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91.
A four-phase model for fluidized-bed catalytic reactors is developed. The bed is divided into four phases, i.e., bubble, cloud-wake, emulsion upflow, and emulsion downflow phases. In the model, gas back mixing in the emulsion phase and gas interchange as well as gas cross flow between phases are all considered. Model predictions are shown to compare well with various published experimental data on both axial concentration profiles and overall conversions. Parameters effects on the reaction performance were also illustrated. It was found that neglecting cross flow will result in 13% lower on the predicted conversion. 相似文献
92.
Ching-Yeh Shiau Shou-Wen Jung 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,56(1):27-33
Selective separation of metal ion from a liquid solution with the help of different permeation rate of solutes through liquid membranes was performed. The salts used were ZnCl2, CdCl2, NiCl2. D2EHPA and LIX64N were used as carrier to study the extraction rate of the solutes. The results show that at low pH value of external phase the order of degree of extraction by D2EHPA or LIX64N is Zn > Cd > Ni, while at high pH value with the presence of ammonia in the feed solution the order of degree of extraction is reversed to Ni > Cd > Zn. The results also indicate that when the mixed carrier is used an enhanced effect on the extraction was observed. Synergistic effect was also noted when comparing the cases with mixed carriers to those with pure carriers. 相似文献
93.
94.
The optimal design of rotating pretwisted blades subject to dynamic behavior constraints is studied. The restrictions on multiple blade natural frequencies and on maximum blade dynamic deflections are considered the dynamic behavior constraints. The aerodynamic forces acting on the rotating blades are simulated as harmonic excitations. Optimization techniques of the optimality‐criterion method and the method of modified feasible directions have been successfully developed and applied to minimize the weight of rotating pretwisted blades. Based on these techniques, the numerical results show that the effect of setting angle on the optimal design weight for the first frequency‐constraint case is more significant than that for the second frequency‐constraint case. It is also shown that the changes of pretwist angle will considerably affect the optimal design weight for the second frequency‐constraint case. However the effect is not significant for the fundamental frequency‐constraint case. The results also indicate that the increase of rotating speed will decrease the optimal design weight. 相似文献
95.
The dynamic stability and response of a spinning tapered blade under the effect of gyroscopic forces induced by precession of the rotor spin axis is investigated. The stability of the system is studied using a perturbation method as well as the Floquet theory. For the constant precession case, the increase of the taper effect will destabilize the system. For the harmonic precession case, the increase of the initial condition will stabilize the taper‐blade system and does not affect the stability of the uniform straight‐blade system very much. The stability results are shown to be in good agreement with both methods. A technique based on the Floquet theory and periodicity condition is presented to find the initial condition for steady‐state periodic response by only one period of integration. By proper choice of initial condition, the steady‐state periodic response can be obtained by integrating through only one period. The results show that the blade‐tip displacement is monotonically dependent on the gyroscopic effect. 相似文献
96.
Robin K. Huang Christine A. Wang Christopher T. Harris Michael K. Connors Daniel A. Shiau 《Journal of Electronic Materials》2004,33(11):1406-1410
An investigation with the objective of improving n-type ohmic contacts to GaSb-based devices is described. This study involves
a series of n-GaInAsSb and n-GaSb samples with varying doping, grown on semi-insulating (SI) GaAs substrates. These samples
were fabricated into mesa-etched, transfer-length method (TLM) structures, and the specific-contact resistivity and sheet
resistance of these layers as a function of majority electron concentration were measured. Extremely low specific-contact
resistivities of about 2 × 10−6 Ω-cm2 and sheet resistances of about 4 Ω/▭ are found for n-type GaInAsSb doped at about 3 × 1018 cm−3. 相似文献
97.
A new soft switching converter is presented for medium power applications. Two full-bridge converters are connected in series at high voltage side in order to limit the voltage stress of power switches at Vin/2. Therefore, power metal–oxide–semiconductor field-effect transistors (MOSFETs) with 600 V voltage rating can be adopted for 1200 V input voltage applications. In order to balance two input split capacitor voltages in every switching cycle, two flying capacitors are connected on the AC side of two full-bridge converters. Phase-shift pulse-width modulation (PS-PWM) is adopted to regulate the output voltage. Based on the resonant behaviour by the output capacitance of MOSFETs and the resonant inductance, active MOSFETs can be turned on under zero voltage switching (ZVS) during the transition interval. Thus, the switching losses of power MOSFETs are reduced. Two full-bridge converters are used in the proposed circuit to share load current and reduce the current stress of passive and active components. The circuit analysis and design example of the prototype circuit are provided in detail and the performance of the proposed converter is verified by the experiments. 相似文献
98.
