Active damping of geometrically nonlinear vibrations of doubly curved laminated composite shells

This paper deals with the analysis of active constrained layer damping (ACLD) of geometrically nonlinear transient vibrations of doubly curved laminated composite shells. Vertically/obliquely reinforced 1–3 piezoelectric composite (PZC) and active fiber composite (AFC) materials are used as the materials of the constraining layer of theACLD treatment. The Golla–Hughes–McTavish (GHM) method has been implemented to model the constrained viscoelastic layer of the ACLD treatment in time domain. The first-order shear deformation theory (FSDT) and the Von Kármán type non-linear strain displacement relations are used for analyzing this coupled electro-elastic problem. A three dimensional finite element (FE) model of doubly curved laminated smart composite shells integrated with ACLD patches has been developed to investigate the performance of these patches for controlling the geometrically nonlinear transient vibrations of the shells. The numerical results indicate that the ACLD patches significantly improve the damping characteristics of the doubly curved laminated cross-ply and angle-ply shells for suppressing their geometrically nonlinear transient vibrations. It is found that the performance of the ACLD patch with its constraining layer being made of the AFC is significantly higher than that of the ACLD patch with vertically/obliquely reinforced 1–3 PZC constraining layer. The effects of variation of piezoelectric fiber orientation in both the obliquely reinforced 1–3 PZC and the AFC constraining layers on the control authority of the ACLD patches have also been investigated.     

An efficient method for electromagnetic scattering analysis

We present a novel method to solve the magnetic field integral equation (MFIE) using the method of moments (MoM) efficiently. This method employs a linear combination of the divergence-conforming Rao-Wilton-Glisson (RWG) function and the curl-conforming n×RWG function to test the MFIE in MoM. The discretization process and the relationship of this new testing function with the previously employed RWG and n×RWG testing functions are presented. Numerical results of radar cross section (RCS) data for objects with sharp edges and corners show that accuracy of the MFIE can be improved significantly through the use of the new testing functions. At the same time, only the commonly used RWG basis functions are needed for this method.     

Synthesis and characterization of electrochromic poly(amide–imide)s bearing methoxy-substituted triphenylamine units

New poly(amide–imide)s (PAIs) 3a–d and 3′a–d with methoxy-substituted triphenylamine (TPA) units were prepared by the direct polycondensation from various imide ring-preformed dicarboxylic acids 2a–d with 4,4′-diamino-2″,4″-dimethoxytriphenylamine (1) and 4,4′-diamino-4″-methoxytriphenylamine (1′), respectively, using triphenyl phosphite and pyridine as condensing agents. For the comparative study, the referenced PAIs 3″a–d without methoxy substituents on the TPA unit were also prepared from 2a–d with 4,4′-diaminotriphenylamine (1″). All the polymers were readily soluble in many organic solvents and could be solution-cast into tough and flexible polymer films. The glass-transition temperatures (T_gs) of these PAIs ranged from 196 to 298 °C and the 10% weight-loss temperatures were in excess of 445 °C in nitrogen. Cyclic voltammograms of the PAI films cast onto the indium–tin oxide (ITO)-coated glass substrate exhibit one reversible oxidation redox couples at 0.73–0.89 V vs. Ag/AgCl in an electrolyte/acetonitrile solution. The polymer films revealed good electrochemical and electrochromic stability, with coloration change from a pale yellow neutral form to a green oxidized form. After over 100 redox cycles, the polymer films still exhibited good redox and electrochromic reversibility. The 3 and 3′ series PAIs exhibited enhanced redox-stability and electrochromic performance as compared to the parent 3″ analogs without methoxy substituents on the TPA unit.     

