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• In this study, the apparent digestibility of protein and amino acids of  ten types of plant and animal feed ingredients as the main sources of protein was evaluated in Siberian sturgeon diet (290-250 g).

Materials and Methods: Feedstuffs included fish meal, meat and bone meal, poultry byproduct meal, blood meal, feather meal, soybean meal, rapeseed meal, wheat gluten, corn gluten and bakery yeast. The dietary treatments included: reference diet and ten different experimental rations (30% of the target feed ingredient + 70% of the reference diet). Chromic oxide was used as an indigestible marker in dietary feed. A group of 165 Siberian sturgeons stocked into 33 tanks with 500 liters volume and fed with test diets (3 replicates per diet).

• At the end of the experiment, the highest and lowest protein digestibility was observed in fish meal (92.87%) and poultry byproduct meal (59.96%), respectively. Also, the highest level of amino acid digestibility in fish meal was measured (90.9% and 88.13% for total essential and non-essential amino acids respectively). The lowest digestibility of the essential amino acids was observed in rapeseed meal (65.5%) and non-essential amino acids in poultry powder (60.68%). Conclusion: Based on the results of the present study, fishmeal, meat and bone meal, poultry byproduct meal, corn gluten and wheat gluten were identified as feed ingredients with high protein and amino acids digestibility for Siberian sturgeon.

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This research is devoted to the adaptive solution and control point net improvement of axisymmetric problems in isogeometric analysis using the error estimation based methods for stress recovery. For this purpose, after the calculation of the energy norm, the estimated value of error in the vicinity of each control point is assigned to the neighboring members of a hypothetical truss-like structure as an artificial thermal gradient. By analysis of this network of rods under the temperature variations a new arrangement of control points is obtained. Repeating this process of thermal isogeometric analysis will eventually lead to a better distribution of errors in the domain of the problem and results in an optimal net of control points for the calculation of the integrals. To demonstrate the performance and efficiency of the proposed method, two axisymmetric elasticity problems with available analytical solutions are considered. The obtained results indicate that this innovative approach is effective in reducing errors of axisymmetric problems and can be employed for improving the accuracy in the context of the isogeometric analysis method. Innovated method of this research focuses on adaptive analysis and Network improving of axisymmetric problems in isogeometric analysis using error estimation methods based on stress recovery. For this purpose after calculation the energy norm, estimated value of error in the vicinity of control points is assigned to each rod as the thermal gradient. Thus after analyzing the hypothetical rods network under the temperature changes a new arrangement of control points and knot vectors can be obtained. The use of multi-cycle of this process in isogeometric analysis will lead to a better distribution of errors in the domain and thus achieve optimal network to calculate the integrals. To measure the efficiency of this method and demonstrate the increased carefully in axisymmetric problems, which has the analytical solution, two elasticity problem is evaluated. The results show that innovative network improving method has good efficiency to reduce the error rate and can be used to increase the accuracy of isogeometric analysis results. Innovated method of this research focuses on adaptive analysis and Network improving of axisymmetric problems in isogeometric analysis using error estimation methods based on stress recovery. For this purpose after calculation the energy norm, estimated value of error in the vicinity of control points is assigned to each rod as the thermal gradient. Thus after analyzing the hypothetical rods network under the temperature changes a new arrangement of control points and knot vectors can be obtained. The use of multi-cycle of this process in isogeometric analysis will lead to a better distribution of errors in the domain and thus achieve optimal network to calculate the integrals. To measure the efficiency of this method and demonstrate the increased carefully in axisymmetric problems, which has the analytical solution, two elasticity problem is evaluated. The results show that innovative network improving method has good efficiency to reduce the error rate and can be used to increase the accuracy of isogeometric analysis results.

