• 한국재료학회지
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• 제22권11호
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• pp.620-625
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• 2012

A general synthetic method to make $Fe_3O_{4-{\delta}}$ (activated magnetite) is the reduction of $Fe_3O_4$ by $H_2$ atmosphere. However, this process has an explosion risk. Therefore, we studied the process of synthesis of $Fe_3O_{4-{\delta}}$ depending on heat-treatment conditions using $FeC_2O_4{\cdot}2H_2O$ in Ar atmosphere. The thermal decomposition characteristics of $FeC_2O_4{\cdot}2H_2O$ and the ${\delta}$-value of $Fe_3O_{4-{\delta}}$ were analyzed with TG/DTA in Ar atmosphere. ${\beta}-FeC_2O_4{\cdot}2H_2O$ was synthesized by precipitation method using $FeSO_4{\cdot}7H_2O$ and $(NH_4)_2C_2O_4{\cdot}H_2O$. The concentration of the solution was 0.1 M and the equivalent ratio was 1.0. ${\beta}-FeC_2O_4{\cdot}2H_2O$ was decomposed to $H_2O$ and $FeC_2O$4 from $150^{\circ}C$ to $200^{\circ}C$. $FeC_2O4$ was decomposed to CO, $CO_2$, and $Fe_3O_4$ from $200^{\circ}C$ to $250^{\circ}C$. Single phase $Fe_3O_4$ was formed by the decomposition of ${\beta}-FeC_2O_4{\cdot}2H_2O$ in Ar atmosphere. However, $Fe_3C$, Fe and $Fe_4N$ were formed as minor phases when ${\beta}-FeC_2O_4{\cdot}2H_2O$ was decomposed in $N_2$ atmosphere. Then, $Fe_3O_4$ was reduced to $Fe_3O_{4-{\delta}}$ by decomposion of CO. The reduction of $Fe_3O_4$ to $Fe_3O_{4-{\delta}}$ progressed from $320^{\circ}C$ to $400^{\circ}C$; the reaction was exothermic. The degree of exothermal reaction was varied with heat treatment temperature, heating rate, Ar flow rate, and holding time. The ${\delta}$-value of $Fe_3O_{4-{\delta}}$ was greatly influenced by the heat treatment temperature and the heating rate. However, Ar flow rate and holding time had a minor effect on ${\delta}$-value.

• 한국전통조경학회지
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• 제33권3호
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• pp.58-65
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• 2015

중국 강남지방 고전 사가원림의 포장문양은 황가원림보다 종류도 다양하고 변화도 많다. 쑤저우 사가원림에서 다양한 문양을 도입하게 된 사상적 배경을 규명하기 위해서 세계문화유산으로 지정된 9개소의 원림을 조사 분석하였다. 그 결과 원시 자연숭배신앙인 애니미즘과 토테미즘의 영향은 소수로 나타났다. 쑤저우 고전원림 포장문양 가운데 큰 영향을 미친 것은 유교, 도교, 불교 사상인 것으로 나타났다. 유교 사상이 나타난 사례는 간방식, 팔방식, 육방식 문양으로 주로 진입로나 정당건물 앞에 넓은 면적에 포설된다. 도교 사상이 나타나는 문양은 오복봉수(五福捧壽), 반도(蟠桃), 암팔선 문양이다. 불교 사상이 나타나는 사례는 팔보 문양인데 그 가운데 윤회사상을 나타내는 반장 문양이 제일 많이 나타난다. 이밖에 쑤저우 고전원림 포장 문양 76 종류 가운데에는 복(福), 재물, 다산(多産), 신분상승을 기원하는 의미에서 선호하고 믿었던 민속문화라는 범주의 문양들이 있다. 박쥐, 나비, 잠자리, 사슴, 개구리, 금섬, 잉어, 동전 등이 있다.

• 초등상담연구
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• 제10권1호
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• pp.57-76
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• 2011

초등학교 집단상담은 교육적인 목표의 달성이라는 측면에서 성인대상의 집단상담과 성격상 매우 다르다. 발달과정을 거치고 있는 아동이기 때문에 예방적 차원의 집단상담은 더 많이 필요하다. 그렇지만 초등학교의 집단상담은 재량활동 시간과 자투리 시간을 이용하여 이루어지고 있으며, 이것조차 담임교사의 의지가 없으면 불가능하다. 또한, 아동의 특성에 적합한 형태의 집단상담 프로그램이 개발되어야 함에도 불구하고 성인대상의 상담프로그램을 적절히 재구성하거나 약화시켜 사용하는 경우가 많았다. 본고에서는 이러한 문제점을 개선하기 위하여, 먼저 연구자가 이론에 근거하여 초등학교 집단상담 프로그램이 갖춰야 할 기본적인 틀(frame)을 제시하고 16시간에 걸쳐 초등상담대학원 석사과정의 교사들과 프로그램의 개발에 대한 논의를 하였다. 그 결과 초등학교 집단상담 프로그램을 개발할 때에는 요구도 조사, 내용구성, 조직화, 운영, 평가가 중요하다는 데 의견일치를 보았다. 위의 다섯 가지 영역에 대한 검토를 통하여 새로운 프로그램 개발의 근거로 제시하고자 한다. 또한 현재까지 국내에서 진행된 초등학교 집단상담 프로그램에 대한 현황을 점검하여 새로운 프로그램의 개발과 관련된 문제점과 개선책을 본고의 과제로 기술하였다.

