conference paper
Towards Adaptive Incident Detection Algorithms
6th ITS World Congress
Publication Date
November 1, 1999
Area of Expertise: Unspecified
conference paper
CrowdWiFi. efficient crowdsensing of roadside WiFi networks
Proceedings of the 15th international middleware conference on - middleware '14
Publication Date
January 1, 2014
Author(s)
Abstract
In this paper, we present CrowdWiFi, a novel vehicular middleware to identify and localize roadside WiFi APs that are located outside or inside buildings. Our work is motivated by the recent surge in availability of open WiFi access points (APs) that are enabling opportunistic data services to moving vehicles. Two key elements of CrowdWiFi that provide vehicles with opportunistic WiFi access include (a) an online compressive sensing component and (b) an offline crowd-sourcing module. Online compressive sensing (CS) techniques are primarily used to for the coarse-grained estimation of nearby APs along the driving route; here, the received signal strength (RSS) values are recorded at runtime, and the number and locations of APs are recovered immediately based on limited RSS readings. The offline crowdsourcing mechanism assigns the online CS tasks to crowd-vehicles and aggregates answers using a bipartite graphical model. This offline crowdsourcing executes at a crowd-server that iteratively infers the reliability of each crowd-vehicle from the aggregated sensing results and refines the estimation of APs using weighted centroid processing. Extensive simulation results and real testbed experiments confirm that CrowdWiFi can successfully reduce the number of measurements needed for AP recovery, while maintaining satisfactory counting and localization accuracy. In addition, the impact of CrowdWiFi middleware on WiFi handoff and data transmission applications is examined.
Suggested Citation
Di Wu, Qiang Liu, Yuan Zhang, Julie McCann, Amelia Regan and Nalini Venkatasubramanian (2014) “CrowdWiFi. efficient crowdsensing of roadside WiFi networks”, in Proceedings of the 15th international middleware conference on - middleware '14. ACM Press, pp. 229–240. Available at: 10.1145/2663165.2663329. conference paper
Impact of VSL location on capacity drop: A case of sag and tunnel bottlenecks
INTERNATIONAL SYMPOSIUM OF TRANSPORT SIMULATION (ISTS'18) AND THE INTERNATIONAL WORKSHOP ON TRAFFIC DATA COLLECTION AND ITS STANDARDIZATION (IWTDCS'18) - EMERGING TRANSPORT TECHNOLOGIES FOR NEXT GENERATION MOBILITY
Publication Date
January 1, 2018
Author(s)
Abstract
When there is upstream congestion the discharging flow-rate of a tunnel or sag bottleneck can drop, which leads to additional traffic jams. Therefore, control strategies such as variable speed limit (VSL) have been developed aiming to prevent or mitigate upstream traffic congestion. Understanding traffic dynamics at bottlenecks, especially the mechanism of capacity drop, is critical for developing such models. Many studies are centered on the control algorithm design of VSL. However, there are few studies that systematically anayze the effect that the VSL application area has on the control effectiveness. This paper extends to sag and tunnel bottlenecks the theoretical framework to analytically solve the optimal location of the speed limit application area (first developed in Martinez and Jin (2018)). Moreover, we prove that the optimization formulation can be simplified. Consequently, it can be applied to further bounded acceleration models than the constant one. Finally, for an open-loop control with a constant speed limit for the Kobotonoke tunnel bottleneck, we validate the analytic definition of optimal location by preventing capacity drop in numerical simulations. (C) 2018 The Authors. Published by Elsevier Ltd.
Suggested Citation
Irene Martinez and Wen-Long Jin (2018) “Impact of VSL location on capacity drop: A case of sag and tunnel bottlenecks”, in . Yoshii, T and Shiomi, Y and Kusakabe, T and Wada, K (ed.) INTERNATIONAL SYMPOSIUM OF TRANSPORT SIMULATION (ISTS'18) AND THE INTERNATIONAL WORKSHOP ON TRAFFIC DATA COLLECTION AND ITS STANDARDIZATION (IWTDCS'18) - EMERGING TRANSPORT TECHNOLOGIES FOR NEXT GENERATION MOBILITY. ELSEVIER SCIENCE BV (Transportation research procedia), pp. 12–19. Available at: 10.1016/j.trpro.2018.11.008.
published journal article
Elements of an ideal urban policy
KOREAN ECONOMIC REVIEW
Publication Date
January 1, 2013
Author(s)
Abstract
This paper sketches a number of elements of an ideal urban policy. The features of an ideal fiscal system are discussed, and the potential need for modifications to that system to account for special features of the urban economy are noted. The discussion also considers a number of policies that affect the spatial sizes of cities, the size and composition of their populations, and their industrial makeups.
