January 2022
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2 Reads
SSRN Electronic Journal
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January 2022
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2 Reads
SSRN Electronic Journal
February 2021
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72 Reads
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7 Citations
An effective semi-classical method is introduced for controlling the high-order harmonic generation process and extending the cutoff frequency. This method is capable of defining the proper specification of the driving laser for maximizing the cutoff frequency. This method is evaluated by examining the high harmonic spectrum from the hydrogen atom and the fluorine (F2) molecule irradiated by single-, two-, and three-color laser fields. This study is done using the time-dependent density functional theory in a three-dimensional space. The results show that the single-, two-, and three-color laser pulses tuned by proper specifications could extend the cutoff frequency by up to 85%, 176%, and 241% compared to their non-tuned forms, respectively. Also, single attosecond pulses with a duration of 161 as and 129 as are obtained by applying the tuned three-color laser for the hydrogen atom and the fluorine molecule, respectively.
January 2021
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35 Reads
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6 Citations
Abstract A new photocatalytic filtration membrane was prepared by grafting of Ag–Au bi‐plasmonic shell‐on TiO2@Fe3O4 nanoparticles as a magnetically‐separable heterogeneous photocatalyst to a poly acrylic acid‐modified cellulose acetate membrane for decomposition and removal of methyl orange as a model pollutant from textile wastewater samples. Eight photocatalysts including five Au NPs‐modified TiO2@Fe3O4 NPs and three Ag‐Au bi‐plasmonic NPs‐decorated TiO2@Fe3O4 NPs with different shell thickness were synthesized and characterized by TEM, UV–vis, and SEM techniques and their photocatalytic activity was assessed using two radiation sources. After selection of optimum photocatalyst and modification of cellulose acetate membrane, the photodegradation of methyl orange was evaluated in a dead‐end membrane reactor using the prepared membrane. The flux performance, antifouling property and pollutant removal efficiency of the membrane were evaluated using textile wastewater samples. It was demonstrated that the prepared membrane reactor is able to produce cleaner water with more stable flux performance and good antifouling property.
March 2020
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226 Reads
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13 Citations
Material characteristics and input-field specifics limit controllability of nonlinear electromagnetic-field interactions. As these nonlinear interactions could be exploited to create strongly localized bright and dark waves, such as nonlinear surface polaritons, ameliorating this limitation is important. We present our approach to amelioration, which is based on a surface-polaritonic waveguide reconfiguration that enables excitation, propagation and coherent control of coupled dark rogue waves having orthogonal polarizations. Our control mechanism is achieved by finely tuning laser-field intensities and their respective detuning at the interface between the atomic medium and the metamaterial layer. In particular, we utilize controllable electromagnetically induced transparency windows commensurate with surface-polaritonic polarization-modulation instability to create symmetric and asymmetric polaritonic frequency combs associated with dark localized waves. Our method takes advantage of an atomic self-defocusing nonlinearity and dark rogue-wave propagation to obtain a sufficient condition for generating phase singularities. Underpinning this method is our theory which incorporates dissipation and dispersion due to the atomic medium being coupled to nonlinear surface-polaritonic waves. Consequently, our waveguide configuration acts as a bimodal polaritonic frequency-comb generator and high-speed phase rotator, thereby opening prospects for phase singularities in nanophotonic and quantum communication devices.
October 2019
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109 Reads
Material characteristics and specifics of the input field limit controllability of nonlinear electromagnetic-field interactions aiming to create strongly localized bright and dark waves, including for nonlinear surface polaritons. We ameliorate this limitation, by proposing a surface-polaritonic waveguide reconfiguration to enable excitation, propagation and coherent control of coupled dark rogue waves with orthogonal polarizations, especially by finely tuning laser-field intensities and their respective detuning at the interface between the atomic medium and the metamaterial layer. We exploit controllable electromagnetically induced transparency windows commensurate with the surface-polaritonic polarization modulation instability to create symmetric and asymmetric polaritonic frequency combs associated with dark localized waves. We take advantage of an atomic self-defocusing nonlinearity and dark rogue-wave propagation to obtain a sufficient condition for generating phase singularities. Our theory incorporates dissipation and dispersion of the atomic medium to the coupled nonlinear SPWs. Consequently, our waveguide configuration acts as a bimodal polaritonic frequency-comb generator and high-speed phase rotator, thereby opening prospects for phase singularities in nanophotonic and quantum communication devices.
