scholarly journals On Dispersion and Multipath Effects in Harmonic Radar Imaging Applications

2021 ◽  
Vol 13 (24) ◽  
pp. 5013
Author(s):  
Florian Bischeltsrieder ◽  
Markus Peichl ◽  
Wolfgang Utschick
Keyword(s):  
Transfer Functions ◽  
Multipath Propagation ◽  
Measurement Data ◽  
Radar Data ◽  
Radar Imaging ◽  
Signal Model ◽  
Harmonic Radar ◽  
Nonlinear Character ◽  
Transfer Behavior ◽  
Radar Applications

In harmonic radar applications, images produced using algorithms of conventional radar applications experience some defocusing effects of the electronic targets’ impulse responses. This is typically explained by the dispersive transfer functions of the targets. In addition, it was experimentally observed that objects with a linear transfer behavior do not contribute to the received signal of a harmonic radar measurement. However, some signal contributions based on a multipath propagation can overlay the desired signal, which leads to an undesired and unusual interference caused by the nonlinear character of the electronic targets. Here, motivated by the analysis of measured harmonic radar data, the effects of both phenomena are investigated by theoretical derivations and simulation studies. By analyzing measurement data, we show that the dispersion effects are caused by the target and not by the measurement system or the measurement geometry. To this end, a signal model is developed, with which it is possible to describe both effects, dispersion and multipath propagation. In addition, the discrepancy between classic radar imaging and harmonic radar is analyzed.

Aspect-dependent efficient multipath ghost suppression in TWRI with sparse reconstruction

2017 ◽  
Vol 9 (9) ◽  
pp. 1839-1852 ◽  
Author(s):  
Ali Hussein Muqaibel ◽  
Abdi Talib Abdalla ◽  
Mohammad Tamim Alkhodary ◽  
Suhail Al-Dharrab
Keyword(s):  
Image Reconstruction ◽  
Multipath Propagation ◽  
Radar Imaging ◽  
Sparse Reconstruction ◽  
Front Wall ◽  
Sensing Matrix ◽  
Signal Model ◽  
Reconstruction Process ◽  
Real Experiment ◽  
Single View

In through-the-wall radar imaging, multipath propagation can create ghost targets, which can adversely affect the image reconstruction process. However, unlike genuine targets, ghost positions are aspect-dependent, which means their position changes with the transceiver location. This paper proposes efficient ghost suppression methods exploiting aspect dependence feature under compressive sensing framework. This paper proposes a generalized signal model that accommodates for the reflections of the front-wall and target-to-target interactions, making the scheme more practical, yet the knowledge of the location of reflecting geometry is not a requirement as in most of the recent literatures. In addition, the sensing matrix is greatly reduced making the methods more attractive. Moreover, this paper investigates the influence of array configurations by examining two antenna array configurations: multimonostatic, and single-view bistatic configurations. Results based on synthesized data and real experiment show that the proposed method can greatly suppress multipath ghosts and hence increase signal-to-clutter ratio.

Observed Natural Frequencies, Damping Ratios, and Mode Shapes of Vibration of a 30-Story Building Excited by a Major Earthquake and Typhoon

2010 ◽  
Vol 26 (2) ◽  
pp. 371-397 ◽  
Author(s):  
Kun-Sung Liu ◽  
Yi-Ben Tsai
Keyword(s):  
Natural Frequencies ◽  
Transfer Functions ◽  
Measurement Data ◽  
Spectral Ratio ◽  
Transverse Mode ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Building Structures ◽  
Ambient Vibrations ◽  
Frequency Changes

