赤潮生物监测荧光成像系统背景光源改进

介绍了一种海洋赤潮生物监测荧光成像系统,该系统的背景光源为海洋赤潮生物监测荧光成像系统的重要组成部分,赤潮生物监测荧光成像系统背景光源选择是否合理将直接影响着藻类成像清晰度,由于各种赤潮藻含有不同的特征纹理,其纹理特征将决定是否能准确识别出藻类并对其进行分类,进而影响到对赤潮的准确预报。为了解决赤潮藻图像的清晰度等问题,作者利用自行设计的荧光成像系统,对不同成像光源的成像效果进行了分析和比较。实验证明,近红外光源可以有效地获得清晰的藻类纹理信息,使得后继的图像处理工作更加容易,从而解决了藻类图像暗黑以至于图像处理起来较为困难等问题。     

静电纺丝法制备硼掺杂氧化硅纳米纤维用于低碳烷烃氧化脱氢制烯烃

乙烯和丙烯等低碳烯烃是重要的基础有机化工产品,广泛应用于化工生产的各个领域.相比于其他工艺,低碳烷烃氧化脱氢制烯烃工艺具有不受热力学平衡限制、无积炭等特点而被广泛研究.近年发现六方氮化硼(h-BN)、硼化硅(SiB6)和磷酸硼(BPO4)等非金属硼基催化剂能够高效催化烷烃氧化脱氢反应,并抑制产物烯烃的过度氧化,表现出高的催化活性和烯烃选择性.大量的研究表明,硼基催化剂活性起源于催化剂表面的"BO"物种(如B-O和B-OH等基团).氧化硼(B2O3)作为一种氧化气氛中化学性质稳定的含硼化合物,兼具丰富的"BO"位点,在反应条件下可形成多种结构以适用不同的化学环境,为制备高效的烷烃氧化脱氢催化剂提供了可能.在之前的研究中,多将B2O3浸渍在常规的TiO2,SiO2,A12O3等三维多孔载体上用于氧化脱氢反应.考虑到B2O3结构的灵活性和易于成键特性,需开发更为有效的合成策略,以提升B2O3催化剂在氧化脱氢反应中的活性和稳定性.本文采用静电纺丝技术合成了直径为100～150 nm的多孔掺硼二氧化硅纳米纤维(PBSN)用于低碳烷烃氧化脱氢反应.静电纺丝法合成的催化剂中硼物种在开放的氧化硅纤维骨架上均匀分散且稳定固载.一维纳米纤维结构不仅有利于扩散,且赋予催化剂在高重时空速(WHSV)条件下优异的烷烃氧化脱氢反应活性.在乙烷氧化脱氢反应中,当乙烷的转化率达到44.3％时,乙烯的选择性和产率分别为84％和44.2 μmol gcat-1 s-1.而在丙烷脱氢反应中,当丙烷转化率为19.2％时,总烯烃选择性及丙烯产率分别为90％和76.6 μmol gcat-1 s-1.在温度为545 ℃,丙烷WHSV高达84.6 h-1的条件下,催化剂保持长时间稳定.与其他负载型氧化硼催化剂相比,PBSN催化剂具有更高的烯烃选择性和稳定性.研究表明,在氧化硅负载B2O3催化剂催化丙烷氧化脱氢反应中,载体中Si-OH基团的存在可能会降低丙烯的选择性.瞬态分析和动力学实验表明,硼基催化剂催化烷烃氧化脱氢反应过程中O2的活化受到烷烃的影响.本文不仅为高效硼基催化剂的合成提供了新思路,也为深入理解该类催化剂上烷烃氧化脱氢反应过程提供了实验支撑.     

发光二极管诱导荧光用于毛细管电泳检测

利用发光二极管作为激发光源，组装了用于毛细管电泳的荧光检测器。光纤用于传输荧光信号；光纤端面修饰成球形使耦合效率比平面端光纤提高了50．8％；光阑、光纤及毛细管检测池之间的光学校准简单、便捷。荧光素染料用于评价该体系性能，得到了fmol的质量检出限。     

Magnetorheology in viscoplastic media

Suspensions of iron particles in media with yield stresses were investigated to determine the effect of the continuous phase yield stress on the magnetorheological (MR) response. The steady-shear MR response was independent of the continuous phase yield stress for yield stresses in the range 0.9–37 Pa. The field-induced suspension yield stress increased sub-quadratically with the flux density. The small amplitude oscillatory shear response exhibited history dependence. The storage modulus depended not only on the magnitude of the applied magnetic field, but also on its history. This history dependence can be explained in terms of the field-dependent evolution of the suspension microstructure. Received: 24 February 1999 Accepted: 12 July 1999     

