• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.2
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• pp.132-139
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• 2001

We considered the uniformity of fabricated micromirror arrays by characterizing the fabrication process and calculating the appropriate driving voltages of micromirrors used as virtual photomask in maskless photolithography. The uniformity of the micromirror array in terms of driving voltage and optical characteristics is adversely affected by factors, such as the air gap between the bottom electrode and the mirror plate, the spring shape and the deformation of the mirror plate or torsion spring. The thickness deviation of the photoresist sacrificial layer, the misalignment between mirror plate and bottom electrode, the aluminum deposition condition used to produce the spring and the mirror plate, and initial mirror deflection were identified as key factors. Their importance lies in the fact that they are related to air gap deviations under the mirror plate, asymmetric driving voltages in left and right mirror directions, and the deformation of the Al sring or mirror plate after removal of the sacrificial layer. The plasma ashing conditions used for removing the sacrificial layer also contributed to the deformation of the mirror plate and spring. Driving voltages were calculated for the pixel operation of the micromirror array, and the non-uniform characteristics of fabricated micromirrors were taken into consideration to improve driving performance reliability.

• Journal of the Korean Society for Precision Engineering
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• v.2 no.2
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• pp.43-59
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• 1985

In relation to the machinability of drilling operation, experiments were made to investigate the effect of cutting condition on static as well as dynamic cutting resistances in cutting plane carbon steel (SM 45 C) with H.S.S. twist drills. The results were as follows. 1) The static cutting resistances on carbon steel can practically be calculated by the following equations which were derived from experimental result. The deviation from the experimental values was less than 8% and 13% for cutting torque and thrust respectively. For cutting torque M: M=0.019 $H_B\;{f^{0.68}d^{1.68}$ For thrust T: T=0.400406 $r^{0.6}d^{0.68}$ + 0.1835 $H_BC^2$(where $H_B$: Brinnel hardness) 2) The static components of cutting resistance are increased exponentially with increasing drill diameter and feed rate. On the effect of drill diameter, the dynamic components of torque are decreased with increasing dirll diameter because of rigidity, the dynamic components of thrust being not effected with the changes. 3) As feed rates increase, the dynamic components of torque rather decrease although its changes on thrust components are unstable. 4) The static components of cutting resistance and dynamic component of torque are slightly decreased in accordance with the increase of spindle speed although its dynamic thrust components are not effected by the spindle speed.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2152_2153
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• 2009

In this study, the dynamic characteristic of a contact wire and pantograph suppling electrical power to high-speed trains are investigated from an electrical response point of view. To analysis power line disturbance by induced contact loss phenomenon for high speed operation, a hardware Simulator which considered contact loss between contact wire and the pantograph as well as contact wire deviation is developed. It is confirmed that a contact wire and pantograph model are necessary for studying the dynamic behavior of the pantograph system. One of the most important needs accompanied by increasing the speed of high-speed train is reduced that an arc phenomenon by loss of contact brings out EMI. In case of a high-speed train using electrical power, as comparison with diesel rolling stock, PLD(Power Line Disturbance) such as harmonic, transient voltage and current, EMI, dummy signal injection etc usually occurs. Throughout experiment, it is verified that an arc phenomenon is brought out for simulator operation and consequently conducted noise is flowed in electric circuit by power line disturbance.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.427-431
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• 2009

In this study, the dynamic characteristic of a contact wire and pantograph suppling electrical power to high-speed trains are investigated from an electrical response point of view. To analysis power line disturbance by induced contact loss phenomenon for high speed operation, a hardware Simulator which considered contact loss between contact wire and the pantograph as well as contact wire deviation is developed. It is confirmed that a contact wire and pantograph model are necessary for studying the dynamic behavior of the pantograph system. One of the most important needs accompanied by increasing the speed of high-speed train is reduced that an arc phenomenon by loss of contact brings out EMI. In case of a high-speed train using electrical power, as comparison with diesel rolling stock, PLD(Power Line Disturbance) such as harmonic, transient voltage and current, EMI(Electromagnetic Interference), dummy signal injection etc usually occurs. Throughout experiment, it is verified that an arc phenomenon is brought out for simulator operation and consequently conducted noise is flowed in electric circuit by power line disturbance.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.231-237
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• 2005

Interruption of good fluidization in a fluidized bed ash cooler(FBAC) for discharging bed materials such as sand or coal ash particles from the CFB combustor is frequently happened because of agglomeration of the particles in the bed. This unstable operation may, in the worst case, result in an unscheduled boiler shut down. In this study, we examined the operation problems of the FBAC of Tonghae CFB boiler and studied and introduced the simple detection and solution techniques with analyzing the mixing property and the occurrence of defluidization in a simulated fluidized bed ash cooler system (0.5m-H x 0.5m-W x 1.0m-L). The bridge of the large particles at the bed surface could be observed, and this caused to form the defluidization area at the entrance of the FBAC. The defluidization was affected not only by airflow rates but also by the particles discharging rates as well as particle size distribution in the FBAC. The local defluidization could be detected by analysis of the accumulated standard deviation error at a given period of time. Also, the regulation of the overall or local airflow rate made clearing up the local defluidization possible.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.1
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• pp.51-57
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• 1996

