Gas marbles: ultra-long-lasting and ultra-robust bubbles formed by particle stabilization

Bubbles and foams are ubiquitous in daily life and industrial processes. Studying their dynamic behaviors is of key importance for foam manufacturing processes in food packaging, cosmetics and pharmaceuticals. Bare bubbles are inherently fragile and transient; enhancing their robustness and shelf lives is an ongoing challenge. Their rupture can be attributed to liquid evaporation, thin film drainage and the nuclei of environmental dust. Inspired by particle-stabilized interfaces in Pickering emulsions, armored bubbles and liquid marble, bubbles are protected by an enclosed particle-entrapping liquid thin film, and the resultant soft object is termed gas marble. The gas marble exhibits mechanical strength orders of magnitude higher than that of soap bubbles when subjected to overpressure and underpressure, owing to the compact particle monolayer straddling the surface liquid film. By using a water-absorbent glycerol solution, the resulting gas marble can persist for 465 d in normal atmospheric settings. This particle-stabilizing approach not only has practical implications for foam manufacturing processes but also can inspire the new design and fabrication of functional biomaterials and biomedicines.     

A novel microstrip ring hybrid incorporating a PBG cell

An experimental investigation of a novel compact microstrip 180° ring hybrid incorporating a one-dimensional (1-D) slow-wave structure, in the form of perforations on the ring itself, is presented. The size of the hybrid is reduced by 23% due to the slow-wave effect, and this size reduction technique has potential applications in MICs and MMICs. The measured insertion loss is comparable to that of a conventional microstrip hybrid     

Closed form optimal solution of a tuned liquid column damper for suppressing harmonic vibration of structures

Building vibration has become one of the major concerns to structural engineers. Being a vibration absorber, a tuned liquid column damper (TLCD) not only suppresses building vibration, but also acts as the water storage facility of a building. In view of this, the application of such damper is particularly suited for building structures. However, due to inherent nonlinear liquid damping, it is no doubt that a great deal of computational effort is required to search the optimum parameters of TLCD numerically. Therefore, this paper aims to develop a closed form solution scheme of TLCD-structure systems and the optimum parameters of TLCD that lead to the maximum vibration reduction of building structure, so as to facilitate the design of dampers. The developed closed form solution of TLCD-structure system is verified by comparing results obtained from the conventional iterative method. After having a satisfactory verification, the existence of the invariant points of a TLCD-structure system for the case of undamped primary structure is demonstrated. Explicit design formulas of TLCD for the case of undamped primary structures are obtained by optimizing the response at the two invariant points. The optimum parameters of TLCD for the case of damped primary structures are also investigated numerically. An approach for determining the optimum head loss coefficient of TLCD is proposed. Finally, an example is given to illustrate the design procedures of TLCD for suppressing harmonic type vibrations     

ScholOnto: an ontology-based digital library server for research documents and discourse

The internet is rapidly becoming the first place for researchers to publish documents, but at present they receive little support in searching, tracking, analysing or debating concepts in a literature from scholarly perspectives. This paper describes the design rationale and implementation of ScholOnto, an ontology-based digital library server to support scholarly interpretation and discourse. It enables researchers to describe and debate via a semantic network the contributions a document makes, and its relationship to the literature. The paper discusses the computational services that an ontology-based server supports, alternative user interfaces to support interaction with a large semantic network, usability issues associated with knowledge formalisation, new work practices that could emerge, and related work. Published online: 22 September 2000     

Towards a local learning (innovation) model of solar photovoltaic deployment

It is by now familiar that in the deployment of solar photovoltaic (PV) systems, the cost dynamics of major system component like solar cell/module is subjected to experience curve effects driven by production learning and research and development at the supplier side. What is less clear, however, is the economics of system integration or system deployment that takes place locally close to the user, involving other market players, in the downstream solar PV value chain. Experts have agreed that suppliers of solar PV system must customize their flexible characteristics to address local unique users’ and applications requirements and compete on price/performance basis. A lack of understanding of the drivers of the economics of system customization therefore is a deficiency in our understanding of the overall economics of this renewable energy technology option.     

Propagation of short pulses in an active nonlinear two-core optical fiber

The switching dynamics of short pulses in an active nonlinear two-core fiber coupler is investigated theoretically. The analysis takes into account the effects of coupling-coefficient dispersion, gain bandwidth, and gain saturation. In particular, we demonstrate that the pulse breakup effect due to coupling-coefficient dispersion can be suppressed by limiting the bandwidth of the linear gain, whether gain saturation is considered or not.     

Bandwidth-efficient WDM channel allocation for four-wave mixing-effect minimization

A novel channel-allocation method that allows reduction of the four-wave mixing (FWM) effect while maintaining bandwidth efficiency is presented. It is composed of a fractional bandwidth-allocation algorithm, taking into consideration the use of parameters with distinct differences. This proposed technique allows the computation of an optimal channel-allocation set, where degradation caused by interchannel interference and FWM is minimal. Simulation is carried out to show significant performance improvement, such as an average bit-error rate improvement factor of 1.336 for an eight-channel wavelength-division multiplexing system, without the requirement of increased bandwidth, unlike existing channel-allocation methods.     

Honeycomb photonic bandgap fiber with a modified core design

Air-silica honeycomb fiber with a modified core design is introduced. The core has a concentrated high-index region. Such core design helps defect core mode stay in the cladding's photonic bandgap for a longer wavelength range (>1000 nm) as compared to conventional design. We further point out the importance of our core design in reducing the number of defect modes supported by the fiber structure.     

NOLM-NALM fiber ring laser

We study the bidirectional lightwave propagations in an erbium-doped fiber ring laser and an inverted-S fiber ring laser, and observe their optical bistability behaviors. We develop a model for the inverted-S fiber ring laser using nonlinear optical loop mirror and nonlinear amplifying loop mirror (NOLM-NALM) principle, which operates in the nonlinear region. Good agreements between the laser experimental performance and the developed model are achieved. The laser shows good switching and pulse compression capabilities. In addition, the laser model illustrates the route to chaotic operation via period doubling bifurcation, when the input power increases. We also obtain quasi-periodic operation when the laser is amplitude modulated experimentally.     

Analysis of linearly tapered fiber Bragg grating for dispersion slope compensation

We demonstrate that linearly tapered fiber Bragg gratings (FBGs) display nonlinear group delay under strain or stress. The nonlinear group delay of the tapered FBG is analyzed theoretically. Experimental results show a good agreement with the analysis. We are the first to find that linearly tapered FBGs can be used in dispersion slope compensation.