- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Benchmarking of Laser Powder Bed Fusion Machines
摘要： This paper presents the methodology and results of an extensive benchmarking of laser powder bed fusion (LPBF) machines conducted across five top machine producers and two end users. The objective was to understand the influence of the individual machine on the final quality of predesigned specimens, given a specific material and from multiple perspectives, in order to assess the current capabilities and limitations of the technology and compare them with the capabilities of an 11-year-old machine belonging to one of the end users participating in this investigation. The collected results give a clear representation of the status of LPBF technology considering its maturity in terms of process capabilities and potential applications in a production environment.
关键词： laser powder bed fusion,technology evaluation,benchmarking,additive manufacturing,repeatability,selective laser melting,accuracy
更新于2025-09-16 10:30:52
-
Digital Magnetic Compass Integration with Stationary, Land-Based Electro-Optical Multi-Sensor Surveillance System
摘要： Multi-sensor imaging systems using the global navigation satellite system (GNSS) and digital magnetic compass (DMC) for geo-referencing have an important role and wide application in long-range surveillance systems. To achieve the required system heading accuracy, the specific magnetic compass calibration and compensation procedures, which highly depend on the application conditions, should be applied. The DMC compensation technique suitable for the operation environment is described and different technical solutions are studied. The application of the swinging procedure was shown as a good solution for DMC compensation in a given application. The selected DMC was built into a system to be experimentally evaluated, both under laboratory and field conditions. The implementation of the compensation procedure and magnetic sensor integration in systems is described. The heading accuracy measurement results show that DMC could be successfully integrated and used in long-range surveillance systems providing required geo-referencing data.
关键词： soft iron compensation,compass integration,swinging method,electro-optical surveillance system,hard iron compensation,measurement accuracy,magnetic heading angle,digital magnetic compass
更新于2025-09-16 10:30:52
-
Manufacturing of a parabolic trough concentrating collector test rig and a “LASER-Screen” technique for measuring actual focal length and light interceptance of the collector
摘要： A portable parabolic trough-concentrating solar collector test rig was designed, and fabricated using locally available materials and technique. A trough made of any materials and the energy collection element of any geometry with maximum aperture area of 80×100cm2 and 2.5×100cm2 respectively can be fitted readily in the support structure of the rig. A two-axis manual tracking system allows the rig to track the sun daily from east to west for every 5° interval, and seasonally from 50°North to 80°South for every 15°. In addition to this, actual focal length and light interceptance were investigated applying customised “LASER-Screen” technique. An average light interceptance of the rig for a 2.5 cm diameter absorber tube was measured to be 85.9%. The focal length of the 100 cm long test rig was found to be 18.167±1.35cm. The test rig will facilitate to investigate the energy potential in Chittagong region of Bangladesh.
关键词： parabolic profile accuracy,concentrating solar power,slope error measurement,LASER-Screen technique,Parabolic trough concentrating collector
更新于2025-09-12 10:27:22
-
Selection of spectrum model in estimation of Brillouin frequency shift for distributed optical fiber sensor
摘要： To improve real-time performance in distributed optical ?ber sensor, the in?uence of Brillouin spectrum models on performance in estimation of Brillouin frequency shift (BFS) is systematically investigated. First, the related Brillouin spectrum models, objective functions, optimization algorithms and convergence criterion in estimation of BFS are introduced. The BFS estimation algorithms based on the Lorentzian, Gaussian, pseudo-Voigt and Voigt models are written in MATLAB. The algorithms are used to estimate BFS for numerically generated Brillouin spectra with di?erent values of SNR (Signal to Noise Ratio) and measured Brillouin spectra with di?erent values of pulse width and average time. The results reveal that regardless of the simpli?ed Lorentzian and Gaussian models or more accurate pseudo-Voigt and Voigt model-based algorithms used, the estimated BFS between di?erent algorithms is quite similar. However, the ?tting error of the simpli?ed model-based algorithms is larger than that of the more accurate model-based algorithms especially for the cases with high value of SNR. The computational burden of the former is less than that of the latter. The Voigt model-based algorithm requires the most computational e?ort. If the nonlinear least-square ?t method is used, the selection of spectrum model has no big in?uence on the accuracy in the estimated BFS. Therefore, the algorithm based on simpli?ed Lorentzian and Gaussian models should be selected in BFS estimation. Thus, not only high accuracy in BFS estimation is ensured, but also the computation time can, at best, decrease to one-tenth of the maximum value.
