基于最小可分辨对比度的CCD成像系统最佳角放大率研究

光电成像系统存在一个最佳角放大率,使人眼与成像系统达到最佳匹配状态,系统获得最佳性能.基于MRC物理意义,提出MRC信道宽度CCD成像系统综合性能评价方法,通过实际CCD成像系统的观察实验确定了评价模型的表达式,分析了各种系统参数变化对该方法的影响.结果表明,利用MRC信道宽度评价方法描述的最佳角放大率变化与实际情况一致.在最佳角放大率情况下,系统与人眼视觉得到最佳匹配.     

利用二次球形配位构筑亲水型隧道框架结构

质子化N,N,N’,N’-四苄基乙二胺可与[Fe(CN)6]3－, [SnCl6]2－和[TeCl6]2－二次球形配位分别形成可容纳客体分子的包结物晶体(1～3). 晶体1通过NH＋…NC－, NH＋…p(NC)和CH…p(NC)组合合成子, 构筑了亲水性层柱隧道结构, 孔径尺寸为1.03 nm×1.12 nm, 两个乙醇分子和两个水分子填充于隧道中; 晶体2通过CH…Cl－合成子, 构筑了亲水性层间隧道结构, 孔径尺寸为0.94 nm×0.73 nm, 三个水分子和两个氯离子填充于隧道中; 晶体3的结构与晶体2相似, 也是通过CH…Cl－合成子, 构筑了层间亲水性隧道结构, 孔径尺寸为0.94 nm×0.72 nm, 两个水分子填充于隧道中.     

Dynamic action of a tsunami wave traveling along a channel

The results of experiments, in which the propagation of a tsunami-type wave along rectangular channels with horizontal and inclined bottoms, are presented. Emphasis is placed on the mechanical action of the wave on a vertical wall. The force is shown to be appreciably dependent on the shape of the leading front of the wave. Experimental data are obtained for both smooth and breaking waves, as well as for waves in different stages of the wave-breaking process.     

Motion analysis of a diaphragmless driver section for a narrow channel shock tube

We set up a diaphragmless driver section as the first step towards developing a shock tube at microscale which has high experimental efficiency, independent of tube dimensions or the ratio of driver and driven pressure. The experiment described in this paper is performed by using our diaphragmless driver section. We measured the operating time and the velocity of the fast opening valve. Additionally we have introduced and calculated the differential equation, by using the Runge–Kutta–Gill method, to understand the motion of the fast opening valve. We achieved good agreement between experimental and calculated results for the velocity. We can conclude that the diaphragmless driver section is highly suitable for a narrow channel shock tube.      

On the Non-Adaptive Zero-Error Capacity of the Discrete Memoryless Two-Way Channel

We study the problem of communicating over a discrete memoryless two-way channel using non-adaptive schemes, under a zero probability of error criterion. We derive single-letter inner and outer bounds for the zero-error capacity region, based on random coding, linear programming, linear codes, and the asymptotic spectrum of graphs. Among others, we provide a single-letter outer bound based on a combination of Shannon’s vanishing-error capacity region and a two-way analogue of the linear programming bound for point-to-point channels, which, in contrast to the one-way case, is generally better than both. Moreover, we establish an outer bound for the zero-error capacity region of a two-way channel via the asymptotic spectrum of graphs, and show that this bound can be achieved in certain cases.     

Synthesis of polymethacrylate derivatives having sulfated maltoheptaose side chains with anti‐HIV activities

Anti‐HIV (human immunodeficiency virus) active polymethacrylates having pendant sulfated oligosaccharides were synthesized, and the relationship between structures and biological activities of the polymethacrylates was examined. Acetylated 1‐O‐methacryloyl maltoheptaoside (MA‐AcM7) was polymerized with AIBN as an initiator to give polymethacrylates having a pendant acetylated maltoheptaose in every repeating unit, poly(MA‐AcM7)s. After hydroxyl groups were recovered by deacetylation, the polymethacrylates having maltoheptaose units, poly(MA‐M7)s, were sulfated to give polymethacrylates having sulfated maltoheptaose side‐chains, poly(MA‐SM7)s, with degrees of sulfation of 1.1 to 2.7 (maximum, 3.0). These polymethacrylates including sulfated oligosaccharides exhibited low anti‐HIV activities represented by the 50% protecting concentration (EC₅₀) in the range of 15–62 μg/mL and low blood anticoagulant activities around 10 unit/mg (standard dextran sulfate, 22.7 unit/mg). The anti‐HIV activity increased with increasing degree of sulfation to reach EC₅₀ of 15–16 μg/mL. In addition, copolymerization of MA‐AcM7 with methyl methacrylate (MMA) and subsequent sulfation gave polymethacrylates consisting of various proportions of highly sulfated maltoheptaose and MMA units. It was revealed that the anti‐HIV activity increased with decreasing proportion of the sulfated oligosaccharide moiety and that a copolymethacrylate having 22 mol % of sulfated maltoheptaose units (DS = 3.0) had a high anti‐HIV activity in the EC₅₀ of 0.3 μg/mL. The blood anticoagulant activity increased slightly from 9 to 18 unit/mg with decreasing proportion of the sulfated maltoheptaose units. These results suggested that the biological activities were influenced strongly by the spatial distance between sulfated oligosaccharide substituents in the polymethacrylate main chain. Distinction and conformation of the oligosaccharide side chains also played an important role. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 789–800, 1999     

