Nowadays, for optimal control of oil pressure and reduction of energy consumption in hydraulic circuits used in fixed and moving machines, it is necessary to change the displacement volume of the pump proportional to the load on the moving part of the hydraulic actuator. For this purpose, in this paper, a displacement control valve with negative overlap is used in the axial piston pump structure. In order to evaluate the performance of the displacement control valve, the mathematical relations governing the axial piston pump were written in the frequency domain. Examining the presented mathematical model showed that the order of transform function of the axial piston pump in three different working conditions, including increase, decrease, and stabilization of the displacement volume is 7, 5, and 3, respectively. To evaluate the correctness of the presented mathematical model, the design and construction of the hydraulic power transmission system including the axial piston pump, fixed displacement hydraulic motor, and flow control valve without pressure compensator was carried out. The appropriate matching of the frequency response obtained from the experimental results with the results obtained from the mathematical model, especially at low frequencies, confirmed the validity of the presented mathematical model. Further investigations showed that the use of the displacement control valve to change the flow rate of the axial piston pump in three working conditions resulted in the stable operation of the pump in the hydraulic power transmission system.

In this study, vibration analysis of axial symmetric circular cylindrical shell has been investigated. The high-order theory is used to approximate the transverse displacement in this study. Hence, the transverse displacement based on the Fourier expansion is extended to three terms. Due to the symmetry of the cylindrical shell, only the axial mode has been investigated. The strain and kinetic energies are obtained for the circular cylindrical shell. The Hamiltonian principle was used to derive the equations of motion. The stiffness and mass matrices have been obtained by applying Galerkin method and finite element method. For this purpose, the linear shape function is used for all unknowns. In order to validate the research, comparing the axisymmetric frequencies of the results with previous studies has been used. Finally, the axisymmetric frequencies and axial mode shapes of the circular cylindrical shell for various boundary conditions are given, including simply support-simply support, clamped-clamped, clamped-simply support and clamped-free.

In this study loss measurements in axial fiber displacements in a fiber-to-fiber design using two different light sources (white lamp & red LED) is reported. A fiber-to-fiber arrangement is used in which the source light is directly coupled to the first fiber and the second fiber delivers the light to a power meter. Using this arrangement the variation of the power and loss as a result of axial (Z-direction) displacements of the second fiber are monitored. Theoretical model is also to evaluate the power transmissions for comparison is made with the experimental results. Our results in general agree with the theoretical predictions and the small deviation is because of the fact that those theoretical formulas are more precise for the case of small core fibers for small axial displacements while we are using large core fibers and relatively long displacements. Important parameters of the reported optical system such as measurements reproducibility (about 0.001%), and hysteresis effect (about 0.034), are also investigated that verify the reasonable operation of such an optical system. The result of this experiment verify that fiber material and other fiber parameters affect the power transmission and such parameters can be investigated experimentally using the reported fiber-to-fiber arrangement.

Background: In Genu-valgum tibiofemoral angle increases above its normal value of 6°. This disorder causes difficulty in walking and sport activities in short-.term. But in long-term, because of increased force on lateral compartment of the knee, osteoarthritic changes of the lateral side of the knee and ligamentous laxity of medial side of knee could happen. In the past, osteotomies have been done on lateral side of distal femur for correction of Genuvalgum. We are suggesting a medial approach, posterior to vastus medialis with close-wedge osteotomy from medial side as an alternative approach for correction of genovalgum. Method: A Clinical trial study of 20 lower limbs operated between 1988 to 2002. Results: 20 lower limbs were operated with this technique. The mean age was 23.2, 14 patients were female and 2 male. 10 limbs were left and the other 10 were right side. Mean valgus angle was 14.75° preoperatively and 3° postoperatively the mean follow-up period was 628 days (Minimum 50 and maximum 1111 days). At follow-up, the range of knee motion in all limbs was normal. There was no infection postoperatively, quadriceps force was 5/5 in 18 and 4/5 in two limbs. Functional improvement was observed in 15 cases and all 16 patients had full satisfaction from the appearance of the limbs.

Using renewable energy sources instead of fossil fuels is a fundamental way to reduce environmental pollution caused by greenhouse gases. Geothermal energy is available all over the world and has an important role in the supply of renewable energy. In order to collect geothermal energy various heat exchanger systems have been developed in recent years that thermal activated piles (energy piles) are one most of them. Reinforced concrete piles have been widely used as a geothermal heat exchanger to access the relatively constant temperature of the ground for efficient heating and cooling of buildings. Energy piles are heat capacity systems that have been increasingly exploited to provide both supplies of energy and structural support to civil structures (Batini et al., 2015). Concrete has a good thermal conductivity and thermal storage capacity, which makes it an ideal medium as an energy absorber (heat exchanger). To use these properties for energy foundations, high-density polyethylene plastic pipes have to be installed within the concrete. The plastic piping can be fixed to the reinforcement cages of the energy foundation in a plant or on the site (Fig. 1).

In this study, we attempt to have numerical and software analysis of behavior, deformation and strain caused by local dental loads (dent) in GFRP tanks. The load-displacement and the load- Strain diagrams in experimental and software conditions have also been analyzed, compared and evaluated. The research can be used in oil company projects, water organization and different types of tanks which are exposed to local loads. the experimental and theoretical researches on GFRP tubes and tanks under dental loads and concluded that all samples have linear behavior from beginning to end and proceed with the same slope which is due to the behavior of the GFRP materials (Zarrin, 2018). To test the behavior of experimental specimen under the influence of Dent’s load, wedge is used. In another studies different types of dental loads are applied to the tanks like Dome-shaped dental load, Circular dental load and Rectangular dental load (Jajo, 2014). To understand the importance and necessity of research, we must first study the dental load, how it is applied to the tanks, the dangers of applying it to the tanks and the ways of resistance against these loads.

This paper deals with experimental results of an axial compressor of a small power plant gas turbine engine. Tests were carried out during the engine operation (along operating line of the compressor). Time averaged axial and radial pressure distributions in each individual stage were measured at different rotational speeds. Acceleration and deceleration phases of the engine were divided into reasonable time intervals of constant rotational speeds. Consequently, data logging was performed during steady operation of the engine. Measured parameters included pressure and temperature distributions and air mass flow rate. Test results were used to calculate axial distribution of load factor along the compressor mean line. Experimental results showed that the span wise total pressure reduces from mean line region towards the hub and casing at each stage. No significant variations in load factor of each stage were observed during acceleration and deceleration phases of the engine. Meanline load factor distribution was increasing from compressor head towards its end within experimental rotational speed range.