Stationary phase point extraction based on high-resolution radon transform and its application to multiple attenuation by wavefield extrapolation

Multiple prediction and subtraction techniques based on wavefield extrapolation are effective for suppressing multiple related to water layers. In the conventional wavefield extrapolation method,the multiples of the seismic data are predicted from the known total wave field by the Green function convoluted with each point of the bottom. However,only the energy near the stationary phase point has an effect on the summation result when the convolutional gathers are added. The research proposed a stationary phase point extraction method based on high-resolution radon transform. In the radon domain,the energy near the stationary phase point is directly added along the convolutional gathers curve,which is a valid solution to the problem of the unstable phase of the events of multiple. The Curvelet matching subtraction technique is used to remove the multiple,which improved the accuracy of the multiple predicted by the wavefield extrapolation and the artifacts appearing around the events of multiple are well eliminated. The validity and feasibility of the proposed method are verified by the theoretical and practical data example.

Design of a coated thinly clad chalcogenide long-period fiber grating refractive index sensor based on dual-peak resonance near the phase matching turning point

A novel method for designing chalcogenide long-period fiber grating(LPFG) sensors based on the dual-peak resonance effect of the LPFG near the phase matching turning point(PMTP) is presented. Refractive index sensing in a high-refractive-index chalcogenide fiber is achieved with a coated thinly clad film. The dual-peak resonant characteristics near the PMTP and the refractive index sensing properties of the LPFG are analyzed first by the phase-matching condition of the LPFG. The effects of film parameters and cladding radius on the sensitivity of refractive index sensing are further discussed. The sensor is optimized by selecting the appropriate film parameters and cladding radius. Simulation results show that the ambient refractive index sensitivity of a dual-peak coated thinly clad chalcogenide LPFG at the PMTP can be 2400 nm/RIU, which is significantly higher than that of non-optimized gratings. It has great application potential in the field of chemical sensing and biosensors.

Microstructures and Phase Transition Points of As-Cast Mg-Zn-Y System Alloys

As-east mierostruetures and their distribution of Mg-Zn-Y ternary alloy with high magnesium, low zinc and yttrium were examined using Nikon Epiphot optical microscopy （OM）, RigakuD/max-3C X- ray diffraetion （XRD）, and JEOL JSM-6700F scanning electron microscopy （SEM） equipped with an energydispersive X-ray spectroscopy （EDS）. In the as-east mierostructures, Yttrium and zinc tend to segregate at grain boundaries,

Optimal design of sintered Ce_9Nd_(21)Fe_(bal)B_1 magnets with a low-melting-point (Ce,Nd)-rich phase

A systemic investigation was done on the chemistry and crystal structure of boundary phases in sintered Ce9Nd21FebalB1 （wt%） magnets. Ce2Fe14B is believed to be more soluble in the rare-earth （RE）-rich liquid phase during the sintering process. Thus, the grain size and oxygen content were controlled via low-temperature sintering, resulting in high coercivity and maximum energy products. In addition, Ce formed massive agglomerations at the triple-point junctions, as confirmed by elemental mapping results. Transmission electron micros- copy （TEM） images indicated the presence of （Ce,Nd）Ox phases at grain boundaries. By controlling the composition and optimizing the preparation process, we successfully obtained Ce9Nd21FebalBx sintered magnets; the prepared magnets exhibited a residual induction, coerciv- ity, and energy product of 1.353 T, 759 kA/m, and 342 kJ/m3, respectively.

Determining the structural phase transition point from the temperature of ^(40)Ca^+ Coulomb crystal

We observed the linear-to-zigzag structural phase transition of a ^40Ca^＋ crystal in a homemade linear Paul trap. The values of the total temperature of the ion crystals during the phase transition are derived using the molecular-dynamics（MD） simulation method. A series of simulations revealed that the ratio of the radial to axial secular frequencies has a dependence on the total temperature that obeys different functional forms for linear and zigzag structures, and the transition point occurs where these functions intersect; thus, the critical value of the ratio of secular frequencies that drives the structure phase transition can be derived.

