• Journal of Technology Innovation
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• v.24 no.4
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• pp.27-53
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• 2016

This case analyzed the efficiency of 79 R&D projects performed within one private research center in machine tools industry. DEA was used for efficiency analysis. Input variables were R&D investment expense and man-month. Output variables were achievement rate on target development period and expected net sales within 5-years. Samples are divided into product development, Prior technology development, and control technology development. The key result is that Prior technology showed the lowest efficiency because of high uncertainty. It was so difficult to determine its goals and to make its specific plans. With respect to scale, the proportions of CRS(constant returns to scale) were 34.6%, 14.3% and 38.9% for product development, prior technology, control technology respectively. As for IRS(increase returns to scale), they were 53.8%, 85.7% and 38.9% for product development, prior technology, control technology respectively. As for DRS(decrease returns to scale) they were 11.5%, 0% and 22.2% for product development, prior technology, control technology respectively. On the whole, in this case, insufficient input was more problematic than excessive input, which means the lack of investment in R&D. Prior technology can be the source of the future competitiveness of companies. To operate inefficient DMU efficiently, the optimal input should be managed and it is derived from comparison with the reference group.

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.736-739
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• 2011

이 연구는 스스로 건강상태를 올바르게 인식하고 있는지 알아보고 건강상태 인식 유형에 따른 건강행동과의 관계를 살펴봄으로 건강수준의 향상과 더불어 건강한 노후를 맞이할 수 있도록 하고자 하였다. 2008년 1월부터 12월까지 실시된 국민건강영양조사 제4기 2차년도(2008) 자료원을 사용하였으며, 200개 조사구 약 4600가구의 만1세 이상 9,744명중 만19세 미만을 제외하고 건강설문 및 검진조사에 참여한 4,688 명을 최종대상자로 분석하였다. 자료는 SPSS 18.0을 이용하여 성별에 따른 인구사회학적 특성, 건강상태 인식 유형별 분포, 주관적 건강상태에 따른 객관적 건강상태와 일반적특성 및 건강행동을 교차분석관적 시에 카이제곱검정을 하였으며, 단변량 분석에서 의미 있는 변수들을 독립변수로 하고 올바른 인식군과 그릇된 인식군으로 나눈 건강상태인식유형을 종속변수로 하여 로지스틱회귀분석을 실시하였다. 이 연구의 주요 결과를 요약하면 다음과 같다. 주관적 건강상태에 따라 실제 객관적인 건강상태를 살펴본 결과, 건강상태를 과대평가하는 사람의 비율이 가장 높았으며, 건강상태를 올바르게 인식하는 사람보다 그릇되게 인식하는 사람이 더 많았다. 2. 주관적 건강상태를 좋음으로 인식하는 군에서 객관적 건강상태는 여자보다 남자가 건강을 과대평가하였고, 연령이 증가할수록, 읍/면지역에서, 결혼상태는 별거 사별 이혼상태에서, 교육수준은 낮아질수록 건강을 그릇되게 인식하여 과대평가하였다. 3. 주관적 건강상태를 나쁨으로 인식하는 군에서 객관적 건강상태는 연령이 낮아질수록 건강을 과소평가하는 경향이었고, 읍/면지역보다 동지역에서, 미혼일 경우, 교육수준은 높아질수록 건강상태를 그릇되게 인식하여 과소평가하였다. 4. 건강상태 인식 유형별로 건강행동을 살펴본 결과 주관적 건강상태를 좋음으로 인식하는 군에서는 체중조절, 월간음주, 우울증상경험, 건강검진에서 유의한 결과를 나타냈고, 주관적 건강상태를 나쁨으로 인식하는 군에서는 현재흡연과 월간음주에서 유의한 결과를 나타내었다. 5. 주관적 건강상태를 좋음으로 인식한 군에서 객관적 건강상태를 종속변수로한 로지스틱회귀분석결과를 살펴보면, 건강을 과대평가하는 그릇된 인식군으로 될 위험도가 남자보다 여자에서 감소하였고, 70대에 비하여 연령이 낮아질수록 위험도가 감소하였으며, 미혼에 비하여 기혼, 별거 사별 이혼에서 위험도가 증가하였고, 체중조절을 하는 사람이 체중조절을 하지 않은 사람보다 위험도가 높았다. 6. 주관적 건강상태를 나쁨으로 인식한 군에서 객관적 건강상태를 종속변수로한 로지스틱 회귀분석결과를 살펴보면, 연령을 제외한 모든 변수에서 통계적으로 유의하지 않았다.

