Solution of the Inverse Problems of Scattering of Electromagnetic Fields by Elongated Defects

We formulate the inverse problem of scattering of electromagnetic fields by thin defects and analyze numerical algorithms used for its solution. It is shown that, in the two-dimensional case, the shape of a thin defect is completely determined by the scattered field given on a certain curve for a fixed value of the wave number. For the solution of the inverse scattering problem, we propose to use the procedure of iterative regularization based on the gradient methods. We deduce expressions for the Fréchet derivative of the operator of direct scattering problem with Dirichlet conditions imposed on the surface of a scatterer.     

Ampacities of power cables wound on reels

This paper presents a mathematical model that is capable of calculating the ampacity of a wide variety of power cable designs consisting of an arbitrary number of layers on a cable reel. The model considers round cables with copper conductors. The validity and accuracy of the ampacity model were verified by comparing the predicted temperature distribution within the reel with measured temperatures collected during an extensive testing program conducted at the US Bureau of Mines (USBM). The mathematical model predicted a temperature distribution within the cable layers that was very close to the measured variation in temperature. The value of the program is illustrated by calculating ampacities for several copper conductor sizes     

Calculation and design of vibrational mills

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 1, pp. 14–15, January, 1992.     

Optimal Design of the High-Power Plate and Grid Modulated HF Amplifier by High Modulation Levels

The optimal design of the high power plate and grid modulated selective amplifier is examined in this paper. For the analysis purposes, the linear model of constant plate current characteristics for HF power triode is applied. The carrier wave state of the unmodulated amplifier is chosen so to enable the realization of the high levels of modulation. The results are obtained immediateZy, and the estimated error is acceptable. The estimated characteristic values of this high power and high efficiency HF amplifier are shown in the corresponding diagrams.     

Suppression of boron penetration in p+ polysilicon gateP-MOSFETs using low-temperature gate-oxide N2O anneal

It has been reported that high-temperature (~1100°C) N₂ O-annealed oxide can block boron penetration from poly-Si gates to the silicon substrate. However, this high-temperature step may be inappropriate for the low thermal budgets required of deep-submicron ULSI MOSFETs. Low-temperature (900~950°C) N₂O-annealed gate oxide is also a good barrier to boron penetration. For the first time, the change in channel doping profile due to compensation of arsenic and boron ionized impurities was resolved using MOS C-V measurement techniques. It was found that the higher the nitrogen concentration incorporated at Si/SiO₂ interface, the more effective is the suppression of boron penetration. The experimental results also suggest that, for 60~110 Å gate oxides, a certain amount of nitrogen (~2.2%) incorporated near the Si/SiO₂ interface is essential to effectively prevent boron diffusing into the underlying silicon substrate     

Enhancement of oxide break-up by implantation of fluorine inpoly-Si emitter contacted p+-n shallow junctionformation

In this study, it is demonstrated that the incorporation of fluorine can enhance poly-Si/Si interfacial oxide break-up in the poly-Si emitter contacted p⁺-n shallow junction formation. The annealing temperature for breaking up the poly-Si/Si interfacial oxide has been found to be as low as 900°C. As a result, the junction depth of the BF₂-implanted device is much larger than that of the boron-implanted device     

E-BAMA vs. RAMA [multiple access protocols]

The article presents a performance comparison of two random access protocols for wireless mobile signaling in which a single channel is dedicated to the signaling function, enhanced beacon assisted multiple access (E-BAMA) and resource auction multiple access (RAMA). Data traffic is transported separately on a set of orthogonal channels. The beacon assisted multiple access (BAMA) protocol was first presented as a method of providing mobility management functions, e.g., handover, while minimizing the processing burden placed on the mobile. In BAMA, throughout the duration of its call, an active user repeatedly and quasi-periodically broadcasts a beacon containing its ID using the Aloha protocol. Quasi-periodicity prevents a pair of users from repeatedly colliding with each other. When a base successfully receives the beacon and assigns a channel, it uses a separate downstream channel to send to the mobile an acknowledgement that contains the number of the assigned channel. The BAMA protocol includes a scheme to maintain lists of active mobiles in nearby cells and to exchange periodically these lists among the base-stations. The authors evaluate the capacity and delay performance of E-BAMA and RAMA. Then, they present a numerical comparison of the parameters. Finally, the results are summarized qualitatively. Some additional derivation is included in the appendix     

Photovaractor for remote optical control of microwave circuits

A photovaractor for the remote optical control of microwave circuits was studied. The photovaractor was fabricated as a p-i-n photodiode placed in a pigtailed fiber optical module. The study of the impedance in the frequency range up to 3 GHz in darkness and under illumination has shown that the photovaractor capacitance strongly depends on the incident optical power. The capacitance variation of the photovaractor diode under illumination is discussed