On the total choosability of planar graphs and of sparse graphs

In the current paper, we prove the 11-total choosability of planar graphs with maximum degree Δ?8, the (Δ+1)-total choosability of 5-cycle-free planar graphs with maximum degree Δ?8, the 5-total choosability of graphs with maximum degree Δ=4 and maximum average degree mad<3, and the 4-total choosability of subcubic graphs with maximum average degree .     

Wooden Geometric Puzzles: Design and Hardness Proofs

We discuss some new geometric puzzles and the complexity of their extension to arbitrary sizes. For gate puzzles and two-layer puzzles we prove NP-completeness of solving them. Not only the solution of puzzles leads to interesting questions, but also puzzle design gives rise to interesting theoretical questions. This leads to the search for instances of partition that use only integers and are uniquely solvable. We show that instances of polynomial size exist with this property. This result also holds for partition into k subsets with the same sum: We construct instances of n integers with subset sum O(n ^k+1), for fixed k. Part of this research was done when the first author was visiting Utrecht University, and during the Dagstuhl Seminar No. 06481 on Geometric Networks and Metric Space Embeddings in 2006.     

Interaction with large ubiquitous displays using camera-equipped mobile phones

In the ubiquitous computing environment, people will interact with everyday objects (or computers embedded in them) in ways different from the usual and familiar desktop user interface. One such typical situation is interacting with applications through large displays such as televisions, mirror displays, and public kiosks. With these applications, the use of the usual keyboard and mouse input is not usually viable (for practical reasons). In this setting, the mobile phone has emerged as an excellent device for novel interaction. This article introduces user interaction techniques using a camera-equipped hand-held device such as a mobile phone or a PDA for large shared displays. In particular, we consider two specific but typical situations (1) sharing the display from a distance and (2) interacting with a touch screen display at a close distance. Using two basic computer vision techniques, motion flow and marker recognition, we show how a camera-equipped hand-held device can effectively be used to replace a mouse and share, select, and manipulate 2D and 3D objects, and navigate within the environment presented through the large display.     

Modular Neural Tile Architecture for Compact Embedded Hardware Spiking Neural Network

Biologically-inspired packet switched network on chip (NoC) based hardware spiking neural network (SNN) architectures have been proposed as an embedded computing platform for classification, estimation and control applications. Storage of large synaptic connectivity (SNN topology) information in SNNs require large distributed on-chip memory, which poses serious challenges for compact hardware implementation of such architectures. Based on the structured neural organisation observed in human brain, a modular neural networks (MNN) design strategy partitions complex application tasks into smaller subtasks executing on distinct neural network modules, and integrates intermediate outputs in higher level functions. This paper proposes a hardware modular neural tile (MNT) architecture that reduces the SNN topology memory requirement of NoC-based hardware SNNs by using a combination of fixed and configurable synaptic connections. The proposed MNT contains a 16:16 fully-connected feed-forward SNN structure and integrates in a mesh topology NoC communication infrastructure. The SNN topology memory requirement is 50 % of the monolithic NoC-based hardware SNN implementation. The paper also presents a lookup table based SNN topology memory allocation technique, which further increases the memory utilisation efficiency. Overall the area requirement of the architecture is reduced by an average of 66 % for practical SNN application topologies. The paper presents micro-architecture details of the proposed MNT and digital neuron circuit. The proposed architecture has been validated on a Xilinx Virtex-6 FPGA and synthesised using 65 nm low-power CMOS technology. The evolvable capability of the proposed MNT and its suitability for executing subtasks within a MNN execution architecture is demonstrated by successfully evolving benchmark SNN application tasks representing classification and non-linear control functions. The paper addresses hardware modular SNN design and implementation challenges and contributes to the development of a compact hardware modular SNN architecture suitable for embedded applications     

A rotated nonconforming rectangular mixed element for elasticity

We present a low-order nonconforming mixed element for plane elasticity on rectangular meshes. The 3-dimensional space of rigid body motions is used to approximate the displacement and a 16-dimensional space is used to discretize the space of symmetric tensors. This element may be viewed as the rectangular analogue of the nonconforming Arnold-Winther element and is related to a discrete version of the elasticity differential complex with a nonconforming H ² element related to the rotated Q ₁ element.      