• Journal of the Korean GEO-environmental Society
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• v.21 no.4
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• pp.19-30
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• 2020

This numerical study is to investigate the seepage characteristics of the side of the structure in the event of leakage from the structural connection part of the drainage structure installed through the enlarged levee, and to analyze the effect of piping on the stabilization of the levee by the lateral penetration behavior. To take into account lateral seepage behavior, 2D and 3D numerical analyses were performed on the same model, and the effect of lateral seepage was analyzed to assess the validity of the numerical analysis. As a result, when leakage occurs and a lateral seepage is considered with the gate located on the riverside land, the maximum pore water pressure near the leakage point of the structure has been reduced by half compared to the normal seepage state where no leakage occurred. Excessive variation in the pore pressure was shown at the lower part of the structure, especially if lateral seepage is not considered. As a water level rises to the high water level, it shows the hydraulic gradient was larger than the critical hydraulic gradient, which will be vulnerable to long-term piping. If a gate is located in the inland and side seepage is not considered, the effect of the seepage water such as hydraulic gradient and seepage velocity is underestimated compared with the case of considering side seepage. The maximum hydraulic gradient is relatively small when lateral seepage is neglected if a gate is located in the riverside land and there was might be a risk of piping or loss of material. In addition, the period exceeding the critical hydraulic gradient was interpreted as a short time zone. As a result, it is considered that the possibility of piping can be underestimated if side seepage is ignored.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.133-140
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• 2005

In order to accelerate the rate of consolidation settlement and gain a required shear strength for a given soft clay deposit, vertical drain method combined with a preloading technique has been widely applied. In this paper, a theory of axisymmetric nonlinear consolidation fer drainage-installed deposit, which considers secondary compression (or creep) during primary consolidation, as well as the variations of compressibility and permeability during the consolidation process, has been developed. A computer program named AXICON based on Hypothesis B fur the analysis of axisymmetric nonlinear consolidation was developed by adopting finite difference method. The results of AS(ICON were compared with Hansbo's solution based on Hypothesis A, as well as in-situ settlements and pore pressures measured in test embankment of Ska-Edeby. The results indicated that Hypothesis A usually underestimated the in-situ settlement and Hypothesis B was considered to be logically correct. It was also shown that one may able to appropriately predict the real in-situ behaviors using the proposed program.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.305-311
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• 1999

This study aims to decipher surface water mass interaction in summer in the South China Sea and East China Sea by radium isotope distribution pattern. Salinity and activity ratio of radium ($^{228}Ra/^{226}Ra$) showed gradual changes, which were adequate to apply simple two end-member mixing between Kuroshio surface water and Changjiang Dilute Water for the East China Sea and the former and Nearshore Diluted Watermass (NDW) for the South China Sea. Two tracer methods, salinity and Ra isotope ratio, were compared for East China Sea. Results showed remarkable consistency for waters near Kuroshio, however, discrepancy were noticeable after Tsushima Warm Current branching. Mixing with subsurface waters may cause the discrepancy. When mixed with subsurface waters, salts and radium isotope ratio are expected to be biased in opposite direction, i. e. prone to underestimate the fraction of less saline water in the case of salts and vice versa for Ra isotope ratio. Taking the mean values of two different results seems more realistic to estimate fraction of end-members.

• Journal of the Korean Geotechnical Society
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• v.32 no.8
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• pp.15-25
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• 2016

In order to analyze undrained shear strength for clayey silt with low plasticity from Hwaseong site, a series of laboratory and in-situ tests were performed. The Unconfined Compressive (UC) test and Simple Consolidated-Undrained Triaxial (SCU) test were examined in order to assess their applicability to the measurement of the undrained strength of this soil. In the case of clayey silt with low plasticity, although the samples were properly taken by undisturbed sampling method, the residual effective stress and the unconfined compressive strength were reduced considerably. Therefore, an effective confining pressure that corresponds to the typical marine clay should be applied to the soil specimen before shearing in order to compensate for the loss of residual effective stress. By evaluating the shear strengths of clayey silt with low plasticity as 75% of $s_{u(scu)}$, the in-situ shear strength of this kind of soil can be duplicated.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.331-335
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• 2011

