Spectroscopic and nonlinear photophysical characterization of organic octupolar-compounds supported by anodic-alumina nanotube-arrays

Amorphous anodic alumina membranes (AAM) comprising highly ordered nanometric porous arrays (porous anodic aluminas: PAA) with 1D-nanotube dimensions of ∼75 nm in diameter and 45 microns in depth were successfully prepared and used as nanostructured host networks for different functionalized octupolar chromophores (named here Oct-(n)). Atomic force microscopy (AFM) studies performed on the developed hybrid systems confirmed a homogeneous insertion of these organic molecules into the PAA nanotube-arrays. Samples with high structural quality were selected for several photophysical characterizations: Comprehensive X-ray diffraction (XRD) and optical spectroscopic characterizations performed according to UV-vis absorption, photoluminescent (PL) and Raman measurements revealed the structural and optical performance of these molecules within the PAA-confinement. Since the implemented optical chromophores were specifically functionalized for nonlinear optical (NLO) applications, the obtained Oct-(n)/PAA-based amorphous hybrids were also characterized according to cubic NLO-techniques such as third harmonic generation (THG) and the Z-Scan method. PAA-confined octupolar chromophores have shown interesting linear and NLO optical properties which have not yet been intensively investigated in bulk hybrid systems; hence, the obtained hybrid nanostructures represent a promising field of investigation in the route to functional octupolar-based materials, where different self-assembled molecular structures may be formed, giving rise to enhanced linear and NLO-properties.     

Design of a test method to simulate the stresses encountered by packaging during sea transport

The aim of this research was to design a specific testing method to simulate the mechanical hazards encountered in sea transport regardless of sea routes and sea conditions and to put it into practice with specially designed devices. The Laboratoire National d'Essais (LNE) has carried out this research in cooperation with the French Ship-Building Research Institute. Eight sea routes of major commercial importance have been chosen and among them five zones in which heavy swells are likely to occur. The behaviour of four types of ships (representative of the present merchant fleet) submitted to various sea conditions has been calculated by computer. Moreover, the stacking conditions on board have been observed directly by the LNE. The analysis of parameters which describe the movement of the ship and affect the packagings are, respectively, rolling, pitching and slamming. Consequently, the forces applied to packagings at the bottom of a stack are a vertical compression force and a horizontal force applied by the moving stacked packagings. A special testing device has been designed applying simultaneously to a packaging both a stacking load and a dynamic horizontal force to this load. The test parameters have been adjusted through experimental ranges of tests on box-pallets, the behaviour of which were well known in field trials.     

Polarization-dependent photothermal beam deflection for the determination of the order parameter C(2) in a laser-oriented polymer system

We demonstrate polarization-dependent photothermal beam deflection as a powerful tool for analyzing quasi-two-dimensional molecular orientation. As examples we used two laser-beam-oriented polymer systems: DR1 in poly(methyl methacrylate) (PMMA) and PMMA with covalently bound DR1 and for comparison Phenol Blue in PMMA. Different order parameters C(2), for these systems have been found. It was also possible to orient by laser beam the DR1 chromophores cyclically by changing the polarization direction of the orienting laser beam and following these chromophore reorientations. The long-term stability of the orientation was investigated as well. The irreversible bleaching that is due to this laser treatment could be determined. Angular hole burning could easily be detected in these systems.     

Influence of Sputtering Pressure on the Structure and Mechanical Properties of Nanocomposite Ti-Si-N Thin Films

Nanocomposite Ti-Si-N thin films have been deposited on Si (100) substrate by direct current/radio frequency (DC/RF) magnetron sputtering. The effect of varying deposition parameters on the structure and mechanical properties of Ti-Si-N films has been investigated by characterization techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and nanoindentation, respectively. XRD analysis of the thin films exhibit all (111), (200) and (220...     

