STRESS HYSTERESIS AND DOMAIN EVOLUTION IN THERMOELASTIC TENSION STRIPS

Martensite domain formation, evolution and annihilation are widely observed in stress-induced phase transformation of superelastic NiTi polycrystalline shape memory alloys. By the calculation of the thermodynamic driving force and the incorporation of friction kinetics of the interface, the domain morphology and its evolution were successfully simulated by the interface-tracking technique. The computational results agree well with the experimental observation of tensile strips. Based on theoretical and computational results, we discussed the effects of critical driving force and the existence of metastability on the transition between different domain patterns.

Effect of TbF_(3)diffusion on the demagnetization behavior and domain evolution of sintered Nd-Fe-B magnets by electrophoretic deposition

We studied the magnetic properties and domain evolution of annealed and TbF3-diffused sintered Nd-Fe-B magnets using the electrophoretic deposition method.After TbF_(3)diffusion,the coercivity increased significantly by 9.9 kOe and microstructural analysis suggested that Tb favored the formation of the(Nd,Tb)_(2)Fe_(14)B shell phase in the outer region of the matrix grains.The first magnetization reversal and the dynamic successive domain propagation process were detected with a magneto-optical Kerr microscope.For the TbF_(3)-diffused magnet,the magnetization reversal appeared at a larger applied field and the degree of simultaneous magnetization reversal decreased compared with an annealed magnet.During demagnetization after full magnetization,the occurrence of domain wall motion(DWM)in the reproduced multi-domain regions was observed by the step method.The maximum polarization change resulting from the reproduced DWM was inversely related to the coercivity.The increased coercivity for the diffused magnet was mainly attributed to the more difficult nucleation of the magnetic reversed region owing to the improved magneto-crystalline anisotropy field as a result of Tb diffusion.

Bubble domain evolution in well-ordered BiFeO_(3) nanocapacitors

Ferroelectric nanocapacitors have attracted intensive research interest due to their novel functionalities and potential application in nanodevices.However,due to the lack of knowledge of domain evolution in isolated nanocapacitors,precise manipulation of topological domain switching in the nanocapacitor is still a challenge.Here,we report unique bubble and cylindrical domains in the well-ordered BiFeO_(3) nanocapacitor array.The transformation of bubble,cylindrical and mono domains in isolated ferroelectric nanocapacitor has been demonstrated via scanning probe microscopy(SPM).The bubble domain can be erased to mono domain or written to cylindrical domain and mono domain by positive and negative voltage,respectively.Additionally,the domain evolution rules,which are mainly affected by the depolarization field,have been observed in the nanocapacitors with different domain structures.This work will be helpful in understanding the domain evolution in ferroelectric nanocapacitors and providing guidance on the manipulation of nanoscale topological domains.

Evolution of Magnetic Domain Structure in a YIG Thin Film

The evolution of a magnetic domain structure induced by temperature and magnetic field is reported in silicon- doped yttrium iron garnet （YIG） films with perpendicular anisotropy. During a cooling-down procedure from 300K to 7K, a 20% change in the domain width is observed, with the long tails of the stripes being shortened and the twisting stripes being straightened. Under the influence of the stray field of a barium ferrite, the garnet presents an interesting domain structure, which shows an appearance of branching protrusions. The intrinsic mechanisms in these two processes are also discussed.

Exact Evolution of Ultrashort Hollow-Airy Pulses in the Spatiotemporal Domain

An exact analytic expression for an ultrashort hollow-Airy wave packet is presented beyond the slowly varying envelope approximation. The hollow-Airy wave packet combines the hollow-Gaussian beam in the spatial domain and the Airy pulse in the temporal domain. The spatiotemporal propagation dynamics of the ultrashort hollow- Airy pulse are analyzed by the numerical simulations. During the propagation in free space, the spatial intensity profile evolves from hollow-Gaussian to Gaussian shape; the temporal intensity profile retains Airy shape over several Rayleigh ranges. The acceleration property of the ultrashort Airy pulse is also demonstrated.

