published journal article

Nonstandard second-order formulation of the LWR model

Transportmetrica B: Transport Dynamics

Publication Date

December 23, 2019

Author(s)

Wenlong Jin

View published journal article

Abstract

In this study, we present an equivalent second-order formulation of the LWR model based on Phillips’ model, in which the acceleration rate equals a relaxation term with an infinitesimal relaxation time. We convert the model into a continuum car-following model and demonstrate its equivalence to that of the LWR model. We demonstrate that the nonstandard second-order model is stable, but the original Phillips model is not. We derive conditions for the nonstandard model to be forward-traveling and collision-free, prove that the collision-free condition is consistent with but more general than the CFL condition, and demonstrate that only anisotropic and symplectic Euler discretization methods lead to physically meaningful solutions. Numerically, the nonstandard second-order model has the same shock and rarefaction wave solutions as the LWR model for both Greenshields and triangular fundamental diagrams; for a non-concave fundamental diagram, the collision-free condition, but not the CFL condition, yields physically meaningful results.

Suggested Citation

Wen-Long Jin (2019) “Nonstandard second-order formulation of the LWR model”, Transportmetrica B: Transport Dynamics, 7(1), pp. 1338–1355. Available at: 10.1080/21680566.2019.1617803.

Phd Dissertation

Research universities as gateways the expanding roles of higher education institutions and their contribution to economic development

Publication Date

January 1, 2021

Author(s)

N Osutei

View Phd Dissertation

Abstract

The past 30 years have witnessed a gradual expansion in the missions of many universities, and in the ways in which they contribute to local and regional economic development. While teaching and research continue to serve as the foundational core of most university missions, increased attention has been afforded to how universities, by their presence and functions, influence the spatial geographies of neighborhoods, cities, and regions. This dissertation research explores the changing roles of research universities in small and medium-sized metropolitan areas with an emphasis on their impacts across the different geographical scales by investigating associations between university presence and (1) growth in foreign-born populations; (2) the attraction and retention of highly educated residents; and (3) student-driven neighborhood change dynamics. The findings of this dissertation extend previous studies emphasizing the increasing importance of higher education institutions to economic development activities at various scales. Results from metropolitan area level analyses demonstrate that counties with large research universities were associated with an increase in foreign-born residents following the 1990 Immigration and Naturalization Act, as well as an increase in highly educated residents in the 2000-2014 period. More specifically, while findings revealed that the presence of research universities generate significant spatial spillovers of highly educated residents from university host counties to metropolitan levels, there was little evidence of such spatially-explicit dynamics occurring amongst foreign-born residents. Furthermore, findings from neighborhood-level analyses indicated that proximity to large research university campuses may play an outsized role on the likelihood of neighborhoods undergoing studentification (i.e., student-driven neighborhood change) in the 2000-2014 period. These results may be indicative of a bifurcation of neighborhoods in university-dominant counties into wealthy and highly educated renter populations situated near the university campus, and relatively less wealthy and less educated homeowners residing on the further away from the campus or on the periphery of the county. By exploring university contributions beyond the spheres of research, teaching, and service contributions, this dissertation presents scholars, urban planners, and policymakers with a more comprehensive portrait of the relationship between universities and their host communities. The evidence of this work suggests that the evolving role of higher education institutions, including their role as gateways for new populations, should be reflected in policymaking which seeks to leverage the locational advantages of research universities for city building or revitalization efforts. Further, policymakers and planners should also be cognizant that scale matters when considering how higher education institutions can better serve their surrounding communities. The contributions of research universities should not be thought of as monolithic or uniform, but should rather be seen as presenting different opportunities and challenges at different geographical levels.

