background & aim: energy is one of important debates in agriculture ecology and for this reason; the ratio of output and input energy in different agriculture ecosystems has been calculated. if one can reduce, input energy level into farms through the indices like poisons, fertilization, tractor energy and lab our force. in addition to the net income of the farmers, this issue would play a ...

The SIMP approach is one of the most frequently used methods for topology optimization of structures. In this method, the relative density is expressed as a function of coordinates and varies from 0 to 1 within the design domain. Relative densities of 0 and 1 are associated to the existence and non-existence of the material, respectively. The finite element approach is usually utilized to analy...

the brass tubes with foam cores of alsi7sic3, alsi7sic3fe1 and alsi7sic3fe3 were produced as the crush-boxes with circle and square cross-section. then axial compressive behavior and energy absorption capability of the foam-filled tubes were investigated during the quasi-static progressive plastic buckling. the uniaxial compressive stress–strain curves of the foam-filled brass tubes exhibited t...

three experiments were conducted to evaluate the nutritional value of bitter vetch. experiment 1 was conducted to determine the metabolisable energy content of bitter vetch. sixteen adult leghorn roosters were used. forty grams of bitter vetch were precision-fed individually to 12 roosters. in addition, 4 birds were not fed and served as a control treatment in the measurement of metabolic fecal...

Nowadays, the technology intends to use materials such as magnesium alloys due to their high strength to weight ratio in engine components. As usual, engine cylinder heads and blocks has made of various types of cast irons and aluminum alloys. However, magnesium alloys has physical and mechanical properties near to aluminum alloys and reduce the weight up to 40 percents. In this article, a new ...

by minimizing the total potential energy function and deploying the virtual work principle, a higher-order stiffness matrix is achieved. this new tangent stiffness matrix is used to solve the frame with geometric nonlinear behavior. since authors’ formulation takes into account the higher-order terms of the strain vector, the convergence speed of the solution process will increase. in fact, bot...

in order to restrain the potential of wind energy, the first step is to determine the wind energy potential. in this study the wind data was used from the three-hour frequency recording of 10-year period (2002-2011). to predict the occurrence probability of each wind speed, the two-parameter weibull function was used. the goodness of fit test by chi-square test showed that the wind speed distri...

BACKGROUND Steric strain in protein three-dimensional structures is related to unfavorable inter-atomic interactions. The steric strain may be a result of packing or functional requirements, or may indicate an error in the coordinates of a structure. Detailed energy functions are, however, usually considered too noisy for error detection. RESULTS After a short energy refinement, a full-atom, ...