• 한국자동차공학회논문집
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• 제21권1호
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• pp.23-29
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• 2013

In recent years, development of energy conversion systems using hydrogen as an energy source has been accelerated globally. Even though hydrogen is an environment-friendly energy source, safety and effectiveness issues in storage, transportation, and usage of hydrogen should be clearly resolved in every application. Therefore, sensors for detecting hydrogen leakage, especially for fuel cell electric vehicles, should be designed to have much higher resolution and accuracy in comparison with conventional gas sensors. In this study, we conducted to determine the design parameters for the semiconductor hydrogen sensor with optimized sensing conditions under the thermal distribution characteristic and thermal transfer characteristic. The heat generation study on power supply voltage was studied for correlation analysis of thermal energy according to the power supply voltage variation from 1.0 voltage to 10.0 voltage every 0.5 voltage. And we studied for the temperature coefficient of resistance with hydrogen sensor.

• 한국수소및신에너지학회논문집
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• 제34권5호
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• pp.526-534
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• 2023

To evaluate the risk of leakage when using liquid hydrogen, a leakage test was conducted using liquid nitrogen in an outdoor environment rather than a laboratory environment. To assume a real-scale continuous leak, liquid nitrogen was allowed to leak for 5 minutes through a pipe with a diameter of 25.4 mm at a design spill rate of 60 L/min. The measurement system consisted of devices for climate conditions, LN2 spread and vapor clouds. The main experimental results are the liquid pool radius and the concentration of vapor cloud, and the radius of the liquid pool was compared with the numerical analysis results.

• 한국지반신소재학회논문집
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• 제17권4호
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• pp.81-92
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• 2018

최근 천연가스에 대한 수요가 높아지면서 이를 저장하기 위한 LNG 탱크의 건설이 증가하고 있다. LNG는 효율적인 저장을 위해 극저온의 유체로 액화되므로, LNG 탱크의 결함으로 인한 LNG 유출은 막대한 피해를 야기할 수 있다. 많은 연구자들이 다양한 LNG 유출 상황에 대하여 발생가능 한 피해 영향을 평가하였으나, 극저온의 LNG 유체가 유출될 경우 LNG 탱크를 지지하고 있는 지반에 미치는 영향에 대한 연구는 제한적이다. 따라서 본 논문에서는 LNG 탱크 및 지반의 다양한 조건을 고려하여 LNG 유출에 따른 동결 지반의 역학적, 열적 거동 변화에 대한 연구를 수행하였다. 유출 시나리오의 구현을 위해 수치해석을 수행하였으며, 상재하중, 온도 경계조건, 흙의 동결 민감성 변화에 따른 지반과 기초구조물 거동을 조사하고자 하였다. 이를 통해 LNG 유출 이후 지반의 단기 및 장기 온도변화를 평가하였으며, 지반 동결에 따른 간극 및 연직변위 변화를 분석하였다.

• 한국지구과학회지
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• 제31권6호
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• pp.563-572
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• 2010

흙댐에서의 누수 구역을 판별하기 위해 다채널 연속 온도 모니터링을 수행하고 이를 검증하기 위해 전기비저항 물리탐사를 함께 수행하였다. 일반적으로 댐이나 사면과 같은 인공구조물의 내부는 시간과 위치에 따라 상이한 온도 분포를 갖는 것으로 여겨진다. 이와 같은 분포는 구조물의 안전성을 판단하는 데 매우 중요한 기본 자료로 이용될 수 있으며, 특히 댐 구조물의 경우 과도 침투수나 누수에 의한 위험 대역을 파악할 수 있는 기술로 이용될 수 있다. 그러나 기존의 온도 측정 방식은 대형 구조물의 온도를 연속적으로 동시에 측정할 수 없는 단점을 가지고 있다. 본 연구에서는 이를 극복한 새로운 온도 모니터링 장비를 이용하여 댐의 상부 및 하부에 걸쳐, 여러 지점에서 동시에 온도 분포를 측정하였으며, 실내 시험을 통해 누수 대역이 온도 분포의 이상을 충분히 반영하고 있음을 관측하였다. 또한 대상 댐의 전 구역에 걸쳐 전기비저항 조사를 수행한 결과와 온도 모니터링 자료를 비교 분석하여 누수구역의 판별력을 높일 수 있는 방법을 제시하고자 하였다.

