Sunday, November 21, 2010

Why is Arctic ice melting 50 years too fast?

On Aug. 19, 2007, a joint survey by the Japan Agency for Marine-Earth Science and Technology and the Japan Aerospace Exploration Agency revealed that Arctic ice was melting at a far quicker rate than anticipated. What's particularly alarming about this discovery is that the United Nations' scientific models anticipated that the ice levels measured by the Japanese team would not be reached until after 2040 -- and possibly not until 2050.

Global Warming Image Gallery

satellite image of Arctic ice levels
Image courtesy National Snow and Ice Data Center This satellite image shows that Arctic ice levels in 2007 (left)
were less than even the record low levels of 2005 (right).
See more global warming images.

A researcher at the Colorado Center for Astrodynamics said that Arctic ice is melting at previously unseen rates [source: Science Daily]. The melting has caused coastal ice in parts of Canada and Alaska to become quite brittle. That ice easily breaks away in large chunks (a process known as calving) and melts in the open ocean. There's also less sea ice in the Arctic Ocean
because ice has floated into the Atlantic Ocean. The previous record low for Arctic sea ice was recorded on Aug. 15, 2005, though scientists said there was a high probability that the record would be breached in 2007.
The Arctic saw another milestone in the summer of 2007. In August, the Northwest Passage had almost no floating ice. It was the first time the Passage had been completely open to shipping since people started keeping records in 1972. Scientists say that the lack of ice represents clear proof that the planet is warming. The now-open sea lane means that someone could sail from New York to Korea without encountering any ice, though bad weather is always possible. In comparison, the first explorer to navigate the Northwest Passage successfully, Roald Amundsen, took three years to get through the waterway's thick ice.
Sea ice is measured primarily through three methods: microwave scanners on orbiting satellites, buoys and observation platforms. The latter two are generally equipped with several types of measuring devices. Scientists focus their measurements on the extent of sea ice, rather than the thickness, since it's easier for satellites to measure extent. When examining sea ice, scientists look at the minimum and maximum extent, thickness, environmental conditions and changes in the melting season. The Arctic sea ice melting season usually lasts from March to the middle of September.
This record pace of Arctic ice melt has scientists concerned about rising sea levels, diminished habitats for polar bears and other animals and an impending rush for fossil fuels in the region. Increased traffic through the Northwest Passage and the Northeast Passage (which runs by Siberia) may increase pollution in the area.
Ice re-forms during winter, but due to warmer waters the amount of re-formed ice appears to be decreasing. Ice that was previously considered "permanent" is now melting. That leaves an ever-decreasing base of ice at the beginning of each melting season.
Sea ice plays an important role in keeping temperatures down around the world. Whereas sea ice reflects 80 percent of sunlight back into the atmosphere, ocean water absorbs 90 percent of sunlight [source: National Snow and Ice Data Center]. As melting ice exposes more ocean to direct sunlight, scientists expect water temperatures to rise, accelerating the ice melt.
On the next page, we'll take a look at more consequences of melting Arctic ice, including the rush to claim the seabed and the valuable energy stores underneath it.

Saturday, November 20, 2010

What is Global Warming?

What is Global Warming?

Global warming is the unusually rapid increase in Earth’s average surface temperature over the past century primarily due to the greenhouse gases released by people burning fossil fuels.

How Does Today’s Warming Compare to Past Climate Change?

Earth has experienced climate change in the past without help from humanity. But the current climatic warming is occurring much more rapidly than past warming events.

Why Do Scientists Think Current Warming Isn’t Natural?

In Earth’s history before the Industrial Revolution, Earth’s climate changed due to natural causes unrelated to human activity. These natural causes are still in play today, but their influence is too small or they occur too slowly to explain the rapid warming seen in recent decades.

How Much More Will Earth Warm?

