No description available.

Abstract Not Provided / Thesis / Bachelor of Science (BSc)

International Telemetering Conference Proceedings / October 29-November 02, 1990 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper briefly reviews past techniques for measuring FM deviation and discusses the limitations of past technology. Graphs of the Bessel functions are presented in terms of decibels (dB), offering a better method of measurement when used with a modern spectrum analyzer.

The Retarding Field Energy Analyzer (RFEA, RFA) is a simple and reliable diagnostic technique to measure the ion temperature in the Scrape-Off Layer (SOL) and edge of magnetic fusion devices. Design and operation features of a single-sided (facing the ion down stream side) RFEA for ion temperature measurements in the STOR-M tokamak are described. Its compact size (21 × 15 × 20 mm3 ) allows RFEA measurements without perturbing plasma significantly. Both ion and electron tem- perature have been measured by RFEA in the STOR-M tokamak. A method is proposed to correct the effects of ion flow on the ion temperature using the simultaneously measured Mach number. The measured electron temperature is consistent with the previously reported Langmuir probe data. Abnormal behavior of the RFEA has been observed in both ion and electron modes when RFEA is inserted deep into the plasma.

Analyzer crystal based imaging techniques such as diffraction enhanced imaging (DEI) and multiple imaging radiography (MIR) utilize the Bragg peak of perfect crystal diffraction to convert angular changes into intensity changes. These X-ray techniques extend the capability of conventional radiography, which derives image contrast from absorption, by providing a large change in intensity for a small angle change introduced by the X-ray beam traversing the sample. Objects that have very little absorption contrast may have considerable refraction and ultra small angle X-ray scattering (USAXS) contrast thus improving visualization and extending the utility of X-ray imaging. To improve on the current DEI technique this body of work describes the design of an X-ray prism (XRP) included in the imaging system which allows the analyzer crystal to be aligned anywhere on the rocking curve without moving the analyzer from the Bragg angle. By using the XRP to set the rocking curve alignment rather than moving the analyzer crystal physically the needed angle sensitivity is changed from ìradians for direct mechanical movement of the analyzer crystal to milliradian control for movement the XRP angle. In addition to using an XRP for the traditional DEI acquisition method of two scans on opposite sides of the rocking curve preliminary tests will be presented showing the potential of using an XRP to scan quickly through the entire rocking curve. This has the benefit of collecting all the required data for image reconstruction in a single fast measurement thus removing the occurrence of motion artifacts for each point or line used during a scan. The XRP design is also intended to be compatible with combined imaging systems where more than one technique is used to investigate a sample. Candidates for complimentary techniques are investigated and measurements from a combined X-ray imaging system are presented.

FFT-based digital spectral analyzer has become more and more widely used as a result of the development of Digital Signal Processing (DSP) techniques. Modern Analog-to-Digital Converters (ADC) and processors have made it possible to make fast measurements with a limited number of hardware.   In this thesis, a design of a simple low-cost FFT-based digital spectrum analyzer was presented. The author discusses the design of each components of the system in qualitatively and quantitatively. The report presents the whole system design in detail which contains filter design, micro-controller design, UART transmission design and MATLAB GUI design. Some satisfying measurement result of the system were presented in the paper. The system can provide fast measurement with good accuracy. But the measured result has a limited range and resolution of the display is not very high. At last, the advantages and disadvantages of the system was discussed which is considered as guidelines for further work.

The Retarding Field Energy Analyzer (RFEA, RFA) is a simple and reliable diagnostic technique to measure the ion temperature in the Scrape-Off Layer (SOL) and edge of magnetic fusion devices. Design and operation features of a single-sided (facing the ion down stream side) RFEA for ion temperature measurements in the STOR-M tokamak are described. Its compact size (21 × 15 × 20 mm3 ) allows RFEA measurements without perturbing plasma significantly. Both ion and electron tem- perature have been measured by RFEA in the STOR-M tokamak. A method is proposed to correct the effects of ion flow on the ion temperature using the simultaneously measured Mach number. The measured electron temperature is consistent with the previously reported Langmuir probe data. Abnormal behavior of the RFEA has been observed in both ion and electron modes when RFEA is inserted deep into the plasma.

Analyzer crystal based imaging techniques such as diffraction enhanced imaging (DEI) and multiple imaging radiography (MIR) utilize the Bragg peak of perfect crystal diffraction to convert angular changes into intensity changes. These X-ray techniques extend the capability of conventional radiography, which derives image contrast from absorption, by providing a large change in intensity for a small angle change introduced by the X-ray beam traversing the sample. Objects that have very little absorption contrast may have considerable refraction and ultra small angle X-ray scattering (USAXS) contrast thus improving visualization and extending the utility of X-ray imaging. To improve on the current DEI technique this body of work describes the design of an X-ray prism (XRP) included in the imaging system which allows the analyzer crystal to be aligned anywhere on the rocking curve without moving the analyzer from the Bragg angle. By using the XRP to set the rocking curve alignment rather than moving the analyzer crystal physically the needed angle sensitivity is changed from ìradians for direct mechanical movement of the analyzer crystal to milliradian control for movement the XRP angle. In addition to using an XRP for the traditional DEI acquisition method of two scans on opposite sides of the rocking curve preliminary tests will be presented showing the potential of using an XRP to scan quickly through the entire rocking curve. This has the benefit of collecting all the required data for image reconstruction in a single fast measurement thus removing the occurrence of motion artifacts for each point or line used during a scan. The XRP design is also intended to be compatible with combined imaging systems where more than one technique is used to investigate a sample. Candidates for complimentary techniques are investigated and measurements from a combined X-ray imaging system are presented.

With the rapid development of Internet technology, as well as extensive use of broadband networks, the issues of network security are increasing. In order to deal with these complex issues, network adminstrators adopt firewalls, intrusion detection systems, intrusion prevention systems to prevent them, in addition, the collection and analysis of log are also very important. By the log analysis, administrators can understand the error messages generated by system and the abnormal behavior of external connections, and develop the corresponding security policy on the use of the security tools. The current log analyzer, besides default rules, administrators have to spend much time reviewing the syslog of their system in detail to set the corresponding rules for their system, and each analyzer has its own unique rules of definitions. The purpose of this study is to transform tens of thounds of logs into a small number of valuable patterns, classify these patterns into abnormal ones and normal ones, and sum up the logs corresponding with listed patterns to assist administrator to review. In this study, we adopt the concept of string similarity comparison, and do similarity comparison for each log to find out all patterns which presented by regular expression. After experimental evaluation, this study can indeed analyze and generate all patterns of logs automatically, and these patterns can be applies to a practical tool of network security.

The focus of this work is the experimental investigation of electron velocity distribution functions in the plasma of the Texas Helimak experiment. Texas Helimak has a cylindrical geometry and relatively moderate plasma parameter, which allow the use of a retarding field analyzer that is located approximately in the middle of the vacuum vessel. Electron velocity distribution functions were measured for a variety of different operating conditions and for two gas species, namely argon and helium. Parameter scans, whereby all parameter except the scan parameter were kept constant, were done in order to investigate the influence of the scan parameter on the velocity distribution. It was found, that most electron velocity distribution functions are not alone Maxwellian. One of the reasons therefore is electron cyclotron resonance heating, which was used for ionizing and heating the plasma and what produces a suprathermal tail. It is possible, however, to obtain effective electron temperatures. These effective electron temperatures range from about 10 eV , what is similar to the electron bulk temperature, to more than 150 eV. / text