聚酰胺共混物的结构与性能

就近年来国内聚酰胺共混物的形态结构、相容性、流变行为、力学性质四方面的研究进展作一综述。     

Audio signal separation via a combination procedure of time-reversal and deconvolution process

Time-reversal method (TRM) is based on principle of reciprocity of sound by propagating of a reversal signal in time series to compensate distortion due to path effect in propagation and to focus the signal at the original source location. In recent years, the technique has been applied in optics, ultrasound and underwater acoustic communication. In the present study, a procedure for audio signal separation is developed by applying time-reversal and deconvolution process. The procedure separates sources from audio signal in time domain. The advantages of this procedure are to separate a specific source from a combination signal of multiple sources and to reduce reverberation effectively. Finally, a deconvolution process of finding impulse response function (IRF) is developed where single value decomposition (SVD) and Tikhonov regularization process are used to solve ill-conditioned and singular linear systems. In addition, the effect of signal-to-noise ratio (SNR) and number of array sensors are discussed in details.     

Sony“迷你MV随身存”USB2．0简配装——小巧时尚 更多选择

Sony旗下出色的移动存储产品“迷你MV随身存”专门配备的桌面应用的USB底座，不仅方便易用，更是格外美观，成为用户桌面上的一道风景。“迷你MV随身存”更因其卓越的性能在权威媒体的评测中屡获殊荣，在国内著名IT门户网站太平洋电脑网评测室的超小型闪存盘测试活动中，Sony“迷你MV随身存”就曾夺得最佳性能奖桂冠，尤其在传输速度方面，“迷你MV随身存”更是以绝对优势技压群芳，成为众多品牌中的佼佼者。     

Acoustic Emission Study on Effect of Stress Triaxiality on Damage Micromechanisms in Near Alpha Titanium Alloy

Acoustic Emission (AE) studies have been performed on smooth and notched specimens of a near alpha titanium alloy under monotonic loading condition to study the effect of stress triaxiality on damage micromechanisms. The damage in the notched specimen was found to be of cleavage type as against the ductile type of damage in smooth specimen. This difference was distinguished in the AE energy evolution with notched specimen producing higher energy rate with lower total energy than that of smooth specimen.     

球状活性炭及其应用进展

球状活性炭是七十年代后期发展起来的一种新型高效吸附功能材料,它正越来越广泛地受到重视并在许多领域推广应用。本文概述了球状活性炭的制备、结构、性能及其应用进展现状及前景。     

Optimization of Human Hair Length in a Natural Rubber Based Composite

Human hair is a non-biodegradable waste available in plenty throughout the world but is rarely explored for applications in engineering fields. Tensile strength of human hair ranges from 170 to 220 MPa (Xiao et al., Nano Tensile Study Single Hum Hair Fiber, 2006). This property of human hair can be made use in the field of making bio-composites. The composite is prepared by commixing the human hair and natural rubber in a two roll mill along with additives followed by vulcanization. Here the length of the human hair is varied by fine-tuning the fibre loading as 20 parts per hundred rubber and sundry tests like tensile, abrasion, tear and hardness were conducted. While incrementing the fibre length up to a certain range the mechanical properties shows superior amendments.     

A general purpose Fortran 90 electronic structure program for conjugated systems using Pariser-Parr-Pople model

Pariser-Parr-Pople (P-P-P) model Hamiltonian has been used extensively over the years to perform calculations of electronic structure and optical properties of π-conjugated systems successfully. In spite of tremendous successes of ab initio theory of electronic structure of large systems, the P-P-P model continues to be a popular one because of a recent resurgence in interest in the physics of π-conjugated polymers, fullerenes and other carbon-based materials. In this paper, we describe a Fortran 90 computer program developed by us, which uses P-P-P model Hamiltonian to not only solve Hartree-Fock (HF) equation for closed- and open-shell systems, but also for performing correlation calculations at the level of single configuration interactions (SCI) for molecular systems. Moreover, the code is capable of computing linear optical absorption spectrum at various levels, such as, tight-binding (TB) Hückel model, HF, SCI, and also of calculating the band structure using the Hückel model. The code also allows the user to solve the HF equation in the presence of finite external electric field, thus, permitting calculations of quantities such as static polarizabilities and electro-absorption spectra. Additionally, it can perform transformation of P-P-P model Hamiltonian from the atomic orbital (AO) representation (also called site representation) to the molecular orbital (MO) one, so that the transformed matrix elements can be used for high level post-HF calculations, such as, full CI (FCI), quadruple CI (QCI), and multi-reference singles-doubles CI (MRSDCI). We demonstrate the capabilities of our code by performing calculations of various properties on conjugated systems such as trans-polyacetylene (t-PA), poly-para-phenylene (PPP), poly-para-phenylene-vinylene (PPV), oligo-acenes, and graphene nanodisks.

