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I have searched through the internet, climbed the longest of low-quality lists on blogs, and journeyed to the very depths of Wikipedia to bring to you on this day the Seven Wonders of the World’s Punctuation. Some are widely used; some are now outdated even in their source languages but are wholly deserving of revival. I hope only that Quora shall render these characters successfully upon the digital page before ye.1. The Ge’ez Preface ColonI have covered the superior Ge’ez punctuation before; I maintain that its characters fully deserve importation into the English language, as well as all others.Alas, I may choose only one symbol from the glorious system for the purposes of the answer. Of its numerous treasures the greatest would be the preface colon ፦, which not only lowers the number of characters needed to type a nose-imbued smiley face but also notes that someone has said something.For example:A፤ B (using the regular Ge’ez colon): A is B.A፦ B (using the preface colon): A says B.The distinction is beautiful, isn’t it? See the linked answer above for further Ge’ezly punctual wonder.2. Chinese Quotation MarksRoughly one Asia away from Ge’ez’s habitat lies our second masterpiece. Plenty of languages have their takes on quotation marks - English’s “”, French’s «», German’s „“, to name a few - but the most elegant are, I believe, the 「」 of modern Chinese and Japanese. They appear equally well on a computer screen, printed book, handwritten note, or calligraphed page.What if you want to write vertically? Simply rotate them ninety degrees and print your text normally from there.Vertical Chinese with its literally wonderful quotation marks-at-an-angle. Image from here.3. The Armenian Abbreviation MarkHow many times have you stumbled over a sentence ending with an abbreviation, eg. “etc.” or “U.S.”, because the period’s double use as a full stop and as an abbreviation mark made it seem like the sentence wasn’t over yet? With the awesome although admittedly archaic Armenian abbreviation mark ՟, you’ll never have to worry again.Compare, for instance, the following two paragraphs:Did Team Red or Team Blue win? Because of good players like Todd, Gerald, Sean, etc. Team Blue lost by six points.Did Team Red or Team Blue win? Because of good players like Todd, Gerald, Sean, etc՟ Team Blue lost by six points.In the first paragraph, it’s not clear whether there are two sentences or three. In one interpretation, the second sentence is answering the first, and then the third sentence is stating how much Team Blue lost by. Another way of looking at it is that the second sentence is saying Todd, Gerald, Sean, etc. caused Team Blue to lose by six points. All because of a single ambiguous period!The second fixes this with the abbreviation mark. The full stop . is now dedicated solely to marking sentences’ ends, so the only possible interpretation is that Todd, Gerald, Sean, etc՟ caused Team Blue to lose by six points.Traditionally, the mark should be placed over the final letter, which looks much more appealing than shown here.4. The InterrobangThis is technically not “from other languages”, but it’s well worthy of Wonder status. Rather than writing the two-character ?! and using up unnecessary space, you can combing them into an exclamatory question mark: the interrobang‽Are you serious‽, you may ask, fully aware of the irony. First, that’s reserved for a completely different character, and second, I certainly am.The interrobang in all its glory. Depending on your device, it may not render on mobile, so imagine this character where all the little boxes are. Image from Wikipedia (https://en.wiktionary.org/wiki/interrobang#/media/File:Interrobang.svg).Should you be surprised, you may say What‽ and make full use of its power. If you happened to live in the mid-20th century, you could gaze upon one of the many technological advancements the period had to offer and exclaim What‽ A Refrigerator That Makes Its Own Ice Cubes‽The symbol is the greatest element of advertiser Martin K. Speckter’s legacy, so much so that his obituary (New York Times, 1988) begins:Martin K. Speckter, a retired advertising executive known to