| This week’s blog will continue our on-again off-again discussion on challenges faced by today’s engineers. Our focus today will be on different approaches taken towards education.
You don’t need to be a history buff to know that the American educational system is based on the “farm model” and the needs of yesteryear’s mostly rural culture. Summers were devoted to crops, not book learning, and the children were put to work in the fields to help support the family’s farm. Although this model is clearly antiquated, it has held on to the present time, and here we must acknowledge the strength of the teachers’ unions and their protest of a longer work year. Our family has several who name teaching as their profession, and I have heard each of them exclaim in anger at the possibility of working year-round. “I got into this in large part for the summers off!” is their battle cry. Their barely nine-month work year is something they have come to expect and unions fight vigorously to uphold.
Now let’s look at the Asian school system. And yes, they do spend more time in school than American students. There is hardly an individual who would not exhort the overall superiority of the Asian systems and their students, and later workers. I’ve heard many Anglo’s declare, “They’re just plain smarter.” But what is behind their smarts? Is it as simple a case as possessing superior genes? Although the Missing Link has yet to be discovered, surely we all hale from the same good human stock, and wouldn’t proclaiming otherwise open one up to be declared racist?
Here’s an example I feel is analogous to our discussion. One of my daughters is a gifted violinist, but like most children she hated to practice, leading her teacher to get on his soap box and preach to her about the importance of it. “You know, my best students aren’t the ones who are the most gifted, they’re the ones that work the hardest!” He went on to explain to her– as her thoughts strayed to the squirrel scampering across his roof– that although she, because of her inherent talent, didn’t have to practice as much as less talented students, she still needed to practice.
And therein lies the rub. It’s true for the violin, and it’s equally true for other forms of learning, as it is with most things in life. You’ve got to work for it.
I recently stumbled upon an interesting blog written by an Asian college student, wherein she makes an honest comparison of the Asian versus American educational system and its students. Rather than reproduce it here, I highly recommend you take a moment to look at it.
Some highlights of the Malaysian system of which she is a product include: mandatory after school tutorial sessions and incredible amounts of homework, or to put it in her words, “So much so that you will die from exhaustion at young age,” whereas Americans “seldom have homework.” Asian classrooms also support up to twice as many students per room, which of course flies in the face of American teachers’ often-heard demand that classes be made smaller to ensure a better education.
But perhaps the most striking attribute to me was the fact that attitudes on behalf of the typical American student towards their teachers and learning in particular are typically characterized as “whatever.” In fact, American students have no problem openly shunning teachers they do not like, something which is strictly prohibited in the Malaysian schools.
Hmm, could it really all boil down to good attitudes and hard work?
As for the differences between the sexes, that seems to be a universal, as the blog’s author states, “Girls talk about boys, fashion and makeup; boys talk about cars and girls.” She did not make note of the fact that premarital sex is taboo in most Asian cultures, effectively eliminating a very disruptive element that is present in young Americans’ lives.
This young woman’s blog is best viewed using Firefox, which does not break up the table she has painstakingly built: http://toc-py.blogspot.com/2009/02/difference-between-asian-school-and.html
Archive for September, 2010
| My dear daughter is at times forgetful? On one occasion in particular she forgot that she had placed a can of pop in the freezer to speed-chill it. Later that evening when my wife went to get something out of the freezer she was not too pleasantly surprised to find that a black, semi-solid mess had covered most of the freezer’s interior. You got it. The pop can exploded, shooting its pressurized contents all over the place.
You may not have thought much about it before, but pressurized containers are all around us, from pop to aerosol cans, car tires, water heaters, and liquid petroleum gas tanks. Pressurized containers are even more obvious in industrial settings such as oil refineries, power plants, and factories.
As its name would imply, pressurized containers, or pressure vessels, are under a lot of pressure, as such, they are no stronger than their weakest point. Whether that point be its sides, as in the case of my daughter’s ruptured pop can, or its ends, weld joints, rivets, or any of the other components that are included in the vessel’s construction. As with anything, the integrity of something is only as good as its weakest part. In an industrial setting, this fact, depending on the vessel’s contents and the severity of the failure, can prove deadly.
