Abstract: The governing equations of motion for a drill string considering coupling between axial, lateral and torsional vibrations are obtained using a Lagrangian approach. The result leads to a set of non-linear equations with time varying coefficients. A fully coupled model for axial, lateral, and torsional vibrations of drill strings is presented. The bit/formation interactions are assumed ...

Statins are most effective pharmacologically agents to decrease total plasma cholesterol level by competitive inhibition of HMG-Co A reductase. Apart from the well-known LDL and cholesterol lowering effect, statins have been postulated to exert other beneficial effects also called pleotropic or non-lipid effects. Better understanding of various pleotropic effects of statins has prompted a new s...

In this paper, surface and piezoelectric effects on the vibration behavior of nanowires (NWs) are investigated by using a Timoshenko beam model. The electric field equations and the governing equations of motion for the piezoelectric NWs are derived with the consideration of surface effects. By the exact solution of the governing equations, an expression for the natural frequencies of NWs with ...

polyhydroxyalkanoates (phas) are bioplastics derived from renewable resources such as vegetable oils, corn starch, or microbes. the polyhydroxybutyrate (phb) is a short-chain-length pha, and the most important bioplastic produced by certain microorganisms in the presence of excess carbon sources. in this study batch cultivation of alcaligenes eutrophus with the aim of increasing phb production ...

the main objective of this study was to investigate the environmental impacts of cotton production in golestan province of iran using life cycle assessment methodology. the data used in the study were obtained from cotton farmers with face-to-face questionnaire method during 2011-2012. the questionnaires included total inputs of cotton production in the region and yield weight. environmental im...

Production planning and control (PPC) systems have to deal with rising complexity and dynamics. The complexity of planning tasks is due to some existing multiple variables and dynamic factors derived from uncertainties surrounding the PPC. Although literatures on exact scheduling algorithms, simulation approaches, and heuristic methods are extensive in production planning, they seem to be ineff...

It is expected that residential units may replace   traditional heat and power production systems with cogeneration ones. Among the different cogeneration systems, fuel cell based systems are a suitable choice due to their high efficiency, high power density, low emission and low noise. In this paper, a cogeneration system based on solid oxide fuel cells is examined. The system, including the f...