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Fractional Chaos Maps with Flower Pollination Algorithm for Partial Shading Mitigation of Photovoltaic Systems
摘要： Solar Photovoltaic (PV) systems have become prominent and have attained the attention of energy engineers, governments and researchers. To achieve the maximum bene?t from the PV system in spite of its nonlinear characteristic and environmental conditions, ?nding a robust maximum power point tracking method is essential. Over two decades, various researchers proposed numerous MPPT methods, but they failed to evaluate their methods on consistency, reliability, and robustness over several numbers of runs. Most of the researchers examined one con?guration and they did not to consider the dynamic change in the irradiation conditions. Therefore, in this manuscript, the authors introduced a novel optimization technique Fractional chaotic Flower Pollination Algorithm (FC-FPA), by merging fractional chaos maps with ?ower pollination algorithm (FPA). The proposed technique, help FPA in extracting the Global Maximum Power Point (GMPP) under different partial shading patterns including with different PV array con?gurations. The proposed FC-FPA technique is tested and evaluated over 5 different patterns of partial shading conditions. The ?rst three patterns are tested over 4S con?guration made with Shell S36 PV module. The other two patterns are applied to the 4S2P con?guration of Shell SM55 PV panels. The performance of the proposed variant is investigated by tracking the GMPP for abruptly changing shade pattern. Exclusive statistical analysis is performed over several numbers of runs. Comparison with perturb and observe MPPT technique is established. These results con?rm that, the proposed method shows fast convergence, zero oscillation and rapid response for the dynamic change in irradiation with consistent behavior.
关键词： maximum power point tracker,?ower pollination algorithm,fractional chaos maps,partial shading conditions
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Direct Observation of Intracavity Pulse Dynamics in All-Normal Dispersion All-Fiber Oscillator
摘要： Ultrafast science and technology depend strongly on the development of novel ultrafast sources, thus good understanding of nonlinear phenomena in such systems is of essence. In this paper, we present the experimental observation and theoretical analysis of various pulse dynamics in all-normal dispersion cavity producing dissipative soliton pulses. We report the results of an extensive study regarding the Stimulated Raman Scattering (SRS) process, which creates a main upper limitation for the pulse energy achievable from all-normal dispersion fiber oscillators. We report the measurements of real-time, single shot spectra registered using Dispersive Fourier Transform (DFT) technique together with measured averaged spectral phase of the pulses generated from an all-PM-fiber oscillator mode-locked with Nonlinear Optical Loop Mirror (NOLM). It is found that NOLM parameters directly influenced the pulse stability and dynamics. The Yb-doped fiber was used as an active medium and Dissipative Soliton (DS) pulses centered at 1030 nm were generated together with Stokes radiation shifted by 440 cm-1 (centered approximately at 1078 nm) produced in SRS process. The light generated in SRS process was suppressed from round-trip to round-trip by a narrow pass-band spectral filter centered at 1030 nm placed inside the laser cavity. We present the broad experimental study of ultrashort pulse dynamics with strong presence of SRS process. Spectral intensity correlation maps were calculated to describe how the SRS process disturbs the ultrashort pulse during propagation in the cavity (Fig. 1). The intensities of longer wavelengths (1040 – 1050 nm) in the pulse spectrum were destabilized due to the SRS process. In normal dispersion fiber Stokes SRS components have higher group velocity than the pulse spectral components. For positively chirped pulse SRS affects only the leading edge of the pulse which is manifested as negative correlation (Fig. 1(c)). The phenomena of repetitive partial dissipative soliton explosions and bistability of the pulse operation in an all-PM-fiber all-normal dispersion oscillator cavity were investigated as well. The clear signature of bistable operation was the hysteresis of the laser pulse power versus input pump power. Furthermore, we registered significant differences between the measured pulses spectral phases for each case. Another set of measurements was performed to analyze the pulse self-starting dynamics. We present the experimental study and numerical simulations of DS pulse dynamics in an all-normal dispersion all-fiber cavity. The numerical simulations were performed using the standard split-step Fourier-transform method employing the multi-vibrational model of SRS. DS lasers are important pulse sources and an effective platform to investigate the pulse dynamics and nonlinear processes inside the all-fiber cavities.