lexicographers as the creator of the interrobang, a punctuation mark used to convey disbelief, died of bone cancer Sunday at Beth Israel Medical Center in Manhattan. He was 73 years old and lived in Manhattan.From 1956 to 1969, Mr. Speckter was president of Martin K. Speckter Associates Inc., which handled promotion for The Wall Street Journal, The National Observer, Barron's weekly and the Dow Jones News Service. In 1962, Mr. Speckter developed the interrobang, since recognized by several dictionaries and some type and typewriter companies.The interrobang predictably fell out of use soon afterwards, but has noticed something of a revival on the internet since then. For more on its history, see here; to carry on the tradition, the ‽’s alt code is Alt+8253.5. ꧁The Javanese Rerengan꧂The Javanese writing system never fails to be as flashy as orthographically possible. Its colons ꧌ and ꧍ resemble a pair of torches; to begin a poem, all you need is a special punctuation mark called a purwapada, which happens to be the relatively simple character ꧅ꦧ꧀ꦖ꧅.A full paragraph of Javanese looks like this:꧋ꦱꦧꦼꦤ꧀ꦲꦸꦮꦺꦴꦁꦏꦭꦲꦶꦂꦫꦏ꧀ꦏꦺꦏꦤ꧀ꦛꦶꦩꦂꦢꦶꦏꦭꦤ꧀ꦢꦂꦧꦺꦩꦂꦠꦧꦠ꧀ꦭꦤꦲꦏ꧀ꦲꦏ꧀ꦏꦁꦥꦝ꧉ꦏꦧꦺꦃꦥꦶꦤꦫꦶꦁꦔꦤ꧀ꦲꦏꦭ꧀ꦭꦤ꧀ꦏꦭ꧀ꦧꦸꦱꦂꦠꦏꦲꦗꦧ꧀ꦥꦱꦿꦮꦸꦁꦔꦤ꧀ꦲꦁꦒꦺꦴꦤ꧀ꦤꦺꦩꦼꦩꦶꦠꦿꦤ꧀ꦱꦶꦗꦶꦭꦤ꧀ꦱꦶꦗꦶꦤꦺꦏꦤ꧀ꦛꦶꦗꦶꦮꦱꦸꦩꦢꦸꦭꦸꦂ꧉(Article 1 of the Universal Declaration of Human Rights. Text from Omniglot.)The objectively best Javanese punctuation marks - which is saying something - are the rerengan, ꧁꧂, a pair of characters used around a title as I’ve done above. One does not get fancier typography than in Javanese, and for this I name the rerengan the fifth Wonder.(If this text didn’t load properly, see here.)6. The Khmer Cock’s Eye and Cow’s UrineAs much as it may seem like it, this is not a lost line from Macbeth; it’s a pair of the Southeast Asian language Khmer’s sandwichly introductory and final punctuation, respectively. If you’d like to note the absolute beginning of a text, you use the pnɛɛk moan, ៙, literally the “cock’s eye”; to say that it’s all over, the koo moot (“cow’s urine), ៚, ends the text. An example paragraph (from here) utilizing the eye and urine would look like this:៙เขมร ភាសាខ្មែខ្រមែរ ឬ ខេមរភាសា គឺជាភាសារបស់ ប្រជាជាតិខ្មែរ ។ ភាសាសំស្ក្រឹត និងភាសាបាលីបាន​ជួយបង្កើតខេមរភាសា ព្រោះភាសាខ្មែរបានខ្ចីពាក្យច្រើនពីភាសាអស់នោះ ។ ​เขมรមានអក្សរក្រមវែងជាងគេនៅលើពិភពលោក ។​ វាជាភាសាមួយដ៏ចំណាស់​ ដែលប្រហែលជាមានដើមកំណើតតាំងតែពី​ ២០០០ ឆ្នាំមុនមកម៉្លេះ ។៚Not only do they look and sound fantastic, they’d be an invaluable addition to any language’s writing system. Gone shall be any uncertainty of where a story begins or ends!These are unfortunately no longer regularly used in Khmer, though they clearly should be.7. Spanish Inverted PunctuationYes, you’re all familiar with it, but you can’t go wrong with a classic, ¿can you?Just as English has parentheses and quotation marks on both ends of the text they refer to, Spanish encloses ¡exclamations! and ¿questions? with punctuation in both directions. Makes sense, ¿doesn’t it? It’s especially useful for Spanish, which only distinguishes between a statement and its question form by rising intonation, so it needs all the written interrogative-marking it can get.If you’d like to do both at once along the lines of the interrobang, you have three options:¡Qué?, with one on each side.¡¿Qué?!, with both on both sides.⸘Qué‽, with an inverted interrobang, because the Spanish weren’t going to let themselves be excluded from this combined punctuation business.Thanks for asking!

Note: This answer is about the history of adaptive optics, not a technical discussion of how it works. I apologize for any confusion the Quora bot caused by merging these questions from time to time.How did Adaptive Optics (AO) technology get started, who was involved, and how were they first applied to astronomical telescopes?Disclaimer: Some of the history of adaptive optics is still classified and so is a dozen years of my life, so, unfortunately I can’t discuss that, and that’s unfortunate, because a lot of the development of adaptive optics into practical use that led to astronomical wide-spread use occurred there.Adaptive optics can clear up atmospheric turbulence allowing ground-based telescopes to see with Hubble clarity.HistoryEvery