• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.1
• /
• pp.147-155
• /
• 1999

In this work, the defrosting characteristics of PTC heating sheet used as a defrosting heat source of fin-tube heat exchanger in a refrigerator have been experimentally compared with those of conventional electric heater. It is found that the characteristics of water draining rate with defrosting time show smoothly oscillating pattern when PTC heating sheet is used, and the drained water is completely melted. The defrosting efficiency of the PTC heating sheet is about 75%, which represents about 25% higher than that of the electric heater. A reduction of defrosting time and an increase of defrosting efficiency may be obtained by improving the arrangement of heating elements of the heating sheet. It is shown that the defrosting time of PTC heating sheet increases linearly with the amount of frost, however the defrosting efficiency is nearly constant. In the application to the refrigerating system, one should notice the fact that the defrosting performance of PTC heating sheet may be defraded due to the repeated operations.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.1
• /
• pp.9-16
• /
• 2012

This paper describes a measuring apparatus that can be used to appraise the effectiveness of nanofluids as new heat-transfer-enhancing fluids. A couple of apparatuses using fine hot wires as sensors have been proposed for this purpose; however, they have a technical weakness related to the uncertain working conditions of the sensor. The present method uses the convective heat transfer coefficient from a hot wire as an indication of the heat transfer effectiveness of the nanofluid, where the temperature of the wire remains constant during the experiment. The operating principle and experimental procedure are explained in detail, and the validity of the system is tested with pure base fluids. The effects of particle concentration, velocity, and temperature on the heat transfer coefficients of the nanofluids are discussed comprehensively using the experimental data for graphite nanolubrication oil.

• Journal of Korea Society of Industrial Information Systems
• /
• v.7 no.1
• /
• pp.34-41
• /
• 2002

There m many noise sources in living environment. Especially, noise that happen in apartment or tenement house may make neighborhood serious troubles. Thus, the development of new materials to reduce and improve the living noises is required. During past decade, various methodologies have been developed and researched to reduce and improve the living noises. However, there are many problems to apply these methodologies to practical our environment. In this thesis, we develop the new artificial material supporting high porous materials and lower pressure density to improve the problem caused in the safety design and sound absorbing material. To prove the efficiency of the developed methodology, we compare our methodology with conventional methodologies and also suggest an alternative methodology to contribute quiet life environments.

• Magazine of the Korea Concrete Institute
• /
• v.8 no.5
• /
• pp.179-187
• /
• 1996

Many underwater concrete structures have been constructed recently in proportion to the increase of ocean developments. The research for the underwater concrete construction was mainly focused in view of placing method. Recently, special admixture agents of concrete were developed for antiwashout concrete under water in some foreign nations. They had successful results in experiments and site constructions. However. there are seldom experimental results or placements in domestic contry. In this paper. We had carried out property tests of fresh and hardened concrete with refer to successful results in experiments and site construction and investigated the physical variation of the antiwashout underwater concrete considering the interaction between antiwashout admixture and other ones. We have decided the optimal mix proportion fb;r antiwashout underwater concrete under standerd sea state.

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1339-1340
• /
• 2006

일반적으로 저압계통의 고장전류를 차단하기 위해서, 기중차단기(LVPCB, ACB), 배선용차단기 등을 사용하고 있는데, 저압차단기는 저압계통의 고장전류를 차단할 수 있으나, 고장전류를 효과적으로 제한하지 못하며, 차단기 내부의 아킹시간이 상대적으로 길므로, 저압차단기는 물론 주변 전력기기에 전기적/열적/기계적 스트레스를 주게 된다. 또한 지속적인 부하의 증가로 인해 저압계통의 단락전류는 점점 증가하는 추세에 있으므로 저압계통은 물론 고압계통에서도 고장전류를 보다 빠르고 효과적으로 제한 및 차단을 할 수 있는 한류형 차단기가 제안되고 있다. 본 연구에서는 정온도계수(PTC, Positive Temperature Coefficient) 특성을 가지는 소자를 이용하여 저압계통에 적용가능한 한류소자를 개발하였으며, 기존 차단기에 직렬 혹은 병렬로 연결하여 저압계통의 고장전류를 매우 빠르고 효과적으로 제한 및 차단할 수 있으며, 아울러 저압계통의 차단보호 협조를 효과적으로 구현할 수 있는 한류형 차단기를 제안하였다. 한류소자를 전력기기에 적용하는 방법은 크게 기존 차단기와 직렬로 연결되는 방식과 기존 차단기를 수정하여 차단기 내부의 접점과 비직렬 연결되는 방식으로 구분 할 수 있는데, 본 논문에서는 직렬방식/비직렬방식으로 기존 차단기에 한류소자를 적용항에 있어서 대응가능한 대전류 PTC소자를 개발하였으며, 또한 각 방안에 대한 시제품을 제작하여 제한 성능을 검증하였다.

