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소형 디젤엔진에서 분사전략이 나노입자 배출 특성에 미치는 영향
엄동섭(Dong-Seop Eom),김민석(Min-Seok Kim),박진혁(Jin-Hyuk Park),권상일(Sang-Il Kwon),이성욱(Seang-Wook Lee),조용석(Yong-Seok Cho),백두성(Doo-Sung Baik) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
This research aims to investigate the characteristics of regulated emissions such as particulate materials and vehicle performance by variations of injection strategy and control of air quantity affecting on combustion conditions in a compact diesel engine. In this experiment a 3.0 liter high speed diesel engine is used equipped with CRDI fuel injection system where the injection pressure is 160㎫ and E-VGT is applied. In order to investigate exhaust emissions and variations of power due to injection strategy, main and pilot injection are changed and compared with their engine performance and amounts of emissions which are obtained by a conventional ECU. From the results, the characteristics of torque tend to decrease when the number of injection times increases but the torque increases as air fuel ratio increases, but the torque decreases due to increased back pressure specially in lower engine loads. The nano-particle is not affected by the variation of air-fuel ratio but the amount increase as the number of pilot injection time increases and engine load is lower, and similar emission characteristics are shown both in ranges of low and high speeds. PM emission emitted more in lower engine speed or higher load, and pilot injection gives disadvantage on PM emission since PM increase when the number of pilot injection time increases, but the reduction effect is appeared apparently due to the increase of air quantity. NOX emission increases in accordance with increasing air-fuel ratio in overall ranges but the reduction rate is very effective by pilot injection.
A Fair Scalable Inter-Domain TCP Marker for Multiple Domain DiffServ Networks
Hur, Kyeong,Eom, Doo-Seop The Korea Institute of Information and Commucation 2008 Journal of communications and networks Vol.10 No.3
The differentiated services (DiffServ) is proposed to provide packet level service differentiations in a scalable manner. To provide an end-to-end service differentiation to users having a connection over multiple domains, as well as a flow marker, an intermediate marker is necessary at the edge routers, and it should not be operated at a flow level due to a scalability problem. Due to this operation requirement, the intermediate marker has a fairness problem among the transmission control protocol (TCP) flows since TCP flows have intrinsically unfair throughputs due to the TCP's congestion control algorithm. Moreover, it is very difficult to resolve this problem without individual flow state information such as round trip time (RTT) and sending rate of each flow. In this paper, to resolve this TCP fairness problem of an intermediate marker, we propose a fair scalable marker (FSM) as an intermediate marker which works with a source flow three color marker (sf-TCM) operating as a host source marker. The proposed fair scalable marker improves the fairness among the TCP flows with different RTTs without per-flow management. Through the simulations, we show that the FSM can improve TCP fairness as well as link utilization in multiple domain DiffServ networks.
A Modified REDP Aggregate Marker for improving TCP Fairness of Assured Services
Hur Kyeong,Eom Doo-Seop,Tchah Kyun-Hyon The Korea Institute of Information and Commucation 2004 韓國通信學會論文誌 Vol.29 No.1B
To provide the end-to-end service differentiation for assured services, the random early demotion and promotion (REDP) marker in the edge router at each domain boundary monitors the aggregate flow of the incoming in-profile packets and demotes in-profile packets or promotes the previously demoted in-profile packets at the aggregate flow level according to the negotiated interdomain service level agreement (SLA). The REDP marker achieves UDP fairness in demoting and promoting packets through random and early marking decisions on packets. But, TCP fairness of the REDP marker is not obvious as for UDP sources. In this paper, to improve TCP fairness of the REDP marker, we propose a modified REDP marker where we combine a dropper, meters and a token filling rate configuration component with the REDP marker. To make packet transmission rates of TCP flows more fair, at the aggregate flow level the combined dropper drops incoming excessive in-profile packets randomly with a constant probability when the token level in the leaky bucket stays in demotion region without incoming demoted in-profile packets. Considering the case where the token level cannot stay in demotion region without the prior demotion, we propose a token filling rate configuration method using traffic meters. By using the token filling rate configuration method, the modified REDP marker newly configures a token filling rate which is less than the negotiated rate determined by interdomain SLA and larger than the current input aggregate in-profile traffic rate. Then, with the newly configured token filling rate, the token level in the modified REDP marker can stay in demotion region pertinently fir the operation of the dropper to improve TCP fairness. We experiment with the modified REDP marker using ns2 simulator fur TCP sources at the general case where the token level cannot stay in demotion region without the prior demotion at the negotiated rate set as the bottleneck link bandwidth. The simulation results demonstrate that through the combined dropper with the newly configured token filling rate, the modified REDP marker also increases both aggregate in-profile throughput and link utilization in addition to TCP fairness improvement compared to the REDP marker.
