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Metrology Data-Based Simulation of Freeform Optics
摘要： This paper describes the approach to use measurement data to enhance the simulation model for designing freeform optics. Design for manufacturing of freeform optics is still challenging, since the classical tolerancing procedures cannot be applied. In the case of spherical optics manufacturing, tolerances are more or less isotropic, and this relationship is lost in case of freeform surfaces. Hence, an accurate performance prediction of the manufactured optics cannot be made. To make the modeling approach as accurate as possible, integration of measured surface data of fabricated freeform optics in the modeling environment is proposed. This approach enables performance prediction of the real manufactured freeform surfaces as well as optimization of the manufacturing process. In our case study this approach is used on the design of an Alvarez-optics manufactured using a microinjection molding (μIM) process. The parameters of the μIM process are optimized on the basis of simulation analysis resulting in optics, with a performance very close to the nominal design. Measurement of the freeform surfaces is conducted using a tactile surface measurement tool.
关键词： systems design,simulation,form measurements,3D measurements
更新于2025-09-09 09:28:46
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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Deep residual learning in CT physics: scatter correction for spectral CT
摘要： Recently, spectral CT has been drawing a lot of attention in a variety of clinical applications primarily due to its capability of providing quantitative information about material properties. The quantitative integrity of the reconstructed data depends on the accuracy of the data corrections applied to the measurements. Scatter correction is a particularly sensitive correction in spectral CT as it depends on system effects as well as the object being imaged and any residual scatter is amplified during the non-linear material decomposition. An accurate way of removing scatter is subtracting the scatter estimated by Monte Carlo simulation. However, to get sufficiently good scatter estimates, extremely large numbers of photons are required, which may lead to unexpectedly high computational costs. Other approaches model scatter as a convolution operation using kernels derived using empirical methods. These techniques have been found to be insufficient in spectral CT due to their inability to sufficiently capture object dependence. In this work, we develop a deep residual learning framework to address both issues of computation simplicity and object dependency. A deep convolution neural network is trained to determine the scatter distribution from the projection content in training sets. In test cases of a digital anthropomorphic phantom and real water phantom, we demonstrate that with much lower computing costs, the proposed network provides sufficiently accurate scatter estimation.
关键词： convolutional neural network,deep residual learning,Monte Carlo simulation,scatter correction,spectral CT
更新于2025-09-09 09:28:46
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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Deep Learning Models for PET Scatter Estimations
摘要： Projection data acquired from a positron emission tomography (PET) scanner consist of true, scattered and random events. Scattered events can cause severe artifacts and quantitation errors in reconstructed PET images unless corrected for properly. A scatter correction algorithm is required to predict scattered events from the measurement. Scatter correction requires estimation of both single scatter and multiple scatter profiles. Usually, single scatter profiles are calculated by model-based simulation and multiple scatter profiles are estimated by a kernel-based convolution method. However, design of the convolution kernels for multiple scatter estimation is sophisticated and requires fine parameter tuning. In this work, we adopt deep learning techniques for scatter estimation. We propose two convolutional neural networks. The first network estimates multiple scatter profiles from single scatter profiles, replacing the kernel-based convolution method. The second network is designed to predict the total scatter profiles (including single and multiple scatters) directly from the input of emission and attenuation sinograms. Initial results from both networks show a promise with the potential for more accurate and faster scatter correction for PET.
