LEAP Responds To White House: Pot More Popular Than Obama

http://www.tokeofthetown.com/2011/10/leap_responds_to_white_house_pot_more_popular_than.php

People v. Colvin Affirms That Dispensing Collective Members Are Not Required To Help Cultivate Their Medication

In a major victory for medical marijuana patients, the California Supreme Court denied review yesterday of an important dispensary case out of Los Angeles. Rejecting calls from State Attorney General Kamala Harris and law enforcement to review the Court of Appeal ruling in People v. Colvin, the California Supreme Court upheld certain protections for medical marijuana patients and providers. The Attorney General had argued that some undefined percentage of patients were legally required to participate in the operation of the medical marijuana dispensaries in order to obtain medication from them.

The landmark ruling in Colvin held that the Attorney General’s argument that member-patients must engage in unspecified “united action or participation” to qualify for protection under the state’s medical marijuana law would likely “limit drastically the size of medical marijuana establishments,” and provide “little direction or guidance to, among others, qualified patients, primary caregivers, law enforcement, and trial courts.” Furthermore, the Colvin Court held that the Attorney General’s requirement would “contravene the intent of [state law] by limiting patients’ access to medical marijuana.”

The Court of Appeal also held in People v. Colvin that, “collectives and cooperatives may cultivate and transport marijuana in aggregate amounts tied to its membership numbers.” In addition, the Colvin decision affirmed that possession of extracted or concentrated forms of medical marijuana was legal under state law.

“The decision not to review People v. Colvin should now put to rest this unfounded notion that patients must ’till the soil’ or somehow participate in the production of the medicine they purchase at a dispensary,” said Joe Elford, Chief Counsel with Americans for Safe Access (ASA), the country’s leading medical marijuana advocacy organization. “This landmark case also affirms the right of patients to purchase extracted or concentrated forms of medical marijuana and the right to transport medication from an off-site cultivate site.”

A number of medical marijuana dispensary cases were granted review by the California Supreme Court earlier this year, including Pack v. City of Long Beach, Riverside v. Inland Empire Patient’s Health and Wellness Center, and City of Lake Forest v. Evergreen Holistic Collective. The Pack case addresses issues of federal preemption, which have already come before the High Court, whereas the Riverside and Lake Forest cases address the issue of whether localities have a right to permanently ban dispensaries.

“The Colvin decision has far-reaching, positive implications for medical marijuana patients and providers,” continued Elford. ASA is currently appealing the conviction of Jovan Jackson, a San Diego dispensary operator who was tried in September 2010 and denied a medical marijuana defense. “The Colvin decision is bad news for the Attorney General, who was relying on the same argument in the Jackson case.” There are also other trial court cases that will invariably be affected by the Supreme Court’s decision not to review the Colvin case.

Further information:

Landmark Court of Appeal decision in People v. Colvin:http://AmericansForSafeAccess.org/downloads/People_v_Colvin.pdf

The method of loci (plural of Latin locus for place or location), also called the memory palace, is a mnemonic device introduced in ancient Roman rhetorical treatises (in the anonymous Rhetorica ad Herennium, Cicero's De Oratore, and Quintilian's Institutio oratoria). It relies on memorized spatial relationships to establish, order and recollect memorial content. The term is most often found in specialised works on psychology, neurobiology and memory, though it was used in the same general way at least as early as the first half of the nineteenth century in works on rhetoric, logic and philosophy.^[1]

The method of loci is also commonly called the mental walk. In basic terms, it is a method of memory enhancement which uses visualization to organize and recall information. Many memory contest champions claim to use this technique in order to recall faces, digits, and lists of words. These champions’ successes have little to do with brain structure or intelligence, but more to do with their technique of using regions of their brain that have to do with spatial learning. Those parts of the brain that contribute most significantly to this technique include the medial parietal cortex, retrosplenial cortex, and the right posterior hippocampus.

