Construction of MnS/MoS_(2) heterostructure on two-dimensional MoS_(2) surface to regulate the reaction pathways for high-performance Li-O_(2) batteries

The inherent catalytic anisotropy of two-dimensional(2D) materials has limited the enhancement of LiO_(2) batteries(LOBs) performance due to the significantly different adsorption energies on 2D and edge surfaces.Tuning the adsorption strength in 2D materials to the reaction intermediates is essential for achieving high-performance LOBs.Herein,a MnS/MoS_(2) heterostructure is designed as a cathode catalyst by adjusting the adsorption behavior at the surface.Different from the toroidal-like discharge products on the MoS_(2) cathode,the MnS/MoS_(2) surface displays an improved adsorption energy to reaction species,thereby promoting the growth of the film-like discharge products.MnS can disturb the layer growth of MoS_(2),in which the stack edge plane features a strong interaction with the intermediates and limits the growth of the discharge products.Experimental and theoretical results confirm that the MnS/MoS_(2) heterostructure possesses improved electron transfer kinetics at the interface and plays an important role in the adsorption process for reaction species,which finally affects the morphology of Li_2O_(2),In consequence,the MnS/MoS_(2) heterostructure exhibits a high specific capacity of 11696.0 mA h g^(-1) and good cycle stability over 1800 h with a fixed specific capacity of 600 mA h g^(-1) at current density of100 mA g^(-1) This work provides a novel interfacial engineering strategy to enhance the performance of LOBs by tuning the adsorption properties of 2D materials.

Two-dimensional plane strain consolidation of unsaturated soils considering the depth-dependent stress

In practical engineering,the total vertical stress in the soil layer is not constant due to stress diffusion,and varies with time and depth.Therefore,the purpose of this paper is to investigate the effect of stress diffusion on the two-dimensional(2D)plane strain consolidation properties of unsaturated soils when the stress varies with time and depth.A series of semi-analytical solutions in terms of excess pore air and water pressures and settlement for 2D plane strain consolidation of unsaturated soils can be derived with the joint use of Laplace transform and Fourier sine series expansion.Then,the inverse Laplace transform of the semi-analytical solution is given in the time domain using a self-programmed code based on Crump’s method.The reliability of the obtained solutions is proved by the degeneration.Finally,the 2D plots of excess pore pressures and the curves of settlement varying with time,considering different physical parameters of unsaturated soil stratum and depth-dependent stress,are depicted and analyzed to study the 2D plane strain consolidation properties of unsaturated soils subjected to the depthdependent stress.

DETERMINATION OF PARAMETERS IN A TWO-DIMENSIONAL MODEL FOR FIXED-BED ADSORBERS

A new method is proposed for the determination of the parameters in a two-dimensionalmodel which characterizes the properties of axial and radial mixing and mass transport in afixed-bed adsorber.Parameter estimation for the model is carried out with methane-air-5A molecularsieve in a bed under the condition of step injection of tracer from a point on the main axis of thebed by the curve fitting method in the time domain.

Fault plane parameters of Tancheng M81/2 earthquake on the basis of present-day seismological data

The great Tancheng earthquake of M81/2 occurred in 1668 was the largest seismic event ever recorded in history in eastern China. This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area. We relocated those earthquakes with the double-difference method and found focal mechanism solutions using gird test method. The inversion results are as follows： the strike is 21.6°, the dip angle is 89.5°, the slip angle is 170°, the fault length is about 160 km, the lower-boundary depth is about 32 km and the buried depth of upper boundary is about 4 km. This shows that the seismic fault is a NNE-trending upright right-lateral strike-slip fault and has cut through the crust. Moreover, the surface seismic fault, intensity distribution of the earthquake, earthquake-depth distribution and seismic-wave velocity profile in the focal area all verified our study result.

