• Journal of the Korean Institute of Telematics and Electronics
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• v.9 no.3
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• pp.1-8
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• 1972

The characteristics of tunnel diode pair circuit biased within the negative resistance region has also the voltage-control type negative resistance region, and the voltage at the center point of negative resistance region is described as the square-wave relaxation oscillation. In this paper, the period T, positive duration T1, negative duration T2 of the pulse are obatined from the characteristic curve T, positive duration T1, negative duration T2 of the pulse are obtained from the characteristic curve and observed actually, considring the fact that the pulse width and the period of square-wave at the center point of the negative resistance region is able to be controlle dby the blas volgate. Mereover, the relationship between T, T1 or T2 and circuit parameters is searched for and the Circuit parameters that satisfy the conditions of T1-T2 being proportional to the variation of bias voltage with Teonstant are determined. Thereafter, the bias voltage and the signal voltage are inserted serially to the PWM circuit and the characteristics of that circuit is analyzed.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1072-1076
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• 2004

도시 개발에 의해 우수의 불투수지역 확대, 하천부지의 축소, 산림 및 유수지의 감소 등이 급속히 진행되어 하천유량의 변화, 지하수위의 저하, 용수의 고갈, 생태계의 파괴 등이 발생되어 왔다. 도시지역은 도시형 수해발생, 갈수시의 급수안전도 지하, 평시 하천유량의 감소, 공공수역의 수질악화, 지하수 오열 등 여러 가지 문제에 직면하고 있다. 이러한 문제들은 서울의 경우도 예외는 아니며 청계천 복원 사업과 더불어 그동안 방치되었던 도시유역의 물순환 체계를 분석할 필요가 있다. 본 연구에서는 SWAT 모형을 이용하여 도시하천 유역의 물순환을 해석하였다. SWAT모형은 미국 농무성 농업연구소(Agricultural Research Service, ARS)에서 개발된 모델로서, 내규모의 복잡한 유역에서 장기간에 걸친 다양한 종류의 토양과 토지이용 및 토지관리 상태에 따른 물과 유사 및 농업화학물질의 거동에 대한 토지관리 방법의 영향을 예측하기 위해 개발되었다. SWAT 모형은 물리적 이론에 근거한 연속모형으로 준분포형 (Semi-Distributed) 모형이다. 본 연구는 도시하천 유역의 물순환체계 변동을 고려한 물순환 정상화 기술을 개발하기 위한 기초단계로서, 청계천 유역에 내해 모형을 적용하였다. 청계천은 중랑천의 제1지류인 지방2급 하천으로 유역면적 $50.96km^2$, 유로연장 13.75km이며, 2003년 7월부터 ,5.9km의 본류구간에 대한 복원공사가 진행 중이다. 적용유역의 수문${\cdot}$기상${\cdot}$지하수 자료는 1993널 1월 1일 $\~$ 2002년 12월 31일까지의 서울 기상청 자료를 이용하였으며, 지형, 토양, 토지이용 자료는 기존에 구축된 GIS 자료를 이용하였다. 모형 적용결과, 도시하천 유역에 대한 SWAT 모형의 적용성을 확인할 수 있었으며 유역의 물순환계를 구성하는 강수, 지표수, 토양수, 지하수 및 하천수 등의 상호 관계 분석을 통해 장기간의 유역 물순환체계 변화를 분석할 수 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.2
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• pp.179-190
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• 1998

One of the most important topics of recent years is that a multimedia technology such as wireless ATM has been introduced in radio systems for video, voice and data transmission. A major problem in such systems is the occurrence of errors due to multipath fading or interference. To combat this problem, forward error correction (FEC) coding is commonly used as a means of eliminating these errors. This paper has analyzed theoretically the effect of fading to design effective wireless ATM system. The BER, CLR, and CER of wireless ATM system adopting FEC coding and diversity reception techniques have been derived in fading environment. Also, simulations of BER and CLR have been carried out and compared with the above theoretical results.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.2 s.302
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• pp.33-38
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• 2005

In this paper, the sensing unit of a non-invasive blood glucose sensor for home users, using a magneto-resonance absorption method, have been designed and manufactured. The sensor is capable of non-invasively determining blood glucose levels through measuring the 1H spin-lattice relaxation time in human body, The comparison of initial models, with different dimensions and shapes, for the sensing unit has led us to select the materials of the final model, which has adequate size and weight for home use. Through the design optimization using the FEM model, the dimension of final model has been determined to satisfy the required strength and uniformity of the magnetic field in the detecting area.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.6
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• pp.821-827
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• 2009

Human emotion can be reflected by their facial expressions. So, it is one of good ways to understand people's emotions by recognizing their facial expressions. General recognition system of facial expressions had selected interesting points, and then only extracted features without analyzing physical meanings. They takes a long time to find interesting points, and it is hard to estimate accurate positions of these feature points. And in order to implement a recognition system of facial expressions on real-time embedded system, it is needed to simplify the algorithm and reduce the using resources. In this paper, we propose a real-time recognition algorithm of facial expressions that project the grid points on an expression space based on Gabor wavelet feature. Facial expression is simply described by feature vectors on the expression space, and is classified by an neural network with its resources dramatically reduced. The proposed system deals 5 expressions: anger, happiness, neutral, sadness, and surprise. In experiment, average execution time is 10.251 ms and recognition rate is measured as 87~93%.