关键词： Monte Carlo Simulation,Deep Learning,Scatter Estimation,Convolutional Neural Networks,PET
更新于2025-09-09 09:28:46
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Aerosol synthesis of germanium nanoparticles supported by external seeding: Theoretical and experimental analysis
摘要： In this work we present a detailed study of the effect of heterogeneous nucleation on the formation of germanium nanoparticles (Ge NPs) produced from monogermane (GeH4) in a hot wall reactor gas phase synthesis. As external seeding unit we use a hot wire generator (HWG) which produces a stable concentration of aerosol particles. The particle concentration and size of the seeds is easily controllable via the applied voltage and used metal. We demonstrate the importance of seed particles for the production of narrowly distributed Ge NPs with geometrical standard deviations (GSD) < 1.1 in our setup. Thereby, molybdenum and tungsten as wire metal show the best seeding results. The size of the final Ge NPs can be precisely controlled in the range of 20 to 60 nm. The expansion of Ge lattice seen in XRD and tiny amount of Mo probed by high-resolution STEM-EDXS analysis indicate that the Mo seed particles are most likely dissolved and incorporated in the Ge lattice during growth. Furthermore, we demonstrate an approach to investigate the effect of heterogeneous nucleation on the particle formation by population balance modeling. The results are in good agreement with experimental data. The seed concentration is the key parameter and has a major influence on the nucleation rate.
关键词： Germanium,Nanoparticles,Simulation,Hot wire generator,Gas phase synthesis,Heterogeneous nucleation
更新于2025-09-09 09:28:46
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Entanglement Reduction Induced by Geometrical Confinement in Polymer Thin Films
摘要： We report simulation results on melts of entangled linear polymers confined in a free-standing thin film. We study how the geometric constraints imposed by the confinement alter the entanglement state of the system compared to the equivalent bulk system using various observables. We find that the confinement compresses the chain conformation uniaxially, decreasing the volume pervaded by the chain, which in turn reduces the number of the accessible interchain contact that could lead to entanglements. This local and nonuniform effect depends on the position of the chain within the film. We also test a recently presented theory that predicts how the number of entanglements decreases with geometrical confinement.
关键词： simulation,polymer thin films,primitive path,geometrical confinement,entanglement
更新于2025-09-09 09:28:46
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Extracting the turbulent flow-field from beam emission spectroscopy images using velocimetry
摘要： The 2D turbulent E × B flow-field is inferred from density fluctuation images obtained with the beam emission spectroscopy diagnostic on DIII-D using the orthogonal dynamic programming velocimetry algorithm. A synthetic turbulence model is used to test the algorithm and optimize it for measuring zonal flows. Zonal flow measurements are found to require a signal-to-noise ratio above ～10 and a zonal flow wavelength longer than ～2 cm. Comparison between the velocimetry-estimated flow-field and the E × B flow-field using a nonlinear gyrokinetic GENE simulation finds that the flow-fields have identical spatial structure and differ only by the mean turbulence phase velocity, which is spatially uniform in this flux tube simulation.
关键词： beam emission spectroscopy,turbulent flow-field,zonal flows,velocimetry,GENE simulation
更新于2025-09-09 09:28:46
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Preparation of Tin Dioxide Nanoparticles by the Reverse Micelle Method: Experiment and Preliminary Calculations
摘要： Synthetic and computational experiments were carried out to study the influence of the nature and structure of surfactants, and also of the reaction medium on the size of tin dioxide nanoparticles obtained by the reverse micelle method.
关键词： tin dioxide,microemulsions,nanoparticles,molecular-thermodynamic simulation,synthesis in inverted micelles
更新于2025-09-09 09:28:46
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Experimental investigation and CFD analysis of a solar hybrid PV/T system for the sustainable development of the rural northern part of Bangladesh
摘要： An attempt has been made to utilise solar energy more e?ciently by developing the single pass hybrid photovoltaic thermal system at the climatic condition of Bangladesh. As the electric energy conversion e?ciency of the photovoltaic module falls with the surrounding temperature and air or water used as a suitable solution to make it cool. In this study, air was used as the cooling medium for the solar panel and circular copper tube was placed on the glazed collector for water heating to ensure maximum exploitation of solar energy. Moreover, the photovoltaic panel power was used to circulate the air and make the system self-powered. Maximum collector e?ciency was 24.64% for water and 11.20% for air is observed at a mass ?ow rate 0.00158 and 0.00221 kg/s for water and air respectively at a solar radiation of 1050 W/m2. In addition, the combined e?ciency of the hybrid system was about 39.68%. By adding glycerin with water at a ratio of 50:1 (% of weight) the combined e?ciency reached up to 45.76%. The computational ?uid dynamics (CFD) simulation and economic analysis of the designed system strongly support the feasibility of the solar hybrid photovoltaic thermal system as the future sustainable energy source.
