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5G Millimeter Wave Channel Sounders, Measurements, and Models: Recent Developments and Future Challenges
摘要： Millimeter wave (mmWave) communication is a key technology for fifth generation (5G) wireless communication systems due to its tremendous bandwidth available to support high data rate transmission. This article investigates the recent developments and future challenges in 5G mmWave channel sounders, measurements, and models. Various channel sounders are comprehensively classified and compared. Channel measurements in diverse indoor and outdoor scenarios for different mmWave bands are surveyed. Meanwhile, a comparison of multiple mmWave bands, validation of mmWave massive multiple-input multiple-output (MIMO) channel properties, and measurement and modeling of human blockage effects are shown. Different channel modeling approaches including deterministic, semi-deterministic, and stochastic modeling methods are summarized. Some future research directions are also given.
关键词： 5G,measurements,channel sounders,mmWave,models
更新于2025-09-09 09:28:46
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Comparison of Artificial Intelligence and Physical Models for Forecasting Photosynthetically-Active Radiation
摘要： Different kinds of radiative transfer models, including a relative sunshine-based model (BBM), a physical-based model for tropical environment (PBM), an efficient physical-based model (EPP), a look-up-table-based model (LUT), and six artificial intelligence models (AI) were introduced for modeling the daily photosynthetically-active radiation (PAR, solar radiation at 400–700 nm), using ground observations at twenty-nine stations, in different climatic zones and terrain features, over mainland China. The climate and terrain effects on the PAR estimates from the different PAR models have been quantitatively analyzed. The results showed that the Genetic model had overwhelmingly higher accuracy than the other models, with the lowest root mean square error (RMSE = 0.5 MJ m?2day?1), lowest mean absolute bias error (MAE = 0.326 MJ m?2day?1), and highest correlation coefficient (R = 0.972), respectively. The spatial–temporal variations of the annual mean PAR (APAR), in the different climate zones and terrains over mainland China, were further investigated, using the Genetic model; the PAR values in China were generally higher in summer than those in the other seasons. The Qinghai Tibetan Plateau had always been the area with the highest APAR (8.668 MJ m?2day?1), and the Sichuan Basin had always been the area with lowest APAR (4.733 MJ m?2day?1). The PAR datasets generated by the Genetic model, in this study, could be used in numerous PAR applications, with high accuracy.
关键词： photosynthetically-active radiation,climate zones,physical models,artificial neural network,terrain features
更新于2025-09-09 09:28:46
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Ocean Wind Retrieval Models for RADARSAT Constellation Mission Compact Polarimetry SAR
摘要： We propose two new ocean wind retrieval models for right circular-vertical (RV) and right circular-horizontal (RH) polarizations respectively from the compact-polarimetry (CP) mode of the RADARSAT Constellation Mission (RCM), which is scheduled to be launched in 2019. For compact RV-polarization (right circular transmit and vertical receive), we build the wind retrieval model (denoted CoVe-Pol model) by employing the geophysical model function (GMF) framework and a sensitivity analysis. For compact RH polarization (right circular transmit and horizontal receive), we build the wind retrieval model (denoted the CoHo-Pol model) by using a quadratic function to describe the relationship between wind speed and RH-polarized normalized radar cross-sections (NRCSs) along with radar incidence angles. The parameters of the two retrieval models are derived from a database including wind vectors measured by in situ National Data Buoy Center (NDBC) buoys and simulated RV- and RH-polarized NRCSs and incidence angles. The RV- and RH-polarized NRCSs are generated by a RCM simulator using C-band RADARSAT-2 quad-polarized synthetic aperture radar (SAR) images. Our results show that the two new RCM CP models, CoVe-Pol and CoHo-POL, can provide efficient methodologies for wind retrieval.
