• Journal of the Korean Society for Precision Engineering
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• v.1 no.2
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• pp.10-14
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• 1984

연삭가공은 숫돌을 구성하는 하나 하나의 입자가 공작물을 절삭하는 과정이므로 연삭현상을 이해하기 위해서는 먼저 개개 절돈의 절삭현상을 알지 않으면 안된다. 연삭입자의 절삭현상을 해명함에 있어서 기초가 되는 것은 입자와 공작물과의 간섭형상이다. 종래의 연삭 이론은 이와같은 기하학적 간섭형상이 모두 chip이 되어 제거된다(연소입자와 공작물과의 간섭 과정에서는 절삭현상만이 존재한다.)는 가정하에 연삭기구를 해석하려 하였으나 최근에 이르러 상호간섭 조건을 경계조건으로 하여 많은 사람들에 의해 연소입자의 절삭현상을 연구한 결과 연삭입자의 절삭과정은 과도적 절삭임이 밝혀졌다. 이와같은 연삭현상은 새로운 연삭이론에 기초가 될 뿐만아니라 Chip 과 표면생성기구의 관점에서도 극히 중요한 것이 된다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.256-259
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• 1996

수명시험에서는 시험기간을 단축하기 위해 중도절단(consoring) 방법을 사용한다. 혼합 관측중단방법은 정시에 시험을 끝낼 수 있으며 고장시간을 관찰할 필요가 없다는 장점 때문에 널리 사용되고 있다. 본 논문에서는 제품의 수명이 와이블 분포를 따르고 형상모수를 알고 있다는 가정아래, 혼합 관측중단하에서 생산자 위험과 소비자 위험을 고려한 신뢰도 합격판정 샘플링 계획을 개발하였다. 아울러, 형상모수값에 개재된 불확실성이 실제 생산자 위험과 소비자 위험, 그리고 의사결정까지의 평균 고장개수에 미치는 영향을 민감도 분석을 통해 파악하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.319-326
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• 2006

A new enhanced 8-node hybrid/mixed plane stress elements based on assumed stress fields and modifed shape functions has been presented. The assumed stress fields are derived from the non-conforming displacement modes, which are less sensitive to geometric distortion. Explicit expression of shape functions is modifed so that it can represent any quadratic fields in Cartesian coordinates under the same condition as 9-node isoparametric element. The newly developed element has been designated as 'HQ8-$14{\beta}$'. The presented element is compared with existing elements to establish its accuracy and efficiency. Over a wide range of mesh distortions, the element presented here is found to be exceptionally accurate in predicting displacements.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.2
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• pp.193-205
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• 2008

The construction of underground structures such as oil and food storage caverns are recently increasing in our country. The stability of those underground caverns are greatly influenced by their shape and size. In this study therefore, the effect that the shape of an underground cavern have on its stability were analyzed in terms of safety factor. To this end, caverns with 5 different shapes were investigated and sensitivity analyses were performed based on rock class, overburden, and lateral earth pressure coefficient. The proper amount of shotcrete and rockbolt as supports of a cavern was also assumed based on the shape and site of the cavern and rock conditions. This study is expected to be helpful in designing and evaluating the stability of caverns in future.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.3
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• pp.22-31
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• 2022

Existing Finocyl grain designs assume configurations and repeat the process of configuration modification and confirmation of the requirements through burn-back analysis. Such a design increases the design fatigue of workers and has a problem of different design completeness depending on capabilities. Therefore, this study devised an optimal design method that applied genetic algorithms to the Burn-back automation analysis program to solve the problem of existing design. For stable search, variable-offset and non-drawable configuration control techniques were developed. The program performance was verified through the searching neutral and double thrust grains.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.187-190
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• 2003

복잡한 형상을 지나는 고분자 유체의 유동 해석은 학문적인 관심 뿐만 아니라 고분자 가공 공정을 이해하는데 많은 도움을 주기 때문에 산업적으로도 그 중요성이 높다. 그러나, 기하학적 복잡성이나 재료 자체의 비선형성으로 인하여 해석적인 접근에 한계가 있기 때문에 다양한 수치 해석법을 이용한 유동 해석이 주를 이루고 있다. 특히 고분자 가공 공정의 수치 모사에 있어서는 수치 해석법을 적용하는데 있어서도 완전한 3차원 해석보다는 여러 가지 가정을 적용한 2차원 내지는 2.5차원 해석이 주를 이루고 있어서도 완전한 3차원 해석보다는 여러 가지 가정을 적용한 2차원 내지는 2.5차원 해석이 주를 이루고 있는 실정이다. (중략)

• Journal of Sensor Science and Technology
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• v.7 no.6
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• pp.437-445
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• 1998

The actuator using shape memory alloy spring with bias spring can act as a bidirectional actuator due to the restoring force of the bias spring. In the design of shape memory actuator with bias spring, the required design specifications are the generated force and the necessary stroke. To fulfill these requirements, shape memory alloy spring and bias spring should be designed carefully considering the specified application. In this paper, the novel design method for shape memory alloy actuator with bias spring, which does not require any assumptions from experience, has been proposed and verified by the test of fabricated shape memory alloy actuator. The experimental results show good agreements with calculated values, which guarantees the practical validity of our proposed design method.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.4
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• pp.11-18
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• 2000

This paper is concerned with the generation of an optimal forward hull form by a nonlinear programming method. A Rankine source panel method based on the inviscid and potential flow approximation is employed to calculate the wave-making resistance and SQP method is also used for the optimization. The hull form is represented by a spline function. The forward hull form of a minimum wave resistance with the given design constraints is generated. In addition, the forward hull form of a minimum total resistance by considering the frictional resistance together with an empirical form factor is produced and compared with the former result.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.1
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• pp.147-158
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• 2000

For the large scale reinforced concrete cooling tower shells, the shape imperfection can be introduced due not only to mistakes in the process of construction but also to the long term behavior of concrete. The shape imperfection evokes the additional responses such as displacements and stresses in addition to the design values. In this study, the statistical behavior of the RC cooling tower shell due to the shape imperfection is investigated using the Monte Carlo simulation. The radius of cooling tower and the shell thickness are adopted as the parameters which cause the shape imperfection. The shape imperfection is modeled as a stochastic field rather than the local one of axisymmetric or bulge type of imperfection. The randomness in the radius is shown to be more affecting the structural responses than the randomness in the shell thickness. In addition to the geometrical randomness, the effect of randomness in the modulus of elasticity on the structural response is also investigated and compared with that of the geometrical ones.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.271-277
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• 2014

Internal structures, especially those located in the upstream of a reactor core, may have a significant influence on the core inlet flow rate distribution depending on both their shapes and the relative distance between the internal structures and the core inlet. In this study, to examine the effect of the reactor internal structure geometry treatment method on the prediction accuracy for the scale-down APR+ flow distribution, simulations with real geometry modeling were conducted using ANSYS CFX R.14, a commercial computational fluid dynamics software, and the predicted results were compared with those of the porous medium assumption. It was concluded that the core inlet flow distribution could be predicted more accurately by considering the real geometry of the internal structures located in the upstream of the core inlet. Therefore, if sufficient computational resources are available, an exact representation of these internal structures, for example, lower support structure bottom plate and ICI nozzle support plate, is needed for the accurate simulation of the reactor internal flow.