Probing molecular interactions in bone biomaterials: Through molecular dynamics and Fourier transform infrared spectroscopy

Polymer-hydroxyapatite (HAP) composites are widely investigated for their potential use as bone replacement materials. The molecular interactions at mineral polymer interface are known to have significant role of mechanical response of the composite system. Modeling interactions between such dissimilar molecules using molecular dynamics (MD) is an area of current interest. Molecular dynamics studies require potential function or force field parameters. Some force fields are described in literature that represents the structure of hydroxyapatite reasonably well. Yet, the applicability of these force fields for studying the interaction between dissimilar materials (such as mineral and polymer) is limited, as there is no accurate representation of polymer in these force fields. We have obtained the parameters of consistent valence force field (CVFF) for monoclinic hydroxyapatite. Validation of parameters was done by comparing the computationally obtained unit cell parameters, vibrational spectra and atomic distances with XRD and FTIR experiments. Using the obtained parameters of HAP, and available parameters of polymer (polyacrylic acid), interaction study was performed with MD simulations. The MD simulations showed that several hydrogen bonds may form between HAP and polyacrylic acid depending upon the exposed surface of HAP. Also there are some favourable planes of HAP where polyacrylic acid is most likely to attach. We have also simulated the mineralization of HAP using a “synthetic biomineralization”. These modeling studies are supported by photoacoustic spectroscopy experiments on both porous and non porous composite samples for potential joint replacement and bone tissue engineering applications.     

Comparative Study on the Machinability Aspects of Aluminium Silicon Carbide and Aluminium Graphite Composites

Aluminium matrix composites find wide applications in the present industrial scenario due to their desirable properties. Study of the effect of process parameters on machinability of aluminium matrix composites is of paramount importance in the field of manufacturing engineering. Machining of a composite depends on the properties and relative content of the reinforcement and the matrix materials as well as on its response to the machining process. In this article, investigations on the machinability aspects of aluminium-silicon carbide and aluminium-graphite composites are presented. Experiments have been carried out through the Design of Experiments technique and regression machinability models have been developed, which express the degree to which the resultant force depends upon the cutting parameters and the percentage of reinforcement present in the aluminium matrix composites machined. A comparative study of the effect of cutting parameters on the resultant force has been presented.     

Modelling photosystem I as a complex interacting network

In this paper, we model the excitation energy transfer (EET) of photosystem I (PSI) of the common pea plant Pisum sativum as a complex interacting network. The magnitude of the link energy transfer between nodes/chromophores is computed by Forster resonant energy transfer (FRET) using the pairwise physical distances between chromophores from the PDB 5L8R (Protein Data Bank). We measure the global PSI network EET efficiency adopting well-known network theory indicators: the network efficiency (Eff) and the largest connected component (LCC). We also account the number of connected nodes/chromophores to P700 (CN), a new ad hoc measure we introduce here to indicate how many nodes in the network can actually transfer energy to the P700 reaction centre. We find that when progressively removing the weak links of lower EET, the Eff decreases, while the EET paths integrity (LCC and CN) is still preserved. This finding would show that the PSI is a resilient system owning a large window of functioning feasibility and it is completely impaired only when removing most of the network links. From the study of different types of chromophore, we propose different primary functions within the PSI system: chlorophyll a (CLA) molecules are the central nodes in the EET process, while other chromophore types have different primary functions. Furthermore, we perform nodes removal simulations to understand how the nodes/chromophores malfunctioning may affect PSI functioning. We discover that the removal of the CLA triggers the fastest decrease in the Eff, confirming that CAL is the main contributors to the high EET efficiency. Our outcomes open new perspectives of research, such comparing the PSI energy transfer efficiency of different natural and agricultural plant species and investigating the light-harvesting mechanisms of artificial photosynthesis both in plant agriculture and in the field of solar energy applications.     

Electro-optics poled sol–gel materials doped with heterocycle push–pull chromophores

Hybrid organic–inorganic materials doped with zwitterionic push–pull chromophores with high hyperpolarizability have been synthesized via sol–gel, based on glycidoxypropyltrimethoxysilane (GPTMS) and glycidoxypropylmethyldimethoxysilane (GDMMS). Homogeneous films doped with chromophores, have been obtained using N-hydroxyethylcarbazole as a physical spacer avoiding dye aggregation. The waveguiding properties of the spin-coated doped films electrically poled in N₂ atmosphere showing second harmonic generation measurements, have been preliminarily measured by m-line spectroscopy before and after poling; the feasibility of channel waveguiding structures has been demonstrated.     