answer on adaptive optics must mention Archimedes. The use of a large number of mirror segments each controlled by a simple technique is, of course, the source of legend if not myth. Polished metal shields could easily have accomplished the feat with a simple hole in a flat shield that could have been used to align the Sun’s spot on the ground through the hole with the line of sight to the ship viewed through the same hole. The history of determining that this myth is “plausible” is recounted here: Mythbusters were scooped — by 130 years! (Archimedes death ray)Horace Babcock first proposed using adaptive optics in 1953, but the state of technology was not up to the task at the time. He proposed using a thin oil film bombarded with an electron beam to modulate the phase. (This was a technique used in projection TVs at the time.)Several people working at Itek produced an elegant system for compensated imaging. Some of these people started their own companies. Some notable examples:John W Hardy - worked much of the optics and physicsAdaptive Optics for Astronomical TelescopesJames Wyant (WYCO) made a wavefront sensor from a white light shearing interferometer using photomultiplier tubeshttps://wp.optics.arizona.edu/jcwyant/Julius Feinleib (Adaptive Optics Associates) worked the system aspects and advocated Hartmann sensing for the wavefront sensor, and he introduced the idea of a laser guide starRich Hutchin (aka Richard Hudgin) (Optical Physics Company, Incorporated) developed a lot of theory associated with the shearing interferometersIn the late 1960s, work had progressed on lasers to the point that very powerful CO[math]_2[/math] lasers were being tested as possible anti-missile weapons. Almost since the beginning of the laser, the Army was interested in its use as a missile defense. A high energy laser was being tested on ALL (Airborne Laser Laboratory) to defend against cruise missiles. One of the obvious problems was that the CO[math]_2[/math] laser beam was absorbed enough by the air to cause heating which in turn caused thermal lensing. This whole process was called thermal blooming. That and the fact that the laser beam wavefront was not so great coming out of the laser led to a sudden renewed interest in adaptive optics.The Air Force turned to MIT Lincoln Laboratory for help. Darryl Greenwood and Chuck Primmerman pondered the problem, scoped out what needed to be done, worked out some of the equations, and published a couple of papers. What followed was a COAT system (Coherent Optical Adaptive Technique) and Hughes (O’Meara and Pearson) worked on the HICLAS deformable mirrors (HI power Closed-Loop Adaptive System). This system was not based on wavefront sensing. It was a multi-dither approach that resulted in limited bandwidth and for targets that were a good distance away, had severe latency issues.Darryl GreenwoodChuck PrimmermanA history of adaptive optics at MIT LL was published in the 1992 Lincoln Laboratory Journal here: https://pdfs.semanticscholar.org/7f7c/dde589652e8b49e81441bc4d6664caa9cf02.pdfJim Pearson came to Pratt & Whitney Aircraft in the late 1970s and deformable mirrors (HICLAS) started to be produced there. COAT work was being done there in the field at the XLD (experimental laser device) test range in the late 1970s in support of future use on ALL-like programs.Jim PearsonMeanwhile, the Air Force was imaging satellites such as Skylab from its AMOS (Air Force Maui Optical Station) high on Mount Haleakala. They recognized that adaptive optics technique, which they called “compensated imaging” could give them better images of satellites, and potentially be used to discriminate ballistic missile post-boost objects optically from the ground. This history of this is given in a Lincoln Laboratory Journal Article here: http://baseballanalysts.com/archives/12_2devcoherentlaserradarv.2.pdfThe HF/DF chemical laser was quickly outpacing the CO[math]_2[/math] laser and was being planned for the DARPA Triad, a space based laser to defend against ICBMs. To correct the outgoing wavefront of the laser and segmented giant telescope mirror, adaptive optics were used sampled by Holographic Optical Elements placed on the primary mirror. A lot of