• Journal of Chest Surgery
• /
• v.34 no.10
• /
• pp.797-799
• /
• 2001

Open heart surgery with hypothermia in patients with cold agglutinin can cause severe complications by hemolysis and hemagglutination of red blood cells. A 41 year-old male patient with mitral stenosis was admitted due to fever and cough. After antibiotics treatment, he was scheduled to undergo mitral valve replacement. In the operation room, we found agglutination of blood cardioplegia during lowering temperature of cardioplegia. And then, the cardioplegia was changed to warm cardioplegia and the operation was performed under normothermia due to the suspicion of the cold reactive protein. The operation was performed uneventfully. Postoperatively, cold agglutinin was confirmed by immunochemistry of the patient\`s serum.

• Fire Science and Engineering
• /
• v.23 no.3
• /
• pp.67-72
• /
• 2009

This paper is for response feature of fire detectors not only to analysis response feature of fire detector, but also to observe flame spread of inside-building and fire enlargement by using the row house which is supposed to be broken up. Many kinds of popular detectors such as heat type detector(differential type, fixed temperature type, Analogue type)and smoke type(light scattered type, Analogue type, single alarm type) were installed in the house in order to check for the change of temperature by installing of thermocouples. As a result, smoke detectors are better than heat detectors when it comes to making effective fire-detect system in the row house.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.10a
• /
• pp.215-222
• /
• 2004

We synthesized a aziridine bonding agent that play an important role in increasing the adhesion property between polymer binders and solid particles. It increases the physical properties of polymer-based propellant. Chemical reaction between two materials increase the interface adhesion. We analyzed and studied the chemical characteristics of the material and physical properties of a liner applied the aziridine bonding agent. We also studied the adhesion property of a liner/propellant applied the aziridine bonding agent. 3M was use as control group. In accordance with US MIS (Missile Interim Specification) we examined the chemical properties. As a result of our study, newly synthesized aziridine bonding agent was as good as quality of 3M HX-868.

• Journal for History of Mathematics
• /
• v.31 no.6
• /
• pp.273-289
• /
• 2018

The KaiFangFa開方法 of traditional mathematics was completed in ${\ll}$JiuZhang SuanShu九章算術${\gg}$ originally, and further organized in Song宋 $Yu{\acute{a}}n$元 dinasities. The former is the ShiSuoKaiFangFa釋鎖開方法 using the coefficients of the polynomial expansion, and the latter is the ZengChengKaiFangFa增乘開方法 obtaining the solution only by some mechanical numerical manipulations. ${\ll}$SanHak JeongEui算學正義${\gg}$ basically used the latter and improved the estimate-value array by referring to the written-calculation in ${\ll}$ShuLi JingYun數理精蘊${\gg}$. As a result, ZengChengKaiFangFa was more refined so that the KaiFangFa algorithm is more consistent.

• Research in Community and Public Health Nursing
• /
• v.33 no.1
• /
• pp.63-73
• /
• 2022

Purpose: The purpose of this study was to identify the predictors influencing fear of falling in community-dwelling elderly women with mild cognitive impairment (MCI). Methods: A secondary data analysis was performed using data of 65 years or older elderly women with MCI participating in the 7th Korea Longitudinal Study of Ageing of the Korea Employment Information Service. The study subjects included 368 elderly women with MCI. For data analysis, descriptive statistics and logistic regression with complex samples were performed using IBM SPSS ver. 23.0. Results: 89.9% of the elderly women with MCI had fear of falling. There were significant factors such as religion (OR=8.85, 95% CI: 3.39~23.15), restriction of activity (OR=6.84, 95% CI: 2.14~21.90), depression (OR=0.75, 95% CI: 0.62~0.90), and MMSE (OR=1.30, 95% CI: 1.03~1.63), predicting fear of falling in community-dwelling elderly women with MCI. Conclusion: Differentiated strategies should be developed for elderly women with MCI to decrease fear of falling and prevent falls with understanding of contributing factors. This study will provide fundamental information on programming and a policy proposal related to fear of falling for elderly women with MCI.