Streamline curvature effects in side-channel spillway flow

Summary Steady flow in side channel spillways is investigated, thereby accounting for the effects of the streamline slope and curvature on the free surface profile. The governing system of equations is linearized in order to discuss the main features of the solutions. Subsequently, the non-linear version is solved by an implicit numerical procedure; particular attention is paid to the stability of the chosen scheme. Finally, the solutions are compared to observations and an almost perfect agreement is found.Notation a reference flow depth - b channel width - F Froude number - g gravitational acceleration - h flow depth - J average energy gradient - K Strickler's roughness coefficient - L lateral inflow length - m root of characteristic polynomial - n Manning's roughness coefficient - p lateral inflow intensity per unit channel width - q lateral inflow intensity - Q discharge - R hydraulic radius - S specific momentum - S _f frictional slope - S ₀ bottom slope - V average cross-sectional velocity - x longitudinal coordinate - X normalized longitudinal coordinate - y normalized flow depth - factor, 01 - factor, 01 - perturbative change in flow depth - relative discharge intensity - relative specific momentum With 7 FiguresSeveral symbols may appear with indices u, d, N, c and then refer to the up-and downstream end of the lateral inflow zone, and to uniform and critical flow conditions, respectively. Primes indicate derivatives with respect to the longitudinal coordinate.     

Simulations and experimental investigation of paint film leveling

The surface structure of a paint film is the result of the interplay of a variety of physical influences, e.g., the superposition of droplets during spray application, the surface tension-driven leveling, and the viscosity increase in the leveling phase. A numerical simulation program is presented that incorporates all the relevant mechanisms of paint film structure formation during and after spray application. The simulation program was validated by comparing simulations and leveling experiments. The influence of the initial film geometry and viscosity on the leveling behavior is demonstrated. For the investigations, model liquids and commercial paints with an increasing complexity of the physical properties were chosen: Newtonian flow behavior without solvent evaporation, Newtonian flow behavior with solvent evaporation, viscoelastic paints with non-Newtonian flow behavior. Four variants are proposed regarding how thixotropy can be measured and how a mathematical model can be created. The advantages and disadvantages of the variants with regard to the implementation of thixotropy in the simulations are listed. A method to predict the leveling behavior of thixotropic paints with simultaneous recovery of the viscous and elastic properties from rheological measurements using discrete relaxation time spectra is presented.     

Non-linear diffusive flood routing

Summary A flood routing model based on a non-linear diffusion-convection equation is presented. Simplifying assumptions are made regarding the river geometry, and for the initial and boundary conditions. Solutions of the non-linear equation are discussed in terms of applicability and compared to solutions of the corresponding linearized equation. Stability aspects are investigated and two different numerical schemes are examined. Finally, results are compared to prototype observations, and the computation procedure is explained in detail.Notation A cross-sectional area - b constant river width - B variable river width - F Froude number - g gravitational acceleration - h flow depth - S _f frictional gradient - S ₀ bottom slope - K roughness coefficient - m cotangent of channel side-wall angle - p lateral inflow intensity - q discharge per unit width - q ₀ initial discharge per unit width - q ^* maximum discharge per unit width - Q non-dimensional discharge - Q ₀ non-dimensional initial discharge - Q ^* non-dimensional initial discharge surplus - Q _max non-dimensional maximum discharge - relative maximum discharge - dimensional discharge - r hydrograph shape parameter - R hydraulic radius - t time - T non-dimensional time - v average velocity - x longitudinal coordinate - X non-dimensional longitudinal coordinate - y relative flow depth - Y non-dimensional flow depth - diffusion coefficient With 11 Figures     

作为添加剂的颗粒状有机硅树脂在热塑性塑料中的应用

描述了一种以超高分子量(uhmw)的聚二甲基硅氧烷(PDMS)为基料的新型、多功能固体有机硅添加剂，着重描述了这些新型颗粒状有机硅树脂作为添加剂应用于热塑性塑料挤出。通过实例说明了颗粒状有机硅树脂能非常有效地改善热塑性塑料的加工性和流动性，尤其适用于充填的聚烯烃混合物。此外，它们能进一步提高冲击强度和抗张强度等机械性能，并且对于改善表面光滑性和抗磨损性也十分有效。     

Polyether-based thermoplastic polyurethanes. I. Effect of the hard-segment content

A series of Polyether-based thermoplastic polyurethanes, varying in hard-segment content between 20 and 80 wt. %, was prepared using an (oxypropylene-oxyethylene) diol of M _n = 2000 as the soft segment and 4,4′-diphenylmethane diisocyanate extended with 1,4-butanediol as the hard segment. Physical-mechanical, dynamic-mechanical, and specific heat (DSC) data are used to elucidate the mechanical and morphological behavior of these materials. The polyurethanes varied from soft elastomeric (continuous soft phase) to high-modulus plastic (continuous hard phase) and showed changes in their tensile properties at about 60% hard-segment content, possibly due to phase inversion.     

Remote Usability Evaluation: Overview and Case Studies

Traditional laboratory-based usability evaluations have many costs associated with them: financial costs, temporary loss in participant productivity, travel issues. For this reason, many human-computer interaction practitioners cannot conduct as many test iterations as they would like or may fail to secure representative samples, especially as user groups become more global. In recent years, we have begun to use less expensive remote evaluation techniques to complement traditional methods. This article describes some collaborative software that allows remote evaluations, along with the necessary hardware, to reproduce, as closely as possible, traditional evaluation techniques. It also describes the types of activities that lend themselves to this sort of approach and provides tips for conducting these sorts of sessions. Finally, this article provides data that suggest remote techniques are not only effective at improving interface designs, but also produce results comparable to traditional approaches for typical measures.     

Dynamic Template Tracking and Recognition

In this paper we address the problem of tracking non-rigid objects whose local appearance and motion changes as a function of time. This class of objects includes dynamic textures such as steam, fire, smoke, water, etc., as well as articulated objects such as humans performing various actions. We model the temporal evolution of the object’s appearance/motion using a linear dynamical system. We learn such models from sample videos and use them as dynamic templates for tracking objects in novel videos. We pose the problem of tracking a dynamic non-rigid object in the current frame as a maximum a-posteriori estimate of the location of the object and the latent state of the dynamical system, given the current image features and the best estimate of the state in the previous frame. The advantage of our approach is that we can specify a-priori the type of texture to be tracked in the scene by using previously trained models for the dynamics of these textures. Our framework naturally generalizes common tracking methods such as SSD and kernel-based tracking from static templates to dynamic templates. We test our algorithm on synthetic as well as real examples of dynamic textures and show that our simple dynamics-based trackers perform at par if not better than the state-of-the-art. Since our approach is general and applicable to any image feature, we also apply it to the problem of human action tracking and build action-specific optical flow trackers that perform better than the state-of-the-art when tracking a human performing a particular action. Finally, since our approach is generative, we can use a-priori trained trackers for different texture or action classes to simultaneously track and recognize the texture or action in the video.     

Blick hinter die Kulissen der Ausgleichsenergie — Technisch betrachtet

This paper describes the IT-system for the technical clearing of balancing energy based on the implemented balance group model. The model is adapted to the specific needs of the balancing energy clearing center for the control area of Austrian Power Grid (APG). The required tasks were realized with a complex IT-system. The system is fully web based and administrates the organization and data management of the different balance groups and their relationship among them. Based on this information it determines the balancing energy and the related fees for each individual balancing group.