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Aims: In bone tissue engineering, the scaffold as a supportive structure, plays a vital role. Putting the scaffold in dynamic cell culture, such as perfusion bioreactor, makes the role of mechanical parameters such as shear stress and hydrodynamic pressure more important. On the other hand, these mechanical parameters are influenced by scaffold architecture. In this study, the effects of bone scaffold architecture on mechanical stimuli have been analyzed and their effects on the mesenchymal stem cell fate have been predicted.
Material & Methods: Using the tools of computer simulation, five bone scaffolds (Gyroid, high porous Gyroid, Diamond, IWP, and gradient architecture Gyroid) based on mathematical functions of minimal surfaces were designed and exposed in a simulated dynamic cell culture under the inlet velocities of 1, 10, 25, 50, and 100μm/s. Cell accumulation on the inner part of the scaffold was considered as an 8.5-micron layer. This layer was designed for Gyroid and IWP scaffolds.
Findings: Based on the results, Diamond scaffold showed the most efficient performance from the homogeneity of stresses point of view. In the presence of the cell layer, the von Mises stress was reported as 60 and 50 mPa on the Gyroid and IWP scaffolds, respectively which eases osteogenic differentiation.
Conclusion: In gradient architecture scaffolds under dynamic conditions, there is a gradient in shear stress that causes various signaling in different positions of theses scaffold and facilitates multi-differentiation of the cells on the same scaffold.

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Microbial spoilage and staling are the most important reasons for the amount of bread waste. In order to extend the bread shelf life, either different bread improvers such as hydrocolloids or appropriate specific packaging like modified atmosphere packaging (MAP) can apply. In this study, the effects of hydrocolloid on quality properties of Sangak bread were investigated. The gum Hydroxypropylmethylcellulose (HPMC) was added to the formulation at 0.5 and 1%) w/w of flour) concentration. As a control, no gum added formulations were used. Wheat bread samples were packaged in polyamid/ polyethylene bags with different gas combinations. Two gas concentrations tested included: air, and 100% CO₂. All packaged bread samples were stored at 25°C for 15 days. Quality and microbial features of bread such as moisture, texture, and mold and yeast count were assessed at intervals of three days during storage. Statistical analysis of the results of bread quality characteristics during storage revealed that, the gas in headspace of package did not significantly affect the product moisture content, while shear stress, maximum force and the microbial load of the samples were thoroughly impressed by it. So that with carbon dioxide, the growth of mold and yeasts was more limited. Also was observed all product quality characteristics change significantly during storage time. So that the reduced moisture were observed up to 12th day. Conversely hardness, shear stress and microbial load increased during the storage period. The breads containing 1% HPMC showed the lowest maximum force and shear stress. Control showed the highest moisture and mold and yeast count all over the storage period.  

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Abstract: In this paper the experimental study of the flow pattern around a round wall jet has been carried out to investigate the effect of the bed roughness on the turbulence characteristics, including Reynolds stress and turbulence intensities. Measurements were conducted using the three-dimensional velocimeter, ADV and time series of the velocity components are used to investigate the variation of the turbulent flow parameters along the measuring domain. The results showed that by increasing the bed roughness, the streamwise and vertical turbulence intensities increase by downstream distance and for a specific bed roughness the streamwise turbulence intensity is higher than the vertical one. Furthermore, by going downstream from the jet entrance the bed shear stress reduces and by increasing the bed roughness, the bed shear stress has an increasing trend along the jet centerline. Location of the maximum bed shear stress does not change by changing the bed roughness.

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The research was conducted in order to determine the bending stress, Young’s modulus, shearing stress, and shearing energy of safflower stalk as a function of moisture content and stalk region. The bending forces were measured at different moisture contents and the bending stress and the Young’s modulus were calculated from these data. For measuring the shear forces, the stalk specimens were severed by using a computer aided cutting apparatus. The shear energy was calculated by using the area under the shear force versus displacement curve. The experiments were conducted at four moisture contents (8.61, 16.37, 25.26, and 37.16% wb) and at three stalk regions (bottom, middle, and top). Based on the results obtained, the bending stress decreased as the moisture content increased. The value of the bending stress obtained at the lowest moisture content was approximately 2 times higher than that of the highest moisture content. Bending stress values also decreased from top to the bottom of stalks. The average bending stress value varied from 21.98 to 59.19 MPa. The Young’s modulus in bending also decreased as the moisture content and diameter of stalks increased. The average Young's modulus varied between 0.86 and 3.33 GPa. The shear stress and the shear energy increased with increasing moisture content. Values of the shear stress and energy also increased from top to the bottom of stalks due to the structural heterogeneity. The maximum shear stress and shear energy were found to be 11.04 MPa and 938.33 mJ, respectively, both occurring at the bottom region with the moisture content of 37.16%.

