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A PENTA-BAND REJECT INSIDE CUT KOCH FRACTAL HEXAGONAL MONOPOLE UWB MIMO ANTENNA FOR PORTABLE DEVICES
摘要： In this paper, a novel compact hexagonal shaped ultra-wideband multiple-input multiple-output (UWB-MIMO) Koch fractal antenna is designed with penta-band rejection characteristics for portable devices. The antenna rejects the C-band downlink frequency from 3.7–4 GHz, the C-band uplink frequency from 5.75–6.05 GHz and the satellite bands from 7.45 to 8.4 GHz. The band 7.45–7.55 GHz is used by the meteorological satellite service for the geostationary satellite services. The band 7.75–7.9 GHz is used by the meteorological satellite service for non-geostationary satellite services. The band 8.025–8.4 GHz is used by the Earth exploration satellites for geostationary satellite services. The C-band and satellite bands interfere with the UWB and have been rejected using a band reject ?lter. A spiral shaped slot is introduced inside the fractal hexagonal monopole to introduce band reject characteristics. The band suppression and widening of the impedance bandwidth are achieved by using defected ground structures. The antenna has wideband impedance matching with S11 < ?10 dB in the UWB frequency range from 3.1 to 13.6 GHz and has a low mutual coupling with S21 < ?19 dB. The antenna has very low envelope correlation coe?cient of less than 0.17 and low capacity loss of 0.254, which proves that the MIMO antenna shows good diversity performance.
关键词： Koch fractal,defected ground structures,UWB-MIMO,spiral slot,penta-band rejection
更新于2025-09-23 15:21:01
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Nanoscaled Fractal Superstructures via Laser Patterninga??A Versatile Route to Metallic Hierarchical Porous Materials
摘要： A laser-based procedure for the preparation of metallic hierarchical porous materials is introduced and exemplified on tin, copper, silicon, titanium, and tungsten surfaces to demonstrate its general applicability. The impact of suitably tuned nanosecond laser pulses triggers a process in which laser-induced metal ablation and instantaneous recondensation of partially oxidized metals lead to cauliflower-like superstructures comprising a hybrid micro-/nanopatterning. Repeated scanning with the intense focused beam over the surface creates microstructures of hierarchically tunable porosity in a layer-by-layer design. The 3D morphology of these superstructures is analyzed using tomographic data based on focused ion-beam scanning electron microscopy to return a fractal dimension of Df = 2.79—practically identical to a natural cauliflower (Df ≈ 2.8), even though the plant is four orders of magnitude larger than the superstructures generated through the laser process. The high Df value signifies a complex morphology that boasts a huge external surface. The introduced concept enables convenient access to a variety of metallic hierarchical porous materials, which are key to performance in environmentally and technologically relevant areas like energy generation, storage, and conversion, as well as sensing and catalysis.
关键词： fractal morphology,cauliflower-like superstructures,porous nanostructures,self-organizing microstructures,scalable patterning
更新于2025-09-23 15:19:57
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Fractal Analysis - Applications in Physics, Engineering and Technology || Fractals in Antennas and Metamaterials Applications
摘要： Recently, telecommunications systems have been requiring more advanced features in the design and operation. Among others a smaller size of devices, which can be integrated for multiple mobile communications systems, applied in one user's device board, such as PDA or smartphone. Moreover, the cost of mass production should be minimized as much as possible. To meet part of that request, the antennas of these devices should have small size, lower weight, operating in multiple frequency bands and/or be broadband. There are many research methods to achieve this goal, one of which is using the fractal geometries for the shape of antenna elements. In recent years, there are many fractal shapes that have been proposed for such applications, and the designed antennas have significantly improved antenna features such as smaller size, operating in multi-frequency bands, with improved power gain and efficiency. In recent years, the new approach for modern antenna the metamaterials, MTM, is adopted, and sometimes that based on the fractal geometry is adopted.
