ALBERT

Beschreibung: Systematic numerical study of near-infrared radiation formed during filamentation in air revealed the formation of robust light bullet first registered in the experiment (Chen et al. in Appl Phys B 91:219, 2008 ). The near-infrared light bullet propagates along the filament axis with the divergence 〈1 mrad and the quasi-constant duration of ~30 fs. The central wavelength of the bullet gradually increases from 860 to 900 nm during the propagation. The results of our numerical simulation are in agreement with the experiments (Chen et al. in Appl Phys B 91:219,  2008 ; Uryupina et al. in Appl Phys B 110:123, 2013 ).

Beschreibung: Flame flatness is one of the most critical factors in evaluating the performance of a flat-flame burner. In this paper, the flame flatness of a flat-flame burner is validated using a resolution-doubled one-dimensional wavelength modulation spectroscopy tomography (1D-WMST) technique that only uses one view of multiple parallel laser beams. When the interval of two neighboring parallel laser beams is Δ r , a designed novel geometry of the parallel laser beams realizes a doubled tomographic resolution of Δ r /2. Using the proposed technique, the distributions of temperature and H 2 O mole fraction in an axisymmetric premixed flame are simultaneously reconstructed and hence the flame flatness of a flat-flame burner can be validated. The flatness factor is quantitatively described by the similarity between the reconstructed and expected distributions of H 2 O mole fraction. For flat and non-flat flames, the experimental results agree well with the CFD simulation results, denoting that the resolution-doubled 1D-WMST technique provides a noninvasive, reliable and low cost way to validate the flame flatness of the flat-flame burner.

Beschreibung: We report on the optical performances of laccaic acid dye in solution at different concentrations and dye–poly(methyl methacrylate) composite thin films. The linear spectral characteristics including optical constants, i.e. refractive index ( n ) and extinction coefficient ( k ), were carried out in a comprehensive way through absorbance, fluorescence and ellipsometric studies. The nonlinear optical parameters such as nonlinear absorption coefficient β eff (or β 2 ), the imaginary third-order susceptibility (Im[ χ (3) ]) and the imaginary part of second-order hyperpolarizability ( γ ) of the samples were evaluated using the open-aperture Z-scan technique with a laser pulse duration of 10 ns at 532 nm wavelength. The corresponding numerical values of these parameters were of 10 −10 , 10 −11 and 10 −32 order, respectively. Two-photon absorption was revealed to be the main driving physical mechanism in the nonlinear response. This suggests that laccaic acid dye can be a potential candidate for NLO materials application.

Beschreibung: We demonstrate a sensor based on tunable diode laser absorption spectroscopy for the detection of hydrogen fluoride (HF) gas at ambient pressure. Absorption from the HF R(1) ro-vibrational peak at ν̃  = 4038.962 cm −1 (2.476 µm) in the fundamental (Δ ν  = 1) band is measured. A quantitative spectral fit based on HITRAN data is used to account for overlapping spectral peaks of HF and water vapor, with an rms residual noise of 5 × 10 −4 absorbance units. The sensor is optimized for the detection of transient variations in HF concentration. We measure noise-equivalent concentrations for HF of 38 parts-per-trillion by volume (ppt) for 1-s integration times and 2.3 ppt for 10-min integration times.

Beschreibung: We report on the absorption profile of the monoclinic holmium-doped \(\hbox {KY}(\hbox {WO}_4)_2\) crystal near the optic axis for the maximal absorption wavelength at 1960 nm. The full angular distribution of the absorption coefficient at the vicinity of such optical singularity has been experimentally and numerically investigated. Furthermore, laser experiments along the optic axis have been carried out. So-called conical refraction laser and classical Gaussian laser operation are compared near the optic axis, taking into account the complex absorption profile.

Beschreibung: We demonstrate a novel and compact fiber-probe pressure sensor based on a micro-Fabry–Perot interferometer (FPI). The device is fabricated by splicing both ends of a short-section simplified hollow-core photonic crystal fiber (SHC-PCF) with single-mode fibers. Then, a microchannel is drilled by a femtosecond laser micromachining in the SHC-PCF to allow air to diffuse in. The pressure sensing mechanism is based on the dependence of the air refractive index on pressure. We use both theory and experiment to investigate the sensing characteristics. A micro-FPI with a length of 272 μm demonstrates a pressure sensitivity of 4.071 nm/MPa at 1580 nm and a low-temperature sensitivity of 1.1 pm/°C at atmospheric pressure. We further study the temperature cross sensitivity of the sensor under different pressures. The sensor also shows strong stability and good reversibility, and may be potentially used in pressure sensing applications.

Beschreibung: We study the thermo-optic Goos–Hänchen (TOGH) effect in a prism–waveguide coupling structure with silicon-on-insulator waveguide. Stationary-phase method is utilized to calculate the TOGH shift. When the waveguide is regarded as a two-dimensional planar waveguide, a nonlinear relation between GH shift and temperature is obtained. Based on the noticeable TOGH effect, a sensitive temperature modulator or sensor can be realized. As the waveguide width is limited, the proposed structure can be regarded as a three-dimensional rectangular waveguide. We explore the GH shift and TOGH effect for different modes propagating in rectangular waveguide which show different linear relations between GH shift and temperature, which can be used to design mode-selective device based on TO effect.

Beschreibung: We report on an experimental study of vacuum-induced suppression and enhancement of four-wave mixing (FWM) signal in a composite atom–cavity system. By scanning the additional dressing field, the suppression ratio of the FWM signal can reach 90 % compared with 40 % without cavity. We attribute the enhanced suppression and enhancement to the atom–cavity coupling arising from a vacuum-induced Raman process, which amplifies the dressing effect from the additional field. Also, the dressing asymmetry of the atom–cavity coupling is discussed and used to estimate the nonlinearity of atomic medium in the cavity. The suppression and enhancement can be interpreted by a dressed-state picture and agree with theoretical calculations. The investigation may find applications in optical switch and quantum memory controlled by cavity.

