• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.888-895
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• 2003

Combustion chamber crevices in SI engines are identified as the largest contributors to the engine-out hydrocarbon emissions. The largest crevice is the piston ring-pack crevice. A numerical simulation method was developed, which would allow to predict and understand the oxidation process of piston crevice hydrocarbons. A computational mesh with a moving grid to represent the piston motion was built and a 4-step oxidation model involving seven species was used. The sixteen coefficients in the rate expressions of 4-step oxidation model are optimized based on the results from a study on the detailed chemical kinetic mechanism of oxidation in the engine combustion chamber. Propane was used as the fuel in order to eliminate oil layer absorption and the liquid fuel effect. Initial conditions of the burned gas temperature and in-cylinder pressure were obtained from the 2-zone cycle simulation model. And the simulation was carried out from the end of combustion to the exhaust valve opening for various engine speeds, loads, equivalence ratios and crevice volumes. The total hydrocarbon (THC) oxidation in the crevice during the expansion stroke was 54.9% at 1500 rpm and 0.4 bar (warmed-up condition). The oxidation rate increased at high loads, high swirl ratios, and near stoichiometric conditions. As the crevice volume increased, the amount of unburned HC left at EVO (Exhaust Valve Opening) increased slightly.

• Journal of Biosystems Engineering
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• 제26권2호
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• pp.155-162
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• 2001

The greenhouse heating system with heat pump was built for development of simulation model and validation. The computer simulation model for the system to predict temperature of air and soil and moisture content of soil in the greenhouse were developed, and its validity was justified by actual data. From the analysis of experimentally measured data and the simulation output, following results were obtained. 1. The expected values of inside air temperature for the heating system with heat pump were very much close to the experimental values. 2. In the heating system with heat pump, the expected values of day time surface temperature of soil by computer simulation were very much similar to the measured values, but those of night time were higher than the measured value by at most 2.0$\^{C}$. 3. The simulation model predicted temperature of greenhouse film as of 1$\^{C}$ below than the mean value of ambient air and greenhouse air temperature. 4. Heat loss value of daytime was found to be larger than that of nigh as much as 1.3 to 2.3 times for the heating system with heat pump. 5. In the heating system with heat pump, when the lowest ambient temperature was -8$\^{C}$∼-7$\^{C}$ the air temperature of greenhouse was 5$\^{C}$∼6$\^{C}$, thus the heat pump heating system contributed in greenhouse heating by 13$\^{C}$.

• The Journal of Asian Finance, Economics and Business
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• 제7권11호
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• pp.393-400
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• 2020

Banking service is provided by a bank that allows its customers to conduct banking transactions and so the purpose of this study was to identify the factors that influenced the behavioral intention to accept and use banking services in Vietnam. The research methodology was implemented through two steps: qualitative research and quantitative research. Qualitative research was conducted with a sample of 30 people. Quantitative research was carried out as soon as the question was edited from the test results with a sample of 217 customers living in Ho Chi Minh City, Vietnam. The research model was proposed from the studies of the behavioral intentions to accept and use banking service. The reliability and validity of the scale were evaluated by Cronbach's Alpha, Average Variance Extracted (Pvc), and Composite Reliability (Pc). The model selection of AIC showed that the behavioral intention to accept and use banking service was impacted by four components. The outcomes showed that the model of research intended to accept and use banking services in Ho Chi Minh, Vietnam showing the effects of 4 scales is built as perceived ease of use, trust, social norm, and innovation about banking services.

• 한국주거학회논문집
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• 제22권3호
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• pp.101-111
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• 2011

This study was conducted to investigate the indiscriminate development occuring as a result of high-density land use per lot in residential areas of Seoul, which mainly consist of detached houses. The primary goals of this study were: (1) to suggest a block unit development method as an alternative architectural method of the current uniform development, in which high-rise and high-density apartments are usually built; and (2) to check the feasibility of the suggested method. Based on the analyses of the existing block composition types of residential areas, the prerequisite planning indices for applying a collective housing model were investigated. Subsequent to applying a collective housing type within each unit block, the collective housing model was analyzed. The results of the analyses showed that indiscriminate development was rampant in detached urban houses areas, and more than 70% of the buildings constructed before the 1980s needed re-development. The feasibility of the models was investigated depending on the models of low-rise and high-density collective housing, which utilize various block arrangements such as the court type, linear type, villa type, and composite type. The results of this study showed that the newly applied low-rise and highdensity multiple dwelling housing model in urban individual residential area significantly contributed to creating a good living environment in terms of both physical and psychological aspects.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2901-2909
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• 2020

Thermal creep is a key property of zircaloy cladding. CZ developed by CGN is a new zircaloy used as PWR fuel cladding. This research is devoted to investigating the thermal creep behavior of CZ and build the thermal creep model of CZ. Twenty internal pressure creep tests were conducted, and the ranges of temperature and Tresca stress were 320-430 ℃ and 70-300 MPa, respectively. Real-time creep data were analyzed by separating primary creep and steady-state creep. Based on Soderberg model and creep test data, CZ thermal creep model is derived. As a whole, the mean value and the standard deviation of P/M of CZ saturated primary creep strain are very close to these from steady-state creep rate, however, the predictive effect of primary creep is less satisfactory. Four conditions, where there exists large deviation between predicted values and test data, are 320 ℃ and 300 MPa, 350 ℃ and 190 MPa, 380 ℃ and 160 MPa, 380 ℃ and 190 MPa, respectively. As primary creep was much smaller than steady-state creep in long-time operation, the thermal creep model built can be applied to predict the thermal creep behavior of CZ cladding.

