Hydrogel Nanocomposite as a Synthetic Intra-Ocular Lens Capable of Accommodation

A hydrogel nanocomposite was designed, synthesized, and evaluated for use as an auto-focusing intra-ocular lens. The hydrogel scaffold was composed of a monomer-free, thiol that contained polyacrylamide (5%), which was allowed to gel in the presence of nanoparticles at pH 7.4, 25°C. The nanoparticles consisted of a proteo-mimetic polyacrylamide nanogel (∼42 nm), bovine serum albumin (BSA) (∼6 nm), and hydrophilized silica (∼3 nm). The extent of nanoparticle loading increased with decreasing particle size. The elastic modulus increased with increasing loading of the proteo-mimetic nanogels and BSA, and it decreased with hydrophilized silica. In this investigation, the hydrogel that contained silica was the most promising class of nanocomposite hydrogels with properties comparable to that of a young porcine lens. A nanocomposite that consisted of 10% hydrogel scaffold and 24% hydrophilized silica (elastic [E] modulus of ∼1.0 kPa and refractive index [RI] of 1.42) was injected into a pre-evacuated porcine lens capsular bag. The composite lens was evaluated in a custom-designed four-arm radial stretcher, and its force-time spectrum was characterized by time constants of 60 ± 8.9 and 800 ± 32 ms. These results were comparable to a young porcine lens (E Modulus of 1.2 kPa; RI of 1.4105; time constants of 48.3 ± 0.58 and 668 ± 24.6 ms, respectively)     

西部凹陷深层沙河街组生储盖组合的层序分析

通过钻井、岩芯和地震等资料的综合分析,可从辽河盆地西部凹陷深层沙河街组中识别出６ 个钻井长期旋回层序和６ 个相对应的地震层序。较为详细地讨论了沙河街组层序与生储盖组合的关系,认为：（１）在以中、长期旋回层序为等时地层对比单元的地层格架中,生储盖组合特征与长期基准面旋回关系最为密切,有利储层发育位置主要出现在基准面上升早中期和下降中晚期,转换处则是烃源岩或盖层的发育位置。（２）各长期旋回层序的生储盖组合具不同的特征,明显受基准面升降的频率、幅度及其所影响的湖平面升降变化速率、相组合、相序、可容纳空间和Ａ／Ｓ值的变化控制。（３）按生储盖组合在垂向上和纵向上的配置关系,可划分为上生下储、下生上储和仅发育储盖的３种基本组合类型,第一种和第二种分别形成于中—高可容纳空间的基准面上升期和下降期,第三种形成于低可容纳空间的基准面完整升降旋回过程中。由第二种与第一种,或第二种与第三种基本组合类型的叠加组成２ 种跨层序发育的复杂组合模式。相对前３种基本类型,复杂组合模式更有利于油气聚集成藏     

基于逆系统方法的非线性系统故障调节

针对一类多输入多输出非线性可逆系统,提出一种基于逆系统原理的故障调节方法.该方法通过设计被控对象的自适应观测器来估计执行器故障,并根据故障估计值,基于逆系统方法产生附加控制律对逆系统进行调节补偿,使得被控对象和经调节后逆系统的串联仍能保持为无故障时的伪线性系统模型,从而在无需改变系统正常控制器参数的情形下,方便地实现对执行器故障的良好性能容错目标.     

Dissipative Processes in a One-Dimensional Supersonic Gas Flow Across a Permeable Obstacle

One-dimensional supersonic gas flow across an infinite permeable surface (obstacle of zero thickness) is investigated by the direct statistical simulation (Monte-Carlo) method. Both the characteristic features of the formation of a shock perturbation in the interaction between the plane supersonic flow and the permeable obstacle and the effect of the perturbation on the flow parameters behind the obstacle are found. It is concluded that the accommodation coefficient can be determined from the data on the equilibrium flow macroparameters behind the obstacle.     

基于“双证融通”的高职电子测量技术课程教学探析

“双证融通”课程教学模式是深化高职课程教学的有效途径,研究高职学生的岗位目标要求和国家职业资格标准,探索高职“电子测量技术”课程教学与国家职业资格标准的理论和技能的要求,改进高职“电子测量技术”课程教学方法,采取多种教学方法,以职业需要和证书内容为目标导向,建立有效的“双证融通”的课程教学模式是激发学生课程学习兴趣,不断提高学习效果,为学生零距离上岗奠定基础的保障。     

Accommodation mechanisms for grain boundary sliding as inferred from texture evolution during superplastic deformation

To gain insight into accommodation mechanisms for local stress concentrations produced by grain boundary sliding (GBS), we systematically examined texture evolution within a superplastic magnesium alloy undergoing deformation at a relatively low deformation temperature (at which basal slip is known to be the preferred slip system in magnesium). Although we did observe an overall weakening of the initial basal texture during superplastic deformation, we also observed within the interior of the specimen a convergent evolution that depends on loading direction. We attribute this texture evolution within the bulk to the competing effects of (a) orientation divergence due to grain rotation accompanied by GBS and (b) convergent evolution due to slip, which acts primarily as an accommodation mechanism for GBS. In contrast, at the near-surface, we found the initial orientation to be preserved, indicating that slip accommodation is less important near the surface than within the bulk.     

