Introduction Due to problems with on-site irrigation channels, such as occupying a high level of the land, a lack of suitable loan materials, and the possibility of dealing with multiple complications, the use of prefabricated channels is one of the most competitive options available for the existing channels. From the theoretical point of view, the most effective hydraulic cross-section for the coated channels in which smooth water flows is the semicircular section. Nevertheless, in terms of implementation, the use of the semicircular cross-section is generally limited to the reinforced concrete channel. One of the important issues in outdoor hydraulic engineering is having sufficient knowledge about the amount of hydraulic resistance against the flow. The estimation of hydraulic resistance of the flow in open channels has always faced a serious challenge because of the presence of secondary currents and the vortex viscosity. The determination of the contribution of flow pipes in the bed and wall is faced with errors due to the effects of the walls on the maximum velocity position. Accurate prediction of boundary shear stress distributions in the open-channel flow is crucial in many engineering problems, such as channel design, the balance of energy, and sedimentation. Determining the exact bed and wall shear stress is important from a theoretic and applied point of view, for example, its role in scour and sedimentation studies and designing shield conservations...

Blood flow to the living tissues of the body is the most critical processes in living organisms. Blood pressure and velocity in the blood vessels depend on the pumping ability of the heart rate, vessel diameter and flexibility, and the presence or absence of stenosis. Computational simulation and modeling is an effective tool to investigate the behavior of blood flow. Using the mentioned method it can be obtained detailed information about velocity profile, shear stress, pressure drops, stagnation points, stenosis, and clotting. In this paper, Computational Fluid Dynamics (CFD) is used to investigate aggregation of red blood cells in a rigid vessel wall while asymmetric stenosis occurred within it. The governing equations of the momentum, shear stress on the wall of blood vessel, and red blood cells movement in both normal and in the presence of a clot are numerically solved. The simulation results show that the presence of a clot in blood significantly affects the velocity, pressure, and shear stress, especially in stenosis.

Background & Aim: The purpose of this study was to evaluate the micro-shear bond strength of two kinds of resin-based cements with fluoride release with the usage of five adhesive systems to enamel and dentin. Materials & methods: Bovine flat enamel or dentin surfaces were used in this study. Micro cylinders of resin cement with Xeno Cem Plus (XCP) or Panavia Fluoro Cement (PFC) were bonded to enamel or dentin as followed: XCP or PFC as instructions prior to the usage of their own adhesive systems, Xeno CF II+XCP, SE Bond+PFC, or Clearfil Liner Bond II (CLB) + PFC. After the storage in 37°c water for 24 hrs, micro-shear bond test was applied for all the test groups. The data were statistically analyzed using two-way analysis of variance (ANOVA). After two-way ANOVA, one-way ANOVA and multiple comparisons with Fishers PLSD test were made.Results: Are given as follow (enamel and dentin, mean±SD in MPa); XCP, 13.7±4.0 and 15.5±9.2; PFC, 23.7±10.6 and 15.0±7.3; XCP+XCF II, 35.4±11.5 and 17.1±4.0; PFC+SE, 54.2±9.8 and 41.7±12.0; PFCCLB, 31.39±3.09 and 15.09±4.35. ANOVA (α=0.05) analyze revealed the usage of SE Bond under PFC significantly increased the bond strength to both enamel and dentin. Bonding of Xeno CFII was only improved the bonding to enamel with the application of XCP.Conclusion: Light-cure adhesive systems significantly improve the bonding of current resin cements.

Long span beams with heavy load require increasing the thickness of web and in many cases using a number of stiffeners needs to improve the lateral buckling difficulty. Development and application of corrugated steel web provides facilities to modify the web thickness of beam girders in the design and construction procedure. The attractiveness for using corrugated webs in bridges and composite sections has been increased in recent years. The new system combines the usage of either corrugated steel plates as webs or steel or reinforced/ prestressed concrete slabs as flanges.The application of corrugated steel web may reduce the thickness of webs and restricts it between 2 to 5mm while increases the portion of height/thickness of corrugated web girders in industrial structures up and about 260 and even for long span bridges up to 400.Manufacturers have produced different corrugated profiles such as sinusoid, trapezoid and other forms. The investigations show that the most significant weakness of application of the corrugated web beams is failure due to shear stress. The flanges are assumed to provide the flexural strength of the girder with no contribution from the corrugated web, which is assumed to provide the entire shear capacity of the girder. The corrugated web is thus, subjected to an “almost” pure shear stress state. Failure of a corrugated steel web plate may occur by the classical steel yielding of the web under a pure shear stress state. It may also occur by web buckling due to either local instability of any “panel” between two folds or overall instability of the web over two or more panels. An interactive failure mode between these different failure criteria represents another possibility of failure and so many researchers have considered global, local and semi global buckling in phenomena due to shear strength in their research work.In this paper nonlinear 3D Finite Element Model with regarding buckling modes phenomena for shear analysis of different profile shape of available manufacture corrugated webs is intended.  The model is verified with published experimental results and sensitivity of the involved parameters is investigated. As presented in the following figure, the post-buckling strength of girders with corrugated steel webs could be investigated by this model.The geometric parameters that influence the shear resistance of trapezoidal corrugated web girders investigated in this study, involve:1) Corrugation angle 2) Width of the plane sub panel of the web 3) Web thickness 4) Height of the web 5) Corrugation depth of the web. The parameter study is developed for the sine corrugated web by focusing on amplitude of the central curve of the web and the wave length of the central curve of the web. Corrugated web shear capacity is changed by altering of the amplitude and wave length of the sinusoidal corrugated web. These changing manners are presented in the following figures respectively:Results show, the sinusoidal webs have better performance than trapezoidal webs in the same conditions. The optimum size of trapezoid and sinusoid dimensions depends to the thickness of applied plate for producing the profile. Concerning to the manufacture restriction for production of profile, the study shows that the maximum shear strength will appear in the sinusoid profile for amplitude of 3 to 4 centimeter while in the trapezoid profile the equal dimension for flat and inclined part in the profile provides maximum shear strength.