• Journal of Communications and Networks
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• 제7권4호
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• pp.462-470
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• 2005

We propose a multi-rate and multi-BEP transmission scheme using adaptive overlapping pulse-position modulator (OPPM) and optical power controller in optical code division multiple access (CDMA) networks. The proposed system achieves the multi-rate and multi-BEP transmission by accommodating users with different values of OPPM parameter and transmitted power in the same network. The proposed scheme has advantages that the system is not required to change the code length and number of weight depending on the required bit rate of a user and the difference of bit rates does not have so much effect on the bit error probabilities (BEPs). Moreover, the difference of transmitted powers does not cause the change of bit rate. We analyze the BEPs of the four multimedia service classes corresponding to the com­binations of high/low-rates and low/high-BEPs and show that the proposed scheme can easily achieve distinct differentiation of the service classes with the simple system configuration.

• 전기학회논문지
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• 제56권6호
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• pp.1170-1176
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• 2007

The conventional urodynamic monitoring is fulfilled by artificially filling a bladder with saline. Generally. it is difficult to evaluate the physiological functions of the storage and voiding of a bladder. With this aim, we constructed an ambulatory urodynamic monitoring (AUM) system and proposed a novel method estimating abdominal pressure by measuring bio-impedance variations. Our system was clinically evaluated for 10 patients. It turned out to be that as the intensity of the abdomen contraction increased, the amplitude of bio-impedance signal and the RMS value of EMG increased more as compared to those who observed during the rest mode. Also, we determined the optimum electrode pair for estimating the abdominal pressure using bio-impedance method and consequently compared with the conventional methods. Because impedance changes differ from a weight, a height, contractile force, volume of muscle and blood other or whatever of individuals, it was quantified in terms of impedance change, correlation coefficient and SNR Our results showed the optimum electrode pair (1,9) which could detect impedance changes due to the increase of the intensity in the abdominal pressure. The correlation coefficient and quadratic function between the RMS values of EMG and the impedance changes were 0.87 and $y=0.0014x^2+0.0620x+0.6958$, respectively. Thus, our system demonstrated that the abdominal pressure could be measured noninvasively and conveniently by simply estimating bio-impedance values. We propose that this optimum electrode configuration would be useful for the future studies involving the handy measurements of abdominal pressure with our suggested ambulatory urodynamics monitoring system.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권8호
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• pp.506-509
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• 2003

This paper describes the possibility of analyzing gait pattern from the changes of the lower leg electrical impedance. This impedance was measured by the four-electrode method. Two current electrodes were applied to the thigh, knee, and foot., and two potential electrodes were applied to the lateral, medial, and posterior position of human leg. The correlation coefficients of the joint angle and the impedance change from human leg movement was obtained using a electrogoniometer and 4ch impedance measurement system developed in this study. We found the optimal electrode position for knee and ankle joint movements based on high correlation coefficient, least interference, and maximum magnitude of impedance change. The correlation coefficients of the ankle, knee, and the hip movements were -0.913, 0.984 and 0.823, respectively. From such features of the human leg impedance, it has been made clear that different movement patterns exhibit different impedance patterns and impedance level. This system showed feasibility that lower leg movement could be easily measured by impedance measurement system with a few skin-electrodes.

• 대한조선학회논문집
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• 제42권1호
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• pp.10-17
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• 2005

Due to emission of vehicles during loading/unloading, ventilation system in Roll-on/Roll-off ship is inevitable; however it is very difficult to predict the ventilation performance before it is finally built in. Although the requirements for the ventilation system include air change rate and maximum allowable concentration of CO in the cargo holds, even prototype tests are hardly able to quantify the ventilation performance. In the present paper, a new method to assess the ventilation performance of Roll-on/Roll-off ship is proposed by using computational fluid dynamics. The air exchange is modeled by introducing multi-species transport of existing air In the holds and new air from the ventilation system. Conservation of multi-species as well as 3D Navier-Stokes equation are solved numerically in time dependent manner. Several cases of different configuration are considered. The results include predicted mass fraction of new air in the holds. It is also presented that CO concentration can be estimated based on the predicted air change performance. Due to the lack of experimental data, the computed results are not verified; however the proposed method can be applied as au assessment tool.

