Mg-5Al-0.8Ca-0.2La-xSr合金的显微组织及高温力学性能

采用真空熔化、精炼和无氧化重力铸造工艺，制备了不同Sr含量的Mg-5Al-0．8Ca-0．2La镁合金试样。研究了Sr对该镁合金的显微组织、室温与150～200℃温度区间内力学性能的影响。结果表明：基体合金组织除含α-Mg相外，主要由骨骼状和条状的Al2Ca相、点状的Al11La3颗粒相以及少量的β-Mg17Al12相组成；Sr的加入显著细化了基体合金的显微组织，抑制β-Mg17Al12相的析出，并在晶界上析出Mg-Al-Sr三元耐热相，提高了合金的高温力学性能；随着Sr含量的增加，虽然合金的室温抗拉强度和伸长率呈下降趋势，但合金的高温抗拉强度（σb）和屈服强度（σ0．2）得到明显提高；当Sr含量在0．5％时，合金的综合力学性能最佳。

R_(m+n)Co_(5m+3n)B_(2n)的合成、晶体结构和磁性能

综述了作者测定的R-Co-B三元系R=Nd,Pr,600℃长时间退火和R=Sm,Gd,700℃长时间退火的等温截面相关系。应用结构组合概念,对于R_m+_nCo_(5m)+_(3n)B_(2n)化合物设计合成了m=2,n=1的R_3Co_(13)B_2(R=Nd,Pr,Sm,Gd,Dy,Ho,Er,Y)和m=2,n=3的R_5Co_(19)B_6(R=Pr,Nd)新型化合物。用X射线粉末衍射和Rietveld峰型拟合法测定并修正了它们的晶体结构以及化合物的易磁化方向,应用振动样品磁强计、提拉样品磁强计以及不同磁取向样品的M(H)-H曲线,测定了新化合物R_3C0_(13)B_2和R_5Co_(19)B_6的Curie温度T_c、饱和磁化强度M_8和各向异性场H_A。R_(m+n)Co_(5m)+3_(2n)在相同n的情况下,随m值的增加,化合物的T_c和M_s增大,在m相同的情况下,随n值的增加,H_A增大。并研究了Ni部分替代Nd_3Co_(13)B_2中的Co,对Nd_3Co_(13-x)Ni_xB_2化合物磁性的影响,Ni含量的增加,自旋转变温度T_(SR)单调的降低,并在x=3时室温下磁化方向为易轴,讨论了R_(m+n)Co_(5m)+_(3n)B_(2n)的晶体结构与磁性能的关系,探讨了作为永磁材料的可能的合成途径.

FEM simulation and experimental verification of temperature field and phase transformation in deep cryogenic treatment

Combining with the low temperature material properties and the boiling heat transfer coefficient of specimen immersed in the liquid nitrogen, a numerical model based on metallo-thermo-mechanical couple theory was established to reproduce the deep cryogenic treatment （DCT） process of a newly developed cold work die steel Cr8Mo2SiV （SDC99）. Moreover, an experimental setup for rapid temperature measurement was designed to validate the simulation results. The investigation suggests that the differences in temperature and cooling rate between the surface and core of specimen are very significant. However, it should be emphasized that the acute temperature and cooling rate changes during DCT are mainly concentrated on the specimen surface region about 1/3 of the sample thickness. Subjected to DCT, the retained austenite of quenched specimen continues to transform to martensite and finally its phase volume fraction reduces to 2.3%. The predicted results are coincident well with the experimental data, which demonstrates that the numerical model employed in this study can accurately capture the variation characteristics of temperature and microstructure fields during DCT and provide a theoretical guidance for making the reasonable DCT procedure.

Analysis and optimization of power spectrum on EBPSK modulation in throughput-efficient wireless system

In order to satisfy increasingly greater demand for the performance of communication systems, a throughput efficient wireless system based on the extended binary phase shift keying （EBPSK） modulation is presented. Simultaneously, corresponding analysis of power spectra is also given with a brief process. The optimal waveform is proposed without useful information loss, by removing linear spectra presenting periodic components. On this basis, the reasonable definition of bandwidth is discussed, which indicates that the EBPSK belongs to the category of the ultra narrow band （UNB） throughput-efficient communication. Meanwhile, the modulation parameters＇ effects on bandwidth, transmission rate and transmission performance are analyzed. Results illustrate the validity of theoretical analysis and spectrum optimization. Results also prove that this UNB system can obtain good bit error rate （BER） performance with high spectra efficiency.

