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排序方式: 共有855条查询结果,搜索用时 31 毫秒
81.
Khac An Dao Anh Tuan Phan Hung Manh Do Tien Hung Luu Meiken Falke M. MacKenzie 《Journal of Materials Science: Materials in Electronics》2011,22(2):204-216
The synthesis of semiconductor nanowires is more and more interested to the applications for building blocks of the innovative
nano-sized devices and circuits, but the research and fabrication of these nanowires are also holding a number of difficulties
and challenges. Among many different kinds of semiconductor nanowires, Ga2O3 is increasingly grown for many promising applications in nano-device production, namely nanowire LED and Laser. So far there
are many synthesizing methods of semiconductor nanowires, among them the vapor–liquid–solid (VLS) method is simple, cheap
and popular. However, when we use the VLS method for nanowire growth, various technological problems exist. This paper aims
at investigating some influences of the growth technological conditions and Au metal catalyst on the morphology of Ga2O3 nanowire grown by VLS on GaAs substrate. The main considering factors include the different growing temperatures and times,
the effects of Au diffusion, Au droplets formation, Au cluster islands formation, and gas volume of the growing tube/ampoule
at the 10−1 torr low air pressure. The obtained experimental results regarding the structural properties of nanowires under these effects
investigated by scanning electron microscopy, field emission scanning electron microscopy, high angle annular dark field and
bright field, scanning transmission electron microscopy, energy-dispersive X-ray techniques, and focus ion beam are presented
and discussed. 相似文献
82.
Efficient conversion of glycerol waste from biodiesel manufacturing processes into biohydrogen by the hyperthermophilic eubacterium Thermotoga neapolitana DSM 4359 was investigated. Biohydrogen production by T. neapolitana was examined using the batch cultivation mode in culture medium containing pure glycerol or glycerol waste as the sole substrate. Pre-treated glycerol waste showed higher hydrogen (H2) production than untreated waste. Nitrogen (N2) sparging and pH control were successfully implemented to maintain the culture pH and to reduce H2 partial pressure in the headspace for optimal growth rate and to enhance hydrogen production from the glycerol waste. It was found that hydrogen production increased from 1.24 ± 0.06 to 1.98 ± 0.1 mol-H2 mol−1 glycerolconsumed by optimising N2 sparging and pH control. We observed that in medium containing 0.05 M HEPES, with three cycles of N2 sparging, the H2 yield increased to 2.73 ± 0.14 mol-H2 mol−1 glycerolconsumed, which was 2.22-fold higher than the non-N2 sparged H2 yield (1.23 ± 0.06 mol-H2 mol−1 glycerolconsumed). 相似文献
83.
Tien Manh Nguyen 《International Journal of Communication Systems》1993,6(4):183-192
This paper presents mathematical models with associated analysis of the deleterious effects which a spacecraft's subcarrier unbalanced modulator has on the performance of a phase-modulated residual carrier communications link. The undesired spectral components produced by the phase and amplitude imbalances in the subcarrier modulator can cause (1) potential interference to the carrier tracking and (2) degradation in the telemetry bit signal-to-noise ratio (SNR). A suitable model for the unbalanced modulator is developed and the threshold levels of undesired components that fall into the carrier tracking loop are determined. The distribution of the carrier phase error caused by the additive White Gaussian noise (AWGN) and undesired component at the residual RF carrier is derived for the limiting cases. Further, this paper analyses the telemetry bit signal-to-noise ratio degradations due to undesirable spectral components as well as the carrier tracking phase error induced by phase and amplitude imbalances. Numerical results which indicate the sensitivity of the carrier tracking loop and the telemetry symbol-error rate (SER) to various parameters of the models are also provided as a tool in the design of the subcarrier balanced modulator. 相似文献
84.
85.
Recently, great attention has been devoted to the pulsed direct current (DC) reactive magnetron sputtering technique, due
to its ability to reduce arcing and target poisoning, and its capability of producing insulating thin films. In this study,
chromium nitride (CrN) coatings were deposited by the bipolar symmetric pulsed DC magnetron reactive sputtering process at
different pulse frequency, substrate bias voltage, and the substrate temperature. It was observed that the texture of CrN
changed from (111) to (200) as substrate temperature increased to 300°C as deposited at 2 kHz without substrate bias. With
increasing pulsing bias and pulse frequency of target, predominated (200) orientation of CrN film was shown due to the ion
bombardment/channeling effect to preferentially sputter those unaligned planes. For the CrN coatings deposited with pulsed
biasing, the grain size decreased with increasing pulse frequency and substrate bias, whereas the surface roughness showed
a reverse trend. The deposition rate of the CrN films decreased with increasing pulse frequency. It was concluded that the
pulse frequency, substrate bias, and substrate temperature played important role in the texture, microstructure, and surface
roughness of the CrN coatings deposited by the pulsed DC magnetron sputtering process. 相似文献
86.
Das C.R. Mohapatra P. Tien L. Bhuyan L.N. 《Parallel and Distributed Systems, IEEE Transactions on》1993,4(10):1118-1129
System decomposition is a novel technique for modeling the dependability of complex systems without constructing a single-level Markov Chain (MC). This is demonstrated in this paper for the availability computation of a class of multiprocessors that uses 4×4 switching elements for the multistage interconnection network (MIN). The availability model is known as task-based availability, where a system is considered operational as long as the task requirements are satisfied. The authors develop two simple MC's for the processors and memories and solve them using a software package, called HARP. The probabilities of i processing elements (PE's) and j memory modules (MM's) working at any time t, denoted as Pi(t) and Pj(t), are obtained from their corresponding MC's. The effect of the MIN is captured in the model by finding the number of switches required for the connection of i PE's and j MM's. A third MC is then developed for the switches to find the probability that the MIN provides the required (i×j) connection. Multiplying this term with Pi(t) and Pj(t), the probability of an (i×j) working group is obtained. The methodology is generalized to model arbitrary as well as larger size systems. Transient and steady state availabilities are computed for a variety of MIN configurations and the results are validated through simulation 相似文献
87.
88.
Experiments were conducted to study the deposition of particles from suspensions flowing through packed beds. The experimental data obtained include both the initial and transient state particle collection. The initial collection efficiencies were compared with predictions based on existing theories. Agreement between experiments and predictions was generally good except for the case when significant repulsive force barrier exists between filter grains and particles. The transient state data obtained under the presence of unfavorable surface interactions show a steady decline in collection efficiency with time, which cannot be reconciled with any existing theories. 相似文献
89.
Experimental investigations of thermal bulk polymerization of styrene in pilot plants of different sizes have been performed. Each pilot plant is composed of a tubular recycle reactor, connected in series with a tubular reactor, both completely filled with Sulzer motionless mixers. Kinetic, reactor and viscosity models have been verified in a wide range of styrene conversions (up to 96%) temperatures (up to 210 °C) and polystyrene molar masses (up to 360 000). Scale-up studies were carried out which confirmed that multitubular reactors of special design can be applied for industrial polymerization process. 相似文献
90.
Atomic mobility and self-diffusion was studied by NMR for nanostructured liquid gallium and indium embedded into nanoporous matrices—porous glasses and artificial opals. Drastic increase in the correlation time of atomic mobility was found compared to the relevant bulk melts that depends on pore size. Additional alterations were observed at temperatures when confined melts were partially frozen. 相似文献