The safety of building structures and contents, as well as the comfort of occupants, under such strong forces as earthquakes and typhoons remain major engineering concerns. In order to improve our understanding of building structural responses, records of a structural array in the 30-story PS Building in Taipei from the M7.6 Chi-Chi earthquake and Typhoon Aere are analyzed. In addition, wind data measured at the Taipei Meteorological Station are also used. First, the field measurement data clearly demonstrate that serviceability of the PS Building met the criteria for occupant comfort during Typhoon Aere. Secondly, several structural vibration parameters of this highrise building, including the transfer functions, natural frequencies, damping ratios and mode shapes, excited by the Chi-Chi earthquake, Typhoon Aere, and ambient vibrations are also determined and compared. The results show the frequency of the first mode for the longitudinal components is approximately 8.6% lower for the earthquake than the ambient vibrations. The transverse mode frequencies behave similarly. In contrast, frequency changes from the typhoon to ambient vibrations are in the third decimal (1.3% and 0.9% lower in the longitudinal and transverse directions, respectively), indicating little nonlinearity. The damping ratios of the PS Building apparently increase with vibration amplitudes. Finally, results of a spectral ratio analysis of the Chi-Chi earthquake data do not indicate significant SSI effects in the longitudinal and transverse directions.

Image Reconstruction Algorithm Based On PCA and WNN for ECT

2013 ◽  
Vol 5 (4) ◽  
pp. 33-40
Author(s):  
Lifeng Zhang
Keyword(s):  
Image Reconstruction ◽  
Adaptive Learning ◽  
Transfer Functions ◽  
Measurement Data ◽  
Principal Component ◽  
Reconstruction Algorithm ◽  
Simulation Software ◽  
Iteration Algorithm ◽  
Two Phase ◽  
Image Reconstruction Algorithm

Electrical capacitance tomography (ECT) technique is a new technique for two-phase flow measurement. ECT is a complex nonlinear problem. To solve the ill-posed image reconstruction problem, image reconstruction algorithm based on wavelet neural networks (WNN) was presented. The principal component analysis (PCA) method was used to reduce the dimension of the input vectors. The transfer functions of the neurons in the WNN were wavelet base functions which were determined by retract and translation factors. The input measurement data were obtained using the ECT simulation software developed by the author. BP algorithm was used to train the WNN, and self-adaptive learning rate and momentum coefficient were also used to accelerate the learning speed. Experimental results showed the image quality has been improved markedly, compared with the typical linear back projection (LBP) algorithm and Landweber iteration algorithm.

A Comparison of Scan Speedup Strategies and Their Effect on Rapid-Scan Weather Radar Data Quality

2020 ◽  
Vol 37 (11) ◽  
pp. 1955-1972
Author(s):  
Andrew Mahre ◽  
Tian-You Yu ◽  
David J. Bodine
Keyword(s):  
High Resolution ◽  
Data Quality ◽  
Wrf Model ◽  
Weather Radar ◽  
Radar Data ◽  
Radar Imaging ◽  
Strong Argument ◽  
Scan Time ◽  
Replacement System ◽  
Scanning Strategies

AbstractAs the existing NEXRAD network nears the end of its life cycle, intense study and planning are underway to design a viable replacement system. Ideally, such a system would offer improved temporal resolution compared to NEXRAD, without a loss in data quality. In this study, scan speedup techniques—such as beam multiplexing (BMX) and radar imaging—are tested to assess their viability in obtaining high-quality rapid updates for a simulated long-range weather radar. The results of this study—which uses a Weather Research and Forecasting (WRF) Model–simulated supercell case—show that BMX generally improves data quality for a given scan time or can provide a speedup factor of 1.69–2.85 compared to NEXRAD while maintaining the same level of data quality. Additionally, radar imaging is shown to improve data quality and/or decrease scan time when selectively used; however, deleterious effects are observed when imaging is used in regions with sharp reflectivity gradients parallel to the beam spoiling direction. Consideration must be given to the subsequent loss of sensitivity and beam broadening. Finally, imaging is shown to have an effect on the radar-derived mesocyclone strength (ΔV) of a simulated supercell. Because BMX and radar imaging are most easily achieved with an all-digital phased array radar (PAR), these results make a strong argument for the use of all-digital PAR for high-resolution weather observations. It is believed that the results from this study can inform decisions about possible scanning strategies and design of a NEXRAD replacement system for high-resolution weather radar data.

scholarly journals Average and Small Signal Modeling of Negative-Output KY Boost Converter in CCM Operation