• Asia pacific journal of information systems
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• 제29권1호
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• pp.35-49
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• 2019

The paper attempts to document the application of relevant Machine Learning (ML) models on Yelp (a crowd-sourced local business review and social networking site) dataset to analyze, predict and recommend business. Strategically using two cloud platforms to minimize the effort and time required for this project. Seven machine learning algorithms in Azure ML of which four algorithms are implemented in Databricks Spark ML. The analyzed Yelp business dataset contained 70 business attributes for more than 350,000 registered business. Additionally, review tips and likes from 500,000 users have been processed for the project. A Recommendation Model is built to provide Yelp users with recommendations for business categories based on their previous business ratings, as well as the business ratings of other users. Classification Model is implemented to predict the popularity of the business as defining the popular business to have stars greater than 3 and unpopular business to have stars less than 3. Text Analysis model is developed by comparing two algorithms, uni-gram feature extraction and n-feature extraction in Azure ML studio and logistic regression model in Spark. Comparative conclusions have been made related to efficiency of Spark ML and Azure ML for these models.

• 한국수소및신에너지학회논문집
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• 제28권1호
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• pp.98-105
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• 2017

In recent years, compression ignition engine has been equipped with some control devices such as common rail injection system and turbocharger. In order to control the large number of input parameter appropriately in consideration of $NO_x$, HC and engine power as the engine output objectives. The model construction which reproduces the characteristic value of $NO_x$, HC and engine power from input parameter is needed. In this research, the stepwise method was applied to construct the compression ignition engine model. By using the preliminary experimental data of single cylinder compression ignition engine, the prediction model of $NO_x$, HC and engine power on single injection compression ignition engine was built and compared with the main experimental data.

• 응용통계연구
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• 제11권1호
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• pp.65-81
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• 1998

많은 실증분석에 사용되고 있는 연립방정식모형은 연구대상분야의 구조를 더욱 현실에 가깝게 표현하고 또 상세한 분석을 위해 점차 복잡해지고 대형화되어 가는 추세다. 그러나 이러한 다중방정식체계의 설정시, 각 회귀방정식이 결합되어 동시에 추정될 때 발생할 수도 있는 모형체계의 구조적 불안정성으로 인해 추정된 모형의 사용 및 그에 따른 분석은 오류를 가져올 수 있다. 특히 시뮬레이션 수행이 무의미해질 가능성이 있음에도 연립방정식모형을 사용하는 대부분의 연구들이 이러한 모형의 구조적 안정성문제를 간과하고 있는 실정이다. 따라서 본 연구에서는 동태적 관점에서 모형체계의 안정성 진단을 위한 조건을 제시하여 보고, 실제의 연립방정식모형을 예로 들어 적용시켜 본 후 그 결과가 모형의 구조적 특징에 관해 어떠한 유용한 정보를 제공하여 주는가를 추가로 분석하여 보았다.

• Advances in Computational Design
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• 제2권4호
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• pp.333-348
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• 2017

Inspections of ancient metallic bridges have illustrated fatigue cracking in riveted connections. This paper presents a comparison between two alternative finite element (FE) models proposed to predict the fatigue strength of a single shear and single rivet connection. The first model is based on solid finite elements as well as on contact elements, to simulate contact between the components of the connection. The second model is built using shell finite elements in order to model the plates of the riveted connection. Fatigue life predictions are carried out for the shear splice, integrating both crack initiation and crack propagation lives, resulting from the two alternative FE models. Global fatigue results, taking into account several clamping stresses on rivet, are compared with available experimental results. Proposed comparisons between predictions and experimental data illustrated that the proposed two-stage model yields consistent results.

• Structural Engineering and Mechanics
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• 제58권5호
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• pp.905-929
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• 2016

This paper assesses efficiency of the continuum method as the idealized system of building structures. A modified Coupled Two-Beam (CTB) model equipped with classical and non-classical damping has been proposed and solved analytically. In this system, complementary (non-classical) damping models composed of bending and shear mechanisms have been defined. A spatial shear damping model which is non-homogeneously distributed has been adopted in the CTB formulation and used to equivalently model passive dampers, viscous and viscoelastic devices, embedded in building systems. The application of continuum-based models for the dynamic analysis of shear wall systems has been further discussed. A reference example has been numerically analyzed to evaluate the efficiency of the presented CTB, and the optimization problems of the shear damping have been finally ascertained using local and global performance indices. The results reveal the superior performance of non-classical damping models against the classical damping. They show that the critical position of the first modal rotation in the CTB is reliable as the optimum placement of the shear damping. The results also prove the good efficiency of such a continuum model, in addition to its simplicity, for the fast estimation of dynamic responses and damping optimization issues in building systems.