Hybrid and multi-field variational principles for geometrically exact three-dimensional beams

This paper addresses the development of several alternative novel hybrid/multi-field variational formulations of the geometrically exact three-dimensional elastostatic beam boundary-value problem. In the framework of the complementary energy-based formulations, a Legendre transformation is used to introduce the complementary energy density in the variational statements as a function of stresses only. The corresponding variational principles are shown to feature stationarity within the framework of the boundary-value problem. Both weak and linearized weak forms of the principles are presented. The main features of the principles are highlighted, giving special emphasis to their relationships from both theoretical and computational standpoints.     

Dual extremum principles for geometrically exact finite strain beams

Both necessary and sufficient conditions for the existence of two complementary-dual extremum principles for geometrically exact finite strain (one-dimensional) beam models are investigated by means of two different approaches. One is based on the results published by Gao and Strang, and the other relies on the approach proposed by Noble and Sewell. While the former is limited to beam models restricted to moderate large deformations, the latter is valid for arbitrarily large deformations (and strains). The numerical implementation of the complementary-dual extremum principles can lead to simple true global upper bounds of the error of the approximate solutions.     

Comments on the use of loop reactors in sonochemical processes

For sonochemical processing on an industrial scale the traditional choice is either a batch or flow system. The former is straightforward in concept but it requires large scale powerful ultrasonic transducers capable of delivering high intensity ultrasound to large volumes of liquid. Unfortunately at the moment the cost and problems involved in building very large sonication devices for batch processes cannot justify the replacement of existing industrial processes. For this reason most sonochemists prefer some form of flow system where small quantities of reagents can be treated as they are pumped from a large vat of reagents through a smaller sonochemical reactor where high intensity ultrasound can be applied. In this short paper we draw attention to a problem which seems common in a number of papers dealing with such flow systems – a confusion between the terms continuous reactor and loop reactor. Further we emphasise the importance of calculating the actual amount of ultrasonic processing experienced by the reaction mixture within the sonication zone of a loop reactor during its operation. The parameters required for such a calculation are: ultrasonic processor volume (R_v in L), pump flow rate (F_r in L/min), stock solution volume in the reservoir (S_v in L) and the overall system operating time (S_o in min).     

卷积型最小二乘法求解梁的动力学问题

提出了卷积型最小二乘法,并用其计算了不同初始条件和不同边界条件下梁的动力学问题,算例表明,方法概念简单,计算方便,精度高,计算工作量少,卷积型最小二乘法是计算结构动力学问题的一种简单、高效的方法,试函数可以不满足边界条件.     

Performance of textile and building materials for a particular evaporative cooling purpose

High energy demand associated to the massive use of air conditioning systems requires careful consideration of passive cooling strategies, with evaporative cooling being recognized as a useful possibility for that purpose. One important factor that influences the performance of evaporative cooling systems is the media material that supports water evaporation process. In this work evaporative cooling capabilities of different building and textile materials were experimentally determined. The major purpose of the study was to select an evaporative cooling material to be used in a more complex passive cooling unit under research development. A test tunnel was constructed for this particular work and the behavior of several samples was analyzed. Results show that among the studied materials a polyester spacer fabric with honeycomb structure presents best performance.     

Shear flow over cylindrical rods attached to a substrate

Shear flow over a periodic array of cylindrical rods attached to a substrate is studied as a model of flow over a nanomat consisting of aligned carbon nanotubes. The objectives are to evaluate the macroscopic slip velocity, compute the hydrodynamic load exerted at the rod side surface and tip, and estimate the flow-induced deflection. The hydrodynamic traction and macroscopic slip velocity are computed by solving the equations of Stokes flow for a doubly periodic square or hexagonal arrangement using a boundary-element method. The results illustrate the dependence of the slip velocity on the surface coverage expressed by the ratio of the rod radius to separation, and confirm the occurrence of hydrodynamic screening due to surrounding rods confining the traction near the exposed tip of each rod. An estimate for the flexural stiffness of nanotubes is made using available information on the flow-induced deflection. Computations for shear flow past an isolated attached rod are carried out using a highly accurate boundary-element method coupled with a finite-element method for solving the Euler–Bernoulli beam equation, and an iterative procedure involving a boundary-element implementation coupled with a boundary-value formulation involving ordinary differential equations for describing large beam deformation. The results illustrate the precise shape of deflected rods.     

Indirect target detection method in FLIR image sequences

Due to the complexity of the scene, target detection in forward-looking infrared (FLIR) imagery is a challenging problem, especially for occluded target. The main contribution of this paper is to propose an indirect detection method for improving the recognition probability and effectiveness of target detection method in FLIR image sequences under complex conditions. The proposed method mainly includes four steps: preparation of forward-looking reference image of landmark, extraction of the real-time scene image, template matching and target location, in which some key technologies are proposed, such as perspective transformation used to solve projective problems, position prediction for improving real-time performance, and target location used for identifying the target’s position. Experimental results are shown to demonstrate the robustness and efficiency of proposed method in FLIR image sequences.     

Frame expansions in separable Banach spaces

Banach frames are defined by straightforward generalization of (Hilbert space) frames. We characterize Banach frames (and Xd-frames) in separable Banach spaces, and relate them to series expansions in Banach spaces. In particular, our results show that we can not expect Banach frames to share all the nice properties of frames in Hilbert spaces.