A convergence study of a new partitioned fluid–structure interaction algorithm based on fictitious mass and damping

We develop, analyze and validate a new method for simulating fluid–structure interactions (FSIs), which is based on fictitious mass and fictitious damping in the structure equation. We employ a partitioned method for the fluid and structure motions in conjunction with sub-iteration and Aitken relaxation. In particular, the use of such fictitious parameters requires sub-iterations in order to reduce the induced error in addition to the local temporal truncation error. To this end, proper levels of tolerance for terminating the sub-iteration procedure have been obtained in order to recover the formal order of temporal accuracy. For the coupled FSI problem, these fictitious terms have a significant effect, leading to better convergence rate and hence substantially smaller number of sub-iterations. Through analysis we identify the proper range of these parameters, which we then verify by corresponding numerical tests. We implement the method in the context of spectral element discretization, which is more sensitive than low-order methods to numerical instabilities arising in the explicit FSI coupling. However, the method we present here is simple and general and hence applicable to FSI based on any other discretization. We demonstrate the effectiveness of the method in applications involving 2D vortex-induced vibrations (VIV) and in 3D flexible arteries with structural density close to blood density. We also present 3D results for a patient-specific aneurysmal flow under pulsatile flow conditions examining, in particular, the sensitivity of the results on different values of the fictitious parameters.     

Scanning the energy dissipation process of energetic materials based on excited state relaxation and vibration–vibration coupling

The energy dissipation mechanism of energetic materials(EMs) is very important for keeping safety. We choose nitrobenzene as a model of EM and employ transient absorption(TA) spectroscopy and time-resolved coherent anti-stokes Raman scattering(CARS) to clarify its energy dissipation mechanism. The TA data confirms that the excited nitrobenzene spends about 16 ps finishing the twist intramolecular charge transfer from benzene to nitro group, and dissipates its energy through the rapid vibration relaxation in the initial excited state. And then the dynamics of vibrational modes(VMs) in the ground state of nitrobenzene, which are located at 682 cm~(-1)(v_1), 854 cm~(-1)(v_2), 1006 cm~(-1)(v_3), and 1023 cm~(-1)(v_4),is scanned by CARS. It exhibits that the excess energy of nitrobenzene on the ground state would further dissipate through intramolecular vibrational redistribution based on the vibrational cooling of vi and v_2 modes, v_1 and v_4 modes, and v_3 and v_4 modes. Moreover, the vibration-vibration coupling depends not only on the energy levels of VMs, but also on the spatial position of chemical bonds relative to the VM.     

Protonation state and free energy calculation of HIV-1 protease–inhibitor complex based on electrostatic polarisation effect

The protonation states of catalytic Asp25/25′ residues remarkably affect the binding mechanism of the HIV-1 protease–inhibitor complex. Here we report a molecular dynamics simulation study, which includes electrostatic polarisation effect, to investigate the influence of Asp25/25′ protonation states upon the binding free energy of the HIV-1 protease and a C₂-symmetric inhibitor. Good agreements are obtained on inhibitor structure, hydrogen bond network, and binding free energy between our theoretical calculations and the experimental data. The calculations show that the Asp25 residue is deprotonated, and the Asp25′ residue is protonated. Our results reveal that the Asp25/25′ residues can have different protonation states when binding to different inhibitors although the protease and the inhibitors have the same symmetry. This study offers some insights into understanding the protonation state of HIV-1 protease–inhibitor complex, which could be helpful in designing new inhibitor molecules.     

Fabry–Pérot cavities based on chemical etching for high temperature and strain measurement

In this paper, two hybrid multimode/single mode fiber Fabry–Pérot (FP) cavities were compared. The cavities fabricated by chemical etching are presented as high temperature and strain sensors. In order to produce this FP cavity a single mode fiber was spliced to a graded index multimode fiber with 62.5 μm core diameter. The Fabry–Pérot cavities were tested as a high temperature sensor in the range between room temperature and 700 °C and as strain sensors. A reversible shift of the interferometric peaks with temperature allowed to estimate a sensitivity of 0.75 ± 0.03 pm/°C and 0.98 ± 0.04 pm/°C for the sensor A and B respectively. For strain measurement sensor A demonstrated a sensitivity of 1.85 ± 0.07 pm/μ? and sensor B showed a sensitivity of 3.14 ± 0.05 pm/μ?. The sensors demonstrated the feasibility of low cost fiber optic sensors for high temperature and strain.     

