• 대한조선학회논문집
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• 제48권2호
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• pp.147-157
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• 2011

A RANS(Reynolds averaged Navier-Stokes) based numerical method is developed for the evaluation of ship resistance and self-propulsion performances. In the usability aspect of CFD for the hull form design, the field grid around practical hull forms is generated by solving a grid Poisson equation based on the hull surface grid generated from station offsets and centerline profile. A body force technique is introduced to model the effects of the propeller in which the propeller loads are obtained from potential flow analysis using an unsteady lifting surface method. The free surface is captured by using a two-phase level-set method and the realizable $k-{\varepsilon}$ model is used for turbulence closure. The hull attitude in vertical plane, i.e., trim and sinkage, is calculated by using a quasi-steady method and then considered in the computation by translating and rotating the grid system according to the values. For the validation of the proposed method, the numerical results of resistance tests for KCS, KLNG, and KVLCC1 and of self-propulsion test for KCS are compared with experimental data.

• 한국화재소방학회논문지
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• 제33권5호
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• pp.86-93
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• 2019

IoT 기술의 발달과 함께 소방시설의 변화는 가속화되고 있으며, 이 중 대표적인 변화는 소방시설과 스마트폰 앱을 연계한 대피안내시스템의 개발이다. 하지만 이와 관련된 선행연구들은 시스템의 구성에 초점을 두고 수행되고 있으며, 표준화된 피난안내도의 작성매뉴얼과 관련된 연구는 부족한 실정이다. 이에 본 연구진은 표준화된 스마트폰 피난안내도의 기준을 수립하기 위한 기초연구로서, 스마트폰 피난안내도의 구성요소별 표시방법의 유형과 크기에 따른 의사결정시간을 분석하였다. 선행연구 고찰과 법규 고찰을 통해 실험요소를 도출하였으며, 30명의 피실험자를 대상으로 구성요소 표시방법의 유형과 크기에 따른 의사결정시간을 분석하였다. 이후 통계검정을 통해, 스마트폰 피난 안내도 구성요소별 작성기준을 제시하였다.

• Physical Therapy Rehabilitation Science
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• 제4권1호
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• pp.38-43
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• 2015

Objective: To investigate and compare the size of the rectus femoris (RF), tibialis anterior (TA), and medial gastrocnemius (GMM) using ultrasound (US) imaging in young, elderly, and very elderly groups. Design: Cross sectional study. Methods: This study consisted of 25 young (age 20 years), 24 elderly (age 65-74 years), and 25 very elderly (age 75-90 years) people with no physical dysfunctions. The cross sectional area (CSAs) of the RF and muscle thickness of the TA and GMM were measured at rest and during contraction using an US system. Results: The CSA of the RF and thickness of the TA and GMM were significantly smaller in the elderly and very elderly groups than in the young group (p<0.05). There was a significant difference of the CSA of the RF at rest and during contraction between elderly and very elderly group (p<0.05). In the comparison of the TA and GMM thickness between elderly and very elderly groups, there were no significant differences except for the TA thickness during contraction. There was a significant difference in the percentage change in RF CSA among the three groups (p<0.05). Conclusions: Our results revealed loss of muscle mass in the RF, TA, and GMM in elderly and very elderly people (${\geq}65$ years old). In particular, the greatest age-related decline in muscle mass was observed for the RF. Furthermore, the CSA of the RF declined with aging in the very elderly groups (${\geq}75$ years old).

• 전자공학회논문지
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• 제53권1호
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• pp.51-58
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• 2016

반도체 제조공정의 발달로 칩의 성능은 더욱 향상되었으나 회로가 미세해지고 복잡해져 동작 환경에 의한 회로의 노화가 가속화 될 수 있다. 회로의 노화는 성능 저하로 나타나며, 결과적으로 시스템 오류를 발생 시킬 수 있다. 고신뢰 시스템에서는, 노화로 인한 오류가 큰 재난으로 이어질 수 있으므로, 사고를 예방하기 위한 오류 발생 예측 기술이 필수적이다. 본 논문에서는 회로의 정상동작 중에 성능 저하를 감지하여 오류를 예측 할 수 있는 모니터링 기법을 제시한다. 모니터링을 위한 별도의 회로를 추가하지 않고 경계 스캔 셀과 TAP 제어기를 재활용한 IEEE 1149.1 경계 스캔 기반의 온-라인 성능 저하 모니터링 방법을 제시한다. 시뮬레이션을 통하여 제안하는 성능 저하 모니터링 기법을 검증한다.

