• Journal of the Optical Society of Korea
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• 제4권1호
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• pp.11-13
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• 2000

We experimentally measured the cold cavity loss of a mode-locked erbium-doped fiber ring laser in situ by using the relaxation oscillation frequency method. The relaxation oscillation frequency is measured for various pumping powers and the data is fitted by the least squares method with a theoretical curve of parameters including the cavity loss. We obtained a cavity loss of 15.3$\pm$0.5 dB which was found to agree with the results of direct transmission loss measurements.

• 동력기계공학회지
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• 제19권2호
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• pp.49-56
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• 2015

As an alternative fuel that can be used in SI engine, LPG is one of clean fuels with larger H/C ratio compared to gasoline, low $CO_2$ emission, and small amount of pollutants such as sulfur compounds. When LPG is used in spark ignition engine, volumetric efficiency of the engine can be improved and pumping loss can be reduced by performing direct injection into the combustion chamber instead of port fuel injection. LPG-DI engine allows for lean combustion and stratified combustion under low load. In case of stratified combustion, air fuel ratio can be greatly increased compared to theoretic mixture ratio combustion. Improved thermal efficiency of the engine and reduced pumping loss can be expected from stratified combustion. Accordingly in this study, an experimental apparatus for visualization was designed and manufactured to study the combustion process of LPG after injection and ignition, intended to examine ignition probability and combustion characteristics of spark ignition direct injection(SIDI) LPG fuel. Ambient pressure, ambient temperature and fuel injection pressure were found as important variables that affect ignition probability and flame propagation characteristics of LPG-air mixture. Also, it was verified that the injected LPG fuel can be directly ignited by spark plug under appropriate ambient conditions.

• 한국콘텐츠학회논문지
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• 제17권4호
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• pp.95-107
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• 2017

최근 기후변화의 영향에 의해 재난의 규모가 점차 대형화 되어감에 따라 사회 및 국민경제에 미치는 영향이 증대되고 있다. 그러나 기존의 재해손실 통계는 직접적인 인명피해를 제외하면 물리적인 피해에만 국한되어 있어 피해규모가 과소 집계되는 문제가 있다. 이로 인해 피해자의 보상 및 정부 지자체의 재난정책 수립에도 장애요소로 작용되고 있다. 따라서 본 연구는 그동안 간과되어 온 사회경제적 직 간접 손실의 피해항목을 조사 분석하여 국내의 실정에 맞는 기본통계 항목을 도출하는 데 그 목적이 있다. 이를 위해 국내외의 재해피해 통계 현황과 선행연구 등을 검토하여 사회경제적 직 간접 손실에 대한 개념 및 프레임워크를 설정하고, 예비 통계항목을 도출하였다. 이후, 통계항목의 선별기준을 정립하여 최종 통계항목을 선정하였다. 본 연구의 결과는 풍수해의 사회경제적인 영향과 피해규모를 산정하고 예측하는 기술개발 연구에 기초자료로 활용될 수 있다.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.24-31
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• 2004

A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyzer the heat quantity of inhomogeneous charge methane-air mixture. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. It is shown that the effect of stratification is not significant in case of the overall excess air ratio of 1.1, mainly due to the higher heat loss and lower thermal efficiency compared to those of homogeneous condition. In the case of the overall excess air ratio of 1.4, as the initial charge pressure decreases, the CHR ratio has been decreased while the HL ratio has been increased, Generally, as the initial charge pressure increases, the amount of injection mixture has been decreased and has resulted in lower mean velocity and turbulence intensity for injection mixture. Also, the injected mixture is too rich to result in mixing deficiency in combustion chamber. From these results, it could be possible to acquire the improvement of thermal efficiency and the reduction of heat loss simultaneously through the 2-stage injection in CNG direct injection engine.

• Elastomers and Composites
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• 제53권3호
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• pp.141-149
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• 2018

A series of aromatic poly(o-hydroxyamide)s (PHAs) were synthesized by the direct polycondensation reaction of 4,4′-(2,3-quinoxalinedioxy) dibenzoic acid and/or 4,4′-(2,3-pyridinedioxy) dibenzoic acid with bis(o-aminophenol) including 2,2-bis-(amino-4-hydroxyphenyl)hexafluoropropane. The PHAs exhibited inherent viscosities in the range of 0.17-0.35 dL/g at $35^{\circ}C$ in a DMAc solution. These polymers showed low inherent viscosities and yielded brittle films. All the PHAs showed excellent solubility in aprotic solvents such as DMAc, DMSO, NMP, and DMF at room temperature and in less polar solvents such as pyridine and THF. However, all the PBOs were only partially soluble in $H_2SO_4$. The PBOs exhibited 10% weight loss at temperatures in the range of $537-551^{\circ}C$. The maximum weight loss temperature increased with an increase in the content of the quinoxaline-containing monomer. The residue of the PBOs showed a weight loss of 45.8-56.7% at $900^{\circ}C$ in a nitrogen atmosphere.

