Mathematical modelling of temperature induced moisture migration in bulk powders

This paper reviews the importance of temperature gradient induced moisture diffusion in powder beds. Redistribution of moisture by this mechanism is important for a wide variety of products, especially those which are crystalline in nature. Moisture transfer in these products can result in very high local water activity and lead to microbial spoilage and caking problems. A conceptual model was developed for heat and moisture transfer due to the application of thermal gradients across a one-dimensional powder bed. The validity of the key assumptions in the model formulation were demonstrated and a mathematical model was derived and solved numerically. The model was validated against experimental data collected using crystalline lactose powders as a working example.     

Simulation of autothermal reforming in a staged‐separation membrane reactor for pure hydrogen production

Steam methane reforming with oxygen input is simulated in staged‐separation membrane reactors. The configuration retains the advantage of regular membrane reactors for achieving super‐equilibrium conversion, but reaction and membrane separation are carried out in two separate units. Equilibrium is assumed in the models given the excess of catalyst. The optimal pure hydrogen yield is obtained with 55% of the total membrane area allocated to the first of two modules. The performance of the process with pure oxygen input is only marginally better than with air. Oxygen must be added in split mode to reach autothermal operation for both reformer modules, and the oxygen input to each module depends on the process conditions. The effects of temperature, steam‐to‐carbon ratio and pressure of the reformer and the area of the membrane modules are investigated for various conditions. Compared with a traditional reformer with an ex situ membrane purifier downstream, the staged reactor is capable of much better pure hydrogen yield for the same autothermal reforming operating conditions.     

Recycled carbon fiber filled polyethylene composites

Composites of recycled carbon fiber (CF) with up to 30 wt % loading with polyethylene (PE) were prepared via melt compounding. The morphology of the composites and the degree of dispersion of the CF in the PE matrix was examined using scanning electron microscopy, and revealed the CF to be highly dispersed at all loadings and strong interfacial adhesion to exist between the CF and PE. Raman and FTIR spectroscopy were used to characterize the surface chemistry and potential bonding sites of recycled CF. Both the Young's modulus and ultimate tensile stress increased with increasing CF loading, but the percentage stress at break was unchanged up to 5 wt % loading, then decreased with further successive addition of CF. The effect of CF on the elastic modulus of PE was examined using the Halpin‐Tsai and modified Cox models, the former giving a better fit with the values determined experimentally. The electrical conductivity of the PE matrix was enhanced by about 11 orders of magnitude on addition of recycled CF with a percolation threshold of 7 and 15 wt % for 500‐μm and 3‐mm thick samples. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effects of filler size on the properties of thermoplastic polyolefin blends

The effects of filler size on the properties of a thermoplastic polyolefin (TPO) blend were examined by using wollastonite and talc with particle sizes ranging from 1.2 to 40 μm. While addition of filler produced significant changes in the mechanical properties of the blend, filler size affected only impact strength. However, filler size, filler coating, and injection speed had a major effect on the surface properties of the blend. Faster injection produced denser “shear zone layers” which exhibited better scratch resistance and poorer paint adhesion than those obtained with slower injection. Scartch resistance and paint adhesion also decreased with increasing filler particle size. Filler coatings altered the scratch and adhesion properties of the polypropylene (PP) blends.     

Compatibilization of an immiscible blend of EPDM and POM with an Ionomer

Immiscible blends of ethylene-propylene-diene-monomer (EPDM) and polyoxymethylene (POM), when EPDM is the major phase were compatibilized on the addition of an ionomer, poly(ethylene-co-methacrylic acid). The inclusion of the ionomer reduced the interfacial tension between the two phases, such that the diameter of the POM domains were significantly reduced to between 0.5 and 2 μm, typical of that required to toughen ductile polymers. The mechanical properties of the resultant compatibilized blends were significantly enhanced with increases in Young's modulus (↑54%), tensile strength (σ, ↑139%), elongation at break (ε, ↑97%), and tensile toughness (↑500%) with increasing ionomer content, relative to EPDM rubber alone. The ShoreA hardness of the compatibilized blend was 70.1 compared with 56.8 for the immiscible binary blend and, 50.2 for neat EPDM rubber.     

