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A new version of a low concentration evacuated tube solar collector: Optical and thermal investigation
摘要： This work is focused on investigating the performance of a new version of evacuated tube solar collector with and without solar tracking system. The evacuated tube solar collector is composed of an absorbing copper tube positioned eccentrically inside a transparent glass cover tube which has a reflective film insert on its inner surface and vacuum in eccentric annular space. Modeling of the proposed evacuated tube collector is based on the conservation equations of mass, momentum and energy and discretized by using the finite volumes method. A home-built numerical code is developed, tested and its grid size optimized. This code is validated against available experimental and numerical results. Effects of the tilt angle and tracking systems are also evaluated. The results showed maximum and minimum daily efficiencies of the collector of about 73% and 42%, respectively. The annual efficiency of this collector was evaluated as 61.5% for the city of S?o Luís, Brazil. The new contributions from the present work include the reflective film, the eccentricity of the absorber and the presence of vacuum in the annular space. The reflective film helps to keep the absorber at uniform temperature and reduce thermal induced stress. The eccentricity is introduced to create concentration effect which helps to increase the outlet temperature of the working fluid and reduce the mass of the collector system. The presence of vacuum in the eccentric annular space reduces effectively the thermal losses, improves the efficiency.
关键词： Solar energy,Eccentric evacuated tube collector,Evacuated tube solar collector,Solar tracking systems,Collector modeling
更新于2025-09-19 17:15:36
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Modeling the Optimal Conditions for Improved Efficacy and Crosslink Depth of Photo-Initiated Polymerization
摘要： Optimal conditions for maximum ef?cacy of photoinitiated polymerization are theoretically presented. Analytic formulas are shown for the crosslink time, crosslink depth, and ef?cacy function. The roles of photoinitiator (PI) concentration, diffusion depth, and light intensity on the polymerization spatial and temporal pro?les are presented for both uniform and non-uniform cases. For the type I mechanism, higher intensity may accelerate the polymer action process, but it suffers a lower steady-state ef?cacy. This may be overcome by a controlled re-supply of PI concentration during the light exposure. In challenging the conventional Beer–Lambert law (BLL), a generalized, time-dependent BLL (a Lin-law) is derived. This study, for the ?rst time, presents analytic formulas for curing depth and crosslink time without the assumption of thin-?lm or spatial average. Various optimal conditions are developed for maximum ef?cacy based on a numerically-?t A-factor. Experimental data are analyzed for the role of PI concentration and light intensity on the gelation (crosslink) time and ef?cacy.
关键词： optimal ef?cacy,crosslinking,polymerization modeling,photoinitiator,kinetic
更新于2025-09-19 17:15:36
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[IEEE 2018 Eighth International Conference on Image Processing Theory, Tools and Applications (IPTA) - Xi'an, China (2018.11.7-2018.11.10)] 2018 Eighth International Conference on Image Processing Theory, Tools and Applications (IPTA) - Video Tracking of Insect Flight Path: Towards Behavioral Assessment
摘要： In this paper, we propose a cohort of new methods that cooperate together to improve the detection/tracking of mosquitos in a 2D video clip. A commonly recognized challenge in the biotechnology research field is evaluating the effect of a repellent which entails tracking the unpredictable flight paths of the insects, which may be swift flying or slow moving. Our work presented in this paper provides an efficient tool to deal with tracking the small insects with unpredictable moving patterns by proposing a new dual foreground and background modeling/updating system for target detecting and tracking. The proposed processing elements take advantage of the similarity of the frames and use the estimated speeds to collectively capture the relevant information and contribute in concert to ensure fast and accurate measurement to reach the goal of behavior evaluation of mosquitos in response to a repellent.
关键词： multiple target tracking,Video object detection,foreground and background modeling/updating
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE Power & Energy Society General Meeting (PESGM) - Portland, OR, USA (2018.8.5-2018.8.10)] 2018 IEEE Power & Energy Society General Meeting (PESGM) - An LMI Based Stability Margin Analysis for Active PV Power Control of Distribution Networks with Time-Invariant Delays
摘要： High penetration of photovoltaic (PV) generators can lead to voltage issues in distribution networks. Various approaches including the real power control through PV inverters have been proposed to address voltage issues. However, among different control strategies, communication delays are inevitably involved and they need to be carefully considered in the control loop. Those delays can significantly deteriorate the system performance with undesired voltage quality, and may also cause system instability. In this paper, according to the inverter based active power control strategy, a linearized state space model with communication delay is presented. A delay dependent stability criterion using linear matrix inequality (LMI) approach is used to rigorously obtain the delay margins based on different system parameters. The method can handle multiple PVs in the distribution network as well.