Study of Dielectric and Mechanical Spectra on Point Defects and Phase Transition in Ferroelectric Ceramics

Ferroelectric materials have enormous potential applications in advanced techniques. However, there are still many problems in its practical application. Dielectric and mechanical (internal friction) measurements are very sensitive to phase transitions, relaxation process of point defects, domain walls and their mobility, which have severe effect on ferroelectric properties. These make them become very good means to investigate substantial information on structural features and to explore the fundamental principles in ferroelectric materials and their applications. In this paper, the dielectric and internal friction measurement were used to investigate the behaviors for point defects and phase transition in ferroelectric ceramics such as Bi_ 4-x La_ x Ti_ 3 O_ 12 , Bi_ 4 Ti_ 3-y Nb_ y O_ 12 , SrBi_ 2 Ti_ 2 O_ 9 , PbZr_ x Ti_ 1-x O_ 3 ,_ PMN-PT. They were used to clarify the mechanism for some ferroelectric behaviors.

Directional Analysis of the Chaotic Superlattice around the Equilibrium Point in the Phase Space

The recently proposed method of our research group named as directional Lyapunov exponents（DLEs） is presented. Then, DLEs are used to analyze the eigenstructure of the output phase space around the equilibrium points. Finally, the impacts of the superlattice parameter changes on the characteristics of the output chaotic signal are analyzed. The experimental results show that parameter changes of the superlattice will affect the eigenstructure around the equilibrium points in the output phase space, and DLEs are sensitive to these changes.

Potential Correlation between Spontaneous Emulsification and the Plait Point in the System Water/Benzene/Ethanol: A Phase Diagram Approach

The separation of phases after the stability composition at a plait point is exceeded has significant effect on the reactions during spontaneous emulsification, but experimental efforts to obtain accurate information are extremely difficult, because even the smallest scattering of the numbers has a large effect on the result. In the present contribution a model system was applied that closely mirrored experimental values and the mass ratio of the two phases could be calculated with high accuracy. Extrapolation of the ratio between phase masses towards the critical composition showed the two phase masses each close to 0.5, while a composition with a miniscule difference from this composition extrapolated to 1.0. The results showed spontaneous emulsification between solutions at the plait point and water to consist of two processes;an initial extremely fast reaction and a slower process between the aqueous phase formed in the primary emulsification and water.

INTERSECTION POINT RULE OF THE RETENTION VALUE AND MOBILE PHASE COMPOSITION OF THE HOMOLOGUES IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

Based on the intersection point rule of the retention value and normal boiling point of homologues in reversed-phase high-performance liquid chromatography(RPLC), the intersection point rule of the retention value of homologues and mobile phase composition has been derived, and was testified by a lot of experimental data from the literature. With this newly proposed equation, we can use the retention value of the compound in one mobile phase composition to predict its retention value in any other mobile phase composition. For fourteen groups of homologues in five mobile phase compositions on five Kinds of columns, the overall average absolute error of 721 data sets is 2.8%.

Fluid phases of argon: A debate on the absence of van der Waals’ “critical point”

A phase diagram of argon based upon percolation transition loci determined from literature experimental p-V isotherms, and simulation values using a Lennard-Jones model shows three fluid phases. The liquid phase spans all temperatures, from a metastable amorphous ground state at 0K, to ultra-high T. There is a supercritical mesophase bounded by percolation transition loci, and a gas phase. Intersection of two percolation loci in the p-T plane thermodynamically defines a critical line between two coexisting gas and liquid critical states at T = Tc, and the single mesophase for T > Tc. A debate on the absence of a van der Waals critical point in the Gibbs p-T density surface is appended.

