• Structural Engineering and Mechanics
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• 제6권4호
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• pp.395-409
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• 1998

This paper concerns the development and implementation of an orthotropic, stress resultant elasto-plastic finite element model for the collapse load analysis of reinforced concrete plates. The model implements yield line plasticity theory for reinforced concrete. The behaviour of the yield functions are studied, and modifications introduced to ensure a robust finite element model of cases involving bending and twisting stress resultants ($M_x$, $M_y$, $M_{xy}$). Onset of plasticity is always governed by the general yield-line-model (YLM), but in some cases a switch to the stress resultant form of the von Mises function is used to ensure the proper evolution of plastic strains. Case studies are presented, involving isotropic and orthotropic plates, to assess the behaviour of the yield line approach. The YLM function is shown to perform extremely well, in predicting both the collapse loads and failure mechanisms.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.390-394
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• 2001

A dynamic simulation model for the brush less dc (BLDC) motor drives using Matlab is presented. In this model, an entire BLDC motor drive, including power conversion unit, BLDC motor, and speed/torque control system, is investigated. Especially, the PWM inverter is modeled using switching function concept, so that the detailed voltage and current waveforms, such as line-to-line voltages, inverter input current, ac line current, and switch/diode currents, can be obtained and average/rms ratings of the components can be easily calculated. Also, the proposed model is made into modular blocks and it can be easily extended to other ac motor applications with a little modification. The detailed modeling method is explained and its actual implementation is described. The validity of the proposed model is verified by various simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.550-552
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• 1997

This paper describes a detailed performance analysis of TCSC using experiment with a scaled model. A 3-phase scaled model of TCSC was built with rating of 2kVA to verify the operation. The variable reactance of TCSC with respect to the firing angle of thyristor switch analyzed theoretically and experimentally. And the limit of TCSC operation was investigated in whole range of the thyristor firing-angle. The experimental results with scaled model were compared with the simulation results for a periodic state space model using MATLAB.

• 한국정보과학회논문지:시스템및이론
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• 제34권12호
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• pp.630-640
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• 2007

센서 네트워크의 응용 범위가 점차 넓어지면서 군사 분야나 방사능 감지와 같이 실시간성을 요구하는 응용분야가 생겨나게 되었다. 하지만 기존의 센서 운영체제 연구는 효율적인 자원 활용에 초점을 두고 연구가 진행되었기 때문에 실시간성을 만족시켜 주기 어려운 구조를 가지고 있다. 본 논문에서는 정시성을 보장하는 실시간 분산 객체 TMO 모델을 센서 네트워크의 제한된 자원 환경에 알맞도록 경량화 시킨 ${\mu}TMO$ 모델을 제안한다. ${\mu}TMO$ 모델을 이용한 실시간 센서 네트워크 운영체제를 개발하기 위하여 한국전자통신연구원에서 개발한 센서 노드용 운영체제인 Nano-Q+를 이용하였다. Nano-Q+의 타이머 모듈을 높은 해상도를 가질 수 있도록 수정하였으며, EDF(Earliest-Deadline-First)기반의 실시간 스케줄러에 CST(Context Switch Threshold)와 PAS(Power Aware Scheduling) 기법을 적용하여 센서 노드에 적합한 실시간 스케줄러로 변경하였다. ${\mu}TMO$ 모델을 지원하기 위해 채널 기반의 통신 수단인 ITC-Channel을 새롭게 구현하였으며, 주기적인 스레드를 관리하는 WTMT(Watchdog TMO Management Task) 모듈을 구현하여 SpM 스레드를 주기에 맞게 실행할 수 있도록 하였다.

• 보건행정학회지
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• 제24권1호
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• pp.24-34
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• 2014

Background: Bankrupted households have recently been increased due to excessive medical expenditure in Korea. They have not been protected from economic risk when household's member has severe diseases that need a lot of money for treatment. Purpose of this study examines policy effect by comparing unmet needs' change of policy object households and non-object groups. Methods: We used Korea Health panel 2nd 4th data collected by Korea Institute for Health and Social Affairs and National Health Insurance Service. Analysis subjects were 381 households (pre-policy) and 393 households (post-policy) that had cancer and cardiovascular and cerebrovascular diseases. Since it was major concern that estimates benefit strengthening policy started by certain time, we setup comparing households which had diabetes, hypertension disease. Comparison subjects were 393,247 households, respectively and we evaluated policy effect using difference in difference (DID) model. Results: Although unmet needs of policy object households were higher than non-object groups, policy execution variable affected negative direction. But interaction-term which shows pure effect of policy was not statistically significant. We utilized multi-DID model to examine factors affecting unmet needs causes. Copayment assistance policy did not significantly affect households that responded to 'economic reason,' and 'no have time to visit' for unmet needs causes. Conclusion: The second copayment assistance policy did not significantly give positive effect to beneficiary households than non-beneficiary groups. When we consider that primary purpose of public insurance guarantee high medical expenditure occurred by unexpected events, it needs to deliberate on switch of benefit strengthening policy that can assist vulnerable people. Also, we suggest that government forward a policy covering non-reimbursable medical expenses as well as switch of benefit strengthening direction because benefit policy do not affect non-covered medical cost which accounts for quarter of total health expenditure.