Effects of spot size on the operation mode of Ga As photoconductive semiconductor switch employing extrinsic photoconductivity

To guide the illuminating design to improve the on-state performances of gallium arsenide(GaAs)photoconductive semiconductor switch(PCSS),the effect of spot size on the operation mode of GaAsPCSS based on a semi-insulating wafer with a thickness of 1 mm,triggered by a 1064-nm extrinsic laser beam with the rectangular spot,has been investigated experimentally.It is found that the variation of the spot size in length and width can act on the different parts of the output waveform integrating the characteristics of the linear and nonlinear modes,and then significantly boosts the PCSS toward different operation modes.On this basis,a two-channel model containing the active and passive parts is introduced to interpret the relevant influencing mechanisms.Results indicate that the increased spot length can peak the amplitude of static domains in the active part to enhance the development of the nonlinear switching,while the extended spot width can change the distribution of photogenerated carriers on both parts to facilitate the linear switching and weaken the nonlinear switching,which have been proved by comparing the domain evolutions under different spot sizes.

地图演化论及其启示

试图引入"演化论",采用"来源域"到"目标域"的"隐喻映射"方法,勾勒地图演化过程的历史脉络;并从地图演化与人类社会的演进及生产力发展、地图演化过程中出现的连续性和非连续性与社会演进的连续性与非连续性、地图演化与社会科技进步、地图演化与文化变迁、地图演化与地图哲学思维等5个方面分析了它们之间的关系。对于深入开展地图演化论研究会有新的启发。

归纳逻辑的进化主义进路——施泰默的“自然预期假设”再发现

施泰默运用"自然预期"假设解决了古德曼的"绿蓝悖论"。"自然预期"是指,当有机体观察到一般化类别中一些元素具有某种属性时,能够本能地"预期"这个类别的另一些元素也具有这种属性。施泰默认为,有机体具有先天的概括性倾向,在观察到一些个例具有某种显著特征以后,会本能地将这种属性推延到整个类别。有机体建立类别、进行属性推延的能力都是进化过程中自然选择的结果。施泰默用进化论范式解释了"归纳推理如何可能"的问题,其直接贡献是推进了归纳问题研究的心理学转向,将进化论范式导入归纳问题的研究。

Time evolutions of scalar field perturbation in Schwarzschild de-Sitter black hole from Einstein-scalar–Gauss–Bonnet theory

The scalar-free black hole could be unstable against the scalar field perturbation when it is coupled to a Gauss–Bonnet(GB)invariant in a special form.It is known that the tachyonic instability in this scenario is triggered by the sufficiently strong GB coupling.In this paper,we focus on the time domain analysis of massive scalar field perturbation around the Schwarzschild de-Sitter black hole in Einstein-scalar–Gauss–Bonnet gravity.By analyzing the scalar field propagation,we find that the scalar field will finally grow when the GB coupling is large enough.This could lead to the instability of the background black hole.Furthermore,we demonstrate how the mass of the scalar field and the GB coupling strength affect the onset of tachyonic instability.

An unconventional phase field modeling of domains formation and evolution in tetragonal ferroelectrics

Based on characteristic functions of variants, we developed an unconventional phase field modeling for investigating domains formation and evolution in tetragonal ferroelectrics. In order to develop this computational approach, we constructed the anisotropy energy of tetragonal variants, which is used instead of Landau-Devonshire potential in the conventional phase field method, resulting in that much fewer parameters are needed for simulations. This approach is advantageous in simulations of emerging ferroelectric materials. We employ it to study the formation and evolution of domains in tetragonal barium titanate single crystal, as well as the nonlinear behaviors under cyclical stress and electric field loading. A multi-rank laminated ferroelectric domain pattern, 90° domain switching accompanied by polarization rotation, and 180° domain switching accompanied by move of domain wall are predicted. It is found that the speed of 90° domain switching is slower than that of 180° domain switching, due to both polarization and transformation strain changed in 90° domain switching. It also suggests that large strain actuation can be generated in single crystal ferroelectrics via combined electromechanical loading inducing 90° domain switching. The good agreement between simulation results and experimental measurements is observed.

