Journal articles on the topic 'Modelling of microwave systems'
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Pittella, Erika, Emanuele Piuzzi, Pietro Russo, and Francesco Fabbrocino. "Microwave Characterization and Modelling of PA6/GNPs Composites." Mathematical and Computational Applications 27, no. 3 (May 11, 2022): 41. http://dx.doi.org/10.3390/mca27030041.
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The interest in composite materials has increased in the last decades since they have the advantages of combining intrinsic properties of each component and offer better performance with respect to the base constituents. In particular, these kinds of materials can have different electrical characteristics by varying the filling percentage and, therefore, they can be used in diverse applications. Thus, a detailed study of the microwave response of these composite systems is of great practical importance. In fact, the dielectric constant and loss tangent are key factors in the design of microwave components. In this frame, the outstanding properties of graphene-like fillers may be exploited to develop new very interesting materials to study and characterize. In this paper, microwave characterization of compounds, based on nylon 6 containing different percentages of graphene nanoplatelets, is carried out taking the neat matrix sample processed under the same conditions as benchmark. The measurements were carried out using two microwave systems, operating at two different frequency bands, appropriate to characterize solid and compact material samples. The achieved results, in line with limited data from the literature and from material data sheets, highlight the possibility to use the present polymers as an excellent electromagnetic interference shielding, as confirmed by full wave electromagnetic numerical simulations that were conducted with a numerical electromagnetic software.
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Ostaszewska-Liżewska, Anna, Dominika Kopala, Jakub Szałatkiewicz, Roman Szewczyk, and Peter Råback. "The Influence of Mesh Granularity on the Accuracy of FEM Modelling of the Resonant State in a Microwave Chamber." Applied Sciences 11, no. 17 (August 27, 2021): 7932. http://dx.doi.org/10.3390/app11177932.
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Microwave technology is widely used in different areas of advanced industry when energy must be provided to water-containing and other materials. The main barrier in the development of microwave devices is the possibility of efficient design by modelling a microwave system in a resonant state. For technical systems, the finite element method is widely used. However, the convergence process in the microwave finite element solver is sophisticated. The process itself and the influence of mesh granularity on the accuracy of modelling of microwave chambers in resonant states have not been investigated previously. The present paper aims to fill this gap. The resonance conditions of a microwave chamber were tested from the point of view of spatial resolution of the tetrahedral mesh used for open-source ELMER FEM software. The presented results experimentally determine the limits of accuracy of the geometry of microwave resonant chamber finite element method-based models. The determined values of microwave resonant chamber dimension tolerances should be considered for both open-source and commercial software for microwave modelling.
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Gal, B., and K. Granat. "Electrical Properties of Multilayer Systems Composed of Foundry Tooling and Moulding Sand." Archives of Foundry Engineering 17, no. 2 (June 27, 2017): 21–24. http://dx.doi.org/10.1515/afe-2017-0044.
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Abstract Within the research, selected multilayer technological systems created as combinations of water-glass containing moulding sand with foundry tooling, were characterised on the grounds of their electrical properties. By measuring resonance frequency and quality factor of a waveguide resonance cavity, real component of permittivity εr’ and loss tangent tgδ were determined for multilayer foundry systems with various qualitative and quantitative compositions. It was demonstrated that combination of a sandmix and foundry tooling with known dielectric properties results in a system with different physico-chemical properties, whose relation to the parameters of individual components of the system is undefined at this research stage. On the grounds of measurement results, theoretical value of microwave heating power, dissipated in unit volume of the selected multilayer foundry system, was determined. Knowledge of theoretical heating power and evaluation of physical, chemical and structural changes occurring in moulding sands exposed to microwaves in such a technological system makes a ground for empirical modelling of the process of microwave heating of foundry moulds and cores.
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Ermolova, Natalia, and Pertti Vainikainen. "On modelling nonlinear microwave power amplifiers in multi-carrier transmission systems." European Transactions on Telecommunications 15, no. 1 (January 2004): 1–6. http://dx.doi.org/10.1002/ett.940.
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Salgado, H. M., and J. J. O'Reilly. "Experimental validation of Volterra series nonlinear modelling for microwave subcarrier optical systems." IEE Proceedings - Optoelectronics 143, no. 4 (August 1, 1996): 209–13. http://dx.doi.org/10.1049/ip-opt:19960081.
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Manivannan, N., W. Balachandran, R. Beleca, and M. Abbod. "Microwave Plasma System Design and Modelling for Marine Diesel Exhaust Gas Abatement of NOx and SOx." International Journal of Environmental Science and Development 6, no. 2 (2015): 151–54. http://dx.doi.org/10.7763/ijesd.2015.v6.579.
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Donelli, M., I. Craddock, D. Gibbins, and M. Sarafianou. "Modelling complex electromagnetic sources for microwave imaging systems with wave field synthesis technique." Electronics Letters 48, no. 23 (2012): 1478. http://dx.doi.org/10.1049/el.2012.2627.
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Shabunin, Sergey, Sergey Plokhov, Ilia Bukrin, and Victor Chechetkin. "Microwave phased array for aerological radar." ITM Web of Conferences 30 (2019): 05022. http://dx.doi.org/10.1051/itmconf/20193005022.
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The use of radars with phased antenna arrays in aerological atmospheric sounding systems significantly increases the technical characteristics of the radio channel, ensures reliable auto-tracking in the near zone at high angular velocities of the aerological probe, and reduces the overall dimensions of the radar station. Modelling and optimization of the parameters of the phased array and phase shifters were carried out in the NI AWR Design Environment. The results of the study showed that when designing a radar station, it is possible to reduce the level of side lobes of the phased array antenna pattern and the effect of reflections from the underlying surface under operating conditions significantly.
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Hirahara, Yoichi, Patricia de Rosnay, and Gabriele Arduini. "Evaluation of a Microwave Emissivity Module for Snow Covered Area with CMEM in the ECMWF Integrated Forecasting System." Remote Sensing 12, no. 18 (September 11, 2020): 2946. http://dx.doi.org/10.3390/rs12182946.
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The Community Microwave Emission Modelling platform (CMEM) has been developed by the European Centre for Medium-Range Weather Forecasts (ECMWF) as the forward operator radiative transfer model for low frequency passive microwave brightness temperatures (TB). It is used at ECMWF for L-band TB monitoring over snow free areas. In this paper, upgrades to CMEM are presented in order to explore forward modelling in snow-covered areas for coupled land-atmosphere numerical weather prediction systems. The upgrades enable to use CMEM on an extended range of frequencies and the Helsinki University of Technology multi-layer snow emission model is implemented. Offline CMEM experiments are evaluated against AMSR2 (Advanced Microwave Scanning Radiometer 2) observations showing that simulated TB is improved when using a multi-layer snow scheme, compared to a single-layer scheme. The improvements mainly result from a better representation of snow characteristics in the multi-layer snowpack model. CMEM is also evaluated in the Integrated Forecasting System and coupled to RTTOV (Radiative Transfer for TOVS). The numerical results show improved simulated TB at low frequency V polarization over snow-covered area compared to a configuration using emissivity atlas. Degradations at frequencies higher than 20 GHz indicate that further improvements are required in the emissivity and snowpack properties modelling.
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Ambrosanio, M., R. Scapaticci, and L. Crocco. "A Simple Quantitative Inversion Approach for Microwave Imaging in Embedded Systems." International Journal of Antennas and Propagation 2015 (2015): 1–18. http://dx.doi.org/10.1155/2015/129823.
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In many applications of microwave imaging, there is the need of confining the device in order to shield it from environmental noise as well as to host the targets and the medium used for impedance matching purposes. For instance, in MWI for biomedical diagnostics a coupling medium is typically adopted to improve the penetration of the probing wave into the tissues. From the point of view of quantitative imaging procedures, that is aimed at retrieving the values of the complex permittivity in the domain under test, the presence of a confining structure entails an increase of complexity of the underlying modelling. This entails a further difficulty in achieving real-time imaging results, which are obviously of interest in practice. To address this challenge, we propose the application of a recently proposed inversion method that, making use of a suitable preprocessing of the data and a scenario-oriented field approximation, allows obtaining quantitative imaging results by means of quasi-real-time linear inversion, in a range of cases which is much broader than usual linearized approximations. The assessment of the method is carried out in the scalar 2D configuration and taking into account enclosures of different shapes and, to show the method’s flexibility different shapes, embedding nonweak targets.
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Adnan, Farasatul, Valon Blakaj, Sendy Phang, Thomas M. Antonsen, Stephen C. Creagh, Gabriele Gradoni, and Gregor Tanner. "Wireless power distributions in multi-cavity systems at high frequencies." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 477, no. 2245 (January 2021): 20200228. http://dx.doi.org/10.1098/rspa.2020.0228.
