Constant stress intensity factors through closed-loop control

A new way of obtaining a constant stress intensity factor is achieved for any test specimen geometry subjected to closed-loop control loading. In contrast to using only load or displacement control the method draws on combined feedback from both displacement and load sensing, reducing the variation in the stress intensity factor by two decades compared to that if tested under constant load or displacement. A change in the signal mix ratio for a rectangular compact tension specimen is equivalent to changing the angle of a tapered compact tension specimen. This method can eliminate the need for the use of ‘complex’ geometries or for geometries in which measured crack lengths are used in conjunction with a computer or some other means to adjust the loading continuously for achieving a constant stress intensity factor.     

Fourier analysis of semi-discrete and space-time stabilized methods for the advective-diffusive-reactive equation: I. SUPG

The goal of this paper is twofold. One the one side, the most common transient Galerkin and SUPG methods are analyzed for the one-dimensional advection-diffusion-reaction equation. The methods analyzed include semi-discrete, time-discontinuous space-time stabilized finite element methods and several predictor multi-corrector versions of them. On the other hand, in the framework of explicit predictor multi-corrector algorithms a novel treatment of the source terms is proposed and analyzed. The technique consists of the diagonally implicit treatment of the negative or dissipative source terms. This technique increases dramatically the phase and damping accuracy of classical explicit methods and, at the same time, removes the source terms from stability considerations for low viscosity flows, thus, leading to very economic procedures.     

Sous vide cooked beef muscles: effects of low temperature–long time (LT–LT) treatments on their quality characteristics and storage stability

Beef muscles were sous vide cooked by applying different low temperature-long time treatments and changes in their physical properties were measured. The effects of selected treatments on pasteurization values and chilled storage stability were investigated. The results obtained indicated that cooking weight loss increased and shear force values decreased as the treatment temperature was raised from 50 to 65 °C, while processing times (90–360 min) did not have a significant effect on these variables. The colour parameter a was strongly affected by the different treatments. The pasteurization values obtained were enough to inactivate vegetative cells but were insufficient to achieve a significant reduction of Clostridium botulinum spores. The microbial quality of the product remained acceptable during the storage period. Over the storage time, thiobarbituric acid reactive substance (TBARS) numbers were significantly affected by the thermal treatment applied. Maximum TBARS values obtained were lower than those reported for meat processed without vacuum. Cooked beef flavours for all treatments decreased uniformly after 21 days of storage.     

Interpretation of the Electric Field Sensitivity of the Primary Charge Separation in Photosynthetic Reaction Centers

Popovic et al. (Biochim. Biophys. Acta, 1986, 851 : 38–48) have shown that the efficiency of light-induced charge separation in a monolayer of oriented photosynthetic reaction center (RC) is sensitive to the electric field. With the data provisionally interpreted as indicating a sensitivity of the picosecond electron transfer to field-induced free-energy change of the charge-separated states, current models for the light-induced picosecond electron transfer in the RC from bacteriochlorophyll dimer (BChl₂) to bacteriopheophytin, assisted by an interposed bacteriochlorophyll monomer (BChl), are challenged to fit the results. A model presuming a simple field-sensitive Franck-Condon overlap between BChl₂ and BChl, based on single classical vibration coupled to electron transfer, can only fit the data if the free-energy change does not match the reorganization energy. An even simpler model presuming a rapid field-sensitive thermal equilibrium between BChl₂ and the nearby BChl fits equally well. However, a model involving a superexchange electronic coupling between the excited BChl₂ and BChl, with or without similar field-dependent Franck- Condon overlap factors, provides the best fits to the data and suggests that the relevant dielectric constant of the RC may be about 1 with a BChl₂-BChl energy gap of about 100 meV.     