Different angle-resolved polarization configurations of Raman spectroscopy: A case on the basal and edge plane of two-dimensional materials

Angle-resolved polarized Raman（ARPR） spectroscopy can be utilized to assign the Raman modes based on crystal symmetry and Raman selection rules and also to characterize the crystallographic orientation of anisotropic materials.However, polarized Raman measurements can be implemented by several different configurations and thus lead to different results. In this work, we systematically analyze three typical polarization configurations： 1） to change the polarization of the incident laser, 2） to rotate the sample, and 3） to set a half-wave plate in the common optical path of incident laser and scattered Raman signal to simultaneously vary their polarization directions. We provide a general approach of polarization analysis on the Raman intensity under the three polarization configurations and demonstrate that the latter two cases are equivalent to each other. Because the basal plane of highly ordered pyrolytic graphite（HOPG） exhibits isotropic feature and its edge plane is highly anisotropic, HOPG can be treated as a modelling system to study ARPR spectroscopy of twodimensional materials on their basal and edge planes. Therefore, we verify the ARPR behaviors of HOPG on its basal and edge planes at three different polarization configurations. The orientation direction of HOPG edge plane can be accurately determined by the angle-resolved polarization-dependent G mode intensity without rotating sample, which shows potential application for orientation determination of other anisotropic and vertically standing two-dimensional materials and other materials.

Optimization of Honing Wheel Structure Parameters in Ultra-precision Plane Honing

Free abrasive particle machining in simple machine such as: honing, polishing can get higher surface finish mirror, but surface error, and working procedure is hard to control. Therefore, the vertical disposed ultra-precision plane honing method by ultra-particle diamond honing wheel is put forward to. The results of experiments indicate: plane-honing wheel has higher machining accuracy and machining efficiency. But at the same time the structure parameters of honing wheel effects on machining accuracy. By analyzing the relation of honing wheel structure parameters and workpiece machining accuracy, the relation of honing wheel and wear coefficient, then this paper gets honing wheel structure parameters in the condition of best accuracy coefficient and wear coefficient, and resolve the problem of choosing honing wheel structure parameters in ultra-precision plane honing at last. This paper analyses the relation of honing wheel structure parameters and workpiece machining accuracy coefficient and wear coefficient, by building relative movement math model of honing wheel and workpiece in plane honing. Through theory calculating, the result indicate: about honing machine tools for large volume manufacture, honing wheel wear is main effect factor, so honing wheel should adopt obverse triangle radial structure. About honing machining for high accuracy and low-batch quantities, machining accuracy coefficient is main factors; so honing wheel should adopt reverse triangle radial structure. Neglected the manufacturing factors of honing wheel, then we can design honing wheel with high power curve structure to meet the need of machining accuracy coefficient and honing wheel wear coefficient in higher accuracy honing.

Development and application of a two-dimensional water quality model for the Daqinghe River Mouth of the Dianchi Lake

Water quality models are important tools to support the optimization of aquatic ecosystem rehabilitation programs and assess their efficiency. Basing on the flow conditions of the Daqinghe River Mouth of the Dianchi Lake, China, a two-dimensional water quality model was developed in the research. The hydrodynamics module was numerically solved by the alternating direction iteration （ADI） method. The parameters of the water quality module were obtained through the in situ experiments and the laboratory analyses that were conducted from 2006 to 2007. The model was calibrated and verified by the observation data in 2007. Among the four modelled key variables, i.e., water level, COD （in CODcr）, NH4＋-N and PO43-P the minimum value of the coefficient of determination （COD） was 0.69, indicating the model performed reasonably well. The developed model was then applied to simulate the water quality changes at a downstream cross-section assuming that the designed restoration programs were implemented. According to the simulated results, the restoration programs could cut down the loads of COD and PO43-P about 15%. Such a load reduction, unfortunately, would have very little effect on the NH4^＋-N removal. Moreover, the water quality at the outlet cross-section would be still in class V （3838-02）, indicating more measures should be taken to further reduce the loads. The study demonstrated the capability of water quality models to support aquatic ecosystem restorations.

