Microstructural evolution and dynamic recrystallization mechanisms of additively manufactured TiAl alloy with heterogeneous microstructure during hot compression

Microstructural evolution and dynamic recrystallization(DRX)mechanisms of a Ti-48Al-2Cr-2Nb(at.%)alloy prepared by selective electron beam melting(SEBM)during hot deformation at 1150℃and 0.1 s^(-1)were investigated by hot compression tests,optical microscope(OM),scanning electron microscope(SEM),electron back-scattered diffraction(EBSD)and transmission electron microscope(TEM).The results show that the initial microstructure of the as-SEBMed alloy exhibits layers of coarseγgrains and fineγ+α_(2)+(α_(2)/γ)lamellar mixture grains alternately along the building direction.During the early stage of hot deformation,deformation twins tend to form within the coarse grains,facilitating subsequent deformation,and a small number of DRX grains appear in the fine-grained regions.With the increase of strain,extensive DRX grains are formed through different DRX mechanisms in both coarse and fine-grained regions,involving discontinuous dynamic recrystallization mechanism(DDRX)in the fine-grained regions and a coexistence of DDRX and continuous dynamic recrystallization(CDRX)in the coarsegrained regions.

湘方言“连不P”句式的强否定极性及其句法、语义允准机制

湘方言"连不P"句式作为非典型的"连"字句具有独特的句法表现特征。文章从生成句法学和词汇语义学两个层面来考察湘方言"连不P"句式的强否定极性及其语义允准机制:生成在[Spec,NegP]位置上的强否定极项"连"字与否定标记词"不"形成"标志语—核心词一致关系"而得到强否定极性的允准;该极项必须在逆真实性语境中得到允准。

Inferring Genome Ancestry and Estimating Molecular Relatedness Among 187 Chinese Maize Inbred Lines

The inference of genome ancestry and the estimation of molecular relatedness are of great importance for breeding efficiency and association studies. Seventy SSR loci, evenly distributed in 10 chromosomes, were assayed for polymorphism among 187 commonly used maize （Zea mays L.） inbreds which represent the genetic diversity in China. The identified 290 alleles served as raw data for estimating population structure using the coalescent linked loci, based on the ADMIXTURE model. Population number, K, has been inferred to be between five and seven. Specifying five subpopulations （K = 5） led to a distinct decrease and specifying K to be greater than six resulted in only minimal increases in the likelihood value. Therefore, population number, K, has been inferred into six subpopulations, which are PA, BSSS （includes Reid）, PB, Lan （Lancaster Sure Crop）, LRC （Luda Reb Cob, a Chinese landrace, and its derivatives）, and SPT （Si-ping-tou, a Chinese landrace and its derivatives）. The Kullback-Leibler distance of pairwise subpopulation was also inferred as n × p （187 ×6） Q matrices, which gave a detailed percentage of genetic composition of six subpopulations and molecular relatedness of each line. The genome-wide linkage disequilibrium （LD） indicated that the asso- ciation studies in QTLs and/or candidate genes might avoid nonfunctional and spurious associations, as most of the LD blocks were broken among diverse germplasm. The defined population structure has given us a clear genetic structure of these lines for breeding practice and established a good basis for association analysis.

Characterization of discontinuous yielding phenomenon in isothermal compression of TC8 titanium alloy

The discontinuous yielding phenomenon （DYP） during high temperature deformation was investigated based on the isothermal compression of TC8 titanium alloy. The DYP of TC8 titanium alloy was characterized by quantifying the yield drop of the DYP （△σUL） and ending strain of flow oscillation （εOSC） based on the flow stress？strain curves, and then the effect of deformation parameters on the △σUL and εOSC values was analyzed. The results show that the △σUL and εOSC values increase with the increase of strain rate. The effect of deformation temperature on the ？σUL value depends on the strain rate. Finally, the transmission electron microscope （TEM） observation shows the evidence for the dynamic theory, which ascribes the DYP to the generation of mobile dislocation at the grain boundary. Meanwhile, the optical microscope （OM） observation shows that both the primary α grain and β grain become smaller with the increase of strain, which well interprets the effect of deformation parameters on the △σUL and εOSC values.

