• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.310-312
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• 2006

Maglev using EMS becomes unstable by unexpected big air-gap disturbance. The main causes of the unexpected air-gap disturbance are step-wise rail joint and large distance between rail splices. For the stable operation of the Maglev, the conventional system uses the threshold method, which selects one gap sensor among two gap sensors installed on the magnet to read the gap between magnet and guide rail. But the threshold method with a wide bandwidth makes the discontinuous air-gap signal at the rail joints because of the offset in air gap sensors and/or the step-wise rail joins. Further more, in the case of the one with a narrow bend-width, it makes Maglev system unstable because of frequent alternation. In this paper, a new method using fuzzy rule to reduce air-gap disturbances proposed to improve the stability of Maglev system. It treats the air-gap signal from dual gap sensors effectively to make continuous signal without air gap disturbance. Simulation and experiment results proved that the proposed scheme was effective to reduce air-gap disturbance from dual gap sensors in rail joints.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.546-549
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• 2009

Dynamic model for supersonic engine is proposed to design control law. The model structure is constructed to capture the local characteristics of supersonic and subsonic flow by using conservation equations. To evaluate the stability of control law under the disturbances, the air turbulence model is incorporated with the engine model. The combined model shows analogous results compared to performance analysis model which is good coincidence with CFD results and disturbance effects.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.5
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• pp.58-65
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• 2009

A forest fire in the area of power line installations may be caused by flashover disturbances in power systems. In this study, experiments were conducted so as to investigate the reduction in dielectric strength caused by combustion flame, and flashover characteristics in the simulated condition of vertical-type model power lines were examined by making shorter and longer the horizontal distance(s) between combustion flame and high-voltage conductors under the application of 60[Hz] a.c. and d.c. high-voltages. As the results of the experimental investigation it is demonstrated that flame can reduce flashover voltages of the model air-gap in shorter range of the horizontal distance(s). Relative air density is considered in order to analyze the reduction causes of the flashover voltages, and it can be seen that the relative air density has a great influence on the flashover characteristics under the presence of combustion flame.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.2
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• pp.92-96
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• 2006

Large glass furnaces to produce glass for CRT are housed in huge chambers. It is costly to maintain such a chamber in constant temperature, humidity, and(air) pressure. In this study, first, we show that the process of such a huge furnace, which requires the steady maintenance of high temperature, is badly affected by the ambient temperature of surrounding air. Second, an alternative process which not only maintains the relatively constant temperature dispersion around the furnace, but is also economical will be proposed. We calculate the necessary volume of air inflow in the appendix.

• Journal of the Korean Society of Clothing and Textiles
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• v.9 no.3
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• pp.45-51
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• 1985

The purpose of this study is to research into the thermal condition and the weight of clothes suitable for the officers engagged in light works in an air-conditioned room in summer. The Major findings are as follows: 1. Thermal conditions of the working environment are $24.5^{\circ}C$ (Dry bulb temp.), $68\%$ (Relative humidity) and 2.6m/sec (Air Velocity). 2. Total clothing weights are 416.6 g/$m^2$ (male) and 340.9 g/$m^2$ (female). Underwear weights are 96.8g/$m^2$ (male) and 85.1g/$m^2$ (female). The latter turned out to be statistically significant in Sexual difference. 3. Means of the thermal sensation are 3.0 (comfortable; male) 2.7 ('Slightly cool' -'Comfortable'; female) and the relationship between clothing weights and thermal sensation proves to be significantly correlated in the case of female. 4. $66.7\%$ of the women and $37.1\%$ of the men feel sensation of coldness at the body's specific area and $79.5\%$ of the women and $54.3\%$ of the men reveals air-conditioning disturbance. 5. As the thermal sensation is close to 'cool-cold', sensation of coldness or air conditioning disturbance are showed up more frequently which is reversely related with weight of under-wear. It is also proved that air conditioning disturbances are influenced by sexual difference in addition to sensation of coldness and thermal sensation. 6. According to the result of experiment, we can have the idea that at condition $X_1$, the drop of limbs' skin temp. is remarkable. At condition $X_2$ skin temp. for distal limbs and mean skin temp. are raised and the falling degree is similar. At condition $X_3$, mean skin temp. and distal skin temp. are remarkably raised, and the falling degree decreases and the beats of pulse rate increase and diastoric blood pressure is lowered.