Discrete gap breathers in a two-dimensional diatomic face-centered square lattice

In this paper we study the existence and stability of two-dimensional discrete gap breathers in a two-dimensional diatomic face-centered square lattice consisting of alternating light and heavy atoms, with on-site potential and coupling potential. This study is focused on two-dimensional breathers with their frequency in the gap that separates the acoustic and optical bands of the phonon spectrum. We demonstrate the possibility of the existence of two-dimensional gap breathers by using a numerical method. Six types of two-dimensional gap breathers are obtained, i.e., symmetric, mirror-symmetric and asymmetric, whether the center of the breather is on a light or a heavy atom. The difference between one-dimensional discrete gap breathers and two-dimensional discrete gap breathers is also discussed. We use Aubry＇s theory to analyze the stability of discrete gap breathers in the two-dimensional diatomic face-centered square lattice.

Flower Pollination Heuristics for Parameter Estimation of Electromagnetic Plane Waves

For the last few decades,the parameter estimation of electromagnetic plane waves i.e.,far field sources,impinging on antenna array geometries has attracted a lot of researchers due to their use in radar,sonar and under water acoustic environments.In this work,nature inspired heuristics based on the flower pollination algorithm(FPA)is designed for the estimation problem of amplitude and direction of arrival of far field sources impinging on uniform linear array(ULA).Using the approximation in mean squared error sense,a fitness function of the problem is developed and the strength of the FPA is utilized for optimization of the cost function representing scenarios for various number of sources non-coherent located in the far field.The worth of the proposed FPA based nature inspired computing heuristic is established through assessment studies on fitness,histograms,cumulative distribution function and box plots analysis.The other worthy perks of the proposed scheme include simplicity of concept,ease in the implementation,extendibility and wide range of applicability to solve complex optimization problems.These salient features make the proposed approach as an attractive alternative to be exploited for solving different parameter estimation problems arising in nonlinear systems,power signal modelling,image processing and fault diagnosis.

Verifiable Secret Sharing Scheme Based on the Plane Parametric Curve

Verifiable secret sharing is a special kind of secret sharing. In this paper, A secure and efficient threshold secret sharing scheme is proposed by using the plane parametric curve on the basis of the principle of secret sharing. And the performance of this threshold scheme is analyzed. The results reveal that the threshold scheme has its own advantage of one-parameter representation for a master key, and it is a perfect ideal secret sharing scheme. It can easily detect cheaters by single operation in the participants so that the probability of valid cheating is less than 1/p (where p is a large prime).

Comment on “Band gaps structure and semi-Dirac point of two-dimensional function photonic crystals” by Si-Qi Zhang et al.

Recently, Zhang et al. （Chin. Phys. B 26 024208 （2017）） investigated the band gap structures and semi-Dirac point of two-dimensional function photonic crystals, and the equations for the plane wave expansion method were induced to obtain the band structures. That report shows the band diagrams with the effects of function coefficient k and medium column ra under TE and TM waves. The proposed results look correct at first glance, but the authors made some mistakes in their report. Thus, the calculated results in their paper are incorrect. According to our calculations, the errors in their report are corrected, and the correct band structures also are presented in this paper.

On Two-Dimensional Above-Barrier Penetration and Sub-Barrier Tunneling for Non-Relativistic Particles and Photons

We study the two-dimensional above-barrier penetration and the sub-barrier tunneling of non-relativistic particles and photons, described in the quasi-monochromatic approximation by simple plane waves. Our scheme represents the motion from the left free-motion zero-potential region to the right zero-potential region through the intermediate region with a one-dimensional rectangular potential barrier along the axis, normal to the both parallel interfaces between all three regions, and with the zero potential along the axis, parallel to the those interfaces. We have firstly obtained the analytical expressions for the infinite series of multiple internal and external reflections and also of multiple transmitted waves of particles and photons, with equal shifts between them along the interfaces for the above-barrier penetration and with various shifts between them in the case of the sub-barrier tunneling. Finally the Hartman and Fletcher effect for any transmitted wave is established.