Optical fiber strain and temperature sensor based on an in-line Mach–Zehnder interferometer using thin-core fiber

We propose and demonstrate a fiber in-line Mach–Zehnder interferometer using thin-core fibers. This in-line interferometer is composed of a short section of thin-core fiber inserted between two single mode fibers (SMF), and demonstrated as a strain and temperature sensor in this study. A strain sensitivity of ?1.83 pm/με with a measurement range of 0?2000 με, and the temperature sensitivity of ?72.89 pm/°C with a temperature variation of 50 °C are achieved. We also discussed that the influence of strain and temperature change on the relative power ratios among the excited cladding modes in thin-core fibers.     

Synthesis of hybrid organic–inorganic nanocomposite materials based on CdS nanocrystals for energy conversion applications

Efficient solar energy conversion is strongly related to the development of new materials with enhanced functional properties. In this context, a wide variety of inorganic, organic, or hybrid nanostructured materials have been investigated. In particular, in hybrid organic–inorganic nanocomposites are combined the convenient properties of organic polymers, such as easy manipulation and mechanical flexibility, and the unique size-dependent properties of nanocrystals (NCs). However, applications of hybrid nanocomposites in photovoltaic devices require a homogeneous and highly dense dispersion of NCs in polymer in order to guarantee not only an efficient charge separation, but also an efficient transport of the carriers to the electrodes without recombination. In previous works, we demonstrated that cadmium thiolate complexes are suitable precursors for the in situ synthesis of nanocrystalline CdS. Here, we show that the soluble [Cd(SBz)₂]₂·(1-methyl imidazole) complex can be efficiently annealed in a conjugated polymer obtaining a nanocomposite with a regular and compact network of NCs. The proposed synthetic strategies require annealing temperatures well below 200 °C and short time for the thermal treatment, i.e., less than 30 min. We also show that the same complex can be used to synthesize CdS NCs in mesoporous TiO₂. The adsorption of cadmium thiolate molecule in TiO₂ matrix can be obtained by using chemical bath deposition technique and subsequent thermal annealing. The use of NCs, quantum dots, as sensitizers of TiO₂ matrices represents a very promising alternative to common dye-sensitized solar cells and an interesting solution for heterogeneous photocatalysis.     

Effects of strain on Goos–Hänchen-like shifts of graphene

We have studied the Goos–Hänchen-like (GHL) shifts for massless Dirac electrons passing across a potential barrier in strained graphene. The analytical solutions of the transmission coefficient and the GHL shifts are obtained. The GHL shifts as the function of the strain tensor and direction, the incidence angle and the barrier's width are discussed. We also explore how critical angles change as the strain tensor and incidence electron energy change. Finally, we make a proposal of experimental measurement of the GHL shifts. The study of the GHL shifts will make for applications in graphene-based nano-electronics.     

Adaptive higher-order finite element methods for transient PDE problems based on embedded higher-order implicit Runge–Kutta methods

We present a new class of adaptivity algorithms for time-dependent partial differential equations (PDE) that combine adaptive higher-order finite elements (hp-FEM) in space with arbitrary (embedded, higher-order, implicit) Runge–Kutta methods in time. Weak formulation is only created for the stationary residual, and the Runge–Kutta methods are specified via their Butcher’s tables. Around 30 Butcher’s tables for various Runge–Kutta methods with numerically verified orders of local and global truncation errors are provided. A time-dependent benchmark problem with known exact solution that contains a sharp moving front is introduced, and it is used to compare the quality of seven embedded implicit higher-order Runge–Kutta methods. Numerical experiments also include a comparison of adaptive low-order FEM and hp-FEM with dynamically changing meshes. All numerical results presented in this paper were obtained using the open source library Hermes (http://www.hpfem.org/hermes) and they are reproducible in the Networked Computing Laboratory (NCLab) at http://www.nclab.com.     

