• Journal of the Korea Society of Computer and Information
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• v.16 no.11
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• pp.153-161
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• 2011

As the problem of GOSST building belongs to NP compete domain, heuristics for the problem ask for immense amount execution time and computations in large scale inputs. In this paper, we propose an efficient mechanism for GOSST construction using space locality PTAS. For 40,000 input nodes with maximum weight 100, the proposed space locality PTAS GOSST with 16 unit areas can reduce about 4.00% of connection cost and 89.26% of execution time less than weighted minimum spanning tree method. Though the proposed method increases 0.03% of connection cost more, but cuts down 96.39% of execution time less than approximate GOSST method (SGOSST) without PTAS. Therefore the proposed space locality PTAS GOSST mechanism can work moderately well to many useful applications where a greate number of weighted inputs should be connected in short time with approximate minimum connection cost.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.2
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• pp.56-67
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• 2006

The reliability and failure mode effect analysis are effective means to achieve efficient and cost-reduction design for satellite development. The failure rate of COTS (Commercial-Off-The-Shelf) parts required for reliability analysis is not usually provided from the manufacturer. Space environment factors based on empirical data obtained from MIL-HDBK-217F can be applicable to the reliability calculation. As a radiation environment factor, the occurrence rate of SEL (Single Event Latch-up) is additionally incorporated for the failure rate prediction. In this paper, the statistical reliability analysis method for low-cost small satellite using COTS parts is suggested. This statistical reliability analysis was applied to HAUSAT-2 small satellite whose electronic boxes are consisted of many COTS parts to calculate the system reliability at the end of design mission life.

• Journal of the Chungcheong Mathematical Society
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• v.28 no.1
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• pp.1-12
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• 2015

We present a local convergence analysis for inexact Newton-like method in a Banach space under weaker Lipschitz condition. The convergence ball is enlarged and the estimates on the error distances are more precise under the same computational cost as in earlier studies such as [6, 7, 11, 18]. Some special cases are considered and applications for solving nonlinear systems using the Newton-arithmetic mean method are improved with the new convergence technique.

• Journal of the Korean Mathematical Society
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• v.54 no.1
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• pp.17-33
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• 2017

We present a new local as well as a semilocal convergence analysis for Steffensen's method in order to locate fixed points of operators on a Banach space setting. Using more precise majorizing sequences we show under the same or less computational cost that our convergence criteria can be weaker than in earlier studies such as [1-13], [21, 22]. Numerical examples are provided to illustrate the theoretical results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.4
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• pp.334-340
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• 2015

Engine derating is often considered for reliability benefits because lower power operation reduces its failure probability. To be derated during operation, however, the engine must be initially overdesigned. The engine overdesign is cost effective only if reliability increased from derating is enough to offset the initial increase in the development cost caused from the overdesign. The purpose of this paper is to provide an analytical model to consider a trade-off between the engine overdesign and derating. We use a logistic regression model to explain reliability growth in the number of hot firing tests for a fixed power level. Using the Transcost model with the reliability growth model, we show that 10% overdesign of Titan rocket engine decreases its development cost by about 9% and 23% depending on the reliability requirement. We also point out that such a cost reduction depends on the fuel type a rocket uses.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.2
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• pp.161-174
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• 2003

Applicability of the Decision Aids for Tunneling (DAT) technique is investigated in this study to better understand the efficiency of the decision making process during tunnel construction. For this, a traffic tunnel under construction is adopted and information on the construction procedure, i.e., overall geology, unit cost and construction time for each excavation process, is provided periodically. Various scattergrams in which cost-time simulation results are plotted are obtained according to the simulation methods and final prediction on the construction time/cost is made. It is found that the uncertainty in the cost distribution is greater than the uncertainty in the time distribution for each cycle simulation and the uncertainties in time and cost for the one time simulations are comparable. Future work will be concentrated on the updating scheme using the face mapping data and various parametric studies will also be performed.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.624-635
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• 2015

Design space exploration has been much neglected in aircraft conceptual design phase, which often leads to a waste of time and cost in design, manufacture and operation process. It is necessary to explore design space based on operational system-of-systems (SoS) simulation during the early phase for a competitive design. This paper proposes a methodology to analyze aircraft performance parameters in four steps: combination of parameters, object analysis, operational simulation, and key-parameters analysis. Meanwhile, the design space of an unmanned aerial vehicle applied in earthquake search and rescue SoS is explored based on this methodology. The results show that applying SoS simulation into design phase has important reference value for designers on aircraft conceptual design.

• Structural Engineering and Mechanics
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• v.28 no.6
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• pp.715-725
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• 2008

New types of armor, including space armor, multiple-layered armor, composite armor and modular armor have been successfully developed and installed on the armored vehicles of several nations. The protective capability of armor against penetration is established. Of developed composite armor, space armor has a simple structure and is easy to produce and can be produced at low cost. This study uses the finite element package DYTRAN and the pre and post processor PNTRAN to elucidate the ballistic resistance and penetration of space armor. Factors such as armor thickness, space between armors and projectile profile are considered. A technique for simulating the protection afforded by armor and supporting the design of space armor is developed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.1
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• pp.13-20
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• 2022

Aircraft weight is an important factor affecting performance and fuel efficiency. In the conceptual design stage of the aircraft, the process of balancing cost and weight is performed using empirical formulas such as fuel consumption cost per weight in estimating element weight. In addition, when an airline operates an aircraft, it promotes fuel efficiency improvement, fuel saving and carbon reduction through weight management activities. The relationship between changes in aircraft weight and changes in fuel consumption is called the cost of weight, and the cost of weight is used to evaluate the effect of adding or reducing weight to an aircraft on fuel consumption. In this study, the problems of the existing cost of weight calculation method are identified, and a new cost of weight calculation method is introduced to solve the problem. Using Breguet's Range Formula and actual flight data of the A350-900 aircraft, two weight costs are calculated based on take-off weight and landing weight. In conclusion, it was suggested that it is reasonable to use the cost of weight based on the take-off weight and the landing weight for other purposes. In particular, the cost of weight based on the landing weight can be used as an empirical formula for estimating element weight and optimizing cost and weight in the conceptual design stage of similar aircraft.

• Korean Institute of Interior Design Journal
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• v.24 no.2
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• pp.142-150
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• 2015

The purpose of this study is to analysis the change of rural house type and house plans in Bonghwa province. According to definition of rural area, the scopes of the research of rural houses limited the Bonghwa rural area(1 eup, 9 myeon). The method of study is to compare and analyze about housing situation, structure of house, housing type and construction of house space etc. through the statistical data of Bongwha statistical yearbook, space syntax(convex analysis) and other various data etc. during these 10 years. As a results of the analysis 1) According to Change of family member the supply ratio of detached house is steadily decreasing and changing from a detached house to multi-household house in Bongwha areas. 2) Most of houses structure were using lightweight steel construction because of cost-cutting of construction and easy way to construct etc.. 3) The highest Integration space is living space in rural house plans 4) The highest segregation space is bathroom space of master bed room in rural house plans. Some of bed rooms are classed as segregation space regardless of Integration space 5) Traditional front yard's function is changing from the place with the various functions to the place with the specific functions.