关键词： CFD simulation,Solar energy,feasibility analysis,hybrid PV/T
更新于2025-09-09 09:28:46
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NOVEL TRANSFORMATION TO DESIGN TRI-BAND FILTERS
摘要： This paper introduces novel derived transformation equations to design Tri-band ?lters. The design utilizes the approach adopted for tri-band bandpass ?lter design based on asymmetric half-wavelength resonator. The obtained optimized ?lter by this approach is used as a reference, and the proposed transformation is applied to calculate the new ?lter design hardware parameters that satisfy its given speci?cations. The reference tri-band ?lter is designed to have: insertion better than 1.3 dB and return loss less than ?10 dB at the resonance frequencies 1.4 GHz, 4 GHz and 5.6 GHz for L-Band DAB, Radar (G-band) and Radar (C-band) applications, respectively. To verify the transformation technique two tri-band ?lters are designed. The ?rst tri-band ?lter is for WVL, WiMAX and WiLAN while the second tri-band ?lter is for UMTS, WiLAN and X-band Satellite applications. The momentum simulations for these ?lters show that the resulting ?lters speci?cations are: the insertion loss is better than 1.3 dB and the return loss is less than ?10 dB at the resonance frequencies 1.3 GHz, 3.6 and 5.7 GHz for the ?rst one. While the insertion loss is better than 1.4 dB and the return loss is less than ?10 dB at the resonance frequencies 1.9 GHz, 5.35 GHz and 8.25 GHz for the second ?lter, respectively. A set of prototype of the ?nal design of the proposed ?lters with optimal parameters was fabricated for experimental veri?cation. The RT 5880 substrate is utilized in this design All the results are obtained using circuit and momentum simulation of the Agilent Design Simulator (ADS) package and the performance characteristics have been measured using the Rohde & Schwarz ZVB20 vector 4 port network analyzer. Analysis and comparison of the obtained results show that all the simulated and the measured results agree well.
关键词： asymmetric half-wavelength resonator,transformation technique,Tri-band ?lters,momentum simulation
更新于2025-09-09 09:28:46
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Optical admittance method for light-matter interaction in lossy planar resonators
摘要： Advanced optoelectronic simulation models are needed to study and optimize emerging photonic devices such as thin-film solar cells, lasers, and light-emitting diodes (LEDs). In particular, better tools are required for self-consistent modeling of coupled electrical and optical systems. The recently introduced quantized fluctuational electrodynamics (QFED) and the associated interference-exact radiative transfer equations have been developed for this purpose, but their use is in part complicated by the need to calculate the full dyadic Green’s functions. To make QFED and the underlying physical quantities more accessible for new device studies, we introduce a directly usable method where Green’s functions are obtained through optical admittances. The optical admittances can be solved analytically for piecewise-homogeneous layer structures and selected graded-index profiles, and numerically for arbitrary position-dependent refractive index profiles using well-known techniques. The solutions enable direct construction of the dyadic Green’s functions and all the related optical quantities. To give examples of the general applicability of the method, we calculate the local and nonlocal optical densities of states for selected devices, including GaN-based flip-chip LEDs and vertical-cavity surface-emitting lasers. Using only the rather simple framework presented in this paper, one can analyze energy transport in a wide range of planar photonic devices accurately without additional difficulties or inputs from external solvers.
关键词： dyadic Green’s functions,quantized fluctuational electrodynamics,GaN-based flip-chip LEDs,optoelectronic simulation models,photonic devices,optical admittances,vertical-cavity surface-emitting lasers
更新于2025-09-09 09:28:46