Association of the serotonin transporter gene promoter region (5-HTTLPR) polymorphism with biased attention for emotional stimuli.

A deletion polymorphism in the serotonin transporter-linked polymorphic region (5-HTTLPR) has been associated with vulnerability to affective disorders, yet the mechanism by which this gene confers vulnerability remains unclear. Two studies examined associations between the 5-HTTLPR polymorphism and attentional bias for emotional stimuli among nondepressed adults. Biased attention, attention engagement, and difficulty with attention disengagement were assessed with a spatial cuing task using emotional stimuli. Results from Study 1 (N = 38) indicated that short 5-HTTLPR allele carriers experienced greater difficulty disengaging their attention from sad and happy stimuli compared with long allele homozygotes. Study 2 participants (N = 144) were genotyped for the 5-HTTLPR polymorphism, including single nucleotide polymorphism rs25531 in the long allele of the 5-HTTLPR. Consistent with Study 1, individuals homozygous for the low-expressing 5-HTTLPR alleles (i.e., S and LG) experienced greater difficulty disengaging attention from sad, happy, and fear stimuli than high-expressing 5-HTTLPR homozygotes. Because this association exists in healthy adults, it may represent a susceptibility factor for affective disorders that becomes problematic during stressful life experiences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A graphical approach for confidence limits of optimal preventive maintenance cycles

Facilities management (FM) is the management of infrastructure resources and services to support and sustain the operational strategy of an organization over time. Maintenance is often the business process that has not been optimized and is considered as a liability of business operations. Therefore, extensive studies have been done to determine the optimal replacement interval for irreparable parts of repairable systems where typically the time between failures is characterized by lifetime distribution in which the parameters are estimated from failure data. As a result, the optimal preventive maintenance (PM) interval computed is exposed to sampling risk as the repair cost and failure data used for estimation are typically highly censored due to issues related to data collection and unobserved failures. In this paper, we present a graphical approach to obtain the confidence interval for the optimal PM interval that resulted from sampling variations parameter estimates. The proposed methodology is applied in the context of FM as a strategy for opportunistic replacement and for the purpose of validating the cost components in maintenance. Copyright © 2008 John Wiley & Sons, Ltd.     

延长采用微硬盘并由电池供电的便携产品的工作时间

就由电池供电并以微硬盘（HDD）作为主要存储介质的手持产品而言，目前有3种市场驱动因素汇聚在一起，可能导致在这些便携式产品的电池工作时间方面产生极大的突破。这类便携式产品包括便携式播放器（PMP）、MP3播放器、数码相机（DSC）、数字录像机（DVR）、智能电话和GPS系统等。     

Error Analysis for Image Inpainting

Image inpainting refers to restoring a damaged image with missing information. In recent years, there have been many developments on computational approaches to image inpainting problem [2, 4, 6, 9, 11–13, 27, 28]. While there are many effective algorithms available, there is still a lack of theoretical understanding on under what conditions these algorithms work well. In this paper, we take a step in this direction. We investigate an error bound for inpainting methods, by considering different image spaces such as smooth images, piecewise constant images and a particular kind of piecewise continuous images. Numerical results are presented to validate the theoretical error bounds. Tony F. Chan received the B.S. degree in engineering and the M.S. degree in aerospace engineering in 1973, from the California Institute of Technology, and the Ph.D. degree in computer science from Stanford University in 1978. He is Professor of Mathematics and currently also Dean of the division of Physical science at University of California, Los Angeles, where he has been a Professor since 1986. His research interests include mathematical and computational methods in image processing, multigrid, domain decomposition algorithms, iterative methods, Krylov subspace methods, and parallel algorithms. Sung Ha Kang received the Ph.D. degree in mathematics in 2002, from University of California, Los Angeles, and currently is Assistant Professor of Mathematics at University of Kentucky since 2002. Her research interests include mathematical and computational methods in image processing and computer vision.