Correlation of film structure and molecular oxygen reduction at nitrogen doped amorphous carbon thin film electrochemical electrodes

Nitrogen doped amorphous carbon (a-C:N) thin film electrodes with a range of film structures have been deposited using a filtered cathodic vacuum arc system. The correlation between film structure and electro-reduction of molecular oxygen in aqueous media at the electrodes has been explored. In aqueous 0.1 M NaOH, dioxygen reduction is inhibited at all the a-C:N electrodes compared with that at glassy carbon electrodes. The potential of the dioxygen reduction current peak shifts negatively at a-C:N electrodes as the sp³ C fraction in the a-C:N materials increases, while the current peak height decreases simultaneously. The a-C:N electrodes possess high sensitivity for investigating the mechanism of dioxygen reduction. It was found that the catalytic H₂O₂ reduction to H₂O on carbon materials is attributed to oxygen species at sp² C sites.     

Structure and Optical Properties of CeO2 Nanoparticles Synthesized by Precipitation

Cerium dioxide (CeO₂) has special electrical and optical properties, and chemical and thermal stability. It has been used in semiconductor devices and as a luminescent material. In this work, CeO₂ nanoparticles were synthesized by the precipitation method and the product annealed at various temperatures. Thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC) results show that the optimum annealing temperature for fabrication of CeO₂ nanoparticles is greater than 500°C. When the calcination temperature is increased from 550°C to 1050°C, Fourier-transform infrared (FTIR) results show that the water and impurities are almost completely removed, after calcination at 750°C. The x-ray diffraction (XRD) results suggest that the synthesized CeO₂ exhibits a cubic fluorite structure. The crystallite size of the CeO₂ increases from 8 nm to 75 nm when the calcination temperature is increased from 550°C to 1050°C. The absorption spectrum in the ultraviolet (UV) region from 372 nm to 395 nm demonstrates their applicability as UV-filter materials, and the shift of the estimated E _g,eff from 3.21 eV to 3.65 eV demonstrates their applicability in photoelectric devices. CeO₂ would be potentially important for applications such as insulator structures, stable capacitor devices, and light-emitting diodes (LEDs).     

Semiconductor properties and redox responses at a-C:N thin film electrochemical electrodes

The semiconductor capacitances of the nitrogen-doped amorphous carbon (a-C:N) materials with different sp³/sp² C ratios were studied as a function of electrode potential in a-C:N/aqueous electrolyte systems. This dependence of capacitance on electrode potential in aqueous 0.1 M NaOH shows that the investigated a-C:N materials are intrinsic semiconductors. The space-charge layers inside the a-C:N electrodes behave similar to a Helmholtz layer because of the presence of surface states when the electrolytes contain O₂ or anions other than OH⁻. The lower density and mobility of carriers of materials with a higher sp³ C fraction within the a-C:N material causes a suppression of redox reactions, and the lower density of carriers contributes to a lower capacitance.     

Ethnic origin, belief, and personality information in interpersonal attraction.

To test the effects on interpersonal attraction of 3 categories of information, 78 English-speaking undergraduates made liking and social distance ratings about a derived target. The person rated was either English or French Canadian, pro- or anti-capital-punishment and the harsh treatment of criminals, and high or low on the Cognitive Structure and Order scales of the Personality Research Form. Results show that the judges were all anti-capital-punishment and low on the personality traits. Belief and belief-congruence were the primary determinants of attraction. The 3 categories of information interacted on 2 measures. French Canadians were rated more favorably than English-Canadians when similar to the judge in belief or personality but less favorably when similar in neither belief nor personality. (French summary) (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Minimizing control variation in nonlinear optimal control

In any real system, changing the control signal from one value to another will usually cause wear and tear on the system’s actuators. Thus, when designing a control law, it is important to consider not just predicted system performance, but also the cost associated with changing the control action. This latter cost is almost always ignored in the optimal control literature. In this paper, we consider a class of optimal control problems in which the variation of the control signal is explicitly penalized in the cost function. We develop an effective computational method, based on the control parameterization approach and a novel transformation procedure, for solving this class of optimal control problems. We then apply our method to three example problems in fisheries, train control, and chemical engineering.     

Translating Singapore architects' environmental awareness into decision making

Construction activity is known to have a major impact on the environment. Construction is a major consumer of a wide range of naturally occurring and synthesized resources. The extraction, processing and utilization of these resources can have various negative impacts on the environment. With increased awareness and knowledge of these impacts, efforts are being made to avoid these adverse effects. Among these is the selection and specification of appropriate materials. This paper studies the level of environmental awareness and knowledge of architects in Singapore when selecting and specifying materials during the design stage. Responses to a questionnaire indicate that the architects are aware of the environmental impacts of building materials, and knowledgeable about possible measures which could help avoid the problems. However, they are not adopting green design approaches. Key policy directions for government, professional bodies, educators and clients are made to enable Singapore architects to apply their knowledge of environmental issues in their design decisions.     