Simulated and experimental investigation on discontinuous dynamic recrystallization of a near-α TA15 titanium alloy during isothermal hot compression in βsingle-phase field

A cellular automaton（CA） modeling of discontinuous dynamic recrystallization（DDRX） of a near-α Ti-6Al-2Zr-1Mo-1V（TA15） isothermally compressed in the β single phase field was presented.In the CA model,nucleation of the β-DDRX and the growth of recrystallized grains（re-grains） were considered and visibly simulated by the CA model.The driving force of re-grain growth was provided by dislocation density accumulating around the grain boundaries.To verify the CA model,the predicted flow stress by the CA model was compared with the experimental data.The comparison showed that the average relative errors were10.2%,10.1%and 6%,respectively,at 1.0,0.1 and 0.01 s^-1 of 1020 ℃,and were 10.2%,11.35%and 7.5%,respectively,at 1.0,0.1and 0.01 s^-1 of 1050 ℃.The CA model was further applied to predicting the average growth rate,average re-grain size and recrystallization kinetics.The simulated results showed that the average growth rate increases with the increasing strain rate or temperature,while the re-grain size increases with the decreasing strain rate;the volume fraction of recrystallization decreases with the increasing strain rate or decreasing temperature.

Rapid Constructing a Genetic Linkage Map by AFLP Technique and Mapping a New Gene tms5

In this study, we reported the repaid construction of a molecular marker linkage map of rice (Oryza sativa L.). An F-2 population from the cross between Annong S-1 and Nanjing 11 was used to construct a genetic linkage map of rice. Total of 142 newly screened AFLP markers and 30 anchor markers (25 SSR markers and 5 RFLP markers) were mapped on the 12 chromosomes covering 1537.4 cM of rice genome. The average interval between these markers was 9.0 cM. The total work which usually was finished in more than one year was finished within only 3 months by one person. This is the first plant AFLP map developed in China. A new thermosensitive genic male sterile gene in rice, tms5, was Egged and mapped onto chromosome 2 during the development of the linkage map.

Calculation connectivity reliability of road networks based on recursive decomposition arithmetic

In order to decrease the calculation complexity of connectivity reliability of road networks, an improved recursive decomposition arithmetic is proposed. First, the basic theory of recursive decomposition arithmetic is reviewed. Then the characteristics of road networks, which are different from general networks, are analyzed. Under this condition, an improved recursive decomposition arithmetic is put forward which fits road networks better. Furthermore, detailed calculation steps are presented which are convenient for the computer, and the advantage of the approximate arithmetic is analyzed based on this improved arithmetic. This improved recursive decomposition arithmetic directly produces disjoint minipaths and avoids the non-polynomial increasing problems. And because the characteristics of road networks are considered, this arithmetic is greatly simplified. Finally, an example is given to prove its validity.

Effect of electropulsing treatment on corrosion behavior of nickel base corrosion-resistant alloy

Electropulsing treatment（EPT） was performed on a nickel base corrosion resistant alloy during aging.The effect of EPT on the microstructure and corrosion resistance of the alloy and the mechanisms were investigated.The results show that the intergranular corrosion resistance can be improved substantially without the degradation of mechanical properties of the alloy by EPT.The EPT has an effect of enhancing the interface diffusion rate of the alloying element,which is higher than the body diffusion rate.And thus discontinuous precipitation of M23C6 type carbides appears at the grain boundary in the alloy by EPT,which decreases the depletion extent of the alloying elements at the grain boundary substantially.As a result,the intergranular corrosion resistance of the alloy can be improved by the EPT without any degradation of mechanical properties.