September 2019
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622 Reads
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8 Citations
Ultrasonics
The effects of liquid density variation at the bubble surface on the dynamics of a single acoustic cavitation bubble are numerically studied. The Gilmore model together with a comprehensive hydrochemical model is used. The evaporation and condensation of water vapor are included in the hydrochemical model. The simulation results are compared to those resulting from the widely known Keller-Miksis model, which assumes a constant liquid density at the bubble surface. The numerical results for a single argon bubble in water reveal that the pressure and the temperature inside the bubble in collapse phase significantly increase, when the non-constant liquid density is used. These differences increase by raising the ultrasonic amplitude and by decreasing the bubble ambient radius and ultrasonic frequency. More importantly, at higher ultrasonic frequencies, the models give the same results regarding the cavitation dynamics and much more remarkably on the thermodynamic behavior of the bubble contents. Also, it is revealed that the entered number of water vapor molecules into the bubble in expansion phase through evaporation are less than the simulated one by the diffusion limited model. Notably, in the case of an argon bubble in aqueous solution of H2SO4(85wt%), a better match between the results of two models is observed. In addition, it is shown that considering the liquid bulk viscosity, arising from the rapid liquid density variation at the end of bubble collapse, in the Gilmore model leads to a slight growth in the collapse strength, temperature, and pressure within the bubble.
June 2019
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21 Reads
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46 Citations
Ceramics International
The synergistic effect of plasmonic Au-Ag nanoparticles (NPs) on the increase of absorption band of nano-sized TiO2 and magnetic property of Fe3O4 NPs on the separation-ability of this semiconductor was applied for preparation of eight magneto-plasmonic photocatalysts for degradation of rhodamine-6G (Rh6G) in textile wastewater. The size, structure, morphology, crystallinity and optical and magnetic properties of prepared photocatalysts have been evaluated by various characterization techniques. Their photocatalytic activities were assessed under irradiation of an intense linear 405-nm laser and a continuous solar-simulated xenon lamp. The results were demonstrated that in comparison to the magnetic TiO2, the mono- and bi-plasmonic alloyed photocatalysts reveal more efficient photocatalytic activity due to the presence of one/two SPR generated hot electrons from excited Au/Ag shells under solar-simulated light radiation so that the ternary [email protected]2@Fe3O4 NPs revealed ∼4 times more photocatalytic activity under xenon lamp irradiation. Effect of different parameters such as type of photocatalyst, pH and photocatalyst dose on the degradation efficiency of Rh6G was investigated and reusability studies were revealed only a slight decrease (below 8%) in the photocatalytic performance of the catalysts after carrying out five consecutive cycles of dye photodegradation which makes them promising platforms for development of photocatalytic wastewater treatment and other applications.
May 2019
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99 Reads
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8 Citations
Physical Chemistry Chemical Physics
Enhanced high harmonics are generated by local and global optimization approaches to achieve a supercontinuum spectrum. Based on time-dependent density functional theory calculations, the optimum convolution of a two-color chirped pulse from an N 2 O molecule implements a significant enhancement of cutoff frequency and high harmonic yield. The optimization is done by controlling the effective chirp parameters and the carrier-envelope phase of the designed laser field. Indeed, all of the effective parameters are adjusted simultaneously for the global optimization; whereas, just two variables are tuned to obtain the desired cutoff frequency based on the local optimization. The results show that the global optimization approach extends the cutoff frequency by 96% compared to the single-color field, which could produce an isolated 25 as output pulse. This method opens up a valuable route by a pulse shaping mechanism for the control of high harmonic generation and ultrafast measurements for reducing the computational time and repeatability of an experiment with high accuracy.
December 2018
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59 Reads
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7 Citations
Contributions to Plasma Physics
Body stress flow can be expected in the fast ignition imploding of the inertial fusion process that strongly damps small‐scale velocity structures. The Weibel instability is one of the plasma instabilities that require anisotropy in the distribution function. The body stress effect was neglected in the calculation of the Weibel instability growth rate. In this article, the propagation condition of impinging waves and the growing modes of the Weibel instability on the plasma density gradient of the fuel fusion with the body stress flow are investigated. Calculations show that the minimum value of the body stress rate threshold in the linear polarization is about 2.96 times greater than that of the circular polarization. Increasing 10 times of the density gradient and decreasing 2 times of the wavelength in the linear polarization and the circular polarization, respectively, lead to about 1.78 × 10⁶ times increment and 0.019 times decrement in the maximum of the Weibel instability growth rate. Also, the Weibel instability growth rate maximum in the circular polarization is about 10⁷ times greater than that of the linear polarization. The body stress flow and the density gradient tend to stabilize the Weibel instability in the circular polarization and act as a destabilizing source in the linear polarization. Therefore, by increasing steps of the density gradient plasma near the relativistic electron beam‐emitting region, in the circular polarization, the Weibel instability occurs at a higher stress flow.
October 2018
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40 Reads
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3 Citations
... Therefore, plasmonic membranes are immune to biofouling and can be used to remove pathogens from water. Many researchers have investigated and developed cheap and environmentally friendly bioactive materials to replace more expensive commercially available membranes [83,98,138,139,183]. These membranes can be chemically modified and coated with a layer of plasmonic NPs to produce bioactive membranes with various desirable properties. ...
