• Communications for Statistical Applications and Methods
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• 제5권1호
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• pp.231-238
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• 1998

A two stage shrinkage testimator for the mean of an exponential distribution is considered with the assumption that an initial estimate of the mean is available. Mean squared error(MSE) of testimator and its relative efficiency (to usual single sample mean) are briefly reviewed. It is shown that relative efficiency depends only on the ratio of true mean value and its initial estimate.

• 산업기술연구
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• 제17권
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• pp.313-322
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• 1997

As the weight of trucks increases, the need for concrete pavement also increases. Therefore, the addition of fly-ash may improve the properties of pavement concrete as well as recycle fly-ash. A full factorial experiment was performed using the primary variables, such as water-cement ratio, fly-ash substitution ratio, and maximum size of coarse aggregate, as a preliminary study for optimum mixture design for pavement concrete. The results of preliminary study indicates that the addition of fly-ash is the most important factor determining concrete strength, followed by the maximum size of coarse aggregate and water-cement ratio. It, also, shows the relative importance of fly-ash substitution ratio, compared to the water-cement ratio, and the interaction effects between the primary variables. Optimum mixture designs for pavement concrete incorporating fly-ash, that satisfied the target responses, were proposed in terms of fly-ash substitution ratio, water cement ratio and maximum size of coarse aggregate.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.331-336
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• 1999

Permeable polymer concrete in this study is one of the environment conscious concrete that can be applied at road, side walks and river embankment, etc. The purpose of this study is to evaluate the effects of mix proportions such as resing content, filler-binder ratio and aggregate ratio on the freezing and thawing resistance of permeable polymer concrete. The permeable polymer concrete are prepared with the resin ratio of 5%, 6% and 7%, filler-binder ratio of 0, 0.5 and 1.0, and 2.5~5mm sized aggregate ratio to standard sand of 10:10, 10:20, 20:10 and 20:20. It is tested for freezing and thawing test according to ASTM C 666092, and then, weight change, length change, relative dynamic modulus, durability factor, and compressive and flexural strengths after test are measured. From the test results, the resistance to freezing and thawing of permeable polymer concrete increased with increase the resing content, filler-binder ratio and fine aggregate ratio.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.485-492
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• 2001

Weathered soil is one of the most representative soils in Korea. In this study, a series of cyclic triaxial tests was carried out to predict the post-cyclic deformation behavior of weathered soils in case of non-liquefaction. Excess pore pressure response during cyclic loading and volumetric strain during the dissipation of excess pore pressure were measured varying the confining pressure, relative density and cyclic stress ratio. Based on the test results, it Is found that the modified excess pore pressure ratio, excess pore pressure ratio normalized by cyclic stress ratio, is uniquely correlated with the number of cycles irrespective of confining pressure and cyclic stress ratio. Using the newly proposed MEPPR(modified excess pore pressure ratio) concept, it is possible to easily evaluate the excess pore pressure and the settlement of weathered soils due to cyclic loading by greatly reduced number of tests. It is also verified that the reconsolidation volumetric strain is independent of the way how the excess pore pressure was generated.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2017년도 임시총회 및 하계학술연구발표회
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• pp.14-15
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• 2017

• 대한한의학회지
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• 제24권4호
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• pp.1-5
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• 2003

Leptin has a close correlation with obesity, which is known to be a major factor for stroke. This study was performed to determine whether serum leptin level would be an independent risk factor for stroke and whether it would change significantly early after stroke. Subjects were selected from those within I month after onset and non-stroke referents at Kyung Hee Oriental Medical Center in Seoul, Korea. We compared leptin and the other characteristics between stroke subjects and referents. Body mass index, hypertension history, presence of drinking and smoking, waist/hip ratio, total cholesterol and triglyceride were recorded. To assess odds ratio of leptin for stroke, we used logistic regression analysis. Leptin was rechecked 2 weeks later and compared with the former value in acute stroke subjects. In this study, serum leptin did not differ significantly between stroke subjects and referents, and its odds ratio was not significant in male (OR=0.52, 95％ Cl; 0.13-2.08) and female (OR=1.57, 95％ Cl; 0.53-4.67). In acute stroke subjects, leptin did not change significantly 2 weeks later. Hypertension had a significant odds ratio in male (OR=3.39, 95％ Cl; 1.02-11.24) and female (OR=12.37, 95％ Cl; 3.67-41.65). High waist/hip ratio was only in female (OR=6.70, 95％ Cl; 1.73-26.02). In conclusion, leptin was not an independent risk factor for stroke and its serum level did not change significantly early after stroke. Hypertension and waist/hip ratio had significant relative risks.

