• Smart Structures and Systems
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• 제20권2호
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• pp.197-205
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• 2017

The dynamic performance of railway bridges under high-speed trains draws the attention of bridge engineers. The vibration issue for long-span bridges under high-speed trains is still not well understood due to lack of validations through structural health monitoring (SHM) data. This paper investigates the correlation between bridge acceleration and train speed based on structural dynamics theory and SHM system from three foci. Firstly, the calculated formula of acceleration response under a series of moving load is deduced for the situation that train length is near the length of the bridge span, the correlation between train speed and acceleration amplitude is analyzed. Secondly, the correlation scatterplots of the speed-acceleration is presented and discussed based on the transverse and vertical acceleration response data of Dashengguan Yangtze River Bridge SHM system. Thirdly, the warning indexes of the bridge performance for correlation scatterplots of speed-acceleration are established. The main conclusions are: (1) The resonance between trains and the bridge is unlikely to happen for long-span bridge, but a multimodal correlation curve between train speed and acceleration amplitude exists after the resonance speed; (2) Based on SHM data, multimodal correlation scatterplots of speed-acceleration exist and they have similar trends with the calculated formula; (3) An envelope line of polylines can be used as early warning indicators of the changes of bridge performance due to the changes of slope of envelope line and peak speed of amplitude. This work also gives several suggestions which lay a foundation for the better design, maintenance and long-term monitoring of a long-span high-speed bridge.

• 한국강구조학회 논문집
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• 제18권1호
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• pp.47-51
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• 2006

고속철도 궤도검측은 공사관리는 물론, 궤도유지관리 측면에서 매우 중요한 과제이며 향후 유지보수 시 작업계획수립, 작업량산출, 열차속도제한 등 유지보수 시 기본적인 자료로 제공되는 만큼 궤도검측치의 정확성은 매우 중요하며, 이러한 관점에서 국내 궤도검측차(EM-120)의 검측성능과 정확성을 검증하고자 하였다. 본 논문에서는 현재 일반철도구간에 대한 궤도검측 시 사용하고 있는 궤도검측차 (EM-120)의 선형검측자료를 Spectrum 분석한 결과, 파장 1m 부근의 검측치에 Noise가 있는 것을 확인할 수 있었다. 또한 이러한 Noise를 제거하기 위해 Spectrum 분석을 통한 새로운 Filter를 적용한 결과 실제 궤도틀림치에 보다 더 근접한 검측결과를 얻을 수 있었으며 사용기간에 따른 틀림전진 경향 또한 파악할 수 있었다.

• Progress in Superconductivity
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• 제6권1호
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• pp.7-12
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• 2004

Due to the very fast switching speed of Josephson junctions, superconductive digital circuit has been a very good candidate fur future electronic devices. High-speed and Low-power microprocessor can be developed with Josephson junctions. As a part of an effort to develop superconductive microprocessor, we have designed an RSFQ 4-bit ALU (Arithmetic Logic Unit) in a pipelined structure. To make the circuit work faster, we used a forward clocking scheme. This required a careful design of timing between clock and data pulses in ALU. The RSFQ 1-bit block of ALU used in this work consisted of three DC current driven SFQ switches and a half-adder. We successfully tested the half adder cell at clock frequency up to 20 GHz. The switches were commutating output ports of the half adder to produce AND, OR, XOR, or ADD functions. For a high-speed test, we attached switches at the input ports to control the high-speed input data by low-frequency pattern generators. The output in this measurement was an eye-diagram. Using this setup, 1-bit block of ALU was successfully tested up to 40 GHz. An RSFQ 4-bit ALU was fabricated and tested. The circuit worked at 5 GHz. The circuit size of the 4-bit ALU was 3 mm ${\times}$ 1.5 mm, fitting in a 5 mm ${\times}$ 5 mm chip.

• 한국기계가공학회지
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• 제15권5호
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• pp.80-85
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• 2016

In recent years, work to improve the power of a tractor has been in development. This study, using the mid-PTO power of a compact tractor, attempted to develop a high-speed mid-mower by setting the rotation to more than 3,000 RPM designed/manufactured major components of the high speed mid-mower. The performance of high-speed mid-mower was evaluated by the precision of straight bevel gears, and durability, the noise of the gearbox, the gearbox internal temperature, the maximum rotation speed of the mid-mowers, and the grass cutting test. Through the performance test results, the maximum number of revolutions of the mid-mower was measured over 3,000RPM, the gearbox noise and gearbox internal temperature satisfied the performance requirements of a high speed mid-mower.

