Tunable microwave filter that uses a high-birefringent fiber and a differential-group-delay element

We propose and experimentally demonstrate a novel and simple photonic microwave notch filter that uses a high-birefringent fiber that gives a fixed differential group delay (DGD), together with a DGD element that gives a tunable DGD. This configuration overcomes the problems of optical coherence interference and chromatic dispersion, which may occur in schemes that use fiber delay lines or fiber gratings. Also presented is a theoretical analysis for the performance of the microwave filter that uses the present configuration. The present scheme provides a continuous tuning capability for changing the notch frequency. Measured notch rejection is greater than 40 dB. This scheme can operate over a wide wavelength range of the optical carrier. There is good agreement between experiment results and theoretical analysis.     

Outward-looking circular motion analysis of large image sequences

This work presents a novel and simple method of analyzing the motion of a large image sequence captured by a calibrated outward-looking video camera moving on a circular trajectory for large-scale environment applications. Previous circular motion algorithms mainly focus on inward-looking turntable-like setups. They are not suitable for outward-looking motion where the conic trajectory of corresponding points degenerates to straight lines. The circular motion of a calibrated camera essentially has only one unknown rotation angle for each frame. The motion recovery for the entire sequence computes only one fundamental matrix of a pair of frames to extract the angular motion of the pair using Laguerre's formula and then propagates the computation of the unknown rotation angles to the other frames by tracking one point over at least three frames. Finally, a maximum-likelihood estimation is developed for the optimization of the whole sequence. Extensive experiments demonstrate the validity of the method and the feasibility of the application in image-based rendering.     

Nonlinear soliton propagation by use of the split-step reconstruction technique

A split-step reconstruction technique is proposed to solve a nonlinear wave equation. A nonlinear wave equation can be segmented into a set of linear equations that can be solved in the time domain by use of the split-step reconstruction technique. With this technique, one can avoid the propagation errors that occur as a result of nonlinear wave equation splitting. We propose an adaptive mesh control to increase the speed with which nonlinear wave equations can be calculated.     

Pulse Shaping in Bandlimited Digital Satellite Systems

Recent work on proper design of signals in single carrier 4φ-PSK systems is summarized. The main conclusion is that it is possible to minimize the overall degradation due to nonlinearities and adjacent channel interference by careful choice of pulse shaping filters. We also show that the penalty, in terms of power, for not being careful can be high. An example is given showing effects of co-channel interference degradation as well as timing jitter degradation.     

A Geometric Analysis of Light Field Rendering

Recently, many image-based modeling and rendering techniques have been successfully designed to render photo-realistic images without the need for explicit 3D geometry. However, these techniques (e.g., light field rendering (Levoy, M. and Hanrahan, P., 1996. In SIGGRAPH 1996 Conference Proceedings, Annual Conference Series, Aug. 1996, pp. 31–42) and Lumigraph (Gortler, S.J., Grzeszczuk, R., Szeliski, R., and Cohen, M.F., 1996. In SIGGRAPH 1996 Conference Proceedings, Annual Conference Series, Aug. 1996, pp. 43–54)) may require a substantial number of images. In this paper, we adopt a geometric approach to investigate the minimum sampling problem for light field rendering, with and without geometry information of the scene. Our key observation is that anti-aliased light field rendering is equivalent to eliminating the double image artifacts caused by view interpolation.Specifically, we present a closed-form solution of the minimum sampling rate for light field rendering. The minimum sampling rate is determined by the resolution of the camera and the depth variation of the scene. This rate is ensured if the optimal constant depth for rendering is chosen as the harmonic mean of the maximum and minimum depths of the scene. Moreover, we construct the minimum sampling curve in the joint geometry and image space, with the consideration of depth discontinuity. The minimum sampling curve quantitatively indicates how reduced geometry information can be compensated by increasing the number of images, and vice versa. Experimental results demonstrate the effectiveness of our theoretical analysis.     

Logistic regression modelling of storm-induced shallow landsliding in time and space on natural terrain of Lantau Island,Hong Kong

This study is aimed at developing a method for modelling the probability of landsliding using a geographical information system (GIS), rainstorm events and associated landslide distributions, with an attempt to assess where landslides are likely to occur when certain rainstorm events happen. This research focuses on the natural terrain of Lantau Island, Hong Kong. In order to derive a logistic regression model for statistical prediction of the probability of landsliding, topographic attributes derived from digital elevation model (DEM) data are combined with a variety of other digital datasets including 24 h rainfall, lithology and vegetation cover in a GIS. The model was then applied to given rainstorm events and rainfalls of a variety of periods of return time in order to predict the probability of landsliding on natural slopes in space and time. The modelling techniques described here can be used to develop effective mitigation strategies.     

Robust generation of high‐quality unstructured meshes on realistic biomedical geometry

In this paper, we propose efficient and robust unstructured mesh generation methods based on computed tomography (CT) and magnetic resonance imaging (MRI) data, in order to obtain a patient‐specific geometry for high‐fidelity numerical simulations. Surface extraction from medical images is carried out mainly using open source libraries, including the Insight Segmentation and Registration Toolkit and the Visualization Toolkit, into the form of facet surface representation. To create high‐quality surface meshes, we propose two approaches. One is a direct advancing front method, and the other is a modified decimation method. The former emphasizes the controllability of local mesh density, and the latter enables semi‐automated mesh generation from low‐quality discrete surfaces. An advancing‐front‐based volume meshing method is employed. Our approaches are demonstrated with high‐fidelity tetrahedral meshes around medical geometries extracted from CT/MRI data. Copyright © 2005 John Wiley & Sons, Ltd.     

Photovoltaic deployment strategy in Japan and the USA—an institutional appraisal

Photovoltaic (PV) is a renewable energy technology, along side with other modular energy generation technologies such as micro-turbines, fuel cells, etc., which will enable the alternative distributed generation paradigm compared to the incumbent fossil fuel based centralized generation paradigm. Distributed generation utilizing renewable energy resources offers opportunities for significant carbon dioxide and emissions reductions thus contributing solutions to broader climate change issues.