Influence of cathodic reduction on the photoelectrochemical behaviour of titanium dioxide under UV radiation measurement of the photocurrent in chloride medium

It is established that a cathodic pretreatment of thermic titanium dioxide increases considerably the photoresponse to TiO₂ under uv radiation in chloride solution. The effects of the duration of the pretreatment and of the nature of the acidic media used to perform the cathodic pretreatment are investigated. The variation law of the increase of the photocurrent with the pretreatment duration, which is the sum of two exponential laws at least, reveals the presence of various phenomena in the improvement of the energetic efficiency. The various mechanism involved there are discussed according to different hypotheses.     

Passively recognising human activities through lifelogging

Lifelogging is the process of automatically recording aspects of one’s life in digital form. This includes visual lifelogging using wearable cameras such as the SenseCam and in recent years many interesting applications for this have emerged and are being actively researched. One of the most interesting of these, and possibly the most far-reaching, is using visual lifelogs as a memory prosthesis but there are also applications in job-specific activity recording, general lifestyle analysis and market analysis.In this work we describe a technique which allowed us to develop automatic classifiers for visual lifelogs to infer different lifestyle traits or characteristics. Their accuracy was validated on a set of 95 k manually annotated images and through one-on-one interviews with those who gathered the images. These automatic classifiers were then applied to a collection of over 3 million lifelog images collected by 33 individuals sporadically over a period of 3.5 years. From this collection we present a number of anecdotal observations to demonstrate the future potential of lifelogging to capture human behaviour. These anecdotes include: the eating habits of office workers; to the amount of time researchers spend outdoors through the year; to the observation that retired people in our study appear to spend quite a bit of time indoors eating with friends. We believe this work demonstrates the potential of lifelogging techniques to assist behavioural scientists in future.     

Direct physical factors and PGI2 and TXA2 secretions by a human endothelial cell line: in vitro investigation of pressure and shear stress applied independently or in synergy

The direct effect of two types of mechanical stress was measured through the prostacyclin (PGI2) and thromboxane A2 (TXA2) secretions by a confluent monolayer of cells from the EA.hy926 line. Eight values of constant pressure were applied in the gas phase above the culture medium, around atmospheric pressure taken as a control (0 mm Hg), from -500 to +760 mm Hg. Three amplitudes of sinewave modulated pressure (+/- 40; +/- 80; +/- 160 mm Hg) were explored at a frequency of 1 Hz. Modulated pressure (+/- 40 mm Hg) was also applied synergetically to a shear stress generated under steady state conditions by a rectilinear laminar motion of the medium. The cells remained adherent and exhibited unchanged morphology and viability. Constant pressure or depressure increased both PGI2 and TXA2 release but to an extent depending on the pressure value. Under pressure, the PGI2/TXA2 ratio was unchanged, but was higher under depressure, compared to the control. Pressure modulation strongly stimulated the secretion of PGI2 but had no effect on TXA2. Modulation strongly increased the PGI2/TXA2 ratio to a similar extent for the three amplitudes. Pressure-shear synergy enhanced secretion of PGI2 markedly more than shear stress alone, but the level reached was similar to the one induced by pressure modulation. No cumulative effect on the secretion of PGI2 was observed, whereas TXA2 synthesis undergoes a more than cumulative effect. The PGI2/TXA2 ratio remained unchanged under shear alone or under combined shear-pressure modulation but was higher with the modulated pressure alone. These results demonstrate that pressure has an outstanding effect on secretion that may be origin to local disturbances of the vascular system, thus inducing pathologies such as thrombosis or atherosclerosis.     

Robust and Efficient Ray Intersection of Implicit Surfaces

The generation of ray traced images of a variety of surfaces plays a central role in computer graphics. One of the main operations in ray tracing is the calculation of intersections between rays and surfaces. In case of implicitly given surfaces the intersection problem can be formulated as that of finding the smallest non-negative root of an equation in one variable. If the root finding is carried out by means of conventional numerical methods based on point sampling (such as bisection, regula-falsi or Newton) the resulting image can be wrong, e.g. when the surface is thin the ray may "miss" the surface, which may result in an image with background color spots on the surface. To obtain robust intersection detection, methods based either on Lipschitz constants for the function and its derivative or an interval inclusions for the function and its derivative have been suggested. In this paper robust methods are obtained with interval inclusions in a variant of Alefeld-Hansens globally convergent method for computing and bounding all the roots of a single equation. Alefeld-Hansens method has been modified so instead of searching for all roots, a recursive depth-first search is carried out to obtain the smallest non-negative root. When compared to other methods suggested, it is found that this variant of Alefeld-Hansens method is not only robust but also an efficient method for finding the ray intersections.     

