are closely related in some reactors. in a pressurized water reactor, a loca can also cause a " steam bubble " to form in the core due to excessive heating of stalled coolant or by the subsequent loss - of - pressure - control accident caused by a rapid loss of coolant. in a loss - of - forced - circulation accident, a gas cooled reactor ' s circulators ( generally motor or steam driven turbines ) fail to circulate the gas coolant within the core, and heat transfer is impeded by this loss of forced circulation, though natural circulation through convection will keep the fuel cool as long as the reactor is not depressurized. - in a loss - of - pressure - control accident, the pressure of the confined coolant falls below specification without the means to restore it. in some cases this may reduce the heat transfer efficiency ( when using an inert gas as a coolant ) and in others may form an insulating " bubble " of steam surrounding the fuel assemblies ( for pressurized water reactors ). in the latter case, due to localized heating of the "


efficiency ( when using an inert gas as a coolant ) and in others may form an insulating " bubble " of steam surrounding the fuel assemblies ( for pressurized water reactors ). in the latter case, due to localized heating of the " steam bubble " due to decay heat, the pressure required to collapse the " steam bubble " may exceed reactor design specifications until the reactor has had time to cool down. ( this event is less likely to occur in boiling water reactors, where the core may be deliberately depressurized so that the emergency core cooling system may be turned on ). in a depressurization fault, a gas - cooled reactor loses gas pressure within the core, reducing heat transfer efficiency and posing a challenge to the cooling of fuel ; however, as long as at least one gas circulator is available, the fuel will be kept cool. - in an uncontrolled power excursion accident, a sudden power spike in the reactor exceeds reactor design specifications due to a sudden increase in reactor reactivity. an uncontrolled power excursion occurs due to significantly altering a parameter that affects the neutron multiplication rate of a chain reaction ( examples include ejecting a control rod or significantly altering the nuclear characteristics of the moderator, such as by rapid cooling ). in extreme cases the reactor may proceed to a condition known as prompt critical. this is especially a problem in reactors that have a positive void coefficient of reactivity, a positive temperature coefficient, are overmoderated, or can trap excess quantities of deleterious fission products within their fuel or moderators. many of these characteristics are present in the rbmk design, and the chernobyl disaster was caused by such deficiencies as well as by severe operator negligence. western light water reactors are not subject to very large uncontrolled power excursions because loss of coolant decreases, rather than increases, core reactivity ( a negative void coefficient of reactivity ) ; " transients, " as the minor power fluctuations within western light water reactors are called, are limited to momentary increases in reactivity that will rapidly decrease with time ( approximately 200 % - 250 % of maximum neutronic power for a few seconds in the event of a complete rapid shutdown failure combined with a transient ). - core - based fires endanger the core and can cause the fuel assemblies to melt. a fire may be caused by air entering a graphite moderated reactor, or a liquid - sodium cooled reactor. graphite is also subject to accumulation of wigner energy, which can overhea


the core and can cause the fuel assemblies to melt. a fire may be caused by air entering a graphite moderated reactor, or a liquid - sodium cooled reactor. graphite is also subject to accumulation of wigner energy, which can overheat the graphite ( as happened at the windscale fire ). light water reactors do not have flammable cores or moderators and are not subject to core fires. gas - cooled civilian reactors, such as the magnox, ungg, and agcr type reactors, keep their cores blanketed with non reactive carbon dioxide gas, which cannot support a fire. modern gas - cooled civilian reactors use helium, which cannot burn, and have fuel that can withstand high temperatures without melting ( such as the high temperature gas cooled reactor and the pebble bed modular reactor ). - byzantine faults and cascading failures within instrumentation and control systems may cause severe problems in reactor operation, potentially leading to core damage if not mitigated. for example, the browns ferry fire damaged control cables and required the plant operators to manually activate cooling systems. the three mile island accident was caused by a stuck - open pilot - operated pressure relief valve combined with a deceptive water level gauge that misled reactor operators, which resulted in core damage. light water reactors ( lwrs ) before the core of a light water nuclear reactor can be damaged, two precursor events must have already occurred : - a limiting fault ( or a set of compounded emergency conditions ) that leads to the failure of heat removal within the core ( the loss of cooling ). low water level uncovers the core, allowing it to heat up. - failure of the emergency core cooling system ( eccs ). the eccs is designed to rapidly cool the core and make it safe in the event of the maximum fault ( the design basis accident ) that nuclear regulators and plant engineers could imagine. there are at least two copies of the eccs built for every reactor. each division ( copy ) of the eccs is capable, by itself, of responding to the design basis accident. the latest reactors have as many as four divisions of the eccs. this is the principle of redundancy, or duplication. as long as at least one eccs division functions, no core damage can occur. each of the several divisions of the eccs has several internal " trains " of components. thus the eccs divisions themselves have internal redundancy – and can withstand failures of components within them. the three mile island accident was a compounded


