• Journal of Communications and Networks
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• 제9권3호
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• pp.330-341
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• 2007

This work analyzes the performance of the parallel packet switch (PPS) with a sliding window (SW) method. The PPS involves numerous packet switches that operate independently and in parallel. The conventional PPS dispatch algorithm adopts a round robin (RR) method. The class of PPS is characterized by deployment of parallel low-speed switches whose all memory buffers run more slowly than the external line rate. In this work, a novel SW packet switching method for PPS, called SW-PPS, is proposed. The SW-PPS employs memory space more effectively than the existing PPS using RR algorithm. Under identical Bernoulli and bursty data traffic, the SW-PPS provided significantly improved performance when compared to PPS with RR method. Moreover, this investigation presents a novel mathematical analytical model to evaluate the performance of the PPS using RR and SW method. Under various operating conditions, our proposed model and analysis successfully exhibit these performance characteristics including throughput, cell delay, and cell drop rate.

• 산업공학
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• 제17권3호
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• pp.282-293
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• 2004

Line Balancing is the problem to assign tasks to stations while satisfying some managerial viewpoints. Most researches about the Mixed-Model Line Balancing problems are focused on the minimizing the total processing time or the number of workstations. Independently, some research reports consider the balance issues of the physical workloads on the assembly line. In this paper, we are presenting a new mathematical model to accomplish the line balance considering both the processing time and the workloads at the same time. To this, end, we propose an zero-one integer program problem, and we use the Chebyshev Goal Programming approach as the solution method. Some computational test runs are performed to compare the pay-offs between the processing time and the workloads. And, the test results show us that the reliable balanced work schedules can be obtained through the proposed model.

• 환경영향평가
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• 제2권2호
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• pp.27-32
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• 1993

The German society for promotion of EIA was founded in 1987 with the aim to support the introduction of EIA in Germany. The society with its center in Hamm where there is a plenty collection of literature, studies and further scientific sources does an enormous work in EIA-consulting all over the country. This work practically is done without any governmental support, only by private activities. The EIA society is structured within 9 regional as well as 19 specialized working groups and consisits of about 1,000 members. The unification of Germany in 1989/90 also influenced the development in this field, of course. While in the former Western part of Germany the already existing environmental administrations were able to react on the EIA-law of 1990 with their long time experiences, in the Eastern part the corresponding structures must be built up newly from the beginning. Since 1990 a great number of interested people also from Eastern Germany became numbers of the EIA-Society. By them an additional pool of knowledge and activity was brought into the society. This also applies for methods and means of EIA which were developed in the East during the time ago independently.

• 한국컴퓨터정보학회논문지
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• 제17권4호
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• pp.83-90
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• 2012

대규모의 상품을 다루는 전자상거래 시스템에서 개인화된 추천은 필수적인 기능이 되고 있다. 대표적 추천 알고리즘인 협업필터링은 내용기반 추천에 비하여 뛰어난 추천성능을 제공해 주고 있으나, 희박성, 신규 아이템 문제(Cold-start), 확장성 등의 근본적인 한계를 갖고 있다. 본 연구에서는 추가적으로 협업필터링이 목표 대상자에 따라 비일관된 예측 능력의 차이를 보이는 추천 성능의 편차 문제를 제기하고자 한다. 추천성능의 편차는 기존의 Mean Absolute Error(MAE)에 의해서는 측정되기 어려우며 또한 정확도, 재현율 지표와도 독립적으로 평가되고 있다. 협업알고리즘의 정확한 성능평가를 위해서 본 연구에서는 MAE, MAE 편차, 정확도, 재현율을 포괄적으로 평가할 수 있는 확장 성능평가모델을 제안하고 이를 클러스터링 기반 협업필터링에 적용하여 성능을 비교 분석한다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.252-257
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• 2003

It is necessary to have a maintenance of track and its equipment for safety and s the railroad transportation. In the paper, we examine the safety problems, protecti and composition of protection system for safety within the track which RTRI develo system consists of a mobile business tool carried by each worker. a terminal of t platform temporarily installed in the maintenance car. a connector attached to signalling system and a central administrative device installed at the control cen used independently to detect positions of workers and maintenance cars. Each m correctly grasp the geometrical relations with other workers cars and other objects conditions based on the state information exchanged between the machines by the control protocol. the track occupancy monitor information broadcast by th administrative device and the line information. The protection system executes its f this basic structure.

• 한국정밀공학회지
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• 제16권11호
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• pp.55-61
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• 1999

The torsional and axial vibrations of shaft system have been calculated independently because of both the limitation of computing time and the complexity of crankshaft model. In actual system, however, the torsional and axial vibrations are coupled. Therefore, in recent, many works in the coupled vibration analysis have been done to find out the more exact dynamic behavior of shaft system. The crankshaft model is very important in the vibration analysis of shaft system because most of excitation forces act on the crankshaft. It is, however, difficult to establish an exact model of crankshaft since its shape is very complex. In this work, an efficient method is proposed to construct the stiffness matrix of crankshaft using a finite element model of half crankthrow. The proposed and existing methods are compared by applying to both a simple thick beam with circular cross section and an actual crankshaft.