O'Keefe and Nadel refer to

'the method of loci', an imaginal technique known to the ancient Greeks and Romans and described by Yates (1966) in her book The Art of Memory as well as byLuria (1969). In this technique the subject memorizes the layout of some building, or the arrangement of shops on a street, or any geographical entity which is composed of a number of discrete loci. When desiring to remember a set of items the subject literally 'walks' through these loci and commits an item to each one by forming an image between the item and any distinguishing feature of that locus. Retrieval of items is achieved by 'walking' through the loci, allowing the latter to activate the desired items. The efficacy of this technique has been well established (Ross and Lawrence 1968, Crovitz 1969, 1971, Briggs, Hawkins and Crovitz 1970, Lea 1975), as is the minimal interference seen with its use.^[2]

[edit]Applicability of the term

The designation is not used with strict consistency. In some cases it refers broadly to what is otherwise known as the art of memory, the origins of which are related, according to tradition, in the story of Simonides of Ceos and the collapsing banquet hall.^[3] For example, after relating the story of how Simonides relied on remembered seating arrangements to call to mind the faces of recently deceased guests, Steven M. Kosslyn remarks "[t]his insight led to the development of a technique the Greeks called the method of loci, which is a systematic way of improving one's memory by using imagery."^[4] Skoyles and Sagan indicate that "an ancient technique of memorization called Method of Loci, by which memories are referenced directly onto spatial maps" originated with the story of Simonides.^[5] Referring to mnemonic methods, Verlee Williams mentions, "One such strategy is the 'loci' method, which was developed by Simonides, a Greek poet of the fifth and sixth centuries BC"^[6] Loftus cites the foundation story of Simonides (more or less taken from Frances Yates) and describes some of the most basic aspects of the use of space in the art of memory. She states, "This particular mnemonic technique has come to be called the "method of loci".^[7] While place or position certainly figured prominently in ancient mnemonic techniques, no designation equivalent to "method of loci" was used exclusively to refer to mnemonic schemes relying upon space for organization.^[8]

In other cases the designation is generally consistent, but more specific: "The Method of Loci is a Mnemonic Device involving the creation of a Visual Map of one's house."^[9]

This term can be misleading: the ancient principles and techniques of the art of memory, hastily glossed in some of the works cited above, depended equally upon images andplaces. The designator "method of loci" does not convey the equal weight placed on both elements. Training in the art or arts of memory as a whole, as attested in classical antiquity, was far more inclusive and comprehensive in the treatment of this subject.

[edit]Spatial mnemonics and the hippocampus

In a classic study in cognitive neuroscience O'Keefe and Nadel proposed "that the hippocampus is the core of a neural memory system providing an objective spatial framework within which the items and events of an organism's experience are located and interrelated."^[10] This theory has generated considerable debate and further experiment. It has been noted that "[t]he hippocampus underpins our ability to navigate, to form and recollect memories, and to imagine future experiences. How activity across millions of hippocampalneurons supports these functions is a fundamental question in neuroscience, wherein the size, sparseness, and organization of the hippocampal neural code are debated."^[11]

"Using neuropsychological, structural, and functional brain imaging measures, we found that superior memory is not driven by exceptional intellectual ability or structural brain differences. Rather, we found that superior memorizers used a spatial learning strategy (the method of loci; Yates, 1966) while preferentially engaging brain regions critical for memory and for spatial memory in particular, including the hippocampus."^[12]

The "method of loci," as first described by Simonides (cf. Yates, 1966), is explicitly spatial. In this technique, subjects improve memory by putting to-be-remembered items into some place or spatial context. Retrieval is effected simply by "going" to that place in thought [...] Events occurring within separate contexts are efficiently recalled in those contexts and minimally confused between contexts, though the events themselves might be highly similar. The mental maps we have of our home town, our neighborhood, and our house are all examples of the kinds of spatial contexts within which events occur, can be coded internally, and can subsequently be effectively retrieved or recalled: Studies by Smith, Glenberg, and Bjork (1978) and Bellezza and Reddy (1978) indicate that the power of the method of loci might lie in its ability to take advantage of this natural state of affairs.^[13]

[edit]Parietal cortex and retrosplenial cortex contributions to spatial mnemonics

The medial parietal cortex is most associated with encoding and retrieving of information. Patients who suffered from medial parietal cortex damage had troubles linking landmarks with certain locations. Many of these patients were unable to give or follow directions and often got lost.

