Performance of a p-adaptive finite element method for shakedown analysis

This paper is concerned with the application of the p-version finite element method in carrying out a shakedown analysis. In particular, an adaptive scheme, implemented within the discretized framework of a static approach and mathematical programming, is proposed. The primary motivation of the present work is to overcome the well-known locking behavior caused by the incompressibility constraint that may occur in computational plasticity, and yet is still able to process the underlying nonlinear optimization problem efficiently. Quadrilateral elements and plane problems are specifically considered. A number of examples, some being benchmarks problems, are given to illustrate suitability of the approach.     

Study on the preparation of ordered mesoporous carbon-based catalyst from waste microalgal biomass for the synthesis of biokerosene

Investigation on preparation of novel ordered mesoporous carbon-based catalyst (MCC catalyst) containing super-acid sites from waste microalgal biomass was established. The waste microalgal biomass was partially carbonized at 400 °C for 2 h obtaining biochar; then the obtained biochar was introduced to a sulfonation process using concentrated sulfuric acid. The sulfonation was established at 150 °C for 15 h producing sulfonated biochar. The MCC catalyst was prepared through condensation–evaporation method in an alkaline media containing cetyltrimethylammonium bromide (CTAB) as structure directing agent. The parameters of the condensation including time of evaporating and CTAB content were investigated while fixing temperature at 90 °C during the process. A special hydrothermal treatment was also applied to the preparation of the MCC catalyst in order to expand its mesopores for more convenient with large molecule diffusion. The catalyst activity was well demonstrated by converting linseed oil to biokerosene which could be used as biokerosene—component for blending with aviation fuels. The MCC catalysts were characterized by X-ray diffraction, infrared spectroscopy, energy dispersive X-ray, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption method and ammonia-temperature programmed desorption techniques. The biokerosene composition was determined by gas chromatography–mass spectroscopy method.     

Electronic structure and magnetic properties of Al‐doped Ca2Fe2O5 brownmillerite compounds

Polycrystalline Ca₂Fe_2?xAl_xO₅ (x = 0‐1.4) samples were prepared by conventional solid‐state reactions. Their crystalline/electronic structures and magnetic properties were characterized in detail. Powder X‐ray diffraction analyses revealed that the samples crystallized in orthorhombic brownmillerite‐type structures with the occurrence of the Pcmn‐Ibm2 phase separation in the region between x = 0.4 and 0.6. The results obtained from analyzing Raman scattering and X‐ray‐absorption fine‐structure spectra also indicated this phase separation. Although x in Ca₂Fe_2?xAl_xO₅ varies in a wide range from 0 to 1.4, the +3 oxidation state of Fe remained almost unchanged. Magnetization measurements revealed that all Ca₂Fe_2?xAl_xO₅ samples have weak ferromagnetic order, and both the saturation magnetization and coercive force are dependent on the temperature, x, and structure phases.     

Conductive-probe atomic force microscopy characterization of silicon nanowire

The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs) were investigated using a conductive-probe atomic force microscopy (AFM). Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V). Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated.     

Zeolite‐catalyzed isomerization of oleic acid to branched‐chain isomers

Branched‐chain (bc) saturated fatty acids (SFA) have potential as oleochemical intermediates since they have better oxidative stability than linear unsaturated fatty acids (UFA) and have better low‐temperature properties than linear SFA. Previous studies in converting UFA to bc‐FA using clay catalysts have resulted in only modest yields and conversions. Recent reports, however, have suggested that certain zeolites can be effective catalysts for converting UFA to bc‐FA in higher yields and conversions. In this work, we examined the scope and potential of the zeolite‐catalyzed synthesis of bc‐FA starting from readily available monounsaturated linear FA. Our results show that common UFA such as oleic acid can be converted to bc‐isomers using modified Ferrierite zeolite catalysts with high conversions (98%) and high selectivity (85%) and that the zeolite catalysts are reusable for at least three cycles. The positions of branching (methyl) on the FA chain were determined from the GC‐MS spectra of the picolinyl esters of the bc‐FA.     

A novel dynamic survivable routing in WDM optical networks with/without sparse wavelength conversion

In this paper, we study the dynamic survivable routing problem, both in optical networks without wavelength conversion and in optical networks with sparse wavelength conversion, and propose a novel hybrid algorithm for it based on the combination of mobile agents technique and genetic algorithms (GA). By keeping a suitable number of mobile agents in the network to cooperatively explore the network states and continuously report cycles (that are formed by two disjoint-link routes) into the routing tables, our new hybrid algorithm can promptly determine the first population of cycles for a new request based on the routing table of its source node, without the time consuming process associated with current GA-based lightpath protection schemes. We further improve the performance of our algorithm by introducing a more advanced fitness function that is suitable for both the above networks. Extensive simulation studies on the ns-2 network simulator show that our hybrid algorithm achieves a significantly lower blocking probability than the conventional survivable routing algorithms for all the cases we studied.     

Simulating a Smartboard by Real-Time Gesture Detection in Lecture Videos

Gesture plays an important role for recognizing lecture activities in video content analysis. In this paper, we propose a real-time gesture detection algorithm by integrating cues from visual, speech and electronic slides. In contrast to the conventional “complete gesture” recognition, we emphasize detection by the prediction from “incomplete gesture”. Specifically, intentional gestures are predicted by the modified hidden Markov model (HMM) which can recognize incomplete gestures before the whole gesture paths are observed. The multimodal correspondence between speech and gesture is exploited to increase the accuracy and responsiveness of gesture detection. In lecture presentation, this algorithm enables the on-the-fly editing of lecture slides by simulating appropriate camera motion to highlight the intention and flow of lecturing. We develop a real-time application, namely simulated smartboard, and demonstrate the feasibility of our prediction algorithm using hand gesture and laser pen with simple setup without involving expensive hardware.      

On the SEP of Cooperative Diversity with Opportunistic Relaying

We analyze the exact symbol error probability (SEP) of cooperative diversity with opportunistic amplify-and-forward (AF) relaying. The benefit of this opportunism to the SEP is assessed by comparing with maximal ratio combining of orthogonal multiple AF relay transmissions.