Existence of asymptotically almost periodic solutions and stability properties for functional difference equations

For functional difference equations with unbounded delay,we characterized the existence of totally stable and asymptotically almost periodic solution by using stability properties of a bounded solution in a certain limiting equation.

Synthesis,Crystal Structure and Fluorescent and Thermal Stability Properties of the Zinc(Ⅱ) Complex [Zn(C_(15)H_(11)O_3)_2(C_(12)H_8N_2)_2]·5H_2O

A new complex has been synthesized with o-methylbenzoyl-benzoic acid（HL） and 1,10-phenanthroline（phen） in the mixture of water and ethanol. It crystallizes in monoclinic, space group C2/c with a = 13.6328（18）, b = 17.7876（18）, c = 19.998（2）, β = 104.720（4）o, C54H48N4O11Zn, Mr = 994.33, V = 4690.2（9）3, Dc = 1.408 g/cm3, Z = 4, F（000） = 2072, μ（MoKα） = 0.59 mm-1, R = 0.0736 and wR = 0.2029. The crystal structure shows that the zinc ions are coordinated with two oxygen atoms from two HL molecules and four nitrogen atoms from two phen molecules, forming distorted octahedral coordination geometry. The fluorescent and thermal stability properties of the complex are studied. The result shows that it has one fluorescent emission band at around 412 nm. In addition, the complex is stable under 210 ℃.

Crystal Structure,Fluorescence and Thermal Stability Properties of a Dinuclear Copper(Ⅱ) Complex[Cu_2(L)_2(phen)_2]-5H_2O(H_2L = Bicycle[2.2.1]hept-2-en-5,6-dicarboxylic acid)

A new dinuclear copper（II） complex [Cu2（L）2（phen）2]·5H2O （1） with bicycle[2.2.1 ]hept- 2-en-5, 6-dicarboxylic acid （H2L） and 1,10-phenanthroline （phen） as ligands has been synthesized in the mixed solvents of ethanol and water. It crystallizes in the monoclinic space group P21/c, with a = 17.925（4）, b = 19.908（4）, c = 11.235（2） A, β = 97.65（3）°, V= 3973.4（14） A3, Dc = 1.552 g/cm^3, Z = 8, F（000） = 1910, the final GOOF = 1.056, R= 0.0519 and wR= 0.1293. The crystal structure shows that the whole molecule consists of two independent dinuclear units, in which two copper ions are bridged by twoμ2-η1 ：η0-3-carboxylate groups of L^2- anions. The fluorescence and thermal stability properties of 1 were studied. The results show that 1 has an intense fluorescent emission at around 381 rim. The TG analysis shows that I is stable below 143 ℃.

Crystal Structure and Thermal Stability Properties of a New 1D Chain Cu(Ⅱ)Coordination Polymer with2,3-Pyridinedicarboxylic Acid as the Ligand

A new 1D chain copper coordination polymer [CuE（H2L）2（C10HsN2）（HEO）2]n＇3n（H20） with 2,3-pyridinedi carboxylic acid （H2L） and 2,2＇-bipyridine （2,2＇-bipy） as ligands has been synthesized in the mixed ethanol and water solvents. Crystal data for this complex are as follows： monoclinic, space group P2Jc, a = 7.7713（7）, b = 27.478（3）, c = 13.2621（13）/1,, fl = 100.6940（10）, V= 2782.8（5） A3, Dc = 1.722 g/cm3, Z = 4, p = 1.61 mm-1, F（000） = 1472, the final R = 0.0363 and wR = 0.0933. In the crystal structure, the whole molecule consists of two cooper ions, two H2L, one 2,2＂-bipy molecule and six water molecules. Each central copper ion is coordinated with three oxygen atoms from two H2L and one water molecule, two nitrogen atoms from one 2,2＇-bipy molecule and two H2L, giving a distorted tetragonal pyramidal geometry. Thermal stability properties of the complex were investigated.