흔히 진흙으로 불리는 점착성 유사는 모래 등의 비점착성 유사와는 다른 특성을 보인다. 가장 큰 특징은 점착력에 의해 서로 엉겨 붙어 큰 덩어리(플럭)를 형성하고 다시 큰 플럭이 파괴되는 과정인 응집현상(Flocculation Process)을 보인다는 것이다. 이 응집현상의 과정을 통해 플럭은 크기 및 밀도를 지속적으로 변화시킨다. 크기 및 밀도의 변화는 플럭의 침강속도를 변화시켜 점착성 유사의 부유, 퇴적, 이송, 확산의 과정에 직접적인 영향을 미친다. 응집현상은 플럭의 침강속도 뿐 아니라 부피농도와 질량농도 사이의 비선형적 관계를 야기하여 흐름 운동량 방정식 유도, 난류의 모형화 등에서도 비점착성 유사와 다른 방향으로 진행된다. 점착성 유사가 우세한 지역의 또 다른 특성은 자기하중에 의한 압밀현상에 따라 발생하는 가변적인 한계소류력이다. 따라서 점착성 유사의 이동을 모형화 하는 과정에서는 가변적인 침식율의 가정 등을 통해 이에 대한 고려가 반드시 이루어져야 한다. 흐름의 운동량 방정식 및 난류 모형에서는 플럭의 부피 농도와 질량농도가 각 항의 물리적 의미에 부합하도록 개별적으로 선택 및 적용되어야 질량보존의 문제 등으로 발생할 수 있는 계산상의 오류를 배제할 수 있다. 적용 결과, 점착성 유사가 우세한 지역에서 나타나는 높은 부유 및 흐름정체기에서의 부유사 존재 등의 특성이 점착성 유사 이동을 위한 모형에서 보다 합리적으로 계산된다는 사실이 확인되었다. 그리고 비점착성 유사에 적합한 이동 모형이 점착성이 우세한 지역에 적용될 경우, 상황에 따라 유사량을 과대 및 과소 산정할 수 있다는 결론이 도출되었다. 조류의 영향이 존재하는 하구부의 경우에는 조류의 형태와 비대칭성에 따라 유사량의 차이가 큰 것으로 나타났다. 조류의 형태는 주로 하구부의 지형에 의해 결정되므로 준설, 매립, 확폭 등과 같은 하구부에서의 사업이 진행되는 경우, 유사량 변화에 대한 고려가 반드시 이루어져야 할 것으로 판단된다.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.1-8
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• 2006

Nonseismic designed RC frame have a possibility of shear failure because of deficiencies of reinforcing details. To model the shear failure in numerical analysis, shear strength degradation models which Include Moehle's and ATC 40 are compared and applied to push-over analysis. For numerical analysis, three storied building frame is selected and designed according to Korean Concrete Design Code(2003). As results, It is shown that Moehle's shear strength degradation model estimates the shear strength lower than NZSEE model and has less variation than ATC 40 model and all the shear strengths of models are greater than the nominal shear strength of ACI 318. Also, from the numerical analysis, it is pointed out that there may be great difference in lateral drift capacity if a different shear strength model is used. And the capacity can be severely underestimated if the restraining model of plastic rotation of ATC 40 is used, compared to the use of shear spring model for shear degradation.

• Microbiology and Biotechnology Letters
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• v.12 no.4
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• pp.271-276
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• 1984

Effect of C/N ratios on the cell growth, cell lipid, cell protein and fatty acids of Rhodotorula sp. was examined. At low concentration of nitrogen in cultural medium the growth of the yeast was retarded, whereas its growth was favorable at high concentration but lipid yield was decreased due to a high content of cell protein. In order to increase lipid yield, the optimum C/N ratio obtained was 45-50 (5% glucose, 0.0414% nitrogen). During the cultivation cell protein synthesis occurred mainly in initia stage and the lipid was accumulated rapidly at the late phase. The highest content of total fatty acid was observed at the optimum C/N ratio. The higher C/N ratio was the more unsaturation degree of fatty acid decreased. It was attributed principally to a decreased oleic acid with palmitic acid increased. No significant changes occurred in content of other fatty acids.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.44-48
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• 2012

Purpose : Arm motion can give rise to striking cold artifact on PET/CT. We investigated that evaluation of scatter-limit correction and correct the patient arm motion artifact in Discovery 600 PET/CT. Materials and Methods : To evaluate a radioactivity uptake (Bq/ml) and a standard uptake value (SUV), the scatter limit correction and scatter correction were compared using 1994 NEMA Phantom$^{TM}$ in Discovery 600 PET/CT (GE Healthcare, Mi, We). Arm motion phantom study was involved a central 20 cm diameter cylinder simulating the neck and 2 peripheral 10 cm diameter cylinders simulating arms. The positions of the arms were altered so as to introduce different amounts of misalignment. The evaluation of arm motion phantom study used the radioactivity uptake and SUV in scatter correction and scatter limit correction. Results : The statistical significance of radioactivity uptake and SUV did not show the differences in comparisons of the scatter limit correction and the scatter correction that not show (p<0.05). Radioactivity uptake of the scatter correction was up to 3.1 kBq/ml in the 0.04 kBq/ml. It was approximately 98.7% undervalued in the arm motion phantom study. However, Radioactivity uptake of the scatter limit correction was up to 3.0 kBq/ml in the 2.11 kBq/ml. It was approximately 30% undervalued in arm motion phantom study. SUV of the scatter correction was 1.05 to 0.006 and underestimated about 98%. However, an applying SUV of the scatter limit correction changed the value as 0.67 which is underestimated about 25%. Radioactivity uptake and SUV of the scatter limit correction was increased approximately 60%, or more than the scatter correction. Conclusion : It is considered that if the patient arm motion artifact was occurred the scatter limit correction will be applicable to give an accurate diagnosis.