Semiviscosity flow equation with variable parameters under superplastic tension conditions

Ａｓｅａｒｌｙａｓｉｎ1964,Ｂａｃｋｏｆｅｎｅｔａｌ.ｂｅｌｉｅｖｅｄｔｈａｔｕｎｄｅｒｓｕｐｅｒｐｌａｓｔｉｃｃｏｎｄｉｔｉｏｎｓｈａｒｄｌｙａｎｙｓｔｒａｉｎｈａｒｄｅｎｉｎｇｔａｋｅｓｐｌａｃｅｄｕｒｉｎｇｔｈｅｄｅｆｏｒｍａｔｉｏｎｏｆｍａｔｅｒｉａｌｂｕｔｔｈｅｒｅｉｓａｓｔｒｏｎｇｓｔｒａｉｎｒａｔｅｈａｒｄｅｎｉｎｇ[1].Ａｎｄｔｈｅｙａｌｓｏｅｓｔａｂｌｉｓｈｅｄｔｈｅｓｅｍｉｖｉｓｃｏｓｉｔｙｅｑｕａｔｉｏｎσ=ｋεｍ,(1)ｗｈｉｃｈｉｎｄｉｃａｔｅｓｔｈｅｒｅｌａｔｉｏｎｂｅｔｗｅ…     

K-bitonic sort

Ak-bitonic sort which generalizes the bitonic sort is proposed. The theorem of the bitonic sort, which merges two monotonic sequences into one order sequence, is extended into the theorem ofk-bitonic sort. Thek-bitonic sort merges (K (=2k or 2k−1) monotonic sequences into one order sequence in steps, where is an integer andk≥1. Thek-bitonic sort is the Batcher's bitonic sort whenk=1. Project supported by the National 863 Foundation of China (863-306-05-01-1) and the National Natural Science Foundation of China (Grant No. 69673037).     

Dynamic recrystallization behavior of 35CrMo structural steel

1　ＩＮＴＲＯＤＵＣＴＩＯＮＤｕｒｉｎｇｈｏｔｗｏｒｋｉｎｇ ,ｓｅｖｅｒａｌｍｅｔａｌｌｕｒｇｉｃａｌｐｈｅｎｏｍｅｎａｓｕｃｈａｓｗｏｒｋ ｈａｒｄｅｎｉｎｇ (ＷＨ ) ,ｄｙｎａｍｉｃｒｅｃｏｖｅｒｙ (ＤＲＶ) ,ａｎｄｄｙｎａｍｉｃｒｅ ｃｒｙｓｔａｌｌｉｚａｉｔｏｎ (ＤＲＸ )ｏｃｃｕｒｓｉｍｕｌｔａｎｅｏｕｓ ｌｙ[1 5 ] .Ｅｓｐｅｃｉａｌｌｙ ,ｔｈｅｏｃｃｕｒｒｅｎｃｅｏｆＤＲＸ ,ｃａｎｒｅｆｉｎｅｇｒａｉｎａｎｄｒｅｄｕｃｅｄｅｆｏｒｍａｔｉｏｎｒｅｓｉｓｔａｎｃｅｉｎｐｒａｃｔｉｃａｌｈｏｔ ｗ…     

Fine structure and interface structure of ion-bombardment nitrided layers

ＧｅｒａｒｄｉｎａｎｄＭｉｃｈｅｌｏｂｓｅｒｖｅｄｔｈｅｉｏｎｎｉｔｒｉｄｅｄｌａｙｅｒｏｆｐｕｒｅｉｒｏｎｗｉｔｈＴＥＭ[1].Ｔｈｅｒｅｓｕｌｔｓｓｈｏｗｅｄｔｈａｔｔｈｅｒｅａｒｅｏｎｌｙｔｗｉｎｓ,ｓｏｗｈｅｔｈｅｒｔｈｅｒｅａｒｅｄｉｓｌｏｃａｔｉｏｎｓａｎｄｗｈａｔｉｓｔｈｅｉｒｃｏｎｆｉｇｕｒａｔｉｏｎａｒｅｎｏｔｑｕｉｔｅｃｌｅａｒ.Ｔｈｅａｕｔｈｏｒｓｈａｖｅｆｏｕｎｄｔｈａｔｔｈｅｒｅａｒｅｖａｃａｎｃｉｅｓｉｎｉｏｎｎｉｔｒｉｄｅｄｌａｙｅｒｓ[2],ｂｕｔｔｈｅｐｒｏｏｆｏｆａｔｏ…     

