• Structural Engineering and Mechanics
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• 제84권3호
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• pp.413-421
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• 2022

Modal parameters are the main dynamic characteristics of bridge. This study aims to propose an innovative route to estimate the modal parameters for bridges by using a parked vehicle in which mode shapes with high accuracy and spatial resolution are identified by frequency measurement. Based on the theory of dynamic modification and modal identification, the mathematical formulation between the parked mass induced frequency variation and the modal parameters of a bridge is derived. Then this mathematical formulation is extended to a parked vehicle-bridge system. The arithmetic and processes for estimating the modal parameters based on the identified frequency variation of the vehicle-bridge systems when the vehicle locates at sequentially arranged positions are presented. Finally the proposed method is applied to several simulated bridges of different types. The results indicate that it can estimate the modal parameters with high accuracy and efficiency.

• 대한원격탐사학회지
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• 제32권2호
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• pp.119-131
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• 2016

한반도 에어로졸 라이다 관측 네트워크(Korea Aerosol Lidar Observation Network; KALION)의 라이다 관측자료 처리 및 실시간 표출을 위한 표준 알고리즘을 개발하였다. KALION 표준 알고리즘은 라이다 관측으로부터 얻어진 후방산란강도와 편광소멸도 자료를 이용하여 (1) 에어로졸과 구름 구분, (2) 에어로졸 유형 구분, (3) 에어로졸 소산계수 그리고 (4) 에어로졸 질량농도를 산출하는 단계로 구성이 되어 있다. 에어로졸의 유형은 후방산란강도와 편광소멸도 자료에 근거하여, (대륙 기원) 청정기단 에어로졸(clean continental aerosol), 황사(dust aerosol) 그리고 오염 입자(polluted continental/urban pollution aerosol)로 구별된다. 에어로졸 소산계수에 필요한 라이다 상수는 약 9년간의 라이다와 스카이 라디오미터 자료로부터 도출된 63.31 sr을, 에어로졸 질량소산효율은 약 9년간의 라이다와 기상청 Particulate Matter($PM_{10}$) 질량농도 자료를 이용하여 도출된 $3.36m^2\;g^{-1}$ (황사는 $1.39m^2\;g^{-1}$)을 적용한다. 2015년 3월 28일부터 30일까지 라이다 관측 사례(서울 관악)에서 KALION 표준 알고리즘을 통해 산출된 에어로졸 유형 구분, 특히 황사 판별 결과는 기상청의 황사 보고와 잘 일치하였으며, 2006년 6월부터 약 9년 동안의 라이다 관측자료로부터 산출된 에어로졸 질량농도 역시 지상 $PM_{10}$ 농도와 약 $3{\mu}g\;m^{-3}$ 내에서 잘 일치하였다. 향후 에어로졸의 유형에 따른 서로 다른 라이다 상수 및 에어로졸 질량소산효율 적용 알고리즘, 빙정 구름(ice cloud)과 물방울 구름(water droplet cloud) 구분 알고리즘, 그리고 운저 고도와 혼합고 판별 알고리즘을 개발할 계획에 있다.

• 대한한의학방제학회지
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• 제25권2호
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• pp.193-207
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• 2017

Objectives : This study was designed to investigate anti-obesity effects of DF in a ob/ob mouse model. Methods : Fifteen-week-old ob/ob mice were divided into four groups: a normal lean group given a standard diet, an ob/ob control group given a standard diet, and DF(1) and DF(2) groups given a standard diet with DF(1) (300 mg/kg), and DF(2) (600 mg/kg), respectively. After 10 weeks of treatment, body weight gain, feeding efficiency ratio, blood lipid markers, fat weight and histology were examined. Results : Body weight gain and fat mass were significantly decreased in DF(1) and DF(2) groups compared with control. The extent of decreases was eminent in DF(2) group. Feeding efficiency ratio were significantly decreased in DF(2) group compared with control. Consistent with their effects on body weight gain and fat mass, circulating concentrations of LDL, total cholesterol, free fatty acid, and insulin were decreased in DF(2) group compared with control. The size of adipocytes were significantly decreased by DF(2) compared with control. Consistent with their effects on body weight gain, hepatic lipid accumulation and liver weights were reduced in DF compared with control. Conclusions : In conclusion, these results suggest that DF not only decrease feeding efficiency ratio, and blood anti-obesity biomarkers, but also reduce fat mass, contributing to the improvement of obesity. DF also inhibits hepatic lipid accumulation.