关键词： modeling,photovoltaic generators,communication delay,active power curtailment,LMI
更新于2025-09-19 17:15:36
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Wireless Energy Transmission Channel Modeling in Resonant Beam Charging for IoT Devices
摘要： Power supply for Internet of Things (IoT) devices is one of the bottlenecks in IoT development. To provide perpetual power supply for IoT devices, resonant beam charging (RBC) is a promising safe, long-range and high-power wireless power transfer solution. How long distance RBC can reach and how much power RBC can transfer? In this paper, we analyze the consistent and steady operational conditions of the RBC system, which determine the maximum power transmission distance. Then, we study the power transmission efficiency within the operational distance, which determines the deliverable power through the RBC energy transmission channel. Based on the theoretical model of the wireless energy transmission channel, we establish a testbed. According to the experimental measurement, we validate our theoretical model. The experiments verify that the output electrical power at the RBC receiver can be up to 2W. The maximum energy transmission distance is 2.6m. Both the experimental and theoretical performance of the RBC system are evaluated in terms of the transmission distance, the transmission efficiency, and the output electrical power. Our theoretical model and experimental testbed lead to the guidelines for the RBC system design and implementation in practice.
关键词： Wireless Power Transfer,Energy Transmission Channel Modeling,Experimental Testbed,Resonant Beam Charging
更新于2025-09-19 17:15:36
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Absorption of light in a single vertical nanowire and a nanowire array
摘要： Both a single III–V semiconductor nanowire and an array of such nanowires have shown promise for solar cell applications. However, the correspondence between the optical properties of the single nanowire and the nanowire array has not been studied. Here, we perform electromagnetic modeling of InP nanowires to study this relationship. We find that a single nanowire can show at an absorption peak, a remarkably high absorption cross-section that is more than 50 times the geometrical cross-section. With optimization of the diameter of the single nanowire, the short-circuit current density is 30 times higher than in a bulk solar cell. With such a strong absorption, we predict an apparent efficiency >500% for the single nanowire solar cell. In contrast, we show that an efficient nanowire array solar cell cannot rely on strong absorption just through the absorption peak. Instead, the nanowires need to be packed rather closely to enhance the absorption of the full solar spectrum. At the optimum diameter for the nanowire array, neighboring nanowires compete strongly for absorption of incident photons at the absorption peak, which limits the absorption per nanowire by a factor of 18. As a result, the single InP nanowire is optimized at a diameter of 110 nm while the nanowires in the array are optimized at a considerably larger diameter of 180 nm. Importantly, we show analytically the coupling efficiency of incident light into the fundamental HE11 guided mode and consecutive absorption of the mode in the nanowires. With that analysis, we explain that a single nanowire shows two different absorption pathways—one through coupling into the guided mode and another by coupling into the nanowire through the sidewall. This analytical analysis also shows at which period the neighboring nanowires in an array start to compete for absorption of incident photons.
关键词： III–V semiconductor nanowire,optics modeling,absorption,solar cell
更新于2025-09-19 17:15:36
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Study of modeling optimization for hyperspectral imaging quantitative determination of naringin content in pomelo peel
摘要： With the development of modern computational science and data metrology, hyperspectral imaging technology has been utilized in the field of remote sensing for the application in precision agriculture and crop quality testing. In this paper, the near infrared hyperspectral imaging (NIRHSI) technique was applied to quantitatively determine the naringin content in pomelo peel samples. Model optimization was studied by investigating the influence of system measuring conditions and parameters of the built-up HSI instrumental system. The HSI data acquisition was built up using a prevalent pushbroom scanner in the near infrared region. Calibration models were established using the partial least squares (PLS) regression in the mode of cross validation, in combined use of the Savitzky-Golay smoother (SGS) for data pretreatment. These multivariate analytical models were optimized in comparison about the region of interest (ROI) for NIRHSI model optimization. In the process of NIRHSI data acquisition, the rational values of some system measurement parameters were also tuned and tested, such as the use of different watts for light intensity, different lenses and different materials as the scanning backgrounds. Results showed that the cross-validation PLS regression methods performed well in the calibration and prediction processes, working well together with the parameter tuning of the SGS pretreatment. In addition to the fact that different materials as the scanning backgrounds obviously affected the quantitative result, there is no apparent difference in the comparing cases of different light intensities and different lenses. This work validates the capability of applying NIRHSI technique to quantitative determine the content of naringin in pomelo peel samples. The test for model optimization by comparing the measurement parameters and the system properties has prospective application ability in fields of other spectral/hyperspectral data analysis. It is an important lab simulation of remote sensing. It contributes significant theoretical reference to the design of the large-scale online hyperspectral data acquisition systems.