• The Journal of Asian Finance, Economics and Business
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• 제6권3호
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• pp.9-18
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• 2019

The purpose of this study is to investigate the relation between conservative loan loss accounting practice of banks, defined as accounting behavior that increases loan loss allowances against expected credit losses, and bank lending. Furthermore, we specify the macroeconomic conditions reflecting debtors' borrowing environments and analyze how these conditions affect the relation between conservative loan loss allowances and bank lending. Although existing literature reports that accounting conservatism has a direct effect on non-financial firms' investment behavior, there is little evidence about an effect of conservatism on banks' lending behavior. By exploiting data showing the links between individual Japanese firms and their individual lenders to control both loan demand and supply, we estimate OLS regressions to test the relationships among conservative loan loss allowance, bank lending, and macroeconomic conditions using a unique dataset containing bank-firm-year observations between 2001 and 2013. We find banks that have conservative loan loss allowances tend to provide fewer loans to firms with financing needs when macroeconomic conditions are good and these conservative banks are likely to provide more loans to firms when macroeconomic conditions are bad. Our findings suggest that reflecting expected credit loss into loan loss allowances can mitigate the procyclical behavior of banks.

• 대한치과보철학회지
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• 제35권1호
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• pp.165-180
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• 1997

The purpose of this study was to observe bone apposition and marginal bone loss and to check the possibility of success on titanium implant, HA coated implant and the implant with natural coral that were place immediately after teeth extraction in dogs. Experimental subjects were divided into 4 groups ; the 1st group is the titanium implant, second the HA coated implant, third the implant with natural coral, and the last the control group that was prepared in the extraction sockets. After 12 weeks, the dogs were sacrificed for visual observation and microscopic examination approaching histologic and histomorphometric analysis. The results were as follows : 1. Neither the infection nor the exposure of implant was found at the sites of all implant. 2. In a histomorphometric analysis, mean percentage of direct bone contact with the titanium implant was 80.7% and the HA coated implant showed 81.5% apposition, but the implant with natural coral showed 64.9% apposition(P<0.05). 3. In a microscopic examination, mature lamellated bone was found around the immediate implants and control group, while unabsorbed natural coral around the immediate implants with natural coral was found. 4. All immediate implant groups showed the loss of marginal bone in order from implant with natural coral, titanium implant, and HA coated implant. 5. Implant with natural coral that was placed by the type I interface of the Barzilay's classification immediately after teeth extraction showed low percentage of direct bone contact area, low success rate and a lot of marginal bone loss. Above results suggested that the immediate implants are osseointegrated successfully, although slightly marginal bone was loss.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.290-299
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• 2017

Reconfigurable flight control using various kinds of adaptive control methods has been studied since the 1970s to enhance the survivability of aircraft in case of severe in-flight failure. Early studies were mainly focused on the failure of actuators. Recently, studies of reconfigurable flight controls that can accommodate complex damage (partial wing and tail loss) in conventional aircraft were reported. However, the partial wing loss effects on the aerodynamics of conventional type aircraft are quite different to those of BWB(blended wing body) aircraft. In this paper, a reconfigurable flight control algorithm was designed using a direct model reference adaptive method to overcome the instability caused by a complex damage of a BWB aircraft. A model reference adaptive control was incorporated into the inner loop rate control system enhancing the performance of the baseline control to cope with abrupt loss of stability. Gains of the model reference adaptive control were polled out using the Liapunov's stability theorem. Outer loop attitude autopilot was designed to manage roll and pitch of the BWB UAV as well. A 6-DOF dynamic model was built-up, where the normal flight can be made to switch to the damaged state abruptly reflecting the possible real flight situation. 22% of right wing loss as well as 25% loss for both vertical tail and rudder control surface were considered in this study. Static aerodynamic coefficients were obtained via wind tunnel test. Numerical simulations were conducted to demonstrate the performance of the reconfigurable flight control system.

• 산업기술연구
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• 제24권A호
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• pp.119-126
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• 2004

BLDC Motor is one of the widely utilizable motors in servo system. The accurate calculation of the power loss for the IGBT and Inverse diode with Bipolar and Unipolar switching modes the driving modes is important for the design of drives for their heat treatment. If it were not for temperature-sensors in devices, it is difficult to get direct power loss, so. Power losses may be modeled by computer modeling to obtain the Calculation of the Power loss for Inverter in BLDC Motor with switching modes which is presented in this paper. The computer modeling is carried out by Matlab simulation. The power loss consists of conduction losses Conduction losses are the source of occurrence due to The IGBT and Inverse diode currents. Switching losses are the source of occurrence due to switching on/off in the devices, and gives the dominant influence to the loss. As a result, the unipolar I mode is best in reducing the heat losses.

• 한국인터넷방송통신학회논문지
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• 제10권4호
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• pp.105-113
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• 2010

240 GHz 대역의 캐리어 주파수를 이용하여 1.485 Gbps 비디오 전송 시스템을 설계 및 시뮬레이션 하였다. 송수신기는 Schottky Barrier 다이오드 기반의 Sub-harmonic 믹서를 이용하였으며 특히, 수신기는 Heterodyne 및 Direct Detection 두 가지 방식을 적용하여 각각의 성능을 시뮬레이션 하였다. 변조방식은 ASK이며, 수신기에서는 Envelop 검출 방식을 사용하였다. 송신기 시뮬레이션 결과 Sub-harmonic 믹서의 LO 전력 7 dBm(5 mW)에서 IF 입력 전력 -3 dBm(0.5 mW)일 때 RF 출력 전력은 -11.4 dBm($73{\mu}W$)이었으며, SSB(Single Side Band) Conversion Loss는 8.4 dB이다. VDI사의 상용모델 WR3.4SHM(220~325 GHz)의 240 GHz에서의 Conversion loss 8.0 dB(SSB)와 근접한 결과를 얻었다. 1.485 Gbps NRZ 신호전송 시뮬레이션 결과 전송신호와 동일한 수신 파형을 얻었다.