基于多点源的W-phase反演及其在2004年苏门答腊MW9.1大地震中的应用

在大地震发生后,快速准确地获得地震震源信息对应急救援十分重要,但是现有技术方法往往难以在快速准确地获取地震震源机制的同时获得破裂空间的分布特征。文章在传统W-phase反演技术的基础上开发了多点源W-phase反演方法,实现对大震破裂空间尺度上能量释放特征及震源机制的快速测定,并以2004年苏门答腊MW9.1大地震为例,测试程序的有效性。研究中设置了1、2、3、4、5、6个点源来分别测定此次地震的能量释放特征及震源机制。结果显示,震源机制随着空间位置由南向北的变化与俯冲面走向变化一致,与设定点源附近的历史地震震源机制高度吻合。因此,基于多点源的W-phase快速反投影技术将能更好获得大震空间能量释放特征,为震后应急及海啸预警提供科学支持。

铝基材料水解制氢技术研究进展

氢能是全球公认的清洁能源,被认为是化石能源的理想替代品,具有广泛的市场前景。铝价格低廉、密度较低且能量密度高,铝水解产氢是一种有效提供氢能的方法。简述了铝水反应的原理,介绍了目前国内外主流的3种铝基材料水解制氢技术(纯铝与酸碱溶液反应、机械球磨法制备铝基复合材料、熔铸法制备铝基低熔点合金)的研究进展,并探讨了不同技术的反应原理、不同添加物的作用机理,对比了各种技术的特点,提出熔铸法制备低熔点合金将成为日后研究的重点,最后对未来熔铸法制备铝基低熔点合金的前景进行了展望。

TOPOLOGICAL STRUCTURE OF THE SINGULAR POINTS OF THE THIRD ORDER PHASE LOCKED LOOP EQUATIONS WITH THE CHARACTER OF DETECTED PHASE BEING g(φ)=(1+k)sinφ/(1+kcosφ)

In this paper, we study the topological structure of the singular points of the third order phase locked loop equations with the character of detected phase being g(?) =(1+k)sin?/1+kcos?.

海上超稠油高温脱水技术研究

某海上超稠油富含胶质和沥青质,原油密度大、黏度高、油水密度差小、原油流动性差,并且油水乳化严重,导致热化学沉降脱水速度慢、脱水周期长。因海上平台空间受限和缺少稀油资源,该超稠油脱水不能采用陆上油田掺混稀油和长时间大罐沉降脱水的常规方法。开展了超稠油高温脱水技术研究,优选出耐高温破乳剂,破乳剂加剂量400 mg/L,在150℃高温、0.6~0.7 MPa压力下沉降4 h,含水15%~65%超稠油的原油含水率均达到<1%,实现了较好的脱水效果。根据室内脱水实验结果,获得海上超稠油高温脱水工艺参数,确定最佳破乳剂加药量、脱水温度和沉降时间,推荐了海上超稠油二段热化学脱水工艺方案。

松辽盆地白垩系青山口组一段页岩生、排烃组分特征及页岩油相态演化

松辽盆地白垩系青山口组一段(青一段)页岩有机质热演化程度跨度大、烃类流动性差异强。页岩油相态分析预测是页岩油勘探开发的重要难题。用低成熟页岩样品开展封闭体系及半封闭体系有机质热解实验,根据生、排烃组分特征对滞留烃的轻烃散失进行补偿校正,研究了页岩油组分演化特征。结合中央坳陷区主要生油凹陷典型井埋藏史、热演化史,研究了页岩油相态演化规律,提出了轻质页岩油勘探有利区和开发压力保护条件。研究结果表明:地质条件下随着有机质成熟度的升高,页岩油组分中轻质组分比例不断增加、气体逐渐增多,相包络线从高露点温度、低泡点压力依次向低露点温度、高泡点压力演化。齐家-古龙凹陷青一段页岩油在嫩江组中期油藏向挥发油油藏转化,长岭凹陷青一段页岩油从嫩江组末期开始油藏向挥发油油藏转化,三肇凹陷青一段页岩油则始终为黑油油藏。无论是黑油油藏还是挥发油油藏,均为单一液相。松辽盆地中央坳陷区青一段页岩油挥发油油藏主要分布在齐家-古龙凹陷中心和长岭凹陷北部有机质成熟度(镜质体反射率Ro)为1.3%~1.6%、地层压力为12.2~22.4 MPa的区域。

