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排序方式: 共有168条查询结果,搜索用时 0 毫秒
1.
Tavakoli Rouhollah Mohseni Seyyed Mohammad 《Structural and Multidisciplinary Optimization》2014,49(4):621-642
Structural and Multidisciplinary Optimization - A new algorithm for the solution of multimaterial topology optimization problems is introduced in the present study. The presented method is based on... 相似文献
2.
Scaling the Aspect Ratio of Nanoscale Closely Packed Silicon Vias by MacEtch: Kinetics of Carrier Generation and Mass Transport 下载免费PDF全文
Jeong Dong Kim Parsian K. Mohseni Karthik Balasundaram Srikanth Ranganathan Jayavel Pachamuthu James J. Coleman Xiuling Li 《Advanced functional materials》2017,27(12)
Metal‐assisted chemical etching (MacEtch) has shown tremendous success as an anisotropic wet etching method to produce ultrahigh aspect ratio semiconductor nanowire arrays, where a metal mesh pattern serves as the catalyst. However, producing vertical via arrays using MacEtch, which requires a pattern of discrete metal disks as the catalyst, has often been challenging because of the detouring of individual catalyst disks off the vertical path while descending, especially at submicron scales. Here, the realization of ordered, vertical, and high aspect ratio silicon via arrays by MacEtch is reported, with diameters scaled from 900 all the way down to sub‐100 nm. Systematic variation of the diameter and pitch of the metal catalyst pattern and the etching solution composition allows the extraction of a physical model that, for the first time, clearly reveals the roles of the two fundamental kinetic mechanisms in MacEtch, carrier generation and mass transport. Ordered submicron diameter silicon via arrays with record aspect ratio are produced, which can directly impact the through‐silicon‐via technology, high density storage, photonic crystal membrane, and other related applications. 相似文献
3.
Samira Mohseni Bababdani Farhad Shahriari Nogorani 《Metallurgical and Materials Transactions A》2014,45(4):2116-2122
Overaluminizing is a commercially accepted treatment to enhance high temperature oxidation resistance of MCrAlY overlay coatings. In the current investigation, a low pressure plasma-sprayed CoNiCrAlY coating was aluminized by two different growth modes: outward growth and inward growth. The resultant microstructures were characterized by means of scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction analysis. The results showed that the final microstructure of both types of overaluminized coatings was similar and included Al-rich NiAl and Ni-rich NiAl zones from the top to the bottom. The details of the microstructures are discussed and compared with the results of simple aluminizing of the nickel-based substrate. 相似文献
4.
5.
In this study, glass flakes were incorporated into the spherical nanosilica component of the dental composites and its effect on the mechanical properties of these composites was investigated. To achieve a good interfacial adhesion between matrix resin and fillers, the particles were surface treated with a silane coupling agent (γ-MPS). Composites with different plate-like and spherical nanoparticle contents were prepared and their mechanical properties, including flexural strength, flexural modulus and fracture toughness were measured. The morphology of the particles and fracture surface of the composites were studied by SEM. The distribution of the flakes in the composite was also monitored using EDXA. Statistical analysis of the data was performed with ANOVA and the Tukey’s post hoc test was at a significance level of 0.05. The results showed that the flexural modulus and fracture toughness of specimens were improved with increasing the glass flake content up to 15 vol % which then declined upon further increase due to the stacking of the flakes on each other. A good interfacial adhesion was observed between matrix resin and particles in the SEM micrographs. The results of this study suggest that incorporation of glass flakes into the dental composites containing spherical nanosilica particles may enhance their mechanical properties. 相似文献
6.