Beschreibung: By simultaneously using a multi-walled carbon nanotube (MWCNT) and a monolayer graphene saturable absorber (SA) in the cavity, a laser-diode-pumped dual-loss-modulated passively Q-switched Tm:LuAG laser at 2 μm is demonstrated for the first time. In comparison with the singly passively Q-switched laser with MWCNT or monolayer graphene SA, the doubly passively Q-switched laser with both MWCNT and monolayer graphene SA can generate shorter pulse width and higher peak power. A maximum pulse width compression ratio of 2.8 and a highest peak power enhancement factor of 4 were obtained at the incident pump power of 5.8 W, respectively. The experimental results show that the dual-loss modulation is an efficient method to compress the pulse widths and improve the peak powers of the Q-switched lasers at 2 μm.

Beschreibung: Photoexcitation dynamics in a three-step photoionization of atomic uranium has been investigated using time-resolved two-color three-photon and delayed three-color three-photon photoionization signals. Investigations are carried out in an atomic beam of uranium coupled to a high-resolution time-of-flight mass spectrometer using three tunable pulsed dye lasers. Dependence of both the signals on the second-step laser photon fluence is studied. Excited-level-to-excited-level photoexcitation cross section and photoionization cross section from the second excited level are simultaneously determined by analyzing the two-color three-photon and three-color three-photon photoionization signals using population rate equation model. Using this methodology, photoexcitation and photoionization cross sections at seven values of the second-step laser wavelength have been measured. From the measured values of the photoexcitation cross sections, we have obtained excited-level-to-excited-level transition probabilities and compared these with the values reported in the literature.

Beschreibung: A theoretical analysis of the photorefractive sensitivity of Ti:PPLN ridge waveguides in comparison with conventional Ti:PPLN channel waveguides is presented. In particular, intensity-dependent photorefraction, effective indices, waveguide modes and power-dependent SHG in Ti:PPLN ridge and channel waveguides are modeled for a wide range of parameters. Results predict a much better damage resistance of Ti:PPLN waveguides with ridge geometry in comparison with conventional indiffused channels. This superiority of ridge waveguides is attributed to their higher effective refractive index contrast and more tightly confined guided modes. The theoretical predictions are supported by experimental results for second harmonic generation (SHG) at room temperature and for light-induced detuning characteristics of the phase-matching wavelength.

Beschreibung: In this paper, the (2+1)-dimensional Saweda-Kotera-Kadomtsev-Petviashvili (SK-KP) equation is investigated, which can be used to describe certain situations from the fluid mechanics, ocean dynamics and plasma physics. With the aid of generalized Bell’s polynomials, the Hirota’s bilinear equation and N -soliton solution are explicitly constructed to the SK-KP equation, respectively. Based on the Riemann theta function, a direct and lucid way is presented to explicitly construct quasi-periodic wave solutions for the SK-KP equation. The two-periodic waves admit two independent spatial periods in two independent horizontal directions, which are a direct generalization of one-periodic waves. Finally, the relationships between soliton solutions and periodic wave solutions are strictly established, which implies the asymptotic behaviors of the periodic waves under a limited procedure.

Beschreibung: . This work is a continuation of the previous series related to the construction of the energy matrix for complex atoms. The effects of the second-order configuration interaction perturbations on the energy-level structure of \(nl^{N}\) , \( nl^{N}n_{1}l_{1}^{N_{1}}\) and \( nl^{N}n_{1}l_{1}^{N_{1}}n_{2}l_{2}\) configurations were studied. In this paper we consider one-electron core excitations for and between the configurations under study. This work combined with Part II and III is a complete description of an electrostatic interaction. In Part I we presented a method which allows to analyse complex electronic systems. They constitute the basis for the design of an efficient computer program package allowing large scale calculations which provide accurate wave functions.

Beschreibung: Following the recent establishment of an exact kinetic theory realized by the Master kinetic equation which describes the statistical behavior of the Boltzmann-Sinai Classical Dynamical System (CDS), in this paper the problem is posed of the construction of the related global existence and regularity theorems. For this purpose, based on the global prescription of the same CDS for arbitrary single- and multiple-collision events, first global existence is extablished for the N -body Liouville equation which is written in Lagrangian differential and integral forms. This permits to reach the proof of global existence both of generic N -body probability density functions (PDF) as well as of particular solutions which maximize the statistical Boltzmann-Shannon entropy and are factorized in terms of the corresponding 1-body PDF. The latter PDF is shown to be uniquely defined and to satisfy the Master kinetic equation globally in the extended 1-body phase space. Implications concerning the global validity of the asymptotic Boltzmann equation and Boltzmann H-theorem are discussed.

Beschreibung: We show that single-slit two-photon ghost diffraction can be explained very simply by using a wave-packet evolution of a generalised EPR state. Diffraction of a wave travelling in the x -direction can be described in terms of the spreading in time of the transverse ( z -direction) wave-packet, within the Fresnel approximation. The slit is assumed to truncate the transverse part of the wave function of the photon to within the width of the slit. The analysis reproduces all features of the two-photon single-slit ghost diffraction.

Beschreibung: In this paper, the combined effects of Hall current and magnetic field on the onset of convection in an electrically conducting nanofluid layer heated from below is investigated. A physically more realistic boundary condition on the nanoparticle volume fraction is taken i.e. the nanoparticle flux is assumed to be zero rather than prescribing a nanoparticle volume fraction on the rigid impermeable boundaries. The employed model incorporates the effects of Brownian motion and thermophoresis. The resulting eigenvalue problem is solved using the Galerkin method. The results obtained during the analysis are presented graphically for an alumina-water nanofluid. It is observed that the effect of smaller values of the Hall current parameter and the nanoparticle parameters accelerate the onset of convection, while larger values of the Hall current parameter (≥ 15) have no effect on the system stabilities.

