• Geomechanics and Engineering
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• 제10권1호
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• pp.49-57
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• 2016

The high permeability-high strength concrete belongs to the typical of porous materials. It is mainly used in underground engineering for cold area, it can act the role of heat preservation, also to be the bailing and buffer layer. In order to establish a suitable model to predict the thermal conductivity and directly applied for engineering, according to the structure characteristics, the thermal conductivity predicting model was built by resistance network model of parallel three-phase medium. For the selected geometric and physical cell model, the thermal conductivity forecast model can be set up with aggregate particle size and mixture ratio directly. Comparing with the experimental data and classic model, the prediction model could reflect the mixture ratio intuitively. When the experimental and calculating data are contrasted, the value of experiment is slightly higher than predicting, and the average relative error is about 6.6%. If the material can be used in underground engineering instead by the commonly insulation material, it can achieve the basic requirements to be the heat insulation material as well.

• 한국결정성장학회지
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• 제19권4호
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• pp.190-195
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• 2009

스컬용융법에 의해 Na사규소운모를 합성하였다. $Mg_3(OH)_2Si_4O_{10}:Na_2SiF_6:SiO_2=8.3:24.8:66.9$ mol% 비율로 혼합한 출발원료를 ${\phi}13{\times}H14cm$의 냉각도가니에 채우고 2.84MHz 출력주파수의 고주파발진기를 이용하여 가열하였다. 원료는 융액상태에서 1시간 유지하였으며 도가니 내에서 냉각시켰다. 운모의 비저항은 추정하였으며, 원주모양과 판상으로 합성할 수 있었다.

• Steel and Composite Structures
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• 제22권4호
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• pp.745-752
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• 2016

An investigation has been done to study the evolution of the microstructure, mechanical and electrical properties of AlMgSi alloy destined for the transport of electric energy, in function of the deformation caused by the cold drawing process. We identified that drawing of aluminum wire causes development of a fibrous texture of type <111> and <100>. We notice also that the electrical resistivity and mechanical resistance increases with the increasing of the deformation level. Characterization methods used in this work is: The Electron Back Scattered Diffraction EBSD, X-Ray diffraction, Vickers microhardness, Tensile test, Measuring electrical resistivity, the Scanning Electron Microscope (SEM) and Energy Diffraction Spectrum (EDS).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.17-18
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• 2006

Laser welding of metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for metals with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the butt welding, the welding quality of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding quality is 1400W of the laser power, 0.8m/min, 0.9m/min of welding speed and $4{\ell}$ in of pressure for shielding gas.

• 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.

• 한국재료학회지
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• 제16권6호
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• pp.386-393
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• 2006

Increasing environmental concerns require to solve the problem produced due to the use of heavy metals in coating formulations. Therefore, it is necessary to develop new coating strategy employing inherently conducting polymers such as polyaniline. Polyaniline is a conductive polymer that is synthesized by oxidation polymerization, and the electrochemical and chemical polymerization are possible for the oxidation of aniline. Electrochemical oxidation polymerization produces a fine surface and although voltage control is more convenient, it require electrolytic cells, and elaborate thin film can be acquired with the polymerization. Polyaniline films were electro-polymerized on cold rolled sheets using the galvanostat mode in the oxalic acidaniline-sodium molybdate electrolyte. The structure and properties of polyaniline film were studied using Potentiostat/Galvanostat 263A, FE-SEM,, AFM, SST, Colorimetry. A high corrosion resistance of polyaniline film was observed with an increase of corrosion potential by $500{\sim}600$ mV for the substrate covered with polyaniline.

• Tribology and Lubricants
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• 제20권3호
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• pp.145-151
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• 2004

A modified surface layer by ion implantation is very thin (under 1 $\mu\textrm{m}$) but has superior mechanical characteristics. therefore ion implantation has been used successfully as a surface treatment technology to improve the wear, fatigue, and corrosion resistances of materials. MEVVA which is a kind of ion beam apparatus has merits of low cost and is usable to various metals, but occurs a droplet ranging from micron to tens of micron on the implanted surface at ion implantations. wear is a dynamic phenomenon on interacting surfaces with rotative motion. Since wear changes in condition of the surface, we should control to surface. In order to improve a wear resistance of Ti ion implanted 1C-3Cr steel(material for roller in the cold working process), it is essential to investigate the effect of the droplets on the wear characteristics. In this study, we investigate the effect of the droplets on the wear characteristics of 1C-3Cr steel using SEM Tribosystem as in-situ system. Results show that the droplet occurred at ion implantation becomes the cause of severe wear. Therefore, the ion-implanted surface should be removed the droplet to improve wear resistance.