A selective and sensitive tert-butylhydroquinone sensor based on synergy of CTAB and AuNPs–PVP–graphene nanohybrids

Gold nanoparticles (AuNPs)–polyvinylpyrrolidone (PVP)–graphene (Gr) nanohybrids were prepared by a facile one-pot green strategy. The obtained Au–PVP–Gr composites were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Then, a novel electrochemical sensor for highly sensitive and selective detection of tert-butylhydroquinone (TBHQ) is proposed based on cetyltrimethyl-ammonium bromide (CTAB) and Au–PVP–Gr modified glassy carbon electrode (GCE). Due to the synergistic effect of CTAB and Au–PVP–Gr, the developed sensor displays a wide linear range from 0.02 to 0.1 and 0.1 to 100.0 μM. A low detection limit of 0.009 μM was observed. Further, the sensitivity and selectivity of PVP–CTAB/Au–PVP–Gr/GCE was demonstrated by its practical application in the determination of TBHQ in real samples.     

Hierarchical structure of countries based on carbon dioxide emission over the periods of 1971–2012; the relationships economic growth and energy consumption

This study uses hierarchical structure methods (minimal spanning tree, (MST) and hierarchical tree, (HT)) to examine the hierarchical structures of the carbon dioxide emission from the 84 countries by three main sectors, namely electricity/heat, manufacturing/construction and transportation sectors. We obtain the topological properties among the countries based on carbon dioxide emission over the periods of 1971–2012. We also perform the bootstrap techniques to investigate a value of the statistical reliability to the links of the MSTs. The results of the topologies structural of these trees are as follows: (i) We identified different groups of countries according to their economic growth and geographical location. (ii) Our results show that the high income and low energy consuming country groups are more important within the network.     

Gradient multilayer tribilogical coatings based on Mo–S–Ti–C formed by hybrid ion-plasma methods

Mechanical, physical and tribological properties of layer-gradient multi-component coatings based on the Mo–S–Ti–C composition are investigated. The coatings are formed by combining the magnetron sputtering and the hybrid magnetron and vacuum arc deposition assisted by a gas plasma generator. A correlation is established between the physic mechanical and tribological properties of the resulting coatings, which allows identifying their potential applications. The physical principles of the combined technologies of lowtemperature ion-plasma deposition of tribological Mo–S–Ti–C coatings onto hardened steel machine parts are developed.     

Effect of 300 and 500 MPa pressure treatments on starch–water adsorption/desorption isotherms and hysteresis

Pressure treatments of 300 and 500?MPa during 15?min were found to change starch–water sorption (adsorption and desorption) isotherms and the hysteresis effect, particularly the 500?MPa. This last treatment shifted the adsorption/desorption isotherms downward, compared with non-treated starch and starch treated at 300?MPa. The observed hysteresis effect decreased with the increase in pressure level in the whole a_w range, indicating that adsorption and desorption isotherms became closer. Guggenheim–Anderson–De Boer and Brunauer–Emmett–Teller model parameters Cb, Cg, K and Mm also showed changes caused by pressure, the latter being lower in the pressure-processed samples, thus indicating possible changes on microbial and (bio)chemical stabilities of pressure-processed food products containing starch.     

Effect of exchange–correlation on quantum ion-acoustic soliton energy

The electrons exchange–correlation influence on the energy carried by the quantum ion-acoustic soliton (QIAS) is succinctly discussed. Starting from the one-dimensional quantum hydrodynamic model (in which the term of exchange–correlation for electrons is included), a deformed Korteweg–de Vries-like equation is derived. It is found that the QIAS energy experiences a depletion as a result of quantum diffraction. This quantum energy depletion may be counteracted by the exchange–correlation effect. The present work can be viewed as a first step towards the investigation of the exchange–correlation effects on the dynamics of solitary waves in quantum plasmas.     

