Resistive switching behavior and mechanism of HfO_(x) films with large on/off ratio by structure design

Different bilayer structures of HfO_(x)/Ti(TiO_(x)) are designed for hafnium-based memory to investigate the switching characteristics. The chemical states in the films and near the interface are characterized by x-ray photoelectron spectroscopy,and the oxygen vacancies are analyzed. Highly improved on/off ratio(~104) and much uniform switching parameters are observed for bilayer structures compared to single layer HfO_(x) sample, which can be attributed to the modulation of oxygen vacancies at the interface and better control of the growth of filaments. Furthermore, the reliability of the prepared samples is investigated. The carrier conduction behaviors of HfO_(x)-based samples can be attributed to the trapping and de-trapping process of oxygen vacancies and a filamentary model is proposed. In addition, the rupture of filaments during the reset process for the bilayer structures occur at the weak points near the interface by the recovery of oxygen vacancies accompanied by the variation of barrier height. The re-formation of fixed filaments due to the residual filaments as lightning rods results in the better switching performance of the bilayer structure.

Structure and superconducting properties of Ru_(1-x)Mo_(x)(x=0.1-0.9)alloys

We report the detailed crystal structures and physical properties of Ru_(1-x)Mo_(x)alloys in the solid solution range of x=0.1-0.9.Structure characterizations indicate that the crystal structure changes from the hcp-Mg-type,toβ-CrFe-type,and then bcc-W-type.The measurements of physical properties show that the Ru_(1-x)Mo_(x)samples with x≥0.2are superconductors and the superconducting transition temperature T_c as a function of Mo content exhibits a dome-like behavior.

Surface plasmon assisted high-performance photodetectors based on hybrid TiO_(2)@GaO_(x)N_(y)-Ag heterostructure

In this work,we reported a high-performance-based ultraviolet-visible(UV-VIS)photodetector based on a TiO_(2)@GaO_(x)N_(y)-Ag heterostructure.Ag particles were introduced into TiO_(2)@GaO_(x)N_(y)to enhance the visible light detection perfor-mance of the heterojunction device.At 380 nm,the responsivity and detectivity of TiO_(2)@GaO_(x)N_(y)-Ag were 0.94 A/W and 4.79×109 Jones,respectively,and they increased to 2.86 A/W and 7.96×1010 Jones at 580 nm.The rise and fall times of the response were 0.19/0.23 and 0.50/0.57 s,respectively.Uniquely,at 580 nm,the responsivity of fabricated devices is one to four orders of magnitude higher than that of the photodetectors based on TiO_(2),Ga_(2)O_(3),and other heterojunctions.The excellent optoelectronic characteristics of the TiO_(2)@GaO_(x)N_(y)-Ag heterojunction device could be mainly attributed to the synergistic effect of the type-Ⅱband structure of the metal-semiconductor-metal heterojunction and the plasmon resonance effect of Ag,which not only effectively promotes the separation of photogenerated carriers but also reduces the recombination rate.It is fur-ther illuminated by finite difference time domain method(FDTD)simulation and photoelectric measurements.The TiO_(2)@GaO_(x)N_(y)-Ag arrays with high-efficiency detection are suitable candidates for applications in energy-saving communica-tion,imaging,and sensing networks.

时间分辨热化学原位XAFS方法

为了利用X射线吸收精细结构(X-ray absorption fine structure,XAFS)谱学技术开展热化学反应动力学研究,在上海光源X射线吸收精细结构谱学线站(BL14W1)开展了时间分辨热化学原位XAFS方法的研究。采用自主研制的数据采集设备解决了时间分辨XAFS技术中不同类型信号同步触发和同步采集的问题,实现了数据间的精准匹配。在单色器转速为720"/s、数据采集设备采样率为2MS/s、数据长度为1200eV的条件下,获得了一个9.6s的Cu标样的数据谱,通过与常规XAFS数据和标准XAFS数据进行对比,结果表明本文得到的时间分辨XAFS实验系统具有良好的准确性、分辨率和信噪比。在此基础上,进一步结合线站自主研制的原位装置开展了时间分辨热化学原位XAFS方法,并利用高温常压原位装置开展了CuO还原为金属Cu的验证性实验。在230℃恒温氢气气氛下30min内观测到Cu吸收边能量逐渐向低能量处偏移,同时它位于8998eV的主峰强度逐渐减弱并且劈裂为双峰结构,出现明显的金属Cu的特征。实验结果表明此方法达到了捕获物质动态演化过程的预期目的,在拓展XAFS谱学实验平台的同时,为热化学反应的动力学过程研究提供了一种强大的实验手段。