• International Journal of Advanced Culture Technology
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• 제11권3호
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• pp.277-296
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• 2023

The South Korean ethnic diaspora US lobby shows efficacy as an interest group in generating influence in American foreign and domestic public policy making. The persuasive portrayal of South Korea as a critical Cold War US ally reinforced US amenability to pro-South Korea lobbying. Also, the South Korean US diaspora is a comparatively recent immigrant group, thus its lingering resistance to assimilation facilitates its political mobilization to lobby the US government. One source of this influence includes the foundational legacy of proselytizing Western and particularly American religious social movement representatives in Korean religiosity and society. US protestant Christianity acquired a strong public association with emerging Korean nationalism in response to Japanese imperialism and occupation. Hostility towards Japanese colonialism followed by the threat from Soviet-sponsored, North Korean Communism meant Christianity did not readily become a cultural symbol of excessive external, US interference in South Korean society by South Korean public opinion. The post-Cold War shift in US foreign policy towards targeting so-called rogue state vestiges of the Cold War including North Korea enhanced further South Korea's influence in Washington. Due to essential differences in the perceived historical role of American influence, extrapolation of the South Korean development model is problematic. US hegemony in South Korea indicates that perceived alliance with national self-determination constitutes the core of soft power appeal. Civilizational appeal per se in the form of religious beliefs are not critically significant in promoting American polity influence in target polities in South Korea or, comparatively, in the Middle East. The United States is a perceived opponent of pan-Arab nationalism which has trended towards populist Islamic religious symbolism with the failure of secular nationalism. The pronounced component of evangelical Christianity in American core community nationalism which the Trump campaign exploited is a reflection of this orientation in the US.

• 대한기계학회논문집A
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• 제27권8호
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• pp.1398-1408
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• 2003

Tensile and LCF(low cycle fatigue) tests were carried out in air at wide temperature range 20$^{\circ}C$-750$^{\circ}C$ and strain rates of 1${\times}$10$\^$-4//s-1${\times}$10$\^$-2/ to ascertain the influence of strain rate on tensile and LCF properties of prior cold worked 316L stainless steel, especially focused on the DSA(dynamic strain aging) regime. Dynamic strain aging induced the change of tensile properties such as strength and ductility in the temperature region 250$^{\circ}C$-600$^{\circ}C$ and this temperature region well coincided with the negative strain rate sensitivity regime. Cyclic stress response at all test conditions was characterized by the initial hardening during a few cycles, followed by gradual softening until final failure. Temperature and strain rate dependence on cyclic softening behavior appears to result from the change of the cyclic plastic deformation mechanism and DSA effect. The DSA regimes between tensile and LCF loading conditions in terms of the negative strain rate sensitivity were well consistent with each other. The drastic reduction in fatigue resistance at elevated temperature was observed, and it was attributed to the effects of oxidation, creep and dynamic strain aging or interactions among them. Especially, in the DSA regime, dynamic strain aging accelerated the reduction of fatigue resistance by enhancing crack initiation and propagation.

• 한국압력기기공학회 논문집
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• 제19권2호
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• pp.102-108
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• 2023

A Chloride-induced stress corrosion cracking (CISCC) of austenite stainless steel in dry cask storage system (DCSS) can occur with extending service time than originally designed. Cold spray coating (CSC) not only form a very dense microstructure that can protect from corrosive environments, but also can generate compressive stress on the surface. This characteristic of CSC process is very helpful to increase the resistance for CISCC. CSC with several powders, such as 304L, 316L and Ni can be optimized to form very dense coating layer. In addition, the impact energy generated as the CSC powder collides with the surface of base metal at a speed of Mach 2 or more can remove the residual tensile stress of welding area and serve the compress stress. CSC layers include no oxidation and no contamination with under 0.2% porosity, which is enough to protect from the penetration of corrosive chloride. Therefore, the CSC coating layer can be accompanied by a function that can be disconnected from the corrosive environment and an effect of improving the residual stress that causes CISCC, so the canister's CISCC resistance can be increased.