Template-Based Growth of Oxide Nanorod Arrays by Centrifugation

This paper reports template-based growth of nanorod arrays by combination of sol–gel processing and centrifugation. The technical concept is simple and straightforward; centrifugation force drives the sol nanoclusters into the pores of the template, filling the pores completely to form nanorods. However, simulation reveals the formation of nanorods inside pores is more complex; centrifugation force is insufficient to overcome the energy barrier that prevents agglomeration of two nanoclusters. Thermal fluctuation and solvent evaporation upon drying are considered to be the forces leading to the eventual agglomeration of concentrated nanoclusters inside template pores. Dense nanorods with 200 nm diameter and 10 m length were readily obtained from polymeric SiO₂, colloidal SiO₂, TiO₂ and PZT sols after heat treatment.     

Equity Models in Planar Location

In this paper we investigate planar location models with equity objectives. Two objectives are analyzed: (1) Minimizing the variance of the distances to the facility, and (2) minimizing the range of the distances. The problems are solved using the global optimization technique “Big Triangle Small Triangle”. Computational experiments provided excellent results. Solving a problem with 10,000 demand points required less than 5 s of computer time for finding the minimum variance, and less than half that time for finding the minimum range.     

A Longitudinal Study of Elementary Pre‐service Teachers' Mathematics Beliefs and Content Knowledge

This study investigated the mathematics beliefs and content knowledge of 103 elementary pre‐service teachers in a developmental teacher preparation program that included a two course mathematics methods sequence. Pre‐service teachers' pedagogical beliefs became more cognitively‐oriented during the teacher preparation program with these changes occurring during the two methods courses. Pedagogical beliefs remained stable during student teaching. The pre‐service teachers also significantly increased their personal efficacy for teaching mathematics throughout the program with these shifts occurring across both methods courses and into student teaching. Pedagogical beliefs and teaching efficacy beliefs were not related at the beginning of the program, but, in general, were positively related throughout the program. In addition, the pre‐service teachers' pedagogical beliefs were positively related to their specialized content knowledge for teaching mathematics at the end of the program.     

Polydisperse Aggregates of ZnO Nanocrystallites: A Method for Energy‐Conversion‐Efficiency Enhancement in Dye‐Sensitized Solar Cells

ZnO films consisting of either polydisperse or monodisperse aggregates of nanocrystallites were fabricated and studied as dye‐sensitized solar‐cell electrodes. The results revealed that the overall energy‐conversion efficiency of the cells could be significantly affected by either the average size or the size distribution of the ZnO aggregates. The highest overall energy‐conversion efficiency of ～4.4% was achieved with the film formed by polydisperse ZnO aggregates with a broad size distribution from 120 to 360 nm in diameter. Light scattering by the submicrometer‐sized ZnO aggregates was employed to explain the improved solar‐cell performance through extending the distance travelled by light so as to increase the light‐harvesting efficiency of photoelectrode film. The broad distribution of aggregate size provides the ZnO films with both better packing and an enhanced ability to scatter the incident light, and thus promotes the solar‐cell performance.     

Optimization of reverse-flow,two-temperature,dilute-acid pretreatment to enhance biomass conversion to ethanol

Applied Biochemistry and Biotechnology - A reverse-flow, two-temperature dilute-acid prehydrolysis process of commercial yellow poplar sawdust using two percolation reactors was designed to...     

On the fine structure of the polygroup blow-up

We study in detail the blow-up procedure described in [BTW01]. We obtain a structure theorem for coreless polygroups as a double quotient space G//H, and a polygroup chunk theorem. Seeking to remove the arbitrary parameter needed for the blow-up, we find canonical Ø-invariant groupoids analogous to G and H above, and show that contains precisely all the arbitrary choices related to the blow-up. Mathematics Subject Classification (2000): 03C45, 03C60     

Validating the Gravity-Based Competitive Location Model Using Inferred Attractiveness

The attractiveness of retail facilities is an essential component of models analyzing competition among retail facilities. In this paper we introduce an innovative method for inferring retail facility attractiveness. Readily available data from secondary sources about customers' buying power and sales volumes obtained by competing retail facilities are used. The gravity-based competitive facility location model is used to predict sales. The attractiveness of the retail facilities are inferred from these data.The procedure is used to confirm the gravity competitive facility location model. Inferred attractiveness results based on empirical data from Orange County, California, were compared with an independent survey with excellent match.     

The Quintile Share Ratio in location analysis

The inequality measure “Quintile Share Ratio” (QSR or sometimes S80/S20) is the primary income inequality measure in the European Union’s set of indicators on social cohesion. An important reason for its adoption as a leading indicator is its simplicity. The Quintile Share Ratio is “The ratio of total income received by the 20% of the population with the highest income (top quintile) to that received by the 20% of the population with the lowest income (lowest quintile)”. The QSR concept is used in this paper in the context of obnoxious facility location where the inequality is in distances to the obnoxious facility. The single facility location problem minimizing the QSR is investigated. The problem is investigated for continuous uniform demand in an area such as a disk, a rectangle, and a line; when demand is generated at a finite set of demand points; and when the facility can be located anywhere on a network. Optimal solution algorithms are devised for demand originating at a finite set of demand points and at nodes of the network. Computational experiments demonstrate the effectiveness of the algorithms.