January 2021
... The surplus kinetic energy acquired by the electron during its acceleration is emitted as higher harmonics of the fundamental frequency of the interacting laser pulse. The free propagation of the ionized electron in the continuum presents an opportunity to guide its trajectory by shaping the waveform of the driving field [30][31][32]. An elegant and experimentally feasible approach to shape of the laser field is superposing a different frequency field to the existing one [13,14,[33][34][35][36][37][38][39][40][41]. ...
February 2021
... Besides, plasmonic structures act as nanoscopic nonlinear waveguides that transport surface-plasmon polaritons (SPPs) instead of photons. Nonlinear SPP (NSPP) wave propagation is a well-explored topic within these media both in the presence and absence of gain [15][16][17]. It is also well-known that the combination of nonlinear response and gain amplification can be exploited to excite and sustain nonlinear waves such as different classes of solitons. ...
March 2020
... According to previous research, small cavitation bubbles also generate force on large cavitation bubbles during the shrinkage process. However, this force may be weakened due to (1) the substantial distance and significant relative distance between the bubbles, leading to a reduction in the effectiveness of force due to the weakening resistance of the liquid medium [19]; (2)the interaction force between cavitation bubbles being dependent on the size of the cavitation bubbles that generate and withstand the cavitation bubbles. In essence, larger bubble generate more substantial fluctuating forces, while smaller bubble experience a greater impact from the fluctuating force.On the contrary, the effect of the fluctuating force on the cavitation bubble will be smaller. ...
September 2019
Ultrasonics
... The matched pair of energy bands in the TiO 2 -ZnO hybrid makes it possible to eliminate photoelectron-hole recombination and synergistic enhance light absorption [27,28]. Similar ionic radii and energy states of nitrogen and oxygen suggest that nitrogen doping further improves the photocatalytic activity of the ZnO and TiO 2 , making the composite effective under visible light [29][30][31][32][33]. Silver exhibits a broad light absorption spectrum due to Plasmon excitation efficiency [14]. ...
June 2019
Ceramics International
... Some attempts have been reported to maximize the harmonic cutoff energies, enhance the harmonic yield, and improve the pulse duration of the IAP. [45][46][47][48][49][50][51][52][53][54][55][56][57][58] In 2009, Chipperfield et al. 45 proposed the so-called "ideal waveform" to significantly increase the cutoff energy of the single-atom HHG spectrum, which can be synthesized using five-color laser pulses. Later, He et al. 46 introduced chirp characteristics in two-color laser pulses and demonstrated that optimized two-color waveforms can extend the harmonic cutoff energy and simultaneously generate IAPs compared to the "ideal waveform." ...
May 2019
Physical Chemistry Chemical Physics
... The bimetallic core of NCs is activated by wavelengths to produce heat energy, which not only can increase the surrounding temperature over the upper critical solubility temperature of the polymer to open its valves and promote drug diffusion, but also can kill cancer cells through photo-thermal effects increasing the environment temperature by nearly 18 °C in 5 min. After radiation [10]. Changes of the composition and structure of bimetallic NPs modify the optical resonances that can be tuned over a broad range of wavelengths (e.g., ultra-violet-visible, UV-VIS, and near-infrared, NIR). ...
October 2018
... These NHs were loaded with letrozole and were then tested for their cytotoxic activity on L929 and MDA-MB-231in combination or absence of laser radiation. The NHs with the gold in them produced the best activity under the influence of laser radiation [107]. Che et al.prepared CO 2 -responsive magneto-polymeric nanohybrids (Fe 3 O 4 @SiO 2 -PDMAEMA) by using Fe 3 O 4 NPs as the core and layer of SiO 2 , followed by a layer of the polymer PDMAEMA poly(N,N dimethylaminoethyl methacrylate), which were formed on it like a core-shell-corona structure. ...
September 2018
Journal of Pharmaceutical Sciences
... and SPPs can be excited at a proper incident angle θ [6]. Coupler-free excitation of SPPs at the interface of negative-index metamaterials (NIMMs) and four-level EIT media has been demonstrated in both linear and nonlinear regimes [11,12]. The propagation of linear and non-linear SPPs has also been studies by introducing a four-level active Raman gain medium between dielectric and NIMMs [13]. ...
July 2018
Physical Review A
... It took nearly one-hundred years following Stokes' 1845 paper on viscous fluids for experiments in acoustics to make clear that sound absorption cannot be understood without a proper coefficient of bulk viscosity [4,5]. Since then, bulk viscosity has also been shown to impact shock wave structure [6][7][8], turbulence [9][10][11], and instabilities [12,13], among other phenomena [14][15][16][17]. ...
July 2018
Ultrasonics Sonochemistry