Synthesis of quantitative and qualitative evidence for accident analysis in risk-based highway planning

Accident analysis involves the use of both quantitative and qualitative data in decision-making. The aim of this paper is to demonstrate the synthesis of relevant quantitative and qualitative evidence for accident analysis and for planning a large and diverse portfolio of highway investment projects. The proposed analysis and visualization techniques along with traditional mathematical modeling serve as an aid to planners, engineers, and the public in comparing the benefits of current and proposed improvement projects. The analysis uses data on crash rates, average daily traffic, cost estimates from highway agency databases, and project portfolios for regions and localities. It also utilizes up to two motivations out of seven that are outlined in the Transportation Equity Act for the 21st Century (TEA-21). Three case studies demonstrate the risk-based approach to accident analysis for short- and long-range transportation plans. The approach is adaptable to other topics in accident analysis and prevention that involve the use of quantitative and qualitative evidence, risk analysis, and multi-criteria decision-making for project portfolio selection.     

Study of thermally coupled distillation systems for energy-efficient distillation

Distillation is one of the most widely used separation unit operations in process industries, although it is quite energy intensive. In many cases, the enormous energy requirements for distillation make it economically infeasible to carry out the separation. Thermally coupled distillation system (TCDS) is an advanced distillation method that provides significant energy savings of about 30% as compared with conventional distillation column sequences. The most well-known TCDS sequence, the Petlyuk configuration, has some operational challenges due to bidirectional vapour flow, which makes its implementation difficult in two-column mode. To overcome these limitations, a number of unidirectional vapour flow configurations have been proposed in the literature. The work on simulation analysis for such configurations is limited. In this paper, simulation models for two such configurations are developed, analyzed and compared with the Petlyuk and conventional distillation column sequences for separation of equimolar mixture of benzene–toluene–ethylbenzene.     

True Meaning of Pseudocapacitors and Their Performance Metrics: Asymmetric versus Hybrid Supercapacitors

The development of pseudocapacitive materials for energy‐oriented applications has stimulated considerable interest in recent years due to their high energy‐storing capacity with high power outputs. Nevertheless, the utilization of nanosized active materials in batteries leads to fast redox kinetics due to the improved surface area and short diffusion pathways, which shifts their electrochemical signatures from battery‐like to the pseudocapacitive‐like behavior. As a result, it becomes challenging to distinguish “pseudocapacitive” and “battery” materials. Such misconceptions have further impacted on the final device configurations. This Review is an earnest effort to clarify the confusion between the battery and pseudocapacitive materials by providing their true meanings and correct performance metrics. A method to distinguish battery‐type and pseudocapacitive materials using the electrochemical signatures and quantitative kinetics analysis is outlined. Taking solid‐state supercapacitors (SSCs, only polymer gel electrolytes) as an example, the distinction between asymmetric and hybrid supercapacitors is discussed. The state‐of‐the‐art progress in the engineering of active materials is summarized, which will guide for the development of real‐pseudocapacitive energy storage systems.     

Morphology,structural, optical,magnetic, and photocatalytic properties of Co1−xZnxFe2−yCeyO4 NPs

Journal of Materials Science: Materials in Electronics - In the current study, we looked into the effects of simultaneous trivalent Ce and divalent Zn doping on the optical, magnetic, and...     

In situ transmission electron microscopy observation of microstructure and phase evolution in a SnO₂ nanowire during lithium intercalation

Recently we have reported structural transformation features of SnO(2) upon initial charging using a configuration that leads to the sequential lithiation of SnO(2) nanowire from one end to the other (Huang et al. Science2010, 330, 1515). A key question to be addressed is the lithiation behavior of the nanowire when it is fully soaked into the electrolyte (Chiang Science2010, 330, 1485). This Letter documents the structural characteristics of SnO(2) upon initial charging based on a battery assembled with a single nanowire anode, which is fully soaked (immersed) into an ionic liquid based electrolyte using in situ transmission electron microscopy. It has been observed that following the initial charging the nanowire retained a wire shape, although highly distorted. The originally straight wire is characterized by a zigzag structure following the phase transformation, indicating that during the phase transformation of SnO(2) + Li ? Li(x)Sn + Li(y)O, the nanowire was subjected to severe deformation, as similarly observed for the case when the SnO(2) was charged sequentially from one end to the other. Transmission electron microscopy imaging revealed that the Li(x)Sn phase possesses a spherical morphology and is embedded into the amorphous Li(y)O matrix, indicating a simultaneous partitioning and coarsening of Li(x)Sn through Sn and Li diffusion in the amorphous matrix accompanied the phase transformation. The presently observed composite configuration gives detailed information on the structural change and how this change takes place on nanometer scale.     

