• International Journal of Advanced Culture Technology
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• v.10 no.4
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• pp.555-560
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• 2022

In this study, the insertion loss and phase delay according to the multi-layer structure radome parameters were analyzed using the boundary value solution approach, and the multi-layer structure and hexa mesh structures with low-loss electrical characteristics for the Ku-band transmission/reception frequency of 10.7 ~ 14.5 GHz were designed and manufactured. A hexa mesh was applied to minimize radio wave transmission and scattering, which lowered the transmittance refractive index according to the radio incident angle and minimized dielectric loss through high-density foam. Similar to the simulation result, the transmission loss obtained the gain in a specific receiving frequency band, and in the transmission frequency band, an excellent low loss characteristic was obtained with an insertion loss of 0.8dB or less. The results of this study can be used in radio transmission radomes of low-weight, low-cost end-system protection devices.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.202-212
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• 2008

A three-dimensional computation was conducted to understand effects of the low Reynolds number on the loss characteristics in a transonic axial compressor, Rotor67. As a gas turbine becomes smaller in size and it is operated at high altitude, the operating condition frequently lies at low Reynolds number. It is generally known that wall boundary layers are thickened and a large separation occurs on the blade surface in axial turbomachinery as the Reynolds number decreases. In this study, it was found that the large viscosity did not affect on the bow shock at the leading edge but significantly did on the location and the intensity of the passage shock. The passage shock moved upstream towards leading edge and its intensity decreased at the low Reynolds number. This change had large effects on the performance as well as the internal flows such as the pressure distribution on the blade surface, tip leakage flow and separation. The total pressure rise and the adiabatic efficiency decreased about 3% individually at the same normalized mass flow rate at the low Reynolds number. In order to analyze this performance drop caused by the low Reynolds number, the total pressure loss was scrutinized through major loss categories such as profile loss, tip leakage loss, endwall loss and shock loss.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.2
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• pp.83-91
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• 2008

A three-dimensional computation was conducted to understand effects of the low Reynolds number on the performance in a low-speed axial compressor at the design condition. The low Reynolds number can originates from the change of the air density because it decreases along the altitude in the troposphere. The performance of the axial compressor such as the static pressure rise was diminished by the separation on the suction surface with full span and the boundary layer on the hub, which were caused by the low Reynolds number. The total pressure loss at the low Reynolds number was found to be greater than that at the reference Reynolds number at the region from the hub to 85% span. Total pressure loss was scrutinized through three major loss categories in a subsonic axial compressor such as the profile loss, the tip leakage loss and the endwall loss using Denton#s loss model, and the effects of the low Reynolds number on the performance were analyzed in detail.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.138-141
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• 2007

A three-dimensional computation was conducted to understand effects of the low Reynolds number on the performance in a low-speed axial compressor at the design condition. The low Reynolds number can originates from the change of the air density became it decreases along the altitude in the troposphere. The performance of the axial compressor such as the static pressure rise wag diminished by the separation on the suction surface and the boundary layer on the hub, which were caused by the low Reynolds number. The total pressure loss at the low Reynolds number was found to be greater than that at the reference Reynolds number at the region from the hub to 90% span. Total pressure loss was scrutinized through three major loss categories in a subsonic axial compressor such as profile loss, tip leakage loss and endwall loss using Denton's loss model, and effects of the low Reynolds number on the performance were analyzed in detail.

• Journal of Industrial Technology
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• v.28 no.A
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• pp.177-184
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• 2008

A low loss frequency doubler operated on low power for the RFID harmonic tags is presented. Using the excellent nonlinear characteristics of the Schottky barrier diode and proper matching networks between the diode and ports, the low conversion loss of the harmonic tag is accomplished. This doubler could be used to increase the detectable distance of the conventional RFID system adopted harmonic tags.

