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Sun Z.,South China University of Technology
Automatica | Year: 2012

In this work, we address the problem of robust switching design, which seeks a switching signal that makes the switched system exponentially stable and robust against switching perturbations. To properly capture the sensitivity of a switching signal undergoing various switching perturbations, we define the relative distance between state-feedback path-wise switching signals. We establish that any stabilizing state-feedback path-wise switching signal is robust with respect to switching perturbations. A lower bound of the robustness margin is explicitly presented. © 2011 Elsevier Ltd. All rights reserved.

Zhang L.-Z.,South China University of Technology
Journal of Heat Transfer | Year: 2011

Hollow fiber membrane contactors are used in air dehumidification. The benefit of this technology is that the liquid desiccant is not in a direct contact with the process air; therefore, the problem of liquid droplets crossover is prevented. The equations governing the heat and moisture transfer from the air to the liquid, through the membranes, are described. An analytical solution is obtained for the dimensionless differential equations, with which the dehumidification effectiveness could be estimated by simple algebraic calculations. It provides a convenient yet accurate tool for the component design and system optimization. The model is validated by experiments. The effects of varying operating conditions on system performance are investigated. It is found that the total number of transfer units for sensible heat and the overall Lewis number are the most dominant parameters influencing heat and mass transfer. © 2011 American Society of Mechanical Engineers.

Meier H.,University of Mainz | Cao D.,South China University of Technology
Chemical Society Reviews | Year: 2013

The dimerization of anthracene by a [4π + 4π] cycloaddition is one of the oldest and best known reactions in photochemistry. In the series of tethered bichromophoric arenes, this reaction type could be extended to anthracene-naphthalene, naphthalene-naphthalene and recently even to anthracene-benzene and naphthalene-benzene systems. Cyclophanes, which can be regarded as twofold or multiple tethered systems, are not discussed here. The cycloisomerizations are performed by irradiation at the long-wavelength absorption (λ > 270 nm), whereas shorter wavelengths (λ < 270 nm) lead to cycloreversions, which can be also achieved by a thermal route. The systems represent therefore a P- and T-type photochromism, which can be used for optical or chiroptical switches. An acceleration of the switch is possible by a singlet energy transfer (light harvesting antenna effect) in dendritic compounds. In the past 5 to 10 years many applications of these switches were studied in the context of photonic devices, sensor techniques, lithographic processes, imaging techniques, data processing and data storage.

Zhang H.,South China University of Technology
Applied Physics Letters | Year: 2011

In this letter, on the basis of Stoner-Wohlfarth model, the changes in magnetization of Tb0.3Dy0.7 Fe2 alloy have been calculated with a compressive stress along the [111] and [112] axes. The results have shown that the significant change in magnetization for Tb 0.3 Dy0.7 Fe2 alloy can be induced by the compressive stress. A feasible application of power generation floor which can convert the energy from the vibration created by a walking person on it into electric energy has been proposed, and its structure and performance also have been revealed. © 2011 American Institute of Physics.

Zhang L.-Z.,South China University of Technology
Energy Conversion and Management | Year: 2012

Energy consumption by air conditioning accounts for 1/3 of the total energy use by the whole society. Cooling and dehumidifying fresh ventilation air constitutes 20-40% of the total energy load for air conditioning in hot and humid regions. Heat and moisture recovery from ventilation air has become a hot topic for building energy conservation in these years. Of the various technologies for heat and moisture recovery, membrane-based total heat exchanger is a promising alternative. Over the past 10 years, much work has been conducted in South China University of Technology for the research on membrane-based heat and moisture recovery, from fundamentals to engineering applications. In this review, the progress of these researches is introduced. More specifically, some novel concepts are proposed for heat and moisture transfer analysis. Several novel membranes are designed to accomplish the goal. Some novel exchanger structures are constructed and the heat and mass transport phenomena is investigated. Novel prototypes are built for engineering applications. The results are that a sensible effectiveness of 0.8 and a latent effectiveness of 0.7 are obtained for a total heat exchanger with novel materials and new constructions. When the total heat exchanger is combined with a fresh air refrigeration dehumidification unit, the system COP is improved to 5.8. The membrane systems have been extended to other areas like air humidification, liquid desiccant air dehumidification, and fabrication of selective adsorbents. This review gives a summary of these works and also points out the future research directions. © 2012 Elsevier Ltd. All rights reserved.

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