• Steel and Composite Structures
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• 제18권4호
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• pp.873-887
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• 2015

The continuous composite I-girder should have a sufficient rotation capacity (or ductility) to redistribute the negative bending moment into an adjacent positive bending moment region. However, it is generally known that the ductility of the high strength steel is smaller than that of conventional steel, and application of high strength steel can cause ductility problems in a negative moment region of the I-girder. In this study, moment redistribution of the continuous composite I-girder with high strength steel was studied, where high strength steel with yield stress of 690 MPa was considered (the ultimate stress of the steel was 800 MPa). The available and required rotation capacity of the continuous composite I-girder with high strength steel was firstly derived based on the stress-strain curve of high strength steel and plastic analysis, respectively. A large scale test and a series of non-linear finite element analysis for the continuous composite I-girder with high strength steel were then conducted to examine the effectiveness of proposed models and to investigate the effect of high strength steel on the inelastic behavior of the negative bending moment region of the continuous composite I-girder with high strength steel. Finally, it can be found that the proposed equations provided good estimation of the requited and available rotation capacity of the continuous composite I-girder with high strength steel.

• 한국안전학회지
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• 제17권4호
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• pp.146-152
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• 2002

The steel shows plastic deformation after the yield point exceeds. Because of overloads, the plastic deformation occurs at the interior support of a continuous bridge. The plastic deformation is concentrated at the interior support, and the permanence deformation at the interior support remains after loads pass. Because local yielding causes the positive moment at the interior support, it is called "auto moment". Auto moment redistributes the elastic moment. Because of redistribution, auto moment decreases the negative moment at the interior support of a continuous bridge. In this paper, the moment-rotation curve from Schalling is used. The Plastic rotation is computed by using Beam-line method, and auto moment is calculated based on the experiment curve. The design example is presented using limit state criterion.

• Geomechanics and Engineering
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• 제30권4호
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• pp.383-392
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• 2022

Although pipelines are composed of segmental tubes commonly connected by rubber gasket or push-in joints, current studies mainly simplified pipelines as continuous structures. Effects of joints on three-dimensional deformation mechanisms of existing pipelines due to tunnel excavation are not fully understood. By conducting three-dimensional numerical analyses, effects of pipeline burial depth, tunnel burial depth, volume loss, pipeline stiffness and joint stiffness on bending strain and joint rotation of existing pipelines are explored. By increasing pipeline burial depth or decreasing tunnel cover depth, tunneling-induced pipeline deformations are substantially increased. As tunnel volume loss varies from 0.5% to 3%, the maximum bending strains and joint rotation angles of discontinuous pipelines increase by 1.08 and 9.20 times, respectively. By increasing flexural stiffness of pipe segment, a dramatic increase in the maximum joint rotation angles is observed in discontinuous pipelines. Thus, the safety of existing discontinuous pipelines due to tunnel excavation is controlled by joint rotation rather than bending strain. By increasing joint stiffness ratio from 0.0 (i.e., completely flexible joints) to 1.0 (i.e., continuous pipelines), tunneling-induced maximum pipeline settlements decrease by 22.8%-34.7%. If a jointed pipeline is simplified as a continuous structure, tunneling-induced settlement is thus underestimated, but bending strain is grossly overestimated. Thus, joints should be directly simulated in the analysis of tunnel-soil-pipeline interaction.

• 대한수학회보
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• 제36권4호
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• pp.707-716
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• 1999

In this pater we study the continuity of rotation numbers of liftings of circle maps with degree one. And apply our result to prove that a positively equicontinuous flow of homeomorphisms on the circle $S^1$ is topologically conjugate to a continuous flow of rotation maps.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.103-106
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• 2004

The new rheology fabrication process has been developed to rheo die casting and rheo forming process. Thixoforming process has disadvantages in terms of induction reheating process, scrap recycling, loss of raw material and cycle time. Therefore, to reduce the number of process, new rheology fabrication process with specially designed the rotational barrel type equipment has been proposed to apply in various part productions. The barrel type equipment, which could continuously fabricate the rheology materil, was specially designed to have a function to control cooling rate, shear rate and temperature. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed. The barrel surface has both the induction heating system and the cooling system to control the temperature of molten metal. By using this system, the effect of the rotation speed and the rotation time on the microstructure was widely examined. The possibility for the rheoforming process was investigated with microstructural characteristic.

• 한국토양비료학회지
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• 제39권4호
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• pp.209-213
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• 2006

본 연구는 미사양토인 호남평야지 논토양에서 벼와 콩의 윤작재배에 의한 토양화학성 변화와 작물생육에 미치는 영향을 구명하였다. 벼 연작, 콩-벼 1년 윤작, 콩 2년-벼 1년 윤작, 콩 3년-벼 1년 윤작의 처리를 두었다. 논 토양에서 벼를 연작 후 토양 중 pH, 토양 유기물, $Ca^{2+}$와 $K^+$함량은 별 변화가 없었으나 유효 인산함량은 점차 감소하였다. 한편 벼와 콩의 윤작으로 토양 중 유기물 함량은 감소하고, 유효인산과 $Ca^{2+}$와 $K^+$함량은 증가하였으며, 벼 생육기간 중 토양 중 암모니아태 질소함량도 높아졌다. 이러한 토양 중 양분함량의 변화로 인해 벼의 $m^2$당 수수와 수당립수가 많아져서, 쌀 수량은 1~4%증가하였다. 콩은 연작 연수가 길어질수록 수량이 낮아지는 경향이어서, 콩 논 재배 시에는 벼와 매년 윤작하는 것이 수량 저하를 방지하였다.

