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🔗 Computing

Technical debt (also known as design debt or code debt, but can be also related to other technical endeavors) is a concept in software development that reflects the implied cost of additional rework caused by choosing an easy (limited) solution now instead of using a better approach that would take longer.

As with monetary debt, if technical debt is not repaid, it can accumulate 'interest', making it harder to implement changes. Unaddressed technical debt increases software entropy. Technical debt is not necessarily a bad thing, and sometimes (e.g., as a proof-of-concept) is required to move projects forward. On the other hand, some experts claim that the "technical debt" metaphor tends to minimize the impact, which results in insufficient prioritization of the necessary work to correct it.

As a change is started on a codebase, there is often the need to make other coordinated changes in other parts of the codebase or documentation. Changes required that are not completed are considered debt, and until paid, will incur interest on top of interest, making it cumbersome to build a project. Although the term is used in software development primarily, it can also be applied to other professions.

🔗 Electronics

In signal processing, the Nyquist frequency (or folding frequency), named after Harry Nyquist, is a characteristic of a sampler, which converts a continuous function or signal into a discrete sequence. For a given sampling rate (samples per second), the Nyquist frequency (cycles per second) is the frequency whose cycle-length (or period) is twice the interval between samples, thus 0.5 cycle/sample. For example, audio CDs have a sampling rate of 44100 samples/second. At 0.5 cycle/sample, the corresponding Nyquist frequency is 22050 cycles/second (Hz). Conversely, the Nyquist rate for sampling a 22050 Hz signal is 44100 samples/second.

When the highest frequency (bandwidth) of a signal is less than the Nyquist frequency of the sampler, the resulting discrete-time sequence is said to be free of the distortion known as aliasing, and the corresponding sample rate is said to be above the Nyquist rate for that particular signal.

In a typical application of sampling, one first chooses the highest frequency to be preserved and recreated, based on the expected content (voice, music, etc.) and desired fidelity. Then one inserts an anti-aliasing filter ahead of the sampler. Its job is to attenuate the frequencies above that limit. Finally, based on the characteristics of the filter, one chooses a sample rate (and corresponding Nyquist frequency) that will provide an acceptably small amount of aliasing. In applications where the sample rate is pre-determined (such as the CD rate), the filter is chosen based on the Nyquist frequency, rather than vice versa.

🔗 Finance & Investment 🔗 Philosophy 🔗 Philosophy/Ethics

Usury () is the practice of making unethical or immoral monetary loans that unfairly enrich the lender. The term may be used in a moral sense—condemning taking advantage of others' misfortunes—or in a legal sense, where an interest rate is charged in excess of the maximum rate that is allowed by law. A loan may be considered usurious because of excessive or abusive interest rates or other factors defined by the laws of a state. Someone who practices usury can be called a usurer, but in modern colloquial English may be called a loan shark.

In many historical societies including ancient Christian, Jewish, and Islamic societies, usury meant the charging of interest of any kind, and was considered wrong, or was made illegal. During the Sutra period in India (7th to 2nd centuries BC) there were laws prohibiting the highest castes from practicing usury. Similar condemnations are found in religious texts from Buddhism, Judaism (ribbit in Hebrew), Christianity, and Islam (riba in Arabic). At times, many states from ancient Greece to ancient Rome have outlawed loans with any interest. Though the Roman Empire eventually allowed loans with carefully restricted interest rates, the Catholic Church in medieval Europe, as well as the Reformed Churches, regarded the charging of interest at any rate as sinful (as well as charging a fee for the use of money, such as at a bureau de change). Religious prohibitions on usury are predicated upon the belief that charging interest on a loan is a sin.

