Advantages And Disadvantages Of Standard Commercial Software Meaning' title='Advantages And Disadvantages Of Standard Commercial Software Meaning' />Basic Design Atomic Rockets. This section is intended to address some gaps in available information about spacecraft design in the Plausible Mid Future PMF, with an eye towards space warfare. It is not a summary of such information, most of which can be found at Atomic Rockets. The largest gap in current practice comes in the preliminary design phase. A normal method used is to specify the fully loaded mass of a vessel, and then work out the amounts required for remass, tanks, engine, and so on, and then figure out the payload habitat, weapons, sensors, cargo, and so on from there. While there are times this is appropriate engineering practice notably if youre launching the spacecraft from Earth and have a fixed launch mass, in the majority of cases the payload mass should be the starting point. The following equation can be used for such calculations Where P is the payload mass any fixed masses, such as habitats, weapons, sensors, etc., M is the loaded wet mass, R is the mass ratio of the rocket, T is the tank fraction or any mass that scales with reaction mass as a decimal ratio of such mass e. E is any mass that scales with the overall mass of the ship, such as engines or structure, also as a decimal. This equation adequately describes a basic spacecraft with a single propulsion system. It is possible to use the same equation to calculate the mass of a spacecraft with two separate propulsion systems. Hybrid cloud is a cloud computing environment which uses a mix of onpremises, private cloud and thirdparty, public cloud services with orchestration between the two. This article is the part software testing question and answer series. Here I will answer some readers questions asked to me in comments or using contact form. If. The terms in this equation are identical to those in the equation above, with R1 and T1 representing the mass ratio and tank fraction for the arbitrary first engine, and R2 and T2 likewise for the second. Calculate both mass ratios based on the fully loaded spacecraft. If both mass ratios approach 2, then the bottom of the equation will come out negative, and the spacecraft obviously cannot be built as specified. Note that when doing delta V calculations to get the mass ratio, each engine is assumed to expend all of its delta V while the tanks for the other engine are still full. In reality, the spacecraft will have more delta V than those calculations would indicate, but solving properly for a more realistic and complicated mission profile requires numerical methods outside the scope of this paper. One design problem that is commonly raised is the matter of artificial gravity. In the setting under discussion, this can only be achieved by spin. The details of this are available elsewhere, but these schemes essentially boil down to either spinning the entire spacecraft or just spinning the hab itself. Both create significant design problems. Spinning the spacecraft involves rating all systems for operations both in free fall and under spin, including tanks, thrusters, and plumbing. The loads imposed by spin are likely to be significantly larger than any thrust loads, which drives up structural mass significantly. For some good general notes on designing spacecraft in general, read Rick Robinsons Rocketpunk Manifesto essay on Spaceship Design 101. Also worth reading are Ricks. This employment contract is a straightforward standard contract, simple to use in a variety of roles and organisations. The template has been designed to be used by. ERP Enterprise Resource Planning is principally an integration of business management practices and modern technology. Information Technology IT integrates with a. This can be minimized by keeping things close to the spin axis, but that is likely to stretch the ship, which imposes its own structural penalties. A spinning hab has to be connected to the rest of the spacecraft, which is not a trivial engineering problem. The connection will have to be low friction, transmit thrust loads, and pass power, fluids, and quite possibly people as well. And it must work 2. All of this trouble with artificial gravity is required to avoid catastrophic health problems on arrival. However, there is a potential alternative. Medical science might someday be able to prevent the negative effects of Zero G on the body, making the life of the spacecraft designer much easier. When this conclusion was put before Rob Herrick, an epidemiologist, he did not think it was feasible. The problem is that they the degenerative effects of zero G are the result of mechanical unloading and natural physiological processes. The muscles dont work as hard, and so they atrophy. The bones dont carry the same dynamic loads, so they demineralize. Both are the result of normal physiological processes whereby the body adapts to the environment, only expending what energy is