Laser transmission welding of poly(ethylene terephthalate) and biodegradable poly(ethylene terephthalate) – Based blends

Joining of Poly(Ethylene Terephthalate) PET and its biodegradable derivatives is of high relevance to ensure good productive rate, low cost and operational safety for fabrication of medical and electronic devices, sport equipments as well as for manufacturing of food and drug packaging solutions. In the present investigation, granules of PET and PETs modified by organic additives, which promote biodegradation of the polymeric chains, were prepared by extrusion compounding. The achieved granules were subsequently re-extruded to shape thin (330 μm) flat sheets. Substrates cut from these sheets were joined by Laser Transmission Welding (LTW) with a continuous wave High Power Diode Laser (cw-HPDL). First, based on a qualitative evaluation of the welded joints, the most suitable operational windows for PETs laser joining were identified. Second, characterization of the mechanical properties of the welded joints was performed by tensile tests. Accordingly, Young's modulus of PET and biodegradable PET blends was studied by Takayanagi's model and, based on the experimental results, a novel predicting analytical model derived from the mixture rule was developed. Lastly, material degradation of the polymeric joints was evaluated by FT-IR analysis, thus allowing to identify the main routes to thermal degradation of PET and, especially, of biodegradable PET blends during laser processing.     

Application of the Transmission Line Matrix method for outdoor sound propagation modelling – Part 2: Experimental validation using meteorological data derived from the meso-scale model Meso-NH

Outdoor sound prediction is both a societal concern and a scientific issue. This paper deals with numerical simulations of micrometeorological (temperature and wind) fields for environmental acoustics. These simulations are carried out using the reference meso-scale meteorological model at the Meteo-France weather agency (Meso-NH). Meso-NH predictions at very fine scales (up to 3 m), including new developments (drag force approach), are validated both numerically and experimentally under stable, unstable and neutral conditions. Then, this information can be used as input data for the acoustic propagation model. The time-domain acoustic model is based on the Transmission Line Matrix method. Its development has also been promoted for application to outdoor sound propagation, i.e. to take into account topography, ground impedance, meteorological conditions, etc. In part 1, the presentation and evaluation of the Transmission Line Matrix method showed the relevance of this method’s use in the context of environmental acoustics. Finally, simulated noise levels under different propagation conditions were compared to in situ measurements. Satisfactory results were obtained regarding the variability of the observed phenomena.     

Experimental Quantum Teleportation of Laser Beams

We experimentally demonstrate quantum teleportation for continuous variables by using squeezed-state entanglement. A fidelity expression for a real experimental system is presented, where all the imperfection factors are considered, including losses and phase fluctuations. The measured fidelity for input coherent states is 0.62 and the prospective result with our measured entanglement and efficiencies is 0.69. We will show the details of the quantum teleportation for continuous variable and discuss the problems for further improvement in this experiment.     

Experimental Investigation of an L-Shaped Very-Small-Aperture Laser

An L-shaped very-small-aperture laser （VSAL） with high power output and field enhancement effect is fabricated and characterized. As a comparison, a conventional rectangular VSAL and a double-aperture VSAL containing one L-aperture and one rectangular aperture are also fabricated and measured. The confined optical fields in the vicinity of apertures of VSAL are detected using an apertured near-field scanning optical microscope. The experimental results reveal that the power output from the L-shaped VSAL increases about 13 times than the rectangular VSAL with a comparable aperture area. It is indicated that the L-shaped VSAL has strong power output enhancement effect. The near-field distribution of the double-aperture VSAL indicates that the L-aperture has the field confinement and enhancement effect stronger than the rectangular aperture.     

Laser initiation of PETN–iron nanoparticle composites

The dependences of the probability of explosion initiation in pentaerythritol tetranitrate samples with different contents of iron nanoparticles on the fluence of the first- (λ = 1064 nm) and second-harmonic (λ = 532 nm) pulses of a neodymium laser are measured. The laser initiation threshold for PETN–iron nanoparticle composites nonmonotonically depends on the mass fraction of nanoparticles. The optimal values of the mass fraction of iron nanoparticles at which the sensitivity to laser irradiation is maximal (0.4 wt % for the first harmonic and 0.15 wt % for the second) are determined. It is demonstrated that the amplitude of the optoacoustic signal under non-explosion conditions reaches its maximum for composites with the optimal values of the mass fraction of nanoparticles.     

