• Solar Energy
• /
• v.20 no.1
• /
• pp.97-108
• /
• 2000

The purpose of this study is to minimize the heat transfer surface area and cold fluid exit temperature of heat exchanger which applied to the refrigeration and air-conditioning system by utilizing the thermoelectric principle. Both uniform and non-uniform current distribution methods which applied to the analysis of the TE elements that incorporates heat exchanger were investigated. The non-uniform current distribution method had the better coefficient of performance and had the lower cold fluid exit temperature of the TE cooling system than the uniform current distribution method. It was found that if a TE cooling system incorporates a heat exchanger, a non-uniform current distribution should guarantee to the lowest cold fluid exit temperature. Also, the hybrid method (combination of the uniform and non-uniform current distribution method) is investigated to achieve the best results by combining the uniform and non-uniform current distributions. The results show that it can lower the cold fluid exit temperature and reduce the heat transfer surface area for the parallel flow arrangement if we apply the constant current in some entry region and the non-uniform increasing current in the direction of the cold fluid flow afterwards.

• Progress in Superconductivity and Cryogenics
• /
• v.19 no.3
• /
• pp.44-48
• /
• 2017

Current lead is a device that connects the power supply and superconducting magnets. High temperature superconductor (HTS) has lower thermal conductivity and higher current density than normal metal. For these reasons, the heat load can be reduced by replacing the normal metal of the current lead with the HTS. Conventional HTS current lead has same cross-sectional area in the axial direction. However, this is over-designed at the cold-end (4.2 K) in terms of current. The heat load can be reduced by reducing this part because the heat load is proportional to the cross-sectional area. Therefore, in this paper, heat load was calculated from the heat diffusion equation of HTS current leads with uniform and non-uniform cross-sectional areas. The cross-sectional area of the warm-end (65K) is designed considering burnout time when cooling system failure occurs. In cold-end, Joule heat and heat load due to current conduction occurs at the same time, so the cross-sectional area where the sum of the two heat is minimum is obtained. As a result of simulation, current leads for KSTAR TF coils with uniform and non-uniform cross-sectional areas were designed, and it was confirmed that the non-uniform cross-sectional areas could further reduce the heat load.

• Fashion & Textile Research Journal
• /
• v.10 no.2
• /
• pp.228-235
• /
• 2008

The purpose of this study is to examine the functionality with material-improved working uniform(protocol, P) and current working uniform(control, C). Movement functionality evaluation of material-improved working uniform was carried out through sensory evaluation of working uniform. And Oxygen uptake was explored to different working uniform(P, C) in relation to a physiological functionality measurement. The results have been shown as follows: It was found that the workers feel uncomfortable with the parts of the wrist, the back width, the shoulder seam and the side in the current working uniform when they move their arms up and down, but the inconvenience has been reduced in the material-improved working uniform. And It was found that the workers feel uncomfortable with the parts of the back width, the wrist and the side seam of the jacket, and the waist, the hips and the thigh of the trousers in the current working uniform when they move their waist, but the inconvenience has been reduced in the material-improved working uniform. In the current working uniform, it was also found that they feel uncomfortable with the parts of the horse riding position in which they stand straight in their slightly bended knees, with the parts of the hips, the side seam, the thigh and the knees when they crouch down, and with the parts of the hips and the thigh when they put one of their legs onto a higher place. However, the inconvenience was reduced in the material-improved working uniform. Oxygen uptake, which was measured to assess physiological dressing functionality, was found to be higher when people work in an uncomfortable uniform than when they work in a uniform of better functionality by an increase in metabolic rate, which can be a cause of workers' inefficiency of fatigue.

• Progress in Superconductivity
• /
• v.5 no.2
• /
• pp.144-148
• /
• 2004

Uniform current distribution among conductor layers in HTS cables using IPTs (inter-phase transformers) was investigated. Conventional methods for current distribution, in which resistors are inserted to conductor layers, causes additional loss. In contrast, IPTs, which use magnetic coupling, make it possible that the current in parallel circuits is distributed uniformly with any load, and minimize the loss. In this study, IPTs were designed and fabricated for examination of uniform current distribution in the conductor layers of HTS cables. The ITP was designed through calculation of its impedance that can cancel the inductance of the conduction layers. The experimental setup consisted of four IPTs and four inductors that simulate the conductor layer inductance. Each layer was designed to feed 10 A. We examined the behavior of current distribution with IPTs for various layer inductances.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.27 no.5
• /
• pp.545-553
• /
• 2003

A good school uniform leads students to good behavior and have them enjoy desirable school life. Therefore a better fabric for girls' high school uniform suggested through two series of studies; first, examined the various aspects of current uniforms. Second, made a new fabric for uniform considering elasticity for activity and comfortableness, and compared its characteristics with those of the current uniforms. The results are as follows; 1 Most of students wanted uniforms considering elasticity for activity and wearing. 2. The measurement of the elasticities of the uniform materials showed that the material which was made using the elastic material was more elastic than the currently used material by 42.12% in summer material and 20.05% in winter one. 3. The analysis using the combination of the values of mechanical properties showed that the elastic material was better in the wearing, tactile senses, and drape properties than the current material, even though it was a little worse in shape-stability. 4. To compare the thermal insulation, clo values were measured. For winter uniform, the elastic material was better than the current one in keeping warm. However, This study did not find any big difference between summer uniform materials.

