• Journal of KIISE:Information Networking
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• v.29 no.6
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• pp.738-748
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• 2002

In this paper, a performance evaluation model of the Multistage Interconnection Network(MIN) with the multiple-buffered crossbar switches is Proposed and examined. Buffered switch technique is well known to solve the data collision problem of the MIN. The proposed evaluation model is developed by investigating the transfer patterns of data packets in a switch with output-buffers. The performance of the multiple-buffered${\alpha}{\times}{\alpha}$ crossbar switch is analyzed. Steady state probability concept is used to simplify the analyzing processes, Two important parameters of the network performance, throughput and delay, are then evaluated, To validate the proposed analysis model, the simulation is carried out on a Baseline network that uses the multiple buffered crossbar switches. Less than 2% differences between analysis and simulation results are observed. It is also shown that the network performance is significantly improved when the small number of buffer spaces is given. However, the throughput elevation is getting reduced and network delay becomes increasing as more buffer spaces are added in a switch.

• Resources Recycling
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• v.16 no.5
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• pp.65-70
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• 2007

This study presents the findings of the experiments that were conducted on single- and multi-stage solvent extractors using the stimulus-response method, with the am of identifying flow characteristics of the material inside the mixer-settler-type extractor. The results of this study show that the response characteristics of a single-stage mixer is the same as that of a completely stirred tank reactor (CSTR), and that the lag time of a mixer-settler-type extractor increases with the number of its extraction stages. The experimental data for the single- and multiple-stage extractors were analyzed using K-RTD, a response analysis program, to obtain a retention time distribution (RTD) model of one-stage and four-stage extractors. The correlation coefficient between the calculated values and the experimental data was 0.963 for the one-stage extractor and 0.995 for the four-stage extractor, showing quite a good correlation.

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.56-64
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• 2017

A high altitude long endurance aircraft which carries out missions of environmental research communication relay or ground surveillance, should have the capacity to cruise in the stratosphere at a relatively low speed for a long dwell time without the necessity of refueling. When one considers the propulsion system for such an aircraft, a reciprocating engine with a serial turbo-charger system to boost rarefied ambient air up to sea level condition, would represent an good, informed and practical choice regardless of the cruising altitude of the aircraft. In this paper, high altitude long endurance aircraft developed by overseas research groups and research trends, regarding multi-stage turbocharger systems, are introduced.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.151.2-151.2
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• 2012

터보펌프 구동에 사용된 가스발생기 생성가스를 연소기로 공급하여 주추력 발생에 사용하는 다단연소 사이클 로켓엔진은 고추력을 요하는 우주 발사체에 널리 사용되고 있다. 다단연소 사이클 로켓엔진에 사용되는 가스발생기를 예연소기라 부르며 케로신과 액체산소를 추진제로 하는 다단연소 사이클 로켓엔진에는 산화제 과잉 예연소기가 사용된다. 예연소기는 터보펌프 구동을 목적으로 하기 때문에 예연소기 생성가스의 횡단면 온도분포는 터빈에 의해 제한되는 온도범위 내에서 균일하여야 하며 넓은 운전영역에서 안정적인 연소가 이루어져야 한다. 산화제 과잉 예연소기는 모든 추진제가 혼합헤드를 통해 분사되는 방식과 추진제를 혼합헤드와 연소실로 나누어 공급하는 방식이 있다. 기술검증을 위해 산화제 일부와 연료를 혼합헤드를 통해 연소실에 공급하여 1차 연소시키고 나머지 산화제를 연소실 냉각채널을 거쳐 연소실 중앙의 분사공을 통해 연소실로 주입하여 기화시키는 형태로 최종적으로 연소압 20MPa, 혼합비 60에서 작동하는 산화제 과잉 예연소기를 설계하여 연소시험을 수행하였다. 혼합헤드에는 별도의 점화용 분사기 없이 전체 연료 분사기를 통해 점화용 연료인 TEA/TEB 혼합물을 분사하여 점화하였다. 추진제를 2단으로 공급할 수 있도록 고안된 가압식 연소시험 설비에서 10회, 누적 60초 이상의 연소시험이 성공적으로 수행되었다. 연소시험결과 넓은 작동영역에서 안정적 연소특성과 생성가스 온도 분포의 균일성을 확인할 수 있었다. 고온 고압의 산화제 과잉 예연소기 기술 확보를 통해 케로신/액체산소 다단연소 사이클 로켓엔진 개발을 위한 기술적 기반을 마련하였다.

