Customer credit scoring based on HMM/GMDH hybrid model
Ge-Er Teng · Chang-Zheng He · Jin Xiao ·Xiao-Yi Jiang
Abstract :
Hidden Markov model (HMM) has made great achievements in many fields
such as speech recognition and engineering. However, due to its assumption of state condi-
tional independence between observations, HMM has a very limited capacity for recogniz-
ing complex patterns involving more than first-order dependencies in customer relationships
management. Group Method of Data Handling (GMDH) could overcome the drawbacks
of HMM, so we propose a hybrid model by combining the HMM and GMDH to score cus-
tomer credit. There are three phases in thismodel: training HMMwithmultiple observations,
adding GMDH into HMM and optimizing the hybrid model. The proposed hybrid model is
compared with other exiting methods in terms of average accuracy, Type I error, Type II error
and AUC. Experimental results show that the proposed method has better performance than
HMM/ANN in two credit scoring datasets. The implementation of HMM/GMDH hybrid
model allows lenders and regulators to develop techniques to measure customer credit risk.
Monday, February 11, 2008
Sunday, February 3, 2008
How Graphics Cards Work
by Tracy V. Wilson and Jeff Tyson
The images you see on your monitor are made of tiny dots called pixels. At most common resolution settings, a screen displays over a million pixels, and the computer has to decide what to do with every one in order to create an image. To do this, it needs a translator -- something to take binary data from the CPU and turn it into a picture you can see. Unless a computer has graphics capability built into the motherboard, that translation takes place on the graphics card.
A graphics card's job is complex, but its principles and components are easy to understand. In this article, we will look at the basic parts of a video card and what they do. We'll also examine the factors that work together to make a fast, efficient graphics card.
Graphics Card Basics
Think of a computer as a company with its own art department. When people in the company want a piece of artwork, they send a request to the art department. The art department decides how to create the image and then puts it on paper. The end result is that someone's idea becomes an actual, viewable picture.
A graphics card works along the same principles. The CPU, working in conjunction with software applications, sends information about the image to the graphics card. The graphics card decides how to use the pixels on the screen to create the image. It then sends that information to the monitor through a cable.
The Evolution of Graphics Cards
Graphics cards have come a long way since IBM introduced the first one in 1981. Called a Monochrome Display Adapter (MDA), the card provided text-only displays of green or white text on a black screen. Now, the minimum standard for new video cards is Video Graphics Array (VGA), which allows 256 colors. With high-performance standards like Quantum Extended Graphics Array (QXGA), video cards can display millions of colors at resolutions of up to 2040 x 1536 pixels.
Creating an image out of binary data is a demanding process. To make a 3-D image, the graphics card first creates a wire frame out of straight lines. Then, it rasterizes the image (fills in the remaining pixels). It also adds lighting, texture and color. For fast-paced games, the computer has to go through this process about sixty times per second. Without a graphics card to perform the necessary calculations, the workload would be too much for the computer to handle.
The graphics card accomplishes this task using four main components:
1.A motherboard connection for data and power
2.A processor to decide what to do with each pixel on the screen
3.Memory to hold information about each pixel and to temporarily store completed
pictures
4.A monitor connection so you can see the final result
The images you see on your monitor are made of tiny dots called pixels. At most common resolution settings, a screen displays over a million pixels, and the computer has to decide what to do with every one in order to create an image. To do this, it needs a translator -- something to take binary data from the CPU and turn it into a picture you can see. Unless a computer has graphics capability built into the motherboard, that translation takes place on the graphics card.
A graphics card's job is complex, but its principles and components are easy to understand. In this article, we will look at the basic parts of a video card and what they do. We'll also examine the factors that work together to make a fast, efficient graphics card.
Graphics Card Basics
Think of a computer as a company with its own art department. When people in the company want a piece of artwork, they send a request to the art department. The art department decides how to create the image and then puts it on paper. The end result is that someone's idea becomes an actual, viewable picture.