The retrosplenial cortex is also greatly linked to memory and navigation. In Pothuzien HH’s study on the effects of selective granular retrosplenial cortex lesions in rats, the researcher found that damage to the retrosplenial cortex lead to impaired spatial learning abilities. Rats with damage to this area failed to recall which areas of the maze they had already visited, rarely explored different arms of the maze, almost never recalled the maze in future trials, and took longer to reach the end of the maze, as compared to rats with a fully working retrosplenial cortex.

The mental walk originated from the idea that you can best remember things that you are familiar with. Therefore, by associating a certain object with a familiar landmark, you increase your chances of remembering that object. Since the mental walk revolves around the idea of visualizing a familiar place and associating certain ideas or items with landmarks within that familiar place, the medial parietal cortex plays a huge role in this technique. Without the ability to mentally “walk” through a familiar route, this method cannot work.

[edit]Contemporary usage

All top memorisers today use the 'method of loci' to a greater or lesser degree. Contemporary memory competition was initiated in 1991^[14] and introduced to the USA in 1997. Part of the competition requires committing to memory and recalling a sequence of digits, two-digit numbers, alphabetic letters, or playing cards. In a simple method of doing this, contestants, using various strategies well before competing, commit to long-term memory a unique vivid image associated with each item. They have also committed to long-term memory a familiar route with firmly established stop-points or loci. Then in the competition they need only deposit the image that they have associated with each item at the loci. To recall, they retrace the route, "stop" at each locus, and "observe" the image. They then translate this back to the associated item. Memory champions elaborate on this by combining images. Eight-time World Memory Champion Dominic O'Brien^[15] advocates this technique. His name for it is The Journey Method. The 2006 World Memory Champion, Clemens Mayer from Germany, used a 300-point-long journey through his house for his world record in "number half marathon", memorising 1040 random digits in a half hour. One individual has used the method of loci to memorise pi to 65,536 digits.^[16]

Using this technique a person with ordinary memorization capabilities, after establishing the route stop-points and committing the associated images to long-term memory, with less than an hour of practice, can remember the sequence of a shuffled deck of cards. The world record for this is held by Simon Reinhard at 21.19 seconds^[17]

The technique is taught as a metacognitive technique in learning to learn courses. It is generally applied to encoding the key ideas of a subject. Two approaches are:

1. Link the key ideas of a subject and then deep-learn those key ideas in relation to each other, and;
2. Think through the key ideas of a subject in depth, re-arrange the ideas in relation to an argument, then link the ideas to loci in good order.

It has been found that teaching such techniques as pure memorization methods often leads students towards surface learning only. Therefore, it has been recommended that the method of loci should be integrated thoroughly with deeper learning approaches.

Mark Sadler, author of “The Secret of Rapid Learning” (2007) believes references to “deeper learning approaches” are without clear meaning, therefore unscientific, and probably a reflection of continuing opposition to efficient and deliberate learning.

This opposition should be put in historical and present context. In a paper in the American Journal of Psychology (1957) Irvin Rock challenged the then view that learning resulted from the gradual strengthening of memory traces by means of “repetition”. He claimed, as a result of his experiments, that “associations are formed in one trial, and improvement with repetition is only an artefact of work with long lists of items” (in other words, instead of there being a gradual strengthening of all connections, with inefficient methods, some items are connected at a first run through, more at a second, and so on).

Readers of psychology journals of that time will know that Rock’s paper led to furious debate for some years. In some universities experiments with memory drums and nonsense syllables continued, the aim being to measure “the number of repetitions required for learning”.

