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Photophoretic force measurement on microparticles in binary complex plasmas
摘要： This article presents a method to measure the photophoretic force on microparticles in complex plasmas. A laser heating setup is used to increase the kinetic temperatures of binary mixtures composed of melamine-formaldehyde (MF) and silica (SiO2) particles. The temperature gain of both particle species due to the additional thermal reservoir is compared to a laser force model. Contributions of radiation pressure and photophoretic forces are determined through a variation of neutral gas pressure and application of Lorenz-Mie theory. The photophoretic force is found to be significant for MF particles at typical conditions in complex plasma experiments.
关键词： photophoretic force,microparticles,radiation pressure,complex plasmas,Lorenz-Mie theory,binary mixtures,laser heating
更新于2025-09-23 15:22:29
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Simulations of some physical parameters of homologous series of nBT and nCHBT at 0.3–20.0 THz
摘要： In this work, the terahertz (THz) absorption of homologous series of isothiocyanobiphenyls (nBT) and 4-(trans-4?-n-alkylcyclohexyl)isothiocyanato-benzene (nCHBT) are simulated by using the density functional theory (DFT) method. Numerical results show that absorption of the tested nematic liquid crystals (NLCs) varies up to 0.04 in the broad range of 0.3–20.0 THz and takes maximum value in the range of 9–14 THz. In addition, the values of molecular polarisabilities (αo, αe) increase with the increase in the number of carbon atoms in the alkyl chain, while refractive indices (no, ne) decreases. The calculated birefringence (Δn) values for nCHBT are approximately twice as large as the birefringence value for nBT. It is crucial to examine these series of nematic liquid crystals at THz frequencies due to the role of soft matter in various switchable THz components.
关键词： Numerical calculations,refractive index,terahertz radiation,birefringence,nematic liquid crystals
更新于2025-09-23 15:22:29
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Optical matching of a multimode gradient fibre and single-mode stepped-index fibre in a photopolymerizable composition
摘要： The opportunity to optically match waveguides characterized by an essentially different field structure in a photopolymerizable medium is investigated. The example of a multimode gradient fibre (core diameter 50 μm) and a single-mode stepped-index fibre SMF-28 (core diameter 8.2 μm) shows that the efficiency of radiation transmission from the wide fibre into the narrow one can reach 60% at a distance between their end faces of about 900 μm.
关键词： nonlinear optics,photopolymer,optical matching of fibres,fibre optics,laser radiation
更新于2025-09-23 15:22:29
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Towards a physical model for energy deposition via cosmic rays into sub-K bolometric detectors
摘要： Cosmology space missions have been known to be particularly sensitive to systematic effects arising from the interaction between cosmic rays and highly sensitive detectors below 200 mK. To remove this signal, one must first understand the deposition and dissipation of energy into these detectors. Using a well-known NTD germanium composite bolometer, we simulate the effect of cosmic rays using a radioactive source in the laboratory. Through analysis of experimental data, we find that the glitch signal shape is a function of incoming particle position, as well as the incoming particle energy. We report also on nonlinear effects in the fit, in order to lay the groundwork towards a new physical model for this energy propagation in the bolometer.
关键词： Interaction of radiation with matter,Cryogenic detectors,Systematic effects,Space instrumentation
更新于2025-09-23 15:22:29
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Study of the effect of irradiation with Fe<sup>7+</sup> ions on the structural properties of thin TiO<sub>2</sub> foils
摘要： Thin foils based on the TiO2 phase of brookite, 620 nm thick, were obtained by magnetron sputtering. The samples were irradiated at the DC-60 heavy ion accelerator of the Astana branch of the Institute of Nuclear Physics with Fe7+ ions with an energy of 85 MeV with a fluence of 1×1011 to 1×1014 ions/cm2. The dependences of the change in the concentration of defects in the structure of thin films on the radiation dose are established. It has been established that an increase in the irradiation fluence of up to 1014 ions/cm2, characteristic of the formation of defect overlap regions, leads to a sharp decrease in the degree of crystallinity and an increase in the lattice parameters. That is caused by the formation of a large number of disorder regions and displaced atoms in the structure, which migrate along the crystal lattice to additional distortions and voltages, with the subsequent formation of hillocks.
关键词： ionizing radiation,thin foils,crystal structure defects,magnetron sputtering
更新于2025-09-23 15:22:29
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Optical and <i>J, K</i> -photometry of the quiescent black hole X-ray nova A0620?00 in the passive and active states
摘要： In 2015–2016, the X-ray nova A0620?00 in quiescence was observed in the passive state, according to the terminology of Cantrell et al., and in less than 230 d it transited into the active state. The system mean luminosity increased by 0.20 mag in the optical and by 0.25 and 0.30 mag in J and K infrared bands, respectively, while the orbital light curves changed drastically, and the ?ickering amplitude more than doubled. The mean light-curve analysis performed in the context of two models argued that the interaction region where the gas stream reaches the disc is responsible for these effects. The growth of this region’s luminosity in the active state implies the increase of the mass transfer rate via the L1 point, likely due to non-stationary processes in the donor star atmosphere. The non-stellar spectrum Fλ in the observed range λλ6400–22 000 ? obeys a power law of λα where α = ?(2.13 ± 0.1) in the passive state and α = ?(1.85 ± 0.1) in the active, while the absolute mean square ?ickering amplitude behaves like (cid:4)F?(λ) ～ λ?2.36 in both states of activity.
