Model concrete beam-column joints subjected to cyclic loading at two rates

Small-scale models of reinforced concrete beam-column joint were subjected to large cyclic displacements at two rates: 2.5×10⁻³ and 1.0 Hz. To assess damage, free-vibration tests were conducted. The reliability of the modelling techniques was established by comparison of the results for the slower rate with those obtained from the full-scale tests on prototype. The higher rate of loading caused a greater damage than that at the lower rate. This was evidenced by the measurements of the energy absorbed in the hysteresis loops, equivalent damping, and the stiffness and damping obtained from the free-vibration test. The relatively greater extent of damage appears to result from the different bond behaviour at different rates of loading.     

EDTA interfacial chelation Ca2+incorporates superhydrophobic coating for scaling inhibition of CaCO3 in petroleum industry

In this paper,the superhydrophobic poly(vinylidene fluoride)/fluorinated ethylene propylene/SiO2/CNTs-EDTA(PFSC-EDTA)composite coating was successfully fabricat...     

无机结垢趋势预测技术在油田开采中的应用

在油田注水开发过程中结垢问题变得越来越严重,结垢造成了油田开采过程中大量的经济损失,尤其是低渗透油田损失更大,为了高效开发低渗透油田,应对油田水结垢进行科学预测并提出合理的防垢措施。本文首次对大庆龙虎泡油田水结垢进行了定性分析,在前人研究基础上利用经典溶液理论、离子缔合理论及多元非线性回归技术建立了地层无机结垢饱和度指数预测方程,编帛了预测软件PIOS1．0,应用该预测软件对大庆龙虎泡油田水进行了结垢预测。本工作结果表明,龙虎泡油田结垢主要是碳酸钙垢,含有少量硫酸钙垢,结垢最严惩区域,主要在油气井近井地带,与实际情况基本吻合。     

Effect of oxide additives on the low-temperature sintering of dielectrics (Zn,Mg)TiO3

The effect of oxide additives on the low-temperature sintering and dielectric properties of microwave dielectrics (Zn,Mg)TiO₃ have been investigated. The study showed that a small amount of V₂O₅ accelerated the densification rate of (Zn,Mg)TiO₃ dielectrics as compared with the other oxide additives. In addition to lower sintering temperature of zinc titanate dielectrics, the addition of V₂O₅ decreased the decomposition temperature of (Zn,Mg)TiO₃. Additionally, the increased amount of magnesium raised both the sintering temperature and the decomposition temperature of (Zn,Mg)TiO₃. Relative permittivity of (Zn,Mg)TiO₃ dielectrics decreased accompanied with increase of Q × f as the amount of magnesium content increased. The temperature coefficient of resonant frequency of (Zn,Mg)TiO₃ shifted to more negative values as the amount of magnesium increased.     

Synthesis and characterization of V–C60/TiO2 photocatalysts designed for degradation of methylene blue

C₆₀/TiO₂ and V–C₆₀/TiO₂ composite photocatalysts were prepared with titanium (IV) n-butoxide (TNB) by a sol–gel method. Fullerene had absorptive and semiconducting properties, and vanadium could enhance the photogenerated electron transfer. The V–C₆₀/TiO₂ composite shows a good photo-degradation activity. XRD patterns of the composites showed that the C₆₀/TiO₂ composite contained a mixture of anatase and rutile phase forms while the V–C₆₀/TiO₂ composite contained a typical single and clear anatase phase. The surface properties seen by SEM and FE-SEM present a characterization of the texture on C₆₀/TiO₂ and V–C₆₀/TiO₂ composites and showed a homogenous composition in the particles for the titanium sources used. The EDX spectra for the elemental identification showed the presence of C and Ti with strong V peaks for the V–C₆₀/TiO₂ composite. From the photocatalytic results, the excellent activity of the C₆₀/TiO₂ and V–C₆₀/TiO₂ composites for degradation of methylene blue under UV irradiation could be attributed to both the effects between photocatalysis of the supported TiO₂ and charge transfer of the fullerene, and the introduction of vanadium to enhance the photogenerated electrons transfer.     

Qualitative Analysis of the Helical Electronic Energy of Inherently Chiral Calix[4]arenes: An Approach to Effectively Assign Their Absolute Configuration

For all microhelices on aromatic rings of inherently chiral calix[4]arene, an expression was derived from one approximation and one hypothesis on the basis of the electron-on-a-helix model of Tinoco and Woody as follows: , where µ = 1 for the right-handed microhelix and µ = −1 for the left-handed microhelix; and H and K are constant and greater than zero. The expression correlates microhelical electronic energy (E) with the atom polarizability difference (Δα) on both microhelix ends, which intuitively and clearly shows the impact of helical substituent polarizability on helical electronic energy. The case analysis almost entirely proves that the qualitative analysis of the helical electronic energy of inherently chiral Calix[4]arenes with the expression is scientific and can be used to effectively assign their absolute configuration.     

