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991.
Caire G. Biglieri E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1995,41(5):1246-1256
The main building block for the construction of a geometrically uniform coded modulation scheme is a subgroup of GI, where G is a group generating a low-dimensional signal constellation and I is an index set. In this paper we study the properties of these subgroups when G is cyclic. We exploit the fact that any cyclic group of q elements is isomorphic to the additive group of Zq (the ring of integers modulo q) so that we can make use of concepts related to linearity. Our attention is focused mainly on indecomposable cyclic groups (i.e., of prime power order), since they are the elementary “building blocks” of any abelian group. In analogy with the usual construction of linear codes over fields, we define a generator matrix and a parity check matrix. Trellis construction and bounds on the minimum Euclidean distance are also investigated. Some examples of coded modulation schemes based on this theory are also exhibited, and their performance evaluated 相似文献
992.
A model is developed to investigate starfish and coral dynamics at the macro-scale of the whole Great Barrier Reef. This stochastic near-equilibrium theory is consistent with all available data for the mean rates of change of reef-state relative to abundances of the starfishAcanthaster planci and the scleractinian corals upon which it preys. This result is in striking contrast to the stably cyclic behaviour which dominates the meso-scale of individual reefs as reported previously by the authors. For the first time, a number of important numerical estimates have been made and are reported here. Generally, the starfish dynamics is dominated by randomness, being indistinguishable from Brownian motion in the state-space. On the other hand, the coral process is embedded in a drift field which is always directed towards the low coral state. In fact, the high coral state is inaccessible on the Great Barrier Reef. 相似文献
993.
An analysis of a wide rectangular radiating slot excited by a microstrip line is described. Coupled integral equations are formulated to find the electric current distribution on the feed line and the electric field in the aperture. The solution is based on the method of moments and using the space domain Sommerfeld-type Green's function. The information about the input impedance or reflection coefficient is extracted from the electric current distribution on the microstrip line utilizing the matrix pencil technique. The theoretical analysis is described and data are presented and compared with other theoretical and experimental results 相似文献
994.
995.
J Lorenz K Wilhelm M Kessler C Peschel U Schwulera R Lissner WG Struff E Huland C Huber WE Aulitzky 《Canadian Metallurgical Quarterly》1996,2(7):1115-1122
Safety, local and systemic immunomodulation, and tumor response to treatment with aerosolized natural interleukin 2 (nIL-2) applied five times a day were studied in a Phase I trial in 16 patients with pulmonary malignancies refractory to conventional therapy. The toxicity of inhaled nIL-2 was different from that observed after systemic administration. Reversible airway irritation causing a nonproductive cough represented the dose-limiting toxicity. Mild to moderate reduction of the vital capacity and forced expiratory volume (FEV1) with minor effects on relative FEV1, peak expiratory flow, airway resistance, and PaO2 was experienced by individual patients. In 14 patients suffering from pulmonary metastases due to renal cell cancer, one durable complete response, one partial response, and one mixed response were observed. Inhalation of nIL-2 aerosol resulted in a dose-dependent expansion of pulmonary immunocompetent cells in bronchoalveolar lavage fluid. Posttreatment bronchoalveolar lavage showed an activated lymphocyte phenotype with increased HLA-DR expression. The only systemic biological effect detectable in peripheral blood was a marked increase of soluble interleukin 2 receptor serum levels. We conclude that treatment with aerosolized nIL-2 is an effective means for site-specific immunomodulation and deserves further investigation for the treatment of malignant and inflammatory lung disease. 相似文献
996.
997.
A laser pumped zig-zag dye laser operating at 568 nm with a pulse length ~2 μs has been sealed to high power using a MOPA configuration. Pulse energies in excess of 7 J with beam quality <2 XDL have been achieved under repetitively pulsed, 10 Hz operation. RMS jitter was measured as 0.12 of a 1 XDL spot. The device has operated with over 70 W output for runs up to 5 s. Substantially longer run times and output powers are possible. This device represents an advance in dye laser capabilities. Improvement in pointing accuracy of better than an order of magnitude have been demonstrated. In addition, an improvement in beam quality by about an order of magnitude has been achieved compared to other dye lasers operating in this power range 相似文献
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