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51.
The combination of metal oxides Bi2O3:Li2O in a ratio 89:11 gives a eutectic with a melting point of ~680°C. Such a low melting point oxide combination creates a working liquid phase at a highly favorable temperature for use as a densification aid. A liquid—phase sintering aid incorporating Bi2O3 and Li2O is presented which demonstrates not only a reduction in the required sintering temperature but also shows relatively higher ‘c/a’ ratio (tetragonality) of PbTiO3 ceramics with no fragility of the samples. Detailed dilatometric investigations have been performed in order to study the dominant shrinkage mechanism in the present system. Besides acting as a liquid phase fluxing agent, Bi2O3/Li2O also behave as Curie shifter, which decreases Curie temperature in lead titanate system. The Curie temperature has also been verified from the thermal expansion behavior of sintered specimens. The value of dielectric constant increases after poling which may be due to the dominance of 180° domain wall over 90°. 相似文献
52.
The influence of the natural (or artificially induced) structure of a geomaterial on its compression behavior is investigated. An approach for modeling this influence for various structured geomaterials is proposed by using the disturbed state concept. An isotropic compression model is formulated on three basic assumptions. A special version of the proposed model is also described for situations where the compression is one-dimensional. The proposed compression model is used to simulate the behavior of a variety of structured geomaterials such as clays, sands, calcareous soils, clay-shale, soft rock, unsaturated soils, and soils artificially treated by adding chemical agents or mechanical reinforcement, and the model is evaluated on the basis of these simulations. A general discussion on the influence of the structure of geomaterials on their mechanical properties is also presented. 相似文献
53.
2D Materials: Re Doping in 2D Transition Metal Dichalcogenides as a New Route to Tailor Structural Phases and Induced Magnetism (Adv. Mater. 43/2017) 下载免费PDF全文
54.
Phosphorene as a Polysulfide Immobilizer and Catalyst in High‐Performance Lithium–Sulfur Batteries 下载免费PDF全文
55.
In this work, we report the preparation of phospho-silicate-glass (PSG) films using RF magnetron sputtering process and its application as a sacrificial layer in surface micromachining technology. For this purpose, a 76 mm diameter target of phosphorus-doped silicon dioxide was prepared by conventional solid-state reaction route using P2O5 and SiO2 powders. The PSG films were deposited in a RF (13.56 MHz) magnetron sputtering system at 200-300 W RF power, 10-20 mTorr pressure and 45 mm target-to-substrate spacing without external substrate heating. To confirm the presence of phosphorus in the deposited films, hot-probe test and sheet resistance measurements were performed on silicon wafers following deposition of PSG film and a drive-in step. As a final confirmatory test, a p-n diode was fabricated in a p-type Si wafer using the deposited film as a source of phosphorus diffusion. The phosphorus concentration in the target and the deposited film were analyzed using energy dispersive X-rays (EDAX) tool. The etch rate of the PSG film in buffered HF was measured to be about 30 times higher as compared to that of thermally grown SiO2 films. The application of RF sputtered PSG film as sacrificial layer in surface micromachining technology has been explored. To demonstrate the compatibility with MEMS process, micro-cantilevers and micro-bridges of silicon nitride were fabricated using RF sputtered PSG as a sacrificial layer in surface micromachining. It is envisaged that the lower deposition temperature in RF sputtering (<150 °C) compared to CVD process for PSG film preparation is advantageous, particularly for making MEMS on temperature sensitive substrates. 相似文献
56.
Shailendra Singh Subhash Chandra Bera Punam Pradeep Kumar Dhaval Pujara 《Radioelectronics and Communications Systems》2017,60(11):479-484
In this paper, formulae to determine the lowest order and other higher order spurious frequencies that coincide with desired output signal frequencies of mixers have been derived. The proposed formulae give general expressions that are suitable for any order of heterodyne mixing. The formulae have been verified using a suitable example and compared with the simulation results obtained through the radio frequency simulation software of Advanced Design System. The formulae directly reveal the order of the troublesome spurious frequencies that the designers would encounter in heterodyne systems. In comparison with these direct formulae, the results of existing spurious analysis software are based on the maximum order of simulation carried out. Based on these simulations, the coinciding spurious components have to be manually sorted out. Proposed formulae are quick tools used by the microwave system and circuit designers for choosing and finalizing heterodyne frequencies in their designs without the need for any simulations. 相似文献
57.