🔗 Computing 🔗 Computing/Software

NeWS (Network extensible Window System) is a discontinued windowing system developed by Sun Microsystems in the mid-1980s. Originally known as "SunDew", its primary authors were James Gosling and David S. H. Rosenthal. The NeWS interpreter was based on PostScript (as was the later Display PostScript, although the two projects were otherwise unrelated) extending it to allow interaction and multiple "contexts" to support windows. Like PostScript, NeWS could be used as a complete programming language, but unlike PostScript, NeWS could be used to make complete interactive programs with mouse support and a GUI.

🔗 Mathematics 🔗 Maps

The coastline paradox is the counterintuitive observation that the coastline of a landmass does not have a well-defined length. This results from the fractal curve-like properties of coastlines, i.e., the fact that a coastline typically has a fractal dimension (which in fact makes the notion of length inapplicable). The first recorded observation of this phenomenon was by Lewis Fry Richardson and it was expanded upon by Benoit Mandelbrot.

The measured length of the coastline depends on the method used to measure it and the degree of cartographic generalization. Since a landmass has features at all scales, from hundreds of kilometers in size to tiny fractions of a millimeter and below, there is no obvious size of the smallest feature that should be taken into consideration when measuring, and hence no single well-defined perimeter to the landmass. Various approximations exist when specific assumptions are made about minimum feature size.

The problem is fundamentally different from the measurement of other, simpler edges. It is possible, for example, to accurately measure the length of a straight, idealized metal bar by using a measurement device to determine that the length is less than a certain amount and greater than another amount—that is, to measure it within a certain degree of uncertainty. The more accurate the measurement device, the closer results will be to the true length of the edge. When measuring a coastline, however, the closer measurement does not result in an increase in accuracy—the measurement only increases in length; unlike with the metal bar, there is no way to obtain a maximum value for the length of the coastline.

In three-dimensional space, the coastline paradox is readily extended to the concept of fractal surfaces whereby the area of a surface varies, depending on the measurement resolution.

🔗 Mass surveillance 🔗 Spaceflight 🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Intelligence 🔗 Cold War

The Corona program was a series of American strategic reconnaissance satellites produced and operated by the Central Intelligence Agency Directorate of Science & Technology with substantial assistance from the U.S. Air Force. The Corona satellites were used for photographic surveillance of the Soviet Union (USSR), the People's Republic of China, and other areas beginning in June 1959 and ending in May 1972.

🔗 Architecture 🔗 New Jersey 🔗 National Register of Historic Places

The Bell Labs Holmdel Complex, in Holmdel Township, Monmouth County, New Jersey, United States, functioned for 44 years as a research and development facility, initially for the Bell System and later Bell Labs. The centerpiece of the campus is an Eero Saarinen–designed structure that served as the home to over 6,000 engineers and researchers. This modernist building, dubbed "The Biggest Mirror Ever" by Architectural Forum due to its mirror box exterior, was the site of a Nobel Prize discovery, the laser cooling work of Steven Chu.

Restructuring of the company's research efforts reduced the use of the Holmdel Complex, and in 2006 the building was put up for sale. The building has undergone renovations into a multi-purpose living and working space, dubbed Bell Works by its redevelopers. Since 2013 it has been operated by Somerset Development, who redeveloped the building into a mixed-use office for high-tech startup companies. The complex was listed on the National Register of Historic Places in 2017. A number of movies, television programs, and commercials have been filmed at Bell Works, including Severance, The Crowded Room, and Law & Order: Organized Crime.

🔗 Military history/Early Muslim military history 🔗 Games

The two envelopes problem, also known as the exchange paradox, is a brain teaser, puzzle, or paradox in logic, probability, and recreational mathematics. It is of special interest in decision theory, and for the Bayesian interpretation of probability theory. Historically, it arose as a variant of the necktie paradox. The problem typically is introduced by formulating a hypothetical challenge of the following type:

It seems obvious that there is no point in switching envelopes as the situation is symmetric. However, because you stand to gain twice as much money if you switch while risking only a loss of half of what you currently have, it is possible to argue that it is more beneficial to switch. The problem is to show what is wrong with this argument.