We theoretically study the Casimir-Polder force on an atom in an arbitrary initial state in a rather general electromagnetic environment wherein the materials may have a nonreciprocal bianisotropic ...dispersive response. It is shown that under the Markov approximation the force has resonant and nonresonant contributions. We obtain explicit expressions for the optical force both in terms of the system Green function and of the electromagnetic modes. We apply the theory to the particular case wherein a two-level system interacts with a topological gyrotropic material, showing that the nonreciprocity enables exotic light-matter interactions and the opportunity to sculpt and tune the Casimir-Polder forces on the nanoscale. With a quasistatic approximation, we obtain a simple analytical expression for the optical force and unveil the crucial role of surface plasmons in fluctuation-induced forces. Finally, we derive the Green function for a gyrotropic material half-space in terms of a Sommerfeld integral.
Thin-cap fibroatheroma (TCFA) is a prominent risk factor for plaque rupture. Intravascular optical coherence tomography (IVOCT) enables identification of fibrous cap (FC), measurement of FC ...thicknesses, and assessment of plaque vulnerability. We developed a fully-automated deep learning method for FC segmentation. This study included 32,531 images across 227 pullbacks from two registries (TRANSFORM-OCT and UHCMC). Images were semi-automatically labeled using our OCTOPUS with expert editing using established guidelines. We employed preprocessing including guidewire shadow detection, lumen segmentation, pixel-shifting, and Gaussian filtering on raw IVOCT (r,θ) images. Data were augmented in a natural way by changing θ in spiral acquisitions and by changing intensity and noise values. We used a modified SegResNet and comparison networks to segment FCs. We employed transfer learning from our existing much larger, fully-labeled calcification IVOCT dataset to reduce deep-learning training. Postprocessing with a morphological operation enhanced segmentation performance. Overall, our method consistently delivered better FC segmentation results (Dice: 0.837 ± 0.012) than other deep-learning methods. Transfer learning reduced training time by 84% and reduced the need for more training samples. Our method showed a high level of generalizability, evidenced by highly-consistent segmentations across five-fold cross-validation (sensitivity: 85.0 ± 0.3%, Dice: 0.846 ± 0.011) and the held-out test (sensitivity: 84.9%, Dice: 0.816) sets. In addition, we found excellent agreement of FC thickness with ground truth (2.95 ± 20.73 µm), giving clinically insignificant bias. There was excellent reproducibility in pre- and post-stenting pullbacks (average FC angle: 200.9 ± 128.0°/202.0 ± 121.1°). Our fully automated, deep-learning FC segmentation method demonstrated excellent performance, generalizability, and reproducibility on multi-center datasets. It will be useful for multiple research purposes and potentially for planning stent deployments that avoid placing a stent edge over an FC.
Light-matter interactions in conventional nanophotonic structures typically lack directionality. For example, differently from microwave antenna systems, most optical emitters (e.g., excited ...atoms/molecules and simple nanoantennas) exhibit quasi-isotropic dipolar radiation patterns with low directivity. Furthermore, surface waves supported by conventional material substrates do not usually have a preferential direction of propagation, and their wavefront tends to spread as it propagates along the surface, unless the surface or the excitation is properly engineered and structured. In this article, we theoretically demonstrate the possibility of realizing unidirectional and diffractionless surface plasmon polariton modes on a nonreciprocal platform, namely, a gyrotropic magnetized plasma. Based on a rigorous Green's function approach, we provide a comprehensive and systematic analysis of all the available physical mechanisms that may bestow the system with directionality, both in the sense of one-way excitation of surface waves and in the sense of directive diffractionless propagation along the surface. The considered mechanisms include (i) the effect of strong and weak forms of nonreciprocity, (ii) the elliptic-like or hyperbolic-like topology of the modal dispersion surfaces, and (iii) the source polarization state, with the associated possibility of chiral surface-wave excitation governed by angular-momentum matching. We find that three-dimensional gyrotropic plasmonic platforms support a previously unnoticed wave-propagation regime that exhibit several of these physical mechanisms simultaneously, allowing us to theoretically demonstrate unidirectional surface plasmon polariton modes that propagate as a single ultranarrow diffractionless beam. We also assess the impact of dissipation and nonlocal effects. Our theoretical findings may enable a new generation of plasmonic structures and devices with highly directional response.