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The next generations of wireless networks will work in frequency bands ranging from sub-6 GHz up to 100 GHz. Radio signal propagation differs here in several critical aspects from the behaviour in the microwave frequencies currently used. With wavelengths in the millimetre range (mmWave), both penetration loss and free-space path loss increase, while specular reflection will dominate over diffraction as an important propagation channel. Thus, current channel model protocols used for the generation of mobile networks and based on statistical parameter distributions obtained from measurements become insufficient due to the lack of deterministic information about the surroundings of the base station and the receiver-devices. These challenges call for new modelling tools for channel modelling which work in the short-wavelength/high-frequency limit and incorporate site-specific details—both indoors and outdoors. Typical high-frequency tools used in this context—besides purely statistical approaches—are based on ray-tracing techniques. Ray-tracing can become challenging when multiple reflections dominate. In this context, mesh-based energy flow methods have become popular in recent years. In this study, we compare the two approaches both in terms of accuracy and efficiency and benchmark them against traditional power balance methods.
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Fencl, M., J. Rieckermann, M. Schleiss, D. Stránský, and V. Bareš. "Assessing the potential of using telecommunication microwave links in urban drainage modelling." Water Science and Technology 68, no. 8 (October 1, 2013): 1810–18. http://dx.doi.org/10.2166/wst.2013.429.
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The ability to predict the runoff response of an urban catchment to rainfall is crucial for managing drainage systems effectively and controlling discharges from urban areas. In this paper we assess the potential of commercial microwave links (MWL) to capture the spatio-temporal rainfall dynamics and thus improve urban rainfall-runoff modelling. Specifically, we perform numerical experiments with virtual rainfall fields and compare the results of MWL rainfall reconstructions to those of rain gauge (RG) observations. In a case study, we are able to show that MWL networks in urban areas are sufficiently dense to provide good information on spatio-temporal rainfall variability and can thus considerably improve pipe flow prediction, even in small subcatchments. In addition, the better spatial coverage also improves the control of discharges from urban areas. This is especially beneficial for heavy rainfall, which usually has a high spatial variability that cannot be accurately captured by RG point measurements.
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Feng, Jian, Kaihong Song, Ming Fang, Wei Chen, Guoda Xie, Zhixiang Huang, and Xianliang Wu. "Heterogeneous CPU-GPU Accelerated Subgridding in the FDTD Modelling of Microwave Breakdown." Electronics 11, no. 22 (November 14, 2022): 3725. http://dx.doi.org/10.3390/electronics11223725.
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Microwave breakdown is crucial to the transmission of high-power microwave (HPM) devices, where a growing number of studies have analyzed the complex interactions between electromagnetic waves and the evolving plasma from theoretical and analytical perspectives. In this paper, we propose a finite-difference time-domain (FDTD) scheme to numerically solve Maxwell’s equation, coupled with a fluid plasma equation for simulating the plasma formation during HPM air breakdown. A subgridding method is adopted to obtain accurate results with lower computational resources. Moreover, the three-dimensional subgridding Maxwell–plasma algorithm is efficiently accelerated by utilizing heterogeneous computing technique based on graphics processing units (GPUs) and multiple central processing units (CPUs), which can be applied as an efficient method for the investigation of the HPM air breakdown phenomena.
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Batty, W., A. J. Panks, R. G. Johnson, and C. M. Snowden. "Electro-thermal Modelling of Monolithic and Hybrid Microwave and Millimeter Wave IC's." VLSI Design 10, no. 4 (January 1, 2000): 355–89. http://dx.doi.org/10.1155/2000/86517.
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The first completely physical electro-thermal model is presented that is capable of describing the large signal performance of MESFET- and HEMT-based, high power microwave and millimeter wave monolithic and hybrid ICs, on timescales suitable for CAD. The model includes the effects of self-heating and mutual thermal interaction on active device performance with full treatment of all thermal non linearities. The electrical description is provided by the rapid quasi-2D Leeds Physical Model and the steady-state global thermal description is provided by a highly accurate and computationally inexpensive analytical thermal resistance matrix approach. The order of the global thermal resistance matrix describing 3-dimensional heat flow in complex systems, is shown to be determined purely by the number of active device elements, not the level of internal device structure. Thermal updates in the necessarily iterative, fully coupled electro-thermal solution, therefore reduce to small matrix multiplications implying orders of magnitude speed-up compared to the use of full numerical thermal solutions capable of comparable levels of detail and accuracy.
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Glushkov, Alexander, Valentin Ternovsky, and Georgy Prepelitsa. "Geometry of a Relativistic Quantum Chaos: New approach to dynamics of quantum systems in electromagnetic field and some applications." Proceedings of the International Geometry Center 8, no. 3-4 (February 25, 2020): 79–86. http://dx.doi.org/10.15673/tmgc.v8i3-4.1611.
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In the paper we present development of a new relativistic chaos-geometric and quantum-dynamic approach to solve problems of complete modelling relativistic chaotic dynamics of atoms in an electromagnetic field. As usually the approach consistently includes a number of new relativistic quantum models and a number of new or improved methods of analysis (correlation integral, fractal analysis, algorithms, average mutual information, false nearest neighbors, Lyapunov exponents, surrogate data, non-linear prediction, spectral methods, etc.) For the first time we present the corresponding atomic ionization quantitative data for some atoms in a microwave external field.
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Kim, Do-Kyung, Muhammet S. Toprak, Maria Mikhaylova, Yun Suk Jo, Steven J. Savage, Hyung Bock Lee, Thomas Tsakalakos, and Mamoun Muhammed. "Polymeric Nanocomposites of Complex Ferrite." Solid State Phenomena 99-100 (July 2004): 165–68. http://dx.doi.org/10.4028/www.scientific.net/ssp.99-100.165.
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The influence of mixtures of Ni0.5Zn0.4Cu0.1Fe2O4, CoFe2O4, and graphite on the permeability, permittivity and microwave absorption properties in a composite embedded with insulating polymeric matrix, that can be used for X- and P-band radar absorption, has been investigated. Thermodynamic modelling of the complex ferrite system has been demonstrated by the controlled simultaneous coprecipitation of all ions inolved in the composite in the selected working pH ranges. The method employed is very convenient for the synthesis of multicomponent systems with a homogenous distribution of compositions.
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Bliokh, Yu P., M. G. Lyubarsky, and V. O. Podobinsky. "About chaotization mechanisms of the distributed dynamical systems which are close to discrete." Discrete Dynamics in Nature and Society 1, no. 3 (1997): 233–41. http://dx.doi.org/10.1155/s102602269700023x.
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The investigations of stochastization mechanisms of distributed dynamical systems (DDS) are developed not so complete as stochastization of dynamical systems with concentrated parameters (CDS). Therefore the corresponding DDS which is close (in one or other sense) to the CDS under consideration is used. Such substitution means some roughening of an initial problem. However, there are such important stochastization mechanisms understanding properties, which are connected with system “distributivity” on principle. In this paper the conception of a proximity to the CDS is introduced for one particular class of the DDS. It is shown that such kind of systems has two stochastization mechanisms, one of which is common to the DDS and the corresponding CDS. Another stochastization mechanism inherent in DDS disappears under transition from DDS to CDS.Distributed dynamical system considered below is not abstract but describes the set of concrete physical devices, for example, microwave oscillators. It may be devices in which kinetic energy of an accelerated electron beam is transformed into electromagnetic radiation energy, or oscillators with delayed feedback.
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Meshcheriakov, Viktor V., Natalia V. Markova, and Pavel D. Iurmanov. "Modeling and Practical Implementation of a Broadband Double-Ridged Horn Antenna with an Operating Range More Than an Octave and a High Level of Cross-Polarization Discrimination." Journal of the Russian Universities. Radioelectronics 22, no. 5 (December 4, 2019): 42–51. http://dx.doi.org/10.32603/1993-8985-2019-22-5-42-51.