occur. each of the several divisions of the eccs has several internal " trains " of components. thus the eccs divisions themselves have internal redundancy – and can withstand failures of components within them. the three mile island accident was a compounded group of emergencies that led to core damage. what led to this was an erroneous decision by operators to shut down the eccs during an emergency condition due to gauge readings that were either incorrect or misinterpreted ; this caused another emergency condition that, several hours after the fact, led to core exposure and a core damage incident. if the eccs had been allowed to function, it would have prevented both exposure and core damage. during the fukushima incident the emergency cooling system had also been manually shut down several minutes after it started. if such a limiting fault were to occur, and a complete failure of all eccs divisions were to occur, both kuan, et al and haskin, et al describe six stages between the start of the limiting fault ( the loss of cooling ) and the potential escape of molten corium into the containment ( a so - called " full meltdown " ) : - uncovering of the core – in the event of a transient, upset, emergency, or limiting fault, lwrs are designed to automatically scram ( a scram being the immediate and full insertion of all control rods ) and spin up the eccs. this greatly reduces reactor thermal power ( but does not remove it completely ) ; this delays core becoming uncovered, which is defined as the point when the fuel rods are no longer covered by coolant and can begin to heat up. as kuan states : " in a small - break loca with no emergency core coolant injection, core uncovery [ sic ] generally begins approximately an hour after the initiation of the break. if the reactor coolant pumps are not running, the upper part of the core will be exposed to a steam environment and heatup of the core will begin. however, if the coolant pumps are running, the core will be cooled by a two - phase mixture of steam and water, and heatup of the fuel rods will be delayed until almost all of the water in the two - phase mixture is vaporized. the tmi - 2 accident showed that operation of reactor coolant pumps may be sustained for up to approximately two hours to deliver a two phase mixture that can prevent core heatup. " - pre - damage heat up – " in the absence of a two - phase mixture going through the core


operation of reactor coolant pumps may be sustained for up to approximately two hours to deliver a two phase mixture that can prevent core heatup. " - pre - damage heat up – " in the absence of a two - phase mixture going through the core or of water addition to the core to compensate water boiloff, the fuel rods in a steam environment will heat up at a rate between 0. 3 °c / s ( 0. 5 °f / s ) and 1 °c / s ( 1. 8 °f / s ) ( 3 ). " - fuel ballooning and bursting – " in less than half an hour, the peak core temperature would reach 1, 100 k ( 1, 520 °f ). at this temperature the zircaloy cladding of the fuel rods may balloon and burst. this is the first stage of core damage. cladding ballooning may block a substantial portion of the flow area of the core and restrict the flow of coolant. however complete blockage of the core is unlikely because not all fuel rods balloon at the same axial location. in this case, sufficient water addition can cool the core and stop core damage progression. " - rapid oxidation – " the next stage of core damage, beginning at approximately 1, 500 k ( 2, 240 °f ), is the rapid oxidation of the zircaloy by steam. in the oxidation process, hydrogen is produced and a large amount of heat is released. above 1, 500 k ( 2, 240 °f ), the power from oxidation exceeds that from decay heat ( 4, 5 ) unless the oxidation rate is limited by the supply of either zircaloy or steam. " - debris bed formation – " when the temperature in the core reaches about 1, 700 k ( 2, 600 °f ), molten control materials [ 1, 6 ] will flow to and solidify in the space between the lower parts of the fuel rods where the temperature is comparatively low. above 1, 700 k ( 2, 600 °f ), the core temperature may escalate in a few minutes to the melting point of zircaloy [ 2, 150 k ( 3, 410 °f ) ] due to increased oxidation rate. when the oxidized cladding breaks, the molten zircaloy, along with dissolved uo2 [ 1, 7 ] would flow downward and freeze in the cooler, lower region of the core. together with solidified control materials from earlier down - flows, the relocated zircaloy and uo2 would form the lower crust of a developing