• Tribology and Lubricants
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• 제21권5호
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• pp.227-235
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• 2005

This paper presents a tribological study on the failure cases of automatic transmission components in a passenger car. The automatic transmission system is composed of torque converter, clutch, brake, planetary gear, and valve body controlling oil pressure of an automatic transmission fluid. The most largest influence components in an automatic transmission are a torque converter and clutch plate in which are influenced by a wear and torque converting energy loss. The failure case study of an automatic transmission indicates that the tribological design and maintenance technologies should be considered as a key design concept. This means that the failure and power energy loss come from the friction, wear and a oil leakage of an automatic transmission, which is related to the oil seal and O-ring seal failures.

• 한국재료학회지
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• 제28권8호
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• pp.440-444
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• 2018

An effective cleaning method for Ni removal in Ni-induced lateral crystallization(Ni-MILC) poly-Si TFTs and their electrical properties are investigated. The HCN cleaning method is effective for removal of Ni on the crystallized Si surface, while the nitric acid treatment results decrease by almost two orders of magnitude in the Ni concentration due to effective removal of diffused Ni mainly in the poly-Si grain boundary regions. Using the HCN cleaning method after the nitric acid treatment, re-adsorbed Ni on the Si surfaces is effectively removed by the formation of Ni-cyanide complexions. After the cleaning process, important electrical properties are improved, e.g., the leakage current density from $9.43{\times}10^{-12}$ to $3.43{\times}10^{-12}$ A and the subthreshold swing values from 1.37 to 0.67 mV/dec.

• 한국연소학회지
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• 제16권1호
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• pp.46-51
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• 2011

Exhaust gas of an industrial furnace used at such as metallurgy or ceramic manufacturing usually contains thermal energy with high temperature which can be recycled by heat exchanger. However, when the temperature of the exhaust gas is high such as more than $1,000^{\circ}C$, ordinary metallic heat exchanger cannot fully recover the heat due to the limitation of operating temperature depending on the material property. In the present study, a compact ceramic heat exchanger of cross flow type is introduced and evaluated by heat exchange rate and operating temperature. The ceramic heat exchanger can endure the gas temperature more than $1,300^{\circ}C$, and its volumetric heat exchanging rate exceeds 1 MW/$m^3$. The experimental data is also compared with the previous numerical result which shows reasonable agreement. Meanwhile, the gas leakage rate is measured to be about 3~4%, and heat loss to environmental air is about 23~26% of the fuel energy.

• 유공압시스템학회논문집
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• 제3권4호
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• pp.1-7
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• 2006

A water hydraulic pump is likely to have serious problems of high leakage, friction and low energy efficiency. A water hydraulic pump has commonly a fixed displacement type and its outlet flow is adjusted by controlling rotation speed of the pump, which can be implemented by using an electric inverter. This study aims to investigate energy efficiency of the water hydraulic pump system which is driven by an electric inverter. The study is based on the experimental results. The pump which is used in the study shows relatively good efficiency and low leakage, low friction as well. The reasons for the good performance of pump is also investigated.

• 전력전자학회논문지
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• 제28권1호
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• pp.1-7
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• 2023

A grid-connected 3-level NPC inverter is a power conversion device that connects renewable energy generators, such as photovoltaic or wind turbines to the grid. Although many studies have focused on this inverter, commercializing it requires strictly satisfying various safety and power quality-related standards. Among many standards, leakage current and grid current total harmonic distortion(THD) can be affected by external factors such as installation environment, aging, and grid conditions. Hence, inverter operations that can satisfy these standards need to be explored. In this study a 3-level NPC inverter operation algorithm using the Phase Opposition Disposition-PWM method that can effectively reduce leakage current and switching frequency adjustment to reduce THD effectively has been proposed.

• 한국수소및신에너지학회논문집
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• 제34권6호
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• pp.698-711
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• 2023

Consequence analysis using an ALOHA program is conducted to calculate the accidental impact ranges in the cases of hydrogen leakage, explosion, and jet fire in a hydrogen fueled combined cycle power plant. To evaluate the effect of weather conditions and topographic features on the damage range, ALOHA is executed for the power plants located in the inland and coastal regions. The damage range of hydrogen leaked in coastal areas is wider than that of inland areas in all risk factors. The obtained results are expected to be used when designing safety system and establishing safety plans.