Crystal Structure, Spectroscopic Characterization, and Electrochemical and Thermal Stability Properties of a Dinuclear Nickel(Ⅱ) Complex

A new nickel（Ⅱ） complex Ni2（L）2（2,2＇-bipy）2·5.5H2O with methy-bicycle[2.2.1]hept-5-ene-2,3-dicarboxylic acid（H2L） and 2,2？-bipyridine（2,2＇-bipy） as ligands has been synthesized in the mixed solvent DMF and water（v：v = 5：2）. It crystallizes in the triclinic space group P1 with a = 10.414（2）, b = 12.884（3）, c = 16.176（4） A, α = 70.715（5）, β = 80.599（5）, γ = 77.383（6）°, V = 1989.4（8） A^3, Dc = 1.531 g/cm^3, Z = 2, F（000） = 958, GOOF = 1.028, the final R = 0.0808 and w R = 0.2036. The crystal structure shows that the whole molecule consists of two independent dinuclear units, in which two nickel ions are bridged by two μ2-η1：η0 3-carboxylate groups of L2- anions. The coordination environment of Ni（Ⅱ） ion is Ni N2O3, giving a distorted square pyramidal geometry. The thermal stability and electrochemical properties of the complex were investigated.

Synthesis, Crystal Structure and Thermal Stability Properties of the Supramolecular Complex [Co(phen)_3][(C_6H_5)_2C(OH)COO]_2·7H_2O

One new cobalt complex [Co（phen）3][（C6Hs）2C（OH）COO]2·7H2O with benzeneacetic acid （BAA）, 1,10-phenanthroline and cobaltous perchlorate has been synthesized by means of solvent method. It crystallizes in the triclinic system, space group P^-1, with a = 1.14181（13）, b = 1.64417（18）, c = 1.65342（18） nm, α = 74.2830（10）, β= 84.4490（10）, γ = 74.9430（10）°, V = 2.8842（6） nm^3, Dc = 1.359 g/cm^3, Z = 2, F（000） = 1234, R = 0.0621 and wR = 0.1673. The crystal structure shows that the cobalt ion is coordinated with six nitrogen atoms from three 1,10-phenanthroline molecules, giving a distorted octahedral coordination geometry. There are a lot of hydrogen bonds in the complex, from which a two-dimensional network is constructed. The result of TG analysis shows that the title complex is stable below 130.0 ℃.

Synthesis,Structure,Luminescence and Thermal Stability Properties of a New(3,4)-Connected 2D Zn Coordination Polymer

A new zinc coordination polymer{[Zn2(ttmb)2(dca)4(H2O)].H2O}n(1.H2O)was synthesized by the reaction of 1,3,5-tris(1,2,4-triazol-1-ylmethyl)benzene(ttmb),Zn(Ⅱ)salt and sodium dicyanamide(Na(dca)).The structure of the title compound was determined by single-crystal X-ray diffraction,elemental analyses and IR spectra.1 exhibits a(3,4)-connected 2D double-layer network with the point symbol of{63}{(66}.The solid-state luminescence shows a strong emission band at 485 nm upon excitation at 384 nm.The thermal stability properties were also studied.

Synthesis, Crystal Structure, Fluorescence, Thermal Stability and Magnetic Properties of the Dinuclear Manganese(Ⅱ) Complex [Mn_2(L)_2(2,2'-bipy)_2(H_2O)_5]_2·3H_2O

A new dinuclear manganese complex [Mn2（L）2（2,2＇-bipy）2（H2O）512·3H2O has been synthesized with MnSO4·H2O, 2,2＇-bibenzoic acid （H2L） and 2,2＇-bipyridine（2,2＇-bipy） in the mixed solvent ethanol and water. It crystallizes in monoclinic, space group Pi with a = 9.9944（10）, b = 21.939（2）, c = 25.628（3） A, a = 108.429（3）, β = 100.613（4）, 7 = 102.821（3）°, V = 4997.9（9） A3, Dc= 1.355 g/cm^3, Z = 2, F（000） = 2108, GOOF = 1.074, the R= 0.0626 and wR= 0.1531. The structure of the complex contains two [Mn2（L）2（2,2＇-bipy）2] units, ten coordinated H2O molecules and three uncoordinated H2O molecules. The fluorescence, thermal stability and magnetic properties of the complex were investigated.