Theoretical and metrical standardization of strain rate sensitivity index

Strain rate sensitivity index m is one of the vital mechanical parameters for determining material superplasticity. In this paper, the existing formulae for measuring m value are reviewed, and it is found that the m values can be classified into three classes mi under constant length, mv under constant velocity, and mp under constant load. The constraint equation of the generalized m value is established according to the tensile constitutive equation and the basis theory for plastic mechanics. Based on three typical deformation paths, the m value is redefined. Furthermore, from the formula of generalized m value, the formulae for measuring mi, mv and mp are theoretically deduced. The precise methods with numerical simulation are presented. The results prove that the m value is a non-constant and its dependence on (ε) changes with the deformation path. Under different deformation paths, the m values calculated from the same formula are different. Using different formulae, the m values under the same deformation path are also different. Therefore, deformation path and corresponding formula should be given during the measurement of the m value. Moreover, it is explained theoretically and experimentally that why the mv value under constant velocity is sometimes negative but the mp value under constant load is sometimes lager than 1. The aim of the analysis and measurement of the m value is to facilitate the study on the relationship between macroscopical mechanical laws and microscopic physical mechanisms during superplastic deformation.     

Isotope systematics and metallogenetic age of Zhuanghe gold deposit, Liaoning province, China

Based on the metallogenetic geology conditions, the H, O, C and S isotopic compositions were measured by MAT-251 mass spectrometer, and Pb isotope and Rb-Sr dating were carried with MAT-261 multi-acceptor mass spectrometer. The results show that the δ18O values of gold-bearing vein quartz from different levels are 1.19%-1.42%. The calculated δ18O values of ore fluids are 0.55%-0.78%, and δD values are from –8.64% to –6.66%. The calculated values of δ 34 SH2Sby the δ34Spy values in quartz veins display sulfur isotope compositions from -0.053% to 0.413%. Carbon isotope compositions of carbonates are from -0.612% to 0.140%. The mole ratios of 206Pb to 204Pb, 207Pb to 204Pb and 208Pb to 204Pb in auriferous quartz vein are 16.987-17.545, 15.342-15.623, and 38.254-38.744, respectively. The age of the Zhuanghe gold deposit determined by Rb-Sr isochron of the fluid inclusions in quartzes is (143.0±5.8) Ma. These isotopic data suggest that the metallogenetic fluids are generated from magmatic hydrotherm and the origin of ore-forming matters is related to the deep-derived magmatic activities. Meanwhile, the metallogenetic epoch of the Zhuanghe gold deposit is in Yanshanian period.     

Existence of positive solutions in a delay logistic difference equation

The author studied the existence of positive solutions of the delay logistic difference equationΔyn=pnyn(1-yτ(n)), n=0,1,2,....where {pn} is a sequence of positive real numbers, {τ(n)} is a nondecreasing sequence of integers, τ(n)＜n and limn→∞τ(n)=∞. A sufficient condition for the existence of positive solutions of the equation was given.     

Magnetohydrodynamic study of electromagnetic separation of nonmetallic inclusions from aluminum melt

Magnetohydrodynamic flow around the nonmetallic inclusions in aluminum melt and the force exerted on the inclusions were explored by dimensional analysis and numerical calcula-tions. Dimensional analysis shows that the invariant characterizes the force exertedon the inclusions and the flow intensity of the melt. The physical significance of A is represented as a modified particle Reynolds number that reflects the effects of electromagnetic force. The fluid flow around the particle becomes unstable when A>2×103. It is shown that the neglect of the in-ertial terms has little effect on the force exerted on the inclusions in the range of A≤1×106. However, the analytical solution of the maximum velocity inside the melt does not apply due to the appearance of turbulent flow in the case of A>2?103.     

