Differences in physical phenomena governing laser machining of structural ceramics

Several structural ceramics such as alumina, silicon nitride, silicon carbide and magnesia were machined using a pulsed Nd:YAG laser. Laser processing conditions and temperature dependent thermo-physical properties govern the physical phenomena that machine these ceramics. Melting, dissociation and evaporation are some of the vital mechanisms associated with material removal. Discrimination and incorporation of these physical processes into a hydrodynamic machining model to predict different machining parameters was conducted. The model provides an outstanding tool for advance prediction of thermal energy and time required for machining desired depth of material.     

Development of Fe‐, Sb‐, Bi‐ and Al‐impregnated silica catalysts using rice husk silica as a support for Friedel–Crafts benzylation of arenes

The milling by‐product of rice, rice husk, constitutes a major waste of the agricultural industry. It is mainly used as a fuel additive for various purposes, leaving behind residual ash which is rich in silica (Biogenic silica). In the present project, rice husk silica was impregnated with Fe³⁺, Sb³⁺, Bi³⁺ and Al³⁺ from both their aqueous and organic solutions. The resultant catalysts were activated at 120 °C and 550 °C and used for the Friedel–Crafts benzylation of benzene using benzyl chloride. Copyright © 2003 Society of Chemical Industry     

Claisen–Schmidt reaction in a hydrotropic medium

The Claisen–Schmidt condensation of benzaldehydes with acetophenones was carried out in an aqueous medium using sodium butylmonoglycolsulfate (NaBMGS) and sodium salts of aromatic sulfonic acids as hydrotropes. Substantial enhancement in the rate of the reaction was obtained, along with the easy recovery of the product. Recycling of the hydrotrope solutions has been tested without any loss in the rate of the reaction.     

Interfaces for high speed fiber-optic links: analysis andexperiment

An analysis of directly and externally modulated fiber-optic links is presented. The theoretical analysis is based on the signal flow diagram of the interface circuits to the laser diode, Mach-Zehnder electro-optic modulator, and p-i-n photodiode. System parameters such as gain, noise figure, two-tone intermodulation distortion, and spurious free and compression dynamic range are expressed as a function of frequency and operating point of the laser and external modulator. Two directly and externally modulated fiber-optic links were designed and fabricated to verify the analytical models. The direct modulation FO link was developed at the Ku-band (11.6-12.4 GHz), whereas the external modulation link was at L-band (875-925 MHz). Spurious-free dynamic ranges of 95.8 dB Hz^2/3 and 113 dB Hz ^2/3, respectively, were achieved. The predictions based on the analytical models match the measured results     

Enhancing Neural Network Traffic Incident-Detection Algorithms Using Wavelets

Researchers have presented freeway traffic incident-detection algorithms by combining the adaptive learning capability of neural networks with imprecision modeling capability of fuzzy logic. In this article it is shown that the performance of a fuzzy neural network algorithm can be improved through preprocessing of data using a wavelet-based feature-extraction model. In particular, the discrete wavelet transform (DWT) denoising and feature-extraction model proposed by Samant and Adeli (2000) is combined with the fuzzy neural network approach presented by Hsiao et al. (1994). It is shown that substantial improvement can be achieved using the data filtered by DWT. Use of the wavelet theory to denoise the traffic data increases the incident-detection rate, reduces the false-alarm rate and the incident-detection time, and improves the convergence of the neural network training algorithm substantially.     

Transgenic N-myc mouse model for indolent B cell lymphoma: tumor characterization and analysis of genetic alterations in spontaneous and retrovirally accelerated tumors

Little is known about stepwise deregulation of specific genes leading to lymphoid malignancy. Aberrant myc gene expression in transgenic mice is correlated with B cell lymphomagenesis. We generated a unique transgenic mouse model in which deregulated murine E mu-N-myc transgene expression leads to development of indolent B cell lymphoma. Tumor cells were monoclonal, morphologically mature and surface immunoglobulin expressing B cells. Tumors arose in a disease course and exhibited a cytoarchitectural appearance reminiscent of human follicular lymphoma. Yet tumor cells were staged as preB since they failed to rearrange the immunoglobulin light chain genes. Retroviral insertion mutagenesis analyses of adult transgenic mice infected as newborns with murine leukemia virus revealed decreased disease latency, increased lymphoma incidence and a histologically more mature tumor type. Proviral insertion sites were not equivalent when accelerated E mu-N-myc indolent lymphomas were compared to accelerated c-myc preB cell lymphomas. The bcl-2 gene was not disrupted in either spontaneous or provirally accelerated E mu-N-myc lymphomas. These findings suggest that tumor progression in N-myc-associated indolent B cell lymphoma can proceed along diverse pathways involving distinctly different combinations of deregulated and/or intact genes than those pathways described in highly aggressive forms of myc-related murine preB cell disease.     

Effects of test temperature, grain size, and alloy additions on the cleavage fracture stress of polycrystalline niobium

The current work investigates the effects of test temperature (77 to 131 K), grain size (63 to 165 μm), and solid solution alloying additions of zirconium on the cleavage fracture stress (σ _F) of polycrystalline niobium. Extensive fracture surface analyses of fractured notched-bend specimens revealed the location of the apparent cleavage fracture nucleation sites, while comparisons have been made to peak stress locations using existing finite element models. The effects of such microstructural changes on the magnitude of the cleavage fracture stress are rationalized via comparisons to models for cleavage fracture.