► Obtaining critical and erosion velocities in cold spray process. ► A new combined numerical-analytical model is proposed. ► The model considers porosity of the particles and adhesion phenomena. ► ...Equations for calculating critical/erosion velocity for Cu and SS316 are proposed. ► Equations are function of particle's porosity, temperature and diameter.
Cold spray is a coating process in which bonding is obtained when the impact velocity of small particles exceeds a critical value called critical velocity (CV) but it is less than an upper limit beyond which erosion happens. The success of the cold spray process mainly depends on the correct choice of the process velocity which should be set to be between CV and erosion velocity (EV), that are influenced by many parameters. This justifies the interest of many researchers to define models for the CV assessments. In the present work, we propose a new model, combination of numerical and analytical solutions, to calculate not only the CV but also EV. Compared with previous works, porosity of particles and adherence phenomena between particle and the substrate have been taken into account as a novelty. Results of the proposed approach have been compared with experimental data and good agreement was found. Finally, based on the procedure results, a representative equation was established for calculating critical and erosion velocities as a function of particle porosity, diameter and temperature for Cu and stainless steel 316L particles.
As the demand for higher specific energy density in lithium-ion battery packs for electric vehicles rises, addressing thermal stability in abusive conditions becomes increasingly critical in the ...safety design of battery packs. This is particularly essential to alleviate range anxiety and ensure the overall safety of electric vehicles. A liquid cooling system is a common way in the thermal management of lithium-ion batteries. This article uses 3D computational fluid dynamics simulations to analyze the performance of a water-cooled system with rectangular channels for a cylindrical battery pack. A finite volume method is used, validating the results with experimental data. Firstly, the effects of converging and diverging of channels on the thermal and hydraulic characteristics of the considered cooling system are investigated. Then, the co- and counter-flow pattern strategies of the coolant are studied. The results indicate that converging the channels leads to the Nusselt number enhanced by about 21% compared to the conventional design of the system. However, better hydraulic performance is found for the case with diverging channels. The decrement in the friction loss of the cooling system with diverging channels is about 70%. It is also found that the flow pattern is considerably effective in controlling the temperature uniformity of the battery pack. The counter-flow pattern of the channels provides lower temperatures, and the maximum deviation from the co-flow pattern (∼ 5.2 K) can be found for the case with diverging channels.
Explosive welding of metal plates Akbari-Mousavi, S.A.A.; Barrett, L.M.; Al-Hassani, S.T.S.
Journal of materials processing technology,
06/2008, Letnik:
202, Številka:
1
Journal Article
Recenzirano
This paper describes a study of explosive welding of metal plates. The properties of a locally prepared mix of 77/23 ammonium nitrate and fuel oil (ANFO) explosive and the dynamics of the plates are ...investigated and the results from welding tests presented. The strength of the clad plates is measured and ultrasonic inspection performed to identify and locate defects. The welding process is simulated using a finite element-based computer model. A brief description of the modeling process is given along with the results from the simulations for comparison with measured parameters.
We investigate the quantum recoil force acting on an excited atom close to the surface of a nonreciprocal photonic topological insulator (PTI). The main atomic emission channel is the unidirectional ...surface plasmon propagating at the PTI-vacuum interface, and we show that it enables a spontaneous lateral recoil force that scales at short distances as 1/d4, where d is the atom-PTI separation. Remarkably, the sign of the recoil force is polarization and orientation independent, and it occurs in a translation-invariant homogeneous system in thermal equilibrium. Surprisingly, the recoil force persists for very small values of the gyration pseudovector, which, for a biased plasma, corresponds to very low cyclotron frequencies. The ultrastrong recoil force is rooted in the quasihyperbolic dispersion of the surface plasmons. We consider both an initially excited atom and a continuous pump scenario, the latter giving rise to a steady lateral force whose direction can be changed at will by simply varying the orientation of the biasing magnetic field. Our predictions may be tested in experiments with cold Rydberg atoms and superconducting qubits.
