Distribution and nature of organic/mineral bound elements in Assam coals, India

This study focuses on the determination and concentration of twelve elements (Na, K, Ca, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn and Cd) occurring in sub-bituminous Assam coals and their geochemical association. Distribution of these elements between organic and mineral matters was studied. Comparison of the results of three coals has shown that three elements (Mg, Ca and Mn) are significantly organic bound, while five elements (Fe, Co, Ni, Cu and Zn) are significantly mineral bound; Cd is 50% bound to either organic or mineral matter. FTIR and XRD studies reveal qualitative information about the bonding pattern and nature of components of the mineral matters. The results obtained in this study have considerable geochemical and technological interests.     

Covulcanization of LLDPE/EMA blends using dicumyl peroxide

The effect of dicumyl peroxide (DCP) content on the gel fraction, mechanical, dynamic mechanical, and thermal properties of linear low‐density polyethylene (LLDPE)/ethylene‐co‐methyl acrylate (EMA) blends were studied. Gel content of the blends increases with increasing DCP content, and EMA is more prone to crosslinking than LLDPE. Wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to study the effect of DCP crosslinking on percent crystallinity and crystalline structure of the blends and individual components. At lower level of DCP loading, crosslinking process does not have significant effect on the crystalline structure of the LLDPE, which was confirmed from the percent crystallinity and lattice distance value. However, at higher DCP content, percent crystallinity decreases significantly. At lower EMA concentration (<50%), percent crystallinity and lattice distance remain unchanged up to 2 wt % of DCP. For EMA contents of more than 50 wt %, increasing DCP content reduces the crystallinity of the blends and increases the lattice distance. The highest level of mechanical and dynamic mechanical properties was observed for 60/40 LLDPE/EMA blends at 2 wt % DCP. Addition of LLDPE‐g‐MA (3 wt %) as a compatibilizer enhances the properties of the vulcanizates. Blends crosslinked with DCP up to 0.3 wt % can easily be reprocessed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Soft Graphoepitaxy for Large Area Directed Self‐Assembly of Polystyrene‐block‐Poly(dimethylsiloxane) Block Copolymer on Nanopatterned POSS Substrates Fabricated by Nanoimprint Lithography

Polyhedral oligomeric silsequioxane (POSS) derivatives have been successfully employed as substrates for graphoepitaxial directed self‐assembly (DSA) of block copolymers (BCPs). Tailored POSS materials of tuned surface chemistry are subject to nanoimprint lithography (NIL) resulting in topographically patterned substrates with dimensions commensurate with the BCP block length. A cylinder forming polystyrene‐block‐polydimethylsiloxane (PS‐b‐PDMS) BCP is synthesized by sequential living anionic polymerization of styrene and hexamethylcyclotrisiloxane. The patterned POSS materials provide a surface chemistry and topography for DSA of this BCP and after solvent annealing the BCP shows well‐ordered microphase segregation. The orientation of the PDMS cylinders to the substrate plane could be controlled within the trench walls by the choice of the POSS materials. The BCP patterns are successfully used as on‐chip etch mask to transfer the pattern to underlying silicon substrate. This soft graphoepitaxy method shows highly promising results as a means to generate lithographic quality patterns by nonconventional methods and could be applied to both hard and soft substrates. The methodology might have application in several fields including device and interconnect fabrication, nanoimprint lithography stamp production, nanofluidic devices, lab‐on‐chip, or in other technologies requiring simple nanodimensional patterns.     

Impedance Studies of La2Mo2-xSnxO（9-δ） Oxide Ion Conductors

A series of compounds La₂Mo_2-xSn_xO（9-δ）（x=0-0.3） have been synthesized by solid-state reaction technique.Materials have been characterized by XRD,SEM,DSC and impedance study.In the temperature regime 520℃-590℃,the specimens with x ≤ 0.05 have the conductivity higher than La2Mo2O9.Conductivity of Sn-doped compound decreases consistently with increasing Sn-doping,compared to the undoped compound both below and above phase transition,barring the specimens with x ≤ 0.05,where conductivity values remains almost same as that of undoped specimen in high temperature region.In the intermediate temperature regime（520℃-590℃）,the conductivity of doped compounds increases for x ≤ 0.05 as compared to parent compound.Also,there is no indication of phase stabilization with Sn-doping in this compound even with the highest doping level,x=0.3.Electric modulus analysis suggests that thermally activated oxygen ion hopping mechanism is responsible for the conduction in Sn-doped compound.     

Determination of Mineral Content in Commonly Consumed Leafy Vegetables

Vegetables used by the people of Assam (India) found to be highly nutritious to maintain general balance diet. Nutritional information is used increasingly by public agencies and agricultural industries to promote different traditional fresh product. The work aimed at determining few nutritionally important minerals (calcium, iron, magnesium, phosphorus, and potassium) in leafy green vegetables widely consumed in Assam. The objective of the present work was to examine the variability in the mineral content.     

Estimation of frequency-selective CDMA channels with large possible delay and Doppler spreads

The problem of estimating channels with a large number of unknown coefficients is considered. A matching pursuit (MP) followed by cancellation (MPC) algorithm is presented. The algorithm consists of two steps. In the first step, a basic MP algorithm that identifies the strongest channel taps and successively cancels them is used. The second step of the algorithm uses the already identified channel taps to estimate the channel coefficients more accurately. The algorithm has several benefits: low complexity, significantly improved performance over conventional least squares (LS) in sparse channels, and handling of time-varying channels including carrier offsets. Methods to successfully terminate the MP step of the algorithm are presented and are shown to perform well. The statistical behavior of MPC is studied. The MPC estimator is found to achieve a performance close to the Cramer-Rao lower bound. Further, MPC is found to outperform conventional LS in terms of bit error rate when low training overhead is used.     

Intelligent stuttering speech recognition: A succinct review

Stuttering speech recognition is a well-studied concept in speech signal processing. Classification of speech disorder is the main focus of this study. Classification of stuttered speech is becoming more important with the enhancement of machine learning and deep learning. In this study, some of the recent and most influencing stuttering speech recognition methods are reviewed with a discussion on different categories of stuttering. The stuttering speech recognition process is divided mainly into four segments-input speech pre-emphasis, segmentation, feature extraction, and stutter classification. All these segments are briefly elaborated and related researches are discussed. It is observed that different traditional machine learning and deep learning classification approaches are employed to recognize stuttered speech in last few decades. A comprehensive analysis is presented on different feature extraction and classification method with their efficiency.

     

有机化学课程全英语教学的探索与思考

顺应高等教育国际化的形势,本科生的全英文教学是我校近几年进行的重要教学改革与创新。在有机化学课程全英语教学改革试验中,从学生的实际出发,我们选择了合适的全英文原版教材,也大胆地尝试了新的教学模式。同时,我们探讨了全英教学过程中存在的问题及解决的对策。在近一年的教学实践中,学生获取了有机化学相关知识,也锻炼和提高了英语表达能力。