• Journal of the Korea Society of Computer and Information
• /
• v.8 no.3
• /
• pp.179-187
• /
• 2003

This study investigate the reasons of organizational failure in detection and appropriate response to risk signal. The Crisis does not come true suddenly, there is some risk signals in crisis. If Organization detect the risk signals the crisis is come true opportunities, if not the crisis is come true disastrous outcome. This is use the system dynamics approach. System Dynamics assume the system as a collection of causal feedback loop, so we understand the dynamics around the problems. This investigate suggest that, the focus on growth is the a kind of promotional pressure and the pressure drive the organization to less attention the risk signal, so the risk is underestimate In proportion to real risk. Ultimate, the organization entrap the promotional climate and insensible to security. This study is a kind of hypothesis-discovering research, in the further study, the discovered hypothesis will be empirically tested.

• Proceedings of the KOR-KST Conference
• /
• 1995.12a
• /
• pp.45-73
• /
• 1995

The current paper presents a system dynamics model which can generate the land use anq transportation system performance simultaneously is proposed. The model system consists of 7 submodels (population, migration of population, household, job growth-employment-land availability, housing development, travel demand, and traffic congestion level), and each of them is designed based on the causality functions and feedback loop structure between a large number of physical, socio-economic, and policy variables. The important advantages of the system dynamics model are as follows. First, the model can address the complex interactions between land use and transportation system performance dynamically. Therefore, it can be an effective tool for evaluating the time-by-time effect of a policy over time horizons. Secondly, the system dynamics model is not relied on the assumption of equilibrium state of urban systems as in conventional models since it determines the state of model components directly through dynamic system simulation. Thirdly, the system dynamics model is very flexible in reflecting new features, such as a policy, a new phenomenon which has not existed in the past, a special event, or a useful concept from other methodology, since it consists of a lots of separated equations. In Chapter I, II, and III, overall approach and structure of the model system are discussed with causal-loop diagrams and major equations. In Chapter V _, the performance of the developed model is applied to the analysis of the impact of highway capacity expansion on land use for the area of Montgomery County, MD. The year-by-year impacts of highway capacity expansion on congestion level and land use are analyzed with some possible scenarios for the highway capacity expansion. This is a first comprehensive attempt to use dynamic system simulation modeling in simultaneous treatment of land use and transportation system interactions. The model structure is not very elaborate mainly due to the problem of the availability of behavioral data, but the model performance results indicate that the proposed approach can be a promising one in dealing comprehensively with complicated urban land use/transportation system.

• Journal of the Institute of Convergence Signal Processing
• /
• v.2 no.1
• /
• pp.95-100
• /
• 2001

In this paper, we proposed the robust control scheme for a class of nonlinear dynamical systems using output feedback linearization method. The presented control scheme is based on the VSS. We assume that the nonlinear dynamical system is minimum phase, the relative degree of the system is r＜n and zero dynamics is stable. It is also shown that the global asymtotically stability is guaranted. And we verified that the proposed control scheme Is the feasible through a computer simulation.

• Proceedings of the KIEE Conference
• /
• 1999.07f
• /
• pp.2490-2492
• /
• 1999

본 논문에서는 벡터 제어 유도전동기 구동 시스템에서 과변조시 출력 토오크 향상을 위한 새로운 과변조 기법을 제안한다. 제안된 과변조 기법은 인버터의 전압 제한과 유도 전동기의 전류 다이나믹스를 동시에 고려하여, 과변조시 동기좌표계 d축 전압을 감소시킴으로써 순시적으로 d축 전류를 감소시키고 q축 전류 제어를 위한 전압 여유를 확보한다. 따라서 과변조시에도 q축 전류 제어가 원활하게 수행됨에 따라 전동기의 출력 토오크를 향상시킨다. 기존의 기법과의 비교 실험에서 제안된 기법이 우수함을 증명하였다.

• Proceedings of the Korea Society for Industrial Systems Conference
• /
• 1999.05a
• /
• pp.36-44
• /
• 1999

임금이란 사용자의 입장에서는 비용으로, 근로자의 입장에서는 생활의 원천이 되는 소득으로 자본주의 경제에 있어서 기업측과 근로자측은 임금을 둘러싸고 상반된 이해관계에 놓이게 된다. 그러한 사정은 노사갈등의 직접적인 원인이 될 수 있으므로 근로자의 욕구를 충족시키면서 기업의 이익을 보장할 수 있는 합리적인 임금관리가 요청된다. 본 논문에서는 임금과 관련된 주요 변수들을 시스템 다이나믹스 개념 측면에서 분석하여 문제발생의 원인과 해결방법을 모색하고 이를 단순화된 상황속에서 가상 시뮬레이션을 해 봄으로써 이상적인 임금체계 설계의 방향을 제시 해보았다.

