课程文献中心 更多>>

关键词： Bessel-like beam   DMD   Diffraction   Scalar Fresnel-Kirchhoff integration   MATLAB   PROPAGATION  

摘要： We provide numerical software based on the MATLAB programming language to study the Bessel-like beams generated by special instruments such as DMD. The calculations are based on the scalar Fresnel-Kirchhoff integration within the scope of Fourier Optics. This analysis is particularly important because the addition of higher-order Bessel terms may produce additional unexpected experimental results in some applications. We emphasize the seldom-mentioned imaging characteristic on the lens, where the central point is shifted, and provide numerical software to understand the expression of the Bessel-like function obtained from important theoretical derivation. It also benefits to verify and explain the experimental results.

关键词： MATLAB   Hierarchical clustering   Image processing   Additive manufacturing   Process selection   SolidWorks   CAD   CLASSIFICATION   SELECTION  

摘要： This paper presents an image clustering algorithm that classifies parts to be fabricated using traditional and additive manufacturing (AM) technologies. The proposed algorithm is a MATLAB-based software tool that clusters 3D CAD models of parts considering their geometry only. The algorithm can classify image datasets, CAD datasets, and combined datasets that contain both images and CAD models. The software tool reduces the time and effort spent during process selection by offering a preselected set of parts that are more suitable for AM. The software tool is aimed at supporting decision-making for traditional manufacturing companies that consider expanding their production capability by introducing AM processes in their production facilities. The HICA software tool expands the scope of scientific applications in manufacturing process selection by providing an unsupervised approach that does not require data labelling. The tool is made available as a MATLAB function through a permanent link.

关键词： Topology optimization   Level set method   Gradient field estimation   Body-fitted mesh   Educational Matlab code   EVOLUTIONARY STRUCTURAL OPTIMIZATION   DESIGN   WRITTEN   SHAPE   ALGORITHMS   GENERATOR   DOMAIN  

摘要： Topology optimization is an influential technique engineers and designers employ to achieve desirable material distribution within a designated domain. This educational article introduces a concise and efficient Matlab code, comprising only 262 lines, developed explicitly for the Level Set topology optimization based on the estimated Gradient Field (GFLS) in the body-fitted mesh. Unlike conventional level set methods that rely on the upwind scheme employed in the structured meshes, the proposed algorithm adopts the per-cell linear estimation of the discrete gradient vectors in the body-fitted mesh framework to obtain the velocity field and update the level set function. The Matlab code, named GFLS262, consists of a 62-line main program, 41-line finite element analysis function, and 48-line sub-functions, enabling the implementation of the GFLS method in 2D scenarios. Additionally, a 111-line function describes an improved mesh generator incorporated in the code to facilitate the generation of body-fitted meshes. The superiority of this innovative approach over the previous optimization methods with invariant meshes is demonstrated through various benchmark examples. For ease of access and further learning, the educational Matlab code is available on the website and can also be found in the Appendix section of this article.

关键词： color stability   mixed halide perovskite   low efficiency roll-off   high brightness   ion migration   ION MIGRATION   PASSIVATION   PERFORMANCE   EMISSION   CSPBX3   FILMS   BR  

摘要： We report a simple, effective, and universal lattice reconstruction approach to improve the quality of perovskite films by using nonpolar solvents with high Gutmann donor numbers (DNs). We find that high-DN nonpolar solvents, for instance, ethyl acetate, can interact with perovskite precursors. Such a solvent can make the perovskite lattice more ordered and "harder" and promote the formation of heterostructures with low-dimensional perovskite impurities and residual solvent molecules. As a result, the lattice-reconstructed perovskite films exhibit reduced defect densities and suppressed ion migration. The resultant mixed-halide blue perovskite light-emitting diodes (PeLEDs) show greatly enhanced tolerance to high driving current densities and voltages, demonstrating high brightness, outstanding color stability and low efficiency roll-off. Our work provides a deep understanding of the interactions between nonpolar solvents and perovskites and offers useful guidelines for further development of high-power PeLEDs.

关键词： Biomarkers   Hydrocarbon index   MATLAB   Chromatography   Biogeochemistry   N-ALKANE DISTRIBUTIONS   PLANT   INDICATORS   DELTA-C-13   HOLOCENE   PROXY   BOG  

摘要： The molecular ratio indices of biological markers (biomarkers), such as the Carbon Preference Index (CPI) or Paq, are frequently used as proxies for paleoclimatic and palaeoecological conditions. These indices are regularly extracted from the relative abundances of target molecules detected by a Gas Chromatography analyzer with a Flame Ionization Detector (GC-FID). Despite their use in biogeochemical studies for over a half-century, it remains common procedure to quantify the abundance of individual compounds by manual integration of chromatogram peaks (i.e., interpret baselines visually and characterize peaks by hand), which is time consuming and can lead to inconsistent results. Here, we introduce a new MATLAB package (Chroma) for the automatic detection and integration of standard-referenced biomarker abundances and the calculation of a variety of established hydrocarbon indices commonly reported in the published literature. The algorithm identifies the detector response timing of specific target peaks in a sample chromatogram by cross-referencing to a standard (e. g., Mix-A6, Schimmelmann, Indiana University Bloomington), then calculates the peak areas for an approximation of molecular abundance. This new toolkit for automatic and rapid integration of GC-acquired data provides a consistent and reproducible approach for the calculation of hydrocarbon indices and offers a standardized inter-laboratory platform for data comparisons and exchange. We validate the utility of the Chroma package with the chromatograms of plant wax n-alkanes, a widely used proxy for ecology and hydrology, from six stratigraphic sections in the Tibetan Plateau. Chroma is an effective tool for efficient data processing and will continuously evolve to accommodate extended uses in related areas of biomarker research beyond n-alkanes.

