玛纳斯河流域民主参与式的水资源统一管理

本文针对玛纳斯河流域水资源管理存在逐利、水资源被分割管理,以及缺乏民主参与等问题,提出流域实行水资源统一管理,成立利益相关者参与的民主管理监督机构.     

抓住竞赛契机 深化计算机专业教学改革

各种计算机类竞赛对高校计算机专业的教学改革起到了积极的促进作用,本文倡导抓住竞赛契机,引导和深化计算机专业教育教学改革,并对教学模式的改革、新课程体系的制定和强化教师队伍的建设提出了具体举措.     

Metal-insulator transition in chains with correlated disorder

According to Bloch's theorem, electronic wavefunctions in perfectly ordered crystals are extended, which implies that the probability of finding an electron is the same over the entire crystal. Such extended states can lead to metallic behaviour. But when disorder is introduced in the crystal, electron states can become localized, and the system can undergo a metal-insulator transition (also known as an Anderson transition). Here we theoretically investigate the effect on the physical properties of the electron wavefunctions of introducing long-range correlations in the disorder in one-dimensional binary solids, and find a correlation-induced metal-insulator transition. We perform numerical simulations using a one-dimensional tight-binding model, and find a threshold value for the exponent characterizing the long-range correlations of the system. Above this threshold, and in the thermodynamic limit, the system behaves as a conductor within a broad energy band; below threshold, the system behaves as an insulator. We discuss the possible relevance of this result for electronic transport in DNA, which displays long-range correlations and has recently been reported to be a one-dimensional disordered conductor.     

The appearance of single-ion channels in unmodified lipid bilayer membranes at the phase transition temperature

Ion-specific channels in artificial membranes have been formed by the addition of gramicidin A, alamethicin, polyene antibiotics and some proteins to the solution surrounding the bilayer lipid membrane. Until now there have been no reports of single-ion channels in unmodified lipid membranes. We have now studied the electrical conductance of planar lipid bilayers membranes made of synthetic distearoylphosphorylcholine (DSPC). Current fluctuations of amplitude approximately 1pA and duration approximately 1 s have been discovered at phase transition temperature, which shows that the appearance of ionic channels may be the result of lipid domain interactions. This would explain the dramatic increase in ion permeability observed in liposomes during phase transition. We suggest that these channels could conduct the transmembrane ionic current in biological membranes without the involvement of peptides and proteins.     

富锗面包的研制

富锗面包是以面包专用粉为主要原料,以白砂糖、奶油、奶粉、鸡蛋、面包改良剂为辅料,加入富锗酵母,采取快速发酵法,经过调粉、发酵、烘烤精制而成。通过正交实验确定产品的最佳配方,利用ICP-AES方法测定富锗面包中有机锗的含量。     

基于角色和任务的工作流访问控制管理模型

针对现有访问控制模型在工作流系统安全方面存在的不足,提出一种基于角色和任务的工作流访问控制管理模型(ATRBAC).该模型将ARBAC模型中的管理思想融入TRBAC模型,并引入管理员及管理权限,同时对管理员实行层次管理,解决了系统管理员的权限过大而产生的隐患,加强了系统的安全性.     

基于TrustZone的嵌入式系统安全性研究

嵌入式系统安全性的研究逐渐成为网络安全领域的一个重要课题。对基于TrustZone技术的嵌入式系统的安全性进行了研究,介绍了嵌入式安全操作系统、可信计算、CPU特权体系结构以及TrustZone技术。研究表明,基于可信硬件和安全操作系统的嵌入式系统安全体系,是解决嵌入式系统安全问题的可行方案。胡：2011一06—08     

MARSIS radar sounder evidence of buried basins in the northern lowlands of Mars

A hemispheric dichotomy on Mars is marked by the sharp contrast between the sparsely cratered northern lowland plains and the heavily cratered southern highlands. Mechanisms proposed to remove ancient crust or form younger lowland crust include one or more giant impacts, subcrustal transport by mantle convection, the generation of thinner crust by plate tectonics, and mantle overturn following solidification of an early magma ocean. The age of the northern lowland crust is a significant constraint on these models. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument on the European Space Agency's Mars Express spacecraft is providing new constraints on the martian subsurface. Here we show evidence of buried impact basins ranging in diameter from about 130 km to 470 km found over approximately 14 per cent of the northern lowlands. The number of detected buried basins >200 km in diameter indicates that the lowland crust is ancient, dating back to the Early Noachian epoch. This crater density is a lower limit because of the likelihood that not all buried basins in the area surveyed by MARSIS have been detected. An Early Noachian age for the lowland crust has been previously suggested on the basis of a large number of quasi-circular topographic depressions interpreted to be evidence of buried basins. Only a few of these depressions in the area surveyed by MARSIS, however, correlate with the detected subsurface echoes. On the basis of the MARSIS data, we conclude that the northern lowland crust is at least as old as the oldest exposed highland crust. This suggests that the crustal dichotomy formed early in the geologic evolution of Mars.     

固体激光器的快速电光Q开关驱动电路的实验研究

比较了三种不同的电光调Q驱动电路。电子管式调Q电路工作稳定,退压沿70ns左右,但空间体积大,激光脉冲能量较低;雪崩管串联武调Q电路退压时间大约为20ns,输出激光脉冲能量高,脉宽窄;MOSFET管串联调Q电路,简单可靠,单管耐压高,退压时间为50ns。