Evolution of secondary phases and properties of 7B04 aluminum alloy during DC homogenization

The effects of the direct current （DC） on the evolutions of hardness and morphology of the secondary phases in 7B04 aluminum alloy homogenized at 380？465 ℃ for 2 h were investigated in detail by electric conductivity measurement, hardness test, X-ray diffraction analysis, field emission scanning electron microscopy and energy dispersive spectrometry. The results show that with increasing temperature from 380 to 465 ℃, the electric conductivity of normal homogenized sample decreases from 34.9%IACS to 28.7%IACS, the hardness increases from HV 96 to HV 146, and the area fraction of secondary phase reduces from 4.5% to 1.89%. While, DC homogenized sample has a higher hardness, a lower electric conductivity and a smaller area fraction of secondary phases at the same temperature. The DC enhances the homogenization process by promoting the diffusibility of the solute atoms and the mobility of vacancy.

Tuning mechanical properties for β(B2)-containing TiAl intermetallics

Based on the analyses of the microstructures and phase diagrams of the TiAl-based alloy, the relationship among the composition, structure and mechanical properties of the B2-containing y-TiAI alloys was reviewed. The refinement of microstructures and improvement of mechanical properties of TiA1 alloy through stabilization of the β/B2 phase were reviewed. The mechanism of the superplastic behavior of the B2-containing y-TiAI alloys was discussed. With a reasonable addition of β-stabilizer, metastable B2 phase can be maintained, which is favorable for fine-grained structure and better high-temperature deformation behaviors. The mechanical properties of the B2-containing TiAI alloy, including the deformability and elevated temperature properties, can also be improved with doping elements and subsequent hot-working processes. The above mentioned researches discuss a new way for developing TiAI alloys with comprehensive properties, including good deformability and creep resistance.

Phase field simulation for non-isothermal solidification of multicomponent alloys coupled with thermodynamics database

In order to quantitively model the real solidification process of industrial multicomponent alloys, a non-isothermal phase field model was studied for multicomponent alloy fully coupled with thermodynamic and diffusion mobility database, which can accurately predict the phase equilibrium, solute diffusion coefficients, specific heat capacity and latent heat release in the whole system. The results show that these parameters are not constants and their values depend on local concentration and temperature. Quantitative simulation of solidification in multicomponent alloys is almost impossible without such parameters available. In this model, the interfacial region is assumed to be a mixture of solid and liquid with the same chemical potentials, but with different composition. The anti-trapping current is also considered in the model. And this model was successfully applied to industrial A1-Cu-Mg alloy for the free equiaxed dendrite solidification process.

Preparation on Nanoemulsion of Pomegranate Peel Polyphenol

[Objective] The aim was to obtain the preparation technology of the pomegranate peel polyphenol nanoemulsion. [Method] The pomegranate peel polyphe- nol nanoemulsion was prepared by the titration methods and the pseudo ternary dia- gram. The effect of various elements on the formation of the nanoemulsion was stud- ied. [Results] The optimal prescription of the pomegranate peel polyphenol nanoemul- sion was 4.4%（w/w） of pomegranate peel polyphenol, 34.1%（w/w） of EL-40, 17.1%（w/w） of anhydrous ethanol, 5.7%（w/w） of IPM and 38.7%（w/w） of distilled water. [Conclusion] It is feasible to produce the pomegranate peel polyphenol nanoemulsion by the titration methods and the pseudo ternary diagram. It consists of pomegranate peel polyphe- nol, EL-40, anhydrous ethanol, IPM and distilled water. There is 4.4%（w/w） of the pomegranate peel polyphenol in the nanoemuJsion.

Comparative analysis of isothermal and non-isothermal solidification of binary alloys using phase-field model

Based on the entropy function, a two-dimensional phase field model of binary alloys was established. Meanwhile, an explicit difference method with uniform grid was adopted to solve the phase field and solute field controlled equations. And the alternating direction implicit(ADI) algorithm for solving temperature field controlled equation was also employed to avoid the restriction of time step. Some characteristics of the Ni-Cu alloy were captured in the process of non-isothermal solidification, and the comparative analysis of the isothermal and the non-isothermal solidification was investigated. The simulation results indicate that the non-isothermal model is favorable to simulate the real solidification process of binary alloys, and when the thermal diffusivity decreases, the non-isothermal phase-field model is gradually consistent with the isothermal phase-field model.

