Evaluating the limitations of and alternatives in beaconing

In position-based routing protocols, each node periodically transmits a short hello message (called beacon) to announce its presence and position. Receiving nodes list all known neighbor nodes with their position in the neighbor table and remove entries after they have failed to receive a beacon for a certain time from the corresponding node. In highly dynamic networks, the information stored in the neighbor table is often outdated and does no longer reflect the actual topology of the network causing retransmissions and rerouting that consume bandwidth and increase latency. An analysis on the possible impact of beacons due outdated and inaccurate neighbor tables is needed. We quantify by analytical and simulation means the possible performance loss and explore the limitations of position-based routing protocols which use beaconing. In highly mobile ad-hoc networks, the delay can increase by a factor of 20. The neighbor table inaccuracy is the main source of packet loss in uncongested networks. We propose and evaluate several concrete mechanisms to improve the accuracy of neighborhood information, e.g., by dynamic adaptation of the timer values when beacons are broadcasted, and show their effectiveness by extensive simulation.     

Modelling and validation of granulation with heterogeneous binder dispersion and chemical reaction

In this paper a multidimensional model for binder granulation is presented. The particles undergo different transformations such as coalescence, compaction, and breakage. Further chemical reaction in the granules is taken into account in order to incorporate binder solidification which is observed to be a significant transformation in many industrial applications. The equations of the model framework are solved numerically with a direct simulation Monte Carlo (DSMC) algorithm. In addition to the comparison between experiment and simulation, the model framework also enables the study of critical parameters in binder granulation such as reaction rate (solidification of binder) and size of the added binder droplets, which demonstrates its promising potential.     

Coordinate transformations in object recognition.

A basic problem of visual perception is how human beings recognize objects after spatial transformations. Three central classes of findings have to be accounted for: (a) Recognition performance varies systematically with orientation, size, and position; (b) recognition latencies are sequentially additive, suggesting analogue transformation processes; and (c) orientation and size congruency effects indicate that recognition involves the adjustment of a reference frame. All 3 classes of findings can be explained by a transformational framework of recognition: Recognition is achieved by an analogue transformation of a perceptual coordinate system that aligns memory and input representations. Coordinate transformations can be implemented neurocomputationally by gain (amplitude) modulation and may be regarded as a general processing principle of the visual cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

气泡城市

Spacebuster是个动态的充气结构，它是便携式、可拓展的场馆。设计旨在将各种公共空间转变为可以进行社交集会的场所。事实上，Spacebuster是Raumlabo健筑设计事务所对上一个项目Kuechenmonumenl的迭代创新，它使得曼哈顿和布鲁克林的春天大放异彩，承办了很多各种社交和公众活动。     

Nano- and micromechanical properties of hierarchical biological materials and tissues

The mechanical properties of biological materials have been the focal point of extensive studies over the past decades, leading to formation of a new research field that intimately connects biology, chemistry and materials science. Significant advances have been made in many disciplines and research areas, ranging throughout a variety of material scales, from atomistic, molecular up to continuum scales. Experimental studies are now carried out with molecular precision, including investigations of how molecular defects such as protein mutations or protein knockout influence larger length- and time-scales. Simulation studies of biological materials now range from electronic structure calculations of DNA, molecular simulations of proteins and biomolecules like actin and tubulin to continuum theories of bone and collagenous tissues. The integration of predictive numerical studies with experimental methods represents a new frontier in materials research. The field is at a turning point when major breakthroughs in the understanding, synthesis, control and analysis of complex biological systems emerge. Here we provide a brief perspective of the state of this field and outline new research directions.     

Contact Behavior of Microcrystalline Cellulose Pellets Depending on their Water Content

Microcrystalline cellulose pellets for oral drug delivery are often produced by a combined wet extrusion-spheronization process. During the entire process, the cylindrical as well as the spherical pellets are exposed to various stresses resulting in a change of their shape and size due to plastic deformation and breakage. In this work, the effect of moisture content of pellets on their mechanical behavior is studied. In static compression tests, the strong influence of water content on deformation behavior of pellets is confirmed. Moreover, impact tests are performed using a setup consisting of three high-speed cameras to record pellet-wall collisions. Material properties, such as stiffness, restitution coefficient, breakage force, and displacement, were analyzed depending on the water content.     

Processing of the Multifunctional Polymer Poly(phenylene methylene) into Fibers,Films, Foams,and Microspheres

Poly(phenylene methylene) (PPM) has recently emerged as a promising multifunctional polymer, requiring straightforward one‐step synthesis to achieve high molar mass and featuring a range of attractive properties. Its processability, however, has not been explored in detail to date. Therefore, this study presents a comprehensive investigation of the processability of PPM into a wide range of forms by employing various polymer processing techniques. Thin fibers (diameter ≈100 µm) over 1 km in length and shorter thick fibers (diameter ≈1 mm) are produced by melt spinning. Although no crystallinity is observed, the fibers surprisingly exhibit pronounced birefringence. The capability for waveguiding red light within the fibers is also demonstrated. Furthermore, films with a broad thickness range, spanning nanometer to millimeter length scales, are fabricated using different approaches such as spin‐coating, hot pressing, and die casting. All films feature a very smooth and crack‐free surface topography. Additionally, freestanding foams of PPM are obtained by foaming highly concentrated solutions, and quasi‐monodisperse microspheres are prepared by a microfluidic high‐throughput emulsification. The material properties of these different specimen forms are investigated and discussed for implementation as products ranging from plastic optical fibers and light emitting diodes, to protective coatings and packaging, as well as insulators and separation membranes.