Two novel demountable shear connectors for precast steel-concrete composite bridges are presented. The connectors use high-strength steel bolts, which are fastened to the steel beam with the aid of a special locking configuration that prevents slip of bolts within their holes. Moreover, the connectors promote accelerated construction and overcome typical construction tolerances issues of precast structures. Most importantly, the connectors allow bridge disassembly, and therefore, can address different bridge deterioration scenarios with minimum disturbance to traffic flow, i.e. (1) precast deck panels can be rapidly uplifted and replaced; (2) connectors can be rapidly removed and replaced; and (3) steel beams can be replaced, while precast decks and shear connectors can be reused. A series of push-out tests and a beam test were conducted to assess the behavior of the connectors and quantify the effect of important parameters. The experimental results showed that shear resistance and slip capacity can reach 2.5 and 2.7 times respectively of those of welded shear studs along with superior stiffness and strength against slab uplift. Additionally, shear stiffness of M16 mm LNSC was equal to that of M19 mm welded studs. Identical tests reveal negligible scatter in the shear load – slip displacement behavior. Design equations are proposed to predict the shear resistance with minimum deviations.
Carbonized nonwoven nanofibers composite were fabricated using the electrospinning method of a polymeric solution composite followed by heat treatment including stabilization and calcination steps. The spun polymeric solution was a binary polymer mixture/organic solvent. In this study, two types of polymers (Polymethylmethacrylate (PMMA) and Polyethylene glycol (PEG)) were used separately as a copolymer with the base polymer (Polyacrylonitrile (PAN)) to prepare a binary polymer mixture in a mixing ratio of 50:50. The prepared precursor solutions were used to prepare the precursor nanofibers composite (PAN: PMMA) and (PAN: PEG). The fabricated precursors nonwoven fibers composite were stabilized and carbonized to produce carbon nonw
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Background: This study compared in vitro the marginal adaptation of three different, low shrink, direct posterior composites Filtekâ„¢ P60 (packable composite), Filtekâ„¢ P90 (Silorane-based composite) and Sonic fillâ„¢ (nanohybrid composite) at three different composite/enamel interface regions (occlusal, proximal and gingival regions) of a standardized Class II MO cavity after thermal changes and mechanical load cycling by scanning electron microscopy. Materials and methods:Thirty six sound human maxillary first premolars of approximately comparable sizes were divided into three main groups of (12 teeth) in each according to the type of restorative material that was used: group (A) the teeth were restored with Filtekâ„¢ P6
... Show MoreThis study aims to evaluate the influence of the air abrasion of dentin on the shear bond strength of lithium disilicate using three different types of luting cements. Sixty cylindrical specimens were milled from lithium disilicate CAD/CAM blocks (IPSe.max CAD). Sixty sound human maxillary premolar teeth were decoronated to the level of peripheral dentin, then randomly divided into three groups according to the type of luting cement used for the cementation of the lithium disilicate specimens (n = 20); Group A: Glass ionomer cement (Riva Self- Cure); Group B: Adhesive resin cement (Rely X Ultimate); Group C: Self-adhesive resin cement (Rely X U200). Each group was then further subdivided into two subgroups (n=10); Subgroups AI, BI, and CI,
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The importance of research is to be considered by highlighting the tax policy in Iraq which extended for successive measurement of the amount of tax receipts for respective periods, the research problem represents security, economic and political issues that Iraq suffered which were very difficult since Nineties of the last century until now that led to a lake of clarity in tax policy trends, volatility in it and finally reflected on the tax revenues increase or decrease. One of the main recommendations of the research is: (The necessity to develop a deliberate strategy for tax policy in Iraq which should take into account financial, economic, and social goals in appropriate way).
Objective : Multiple sclerosis (MS) is a common neurological disease deeply linked with the immune-inflammatory disorders whereas the term (multiple) mostly refers to the multi-focal zones of Inflammation caused by lymphocytes and macrophages infiltration besides oligodendrocytes death. Accordingly , the dysfunctional immune system able to damage myelin ( a pivotal component of the central nervous system ) which responsible for communication among neurons. The aim of the present study is to innovate a biochemical relationship between MS and thyroid hormones (THs) by highlighting immunological responses and also to examine the action of Interferon beta (IFNβ) drug on thyroid hormone (THs) and thyroid stimulation hormone (TSH). Materials and
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Abstract
The research aims to identify tax exemptions, their objectives and types, as well as to shed light on the concept of sustainable development, its objectives, dimensions and indicators (economic, social and environmental), as well as to analyze the relationship between tax exemptions and economic development, in addition to measuring and analyzing the impact of tax exemptions on economic development in Iraq for the period ( 2015 - 2021) using the NARDL model. The research problem centers on the fact that failure to employ financial policy tools correctly led to a weakness in achieving economic justice, which leads to a failure to improve social welfar
... Show MoreIt is known that energy subiect has ocuppied a lot of scientests minds about
how to treat the traditional energy and the renewing energy . we know that
most traditional energy coal , oil , Natural gas, neuclear fuel , are limited
guantiy and alsow subjected to be ended .Statics studies refer to reserve
of oil in world will exhausted btween ( 2075- 2100) and alsow cosl too .
While neuclear fuerl which the world seek today through explod the uranium
atom ( 233) the therum atom (239) and neuclear mxied through ruemlear
mixing , These energy have effect on environment and humanity speciaty if
they are used in militery purposes .
For all theses scientests srarch for resources of renewing enery through
researches
In the present work, Response Surface Methodology (RSM) was utilized to optimize process variables and find the best circumstances for indirect electrochemical oxidation of mimicked wastewater to remove phenol contaminants using prepared ternary composite electrode. The electrodeposition process is used for the synthesis of a ternary composite electrode of Mn, Co, and Ni oxides. The selected concentrations of metal salts of these elements were 0.05, 0.1, and 1.5 M, with constant molar ratio, current density, and electrolysis time of 1:1:1, 25 mA/cm2, and 2 h. Interestedly, the gathered Mn-Co-Ni oxides were deposited at both the anode and cathode. X-ray diffraction (XRD) and scanning electron microscopy (SEM) facilitated the qualitative char
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Experimental investigations had been done in this research to demonstrate the effect of carbon fiber and Ceramic fillers contents on the tribological behaviour of (15% volume fraction) carbon-epoxy composite system under varying volume fraction, load, time and sliding distance. The wear resistance were investigated according to ASTM G99-05standard using pin on disc machine to present the composite tribological behaviour. The influence of three ceramic fillers, granite, perlite and calcium carbonate (CaCO3), on the wear of the carbon fabric reinforced epoxy composites under dry sliding conditions has been investigated. The effect of variants in volume fraction, applied load, time and sliding distance on the wear behaviour of po
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