COLLABORATION IN THE SEMANTIC GRID: A BASIS FOR e-LEARNING

The CoAKTinG project aims to advance the state of the art in collaborative mediated spaces for the Semantic Grid. This paper presents an overview of the hypertext and knowledge-based tools that have been deployed to augment exiting collaborative environments, and the ontology that is used to exchange structure, promote enhanced process tracking, and aid navigation of resources before, after, and during a collaboration. While the primary focus of the project has been supporting e-Science, this paper also explores the similarities and application of CoAKTinG technologies as part of a human-centered design approach to e-Learning.     

Vector quantisation codebook initialisation for discrete multiwavelet transform

A novel vector quantisation codebook initialisation method called vector component difference is proposed for image coding using the discrete multiwavelet transform. Simulation results show that it is superior to the currently available methods when using with the Linde-Buzo-Gray codebook generation algorithm.     

Generalized Discrete Multiwavelet Transform With Embedded Orthogonal Symmetric Prefilter Bank

Prefilters are generally applied to the discrete multiwavelet transform (DMWT) for processing scalar signals. To fully utilize the benefit offered by DMWT, it is important to have the prefilter designed appropriately so as to preserve the important properties of multiwavelets. To this end, we have recently shown that it is possible to have the prefilter designed to be maximally decimated, yet preserve the linear phase and orthogonal properties as well as the approximation power of multiwavelets. However, such design requires the point of symmetry of each channel of the prefilter to match with the scaling functions of the target multiwavelet system. It can be very difficult to find a compatible filter bank structure; and in some cases, such filter structure simply does not exist, e.g., for multiwavelets of multiplicity 2. In this paper, we suggest a new DMWT structure in which the prefilter is combined with the first stage of DMWT. The advantage of the new structure is twofold. First, since the prefiltering stage is embedded into DMWT, the computational complexity can be greatly reduced. Experimental results show that an over 20% saving in arithmetic operations can be achieved comparing with the traditional DMWT realizations. Second, the new structure provides additional design freedom that allows the resulting prefilters to be maximally decimated, orthogonal and symmetric even for multiwavelets of low multiplicity. We evaluated the new DMWT structure in terms of computational complexity, energy compaction ratio as well as the compression performance when applying to a VQ based image coding system. Satisfactory results are obtained in all cases comparing with the traditional approaches.     

Dual Orthogonal Polarization States in an Active Mode-Locked Birefringent Fiber Ring Laser

We report the generation of dual amplitude pulses in an active mode-locked fiber laser within a birefringent cavity. Different to normal mode-locked pulses with identical amplitude and polarization state, and pulses polarized on both x- and y-axes simultaneously exist in the output pulse train. The two orthogonal pulse sequences have different amplitudes and lase at different wavelengths. Dual wavelengths are the result of red shift and blue shift of the x- and y-polarization states of the generated pulses, respectively, due to the detuning phenomena. Locking to individual x- or y-polarized pulse is also obtained by adjusting polarization controllers     

Phase-plane analysis of rational harmonic mode-locking in an erbium-doped fiber ring laser

We investigate the system performance of rational harmonic mode-locking in an erbium-doped fiber ring laser using the phase-plane technique of the nonlinear control engineering. Contributions from harmonic distortion, a Gaussian-like modulating signal, and its duty cycle to the system behavior are studied. We also demonstrate 660/spl times/ and 1230/spl times/ repetition rate multiplications on a 100-MHz pulse train generated from an active harmonically mode-locked fiber ring laser, and we hence achieve 66- and 123-GHz pulse operations by using the above-mentioned technique. It has been found out that the maximum obtainable rational harmonic order is limited by the harmonic distortion of the system as well as the pulse width of the generated signal, which in turn is determined by the duty cycle of the modulating signal. Furthermore, the rational harmonic order increases the complexity of the pulse formation process and hence challenges its stability.     