[ 1, 7 ] would flow downward and freeze in the cooler, lower region of the core. together with solidified control materials from earlier down - flows, the relocated zircaloy and uo2 would form the lower crust of a developing cohesive debris bed. " - ( corium ) relocation to the lower plenum – " in scenarios of small - break locas, there is generally a pool of water in the lower plenum of the vessel at the time of core relocation. release of molten core materials into water always generates large amounts of steam. if the molten stream of core materials breaks up rapidly in water, there is also a possibility of a steam explosion. during relocation, any unoxidized zirconium in the molten material may also be oxidized by steam, and in the process hydrogen is produced. recriticality also may be a concern if the control materials are left behind in the core and the relocated material breaks up in unborated water in the lower plenum. " at the point at which the corium relocates to the lower plenum, haskin, et al relate that the possibility exists for an incident called a fuel - coolant interaction ( fci ) to substantially stress or breach the primary pressure boundary when the corium relocates to the lower plenum of the reactor pressure vessel ( " rpv " ). this is because the lower plenum of the rpv may have a substantial quantity of water - the reactor coolant - in it, and, assuming the primary system has not been depressurized, the water will likely be in the liquid phase, and consequently dense, and at a vastly lower temperature than the corium. since corium is a liquid metal - ceramic eutectic at temperatures of 2, 200 to 3, 200 k ( 3, 500 to 5, 300 °f ), its fall into liquid water at 550 to 600 k ( 530 to 620 °f ) may cause an extremely rapid evolution of steam that could cause a sudden extreme overpressure and consequent gross structural failure of the primary system or rpv. though most modern studies hold that it is physically infeasible, or at least extraordinarily unlikely, haskin, et al state that that there exists a remote possibility of an extremely violent fci leading to something referred to as an alpha - mode failure, or the gross failure of the rpv itself, and subsequent ejection of the upper plenum of


al state that that there exists a remote possibility of an extremely violent fci leading to something referred to as an alpha - mode failure, or the gross failure of the rpv itself, and subsequent ejection of the upper plenum of the rpv as a missile against the inside of the containment, which would likely lead to the failure of the containment and release of the fission products of the core to the outside environment without any substantial decay having taken place. breach of the primary pressure boundary there are several possibilities as to how the primary pressure boundary could be breached by corium. - steam explosion as previously described, fci could lead to an overpressure event leading to rpv fail, and thus, primary pressure boundary fail. haskin, et al. report that in the event of a steam explosion, failure of the lower plenum is far more likely than ejection of the upper plenum in the alpha - mode. in the even of lower plenum failure, debris at varied temperatures can be expected to be projected into the cavity below the core. the containment may be subject to overpressure, though this is not likely to fail the containment. the alpha - mode failure will lead to the consequences previously discussed. - pressurized melt ejection ( pme ) it is quite possible, especially in pressurized water reactors, that the primary loop will remain pressurized following corium relocation to the lower plenum. as such, pressure stresses on the rpv will be present in addition to the weight stress that the molten corium places on the lower plenum of the rpv ; when the metal of the rpv weakens sufficiently due to the heat of the molten corium, it is likely that the liquid corium will be discharged under pressure out of the bottom of the rpv in a pressurized stream, together with entrained gases. this mode of corium ejection may lead to direct containment heating ( dch ). severe accident ex - vessel interactions and challenges to containment haskin, et al identify six modes by which the containment could be credibly challenged ; some of these modes are not applicable to core melt accidents. - dynamic pressure ( shockwaves ) - internal missiles - external missiles ( not applicable to core melt accidents ) standard failure modes if the melted core penetrates the pressure vessel, there are theories and speculations as to what may then occur. in modern russian plants, there is a " core catching device " in the


