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- 2018
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- KNIT
- Rajarshi Rananjay Sinh Institute of Management and Technology
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Investigation of cut quality in fiber laser cutting of CFRP
摘要： Fiber laser cutting of CFRP sheets was investigated using a 2 kW multi-mode fiber laser, focusing on how the cut quality factors, such as kerf width, kerf depth, matrix evaporation width, matrix recession width, kerf taper angle, matrix damage zone, and cut surface morphology, change as laser power, laser scanning speed, and the number of laser passes are varied. By designing a systematic experiment on a large process window, several important parameters for kerf width, kerf depth, matrix evaporation width, and matrix recession width were identified, and using them, it was verified that the beam scanning speed is a dominant factor for minimizing thermal damages. Also, circular rings were observed in each carbon fiber at the cut surfaces, and it looked as if they were generated when each fiber was thermally fused in the radial direction. A larger number of laser passes was found to contribute to a smooth surface morphology, because of the formation of highly-fused surfaces, which prevents fiber delamination and pull-outs. Optimum process conditions were also identified by comparing various cut quality factors.
关键词： Fiber laser cutting,Optimal process conditions,Cut quality factors,Thermal damage,Carbon fiber reinforced plastic (CFRP)
更新于2025-11-28 14:24:20
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Process control and quality assurance in remote laser beam welding by optical coherence tomography
摘要： Remote laser beam welding significantly outperforms conventional joining techniques in terms of flexibility and productivity. This process benefits in particular from a highly focused laser radiation and thus from a well-defined heat input. The small spot sizes of high brilliance laser beam sources, however, require a highly dynamic and precise positioning of the beam. Also, the laser intensities typically applied in this context result in high process dynamics and in demand for a method to ensure a sufficient weld quality. A novel sensor concept for remote laser processing based on optical coherence tomography (OCT) was used for both quality assurance and edge tracking. The OCT sensor was integrated into a 3D scanner head equipped with an additional internal scanner to deflect the measuring beam independently of the processing beam. With this system, the surface topography of the process zone as well as the surrounding area can be recorded. Fundamental investigations on aluminum, copper, and galvanized steel were carried out. Initially, the influence of the material, the angle of incidence, the welding position within the scanning field, and the temperature on the OCT measuring signal were evaluated. Based on this, measuring strategies for edge tracking were developed and validated. It was shown that orthogonal measuring lines in the advance of the process zone can reliably track the edge of a fillet weld. By recording the topography in the trailing area of the process zone, it was possible to assess the weld seam quality. Comparing the results to microscopic measurements, it was shown that the system is capable of clearly identifying characteristic features of the weld seam. Also, it was possible to observe an influence of the welding process on the surface properties in the heat-affected zone, based on the quality of the measuring signal.
关键词： inline quality assurance,optical coherence tomography,remote laser beam welding,process control
更新于2025-11-28 14:24:20
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Fiber-Optic Magnetic Field Sensing Based on Microfiber Knot Resonator with Magnetic Fluid Cladding
摘要： A kind of all-fiber magnetic field sensing structure is proposed and demonstrated here. The sensing element includes a microfiber knot resonator (MKR) cladded with magnetic fluid (MF). The low-index MgF2 slab is adopted as the substrate. The sensitivity increases with the decrease of the MKR ring diameter. The achieved maximum magnetic field sensitivity is 277 pm/mT. The results of this work have the potential to promote the development of magnetically controllable optical devices and the design of ultra-compact cost-effective magnetic field sensors.