Anisotropy of the spectroscopy properties of the wurtz-stannite Cu2ZnGeS4 single crystals

In this study, the near band edge anisotropic optical properties of wurtz-stannite (WS) Cu₂ZnGeS₄ single crystals were characterized using polarization-dependent transmittance and electrolyte electroreflectance (EER) techniques. Single crystals of Cu₂ZnGeS₄ were grown by chemical vapor transport method using iodine as a transport agent. Analysis of absorption spectra revealed indirect allowed transitions for Cu₂ZnGeS₄ with the band gaps of 2.02 (2.07) and 2.08 (2.14) eV for E‖b and Е‖a polarization configurations at 300 (10) K. The room-temperature EER spectra in the vicinity of the direct band edge showed anisotropic transitions at around 2.38, 2.44 and 2.45 eV for E‖b, Е‖a and Е‖c polarizations, respectively. Based on the experimental observations and recent band-structure calculations a plausible band diagram near band edge of WS-Cu₂ZnGeS₄ was constructed.     

Synthesis of diketopyrrolopyrrole (DPP)-based small molecule donors containing thiophene or furan for photovoltaic applications

Two π-conjugated small molecules based on diketopyrrolopyrrole (DPP), DPP4T and DPP2F2T, were synthesized using the Suzuki coupling reaction. DPP4T and DPP2F2T contained furan and thiophene, respectively, next to a DPP core. Organic photovoltaic cells (OPVs) were fabricated using two DPP-based oligothiophenes as donors. DPP4T showed higher power conversion efficiency (PCE) (1.44%) than DPP2F2T (0.85%). The short-circuit current (J_SC) of DPP4T (4.38 mA cm⁻²) was nearly twice that of DPP2F2T (2.49 mA cm⁻²). The improved photovoltaic properties of DPP4T could be explained by the optical properties and the film morphology.     

Multilayer films consisted of azulene-based dye molecules and polyelectrolyte: Preparation, characterization and photoluminescent property

Ultrathin multilayer films of two azulene-based (Az-based) dye molecules (Az), 3-methylazulene-1-carboxylic acid hydrazide (Az-1) and 5-(4-phenylamine)-2-(3-methylazulene-1-yl)-1,3,4-oxadiazoles (Az-2), and poly(sodium 4-styrenesulfonate) (PSS) have been prepared by layer-by-layer self-assembly and characterized by UV-vis spectroscopy, fluorescence spectroscopy, small-angle X-ray reflectivity measurements and atomic force microscopy (AFM) imaging. UV-vis spectra show that the characteristic absorbance values of the multilayer films increase almost linearly with the number of PSS/Az bilayers, suggesting that the deposition process is regular and highly reproducible from layer to layer. Average thicknesses for the PSS/Az-1 and PSS/Az-2 bilayers of the multilayer films are ca. 0.9 and 1.4 nm, respectively. AFM images provide the surface morphology of the PSS/Az films, indicating that the film surface is relatively uniform and smooth. The occurrence of photoluminescent activity conforms the potential for creating luminescent multilayer films with Az-based dye molecules.     

Synthesis and properties of polycyclic quinones condensed with 1,6-methano[10]annulene

Two types of polycyclic quinones condensed with 1,6-methano[10]annulenes as type A: 1,6-methanonaphtho[2,3-c][10]annulene-7,12-dione 5a, and type B: 1,6-methanonaphtho[2,3-c][10]annulene-5,14-dione 18, bis(1,6-methano[10]annuleno[3,4-b; 3,4-g])anthracene-10,21-dione 20, 1,6-methanoanthraceno[2,3-c][10]annulene-5,16-dione 22, 1,6-methanotetraceno[2,3-c][10]annulene-6,17-dione 23, and 1,6-methano phenanthreno[2,3-c][10]annulene-5,6-dione 24 have been synthesized. The acene derivative 6 corresponding to that of 5a was synthesized by the reduction of quinone 5a. The physical, spectral, and chemical properties of these new compounds have been investigated.     