missiles ( not applicable to core melt accidents ) standard failure modes if the melted core penetrates the pressure vessel, there are theories and speculations as to what may then occur. in modern russian plants, there is a " core catching device " in the bottom of the containment building, the melted core is supposed to hit a thick layer of a " sacrificial metal " which would melt, dilute the core and increase the heat conductivity, and finally the diluted core can be cooled down by water circulating in the floor. however there has never been any full - scale testing of this device. in western plants there is an airtight containment building. though radiation would be at a high level within the containment, doses outside of it would be lower. containment buildings are designed for the orderly release of pressure without releasing radionuclides, through a pressure release valve and filters. hydrogen / oxygen recombiners also are installed within the containment to prevent gas explosions. in a melting event, one spot or area on the rpv will become hotter than other areas, and will eventually melt. when it melts, corium will pour into the cavity under the reactor. though the cavity is designed to remain dry, several nureg - class documents advise operators to flood the cavity in the event of a fuel melt incident. this water will become steam and pressurize the containment. automatic water sprays will pump large quantities of water into the steamy environment to keep the pressure down. catalytic recombiners will rapidly convert the hydrogen and oxygen back into water. one positive effect of the corium falling into water is that it is cooled and returns to a solid state. extensive water spray systems within the containment along with the eccs, when it is reactivated, will allow operators to spray water within the containment to cool the core on the floor and reduce it to a low temperature. these procedures are intended to prevent release of radiation. in the three mile island event in 1979, a theoretical person standing at the plant property line during the entire event would have received a dose of approximately 2 millisieverts ( 200 millirem ), between a chest x - ray ' s and a ct scan ' s worth of radiation. this was due to outgassing by an uncontrolled system that, today, would have been backfitted with activated carbon and hepa filters to prevent radionuclide release. however in case of fukushima incident this design also at least partially failed : large amounts of highly radioactive water were produced and


system that, today, would have been backfitted with activated carbon and hepa filters to prevent radionuclide release. however in case of fukushima incident this design also at least partially failed : large amounts of highly radioactive water were produced and nuclear fuel has possibly melted through the base of the pressure vessels. cooling will take quite a while, until the natural decay heat of the corium reduces to the point where natural convection and conduction of heat to the containment walls and re - radiation of heat from the containment allows for water spray systems to be shut down and the reactor put into safe storage. the containment can be sealed with release of extremely limited offsite radioactivity and release of pressure within the containment. after a number of years for fission products to decay - probably around a decade - the containment can be reopened for decontamination and demolition. unexpected failure modes another scenario sees a buildup of hydrogen, which may lead to a detonation event, as happened for three reactors during fukushima incident. catalytic hydrogen recombiners located within containment are designed to prevent this from occurring ; however, prior to the installation of these recombiners in the 1980s, the three mile island containment ( in 1979 ) suffered a massive hydrogen explosion event in the accident there. the containment withstood the pressure and no radioactivity was released. however, in fukushima recombiners did not work due the absence of power and hydrogen detonation breached the containment. speculative failure modes one scenario consists of the reactor pressure vessel failing all at once, with the entire mass of corium dropping into a pool of water ( for example, coolant or moderator ) and causing extremely rapid generation of steam. the pressure rise within the containment could threaten integrity if rupture disks could not relieve the stress. exposed flammable substances could burn, but there are few, if any, flammable substances within the containment. another theory called an ' alpha mode ' failure by the 1975 rasmussen ( wash - 1400 ) study asserted steam could produce enough pressure to blow the head off the reactor pressure vessel ( rpv ). the containment could be threatened if the rpv head collided with it. ( the wash - 1400 report was replaced by better - based [ original research? ] newer studies, and now the nuclear regulatory commission has disavowed them all and is preparing the overarching state - of - the - art reactor consequence analyses [ soarca ] study - see the disclaimer in nureg - 115