Dynamic control and coupling of a free-flying space robot system

In this article we discuss the problem of dynamic coupling and control of a space robot with a free-flying base, which could be a spacecraft, space station, or satellite. We formulate the dynamics of the system systematically and demonstrate nonlinearity of parameterization of the dynamics structure. We study the dynamic coupling of the robot and base system, and propose a concept, i.e., coupling factor, to illustrate the motion and force dependencies. Based on the coupling factor, we define a measure to characterize the degree of the dynamic coupling. The measure can be considered as a performance index in planning robot motion, or in evaluating robot trajectory for minimizing base motion, or in optimizing the robot configuration design and selecting the robot base location. Based on the dynamics analysis, we propose control schemes for position regulation and trajectory tracking problems. The regulation controller is simple to implement and will be useful in regular material transporting tasks. The tracking controller uses a dynamic model and provides more accurate and faster motion, and will be feasible for tracking moving objects or structural inspection tasks. A simulation study is shown at the end of the article. © 1994 John Wiley & Sons, Inc.     

All-Fiber ${Q}$-Switched Ring Laser With Increased Repetition Rate

We demonstrate a novel approach to increase the Q-switching repetition rate of the fiber ring laser. This Q-switched fiber laser integrates an apodized fiber-Bragg-grating (FBG) reflector and a Fabry-Perot (FP) etalon constructed from cascaded chirped FBGs into the cavity. The apodized FBG reflector acts as wavelength discriminative component for oscillation, while the FP etalon is tuned periodically using the piezoelectric transducer (PZT) and functions as a Q-switching component. By adjusting the tuning range of the FP etalon, we obtain 3.5-, 7-, and 14-kHz Q-switched pulses train with constant PZT modulation frequency of 3.5 kHz.     

Relationship between altered axial curvature and neural tube closure in normal and mutant (curly tail) mouse embryos

In isolated smooth muscles of the rat stomach, the properties of electrical responses of the membrane elicited by transmural nerve stimulation were studied. The smooth muscle membranes were quiescent in the fundus and spontaneously active with slow waves and often action potentials superimposed on top of the slow wave in the antrum and pylorus. The maximum membrane potentials were larger in the antrum (-50 to -55 mV) than in the fundus (-40 to -45 mV). Transmural nerve stimulation elicited an excitatory junction potential (e.j.p.) which was followed by an inhibitory junction potential (i.j.p.) in the fundus, and an i.j.p. alone in the antrum. The e.j.p. was inhibited by atropine, indicating that this potential was cholinergic in nature. The amplitude of the e.j.p. was increased by apamin or nitroarginine, and the latter was more potent than the former. The i.j.p. was inhibited by apamin or nitroarginine, and was resistant to adrenergic and cholinergic blocking agents, and therefore this potential was non-adrenergic non-cholinergic (NANC) in nature. The inhibitory actions of nitroarginine on the i.j.p. were antagonized by L-arginine, suggesting the involvement of nitric oxide (NO) in this junctional transmission. The results indicate that smooth muscles of the rat stomach receive cholinergic excitatory and NANC inhibitory nerves, and that endogenous NO may either be partly responsible for the generation of the i.j.p. or may modulate the junctional transmissions.     

Decorating surfaces with bidirectional texture functions

We present a system for decorating arbitrary surfaces with bidirectional texture functions (BTF). Our system generates BTFs in two steps. First, we automatically synthesize a BTF over the target surface from a given BTF sample. Then, we let the user interactively paint BTF patches onto the surface such that the painted patches seamlessly integrate with the background patterns. Our system is based on a patch-based texture synthesis approach known as quilting. We present a graphcut algorithm for BTF synthesis on surfaces and the algorithm works well for a wide variety of BTF samples, including those which present problems for existing algorithms. We also describe a graphcut texture painting algorithm for creating new surface imperfections (e.g., dirt, cracks, scratches) from existing imperfections found in input BTF samples. Using these algorithms, we can decorate surfaces with real-world textures that have spatially-variant reflectance, fine-scale geometry details, and surfaces imperfections. A particularly attractive feature of BTF painting is that it allows us to capture imperfections of real materials and paint them onto geometry models. We demonstrate the effectiveness of our system with examples.