Low Force Measurement Based on Impedance of a Piezo-resonator

Piezoelectric transducers have effectively been used for force measurement due to their inherently large stiffness. The primary transduction parameter of piezoelectric transducer is voltage which is used mostly for dynamic and sometimes for quasi-static force measurement. Other parameters of piezoelectric transducers such as resonant frequency, electrical impedance, etc. have also been used for force measurement. In the present work, precision measurement of conductance of a radial mode piezo-resonator has been carried out under different static loading and the resultant change in resonant conductance of the resonator have been evaluated as a function of loading force. This method based on resonant conductance measurement can prove to be effective in measuring forces between two interfaces which is an important requirement in many scientific and technical problems.     

动圈式扬声器数值分析方法

为了全面和准确地预估扬声器的声学特性,提出了一种动圈式扬声器数值分析的完整方法。该方法包括磁路分析、振动分析和声场分析三个方面,基于有限元和边界元法实现对数值模型的求解。以某型号动圈式扬声器为例,详细介绍了三方面的数值分析网格模型、方法、原理、技术难点和结果,同时利用Klippel R&D测量系统和B&K Pulse系统等设备进行了精确测量,将数值分析结果与实际测量结果进行比较分析。实验结果表明,分析得到的力因子Bl值、共振频率、振幅响应以及频率响应曲线等都与实际测量结果基本吻合。     

Effect of flapping kinematics on aerodynamic force of a flapping two-dimensional flat plate

Potential applications of flapping-wing micro-aerial vehicles (MAVs) have prompted enthusiasm among the engineers and researchers to understand the flow physics associated with flapping flight. An incompressible Navier–Stokes solver that is capable of handling flapping flight kind of moving boundary problem is developed. Arbitrary Lagrangian–Eulerian (ALE) method is used to handle the moving boundaries of the problem. The solver is validated with the results of problems like inline oscillation of a circular cylinder in still fluid and a flat plate rapidly accelerating at constant angle of attack. Numerical simulations of flapping flat plate mimicking the kinematics of those like insect wings are simulated, and the unsteady fluid dynamic phenomena that enhance the aerodynamic force are studied. The solution methodology provides the velocity field and pressure field details, which are used to derive the force coefficients and the vorticity field. Time history of force coefficients and vortical structures gives insight into the unsteady mechanism associated with the unsteady aerodynamic force production. The scope of the work is to develop a computational fluid dynamic (CFD) solver with the ALE method that is capable of handling moving boundary problems, and to understand the flow physics associated with the flapping-wing aerofoil kinematics and flow parameters on aerodynamic forces. Results show that delayed stall, wing–wake interaction and rotational effect are the important unsteady mechanisms that enhance the aerodynamic forces. Major contribution to the lift force is due to the presence of leading edge vortex in delayed stall mechanism.     

Strain insensitive Ni-Co films over a wide composition range

The magnetic properties of vacuum deposited Ni-Co films have been studied as a function of film composition, film thickness, and substrate temperature. The experimental parameters ranged from 400-1000 Å for thickness 17-41-percent Ni for composition and room temperature to 300°C for the substrate temperature. It was found that the magnetoelastic strain coefficient approaches zero in the vicinity of 35-percent Ni in agreement with Tolman's result[1] and remains insensitive to film composition from 30-40- percent Ni. These results are in reasonably good agreement with calculations based on single crystal data and the expression of Callen and Goldberg [10]. The coercive force and anisotropy field are an order of magnitude larger than of nonmagnetostrictive Permalloy films. An unexpected result is an increased coercive field with increasing film thickness while the anisotropy field remains practically constant; the films become inverted at a critical thickness in the order of 750 Å For a wide variation of preparation parameters the crystallite size remained less than 100 Å     

