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Autogenous fiber laser welding of 70/30 Cu-Ni alloy plates
摘要： Cupronickel alloys such as 70/30 Cu-Ni have excellent resistance to sea water corrosion and anti-fouling properties, and thus have been widely used for naval and offshore applications. Traditionally, arc welding and brazing processes have been used to weld such materials. In contrast, laser beam welding is a promising technology due to its high productivity, good process flexibility and reliability, and good welding integrity. In the present work, a high power fiber laser system is used to weld 5-mm thick 70/30 Cu-Ni alloy plates in a configuration of butt joints. Then, the laser welded joints are evaluated in terms of microstructures, defects, and mechanical properties (hardness, face and root bend, and tensile) in accordance with the applicable International Organization for Standardization and Defence Standard specifications.
关键词： Tensile Properties,Microstructure,Butt Joint,Cupronickel Alloy,Bend testing,Laser Welding
更新于2025-11-28 14:24:20
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Laser markability of PVC coated automotive electric cables
摘要： This article describes the test results for laser markability of automotive electrical cables. The insulation is PVC, but the colour and construction of the insulations are different. Two types of laser workstations were used, one with a wavelength of 1064 nm and another with 532 nm. The penetration depth of the laser beam was determined by optical microscopy on cross sections. The 1064 nm laser beam can mark all investigated materials with good contrast, except the yellow insulation. The 532 nm laser beam with fast speed can hardly produce contrast with any of the materials. The laser markability of the yellow insulation was found to be the most problematic. On the two-layer insulation, despite the whitening of the inner material, dark marking is produced because the heat developing on the interface of the two layers will heat up and carbonize the transparent layer.
关键词： PVC coated cable,materials testing,industrial application,laser markability
更新于2025-11-21 11:18:25
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Acceptance criteria for accelerated aging testing of silvered-glass mirrors for concentrated solar power technologies
摘要： Solar reflectors for Concentrating Solar Power (CSP) technologies are required to maintain their optical properties in demanding environments for more than 20 years of service-life. The durability of the commonly used silvered-glass reflectors is typically qualified by means of accelerated aging. Recently, the Spanish standardization committee UNE has published the first specific standard for this topic, which defines a set of accelerated aging tests for CSP reflectors. However, the standard does not contain pass/fail criteria. This paper proposes useful acceptance criteria for the accelerated tests defined by UNE, helping to interpret the obtained degradation results. The criteria have been determined by analyzing the collected accelerated aging data over the past 5 years in the OPAC laboratory, a joint research group of DLR and CIEMAT. Data from six different 4 mm silvered-glass manufacturers is presented, covering nearly the entire market of commercially available silvered-glass mirrors, and going way beyond the recommended testing times of the UNE standard. The data may be used to benchmark initial reflective properties (before aging) and the performance during accelerated durability testing. In addition, recommendations for improvements of the standard are given and an estimate of the acceleration factor of the Copper Accelerate Salt Spray (CASS) test with respect to a highly corrosive outdoor environment is presented.
关键词： Durability,Accelerated aging testing,Reflectance,Acceptance criteria,Solar reflector,Concentrated solar power
更新于2025-10-22 19:40:53
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Three-dimensional holographic imaging using data collected over cylindrical apertures
摘要： The previously proposed near-field holographic imaging algorithms are based on the data collected over rectangular apertures. In this letter, we propose an approach for three-dimensional near-field holographic imaging with data collected over cylindrical apertures. Circular deconvolution is employed to deal with the periodicity of the functions along the azimuthal direction.
关键词： holography,microwave imaging,non-destructive testing
更新于2025-09-23 15:23:52
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Performance Evaluation of Short Parabolic Trough Collectors Integrated with a Small-Scale Solar Power and Heating System
摘要： An investigation is presented on the performance of a small-scale solar power and heating system with short parabolic trough collectors (PTCs). The steady-state model of the short PTCs is evaluated with outside experiments. The model mainly contains the heat loss of the receiver, the peak optical efficiency and the incident angle factor consisting of incident angle modifier and end loss. It is found that the end loss effect is essential in this model when the length of the PTCs is less than 48 m, especially in the winter. The standard deviation of the steady-state model is 1.4%. Moreover, the potential energy efficiency ratio of the solar power and heating system is considerably larger than the coefficient of performance (COP) of general air-source heat pumps, and increases with the decrease of the condensation temperature. An overall system efficiency of 49% can be reached. Lastly, the existence of a water storage tank improves the flexibility of heating the building, and the volume of the water storage tank decreases with the increase of the heating water temperature.
