Evaluation of hydrogen and methanol fuel cell performance of sulfonated diels alder poly(phenylene) membranes

Hydrogen fuel cell performance of sulfonated diels alder poly(phenylene) (SDAPP) with IECs ≥ 1.8 meq g⁻¹ is comparable to Nafion 212 under fully humidified conditions at 80 °C. However, as relative humidity is reduced, performance loss is substantial for SDAPP when compared to Nafion 212. This loss can be attributed to the large drop in proton conductivity in SDAPP as relative humidity is reduced; the proton conductivity of SDAPP with an IEC of 2.3 meq g⁻¹ dropped from 0.117 S cm⁻¹ to 0.001 S cm⁻¹ as the relative humidity was reduced from 100% to 25% at 80 °C. Methanol fuel cell experiments using 3 M methanol result in a 60 mV performance improvement at 25 mA cm⁻² when using SDAPP with an IEC of 1.2 meq g⁻¹ instead of Nafion 212. This improvement is due to lower methanol permeability of SDAPP (1.4 meq g⁻¹) over Nafion 212, with SDAPP films having methanol permeabilities less than 25% of Nafion 212.     

Waves: A FORTRAN IV Program on the Stochastic Simulation of Waves in the coastal Environment

A FORTRAN IV program for the stochastic simulation of waves and tidal characteristics in any coastal environment is presented. The Airy, Stokes', and cnoidal wave theories are used in the simulation depending on the ratio of water depth to wave length.During each iteration of the program, the movement of a set of waves from deep water to the shore is simulated. Deep-water wave heights, and periods vary randomly from one iteration to the next, such that these values conform to a Rayleigh probability distribution. Each iteration represents one twelfth of a tidal cycle or approximately 70 min. The tidal range, which changes every 12 iterations is a normally-distributed random variate.Wave height, length, celerity, and horizontal components of water particle velocities change at a user-specified number of equally-spaced points along the near shore slope, or at varying water depths. Shoaling equations for the Stokes' and cnoidal wave theories are used, and wave heights are adjusted for breaking conditions.The modulus, k, of the cnoidal functions used to calculate the characteristics of the cnoidal waves, is estimated by an efficient bisection technique.     

Photosynthetic cathodes for Microbial Fuel Cells

One of the major limiting factors in the practical implementation of Microbial Fuel Cells is finding efficient and sustainable catalysts for the cathode half reaction, in an attempt to avoid expensive and/or toxic catalysts. The use of phototrophic organisms is one good option since they can act as efficient in-situ oxygenators thus facilitating the cathodic reaction. In the present study, the oxygen production by photosynthetic organisms was shown to be light dependant, which resulted in increasing the power generation by 42%. Furthermore, this study showed that a previously abiotic cathode that turned biotic showed a clear light response with an improved performance of 48%. Oxygen depletion in a water-based cathode can be avoided with the use of photosynthetic biocatalysts, thus providing sustainable operation for MFCs.     

High-performance and cost-effective membrane electrode assemblies for advanced proton exchange membrane water electrolyzers: Long-term durability assessment

Improved activity and durability performance of a two-cell (86 cm²) proton exchange membrane water electrolyzer (PEMWE) stack is reported for the first time. Both membrane electrode assemblies (MEAs) contain one order of magnitude lower platinum group metal (PGM) loadings compared to the state-of-the-art PEMWEs and incorporate novel Pt recombination layers. The high-performance and cost-effective MEAs are fabricated by the unique reactive spray deposition technology (RSDT). This advanced methodology allows for one-step fabrication of MEAs and ensures precise control and distribution of the catalyst composition and loading. The RSDT-fabricated MEAs contain only 0.2 and 0.3 mg_PGM cm^?2 loading in the cathode and anode electrodes, respectively, and demonstrate excellent activity and durability for over 3000 h of operation at industrially-relevant operating conditions without showing significant loss in performance. This novel work shows that a significant cost reduction for PEMWEs is achieved while maintaining excellent durability, high catalysts activities, and low hydrogen cross-over.     

