- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Graphene Foam: Hole-Flake Network for Uniaxial Supercompression and Recovery Behavior
摘要： We employed the coarse-grained molecular dynamics simulation method to systematically study the uniaxial supercompression and recovery behavior of multi-porous graphene foam, in which a mesoscopic three-dimensional network with hole-graphene flakes was proposed. The network model not only considers the physical cross-links and interlayer van der Waals interactions, but also introduces a hole in the flake to approach the imperfection of pristine graphene and the hierarchical porous configuration of real foam material. We first recreated a typical two-stage supercompression stress?strain relationship and the corresponding time-dependent recovery as well as a U-type nominal Poisson ratio. Then the recovery unloading at different strains and multicycle compression?uncompression were both conducted; the initial elastic moduli in the multicycles were found to be the same, and a multilevel residual strain was disclosed. Importantly, the residual strain is not exactly the plastic one, part of which can resurrect in the subsequent loading?unloading?holding. The mesoscopic mechanism of viscoelastic and residual deformation for the recovery can be attributed to the van der Waals repulsion and mechanical interlocking among the hole-flakes; interestingly, the local tensile stress was observed in the virial stress distribution. Particularly, an abnormal turning point in the length-time curve for the mean bead-bond length was captured during the supercompression. After the point, the length abnormally increases for different size ratios of the hole to the flake, which is in line with the mesostructure evolution. The finding may provide a mesoscopic criterion for the supercompression of graphene foam related materials.
关键词： supercompression,strain history,recovery behavior,mesoscale,van der Waals interaction,viscoelastoplasticity,graphene foam,coarse-grained molecular dynamics
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE 3rd International Conference on Image, Vision and Computing (ICIVC) - Chongqing, China (2018.6.27-2018.6.29)] 2018 IEEE 3rd International Conference on Image, Vision and Computing (ICIVC) - Extended Secret Image Sharing with Lossless Recovery Based on Chinese Remainder Theorem and Quick Response Code
摘要： Extended secret image sharing (SIS) has meaningful shadow, the meaningful shadow will decrease encryption suspiciousness when we transfer secret image via public channels. Chinese Remainder Theorem (CRT) based SIS (CRTSIS) has the advantages of lossless recovery and low recovery computation complexity. Quick Response Code (QR) has become more and more common in our daily life. In this paper, based on CRT and QR, we propose a SIS algorithm for (k, n) threshold with meaningful share and lossless recovery. We choose QR code as the carrier to output valid QR code, which can be scanned to decode. When we collect any k or more shares out of total n shares, the secret image will be recovered losslessly by CRT. We carry out three experiments to illustrate the feasibility and effectiveness of our algorithm.
关键词： (k, n) threshold,Chinese remainder theorem,lossless recovery,secret image sharing,QR code
更新于2025-09-23 15:21:01
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Influence of Ag NPs on Silicon Nanocolumns NH <sub/>3</sub> Gas Sensors
摘要： Two NH3 gas sensor devices, Al/Si nanocolumns/n-Si/Al and Al/Ag NPs/Si nanocolumns/n-Si/Al hybrid structures, have been fabricated and tested. A bare silicon nanocolumns layer was synthesized by a laser-assisted electrochemical etching process in HF solutions. The surface morphology of bare Si nanocolumns was modified by incorporating Ag NPs into Si nanocolumns by simple and fast immersions methods in an aqueous solution of AgNO3 to synthesize a hybrid structure. Characteristic features of bare Si nanocolumns and hybrid structure were investigated using scanning electron microscopy, EDS analysis, FTIR spectra, X-ray diffraction, and photoluminescence spectra (PL). The electrical characteristics of sensors with and without NH3 gas were measured at room temperature. The results showed that the nanoparticles grain size, nature, specific surface area (S.S.A) of Ag NPs, and morphological structure of the Si nanocolumns strongly affected the property characteristics. A significant enhancement in sensitivity, response, and recovery times of gas sensor for a hybrid structure was realized after compared with Al/Si nanocolumns/n-Si/Al gas sensor due to the high specific surface area.
