• Journal of Advanced Marine Engineering and Technology
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• v.38 no.8
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• pp.1004-1009
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• 2014

The redundancy allocation problem has usually considered only the component redundancy at the lowest-level for the enhancement of system reliability. A system can be functionally decomposed into system, module, and component levels. Modular redundancy can be more effective than component redundancy at the lowest-level because in modular systems, duplicating a module composed of several components can be easier, and requires less time and skill. We consider a multi-level redundancy allocation problem in which all cases of redundancy for system, module, and component levels are considered. A tabu search of memory-based mechanisms that balances intensification with diversification via the short-term and long-term memory is proposed for its solution. To the best of our knowledge, this is the first attempt to use a tabu search for this problem. Our tabu search algorithm is compared with the previous genetic algorithm for the problem on the new composed test problems as well as the benchmark problems from the literature. Computational results show that the proposed method outstandingly outperforms the genetic algorithm for almost all test problems.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.206.2-206.2
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• 2005

• Nuclear Engineering and Technology
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• v.42 no.6
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• pp.608-619
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• 2010

A multi-scale analysis of water-cooled reactor thermalhydraulics can be used to take advantage of increased computer power and improved simulation tools, including Direct Numerical Simulation (DNS), Computational Fluid Dynamics (CFD) (in both open and porous mediums), and system thermalhydraulic codes. This paper presents a general strategy for this procedure for various thermalhydraulic scales. A short state of the art is given for each scale, and the role of the scale in the overall multi-scale analysis process is defined. System thermalhydraulic codes will remain a privileged tool for many investigations related to safety. CFD in porous medium is already being frequently used for core thermalhydraulics, either in 3D modules of system codes or in component codes. CFD in open medium allows zooming on some reactor components in specific situations, and may be coupled to the system and component scales. Various modeling approaches exist in the domain from DNS to CFD which may be used to improve the understanding of flow processes, and as a basis for developing more physically based models for macroscopic tools. A few examples are given to illustrate the multi-scale approach. Perspectives for the future are drawn from the present state of the art and directions for future research and development are given.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.3
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• pp.35-43
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• 2012

Medium size rotorcraft consist of approximately 5,000 key components. The components must satisfy the target weight and performance requirement through optimization. Therefore a rotorcraft component has approximately 100 times higher unit cost for mass production than the equivalent of an automobile's, along with huge development cost. Configuration management consists of four main parts : configuration identification, configuration control, configuration audit, and data management. In development programme, configuration management is one of the methods to save development cost, and setting a well-structured configuration management system according to the Military Standard is an important factor in success of the programme. The paper proposes a configuration management system suitable for development of various multi-use components development and presents that the configuration management was performed successfully during dual-use component development programme using the established system.

• Communications of the Korean Mathematical Society
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• v.38 no.2
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• pp.509-524
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• 2023

In this study, we characterize the structure of the multivariable mappings which are sextic in each component. Indeed, we unify the general system of multi-sextic functional equations defining a multi-sextic mapping to a single equation. We also establish the Hyers-Ulam and Găvruţa stability of multi-sextic mappings by a fixed point theorem in non-Archimedean normed spaces. Moreover, we generalize some known stability results in the setting of quasi-𝛽-normed spaces. Using a characterization result, we indicate an example for the case that a multi-sextic mapping is non-stable.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.3
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• pp.200-207
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• 2024

A multi-component force sensor has been developed to measure force and moment components in high-speed flow media for submerged models. The size of the test model is determined based on the Reynolds number of the model at the test speed and expected blockage effect. A two-component force sensor unit has been created by assembling pairs of column elements arranged symmetrically under an eccentric load. The six-component force sensor is constructed with symmetric arrangements of two-component force sensor units in a rectangular plane. The signals generated from the strain gauges attached to the surface of the elements can be converted into force signals. The performance of the waterproof six-component force sensor has been evaluated through calibration. A simplified interference decomposition procedure has been introduced to increase the accuracy of measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.297-302
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• 2007

Vibrating test of vehicle component can be possible in lab-based simulators instead of field testing owing to the development of technology in control algorithm as well as computational process. Currently, Multi-Axial Simulation Table(MAST) is recommended as a vibrating equipment, which excites a target component for 3-directional translation and rotation motion simultaneously and hence, vibrational condition can be fully approximated to that of real road test. But, the vibration-free performance of target component is not guaranteed with MAST system, which is only simulator subjective to the operator. Rather, the reliability of multi-axial vibration test is dependent on the quality of input profile which should cover the required severity of vibrating condition on target component. In this paper, multi-axial vibration testing methodology of vehicle component is presented here, from data acquisition of vehicle accelerations to the obtaining the input profile of MAST using severe data at proving ground. To compare the severity of vibration condition, between real road test and proving ground one, energy principle of equivalent damage is proposed to calculate energy matrices of acceleration data and then, it is determined the optimal combination of special events on proving ground which is equivalent to real road test at the aspects of vibration fatigue using sequential searching optimal algorithm. To explain the vibration methodology clearly, seat and door component of vehicle are selected as a example.

• IE interfaces
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• v.22 no.2
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• pp.165-173
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• 2009

This paper considers a two-component assembly system that makes different types of purchasing contracts by component type and studies the issue of coordinating those contracts. Acquisition of type 1 component is based on the long-term contract. In contrast, type 2 component is intermittently purchased under the sort-term contract. We identify the structural properties of the optimal short-term contract and investigate how the changes in system parameters affect the optimal performance. To provide managerial insights, we compare the short-term and long-term contracts for type 2 component and discuss the conditions that make the short-term contract preferable to the long-term contract. We also present a result which shows that coordinating the contracts of type 1 and type 2 components can be significantly profitable over uncoordinating them.

• Nuclear Engineering and Technology
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• v.41 no.10
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• pp.1347-1360
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• 2009

A multi-dimensional component for the thermal-hydraulic system analysis code, MARS, was developed for a more realistic three-dimensional analysis of nuclear systems. A three-dimensional and two-fluid model for a two-phase flow in Cartesian and cylindrical coordinates was employed. The governing equations and physical constitutive relationships were extended from those of a one-dimensional version. The numerical solution method adopted a semi-implicit and finite-difference method based on a staggered-grid mesh and a donor-cell scheme. The relevant length scale was very coarse compared to commercial computational fluid dynamics tools. Thus a simple Prandtl's mixing length turbulence model was applied to interpret the turbulent induced momentum and energy diffusivity. Non drag interfacial forces were not considered as in the general nuclear system codes. Several conceptual cases with analytic solutions were chosen and analyzed to assess the fundamental terms. RPI air-water and UPTF 7 tests were simulated and compared to the experimental data. The simulation results for the RPI air-water two-phase flow experiment showed good agreement with the measured void fraction. The simulation results for the UPTF downcomer test 7 were compared to the experiment data and the results from other multi-dimensional system codes for the ECC delivery flow.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.636-642
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• 2007

Software program to predict the packing density of multi-sized and multi-component particulate system was developed. For this purpose, the experiment to measure the packing density of AP (ammonium perchlorate) and Al (aluminum) particles with different sizes and their mixtures was carried out. The packing densities obtained from various experiments were compared with the predicted data from the developed software program. In the case of the packing density of the binary system, which is comprised of two different size particles and/or two different components, the relative errors were ranged 0.25~13.13%, and in the same venue the relative errors of the ternary system were 0.25~13.13%. Agreement between experimental data and the predicted results is reasonably accurate. In order to achieve the targeted packing density, the software program calculated the contour of the component particles and this will contribute the formulation of optimal packing systems.