Gift-wrapping based preimage computation algorithm

Based on a classical convex hull algorithm called gift-wrapping, the purpose of the paper is to provide a new algorithm for computing the vertices of a polytope called preimage—roughly the set of naive digital planes containing a finite subset S of Z³. The vertices of the upper hemisphere, the ones of the lower hemisphere and at last the equatorial vertices are computed independently. The principle of the algorithm is based on duality and especially on the fact that the vertices of the preimage correspond to faces of the input set S or of its chords set S?S∪{(0,0,1)}. It allows to go from one vertex to another by gift-wrapping until the whole region of interest has been explored.     

Tailoring Structure-Borne Sound through Bandgap Engineering in Phononic Crystals and Metamaterials: A Comprehensive Review

In solid state physics, a bandgap (BG) refers to a range of energies where no electronic states can exist. This concept was extended to classical waves, spawning the entire fields of photonic and phononic crystals where BGs are frequency (or wavelength) intervals where wave propagation is prohibited. For elastic waves, BGs are found in periodically alternating mechanical properties (i.e., stiffness and density). This gives birth to phononic crystals and later elastic metamaterials that have enabled unprecedented functionalities for a wide range of applications. Planar metamaterials are built for vibration shielding, while a myriad of works focus on integrating phononic crystals in microsystems for filtering, waveguiding, and dynamical strain energy confinement in optomechanical systems. Furthermore, the past decade has witnessed the rise of topological insulators, which leads to the creation of elastodynamic analogs of topological insulators for robust manipulation of mechanical waves. Meanwhile, additive manufacturing has enabled the realization of 3D architected elastic metamaterials, which extends their functionalities. This review aims to comprehensively delineate the rich physical background and the state-of-the art in elastic metamaterials and phononic crystals that possess engineered BGs for different functionalities and applications, and to provide a roadmap for future directions of these manmade materials.     

Electrical Systems for Automatic Handling and Electric Heating of Slabs

The availability of large quantities of electrical power and sophisticated means of control has justified the use of induction methods in heating large steel slabs to rolling mill temperatures. Capable of delivering 210 MW, a unique power system, comprising power transformers, autotransformers, static switches, and capacitor banks, provides eighteen induction heaters with controlled electrical energy. The entire system can deliver 600 ton/h of steel to the rolling mill. The basic overall automatic control scheme involves the operations of slab handling control, heater control, static power switching, and computer control. The control functions, including phase balance and demand limit control, are described and discussed. The features and operation of the static power switch, capable of switching close to 10 000 A, are presented. Used as a protective device, the switch can clear up to 210 000-A faults in less than one cycle.     

Modelling and experimental evaluation of reaction kinetics in reactive extraction for chiral separation of amines, amino acids and amino-alcohols

This paper reports on determination of the intrinsic reaction kinetics in reactive extraction of chiral compounds. It is important to know the mass transfer rates and reaction kinetics separately for a reliable scale-up. A kinetic model is developed to interpret the experimental data from the selected model reactor, the modified Lewis cell. The two-phase homogeneous reaction model was selected over the interfacial reaction model, because physical partitioning is considerable in all systems studied. It was shown by simulations and by theoretical considerations that conventional regime analysis fails for reactive extraction in a number of regimes, because the conditions of an irreversible reaction and a negligible resistance to mass transfer in the non-reactive phase are generally not fulfilled in reactive extraction. Furthermore, it follows from the simulations that enhancement of mass transfer by reaction may be partly invisible. Finally, it becomes clear that only the fraction of the species that is in the right ‘extractable’ form should be used in the calculations. As the conventional regime analysis cannot be applied to determine the reaction kinetics in the chiral systems, first the mass transfer rate was measured during physical extraction to determine the location of the main resistance to mass transfer. Then the enhancement of mass transfer was measured during reactive extraction. By model simulation, it was determined how much enhancement of mass transfer should be observable. In this way, it was concluded that the reaction kinetics of the azophenolic crown ether system are between fast and instantaneous, and the reaction kinetics of the Cu(II)-N-dodecyl-L-hydroxyproline system are between slow and fast. The Lewis cell is not the most suitable model contactor to determine reaction kinetics in reactive extraction systems.     

Transient relaxation of the normal state resistance of tin microstrips in the presence of current bias

The transient relaxation of the normal state resistance in tin microstrips has been measured. The microstrips were current-biased below their dc critical current and excited into the normal state with electro optically produced current pulses, with durations as short as 600 psec, by temporarily exceeding the critical current. The effective relaxation time was measured by directly observing the voltage across the microstrip during the normal-superconducting transient. A region was observed in which the relaxation time decreased with increasing current pulse height. The relaxation time was found to be independent of temperature over the range 0.95T/T _c 0.77.