陶瓷微球增强铝基复合材料

介绍一种以铝土矿陶瓷微球增强的铝基复合材料，具有价格低、增强物与基体合金润湿性好、界面反应几乎不存在等优点。又因其增强物为微球，有利于减小应力集中，延缓裂纹萌生与扩展，同时也提高了铸造流动性和塑性成形能力。讨论了其制造工艺、有关特性和问题。     

基于遗传算法的落差指数法参数优选

利用遗传算法的全局寻优能力，对落差指数法中的参数进行优化，通过实例分析表明，这种方法是可行的，且能弥补传统作法中的不足，值得推广。     

Compomer的摩擦磨损特性

采用Compoglass，F2000，Elan，Dyract AP4种牙科用复合体材料(Compomer)，对其玻璃颗粒含量和表面硬度进行了测量，并在球一盘往复摩擦磨损试验机上考察了它们的摩擦磨损特性。结果表明：F2000的摩擦系数最高，Elan的摩擦系数次之，Compoglass和DyractAP的摩擦系数分别为第三和第四．摩擦系数随玻璃颗粒含量的增加而增加．在同样试验条件下，低摩擦系数的DyractAP和Compoglass与高摩擦系数的F2000和Elan相比具有较好的耐磨性．磨损机理主要表现为由玻璃颗粒脆性断裂引起的玻璃颗粒脱落和磨粒磨损。     

A review of modeling approaches for oriented semi-crystalline polymers

Modeling changes in the physical properties of oriented semi-crystalline polymer films is beneficial for understanding the fundamentals associated with structure property relationships and could be used for developing new polymer films with significantly enhanced physical properties. Relating the molecular changes observed in oriented polymer films to inherent polymer characteristics provides valuable insight for the development of new polymers which exhibit enhanced physical properties upon orientation. Modeling efforts will be reviewed that have attempted to use fiber composite theory to explain the transitions seen during the orientation process.     

Surface Actuation of Lightweight Mirrors with Shape Memory Alloy

The ability to create lightweight mirrors that can maintain surface accuracy is a major technical challenge for future space telescopes. Processing-induced errors and surface errors due to temperature excursions and gravity sag (zero gravity in space) make it impossible to correct the surface of thin mirror face-sheets by conventional point actuators. The challenges are compounded by the requirements for mirrors to have adequate stiffness for pointing accuracy. An experimental and analytical study was conducted to explore the feasibility of correcting the shape of lightweight (≈1 kg/m2) mirrors using a “Nitinol” (nickel-titanium) shape memory alloy (SMA). Shape memory alloys are increasingly used as smart devices in aerospace applications. Their primary advantage over other smart materials (i.e., piezo-ceramics and piezo-polymers) is in their ability to undergo large strains and displacements and thus enable the development of smart mechanisms. Active shape correction is the only means of mitigating heat and zero-gravity-induced distortions in space-based optical imaging systems. The repeatability and reliability of a possible actuation system based on properties of the SMA wires were studied by testing the stress-strain and stress recovery behavior under controlled conditions. Embedded SMA wires were then used to actuate a composite beam, and the movement induced by actuation was monitored with the Moiré interferometry method.     

Sensitivity of spectral reflectance to variation in live fuel moisture content at leaf and canopy level

Wildland fires burn large areas of the earth's land surface annually, causing significant environmental damage and danger to human health. In order to mitigate the effects, and to better manage the incidence of such fires, fire behaviour models are used to predict, among other things, the likelihood of ignition, the rate of spread, and the intensity and duration of burning. A key input parameter to these models is the amount of water in the vegetation, described as the fuel moisture content (FMC). A number of studies have shown that vegetation indices (VI) calculated from red and NIR reflectances may be used to map spatial and temporal variation in FMC in a range of fire-prone environments, with varying degrees of success. Strong empirical relationships may be established between VI and FMC over grasslands, yet over shrublands and forests, the relationships are weaker. If FMC is to be estimated with greater accuracy and consistency than is currently achieved, it is necessary to fully understand the relative contribution that spatial and temporal variation in the various biophysical and geometrical variables make to reflectance variability at the leaf and canopy level.This paper uses a modelling approach to investigate the sensitivity of reflectance data at leaf and canopy level to variation in the biophysical variables that are used to compute FMC. At the leaf level, the results show that the sensitivity of reflectance to variation in leaf water and dry matter content, used to compute FMC, is greatest in the SWIR and NIR, respectively. Variation in FMC has no effect in the visible wavelengths. At the canopy level, the results show that the sensitivity of reflectance to variation in leaf water and dry matter content is heavily dependent upon the type of model used and the range of variation over which the variables are tested. In the longer wavelengths of the SWIR, the competing influence of variable leaf area index, fractional vegetation cover, and solar zenith angle is shown to be greater than that at the shorter wavelengths of the SWIR and NIR. Empirical relationships between the normalised difference water index (NDWI) and FMC are shown to be weaker than that with canopy water content. However, when the range of the variables under study is more limited, useful empirical relationships between FMC and remotely sensed VI may be established.     

菜地土壤评价中参评因素的选定与分级指标的划分

菜地选片规划应通过土壤详查和评价工作,选出最适地区,才能经济有效、持续发展。土壤评价中参评因素的选定与分级指标的划分是工作的核心。应选取对蔬菜的生长发育和生产力具有重大影响的、稳定性较高的限制因素,并以土壤属性为主,结合环境条件,因地制宜选定。参评因素的分级应尽量采用定量指标,为分等定级提出定量依据,其主要级差应尽量利用有生物学意义的临界指标。在目前全国无统一规定下,试图面向全国选定参评因素及划分为五等六级的分级指标。     

The effects of refractive index heterogeneity within kidney tissue on multiphoton fluorescence excitation microscopy

Although multiphoton fluorescence excitation microscopy has improved the depth at which useful fluorescence images can be collected in biological tissues, the reach of multiphoton fluorescence excitation microscopy is nonetheless limited by tissue scattering and spherical aberration. Scattering can be reduced in fixed samples by mounting in a medium whose refractive index closely matches that of the fixed material. Using optical 'clearing', the effects of refractive index heterogeneity on signal attenuation with depth are investigated. Quantitative measurements show that by mounting kidney tissue in a high refractive index medium, less than 50% of signal attenuates in 100 μm of depth.     

一类含参数二阶两点边值问题正解的存在性

运用不动点指数理论,讨论了二阶两点边值问题u″（t）＋λu（t）＋f（u）=0 t∈（0,1）,u（0）=u（1）=0.正解的存在性,其中λ∈[0,∞）为参数,f∈C（[0,∞）,[0,∞））.     

用moire技术测量平板玻璃折射率

本文描述了使用moire技术测量平板玻璃折射率的理论并进行了实验论证。测量方法简单且快捷。可精确测量任何透明材料的折射率。测量精确度可达10~(-5)。