Yuh‐Shyan Tsai Yu‐Hung Chen Pai‐Chiao Cheng Hsin‐Tzu Tsai Ai‐Li Shiau Tzong‐Shin Tzai Chao‐Liang Wu 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(12):2119-2128
Gold nanoparticles (AuNPs) are widely used as carriers or therapeutic agents due to their great biocompatibility and unique physical properties. Transforming growth factor‐beta 1 (TGF‐β1), a member of the cysteine‐knot structural superfamily, plays a pivotal role in many diseases and is known as an immunosuppressive agent that attenuates immune response resulting in tumor growth. The results reported herein reflect strong interactions between TGF‐β1 and the surface of AuNPs when incubated with serum‐containing medium, and demonstrate a time‐ and dose‐dependent pattern. Compared with other serum proteins that can also bind to the AuNP surface, AuNP–TGFβ1 conjugate is a thermodynamically favored compound. Epithelial cells undergo epithelial–mesenchymal transition (EMT) upon treatment with TGF‐β1; however, treatment with AuNPs reverses this effect, as detected by cell morphology and expression levels of EMT markers. TGF‐β1 is found to bind to AuNPs through S–Au bonds by X‐ray photoelectron spectroscopy. Fourier transform infrared spectroscopy is employed to analyze the conformational changes of TGF‐β1 on the surface of AuNPs. The results indicate that TGF‐β1 undergoes significant conformational changes at both secondary and tertiary structural levels after conjugation to the AuNP surface, which results in the deactivation of TGF‐β1 protein. An in vivo experiment also shows that addition of AuNPs attenuates the growth of TGF‐β1‐secreting murine bladder tumor 2 cells in syngeneic C3H/HeN mice, but not in immunocompromised NOD‐SCID mice, and this is associated with an increase in the number of tumor‐infiltrating CD4+ and CD8+ T lymphocytes and a decrease in the number of intrasplenic Foxp3(+) lymphocytes. The findings demonstrate that AuNPs may be a promising agent for modulating tumor immunity through inhibiting immunosuppressive TGF‐β1 signaling. 相似文献
99.
After a comprehensive literature review and analysis, a unified cloud computing framework is proposed, which comprises MapReduce, a vertual machine, Hadoop distributed file system (HDFS), Hbase, Hadoop, and virtualization. This study also compares Microsoft, Trend Micro, and the proposed unified cloud computing architecture to show that the proposed unified framework of the cloud computing service model is comprehensive and appropriate for the current complexities of businesses. The findings of this study can contribute to the knowledge for academics and practitioners to understand, assess, and analyze a cloud computing service application. 相似文献
100.
Water-soluble fluorescent hyperbranched poly(amido acids) (HBPAAs), based on wholly aliphatic structures were prepared through direct self-condensation of N-(3-aminopropyl) diethano succinate amine (APDESA, AB2 monomer) in the presence of N,N-dicyclohexylcarbodiimide (DCC) as a condensation agent. The resulting HBPAAs were soluble in water, DMF and THF, and the structure of synthesized AB2 monomer and polymers was confirmed by IR, 1H, and 13C NMR measurements. TEM image indicated that the HBPAAs self-assembled in H2O to form a spherical micelle with a diameter ranging from 30 to 50 nm. A significant pH-dependent profile of fluorescent intensity in the pH range from 3 to 10 was observed, wherein pH 4 provided a critical jump as the solution pH was increased. Further increasing the pH to 10 decreased the fluorescence because of partial hydrolysis. Strong fluorescence emission was observed at 395 nm in aqueous media and the fluorescence quantum yields are to 23%. These amphiphilic HBPAAs, with excellent water-solubility, void-rich space, multiple functional peripheries and high blue fluorescence, have potential uses as tracing nanocarriers and molecular-level containers. 相似文献