22 research outputs found
Dynamically Reconfigurable Architectures and Systems for Time-varying Image Constraints (DRASTIC) for Image and Video Compression
In the current information booming era, image and video consumption is ubiquitous. The associated image and video coding operations require significant computing resources for both small-scale computing systems as well as over larger network systems. For different scenarios, power, bitrate and image quality can impose significant time-varying constraints. For example, mobile devices (e.g., phones, tablets, laptops, UAVs) come with significant constraints on energy and power. Similarly, computer networks provide time-varying bandwidth that can depend on signal strength (e.g., wireless networks) or network traffic conditions. Alternatively, the users can impose different constraints on image quality based on their interests. Traditional image and video coding systems have focused on rate-distortion optimization. More recently, distortion measures (e.g., PSNR) are being replaced by more sophisticated image quality metrics. However, these systems are based on fixed hardware configurations that provide limited options over power consumption. The use of dynamic partial reconfiguration with Field Programmable Gate Arrays (FPGAs) provides an opportunity to effectively control dynamic power consumption by jointly considering software-hardware configurations. This dissertation extends traditional rate-distortion optimization to rate-quality-power/energy optimization and demonstrates a wide variety of applications in both image and video compression. In each application, a family of Pareto-optimal configurations are developed that allow fine control in the rate-quality-power/energy optimization space. The term Dynamically Reconfiguration Architecture Systems for Time-varying Image Constraints (DRASTIC) is used to describe the derived systems. DRASTIC covers both software-only as well as software-hardware configurations to achieve fine optimization over a set of general modes that include: (i) maximum image quality, (ii) minimum dynamic power/energy, (iii) minimum bitrate, and (iv) typical mode over a set of opposing constraints to guarantee satisfactory performance. In joint software-hardware configurations, DRASTIC provides an effective approach for dynamic power optimization. For software configurations, DRASTIC provides an effective method for energy consumption optimization by controlling processing times. The dissertation provides several applications. First, stochastic methods are given for computing quantization tables that are optimal in the rate-quality space and demonstrated on standard JPEG compression. Second, a DRASTIC implementation of the DCT is used to demonstrate the effectiveness of the approach on motion JPEG. Third, a reconfigurable deblocking filter system is investigated for use in the current H.264/AVC systems. Fourth, the dissertation develops DRASTIC for all 35 intra-prediction modes as well as intra-encoding for the emerging High Efficiency Video Coding standard (HEVC)
Tuning Multipolar Mie Scattering of Particles on a Dielectric-Covered Mirror
Optically resonant particles are key building blocks of many nanophotonic
devices such as optical antennas and metasurfaces. Because the functionalities
of such devices are largely determined by the optical properties of individual
resonators, extending the attainable responses from a given particle is highly
desirable. Practically, this is usually achieved by introducing an asymmetric
dielectric environment. However, commonly used simple substrates have limited
influences on the optical properties of the particles atop. Here, we show that
the multipolar scattering of silicon microspheres can be effectively modified
by placing the particles on a dielectric-covered mirror, which tunes the
coupling between the Mie resonances of microspheres and the standing waves and
waveguide modes in the dielectric spacer. This tunability allows selective
excitation, enhancement, and suppression of the multipolar resonances and
enables scattering at extended wavelengths, providing new opportunities in
controlling light-matter interactions for various applications. We further
demonstrate with experiments the detection of molecular fingerprints by
single-particle mid-infrared spectroscopy, and, with simulations strong optical
repulsive forces that could elevate the particles from a substrate.Comment: 16 pages, 4 figure
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Room-temperature observation of near-intrinsic exciton linewidth in monolayer WS2
