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  • saurabhjain

    Calling Mechanical Engineers to collaborate on Twitter

    By saurabhjain

    If you are a mechanical engineering professional and have a twitter account .. we invite you in our mechanical engineering  campaign to collaborate on twitter.. Retweet the following status on https://twitter.com/mechportal/status/646544243649961985 Look forward for your presence. Regards Mechanical Engineeirng forum
    • 5 comments
    • 1,478 views
  • DrD

    #20 -- A Question of Stability (Revised)

    By DrD

    Mechanics Corner
        A Journal of Applied Mechanics and Mathematics by DrD, #20
        © Machinery Dynamics Research, 2015
    A Question of Stability Introduction     The word stability in its several forms is widely used in nontechnical communication. A person whose life it highly consistent from day to day is said to have a stable life. When the political situation in a particular area appears to be unlikely to change, it is said to be stable. A person who is well balanced and unlikely to be easily provoked to anger is said to be a stable person. When the medical condition of a sick or injured person ceases to get worse, the person is said to be stabilized. A company on the verge of bankruptcy is said to be an unstable company. But what does the word stability mean in a technical context? Each of the foregoing examples hints at the technical meaning without really being explicit about it.   A factor g = accel of gravity was missing in the potential energy expression. That is now corrected.
        
     
        Stability.pdf
    • 16 comments
    • 5,709 views
  • DrD

    A Question for Readers

    By DrD

    Many of you have asked me various questions, so now it is my turn. Let me lay a bit of background first, and then the questions.   I have had some conversations recently with JAG (one of the other writers here at ME Forums) regarding the choice of software for 3D modeling and analysis. JAG has made some excellent suggestions, specifically a cloud based program called Onshape. Unfortunately, for reasons that are unclear, my computer cannot run Onshape; I have worked with their help people for several hours, all to no avail. JAG recommends this in part because there is a "free version for the hobbyist" and a relatively inexpensive "full version for the professional." That is pretty attractive, but since I can't run it, I'm stuck.   I gather that virtually all engineering colleges these days are teaching some sort of 3D modeling and analysis software, but that raises a few questions in my mind. 1. If your college teaches brandX 3D software, what will you do when you go to work for a small company that cannot afford anything more than 2D drafting (simple CAD), with no analysis capability at all? How will you do your job then? You probably have your own pocket calculator, but will you have your own copy of ANSYS or Pro-E? 2. What software does your school teach (every students should have an answer to this question, so I expect lots of replies on this one!)? 3. If you have used software extensively for analysis of engineering problems (beam deflections, stress analysis, fluid flow, heat transfer, etc), are you confident  that you will be able to work all of those problems if there is no such software available to you on the job?   I might add, as sort of a postscript, most of you know that I am older than dirt (I just had another birthday, so the situation is even worse!), so I tend to look at things from an elderly perspective. One of my great fears as a working engineer was "What will happen when I'm ask to do something that I don't know how to do?" It happened more than once, and it usually resulted in a flurry of intense research to come up to speed on whatever topic was involved. I could usually do that because I have a pretty good library, and I knew how to use a university library as well. But in terms of software, I was always concerned that I had no FEA program, so how could I do problems that others were doing by FEA? I have come up with some interesting work-arounds, including writing my own FEA for some problems, but I never wanted to be dependent on software that I could not afford to own. So, back to my questions about: How are you going to buy your own copy of ANSYS? DrD
    • 28 comments
    • 2,878 views
 

Rocket Homework Problem

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, #38
      Machinery Dynamics Research, 2017
Rocket Homework Problem Introduction     Most engineers find problems involving rockets to be exciting. There is something about a rocket that fires our imagination, whether we think of going to the moon or one of the planets, or simply of shooting down an incoming missile. The subject of this post involves a rocket on a mobile launcher. The rocket is intended to be transported in a horizontal position, but it must be elevated in order to be fired. Both positions are shown in the accompanying figure. Read the attached PDF for more on this problem. RocketHWProblem.pdf   Addendum:  One reader has posted a proposed solution for this problem as a comment. It was not my intent that solutions be posted in the comments at all. I only want solutions sent to me by the personal message system. DO NOT POST YOUR SOLUTION IN THE COMMENTS!! Regarding the solution that has been posted, let me say the following: 1. Some of the answers are correct, while others are not. Do not be misled into following this solution because there are errors therein. 2. Even where the results are correct, there are a number of methods that I would not recommend using. Thus again, I say to all other readers, do not follow this solution, but work it out for yourself. 3. Be sure to document your solution, so that if someone else were to ask how you obtained a particular result, you would be able to explain it in a clear and reasonable manner.      

