- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2019 49th European Microwave Conference (EuMC) - Paris, France (2019.10.1-2019.10.3)] 2019 49th European Microwave Conference (EuMC) - Waveguide Coupler Design Method for Permittivity Measurement at millimeter-wave applications
摘要： In this paper, novel waveguide coupler technique for relative permittivity measurement of dielectric materials is proposed. Unlike two conventional port methods measurements, this technique provides extra information to precisely measure tangent loss and permittivity. This type of coupler is composed of a waveguide section of four arms connected by a central junction. Quasi-optical coupler technique is realized on standard waveguide by simply inserting circular holes with different values of permittivity in the central section to act as a mirror. Characteristics of the proposed coupler are introduced and studied with regard to different parameters. This design provides an precise technique for measuring permittivity and tangent loss throughout two extra ports. A prototype at mm-wave is designed, fabricated and measured. Experimental results show that the proposed waveguide coupler has accurate measured results of permittivity for milk 2 % and creamer 10 %.
关键词： Permittivity measurements,Waveguide coupler,millimetres wave applications,Four ports devices
更新于2025-09-11 14:15:04
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Equivalent source and pattern reconstruction from oversampled measurements in highly-reflective environments
摘要： Measurement errors due to echoes are a major challenge for accurate antenna pattern measurements. In particular in highly-reflective measurement environments, the echo contribution can easily have more influence on the measurement signal than the desired line-of-sight contribution between the antenna under test and the measurement probe. A large number of redundant measurement samples at different locations and for different frequencies is used together with appropriate post-processing techniques to mitigate the echo influences on the measurements. The frequency diversity is used for time gating. A virtual array, less sensitive to the undesired echo fields, is formed using probe diversity. In this work, the common time gating technique is enhanced and the impact of different probe configurations for creating a virtual array is investigated. The utilised time gating method extends the measured frequency domain signal to mitigate the Gibbs phenomenon. Processing measurements in a quasi-metallic room, the signal contributions at the edges of the measured bandwidth do not suffer from distortions with the enhanced time gating method. Combining up to 115 probes to form a virtual array, it is found that the results improve with an increasing number of probes as long as the probes are distant enough from the walls.
关键词： time gating,echo suppression,highly-reflective environments,antenna pattern measurements,virtual array
更新于2025-09-11 14:15:04
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Solar irradiance estimations for modeling the variability of photovoltaic generation and assessing violations of grid constraints: A comparison between satellite and pyranometers measurements with load flow simulations
摘要： Global horizontal irradiance (GHI) is typically used to model the power output of distributed photovoltaic (PV) generation. On the one hand, satellite estimations are nonpervasive and already available from commercial providers, but they have a limited spatiotemporal resolution. On the other hand, local estimations, e.g., from pyranometers, sky-cameras, and monitored PV plants, capture local irradiance patterns and dynamics, but they require in situ monitoring infrastructure and upgrading the asset of electrical operators. Considering that in most power systems, PV generation is typically the aggregated contribution of many distributed plants, are local GHI estimations necessary to characterize the variability of the power ?ow at the grid connection point (GCP) and detect violations of the limits of voltages and line currents accurately? To reply, we consider GHI measurements from a dense network of pyranometers (used to model the ground truth GHI potential), satellite estimations for the same area, and information about a medium and low voltage distribution system. We perform load ?ows at different levels of installed PV capacity and compare the nodal voltages, line currents, and the power at the GCP when the irradiance is from pyranometers and when from satellite estimations, deriving conclusions on the necessity, or not, of highly spatiotemporally resolved irradiance estimations.
关键词： solar irradiance,grid constraints,satellite measurements,pyranometers,load flow simulations,photovoltaic generation
更新于2025-09-11 14:15:04
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Search for Best Astronomical Observatory Sites in the MENA Region using Satellite Measurements
摘要： We perform a systematic search for astronomical observatory sites in the MENA (Middle-East and North Africa) region using space-based data for all the relevant factors, i.e. altitude (DEM), cloud fraction (CF), light pollution (NTL), precipitable water vapor (PWV), aerosol optical depth (AOD), relative humidity (RH), wind speed (WS), Richardson Number (RN), and diurnal temperature range (DTR). We look for the best locations overall even where altitudes are low (the threshold that we normally consider being 1,500 m) or where the combination of the afore-mentioned determining factors had previously excluded all locations in a given country. In this aim, we use the rich data that Earth-observing satellites provide, e.g. the Terra and Aqua multi-national NASA research satellites, with their MODIS (Moderate Resolution Imaging Spectroradiometer) and AIRS (Atmospheric Infrared Sounder) instruments, the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS), and other products from climate diagnostics archives (e.g. MERRA). We present preliminary results on the best locations for the region.
关键词： diurnal temperature range,Richardson Number,MENA region,wind speed,precipitable water vapor,cloud fraction,relative humidity,aerosol optical depth,light pollution,astronomical observatory sites,satellite measurements
更新于2025-09-11 14:15:04
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Luminescence lifetime encoding in time-domain flow cytometry
摘要： Time-resolved flow cytometry represents an alternative to commonly applied spectral or intensity multiplexing in bioanalytics. At present, the vast majority of the reports on this topic focuses on phase-domain techniques and specific applications. In this report, we present a flow cytometry platform with time-resolved detection based on a compact setup and straightforward time-domain measurements utilizing lifetime-encoded beads with lifetimes in the nanosecond range. We provide general assessment of time-domain flow cytometry and discuss the concept of this platform to address achievable resolution limits, data analysis, and requirements on suitable encoding dyes. Experimental data are complemented by numerical calculations on photon count numbers and impact of noise and measurement time on the obtained lifetime values.
