• 전기의세계
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• v.22 no.4
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• pp.11-16
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• 1973

This paper presents an optimum control of the field resistance for the self-excited DC shunt generator to keep a constant terminal voltage in case of the load change or the torque variation in the system. The non-linearity of the system is linearized by applying the small signal technique and the linearized equation is solved by the maximum principle with the digital computer. The optimal control value of the field resistance for the step error of the generator output voltage is obtained and the transient voltage characteristics in the system are investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.105-110
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• 1998

The propose of this study is to examine the mechanical properties of mortar using ground granulated blast-furnace(GGBF) slag. In this study, the mortar replaced by varying fineness and content of GGBF slag is investigated through the change of compressive strength, chemical resistance and weight loss. As the result, it has been found that GGBF slag increase somewhat higher flow value and compressive strength. In addition, the chemical resistance of motar using GGBF slag shows higher flow that of motar not containing GGBF slag.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.303-306
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• 1997

In this paper, we carried out the fundamental experiments on the resistance of chemical attack of mortar using the electric arc furnace slag as fine aggregate. The mortar specimens made from the electric arc furnace slag (EAF slag) as fine aggregate were immersed in artificial seawater and two sorts of chemical solutions, and measured to investigate the change of compressive strength and weight.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.183-188
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• 1996

The durability of concrete structures decrease due to deterioration of concrete when they are constructed in marine or pollutional environments. In this study, the mortar specimens made from the five different types of cement were immersed in artificial seawater and four kinds chemical solution, and were measured the change of compressive strength and weight. The results show that the longer the immersed days are, the more the compressive strength reduction is. It has been remarked that the resistance of slag cement and ground granulated blast-furnace slag is excellent in chemical attack.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.4
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• pp.377-381
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• 1988

Effects of thermal resistance of mold during freezing processes have been investigated. Saturated liquid is chosen to present one-dimensional quasi-steady solution and this solution is compared with numerical solutions. Front tracking finite element method has been applied for the numerical solutions. Results show that mold should be considered as well as phase change material except the cases when the very thin mold with relatively high thermal conductivity is used.

• Biomolecules & Therapeutics
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• v.25 no.1
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• pp.1-3
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• 2017

• Polymer(Korea)
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• v.26 no.3
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• pp.367-374
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• 2002

Electrical characteristics of crystalline polymer composites filled with nano-sized carbon black particle were studied. The developed composite system exhibited a typical positive temperature coefficient resistance (PTCR) characteristic, where the electrical resistance sharply increased at a specific temperature. The PTCR effect was sometimes followed by a negative temperature coefficient resistance (NTCR) feature with temperature, which seemingly caused by the coagulation of nano-sized carbon black particles in the excessive quantity. The PTCR temperature was controlled by the carbon black content and the external voltage. The change of electric conductivity was shown as a function of carbon black content, and the resistance was constant when the carbon black content was over 20 wt%. The room-temperature resistance was maintained by a repeated heating and cooling. The excellent PTCR characteristic was demonstrated by the low resistance in the initial stage and the instantaneous heating capability.

• The Journal of Internal Korean Medicine
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• v.28 no.4
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• pp.709-716
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• 2007

Objective : We present reference values of flow velocities of intracranial and extracranial cerebral arteries and relation with change factor. Method : We checked transcranial Doppler ultrasonography on mean velocity, systolic velocity, pulsatility index, and resistance index of 252 patients. We also compared differences of change factor. Result : The result showed a difference by sex and age and relevance between vessels besides mean velocity of vessels related with past history and social history. Conclusion : According to the above results, females showed higher velocity of all vessels. With advancing age, subjects showed reduction in velocity and increase in pulsatility index and resistance index. Anterior cerebral, middle cerebral, and posterior cerebral artery increased in proportion to velocity of internal carotid artery and basilar artery. Vessel velocity correlated with diabetes mellitus, hypertension and hyperlipidemia.

• Journal of Ocean Engineering and Technology
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• v.23 no.5
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• pp.54-60
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• 2009

Exposed to various environments, concrete confronts degradation by a lot of physical and chemical reaction. Though so many experiments and theorizations on the single condition of concrete degradation have been carried out by constant studies, the truth for now is that there are few studies on the compound phenomenon of degradation related with marine environments. Accordingly, this study measured the degree of degradation in the change of external shape, the change of unit weight and compressive strength, ultrasonic velocity test, and the change of length, etc. after exposing the specimen of cement mortar to the environment between 0 cycle and the maximum of 300 cycles under the condition of aquatic curing, freezing and thawing, and compound degradation, using mineral admixture effective for concrete degradation as a binder. The result indicated that the case of adding mineral admixture showed greater resistance than that of using OPC only, and specifically, the specimen with the additive of slag powder and three component system showed very excellent resistance to freezing and thawing, and compound degradation.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.361-367
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• 2009

The criteria such as ASTM recommends that the zero reading process of CPT must be performed in the same temperature condition with underground in order to reduce the effect of temperature. However, this method can not consider the change of temperature occurred during penetration. In this study, ultra small size temperature sensor with 0.5mm in diameter is manufactured to estimate and compensate the effect of temperature by using FBG sensor. The continuous temperature changes are monitored during cone penetration by using FBG temperature sensor installed in cone penetrometer. The temperature compensated tip resistances show the uniform and similar distributions with depth in different with originally measured tip resistance in cohesive soil. This study verifies that the tip resistances measured by previous zero reading method are affected by the change of underground temperature, and suggests the new temperature compensation technique using by FBG temperature sensor.