DrD

DrD

 

Where Would You Publish It?

Mechanics Corner Where Would You Publish It? Since long before my time, there has been a desire to have important results published where they become accessible to many others. Some of the great names, such as Newton, Euler, Bernoulli, and others, we know primarily because of what they published. Their work formed the fundamentals upon which modern engineering and science is built. Publication of research results has long been particularly important to faculty members; it is often taken as a measure of just how intelligent and useful they are (there is a lot of doubt about the validity of this measurement, but that has not prevented it use). When I was a young faculty member (many, many years ago), there was the mantra "Publish or Perish." This referred to the idea that those faculty members that did not publish research work would not receive tenure, and would be out of employment after several years. Agencies that funded research were eager to see publication of results that they had funded; it was considered evidence of the importance of the work supported by the agency. This was particularly true of the National Science Foundation (NSF) and other governmental funding sources in the USA. It was not too long before publication was replaced as the measure of academic value, to be replaced by funding. A faculty member was expected to write research grant proposals, and the Dean's Office expected a significant cut of the proceeds, ostensibly for their role in "supervision." In practical terms, Dean's Offices almost never contributed anything of value to research efforts, but this was a form of graft to assure their cooperation. But publication remained essential as well. Any research that could not be published in a reputable journal was considered to be unworthy, a waste of time. So the criteria for success became, get money and publish, a tougher goal that simply publishing. More recently, the goal posts have been moved again. Today the big cry is for "undergraduate research." To my mind, this is the height of absurdity. For folks who are just beginning to learn a profession, how can anyone think that they are capable of fundamental new discoveries? For undergraduates that are still struggling with Mechanics of Materials, do we really expect them to discover new understanding of fatigue or fracture mechanics? For a student laboring to understand dynamics, do we really expect them to come up with breakthroughs in orbital mechanics, seismic shock resistance, or multidegree of freedom models for gear box noise? But, rest assure, there is no place more insane than a university!! The utterly absurd is treated as absolutely essential!! Thus far, I've talked a lot about academia, but we must not neglect industry. Publication is important to industrial firms as well, although for different reasons. Published research, done by your firm, is a way of establishing the technical excellence of your company. If you want to be known as an industry leader in your area, you want your employees to publish work that makes the company look like it is on the cutting edge of new technology. Often industry imposes constraints on what can be published; they do not want proprietary information to be put into the public domain. But they really like to have results published that make them look sophisticated, ahead of the pack, so to speak. For consulting engineers, publication can be important as a means to establish your expertise in an area. If you publish a lot in a particular subject area, people begin to think you kow something about the area and come to you when they have problems. New work is the life blood of consulting engineers, so this can be very important. You will also be asked to review the work of others and to sit on panel discussions and other public appearances that can upgrade your image and bring in more work. I hope that it is evident that most engineers will need to publish some work at some point in their career. It may be a central matter of those in more research oriented areas, or it may be only occasional for those in less cutting edge business sectors, but everyone will eventually need to publish something. So, back to the original question: Where Would You Publish It? Most professional societies publish research work, and there are also a vast number of trade magazines. Fifty years ago, when the volume of "research" was much less, it was not too difficult to publish through any number of venues. I have published articles through the various Transactions of the American Society of Mechanical Engineers (ASME), through the Transactions of the Society of Automotive Engineers (SAE), and the Journal of Mechanism and Machine Theory. I have also published through some much less well known venues such as Machine Design magazine, and most recently through IPTEK Journal, a small journal headquartered in Indonesia (that was an experience!) and other places. But the game is ever changing! When I first began to publish papers back in the 1960s, it was a fairly simple process. You wrote up your text, with figures and equations, and mailed it to the editor in type written form (this before the days of word processing). After a few months, you would get something back from the editor. It might be an outright acceptance (rare), a conditional acceptance which meant that the paper would be accepted with certain modifications/corrections that were described in the letter (fairly common), or it might be a flat rejection (not extremely uncommon). If you got a conditional acceptance, you made the revisions, and about 6 months later, it would be published in whatever journal you were dealing with. The classier the journal, the higher the standards were, but all worked about the same. Many of these organizations that publish papers also hold meetings, and they want people to come to the meetings. I have presented papers at the ASME Winter Annual Meeting (always in New York), at various SAE meetings, etc. But, there is a problem. It is expensive to go to these meetings. There is the travel expense (transportation, hotel, food, etc), and there is usually an admission fee (you have to pay money to present your own paper, an absurdity, but very real). Often the papers is only accepted for publication if you agree to come to the meeting to present it and pay the admission fee. Now if your paper is the result of funded research, or if your employer will pay the expenses, this is usually not a personal burden. If neither of these apply, the burden of the costs fall of the individual, and it is often prohibitive, often approaching $1000. The publisher then sell your work for a subscription fee, usually several hundred dollars per year. Libraries are the principal subscribers (university, municipal, and industrial libraries), along with a few individual. In recent years, there has been a glut of material offered for publication, and everybody thinks that their paper is extremely important for the world to see. The volume of publications have increased drastically, but so has the cost. Who will pay for all the paper, printing, etc.? For years, it has been common to impose what are called "page charges," typically around $100 per page, to publish in most journals. Funded research usually included a line item for page charges, so that paid those bill. In the past, any unfunded research, if it was accepted, would usually be published with the page charges waived. Today, that is not longer true, and page charges are usually mandatory. But it gets worse. We all know the Internet is a wonderful thing, but it does have some downsides as well. One of those downsides is in the area of publication. There is a relatively recent trend in publication called "Open Access," and it is particularly popular with a number of on-line journals. These journals are free to all on the internet, but the journals charge the authors a very steep price to publish their work. Thus you, as an author, must prepare the article according some very demanding rules about formatting, style, etc, then you must pay several thousand dollars, just so the world can see your work. It means that your work becomes available to all for free (which is a good thing), but it means that you the author must bear the full cost of supporting the publishing operation. I know that I, as an individual, cannot afford this, and thus it is almost impossible for me to publish anything now. It means that those with money will get their work published, and those without money will not. The quality of the published work is virtually certain to decline, but that is modern life. What can you do? As a closing note, I'm currently writing another technical paper that I would like to publish, preferably where folks who work with IC engines will read it. I think I have something of real value to present, but I have no idea where I will publish it, or if I will be able to find a publisher at all. If any readers have a suggestion for an appropriate journal, I would certainly appreciate a suggestion in the comments. DrD    

