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排序方式: 共有594条查询结果,搜索用时 23 毫秒
61.
The electrochemical properties of Li2SiS3 were investigated in a solid electrolyte. Li2SiS3 was converted to elemental Si, and the resultant Si was formed into Si-Li alloy in the reduction process; however, the reverse reaction was not completed due to the loss of electronic conduction upon reoxidation. FeS was dispersed as a conductive additive in Li2SiS3 films by pulsed laser deposition (PLD). The addition allowed successive reactions to proceed at a large capacity with small capacity-fading during the cycling process in spite of the small FeS fraction. This result indicates that Li2SiS3 + FeS thin film is a promising anode for solid-state lithium batteries. 相似文献
62.
This is a series of two articles on the control of an aluminum casting furnace to bring a mass of liquid aluminum from a known
initial temperature to a desired final temperature in a given time with minimal fuel cost. An analytic model of the furnace
already exists but is too complex for control purposes. Here in Part I, a simplified nonlinear control model is derived from
the analytic model. In Part II, an optimization of the fuel flow is performed on the control model using Pontryagin’s maximum
principle. The first article shows that despite the complexity of the analytic model, a tenth-order nonlinear control model
with good representativity can be obtained. The second article shows that the maximum principle applied to this problem leads
to a solution with optimal fuel cost. If modeling industrial processes is a complex problem in itself, obtaining a control
model therefrom is just as delicate. This series of articles proposes an approach that works for the casting furnace and is
indeed applicable to other industrial processes as well. In the existing analytic model, the casting furnace is treated as
two one-dimensional conducting media (metal and refractories), while its chamber is seen as a well-stirred reactor. In this
article, a control model is derived therefrom by a statistical method. The analytic model is run several times to obtain a
set of predicted data on which a least-squares approximation is performed to determine the best parameter values to be used
for the control model equations. The conduction equations in the two media are linear. The expressions for heat generation
in the chamber and for radiative-convective heat transfer from the chamber to the two media are nonlinear and are kept to
ensure maximum representativity. The result is a highly representative tenth-order control model, the degree of representativity
being assessed by comparing the temperature outputs and the energy balances obtained from the analytic model with those obtained
from the control model. 相似文献
63.
In the present study, K2S and Bi2S3 were used as additives in electrolytes and electrodes, respectively. The effects of these additives on the electrochemical properties of nano-sized Fe2O3-loaded carbon electrodes were investigated using cyclic voltammetry (CV), galvanostatic cycling performance and scanning electron microscopy (SEM), along with electron dispersive spectroscopy (EDS). The results showed that both K2S and Bi2S3 significantly reduced hydrogen evolution and benefited the Fe2O3-loaded carbon electrode, such as by retarding passivation and improving the discharge capacity. The effects of metal sulfide additives depended on the carbon used. For Bi2S3 additive, all carbons provided larger capacities than acetylene black (AB) while AB gave greater capacity than other carbons when K2S was used. 相似文献
64.
Indentation tests were performed on flat coupons of poly(formaldehyde), three types of reinforced nylon and reinforced poly(ethyl terephthalate) using a device developed for a typical universal tensile testing machine. Spherical, conical and cylindrical indenters were selected for this study and the effects of indenter shape combined with the rate of indentation on the behavior of these materials were examined. The load‐depth relationship during the indentation process revealed the emergence of step‐like transitions at high indentation rates. The effects of the assessed parameters on the indentation resistance, as defined in this study, were analyzed. Interest was also focused on the investigation of the deformation work as well as the plastic work taking place for a total depth that incorporated both the skin and part of the bulk of the material. The modeling of the data was based on a previously developed approach and the introduction of a modified parameter that took not only the geometrical characteristics of the indenter into account but also the indentation depth. The proposed method has proven to be useful since a steady state of the indentation pressure was observed for all materials after a certain depth of indentation. This was valid for the results obtained using both conical and cylindrical indenters. Polym. Eng. Sci. 44:1439–1447, 2004. © 2004 Society of Plastics Engineers. 相似文献
65.
Sokolich M. Chen M.Y. Rajavel R.D. Chow D.H. Royter Y. Thomas S. III Fields C.H. Binqiang Shi Bui S.S. James Chingwei Li Hitko D.A. Elliott K.R. 《Solid-State Circuits, IEEE Journal of》2004,39(10):1615-1621
We describe a quasi-planar HBT process using a patterned implanted subcollector with a regrown MBE device layer. Using this process, we have demonstrated discrete SHBT with f/sub t/>250 GHz and DHBT with f/sub t/>230 GHz. The process eliminates the need to trade base resistance for extrinsic base/collector capacitance. Base/collector capacitance was reduced by a factor of 2 over the standard mesa device with a full overlap between the heavily doped base and subcollector regions. The low proportion of extrinsic base/collector capacitance enables further vertical scaling of the collector even in deep submicrometer emitters, thus allowing for higher current density operation. Demonstration ring oscillators fabricated with this process had excellent uniformity and yield with gate delay as low as 7 ps and power dissipation of 6 mW/CML gate. At lower bias current, the power delay product was as low as 20 fJ. To our knowledge, this is the first demonstration of high-performance HBTs and integrated circuits using a patterned implant on InP. 相似文献
66.