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Introduction. The resolution of the problem of radio polarimetry in multiposition microwave screening systems (MMSS) with aperture synthesis requires the use of antennas with a high level of cross-polarization discrimination (XPD) in a wide spatial angle. The radio images are reconstructed in MMSS at distances commensurate with the aperture of the antenna structures. Therefore, the value of the spatial angle, at which high XPD is required, can reach 30°. This leads to a new problem of creating an antenna configuration of the X and Ku band, the application of which in MMSS will resolve the problem of constructing a radio image of depolarized microwave radiation scattered on the human body in the form of hidden dangerous objects.Aim. To develop a double-ridged receiving antenna for long-term operation in MMSS with an XPD level of 28 dB at a spatial angle of 30° and operating frequencies of 8…20 GHz.Materials and methods. The requirements for the receiving antenna in MMSS were determined. Theoretical justifications were proposed for the choice of antenna design. Aperture synthesis was used to construct microwave images in MMSS. The stages and results of modelling broadband double-ridge antennas were presented using the CST Studio software broadly applied for three-dimensional electro-magnetic field modelling. The results of modelling pyramidal and conical double-ridged antennas, as well as those in circular and elliptical waveguides, were analyzed. The designed antenna was tested in an anechoic chamber. The measurement results were compared with those obtained during simulation.Results. An elliptical double-ridged horn antenna with a VSWR of no more than 2 and cross-polarization discrimination in a spatial angle of 30° of no less than 28 dB for the frequency range that covers an octave was designed and constructed.Conclusion. The developed antenna can be used in MMSS for the purpose of detecting the effect of micro-wave radiation depolarization as hidden dangerous objects on a human body. Such characteristics of the antenna as its high XPD value in a wide spatial angle will allow the future introduction of microwave polarimetry in MMSS.
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Torres, Manuel, and Alejandro Kunold. "Symmetries in Hall-like systems: microwave and nonlinear transport effects." Journal of Physics A: Mathematical and Theoretical 41, no. 30 (July 15, 2008): 304036. http://dx.doi.org/10.1088/1751-8113/41/30/304036.
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Sandells, Melody, Richard Essery, Nick Rutter, Leanne Wake, Leena Leppänen, and Juha Lemmetyinen. "Microstructure representation of snow in coupled snowpack and microwave emission models." Cryosphere 11, no. 1 (January 27, 2017): 229–46. http://dx.doi.org/10.5194/tc-11-229-2017.
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Abstract. This is the first study to encompass a wide range of coupled snow evolution and microwave emission models in a common modelling framework in order to generalise the link between snowpack microstructure predicted by the snow evolution models and microstructure required to reproduce observations of brightness temperature as simulated by snow emission models. Brightness temperatures at 18.7 and 36.5 GHz were simulated by 1323 ensemble members, formed from 63 Jules Investigation Model snowpack simulations, three microstructure evolution functions, and seven microwave emission model configurations. Two years of meteorological data from the Sodankylä Arctic Research Centre, Finland, were used to drive the model over the 2011–2012 and 2012–2013 winter periods. Comparisons between simulated snow grain diameters and field measurements with an IceCube instrument showed that the evolution functions from SNTHERM simulated snow grain diameters that were too large (mean error 0.12 to 0.16 mm), whereas MOSES and SNICAR microstructure evolution functions simulated grain diameters that were too small (mean error −0.16 to −0.24 mm for MOSES and −0.14 to −0.18 mm for SNICAR). No model (HUT, MEMLS, or DMRT-ML) provided a consistently good fit across all frequencies and polarisations. The smallest absolute values of mean bias in brightness temperature over a season for a particular frequency and polarisation ranged from 0.7 to 6.9 K. Optimal scaling factors for the snow microstructure were presented to compare compatibility between snowpack model microstructure and emission model microstructure. Scale factors ranged between 0.3 for the SNTHERM–empirical MEMLS model combination (2011–2012) and 3.3 for DMRT-ML in conjunction with MOSES microstructure (2012–2013). Differences in scale factors between microstructure models were generally greater than the differences between microwave emission models, suggesting that more accurate simulations in coupled snowpack–microwave model systems will be achieved primarily through improvements in the snowpack microstructure representation, followed by improvements in the emission models. Other snowpack parameterisations in the snowpack model, mainly densification, led to a mean brightness temperature difference of 11 K at 36.5 GHz H-pol and 18 K at V-pol when the Jules Investigation Model ensemble was applied to the MOSES microstructure and empirical MEMLS emission model for the 2011–2012 season. The impact of snowpack parameterisation increases as the microwave scattering increases. Consistency between snowpack microstructure and microwave emission models, and the choice of snowpack densification algorithms should be considered in the design of snow mass retrieval systems and microwave data assimilation systems.
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Poutiainen, H., H. Niska, H. Heinonen-Tanski, and M. Kolehmainen. "Use of sewer on-line total solids data in wastewater treatment plant modelling." Water Science and Technology 62, no. 4 (August 1, 2010): 743–50. http://dx.doi.org/10.2166/wst.2010.317.
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We describe a neural network model of a municipal wastewater treatment plant (WWTP) in which on-line total solids (TS) sewer data generated by a novel microwave sensor is used as a model input variable. The predictive performance of the model is compared with and without sewer data and with modelling with a traditional linear multiple linear regression (MLR) model. In addition, the benefits of using neural networks are discussed. According to our results, the neural network based MLP (multilayer perceptron) model provides a better estimate than the corresponding MLR model of WWTP effluent TS load. The inclusion of sewer TS data as an input variable improved the performance of the models. The results suggest that increased on-line sensing of WWTPs should be stressed and that neural networks are useful as a modelling tool due to their capability of handling the nonlinear and dynamic data of sewer and WWTP systems.
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Keglevich, György, Nóra Kiss, Alajos Grün, Erika Bálint, and Tamara Kovács. "Advantages of the Microwave Tool in Organophosphorus Syntheses." Synthesis 49, no. 14 (June 20, 2017): 3069–83. http://dx.doi.org/10.1055/s-0036-1589031.
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The microwave (MW) technique has become an important tool also in the organophosphorus field of organic chemistry. On the one hand, otherwise reluctant reactions, such as the esterification of P-acids, may be enhanced by the effect of MW, while on the other hand, catalysts may be omitted, or catalyst systems may be simplified on MW irradiation. This later group includes the Kabachnik–Fields reactions, alkylation of active methylene-containing compounds, O-alkylations, deoxygenations, as well as the Hirao reaction. It is also the purpose of this review to elucidate the scope and limitations of the MW tool, to interpret the MW effects, and to model the distribution of local overheatings and their beneficial effect.1 Introduction2 The Esterification of Phosphinic Acids2.1 Synthetic Results2.2 Scope and Limitation of the Application of MWs2.3 Modelling the Distribution of the Local Overheatings and Predicting Their Effect3 The Simplification of Catalytic Systems3.1 Replacement of the Catalyst by MW Irradiation3.1.1 The Kabachnik–Fields Reaction3.1.2 Solid–Liquid Phase Alkylation of Active Methylene-Containing Compounds3.1.3 Solid–Liquid Phase Alkylation of Phosphinic Acids3.1.4 The Deoxygenation of Phosphine Oxides3.2 The Hirao Reaction without Added P-Ligands4 Conclusions
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Kurien, Caneon, Ajay Kumar Srivastava, Niranajan Gandigudi, and Karan Anand. "Soot deposition effects and microwave regeneration modelling of diesel particulate filtration system." Journal of the Energy Institute 93, no. 2 (April 2020): 463–73. http://dx.doi.org/10.1016/j.joei.2019.07.005.
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Larger, Laurent. "Complexity in electro-optic delay dynamics: modelling, design and applications." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 1999 (September 28, 2013): 20120464. http://dx.doi.org/10.1098/rsta.2012.0464.
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Nonlinear delay dynamics have found during the last 30 years a particularly prolific exploration area in the field of photonic systems. Besides the popular external cavity laser diode set-ups, we focus in this article on another experimental realization involving electro-optic (EO) feedback loops, with delay. This approach has strongly evolved with the important technological progress made on broadband photonic and optoelectronic devices dedicated to high-speed optical telecommunications. The complex dynamical systems performed by nonlinear delayed EO feedback loop architectures were designed and explored within a huge range of operating parameters. Thanks to the availability of high-performance photonic devices, these EO delay dynamics led also to many successful, efficient and diverse applications, beyond the many fundamental questions raised from the observation of experimental behaviours. Their chaotic motion allowed for a physical layer encryption method to secure optical data, with a demonstrated capability to operate at the typical speed of modern optical telecommunications. Microwave limit cycles generated in similar EO delay oscillators showed significantly improved spectral purity thanks to the use of a very long fibre delay line. Last but not least, a novel brain inspired computational principle has been recently implemented physically in photonics for the first time, again on the basis of an EO delay dynamical system. In this latter emerging application, the computed result is obtained by a proper ‘read-out’ of the complex nonlinear transients emerging from a fixed point, the transient being issued by the injection of the information signal to be processed.
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Geer, Alan J. "Physical characteristics of frozen hydrometeors inferred with parameter estimation." Atmospheric Measurement Techniques 14, no. 8 (August 6, 2021): 5369–95. http://dx.doi.org/10.5194/amt-14-5369-2021.
