• Korean Journal of Computational Design and Engineering
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• v.7 no.3
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• pp.157-169
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• 2002

In the initial stages of ship design, designers represent geometry, arrangement, and dimension of hull structures with 2D geometric primitives such as points, lines, arcs, and drawing symbols. However, these design information(‘2D geometric primitives’) defined in the drawing sheet require more intelligent translation processes by the designers in the next design stages. Thus, the loss of design semantics could be occurred and following design processes could be delayed. In the initial design stages, it is not easy to adopt commercial 3D CAD systems, which have been developed f3r being used in detail and production design stages, because the 3D CAD systems require detailed input for geometry definition. In this study, a semantic product model data structure was proposed, and an initial structural CAD system was developed based on the proposed data structure. Contents(‘product model data and design knowledges’) of the proposed data structure are filled with minimal input of the designers, and then 3D solid model and production material information can be automatically generated as occasion demands. Finally, the applicability of the proposed semantic product model data structure and the developed initial structural CAD system was verified through application to deadweight 300,000ton VLCC(Very Large Crude oil Carrier) product modeling procedure.

• Journal of the Korean Society of Safety
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• v.25 no.1
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• pp.50-56
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• 2010

The safety accidents of domestic construction happened more than other industries is performed only under the construction stage. In the foreign countries, however, owners and designers play an important role on safety in an early stage. Therefore, numerous studies were carried out by getting rid of accident risks and institutionalizing prevention activities in an construction stages. Accordingly, this study have performed to deduce the pivotal point of safety management items classified by the subject suitable for construction by introducing of safety conception of domestic and international design and suggested the improvement methods of safety management plans of the planning design stage so as to perform more efficient safety management.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.742-745
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• 2003

Piezoelectric elements driven ultra-precision stages have been used for high accuracy, fast response and high load rapacity. which are allowable to apply the stages to AFMs. Most of the piezoelectric driven stages are guided by flexure hinges for force transmission and mechanical amplification. However the flexure hinge mechanisms cause lack of position accuracy due to coupled and parasitic motions. Hence it is important that the mechanism design of the stage is focused on the stiffness of the flexure hinges to accomplish fast response and hish accuracy without the coupled and parasitic motions. In this study, some constraints for optimal design of a piezoelectric elements driven stage and a design method are proposed. Next, an optimal design is carried out using mathematical calculation. Finally the designed results are verified by FEM.

• Korean Institute of Interior Design Journal
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• v.14 no.2 s.49
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• pp.120-127
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• 2005

The purpose of this study was to examine preferential unit planning components of high-rise residential buildings across family life cycle stages. The questionnaire survey was adopted in this study, and 110 cases were used for data analysis. Based on the age of the oldest child, the family life cycles used in the study were divided into four stages: early childhood, elementary school, adolescence, and adulthood. The findings showed that the preference of the unit planning components across the stages was distinct; families in the stage of early childhood and adolescence had the growing needs for spatial features, and regarded living-related features as important. Families in the stage of adulthood tended to have larger spaces. It was noticed that unit planning components needed to be more differential when the combined effect of both family life cycle stages and housing size was considered.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2697-2711
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• 2023

In this study, the validity of reducing the number of gas turbine stages designed for a nitrogen Brayton cycle coupled to a sodium-cooled fast reactor was assessed. The turbine performance was evaluated through computational fluid dynamics (CFD) simulations under different off-design conditions controlled by a reduced flow rate and reduced rotational speed. Two different multistage gas turbines designed to extract almost the same specific work were selected: two- and three-stage turbines (mid-span stage loading coefficient: 1.23 and 1.0, respectively). Real gas properties were considered in the CFD simulation in accordance with the Peng-Robinson's equation of state. According to the CFD results, the off-design performance of the two-stage turbine is comparable to that of the three-stage turbine. Moreover, compared to the three-stage turbine, the two-stage turbine generates less entropy across the shock wave. The results indicate that under both design and off-design conditions, increasing the stage loading coefficient for a fewer number of turbine stages is effective in terms of performance and size. Furthermore, the Ellipse law can be used to assess off-design performance and increasing exponent of the expansion ratio term better predicts the off-design performance with a few stages (two or three).

