• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1534-1536
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• 2005

A DC-DC converter is being widely used for various household appliances and for industry applications. The DC-DC converter is powered from single battery, and the voltage is varied according to the purpose. In the vehicle, various accessories whose electric power is different are being used. Thus, plural number of DC-DC converter should be provided, so these situations bring complicated circuits, and accordingly, higher cost. Under such backgrounds, in this paper, we propose a novel buck-boost chopper circuit with simply configuration which can supply to two or more different output loads. The propose chewer circuit can control output voltages by controlling duty ratio by using typically two switching devices, which is composed by single boost-switch and single buck-switch. The output voltage can be controlled widely. A few modified circuits developed from the fundamental circuit are represented including the general multi-load circuit. And all this merits and appropriateness was proved by computer simulation and experience.

• Laser Solutions
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• v.18 no.1
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• pp.1-6
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• 2015

High welding speed and narrow weld seam are favorable for welding of magnesium alloy. Magnesium alloy is recommended for the smart frame because it has several advantages such as low density, high thermal conductivity, EMI shielding capability and good cast ability. This study is for the assembly welding of the magnesium smart frame with high productivity, good performance and low cost. The window for battery on AZ91D frame produced by die-casting was prepared by CNC machining. Corresponding AZ31 blank of 0.2mm thickness was prepared by die-blanking cut. All system set was fixed at the stationary bed but the laser beam was manipulated by scanner up-to 1,000mm/s speed. The weld joint between AZ31 sheet and AZ91D frame was welded by fiber laser on 850~1,000W output power. The joint showed penetration enough but some humping bead. The distortion by the weld heat was almost free because of the quick dissipation of the heat by small beam size and fast welding. Consequently, the thinner magnesium foil was assembled successfully to the magnesium frame of mobile phone.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.351-353
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• 2010

본 논문에서는 쉽고 빠르게 정확한 리튬 이온 배터리 모델을 구현할 수 있는 방법을 제시하고 있으며, 구현된 모델을 MATLAB(R)/Simulink(R)환경에서 검증한다. 모델을 구현함에 있어서 절차를 간소화하기 위해 비선형 개방 전압은 배터리 충전 및 방전 전압의 평균으로 근사하고, 배터리 내부 비선형 파라미터는 방전 초기에 발생하는 과도응답을 측정한 이산 데이터를 곡선 접합하여 구한다. 구현된 모델을 이용하여 시뮬레이션을 하고 이를 실험 데이터와 비교해본 결과, 평균 절대오차는 기존 연구보다 0.1% 낮은 0.091%로 측정되었다. 측정된 오차의 수준은 본 논문에서 제안한 방법이 파라미터 추출에 필요한 시간을 단축하고 시뮬레이션 모델을 쉽게 구현 가능하게 함에도 불구하고 여전히 리튬 이온 배터리의 출력 특성을 정확하게 예측함을 보여준다.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.207-214
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• 2012

This paper is to improve an identification ratio of tags by analyzing Slotted ALOHA, Dynamic Slotted ALOHA, Binary-tree and Query-tree and shortening the tag identification time in mobile RFID. Also, it enables the stable information transmission of tags by saving backscattering power of tags through shortening of identification time. As a result, this increases the available time of the battery and accessibility to a RFID service. For this, we proposed the energy-efficient tag anti-collision protocol for mobile RFID. The proposed scheme shows advanced result in identification time and collision counts. This scheme may be the first attempt for the mobile anti-collision.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.4
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• pp.501-508
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• 2019

In this paper, a study on a wireless check-up method of test equipment for captive flight test(CFT) was conducted. For CFT, test equipment is mounted on a POD, and check-up is carried on the test equipment's. For check-up the POD wirelessly, battery, power distribution unit, wireless communication devices were designed within the POD, and a check-up device is designed outside of the POD. Once the external check-up device sends a 'start signal' to the POD, it performs the overall check-up procedures and transmits the 'end signal' to the external check-up device. Detailed check-up results are stored in an internal storage device, and are possible to read from external check-up device if necessary, thereby improving the reliability of the wireless check-up. By implementing and applying these wireless check-up system, the reliability of the check-up was enhanced by dynamical and movable check-up, and safety is guaranteed as the check-up was carried without access to the aircraft.