Fine-tuning supramolecular assemblies of fullerenes bearing long alkyl chains

Fine-tuning of the supramolecularly organized nanometer scale architectures of fullerene derivatives, fulleropyrrolidines substituted with a mono-, di-, or tri(n-hexadecyloxy)phenyl group is described. These synthetic fullerene derivatives possess one- (1), two- (2), or three- (3) long alkyl chains. The correlation between the number of alkyl chain multiplicity and the self-organized bilayer structures as the fundamental subunit as well as the superstructures formed in different solvents were investigated using microscopic and spectroscopic techniques. The fullerene derivatives studied formed interdigitated lamellar bilayer structures whose d spacing values, estimated by X-ray diffraction patterns, are 2.63 nm for 1, 3.50 nm for 2, and 4.28 nm for 3, respectively. There are the two differing intermolecular forces present due to C₆₀ (sp²-carbons) or alkyl chains (sp³-carbons). Fullerene moieties always exhibit strong π-π interactions, while van der Waals interactions between alkyl chains can be altered by variation of their multiplicity. Substitution of three alkyl chains at the fullerene moiety (3) was the most effective method for stimulating polymorphism in its derivatives in different solvents.     

Role of chain length and spacers in the organization of long chain Schiff base compounds at air/water and solid/liquid interfaces

Langmuir films of long chain Schiff base compounds: N-(4-fluorobenzylidene)hexadecanamine (compound 1), N-(4-fluorobenzylidene)octadecanamine (compound 2) and 4-{[(4-fluorobenzylidene)amino]methyl}-N-hexadecylaniline (compound 3) have been studied at air/water interface using the characteristic surface pressure-molecular area (π-A) and surface potential-molecular area (ΔV-A) isotherms. Photoelastic modulated Fourier transform infrared spectroscopy has been used to analyze the films of the three compounds at air/water interface. The Langmuir-Blodgett films of these compounds have been characterized using X-ray diffraction that shows layered structures, with interlayer distances of up to 4.4 nm for compound 3. The results show that the layer-to-layer distance can be easily and rationally designed by choosing alkyl chains of different lengths and spacer. Compound 3 packs in an interdigitated bilayer structure with longer lamellar spacing whereas compounds 1 and 2 show a noninterdigitated monolayer structure. Atomistic model calculations have been carried out on the three compounds and the dipole moment values obtained agreed well with the experimental results of surface potential in Langmuir films. Among the three compounds, compound 3 forms stable vesicles spontaneously at room temperature.     

Cationic triblock copolymer micelles deliver anionic spacer chains substituted aluminum phthalocyanine for enhancement intracellular photodynamic efficacy

A novel spacer chains substituted aluminum phthalocyanine (Pc), naming tetra-carboxylaminohexanoicsulfonyl aluminium phthalocyanine 4 was synthesized. Its structure was characterized by elemental analysis, IR, ¹H NMR and MS. Polyion complex micelle (PIC) between the 4 and amphiphilic triblock copolymer poly(L-lysin)-block-poly(ethylene glycol)-block-poly(L-lysin) (PLL-b-PEG-b-PLL) was formed via an electrostatic interaction between the positively charged poly(L-lysin)(PLL) segment and negatively charged periphery of the 4. Dynamic light scattering (DLS) and atom force microscopy (AFM) image showed that 4-loaded PIC formed a spherical nanocarrier micelle with approximately 85 nm in diameter. The fluorescence intensity and lifetime of 4-loaded PIC were significantly enhanced by the incorporation 4 into PIC nanocarrier. The time-dependent intracellular uptake amount and in vitro photodynamic photocytotoxicity of the 4 within the nanocarrier were drastically improved compared with the free 4.     