关键词： spectral intensity correlation maps,Yb-doped fiber,dissipative soliton pulses,Dispersive Fourier Transform,split-step Fourier-transform method,Nonlinear Optical Loop Mirror,Stimulated Raman Scattering,ultrafast science
更新于2025-09-12 10:27:22
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Non-dimensional process maps for normalized dilution limits in laser direct metal deposition
摘要： The quality and integrity of laser direct metal deposition (DMD) processes primarily depend on the substrate dilution and the nature of residual stresses in the deposited layer. An adequate amount of melting of the substrate is required to ensure the formation of sound metallurgical bond between the deposited layer and substrate. Insufficient melting and excessive dilution may lead to adverse effects. Furthermore, the dilution also controls the location of the melt front in substrate where maximum tensile residual stresses occur. The presence of tensile residual stresses in the deposited layer may be detrimental to service life, especially, for components repaired using DMD. These challenges can be overcome by predicting and controlling the dilution and the nature of residual stress as a function of process parameters. To model the direct metal deposition process, a 3D coupled metallo-thermomechanical finite element model is employed to predict the temperature and the residual stress due to thermomechanical interactions and metallurgical transformations and the substrate dilution. Non-dimensional process parameters affecting the dilution in laser DMD have been identified using Buckingham-Π theorem. The metallo-thermomechanical model is used to develop empirical relationships via regression to correlate the dimensionless process parameters with the dilution. These correlations are employed in developing the isopleths in the form of process maps, which could predict regions of inadequate fusion and excessive dilution (unduly large substrate melting). It may be noted that the limiting value of dilution corresponds to the condition where the entire deposited layer (cladding) is under compressive residual stresses. Any dilution higher than this will result in excess substrate melting which is undesirable. The limiting values of normalized dilution are estimated to be 1 and ~1.3 corresponding to complete deposit-substrate fusion and presence of entirely compressive residual stress in deposition, respectively. These process maps are designed to provide a theoretical framework for understanding the influence of process parameters and provide informed decisions on the selection of appropriate process parameters for ensuring the quality and integrity of the deposition.
关键词： Laser cladding,residual stress,metallo-thermomechanical finite element model,process maps,dilution,non-dimensional parameters
更新于2025-09-12 10:27:22
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A quantum mechanical study of optical excitations in nanodisk plasmonic oligomers
摘要： Using state-of-the-art quantum-mechanical calculations, we investigate the optical excitations in plasmonic nanodisk oligomers. We show that different tuning parameters such as the constitution (size and intrinsic optical properties of individual nanodisks), configuration (number of satellite nanodisks), and the spatial arrangement of satellite nanodisks critically influence the optical features of nanodisk oligomers. Our theoretical results demonstrate significantly enhanced absorption in nanodisk oligomers in comparison to individual nanodisks and, additionally, vivid optical modulations due to the creation of nanodisk oligomer homotops. Transition density maps corresponding to the main peaks in the absorption spectra provided new insight into the nature of the optical excitations. The insights gained from this theoretical study will be useful in the design of novel plasmonic nanodisk oligomers.
关键词： quantum-mechanical calculations,transition density maps,plasmonic nanodisk oligomers,absorption enhancement,optical excitations
更新于2025-09-12 10:27:22
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[Handbook of Numerical Analysis] Processing, Analyzing and Learning of Images, Shapes, and Forms: Part 1 Volume 19 || Shape Correspondence and Functional Maps
摘要： Notions of similarity and correspondence between geometric shapes and images are central to many tasks in geometry processing, computer vision and computer graphics. The goal of this chapter is to give an overview of a set of recent techniques that greatly facilitate the computation of mappings or correspondences between geometric datasets, such as 3D shapes or 2D images by formulating them as mappings between functions rather than points or triangles. Methods based on the functional map framework have recently led to state-of-the-art results in problems as diverse as nonrigid shape matching, image cosegmentation and even some aspects of tangent vector field design. In this chapter, we try to provide all the necessary foundation to appreciate and use these techniques, while assuming very little background knowledge. We also aim to provide practical implementation details for the methods within this domain and, at the same time, hint at the generality of the “functional” point of view, which can help tackle many problems in the analysis and creation of visual content.
关键词： Correspondence,Shape matching,Geometry processing,Functional maps
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Introducing a Framework of Self-Organizing Maps for Regression of Soil Moisture with Hyperspectral Data
摘要： In this paper, we introduce a framework to solve regression problems based on high-dimensional and small datasets. This framework involves two self-organizing maps (SOM) and combines unsupervised with supervised learning. We investigate the impacts of SOM hyperparameters on the regression performance and compare the results of the SOM framework with two established regressors on a measured dataset. The derived results reveal the potential of the SOM framework. Finally, we propose further research aspects for the SOM framework to analyze its capabilities and limitations. We have published our dataset in [1] to ensure the reproducibility of the results.