Correlation of material properties to reliability performance of anisotropic conductive adhesive flip chip packages

The anisotropic conductive adhesive (ACA) is a promising solder alternative candidate that shows potential for further pitch reduction. Although much work has been published on ACA joint behavior, study on correlation of material properties with reliability performance is still lacking. The main objective in this study was to identify the impact of material properties on reliability, so as to engineer highly reliable microelectronics assemblies. Four representative ACA materials (both film and paste types) with diverse properties were selected. Material properties were characterized as close as possible to "stress test" conditions so as to allow more accurate correlation predictions. Reliability performance was obtained by assembling test chips of 200-/spl mu/m pitch onto BT-substrates, then subjecting them to reliability tests. Correlation analysis was conducted and key material properties that contributed to good reliability performance were identified. Findings indicated that the best properties for high reliability assemblies were: high adhesion strength after subjecting to "stress aging", low coefficient of moisture expansion (CME) and low elastic modulus (E).     

Influences of pH and hydraulic retention time on anaerobes converting beer processing wastes into hydrogen.

To convert high-solids organic wastes (3% w./w.) to high-value hydrogen, a full factorial experimental design was employed in planning the experiments for learning the effects of pH and hydraulic retention time (HRT) on the hydrogen production in a chemostat reactor using waste yeast obtained from beer processing wastes. For determining which experimental variable settings affect hydrogen production, predictive polynomial quadratic equation and response surface methodology were employed to determine and explain the conditions required for high-value hydrogen production. Experimental results indicate that a maximum hydrogen production rate of 460 mL/gVSS/d was obtained at pH = 5.8 and HRT = 32 hours. Moreover, hydrogenase targeted RT-PCR results indicate that Clostridium thermocellum and Klebsiella pneumoniae predominated.     

Effect of Cooling Rates on γ → α Transformation and Metastable States in Fe–Cu Alloys with Addition of Ni

α/γ phase transformations occurring in Fe–10Cu–xNi alloys (0?≤?x?≤?15 in mass%) were studied using X-ray diffraction, scanning electron microscopy, electron back scattered diffraction, transmission electron microscopy and chemical analysis, combining X-ray microanalysis with energy dispersive spectrometry in the scanning electron microscope and electron microprobe analysis with wavelength dispersive spectrometry. The influence of cooling rate on the microstructure was investigated using ice-brine quenching and 2 °C/min slow cooling rate performed with dilatometry. Ni addition induces metastable transformations on cooling: massive and bainitic ferrite are formed depending on the alloy composition and cooling rate. Moreover, most of the Cu phase precipitates on cooling giving rise to a fine distribution of Cu particles in the ferrite grains. For both cooling conditions, the hardness increases with increasing Ni content and a higher hardness is obtained in the quenched alloy for each composition. The change in hardness is correlated to the effect of Ni solid solution, transformation structure and size of Cu particles.     

A wave flume experiment for studying erosion mechanism of revetments using geotextiles

Unfavorable erosion to a revetment can affect the stability of the bank and may jeopardize the safety of adjacent structures, thus improvement work is needed to increase the stability of the revetment as well as reducing the possibility of failure. The use of geotextiles as a protection material for banks is not only environmentally friendly, but also stable in the long run. However, improper design of geotextiles may cause considerable loss of soil, which might result in failure. The actual flow behavior in revetments using geotextiles is rather complicated and can be categorized into three zones, namely, the uni-directional flow zone, the cyclic flow zone, and the tangential flow zone. In this study, a wave flume experiment was performed on model revetments using two kinds of geotextiles as the filter material to prevent erosion induced by cyclic flows. Soil migration behaviors were monitored. Furthermore, two kinds of cover blocks, riprap and concrete blocks, were carefully placed on the revetments in order to avoid puncture and abrasion of geotextiles during construction of revetments. The main purpose of this study is to elucidate the erosion control and filtration performance of soil-geotextile filtration systems under wave action. Two nonwoven needle punched geotextiles were tested. The geotextiles both have the same characteristic opening size, but have a different number of constrictions and different structures. One is a thin double-layer nonwoven material consisting of continuous filaments and the other is a thick one-layer nonwoven material consisting of short fibers.