Chemical modification of polystyrene

Summary Sulfinate functional groups have been introduced on selected positions of the aromatic rings of soluble or crosslinked polystyrene via lithiation reactions followed by quenching with sulfur dioxide. The sulfinate polymers have good stability, can be stored at room temperature, and can be used for ion-exchange or as nucleophiles to produce polymer-bound sulfones. Good functional yields of polystyrene resins with sulfone pendant groups can be obtained by reaction of the polymeric sulfinates with various alkyl halides under phase transfer or classical conditions.     

A case study on consistency management of business and IT process models in banking

Organizations that adopt process modeling often maintain several co-existing models of the same business process. These models target different abstraction levels and stakeholder perspectives. Maintaining consistency among these models has become a major challenge for such organizations. Although several academic works have discussed this challenge, little empirical investigation exists on how people perform process model consistency management in practice. This paper aims to address this lack by presenting an in-depth empirical study of a business-driven engineering process deployed at a large company in the banking sector. We analyzed more than 70 business process models developed by the company, including their change history, with over 1,000 change requests. We also interviewed 9 business and IT practitioners and surveyed 23 such practitioners to understand concrete difficulties in consistency management, the rationales for the specification-to-implementation refinements found in the models, strategies that the practitioners use to detect and fix inconsistencies, and how tools could help with these tasks. Our contribution is a set of eight empirical findings, some of which confirm or contradict previous works on process model consistency management found in the literature. The findings provide empirical evidence of (1) how business process models are created and maintained, including a set of recurrent patterns used to refine business-level process specifications into IT-level models; (2) what types of inconsistencies occur; how they are introduced; and what problems they cause; and (3) what stakeholders expect from tools to support consistency management.     

Glyceryl ether containing lipids of whole brains from germ-free and conventional rats

The percentage alkyl and alk-1’-enyl glyceryl ethers of the polar lipids isolated from germ-free and conventional rat brain tissue has been determined. No difference could be detected in the quantity of the ether-containing lipids in these animals. Similarly, the composition of the aldehydic chain of the alk-1’-enyl glyceryl ethers from germ-free and conventional rat brain tissue was shown to be the same. The microbial flora, therefore, do not influence either the quantity of the ether-containing lipids or the composition of the aldehyde chain of the alk-1’-enyl glyceryl ethers in the rat brain.     

Household robots look and learn: environment modeling and localization from an omnidirectional vision system

The work illustrates that a catadioptric omnidirectional vision system can be successfully applied for basic mobile robot navigation tasks, such as localization and environment learning. In combination with other capabilities of such a sensor, such as the recognition and tracking of humans, and because the price of such systems can be made low, this system is particularly suited for systems that are expected to operate in offices and homes in the near future, such as robotic servant systems, entertainment robots, and help for the elderly and disabled.     

Distributed control design for parabolic evolution equations: application to compressor stall control

We present a theoretical study of distributed control design for semilinear parabolic nonlocal evolution equations with an application to axial compressor stall control using air injection. By taking advantage of the spatial invariance of the equations, a linear controller is constructed (following Bamieh et al.) via linear quadratic control of each Fourier mode. We derive sufficient conditions for the linear controller to stabilize the full nonlinear system. Concepts such as controller decentralization, finite-dimensional implementation, inverse-optimality, and beneficial nonlinearities are discussed. In the second part of this paper, these developments are applied to a model of axial compressor control with air injection. The unactuated model is derived following the work of Moore and Greitzer and the model coupled with air injection actuation follows the works of Behnken et al. and Weigl et al. A numerical study of the control designs is pursued and the comparison of controller performance is discussed. The techniques presented here are expected to be useful for distributed control design of a much broader class of nonlinear reaction-diffusion systems.     

Illustrative visualization: interrogating triangulated surfaces

Geometrical modeling is a crucial aspect of simulations involving manufactured objects and is usually performed using free-form surfaces. However, to simulate the flow through or about a manufactured object or to simulate structural integrity, the free-form surfaces must be tessellated into triangulated surfaces. To concurrently visualize the simulation results and the quality of the surfaces, we present two novel visualization algorithms for triangulated surfaces as opposed to the traditional freeform surfaces. The proposed algorithms are for curvature estimation based on local surface fitting with cubic triangular Bézier patches and for reflection-line computation.     