关键词： Spike -wave discharges   Automatic detection   Short -time Fourier   Rats   Absence Epilepsy   Normal modelling   ABSENCE SEIZURES   EPILEPSY   DISCHARGES   MODELS   SLEEP   EEG   FEATURES   STRAIN   CORTEX   RATS  

摘要： Background: There are many automated spike-wave discharge detectors, but the known weaknesses of otherwise good methods and the varying working conditions of different research groups (mainly the access to hardware and software) invite further exploration into alternative approaches. New method: The algorithm combines two criteria, one in the time-domain and one in the frequency-domain, exploiting morphological asymmetry and the presence of harmonics, respectively. The time-domain criterion is additionally adjusted by normal modelling between the first and second iterations. Results: We report specificity, sensitivity and accuracy values for 20 recordings from 17 mature, male WAG/Rij rats. In addition, performance was preliminary tested with different hormones, pharmacological injections and species (mice) in a smaller sample. Accuracy and specificity were consistently above 91 %. The number of automatically detected spike-wave discharges was strongly correlated with the numbers derived from visual inspection. Sensitivity varied more strongly than specificity, but high values were observed in both rats and mice. Comparison with existing methods: The algorithm avoids low-voltage movement artifacts, displays a lower false positive rate than many predecessors and appears to work across species, i.e. while designed initially with data from the WAG/Rij rat, the algorithm can pick up seizure activity in the mouse of considerably lower inter-spike frequency. Weaknesses of the proposed method include a lower sensitivity than several predecessors. Conclusion: The algorithm excels in being a selective and flexible (based on e.g. its performance across rats and mice) spike-wave discharge detector. Future work could attempt to increase the sensitivity of this approach.

关键词： Calcium imaging   GUI   CNMF   Spike estimation   Motion correction   EarthMover's Distance   NETWORK ACTIVITY   VISUAL-CORTEX   OSCILLATIONS   DECONVOLUTION   INHIBITION   PATTERNS   NEURONS   SLICE   MODEL  

摘要： Background: Fluorescence imaging of calcium dynamics in neuronal populations is powerful because it offers a way of relating the activity of individual cells to the broader population of nearby cells. The method ' s growth across neuroscience has particularly been driven by the introduction of sophisticated mathematical techniques related to motion correction, image registration, cell detection, spike estimation, and population characterization. However, for many researchers, making good use of these techniques has been difficult because they have been devised by different workers and impose differing - and sometimes stringent - technical requirements on those who seek to use them. New method: We have built a simple toolbox of analysis routines that encompass the complete workflow for analyzing calcium imaging data. The workflow begins with preprocessing of data, includes motion correction and longitudinal image registration, detects active cells using constrained non -negative matrix factorization, and offers multiple options for estimating spike times and characterizing population activity. The routines can be navigated through a simple graphical user interface. Although written in MATLAB, a standalone version for researchers who do not have access to MATLAB is included. Results: We have used the toolbox on two very different preparations: spontaneously active brain slices and microendoscopic imaging from deep structures in awake behaving mice. In both cases, the toolbox offered a seamless flow from raw data all the way through to prepared graphs. Conclusion: The field of calcium imaging has benefited from the development of numerous innovative mathematical techniques. Here we offer a simple toolbox that allows ordinary researchers to fully exploit these techniques.

关键词： Topology optimization   MATLAB code   Piezoelectric actuator   Piezoelectric energy harvester   Finite element model   PIEZO MODAL TRANSDUCERS   PIEZOCOMPOSITE MATERIALS   DESIGN   DEVICES   HOMOGENIZATION   SYSTEMS   WRITTEN  

摘要： This paper presents two MATLAB codes for topology optimization of multi-material piezoelectric actuators and energy harvesters. These codes provide the extensions of the previously published 2D topology optimization codes for piezoelectric actuators and energy harvesters (Struct Multidisc Optim 63 (2), 983-1014) with two major contributions: (1) extension to the third dimension, (2) combination of piezoelectric (active) and non-piezoelectric (passive) materials in the design domain. The codes are written in the most flexible form to be compatible with different optimization problems and practical case studies of piezoelectricity that exist in the literature. The codes address unique challenges that emerge by introducing the third dimension to non-isotropic piezoelectric materials including the polarization direction and definition of electrodes. The finite element discretization has been done with two different types of 3D hexahedral elements: (1) 8-node trilinear elements, (2) 20 node quadratic elements. The users are free to choose between these element types for the finite element model of the structure based on having preferences for accuracy or computation time. A new method of indexing the elements, nodes, and degrees of freedom is introduced to facilitate the definition of loads, boundary conditions, electrodes, etc. The inclusion of piezoelectric material and non-piezoelectric material in the design domain is by default. In comparison to previously published 2D codes, the codes in this paper benefit from the latest advancements in optimization algorithms, filtering methods, and speed-up techniques. The codes are independent and hence can be run without calling any external code. Different parts of the codes are explained in detail to make them comprehensive for newcomers in the field of topology optimization of piezoelectric structures.

关键词： 建筑工程   暖通设计   实例   要点  

摘要： 随着我国城市化进程的持续推进,社会各个行业领域都在不断地发展和进步,其中建筑业作为国民经济支柱型产业之一,也获得了良好的发展空间,取得了显著的发展成绩.尤其是各种智能化、综合化的建筑不断涌现,对建筑设计工作提出了更高要求和标准,在这种背景下,积极加强建筑工程暖通设计方法的研究具有重要意义.基于此,本文主要从建筑暖通设计的概述出发,结合实例探讨了建筑暖通设计的相关要求,最后提出了若干强化策略,以期推动建筑事业的健康发展.