Experimental study on bond behavior between corrosion-cracked reinforced concrete and CFRP sheets

Bond behavior between corrosion damaged reinforced concrete and carbon fiber reinforced concrete polymer (CFRP) sheets was experimentally investigated. Forty ordinary strength concrete blocks (150 × 150 × 200 mm) were reinforced at one side across the 200-mm-dimension using three conventional ?12 mm steel bars at a spacing of (30, 40, and 50 mm) at a concrete clear cover of 15 mm. Thirty blocks were subjected to a cyclic treatment in 3% chloride solution until corrosion initiated and resulted in three different global cracking widths of up to 0.90 mm. Both control and corrosion damaged blocks were attached to CFRP sheets over their steel reinforced zone at bond lengths and widths ranging from (90 to 150 mm) and (50 to 150 mm), respectively, with CFRP bond length-to-bar spacing ratio kept constant at 1/3. Near-end pull-off tests were carried out using a special setup, mounted on a Universal Testing machine. Corrosion cracking caused significant reductions in bond strength, and slippage at ultimate stress at (41 and 68%), respectively. Other bond characteristics such as stress at first slippage, and bond stiffness and toughness were reduced, as well, by as high as (83, 44 and 67%) of those of control specimens, respectively. Corrosion cracks were more detrimental for smaller bond length and width values; especially after first and second corrosion stages, where bond failure was categorized by concrete skin peeling-off.     

基于Netmeeting及Multimedia Author的网络互动教学平台开发

基于NetMeeting for Windows的网络功能以及Multimedia Author的强大的多媒体构架以及photoshop7.0,SWiSH v2.0,RealSlideshow,flash等软件,开发出基于网络的互动教学平台.该平台实现了局域网及远程网络教学环境内的网络课堂教学,具有超强的连接与互动功能,内部嵌入实验范例仿真、视频资料及动画,不仅弥补了目前计算机辅助教学形式单一,功能简单的问题,而且可以单机安装和通过Web进行自学及测试.     

Vapour side corrosion in a ME desalination plant at Jebel Dhana

Jebel Dhana, from the Abu Dhabi Water and Electricity Authority (ADWEA), operates two 2 MGD multi-effect thermo-compression distillers commissioned in 1996. Tube failures were first reported approximately 16 months after commissioning. The initial tube failures were from the upper rows, but more recent failures were apparently randomly distributed throughout the tube bundle. Ten tubes were removed and their corrosion morphology was examined macroscopically and microscopically. The corrosion products were analysed by X-ray, EDAX, and EPMA techniques. The copper nickel alloy tubes were found to have suffered from vapour side corrosion; however, there was no sign of any copper oxide deposition, as has often been seen in failed tubes from MSF distillers. The failures took two forms: corrosion fatigue cracking, and pitting corrosion. The corrosion fatigue was in the form of a circumferential crack at a flat portion of the tube in the centre of a tube span. It was believed that the flat surface had developed as a result of fretting against a neighbouring tube, and had been worn away to the point of failure. Unfortunately, the position of the tubes in the tube bundle had not been identified during their removal, but it is suspected that the damaged tube had been in the top row, with the flattened portion directly below one of the two vapour inlet pipes. The other tubes sampled showed pitting corrosion. Some of the pitting had perforated the tube walls whilst others showed pitting on the outer surface only. Some of the pits contained corrosion products whilst others were free of them. This pitting corrosion is attributed to the formation of carbonic acid in the presence of oxygen (air). A weak acid is formed due to the dissolution of CO₂ in the condensing water vapour. The gas concentration varies within the tube bundle, due to the vapour phase, allowing the gas concentration to increase in specific areas of the tube bundle, causing the non-uniformity of attack. There was no immediate tie-up between the pitting corrosion and the two steam inlet pipes due to the unknown position of the sampled tubes within the tube bundle. It is recommended that the oxygen level be reduced by ensuring that the distiller vessels are as air-tight as possible, thus reducing the tendency towards pitting corrosion.     

Modification of sandy soil using water‐borne polymer

A new polymeric system has been applied for structural modification of (noncompactable) sandy soils. The system is based on a water‐borne styrene acrylic polymeric formulation (emulsion) containing varying amounts of solid polymer. The present work deals with system optimization and measurements designed to examine the effects of polymer content on hydraulic conductivity and compressive strength. Samples were prepared from prescribed amounts of polymer, water, and sand by using two different preparations methods (mixing and spraying). Measurements of hydraulic conductivity for both sets of samples were conducted in a flexible membrane test apparatus. For the first set of samples, the permeability coefficient of the sand was noted to be reduced 10‐fold (from 10^?5 to 10^?6 m s^?1) upon the incorporation of about 2% polymer. In the second set (samples prepared with the spraying method), the hydraulic conductivity was further reduced to 7.2 × 10^?7 at a polymer concentration of about 2%. Stress–strain measurements made on dry cylindrical specimens disclosed remarkable enhancement in the mechanical behavior of the system. For both types of preparation methods, the compressive strength and modulus of elasticity increased linearly with the polymer concentration in the sample. Scanning electron microscopic examination revealed that the dramatic reduction in the permeability and the improved mechanical properties are attributed to the polymer coverage of the sand particles and the development of interconnecting ties between them. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2484–2491, 2003     

New Type Anode for Calcium Ion Batteries Based on Silicon Carbide Monolayer

Silicon - A theoretical research study was conducted into the possibility of using a two-dimensional graphene-like material silicon carbide nano-sheet (2D-SiCNS) as an anode in rechargeable Ca-ion...     