So what causes pressure in a vessel to get too high? Many factors could be at play, from a safety valve which fails to do its job of relieving excess pressure, to absence of this feature entirely. Many of us learned in grade school science class that when a substance heats up, its molecules vibrate, causing its atoms to want to distance themselves from each other. If this vibrating is taking place within a closed vessel, heated atoms will be prevented from carrying out their desired separation. The result is pressure increases, and along with it the propensity for the weakest points to fail. Whether it’s a slow ooze, high spirited fizz, or outright explosion, the end result is generally the same – it’s a big mess.
The behavior of gases in pressurized vessels exposed to heat can be summed up by the Boyle-Charles Law, named after the 17th Century scientist, Robert Boyle, and a 19th Century scientist named Jacques Charles. Both were pioneers in their study of how gases behave under various conditions. The science behind their observations can be summarized into a neat little formula, known as the Boyle-Charles Law for sealed pressure vessels. It looks like this:
P1÷T1 = P2÷T2
where P is absolute pressure and T is absolute temperature.
What is absolute pressure? It’s the pressure that’s measured when you add the pressure of the air that we live in, our atmosphere, which has been measured to be 14.7 PSI, or pounds per square inch, to whatever pressure you are reading on a pressure gauge. This ultimate pressure is measured at pounds per square inch absolute, or PSIA.
Now what is meant by absolute temperature is calculated a little differently. It basically means that you add 460 degrees to the temperature reading on a thermometer. This 460 degrees acts as a kind of fudge factor to keep equations that concern themselves with temperature at or below 0°F to work. The result is said to be in degrees Rankine, and it is denoted by °R.
So why do we need this fudge factor? Here’s an example. In the equation above, if temperature is 0°F, then you would be dividing the pressure by zero in the equation above. That’s a no-no in mathematics. Try dividing any number by zero on your calculator and see what I mean.
Okay, for those of you who are not mathematically inclined that may not have been very clear. Let’s try a different approach.
Probably the best way to show you how the Boyle-Charles Law works is by the following example. Suppose you have a sealed container filled with pressurized gas. The gas is at a temperature of 70°F, and a pressure gauge on the vessel reads 100 PSI. So this condition of pressure and temperature goes into the Boyle-Charles Law equation as P1 = (100 PSI + 14.7 PSI) = 114.7 PSIA and T1 = (70°F + 460) = 530°R.
Now let’s introduce a complicating factor. Suppose you leave the container in your car on a hot day. The gas in the container increases in temperature to 150°F. Okay, so this temperature would go into the Boyle-Charles Law equation as T2 = (150°F + 460) = 610°R. Now, suppose the pressure gauge was damaged and the needle fell off. What would the gas pressure in the container be at this temperature? Let’s use the Boyle-Charles Law equation and a little algebra to find out:
P1÷T1 = P2÷T2
114.7 PSIA ÷ 530°R = P2÷ 610°R
P2 = (114.7 PSIA ÷ 530°R) × 610°R
P2 = 132 PSIA = 117.3 PSI
What this means is that if the weakest link in a container was made to withstand no more than 110 PSI of pressure, and the pressure inside the vessel in our case has risen to 117.3 PSI, the integrity of our container will be compromised. We’ll return to our vehicle and find a big mess.
We’ll continue our discussion of pressure vessels, leaks, and how they can be prevented in the future.
| Did you ever hear the saying, “garbage in, garbage out?” Perhaps you’ve used it yourself at times, as when your teenager insists on writing their 20-page term paper the night before it’s due. Parents, having the benefit of decades of life experience, know that the outcome of a last ditch effort of this type will most likely not turn out well.
This wisdom also applies particularly well to the medical manufacturing process. The FDA is like the parent in this instance, mandating that Design Transfer Procedures be in place to avert the types of disasters which might ensue if the “garbage” philosophy were carried out. Meant to ensure that medical device designs are correctly translated into production specifications for manufacturing, Design Transfer Procedures keep those directly involved with the manufacturing process in check. It is absolutely vital that those involved in manufacturing receive accurate and complete information.
Imagine what would happen if an engineer provided a manufacturer with faulty design information. Components could be made to the wrong specifications or of a material that proves toxic to the application. These errors range in negative effect from being costly in terms of dollars wasted to perhaps costing someone their life.