At the University of Canterbury, Christchurch, New Zealand, in 1956, Mark Sadler, then a young graduate, did experiments on one-trial learning with 32 student volunteers using, not nonsense syllables, but non-abstract nouns, one written on each “learning card”. Before the experiment, one psychology lecturer, Mr R. L. Reid said “You might be able to do one-trial learning, but nobody else can”.

In fact, Sadler’s experiments showed that, without any pre-learning of “places” or “loci”, and by the use of imagined placings in real or imagined places, most people can master one-trial leaning in less than an hour. Few do it correctly at the first attempt, but most can be guided to alter mistaken approaches and to discover for themselves the mental trick of it.

These experiments whereby a new graduate challenged the beliefs of established lecturers aroused, not approval, but hostility and a reluctance to publish any account of the experiments. Students using the one-trial method learned more than twice as fast as those using other methods, and a statistical calculation indicated that the likelihood that the results were due to chance was less than one in a thousand. Nevertheless, one lecturer, Dr Harry Scott said, “I would rather believe in that one chance in a thousand than believe there is anything in your ideas or experiments”.

In 2011, Sadler again attempted to get his 1956 paper on his experiments published since, for instance, the New Zealand Education Department continues to refer to deliberate learning as “rote” or repetition learning. Dr John Fitzgerald, editor of the New Zealand Journal of Psychology, rejected this fresh attempt at publication, saying he “does not see how subjective experiment conducted more than 50 years ago will advance our understanding”.

How can objective and large differences in learning times, between those using one-trial learning and those using other methods, such as “making up stories”, or just trying to remember in various ways, be dismissed as “subjective”?

In contrast to the approach of the New Zealand Education Department, which opposes deliberate learning, Sadler believes there are advantages in students remembering as much as possible. Commenting on this in rejecting publication of the 1956 paper, Dr Fitzgerald commented (4 August 2011): “Our socio-cultural and educational environments have changed so dramatically during the intervening years that the experiments have little social-education relevance”.

In other words, challenges to the current disapproval of deliberate learning should not be published.

Back in 1956, one psychology lecturer said of the one-trial learning method: “This is based on visual images”, Sadler replied: “It is not based on visual images. To prove it, I will teach the method to a person blind from birth!” This, with the cooperation of the local Institute for the Blind, he succeeded in doing.

This experiment seems to indicate that the learning method is based on the mind’s ability to remember spatial journeys and learned shapes of objects rather than on visual images.

The method should be attempted with the aid of learning cards – one noun to a card – until the ability to rapidly achieve 100% recall after going through the pack of cards once has been mastered. (Although one goes through the cards just once, each connection requires the learner to do two things. Doing this consistently requires sustained attention and concentration. The need for the “two things” explains why, as Sadler says in the Introduction to his book, “The secret of convenient and efficient learning is hidden within the Ancient Greek ‘method of loci’, rather than revealed by it”.)

Once the basic method has been mastered with the aid of nouns on cards, the method can then be applied to learning poetry or prose passages with some reduction in accuracy. In December 1955, prior to the 1956 experiment with student volunteers, Sadler learned a 1,000 word passage (never previously read) in 51 minutes 33 seconds. The whole 1,000 words was then recited from memory in 11 min 42 seconds. Overall accuracy was 96%, counting synonyms as errors, or 99% neglecting synonyms. (By comparison, Lyons, described by Robert S. Woodworth as “a very skilled and practised learner”, gives his time to learn 1,000 words as 2 hours 43 minutes).

To achieve such accuracy, even with rather abstract material, 1,000 words is roughly divided into lots of about 100 words. One then learns 100 words going through them slowly once, recites from memory, learns the next 100 words, recites, and so on. Finally, one recites the whole 1,000 words. One may learn things for personal interest or enjoyment, eg jokes or poems, or to pass exams, eg chemistry notes, or the vocabulary of a foreign language. Note that among the 1956 student volunteers, two, a young man and a young woman, proved to be able to learn considerably faster than Sadler. This shows that the above learning time was based on the method, and not on any exceptional personal ability.