Application of the transmission line matrix method for outdoor sound propagation modelling – Part 1: Model presentation and evaluation

The present paper deals with an original time-domain approach applied to outdoor sound propagation under meteorological effects. The transmission line matrix method, based on the Huygens’ principle, had already been validated over impedant grounds and complex topography. The presented formulation proposes to take into account meteorological effects (wind speed and temperature) through the relative sound speed. The necessary wavefront direction is determined through the calculation of the averaged intensity vector direction. A good agreement is found between simulations of both the transmission line matrix and parabolic equation methods. A relevant use of the method is shown in the framework of environmental acoustics and initial applications are proposed in Part 2.     

Experimental Study on Intracavity SHG of a Q-Switched Tunable Cr:LiSAF Laser

In this paper, a Q-switched intracavity frequency doubling Cr: LiSAF laser is reported. The relation of laser output behaviors with input energy was studied experimentally. The second harmonic output energy of 15.6 mJ at 450.1 nm for pumping energy of 83 J, the second harmonic output energy of 16 mJ at 445.1 nm for pumping energy of 75 J, and a tunable range of 445.1 ～465.1 nm were obtained in experiments.     

The Experimental Study of a 100W Copper Vapor Laser

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Experimental validation for time-domain fluorescence diffuse optical tomography of linear scheme

We present a full three-dimensional,featured-data algorithm for time-domain fluorescence diffuse optical tomography that inverts the Laplace-transformed time-domain coupled diffusion equations and employs a pair of appropriate transform-factors to effectively separate the fluorescent yield and lifetime parameters. By use of a time-correlation single-photon counting system and the normalized Born formulation,we ex- perimentally validate that the proposed scheme can achieve simultaneous reconstruction of the fluorescent yield and lifetime distributions with a reasonable accuracy.     

Experimental Investigation of Tm3＋-Doped Silica Double-Cladding Fibre Laser

Using a Tm^3＋-doped double-cladding silica fibre, we produce a maximum cw 2.2 W output at approximately 2μm. The highest achieved slope efficiency is 29.3% respect to the launched pump power. The lowest threshold is 1.85 W using the double pass pump method with the fibre length 2. 7m, which is the lowest reported threshold of cladding pump of the ^3H4 level. The fibre laser output peak wavelength ranges from 1.967μm to 2.018μm with cavity 1 （R1 = 1 and R2=0.04） and from 1.95μm to 1.99μm with cavity 2 （R1=0.04 and R2=0.04）, as the fibre length varies.     

Experimental Investigation of High Power Erbium-Ytterbium Co-doped Double Clad Fibre Laser

All-fibre high power erbium-ytterbium co-doped double clad fibre lasers are proposed and demonstrated. By using different back-cavity mirrors, the different double clad fibre lasers are constructed. It is experimentally found that the output behaviour of laser can be controlled by a back-cavity mirror. The lower the reflectivity of the back-cavity mirror, the higher the output power and the high the slop efficiency. The maximum output power is about 1.6 W and the slop efficiency is 27.6%.     

An Experimental Study of Ultrashort Pulsed Ytterbium-Doped Fibre Laser and Amplifier

We report the generation of ultrashort pulses in ytterbium-doped fibre oscillator emitting around 1.05μm at a repetition rate of 17.6 MHz. A diode laser with single silica fibre at 976nm pumps the ytterbium fibre laser, the all-fibre picosecond pulsed oscillator has excellent stability and compact size, and freedom from misalignment. After amplifying, pulse energy of 3.4 nJ and an average power of 60 m W are obtained. The compression is obtained with a grating pair out of the cavity. The compressor produces 307fs with the peak power 5.47kW. A practical fibre-based source with good performance is thus demonstrated.     

Oxidation of pentan-2-ol – part II: Experimental and modeling study

The oxidation of pentan-2-ol was investigated at high-pressure in a jet-stirred reactor and in a shock tube. Experiments in the JSR were carried out at 10 atm, between 500 and 1180 K, for five different equivalence ratios of φ = 0.35, 0.5, 1, 2, 4 and 1000 ppm of fuel, at a constant residence time of 0.7 s. Reactant, product and intermediate species mole fractions were quantified using Fourier transform infrared spectrometry (FTIR) and gas chromatography (GC). Ignition delay times were measured for pentan-2-ol/O₂ mixtures in argon in a shock tube at 20 and 40 bar, in a temperature range of 1070–1460 K and for equivalence ratios of φ = 0.5, 1 and 2. Ignition delay times of a stoichiometric mixture were also measured in air at 20 bar. Under these conditions, this alcohol exhibited no low-temperature reactivity in either experimental set-ups. Based on ab initio calculations presented in the companion paper, a detailed kinetic mechanism was developed in order to reproduce the present data and analyze the reaction pathways.     