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Abstract. Frozen hydrometeors are found in a huge range of shapes and sizes, with variability on much smaller scales than those of typical model grid boxes or satellite fields of view. Neither models nor in situ measurements can fully describe this variability, so assumptions have to be made in applications including atmospheric modelling and radiative transfer. In this work, parameter estimation has been used to optimise six different assumptions relevant to frozen hydrometeors in passive microwave radiative transfer. This covers cloud overlap, convective water content and particle size distribution (PSD), the shapes of large-scale snow and convective snow, and an initial exploration of the ice cloud representation (particle shape and PSD combined). These parameters were simultaneously adjusted to find the best fit between simulations from the European Centre for Medium-range Weather Forecasts (ECMWF) assimilation system and near-global microwave observations covering the frequency range 19 to 190 GHz. The choices for the cloud overlap and the convective particle shape were particularly well constrained (or identifiable), and there was even constraint on the cloud ice PSD. The practical output is a set of improved assumptions to be used in version 13.0 of the Radiative Transfer for TOVS microwave scattering package (RTTOV-SCATT), taking into account newly available particle shapes such as aggregates and hail, as well as additional PSD options. The parameter estimation explored the full parameter space using an efficient assumption of linearly additive perturbations. This helped illustrate issues such as multiple minima in the cost function, and non-Gaussian errors, that would make it hard to implement the same approach in a standard data assimilation system for weather forecasting. Nevertheless, as modelling systems grow more complex, parameter estimation is likely to be a necessary part of the development process.
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Stepanets, I. V., V. A. Stepanets, E. M. Zaychik, and S. M. Odoevsky. "FEATURES OF THE APPLICATION AND PLANNING OF THE MICROWAVE TRANSMISSION IN THE 5th GENERATION NETWORKS." Informatization and communication, no. 3 (May 24, 2019): 77–83. http://dx.doi.org/10.34219/2078-8320-2019-10-3-77-83.
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Goal. Architecture and radio access technologies of 5G networks set high requirements towards throughput, latency and reliability of the distributive transport networks. Regarding to this, the goal of this paper is to carry out the analysis of actual characteristics of microwave transmission planning and its application, which is essential for the wireless segment of the distributive transport network of 5G. Materials and methods. The requirements for automatization of the planning processes were defined for communication networks in general and for microwave transmission in particular. This requirements definition is based on analysis of 5G network architecture, its characteristics and development tendency. The automatization must embrace all of the planning phases, including the solutions of the calculation and information tasks. Moreover, the automatization must represent an instrument for the decision support in development, modernization and optimization of the telecommunication networks, including microwave transmission. This must be based on the modelling within a specialized software platform, which is able to cooperate with the external databases and management systems. Results. The longstanding research of the authors is embodied in the software complex for planning and optimization of telecommunication networks ONEPLAN, which has a module architecture. This allows to carry out the planning and optimization of microwave transmission, throughput capabilities and data traffic distribution within the transport networks, as well as to make the analysis for data traffic reliability. Conclusion. Planning process automatization by the software platform ONEPLAN maintains efficiently the forehanded, technically and economically reasonable decision making for the development, modernization and optimization of the telecommunication networks including the wireless segment of 5G transport networks based on microwave transmission.
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Gu, Taochen, Fayu Wan, Jamel Nebhen, Nour Mohammad Murad, Jérôme Rossignol, Sebastien Lallechere, and Blaise Ravelo. "Bandpass NGD investigation of O-shape fully distributed structure with S-matrix modelling." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 40, no. 3 (July 14, 2021): 640–59. http://dx.doi.org/10.1108/compel-01-2021-0019.
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Purpose The aim of this paper is to provide the theoretical conceptualization of a bandpass (BP) negative group delay (NGD) microstrip circuit. The main objective is to provide a theorization of the particular geometry of the microstrip circuit with experimental validation of the NGD effect. Design/methodology/approach The methodology followed in this work is organized in three steps. A theoretical model is established of equivalent S-parameters model using Y-matrix analysis. The GD analysis is also presented by showing that the circuit presents a possibility to generate NGD function around certain frequencies. To validate the theoretical model, as proof-of-concept (POC), a microstrip prototype is designed, fabricated and tested. Findings This work clearly highlighted the modelled (analytical design model), simulated (ADS simulation tool) and measured results are in good correlation. Relying on the proposed theoretical, numerical and experimental models, the BP NGD behaviour is validated successfully with GD responses specified by the NGD centre frequency: it is observed around 2.35 GHz, with an NGD value of about −2 ns. Research limitations/implications It is to be noticed the proposed GD analysis requires limitations of the theoretical NGD model. It is depicted and validated through a POC demonstrating that the circuit presents a possibility to generate NGD function around certain frequencies (assuming constraints around usable frequency and bandwidth). Practical implications The NGD O-shape topology developed in this work could be exploited in the future in the microwave and radiofrequency context. Thus, it is expected to develop GD equalization technique for radiofrequency and microwave filters, GD compensation of oscillators, filters and communication systems, design of broadband switch-less bi-directional amplifiers, efficient enhancement of feedforward amplifiers, design method of frequency independent phase shifters with negligible delay, synthesis method of arbitrary-angle beamforming antennas. The BP NGD behavior may also be successfully used for the reduction of resonance effect for the electronic compatibility (EMC) of electronic devices. Social implications The non-conventional NGD O-circuit theoretical development and validation through experimental POC could be exploited by academic and industrial developers in the area of wireless communications including, but not restricted to, 5-generation communication systems. The use of the remarkable NGD effect is also useful for the mitigation of electromagnetic interferences between electronic devices and more and more complex electromagnetic environment (current development of Internet of Things[ IoT]). Originality/value The originality of this work relies on the new NGD design proposed in this work including the extraction of S-matrix parameters of the microstrip novel structure designed. The validation process based upon an experimental POC showed very interesting levels of NGD O-circuit (nanosecond-GD duration).
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Tsudik, A. V., and A. V. Glushkov. "SPECTROSCOPY AND DYNAMICS OF NONLINEAR PROCESSES IN RELATIVISTIC BACKWARD-WAVE TUBE WITH ACCOUNTING FOR EFFECTS OF SPACE CHARGE, DISSIPATION AND WAVE REFLECTIONS." Photoelectronics, no. 30 (August 21, 2022): 89–96. http://dx.doi.org/10.18524/0235-2435.2021.30.262863.
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An effective universal, approach to solving the problems of quantitative modelling and analysis of the fundamental characteristics of spectroscopy and dynamics of the nonlinear processes in relativistic microwave electronics devices, in particular, a relativistic backward wave tube (RBWT) has been developed and implemented. It has been performed modelling, analysis, and prediction of chaotic dynamics of RBWT with simultaneous consideration of not only relativistic effects, but also the effects of dissipation, presence of space charge, wave reflections at the ends of the decelerating system, etc in a wide range of changes at different values of control parameters, which are characteristic for the distributed relativistic electron-wave self-oscillating systems. From physical viewpoint the transition to chaos in the dynamics of the studied RBWT occurs according to the scenario everywhere in the sequence of period-doubling bifurcations, but with the growth of relativism, the dynamics become fundamentally complicated with the alternation of quasi-harmonic and chaotic regimes (including the appearance of the "beak" effect on the bifurcation diagram) and the transition everywhere intermittency to the high-D attractor.
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Bartsch, A., A. M. Trofaier, G. Hayman, D. Sabel, S. Schlaffer, D. Clark, and E. Blyth. "Detection of wetland dynamics with ENVISAT ASAR in support of methane modelling at high latitudes." Biogeosciences Discussions 8, no. 4 (August 12, 2011): 8241–68. http://dx.doi.org/10.5194/bgd-8-8241-2011.
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Abstract. Spatial information on inundation dynamics is expected to improve greenhouse gas estimates in climate models. Satellite data can provide land cover information from local to global scale. The detection capability for dynamics is however limited. Cloud cover and daylight independent methods are required for frequent updates. Suitable are therefore sensors which make use of microwaves. The purpose of the present study is to assess such data for determination of wetland dynamics from the viewpoint of use in climate models of the boreal and tundra environments. The focus is on synthetic aperture radar (SAR) operating in C-band due to, among microwave systems, comparably good spatial resolution and data availability. Continuity is also expected for such systems. Simple classification algorithms can be applied to detect open water in an automatised way allowing the processing of time series. Such approaches are robust when the water surface is smooth. C-band data from ENVISAT ASAR (Advanced SAR) operating in wide swath mode (150 m resolution) have been investigated for implementation of an automated detection procedure of open water fraction. More than 4000 samples (single acquisitions tiled into 0.5 degree grid cells) have been analysed for July/August 2007 and 2008. Modification of input parameters results in differences below 1 % open water fraction. The actual challenge is the frequent occurrence of waves due to wind and precipitation. This reduces the separability of the water class from other land cover. The possible update intervals for surface water extent are therefore decreased considerably. Statistical measures of the backscatter distribution can be applied in order to retrieve the for classification suitable data. The Pearson correlation between each sample dataset and a location specific representation of the bimodal distribution has been used for assessment. On average only 40 % of acquisitions allow a separation of the open water class. Satellite data are available every 2–3 days over the Western Siberian study region. With respect to the irregular acquisition intervals and varying length of unsuitable weather periods a minimum update interval of 10 days is suggested for the Northern Eurasian test case. Although SAR data availability is currently constraint future satellite missions which aim for operational services such as Sentinel-1 with its C-band SAR instrument may provide the basis for inundation monitoring in support of climate modelling.