necessary. The only way to treat that pharmacologically is to block those natural processes, and that opens up a really bad can of worms. All kinds of transporters would have to be knocked out, youd have to monkey with the natural muscle processes, and God knows what else. Essentially, youre talking about chemically overriding lots of homeostasis mechanisms, and we have no idea if said overrides are reversible, or what the consequences of that would be in other tissues. My bet is bad to worse. As the whole field of endocrine disruptors is discovering, messing with natural hormonal processes is very very dangerous. Even if it worked with no off target effects, youd have major issues. Body development would be all kinds of screwed up, so its not something youd want to do for children or young adults. Since peak bone mass is not accrued until early twenties, a lot of your recruits would be in a window where theyre supposed to still be growing, and youre chemically blocking that. Similarly, would you have issues with obesity If your musculature is not functioning normally to prevent atrophy, how will that effect the bodys energy balanceWhat other bodily processes that are interconnected will be effected Then you get into all the effects of going back into a gravity well. Would you come off the drugs and thus require a washout period before you go downside, and a ramp up period before you could go topside again     Spin and gravity is an engineering headache, but a solvable one. Pharmacologically altering the body to prevent the loss of muscle and bone mass that the body seems surplus to requirements has all kinds of unknowns, off target effects and unintended consequences. Youre going to put people at severe risk for medical complications, some of which could be lifelong or even lethal. This is a compelling case that it is not possible to treat the effects of zero G medically. However, if for story reasons a workaround is needed, medical treatment is no less plausible than many devices used even in relatively hard Sci Fi. The task of designing spacecraft for a sci fi setting is complicated by the need to find out all the things that need to be included, and get numbers for them. The author has created a spreadsheet to automate this task, including an editable sheet of constants to allow the user to customize it to his needs. The numbers there are the authors best guess for Mid PMF settings, but too complicated to duplicate here. Rick Robinsons rule of thumb is that spacecraft will in the sort of setting examined here become broadly comparable to jetliners in cost, at about 1 millionton in current dollars. This is probably fairly accurate for civilian vessels, at least to a factor of 3 or so. Warships are likely to be more expensive, as most of the components that separate warships from civilian ships are very expensive for their mass. In aircraft terms, an F 1. F 1. 5, while the FA 1. EF Super Hornet is closer to 4 millionton. This is certainly a better approximation than the difference between warships and cargo ships, as spacecraft and aircraft both have relatively expensive structures and engines, unlike naval vessels, where by far the most expensive component of a warship is its electronics. For example, the ships of the Arleigh Burke class of destroyers seem to be averaging between 1. As mentioned in Section 5, some have suggested that the drive would be modular, with the front end of the ship containing weapons, crew, cargo, and the like built separately and attached for various missions. This is somewhat plausible in a commercial context, but has serious problems in a military one. However, the idea of buying a separate drive and payload and mating them together is quite likely, and could see military and civilian vessels sharing drive types. This is not as strange as present experience would lead us to believe. Comparison of data analysis packages R, Matlab, Sci. Convert Wmv To Mp3 With Windows Media Player. Py, Excel, SAS, SPSS, Stata. Lukas and I were trying to write a succinct comparison of the most popular packages that are typically used for data analysis. I think most people choose one based on what people around them use or what they learn in school, so Ive found it hard to find comparative information. Im posting the table here in hopes of useful comments. Name. Advantages. Disadvantages. Open source Typical users. RLibrary support visualization. Steep learning curve. Yes. Finance Statistics. Matlab. Elegant matrix support visualization. Expensive incomplete statistics support. No. Engineering. Sci. PyNum. PyMatplotlib. Python general purpose programming languageImmature. Yes. Engineering. Excel. Easy visual flexible. Large datasets. No. Business. SASLarge datasets. Expensive outdated programming language. No. Business Government. Stata. Easy statistical analysis. No. Science. SPSSLike Stata but more expensive and worse70. SAS, SPSS, and Stata. Theres a bunch more to be said for every cell. Among other things Two big