newer studies, and now the nuclear regulatory commission has disavowed them all and is preparing the overarching state - of - the - art reactor consequence analyses [ soarca ] study - see the disclaimer in nureg - 1150. ) it has not been determined to what extent a molten mass can melt through a structure ( although that was tested in the loss - of - fluid - test reactor described in test area north ' s fact sheet ). the three mile island accident provided some real - life experience, with an actual molten core within an actual structure ; the molten corium failed to melt through the reactor pressure vessel after over six hours of exposure, due to dilution of the melt by the control rods and other reactor internals, validating the emphasis on defense in depth against core damage incidents. some believe a molten reactor core could actually penetrate the reactor pressure vessel and containment structure and burn downwards into the earth beneath, to the level of the groundwater. by 1970, there were doubts about the ability of the emergency cooling systems of a nuclear reactor to prevent a loss of coolant accident and the consequent meltdown of the fuel core ; the subject proved popular in the technical and the popular presses. in 1971, in the article thoughts on nuclear plumbing, former manhattan project ( 1942 – 1946 ) nuclear physicist ralph lapp used the term " china syndrome " to describe a possible burn - through, after a loss of coolant accident, of the nuclear fuel rods and core components melting the containment structures, and the subsequent escape of radioactive material ( s ) into the atmosphere and environment ; the hypothesis derived from a 1967 report by a group of nuclear physicists, headed by w. k. ergen. the geographic, planet - piercing concept of the china syndrome derives from the misperception that china is the antipode of the united states ; to many americans, it is the “ the other side of the world ”. moreover, the hypothetical transit of a meltdown product to the other side of the earth ( i. e. china ) ignores the fact that the earth ' s gravity tends to pull all masses towards its center. assuming a meltdown product could persist in a mobile molten form for long enough to reach the center of the earth ; gravity would prevent it continuing to the other side. other reactor types other types of reactors have different capabilities and safety profiles than the lwr does. advanced varieties of several of these reactors have the potential to be inherently safe. candu reactors candu reactors, canadian - invented de


to the other side. other reactor types other types of reactors have different capabilities and safety profiles than the lwr does. advanced varieties of several of these reactors have the potential to be inherently safe. candu reactors candu reactors, canadian - invented deuterium - uranium design, are designed with at least one, and generally two, large low - temperature and low - pressure water reservoirs around their fuel / coolant channels. the first is the bulk heavy - water moderator ( a separate system from the coolant ), and the second is the light - water - filled shield tank. these backup heat sinks are sufficient to prevent either the fuel meltdown in the first place ( using the moderator heat sink ), or the breaching of the core vessel should the moderator eventually boil off ( using the shield tank heat sink ). other failure modes aside from fuel melt will probably occur in a candu rather than a meltdown, such as deformation of the calandria into a non - critical configuration. all candu reactors are located within standard western containments as well. gas - cooled reactors one type of western reactor, known as the advanced gas - cooled reactor ( or agcr ), built by the united kingdom, is not very vulnerable to loss - of - cooling accidents or to core damage except in the most extreme of circumstances. by virtue of the relatively inert coolant ( carbon dioxide ), the large volume and high pressure of the coolant, and the relatively high heat transfer efficiency of the reactor, the time frame for core damage in the event of a limiting fault is measured in days. restoration of some means of coolant flow will prevent core damage from occurring. other types of highly advanced gas cooled reactors, generally known as high - temperature gas - cooled reactors ( htgrs ) such as the japanese high temperature test reactor and the united states ' very high temperature reactor, are inherently safe, meaning that meltdown or other forms of core damage are physically impossible, due to the structure of the core, which consists of hexagonal prismatic blocks of silicon carbide reinforced graphite infused with triso or quadriso pellets of uranium, thorium, or mixed oxide buried underground in a helium - filled steel pressure vessel within a concrete containment. though this type of reactor is not susceptible to meltdown, additional capabilities of heat removal are provided by using regular atmospheric airflow as a means of backup heat removal, by having it pass through a heat exchanger and rising into the atmosphere due to convection, achieving full residual heat


