Part-list cuing can be transient and lasting: The role of encoding.

The presentation of a subset of learned items as retrieval cues can have detrimental effects on recall of the remaining items. For 2 types of encoding conditions, the authors examined in 3 experiments whether such part-list cuing is a transient or a lasting phenomenon. Across the experiments, the detrimental effect of part-list cues was consistently found to be transient with a high degree of interitem associations and lasting with a low degree. These results indicate that the persistence of part-list cuing depends on encoding, thus challenging both strategy disruption and retrieval inhibition as general accounts of part-list cuing. A 2-mechanism account is provided according to which the 2 mechanisms mediate the effect in different encoding conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of the effect of rake angle on main cutting force

This paper presents a study of comparison of empirical and experimental results for main cutting force during machining rotational parts by unworn cutting tools. A dynamometer was designed and produced for measuring the forces. Two strain gauges were placed at the correct position on the machine tool and cutting tool at the design stage. Correct gauge positioning sensed displacements of the tool caused by cutting forces. AISI 1040 was used as the workpiece material. Main cutting force (F_c) was measured for eight different rake angles changing from negative to positive values at five different cutting speeds. The depth of cut and feed rate were kept throughout the experiments. Empirical results according to Kienzle approach were compared with experimental results. Main cutting force was observed to have a decreasing trend as the rake angle increased from negative to positive values. The deviation between empirical approach and experiments was in the order of 10–15%.     

A new method for determination of fine particle breakage

Material characterization plays a crucial role by means of equipments efficiency and overall circuit performance. Material properties such as grindability, breakage, crushability, mineralogy can easily be determined by laboratory studies. These parameters are required for modeling and simulation works.Breakage behaviour of material is important for size reduction equipments and it is defined by breakage distribution function. Commonly, single particle breakage method is used to determine breakage behaviour of materials which assumes that breakage is not size dependent. As new surfaces formed material behaviour changes so particle size effect should also be introduced into the grinding model structure. Determination of fine particle breakage becomes important. This will make models more reliable. With this aim a bed breakage method was developed for determination of fine particle breakage. In this study new breakage model is presented and effects of different breakage distribution functions on breakage rate and discharge function is investigated. The bed breakage test results are compared with single size drop-weight test results in the aspect of modeling. It was observed that, the breakage rate and discharge function variation by size indicates a characteristic change at fine size ranges compared to regular curve.     

Low-Loss Optical Waveguides for the Near Ultra-Violet and Visible Spectral Regions with Al(2)O(3) Thin Films from Atomic Layer Deposition

In this work, we report low-loss single-mode integrated optical waveguides in the near ultra-violet and visible spectral regions with aluminum oxide (Al₂O₃) films using an atomic layer deposition (ALD) process. Alumina films were deposited on glass and fused silica substrates by the ALD process at substrate/chamber temperatures of 200 °C and 300 °C. Transmission spectra and waveguide measurements were performed in our alumina films with thicknesses in the range of 210-380 nm for the optical characterization. Those measurements allowed us to determine the optical constants (n_w and k_w), propagation loss, and thickness of the alumina films. The experimental results from the applied techniques show good agreement and demonstrate a low-loss optical waveguide. Our alumina thin-film waveguides are well transparent in the whole visible spectral region and also in an important region of the UV; the measured propagation loss is below 4 dB/cm down to a wavelength as short as 250 nm. The low propagation loss of these alumina guiding films, in particular in the near ultra-violet region which lacks materials with high optical performance, is extremely useful for several integrated optic applications.     

