Loess in the Tian Shan and its implications for the development of the Gurbantunggut Desert and drying of northern Xinjiang

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.     

EMG信号的一种合成方法研究

利用改进了的肌电信号模型，完成了单纤维动作电位（ＳＰＡＰ）和运动单位动作电位（ＭＵＡＰ）的计算机模拟．以此为基础，结合肌肉组织的生理结构和肌电信号的产生原理，首先由多路ＳＰＡＰ信号经过符合生理特性的变换处理后，合成一路ＭＵＡＰ信号，然后考虑人体组织对肌电信号的衰减作用，对具有不同发放率的ＭＵＡＰ序列进行ＥＭＧ信号的合成．这种人工合成的ＥＭＧ信号有助于从理论上研究肌电信号的发放率和传导速度等特性，并将为肌电信号的分解给出一个合理标准．     

燃油炉火焰辐射的双色法实验研究

在双色法测试系统的标定和改善测量计算精度方面进行了有益的尝试， 验证了测试系统的良好线性，并利用自行装配的燃油炉和双色法测试系统对 燃油炉火焰温度和吸收系数进行了测量．结果表明，对火焰温度进行测量计 算时，在一定条件下可以忽略壁面反射和辐射的影响，而对单色辐射率、单色 吸收系数和碳粒浓度的测量则必须考虑它们的影响．     

关节水平的“共驱动”研究

本文以主动肌和拮抗肌的协同作用机理为依据,从表面肌电(EMG)信号的频率参数和肌肉平均传导速度两个方面,对近年来提出的正常人体神经肌肉系统控制的新理论——“共驱动”概念,在关节水平上进行了探讨和研究,实验结果表明:膝关节的主动肌和拮抗肌在持续恒力收缩下,其表面EMG信号功率谱的归一化中值频率随着时间的增加而同时下降;两路EMG信号的归一化中值频率之间的互相关系数随着收缩力的减小而减小,肘关节的肱二头肌不论是作为主动肌还是拮抗肌,在持续恒力收缩下,由表面EMG信号估计得到的肌肉的平均传导速度均随着收缩时间的增加而下降;肱二头肌作为拮抗肌时,平均传导速度明显高于其作为主动肌时的平均传导速度。     

Crystal structure of spinach major light-harvesting complex at 2.72 A resolution

The major light-harvesting complex of photosystem II (LHC-II) serves as the principal solar energy collector in the photosynthesis of green plants and presumably also functions in photoprotection under high-light conditions. Here we report the first X-ray structure of LHC-II in icosahedral proteoliposome assembly at atomic detail. One asymmetric unit of a large R32 unit cell contains ten LHC-II monomers. The 14 chlorophylls (Chl) in each monomer can be unambiguously distinguished as eight Chla and six Chlb molecules. Assignment of the orientation of the transition dipole moment of each chlorophyll has been achieved. All Chlb are located around the interface between adjacent monomers, and together with Chla they are the basis for efficient light harvesting. Four carotenoid-binding sites per monomer have been observed. The xanthophyll-cycle carotenoid at the monomer-monomer interface may be involved in the non-radiative dissipation of excessive energy, one of the photoprotective strategies that have evolved in plants.     

Broadband dispersion compensation using microstructure fibers

Beijing University of Posts and Telecommunications, Beijing 100876Dispersion and dispersion slope compensation of 10-Gb/s pulses using microstructure fibers (MFs) is demonstrated experimentally. A 26-m MF is used to compensate the dispersion of 2-km standard singe mode fiber in a 20-nm range in C band. The experimental results show that a significant improvement can be achieved in the quality of the observed pulses with the dispersion compensation. Moreover, the further research shows that the MF can compensate the anomalous dispersion of a single mode fiber within ±0.27 ps/(nm·km) over a 50-nm wavelength range from 1520 to 1570 nm.     

高效快速多种燃气组分色谱分析法

采用热导检测器，通过几种柱的组合．采用多维柱切换系统，并自动完成阀的驱动和信号切换，实现性质不同的人工煤气和液化石油气主要成分一次进样全自动分析，该方法操作简便、分离效果好、灵敏度高、结果准确可靠．     

基于高频信号注入的永磁电机转子位置估计方法中的电压输入

运用高频信号注入法估计永磁同步电机转子位置要求给电机同时施加基本电压和高频电压. 本文讨论了通过采用PWM调节的逆变器同时注入这两种电压的可行性,并进行了仿真研究. 结果表明,只要选择合适的调制信号和载波比就能够实现电压的叠加输入. 同时,对逆变器的非线性行为所带来的影响也作了深入的探讨,证明其仅在电流流过零处对输出结果产生影响. 根据这一特点,提出了相对比较简单的补偿措施,仿真结果证明了这一措施的正确性.     

Synthesis and properties of porous polyvinylamine microspheres from acrylonitrile

A novel route to synthesize crosslinked porous polyvinylamine (PVAm) microspheres from acrylonitrile (AN) was developed. In the first step, crosslinked porous polyacrylonitrile (PAN) spheres were prepared by copolymerization of AN and divinylbenzene (DVB). Then they were hydrolyzed to form polyacrylamide (PAM) spheres. And lastly, the porous PVAm spheres were successfully obtained via Hofmann degradation of PAM spheres. Scanning electron microscope (SEM) indicated that these PVAm microspheres have rough surfaces and porous interior structure. The pore size, the amino content, and the content of equilibrium water were also investigated. The pore size of these PVAm microspheres increased with the hydrolytic process. The contents of equilibrium water was changed from 49.6 to 96.5% depending on the different crosslinking degrees, and the amino contents were varied between 9.60 and 15.30 mmol/g depending on the different molar ratio of n(NaClO)/n(NaOH). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1674–1682, 2008     

α次积分C余弦算子函数的逼近定理

利用生成元预解式来刻画α次积分C余弦函数的Trotter-Kato逼近,给出α次积分余弦C函数的定义及基本性质,通过Laplace变换得到了α次积分C余弦函数逼近的4个等价条件,且当α为0 时即为经典的C余弦函数相应的逼近结果.