Image-based finite element mesh construction for material microstructures

One way of computing the macroscopic behavior of a material sample with complex microstructure is to construct a finite element model based on a micrograph of a representative slice of the material. The quality of the results produced with such a model obviously depends on the quality of the constructed mesh. In this article, we describe a set of routines that modify and improve the quality of a 2D mesh. Most of the routines are guided by an effective element “energy” functional, which takes into account the shape quality of the elements and the homogeneity of the elements as determined from an underlying segmented image. The interfaces and boundaries in the image arise naturally from the segmentation process. From these routines, we construct a close-to-automatic mesh generator that requires only a few inputs, such as the linear sizes of the largest and smallest features in the micrograph.     

Characterisation and modelling of the elastic properties of poly(lactic acid) nanofibre scaffolds

The aim of this study is to predict the elastic response of poly(lactic acid) (PLA) electrospun nanofibre scaffolds through mathematical models based on homogenisation and the differential replacement method (DRM). These models principally seek to determine and analyse the effects of the internal morphology of the nanofibres on the effective Young’s modulus of polymer nanofibre scaffolds. The microstructure of the nanofibres was first characterised by SEM, XRD, DSC, AFM, and TEM techniques. From this characterisation, strong evidence of a hierarchical core–shell structure was found. With the experimental data, it was possible to design and validate better models than those currently used. In addition, the effects of the electrospinning parameters, such as take-up velocity and thermal treatment, were analysed and correlated with the morphology and the elastic properties of the nanofibres and their scaffolds. To validate the models’ results, we conducted a series of uniaxial tensile tests on the PLA nanofibre scaffolds. Using the data from the nanofibre measurements, the homogenisation approximations and the model based on the DRM predicted an effective Young’s modulus of 667 and 835 MPa, respectively. The predicted data were in excellent agreement with the experimental results (685–880 MPa). These models will be useful in understanding and evaluating the structure–property relationships of oriented nanofibre scaffolds for medical or biological applications.     

SHIP HYDRODYNAMICS BASIC RESEARCH IN THE UNITED STATES

ＳＨＩＰＨＹＤＲＯＤＹＮＡＭＩＣＳＢＡＳＩＣＲＥＳＥＡＲＣＨＩＮＴＨＥＵＮＩＴＥＤＳＴＡＴＥＳ￥ＥｄｗｉｎＰ．Ｒｏｏｄ（ＭｅｃｈａｎｉｃｓａｎｄＥｎｇｅｒｇｙＣｏｎｖｅｒｓｉｏｎ（３３３），ＯｆｆｉｃｅｏｆＮａｖａｌＲｅｓｅａｒｃｈＡｒｌｉｎｇｔｏｎ...     

Using the Megargee MMPI-based classification system with the MMPI-2s of female prison inmates.

This study extends Megargee's Minnesota Multiphasic Personality Inventory (MMPI)-based classification system to female offenders. MMPI-2s of 400 women in state and federal prisons were rescored and reconfigured to estimate their original MMPI profiles. Their MMPIs and MMPI-2s were classified according to the rules devised for the original MMPI. Next, the MMPI-2s were reclassified using new rules for classifying the MMPI-2s of male offenders. Neither approach led to satisfactory agreement between MMPI and MMPI-2. A major problem was that Scale 5 was more prominent in the women's MMPI-2 profiles than on their MMPIs. Using revised rules for classifying the original MMPIs and the MMPI-2s of female offenders, 386 of the 400 women (97%) could be classified on both versions of the MMPI, of whom 336 (87%) were classified identically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Monomeric N-hydroxyethylated amides

Oxyethylated amides that are good wetting agents have been prepared as mixtures by allowing amides to react with ethylene oxide under base catalysis. Individual components of such mixtures can be synthesized by allowing 1-alkylaziridines to react with p-toluenesulfonic acid in monomethylethers of di-, tri- and tetraethylene glycol used as solvents. The aminoethers are then acylated, and the methylether group is removed with trimethylsilyliodide from the resulting amide ethers. The sequence should allow the synthesis of specific wetting agents of quite varied structure (alkyl, aryl groups) with an option for isotopic labeling for more detailed analysis of the wetting properties.     

Effect of self-efficacy, goals, and task strategies on task performance.