关键词： silicon nanocolumns,response time,NH3 gas sensor,sensitivity,Ag NPs,hybrid structure,recovery time
更新于2025-09-23 15:21:01
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Short-term Voltage Stability Enhancement in Residential Grid with High Penetration of Rooftop PV units
摘要： Short-term voltage instability (STVI) imposes a severe threat to modern distribution networks (DNs) where a large number of intermittent distributed generator (DG) units, like rooftop photovoltaic (PV), is being integrated. Consequently, most of the international standards have been revised by incorporating the requirement of dynamic voltage support (DVS) through DG units, which is a promising approach to alleviate the STVI. In this paper, a novel DVS strategy is proposed to improve the short-term voltage stability (STVS) in residential grids. In comparison with other DVS strategies, the proposed DVS scheme maximizes the active power support from PV units following a contingency utilizing maximum allowable current of the PV inverters. Moreover, the inverter design margin is taken into account in designing the proposed scheme to limit the injected grid current within maximum allowable inverter current. The impact of inverter design margin on the STVS is explained, and the effectiveness of the proposed strategy compared with conventional DVS is demonstrated. The feasibility of the DVS control strategies in practical application is studied. Several case studies are carried out on benchmark IEEE 4 bus and IEEE 13 node test feeder systems, and finally on a ring-type DN. The results show that the proposed DVS scheme is feasible, and achieved superior performance compared to the other strategies. Furthermore, it has been shown that implementation of the proposed DVS scheme can avoid the installation of an expensive 1200 kVA D-STATCOM for STVS improvement in the target system.
关键词： Distributed generators,fault induced delayed voltage recovery,low voltage ride-through,dynamic voltage support,short-term voltage stability,distribution system
更新于2025-09-23 15:21:01
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Light source estimation using feature points from specular highlights and cast shadows
摘要： A method for light sources estimation is proposed in this paper. The method utilizes feature points in cast shadows to estimate near light source positions from estimated source directions using specular highlights. There are several methods that can be used to estimate light sources from scene images, using either cast shadows or specular highlights. However, most of them are limited to directional light sources. The proposed method can estimate the positions and intensities of multiple near point light sources. Specular highlights on an object of known geometry are first used for light source direction estimation. Then, a discontinuity point in the object shape and the corresponding cast shadow on a ground plane are used for light source position estimation. Feature points obtained from an image of the cast shadow, however, can be inaccurate due to various factors. Information on diffused light reflected from Lambertian ground-plane surface is subsequently used to improve estimation accuracy. Experimental results were used to evaluate the performance of the proposed method.
关键词： light source recovery,augmented reality,Light source estimation
更新于2025-09-23 15:21:01
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Parallelized and adaptive square-root unscented Kalman filter for carrier recovery in satellite-to-ground coherent optical communications
摘要： An adaptive square-root unscented Kalman filter with a parallelized architecture for carrier recovery is proposed in QPSK based satellite-to-ground coherent optical communication systems. A new observation model is raised in the proposed scheme to make the state estimation more accurate. The process noise covariance (Q) and the measurement noise covariance (R) are adaptively estimated to make them consistent with their theoretical covariance. For verification of the feasibility of the proposed scheme, corresponding simulations of carrier recovery in satellite-to-ground laser links are carried out and compared with the scheme that is based on linear Kalman filter (LKF). The simulation results demonstrate that, compared with parallelized LKF, the proposed scheme has a wider range of block size and laser linewidth options, and it can relax the required transmit power by up to 0.5-3 dB under different zenith angle at the same BER. Moreover, the proposed scheme can achieve high estimation accuracy and fast tracking capability simultaneously in the case of dynamic frequency offset with better tolerance against the initial errors in Q and R.
关键词： Atmospheric propagation,Adaptive Kalman filter,Free space optical communication,Coherent communications,Carrier recovery
更新于2025-09-23 15:19:57
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[IEEE 2019 International Multi-Conference on Engineering, Computer and Information Sciences (SIBIRCON) - Novosibirsk, Russia (2019.10.21-2019.10.27)] 2019 International Multi-Conference on Engineering, Computer and Information Sciences (SIBIRCON) - Numerical Calculation Current Form of Led Lamp PWM Stabilizer
摘要： A traf?c matrix is generally used by several network management tasks in a data center network, such as traf?c engineering and anomaly detection. It gives a ?ow-level view of the network traf?c volume. Despite the explicit importance of the traf?c matrix, it is signi?cantly dif?cult to implement a large-scale measurement to build an absolute traf?c matrix. Generally, the traf?c matrix obtained by the operators is imperfect, i.e., some traf?c data may be lost. Hence, we focus on the problems of recovering these missing traf?c data in this paper. To recover these missing traf?c data, we propose the spatio-temporal Kronecker compressive sensing method, which draws on Kronecker compressive sensing. In our method, we account for the spatial and temporal properties of the traf?c matrix to construct a sparsifying basis that can sparsely represent the traf?c matrix. Simultaneously, we consider the low-rank property of the traf?c matrix and propose a novel recovery model. We ?nally assess the estimation error of the proposed method by recovering real traf?c.