关键词： fractal geometries,fractal antenna,antenna array,efficiency,fractal dimension,IFS,metamaterials,power gain,MTM,multiband,antenna elements,compact size
更新于2025-09-19 17:15:36
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Organic Fractal Nano-Dimensional Structures Based on Fullerene C <sub/>60</sub>
摘要： The ways for a synthesis of nanoporous and close-packed types of fullerene C60 aggregates in two-component organic solvents (toluene + tetrahydrofuran) were established as well as their structural and dimensional features - were studied by high-resolution transmission electron microscopy and atomic-force microscopy methods. The physical features and regularities that characterize the processes of self-organization of fullerene molecules in the initial molecular solution were determined. The method for producing nanoscale fullerene C60 fractal coatings (thickness up to ~1200 nm) on a flat dielectric glass surface was proposed.
关键词： self-assembles,AFM,solvent,fullerene C60,TEM,fractal,nanocoating
更新于2025-09-19 17:15:36
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Charged Particle Oscillations in Transient Plasmas Generated by Nanosecond Laser Ablation on Mg Target
摘要： The dynamics of a transient plasma generated by laser ablation on a Mg target was investigated by means of the Langmuir probe method and fractal analysis. The empirical data showcased the presence of an oscillatory behavior at short expansion times (<1 μs) characterized by two oscillation frequencies and a classical behavior for longer evolution times. Space- and time-resolved analysis was implemented in order to determine main plasma parameters like the electron temperature, plasma potential, or charged particle density. In the motion fractal paradigm, a theoretical model was built for the description of laser-produced plasma dynamics expressed through fractal-type equations. The calibration of such dynamics was performed through a fractal-type tunneling effect for physical systems with spontaneous symmetry breaking. This allows both the self-structuring of laser-produced plasma in two structures based on its separation on different oscillation modes and the determination of some characteristics involved in the self-structuring process. The mutual conditionings between the two structures are given as joint invariant functions on the action of two isomorph groups of SL(2R) type through the Stoler-type transformation, explicitly given through amplitude self-modulation.
关键词： laser ablation,joint invariant functions,Langmuir probe,fractal analysis,charged particle oscillations,Lie groups
更新于2025-09-19 17:13:59
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Overcurrent Electrodeposition of Fractal Plasmonic Black Gold with Broad-Band Absorption Properties for Excitation-Immune SERS
摘要： The dependence of plasmon resonance on the size, shape, and interparticle spacing of single, isolated nanostructures inherently limits their light-harvesting capability to a narrow spectral band. Here, we report a facile overcurrent electrodeposition strategy to prepare fractal plasmonic black gold (B-Au) with broad-band absorption properties (over 80% throughout the range of 300?1800 nm). The broad-band absorption properties are attributed to the excitation of multiple plasmons in the B-Au, which results in strong light?matter interaction over a broad-band spectral window. Consequently, the B-Au can produce strong broad-band surface-enhanced Raman scattering (SERS) regardless of the excitation light used. These ?ndings demonstrate that the fractal B-Au allows e?cient utilization of broad spectral photons and opens up exciting opportunities for highly sensitive SERS detection, photocatalysis, and photovoltaic devices.
关键词： broad-band absorption,surface-enhanced Raman scattering,fractal plasmonic black gold,photocatalysis,SERS,photovoltaic devices
更新于2025-09-19 17:13:59
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High-performance spoof surface plasmon polariton waveguides and splitters based on Greek-cross fractal units
摘要： In this paper, we introduce the fractal geometry into the spoof surface plasmon polariton (SSPP) waveguide and splitter design. We propose a novel SSPP waveguide consisting of periodic corrugated Greek-cross fractal units (GCFUs) connected to a microstrip line. The generation process of periodic corrugated GCFUs is described and the dispersion characteristics are studied. We find we can engineer the property of the waveguide at will by tuning the parameters of the GCFU. To validate the proposed design, a wideband lowpass filter based on double-sided DCFUs with ultra-sharp roll-offs is fabricated and tested. Based on this waveguide concept, we design a wideband Y-splitter including an SSPP waveguide with double-sided GCFUs and two SSPP waveguide branches with single-sided GCFUs. To improve isolations and reduce the reflections between output ports of the Y-splitter, a 100 Ω resistor is loaded in the middle of two symmetrical branches to construct Wilkinson splitter to equally and efficiently split the energy of the SSPPs into two parts. The simulated and measured results show that the SSPP splitter possesses excellent performance in a passband of 1.5 - 4.0 GHz with low insertion loss (S21, S31 > -4 dB), high reflection loss (S11, S22, S33 < -10 dB), and high isolation (S32 < -10 dB). This work may open up a new door for the development of various plasmonic integrated functional devices.