润滑和污染对轴承寿命的影响(一)

轴承寿命受许多因素影响,两个最重要的因素是润滑和污染。通过更好地认识这些因素是如何导致轴承寿命缩短的机理,我们就能改善轴承设计和运行。本文是两个部分的系列之一,首先研究润滑的影响。     

Cassava foliage: Chemical composition,cyanide content and effect of drying on cyanide elimination

The chemical composition and cyanide concentration in the foliage of four cassava cultivars (M Col 113, M Col 22, M Col 1684, CM 342–170) were evaluated at four plant ages (6, 8, 10 and 12 months). The effect on cyanide elimination of sun-drying on a concrete floor and of oven-drying at 60°C was also studied, including some observations on the tannin content of dried foliage. The proximal composition, calcium and phosphorus contents, as well as the amino acid composition of dried cassava foliage compared favourably to that of sun-cured lucerne meal. In most cases, foliage from 6-to 12-month-old plants contained 25 to 30% dry matter, and as dried foliage had 13 to 20% crude protein and 16 to 20% crude fibre. Crude protein and crude fibre were the two chemical constituents which varied the most with plant age. The average gross energy of dried cassava foliage was 4.12 kcal kg^?1 with a range of 3.90 to 4.35 kcal kg^?1. Sun-drying eliminated more cyanide than oven-drying (82 to 94% vs 68 to 76%, respectively) and in addition, most of the cyanide in sun-dried foliage was free cyanide (62 to 77%) whereas only 24 to 36% was found as such in oven-dried foliage. Sun-dried foliage samples had consistently lower tannin content than the corresponding oven-dried samples.     

Development of a Contextual Family Therapy Therapist Action Index.

Developed a contextual therapist action index (TAI). In Exp 1, 20 contextual family therapists (CFTs) contributed to the development of items that correspond to actions of CFTs as practiced in the field. Exp 2, in which 4 raters used the TAI to assess segments from CFT treatment sessions, reported modest construct validity and moderate degrees of reliability. Exp 3 demonstrated high degrees of discriminate validity in differentiating segments of contextual vs psychoeducational family therapy sessions. The TAI may provide an empirical basis on which to train therapists either to increase or decrease specific behaviors during therapy and aid in the supervision and teaching of family therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A study on the states of the non isothermal tubular wall reactor

The thermal behaviour of a cooled tube wall reactor is analyzed.The main goal of this work is the characterization of the steady state. Three different steady state solutions, in which the control through the reactor differs from each other, are presented. The possibility of simultaneous existence of these states is analyzed as a function of the parameters of the model.For the zeroth order reaction here treated, it is possible to get isothermal operating conditions. Minimum thermal levels at the wall reactor for a given conversion are discussed and they result closely related to the isothermal conditions.An analytical solution is developed for the so called “highest steady state” (HISS). This expression makes possible to predict the “quenching” conditions of the reactor.     

Instructional mechanisms in immersive virtual reality serious games: Earthquake emergency training for children

Children are vulnerable in earthquakes, but they are also essential to foster earthquake-resilient communities. It is critical to enhance the preparedness of children against earthquakes through effective education and training. Immersive virtual reality (IVR) and serious games (SGs) are innovative digital technologies that enable realistic and engaging training environments. However, little research has been made on the applications of IVR SGs for earthquake training targeting children. In order to fill this gap, this paper presents an IVR SG training system based on a problem-based gaming framework. Three instructional mechanisms within the training system, namely prior instruction, immediate feedback, and post-game assessment, were investigated to promote learning through effective reflection. A controlled experiment involving 125 secondary school students aged from 11 to 15 years old was undertaken, using leaflets as a traditional training approach for the control group and the IVR SG training system as the main intervention. Results revealed that the IVR SG training system with post-game assessment was the most effective way to train children, with greater knowledge acquisition and self-efficacy improvement observed. Possible improvements, such as increasing the time for reflection and differentiating the stimulation between positive and negative feedback, are suggested for further research.     

Database Management System Verification with Separation Logics

Programming and Computer Software - Program verification consists in finding a formal proof that the program satisfies a given specification. This specification can be described as assertions about...