• Applied Microscopy
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• 제46권1호
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• pp.45-50
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• 2016

Iron containing a high amount of chromium is known to be inferior to ductility due to ${\sigma}$ phase formation so that it is generally difficult to apply the plastic deformation process although the alloy possesses a superior characteristics of an excellent corrosion resistance. In this study, Fe-50mass%Cr alloy was melted using high purity powder and the deformation behavior has been investigated by cold rolling and tensile test. The tensile test yielded that the alloy revealed a serration at an early stage of tensile deformation and then the serrated flow vanished to change to a normal work hardening flow at the later stage. The former was governed by twin formation process, the latter by dislocation multiplication one, bringing about a high ductility of 20% or over. The reduction ratio in cold rolling was attained as high as 90%, thus the high corrosion-resistant alloy is able to possess a high ductility.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2084-2094
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• 2021

Delta-form-based methods for solving high order spatial discretization schemes are introduced into the reactor S_N transport equation. Due to the nature of the delta-form, the final numerical accuracy only depends on the residuals on the right side of the discrete equations and have nothing to do with the parts on the left side. Therefore, various high order spatial discretization methods can be easily adopted for only the transport term on the right side of the discrete equations. Then the simplest step or other robust schemes can be adopted to discretize the increment on the left hand side to ensure the good iterative convergence. The delta-form framework makes the sweeping and iterative strategies of various high order spatial discretization methods be completely the same with those of the traditional S_N codes, only by adding the residuals into the source terms. In this paper, the flux limiter method and weighted essentially non-oscillatory scheme are used for the verification purpose to only show the advantages of the introduction of delta-form-based solving methods and other high order spatial discretization methods can be also easily extended to solve the S_N transport equations. Numerical solutions indicate the correctness and effectiveness of delta-form-based solving method.

• Journal of Power Electronics
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• 제11권1호
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• pp.28-36
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• 2011

In this paper, a three phase cycloconverter type high frequency AC link inverter is discussed. The configuration consists of a high frequency full-bridge inverter and a high frequency transformer followed by a three phase cycloconverter whose switch is composed of anti-series connected MOSFETs with a common source. A simple digital control strategy based on space vector modulation (SVM) and repetitive control for the cycloconverter is proposed although its input voltage is a high frequency AC pulse. The operation principle of the proposed control strategy is analyzed and the equivalent working modes during one interval are also presented. The effectiveness of the proposed control strategy is verified through Matlab/Simulink simulations and experiments on a 1.45kW prototype.

• Steel and Composite Structures
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• 제16권3호
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• pp.289-303
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• 2014

In recent, development of construction and design technology gives taller, larger and heavier steel framed structures. With the tendency of increasing high-rise building, this study is strongly related to structural system, one of significant components in structural design. This study presents an innovative structural system, with high performance steel material, diagrid. Its detail, structural analysis, and structural experiments are all included for the development of new structures.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1323-1324
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• 2006

Refractory materials, such as W and Mo, are very useful elements for use in high-temperature applications. But it is not easy to fabricat pure W and Mo with very high density and retaining very fine grain size because of their high melting point. In this paper, a newly developed method named as resistance sintering under ultra high pressure was use to fabricate pure fine-grained W and Mo. The microstructure was analysis by SEM. The sintering mechanism is primary analyzed. Basic physical property of these sintered pure W and Mo, such as hardness, bend strength, are tested.

• 한국물환경학회지
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• 제20권3호
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• pp.236-240
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• 2004

Autohydrogenotrophic denitrification of high nitrate concentration contaminated wastewater in a batch-scale biofilm reactor has been investigated. High nitrate concentration decreased as pH increased from 7.01 to 9.45. The high nitrate concentrations continuously decrease from $150mg.l^{-1}$ to $0mg.l^{-1}$. Nitrite concentrations increase at about two-thirds way through the denitrification process and thereafter it decreases with time. Autohydrogenotrophic denitrification of high nitrate concentration is passible to use drinking water as well as wastewater, and to deal with wastewater treatment by hetrotrophic denitrification.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.165-170
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• 2009

The Korean high-speed rail network has been made a remarkable growth recording the world's 4th rank passenger transportation scale during last 5 years after opening the revenue service of Kyoung-bu high-speed line in 2004. However, in spite of it's outstanding growth, Korean Rail technology should meet a demand of intensive technology development in order to prepare a severe competition with an advance parties of worldwide high-speed rail technology. In this paper, the characteristics and new trend of world's rail industry was reviewed based on the most recent statistics and papers of worldwide rail network from UIC and WCR32008. In conclusion, new R&D strategy with choice an concentration for the Korean high-speed rail industry was suggested based on an analysis on the trend of evolution of the state of the art technologies in worldwide high-speed rail system.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1998년도 특별강연 및 추계학술발표 개요집
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• pp.11-24
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• 1998

The invention of fusion wilding technology has brought on a revolutionary change in manufacturing industry which enables the construction of large scale high temperature plants in chemical, petrochemical and power generation industries. However, among the failure cases of high temperature components, premature failures of weldments have taken a large percentage that indicates the detrimental effect of welding on structural integrity. The accurate prediction of the high temperature behaviour of welded components is thus becoming increasingly important in order to realise an optimised design and maintenance of a plant life. In the present paper, recent research activities on high temperature behaviour of welded structures are briefly summarised. A local deformation measuring technique is proposed to determine the creep properties of weldment constituents. A damage mechanics approach is introduced to study the life reduction and ductility reduction due to the presence of a weld in high temperature structures. Finally, the high temperature creep crack growth in weldments is discussed.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.460-465
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• 2003

High-speed machining is one of the most effective technology to improve productivity. Because of the high speed and high feed rate, high-speed machining can give great advantages fur the machining of dies and molds. This paper describes on the improvement of machining accuracy in high-speed machining and an estimate about machining accuracy of high-speed machining.

• International Journal of Aeronautical and Space Sciences
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• 제14권2호
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• pp.140-145
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• 2013

The development of high performance fabrics have advanced body armor technology and improved ballistic performance while maintaining flexibility. Utilization of the shear thickening phenomenon exhibited by Shear Thickening Fluids (STF) has allowed further enhancement without hindering flexibility of the fabric through a process of impregnation. The effect of STF impregnation on the ballistic performance of fabrics has been studied for impact velocities below 700 m/s. Studies of STF-impregnated fabrics for high velocity impacts, which would provide a transition to significantly higher velocity ranges, are lacking. This study aims to investigate the effect of STF impregnation on the high velocity impact characteristics of Kevlar fabric by effectively dispersing silica nanoparticles in a suspension, impregnating Kevlar fabrics, and performing high velocity impact experiments with projectile velocities in the range of 1 km/s to compare the post impact characteristics between neat Kevlar and impregnated Kevlar fabrics. 100 nm diameter silica nanoparticles were dispersed using a homogenizer and sonicator in a solution of polyethylene glycol (PEG) and diluted with methanol for effective impregnation to Kevlar fabric, and the methanol was evaporated in a heat oven. High velocity impact of STF-impregnated Kevlar fabric revealed differences in the post impact rear formation compared to neat Kevlar.