• 대한물리의학회지
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• 제5권3호
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• pp.385-394
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• 2010

Purpose : The present study was to examine the difference and severity of asymmetry in independently ambulating stroke survivors and to establish the association between gait asymmetry, velocity, and the motor function of lower extremity. Methods : The subjects used in this study were 43 subjects with hemiparesis being able to walk independently. Motor function of lower extremity was measured clinically with the Fugl Meyer-Lower /Extremity Assessment. Overground gait velocity and spatia-temporal parameters were collected by the GAITRite system. Results : Thirty(69.77%) patients showed statistically significant temporal asymmetry while 28(65.1%) exhibited statistically significant spatial asymmetry. One-way ANOVA results showed a main effect of temporal asymmetry group(normative, mild, severe) for gait velocity(F=74.129), FM-L/E(F=17.270), swing-stance symmetry(F=66.869, F=13.485, respectively), spatio-temporal asymmetry(F=13.166, F=31.800, respectively) 66, F=31.800, respectively). Gait velocity was negatively associated with temporal asymmetry(r=-.83), spatial asymmetry(r=-.60). Motor function of lower extremity was also associated with temporal asymmetry(r=-.58), and spatial asymmetry(r=-.50). Conclusion : The study attempted to establish the standard assessment of hemiparesis gait symmetry in light of the complex relationship with motor impairment and gait velocity. More future work will need to link the degree of gait asymmetry to clinically relevant outcomes to better establish the clinical significance of such observations.

• 한국세라믹학회지
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• 제29권8호
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• pp.623-629
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• 1992

The possible use of bioglass as implant materials is due to its biocompatibility to human body. Even if many animal studies for the bioglasses have been performed, their compositional dependences of structures and physical properties are not fully understood. In the present work, physical property measurements such as density and thermal expansion coefficient were carried out for the bioglasses, with substitution of CaO for Na2O in bioglass composition (46.1%SiO2, 24.4%Na2O, 26.9%CaO, 2.6%P2O5:mol%). Hydroxyapatite formation on the glass surface was also examined after reacted in Tris-buffer solution. As CaO was substituted for Na2O, the bond strength between nonbridging oxygen and modifier became stronger to make glass structure rigid, and resulted in increase in density and decrease in thermal expansion coefficient. When the bioglasses were reacted in Tris-buffer solution, hydroxyapatite was formed on the bioglass surface for all prepared glasses in 2 hours, independently on CaO content, and the thickness of hydroxyapatite layer was decreased a little, while the thickness of SiO2 rich layer was decreased sharply with CaO content.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.256-261
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• 2000

Electro-Rheological(ER) fluid is applied to a controllable squeeze film damper(SFD) for stabilizing a flexible rotor system. ER fluid is a class of functional fluid whose yield stress varies according to the applied electric field strength, which is observed as viscosity variation of the fluid. In applying ER fluid to a SFD, a pair of rings of the damper can be used as electrodes. When the electrodes are divided into a horizontal pair and a vertical one, the SFD can produce damping force in each direction independently. A prototype of the directionally controllable SFD was constructed and its performance was experimentally and numerically investigated in the present work.

• East Asian Economic Review
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• 제17권2호
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• pp.161-206
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• 2013

Since the global financial crisis in 2008, the world economy has been suffering from the Great Recession characterized by high and persistent unemployment as well as drastic fall in asset prices. Real business cycle theory or new-Keynesian economics which has been the dominant paradigm in macroeconomics for the last four decades is unable to explain the high and persistent unemployment during the Great Recession. This implies that the economics of Keynes should be taken seriously again as a tool to explain the Great Recession. Farmer (2012) proposes a new way of interpreting the economics of Keynes by providing it with a solid micro-foundation based on labor markets with search. According to Farmer (2012), aggregate economic activity independently depends on the long-term self-fulfilling expectations about the stock prices. As a consequence, the government or the central bank should implement a policy that influences the public's confidence about the stock market. For an open economy like the Korean economy, it is not only stock price but also the price of asset such as house that matters more for the aggregate economic activity. Households in the Korean economy hold more than 70 percent of their wealth in the form of real estate asset, especially housing asset. This makes the public's confidence about the future prices of houses even more important in explaining the business cycles of the Korean economy. Policymakers should implement policies to improve the confidence of households about the housing market to recover from the recession caused by a fall in house prices. Little theoretical work has been done in explaining fluctuations in the aggregate economic activity from the point of house prices. This paper develops a small open economy model with traded and non-traded capital based on Farmer (2012) and shows that the aggregate economic activity also independently depends on the households' self-fulfilling expectations about the future prices of non-traded asset such as houses.