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Neurological diseases such as cancer, damage blood brain barrier and consequently cause more permeability in tissues. In general if there is damage to the brain tissues, the contrast agent used in MRI, diffuses outside the capillaries and the MRI picture brightness changes. The purpose of this paper is to show the effects of different parameters on the contrast agent diffusion in the brain capillary. In this study, the lattice Boltzmann method with multi-relaxation time (MRT) is used to simulate the flow in the capillary and porous media around it. The results show that the porosity in extravascular tissues (it shows the tissue damage), the kind of contrast agent and capillaries curvature have impact on the contrast agent diffusion in the tissues. The presented results show the effects of curvature on shear stress and thus on mass transfer in the capillary. It should be noted that the presented results have been evaluated by previous statistical and analytical results for flow in the damaged brain capillary with different permeability. It has been shown that the lattice Boltzmann method is able to simulate the complex problems especially in porous media.

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Population and civil infrastructure continue to expand at unprecedented rates. On the one hand, the growing needs for the development and, on the other hand, the environmental crisis, stress the importance of finding methods not harming the environment while they are able to meet the requirements for development. Infrastructure demands are even more severe in other countries, particularly in developing ones. Infrastructure is insufficient in countries such as China, where 10 million people immigrate to major cities each year. Population growth is particularly acute for historic cities and regions where expansion is limited by geographical boundaries and inadequate soil conditions. The confluence of these factors necessitates the exploration and development of new alternative soil improvement methods and associated reliable monitoring techniques. Bio-mediated soil improvement is an innovative, and interdisciplinary technique with the approach of being environmentally friendly, which utilizes some bacteria utilizing some bacteria to precipitate calcite on soil particles. In addition, this system broadly refers to a chemical reaction network that is managed and controlled within soil through biological activity and whose byproducts alter the engineering properties of soil. Therefore, Microbial carbonate precipitation (MCP) has experienced an increased level of interest in recent years for applications such as restoration of calcareous stone materials , bioremediation, wastewater treatment, strengthening of concrete and selective plugging for enhanced oil recovery. In this research, to attain the highest number of experiments without repeating the unnecessary ones, Taguchi design method was utilized. The Taguchi method was developed to improve the implementation of total quality control. The effect of factors on characteristic properties (response) and the optimal conditions of factors can be determined using the Taguchi design. It is feasible to find out the optimal experimental conditions with the least variability. Taguchi analysis is based on choosing the best run by analyzing signal-to-noise ratio (S/N), whose form depends on the experiment objective. A standard L9 orthogonal array with four parameters consisting of bacterial cell concentration, molar concentration ratio of nutrient solution, curing time, and inoculum ratio, each was assigned three levels, was selected. In this regard, soil samples were stabilized in sandy soil columns. Two-phase stabilization were conducted by adding the bacterium Sporosarcina pasteurii PTCC 1642 in the first phase and nutrient in the second phase. Specimens were subjected to direct shear stress test with the normal stress of 12.5, 40, 68 kPa. ANOVA suggested that the effect of each parameter on the direct shear stress. The most effective parameter was curing time with 45.97% of the overall variance of the experimental data followed by bacterial cell concentration (22%), molar concentration ratio of nutrient solution (20%), and inoculum ratio (12%). The direct shear strength increased from 6, 18, 31 kPa for the normal stress of 12.5, 40, 68 kPa to 470, 491, 512 kPa in optimally treated specimens.

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Vertebrobasilar system stenosis is one of the risk factor for deaths caused by stroke, the risk of stenosis in these arteries are highly depend on the people’s age. In the present study, atherosclerosis susceptible sites in vertebrobasilar system at different ages 20, 50 and 70 have been investigated. Numerical method (Fluent software) is employed to solve the equations. Blood flow is simulated in these arteries to investigate probable risky sites (prone to stenosis). To find these locations, critical values of the averaged wall shear stress (AWSS) and oscillatory shear index (OSI) have been studied. By considering the AWSS and OSI criteria in 20 years old person it becomes clear that the risk of stenosis is not considerable at this age, somehow ageing increases OSI figures in the right vertebral artery and in its junction reaching to the critical values, besides at this age, the area of the sites with lower amount of AWSS are stretched significantly. At the age of 70, risky sites are expanded toward right vertebral artery. Furthermore the risk of stenosis in all determined risky sites of age 50 increased at the age of 70.

