Showing papers by "Istanbul Technical University published in 1981"

Closure of "Nonlinear Analysis of Cold-Formed Steel Shear Diaphragms"

Abstract: The method is based on residual forces. Diaphragms are modeled by finite elements of three types: (1)The individual panel units; (2)the supporting steel framing; and (3)the connectors. The connectors are considered to be the sole source of nonlinear behavior, essentially as indicated by experimental evidence. The computer program is user-oriented, and is equipped with an automatic mesh generator as well as an accelerator to improve convergence rate. Applications of the analysis to diaphragms for which full-scale test results are available show good correlation. The method provides full information on displacements and internal force distributions, as well as overall behavior, and thus provides a sound basis for the development of approximate methods suitable for manual design. It may be directly useful for the design of complex systems such as those including large openings or having unusual proportions, or for the design of innovative stressed-skin structures such as folded plates.

Optimum hyperbolic moveout filters with applications to seismic data

Abstract: Optimum multichannel filters can be designed to process seismic events falling on hyperbolic moveout curves using the conventional least-squares method. Contrary to the linear moveout filters, autocorrelation and crosscorrelation functions inherent in the normal equations have to be computed numerically. However, computation times of filter coefficients are comparable to linear moveout operators. For a given source-receiver geometry and assuming straight ray-path, relative moveout of a seismic reflection event is dependent on the two way arrival time and rms velocity. Consequently, to avoid overlapping of pass and reject moveout windows, hyperbolic moveout filters have to be designed over time gates rather than for the whole record lengths. Hyperbolic and hyperbolic-linear moveout filters applied to synthetic and field seismic reflection traces show good signal-to-noise (S/N) ratio improvements. Results of some combined synthetic and field data examples are presented.

ESR studies of some γ-irradiated organic crystals

Abstract: Acrylamide, N-tert-butylacrylamide, and propionamide crystals were irradiated at -196/sup 0/C and the structures of radicals studied by ESR spectroscopy at various temperatures. The ..gamma..-irradiated acrylamide crystals show a five-line spectrum which is similar in shape to the signal obtained from the ..gamma..-irradiated propionamide crystals. Two types of radicals are produced in irradiated acrylamide and propionamide crystals at -196/sup 0/C. When the irradiated samples are kept at -78/sup 0/C the spectrum of propionamide remains the same, except in intensity. In contrast to this, the acrylamide spectrum changes to a triplet because of dimerization. Upon warming the irradiated acrylamide sample to between -50 and -30/sup 0/C, some small new peaks become apparent on either side of the triplet. These new peaks disappear above -20/sup 0/C and the spectrum changes to a triplet because of polymerization. To observe the changes in the ESR spectra of ..gamma..-irradiated N-tert-butylacrylamide we kept the sample at various temperatures from -196 to 100/sup 0/C. From -196/sup 0/C to about room temperature the spectrum is a quintet. At and above 35/sup 0/C, the spectrum changes to a triplet with shoulders on either side of the main peaks. With further warming above 80/sup 0/C the spectrum changes to a broadmore » triplet.« less

Thermal performance of alternative walls and windows

Abstract: Heating season thermal performances of alternative walls and windows are evaluated by computer analysis using the weather data of two cities located on 40 Deg and 41 Deg north latitudes, having distinct climates. 8-inches clay tile wall and frame wall with 2-inches insulation are adopted as wall alternatives. Hourly heat flows from this walls are computed using Transfer Function Coefficients. Single glazing, double glazing, single glazing with night shutters and double glazing with night shutters are adopted as window alternatives. Heating season energy balances of the alternatives are presented in graphical form.

Quasi‐analytic convolution solution of the electromagnetic field*

Abstract: The objective of this study is to generate the separation-distance-domain (r-domain) transformation of the theoretically calculated wave number domain (m-domain) electromagnetic induction field component Bz(m, ω) of a stratified medium and to search for interpretive information which has been absent in the previously achieved numerical solutions of the problem. The r-domain kernel R(r, ω) function defining the induction field appears to adequately reflect the layering and electrical properties of the medium if it is expressed as a function of the frequency if the source-receiver separation r is small with respect to the thickness of the first layer. However, exact values of the conductivity cannot be distinguished from those of the neighboring values unless a resistive basement layer is present. This feature is the result of the truncation in series representation of the kernel function R(m, ω). However, this truncation is regarded as significant in the case of a conductive first layer. In m-domain static-zone studies, a conductive first layer slightly influences its r-domain correspondent. Although the computational cost of obtaining the kernel B(r, ω) by evaluation of the convolution in a cylindrical coordinate system is high, this semi-analytic solution is still superior to those based on the asymptotic assumptions.

A Two-Device Bistable Memory Circuit without Feedback Loop

Abstract: A charge-pumping gate-controlled diode is operated as a bistable device in a two-device configuration without a feedback loop. An application in a dense and low power consuming pseudo-static RAM cell is also considered.