关键词： Spectrum model,Accuracy,Computation time,Brillouin frequency shift,Distributed optical ?ber sensing
更新于2025-09-12 10:27:22
-
Pancreatic Cysts: Diagnostic Role of EUS-Guided Microforceps Biopsy and Confocal Laser Endomicroscopy
摘要： Frequent use of high-quality cross-sectional imaging has led to a significant rise in diagnosis of pancreatic cystic lesions (PCLs). Despite the fact that enormous effort has been put into the research of PCLs within the last two decades and multiple guidelines have been developed, our clinical decision-making especially in regard to mucinous lesions remains limited. Currently, clinical assessment, cross-sectional imaging and EUS with fluid analysis (if appropriate) belong to the standard care in patients with PCLs. For differentiation of mucinous from nonmucinous cysts, the sensitivity of cytological investigation and CEA in the cyst fluid is 42% and 52-79%, respectively. Due to the limited accuracy, further diagnostic tools are warranted. Two EUS-guided approaches have been introduced recently. Through-the-(19-gauge EUS) needle Moray microforceps have been developed, and several studies have acknowledged their contribution to the correct diagnosis as they help to overcome limited cellularity of the EUS-guided cyst fluid aspiration and traditional cytology. Confocal laser endomicroscopy offers real-time images and seems to be a promising method for the diagnosis and differential diagnosis of pancreatic PCLs. Example images of the needle-based confocal laser endomicroscopy criteria for the diagnosis of PCLs have been suggested recently. Before both, Moray microforceps and confocal laser endomicroscopy can be widely accepted, further studies are necessary to determine the real diagnostic yield and the clinical efficacy.
关键词： diagnostic accuracy,EUS-guided microforceps biopsy,mucinous lesions,confocal laser endomicroscopy,pancreatic cystic lesions
更新于2025-09-12 10:27:22
-
Diagnostic accuracy of laser Doppler imaging for the assessment of burn depth: a meta-analysis and systematic review
摘要： An overall assessment of the diagnostic value of laser Doppler imaging (LDI) to assess burn depth in patients is presented based on relevant studies. Both eligible research and relevant articles were identified through specific index searches of Embase, Cochrane and PubMed databases. The latest study included was published in March 2019 and all eligible publications reported on cohort or cross-sectional research. All articles were tested for heterogeneity by using a suitable effect model to calculate amalgamative values of sensitivity, specificity and the diagnostic odds ratio (DOR). Analyses of summary receiver operating characteristic (SROC) are given for burn depth values. After rigorous screening, 14 studies with a total cohort of 1,818 patients were chosen for the meta-analysis to explore the validity of LDI diagnosis to assess the depth of burns. The burn depth overall sensitivity for LDI was 91% (95% CI: 86-95%) and global specificity was 96% (95% CI: 92-98%). The overall positive likelihood ratio of LDI was 20.35 (95% CI: 10.71-38.69) and the overall negative likelihood ratio was 0.09 (95% CI: 0.05-0.15). The overall DOR was 152.93 (95% CI: 69.44-336.81) of LDI. The acreage under the SROC was not low for LDI (AUC = 0.98; 95% CI: 0.96-0.99). In conclusion, the present analysis reviewed the literature and meta-analysis of studies to validate LDI for the diagnosis of burn depth. The results indicated that LDI has a high accuracy for this diagnostic function.