Beschreibung: The rotary oscillation of a composite sphere, consisting of a solid core surrounded by a porous shell, in an incompressible viscous fluid bounded by a concentric spherical cavity is investigated using the Brinkman model. The stress jump condition is applied on the porous-fluid interface and the slip boundary condition is proposed on the surface of the spherical cavity. The couple exerted by the fluid on the porous surface is obtained analytically and its imaginary and real coefficients are represented graphically. The effects of slip parameter, permeability coefficient, stress jump coefficient and effective viscosity ratio on the torque are discussed and special cases are deduced.

Beschreibung: In this paper I consider surfaces in a space-time with a Killing vector ξ α that is time-like and hypersurface-orthogonal on one side of the surface. The Killing vector may be either time-like or space-like on the other side of the surface. It has been argued that the surface is null if ξ α ξ α → 0 as the surface is approached from the static region. This implies that, in a coordinate system adapted to ξ , surfaces with g tt = 0 are null. In spherically symmetric space-times the condition g rr = 0 instead of g tt = 0 is sometimes used to locate null surfaces. In this paper I examine the arguments that lead to these two different criteria and show that both arguments are incorrect. A surface ξ = const has a normal vector whose norm is proportional to ξ α ξ α . This lead to the conclusion that surfaces with ξ α ξ α = 0 are null. However, the proportionality factor generally diverges when g tt = 0, leading to a different condition for the norm to be null. In static spherically symmetric space-times this condition gives g rr = 0, not g tt = 0. The problem with the condition g rr = 0 is that the coordinate system is singular on the surface. One can either use a nonsingular coordinate system or examine the induced metric on the surface to determine if it is null. By using these approaches it is shown that the correct criteria is g tt = 0. I also examine the condition required for the surface to be nonsingular.

Beschreibung: Alba is a 3rd-generation 3 GeV synchrotron facility with an emittance of 4.6nm·rad which has been operational since 2011 and has recently started top-up operation. Photons in a broad energy range of 0.08-80 keV are served to seven beamlines dedicated to a large variety of scientific fields. The portfolio includes two beamlines, XALOC and MSPD, fully dedicated to X-ray crystallography. BL13-XALOC is currently the only macromolecular crystallography beamline. The end-station includes a high-accuracy single-axis diffractometer with a removable minikappa stage, a sample-mounting robot and a large-area, photon-counting detector. The beamline optics, fed by an in-vacuum undulator, deliver a tunable photon beam between 5.5 and 22 keV. The beam size at the sample position can be adjusted by defocusing the mirrors in a range of 50-300μm in the horizontal direction and 5.5-300μm in the vertical direction. Beamline BL04-MSPD, which is fed by a superconducting wiggler, has two in-line end-stations. The first station is devoted to high-pressure/microdiffraction. It offers a \( 15\times 15\) μm beam in the range 20-50 keV, particularly suited for powder diffraction studies requiring a very small beam, e.g. mapping of cultural heritage samples and high-pressures studies. The second station is dedicated to high-resolution/high-throughput powder diffraction. It covers the 8-50 keV range and includes a heavy-duty 3-circle diffractometer equipped with a 13-channel multianalyzer detector with high-angular resolution ( \( \Delta 2\theta=0.004^{\circ}\) FWHM) and a high-throughput, position-sensitive detector spanning \( 40^{\circ}\) in 2 \( \theta\) range allowing millisecond data acquisitions.

Beschreibung: Two-color laser-induced incandescence (LII) measurements are carried out in diffusion flames and at the exhaust of a homemade soot generator, both fueled with ethylene and methane. Two-color prompt LII signals, their ratio and the corresponding temperature have been analyzed as a function of laser fluence. In particular, the effect of fuel, soot load and gas/particle initial temperature on LII measurements have been investigated. LII spectral measurements have also been performed in all conditions for validation. The results suggest that the incandescence is sensitive to both optical and non-optical physical properties of the particles. Moreover, soot volume fraction measurements are dependent on the laser fluence used, indicating that the soot temperature influences the refractive index absorption function. Such issues can be overcome by working at high laser fluences, where the saturation curves are independent from the experimental conditions if the soot absorption function near soot sublimation threshold is known.

Beschreibung: In this research, an AlGaAs film was deposited on a microscope slide by means of the thermionic vacuum arc (TVA) technique which is a novel plasma production technique. AlGaAs structures were grown by this deposition technique for the first time and this process occurred in a very short period of time. In order to characterize the produced film, nano-structural, nano-mechanical, optical, and surface properties were determined by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), X-ray diffractometer (XRD) and interferometer. According to the results of the measurements, the mean thickness value of the produced film was obtained as 1.8 μ m. The band gap value was determined as 2eV from the Kubelka-Munk plot. The refractive index value was obtained as approximately 3.4. Hardness value was determined as 2 GPa from the Oliver-Pharr method. All these values are consistent with the reported values in the literature for the AlGaAs films produced by different methods. TVA technique appeared as a suitable and promising technique for the production of AlGaAs films.

Beschreibung: This paper deals with a numerical study of natural convection flow and heat transfer inside a concentric horizontal annulus filled with a porous medium saturated by a cuprum (Cu)-water nanofluid. The inner and outer cylinders are kept at different constant temperatures. First, the governing partial differential equations in dimensional formulation in a polar coordinate system for the physical domain are transformed in dimensionless form in terms of stream function-temperature formulation. These equations along with the corresponding boundary conditions were solved numerically by the finite difference method. Particular efforts have been focused on the effects of the Rayleigh number, porosity of the porous medium, solid volume fraction parameter of nanoparticles, annulus radius ratio, and the solid matrix of the porous medium (glass balls and aluminum foam) on the local and average Nusselt numbers, streamlines and isotherms. It is found that a very good agreement exists between the present results and those from the open literature.