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Malo-Torreiro, Sergio, Marta Seijas-Iglesias, and Iñigo Cuiñas. "A Comparison of Distribution Models for Fast Variations in the Indoor Radio Channel at 5G Frequency Range 1 Microwave Bands." Electronics 11, no. 3 (February 2, 2022): 449. http://dx.doi.org/10.3390/electronics11030449.
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The use of long-term (slow variations) for modelling radio propagation behavior in indoor scenarios limits the validity of such models, as most of the environments induced fast variations overlapped with the slow ones. Real world data gathered at different locations in two bands within Fifth Generation FR1 spectrum, 3 GHz and 5 GHz, provide insight on the effect of such fast variations and on the distribution models that would be useful to complement the long term analysis with short term behavior in order to improve the design of such 5G microwave networks. Comparisons among short term performance taking into account both the frequency, the visibility conditions and the environment size, shape and furnishing are presented with the focus on modelling as accurate as possible the narrowband channel. The use of ΔBIC (describing the difference between Bayesian Information Criteria indexes of each fitting) complements and confirms the insight provided by direct inspection on traditional fitting plots. This parameter could be interesting for future network deployments.
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Yin, Yihui, Wanli Yang, Shifeng Xie, and Binfeng Yun. "High-Efficiency Mitigation of Nonlinear Distortion in Microwave Photonics Link Assisted by Artificial Neural Network." Wireless Communications and Mobile Computing 2022 (June 1, 2022): 1–8. http://dx.doi.org/10.1155/2022/6327479.
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A microwave photonics radio over fiber link can deliver the radio frequency (RF) signal to realize the antenna remote. When the signal is a broadband and multicarrier RF signal, there are some linear distortions in the link, such as the crossmodulation distortion (XMD) and third-order intermodulation distortion (IMD3). It will destroy the wide-bandwidth performance of the link. Traditional postdigital compensation methods for XMD and IMD3 mitigation extract the baseband signal and reconstruct the compensation signal with calculated compensation factor. Here, a kind of artificial neural network genetic algorithm (ANN-GA) distortion compensation technique is proposed to seek the compensation factor instead of calculations. The neural network algorithm is used to fit the mapping function between the compensation factor and the distortion and give a set of predicted data as the original individual fitness value for the genetic algorithm. Based on the original value, the minimal distortion, the corresponding optimal compensation factors γ and α are found with optimization iterations. Taking advantage of the optimal compensation factors, based on the traditional postdigital compensation method, the distortion is mitigated with a suppression ratio of -84.4 dB. In our paper, the mitigation technology of the XMD and IMD3 can be applied for any kinds of link instead of mathematically modelling the link and calculating the compensation factor. The technology can improve the intelligence and flexibility of microwave photonic link linearization design.
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Denzel, Philipp, Jonathan P. Coles, Prasenjit Saha, and Liliya L. R. Williams. "The Hubble constant from eight time-delay galaxy lenses." Monthly Notices of the Royal Astronomical Society 501, no. 1 (November 25, 2020): 784–801. http://dx.doi.org/10.1093/mnras/staa3603.
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ABSTRACT We present a determination of the Hubble constant from the joint, free-form analysis of eight strongly, quadruply lensing systems. In the concordance cosmology, we find $H_0{} = 71.8^{+3.9}_{-3.3}\, \mathrm{km}\, \mathrm{s}^{-1}\, \mathrm{Mpc}^{-1}{}{}$ with a precision of $4.97{{\ \rm per\ cent}}$. This is in agreement with the latest measurements from supernovae Type Ia and Planck observations of the cosmic microwave background. Our precision is lower compared to these and other recent time-delay cosmography determinations, because our modelling strategies reflect the systematic uncertainties of lensing degeneracies. We furthermore are able to find reasonable lensed image reconstructions by constraining to either value of H0 from local and early Universe measurements. This leads us to conclude that current lensing constraints on H0 are not strong enough to break the ‘Hubble tension’ problem of cosmology.
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Albergel, C., G. Balsamo, P. de Rosnay, J. Muñoz-Sabater, and S. Boussetta. "A bare ground evaporation revision in the ECMWF land-surface scheme: evaluation of its impact using ground soil moisture and satellite microwave data." Hydrology and Earth System Sciences 16, no. 10 (October 16, 2012): 3607–20. http://dx.doi.org/10.5194/hess-16-3607-2012.
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Abstract. In situ soil moisture data from 122 stations across the United States are used to evaluate the impact of a new bare ground evaporation formulation at ECMWF. In November 2010, the bare ground evaporation used in ECMWF's operational Integrated Forecasting System (IFS) was enhanced by adopting a lower stress threshold than for the vegetation, allowing a higher evaporation. It results in more realistic soil moisture values when compared to in situ data, particularly over dry areas. Use was made of the operational IFS and offline experiments for the evaluation. The latter are based on a fixed version of the IFS and make it possible to assess the impact of a single modification, while the operational analysis is based on a continuous effort to improve the analysis and modelling systems, resulting in frequent updates (a few times a year). Considering the field sites with a fraction of bare ground greater than 0.2, the root mean square difference (RMSD) of soil moisture is shown to decrease from 0.118 m3 m−3 to 0.087 m3 m−3 when using the new formulation in offline experiments, and from 0.110 m3 m−3 to 0.088 m3 m−3 in operations. It also improves correlations. Additionally, the impact of the new formulation on the terrestrial microwave emission at a global scale is investigated. Realistic and dynamically consistent fields of brightness temperature as a function of the land surface conditions are required for the assimilation of the SMOS data. Brightness temperature simulated from surface fields from two offline experiments with the Community Microwave Emission Modelling (CMEM) platform present monthly mean differences up to 7 K. Offline experiments with the new formulation present drier soil moisture, hence simulated brightness temperature with its surface fields are larger. They are also closer to SMOS remotely sensed brightness temperature.
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Albergel, C., G. Balsamo, P. de Rosnay, J. Muñoz-Sabater, and S. Boussetta. "A bare ground evaporation revision in the ECMWF land-surface scheme: evaluation of its impact using ground soil moisture and satellite microwave data." Hydrology and Earth System Sciences Discussions 9, no. 5 (May 30, 2012): 6715–52. http://dx.doi.org/10.5194/hessd-9-6715-2012.
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Abstract. In situ soil moisture data from 122 stations across the United States are used to evaluate the impact of a new bare ground evaporation formulation at ECMWF. In November 2010 the bare ground evaporation used in ECMWF's operational Integrated Forecasting System (IFS) was enhanced by adopting a lower stress threshold than for the vegetation, allowing a higher evaporation. It results in more realistic soil moisture values when compared to in situ data, particularly over dry areas. Use was made of the operational IFS and offline experiments for the evaluation. The latter are based on a fixed version of the IFS and make it possible to assess the impact of a single modification while the operational analysis is based on a continuous effort to improve the analysis and modelling systems, resulting in frequent updates (few times a year). Considering the field sites with a fraction of bare ground greater than 0.2, the root mean square difference (RMSD) of soil moisture is shown to decrease from 0.118 m3 m−3 to 0.087 m3 m−3 when using the new formulation in offline experiments, and from 0.110 m3 m−3 to 0.088 m3 m−3 in operations. It also improves correlations. Additionally the impact of the new formulation on the terrestrial microwave emission at a global scale is investigated. Realistic and dynamically consistent fields of brightness temperature as a function of the land surface conditions are required for the assimilation of the SMOS data. Brightness temperature simulated from surface fields from two offline experiments with the Community Microwave Emission Modelling (CMEM) platform present monthly mean differences up to 7 K. Offline experiment with the new formulation presents drier soil moisture, hence simulated brightness temperature with its surface fields are larger. They are also closer to SMOS remotely sensed brightness temperature.