临界荷载作用下通过有限元分析的桥寿命动力放大系数

建立桥梁设计和既有结构评估的精确标准要求需要充分评估重载交通荷载以及重载作用导致的动态交互作用。目前的方法一般是首先计算典型的静态荷载作用,然后加上一个放大系数作为动态作用的限值。这种方法明显减少了高静态荷载和高动态扩大作用同时发生的可能性。提出了一个评估程序,只考虑临界荷载,可以有效和精确地确定典型静力（最大寿命）和动力（包括动态交互作用）荷载的特征值。采用蒙特卡罗模拟确定所选桥的临界静力荷载,建立三维有限元桥梁数据库和模型,对各种车辆荷载组合进行分析。建立识别临界荷载过程的模型,分析得到临界总荷载作用。然后可以得到临界静力荷载作用与相应的总荷载作用的相关性,进而外推确定一个特定的动力扩大系数。     

Anodic behaviour of zirconium and its alloys in fluorinated nitric media dissolution-passivation model

Absract Current-potential curves for zirconium in fluorinated nitric medium were obtained using a rotating disc electrode. The curves exhibited four different domains according to the potential, and suggested a seven-step reaction model composed of three competing paths. Quantitatively verified by comparing computed and experimental curves, this model accounts for the behaviour of either zirconium or its main industrial alloy, Zircaloy 4, over potentials ranging from the corrosion potential up to the zirconia passivation potential. Moreover, the model allows the rate of elementary steps to be determined, as well as the coverage ratio of the intermediate species considered. These results correlated with scanning electron microscopy observations and proved to be particularly sensitive to slight modifications of the electrochemical system. The model can also be considered as a promising tool in the study of zirconium alloy pickling in acidic media and for optimising the resulting surface quality.     

Existence Test for Asynchronous Interval Iteration

In the search for regions that contain fixed points of a real function of several variables, tests based on interval calculations can be used to establish existence or non-existence of fixed points in regions that are examined in the course of the search. The search can e.g. be performed as a synchronous (sequential) interval iteration: In each iteration step all components of the iterate are calculated based on the previous iterate. In this case it is straight forward to base simple interval existence and non-existence tests on the calculations done in each step of the iteration. The search can also be performed as an asynchronous (parallel) iteration: Only a few components are changed in each step and this calculation is in general based on components from different previous iterates. For the asynchronous iteration it turns out that simple tests of existence and non-existence can be based on the component wise calculations done in the course of the iteration. These component wise tests are useful for parallel implementation of the search, since the tests can then be performed local to each processor and only when a test is successful does a processor communicate this result to other processors.     

The influence of chromium on the mass transfer limitation of the anodic dissolution of ferritic steels FeCr in molar sulphuric acid

By tracing steady-state, ohmic drop corrected anodic polarization curves, the influence of chromium on the limitation caused by mass transfer onto the anodic dissolution of ferritic steels FeCr containing 10, 12, 17 and 22% of chromium in a molar sulphuric acid medium has been determined. This investigation which was carried out with a rotating disc electrode revealed a partial blockage of the reaction surface from a diffusion standpoint, and the existence of two parallel dissolution processes. Thus, it has been possible to determine the influence of chromium on each of these two processes, only one of which is partially limited by mass transfer, given that the proportion of this latter process in the overall current increases with the chromium concentration of the alloy.     

Study of partially blocked electrodes by means of electromechanical impedance measurements

The study of the reduction of dissolved oxygen, in an aerated sulphuric acid medium, to the surface of a rotating disc electrode of iron has been carried out so as to determine the nature of coverages involved in the processes taking place on both sides of the corrosion potential.The measurements of the diffusional component due to the reduction of oxygen was derived from the frequency analysis of the current response to a sine wave modulation of the disc velocity (eletromechanical impedance).The treatment of our data shows that a blocking of the reactional area with respect to the oxygen reduction is caused by a hydrogenated species having a long time. This blocking remains very important (80%) at the corrosion potential and decreases to zero for anodic currents higher than 5 mA cm^?2.     

Anodic behaviour of titanium in acidic chloride containing media (HCl---NaCl). Influence of the constituents of the medium—I. Study of the stationary current. Calculation of the overall reaction orders

In concentrated hydrochloric acid solutions, the overall dissolution rate depends on the acid concentration. Using mixed electrolytes (HCl---NaCl) we have established the influence on the overall anodic stationary current, of each of the H⁺ and Cl⁻ ions. Considering the logarithmic derivative of the overall current with respect to the activities in the various constituents of the medium reveals the complexity of the reaction mechanism especially in the activity and passivation ranges.