• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.230-237
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• 2003

Ultrasonic testing method has been developed to evaluate adhesive layers in blast tube for the reliability of the rocket. The main objective of the present work was to find debonding and missing adhesive in epoxy layer between steel and FRP layers. In this approach, the ultrasonic reflection from the interface between the steel sheet and the epoxy adhesive is measured with a high-frequency pulse-echo setup in order to identify contact debonding and missing adhesive. Then, the steel sheet is excited to resonance by low-frequency ultrasound, and the gap size underneath the measuring location is estimated from the resonance responses. For practical application in industry an automated testing system has been developed where the proposed approach is implemented. The performance of the proposed approach has been verified by actual measurement of gap sizes from the cross-sections of cut specimens using an optical microscope.

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.115-123
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• 2012

As the market of lithium secondary batteries moves from mobile IT devices to large-format electric vehicles or energy storage systems, the strengthened battery specifications such as long-term reliability longer than 10 years, pack-level safety and tough competitive price have been required. Moreover, even though high power properties should also be achieved for hybrid electric vehicles, it is not easy to measure accurate power values at various conditions. Because it is difficult to choose a proper measurement method and its experimental condition is more complex comparing to capacity measurement. In addition, the power values are very sensitive to power duration time, state-of-charge (SOC) of cells, cut-off voltages, and temperatures, whereas capacity values are not. In this paper, we introduce three kinds of power measurement methods, hybrid pulse power characterization (HPPC) suggested by US FreedomCar, so-called J-pulse by Japan electric vehicle association standards (JEVS) and constant power measurement, respectively. Moreover, with pouch-type unit cells for HEV, experimental power data are discussed in order to compare each power measurement.

• Journal of the Korean Electrochemical Society
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• v.15 no.1
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• pp.1-11
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• 2012

Recently lithium ion secondary batteries (LIB) have rapidly developed because of their advantages such as high energy densities and capacities. Among them, an electrical vehicle which is the one of the environmental-friendly transportation facilities has been received a great attention, but, it is needed to overcome several obstacles of the LIB performances. LIB is practically adapted to Hybrid Electric Vehicle (HEV), but the issues for high capacities, long life time and safety should be solved. Moreover, LIBs still have some possibilities of explosion in the case of overheating of the used organic electrolyte and overcharging of the cell. Hence, it is urgently needed to replace the liquid electrolytes into the solid electrolytes due to the safety issues. Therefore, in this review, we summarized and discussed the research trends of the solid electrolyte to solve the concerns of safety and capacity of LIBs and published patents and articles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.867-872
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• 2010

Unused energy derived from sources in nature can be captured and stored for future use, for example, to recharge a battery or power a device; this process of capturing and storing energy is called energy harvesting. Extensive investigations are being carried out in order to use piezoelectricity to harvest the energy generated by body movements or machine vibrations. This paper presents a simple analytical model that describes the output voltage effectiveness of a Piezocomposite Generating Element (PCGE) from vibration and its experimental verification. PCGE is composed of carbon/epoxy, PZT, and glass/epoxy layers. During the manufacturing process, the stacked layers were cured at $177^{\circ}C$ in an autoclave, which created residual stresses in PCGE and altered the piezoelectric properties of the PZT layer. In the experiments, three kinds of lay-up configurations of PCGE were considered to verify the proposed prediction model and to investigate its capability to convert oscillatory mechanical energy into electrical energy. The predicted performance results are in good agreement with observed experimental ones.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.597-602
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• 2020

The study was conducted to improve the efficiency of the test and to reduce the exposure dose of patients and operators by analyzing the difference in the moving speed of Lipiodol according to the temperature during lymphography. The device for injecting Lipiodol at a constant pressure was self-made, and after inserting Lipiodol into the Connecting Tube, the moving speed of the contrast agent was photographed at temperatures of 26℃, 36℃, and 46℃ using a heat transfer device. Lipiodol movement time from the Support Catheter to 20cm was measured and analyzed, and statistical significance was confirmed. In the 46℃ environment, the average moving time was 11 seconds, at 36℃ the average was 13 seconds, and at 26℃ the average was 17 seconds. Lipiodol showed a significant difference in moving time with increasing temperature (p<.001), and it was confirmed that the higher the temperature, the faster the moving speed. In the case of lymphangiography, when heated to a certain temperature (46 degrees) rather than injecting Lipiodol at room temperature, the injection speed can be increased and the speed of movement in the lymphatic vessel can be improved.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.11a
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• pp.54-54
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• 2000