Effect of the Nature of the Interaction between a Gas and a Surface on the Relations for the Knudsen Layer in the Case of Strong Evaporation

The effect of the temperature accommodation coefficient _T on the relations at the Knudsen layer edge is investigated for strong evaporation using the moment method. An explicit expression for the dimensionless density as a function of the temperature and the Mach number M is obtained for 0 < _T < 1. For _T = 0 the entire solution is obtained in explicit form. It is shown that for = 0 and a condensation coefficient << 1 the temperature outside the Knudsen layer changes sharply as M varies from 0 to a certain value much less than unity after which the temperature ceases to depend on . For the model of specular reflection of the molecules from the surface the density and the temperature outside the Knudsen layer are found in explicit form as functions of the Mach number.     

Transformation-rate maxima during lath martensite formation: plastic vs. elastic shape strain accommodation

Recently, a modulated formation behaviour of lath martensite in Fe–Ni(-based) alloys was observed, exhibiting a series of transformation-rate maxima. This peculiar transformation behaviour was explained on the basis of the hierarchical microstructure of lath martensite, minimising the net shape strain associated with martensite formation, by a block-by-block formation of martensite packages occurring simultaneously in all packages. In the present work, the martensitic transformation upon slow cooling of two Fe–Ni alloys, containing 22 and 25 at.% of Ni, respectively, was investigated by high-resolution dilatometry with the aim of identifying the influence of alloy composition on the modulated transformation behaviour. The differences observed for the two alloys, a more rapid sequence of the transformation-rate maxima and a narrower temperature range in case of Fe-25 at.% Ni, can be explained consistently as a consequence of the lower transformation temperatures in Fe-25 at.% Ni, highlighting the role of temporary accommodation of the shape strain during formation of the lath martensite microstructure: the depression of the transformation toward lower temperatures leads to a higher strength of the austenite, hence resulting in a more elastic (less plastic) temporary accommodation of the shape strain upon block formation and thereby in a more effective mutual compensation of the shape strain by neighbouring blocks. A kinetic model on the basis of energy-change considerations is presented which is able to describe the observed modulated transformation behaviour.     

气体传热对多层绝热性能影响的试验研究

文中通过建立的能进行夹层气体置换的稳态量热器试验系统,试验分析了夹层气体传热对多层绝热材料有效热导率的影响,重点对置换气体种类、气体压强、材料层数及冷热边界温度对多层材料的影响进行试验研究。试验表明在10—60层/cm层密度范围,真空度低于100Pa时,Kn数属于自由分子状态区域和中间压强区域,此时材料的有效热导率随残留气体热适应系数的增大而减小,并随着真空度的降低而增大,当残留气体为空气时,为保证多层材料的绝热性能,应尽量维持真空度不低于10-2Pa。同时,分析表明为有效降低低真空下稀薄气体传热对多层绝热性能的影响,可以采用综合热适应系数较低的气体置换夹层中的空气,以减少低真空多层绝热材料的有效热导率,改善绝热性能。     

Texture change through film thickness and off-axis accommodation of (0 0 2) planes

We present our recent experimental results on the formation of off-axis texture and crystallographic tilting of crystallites that take place in thin film of transition metal nitrides. For this purpose, the microstructural development of TiAlN film was studied, specially the change in texture with film thickness. Fiber texture was measured using θ-2θ and pole figure X-ray diffraction (XRD), while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microstructure and changes in texture with thickness. The sin²ψ method was applied to determine the stresses on (1 1 1) and (0 0 2) plane. With deposition parameters chosen, the growth texture mechanism is discussed in three different stages of film growth. Surface energy minimization at low thickness leads to the development of (0 0 2) orientation. On the other hand, the competitive growth promotes the growth of (1 1 1) planes parallel to film surface at higher thickness. However, contrary to the prediction of growth models, the (0 0 2) grains are not completely overlapped by (1 1 1) grains at higher thickness. Rather the (0 0 2) grains still constitute the surface, but are tilted away from the substrate normal showing substantial in-plane alignment to allow the (1 1 1) planes remain parallel to film surface. Intrinsic stress along (1 1 1) and (0 0 2) shows a strong dependence with preferred orientation. The stress level in (0 0 2) grains which was compressive at low thickness changes to tensile at higher thickness. This change in the nature of stress allows the (0 0 2) planes to tilt away in order to promote the growth of 〈1 1 1〉 parallel to film normal and to minimize the overall energy of system due to high compressive stress stored in the (1 1 1) grains. The change in surface morphology with thickness was observed using SEM. An increase in surface roughness with film thickness was observed which indicates the development of (1 1 1) texture parallel to film surface. TEM observations support the XRD results regarding texture change. Film hardness was measured by nanoindentation and a correlation between (1 1 1) texture, stress and hardness is obtained. The results indicate that texture development is a complex interplay between thermodynamic and kinetic forces. An attempt is made to understand this phenomenon of off-axis accommodation of (0 0 2) at higher thicknesses, which is a new result not reported previously.