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951.
Current uplink power control algorithm of code division multiple access (CDMA) time division duplex(TDD) system contains signal-to-interference-ratio(SIR) and interference measurement, which is based on history information. However, the adjustment of transmission power of one user equipment(UE) will affect SIR of the others, because the power control is done independently of the power adjustment of other UE's. So the convergence speed of power control is not fast and the system performance degrades. In the proposed algorithm, all UE's assigned in same time slot adjust their transmission power based on current information, which takes into account the adjustments of transmission power of all UE's. The simulation results indicated that the proposed algorithm outperforms the old algorithm.  相似文献   
952.
H.Janka  谢懿 《世界科学》2002,(10):22-22,34
在宇宙的某个地方每一秒钟都会发生超新星爆发。即使它们的距离极为遥远,这一恒星灾变现象仍能为我们提供有关恒星形成的重要信息——其抛射出几个太阳质量的恒星碎片丰富了星际空间重元素和放射性元素的含量。 尽管超新星非常的明亮,但是超新星爆发的能量  相似文献   
953.
极低频磁场的生物学效应   总被引:5,自引:0,他引:5  
赵昆  黄康权 《自然杂志》2002,24(6):311-314
极低频磁场的生物学效应是当前国际上关注的研究热点 .本文介绍了极低频磁场生物学效应的物理原理及实验研究 ,并综述了极低频磁场对中枢神经的影响以及在临床上的应用 .  相似文献   
954.
在对中国和加拿大苔藓学者联合于中国东北最高的长白山采集的2千余份标本鉴定的基础上。认定有苔藓植物59科,152属,300种。报道了中国大陆新记录1属-小曲柄藓属(Campylostelium)。中国东北新记录2属-直蓑衣藓属(Macrocoma)和同叶藓属(Isopterygium)。中国东北新记录5种-褶叶裂叶苔(Lophozia incisa)。假狗牙藓(Cynodontium fallax)。细枝牛毛藓(Ditrichum gracile)。散叶牛毛藓(Ditrichum divarcatum)和细叶棉藓(Plagiothecium latebricola)。  相似文献   
955.
956.
957.
Eolian loess is widely distributed on the various geomorphic surfaces between 700–2400 m a.s.l. on the northern slope of the Tian Shan. It is formed in a synchronous manner with dust transported from the Gurbantunggut Desert in the Junggar Basin. The thickest section of loess was found in the Shawan and Shihezi regions. Paleomagnetic and climatic proxy analyses of over 71 m of a loess-paleosol sequence on the highest terrace of the Qingshui He (River) in the Shawan show that the paleomagnetic Bruhues/Matuyama (B/M) boundary lies at the bottom of paleosol S8, at a depth of 69.5 m, and the bottom of the sequence was estimated to be ∼0.8 Ma. This implies that the extremely dry climatic conditions in the Junggar Basin and the initial Gurbantunggut Desert were present at least by 0.8 Ma. High-resolution grain size series demonstrate that this area and desert expansion experienced two dramatic periods of desert expansions that occurred at ∼0.65 Ma and 0.5 Ma, respectively; and the subsequent continuous enhancement led to the environment presently observed. This tremendous environmental effect, caused by large-scale expansion of the desert and arid region of inner Asia, might be an important driving force for the global temperature drop that occurred in the mid-Pleistocene.  相似文献   
958.
By comparing PGE patterns of sulfide ores with that of basic-ultrabasic dikes occurring in the Dajing Cu-polymetallic deposit, we discover that there are similar positive slopes between the basic-ultrabasic dikes and the black ores composed mainly of sphalerite and galena, reflecting affinity of their source. The PGE patterns of the yellow ores composed basically of chalcopyrite, arsenopyrite and pyrite are actually different. One is close to the pattern of the mantle lherzolite, and others resemble the pattern of the basic rocks. However, the concentrations of Ru are higher in the yellow ores, reflecting that sulfur attains or approaches saturation in their parent magma. The PGE characteristics of ores and dikes show that the magmas derived from the deep of crust and the metallogenic elements were supplied mainly by growth material of the crust. In addition, the mantle-derived magma also offered some elements.  相似文献   
959.
Comprehensive field investigations and laboratory analyses show that palaeolakes, including fresh- mesohaline water Megalake Tengger and other semi-con- nected, isolated water bodies, during late Pleistocene covered an area of more than 20000 km2, which is more than half of the Tengger Desert in NW China. Stratigraphic correlation and chronological evidence indicate that before ca. 42000 aBP the area was more arid. The palaeolakes started to develop around 40000 uncal. 14C aBP but until 37000 14C aBP their scope was limited. High water levels established from 35000 14C aBP lasted until 22000 14CaBP. Lake levels regressed between 22000 and 20000 14C aBP but transgressed from 20000 to 18600 14C aBP. Subsequently, water level declined further and the Megalake Tengger finally desiccated at around 18000 14C aBP. Megalake Tengger possessed a fresh-mesohaline water property, implying that the regional precipitation increased significantly. During the period of Megalake Tengger, the climate was warmer-humid than present. The annual rainfall was 250 to 350 mm more than that of today and the temperature was 1.5 to 3.0℃ higher.  相似文献   
960.
Microbial desulfurization of fuel oil   总被引:2,自引:0,他引:2  
Culture conditions of desulfurization microbes were investigated with a bioreactor controlled by computer.Factors such as pH, choice of carbon source, optimal concentrations of carbon, nitrogen and sulfur sources were determined. The addition of carbon in a culture with a constant pH greatly improved the growth of Rhodococcus. Cells and cell debris from microbes rested using a sulfur- specific pathway were used to desulfurize diesel oil treated by hydrodesulfurization (acquired from the Research Institute of Fushun Petroleum with total sulfur level at 205 μg/mL).Strains 1awq, IG, X7B, ZT, ZCR, and a mixture of No. 5 and No. 6, were used in the biodesulfurization process. The reduction of total sulfur was between 10.6% and 90.3%.  相似文献   
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