Bi-velocity hydrodynamics: Single-component fluids

Acceptance of the Navier-Stokes-Fourier (NSF) equations as the fundamental equations of single-component continuum fluid mechanics for liquids and gases is noted to be inseparably linked to Euler’s implicit, but unproved, hypothesis that but a single-velocity field is required to characterize the four physically different, context-specific, velocities appearing in the mass, momentum, and energy equations. To test Euler’s hypothesis, velocity is added to the usual list of quantities requiring constitutive formulation - namely the heat flux q and viscous stress T - in order to effect closure of the mass, momentum, and energy equations. Establishment of this enlarged set of constitutive relations is effected by using conventional linear irreversible thermodynamics (LIT) principles governing the behavior of simple fluid continua, importantly including satisfaction of Onsager reciprocity as a fundamental continuum requirement. The resulting analysis shows that, in general, two velocities rather than one are required and, concomitantly, that additional driving forces must be added to each of the standard constitutive equations for the Fourier’s-law heat flux q = −k∇T and the Newton’s-law viscous stress (wherein the “mass velocity” v_m is the context-specific velocity appearing in the continuity equation ∂ρ/∂t + ∇ · (ρv_m) = 0). For the particular case of dilute gaseous continua explicit expressions are established for the phenomenological coefficients appearing in these additional constitutive contributions. Determination of these coefficients is effected using data derived from the Chapman-Enskog-Burnett constitutive expressions for q and T, the latter obtained by solving the Boltzmann equation at small Knudsen numbers, including so-called rarefied-gas contributions. These coefficients are found to be nonzero, confirming the conclusion, inter alia, that two velocities are constitutively required to quantify hydrodynamic behavior for gases and, by inference, for liquids too. Collectively, these velocity, heat flux, and stress constitutive findings collectively negate the current belief that the NSF equations fully describe the physics of viscous fluid continua. Rather, they do so only in limiting cases where the additional constitutive terms than we have found necessary for completeness are asymptotically small.     

The effect of solution chemistry on the preparation of MgAl2O4 by hydrothermal-assisted sol-gel processing

Preparation of magnesium aluminate spinel powder by hydrothermal-assisted sol-gel processing from MgAl₂(OCH₂CH₂OR)₈, RCH₃ (1), CH₂CH₂OCH₃ (2), MgAl₂[OCH(CH₃)₂]₈ (3) and MgAl₂(O-^sBu)₈ (4) in toluene and parent alcohol has been investigated. Coordination status of aluminum atom in precursors was determined by ²⁷Al NMR and correlation between coordination number of aluminum and development of spinel phase in hydrothermal-assisted sol-gel processing has been studied. The gels obtained from hydrothermal-assisted hydrolysis of magnesium-aluminum alkoxides that contain six-coordinated aluminum atoms in solution (1 and 2) after calcination at 700 °C resulted in the formation of pure spinel phase, whereas in similar hydrolysis and calcination processes of precursors that contain four-coordinated aluminum (3 and 4) spinel phase forms along with some Al₂O₃ and MgO. Selected powders obtained from hydrothermal-assisted sol-gel processing were characterized by thermal analysis (TGA/DSC), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Results indicate that the coordination status of aluminum in the precursor is very crucial for the formation of pure phase spinel. The morphology of prepared spinels was studied by SEM and the results showed that the solvent in hydrothermal-assisted sol-gel processing has a marked effect on the morphology of the resulting MgAl₂O₄. In hydrothermal-assisted sol-gel processing of aluminum-magnesium alkoxides in hydrophobic solvent, spherical particles are formed, while in the parent alcohol, non-spherical powders are formed.     

Crystal structure,nonlinear optical and photophysical properties of a novel chromophore constructed with terpyridine,triphenylamine and ethyl cyanocaetate functional moieties

A novel chromophore (Z)-ethyl-3-(4-((4-([2,2′:6′,2″-terpyridin]-4′-yl)phenyl) (phenyl) amino)phenyl)-2-cyanoacrylate(3), constructed with triphenylamine moiety as the electron donor (D), 2, 2: 6, 2-terpyridine moiety as an electron acceptor (A), and ethyl cyanocaetate group as an auxiliary electron acceptor (A′), has been designed and synthesized. The crystal structures of 3 and its mediator 2 (4″-(4′-(4-(Diphenylamino) phenyl) aldehyde)-2,2′:6′,2″-Terpyridine), have been determined by single crystal X-ray diffraction analysis. The linear and nonlinear spectra of these chromophores were investigated on the basis of experimental and calculation methods. The two-photon absorption (TPA) cross-sections of 1–3 were determined by a femtosecond open-aperture Z-scan technique. The maximum value of the TPA cross-section (σ) for 3 is 7938.3 GM in DMF solution. However, much weaker two-photon absorption responses were observed at the same condition for chromophore 1 and 2, respectively. The results of the work indicate that, the photophysical properties of the D–A configuration group are influenced largely by the auxiliary moiety (A′) attached.     