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Wymysłowski, Artur, Waldemar Wiejak, and Piotr Słupski. "MICROWAVE TRAVELLING WAVE TUBE - A SUMMARY OF AN ANALYTICAL, NUMERICAL AND EXPERIMENTAL THERMAL ANALYSIS." International Journal of Research -GRANTHAALAYAH 5, no. 6 (June 30, 2017): 353–61. http://dx.doi.org/10.29121/granthaalayah.v5.i6.2017.2042.
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Travelling Wave Tube (TWT) is an electronic vacuum microwave device, which is used as a high power microwave amplifier, mainly in telecommunication purposes and radar systems. TWT's seem to be an alternative and a more reliable solution than semiconductor devices when building high power and high frequency applications. Thermal behaviour of TWT is one of the key aspects influencing its reliability and working parameters. In fact, the standard TWT is treated as a high power device and the supplied power is dissipated mainly through conduction and convection phenomena. In practical applications, depending on a type of TWT, they can be cooled either by a forced liquid or air circulation. The main goal of the presented research was to perform analytical, experimental and numerical analysis of temperature distribution of a low band TWT in case of a typical working condition. Because theoretical analysis seems to be very complex, thus it was decided to support it with experimental measurements and numerical simulations as well as with the simplified analytical formulas. As a first step of the presented research, the analytical analysis and numerical modelling of the helix TWT was carried out. The objective of the thermal analysis was to assess the temperature distribution in different parts of the helix TWT assembly during extreme standard and working conditions. Afterwards, the obtained numerical results were validated by experimental measurements, which were carried out using a custom designed TWT test sample and corresponding experimental measurement tools.
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Bartsch, A., A. M. Trofaier, G. Hayman, D. Sabel, S. Schlaffer, D. B. Clark, and E. Blyth. "Detection of open water dynamics with ENVISAT ASAR in support of land surface modelling at high latitudes." Biogeosciences 9, no. 2 (February 8, 2012): 703–14. http://dx.doi.org/10.5194/bg-9-703-2012.
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Abstract. Wetlands are generally accepted as being the largest but least well quantified single source of methane (CH4). The extent of wetland or inundation is a key factor controlling methane emissions, both in nature and in the parameterisations used in large-scale land surface and climate models. Satellite-derived datasets of wetland extent are available on the global scale, but the resolution is rather coarse (>25 km). The purpose of the present study is to assess the capability of active microwave sensors to derive inundation dynamics for use in land surface and climate models of the boreal and tundra environments. The focus is on synthetic aperture radar (SAR) operating in C-band since, among microwave systems, it has comparably high spatial resolution and data availability, and long-term continuity is expected. C-band data from ENVISAT ASAR (Advanced SAR) operating in wide swath mode (150 m resolution) were investigated and an automated detection procedure for deriving open water fraction has been developed. More than 4000 samples (single acquisitions tiled onto 0.5° grid cells) have been analysed for July and August in 2007 and 2008 for a study region in Western Siberia. Simple classification algorithms were applied and found to be robust when the water surface was smooth. Modification of input parameters results in differences below 1 % open water fraction. The major issue to address was the frequent occurrence of waves due to wind and precipitation, which reduces the separability of the water class from other land cover classes. Statistical measures of the backscatter distribution were applied in order to retrieve suitable classification data. The Pearson correlation between each sample dataset and a location specific representation of the bimodal distribution was used. On average only 40 % of acquisitions allow a separation of the open water class. Although satellite data are available every 2–3 days over the Western Siberian study region, the irregular acquisition intervals and periods of unsuitable weather suggest that an update interval of 10 days is more realistic for this domain. SAR data availability is currently limited. Future satellite missions, however, which aim for operational services (such as Sentinel-1 with its C-band SAR instrument), may provide the basis for inundation monitoring for land surface and climate modelling applications.
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Tultemirova, G. U., N. T. Momunalieva, and A. J. Akkozov. "COMPUTER MODEL OF HOLOGRAM SYNTHESIS BY THE REAL PHASE." Herald of KSUCTA, №2, Part 1, 2022, no. 2-1-2022 (April 30, 2022): 289–94. http://dx.doi.org/10.35803/1694-5298.2022.2.289-294.
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Computer-synthesized holograms are widely used in areas such as optical information processing, image recognition, three-dimensional display of digital data, and modelling of holographic processes. It is difficult to overestimate the usefulness of the use of synthesized holograms for image reconstruction in acoustic and microwave holography. The use of synthesized holograms as elements of holographic storage devices is promising. Computer synthesis is often the only way to obtain holograms with desired properties. The main advantage of the synthesized hologram is that it is an effective means for converting digital information into optical. Due to this, it is possible to create hybrid-computing systems that are unique in performance, including digital electronic and optical processors and combining the flexibility and versatility of an electronic computer with the enormous performance inherent in an optical processor due to the parallelism of optical information processing. The use of digital holograms as elements in holographic storage devices is promising.
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Shen, Liuyang, Yong Zhu, Chenghai Liu, Lei Wang, Hui Liu, Md Kamruzzaman, Chai Liu, Youpeng Zhang, and Xianzhe Zheng. "Modelling of moving drying process and analysis of drying characteristics for germinated brown rice under continuous microwave drying." Biosystems Engineering 195 (July 2020): 64–88. http://dx.doi.org/10.1016/j.biosystemseng.2020.05.002.
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Huang, Guocheng, Meicheng Fu, Junli Qi, Jinghan Pan, Wenjun Yi, and Xiujian Li. "Design of Broadband Flat Optical Frequency Comb Based on Cascaded Sign-Alternated Dispersion Tellurite Microstructure Fiber." Micromachines 12, no. 10 (October 15, 2021): 1252. http://dx.doi.org/10.3390/mi12101252.
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We designed a tellurite microstructure fiber (TMF) and proposed a broadband optical frequency comb generation scheme that was based on electro-optical modulation and cascaded sign-alternated dispersion TMF (CSAD-TMF). In addition, the influence of different nonlinear effects, the ultrashort pulse evolution in the CSAD-TMF with the anomalous dispersion (AD) zones and the normal dispersion (ND) zones were analyzed based on the generalized nonlinear Schrodinger equations (GNLSE) modelling. According to the simulations, when the input seed comb had a repetition rate of 20 GHz and had an input pulse peak power of 30 W, the generation scheme could generate optical frequency combs with a 6 dB spectral bandwidth spanning over 170 nm centered at 1550 nm. Furthermore, the generated combs showed good coherence in performance over the whole 6 dB spectral bandwidth. The highly coherent optical frequency combs can be used as high-repetition-rate, multi-wavelength light sources for various integrated microwave photonics and ultrafast optical signal processing applications.
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Rios Gaona, M. F., A. Overeem, H. Leijnse, and R. Uijlenhoet. "Measurement and interpolation uncertainties in rainfall maps from cellular communication networks." Hydrology and Earth System Sciences 19, no. 8 (August 14, 2015): 3571–84. http://dx.doi.org/10.5194/hess-19-3571-2015.
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Abstract. Accurate measurements of rainfall are important in many hydrological and meteorological applications, for instance, flash-flood early-warning systems, hydraulic structures design, irrigation, weather forecasting, and climate modelling. Whenever possible, link networks measure and store the received power of the electromagnetic signal at regular intervals. The decrease in power can be converted to rainfall intensity, and is largely due to the attenuation by raindrops along the link paths. Such an alternative technique fulfils the continuous effort to obtain measurements of rainfall in time and space at higher resolutions, especially in places where traditional rain gauge networks are scarce or poorly maintained. Rainfall maps from microwave link networks have recently been introduced at country-wide scales. Despite their potential in rainfall estimation at high spatiotemporal resolutions, the uncertainties present in rainfall maps from link networks are not yet fully comprehended. The aim of this work is to identify and quantify the sources of uncertainty present in interpolated rainfall maps from link rainfall depths. In order to disentangle these sources of uncertainty, we classified them into two categories: (1) those associated with the individual microwave link measurements, i.e. the errors involved in link rainfall retrievals, such as wet antenna attenuation, sampling interval of measurements, wet/dry period classification, dry weather baseline attenuation, quantization of the received power, drop size distribution (DSD), and multi-path propagation; and (2) those associated with mapping, i.e. the combined effect of the interpolation methodology and the spatial density of link measurements. We computed ~ 3500 rainfall maps from real and simulated link rainfall depths for 12 days for the land surface of the Netherlands. Simulated link rainfall depths refer to path-averaged rainfall depths obtained from radar data. The ~ 3500 real and simulated rainfall maps were compared against quality-controlled gauge-adjusted radar rainfall fields (assumed to be the ground truth). Thus, we were able to not only identify and quantify the sources of uncertainty in such rainfall maps, but also test the actual and optimal performance of one commercial microwave network from one of the cellular providers in the Netherlands. Errors in microwave link measurements were found to be the source that contributes most to the overall uncertainty.
