• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.475-483
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• 1993

A computer simulation model of a hermetic reciprocating type of refrigeration compressor has been developed. The compressor simulation model constitutes 6 control volumes, to each of which conservation laws of mass and energy are applied to yield full description of the refrigerant state along its passage. Instead of ideal gas assumption. real gas equation is employed. Some of valve-related input data required for the simulation are acquired from test bench experiments. The refrigerant states such as pressure and temperature, etc., mass flow rates, and valve motions can be predicted by the simulation. The calculated P-V diagram shows a good agreement with experimental result.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.397.2-397
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• 2002

There are 4 servo systems in a DVD drive such as a focus servo system, a tracking servo system, a sled servo system and a spindle servo system. Focus servo system maintains relative distance between lens and disk. In this paper, two plant models for the focus servo system will be presented. One of them is newly developed and the other is conventional. Focus error signal between lens and disk is detected using LDV 2 beam method. (omitted)

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1000-1007
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• 2007

Recently, many critical control systems are developed using formal methods. When software applied to such systems is developed, the employment of formal methods in the software requirements specification and verification will provide increased assurance for such applications. Earlier error of overlooked requirement specification can be detected using formal specification method. Also the testing and full verification to examine all reachable states using model checking to undertake formal verification are able to be completed. In the comparison of other formal specification methods, we choose the Z formal language for applying to the train control system. Using Z is able to realize higher correctness in the requirement specification, and we propose the Statemate of the best solution in formal verification tools for the system modeling and verification. The Statemate makes it possible to prove thoroughly the system execution from the simple graphical modeling of the complicated train control system. Then we can expect that the model-based formal method combining Z with Statemate will be utilized widely for the railway systems due to various strong points.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.684-689
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• 2000

In this paper, the equations of motion about vehicle, powertrain and brake system were derived. The vehicle has eight degrees of freedom with nonlinear tire model and the powertrain has two degrees of freedom containing engine, torque converter and four speed automatic transmission. The brake system has two states about front and rear brake line pressures. The transient tire model with first order time lag is also subjoined for low speed or stop-and-go simulation. The modeling was derived considering two points - the fidelity and the simplicity. The simulation using this model is similar with real vehicle dynamic behavior and the model is made as simple as possible far fast simulation. It is validated that the derived vehicle model can be applicable to the real time simulation.

• Korean Journal of Biological Psychiatry
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• v.18 no.4
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• pp.197-202
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• 2011

Subsyndromal anxiety disorder indicates mental states of having anxiety symptoms not fulfilling criteria for anxiety disorders. Despite of the lack of previous objective findings of the subsyndromal anxiety disorder, its clinical importance has increased. It can cause many kinds of clinical anxiety symptoms and functional disabilities. But the early intervention and early treatment make it possible not only to attenuate the anxiety symptoms and functional disabilities but also to prevent disease progression to a full syndromal anxiety disorder. In this article, we will review the previous studies about the subsyndromal anxiety disorder and discuss its clinical characteristics and importance.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.3
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• pp.30-41
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• 1992

For the state feedback controller which measures only partial state variables, a state observer can be used to give the estimates of unmeasurable states. In this paper, the delayed state feedback method instead of the state observer for desingning a tracking controller of electro-hydraulic control system is presented. The controller design is based on augmenting the original system by one additional integral and proportional element which compensates for the effect of the integral control and on feeding back the measurable state variables and their delayed values. The performance of the proposed position control system is compared with both that of the full state feedback control system and that of the digital PID control system tuned by the Ziegler-Nichols method and by the parameter readjustment through the computer simulation. And then robustness against unmeasurable constant disturbace and parameter variations during operations is also checked.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.9
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• pp.622-629
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• 2004

In practical control systems, the capacity of actuators is limited and this degrades the system performances and it is often a source of instability. To use full capacity of actuators, we adopt the gain scheduled control permitting the over saturation in controls. The basic idea of gain scheduled control is to use a higher gain control when the state variables are smaller and a lower gain control when the state variables are larger. First, we derive a constant H control and a reachable set while satisfying the degree of over saturation. Next, we divide this set into nested subsets and find $H_{\infty}$ controls at rack subsets while satisfying the degree of over saturation. Finally, the control gain is applied according to the status of states. Note that all procedures are done by solving linear matrix inequalities(LMI). Finally, we show the validity and applicability of our proposed control using the simulations of a six-story building subjected to the earthquake excitation.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.493-498
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• 2003

The 3D nonlinear analysis for steel-concrete hybrid deck is carried out by utilizing 2D plane interface element. The effect of the slip occurred between steel and concrete can be modeled by this element. This analysis focuses on not only global behavior of steel-concrete hybrid deck but also local behaviors of members of it such as lower steel plate, I-beam, and concrete which are varied by slip modulus. In this analysis, it was founded that the limit slip modulus could classify the states of steel-concrete hybrid deck into three parts such as full-composite, partial-composite, and non-composite, considering the behavior of lower steel plate, I-beam, and concrete at the mid span and the support as well as the yield load and ultimate load of it.

• Journal of Engineering Education Research
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• v.16 no.2
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• pp.37-49
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• 2013

In this paper, articles in full body of JEER in Korea and JEE in U.S. were classified into two categories- Research area and Key words-to endeavor a comparative study of the engineering education research(EER) topics and their temporal changes. In the recent 4 year term, 'Accreditation of Engineering Education' and 'Courses & Curriculum' were the most common key words appearing in JEER and 'Researches on EER' and 'Learner's Factor' in JEE. If we put curriculum/teaching materials/teaching as the input elements and learning/assessment as the output elements for education achievement, JEE demonstrates that many of the research topics have shifted from input to output in the recent years, while JEER research is in the transient stage.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.1
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• pp.162-173
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• 1997

A 3-dimensional finite element model was developed for the analysis of the automotive diesel engine piston. The model, which consists of a full piston to accomodate the eccentric bowl in the piston crown, is used to calculate steady state operating temperature, thermal stress and thermal deformation of the piston. Roundness measurement tests, which are new approaches to the analysis of piston abrasion and deformation, were done for the comparision of two states of a piston-before and after operation. Numerical prediction shows good agreement with roundness measurement test results.