• Journal of Convergence for Information Technology
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• v.8 no.4
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• pp.9-14
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• 2018

The purpose of this study was to analyse the relationship between the characteristics of the patients who received oral antihyperglycemic drugs and their medical adherence in Korea. The study method was a cross-sectional study using the patient sample data of the Health Insurance Review and Assessment Service for 2016, and it was analyzed with 109 major components of diabetes drug. The medical adherence was slightly higher in male than female. The patriots & veterans(free) type had the highest medication adherence because they have low self burden to access medical institutions compared to other insurance types. It is expect that this study result will be used as a basic data to understand the burden of outpatients with health insurance and establish a policy to reduce of the self outpatients' burden with chronic diseases such as type 2 diabetes.

• Transactions of Materials Processing
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• v.33 no.3
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• pp.200-207
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• 2024

In this study, we developed a semi-analytical approach for the numerical analysis of residual stress in oxide scales formed on hot-rolled steels. The oxide scale, formed during the hot rolling process, experiences complex interactions due to thermal and mechanical influences, significantly affecting the material's integrity and performance. Our research focuses on integrating various stress components such as thermal stress, growth stress, and creep behavior to predict the residual stress within the oxide layer. The semi-analytical method combines analytical expressions for each stress component with numerical integration to account for their cumulative effects. Validation through instrumented indentation tests confirms the reliability of our model, which considers thermal expansion coefficient (CTE) differences, scale growth, and creep-induced stress relaxation. Our findings indicate that thermal stress resulting from CTE differences significantly impacts the overall residual stress, with growth stress contributing a compressive component during cooling, and creep behavior playing a minor role in stress relaxation. This comprehensive approach enhances the accuracy of residual stress prediction, facilitating the optimization of material design and processing conditions for hot-rolled steel products.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.157-170
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• 2013

In this study, flood runoff characteristics is analyzed according to subbasin divisions by physically based rainfall-runoff model and appropriate number of subbasin divisions is suggested for midsize test basins. The Clark method, a lumped model in HEC-HMS, and the ModClark method, a semi-distributed model are used to simulate rainfall-runoff processes on Andong-reservoir basin, Imha-reservoir basin, and Pyeongchang river basin. The test basins were divided into nine subdivision cases by equal-area subdivision method such as single basin, 3, 5, 6, 7, 9, 10, 12, and 15 subbasins, and compared the simulated and observed values in terms of the peak flow and the peak time. The simulation results indicated that the peak flows tended to increase and the peak time shifted earlier as the number of subdivisions increased and this tendency weakened after the certain number of subdivisions. In this research, the specific number of subdivision was defined as the minimum number of subdivision considering both peak flow and peak time. Consequently, the minimum number of subdivisions is determined as 5 for Andong and Imha reservoir basins and 7 for Pyeongchang river basin.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.169-179
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• 2013

Well testing in unconventional reservoirs, such as tight or shale gas formations, presents considerable challenges. It is difficult to estimate the reservoir properties in ultra-low permeability formation because of poor inflow prior to stimulation and excessive test duration. Moreover, radial flow may not develop in hydraulically fractured horizontal wells. For these reasons, the cost of test is high and the accuracy is relatively low. Accordingly, industry is turning to an alternate testing method, diagnostic fracture injection test (DFIT), which is conducted prior to the main hydraulic fracture treatments. Nowadays, DFIT are regarded as the most practical way to obtain good estimates of reservoir properties in unconventional reservoirs. Various methods may be used for interpreting DFIT data. This paper gives an explanation of those methods in detail and examines three actual field data. These show how various analysis methods can be applied to consistently interpret fracture closure pressure and time, as well as before and after closure flow regimes and reservoir properties from field data.

• Journal of Digital Contents Society
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• v.15 no.6
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• pp.683-699
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• 2014

This study examines the key factors which influence the strategic consideration and intention of adoption of internet marketing of small-and-medium sized companies, based on theoretical consideration of innovation diffusion theory and previous studies related. The result of analysis shows that the degree of market competitiveness, customer dependency, the level of internet marketing knowledge and experience have significant effects on both of strategic consideration and adoption intention for internet marketing. Also, learning commitment has negative influence on strategic consideration only, while environmental dynamism does on adoption intention. Comprehensively, the findings implies that firms consider selection of internet marketing to reduce the severity of competitiveness and that firms which has more knowledge or experience about internet marketing seems to consider selection of internet marketing through the perception of the effects of internet marketing or possible access to internet marketing. Based on the findings that the level of internet marketing knowledge and experience have much significant effects on both of strategic consideration.