Although the system for establishing grinding operation standards mainly depends on the simulation method, it is desirable to obtain highly reliable grinding data and to develop experimental technology, And, it also needs to modify the simulation models if the simulation results do not coincide with special situation due to the difference of grinding machine, wheels and workpiece materials. If simple tests are carried out to evaluate these specificity, the reliability and utility of the system can be raised higher. Therefore, it is required for evaluating wheel ability and confirming the validity of the experimental methods as well as the possibility of exchanging the experimental data between Korea and Japan to preform several kinds of grinding experiments. In this paper, experiments of cylindrical plunge grinding were conducted using the wheels of the same specification made by three typical grinding wheel manufacturers both in Korea and Japan, respectively. The grinding power consumption grinding force, the ground surface roughness, and wheel wear were measured under the same dressing the grinding conditions. The average value and standard deviation of the experiment results were calculated to compared the grinding performance of the wheels made in both countries. The experiment results show that the grinding wheel performance of Korea's is nearly equal to that of Japan's for general purpose of grinding operation. In conclusion, it is possible to exchange the experimental data between Korea and japan.

• Journal of Chest Surgery
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• v.6 no.1
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• pp.63-68
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• 1973

Two patients operated upon for tricuspid atresia by Glenn operation are presented. They were five years old and four years old females who were cyanotic shortly after birth, and remained cyanotic. On physical examination, cyanosis on digits and lips, clubbing of fingers, thrill and grade III systolic murmur on 4th I.C.S. along left sternal border were noted. In the first case, chest roentgenograms showed normal pulmonary markings, and the electrocardiogram was interpreted as showing left ventricular hypertrophy with left axis deviation and peaked P-wave in lead IL Right heart catheterization showed high pressure in right atrium and the catheter tip was easily inserted into the left atrium through septal defect. In the second case, chest roentgenograms showed cardiomegaly with sparse pulmonary vascular markings and narrowed vascular pedicle, and the electrocardiogram showed left ventricular hypertrophy with some element of right atrial hypertrophy. Angiocardiogram showed changes characteristic of tricuspid atresia, including "right ventricular window" The findings of right heart catheterization were similar to those of first case. On the basis of these observations, they were diagnosed as tricuspid atresia, and Glenn operation was performed. Normal position of great vessels combined with ventricular septal defect and pulmonary stenosis were noted on the first case, and on second case, transposition of great vessels was additional finding. Postoperative course was uneventful and favorable outcome was obtained.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.53-63
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• 2013

To guide the decision making of the expert engineer specialized in power system operation and control; the practical OPF solution should take in consideration the critical situation due to severe loading conditions and fault in power system. Differential Evolution (DE) is one of the best Evolutionary Algorithms (EA) to solve real valued optimization problems. This paper presents simple Differential Evolution (DE) Optimization algorithm to solving multi objective optimal power flow (OPF) in the power system with shunt FACTS devices considering voltage deviation, power losses, and power flow branch. The proposed approach is examined and tested on the standard IEEE-30Bus power system test with different objective functions at critical situations. In addition, the non smooth cost function due to the effect of valve point has been considered within the second practical network test (13 generating units). The simulation results are compared with those by the other recent techniques. From the different case studies, it is observed that the results demonstrate the potential of the proposed approach and show clearly its effectiveness to solve practical OPF under contingent operation states.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.11
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• pp.705-710
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• 2011

Fault detection has to be proceeded by steady state filtering to get rid of transient effect associated with thermal capacity. Coefficient of variance (COV), ratio of standard deviation devided by moving average, was employed as steady-state filter. Engine speed and refrigerant pressures were selected as parameters representing system dynamics. The filtered values were registered as members of steady-state DB. They were found to show good functional relationship with ambient temperature. The relationship was fitted with a second order polynomial and the distribution bounds of the data around the fitted curve were expressed by visual inspection because of varying average and random data interval. Fault data were compared with the steady-state data obtained during normal operation. The fault data were easily isolated from the fault-free one. To make such isolation reliable, tests to construct good DB should be designed in a systematic way.

• Korean Journal of Community Nutrition
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• v.7 no.4
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• pp.559-570
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• 2002

This research was to investigate the operation of contracted food service management and menu preferences of middle school students in Seoul. Questionnaires were distributed between Dec. 1 and 20,2000 in 10 middle schools. Statistical data analyses were completed using the SAS package, including the mean, standard deviation and frequency analysis. The results can be summarized as follows: The average number of meals per middle school was 1,000 and only lunch was served in each school. In terms of facilities and equipment, low rates of the possession of cooking equipment and food carts were the major hindrance to work and production efficiency. The students' main demands were taste, sanitation, variety of food, the introduction of brand foods, the price of foods, and the speed of reaction to their dissatisfaction. Most of the schools provided rice for lunch, while the students preferred noodles, mandu and bread. beef-rib soup was preferred to broth. for side dishes, fish, roasted meat and fried foods were highly favored, along with processed foods, with low preferences for vegetables. The middle school students favored fruits. Lastly, they requested that the quality of school meals be improved through the development and supply of various desserts.