关键词： X-rays: individual: 1A 0620?00,X-rays: binaries,accretion discs,techniques: photometric,starspots,radiation mechanisms: non-thermal,accretion
更新于2025-09-23 15:22:29
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Leptohadronic single-zone models for the electromagnetic and neutrino emission of TXS?0506+056
摘要： While active galactic nuclei with relativistic jets have long been prime candidates for the origin of extragalactic cosmic rays and neutrinos, the BL Lac object TXS 0506+056 is the first astrophysical source observed to be associated with some confidence (～3σ ) with a high-energy neutrino, IceCube-170922A, detected by the IceCube Observatory. The source was found to be active in high-energy γ-rays with Fermi-LAT and in very-high-energy γ-rays with the MAGIC telescopes. To consistently explain the observed neutrino and multiwavelength electromagnetic emission of TXS 0506+056, we investigate in detail single-zone models of leptohadronic emission, assuming cospatial acceleration of electrons and protons in the jet, and synchrotron photons from the electrons as targets for photohadronic neutrino production. The parameter space concerning the physical conditions of the emission region and particle populations is extensively explored for scenarios where the γ-rays are dominated by either (1) proton synchrotron emission or (2) synchrotron-self-Compton emission, with a subdominant but non-negligible contribution from photohadronic cascades in both cases. We find that the latter can be compatible with the neutrino observations, while the former is strongly disfavoured due to the insufficient neutrino production rate.
关键词： gamma rays: galaxies,BL Lacertae objects: individual: TXS 0506+056,radiation mechanisms: non-thermal,neutrinos
更新于2025-09-23 15:22:29
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[IEEE 2018 Applications of Electromagnetics in Modern Techniques and Medicine (PTZE) - Rac?awice (2018.9.9-2018.9.12)] 2018 Applications of Electromagnetics in Modern Techniques and Medicine (PTZE) - Attenuation of High Frequency Electromagnetic Waves by Polymer Composites with Waste Materials
摘要： Composite materials with polymers and waste materials like zinc ore, mill scale, and iron dust are studied with respect to attenuation of electromagnetic radiation of high frequency. Samples of such composites were prepared and tested for several frequencies in 8-12 GHz band. The composites relatively strongly attenuate electromagnetic radiation in the considered band. Using various waste materials has also ecological aspect.
关键词： electromagnetic radiation,high frequency,attenuation,polymer composites,waste materials
更新于2025-09-23 15:22:29
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Uncertainty Analysis and Experimental Design in the Monte Carlo Ray-Trace Environment
摘要： Despite the dominant role of the Monte Carlo ray-trace (MCRT) method in modern radiation heat transfer analysis, the contemporary literature remains surprisingly reticent on the uncertainty of results obtained using it. After first identifying the radiation distribution factor as a population proportion, standard statistical procedures are used to estimate its mean uncertainty, to a stated level of confidence, as a function of the number of surface elements making up the enclosure and the number of rays traced per surface element. This a priori statistical uncertainty is then shown to compare favorably with the observed variability in the distribution factors obtained in an actual MCRT-based analysis. Finally, a formal approach is demonstrated for estimating, to a prescribed level of confidence, the uncertainty in predicted heat transfer. This approach provides a basis for determining the minimum number of rays per surface element required to obtain the desired accuracy.
关键词： Monte Carlo ray-trace,uncertainty analysis,experimental design,radiation heat transfer,distribution factor
更新于2025-09-23 15:22:29
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Characterizing spatiotemporal information loss in sparse-sampling-based dynamic MRI for monitoring respiration-induced tumor motion in radiotherapy
摘要： Purpose: Sparse-sampling and reconstruction techniques represent an attractive strategy to achieve faster image acquisition speeds, while maintaining adequate spatial resolution and signal-to-noise ratio in rapid magnetic resonance imaging (MRI). The authors investigate the use of one such sequence, broad-use linear acquisition speed-up technique (k-t BLAST) in monitoring tumor motion for thoracic and abdominal radiotherapy and examine the potential trade-off between increased sparsification (to increase imaging speed) and the potential loss of 'true' information due to greater reliance on a priori information. Methods: Lung tumor motion trajectories in the superior–inferior direction, previously recorded from ten lung cancer patients, were replayed using a motion phantom module driven by an MRI-compatible motion platform. Eppendorf test tubes filled with water which serve as fiducial markers were placed in the phantom. The modeled rigid and deformable motions were collected in a coronal image slice using balanced fast field echo in conjunction with k-t BLAST. Root mean square (RMS) error was used as a metric of spatial accuracy as measured trajectories were compared to input data. The loss of spatial information was characterized for progressively increasing acceleration factor from 1 to 16; the resultant sampling frequency was increased approximately from 2.5 to 19 Hz when the principal direction of the motion was set along frequency encoding direction. In addition to the phantom study, respiration-induced tumor motions were captured from two patients (kidney tumor and lung tumor) at 13 Hz over 49 s to demonstrate the impact of high speed motion monitoring over multiple breathing cycles. For each subject, the authors compared the tumor centroid trajectory as well as the deformable motion during free breathing. Results: In the rigid and deformable phantom studies, the RMS error of target tracking at the acquisition speed of 19 Hz was approximately 0.3–0.4 mm, which was smaller than the reconstructed pixel resolution of 0.67 mm. In the patient study, the dynamic 2D MRI enabled the monitoring of cycle-to-cycle respiratory variability present in the tumor position. It was seen that the range of centroid motion as well as the area covered due to target motion during each individual respiratory cycle was underestimated compared to the entire motion range observed over multiple breathing cycles. Conclusions: The authors’ initial results demonstrate that sparse-sampling- and reconstruction-based dynamic MRI can be used to achieve adequate image acquisition speeds without significant information loss for the task of radiotherapy guidance. Such monitoring can yield spatial and temporal information superior to conventional offline and online motion capture methods used in thoracic and abdominal radiotherapy.
关键词： k-t BLAST,respiratory motion management,image guided radiation therapy
更新于2025-09-23 15:22:29