Monitoring the spatio-temporal dynamics of geometrid moth outbreaks in birch forest using MODIS-NDVI data

Defoliation caused by repeated outbreaks of cyclic geometrid moths is the most prominent natural disturbance factor in the northern-boreal birch forest. Evidence suggests that recent changes in outbreak distribution and duration can be attributed to climate warming. There is hence an immediate need for methods that can be applied to characterize the geographical distribution of outbreaks. Here we assess the reliability of MODIS (Moderate Resolution Imaging Spectroradiometer) 16-day NDVI data for generating time series of the distribution of defoliation caused by moths attacking birch forest in Fennoscandia. We do so by first establishing the relationship between ground measures of moth larval density and a defoliation score based on MODIS-NDVI. We then calibrate and validate a model with the MODIS-NDVI defoliation score as a classifier to discriminate between areas with and without visible defoliation as identified from orthophotos and provide two examples of application of the model. We found the MODIS defoliation score to be a valid proxy for larval density (R² = 0.88-0.93) above a certain, low threshold (a defoliation score of ~ 5%). Areas with and without visible defoliation could be discriminated based on defoliation score with a substantial strength of agreement (max kappa = 0.736), and the resulting model was able to predict the proportion of area with visible defoliation in independent test areas with good reliability across the range of proportions. We conclude that satellite-derived defoliation patterns can be an invaluable tool for generating indirect population dynamical data that permits the development of targeted monitoring on relevant regional scales.     

Fast Ray Tracing of Arbitrary Implicit Surfaces with Interval and Affine Arithmetic

Existing techniques for rendering arbitrary-form implicit surfaces are limited, either in performance, correctness or flexibility. Ray tracing algorithms employing interval arithmetic (IA) or affine arithmetic (AA) for root-funding are robust and general in the class of surfaces they support, but traditionally slow. Nonetheless, implemented efficiently using a stack-driven iterative algorithm and SIMD vector instructions, these methods can achieve interactive performance for common algebraic surfaces on the CPU. A similar algorithm can also be implemented stacklessly, allowing for efficient ray tracing on the GPU. This paper presents these algorithms, as well as an inclusion-preserving reduced affine arithmetic (RAA) for faster ray-surface intersection. Shader metaprogramming allows for immediate and automatic generation of symbolic expressions and their interval or affine extensions. Moreover, we are able to render even complex forms robustly, in real-time at high resolution .     

Graphics processing unit (GPU) programming strategies and trends in GPU computing

Over the last decade, there has been a growing interest in the use of graphics processing units (GPUs) for non-graphics applications. From early academic proof-of-concept papers around the year 2000, the use of GPUs has now matured to a point where there are countless industrial applications. Together with the expanding use of GPUs, we have also seen a tremendous development in the programming languages and tools, and getting started programming GPUs has never been easier. However, whilst getting started with GPU programming can be simple, being able to fully utilize GPU hardware is an art that can take months or years to master. The aim of this article is to simplify this process, by giving an overview of current GPU programming strategies, profile-driven development, and an outlook to future trends.     

Magnetic Performance of the Main Superconducting Magnets for the LHC

The field strength and homogeneity of all the LHC superconducting magnets were measured as a part of the production control and qualification process that has taken place during the past four years. In addition to field measurements at room temperature performed on the integral of the production, a significant part of the magnets has been subjected to extensive magnetic measurements at cold. The measurements at cryogenic temperatures, generally performed up to excitation currents of 12 kA corresponding to the ultimate LHC energy of 7.6 TeV, were mainly based on static and dynamic field integral and harmonic measurements. This allowed us to study in detail the DC effects from persistent current magnetization and long-term decay during constant current excitation. These effects are all expected to be of relevance for the field setting and error compensation in the LHC. This paper reports the main results obtained during these tests executed at operating conditions. The integrated field quality is discussed in terms of distribution (average and spread) of the field strength and low-order harmonics as obtained for all the main ring magnet families (dipoles, main and matching quadrupoles). The dependence of field quality on coil geometry, magnet and cable manufacturer is analyzed. A projection of the field quality expected for the critical components in the machine is presented.