Data Compression Algorithm for Efficient Data Transmission in Digital Optical Repeaters
Kim, Jae Wan,Eom, Doo Seop The Institute of Electronics and Information Engin 2012 전자공학회논문지 Vol.49 No.12
Today, the demand for high-speed data communication and mobile communication has exploded. Thus, there is a growing need for optical communication systems that convert large volumes of data to optical signals and that accommodate and transmit the signals across long distances. Digital optical communication with these characteristics consists of a master unit (MU) and a slave unit (SU). However, the digital optical units that are currently commercialized or being developed transmit data without compression. Thus, digital optical communication using these units is restricted by the quantity of optical frames when adding diversity or operating with various combinations of CDMA, WCDMA, WiBro, GSM, LTE, and other mobile communication technologies. This paper suggests the application of a data compression algorithm to a digital signal processor (DSP) chip as a field programmable gate array (FPGA) and a complex programmable logic device (CPLD) of a digital optical unit to add separate optical waves or to transmit complex data without specific changes in design of the optical frame.
Method of SSO Noise Reduction on FPGA of Digital Optical Units in Optical Communication
Kim, Jae Wan,Eom, Doo Seop The Institute of Electronics and Information Engin 2013 전자공학회논문지 Vol.50 No.1
There is a growing need for optical communication systems that convert large volumes of data to optical signals and that accommodate and transmit the signals across long distances. Digital optical communication consists of a master unit (MU) and a slave unit (SU). The MU transmits data to SU using digital optical signals. However, digital optical units that are commercially available or are under development transmit data using two's complement representation. At low input levels, a large number of SSOs (simultaneous switching outputs) are required because of the high rate of bit switching in two's complement, which thereby increases the power noise. This problem reduces the overall system capability because a DSP (digital signal processor) chip (FPGA, CPLD, etc.) cannot be used efficiently and power noise increases. This paper proposes a change from two's complement to a more efficient method that produces less SSO noise and can be applied to existing digital optical units.
Ad hoc network에서 TCP 성능 향상을 위한 혼잡 제어 방법
박매진(MAEJIN PARK),엄두섭(Doo-Seop Eom) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.10
무선 통신 기술의 발달로 최근 무선 device 들로 이루어진 ad-hoc network이 주요 Issue가 되고 있으며, ad-hoc network 에서의 성능이 중요한 관심사가 되고 있다. 그러나 유선망에 최적화되도록 설계된 TCP는 무선망이 가지는 링크의 불안정함으로 인한 손실을 네트워크 혼잡에 의한 손실로 인식하여 혼잡 제어 메커니즘이 수행함으로써 전송률을 줄이게 되므로 전체적으로 네크웍의 성능이 저하되는 문제점을 가진다. 본 논문에서는 무선망에서 TCP 성능을 향상시키기 위한 새로운 congestion algorithm을 제안하고 그 성능을 평가하였다. 성능 확인 결과 기존 TCP-vegas 에 비해 더 나은 성능을 보임을 알 수 있다.