Evolutionary dynamics of leucine‐rich repeat receptor‐like kinases and related genes in plants:A phylogenomic approach

Leucine-rich repeat （LRR） receptor-like kinases （RLKs）, evolutionarily related LRR receptor-like proteins （RLPs） and receptor-like cytoplasmic kinases （RLCKs） have important roles in plant signaling, and their gene subfamilies are large with a complicated history of gene duplication and loss. In three pairs of closely related lineages, including Arabidopsis thaliana and A. lyrata （Arabidopsis）, Lotus japonicus, and Medicago truncatula （Legumes）, Oryza sativa ssp. japonica, and O. sativa ssp. indica （Rice）, we find that LRR RLKs comprise the largest group of these LRR-related subfamilies, while the related RLCKs represent the smal est group. In addition, comparison of orthologs indicates a high frequency of reciprocal gene loss of the LRR RLK/LRR RLP/RLCK subfamilies. Furthermore, pairwise comparisons show that reciprocal gene loss is often associated with lineage-specific duplication（s） in the alternative lineage. Last, analysis of genes in A. thaliana involved in development revealed that most are highly conserved orthologs without species-specific duplication in the two Arabidopsis species and originated from older Arabidopsis-specific or rosid-specific duplications. We discuss＆amp;nbsp;potential pitfal s related to functional prediction for genes that have undergone frequent turnover （duplications, losses, and domain architecture changes）, and conclude that prediction based on phylogenetic relationships wil likely outperform that based on sequence similarity alone.

Realizing enhanced energy storage and hardness performances in 0.90NaNbO_(3)-0.10Bi(Zn_(0.5)Sn_(0.5))O_(3)ceramics

Ceramic dielectric capacitors have a broad scope of application in pulsed power supply devices.Relaxor behavior has manifested decent energy storage capabilities in dielectric materials due to its fast polarization response.In addition,an ultrahigh energy storage density can also be achieved in NaNbO_(3)(NN)-based ceramics by combining antiferroelectric and relaxor characteristics.Most of the existing reports about lead-free dielectric ceramics,nevertheless,still lack the relevant research about domain evolution and relaxor behavior.Therefore,a novel lead-free solid solution,(1-x)NaNbO_(3)-xBi(Zn_(0.5)Sn_(0.5))O_(3)(abbreviated as xBZS,x=0.05,0.10,0.15,and 0.20)was designed to analyze the domain evolution and relaxor behavior.Domain evolutions in xBZS ceramics confirmed the contribution of the relaxor behavior to their decent energy storage characteristics caused by the fast polarization rotation according to the low energy barrier of polar nanoregions(PNRs).Consequently,a high energy storage density of 3.14 J/cm^(3)and energy efficiency of 83.30%are simultaneously available with 0.10 BZS ceramics,together with stable energy storage properties over a large temperature range(20-100℃)and a wide frequency range(1-200 Hz).Additionally,for practical applications,the 0.10 BZS ceramics display a high discharge energy storage density(W_(dis)≈1.05 J/cm^(3)),fast discharge rate(t_(0.9)≈60.60 ns),and high hardness(H≈5.49 GPa).This study offers significant insights on the mechanisms of high performance lead-free ceramic energy storage materials.

Enhanced piezoelectricity in 0.7BiFeO_(3)-0.3BaTiO_(3)lead-free ceramics:Distinct effect of poling engineering

BiFeO_(3)-BaTiO_(3) based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature.Since the piezoelectric response of piezoelectric ceramics just appears after poling engineering,in this work,the domain evolution and microscopic piezoresponse were observed in-situ using piezoresponse force microscopy(PFM)and switching spectroscopy piezoresponse force microscopy(SS-PFM),which can effectively study the local switching characteristics of ferroelectric materials especially at the nanoscale.The new domain nucleation preferentially forms at the boundary of the relative polarization region and expands laterally with the increase of bias voltage and temperature.The maximum piezoresponse(Rs),remnant piezoresponse(Rrem),maximum displacement(Dmax)and negative displacement(Dneg)at 45 V and 120C reach 122,69,127 pm and 75 pm,respectively.Due to the distinct effect of poling engineering in full domain switching,the corresponding d33 at 50 kV/cm and 120C reaches a maximum of 205 pC/N,which is nearly twice as high as that at room temperature.Studying the evolution of ferroelectric domains in the poling engineering of BiFeO_(3)-BaTiO_(3)ceramics provides an insight into the relationship between domain structure and piezoelectric response,which has implications for other piezoelectric ceramics as well.