• 한국토양비료학회지
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• 제26권3호
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• pp.181-188
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• 1993

석천미사질(石泉微砂質) 양토(壤土)에서 윤환형태(輪換形態) 및 작부체계(作付體系)에 따른 연차간(年次間) 토양질소(土壤窒素)의 무기화(無機化) 양상(樣相), 토양중(土壤中) 유기물(有機物) 및 인산(燐酸)의 변동(變動) 및 수도수량(水稻收量)과 무기성분(無機成分) 흡수량(吸收量)과의 관계를 검토(檢討)한 몇가지 결과(結果)를 요약(要約)하면 다음과 같다. 1. 긍온담수(恆溫湛水) 토양(土壤)에서 '90~'93년(年) 4년간(年間)의 4주(週) 및 10주(週)째의 질소무기화량(窒素無機化量)과 가급태(可給態) 질소함량(窒素含量)은 수도연작구(水稻連作區)보다 매년윤환구(每年輪換區) 및 2연윤환구(年輪換區)에서, 대두구(大豆區)보다 감자-배추구(區)에서 많았다. 2. 토양(土壤)중 유기물함량(有機物含量) 및 유효인산(有效燐酸)의 연차간(年次間) 변동(變動)은 수도연작구(水稻連作區)에서는 큰 변동이 없었으나 윤환구간(輪換區間)에서는 전전환구(田轉換區)>2연윤환구(年輪換區)>매년윤환구(每年輪換區)의 순(順)으로 감소되었으며 작물(作物)간에는 감자-배추구(區)보다 대두구(大豆區)에서 감소폭(減少幅)이 컸다. 3. 정조수량(正租收量)은 수도연작구(水稻連作區)에 비하여 감자-배추구(區) 및 대두구(大豆區)에서 3개년(個年) 동안 26~20%, 17~5%, 5~4% 증수(增收)되었는데 윤환년수(輪換年數)가 길수록 수량증수율(收量增收率)이 적었다. 4. 3년간(年間)('90~92년)의 수확기(收穫期) 수도(水稻) 식물체(植物體)중 모든 무기성분(無機成分) 흡수량(吸收量)은 수도(水稻) 연작구(連作區)보다 매년(每年) 윤환구(輪換區) 및 2년윤환구(年輪換區)에서, 대두구(大豆區)보다 감자-배추구(區)에서 흡수량(吸收量)이 현저히 증가되었다.

• 한국약용작물학회지
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• 제25권4호
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• pp.244-251
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• 2017

Background: The application of crop rotation systems may reduce the occurrence of soil-borne diseases by releasing allelochemicals and by subsequent microbial decomposition. Methods and Results: For reduction of ginseng root rot by the crop rotation system, after harvesting 6-year-old ginseng, fresh ginseng was grown along with continuous cultivation of sweet potato, peanut, and bellflower. Growth of 2-year-old ginseng was significantly inhibited in the continuous cultivation than in the first cultivation. Sweet potato, peanut and bellflower cultivations assisted in obtaining normal yields of ginseng in the first year after the harvest of 6-year-old ginseng. Salt concentration, potassium and sodium contents were gradually decreased, and, organic matter was gradually increased through cirp rotation. Phosphate, calcium and magnesium contents were not altered. The density of the root rot fungus was gradually decreased by the increase in crop rotation; however it was decreased distinctly in the first year compared to the second and third year. The severity of root rot disease tended to decrease gradually by the increase of crop rotation. Conclusions: Short-term crop rotation for three years promoted the growth of ginseng, however root rot infection was not inhibited significantly, although it was somewhat effective in lowering the density of the root rot pathogen.

• Journal of Yeungnam Medical Science
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• 제3권1호
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• pp.237-241
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• 1986

본 교실에서 백서의 대퇴동맥을 이용하여 혈관감자의 회전없이 continuous suture로 미세혈관 문합을 시행해본 결과 다음과 같은 결론을 얻었다. end-to-end anastomosis시 double c1app의 회전이 어려울 정도로 작업공간이 제한된 경우나 end-to-side anastomosis시 secondary Vessel의 길이가 짧아서 후벽을 잘 볼 수 없는 경우에 continuous suture을 이용하면 Back wall을 완전히 노출시킨 상태에서 쉽게 혈관 문합을 시행할 수 있으며 문합시간도 단축시킬 수 있을 것으로 사료된다.

• Journal of the Korean Statistical Society
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• 제29권1호
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• pp.45-62
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• 2000

Rotation design is a sampling technique to reduce response burden and to estimate the population characteristics varying in time. Park and Kim(1999) discussed a generation of one-level rotation design which is called as {{{{r_1^m ~-r_2^m-1}}}} design has more applicable form than existing before. In the structure of {{{{r_1^m ~-r_2^m-1}}}} design, we derive the exact variances of generalized composite estimators for level, change and aggregate level characteristics of interest, and optimal coefficients minimizing their variances. Finally numerical examples are shown by the efficiency of alternative designs relative to widely used 4-8-4 rotation design. This is continuous work of Part Ⅰ studied by Park and Kim(1999).