493 publications from this institution
N, 1-Bis [5-(3-substituted)-[1, 2, 4] oxadiazolyl] dimethylamines (3) were synthesized through the reaction of creatinine (2) with primary aliphatic nitro compounds (1) and acetyl chloride. The structural determination of 3 by single crystal X-ray analysis is reported.
An active and reactive volt-ampere-hour meter that consists of 12-b analog-to-digital converters and a digital signal processor has been developed. The meter has digital offset canceling filters and digital 90 degrees -phaser-difference filters. The canceling filters cancel offset in the sample-and-hold circuits and in the analog-to-digital converters. Using the phase-difference filters, the meter is able to measure reactive volt-ampere-hour value, not only for the fundamental frequency but also for several orders of harmonics. The voltage and current noise is canceled by the time-domain integrals. Using a digital signal processor, it is possible to realize a smaller size and lower power consumption than for a conventional volt-ampere-hour meter. Highly accurate results were obtained by computer simulation and for a breadboard mockup construction.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
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Analytical study on cracking behavior of concrete due to rebar corrosion in the cases of multi-rebar specimens with various rebar spacings, of specimens with locally corroded rebar and specimens with pitting corrosion rebar was carried out. Three-dimensional Rigid-Body-Spring-Method (RBSM) with three phase material corrosion expansion model was applied to simulate crack initiation, internal cracking patterns and crack width propagation. It was confirmed that rebar spacing, ratio of local corrosion length and rebar length and pitting corrosion pattern played important roles in the cracking behavior.
Snow accumulation on transmission lines increases the conductor load. It may result in damage to transmission facilities due to abnormal load. As such, snow accumulation on transmission lines is one of the crucial problems. A method using the heat generated by the alternating magnetic field of a magnetic material wire has been developed and put into practical use. However, the method using conventional magnetic material can not gain sufficient calorific value to melt snow at some transmission lines through which only low current passes in the winter season. To solve these problems, we attempted to optimize alloy composition of Fe-Ni. In this research, we manufactured snow-melting wires varying Ni content and evaluated these magnetic characteristics and calorific value. In this result, magnetic characteristics and calorific value improved with increasing Ni content. A magnetic material optimized alloy composition showed calorific value of approximately 1.4 times as much as conventional magnetic material.
In this study, the effect of the expansive site ratio on the anisotropy of expansion due to delayed ettringite formation (DEF) was numerically evaluated considering creep. In this analysis, aggregates and mortar were separately modeled using 3D-Rigid Body Spring Model. The expansion strain was applied to the expansive site for 200 days. Each analysis was conducted under stress-free and restraint conditions. As a result of the 1 % expansive site, the expansion under restraint condition was smaller than that under stress-free condition. In the case of a higher expansive site ratio, the expansion under restraint condition was larger, and the larger compressive stress was generated in the restraint direction. The reason why the expansion under restraint condition was smaller for the 1 % expansive site case is the less accumulated compressive stress due to the localization of expansion origin. Consequently, the expansion origin may be scattered in the actual phenomenon.
With a focus on crack propagation in concrete, this Committee concentrated on the morphology of cracking and investigated the current state and future development of the evaluation of crack propagation, while inventorying test and analysis techniques currently available and examining their scope and potential. The topics included testing techniques capable of evaluating crack propagation (digital image processing, etc.), analysis techniques for evaluating crack propagation (FEM, RBSM, etc.), and methods of evaluating crack propagation in deterioration cases due to various causes (drying shrinkage cracking, corrosion cracking, etc.).
This paper presents an electro-mechanical model for evaluating the corrosion-induced damage in reinforced concrete under accelerated conditions. The model consists of structural analysis of concrete and the rebar using the Rigid Body Spring Method and corrosion current analysis with the truss networks model. The electric corrosion process is coupled with concrete cracking conditions by relating current efficiency to local crack width; the predicted radius losses of rebars are used to evaluate concrete crack propagation and residual tensile performance of corroded rebars. The model is validated with the results of accelerated corrosion tests using impressed current and a sodium chloride pond on the concrete cover. Good agreement with the test data is obtained with the proposed model, in terms of corrosion degree and profile, concrete crack pattern, and tensile behavior of corroded rebars. The model offers a corroborative tool with the accelerated corrosion technique to study the mechanical behavior of corroded concrete structures.
Abstract Zero-dimensional computations of nanosecond-order ignition using a nanosecond discharge are performed with two constraints. The effects of these constraints are assessed to study the experimental rapid pressure change properly at the initial stages. The computations are carried out with the following constraints: constant internal energy and volume (U&V) and constant enthalpy and pressure (H&P), revealing differences between the two solutions. As the pressure remains constant under the H&P constraint, the total number density of all species decreases during ignition. In this case, O radicals are less generated and consumed. The progression of all reactions and temperatures increases under the H&P constraint less intensely than under the U&V constraint. Significant differences are found between the results calculated under the U&V and H&P constraints. Therefore, large discrepancies with real phenomena can be caused if the loss due to pressure reduction is not treated well.
