• 한국재료학회지
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• 제23권1호
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• pp.18-23
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• 2013

In this study, the effects of cryogenic treatment cycles on the residual stress and mechanical properties of 7075 aluminum alloy (Al7075) samples, in the form of a tube-shaped product with a diameter of 500 nm, were investigated. Samples were first subjected to solution treatment at $470^{\circ}C$, followed by cryogenic treatment and aging treatment. The residual stress and mechanical properties of the samples were systematically characterized. Residual stress was measured with a cutting method using strain gauges attached on the surface of the samples; in addition, tensile strength and Vickers hardness tests were performed. The detailed microstructure of the samples was investigated by transmission electron microscopy. Results showed that samples with 85 % relief in residual stress and 8% increase in tensile strength were achieved after undergoing three cycles of cryogenic treatments; this is in contrast to the samples processed by conventional solution treatment and natural aging (T4). The major reasons for the smaller residual stress and relatively high tensile strength for the samples fabricated by cryogenic treatment are the formation of very small-sized precipitates and the relaxation of residual stress during the low temperature process in uphill quenching. In addition, samples subjected to three cycles of cryogenic treatment demonstrated much lower residual stress than, and similar tensile strength compared to, those samples subjected to one cycle of cryogenic treatment or artificial aging treatment.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1995년도 제9회 학술발표회 논문개요집
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• pp.154-154
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• 1995

The Xu-Tec process is also called the double glow surface alloying technology and is a new method of surface metallurgy which can produce an alloy layers with sp ecial phisical and chemical properties on the surface of common and inexpensive mater ials. Many super alloys and alloy steels, sueh as nickel base alloys, high speed steels and staiinless steels, have been produced by Xu-Tee Process on the surfaces of carbon steels. The depth of the alloy lasyers may vary from several microns up to 300 micr ons with alloying elements in a concentration of few percentage to 100%. World wide patents for Xu-Tec process have been granted in the United states, Canada, United Ki ngdom, Australia and Japan. High performance saw blades have been successfully produced by the Xu-Tee process with much simper processing steps and less cost than bimetal high speed saw blades. A comparison of the cutting times and wear rates of the Xu-Tee blades with the conventional bimetal blades has been made. The Xu-Tee bIases demonstrates sim ilar or better performance than bimetal blades. A Xu-Tec Unit for the commercial pr oduction of Xu-Tec saw blades has been designed and manufactured. This Unit can t reat 10,000 haek saw blades at one time. Three Xu-Tec hack saw blades production I ines have been set up in China. China.

• 한국안전학회지
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• 제20권4호
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• pp.14-19
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• 2005

One area in which composites have been used rather extensively is for fabricating pressure vessel. These structures can be readily manufactured by filament winding, which is, as far as composite fabrication techniques are concerned, a relatively inexpensive method for producing composite structures. Unfortunately, the higher strength material and fabrication costs are not the only disadvantages of fiber-reinforced polymer composites when they are compared to metals. Additionally, these materials tend to exhibit brittle behavior. This is of particular concern when they are subjected to a low-velocity impact during routine handling a significant amount of structural damage can be introduced into the composites. The goals of this paper are to understand the impact damage behavior and identify the effect of surface coating materials on impact resistance in filament wound composite pressure vessels. For these, a series of low velocity impact tests was performed on specimens cutting from the full scale pressure vessel by the instrumented impact testing machine. The specimens are classified into two types with and without surface protective material. The visualization for impact damage is made by metallurgical microscope. Based on the impact force history and damage, the resistance parameters were employed and its validity in identifying the damage resistance of pressure vessel was reviewed. As the results, the impact resistance of the filament wound composites and its dependency on the protective material were evaluated quantitatively.

• Earthquakes and Structures
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• 제17권2호
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• pp.175-189
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• 2019

The aim of the study is to show the results of complex shaking table experimental investigation focused on the response of two models of cylindrical steel tanks under mining tremors and moderate earthquakes, including the aspects of diagnosis of structural damage. Firstly, the impact and the sweep-sine tests have been carried out, so as to determine the dynamic properties of models filled with different levels of liquid. Then, the models have been subjected to seismic and paraseismic excitations. Finally, one fully filled structure has been tested after introducing two different types of damages, so as to verify the method of damage diagnosis. The results of the impact and the sweep-sine tests show that filling the models with liquid leads to substantial reduction in natural frequencies, due to gradually increasing overall mass. Moreover, the results of sweep-sine tests clearly indicate that the increase in the liquid level results in significant increase in the damping structural ratio, which is the effect of damping properties of liquid due to its sloshing. The results of seismic and paraseismic tests indicate that filling the tank with liquid leads initially to considerable reduction in values of acceleration (damping effect of liquid sloshing); however, beyond a certain level of water filling, this regularity is inverted and acceleration values increase (effect of increasing total mass of the structure). Moreover, comparison of the responses under mining tremors and moderate earthquakes indicate that the power amplification factor of the mining tremors may be larger than the seismic power amplification factor. Finally, the results of damage diagnosis of fully filled steel tank model indicate that the forms of the Fourier spectra, together with the frequency and power spectral density values, can be directly related to the specific type of structural damage. They show a decrease in the natural frequencies for the model with unscrewed support bolts (global type of damage), while cutting the welds (local type of damage) has resulted in significant increase in values of the power spectral density for higher vibration modes.

