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RISS 인기검색어
- 검색키워드
- 저자 : Jinwoo (Brian) Lee (검색결과 5 건)
- 무료
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Proportional-Derivative (PD) Controller for Heuristic Rule-based Motorway Coordinated Ramp Meters
Rui Jiang,Jinwoo (Brian) Lee,Edward Chung 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.9
This study proposes a new control method for rule-based motorway coordinated ramp metering. Coordinated ramp metering makes use of the network-wide measurements and allows multiple meters to participate in the control action to prevent or delay the onset of congestion on motorways. An essential component is a controller to dynamically adjust the level of contribution to coordination of each participating meter. The new control method builds on the concept of proportional-integral-derivative (PID) controller. A comprehensive sensitivity analysis is carried out to formulate the controller structure and coefficients. The final structure takes the form of PD controller with P-term as the main controller and D-term as supplementary to accelerate response speed and to improve the control stability. The PD controller is embedded in a rule-based coordinated ramp metering strategy for performance evaluation. A simulation study demonstrates the effectiveness of the PD controller. The coordinated control improves the mainstream traffic condition by reducing 60% and 8.4% of average traffic delay time over the base case assuming no metering and the local metering control scenario, respectively. The overall traffic travel time also decreased by the coordinated control by 25.1% and 2.0% over the base case and local metering, respectively. The enhanced mainstream traffic flow is achieved by balanced utilization of local meters and on-ramp spaces.
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An Analysis of Threshold Criteria and Conditions for Variable Speed Limit Deactivation
Gongbin Qian,Jinwoo (Brian) Lee 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.4
The study demonstrates the relative effectiveness and trade-offs amongst various threshold conditions for Variable Speed Limits (VSL) deactivation in terms of the control stability and efficiency. Reduced speed limits must be restored when the traffic interruption is resolved in a prompt and safe manner. Most VSLs in practice rely on a threshold-based control, which determines the speed limit adjustment by comparing detector readings to pre-determined threshold conditions. We tested three types of algorithmic parameters including occupancy, average speed, and consistency-check conditions. The test was carried out using the actual detector data, collected from three different segments of Pacific Motorway in Brisbane, Australia. Our analysis revealed that occupancy could be the most effective threshold over average speed. Operational fluctuation of VSL can be significantly reduced by selecting appropriate occupancy threshold values. We also tested four different consistency check conditions including a conditional deactivation approach. This approach makes the deactivation decision conditional upon the traffic status in the immediate downstream segment toavoid flushing upstream traffic into an active or potential bottleneck downstream. The test results and findings of this study may be useful for practitioners and researchers for developing VSL deactivation rules and associated operational strategies.
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Kim, Sung-Jo,Kook, Seungho,O'Rourke, Brian E.,Lee, Jinwoo,Hwang, Moonhyun,Kobayashi, Yoshinori,Suzuki, Ryoichi,Kim, In S. Elsevier 2017 Journal of membrane science Vol.527 No.-
<P><B>Abstract</B></P> <P>We systematically investigate the pore structure of cellulose triacetate (CTA) and polyamide (PA) forward osmosis (FO) membranes with positron annihilation lifetime spectroscopy (PALS) and fractional rejection (FR) method to better understand the relationship between membrane pores (atomic-scale free volume) and separation performance. The results reported in this study suggest a range of membrane pore sizes and inner structures appropriate for the osmotic membrane process regardless of membrane materials. The PALS data suggest that the active layer of both FO membranes is mainly composed of generally uniform pores of larger size (0.29−0.30nm) compared to seawater reverse osmosis (SWRO) (0.20−0.24nm) membranes. The membrane pore size distribution (PSD) deduced by the FR method suggest that the PSD of both FO membranes are significantly shifted to smaller sizes under pressurized conditions, possibly due to the overall compression of the FO membranes. The effects of applied pressure on the structure and performance of active layer should be further investigated along with other properties such as thickness, swelling and sorption properties.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This research provide first suggestion about the active layer pore size and structure of FO membranes. </LI> <LI> Both FO membranes are consisted of active layer with larger free-volume than commercial SWRO and NF membranes. </LI> <LI> The mean pore radius determined by FR method was smaller than the PALS due to hydraulic compression. </LI> <LI> Both PALS and the FR method can be utilized to investigate the dense active layer. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Detectivity analysis for organic photodetectors
Kim, Il Ku,Jo, Jun Hyung,Lee, Jinwoo (Brian),Choi, Young Jin Elsevier 2018 Organic Electronics Vol.57 No.-
<P><B>Abstract</B></P> <P>In this perspective letter, we report that there is a problem with a detectivity estimation method based on dark current measurement for organic photodiodes (OPDs). Based on dark current, calculated detectivity for fabricated OPD was 4.22 × 10<SUP>13</SUP> cmHz<SUP>1/2</SUP>/W at 520 nm. However, calculated detectivity for OPD based on measured noise current was 8.4 × 10<SUP>10</SUP> cmHz<SUP>1/2</SUP>/W at 520 nm. Therefore, we found that there are huge differences (more about 3 magnitudes of order) of detectivity calculations based on dark current measurement assumption and our noise measurement analysis. From the calculations of detectivities, it is concluded that noise current analysis should be addressed to clarify the organic photodiode characteristics.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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