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81.
Li Fung Chang Noerpel A.R. Ranade A. 《Selected Areas in Communications, IEEE Journal on》1996,14(4):718-727
The FCC has allocated the band between 1920 MHz and 1930 MHz for unlicensed personal communications services (UPCS) using isochronous or circuit operation. The UPCS spectrum is between the licensed PCS spectrum bands of 1850-1910 MHz and 1930-1990 MHz. Terminal interoperability in both the UPCS spectrum on private indoor wireless systems and the licensed spectrum on public PCS systems is desirable and encouraged by the FCC. This paper presents a port channel assignment process for the personal access communications system-unlicensed B (PACS-UB) which abides by the FCC etiquette for UPCS and discusses the corresponding uplink and downlink performance. Uplink power control is employed to improve the uplink performance. PACS-UB has a high degree of commonality with licensed PACS to permit economical licensed/unlicensed terminals and common network services. The results of our simulation show that, at 1% to 2% blocking probability, 99% of downlink local-mean signal-to-noise plus interference ratio (SINR) values are above 17 dB for a 10 to 20 m port separation. For a three-dimensional office environment, the uplink limits the SINR performance, however, with uplink power control, a 5.5 to 7 dB improvement in the uplink SINR can be achieved even for high traffic load 相似文献
82.
Guangyong Li Ning Xi Mengmeng Yu Wai-Keung Fung 《Mechatronics, IEEE/ASME Transactions on》2004,9(2):358-365
Using atomic force microscopy (AFM) as a nanomanipulation tool has been discussed for more than a decade. However, its lack of real-time visual feedback during manipulation has hindered its wide application. Fortunately, this problem has been overcome by our recently developed augmented reality system. By locally updating the AFM image based on real-time force information during manipulation, not only can this new system provide real-time force feedback but also real-time visual feedback. The real-time visual display combined with the real-time force feedback provides an augmented reality environment, in which the operator not only can feel the interaction forces but also observe the real-time changes of the nano-environment. This augmented reality system capable of nanolithography and manipulation of nano-particles helps the operator to perform several operations without the need of a new image scan, which makes AFM-based nano-assembly feasible and applicable. 相似文献
83.
T. C. Fung 《International journal for numerical methods in engineering》2003,56(3):405-432
One of the important issues in the implementation of the differential quadrature method is the imposition of the given boundary conditions. There may be multiple boundary conditions involving higher‐order derivatives at the boundary points. The boundary conditions can be imposed by modifying the weighting coefficient matrices directly. However, the existing method is not robust and is known to have many limitations. In this paper, a systematic procedure is proposed to construct the modified weighting coefficient matrices to overcome these limitations. The given boundary conditions are imposed exactly. Furthermore, it is found that the numerical results depend only on those sampling grid points where the differential quadrature analogous equations of the governing differential equations are established. The other sampling grid points with no associated boundary conditions are not essential. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
84.
85.
86.
Z. L. Du Z. H. He P. C. W. Fung J. C. L. Chow T. F. Yu 《Journal of Materials Science》1995,30(4):964-969
Using the simplified version of the melt-textured growth (MTG) technology with a simple tube furnace, we have fabricated superconductors satisfying the nominal composition Bi1.6Pb0.4Sr2Ca2Cu3O11. We would note that the material used in the fabrication was prepared by mixing a precursor Bi1.6Pb0.4Sr2Cu3O
x
and CaO powder. This two step technique was found to be superior to the single step solid state reaction method after many trials. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) morphologies show that the melt-textured bulk samples are made up of stacks of highly textured single crystal-like layers. X-ray analysis as well as d.c. magnetization measurements were carried out and theJ
c value was found to be 1.3×103 A cm–2 at 77 K using the Bean model. At this stage, thoughJ
c is not so high as that of the best samples obtained from other complicated methods involving special (hot) pressing and sintering techniques, we do not need to apply any mechanical treatment at or after the heating procedure. 相似文献
87.
The paper studies the restoration of colour-quantised images. Restoration of colour-quantised images is rarely addressed in the literature, and direct applications of existing restoration techniques are generally inadequate to deal with this problem. The authors propose a POCS-based restoration algorithm specific to colour-quantised images, which makes a good use of the available colour palette to derive useful a priori information for restoration. The proposed restoration algorithm is shown to be capable of improving the quality of a colour-quantised image to a certain extent. 相似文献
88.
MA Nalesnik AS Rao H Furukawa S Pham A Zeevi JJ Fung G Klein HA Gritsch E Elder TL Whiteside TE Starzl 《Canadian Metallurgical Quarterly》1997,63(9):1200-1205
Lymphoreticular malignancies, collectively called posttransplant lymphoproliferative disorders (PTLD), eventually develop in 2-5% of organ transplant recipients. They frequently undergo regression when immunosuppression is reduced or stopped. This feature has been associated with a previous or de novo Epstein-Barr virus (EBV) infection. We herein describe immunotherapy with autologous lymphokine-activated killer (LAK) cells in seven patients with PTLD (four EBV-positive patients and three EBV-negative patients). Autologous peripheral blood mononuclear cells were obtained by leukapheresis, depleted of monocytes, and cultured in the presence of interleukin 2 for 10 to 11 days. A single dose of 5.2 x 10(9) to 5.6 x 10(10) LAK cells was given intravenously. Systemic interleukin 2 was not administered. The four patients with EBV+ PTLD had complete tumor regression; two of them developed controllable rejection. Three patients are well 13-16 months after treatment; the fourth patient died of pneumonia 41 days after infusion. Three patients with EBV- lymphomas had no response despite prior evidence that their tumors also were subject to immune surveillance. Two of these three patients died after being given other treatment, and the third patient has persistent tumor. In conclusion, autologous LAK cell infusion was effective for treatment of four EBV+ organ transplant recipients. LAK cell efficacy for three patients with EBV- PTLD was not evaluable under the management circumstances in which this treatment was utilized. 相似文献
89.
90.
Electrochemical experiments, including cyclic voltammetry (CV) experiments, galvanostatic experiments, potentiostatic experiments, and kinetic experiments of the LSM electrode, were used to investigate the influence of a deposit on the electrode surface on the electrophoresis of protons in a porous media during electrophoretic deposition (EPD). 相似文献