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Faqiang Wang ◽  
Jing Li ◽  
Xikui Ma
Keyword(s):  
Output Voltage ◽  
Averaging Method ◽  
Transfer Functions ◽  
Boost Converter ◽  
Small Signal ◽  
Signal Model ◽  
Boost Converters ◽  
Small Signal Model ◽  
Small Signal Modeling ◽  
Negative Output

Negative-output KY Boost converter, which can obtain the negative output voltage and could be driven easily, is a good topology to overcome traditional Boost and Buck-Boost converters and it is believed that this converter will be widely used in engineering applications in the future. In this study, by using the averaging method and geometrical technique, the average and small signal model of the negative-output KY Boost converter are established. The DC equilibrium point and transfer functions of the system are derived and analyzed. Finally, the effectiveness of the established model and the correctness of the theoretical analysis are confirmed by the circuit experiment.

scholarly journals Liquid-Based Battery Temperature Control of Electric Buses

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4990
Author(s):  
Sebastian Angermeier ◽  
Jonas Ketterer ◽  
Christian Karcher
Keyword(s):  
Heat Transfer ◽  
Temperature Control ◽  
Control Strategy ◽  
Transfer Functions ◽  
Computational Effort ◽  
Coolant Temperature ◽  
Cell Temperature ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
And Control

Previous research identified that battery temperature control is critical to the safety, lifetime, and performance of electric vehicles. In this paper, the liquid-based battery temperature control of electric buses is investigated subject to heat transfer behavior and control strategy. Therefore, a new transient calculation method is proposed to simulate the thermal behavior of a coolant-cooled battery system. The method is based on the system identification technique and combines the advantage of low computational effort and high accuracy. In detail, four transfer functions are extracted by a thermo-hydraulic 3D simulation model comprising 12 prismatic lithium nickel manganese cobalt oxide (NMC) cells, housing, arrestors, and a cooling plate. The transfer functions describe the relationship between heat generation, cell temperature, and coolant temperature. A vehicle model calculates the power consumption of an electric bus and thus provides the input for the transient calculation. Furthermore, a cell temperature control strategy is developed with respect to the constraints of a refrigerant-based battery cooling unit. The data obtained from the simulation demonstrate the high thermal inertia of the system and suggest sufficient control of the battery temperature using a quasi-stationary cooling strategy. Thereby, the study reveals a crucial design input for battery cooling systems in terms of heat transfer behavior and control strategy.

Going beyond FAIR to increase data reliability

2020 ◽  
Author(s):  
Uta Koedel ◽  
Peter Dietrich
Keyword(s):  
Data Quality ◽  
Information Needs ◽  
Transfer Functions ◽  
Measurement Data ◽  
Secondary Data ◽  
Data Uncertainty ◽  
Calibration Data ◽  
Data Reliability ◽  
Secondary Users ◽  
Site Field

<p>The FAIR principle is on its way to becoming a conventional standard for all kinds of data. However, it is often forgotten that this principle does not consider data quality or data reliability issues. If the data quality isis not sufficiently described, a wrong interpretation and use of these data in a common interpretation can lead to false scientific conclusions. Hence, the statement about data reliability is an essential component for secondary data processing and joint interpretation efforts. Information on data reliability, uncertainty, quality as well as information on the used devices are essential and needs to be introduced or even implemented in the workflow from the sensor to a database if data is to be considered in a broader context.</p><p>In the past, many publications have shown that the same devices at the same location do not necessarily provide the same measurement data. Likewise, statistical quantities and confidence intervals are rarely given in publications in order to assess the reliability of the data. Many secondary users of measurement data assume that calibration data and the measurement of other auxiliary variables are sufficient to estimate the data reliability. However, even if some devices require on-site field calibration, that does not mean that the data are comparable. Heat, cold, internal processes on electronic components can lead to differences in measurement data recorded with devices of the same type at the same location, especially with the increasingly complex devices themselves.</p><p>The data reliability can be increased by implementing data uncertainty issues within the FAIR principle. The poster presentation will show the importance of comparative measurements, the information needs for the application of proxy-transfer functions, and suitable uncertainty analysis for databases.</p>

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