This study was carried out in the poultry field in Jadiriyah, affiliated with the Department of Animal Production / College of Agricultural Engineering Sciences - University of Baghdad. This ...experiment used 480 one-day-old, unsexed broiler chicks of the broiler breed (Ross-308) with an average weight of 39.8 g to investigate the effect of adding different levels of turmeric root (CURCUMA LONGA) (CURCUMA LONGA) powder to the diet on some characteristics and physiology of commercial broilers exposed to heat stress. Chicks were distributed randomly and equally between 4 treatments (120 chicks/treatment), and each treatment included 3 replicates, at a rate of (40 chicks/repeat). Chicks were fed on the starter, growth and final diet for up to 6 weeks, and at the end of the experiment, at 42 days old, 12 birds were selected from each treatment at a rate of 4/duplicate treatment. The birds were placed in their kennel within an isolated space in the breeding hall and exposed to a temperature of (36-39-42°C) for 3 hours. The results of the experiment showed a significant increase (P > 0.05) in total protein, albumin, globulin and high-density lipoprotein. The results also showed a significant decrease in cholesterol, LDL, VLDL, GOT enzyme level, sodium and potassium concentration, heterophil cells and the ratio (H/L), and turmeric treatments did not show a significant effect on basal, acidic and monocyte blood cells, and the results indicated a significant increase in the values of PCV and HDL cells. White blood, lymphocytes, chlorine concentration, GSH-PX and CAT enzyme levels in the blood. It can be concluded from this study that the addition of turmeric root powder at a rate of 6.5% has a positive effect on improving some physiological characteristics of broilers exposed to heat stress.
Polar codes represent one of the major recent breakthroughs in coding theory and, because of their attractive features, they have been selected for the incoming 5G standard. As such, a lot of ...attention has been devoted to the development of decoding algorithms with good error performance and efficient hardware implementation. One of the leading candidates in this regard is represented by successive-cancelation list (SCL) decoding. However, its hardware implementation requires a large amount of memory. Recently, a partitioned SCL (PSCL) decoder has been proposed to significantly reduce the memory consumption. In this paper, we consider the paradigm of PSCL decoding from a practical standpoint, and we provide several improvements. First, by changing the target signal-to-noise ratio and consequently modifying the construction of the code, we are able to improve the performance at no additional computational, latency, or memory cost. Second, we bridge the performance gap between SCL and PSCL decoding by introducing a generalized PSCL decoder and a layered PSCL decoder. In this way, we obtain almost the same performance of the SCL decoder with a significantly lower memory requirement, as testified by hardware implementation results. Third, we present an optimal scheme to allocate cyclic redundancy checks. Finally, we provide a lower bound on the list size that guarantees optimal maximum a posteriori performance for the binary erasure channel.
At frequencies much lower than the plasma frequency, individual subwavelength plasmonic scatterers are typically far from any scattering resonance, with the exception of some extreme geometries. ...Contrary to this conventional behavior, in this paper, we theoretically demonstrate that the application of a weak magnetic bias to a portion of the plasmonic scatterer leads to the emergence of scattering resonances that exist, in principle, for an arbitrarily low frequency. We show that this class of plasmonic resonances originates from ultralow-frequency unidirectional and topological surface modes that emerge at internal interfaces. These topological properties endow the scattering resonances with high robustness against geometrical modifications. Our findings may open new uncharted directions towards the design of robust, shape-independent, subwavelength resonant structures with extreme scattering response.
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