• Design & Manufacturing
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• 제13권2호
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• pp.30-36
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• 2019

Traditional cell culture(2-dimensional) is the method that provide a nutrient and environment on a flat surface to cultivate cells into a single layer. Since the cell characteristics of 2D culture method is different from the characteristics of the cells cultured in the body, attempts to cultivate the cells in an environment similar to the body environment are actively proceeding in the industry, academy, and research institutes. In this study, we will develop a technology to fabricate micro-structures capable of culturing cells on surfaces with various curvatures, surface shapes, and characteristics. In order to fabricate the hemispheric plastic structure(thickness $50{\mu}m$), plastic preform mold (hereinafter as "preform mold") corresponding to the hemisphere was first prepared by injection molding in order to fabricate a two - layer structure to be combined with a flat plastic film. Then, thermoplastic polymer dissolved in an organic solvent was solidified on a preform mold. As a preliminary study, we proposed injection molding conditions that can minimize X/Y/Z axis deflection value. The effects of the following conditions on the preform mold were analyzed through injection molding CAE, [(1) coolant inlet temperature, (2) injection time, (3) packing pressure, (4) volume-pressure (V/P). As a result, the injection molding process conditions (cooling water inlet temperature, injection time, holding pressure condition (V / P conversion point and holding pressure size)) which can minimize the deformation amount of the preform mold were derived through CAE without applying the experimental design method. Also, the derived injection molding process conditions were applied during actual injection molding and the degree of deformation of the formed preform mold was compared with the analysis results. It is expected that plastic film having various shapes in addition to hemispherical shape using the preform mold produced through this study will be useful for the molding preform molding technology and cast molding technology.

• 한국식품위생안전성학회지
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• 제5권3호
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• pp.85-98
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• 1990

서울, 경기지역 에 위치한 도시락 제조업체 중 규모별로 대, 중, 소규모 1개 업체씩 총 3개 업체를 대상으로 하여 도시락 유통과정 중에서 음식의 미생물적 품질에 영향을 미치는 소요시간 및 온도 요인, 인적, 환경적 요인, 시설 구비에 의한 요인 등을 종합적으로 평가하였다. 도시락이 조리된 이후 급식까지의 전단계, 즉, 냉장, 포장, 보관, 운반 및 급식까지의 보관단계에서 온도상태 및 소요시간이 품질이 저하를 초래할 수 있는 위험한 실정이어서 도시락 유통과정 중의 소요시간 및 온도의 통제문제가 매우 심각하다. 조사대상 업체에서 생산한 도시락이 현재의 유통시간대에서 여름철에 냉장 시설없이 유통된다면 급식 시 미생물적 품질이 크게 저하될 것이다. 도시락이 슈퍼마켓에서 열장고에서 진열되었다가 판매되는 경우 열장고의 온도가 위험온도 범주내에 있기 때문에 보관시간이 지연됨에 따라 미생물 수치는 급격히 증가하였다.

• 한국정밀공학회지
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• 제19권2호
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• pp.114-125
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• 2002

As semi-solid forging (SSF) is compared with conventional easting such as gravity die-easting and squeeze casting, the product without inner defects can be obtained from semi-solid forming and globular microstructure as well. Generally speaking. SSF consists of reheating, forging, ejecting precesses. In the reheating process, the materials are heated up to the temperature between the solidus and liquidus line at which the materials exists in the form of liquid-solid mixture. The process variables such as reheating time, reheating temperature, reheating holding time, and induction heating power have much effect on the quality of the reheated billets. It is difficult to consider all the variables at the same time when predicting the quality. In this paper, Taguchi method, regression analysis and neural network were applied to analyze the relationship between processing conditions and solid fraction. A356 alloy was used for the present study, and the learning data were extracted by the reheating experiments. Results by neural network were on good agreement with those by experiment. Polynominal regression analysis was formulated by using the test data from neural network. Optimum processing condition was calculated to minimize the grain size, solid fraction standard deviation, otherwise, to maximize the specimen temperature average. In this time, discussion is liven about reheating process of row material and results are presented with regard to accurate process variables for proper solid fraction, specimen temperature and grain size.