Synthesis and characterization of fully rodlike poly(4,4′‐biphenylene pyromellitimide)s with various short side groups

Fully rodlike poly(4,4‐biphenylene pyromellitimide) (PMDA–BZ) is so brittle in spite of its extremely high modulus. In this study, the brittleness was attempted to be improved without a significant sacrifice of the high modulus by incorporating short side groups. For this, benzidine monomers, which contain methyl, methoxy, fluoro, and trifluoromethyl at the 2,2′‐positions, were synthesized and then used for polycondensation reactions with pyromellitic dianhydride in N‐methyl‐2‐pyrrolidone, producing soluble poly(amic acids)s. The synthesized poly(amic acid)s were converted to the fully rodlike polyimides in films by a conventional spin‐coating on substrates, soft bake, and thermal imidization. The brittleness of PMDA–BZ was successfully healed with a small portion of sacrifice in the modulus by incorporating methyl, methoxy, and trifluoromethyl groups but could not be healed by the fluoro side group. The improvement in the brittleness might be contributed from the chain mobility and lateral chain packing order enhanced by the incorporation of the side groups, which are evident on the measured structures and properties. The structure and other properties were detected to be influenced by the incorporated side groups. The detailed structures and properties were interpreted by considering roles of side groups and the correlation between structure and properties, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 937–957, 1999     

Compact finite difference schemes on non‐uniform meshes. Application to direct numerical simulations of compressible flows

In this paper, the development of a fourth‐ (respectively third‐) order compact scheme for the approximation of first (respectively second) derivatives on non‐uniform meshes is studied. A full inclusion of metrics in the coefficients of the compact scheme is proposed, instead of methods using Jacobian transformation. In the second part, an analysis of the numerical scheme is presented. A numerical analysis of truncation errors, a Fourier analysis completed by stability calculations in terms of both semi‐ and fully discrete eigenvalue problems are presented. In those eigenvalue problems, the pure convection equation for the first derivative, and the pure diffusion equation for the second derivative are considered. The last part of this paper is dedicated to an application of the numerical method to the simulation of a compressible flow requiring variable mesh size: the direct numerical simulation of compressible turbulent channel flow. Present results are compared with both experimental and other numerical (DNS) data in the literature. The effects of compressibility and acoustic waves on the turbulent flow structure are discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Explicit finite volume non‐oscillatory schemes for 2D transient free‐surface flows

A class of high‐resolution non‐oscillatory shock‐capturing Roe, TVD and ENO explicit schemes in finite volume approach are presented for the computation of 2D unsteady rapidly varied open channel flows. In order to apply these schemes to simulate the hydraulic phenomena in field, the Strang‐type operator splitting technique is adopted to treat the flow with bottom slope and friction terms. Verifications of the proposed schemes are made by comparison with analytical solutions or experimental data, and very good agreements are obtained. To illustrate the efficiency and stability of the present algorithms, four typical problems of rapidly varied flows are solved and the results of different schemes are compared. It is demonstrated that the proposed method is accurate, robust and highly stable even in the flows with very strong discontinuites, which need no tuning of any adjustable parameter, such as artificial viscosity coefficient, as other methods do, and is a reliable mathematical modeling for 2D practical hydraulic engineering applications. Copyright © 1999 John Wiley & Sons, Ltd.     

Pt/Al2O3整体催化剂上选择性氧化脱除甲醇重整氢源中CO --副反应对CO脱除效果的影响分析

移动甲醇重整制氢是质子交换膜燃料电池（PEMFC）可行的供氢方式之一,包括水蒸气重整、部分氧化重整和自热重整。甲醇重整制氢方法不同,重整气体积组成在H245％～75％,CO215％～25％,CO1％～10％,H2O10％～20％和N20—20％变化。重整气进入PEMFC之前要经过CO水蒸气变换反应（如果采用水蒸气重整,不需要变换过程）,