Developing surface-enhanced microcantilevers with improved sensitivities is of longstanding interest.In this paper,the design of surface-enhanced cantilever sensors using nano(micro-) porous films as surface layers is proposed.The static deformation and resonance frequencies of these surface-enhanced sensors with the simultaneous effects of the eigenstrain,the surface stress and the adsorption mass are analyzed.It is shown that the sensitivities of these novel cantilever sensors for the static deformation and resonance frequencies can be tuned by the porosity,the size of the pores and the structure of the porous films.For the three kinds of cantilever consisting of solid films,films with aligned cylindrical micro-scale pores,and those with nano-scale pores,the nano-porous one has the highest static and dynamic sensitivities,whereas the solid one has the lowest.
Huiling Duan(State Key Laboratory for Turbulence and Complex System,CAPT and Department of Mechanics and Aerospace Engineering,College of Engineering,Peking University,Beijing 100871,China)
Sediments are ultimate sinks of nutrients in lakes that record the pollution history evolutionary processes, and anthropogenic activities of a lake. However, sediments are considered as inner sources of environmental factor changes such as the variation in hydrodynamic conditions because of the nutrients they release. How does this process happen? This study investigates a typical nutrient phosphorus(P) exchange among sediment, suspended particle matter(SPM), and water. Compared with numerical and experimental studies, this study confirms that the critical velocity that occurs at a lower flow rate state exists in the range of 7 to 15 cm/sec. Critical velocity below the critical flow rate promotes the migration of particulate phosphorus(PP) to the SPM. On the other hand, critical velocity above the critical flow rate promotes the release of PP in water.
By using molecular dynamics simulations,we studied the ion irradiation induced damage in mechanically strained Cu nanowires and evaluated the effects of damage on the mechanical properties of nanowires.The stresses in the pre-strained nanowires can be released significantly by the dislocation emission from the cascade core when the strain is greater than 1%.In addition,comparison of the stress-strain relationships between the defect-free nanowire and the irradiated ones indicates that ion irradiation reduces the yield strength of the Cu nanowires,and both the yield stress and strain decrease with the increase of irradiation energy.The results are consistent with the microscopic mechanism of damage production by ion irradiation and provide quantitative information required for accessing the stability of nanomaterials subjected to mechanical loading and irradiation coupling effects.
This paper studies the effective properties of multi-phase thermoelastic composites. Based on the Helmholtz free energy and the Gibbs free energy of individual phases, the effective elastic tensor, thermal-expansion tensor, and specific heats of the multi-phase composites are derived by means of the volume average of free-energies of these phases. Particular emphasis is placed on the derivation of new analytical expressions of effective specific heats at constant-strain and constant-stress situations, in which a modified Eshelby's micromechanics theory is developed and the interaction between inclusions is considered. As an illustrative example, the analytical expression of the effective specific heat for a three-phase thermoelastic composite is presented.