关键词： Pomelo peel Naringin,Near infrared hyperspectral imaging,Pushbroom scanner,Modeling optimization,Region of interest
更新于2025-09-19 17:15:36
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Gaussian random number generator: Implemented in FPGA for quantum key distribution
摘要： Quantum key distribution is the process of using quantum communication to establish a shared key between two parties. It has been demonstrated the unconditional security and effective communication of quantum communication system can be guaranteed by an excellent Gaussian random number (GRN) generator with high speed and an extended random period. In this paper, we propose to construct the Gaussian random number generator by using field‐programmable gate array (FPGA), which is able to process large data in high speed. We also compare three algorithms of GRN generation: Box‐Muller algorithm, polarization decision algorithm, and central limit algorithm. We demonstrate that the polarization decision algorithm implemented in FPGA requires less computing resources and also produces a high‐quality GRN through the null hypothesis test.
关键词： field‐programmable gate array,numerical modeling,quantum key distribution,Gaussian random numbers
更新于2025-09-19 17:15:36
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Thermal and illumination effects on a PbI <sub/>2</sub> nanoplate and its transformation to CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> perovskite
摘要： Movie highlights are composed of video segments that induce a steady increase of the audience’s excitement. Automatic movie highlights’ extraction plays an important role in content analysis, ranking, indexing, and trailer production. To address this challenging problem, previous work suggested a direct mapping from low-level features to high-level perceptual categories. However, they only considered the highlight as intense scenes, like fighting, shooting, and explosions. Many hidden highlights are ignored because their low-level features’ values are too low. Driven by cognitive psychology analysis, combined top-down and bottom-up processing is utilized to derive the proposed two-way excitement model. Under the criteria of global sensitivity and local abnormality, middle-level features are extracted in excitement modeling to bridge the gap between the feature space and the high-level perceptual space. To validate the proposed approach, a group of well-known movies covering several typical types is employed. Quantitative assessment using the determined excitement levels has indicated that the proposed method produces promising results in movie highlights’ extraction, even if the response in the low-level audio-visual feature space is low.
关键词： movie exciting degree,movie highlights’ extraction,affective computing,excitement modeling
更新于2025-09-19 17:15:36
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Identification of the Pain Process by Cold Stimulation: Using Dynamic Causal Modeling of Effective Connectivity in Functional Near-Infrared Spectroscopy (fNIRS)
摘要： Background: Pain is an unpleasant sensory and emotional experience followed by anxiety, depression, and frustration. Functional Near-Infrared Spectroscopy (fNIRS) as an optical technique identifies the brain functional networks by investigating connectivity between functionally linked of different anatomical regions in response to pain stimulation. Methods: In this research, fNIRS was performed in order to study the difference in effective functional connectivity of the brain prefrontal cortex between the two modes of pain and rest based on the dynamic causal modeling (DCM) method. Effective functional connectivity changes in the prefrontal cortex between pain and rest states were calculated using DCM approach to investigate (1) areas known for pain sensation and (2) to analyze inter-network functional connectivity strength (FCS) by selecting several brain functional networks based on the analysis findings. All analyses were performed using toolboxes SPM-fNIRS and SPM8, Matlab software. Results: Regional hemodynamics changes caused deoxyhemoglobin concentration to decrease in the prefrontal cortex of both hemispheres, particularly on the right side. We found a simultaneous increase in the concentration of oxyhemoglobin in the prefrontal cortex of the left hemisphere in comparison to the right hemisphere, that there was a trend toward reduction in oxyhemoglobin concentration. The results indicate that during the cold pain stimulation, the connectivities between prefrontal cortex regions were significantly changed. Specifically, a significantly consistent increase in the RPFC to MPFC connectivity was found while a significant consistent decrease was observed in the both MPFC to LPFC and LPFC to MPFC connectivities. Conclusion: This study contributes to the pain research field to identify the directionality and causality of neuronal connections in the prefrontal cortex by applying DCM to fNIRS data. The results suggest that the proposed method infers directional interactions between hidden neuronal states in the brain under neuronal dynamic conditions based on optical density changes measurement.
关键词： Diagnosing pain,Neurology,Effective connectivity,Brain mapping,Dynamic causal modeling,fNIRS,Pain
更新于2025-09-19 17:15:36