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Performance characteristics of the digital Biograph Vision PET/CT system
摘要： This study evaluates the performance of the Siemens Biograph Vision digital PET/CT system (Siemens Healthineers, Knoxville, USA) according to the NEMA NU 2‐2012 standard (published by the National Electrical Manufacturers Association (NEMA)) to allow for a reliable, reproducible, and inter‐system comparable performance measurement. Methods: The new digital PET/CT features silicon photomultiplier (SiPM)‐based detectors with 3.2 mm lutetium oxyorthosilicate (LSO) crystals and full coverage of the scintillator area. The PET components incorporate eight rings of 38 detector blocks and each block contains 4x2 mini‐blocks. Each mini‐block consists of a 5x5 LSO‐array of 3.2x3.2x20 mm crystals coupled to a SiPM‐array of 16x16 mm, resulting in an axial field of view (FOV) of 26.1 cm. In this study PET/CT system performance will be evaluated conform the NEMA NU 2‐2012 standard with additional measurements described in the new NEMA NU 2‐2018 standard. Spatial resolution, sensitivity, count‐rate performance, accuracy of attenuation and scatter correction, Time‐of‐Flight (TOF) performance, and image quality will be determined. Measurements will be directly compared to results from its predecessor, the Biograph mCT Flow, using existing literature. Moreover, feasibility to comply with the European Association of Nuclear Medicine (EANM) Research Ltd (EARL) criteria will be evaluated and some illustrative patient PET images will be shown. Results: The Biograph Vision shows a transverse (resp. axial) spatial resolution at Full Width Half Maximum (FWHM) of 3.6 mm (resp. 3.5 mm) at 1 cm offset of the center of the FOV (measured with a 22Na 0.25 mm point‐source), a NEMA sensitivity of 16.4 kcps/MBq, and a NEMA peak NECR of 306 kcps at 32 kBq/mL. TOF resolution varied from 210 to 215 as count‐rate increased up to the peak NECR. The overall image contrast seen with the NEMA image quality phantom ranged from 77.2% to 89.8%. Furthermore, the system was able to comply with the current and future EARL performance criteria. Conclusions: The Biograph Vision outperforms the analog Biograph mCT Flow and the system is able to meet European harmonizing performance standards.
关键词： PET/CT,Digital detectors,NEMA,performance evaluation
更新于2025-09-23 15:22:29
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Mass measurement of grasped object with tweezers employing bimorph piezoelectric actuators
摘要： This paper deals with tweezers for a mass detection during micromanipulation. It measures 52 mm×30 mm×10 mm and weighs 37 g. Each ?nger consists of a bimorph piezoelectric actuator with a stainless steel tip. One of the tweezers working as a vibrator was oscillated at its resonance frequency, and another working as a grasper opened and closed the gap between the tips of the bimorph piezoelectric actuators. The simulation model that represents the contact of two beams and a lumped mass as springs was described. The resonance frequency was increased when the tweezers grasped an object. The relationship between the mass of the object and frequency was obtained experimentally. Because the charge generated by the piezoelectric effect also affected the resonance frequency, the frequency change in the experiments was smaller than that in the simulation.
关键词： resonance frequency,mass evaluation,cantilever,Piezoelectric actuator,vibration
更新于2025-09-23 15:22:29
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A Comprehensive Evaluation of Approaches for Built-Up Area Extraction from Landsat OLI Images Using Massive Samples
摘要： Detailed information about built-up areas is valuable for mapping complex urban environments. Although a large number of classification algorithms for such areas have been developed, they are rarely tested from the perspective of feature engineering and feature learning. Therefore, we launched a unique investigation to provide a full test of the Operational Land Imager (OLI) imagery for 15-m resolution built-up area classification in 2015, in Beijing, China. Training a classifier requires many sample points, and we proposed a method based on the European Space Agency’s (ESA) 38-m global built-up area data of 2014, OpenStreetMap, and MOD13Q1-NDVI to achieve the rapid and automatic generation of a large number of sample points. Our aim was to examine the influence of a single pixel and image patch under traditional feature engineering and modern feature learning strategies. In feature engineering, we consider spectra, shape, and texture as the input features, and support vector machine (SVM), random forest (RF), and AdaBoost as the classification algorithms. In feature learning, the convolutional neural network (CNN) is used as the classification algorithm. In total, 26 built-up land cover maps were produced. The experimental results show the following: (1) The approaches based on feature learning are generally better than those based on feature engineering in terms of classification accuracy, and the performance of ensemble classifiers (e.g., RF) are comparable to that of CNN. Two-dimensional CNN and the 7-neighborhood RF have the highest classification accuracies at nearly 91%; (2) Overall, the classification effect and accuracy based on image patches are better than those based on single pixels. The features that can highlight the information of the target category (e.g., PanTex (texture-derived built-up presence index) and enhanced morphological building index (EMBI)) can help improve classification accuracy. The code and experimental results are available at https://github.com/zhangtao151820/CompareMethod.