AZ31 镁合金压痕-压平复合形变数值模拟

目的研究AZ31镁合金压痕-压平复合形变过程中工艺参数对形变区温度场、应力场、应变场、塑性变形力的影响规律。方法采用有限元模拟软件,对复合形变过程进行数值模拟研究,获得不同工艺参数条件下,温度场、应力场、应变场、塑性变形力的变化规律。结果在压痕形变过程中,随着形变温度的增大,形变区温度场的最高温度随之增大,最大塑性变形力的随之减小。在压痕形变过程中,随着模具温度的增大,形变区温度场的最高温度随之增大,最大塑性变形力随之减小。结论实验结果与数值模拟结果相吻合,说明数值模拟过程中的几何模型及相关参数设定是合理的。     

Calculation of the thermodynamic parameters of helium in a centrifugal force field

The design of cooling systems for a cryoalternator's superconducting field windings must be based on the knowledge of the distribution of the thermodynamic parameters (primarily temperature) of the helium in both its liquid and gaseous phases in centrifugal force fields. This paper proposes a set of ordinary differential equations describing the distributions. By numerically solving the set, the effects of the angular velocity of rotation, filling factor and temperature (pressure) at the axis of rotation upon the pressure, temperature and density distributions in helium in rotating vessels have been studied. Formulee for the approximation of the distributions have been obtained, which are applicable to rotation axis temperatures from 3 to 4.6 K (corresponding to saturation pressures 0.24 × 10⁵ to 1.4 × 10⁵ Pa), angular velocities of rotation from 50 to 300 rad s^?1 and filling factors from 0.1 to 0.9.     

Spin-up and spin-down of a viscous fluid over a heated disk rotating in a vertical plane in the presence of a magnetic field and a buoyancy force

Summary The hydromagnetic spin-up and spin-down of an incompressible electrically conducting fluid on a heated infinite disk rotating in a vertical plane in the presence of a magnetic field and a buoyancy force have been studied. The flow is non-axisymmetric due to the imposition of the buoyancy force. We have considered the situation where there is an initial steady state which is perturbed by suddenly changing the angular velocity of the disk. By using suitable transformations the Navier-Stokes and energy equations with four independent variables (x, y, z, t) are reduced to a system of partial differential equations with two independent variables (,t ^*). Also, these transformations uncouple the momentum and energy equations, resulting in a primary axisymmetric flow with an axial magnetic field, in an energy equation dependent on the primary flow and in a buoyancy induced secondary cross flow dependent on both primary flow and energy.The results indicate that the effect of the step-change in the angular velocity of the disk is more pronounced on the primary flow than on the secondary flow and the temperature field. For both spin-up and spin-down cases the surface shear stress in the non-axial direction normal to gravity for the primary flow and the surface shear stresses for the secondary flow increase with the magnetic parameter, whilst the surface shear stress in the vertical direction and the heat transfer at the surface decrease as the magnetic parameter increases. Also, the secondary flow near the disk dominates the primary flow. We have also developed an asymptotic analysis for large magnetic parameters which complements well the numerical results obtained in the lower magnetic parameter range.     

海洋平台结构环境激励的实验模态分析

介绍了对位于渤海湾的“埕岛二号”中心生活平台所进行的现场测试实验,该平台为直立式导管架钢结构平台。此次现场实验是在波浪力、风等环境载荷激励下测试结构动力响应的。利用频域的模态识别法峰值法(PP)和时域中的自然激励法(NExT)结合特征系统实现算法(ERA)分别对海洋平台结构现场测试的动力响应数据进行模态参数识别;利用ANSYS建立了该平台结构的三维有限元模型,并进行结构的模态分析。海洋平台结构的理论和实验模态分析结果吻合较好,分析结果表明该类模态参数识别方法能够为结构损伤诊断提供基准模型,可以运用于实际结构的健康监测以及维护维修。     

MHD Boundary Layer Flow of a Power-Law Nanofluid Containing Gyrotactic Microorganisms Over an Exponentially Stretching Surface