종이의 생산성을 향상 시키기 위한 방법에는 초지기의 광폭화오} 생산 속도의 증가 가 있다. 현재 초지기는 10m까지 생산 폭이 확대 되었고, 생산 속도에 있어서는 최 신 설비의 경우 2,OOOm/min로 설계 되고 있다. 따라서 생산 폭과 속도의 증가는 이 전의 소폭과 저속의 생산 셜비에서와 동일한 원료 배합과 생산 관리로는 최적의 생 산 효율을 달성하는데 문제점이 있다. 그러므로 현재 각국의 신규 제지 설비에 적 용되 고 있는 twin wire system역 시 생 산 속도의 증가를 극복하고 기 존의 fourdrinier s system 이 지니고 있는 문제점을 극복하기 위해 도입되었다. 두 가지의 생산 설비에서 제조된 종이의 가장 큰 차이점은 미세 입자들의 분포와 종이의 구조적 특성에 있다. 특히 fourdrinier system에서 미세 입자들의 분포는 횡단 면을 기준으로 볼 때 표면에서 와이어 면으로 진행됨에 따라 급격히 감소된다는 것 을 알 수 있다. 이러한 사실은 주지하는 바와 같이 초지 형성부에서 효과적인 탈수 를 달성하기 위해 부착되어 있는 여러가지 탈수 장치들의 영향으로 와이어 방향으 로만 급격한 탈수가 일어나기 때문이다. 그러나 twin wire system 2.! gap former어$\mid$ 있 어서 미세 섬유와 충전제가 횡단면상에서 분포하는 형태는 "U"자 형태로 상면과 하 면에서 가장 높은 미세분의 분포를 나타내고 줄간층에는 상대적으로 낮은 미세분이 분포하고 있을을 알수 있다. 따라서 종이의 중간층 미세분 분포의 감소는 섬유간 표면적의 감소를 의미하고 이로 인하여 결합력이 약해진다는 것을 알 수 있다. 특 히 도공 원지로 사용되었을 경우 heat off-set 인쇄시 블리스터와 같은 문제점을 일 으키기도 한다. 앞서 언급한 바와 같이 종이의 제조 설비에 따라 제조되는 종이의 구조적 특성이 변하게 되므로 동일한 도공 공정에 적용 되었을 경우 이들로부터 제 조된 도공지의 특성에도 영향을 미칠것으로 예측된다. 따라서 본 연구에서는 두 가지 초지기의 형태에서 제조된 원지가 도공 작업성과 도공지의 특성에 미치는 영향에 대해 고찰코자 하였다.대해 고찰코자 하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1135-1140
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• 2016

The main challenge in designing wearable WBANs is to guarantee the balance of QoS demands in the network with the low power constraints of limited battery powered nodes. Low power devices implanted in or attached to the body should be designed to meet minimum energy requirements due to their limited battery life and be small in size to be easily wearable. In this paper, we propose a method for optimizing channel allocation method that is compatible with the IEEE 802.15.6 standard, enables the maximum amount of power charge at idle, guarantees the QoS of a WBAN, and provides the reliable date transmission between nodes and hubs in the network. Our extensive simulations will show that the method we propose not only maximizes the QoS in packet transmission but also improves the level of energy efficiency.

• Applied Biological Chemistry
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• v.34 no.2
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• pp.154-161
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• 1991

An objective method for measuring rancidity in soybean oil was developed based on the volatile contents obtained by headspace gas chromatographic analysis. Apparatus for headspace volatile cold trapping-thermal desorption was described, designed to collect and analyze volatiles of soybean oil. Samples of commercially processed soybean oil were stored under controlled condition and then evaluated for flavor by a eight member trained panel and for volatile contents by headspace gas chromatographic analysis. Twenty-three GC peaks were identified on the basis of relative retention time of reference compounds and gas chromatography-mass spectrometry. The volatile compounds identified were autoxidation products of principal unsaturated fatty acids of soybean oil. The simple linear regressions of flavor score with the pentanal or hexanal contents in aged soybean oil gave correlation coefficient of 0.990 and 0.994. respectively. Pentanal and hexanal contents could be used as a potentially useful index for predicting flavor scores of soybean oil.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.171-171
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• 2011