DrD

DrD

 

The True Value of Certification

The link below is an article about the value of certification for manufacturers. It is a heavy sell for certification. In my opinion it misses the most basic benefit of certification, which is the path to getting certified. http://www.machinedesign.com/industrial-automation/why-do-manufacturing-certifications-matter?NL=MACD-001&Issue=MACD-001_20170523_MACD-001_398&sfvc4enews=42&cl=article_1_b&utm_rid=CPG05000005789847&utm_campaign=11223&utm_medium=email&elq2=ac7bbf3354354d12ba54569ff985ae31 When people ask me about ISO 9000, the simple explanation I give, “the process of certification requires you to write down your process and demonstrate that you follow the process.” The certification system does not dictate your process. The mere action of writing down and maintaining the written procedure is the real value. In one of my blogs “Dumbest Guy in the Room", written in two parts, http://www.jagengrg.com/blog, I touch on the value of the written word and the perils of oral communication.  Writing it down allows everyone to see exactly what the author thinks is being done or should be done. Others can read the written word and identify ambiguous sections, missing information, or errors that can easily be overlooked using oral communication. When everyone is carrying the information in their head’s via oral direction I can guarantee there is more than one interpretation. I would venture to say you will have as many interpretations as you have people involved. When written procedures do exist but do not come under the scrutiny of a certification body, it is very common for procedures to become stale, be incomplete, rely on undocumented knowledge, and for steps in the process to be missed from time to time. The subject article closes with a realistic assessment of the value for certification. “Is having a certification the end-all-be-all of manufacturing? No. However….” You reach the "however" stage, not my hanging the certification on the wall, but the process for obtaining it. 
 