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Pelicano, Ana Catarina, and Raquel C. Conceição. "Development of a 3D Anthropomorphic Phantom Generator for Microwave Imaging Applications of the Head and Neck Region." Sensors 20, no. 7 (April 4, 2020): 2029. http://dx.doi.org/10.3390/s20072029.
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The development of 3D anthropomorphic head and neck phantoms is of crucial and timely importance to explore novel imaging techniques, such as radar-based MicroWave Imaging (MWI), which have the potential to accurately diagnose Cervical Lymph Nodes (CLNs) in a neoadjuvant and non-invasive manner. We are motivated by a significant diagnostic blind-spot regarding mass screening of LNs in the case of head and neck cancer. The timely detection and selective removal of metastatic CLNs will prevent tumor cells from entering the lymphatic and blood systems and metastasizing to other body regions. The present paper describes the developed phantom generator which allows the anthropomorphic modelling of the main biological tissues of the cervical region, including CLNs, as well as their dielectric properties, for a frequency range from 1 to 10 GHz, based on Magnetic Resonance images. The resulting phantoms of varying complexity are well-suited to contribute to all stages of the development of a radar-based MWI device capable of detecting CLNs. Simpler models are essential since complexity could hinder the initial development stages of MWI devices. Besides, the diversity of anthropomorphic phantoms resulting from the developed phantom generator can be explored in other scientific contexts and may be useful to other medical imaging modalities.
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Rios Gaona, M. F., A. Overeem, H. Leijnse, and R. Uijlenhoet. "Sources of uncertainty in rainfall maps from cellular communication networks." Hydrology and Earth System Sciences Discussions 12, no. 3 (March 25, 2015): 3289–317. http://dx.doi.org/10.5194/hessd-12-3289-2015.
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Abstract. Accurate measurements of rainfall are important in many hydrological and meteorological applications, for instance, flash-flood early-warning systems, hydraulic structures design, irrigation, weather forecasting, and climate modelling. Whenever possible, link networks measure and store the received power of the electromagnetic signal at regular intervals. The decrease in power can be converted to rainfall intensity, and is largely due to the attenuation by raindrops along the link paths. Such alternative technique fulfills the continuous strive for measurements of rainfall in time and space at higher resolutions, especially in places where traditional rain gauge networks are scarce or poorly maintained. Rainfall maps from microwave link networks have recently been introduced at country-wide scales. Despite their potential in rainfall estimation at high spatiotemporal resolutions, the uncertainties present in rainfall maps from link networks are not yet fully comprehended. The aim of this work is to identify and quantify the sources of uncertainty present in interpolated rainfall maps from link rainfall depths. In order to disentangle these sources of uncertainty, we classified them into two categories: (1) those associated with the individual microwave link measurements, i.e., the errors involved in single-link rainfall retrievals such as wet antenna attenuation, sampling interval of measurements, wet/dry period classification, quantization of the received power, drop size distribution (DSD), and multi-path propagation; (2) those associated with mapping, i.e., the combined effect of the interpolation methodology and the spatial density of link measurements. We computed ~3500 rainfall maps from real and simulated link rainfall depths for 12 days for the land surface of the Netherlands. Simulated link rainfall depths were obtained from radar data. These rainfall maps were compared against quality-controlled gauge-adjusted radar rainfall fields (assumed to be the ground truth). Thus, we were able to not only identify and quantify the sources of uncertainty in such rainfall maps, but also to test the actual and optimal performance of one commercial microwave network from one of the cellular providers in the Netherlands.
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Massari, C., L. Brocca, S. Barbetta, C. Papathanasiou, M. Mimikou, and T. Moramarco. "Using globally available soil moisture indicators for flood modelling in Mediterranean catchments." Hydrology and Earth System Sciences Discussions 10, no. 8 (August 22, 2013): 10997–1033. http://dx.doi.org/10.5194/hessd-10-10997-2013.
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Abstract. Floods are one of the most dangerous natural hazards in Mediterranean regions. Flood forecasting tools and early warning systems can be very beneficial to reduce flood risk. Event-based rainfall runoff models are frequently employed for operational flood forecasting purposes because of their simplicity and the reduced number of parameters involved with respect to continuous models. However, the advantages that are related with the reduced parameterization face against the need for a correct initialization of the model, especially in areas affected by strong climate seasonality. On the other hand, the use of continuous models may be very problematic in poorly gauged areas. This paper introduces a simplified continuous rainfall-runoff model, which uses globally available soil moisture retrievals to identify the initial wetness condition of the catchment, and, only event rainfall data to simulate discharge hydrographs. The model calibration involves only 3 parameters. For soil moisture, beside in situ and modelled data, satellite products from the Advanced SCATterometer (ASCAT) and the Advanced Microwave Scanning Radiometer for Earth observation (AMSR-E) sensors are employed. Additionally, the ERA-LAND reanalysis soil moisture product of the European Centre for Medium Range Weather Forecasting (ECMWF) is used. The model was tested in the small catchment of Rafina, 109 km2 located in the Eastern Attica region, Greece. Specifically, fifteen rainfall-runoff events were modelled by considering different configurations for the initial soil moisture conditions. Comparing the performance of the different soil moisture products, it was found that all global indicators allow reproducing fairly well the selected flood events providing much better results than the situation where a constant initial condition is provided. ERA-LAND slightly outperforms the satellite soil moisture products and in general, all the indicators give the same performance obtained by ground and continuously simulated soil moisture data. Due to the wide diffusion of globally available soil moisture retrievals and the small amount of parameters used, the proposed modelling approach is very suitable for runoff prediction in poorly gauged areas.
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Han, X., X. Li, G. He, P. Kumbhar, C. Montzka, S. Kollet, T. Miyoshi, et al. "DasPy 1.0 – the Open Source Multivariate Land Data Assimilation Framework in combination with the Community Land Model 4.5." Geoscientific Model Development Discussions 8, no. 8 (August 28, 2015): 7395–444. http://dx.doi.org/10.5194/gmdd-8-7395-2015.
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Abstract. Data assimilation has become a popular method to integrate observations from multiple sources with land surface models to improve predictions of the water and energy cycles of the soil-vegetation-atmosphere continuum. Multivariate data assimilation refers to the simultaneous assimilation of observation data from multiple model state variables into a simulation model. In recent years, several land data assimilation systems have been developed in different research agencies. Because of the software availability or adaptability, these systems are not easy to apply for the purpose of multivariate land data assimilation research. We developed an open source multivariate land data assimilation framework (DasPy) which is implemented using the Python script language mixed with the C++ and Fortran programming languages. LETKF (Local Ensemble Transform Kalman Filter) is implemented as the main data assimilation algorithm, and uncertainties in the data assimilation can be introduced by perturbed atmospheric forcing data, and represented by perturbed soil and vegetation parameters and model initial conditions. The Community Land Model (CLM) was integrated as the model operator. The implementation allows also parameter estimation (soil properties and/or leaf area index) on the basis of the joint state and parameter estimation approach. The Community Microwave Emission Modelling platform (CMEM), COsmic-ray Soil Moisture Interaction Code (COSMIC) and the Two-Source Formulation (TSF) were integrated as observation operators for the assimilation of L-band passive microwave, cosmic-ray soil moisture probe and land surface temperature measurements, respectively. DasPy has been evaluated in several assimilation studies of neutron count intensity (soil moisture), L-band brightness temperature and land surface temperature. DasPy is parallelized using the hybrid Message Passing Interface and Open Multi-Processing techniques. All the input and output data flows are organized efficiently using the commonly used NetCDF file format. Online 1-D and 2-D visualization of data assimilation results is also implemented to facilitate the post simulation analysis. In summary, DasPy is a ready to use open source parallel multivariate land data assimilation framework.
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Shajib, A. J., S. Birrer, T. Treu, A. Agnello, E. J. Buckley-Geer, J. H. H. Chan, L. Christensen, et al. "STRIDES: a 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408−5354." Monthly Notices of the Royal Astronomical Society 494, no. 4 (March 28, 2020): 6072–102. http://dx.doi.org/10.1093/mnras/staa828.
