• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.3
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• pp.110-115
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• 2002

This paper proposes the adaptive fuzzy control system using the microprocessesor for high precision control of automation systems which exist non-linearities such as saturation, relays, hysteresis, and dead zones. The proposed system which provides the improvement in terms of the control region in transient and adaptive control, first used the frequence-locked mothed driving a system to generate a output voltage proportional to the frequency diffierence of relnence input signal and feedback signal for fast transient response,, and when the error reaches the preset value, used the adaptive fuzzy logic for precision control. The theoretical and experimental studies have been carried out. The presented results from the above investigation show considerable improved performance in the precision control of servo control systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.4
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• pp.758-765
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• 2008

Wide-spread deployment of infrastructure WLANs has made Wi-Fi an integral part of today's Internet access technology. WLANs suffer from degraded system throughput and each node's throughput fluctuates significantly in the saturation regime. In this paper, we propose a link layer traffic control mechanism which controls the offered load of DCF system. It is shown that the link layer traffic controller can improve DCF system throughput and reduce nodes' throughput fluctuation with properly controlled offered load. We propose a dynamic traffic control algorithm which can find an optimal offered load and show its performance improvement with ns-2 simulation.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.191-191
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• 2023

기후변화 대응을 위한 탄소 중립의 중요성이 대두되는 요즘, 생태계의 가장 큰 메탄 저장소로서 지구의 탄소 순환에 주요한 영향을 미치는 습지에 대한 이해는 필수적이다. 전지구 지면 모델인 Community Land Model(CLM)에 Functionally Assembled Terrestial Ecosystem Simulator(FATES) 외부 모듈을 함께 구동한 지면 생태계 모델 CLM-FATES는 지면 heterogeneity와 다양한 식생 종류를 고려하여 에너지 플럭스, 토양 수문, 생화학적 과정 등을 모의함으로써 탄소 동태 변화를 포함한 장기적 생태계 동태 변화 모의를 가능하게 한다. 본 연구는 CLM-FATES 모델을 미국 캘리포니아주 Mayberry Wetland (US-Myb)와 Twitchell East End Wetland (US-Tw4)에 적용하였다. 모델의 대기 입력 자료로는 FLUXNET-CH4에서 제공하는 에디 공분산 기반 플럭스 관측 자료를 사용하였다. 기존 CLM-FATES 모델은 토양이 장기간 포화 혹은 침수되어 지표 위 혹은 지표면 가까이 발달한 지하수면을 가지고 있는 습지의 수문학적 특성을 잘 반영하지 못해 정밀한 습지 생태계 동태 변화 모의에 한계를 가지고 있다. 본 연구에서는 CLM-FATES를 통한 보다 정확한 습지 생태계 모의를 위해 모델 내 토양 수문 관련 모듈을 수정하여 모델이 습지의 수문학적 특성을 반영할 수 있도록 하였다. 모델 구동 결과 도출한 잠열, 총일차생산량(Gross Primary Production: GPP)과 순생태계생산량(Net Ecosystem Production, NEP) 플럭스, 메탄 플럭스, 엽면적지수(Leaf Area Index; LAI)와 지표수 높이에 대해 관측값 대비 RMSE 및 R² 값을 계산하여 모의 결과의 적절성을 분석하였다. 이러한 모델 개선 경험을 바탕으로 추후 우리나라 습지 사이트에 모델을 적용하여 습지 탄소 동태 예측에 활용할 계획이다.

• Journal of the Korean Geotechnical Society
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• v.39 no.11
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• pp.53-62
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• 2023

The characteristics of unfrozen water content in frozen soils significantly impact the thermal, hydraulic, and mechanical behavior of the ground. A thorough analysis of the unfrozen water content characteristics of the target subsoil material is crucial for evaluating the stability of frozen ground. This study conducted indoor experiments to measure the freezing point and unfrozen water content of sandy soil while considering pore water salinity. Utilizing the experimental data, we introduced a novel empirical model to conveniently estimate the unfrozen water retention curve. Furthermore, the validity of the unfrozen water retention curve was assessed by comparing the experimental data with the results of a simulation model that utilized the proposed empirical model as input data.