• Tribology and Lubricants
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• v.21 no.6
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• pp.249-255
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• 2005

In this paper, the friction characteristic of engine bearings has been analyzed in terms of a friction loss power, a minimum film thickness and an oil film pressure. This analysis has been focused on the fuel economy improvement with a low viscosity engine oil such as SAE 0W-40, which is used for a friction loss reduction and increased for a Diesel fuel economy. The friction loss power, the minimum oil film thickness and oil film pressure distribution for plain bearings of a Diesel engine are analyzed using an AVL's EXCITE program with a conventional engine oils of SAE 5W-40 and 10W-40, and a low viscosity engine oil of SAE 0W-40. The computed results indicate that a viscosity of engine oils is closely related to the friction loss power and the decreased minimum film thickness in which is a key parameter of a load carrying capacity of an oil film pressure distribution. When the low viscosity engine oil is supplied to engine bearings, it does not affect to the formation of a minimum oil film thickness. But the friction loss power has been significantly affected by low viscosity engine oil at a low operating temperature of 0. Based on the FEM computed results, the low viscosity engine oil at a low temperature range will be an important factor for an improvement of the fuel economy improvement.

• Journal of the Korean Home Economics Association
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• v.17 no.3
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• pp.53-59
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• 1979

Vitamin contents of three grades of Korean laver high, medium and low were measured. They were cooked by different methods to examine changes in their vitamin content. Results of this experiment are as follows ; 1. Vitamin contained in loogr of laver amount to 13,200 I.U, for high grade, 16,100 for mediium grade, and 16,400 for low grade . The low -grade laver, which is interwoven with green laver, showed the highest vitamin content. 2. When laver was broiled sheet by sheet, its vitamin loss rate was 11% for high grade, 19% for medium grade, and 20% for low grade. Thus , the one with a higher vitamin content showed a higher vitamin loss rate. When two sheets of laver, which were put upon each other, were broiled, their vitamin loss rates were 2.3% for high grade, 1.73 % for medium grade, and 2.64% for low grade. Thus broiling laver at the unitof two to three sheets together is a way of decreasing the vitamin loss rate. 3. When laver was broiled with salt applied on its surface , its vitamin loss rate was 8.3% for high grade, 13% for medium grade, and 10.9% for low grade. When laver was broied at the unit of two sheets together after salt and sesame oil were added, its vitamin loss rate was 2.2% for high grade, 5.2% for medium grade, and 8.2% for low grade . The one with a higher vitamin content showed a higher vitamin loss rate. 4. When laver was mixed seasoned soysauce, its vitamin loss rate increased in process of time. In 48 hours after laver was mixed with seasoned soysauce , its vitamin loss rate read 24.2%, 27.1% and 35% respectively, for the three grades of laver. Thus the laver mixed with seasoned soysauce has to be used right after so cooked so as to obtained the highest possible vitamin content.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.255-258
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• 1996

A new low conduction loss, low cost zero-voltage-transition power factor correction circuit(PFC) is presented. Conventional PFC which consists of a bridge diode and a boost converter(one switch) always has three semiconductor conduction drops. Two switch type PFCs reduces conduction loss by reducing one conduction drop but the cost is increased because of increased number of active switches. The proposed PFC reduces conduction loss with one switch, which allows low cost. Conduction loss improvement is a little bit less than that of two switch type, but very close up. Operation and features are comparatively illustrated and verified by simulation and experimental results of 1 kW laboratory prototype.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2006.10a
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• pp.255-267
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• 2006

LTCC Technology is very suitable for 60 GHz application $\blacksquare$ LTCC substrate shows low loss at 60 GHz. - low insertion and return losses $\blacksquare$ Microstrip or CBCPW line is sultable for transmission lines at 60 GHz. - low loss (0.1dB/mm) $\blacksquare$ Single ribbbon bonding is adequate for interconnection - simple - low loss (0.1dB/bonding) $\blacksquare$ Characteristics of MMIC module - Gain difference (${\Delta}S21$) : 0.4 dB

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.3
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• pp.164-168
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• 2016

A low insertion-loss, high-isolation switch based on single pole double throw (SPDT) for a 2.4GHz Bluetooth low-energy transceiver is presented in this paper. In order to increase isolation, the body floating technique is implemented. Based on characteristics whereby the ratio of the sizes of the shunt and the series transistors significantly affect the performance of the switches, the device sizes are optimized. A simple matching network is also designed to enhance the insertion loss. Thus, the SPDT switch has high isolation and low insertion loss without increasing the complexity of the circuit. The proposed SPDT is designed and simulated in a complementary metal-oxide semiconductor 65nm process. The switch has a $530{\mu}m{\times}270{\mu}m$ area and achieves 0.9dB, 1.78dB insertion loss and 40dB, 41dB isolation of transmission, reception modes, respectively.