Engineering solid oxide fuel cell electrode microstructure by a micro-modeling tool based on estimation of TPB length

In this study, a typical solid oxide fuel cell (SOFC) electrode microstructure is numerically optimized in terms of the volume fraction of the catalyst, electrolyte and pore phases via a novel tool based on Dream.3D for the synthetic microstructure reconstruction and COMSOL Multiphysics® Modeling for visualizing and computing three/triple phase boundaries (TPBs). First, the properties of the representative volume element are studied by a parameter independence analysis based on the average particle size. The results indicate that the size of the representative volume element should be at least 10 times greater than the largest average particle size in the microstructure, while the number of mesh elements should be selected such that the smallest average particle size in the system is divided into at least 5. The method is then validated with the available studies in the literature and seems to agree well. Therefore, numerical reconstruction of SOFC electrodes by the proposed method is found to be a very useful tool in the viewpoints of accuracy, flexibility and cost. Finally, SOFC electrode microstructures having the same particle size distribution of an average particle size of 0.5 μm for each phase but with various phase volume fractions are generated and the resultant TPBs are computed similarly. It is found out that the volume fraction of each phase should be close to each other as much as possible to maximize the active TPB density and among the cases considered, the highest active TPB density of 9.53 μm/μm³ is achieved for an SOFC electrode including 35 vol% catalyst, 35 vol% electrolyte and 30 vol% porosity. The active TPB density is also found to be around 93% of the total TPB density.     

An overview of the methanol reforming process: Comparison of fuels,catalysts, reformers,and systems

One of the main challenges facing power generation by fuel cells involves the difficulties related to hydrogen storage. Several methods have been suggested and studied by researchers to overcome this problem. Among these methods, using fuel reformers as a component of the fuel cell system is a practical and promising alternative to hydrogen storage. Among many hydrogen carrier fuels used in reformers, methanol is one of the most attractive ones because of its distinctive properties. To design and improve of the methanol reformate gas fuel cell systems, different aspects such as promising market applications for reformate gas–fueled fuel cell systems, and catalysts for methanol reforming should be considered. Therefore, our goal in this paper is to provide a comprehensive overview on the past and recent studies regarding methanol reforming technologies, while considering different aspects of this topic. Firstly, different fuel reforming processes are briefly explained in the first section of the paper. Then properties of various fuels and reforming of these fuels are compared, and the characteristics of commercial reformate gas–fueled systems are presented. The main objective of the first section of the paper is to give information about studies and market applications related to reformation of various fuels to understand advantages and disadvantages of using various fuels for different practical applications. In the next sections of the paper, advancements in the methanol reforming technology are explained. The methanol reforming catalysts and reaction kinetics studies by various researchers are reviewed, and the advantages and disadvantages of each catalyst are discussed, followed by presenting the studies accomplished on different types of reformers. The effects of operating parameters on methanol reforming are also discussed. In the last section of this paper, methanol reformate gas–fueled fuel cell systems are reviewed. Overall, this review paper provides insight to researchers on what has been accomplished so far in the field of methanol reforming for fuel cell power generation applications to better plan the next stage of studies in this field.     

Enhancement of hydrogen storage capacity of multi-walled carbon nanotubes with palladium doping prepared through supercritical CO2 deposition method

Pd doped Multi-Walled Carbon Nanotubes were prepared via supercritical carbon dioxide deposition method in order to enhance the hydrogen uptake capacity of carbon nanotubes at ambient conditions. A new bipyridyl precursor that enables reduction at moderate conditions was used during preparation of the sample. Both XRD analyses and TEM images confirmed that average Pd nanoparticle size distribution was around 10 nm. Hydrogen adsorption and desorption experiments at room temperature with very low pressures (0–0.133 bar) were conducted together with temperature programmed desorption (TPD) and reduction (TPR) experiments on undoped and doped materials to understand the complete hydrogen uptake profile of the materials. TPD experiments showed that Pd nanoparticles increased the hydrogen desorption activity at moderate temperatures around at 38 °C while for undoped materials it was determined around at 600 °C. Moreover, a drastic enhancement of hydrogen storage was recorded from 44 μmol/g sample for undoped material to 737 μmol/g sample for doped material through adsorption/desorption isotherms at room temperature. This enhancement, also verified by TPR, was attributed to spillover effect.