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Re-vegetation of bare soil is believed to increase, or at least maintain the organic matter levels of soil. The aim of this study was to investigate the soil characteristics changes, nutrient pool sizes and their availability under mid canopy, and canopy gap positions of saltbush in an area re-vegetated with Atriplex lentiformis. Some of the physical and chemical soil characteristics (the particle size distribution, soil bulk density, EC, pH, Na, K, organic C, N, P, C/N ratio and C/P ratio) were measured in two different soil depths at both planted shrublands and control area. The results from samples analysis showed that the soil of the control area is significantly different from the Atriplex shrublands area. Maximum of K and Na proportion were measured in 0 to 20 cm under mid canopy in the planted sites. K and Na in different soil layer showed a significant difference between ungrazed area, grazing area and control area (P

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The Western flower thrips Frankliniella occidentalis, an important greenhouse pest, has acquired rapid resistance to the chemical pesticides. Therefore, biological control is worth consideration as an alternative control method. Among the biological control agents, entomopathogenic fungi showed to be quite successful in some occasions. In this study, three Iranian isolates of Metarhizium anisopliae (‘DEMI001’, ‘DEMI002’ and ‘DEMI003’) were bioassayed for their lethal effects on the adults of the F. occidentalis, in vitro. The ‘DEMI002’ and ‘DEMI003’ had the lowest and highest LC₅₀ at concentrations of 3.06 ´ 10⁴ and 1.90 ´ 10⁵ conidia/ml, respectively. Also, the isolate ‘DEMI002’ had the lowest LT₅₀ of 4.39 ± 2.13 days at the concentration of 10⁶ conidia/ml. The mean comparison showed that there was a significant difference between DEMI002 and DEMI003 in terms of virulence at most of the concentrations. Consequently, the ‘DEMI002’ can be considered as a promising tool in biological control programs of the F. occidentalis.

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Background: A design storm is a theoretical storm event based on rainfall intensities associated with frequency of occurrence and having a set duration. Estimating design storm via rainfall intensity–duration–frequency (IDF) curves is important for hydrological planning of urban areas.
Material and Methods: The impact of changes in rainfall intensity–duration–frequency (IDF) curves on flood properties in an urban area of Zanjan city was investigated, using Storm Water Management Model (SWMM). For the IDF curve generation, Sherman and Ghahreman-Abkhezr methods were compared.
Results: According to results, the estimated rainfall depth and, consequently the peak runoff rate for different return periods had decreased in the recent years, except for 2-year return period. Decrease in peak runoff rate was 30, 39, 41 and 42 percent for 5-10-20 and 50-year return periods, respectively. Based on the results, for peak runoff evaluated in 50-year return period using Sherman and Ghahreman-Abkhezr hyetograph, percent of flood that occurred before the peak runoff were 27 and 22 percent, respectively.
Discussion and Conclusion: Design rainfall hyetograph showed that Sherman method gave larger rainfall intensity compared to Ghahreman-Abkhezr method. Estimated peak and total runoff volume follow trend of rainfall intensity. As Ghahreman-Abkhezr method use longer and newer rainfall data for creating IDF curves, we can conclude that climate change cause change in rainfall characteristics. The runoff modeling show that main urban drainage system had enough transfer capacity against the flood condition, but survey information indicated several inundations in some flat areas, curbs and gutters. Inappropriate design and obstruction of the runoff paths via urban garbage and sediments are some parameters that could lead to such local inundation.

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Beauveria bassiana (Balsamo) is one of the promising microbial control agents for the management of Oryzaephilus surinamensis (L.) Death rate, lethal time and survival expectancy were calculated for an infected population of O. surinamensis at 15, 20, 25, 30 and 35 °C. Results showed that the mean death rate under above mentioned temperatures was 0.89, 1.15, 1.40, 1.21, and 1.11 larvae/day, respectively. The values were 0.99, 1.38, 1.47, 1.18 and 1.16 insects/day for adults respectively. LT₅₀s, at the same temperatures, were 7.11, 7.04, 4.82, 6.07 and 6.89 days for larvae and 7.03, 6.31, 4.83, 5.58, and 6.55 for adults, respectively. Survival curves for both larval and adult populations were more similar at 25, 30 and 35 °C compared to 15 and 20 °C. The survival rates in infected populations were low during 3^rd and 4^th days post inoculation and decreased with a sharp slope toward the end of the experiments under different temperatures. In every case, survival curves were of the 2^nd type in which the mortality decreases in a steady linear form.

