• KIEE International Transactions on Power Engineering
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• 제3A권1호
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• pp.27-34
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• 2003

In this paper, the power conditioner composed of the stand-alone single-phase squirrel cage rotor type self-excited induction generator (SEIG) driven by prime movers such as a wind turbine and a micro gas turbine (MGT) is presented by using the steady-state circuit analysis based on the two nodal admittance approaches using the per-unit frequency in addition to a new state variable defined by the per-unit slip frequency along with its performance evaluations for the stand-alone energy utilizations. The stande-alone single-phase SEIG operating performances in unregulated voltage control loop are then evaluated on line under the conditions of the speed change transients of the prime mover and the stand-alone electrical passive load power variations with the simple theoretical analysis and the efficient computation processing procedures described in the part I of this paper. In addition, a feasuible PI controlled feedback closed-loop voltage regulation scheme of the stande-alone single-phase SEIG is designed on the basis of the static VAR compensate. (SVC) and discussed in experiment for the promising stand-alone power conditioner. The experimental operating performance results are illustrated and give good agreements with the simulation ones. The simulation and experimental results of the stand-alone single-phase SEIG with the simple SVC controller for its stabilized voltage regulation prove the practical effectiveness of the additional SVC control loop scheme including the PI controller with fast response characteristics and steady-sate performance improvements.

• Nutrition Research and Practice
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• 제13권2호
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• pp.159-168
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• 2019

BACKGROUND/OBJECTIVES: Over the past few decades, Malaysia has been experiencing an increased prevalence of overweight and obesity that threatens the health of Malaysians. Poor dietary intake is one of the major contributors to the development of obesity and many non-communicable diseases. The dietary intakes of adults in Malaysia were assessed to determine the association between the dietary intake variables and the body mass index (BMI) and waist circumference (WC) measurements. This study examined whether the dietary intake achieved the recommended nutritional guidelines and compared the intakes between both sexes. SUBJECTS/METHODS: The height, weight, and WC of four-hundred-and-ninety adults (n = 490) in Malaysia were measured using standard procedures. The three-day 24-hour dietary recalls were conducted on 422 out of the 490 adults and their dietary intakes were evaluated in detail. The selected dietary intake variables were used to determine the associations with the obesity indicators. RESULTS: Among the participants, 52.8% were overweight or obese. After data analysis, the mean energy intake was 1,550 kcal/day, in which male participants had a significantly higher energy and macronutrients intake than females. Protein consumption and its percentage of energy contribution exceeded the recommended range. The consumption of fruits, vegetables, and milk and milk products were lower than the recommended number of servings for a healthy diet. The male participants consumed significantly more servings of carbohydrate-based foods, meat, and fats, oils, and sweets than females. Among the selected dietary intake variables, only the carbohydrate intake was negatively associated with the BMI (Estimate b = -0.008) and WC measurements (Estimate b = -0.019) after adjusting for covariates. CONCLUSIONS: This study evaluated the dietary intakes of a sample of Malaysian adults and its association with the obesity indicators. The results highlight the need for improvements and modifications of the dietary intake of Malaysians to reduce the overweight and obesity rates.

• 한국안전학회지
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• 제34권1호
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• pp.62-69
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• 2019

Korean shipbuilding companies have taken many efforts for safety over the years by developing Health, Safety & Environment (HSE) Management Systems, Procedures, Training, and studying Programs for prevention of incidents. As a result, the shipbuilding industry has succeeded in reducing overall injury rates. Nevertheless, the industry also noticed that incident rates are still not at zero and more importantly, serious injuries and fatalities are still occurring. One factor that may be attributing to this is the lack of managing potential severity during incident investigations, most incident investigations are implemented based on the actual result. Generally, each shipbuilding company develops their customized incident investigation programs and these are also commonly being focused on actual result. This study aimed to develop a shift in strategy toward safety to classify the criteria of potential severity from any incidents and manage that to prevent any recurrence or causing any serious injuries or fatalities in the shipbuilding industry. Several global energy companies have already developed potential severity management tools and applied them in their incident investigations. In order to verify the necessity of improvement for current systems, a case study and comparative analysis between a domestic shipbuilding company and several global energy companies from foreign countries was implemented and comparison of two incident investigation cases from specific offshore projects was conducted to measure the value of a potential severity system. Also, a checklist was established from the data of fatalities and serious injuries in recent 5 years that occurred in Korea shipbuilding industry and a proposal to verify high potential incidents in the incident investigation process and comparative analysis between the assessment by appling proposed checklist and the assessment from a global energy company by using their own system was implemented. As a measure to prevent any incidents, it is required to focus on potential severity assessment during the incident investigation rather than to only control actual result. Hence, this study aims to propose a realistic plan which enables to improve the existing practices of incident investigation and control in the shipbuilding industry.