Optimal decay rate of vibrating beam equations controlled by combined boundary feedback forces

The optimal decay rate problem is considered for boundary control system modeling by a flexible structure consisting of a Eular-Bernoulli beam. Controls are a bending moment in proportion to angular velocity and a shear force in proportion to velocity. A sensitivity asymptotic analysis of the system' s eigenvalues and eigenfunctions is set up. It is proved that, for every 00, y(0)=Y_0, Y_0=(Y_1,Y_2)~T ∈V×H form a Riesz basis of V×H, and the optimal exponential decay rate can be obtained from the spectrum of the system.     

Thermodynamic properties of aqueous aluminate ion, AI(OH) 4? (aq)

The heat effect of the reactions between metallic aluminum and NaOH(aq) solution of various concentrations were calorimetrically determined. Combining with the thermodynamic properties of related substances led to the thermodynamic properties of Al(OH) ₄ ⁻ (aq) as following: Project supported by the National Doctorate Program Fund of China Synopsis of the first author Chen Qiyuan, professor, born in 1948, major research field is metallurgical physicochemistry (metallurgical thermodynamics and kinetics)     

The dynamics of acid treatment in the preparation of porous glass

1　IntroductionPorousglasswithahighsilicacontentisoneofnewfunctionalmaterials ,andithasaprosperousprospectinapplications .Inrecentyears ,porousglasswaspaidatten tionbyinternationalmaterialspecialistsandscholars[1 4] .However,thephase separationglasseswerefragileandbreakableduringtheacidtreatment,limitingtheapplica tionsofporousglass .Herein ,inthispapertheeffectsoftreatmenttime ,temperatureandacidconcentrationinthepreparationofporousglasswithhighsilicawereemphas izedonandthedynamicsandmechanis…     

Hydrogen-induced cracking and its anisotropy of a PZT ferroelectric ceramics

The physical properties of ceramics will be degraded by charging and restored by outgassing at 650℃[1,2]. This means that atomic hydrogen can enter into ceramics through diffusion during charging. The electrical properties of the integrated PZT capacitors will be deteriorated by an-nealing in low pressure hydrogen, and the inter-layer dielectric or top electrode adhesion will be destroyed in high pressure hydrogen[3]. For an aluminum ceramics, hydrogen-induced cracking (HIC) or delayed fail…     

Synthesis and photoluminescence property of red phosphors LiEu1?xYx(WO4)0.5(MoO4)1.5 for white LED

A series of novel red phosphors LiEu_1−x Y _x (WO₄)_0.5(MoO₄)_1.5 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8) were synthesized by conventional solid state reaction method with the starting materials: WO₃, MoO₃, Eu₂O₃, Li₂CO₃ and Y₂O₃. The spectrum and the crystal structure of the phosphors were characterized by F-4500 and XRD respectively. Meanwhile the effects of flux and Y³⁺ concentration on the crystal structure and luminescent properties of the phosphors were investigated. The results showed that the optimal content of flux () was 1 wt% and the optimal doping concentration of Y³⁺ was 0.5 mol. The emission spectrum showed the most intense peak was located at 615 nm, which corresponds to the ⁵ D ₀→⁷ F ₂ transition of Eu³⁺ and that Eu³⁺ occupied the lattice site of noncentrosymmetric environment in the scheelite phases. The excitation spectrum displayed that these phosphors could be effectively excited by ultraviolet (UV) (396 nm) and blue (466 nm) light, nicely in correspondence with the widely applied output wavelengths of ultraviolet or blue LED chips. The influence of flux on the luminescent properties of LiEu_0.5Y_0.5(WO₄)_0.5(MoO₄)_1.5 phosphor was analyzed. The XRD spectra indicated that the flux could help to crystallize the phosphor, and no other phases were formed except the tetragonal. When adding flux, the relative intensity of LiEu_0.5Y_0.5(WO₄)_0.5(MoO₄)_1.5 became much stronger and the average particle size of the phosphor decreased. Supported by the Key Programs for Science and Technology Development of Hubei Province (Grant No. 2005AA105A05)     