Resistivity Instability in Polysilicon Resistors Under Metal Interco-nnects and Its Suppression by Compensating Ion Implantation

The resistivity instability of the boron-doped polysilicon resistors being a line resistance element of ICs is within the range of several kΩ's,especially when our running the underneath metal interconnects.Polysilicon resistors have been fabricated under various processing conditions as well as some electrical and crystallographic characteristics have been obtained.It is shown the resistivity instability mainly results from the variational carrier mobility.By analyzing the Seto's model,the barrier height and trapped charge density are observed reducing under the Al over layer.Therefore,the resistance instability is also caused by both the charge trapping/detrapping occurring at polysilicon grain boundaries and the resultant variation in the potential barrier height.The formation of high-stability polysilicon resistors in the range of several kΩ's has been decided by compensating the ion implantation,which makes the charge trapping/detrapping at the grain boundary less susceptible to the hydrogen annealing.

Microstructural characteristics of joint region during diffusion-brazing of magnesium alloy and stainless steel using pure copper interlayer

A novel joining method,double-stage diffusion-brazing of an AZ31 magnesium alloy and a 304L austenitic stainless steel,was carried out using a pure copper interlayer.The solid-state diffusion bonding of 304L to copper was conducted at 850 ℃ for 20 min followed by brazing to AZ31 at 520 ℃ and 495 ℃ for various time.Microstructural characteristics of the diffusion-brazed joints were investigated in detail.A defect free interface of Fe-Cu diffusion area appeared between the Cu alloy and the 304L steel.Cu-Mg reaction products were formed between AZ31 and Cu alloys.A layered structure including AZ31/Cu-Mg compounds/Cu/Fe-Cu diffusion layer/304L was present in the joint.With time prolonging,the reduction in the width of Cu layer was balanced by the increase in the width of Cu-Mg compounds zone.Microhardness peaks in the zone between AZ31 and Cu layer were attributed to the formation of Mg-Cu compounds in this zone.

Existence of Solutions to Differential-Iterative Equation

The existence and the behavior of solutions to the differential-iterative equation arestudied without the restriction that f is monotone An error in and available paper is correctedhere.

Design and Realization of CPW Circuits Using EC-ANN Models for CPW Discontinuities

Novel accurate and efficient equivalent circuit trained artificial neural-network （EC-ANN） models,which inherit and improve upon EC model and EM-ANN models＇ advantages,are developed for coplanar waveguide （CPW） discontinuities. Modeled discontinuities include ： CPW step, interdigital capacitor, symmetric cross junction, and spiral inductor, for which validation tests are performed. These models allow for circuit design, simulation, and optimization within a CAD simulator. Design and realization of a coplanar lumped element band pass filter on GaAs using the developed CPW EC-ANN models are demonstrated.

ADAPTIVE PREDICTIVE CONTROL OF NEAR-SPACE VEHICLE USING FUNCTIONAL LINK NETWORK

A novel nonlinear adaptive control method is presented for a near-space hypersonic vehicle （NHV） in the presence of strong uncertainties and disturbances. The control law consists of the optimal generalized predictive controller （OGPC） and the functional link network （FLN） direct adaptive law. OGPC is a continuous-time nonlinear predictive control law. The FLN adaptive law is used to offset the unknown uncertainties and disturbances in a flight through the online learning. The learning process does not need any offline training phase. The stability analyses of the NHV close-loop system are provided and it is proved that the system error and the weight learning error are uniformly ultimately hounded. Simulation results show the satisfactory performance of the con- troller for the attitude tracking.

Uniqueness of Solutions to Differential-Iterative Equation

Conditions for the uniqueness of solutions to the differential-iterative equations x'(t)=f(x(x(t))) are given by use of fixed point theorems.

