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过滤筛选
- 2019
- low-temperature electronics
- class AB operation
- optimization of analog electronic circuit
- operational amplifier
- LTspice environment
- buffer amplifier
- junction field-effect transistors
- Electronic Science and Technology
- Don State Technical University
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Real time video image enhancement approach using particle swarm optimisation technique with adaptive cumulative distribution function based histogram equalization
摘要： Recent years, real time videos are playing an important role in different applications such as pattern recognition, security purpose, news analysis, weather digest, and video browser and so on. Due to the importance of real time video applications, the quality of the real time video must be improved for making effective results in real time video analysis process. This paper introduces the particle optimization with adaptive cumulative distribution based histogram enhancement technique (PACDHE) for improving the real time video quality. Initially the videos are collected, each incoming frame has been analyzed and noise present in the video frame is eliminated by applying the non-divisional median filter. After that, quality of real time video is enhanced iteratively by examining each pixel present in video frames using the optimized fitness and cumulative distribution function. This process is repeated continuously until to enhance the real time video frames contrast and quality. Then the performance of the system is analyzed by using CV online video database and the efficiency is examined in terms of peak signal to noise ratio (PSNR), Absolute Mean Brightness Error (AMBE) and Entropy. The experimental results of PSO are compared with genetic algorithm based approach and found that PSO outperforms the GA approach and the existing histogram equalization approach and the existing histogram equalization approaches.
关键词： contrast enhancement,particle optimization based adaptive cumulative distribution based histogram enhancement technique (PACDHE),fitness and cumulative distribution function,CV online video database,Video quality
更新于2025-09-23 15:23:52
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Impact of Backup Power in Optimizing Deployment Cost of Hybrid Optical Wireless Broadband Access Network (HOWBAN) with Survivability
摘要： The dependence on broadband to enhance the economy and environment sustainability is imposing immense urgency to provide ubiquitous wireless broadband access which is a key enabler to a greater spread of society. One of the key barriers to the network connectivity and survivability identified is the lack of or unreliable infrastructure. In our previous studies we have identified that the most unreliable component in a hybrid optical wireless broadband access network infrastructure is the power grid in remote areas and least developed countries. In this paper we extend our studies to evaluate the effect of the costs of backup power on sustaining survivability at the front end of two types of network configurations in a hybrid optical wireless broadband access network. The configurations investigated are full survivability and alternative path survivability networks. Our results show that the provision of backup power to all the nodes in a network configuration with one alternative path is able to reduce the cost of deployment compared to that of a full survivability network configuration without significantly affecting the network survivability.
关键词： Survivability,Hybrid,Backup power,Optimization,Wireless mesh
更新于2025-09-23 15:23:52
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Ultra-low-distortion optical system design based on tolerance sensitivity optimization
摘要： This study theoretically analyzed the relationship between the primary aberrations and tolerances to meet the distortion requirements of an ultra-low-distortion optical system. Theoretical analysis shows that the distortion sensitivities of the optical system are related to the primary aberrations of the optical surfaces. Consequently, a method of optimizing the primary aberrations on the surface of the optical system to reduce the distortion sensitivities of sensitive tolerances is proposed. A distortion sensitivity analysis of manufacturing and assembly tolerance was carried out for the designed ultra-low-distortion and telecentric optical system. The distortion sensitivities of the sensitive tolerances were reduced by optimizing the primary aberrations on the surface of the optical system. A Monte Carlo analysis of the optimized ultra-low-distortion optical system showed that the proposed method has a remarkable effect on the distortion sensitivity optimization of the tolerances.
关键词： primary aberration,ultra-low distortion,optimization,tolerance sensitivity,optical design
更新于2025-09-23 15:23:52
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On the efficient optimization of unicast, anycast and multicast flows in survivable elastic optical networks
摘要： The paper investigates efficient allocation of three types of flows (unicast, anycast, multicast) in elastic optical network with dedicated path protection. We model the problem as an integer linear programming and propose efficient solution methods: greedy randomized algorithm (GRA) and column generation (CG)-based approach implemented in two versions, which differ in the method used to find a final problem solution for the selected columns. Then, we evaluate in detail methods efficiency with respect to four reference algorithms. What is more, for CG-based methods we use five different algorithms to find initial sets of columns and, by these means, evaluate how the quality of these methods influences the efficiency of CG-based approaches. The simulation results show that the proposed GRA significantly outperforms reference greedy methods and finds very good solutions (the average gap to optimal result was not higher than 13.4%). The CG-based methods allow to further improve results and obtain solutions very close to optimal ones (for the best CG-based version, the highest average gap to optimal result was 2.1%). Moreover, the results show that the traffic pattern influences the algorithms performance. The methods perform the best for scenarios with high amount of multicast volume while high anycast volume brings the most difficult problem instances. Eventually, the study reveals that the efficiency of CG-based methods depends strongly on the quality of initial columns as well as on the method used to find final solution for the selected columns.
