Sources of an excess noise in avalanche photodiodes and photomultiplier tubes are considered in this paper. Special techniques for minimizing the noise contribution in detected signals are discussed. Typical applications of detectors in atomic spectroscopy and optical communication are used as illustration of the proposed tools for noise reduction.
In this paper we present our system for distant learning support, and its current content -- neural networks and distributed systems courses. The system provides users with remote access to learning materials, features dynamic glossary of terms and supports inline multimedia.
Web-based learning applications open new horizons for educators. In this work we present the computer encyclopedia designed to overcome drawbacks of traditional paper information sources such as awkward search, low update rate, limited copies count and high cost. Moreover, we intended to improve access and search functions in comparison with some Internet sources in order to make it more convenient. The system is developed using modern Java technologies (Jave Servlets, Java Server Pages) and contains systemized information about most important and explored physical effects. It also may be used in other fields of science. The system is accessible via Intranet/Internet networks by means of any up-to-date Internet browser. It may be used for general learning purposes and as a study guide or tutorial for performing laboratory works.
The method of data analysis in intracavity laser spectroscopy is considered. The artificial neural network was used as an analyzing tool for the determination of elements concentration in trace amounts samples using absorption spectra. The special neural network training algorithm based on simulation of experimental spectra was developed to solve the problem of non-sufficient experimental data set. The application of this method allows achieve the better sensitivity than conventional analytical methods and proved itself more robust. The proposed method was tested on spectra of Cs water solution.
Methods of absorption spectra processing in intracavity laser spectroscopy are investigated for the case of very low quantities of cesium in water solutions. Common procedures in such case require fitting or filtering of the laser generation broadband spectrum, search for the investigated atomic or molecular absorption lines, calculating the examined substance concentration in qualitative analysis or its state determination in quality analysis. In this study various methods of absorption spectra processing in the case of atomic cesium line (lambda) equals 455.531 nm in the intracavity laser spectrometer are examined. Methods based on digital filtering and approximation were tested. The artificial neural network algorithm was tired as a tool to reduce the apparatus error. For the trace concentration definition the mean-square error was decreased to a value less than 9 percent.