在表面活性剂存在下铬铁矿表土中镍的微生物萃取(英文)

加入表面活性剂吐温20,用Aspergillus niger对预处理过的印度Sukinda铬铁矿表土在摇瓶中生物浸取镍。考察添加表面活性剂吐温20对黑曲霉菌Aspergillus niger生长及浸镍效果的影响。结果表明,添加低浓度的表面活性剂吐温20对黑曲霉菌从预处理过的铬铁矿表土中提取镍是有利的。通常,Aspergillus niger利用培养基中的碳源来进行细胞代谢,产生有机代谢物,从而生物浸出矿。添加表面活性剂吐温20加速了黑曲霉菌对碳源的消耗,从而改善了镍浸出效果。在预处理矿浆浓度为2%和温度为30°C的条件下,添加表面活性剂吐温20的镍浸取率能达到39%,没有表面活性剂的镍浸取率只有24%。     

Design, fabrication, testing and packaging of a silicon micromachined radio frequency microelectromechanical series (RF MEMS) switch

RF characterization and packaging of a single pole single throw (SPST) direct contact microelectromechanical (MEMS) series radio frequency (RF) switch is reported. Precise thickness of the silicon MEMS structure is achieved using a specially developed silicon Deep Reactive Ion Etching (DRIE) thinning process. A stress free release process is employed which ensures a high yield of released microstructures. The design of the device is based on stiffness equations derived from first principles. Displacement of the actuator under applied field is measured to confirm electrostatic pull in, which occurs in the 30–50 V range. The variation of contact resistance with time has been measured and is found to have a power law decay, in agreement with theoretical models. At the bare die level the insertion loss, return loss and the isolation of the switch were measured to be ?0.43 dB, ?25 dB and ?21 dB, respectively at 10 GHz. The devices were packaged in commercially available RF packages and mounted in alumina boards for post package characterization. Due to the presence of bond wires in the signal path of the packaged devices, the RF performance was found to degrade at high frequencies. However, losses were measured to be at acceptable levels up to 2 GHz. Factors contributing to insertion loss at the die and package device levels are discussed in detail with possible solutions.     

Ensemble of randomized soft decision trees for robust classification

For classification, decision trees have become very popular because of its simplicity, interpret-ability and good performance. To induce a decision tree classifier for data having continuous valued attributes, the most common approach is, split the continuous attribute range into a hard (crisp) partition having two or more blocks, using one or several crisp (sharp) cut points. But, this can make the resulting decision tree, very sensitive to noise. An existing solution to this problem is to split the continuous attribute into a fuzzy partition (soft partition) using soft or fuzzy cut points which is based on fuzzy set theory and to use fuzzy decisions at nodes of the tree. These are called soft decision trees in the literature which are shown to perform better than conventional decision trees, especially in the presence of noise. Current paper, first proposes to use an ensemble of soft decision trees for robust classification where the attribute, fuzzy cut point, etc. parameters are chosen randomly from a probability distribution of fuzzy information gain for various attributes and for their various cut points. Further, the paper proposes to use probability based information gain to achieve better results. The effectiveness of the proposed method is shown by experimental studies carried out using three standard data sets. It is found that an ensemble of randomized soft decision trees has outperformed the related existing soft decision tree. Robustness against the presence of noise is shown by injecting various levels of noise into the training set and a comparison is drawn with other related methods which favors the proposed method.     

Effect of TiN particulate reinforcement on corrosive behaviour of aluminium 6061 composites in chloride medium

In the present investigation, the corrosive behaviour of Al 6061–TiN particulate composites prepared by liquid metallurgy has been studied in chloride medium using electroanalytical techniques such as Tafel, cyclic polarization and electrochemical impedance spectroscopy (EIS). Surface morphology of the sample electrodes was examined using scanning electron micrography and energy dispersive X-ray methods. X-ray diffraction technique was used to confirm inclusion of TiN particulates in the matrix alloy and identify the alloying elements and intermetallic compounds in the Al 6061 composites. Polarization studies indicate an increase in the corrosion resistance in composites compared to the matrix alloy. EIS study reveals that the polarization resistance (R _p) increases with increase in TiN content in composites, thus confirming improved corrosion resistance in composites. The observed decrease in corrosion rate in the case of composites is due to decoupling between TiN particles and Al 6061 alloy. It is understood that after the initiation of corrosion, interfacial corrosion products may have decoupled the conducting ceramic TiN from Al 6061 matrix alloy thus eliminating the galvanic effect between them.     

On Some Aspects of Statistical Linearization of Non-linear Elements†

A simple expression given by West (1900) for Booton's equivalent gain is applied to the case of a general piece-wise linear element with jump discontinuities. Similar expressions are derived for the two coofficients of statistical linearization of a memory typo non-linearity. The criterion of minimizing the mean-square error between the time derivatives of actual output of the non-linearity and the output of the linearized model is examined. It is shown that this leads to the same equivalent gains as Booton’3 criterion for the case of zero-memory non-linearity and also for the case of a special class of memory type non-linearities. Illustrative examples are given.     