Beschreibung: Multifunctional zinc oxide nanoparticles (ZnO Nps) were synthesized by solution combustion synthesis using beetroots ( Beta vulgaris ). The structure and morphology of the product were studied by powder X-ray diffraction, UV-visible spectroscopy and scanning electron microscopy. XRD studies indicate the formation of Nps with hexagonal wurtzite structure having crystallite sizes in the range of ∼ 52–76 nm. The UV-visible spectrum of Nps shows maximum absorption at 373 nm. The SEM analysis indicates the formation of porous, sponge-like agglomerated structures. Very interesting room temperature luminescence phenomena were observed with violet, green and red emissions upon exciting the ZnO Nps at 378 nm. This phenomenon could be due to oxygen vacancy and ZnO interstitial defects. ZnO Nps effectively degrade malachite green (MG) and methylene blue (MB) dyes in the presence of UV light. Nps show good antioxidant activity by scavenging 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radicals. The study successfully demonstrates simple, economical and ecofriendly methods of synthesis of multifunctional ZnO Nps. Nps may be used as good color tunable phosphor materials. The method demonstrated in this study is suggested as an effective replacement for the hazardous chemical methods of production of zinc oxide nanoparticles.

Beschreibung: In this study, In 2 O 3 /Ag/MoO 3 (IAM) nano-multilayer films are designed, and optimum thickness of each layer is calculated. These films were deposited by thermal evaporation technique and then annealed in air atmosphere at different temperatures for 1 h. The effects of annealing temperature on electrical, optical, and structural properties of the IAM system were investigated. The UV–visible–near-IR transmittance and reflectance spectra confirmed that the annealing temperature has significant influence on the electro‐optical characteristics of IAM films. High-quality IAM films with a low sheet resistance of 8.2 (Ω/□) and the maximum optical transmittance of 85 % at 120 °C annealing temperature were obtained. The effect of heat treatment on surface roughness of the layers was also investigated. Figure-of-merit quantity showed that the IAM films annealed at 120 °C have the best performance. X-ray diffraction patterns showed that the crystallinity of the structures enhanced with increase in annealing temperature. Organic light-emitting diodes (OLEDs) were fabricated on IAM anodes. The current density–voltage–luminance (J–V–L) characteristic measurements show that the electroluminescence performances of OLED with IAM anode are improved compared with the conventional ITO-based device. The results indicate that the designed system is suitable for use as transparent conductive anode in optoelectronic devices.

Beschreibung: We demonstrate the effectiveness of silicon phase masks to implement spatially resolved, multispectral imaging capabilities in the range of terahertz frequencies, using a standard setup of basic interest for time-domain spectrometry with a single-cell source and a single-cell detector. Our principle primarily aims at the development of robust and inexpensive systems. It consists of appropriate space-to-time encoding, in order to ensure single-scan triggering and then take advantage of rapid and self-consistent measurements in the two-dimensional space. The process enables very efficient discrimination giving access to a relevant spatial resolution in the analysis of small size, planar assemblies made of inhomogeneous materials. Benchmark results are provided to validate the concept, thanks to prototyping phase masks with 2 × 2 pixels, prior evidencing actual performance limitations in the case of 3 × 3 pixels. Due to the frequency bandwidth of 0.1–1.5 THz in our setup and to the available operating conditions, currently acceptable pixel resolutions lie in the range of 3–4 mm. Numerical modeling by means of finite elements helps to discuss these numbers and to investigate the relevant theoretical issues, figuring the main propagation issues in connection with a sub-picosecond seed pulse throughout various masks. This involves diffraction and trailing edge effects when crossing the mask together with residual, parasitic reflections. Finally, we give a consistent prospective for improved performance, via realistic updates regarding the architecture of the setup and complementary post-processing. Further values for the attainable spatial resolution then range from 5 × 5 to 6 × 6 pixels.

Beschreibung: We derive the effective low-energy Hamiltonian for the tight-binding model with the hopping integral slowly varying along the chain. The effective Hamiltonian contains the kinetic energy with position-dependent mass, which is inverse to the hopping integral, and effective potential energy. Changing of ordering in the kinetic energy leads to change of the effective potential energy and leaves the Hamiltonian the same one. Therefore, we can choose arbitrary von Roos ordering parameters in the kinetic energy without changing the Hamiltonian. Moreover, we propose a more general form for the kinetic energy than that of von Roos, which nevertheless together with the effective potential energy represent the same Hamiltonian.

Beschreibung: A combination of optical emission spectroscopy (OES) and cavity ring-down spectroscopy (CRDS) has enabled to determinate the number densities of CH(A 2 Δ) and CH(X 2 Π) radicals simultaneously in a cascaded arc plasma reactor operating with a CH 4 /Ar mixture. It is found that the number density of CH(A 2 Δ) radical increases with discharge current at first and then decreases. However, the number density of CH(X 2 Π) radical decreases with discharge current when the rate of CH 4 flow to total flow is lower than 1 %, while it increases slightly with discharge current when the rate is 1.5 %. The results reveal that CH radicals are deviation from excitation equilibrium. Although OES is the simplest and most straightforward means to investigate the CH radical behavior, it is not enough to provide the information of the CH(X 2 Π) number density, and additional methods, such as CRDS, are needed in the cascaded arc plasma jet.

Beschreibung: In this paper, we present a numerical study based on 3D FDTD (finite-difference time-domain) simulations that demonstrate the high sensitivity of the optical response of a bowtie nano-aperture antenna (BNA), engraved at the apex of a metal-coated tip, to the distance variation between it and a given substrate. This study mainly discussed the case of the collection mode regime of the BNA and considered the case of two different substrates (high and low refractive index). The coupling between the substrate and the BNA may greatly affect the properties of the optical resonance of the nano-antenna. A blueshift of the resonance wavelength, as large as \(\frac{\varDelta \lambda }{\lambda }=0.3\) , is obtained when the tip moves away over only 10 nm from the substrate (InP) interface. These results open the way to the design of stand-alone optical near-field probes that allow faithful interaction control with a given sample as a function of the distance between them.