The Exponential Age

This came to me via e-mail. I am sure little of this is 100% correct. But just think if just 50% are 50% correct.   The Exponential Age?  Just a few things for us all to ponder, especially the younger ones amongst us.  Did you think back in 1998 that 3 years later you would never take pictures on film again?        In 1998 Kodak had 170,000 employees and sold 85 % photo paper worldwide. Within just a few years their business model disappeared and they went bankrupt. What happened to Kodak will happen in a lot of industries in the next 10 years and, most people  won't see it coming.   Yet digital cameras were invented in 1975. The first ones only had 10,000 pixels, but followed Moore's law.  So as with all exponential technologies, it was a disappointment for a time, before it became way superior and became mainstream in only a few short years. It will now happen  again with Artificial Intelligence, health, autonomous and  electric cars, education, 3D printing, agriculture and jobs.  Welcome to the  4th Industrial Revolution.  Welcome to the Exponential Age.                       Software will disrupt most traditional industries in the next 5-10 years.          Uber is just a software tool, they don't own any cars, and are now the biggest taxi company in the  world.                   Airbnb is now the biggest hotel company in the world, although they don't own any properties.                     Artificial  Intelligence:  Computers become exponentially better in understanding the world. This year, a computer beat the best Go-player in the world, 10 years  earlier than expected.                       In the US , young lawyers already don't get jobs. Because of IBM's Watson you can get legal advice (so far for more or less basic stuff) within seconds. With 90% accuracy compared with 70% accuracy when done by humans.                                  So if you study law, stop  immediately. There will be 90 % less lawyers in the future. Only specialists will remain.              Watson already helps nurses diagnosing cancer,  which is 4 times more accurate than human nurses.             Facebook now has a pattern recognition software that can recognize faces better than humans. In 2030 computers will become more intelligent than humans. (NEVER says Albert)         Autonomous cars: In 2018  the first self driving cars will appear for the public. Around 2020 the complete industry will  start to be disrupted. You won't want to own a car anymore.  You will call a car with your phone, it will show up at your location and drive you to your destination. You will not need to park it, you only pay for the driven distance and can be productive while being driven.                              Our kids will never need to get a  driver's licence and will never own a car.                   It will change the cities,  because we will need 90-95% less cars for that. We can transform former parking spaces into parks.                             1.2  million people die each  year in car accidents worldwide. We now have one accident every 60,000 miles  ( 100,000  km), with autonomous driving that will drop to 1 accident in 6 million miles (10 million km). That will save  a   million  lives each  year.                       Most car companies will probably become bankrupt. Traditional car companies try the evolutionary approach and just build a better car, while tech companies like Tesla, Apple, Google will do the revolutionary approach and build a computer on  wheels.                                  Many engineers from  Volkswagen and Audi are completely terrified of Tesla.                             Insurance  companies  will have massive trouble  because without accidents, the insurance will become 100x cheaper. Their car insurance business model will disappear.                            Real Estate will change.  Because if you can work while you commute, people  will move further away to live in a more beautiful neighbourhood.                                   Electric cars will become  mainstream about 2020.  Cities will be less noisy  because all new cars will run on electricity.                           Electricity will become  incredibly cheap and clean. Solar production has been  on an exponential curve for 30 years, but you can now see the burgeoning impact.                           Last year, more solar energy was installed worldwide than fossil.  Energy companies are desperately trying to limit access to the grid to prevent competition from home solar installations, but that can't last.  Technology will take care of that strategy.                               With cheap electricity comes cheap and abundant water.   Desalination of salt water now only needs 2k Wh per cubic meter at 0.25 cents). We don't have  scarce water in most places, we only have scarce drinking water. Imagine what will be possible if anyone can have as much clean water as he wants, for nearly no cost.                    Health: The Tricorder X price will be announced this year. There are companies who will build a medical device (called the " Tricorder " from Star Trek) that works  with your phone, which takes your retina scan, your blood sample  and you simply  breath into it.                             It then analyses 54 bio-markers  that will identify nearly  any   disease.  It will be cheap, so in a  few years everyone on this planet will have access to world class medical analysis, nearly for free. Goodbye medical  establishments.               3 D printing: The price of the cheapest 3D  printer came down from  $18,000 to $400 within 10 years. In the same time, it  became 100 times faster. All major shoe companies have already started 3D printing  shoes.               Some spare airplane parts  are already 3D printed in remote airports. The space station now has a printer that eliminates the  need for the large amount of spare parts they used to have in the past.                             At the end of this year, new  smartphones will have 3D scanning possibilities. You can then 3D scan your feet and print  your perfect shoe at home.                              In China they have already 3D printed and built a complete 6 storey office building.  By 2027 10% of everything that's being produced will be 3D printed.                                      Business  Opportunities: If you think of a niche you want to go in, first ask yourself, "In the future, do I think we will have that?" If the answer is yes, how can you make that happen sooner? If it doesn't work with your phone, forget the idea.  And any idea designed for success in the 20th century is doomed to failure in the 21st century. Work:   70-80 % of jobs will disappear in the next 20 years. There will be a lot  of new jobs, but it is not clear if there will be enough new  jobs in such a short time.  This will require a rethink on wealth distribution. Agriculture: There will be a $100  agricultural robot in the future.  Farmers in 3rd world countries can then become managers of their field instead of working all day on their  fields.  Aeroponics: Will need much less water. The first Petri dish produced veal, is now available and will be cheaper than cow produced veal in 2018. Right now, 30 % of all agricultural surfaces is used for cows.  Imagine if we don't need that space  anymore. The Times They Are A Changing!
 