Wireless multichannel biopotential recording using an integrated FM telemetry circuit. 总被引:4,自引:0,他引:4
Pedram Mohseni Khalil Najafi Steven J Eliades Xiaoqin Wang 《IEEE transactions on neural systems and rehabilitation engineering》2005,13(3):263-271
This paper presents a four-channel telemetric microsystem featuring on-chip alternating current amplification, direct current baseline stabilization, clock generation, time-division multiplexing, and wireless frequency-modulation transmission of microvolt- and millivolt-range input biopotentials in the very high frequency band of 94-98 MHz over a distance of approximately 0.5 m. It consists of a 4.84-mm2 integrated circuit, fabricated using a 1.5-microm double-poly double-metal n-well standard complementary metal-oxide semiconductor process, interfaced with only three off-chip components on a custom-designed printed-circuit board that measures 1.7 x 1.2 x 0.16 cm3, and weighs 1.1 g including two miniature 1.5-V batteries. We characterize the microsystem performance, operating in a truly wireless fashion in single-channel and multichannel operation modes, via extensive benchtop and in vitro tests in saline utilizing two different micromachined neural recording microelectrodes, while dissipating approximately 2.2 mW from a 3-V power supply. Moreover, we demonstrate successful wireless in vivo recording of spontaneous neural activity at 96.2 MHz from the auditory cortex of an awake marmoset monkey at several transmission distances ranging from 10 to 50 cm with signal-to-noise ratios in the range of 8.4-9.5 dB. 相似文献
7.
This paper presents a low-power low-noise fully integrated bandpass operational amplifier for a variety of biomedical neural recording applications. A standard two-stage CMOS amplifier in a closed-loop resistive feedback configuration provides a stable ac gain of 39.3 dB at 1 kHz. A subthreshold PMOS input transistor is utilized to clamp the large and random dc open circuit potentials that normally exist at the electrode-electrolyte interface. The low cutoff frequency of the amplifier is programmable up to 50 Hz, while its high cutoff frequency is measured to be 9.1 kHz. The tolerable dc input range is measured to be at least +/- 0.25 V with a dc rejection factor of at least 29 dB. The amplifier occupies 0.107 mm2 in die area, and dissipates 115 microW from a 3 V power supply. The total measured input-referred noise voltage in the frequency range of 0.1-10 kHz is 7.8 microVrms. It is fabricated using AMI 1.5 microm double-poly double-metal n-well CMOS process. This paper presents full characterization of the dc, ac, and noise performance of this amplifier through in vitro measurements in saline using two different neural recording electrodes. 相似文献
8.
Bin Lee Cioffi J.M. Jagannathan S. Kibeom Seong Youngjae Kim Mohseni M. Brady M.H. 《Communications, IEEE Transactions on》2007,55(8):1617-1628
This paper introduces a multiple-input multiple-output channel model for the characterization of a binder of telephone lines. This model is based on multiconductor transmission line theory, and uses parameters that can be obtained from electromagnetic theory or measured data. The model generates frequency-dependent channel/binder transfer function matrices as a function of cable type, geometric line-spacing and twist-length parameters, and source--load configurations. The model allows the extraction of the magnitude and the phase of individual near end crosstalk, far end crosstalk, split-pair, and phantom transfer functions from the transfer function matrix of the binder. These individual crosstalk transfer functions are often found to be very sensitive to small imperfections in the binder. Examples of category 3 twisted pair American telephone lines and ldquoquadrdquo telephone cables are also presented. 相似文献
9.
This paper presents a novel approach for the modelling of transformer windings, which is valid in the frequency range of 10 kHz to a few MHz. It is a hybrid model; coil-by-coil detailed plus inter-coil black box model. The parameter estimation of the detailed model and the synthesis of the black box model is based on frequency domain measurements. The technique is applied to a high-voltage transformer winding. The comparison of the measurements and the frequency domain simulation of the model with EMTP confirms the validity and accuracy of the model for the intended frequency range. Experiments in the frequency range of several MHz reveal that remarkable overvoltages appear at the connecting point of the inverted and interleaved part of this winding. It is shown that the reason of the VFTO (very fast transient overvoltage) in the MHz range is the inhomogeneity of the winding parts 相似文献
10.
In the present article, higher-order shear and normal deformable plate theory together with modified couple stress theory are developed to study the bending analysis of thick functionally graded rectangular micro-plates. One material length scale parameter is used for capturing the size effects. Utilizing the variational approach and also a principle of virtual displacement, a new form of equilibrium equations and the corresponding boundary conditions are derived. It is assumed that material properties vary through the thickness according to the power law function. Finally, an analytical solution for the bending problem of a simply supported FG rectangular micro-plate is presented. 相似文献