Program summary

Program title: ppp.xCatalogue identifier: AEFW_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFW_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC license, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 79 900No. of bytes in distributed program, including test data, etc.: 508 285Distribution format: tar.gzProgramming language: Fortran 90. Compilers used: Program has been tested with Intel Fortran Compiler (noncommercial version 11.1) and gfortran compiler (gcc version 4.4.0) with optimization option -OComputer: PCs, workstationsOperating system: Linux. Code was developed and tested on various recent versions of Fedora including Fedora 11 (kernel version 2.6.29.4-167)Classification: 7.3, 16.1External routines: This program needs to link with LAPACK/BLAS libraries compiled with the same compiler as the program. For the Intel Fortran Compiler we used the ACML library version 4.3.0, while for gfortran compiler we used the libraries supplied with the Fedora distribution.Nature of problem: The problem of interest at hand is the electronic structure of π-conjugated systems. For such systems, the effective π-electron P-P-P semi-empirical model Hamiltonian proposed by Pariser, Parr, and Pople offers an attractive alternative as compared to the ab initio approaches. The present program can solve the HF equations for both open- and closed-shell systems within the P-P-P model. Moreover, it can also include electron correlation effects at the singles CI level. Along with the wave functions and energies, various properties such as linear absorption spectra can also be computed.Solution method: The single-particle HF orbitals of a π-conjugated system are expressed as linear combinations of the pz-orbitals of individual atoms (assuming that the system is in the xy-plane). Then using the hopping and Coulomb parameters prescribed for the P-P-P method, the HF integro-differential equations are transformed into a matrix eigenvalue problem. Thereby, its solutions are obtained in a self-consistent manner, using the iterative diagonalizing technique. The HF orbitals thus obtained can be used to perform a variety of calculations such as the SCI, linear optical absorption spectrum, polarizability, electro-absorption spectrum, etc.Running time: The examples provided each only take a few seconds to run. For a large molecule or a polymer, however, the run time may be a few minutes.     

Particle size coarsening induced by valve silicone in a metered dose inhaler

The objective of this study was to evaluate the effect of valve silicone on the delivered particle size distribution of a suspension metered dose inhaler (MDI). Valves were manufactured with distinct levels of silicone, which could be differentiated with Fourier transform infrared spectroscopy (FT-IR). The amount of silicone in the valve was proportional to the amount of silicone that entered the formulation and the subsequent decrease in fine particle fraction (FPF) of the active pharmaceutical ingredient (API) measured by Andersen cascade impaction. The effect of silicone content was not linear as even small amounts of silicone made a significant contribution to particle size coarsening. This coarsening was also a function of storage time and temperature. Accelerated stability conditions greatly increased coarsening kinetics as 1 month at 40°C and 75% RH induced significantly more coarsening than 12 months at room temperature. Field emission scanning electron micrograph images suggest that the primary mechanism of particle size change may be aggregation as particle clusters were seen. This study indicates that silicone can be a critical process parameter for particle size distribution of a suspension MDI product. Thus, the amount of silicone in the valves needs to be minimized and controlled.     

Remarkable improvement in tribological behavior of plasma sprayed carbon nanotube and graphene nanoplatelates hybrid reinforced alumina nanocomposite coating

Addition of 0.5?wt% of graphene nanoplatelates (GNPs) and 1?wt% carbonnanotube (CNTs) in plasma sprayed Al₂O₃ coating showed the reduction of 93.25% in wear volume loss and 90.94% in wear rate. This could be attributed to the simultaneous effect of enhanced densification, presence of the transferred layer from the counterpart, strong interface between Al₂O₃, GNP and CNTs and toughening offered by the GNPs and CNTs. The lowest COF value of 0.27 was recorded on addition of 0.5?wt% of GNP in Al₂O₃ coating, which could be attributed to the graphitic lubrication on the worn track during the wear.     

Synthesis of Ruthenium Dioxide Thin Films by a Solution Chemistry Technique

Smooth, fine-grained RuO₂ thin films have been synthesized and deposited onto 〈100〉 silicon substrates via a solution chemistry technique. Ruthenium(III) chloride n-hydrate dissolved in ethanol was used as the precursor solution. Thin films from a 0. 38M solution were spun at 4000 rpm for 20 s onto the substrates and fired at temperatures between 400° and 800°C. XRD analysis shows that RuO₂ forms over this entire temperature range. Using an appropriate firing schedule, the grain growth can be controlled and reproduced to provide for a uniform grain size distribution consisting of equiaxed, submicrometer diameter grains. The electrical resistance of the films has been measured at 300 K using the conventional four-point probe technique. The resistivity values range from 1. 8 μΩ·m for the films with an average grain size of 250 nm to 3.1 μΩ·m for the films with 30 nm grains. The presence of residual carbon and hydrogen is not believed to have a significant effect on the resistivity.