Of the method, one student protested, “But, by this method of learning there are no associations!”. To this the reply was: “By this method of learning there don’t have to be any associations. Just do it!!”. This contrasts with the learning instruction given by Ed Cook to Joshua Foer (“Moonwalking with Einstein”, p.99): “The more associative hooks a new piece of information has, the more securely it gets embedded into the network of things you already know. It is important to deeply process that image”.

Like other writers of books on mnemonics, eg “The Memory Book”, by Harry Lorayne and Jerry Lucas, Joshua talks of “elaborate, engaging, vivid images”. To connect “pickled garlic” to “cottage cheese” one is supposed to imagine the smell of pickled garlic and thus create “a complete multisensorial picture of picked garlic”. This is followed by “I want you to close your eyes and see an enormous wading pool size tub of cottage cheese”. For some unclear purpose one is then asked to “imagine Claudia Schiffer swimming in this tub of cottage cheese”. On page 100, Ad Herennium is quoted as saying of images “the funnier, lewder, and more bizarre, the better”.

In comparison with the simple quick method advocated in Sadler’s book, all this is extraordinary. Perhaps imagining a woman swimming in cottage cheese helps in long-term retention, but the alternative view is that a scientific approach to preventing forgetting by spaced recalls is more generally effective. Indeed, most books on mnemonics advocate time wasting elaborations because of an imperfect understanding of one-trial spatial learning. In the pursuit of coherent simplicity, even Sadler’s book is deficient, perhaps, in not stressing the need to quickly imagine the shapes of objects being linked together.

A recent variation of the "method of loci" involves creating imaginary locations (houses, palaces, roads and cities) to which the same procedure is applied. It is accepted that there is a greater cost involved in the initial setup, but thereafter the performance is in line with the standard loci method. The purported advantage is to create towns and cities that each represent a topic or an area of study, thus offering an efficient filing of the information and an easy path for the regular review necessary for long term memory storage.^[18]

Something that is likely a reference to the "method of loci" techniques survives to this day in the common English phrases "in the first place", "in the second place", and so forth.^[19]

[edit]In popular culture

In popular culture, the technique is employed by the fictional serial killer Dr. Hannibal Lecter in Hannibal (1999) the third of a series of novels by American author Thomas Harris. In several passages in the book, Dr. Lecter is described as mentally walking through an elaborate memory palace to remember facts.^[20]

In the 1981 fantasy classic Little, Big by John Crowley, an advisor-mage Ariel Hawksquill uses the method to link obscure information to aid her clients, and notes that:

"...the greatest practitioners of the old art discovered some odd things about their memory houses the longer they lived in them ... it was discovered, for instance, that the symbolic figures with vivid expressions, once installed in their proper places, are subject to subtle change as they stand waiting to be called forth... also, as the memory house grows, it makes conjunctions and vistas that its builder can't conceive of beforehand..."

The technique was depicted in the BBC series 'Sherlock' in "The Hounds of Baskerville", where Holmes uses his "mind palace" to seek important facts and associations in his memory relevant to the case.^{[citation needed]}

The memory palace concept is also used in several episodes of the TV series The Mentalist by the titular mentalist Patrick Jane to help collegues and witnesses remember things such as playing card locations in a deck or information and names of guests at a party.