• 한국지진공학회논문집
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• 제11권2호
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• pp.57-68
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• 2007

메가골조시스템은 사용되는 구조재료를 절약하면서도 구조물의 강성을 효과적으로 높일 수 있는 장점 때문에 고층건물의 설계에 많이 사용되고 있다. 이러한 메가골조시스템이 주로 적용되고 있는 초고층건물의 구조설계에서는 횡하중에 대한 거주자의 불안감을 최소화시키는 것이 주요한 관심사중의 하나이다. 따라서 본 연구에서는 메가골조구조물의 사용성을 향상시키기 위한 방법으로 일반적인 수동 TMD의 제어성능을 개선한 준능동 TMD(STMD)를 사용하였다. 이를 위하여 TMD에서 일반적으로 사용되고 있는 수동감쇠기 대신 준능동 MR 감쇠기를 사용하여 STMD를 구성하였다. 메가골조구조물의 일반적인 유한요소해석모델은 매우 많은 수의 자유도로 구성되어 있기 때문에 원형모델을 사용하여 STMD의 제어성능을 검토하는 것은 현실적으로 불가능하다. 따라서 메가골조구조물의 동적 거동을 정확하게 표현할 수 있는 최소한의 자유도를 가진 응축모델을 행렬응축기법을 이용하여 제안하였다. 또한 일반적인 행렬응축기법의 효율성을 향상시키기 위하여 메가골조구조물의 특성을 활용한 다단계 행렬응축기법을 제안하였다. 본 연구에서 제안된 응축모델을 사용한 제어의 효율성과 정확성 및 메가골조구조물에 대한 STMD의 제어성능을 예제해석을 통하여 검증하였다.

• 대한한방부인과학회지
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• 제31권1호
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• pp.20-42
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• 2018

Objectives: This study was designed to investigate anti-obesity effects the improvement effects of Gyejibongnyeong-hwan and Gyejibongnyeong-hwan-Gangji-hwan (CIPPDF) in a ob/ob mouse model. Methods: Seven-week old mice (wild-type C57BL/6J and ob/ob) were used for all experiments. Wild-type C57BL/6J mice were used as normal group and obese ob/ob mice were randomly divided into 4 groups. a normal group given a standard diet, an obese control group given a standard diet with CIPP (300 mg/kg), CIPPDF (1) (300+300 mg/kg), CIPPDF (2) (300+600 mg/kg) respectively. After 10 weeks of treatment, body weight gain, feeding efficiency ratio, blood lipid markers, mRNA levels of genes involved in fatty acid ${\beta}-oxidation$ and lipogenesis in in-vivo, were examined. Results: 1. Body weight gain and Feeding efficiency ratio were significantly decreased in CIPPDF (1) compared with control. Fat mass was significantly decreased in CIPPDF (2) in EAT compared with control. 2. Consistent their effects on body weight gain and fat mass, circulating concentrations of LDL-cholesterol were decreased in CIPPDF (1), CIPPDF (2) groups compared with control. 3. MCAD mRNA levels of genes was increased in CIPPDF (1), CIPPDF (2) groups in the liver, epididymal adipose tissue compared with control. VLCAD mRNA levels of genes was increased in CIPPDF (1), CIPPDF (2) groups in the skeletal muscle compared with control. 4. $PPAR{\gamma}$ mRNA was decreased in CIPPDF (1) in the liver compared with control. SCD1 mRNA was decreased in CIPPDF (1), CIPPDF (2) groups in the epididymal adipose tissue compared with control. Conclusions: In conclusion, These results suggest that CIPPDF not only decrease feeding efficiency ratio, and LDL-cholesterol, but also reduce EAT fat mass contributing to the improvement of ovesity. CIPPDF also were increased in mRNA levels of genes involved in fatty acid ${\beta}-oxidation$ and decreased in mRNA levels of genes involved in lipogenesis.

• Safety and Health at Work
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• 제8권3호
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• pp.296-305
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• 2017

Background: Surfactant-containing water sprays are commonly used in coal mines to collect dust. This study investigates the dust collection performance of different surfactant types for a range of coal dust particle sizes and charges. Methods: Bituminous coal dust aerosol was generated in a wind tunnel. The charge of the aerosol was either left unaltered, charge-neutralized with a neutralizer, or positively- or negatively-charged using a diffusion charger after the particles were neutralized. An anionic, cationic, or nonionic surfactant spray or a plain water spray was used to remove the particles from the air flow. Some particles were captured while passing through spray section, whereas remaining particles were charge-separated using an electrostatic classifier. Particle size and concentration of the charge-separated particles were measured using an aerodynamic particle sizer. Measurements were made with the spray on and off to calculate overall collection efficiencies (integrated across all charge levels) and efficiencies of particles with specific charge levels. Results: The diameter of the tested coal dust aerosol was $0.89{\mu}m{\pm}1.45$ [geometric $mean{\pm}geometric$ standard deviations (SD)]. Respirable particle mass was collected with $75.5{\pm}5.9%$ ($mean{\pm}SD$) efficiency overall. Collection efficiency was correlated with particle size. Surfactant type significantly impacted collection efficiency: charged particle collection by nonionic surfactant sprays was greater than or equal to collection by other sprays, especially for weakly-charged aerosols. Particle charge strength was significantly correlated with collection efficiency. Conclusion: Surfactant type affects charged particle spray collection efficiency. Nonionic surfactant sprays performed well in coal dust capture in many of the tested conditions.