Beschreibung: The present paper describes the research of the optical device for two-dimensional straightness measurement of technological machines. Mathematical study of an optical device, operating on the phase principle and measuring transversal displacements of machine parts in two directions ( X and Y ) during their linear longitudinal motion in a machine (alongside the Z axis), is presented. How to estimate the range of travel along the Z axis is analytically shown. At this range, the measurer gives correct measurements of transverse displacement. The necessary distance from the objective focus to the image plane was defined mathematically. The sample results of measuring the displacement of the table of a technological machine by using the optical device are presented in the paper. This optical device for non-contact straightness measurement can be used for measurement straightness in turning, milling, drilling, grinding machines and other technological machines, also in geodesy and cartography, and for moving accuracy testing of mechatronic devices, robotics and others.

Beschreibung: Non-resonant laser-induced thermal acoustics (LITA), a four-wave mixing technique, was applied to post-shock flows within a shock tube. Simultaneous single-shot determination of temperature, speed of sound and flow velocity behind incident and reflected shock waves at different pressure and temperature levels are presented. Measurements were performed non-intrusively and without any seeding. The paper describes the technique and outlines its advantages compared to more established laser-based methods with respect to the challenges of shock tube experiments. The experiments include argon and nitrogen as test gas at temperatures of up to 1000 K and pressures of up to 43 bar. The experimental data are compared to calculated values based on inviscid one-dimensional shock wave theory. The single-shot uncertainty of the technique is investigated for worst-case test conditions resulting in relative standard deviations of 1, 1.7 and 3.4 % for Mach number, speed of sound and temperature, respectively. For all further experimental conditions, calculated values stay well within the 95 % confidence intervals of the LITA measurement.

Beschreibung: Airflow induced by femtosecond laser (800 nm/1 kHz/25 fs) filamentation with different lengths was investigated in a laboratory cloud chamber. Various filament lengths were generated by adjusting laser energy and lens focal length. It was found that airflow patterns are closely related to filament intensity and length. Intense and long filaments are beneficial in updraft generation with large vortices above the filament, while intense and short filaments tend to promote the formation of well-contacted vortices below the filament. Differently patterned airflows induced elliptical snow piles with different masses. We simulated airflow in a cloud chamber numerically taking laser filaments as heat sources. The mechanisms of differently patterned airflow and snow formation induced by filaments were discussed.

Beschreibung: Tissue simulators, the so-called tissue phantoms, have been used to mimic human tissue for spectroscopic applications. Phantoms’ design depends on patterning the optical properties, namely absorption and scattering coefficients which characterize light propagation mechanisms inside the tissues. In this work, two calibration models based on measurements adopting integrating sphere systems have been used to determine the optical properties of the studied solid phantoms. Integrating sphere measurement results were fed into the calibration models using the multiple polynomial regression method and Newton–Raphson algorithm. The third-order polynomials have been used for optical properties predictions. Good agreement between the two models has been obtained. Role of solid phantoms’ components, namely titanium dioxide as a scatterer and black carbon as an absorber, has been discussed. Both of the two components showed observable effects on the absorption and scattering of light inside the solid tissue phantoms.

Beschreibung: We report a novel time-resolved photoacoustic-based technique for studying the thermal decomposition mechanisms of some secondary explosives such as RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), picric acid, 4,6-dinitro-5-(4-nitro-1 H -imidazol-1-yl)-1 H -benzo[ d ] [ 1 – 3 ] triazole, and 5-chloro-1-(4-nitrophenyl)-1 H -tetrazole. A comparison of the thermal decomposition mechanisms of these secondary explosives was made by detecting NO 2 molecules released under controlled pyrolysis between 25 and 350 °C. The results show excellent agreement with the thermogravimetric and differential thermal analysis (TGA–DTA) results. A specially designed PA cell made of stainless steel was filled with explosive vapor and pumped using second harmonic, i.e., λ  = 532 nm, pulses of duration 7 ns at a 10 Hz repetition rate, obtained using a Q-switched Nd:YAG laser. The use of a combination of PA and TGA–DTA techniques enables the study of NO 2 generation, and this method can be used to scale the performance of these explosives as rocket fuels. The minimum detection limits of the four explosives were 38 ppmv to 69 ppbv, depending on their respective vapor pressures.

Beschreibung: Distributions of secondary cosmic muons were measured by the Multigap Resistive Plate Chambers (MRPC) telescopes of the Extreme Energy Events (EEE) Project, spanning a large angular and temporal acceptance through its sparse sites, to test the possibility to search for any anomaly over long runs. After correcting for the time exposure and geometrical acceptance of the telescopes, data were transformed into equatorial coordinates, and equatorial sky maps were obtained from different sites on a preliminary dataset of 110M events in the energy range at sub-TeV scale.

Beschreibung: This paper deals with a theoretical investigation of flow and heat transfer of a Casson fluid from a horizontal circular cylinder in a non-Darcy porous medium under the action of slips and thermal radiation parameters. A model of Casson fluid flow for a circular cylinder has been developed to simulate the transport phenomena. The numerical solution has been obtained for the dimensionless velocity and temperature of the Casson fluid. The effects of various important parameters on the dimensionless velocity, temperature as well as on the skin friction and the dimensionless heat transfer rates are investigated and presented graphically. A comparison with previous published data has been done and we found a good agreement with them.

Beschreibung: For the first time, spatial distribution of major and trace elements has been studied in cholesterol gallstones using time-of-flight secondary mass ion mass spectrometry (TOF-SIMS). The TOF-SIMS has been used to study the elemental constituents of the center and surface parts of the gallstone sample. We have classified the gallstone sample using Fourier transform spectroscopy. The detected elements in cholesterol gallstone sample were carbon (C), hydrogen (H), calcium (Ca), sodium (Na), potassium (K), strontium (Sr), copper (Cu), iron (Fe), chromium (Cr), mercury (Hg) and lead (Pb). The detected molecules in the cholesterol gallstone were CH 3 + , CO 3 + , CaCO 3 + and C 3 H + . Our results revealed that the contents of these elements in cholesterol gallstone were higher in the center part than that in the surface part. In the present paper, we have also presented the UV–Vis spectroscopic studies of the center and surface parts of the gallstone sample which indicated the presence of a higher content of cholesterol in the surface part and bilirubin in the center part.

