Coming: Better Solar Cells

‘Magic’ Alloy Could Spur Next
Generation of Solar Cells

ANN ARBOR—June 15, 2017 -- In what could be a major step forward for a new generation of solar cells called "concentrator photovoltaics," University of Michigan researchers have developed a new semiconductor alloy that can capture the near-infrared light located on the leading edge of the visible light spectrum.

Easier to manufacture and at least 25 percent less costly than previous formulations, it's believed to be the world's most cost-effective material that can capture near-infrared light—and is compatible with the gallium arsenide semiconductors often used in concentrator photovoltaics.

Concentrator photovoltaics gather and focus sunlight onto small, high-efficiency solar cells made of gallium arsenide or germanium semiconductors. They're on track to achieve efficiency rates of over 50 percent, while conventional flat-panel silicon solar cells top out in the mid-20s.

"Flat-panel silicon is basically maxed out in terms of efficiency," said Rachel Goldman, U-M professor of materials science and engineering, and physics, whose lab developed the alloy. "The cost of silicon isn't going down and efficiency isn't going up. Concentrator photovoltaics could power the next generation."

Varieties of concentrator photovoltaics exist today. They are made of three different semiconductor alloys layered together. Sprayed onto a semiconductor wafer in a process called molecular-beam epitaxy—a bit like spray painting with individual elements—each layer is only a few microns thick. The layers capture different parts of the solar spectrum; light that gets through one layer is captured by the next.

But near-infrared light slips through these cells unharnessed. For years, researchers have been working toward an elusive "fourth layer" alloy that could be sandwiched into cells to capture this light. It's a tall order; the alloy must be cost-effective, stable, durable and sensitive to infrared light, with an atomic structure that matches the other three layers in the solar cell.

Getting all those variables right isn't easy, and until now, researchers have been stuck with prohibitively expensive formulas that use five elements or more.

To find a simpler mix, Goldman's team devised a novel approach for keeping tabs on the many variables in the process. They combined on-the-ground measurement methods including X-ray diffraction done at U-M and ion beam analysis done at Los Alamos National Laboratory with custom-built computer modeling.

Using this method, they discovered that a slightly different type of arsenic molecule would pair more effectively with the bismuth. They were able to tweak the amount of nitrogen and bismuth in the mix, enabling them to eliminate an additional manufacturing step that previous formulas required. And they found precisely the right temperature that would enable the elements to mix smoothly and stick to the substrate securely.

"'Magic' is not a word we use often as materials scientists," Goldman said. "But that's what it felt like when we finally got it right."

The advance comes on the heels of another innovation from Goldman's lab that simplifies the "doping" process used to tweak the electrical properties of the chemical layers in gallium arsenide semiconductors. During doping, manufacturers apply a mix of chemicals called "designer impurities" to change how semiconductors conduct electricity and give them positive and negative polarity similar to the electrodes of a battery. The doping agents usually used for gallium arsenide semiconductors are silicon on the negative side and beryllium on the positive side.

The beryllium is a problem—it's toxic and it costs about 10 times more than silicon dopants. Beryllium is also sensitive to heat, which limits flexibility during the manufacturing process. But the U-M team discovered that by reducing the amount of arsenic below levels that were previously considered acceptable, they can "flip" the polarity of silicon dopants, enabling them to use the cheaper, safer element for both the
positive and negative sides.

"Being able to change the polarity of the carrier is kind of like atomic 'ambidexterity,'" said Richard Field, a former U-M doctoral student who worked on the project. "Just like people with naturally born ambidexterity, it's fairly uncommon to find atomic impurities with this ability."

Together, the improved doping process and the new alloy could make the semiconductors used in concentrator photovoltaics as much as 30 percent cheaper to produce, a big step toward making the high-efficiency cells practical for large-scale electricity generation.

"Essentially, this enables us to make these semiconductors with fewer atomic spray cans, and each can is significantly less expensive," Goldman said. "In the manufacturing world, that kind of simplification is very significant. These new alloys and dopants are also more stable, which gives makers more flexibility as the semiconductors move through the manufacturing process."

The new alloy is detailed in a paper titled "Bi-enhanced N incorporation in GaAsNBi alloys," published June 15 in Applied Physics Letters. The research is supported by the National Science Foundation and the U.S. Department of Energy Office of Science Graduate Student Research.