关键词： Network optimization,Multicast traffic,Anycast traffic,Column generation technique,Elastic optical networks,Dedicated path protection
更新于2025-09-23 15:23:52
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Performance improvement of baffle-type solar air collector based on first chamber narrowing
摘要： This paper proposes a novel idea to optimize thermal performance of baffle-type solar air collector by narrowing the first chamber through rearranging the baffles in the collector. The collector with five chambers divided by four baffles was investigated numerically and experimentally, and the mechanism of performance improvement was revealed by flow and heat transfer analysis. The simulation results show that the width of first chamber has significant influence on thermal efficiency, while has little influence on pressure drop. The maximum thermal-efficiency growth rate can be achieved when the width of the first chamber is 200 mm with the total chamber size of 2000 mm × 1000 mm × 120 mm, and the value is up to 16.90% compared with the model with evenly distributed baffles during the Reynolds number ranges from 1.8–5.5 × 10^3. A test rig was developed at the ratio of 1:0.5 to the numerical model. Four collector models were studied under three working conditions, and effectiveness of this method is verified. The results show that the first-chamber narrowing method has relatively stable optimization effect with a thermal-efficiency growth rate ranges from 9.73% to 16.10% in the experiment. It means that this method is not sensitive to scale change and has certain adaptability.
关键词： Experimental verification,Numerical simulation,Performance optimization,First chamber narrowing,Solar air collector
更新于2025-09-23 15:23:52
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Accuracy Assessment of Bio-optical Models to Retrieve Backscattering Coefficients in Case 1 Waters of the Bay of Bengal
摘要： The backscattering coef?cient (bb) has been obtained either in situ observations/measurements or semi-analytical/analytical and empirical algorithms that depend on the relationship between ‘bb’ and the remote sensing re?ectance (Rrs). Several models were developed to estimate backscattering coef?cient from the satellite imagery. The present study aims to assess the accuracy of bio-optical models and infer the best suitable model for Ocean Colour Monitoring (OCM-2) and for the upcoming OCM-3 sensors of Indian Space Research Organization. For this purpose, the bio-optical algorithms/models such as quasi-analytical algorithm (QAA), QAA version 5, Generalized Inherent Optical Properties (GIOP) and optimization of semi-analytical models in case 1 waters of the Bay of Bengal (BoB) were considered. For this analysis, three satellite sensors Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua, Visible Infrared Imaging Radiometer Suite (VIIRS), and OCM-2 datasets has been used to assess the model’s accuracy. The results showed that the optimization technique performs better (bias = 0.002, 0.179 and root-mean-square error (RMSE) = 8%, 20%) for MODIS-A and OCM-2, respectively, whereas GIOP performs better (bias = 0.08, RMSE = 14%) for VIIRS in case 1 waters of the BoB. From the statistical analysis of each model for all stations, it is recommended to use the optimization technique rather than GIOP technique for estimation of satellite based ‘bb’ in Indian waters.
关键词： Case 1 waters,QAA,QAA_v5,GIOP,Backscattering coef?cient,Optimization
更新于2025-09-23 15:23:52
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Investigative study of the thermal performance of a trial solar air heater
摘要： Solar collectors need to be inclined at the optimum angle to maximize the receiving energy. The evaluation of the thermal performance of solar air collectors is important for the proper design and sizing of the collector for a given application. In our experimental/theoretical study, which consists of a thermal performance investigation, we have sought to optimize the efficiency–temperature rise couple of the designed solar air heater by considering the appropriate assembling materials regarding the absorber, the glazing and the insulation. Obviously, efficiency is dependent on the orientation of solar collectors and the measured parameters climate conditions such as wind speed, solar radiation and ambient temperature. In order to achieve possible performance optimization of the receiver plane using a low number of variables and equations, the calculations were carried out considering four values of azimuth angle, γ = 0°, 22.5°, 45° and 67.5°, and by varying the tilt angle β by 5 degrees from 15° to 70°.