Beschreibung: Numerical experiments are carried out to calculate continuum emissivity and opacity of plasmas produced from laser-irradiated Au and Pb targets as hohlraum wall materials. Targets are considered to be solid or porous with different initial densities. Simulation results show a good agreement compared with the measured data. The results show that under identical conditions, X-ray emission is higher for Au plasma; however, by decreasing initial densities, X-ray yield enhancement is greater for Pb plasma. By using a Pb target with initial density of about 1.14 g cm −3 instead of solid Au target, the same X-ray yield even more can be obtained. Calculations also show that in the conditions of solid density targets, Pb plasma offers a little lower opacity in soft X-ray region. Decreasing initial density of Pb causes its opacity to increase and get closer to the opacity of solid Au which in turn reduces energy losses in hohlraum wall.

Beschreibung: . The photogravitational oblate restricted three-body problem is carried out within the post-Newtonian framework. The primaries are assumed to be oblate as well as radiant sources. The perturbed location of the collinear point \( L_{3}\) is computed. A series form of \( L_{3}\) location is obtained as a new analytical results. In order to introduce a semi-analytical view, a Mathematica program is constructed so as to draw the locations of collinear point \( L_{3}\) versus the mass ratio \( \mu\in (0, 0.5)\) taking into account one or more of the considered perturbations. All the obtained figures are analyzed.

Beschreibung: We report the two-photon interference properties of a photon pair generated in a type-II collinear periodically poled KTiOPO 4 (PPKTP) crystal pumped by a 406-nm diode laser capable of producing a single or dual longitudinal mode (LM). When the Hong–Ou–Mandel (HOM) interference signals in the PPKTP crystal pumped by a dual-mode diode laser were investigated at various crystal temperatures, it was found that the maximum visibility of the HOM interference signal depends on the relative strength of the dual LMs of the pump laser. The HOM interference pattern was numerically calculated considering the dual LM components of the pump laser diode and the crystal temperature, and was found to be in good agreement with the experimental results.

Beschreibung: One- and two-ring aromatics such as toluene and naphthalene are frequently used molecular tracer species in laser-induced fluorescence (LIF) imaging diagnostics. Quantifying LIF signal intensities requires knowledge of the photo-physical processes that determine the fluorescence quantum yield. Collision-induced and intramolecular energy transfer processes in the excited electronic state closely interact under practical conditions. They can be separated through experiments at variable low pressures. Effective fluorescence lifetimes of gaseous toluene, 1,2,4-trimethylbenzene, anisole, naphthalene, and 1-methylnaphthalene diluted in CO 2 were measured after picosecond laser excitation at 266 nm and time-resolved detection of fluorescence intensities. Measurements in an optically accessible externally heated cell between 296 and 475 K and 0.010–1 bar showed that effective fluorescence lifetimes generally decrease with temperature, while the influence of the bath-gas pressure depends on the respective target species and temperature. The results provide non-radiative and fluorescence rate constants and experimentally validate the effect of photo-induced cooling.

Beschreibung: We present a mid-infrared pulsed cavity ring-down spectroscopy (CRDS) setup based on difference frequency mixing of a tunable dye laser pumped by a Nd:YAG laser and the residual 1064 nm pulse in a temperature-stabilized lithium niobate (LiNbO 3 ) crystal. The performances of such a spectrometer have been investigated by studying the absorption spectrum of methane around 3 µm at room temperature. Our results show a minimum detectable absorption coefficient of 5 × 10 −8  cm −1 . Our approach combines the excellent sensitivity of CRDS with the wide tunable range of difference frequency generation (DFG) with a dye laser. However, the relatively low resolution of this spectrometer prevents the quantification of methane in a wide pressure range. To our knowledge, we report here the first realization and application of a pulsed DFG-based CRDS experiment used for sensitive trace gas detection.

Beschreibung: A telescope-grating-deformable scheme is proposed to compensate the angular dispersion of ultrabroadband spectrum. A simple design consideration is formulated based on the large angular dispersion of the idler from noncollinear optical parametric amplification. A proof of principle experiment is demonstrated. A 3-μJ ultrabroadband near-infrared pulse with spectrum range from 700 to 1400 nm has been generated. The technique has great potential to provide an ultrabroadband seed with negligible angular dispersion for high-power amplification of few-cycle pulses.

Beschreibung: We report an experimental study of the acoustic signal produced by the rupture of an elastic membrane that initially closes a cylindrical overpressurized cavity. This configuration has been recently used as an experimental model system for the investigation of the acoustic emission from the bursting of elongated gas bubbles rising in a conduit. Here, we investigate the effect of the membrane rupture dynamics on the acoustic signal produced by the pressure release by changing the initial tension of the membrane. The initial overpressure in the cavity is fixed at a value such that the system remains in the linear acoustic regime. For large initial membrane deformation, the rupture time τ rup is small compared to the wave propagation time in the cavity and the pressure wave inside the conduit can be fully captured by the linear theory. For low membrane tension, a hole is pierced in the membrane but its rupture does not occur. For intermediate deformation, finally, the rupture progresses in two steps: first the membrane opens slowly; then, after reaching a critical size, the rupture accelerates. A transversal wave is excited along the membrane surface. The characteristic signature of each opening dynamics on the acoustic emission is described.

Beschreibung: We have carried out the structural properties, magnetization measurements and magnetocaloric effects in La 0.5 Sr 0.5 MnO 3 perovskite prepared by the solid-state reaction formula. Crystallographic analysis was realized by Rietveld refinement of experimental X-ray diffraction data. Results show that this material has tetragonal crystal structure and exhibits a sharp ferromagnetic-paramagnetic (FM-PM) transition at a Curie temperature T C (352 K). The experimental magnetic entropy change − ΔS M and the relative cooling power (RCP) have been determined. The magnetocaloric data show a moderate low field magnetic entropy change above room temperature. In addition, the RCP values vary from 46.40 to 228.35 J kg −1 upon variation of the applied magnetic field at 1 and 5 T, which is about 56% of the conventional refrigerant Gd material under 5 T. A good agreement is found between the experimental − ΔS M and the one estimated by the Landau theory at the ferromagnetic region. However, the discrepancy at paramagnetic region was assigned to the contribution of itinerant electron to the large magnetic entropy change.

