• Journal of Advanced Marine Engineering and Technology
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• 제26권2호
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• pp.248-255
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• 2002

Miller cycle was studied and analyzed by engine performance simulation to achieve very low fuel consumption and to meet the IMO NOx regulation on a medium speed diesel engine. Based on the performance simulation results the intake valve closing time for HYUNDAI HiMSEN 6H21/32 engine was set at 0deg.ABDC(After Bottom Dead Center). Also, the simulation results indicated that significant NOx reduction could be achieved with low reduction of fuel consumption. The performance simulation investigated the effect of compression ratio and turbocharger on fuel consumption and NOx concentration in combination with Miller cycle. The results indicated a significant reduction of fuel consumption with keeping NOx concentration. The results of performance simulation were compared with measured data to verify simulation results. The comparison showed the maximum error was 2.34% in exhaust temperature. Also, the experimental result showed that improvement in BSFC(Brake Specific Fuel Consumption) was 5.8g/kwh with keeping NOx level similar to simulation result.

• 품질경영학회지
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• 제42권4호
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• pp.591-606
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• 2014

Purpose: The purpose of this study is to design an experimental simulation model for evaluating the UGV(Unmanned Ground Vehicle) effectiveness in a small unit combat scenario. Methods: We design and build a simulation model to evaluate the combat effectiveness of UGV in a small unit combat scenario. In order to build a simulation model, we used AnyLogic software tool which has functional advantages to describe agent-based simulation model. As for the combat scenario, we applied the typical engagement of mechanized unit equal or lower than battalion level. Analysis process follows the three phases. 1) Design an agent based conceptual medel in a small unit combat scenario. 2) Build a simulation medel using AnyLogic tool. 3) Analyze the simulation results and evaluate the UGV effectiveness. Results: The UGV effectiveness was measured and presented as a numeric values. Those numeric values were represented as a MOE(Measure of Effectiveness) which was the blue survival ratio. Conclusion: We developed an agent based simulation model which can provide a pattern of change how UGV effectiveness varied depending upon the number of UGV in a small unit combat scenario. We also found that the UGV effectiveness grows in the given scenario as the number of UGV increases.

• 성인간호학회지
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• 제22권4호
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• pp.375-383
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• 2010

Purpose: The purpose of this study was to examine if simulation training affects new graduate critical care nurses' knowledge, self-efficacy, and performance ability in emergency situations. Methods: Forty new graduate critical care nurses were randomly assigned to either an experimental or a control group. The experimental group had didactic with simulation. The control group received only didactic without simulation about emergency situations. The data were collected before and after the training interventions. An independent t-test used for difference among variables. Results: There were no significant demographic differences between the two groups or any differences on data collected knowledge, self-efficacy and performance ability. Following the training, there were significant performance ability scores (p<.001) among the nurses receiving didactic with simulation. There were no significant difference between the two groups relative to knowledge scores (p=.117), or the self-efficacy scores (p=.100). Conclusion: This study showed that simulation training for new graduate critical care nurses is useful to improve performance ability on emergency situations. Hence, providing simulation training to critical care nurses during an orientation period would improve quality of critical care nursing and help the new graduates nurse's adaptation.

• Computers and Concrete
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• 제26권3호
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• pp.239-255
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• 2020

Experimental and discrete element method were used to investigate the effects of joint number and its angularities on the shear behaviour of joint's bridge area. A new shear test condition was used to model the gypsum cracks under shear loading. Gypsum samples with dimension of 120 mm×100 mm×50 mm were prepared. the length of joints was 2cm. in experimental tests, the joint number is 1, 2 and 3 and its angularities change from 0° to 90° with increment of 45°. Assuming a plane strain condition, special rectangular models are prepared with dimension of 120 mm×100 mm. similar to joints configuration in experimental test, 9 models with different joint number and joint angularities were prepared. This testing show that the failure process is mostly governed by the joint number and joint angularities. The shear strengths of the specimens are related to the fracture pattern and failure mechanism of the discontinuities. The shear behaviour of discontinuities is related to the number of induced tensile cracks which are increased by increasing the rock bridge length. The strength of samples decreases by increasing the joint number and joint angularities. Failure pattern and failure strength are similar in both of the experimental test and numerical simulation.

• Steel and Composite Structures
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• 제34권1호
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• pp.35-51
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• 2020

Integral abutment bridges (IABs) are those bridges without expansion joints. A single row of steel H-piles (SHPs) is commonly used at the thin and stub abutments of IABs to form a flexible support system at the bridge ends to accommodate thermal-induced displacement of the bridge. Consequently, as the IAB expands and contracts due to temperature variations, the SHPs supporting the abutments are subjected to cyclic lateral (longitudinal) displacements, which may eventually lead to low-cycle fatigue (LCF) failure of the piles. In this paper, the potential of using finite element (FE) modeling techniques to estimate the LCF life of SHPs commonly used in IABs is investigated. For this purpose, first, experimental tests are conducted on several SHP specimens to determine their LCF life under thermal-induced cyclic flexural strains. In the experimental tests, the specimens are subjected to longitudinal displacements (or flexural strain cycles) with various amplitudes in the absence and presence of a typical axial load. Next, nonlinear FE models of the tested SHP specimens are developed using the computer program ANSYS to investigate the possibility of using such numerical models to predict the LCF life of SHPs commonly used in IABs. The comparison of FE analysis results with the experimental test results revealed that the FE analysis results are in close agreement with the experimental test results. Thus, FE modeling techniques similar to that used in this research study may be used to predict the LCF life of SHP commonly used in IABs.