[edit]Example of usage of the method of loci/mental walk

During the mental walk, people remember lists of words by mentally walking a familiar route and associating these objects with specific landmarks on their route. An example of this would be to remember your grocery shopping list in a mental walk from your bedroom to kitchen in your house. Let's say the first item on your list was bread; then mentally you can place a loaf of bread on your bed. As you continue mentally walking you can place the next item, assume it is eggs, on your dresser. The mental walk continues like this as you place consecutive items along a familiar route that you walk. So when you are at the grocery store, you can then think about this walk and “see” what you placed at each location. In your head you will remember bread being on your bed, and eggs being on the dresser. This can continue for as many items as you want to place on your path as long as the route continues. The more dramatic the images, the more vivid the memory. For instance: instead of "bread", try to visualize a giant loaf of bread; instead of "eggs", imagine broken eggs all over the place.^{[original research?]}

[edit]See also

• Art of memory

[edit]Notes

[edit]References

• Yates, Frances A. (1966). The Art of Memory. Chicago: University of Chicago Press. ISBN [[Special:BookSources/10226950018|10226950018]].
• Spence, Jonathan D. (1984). The Memory Palace of Matteo Ricci. New York: Viking Penguin. ISBN 0-14-008098-8.
• Carruthers, Mary (1990). The Book of Memory. Cambridge University Press.
• Carruthers, Mary (1998). The Craft of Thought. Cambridge University Press.
• Rossi, Paolo (2000). Logic and the Art of Memory. University of Chicago Press.
• Bolzoni, Lina (2001). The Gallery of Memory. University of Toronto Press.
• Bolzoni, Lina (2004). The Web of Images. Ashgate Publishers.
• Dudai, Yadin (2002). Memory from A to Z. Oxford University Press.
• Small, Jocelyn P. (1997). Wax Tablets of the Mind. London: Routledge.
• Carruthers, Mary; Ziolkowski, Jan (2002). The Medieval Craft of Memory: An anthology of texts and pictures. University of Pennsylvania Press.

• Dann, Jack (1995) The Memory Cathedral: A Secret History of Leonardo da Vinci: Bantam Books

Screenshot from the original demo video on youtube

Hooper Selection is a method of cursor movement and text selection for tablet devices, designed with the goal of making text editing more efficient. It consists of a set of gestures the user can make over the system keyboard to adjust the cursor or selection position. Its convenience stems from the fact that it allows the user to navigate around the text without having to move their hands away from the keyboard area or incur tap-and-hold delays when beginning a cursor drag action.

The idea was originally conceived by Georgia Tech student Daniel Hooper, and presented in a short video demo. The demo received widespread attention from the tech media, with responses generally being enthusiastic. A number of developers have since announced implementations of the concept in either their own apps, or system extensions that can be used on jailbroken devices (see Implementations).

In the original video posting, Hooper suggested that users who wanted the mechanism implemented in iOS should petition Apple by submitting feature requests through the company's bug reporting website. The directions were removed once viewers began reporting their request was classified as a "Known issue". To date, Apple has yet to comment on the suggestion.

[edit]Operation

Cursor movement: To move the cursor, the user simply drags their finger across the keyboard in any direction. A one-finger drag moves the cursor slowly, and a two-finger drag moves the cursor faster, placing cursor at word boundaries.

Text selection: To select text, the user holds down the shift key while dragging across the keyboard in the same manner as above. As with cursor movement, the dragging speed depends on whether one or two fingers are used.

[edit]Reception

The video received an enthusiastic response, receiving coverage on many tech news sites including Cult of Mac ^[1] iDownloadBlog,^[2] Forbes,^[3] TechCrunch,^[4] Macrumors,^[5]Gizmodo,^[6] Daring Fireball,^[7] IT World,^[8] Engadget,^[9] The Verge,^[10] and Business Insider.^[11]

[edit]Implementations

Developers of the following applications and Jailbreak extensions have announced their own implementations of the concept:

• Codea ^[12]
• SlideWriter ^[13]
• SwipeSelection ^[14]
• Genesis ^[15]
• UX Write ^[16]
• Scribbie ^[17]

The following libraries implement the idea in a fashion that can be reused in other applications:

• SelectWithSwipes ^[18]
• SlideSelection ^[19]

[edit]References

Comments

Component ofStirling radioisotope generator is heated by induction during testing

Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, where eddy currents (also called Foucault currents) are generated within the metal and resistance leads to Joule heating of the metal. An induction heater (for any process) consists of an electromagnet, through which a high-frequency alternating current (AC) is passed. Heat may also be generated by magnetic hysteresis losses in materials that have significant relative permeability. The frequency of AC used depends on the object size, material type, coupling (between the work coil and the object to be heated) and the penetration depth.

