Microstructural and mechanical properties of Al-4.5wt% Cu reinforced with alumina nanoparticles by stir casting method

The microstructure and mechanical properties of A1-4.5wt% Cu Mloy reinforced with different volume fractions （1.5vo1%, 3vo1%, and 5vo1%） of alumina nanoparticles, fabricated using stir casting method, were investigated. CMculated amounts of alumina nanoparticles （about ~50 nm in size） were ball-milled with aluminum powders in a planetary ball mill for 5 h, and then the packets of milled powders were incorporated into molten Al-4.5wt% Cu alloy. Microstructural studies of the nanocomposites reveal a uniform distribution of alumina nanoparticles in the A1-4.5wt% Cu matrix. The results indicate an outstanding improvement in compression strength and hardness due to the effect of nanoparticle addition. The aging behavior of the composite is also evaluated, indicating that the addition of alumina nanoparticles can accelerate the aging process of the Mloy, resulting in higher peak hardness values.

Mechanical properties of TiO_2-hydroxyapatite nanostructured coatings on Ti-6Al-4V substrates by APS method

TiO2-hydroxyapatite （HA） nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy （SEM）. It is found that the coating with 10% HA has the best mechanical properties. Based on Rietveld refinement method, the mean grain size of the as-received powder （212 nm） extensively decreases to 66.4 nm after 20 h of high-energy ball milling. In spite of grain growth, the deposited coatings maintain their nanostructures with the mean grain size of 112 nm. SEM images show that there is a lower porosity in the coating with a higher HA content. Optical microscopy images show that uniform thickness is obtained for all the coatings.

The second Eshelby problem and its solvability

It is still a challenge to clarify the dependence of overall elastic properties of heterogeneous materials on the microstructures of non-elliposodal inhomogeneities （cracks, pores, foreign particles）. From the theory of elasticity, the formulation of the perturbance elastic fields, coming from a non-ellipsoidal inhomogeneity embedded in an infinitely extended material with remote constant loading, inevitably involve one or more integral equations. Up to now, due to the mathematical difficulty, there is almost no explicit analytical solution obtained except for the ellipsoidal inhomo- geneity. In this paper, we point out the impossibility to trans- form this inhomogeneity problem into a conventional Eshelby problem by the equivalent inclusion method even if the eigenstrain is chosen to be non-uniform. We also build up an equivalent model, called the second Eshelby problem, to investigate the perturbance stress. It is probably a better template to make use of the profound methods and results of conventional Eshelby problems of non-ellipsoidal inclusions.

Mechano-chemical selections of two competitive unfolding pathways of a single DNA i-motif

The DNA i-motif is a quadruplex structure formed in tandem cytosine-rich sequences in slightly acidic conditions. Besides being considered as a building block of DNA nano-devices, it may also play potential roles in regulating chromo- some stability and gene transcriptions. The stability of i-motif is crucial for these functions. In this work, we investigated the mechanical stability of a single i-motif formed in the human telomeric sequence 51-（CCCTAA）3CCC, which revealed a novel pH and loading rate-dependent bimodal unfolding force distribution. Although the cause of the bimodal unfolding force species is not clear, we proposed a phenomenological model involving a direct unfolding favored at lower loading rate or higher pH value, which is subject to competition with another unfolding pathway through a mechanically stable inter- mediate state whose nature is yet to be determined. Overall, the unique mechano-chemical responses of i-motif-provide a new perspective to its stability, which may be useful to guide designing new i-motif-based DNA mechanical nano-devices.

A density-functional theory for (BAs) n clusters (n=1-14):structures,stabilities and electronic properties

This paper investigates the lowest-energy structures, stabilities and electronic properties of （BAs）n clusters （n=1- 14） by means of the density-functional theory. The results show that the lowest-energy structures undergo a structural change from two-dimensional to three-dimensional when n ： 4. With the increase of the cluster size （n=6）, the （BAs）n clusters tend to adopt cage-like structures, which can be considered as being built from B2As2 and six-membered rings with B-As bond alternative arrangement. The binding energy per atom, second-order energy differences, vertical electron affinity and vertical ionization potential are calculated and discussed. The caculated HOMO-LUMO gaps reveal that the clusters have typical semiconductor characteristics. The analysis of partial density of states suggests that there are strong covalence and molecular characteristics in the clusters.