• 농업과학연구
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• 제47권4호
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• pp.743-752
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• 2020

The purpose of this study was to estimate the economic evaluation of a smart farm investment for tomatoes and strawberries. In addition, the potential adoption rate of the smart farm was derived for different scenarios. This study analyzed the economic evaluation with the net present value (NPV) method and estimated the adoption potential of the smart farm with the trade-off analysis, minimum data (TOA-MD) model. The results were as follows: The analysis of the net present value shows that the smart farm investment for the two crops are economically feasible, and the minimum prices for the tomatoes and strawberries should be 1,179 and 3,797 won/kg to secure a sufficient economic feasibility for the smart farm investment. Next, the analysis of the potential adoption rates for smart farms through the TOA-MD model showed that when the support ratio for the adoption of a smart farm system was 50% and the price increase rates were, respectively, - 5, 2.5, 0, 2.5, and 5%, the conversion rates for tomato farms to switch to smart farms were 0.97, 1.78, 3.05, 4.91, and 7.47%, while the ratios of the strawberry farms to switch to smart farms were 0.12, 0.29, 0.65, 1.33, and 2.53%, respectively. This study has some known limitations, but it provides useful information on decision making about smart farm adoption and can contribute to government policies on smart farms.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.942-949
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• 2002

The use of a combined starter/generator integrated into the drive train of an automobile offers several possibilities for improvement of fuel economy The use of such a starter/generator system is made feasible by a switch from a 14 volts electrical system to a 42 volts system, however, the sizing of the components is not a trivial problem. This study combines a dynamic electromechanical model of the starter, battery and power electronics with the nonlinear mechanics of the piston/crankshaft system and a thermofluid model of the compression and expansion processes to investigate the cold start problem. The example involves the start of an eight cylinder engine at -25 degrees Celsius. This paper shows how the mechatronic V8 engine of an automotive starter/generator system for the startability works well.

• 유공압시스템학회논문집
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• 제4권4호
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• pp.8-14
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• 2007

The electro-hydraulic pump is usually used in testing equipments which require one control function. But until now, it is not applied to industrial equipments which are exposed to severe working environment and require various control functions. This paper proposes a technique which controls continuously flow, pressure and power by utilizing switching control mode. Mathematical model is developed from the continuity equation for the pressurized control volume and the torque balance for the swash plate motion. To simplify the model we make the linear state equation by differentiating the nonlinear model. We analyze the stability and disturbance by using the state variable model. Finally, we review the control performances of flow, pressure and power by tests using PID controller.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.863-866
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• 2003

Recently, there has been growing interests in the magneto-resistive random access memory (MRAM) because of its great potential as a future nonvolatile memory. In this paper, a CMOS macro-model for MRAM cell based on a twin cell structure is proposed. The READ and WRITE operations of the MTJ cell can be emulated by adopting data latch and switch blocks. The behavior of the circuit is confirmed by HSPICE simulations in a 0.35-${\mu}{\textrm}{m}$ CMOS process. We expect the macro model can be utilized to develope the core architecture and the peripheral circuitry. It can also be used for the characterization and the direction of the real MTJ cells.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.422-428
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• 2005

In this paper, the contact force between two colliding bodies is modeled by using Hertz's force-displacement law and nonlinear damping function. In order to verify the appropriateness of the proposed contact force model, the drop type impact test is carried out for different impact velocities and different materials of the impacting body, such as rubber, plastic and steel. In the drop type impact experiment, six photo interrupters in series close to the collision location are installed to measure the velocity before impact more accurately. The characteristics of contact force model are investigated through experiments. The parameters of the contact force model are estimated using the optimization technique. Finally the estimated parameters are used to predict the impact force between two colliding bodies in opening action of the magnetic contactor, a kind of switch mechanism for switching electric circuits.