Microwave radiometer design and development, volume 1 Final report

Calibration, system, subsystem, and components of microwave radiometer for Nimbus satellit

Problems in Switched-Mode DC and AC Power Conversion

Several issues in the field of Power Electronics are discussed in this thesis. Part I first reviews the method of state-space averaging to analyze steady state and small-signal behavior of switched-mode dc-to-dc converters. The approach is then generalized to encompass multiple inputs and a general form of feedback system. Since the method involves matrix manipulations it is well suited for computer computation. The Switching Converter Analysis Program is developed to implement the state-space averaging method, and requires computational power only of a small desktop computer. This, together with another program which performs frequency response measurement of the actual system, constitute a powerful design tool for power electronics engineers. Part II extends the basic one-quadrant switching dc-to-dc converter to both current and voltage bidirectionality. The proposed "push-pull" power amplifier, being a four-quadrant converter, is capable of interfacing dc and ac ports. This special capability is then exploited to introduce a single-stage ac Uninterruptible Power Supply (UPS), which can process power from dc to ac or from ac to dc. Since with the form used only one of these accomplishments is required at a time, a single converter performs as a complete system. Hence, this UPS system is reliable and economical. Finally, Part III further generalizes the switching power amplifier to polyphase operation in such a way that a minimal number of power converters is required. Then, through a set of steps a new polyphase power amplifier is introduced. The idea is experimentally verified by a 1 hp variable-speed motor drive with regulated output voltages. The technique has many other advantages such as ease of paralleling, dc isolation, and voltage boost, etc. The generality of the technique makes it suitable for many other line related applications such as uninterruptible power supplies, unity power factor battery chargers, and battery-to-three-phase line interfaces.</p

An analysis of the theory- and employment-demands on mathematics for electrical engineering programmes at technikons

A preliminary study indicated a degree of dissatisfaction with the present mathematics curriculum at technikons amongst academic staff members of technikons as well as members of the electrical-engineering industry. The hypothesis of this study is that the present mathematics curricula for electrical-engineering at technikons are not fully compatible with the demands emanating from the theoretical and the industrial-training (in-service or workplace) components of the training of electrical-engineering technicians. The intent of this study is, firstly, to propose a framework of thought supporting engineering-mathematics curriculum-change in the context of electrical-engineering programmes as offered at technikons. The actual formulation of the syllabus content is supported by a curriculum-change model which takes cognisance of both the theoretical-demands and the workplace- demands in accordance with the aims of co-operative education espoused by technikons in South Africa. Secondly, a literature study of relevant past research leads to the development of a research methodology sympathetic to the present philosophy of technikon education for engineering-technicians in the country. The research methodology involves, firstly, a questionnaire response from practising engineers and technicians. Secondly, it involves the gathering of suggestions from technikon academic staff and the analysis thereof by a work-group representative of all technikons, and led by the researcher. Thirdly, seventy-nine (79) reference-texts to the electrical-engineering programmes (study-levels 1 to 4), offered at the Peninsula Technikon, were analysed for its mathematical content. The research findings supports the hypothesis. The thesis culminates in set of recommendations with regard to the applicability and composition of mathematics syllabi for electrical-engineering programmes at technikons

Design, fabrication and mechanical optimization of a flexural high speed nanopositioning imaging stage

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (p. 204-206).The intent of this research is to generate the knowledge required to design, fabricate and operate a device capable of high speed nano-scale vertical positioning of microscopy samples. The high speed focusing device (HSFD) created during this research utilizes a new combination of technologies for the purpose of imaging: Lorentz coil actuation, flexural bearings and strain gage sensing. The application of the technologies combined with precision design principles, as used in the HSFD, result in a demonstrated combination of performance and cost gains over a measured commercially available system. The HSFD is able to perform steps with 8 ms 95% settling time, 2% dynamic accuracy, and 0.005% static accuracy while operating with a resolution of 10.5 nm (l[sigma]) over a range of 500 [mu]m at a cost of about $1400. This performance is 3x faster stepping, 2x better dynamic accuracy, ~~100x better static accuracy, equivalent resolution and range to the top of the line commercial devices at less than half of the cost. The reduced cost is envisioned to enable greater distribution and use of nano-positioning imaging stages, while the increased performance is envisioned to enable faster, more benign (in the case of biological sciences) and more precise imaging. The increased use and data gathering ability of the new device are envisioned to enable fields of research such as biology and materials science to extend their bounds further into the micro/nano-scale as well as further along the time scale for both high speed and low speed processes.by Robert M. Panas.S.M

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 13)

This issue of the Index Section contains entries for 3386 patent and application for patent citations covering the period May 1969 through June 1978. The Index Section contains five indexes --- subject, inventor, source, number, and accession number

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 12)

For abstract, see N78-27983

NASA Patent Abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 20)

Entries for approximately 4000 citations for the period May 1969 through December 1981 are listed. Subject, invention, source, number, and accession number indexes are included