• Journal of IKEEE
• /
• v.1 no.1 s.1
• /
• pp.164-175
• /
• 1997

In this paper, the CE-OQPSK that has constant envelope was designed for applying PSK to the nonlinear amplifier so as to improve power efficiency. For this realization. ROM and D/A converter that have relative low power consumption were used. As a result of comparing the PSD (Power spectrum density) of CE-OQPSK with that of conventional OQPSK through simulation for estimating the performance. In case of correlation factor ${\alpha}$ = 0.707. the improvement of bandwidth efficiency of 5% and 20% is achieved in the main lobe and the sidelobe, respectively. And, in case additional bandwidth-limiting-filter is added, it can be shown that the PSD of CE-OQPSK meet the FCC wireless LAN spectrum specification.

• Journal of Biosystems Engineering
• /
• v.22 no.4
• /
• pp.391-400
• /
• 1997

Using the soil bin systems, this study was carried out to investigate the tilling load characteristic for the three kinds of Japanese rotary blade and the possibility of common use for power tiller and tractor rotary. The results obtained from the study are summarized as follows : 1. At all tested soils. the average and maximum tilling torque of all tested blades increased as the tillage pitch did. 2. The torque requirements of newly designed and produced blade was less than that of blade which has been used on power tiller and tractor rotary. 3. The maximum tilling torque of new ONE were decreased 7%, 10~11％, 27% in comparing with another blades at clay loam, loam and sandy loam, respectively. 4. According to observation of the extent of soil adhesion on blade and the contact aspect of blade, new ONE is the most excellent of all tested rotary blades and till smoothly not to compress the untilled soil. From the results of this study. the newly developed blade(new ONE) proved to be good tilling load performance and had a conclusion that it is possible to use it on power tiller and tractor rotary in common.

• Convergence Security Journal
• /
• v.17 no.2
• /
• pp.137-144
• /
• 2017

Mental power, which is the intangible power of soldiers in our security situation, is very important recently. As for the history of war in East and West Korea, intangible combat power is regarded as a key factor that determines the rise and fall of the nation and the victory and defeat of the war. Recently, we are trying to improve the mental education in the military, but we still regard it as formal education, boring education, and time - consuming education. And continues to present the problem. The purpose of this study is to examine the problems of current mental education and to find out the direction of development of cognitive centered mental education. I would like to suggest a direction for fostering a strong group that is suitable for the diversification era.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.51 no.10
• /
• pp.581-586
• /
• 2002

To improve the current waveform of diode rectifiers, we propose a new operating principle for the voltage-doubler diode rectifiers. In the conventional voltage-doubler rectifier circuit, relatively large capacitors are used to boost the output voltage, while the proposed circuit uses smaller ones and a small reactor not to boost the output voltage but improve the input current waveform. A circuit design method is shown by experimentation and confirmed simulation. The experimental results of the proposed diode rectifier satisfies the harmonic guide lines. A high input power factor of 97(%) and an efficiency of 98[%] are also obtained. The new rectifier with no controlled switches meet the harmonic guide lines, resulting in a simple, reliable and low-cost at-to dc converters in comparison with the boost-type current-improving circuits. This paper proposes a nonlinear impedance circuit composed by diodes and inductors or capacitors. This circuit needs no control circuits and switches, and the impedance value is changed by the polarity of current or voltage. And this paper presents one of these applications to improve the input current of capacitor input diode rectifiers. The rectifier using the nonlinear impedance circuit is constructed with four diodes and four capacitors in addition to the conventional rectifiers, that is, it has eight diodes and five capacitors, including a DC link capacitor. It makes harmonic components of the input current reduction and the power factor improvement. Half pulse-width modulated (HPWM) inverter was explained compared with conventional pulse width modulated(PWM) inverter. Proposed HPWM inverter eliminated dead-time by lowering switching loss and holding over-shooting.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.6
• /
• pp.805-810
• /
• 2002

Development of a small gas-turbine combustor for 100㎾ class APU(Auxiliary Power Unit) has been performed. This combustor is a reverse-annular type and has a tangential swiller in the liner head to improve the fuel/air mixing and flame stability. Three main and three pilot fuel injectors of the simplex pressure-swirl type are used. The performance target at the design condition includes a turbine inlet temperature of l170k, a combustion efficiency of 99%, a pattern factor of 30%, and an engine durability of 3000 hours. Under developing the combustor, we conducted the performance test of our first prototype(TS1) with some variants. As a result of the test, the performance targets of the combustor are satisfied except that the pattern factor is about 4% higher than the target value. Therefore, the second prototype(TS2) was redesigned and the performance test was conducted with the critical focus on the pattern factor and the exit mean temperature. We adopted TS2 four variants to check the improvement of the pattern factor. As a result, the pattern factors of several variants were satisfied with the performance target. Finally, the TS2A variant was chosen as a final combustor fur our APU model.