Beschreibung: In this paper we will be concerned with some combinatorial methods that enable us to determine the number of spanning trees of a graph. Although these methods apply only to rather restricted classes of graphs, sometimes strikingly simple calculations reveal the number of spanning trees of seemingly complex graphs, we presented techniques to derive spanning trees recursions in graphs. Then, we gave the generalization for these techniques. Finally, making use of our results, we investigated the complexity of some new graphs.

Beschreibung: . In the last decades, infrared thermography has been successfully applied to various materials and structures for the assessment of their state of conservation and planning suitable restoration works. To this aim, mathematical models are required to characterize thermal anomaly sources, such as detachments, water infiltration and material decomposition processes. In this paper, an algorithm based on the conservative finite difference method is used to analyse pulse thermography data acquired on an ancient building in the Pompeii archaeological site (Naples, Italy). The numerical study is applied to both broad and narrow elongated thermal anomalies. In particular, from the comparison between simulated and experimental thermal decays, the plaster thickness was characterized in terms of thermal properties and areas of possible future detachments, and moisture infiltration depths were identified.

Beschreibung: We examine a vibrational energy harvester consisting of a mechanical resonator with a fractional damping and electrical circuit coupled by a piezoelectric converter. By comparing the bifurcation diagrams and the power output we show that the fractional order of damping changes the system response considerably and affects the power output. Various dynamic responses of the energy harvester are examined using phase trajectory, Fourier spectrum, Multi-scale entropy and 0–1 test. The numerical analysis shows that the fractionally damped energy harvesting system exhibits chaos, and periodic motion, as the fractional order changes. The observed bifurcations strongly influence the power output.

Beschreibung: Up-conversion can be the main mechanism of energy losses in laser glasses with high concentration of erbium ions. This investigation is devoted to the evaluation of up-conversion parameters in several phosphate and silicate Er-doped glasses. Analysis of the luminescent lifetime shortening at high excitation level has shown that the up-conversion parameters in different glasses can differ by an order of magnitude. The smallest up-conversion was observed in Ba crown silicate glass and Li–Ln-phosphate glass.

Beschreibung: Wavefront aberrations are one of the largest uncertainty factors in present atom interferometers. We present a detailed numerical and experimental analysis of this effect based on measured aberrations from optical windows. By placing windows into the Raman beam path of our atomic gravimeter, we verify for the first time the induced bias in very good agreement with theory. Our method can be used to reduce the uncertainty in atomic gravimeters by one order of magnitude, resulting in an error of 〈3 × 10 −10 g, and it is suitable in a wide variety of atom interferometers with thermal or ultracold atoms. We discuss the limitations of our method, potential improvements, and its role in future generation experiments.

Beschreibung: In this review, we have discussed the potential application of the emerging imaging modality, i.e., optical coherence tomography (OCT) for glucose monitoring in biological tissues. OCT provides monitoring of glucose diffusion in different fibrous tissues like in sclera by determining the permeability rate with acceptable accuracy both in type 1 and in type 2 diabetes. The maximum precision of glucose measurement in Intralipid suspensions, for example, with the OCT technique yields the accuracy up to 4.4 mM for 10 % Intralipid and 2.2 mM for 3 % Intralipid.

Beschreibung: Optical-feedback cavity-enhanced absorption spectroscopy is a highly sensitive trace gas sensing technique that relies on feedback from a resonant intracavity field to successively lock the laser to the cavity as the wavelength is scanned across a molecular absorption with a comb of resonant frequencies. V-shaped optical cavities have been favoured in the past in order to avoid additional feedback fields from non-resonant reflections that potentially suppress the locking to the resonant cavity frequency. A model of the laser–cavity coupling demonstrates, however, that the laser can stably lock to a resonant linear cavity, within certain constraints on the relative intensity of the two feedback sources. By mode mismatching the field into the linear cavity, we have shown that it is theoretically and practically possible to spatially filter out the unwanted non-resonant component in order for the resonant field to dominate the feedback competition at the laser. A 5.3  \(\upmu \hbox {m}\)  cw quantum cascade laser scanning across a \(\hbox {CO}_2\) absorption feature demonstrated stable locking to achieve a minimum detectable absorption coefficient of \(2.7\,\times \,10^{-9}\,\hbox {cm}^{-1}\) for 1-s averaging. Detailed investigations of feedback effects on the laser output verified the validity of our theoretical models.

Beschreibung: Energy levels, wavelengths, oscillator strengths, transition probabilities and lifetimes have been calculated for Be-like Xe, Cs, Ba, La, and Ce ions among the fine-structure levels of terms belonging to the 2s 2 , 2s2p, 2p 2 , 2s3s, 2s3p, 2s3d, and 2p3d configurations. The calculations have been performed using the fully relativistic multiconfiguration Dirac-Fock (MCDF) method, taking the quantum electrodynamic corrections (QED) into account. The results are compared with the available other theoretical results.

Beschreibung: We study the late-time dynamics of a flat Friedmann-Robertson Walker universe in the context of a non-minimal fractional cosmology characterized by fractional weight in time. By considering the conformal coupling between the scalar field and gravity, a negative time-dependent quadratic potential and provided that the scale factor of the universe is related to the scalar field through a power-law ansatz, the universe is oscillating with time and the oscillating behavior of the EoS parameter can be realized around the magical value −1 by crossing the phantom divide line an infinite number of times. Some additional solutions are obtained and discussed accordingly.