A graphics card works along the same principles. The CPU, working in conjunction with software applications, sends information about the image to the graphics card. The graphics card decides how to use the pixels on the screen to create the image. It then sends that information to the monitor through a cable.
The Evolution of Graphics Cards
Graphics cards have come a long way since IBM introduced the first one in 1981. Called a Monochrome Display Adapter (MDA), the card provided text-only displays of green or white text on a black screen. Now, the minimum standard for new video cards is Video Graphics Array (VGA), which allows 256 colors. With high-performance standards like Quantum Extended Graphics Array (QXGA), video cards can display millions of colors at resolutions of up to 2040 x 1536 pixels.
Creating an image out of binary data is a demanding process. To make a 3-D image, the graphics card first creates a wire frame out of straight lines. Then, it rasterizes the image (fills in the remaining pixels). It also adds lighting, texture and color. For fast-paced games, the computer has to go through this process about sixty times per second. Without a graphics card to perform the necessary calculations, the workload would be too much for the computer to handle.
The graphics card accomplishes this task using four main components:
1.A motherboard connection for data and power
2.A processor to decide what to do with each pixel on the screen
3.Memory to hold information about each pixel and to temporarily store completed
pictures
4.A monitor connection so you can see the final result
How is the LCD in a laptop computer so bright?
Most computer Liquid Crystal Display (LCD) panels are lit with built-in fluorescent tubes above, beside and sometimes behind the LCD. A white diffusion panel behind the LCD redirects and scatters the light evenly to ensure a uniform display. This is known as a backlight.
A fluorescent light is most often a long straight glass tube that produces white light. Inside the glass tube there is a low-pressure mercury vapor. When ionized, mercury vapor emits ultraviolet light. Human eyes are not sensitive to ultraviolet light (although human skin is). The inside of a fluorescent light is coated with phosphor. Phosphor is a substance that can accept energy in one form and emit the energy in the form of visible light. For example, energy from a high-speed electron in a TV tube is absorbed by the phosphors that make up the pixels. The light we see from a fluorescent tube is the light given off by the phosphor coating the inside of the tube. The phosphor fluoresces when energized, hence the name.
A typical laptop display uses a tiny Cold Cathode Fluorescent Lamp (CCFL) for the backlight. One of these small tubes is able to provide a bright white light source that can be diffused by the panel behind the LCD. In addition to providing ample light, CCFLs do not rise far above the ambient temperature. This makes them ideal for LCD panels since the light source is in close proximity to other components that could be ruined by excessive heat.
One amazing thing about these lamps is their incredible size. They are very thin and the board that drives the lamp is very small as well. However, it is not that hard to break them, which is why your display may go dark if you drop your laptop.
A fluorescent light is most often a long straight glass tube that produces white light. Inside the glass tube there is a low-pressure mercury vapor. When ionized, mercury vapor emits ultraviolet light. Human eyes are not sensitive to ultraviolet light (although human skin is). The inside of a fluorescent light is coated with phosphor. Phosphor is a substance that can accept energy in one form and emit the energy in the form of visible light. For example, energy from a high-speed electron in a TV tube is absorbed by the phosphors that make up the pixels. The light we see from a fluorescent tube is the light given off by the phosphor coating the inside of the tube. The phosphor fluoresces when energized, hence the name.
A typical laptop display uses a tiny Cold Cathode Fluorescent Lamp (CCFL) for the backlight. One of these small tubes is able to provide a bright white light source that can be diffused by the panel behind the LCD. In addition to providing ample light, CCFLs do not rise far above the ambient temperature. This makes them ideal for LCD panels since the light source is in close proximity to other components that could be ruined by excessive heat.
One amazing thing about these lamps is their incredible size. They are very thin and the board that drives the lamp is very small as well. However, it is not that hard to break them, which is why your display may go dark if you drop your laptop.
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