Photoelectrocatalytic properties and bactericidal activities of silver-treated carbon nanotube/titania composites

Two types of carbon nanotube/TiO₂ and silver-treated carbon nanotube/TiO₂ electrodes were prepared and characterized by X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray analysis, photoelectrocatalytic activity and antibacterial activity. The photoelectrocatalytic degradation of a methylene blue solution was attributed to the combined effects of the photo-degradation of TiO₂, the electron assistance of carbon nanotube network and the enhancement of silver and was a function of the applied potential. The composites treated with silver showed enhanced photo-degradation of methylene blue, and the photoelectrocatalytic activity increased with increasing amount of silver. The silver-treated carbon nanotube/TiO₂ prepared as bactericides have stronger antibacterial activity against Escherichia coli K-12 than standard ampicillin, tetracycline and carbon nanotube/TiO₂ under sunlight or dark conditions. The presence of silver in the silver-treated carbon nanotube/TiO₂ composites enhanced the inactivation of the E. coli K-12.     

The shock of vacuolar PrA on glycolytic flux,oxidative phosphorylation,and cell morphology by industrial <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> WZ65

Proteinase A (PrA) is one of the most significant vacuolar proteinase in S. cerevisiae, and it plays an important role in S. cerevisiae physiology and metabolism, especially under unfavorable environment. In this study, the differences in pyruvate kinase (PYK) level under fructose-1,6-diphosphate (FDP) induction and ATP synthesis block among SC1 (the wild-type yeast that was industrial Saccharomyces cerevisiae WZ65), SC2 (PEP4 partial deletion) and SC3 (PEP4 complete deletion) were examined. Results showed that the induction caused by FDP clearly increased PYK expression no matter for which strain, but the increasing effect is more significant for SC2 (P < 0.05). The comparative results of intracellular ATP accumulation showed that the induction by FDP may be affected at the presence of PrA. The block experiment of ATP synthesis showed that PYK activities in PEP4-modified strains are lower than that of the wild type, but the intracellular ATP levels in the wild-type one are generally higher than the PEP4-modified strains after rotenone treatment (P < 0.01). This implies that the effect of PrA deficiency on intracellular ATP accumulation was much more pronounced than the effect of rotenone on oxidative phosphorylation. The cell morphology of three strains was comparatively examined by means of transmission electron microscopy (TEM). The PEP4-modified strains possessed more vacuoles, and cell structure were more integrated than the wild-type strain. Current data preliminarily indicated that the deletion of PEP4 gene in industrial S. cerevisiae WZ65 may not only affected PYK expression but also modulated the oxidative phosphorylation flux.     

一种单层铰接折面网壳结构的试验研究

形如深圳大运会体育馆的单层折面网壳结构其基本构形的铰接体系为空间静定桁架结构,为改善该类单层折面网壳的受力性能、提高结构刚度,可在基本体系的基础上增设若干道环杆.对铰接单层折面网壳结构基本体系及环杆加强体系进行进行了全跨、半跨荷载下的静载试验及动力特性试验,并将试验实测数据与理论分析结果进行了比较分析.结果表明,实测数据与理论分析之间差异较小,模型设计和试验方法合理,理论分析方法正确.     

Partial hybrid stress element for the analysis of thick laminated composite plates

A new element—a partial hybrid stress element—is proposed in this paper for the analysis of thick laminated composite plates. The variational principle of this element can be derived from the Hellinger–Reissner principle through dividing six stress components into a flexural part (σ_x, σ_y, σ_xy, σ_z) and a transverse shear part (τ_xy, τ_yz). The element stiffness matrix can be formulated by assuming a stress field only for transverse shear stresses, while all the others are obtained from an assumed displacement field. Consequently, this new element combines the benefits of the conventional displacement method and the hybrid stress method. A twenty-node hexahedron element is employed in each layer for the displacement field. For the assumed transverse shear stress field, only the traction-free boundary conditions and interface traction continuity are satisfied. The equilibrium equation is enforced by the variational principle. Hence, the complicated work of searching an equilibrating stress field for all the six stress components in the hybrid stress method can be avoided. Furthermore, the interlaminar traction discontinuity, especially transverse shear, encountered by the conventional displacement method and higher-order plate element for laminated plate analysis can also be overcome. Examples are illustrated to demonstrate the accuracy and efficiency of this proposed partial hybrid stress element.