关键词： Spoof surface plasmon polaritons,Waveguides,Wilkinson splitters,Greek-cross fractal unit
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Topological Model of Laser Emission Parameters Research
摘要： The research paper presents a model for studying both the parameters and dynamics of laser light as a nonlinear dynamic system. The model provides for the measurement of the values of physical quantities by non-linear metrology methods and the analysis of the research findings with topological tools. The model is based on the assumption of interval values of the measured values and the possibility of changing the stationary dynamics into the random one. The model contains an experiment scheme and a procedure for evaluating measurement results. The peculiarity of the model lies in its systemic approach and suitability for measuring and researching stationary and chaotic modes. The model provides for the measurement of the emission parameter values intervals in various modes, of their stability values and time series prediction. Classification of the system dynamics is performed using the fractal dimension. The model can be used both to ensure the stability of the laser light parameters, and to obtain and control random emission.
关键词： chaos,fractal dimension,laser emission parameters stability
更新于2025-09-19 17:13:59
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ANALYSIS OF A NON-INTEGER DIMENSIONAL TUNNEL AND PERFECT ELECTRIC CONDUCTOR WAVEGUIDE
摘要： Solutions to the Maxwell equations for a planar non-integer dimensional perfect electric conductor (NID-PEC) waveguide are obtained. The space within the guide is NID in direction normal to walls of the waveguide. Field behavior within the waveguide is noted for di?erent values of the parameter, D, describing dimension of the NID space. For D = 2, classical results are recorded. The discussion is further extended by treating propagation in a tunnel within unbounded dielectric medium. The space within tunnel is also NID in direction perpendicular to walls of the tunnel. For di?erent values of D ?eld behaviors are also presented. It has been noted that for D = 2 and taking very high values of permittivity ((cid:2) → ∞) classical results for PEC waveguide are recorded, whereas for (cid:2) → ∞, ?eld behavior within tunnel matches with NID-PEC waveguide.
关键词： TE/TM modes,Maxwell equations,PEC waveguide,Non-integer dimensional space,fractal medium
更新于2025-09-19 17:13:59
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In-Situ Plasma Monitoring during the Pulsed Laser Deposition of Ni60Ti40 Thin Films
摘要： The properties of pulsed laser deposited of Ni60Ti40 shape memory thin films generated in various deposition conditions were investigated. In-situ plasma monitoring was implemented by means of space- and time-resolved optical emission spectroscopy, and ICCD fast camera imaging. Structural and chemical analyses were performed on the thin films using SEM, AFM, EDS, and XRD equipment. The deposition parameters influence on the chemical composition of the thin films was investigated. The peeled layer presented on DSC a solid-state transformation in a different transformation domain compared to the target properties. A fractal model was used to describe the dynamics of laser produced plasma through various non-differentiable functionalities. Through hydrodynamic type regimes, space-time homographic transformations were correlated with the global dynamics of the ablation plasmas. Spatial simultaneity of homographic transformation through a special SL(2R) invariance implies the description of plasma dynamics through Riccati type equations, establishing correlations with the optical emission spectroscopy measurements.
关键词： thin films,in situ plasma monitoring,nitinol,pulsed laser deposition,fractal modelling,SL(2R) invariance,homographic transformations,Riccati equation
更新于2025-09-19 17:13:59