divisions on the table The more programming oriented solutions are R, Matlab, and Python. More analytic solutions are Excel, SAS, Stata, and SPSS. Python immature matplotlib, numpy, and scipy are all separate libraries that dont always get along. Why does matplotlib come with pylab which is supposed to be a unified namespace for everything  Isnt scipy supposed to do that  Why is there duplication between numpy and scipy e. And then theres package compatibility version hell. You can use SAGE or Enthought but neither is standard yet. In terms of functionality and approach, Sci. Py is closest to Matlab, but it feels much less mature. Matlabs language is certainly weak. It sometimes doesnt seem to be much more than a scripting language wrapping the matrix libraries. Python is clearly better on most counts. Rs is surprisingly good Scheme derived, smart use of named args, etc. Everyone says SAS is very bad. Matlab is the best for developing new mathematical algorithms. Very popular in machine learning. Ive never used the Matlab Statistical Toolbox. Im wondering, how good is it compared to R Heres an interesting reddit thread on SASStata vs R. SPSS and Stata in the same category they seem to have a similar role so we threw them together. Stata is a lot cheaper than SPSS, people usually seem to like it, and it seems popular for introductory courses. I personally havent used eitherSPSS and Stata for Science weve seen biologists and social scientists use lots of Stata and SPSS. My impression is they get used by people who want the easiest way possible to do the sort of standard statistical analyses that are very orthodox in many academic disciplines. ANOVA, multiple regressions, t and chi squared significance tests, etc. Certain types of scientists, like physicists, computer scientists, and statisticians, often do weirder stuff that doesnt fit into these traditional methods. Another important thing about SAS, from my perspective at least, is that its used mostly by an older crowd. I know dozens of people under 3. SAS.   At that R meetup last week, Jim Porzak asked the audience if there were any recent grad students who had learned R in school. Many hands went up. Then he asked if SAS was even offered as an option. All hands went down. There were boatloads of SAS representatives at that conference and they sure didnt seem to be on the leading edge. But is there ANY package besides SAS that can do analysis for datasets that dont fit into memory  That is, ones that mostly have to stay on disk  And exactly how good as SASs capabilities here anyway If your dataset cant fit on a single hard drive and you need a cluster, none of the above will work. There are a few multi machine data processing frameworks that are somewhat standard e. Hadoop, MPI but Its an open question what the standard distributed data analysis framework will be. Hive Pig  Or quite possibly something else. This was an interesting point at the R meetup. Porzak was talking about how going to My. SQL gets around Rs in memory limitations. But Itamar Rosenn and Bo Cowgill Facebook and Google respectively were talking about multi machine datasets that require cluster computation that R doesnt come close to touching, at least right now. Its just a whole different ballgame with that large a dataset. SAS people complain about poor graphing capabilities. R vs. Matlab visualization support is controversial. One view Ive heard is, Rs visualizations are great for exploratory analysis, but you want something else for very high quality graphs. Matlabs interactive plots are super nice though. Matplotlib follows the Matlab model, which is fine, but is uglier than either IMO. Excel has a far, far larger user base than any of these other options. Thats important to know. I think its underrated by computer scientist sort of people. But it does massively break down at 1. Another option Fortran and CC. They are super fast and memory efficient, but tricky and error prone to code, have to spend lots of time mucking around with IO, and have zero visualization and data management support. Most of the packages listed above run Fortran numeric libraries for the heavy lifting. Another option Mathematica. I get the impression its more for theoretical math, not data analysis. Can anyone prove me wrong Another option the pre baked data mining packages. The open source ones I know of are Weka and Orange. I hear there are zillions of commercial ones too. Jerome Friedman, a big statistical learning guy, has an interesting complaint that they should focus more on traditional things like significance tests and experimental design. Here the article that inspired this rant. I think knowing where the typical users come from is very informative for what you can expect to see in the softwares capabilities and user community. Id love more information on this for all these options. What do people thinkAug 2. Serbo Croatian translation. Apr 2. 01. 5 update Slovenian translation. May 2. 01. 7 update Portugese translation.