• Journal of Advanced Navigation Technology
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• v.23 no.4
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• pp.309-315
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• 2019

This paper proposes an implementation of unequal power divider with 1:3 and 1:4 splitting ratio in multi-section structure using CPW and offset coupled transmission line. The power divider consists of a multi-section transmission line and a circuit with parallel capacitors and resistors. A multi-section transmission line was implemented by decomposing a ${\lambda}/4$ single transmission line terminated by an arbitrary impedance and converging it with a multi-section transmission line shorter than $90^{\circ}$ electrical length, and RC parallel circuits were connected between transmission lines to obtain reflection coefficient of output port and isolation characteristics between the output port. In this way, it was confirmed that the transmission lines at the unequal power divider designed at 2 GHz were shorter than ${\lambda}/4$ and implemented at least 27% less than the conventional ones, and that the broadband characteristics could be obtained.

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.557-562
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• 2023

This study reviewed the use of soil injection materials using circulating resources as injection materials for the steel pipe multi-stage construction method. The tests performed were homogel time and homogel compressive strength. The steel pipe multi-stage construction method is an auxiliary construction method for tunnels, and the expression of initial strength after construction is an important factor. The better the strength development in the initial stage, the more it can be used as an injection material suitable for the multi-stage steel pipe construction method. As a result of laboratory test, it was found that the homogel time of the injection material using circulating resources required more time than the mixing ratio using cement as the injection material. In addition, it was found that the initial strength curing time satisfying 2MPa was required for more than 24 hours. Therefore, it was confirmed that the injection material using recycled resources required a longer initial curing time than cement of the same mixing ratio.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.166-168
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• 2005

본 논문에서는, axa 출력 버퍼 스위치로 구성된 핫스팟이 발생된 상황 하에서 다단 연결 망(Multistage interconnection Network, MIN)의 성능 예측 모형을 제안하였다. 제안한 성능 예측 오형은 먼저 네트워크 내부 임의 스위치 입력 단에 유입되는 데이터 패킷이 스위치 내부에서 전송되는 유형을 확률적으로 분석하여 설계하였다. 성능분석 모형은 스위치에 장착된 버퍼의 개수와 무관하게 버퍼를 장착한 axa 스위치의 성능, 네트워크 정상상태 처리율(Normalized Throughput, NT)과 네트워크 지연시간(Network Delay)의 예측이 가능하고, 나아가서 이들로 구성진 모든 종류의 다단 연결망 성능 분석에 적용이 용이하다. 제안한 수학적 성능 분석 연구의 실효성 검증을 위하여 병행된 시뮬레이션 결과는 상호 미세한 오차 범위 내에서 모형의 예측 데이터와 일치하는 결과를 보여 분석 모형의 타당성을 입증하였다.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.117-118
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• 2017

다단 듀얼 벅 AC-AC 컨버터는 암단락 사고가 없고 정류 문제가 없으며, MOSFET을 사용하여 효율을 향상시킬 수 있다. 해당 컨버터의 주된 단점은 기존의 다단 AC-AC 컨버터보다 인덕터가 많이 사용되고, 제한 인덕터의 50 % 만 사용한다는 것이다. 이러한 사실은 전력 밀도를 감소시키고 시스템 비용을 증가시킨다. 본 논문은 결합 인덕터를 사용하는 개선 된 컨버터를 제시한다. 제안 된 컨버터에서 각 셀 사이에 연결된 제한 인덕터는 하나의 코어에 결합되어있다. 따라서 전체 인덕턴스, 인덕터 풋프린트 및 자기소자부피 모두 줄일 수 있다. 제안 된 컨버터의 성능을 검증하기 위해 컨버터의 동작 및 실험 결과를 제시하였다.

• Journal of Internet Computing and Services
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• v.6 no.4
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• pp.141-147
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• 2005

Ding and Bhuyan, however, has shown that the performance of multistage interconnection networks(MIN's) can be significantly improved if the packet movements are confined within each pair of adjacent stages using small clock cycles. In this paper, an effective model for estimating the performance of multibuffered MIN's employing the approach is proposed. the relative effectiveness of the proposed model is identified compared to the traditional design.

• Explosives and Blasting
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• v.23 no.1
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• pp.41-46
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• 2005

Overbreak is an inevitable during tunnel excavation. It significantly affects tunnel construction cost and safety The overbreak occurs due to incorrect expectations to the geologic structures, excessive charge or strength of explosives, etc. This paper introduces multi-hole drilling method to minimize the overbreak in tunnel excavation. Although the drilling cost of the method is more expensive than those of the existing other drilling method, it is expected at that cost will be reduced.