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Research subject: The present study was conducted with the aim of investigating the degree of compatibility of research topics in the field of chemical engineering in Shahid Chamran University of Ahvaz with Iran and the world. Also, prominent engineering issues in the field of chemistry have been identified.
Research approach: The research is considered a type of scientometric applied studies. The statistical population is made up of researches related to the field of chemical engineering in the Web of Science database. Taking into account the key words of sources that were extracted from the Web of Science database, the information was transferred to the PreMap program and by applying restrictions, the terms were unified for all three files of the world, Iran and Shahid Chamran University of Ahvaz. In order to check the thematic alignment, the clustering method was done with VOSviewer software. The index of structural similarity of subjects has also been used to determine the level of research alignment.
Main results:The researchers have searched for the subject areas of the chemical engineering department in Shahid Chamran University, Iran and the world. With the percentage of structural similarity, it was found that over time, the subjects of chemical engineering in Shahid Chamran University have aligned with Iran and the world, as well as Iran with the world, but the percentage of alignment with the world is low. To increase the alignment of chemical engineering subjects, platforms for sharing information and learning can be created for students, professors, researchers and experts in the field of chemical engineering. Also, a comprehensive approach to monitoring and evaluating research processes, including their alignment with leading research institutions, can provide research policymakers with valuable insights to improve research policies and foster scientific and technological innovation.
 

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Abstract- In this study, dynamic stability of a system consisting of three torsionally elastic shafts with different rotation axises is analyzed. The system stability have been investigated by means of a three degree-of-freedom model in a spatial coordinate (three dimensional). Each shaft carrying a rigid disk at one end and have been linked through two Hooke's joints. Equations of motion for the system were derived. These equations are linearised. After linearization of the differential equations are shown to consist of a set of Mathieu–Hill equations. Their stability are analyzed by means of a monodromy matrix method. Finally dynamic stability regions have been shown on different system parameters such as rotational velocity, misalignment angle’s of shaft axis, stiffness and rigidity of shafts. The stability charts constructed on various parameters. It was observed that with increasing inertia disk ratio and decreasing Hooke's joint angle, the stable region increases. Keywords: Dynamic Stability, Shaft System, Torsional Vibration, Hooke’s Joint

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To prevent unpleasant incidents, preservation high-speed railway vehicle stability has vital importance. For this purpose, the Railway vehicle dynamic is modeled using a 38-DOF includes the longitudinal, lateral and vertical displacements, roll, pitch and yaw angles. A heuristic nonlinear creep model and the elastic rail are used for simulation of the wheel and rail contact. To solve coupled and nonlinear differential equations, Matlab software and Runge Kutta methods are used. In order to study stability, bifurcation analyses are performed. In bifurcation analysis, speed is considered as the bifurcation parameter. These analyses are carried out for different wheel conicity and radius of the curved track. It is revealed that critical hunting speed decreases by increasing the wheel conicity or decreasing the radius of the curved track. Keywords: railway vehicle dynamics, nonlinear creep model, critical hunting speed, numerical simulation, bifurcation analysis Keywords: railway vehicle dynamics, nonlinear creep model, critical hunting speed, numerical simulation, bifurcation analysis

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In the paper, a three-axis power transmission system is modeled mathematically and simulated by software. In mathematically method, a system consisting of three flexible shafts with different rotation axis which connected through two universal joints is investigated via a three degree-of-freedom model. The stability is analyzed by means of a monodromy matrix technique. This is verified by comparing the results with dynamic analytical software AdamsView simulation and the results of the previous research. Then, the effects of rotational velocity, non-aligned angles, shaft's properties (stiffness and damping) on the stability are investigated. Finally, the stability charts constructed on various parameters is presented. It is observed that decreasing shaft stiffness and universal joint angle due to more stability, while decreasing shaft damping has the opposite effect.

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Wear phenomena in wheel-rail contact for railway vehicle is very important parameter. For this purpose, simulation and dynamic analyze of new and worn wheel profiles are done. Then wagon’s derailment factor along curved track is determined. Analytic solution is achieved by using Hertz contact theory and Kalker linear theory. Also, simulation and analysis is done in ADAMS/Rail software and for different wheel profiles and derailment factor is determining using derailment criteria. Results showing that derailment factor are low initially but vertical forces decreases and centrifugal force increases lateral forces and consequently derailment factor increases along wagon entering curved track and worn profiles have more tendencies exposed to derailment. However, permitted wear limit must be defined. In many cases, worn profiles havefewer tendencies to derailment. Using this method can determine wear limit of wheel profile to maintenance and re-profileoperation. It is revealed that the curve length does not affect on derailment factor. Also, damper coefficient does not affect on mean derailment factor But it is much more turbulence. Perturbation in curve beginning is considerable and at the end of the curve, it restores to initial value.