The doping advances are detailed in a paper titled "Influence of surface reconstruction on dopant incorporation and transport properties of GaAs(Bi) alloys." It was published in the Dec. 26, 2016, issue of Applied Physics Letters. The research was supported by the National Science Foundation.

http://www.ns.umich.edu/new/releases/24903-magic-alloy-could-spur-next-generation-of-solar-cells

Grenfell Tower Fire

The Grenfell Tower fire occurred on 14 June 2017, at the 24-storey Grenfell Tower, a block of public housing flats in the upmarket area of North Kensington, western London, England. The fire started shortly before 1 a.m. local time.

                                   The fire at 4:43am local time

Hundreds of firefighters and 45 fire engines were involved in efforts to control the fire. Firefighters were trying to control pockets of fire on the higher floors after most of the rest of the building had been gutted. Residents of surrounding buildings were evacuated out of concerns that the tower could collapse, though the building was later determined to still be structurally sound.

There could have been up to 600 people in the 120 one- and two-bedroom flats of the block at the time of the fire. By the afternoon of 14 June, twelve had been confirmed dead, with more fatalities expected to be reported; police spoke of "around 200 residents and a lot unaccounted for". Sixty-five were rescued by firefighters. Seventy-four people were confirmed to be in five hospitals across London, twenty of whom were in a critical condition. Ongoing fires on the upper floors and fears of structural collapse hindered the search and recovery effort.

The cause of the fire is not yet known. Mayor of London Sadiq Khan said there were "questions that have to be answered" about the fire safety conditions at the Grenfell Tower. Khan criticised the safety instructions telling people to stay in their flats in particular: "We can't have people's lives being put at risk because of bad advice or lack of maintenance." The residents' organisation, Grenfell Action Group, had repeatedly warned of major fire safety lapses since 2013. The group warned in November 2016 that only a "catastrophic" fire would finally force the block's management to treat fire precautions and maintenance of fire-related systems to a proper standard

Description of the Fire

Fire broke out in the 24-storey Grenfell Tower block of flats on the Lancaster West Estate in North Kensington, western London early in the morning of 14 June 2017; the London Fire Brigade were first called to the fire at 00:54 BST (UTC+1). The fire reportedly began on the second floor but spread at a "terrifying rate" upward and to the other side of the building. A team of 250 firefighters from forty fire engines attempted to control the blaze and rescue people, the first responders arriving six minutes after the alarm, but the fire's extreme temperature hindered rescue attempts. At 04:14, officials from the Metropolitan Police addressed the large crowd of onlookers and urgently instructed them to contact anyone they knew who was trapped in the building—if they are able to reach them via phone or social media—to tell them they must try to self-evacuate and not wait for the fire brigade. Firefighters entered the building to try to rescue people but reported they were hindered by the extreme heat.

According to witnesses, there were people trapped inside, waving from windows for help, some holding children. There were two witness accounts of parents dropping their children down to people below, including a baby who was caught after being thrown from the ninth or tenth floor, and a small boy thrown from the fifth or sixth floor. There were also eyewitness reports that some people were jumping out. At least one person used knotted blankets to make a rope and escape from the burning building. Frequent explosions that were reported to be from gas lines in the building were heard.

After three hours, the original crew of firefighters were replaced by a new crew. By sunrise, the firefighters were still battling the fire and trying to spray areas where people were seen trapped. The watching crowd were pushed back from the building because of falling debris. At 05:00, the building was still burning and severely damaged. Assistant fire commissioner Dan Daly said, "Firefighters wearing breathing apparatus are working extremely hard in very difficult conditions to tackle this fire. This is a large and very serious incident and we have deployed numerous resources and specialist appliances."

The fire continued to burn on the tower's upper floors into the afternoon of 14 June. Firefighters were expecting to continue tackling the blaze for at least a further 24 hours. Although fears were expressed that the building could collapse, structural engineers determined that it was not in danger and that rescue teams could enter it to search for survivors and casualties.

Cause of the Fire

The cause of the fire has not yet been determined. Several media outlets reported that it may have been caused by a faulty appliance. A fourth-floor resident told the media that it was his neighbour's refrigerator that caught fire around 1:00 am, and that they immediately began knocking on doors to alert people. He said that within half an hour the building was entirely engulfed in flames.

