Resistive behavior of high-Tc superconductors with a logarithmiclike pinning potential

The flux motion in a superconductor with a periodic logarithmiclike bare pinning potential is investigated. The effective barrier UJ(J) is derived and is shown to bear close resemblance with the related experimental results. The details of the pinning potential profile turn out to have significant influences on the functional form of the effective barrier. The linear response of the superconductor under a small current is analyzed and a slightly new formula is derived for resistivity in the thermally activated flux flow regimes. The distinct regimes for flux creep and flux flow and the crossover in between are treated simultaneously, and the familiar power-law behavior is demonstrated and is further confirmed by examining the dln E/dJ versus H relation. Satisfactory agreement is found between our results and related experimental observations. The experimentally observed field-dependent resistance broadening effect is also reproduced in this model. © 1994 The American Physical Society.published_or_final_versio

Spontaneous recovery of hydrogen-degraded TiO₂ ceramic capacitors

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

General study on piezoelectric transformer

Author name used in this publication: Cheng K. W. E.Author name used in this publication: Kwok K. W.Power Electronics Research Center, Department of Electrical EngineeringAuthor name used in this publication: Chan H.Refereed conference paper2004-2005 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Modeling and analysis of piezoelectric transformer using multi-mesh loop matrix circuit under square-wave excitation conditions

K. W. Kwok, X. X. Wang and H. Chan, Department of Applied PhysicsAuthor name used in this publication: K. W. E. ChengAuthor name used in this publication: S. L. HoAuthor name used in this publication: K. W. KwokAuthor name used in this publication: H. ChanAuthor name used in this publication: X. D. XueRefereed conference paper2005-2006 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Basal paravian functional anatomy illuminated by high-detail body outline

Body shape is a fundamental expression of organismal biology, but its quantitative reconstruction in fossil vertebrates is rare. Due to the absence of fossilized soft tissue evidence, the functional consequences of basal paravian body shape and its implications for the origins of avians and flight are not yet fully understood. Here we reconstruct the quantitative body outline of a fossil paravian Anchiornis based on high-definition images of soft tissues revealed by laser-stimulated fluorescence. This body outline confirms patagia-bearing arms, drumstick-shaped legs and a slender tail, features that were probably widespread among paravians. Finely preserved details also reveal similarities in propatagial and footpad form between basal paravians and modern birds, extending their record to the Late Jurassic. The body outline and soft tissue details suggest significant functional decoupling between the legs and tail in at least some basal paravians. The number of seemingly modern propatagial traits hint that feathering was a significant factor in how basal paravians utilized arm, leg and tail function for aerodynamic benefit.published_or_final_versio

Wideband Transmitarray Antenna Using Compact 2-Bit Filtering Unit Cells

A wideband transmitarray (TA) antenna using compact 2-bit filtering unit cells is presented with the center frequency designed at 10 GHz. The presented TA antenna features wide bandwidth with a compact aperture size, filtering radiation performance, and low cross-polarization levels. A novel compact 2-bit phasing scheme is first proposed and illustrated by utilizing the resonating characteristics of resonators. Charging and discharging principle of a resonator is utilized to realize a 180° phase shift, while J-invertor originating from the coupling between resonators is utilized to realize a 90° phase shift. Based on the proposed phasing scheme, novel 2-bit compact filtering unit cells are designed with a compact four-copper-layer configuration. Finally, a high-gain TA antenna was designed, fabricated, and measured for radiation performance verification. Owing to the elaborately designed unit cells and the cut-off effect of the feed horn, a filtering radiation performance with flat in-band gain and high out-of-band suppressions is obtained. Measured results show that a flat 3dB gain bandwidth of 21.3% is achieved with a thin thickness of 0.11λ 0 . High suppressions of 34.3 dB and 30.1 dB are measured over the lower and upper out-of-bands. In addition, a low cross-polarization level of -38.5 dB is obtained for high-quality wireless communications

Fashion sketch design by interactive genetic algorithms

Author name used in this publication: Mok, P.Y.Author name used in this publication: Kwok, Y.L.Refereed conference paper2012-2013 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Fashion sketch design by interactive genetic algorithms

Computer aided design is vitally important for the modern industry, particularly for the creative industry. Fashion industry faced intensive challenges to shorten the product development process. In this paper, a methodology is proposed for sketch design based on interactive genetic algorithms. The sketch design system consists of a sketch design model, a database and a multi-stage sketch design engine. First, a sketch design model is developed based on the knowledge of fashion design to describe fashion product characteristics by using parameters. Second, a database is built based on the proposed sketch design model to define general style elements. Third, a multi-stage sketch design engine is used to construct the design. Moreover, an interactive genetic algorithm (IGA) is used to accelerate the sketch design process. The experimental results have demonstrated that the proposed method is effective in helping laypersons achieve satisfied fashion design sketches.Institute of Textiles and ClothingAuthor name used in this publication: Mok, P.Y.Author name used in this publication: Kwok, Y.L.Refereed conference pape

Superior catalytic performance of phosphorus-modified molybdenum oxide clusters encapsulated inside SBA-15 in the partial oxidation of methane

Small phosphorus- modified molybdenum oxide clusters encapsulated inside the mesoporous channels of SBA-15 exhibit excellent catalytic performance for the partial oxidation of methane to formaldehyde with oxygen. A formaldehyde selectivity of 90% has been obtained at a single-pass methane conversion of 5.8%