• 전기학회논문지
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• 제60권1호
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• pp.184-192
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• 2011

In this study, we introduce a identification methodology for FCM-based fuzzy model. The two underlying design mechanisms of such networks involve Fuzzy C-Means (FCM) clustering method and Particle Swarm Optimization(PSO). The proposed algorithm is based on FCM clustering method for efficient processing of data and the optimization of model was carried out using PSO. The premise part of fuzzy rules does not construct as any fixed membership functions such as triangular, gaussian, ellipsoidal because we build up the premise part of fuzzy rules using FCM. As a result, the proposed model can lead to the compact architecture of network. In this study, as the consequence part of fuzzy rules, we are able to use four types of polynomials such as simplified, linear, quadratic, modified quadratic. In addition, a Weighted Least Square Estimation to estimate the coefficients of polynomials, which are the consequent parts of fuzzy model, can decouple each fuzzy rule from the other fuzzy rules. Therefore, a local learning capability and an interpretability of the proposed fuzzy model are improved. Also, the parameters of the proposed fuzzy model such as a fuzzification coefficient of FCM clustering, the number of clusters of FCM clustering, and the polynomial type of the consequent part of fuzzy rules are adjusted using PSO. The proposed model is illustrated with the use of Automobile Miles per Gallon(MPG) and Boston housing called Machine Learning dataset. A comparative analysis reveals that the proposed FCM-based fuzzy model exhibits higher accuracy and superb predictive capability in comparison to some previous models available in the literature.

• KIEAE Journal
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• 제3권3호
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• pp.35-42
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• 2003

It is required impressive expression of urban night environment that makes city as the safe pleasant, convenient place for the economic activity, cultural pleasure and landmarks. This study aims to establish the proper direction to the outdoor lighting in Seoul by analyzing and comparing the lighting situation and policies among Seoul, Shanghai and Yokohama. 1986 Asian Game and 1988 Olympic Game became very important role of activation of outdoor lighting in Korea. Then, outdoor lighting were facilitated in the cultural heritages and bridges along Han river. Millenium Light Plan, Outdoor Lighting Field of Seoul Architectural Award, 2002 Lightscape Local Plan, hosting 2002 World Cup have been good opportunities for the improvement of outdoor lighting in Seoul. In China, outdoor lighting was introduced to the city of Shanghai according to the orders of the president in 1988. Outdoor lighting of Shanghai have created unique lighting with beautiful color and intensive brightness under the direction of city government. Outdoor lighting of Shanghai needs the standard of lighting design and improvement of lighting facilities. Outdoor lighting was introduced to Japan with 1964 Tokyo Olympic games. Urban outdoor lighting plan was carried out in Yokohama in 1986. In Yokohama, outdoor lighting of civilian and public facilities have been harmonized. And the city government of Yokohama established the committee of promotion of outdoor lighting in its government to support and manage the outdoor lighting with corporation of civilian organization. As the result of comparative analysis on Seoul, Shanghai, Yokohama, Seoul Metropolitan Government needs the criteria and incentive system of outdoor lighting.

• 한국통신학회논문지
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• 제29권4A호
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• pp.458-465
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• 2004

본 논문에서는 CMOS 공정을 사용하여 선형적으로 제어가 가능한 П모델 감쇄기를 구현하였고, 브릿지 T모델을 사용한 감쇄기를 제안하였다. CMOS 공정으로 코어의 수동소자를 트랜지스터로 구현하여 기존의 수동소자나 능동소자를 사용하는데 따른 문제점을 개선하였으며 GaAs MESFET공정의 문제점인 높은 비용 또한 해결하였다. П모델 감쇄기는 2-poly 4-metal 0.35$\mu\textrm{m}$ CMOS 공정을 사용하여 구현하였으며 기존의 수백 MHz의 동작 주파수범위를 DC-l㎓ 대역으로 향상시켰다. 또한 700$\mu\textrm{m}$${\times}$300$\mu\textrm{m}$ 로 면적을 줄였으며 일정한 주파수에서 감쇄 값과 제어 전압 사이의 선형적인 관계를 개선하였다. 제안된 브릿지 T모델 감쇄기는 П모델에서 동작주파수를 제한하던 매칭 특성을 향상시킴으로써 동작 주파수 템위를 DC-2㎓ 대역으로 넓혔다.

