Prediction of the penetrated rust into the microcracks of concrete caused by reinforcement corrosion

Consider a steel-rust-concrete composite consisting of a circular cylindrical concrete cover and a coaxial uniformly corroding steel reinforcement. Prediction of the amount of rust penetrated into the microcracks of concrete cover from a set of data measured at the surface of the concrete is of particular interest. The steel is assumed to be linear isotropic and rust follows a power law stress–strain relation. For the concrete, anisotropic behavior and post-cracking softening model is employed. The formulations lead to a nonlinear boundary value problem which is solved analytically. A key parameter β, defined as the ratio of the volume of corrosion products inside the cracks to the volume of the cracks, is calculated. With some efforts, this parameter is also extracted from the available theoretical and experimental studies for the purpose of comparison. The effects of the mechanical properties of rust and concrete on β is addressed.     

An exact deformation analysis for the magneto-electro-elastic fiber-reinforced thin plate

A closed form expressions for bending problem of magneto-electro-elastic (MEE) rectangular thin plates are derived, the exact solutions for the deformation behaviors of the fiber-reinforced BaTiO₃/CoFe₂O₄ composites subjected to certain types of surface loads are analytically obtained. Based on Kirchhoff thin-plate theory, structural characteristics such as elastic displacements, electric potential and magnetic induction for magneto-electro-elastic (MEE) rectangular plates are investigated, the governing equation in terms of the transverse displacement is presented in a rather compact form due to the omission of the transverse shear deformation and rotatory inertia. The material coefficients for the MEE plate can be uniquely expressed by the volume-fraction (v.f.) of piezoelectric constituent BaTiO₃ in the fiber-reinforced composite, and are tabulated with 25% offset of the volume-fraction. The deformation variations of the MEE thin plate with closed-circuit electric restriction are evaluated analytically according to their specified boundary conditions, and the effects of the volume-fractions on the deformations variations are discussed. It can be found that all the results obtained by using the proposed model have reached good agreements with the other available research works, whereas, the present study provides a much simpler way in seeking the analytic solutions for the interactively coupled quantities of a multiphase medium.     

奇完全数的几个命题

本文证明形如3m-1的正整数不是完全数,由此推出当所有的qi≡-1(mod 3)时,奇数n=p~αП_(i=1)~sq_i~(2β_i)若是完全数,那么1/2σ(p~α)必是合数.指出k倍完全数的素因子必须满足一个不等式.运用此不等式证明当a≥n-2时形如a~(2~n)+b~(2~n)(a>b>0,a,b,n∈N~+)的奇数不是完全数.还指出当a与b都与3互素时,对于任意的正整数m,n,奇数a~(2~n)+b~(2~m)不是完全数.     

PEGylated inorganic nanoparticles

Application of inorganic nanoparticles in diagnosis and therapy has become a critical component in the targeted treatment of diseases. The surface modification of inorganic oxides is important for providing diversity in size, shape, solubility, long-term stability, and attachment of selective functional groups. This Minireview describes the role of polyethylene glycol (PEG) in the surface modification of oxides and focuses on their biomedical applications. Such a PEGylation of surfaces provides "stealth" characteristics to nanomaterials otherwise identified as foreign materials by human body. The role of PEG as structure-directing agent in synthesis of oxides is also presented.     

Kinetic Magnetic‐Field Effect Involving the Small Biologically Relevant Inorganic Radicals NO and O2.−

Oxidation of dihydrorhodamine 123 (DHR) to rhodamine 123 (RH) by oxoperoxonitrite (ONOO^?), formed through recombination of NO and O₂^.? radicals resulting from thermal decomposition of 3‐morpholinosydnonimine (SIN‐1) in buffered aerated aqueous solution at pH 7.6, represents a kinetic model system of the reactivity of NO and O₂^.? in biochemical systems. A magnetic‐field effect (MFE) on the yield of RH detected in this system is explored in the full range of fields between 0 and 18 T. It is found to increase in a nearly linear fashion up to a value of 5.5±1.6 % at 18 T and 23 °C (3.1±0.7 % at 40 °C). A theoretical framework to analyze the MFE in terms of the magnetic‐field‐enhanced recombination rate constant k_rec of NO and O₂^.? due to magnetic mixing of T₀ and S spin states of the radical pair by the Δg mechanism is developed, including estimation of magnetic properties (g tensor and spin relaxation times) of NO and O₂^.? in aqueous solution, and calculation of the MFE on k_rec using the theoretical formalism of Gorelik at al. The factor with which the MFE on k_rec is translated to the MFE on the yield of ONOO^? and RH is derived for various kinetic scenarios representing possible sink channels for NO and O₂^.?. With reasonable assumptions for the values of some unknown kinetic parameters, the theoretical predictions account well for the observed MFE.     

DNA/羟基磷灰石杂化膜修饰电极用于研究DNA与量子点的相互作用

首次利用溶胶-凝胶一步法制备了纳米多孔羟基磷灰石(HAp)-DNA杂化膜修饰玻碳电极,HAp优良的生物相容性和独特的吸附性可以将DNA固定在HAp多孔薄膜上,而DNA的大分子结构对HAp膜起到稳定剂的作用.采用循环伏安法和交流阻抗法系统地研究了电极表面固定DNA的稳定性以及固定的DNA与非电活性核壳型量子点CdTe/C...     

Unsteady generalized Couette flow in composite microchannel

A numerical study is reported on the fully developed unsteady laminar fluid flow in microchannel parallel-plates partially filled with a uniform porous medium and partially filled with a clear fluid. The flow is induced by the movement of one of the plates and the pressure gradient. The Brinkman-extended Darcy model is utilized to model the flow in the porous region, while the Stokes equation is used in the clear fluid region. A theoretical analysis is also presented for the fully developed steady flow to find closedform expressions for the interfacial velocity and the velocity and skin frictions at the bounding plates. Numerical computations shows excellent agreement between the closedform solutions for fully developed steady flow and the numerical solution to unsteady flow at large values of time.