A new dynamic scheduling strategy, Parts-Machines Matching (PMM), is developed and tested in simulated flexible manufacturing systems. This strategy is aimed to achieve globally optimal matching between parts and machines by a semi-qualitative optimization algorithm, originally developed for the Stable Marriage Problem. Global and Partial implementations of PMM are presented and compared with other conventional part-flow rules. They are found to achieve better shop performance than conventional rules, in terms of system throughput, robustness against travel time uncertainties, and recovery from machine breakdowns. The prospect of bringing about system-wide optimization-based performance improvements into bidding schemes makes the proposed framework very significant. 相似文献
58.
In the modeling of brain mechanics subjected to primary blast waves, there is currently no consensus on how many biological components to be used in the brain–meninges–skull complex, and what type of constitutive models to be adopted. The objective of this study is to determine the role of layered meninges in damping the dynamic response of the brain under primary blast loadings. A composite structures composed of eight solid relevant layers (including the pia, cerebrospinal fluid (CSF), dura maters) with different mechanical properties are constructed to mimic the heterogeneous human head. A hyper-viscoelastic material model is developed to better represent the mechanical response of the brain tissue over a large strain/high frequency range applicable for blast scenarios. The effect of meninges on the brain response is examined. Results show that heterogeneous composite structures of the head have a major influence on the intracranial pressure, maximum shear stress, and maximum principal strain in the brain, which is associated with traumatic brain injuries. The meninges serving as protective layers are revealed by mitigating the dynamic response of the brain. In addition, appreciable changes of the pressure and maximum shear stress are observed on the material interfaces between layers of tissues. This may be attributed to the alternation of shock wave speed caused by the impedance mismatch. 相似文献
59.
Kotharu Venkateswarlu Nagumothu Rameshbabu Arumugam Chandra BoseVeerappan Muthupandi Sankaran SubramanianDavoodbasha MubarakAli Nooruddin Thajuddin 《Ceramics International》2012,38(1):731-740
The present work is aimed at developing a bioactive, corrosion resistant and anti bacterial nanostructured silver substituted hydroxyapatite/titania (AgHA/TiO2) composite coating in a single step on commercially pure titanium (Cp Ti) by plasma electrolytic processing (PEP) technique. For this purpose 2.5 wt% silver substituted hydroxyapatite (AgHA) nanoparticles were prepared by microwave processing technique and were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM) methods. The as-synthesized AgHA particles with particle length ranging from 60 to 70 nm and width ranging from 15 to 20 nm were used for the subsequent development of coating on Cp Ti. The PEP treated Cp Ti showed both titania and AgHA in its coating and exhibited an improved corrosion resistance in 7.4 pH simulated body fluid (SBF) and 4.5 pH osteoclast bioresorbable conditions compared to untreated Cp Ti. The in vitro bioactivity test conducted under Kokubo SBF conditions indicated an enhanced apatite forming ability of PEP treated Cp Ti surface compared to that of the untreated Cp Ti. The Kirby-Bauer disc diffusion method or antibiotic sensitivity test conducted with the test organisms of Escherichia coli (E. coli) for 24 h showed a significant zone of inhibition for PEP treated Cp Ti compared to untreated Cp Ti. 相似文献
60.
Ram Swaroop Verma Rajendra Chandra Padalia Amit Chauhan 《Journal of the science of food and agriculture》2012,92(3):626-631
BACKGROUND: Two Ocimum basilicum cultivars, ‘Vikarsudha’ and ‘CIM‐Saumya’, grown in the Kumaon region of western Himalaya were evaluated for their essential oil yield and composition at different stages of plant growth during two distinct cropping seasons (spring–summer and rain–autumn). RESULTS: The highest yield of essential oil was obtained at full bloom stage in both cultivars in both cropping seasons. The essential oils obtained from different stages in two cropping seasons were analysed by capillary gas chromatography with flame ionisation detection, and gas chromatography–mass spectrometry. The major component of cultivar ‘Vikarsudha’ was methyl chavicol (84.3–94.3%), while for cultivar ‘CIM‐Saumya’ the main components were methyl chavicol (62.5–77.6%) and linalool (14.4–34.1%). CONCLUSION: This study clearly indicated that cultivar, cropping season, plant ontogeny and plant part had significant effects on the yield and quality of the essential oil of O. basilicum. Further, the amount of methyl chavicol in the cultivars grown in this region was higher than in cultivars from other parts of India. Copyright © 2011 Society of Chemical Industry 相似文献