• Ocean Systems Engineering
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• 제7권2호
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• pp.143-155
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• 2017

For complex flexible structures such as nets, the determination of drag forces and its deformation is a challenging task. The accurate prediction of loads on cages is one of the key steps in designing fish farm facilities. The basic physics with a simple cage, can be addressed by the use of experimental studies. However, to design more complex cage system for various environmental conditions, a reliable numerical simulation tool is essential. In this work, the current load on a cage is calculated using a Morison-force model applied at instantaneous positions of equivalent-net modeling. Variations of solidity ratio ($S_n$) of the net and current speed are considered. An equivalent array of cylinders is built to represent the physical netting. Based on the systematic comparisons between the published experimental data for Raschel nets and the current numerical simulations, carried out using the commercial software OrcaFlex, a new formulation for $C_d$ values, used in the equivalent-net model, is presented. The similar approach can also be applied to other netting materials following the same procedure. In case of high solidity ratio and current speed, the hybrid model defines $C_d$ as a function of Re (Reynolds number) and $S_n$ to better represent the corresponding weak diffraction effects. Otherwise, the conventional $C_d$ values depending only on Re can be used with including shielding effects for downstream elements. This new methodology significantly improves the agreement between numerical and experimental data.

• 전자공학회논문지C
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• 제35C권10호
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• pp.22-29
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• 1998

본 논문에서는 휴대용 영상신호처리 시스템에 집적화할 수 있는 전류예측기와 모듈형 기준전류원을 이용한 10비트 저전력 전류구동 CMOS A/D 변환기를 설계하였다. 전류예측기와 모듈형 기준 전류원을 사용함으로써 2단 플래시구조를 갖는 A/D 변환기에 비해 비교기와 기준전류원의 개수를 줄일 수 있게 되었고, 따라서 설계된 A/D변환기의 저전력 동작이 가능하였다. 설계된 10비트 저전력 전류구동 CMOS A/D 변환기는 0.6㎛ n-well single-poly triple metal CMOS 공정을 사용하여 제작되었다. +5V 단일 공급전압하에서 동작할 때 측정된 전력소모는 94.4mW이며, 아날로그 입력 전류범위는 16㎂에서 528㎂로 측정되었으며, INL과 DNL은 각각 ±1LSB, ±0.5LSB이하로 나타났다. 또한 10MSamples/s의 변환속도를 나타내었고, 제작된 10비트 전류구동 CMOS 4/D 변환기의 유효 칩면적은 1.8㎜ x 2.4㎜이다.

• 전자공학회논문지
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• 제51권11호
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• pp.107-113
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• 2014

60GHz 무선 통신 시스템에 적용 가능한 전압 제어 발진기와 고속 4분주기를 65nm CMOS 공정을 사용하여 설계했다. 전압제어 발진기는 전류소스와 NMOS 차동쌍 LC구조로 설계하였으며 분주기는 차동 인젝션 록킹 구조에 베렉터를 추가하여 동작주파수 범위를 조절할 수 있는 구조로 설계했다. 전압 제어 발진기와 분주기에 모두 전류소스를 추가하여 전원잡음에 따른 위상잡음 특성을 개선하였다. 전압 제어 발진기는 64.36~67.68GHz의 동작범위가 측정됐고, 고속 4분주기는 전압 제어 발진기의 동작범위에 대해 정확한 4분주가 가능하며 5.47~5.97dBm의 높은 출력전력이 측정됐다. 분주기를 포함한 전압제어 발진기의 위상잡음은 1MHz 오프셋 주파수에서 -77.17dBc/Hz이고 10MHz 오프셋 주파수에서 -110.83dBc/Hz이다. 소모전력은 전원전압 1.2V에서 38.4mW 이다 (VCO 포함).