31,291 research outputs found
Processing of figure and background motion in the visual system of the fly
Get PDFReichardt W, Egelhaaf M, Guo A-K. Processing of figure and background motion in the visual system of the fly. Biological Cybernetics. 1989;61(5):327-345
Burst-by-burst Adaptive Joint-Detection CDMA/H.26L Based Wireless Video Telephony using TTCM and LDPC Codes
No full textA low bit-rate video coding techniques using the H.26L standard codec for robust transmission in mobile multimedia environments are presented. For the sake of achieving error resilience, the source codec has to make provisions for error detection, resynchronization and error concealment. Thus a packetization technique invoking adaptive bit-rate control was used in conjunction with the various modulation scheme employed. In this contribution, we propose a Burst-by-Burst Adaptive Coded Modulation-Aided Joint Detection-Based CDMA (ACM-JD-CDMA) scheme for wireless video telephony and characterise its performance when communicating over the UTRA wideband vehicular fading channels. The coded modulation schemes invoked in our fixed modulation mode based systems are Low Density Parity Check code based Block Coded Modulation (LDPC-BCM) and Turbo Trellis Coded Modulation (TTCM). The performance of LDPC-BCM was evaluated and compared to that of TTCM in the context of the ACM-JD-CDMA system using a practical modem mode switching regime. Both schemes exhibited a similar transmission integrity, although the LDPC arrangement is capable of achieving this at a lower complexity
PtTe2-Based Type-II Dirac Semimetal and Its van der Waals Heterostructure for Sensitive Room Temperature Terahertz Photodetection
No full textRecent years have witnessed rapid progresses made in the photoelectric performance of two-dimensional materials represented by graphene, black phosphorus, and transition metal dichalcogenides. Despite significant efforts, a photodetection technique capable for longer wavelength, higher working temperature as well as fast responsivity, is still facing huge challenges due to a lack of best among bandgap, dark current, and absorption ability. Exploring topological materials with nontrivial band transport leads to peculiar properties of quantized phenomena such as chiral anomaly, and magnetic-optical effect, which enables a novel feasibility for an advanced optoelectronic device working at longer wavelength. In this work, the direct generation of photocurrent at low energy terahertz (THz) band at room temperature is implemented in a planar metal–PtTe2–metal structure. The results show that the THz photodetector based on PtTe2 with bow-tie-type planar contacts possesses a high photoresponsivity (1.6 A W−1 without bias voltage) with a response time less than 20 μs, while the PtTe2–graphene heterostructure-based detector can reach responsivity above 1.4 kV W−1 and a response time shorter than 9 μs. Remarkably, it is already exploitable for large area imaging applications. These results suggest that topological semimetals such as PtTe2 can be ideal materials for implementation in a high-performing photodetection system at THz band
Bioelectrochemical system in wastewater treatment: Resource recovery from municipal and industrial wastewaters
No full textDue to large quantity and containing rich resources (e.g., chemical energy, metals, fresh water and nutrients), recovery resources from municipal and industrial wastewaters can be considered where resource recovery economies can be applied. Simultaneously, resource recovery during wastewater treatment will make treatment processes more economically viable and compliant to increasingly tight environmental regulations. Bioelectrochemical system (BES) has been emerged as a platform technology to recover resources from wastewater treatment. In this chapter, a comprehensive and critical review of resource recovery via BES from wastewater is conducted. The basic information of BES as well as the processes of resource recovery through BES at the laboratory- and plant-scale are introduced. Furthermore, the current challenges related to the BES applications for the resource recovery and the possible development directions are discussed
Observations of isoprene, methacrolein (MAC) and methyl vinyl ketone (MVK) at a mountain site in Hong Kong
No full textAuthor name used in this publication: Guo, H.Author name used in this publication: Wang, D. W.2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishedVoR allowe
Kinematic Simulation and Structure Analysis of a Morphing Flap
Get PDFThis thesis presents a study on the design and analysis of a morphing flap
structure integrated with actuation mechanism for potential application to large
aircraft. Unlike the conventional rigid flap mounted on the wing trailing edge,
the morphing flap is designed as a unitized structural system integrated with
three primary components: the upper and lower flexible skins reinforced by
stringers, an eccentric beam actuation mechanism (EBAM) with discs fixed on it,
and the connection of the discs with the stringers. Based on the EBAM concept
proposed by Dr Guo in previous research [1], the current study has been
focused on the EBAM design and optimization, kinematic simulation and
structural modelling of the morphing flap.
Although a lot of efforts have been made to develop the morphing flap in
previous research, it is lack of detailed design of the disc-skin linkage and clear
view on the mechanism optimization in relation to the shape requirement. The
main objective of this research is to meet the morphing shape requirements and
calculate the actuation torque for a specified morphing flap. Firstly effort was
made to design and optimize the disc shape and locations in the EBAM for the
best matching of the specified morphing shape with minimum actuation torque
demand. It is found that minimum three discs are required and their locations
have little effect on the actuation torque. Secondly attention was focused on
designs of the disc and a C-linkage with the stringers. To ensure that the C-
linkage works in practice, a twisted stringer flange design was proposed. Thirdly
the actuation mechanism was integrated with the stiffened skin to play the role
of an active rib in the flap structure. Based on the design, FE modelling and
analysis of the morphing flap structure was carried out. The behaviour of the
morphing flap under the internal actuation and external aerodynamic load was
applied for stress analysis and detailed design of the structures. Finally the
kinematics of the integrated morphing flap was simulated by using CATIA to
demonstrate the feasibility and the effectiveness of the improved design
Dynamic response properties of movement detectors: Theoretical analysis and electrophysiological investigation in the visual system of the fly
Get PDFEgelhaaf M, Reichardt W. Dynamic response properties of movement detectors: Theoretical analysis and electrophysiological investigation in the visual system of the fly. Biological Cybernetics. 1987;56(2-3):69-87
Transverse force generated by an electric field and transverse charge imbalance in spin-orbit coupled systems
No full textThree-Dimensional Numerical Simulation of Rear Point Contact Crystalline Silicon Solar Cells
No full textHigh efficiency monocrystalline solar cells commonly adopts circular rear point contacts of limited extension and passivation of the uncontacted bottom silicon surface region in order to improve performance. Modeling and analysis of advanced solar cells is strategic to optimize the device design and to minimize the losses. Several competing physical mechanisms must be accounted for in order to properly analyze rear point contact solar cells and a three-dimensional (3D) analysis of complex geometries is required. In this work we describe the issues related to the design of the mesh grid for the 3D numerical simulations, the definition of appropriate boundary conditions and the main adopted assumptions. Examples of numerical simulations are reporte
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