Presented in this paper is a precise investigation of the effect of surface stress on the vibration characteristics and instability of fluid-conveying nanoscale pipes.To this end,the nanoscale pipe is modeled as a Tim...Presented in this paper is a precise investigation of the effect of surface stress on the vibration characteristics and instability of fluid-conveying nanoscale pipes.To this end,the nanoscale pipe is modeled as a Timoshenko nanobeam.The equations of motion of the nanoscale pipe are obtained based on Hamilton＇s principle and the Gurtin-Murdoch continuum elasticity incorporating the surface stress effect.Afterwards,the generalized differential quadrature method is employed to discretize the governing equations and associated boundary conditions.To what extent important parameters such as the thickness,material and surface stress modulus,residual surface stress,surface density,and boundary conditions influence the natural frequency of nanoscale pipes and the critical velocity of fluid is discussed.展开更多
A novel size-dependent model is developed herein to study the bending behavior of beam-type micro/nano-structures considering combined effects of nonlocality and micro-rotational degrees of freedom. To accomplish this...A novel size-dependent model is developed herein to study the bending behavior of beam-type micro/nano-structures considering combined effects of nonlocality and micro-rotational degrees of freedom. To accomplish this aim, the micropolar theory is combined with the nonlocal elasticity. To consider the nonlocality, both integral (original) and differential formulations of Eringen’s nonlocal theory are considered. The beams are considered to be Timoshenko-type, and the governing equations are derived in the variational form through Hamilton’s principle. The relations are written in an appropriate matrix-vector representation that can be readily utilized in numerical approaches. A finite element (FE) approach is also proposed for the solution procedure. Parametric studies are conducted to show the simultaneous nonlocal and micropolar effects on the bending response of small-scale beams under different boundary conditions.展开更多
In the present paper, the dynamic stability of multi-walled carbon nanotubes （MW- CNTs） embedded in an elastic medium is investigated including thermal environment effects. To this end, a nonlocal Timoshenko beam mo...In the present paper, the dynamic stability of multi-walled carbon nanotubes （MW- CNTs） embedded in an elastic medium is investigated including thermal environment effects. To this end, a nonlocal Timoshenko beam model is developed which captures small scale effects. Dynamic governing equations of the carbon nanotubes are formulated based on the Timoshenko beam theory including the effects of axial compressive force. Then a parametric study is conducted to investigate the influences of static load factor, temperature change, nonlocal parameter, slenderness ratio and spring constant of the elastic medium on the dynamic stability characteristics of MWCNTs with simply-supported end supports.展开更多
Each year 750,000 Americans are diagnosed with sepsis and approximately 220,000 of those patients die. In addition to the toll on human life, sepsis is the most expensive disease to care for in the hospital costing ap...Each year 750,000 Americans are diagnosed with sepsis and approximately 220,000 of those patients die. In addition to the toll on human life, sepsis is the most expensive disease to care for in the hospital costing approximately 17 billion dollars annually. National and international initiatives have demonstrated the benefits of recognition, early fluid resuscitation and broad spectrum antibiotics to reduce sepsis mortality. The Surviving Sepsis Campaign recently issued the third iteration of clinical bundles for the management of severe sepsis and septic shock. Robust Process Improvement （RPITM） which integrates the principles of Six Sigma, Lean and Change Management was applied to increase overall compliance to implement the elements of the three hour sepsis bundle in a complex healthcare system. The elements of the three hour sepsis bundle are drawing blood cultures before ordering antibiotics, timely antibiotic administration, obtaining lactate and administering fluid bolus. It has been demonstrated for severe sepsis and septic shock that bundle compliance is associated with a reduction in hospital mortality. The results of this study indicated that the overall bundle compliance increased by 30% which resulted in reducing the sepsis mortality rate by 27%.展开更多
文摘Presented in this paper is a precise investigation of the effect of surface stress on the vibration characteristics and instability of fluid-conveying nanoscale pipes.To this end,the nanoscale pipe is modeled as a Timoshenko nanobeam.The equations of motion of the nanoscale pipe are obtained based on Hamilton＇s principle and the Gurtin-Murdoch continuum elasticity incorporating the surface stress effect.Afterwards,the generalized differential quadrature method is employed to discretize the governing equations and associated boundary conditions.To what extent important parameters such as the thickness,material and surface stress modulus,residual surface stress,surface density,and boundary conditions influence the natural frequency of nanoscale pipes and the critical velocity of fluid is discussed.
文摘A novel size-dependent model is developed herein to study the bending behavior of beam-type micro/nano-structures considering combined effects of nonlocality and micro-rotational degrees of freedom. To accomplish this aim, the micropolar theory is combined with the nonlocal elasticity. To consider the nonlocality, both integral (original) and differential formulations of Eringen’s nonlocal theory are considered. The beams are considered to be Timoshenko-type, and the governing equations are derived in the variational form through Hamilton’s principle. The relations are written in an appropriate matrix-vector representation that can be readily utilized in numerical approaches. A finite element (FE) approach is also proposed for the solution procedure. Parametric studies are conducted to show the simultaneous nonlocal and micropolar effects on the bending response of small-scale beams under different boundary conditions.
文摘In the present paper, the dynamic stability of multi-walled carbon nanotubes （MW- CNTs） embedded in an elastic medium is investigated including thermal environment effects. To this end, a nonlocal Timoshenko beam model is developed which captures small scale effects. Dynamic governing equations of the carbon nanotubes are formulated based on the Timoshenko beam theory including the effects of axial compressive force. Then a parametric study is conducted to investigate the influences of static load factor, temperature change, nonlocal parameter, slenderness ratio and spring constant of the elastic medium on the dynamic stability characteristics of MWCNTs with simply-supported end supports.
文摘Each year 750,000 Americans are diagnosed with sepsis and approximately 220,000 of those patients die. In addition to the toll on human life, sepsis is the most expensive disease to care for in the hospital costing approximately 17 billion dollars annually. National and international initiatives have demonstrated the benefits of recognition, early fluid resuscitation and broad spectrum antibiotics to reduce sepsis mortality. The Surviving Sepsis Campaign recently issued the third iteration of clinical bundles for the management of severe sepsis and septic shock. Robust Process Improvement （RPITM） which integrates the principles of Six Sigma, Lean and Change Management was applied to increase overall compliance to implement the elements of the three hour sepsis bundle in a complex healthcare system. The elements of the three hour sepsis bundle are drawing blood cultures before ordering antibiotics, timely antibiotic administration, obtaining lactate and administering fluid bolus. It has been demonstrated for severe sepsis and septic shock that bundle compliance is associated with a reduction in hospital mortality. The results of this study indicated that the overall bundle compliance increased by 30% which resulted in reducing the sepsis mortality rate by 27%.