Hydrothermal Synthesis, Crystal Structure, Thermal Stability and Magnetic Properties of a Dinuclear Copper(Ⅱ) Complex

A new dinuclear copper（Ⅱ） complex [Cu（CH3COO）（C7H5N4）（H2O）]2·3.5H2 O has been hydrothermally synthesized with copper acetate, o-acetamidobenzoic acid and 3-（pyridin-2-yl）-1,2,4-triazole. It crystallizes in the monoclinic space group P21/c, with a = 12.0188（7）, b = 13.7993（8）, c = 8.7488（5） A, β = 101.7350（10）o, V = 1420.67（14） A3, D3 c = 1.568 g/cm, Z = 1, F（000） = 690, the final GOOF = 1.145, R = 0.0437, and w R = 0.1097. The crystal structure shows that the whole molecule consists of two copper ions bridged by two μ2-η1：η0 3-（pyridin-2-yl）-1,2,4-triazole anions. The coordination environment of Cu（Ⅱ） ion is Cu O2N3, giving a distorted square pyramidal geometry. The thermal stability and magnetic properties of the complex were investigated.

Effects of terbium sulfide addition on magnetic properties,microstructure and thermal stability of sintered Nd-Fe--B magnets

To increase coercivity and thermal stability of sintered Nd–Fe–B magnets for high-temperature applications, a novel terbium sulfide powder is added into（Pr（0.25）Nd（0.75））（30.6）Cu（0.15）Fe（bal）B1（wt.%） basic magnets. The effects of the addition of terbium sulfide on magnetic properties, microstructure, and thermal stability of sintered Nd–Fe–B magnets are investigated.The experimental results show that by adding 3 wt.% Tb2S3, the coercivity of the magnet is remarkably increased by about 54% without a considerable reduction in remanence and maximum energy product. By means of the electron probe microanalyzer（EPMA） technology, it is observed that Tb is mainly present in the outer region of 2：14：1 matrix grains and forms a well-developed Tb-shell phase, resulting in enhancement of HA, which accounts for the coercivity enhancement.Moreover, compared with Tb2S3-free magnets, the reversible temperature coefficients of remanence（α） and coercivity（β） and the irreversible flux loss of magnetic flow（hirr） values of Tb2S3-added magnets are improved, indicating that the thermal stability of the magnets is also effectively improved.

Stability and Electronic Properties of Hydrogenated Zigzag Carbon Nanotube Focused on Stone-Wales Defect

We present a first-principles study of the chemisorption of hydrogen on a Stone-Wales （SW） defective carbon nanotube （10,0）. The investigated configurations include four configurations covering single defects and double defects. One hydrogen dimer adsorption is energetically favored on bonds shared by carbon heptagon-heptagon for configurations with the defect parallel to the tube axis compared with the carbon pentagon-hexagon sites for ones with a slanted defect. This different behavior is also demonstrated for hydrogen dimer chain adsorption, the favored site for the former ones is through the defect, which is the nearest neighbor site to defect for the latter ones. It is found that the energy band gaps of hydrogenated configurations may be enlarged or decreased by altering the adsorption site or defect position. The semiconductor-to-metal transition may occur for configurations with the defect or defects parallel to the tube axis due to low electronic localization. Our results highlight the interest of the interaction of multi-factor system by providing a detailed bond and position picture of a hydrogenated defective carbon nanotube （10,0）.

Magnetic Properties and Thermal Stability of Pr_(1-x)La_xCo_(5-y)Alloys

Pr1-xLaxCo5-y (x=0, 0.15. 0.25, 0.35,1.0, y=0.5, 0.7, 0.9, 1.0) alloys were investigated. The effect of the variation of x and y on magnetic properties and thermal stability of the alloys were studied. The magnetic properties for the Pr0.85La0.15Co4.3 and Pr0.75La0.25Co4.1 magnets are iHc=368 kA/m, Br=0.91 T, (BH)max=145.6 kJ/m3, αBr=-0.03%/℃ and iHc=568 kA/m,Br=0.8 T, (BH)max=127.2 kJ/m3,αBr,=-0.06%/℃, respectively The phase structures of as-cast alloys and magnets were investigated