关键词： lifetime-encoded beads,multiplexing,Time-resolved flow cytometry,bioanalytics,time-domain measurements
更新于2025-09-11 14:15:04
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Reconstructing charge-carrier dynamics in porous silicon membranes from time-resolved interferometric measurements
摘要： We performed interferometric time-resolved simultaneous reflectance and transmittance measurements to investigate the carrier dynamics in pump-probe experiments on thin porous silicon membranes. The experimental data was analysed by using a method built on the Wentzel-Kramers-Brillouin approximation and the Drude model, allowing us to reconstruct the excited carriers’ non-uniform distribution in space and its evolution in time. The analysis revealed that the carrier dynamics in porous silicon, with ~50% porosity and native oxide chemistry, is governed by the Shockley-Read-Hall recombination process with a characteristic time constant of 375 picoseconds, whereas diffusion makes an insignificant contribution as it is suppressed by the high rate of scattering.
关键词： carrier dynamics,porous silicon,Drude model,Shockley-Read-Hall recombination,interferometric measurements
更新于2025-09-11 14:15:04
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Compact Distributed Digitizers with Metrological Precision
摘要： Prototype distributed digitizers have been developed with metrological precision of the individual measurement nodes. A master controller aggregates the data of the nodes and performs all computational tasks. A crucial part of the system is the synchronization of the individual nodes at nanosecond level using white-rabbit technology. Fibre-optic communication is used to reduce interference and to obtain high isolation. When operated on battery power, this allows for special applications such as the measurement of currents in high-voltage lines. First results show that a phase difference between nodes of a few μrad can be achieved with a resolution of better than 0.1 μrad.
关键词： calibration,current transformers,measurement uncertainty,ADCs,high-voltage,wide area measurements,digitizers,power system measurements,precision measurements
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - A High Precision Multi-Ratio Three-Stage Current Transformer (CT) for Loss Measurements of Extra High Voltage (EHV) Three-Phase Shunt Reactors with Test Voltages up to 1100 kV
摘要： An overview of the development and performance of special high precision multi-ratio three-stage CT and its application for loss measurement of EHV three-phase shunt reactors with AC test voltages up to 1100 kV at Royal SMIT Transformers are presented and discuss. It features current ratios of 500A/1A, 400A/1A, 300A/1A, 200A/1A, and 100A/1A with ratio errors within 3×10-6 in both magnitude and phase with burdens up to 1.0 ? and at power frequencies of 50 Hz - 60 Hz.
关键词： multi-ratio,ratio errors,multistage,Extra High Voltage (EHV),loss measurements,uncertainty,shunt reactor,three-stage,precision measurements
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Transfer Learning with Convolutional Networks for Atmospheric Parameter Retrieval
摘要： The Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp satellite series provides important measurements for Numerical Weather Prediction (NWP). Retrieving accurate atmospheric parameters from the raw data provided by IASI is a large challenge, but necessary in order to use the data in NWP models. Statistical models performance is compromised because of the extremely high spectral dimensionality and the high number of variables to be predicted simultaneously across the atmospheric column. All this poses a challenge for selecting and studying optimal models and processing schemes. Earlier work has shown non-linear models such as kernel methods and neural networks perform well on this task, but both schemes are computationally heavy on large quantities of data. Kernel methods do not scale well with the number of training data, and neural networks require setting critical hyperparameters. In this work we follow an alternative pathway: we study transfer learning in convolutional neural nets (CNNs) to alleviate the retraining cost by departing from proxy solutions (either features or networks) obtained from previously trained models for related variables. We show how features extracted from the IASI data by a CNN trained to predict a physical variable can be used as inputs to another statistical method designed to predict a different physical variable at low altitude. In addition, the learned parameters can be transferred to another CNN model and obtain results equivalent to those obtained when using a CNN trained from scratch requiring only fine tuning.
关键词： Infrared measurements,Convolutional Neural networks,parameter retrieval,Transfer Learning
更新于2025-09-10 09:29:36
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A suspended 3-omega technique to measure the anisotropic thermal conductivity of semiconducting polymers
摘要： Anisotropic thermal conductivity can complicate the performance of semiconducting polymer thin-films in applications such as thermoelectrics and photovoltaics. Anisotropic measurements of low thermal conductivity polymers are challenging, and there are a limited number of appropriate measurement techniques. Suspended film 3-omega is an appropriate technique but has often required unfavorable microfabrication. Herein, we report on the utility of the suspended 3-omega technique that uses shadow masking, and no other microfabrication techniques, in performing anisotropic (in-plane and through-plane) thermal conductivity measurements of polymer films. We report on the necessary conditions for the validity of the 1D suspended-film heat transfer model and provide experimental guidelines for in-plane thermal conductivity measurements of polymer thin-films. Furthermore, for the first time, we report the anisotropic thermal conductivities of N2200 and a low molecular weight P3HT, which are two common n-type and p-type semiconducting polymers. Measured thermal conductivities are compared with predictions from the conventional Cahill-Pohl model and a recent empirical model that more accurately predicts the temperature dependence.
关键词： semiconducting polymers,thermal conductivity measurements,3-omega technique,anisotropic thermal conductivity,shadow masking
更新于2025-09-10 09:29:36