《元刊全相平话五种》中的处置式

《元刊全相平话五种》中的处置式有“以”字句、“将”字句和“把”字句三种,本文采用定量和定性的分析方法,对这三种句式做了全面静态的考察和描写,发现《元刊全相平话五种》中的处置式的结构形式复杂,这主要体现为:一,谓语部分比较复杂;二,动词后带宾语的用例很多;三,助动词和否定副词都位于介词“将”“把”之后、谓语动词之前;四,介词宾语和动词宾语(均为代词“之”)所指完全相同的用例在“将”字式和“把”字式中都有出现。

A new detector in EBPSK communication system

In order to raise the detection precision of the extended binary phase shift keying （EBPSK） receiver, a detector based on the improved particle swarm optimization algorithm （IMPSO） and the BP neural network is designed. First, the characteristics of EBPSK modulated signals and the special filtering mechanism of the impacting filter are demonstrated. Secondly, an improved particle swarm optimization algorithm based on the logistic chaos disturbance operator and the Cauchy mutation operator is proposed, and the EBPSK detector is designed by utilizing the IMPSO-BP neural network. Finally, the simulation of the EBPSK detector based on the MPSO-BP neural network is conducted and the result is compared with that of the adaptive threshold-based decision, the BP neural network, and the PSO-BP detector, respectively. Simulation results show that the detection performance of the EBPSK detector based on the IMPSO-BP neural network is better than those of the other three detectors.

Modulation classification of MPSK signals based on nonparametric Bayesian inference

A nonparametric Bayesian method is presented to classify the MPSK （M-ary phase shift keying） signals. The MPSK signals with unknown signal noise ratios （SNRs） are modeled as a Gaussian mixture model with unknown means and covariances in the constellation plane, and a clustering method is proposed to estimate the probability density of the MPSK signals. The method is based on the nonparametric Bayesian inference, which introduces the Dirichlet process as the prior probability of the mixture coefficient, and applies a normal inverse Wishart （NIW） distribution as the prior probability of the unknown mean and covariance. Then, according to the received signals, the parameters are adjusted by the Monte Carlo Markov chain （MCMC） random sampling algorithm. By iterations, the density estimation of the MPSK signals can be estimated. Simulation results show that the correct recognition ratio of 2/4/8PSK is greater than 95% under the condition that SNR 〉5 dB and 1 600 symbols are used in this method.

DUAL QUATERNION CURVE INTERPOLATION ALGORITHM FOR FORMATION SATELLITES

The traditional algorithms for formation flying satellites treat the satellite position and attitude sepa- rately. A novel algorithm combining satellite attitude with position is proposed. The principal satellite trajectory is obtained by dual quaternion interpolation, then the relative position and attitude of the deputy satellite are ob- tained by dual quaternion modeling on the principal satellite. Through above process, relative position and atti- tude are unified. Compared with the orbital parameter and the quaternion methods, the simulation result proves that the algorithm can unify position and attitude, and satisfy the precision requirement of formation flying satel- lites.

如何导入“小数加减法”新课

学生对什么是小数及小数的意义,刚刚有个初步的认识,在此基础上,如何导入小数加、减法很重要。小数加、减法的计算方法跟整数加、减法的计算方法实质上是相同的。都是单位相同才能相加减,并且相同数位对齐。相同数位对齐和小数点对齐是一致的。在讲六年制第八册第五单元小数加、减法时。

Probabilistic durability assessment approach of deteriorating RC bridges

A stochastic finite element computational methodology for probabilistic durability assessment of deteriorating reinforced concrete（RC） bridges by considering the time-and space-dependent variabilities is presented.First,finite element analysis with a smeared cracking approach is implemented.The time-dependent bond-slip relationship between steel and concrete,and the stress-strain relationship of corroded steel bars are considered.Secondly,a stochastic finite element-based computational framework for reliability assessment of deteriorating RC bridges is proposed.The spatial and temporal variability of several parameters affecting the reliability of RC bridges is considered.Based on the data reported by several researchers and from field investigations,the Monte Carlo simulation is used to account for the uncertainties in various parameters,including local and general corrosion in rebars,concrete cover depth,surface chloride concentration,chloride diffusion coefficient,and corrosion rate.Finally,the proposed probabilistic durability assessment approach and framework are applied to evaluate the time-dependent reliability of a girder of a RC bridge located on the Tianjin Binhai New Area in China.