关键词： practical operating characteristics,parabolic trough solar collector,thermal performance,testing method,small-scale
更新于2025-09-23 15:23:52
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Application of TG-100 risk analysis methods to the acceptance testing and commissioning process of a Halcyon linear accelerator
摘要： Purpose: A new type of linear accelerator (linac) was recently introduced into the market by a major manufacturer. Our institution is one of the early users of this pre-assembled and pre-configured dual-layer MLC, ring-gantry linac – HalcyonTM (1st version). We performed a set of full acceptance testing and commissioning (ATC) measurements for three Halcyon machines and compared the measured data with the standard beam model provided by the manufacturer. The ATC measurements were performed following the guidelines given in different AAPM protocols as well as guidelines provided by the manufacturer. The purpose of the present work was to perform a risk assessment of the ATC process for this new type of linac and investigate whether the results obtained from this analysis could potentially be used as a guideline for improving the design features of this type of linac. Methods: AAPM’s TG100 risk assessment methodology was applied to the ATC process. The acceptance testing process relied heavily on the use of a manufacturer-supplied phantom and the automated analysis of EPID images. For the commissioning process, a conventional measurement setup and process (e.g. use of water tank for scanning) was largely used. ATC was performed using guidelines recommended in various AAPM protocols (e.g. TG-106, TG-51) as well as guidelines provided by the manufacturer. Six medical physicists were involved in this study. Process maps, process steps and failure modes (FMs) were generated for the ATC procedures. Failure Modes and Effects Analysis (FMEA) were performed following the guidelines given in AAPM TG-100 protocol. The top 5 and top 10 highest-ranked FMs were identified for the acceptance and commissioning procedures respectively. Quality control measures were suggested to mitigate these FMs. Results: A total of 38 steps and 88 FMs were identified for the entire ATC process. 14 steps and 34 FMs arose from acceptance testing. The top 5 FMs that were identified could potentially be mitigated by the manufacturer. For commissioning, a total of 24 steps and 54 potential FMs were identified. The use of separate measurement tools that are not machine-integrated has been identified as a cause for the higher number of steps and FMs generated from the conventional ATC approach. More than half of the quality control measures recommended for both acceptance and commissioning could potentially be incorporated by the manufacturer in the design of the Halcyon machine. Conclusion: This paper presents the results of Failure Modes and Effects Analysis and quality control measures to mitigate the failure modes for the acceptance testing and commissioning process for Halcyon machine. Unique FMs that result from the differences in the ATC guidelines provided by the vendor and current conventional protocols, and the challenges of performing the ATC due to the new linac features and ring-gantry design were highlighted for the first time. The FMs identified in the present work along with the suggested quality control measures, could potentially be used to improve the design features of future ring-gantry type of linacs that are likely to be pre-assembled, pre-configured, and heavily reliant on automation and image-guidance.
关键词： new ring-gantry linac,reference dosimetry,TG100,TG-51,Failure Modes and Effects Analysis (FMEA),Acceptance testing and Commissioning
更新于2025-09-23 15:23:52
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Neural network-based hybrid signal processing approach for resolving thin marine protective coating by terahertz pulsed imaging
摘要： A novel approach was presented to enhance the capability of resolving thin coating layers using terahertz pulsed imaging (TPI) based on a neural network-based hybrid signal procession method, which is of great significance for in-line painting applications. In the present work, Terahertz detected signals were obtained by numerical simulation using finite difference time domain (FDTD) method. Models of marine protective coatings with different coating structures were calculated and analyzed. Different signal pre-processing techniques, including Fourier deconvolution, Fast Fourier Transform and wavelet analysis, were employed on the terahertz signals respectively to obtain various signal features. The processed signal was subsequently adopted as the input vectors for a neural network (NN). The optimization procedure for determining the architecture of neural network was investigated and the evaluated results obtained by the different networks were compared. Furthermore, the predicted results of thinner coating layer obtained by multiple-regression analysis method and BP network prediction method respectively were compared. The analysis demonstrated that the best prediction performance was achieved by neural network technique combined with wavelet analysis. Therefore, the hybrid signal processing approach could be recommended for terahertz non-destructive testing applications of marine protective coating.
