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11.
Compensating for near/far effects is critical for satisfactory performance of DS/CDMA systems. So far, practical systems have used power control to overcome fading and near/far effects. Another approach, which has a fundamental potential in not only eliminating near/far effects but also in substantially raising the capacity, is multiuser detection and interference cancellation. Various optimal and suboptimal schemes have been investigated. Most of these schemes, however, get too complex even for relatively simple systems and rely on good channel estimates. For interference cancellation, estimation of channel parameters (viz. received amplitude and phase) is important. We analyze a simple successive interference cancellation scheme for coherent BPSK modulation, where the parameter estimation is done using the output of a linear correlator. We then extend the analysis for a noncoherent modulation scheme, namely M-ary orthogonal modulation. For the noncoherent case, the needed information on both the amplitude and phase is obtained from the correlator output. The performance of the IC scheme along with multipath diversity combining is studied 相似文献
12.
R. G. Patel D. C. Killoh L. J. Parrott W. A. Gutteridge 《Materials and Structures》1988,21(3):192-197
The reduction in relative humidity within drying concrete depends mainly on the depth from the exposed surface, exposure duration,
temperature and environmental humidity; this limits hydration and coarsens pore structure, thus impairing durability. OPC
paste, of 0.59 water/cement ratio, was cured for 2 days and then exposed to controlled relative humidity environments. After
14 and 90 days exposure, hydration of the individual compounds was measured using quantitative X-ray diffraction and thermogravimetry.
Methanol adsorption was used to monitor porosity and gel formation. Even a small drop in relative humidity below 95% r.h.
significantly limited cement hydration. Gel porosity increased with amount of hydration and, for a given level of hydration,
decreased with drying. Curing below 80% r.h. produced a coarsened pore structure with a large-diameter porosity three times
greater than that obtained with saturated curing. 相似文献
13.
Pseudoexstrophy is a rare, mild exstrophy variant which involves the major musculoskeletal defects of the exstrophy complex without any associated defect in the urinary system. A case is reported presenting at birth as an umbilical positional anomaly. Differential diagnosis and management are reviewed. 相似文献
14.
15.
GV Naccarelli DL Wolbrette JT Dell'Orfano HM Patel JC Luck 《Canadian Metallurgical Quarterly》1998,9(8):864-891
Multiple trials using antiarrhythmic drugs, pharmacologic therapy, and implantable cardioverter defibrillators have been performed in an attempt to improve survival in patients: (1) postmyocardial infarction; (2) with congestive heart failure, with and without nonsustained ventricular tachycardia; and (3) with sustained ventricular tachycardia and those who have survived an out-of-hospital cardiac arrest. This article reviews some of the key findings and limitations of completed and ongoing trials. We also make recommendations for the current treatment of such patients based on the results of these trials. 相似文献
16.
17.
M Patel RF Kaltenbach DA Nugiel RJ McHugh PK Jadhav LT Bacheler BC Cordova RM Klabe S Erickson-Viitanen S Garber C Reid SP Seitz 《Canadian Metallurgical Quarterly》1998,8(9):1077-1082
Cyclic urea SD146, a potent HIV protease inhibitor bearing a flat resistance profile, possessed poor solubility and bioavailability, which precluded further development of the compound. In an effort to improve upon the pharmacokinetic profile of the compound, several analogs modified at the P1/P1' residues were prepared and evaluated. Several of those compounds displayed significant improvement of physical properties. 相似文献
18.
RI Senderoff KM Kontor L Kreilgaard JJ Chang S Patel J Krakover JK Heffernan LB Snell GB Rosenberg 《Canadian Metallurgical Quarterly》1998,87(2):183-189
This article summarizes the results of a combined analysis from two identical multicenter clinical trials that investigated the efficacy and safety of sertraline versus placebo for treating panic disorder. Patients with panic disorder who were treated with sertraline had a statistically significant reduction in the mean number of panic attacks per week (the primary efficacy measure) as compared with placebo (4.8 vs. 2.5, p < .001). Sertraline-treated patients also showed greater improvement that was statistically significant on several ratings of panic disorder symptomatology and functioning. The design characteristics, clinical rating measures, and outcome measures in these trials included most of the features deemed essential by Shear and Maser (1994) in their summary of the NIMH Consensus Conference for the development of standardized assessments for panic disorder. This suggests that the NIMH Consensus Conference played a key role in developing successful multicenter pharmacological treatment studies, such as this one that ultimately demonstrated that sertraline was an effective treatment for panic disorder. 相似文献
19.
Production of alumina fibre through jute fibre substrate 总被引:1,自引:0,他引:1
Alumina fibre has been produced using jute fibre as substrate material at temperatures lower than 1600 C in a reducing atmosphere. Processed jute fibre was chemically pretreated by saturation with Al2Cl6 · 12H2O, coked and then pyrolysed to obtain alumina fibre. Chemical pretreatment conditions have been determined by following weight loss measurements of the jute fibre at 0.1 to 0.6 N solutions of NaOH, KOH, NH4OH, Na2CO3, K2CO3, HCl and acetic acid. The effect of heat treatment on the jute fibre and jute fibre + aluminium salt has been studied from 150 to 1600 C. Trace elements present (Fe2O3, SiO2, K2O, Na2O, CaO, MgO, ZnO, MnO, V2O5, P2O5, CuO) on heat-treated products have been determined by atomic absorption spectrometry. Optical and scanning electron micrographs of representative samples showing growth mechanism are presented. The effect of copper, nickel and platinum catalysts and fluxing agents such as K2O and Na2O in fibre formation has also been examined. Particle size and surface area analyses of intermediate and final products have been carried out. Changes in 2 values are plotted for various products from X-ray diffraction studies. It is conceived that the porous surface of cellulosic fibrils in the jute fibre adsorbs the AlCl3 molecules which decompose to oxide and are gradually shaped to the fibrous form during the course of thermal treatment in a reducing atmosphere and due to the high surface area. 相似文献
20.
S. L. Oswal R. G. Sindhe A. T. Patel J. P. Dave S. G. Patel B. M. Patel 《International Journal of Thermophysics》1992,13(4):617-628
Viscosities of several mono-, di-, and trialkylamines have been measured in the temperature range 298 to 333 K. It is observed that viscosities are highly dependent on shape, size, and association through H-bond or through dipole. Following the transition state theory, energy, Gibbs free energy, and entropy of activation of viscous flow have been calculated. The values of expansion energy for these liquids have also been calculated using free volume theory, and subsequently amines have been classified as volume-restrained or energy-restrained liquids. The group contribution method of Van Velzen, Cardozo, and Langenkamp for estimating viscosity has been examined with the present and literature data, and the new group contribution increments N
i and B
i for amines have been evaluated. 相似文献