• KIPS Transactions on Computer and Communication Systems
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• v.12 no.5
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• pp.171-180
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• 2023

The three major sleep disorders in Korea are snoring, sleep apnea, and insomnia. Lack of sleep is the root of all diseases. Some of the most serious potential problems associated with sleep deprivation are cardiovascular problems, cognitive impairment, obesity, diabetes, colitis, prostate cancer, etc. To solve these problems, the Korean government provided low-cost national health insurance benefits for polysomnography tests in July 2018. However, insomnia patients still have problems getting treated in terms of time, space, and economic perspectives. Therefore, it would be better for insomnia patients to be allowed to test at home. The measuring device can measure six biosignals (eye movement, tossing and turning, body temperature, oxygen saturation, heart rate, and audio). A gyroscope sensor (MPU9250, InvenSense, USA) was used for eye movement, tossing, and turning. The input range of the sensor was in 258°/sec to 460°/sec, and the data range was in the input range. Body temperature, oxygen saturation range, and heart rate were measured by a sensor (MAX30102, Analog Devices, USA). The body temperature was measured in 30 ℃ to 45 ℃, and the oxygen saturation range was 0% for the unused state and 20 % to 90 % for the used state. The heart rate measurement range was in 40 bpm to 180 bpm. The measurement of audio signal was performed by an audio sensor (AMM2742-T-R, PUIaudio, USA). The was -42 dB ±1 dB frequency range was 20 Hz to 20 kHz. The measured data was successfully received in wireless network conditions. The system configuration was consisted of a PC and a mobile app for bio-signal measurement and data collection. The measured data was collected by mobile phones and desktops. The data collected can be used as preliminary data to determine the stage of sleep and perform the screening function for sleep induction and sleep disturbances. In the future, this convenient sleep measurement device could be beneficial for treating insomnia.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.469-477
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• 2001

In this Paper. we describe a home health care service using electronic health questionnaires and routine checkup of vital signs Including ECG (Electrocardiography) , blood pressure. and SpO$_2$ (Oxygen Saturation) . This system is for patients at home with chronic diseases, discharged Patients, or any normal people for the Prevention of disease The service requires a home health care terminal and a PC with Interned connection installed at Patient home. The distance health care management center is equipped with a vital-sign and questionnaire interpreter as well as database, Web, and notification servers with UMS (Unified Messaging System). Participating Physician can access the servers at the center using a Web browser running on a PC available to them at any time. These components are linked together through various kinds of data and voice communication channels including PSTN (Public Switched Telephone Network) . CATV(Community Antenna TV) . Interned. and mobile communication network. Following the Physician's direction given to a Patient. he or she uses the home health care terminal to collect vital signs and fill out the questionnaire. When the terminal automatically transmits these data to the management center. the data interpreter and servers at the center process the information fo1lowing the Protocol implemented on the system. Physicians can retrieve and review data corresponding to their Patients and send back their diagnostic reports to the center. UMS at the center delivers the physician 's recommendation to the corresponding patient through the notification server. Patients can also reprieve and review their own records as well as diagnostic reports from physicians. The system Provides a new way of collecting diagnostic information and delivering doctor's recommendation to patients at home for their health management. Future works are needed in the development of new technology for measurements and interpretations of various vital signs .

• The KIPS Transactions:PartC
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• v.9C no.4
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• pp.531-542
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• 2002

An input and output buffering ATM switch conventionally operates in either Queueloss mode or Backpressure mode. Recently, a new mode, which is called Hybrid mode, was proposed to overcome the drawbacks of Queueloss mode and Backpressure mode. In Hybrid mode, when both the destined output buffer and the originfted input buffer are full, a cell is dropped. This thesis analyzes the cell loss rate and the cell delay of Queueloss, Backpressure and Hybrid modes in a switch adopting output-port expansion scheme under uniform traffic. Output-port expansion scheme allows only one cell from an input buffer to be switched during one time slot. If several cells switch to a same destined output port, the number of maximum transfer cells is restricted to K (Output-port expansion ratio). The simulation results show that if an offered load is less than 0.9, Hybrid mode has lower cell loss rate than the other modes; otherwise, Queueloss mode illustrates the lowest cell loss rate, which is a different result from previous researches. However, the difference between Hybrid and Queueloss modes is comparably small. As expected, the average cell delay in Backpressure mode is lower than those of Queueloss mode and Hybrid mode, since the cell delay due to the retransmission of higher number of dropped cells in Backpressure mode is not considered.

