THE USE OF CRITICAL STRESS INTENSITY FACTOR TO QUANTIFY "HARDNESS" AND "CRUNCHINESS" OBJECTIVELY

A simple test from materials science, in which a notched beam is bent so that the notch increases in length due to the propagation of a crack, allows determination of a parameter called the Critical Stress Intensity Factor in Mode I fracture, K_IC, by means of which the conditions under which the crack will propagate can be quantified. This is shown to track sensory hardness of several apples, carrot, celery and cucumber with remarkable precision, a result predicted by theoretical analysis due to Lucas et al. (2002). Hardness and crunchiness are shown to be indistinguishable and therefore must be identical. Therefore, a mechanical test can reliably replace a sensory test resulting in quicker, cheaper and more accurate estimate of a sensory parameter.     

Adaptive backstepping control and synchronization of a modified and chaotic Van der Pol-Duffing oscillator

In this paper,we propose a backstepping approach for the synchronization and control of modified Van-der Pol Duffing oscillator circuits.The method is such that one controller function that depends essentially on available circuit parameters that is sufficient to drive the two coupled circuits to a synchronized state as well achieve the global stabilization of the system to its regular dynamics.Numerical simulations are given to demonstrate the effectiveness of the technique.     

A neural network assisted computed torque method for manipulator tracking control problems

Based on the structure of the computed torque method, this paper develops a neural control method for manipulator trajectory tracking problems. Compared with conventional approaches, the proposed method has the following novel features. First, by using a neural network as the plant model, the proposed method can handle structural as well as unstructural uncertainties. Secondly, with a simple compensation scheme, the proposed approach can effectively avoid tracking performance degradation caused by unmodelled dynamics and/or neural network learning errors. Computer simulation results are given to demonstrate the feasibility of the proposed control method.     

On the asymptotic stability of boundary trajectories

For a class of dynamical systems, it is shown that trajectories which remain on the boundary of a non-empty, connected subset of a reachable set must be asymptotically stable. Using this result and a reachability maximum principle, we obtain a control law which will drive the system from the origin to the boundary of the reachable set for a class of two-dimensional linear control systems. Using this control law, the reachable set is easily constructed.     

心有所属

CLIMACOOL 是ADIDAS独步春夏季跑鞋市场的重要科技之一,CLIMACOOL跑鞋家族就以极佳的透气特性与吸引人的设计受到了春夏跑者的青睐。     

The elusive ettringite under the high‐vacuum SEM – a reflection based on natural samples,the use of Monte Carlo modelling of EDS analyses and an extension to the ettringite group minerals

Ettringite, Ca₆Al₂(SO₄)₃(OH)₁₂.26H₂O, or C₆A₃H₃₂ as it is known in cement chemistry notation, is a major phase of interest in cement science as an hydration product and in polluted soil treatment since its structure can accommodate with many hazardous cations. Beyond those anthropogenic features, ettringite is first of all a naturally occurring mineral (although rare). An example of its behaviour under the scanning electron microscope and during energy dispersive spectroscopy (EDS) qualitative analysis is presented, based on the study of natural ettringite crystals from the N'Chwaning mine in South Africa. Monte Carlo modelling of the electron‐matter interaction zone at various voltages is presented and confronted with actual, observed beam damage on crystals, which burst at the analysis spot. Finally, theoretical energy dispersive spectroscopy spectra for all the ettringite group minerals have been computed as well as Monte Carlo modelling of the electron‐matter interaction zone. The knowledge of the estimation of the size of this zone may thus be helpful for the understanding of energy dispersive spectroscopy analysis in cement pastes or ettringite‐remediated soils.     

MEASUREMENT OF THERMAL CONDUCTIVITY OF DAIRY PRODUCTS AND MARGARINES

A line heat source thermal conductivity probe was used to measure the thermal conductivity of 28 dairy products and margarines at 0, 20, and 40?C. Water and fat contents and mass density of each sample were also measured and correlated to thermal conductivity. There was a strong positive correlation between thermal conductivity and water content, and an inverse correlation between thermal conductivity and fat content. Temperature did not appear to be a significant factor over the limited temperature range studied. Although there was some correlation between mass density and non-fat solids fraction, no correlation was observed between mass density and thermal conductivity.     

硫回收装置尾气管道伴热的经济性

论述了充分加热对于防止硫回收装置尾气管道堵塞和腐蚀的重要性。对ControTrace元件与两种圆管（裸管和强化管）伴热的经济性进行了比较。结果表明,如果将装置的基础设施费用考虑在内,ControTrace元件较强化圆管伴热节约费用28％,并且其幅度随着管径的增加、蒸汽压力的降低而增大。