Two Balls Rolling On An Incline

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, # 37
    29 April 2017
Two Balls Rolling On An Incline
A Problem Where I Learned Something New
Introduction     In previous articles, I have mentioned another web site called Physics Forums (PF) where people post problems for which they need help. In this note, I want to present to you one such problem and it solution, along with a new insight that came from another commenter at PF, one of the advisory folk on that site. At first, I thought the adviser was wrong, but it turns out that he was correct and had something new that I had never seen before. Here is the problem. Problem Statement     A thin wall spherical shell with a mass of 0.605 kg and a radius of 0.0402 m is released from rest at the top of an incline. The spherical shell rolls down the incline without slipping. The spherical shell takes 7.49 s to get to the bottom of the incline.
    A solid sphere with mass of 0.127 kg and a radius of 0.1123 m is released from rest at the top of the same incline. The solid sphere rolls down the incline without slipping. How much time does it take for the solid sphere to reach the bottom of the incline.
    Note that ---
Thin spherical shell        I=(2/3)MR^2
Solid sphere        I=(2/5)MR^2 Discussion     The original problem statement is above. Note what is given, and perhaps more importantly, what is not given. In particular, we are not given 1.The time for the solid sphere to reach the bottom -- this is the item to be determined;
2.The angle of the incline;
3.The length of the incline;
4.The local value of g, the acceleration of gravity.     The last three items are things that we might expect to have given in such a problem, but here they are not. This is the major difficulty in this problem, and the solution must find a way to work around this missing information. TwoBallsRollingOnAnIncline.pdf

DrD

DrD

 

Difference between refrigeration and air conditioning

what is the difference between refrigeration and air conditioning? A major difference between refrigeration and air conditioning is the point of supply for the gases. Refrigeration systems have gas installed in a series of tubes. In old refrigerators, this gas was chloro-flouro-carbon, or CFC, but this has harmful effects on people, so refrigerators not contain HFC-134a. HFC-134a is the sole gas used as a coolant in refrigeration systems. Air conditioning systems use built-in chemicals, but also air from the room or rooms being heated. Gases built into air conditioning units cool air that circulates through the unit; the unit then redistributes the cooled air through the room. Air conditioners have circulation systems designed to project cool air away from the units while refrigeration units have circulation systems designed to retain coolant in a confined space. Refrigeration systems circulate cool liquids and gases through a series of tubes and vents. Cool air from within a refrigerator is sucked into a compressor that recycles the gas through the tubes. Air conditioners, while also employing tubes in the coolant system, have fans for the dispersal of air. Unlike refrigeration systems, which keep gases contained to a pre-determined space, air conditioning systems disperse cool air throughout areas of unknown volume. Refrigeration refers to processes that take thermal energy away from a place and gives off that energy to a place with a higher temperature. Naturally, thermal energy flows from a place with a higher temperature to a place with a lower temperature. Therefore, refrigeration runs against the natural heat flow and so it requires work to be done.Refrigerator is a name that we use for devices that are used to keep food at low temperatures. A refrigerator consists of a fluid called refrigerantwhich gets expanded and compressed in a cycle:  

AFZALKHAN

AFZALKHAN

 

La fabricación de piezas por maquinado. Introducción.