Structural Stability and Electronic Properties of the I41/amd Vanadium Dioxide

By using LDA＋U approach based on the density functional theory, the structural stability of I41/amd VO2 is investigated. According to the phonon dispersion and stability criteria, the I41/amd is suggested to be another possible and stable structure for the VO2. Lattice parameters of the I41/amd VO2 are determined by geometry optimization. The energy band structure shows that the I41/amd VO2 should be a metal. Furthermore, the upper valence band has dominant 2p-orbital characters, but the lower conduction band shows distinctive 3d-orbital characters. Obvious hybridization between the O-2p and V-3d orbitals is observed.

Synthesis, Crystal Structure and Thermal Stability of a New Binuclear Cu(Ⅱ) Complex with 2-Benzoylbenzoic Acid as the Ligand

A new complex Cu2（o-C6H5COC6H5COO）4（C10H8N2）2（H2O）2 with 2-benzoylben- zoic acid and 2,2′-bipyridine as ligands has been synthesized in mixed methanol and water solvent. Crystal data are as follows： monoclinic, space group Co, a = 14.0133（14）, b = 16.0409（16）, c = 30.372（3） A, β = 100.8950（10）°, V = 6704.1（12） A3, Dc = 1.364 g/cm3, Z = 8,μ（MoKa） = 0.704 mml, F（000） = 2840, the final R= 0.0552 and wR = 0.1431. In the crystal structure, the whole molecule consists of two copper ions, four 2-benzoylbenzoic acid molecules, two 2,2′-bipyridine molecules and two water molecules. Each central copper ion is coordinated with two nitrogen atoms from one 2,2′-bipyridine molecule and three oxygen atoms from two 2-benzoylbenzoic acids and one water molecule, respectively, giving a distorted tetragonal pyramidal geometry. Thermal stability properties of the complex were investigated.

Chemical modification of barite for improving the performance of weighting materials for water-based drilling fluids

With increasing drilling depth and large dosage of weighting materials,drilling fluids with high solid content are characterized by poor stability,high viscosity,large water loss,and thick mud cake,easier leading to reservoir damage and wellbore instability.In this paper,micronized barite(MB)was modified(mMB)by grafting with hydrophilic polymer onto the surface through the free radical polymerization to displace conventional API barite partly.The suspension stability of water-based drilling fluids(WBDFs)weighted with API barite:mMB=2:1 in 600 g was significantly enhanced compared with that with API barite/WBDFs,exhibiting the static sag factor within 0.54 and the whole stability index of 2.The viscosity and yield point reached the minimum,with a reduction of more than 40%compared with API barite only at the same density.Through multi-stage filling and dense accumulation of weighting materials and clays,filtration loss was decreased,mud cake quality was improved,and simultaneously it had great reservoir protection performance,and the permeability recovery rate reached 87%.In addition,it also effectively improved the lubricity of WBDFs.The sticking coefficient of mud cake was reduced by 53.4%,and the friction coefficient was 0.2603.Therefore,mMB can serve as a versatile additive to control the density,rheology,filtration,and stability of WBDFs weighted with API barite,thus regulating comprehensive performance and achieving reservoir protection capacity.This work opened up a new path for the productive drilling of extremely deep and intricate wells by providing an efficient method for managing the performance of high-density WBDFs.

Determination and stability analysis of ultimate open-pit slope under geomechanical uncertainty

In open-pit mines,pit slope as one of the important parameters affects the mine economy and total minable reserve,and it is also affected by different uncertainties which arising from many sources.One of the most critical sources of uncertainty effects on the pit slope design is rock mass geomechanical properties.By comparing the probability of failure resulted from deterministic procedure and probabilistic one,this paper investigated the effects of aforesaid uncertainties on open-pit slope stability in metal mines.In this way,to reduce the effect of variance,it implemented Latin Hypercube Sampling(LHS)technique.Furthermore,a hypothesis test was exerted to compare the effects on two cases in Middle East.Subsequently,the investigation approved high influence of geomechanical uncertainties on overall pit steepness and stability in both iron and copper mines,though on the first case the effects were just over.