ground testing of this system, including ALI (Alpha-Lamp Integration experiment) continued up to the end of the 1990s. It was successful. This work was led by Fritz Benning (Rockwell/Hughes) and Sam Williams (Lockheed/Hughes).Fritz BenningSam WilliamsMeanwhile, Darryl Greenwood and Chuck Primmerman wrote a history of adaptive optics at MIT LL here: https://www.spiedigitallibrary.org/conference-proceedings-of-spie/1920/0000/History-of-Adaptive-Optics-Development-at-the-MIT-Lincoln-Laboratory/10.1117/12.152685.fullThere is an out-of-print set of adaptive optics papers edited by Jim Pearson here: Selected Papers on Adaptive Optics for Atmospheric CompensationThe table of contents of this publication is an interesting index to who was working on adaptive optics. I should mention Dave Fried and Glenn Tyler (The Optical Sciences Corporation) as having developed a lot of theory related to the atmospheric turbulence characteristics and the requirements on an adaptive optics system to correct images or laser beams to a particular accuracy.Glenn Tyler (tOSC)In April, 1981, compensated imaging was used from The Air Force Malabar site to examine shuttle tile damage on STS-1 for NASA. A couple of photos were mistakenly released to the press and were shown on the news Saturday morning. They were quickly and quietly withdrawn, having caused unwanted attention to the Air Force capabilities.In 1981, Julius Feinleib was thinking about the problem that a relatively bright natural star is needed as a reference to use to measure the wavefront needed to do the adaptive optics correction. It occurred to him that if a suitable star is not present, a bright laser could be focused on a layer of atmosphere and the Rayleigh scatter could be used as a reference for the wavefront sensor. This idea was immediately classified. The idea was put to use at Starfire Optical Range by the Air Force under the direction of Bob Fugate.The original laser guide star at Starfire Optical Range in the 1980s.In 1985, Julius Feinleib and several of his staff got a patent on adaptive optics systems. Filed: December 6, 1985 Date of Patent: April 12, 1988 Assignee: Adaptive Optics Assoc., Inc. Inventors: Thomas Gonsiorowski, Julius Feinleib, Peter F. Cone, Andrew J. Jankevics, Kelsey S. Nikerson, Lawrence E. Schmutz, Anthony Vidmar, Allan WirthThe problem with adaptive optics at that time was that you needed a reasonably bright star, say 10th magnitude, within an arc second or two of what you wanted to image. At that point, using a laser beam as an artificial “guide star” (LGS = Laser Guide Star) became the norm. The Air Force was quietly doing this at places like Sandia Optical Range, later named Starfire Optical Range in Albuquerque, New Mexico.In 1983, Bob Fugate, the director of the Starfire Optical Range, achieved closed loop operation with a laser guide star. In 1985, Foy and Labeyrie independently introduced the laser guide star idea in open literature. This caused a little stir at the Air Force because the subject was classified (but the authors did not know that), but the paper did not receive a lot of notice.(Foy, R. and A. Labeyrie (1985). Feasibility of adaptive optic telescope with laserprobe. ASTRON. ASTROPHYS. 152:29-31)In 1991, Fugate was successful in getting compensated imaging and laser guide star work declassified. An avid amateur astronomer, Bob was passionate about the impact that this would have on astronomy. It was a long and difficult path for getting the declassification, but the Foy and Labeyrie paper helped, and the value to astronomy was immeasurable.Bob FugateA NEW GENERATION OF HIGH RESOLUTION OPTICS WITHOUT ADAPTIVE OPTICSAn imaging technique that does not use adaptive optics is getting a lot of attention these days. It is called multi-frame blind deconvolution.Raw telescope image and restored imageImage of Hubble Telescope from the ground using blind deconvolutionBlind DeconvolutionSee also: https://www.photonics.com/Articles/Adaptive_Optics_Taming_Atmospheric_Turbulence/a25129Issue | New Scientist (requires subscription)