The homogeneous exciton linewidth, which captures the coherent quantum dynamics of an excitonic state, is a vital parameter in exploring light-matter interactions in two-dimensional transition metal dichalcogenides (TMDs). An efficient control of the exciton linewidth is of great significance, and in particular of its intrinsic linewidth, which determines the minimum timescale for the coherent manipulation of excitons. However, such a control has rarely been achieved in TMDs at room temperature (RT). While the intrinsic A exciton linewidth is down to 7 meV in monolayer WS2, the reported RT linewidth was typically a few tens of meV due to inevitable homogeneous and inhomogeneous broadening effects. Here, we show that a 7.18 meV near-intrinsic linewidth can be observed at RT when monolayer WS2 is coupled with a moderate-refractive-index hydrogenated silicon nanosphere in water. By boosting the dynamic competition between exciton and trion decay channels in WS2 through the nanosphere-supported Mie resonances, we have managed to tune the coherent linewidth from 35 down to 7.18 meV. Such modulation of exciton linewidth and its associated mechanism are robust even in presence of defects, easing the sample quality requirement and providing new opportunities for TMD-based nanophotonics and optoelectronics.J.F., K.Y., and
Y.Z. acknowledge the financial support of the National Aeronautics and Space Administration Early
Career Faculty Award (80NSSC17K0520), the National Science Foundation (NSF-ECCS-2001650),
and the National Institute of General Medical Sciences of the National Institutes of Health
(DP2GM128446). M.W. and A.A. acknowledge the financial support of the Air Force Office of
Scientific Research MURI program (FA9550-17-1-0002), the Vannevar Bush Faculty Fellowship, and
the Simons Foundation. T.Z. and M.T. acknowledge the financial support of the Air Force Office of
Scientific Research (FA9550-18-1-0072). T.J. and B.A.K. acknowledge the financial support of the
Robert A. Welch Foundation (F-1464), and the Center for Dynamics and Control of Materials
(CDCM), Materials Research Science and Engineering Center (MRSEC) (DMR-1720595).Center for Dynamics and Control of Material
Light-driven C-H bond activation mediated by 2D transition metal dichalcogenides
C-H bond activation enables the facile synthesis of new chemicals. While C-H
activation in short-chain alkanes has been widely investigated, it remains
largely unexplored for long-chain organic molecules. Here, we report
light-driven C-H activation in complex organic materials mediated by 2D
transition metal dichalcogenides (TMDCs) and the resultant solid-state
synthesis of luminescent carbon dots in a spatially-resolved fashion. We
unravel the efficient H adsorption and a lowered energy barrier of C-C coupling
mediated by 2D TMDCs to promote C-H activation. Our results shed light on 2D
materials for C-H activation in organic compounds for applications in organic
chemistry, environmental remediation, and photonic materials
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Light-driven C-H activation mediated by 2D transition metal dichalcogenides
C-H bond activation enables the facile synthesis of new chemicals. While C-H activation in short-chain alkanes has been widely investigated, it remains largely unexplored for long-chain organic molecules. Here, we report light-driven C-H activation in complex organic materials mediated by 2D transition metal dichalcogenides (TMDCs) and the resultant solid-state synthesis of luminescent carbon dots in a spatially-resolved fashion. We unravel the efficient H adsorption and a lowered energy barrier of C-C coupling mediated by 2D TMDCs to promote C-H activation. Our results shed light on 2D materials for C-H activation in organic compounds for applications in organic chemistry, environmental remediation, and photonic materials
Recommended from our members
Light-driven C–H activation mediated by 2D transition metal dichalcogenides
C-H bond activation enables the facile synthesis of new chemicals. While C-H activation in short-chain alkanes has been widely investigated, it remains largely unexplored for long-chain organic molecules. Here, we report light-driven C-H activation in complex organic materials mediated by 2D transition metal dichalcogenides (TMDCs) and the resultant solid-state synthesis of luminescent carbon dots in a spatially-resolved fashion. We unravel the efficient H adsorption and a lowered energy barrier of C-C coupling mediated by 2D TMDCs to promote C-H activation and carbon dots synthesis. Our results shed light on 2D materials for C-H activation in organic compounds for applications in organic chemistry, environmental remediation, and photonic materials
Scalable Open-Source Architecture for Real-Time Monitoring of Adaptive Wiring Panels
We recently introduced the first prototype of an Adaptive Wiring Panel (AWP) which implemented a reconfigurable switch fabric that allows dynamic routing of analog, digital, and power signals for space system applications. In this paper, we consider a complete redesign and re-implementation of the AWP system to address issues associated with scalability, reliability and real-time monitoring of the switching fabric. We demonstrate the new system using 48 cells as opposed to the 6 cells of the first AWP prototype. We make our hardware and software systems open source and provide recommendations to support further extensions to our system