• International Journal of Aerospace System Engineering
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• 제2권2호
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• pp.58-61
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• 2015

Combustion instability in solid rocket motors is a long-term open problem since the first rockets were used. Based on the numerous previous studies, it is known that the limit cycle amplitude is one of the key characteristics of the nonlinear combustion instability in solid rocket motors. Flandro's extended energy balance corollary, aims to predict the limit cycle amplitude of complex, nonlinear pressure oscillations for rockets or air-breathing engines, and leads to a precise assessment of nonlinear combustion instability in solid rocket motors. However, based on the comparison with experimental data, it is revealed that the Flandro's method cannot accurately describe such a complex oscillatory pressure. Thus in this work we make modifications of the nonlinear term in the nonlinear wave equations which represents the interaction of different modes. Through this modified method, a numerical simulation of the cylindrical solid rocket has been carried out, and the simulated result consists well with the experimental data. It means that the added coefficient makes the nonlinear wave growth equations describe the experimental data better.

• Computers and Concrete
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• 제31권1호
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• pp.71-84
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• 2023

In this paper, the effects of the thickness of cubic samples on the tensile strength of concrete blocks were studied using experimental tests in the laboratory and numerical simulation by the particle flow code in three dimensions (PFC3D). Firstly, the physical concrete blocks with dimensions of 150 mm×190 mm (width×height) were prepared. Then, three specimens for each of seven different samples with various thicknesses were built in the laboratory. Simultaneously with the experimental tests, their numerical simulations were performed with PFC3D models. The widths, heights, and thicknesses of the numerical models were the same as those of the experimental samples. These samples were tested with a new tensile testing apparatus. The loading rate was kept at 1 kg/sec during the testing operation. Based on these analyses, it is concluded that when the thickness was less than 5 cm, the tensile strength decreased by increasing the sample thickness. On the other hand, the tensile strength was nearly constant when the sample thickness was raised to more than 5 cm (which can be regarded as a threshold limit for the specimens' thickness). The numerical outputs were similar to the experimental results, demonstrating the validity of the present analyses.

• 복식
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• 제58권7호
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• pp.43-59
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• 2008

This study aims to improve the uniform functionality of the workers who work in Electric Technology Division, Korea Railroad Corporation. Former study of questionnaire survey was taken to examine the current state of wearing working clothes for the workers. Based on the results of the former study, an experimental clothes, the functionality of which has improved in terms of design, materials, and patterns, was created, and existing working clothes and the treated experimental clothes were compared through simulation wearing evaluation comprising appearance, activity adaptability, quantitativeness, and on-site adaptability evaluation comprising appearance and activity adaptability. The followings are the results of the study: Simulation wearing evaluation is composed of 5subjects and 11experts specializing in costume, and as a result of evaluation the experimental clothes were evaluated superior to the existing working clothes in all items. On-site adaptability evaluation was conducted by workers in the Electric Technology Division, who are the subjects in this study. In that evaluation, the experimental clothes were also evaluated superior to the existing working clothes in all items. While the five subjects who participated in the simulation wearing evaluation move, the quantitative evaluation measured the distance of location transfer of the back length in the jacket and the distance of location transfer of the back waist in the trousers. As the distances in the experimental clothes were measured shorter than the distances in the existing working clothes, the subjective evaluation results are objectively supported.

• 한국간호교육학회지
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• 제21권1호
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• pp.95-107
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• 2015

Purpose: The purpose of this study was to develop a tailored simulation learning (SL) program and to evaluate the effects of the program on the clinical competency, clinical decision-making competency, and communicative competency of new nursing staffs in intensive care units (ICU) and emergency rooms (ER). Methods: In this quasi-experimental study, fifteen nurses were assigned to the experimental group and fifteen to the control group. The experimental group was given the SL program of four sessions, whereas the lectures of four sessions were given to the control group. Data were analyzed using a $x^2$-test, Mann-Whitney U test, and Kruskal-Wallis test with an SPSS program. Analysis of covariance was used to treat the covariate of pre communicative competency between the experimental and control groups. Results: Based on the education needs of new nursing staffs in ICUs and ERs, three learning scenarios and one evaluating scenario were developed for the SL program. The score for clinical competency, clinical decision-making competency, and communicative competency were significantly higher in the experimental group compared with the control group. Conclusion: The SL program is an effective learning strategy for new nursing staffs in ICUs and ERs. These findings suggest that an SL program be offered as an alternative for new nurse orientation and continuing nurse education.

• 한국화재소방학회논문지
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• 제33권4호
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• pp.50-58
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• 2019

구획실 내 가연물들의 화재거동에 대한 B-RISK의 예측성능을 Fire dynamics simulator (FDS)와 연계하여 검토하였다. 먼저 열발생률(Heat release rate, HRR)에 대한 B-RISK의 예측성능을 검토하기 위해 가연물 한 세트의 실험에서 측정된 HRR 값과 디자인 화재곡선을 B-RISK의 입력조건으로 사용하여 가연물 두 세트에 대한 HRR 곡선을 계산하고 실험에서 측정된 가연물 두 세트의 HRR 값과 비교하였다. B-RISK 결과와 실험결과를 비교하여 B-RISK가 화재성장률에 대한 예측은 어렵지만 최대 HRR 값과 총 열발생량에 대해서는 충분히 예측할 수 있음을 확인하였다. 그리고 B-RISK 계산을 통해 예측된 HRR 값을 FDS의 입력조건으로 사용하여 계산된 결과와 실험결과를 비교하여 B-RISK 계산을 통해 예측된 HRR 값의 화재거동에 대해 검토하였다. 실험에서 측정된 온도 및 화학종 농도 결과와 비교하여 화재성장구간에 대해 차이가 있는 것을 확인하였지만 예측된 HRR 값에서 Percentile이 약 70%인 HRR 값을 사용하더라도 충분히 전체적인 화재거동을 예측할 수 있음을 확인하였다.