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981.
Sónia Simões Filomena Viana Mustafa Koçak A. Sofia Ramos M. Teresa Vieira Manuel F. Vieira 《Journal of Materials Engineering and Performance》2012,21(5):678-682
In this article, the characterization of the interfacial structure of diffusion bonding a TiAl alloy is presented. The joining
surfaces were modified by Ni/Al reactive multilayer deposition as an alternative approach to conventional diffusion bonding.
TiAl substrates were coated with alternated Ni and Al nanolayers. The nanolayers were deposited by dc magnetron sputtering
with 14 nm of period (bilayer thickness). Joining experiments were performed at 900 °C for 30 and 60 min with a pressure of
5 MPa. Cross sections of the joints were prepared for characterization of their interfaces by scanning electron microscopy
(SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), high resolution TEM (HRTEM),
energy dispersive x-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). Several intermetallic compounds form
at the interface, assuring the bonding of the TiAl. The interface can be divided into three distinct zones: zone 1 exhibits
elongated nanograins, very small equiaxed grains are observed in zone 2, while zone 3 has larger equiaxed grains. EBSD analysis
reveals that zone 1 corresponds to the intermetallic Al2NiTi and AlNiTi, and zones 2 and 3 to NiAl. 相似文献
982.
This paper investigates the manufacturing distortion of curved composite parts manufactured by a new Liquid Composite Molding (LCM) process called Flexible Injection (FI). This technique uses a deformable tool to speed up the fabrication but may generate manufacturing defects when strongly curved shapes are processed. The goal of the study is to evaluate the impact of such heterogeneities on the dimensional stability of the product. Curved components were first manufactured with varying processing conditions to achieve a wide range of layup quality. The shape stability of the samples was then recorded as a function of temperature to measure the thermoelastic component of distortion and experimental results were compared with predictions made by two modeling techniques. Under certain conditions, manufacturing defects can significantly affect the distortion behavior. This suggests that a robust preforming procedure is of primary importance to produce curved parts by Flexible Injection with a high level of repeatability. 相似文献
983.
Zhao Ren Kun Qian Zixing Zhang Vedhas Pandit Alice Baird Bj?rn Schuller 《IEEE/CAA Journal of Automatica Sinica》2018,5(3):662-669
Spectrogram representations of acoustic scenes have achieved competitive performance for acoustic scene classification. Yet, the spectrogram alone does not take into account a substantial amount of time-frequency information. In this study, we present an approach for exploring the benefits of deep scalogram representations, extracted in segments from an audio stream. The approach presented firstly transforms the segmented acoustic scenes into bump and morse scalograms, as well as spectrograms; secondly, the spectrograms or scalograms are sent into pre-trained convolutional neural networks; thirdly, the features extracted from a subsequent fully connected layer are fed into (bidirectional) gated recurrent neural networks, which are followed by a single highway layer and a softmax layer; finally, predictions from these three systems are fused by a margin sampling value strategy. We then evaluate the proposed approach using the acoustic scene classification data set of 2017 IEEE AASP Challenge on Detection and Classification of Acoustic Scenes and Events (DCASE). On the evaluation set, an accuracy of 64.0% from bidirectional gated recurrent neural networks is obtained when fusing the spectrogram and the bump scalogram, which is an improvement on the 61.0% baseline result provided by the DCASE 2017 organisers. This result shows that extracted bump scalograms are capable of improving the classification accuracy, when fusing with a spectrogram-based system. 相似文献
984.
A recent Quantum Private Set Intersection (QPSI) scheme is crypt-analyzed. The original claimed communication overhead is shown to be not accurate. And the original security definition is passive and not fair. To ensure fairness, a passive third party is introduced. It is also shown that unconditional fairness of QPSI protocol is impossible. Since otherwise, it would violate a well-known impossible quantum cryptography result. 相似文献
985.
Nur Koçberber Kιlιç Pιnar Karacakaya Ergin Duygu Gönül Dönmez 《Water and Environment Journal》2012,26(1):94-99
Phenol removal levels of Synechocystis sp. were investigated in BG11 media with 10 mg/L triacontanol (TRIA) and without it to test whether the hormone could increase the removal efficiency by increasing biomass. The assays were performed to determine the effect of light on degradation, in media with 119.0–492.8 mg/L phenol under light and dark conditions. At increasing phenol concentrations, the degradation ranged between 98.5 and 100% regardless of a dark or a light condition. Experiments were carried out under light to determine the optimum pH for effective degradation. Optimum pH was found to be 6.5 at 200 mg/L phenol with or without TRIA. Phenol degradation was investigated in the 120.2–826.9 mg/L range. Although 377.4 mg/L phenol was completely degraded in hormone controls within 120 h, degradation was increased by TRIA, and the process was completed in 96 h. These data suggest that Synechocystis sp. has potential for use in the treatment of wastewaters containing phenol. 相似文献
986.
Yunpeng Ren J.K. Chen Yuwen Zhang 《International Journal of Heat and Mass Transfer》2012,55(5-6):1620-1627
A semi-classical two-temperature (2T) model, together with the extended Drude model for temperature-dependent optical properties, is proposed to describe ultrafast thermal transport and phase changes in gold films irradiated by an ultrashort laser pulse. This model reduces to a classical 2T model when the electron momentum equation and the two terms related to electron drifting velocity in the electron energy equation are dropped off. It is found that the significant changes in reflectivity and absorption coefficient due to rapid temperature rise could drastically alter laser energy deposition and in turn, the thermal response in metal films. It is also found that the semi-classical 2T model could predict lower electron and lattice temperature and less severe solid–liquid and liquid–vapor phase change than the classical 2T model. The difference could be more distinct with increase of laser fluence and/or increase of laser pulse duration. 相似文献
987.
We present particle counting ultrahigh-resolution optical Doppler tomography (pc-μODT) that enables accurate imaging of red blood cell velocities (ν(RBC)) of cerebrovascular networks by detecting the Doppler phase transients induced by the passage of a RBC through a capillary. We apply pc-μODT to image the response of capillary ν(RBC) to mild hypercapnia in mouse cortex. The results show that ν(RBC) in normocapnia (ν(N)?=?0.72?±?0.15?mm/s) increased 36.1%?±?5.3% (ν(H)?=?0.98?±?0.29?mm/s) in response to hypercapnia. Due to uncorrected angle effect and low hematocrit (e.g., ~10%), ν(RBC) directly measured by μODT were markedly underestimated (ν(N) ≈ 0.27?±?0.03?mm/s, ν(H) ≈ 0.37±?0.05?mm/s). Nevertheless, the measured ν(RBC) increase (35.3%) matched that (36.1%?±?5.3%) by pc-μODT. 相似文献
988.
We present and investigate techniques for optimizing particle dispersions in all kinds of Reynolds number flows. In particular,
we show the range of application, power and efficiency of space mapping approaches that are based on a hierarchy of models
ranging from a complex (fine, accurate, costly) to simple (coarse, rough, cheap) model. Space mapping turns out to be a reasonable
approximation to optimal control and a competitive alternative to instantaneous control regarding speed and memory demands
when dealing with complex, non-stationary problems. Moreover it allows the easy and efficient treatment of stochastic design
problems. To control random particle dynamics in a turbulent flow, we suggest a Monte-Carlo aggressive space mapping algorithm
which yields very convincing numerical results. 相似文献
989.
990.
Ultrafiltration based purification strategies for surfactin produced by Bacillus subtilis LB5A using cassava wastewater as substrate
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