Chemosensory rhodamine-immobilized mesoporous silica material for extracting mercury ion in water with improved sensitivity

Mesoporous silica material, SBA-15, is an excellent support for constructing fluorescent surface sensor. In this paper, we reported a three-step surface reaction involved strategy to construct efficient fluorescent surface sensor for mercury ion by clicking rhodamine fluoroionophores onto APES-functionalized SBA-15, which is fully characterized by IR spectra, TGA analysis, elemental analysis, nitrogen adsorption experiment and TEM. Our experimental results indicated that such a strategy exhibits an obviously higher loading efficiency within SBA-15 than a previously reported strategy. The Hg²⁺ extracting efficiency for SBAIR was found to be enhanced (ca. 89%). In addition to the high selectivity, the current chemosensor shows improved sensitivity and can respond to Hg²⁺ as low as ppb level (1.0 × 10⁻⁸ M, 2 ppb) in water.     

Near-infrared luminescent polymer thin films containing Yb(III) complex and photosensitized dye

Polymethylmethacrylate (PMMA) thin films containing Yb(pms)₃(H₂O)₈ (pms: bis(perfluoromethanesulfonyl)imide) and dipyridophenazine with DMSO and DMSO-d₆ were fabricated on the glass substrates. The films show photosensitized near-IR luminescence under UV light irradiation of 370 nm in wavelength. The emission quantum yields of Yb(III) complex in PMMA (film 1), PMMA containing DMSO (film 2), and PMMA containing DMSO-d₆ (film 3) thin films are 0.18, 0.26, and 0.26%, respectively. The emission quantum yields of films 1 and 2 were considerably enhanced after the annealing at 80 °C.     

Approach to a block polymer precursor from poly(3-hexylthiophene) nitroxide-mediated in situ polymerization for stabilization of poly(3-hexylthiophene)/ZnO hybrid solar cells

A cross-linked block copolymer poly(3-hexylthiophene)-b-poly(zinc dimethacrylate) (P3HT-b-PZn(MA)₂), which acted as precursor for the preparation of poly(3-hexylthiophene)/ZnO (P3HT/ZnO) hybrid film by in-situ hydrolysis, was rationally designed and synthesized via nitroxide-mediated in-situ polymerization of zinc methacrylate (Zn(MA)₂) using poly(3-hexylthiophene) alkoxyamine (P3HT-TIPNO) as macroinitiator for the purpose of stabilizing the P3HT/ZnO hybrid solar cells. The cross-linking was confirmed by the insolubility of the film in organic solvents and Fourier-transform infrared experiment. With the function of the cross-linked template, the diffusion of ZnO nanoparticles prepared by in-situ hydrolysis could be lowered to suppress the formation of large aggregations, which favored the formation of a better and more stable interpenetrating network and provided more heterojunction interfaces for exciton dissociation. As a result, the inverted device based on cross-linked P3HT/ZnO hybrid film obtained by in situ hydrolyzing P3HT-b-PZn(MA)₂ block copolymer yielded a power conversion efficiency of 0.45% under AM 1.5G illumination from a calibrated solar simulator with an intensity of 100 mW/cm², and the deterioration of the photoconversion performance was suppressed in the hybrid solar cells with the cross-linked P3HT/ZnO compared to cells with non-cross-linked P3HT/ZnO obtained by in situ hydrolyzing P3HT-TIPNO/Zn(MA)₂ blend film.     