关键词： CoVe-Pol and CoHo-Pol models,compact polarization (CP),RADARSAT Constellation Mission (RCM),right circular horizontal polarization model,right circular vertical polarization model,wind retrieval,geophysical model function (GMF)
更新于2025-09-09 09:28:46
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Mouse Idh3a mutations cause retinal degeneration and reduced mitochondrial function
摘要： Isocitrate dehydrogenase (IDH) is an enzyme required for the production of α-ketoglutarate from isocitrate. IDH3 generates the NADH used in the mitochondria for ATP production, and is a tetramer made up of two α, a β and a γ subunit. Loss of function and missense mutations in both IDH3A andIDH3B have previously been implicated in families exhibiting retinal degeneration. Using mouse models we have investigated the role of IDH3 in retinal disease and mitochondrial function. We identified mice with late-onset retinal degeneration in a screen of ageing mice carrying an ENU-induced mutation, E229K, in Idh3a. Mice homozygous for this mutation exhibit signs of retinal stress, indicated by GFAP staining, as early as 3 months, but no other tissues appear to be affected. We produced a knockout of Idh3a and found that homozygous mice do not survive past early embryogenesis. Idh3a-/E229K compound heterozygous mutants exhibit a more severe retinal degeneration when compared to Idh3aE229K/E229K. Analysis of mitochondrial function in mutant cell lines highlighted a reduction in mitochondrial maximal respiration and reserve capacity levels in both Idh3aE229K/E229K and Idh3a-/E229K cells. Loss-of function Idh3b mutants do not exhibit the same retinal degeneration phenotype, with no signs of retinal stress or reduction in mitochondrial respiration. It has been previously reported that the retina operates with a limited mitochondrial reserve capacity and we suggest that this, in combination with the reduced reserve capacity in mutants, explains the degenerative phenotype observed in Idh3a mutant mice.
关键词： Isocitrate dehydrogenase,retinal degeneration,mouse models,mitochondrial function,IDH3
更新于2025-09-09 09:28:46
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Determining the Shortwave Radiative Flux From Earth Polychromatic Imaging Camera
摘要： The Earth Polychromatic Imaging Camera (EPIC) onboard Deep Space Climate Observatory provides 10 narrowband spectral images of the sunlit side of the Earth. The blue (443 nm), green (551 nm), and red (680 nm) channels are used to derive EPIC broadband radiances based upon narrowband-to-broadband regressions developed using collocated MODIS equivalent channels and Clouds and the Earth’s Radiant Energy System (CERES) broadband measurements. The pixel-level EPIC broadband radiances are averaged to provide global daytime means at all applicable EPIC times. They are converted to global daytime mean shortwave (SW) ?uxes by accounting for the anisotropy characteristics using a cloud property composite based on lower Earth orbiting satellite imager retrievals and the CERES angular distribution models (ADMs). Global daytime mean SW ?uxes show strong diurnal variations with daily maximum-minimum di?erences as great as 20 W/m2 depending on the conditions of the sunlit portion of the Earth. The EPIC SW ?uxes are compared against the CERES SYN1deg hourly SW ?uxes. The global monthly mean di?erences (EPIC-SYN) between them range from 0.1 W/m2 in July to ?4.1 W/m2 in January, and the RMS errors range from 3.2 to 5.2 W/m2. Daily mean EPIC and SYN ?uxes calculated using concurrent hours agree with each other to within 2% and both show a strong annual cycle. The SW ?ux agreement is within the calibration and algorithm uncertainties, which indicates that the method developed to calculate the global anisotropic factors from the CERES ADMs is robust and that the CERES ADMs accurately account for the Earth’s anisotropy in the near-backscatter direction.