基于x-LMS算法的直升机主动消振电力作动器系统研究

直升机前飞时,气动环境会导致不同方位角的桨叶出现气动载荷的瞬间不对称,通过基础结构传递会在机身形成大幅度的低频振动。为了消除多方向幅值变化的振动力,利用结构响应主动控制原理,设计了基于x-LMS算法的主动消振电力作动器系统,并进行了减振实验。首先,通过比较确定了单台作动器中两台电机同向旋转的方案。通过两台作动器的组合使用,推导出输出力的数学模型。其次,采用负载相位差交叉耦合的控制策略设计系统控制框图。针对存在耦合的相位外环,通过回差阵特征值法确定满足系统稳定裕度要求的参数范围,再根据灵敏度函数和输入跟踪性能在所得的参数稳定域内寻找最优解。然后,提出了基于x-LMS算法的直升机主动振动控制系统,并通过仿真验证了该系统的减振效果。最后,研制的实验样机进行了动稳态实验以及减振实验,验证了系统的实际减振效果。

Critical behaviour in nuclear structure from spherical to axially symmetric deformed shape in IBM

To compare with the predictions of the transitional dynamical symmetry X（5） proposed by Iachello （2001 Phys. Rev. Lett. 87 052502）, the critical behaviours of U（5） SU（3） are studied in the space of two control parameters in the interacting boson model （IBM）. A simple-shaped phased diagram has been presented. It is found that X（5） predictions cannot be exactly reproduced by our calculations and that the best agreement is close to the calculations with boson numbers N = 11 and 12. By comparing with experimental data on X（5）-like nuclei, we find that X（5） predictions and IBM calculations can reproduce the energy ratios and E2 transition ones.

Quantum and classical correlations for a two-qubit X structure density matrix

We derive explicit expressions for quantum discord and classical correlation for an X structure density matrix. Based on the characteristics of the expressions, the quantum discord and the classical correlation are easily obtained and compared under different initial conditions using a novel analytical method. We explain the relationships among quantum discord, classical correlation, and entanglement, and further find that the quantum discord is not always larger than the entanglement measured by concurrence in a general two-qubit X state. The new method, which is different from previous approaches, has certain guiding significance for analysing quantum discord and classical correlation of a two-qubit X state, such as a mixed state.

基于X射线荧光光谱的温稠密物质离化分布实验方法研究

受温度及密度等环境效应影响,温稠密物质的电子结构发生显著变化,其理论描述非常复杂,精密实验测量亦极其困难.本文发展了基于X射线荧光光谱研究温稠密物质离化分布的实验方法,结合理论研究有助于深入理解温稠密物质的电子结构变化.在万焦耳激光装置上,设计特殊构型黑腔复合加载产生数十eV、近固体密度的稠密Ti物质,利用激光辐照V产生的热发射线泵浦Ti的荧光,并采用晶体谱仪诊断样品的X射线荧光光谱.实验中获得冷样品和加载样品的荧光光谱,观测到加载样品K_(α)及K_(β)荧光谱线相对于冷样品光谱在高能侧的显著变化,结合理论计算解释了加载样品荧光谱线的变化主要来源于其温度上升后离化分布的改变,建立了基于X射线荧光光谱的温稠密物质离化分布实验研究能力.

