• 한국세라믹학회지
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• 제35권1호
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• pp.66-78
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• 1998

the microstructure and mechanical properties of seeded and ball-milled dry gels prepared by boehmite sol-gel method were discussed. The densification of seeded gels was improved with increasing seed content namely the number of seed The number of seed was 1.09, 3.35, 5.72${\times}$1012/cm3 boehmite when seeded with 1, 3, 5wt% respectively The ball milled gel contained about 0.5wt% seed and the number of seed was 4.72${\times}$1012/cm3 boehmite. The sintered density of 5wt% seeded gel was below 80% when sintered at 1300$^{\circ}C$ for 1h. On the other hand that of ball milled gel was very improved and reached to 97% In the case of 3wt% seeded gels the density over 97% was attained when sintered at 1500$^{\circ}C$for 1h. and the grain of the sintered body was several micrometers in size. However the sintered body of ball milled gel showed grain size of submicrometer when sintered at 1300$^{\circ}C$ for 1h. And this specimen showed highest harness value of 1900kg/mm2 The fracture toughness increased with increasing sintering temperature. The sintered body of ball milled gel showed the largest grain size and the highest fracture toughness without regard to sint-ering temperature.

• 한국작물학회지
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• 제35권6호
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• pp.539-542
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• 1990

들깨의 종실ㆍ엽 겸용 신품종인 '엽실들깨'를 공시하여 정식기별로 채엽회수와 채엽시기를 달리할 경우 생육특성, sink 관련형질 및 종실수량에 미치는 영향을 구명하기 위해 시험을 실시한 바 그 결과를 요약하면 다음과 같다. 1. 상품가치가 있다고 보여지는 충분히 전개된 잎을 대상으로 채엽한 결과 경장은 무채엽구에 비하여 작아지는 경향이었다. 2. 채엽이 경태, 절수, 분지수 등에는 크게 영향을 주지 않았다. 3. 채엽에 의해 sink 관련형질인 화방수, 천립중을 감소시켜 종실수량이 낮아졌으며, 채엽회수가 많을수록 채엽시기가 늦을수록 영향이 큰 경향이었다. 4. 종실ㆍ엽 겸용 들깨재배시에는 종실수량 감소가 크지 않고 채엽에 의한 소득이 증대될 수 있는 조기채엽이나 1-2회 채엽이 바람직하였다. 5. 재배목적이 종실과 엽을 동시에 생산하고자 할 경우에는 5월 10일 파종 6월 20일 정식이 가장 적기이며, 6월 10일 파종 7월 20일 정식까지는 재배가 가능할 것으로 보였다.

• 소성∙가공
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• 제32권5호
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• pp.239-246
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• 2023

To reduce the forming load due to the temperature drop, during the hot forging process, a reheating hot forging process design is required that to repeat heating and forging. However, if the critical strain required for recrystallization is not induced during forging and grain growth becomes dominant due to the reduction in dislocation density due to repeated heating, the mechanical properties may deteriorate. Therefore, in this study, Inconel 706 alloy was applied, and the grain refinement behavior was comparatively analyzed according to the number of reheating times and effective strain during reheating hot forging process. Reheating was carried out with a total compression rate of 40% up to 4 times. The Inconel 706 compression test specimens heated once showed finer grains as the effective strain increased due to the dynamic recrystallization phenomenon. However, as the number of heating increases, grain refinement was observed even in a low effective strain distribution of 0.43 due to static recrystallization during reheating. Moreover, grain growth occurs at a relatively low effective strain of 0.43 when the number of reheating is four or more. Therefore, it was effective to apply an effective strain of 0.43 or more during hot forging to Inconel 706 in order to induce crystallization through grain refinement and improve the properties of forged products. In addition, we could notice that up to three reheating times condition was appropriate to prevent grain growth and maintain fine grain size.

