As you may already know, designing products and systems to meet the needs of customers and end-users is perhaps the most important job of an engineer. Fast Company released an article a few months ago describing a particular bridge that was designed to solve a peculiar vehicular traffic problem between China and Hong Kong – something that you don’t hear about everyday.

As the article describes, the problem at hand is that Hong Kong drivers drive on the left side of the road, while in China people drive on the right side of the road. So, what do you do about drivers crossing the border and needing to switch which side of the road they drive on? Naturally, smooth and continuous paths are more comfortable to drive on than paths consisting of sharp turns and stops, and the proposed Flipper Bridge addresses all of these needs brilliantly and elegantly in a neat figure 8 shape. Drivers that leave China on the right side of the road will enter Hong Kong on the left side of the road after driving across this bridge, perhaps hardly even noticing, and vice versa. While taking in the beautiful watery scenery, might we add.

Of course, just like many engineering designs, the Flipper Bridge is without shortcomings, as some people have pointed out. Some examples from the article and corresponding comments include questioning the safety of driving on the lower section of the bridge in the midst of high waves and mean weather in the vicinity, as well as making drivers aware that they are crossing into a region in which drivers drive on the opposite side of the road from where the drivers originated from. The seamless transition from right side to left side, or vice versa, can be dangerous to unsuspecting drivers.

Anyway, the images in the article depict the design quite well, especially the smooth curves and the grand figure 8 design. Check them out!

When you pluck a guitar string, you are essentially inducing what is known as a standing wave on the string. The plucked string is fixed at both ends, while the middle oscillates up and down very quickly, resulting in what looks like a standing oval along the string. Therefore, the term “standing wave” is aptly and intuitively named. In this particular case where the standing wave looks like one oval (not two or three, etc.), the wavelength of the standing wave is simply twice the length of the “oval.”

Standing waves on guitar strings look sort of like single ovals.

To understand how you can get different tones of sound from one guitar string, we need to understand how sound and wavelength of the standing wave are related. One basic relation in mechanics is that speed equals the product of wavelength and frequency. We can apply that to sound: the speed of sound equals the wavelength times the frequency of oscillations of the vibrating object. The vibrating object in this case is the plucked guitar string. We can assume that the speed of sound in air is constant (the speed of sound is different in other media, such as water), so essentially the wavelength and frequency of the standing waves are inversely proportional – a short wavelength leads to a high frequency, and vice versa.

Now, where does the actual sound that we hear come in? The induced frequency from the standing wave’s wavelength gives rise to the sound that we hear. As long as there is an active wave on the guitar string (meaning the string is moving due to plucking and not just sitting there doing nothing), there is an associated wavelength and therefore a frequency as well. High-pitched sounds have high frequencies, and low-pitched sounds have low frequencies. Therefore, to get a high-pitched high-frequency sound from a guitar string, you want to fix one end of the string with your finger so that the wavelength is short, and this happens to be the part of the fingerboard closest to where your plucking fingers are. Using the same logic, you can get a variety of pitches by fixing the string’s end at various locations while plucking, which is exactly what guitar players do.

This is how you get different pitches of sound from one guitar string. There are other interesting aspects of musical instrument design, such as why different guitar strings have different pitches themselves, and how wind instruments (such as flutes) work.

Brooklyn Bridge Gothic Arches

Being a (slightly) proud New York City native, I couldn’t pass up this opportunity to share video that I watched this past Independence Day weekend. It’s an episode of the show “Man Made” titled Bridges of NYC (via Hulu). In its history, New York City has held consecutive world records for the longest bridge, and not just once too. From the times of New Amsterdam, we had the Brooklyn Bridge, which was the longest bridge of its time, followed by the Williamsburg Bridge, which was the longest of its time, to the Queensboro Bridge, to the George Washington Bridge, etc. Each has its specialty and each has its interesting history.

If you like bridges or if you live in New York City, this is a must see. Watch the video here on Hulu, or below. (It’s about 45 minutes long.)

