Self-assembly of boehmite nanopetals to form 3D high surface area nanoarchitectures

A flower-like boehmite nanostructure was prepared through a template-free chemical route by the self-assembly process of nanosize petals 800–1000 nm long, 200–250 nm wide, 20–50 nm thick and having an average crystallite size of about 2.21 nm. X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), DTA/TGA analyses and Brunauer–Emmet–Teller (BET-N₂) analyses were used in order to characterize the product obtained. XRD results exhibited that the obtained nanostructures composed of pure orthorhombic AlOOH phase. The effects of Cl⁻ ions and TEA on the growth of boehmite three-dimensional nanoarchitectures in the presence of NO₃^-\mathrm{NO}_{3}^{-} ions were investigated. BET analyses of as-prepared material demonstrate that this nanostructure material has a high specific surface area, as high as 123 m² g⁻¹.     

Index for vehicle acoustical comfort inside a passenger car

Sound quality is among the main factors that influence customers’ preference for choosing good automobile products. It all started more than 10 years ago and grows up so fast due to high competition in the automotive industries. A-weighted noise levels and sound power are usually utilised to measure the noise but they are not adequate to characterise the impact sound inside a car. The most popular approach to determine sound quality of a product is to define an annoyance or specific index, which involves both subjective and objective evaluations. Subjective and objective tests should be studied concurrently in order to determine the sound quality inside a passenger car. This approach is used in this paper to evaluate vehicle comfort index according to most frequently used sound quality metrics, namely; Zwicker loudness, sharpness, roughness and fluctuation strength. As a result researchers of different fields of automotive acoustics investigations can use this index according to the type of road (international road roughness) without any need to perform time-consuming jury tests. The metrics are correlated with jury test results that show which of them and how much has affected the acoustical comfort of the vehicle. The relation between road roughness and vehicle acoustical comfort index is another point of interest in this research.     

Density-Dependent Conformable Space-time Fractional Diffusion-Reaction Equation and Its Exact Solutions

In this article, a special type of fractional differential equations(FDEs) named the density-dependent conformable fractional diffusion-reaction(DDCFDR) equation is studied. Aforementioned equation has a significant role in the modelling of some phenomena arising in the applied science. The well-organized methods, including the exp(-φ(ε))-expansion and modified Kudryashov methods are exerted to generate the exact solutions of this equation such that some of the solutions are new and have been reported for the first time. Results illustrate that both methods have a great performance in handling the DDCFDR equation.     

Pull-in Instability Analysis of Nanoelectromechanical Rectangular Plates Including the Intermolecular,Hydrostatic, and Thermal Actuations Using an Analytical Solution Methodology

The current paper presents a thorough study on the pull-in instability of nanoelectromechanical rectangular plates under intermolecular, hydrostatic, and thermal actuations. Based on the Kirchhoff theory along with Eringen's nonlocal elasticity theory, a nonclassical model is developed. Using the Galerkin method(GM), the governing equation which is a nonlinear partial differential equation(NLPDE) of the fourth order is converted to a nonlinear ordinary differential equation(NLODE) in the time domain. Then, the reduced NLODE is solved analytically by means of the homotopy analysis method. At the end, the effects of model parameters as well as the nonlocal parameter on the deflection, nonlinear frequency, and dynamic pull-in voltage are explored.     

Controlling a bunch of multiple filaments by means of a beam diameter

We demonstrate a three orders of magnitude increase and stability in the backscattered fluorescence signal from nitrogen molecules by terawatt femtosecond laser pulse induced air filaments using a new method. The method is based on squeezing the initial beam diameter using a telescope. The effect of laser shot-to-shot fluctuations was included in numerical simulations by a random distribution of the initial intensity in both squeezed and non-squeezed beams. Statistical processing of the simulation results shows that the average diameter of plasma channels as well as the total amount of free electrons generated in a bunch of multiple filaments in air is larger in the squeezed beam. Shot-to-shot stability of the simulated plasma density increases in the squeezed beam. The change of this plasma density with propagation distance is in good qualitative agreement with the change of the range-corrected nitrogen fluorescence signal with distance. PACS 42.65.Jx; 42.60.Jf; 42.68.Ay; 42.68.Wt     

Measurement of filament length generated by an intense femtosecond laser pulse using electromagnetic radiation detection

We present a new method to measure the length of a filament induced by the propagation of intense femtosecond laser pulses in air. We used an antenna to detect electromagnetic pulses radiated from multipole moments inside the filament oscillating at the plasma frequency. The results are compared with the values detected from the backscattered fluorescence induced by multiphoton ionization of nitrogen molecules excited inside the filament. The values are found to be in good agreement. Received: 6 November 2002 / Revised version: 27 January 2003 / Published online: 24 April 2003 RID="*" ID="*"Corresponding author. Fax: +1-418/656-2623, E-mail: shosseini@phy.ulaval.ca     

Fabrication and Determination of Refractive Index Profile of the Planar Waveguides by Wedge Technique

Several planar waveguides have been fabricated. The waveguides have been polished for determination of their refractiveindex profiles (RIP) by wedge method. The RIP determined by inserting the sample in a Mach-Zehnder interferometer andapplying fringe analysis methods.     

Surfactant effect on the conductivity behavior of CsH2PO4: Characterization by electrochemical impedance spectroscopy

Cesium dihydrogen phosphate (CDP) nanoparticles were synthesized using the surfactants cetyltrimethyl ammonium bromide (CTAB), polyoxyethylene-polyoxypropylene (F-68) and (F-68:CTAB) with molar ratio 0.06. The samples conductivity such as CDP_CTAB, CDP_F-68 and CDP_{(F-68:CTAB)0.06} was studied by impedance spectroscopy in the frequency range 0.01 Hz to 1 MHz. The Nyquist plots were drawn at different temperatures of 210, 230 and 260 °C, which are defined below transition, phase transition and above transition, respectively. The measured conductivities obey the Arrhenius relation. The influence of surfactants on conductivity are more significant at higher temperature due to grain boundary. The conductivity of CDP_CTAB increased slightly with increasing temperature to 260 °C, whereas the conductivity of other samples decreased with increasing temperature over 230 °C. The results indicated that the conductivities increase in the order of CDP_CTAB>CDP_{(F-68:CTAB)0.06}>CDP_F-68. These are in accordance to the ion exchange capacities of the samples that the surfactant shows a direct influence on the samples proton mobility. It is found that the conductivity of CsH₂PO₄ is influenced by surfactant type.