Intergroup helping as status relations: Effects of status stability, identification, and type of help on receptivity to high-status group's help.

Integrating research on social identity processes and helping relations, the authors proposed that low-status group members who are high identifiers will be unwilling to receive help from the high-status group when status relations are perceived as unstable and help is dependency-oriented. The first experiment, a minimal group experiment, found negative reactions to help from a high-status outgroup when status relations were unstable. The 2nd and 3rd experiments, which used real groups of Israeli Arabs and Israeli Jews, replicated this finding and showed that high identifiers were less receptive to help from the high-status outgroup than low identifiers. The 4th experiment, a help-seeking experiment with real groups of competing high schools, found that the least amount of help was sought from a high-status group by high identifiers when status relations were perceived as unstable and help was dependency-oriented. Theoretical and applied implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Order Reduction Is Invalid for Singularly Perturbed Control Problems with a Vector Fast Variable

The order reduction method for singularly perturbed optimal control systems consists of employing the system obtained while setting the small parameter to zero. In many situations the differential-algebraic system thus obtained indeed provides an appropriate approximation to the singularly perturbed optimal control problem under consideration. In this paper we show, however, that the set of singularly perturbed optimal control systems for which the order reduction approach is invalid is dense (in the L ^∞ norm) in the class of systems which we consider. This is established under the assumption that the fast variable in the singularly perturbed system is not a scalar. Date received: June 8, 2001. Date revised: December 30, 2001.     

Flow around a cubic body immersed in a turbulent boundary layer

This paper reports the results of an experiment concerning flow in the vicinity of a cubic body immersed in a turbulent boundary layer which is fully developed along a tunnel floor. By changing the flow direction and body height, measurements were made of the pressure and drag acting on the body, and of the flow pattern and pressure distribution on the floor. The results indicate the changes taking place in the pressure distribution over the surface of a cubic body, the pressure drag acting on it, and the flow pattern and pressure distribution over the floor surface as the angle of incidence α is varied.     

Lattice-based flow field modeling

We present an approach for simulating the natural dynamics that emerge from the interaction between a flow field and immersed objects. We model the flow field using the lattice Boltzmann model (LBM) with boundary conditions appropriate for moving objects and accelerate the computation on commodity graphics hardware (GPU) to achieve real-time performance. The boundary conditions mediate the exchange of momentum between the flow field and the moving objects resulting in forces exerted by the flow on the objects as well as the back-coupling on the flow. We demonstrate our approach using soap bubbles and a feather. The soap bubbles illustrate Fresnel reflection, reveal the dynamics of the unseen flow field in which they travel, and display spherical harmonics in their undulations. Our simulation allows the user to directly interact with the flow field to influence the dynamics in real time. The free feather flutters and gyrates in response to lift and drag forces created by its motion relative to the flow. Vortices are created as the free feather falls in an otherwise quiescent flow.     

Footprint area sampled texturing

We study texture projection based on a four region subdivision: magnification, minification, and two mixed regions. We propose improved versions of existing techniques by providing exact filtering methods which reduce both aliasing and overblurring, especially in the mixed regions. We further present a novel texture mapping algorithm called FAST (footprint area sampled texturing), which not only delivers high quality, but also is efficient. By utilizing coherence between neighboring pixels, performing prefiltering, and applying an area sampling scheme, we guarantee a minimum number of samples sufficient for effective antialiasing. Unlike existing methods (e.g., MlP-map, Feline), our method adapts the sampling rate in each chosen MlP-map level separately to avoid undersampling in the lower level l for effective antialiasing and to avoid oversampling in the higher level l+1 for efficiency. Our method has been shown to deliver superior image quality to Feline and other methods while retaining the same efficiency. We also provide implementation trade offs to apply a variable degree of accuracy versus speed.     

Interactive wireless virtual colonoscopy

We present an interactive virtual colon navigation system on a PDA that is a client-server system over a wireless network. For improving the quality of the rendering results on the PDA, the overall rendering speed, and the user interactivity, we propose three novel methods and adapt a GPU-based direct volume rendering technique. Using these proposed methods, our system can support approximately a two times faster navigation speed and 17 percent better PSNR than previous remote visualization methods with a 512×512×361 volumetric colon CT data using a PDA device over 802.11b wireless network.     

Principles of 2-sliding mode design

Second-order sliding modes are used to keep exactly a constraint of the second relative degree or just to avoid chattering, i.e. in the cases when the standard (first order) sliding mode implementation might be involved or impossible. Design of a number of new 2-sliding controllers is demonstrated by means of the proposed homogeneity-based approach. A recently developed robust exact differentiator being applied, robust output-feedback controllers with finite-time convergence are produced, capable to control any general uncertain single-input-single-output process with relative degree 2. An effective simple procedure is developed to attenuate the 1-sliding mode chattering. Simulation of new controllers is presented.     

A robust optimisation model and cutting planes for the planning of energy-efficient wireless networks

In this paper, we present an optimisation model for the energy-efficient planning of future wireless networks. By applying robust optimisation, we extend this model to a robust formulation which considers demand uncertainties. The computability of the resulting model is moderate. Hence, we apply three different cutting plane approaches for an improvement. Furthermore, an extensive case study is performed to examine the price of robustness, to compare the robust solution to conventional planning, and to explore the performance of the cutting planes.