• 센서학회지
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• 제13권2호
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• pp.139-143
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• 2004

This paper presents a method that the engine oil condition is detected using a natural convection heat transfer in a engine oil. A sensor circuit maintains a constant temperature difference between a heat plate and engine oil for detecting a natural convection heat transfer rate on the constant temperature. The natural convection heat transfer rate is measured by a current through the heat plate of the sensor circuit. The sensor is tested by a fresh oil. 6,000 km and 10,000 km driven oil in the oil temperature range from $20^{\circ}C$ to $100^{\circ}C$. In the experimental result, when the current through the heat plate is altered by variation of a engine oil temperature and flows driven oil more than fresh oil, the sensor could inform a engine oil deterioration to a car driver.

• 한국수정란이식학회:학술대회논문집
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• 한국수정란이식학회 2001년도 발생공학 국세심포지엄
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• pp.5-5
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• 2001

• 동서간호학연구지
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• 제11권1호
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• pp.12-24
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• 2005

The objective of this research is to explore the attitude on the transfer of duty post and job satisfaction of nurses. The subjects of this study were 512 nurses who have engages in the K-university hospital. The measurement tool consisted of attitude on the transfer of duty post, job satisfaction. The collected data have been processed using SPSS/PC 12.0 program: The results of this study were as follows: 1. The age the subjects was from 21 to 56 and average 32, blow 3 years experience in current duty post occupied most by 37.1%. The experience of the transfer of duty post showed 50.2%. 51.4% of the nurses wanted $3{\sim}5$ years as the suitable periods for the transfer of duty post showing the highest degree of frequency. 2. The positive degree of the attitude on the transfer of duty post of the nurses appeared average (3.36) to maximum evaluation point 5, and when asked about 4 factors the nurses wanted individual development most by (3.72) while administration management was lowest by (2.65). The satisfaction degree on their job appeared to be average (3.06) to the maximum point 5, and when asked about 7 factors, interaction appeared to be the highest by (3.63), here we saw that interaction was the most important elevating factor of the job satisfaction degree. 3. In the relation of the attitude on the transfer of duty post according to general characteristics, there were the significant difference according to whether it is necessary for the current duty post and periodical duty post to be transferred. In the relation between general characteristics and job satisfaction degree there were the significant differences according to age, marital status, education, position of nurse, hospital clinical nursing experiences, satisfaction degree with current post and the hope of the transfer of duty post from current post. 4. The correlation between attitude on the transfer of duty post and job satisfaction degree was positive relation(r=0.137, p=.002), that the higher the degree of positive attitude on the transfer of duty post the higher the degree of job satisfaction.

• 한국전자통신학회논문지
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• 제15권1호
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• pp.79-84
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• 2020

무선 전력 전송은 유선 전력 전송 보다 편리하지만 전송거리가 짧고 효율이 낮다. 또한, 여러 장치를 동시에 충전하기 어렵다. 본 논문에서는 무선 전력 전송의 전송 거리를 증가시키고 효율을 향상시키기 위해 다수의 송신코일을 이용해서 Magnetic Beam을 형성하는 방법을 제안한다. 이를 위해 송신코일 전류와 수신코일 중심에서의 자속밀도 사이의 관계를 모델링하고, 의사역행렬(Pseudoinverse)의 특성을 이용해 최적의 송신코일 전류를 계산한다. 마지막으로 Simulation을 통해 제안한 방법의 타당성을 검증한다.

• KIEAE Journal
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• 제7권5호
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• pp.53-58
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• 2007

In order to predict the indoor air pollutant, the VOCs emission rate is used through small chamber in the design process. However, the small chamber method has limitations as the convective mass transfer coefficient, the most important factor when predicting VOCs contamination of indoor air, is different between the small chamber result and the measured data in the actual building. Furthermore, the existing studies which analyzed mass transfer coefficient in the small chamber were directed on the small chambers developed at the time and FLEC(Field and Laboratory Emission Cell), thus, are different from the current small chamber which has been changed with improvements. The purpose of this study is to determine the emission rate of pollutant in multi-layered building materials, and predict the indoor pollutant concentration through the CFD(Computational of Fluid Dynamics) and CRIAQ2 based on the mass transfer coefficient on singled-layered building material by using the current small chamber widely used in Korea. Futhermore, this study used the new convective mass transfer coefficient(hm') which indicates the existing convective mass transfer coefficient(hm) including VOC partition coefficient(k). Also, formaldehyde was selected as target pollutant.

