• Journal of Korean Clinical Nursing Research
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• v.14 no.2
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• pp.71-81
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• 2008

Purpose: The objective of this study was to determine the cause-effect and dynamic change mechanism among factors that affect calculation of the nursing workforce in the hemodialysis room and to establish a system dynamics model and create a strategic simulation to be used to increase efficiency in the clinical situation. Method: The system dynamics approach was adapted to build a simulation model for calculating the nursing workforce. The model was built using Vensim 5.0b DSS. Results: The results were as follows for Scenario A: The highest level of nursing service quality, patient satisfaction, and nurse satisfaction, and the lowest level of turnover intention is maintained when the ratio of patients to nurse is 3.5:1 compared to all other situations. Scenario B: At the ratio of patients to nurse 4.0:1 nursing service quality, patient satisfaction, and nurse satisfaction dropped slightly, and turnover intention also rose slightly. However with time the results showed improvement. Conclusion: In terms of economic efficiency in the hemodialysis room, the ratio of patients to nurse for the best nursing workforce should not exceed 4.0:1.

• Journal of Technologic Dentistry
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• v.31 no.1
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• pp.7-15
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• 2009

Purpose: This study was to propose the clear understanding for stress distribution of supporting bone by use of staggered buccal offset tripodal placement of fixtures of posterior 3 crown implant partial dentures. We realized posterior 3 crown implant fixed partial dentures through finite element modeling and analysed stress effect of implant arrangement location to supporting bone under external load using finite element method. Method: To understand stress distribution of 3 crown implant fixed partial dentures which have 2 different arrangement by finite element analysis. In each model, for loading condition, we applied $45^{\circ}$ oblique load to occlusal surface of crown and applied 100 N for 3 crown individually(total 300 N) for imitating possible oral loading condition. at this time, we calculated Von Mises stress distribution in supporting bone through finite element method. Result: When apply $45^{\circ}$ oblique load to in-line arrangement model, maximum stress result for 100 N for each 3 crown 47.566MPa. In tripodal placement, result for 1mm buccal offset tripodal placement implant model was maximum distributed load 51.418MPa, so result was higher than in-line arrangement model. Conclusion: In stress distribution result by placement of implant fixture, the most effective structure was in-line arrangement. The tripodal placement does not effective for stress distribution, gap cause more damage to supporting bone.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.2
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• pp.115-119
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• 2016

Winding is one of the major processes in roll-to-roll systems. Taper tension profile in a winding determines the distribution of stress in the radial direction, i.e., the radial stress in the wound rolls. Maximum radial stress is major cause of material defect, and this study has been actively proceeded. Traditional models of radial stress model were focused on flexible and light substrate. In this study, we developed an advanced radial stress model including effects of both these parameters(weight and stiffness) on the radial stress. The accuracy of the developed model was verified through FEM(Finite Element Method) analysis. FEM result of maximum radial stress value corresponds to 99 % in comparison to result with the model. From this study, the material defects does not occur when the steel winding. And steel industry can be applied to improve the winding process.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.71-77
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• 2008

This paper proposes an Electronic Throttle Body (ETB) model considering a non-linearity of DC motor driver which is integrated with a H-bridge and a gate driver. A propagation delay and reverse recovery time of switching components cause non-linear characteristic of DC motor driver. This non-linearity affects not only the amateur voltage of DC motor, but also entire behaviour and parameters of ETB. In order to analyze the behavior of ETB more accurately, this non-linear effect of DC motor driver is modeled. The developed ETB model is validated by use of the step response and ramp response experiments, and it shows relatively accurate results compared with linear DC motor driver model.

• Korean Journal of Cognitive Science
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• v.13 no.1
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• pp.53-59
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• 2002

This paper presents a model for diagnosing students'learning misconceptions in the domain of heat and temperature using fuzzy cognitive maps(FCM) and fuzzy associative memory(FAM). In a model for diagnosing learning misconceptions. an FCM can represent with cause and effect between preconceptions and misconceptions that students have about scientific phenomenon. An FAM which represents a neurallike memory for memorizing causal relationships is used to diagnose causes of misconceptions in learning. This study will present a new method for more autonomous and intelligent system than a model to diagnose misconceptions that was being done with classical methods in learning and may contribute as an intelligent tutoring system for learning diagnosis within various educational contexts.