Hypermesh is indeed a good preprocessor for FEM as it supports exporting the mesh in different formats for many different solvers.Fig.1 - Hypermesh GUI with labels.Now, coming to meshing, there are some golden rules for meshing mostly irrespective of type of analysis and problems.- The mesh should be finer and accurately represent the geometry in the critical areas i.e. the areas where stress, strain, deformation and loading is going to be important.Fig.2 - Mesh 3 represents the geometry better than all others.- A part with all the three dimensions (x, y, z in a cartesian coordinate) comparable are usually meshed with solid elements. Any feature or part having thickness more than 10 mm should be meshed with solid elements provides any of the other two dimensions are not greater than 100 mm.Fig.3 - A circular cylinder meshed with solid tetrahedron elements.- A part with two dimensions comparable and the remaining one atleast 10 times less than both of the other two is meshed with shell elements. As a rule of thumb, any feature or part having thickness less than 10 mm should be meshed with shell elements provided both of the other two dimensions exceed 100 mm. The mesh should be in mid-surface and then the thickness and section properties should be assigned accordingly.Fig. 4 - Midsurface meshing and visualization of thickness- A part with two dimensions comparable and the remaining one at-least 10 times bigger than both of the other two is meshed with beam elements.Any long feature like a rod/bar/beam having circular cross section with diameter less than 10 mm or rectangular cross section less than 10 mm X 10 mm should be meshed as beam. The type of beam to be used will depend on the loading on the part, whether it is purely axial or bending and twisting is also involved.Fig. 5 - A circular rod is meshed with beam elements and shell elements.These four rules will take care of the mesh for the most part, though there's more depending on type of analysis, computational cost, accuracy and other modeling considerations.The last three rules work on the definition of aspect ratio of the geometric shape. In general, an aspect ratio more than 10 invites the necessity of using shell or beam elements.Preference of elements (only first order elements considered) :- While using solid elements 8 noded hexahedron elements are preferred to 6 noded pentahedron elements and the later preferred to 4 noded tetrahedron elements.Fig. 6 - Shell and solid elements- While using shell elements, 4 noded quad elements are preferred over 3 noded tria elements.The elements in the picture with more nodes than mentioned in my points are second order elements and in general they perform better than their first order counterparts.Element Quality:The elements interpolate the value of field variables from the later's value at the nodes and the intepolation happens according to the element formulations. The element formulation is derived for the ideal topology of elements, say an equilateral triangle or a square rectangle in case of tria and quad elements respectively. Deviation in the topology degrades the quality of mesh i.e. how accurate the interpolation will be and hence the accuracy of your result.The elements of the mesh must satisfy some quality criteria like- Minimum and maximum angles in tria and quad elements. For tria, they may be within 30-120 degrees and for quad, within 45-135 degrees.- Jacobian, a measure of how close the elements to the ideal ones. In Hypermesh, they should be more than 0.6.- Warpage, a measure of how much a quad element deviates from being in a single plane. The warpage angle should be less than 15.- Being within an appropriate length range defined by you, a minimum length of 3mm with most of the elements within the range of 5 mm - 10 mm is ideal for most of the cases.- Within a specified aspect ratio, likely range is 4-6.Mesh quality check is available in Hypermesh, and the menu shortcut is F10.Fig. 7 - Element quality checking panel in Hypermesh.Special Features:- Meshing circular holes: A hole is meshed in different manners according to its diameter.0 mm < D < 3 mm, the hole is ignored.3 mm < D < 5 mm, the hole is meshed as a rectangular hole5 mm < D < 10 mm, the hole is meshed with 6 elementsD> 12 mm, the hole is meshed with 8 elements or more.Fig. 8 - Mesh around a hole- Fillets: Like holes, a fillet is meshed in different manners according to its radius.R < 2 mm, the fillet is ignored.2 mm < R < 8 mm, the fillet is meshed with one element with an edge forming a chord along the circumference.R > 8 mm, the fillet is split with more than one element and the geometry is represented as accurately as possible.Fig. 9 - Accurate representation of a fillet.