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ABSTRACT We present a blind time-delay cosmographic analysis for the lens system DES J0408−5354. This system is extraordinary for the presence of two sets of multiple images at different redshifts, which provide the opportunity to obtain more information at the cost of increased modelling complexity with respect to previously analysed systems. We perform detailed modelling of the mass distribution for this lens system using three band Hubble Space Telescope imaging. We combine the measured time delays, line-of-sight central velocity dispersion of the deflector, and statistically constrained external convergence with our lens models to estimate two cosmological distances. We measure the ‘effective’ time-delay distance corresponding to the redshifts of the deflector and the lensed quasar $D_{\Delta t}^{\rm eff}=$$3382_{-115}^{+146}$ Mpc and the angular diameter distance to the deflector Dd = $1711_{-280}^{+376}$ Mpc, with covariance between the two distances. From these constraints on the cosmological distances, we infer the Hubble constant H0= $74.2_{-3.0}^{+2.7}$ km s−1 Mpc−1 assuming a flat ΛCDM cosmology and a uniform prior for Ωm as $\Omega _{\rm m} \sim \mathcal {U}(0.05, 0.5)$. This measurement gives the most precise constraint on H0 to date from a single lens. Our measurement is consistent with that obtained from the previous sample of six lenses analysed by the H0 Lenses in COSMOGRAIL’s Wellspring (H0LiCOW) collaboration. It is also consistent with measurements of H0 based on the local distance ladder, reinforcing the tension with the inference from early Universe probes, for example, with 2.2σ discrepancy from the cosmic microwave background measurement.
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Vlachos, Evangelos, John Thompson, Aryan Kaushik, and Christos Masouros. "Radio-frequency chain selection for energy and spectral efficiency maximization in hybrid beamforming under hardware imperfections." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, no. 2244 (December 2020): 20200451. http://dx.doi.org/10.1098/rspa.2020.0451.
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The next-generation wireless communications require reduced energy consumption, increased data rates and better signal coverage. The millimetre-wave frequency spectrum above 30 GHz can help fulfil the performance requirements of the next-generation mobile broadband systems. Multiple-input multiple-output technology can provide performance gains to help mitigate the increased path loss experienced at millimetre-wave frequencies compared with microwave bands. Emerging hybrid beamforming architectures can reduce the energy consumption and hardware complexity with the use of fewer radio-frequency (RF) chains. Energy efficiency is identified as a key fifth-generation metric and will have a major impact on the hybrid beamforming system design. In terms of transceiver power consumption, deactivating parts of the beamformer structure to reduce power typically leads to significant loss of spectral efficiency. Our aim is to achieve the highest energy efficiency for the millimetre-wave communications system while mitigating the resulting loss in spectral efficiency. To achieve this, we propose an optimal selection framework which activates specific RF chains that amplify the digitally beamformed signals with the analogue beamforming network. Practical precoding is considered by including the effects of user interference, noise and hardware impairments in the system modelling.
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Maltsev, Alexander A., Valentin M. Seleznev, Alexander S. Rulkov, and Olesya V. Bolkhovskaya. "STEERABLE TOROIDAL BIFOCAL LENS-ARRAY ANTENNA IN 57–64 GHZ RANGE." Journal of the Russian Universities. Radioelectronics 22, no. 3 (July 2, 2019): 36–47. http://dx.doi.org/10.32603/1993-8985-2019-22-3-36-47.
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Introduction. Currently, one of the most promising approaches of the 5th generation mobile wireless systems development is the deployment of heterogeneous networks based on existing LTE cellular systems with large and small cells. The main elements of such networks can be small low cost relay stations equipped with highly directional steerable antenna systems to connect small cells with LTE base station serving macrocell. Objective. Existing solutions are either too expensive or not allowing flexible rearrangement of current information transmission lines. The objective of this work is to develop antenna equipment for low cost relay stations based on simple steerable antenna systems of millimetre wavelength (57-64 GHz), which allow beamsteering in both azimuth and elevation planes. Methods and materials. The developed steerable bifocal lens antenna system is a lens of a special shape made of a high molecular weight polyethylene and integrated with a phased array antenna. A key feature of the designed antenna system is a wide-angle beamsteering in the azimuth plane and ability to adjust the beam in the elevation plane. The calculation of the lens profiles was carried out by means of an approximation of geometrical optics in Matlab, and the main technical characteristics of the lens antenna system were obtained by direct electromagnetic modelling in CST Microwave Studio. Results. The prototype of the steerable bifocal lens-array antenna system is developed and its characteristics are studied. The following technical characteristics are achieved in the 57–64 GHz range: beamsteering in the elevation plane is ±3º, beamsteering in the azimuth plane is ±40º, and antenna gain is from 20 to 27.5 dBi for all angles. Conclusion. It was shown that the developed antenna system can be successfully used as receiving and transmission antenna equipment of small relay stations that transmit information in the frequency range of 57-64 GHz over a distance of 100-300 m.
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Massari, C., L. Brocca, S. Barbetta, C. Papathanasiou, M. Mimikou, and T. Moramarco. "Using globally available soil moisture indicators for flood modelling in Mediterranean catchments." Hydrology and Earth System Sciences 18, no. 2 (February 28, 2014): 839–53. http://dx.doi.org/10.5194/hess-18-839-2014.
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Abstract. Floods are one of the most dangerous natural hazards in Mediterranean regions. Flood forecasting tools and early warning systems can be very beneficial to reducing flood risk. Event-based rainfall–runoff models are frequently employed for operational flood forecasting purposes because of their simplicity and the reduced number of parameters involved with respect to continuous models. However, the advantages related to the reduced parameterization oppose to the need of a correct initialization of the model, especially in areas characterized by strong climate seasonality. In this case, the use of continuous models could be desirable but it is very problematic in poorly gauged areas where continuous rainfall and temperature data are not available. This paper introduces a Simplified Continuous Rainfall–Runoff model (SCRRM), which uses globally available soil moisture retrievals to identify the initial wetness condition of the catchment, and, only event rainfall data to simulate discharge hydrographs. The model calibration involves only three parameters. For soil moisture, besides in situ data, satellite products from the Advanced SCATterometer (ASCAT) and the Advanced Microwave Scanning Radiometer for Earth observation (AMSR-E) sensors were employed. Additionally, the ERA-Land reanalysis soil moisture product of the European Centre for Medium-Range Weather Forecasting (ECMWF) was used. SCRRM was tested in the small catchment of the Rafina River, 109 km2, located in the eastern Attica region, Greece. Specifically, sixteen recorded rainfall–runoff events were simulated by considering the different indicators for the estimation of the initial soil moisture conditions from in situ, satellite and reanalysis data. By comparing the performance of the different soil moisture products, we conclude that: (i) all global indicators allow for a fairly good reproduction of the selected flood events, providing much better results than those obtained from setting constant initial conditions; (ii) the use of all the indicators yields similar results when compared with a standard continuous simulation approach that, however, is more data demanding; (iii) SCRRM is robust since it shows good performances in validation for a significant flood event that occurred on February 2013 (after calibrating the model for small to medium flood events). Due to the wide diffusion of globally available soil moisture retrievals and the limited number of parameters used, the proposed modelling approach is very suitable for runoff prediction in poorly gauged areas.
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Yue, Kai, Yiang Wei, Xiucheng Jin, Xiaochen Sun, and Xinxin Zhang. "Molecular mechanism of thermal sensitization effect of potential materials for microwave hyperthermia." Molecular Simulation 46, no. 12 (July 16, 2020): 932–41. http://dx.doi.org/10.1080/08927022.2020.1792901.
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Said Camilleri, Jeantide, Lourdes Farrugia, Sergio Curto, Dario B. Rodrigues, Laura Farina, Gordon Caruana Dingli, Julian Bonello, Iman Farhat, and Charles V. Sammut. "Review of Thermal and Physiological Properties of Human Breast Tissue." Sensors 22, no. 10 (May 20, 2022): 3894. http://dx.doi.org/10.3390/s22103894.
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Electromagnetic thermal therapies for cancer treatment, such as microwave hyperthermia, aim to heat up a targeted tumour site to temperatures within 40 and 44 °C. Computational simulations used to investigate such heating systems employ the Pennes’ bioheat equation to model the heat exchange within the tissue, which accounts for several tissue properties: density, specific heat capacity, thermal conductivity, metabolic heat generation rate, and blood perfusion rate. We present a review of these thermal and physiological properties relevant for hyperthermia treatments of breast including fibroglandular breast, fatty breast, and breast tumours. The data included in this review were obtained from both experimental measurement studies and estimated properties of human breast tissues. The latter were used in computational studies of breast thermal treatments. The measurement methods, where available, are discussed together with the estimations and approximations considered for values where measurements were unavailable. The review concludes that measurement data for the thermal and physiological properties of breast and tumour tissue are limited. Fibroglandular and fatty breast tissue properties are often approximated from those of generic muscle or fat tissue. Tumour tissue properties are mostly obtained from approximating equations or assumed to be the same as those of glandular tissue. We also present a set of reliable data, which can be used for more accurate modelling and simulation studies to better treat breast cancer using thermal therapies.