High temperature strain glass in Ti–Au and Ti–Pt based shape memory alloys

Strain glass is a frozen short-range strain ordered state found in shape memory alloys recently, which exhibits novel properties around the ideal glass transition temperature T₀. However, the T₀ of current strain glass systems is still very low, limiting their potential applications and experimental studies. In this paper, we reported two new strain glass systems with relatively high T₀. In Ti₅₀Au_50-xCr_x alloys, the strain glass appears at x = 25, and exhibits a T₀ of 251 K, while in Ti₅₀Pt_50-yFey alloys, the strain glass takes place at y = 30, and shows a T₀ of 272 K. Both of them are comparable with the highest T₀ value reported so far. Moreover, the phase diagrams of main strain glass systems in Ti-based alloys were summarized. It is found that the influence of the martensitic transformation temperature of the host alloy on the T₀ of the strain glass is limited. This work may help to design new strain glass systems with higher T₀ above ambient temperature.     

Synthesis and characterisation of highly fluorescent core–shell nanoparticles based on Alexa dyes

Current and future developments in the emerging field of nanobiotechnology are closely linked to the rational design of novel fluorescent nanomaterials, e.g. for biosensing and imaging applications. Here, the synthesis of bright near infrared (NIR)-emissive nanoparticles based on the grafting of silica nanoparticles (SNPs) with 3-aminopropyl triethoxysilane (APTES) followed by covalent attachment of Alexa dyes and their subsequent shielding by an additional silica shell are presented. These nanoparticles were investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM) and fluorescence spectroscopy. TEM studies revealed the monodispersity of the initially prepared and fluorophore-labelled silica particles and the subsequent formation of raspberry-like structures after addition of a silica precursor. Measurements of absolute fluorescence quantum yields of these scattering particle suspensions with an integrating sphere setup demonstrated the influence of dye labelling density-dependent fluorophore aggregation on the signaling behaviour of such nanoparticles.     

Design and analysis of all-optical 4–2 binary encoder based on photonic crystal

In this paper we theoretically propose combining optical waveguides with nonlinear photonic crystal based ring resonators for realizing an all optical 4–2 encoder. Nonlinear resonant rings are constructed from GaAs as the material used for dielectric rods. By application of optical beam to input ports of the structure the on/off states are realized and the resulting truth table confirms functionality of proposed device. The switching threshold and time delay of the device are about 1 kW/µm² and 1 ps, respectively. The normalized power at the output ports for all the ports in ON states is the same and equal to 60%.     

Fabrication and strain investigation of ZnO nanorods on Si composing sol–gel and chemical bath deposition method

High density vertically aligned ZnO nanorods arrays were prepared on Si substrate by the simple and facile sol–gel and chemical bath deposition combination technology. ZnO nanorods, preferentially oriented along the c-axis, were of the hexagonal wurzite structure. The lattice constants of ZnO nanorods a was shrunken by about 0.004 nm, which can result in about 1.29% mismatch between ZnO nanorods and Si substrate. The Raman spectrum was also analyzed in detail, and the result indicates that the stress between ZnO nanorods and Si substrate was about 0.227 GPa, which can be ascribed to the stress relaxation effect of the ZnO nanorods. The room temperature photoluminescence (PL) measurement result has shown a main deep level emission. The forming mechanism for ZnO nanorods was further analyzed.     

Optical sensors based on Fabry–Perot resonator and fringes of equal thickness structure

We propose theoretically two optical sensor structures based on Fabry–Perot resonator and fringes of equal thickness structure. Different from the conventional slab waveguide sensors in which the sample interacts with the evanescent field in the cladding layer, the proposed sensors contain the sample in the core layer. The first proposed sensor comprises a piezoelectric material as a substrate with the driving potential difference as the sensing probe for refractive index changes of the sample. The second sensor comprises fringes of equal thickness structure with the number of fringes per unit length is the probe for changes in the index of the sample. The calculations reveal that the proposed sensors have high sensitivity to changes in the refractive index of the sample.     

Atomic composition and stability of Langmuir–Blodgett monolayers based on siloxane dimer of quaterthiophene on the surface of polycrystalline gold

Physics of the Solid State - Atomic composition of monolayers based on siloxane dimer of quaterthiophene deposited by Langmuir–Blodgett technique on a silicon dioxide surface partially...