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The variation of wall shear stress (WSS) in the microvessels may damage the endothelial layers. It also changes the mass diffusion and sediment and may be considered as an important factor in the formation of the fatty plaques and causing heart disease. According to the importance of the issue, the aim of this paper is to study the effective parameters on the wall shear stress in microvessels. In this paper, the hybrid method, combined lattice Boltzmann and immersed boundary methods is used to simulate the red blood cell (RBC) motion in the plasma flow. It should be mentioned that red blood cell has significant effect on WSS, in this regard; the present results show that the blood rheological behavior has the important effect on WSS. The results also demonstrate the effect of stenosis severity and RBC location in different regions on wall shear stress and consequently causing heart, coronary disease. It should be noted that the presented results have been evaluated by previous numerical results for microvessels and the results show the ability of lattice Boltzmann method to simulate complex problems especially for modeling the deformable solid objects suspended in the fluid.

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Stenting is considered to be the favoured tool for therapy of coronary stenosis disease. However, despite the many advantages of this treatment strategy, its outcome may be undermined by the restenosis occurrence in the stent deployment site. Observations have shown that stent deployment in the artery alters the hemodynamic parameters such as wall shear stress and vortices size and prepares the conditions for in-stent restenosis development. Considering this fact, in this paper, the effect of some geometrical parameters such as the shape and the size of the stent strut on the wall shear stress distribution and vortices size is investigated. Furthermore, employment of a stent with partial flexible strut is suggested to decrease the restenosis risk, and the effect of the flexible part stiffness is explored. For this purpose, the interaction between the blood flow and the flexible part is simulated by arbitrary Lagrangian-Eulerian approach in the framework of the finite element method. The results indicate that in stents with circular strut, the partial flexibility of the cross-section can be effective in reducing the restenosis risk by lowering the maximum value of the wall shear stress and considerably decreasing the vortices size. On the other hand, in stents with rectangular struts, it not only does not decrease the shear stress maximum value but also significantly increases the vortices size and may lead to increase of the restenosis risk.

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Recognizing the relations between different variables of fat replacing, modeling could contribute to an optimum control of the process and accordingly improve the quality of the final low fat product such as yogurt. In the present study, the Response Surface Methodology (RSM) and Central Composite Design (CCD) has been applied to investigate the effects of different concentrations of inulin (0, 3 and 6%) as a fat replacer, heat treatment (70, 82.5 and 95°^c) and various shear stresses using a stirrer (3000, 6000 and 9000 RPM) on gelling properties of yogurt and also different quality attributes of a low fat yogurt. The equations obtained from the study showed that undependent variables had significant effects on the measured attributes (p<0.05). The most effective factor was inulin concentration that improved the low fat yogurt texture, although higher concentrations had negative effect on sensory properties and color. On the other hand, heat treatment had significant effect on gelling ability of yogurt. In sum, sample with 3% inulin, processed at 82.5°^C and stirred at 6000 RPM was selected as optimum condition for prebiotic yogurt processing by inulin.

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Due to low surface energy and hierarchical roughness, fluids on superhydrophobic surfaces are mobile. The slip velocity on these surfaces is formulated using Navier’s slip length. On regular surfaces, slip length is only a few nano-meters. On superhydrophobic surfaces, slip length can be as large as 500 µm. Literature studies usually make the entire surface superhydrophobic which may not be the optimum situation. To find the desirable regions, the problem should be analyzed numerically. Most of the numerical studies are for flat plates. On curved surfaces (e.g. foils), due to the adverse pressure gradient and possibility of separation, analysis is more complicated. Here, the effect of using superhydrophobic surface for a SD7003 hydrofoil is studied numerically and at different Reynolds numbers and slip lengths. The flow pattern is considered laminar, incompressible and isothermal and a hydrofoil made of aluminum with a chord length of 10cm is selected. Results of the shear stress, pressure coefficient and the drag coefficient on the typical boundary condition were compared with the case of slip boundary condition. It was found that by increasing the slip length, the drag coefficient decreases. It was also found that the effectiveness of using superhydrophobic surfaces in decreasing the drag coefficient improves at higher Reynolds numbers. By increasing the Reynolds number from 4.5×〖10〗^4 to 7.5×〖10〗^4 and at the slip length of 50 µm, the drag coefficient reduction increases from 0.7% to 7%.