Microstructure instability of fully lamellar TiAl alloy containing high content of Nb after long-term thermal cycling

Microstructure instabilities of the fully lamellar Ti-45Al-8.5Nb-（W,B,Y） alloy were investigated by SEM and TEM after long-term thermal cycling（500 and 1000 thermal cycles） at 900 °C. Two major categories of microstructure instability were produced in the alloy after the thermal cycling： 1） The discontinuous coarsening implies that grain boundary migrations are inclined to occur in the Al-segregation region after the long-term thermal cycling, especially after 1000 thermal cycles. Al-segregation can be reduced during the process of long-term thermal cycling as a result of element diffusion; 2） The α2 lamellae become thinner and are broken after 1000 thermal cycles caused by the dissolution of α2 lamellae through phase transformation of α2→γ. The γ grains nucleate within the α2 lamellae or（α2＋γ） lamellae in a random direction.

也说周遍性构式中的“都”和“也”

周遍性构式中,"都"分布自由,"也"分布受限;"都"倾向于肯定形式,"也"倾向于否定形式;"都/也"有时可互换而构式义不变。针对这些现象,本文从句法演变的角度和构式与"都/也"的互动入手,考察"都/也"的不均衡分布,提出构式义与"都/也"语义的融合以及构式形成过程中"前附词"的脱落或产生等解释性理论和说明。

Influence of Polarization-Induced Electric Fields on Optical Properties of Intersubband Transitions in Al_xGa_(1-x)N/GaN Double Quantum Wells

The influence of polarization-induced electric fields on the electron distribution and the optical properties of intersubband transitions （ISBT） in AlxGa（1-x）N/GaN coupled double quantum wells （DQWs） is investigated by self-consistent calculation. It is found that the polarization-induced potential drop leads to an asymmetric potential profile of AlxGa（1-x）N/GaN DQWs even though the two wells have the same width and depth. The polarization effects result in a very large Stark shift between the odd and even order subbands,thus shortening the wavelength of the ISBT between the first odd order and the second even order （1odd-2 ） subbands. Meanwhile, the electron distribution becomes asymmetric due to the polarization effects, and the absorption coefficient of the 1odd-2 ISBT decreases with increasing polarization field discontinuity.

Exponential stability criteria on neural networks with continuously distributed delays

The exponential stability of a class of neural networks with continuously distributed delays is investigated by employing a novel Lyapunov-Krasovskii functional. Through introducing some free-weighting matrices and the equivalent descriptor form, a delay-dependent stability criterion is established for the addressed systems. The condition is expressed in terms of a linear matrix inequality （LMI）, and it can be checked by resorting to the LMI in the Matlab toolbox. In addition, the proposed stability criteria do not require the monotonicity of the activation functions and the derivative of a time-varying delay being less than 1, which generalize and improve earlier methods. Finally, numerical examples are given to show the effectiveness of the obtained methods.

SHEsis,a powerful software platform for analyses of linkage disequilibrium,haplotype construction,and genetic association at polymorphism loci

In multiloci-based genetic association studies of complex diseases, a powerful and high efficient tool for analyses oflinkage disequilibrium (LD) between markers, haplotype distributions and many chi-square/p values with a large numberof samples has been sought for long. In order to achieve the goal of obtaining meaningful results directly from raw data,we developed a robust and user-friendly software platform with a series of tools for analysis in association study withhigh efficiency. The platform has been well evaluated by several sets of real data.

Asymmetrical multi-gateways based internet connectivity for MANET6

Mobile ad hoc networks (MANETs) are autonomous and infrastructureless networks that support multi-hop wireless communications among mobile hosts. Providing global internet connectivity to MANETs is a strong trend nowadays, so the mobile hosts can enjoy the tremendous services of the Internet. In this paper, we present an asymmetrical approach that uses multiple Internet Gateways to provide MANETs nodes with Internet connectivity and access to the Internet’s resources. The rational utilization of all available Internet Gateways can meet the load of MANETs balance and reduce the latency of packets communication between MANETs and the Internet; this can be concluded from the results of the simulation experiments.