• Ocean Systems Engineering
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• v.9 no.1
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• pp.79-95
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• 2019

The material analysis of an offshore structure is generally conducted in the contract design phase for the price quotation of a new offshore project. This analysis is conducted manually by an engineer, which is time-consuming and can lead to inaccurate results, because the data size from previous projects is too large, and there are so many materials to consider. In this study, the piping materials in an offshore structure are analyzed for contract design using a big data framework. The big data technologies used include HDFS (Hadoop Distributed File System) for data saving, Hive and HBase for the database to handle the saved data, Spark and Kylin for data processing, and Zeppelin for user interface and visualization. The analyzed results show that the proposed big data framework can reduce the efforts put toward contract design in the estimation of the piping material cost.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.17-21
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• 2001

Theories for optimal design and optimization algorithms have long been well developed. In industries, however, they are not well practiced. To make them work for industry, a new philosophy is necessary and an integration of various software systems required. A review of the history in the aspect of optimal design software is made and a newly developed code DS-Structure is introduced.

• Structural Engineering and Mechanics
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• v.76 no.3
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• pp.367-378
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• 2020

This paper presents a new design concept for ocean nuclear power plants (ONPPs) using a tension leg platform (TLP). The system-integrated modular advanced reactor, which is one of the successful small modular reactors, is mounted for demonstration. The authors define the design requirements and parameters, modularize and rearrange the nuclear and other facilities, and propose a new total general arrangement. The most fundamental level of design results for the platform and tendon system are provided, and the construction procedure and safety features are discussed. The integrated passive safety system developed for the gravity based structure-type ONPP is also available in the TLP-type ONPP with minor modifications. The safety system fully utilizes the benefits of the ocean environment, and enhances the safety features of the proposed concept. For the verification of the design concept, hydrodynamic analyses are performed using the commercial software ANSYS AQWA with the Pierson-Moskowitz and JONSWAP wave spectra that represent various ocean environments and the results are discussed.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.488-493
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• 1994

The global stability of model reference adaptive control system (MRACS) in the ideal case was resolved in the 1980's. Hoever the improvement of the transient, behaviour of MRACS has not been discussed sufficiently even in the ideal case. Only a few attempts have so far been made at the application of MRACS to the practical systems in contrast to the theoretical systematization. Therefore, when we consider the practical usage of MRACS it is necessary to develop an improved design scheme with respect to transient behaviour. In this paper, we propose two design schemes improving transient behaviour of MRACS by mollifying the input synthesis in the conventional design scheme of MRACS. We present a design scheme of MRACS in which we utilize the design approach of variable structure system(VSS). After describing the above design scheme, we also propose the improved design scheme in which we introduce the dead-zone decided by the magnitude of the output-error between the plant and the reference model. The effectiveness of the proposed two design schemes are shown through computer simulations. As the results, by using these methods, the convergence of the transient response is greatly improved in comparison with the conventional one.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1229-1238
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• 2002

In this paper, a method to obtain the sensitivity of eigenvalues and the random responses of the structure with uncertain parameters is proposed. The concept of the proposed method is that the perturbed equation of each uncertain substructure is obtained using the finite element method, and the perturbed equation of the overall structure is obtained using the mode synthesis method. By this way, the reduced order perturbed equation of the uncertain system can be obtained. And the response of the uncertain system is obtained using probability method. As a numerical example, a simple piping system is considered as an example structure. The damping and spring constants of the support are considered as the uncertain parameters. Then the variations of the eigenvalues, the correlation function and the power spectral density function of the responses are calculated. As a result, the proposed method is considered to be useful technique to analyze the sensitivities of eigenvalues and random response against random excitation in terms of the accuracy and the calculation time.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.4
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• pp.375-382
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• 2016

The mechanical property of a carbon-fiber-reinforced plastic (CFRP) is subjected to two elements, carbon fiber and polymer resin, in a first step and the selection of multi-layered structure is second one. Many combination of fabric layers, i.e. plainweave, twillweave, can be derived for candidates of test specimen used for a basic mechanical components so that a reliable identification of dynamic nature of possible multi-layered structures are essential during the development of CFRP based component system. In this paper, three kinds of multi-layered structure specimens were prepared and the dynamic characteristics of service specimens were conducted through classical modal test process with impact hammer. In addition, the design sensitivity analysis based on transmissibility function was applied for the measured response data so that the response sensitivity for each resonance frequency were compared for three CFRP test specimens. Finally, the evaluation of CFRP specimen over different multi-layered fabric structures are commented from the experimental consequences.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.911-917
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• 2008

It was found that more than 60% of the steam turbine blade damages occurred under the condition alternatively repeated wet and dry of vapor and condensed vapor at the lower pressure stage. And also, it has been well known that both the mechanical properties and environmental strength of the steam turbine blade can be changed by the crystal structure. However, in spite of these common facts, it is difficult to find out the quantitative results including the particular environmental condition as well as the actual service conditions. In this study, as a fundamental investigation to provide design information and reliability evaluation of the 12Cr alloy steel used for a steam turbine blade, stress corrosion strength of the 12Cr alloy steel of which its crystal structure is different was assessed under $2.5{\sim}3.5wt.%$ NaCl solution at 90oC. From the results, S-t curves for predicting damage life and design criterion of the 12Cr alloy steel including corrosion environment as well as S.C.C. condition were obtained.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.637-642
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• 2004

This paper presents a new shape design method for the multi-mode sensor that can detect selected multiple modes for the active vibration control of mechanical structures. The structure used for this study is an isotropic cantilever beam type with a PVDF(polyvinylidene fluoride) which is bonded onto the structure as a sensor. Characteristic behaviors of the sensor are related with the electrode shapes of PVDF. The shape optimization problem is solved by defining a new multi-objective function and using the genetic algorithm. Resulting electrode shape functions have good performances to detect the multiple vibration modes. The results of analytical simulations are compared with those of experiment works. The results agree well each other. Hence, the obtained experimental results give evidence for the validity of the presented theoretical analysis of the electrode shape design problem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.782-787
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• 2008

First, the effect of the geometry such as the curved shape of the struts composing the truss structure of WBK is elaborated. Then, analytic solutions for the material properties of WBK and the maximum loads of a WBK-cored sandwich panel under bending are derived. A design optimization with the face sheet thickness and the core height selected as the design variables is presented for given slenderness ratios of the WBK core. Unless the face sheet thickness is limited, the optimal design to give the maximum load per weight is always found at a confluence of three failure modes, namely, face sheet yielding, indentation plastic, and core shear modeB plastic.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.128-134
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• 2006

Topology optimization is an effective scheme to obtain the initial design concept: however, it is hard to apply in case of non-linear or multi-objective problems. In this study, a modified topology optimization method is proposed to generate a structure of a swing arm type actuator satisfying maximum compliance as well. as maximum stiffness using the multi-objective optimization. approach. The multi-objective function is defined to maximize the compliance in the direction of focusing of the actuator and the second eigen-frequency of the structure. The design of experiments are performed and the response surface functions are formulated to construct the multi-objective function. The weighting factors between conflicting functions are determined by the back-error propagation neural network and the solution of multi-objective function is acquired using the genetic algorithm.