[edit]Applications

Induction heating of 25 mm metal bar using 15 kW at 450 kHz.

Induction heating allows the targeted heating of an applicable item for applications including surface hardening, melting,brazing and soldering and heating to fit. Iron and its alloys respond best to induction heating, due to their ferromagneticnature. Eddy currents can, however, be generated in any conductor, and magnetic hysteresis can occur in any magnetic material. Induction heating has been used to heat liquid conductors (such as molten metals) and also gaseous conductors (such as a gas plasma - see Induction plasma technology). Induction heating is often used to heat graphite crucibles (containing other materials) and is used extensively in the semiconductor industry for the heating of silicon and other semiconductors. Supply frequency (mains, 50/60 Hz) induction heating is used for many lower cost industrial applications as inverters are not required.

[edit]Induction furnace

An induction furnace uses induction to heat metal to its melting point. Once molten, the high-frequency magnetic field can also be used to stir the hot metal, which is useful in ensuring that alloying additions are fully mixed into the melt. Most induction furnaces consist of a tube of water-cooled copper rings surrounding a container of refractory material. Induction furnaces are used in most modern foundries as a cleaner method of melting metals than a reverberatory furnace or a cupola. Sizes range from a kilogram of capacity to a hundred tonnes capacity. Induction furnaces often emit a high-pitched whine or hum when they are running, depending on their operating frequency. Metals melted includeiron and steel, copper, aluminium, and precious metals. Because it is a clean and non-contact process it can be used in a vacuum or inert atmosphere. Vacuum furnaces make use of induction heating for the production of specialty steels and other alloys that would oxidize if heated in the presence of air.

[edit]Induction welding

A similar, smaller-scale process is used for induction welding. Plastics may also be welded by induction, if they are either doped with ferromagnetic ceramics (where magnetic hysteresis of the particles provides the heat required) or by metallic particles.

Seams of tubes can be welded this way. Currents induced in a tube run along the open seam and heat the edges resulting in a temperature high enough for welding. At this point the seam edges are forced together and the seam is welded. The RF current can also be conveyed to the tube by brushes, but the result is still the same — the current flows along the open seam, heating it.

[edit]Induction cooking

In induction cooking, an induction coil in the cook-top heats the iron base of cookware. Copper-bottomed pans, aluminium pans and other non-ferrous pans are generally unsuitable. The heat induced in the base is transferred to the food via (metal surface) conduction. Benefits of induction cookers include efficiency, safety (the induction cook-top is not heated itself) and speed. Both permanently installed and portable induction cookers are available.

[edit]Induction brazing

Induction brazing is often used in higher production runs. It produces uniform results and is very repeatable.

[edit]Induction sealing

Induction heating is used in cap sealing of containers in the food and pharmaceutical industries. A layer of aluminum foil is placed over the bottle or jar opening and heating by induction to fuse it to the container. This provides a tamper-resistant seal, since altering the contents requires breaking the foil. ^[1]

[edit]Heating to fit

Induction heating is often used to heat an item causing it to expand prior to fitting or assembly. Bearings are routinely heated in this way using mains frequency (50/60 Hz) and a laminated steel transformer type core passing through the centre of the bearing.

[edit]Heat treatment

Induction heating is often used in the heat treatment of metal items. The most common applications are induction hardening of steel parts, induction soldering/brazing as a means of joining metal components and induction annealing to selectively soften a selected area of a steel part.

Induction heating can produce high power densities which allow short interaction times to reach the required temperature. This gives tight control of the heating pattern with the pattern following the applied magnetic field quite closely and allows reduced thermal distortion and damage.