Models predict that as the world consumes ever more fossil fuel, greenhouse gas concentrations will continue to rise, and Earth’s average surface temperature will rise with them. Based on plausible emission scenarios, average surface temperatures could rise between 2°C and 6°C by the end of the 21st century. Some of this warming will occur even if future greenhouse gas emissions are reduced, because the Earth system has not yet fully adjusted to environmental changes we have already made.

How Will Earth Respond to Warming Temperatures?

The impact of global warming is far greater than just increasing temperatures. Warming modifies rainfall patterns, amplifies coastal erosion, lengthens the growing season in some regions, melts ice caps and glaciers, and alters the ranges of some infectious diseases. Some of these changes are already occurring.

Global Warming

Throughout its long history, Earth has warmed and cooled time and again. Climate has changed when the planet received more or less sunlight due to subtle shifts in its orbit, as the atmosphere or surface changed, or when the Sun’s energy varied. But in the past century, another force has started to influence Earth’s climate: humanity
How does this warming compare to previous changes in Earth’s climate? How can we be certain that human-released greenhouse gases are causing the warming? How much more will the Earth warm? How will Earth respond? Answering these questions is perhaps the most significant scientific challenge of our time.

What is Global Warming?

Global warming is the unusually rapid increase in Earth’s average surface temperature over the past century primarily due to the greenhouse gases released as people burn fossil fuels. The global average surface temperature rose 0.6 to 0.9 degrees Celsius (1.1 to 1.6° F) between 1906 and 2005, and the rate of temperature increase has nearly doubled in the last 50 years. Temperatures are certain to go up further.
Graph of global mean temperature from 1880 to 2009.
Despite ups and downs from year to year, global average surface temperature is rising. By the beginning of the 21st century, Earth’s temperature was roughly 0.5 degrees Celsius above the long-term (1951–1980) average. (NASA figure adapted from Goddard Institute for Space Studies Surface Temperature Analysis.)

Earth’s natural greenhouse effect

Earth’s temperature begins with the Sun. Roughly 30 percent of incoming sunlight is reflected back into space by bright surfaces like clouds and ice. Of the remaining 70 percent, most is absorbed by the land and ocean, and the rest is absorbed by the atmosphere. The absorbed solar energy heats our planet.
As the rocks, the air, and the seas warm, they radiate “heat” energy (thermal infrared radiation). From the surface, this energy travels into the atmosphere where much of it is absorbed by water vapor and long-lived greenhouse gases such as carbon dioxide and methane.
When they absorb the energy radiating from Earth’s surface, microscopic water or greenhouse gas molecules turn into tiny heaters— like the bricks in a fireplace, they radiate heat even after the fire goes out. They radiate in all directions. The energy that radiates back toward Earth heats both the lower atmosphere and the surface, enhancing the heating they get from direct sunlight.
This absorption and radiation of heat by the atmosphere—the natural greenhouse effect—is beneficial for life on Earth. If there were no greenhouse effect, the Earth’s average surface temperature would be a very chilly -18°C (0°F) instead of the comfortable 15°C (59°F) that it is today.
See Climate and Earth’s Energy Budget to read more about how sunlight fuels Earth’s climate.

The enhanced greenhouse effect

What has scientists concerned now is that over the past 250 years, humans have been artificially raising the concentration of greenhouse gases in the atmosphere at an ever-increasing rate, mostly by burning fossil fuels, but also from cutting down carbon-absorbing forests. Since the Industrial Revolution began in about 1750, carbon dioxide levels have increased nearly 38 percent as of 2009 and methane levels have increased 148 percent.
Graphs of atmospheric carbon dioxide and methane from 1750 to 2009.
Increases in concentrations of carbon dioxide (top) and methane (bottom) coincided with the start of the Industrial Revolution in about 1750. Measurements from Antarctic ice cores (green lines) combined with direct atmospheric measurements (blue lines) show the increase of both gases over time. (NASA graphs by Robert Simmon, based on data from the NOAA Paleoclimatology and Earth System Research Laboratory.)
The atmosphere today contains more greenhouse gas molecules, so more of the infrared energy emitted by the surface ends up being absorbed by the atmosphere. Since some of the extra energy from a warmer atmosphere radiates back down to the surface, Earth’s surface temperature rises. By increasing the concentration of greenhouse gases, we are making Earth’s atmosphere a more efficient greenhouse.