is not susceptible to meltdown, additional capabilities of heat removal are provided by using regular atmospheric airflow as a means of backup heat removal, by having it pass through a heat exchanger and rising into the atmosphere due to convection, achieving full residual heat removal. the vhtr is scheduled to be prototyped and tested at idaho national laboratory within the next decade ( as of 2009 ) as the design selected for the next generation nuclear plant by the us department of energy. this reactor will use a gas as a coolant, which can then be used for process heat ( such as in hydrogen production ) or for the driving of gas turbines and the generation of electricity. a similar highly advanced gas cooled reactor originally designed by west germany ( the avr reactor ) and now developed by south africa is known as the pebble bed modular reactor. it is an inherently safe design, meaning that core damage is physically impossible, due to the design of the fuel ( spherical graphite " pebbles " arranged in a bed within a metal rpv and filled with triso ( or quadriso ) pellets of uranium, thorium, or mixed oxide within ). a prototype of a very similar type of reactor has been built by the chinese, htr - 10, and has worked beyond researchers ' expectations, leading the chinese to announce plans to build a pair of follow - on, full - scale 250 mwe, inherently safe, power production reactors based on the same concept. ( see nuclear power in the people ' s republic of china for more information. ) experimental or conceptual designs some design concepts for nuclear reactors emphasize resistance to meltdown and operating safety. the pius ( process inherent ultimate safety ) designs, originally engineered by the swedes in the late 1970s and early 1980s, are lwrs that by virtue of their design are resistant to core damage. no units have ever been built. power reactors, including the deployable electrical energy reactor, a larger - scale mobile version of the triga for power generation in disaster areas and on military missions, and the triga power system, a small power plant and heat source for small and remote community use, have been put forward by interested engineers, and share the safety characteristics of the triga due to the uranium zirconium hydride fuel used. the hydrogen moderated self - regulating nuclear power module, a reactor that uses uranium hydride as a moderator and fuel, similar in chemistry and safety to the triga, also possesses these extreme safety and stability characteristics, and has attracted a good deal


the hydrogen moderated self - regulating nuclear power module, a reactor that uses uranium hydride as a moderator and fuel, similar in chemistry and safety to the triga, also possesses these extreme safety and stability characteristics, and has attracted a good deal of interest in recent times. the liquid fluoride thermal reactor is designed to naturally have its core in a molten state, as a eutectic mix of thorium and fluorine salts. as such, a molten core is reflective of the normal and safe state of operation of this reactor type. in the event the core overheats, a metal plug will melt, and the molten salt core will drain into tanks where it will cool in a non - critical configuration. since the core is liquid, and already melted, it cannot be damaged. advanced liquid metal reactors, such as the u. s. integral fast reactor and the russian bn - 350, bn - 600, and bn - 800, all have a coolant with very high heat capacity, sodium metal. as such, they can withstand a loss of cooling without scram and a loss of heat sink without scram, qualifying them as inherently safe. soviet union - designed reactors soviet designed rbmks, found only in russia and the cis and now shut down everywhere except russia, do not have containment buildings, are naturally unstable ( tending to dangerous power fluctuations ), and also have eccs systems that are considered grossly inadequate by western safety standards. the reactor from the chernobyl disaster was a rbmk reactor. rbmk eccs systems only have one division and have less than sufficient redundancy within that division. though the large core size of the rbmk makes it less energy - dense than the western lwr core, it makes it harder to cool. the rbmk is moderated by graphite. in the presence of both steam and oxygen, at high temperatures, graphite forms synthesis gas and with the water gas shift reaction the resultant hydrogen burns explosively. if oxygen contacts hot graphite, it will burn. the rbmk tends towards dangerous power fluctuations. control rods used to be tipped with graphite, a material that slows neutrons and thus speeds up the chain reaction. water is used as a coolant, but not a moderator. if the water boils away, cooling is lost, but moderation continues. this is termed a positive void coefficient of reactivity. control rods can become stuck if the reactor suddenly heats up and they are moving. xenon - 135