亟盼制定结算规章制度

目前,在结算资金管理上存在的问题,特别是企业委托银行收款的问题,已到了随便毁约、任意拒付,无法无天的紊乱局面,实在令人气愤。兹以我站遭遇,寥举数例: 一、1985年2月4日,按双方协议发货,委托银行收取某县棉纺厂货款246,145.39元,该厂象做小菜生意,讨价还价,以每担“莫须有”理由削减牌价4元相挟,拖到4月17日方一厢情愿地付款240,663.31元。二、1985年4月22日,托收某厂货款一笔367,775.34元,该厂以“未付回扣”为由拒付,

Determination of Trace Elements in Potatoes by Flame Atomic Absorption Spectrometry

[Objective] This study aimed to analyze the contents of trace elements in potatoes from different production areas in Qinghai Province. [Method] By flame atomic absorption spectrometry （FAAS）, the contents of various trace elements in potatoes were determined. [Result] Potatoes contain abundant trace elements such as Cu, Zn, Fe, Mn, Ca, K and Mg. To be specific, the contents of Ca, K and Mg were relatively high. [Conclusion] By using FAAS, the relative standard deviation was 1.17%-2.75% and the recovery rate was 97%-99.5%, indicating accurate and reli-able results with high precision.

Thermodynamic optimization of Bi-Ni binary system

Based on the available experimental data,the Bi-Ni binary system was optimized thermodynamically by the CALPHAD method.The solution phases,including liquid,fcc_A1（Ni） and rhombohedral_A7（Bi）,were described as substitutional solution phases,of which the excess Gibbs energies were expressed with the Redlich-Kister polynomial.The intermetallic compound,BiNi,was modeled using three sublattices（Bi）（Ni,Va）（Ni,Va） considering its crystal structure（NiAs-type） and the compatibility of thermodynamic database in the multi-component systems,while Bi3Ni was treated as a stoichiometric compound.Finally,a set of self-consistent thermodynamic parameters formulating the Gibbs energies of various phases in this binary system were obtained.The calculated results are in reasonable agreement with the reported experimental data.

Thermodynamic assessment of Co-Cr-W ternary system

The Co-Cr-W ternary system was critically assessed using the CALPHAD technique.The solution phases including the liquid,γ-Co,ε-Co and α-Cr were described by a substitutional solution model.The σ,μ and R phases were described by three-sublattice models of（Co,W）8（Cr,W）4（Co,Cr,W）18,（Co,Cr,W）7W2（Co,Cr,W）4 and（Co,W）27（Cr,W）14（Co,Cr,W）12,respectively,in order to reproduce their homogeneity ranges.A self-consistent set of thermodynamic parameters for each phase was derived.The calculated isothermal sections at 1 000,1 200 and 1 350 ℃ are in good agreement with the experimental data.A eutectoid reaction of R μ＋γ-Co＋σ in this ternary system was predicted to occur at 1 022 ℃.

MULTIVARIATE ABSOLUTE DEGREE OF GREY INCIDENCE BASED ON DISTRIBUTION CHARACTERISTICS OF POINTS

The analysis result of absolute degree of grey incidence for multivariate time series is often inconsistent with the qualitative analysis. To overcome this shortage, a multivariate absolute degree of grey incidence based on distribution characteristics of points is proposed. Based on the geometric description of multivariate time se- ries, the neighborhood extrema are extracted in the different regions, and a characteristic point set is constructed. Then according to the distribution of the characteristic point set, a characteristic point sequence reflecting the ge- ometric features of multivariate time series is obtained. The incidence analysis between multivariate time series is transformed into the relational analysis between characteristic point sequences, and a grey incidence model is established. The model possesses the properties of translational invariance, transpose and rank transform invari- ance, and satisfies the grey incidence analysis axioms. Finally, two cases are studied and the results prove the ef- fectiveness of the model.