Growth and transport properties of topological insulator Bi2Se3 thin film on a ferromagnetic insulating substrate

Exchange coupling between topological insulator and ferromagnetic insulator through proximity effect is strongly attractive for both fundamental physics and technological applications. Here we report a comprehensive investigation on the growth behaviors of prototype topological insulator Bi2Se3 thin film on a single-crystalline LaCoO3 thin film on SrTiO3 substrate, which is a strain-induced ferromagnetic insulator. Different from the growth on other substrates, the Bi2Se3 films with highest quality on LaCoO3 favor a relatively low substrate temperature during growth. As a result, an inverse dependence of carrier mobility with the substrate temperature is found. Moreover, the magnetoresistance and coherence length of weak antilocalization also have a similar inverse dependence with the substrate temperature, as revealed by the magnetotransport measurements. Our experiments elucidate the special behaviors in Bi2Se3/LaCoO3 heterostructures, which provide a good platform for exploring related novel quantum phenomena, and are inspiring for device applications.

New ternary superconducting compound LaRu2As2： Physical properties from density functional theory calculations

In this paper, we perform the density functional theory （DFT） -based calculations by the first-principles pseudopo- tential method to investigate the physical properties of the newly discovered superconductor LaRu2As2 for the first time. The optimized structural parameters are in good agreement with the experimental results. The calculated independent elas- tic constants ensure the mechanical stability of the compound. The calculated Cauchy pressure, Pugh＇s ratio as well as Poisson＇s ratio indicate that LaRu2As2 should behave as a ductile material. Due to low Debye temperature, LaRu2As2 may be used as a thermal barrier coating （TBC） material. The new compound should exhibit metallic nature as its valence bands overlap considerably with the conduction bands. LaRu2As2 is expected to be a soft material and easily machinable because of its low hardness value of 6.8 GPa. The multi-band nature is observed in the calculated Fermi surface. A highly anisotropic combination of ionic, covalent and metallic interactions is expected to be in accordance with charge density calculation.

The Electrical and Optical Properties of Zn0.5Li2xMg0.5-xFe2O4 Lithium Doped Nanoparticle Prepared by Coprecipitation Method

In this study, nano ferrite materials were produced to replace costive industrial materials [1]. Ferrite nanoparticles are the interesting material due to their rich and unique physical and chemical properties. They find applications in catalysis, bio-processing, medicine, magnetic recording, adsorption, devices etc. Using co-participation method, five nano ferrite samples Zn0.5Mg0.5-xLi2xFe2O4 (x = 0.00, 0.10, 0.20, 0.30 and 0.40) were prepared. The electrical and optical properties of the Zn0.5Mg0.5-xLi2xFe2O4 samples were studied using the Ultraviolet-visible (UV-Vis) spectroscopy. The results verified that the formation of the absorption coefficient of the five samples of Zn0.5Mg0.5-xLi2xFe2O4 increased with the increase of Lithium (Li2x). The energy band gap of the Zn0.5Mg0.5-xLi2xFe2O4 samples ranged from 3.28 to 3.12 eV [1]. The extinction coefficient (K) for five samples of Zn0.5Li2xMg0.5-xFe2O4 increased with the increase of Lithium (Li2x) at 338 nm from 0.074 to 0.207. The high magnitude of optical conductivity is (1.34 × 1012 sec-1) and the maximum value of electrical conductivity is 42 (Ω.cm)-1. This may due to the electrical and optical properties of lithium.

Attractors of Dissipative Soliton Equation

In the paper ,we study longtime dynamic behavior of dissipative soliton equation existence of attractor ,geometrical structure of attractor dynamic behavior under the parametric perturbation of dissipative soliton equation.estimate of fractal dimension of attractor.

Gas-in-Place(GIP) Variation and Main Controlling Factors for the Deep Wufeng-Longmaxi Shales in the Luzhou Area of the Southern Sichuan Basin,China

The Wufeng-Longmaxi Formation shales with burial depths > 3 500 m in the southern Sichuan Basin are believed to have large shale gas potentials.However,the reservoir properties and gasin-place(GIP) contents of these shales exhibit variations across different sublayers.In this study,a set of Wufeng-Longmaxi shales with burial depths of 4 000–4 200 m was derived from the Well Y101H2 in the Luzhou area,and the differences in geological and geochemical characteristics,porosity,water saturation and GIP content of various sublayer shales were investigated.The results indicate that the TOC content and effective porosity of the upper(LMX1-4) and lower(LMX1-3) sublayer shales of the first member of the Longmaxi Formation are better than those of the Wufeng Formation(WF) shales,which results in the LMX1-4 and LMX1-3 shales having higher GIP contents than the WF shales.The GIP contents of the LMX1-3 shales are higher than those of the LMX1-4 shales,and this is likely because the organic matter of the LMX1-3 shales had more aquatic organisms and was preserved in a stronger reductive environment,which leads to a stronger gas generation potential.In contrast to the middle-shallow LMX1-4 shales in the Sichuan Basin,the deep LMX1-4 shales in the Luzhou area have advantageous reservoir properties and GIP contents,and thus it is promising to synchronously exploit the deep LMX1-4 and LMX1-3 shales in some regions of the southern Sichuan Basin.