• 식품과학과 산업
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• 제50권2호
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• pp.12-26
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• 2017

Processing steps such as washing and cutting, involved in preparing fresh-cut produce causes tissue damage, leading to rapid quality deterioration. Major defects of fresh-cut produce are discoloration, softening, off-odor development, and microbial growth. Packaging of fresh-cut produce has been changed to reduce these quality problems. Flexible packaging film is widely used to pack fresh-cut produce. Vacuum packaging was the popular packaging method in the beginning of fresh-cut industry in Korea. Vacuum packaging creates high $CO_2$ and low $O_2$ levels to control browning of fresh-cut produce. However, these conditions induce some visual defects and off-odor development. Discoloration problem was also found when fresh-cut produce was packaged with conventional packaging film or plastic tray. Modified atmosphere (MA) packaging is effective for prolonging shelf-life of fresh-cut produce by decreasing $O_2$ and increasing $CO_2$ concentration in the package. Retail MA packaging using different oxygen transmission rate (OTR) film and micro-perforated film has started to be applied to fresh-cut produce in Korea. Proper MA package design that provides optimum range of $O_2$ and $CO_2$ partial pressures is one of the major challenges in the industry. An initial package flushing with $N_2$ or an low $O_2$/high $CO_2$ atmosphere is also used to more rapidly establish steady-state MA condition. Film OTR and $O_2$ flushing affects the fermentative volatile production, off-odor development, electrolyte leakage, discoloration, $CO_2$ injury, microbial population of fresh-cut produce. There is also a demand for convenient packaging to attract consumers. Rigid fresh-cut produce container for retail market has increased since the packaging provides excellent protection from physical damage during transport. Rigid tray used as actual serving vessel for the consumer is increasing in Korea. The tray with flexible lid to wrap or seal fresh-cut produce is more and more gaining popularity. Further practical technology to control quality change and microbial growth for each fresh-cut product has been studied since various fresh-cut items were required. The fresh-cut industry also focuses on searching for more convenient and environmentally friendly packaging.

• 인간식물환경학회지
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• 제24권5호
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• pp.469-483
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• 2021

Background and objective: If the Nelumbo nucifera spreads in a wetland at a high density, it can have considerable positive and negative ecological effects on habitats. For this reason, it is necessary to precisely investigate the impacts of its rapid proliferation. This study was conducted to propose the distribution and management of N. nucifera, which can cause the degradation of wildlife habitats due to the rapid spread of internal and external environmental factors that may affect the Junam wetland ecosystem. Methods: For the investigation and analysis of physical and ecological characteristics, factors of the abiotic environment such as general weather conditions, topography and water depth structure, and soil and water quality analysis, and bioenvironment characteristics such as changes in the N. nucifera community distribution were evaluated. To assess whether the differences in the soil depth and physicochemical characteristics between the N. nucifera community and the aquatic plant community are statistically significant, a One-way ANOVA was executed. Results: N. nucifera was presumably introduced in approximately 2007 and observed at a prevalence of only 0.8% in 2009, but had expanded to 11.1% in 2014. After that, the area was increased to 19.3% in 2015 and 40.0% in 2017, about twice that of the previous survey year. The rapid diffusion of an N. nucifera colony can have adverse effects on wildlife habitats and biodiversity at Junam Wetland. To solve these problems, four management methods can be proposed; water level management, mowing management, installation of posts and removal of lotus roots. Control of the N. nucifera community using these methods was judged to be suitable for cutting and water level management when considering expansion rate, water level variation, and wildlife habitat impacts. Conclusion: As the biotic and abiotic environmental factors are different for each wetland, it is necessary to determine the timing and method of management through a detailed investigation.

• 식물병연구
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• 제19권2호
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• pp.95-101
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• 2013

Xanthomonas campestris pv. campestris(Xcc)에 의한 검은썩음병은 세계적으로 배추과 작물에 발생하여 큰 피해를 주고 있는 주요 식물병이다. Xcc에 대한 양배추의 효율적인 저항성 검정법을 확립하기 위해, Xcc에 대한 저항성 정도가 서로 다른 '루비아', '오조라', '그린핫', 'Saint', 'Joeun-ACE', 'Wonderball' 및 'XCCR 500' 등 7개 양배추 품종을 대상으로 접종 방법, 접종 위치, 재배 기간 그리고 재배 온도에 따른 검은썩음병 발생을 조사하였다. 양배추 품종들의 저항성은 18핀이나 가위를 사용하여 접종하는 것보다 핀셋(mouth-tooth forceps)을 사용하여 접종하였을 때 가장 큰 차이를 보이며, 직접적으로 엽맥에 접종하는 것보다 엽맥 주변에 접종이 더 효과적이었다. 그리고 접종한 유묘를 $30^{\circ}C$ 보다 $22^{\circ}C$에서 재배하였을 때에 감수성과 저항성 반응이 더 분명하게 나타났다. 이상의 결과로부터 양배추 검은썩음병에 대한 효과적인 저항성 검정법으로 4주 재배한 유묘의 엽맥 주변을 핀셋(mouth-tooth forceps)으로 상처 접종한 후 $22^{\circ}C$ 생육상에서 재배하는 방법을 제안하고자 한다.