Suggested Citation
Jan K. Brueckner (2013) “Elements of an ideal urban policy”, KOREAN ECONOMIC REVIEW, 29(1), pp. 5–22. Available at: https://www.kci.go.kr/kciportal/ci/sereArticleSearch/ciSereArtiView.kci?sereArticleSearchBean.artiId=ART001778678. published journal article
Socioeconomic Disparities of Low-Cost Air Quality Sensors in California, 2017–2020
American Journal of Public Health
Publication Date
March 1, 2022
Author(s)
Yi Sun, Amirhosein Mousavi, Shahir Masri, Jun Wu
Abstract
Objectives. To (1) examine the disparity in availability of PurpleAir low-cost air quality sensors in California based on neighborhood socioeconomic status (SES) and exposure to fine particulate matter smaller than 2.5 micrometers (PM2.5), (2) investigate the temporal trend of sensor distribution and operation, and (3) identify priority communities for future sensor distribution. Methods. We obtained census tract–level SES variables and PM2.5 concentrations from the CalEnviroScreen4.0 data set. We obtained real-time PurpleAir sensor data (July 2017–September 2020) to examine sensor distribution and operation. We conducted spatial and temporal analyses at the census tract level to investigate neighborhood SES and PM2.5 concentrations in relation to sensor distribution and operation. Results. The spatial coverage and the number of PurpleAir sensors increased significantly in California. Fewer sensors were distributed in census tracts with lower SES, higher PM2.5, and higher proportions of racial/ethnic minority populations. Furthermore, a large proportion of existing sensors were not in operation at a given time, especially in disadvantaged communities. Conclusions. Disadvantaged communities should be given access to low-cost sensors to fill in spatial gaps of air quality monitoring and address environmental justice concerns. Sensor purchasing and deployment must be paired with regular maintenance to ensure their reliable performance. (Am J Public Health. 2022;112(3):434–442. https://doi.org/10.2105/AJPH.2021.306603)
Suggested Citation
Yi Sun, Amirhosein Mousavi, Shahir Masri and Jun Wu (2022) “Socioeconomic Disparities of Low-Cost Air Quality Sensors in California, 2017–2020”, American Journal of Public Health, 112(3), pp. 434–442. Available at: 10.2105/AJPH.2021.306603. published journal article
Violence associated with combat-related posttraumatic stress disorder: The importance of anger.
Psychological Trauma: Theory, Research, Practice, and Policy
Publication Date
January 1, 2015
Author(s)
Raymond Novaco, Claude M. Chemtob
Suggested Citation
Raymond W. Novaco and Claude M. Chemtob (2015) “Violence associated with combat-related posttraumatic stress disorder: The importance of anger.”, Psychological Trauma: Theory, Research, Practice, and Policy, 7(5), pp. 485–492. Available at: 10.1037/tra0000067. research report
Optimal sensor locations for advanced truck surveillance on California freeways
Publication Date
September 1, 2013
Author(s)
Abstract
A new hybrid sensor technology integrating existing Weigh-In-Motion (WIM) axle configuration data with inductive signature data obtained from advanced Inductive Loop Detector (ILD) is gaining interest due to its potential to provide detailed classification of truck body types as well as anonymous tracking of truck movements on freeways. This paper describes the methodologies and analysis of two alternative strategies for optimal deployment locations for this new technology at existing WIM locations by utilizing sampled truck GPS trajectories on California freeways: (1) Flow-interception approach to maximize the total amount of net origin-destination (OD) flows captured; (2) Re-identification approach to maximize insights into origins and destinations of sampled truck trips, as well as routes of those trips. The truck GPS samples used in this study is obtained from the American Transportation Research Institute (ATRI), which provides position and time stamp information of truck movements. The model designed for flow-interception is capable of selecting locations emphasizing different body types by employing the flow-based weight factor. The RSP model investigates the best locations for heavy truck movement identification on freeways by selecting pairwise locations, and is shown to be sensitive to the re-identification decay factor assumed.
Suggested Citation
Jaeyoung Jung, Andre Tok, Stephen G. Ritchie and Irvine University of California (2013) Optimal sensor locations for advanced truck surveillance on California freeways, p. 21p. conference paper
Circuit inspired modeling method for irrigation
2018 21st euromicro conference on digital system design (DSD)
Publication Date
August 1, 2018
Author(s)
Davit Hovhannisyan, Ahmed Eltawil, Mohammad Al Faruque, Fadi Kurdahi
Suggested Citation
Davit Hovhannisyan, Ahmed Eltawil, Mohammad Al Faruque and Fadi Kurdahi (2018) “Circuit inspired modeling method for irrigation”, in 2018 21st euromicro conference on digital system design (DSD). IEEE, pp. 328–335. Available at: 10.1109/dsd.2018.00064. published journal article
A model of scheduling in airline networks: How a hub-and-spoke system affects flight frequency, fares and welfare
Journal of Transport Economics and Policy
Publication Date
January 1, 2001
Author(s)
Abstract
This paper provides a comprehensive economic analysis of scheduling decisions in airline networks. Although it is widely believed that the growth of hub-and-spoke networks has raised flight frequencies, the only analysis of this question is contained in a recent paper by Berechman and Shy (1998), who analyze an incomplete model. The present analysis shows that flight frequency is higher in a hub-and-spoke (HS) network than in a fully-connected (FC) network, confirming the conventional wisdom. Another result is that, despite lower cost per passenger under the HS network, greater flight frequency allows the airline to charge a higher fare to local passengers. This finding suggests that the downward pressure on fares due to economies of density may be partly or fully offset by the effect of higher flight frequency in an HS network, so that the net fare impact of such networks becomes uncertain. Finally, the paper’s welfare analysis shows that the airline provides excessive flight frequency relative to the social optimum, and that it may select the wrong network type.
Suggested Citation
Jan K. Brueckner and Yimin Zhang (2001) “A model of scheduling in airline networks: How a hub-and-spoke system affects flight frequency, fares and welfare”, Journal of Transport Economics and Policy, 35(2), pp. 195–222. Available at: http://www.jstor.org/stable/20053867. published journal article
A GPS data processing framework for analysis of drayage truck tours
Ksce Journal of Civil Engineering
Publication Date
April 1, 2018