3D model alignment based on minimum projection area

3D model alignment is an important step for applications such as 3D model retrieval and 3D model recognition. In this paper, we propose a novel Minimum Projection Area-based (MPA) alignment method for pose normalization. Our method finds three principal axes to align a model: the first principal axis gives the minimum projection area when we perform an orthographic projection of the model in the direction parallel to this axis, the second axis is perpendicular to the first axis and gives the minimum projection area, and the third axis is the cross product of the first two axes. We devise an optimization method based on Particle Swarm Optimization to efficiently find the axis with minimum projection area. For application in retrieval, we further perform axis ordering and orientation in order to align similar models in similar poses. We have tested MPA on several standard databases which include rigid/non-rigid and open/watertight models. Experimental results demonstrate that MPA has a good performance in finding alignment axes which are parallel to the ideal canonical coordinate frame of models and aligning similar models in similar poses under different conditions such as model variations, noise, and initial poses. In addition, it achieves a better 3D model retrieval performance than several commonly used approaches such as CPCA, NPCA, and PCA.     

Prediction of noisy chaotic time series using an optimal radialbasis function neural network

This paper considers the problem of optimum prediction of noisy chaotic time series using a basis function neural network, in particular, the radial basis function (RBF) network. In the noiseless environment, predicting a chaotic time series is equivalent to approximating a nonlinear function. The optimal generalization is achieved when the number of hidden units of a RBF predictor approaches infinity. When noise exists, it is shown that an optimal RBF predictor should use a finite number of hidden units. To determine the structure of an optimal RBF predictor, we propose a new technique called the cross-validated subspace method to estimate the optimum number of hidden units. While the subspace technique is used to identify a suitable number of hidden units by detecting the dimension of the subspace spanned by the signal eigenvectors, the cross validation method is applied to prevent the problem of overfitting. The effectiveness of this new method is evaluated using simulated noisy chaotic time series as well as real-life oceanic radar signals. Results show that the proposed method can find the correct number of hidden units of an RBF network for an optimal prediction.     

NodeTrix: a hybrid visualization of social networks

The need to visualize large social networks is growing as hardware capabilities make analyzing large networks feasible and many new data sets become available. Unfortunately, the visualizations in existing systems do not satisfactorily resolve the basic dilemma of being readable both for the global structure of the network and also for detailed analysis of local communities. To address this problem, we present NodeTrix, a hybrid representation for networks that combines the advantages of two traditional representations: node-link diagrams are used to show the global structure of a network, while arbitrary portions of the network can be shown as adjacency matrices to better support the analysis of communities. A key contribution is a set of interaction techniques. These allow analysts to create a NodeTrix visualization by dragging selections to and from node-link and matrix forms, and to flexibly manipulate the NodeTrix representation to explore the dataset and create meaningful summary visualizations of their findings. Finally, we present a case study applying NodeTrix to the analysis of the InfoVis 2004 coauthorship dataset to illustrate the capabilities of NodeTrix as both an exploration tool and an effective means of communicating results.     

Internationale Zusammenarbeit zum Nachweis bestrahlter Lebensmittel

Zusammenfassung Es wird eine Übersicht über die neuesten internationalen Entwicklungen, insbesondere die Programme von ADMIT (FAO/IAEA) und dem BCR (Europäische Gemeinschaft) zum Nachweis einer erfolgten Bestrahlung von Lebensmitteln gegeben. Eine Kontrolle bestrahlter Lebensmittel direkt am Produkt ist wünschenswert, um Kennzeichnung und eventuell bestehende Verbote zu überwachen, aber auch um das Vertrauen des Verbrauchers in eine korrekte Anwendung des Verfahrens zu stärken und sein Recht auf freie Wahl zwischen bestrahlten und unbestrahlten Lebensmitteln zu schützen. Auf internationaler Ebene haben bereits mehrere größere Ringversuche stattgefunden, z. B. Messung der Elektronen-Spin-Resonanz in Knochen von Geflügel, Schwein, Rind, Froschschenkeln und Fisch; Messung der Thermoluminescenz von unlöslichen Mineralien, isoliert aus Gewürzen und Kräutern; die gaschroma- tographische Analyse von Kohlenwasserstoffen und Alkylcyclobutanonen aus der Lipidfraktion von Hähnchen; und die mikrobiologische DEFT/APC-Analyse von Gewürzen. Diese Methoden sollen in naher Zukunft als internationale Standardmethoden etabliert werden.

