Digital beamforming (DBF) technique is a promising technique for future synthetic aperture radar (SAR). In this paper, we present the preliminary experiment and results. The measurements were ...accomplished by a ground-based DBF SAR system for a single target. The system is evaluated by mono-static SAR operation first. Comparing between DBF SAR and mono-static SAR images the channel imbalance effect is investigated. Since the experiment provides the SAR raw data containing the system response, from this raw data we estimate the linear phase error due to the channel imbalance and compensate it. The reconstructed DBF SAR images show that the minimum variation of the phase between the receive channel is crucial to obtain the theoretical improvement factor.
Novel concepts for synthetic radar (SAR) systems are designed to use the potential of multiple transmit or/and receive front-ends. The DBF SAR, HRWS SAR or MIMO SAR improve the quality of the radar ...image using multiple receiver signals and adequate signal processing algorithms. The processing algorithms are developed with assumption of an ideal transmit and receive system. The effects that could occur in the transmitter or receiver front-end disturb the received signal and resulting Radar image. This paper is a contribution to the investigation of the influence of nonidealities of the SAR receiver. Presented are VKA-representation models of HRWS SAR receiver developed simulation considers also effects resulting from quantization and digital beamforming processing (DBF). The VKA-representation enables description of the receiver in a compact and simple way.
In conventional SAR system high azimuth resolution and wide swath width are parameters that can not be improved simultaneously. A High-Resolution Wide-Swath (HRWS) Synthetic Aperture Radar (SAR) ...system was design to reconcile those two contradictory requirements. In the paper presented is a simulation of the HRWS SAR system including some of possible system failures and nonidealities of system components. The goal of the simulation is the evaluation of the influence of distortions and failures and prediction of the systems performance in elevation.
Digital beamforming (DBF) technique is a promising technique for future Synthetic Aperture Radar (SAR). In this paper, we present the preliminary experiments and investigate the crucial parameters ...for the optimization of the DBF SAR. The measurements were accomplished by a ground-based DBF SAR system for a single target. The demonstrator provides the raw data including the system response. SAR images were reconstructed with numerous spatial sampling distances, not only by DBF SAR processing, but also conventional mono-static SAR processing. The reconstructed images show that the minimum variation of the phase between the receive channel is crucial to obtain the theoretical improvement factor and achieve the wide area observation with fine resolution.
The zona incerta has recently become an important target for deep-brain stimulation (DBS) in Parkinson’s disease (PD). The present review summarizes clinical, animal and anatomical data which have ...indicated an important role of this structure in PD, and discusses potential mechanisms involved in therapeutic effects of DBS. Animal studies have suggested initially some role of neurons as well as GABAergic and glutamatergic receptors of the zona incerta in locomotion and generation of PD signs. Anatomical data have indicated that thanks to its multiple interconnections with the basal ganglia, thalamus, cerebral cortex, brainstem, spinal cord and cerebellum, the zona incerta is an important link in a neuronal chain transmitting impulses involved in PD pathology. Finally, clinical studies have shown that DBS of this structure alleviates parkinsonian bradykinesia, muscle rigidity and tremor. DBS of caudal zona incerta seemed to be the most effective therapeutic intervention, especially with regard to reduction of PD tremor as well as other forms of tremor.
The polymorphism of resorcinol has been complementary studied by combining Raman, time-domain terahertz, and inelastic neutron scattering spectroscopy with modern solid-state density functional ...theory (DFT) calculations. The spectral differences, emerging from the temperature-induced structural phase transition, have been successfully interpreted with an emphasis on the low-wavenumber range. The given interpretation is based on the plane-wave DFT computations, providing an excellent overall reproduction of both wavenumbers and intensities and revealing the source of the observed spectral differences. The performance of the generalized gradient approximation (GGA) functionals in prediction of the structural parameters and the vibrational spectra of the normal-pressure polymorphs of resorcinol has been extensively examined. The results show that the standard Perdew, Burke, and Ernzerhof (PBE) approach along with its “hard” revised form tends to be superior if compared to the “soft” GGA approximation.
The results of studies conducted by means of complementary methods, differential scanning calorimetry, transmitted light intensity measurements, polarized optical microscopy, the electro-optical ...method, as well as dielectric relaxation spectroscopy of two new liquid crystal mixtures are presented. The first mixture is an equimolecular binary mixture consisting of two ferroelectric chiral liquid crystals from the homologous series, abbreviated as (S)-MHOBSn. The second mixture is a multicomponent mixture and consists of four mesogens from the homologous series of nOS5 as the base of the mixture, abbreviated as 610712 and chiral MHOBS8. The binary MHOBS4 + MHOBS7 mixture has an enantiotropic phase sequence, as follows: Cr, SmG*, SmI*, SmC*, N*. The second mixture has the same phase sequence but a much wider temperature range of ferroelectric SmC* phase. The switching time changes from 50 to 90 μs in the SmC* phase of the binary MHOBS4 + MHOBS7 mixture, whereas in 610712 + MHOBS8, the change is more than an order of magnitude higher, ranging from 500 to 3500 μs. Numerical analysis of the dielectric spectra results point toward the complex dynamics of the MHOBS4 + MHOBS7 and 610712 + MHOBS8 mixtures. The relaxation processes in the crystalline, SmC*, SmI*, and SmG* subphases have been observed and described. The relaxation processes have been detected up to 12 °C. There is a very low intensity Goldstone mode in SmC* and a low-frequency noncancellation mode in the SmI* and SmG* phases.
The aim of the research is to assess the potential of agricultural biomass available in European Union countries that can be used for energy purposes. The research took into account the potential of ...agricultural biomass from: straw from cereal crops, hay from permanent grasslands, natural fertilizers from animal husbandry, cultivation of energy crops on fallow land and waste wood from permanent crops. The study estimated the theoretical potential presenting the energy value of all existing agricultural biomass resources in EU countries and the technical potential taking into account agricultural biomass resources that are not used in agriculture. The research was based on Eurostat data for 2019. The conducted research shows that European Union countries are characterized by a significant potential of agricultural biomass. However, due to the high demand for this resource in agriculture, about 15% of the existing potential can be used for energy purposes. Among the analyzed sources, the highest potential is characterized by straw from cereal crops and by the cultivation of energy crops on fallow land. The conducted research also indicates a large spatial differentiation of the potential of agricultural biomass in European Union countries, which may have a negative impact on the economic efficiency of using this renewable energy source.
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