• 한국초전도ㆍ저온공학회논문지
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• 제24권3호
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• pp.52-56
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• 2022

Single-grain (c-normal or c-parallel) and multi-grain YBCO superconductors were prepared by a melt growth process with/without seeding. The magnetic levitation force and trapped magnetic field at liquid N₂ temperature (77 K) of the YBCO superconductors were investigated. Samples for the levitation force measurement were zero-field cooled (ZFC) to 77 K, and samples for trapped field measurement were field-cooled (FC) using Nd magnets. As for the magnetic levitation force, the c-normal, single grain sample showed the largest value, whereas the multi-grain sample showed the lowest value. The trapped magnetic field of the c-normal and c-parallel single-grain samples was 4-5 times that of the multi-grain sample. In addition, as the external magnetic field (the number of magnets) increased, the both properties increased proportionally. These results were explained in terms of the orientation dependence of the levitation forces and the magnetic field trapping capability of the YBCO superconductor.

• Current Research on Agriculture and Life Sciences
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• 제1권
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• pp.27-34
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• 1983

소맥(小麥) $F_2$집단(集團)에 있어서 조숙(早熟) 다수성(多收性) 계통(系統)의 효율적(效率的)인 선발(選拔)에 관(關)한 기초자료(基礎資料)를 얻고자 중숙(中熟)${\times}$조숙(早熟)(올밀/새밀), 만숙${\times}$중숙(中熟)(Naphal/청계밀) 두 조합(組合)을 공시(供試)하여 $F_2$집단(集團)의 유전적(遺傳的) 변이(變異)를 조사(調査)하고 경로분석(徑路分析)을 한바 얻어진 결과(結果)는 다음과 같다. 유전변이계수(遺傳變異係數)는 올밀${\times}$새밀 조합(組合)에서는 수획지수(收獲指數), 립수(粒數), 수량(收量), 간장(稈長)의 순(順)으로, Naphal${\times}$청계밀 조합(組合)에서는 수획지수(收獲指數), 간장(稈長), 1,000 립중(粒重)의 순(順)으로 높았다. 유전력(遺傳力)(협의(狹意))은 양조합(兩組合)에서 출수기(出穗期), 성숙기(成熟期), 간장(稈長), 수획지수(收獲指數)가 높았고(0.525~0.808) 립수(粒數), 수량(收量)은 낮았다. 유전획득량(遺傳獲得量)(%)은 출수기(出穗期), 성숙기(成熟期)가 양조합(兩組合)에서 모두 높았고 수량(收量)은 낮았다. 1,000립중(粒重)의 유전획득량(遺傳獲得量)(%)은 Naphal${\times}$청계밀 조합(組合)에서는 높게 나타났다. 수량(收量)과 수수(穗數) 및 립수(粒數)와는 높은 정(正)의 유의상관(有意相關)을 보였고 수량(收量)에 대(對)한 직접효과(直接效果)는 수수(穗數)가 가장 컸고 다음은 립수(粒數)였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1361-1363
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• 1998

Poly-Si grain boundaries act as potential barriers as well as recombination centers for the photo-generated carriers in solar cells. Thereby, grain boundaries of poly-Si are considered as a major source of the poly-Si cell efficiency was reduced This paper investigated grain boundary effect of poly-Si wafer prior to the solar cell fabrication. By comparing I-V characteristics inner grain, on and across the grain boundary, we were able to detect grain potentials. To reduce grain boundary effect we carried out pretreatment, $POCl_3$ gettering, and examined carrier lifetime. This paper focuses on resistivity variation effect due to grain boundary of poly-Si. The resistivity of the inner grain was $2.2{\Omega}-cm$, on the grain boundary$2.3{\Omega}-cm$, across the grain boundary $2.6{\Omega}-cm$. A measured resistivity varied depending on how many grains were included inside the four point probes. The resistivity increased as the number of grain boundaries increased. Our result can contribute to achieve high conversion efficiency of poly-Si solar cell by overcoming the grain boundary influence.