• 산업공학
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• 제9권1호
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• pp.1-10
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• 1996

In this study, expert system for the selection of the optimal cutting speed and feed rate was developed using NEXPERT system shell. The NC system has been usually used inefficiently because the input command, which contains cutting speed, feed-rate and the depth of cut, is fixed value which depends on principally operator's experience and machining handbooks providing a guideline for applicable ranges. On the other hand, the optimal cutting conditions vary with time, and depend on tool and machine characteristics, work materials, and cost factor and so on. In this study, if cutting factors, such as, cutting method, material type, cutting depth, and tool nose radius are specified, our expert system gets the information about the standard cutting speed form the cutting speed database, and provides optimum feed rate for these cutting conditions. This cutting speed database can be updated by inputting valid cutting speed which is obtained form the practices.

• Journal of Biosystems Engineering
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• 제27권2호
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• pp.89-96
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• 2002

The trend of consumption of vegetable soybeans is increasing because they are recognized as the clean vegetable. The works requiring the most intensive labor are threshing and seperation ones, and they form about 80% of total labour for vegetable soybeans production. It is necessary to develop the vegetable soybeans-thresher for the sake of cost down of vegetable soybeans production. The purpose of this study is to acquire the basic informations to design of the vegetable soybeans-thresher. We make the experimental system which control the speed of threshing cylinder and the teeth gap and investigate the detachment forces. The result are as follows ; The ratio of un-threshed soybeans-pod to stem after threshing work is decreasing as the threshing cylinder speed increases: 0.0% and 2.8% at 55m/s and 18m/s of threshing cylinder speed respectively. Also the ratio of un-threshed soybeans-pod to stem is shown as 2.0% below in the condition of 64~160mm of teeth gap and over 28m/s of threshing cylinder speed. The damaged pod ratio of detached soybeans after threshing work is decreasing as the threshing cylinder speed increases: 4.8% and 1.3% at 55m/s and 18m/s of threshing cylinder speed respectively. The minimum damaged pod ratio of detached soybeans are shown as 1.0%, 1.5% and 1.9% at 18m/s, 28m/s and 37m/s of threshing cylinder speed respectively. The average detachment forces of pods are shown as 1.5kg$_{f}$ for 3 grains, 1.2kg$_{f}$ for 2 grains and 0.8kg$_{f}$ for 1 grain respectively. The maximum detachment force of pod is shown as 2.7kg$_{f}$ for 3 grains. grains.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.137-142
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• 2002

This paper shows the results of exterior and interior design of a prototype test train(HSR 350X) which was developed in R＆D project titled "Development of High Speed Railway Technology". The prototype test train, which has two power cars, two motorized trailers and three trailers, is now being tested on high speed line. The improved conceptual design work of a new commercial train and next generation′s train is also peformed for future needs.

• 대한전기학회논문지
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• 제33권1호
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• pp.17-20
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• 1984

The motivation in this paper is in constructing the controller with faster adapting speed than the one using the errors between the states of the plant and the model as the adaptive criterion. In the first part of this work, the adaptive law is found by using the state errors. In the later part, the adaptive law is obtained by introducing the companion model method. Finally the justification for the adaptive speed characteristics are compared.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1161-1162
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• 2007

In year 2004 korea runs high speed train KTX for the 5th time in the world. And now the traction power system is quite stabilized. But still a lot of work to develop and abnormal voltage problem is one of them. In this paper, by actual measuring we have collected the abnormal data on the high speed train sub-staion for more than 15 days. The collected data has been evaluated. In the near future collected data will be used planing a countermeasure.

• 대한토목학회논문집
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• 제30권5D호
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• pp.461-465
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• 2010

본 연구의 목적은 예비타당성조사에서 수행한 도시부 간선도로 확장공사로 인한 부(-)의 편익을 산정하고 이것이 경제성 평가에 미치는 영향을 분석하는 것이다. 북부간선도로 태릉-구리 간 확장사업의 실제 예비타당성조사 단계에서 통상적인 편익 산출 방법론을 적용하였으며, 공사로 인한 차량운행비용, 통행시간, 교통사고, 환경비용의 부(-)의 편익을 산출하였다. 분석 결과, 부(-)의 편익의 적용여부는 사업의 경제적 타당성 평가에 많은 영향을 주는 것으로 나타났다. 하지만 공사기간, 공사의 종류, 공사구간 및 교통량 등에 따라 부(-)의 편익에 많은 영향을 주는 감소되는 용량 및 자유속도가 현저하게 다를 수 있으며, 향후에는 이러한 요소와 용량 및 자유속도에 대한 상세한 연구가 필요할 것이다.