新见十九祀免簋历日与王年考

据新见十九祀免簋铭文“隹王十又九祀,正月既生霸庚戌”之记载,可知该器是一件王年、月份、日干支及月相四要素俱全的西周时期重要青铜器。文章在学界判定该器为西周中期之器的基础上,以月相定点说,采用“四分历”的古天文历术为技术手段,考定免簋所载王年与历日应当是:周穆王十九年(前988)正月十五日,正月初一朔日为乙未,实际用历司历应取为丙申朔。

超长空间激光传输数值模拟研究进展

文章主要围绕空间引力波探测中超长空间链路传输部分进行介绍,概述了目前国内外星间传输仿真时采用的计算方法,以及指向抖动引起的相位噪声分析方法。相较于地基引力波探测,空间引力波探测可以有效降低噪声,增加干涉臂长度,从而实现更高精度、更低频率的探测。在长达数百万公里的传输距离,以及皮米量级数值模拟的精度要求下,需要考虑指向角变化引起的相位噪声。研究表明,在2.5×10~9 m的传输距离下,离焦和像散是影响指向抖动噪声的主要像差。通常情况下,相位驻点位置与原点位置存在一定偏离,需要对望远镜角度进行调整,才能使相位噪声最小化。在相位驻点位置进行引力波探测,可以有效降低相位噪声,并降低望远镜出瞳波前的质量要求。而大的离焦像差与小的彗差可以使相位驻点接近光轴,提高接收到的激光功率。

经络腧穴学课程“三段四相”创新教学改革

针对经络腧穴学课程的学习内容庞杂、基础知识缺乏临床应用、考核形式单一,以及学生的专业学习能力急需培养等问题,教学团队积极开展以学生为中心的“三段四相”课程教学改革设计与实践。“三段实施”即线上自主探索、线下任务驱动、课后交流应用;“四相整合”为线上与线下混合式教学、课程思政融入日常教学、基础课程渗透临床应用、课堂学习延伸与课外拓展。“三段四相”模式结合了丰富的线上学习资源、通畅的讨论答疑渠道、多维的评价体系,促成经络腧穴学的教学改革进一步深化。

循环热力作用岩石I型断裂试验方法及其可行性研究

探明岩石在循环应力和循环温度作用后的断裂特性对于保障地下洞室压缩空气储能这一“双碳”工程的稳定性具有重要现实意义。提出了循环热力作用岩石I型断裂试验方法并对该试验方法的可行性进行了研究。为研究经循环应力和循环温度作用后的岩石受力变形特性和I型断裂特性,设计了相应的带裂缝岩石试件,并提出了相应的试验步骤;采用COMSOL Multiphysics软件对设计的试件进行升降温和单轴压缩试验模拟,采用相场断裂方法模拟三点弯梁断裂试验,获得相应热力响应和裂缝路径,论证试验方法的适用性与可行性。数值模拟结果表明,所提出的试验方法可获得与理论解误差极小的温度场、应力场和裂缝扩展路径,可只对一个试件进行试验而获得循环热力作用过程中的岩石受力变形特性以及循环后的I型断裂特性。

基于弱磁探测的三相电缆路径快速定位方法

城市地下电缆的快速定位对于城市的安全稳定发展具有重要的意义,然而目前城市内地下电缆探测精度较差,可探测区域较小。针对上述难点问题,该文提出一种基于弱磁探测的三相电缆路径快速定位方法,并推导三相电缆磁场辐射的基本规律,通过测量空间中任意五点的磁场幅值信息,结合粒子群数值迭代计算方法,利用五点定位原理,推算得到地下三相电缆的路径。最后,通过仿真和实验验证该方法的可行性,并进行定位误差分析。该方法对于提高地下电缆探测精度和深埋电缆的探测能力有一定的参考价值。