• 시스템엔지니어링학술지
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• 제8권2호
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• pp.19-25
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• 2012

As modern weapon systems have evolved into embedded software systems, the capability to develop, install, and maintain high-quality software products is becoming increasingly valuable in today's competitive aerospace and defense industry. It is desirable, especially for government-contracted projects whose end-users are military personnel, that specific types of software quality elements are assured early during product development; namely, functionality and usability. Motivated by this need to approach improving software quality from a user's perspective, this paper presents a case study that analyzes system-level software integration testing results for a weapon system indigenously developed in the Republic of Korea. Quantitative data, such as software defect ratios and configuration change rates, are computed to observe meaningful trends with respect to functionality - represented by tests designed to verify the system's electrical signal interfaces - and usability, which is evaluated in terms of how often the initial human-computer interface had to be re-designed. Insights gained from these exercises are subsequently presented as a set of "lessons learned" to take into account when developing new software items for complex weapon systems.

• 제어로봇시스템학회논문지
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• 제8권8호
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• pp.698-705
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• 2002

The redundant sensor configuration problem of inertial navigation system(INS) is considered and analyzed the navigation and fault detection performance according to various sensor configurations. We considered various kinds of redundant sensor configurations for symmetric, cone, and orthogonal configurations and compare the navigation and fault detection performance for the configurations. We show that the navigation and fault detection performance is not affected by the coordinate change for a fixed configuration.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.446-451
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• 2011

External vibration occurred during vehicle's movement can affect performance of communication equipment and reliability of internal critical components of it. Therefore, through environmental testing, verification is performed prior to system test in order to prevent these problems. In this study, anti-vibration design is applied to compensate for the failure in certain frequencies during environmental test. Through the dynamic analysis according to the changes of mount configuration, optimization of the mount assemble structure was performed.

• Journal of Electrical Engineering and Technology
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• 제4권1호
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• pp.13-18
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• 2009

Because the existing Human-Machine Interface (HMI) for the conventional substation cannot dynamically indicate the configuration information of the Substation Automation System (SAS). In this paper, an intelligent station HMI is proposed for IEC 61850 based substation. The program of the proposed HMI not only can automatically generate the layout of single line diagram, but can also indicate the communication network and functions of IEDs by reading SCL files. It greatly helps monitor the operation status, communication network and each IED dynamically, such as failure detection in SAS. Furthermore, this paper presents the possibility of developing new software for SAS with the full use of IEC 61850-6. Once the software is complete, there is no need to change it when the substation is upgraded or when it is migrated to other IEC 61850 based substations, which is a cost-effective solution.

• 조명전기설비학회논문지
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• 제28권3호
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• pp.26-31
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• 2014

High temperature fuel cell system, such as molten carbonate fuel cells(MCFC) and solid oxide fuel cells(SOFC), are capable of operating at MW rated power output. The power output change of high temperature fuel cell imposes the thermal and mechanical stresses on the fuel cell stack. To minimize the thermal-mechanical stresses on the stack and increase the systems reliability, we should divide the power plant configuration to several banks. However, the improvement of reliability in fuel cell power plant system causes an increase of the investment cost, for example, replacement costs, labor costs, and so on. For this reason - the balance between investment and reliability improvement - many studies about the appropriate level of investment have been conducted. In this paper, we evaluate the cost for operation and installation, the benefit for electric energy and thermal energy sales, and the system reliability for several cases : these cases relate with the bank configuration.

• 실천공학교육논문지
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• 제15권2호
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• pp.429-438
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• 2023

최근 4차 산업혁명 시대에 부응하여 스마트 팩토리 수요가 증가하고 있다. 스마트 팩토리는 기본적으로 방대한 데이터를 기반으로 하는 제조업으로 많은 데이터 처리를 위한 IT 서비스를 필요로 하게 되고 이는 데이터센터의 건립을 가속화하고 있다. 데이터센터의 전산장비는 발열부하와 사용시간 측면에서 일반적인 시설의 냉방 기술과는 다른 차원으로 접근이 필요하다. 본 연구는 최근 데이터센터 냉방 시스템 설계에서 검토해야 할 요인과 기술 변화 트렌드를 조사하고 사례기업의 시설 구성을 위한 각종 기술적 방식을 비교 검토하여 설계안을 결정하는 프로세스를 도출하고 결론에 해당하는 개념 설계안을 제시하고자 한다.