While there was much criticism of the lack of sprinkler systems, Geoff Wilkinson, the building regulations columnist for the Architects' Journal, wrote in a comment on 14 June, before the cause was known ("we should avoid speculating"), that if a leaking gas riser or the cladding were at fault, sprinklers would have had little effect. He said he had seen extracts of a fire risk assessment and talk of combustible material stored in the common walkways, suggesting poor overall management.

Criticism of the Building and of Management

Some residents said no fire alarms went off when the fire started. Residents said they were alerted to the fire only by people screaming for help or knocks on the door and not by a fire alarm. Others reported that they survived by ignoring the council's "stay put" policy, its directive instructing residents to remain in their flat in case of fire.

The London-wide Radical Housing Network, a citizens' action "group of groups... fighting for housing justice across London" of which the Grenfell Action Group is a member, said that the fire was "a horrific, preventable tragedy" that was the result of a "combination of government cuts, local authority mismanagement, and sheer contempt for council tenants and the homes they live in".

https://en.wikipedia.org/wiki/Grenfell_Tower_fire

Powerful Oceanic Lightning

Florida Tech Study Confirms Lightning More Powerful Over Ocean Than Land

Findings Could Help Guide Improved
Development of Ships, Off-Shore Structures        

MELBOURNE, FLA. — June 9, 2017 -- People who live and work along Florida’s coasts – and coastlines everywhere – may be more likely to experience a super-charged lightning strike, according to new research from Florida Institute of Technology that shows lightning can be much more powerful over the ocean than land.

Florida Tech’s Amitabh Nag, assistant professor of physics and space sciences, and Kenneth L. Cummins, research professor at Florida Tech and the University of Arizona, recently published, “Negative First Stroke Leader Characteristics in Cloud to-Ground Lightning Over Land and Ocean” in the American Geophysical Union’s Geophysical Letters.  The scientists analyzed lightning over parts of Florida and its coasts using data provided by the U.S. National Lightning Detection Network.

Some previous indirect observations led scientists and others to believe that strikes over sea water tend to be more powerful, but the Nag and Cummins study represents the first time that an independent measurement has validated those beliefs.

Lightning scientists break down every cloud-to-ground strike into sub-processes to get a better understanding of the way it formed. Plenty of physics is packed into fractions of a second from when charged particles in thunderclouds form into downward channels of electricity that “attach” to electrical, charge-carrying channels rising from land or water to form that familiar zigzag bolt.

In their study, which measured peak currents of various cloud-to-ground lightning strikes over land and ocean from 2013 to 2015, Nag and Cummins calculated the duration of the “negative stepped leader” – the electrical channel that moves down toward ground from a thundercloud. When this leader touches ground a surge of current, typically with a peak value of around 30 kilo amperes, flows upward to the cloud. The durations of negative stepped leaders over the ocean were significantly shorter than those over land, which indicates that they carry more charge in them. This leads to a higher following current surge from ground.

Nag and Cummins found that with strikes over water in western Florida, the median stepped-leader duration was 17 percent shorter over ocean than over land, and in eastern Florida the median durations were 21 and 39 percent shorter over two oceanic regions than over land. Using a relationship between leader duration and lightning peak current derived in this study, the authors estimate that lightning with peak currents over 50 kilo amperes is twice as likely to occur in oceanic thunderstorms.

These findings suggest that people living on or near the ocean may be at greater risk for lightning damage if storms develop over oceans and move on-shore. This new understanding of the nature of lightning could inform how off-shore infrastructure and vessels are to be built to minimize the risk of super-powerful lightning bolts from thunderstorms formed over the sea.

https://newsroom.fit.edu/2017/06/09/florida-tech-study-confirms-lightning-powerful-ocean-land/

"Outlier" Laboratory Results

In statistics, an outlier is an observation point that is distant from other observations. An outlier may be due to variability in the measurement or it may indicate experimental error; the latter are sometimes excluded from the data set.

Outliers can occur by chance in any distribution, but they often indicate either measurement error or that the population has a heavy-tailed distribution. In the former case one wishes to discard them or use statistics that are robust to outliers, while in the latter case they indicate that the distribution has high skewness and that one should be very cautious in using tools or intuitions that assume a normal distribution. A frequent cause of outliers is a mixture of two distributions, which may be two distinct sub-populations, or may indicate 'correct trial' versus 'measurement error'; this is modeled by a mixture model.

