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61.
Do multiple cycles of aeolian deposit-pedogenesis exist in the reticulate red clay sections in southern China? 总被引:4,自引:0,他引:4
HU Xuefeng CHENG Tianfan & WU Hexin Department of Environmental Science Engineering Shanghai Uni-versity Shanghai China Correspondence should be addressed to Hu Xuefeng 《科学通报(英文版)》2003,48(12):1251-1258
Since the Quaternary scientists successfully dis-closed the paleoclimatic significance of the loess-paleo- sol sequence in the Loess Plateau, Northwest China, the loess-paleosol sequence has become well-known terres-trial materials revealing the multiple cyclic changes of Quaternary climates. As a carrier of paleoenvironmental information, it could compare beauty with the deep ocean deposit[8]. In recent years, however, the researchers began to put their sights to southern China. They try t… 相似文献
62.
The age of formation of the mirabilite and sand wedges in the Hexi Corridor and their paleoclimatic interpretation 总被引:7,自引:0,他引:7
WANG Nai''''ang ZHANG Jianming CHENG Hongyi GUO Jianying & ZHAO Qiang . College of Earth Environment Sciences Lanzhou University Lanzhou China . Cold Arid Regions Environmental Engineering Research Institute Chinese Academy of Sciences Lanzhou China 《科学通报(英文版)》2003,48(14):1439-1445
The Hexi Corridor is located at the transition zone of the Asian summer monsoon and westerly airflow, and lies in an important position in terms of its ecological fragility and climatic sensitivity. During a recent field expedition to this region, we found a sedimentary mirabilite layer in a number of localities including Suwushan, Yanchi, Baitujing, Yanchi Gaotai, Huahai, Yumen, Halanuo扙r, and Dunhuang (Fig. 1), which have the potential to provide important information about environmenta… 相似文献
63.
YANGBao A.Braeuning SHIYafeng ZHANGJiawu 《科学通报(英文版)》2003,48(14):1446-1450
The paleoclimate data recovered from ice cores,tree rings and lake sediments indicate regional features of cfimatic change on the Tibeta n Plateau (TP) during the last 2000 years. The composite temperature reconstructions in-dicate that several main climatic episodes, such as the “LittleIce Age“ between 1400 and 1900, the “Medieval Warm Pe-riod“ in 1150-1400, a less warm period in 800-1100, and an earlier cold period between the 3rd and 5th centuries,occurred in the TP. In addition, temperature varied from region to region. The period from AD 800 to 1100, which waswarm in northeastern TP, was contemporaneous with cool-ing in the western and southern TP. The southern TP ex-perienced warming between 1150 and 1400. For western TP,the δ^18O records of the Guliya ice core indicate that the pe-Hod 1250-1500 witnessed a clear warming. Large-scaletrends in the temperature history from northeastern TP aremore similar to those in eastern China than are the trendsfrom the Guliya ice cap far to the west and southern TP. The most prominent similarities between the temperature varia-tions of the TP and eastern China are such cold phases as 1100-1150, 1500-1550, 1650-1700 and 1800-1850, andthe latter three cold events match with three widespreadg lacial advances which occurred on the TP during the Little Ice A2e. 相似文献
64.
WUGuang ZHOUChunyuan ZENGHeping 《科学通报(英文版)》2003,48(16):1704-1708
We introduce a stable, long-distance singlephoton Sagnac interferometer, which has a balanced configuration to efficiently compensate phase drift caused by change of the fiber-optic path. By using time-division phase modulation, single-photon interference was realized at 1550nm in a 5-km-long as well as 27-km-long Sagnac fiber loops,with a fringe visibility higher than 90% and long-term stability. The stable performance of the single-photon interference indicated that the time-division phase-modulated Sagnac interferometer might readily lead to practical applications in single-photon routing and quantum cryptography. 相似文献
65.
66.
微孔草种子化学成分的研究 总被引:2,自引:0,他引:2
从微孔草 (MicroulasikkimenisHemsl)种子中首次分离出 8个已知化合物 :β 谷甾醇 (1)、羽扇豆醇 (2 )、白桦脂醇 (3 )、豆甾 4 烯 3 酮 (4)、豆甾 4 烯 3 二酮 (5 )、羟基豆甾 4 烯 3酮 (6)、诺米林 (7)、如忒文 (8) .报道了这8个化合物的分离纯化和结构鉴定 相似文献
67.
针对现代防空作战特点,对区域防空体系的目标优化分配问题进行了研究,改进了目标优化分配的基本模型,并使用动态规划方法建立了相应的决策模型,给出了求解的步骤和应用实例,结果表明,对于小规模目标的问题,其计算简单,且容易取得全局最优解。 相似文献
68.
添加剂对电解锰矿石中锰浸出率的影响 总被引:4,自引:0,他引:4
研究了几种无机和有机添加剂对电解金属锰矿石(主要是菱锰矿)中锰的浸出率的影响.实验结果表明,葡萄糖、蔗糖等有机添加剂在常规时间里,可使锰的浸出率达到85%以上,是实际工业生产中可取的添加剂;浓硫酸虽也可提高浸出率,但由于具有强腐蚀性而不宜采用. 相似文献
69.
Ni/α—Al2O3上CH4/CO2重整制取合成气的研究 总被引:2,自引:0,他引:2
本文采用固定床流动反应装置对Ni/α-Al2O3上甲烷二氧化碳重整制合成气的反应进行了研究,在一定CH4/CO2配比下,考察了镍负载量、助剂及助剂添加量对催化活性和积炭量的影响。 相似文献
70.
用几何最小二乘法改进 ITD 法的阻尼识别精度 总被引:2,自引:0,他引:2
ITD(IbrahimTimeDomain)模态识别方法可不用输入系统的信息就识别系统的模态参数,但识别的模态参数常常很不精确,且阻尼比的识别精度很差。当激励信号不是独立白噪声信号时,不应该采用ITD法进行模态识别。推导了ITD法识别的模态频率和阻尼比的相对误差公式,由此分析了造成阻尼比识别结果很差的原因,并且引入了I-brahim提出的双最小二乘算法(DLS),在此基础上,提出了几何最小二乘法(GLS)。通过理论推导和算例验证得到:一般情况下,GLS和DLS算法均可提高阻尼比的识别精度,且前者的识别结果优于后者。 相似文献