关键词： quality factor,finesse,magnetic fluid,microfiber knot resonator
更新于2025-11-28 14:24:03
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Investigation on the crack fracture mode and edge quality in laser dicing of glass-anisotropic silicon double-layer wafer
摘要： This work puts forward numerical and experimental investigations on laser dicing of glass-anisotropic single-crystal silicon double-layer wafer using laser induced thermal-crack propagation (LITP). A semiconductor continuous wave laser working at the defocusing mode serves as volumetric heat source for glass layer while as surface heat source for silicon layer. Based on the classical fracture theory, a static seam-type crack is introduced under the circumstance of ABAQUS to simulate the crack fracture modes in glass layer as well as silicon layer with crystal planes of (100), (110) and (111) during laser dicing in different dicing directions. In the experiments, processing parameters are kept the same as the simulations and typical dicing directions obtained from simulations are also used. The surface morphologies of crack edges are measured by the optical microscope and surface profiler. Through the comparison of numerical and experimental results it is discovered that for the specific substrate, the evolution of crack edge qualities in different dicing directions and different layers can be interpreted based on the corresponding stress distribution and stress intensity factor (SIF) ratio explicitly. And most important of all, the anisotropy of silicon layer has significant influence on the fracture mode and edge quality of crack in both layers.
关键词： Crack fracture mode,Laser induced thermal-crack propagation,Glass-anisotropic single-crystal silicon double-layer wafer,Crack edge quality,Static seam-type crack
更新于2025-11-21 11:24:58
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Metasurface for Constructing a Stable High- <i>Q</i> Plano-Planar Open Cavity
摘要： Traditional open cavities are constructed by planar or concave mirrors. A Fabry–Pérot (FP) cavity is convenient to integrate and fabricate, but highly sensitive to the parallelism of the end mirrors. In contrast, a concave cavity is more stable and possesses a lower leaky rate, but the curved geometry brings inconvenience. Here, it is suggested that a planar meta-cavity can simultaneously possess the advantages of both of the above open cavities by using a metasurface to create a planar meta-mirror that mimics the behavior of a concave mirror. For demonstration, a microwave meta-cavity is constructed, whose meta-mirror consists of subwavelength ceramic blocks on a metal substrate. Compared to an FP cavity, the meta-cavity is more robust against the alignment error of the end mirrors, and 15-fold enhancement of the quality factor is observed numerically. Experimental results are in good agreement with the simulated results. The suggested method may be extended to work in high frequency ranges. This work would support the planarization and miniaturization of an open cavity and may also increase the functionality.
关键词： open cavities,cavity stability,high quality factor,metasurfaces
更新于2025-09-23 15:23:52
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Noise-Free Rule-Based Fuzzy Image Enhancement
摘要： Different kinds of noises have considerable effects on most of image sensing systems. Suitable image contrast enhancement algorithms can improve contrast or retain detail information while reducing noises as well. Fuzzy representation of an image provides a reliable analysis when inexactness occurred at the gray level values. This paper presents a fuzzy-based novel image contrast enhancement method. Several image quality indices, such as similarity, naturalness, and mean brightness preserving examined and experimentally show the effectiveness of the proposed technique in comparison with well-known image enhancement methods such as histogram equalization and contrast limited adaptive histogram equalization methods.
关键词： Image Robustness and Naturalness,Image Quality Index,Image Enhancement,Fuzzy System
更新于2025-09-23 15:23:52
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Wintertime Local Wind Dynamics from Scanning Doppler Lidar and Air Quality in the Arve River Valley
摘要： Air quality issues are frequent in urbanized valleys, particularly in wintertime when a temperature inversion forms and the air within the valley is stably stratified over several days. In addition to pollutant sources, local winds can have a significant impact on the spatial distribution and temporal evolution of pollutant concentrations. They can be very complex and difficult to represent in numerical weather prediction models, particularly under stable conditions. Better knowledge of these local winds from observations is also a prerequisite to improving air quality prediction capability. This paper analyses local winds during the Passy-2015 field experiment that took place in a section of the Arve river valley, near Chamonix–Mont-Blanc. This location is one of the worst places in France regarding air quality. The wind analysis, which is mainly based on scanning Doppler lidar data sampling a persistent temperature inversion episode, reveals features consistent with the higher pollutant concentrations observed in this section of the valley as well as their spatial heterogeneities. In particular, an elevated down-valley jet is observed at night in the northern half of the valley, which, combined with a weak daytime up-valley wind, leads to very poor ventilation of the lowest layers. A northeast–southwest gradient in ventilation is observed on a daily-average, and is consistent with the PM10 heterogeneities observed within the valley.
