含纳米Co的新型PDC复合片性能试验研究

提出了用纳米钴代替微米钴作为粘结剂的PDC复合片制备新方法及配套的制备新工艺,并对新型PDC复合片的微观组织结构及性能进行了研究。微观分析结果表明,纳米钴较于微米钴更密实地填充在金刚石颗粒间,有效促进了金刚石颗粒间D-D键的形成,且添加纳米钴的金刚石层对金刚石颗粒的把持力更好,同时纳米钴在金刚石层中形态较小且分布均匀,这些均对提高复合片综合性能有积极作用。性能测试结果表明,相对于传统复合片,新型复合片抗冲击性能提高了1.13倍,其耐磨性和热稳定性也得到了一定的提高,这与微观分析的结论一致。研究成果不仅为提升复合片综合性能提供了新思路,也对实现钻井提速增效、提高PDC钻头使用寿命有重要意义。     

移液器建标报告中不确定度的评定

移液器主要用于环保、医药、食品卫生等科研部门,在生化分析及化验中做液体的取样或加液用,因此移液器的容量误差检定至关重要,同时有利于保证企事业、科研单位生产、检验、研究工作的顺利准确进行,有利于经济发展,具有重要社会意义及巨大经济效益,本文介绍了不同量程范围的移液器在建标报告中的不确定度评定。     

Crystallization‐Induced Emission Enhancement of a Deep‐Blue Luminescence Material with Tunable Mechano‐ and Thermochromism

Organic luminescent materials with the ability to reversibly switch the luminescence when subjected to external stimuli have attracted considerable interest in recent years. However, the examples of luminescent materials that exhibit multiresponsive properties are rarely reported. In this work, a new stimuli‐responsive dye P1 is designed and synthesized with two identical chromophores of naphthalimide, one at each side of an amidoamine‐based spacer. This amide‐rich molecule offers many possibilities for forming intra‐ and intermolecular hydrogen bond interactions. Particularly, P1 has an intrinsic property of cocrystallizing with methanol. Compared with the pristine P1 sample, the as‐prepared two‐component cocrystalline material displays an exceptive deep‐blue emission, which is extremely rare among naphthalimide‐based molecules in the solid state. Furthermore, the target material exhibits an obvious mechanochromic fluorescent behavior and a large spectral shift under force stimuli. On the other hand, the cocrystalline material shows an unusual “turn off” thermochromic luminescence accompanied by solvent evaporation. Moreover, using external stimuli to reversibly manipulate fluorescent quantum yields is rarely reported to date. The results demonstrate the feasibility of a new design strategy for solid‐state luminescence switching materials: the incorporation of solvents into organic compounds by cocrystallization to obtain a crystalline state luminescence system.     

Retracted: Dual Effects of Nanostructuring and Oxygen Vacancy on Photoelectrochemical Water Oxidation Activity of Superstructured and Defective Hematite Nanorods

An Ar atmospheric treatment is rationally used to etch and activate hematite nanoflakes (NFs) as photoanodes toward enhanced photoelectrochemical water oxidation. The formation of a highly ordered hematite nanorods (NRs) array containing a high density of oxygen vacancy is successfully prepared through in situ reduction of NFs in Ar atmosphere. Furthermore, a hematite (104) plane and an iron suboxide layer at the absorber/back‐contact interface are formed. The material defects produced by a thermal oxidation method can be critical for the morphology transformation from 2D NFs to 1D NRs. The resulting hematite NR photoanodes show high efficiency toward solar water splitting with improved light harvesting capabilities, leading to an enhanced photoresponse due to the artificially formed oxygen vacancies.     