This study focusses on the numerical investigations of boundary layer flow for magnetohydrodynamic (MHD) and a power-law nanofluid containing gyrotactic microorganisms on an exponentially stretching surface with zero nanoparticle mass flux and convective heating. The nonlinear system of the governing equations is transformed and solved by Runge-Kutta-Fehlberg method. The impacts of the transverse magnetic field, bioconvection parameters, Lewis number, nanofluid parameters, Prandtl number and power-law index on the velocity, temperature, nanoparticle volume fraction, density of motile microorganism profiles is explored. In addition, the impacts of these parameters on local skin-friction coefficient, local Nusselt, local Sherwood numbers and local density number of the motile microorganisms are discussed. The results reveal that the power law index is considered an important factor in this study. Due to neglecting the buoyancy force term, the bioconvection and nanofluid parameters have slight effects on the velocity profiles. The resultant Lorentz force, from increasing the magnetic field parameter, try to decrease the velocity profiles and increase the rescaled density of motile microorganisms, temperature and nanoparticle volume fraction profiles. Physically, an augmentation of power-law index drops the reduced local skin-friction and reduced Sherwood number, while it increases reduced Nusselt number and reduced local density number of motile microorganisms.     

Synthesis of novel two-dimensional spindle-type fluorinated nonlinear optical chromophores

Two novel two-dimensional spindle-type fluorinated chromophores with fluorinated phenyl as side groups connecting to the π conjugated bridge were prepared for second-order nonlinear optical applications. The detailed synthetic procedure was reported. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed that the spindle-type fluorinated chromophores have excellent thermal stability. Host-guest doped materials had been used to prepare the second-order nonlinear optical films. The nonlinear electro-optic (EO) coefficient of the poled films was measured by Teng-Man technique at the fundamental wavelength of 1310 nm, and the r₃₃ up to 28 pm/V was achieved.     

Equilibrium gradient methods with nonlinear field intensity gradient: a theoretical approach

Equilibrium gradient methods belong to a family of separation techniques in which analytes are forced to unique equilibrium points by a force gradient and a counter force along the separation pathway. The basic theory for equilibrium gradient methods where the force gradient is induced by a field gradient is developed in this paper. The results indicate that peak capacity can be dynamically improved by using a nonlinear field-intensity gradient in which the first section is steep, and the following section is shallow. Using electromobility focusing (EMF) as an example, a separation model is established. EMF is an equilibrium gradient method that uses an electric field intensity gradient to induce a force gradient on charged analytes, such as proteins, and a constant hydrodynamic flow as an opposing force. Equations relating operating parameters with separation performance are given. Although simulation results show that a peak capacity of over 10,000 is theoretically possible using a single channel in a separation time just under 2 months, if 100 parallel separation units are utilized in an array format under the same operating conditions, the same peak capacity can be obtained in just over 12 h.     

Prediction of Performance of an Industrial Poittemill in Production of Limestone Powders

Experimental data were collected from tests using an industrial-scale high-pressure roller mill named the Poittemill grinding limestone materials for a range of parameters (such as force pressure, circumferential speed of roll, and feed size) in a Nordkalk AB plant located in Ignaberga, Sweden. These data were used to develop models of throughput, size reduction, and energy utilization with the parameters. A performance model with a correction coefficient, which has been developed, is able to describe the Poittemill throughput at various force pressures and circumferential speeds of rolls. The materials leaked beside the rolls are found to be empirically related to the circumferential speed of roll in a given force pressure. It is shown that two major parameters, force pressure and circumferential speed of roll, have an influence on the median size (d₅₀) of the ground product. Product fineness is decreased at a higher circumferential speed of roll or at a lower force pressure. The force pressure is the most dominant effect on energy utilization in the mill. The feed size used has a slight influence on the grinding results. Energy to the Poittemill for the comminution is utilized more efficiently at a lower force pressure or a higher circumferential speed of roll. Empirical models can predict the comminution characteristics with respect to the major parameters in the Poittemill system in dry mode. Product size-energy input relations have been also established, independent of the operating parameters used.