• Journal of the Korean GEO-environmental Society
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• v.9 no.1
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• pp.47-54
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• 2008

In this study, the effect of water content condition was investigated on the Mohr-Coulomb shear strength parameters which are commonly used as the input data in the soil slope analysis. For the purpose, a series of direct shear test was conducted in different water content conditions on the two types of weathered soils and a dam core material, obtained from the domestic slope construction sites and the dam construction site, respectively. The comparisons between the values of the Mohr-Coulomb ${\phi}_{peak}$ and $c_{peak}$, estimated from the relationships between the normal stress and the peak shear stress for the samples in the four different water content conditions (i.e., dry side, optimum, wet side, and saturated), showed that overall, the values of $c_{peak}$ decreased gradually while those of ${\phi}_{peak}$ did not vary much with increasing the water content. A rough estimate for the varying ratio of the values of ${\phi}_{peak}$ and $c_{peak}$ indicated that the values of $c_{peak}$ decreased by every 25% of the $c_{peak}$ values in dry side, while those of ${\phi}_{peak}$ were constant, as the water content condition changed from dry, optimum, and wet to saturated, respectively.

• The Journal of Engineering Geology
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• v.21 no.1
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• pp.57-64
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• 2011

Three-dimensional slope stability analysis was applied to a failed dual-lithology slope containing both granite and an andesitic dyke, taking account of the differences in shear strength of the different lithologies. A direct shear test of the soil-rock boundary was performed to examine the shear strength of two different types of failure surfaces within different lithologies, and a laboratory test was performed on an upper, weathered soil layer. The test results indicate that shear strength was lower at the soil-rock boundary than within the weathered soil layer. A representative geological section was subjected to two-dimensional slope stability analysis using a limit equilibrium method to assess whether the distribution of lithologies upon the slope influences the results of stability analysis. The results were then compared with those of three-dimensional slope stability analysis, for which input parameters can be varied according to the distribution of lithologies upon the slope. The three-dimensional analysis yielded safety factors of 1.26 under dry conditions and 0.55 under wet conditions, whereas the two-dimensional analysis yielded unstable safety factors of 0.92 and 0.32, respectively. These findings show that the results of stability analysis are affected by the distribution of different lithologies upon the slope. Given that the studied slope collapsed immediately after rainfall, it is likely that the results of the three-dimensional analysis are more reliable.

• Journal of the Korean Geotechnical Society
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• v.36 no.10
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• pp.33-39
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• 2020

A geological repository has been considered as an option for the disposal of high-level radioactive waste (HLW). The HLW is disposed in a host rock at a depth of 500~1,000 meters below the ground surface based on the concept of engineered barrier system (EBS). The EBS is composed of a disposal canister, buffer material, backfill material, and gap-filling material. The compacted bentonite buffer is very important since it can restrain the release of radionuclide and protect the canister from the inflow of ground water. The saturation of the buffer decreases because high temperature in a disposal canister is released into the surrounding buffer material, but saturation of the buffer increases because of the inflow of ground water. The unsaturated properties of the buffer are critical input parameters for the entire safety assessment of the engineered barrier system. In Korea, Gyeongju bentonite can be considered as a candidate buffer material, but there are few test results of the unsaturated properties considering temperature variation. Therefore, this paper conducted experiment of soil-water characteristic curve for the Gyeongju compacted bentonite considering temperature variation under a constant water content condition. The relative error showed approximately 2% between test results and modified van-Genuchten model values.