• The Korean Journal of Ecology
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• v.16 no.3
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• pp.317-327
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• 1993

Stands profiles, yearly changes in growth of annual rings, age and diameter structure, and spatial distribution pattern of individuals in the Pinus densiflora stands around the Yeocheon industrial complex were investigated. Growth of annual ring in Pinus densiflora, which survived when vegetation of this area was damaged by air pollutants, was suppressed for about 10 years since 1974 when factories in this area began to operate, but since then such suppressed growth tended to be recovered. It was supposed that the suppresed growth was originated from air pollution and that improvement of growth since the suppressed period was due to the release from competition with them by death of neighbouring trees and the resuction of the amount of air pollutants. Physiognomy of Pinus densiflora stands showed mosaic pattern composed of different patches. Spatial distribution pattern of individuals an stand profiles were similar to those of Pinus densiflora stands regenerated after natural and artificial disturbances. In an age distribution diagram, age of Pinus densiflora population ranged from 1 to 33 years, Among these individuals were recrited corresponded to the suppresed period of growth of annual ring in Pinus densiflora survived when the vegetation was damaged by air pollution. On the other hand, from the result of analysis of frequency distribution diagram of diameter, it was postulated that even if whis Pinus densiflora community can be maintained as it is for the time being, it might be changed to Quercus community with the lapse of time. Regeneration; Pinus densiflora; Air pollution; Annual ring; Age structure; Diameter structure; Quercus spp. In these analyses, factors for individual recognition and species recognition were suggested.

• Journal of fish pathology
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• v.17 no.1
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• pp.21-28
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• 2004

In late summer of 2001, a new disease "overturn disease" occurred among mud loach (Misgurnus mizolepis) cultured in a farm Chonbuk Province. The fish exhibited a lethargic, erratic and spiral swimming at the water surface. Affected fish showed swollen abdomen with accumulation of air bubbles in the intestinal canal. The bubbles were much larger in the anterior part than in the posterior part. Hematological and histopathological examinations were done. No significant differences were found in RBC count, Ht value and Hb concentration between the diseased and the healthy fish. Gill filaments showed proximal hyperplasia of the respiratory epithelia and fusing of the gill lamella. Hemorrhage and necrosis occurred in the intestinal epithelia and within the lamina propria, and the mucosal epithelia were separated from the muscularis. Hepatocytes underwent atrophy. In the fish experimentally tied between the annal fin and the anus by a thread to confirm accumulation of air bubbles within intestine, accumulation of air bubbles was confirmed. This disease in mud loach appeared to be induced by circulatory disturbances in the intestinal wall owing to accumulation of air bubbles in the alimentary canal after fed high protein diet throughout all culturing period.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.2
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• pp.260-269
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• 2000

Oil-film flow visualizations and three-dimensional flow measurements have been conducted in the downstream region of a butterfly-type valve used in air-conditioning systems, with the variation of a disk open angle. The flow visualizations in the flow symmetry plane show that there are a pair of counter-rotating separation/recirculation zones as wall as two jet-like near-wall flows. These flow disturbances are strongly depends on the disk open angle. Based on the flow visualization, a qualitative flow model is suggested in the near-field and downstream region of the valve disk. For a small disk open angle, the mean velocities and turbulent intensities have relatively small values in the near-field of the valve disk, but they do not show uniform distributions even in some downstream region. With an increment of the disk open angle, mean velocity variations and turbulent intensities are greatly increased in the immediate downstream region, but uniform distributions are quickly resumed as departing from the valve disk. The mass flow rate remains nearly constant for the disk open angles less than 30 degrees, meanwhile it strongly depends on the disk open angles between 45 and 75 degrees. The pressure loss is found to be about zero for the disk open angles less than 45 degrees, but is substantially increased for those larger than 75 degrees.

• Fire Science and Engineering
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• v.16 no.1
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• pp.30-38
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• 2002

Occurring fire or burning bushes beneath overhead power lines have caused system disturbances in many countries. In this study, various tests in the simulated condition of power lines were conducted so as to investigate the reduction in insulation strength caused by combustion flame. Characteristics of the ac and dc flashover voltages in the vertical needle-plane, sphere-plane and rod-plane electrode system were investigated when the combustion flames were present near the high-voltage electrode. As the results of an experimental investigation, It was found that the average reduction characteristics of flashover voltages with the sphere-plane system, in comparison with the no-flames case, were about 1/3 times when the ac voltages were applied.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.1
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• pp.50-63
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• 2002

The Karman boundary-layer has been numerically investigated for the disturbance wave number, wave velocity, azimuth angle and radius (Reynolds number, Re). The disturbed flow over rotating disk can lead to transition at a much lower Re than that of the well-known Type I instability. This early transition is due to the excitation of the Type II. Presented are the neutral stability results concerning these instabilities by solving newly formulated stability equations with consideration of whole convective terms. When the present numerical results are compared with the previously known results, the value of critical Re corresponding to Type I is moved from ${Re}_{c.1}$=285.3 to 270.2 and the value corresponding to Type II from ${Re}_{c.2}$=69.4 to 36.9, respectively. Also, the corresponding wave number is moved fro)m $k_1$=0.378 to 0.386 for Type I; from $k_2$=0.279 to 0.385 for Type II. For Type II, the upped limit of wave number and azimuth angle is $k_u$=0.5872, $\varepsilon_u$=$-17.5^{\circ}$, while its lower limit is near $k_u$=0, $\varepsilon_u$=$-28.4^{\circ}$. This implies that the disturbances will be relatively fast amplified at small Re and within narrow bands of wave number compared with the previous results.