约束面投影成型室基底微观特征对透光性的影响

为了探明约束成型室基底微观孔隙特征对固化光源传播特性的影响规律,从而对光固化成型精度进行分析和预测,采用时域有限差分软件对成型室约束基底引入微孔特征条件下的透光性及在固化区光能量分布特性进行了数值模拟,并通过实验对模拟结果进行了验证.结果表明,约束基底引入微孔的形状、尺寸以及周期等微观几何特征影响基底的透光性及其透过基底在成型区的光强分布;相对于基底微孔形状,其尺寸和周期的影响更显著,减小微孔尺寸和周期有利于透光性以及光强在成型区分布的均匀性;微孔直径小于半波长、微孔边缘间距与微孔直径的比值小于1∶1时可以显著减小微孔的负面影响;微孔直径远大于半波长时,基底上的微孔将在成型零件表面形成不期望的附加特征,从而影响成型精度.研究结果可以为基底制备提供工艺改进的方向和理论依据.     

The Facet method: A hierarchical multilevel modelling scheme for anisotropic convex plastic potentials

An entirely new analytical expression describing plastic anisotropy is presented. It is designed to be used in combination with multilevel models. It makes use of the theory of dual plastic potentials, which is shortly revisited. An analysis of convexity is presented. Note that the new method is not optimal when not used in combination with a multilevel model; other methods are better suited for identification on the basis of mechanical test data. Compared with already existing methods which work with multilevel models, the new method has the following advantages: (i) it is automatically convex anywhere in the six-dimensional stress or strain rate space; (ii) it can be used for materials with a stress differential effect, such as hcp metals or pre-strained cubic materials; (iii) its identification procedure is such that not only the Taylor theory, but also more advanced theories, such as the Alamel-model or self-consistent models, can be used to identify the parameters; (iv) an analytical expression of the plastic potential can be obtained in both strain rate and stress space, which is an important advantage when implementing the model in finite element codes for metal forming. Equipotential surfaces in strain rate space and corresponding yield loci obtained by the new method for four materials (one ferrite single crystal, one aluminium alloy and two types of steel) are presented and discussed.     

Plane constrained uniaxial extension of a single crystal strip

Within continuum dislocation theory the plane constrained uniaxial extension of a single crystal strip deforming in single or double slip is analyzed. For the single and symmetric double slip, the closed-form analytical solutions are found which exhibits the energetic and dissipative thresholds for dislocation nucleation, the Bauschinger translational work hardening, and the size effect. Numerical solutions for the non-symmetric double slip are obtained by finite element procedures.     

An experimental study of electrorheological fluid flow through a packed bed of glass beads

This paper shows that pressure drop-flow rate performance of an electrorheological (ER) fluid flowing through a packed bed of glass beads is consistent with a modified Ergun equation for yield stress flow through a packed bed. ER fluids are of scientific and engineering interest due to the sensitivity of their rheological properties on the applied electric field. As far as we know ER fluids have not been studied for flows through porous media. In this work a silica particle–silicone oil suspension is pumped through a rectangular packed bed of glass beads with applied electric fields. The silica particles are observed to form fibrous structures parallel to the electric field that stretch between the beads and extend between the electrodes. The pressure drop-flow rate performance agrees well with the expected performance calculated from a modified Ergun equation for a yield stress fluid flow through the packed bed with the viscosity and yield stress as functions of the applied electric field.     

SYNTHESIS AND CHARACTERIZATION OF FULLY SOLUBLE POLYPHENYLENEVINYLENE

Fully soluble poly[2-methoxy-5-(2'-ethylhexyl)-oxy)-p-phenylenevinylene] (MEH-PPV) was synthesized by theaddition of molecular weight modifiers (chain stopper, free radical scavengers) to a polymerization system containingmonomer, catalyst and a solvent. These PPV products synthesized in this work were characterized by IR, NMR, UV-visiblespectroscopy and GPC. Results show that the M_w of polyphenylvinylene (PPV) can be controlled by the addition of chainstopper (benzyl bromide) and radical inhibitor (2,6-di-tert-butyl-4-methyl phenol). The polymerization mechanism in the presence of these additives was also discussed. A dual mechanism involving carbene for PPV polymerization was proposed.     

A rheo-optical method for the study of aggregated particles: application to the characterization of ABO blood group monoclonal antibodies

The adhesive energy of monoclonal antibody induced agglutination can be assessed from the shear dissociation of agglutinates. Anti-A, anti-B, and anti-AB monoclonal antibodies agglutinate erythrocytes with variable strength, depending on the affinity of antibodies and on the antigenic density on the cell surface. The time required for an applied shear stress to dissociate cell agglutinates completely is depending on the strength of the agglutination reaction. The dissociation process under constant shear stress can be followed by measuring intensity of light backscattered by suspended particles. The obtained dissociation curves could be adjusted by an exponential expression governed by a parameter called characteristic time of dissociation. This parameter decreases with increasing antibody concentration. Integration of dissociation curves provided an approach of adhesive energy induced by monoclonal antibody. Received: 7 May 1999 Accepted: 30 May 2000