In most larger samplings of data, some data points will be further away from the sample mean than what is deemed reasonable. This can be due to incidental systematic error or flaws in the theory that generated an assumed family of probability distributions, or it may be that some observations are far from the center of the data. Outlier points can therefore indicate faulty data, erroneous procedures, or areas where a certain theory might not be valid. However, in large samples, a small number of outliers is to be expected (and not due to any anomalous condition).

Outliers, being the most extreme observations, may include the sample maximum or sample minimum, or both, depending on whether they are extremely high or low. However, the sample maximum and minimum are not always outliers because they may not be unusually far from other observations.

Naive interpretation of statistics derived from data sets that include outliers may be misleading. For example, if one is calculating the average temperature of 10 objects in a room, and nine of them are between 20 and 25 degrees Celsius, but an oven is at 175 °C, the median of the data will be between 20 and 25 °C but the mean temperature will be between 35.5 and 40 °C. In this case, the median better reflects the temperature of a randomly sampled object (but not the temperature in the room) than the mean; naively interpreting the mean as "a typical sample", equivalent to the median, is incorrect. As illustrated in this case, outliers may indicate data points that belong to a different population than the rest of the sample set.

Estimators capable of coping with outliers are said to be robust: the median is a robust statistic of central tendency, while the mean is not. However, the mean is generally more precise estimator.

Occurrence and Causes of Outliers

In the case of normally distributed data, the three sigma rule means that roughly 1 in 22 observations will differ by twice the standard deviation or more from the mean, and 1 in 370 will deviate by three times the standard deviation. In a sample of 1000 observations, the presence of up to five observations deviating from the mean by more than three times the standard deviation is within the range of what can be expected, being less than twice the expected number and hence within 1 standard deviation of the expected number – see Poisson distribution – and not indicate an anomaly. If the sample size is only 100, however, just three such outliers are already reason for concern, being more than 11 times the expected number.

In general, if the nature of the population distribution is known a priori, it is possible to test if the number of outliers deviate significantly from what can be expected: for a given cutoff (so samples fall beyond the cutoff with probability p) of a given distribution, the number of outliers will follow a binomial distribution with parameter p, which can generally be well-approximated by the Poisson distribution with λ = pn. Thus if one takes a normal distribution with cutoff 3 standard deviations from the mean, p is approximately 0.3%, and thus for 1000 trials one can approximate the number of samples whose deviation exceeds 3 sigmas by a Poisson distribution with λ = 3.

Outliers can have many anomalous causes. A physical apparatus for taking measurements may have suffered a transient malfunction. There may have been an error in data transmission or transcription. Outliers arise due to changes in system behaviour, fraudulent behaviour, human error, instrument error or simply through natural deviations in populations. A sample may have been contaminated with elements from outside the population being examined. Alternatively, an outlier could be the result of a flaw in the assumed theory, calling for further investigation by the researcher. Additionally, the pathological appearance of outliers of a certain form appears in a variety of datasets, indicating that the causative mechanism for the data might differ at the extreme end (King effect).

                               More at: https://en.wikipedia.org/wiki/Outlier

 

Ranching and Livestock

A ranch is an area of land, including various structures, given primarily to the practice of ranching, the practice of raising grazing livestock such as cattle or sheep for meat or wool. The word most often applies to livestock-raising operations in Mexico, the Western United States and Canada, though there are ranches in other areas. People who own or operate a ranch are called ranchers, cattlemen, or stockgrowers. Ranching is also a method used to raise less common livestock such as elk, American bison or even ostrich, emu, and alpaca.

Ranches generally consist of large areas, but may be of nearly any size. In the western United States, many ranches are a combination of privately owned land supplemented by grazing leases on land under the control of the federal Bureau of Land Management. If the ranch includes arable or irrigated land, the ranch may also engage in a limited amount of farming, raising crops for feeding the animals, such as hay and feed grains.

Ranches that cater exclusively to tourists are called guest ranches or, colloquially, "dude ranches." Most working ranches do not cater to guests, though they may allow private hunters or outfitters onto their property to hunt native wildlife. However, in recent years, a few struggling smaller operations have added some dude ranch features, such as horseback rides, cattle drives or guided hunting, in an attempt to bring in additional income. Ranching is part of the iconography of the "Wild West" as seen in Western movies and rodeos.

