Oberflächenenergetische Charakterisierung

Surface Energetic Characterization of Nanoscale Fillers and Elastomers Almost any technically used rubber material is filled with particles in nanometer size, by which the properties of the material can be specific controlled. In modern car tires the used fillers have crucial influence on driving security (wet grip and ice grip), on fuel consumption (rolling resistance) and on the cost‐effectiveness (life time of the tire) [1].The first fillers used in rubber application were carbon blacks; actually in passenger car tires mostly surface modified silica is applied. The implementation of novel filler systems like organophilic modified layered silicates (organo‐clays) or carbon nanotubes is subject of intense research [2,3]. Surface energy and –polarity of the filler surface is a crucial, but often underestimated determining factor. All surface properties of rubber and filler have to be well balanced to get the nanoscale filler particles finely dispersed in the rubber matrix and also to obtain a good adhesion between polymer and filler surface.     

Development of Ultra-high Purity (UHP) Fe-Based Alloys with High Creep and Oxidation Resistance for A-USC Technology

Metallurgical and Materials Transactions A - The design of ultra-high purity (UHP) Fe-based model alloys for advanced ultra-supercritical (A-USC) technology is attempted in this work. Creep testing...     

Studies on Double Diffusive Convection and Macro-segregation During Solidification of an Al-Alloy Based on Macro–Micro Model

In the present work, a study on the double diffusive convection and the macro-segregation during solidification of an Al-alloy (A356) is considered based on the macro?Cmicro model. The model considers a volume average single-domain approach to represent all the variables and properties as continuum in the entire domain where the transport phenomena during solidification are represented by mass, momentum, energy and species conservation equations. The evolution of solid during solidification, in the model, is predicted based on the microscopic phenomena, i.e. considering the nucleation and the growth of the nuclei. A semi-implicit finite volume method is adopted to discretize the governing equations and the discretized linear simultaneous equations are solved based on the SIMPLER and the TDMA algorithms. The simulation involves prediction of temperature, velocity and species in the computation domain during solidification of the alloy. A parametric study is also considered.     

Synthesis of multistream heat exchangers by thermally linked two-stream modules

A simple yet very efficient algorithm has been devised for the analysis of multistream heat exchangers. In this approach, an n-stream heat exchanger is considered as a stack of (n ? 1) two-stream exchangers separated by diabatic partitions. Starting from the analysis of the basic two-stream units the entire heat exchanger can be designed non-iteratively. The validity of the algorithm has been established through a number of examples, comprising of two-steam exchanger with external heat leakage, three-stream and four-stream exchangers. Excellent agreements with experimental results and published simulation have been observed. Finally the most crucial assumption made in the present work has been assessed critically and its justification has been provided.     

Temperature dependence of electromechanical properties of PLZT <Emphasis Type="Italic">x</Emphasis>/57/43 ceramics

The compositions of lead lanthanum zirconate titanate PLZT [Pb(Zr_0.57Ti_0.43)O₃ + x at% of La, where x = 3, 5, 6, 10 and 12] have been synthesized using mixed oxide route. The temperature dependent electromechanical parameters have been determined using vector impedance spectroscopy (VIS). The charge constant d ₃₁ and elastic compliance s ₁₁ ^E show a peak in all the samples at a temperature T _mt much below the ferroelectric — paraelectric transition temperature, whereas the series resonance frequency f _s shows a dip at these temperatures. The Poisson’s ratio σ ^E increases with temperature T showing a broad peak at a temperature higher than T _mt . The voltage constant g ₃₁ decreases and the planar coupling coefficient K _p remains constant up to half of the T _mt and then falls sharply with T. Half of the T _mt can, therefore, be used for specifying the working temperature limit of the piezoceramics for the device applications.     

Effect of austempering treatment on microstructure and mechanical properties of high-Si steel

In the present investigation, the influence of austempering treatment on the microstructure and mechanical properties of silicon alloyed cast steel has been evaluated. The experimental results show that an ausferrite structure consisting of bainitic ferrite and retained austenite can be obtained by austempering the silicon alloyed cast steel at different austempering temperature. TEM observation and X-ray analysis confirmed the presence of retained austenite in the microstructure after austempering at 400 °C. The austempered steel has higher strength and ductility compared to as-cast steel. With increasing austempering temperature, the hardness and strength decreased but the percentage of elongation increased. A good combination of strength and ductility has been obtained at an austempering temperature of 400 °C.     

Effect of carbon containing SiNx antireflection coating on the screen‐printed contact and low illumination performance of silicon solar cell

Screen‐printed metal contact formation through a carbon containing antireflection coating was investigated for silicon solar cells by fabricating conventional carbon‐free SiN_x and carbon‐rich SiC_xN_y film. An appreciable difference was found in the average shunt resistance (R_sh), which was about an order of magnitude higher for SiC_xN_y‐coated solar cells relative to the counterpart SiN_x‐coated solar cells. Series resistance (R_s) and fill factor (FF) were comparable for both antireflection coatings but the starting efficiency of SiC_xN_y‐coated cell was ~0·2% lower because of slightly inferior surface passivation. However, SiC_xN_y‐coated solar cells showed less degradation under lower illumination (<1000 W/m²) compared with the SiN_x‐coated cells due to reduced FF degradation under low illumination. Theoretical calculations in this paper support that this is a direct result of high R_sh. Detailed photovoltaic system and cost modeling is performed to quantify the enhanced energy production and the reduced levelized cost of electricity due to higher shunt resistance of the SiC_xN_y‐coated cells. It is shown that R_sh value below 30 Ω (7000 Ω cm² for 239 cm² cell) can lead to appreciable loss in energy production in regions of low solar insolation. Copyright © 2011 John Wiley & Sons, Ltd.     

Rapid design space exploration by hybrid fuzzy search approach for optimal architecture determination of multi objective computing systems

Design Space Exploration (DSE) with multi-parametric objective in High Level Synthesis (HLS) involves assessing the various design points in the architecture design space to find the optimum solution for the design according to the system requirements specified. Due to the time to market pressure, the cost of solving the problem of architecture selection by exhaustive analysis is strictly forbidden. The tradeoffs linked to the selection of the appropriate design point during architecture evaluation needs careful assessment for efficient design space exploration. Further DSE requires satisfying multiple conflicting multi objective conditions such as increase in accuracy of evaluation during DSE with simultaneous speedup in the exploration process. This paper presents a novel hybrid design space exploration approach which is a combination of the Priority Factor (PF) method and Fuzzy search technique that is rapid and accurate in architecture evaluation and selection. The proposed approach for DSE when applied on a number of benchmarks yielded superior results compared to the current existing DSE approach for architecture selection. The comparison results of the proposed hybrid approach with the current existing approach for different benchmarks are shown and the speedups obtained are also presented.     

Special issue on wireless sensor networks: from theory to practice

Wireless sensor network(WSN)is characterized by the dense deployment of sensor nodes that continuously observe physical phenomenon.The main advantages of WSN include its low cost,rapid deployment,self-organization,and fault tolerance.WSN has received tremendous interests of various research communities,and significant progresses have been made in various aspects including sensor platform development,wireless communication and networking,signal and information processing,as well as network performance evaluation and design.Such work has established good foundation