a compendium of tech stuff

Jul 31, 2009

On 8:26 PM by Lalith Varun   3 comments





A muffler is a device for reducing the amount of noise emitted by a machine. If you've ever heard a car engine running without a muffler, you know what a huge difference a muffler can make to the noise level. Mufflers are typically installed along the exhaust pipe as part of the exhaust system of an internal combustion engine (of a vehicle, or stationary) to reduce its exhaust noise. The muffler accomplishes this with a resonating chamber, which is specifically tuned to cause destructive interference, where opposite sound waves cancel each other out. Inside a muffler, you'll find a deceptively simple set of tubes with some holes in them. These tubes and chambers are actuall­y as finely tuned as a musical instrument. They are designed to reflect the sound waves produced by the engine in such a way that they partially cancel themselves out.Take a look at the inside of the above muffler:

The exhaust gases and the sound waves enter through the center tube. They bounce off the back wall of the muffler and are reflected through a hole into the main body of the muffler. They pass through a set of holes into another chamber, where they turn and go out the last pipe and leave the muffler.

A chamber called a resonator is connected to the first chamber by a hole. The resonator contains a specific volume of air and has a specific length that is calculated to produce a wave that cancels out a certain frequency of sound. When a wave hits the hole, part of it continues into the chamber and part of it is reflected. The wave travels through the chamber, hits the back wall of the muffler and bounces back out of the hole. The length of this chamber is calculated so that this wave leaves the resonator chamber just after the next wave reflects off the outside of the chamber.

Mufflers that reduced backpressure relative to earlier models became increasingly available in the late 20th century, and resulted in increased engine efficiency, performance, power output, and simultaneously decreased overall wear and tear on the engines' components, as well as sound to levels in compliance with the law. Thus the usage of mufflers in the exhaust system of engines is advisable which has so many merits.

Jul 28, 2009

On 8:27 PM by Lalith Varun   No comments

Photography is undoubtedly one of the most important inven­tions in history -- it has truly transformed how people conceive of the world. Now we can "see" all sorts of things that are actually many miles -- and years -- away from us. Photography lets us capture moments in time and preserve them for years to come.

Digital photography has many advantages over traditional film photography. Digital photos are convenient, allow you to see the results instantly, don't require the costs of film and developing, and are suitable for software editing and uploading to the Internet.

The digital camera is one of ­the most remarkable invention in the field of photography and it is truly different from its predecessors. Conventional cameras depend entirely on chemical and mechanical processes -- you don't even need electricity to operate them. On the other h­and, all digital cameras have a built-in computer, and all of them record images electronically.

In this article, we'll find out exactly what's going on inside these amazing digital-age devices.­

HOW IS THE IMAGE STORED? (or what is a megapixel?)

When you take a picture with a digital camera the light strikes a digital sensor array, instead of a piece of film. These digital sensors are computer "chips" with names like CCD, CMOS, Foveon, or others. They take the place of a piece of film that must be moved across the focal plane of the camera. The digital sensor is made of millions of tiny sensor points called "pixels," which is short for "picture elements." They are laid out in an array with rows and columns, like in a computer spreadsheet or wall calendar. For instance, my camera has an array of sensors in its CCD that is 3008 horizontally, and 2000 pixels vertically (3008x2000). If you do a simple mathematical formula on the pixel array size you will come up with the "Megapixel" rating of the camera. This is the number that most manufacturers use to sell the camera. The simple formula 3008x2000 = 6,016,000 shows that my camera has over six million pixels, or is a "six megapixel" camera.


Think of megapixels as millions of dots of light that are being stored for each picture. The more dots of light there are, the higher the resolution of the image. More pixel dots = bigger pictures. Usually, the more megapixels the better! It takes a lot of megapixels to make prints on photo paper, so it would be best to get a camera with as many megapixels as you can afford.

