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排序方式: 共有707条查询结果,搜索用时 93 毫秒
1.
《Ceramics International》2015,41(6):7366-7373
The accumulative damage behaviour of BN-coated Hi-Nicalon™ SiC fibre-reinforced SiC matrix composite was examined under tensile cyclic loading at room and elevated temperatures. The accumulative damage occurring during the cyclic loading was quantitatively characterised using the damage parameter obtained by the hysteresis loop curves. The damage parameter increased with increasing applied stress beyond the matrix cracking stress, and it subsequently retained a nearly constant value until just before fracture. Moreover, the dielectric constant, dielectric loss and loss tangent of the composite were measured before and after the fracture in the frequency range 1–1000 MHz. The dielectric properties had similar frequency dependency before and after the fracture. However, the dielectric constant, dielectric loss and loss tangent were lower in the post-fractured specimens than in the pristine ones. The reduction of the dielectric properties was associated with the accumulative damage stored in the specimens. In addition, the relationships between the dielectric properties and the damage parameter were described in detail. 相似文献
2.
《Ceramics International》2015,41(6):7478-7488
Gas sensing characteristics of one-electrode sensors based on the In2O3 ceramics doped by gallium and phosphorus have been discussed. In2O3-based ceramic was prepared by sol–gel technology. Ozone, CO, CH4 and H2 were used as tested gases. The doping concentration effect on the sensor parameters such as magnitude of response, operating temperature, response and recovery times, sensitivity to the air humidity, and selectivity have been analyzed. It was shown that In2O3 doping by Ga and P could be used for the sensor performance optimization. It was assumed that the appearance of the second phase (InPO4 and Ga2O3) and the change of structural parameters, taking place during doping process, were the main factors controlling the change of operating characteristics in In2O3:P and In2O3:Ga-based sensors. 相似文献
3.
We use photoluminescence to observe light-induced degradation in silicon in real time. Numerical simulations are used to match our results and lifetime decay data from the literature with theoretical models for the generation of the light-induced boron–oxygen defects. It is found that the existing model of the slowly generated defect SRC, where its saturated concentration is a function of the majority carrier concentration, does not explain certain results in both p- and n-type samples. A new model is proposed in which the saturated SRC concentration is controlled by the total hole concentration under illumination. 相似文献
4.
5.
《Journal of the European Ceramic Society》2005,25(2-3):129-135
A poly(aminoborazine), precursor for hexagonal boron nitride (h-BN) obtained by reaction of borazine B3N3H6 with ammonia, and its pyrolysis derivatives have been extensively characterised by 15N and 11B MAS NMR. The various B and N sites have been identified according to their first neighbouring atoms, as well as to the second ones in the case of 15N, and have also been quantified. This study demonstrates that a suitable choice of NMR techniques together with the use of isotopic enrichment can lead to a large improvement in spectral resolution, which allows a better understanding of such complex BN preceramic polymer structures and permits to follow the polymer-to-ceramic transformation. 相似文献
6.
7.
Aishani Mazumder Chung Kim Nguyen Thiha Aung Mei Xian Low Md. Ataur Rahman Salvy P. Russo Sherif Abdulkader Tawfik Shifan Wang James Bullock Vaishnavi Krishnamurthi Nitu Syed Abhishek Ranjan Ali Zavabeti Irfan H. Abidi Xiangyang Guo Yongxiang Li Taimur Ahmed Torben Daeneke Akram Al-Hourani Sivacarendran Balendhran Sumeet Walia 《Advanced functional materials》2023,33(36):2303641
Miniaturization and energy consumption by computational systems remain major challenges to address. Optoelectronics based synaptic and light sensing provide an exciting platform for neuromorphic processing and vision applications offering several advantages. It is highly desirable to achieve single-element image sensors that allow reception of information and execution of in-memory computing processes while maintaining memory for much longer durations without the need for frequent electrical or optical rehearsals. In this work, ultra-thin (<3 nm) doped indium oxide (In2O3) layers are engineered to demonstrate a monolithic two-terminal ultraviolet (UV) sensing and processing system with long optical state retention operating at 50 mV. This endows features of several conductance states within the persistent photocurrent window that are harnessed to show learning capabilities and significantly reduce the number of rehearsals. The atomically thin sheets are implemented as a focal plane array (FPA) for UV spectrum based proof-of-concept vision system capable of pattern recognition and memorization required for imaging and detection applications. This integrated light sensing and memory system is deployed to illustrate capabilities for real-time, in-sensor memorization, and recognition tasks. This study provides an important template to engineer miniaturized and low operating voltage neuromorphic platforms across the light spectrum based on application demand. 相似文献
8.
We present an analytical framework for the performance analysis of CSMA/CA based wireless mesh networks. This framework can provide an accurate throughput-delay evaluation for both saturated and unsaturated cases. An efficient algorithm that determines the collision domain for each node based on both the interference range and routing in the network is presented. As another important application of this framework, we develop an analytic model that enables us to obtain closed form expressions for delay in terms of multipath routing variables. A flow-deviation algorithm is used to derive the optimal flow over a given set of routes for any number of classes. The model takes into account the effects of neighbor interference and hidden terminals, and tools are provided to make it feasible for the performance analysis and optimization of large-scale networks. Numerical results are presented for different network topologies and compared with simulation studies. 相似文献
9.
The adhesion, friction, wear in micro system or MEMS is more significant than those in macro system. The levitation or suspension
technique is one of the effective techniques to eliminate the adhesion, friction, wear caused by the surfaces contact. The
electromagnetic levitation micromotor with stators embedded (ELMSE) is a kind electromagnetic eddy current levitation system,
which has special structure including the double sided stator and the hollow annular rotor. Different from the electromagnetic
eddy current levitation system with single sided stator, ELMSE has good stability in the vertical and lateral directions.
Using the finite element method, the levitation characteristics and lateral stability characteristics are analyzed. The influence
of structural parameters and electric parameters on the vertical stiffness and the lateral stiffness has been analyzed and
optimized in the paper. The analysis result of the paper provides theoretical reference for the optimal design of ELMSE. 相似文献
10.
Feng Cui Wenyuan Chen Weiping Zhang Qijun Xiao Gaoyin Ma Wu Liu 《Microsystem Technologies》2009,15(12):1885-1896
A micromachined electrostatically suspended gyroscope, with a wheel-like rotor housed by top stator and bottom stator, using
UV-LIGA microfabrication technology, was presented. The designed structure and basic operating principle of the gyroscope
are described. The key steps in the fabrication process, such as wet etching of Pyrex glass pits for soldering, and integration
of thick nickel structures by removal of SU-8 mold, were considered in detail and well solved. Cr/Pt/photoresist was used
as etching mask and the etched pits, in depth of near 30 μm, with aspect ratio (depth to undercutting) of 0.75, were obtained.
With metal foundations constructed for consolidation, successful integration of the nickel structures, in thickness of 200 μm,
was achieved by successful removal of the SU-8 mold using oleum. After the two stators and the rotor were fabricated separately,
they were assembled and soldering bonded to form axial and radial small gaps, hence, the initial prototype of the microgyroscope
was realized. The key techniques described in this paper can be applied to fabrication of other micro devices. The metal foundation
method, associated with removal of SU-8 mold by oleum, is expected to make SU-8 wider applications in making integrated microstructures
with fabricated circuitry on the same chip. 相似文献