Linear Programming Models for the User and System Optimal Dynamic Network Design Problem: Formulations,Comparisons and Extensions

In this paper we formulate a network design model in which the traffic flows satisfy dynamic user equilibrium conditions for a single destination. The model presented here incorporates the Cell Transmission Model (CTM); a traffic flow model capable of capturing shockwaves and link spillovers. Comparisons are made between the properties of the Dynamic User equilibrium Network Design Problem (DUE NDP) and an existing Dynamic System Optimal (DSO) NDP formulation. Both network design models have different objective functions with similar constraint sets which are linear and convex. Numerical demonstrations are made on multiple networks to demonstrate the efficacy of the model and demonstrate important differences between the DUE and DSO NDP approaches. In addition, the flexibility of the approach is demonstrated by extending the formulation to account for demand uncertainty. This is formulated as a stochastic programming problem and initial test results are demonstrated on test networks. It is observed that not accounting for demand uncertainty explicitly, provides sub-optimal solution to the DUE NDP problem.     

Robust Transportation Network Design Under Demand Uncertainty

Abstract:   This article addresses the problem of a traffic network design problem (NDP) under demand uncertainty. The origin–destination trip matrices are taken as random variables with known probability distributions. Instead of finding optimal network design solutions for a given future scenario, we are concerned with solutions that are in some sense "good" for a variety of demand realizations. We introduce a definition of robustness accounting for the planner's required degree of robustness. We propose a formulation of the robust network design problem (RNDP) and develop a methodology based on genetic algorithm (GA) to solve the RNDP. The proposed model generates globally near-optimal network design solutions, f, based on the planner's input for robustness. The study makes two important contributions to the network design literature. First, robust network design solutions are significantly different from the deterministic NDPs and not accounting for them could potentially underestimate the network-wide impacts. Second, systematic evaluation of the performance of the model and solution algorithm is conducted on different test networks and budget levels to explore the efficacy of this approach. The results highlight the importance of accounting for robustness in transportation planning and the proposed approach is capable of producing high-quality solutions.     

Mechanical integrity of thin inorganic coatings on polymer substrates under quasi-static, thermal and fatigue loadings

The interplay between residual stress state, cohesive and adhesive properties of coatings on substrates is reviewed in this article. Attention is paid to thin inorganic coatings on polymers, characterized by a very high hygro-thermo-mechanical contrast between the brittle and stiff coating and the compliant and soft substrate. An approach to determine the intrinsic, thermal and hygroscopic contributions to the coating residual stress is detailed. The critical strain for coating failure, coating toughness and coating/substrate interface shear strength are derived from the analysis of progressive coating cracking under strain. Electro-fragmentation and electro-fatigue tests in situ in a microscope are described. These methods enable reproducing the thermo-mechanical loads present during processing and service life, hence identifying and modeling the critical conditions for failure. Several case studies relevant to food and pharmaceutical packaging, flexible electronics and thin film photovoltaic devices are discussed to illustrate the benefits and limits of the present methods and models.     

A Clustering Algorithm for Bi‐Criteria Stop Location Design with Elastic Demand

This article proposes a bi‐criteria formulation to find the optimal location of light rapid transit stations in a network where demand is elastic and budget is constrained. Our model is composed of two competing objective functions seeking to maximize the total ridership and minimize the total budget allocated. In this research, demand is formulated using the random utility maximization method with variables including access time and travel time. The transit station location problem of this study is formulated using mixed integer programming and we propose a heuristic solution algorithm to solve large‐scale instances which is inspired by the problem context. The elastic demand is integrated with the optimization problem in an innovative way which facilitates the solution process. The performance of our model is evaluated on two test problems and we carry out its implementation on a real‐world instance. Due to the special shape of the Pareto front function, significant practical policy implications, in particular budget allocation, are discussed to emphasize the fact that the trade‐off between cost and benefit may result in large investments with little outcomes and vice versa.     

Near-Field and Plane-Wave Electromagnetic Coupling into a Slotted Circular Cylinder: Hard or TE Polarization

An analytically tractable model is proposed in this initial study of the electromagnetic phenomena that control our ability to synthesize, by using a near-field source, the effect of plane-wave coupling through an aperture into the interior of a vehicle under test. An integral equation for the tangential electric field in the slot aperture of a perfectly conducting, infinitesimally thin-walled circular cylinder is solved using a basis set of Chebyshev polynomials that are properly weighted according to the static edge condition. The resulting matrix elements from a Galerkin procedure are computed to high precision upon extracting the logarithmic singularity of the kernel of the integral operator. Exact expressions for the matrix elements, in the form of rapidly convergent series of elementary terms, are constructed by isolating another logarithmic function of the aperture width. A minimization of the mean-square error between the true plane-wave response and that due to a near-field line-source establishes the optimal complex source strength of the near-field source     

Effect of mixed solvents on PCDTBT:PC70BM based solar cells

We investigated the effect of solvents on the morphology, charge transport and device performance of poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC₇₀BM) based solar cells. To carry out this investigation, chloroform and 1,2-dichlorobenzene were chosen as good solvents of the two compounds. Films prepared with chloroform exhibit larger domains than those prepared with 1,2-dichlorobenzene and their size increases with the amount of PC₇₀BM. Fine tuning of the domain size was realized by using a solvent of mixed chloroform and 1,2-dichlorobenzene. At a mixing ratio of 50%:50%, a power conversion efficiency of 6.1% was achieved on PCDTBT:PC₇₀BM (1:3) devices with an active area of 1 cm², under air mass 1.5 global (AM 1.5 G) irradiation at 100 mW/cm².     

Potential availability of transplantable organs according to factors associated with type of injury event.

Potential availability of transplantable organs from different types of injury fatalities was studied. Factors examined included target organ damage or disease, age of potential donor, duration of survival before circulatory arrest, and universal rejection factors such as sepsis, HIV infection, or systemic malignancy. Motor vehicle fatalities yielded the greatest proportion of potentially viable organs. Delay in discovery and universal rejection factors were important exclusionary issues for fatalities from suicide, homicide, and non-motor vehicle unintentional injury. There was no difference in organ damage or in duration of survival with higher speeds in fatal crashes, suggesting that states with 65 mph speed limits--and consequently higher death rates--may have greater potential availability of donatable organs than do those with 55 mph maximum. The increase in deaths at higher speeds, however, vastly outweighs the benefits of any possible increase in the potential for donor organs.     

The New Zealand Rugby Injury and Performance Project: I. Design and methodology of a prospective follow-up study

Injury resulting from participation in sporting and physical recreational activities is a major contributor to the overall incidence of injury in the developed world. If sports injuries are to be reduced, a comprehensive approach must be taken to define the nature and magnitude of the problem, to establish models of relationships between risk factors, protective factors and injury experience, and to address injury through well designed intervention and evaluation programmes. The Rugby Injury and Performance Project (RIPP) is a prospective cohort study designed to examine the risk and protective factors for rugby injury. Data were collected on potential risk and protective factors from the RIPP cohort pre-season. Data on exposure to rugby, injury events and medical treatments were collected from the players each week during the season through telephone interviews. Pre-season measures were repeated post-season. A key feature of the design was that data were collected on both injured and non-injured players, allowing a longitudinal comparison of the injury experience of players with and without the factors of interest. A wealth of information was collected on each cohort member during the pre-season interview. A contact rate of 90% was achieved during the weekly follow-up phase. Post-season questionnaires were completed by 76% of the players and 88% of the coaches. Recommendations are made for the use of this methodology by other researchers and future directions for RIPP are described.