Suggested Citation

Nene, Osutei (2021) Research universities as gateways the expanding roles of higher education institutions and their contribution to economic development. PhD Dissertation. University of California, Irvine,. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/17uq3m8/alma991035329641804701.

published journal article

A first-order behavioral model of capacity drop

Transportation Research Part B: Methodological

Publication Date

November 1, 2017

Author(s)

Wenlong Jin

View published journal article

Suggested Citation

Wen-Long Jin (2017) “A first-order behavioral model of capacity drop”, Transportation Research Part B: Methodological, 105, pp. 438–457. Available at: 10.1016/j.trb.2017.09.021.

published journal article

Extreme Heat and Severe Maternal Morbidity in Southern California: Evidence of Health Disparities from a Large Pregnancy Cohort

ISEE Conference Abstracts

Publication Date

September 17, 2023

Author(s)

Anqi Jiao, Yi Sun, Chantal Avila, Vicki Chiu, John Molitor, Jeff Slezak, David Sacks, Jiu Chiuan Chen, Tarik Benmarhnia, Darios Getahun, Jun Wu

View published journal article

Abstract

BACKGROUND AND AIM: The rate of severe maternal morbidity (SMM) has continued to increase in the United States. We aimed to examine if maternal exposure to extreme heat is associated with the risk of SMM. METHOD: We conducted a retrospective cohort study and included 425,722 singleton pregnancies from Kaiser Permanente Southern California in 2008-2018. Daily maximum temperature data at a 4 km resolution were obtained. An extreme heat day was defined as a day with the daily maximum temperature exceeding a certain threshold. Four percentiles (i.e., 75th, 90th, 95th, and 98th) of daily maximum temperature during the warm season (May-September) in 2007-2018 in Southern California were selected to define the extreme heat day. Long-term exposures included the proportions of extreme heat days during the entire pregnancy and by trimester. Short-term exposures were measured by 12 different heatwave exposures (combining the four thresholds with three durations, i.e., ≥ 2, ≥ 3, and ≥ 4 consecutive days) during the last gestational week. The discrete-time approach and Cox proportional hazards model were used to estimate the long- and short-term associations between heat exposure and SMM, respectively. Stratified analyses were conducted to examine vulnerable subpopulations and the effectiveness of mitigation measures. RESULTS: There were 7,767 (1.8%) SMM cases during delivery hospitalization in this study. Long-term associations with extreme heat were detected in the entire pregnancy and each trimester. Heatwave exposures during the last gestational week were associated with higher risks of SMM. Stronger associations were observed in mothers who were Hispanic, with lower education or incomes, or smokers. More green space may attenuate heat effects. CONCLUSIONS: Long- and short-term maternal exposure to extreme heat can be associated with an increased risk of SMM. More residential green space can be a potential mitigation strategy.

Suggested Citation

Anqi Jiao, Yi Sun, Chantal Avila, Vicki Chiu, John Molitor, Jeff Slezak, David Sacks, Jiu Chiuan Chen, Tarik Benmarhnia, Darios Getahun and Jun Wu (2023) “Extreme Heat and Severe Maternal Morbidity in Southern California: Evidence of Health Disparities from a Large Pregnancy Cohort”, ISEE Conference Abstracts, 2023(1). Available at: 10.1289/isee.2023.EP-162.

published journal article

Closure to “ digital imaging concepts and applications in pavement management ” by Stephen G. Ritchie (May/June, 1990, vol. 116, no. 3)

Journal of Transportation Engineering

Publication Date

July 1, 1992

Author(s)

Stephen Ritchie

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Suggested Citation

Stephen G. Ritchie (1992) “Closure to “ digital imaging concepts and applications in pavement management ” by Stephen G. Ritchie (May/June, 1990, vol. 116, no. 3)”, Journal of Transportation Engineering, 118(4), pp. 603–605. Available at: 10.1061/(asce)0733-947x(1992)118:4(603.2).

conference paper

Traffic density estimation using radar sensor data from probe vehicles

Proceedings of the ITS World Congress

Publication Date

January 1, 2017

Author(s)

D Nam, Riju Lavanya, Inchul Yang, R. (Jay) Jayakrishnan

Suggested Citation

D Nam, R Lavanya, I Yang and R Jayakrishnan (2017) “Traffic density estimation using radar sensor data from probe vehicles”, in Proceedings of the ITS World Congress.

published journal article

Parsing density changes: An outcome-oriented growth management policy analysis

J Hous and the Built Environ

Publication Date

November 1, 2012

Author(s)