A Design Transfer Procedure would ensure that a variety of mishaps do not occur during the transfer process. The procedure is typically overseen by the medical device company’s management. For example, a Design Transfer Procedure would lay out responsibilities of supervisors and managers to make sure the latest revision of electrical schematics, bills of materials, Gerber files, and quality testing procedures are received by the manufacturer of a device’s printed circuit boards. It’s important that the order is received in a timely manner so as not to hold up the manufacturing process. However, it’s much more important that the printed circuit board is made properly, the correct electrical components are placed on it in the correct orientation, and it is tested to make sure it doesn’t malfunction after assembly.
Design Change Procedures basically ensure that when changes are necessary, the medical device company follows all the procedures for Design and Development Planning, Design Input, Design Output, Design Review, Design Verification, and Design Validation. Once the changes are reviewed, validated, verified, and approved, they can be incorporated into the original device design. This is where the Design Change Procedure must dovetail with the Design Transfer Procedure to make sure the correct information is provided to the company’s management staff in the procurement, manufacturing, product service, and warehouse departments. This is to make sure they can keep component vendors on track with the changes, maintain sufficient inventory of the changed components, put the right components in the device during assembly, and properly support repair technicians in the field.
Yet another aspect of Design Controls promulgated by the FDA comes into play with the establishment of procedures for maintaining a Design History File (DHF). This DHF contains all documentation created during the life cycle of the project, meaning, movement from creation to completion and on into market introduction, sometimes beyond. DHF Procedure sets up protocols for collection and organization of information about the medical device design, starting with design documentation and covering the gamut from design changes, to validation testing, to design verification, and on to design review. All this is done to ensure that the initial product design was developed in accordance with the original design plan and overall product design requirements.
| Recently my wife was on a quest to make the perfect pound cake, but before she put butter to flour she did her research. What’s the best butter? Best flour? Eventually she came up with a recipe she felt would prove to be the Queen of all pound cakes. After the recipe came reviews by her test panel, or family members, including myself. Questions were asked, such as, When you first bite into a pound cake, do you want to be aware of vanilla or lemon? It was only then that she would begin to combine ingredients for the final mouth watering product. Very much this same procedure is used when coming up with a new medical device.
Previously we’ve discussed FDA requirements for medical devices as they concern design controls with respect to design and development planning and design input procedures. We’ll now focus on requirements for Design Output, Design Verification, and Design Review Procedures.
Design Output and Design Verification Procedures go hand in hand to ensure that design output is properly documented, organized, reviewed, and evaluated in light of design input. What this means is that medical device companies must scrutinize and evaluate what is going into the design process, then make a comparison to what is coming out. The design is ultimately verified when all requirements for the medical device as previously set out have been met.
“Design output” is just another name for work product after major phases of the design project are completed, such as when my wife determined which butter would produce the best pound cake. Design output typically takes the form of specifications, notes, calculations, computer programs, mechanical drawings, electrical schematics, printed circuit board (PCB) layouts, bills of materials (BOM), mockups, prototypes, test data, and test reports. These are then utilized by people outside engineering circles to manufacture components and assemble them into a final product.
Design Review Procedures ensure that the design output is evaluated by others not directly involved in or responsible for the design work product, much as when family members served as a reviewing committee for my wife’s inquiries into taste preferences in pound cake. Sometimes she’d even ask a friend or neighbor to put their two cents in, and companies, too, will at times go outside and hire consultants to perform this function. By so doing, unbiased opinions are sought out, in the hopes that this fresh set of eyes will be more likely to spot errors, omissions, and misinterpretations that could prove disastrous if put into play. Design reviews are typically conducted after each major phase of a design project is complete.
Just as a recipe that looks good on paper may not necessarily taste good, a device design will often seem to work perfectly on paper, then prove otherwise when its manufacture begins or it’s used in the field. Ideally bugs are worked out before the product hits production and, later, the marketplace. Design Validation Procedures make use of prototypes for testing and careful evaluation under simulated or actual use conditions. Does the design safely meet requirements for intended use? Does it conform with industry standards? If not, there’ll be a lot of wasted “dough” going into the trash — pun intended!
Next time we’ll explore FDA requirements for Design Transfer and Design Changes. We’ll also talk about procedures for Design History Files.