- Small parts: If any protruding part is present, there should be atleast two lines of element representing the geometry.Of course, for holes and fillets, ignoring the feature will depend on the importance of the same in your analysis. Look at the first golden rule.Automesh:Hypermesh has an automesh feature, where the software automatically meshes a part and decide the optimum meshing for the part. But, automesh doesn't perform well in case of complex geometries. Only for a conventional geometry automesh is sufficient. The best process here is taking out chunks of domain which is rectangular and simple and apply automesh to speed up the process of meshing.Automesh command can be invoked by pressing F12 in Hypermesh. In the 2D panel, there is another command "smooth" which will optimize mesh over a domain you select to make it better. The idea is to use all these commands together to achieve mesh flow.Mesh Flow and Symmetry:Mesh flow is a really important concept. In a complex assembly of parts, the mesh size and density changes from one region to another. When the mesh has to change its form, the transition should be smooth and the flow of mesh should conform with the transition.When the mesh size changes from big to small, it should happen gradually and not instantly in a row or two. The image at the top has a better mesh flow than the one at the bottom. The rule of thumb is, given all other things are right, the mesh is better when it looks good.Also, symmetry plays an important role in meshing. If a part is symmetric, the mesh should also be symmetric. This rule actually follows from the first golden rule, though in a non-obvious way, that the mesh should accurately follow the geometry. The rule of thumb for this is that when there is a symmetric part, the meshing is done only on the half the part and is reflected to maintain the symmetry as it is in the geometry.For example, in the above part the meshing can be done only in the left part and then reflect it to maintain symmetry of the mesh.Hypermesh Shortcuts:Here goes most of the shortcuts for Hypermesh.F1 - HelpShift+F1 - ColorCtrl+F1 - Print fileF2 - DeleteShift+F2 - Temp NodesCtrl+F2 - BMP fileF3 - ReplaceShift+F3 - EdgesF4 - DistanceShift+F4 - TranslateF5 - MaskShift+F5 - FindF6 - Edit elementShift+F6 - SplitCtrl+F6 - JPEG fileF7 - Align nodeShift+F7 - ProjectCtrl+F7 - Full screenF8 - NodesShift+F8 - Node editF9 - Line editShift+F9 - Surface editF10 - Check elementsShift+F10 - NormalsF11 - Quick editShift+F11 - OrganizeF12 - AutomeshShift+F12 - SmoothThere is a nice PDF of the shortcuts which can be printed and kept for ready reference. It can be downloaded from Hypermesh Shortcuts on altairuniversity.comDISCLAIMER:1. This answer is not everything one need to know about meshing in Hypermesh. To learn more about meshing, look at the below answers and links and consult the references mentioned there. This is just a primer.Mukunda Madhava Nath's answer to ANSYS Inc: How should I decide which mesh to use in ansys?Mukunda Madhava Nath's answer to What are some good books to learn finite element analysis?Top 5 misunderstandings on (good) mesh.Accuracy, Convergence and Mesh QualityMeshing Considerations for Linear Static ProblemsMeshing your Geometry: When to Use the Various Element Types2. The measurements and lengths given here are not absolute. They are values usually used by FE analysts and should be considered carefully with guidance.3. The images are taken from internet and I don't own any of them. I will remove them in case of any dispute.Hope this helps.PS: This answer will need a little bit of editing and clarifications. If you have any comments or find any mistakes, please let me know.Things to update: computational cost/memory consumption, references, a few links and of course, grammar.Interested in FEA, check my blog at Practical FEA