A comparative investigation of the properties of coal-water slurries prepared from Australia and Shenhua coals

Two coal samples of similar rank were chosen from Australia and China to investigate the differences in Coal-Water Slurry （CWS） made from them. The effect of ash content and particle size gradation on these properties was also studied. Different grinding times were used when grinding the two coals and particle size analysis of these ground coals was used to select samples with a ＂double-peak＂ particle size distri- bution. All the ＂double-peak＂ samples were used to prepare a CWS. The concentration, viscosity, fluidity, and stability of each CWS were measured. The results show that the properties ofa CWS prepared from a coal sample with a ＂double-peak＂ size distribution are better than those CWS prepared from samples with a mono-modal particle distribution. The ash content of Australian coal is 21.72g higher than the ash content of Shenhua coal. The highest coal concentration in slurry from the Australia coal is 11.01% higher than in CWS from the Shenhua coat. The fluidity and stability of the CWS prepared from the Australian coal are both better than the fluidity and stability of slurry prepared from Shenhua coal. High ash content in the Australian coal imnroves the nulning results of a CWS made from it.

A High-Temperature β-Phase NaMnO2 Stabilized by Cu Doping and Its Na Storage Properties

The high-temperature β-phase NaMnO2 is a promising material for Na-ion batteries（NIBs） due to its high capacity and abundant resources. However, the synthesis of phase-pure -NaMnO2 is burdensome and costineffective because it needs to be sintered under oxygen atmosphere at high temperature and followed by a quenching procedure. Here we first report that the pure β phase can be stabilized by Cu-doping and easily synthesized by replacing a proportion of Mn with Cu via a simplified process including sintering in air and cooling to room temperature naturally. Based on the first-principle calculations, the band gap decreases from 0.7 eV to 0.3 eV, which indicates that the electronic conductivity can be improved by Cu-doping. The designed -NaCu（0.1）Mn（0.9）O2 is applied as cathode in NIBs, exhibiting an energy density of 419 Wh/kg and better performance in terms of rate capability and cycling stability than those in the undoped case.

Effect of Ga_2O_3 on Structure and Properties of Calcium Aluminate Glasses

The effect of Ga_2O_3 on the structure and properties of calcium aluminate glasses fabricated by vacuum melting process was investigated by Raman spectrum, differential scanning calorimeter（DSC）, and infrared spectrum methods. The results show that calcium aluminate glass network only consists of [AlO_4] tetrahedral units. With the gradual addition of Ga_2O_3, the quantity of [GaO_4] tetrahedral units increases. Substitution of Ga_2O_3 for Al_2O_3 results in a decrease in Tg, Tx, and Tp, and an increase in the thermal stable index ΔT. Similarly, the absorption band around 3.0 μm obviously reduces and the transparency in 4.0-6.0 μm rapidly increases with increasing Ga_2O_3 content. However, the chemical stability of calcium aluminate glasses decreases if Ga_2O_3 is introduced due to the increasing of [GaO_4] units in the glass network.

Syntheses, Structure and Properties of a Strontium(Ⅱ) Complex with 5-Sulfoisophthalic Acid Monosodium

A new Sr（Ⅱ） complex, [Sr（Hsip）（H2O）] （1, NaH2sip = 5-sulfoisophthalic acid monosodium）, has been synthesized by solvothermal reaction of SrCO3 and NaH2sip at 120 ℃, and characterized by single-crystal X-ray diffraction studies, elemental analysis and FT-IR. Single- crystal X-ray diffraction reveals that compound 1 has a 3D architecture, and there is only one crystallographically independent Sr（Ⅱ） ion in 1. The coordination geometry of Sr（Ⅱ） is a distorted tetragonai anti-prism. The whole Hsip2- ligand performs aμ6-coordination model. In the solid state, complex 1 shows luminescence with the maximum emission intensity at 417 nm upon excitation at 320 nm. Thermal stability of complex 1 was also investigated.