Experimental Study of Double XeCl Laser with a Phase-conjugate Stimulated Scattering Cavity

SupportedbytheNationalNatureScienceFoundationofChina.1.Intr0ducti0nExcimcrlasersareonekindofthemostefficientsourcesofUVcoherentlight.Theyareusedinmanyficldssuchasn2atcrialpr0ccssing[lJ,photolitography['J,laserfusion[3Jetal..Inmany0ftheseapplicationstheshort-x`,avelcngthexcimerlaserswith1aserbeamsofhighqua1ityarenecessary.Mostoftheexci113crlasersi1regcncra11yfedbydischargecircuitswhichpumpthegasvol-umebutcausedischargeinstabiliticsinthedischargevolume['1j.Thislastphenomenonisduetothepresen…     

Experimental test of the Preisach–Arrhenius model with temperature

The magnetic aftereffect was measured for a magnetic particle tape over a temperature range of 10–380 K. Data were obtained for the saturation magnetization, the coercive field, and the remanent coercive field as a function of temperature. Switching field distributions and other Preisach parameters were also determined as a function of temperature. Based on these data, the Preisach–Arrhenius (PA) model predicts that the decay rate, S, should decrease monotonically as the temperature is reduced. It was found that, for the material studied, S is nearly proportional to temperature, T, for T between about 150 and 380 K, in good agreement with the PA model, but that there is considerable deviation for T<150 K and a temperature range exists over which S increases with decreasing temperature. A modification of the PA model is required to explain this low-temperature behavior is briefly noted.     

Al-doping influence on crystal growth of Ni–Al alloy: Experimental testing of a theoretical model

Recently, a condensing potential model was developed to evaluate the crystallization ability of bulk materials [Ye X X, Ming C, Hu Y C and Ning X J 2009 J. Chem. Phys. 130 164711 and Peng K, Ming C, Ye X X, Zhang W X, Zhuang J and Ning X J 2011 Chem. Phys. Lett. 501 330], showing that the best temperature for single crystal growth is about0.6Tm, where Tm is the melting temperature, and for Ni–Al alloy, more than 6 wt% of Al-doping will badly reduce the crystallization ability. In order to verify these predictions, we fabricated Ni–Al films with different concentrations of Al on Si substrates at room temperature by pulsed laser deposition, and post-annealed the films at 833, 933, 1033(～ 0.6Tm),1133, and 1233 K in vacuum furnace, respectively. The x-ray diffraction spectra show that annealing at 0.6Tm is indeed best for larger crystal grain formation, and the film crystallization ability remarkably declines with more than 6-wt% Al doping.     

Experimental and Numerical Analysis of a Two—Order Cascaded Raman Fibre Laser

A two-order cascaded Raman fibre laser based on GeO2-SiO2 fibre and fibre Bragg gratings is fabricated.output power 309mW of the second Stockes light around 1176.2nm is obtained with a slope efficiency of 45.3%.The experimental results agree well with the simulation results obtained by using the double-pass model.     

Direct Minimization of the least-squares spectral element functional – Part I: Direct solver

This paper describes an equivalent but improved least-squares formulation for the numerical approximation of the solution of partial differential equations. Instead of using variational analysis to impose the conditions for minimizing the residual, the residuals are minimized directly, thus leading to a method we will denote by Direct Minimization (DM). DM circumvents setting up the normal equations which consists of matrix–matrix multiplications. Matrix–matrix multiplications are expensive, may lead to loss of accuracy and destroy the sparsity pattern present in the original system. The condition number of the DM formulation is the square root of the condition number which would be obtained if variational analysis was employed. An element-by-element procedure will be presented which allows for parallelization of DM. A computational comparison between DM and the conventional least-squares formulation based on variational analysis will be presented.     

Interface thermal resistance and thermal conductivity in composites – an abrupt junction thermal diode model

An abrupt junction diode model is proposed to study the interface thermal resistance and thermal conductivity of composite. We have demonstrated that the structure of thermal diode greatly influences the heat flow and hence it is possible to regulate the heat flow via the geometry of the diode. The composite materials can significantly reduce the thermal conductivity compared to an equivalent single material. By tuning the mass ratio of oscillator of right segment to that of oscillator of left segment of the composite, _MR/_ML$M_{\mathrm{R}}/M_{\mathrm{L}}$, crossover between negative differential thermal resistance and positive differential thermal resistance as well as figure of merit for composite material can be tuned. It is also seen that the composite will work as a better thermal insulating material than its pure constituent materials.