• 한국수소및신에너지학회논문집
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• 제12권3호
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• pp.169-176
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• 2001

The purpose of study is to obtain low-emission and high-efficiency in LPG engine with hydrogen enrichment. The test engine was named heavy-duty variable compression ratio single cylinder engine (VCSCE). The fuel supply system provides LPG/hydrogen mixtures based on same heating value. Various sensors such as crank shaft position sensor (CPS) and hall sensor supply spark timing data to ignition controller. Displacement of VCSCE is $1858.2cm^3$. VCSCE was runned 1400rpm with compression ratio 8. Spark timing was set MBT without knocking. Relative air-fuel ratio(${\lambda}$) of this work was varied between 0.76 and 1.5. As a result, i) Maximum thermal efficiency occurred at ${\lambda}$ value 1.0. It was shown that thermal efficiency was increased approximately 5% with hydrogen enrichment at same ${\lambda}$ value. ii) Engine-out carbon monoxide (CO) emissions were decreased at a great rate under LPG/hydrogen mixture fuelling. iii) Total hydrocarbon (THC) emission was much exhausted in rich zone, same as CO. But THC was exhausted a little bit more in lean zone. iv) Finally, engine-out oxides of nitrogen (NOx) was increased with ${\lambda}$ value 1.0 zone at a greater rate with hydrogen enrichment due to high adiabatic flame temperature.

• 환경영향평가
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• 제31권6호
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• pp.438-448
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• 2022

본 연구는 공간계획 단계에서 생태적 건전성 향상을 유도할 수 있는 계획수단으로 환경생태계획 기법과 환경계획지표인 생태면적률의 정량적인 산정지표를 개선하기 위한 연구이다. 현재 운영 중인 공간유형 및 산정지표에 대해 상대적 중요도를 파악하고 공간유형 및 가중치의 개선에 대한 의견분석을 통해 대안을 찾고자 한다. 본 연구의 방법으로는 공간유형 및 산정지표의 심층분석을 위한 공간유형의 상대적 중요도 평가를 위한 AHP 분석을 실시하였다. 연구의 신뢰성과 객관성을 확보하기 위하여 전문가 50인이 참여하였다. 본 연구를 통해 생태면적률 유형별 한계점과 개선에 대한 의견분석을 통해 발전하는 기술과 공법, 유지관리 효율성, 경제성, 시공기술의 향상 등과 연계한 생태면적률 적용을 통해 도시환경의 개선과 생태면적률 활성화에 기여할 것으로 기대된다.

• 한국건축시공학회지
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• 제12권2호
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• pp.194-202
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• 2012

This paper predicts the cementing efficiency of fly-ash(FA) based on mortar test considering binder-water ratio and FA replacement ratio as experimental variables. The cementing efficiency prediction model proposed by statistical analysis enables us to estimate the value according to the binder-water ratio and FA replacement ratio of matrix. When FA replacement ratio is the same, the lower the binder-water ratio, the higher the estimated cementing efficiency. There are significant differences in the values according to binder-water ratio at FA replacement ratios of 15% or less, but there are almost no differences when FA replacement ratio is more than 15%. As the binder-water ratio increases, the variations in the values according to FA replacement ratio are great at FA replacement ratios of 15% or less. As the FA replacement ratios increase, the values increase for FA replacement ratios of 15% or less, but decrease for more than 15%. The values range from -0.71 to 1.24 at binder-water ratio of 1.67-2.86 and FA replacement ratio of 0-70%. The RMSE of the 28-day compressive strength predicted by modified water-cement ratio is 2.2 MPa. The values can be trusted, as there is good agreement between predicted strength and experimental strength.

• 한국산림과학회지
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• 제89권5호
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• pp.591-597
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• 2000

본 실험은 층층나무(Cornus controversa Hemsl)와 말채나무(Cornus walteri Wanger)의 양묘시 적정 차광율을 구명하고자 상대광도가 100%(대조구), 50%, 30%, 10% 및 2%로 조절된 피음포지에서 실시하였다. 두 수종의 수고생장은 상대광도 50%에서 가장 높은 생장을 보였고, 근원경생장은 대조구와 50%구에서 서로 비슷하게 높은 생장을 기록하였다. 물질생산량을 보면 층층나무의 전체 생산량의 경우 50%에서 자연전광의 대조구보다 높은 생산량을 보였으나 지하부의 생산량은 다소 낮았다. 말채나무는 50%에서 전체 생산량은 대조구보다 낮았으나 지상부 생산량은 다소 높은 생산량을 보였다. 30%이하의 상대광도에서는 수고생장, 근원경생장 및 물질생산량이 급격히 감소하였다. 두 수종 모두 30%에서 가장 높은 T/R율을 기록하였으며 전체적으로 말채나무의 T/R율이 층층나무의 T/R율 보다 높았다. 잎의 엽록소 a와 b 및 전체엽록소 함량은 상대광도가 낮을수록 높아지는 경향을 나타내었다.