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International co-operation in the field of detection of irradiated food

A survey over recent international developments to detect the irradiation treatment of foods is given, in particular the programmes of ADMIT (FAO/ IAEA) and of BCR (European Community). The need to detect radiation treatment by analysing the food itself is desirable to check compliance with existing regulations, such as the enforcement of labelling and control of prohibition, to enhance consumer confidence in the correct application of radiation processing, and to protect consumers' freedom of choice between irradiated or unirra-diated food products. Some larger collaborative studies on an international scale have already taken place, e.g. ESR measurements of bones from chicken, pork, beef, frog legs and fish, thermoluminescence of insoluble minerals isolated from herbs and spices, gas Chromatographic analysis of hydrocarbons and alkylcyclobutanones derived from the lipid fraction of chicken and the microbiological DEFT/APC procedure for spices. These methods could soon be implemented in international standard protocols.

     

Impulse approximation in solid helium

The incoherent dynamic form factorS _i(Q, ) is evaluated in solid helium for comparison with the impulse approximation (IA). The purpose is to determine theQ values for which the IA is valid for systems such as helium where the atoms interact via a potential having a steeply repulsive but not infinite hard core. For³He,S _i(Q, ) is evaluated from first principles, beginning with the pair potential. The density of statesg() is evaluated using the self-consistent phonon theory andS _i(Q, ) is expressed in terms ofg(). For solid⁴He reasonable models ofg() using observed input parameters are used to evaluateS _i(Q, ). In both casesS _i(Q, ) is found to approach the impulse approximationS _IA(Q, ) closely for wave vector transfersQ20 Å^–1. The difference betweenS _i andS _IA, which is due to final state interactions of the scattering atom with the remainder of the atoms in the solid, is also predominantly antisymmetric in (–_R), where _R is the recoil frequency. This suggests that the symmetrization procedure proposed by Sears to eliminate final state contributions should work well in solid helium.     

Observations of shadow bands at the total solar eclipse of 16 February 1980

Photoelectric observations of short term light variations (shadow bands) at the 16 Feb. 1980 total solar eclipse have been made using a set of spatially separated PIN diodes. Light variations in a bandpass of 1-500 Hz were detected during the half-minutes preceding and following the total phase. Fourier analysis of the noise spectrum of the variations reveals a sharp drop-off for frequencies above 50 Hz and an overall spectrum quite similar to previously reported power spectra of stellar scintillation. This is consistent with an atmospheric origin for the shadow bands. Cross-correlations between the detector outputs are low, suggesting a short persistence time for the turbulent elements causing the patterns.     

Chemical vapour deposition of chromium onto nickel

The chemical vapour deposition (CVD) of chromium onto a pure nickel substrate was investigated in the presence of hydrogen at three temperatures (950, 1000 and 1050°C) using a pack cementation method.Of the thermochemical reactions generally involved in CVD, such as thermal decomposition, reduction, displacement and disproportionation, the only significant reaction which occurs for this system is a reduction of CrCl₂ by hydrogen according to

$\text{CrCl}{}_2\text{(g)+H}{}_2\text{(g)→Cr(s)+2HCl(g)}$

Two diffusion layers appear during the process. (1) In the early stages of deposition a nickel-rich layer with a face-centred cubic structure develops. (2) Depending on the time and the temperature of the coating, an outer chromium-rich layer with a body-centred cubic structure develops progressively on the sample surface and grows from or together with the inner layer.The deposition rate is controlled by diffusion of the chromium and the nickel atoms through the coating layers, mainly through the inner layer.     

Drawing of optical fiber with internal codrawn wire and conductive coating and electrooptic modulation demonstration

One hundred twenty meters of fiber with an internal codrawn wire and electrically conductive coating was successfully fabricated for the first time. The integration of the conductive coating and wire was all performed during the fiber draw stage, in a process that enabled arbitrarily long lengths of fiber to be made. The wire combined with the conductive coating enables a strong electric field to be formed across the optical core. Such a fiber is ideal for thermally poling long lengths and for nonlinear device applications such as optical switches and modulators.