When the image strikes the sensor, it gets all those megapixels excited. First the image goes through color filters above the individual sensors. The sensor converts the image from light waves into an analog electrical signal. The analog signal is then run through an analog to digital converter (A-D Converter), where it becomes a pure digital signal. Then it is again put through a series of electronic filters that adjust the white balance, color, and aliasing of the image. Next a compression cycle makes the image as small as possible by dumping unnecessary pixels, for more efficient storage. Now the camera has a nice compressed, filtered, digital signal representing your image.

The image is then transferred into a temporary storage area inside the camera called "buffer memory," or simply the "buffer." When the buffer is full, the image is written out to your storage media, such as a memory card. The buffer size in the camera is an important thing. It tells how many images you can take in quick succession. If you have a tiny buffer in your camera, you will have to wait a bit after you take several images.

In fact, the main thing that drives the cost up on digital cameras is the number of megapixels, and the size of the memory buffer. Most cameras have a reasonable amount of both, so you needn't worry. Even if you can only afford a very inexpensive digital camera, you will still have nice images, you just might be limited in their maximum size on photo paper, and will have to wait a bit when taking images quickly. Almost any digital camera is capable of taking pictures for display on the Internet, or for sending across the Internet as email. Images on the Internet are very low resolution -- about 72 to 100 dots per inch -- so any quality digital camera will be capable of making beautiful images for display there.


WHAT ABOUT PRINTING MY DIGITAL IMAGES?

To make a nice 4x6 inch print will require a camera of at least two megapixels. To go up to an 8x10, or 11x14 inches, it is best to have a four to six megapixel camera. Of course, an image processor can make the smaller megapixel cameras do larger prints by stretching the image a bit. This is a process called "interpolation," which simply means adding extra dots of light (pixels) to make the image larger. Image quality degrades a bit when this happens, but is generally acceptable. So a two-megapixel camera could make a print up to 8x10 if needed. A four or six megapixel camera will do an even sharper image, and can make nice images printed all the way up to at least 11x14 inches.

One nice feature that has not yet arrived on film cameras, other than Polaroids, is the freedom to immediately view the image you just took. Since even low-cost digital cameras have small video monitors on the back of the camera, you are able to see if that image is a keeper, or should be deleted. Think of how much money you will save by only printing the images you like, instead of taking a bunch of film images, keeping the best ones, and shoving the rest in a shoebox in the closet. Digital cameras cost more up front, but cost less over the long run to use. You can afford to take many more pictures than you ever could before using a digital camera.

Jul 12, 2009

On 11:01 AM by Lalith Varun   No comments



A CAPTCHA is a program that can generate and grade tests that humans can pass but current computer programs cannot. For example, humans can read distorted text as the one shown above, but current computer programs can't.

The term CAPTCHA (for Completely Automated Public Turing Test To Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University. At the time, they developed the first CAPTCHA to be used by Yahoo. They're also known as a type of Human Interaction Proof (HIP).

Why would anyone need to create a test that can tell humans and computers apart? It's because of people trying to game the system -- they want to exploit weaknesses in the computers running the site. While these individuals probably make up a minority of all the people on the service might find itself bombarded by account requests from an automated program. That automated program could be part of a larger attempt to send out spam mail to millions of people. The CAPTCHA test helps identify which users are real human beings and which ones are computer programs.