Construction of Ultrathin Layered MXene-TiN Heterostructure Enabling Favorable Catalytic Ability for High-Areal-Capacity Lithium-Sulfur Batteries

Catalysis has been regarded as an effective strategy to mitigate sluggish reaction kinetics and serious shuttle effect of Li-S batteries.Herein,a spherical structure consists of ultrathin layered Ti_(3)C_(2)T_(x)-TiN heterostructures(MX-TiN)through in-situ nitridation method is reported.Through controllable nitridation,highly conductive TiN layer grew on the surface and close coupled with interior MXene to form unique 2D heterostructures.The ultrathin heterostructure with only several nanometers in thickness enables outstanding ability to shorten electrons diffusion distance during electrochemical reactions and enlarge active surface with abundant adsorptive and catalytic sites.Moreover,the(001)surface of TiN is dominated by metallic Ti-3d states,which ensures fast transmitting electrons from high conductive MX-TiN matrix and thus guarantees efficient catalytic performance.Calculations and experiments demonstrate that polysulfides are strongly immobilized on MX-TiN,meanwhile the bidirectional reaction kinetics are catalytically enhanced by reducing the conversion barrier between liquid LiPSs and solid Li_(2)S_(2)/Li_(2)S.As a result,the S/MX-TiN cathode achieves excellent long-term cyclability with extremely low-capacity fading rate of 0.022%over 1000 cycles and remarkable areal capacity of 8.27 mAh cm^(−2) at high sulfur loading and lean electrolytes.

X射线超快成像原位表征激光增材制造过程研究进展

在增材制造过程中,熔池经历快速熔化、冷却、凝固的过程,其物理、化学、结构和应力等处于极端非平衡状态,容易导致孔隙、裂纹等缺陷产生,影响制件力学性能。同步辐射X射线具有高空间分辨率和时间分辨率,可以实现增材制造过程中熔池动力学和缺陷演化的原位表征。本文综述了近年来激光增材制造原位实验平台的搭建,并从熔池结构演化、缺陷形成机理和成形工艺优化三个方面介绍了同步辐射X射线原位表征激光增材制造过程的研究进展。最后基于目前增材制造原位观察的局限性,从表征系统改进、原料多样化和计算修正等方面对未来研究进行了展望。

Extraction and Absolute Crystal Structure of Stachyose

The title compound stachyose （C24H42021）, a biologicaly active tetrasaccharide, was characterized by X-ray diffraction analysis. It crystallizes in the orthorhombic system, space group P21212 with C24H42021, a = 23.8760（3）, b = 12.71028（I2）, c = 10.81279（11） A, V = 3281.36（6） A3, Z = 4, Dc= 1.511 g/cm3, Mr = 746.58, F（000） = 1576, and μ = 1.230 mm^-1. The final R = 0.0666 and wR = 0.1797 for 6298 observed reflections （I 〉 2σ（I））. The molecular crystal structure of stachyose shows absolute stereochemistry of fl-D-fructofuranosyl a-D-galactopyranosyl- （1→6）-a-D-galactopyranosyl-（1→6）-a-D-glucopyranoside. The molecule is composed of two a-D-galactoses, one a-D-glucose, and one r-D-fructose and sequentially linked as a-Gal （1 →6） a-Gal （1→6） a-Glc （1→2） fl-Fru. The title compound is stacked into a 3D layer structure through hydrogen bonds. NMR spectra data are also assigned. In the crystal packing, X-ray analysis indicates that there are two intramolecular and eleven intermolecular hydrogen bonds in this compound.

Synthesis and X-ray Crystal Structure of a New Molecular Clip

The synthesis and X-ray crystal structure of a new molecular clip 2 was reported. It （C24H24N4O2, Mr = 400.47） crystallizes in the space group C2/c with a = 15.587（2）, b = 8.5805（12）, c = 15.259（2） A, β = 102.448（3）°, V= 1992.9 （5）A63, Z = 4, Dc = 1.335 g/cm63,μ = 0.087 mm^-1 and F（000） = 848. It remains monomeric in the crystal and a tape-like structure is formed in the crystal structure of molecular clip. The most unusual structural feature of 2 is the boat conformation of its cyclohexyl ring imposed by the ring fusion at C（9）-C（9a）.

