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Download Full Article 99active-blind-noise-suppression-in-some-speech-processing

In many applications of speech processing the noise reveals some specific features. Although the noise could be quite broadband, there are a limited number of dominant frequencies, which carry the most of its energy. This fact implies the usage of narrow-band notch filters that must be adaptive in order to track the changes in noise characteristics. In present contribution, a method and a system for noise suppression are developed. The method uses adaptive notch filters based on second-order Gray-Markel lattice structure. The main advantages of the proposed system are that it has very low computational complexity, is stable in the process of adaptation, and has a short time of adaptation. Under comparable SNR improvement, the proposed method adjusts only 3 coefficients against 250-450 for the conventional adaptive noise cancellation systems. A framework for a speech recognition system that uses the proposed method is suggested.

The noise existence is inevitable in real applications of speech processing. It is well known that the additive noise affects negatively the performance of the speech codecs designed to work with noise-free speech especially codecs based on linear prediction coefficients (LPC). Another application strongly influenced by noise is related to the hands free phones where the background noise reduces the signal to noise ratio (S/N) and the speech intelligibility.

Last but not least, is the problem of speech recognition in a noisy environment. A system that works well in noise-free conditions, usually shows considerable degradation in performance when background noise is present It is clear that a strong demand for reliable noise cancellation methods exists that efficiently separate the noise from speech signal. The endeavors in designing of such systems can be followed some 20 years ago The core of the problem is that in most situations the characteristics of the noise are not known a priori and moreover they may change in time. This implies the use of adaptive systems capable of identifying and tracking the noise characteristics. This is why the application of adaptive filtering for noise cancellation is widely used.

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Download Full Article 100fast-convergence-algorithms-for-active-noise-control-in

When reference signal for the FxLMS algorithm is taken from an acoustic sensor convergence can be very slow due to great eigen value spread. Using a non acoustic sensor, Such as a tachometer, cancellation of narrow band noise in the sensed fundamental frequency and harmonically related ones can be achieved very fast, although other periodic noises and underline broad band noise will remain.

Backward prediction errors resulting at the various stages of an adaptive lattice predictor(ALP) represent a a time-domain orthogonalization of the input signal.An ALP structure, with the acoustic reference has input signal, before a FxLMS makes up the FxGAL algorithm. Due to the orthogonalization, FxGAL can be significantly faster compared to FxLMS with reference from a microphone. When compared to FxLMS with tachometer signal, it is not faster but it can cancel every periodic noise, independently of the harmonical relation between them, as well as the underlined broad band noise. Comparative results between FxLMS (with acoustic and nonacoustic reference) and FxGAL are presented.

The Filtered-x Least Mean Square (FxLMS) algorithm(1) is the most widely used in the context of adaptive active control, due to its simplicity as well as robustness.However the main drawback of this algorithm is its relatively slow and signal dependent convergence, which is determined by the eigen value spread of the underlying corelation matrix of the input signal.When working in nonstationary environments such as automobiles, slow convergence is a critical problem, since we would desire to cancel transient noise, which occurs at the vehicle start-ups, stops or gear-Shifts, or with sudden changes of engine speeds or road noise from tyres.

A practical solution to this problem, very commonly used, is to use non acoustic sensors, such as tachometer instead of acoustic ones and artificially generate the signal to use as reference. This way, convergence can be achieved very fast, since it is possible to generate orthogonal references(in-face and quadrate components).On the other hand, it is only possible to cancel narrow band noises in the fundamental frequency sensed by the non acoustic sensor and other harmonically related frequencies, where as every other periodic or broad band noise will remain uncancelled.

In this paper, we introduce an algorithm the Filtered-x Gradient Adaptive Lattice(FxGAL), that aims to improve the convergence of the whole adaptive systems when using acoustic sensors to get the reference signal, at the expense of increased computational complexity.

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Download Full Article neural-networks

Neural networks include the capacity to map the perplexed & extremely non – linear relationship between load levels of zone and the system topologies, which is required for the feeder reconfiguration in distribution systems. This study is intended to purpose the strategies to reconfigure the feeders by using artificial neural n/w s with the mapping ability. Artificial neural n/w’s determine the appropriate system topology that reduces the power loss according to the variation of load pattern. The control strategy can be easily obtained on the basis of system topology which is provided by artificial neural networks.

Artificial neural networks determine the most appropriate system topology according to the load pattern on the basis of trained knowledge in the training set . This is contrary to the repetitive process of transferring the load & estimating power loss in conventional algorithm.

ANN are designed to two groups:

1) The first group is to estimate the proper load data of each zone .

2)The second is to determine the appropriate system topology from input load level .

In addition, several programs with the training set builder are developed for the design the training & accuracy test of A.N.N.