• Journal of Energy Engineering
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• v.27 no.4
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• pp.92-97
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• 2018

This study deals with the numerical analysis for hood development to improve the cooling effect of the engine related components in engine room. Reducing the component temperature in engine room caused by a sudden temperature deviation can minimize the durability degradation of components. Therefore, in this study, numerical analysis for the development of the hood in engine room was carried out in four parts such as generator, battery, ECU and power steel oil which are relatively easy to control temperature among the main components in engine room. In order to verify the numerical analysis, experiments were conducted under the same conditions as those assumed in the numerical analysis.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2732-2753
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• 2019

With the application of wireless sensor networks in the fields of ecological observation, defense military, architecture and urban management etc., the security problem is becoming more and more serious. Characteristics and constraint conditions of wireless sensor networks such as computing power, storage space and battery have brought huge challenges to protection research. Inspired by the danger theory in biological immune system, this paper proposes an intrusion detection model for wireless sensor networks. The model abstracts expressions of antigens and antibodies in wireless sensor networks, defines meanings and functions of danger signals and danger areas, and expounds the process of intrusion detection based on the danger theory. The model realizes the distributed deployment, and there is no need to arrange an instance at each sensor node. In addition, sensor nodes trigger danger signals according to their own environmental information, and do not need to communicate with other nodes, which saves resources. When danger is perceived, the model acquires the global knowledge through node cooperation, and can perform more accurate real-time intrusion detection. In this paper, the performance of the model is analyzed including complexity and efficiency, and experimental results show that the model has good detection performance and reduces energy consumption.

• Journal of Korean Gerontological Nursing
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• v.20 no.3
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• pp.204-216
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• 2018

Purpose: The purpose of this study was to examine effects of a muscle strength reinforcement exercise program (MSREP) for older adult patients with hemodialysis (OAPHD) which was designed to improve health status and quality of life of these older adult patients. Methods: Participants were 40 patients with OAPHD: 20 in the experimental group and 20 in the control group. MSREP was conducted with the experimental group for 12 weeks at H geriatric hospital. An assessment was done to determine effects on physical performance, inflammation index, fatigue, muscle strength and quality of life. Short physical performance battery, C-Reactive Protein (CRP), visual analog scale for fatigue, object lifting' proposed by the Life Options Rehabilitation Advisory Council, sit-to-stand test, and quality of life index were used to gather data. Results: Between the 2 groups there was no significant difference in scores for physical performance, fatigue or quality of life. However, the 2 groups showed significant difference in CRP values and muscle power scores on post-test. Conclusion: Findings provide evidence for the potential utility of education for older adult patients with hemodialysis. Also, this program could allow these patients to increase muscle strength, and contribute to achieving better health conditions in OAPHD care.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.195-197
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• 2019

자동차용 배터리는 초기 용량의 80% 이하가 되면 교체하게 되며, 근간 폐배터리의 수가 폭발적으로 증가할 것으로 예측되고 있다. 폐배터리의 폐기로 인한 환경 파괴를 방지하고 자원을 재활용하기 위해서 자동차에서 나오는 폐배터리를 에너지저장장치(ESS)로 재사용 하는 것에 대한 관심이 높아지고 있다. 폐배터리를 ESS로 재구성하기 위해서는 폐배터리 모듈의 그레이딩을 통해 비슷한 성능의 모듈끼리 모아서 구성하는 것이 매우 중요하다. 배터리 모듈 간의 불균형은 전체 시스템의 성능을 저하시키며, 따라서 비슷한 성능과 잔존 수명을 가진 모듈을 골라내는 일은 폐배터리의 재사용에 있어서 첫 번째 선결 과제가 된다. 본 연구에서는 폐배터리의 상태 및 잔존수명평가를 위해 배터리 모듈의 임피던스 스펙트럼을 측정할 수 있는 장비를 개발하였다. 폐배터리 모듈에 AC 섭동을 인가하고 이를 측정하여 임피던스 스펙트럼을 계산할 수 있는 하드웨어와 소프트웨어를 개발하였다. 개발 장비는 60V이하의 폐배터리 모듈의 임피던스 스펙트럼을 0.1Hz에서 1kHz까지 측정 가능하며, 측정 결과를 바탕으로 커브 피팅을 통해 등가회로의 파라미터도 계산할 수 있다. SM3에서 얻어진 폐배터리 모듈을 이용하여 측정한 임피던스 스펙트럼을 상용장비인 BIM2로 측정한 결과를 비교하였고, Reduced Chi-Square를 이용한 분석결과 두 데이터가 거의 일치함을 알 수 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.587-590
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• 2019

This paper is about to improve the network life's reduction due to the deviation of sensor node and frequently change of network, the main problem of sensor network. The existing Scalable Topology Organization(STO)-based ZigBee Tree Topology Control Algorithm did not consider ways to consume power so the network lifetime is too short. Accordingly, per each round, electing a new parent node and consisting of the new network topology technique, The Cluster Header Selection, extending the network's overall lifetime. The OMNet++ Simulator yielded results from the existing STO Algorithm and the proposed Cluster Header Selection Technique in the same experimental environment, which resulted in an increase in overall network life by about 40% and an improvement of about 10% in performance in the remaining portion of the battery.