• Journal of KIISE
• /
• v.43 no.11
• /
• pp.1298-1306
• /
• 2016

Backlight has a major factor in power consumption of TFT-LCDs which are most popular in portable devices. There have been a lot of attempts to achieve power savings by backlight dimming. At the same time, the researches have shown image compensation due to decreased brightness of a displayed image. However, existing image compensation methods such as histogram equalization have some limits in completely satisfying the human visual system (HVS)-awareness. This paper proposes an enhanced dimming technique to obtain both power saving and HVS-awareness by combining pixel compensation and histogram specification for TFT-LCDs. This method executes a search algorithm and an automation algorithm employing simplified calculations for fast image processing. Experimental results showed that the proposed method achieved significant improvement in visual satisfaction per power saving over existing backlight dimming.

• The Journal of the Korea Contents Association
• /
• v.9 no.10
• /
• pp.427-435
• /
• 2009

The aim of this study was to examine the effect of a brisk walking intervention for 8weeks on isokinetic muscular function factor(strength, power, endurance). The following results were found from the current study: First, Isokinetic muscle function(strength, power, endurance) on $60^{\circ}/sec$ in extension and flexion was significant exercise group and interaction in left knee flexion and right knee extension(P<.00l). Secondly, Isokinetic muscle function(strength, power, endurance) on $120^{\circ}/sec$ in extension and flexion was significant exercise group and interaction in left knee flexion and right knee extension(P<.001). Thirdly, Isokinetic muscle function(strength, power, endurance) on $180^{\circ}/sec$ in extension and flexion was significant exercise group and interaction in left knee flexion and right knee extension(P<.001). Considering the above result of the study the brisk walking had more improvement knee flexor and extensor muscular power. Therefore the brisk walking in the study can be proposed as effective plan to prevention hurt from a sarcopenia and to raise quality in life.

• Transactions on Electrical and Electronic Materials
• /
• v.13 no.3
• /
• pp.116-120
• /
• 2012

In this paper, ZnO-Epoxy nanocomposites (NEP) were prepared and epoxy composites that contain 5 wt% micro ZnO (MEP) and deliberately not well dispersed nano ZnO (NDNEP) were also prepared for purpose of comparison. The effects of the particle size and dispersion of ZnO on dielectric properties of epoxy resin were chiefly studied. Test results showed that: at a loading of 5 wt%, the three epoxy composites seem to have no significant difference on resistivity compared to epoxy resin; Dielectric constants of all the epoxy composites are also basically the same but they are bigger compared to that of the pure epoxy resin (unfilled); Dielectric dissipation factors ($tan{\delta}$) of NDNEP is greater than that of NEP and MEP. NEP has the minimum dielectric loss factor, whereas dielectric loss factors of the three epoxy composites are larger than that of the pure epoxy resin. The decreasing order of electrical breakdown strength for the three epoxy composites and for the pure epoxy resin is as follows: NEP>MEP>NDNEP>EP. Finally, in order to explain the experimental results the aggregation interface phase was proposed. Furthermore, addition of well dispersed nano filler has proved to have a positive effect on the improvement of the dielectric properties of epoxy resin.

• Journal of radiological science and technology
• /
• v.37 no.3
• /
• pp.187-193
• /
• 2014

The purpose of this study was to analyze the effect on the selectivity on of high-voltage rectification device that measured the performance of the grid, and the contrast improvement ability (K factor) by measuring the scattered radiation content of the transmitted X-rays. The scattered radiation generated when the X-ray flux comes from the diagnostic X-ray generator that passes through an object. Targeting four different rectifications of X-ray generators, the mean value of the tube voltage and the tube current was measured in order to maximize the accuracy of the generating power dose within the same exposure condition. Using fluorescence meter, the content of the scattered rays that are transmitted through the acrylic was measured depending on the grid usage. When grid is not used, the content of the scattered rays was the lowest (34.158%) with the single-phase rectifier, was increased with the inverter rectifier (37.043%) and the three-phase 24-peak rectification method (37.447%). The difference of the scattered radiation content of each device was significant from the lowest 0.404% to the highest 3.289% while using 8:1 grid, the content of the scattered ray was the lowest with the single content of the scattered ray was the lowest with the single-phase rectifier (18.258%), was increased with the rectifier (25.502%) and the 24-peaks rectification (24.217%). Furthermore, there was difference up to content 7.244% to the lowest content 1.285% within three-phase 24-peaks rectification, inverter rectifications, and single-phase rectifier depending on the selectivity of the grid. Drawn from the statistical analysis, there was a similar relationship between the contrast improvement factor and the K factor. As a result, the grid selectivity and the contrast were increased within the single-phase rectifier rather than the constant voltage rectifier.

• Proceedings of the KIEE Conference
• /
• 2002.07b
• /
• pp.1094-1096
• /
• 2002

A new technique for improving the efficiency of single-phase high-frequency boost converter is proposed. This converter includes an additional low-frequency boost converter which is connected to the main high-frequency switching device in parallel. The additional converter is controlled at lower frequency. Most of the current flows in the low-frequency switch and so, high-frequency switching loss is greatly reduced accordingly. Both switching device are controlled by a simple method; each controller consists of a comparator, a frequency generator and an error amplifier. The converter works cooperatively in high efficiency and acts as if it were a conventional high-frequency boost converter with one switching device, The proposed method is verified by simulation and experiment. This paper describes the converter configuration and design, and discusses the steady-state performance concerning the switching loss reduction and efficiency improvement.