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Nowadays wobble motors are widely utilized as actuators with high torque rotary motion producing capability without the need for external gearbox. This study contains theoretical, numerical and experimental analysis of a planar wobble motor with compliant mechanism driven by shape memory alloy (SMA) wires. The cyclic expansion and contraction of SMA wires is converted to the plane curvilinear motion with circular path and then to the continuous unlimited rotary motion by means of a compliant mechanism and a gear system consisting of an internal and an external gear. After gear system designing based on achievable motion range caused by SMA wires length change, the relations between output torque, geometrical properties of motor and stress in SMA wire were derived. Also compliant mechanism parameters consisting of length, height, thickness and number of flexures were analyzed with the aim of mechanism stiffness calculating. Then the frequency analysis with finite element method is performed to investigate structural robustness and operational stability of designed mechanism. The designed motor is fabricated as a prototype to investigate its operational feasibility and working performances. The experimental results demonstrate motor capability in producing unlimited continuous rotary motion and repeatability of maximum output torque. The Maximum output torque was measured as 29.9, 32.7 and 34. 3mN.m for 1.6, 1.8 and 2v applied voltages respectively. With consideration of motor characteristics, it is appropriate for high torque and low speed applications with limited work space.

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With the growth of science and technology, engineering issues are becoming more complex. As problems become more complex and need to be resolved more quickly and accurately, past analytical methods no longer meet the growing needs of societies. With such an attitude, researchers have always tried to develop numerical methods in addition to developing the basics of science. In this direction, several methods have been developed by researchers. Each of these methods has its own applications and still researchers are trying to grow and develop these methods and invent new methods. The most important of these are the nonlinear isogeometric method which is based on non-uniform rational B-Splines (NURBS). In the nonlinear isogeometric method, while using the properties of the basic functions of spline and NURBS in the exact definition of curves and surfaces, they are also used for interpolation and approximation. Using all the capacity of the structure in load bearing causes nonlinear behavior of the structure which is due to improper performance of the structure geometry, weakness of the structural materials and weakness due to the combination of the two previous states. In this study, nonlinearity due to material weakness has been considered. Also, in solving nonlinear equilibrium equations, an incremental and iterative process of load is used and this increase is done until the total loads defined for each problem are entered. In each increase, the iterative process is adopted until convergence or the maximum number of iterations is achieved. Obviously, all numerical methods are approximate methods. The main source of error in numerical methods is related to the discretization error of the continuous environment and is due to the approximation of the displacement field by the shape functions. This group of errors is also reduced by making the elemental mesh smaller and increasing the degree of shape functions used. Error is an integral part of numerical analysis and has always been a concern for researchers in the reliability of the results. Therefore, in this study, the error estimation based on the stress recovery method based on points where the order of gradient convergence of a function is one time higher than the value expected from the approximation of the shape function related to the approximate solution (superconvergent points) is discussed. Thus, by considering the difference between the recovered stress level and the stress level obtained from nonlinear isogeometric analysis for each element, a criterion has been determined approximately to determine the amount of error in that element. All research relationalizations and linearization of equations have been performed using a numerical algorithm with the help of programming in Fortran software environment and the results of the analysis for validation have been compared with its classical solution. The results show acceptable numerical and distributive similarity; Therefore, it can be said that the analysis performed by the program has good performance for nonlinear analysis of problems. Also, the error estimation method used can be called a simple and engineering solution to estimate the error and improve the stress field obtained from elastoplastic analysis of problems by isogeometric method.