• 한국작물학회지
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• 제32권1호
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• pp.78-85
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• 1987

본 실험은 팔당호밀을 사용하여, 우리나라 중북부 지방에서 월동전 청초 이용후 종실을 생산할 수 있는지를 검토코저, 춘천, 수원, 화성 및 청주에서 2개년 동안 실시하였다. 파종기는 각 지역 모두 4파종시기로서, 청초예취는 월동직전 1회 예취하여 실시하였으며 그 결과를 요약하면 다음과 같다. 1. 월동전 예취시 초장, $m^2$당 경수 및 청초수량은 조기파종인 9월 11 일 파종에서 가장 크고 많았으며, 만기파종인 10월 11 일 파종에서 가장 적었는데, 춘천의 9월 11 일 파종에서 청초수량이 10a당 1.803kg으로서 가장 많았다. 2. 청초수량의 기여정도는 주로 초장 및 경수에 의하여 좌우되는데 경수보다는 초장의 기여도가 더 크게 영향하였다. 3. 예취에 의하여 월동중 냉해의 피해를 받았으며, 또한 출수기가 늦고, 초장도 감소되었다. 4. 수량구성형질중 $m^2$9당 수수만이 예취별에 따라 고도의 유의성 있었으며, 타형질들은 파종기 및 예취구분간에 변이가 적었다. 5. 종실수량은 무예취구에서 많았으며 예취구와의 차이는 45kg/10a로서, 예취구의 간장 및 월동률저하는 종자수양을 감소시켰다. 또한 수양구성요소중 $m^2$당 수수는 종자생산에 가장 크게 영향하였다. 6. 청초수량이 많은 조파의 종실수량은 청초예취 및 무예취구간에 변이가 적고 절대수량이 많아 적절한 재배관리에 의하여 축산농가에서 월동전 청초이용후 종실을 생산할 수 있다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 1997년도 추계학술대회발표논문집; 홍익대학교, 서울; 1 Nov. 1997
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• pp.166-169
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• 1997

For parallel processing, the compiler partitions a loaded program into a set of tasks and makes a schedule for the tasks that will minimize parallel processing time for the loaded program. Building an optimal schedule for a given set of partitioned tasks of a program has known to be NP-complete. In this paper we introduce a GA(Genetic Algorithm)-based scheduling method in which a chromosome consists of two parts of a string which decide the number and order of tasks on each processor. An additional computation is used for feasibility constraint in the chromosome. By granularity theory, a partitioned program is categorized into coarse-grain or fine-grain types. There exist good heuristic algorithms for coarse-grain type partitioning. We suggested another GA adaptive to the coarse-grain type partitioning. The infeasibility of chromosome is overcome by the encoding and operators. The number of processors are decided while the GA find the minimum parallel processing time.

• 한국재료학회지
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• 제16권1호
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• pp.68-74
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• 2006

2024 Al alloys were severely deformed by equal channel angular pressing(ECAP) to obtain an ultrafine grain structure. The more deformation amount increased, the more grain size decreased. Most of the grain structure were changed from elongated to equiaxed shape with increasing pass number. The morphology of S' phases was also changed from rod-type to spherical type. The grain size of 6 passed specimen was 100 to 200 nm, and the size of S' phases was about 10 nm in the microstructure. XRD measurements have revealed that the texture formed by plastic deformation disappeared in the 6 passed specimen. SP test results described that the start of crack propagation occurred at the transition zone between plastic bending and membrane stretching because of small elongation. The maximum strength of ECA pressed specimen increased 1.9 GPa to 2.9 GPa with increasing pass number.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1153-1154
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• 2006

Effects of sintering conditions such as sintering temperature and heating rate on oxygen content, density, microstructure and toughness of sintered Mo were investigated. The oxygen content of the sintered Mo significantly depended on the sintering conditions. The oxygen content of the primary sintered(below 1673 K) Mo influenced the densifications. The number of pores at grain boundaries of the secondary sintered(at 2073 K)Mo depended on the oxygen content of the primary sintered Mo. Grain growth of the secondary sintered Mo was inhibited by the existence of pores at the grain boundaries. The secondary sintered Mo having larger number of pore and smaller grain size demonstrated higher strength.