关键词： scanning Doppler wind lidar,Passy-2015 field experiment,cold air pool,local wind dynamics,air quality,alpine valley
更新于2025-09-23 15:23:52
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Correlations among lighting quality metrics for interior lighting
摘要： Correlations between selected lighting quality metrics derived from the spectrum were computed and interpreted for a representative set of interior light source spectra. Metrics of brightness and the melanopic effect were strongly correlated with each other but not with the metrics of colour quality. Results can be used to establish a two-dimensional diagram with criterion values to ensure the general user acceptance of a lighting system. This diagram can be extended in the future by further metrics describing light intensity and spatial and temporal distributions. Relationships between lighting quality metrics and colorimetric quantities as well as photoreceptor signal values are also shown.
关键词： lighting quality metrics,spectral design,correlations,human-centric lighting,interior lighting
更新于2025-09-23 15:23:52
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Harmonizing by reducing inter-run variability: performance evaluation of a quality assurance program for antinuclear antibody detection by indirect immunofluorescence
摘要： Background: The introduction of automated anti-nuclear antibody (ANA) indirect immunofluorescence (IIF) analysis may allow for more harmonized ANA IIF reporting, provided that a thorough quality assurance program controls this process. The aim of this study was to evaluate various quality indicators used for ANA IIF analysis with the final goal of optimizing the iQC program. Methods: In an experimental setup, we introduced artificial errors, mimicking plausible problems during routine practice on a QUANTA-Lyser-NOVA View? system (Inova Diagnostics, San Diego, CA, USA). Predetermined quality indicators were evaluated against predefined acceptance criteria. In addition, we retrospectively investigated the applicability of the selected quality indicators in the daily routine practice during three pre-defined periods. Results: Both the experimental as the retrospective study revealed that pre-analytical, analytical and post-analytical errors were not highlighted by company internal quality control (iQC) materials. The use of patient derived iQC samples, median fluorescence intensity results per run and the percentage of positive ANA IIF results as additional quality indicators ensured a more adequate ANA IIF quality assurance. Furthermore, negative and moderate positive sample iQC materials merit clinical validation, as titer changes of >1 correspond to clinically important shifts. Traditional Westgard rules, including a clinically defined stop limit, revealed to be useful in monitoring of the supplemental quality indicators. Conclusions: A thorough ANA IIF quality assurance for daily routine practice necessitates the addition of supplemental quality indicators in combination with well-defined acceptance criteria.
关键词： automation,indirect immunofluorescence,antinuclear antibodies,quality control
更新于2025-09-23 15:23:52
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A Subwavelength Microstrip Resonator Based on Metamaterials
摘要： A metamaterial-based subwavelength microstrip resonator with high quality factor and simple fabrication process was proposed. For the experimental result, a quality factor of about 70 was achieved when the length of the resonator was about one third of the wavelength. Firstly, the mu-negative metamaterial (MNM) and the epsilon-negative metamaterial (ENM) were implemented by loading only chip capacitors or only chip inductors onto the microstrip. The implementation process is simpler in comparison to the traditional implementation method of the MNM and the ENM based on the microstrip. Then, the transmission characteristics of the heterostructure constructed of the MNM and the ENM fabricated through the simple method were investigated and the results showed that a subwavelength microstrip resonator could be built by the MNM–ENM heterostructure. Moreover, the quality-factor enhancement of the subwavelength microstrip resonator based on the MNM–ENM heterostructure was also explored. The results showed that the quality factor could be notably boosted and increased by about 15 times for the experimental result of the sample owing to more intensive con?nement of the electromagnetic ?eld when the electromagnetically induced transparency-like metamaterial was introduced at the interface of the MNM–ENM heterostructure.
关键词： resonator,quality factor,subwavelength,Metamaterials
更新于2025-09-23 15:23:52