moderator. if the water boils away, cooling is lost, but moderation continues. this is termed a positive void coefficient of reactivity. control rods can become stuck if the reactor suddenly heats up and they are moving. xenon - 135, a neutron absorbent fission product, has a tendency to build up in the core and burn off unpredictably in the event of low power operation. this can lead to inaccurate neutronic and thermal power ratings. the rbmk does not have any containment above the core. the only substantial solid barrier above the fuel is the upper part of the core, called the upper biological shield, which is a piece of concrete interpenetrated with control rods and with access holes for refueling while online. other parts of the rbmk were shielded better than the core itself. rapid shutdown ( scram ) takes 10 to 15 seconds. western reactors take 1 - 2. 5 seconds. western aid has been given to provide certain real - time safety monitoring capacities to the human staff. whether this extends to automatic initiation of emergency cooling is not known. training has been provided in safety assessment from western sources, and russian reactors have evolved in result to the weaknesses that were in the rbmk. however, numerous rbmks still operate. it is safe to say that it might be possible to stop a loss - of - coolant event prior to core damage occurring, but that any core damage incidents will probably assure massive release of radioactive materials. further, dangerous power fluctuations are natural to the design. lithuania joined the eu recently, and upon acceding, it has been required to shut the two rbmks that it has at ignalina npp, as such reactors are totally incompatible with the nuclear safety standards of europe. it will be replacing them with some safer form of reactor. the mker is a modern russian - engineered channel type reactor that is a distant descendant of the rbmk. it approaches the concept from a different and superior direction, optimizing the benefits, and fixing the flaws of the original rbmk design. there are several unique features of the mker ' s design that make it a credible and interesting option : one unique benefit of the mker ' s design is that in the event of a challenge to cooling within the core - a pipe break of a channel, the channel can be isolated from the plenums supplying water, decreasing the potential for common - mode failures. the lower power density of the core greatly enhances thermal regulation. graphite moderation


within the core - a pipe break of a channel, the channel can be isolated from the plenums supplying water, decreasing the potential for common - mode failures. the lower power density of the core greatly enhances thermal regulation. graphite moderation enhances neutronic characteristics beyond light water ranges. the passive emergency cooling system provides a high level of protection by using natural phenomena to cool the core rather than depending on motor - driven pumps. the containment structure is modern and designed to withstand a very high level of punishment. refueling is accomplished while online, ensuring that outages are for maintenance only and are very few and far between. 97 - 99 % uptime is a definite possibility. lower enrichment fuels can be used, and high burnup can be achieved due to the moderator design. neutronics characteristics have been revamped to optimize for purely civilian fuel fertilization and recycling. due to the enhanced quality control of parts, advanced computer controls, comprehensive passive emergency core cooling system, and very strong containment structure, along with a negative void coefficient and a fast acting rapid shutdown system, the mker ' s safety can generally be regarded as being in the range of the western generation iii reactors, and the unique benefits of the design may enhance its competitiveness in countries considering full fuel - cycle options for nuclear development. the vver is a pressurized light water reactor that is far more stable and safe than the rbmk. this is because it uses light water as a moderator ( rather than graphite ), has well understood operating characteristics, and has a negative void coefficient of reactivity. in addition, some have been built with more than marginal containments, some have quality eccs systems, and some have been upgraded to international standards of control and instrumentation. present generations of vvers ( the vver - 1000 ) are built to western - equivalent levels of instrumentation, control, and containment systems. however, even with these positive developments, certain older vver models raise a high level of concern, especially the vver - 440 v230. the vver - 440 v230 has no containment building, but only has a structure capable of confining steam surrounding the rpv. this is a volume of thin steel, perhaps an inch or two in thickness, grossly insufficient by western standards. - has no eccs. can survive at most one 4 inch pipe break ( there are many pipes greater than 4 inches within the design ). - has six steam generator loops, adding unnecessary complexity. - however, apparently steam