My personal favorite is the original one, the Brooklyn Bridge. The photo above was taken from my personal collection. The bridge has far more character than any of the others, I’d say. Which one do you like most, in terms of looks, or design, or whatever? Leave a note in the comments!

Fins are efficient for heat transfer purposes, like in this computer.

What makes fins so ubiquitous in heat transfer applications? First, it is helpful to understand that the amount of heat an object can transfer is directly related to the surface area of the object that is in contact with ambient surroundings, such as air here on Earth. Two other factors that affect heat transfer are temperature difference and type of material (some materials conduct heat better than others: think metal versus cloth, like an oven mitt). So, imagine that we have a flat sheet of metal and a small cube of the same metal. Both are at the same temperature, have the same volume (consist of the same amount of metal), and are in the same room (so the ambient air temperature is the same for both). If the sheet has twice as much exposed surface area to ambient air as compared to the small cube, then the sheet has the capability of transferring twice as much heat as the cube, even though they have the same physical volume in our example.

Second, businesses like to get as much “bang for the buck,” just like consumers. This means a company that needs to design a cooling mechanism for a computer processor would want to maximize cooling ability while minimizing cost for raw materials in their mechanism. Trying to increase the amount of heat transfer by increasing the temperature difference (such as actively cooling the surrounding air) or using a better heat-conducting metal can drive up costs significantly. This leaves the option of increasing exposed surface area for increasing heat transferring capability, and this is where fins come into play.

Fins essentially increase the surface area of an object in need of cooling, which increases the rate at which heat is transferred away from it. By making fins long and slender, like what we see on chipsets inside computers, businesses attain their desired heat transfer capability while keeping the amount of raw material required at a minimum. In the end, we have a win-win situation by using fins: businesses cut down on costs while consumers have devices that don’t overheat and fail.

(Image from Wikipedia.)

Airports already bulldoze bird nests and send dogs to chase off flocks, but engineers are trying new technologies to scare away birds in flight, including using landing lights as strobe lights, the vice chairman of the National Transportation Safety Board said Monday.

The official, Robert L. Sumwalt, spoke on the eve of Tuesday’s safety board hearing on the crash of US Airways Flight 1549, which took Canada geese into both engines shortly after takeoff from La Guardia Airport on Jan. 15 and glided into the Hudson. All 155 people on board survived.

Mr. Sumwalt said turning the landing lights into strobe lights could make a plane, closing in on the birds at more than 100 miles an hour, more conspicuous to them. But, he said, that is only one solution that should be investigated.

“Maybe there’s some other technology out there, a radar that some innovative company can come up with to zap the birds out of the way,” Mr. Sumwalt said in an interview. Some pilots believe that birds try to avoid emissions from the planes’ on-board weather radar, he said, and “we need to find out, is that an urban legend or is there some truth to that?”

“We need to be innovative when we’re looking for solutions here,” he said.

US Airways Flight 1549 had these monstrous birds fly into its engines.

Clearly, people have thought about solutions to flying aircraft near birds. As mentioned in the article, people already attempt to control the bird population near airports by destroying their nearby habitats. However, in the case of the Canada geese in US Airways Flight 1549, habitat destruction would not be practical because Canada geese are migratory in nature, which means they do not have a particular habitat to destroy (wildlife conservation advocates are probably shaking their heads in disgust at that).

Also according to the article, there are regulations in place for aircraft engine design that considers birds flying into them:

Another area to be covered in the three days of safety board hearings is how engine standards are set. There is a rule for how big a bird an engine must be able to take in and spit out while continuing to produce thrust, and another for the maximum size it must be able to take in without breaking up and throwing off dangerous shrapnel. The hearings will look into whether engines can be built to withstand birds as big as the Canada goose. Mr. Sumwalt said the answer was probably not.

If only there was a non-destructive solution to birds disrupting aircraft (such as a scarecrow for all types of birds) …

(Image from Wikipedia)