Ranch Occupations

The person who owns and manages the operation of a ranch is usually called a rancher, but the terms cattleman, stockgrower, or stockman are also sometimes used. If this individual in charge of overall management is an employee of the actual owner, the term foreman or ranch foreman is used. A rancher who primarily raises young stock sometimes is called a cow-calf operator or a cow-calf man. This person is usually the owner, though in some cases, particularly where there is absentee ownership, it is the ranch manager or ranch foreman.

The people who are employees of the rancher and involved in handling livestock are called a number of terms, including cowhand, ranch hand, and cowboy. People exclusively involved with handling horses are sometimes called wranglers.

Origins of Ranching

Ranching and the cowboy tradition originated in Spain, out of the necessity to handle large herds of grazing animals on dry land from horseback. During the Reconquista, members of the Spanish nobility and various military orders received large land grants that the Kingdom of Castile had conquered from the Moors. These landowners were to defend the lands put into their control and could use them for earning revenue. In the process it was found that open-range breeding of sheep and cattle (under the Mesta system) was the most suitable use for vast tracts, particularly in the parts of Spain now known as Castilla-La Mancha, Extremadura and Andalusia.

End of the Open Range in the USA

The end of the open range was not brought about by a reduction in land due to crop farming, but by overgrazing. Cattle stocked on the open range created a tragedy of the commons as each rancher sought increased economic benefit by grazing too many animals on public lands that "nobody" owned. However, being a non-native species, the grazing patterns of ever-increasing numbers of cattle slowly reduced the quality of the rangeland, in spite of the simultaneous massive slaughter of American bison that occurred. The winter of 1886–87 was one of the most severe on record, and livestock that were already stressed by reduced grazing died by the thousands. Many large cattle operations went bankrupt, and others suffered severe financial losses. Thus, after this time, ranchers also began to fence off their land and negotiated individual grazing leases with the American government so that they could keep better control of the pasture land available to their own animals.

Ranches Outside the Americas

In Spain, where the origins of ranching can be traced, there are ganaderías operating on dehesa-type land, where fighting bulls are raised. However, the concept of a "ranch" is not seen to any significant degree in the rest of western Europe, where there is far less land area and sufficient rainfall allows the raising of cattle on much smaller farms.

In Australia, the equivalent agricultural lands are known as 'stations' in the context of what stock they carry — usually referred to as cattle stations or sheep stations. New Zealanders use the term runs and stations.

In South Africa, similar large agricultural holdings are simply known as a farm (occasionally ranch) in South African English or a plaas in Afrikaans.

The largest cattle stations in the world are located in Australia's dry rangeland in the outback. Owners of these stations are known as 'grazier', especially if they reside on the property. Employees are known as stockmen, jackaroos and ringers rather than cowboys. A number of Australian cattle stations are larger than 10,000 km², with the greatest being Anna Creek Station which measures 23,677 km² in area (approximately eight times the largest US Ranch). Anna Creek is owned by S Kidman & Co.

https://en.wikipedia.org/wiki/Ranch

Moore's Law for Transistors

Moore's law is the observation that the number of transistors in a dense integrated circuit doubles approximately every two years. The observation is named after Gordon Moore, the co-founder of Fairchild Semiconductor and Intel, whose 1965 paper described a doubling every year in the number of components per integrated circuit, and projected this rate of growth would continue for at least another decade. In 1975, looking forward to the next decade, he revised the forecast to doubling every two years. The period is often quoted as 18 months because of Intel executive David House, who predicted that chip performance would double every 18 months (being a combination of the effect of more transistors and the transistors being faster).

Moore's prediction proved accurate for several decades, and has been used in the semiconductor industry to guide long-term planning and to set targets for research and development. Advancements in digital electronics are strongly linked to Moore's law: quality-adjusted microprocessor prices, memory capacity, sensors and even the number and size of pixels in digital cameras. Digital electronics has contributed to world economic growth in the late twentieth and early twenty-first centuries. Moore's law describes a driving force of technological and social change, productivity, and economic growth.

Moore's law is an observation or projection and not a physical or natural law. Although the rate held steady from 1975 until around 2012, the rate was faster during the first decade. In general, it is not logically sound to extrapolate from the historical growth rate into the indefinite future. For example, the 2010 update to the International Technology Roadmap for Semiconductors, predicted that growth would slow around 2013, and in 2015 Gordon Moore foresaw that the rate of progress would reach saturation: "I see Moore's law dying here in the next decade or so."

