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81.
82.
Wood A.C.G. O'Neill A.G. Phillips P.J. Biswas R.G. Whall T.E. Parker E.H.C. 《Electron Devices, IEEE Transactions on》1993,40(1):157-162
Delta-doped MOSFETs have been fabricated in MBE-grown silicon using for the first time boron as the dopant within the delta layer. Current-voltage characteristics have been measured, and secondary ion mass spectrometry (SIMS) is used to confirm the location of the delta layer and the extent of layer broadening by diffusion during processing. Precise threshold voltages of the devices are difficult to determine since the devices (which all operate in depletion mode) take several volts to switch off. Transconductances of the devices have been measured, and it is shown how analysis of these results can yield estimates of the carrier mobility for transport along the delta layers despite the uncertainty in the threshold voltage. A clear transition is observed in the results which is attributed to the formation of a parasitic surface-channel field-effect transistor, providing conclusive evidence that the devices are conducting along a delta channel for part of the measured range of applied gate biases 相似文献
83.
S. Biswas T. Nithyanantham N. T. Saraswathi S. Bandopadhyay 《Journal of Materials Science》2009,44(3):778-785
Elastic properties of Ni-8YSZ anode-supported bi-layer SOFC structures were studied at elevated temperatures up to 1,000 °C
in both ambient air and H2 environments. The anode samples with desired porosity and microstructure were fabricated by reducing a NiO-8YSZ anode precursor
structure in a gas mixture of 5% H2–95% Ar at 800 °C for selected time periods up to 8 h. The development of the essential porous microstructure in forming the
Ni-8YSZ cermet phase was analyzed with SEM. It was observed that the room temperature elastic moduli and hardness of the anode
samples decrease significantly with increasing fraction of reduced NiO. Since the elastic properties of fully dense Ni, NiO,
and 8YSZ are comparable to each other, the decrease in the magnitude in elastic moduli and hardness is evidently due to the
colossal increase in porosity in the reduced Ni-8YSZ cermet anodes because of the reduction of NiO to Ni. At elevated temperatures,
the Ni-8YSZ anodes show a complex profile of Young’s modulus as a function of temperature, which is significantly different
from the unreduced NiO-8YSZ samples. When studied in ambient air, the Young’s modulus of the Ni-8YSZ samples decrease slowly
up to ~250 °C, then more rapidly from 250 to 550 °C, and finally it increases monotonically with the increase in temperature.
However, in reducing environment, the Young’s moduli values decrease continuously throughout the temperature range. Two sets
of samples of different thicknesses were studied simultaneously to highlight the effects of the sample thickness on the elastic
properties of the anodes. 相似文献
84.
This paper provides an alternative test procedure for the problem oftesting of normal mean for one sided alternative when the variance is known in case of costly trials. The proposed test is based on a sampling scheme which we call 'continuous adaptive design'. Some exact andasymptotic results related to the test and design are studied. 相似文献
85.
In the context of comparing two treatments in clinical trials randomized play-the-winner rule is used with the goal of treating more patients by the better treatment On its basis we give two decision rules by introducing stopping rule Some performance characteristics of one of the decision rules are discussed and examined .A minimax rule is suggested Finally some exact and asymptotic properties of the decision rule is derived 相似文献
86.
87.
Saptarshi Chattopadhyay Luis B. Modesto-Lopez Chandra Venkataraman Pratim Biswas 《Aerosol science and technology》2013,47(11):972-982
Pulmonary delivery of sustained release formulations needs drug encapsulation in a suitable matrix, as well as the generation of aerosols with high lung penetration and suitable release characteristics. Nanometer sized liposomes offer the potential for biocompatibility, controlled release and easy internalization in the lung. For uniform dose delivery and drug release kinetics, it is of interest to understand generation techniques to obtain aerosols containing nearly monodispered nanometer sized dry particles. Two aerosolization techniques, air-jet atomization and electrohydrodynamic atomization (EHDA) were studied to identify conditions under which the inclusion of one-liposome-per-drop could be achieved. In air-jet atomization, low lipid concentrations resulted in a unimodal aerosol with a median mobility diameter of 94 (± 3.5) nm, while higher concentrations led to larger median diameters, implying possible inclusion of multiple liposomes per drop. In EHDA, tuning drop sizes in the range of 130 to 200 nm, as well as the use of high lipid concentrations, resulted in a bimodal aerosol distribution, with peaks at 35 and 100 nm mobility diameters. TEM images of the liposome aerosol from EDHA showed fused liposomes, resulting in cylindrical structures with different physical diameters. It was hypothesized that deformation of liposomes to cylindrical structures in the micro-capillary liquid tip of the electrospray, and interactions along the axial or cross sectional surfaces led to dry particles with different mobility sizes. 相似文献
88.
In order to develop zein fibers with improved physical properties and solvent resistance, formaldehyde was used as a crosslinking reagent before spinning. The crosslinking reaction was carried out in either acetic acid or ethanolic HCl where the amount of crosslinking reagent was between 1 and 6%. Reactions were carried out at various times and temperatures. When carried out in acetic acid, the maximum amount of formaldehyde that could be used was 1.5% as gelation occurred at higher levels. In ethanolic HCl, 6% formaldehyde could be incorporated into zein. All solutions were successfully electrospun, producing predominantly ribbon and round fibers; the morphology was strongly dependent on solvent and spinning solids. The formaldehyde‐crosslinked zein fabrics had double the tensile strength of control fabrics. SDS‐PAGE analysis clearly showed crosslinking had occurred. Electrospun fabrics from all formaldehyde‐treated zein solutions required an additional heating step in order to be resistant to dissolution in acetic acid, a known very good solvent for zein. Copyright © 2011 Society of Chemical Industry 相似文献
89.
90.
In this present work, Ca-alginate-biochar adsorbent has been synthesized, characterized and tested its effectiveness in the removal of aqueous phase Zn2+ metal. The removal efficiency was studied under various physicochemical process parameters. External mass transfer model, intraparticle diffusion model and pseudo-first-order and pseudo-second-order models were used to fit the experimental Zn2+ adoption kinetic results and to identify the mechanism of adsorption. The desorption studies indicate the possibilities of ion-exchange and physical–chemical adsorption of Zn2+. The adsorption was best described by Langmuir isotherm model. Thermodynamic parameters suggested that the adsorption process becomes spontaneous, endothermic and irreversible in nature. 相似文献