关键词： network management,Kronecker compressive sensing,network measurement,matrix completion,Traf?c matrix recovery
更新于2025-09-23 15:19:57
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Recovery kinetics in high temperature annealed AlN heteroepitaxial films
摘要： Based on the experimental dislocation annihilation rates, vacancy core diffusion-controlled dislocation climb was found as a dominant recovery mechanism in high temperature annealing of AlN heteroepitaxial films. Dislocation annihilation mechanisms via dislocation glide (with or without kinks) and vacancy bulk diffusion were found to be less significant. Cross-slip was also ruled out as a possible mechanism as a majority of dislocations in heteroepitaxial AlN films are threading edge dislocations. While dislocation climb through both vacancy bulk and core diffusion could offer a plausible explanation of the recovery process, the activation energy for the vacancy core diffusion-controlled dislocation climb was relatively low (4.3 ± 0.1 eV), as estimated from an Arrhenius plot. The validity of the vacancy core diffusion mechanism was also supported by a large vacancy mean free path (～240 nm), which was comparable to the sample thickness and thus the average dislocation length. Finally, the experimentally observed dislocation density reduction as a function of the annealing temperature and time was in good agreement with the vacancy core diffusion mechanism.
关键词： dislocation annihilation,high temperature annealing,AlN heteroepitaxial films,recovery kinetics,vacancy core diffusion
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE/ACS 16th International Conference on Computer Systems and Applications (AICCSA) - Abu Dhabi, United Arab Emirates (2019.11.3-2019.11.7)] 2019 IEEE/ACS 16th International Conference on Computer Systems and Applications (AICCSA) - Multi-Layer Laser Scanner Strategy for Obstacle Detection and Tracking
摘要： A traf?c matrix is generally used by several network management tasks in a data center network, such as traf?c engineering and anomaly detection. It gives a ?ow-level view of the network traf?c volume. Despite the explicit importance of the traf?c matrix, it is signi?cantly dif?cult to implement a large-scale measurement to build an absolute traf?c matrix. Generally, the traf?c matrix obtained by the operators is imperfect, i.e., some traf?c data may be lost. Hence, we focus on the problems of recovering these missing traf?c data in this paper. To recover these missing traf?c data, we propose the spatio-temporal Kronecker compressive sensing method, which draws on Kronecker compressive sensing. In our method, we account for the spatial and temporal properties of the traf?c matrix to construct a sparsifying basis that can sparsely represent the traf?c matrix. Simultaneously, we consider the low-rank property of the traf?c matrix and propose a novel recovery model. We ?nally assess the estimation error of the proposed method by recovering real traf?c.
关键词： matrix completion,Traf?c matrix recovery,Kronecker compressive sensing,network management,network measurement
更新于2025-09-23 15:19:57
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Photoluminescence Loss and Recovery of ?±-CsPbI3 Quantum Dots Originated from Chemical Equilibrium Shift of Oleylammonium
摘要： α-CsPbI3 perovskite quantum dots (PQDs) have great potentials in red-emitting LED and solar cell applications. However, their instability with quick photoluminescence loss with time greatly limits their development. In this study, we found that the nonluminous aged α-CsPbI3 PQDs instantly regained fluorescence emission after a surface treatment with trioctylphosphine. Meanwhile, this surface treatment also worked on fresh α-CsPbI3 PQDs to enhance photoluminescence emission. The structures and compositions of fresh and aged PQDs before and after surface treatment were analyzed in detail. We demonstrated that a surface chemical equilibrium shift mechanism involving oleylammonium led to the PL loss and recovery of α-CsPbI3 PQDs. This chemical equilibrium shift also played an important role in other PQD stabilities against long term storage, temperature, UV irradiation and ethanol, which were all significantly improved after treatment. The treated α-CsPbI3 PQDs were phase stable for more than 6 months. Oleic acid and oleylamine are common ligands used in PQD syntheses; this study shall promote the understanding of PQD surface chemistry and the preparation of stable α-CsPbI3 PQDs.
关键词： photoluminescence loss,oleylammonium,recovery,CsPbI3,Perovskite quantum dot
更新于2025-09-23 15:19:57