Jae Hong Kim, Brian Deal, Arnab Chakraborty

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Abstract

Although a considerable number of studies have examined the effectiveness of growth management programs in curbing sprawl and increasing aggregate densities, less attention has been paid to understanding how these noted density improvements are realized. In this paper, we assess the mechanisms that underlie changes in aggregate population densities and empirically examine detailed density changes under various growth management regimes in the US. Our county-level statistical analysis using recent US Census products and land use change data sets, finds that: (a) states with proactive growth management programs do tend to experience relative density gains, but not in jurisdictions with restrictive local land use regulations and (b) the marginal density gains appear to be attributable in large part to smaller housing vacancy rates and housing price escalations. Not surprisingly, our findings suggest that local structures are critical for achieving desired outcomes. Given the critical role of local action, the realization of compact development requires a tightly woven and integrated policy that not only makes logical sense at state levels, but can be followed and implemented at the local level.

Suggested Citation

Jae Hong Kim, Brian Deal and Arnab Chakraborty (2012) “Parsing density changes: An outcome-oriented growth management policy analysis”, J Hous and the Built Environ, 28(3), pp. 529–546. Available at: 10.1007/s10901-012-9327-0.

conference paper

Heuristics for freight procurement auctions with carrier capacity and shipper side constraints

Proceedings of the 88th annual meeting of the transportation research board

Publication Date

January 1, 2009

Author(s)

Matthew Nguyen, Sandra Irani, Amelia Regan

Abstract

Combinatorial auctions, in which trucking companies bid on contracts for bundles of lanes, rather than single ones, hold significant promise for adding efficiencies to contracts for freight transportation services. However, the problems faced by bidders (trucking companies) and auctioneers (large shippers) in order to effectively bid and select contract winners are very computationally complex â?? preventing widespread adoption of such auctions to date. In this research the authors provide heuristics for solving combinatorial auctions for freight procurement and demonstrate that complicated side constraints (favoring incumbents, creating backup assignments, and minimizing the number of winning carriers) can be considered â?? benefiting both shippers and carriers. The authors do this in a setting where carriers can bid on as many lanes or packages as they wish and in which shippers explicitly consider carrier capacities when assigning contracts. Empirical analysis shows that othe authors heuristics, based on the LP rounding technique developed by Shmoys and Tardos for the generalized assignment problem have very good performance.

Suggested Citation

Matthew Nguyen, Sandy Irani and Amelia Regan (2009) “Heuristics for freight procurement auctions with carrier capacity and shipper side constraints”, in Proceedings of the 88th annual meeting of the transportation research board, p. 34p.

published journal article

Bayesian mixture model for estimating freeway travel time distributions from small probe samples from multiple days

Transportation Research Record

Publication Date

January 1, 2009

Author(s)

Klayut Jintanakul, Lianyu Chu, R. (Jay) Jayakrishnan

View published journal article

Abstract

This study formulates a hierarchical Bayesian mixture model for estimating travel time distributions along freeway sections by using small data samples from vehicle probes, which have been collected over multiple days. Two normal components are used to capture the heterogeneity in the experienced travel times and to model various distributional shapes generally known to be skewed or multimodal. Travel time data collected during different intervals under similar traffic conditions are used to construct the prior for model parameters via a hierarchical Bayesian formulation. The posterior distributions can be continuously updated as new data from probes become available, and are used for prediction under different levels of data availability. A simulation study shows that true travel time distribution for each section during each interval can be well-approximated with the use of this proposed model.

Suggested Citation

Klayut Jintanakul, Lianyu Chu and R. Jayakrishnan (2009) “Bayesian mixture model for estimating freeway travel time distributions from small probe samples from multiple days”, Transportation Research Record, 2136(1), pp. 37–44. Available at: 10.3141/2136-05.

conference paper

Private Autonomous Vehicles and Their Impacts on Last-mile Travel: Integrated Mode Choice and Parking Assignment Model

101st Annual Meeting of the Transportation Research Board

Publication Date

January 1, 2022

Author(s)

Younghun Bahk, Michael Hyland, Sunghi (Sunny) An

Suggested Citation

Younghun Bahk, Michael Hyland and Sunghi An (2022) “Private Autonomous Vehicles and Their Impacts on Last-mile Travel: Integrated Mode Choice and Parking Assignment Model”.