Tema I   La fabricación de piezas por maquinado   1.1 Introducción Todo ingeniero debe tener una cultura general integral y, dentro de esta, como es lógico, una cultura de la profesión. Parte de la cultura del ingeniero mecánico consiste en conocer la historia de la ingeniería, y en el caso particular de este blog es importante comenzar por conocer muy brevemente la historia de las máquinas herramienta. Para ello se presentará  más adelante el anexo I, el cual trata sobre la Evolución de las máquinas herramienta [1].     La revolución industrial surgida con la máquina de vapor no hubiera sido posible si no se hubiera construido primero una máquina herramienta capaz de fabricar las piezas fundamentales del invento que sintetizó James Watt: la máquina de vapor. Por cierto, para que Watt llegara a su invento tuvo que haber otros que le precedieron e hicieron sus propios descubrimientos previos en el mismo campo de la energía del vapor de agua a presión, de modo que, como casi siempre ocurre, Watt recopiló esos conocimientos, los organizó, sistematizó, les añadió algo más y construyó, ayudado por Wilkinson y su mandrinadora, la primera máquina de vapor.   Y antes de eso, y después de eso, siempre ha sido así. Sin máquinas herramienta no hay desarrollo posible. Las máquinas herramienta fabrican las piezas que se ven a diario sin que se les preste la debida atención: las del ómnibus que lleva a los pasajeros, las de la termoeléctrica o el grupo electrógeno que produce la electricidad, las del combinado lácteo que procesa la leche, las de los equipos que emplea el médico, las de los equipos que perforan para buscar o bombear petróleo desde las profundidades de la tierra, las del molino del central azucarero. Y como si todo esto fuera poco, las máquinas herramienta fabrican otras máquinas herramienta, se podría decir figuradamente que son las únicas máquinas que garantizan la continuidad de su especie.   Nota: ¿Por qué “máquinas herramienta” y no “máquinas herramientas”? En la lengua castellana los sustantivos formados por dos sustantivos forman el plural solo con el primero de ellos. Así, otros ejemplos pueden ser: profesores guía; palabras clave; fresas madre. No obstante, en ocasiones se puede considerar que el segundo de los dos sustantivos hace función de adjetivo, y entonces sería “máquinas herramientas”. En este blog se prefiere la primera variante.

Sergio Padron

Sergio Padron

 

Check what you know

1. In a steam turbine, the ............ is allowed to rotate? 2. Which valve controls the flow of steam into the turbine?         3. The blades in a ............... turbine are designed so that the pressure below the blade is always higher than the pressure above which causes them to move (or spin) as high velocity fluid flows through them.        4. Where in the steam path is the energy transferred from the steam to the turbine?          5. There is excessive corrosion on the turbine/driven unit train.  The carbon rings have been inspected and are clean, and do not need replacing.  What is the most probable cause of the corrosion?       

EGUAOJE Fredrick

EGUAOJE Fredrick

 