Applications of CAPTCHAs

CAPTCHAs have several applications for practical security, including
  • Preventing Comment Spam in Blogs. Most bloggers are familiar with programs that submit bogus comments, usually for the purpose of raising search engine ranks of some website (e.g., "buy penny stocks here"). This is called comment spam. By using a CAPTCHA, only humans can enter comments on a blog. There is no need to make users sign up before they enter a comment, and no legitimate comments are ever lost!
  • Online Polls. In November 1999, http://www.slashdot.org released an online poll asking which was the best graduate school in computer science (a dangerous question to ask over the web!). As is the case with most online polls, IP addresses of voters were recorded in order to prevent single users from voting more than once. However, students at Carnegie Mellon found a way to stuff the ballots using programs that voted for CMU thousands of times. CMU's score started growing rapidly. The next day, students at MIT wrote their own program and the poll became a contest between voting "bots." MIT finished with 21,156 votes, Carnegie Mellon with 21,032 and every other school with less than 1,000. Can the result of any online poll be trusted? Not unless the poll ensures that only humans can vote.
  • Worms and Spam. CAPTCHAs also offer a plausible solution against email worms and spam: "I will only accept an email if I know there is a human behind the other computer." A few companies are already marketing this idea.
People who maintain Web sites or create online polls need to be aware that several CAPTCHA systems are no longer effective. It's important to do a little research on which CAPTCHA applications are still reliable. And it's equally important to keep up to date on the subject. If one CAPTCHA system fails, the administrator might need to remove the code from his or her site and replace it with another version.
As for CAPTCHA designers, they have to walk a fine line. As computers become more sophisticated, the testing method must also evolve. But if the test evolves to the point where humans can no longer solve a CAPTCHA with a decent success rate, the system as a whole fails. The answer may not involve warping or distorting text -- it might require users to solve a mathematical equation or answer questions about a short story. And as these tests get more complicated, there's a risk of losing user interest. How many people will still want to post a reply to a message board if they must first solve a quadratic equation?
On 10:42 AM by Lalith Varun   No comments










When the first quartz watches came out, it was believed that it was going to be the end of normal mechanical watches, just like video tape was going to be the end of theaters. Somehow, it hasn't worked out that way, and self-winding watches are more popular than ever.

The pictures show you the backside of a typical self-winding watch. This watch happens to have a clear back so you can see inside. Highlighted in the third picture is a semi-circular metal piece that is the heart of a self-winding watch. Relatively speaking, this semi-circular piece is fairly heavy, and it is therefore affected by gravity. As you move the watch, this piece will move so that it is always pointed toward the ground. As you walk, with your arm swinging back and forth, this piece moves back and forth inside the watch.

The piece is attached to a gear train that gears it way down. Each movement of your arm winds the spring the tiniest bit, but since you move your arm so much it keeps the watch wound easily. The spring in the watch stores enough energy to keep the watch going for about a day and a half if you leave it on your dresser.

Jul 5, 2009

On 7:30 PM by Lalith Varun   2 comments




Jaguar Land Rover's official entry to the fast-growing Indian car market was marked by the opening of a flagship showroom facility at Ceejay House in Mumbai by Mr. Ratan N. Tata, Chairman of Tata Sons and Tata Motors on the 28th of june.


Jaguar Land Rover has confirmed Tata Motors as its exclusive importer and the world-class Ceejay House facility in Worli, Mumbai, will offer a wide range of both Jaguar and Land Rover vehicles, with a dedicated showroom section for each brand


Jaguar and Land Rover's award-winning vehicles are well known around the world. Jaguar has become one of the world's leading producers of beautiful fast cars while Land Rover produces the world's most versatile all-terrain vehicles, combining refined luxury with a true breadth of capability.


The exciting new range of premium luxury vehicles available for the Indian market will include the Jaguar XF, XFR and XKR and Land Rover Discovery 3, Range Rover Sport and Range Rover.


Jaguar Land Rover is a business built around two great British car brands that design, engineer and manufacture in the UK. Jaguar Cars Limited, founded in 1922, is one of the world’s premier manufacturers of luxury saloons and sports cars. Since 1948 Land Rover has been manufacturing authentic 4x4s that define 'breadth of capability' in their segments. The Jaguar XF, XJ and XK models are manufactured at the company's Castle Bromwich plant in Birmingham, while the Jaguar X-TYPE is produced alongside the Land Rover Freelander 2 at the Halewood plant in Liverpool. Land Rover's Defender, Discovery 3, Range Rover Sport and Range Rover models are all built at the Solihull plant. The business is a major wealth generator for the UK with 78 percent of Land Rovers exported to over 160 countries and 70 percent of Jaguars exported to 63 countries, with sales to customers conducted principally through franchised dealers and importers.


We are extremely proud that the Jaguar Land Rover has chosen to enter the Indian market and give the discerning Indian customer direct access to their prestigious brands, accompanied by a parts and service network. We hope that they will delight customers in India just as they have done in markets the world over