The wetting balance test was used to study the wettability of Sn-1.0Ag-Ce (Ce content = 0, 0.1, 0.3, and 0.5 wt%) solder alloys on electroless nickel/electroless palladium/immersion gold (ENEPIG) surface finishes with Pd thicknesses of 0, 0.05, 0.1, and 0.15 μm. Scanning electron microscopy was used to evaluate the interfacial reaction between the molten solders and surface finish materials during the wetting test. The Ni3Sn4 intermetallic compound (IMC) plays an important role in promoting wetting properties. The Pd layer retards formation of the Ni3Sn4 IMC and changes its morphology, thereby affecting the wettability of the surface finish/solder systems. ENEPIG surface finishes seem to be suitable for use with cerium-containing solders. 相似文献
67.
A. Meghlaoui R. T. Bui L. Tikasz J. Thibault R. Santerre 《Metallurgical and Materials Transactions B》1998,29(5):1007-1019
In this work, neural networks are built and trained to be used in a predictive control scheme for the aluminum electrolytic
cell. An efficient control of the cell requires the knowledge of predicted future values of the decision variables in order
to enable the standard (nonpredictive) control logic to take anticipated actions to prevent the anode effect, a destabilizing
event occurring during cell operation. The networks are first trained on data obtained from a computer simulator of the cell
prior to undergoing further on-line learning. Trained to predict the cell resistance and the resistance’s trend indicators,
the networks are applied to the control of cells in different cell states, with a view to preventing anode effects, the latter
being deliberately induced by reducing the alumina feed rate or reducing the feeding frequency and duration. Results show
that, with neural-predictive control, anode effects can be avoided, which should result in increased thermal stability, decreased
power consumption, and reduced fluoride emissions. Further, the on-line learning capacity of the networks offers a good perspective
for their application to other complex industrial processes as well. 相似文献
68.
An harmonic loss-minimized optimal PWM strategy for three-level inverters is investigated. The different PWM methods for low-, middle-, and high-speed regions are presented. It is shown that, for three-level inverters, the optimized strategy in all speed regions differs from the optimal PWM strategy of two-level inverters. The developed optimal control ensures a minimum of harmonic losses for a predetermined number of commutations of three-level PWM inverters and for a given value of the fundamental harmonic voltage 相似文献
69.
T. N. Dinh V. A. Bui R. R. Nourgaliev T. Okkonen B. R. Sehgal 《Nuclear Engineering and Design》1996,163(1-2)
The objective of this paper is to study the heat and mass trasnfer processes related to core melt discharge from a reactor vessel in a light water reactor severe accident. The phenomenology modelled includes the convection in, and heat transfer from, the melt pool in contact with the vessel lower head wall, the fluid dynamics and heat transfer of the melt flow in the growing discharge hole and multi-dimensional heat conduction in the ablating lower head wall. A research programme is underway at the Royal Institute of Technology (Kungliga Tekniska Högskolan, KTH) to (1) identify the dominant heat and mass transfer processes determining the characteristics of the lower head ablation process: (2) develop and validate efficient analytical/computational models for these processes; (3) apply models to assess the character of the melt discharge process in a reactor-scale situation; (4) determine the sensitivity of the melt discharge to structural differences and variations in the in-vessel melt progression scenarios. The paper also presents a comparison with recent results of vessel hole ablation experiments conducted at KTH with a melt simulant. 相似文献
70.
L Rampin D Donner P Zucchetta M Zuffante P Faggin F Bui M Gregianin 《Canadian Metallurgical Quarterly》1998,53(11):877-882
BACKGROUND: Meckel's diverticulum (MD) is the most common anomaly of the large intestinal tract (1-3%) and is more frequent in children (62% < 2 years) and in males (66%). It often involves ectopic gastric mucosa which manifests through gastrointestinal bleeding in 50% of cases. 99m-Technetium scintigraphy (99mTcO4) is one of the procedures available for the non-invasive diagnosis of ectopic gastric mucosa. METHODS: Twenty-eight patients (11 females, 17 males), including 16 children and 12 adults, aged 8 months-80 years old, were included in the study. The patients were admitted to hospital for hematochezia and melena (22) associated with abdominal pain (5): 3 patients repeatedly presented occult blood in their stools. Two patients only suffered from abdominal cramps and one only anemia. Patients were studied using plain abdominal radiographs and ultrasound; 10 underwent gastroscopy and colonoscopy; radiological contrast studies were performed in 5 patients. All tests were inconclusive. All the patients were premedicated with oral cimetidine (20 mg/kg in pediatric patients and 300 mg q.i.d. for adults, 48 hours before the test) or with ranitidine i.v. (1 mg/kg, max 50 mg, in 20 minutes, one hour before the test); barium meals and colonoscopy were deferred for 2-3 days after examination. An intravenous injection of 37-180 Mbq of 99mTcO4 was given followed by a dynamic study of the abdomen in anterior projection. Images were acquired for one hour or until the visualisation of abnormal foci of intake: in this case, lateral and oblique images were acquired for a better localisation of the suspicious area. Some patients were administered furosemide i.v. (0.75 mg/kg). All underwent a follow-up period of 12 months. RESULTS: Pertechnetate scintigraphy was positive in 10 cases and the presence of ectopic gastric mucosa was confirmed by surgery. The study was negative in 18 cases: 3 of them were discharged with a diagnosis of Salmonella infection, polyp of the small bowel or ulcer of the large bowel respectively; the other 15 patients did not show symptoms of onset during follow-up. CONCLUSIONS: These results confirm the high diagnostic accuracy of pertechnetate scintigraphy to detect ectopic gastric mucosa if associated with H2-receptor-blocking agent premedication. 相似文献