100% solids ultraviolet curing acrylated chlorinated rubber coatings

Acrylated chlorinated rubber (ACR) has been synthesized from masticated natural rubber and characterized with Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance spectroscopy (NMR), and differential scanning calorimetry (DSC). The ACR products have been used as prepolymers in formulations of 100% solids ultraviolet (UV) cured coatings. The UV cured ACR-based coatings show excellent performance and attractive appearance. Formulation examples and coating performance are reported. © 1994 John Wiley & Sons, Inc.     

Precision instrumentation for rolling element bearing characterization

This article describes an instrument to measure the error motion of rolling element bearings. This challenge is met by simultaneously satisfying four requirements. First, an axial preload must be applied to seat the rolling elements in the bearing races. Second, one of the races must spin under the influence of an applied torque. Third, rotation of the remaining race must be prevented in a way that leaves the radial, axial/face, and tilt displacements free to move. Finally, the bearing must be fixtured and measured without introducing off-axis loading or other distorting influences. In the design presented here, an air bearing reference spindle with error motion of less than 10 nm rotates the inner race of the bearing under test. Noninfluencing couplings are used to prevent rotation of the bearing outer race and apply an axial preload without distorting the bearing or influencing the measurement. Capacitive displacement sensors with 2 nm resolution target the nonrotating outer race. The error motion measurement repeatability is shown to be less than 25 nm. The article closes with a discussion of how the instrument may be used to gather data with sufficient resolution to accurately estimate the contact angle of deep groove ball bearings.     

Subsidiary Interdependencies and International Human Resource Management Practices in German MNCs

• Using the resource-based view, this paper links the degree of interdependence that exists between subsidiaries of multinational corporations (MNCs) to the use of various International Human Resource Management (IHRM) practices.
• We assume that in many MNCs this interdependence has increased the need for cross-border coordination.
• We analyze to what extent MNCs use IHRM practices in order to enhance their coordination capability across national borders.
• We present a framework that addresses these effects and empirically test it using data from a questionnaire survey among 142 majority-owned overseas subsidiaries of German MNCs.
• The findings show that the degree of interdependence is related to the level of international experience of staff employed in subsidiaries, the use of third-country nationals, the provision of training, the use of cross-cultural management teams, and the choice of employee evaluation and reward methods.
• We conclude by discussing the implications of our findings for IHRM practitioners and scholars as well as the limitations of our study.

     

Three-dimensional boundary singularity method for partial-slip flows

This study extends a 3-D method of the fundamental solutions (MFS) to Stokes flows with Knudsen numbers corresponding to partial-slip flows interior and exterior to spherical boundaries. The study focuses on the distribution of the singularities outside the fluid flow domain. Local spherical coordinates systems are thus introduced to accommodate the application of the method to flows with partial-slip boundary conditions, where velocities tangent to solid walls are proportional to shear rates at surfaces. The singularities are subject to variation in location and number to investigate their impacts on numerical accuracy. For the flow about a single sphere, it is shown that the numerical accuracy improves when the singularities move towards the sphere center. When the singularities are located too far away from the observation points toward the center of sphere, the solution of the linear system fails. The reasons that cause the failure are explored and optimal location of singularities is found. The flow between two concentric spheres is used for further validation of the developed method for a combination of convex and concave surfaces. Finally the application of the method to flows about two separately spaced spheres is presented. Numerical results obtained compare favorably with analytical solutions for presented test cases. It is shown that a moderate number of singularities can be used in combination with a proper location of singularities to achieve a prescribed accuracy.     

Assessing Lévy walks as models of animal foraging

The hypothesis that the optimal search strategy is a Lévy walk (LW) or Lévy flight, originally suggested in 1995, has generated an explosion of interest and controversy. Long-standing empirical evidence supporting the LW hypothesis has been overturned, while new models and data are constantly being published. Statistical methods have been criticized and new methods put forward. In parallel with the empirical studies, theoretical search models have been developed. Some theories have been disproved while others remain. Here, we gather together the current state of the art on the role of LWs in optimal foraging theory. We examine the body of theory underpinning the subject. Then we present new results showing that deviations from the idealized one-dimensional search model greatly reduce or remove the advantage of LWs. The search strategy of an LW with exponent μ = 2 is therefore not as robust as is widely thought. We also review the available techniques, and their potential pitfalls, for analysing field data. It is becoming increasingly recognized that there is a wide range of mechanisms that can lead to the apparent observation of power-law patterns. The consequence of this is that the detection of such patterns in field data implies neither that the foragers in question are performing an LW, nor that they have evolved to do so. We conclude that LWs are neither a universal optimal search strategy, nor are they as widespread in nature as was once thought.     