• Journal of the Korean Society of Costume
• /
• v.66 no.5
• /
• pp.66-81
• /
• 2016

This study is designed to understand the problems of existing Korean male soldiers' winter uniform tops by researching its current state, and contribute to developing uniforms with improved size and motion appropriateness. Military bases were visited to research satisfaction of size and motion appropriateness of the current winter uniform tops. 193 soldiers were surveyed and interviewed, and the shape and fit of the standard sizes of the inner and outer layers of the current winter uniform were analyzed. Findings of this study are as follows. 1) Compared to the new combat uniforms that soldiers were wearing in their appropriate size (of the 44 sizes), there were many cases where the soldiers were not wearing winter uniform inner (of the 8 sizes) or outer (of the 18 sizes) layers in the correct size for their body. 2) A total of 37 combat uniform sizes appropriate for the body shapes were expected to be newly applied, and inside and outside layers of winter tops would be presented as sets of 14 different sizes in step with the new combat uniform sizes, instead of the existing 8 inside layer sizes and 18 outside layer sizes. 3) The inner and outer layer of the existing winter uniform tops had several problems with the shape and fit. First, the inner layer was shorter than the combat uniform. Its shoulder width was wide, but the sleeve length was short creating lack of coverage, and the angle connecting the sleeve and bodice was very small creating a high sleeve cap curve and narrow sleeve width that make motions difficult and cause discomfort. As for the outer layer, the hem moved up when soldiers bent over or adjusted the waist string so the top could not sufficiently cover, the shoulder width was wide and the sleeve length was short, requiring improvements.

• Progress in Superconductivity and Cryogenics
• /
• v.13 no.4
• /
• pp.26-29
• /
• 2011

In a High temperature superconducting (HTS) tape with high aspect ratio, the magnetic field applied to the HTS tape can be different considerably within the HTS tape. The current distribution in the HTS tape is generally non-uniform because the current distribution is strongly dependent on the applied magnetic field. Non-uniform current distribution in a HTS tape has not been properly considered when the critical current has been estimated. This paper shows the calculation of critical current of a HTS magnet consisting of pancake windings. Non-uniform distribution of current in the HTS tape is considered during the calculation of the critical current. Results of calculation show the current concentrated in the middle part of the HTS tape which is used for one pancake winding.

• Journal of Power Electronics
• /
• v.18 no.2
• /
• pp.640-650
• /
• 2018

A TRIAC dimmable LED driver with a wide tuning range and a two-stage uniform dimming scheme is proposed in this paper. To solve the restricted dimming range problem caused by the limited conduction ratio of TRIAC dimmers, a conduction ratio compensation technique is introduced, which can increase the output current up to the rated output current when the TRIAC dimmer turns to the maximum conduction ratio. For further optimization, a two-stage uniform dimming diagram with a rapid dimming curve and a slow dimming curve is designed to make the LED driver regulated visually uniform in the whole adjustable range of the TRIAC dimmer. The proposed control chip is fabricated in a TSMC $0.35{\mu}m$ 5V/650V CMOS/LDMOS process, and verified on a 21V/500mA circuit prototype. The test results show that, in the 90V/60Hz~132V/60Hz ac input range, the voltage linear regulation is 2.6%, the power factor is 99.5% and the efficiency is 83%. Moreover, in the dimming mode, the dimming rate is less than 1% when the maximum dimming current is 516mA and the minimum dimming current is only about 5mA.

• Journal of the Korean Society of Costume
• /
• v.57 no.3 s.112
• /
• pp.53-62
• /
• 2007

The purpose of this study was to investigate mechanical and comfort performances of the material for the improved working uniform for a volunteer fire brigade member, to get basic data for its evaluation and to help its material and design development. The results were as follows; The material of the newly developed working uniform was thinner and lighter than the material of the current used working uniform. It had better breathability, air permeability and heat transmission rate than the current one. It also had superior anti-flammability In all mechanical properties(tensile, bending, shearing, compression and surface properties), it showed better performances than the current one. It elongated and bended easier and more in both warp and weft directions. The elastic recovery and shape stability after elongation were also higher. The recovery and resistance to shearing and the resiliency and recovery after compression were also better than the current one. It was more flexible, softer and smoother in primary hand value, and was more suitable for the material for winter suit which needs softness and fullness in total hand value. The material of the improved working uniform showed lower thermal insulation value and higher evaporative resistance value compared to the material of the currently used working uniform from the sweating thermal manikin test. It was shown that the physical performances and the hand value of the textile material used in the newly developed working uniform for a volunteer fiber brigade member was improved compared to the one used in the currently used working uniform.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.53 no.7
• /
• pp.424-429
• /
• 2004

The 4-probe method with a voltage tap on terminals has been used for the measurement of the critical current of multi-strand high-T$_{c}$ superconducting(HTS) cables. And the critical current of cables is obtained as the measured total current divided by the number of conductor when the terminal voltage exceeds the predetermined criterion of critical current. However, because of the non-uniform current distribution due to the different critical current, shapes, and other characteristics of each conductor, this is not applicable method to the multi-strand HTS cable. To determine the critical current of multi-strand HTS cable, the critical current of each conductor must be measured with different method. h this paper, the current distribution and the critical current of each conductors in multi-strand cable were measured with specially made Pick-up coils and voltage taps. It is presented that the real critical current of multi-strand is smaller than sum of each conductors. The main cause of non-uniform current distribution is the difference between the resistances appeared in each HTS wires.s.