Intel stated in 2015 that the pace of advancement has slowed, starting at the 22 nm feature width around 2012, and continuing at 14 nm. Brian Krzanich, CEO of Intel, announced that "our cadence today is closer to two and a half years than two." This is scheduled to hold through the 10 nm width in late 2017. He cited Moore's 1975 revision as a precedent for the current deceleration, which results from technical challenges and is "a natural part of the history of Moore's law."

However, in April 2016, Intel CEO Brian Krzanich stated that "In my 34 years in the semiconductor industry, I have witnessed the advertised death of Moore’s Law no less than four times. As we progress from 14 nanometer technology to 10 nanometer and plan for 7 nanometer and 5 nanometer and even beyond, our plans are proof that Moore’s Law is alive and well". In January 2017, he declared that "I've heard the death of Moore's law more times than anything else in my career," Krzanich said. "And I'm here today to really show you and tell you that Moore's Law is alive and well and flourishing."

Today, hardware has to be designed in a multi-core manner to keep up with Moore's law. In turn, this also means that software has to be written in a multi-threaded manner to take full advantage of the hardware.

https://en.wikipedia.org/wiki/Moore%27s_law

Examples of Malapropisms

A malapropism (also called a malaprop or Dogberryism) is the use of an incorrect word in place of a word with a similar sound, resulting in a nonsensical, often humorous utterance. An example is the statement by baseball player Yogi Berra, "Texas has a lot of electrical votes", rather than "electoral votes". Malapropisms also occur as errors in natural speech and are often the subject of media attention, especially when made by politicians or other prominent individuals. Philosopher Donald Davidson has noted that malapropisms show the complex process through which the brain translates thoughts into language.

Examples from Fiction

The fictional Mrs. Malaprop in Sheridan's play The Rivals utters many malapropisms. In Act 3 Scene III, she declares to Captain Absolute, "Sure, if I reprehend any thing in this world it is the use of my oracular tongue, and a nice derangement of epitaphs!" This nonsensical utterance might, for example, be corrected to, "If I apprehend anything in this world, it is the use of my vernacular tongue, and a nice arrangement of epithets", —although these are not the only words that can be substituted to produce an appropriately expressed thought in this context, and commentators have proposed other possible replacements that work just as well.

Other malapropisms spoken by Mrs. Malaprop include "illiterate him quite from your memory" (instead of "obliterate"), and "she's as headstrong as an allegory" (instead of alligator).

Malapropisms appeared in many works before Sheridan created the character of Mrs. Malaprop. William Shakespeare used them in a number of his plays, almost invariably spoken by comic ill-educated lower class characters. Mistress Quickly, the inn-keeper associate of Falstaff in several Shakespeare plays, is a regular user of malapropisms. In Much Ado About Nothing, Constable Dogberry tells Governor Leonato, "Our watch, sir, have indeed comprehended two auspicious persons" (i.e., apprehended two suspicious persons) (Act 3, Scene V).

Modern writers make use of malapropisms in novels, cartoons, films, television, and other media.

Real-life Examples

Malapropisms do not occur only as comedic literary devices. They also occur as a kind of speech error in ordinary speech. Examples are often quoted in the media. Welsh Conservative leader Andrew Davies, encouraged the Conservative party conference to make breakfast (i.e. Brexit) a success. Bertie Ahern, former Taoiseach of Ireland, warned his country against "upsetting the apple tart" (i.e., apple cart) of his country's economic success.

Former Chicago Mayor Richard J. Daley referred to a tandem bicycle as a "tantrum bicycle" and made mention of "Alcoholics Unanimous" (Alcoholics Anonymous).

It was reported in New Scientist that an office worker had described a colleague as "a vast suppository of information" (i.e., repository or depository). The worker then apologised for his "Miss-Marple-ism" (i.e. malapropism). New Scientist noted this as possibly the first time anyone had uttered a malapropism for the word malapropism itself.

Texas governor Rick Perry has been known to commonly commit malapropisms, for example describing states as "lavatories of innovation and democracy" instead of "laboratories".

https://en.wikipedia.org/wiki/Malapropism