Manipulated self-efficacy and task strategies in the training of 209 undergraduates under high strategy, low strategy, and control conditions. Ss underwent 5 trials and were administered a self-efficacy scale after each trial. Results show that ability, past performance, and self-efficacy were the major predictors of goal choice. Ability, self-efficacy, goals, and task strategies were related to task performance. Self-efficacy was more strongly related to past performance than to future performance but remained a significant predictor of future performance even when past performance was controlled. Self-efficacy ratings for moderate to difficult levels of performance were the best predictors of future performance; a reanalysis of 2 previous goal-setting studies by the first author confirms this finding. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Testing of a sodium/nickel chloride (ZEBRA) battery for electric propulsion of ships and vehicles

One of the promising future batteries for electric propulsion of vehicles and ships is the sodium/nickel chloride or ZEBRA (Zero Emission Battery Research Activities) battery. Despite some disadvantages with respect to the high temperature, the advantages with respect to specific energy and energy density are such that, especially in applications where the battery is used on a more or less continuous basis (e.g., in delivery vans and taxies) it is an interesting candidate battery. Another interesting application is on board of ships, like submarines or future electrical surface ships with electric propulsion. In 1995 a 2 year feasibility study, including experimental testing of a 10 kW h battery, was completed. This investigated the naval applicability of the sodium/sulphur battery, which is also a high temperature battery. Here the limited, experimentally proven, life-time of the batteries of about 1.5 years and this made naval application almost impossible. A paper about this study was presented at the 19th International Power Sources Symposium held at Brighton, England, in April 1995 [R.A.A. Schillemans, C.E. Kluiters, Sodium/sulphur batteries for naval applications, in: A. Attewell, T. Keily (Eds.), Power Sources 15, International Power Sources Symposium Committee, Crowborough UK, 1995. p. 421.]. Because of the more or less comparable specifications on specific energy and the more promising results of the life-time and field tests with sodium/nickel chloride batteries, a ZEBRA battery from AEG Anglo Batteries has been tested for naval applications. This was done by simulating the charge and discharge as it occurs in practice for the applications investigated. With respect to the electrical ship application (investigated for the Royal Netherlands Navy) the power versus time taken from the battery was simulated as well as the charge procedures. The same can be done for the vehicle application: in this case typical drive cycles for a van or taxi are translated to power versus time taken from the battery. The results of the tests for application of the battery in naval ships are very promising.     

Light aversion in mice depends on nonimage-forming irradiance detection.

Detection of light in the eye underlies image-forming vision, but also regulates adaptive responses in physiology and behavior. Typically these adaptive responses do not involve image-forming vision, but depend on a relatively absolute measure of brightness (nonimage-forming irradiance detection). The goal of this study was to further understand how image-forming vision and nonimage-forming irradiance detection contribute to the effects of light on behavior. Three light dependent behaviors were assessed in wild-type, Rpe65-/- and rd1 mice. In Rpe65-/- mice, nonimage-forming irradiance detection is severely attenuated, but rod based visual acuity is relatively preserved. In rd1 mice visual acuity is nonrecordable, but nonimage-forming responses are less severely attenuated than Rpe65-/-. Positive masking, an image-forming vision dependent increase in wheel running, was absent in rd1 and restricted to higher irradiances in Rpe65-/-. Negative masking, a suppression of wheel running sensitivity with nonimage-forming irradiance detection input, was increased in rd1, but reduced in Rpe65-/- mice. By contrast, light aversion, an avoidance of brightly lit areas, was abolished in both Rpe65-/- and rd1. This shows that image-forming vision is not sufficient for light aversion, suggesting nonimage-forming irradiance detection motivates this behavior. Further, the differing effects of disease suggest that negative masking and light aversion are distinct responses with specialized nonimage-forming irradiance detection pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

检查光纤束的LED闪光器

借助图1所示电路,你可以验证光纤束,特别是当链路通过几块插接板时.你能在远端看见它使用的两只高亮度LED.闪光器在大约50分钟后关闭,在关断状态时的功耗微乎其微.电路工作于距离超过1 km的多模光纤上.它还可配合单模光纤,但较难在接收端看到.如果光纤很短,由于LED很亮,因此最好在远端以小角度查看.IC1B是运行频率约5 Hz的施密特触发振荡器,驱动IC2,后者是4020二进制触发器.IC3A是控制双稳态多谐振荡器.按动按钮开关S1,则设置双稳态多谐振荡器,后者启动振荡器,并启用4020,以便开始从它的全零状态起计数.它还启用门电路IC1A和IC1D,二者控制PNP LED驱动晶体管.