• Journal of Radiation Protection and Research
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• 제38권2호
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• pp.100-105
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• 2013

우리나라는 상용 및 연구용 원자로 수출, 그리고 국내 원자력 발전소의 추가 건설로 인하여 원자력 분야 전문 인력의 수요가 급증하고 있다. 이에 따라 원자력 인력 양성이 중요한 현안으로 대두되고 있다. 원자력 관련 주요 기관은 교육에 대한 절차와 자원들이 체계적으로 갖추어져 있지만 중소기업은 규모가 영세한 여건 때문에 교육이 어려울 수밖에 없는 실정이다. 본 연구에서는 '교육의 체계적인 접근법(Systematic Approach to Training: SAT)'을 도입하여 교육과정을 개발하고자 하였다. 이에 따라 중소기업을 대상으로 설문조사를 하였으며 그 결과를 바탕으로 방사선 분야 교육과정으로서 '방사선 기초 시범 교육'을 개발하고 운영한 결과를 요약하였다. '방사선 기초 시범 교육'은 기대감, 만족도, 강사 역량 등에서 4.0 (5.0 만점 기준) 이상의 높은 교육 참여자 평가 결과를 나타냈다. 수요 분석에 기반을 둔 '방사선 기초 시범 교육' 과정 개발 경험은 향후 수요 분석에서 나타난 원자력 발전 분야 및 ASME code 등의 교육과정 개발에 활용될 것이다.

• Earthquakes and Structures
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• 제22권2호
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• pp.185-201
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• 2022

Structural Health Monitoring (SHM) is used to provide reliable information about the structure's integrity in near realtime following extreme incidents such as earthquakes, considering the inevitable aging and degradation that occurs in operating environments. This paper experimentally investigates an integrated wireless sensor network (Wi-SN) based monitoring technique for damage detection in concrete structures. An effective SHM technique can be used to detect potential structural damage based on post-earthquake data. Two novel methods are proposed for damage detection in reinforced concrete (RC) building structures including: (i) Jerk Energy Method (JEM), which is based on time-domain analysis, and (ii) Modal Contributing Parameter (MCP), which is based on frequency-domain analysis. Wireless accelerometer sensors are installed at each story level to monitor the dynamic responses from the building structure. Prior knowledge of the initial state (immediately after construction) of the structure is not required in these methods. Proposed methods only use responses recorded during ambient vibration state (i.e., operational state) to estimate the damage index. Herein, the experimental studies serve as an illustration of the procedures. In particular, (i) a 3-story shear-type steel frame model is analyzed for several damage scenarios and (ii) 2-story RC scaled down (at 1/6th) building models, simulated and verified under experimental tests on a shaking table. As a result, in addition to the usual benefits like system adaptability, and cost-effectiveness, the proposed sensing system does not require a cluster of sensors. The spatial information in the real-time recorded data is used in global damage identification stage of SHM. Whereas in next stage of SHM, the damage is detected at the story level. Experimental results also show the efficiency and superior performance of the proposed measuring techniques.