헬륨냉동계통은 연구용 원자로인 하나로에서 냉중성자를 생산할 수 있도록 설치된 수조내기기 내의 감속재인 수소가 정상적으로 열 사이펀을 유지하기 위한 주요 계통이다. 헬륨냉동계통은 헬륨가스를 압축하는 헬륨 압축부분과 헬륨가스를 팽창시켜 저온을 생성시키는 헬륨 팽창부분으로 나누어진다. 헬륨 압축부분은 두 개의 스크류가 맞물려 회전하면서 약 1.05 bar(a)의 헬륨가스를 최대 13 bar(a)까지 압축시키는 압축기가 있으며, 헬륨 팽창부분인 냉동박스의 팽창 터빈은 self-acting gas bearing에 의해 구동되며, 저온모드 운전 시작시 헬륨 압축부분에서 일부의 가스는 팽창 터빈 축(shaft)으로 유입되어 회전속도가 서서히 증가하면서 고속으로 회전하여 극저온의 헬륨가스(14~18 K)를 생성하는 주요 기기이다. 헬륨을 팽창하는 부분인 냉동박스 내로 헬륨 압축가스를 유입하기 전에 압축된 헬륨가스 내 불순물의 순도를 분석하여 냉동박스의 주요 부품인 팽창터빈의 운전에 영향을 미치지 않는 것이 가장 중요하다. 따라서 헬륨 저압측에 헬륨가스 내 불순물 즉, 수소($H_2$), 수분($H_2O$), 질소($N_2$), 탄화수소류(CxHy) 및 오일(Oilaerosol) 등의 함량을 분석하기위해 가스 분석기가 설치되어 있으며, 냉동박스 내로 유입되기 전에 헬륨압축에서 순환되는 가스 내 불순물인 수분, 질소, 탄화수소류 및 오일은 10 vpm 이하이어야 하며, 수소 함량은 0.1 % 이내이어야 한다. 헬륨 압축부분에서 순환되는 가스의 불순물이 요구 조건에 만족하도록 헬륨 고압측과 헬륨 저압측에 cryogenic adsorber를 설치하여 가스 내 불순물을 제거하는 가스순도제어 작업을 수행해야 한다. cryogenic adsorber를 사용하기 위해서는 장치 내의 불순 가스를 공정진공도(1.33 X $10^{-3}$ mbar) 이하로 진공배기하는 작업이 매우 중요하다. 이는 계통의 헬륨가스가 오염되지 않도록 하는 것으로 cryogenic adsorber 내에는 액체질소를 충전하여 액체질소 온도에 노출된 활성탄층을 헬륨가스가 흐르면서 수분, 질소, 탄화수소류 및 오일 등이 제거된다. 이 논문에서는 헬륨냉동계통의 가스 순도 제어 작업을 통해 헬륨가스의 순도가 요구조건 이하로 만족하며, 팽창 터빈의 운전에 영향을 미치지 않음을 기술하고자 한다.

• Journal of the Korean Solar Energy Society
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• v.29 no.2
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• pp.1-7
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• 2009

Use of the PV(photovoltaic) generation system is increased in such areas as remote mountain places or islands at which electrical energy is not serviced. The stand alone PV system is required the power storage products such as battery, fly wheel and super capacitor. Several lead storage batteries are connected in series to get high voltages. The life of lead storage battery is shortened when over charge or over discharge takes place. So, it is needed to control batteries not to be overcharged or be discharged deeply. Voltage of each battery was ignored in former control methods in which overall voltage was used to control charge or discharge battery. In this study, the charging and discharging voltage variations of sealed lead storage batteries with l2V/l.2A were investigated step by step experiments. The results of the test show that one should consider and specify the state of each battery to prevent overcharge or deep discharge. With the basis of the experiments, we designed a monitoring unit to monitor battery voltages simultaneously using micro-controller. The unit measures voltage of 20 batteries simultaneously and displays data on the color LCD monitor with curved line graph. It also sends data to PC using the RS232C communication port. The designed unit was adapted to stand alone PV system with 1kW capacity and lead storage batteries are connected to the PV generation system. The number of lead storage batteries was 10 in series and 12V/250Ah each. Resistive load with 3kW was used for discharging.