The morphology and orientation of Mn5Si3 precipitates in an Mg-Sn-Mn-Si alloy

This paper reports a preliminary study of Mn₅Si₃ precipitates in an Mg-Sn-Mn-Si alloy. The transmission electron microscopy investigation reveals that the Mn₅Si₃ precipitates have a plate shape, approximately 50 nm in thickness and 200 nm in width. The orientation relationship (OR) between the precipitates and matrix is not unique, but all measured ORs obey the following relationship: g_{(1 0 − 1 0)Mn5Si3} // Δg₁ // Δg₂, where Δg₁ = g_{(2 − 1 − 1 0)Mn5Si3} − g_{(0 0 0 2)Mg}, Δg₂ = g_{(3 − 1 − 2 0)Mn5Si3} − g_{(0 0 0 2)Mg}. The precipitate morphology and their OR with the matrix are explained with a Δg parallelism rule, showing good agreement.     

Synthesis, photophysical, electrochemical and thermal studies on carbazole-based acceptor molecules for heterojunction solar cell

Five small molecules, 3-tricyanovinyl-N-alkylcarbazoles (6-10) have been synthesized in a cost-effective way and characterized. The molecules have high thermal stability, good thin film formation ability and are also air stable. The change of alkyl chain length altered the aggregation pattern in the thin film. Their photophysical and electrochemical studies promise a compatible highest occupied molecular orbital - lowest unoccupied molecular orbital energy level to be potentially useful as good electron acceptor materials in heterojunction solar cell in combination with copper(II)phthalocyanine or poly-3-hexylthiophene (P3HT) as donor. Significant photoluminescence quenching of P3HT in P3HT:6-10 blends were observed.     

Rational design and characterization of high-efficiency planar A–π–D–π–A type electron donors in small molecule organic solar cells: A quantum chemical approach

Taking the reported donor DR3TBDT as reference, a series of A–π–D–π–A type donor molecules involving different planar donor cores were designed and investigated by using density functional theory (DFT)/time-dependent DFT methods. Preliminary calculations on geometries, energy levels and spectrum properties show that four of the designed molecules (4, 5, 12 and 13) could become potential donor replacements of DR3TBDT due to their good planarity, larger light harvesting efficiencies and similar exciton migration capability. Additionally, several factors influencing on short-circuit current density (J_sc) were analyzed by in-depth quantum chemical investigations on the transition density matrix, charge transfer indexes, exciton binding energy and Gibbs free energy loss in charge dissociation process. Comparative analyses demonstrate that 4 with indaceno[1,2-b:5,6-b′]dithiophene donor core has more significant electron transfer character and favorable exciton dissociation capability for enhancing the J_sc, and would be potentially promising donor material in organic solar cells.     

A study of the wide ferroelectric phase in mixtures of chiral and non-chiral tilted smectic C-type liquid crystals

A new liquid crystal of a siloxane dimer with an achiral swallow-tail, C11Si2C11, D, was synthesized and mixed with a chiral material as a chiral dopant, 4′-[11-(1,1,2,2,3,3,3-heptamethyltrisiloxanyl)undecyloxy]biphenyl-4-carboxylate, C11Si3, C, to prepare binary mixtures for this study. All mixtures possess the ferroelectric chiral smectic C phase over a broad temperature range. For respect compound C11Si3, the temperature range of the SmC* phase was only 72.6 °C, and was increased upon the addition of dimer C11Si2C11. The electro-optical properties of the SmC* phase, such as tilt angle, dielectric permittivity and switching behavior were also measured. It appeared that the mixtures had a similar viscosity, but the switching time was decreased due to the larger P_s, which was caused by an increased proportion of C11Si3. Therefore, the mixtures revealed a similar tilt angle at around 37.5° at temperatures within their respective mesophase temperature ranges. As a consequence, the correlation between the electro-optical properties and mixture proportion was determined.