关键词： Insulation,Efficiency,Absorber,Optimization,Experimental solar air collector
更新于2025-09-23 15:23:52
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Pressure dependence of high order harmonic generation in nitrogen molecular gas and atmospheric air
摘要： The effect of the variation of the gas pressure on the high harmonic generation (HHG) from nitrogen molecular gas (N2) and atmospheric air with ultrashort intense laser pulses is measured. The optimum pressure in the interaction region of a gas jet for maximizing the HHG yield is determined for both gases. Enhancement of the HHG output and its extension to higher harmonic orders are observed around the optimum pressure value of 0.33 bar. Theoretical calculations based on one-dimensional models explain this effect and provide reasonable agreement with experimental results.
关键词： Femtosecond laser,Conversion efficiency,High-order harmonic generation (HHG),Phase matching,XUV radiation,Pressure optimization
更新于2025-09-23 15:23:52
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Practical optimal registration of terrestrial LiDAR scan pairs
摘要： Point cloud registration is a fundamental problem in 3D scanning. In this paper, we address the frequent special case of registering terrestrial LiDAR scans (or, more generally, levelled point clouds). Many current solutions still rely on the Iterative Closest Point (ICP) method or other heuristic procedures, which require good initializations to succeed and/or provide no guarantees of success. On the other hand, exact or optimal registration algorithms can compute the best possible solution without requiring initializations; however, they are currently too slow to be practical in realistic applications. Existing optimal approaches ignore the fact that in routine use the relative rotations between scans are constrained to the azimuth, via the built-in level compensation in LiDAR scanners. We propose a novel, optimal and computationally efficient registration method for this 4DOF scenario. Our approach operates on candidate 3D keypoint correspondences, and contains two main steps: (1) a deterministic selection scheme that significantly reduces the candidate correspondence set in a way that is guaranteed to preserve the optimal solution; and (2) a fast branch-and-bound (BnB) algorithm with a novel polynomial-time subroutine for 1D rotation search, that quickly finds the optimal alignment for the reduced set. We demonstrate the practicality of our method on realistic point clouds from multiple LiDAR surveys.
关键词： Branch-and-bound,Exact optimization,Point cloud registration
更新于2025-09-23 15:23:52
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Thermal oxidative decomposition estimation combining TGA and DSC as optimization targets for PMMA
摘要： Thermal analysis techniques play a key role to determine and characterize solid phase thermal decomposition. In this sense, Simultaneous Thermal Analysis (STA, i.e. TGA and DSC tests carried out simultaneously) are widely employed, since it provides information about how mass is lost and energy released while the temperature of the sample increases. Fire computer models combined with methods numerical methods are widely used to represent the results from tests and to achieve the values of the kinetic and thermal parameters. Previous works looked forward achieving those parameters using, as unique optimization target, the mass loss curve (TGA) or its derivative (DTGA). As the study of heat release rate is a decisive element to characterize the material properly, most recent works were adding additional measures. These extra measurements concern the heat transfer and the energy required or released during temperature programmed heating, such as heat rate release, heat of gasification, or the surface temperatures of the samples. The information about the energy is provided by the Differential Scanning Calorimetry curve (DSC). Despite of the employment of the information provided by the DSC, this information usually is not used as a target to approach the DSC simulated curve to the experimental one as TGA does. Based on the lack of use of the DSC curve as numerical approaching process to set the kinetic properties, we decide to explore the possibility of adding this as a new target in the process. Therefore, kinetic and thermal properties might be achieved fitting experimental and simulated curves simultaneously, which should allow us to take into account the decomposition process and their energy released. Results obtained in the present work reveal the major challenge of getting a set of parameters, which can fit DSC curve. The level of accuracy reached when only TGA is utilized as target to approach is higher than the level of accuracy of DSC curve. This fact makes increase the value of the errors when both curves are used as targets to approach. In other words, an approach to both curves simultaneously cannot be directly made. With this consideration in mind, this paper proposes an alternative methodology in order to fit TGA curve considering the optimization of the DSC curve. The methodology proposed in the present work is applied to the analysis of poly(methyl methacrylate) (PMMA).
关键词： DSC,numerical methods,TGA,CFD,Thermal decomposition,PMMA,optimization methods,solid phase chemistry
更新于2025-09-23 15:23:52