• Nuclear Engineering and Technology
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• 제50권6호
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• pp.854-859
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• 2018

Calculating minimal cut sets is a typical quantification method used to evaluate the top event probability for a fault tree. If minimal cut sets cannot be calculated or if the accuracy of the quantification result is in doubt, the Monte Carlo method can provide an alternative for fault tree quantification. The Monte Carlo method for fault tree quantification tends to take a long time because it repeats the calculation for a large number of samples. Herein, proposal is made to improve the quantification algorithm of a fault tree with circular logic. We developed a top-down iteration algorithm that combines the characteristics of the top-down approach and the iteration approach, thereby reducing the computation time of the Monte Carlo method.

• Transactions of the Korean Society of Automotive Engineers
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• 제5권6호
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• pp.13-27
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• 1997

In the modern design technology, a component should be designed to fit into the overall system performance. A design methodology is developed to expedite the mechan- ical design of complex mechanical systems, The relation between the system design and component design is defined by a top-down approach and the results from the system design are utilized in the component design process. As a design example, an automobile exhaust system is selected for the system design and a bellows is chosen for a component design. Design methodology based on the top-down approach consists of five steps; (1) Analysis of service load, (2) Development of a lumped parameter, (3) Completion of the system design, (4) Selection of the component topology, (5) Completion of the component design, A method using a equivalent matrix is developed in order to determine unknown external forces in linear structural analyses. The bellows is also analyzed by the finite element method using a conical frustum shell element. Various experiments are performed to verify the developed theories. The top-down desi- gn approach is demonstrated by a design case using structural and shape optimization technology. Since the method is relatively simple and easy compared to other methods, it can be applied to the general design where system and component designs are involves simultaneously.

• Proceedings of the Korean Nuclear Society Conference
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• 한국원자력학회 2001년도 춘계학술발표회요약집
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• pp.250.2-250
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• 2001

• Korean Journal of Computational Design and Engineering
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• 제7권1호
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• pp.42-56
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• 2002

Presented in this study is a top-down functional requirement analysis procedure and the desired functionalities for PDM system development, and the benefits of top-down approach over a conventional bottom-up approach is also shown. For the purpose of top-down requirement analysis for PDM system, this study proposes 4P modeling view. 4P modeling view is defined as a modeling perspective for classifying functional requirements and integrating product-related information objects that must be man-aged within PDM systems. Based on 4P modeling templates, benchmarking analysis of commercially major PDM products is conducted and as a result of this analysis, this study suggests desired functionalities for PDM system.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권5호
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• pp.462-469
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• 2005

A top-down approach is known to be a useful and effective technique for the design and analysis of metabolic systems. In this Study, we have constructed a grouped metabolic network for Lactococcus lactis under aerobic conditions using grouped enzyme kinetics. To test the usefulness of grouping work, a non-grouped system and grouped systems were compared quantitatively with each other. Here, grouped Systems were designed as two groups according to the extent of grouping. The overall simulated flux values in grouped and non-grouped models had pretty similar distribution trends, but the details on flux ratio at the pyruvate branch point showed a little difference. This result indicates that our grouping technique can be used as a good model for complicated metabolic networks, however, for detailed analysis of metabolic network, a more robust mechanism Should be considered. In addition to the data for the pyruvate branch point analysis, Some major flux control coefficients were obtained in this research.

• Journal of the Korean GEO-environmental Society
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• 제23권12호
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• pp.17-23
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• 2022

This paper analyze the precast panel retaining wall's safety factor changes based on the numerical analysis using PLAXIS 2D software. Numerical analysis conditions include construction method, nail and panel fixing method, backfill material compaction conditions, rainfall conditions. The classification according to the construction method of the precast panel retaining wall includes the top-down and bottom-up methods. The difference between the top-down and bottom-up methods is the presence or absence backfill material and the ground excavation method. The top-down method involves vertically excavating the ground and attaching the panel using mortar, but in the bottom-up method, the ground is vertically excavated and harden the backfill material. As a result of numerical analysis, the top-down method secured a higher safety factor in all cases except the rainfall conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.333-338
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• 2003

Nano-imprint lithography(NIL) is a polymer embossing technique, capable of transferring nano-scale patterns onto a thin film of thermoplastics such as polymethyl methacrylate(PMMA) using this parallel process. Feature size down 10 nm have been demonstrated. In NIL, the pattern is formed by displacing polymer material, which can be squeeze flow of a viscous liquid. Due to the size of the pattern, a thorough understood of the process through experiments may be very different. Therefore we nead to resort to numerical simulation on the embossing process. Generally, there are two ways of numerical simulation on nano-scale flow, namely top-down and bottom-up approach. Top-down approach is a way to simulate the flow assuming that polymer is a continuum. On the contrary, in the bottom-up approach, simulation is peformed using molecular dynamics(MD). However, as latter method is not feasible yet. we chose the top-down approach. For the numerical analysis, two dimensional moving grid was used since the moving grid can predict the flow front. Effects of surface tension as well as the slip at the boundary were also considered.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.337-338
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• 2012

• Journal of the Korea Institute of Military Science and Technology
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• 제14권4호
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• pp.719-725
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• 2011

To apply TMAH-based Py-MS to a field biological detection system for real-time classification of cell-type, reproducible patterns of the TMAH-based Py-MS spectra was known as a critical factor for classification but was seriously disturbed by quantity of cells injected into pyro-tube. This factor is an exterior variable that could not be complemented by improving the performance of the TMAH-based Py-MS instrument. One of idea to solve the knotty problem has been flashed from "Top-down proteomics for identification of intact microoganisms". That is, biomarker peaks are selected from complicate Py-MS spectra for intact microoganisms by tracing out their origins, based on Py-MS spectra for the featured components of different cell-types, in Top-down approach. This idea has been tested in classification of different Gram-type microoganisms. Through the analyses of spectra for the featured components - peptidoglycan and lipoteichoic acid for Gram-positive cells and lipopolysaccharide and lipid A for Gram-negative cells - with comparing to the spectra the corresponding Gram-type cells in the Top-down approach, biomarker peaks were selected to carry out PCA(Principal Component Analysis) in order to see classification of different Gram-types, resulting in significant improvement of their classification. Furthermore, weighting biomarker peaks on intact cell's spectra, based on the data for the featured components of the Gram-types, contributed to elevate classification performance.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제8권1호
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• pp.75-81
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• 2008

This paper presents a top-down approach to implement an MPEG-2 audio encoder in VLSI. As the algorithm of an MPEG-2 audio encoder is heavy-weighted and heterogeneous(to be mixture of several strategies), the encoder design process is undertaken carefully from the algorithmic level to the architectural level. Firstly, the encoding algorithm is analyzed and divided into sub-algorithms, called tasks, and the tasks are partitioned in the way of reusing the same designs. Secondly, the partitioned tasks are scheduled and synthesized to make the most efficient use of time and space. In the end, a real-time 5 channel MPEG-2 audio encoder is designed which is a heterogeneous multiprocessor system; two hardwired logic blocks and one specialized DSP processor.