关键词： machine learning,regression,hyperspectral data,soil moisture,Self-organizing maps
更新于2025-09-10 09:29:36
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Pattern recognition of messily grown nanowire morphologies applying multi-layer connected self-organized feature maps
摘要： Multi-layer connected self-organizing feature maps (SOFMs) and the associated learning procedure were proposed to achieve efficient recognition and clustering of messily grown nanowire morphologies. The network is made up by several paratactic 2-D SOFMs with inter-layer connections. By means of Monte Carlo simulations, virtual morphologies were generated to be the training samples. With the unsupervised inner-layer and inter-layer learning, the neural network can cluster different morphologies of messily grown nanowires and build connections between the morphological microstructure and geometrical features of nanowires within. Then, the as-proposed networks were applied on recognitions and quantitative estimations of the experimental morphologies. Results show that the as-trained SOFMs are able to cluster the morphologies and recognize the average length and quantity of the messily grown nanowires within. The inter-layer connections between winning neurons on each competitive layer have significant influence on the relations between the microstructure of the morphology and physical parameters of the nanowires within.
关键词： Messily grown nanowire morphologies,Artificial neural networks,Monte Carlo simulation,Pattern recognition,Self-organizing feature maps
更新于2025-09-09 09:28:46
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Computer-Aided Panoramic Images Enriched by Shadow Construction on a Prism and Pyramid Polyhedral Surface
摘要： The aim of this study is to develop an efficient and practical method of a direct mapping of a panoramic projection on an unfolded prism and pyramid polyhedral projection surface with the aid of a computer. Due to the fact that straight lines very often appear in any architectural form we formulate algorithms which utilize data about lines and draw panoramas as plots of functions in Mathcad software. The ability to draw panoramic images of lines enables drawing a wireframe image of an architectural object. The application of the multicenter projection, as well as the idea of shadow construction in the panoramic representation, aims at achieving a panoramic image close to human perception. The algorithms are universal as the application of changeable base elements of panoramic projection—horizon height, station point location, number of polyhedral walls—enables drawing panoramic images from various viewing positions. However, for more efficient and easier drawing, the algorithms should be implemented in some graphical package. The representation presented in the paper and the method of its direct mapping on a flat unfolded projection surface can find application in the presentation of architectural spaces in advertising and art when drawings are displayed on polyhedral surfaces and can be observed from multiple viewing positions.
关键词： polyhedra,panoramic projection,shadow construction,Computer Aided Design (CAD),maps on surfaces,descriptive geometry
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE Conference on Control Technology and Applications (CCTA) - Copenhagen (2018.8.21-2018.8.24)] 2018 IEEE Conference on Control Technology and Applications (CCTA) - Improving Occupancy Grid Mapping via Dithering for a Mobile Robot Equipped with Solid-State LiDAR Sensors
摘要： Occupancy grid maps are by far the most used spatial representation of the environment for robot navigation. This paper proposes a simple and effective way to improve the occupancy grid accuracy by superimposing a small oscillation to the robot motion when a predefined path is given. The method is especially suited for range sensors with long range capabilities but poor angular resolution. The innovative solid state LiDAR technology is an example of such sensor configuration and is used in this work for the experimental evaluation of the presented dithering technique. Experimental results quantitatively demonstrated that the proposed oscillating motion is effective especially in speeding up the detection of corridor like clearances in the environment.
关键词： dithering technique,solid state LiDAR,robot navigation,Occupancy grid maps
更新于2025-09-04 15:30:14
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Performance of CMOS pixel sensor prototypes in ams H35 and aH18 technology for the ATLAS ITk upgrade
摘要： Pixel sensors based on commercial high-voltage CMOS processes are an exciting technology that is considered as an option for the outer layer of the ATLAS inner tracker upgrade at the High Luminosity LHC. Here, charged particles are detected using deep n-wells as sensor diodes with the depleted region extending into the silicon bulk. Both analog and digital readout electronics can be added to achieve different levels of integration up to a fully monolithic sensor. Small scale prototypes using the ams CMOS technology have previously demonstrated that it can achieve the required radiation tolerance of 1015 neq∕cm2 and detection efficiencies above 99.5%. Recently, large area prototypes, comparable in size to a full sensor, have been produced that include most features required towards a final design: the H35demo prototype produced in ams H35 technology that supports both external and integrated readout and the monolithic ATLASPix1 pre-production design produced in ams aH18 technology. Both chips are based on large fill-factor pixel designs, but differ in readout structure. Performance results for H35DEMO with capacitively-coupled external readout and first results for the monolithic ATLASPix1 are shown.
关键词： HV-MAPS,Silicon pixel sensor,Monolithic active pixel sensor,High luminosity LHC,ATLAS ITk upgrade,CMOS
更新于2025-09-04 15:30:14