Effect of modifier concentration on the fracture behaviour of rubber-modified PMMA

Izod fracture surfaces of blends of PMMA with various amounts of a rubber modifier were studied using scanning electron microscopy. Attention was focused on modes of crack initiation and propagation and on the role of the modifier in the fracture process. It was found that the impact strength of this class of materials increased monotonically with an increase in modifier concentration, at least up to 40 wt% modifier. Unmodified PMMA was studied to provide a basis for understanding the morphological features on the fracture surfaces of the rubber-modified blends. It was confirmed that PMMA fractures through the formation and rupture of crazes. This phenomenon was also found to occur in blends containing 10 wt% modifier. However, blends with 20 wt% modifier crazed only in the later stages of the fracture process, when the crack speed had exceeded some critical value. No evidence of crazing was found in blends with 30 and 40 wt% modifier loadings, although extensive plastic deformation was observed on the fracture surfaces.     

Superresolution and noise filtering using moving least squares.

An irregularly spaced sampling raster formed from a sequence of low-resolution frames is the input to an image sequence superresolution algorithm whose output is the set of image intensity values at the desired high-resolution image grid. The method of moving least squares (MLS) in polynomial space has proved to be useful in filtering the noise and approximating scattered data by minimizing a weighted mean-square error norm, but introducing blur in the process. Starting with the continuous version of the MLS, an explicit expression for the filter bandwidth is obtained as a function of the polynomial order of approximation and the standard deviation (scale) of the Gaussian weight function. A discrete implementation of the MLS is performed on images and the effect of choice of the two dependent parameters, scale and order, on noise filtering and reduction of blur introduced during the MLS process is studied.     

Use of genetic algorithms in the optimization of free radical polymerizations exhibiting the trommsdorff effect

The genetic algorithm (GA) is adapted and used to obtain optimal temperature histories for methyl methacrylate polymerizations. The reaction time is minimized, while simultaneously requiring the attainment of design values of the final monomer conversion and number average chain length. The technique is robust, and gives near-global optimal solutions. As such, it can easily be used for on-line optimizing control of free radical polymerization reactors in which the reaction is associated with the Trommsdorff effect. The results obtained from GA can be improved further if these are provided as initial guesses to a computer code using the Pontryagin minimum principle with the first order control vector iteration method. © 1997 John Wiley & Sons, Inc.     

Studies on a fiber reinforced plastics honeycomb structure

Based on an adhesive and fabric screening program, a rubber-modified resole adhesive and a flexible grade plain weave glass fabric were found appropriate for the fabrication of a glass-reinforced plastics honeycomb core material. Sandwich structures of different densities were fabricated. A linear regression analysis was performed to correlate the mechanical properties (S) with the density (p) for a wide range of sandwich structures based on honeycomb and cellular plastic core materials. An analytical model of the form S = Kρⁿ was derived, with two empirical constants K and n. The density exponent n was between 1 ≤ n ≤ 2 in all cases. An equation was also derived to relate density with thermal conductivity. The dynamic mechanical analysis (DMA) results revealed that the glass transition temperature of the resin matrix associated with the sandwich structure was higher than that of the corresponding facing laminate or near resin casting.     

The Replication of Multi-year Solutions Using Single Period Models of Electric Utility Capacity Expansion Planning

When fuel prices are projected to change over the planning horizon, a standard approach is to formulate a multiperiod capacity expansion model for a utility. However, multiperiod models are considerably larger and more cumbersome than a single period model. An alternative strategy is to develop a single period model whose optimal solution replicates the first period part of the multiperiod optimal solution. This allows the model builder to trade-off a more aggregate multiperiod model for a more detailed single period, rolling horizon model without increasing computational complexity. When and how this can be accomplished in a model of electric utilities is the subject of this paper.