• 한국초전도ㆍ저온공학회논문지
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• 제17권1호
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• pp.10-13
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• 2015

High-temperature superconducting coated conductors (HTS-CCs) are good candidates for resistive superconducting fault current limiter (RSFCL) applications. However, the high current density they can carry and their low thermal diffusivity expose them to the risk of thermal instability. In order to find the best compromise between stability and cost, it is important to study the heat transfer between HTS-CCs and the liquid nitrogen ($LN_2$) bath. This paper presents an experimental method to monitor in real-time the temperature of a quenched HTS-CC during a current pulse. The current and the associated voltage are measured, giving a precise knowledge of the amount of energy dissipated in the tape. These values are compared with an adiabatic numerical thermal model which takes into account heat capacity temperature dependence of the stabilizer and substrate. The result is a precise estimation of the heat transfer to the liquid nitrogen bath at each time step. Measurements were taken on a bare tape and have been repeated using increasing $Kapton^{(R)}$ insulation layers. The different heat exchange regimes can be clearly identified. This experimental method enables us to characterize the recooling process after a quench. Finally, suggestions are done to reduce the temperature increase of the tape, at a rated current and given limitation time, using different thermal insulation thicknesses.

• KIEAE Journal
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• 제8권5호
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• pp.11-16
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• 2008

This research has established CFD model on pit's cool-tube system through heat and air movement simulations, of which data was based on experimental and verification. This research work verified the effectiveness of the cool-tube system by analysing temperature, humidity and air current of the actually installed case. Also, we analysed heat transfer through air current simulation and the results are as followings. Firstly, we experiment on temperature, humidity and speed of air currents of the cool tube system with pit space during the month of May (spring). The average exterior temperature was $16.1^{\circ}C$, and $18.2^{\circ}C$ for the pit, $24.7^{\circ}C$ for the compressor room. Secondly, based on measured data of real case, we have analysed heat transfer through air current simulation and verified our proposed model. The actual measurement of average temperature of exhaust air of the pit's area is $19.7^{\circ}C$ with tolerance of $-0.33^{\circ}C{\sim}-0.6^{\circ}C$ compared to above simulations. Thirdly, having verified air current simulation model with formation of 260,000 and 1,000,000 cells, we could get reasonable near values with 260,000 cells. Lastly, the next step of research would be focused on proposing the best possible pit's cool-tube system after analysis of heat transfer of the air current simulation based on verified CFD model.

• Journal of Welding and Joining
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• 제14권1호
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• pp.57-67
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• 1996

With an expansion in automation of welding processes, emphasis has been shifted from other welding processes to the GMA welding. However, there is a problem with this process that the spatter occurs very frequently. In GMA welding, there are several types in the way of metal transfer from the electrode wire to the weld pool, which have a close relatonship with the spatter genetration. This study was concerned with the spatter occurring in the short-circuiting transfer. In welding with short-circuiting, the electromagnetic force formed by the welding current facilitatics the rupture of the metal bridge between the wire and workpiece and ensures the normal process of the welding process. However, the spatter can be genetrated from the droplet because of the upward magnetic force, when the droplet contacts with the weld pool. The passage of current through the bridge results in the accumulation of the thermal energy, which causes the bridge to explode in the final stage of short-circuiting, thus forming the spatter. Based on the above phenomena in conjunction with other experimental results published, the physical phenomenon related with the occurrence of spatter was modeled and the current waveform was investigated to reduce the spatter. Finally, the fuzzy rule based method was proposed to predict the time of short-circuiting and arcing in the metal transfer.

• Journal of Power Electronics
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• 제18권4호
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• pp.1190-1200
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• 2018

A current sourced bi-directional wireless power transfer (WPT) system is proposed to solve the problems that exist in the bi-directional WPT for vehicle-to-grid (V2G) systems. These problems include the fact that these systems are not safe enough, the output power is limited and the control methods are complicated. Firstly, the proposed system adopts two different compensation and control methods on both the primary and secondary sides. Secondly, based on an AC impedance analysis, the working principle is analyzed and the parameter configuration method with frequency stability is given. In order to output a constant voltage, a bi-directional DC/DC circuit and a controllable rectifier bridge are adopted, which are based on the "constant primary current, constant secondary voltage" control strategy. Finally, the effectiveness and feasibility of the proposed methods are verified by experimental results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.223-228
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• 1999

The state of the current design practice in designing the so-called hybrid structures with the upper shear-wall and lower frame systems are reviewed through the investigation of the 43 design examples. In particular, the trend in the design of the transfer system between upper wall and lower frame systems are analyzed with respect to the depth, the length and the number of spans of transfer deep girders and the number of upper stories. Finally the most critical portions in this conventional transfer system, which should be studied in depth in the future, are pointed out to improve the current design and analysis practice.