• Journal of the Society of Naval Architects of Korea
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• v.48 no.2
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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.

• Fire Science and Engineering
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• v.33 no.5
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• pp.86-93
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• 2019

Previous studies related to evacuation guidance systems are focused on the system construction, and research on manual of the standard evacuation map is insufficient. Therefore, this research is a basic study to establish the standard evacuation map, and analyzed the decision-making time according to the type and size for each component of the evacuation map. Experimental elements were derived through the review of previous studies and legal regulations. After that, decision-making time was analyzed according to the type and size of the component display method. An experiment was conducted to analyze the decision-making time according to the type and size of the component display method. Afterwards, through the statistical test, the evacuation map guidelines for smartphones were proposed.

• Physical Therapy Rehabilitation Science
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• v.4 no.1
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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).

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.1
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• pp.51-58
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• 2016

As semiconductor technology has developed, device performance has been improved. However, since device structures became smaller, circuit aging due to operational and environmental conditions can be accelerated. Circuit aging causes a performance degradation and eventually a system error. In reliable systems, a failure due to aging might cause a great disaster. Therefore, these systems need a performance degradation prediction function so that they can take action in advance before a failure occurs. This paper presents an on-line circuit performance degradation monitoring scheme for predicting a failure by detecting performance degradation during circuit normal operation. In our proposed scheme, IEEE 1149.1 output boundary scan cells and TAP controller are reused. The experimental result shows that the proposed architecture can monitor the performance degradation during normal operation without stopping the circuit.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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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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• v.3 no.3
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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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.458-465
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• 2004

To reaffirm the use of a mainstream CMOS process for designing passive-like attenuator structures, a linearly controlled variable attenuator is realized with 0.35${\mu}{\textrm}{m}$ 2-poly 4-metal CMOS process. It uses the П configuration for large attenuation range and suitable matching property. Compared to conventional passive-like CMOS attenuators, it is demonstrated that this work advances the frequency band from MHz to ㎓ (DC- l㎓), and reduces the size to 700${\mu}{\textrm}{m}$${\times}$300${\mu}{\textrm}{m}$.. Both simulation results and test results are provided. They show the improved linear relation between attenuation and control voltage. It is very useful in CDMA or GSM band, which uses under 1㎓ frequency band. An alternative topology, Bridged-T configuration, is proposed to get over the limit of applications by elevating operation bandwidth. The proposed topology covers over DC-2㎓ frequency band, which means that the proposed architecture can cover the tripleband (800MHz CDMA/GSM, 1.5㎓ GPS, 1.9㎓z PCS system) in applications as well. The simulation results are provided.

• Ocean Systems Engineering
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• v.7 no.2
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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.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.10
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• pp.22-29
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• 1998

In this paper, an 10 bit current-mode CMOS A/D converter with a current predictor is designed with a CMOS process to be integrated into a portable image signal processing system. A current predictor let the number of comparator reduce to 70 percent compared with the two step flash architecture. The current magnitude of current reference is reduced to 68 percent with a modular current reference. The designed 10 bit Low-power current-mode CMOS A/D converter with a current predictor is simulated with HSPICE using 0.6$\mu\textrm{m}$ N-well single-poly triple-metal CMOS process parameters. It results in a conversion rate of 10MSamples/s. A power consumption is measured to be 94.4mW at single +5V supply voltage. The 10 bit A/D converter fabricated using the same process occupies the chip area of 1.8mm x 2.4mm.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.11
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• pp.107-113
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• 2014

A VCO (Voltage Controlled Oscillator) and a divide-by-4 high speed frequency divider are implemented using 65nm CMOS technology for 60GHz wireless communication system. The mm-wave VCO was designed by NMOS cross-coupled LC type using current source. The architecture of the divide-by-4 high speed frequency divider is differential ILFD (Injection Locking Frequency Divider) with varactor to control frequency range. The frequency divider also uses current sources to get good phase noise characteristics. The measured results show that the VCO has 64.36~67.68GHz tuning range and the frequency divider divides the VCO output by 4 exactly. The high output power of 5.47~5.97dBm from the frequency divider is measured. The phase noise of the VCO including the frequency divider are -77.17dBc/Hz at 1MHz and -110.83dBc/Hz at 10MHz offset frequency. The power consumption including VCO is 38.4mW with 1.2V supply voltage.