Synthesis and Opto-electronic Properties of a Red-Emitting Heteroleptic Platinum Complex Using Pyrazol-based Diketone Derivative as Ancillary Ligand

A red-emitting heteroleptic cyclometalated platinum（II） complex containing an ancillary ligand of pyra- zol-based diketone derivative was synthesized. Its optophysical and electroluminescent properties were studied. Compared to the reported （piq）Pt（acac） complex, this platinum（II） complex exhibited a blue-shifted UV absorption band at 300--450 nm, a low LUMO energy level and improved electroluminescent property. Using this platinum（II） complex as a single doping emitter and a blend of ploy（9,9-dioctylfluorene） and 2-tert-butylphenyl-5-phenyl- 1,3,4-oxadiazole as a host matrix, the fabricated polymer light-emitting devices displayed saturated red emission with a peak at 648 um and a shoulder at 601 nm. Furthermore, the emission quenching of the platinum（II） complex was significantly suppressed in these devices at high current density due to an introduction of the non-planar pyra- zol group into the ancillary ligand.

Synthesis, Photophysical and Electrochemical Properties of Amide-Linked Phthalocyanine-Fullerene Dyad

metry data. The free energy change for charge separation （AGcs） was estimated to be exothermic with --0.51 eV, which favored the formation of charge-separation state. The PET from ZnPc to C60 in ZnPc-C60 made the dyad exhibit stronger reverse saturable absorption performance compared with C60 and the control sample in the Z-scan experiments, which indicated the synergistic effect of two active moieties in the dyad.

Basic properties of a new Nd-doped laser crystal： Nd：GdNbO4

A Nd-doped GdNbO4 single crystals have been grown successfully using the Czochralski technique. The chemical etching method was employed to study the defects in the structural morphology of Nd：GdNbO4 crystal with phosphoric acid etchant. Mechanical proper- ties （such as hardness, yield strength, fracture toughness, and brittle index） of the as-grown crystal were system- atically estimated on the basis of the Vickers hardness test for the first time. The transmission spectrum of Nd： GdNbO4 was measured in the wavelength range of 320- 2400 nm at room temperature, and the absorption peaks were assigned. Results hold great significance for further research on Nd：GdNbO4.

Structural, Electronic and Optical Properties of Multifunctional Iridium（III） and Platinum（II） Metallophosphors for Organic Light-Emitting Diodes

An elaborated theoretical investigation on the optical and electronic properties of three fluorene-based plati- num（II） and iridium（III） cyclometalated complexes Pt-a, Ir-a and lr-b is reported. The geometric and electronic structures of the complexes in the ground state are studied with density functional theory and Hartree Fock ap- proaches, while the lowest triplet excited states are optimized by singles configuration interaction （CIS） methods. At the time-dependent density functional theory （TD-DFT） level, molecular absorption and emission properties were calculated on the basis of optimized ground- and excited-state geometries, respectively. The computational results show that the appearance of triphenylamino （TPA） moiety at the 9-position of fluorene ring favors the hole-creation and leads to red-shifts of absorption and emission spectra. Moreover, Pt-a and Ir-b are nice hole-transporting materials whereas Ir-a has good charge-transfer balance, which render them useful for the realiza- tion of efficient OLEDs （Organic Light-Emitting Diodes）.

EQUIVALENCE BETWEEN NONNEGATIVE SOLUTIONS TO PARTIAL SPARSE AND WEIGHTED l_1-NORM MINIMIZATIONS

Based on the range space property （RSP）, the equivalent conditions between nonnegative solutions to the partial sparse and the corresponding weighted l1-norm minimization problem are studied in this paper. Different from other conditions based on the spark property, the mutual coherence, the null space property （NSP） and the restricted isometry property （RIP）, the RSP- based conditions are easier to be verified. Moreover, the proposed conditions guarantee not only the strong equivalence, but also the equivalence between the two problems. First, according to the foundation of the strict complemenrarity theorem of linear programming, a sufficient and necessary condition, satisfying the RSP of the sensing matrix and the full column rank property of the corresponding sub-matrix, is presented for the unique nonnegative solution to the weighted l1-norm minimization problem. Then, based on this condition, the equivalence conditions between the two problems are proposed. Finally, this paper shows that the matrix with the RSP of order k can guarantee the strong equivalence of the two problems.