MODELING AND OPTIMIZATION OF SINGLE-ELEMENT BULK SiGe THIN-FILM COOLERS

Abstract

Modeling and optimization of bulk SiGe thin-film coolers are described. Thin-film coolers can provide large cooling power densities compared to commercial thermoelectrics. Thin-film SiGe coolers have been demonstrated with maximum cooling of 4°C at room temperature and with cooling power density exceeding 500 W/cm². Important parameters in the design of such coolers are investigated theoretically and are compared with experimental data. Thermoelectric cooling, joule heating, and heat conduction are included in the model as well as non-ideal effects such as contact resistance, geometrical effects, and three-dimensional thermal and electrical spreading resistance of the substrate. Simulations exhibit good agreement with experimental results for bulk Si and SiGe thin-film coolers. It turned out that in many spot cooling applications using two n- and p-elements electrically in series and thermally in parallel does not give significant improvement over single leg elements. This is in contrast to conventional thermoelectric modules and is due to the aspect ratio and special geometry of thin film coolers. With optimization of SiGe thin-film cooler, simulations predict it can provide over 16°C with cooling power density of over 2000 W/cm².     

Control of dual-chambered microbial fuel cell by anodic potential: Implications with sulfate reducing bacteria

Five dual chamber microbial fuel cell reactors were inoculated with a mixed culture of sulfate-reducing bacteria and fed with artificial wastewater containing lactate and sulfate. A negative poised anode potential enhanced the performance of this fuel cell while a positive poised anode potential or no anode potential had no effect on performance. The effect of this anode potential promoted microbial colonization on the anode surface (biofilm) thereby presenting an effective and successful way for the start-up of a sulfate reducing bacterial microbial fuel cell.     

Body-image and eating disturbances predict onset of depression among female adolescents: A longitudinal study.

This study examined data from a 4-year school-based longitudinal study (n?=?1,124), to test whether the increase in major depression that occurs among girls during adolescence may be partially explained by the body-image and eating disturbances that emerge after puberty. Elevated body dissatisfaction, dietary restraint, and bulimic symptoms at study entry predicted onset of subsequent depression among initially nondepressed youth in bivariate analyses controlling for initial depressive symptoms. Although the unique effect for body dissatisfaction was not significant in the multivariate model, this set of risk factors was able to fairly accurately foretell which girls would go on to develop major depression. Results were consistent with the assertion that the body-image- and eating-related risk factors that emerge after puberty might contribute to the elevated rates of depression for adolescent girls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Application Service Providers: Will They Succeed?

This article examines the likelihood of success for application service providers (ASP) drawing from the outsourcing literature, interviews with ASPs in the USA, and the experience of Bennett who has held leadership roles in ASP and ERP in South East Asia. This article proposes that application service providers (ASP) rent packaged software, predominantly over the Internet. It shows why organizations might employ the ASP model to manage their enterprise resource planning systems. Using a framework adapted from Lacity and Hirschheim, it demonstrates that the financial, business, technical and political reasons why organizations evaluate outsourcing can be applied to ASP model. While ASPs generally target the mid-market, large enterprises are also using ASPs to introduce new ERP modules. Potential users of ASP should regard the risks of outsourcing prior to entering into business arrangements. This examination concludes that there are strong financial and technical reasons for adopting the ASP model and therefore it has potential to succeed.     

1∕8 Factorial Study of Metal Effects on Acid Neutralization by Cement

The acid neutralization capacity of a cement/waste product is important because the integrity of the monolithic matrix and contaminant precipitation are dependent on the maintenance of alkaline conditions. A 1∕8 fractional factorial experiment was used to selectively examine the main effects of seven pure metal compounds on strength development and acid neutralization capacity of portland cement paste and to obtain information regarding interactions between the compounds. The hydration products in a portland cement paste appear as plateaus in its titration curve. Metal contaminants were found to affect the pH and acid neutralization capacities of these plateaus, suggesting that they change the hydration products. Cr(NO3)3 and ZnCl2, which exhibited individual effects and also interacted, caused the predominant effects. Comparison between predictions by a simple empirical linear model based on these contaminants and acid neutralization capacity of a real solidified metal plating waste showed that additional factors play an important role in real wastes.     

How knowledge management impacts performance in projects: An empirical study

This paper develops theory and tests the relationships between knowledge management and various aspects of performance in IT-enabled business projects. The proposed theory posits that knowledge management is instrumental to Project Performance when mediated by a new concept, Knowledge Alignment. The research model is tested on survey data from 212 IT-enabled business projects. Findings show that project managers who achieve Knowledge Alignment among the people and the artefacts from three parts of the project – the IT team, the business change team, and the governance team – can have a significant positive impact on the achievement of business value from the project. Achieving higher levels of Knowledge Alignment is shown to have no significant negative impact on attainment of schedule and budget targets. This is the first statistical study to demonstrate the effect of knowledge management and Knowledge Alignment on the attainment of project management targets and of business value in IT-enabled projects.