Coextrusion of Mg–Al macro composites

In this study extrusion experiments were carried out in order to investigate and develop the coextrusion process for light weight magnesium–aluminum macro composites. Seamless tubes were extruded using hybrid billets combining EN AW-6060 tubes as coating material and various Mg-alloys (ZM21, AZ31, AS11, AM10, AM30 and AM50) as core material. Further AZ31/EN AW-6060 rods were produced to investigate the influence of the die angle and different combining techniques of Mg-core and Al-sleeve on the diffusion layer formation. Additionally the effect of mechanically interlocked fittings and a Zn-foil as interlayer material on the coextrusion process and products were examined. For characterization of the compound's shear strength push-out tests were performed.     

Fast and Accurate Thickness Determination of Unknown Materials using Terahertz Time Domain Spectroscopy

We present a fast and accurate time domain based algorithm which extracts simultaneously the thickness and refractive index of highly transparent samples from terahertz time domain spectroscopy data. The utilized transfer function considers the Fabry-Perot oscillations of the sample and enables to analyze data with multiple reflections. The algorithm can also be applied to signals corrupted by vapor absorption lines. Since the data extraction takes only fractions of a second, this computation method is well suited for real-time monitoring of industrial processes. We show that the accuracy of the new algorithm is comparable to that of sophisticated, highly accurate and time consumptive frequency domain algorithms.     

Modelling the effects of environmental conditions on wind turbine failures

Operation and maintenance is one of the main cost drivers of modern wind farms and has become an emerging field of research over the past years. Understanding the failure behaviour of wind turbines (WTs) can significantly enhance operation and maintenance processes and is essential for developing reliability and strategic maintenance models. Previous research has shown that especially the environmental conditions, to which the turbines are exposed to, affect their reliability drastically. This paper compares several advanced modelling techniques and proposes a novel approach to model WT system and component failures based on the site‐specific weather conditions. Furthermore, to avoid common problems in failure modelling, procedures for variable selection and complexity reduction are discussed and incorporated. This is applied to a big failure database comprised of 11 wind farms and 383 turbines. The results show that the model performs very well in several situations such as modelling general WT failures as well as failures of specific components. The latter is exemplified using gearbox failures.     

电力变压器微水在线测量的先进方法

研究了测量变压器油-纸绝缘的电力变压器中水含最的新方法.微水的扩散和平衡是和潜在的水分有关.比较了测量变压器内纸绝缘中水含量的各种方法.微水平衡图的常规应用会导致错误的结果,因此,创建了改成以微水吸收量和相关材料老化参数的微水平衡图.使用变压器油中的相对湿度来绘制微水平衡图先进的表示法,产生了比较好的效果.此外,按变压器油和绝缘材料中的活跃的水分来确定湿度,能提供方便、精确和连续的测量,并且直接反映变压器油-纸绝缘中的水分的破坏性潜力.这些均可在在线系统中显示出来.     

Electrical and Electrochemical Characteristics of Withania somnifera Leaf Extract Incorporation Sodium Alginate Polymer Film for Energy Storage Applications

The current investigation addresses the alternating current electrical properties, electrochemical characteristics on biopolymer as Withania somnifera leaf extract incorporated sodium alginate [WLISA] polymer film prepared by solution casting method. Some crystallinity along with the amorphous nature of sodium alginate emerged due to the incorporation of Withania somnifera leaf extract [WSLE]. Two absorption maximum (λ_max) were obtained for both WLISA and WSLE samples in the UV–Vis spectrum. The blue, green, and red emission of WSLE and weak blue emission of WLISA are studied by PL analysis. The more amount of strain that occurred in crystallization provides broaden peak in X-ray diffraction pattern. With aid of guluronic and mannuronic acids in sodium alginate making hydroxyl bond formation with leaf extract due to the cross-linking process can be analyzed from Fourier transform infrared spectroscopy. The EDAX analysis showed the chemical composition of WSLE. At room temperature, the prepared 5 ml leaf extract WLISA film has demonstrated the highest ionic conductivity in the typical value of 2.80?×?10^–6 S/Cm. The electrochemical window of the prepared polymer film is in the range of ? 0.4 to 0.4 V suggesting that used as an electrolyte for supercapacitor applications.

     

Thermal-hydraulic and aerosol containment phenomena modelling in ASTEC severe accident computer code

Transients in containment systems of different scales (Phebus.FP containment, KAEVER vessel, Battelle Model Containment, LACE vessel and VVER-1000 nuclear power plant containment) involving thermal-hydraulic phenomena and aerosol behaviour, were simulated with the computer integral code ASTEC. The results of the simulations in the first four facilities were compared with experimental results, whereas the results of the simulated accident in the VVER-1000 containment were compared to results obtained with the MELCOR code. The main purpose of the simulations was the validation of the CPA module of the ASTEC code. The calculated results support the applicability of the code for predicting in-containment thermal-hydraulic and aerosol phenomena during a severe accident in a nuclear power plant.     

Spray-flame synthesis of La(Fe,Co)O3 nano-perovskites from metal nitrates

Nano-sized perovskites were synthesized in a spray flame from nitrate precursors dissolved in ethanol and in ethanol/2-ethylhexanoic acid (2-EHA) mixtures. Experiments with ethanol led to a broad particle-size distribution and to the formation of undesired phases such as La₂CoO₄, La₂O₃, and Co₃O₄. The addition of 2-EHA can initiate micro explosions of the burning droplets and has been systematically investigated toward the formation of single-phase, high-surface-area LaCoO₃ and LaFeO₃ with a narrow size distribution. To investigate the effect of 2-EHA, temperature-dependent changes of the chemical composition of the precursor solutions were analyzed with ATR-FTIR between 23 and 70°C. In all cases, the formation of esters was identified while in the solutions containing iron, additional formation of carboxylates was observed. The synthesized materials were characterized by BET SSA, XRD, SAED and EDX-TEM and their catalytic activity was analyzed, reaching 50% CO conversion at temperatures below 160 and 300°C for LaCoO₃ and LaFeO₃, respectively.     

Silicon-nanowire transistors with intruded nickel-silicide contacts

Schottky barrier field effect transistors based on individual catalytically-grown and undoped Si-nanowires (NW) have been fabricated and characterized with respect to their gate lengths. The gate length was shortened by the axial, self-aligned formation of nickel-silicide source and drain segments along the NW. The transistors with 10-30 nm NW diameters displayed p-type behaviour, sustained current densities of up to 0.5 MA/cm2, and exhibited on/off current ratios of up to 10(7). The on-currents were limited and kept constant by the Schottky contacts for gate lengths below 1 microm, and decreased exponentially for gate lengths exceeding 1 microm.