• The Journal of Information Technology and Database
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• v.4 no.2
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• pp.33-45
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• 1998

Database summarization is the procedure to obtain generalized and representative descriptions expressing the content of a large amount of database at a glance. We present a top-down summary refinement procedure to discover database summaries. The procedure exploits attribute concept hierarchies that represent ISA relationships among domain concepts. It begins with the most generalized summary and proceeds to find more specialized ones by stepwise refinements. This top-down paradigm reveals at least two important advantages compared to the previous bottom-up methods. Firstly, it provides a natural way of reflecting the user's own discovery preference interactively. Secondly, it does not produce too large intermediate result that makes it hard for the bottom-up approach to be applied in practical environment. The proposed procedure can also be easily extended for distributed databases. Information content measure of a database summary is derived in order to identify more informative summaries among the discovered results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.6
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• pp.29-32
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• 1983

The paper reports the development of a main memory system with ECC capability based on IEEE 796 bus for a 16 bit microcomputer the development of which was one of the last year's National proj tracts. The top-down approach of the design and the bottom-up approach of the testing resulted in a memory board which demonstrates a better performance and a less expensive cost than those available in the U.S. market.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.3
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• pp.319-329
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• 2016

High-level design aids are mandatory for design of a continuous-time delta-sigma modulator (CTDSM). This paper proposes a top-down methodology design to generate a noise transfer function (NTF) which is compensated for excess loop delay (ELD). This method is applicable to low pass loop-filter topologies. Non-ideal effects including ELD, integrator scaling issue, finite op-amp performance, clock jitter and DAC inaccuracies are explicitly represented in a behavioral simulation of a CTDSM. Mathematical modeling using MATLAB is supplemented with circuit-level simulation using Verilog-A blocks. Behavioral simulation and circuit-level simulation using Verilog-A blocks are used to validate our approach.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.190-191
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• 2019

In complex waterproofing method, the stability of the joint is an important factor. The joints should not be broken for repeated movements and tensile forces. Therefore, we tried to confirm the stability of joints in newly developed joints and general joints. Repeated fatigue resistance performance tests and joint tensile strength tests were carried out on four types of joints. The fatigue resistance performance test showed no abnormality in all four types. It was confirmed that the newly developed top-down joint has higher stiffness than existing joints.

• Journal of the Ergonomics Society of Korea
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• v.19 no.3
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• pp.61-75
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• 2000

To enhance web site's usability, it has been suggested that the depth of tree structured menus should be minimized. In this research, experimental results are reported to quantitatively compare the methods currently used for reducing the depth of menus in web sites. 25 popular web sites were selected and their menu types were categorized into four types: top menu, drop-down menu, boolean menu, and table of contents. The four types of menu were then sub-categorized into 15 different types according to their sub-menu type, existence of menu colors, and the event occurring after mouse activation. Performance tests and subjective evaluation were carried out. The results showed that there were no significant differences in terms of response time among the 15 menu types, while table of contents and drop-down in which the first and second level of menus were visible induced the least number of errors. In the subjective test, the top-menu structure with colors and presentation of its sub-menu without clicking mouse were preferred.

• Electronics and Telecommunications Trends
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• v.15 no.6 s.66
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• pp.150-159
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• 2000

본 논문은 영국의 통신망비용모형을 분석하고 있다. 영국은 1997년 10월부터 가격상한규제방식인 새로운 접속료규제제도를 도입하여 현재 적용해 오고 있다. 이 접속료규제제도는 기본적으로 장기증분비용에 근거한 접속료산정방식으로서 Top-down 방식에 의한 비용모형과 Bottom-up 방식에 의한 비용모형을 절충한 혼합모형을 적용하여 장기증분비용을 산정한 후, 이에 가격상한규제공식을 적용하는 방식이다. 본 논문에서는 우선 영국의 통신망비용모형 개발의 배경으로서 최근의 접속료산정방식의 변화상을 살펴보고 이어 BT가 제시한 Top-down 방식과 ICWG가 개발한 Bottom-up 방식을 각각 분석한 후 이들의 장.단점을 비교 검토하고 우리나라에의 시사점을 제시하고 있다.

• ETRI Journal
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• v.30 no.4
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• pp.535-545
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• 2008

This paper introduces a systematic top-down and bottom-up design methodology to assist the designer in the implementation of continuous-time (CT) cascade sigma-delta (${\Sigma}{\Delta}$) modulators. The salient features of this methodology are (a) flexible behavioral modeling for optimum accuracy-efficiency trade-offs at different stages of the top-down synthesis process, (b) direct synthesis in the continuous-time domain for minimum circuit complexity and sensitivity, (c) mixed knowledge-based and optimization-based architectural exploration and specification transmission for enhanced circuit performance, and (d) use of Pareto-optimal fronts of building blocks to reduce re-design iterations. The applicability of this methodology will be illustrated via the design of a 12-bit 20 MHz CT ${\Sigma}{\Delta}$ modulator in a 1.2 V 130 nm CMOS technology.

• Perspectives in Nursing Science
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• v.13 no.2
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• pp.81-87
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• 2016

Purpose: The aim of this study is to review the nurse demand forecasting methods in empirical studies published during 1991~2014 and suggest ideas to improve the validity in nurse demand forecasting. Methods: Previous studies on nurse demand forecasting methodology were categorized into four groups: time series analysis, top-down approach of workforce requirement, bottom-up approach of workforce requirement, and labor market analysis. Major methodological properties of each group were summarized and compared. Results: Time series analysis and top-down approach were the most frequently used forecasting methodologies. Conclusion: To improve decision-making in nursing workforce planning, stakeholders should consider a variety of demand forecasting methods and appraise the validity of forecasting nurse demand.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.2
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• pp.36-43
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• 1981

This paper describes a met hod of the extraction of phonemes in Hangout recognition. We provide the direction of strokes aid positional information for analyzing the structure of characters based on the regular combinational rules of Hangout according to Top -Down processing, and show the process of Phoneme extraction seq uencially. In this paper, some processing algorithms are described and simulated. The experiment of the phoneme extraction is carried out for 677 characters actully used daily, and extraction rate of 96% is obtained. The experimental results demonstrate the effectiveness of the proposed method.

• Journal of the Korea Society of Computer and Information
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• v.3 no.4
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• pp.63-69
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• 1998

The area optimization of the power distribution network is an important problem in the layout design of VLSI systems. In this paper we propose noval methods to solve the problem of designing minimal area power distribution nets, while satisfying voltage drop and electromigration constraints. We propose two novel greedy heuristics for power net design-one based on bottom-up tree construction using greedy merging and the other based on top-down linearly separable partitioning.