Beschreibung: . The dynamics and the noise correlations of one-dimensional anyons are investigated. We solve the time-dependent Schrödinger equation for the one-dimensional anyons interacting via a repulsive delta-function potential based on the Bethe Ansatz. Then the exact solutions are used to derive the explicit formulae of the noise correlations for both the non-interacting and interacting anyons released from a regular array. For the non-interacting anyons, the noise correlations exhibit striking peaks, where the location, the value and the sign of those peaks differ as the anyonic statistical parameter varies, interpolating between the known results of Bose and Fermi gas. For the interacting anyons, apart from the anyonic statistics, the Hamiltonian also exhibits dynamical interactions. Thus the noise correlations for the interacting anyons have a number of features that distinguish it from the non-interacting problem. A set of line-shapes appear in the noise correlations due to the distribution of scattering phases. The width, the sign and location of the line-shape depend strongly on the interaction strength and the statistical parameter. In the Tonks-Giradeau limit, the anyonic correlations reverse the noise correlations of the non-interacting cases due to the \( \pi\) phase shift in the scattering phase.

Beschreibung: Sine-Gordon deformed defects that exhibit unusual phenomenological features on the topological charge are investigated. The possibility of a smooth and continuous transition between topological (non-null charge) and non-topological (null charge) scenarios of deformed defects supported by sine-Gordon structures is evinced by the analytical calculation of topological charges and localized energy distributions. By describing cyclic deformation chains, we show that a triggering sine-Gordon model simultaneously supports kink- and lump-like defects, whose topological mass values are closed by trigonometric or hyperbolic successive deformations. In spite of preserving analytical closure relations constraining the topological masses of 3- and 4-cyclically deformed defects, the deformation chains produce kinks and lumps which exhibit non-monotonic behavior and extra inflection points. The outcome of our analysis suggests that cyclic deformations create novel scenarios of physical and mathematical applicability of defect structures supported by the sine-Gordon theory.

Beschreibung: This paper presents the design and feasibility of an electron-LINAC-based small-scale system (ADS) for nuclear waste transmutation. FLUKA simulations have been performed to evaluate the photoneutron yield in high- Z metallic targets such as silver, tungsten, lead, tantalum and uranium irradiated by electron beams of 20–200MeV. The parameters involved in the photoneutron production mechanism including electron beam energy, target material and target shape have been investigated in order to obtain maximum photoneutron production. The neutron reflectors of the ADS, in particular, beryllium, lead and beryllium oxide (BeO) with various thicknesses have been studied. The results show that a combination of an internal reflector of Pb with a thickness of 3cm and an external reflector of BeO with a thickness of 10cm improves the fluence rate. The photoneutron energy spectrum, photoneutron fluence distribution and heat deposition in the electron target have also been presented. At incident electron beam energy of 155MeV, a neutron source of ∼ 4.6 × 10 10 (n/cm 2 /s/mA) has been achieved, which is highly applicable for using in nuclear waste transmutation. The designed ADS has the ability to transmute ∼ 1.5 × 10 22 (atoms/y/mA). The obtained results are promising and could lead to the development of a small-scale ADS based on electron LINAC for radioactive waste transmutation and for numerous applications when employed as a photoneutron source.

Beschreibung: A new method of pump-coupling in diode-pumped alkali vapor amplifier is reported, which uses ring-LD to tightly surround the alkali vapor cell for directly coupled side-pumping. The kinetic and fluid dynamic modeling, numerical approaches of the ring-LD side-pumped configuration are proposed and applied to the static and the flowing-gas Cs vapor amplifiers. Pump intensity and temperature distribution in the cell are simulated. Influences of some important factors on laser power are calculated and analyzed. Comparisons of different pumped configurations are made, demonstrating the highest utilizing efficiency of pump power of the ring-LD side-pumped configuration. Thus the model is very helpful for designing high-power side-pumped alkali vapor amplifiers.

Beschreibung: Within the frame of the one-electron approximation, we calculate the electron binding energies of the \(\hbox {Na}_{55}^-\) cluster which allows for the identification of the icosahedral structure of the cluster through comparison with experimental photoelectron spectroscopy data. The surface of the icosahedral cluster is represented as a slightly deformed spherical surface, and the corresponding splitting of the energy levels caused by this symmetry reduction is calculated. Subsequently, we demonstrate that the calculated energies of photoelectrons agree very well with the experimental values. This gives an unambiguous demonstration of the role of the cluster structure in photoelectron spectra, whereas electronic shell filling effects are less important.

Beschreibung: Turbulent mixing is highly important in flows that involve heat and mass transfer. Information on turbulent heat flux is needed to validate the mixing models implemented in numerical simulations. The calculation of turbulent heat fluxes requires instantaneous information on temperature and velocity. Even using minimally intrusive laser optical methods, simultaneous measurement of temperature and velocity is still a challenge. In this study, thermographic phosphor particles are used for simultaneous thermometry and velocimetry: conventional particle image velocimetry is combined with temperature-dependent spectral shifts of BAM:Eu 2+ phosphor particles upon UV excitation. The novelty of this approach is the analysis of systematic errors and verification using the well-known properties of a heated turbulent jet issuing into a low velocity, cold coflow. The analysis showed that systematic errors caused by laser fluence, multiple scattering, or preferential signal absorption can be reduced such that reliable measurement of scalar fluxes becomes feasible, which is a prerequisite for applying the method to more complex heat transfer problems.

Beschreibung: . The illustration of cosmic acceleration under two interacting dark energy models (pilgrim dark energy with Granda-Oliveros cutoff and its generalized ghost version) in the DGP braneworld framework is presented. In the current scenario, the equation of state parameter, deceleration parameter, \( \omega_{D}\) - \( \omega^{\prime}_{D}\) plane and statefinder diagnosis are investigated. The equation of state parameter behaves like the phantom era of the universe. The deceleration parameter shows the accelerated expansion of the universe in both models. The cosmological planes, like \( \omega_{D}\) - \( \omega^{\prime}_{D}\) , and the statefinder correspond to the \( \Lambda\) CDM limit. To conclude, we remark that our results support the phenomena of pilgrim dark energy and cosmic acceleration. Also, the results are consistent with observational data.