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In this paper, static analysis of transversely anisotropic laminate is investigated using improved zig-zag theory. Variation of in-plane displacement is assumed to be sinusoidal while transverse displacement is assumed to remains constant through the thickness. This piece-wise continuous sinusoidal function satisfies transverse shear stresses continuity in interfaces. The Hamilton principle is utilized to derive governing equations and related boundary conditions. The Navier-type solution is presented for simply-supported boundary conditions. The theory has the same unknown variable field as Euler Bernoulli beam although it predicts stresses high accurately. The validity of solutions is confirmed by comparing present model results with that of reported in the literature. Numerical results are given to study the influences the transverse anisotropy on displacement, strain and stress fields through the thickness. The piece-wise continuous sinusoidal function offers more accurate transverse stress distribution in comparison with the piece-wise polynomial function. The present theory provide more slightly accurate stress field through the thickness compared to high order shear deformation theory, which in turn is more accurate than Euler-Bernouli theory. The results shows the continuity of normal strain through thickness predicted by Euler-Bernouli theory has not physical basis. Furthermore, the improved zig-zag theory is capable of capturing precise stress field through the thickness in transversely anisotropic laminate

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One of the focused problem in airway flow simulation is pulmonary airways modeling. There are two kind of Lung models, one is created anatomically based on bronchial data and second is realistic model which is created based on CT scan images. Unfortunately cause of modeling process or simplification cause of restriction of CPU and time, the result model is different from a really pulmonary airways. Anatomically model are many simplification and realistic model from CT scan have major limitation in CT image resolution and smoothing stage of make out the 3D model. Anyway the lung has many rough and the first thing that is vital on this way is cartilage rings as macro scale roughness. So the presented work, compared the airflow in both simple and modified Horsfield model by cartilage rings in term of time averaged wall shear stress which are important in engineering of Cell-Fluid Interactions (CFI). This is shown that cartilage rings affected the trachea and second generation of brunches so this is not reasonable to neglect the cartilage rings.

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In the new sheet metal forming process as incremental sheet forming and spinning forming, this is not perfectly true in Marciniak-Kuczyinski model to assume that sheet deformation occurs in the plane-stress state indispose there are normal compressive stress and through-thickness stress. In this type of forming processes, the obtained limit strains refer to improving the sheet forming. However, in researches the effects of through-thickness shear stresses, also known as out-of-plane shear, has been studied less. The generalized forming limit diagram is a great curve that includes all six components of the stress tensor. In this paper, the effect of normal comprehensive and through-thickness shear stresses on the limit strain AA6011 aluminum sheet using a modified M-K and the anisotropic Yield function, Hill 48 and by using numerical solutions of nonlinear equations, Newton-Raphson method. The first the forming limit diagram was drawn with the assumption that the through-thickness shear stresses and then the effects of normal comprehensive stress and through-thickness shear stress on the limit strains were proved and the generalized forming limit curves were obtained. The results show that forming limits can be increased significantly by both normal compressive stress and through-thickness shear stresses. Also, the effects of normal stress on increasing the formability of sheet compared with the effects of through-thickness shear stress is greater.

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This experiment was conducted in order to determine the hydrodynamic performance of a Triangular Winged Bandal-Like (TWBL) structure, which is a combination of the Bandal-Like (BL) structure and Triangular Vane (TV). For the purposes of this study, the JFE ALEC magnetic velocity meter was used to measure the three components of flow velocity under non-submerged hydraulic conditions at a Froude number of 0.24. The three considered cases for this measurement were the non-structured case and the BL and TWBLs. The results showed that the flow deviation occurred through the impermeable upper part of both structures towards the middle of the channel. At downstream of both structures, bubbling flows were caused by the collision of upward flows with the near-surface flow, causing disturbances in the latter. Both the BL and the TWBL structure reduced the secondary flow strength along the bend within the structure range. Compared to the BL structure, the TWBL structure reduced the secondary flow strength by about 20%, which indicates the weaker inclination of the secondary flow toward the outer bank in the TWBL structure. The relative maximum shear stress in the TWBL structure is on average 17% lower than that of the BL structure.