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  • Engineer & consultants Corner

    Though I am a mechanical/Civil/Structural Engineer, but what the heck. Its not that I have to pay some membership fee
    People are afraid of what they don't understand

  • #2
    yeah...

    PS: shouldn't we have option here to start different TOPICS within a group? otherwise it's just like a thread, with access for group members only.
    A question that sometimes drives me hazy: am I or are the others crazy?

    Comment


    • #3
      You want to have a mini-forum of your own .. haan?
      People are afraid of what they don't understand

      Comment


      • #4
        pssst it was supposed to be our little secret.
        A question that sometimes drives me hazy: am I or are the others crazy?

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        • #5
          Design blunders

          Therac-25
          (Therac-25 was used in the treatment of cancer. Its purpose was to provide radiation to a specific part of the body and hopefully kill the malignant tumor. The Therac-25 was the third system created under the Therac name by the Atomic Energy of Canada Limited (AECL). The AECL is most famous in Canada for their creation of the CANDU reactors which are world renowned. A Therac-6 and Therac-20 were both used in the treatment of cancer. The number that goes along with the word Therac stands for the maximum amount of mega electron volts (MeV) the machine can dispense. It was believed that the new Therac-25 was much more efficient than Therac-6 and Therac-20. The overall size of the machine was reduced and still allowed for two modes; photon mode and electron mode. A tungsten shield was in place for the X-ray mode and removed for the electron mode )

          The accidents occurred when the high-power electron beam was activated instead of the intended low power beam, and without the beam spreader plate rotated into place. The machine's software did not detect that this had occurred, and therefore did not prevent the patient from receiving a potentially lethal dose of radiation. The high-powered X-ray beam struck the patients with approximately 100 times the intended dose of radiation, causing a feeling described by patient Ray Cox as "an intense electric shock". It caused him to scream and run out of the treatment room. Several days later, radiation burns appeared and the patients showed the symptoms of radiation poisoning. In three cases, the injured patients died later from radiation poisoning.


          causes


          AECL did not have the software code independently reviewed.
          AECL did not consider the design of the software during its assessment of how the machine might produce the desired results and what failure modes existed. These form parts of the general techniques known as reliability modeling and risk management.
          The system noticed that something was wrong and halted the X-ray beam, but merely displayed the word "MALFUNCTION" followed by a number from 1 to 64. The user manual did not explain or even address the error codes, so the operator pressed the P key to override the warning and proceed anyway.
          AECL personnel initially did not believe complaints.


          The researchers also found several engineering issues:

          The failure only occurred when a particular nonstandard sequence of keystrokes was entered on the VT-100 terminal which controlled the PDP-11 computer: an "X" to (erroneously) select 25,000 EV mode followed by "cursor up", "E" to (correctly) select 200 EV mode, then "Enter". This sequence of keystrokes was improbable, and so the problem did not occur very often and went unnoticed for a long time.

          The design did not have any hardware interlocks to prevent the electron-beam from operating in its high-energy mode without the target in place.

          The engineer had reused software from older models. These models had hardware interlocks that masked their software defects. Those hardware safeties had no way of reporting that they had been triggered, so there was no indication of the existence of faulty software commands.

          The hardware provided no way for the software to verify that sensors were working correctly ( open-loop controller). The table-position system was the first implicated in Therac-25's failures; the manufacturer revised it with redundant switches to cross-check their operation.

          The equipment control task did not properly synchronize with the operator interface task, so that race conditions occurred if the operator changed the setup too quickly.[clarify] This was evidently missed during testing, since it took some practice before operators were able to work quickly enough for the problem to occur.

          The software set a flag variable by incrementing it. Occasionally an arithmetic overflow occurred, causing the software to bypass safety checks.




          what measures you take to make sure that your team or YOU don't make such mistakes?
          A question that sometimes drives me hazy: am I or are the others crazy?

          Comment


          • #6
            In 2007, a company named Pure Digital released the Flip Video camera. It has quickly become the best selling video camera on Amazon.com. It has captured 13% of the video camera market in just a few months.

            How does a product from an unheard-of company come to challenge an industry dominated by established big players, such as Sony, Panasonic, and Canon? It's simple. Create a better experience.

            JVC and Sony manufactured the first camcorders in 1982, making low-cost video creation a possibility. Before the camcorder, you needed two devices to record: a video camera and a VCR. These combined devices opened up a new market. It was simple for anyone to point the camera, press the record button, and make a movie.

            Over the years, the manufacturers have competed by adding new features, such as digital recording capabilities, longer battery life, and more compact form factors. Today's cameras can do a lot, but they are very complicated to operate. They have a bazillion buttons and a slew of settings, few of which users understand and only get in the way of using it.

            Along Came the Flip
            With the Flip Video camera, Pure Digital's designers have done something very interesting: they've reduced the functionality to just the useful subset of features. The camera has a simple set of buttons, just enough to control the operation. The built-in software works fast and only has the critical features.

            The designers obviously thought about what is necessary to have a great camera experience and did the unthinkable: they trimmed every other bell and whistle out of the design. What's left is a barebones product that does exactly what most users want and need.