I Thought You Knew

Recently I was interviewed by a Mechanical Engineering student on the importance of communications. I’m approaching 40 years in engineering practice so the examples began to flow and the student’s 15 minute time estimate for the meeting quickly turned into two hours. The meeting itself was a lesson in communications. My awareness of the root cause, that I will describe below, I believe made the information more valuable. The student and I covered many issues on the topic of communications, but the emphasis of his questioning was the difference between communicating with other engineers versus business majors or the sales personnel. The root issue of communications I believe goes deeper and must be identified to minimize the occurrence. There have been many occurrences of communication problems in my life and not all involved engineering. In the past, I viewed each incident as individual and isolated events. Of late, I have come to the conclusion there are common causes. Here I address one that I think is more common than realized. Communication problems are often dismissed as the language, generational, or cultural gaps. These all contribute to the issue but are not the root cause of a large portion of communication problems. If fact, obvious language issues often result in precautions being taken to avoid miscommunications. About 25 years ago I was among a group of technical people gathered for a seminar. While waiting for the speaker, conversations started within the group. Two people were carrying on an energetic conversation for 10-15 minutes consisting of acronyms -- just alphabet soup. Just prior to the speaker arriving, the two having the conversation realized each used a particular acronym for entirely different and unrelated meanings. Yet these two had conversed as if they were on the same subject. Imagine if the conversation had developed into a disagreement to the point of anger, and the instructor arrived before these two were able to define terms. Both would have left thinking badly of the other and maybe worse. In another situation I was just hired into a new position by a former coworker, now manager of a program. He asked that I do something which I immediately did. At our next meeting, the manger began to tell me how I should go about doing the task. I was fuming, to say the least. I was saying to myself, "what was wrong with the way I did it?" I fumed and fumed until I finally asked. The manager looked at me in astonishment and said “You did it? I am not use to anything getting done so fast around here.” One final example. A new VP of engineering admonished me for my poor design and release process causing many problems – no specifics were provided. I was shocked to the point of speechlessness, so I did not immediately ask for specifics that would have revealed the root cause of his dissatisfaction. I assumed my 2 + year old procedure had grown stale and caused problems. I printed a copy of my Design and Release Procedure and read it line for line, looking for something that was no longer correct. After failing to find any problems, I wrote in large red letters “Tell me what I need to change.” The boss was not at his desk, so I left it on his seat. Sometime later, a much more humble boss came to my office and asked if the release date on the procedure was correct – it was, and about 2 years old, so I said yes, and he left. All three examples have the same root cause. In each case one or both parties assumed implicitly that the other party knew something that in reality they did not. Case One: Each party assumed that a particular acronym meant the same to each of them. Case Two: I implicitly assumed the manger would know that I would quickly act on the simple assignment. We had worked together for 6 years prior, on a different program. Case Three: The VP had come to believe implicitly that there was no written process. In his mind, every problem that arose appeared to be a result of not having a process. I assumed he was talking directly to the written document that he did not know existed. As an independent Professional Engineer many of my clients are not engineers. What were once safe assumptions while working in an engineering office with other engineers, I learned quickly was no longer acceptable. Current technologies allow people from around the world to communicate with incredible ease. This has resulted in the root-cause I suggested above to run unchecked. When we write we need to be aware of generational, language, or cultural gaps as well as office jargon*. All can easily result in implicit assumptions of other people’s knowledge that are false. The first professional letter I wrote to be send outside the corporation was brought back to me by my supervisor. He called to my attention that office jargon has no place for a formal business letter. Here again, I was implicitly assuming the terms used every day in our group would be universally understood. It took me 40 years to “connect the dots.”** * Special words or expressions that are used by a particular profession or group and are difficult for others to understand. ** To understand the relationship between different ideas or experiences

JAG Engineering LLC

JAG Engineering LLC

 

Base Acceleration Problem -- #36

Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #36   Base Acceleration Problem Introduction In a recent post (#35) I mentioned that I often participate in another forum called Physics Forums (PF). The problem that I want to discuss here is an elaboration on a problem that recently appeared at PF. I'm going to add a little bit of complexity to the problem (the problme as stated at PF was extremely simple) in order to make a particular point. The system of interest is shown in Figure 1, a body with a single wing attached to one side. You might consider this to be one side of an airplane, or perhaps a stirring paddle used to mix paint. The mass of the wing is M, and the center of mass for the wing is at the point marked CM, a known distance u from the main body. We are told that the main body has an acceleration a sub z in the z-direction, and that the whole system is immersed in a viscous liquid such that the drag force is proportional to the square of the velocity in the z-direction. Our concern is with the connection between the wing and the main body. We need to determine the shear and bending moment on that connection due to z-direction motion.   BaseAccelerationProblem-36.pdf

DrD

DrD

 

Discover the remarkable new spray-on coating that’s self-healing, water-repellent and ultra durable