讲好离散数学的第一次课

离散数学是计算机专业的核心基础课,文章针对离散数学内容散、概念多且容易被认为枯燥无味等特点,结合笔者多年的教学经验,分析并提出通过讲好离散数学第一次课提高教学效果的方法,该方法包含笔者总结的离散数学的重要性、离散数学的学习方法和经过加工的教学内容。实践表明该方法效果较好,对青年教师有一定的指导作用。     

Fault tolerant control for singular systems with actuator saturation and nonlinear perturbation

In this paper, the problem of robust fault tolerant control for a class of singular systems subject to both time-varying state-dependent nonlinear perturbation and actuator saturation is investigated. A sufficient condition for the existence of a fixed-gain controller is first proposed which guarantees the regularity, impulse-free and stability of the closed-loop system under all possible faults. An optimization problem with LMI constraints is formulated to determine the largest contractively invariant ellipsoid. An adaptive fault tolerant controller is then developed to compensate for the failure effects on the system by estimating the fault and updating the design parameter matrices online. Both of these two controllers are in the form of a saturation avoidance feedback with the advantage of relatively small actuator capacities compared with the high gain counterpart. An example is included to illustrate the proposed procedures and their effectiveness.     

Modeling MODIS LAI time series using three statistical methods

Leaf Area Index (LAI) is one of the most important variables characterizing land surface vegetation and dynamics. Many satellite data, such as the Moderate Resolution Imaging Spectroradiometer (MODIS), have been used to generate LAI products. It is important to characterize their spatial and temporal variations by developing mathematical models from these products. In this study, we aim to model MODIS LAI time series and further predict its future values by decomposing the LAI time series of each pixel into several components: trend, intra-annual variations, seasonal cycle, and stochastic stationary or irregular parts. Three such models that can characterize the non-stationary time series data and predict the future values are explored, including Dynamic Harmonics Regression (DHR), STL (Seasonal-Trend Decomposition Procedure based on Loess), and Seasonal ARIMA (AutoRegressive Intergrated Moving Average) (SARIMA). The preliminary results using six years (2001-2006) of the MODIS LAI product indicate that all these methods are effective to model LAI time series and predict 2007 LAI values reasonably well. The SARIMA model gives the best prediction, DHR produces the smoothest curve, and STL is more sensitive to noise in the data. These methods work best for land cover types with pronounced seasonal variations.     

Stability and stabilization of Boolean networks

The stability of Boolean networks and the stabilization of Boolean control networks are investigated. Using semi‐tensor product of matrices and the matrix expression of logic, the dynamics of a Boolean (control) network can be converted to a discrete time linear (bilinear) dynamics, called the algebraic form of the Boolean (control) network. Then the stability can be revealed by analyzing the transition matrix of the corresponding discrete time system. Main results consist of two parts: (i) Using logic coordinate transformation, the known sufficient condition based on incidence matrix has been improved. It can also be used in stabilizer design. (ii) Based on algebraic form, necessary and sufficient conditions for stability and stabilization, respectively, are obtained. Copyright © 2010 John Wiley & Sons, Ltd.     

动态ERP系统中Ajax/SOA系统架构模型的构造

为了指导动态ERP系统的开发,引入Ajax的客户端,与基于SOA的服务器端之间相配合和协调,既继承了轻量级客户端/服务器端的应用优势,又满足企业的需求变化,是一种可伸缩的和易扩展的Web应用程序实现方式。依据Client/Server-Brow-ser/Server-Ajax/SOA的思路,从物理视角和逻辑视角构造一个融合Ajax技术的SOA系统架构模型,并给出模型的实现策略以及Ajax技术在其中的应用,完善了动态ERP系统的设计机制。     

一种结合Cat映射和Henon映射的图像加密技术

利用经典的Arnold cat映射通过迭代虽然可以改变图像各像素点的位置,达到加密的目的,但由于Arnold cat映射具有周期性的特点,经过一定次数的迭代后可以恢复原始图像,给系统带来了一定的安全隐患.把经过Arnold cat映射置乱的图像注入Henon映射的混沌系统中,在位置置乱的基础上再进行像素值置乱,充分打乱图像的像素相关性,有效地避免了这一缺点.仿真结果表明,该算法可以达到较好的加密效果,并且具有较强的抗攻击性能.