• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.11a
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• pp.43-49
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• 2000

Heat transfer characteristics of self oscillating heat pipe were experimentally investigated for the effect of fill charge ratios and heat loads. The heat pipe used for this study is made of copper capillary, has 0.002m internal diameter, a 0.34m length in one turn and consists of 19 turns. Heating and cooling section each have a length of 70mm. Water was used as working fluid inside heat pipe. As the experimental results, the self oscillating heat pipe was operated by self-exited oscillation and circulation of working fluid and the oscillation within the self oscillating heat pipe assumed chaotic behavior.

• Water for future
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• v.6 no.1
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• pp.13-18
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• 1973

If the temperature of free water drops below the freezing point the water turns into ice and its volume increases. Analyzing of the results in test, it is hoped that these is broadly used in engineering plan. The compressive strength of frozen soils and the unconfined compressive strength of the ice. The creep strength depends on factors including creep ratio, time, strain and temperature. For a linear decreases in temperature, strength predicts an exponential increasing. The relationships between dry unit weight and compressive strength, water content and freezing with compacted soil samples, have been analyzed to understand the strength of frozen soil. Therefore, it is thankful that the results of analsis shall find useful application as a framework for generalizing experimental information as well as a basis for solving various frozen soil mechanics problems.

• Journal of the Korean Regional Science Association
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• v.13 no.2
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• pp.25-43
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• 1997

This paper empirically estimates gains from capital inflow to a regional ecomomy. It will be a usefulc for indicator for a local government to build a policy for attracting capital. We estimate the respective Cobb-Douglas production function for 11 provinces of Korea, derive its marginal productivity of capital, and then calculate the amount of capital moved between two provinces and gains from the capital movement. With no barriers to capital movement, there would be a strong motive for capital inflow to Seoul, Pusan, and Kyungki, whereas capital outflow would be expected in Chonnam, Chungbuk, Chungnam, and Kyungbuk. The ratio of gains from capital movement to the regional domestic from capital movement to the regional domestic product(RDP) is high in Cheju, Kangwon, Chungbuk, and so on. It turns out that capital flows from an area with lower productivity of capital to one with hihger productivity. This implies that if the local government of an underdeveloped region wants to lure capital investment from outside, it needs to provide it with strong incentives of eax reduction and special loans.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.147-149
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• 2001

The single-phase line-start permanent magnet motor has been shown to be capable of very desirable steady state performance, but known to have undesirable starting performance. This is because magnetic braking torque. So, it is very important to predict starting performance accurately when designing the line-start motors. In this paper, starting performance was calculated by combination of d-q axis voltage equations and mechanical dynamic equations. D-q axis voltage components were derived by winding angle and turns ratio transformations.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.381-387
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• 2002

Curved bridges are composed of curved members which have certain curvatures, comparing to straight bridges. Therefore, their behavior is quite different from one of the straight bridges, mainly due to the geometric characteristics of the curved bridges. In this paper, the curved bridges consisted of the single box-girder span are investigated to study the effects of negative reaction forces. The parameters considered in this study are span lengths, angles of curvature, and the number of shoes. Midas/civil computer program was used for the analysis of the curved bridges. The analysis results show that negative reaction forces are not created with one shoe installed. When two shoes are provided, on the other hands, the uplift forces are developed at the inside shoe. It is also concluded that the increasing ratio of negative reaction forces becomes larger, as the angles of curvature increase, and the elongation of span lengths turns out to increase the magnitudes of the uplift forces.

• Journal of Power Electronics
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• v.6 no.3
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• pp.205-213
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• 2006

A cost-effective magnetic-coupled AC-PDP sustain driver with low switching loss is proposed. The transformer reduces current stress in the energy recovery switches which affects circuit cost and reliability. The turns-ratio can be used to adjust the sustain pulse slopes which affect gas discharge uniformity. Dividing the recovery paths prevents abrupt changes in the output capacitance and thereby switching losses of the recovery switches is reduced. In addition, the proposed circuit has a more simple structure because it does not use the recovery path diodes which also afford a large recovery current. By reducing the current stress and device count in the energy recovery circuit, the proposed driver may have decreased circuit cost and improved circuit reliability.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.225-228
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• 1996

ECG data are used for the diagnostic purposes with many clinical situations, especially heart disease. In this paper, an efficient ECG data compression technique by wavelet transform and high-speed vector quantization on PMS-B algorithm is proposed. In general, ECG data compression techniques are divided into two categories: direct and transform methods. The direct data compression techniques are AZTEC, TP, CORTES, FAN and SAPA algorithms, besides the transform methods include K-L, Fourier, Walsh, and wavelet transforms. In this paper, we applied wavelet analysis to the ECG data. In particular, vector quantization on PMS-B algorithm to the wavelet coefficients in the higher frequency regions, but scalar quantized in the lower frequency regions by PCM. Finally, the quantized indices were compressed by LZW lossless entropy encoder. As the result of simulation, it turns out to get sufficient compression ratio while keeping clinically acceptable PRD.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.493-495
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• 2006

The hysteresis characteristics of flux-lock reactor, which is an essential component of flux-lock type superconducting fault current limiter (SFCL), was investigated. The hysteresis loss of iron core in flux-lock type SFCL does not happen due to its winding's structure especially in the normal state. From the equivalent circuit for the flux-lock type SFCL and the fault current limiting experiments, the hysteresis curves could be drawn. Through the hysteresis curves together with the fault current level due to the inductance ratio for the 1st and 2nd windings, the increase of the number of turns in the 2nd winding of the flux-lock type SFCL had a role to prevent the iron core from saturation.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.181-182
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• 2007

This paper presents the system design of high speed linear synchronous machine in the required speed and thrust considering power of inverter. in this paper, the design of manufacturing motor is optimized by characteristics of motor parameters with the variation of coil turns of rotor and stator. And, the dynamic simulation are performed from the (d-q) transformation of the current and voltage and the mechanical dynamic equation composed of the mover mass and damping ratio. Finally, the results of design and analysis are verificated by finite element analysis.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.24-26
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• 1995

In this paper, we investigated transient fault currents in a magnetic coupling High-Tc superconducting current limiter(HCL). It has an important effect on the reliability and stability of the power system. In order to analyze transient fault characteristics of HCL, we fabricated a magnetic coupling HCL and tested it in different fault conditions. An important parameter of design and manufacture which makes HCL inherently reliable is reduction of inrush fault currents. Without inrush fault currents, the currents flowing under such conditions can be limited to a desired-value within one cycle. Inrush fault current depends on saturation, normal spot propagation velocity, turns ratio and the fault angle.