Carbon Nanotube (10, 0) and Silicon Nanotube (7, 0) as a Novel Material for Drug Delivery of Substituted Eugenols as Antioxidant Drugs

Silicon - The potential of CNT(10, 0) and SiNT(7, 0) and their metal doped CNT(10, 0) and SiNT(7, 0) to adsorb the NH2, OH and Ethyl eugenols are examined. The antioxidant potential of NH2-, OH-...     

CuII Pyrazolyl-Benzimidazole Dinuclear Complexes with Remarkable Antioxidant Activity

Three dinuclear coordination complexes generated from 1-n-butyl-2-((5-methyl-1H-pyrazole-3-yl)methyl)-1H-benzimidazole ( L ), have been synthesized and characterized spectroscopically and structurally by single crystal X-ray diffraction analysis. Reaction with iron(II) chloride and then copper(II) nitrate led to a co-crystal containing 78 % of [Cu(NO₃)(μ-Cl)( L’ )]₂ ( C₁ ) and 22 % of [Cu(NO₃)(μ-NO₃)( L’ )]₂ ( C₂ ), where L was oxidized to a new ligand L^’ . A mechanism is provided. Reaction with copper chloride led to the dinuclear complex [Cu(Cl)(μ-Cl)( L) ]₂ ( C₃ ). The presence of N−H⋅⋅⋅O and C−H⋅⋅⋅O intermolecular interactions in the crystal structure of C₁ and C₂ , and C−H⋅⋅⋅N and C−H⋅⋅⋅Cl hydrogen bonding in the crystal structure of C₃ led to supramolecular structures that were confirmed by Hirshfeld surface analysis. The ligands and their complexes were tested for free radical scavenging activity and ferric reducing antioxidant power. The complex C₁ / C₂ shows remarkable antioxidant activities as compared to the ligand L and reference compounds.     

Structural Study of the Partially Disordered Full‐Length δ Subunit of RNA Polymerase from Bacillus subtilis

The partially disordered δ subunit of RNA polymerase was studied by various NMR techniques. The structure of the well‐folded N‐terminal domain was determined based on inter‐proton distances in NOESY spectra. The obtained structural model was compared to the previously determined structure of a truncated construct (lacking the C‐terminal domain). Only marginal differences were identified, thus indicating that the first structural model was not significantly compromised by the absence of the C‐terminal domain. Various ¹⁵N relaxation experiments were employed to describe the flexibility of both domains. The relaxation data revealed that the C‐terminal domain is more flexible, but its flexibility is not uniform. By using paramagnetic labels, transient contacts of the C‐terminal tail with the N‐terminal domain and with itself were identified. A propensity of the C‐terminal domain to form β‐type structures was obtained by chemical shift analysis. Comparison with the paramagnetic relaxation enhancement indicated a well‐balanced interplay of repulsive and attractive electrostatic interactions governing the conformational behavior of the C‐terminal domain. The results showed that the δ subunit consists of a well‐ordered N‐terminal domain and a flexible C‐terminal domain that exhibits a complex hierarchy of partial ordering.     

Improving the oxygen barrier properties of polyethylene terephthalate by graphite nanoplatelets

Enhancement of the oxygen gas barrier properties of polyethylene terephthalate (PET), used in the packaging industry, is the main objective here. For this purpose, nanocomposites of PET containing graphite nanoplatelets (GNPs) were prepared by melt compounding. The effects of the nanocomposites' structural morphology on oxygen gas permeability were analyzed using a range of thermal, microscopic, and mechanical characterization techniques. The investigated nanocomposite films exhibited GNP exfoliated morphology and good mixing with PET, as well as uniform dispersion within the polymer. All nanocomposite films were shown to possess superior oxygen barrier properties and improved thermal and dimensional stability compared with the plain PET films. In the best case, for 1.5 wt % GNP, the oxygen permeation was reduced by more than 99%. The improved barrier properties are attributed to the direct effect of the GNPs and to their induced increase of degree of crystallinity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Optimization of rotor speed based on stretching,efficiency, and viscous heating in nonintermeshing internal batch mixer: Simulation and experimental verification

Optimization of rotor speed based on stretching, efficiency, and viscous heating in nonintermeshing internal batch mixer has been investigated using polymer melt. A practical optimization technique was followed for optimization. Four different rotor speeds were used and characterized numerically with viscous dissipation and stretching. The heat distribution between rotor edge and mixer wall was calculated. Stretching experienced by the fluid was analyzed and the result was verified experimentally using particle tracking method. Exponential increase of energy dissipation between the rotor edge and the barrel at higher speed highlighted the importance of choosing the thermal properties of the polymer to avoid thermal degradation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013