This ability can be used in hardening to produce parts with varying properties. The most common hardening process is to produce a localised surface hardening of an area that needs wear-resistance, while retaining the toughness of the original structure as needed elsewhere. The depth of induction hardened patterns can be controlled through choice of induction-frequency, power-density and interaction time.

Limits to the flexibility of the process arise from the need to produce dedicated inductors for many applications. This is quite expensive and requires the marshalling of high current densities in small copper inductors, which can require specialized engineering and 'copper-fitting'.

[edit]Plastic processing

Induction heating is used in the industrial applications of plastic process with injection and extrusion machines. The induction heating improves energy efficiency for injection and extrusion plastic processes.^{[citation needed]}

1. The heating is directly generated in the cylindrical barrel reducing heat transfer delays that resistive heating elements have, resulting in:
   • faster machine start up
   • the induction coil is powered within 1/4 the time of resistive heating elements hence reducing energy consumption
   • to replace a heater band element with an induction heating system 40% lower current inverter is used, thereby reducing maximum consumption capacity; even after the reduction in power capacity, the heating capacity is increased by 50%
   • The increased heating capacity further reduces starting up time by 50%
2. The barrel melting the plastic material is insulated with 15 mm ceramic insulation and in that way
   • heat is not escaping to the environment and we have significant energy saving
   • the induction coils are not getting heated up from the heat generated in the barrel so they operate in low temperature resulting in long life expectancy when ornery heater band elements if insulation is used there life expectancy is reduced dramatically
3. The frequencies used start from 30 kHz and are reduced to 5 kHz as the barrel thickness increases
4. The distance of the coil from the barrel surface is reduced as the diameter of the barrel increase

The technology cost of applying to industrial equipment as injection and extrusion machines is reduced as time goes on and inverter technology is advances

[edit]Details

The basic setup is an AC power supply that provides electricity with low voltage but very high current and high frequency. The workpiece to heat is placed inside an air coil driven by the power supply, usually in combination with a resonant tank capacitor to increase the reactive power. The alternating magnetic field induces eddy currents in the workpiece.

Magnetic materials improve the induction heat process because of hysteresis. Materials with high permeability (100–500) are easier to heat with induction heating. Hysteresis heating occurs below the Curie temperature where materials lose their magnetic properties. High permeability below the Curie temperature in the workpiece is useful. Temperature difference, mass, and specific heat influence the workpiece heating.

The energy transfer of induction heating is affected by the distance between the coil and the workpiece. Energy losses occur through heat conduction from workpiece to fixture,natural convection, and thermal radiation.

The induction coil is usually made of copper tubing and fluid cooled. Diameter, shape, and number of turns influence the efficiency and field pattern.

[edit]Core type furnace

The furnace consists of a circular hearth which contains the charge to be melted in the form of angular ring. The metal ring is large in diameter and is magnetically interlinked with an electrical winding energized by an AC source.

[edit]References

1. ^ Valery Rudnev Handbook of Induction HeatingCRC Press, 2003 ISBN 0824708482 page 92

• Brown, George Harold, Cyril N. Hoyler, and Rudolph A. Bierwirth, Theory and application of radio-frequency heating. New York, D. Van Nostrand Company, Inc., 1947. LCCN 47003544
• Hartshorn, Leslie, Radio-frequency heating. London, G. Allen & Unwin, 1949. LCCN 50002705
• Langton, L. L., Radio-frequency heating equipment, with particular reference to the theory and design of self-excited power oscillators. London, Pitman, 1949. LCCN 50001900
• Shields, John Potter, Abc's of radio-frequency heating. 1st ed., Indianapolis, H. W. Sams, 1969. LCCN 76098943
• Sovie, Ronald J., and George R. Seikel, Radio-frequency induction heating of low-pressure plasmas. Washington, D.C. : National Aeronautics and Space Administration ; Springfield, Va.: Clearinghouse for Federal Scientific and Technical Information, October 1967. NASA technical note. D-4206; Prepared at Lewis Research Center.

[edit]External links

• Induction heating at the Open Directory Project