Impact of Surface Passivation on the Electronic Structure and Optical Properties of the Si1-xGex Nanowires

The electronic structures and optical properties of the [llO]-oriented Sil-xGex nanowires （NWs） passivated with different functional groups （-H, -F and-OH） are investigated by using first-principles calculations. The results show that surface passivation influences the characteristics of electronic band structures significantly： the band gap widths and types （direct or indirect） of the Si1-xGe, NWs with different terminators show complex and robust variations, and the effective masses of the electrons in the NWs can be modulated dramatically by the terminators. The study of optical absorption shows that the main peaks of the parallel polarization component of Si1-x Gex NWs passivated with the functional groups exhibit prominent changes both in height and position, and are red-shifted with respect to those of corresponding pure Si NWs, indicating the importance of both the terminators and Ge concentrations. Our results demonstrate that the electronic and optical properties of Si1-xGex NWs can be tuned by utilizing selected functional groups as well as particular Ge concentrations for customizing purposes.

Synthesis, Crystal Structure and Biological Activity of 1,5-Bis(4-methoxyphenyl)-3-(4-methyl-1,2,3-thiadiazol-5-yl)pentane-1,5-dione

The title compound 1,5-bis（4-methoxyphenyl）-3-（4-methyl-1,2,3-thiadiazol-5-yl）-pentane-1,5-dione （C22H22N2O4S, Mr=410.49） has been synthesized by the reaction of 4-methyl-1,2,3-thiadiazole-5-carbaldehyde with 4-methoxyacetophenone, and its structure was characterized by IR, 1H NMR, H RMS, elemental analysis and single-crystal X-ray diffraction. The crystal of the title compound belongs to monoclinic, space group P21/c with a=11.159（3）, b=9.002（3）, c=20.192（6）, β=93.393（5）°, Z=4, V=2024.6（10） 3 , Dc=1.347 g/cm3 , μ=0.191 mm-1 , F（000）=864, R=0.0333 and wR （I〉2σ （I））=0.0840. In this molecule, the 1,2,3-thiadiazol ring is nearly vertical with both phenyl rings, and intermolecular weak hydrogen bonds of C-H…O and C-H…N types together with π-π stacking interactions and interactions between S（1）…N（2） are observed. The above three kinds of interactions extend the molecules into a two-dimensional layer framework. The preliminary biological test showed that the title compound had fungicidal activity.

Extraction and Crystal Structure of β-Sitosterol

The title compound β-sitosterol（C29H50O）, an active phytosterol in many medicinal and edible plants, was characterized by X-ray diffraction analysis and extensive nuclear magnetic resonance（NMR） data. It crystallizes in monoclinic system, space group P21 with C29H50O·1/2H2O, a = 9.4226（7）, b = 7.4824（9）, c = 36.889（3） , V = 2597.0（4） 3, Z = 4, Dx = 1.084 g/cm3, Mr = 423.70, F（000） = 948, and μ = 0.064 mm-1. The final R = 0.0886 and wR = 0.2234 for 10157 observed reflections（I 〉 2σ（I））. The molecular crystal structure of β-sitosterol shows relative stereochemistry of 24R-ethylcholest-5-en-3β-ol. The molecule is composed of one steroid nucleus（3 six-membered rings and 1 five-membered ring） and one sidechain of 10 carbons. There are two C29H50O molecules and one H2O molecule in a symmetrical unit, and the title compound is stacked into a special laminated structure through hydrogen bonds and van der Waal forces. The special laminated structure was first reported.

Influence of supersaturation on structure of sodium aluminate solutions with medium concentration: a solution X-ray diffraction study

Influence of supersaturation on the structure of a series of freshly prepared supersaturated sodium aluminate solutions with medium concentration was investigated by solution X-ray diffraction. Experimental results show that the basic Al-containing species in all kinds of supersaturated solution is four-coordinated ions. Opposite to Al-O distance contracted in highly concentrated solution, a little expand of the Al-O distance from 1.75 *@ to 1.85 *@ occurs with increasing supersaturation, which is consistent with the occurrence of oligomeric aluminate species. Meanwhile, O-O distance in the first shell of H 2O-H 2O(OH) in supersaturated sodium aluminate solution is obviously longer than in hydroxide sodium solution and becomes longer and longer with increasing supersaturation. Na-O bond length is about 2.4 *@ and changes little with supersaturation. The reason for Al-O bond expanding with supersaturation and its influence on the stability of solution was discussed.

