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排序方式: 共有1265条查询结果,搜索用时 15 毫秒
41.
Gómez-Laberge C Adler A Cameron I Nguyen TB Hogan MJ 《IEEE transactions on bio-medical engineering》2008,55(10):2372-2380
Functional MRI (fMRI) may be possible without a priori models of the cerebral hemodynamic response. First, such data-driven fMRI requires that all cerebral territories with distinct patterns be identified. Second, a systematic selection method is necessary to prevent the subjective interpretation of the identified territories. This paper addresses the second point by proposing a novel method for the automated interpretation of identified territories in data-driven fMRI. Selection criteria are formulated using: 1) the temporal cross-correlation between each identified territory and the paradigm and 2) the spatial contiguity of the corresponding voxel map. Ten event-design fMRI data sets are analyzed with one prominent algorithm, fuzzy c-means clustering, before applying the selection criteria. For comparison, these data are also analyzed with an established, model-based method: statistical parametric mapping. Both methods produced similar results and identified potential activation in the expected territory of the sensorimotor cortex in all ten data sets. Moreover, the proposed method classified distinct territories in separate clusters. Selected clusters have a mean temporal correlation coefficient of 0.39+/-0.07 (n=19) with a mean 2.7+/-1.4 second response delay. At most, four separate contiguous territories were observed in 87% of these clusters. These results suggest that the proposed method may be effective for exploratory fMRI studies where the hemodynamic response is perturbed during cerebrovascular disease. 相似文献
42.
Csaba Szeles Scott E. Cameron Stephen A. Soldner Jean-Olivier Ndap Michael D. Reed 《Journal of Electronic Materials》2004,33(6):742-751
The high-pressure electro-dynamic gradient (HP-EDG) crystal-growth technology has been recently developed and introduced at
eV PRODUCTS to grow large-volume, semi-insulating (SI) CdZnTe single crystals for room-temperature x-ray and gamma-ray detector
applications. The new HP growth technology significantly improves the downstream CdZnTe device-fabrication yield compared
to earlier versions of the HP crystal-growth technology because of the improved structural and charge-transport properties
of the CdZnTe ingots. The new state-of-the-art, HP-EDG crystal-growth systems offer exceptional flexibility and thermal and
mechanical stability and allow the growth of high-purity CdZnTe ingots. The flexibility of the multi-zone heater system allows
the dynamic control of heat flow to optimize the growth-interface shape during crystallization. This flexibility combined
with an advanced control system, improved system diagnostics, and realistic heat-transport modeling provides an excellent
platform for continuing process development. Initial results on large-diameter (140 mm), SI Cd1−xZnxTe (x=0.1) ingots grown in low temperature gradients with the HP-EDG technique show reduced defect density and complete elimination
of ingot cracking. The increased single-crystal yield combined with the improved charge transport allows the fabrication of
large-volume, high-sensitivity, high energy-resolution detector devices at increased yield. The CdZnTe ingots grown to date
produced large-volume crystals (≥1cm3) with electron mobility-lifetime product (μτe) in the (3–7) × 10−3 cm2/V range. The lower-than-desired charge-transport uniformity of the HP-EDG CdZnTe ingots is associated with the high density
of Te inclusions formed in the ingots during crystallization. The latest process-development efforts show a reduction in the
Te-inclusion density, an increase of the charge-transport uniformity, and improved energy resolution of the large-volume detectors
fabricated from these crystals. 相似文献
43.
Chris I. Pakes Cameron J. Wellard David N. Jamieson Lloyd C. L. Hollenberg Steven Prawer Andrew S. Dzurak Alex R. Hamilton Robert G. Clark 《Microelectronics Journal》2002,33(12):1053-1058
The nuclear spin quantum computer proposed by Kane [Nature 393 (1998) 133] exploits as a qubit array 31P dopants embedded within a silicon matrix. Single-qubit operations are controlled by the application of electrostatic potentials via a set of metallic ‘A’ gates, situated above the donors, on the silicon surface, that tune the resonance frequency of individual nuclear spins, and a globally applied RF magnetic field that flips spins at resonance. Coupling between qubits is controlled by the application of potentials via a set of ‘J’ gates, between the donors, that induce an electron-mediated coupling between nuclear spins. We report the results of the study of the electric field and potential profiles arising within the Kane device from typical gate operations. The extent to which a single nuclear spin can be tuned independently of its neighbours, by operation of an associated A-gate, is examined and key design parameters in the Kane architecture are addressed. Implications for current fabrication strategies involving the implantation of 31P atoms are discussed. Solution of the Poisson equation has been carried out by simulation using a TCAD modelling package (Integrated Systems Engineering AG). 相似文献
44.
Efficiency Enhancement of Single‐Walled Carbon Nanotube‐Silicon Heterojunction Solar Cells Using Microwave‐Exfoliated Few‐Layer Black Phosphorus 下载免费PDF全文
Munkhjargal Bat‐Erdene Munkhbayar Batmunkh Sherif Abdulkader Tawfik Marco Fronzi Michael J. Ford Cameron J. Shearer LePing Yu Mahnaz Dadkhah Jason R. Gascooke Christopher T. Gibson Joseph G. Shapter 《Advanced functional materials》2017,27(48)
Carbon nanotube‐silicon (CNT‐Si)‐based heterojunction solar cells (HJSCs) are a promising photovoltaic (PV) system. Herein, few‐layer black phosphorus (FL‐BP) sheets are produced in N‐methyl‐2‐pyrrolidone (NMP) using microwave‐assisted liquid‐phase exfoliation and introduced into the CNTs‐Si‐based HJSCs for the first time. The NMP‐based FL‐BP sheets remain stable after mixing with aqueous CNT dispersion for device fabrication. Due to their unique 2D structure and p‐type dominated conduction, the FL‐BP/NMP incorporated CNT‐Si devices show an impressive improvement in the power conversion efficiency from 7.52% (control CNT‐Si cell) to 9.37%. Our density‐functional theory calculation reveals that lowest unoccupied molecular orbital (LUMO) of FL‐BP is higher in energy than that of single‐walled CNT. Therefore, we observed a reduction in the orbitals localized on FL‐BP upon highest occupied molecular orbital to LUMO transition, which corresponds to an improved charge transport. This study opens a new avenue in utilizing 2D phosphorene nanosheets for next‐generation PVs. 相似文献
45.