• 문화기술의 융합
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• 제5권3호
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• pp.209-214
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• 2019

이 연구는 가설적으로써, 하나의 감정을 어떻게 잘라내어 긍정적으로 활성화시킬 수 있는지에 대한 것이다. 이 연구는 AI를 통한 문학치료에 활용될 수 있을 것이다. 이번 연구에서, 황진이의 시조 "동짓달 기나긴 밤을"을 연구하였다. 왜냐하면 이 작품이 감정의 잘라냄과 이어놓음에 대한 연구에 아주 적절하기 때문이다. 이 시조에는 이러한 치유의 셈법이 활용되었다. 황진이의 이 작품은 초장에서 '동짓달 기나긴 밤'을 잘라낸다. 그리고 그 잘라낸 그리움의 시간들을 '춘풍 이불' 아래에 잇대어 놓으면서 감정의 재생산을 꿈꾼다. 그리고 종장에서 그리움의 시간들을 아주 잘게 무한대로 펼쳐낸다. 펼쳐지는 그리움의 시간들은 '춘풍 이불'에 덧대어 놓았던 것이다. 그리움의 시간들을 펼쳐내면서, 종장에서는 끊임없는 사랑에의 그리움 즉 영원한 사랑을 꿈꾼다. 이러한 문학적 행위는 인체의 신경 계통에 많은 변화를 유도할 수 있을 것으로 예측된다. 이것이 문학으로 감정의 치료를 꿈꾸는 사랑법이다. 임은 떠났지만 보내지 않은 임의 사랑이 기쁨의 감정을 증폭시키게 된다. 이러한 감정의 셈법은 앞으로 전개될 AI를 통한 문학치료에 매우 유용하게 사용될 수 있을 것으로 사료된다.

• 한국잡초학회지
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• 제30권2호
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• pp.164-170
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• 2010

유기농 콩 재배에 가장 문제가 되는 잡초를 억제하기 위하여 호밀을 피복작물로 이용하여 콩을 재배하였다. 호밀의 이용방법에 따른 잡초 억제 효과를 보기 위하여 리빙멀치(living mulch), 토양 환원, 호밀 예취구를 두었고, 콩의 재식밀도와 호밀 파종밀도를 다르게 처리하여 잡초의 발생 양상을 비교하였다. 호밀을 리빙멀치로 이용한 처리구가 잡초의 발생과 생 육을 가장 효과적으로 억제하였다. 콩 파종 한달 후의 잡초 억제율은 리빙멀치구가 92.5%에 달하였으며 15일 예취구가 75.4%, 토양 환원구가 67.1%, 30일 예취구가 61.3%에 달하였다. 호밀의 파종 밀도에 따른 효과는 처리구간 차이가 미미하였으나 콩 생육 후기에는 호밀 2줄 파종이 호밀 1줄 파종보다 다소 우수하였다. 콩 재식거리에 따른 효과도 호밀 파종 밀도의 결과와 비슷하여 밀식과 소식간 차이가 인정되지 않았다.

• 한국환경복원기술학회지
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• 제9권2호
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• pp.59-71
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• 2006

Due to the rapid process of industrialization the cities of Korea confront changes of climate, destructions of the habitate and decrease of the green. Recently Seoul and other local governments have implemented policies and projects to improve the environmental surroundings. In reality, however, those policies and projects face difficulties in the course of implementation. The fact that there are no concrete regulations and specific legal procedures turns out to be one of the main difficulties. The aim of this study is to present specific plans and methods of wall-planting and to provide basic guidelines for the future direction of wall-planting and offer ideas of facilitating wall-planting. This study is based on questionnaires from specialists of landscape architecture through individual interviews and/or e-mails. The questionnaire is consisted of following 4 sections. 1. Show the experts current regulations and/or legal procedures and ask them improvements and suggestions. 2. Ask them choose matters of the highest priority by using Ricardo's diagram method. 3. Ask them to make a graded list in terms of the location and method of wall-planting. 4. Study the maketability of the wall-planting products currently in circulation. The city of Seoul and the Ministry of Environment recommend that trellis and/or planting inducement structures be installed on the building wall by regulation. The specialists responded to the questionnaire advocate that green wall without trellis should be allowed as green zone. Therefore regulations concerning the wall-planting should be determined specifically according to the characteristics of individual plants and walls. It has been urged that legal aid and social support must be reinforced to establish rules dealing with wall-planting. The respondents also point out that significant cutting down of the tax is far more effective in accelerating the wall-green instead of administrative support. The highest priority in terms of planting has been given to sound-proof wall, retaining wall and building wall. Concerning the maketability of the wall-planting products, panel products are recommended for early-planting and building planting. It has been suggested that the research and study of new materials and species be done in advance.