How is Today’s Warming Different from the Past?

Earth has experienced climate change in the past without help from humanity. We know about past climates because of evidence left in tree rings, layers of ice in glaciers, ocean sediments, coral reefs, and layers of sedimentary rocks. For example, bubbles of air in glacial ice trap tiny samples of Earth’s atmosphere, giving scientists a history of greenhouse gases that stretches back more than 800,000 years. The chemical make-up of the ice provides clues to the average global temperature.
Using this ancient evidence, scientists have built a record of Earth’s past climates, or “paleoclimates.” The paleoclimate record combined with global models shows past ice ages as well as periods even warmer than today. But the paleoclimate record also reveals that the current climatic warming is occurring much more rapidly than past warming events.
As the Earth moved out of ice ages over the past million years, the global temperature rose a total of 4 to 7 degrees Celsius over about 5,000 years. In the past century alone, the temperature has climbed 0.7 degrees Celsius, roughly ten times faster than the average rate of ice-age-recovery warming.
Graph of multi-proxy global temperature reconstruction and instrumental records.
Temperature histories from paleoclimate data (green line) compared to the history based on modern instruments (blue line) suggest that global temperature is warmer now than it has been in the past 1,000 years, and possibly longer. (Graph adapted from Mann et al., 2008.)
Models predict that Earth will warm between 2 and 6 degrees Celsius in the next century. When global warming has happened at various times in the past two million years, it has taken the planet about 5,000 years to warm 5 degrees. The predicted rate of warming for the next century is at least 20 times faster. This rate of change is extremely unusual.

What is Ethical Hacking?

An Ethical Hacker is an expert hired by a company to attempt to attack their network and computer system the same way a hacker would. Ethical Hackers use the same techniques and tactics as those used by illegal hackers to breach corporate security systems. The end result is the company's ability to prevent an intrusion before it ever occurs.
A company can't know if their security system is solid unless they test it. It's hard, though, for a company's IT team to thoroughly ring out the system. Try as they might, the techs can't go at the system with all the malicious or mischievous motives of a true illegal hacker. To thoroughly uncover vulnerabilities, the theory goes; you must examine your security system through the eyes of an illegal hacker.
The word hacking has strongly negative connotations, and, for the most part, rightly so. But ethical hacking is much different. It takes place with the explicit permission of the company whose system is being attacked. In fact, their "good guy" role is underscored by the nickname "white hat" Ethical Hackers have been given. The nickname is a throwback to old Westerns where the good cowboys could be identified by their white hats.
The company and the Ethical Hacker enter into a legally binding contract. The contract, sometimes called a "get out of jail free card," sets forth the parameters of the testing. It's called the "get out of jail free card" because it's what harbors the Ethical Hacker from prosecution. Hacking is a felony, and a serious one at that. The terms of the agreement are what transform illegal behavior into a legal and legitimate occupation.
Once the hacker has exhausted his attempts, he reports back to the company with a list of the vulnerabilities he uncovered. The list in and of itself, however, is not particularly useful. What's most valuable is the instructions for eliminating the vulnerabilities that the Ethical Hacker provides.
An Ethical Hacker works to uncover three key pieces of information. First, he determines what information an illegal hacker can gain access to. Next, he explores what an illegal hacker could do with that information once gained. Last, the Ethical Hacker ascertains whether an employee or staff member would be alerted to the break-in, successful or not.
At first it might sound strange that a company would pay someone to try to break into their system. Ethical hacking, though, makes a lot of sense, and it is a concept companies have been employing for years. To test the effectiveness and quality of product, we subject it to the worst case scenario. The safety testing performed by car manufacturers is a good example. Current regulatory requirements including HIPAA, Sarbanes Oxley, and SB-1386 and BS 799 require a trusted third party to check that systems are secure.
In order to get the most out of the assessment, a company should decide in advance the nature of the vulnerabilities they're most concerned with. Specifically, the company should determine which information they want to keep protected and what they're concerned would happen if the information was retrieved by an illegal hacker.
Companies should thoroughly assess the qualifications and background of any Ethical Hacker they are considering hiring. This individual will be privy to highly sensitive information. Total honesty and integrity is of the utmost importance.