            Let's look at some of the lessons we can learn from the Flip's design:

            Lesson #1: Minimalist Controls
            The latest Sony camcorders feature a Home Menu button, to bring you quickly to the camera's home menu. Arrow keys let you navigate quickly to the dozens of menu options and settings you'll need to operate the camera. These are just a few of the dozen or so buttons on the outside of the unit, needed to control the variety of available features.

            The Flip doesn't have a Home Menu button. That's because it doesn't have a Home Menu (or any other menus).

            Instead, the buttons are simple. There's a power button, a record button, a play button, and a delete button. There's a +/- toggle for adjusting the zoom when recording, which doubles as the volume control when playing back. And there's a left/right toggle for scrolling through the videos you've recorded, to select one for playing or deleting.

            That's it: four buttons and two toggle sets. It's a very simple and elegant control system. The user can record movies, scroll through them, play them back, and delete them.

            When we think about our designs, we want to ask ourselves: What are the least number of controls we can get away with? Can we get down to the core functionality with only a few buttons? Would that be enough for a great experience?

            Lesson #2: Removing worries
            The designer's have also simplified one of the biggest concerns of budding videographers: will their battery last? Battery life is the bane of modern technology. For a device, such as a camcorder, the user has to remember to charge the battery at the least convenient moment: when they aren't thinking about it back at their home or hotel room. If they forget, they'll end up with a dead camera and no way to capture an exciting moment.

            Worries like this become a burden on the user. It's one more thing for them to keep track of. People who don't want that burden quickly end up foregoing the product, since they can't count on it to be available.

            The Flip uses AA batteries available in any corner store and makes swapping easy. The user no longer needs to worry about whether they remembered to recharge their camera before they left the house. Just throw a couple of extra batteries in your bag and you're covered. The burden is removed from the users, making it more likely they'll carry the camera around and use it when the right moment arises.

            As we create our designs, we want to think about the worries our users have. Is there a way to rethink our design to eliminate their concerns?

            Lesson #3: Eliminate Value-less Steps

            In today's world, we've become accustomed to installing PC software on our computers. Everything needs new software to read the data and control it, so we're used to popping in a disc and slogging through a multi-step installation process. If we're lucky, the installation process will go quickly and not fill up our drives with unnecessary applications. If we're extra lucky, we won't change computers and need to reinstall the software, now from a disc we've long since "put away for safe keeping" and can no longer find.

            While they're accustomed to it, users don't receive any value from this process. Users don't enjoy installing software. At best, it happens without much notice. At worst, it asks troublesome questions and reports issues the user is unprepared to handle. If we eliminate this step, nobody will miss it.

            That's what the Flip's designers did. They put the software right on the camera. When you plug the camera into your computer, using a pop-out USB arm, it automatically loads the camera's software. (On a Mac, you have to click to open the application, while on the PC it automatically starts up.)

            By eliminating the process of loading software from a disc, the designers also allow the camera to become more useful. Users, not near their own computer, can still load up the movies on a nearby PC and enjoy them. This is another example of an improved experience with a simpler design.

            Lesson #4: Integrate the Next Step
            The previous generation of camcorders declared their job done when the movies were on the user's hard disk. Some provided editing software to enhance the videos. Implicit in the design was the decision to leave the users to figure out on their own what they wanted to do with their movies.

            The Flip's designers didn't do that. Their design takes into account the next step: sharing the movie.

            The built-in software has simple functions to email movies for private sharing. For people who want to be a little more public, they provide an easy way to upload the movie directly to YouTube or AOL Video. As with the rest of the design, they've made these processes as simple as possible, so users don't waste effort on value-less steps.

            When someone finishes with your product or service, what is the next thing they do? Is there a way to build that next step into your design?

            Doing More with Less
            The Flip isn't the first to do more with less. When Apple introduced the iPod, it greatly simplified the process of loading and controlling the selection of music on an MP3 player. When Microsoft introduced Word for Windows, it provided a much simpler method to do word processing, making the feature-laden market leader, Word Perfect, obsolete.

            We've noticed there becomes a point where the features in a product set no longer help the user, instead becoming a hindrance to its usage. Video camcorders reached that point, opening an opportunity for someone to come in with a better product that has only those essential features. By studying how the Flip takes advantage of this opportunity, we can all learn how to make better designs by doing more with less.
            A question that sometimes drives me hazy: am I or are the others crazy?

            Comment


            • #7
              I don't wana read anything for now ... but i'll do come back and read it through ...

              Good Job KK
              -- Nauman --

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              • #8
                I am a Mechanical Engineer working in Oil&Gas Industry. If anyone requires information contact me. Specially in Well Cementing, Coiled Tubing, Downhole tools and Wellheads.
                To repeat what others have said, requires education, to challenge it, requires brains.
                - Mary Pettibone Poole

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                • #9
                  welcome to the group LB.
                  A question that sometimes drives me hazy: am I or are the others crazy?

                  Comment


                  • #10
                    I am electrical engineer working in design of Power and distribution transformers. My designed transformer was the largest which was designed and manufactured in pakistan.
                    Now one of my junior broke the record

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