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Vibration of drillstring is the most important factor of its destruction and reduction in drilling operations efficiency. One of the main causes of excessive vibration of drillstring is drillstring-wellbore contact, therefore drillstring-wellbore contact has been studied in several researches. Indeed the contact behavior of drillstring and wellbore is of great concern to drilling companies in the oil and gas exploration industries. In this research, dynamic behavior and vibration of non-linear finite element model of a drillstring in contact with wellbore, has been investigated. By considering total length of drillstring, a three-dimensional timoshenko beam element is employed. In addition the geometric stiffening effect including nonlinear terms, the added fluid mass and the contact between drillstring and borehole wall has been considered using improved contact model with a more complete model than previous studies, that the stiffeness of contact determined form energy balance relations. The equation of motion of drillstring obtained using energy approach and lagrange’s equations and full order equations are used to drive the results. Coupling between various vibrations has been tested and the effect of recent model in analysis of dynamic behavior and vibration of drillstring have been evaluated.

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Rotating machines are one of the kinds of mechanical systems that widely used in industry. The way of connecting axis and vibration of system are among the items that are always discussed in these systems. In the paper, a mechanical rotating system is modeled. In the model, a system consisting of two flexible axes (shafts) with different rotation axis which connected through a cardan joint is investigated via two degrees of freedom model. The stability of the model is analyzed by means of a monodromy matrix technique. The model is verified by comparing the results with the results of the previous researches and different natural frequencies. Then the effects of different system parameters such as axis rotational velocity, cardan angle, shaft's properties (stiffness and damping) on the stability of system are investigated. Also manner and conditions of each parameter on the stability of system are discussed. Finally, the stability charts constructed on various system parameters is presented. It is observed that decreasing shaft stiffness and cardan joint angle due to more stability, while decreasing shaft damping has the opposite effect.

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It is known from the previous studies that blades can cause resonance in bladed rotors under specific conditions. In this paper, the behavior of a nonlinear rotor, which faces with this kind of resonance, is investigated. In order to reach this goal, a bladed rotor, in which the disk and shaft are rigid, is considered. The blades are modeled by flexible beams. It is assumed that the disk is supported by elastic and nonlinear bearings. The nonlinear term of the bearing stiffness function is cubic. The rotating system vibrations include both cylindrical and conical whirling. The bifurcation equation is obtained by the method of multiple time scales method. The nonlinear effects are studied by the bifurcation equation. It is revealed that the system behavior, when it encounters Hamiltonian Hopf bifurcation, is dependent on the bearing stiffness nonlinearity type. Accordingly, both subcritical and supercritical Hopf bifurcation is possible. A numerical simulation is performed in order to study the effects of damping coefficients on the path of rotating disk center. The results and methods, which are used in this paper, are applicable for studying Hamiltonian Hopf bifurcation in other fields.

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In this research, dynamic behavior of non-linear finite element model of a drillstring is investigated. By considering total length of drillstring, a three-dimensional timoshenko beam element is employed. In addition the geometric stiffening effect, the added fluid mass and the contact between different parts of the drillstring and the borehole wall has been considered, with a complete model the effects of these factors have been analyzed separately. The equation of motion obtained and full order equations are used to drive the results. For the first time, a domain of drillstring that contact more possibility to occur in this domain is identified. The natural frequencies of the drillstring are evaluated and compared with the available commercial software results and recorded results for the actual drillstring. Coupling of vibrations of model is tested and the effect of linear and non-linear model in analysis of dynamic behavior and vibration of drillstring, especially in contact with the borehole wall and the effect of weight on bit change on the contact at stabilizers are analyzed and for the first time the contact time in each of stabilizers have been evaluated.

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In general, in dynamic analysis of mechanical systems, joints are assumed to be ideal. However, due to errors in fabrication and assembly of components, existence of joints clearances is an inevitable issue that caused frequent collisions between the journal and bearing and stable periodic behavior of system becomes chaotic. Degradation the dynamic performance of the system, reduction in fatigue life of components and produce undesirable vibrations are all of the factors resulted from impact- contact forces due to joint clearance. First, different contact force models for two surfaces has been introduced and dynamical models of revolute joint with clearance for two modes, namely, dry contact model and lubricated joint model is then presented. In this paper, the dynamic behavior of a slider- crank mechanism with a revolute joint clearance between the slider and connecting rod, using the Lankarani-Nikravesh contact force model is studied and compared to the ideal case. Considering the effect of friction between journal and bearing, governing equations of motion of the system for two phase, contact and non-contact modes are extracted and it is shown that system exhibits chaotic behavior under specified size of clearance. A fluid lubricant is used in clearance between journal and bearing for stabilizing an unstable periodic orbit embedded in the chaotic attractor.