• Advances in concrete construction
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• 제9권3호
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• pp.327-335
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• 2020

Concrete pipes are considered important structures playing integral role in spread of cities besides transportation of gas as well as oil for far distances. Further, concrete structures under seismic load, show behaviors which require to be investigated and improved. Therefore, present research concerns dynamic stress and strain alongside deflection assessment of a concrete pipe carrying water-based nanofluid subjected to seismic loads. This pipe placed in soil is modeled through spring as well as damper. Navier-Stokes equation is utilized in order to gain force created via fluid and, moreover, mixture rule is applied to regard the influences related to nanoparticles. So as to model the structure mathematically, higher order refined shear deformation theory is exercised and with respect to energy method, the motion equations are obtained eventually. The obtained motion equations will be solved with Galerkin and Newmark procedures and consequently, the concrete pipe's dynamic stress, strain as well as deflection can be evaluated. Further, various parameters containing volume percent of nanoparticles, internal fluid, soil foundation, damping and length to diameter proportion of the pipe and their influences upon dynamic stress and strain besides displacement will be analyzed. According to conclusions, increase in volume percent of nanoparticles leads to decrease in dynamic stress, strain as well as displacement of structure.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.169-176
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• 2002

Axial crushing behavior of cylindrical shell Is utilized in the braking of the high-velocity impacting object. In this paper, truncated cone shape brake device is introduced. That is, thickness of the shell is increased gradually from the impacting end to the other end. A detailed experimental investigation on the quasi-static axial crushing behavior of truncated cone type brake devices has been performed. Specimens of various shape were tested to check the influence of design parameters such as length, radius, mean thickness, and conical angle of cylinder. Influence of the material properties were also investigated by adopting aluminum, low carbon steel, and stainless steel as constructing materials. By analyzing deformation procedures of the specimens, it is seen that conical angle influence the deformation mode and the sequence of the wrinkles generation. Braking distance and mean braking force of each specimen were predicted based on the crushing load measured from the tests.

• 한국안전학회지
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• 제21권3호
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• pp.137-142
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• 2006

Quantification of error possibility, in an HRA process, should be performed so that the result of the qualitative analysis can be utilized in other areas in conjunction with overall safety estimation results. And also, the quantification is an essential process to analyze the error possibility in detail and to obtain countermeasures for the errors through screening procedures. In previous studies for the quantification of error possibility, nominal values were assigned by the experts' judgements and utilized as corresponding probabilities. The values assigned by experts' experiences and judgements, however, require verifications on their reliability. In this study, the validity of new error possibility values in new MCR design was verified by using the Onisawa's model which utilizes fuzzy linguistic values to estimate human error probabilities. With the model of error probabilities are represented as analyst's estimations and natural language expression instead of numerical values. As results, the experts' estimation values about error probabilities are well agreed to the existing error probability estimation model. Thus, it was concluded that the occurrence probabilities of errors derived from the human error analysis process can be assessed by nominal values suggested in the previous studies. It is also expected that our analysis method can supplement the conventional HRA method because the nominal values are based on the consideration of various influencing factors such as PSFs.

• 한국정밀공학회지
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• 제18권3호
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• pp.99-106
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• 2001

Model trains should have very similar motion characteristics to real trains in order to provide realistic feeling to their operators. Main purpose of dynamic analysis of model trains is to predict velocities in straight and circular tracks and estimate stopping distance after power shut off. Equations of motion for a model train are derived that relates velocity, traction, rolling resistance, and pulling force. Also, energy equations for calculating stopping distance after power shut off are derived. Experiments with model trains are preformed to measure velocity, rolling resistance, slip, and stopping distance. The results are compared with the prediction based on the equations of motion, and they showed good agreement. It can be concluded that the prediction is more accurate when the slip between wheel and rail is accounted for. The analysis procedures can be applied to determining various design factors in model trains.

• 대한전기학회논문지:전력기술부문A
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• 제53권6호
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• pp.340-349
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• 2004

Recently, the needs and concerns for the power loss are increasing according to the energy conservation at the level of the national policies and power utilities's business strategies. Especially, the issue of the power loss is the main factor for the determining the electric pricing rates in the circumstances of the deregulation of electrical industry. However, because of the lacking of management for power loss load factors (LLF), it is difficult to make a calculation for the power loss and to make a decision for the electric rates. And loss factor(k-factor), which is a most important factor for calculation of the distribution power loss, has been used as a fixed value of 0.32 since the fiscal year 1973. Therefore, This study presents the statistical calculation methods of the loss factors classified by load types and seasons by using the practical data of 65 primary feeders which are selected by proper procedures. Based on the above the algorithms and methods, the optimal method of the distribution loss management classified by facilities such as primary feeders, distribution transformers and secondary feeders is presented. The simulation results show the effectiveness and usefulness of the proposed methods.