关键词： angular distribution models,anisotropy,EPIC,shortwave radiative flux,CERES
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
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[IEEE 2018 IEEE 20th International Conference on e-Health Networking, Applications and Services (Healthcom) - Ostrava (2018.9.17-2018.9.20)] 2018 IEEE 20th International Conference on e-Health Networking, Applications and Services (Healthcom) - Supervised Level Sets For Dermoscopic Image Segmentation
摘要： In this paper, we propose a novel segmentation method that has been used for segmenting lesions in dermoscopy images. This method uses the variational level sets formulation with a novel area term based on supervised learning that results in the global optimization of a cost function, that can potentially result in a robust segmentation of the images. This term uses a mixture of Gaussians that are trained from a set of training images, and evolves an active contour such that the difference between the learned models and the empirical distributions obtained from the evolving curve for both the lesion and the skin are minimized. In the end, our approach is validated on the publicly available PH2 dermoscopy imaging dataset and the results show that the proposed method outperforms the other state-of-the-art methods that have been considered in this paper.
关键词： Gaussian mixture models,Variational level sets,Segmentation,Skin cancer,Dermoscopy
更新于2025-09-09 09:28:46
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A dynamic model for solar radiation in the Tyrrhenian Basin of Central Mediterranean area
摘要： Studying the level of solar radiation is important for problems related to both environmental pollution and alternative energy development. In this work a space-time model for solar radiation in the Tyrrhenian basin is presented. Three main features of the model must be stressed because of their importance in modelling space-time variability of a phenomenon. The first and most important one is that relations between solar radiation in different sites are an outcome of the model’s estimation procedure. With this approach spatial weights are not bound to be symmetrical and proportional to distance between locations or to be constant over time. The second one is the presence of a simultaneous effect among locations as the solar radiation in one of them is a function of what simultaneously happens in all the other ones. The third main feature of the model is represented by constrained estimation on the basis of a priori knowledge about the phenomenon that allows to cope the problem of the increased number of parameters.
关键词： solar radiation,constrained maximum likelihood estimator.,simultaneous effect,space-time models
更新于2025-09-09 09:28:46
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Diagnosis of undesired scenarios in hydrogen production by photo-fermentation
摘要： This study presents the use of a machine learning method from the artificial intelligence area, such as the support vector machines, applied to the construction of data-based classification models for diagnosing undesired scenarios in the hydrogen production process by photo-fermentation, which was carried out by an immobilized photo-bacteria consortium. The diagnosis models were constructed with data obtained from simulations run with a mechanistic model of the process and assessed on both modelled and experimental batches. The results revealed a 100% diagnosis performance in those batches where light intensity was below and above an optimum operation range. Nevertheless, 55% diagnosis performance was obtained in modelled batches where pH was away from its optimum operation range, showing that diagnosis model predictions during the first observations of those batches were classified as normal operation and revealing diagnosis delay in pH oscillations. In general, results demonstrate the reliability of classification models to be used in future applications such as the on-line process monitoring to detect and diagnose undesired operating conditions and take corrective actions on time to maintain high hydrogen productivities.
关键词： hydrogen production,photo-fermentation process,mechanistic model,undesired scenarios,diagnosis models,supervised learning methods
更新于2025-09-09 09:28:46
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Lithography-induced hydrophobic surfaces of silicon wafers with excellent anisotropic wetting properties
摘要： In recent years, hydrophobic surfaces have attracted more and more attentions from many researchers. In this paper, we comprehensively discussed the effects of specific parameters of microstructures on the wetting properties by using the theoretical models, the effects of microstructures on two-dimensional anisotropic properties and the water droplet impact experiment. Firstly, the relationships between the CAs and variable parameters were explored after the formula derivation for three various patterns. Then three different patterns were fabricated successfully on the silicon wafers by lithography technology and the effects of microstructures (including LWD parameters and interval parameters) on surface wettability were studied based on the theoretical research. After that, the effects of microstructures on two-dimensional anisotropic properties were also studied. Finally, the water droplet impact experiment was carried out and the viscoelastic properties were simply investigated. Our research proposed a potential method for fabricating hydrophobic surfaces with excellent anisotropic properties. This method may be widely used in a variety of academic and industrial applications in the future.
关键词： lithography technology,theoretical models,anisotropic wetting,silicon wafers,hydrophobic surfaces
更新于2025-09-09 09:28:46