Diffraction efficiency of 200-nm-period critical-angle transmission gratings in the soft x-ray and extreme ultraviolet wavelength bands

We report on measurements of the diffraction efficiency of 200-nm-period freestanding blazed transmission gratings for wavelengths in the 0.96 to 19.4 nm range. These critical-angle transmission (CAT) gratings achieve highly efficient blazing over a broad band via total external reflection off the sidewalls of smooth, tens of nanometer thin ultrahigh aspect-ratio silicon grating bars and thus combine the advantages of blazed x-ray reflection gratings with those of more conventional x-ray transmission gratings. Prototype gratings with maximum depths of 3.2 and 6 μm were investigated at two different blaze angles. In these initial CAT gratings the grating bars are monolithically connected to a cross support mesh that only leaves less than half of the grating area unobstructed. Because of our initial fabrication approach, the support mesh bars feature a strongly trapezoidal cross section that leads to varying CAT grating depths and partial absorption of diffracted orders. While theory predicts broadband absolute diffraction efficiencies as high as 60% for ideal CAT gratings without a support mesh, experimental results show efficiencies in the range of ～50-100% of theoretical predictions when taking the effects of the support mesh into account. Future minimization of the support mesh therefore promises broadband CAT grating absolute diffraction efficiencies of 50% or higher.     

Soil science and the <Emphasis Type="Italic">h</Emphasis> index

Soil science is a relatively young and specialised field of science. This note discusses the use of the h index as a scientific output measure in soil science. We explore the governing factors of h index in soil science: the number of soil scientists, the number of papers published, the average number of citations, and the age of the scientist. We found the average relationship between h index and scientific age for soil science: h = 0.7 t. The h index for soil science is smaller than other major science disciplines but norms for h need to be established     

Does adolescent alcohol and marijuana use predict suppressed growth in psychosocial maturity among male juvenile offenders?

Multiple theories suggest mechanisms by which the use of alcohol and drugs during adolescence could dampen growth in psychosocial maturity. However, scant empirical evidence exists to support this proposition. The current study tested whether alcohol and marijuana use predicted suppressed growth in psychosocial maturity among a sample of male serious juvenile offenders (n = 1,170) who were followed from ages 15 to 21 years. Alcohol and marijuana use prospectively predicted lower maturity 6 months later. Moreover, boys with the greatest increases in marijuana use showed the smallest increases in psychosocial maturity. Finally, heterogeneity in the form of age-related alcohol and marijuana trajectories was related to growth in maturity, such that only boys who decreased their alcohol and marijuana use significantly increased in psychosocial maturity. Taken together, these findings suggest that patterns of elevated alcohol and marijuana use in adolescence may suppress age-typical growth in psychosocial maturity from adolescence to young adulthood, but that effects are not necessarily permanent, because decreasing use is associated with increases in maturity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transverse cracking and delamination in cross-ply gr/ep composites under dry, saturated and immersed fatigue

Motivated by experimental observations, the finite element method is employed to model the competition between the transverse cracking and delamination modes of failure that occur in cross-ply AS4/3501-6 gr/ep coupons subjected to fatigue. The results explain the extensive delaminations and reduced crack densities that arise under immersed fatigue, as compared with fatigue in air. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fracture in off-axis Unidirectionally Reinforce Ceramic Composites

Multiple fiber-bridged matrix cracks in an unidirectionally reinforced, off-axis, ceramic matrix composite is modeled using a combination of a displacement based finite element scheme and an eigen function expansion method. All cracks are considered to run parallel to the horizontal axis, the load is applied vertically, and all fibers are oriented at an angle φ about the horizontal direction. It is determined that when a crack impinges on an inclined interface tensile and compressive stresses develop along the interface at an angle of φ and φ-π degrees, respectively. This result suggests the emergence of a pattern of interfacial debondings that is consistent with experimental observations. Calculations are performed for φ=60°. The interaction between several cracks is studied for different crack configurations. This revised version was published online in July 2006 with corrections to the Cover Date.