Damage zone development in PVC under a multiaxial tensile stress state

The irreversible deformation mechanisms of poly(vinyl chloride) with a semicircular notch under slow tensile loading have been studied as a function of sheet thickness. Initially, core yielding was observed in the optical microscope as two families of slip lines growing from the notch surface in the centre of the specimen. The size and shape of the core yielding zone could be described by plasticity analysis. A stress-whitened zone subsequently initiated near the tip of the slip line zone. The stress whitening was caused by 1 m voids that were visible in the scanning electron microscope. The mean stress for stress whitening was calculated to be 43.0±1.5 MPa by a plastic stress analysis of a pressure-dependent yield material. By assuming a constant mean stress along the boundary of the stress-whitened zone, the one-dimensional shift of the elastic stress distribution was obtained. At higher stresses, hinge shear and intersecting shear were observed for thick and thin sheet, respectively.     

Alignment control for a long span urban rail-transit cable-stayed bridge considering dynamic train loads

In this paper, bridge alignment control with considering dynamic train loads was experimentally and theoretically investigated. Analytical process of bridge dynamics and the self-adaptive Kalman filter bridge alignment control method with considering the dynamic train loads were briefly introduced. The static measurement, the dynamic test, the field alignment measurement as well as the finite element analysis (FEA) of the second longest rail transit cable-stayed bridge in the world were carried out. Based on the results, the train dynamic load effect on the bridge alignment was obtained quantitatively. Subsequently, alignment control of the rail transit bridge with considering this effect using a self-adaptive Kalman filter method was analyzed. The results show that: (a) the dynamic train loads have effects on alignment control of the bridge and therefore cannot be neglected; (b) the self-adaptive Kalman filter method is applicable and reliable for alignment control of bridges during construction. The analytical method and whole process contribute to develop a related specification and further engineering applications.     

Cytotoxicity and antineoplastic activities of alkylamines and their borane derivatives

The alkylamines and their related boron derivatives demonstrated potent cytotoxicity against the growth of murine and human tissue cultured cells. These agents did not necessarily require the boron atom to possess potent cytotoxic action in certain tumor lines. Their ability to suppress tumor cell growth was based on their inhibition of DNA and protein syntheses. DNA synthesis was reduced because purine synthesis was blocked at the enzyme site of IMP dehydrogenase by the agents. In addition ribonucleotide reductase and nucleoside kinase activities were reduced by the agents which would account for the reduced d[NTP] pools. The DNA template or molecule may be a target of the drugs with regard to binding of the drug to nucleoside bases or intercalaction of the drug between DNA base pairs. Only some Of the agents caused DNA fragmentation with reduced DNA viscosity. These effects would contribute to overall cell death afforded by the agents.     

Finite-element analysis for magnetic resonance image artifact evaluation

The static magnetic field of a magnetic resonance imaging scanner can be distorted by the presence of materials, perturbing the spatial encoding process in magnetic resonance imaging and often resulting in image artifacts. The relationship between the image artifact size and magnetic susceptibility of the material specimen is of interest to engineers for the design of devices that are to be compatible with the imaging volume of the scanner. In this study, a finite-element method was used to simulate the distorted magnetic field of samples with different susceptibilities. With the knowledge of the external- and self- magnetic field interactions, a Lorentz correction was applied to compute the magnetic field deviation. The simulated results were then validated by the corresponding experimental magnetic resonance images.     

Deposition and gas sensing properties of tin oxide thin films by inductively coupled plasma chemical vapor deposition

Tin oxide thin films have been deposited by a custom-designed inductively coupled plasma chemical vapor deposition (ICP-CVD) system in order to explore its application as an alternative approach for thin film gas sensor preparation. The as-deposited SnO₂ films were of polycrystalline structure with nano-size grains of 12 nm. The SnO₂ films exhibited a maximum sensitivity of 43 to 1000 ppm H₂ at an optimum operating temperature of 350^∘C. The response time of the SnO₂ films was 12 s and full recovery was achievable.     

Degrees of freedom in some underspread MIMO fading channels

Consider a multiple-input multiple-output (MIMO) fading channel in which the fading process varies slowly over time. Assuming that neither the transmitter nor the receiver have knowledge of the fading process, do multiple transmit and receive antennas provide significant capacity improvements at high signal-to-noise ratio (SNR)? For regular fading processes, recent results show that capacity ultimately grows doubly logarithmically with the SNR independently of the number of transmit and receive antennas used. We show that for the Gauss-Markov fading process in all regimes of practical interest the use of multiple antennas provides large capacity improvements. Nonregular fading processes show completely different high-SNR behaviors due to the perfect predictability of the process from noiseless observations. We analyze the capacity of MIMO channels with nonregular fading by presenting a lower bound, which we specialize to the case of band-limited slowly varying fading processes to show that the use of multiple antennas is still highly beneficial. In both cases, regular and nonregular fading, this capacity improvement can be seen as the benefit of having multiple spatial degrees of freedom. For the Gauss-Markov fading model and all regimes of practical interest, we present a communication scheme that achieves the full number of degrees of freedom of the channel with tractable complexity. Our results for underspread Gauss-Markov and band-limited nonregular fading channels suggest that multiple antennas are useful at high SNR.     

应用Visual C++开发小波变换应用程序

介绍了Visual C 调用MATLAB引擎函数的方法,利用这种方法在应用软件开发过程中既能发挥VisualC 强大的界面开发和图形绘制功能,又充分利用了MATLAB处理复杂运算的能力,并把这一技术应用于小波变换的程序设计之中,取得了较好的效果.     

Process parameters selection for laser polishing DF2 (AISI O1) by Nd:YAG pulsed laser using orthogonal design

Mechanisms of laser polishing metals in a continuous scanning mode, as envisaged and analyzed in this paper, are rather complex, and experimental optimization of laser polishing metallic material is very time-consuming and difficult. Aiming at shortening the experimental time in achieving a better surface finishing of DF2 (AISI 01) tool steel by pulse Nd:YAG laser, we used the orthogonal experimental design for selecting the laser operational parameters. The results showed that the orthogonal design (OD) allowed the optimum technological parameters for the laser polishing to be obtained quickly and effectively. According to the OD analysis and experimental data, the attainable optimum laser smoothening/polishing parameters from this study are pulse energy (P)?=?1?J, feed rate?=?300–400?mm/min, pulse duration?=?3?ms, and pulse frequency (f)?=?20–25?Hz. The work in this paper demonstrates the relative superiority of orthogonal design in saving experimental times and providing good laser polishing surface in surface texturing and the smoothening process.     

Monte Carlo Data Envelopment Analysis with Genetic Algorithm for Knowledge Management performance measurement

The paper targets to devise a genuine Knowledge Management (KM) performance measurement model in a stochastic setting based on Data Envelopment Analysis (DEA), Monte Carlo simulation and Genetic Algorithm (GA). The proposed model evaluates KM using a set of proxy measures correlated with the major KM processes. Data Collection Budget Allocation (DCBA) that maximizes the model accuracy is determined using GA. Additional data are generated and analyzed using a Monte-Carlo-enhanced DEA model to obtain the overall KM efficiency and KM processes’ efficiency scores. An application of the model has been carried out to evaluate KM performance in higher educational institutions. It is found that with GA, the accuracy of the model has been greatly improved. Lastly, comparing with a conventional deterministic DEA model, the results from the proposed model would be more useful for managers to determine future strategies to improve their KM.