• International conference on construction engineering and project management
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• 2005.10a
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• pp.1193-1198
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• 2005

The pre-assembly takes a large portion of the fabrication cost of steel bridges. In order to save the fabrication cost through the improvement of the conventional pre-assembling process, this research investigates a numerical pre-assembly simulation as an alternative to current pre-assembling process. The 3D laser scanning was utilized in site and measuring data for steel box were analyzed. The productivity of pre-assembly simulation system is compared with the conventional pre-assembling system. This paper identifies feasibility on the alternative pre-assembling process and then proposes the scheme of the pre-assembly simulation system development satisfying the current pre-assembly inspection of standards.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.26 no.4
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• pp.63-71
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• 2003

This paper analyses a deterministic scheduling problem concerned with manufacturing multiple types of components at a pre-assembly stage composed of parallel fabrication machines. Each component part is machined on a fabrication machine specified in advance. The manufactured components are subsequently assembled into products. The completion time of a job(product) is measured by the latest completion time of its all components at the pre-assembly stage. The problem has the objective measure of minimizing the total weighted completion time of a finite number of jobs. Two lower bounds are derived and tested in a branch-and-bound scheme. Also, three constructive heuristic algorithms are developed based on the machine aggregation and greedy strategies. Some empirical evaluation of the performance of the proposed branch-and-bound and heuristic algorithms are also performed.

• Journal of the Korea Institute of Building Construction
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• v.10 no.2
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• pp.125-132
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• 2010

Recently, construction companies have had difficulty in managing their business due to economic hardship domestically and abroad, decreased orders, and low profitability due to intensified competition. To address these issues, construction companies need to develop or introduce construction methods that improve productivity. The purpose of this study is to investigate a re-bar construction method that reduces the high expenses of transport by folding a pre-fabricated re-bar cage. It was concluded that the application of rebar pre-fabrication would be activated and the productivity of construction sites improved by adopting the folding rebar pre-fabrication method.

• KIEAE Journal
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• v.7 no.2
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• pp.39-46
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• 2007

A high-rise building construction in Korea has some problems in engineering, construction and management technologies although the high-rise building construction is recently booming. In addition, the lack of skilled construction labors is increasing, so the development for methods is needed to reduce the labors by prefabrication and mechanization. A re-bar work is one of very important works with regard to cost and schedule management in the high-rise building construction. Nevertheless, the re-bar work has some problems that it is needed many re-bars for joints linking and much time for lifting due to high-rise buildings, and it is difficult to level the skill of labors. So, in this study, the pre-fabrication of three-story height in column re-bars is proposed and the results of an implementation are analyzed and explored by a case study. As the results of case study, the pre-fabrication of three-story heights in column re-bars could reduce the cost in the re-bar work and accelerate the time in the structural frame work. In addition, the pre-fabrication of three-story height in column re-bars could solve the problems such as the waste of many re-bars for joints linking, and the lack of the skilled labors.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.3
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• pp.431-453
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• 2013

The principal purpose of this paper is to present a novel two phases rational scenario applied in constructing an offshore monopod platform; in which the two phases are the all-ground horizontal construction phase and the post-construction phase. Concerning the all-ground construction phase, a brief investigation of its different stages, i.e., pre-fabrication, fabrication, pre-assembling, positioning, assembling, and surface finishing is introduced. The important practical aspects of such construction phase are investigated without going into the nitty-gritty of the details involved therein. Concerning the post-construction phase, a clear investigation of its sequential stages, i.e., lifting, moving and up-righting is introduced. A finite element model (FEM) of the monopod platform is created to perform the structural analysis necessary to decide the suspension points/devices and the handling scenario during the various stages of the post-construction phase on a rational wise. Such structural analysis is performed within the framework of the three dimensional quasi-static modeling and analysis aiming at simulating the realistic handling condition, and hence introducing a reliable physical interpretation of the numerical results. For the whole effort to be demonstrated efficiently, the results obtained are analyzed, the conclusions are presented, and few related recommendations are suggested.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.109-116
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• 2007

Focused ion beams are a potential tool for micro/nano structure fabrication while several problems still have to be overcome. Redeposition of sputtered atoms limits the accurate fabrication of micro/nano structures. The challenge lies in accurately controlling the focused ion beam to fabricate various arbitrary curved shapes. In this paper a basic approach for the focused ion beam induced direct fabricate of fundamental features is presented. This approach is based on the topography simulation which naturally considers the redeposition of sputtered atoms and sputtered yield changes. Fundamental features such as trapezoidal, circular and triangular were fabricated with this approach using single or multiple pass box milling. The beam diameter(FWHM) and maximum current density are 68 nm and $0.8 A/cm^2$, respectively. The experimental investigations show that the fabricated shape is well suited for the pre-designed fundamental features. The characteristics of ion beam induced direct fabrication and shape formation will be discussed.

• Journal of Mechanical Science and Technology
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• v.18 no.3
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• pp.453-459
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• 2004

TiNi/ Al6061 shape memory alloy (SMA) composite was fabricated by hot press method to investigate the microstructure and mechanical properties. Interface bonding between TiNi reinforcement and A1 matrix was observed by using SEM and EDS. Pre-strain was imposed to generate compressive residual stress inside composite. A tensile test for specimen, which under-went pre-strain, was performed at high temperature to evaluate the variation of strength and the effect of pre-strain. It was shown that interfacial reactions occurred at the bonding between matrix and fiber, creating two inter-metallic layers. And yield stress increased with the amount of pre-strain. Acoustic Emission technique was also used to nondestructively clarify the microscopic damage behavior at high temperature and the effect of pre-strain of TiNi/ Al6061 SMA composite.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.52-59
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• 1997

Design and performance of principal four ICs for the 10-Gb/s optical communication system are presented. AlGaAs/GaAs HBTs are basic devices to implement a laser diode driver, apre-amplifier, and a limiting amplifier, and GaInP/GaAs HBTs are used for an AGC amplifier. We fbricated 11.5-GHz LD driver, a pre-amplifier, and a limiting amplifier, an dGaInP/GaAs HBTs are used for an AGC amplifier. We fabricated LD deriver, 10.5 GHz pre amplifier, 7.2 GHz AGC amplifier, and 10.3 GHz limiting amplifier, optimized circuit design and the stabilized MMIC fabrication process.

• Steel and Composite Structures
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• v.25 no.5
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• pp.523-534
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• 2017

Cable-supported ribbed beam composite slab structure (CBS) is proposed in this study. As a new cable-supported structure, it has many merits such as long span availability and cost-saving. Inspired by the previous research on cable-supported structures, the fabrication and construction process are developed. Pre-stress design method based on static equilibrium analysis is presented. In the algorithm, the iteration convergence can be accelerated and the calculation result can be kept in an acceptable precision by setting a rational threshold value. The accuracy of this method is also verified by experimental study on a 1:5 scaled model. Further, important parameters affecting the mechanical features of the CBS are discussed. The results indicate that the increases of sag-span ratio, depth of the ribbed beam and cable diameter can improve the mechanical behavior of the CBS by some extent, but the influence of strut sections on mechanical behavior of the CBS is negligible.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.164-170
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• 2000

Important factors in a casting mold are strength at the mold surface and gas permeability of the mold. This study investigates the effects of pre-pressure and sand particle hardness on gas permeability, with a constraint that the norm of a stiffness array at the mold surface should be higher than a certain value. The constitutive relation is obtained using a hypoplasticity model. This study is firstly attempted to investigate sand behavior in mold fabrication, and will give a theoretical base for fabricating better molds.