• Journal of Welding and Joining
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• 제33권2호
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• pp.56-61
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• 2015

IRW(Inverter Resistance Welding) process and DSW(Delta-spot welding) process for dissimilar materials of DP590 and Al5052 were performed to evaluate the welding quality and mechanical properties. IRW experiment was carried out with changing the welding current. The other welding parameters such as pressure force, weld time, squeezing time and holding time were fixed. On the anther hand, DSW experiment was performed using the process tape at welding current of 11.5kA. The other conditions were same as IRW conditions. The various testes such as shear tensile strength, nugget diameters, EDS, SEM and cross-sectional observation for weld zone was performed. As a result, IMC(Inter Metallic Compound) thickness at 11.5kA was thinner than those of 9.5kA and 10.5kA conditions. In addition, thined IMC layer was observed when high electric current apply to the materials(DP590 and Al5052) in a short time throught dissimilar resistance spot welding controling welding conditions. The relationship between the thickeness of IMC and current intensity was after discussed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.314-314
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• 2010

The SiC-$ZrB_2$ composites were fabricated by combining 40vol.% of Zirconium Diboride(hereafter, $ZrB_2$) powders with Silicon Carbide(hereafter, SiC) matrix. TheSiC+40vol.%$ZrB_2$ composites were manufactured through Spark Plasma Sintering(hereafter, SPS) under argon atmosphere, uniaxial pressure of 50MPa, heating rate of $100^{\circ}C$/min, sintering temperature of $1,500^{\circ}C$ and holding time of 5min. But one on/off pulse sequence(one pulse time: 2.78ms) is 10:9(hereafter, SZ10), and the other is 48:8(hereafter, SZ48). The physical and mechanical properties of the SZ12 and SZ48 were examined. Reactions between $\beta$-SiC and $ZrB_2$ were not observed via X-Ray Diffraction(hereafter, XRD) analysis. The apparent porosity of the SZ10 and SZ48 composites were 9.7455 and 12.2766%, respectively. The SZ10 composite, 593.87MPa, had higher flexural strength than the SZ48 composite, 324.78MPa, at room temperature. The electrical properties of the SiC-$ZrB_2$ composites had Positive Temperature Coefficient Resistance(hereafter, PTCR).

• 한국식품과학회지
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• 제31권5호
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• pp.1216-1220
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• 1999

팽윤도와 용해도는 blanching time이 길어질수록 증가했으며 blanching 온도 $55^{\circ}C$가 $45^{\circ}C$ 보다 낮은 경향을 보였으며 blanching온도 $45^{\circ}C$/15분을 유지시킨 것이 가장 높은 팽윤도와 용해도를 보였고, 수분흡수지수와 수분용해지수는 각 온도에서 holding time이 길어질수록 상대적으로 증가하는 경향을 나타냈으며 수분흡수지수는 blanching 온도 $55^{\circ}C$/15분 유지한 것이, 수분용해지수는 blanching 온도 $45^{\circ}C$/30분 유지한 것이 가장 높은 경향을 나타내었다. Visco/amylograph 측정에서 최대점도는 온도와 시간에 많은 영향을 받는 것으로 나타났으며 blanching 온도 $55^{\circ}C$/60분 유지시킨 것이 가장 높은 점도를 나타내었다. 이와 같은 실험결과로 보아 blanching 온도와 시간이 밤에 존재하는 가용성성분의 변화와 함께 밤가루 내의 전분사슬과 밤가루 표면구조의 변화에 영향을 미쳐 호화 특성에 변화를 준 것으로 보인다. 따라서, blanching처리한 밤가루가 밤가공품의 중간소재로 사용함으로서 다양한 성질을 나타내는 과정으로 생각된다.

• Asian-Australasian Journal of Animal Sciences
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• 제23권12호
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• pp.1645-1656
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• 2010

This study was conducted to investigate the effects of strain on broiler performance, and age at slaughter and postchilling (PC) aging time on meat quality traits. A total of 500 one-day-old chicks (250 Hubbard classic and 250 Lohman) were reared under commercial conditions. Half of the broiler birds from each strain were slaughtered at 32 days and the other half at 42 days old. At each processing day, 168 carcasses were randomly selected (84 Hubbard and 84 Lohman) and divided into groups of 28 carcasses within each strain, and aged for 0, 4 and 24 h after chilling. Average weekly body weight was comparable between strains. Feed conversion ratio was higher (p<0.05) for the Hubbard strain during the second and third week of age. Initial carcass pH was significantly (p<0.05) affected by age where younger birds (32-d-old) had lower pH values than older (41-d-old) birds. Breast temperature was higher (p<0.001) for Lohman than Hubbard at 0, 2 and 4 h of PC. Younger birds had a lower breast temperature (p<0.001) at all measured times of PC. Thaw loss, cook loss and water holding capacity were not significantly affected by strain, age or aging time. Lohman strain had more tender meat (p<0.05) than Hubbard strain, and tenderness was improved with the increase of broiler age and aging time. Meats from Hubbard were lighter and less red than those from Lohman strain where younger birds had darker color. In conclusion, strain, age at slaughter and PC aging duration are critical to breast meat quality characteristics, and 4 h of aging are required before deboning in order to obtain more tender fillets.