It is believed that significant velocity overshoot effects are responsible for the high performance of pseudomorphic HEMTs (PsHEMTs). The overshoot is associated with the low effective mass in the InGaAs channel and the large Γ-L separation. Average channel electron velocities well in excess of 3.0 × 107 cm/s have been predicted in Monte-Carlo PsHEMT simulations. However, average electron velocities extracted from transconductance measurements of such devices are much lower, typically in the range 1.5–2.0 × 107 cm/s. In this paper we analyse real device measurements by using Monte-Carlo and drift diffusion simulations. We show clear evidence that the average velocity in the channel of a 200 nm PsHEMT fabricated in the Nano-electronics Research Centre of Glasgow University exceeds 3.0 × 107 cm/s. 相似文献
46.
Babiker S. Asenov A. Cameron N. Beaumont S.P. Barker J.R. 《Electron Devices, IEEE Transactions on》1998,45(8):1644-1652
A comprehensive RF analysis technique based on ensemble Monte Carlo (EMC) simulation of compound FET's with realistic device geometry is presented. Y-parameters are obtained through Fourier transformation of the EMC transients in response to small changes in the terminal voltages. The terminal currents are statistically enhanced and filtered to allow for reliable y-parameters extraction. Improved analytic procedure for extracting the intrinsic device small-signal circuit components is described. As a result, stable y-parameters and reliable circuit components can he extracted for the whole range of device operation voltages. Parasitic components like contact and gate resistances are included in the y-parameters at a post processing stage to facilitate the forecast of the performance figures of merit of real devices. The developed RF technique has been applied in the EMC simulation of pseudomorphic HEMT's (pHEMT's) fabricated at the Glasgow Nanoelectronics Research Center. Good agreement has been achieved between the simulated and measured small-signal circuit components and performance figures of merit 相似文献
47.
The standard correlation receiver for code-division multiple access (CDMA) systems is susceptible to the near-far problem. Power control techniques attempt to overcome near-far effects by varying transmitted power levels to ensure that all signals are received with equal power levels. Since these algorithms cannot perfectly compensate for power fluctuations in a mobile communications channel, the capacity of the system is reduced for a given bit-error rate (BER). This paper examines the performance of a CDMA system using imperfect power control by extending analytical techniques that account for multiple access interference. Single cell capacity is compared with systems employing perfect power control 相似文献
48.
Cameron T. Loeb G.E. Peck R.A. Schulman J.H. Strojnik P. Troyk P.R. 《IEEE transactions on bio-medical engineering》1997,44(9):781-790
Describes the design, fabrication, and output capabilities of a microminiature electrical stimulator that can be injected in or near nerves and muscles. Each single channel microstimulator consists of a cylindrical glass capsule with hermetically sealed electrodes in either end (2-mm diameter×13-mm overall length). Power and digital control data can be transmitted to multiple implants (256 unique addresses) via a 2-MHz RF field created by an external AM oscillator and inductive coil. In vitro testing demonstrated accurate control of output pulsewidth (3-258 μs in 1-μs steps) and current (0-30 mA in two linear ranges of 16 steps each, up to 8.5 V available compliance voltage). Microstimulators were used successfully for chronic stimulation in hindlimb muscles of cats. Design and fabrication issues affecting yield and reliability of the packaging and electronics are discussed 相似文献
49.
Cameron Derry Yiliang Wu Shiping Zhu Jamal Deen 《Journal of Electronic Materials》2013,42(12):3481-3488
A nonpercolating network of non-covalently functionalized single-walled carbon nanotubes was embedded within air-stable poly[5,5′-bis(3-dodecyl-2-thienyl)-2,2′-bithiophene] (PQT-12) thin films for the purpose of enhancing the field-effect mobility in thin-film transistors. The host polymer was used to stabilize the nanotubes in suspension through π-orbital overlap caused by simple application of ultrasonication. The stable nanotube suspension was cast into two different device architectures, both of which exhibited excellent on/off ratios ranging from 105 to 106 and dramatically improved mobilities compared with pristine PQT-12 semiconductor. A single-layer film with nanotubes embedded throughout was easy to fabricate and had mobility up to 0.34 cm2/Vs, an enhancement of over 3× compared with PQT-12. Placing the nanotubes closer to the dielectric surface in a dual-layer approach resulted in a mobility improvement of up to six times (0.58 cm2/Vs). The effects of the nanotube content on the polymer interaction within the suspension, film morphology, and electrical properties were investigated as well. 相似文献
50.
Turner T.R. Thomson P.J. Cameron M.A. 《IEEE transactions on bio-medical engineering》1993,40(9):985-989
The problem of classifying ventricular arrhythmias from intracardial electrograms is considered. Standard statistical discrimination procedures are applied using a simple parametric model for the shape of the pulse near its peak. This approach makes simultaneous use of the model parameters, has well known statistical properties, and involves computations that can be carried out efficiently. Preliminary analyses of real data sets, using both linear and quadratic discrimination functions, yield promising results 相似文献