Preparation of LiFePO4 for lithium ion battery using Fe2P2O7 as precursor

In order to obtain a new precursor for LiFePO4, Fe2P2O7 with high purity was prepared through solid phase reaction at 650 ℃ using starting materials of FeC2O4 and NH4H2PO4 in an argon atmosphere. Using the as-prepared Fe2P2O7, Li2CO3 and glucose as raw materials, pure LiFePO4 and LiFePO4/C composite materials were respectively synthesized by solid state reaction at 700 ℃ in an argon atmosphere. X-ray diffractometry and scanning electron microscopy（SEM） were employed to characterize the as-prepared Fe2P2O7, LiFePO4 and LiFePO4/C. The as-prepared Fe2P2O7 crystallizes in the Cl space group and belongs to β-Fe2P2O7 for crystal phase. The particle size distribution of Fe2P2O7 observed by SEM is 0.4-3.0 μm. During the Li^＋ ion chemical intercalation, radical P2O7^4- is disrupted into two PO4^3- ions in the presence of O^2-, thus providing a feasible technique to dispose this poor dissolvable pyrophosphate. LiFePO4/C composite exhibits initial charge and discharge capacities of 154 and 132 mA·h/g, respectively.     

Synthesis and characterization of triclinic structural LiVPO4F as possible 4.2 V cathode materials for lithium ion batteries

A potential 4.2 V cathode material LiVPO4F for lithium batteries was prepared by two-step reaction method based on a carbon-thermal reduction （CTR） process. Firstly, V2O5, NH4H2PO4 and acetylene black are reacted under an Ar atmosphere to yield VPO4. The transition-metal reduction is facilitated by the CTR based on C→CO transition. These CTR conditions favor stabilization of the vanadium as V^3＋ as well as leaving residual carbon, which is useful in the subsequent electrode processing. Secondly, VPO4 reacts with ElF to yield LiVPO4F product. The property of the LiVPO4F was investigated by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurement. XRD studies show that LiVPO4F synthesized has triclinic structure（space group p I ）, isostructural with the naturally occurring mineral tavorite, EiFePO4-OH. SEM image exhibits that the particle size is about 2μm together with homogenous distribution. Electrochemical test shows that the initial discharge capacity of LiVPO4F powder is 119 mA·h/g at the rate of 0.2C with an average discharge voltage of 4.2V （vs Ei/Li^＋）, and the capacity retains 89 mA·h/g after 30 cycles.     

Dielectric Properties of Ag（Nb1-xTax）O3 and Bi2O3 Doped Ag（Nb1-xTax）O3 Ceramics

Dielectric properties of Ag（Nb1-xTa）O3 and Bi2O3 doped Ag（Nb1-xTax）O3 solid solutions were investigated. The results show that with the increase of Ta content （x）, the sintering temperature increased, and the dielectric loss （tanδ） and the temperature coefficient （αc） decreased. Ag（Nb1-xa）O3 （x=0.4） ceramics sintered at 1 100℃ had the highest permittivity （516.8） and a lower tanδ （0.0021） at 1 MHz, and its temperature coefficient was about 191 ppm/℃. The sintering temperature of Ag（Nb1-xTa）O3 （x=0.4） was lowered by the addition of Bi2O3, and its dielectric properties were improved. Ag（Nb0.6Ta0.4）O3 ceramics with 2.5 wt% Bi203 addition presented the optimum dielectric properties （ε=566, tanδ= 0.0007 and αc≈0ppm/℃） （1 MHz）,     