关键词： Terahertz pulsed imaging,Non-destructive testing,Neural network,Thin marine protective coating
更新于2025-09-23 15:23:52
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Magneto-optical imaging characteristics of weld defects under alternating and rotating magnetic field excitation
摘要： This paper mainly examines the characteristics of magneto-optical (MO) images of weld defects under alternating and rotating magnetic field excitation. Weld defects including surface and subsurface defects were subjected to magneto-optical imaging (MOI) nondestructive testing (NDT) experiments. The MO images of different weld defects under alternating magnetic field excitation and rotating magnetic field excitation have been compared to determine the best effect of nondestructive testing, and a cruciform welding seam was used to verify the detection effect of rotating magnetic field. Besides, the values of standard deviation and maximum difference have been determined to analyze the difference in the effects of two magnetic fields, and image processing methods were applied to extract defect information, such as histogram equalization. Experimental results show that the optimal excitation voltage and lift-off value of rotating magnetic field are 120 V and 20 mm, respectively; image histogram equalization can significantly improve the contrast of MO images, and there is a distinct difference in the detection effect of two magnetic fields. Under the same excitation conditions, the detection effect of rotating magnetic fields is always better than the effect of alternating magnetic fields, and rotating magnetic field excitation has obvious advantages in detecting multidirection and subsurface defects in that the detection depth can reach about 8 mm.
关键词： Magneto-optical imaging,Electromagnetic optics,Nondestructive testing,Rotating magnetic field
更新于2025-09-23 15:23:52
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AR aided Smart Sensing for In-line Condition Monitoring of IGBT Wafer
摘要： This paper describes an augmented reality (AR) aided smart sensing technique, for in-line condition monitoring of IGBT wafers. A series of signal processing algorithms are applied for enabling sensor intelligence. Based on electromagnetic infrared-visible-fusion (IVF), a supplementary palpable 3-D thermography layer is integrated with an IGBT wafer in real world environment. Before the IVF, independent component analysis (ICA) is implemented to identify defects in the wafer. The proposed AR aided smart sensing technique enhances user's perception and interaction between the industrial systems and the surrounding world. In contrast to conventional sensor techniques, it provides a non-destructive testing and evaluation (NDT&E) based high-throughput in-line condition monitoring method. The advantages of non-contact and time efficient of this smart sensing technique potentially bring huge benefit to yield management and production efficiency. AR aided smart sensing can improve the productivity, quality and reliability of power electronic materials and devices, as well as in other industrial applications.
关键词： Wafers,IGBT,Thermography,Non-destructive testing,Pulsed Eddy Current,Augmented Reality,Smart sensing
更新于2025-09-23 15:23:52
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[IEEE 2018 26th European Signal Processing Conference (EUSIPCO) - Rome (2018.9.3-2018.9.7)] 2018 26th European Signal Processing Conference (EUSIPCO) - Uncertainty Quantification in Imaging: When Convex Optimization Meets Bayesian Analysis
摘要： We propose to perform Bayesian uncertainty quantification via convex optimization tools (BUQO), in the context of high dimensional inverse problems. We quantify the uncertainty associated with particular structures appearing in the maximum a posteriori estimate, obtained from a log-concave Bayesian model. A hypothesis test is defined, where the null hypothesis represents the non-existence of the structure of interest in the true image. To determine if this null hypothesis is rejected, we use the data and prior knowledge. Computing such test in the context of imaging problem is often intractable due to the high dimensionality involved. In this work, we propose to leverage probability concentration phenomena and the underlying convex geometry to formulate the Bayesian hypothesis test as a convex minimization problem. This problem is subsequently solved using a proximal primal-dual algorithm. The proposed method is applied to astronomical radio-interferometric imaging.
关键词： astronomical imaging,proximal primal-dual algorithm,inverse problem,hypothesis testing,Bayesian uncertainty quantification
更新于2025-09-23 15:23:52