Finite element simulation of the mechanics of flat contact pad fretting fatigue tests

An understanding into the macro kinetic and kinematic behaviour of fretted surfaces is provided. Making use of a modified version of a previously developed in‐house two‐dimensional elastic–plastic finite element analysis numerically simulates flat contact pad fretting fatigue tests. Basic macro mechanics concepts are adopted to idealise two bodies with rough contact surfaces and loaded at two different sites with arbitrary axial loading profiles. A time scale factor is devised to recognise the earliest candidate out of the events possibly accommodated at each loading increment. The present analysis utilises a relevant experimental set up developed in the Structural Integrity Research Institute of the University of Sheffield as an application. Computational results accurate to within 1.2% and corresponding to one contact pad span and six constant normal loads acting individually with four amplitudes of two sinusoidal axial load cycles are presented. The present computations include (1) the development of the global and local normal and tangential reactions and relative sliding displacement acting along the fretting surfaces and (2) contact pad deformation, generated stress fields and plasticity development within the neighbouring region of the fretted area.     

Perceptual evaluation of color gamut mapping algorithms

The recommendation of the CIE has been followed as closely as possible to evaluate the accuracy of five color gamut mapping algorithms (GMAs)—two nonspatial and three spatial algorithms—by psychophysical experiments with 20 test images, 20 observers, one test done on paper and a second one on display. Even though the results do not show any overall “winner,” one GMA is definitely perceived as not accurate. The importance of a high number of test images to obtain robust evaluation is underlined by the high variability of the results depending on the test images. Significant correlations between the percentage of out‐of‐gamut pixels, the number of distinguishable pairs of GMAs, and the perceived difficulty to distinguish them have been found. The type of observers is also important. The experts, who prefer a spatial GMA, show a stronger consensus and look especially for a good rendering of details, whereas the nonexperts hardly make a difference between the GMAs. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 470–476, 2008     

响洪甸电站引水隧洞进口水下岩塞爆破施工

响洪甸抽水蓄能电站水下岩塞爆破施工要求高,技术新,难度大.由于施工准备充分,并进行了一系列材料及施工试验,工程进展顺利,排孔造孔、导洞药室开挖、药管与起爆体加工、装药与堵塞、网络施工、充水补气等工程施工质量符合设计要求,岩塞爆破准时成功起爆.     

Laboratory Evaluation of Smear Zone and Correlation between Permeability and Moisture Content

In this study, the extent of the smear zone and the reduction of permeability and water content within the smear zone were investigated using a large-scale consolidometer. The installation of vertical drains by means of a mandrel causes significant disturbance of the subsoil surrounding the mandrel, resulting in a smear zone. The extent of the smear zone for Moruya clay (New South Wales, Australia) was estimated on the basis of normalized permeability and the reduction of water content by taking undisturbed samples (horizontally and vertically) at different locations. This study reveals that a significant reduction in water content and horizontal permeability takes place towards the drain, whereas the variation in the vertical permeability is negligible. The smear zone for Moruya clay was found to be 2.5 times the equivalent radius of the mandrel with the horizontal permeability varying from 1.09 to 1.64, an average of 1.34 times smaller than that of the undisturbed zone. Finally, a correlation between the permeability decrease and water content reduction within smear zone is proposed.     

单粒子效应对航天器的威胁及空间飞行试验评论（二）

列举了若干航天器因单粒子效应而出现的异常或故障。阐述了单粒子效应空间飞行试验方法和预估方法。总结了多颗航天器单粒子效应空间飞行试验结果。依据空间飞行试验结果，对静止卫星、低太阳同步轨道卫星和椭圆轨道卫星在太阳宁静和太阳耀斑期间单粒子效应作了比较。     

运用热模拟压缩试验确定精确的金属流动方程

研究分析在用压缩试验确定金属高温塑性流动方程时影响流动应力，应变值精度的主要因素即试样表面摩擦与变形温升，并提出了相应的的修正方法。     

The importance of the compression test procedure for plastic drums for dangerous goods

Packagings for the transport of dangerous goods are tested by four tests:- free fall, leakproofness, hydraulic pressure and stacking. However, the test procedures can be interpreted in different ways, particularly the stacking test. Some test authorities apply a guided load to the top of the package and others, including the LNE in France, use non-guided loads. The objective of recent research carried out at LNE was to evaluate the risk (in terms of stack stability for dangerous goods packagings) if the stacking tests are performed with guided loads rather than non-guided loads. The stacking tests were carried out on a limited number of plastic drums (200 of four types) submitted for qualification testing using the above four tests, with either guided or non-guided loads. From the results we conclude that:

• i for the transport of dangerous goods of Danger Group I, the field of use is not altered when tested by either procedure.
• ii with goods of Danger Groups II and III, the use of either procedure does not alter the position as far as transport is concerned. However, there is a risk in warehousing: the non-guided procedure being preferred.

     

Cushing’s Syndrome Effects on the Thyroid

The most known effects of endogenous Cushing’s syndrome are the phenotypic changes and metabolic consequences. However, hypercortisolism can exert important effects on other endocrine axes. The hypothalamus–pituitary–thyroid axis activity can be impaired by the inappropriate cortisol secretion, which determinates the clinical and biochemical features of the “central hypothyroidism”. These findings have been confirmed by several clinical studies, which also showed that the cure of hypercortisolism can determine the recovery of normal hypothalamus–pituitary–thyroid axis activity. During active Cushing’s syndrome, the “immunological tolerance” guaranteed by the hypercortisolism can mask, in predisposed patients, the development of autoimmune thyroid diseases, which increases in prevalence after the resolution of hypercortisolism. However, the immunological mechanism is not the only factor that contributes to this phenomenon, which probably includes also deiodinase-impaired activity. Cushing’s syndrome can also have an indirect impact on thyroid function, considering that some drugs used for the medical control of hypercortisolism are associated with alterations in the thyroid function test. These considerations suggest the utility to check the thyroid function in Cushing’s syndrome patients, both during the active disease and after its remission.