Development and characterization of new phosphorus based flame retardant tetraglycidyl epoxy nanocomposites for aerospace application

A study was made in the present investigation on the development and characterization of triphenyl phosphine oxide based phosphorus tetraglycidyl epoxy nanocomposites denoted as ??C?? and to find out its suitability for use in high performance applications. The synthesized resin was characterized by Fourier transform infrared spectra (FT?CIR) and ¹H, ¹³C nuclear magnetic resonance (NMR) spectra. Nanoclay and POSS-amine nano-reinforcements denoted as N1 and N2 were incorporated into the synthesized epoxy resin. Curing was done with diaminodiphenylmethane (DDM) and bis(3-aminophenyl) phenylphosphine oxide (BAPPO) curing agents denoted as X and Y, respectively. Mechanical, thermal, flame retardant, water absorption behaviour and electrical properties of the epoxy nanocomposites were studied and the results are discussed.     

关于金属板材渐进成型的高级特征检测算法(英文)

提出一种关于单点渐进成形(SPIF)部件的特征检测的新型算法。基于自建的关于SPIF的CAPP专家系统,通过对几何形状、曲率、位置、方位、加工参数的综合分析,可以检测33种不同的特征可以检测。为了加快检测过程,首先使用多级边缘分割算法创建一个边缘特征的框架。随后在这个框架中,区域生长算法被用来检测剩余的特征。这个检测方法已经成功地被不同的实验所验证。采用一个双曲面半球的实验案例描述通过对检测的特征进行补偿,从而生成最优的刀具路径。结果显示,优化的刀具路径对于成形部件的精度有很大的提高。     

MICROBIAL. TRANSFORMATION AND BIODEGRADATION OF CALOTROPIS PROCERA LATEX TOWARDS OBTAINING VALUE ADDED CHEMICALS,PHARMACEUTICALS AND FUELS

ABSTRACT

The latex of Calotropia arocera (Ait.) R.Br., (a potential petrocrop) may be exploited to obtain fuels and chemicals. This latex has been subjected to microbial action with Sphaerotilus aeruginosa, Sphaerotilus natans, Streptococcus sp.. Escherichia coli. Penicllllum expanaum and Mucor Sp. with an aim to find out a biochemical route way to obtain fuels and chemicals. The treated latex was extracted with hexane, chloroform and methanol separately. The extracts obtained were analysed using 13CNMR and ¹HNMR spectral techniques to understand the chemical dynamics of biotransformation of latex components. Microbial action was found to degrade, biotransform, oxidise, dehydrogenate and dearomatize the chemical components of the latex. S. aeruginosa and streptococcus sp were found to be the potential candidates for the microbial degradation of latex. Latex mainly contains triterterpenoid, steroid etc. compounds. These acyclic and naphthenic type of compounds are stabler and relatively less reactive compounds. Hydrotreatment of such compounds by thermal degradation would require drastic conditions. The complex degradation reactions at high temperature (under pressure) would be slower. Microbial treatment renders the latex (;and compounds present therein) as reactive substrates or feedstocks close for hydrotreatment for obtaining value added and premium products. These products may include value added chemicals, fuels and pharmaceuticals etc. in the long run. Microbial treatments may reduce the heat panalty of the hydrogen treatment etc. process. This may also make the rates of the hydrotreatment etc. reactions faster to afford the continuous processes in the long run     

Adaptive manipulator trajectory control using neural networks

A unified study of adaptive control and neural network based control schemes for the trajectory tracking problem of robot manipulators is presented. Efficacy of parametrized adaptive algorithms in compensating the structured uncertainties in robot dynamics is verified through extensive simulation. The ability of neural networks to provide a robust adaptive framework in the presence of both structured and unstructured uncertainties is investigated. A case study is carried out in support of a parametrized adaptive scheme using neural networks. Simulation results clearly indicate that the neural network based adaptive controller achieves better tracking in the presence of parametric uncertainties as well as unmodelled effects compared to the simple direct adaptive scheme.     

Electrical conductivity of Gd doped BiFeO3---PbZrO3 composite

The composite, 0.5(BiGd_0.15Fe_0.85O₃)---0.5(PbZrO₃), was synthesized using the solid-state reaction technique. The formation of the compound was confirmed by XRD with an orthorhombic structure at room temperature. The impedance parameters were studied using an impedance analyzer in a wide range of frequency (10²---10⁶ Hz) at different temperatures. The Nyquist plot suggests the contribution of bulk effect and a slight indication of grain boundary effect and the bulk resistance decreases with a rise in temperature. The presence of temperature-dependent relaxation process occurs in the material. Electrical modulus reveals the presence of the hopping mechanism in the materials. The value of exponent n, pre-factor A and σ_dc were obtained by fitting ac conductivity data with Jonscher’s universal power law. The activation energies calculated from the ac conductivity were found to be 0.50, 0.46, 0.44, 0.43, 0.42 and 0.38 eV at 1, 10, 50, 100, 500 kHz and 1 MHz respectively in the temperature region of 110°C---350°C. The dc conductivity was found to increase with the rise in temperature. The activation energy calculated from complex impedance plot and from the fitted Jonscher’s power law are very close, which results similar type of charge carrier exist in conduction mechanism of the material.