Discover the remarkable new spray-on coating that’s self-healing, water-repellent and ultra durable Researchers at the University of Michigan have developed a new spray-on coating that’s self-healing, water-repellent and, importantly, hundreds of times more durable than any other coating that’s currently available. Countless hydrophobic coatings have been developed since the 1980s but their inherent lack of toughness has limited the potential applications for such coatings. The durability of the new coating opens the door to potential automotive, aerospace, construction, medical and marine applications. Read more on the Surface Engineering Blog

surface-engineering

surface-engineering

 

Le problème lors de l'utilisation d'un pointeur laser

Il ya un couple de façons de traiter ce problème de ces pointeur laser . Tout d'abord il y a loft casquettes ou d'incendie hottes permettront de maintenir l'isolation d'un coffre-fort distance de l'aménagement tout en permettant à l'air de circuler. Sinon, l'option la plus facile pour un puissant pointeur laser est d'acheter spécialement conçu appareils laser qui peut être complètement couvert avec de l'isolant. La plupart de ces lasers ont tendance à utiliser 532nm vert 650nm pour le rouge, et certains offrent 445 nm pour le bleu. Depuis le vert de la longueur d'onde la plus visible pour l'oeil humain, je soupçonne qu'ils sont en mesure d'utiliser le puissant 5000mW pointeur laser et la réalisation toujours très visible de sortie. Très visible de sortie semble être attraper les yeux des voleurs partout dans le monde! Vous pouvez acheter 5000mW laser de la boutique en ligne. Malheureusement, ils semblent être en vol droit sortie de la propriété d'autrui tout aussi vite! Un site internet consacré à la vente d'une certaine marque de lumières laser a même une section consacrée à des conseils sur la façon de prévenir de votre éclairage d'avoir volé! ( Laser de Réglage )
C'est un pointeur laser bleu 5000mW. Sur la sécurité, les fabricants affirment que, après leurs lasers passer par un diffuseur (une pratique courante) que "d'habitude" réduit chaque faisceau à moins de 1mw. Cependant, avec des milliers de ces qui brille dans le ciel de la nuit vous pouvez voir comment il peut être gênant et même dangereux pour les pilotes. Alors, voici quelques conseils pour la décoration avec des lasers. Assurez-vous que toutes les lumières laser sont pointés directement à la structure que vous souhaitez éclairer. S'assurer que le diffuseur entre le laser et la surface de projection est en bon état et exemptes de fissures ou de copeaux qui pourrait permettre à plus de niveaux dangereux de laser 10000mw pour atteindre les yeux des enfants ou des adultes entre le laser et la surface de projection. Le verrouiller! Prenez votre laser à l'intérieur de chaque soirée ou le fixer sur un morceau de métal qui peut être ancré au sol pour en faire une cible indésirable pour les voleurs.
Les Lasers sont étonnants, mais "le bon outil pour le bon travail" est quelque chose que nous croyons en trop! Peut-être aller avec classique stylos laser, cette année, à obtenir que le classique mais beau Noël à regarder et se sentir. Ces 10000mW pointeur laser pas cher sont la norme dans la plupart des maisons et sont l'option la plus sûre lors du choix d'un puissant objectif de 10000mW pointeur laser puissant. La réponse courte est que, dans la plupart des cas, vous ne peut pas juste couvrir les lasers avec de l'isolant. Ceux-ci donnent à la fois l'assurance de la protection contre l'incendie et aussi la réduction des coûts caractéristique de pouvoir être couverts avec le laser de choses. https://www.yonlife.com/index.php/blog/197/quelques-conseils-utiles-pour-lutilisation-de-pointeurs-laser/ https://hanshin-now.com/blog/page.php?idx=10013574&post_idx_sel=10067219

boomeonen

boomeonen

 

Good News -- Bad News -- Rolling Disk in a Rolling Ring

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, # 35
      Machinery Dynamics Research, 2017
Good News --- Bad News
Rolling Disk in a Rolling Ring      Introduction     Well, it looks like Mechanics Corner is back, at least in terms of an occasional post. It will probably be less frequent than previously, but there are just too many interesting things to talk about to remain entirely silent! The title for this post may leave you wondering what is the Good News, and what is the Bad News? Why is there both? Well, let me tell you about it ... GoodNews-BadNews-DiskInRing.pdf

DrD

DrD

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