关键词： classification,CNN,feature engineering,built-up area,Landsat 8-OLI,accuracy evaluation,feature learning
更新于2025-09-23 15:22:29
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Non-destructive defect evaluation of polymer composites via thermographic data analysis: A manifold learning method
摘要： Recently, various thermographic data analysis methods have been utilized in the field of non-destructive evaluation (NDE) to process thermal images and enhance the visibility of defects. However, most of them extract only linear features, leading to cumbersome results. In this work, manifold learning is introduced into the thermographic data analysis field. As a nonlinear dimensionality reduction technique, manifold learning can identify an intrinsically low-dimensional manifold in a high-dimensional data space. Specifically, an isometric feature mapping (ISOMAP) based manifold learning thermography (MLT) method is proposed to analyze the thermographic data, which can effectively distinguish the uneven background, noise, and defect characteristics contained in thermal images and make the defect detection easier. The feasibility of MLT is illustrated using a carbon fiber-reinforced polymer (CFRP) specimen. The results show that, comparing to the conventional linear methods, the present method can better determine the defect information, including the positions, sizes, and shapes.
关键词： Thermographic data analysis,Non-destructive evaluation,Manifold learning,Active infrared thermography,Carbon fiber-reinforced polymer
更新于2025-09-23 15:22:29
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Sparse Reconstruction-Based Thermal Imaging for Defect Detection
摘要： This paper proposes an idea of employing sparse reconstruction-based technique for thermal imaging defect detection. The implementation of the reconstruction technique is tested on a carbon fiber reinforced polymer test piece with artificially drilled defects and the test results are compared with the established cross correlation method. The two processes are compared in terms of defect detectability, their SNR variation with defect depth and their computation complexity. When compared with cross correlation algorithm, the technique is expected to solve memory space problems by compressing all information from large cross-correlated pulse video into a single reconstructed image as an output. Furthermore, in existing cross correlation methods, the pulse peak time shifts with defect depth. Hence, defect quantification algorithms, such as SNR calculation, require multiple frame analysis. Such algorithms are comparatively simplified in sparse reconstruction technique. This paper explores sparse reconstruction algorithm for resolving close-spaced defects. This paper further describes cross-validation method for optimization of a user parameter in sparse reconstruction method.
关键词： thermal nondestructive testing,sparse reconstruction,pulse compression,nondestructive evaluation and remote sensing,frequency modulated thermal wave imaging,Cross correlation algorithm
更新于2025-09-23 15:22:29
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[IEEE 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Athens, Greece (2018.7.4-2018.7.6)] 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Modeling Electromagnetic Wireless Nanonetworks in Terahertz Band within NS-3 Platform
摘要： The wireless nanosensor network paradigm has seen a dramatic increase over the last decade. The envisioned concept uses the integrated machines (devices) at the nano-scale level. Those devices interact on a cooperative basis by means of principles known in wireless communication networks. Today, the design of the protocol stack for wireless nanosensor networks represents the crucial issue to be addressed. Currently available tools only support molecular-based approaches without the ability to account for the relevant impact that electromagnetic communications may have in this field. To cover this white spot, in this paper, the theoretical comparison of available simulation tools is given. Further, we focus on the Nano-Sim tool and create the scenario for wireless sensor networks (WNSN) based on electromagnetic communication in terahertz band.
关键词： Nanonetworks,Network Simulator 3,Simulation tools,Performance evaluation,Molecular communication
更新于2025-09-23 15:22:29
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Experimental Study on the Cogeneration Performance of Roll-bond-PVT Heat Pump System with Single Stage Compression During Summer
摘要： Photovoltaic thermal (PVT) heat pump technology refers to the integration of photovoltaic and solar heat pump, representing the deep exploitation and utilization of solar energy. In this paper, roll-bond-PVT heat pump (RB-PVTHP) system with single stage compression is proposed and investigated experimentally. The roll-bond-PVT (RB-PVT) unit is introduced in detail which is combined with the photovoltaic module and single-sided roll-bond evaporation heat exchanger laminating together. The designed experimental system consists of 4 pieces of RB-PVT units, 1HP heat pump unit and 150L heat storage tank, which is also equipped with various monitoring sensors to explore the system operating characteristics. Then the performance evaluation method of the unit and system is proposed. The experimental investigation on the cogeneration performance of the system in northern China during summer is carried out simultaneously, in terms of the thermal efficiency, electrical efficiency, thermal-based overall efficiency of the unit and heating COP of the system. The operating characteristics monitoring results show that the system works in a long-term stable condition during the daytime with considerable cogeneration performance. The detailed performance parameters have been given in this paper. This study demonstrates that the RB-PVTHP system has the large-scale practically feasible application value in northern China.