Tuesday, November 9, 2010

What is a Printed Circuit Board (PCB)?

What is a Printed Circuit Board (PCB)?

Most electronic equipment and products have circuit boards. Pprinted circuit board (PCB / PWB), is a board made out of non-insulating and highly heat-resistant insulating material such as fiberglass. These boards are also called substrates.

A PCB substrate may have only one single layer (single-layer circuit board) or more than one layer (multilayer circuit board). A conductive metal such as copper is used to make conductive pathway or traces to facilitate flow of electricity. Once PCB itching is done, it is termed as a “printed circuit board”.
Circuit Board Prototype

When designing a new circuit, it is important to draw a circuit board schematic prior to making a circuit board prototype. A circuit board schematic will help to debug and fix any mistake made during the process. If the circuitry on the circuit board is simple, one can use proto boards that are quite simple and easy to understand. In case of complex and customized circuit board, making a prototype board is a must.

Circuit Board Layout Editor

To start making a circuit board prototype, one will need a circuit board layout pattern. Layout editors are available for this purpose.

A circuit board layout editor is software to draw a layout of the circuit board with all of the traces and points where electronic components will be soldered on the board. The PCB layout will look like a diagram. PCB layout software allows editing the layout until the desired layout is achieved.
How to Make a Circuit Board

Making or manufacturing a circuit board involves several complex processes.

   1. Photoengraving: Under this process a mask or photomask is combined with chemical etching to subtract the copper areas from the circuit board substrate. The photomask is created with a photo plotter design using a CAD PCB software program. Photomasks are also created using a laser printer.
   2. Lamination: Multi-layer printed circuit boards are made up of multiple layers consisting of several thin etched boards or trace layers and are bonded together through the process of lamination.
   3. Drilling: Each layer of the printed circuit board requires the ability of one layer to connect to another; this is achieved through drilling small holes called "VIAS". Drilling is mostly done with the use of an automated computer-driven drilling machine.
   4. Solder plating: Pads and lands where electronic components are to be soldered on the circuit board are plated to allow soldering of electronic components. Bare copper is not easily solderable. It requires the surface to be plated with a material that facilitates soldering. Earlier lead based tin was used to plate the surfaces, but with RoHS (Restriction of Hazardous Substances) compliance enacted newer materials such as nickel and gold are now used for plating.
   5. Testing the circuit board: Prior to assembly of electronic components on to the board, it needs to be tested. This testing can be done using nails tester, flying probe tester are other computer-operated circuit board testing equipments.

PCB Design Rules

Layer Process Vs Standard Size

    * Minimum trace / space: 7 mils
    * Minimum via / hole size: 14 mils
    * Minimum pad for plated hole / vias: 26 mils
    * Minimum plated slot: 32 mils
    * Minimum soldermask Clearance: 4 mils
    * Minimum silkscreen Clearance: 4 mils
    * Minimum silkscreen line width: 6 mils
    * Minimum board copper/edge margin: 10 mils


While making a PCB prototype, it is important to follow the rules right from photoengraving to testing. Any slight mistake can make the circuit board useless. In case of mass production, PCB prototypes is a must.

Read more at Suite101: Printed Circuit Board Prototype

Computer security

Computer security is the effort to create a secure computing platform, designed so that agents (users or programs) can only perform actions that have been allowed. This involves specifying and implementing a security policy. The actions in question can be reduced to operations of access, modification and deletion. Computer security can be seen as a subfield of security engineering, which looks at broader security issues in addition to computer security. These measures include controls that ensure the security and availability of the information processed, stored, and transmitted by a computer.