• The KSFM Journal of Fluid Machinery
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• v.14 no.2
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• pp.17-24
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• 2011

Temperature gradient focusing (TGF) of analytes via Joule heating is achieved when electric field is applied along a microchannel of varying width. The effect of varying width of the microchannel for the focusing performance of the device was numerically studied. The governing equations were implemented into a quasi-1D numerical model along a microchannel. The validity of the numerical model was verified by a comparison between numerical and experimental results. The distributions of temperature, velocity, and concentration along a microchannel were predicted by the numerical results. The narrower middle width and wider outside width of the channel having the fixed length contribute to improve the focusing performance of the device. However, too narrow middle width of the channel generates a higher temperature which can cause the problems including sample denaturation and buffer solution boiling. Therefore, the channel geometry should be optimized to prevent these problems. The optimal widths of the microchannel for the improvement on TGF were proposed and this model can be easily applied to lab-on-a-chip (LOC) applications where focusing is required based on its simple design.

• Korean System Dynamics Review
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• v.3 no.2
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• pp.49-68
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• 2002

The intent of this study is to develop system dynamics model for assessment of organizational and human factors in nuclear power plant which can contribute to secure the nuclear safety. Previous studies are classified into two major approaches. One is engineering approach such as ergonomics and probability safety assessment(PSA). The other is social science approach such like sociology, organization theory and psychology. Both have contributed to find organization and human factors and to present guideline to lessen human error in NPP. But, since these methodologies assume that relationship among factors is independent they don't explain the interactions among factors or variables in NPP. To overcome these limits, we have developed system dynamics model which can show cause and effect among factors and quantify organizational and human factors. The model we developed is composed of 16 functions of job process in nuclear power, and shows interactions among various factors which affects employees' productivity and job quality. Handling variables such like degree of leadership, adjustment of number of employee, and workload in each department, users can simulate various situations in nuclear power plant in the organization side. Through simulation, user can get insight to improve safety in plants and to find managerial tools in the organization and human side. Analyzing pattern of variables, users can get knowledge of their organization structure, and understand stands of other departments or employees. Ultimately they can build learning organization to secure optimal safety in nuclear power plant.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.843-848
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• 2011

Planning and construction of railway for high speed trains up to 400 km/h are recently driven in Korea. High speed train is one of the environment-friendly fastest mass transportation means but its noise generated by rolling, traction and aerodynamic mechanism can cause public complaints of residents nearby railways. To cost-effectively prevent the troublesome noise in a railway planning stage, the rational railway noise prediction method considering the characteristics of trains as well as railway structures should be required but it is difficult to find authentic methods for Korean high speed trains such as KTX and KTX-II. In this study, we propose a framework of our own railway noise prediction model emitted by Korean high speed trains over 250 km/h based on the recent research results carried out in EU countries. The model considers railway sound power level using several point sources distributed in heights as well as tracks, whose detail speed- and frequency-dependent emission characteristics of Korean high speed trains should be determined in near future by measurement or numerical analysis. The attenuation during propagation outdoors is calculated by the well-known ISO 9613-2 and auxiliary methods to consider undulated terrain and wind effect.

• Journal of the Korea Safety Management & Science
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• v.8 no.1
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• pp.85-96
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• 2006

The oriental life change unit(LCU) models differ from the western LCU model in human behavior, life style, ideas, culture, and psychology factors. Especially, the cause and effect models by behavior scientific approach method have provided the accident proneness concept through the LCU factors. Therefore this paper describes the analytical results of the oriental LCU model and western LCU model. Especially, the death of parents and death of close friend in Korean LCU model feel more acute stress than the western factors. In the case of Korean LCU models between the unmarried and married workers living in the middle area of Korea, death of parents, change in family member's health, change to different line of work, and change in work hours and condition are significant at the significance level of 5%. The priority of life change factors in these models is approved in the order of death of parents, death of spouse, death of close family member, and death of close friend. Finally, the result of this paper can be easily used in order to minimize the industrial accidents by the job stress with the worker and safety manager in real fields.

• Journal of the Korean Society for Railway
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• v.5 no.2
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• pp.118-124
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• 2002

The failure probability of wheel beyond 10$\^$7/ cycles is achieved by the strengths-stress interference model for the evaluation of fatigue strength and reliability in the wheel, From plane bending fatigue test results, the fatigue life (N$\_$f/) for the smooth and 200㎛ holed specimens can be represented as $\sigma$$\_$a/ = 1326N$\_$f/$\^$-0.10/ and $\sigma$$\_$a/ = 2894N$\_$f/$\^$-0.18/. Respectively, fatigue strength of the wheel at beyond 10$\^$7/cycles was about 332 MPa. And, the fatigue strength for the specimen with a micro hole (d=200㎛) which simulated an inclusion on the wheel surface was about 235 MPa. Thus, a micro hole (d=200㎛) caused about 30% reduction of fatigue strength of the specimen. The failure probabilities for the smooth and micro-holed specimens, derived from the strength-stress interference model, are 0.0148% and 13.05%, respectively. The current finding suggests that at least 200 ㎛ sized inclusion, which might be produced during manufacturing process, will cause a critical effect on integrity of the railway vehicle.