关键词： Single-sided roll-bond evaporator,PVT,Cogeneration performance evaluation,Roll-bond-PVT heat pump
更新于2025-09-23 15:21:21
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Electrical characterization of HVPE GaN containing different concentrations of carbon dopants
摘要： A comprehensive study of the electrical characteristics in Schottky diodes made of GaN:C grown by HVPE technology has been reported. The Schottky junctions were made of Ni/Au (25/200 nm) metal stack and ohmic contacts were fabricated by the Ti/Al/Ni/Au (30/90/20/100 nm) e-beam deposition of the metal thin-films followed by the rapid thermal annealing. A good quality of the fabricated Schottky diodes has been proved by considering the transient shape using a pulsed technique of the barrier evaluation under linearly increasing voltage (BELIV). The concentrations of equilibrium carriers of 1×1011 cm-3 and of 2×1010 cm-3 have been evaluated for relatively low and high carbon density doped samples, respectively, using photo-capacitance characteristics dependent on excitation intensity. The effective mobility of carriers of μeff=610 cm2/Vs has been estimated by considering the serial resistance variations dependent on excitation density, through analysis of delay times appeared in formation of peaks within BELIV transients. The optical deep level transient spectroscopy has shown that thermal emission from the rather shallow centres prevails. The centres, ascribed to vacancies as well as to carbon on Ga site, have been identified. It has been demonstrated that Schottky junctions made of heavy carbon doped (NC≥1018 cm-3) HVPE GaN material are capable to withstand voltages of ≥300 V.
关键词： barrier evaluation by linearly increasing voltage pulsed technique,transient current technique,Schottky diodes,carbon doped HVPE GaN grown on Ammono substrates,deep level transient spectroscopy
更新于2025-09-23 15:21:21
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Effects of waveform parameters on the breakdown characteristics of OIP subjected to impulse voltages and evaluation method for waveform equivalence
摘要： The impulse voltage wave invading a transformer is not the double exponential impulse wave (DEIW) specified by the IEC but a non-standard waveform with oscillation attenuation characteristics, and this fact leads to doubts about the scientificity and optimality of insulation coordination. A key solution for this issue is the establishment of an equivalent relationship between the measured non-standard impulse voltage wave and the DEIW. In this study, a test platform of multiparameter impulse voltage was set up. Then, the authors obtained the 50% breakdown voltage (U50%) of the oil-impregnated paper (OIP) for transformer under the bipolar oscillatory attenuated impulse wave (BOAIW) and the DEIW with different waveform parameters. The effects of waveform parameters on the breakdown characteristics of the OIP were finally revealed. On the basis of experimental data and several mathematical methods, the authors established the U50% prediction mathematical models for the OIP under the BOAIW and DEIW. Based on the prediction models and the microfluctuation characteristics of measured overvoltage's waveform parameters, the authors proposed a method for evaluating the waveform equivalence. The characteristics of voltage amplitude and change rate were regarded as the two key factors for the waveform equivalence of this method.
关键词： evaluation method,breakdown characteristics,waveform equivalence,impulse voltage,oil-impregnated paper
更新于2025-09-23 15:21:21
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - The Window Size in Residential House Facades After the Current and New CEN Standard
摘要： Nowadays daylight apertures in buildings are designed on the bases of overcast sky conditions in wintertime in Slovakia and Czech Republic. The criterion is the relative value of the Daylight Factor in its average 0.9% in two reference points in the middle depth of the room. Commonly, in practice as a consequence are designed windows roughly 1.5 – 1.7 m high in living rooms. The proposed European standard FprEN17037 is introducing a new criterion median exterior horizontal illuminance with the required indoor illuminance 300 lx in the middle of the room depth or 100 lx as minimum close to the rear wall. This study discusses problems of the design of window size in residential buildings and consequences of the new median criterion as well as the required interior illuminance in absolute lux values.
关键词： daylighting evaluation,daylighting,daylight availability,standardization of daylighting
更新于2025-09-23 15:21:21