• Journal of Advanced Marine Engineering and Technology
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• 제29권7호
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• pp.750-757
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• 2005

The objective of this study is an understanding of the effect of inlet flow angle on the output power performance of a Francis hydraulic turbine, An optimum induced angle at the inlet of the turbine is one of the most important design parameters to have the best performance of the turbine at a given operating condition, In general. rotating speed of the turbine is varied with the change of water mass flowrate in a volute, The induced angle of the inlet water should be properly adjusted to the operating condition to have maximum energy conversion efficiency of the turbine, In this study. a numerical simulation was conducted to have detail understanding of the flow phenomenon in the flow path and output power of the model Francis turbine. The indicated power produced by the model turbine at a given operating condition was found numerically and compared to the brake power of the turbine measured by experiment at KIER. From comparison of two results, turbine efficiency or energy conversion efficiency of the model turbine was estimated. From the study, it was found that the rotating power of the turbine linearly increased with the rotating speed. It means that the higher volume flow rate supplied. the bigger torque on the turbine shaft generated. The maximum brake efficiency of the turbine is around 46$\%$ at 35 degree of induced angle. The difference between numerical and experimental output of the model turbine is defined as mechanical efficiency. The maximum mechanical efficiency of the turbine is around 93$\%$ at 25$\∼$30 degree of induced angle.

• 한국추진공학회지
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• 제3권4호
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• pp.44-50
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• 1999

Unlike impinging Quadlet injector(OOOF type)에 대한 혼합효율, 혼합특성속도, 혼합특성속도효율을 연소성능을 예측하기 위해 비연소 실험을 통하여 구하였다. 모의 추진제는 물($H_2$O)와 케로신($CH_{1.97}$)을 사용하였고, 혼합상관인자로써 산화제, 연료 분류의 운동량비를 사용하였다. 인젝터 분무특성을 파악하기 위해 오리피스(orifice) 각 hole에 대한 유량계수, 분무형상, 질량분포 획득이 수행되어졌다. 연구 결과, 침투깊이는 혼합효율, 혼합특성속도, 혼합특성속도 효율에 영향을 미침을 알 수 있었다. 또한, 혼합효율 및 혼합특성속도 효율은 MR=1.67(TMR=2.5)에서 87%로 최대값을 가지며 산화제 과잉상태보다 연료 과잉상태에서 더 큰 감소율을 보였다.

• 한국콘텐츠학회논문지
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• 제13권1호
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• pp.366-375
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• 2013

최근 매스미디어 중 신문사의 경영은 인터넷뉴스, 방송 등의 확산으로 인해 신문사간의 경쟁뿐만 아니라 타 매체와의 경쟁도 심화되고 있는 현실이다. 따라서 본 연구에서는 자료포괄분석기법을 이용한 분석을 통해 국내 매스미디어인 신문발행업의 운영 효율성을 평가하여 운영성과 제고를 위한 벤치마킹 대상 신문사와 신문사가 개선해야할 투사값을 제시함으로써 효율적인 신문사 운영에 도움이 될 수 있는 근거를 제시하고자 한다. 분석을 위해 30개 신문발행사을 선정하였으며 평가항목으로는 CCR-O, BCC-O 효율성과 규모효율성(SE), 규모수익성(RTS)을 중심으로 평가하였으며 각각의 분석결과를 살펴보면 30개 신문발행사 중 CCR-O효율성이 1로 나타난 신문사가 10개, BCC-O효율성이 1로 나타난 신문사가 14개, 규모수익성분석을 위해 3가지 측면에서 분석 해 본 결과로는 규모의 보수증가가 1개 업체, 규모의 보수감소가 16업체, 규모의 보수불변이 13업체로 나타났다. 이와 같은 결과를 바탕으로 신문발행업체들이 효율적으로 프론티어에 도달하기 위한 투사값을 투입변수와 산출변수를 가지고 분석함으로써 신문발행업의 효율성에 영향을 주는 변수에 대한 정확한 이해와 기업경영 개선과 관련한 효율성 및 성과에 대해 분석하고자 한다.

• 동력기계공학회지
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• 제17권5호
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• pp.58-63
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• 2013

In this study, the effect of deep ocean condenser inlet temperature ($T_{DOI}$), condenser inlet pressure ($P_{cond,in}$), and thermal diffusivity on system efficiency of some selected refrigerants was analyzed using HYSYS. The proposed DOTEC cycle is similar to the reheat Rankine cycle but eliminates irreversibilities by bleeding a fraction of the steam between certain stages of the turbine. The evaporator inlet mass flow rate, inlet temperature of turbine 1, turbine efficiency and inlet and outlet temperature of heat source were imposed. The working fluids considered are sorted in ascending order of their molecular weights as R717, R600a and R152a. Results indicated that a fluid with a lower boiling point temperature like R717 needs a corresponding high heat source and/or evaporator inlet pressure. Also, the response of thermal diffusivity closely follows the change in TDOI as an increase in $T_{DOI}$ increases $P_{cond,in}$ which reduces thermal diffusivity and system efficiency. Furthermore, the fluid with the nominal boiling point temperature has the highest efficiency with efficiency decreasing with an increase in TDOI.