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Today, the use of functionally graded materials is increasing. In these materials, the mechanical properties change as a continuous function throughout the problem domain. Due to these continuous changes, the problems of non-adhesion of materials, delamination and stress concentration at the joint, which can be problematic in composite structures, do not arise. Numerical methods such as the finite element method can be used to analyze functionally  graded materials, but due to the limitations of this method, we will face many problems. The most important of these problems are the lack of a suitable element for the analysis of problems that can accommodate changes in the properties of materials, or the inability to accurately model the edges of shapes that have complex geometry, so in this research, the isogeometric method is used in which these weaknesses are eliminated. Also, since the error is an inseparable part of any numerical analysis and the reliability of the results has always been the main concern of the researchers, and in general, there is no exact answer to many problems, finding a solution to estimate the error in the calculations is of special importance. Therefore, in this article, for the first time, the isogeometric method has been developed in the analysis of problems with functionally graded materials with the approach of improving the stress field and estimating the error in it. This error estimator is in the category of error estimation methods based on stress recovery, and the goal is to increase the impact index of the error estimator and more adapt the error distribution method obtained from the proposed error estimator with the exact error estimator in solving problems. In this method, by using superconvergent points, where the order of convergence of the gradient of a function is one order higher than the value expected from the approximation of the shape function related to the approximate solution, a hypothetical surface is made for each stress value. To define this surface, we use the same shape functions used in the isogeometric method to approximate unknown functions. This hypothetical level is created when the coordinates x, y and z of its control points are specified. The x and y coordinates of each control point are used to model the geometric shape. The z component of the control points is calculated by minimizing the distance between this hypothetical level and the stress level obtained from isogeometric solution at the gauss-elements points of each region using the minimum square sum method. From the comparison of the exact error norm and the approximate error norm for sample problems, it can be seen that the proposed error estimation has a suitable efficiency for estimating the error in the analysis of problems with functionally graded materials by isogeometric method, and it can be used as a solution to error estimation and calculate the improved stress field level in solving functionally graded problems by isogeometric method. It is also possible to identify areas of the isogeometric solution domain that have a large error with the help of the proposed error estimator method and achieve local improvement of the network in those areas and increase the accuracy of the isogeometric solution.

 

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The degree of connection rigidity has a significant effect on the seismic behavior of steel frames. However, the lack of proper modeling methods or not considering the degree of rigidity of the connection in the design of structures, destroys the accuracy of the design. In conventional methods for the analysis and design of steel frames, the behavior of beam-to-column connections is assumed to be joint or fully braced. With these assumptions, the analysis and design of steel frames becomes easier. But the results of the tests show the existence of a degree of flexibility in the hypothetical clamp joints and a degree of stiffness in the common joint joints. Therefore, for accurate and economic analysis and design of steel frames, it is necessary to consider the tightness of the connections. Few researches have been done on the nonlinear modeling of steel connections with nonlinear shock absorbers, and most of these studies are also on the modeling of connections using the finite element method. This shows the need to deal with the correct and practical modeling of connections. There are various methods for numerical modeling and calibration of experimental and nonlinear behavior of structures, among them, the modeling method with nonlinear springs, plastic joint models, fiber models, and models can be used. Designing finite elements pointed out. One of the advantages of modeling with non-linear springs and plastic joints is the non-linear modeling of the failure zone with minimal degrees of freedom. In this method, calibrated functions are used to model the nonlinear behavior of the structure. But in the method of fiber models and finite elements, the nonlinear behavior of the structure is determined by assigning the nonlinear behavior of the materials. Disadvantages of the fiber modeling method include the absence of shearing and twisting effects, sliding between components, and cracking and crushing of materials. Finite element modeling also provides the ability of three-dimensional behavior, including complex geometries and multiaxial stress and strain states. In the finite element modeling method, determining the size of the elements requires a convergence test. Also, due to the high volume of calculations and its time-consuming nature, this method is used in detailed models to model a part of the structure. In this paper an accurate estimate of the seismic behavior of these joints and damage modes in them is obtained, using the behavior of valid laboratory samples, to be used as a criterion in numerical modeling. For this purpose, four common steel connections, have been investigated and numerical models are presented to consider the nonlinear behavior of the mentioned connections in the Opensees software. Cyclic behavior of experimental samples has been used to calibrate the characteristics of the proposed numerical model. The results show that with the proposed method, the seismic behavior parameters of the studied connections such as load bearing stiffness and ductility capacity in the experimental and numerical model are well matched and can be used to more accurately model in analyzing and applied designing to obtain an accurate estimate of the behavior of the connections and the degree of rigidity in the designs leading to the operation. It is important to compare the plasticity capacity, maximum bearing capacity and initial stiffness in the examined connections compared to their corresponding numerical models, and the difference between 0.29% and 8.42% in different situations confirms this.