This paper will present the strategy of feeder reconfiguration to reduce power loss, by using A.N.N. The approach developed here is basically different from methods reviewed above on flow solution during search process are not required .The training set of A.N.N is the optimal system topology corresponding to various load patterns which minimizes the loss under given conditions.

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Download Full Article nanotechnology

Miniaturization. It’s a word we’ve become accustomed to over the last few decades. We’ve heard that computers that took up whole rooms half a century ago can now easily fit on to a microchip that sits on the tip of your finger. But what if we could go even much, much smaller than that? There are researchers who are trying to do just this. Their Field is called nanotechnology. It is derived from the word nanometer. Nanotechnology is a broad tern that describes many approaches to measurement tools, production methods, and devices that operate on that scale f one-billionth meter. A nanometer is one billionth of a meter. That’s a thousand, million times smaller than a meter.

The major research objectives in molecular nanotechnology are the design, modeling, and fabrication of molecular machines and molecular devices. While the ultimate objective mist clearly is economical fabrication, present capabilities preclude the manufacture of any but the most rudimentary molecular structures. The design and modeling of molecular machines is, however, quite feasible with present technology. More to the point, such modeling is a cheap and easy way to explore the truly wide range of, molecular machines that are accessible, allowing the rapid evaluation and elimination of obvious dead ends and the retention and more intensive analysis of moiré promising designs. It is clear that the right computational support will substantially reduce the development time. Worth appropriate molecular CAD software, molecular modeling software (including available computational chemistry packages, e.g., molecular mechanics, semi empirical and abs iritic programs} and related tools, we can plane the development of molecular manufacture systems on a computer just as Boeing might “build” and “fly” a new plane a computer before actually manufacturing it .

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Download Full Article class-d-amplifiers-2

Class D amplifiers present us with a revolutionary solution, which would help us eliminate loss and distortions caused due to conversion of digital signals to analog while amplifying signals before transmitting it to speakers. This inchoate piece of knowledge could prove to detrimental in improving and redefining essence of sound and take it to a different realm.

This type of amplifiers do not require the use of D-A conversion and hence reduce the costs incurred for developing state of art output technology. The digital output from sources such as CD’s, DVD’s and computers now can directly be sent for amplification without the need for any conversion.

Another important feature of these unique and novel kind of amplifiers are that they give us a typical efficiency of 90% compared to that of the normal ones which give us a efficiency of 65-70%. This obviously means less amount of dissipation that indirectly means lower rated heat sinks and low waste of energy. This makes the use of D type amplifiers in miniature and portable devices all the more apt.

All these years D type amplifiers have been used for purposes where efficiency was the key whereas now developments in this technology have made its entry possible into other domain that are less hi-fi. Thus showing up in MP3 players, portable CD players, laptop computers, cell phones, even personal digital assistants.

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Download Full Article e-bomb

The next Pearl Harbor will not announce itself with a searing flash of nuclear light or with the plaintive wails of those dying of Ebola or its genetically engineered twin. You will hear a sharp crack in the distance. By the time you mistakenly identify this sound as an innocent clap of thunder, the civilized world will have become unhinged. Fluorescent lights and television sets will glow eerily bright, despite being turned off. The aroma of ozone mixed with smoldering plastic will seep from outlet covers as electric wires arc and telephone lines melt. Your Palm Pilot and MP3 player will feel warm to the touch, their batteries overloaded. Your computer, and every bit of data on it, will be toast. And then you will notice that the world sounds different too. The background music of civilization, the whirl of internal-combustion engines, will have stopped. Save a few diesels, engines will never start again. You, however, will remain unharmed, as you find yourself thrust backward 200 years, to a time when electricity meant a lightning bolt fracturing the night sky. This is not a hypothetical, son-of-Y2K scenario. It is a realistic assessment of the damage that could be inflicted by a new generation of weapons–E-bombs.

Anyone who’s been through a prolonged power outage knows that it’s an extremely trying experience. Within an hour of losing electricity, you develop a healthy appreciation of all the electrical devices you rely on in life. A couple hours later, you start pacing around your house. After a few days without lights, electric heat or TV, your stress level shoots through the roof. But in the grand scheme of things, that’s nothing. If an outage hits an entire city, and there aren’t adequate emergency resources, people may die from exposure, companies may suffer huge productivity losses and millions of dollars of food may spoil. If a power outage hit on a much larger scale, it could shut down the electronic networks that keep governments and militaries running. We are utterly dependent on power, and when it’s gone, things get very bad, very fast.

An electromagnetic bomb, or e-bomb, is a weapon designed to take advantage of this dependency. But instead of simply cutting off power in an area, an e-bomb would actually destroy most machines that use electricity. Generators would be useless, cars wouldn’t run, and there would be no chance of making a phone call. In a matter of seconds, a big enough e-bomb could thrust an entire city back 200 years or cripple a military unit.

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