Phase Behavior and Crystal Structure of Perovskite-Type Rare Earth Complex Oxides

Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A0.67Ln0.33 Mn0.33Ti0.6703（A = Ca or Sr and Ln = rare earth） were found to have orthorhombic symmetry with the space group Pnrna, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Cao.67Ln0.33Mn0.33Ti0.6703 for several rare earth elements showed a semiconducting property with the activation energy of 0.4 eV. Some of these compounds of the strontium system show the antiferromagnetic properties below 10 K.

Synthesis and Crystal Structure of(3S,4R,Z)-3,6-dimethyl-2-(3-methylbut-2-enylidene)-2,3,3a,4,7,7a-hexahydrobenzofuran-3,4-diol

The title compound of（3S,4R,Z）-3,6-dimethyl-2-（3-methylbut-2-enylidene）-2,3,3a,4,7,7a-hexahydrobenzofuran-3,4-diol,C15H22O3,as a potential gastric cytoprotective agent has been synthesized by the reduction of bisabolangelone in methanol with sodium borohydride.The title compound was characterized by IR and NMR spectra.Meanwhile,the crystal was obtained and determined by X-ray single-crystal diffraction.Crystal data：monoclinic system,space group P21 with a = 6.0692（12）,b = 8.9954（18）,c = 13.182（3） ,β = 92.59（3）°,V = 718.9（2） 3,Z = 2,F（000） = 272,Dc = 1.156 g/cm3,μ = 0.633 mm-1,R = 0.0362 and wR = 0.1051 for 9490 independent reflections（Rint = 0.0172） and 2461 observed reflections（I 2σ（I））.Intermolecular O-H…O interactions link the molecules into one-dimensional infinite chains running along the b axis,which contributes to the stability of the crystal structure.

广西高职“1+X”证书试点专业与产业适应性研究

职业院校专业设置与区域产业结构的适应性,直接关系到职业教育能否满足产业结构优化升级的需求。采用2019-2022年广西高职专业建设数据及“1+X”证书制度试点建设数据,量化分析“1+X”试点专业与产业结构适应性情况,结果显示:第一产业对应的人才培养结构偏离度均为正值且数值远高于0.2的适应水平,“1+X”证书制度试点专业人才培养规模远远小于广西第一产业的需求;第二产业对应的广西高职人才试点专业结构偏离度均为正值,试点专业人才培养规模小于广西第二产业的需求;第三产业试点专业结构偏离度均为负值,高职试点专业人才培养规模超过了第三产业对人才的需求。据此提出提升试单专业与产业适应性的策略:统筹高职专业布局,主动匹配产业结构调整;借助“1+X”证书制度试点,重构高职专业体系;充分调研市场需求,适时调整专业建设方向。

Structure of MgSO_4 in Concentrated Aqueous Solutions by X-Ray Diffraction

Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X’pert Pro θ-θ diffractometer at 298 K, yielding structural function and radial distribution function（RDF）. The developed KURVLR program was employed for the theoretical investigation in consideration of the ionic hydration and ion association. Multi-peaks Gaussian fitting method was applied to deconvolving the overlapping bands of Differential radial distribution function（DRDF）. The calculation of the geometric model shows that octahedrally six-coordinated Mg（H2O）62＋, with an Mg2＋…OW bond length of 0.201 nm dominates in the solutions. There exists contact ion-pair（CIP） in the more concentrated solution（1：18, H2O/salt molar ratio） with a coordination number of 0.8 and a characteristic Mg…S distance of 0.340 nm. The result indicates the hydrated SO42– ion happens in the solution. The S…OW bond distance was determined to be 0.382 nm with a coordination number of 13. The fraction of CIP increases significantly with the increasing concentration. The symmetry of the hydration structure of sulfate ion is lowered by forming complex with magnesium ion.