• Tribology and Lubricants
• /
• v.37 no.3
• /
• pp.91-98
• /
• 2021

This paper presents a hydrostatic bearing design and rotordynamic analysis of a turbo expander for a hydrogen liquefaction plant. Th~e turbo expander includes the turbine and compressor wheel assembled to a shaft supported by two hydrostatic radial and thrust bearings. The rated speed is 75,000 rpm and the rated power is 6 kW. For the bearing operation, we use pressurized air at 8.5 bar as the lubricant that is supplied to the bearing through the orifice restrictor. We calculate the bearing stiffness and flow rate for various gauge pressure ratios and select the orifice diameter providing the maximum bearing stiffness. Additionally, we conduct a rotordynamic analysis based on the calculated bearing stiffness and damping considering design parameters of the turbo expander. The predicted Cambell diagram indicates that there are two critical speeds under the rated speed and there exists a sufficient separation margin for the rated speed. In addition, the predicted rotor vibration is under 1 ㎛ at the rated speed. We conduct the operating test of the turbo expander in the test rig. For the operation, we supply pressurized air to the turbine and monitor the shaft vibration during the test. The test results show that there are two critical speeds under the rated speed, and the shaft vibration is controlled under 2.5 ㎛.

• Journal of Domestic Journal Test
• /
• v.11 no.2
• /
• pp.221-227
• /
• 2023

− A rotordynamic system consists of components that undergo rotational motion. These components include shafts, impellers, thrust collars, and components that support rotation, such as bearings and seals. The motion of this type of rotating system can be modeled as two-dimensional motion and, accordingly, the equa- tion of motion for the rotordynamic system can be represented using complex coordinates. The directional fre- quency response function (dFRF) can be derived from this complex coordinate system and used as an effective analytical tool for rotating machinery. However, the dFRF is not widely used in the field because most pre- vious studies and commercial software are based on real coordinate systems. The objective of the current study is to introduce the dFRF and show that it can be an effective tool in rotordynamic analysis. In this study, the normal frequency response function (nFRF) and dFRF are compared under rotordynamic analysis for isotropic and unisotropic rotors. Results show that in the nFRF, the magnitude of the response is the same for both pos- itive and negative frequencies, and the response is similar under all modes. Consequently, the severity of the mode cannot be identified. However, in the dFRF, the forward and backward modes are clearly distinguishable in the frequency domain of the isotropic rotor, and the severity of the mode can be identified for the uniso- tropic rotor.

• The Journal of Information Systems
• /
• v.20 no.3
• /
• pp.25-40
• /
• 2011

Small and Medium sized hospitals are exposed to severe managerial environments recently. Around 8.0% of the hospitals are bankrupted every year. The adverse managerial environment does not only come from external factors such as patients' preference for larger hospitals, regulations on the medical charges; more serious problems come from the way the medium and small sized hospitals deal with those exogenous changes including lack of management skills, lack of change management skills, lack of managerial decision support systems, etc. This paper aims to support managers to make decisions regarding the exogenous changes. This paper can be interpreted as an attempt of a merge of the two techniques; BSC and system dynamics. Starting with a BSC system, the development of a system dynamics model can take advantages of the BSC information.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.29 no.3
• /
• pp.25-32
• /
• 2006

자동차 개발 단계는, 본질적으로, 수차례의 개발 단계를 거치면서 설계 그룹들 간의 정보 전달과 교환이 여러 차례 반복적으로 발생하게 된다. 이러한 복잡한 상호 정보 교환 과정을 정확하게 이해하여 업무가 수행되지 못하면 불필요한 재작업을 야기시킬 수 있으며, 이는 비용 낭비 및 계획에 차질이 발생할 수 있다. 이 연구에서는 시스템 다이나믹 모델을 개발하여 빈번한 design-built-test 싸이클이 자동차 개발 단계에 미치는 영향 및 이점들을 고찰하였다.

• Proceedings of the Korea Society for Simulation Conference
• /
• 2003.11a
• /
• pp.193-200
• /
• 2003

급변하는 시장환경에서 고객수요가 불확실한 상황에서 고객서비스를 최우선으로 하는 기업에서는 전략적인 제휴를 통해 기업의 경쟁력을 확보하는 것이 최우선이라고 하겠다. 이러한 환경에서 대두된 경영혁신 기법들이 공급체인관리와 아웃소싱 개념이라고 할 수 있는데, 이에 본 연구에서는 제조기업의 입장에서 제품가격 경쟁력을 확보하기 위한 일환으로 재고량을 줄이고, 판매량을 늘리는 방안을 제고하고자 한다. 비용과 서비스 관점에서 볼 때 이들은 서로 상충관계에 있지만, 본 연구에서 제안하는 재고 공유 시스템을 통한 공동 재고정책은 기업의 입장에서 볼 때, 보다 적은 재고를 보유함으로써, 재고유지비용을 절감하고, 이는 최종 제품가격의 하락으로 이어져 가격효과를 통한 매출량의 증대시킬 수 있게 된다. 이를 검증하기 위해 본 연구에서는 시스템 다이나믹스 방법을 이용하고, 이를 통하여 본 연구에서 제시된 재고 공유 시스템구축의 타당성을 검증하고, 분석하였다