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In order to avoid unpleasant incidents, it is crucial to maintain the stability for a high-speed railway vehicle. In this research, a high-speed railway vehicle dynamics with 38 degrees of freedom was investigated, adding longitudinal movement equations. Another innovation of this investigation is to determine the critical velocity for the studied railway vehicle and using nonlinear elastic rail for the wheel and rail contact. In this study, the stable and hunting behavior of the system was investigated. To identify the chaotic motion of the system, frequency analysis has been performed. Also, by plotting the Poincaré map, dynamic behavior of the system is illustrated in a discrete state space, which could be a good criteria for the chaotic or periodic behavior of the system. Long-term behavior reveals that at Speeds lower than the critical speed, the system oscillates until it reaches the steady-state of the system. In steady motion, the oscillation continues until the critical speed When the system reaches the critical velocity, the motion on the limit cycle occurs for the first time and when the speed is higher than critical speed, the vibration amplitude increased smoothly. It was observed from the frequency response plot that the hunting frequency evaluated via the linear elastic rail is higher than that of derived using a nonlinear model.

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In this research, the stable regions of an unbalanced rotor are specified. Krein’s theorem is applied to this system for the first time. In this case, the disk has six degrees of freedom and there might be coupling between all dynamic modes. The effect of the skew angle is observable in equations of motion. The equations of motion are derived using Lagrange’s equations. Krein’s signature of each mode is calculated in order to find possibility of frequency coalescence. Campbell diagrams are used to verify Krein’s theorem. The damping and unbalancing effect on the system stability are studied. For all effective parameters, the stable and unstable zones are computed. Numerical analysis for the nonlinear governing equations is applied to compare the results. It was observed that, growth of the unbalancing makes the coupling more powerful and increase instability. Cylindrical rotor has more instability than disk-shaped rotor. When the polar moment of inertia is equal to the diametral moment of inertia, the maximum instability occurs. When rotor moves toward bearings, unstable regions shift toward larger velocities. Increasing the rotor mass shifts unstable velocities toward lower velocities.

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Because of their positive effect, probiotic bacteria widely used in the manufacture of food, particularly in the production of dairy products. but having high cholesterol and lactose intolerance problem is an important restrictions on the use of dairy products. Recently, the consumption of non-dairy probiotic foods specifically non-dairy probiotic juices were developed. The aim of this study was to examine the growth trend of Lactobacillus acidophilus in the two varieties of Pomegranate juice Shahreza and Natanz. After inoculation of bacteria to each samples, they were stored at 4 ° C and changes in pH, titratable acidity, the sediment, as well as live cell counts were measured under controlled conditions at distinct times during fermentation. The results showed that there was lower survival of bacteria in Natanz pomegranate juice due to the lower pH. The microbial populations during the first week was decreased from 7.43 to 4.5 logarithmic cycles, While microbial populations of Shahreza pomegranate juice was decreased from 7.49 to 5.33 logarithmic cycle at the same time. In the second week of research, there was no bacteria detected in both treatments. Both treatments showed a significant decrease in pH, sediment and bacteria population at the end of maintenance, but the changes in acidity were not significant (p˂0.01). There was no desirable effect on sensory properties of pomegranate juice after adding probiotics Bacteria

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Dynamics analysis of the rotational axially moving pipe conveying fluid under simply supported condition investigated in this research. The pipe assumed as Euler Bernoulli beam. The gyroscopic force and mass eccentricity were considered in the research. Equations of motion are derived using Hamilton’s principle, resulting in two partial differential equations for the transverse motions. The non-dimensional equations were discretized via Galerkin’ method and were solved using Rung Kutta method (order 15s). The frequency response curve obtained in terms of non-dimensional rotational speed. The bifurcation diagrams are represented in the case that the non-dimensional fluid speed, non-dimensional axial speed and non-dimensional rotational speed were respectively varied and the dynamical behavior is numerically identified based on the Poincare' portrait. Numerical simulations indicated that the system response increases by increasing non-dimensional axial speed of the pipe, non-dimensional fluid speed and non-dimensional rotational speed of the pipe and then decreases after passing critical area. The system is unstable at critical point associated with non-dimensional axial speed. Poincare portrait indicates periodic motion in transverse vibrations of the pipe at some points of control parameters. Phase portrait and FFT (Fast Fourier Transform) diagrams were used for validation of the results.