关键词： diagnostic accuracy,burn depth,meta-analysis,laser Doppler imaging (LDI)
更新于2025-09-12 10:27:22
-
Statistical Detection Theory Approach to Hyperspectral Image Classification
摘要： This paper presents a statistical detection theory approach to hyperspectral image (HSI) classification which is quite different from many conventional approaches reported in the HSI classification literature. It translates a multi-target detection problem into a multi-class classification problem so that the well-established statistical detection theory can be readily applicable to solving classification problems. In particular, two types of classification, a priori classification and a posteriori classification, are developed in corresponding to Bayes detection and maximum a posteriori (MAP) detection, respectively, in detection theory. As a result, detection probability and false alarm probability can also be translated to classification rate and false classification rate derived from a confusion classification matrix used for classification. To evaluate the effectiveness of a posteriori classification, a new a posteriori classification measure, to be called precision rate (PR), is also introduced by MAP classification in contrast to overall accuracy (OA) that can be considered as a priori classification measure and has been used for Bayes classification. The experimental results provide evidence that a priori classifier as Bayes classifier which performs well in terms of OA does not necessarily perform well as a posteriori classifier in terms of PR. That is, PR is the only criterion that can be used as a posteriori classification measure to evaluate how well a classifier performs.
关键词： precision rate (PR),hyperspectral image (HSI) classification,average accuracy (AA),A posteriori classification,overall accuracy (OA),a priori classification
更新于2025-09-11 14:15:04
-
Reply to comment on “Important notes on parameter estimation of solar photovoltaic cell”, by Gnetchejo et al. [Energy Conversion and Management, https://doi.org/10.1016/j.enconman.2019.111870.]
摘要： This study aims to provide a response on the comment done by Dalia et al. on the paper “Important notes on parameter estimation of solar photovoltaic cell”, proposed by Gnetchejo et al. [1] where we have reported the inaccuracy occurred in PV parameter estimation.
关键词： Accuracy,General Algebraic Modeling System,Photovoltaic parameters
更新于2025-09-11 14:15:04
-
Analysis of Laser Ranges and Angular Measurements Data Fusion for Space Debris Orbit Determination
摘要： In the framework of space debris, the orbit determination process is a fundamental step, both, for researchers and for satellite operators. The accurate knowledge of the orbit of space debris objects is needed to allow space debris characterization studies and to avoid unnecessary collision avoidance maneuvers. The accuracy of the results of an orbit determination process depends on several factors as the number, the accuracy, the kind of processed measurements, their distribution along the orbit, and the object-observer relative geometry. When the observation coverage of the target orbit is not homogeneous, the accuracy of the orbit determination can be improved processing di?erent kind of observables. Recent studies showed that the satellite laser ranging technique can be successfully applied to space debris. In this paper, we will investigate the bene?ts of using laser ranges and angular measurements for the orbit determination process. We will analyze the in?uence of the number of used observations, of the covered arc of orbit, of each observable, and of the observation geometry on the estimated parameters. Finally, using data acquired on short observation arcs, we analyze the achievable accuracies for the orbital regimes with the highest space debris density, and to the consequences of the data fusion on catalog maintenance operations. The results shown are obtained using only real data (both angular and laser measurements) provided by sensors of the Swiss Optical Ground Station and Geodynamics Observatory Zimmerwald owned by the Astronomical Institute of the University of Bern (AIUB) and for some studies also using ranges provided from other stations of the International Laser Ranging Service (ILRS).
关键词： orbit determination,real range measurements,data fusion,real angular measurements,accuracy improvements,space debris
更新于2025-09-11 14:15:04
-
3D laser scanning and close-range photogrammetry for buildings documentation: A hybrid technique towards a better accuracy
摘要： This paper presents a study of 3D digital documentation techniques for the mosque of kafrelsheikh University campus namely: Close Range Photogrammetry as a digital smart point cloud mesh production in comparison with laser scanning as an attempt to achieve a hybrid formulation as an improved technique for execute more accurate 3d features documentation, also CRP as measuring technique in comparison with the traditional technique which is total station. The total station was used to survey the geometry properties of the building surface which considered as a base in this study, in computational methods and operation ?elds have been illustrated in the manuscript. The hybrid technique showed the optimum achieved accuracy for 3D digital documentation which has been established based on measuring scanned values, for example the enhancement obtained in accuracy reached its submit in hybrid technique by (80.1, 66.4, and 84.2)% when surveying features point coordinates, lines, and angles, respectively based on a comparative study, the hybrid technique is recommended for surveying instead of traditional ones.
关键词： Accuracy,Total station,Photogrammetry,Documentation,Laser scanner,Surveying
更新于2025-09-11 14:15:04