• Journal of Distribution Science
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• v.11 no.2
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• pp.5-10
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• 2013

Purpose - The current research examines the effect of life cycle stages on capital structure of listed companies in Tehran Stock Exchange. Research design, data, methodology - By aid of 685 year-company data, which collected from financial statements of companies during 2006-2012, first, the companies, are classified into three groups including companies in growth, maturity and decline stages. After removing the companies, which were not in accordance with life cycle model, 86 companies were selected to test two main hypotheses of the research. Results - The results show that the capital structure of the sample companies is different in various life cycle stages. More investigation by LSD test also revealed that the total debt to total assets ratio means of the companies in growth stages were significantly different from those companies in maturity stages and those in growth stages had high level of debt to assets ratio. Conclusions - The result showed the average amount of the working capital for companies in three stages are significantly different and due to high level of operation of the companies in maturity and decline stages, these companies held high amount of working capital than those in the growth stages.

• Journal of the Korea Concrete Institute
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• v.12 no.4
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• pp.121-130
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• 2000

Current engineering practice in determining sectional dimensions of prestressed concrete (PSC) girders for bridges is primarily based on the code-specified allowable concrete stresses at different loading stages. It is customary that tendons and sectional dimensions are calibrated and tendon forces are applied at once at the initial stage to keep the subsequent stresses occurring at different loading stages within the allowable stresses. This traditional tensioning method, however, usually results in a too conservative sectional depth in view of ultimate capacity of a girder. A new design method which can realize the reduction of sectional depth of PSC girders is theoretically suggested in this study. Tendons are tensioned twice at different loading stages: the initial stage and the stage after fresh slab concrete is cast. It can be shown that according to this technique, sectional depth can be significantly reduced and larger span can be realized compared to traditional ones. Parametric studies are performed with due considerations given to its practical applications.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.5
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• pp.650-656
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• 2016

Voltage controlled oscillator (VCO) is widely used circuit component in high-performance microprocessors and modern communication systems as a frequency source. In present work, VCO designs using the different combination of NAND gates with three transistors and CMOS inverter are reported. Three, five and seven stages ring VCO circuits are designed. Coarse and fine tuning have been done using two different supply sources. The frequency with coarse tuning varies from 3.31 GHz to 5.60 GHz in three stages, 1.77 GHz to 3.26 GHz in five stages and 1.27 GHz to 2.32 GHz in seven stages VCO respectively. Moreover, for fine tuning frequency varies from 3.70 GHz to 3.94 GHz in three stages, 2.04 GHz to 2.18 GHz in five stages and 1.43 GHz to 1.58 GHz in seven stages VCO respectively. Results of power consumption and phase noise for the VCO circuits are also been reported. Results of proposed VCO circuits have been compared with previously reported circuits and present circuit approach show significant improvement.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.11-21
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• 2019

In product design, the initial design stage is being increasingly emphasized because it significantly influences the successive product development and production stages. However, for larger and more complex products, it is very difficult to accurately predict product reliability in the initial design stage. Various design methodologies have been proposed to resolve this issue, but maintaining reliability while exploring design alternatives is yet to be achieved. Therefore, this paper proposes a methodology for conceptual design considering reliability issues that may arise in the successive detailed design stages. The methodology integrates the independency of axiomatic design and the hierarchical structure of failure mode, effects, and criticality analysis (FMECA), which is a technique widely used to analyze product reliability. We applied the proposed methodology to a liquefied natural gas fuel gas supply system to verify its effectiveness in the reliability improvement of the design process.

• Korean Journal of Computational Design and Engineering
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• v.16 no.2
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• pp.83-91
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• 2011

There are many researches to make low-energy building. Lots of them focus on facility systems and insulation performance of building materials. However, not only systematic solutions but also approaches in early design stages are important to reduce energy consumption. Using BIM(Building Information Modelling) is considered as an effective and efficient way to simulate building energy and decide alternatives than traditional energy simulation because BIM based energy simulation makes to reduce much time for energy modeling. This study focuses on development of optimized geometry for super tall office buildings in Seoul, Korea. Specifically, length to width ratio and building orientation are main topics of this study because these two topics are the most basic and preceding factors deciding mass design. In this study, Revit MEP 2011 and Ecotect Analysis 2011 are used to make case models and calculate energy load in early design stages. Energy properties of material abide by Korean Standards for Energy Conservation in Building, Korean Guideline for Energy Conservation in Public Office and ASHRAE Standard in USA. This study presents best length to width ratio of plan and optimized orientation by evaluating the case models. Furthermore, this study suggests what should be considered for each case to decrease energy load.