Critical driving force for martensitic transformation fcc (γ)→hcp(ε) in Fe-Mn-Si shape memory alloys

By the application of Chou's new geometry model and the available data from binary Fe-Mn, Fe-Si and Mn-Si systems, as well as SGTE DATA for lattice stability parameters of three elements from Dinsdale, the Gibbs free energy as a function of temperature of the fcc(γ) and hep(ε) phases in the Fe-Mn-Si system is reevaluated. The relationship between the Neel temperature of the γ phase and concentration of constituents in mole fraction, is fitted and verified by the experimental results. The critical driving force for the martensitic transformation fcc (γ)→ hep (ε), △ G_C~(γ→ε), defined as the free energy difference between γ and ε phases at M_s of various alloys can also be obtained with a known M_s. It is found that the driving force varies with the composition of alloys, e. g. △ G_C~(γ→ε) = - 100.99 J/mol in Fe-27.0Mn-6.0Si and △ G_C~(γ→ε) = - 122.11 J/mol in Fe-26.9Mn-3.37Si. The compositional dependence of critical driving force accorded with the expression formulated by Hsu of the     

Effect of barium oxide on the formation and coexistence of tricalcium silicate and calcium sulphoaluminate

Formation and coexistence of tricalcium silicate (C₃S) and calcium sulphoaluminate (C₄A₃ ) minerals in Portland cement clinker containing calcium sulphoaluminate were investigated. The f-CaO content, mineral composite and formation of mineral in the clinker were analyzed respectively by chemical analysis, differential scanning calorimetry(DSC) and X-ray diffraction. The results show that, adding a suitable amount of BaO can improve the burnability of raw meal and promote the f-CaO absorption. Tricalcium silicate and calcium sulphoaluminate minerals can form and coexist in clinkers at 1 234–1 317 °C by the addition of BaO to the raw meal. A suitable amount of BaO expanded the coexistence temperature of two minerals by 58 °. Funded by the National Basic Research Program of China (No. 2009CB623100), National Eleven Five-Year Scientific and Technical Support Plans (No. 2006BAF02A24), the Natural Science Fund for Colleges and Universities in Jiangsu Province(No. 08KJB430006), the Open Fund for the Key Laboratory of Inorganical and Composite Materials in Jiangsu Province(No. wjjqfhxc1200801) and the Innovation Fund of Doctoral Dissertation of Nanjing University of Technology (No. BSCX200705)     

Microstructure and microwave dielectric properties of CaO-B2O3-SiO2 glass ceramics with various B2O3 contents

The effects of B2O3 addition on both the sintering behavior and microwave dielectric properties of CaO-B2O3-SiO2 (CBS) glass ceramics were investigated by Fourier transform infrared spectroscopy (FTIR),X-ray diffractometry (XRD) and scanning electron microscopy (SEM).The results show that the increasing amount of B2O3 causes the increase of the contents of [BO3],[BO4] and [SiO4],which deduces the increase of CaB2O4 and α-SiO2 and the decrease of CaSiO3 correspondingly.No new phase is observed throughout the...     

Thermal expansion properties and hygroscopicity of Y2?xSmxW3O12 (x = 0.0–0.4) compounds

A novel class of solid solutions of Y_2−x Sm _x W₃O₁₂ (x = 0.0−0.4) were synthesized and studied by means of powder X-ray diffraction. All samples crystallize in an orthorhombic space group Pnca. The lattice parameters a, b and c of Y_2−x Sm _x W₃O₁₂ increase with increasing Sm content. Since the compounds of this series hydrate at room temperature, thermogravimetric (TG) analysis was carried out. The result shows that the compound stores less water with increasing Sm content. The thermal expansion properties of Y_2−x Sm _x W₃O₁₂ (x = 0.1, 0.3 and 0.4) were investigated with high temperature X-ray diffraction. Negative thermal expansion coefficient α _I becomes less negative from −6.644×10⁻⁶ to −6.211×10⁻⁶°C⁻¹ when x changes from 0.1 to 0.4.