Value of two-dimensional speckle tracking imaging in quantitative assessment of left ventricular function in patients with OSAS

Objective: To research the clinical application of two-dimensional speckle tracking imaging (2D-STI) in quantitative assessment of left ventricular function in patients with obstructive sleep apnea-hypopnea syndrome (OSAS). Method: From July 2016 to December 2018, 86 patients with OSAS were selected as OSAS group. According to sleep apnea hypopnea index (AHI), they were divided into mild OSAS group (24 cases), moderate OSAS group (29 cases) and severe OSAS group (33 cases). Another 50 healthy volunteers who underwent physical examination in our hospital during the same period were selected as the control group. The left ventricular function of all patients was quantitatively assessed by 2D-STI. The left ventricular function of all patients was quantitatively assessed by 2D-STI. The results of routine echocardiography and left ventricular global strain parameters of the OSAS group, the control group and the OSAS patients with different severity were compared and analyzed. Result: There were no significant differences in the levels of left ventricular ejection fraction (LVEF), left ventricular end diastolic diameter (LVEDd), left ventricular end systolic diameter (LVESd) between the two groups and OSAS patients with different severity (P>0.05). The levels of IVST, LVPW and LVMI in the OSAS group were significantly higher than those in the control group, the levels of end-diastolic interventricular septal thickness (IVS), left ventricular posterior wall thickness (LVPW), left ventricular mass index (LVMI) in the severe OSAS group were significantly higher than those in the mild and moderate OSAS group, and the levels of IVST, LVPW and LVMI in the moderate OSAS group were significantly higher than those in the mild OSAS group, there were significant differences between groups (P<0.05). The levels of GLS, GRS and GCS in the OSAS group were significantly lower than those in the control group (P<0.05). GLS, GRS and GCS levels in the severe OSAS group were significantly lower than those in the mild OSAS group and the moderate OSAS group, while the levels of global longitudinal strain (GLS), global radial strain (GRS) and global circumferential strain (GCS) in the moderate OSAS group were significantly lower than those in the mild OSAS group (P<0.05). Conclusion: The left ventricular systolic function of OSAS patients is obviously impaired. Left ventricular function in OSAS patients can be assessed timely and accurately by two-dimensional speckle tracking imaging.

Experimental study on tensile failure process of double-K fracture parameters in roller compacted concrete layer

Study on failure of soft stratum of roller compacted concrete (RCC) is an important aspect of stability of high RCC dam. Six kinds of specimens with different interfaces were investigated by wedge splitting method. Double-K fracture parameters (initial fracture parameter and unsteady fracture parameter) were calculated by the concrete double-K fracture theory. It is indicated that the approach of construction joint or old joint after RCC final set is the most efficient among the six cases, and its fracture parameter is the largest among them. Its propagation path is sinuous. Its failure surface is scraggly. Bedding plane crack fails at the underside of the concrete surface, bond course or the surface between them for each approach. So disturbance on the underside of the concrete surface should be avoided or decreased at best during RCC construction.

First Determination of Source Parameters of Moderate Earthquakes (4.1 ≤ M ≤ 5.1) in Morocco from Spectral Analysis

Recent installation of an array of broad band seismological stations in Morocco allowed us to study the records of five recent (2005-2008) moderate earthquakes (4.1 ≤ M ≤ 5.1) in order to determine their source parameters (seismic moment, fault slip, rupture area and stress drop) from P-wave spectra. We also studied the older Rissani events of 1992 using teleseismic data. Values of Mo, r, Δu and Δσ are, respectively, 1.1 × 1013 - 6 × 1016 Nm;0.50 - 3.9 km;0.8 - 5.8 cm and 0.3 - 1.49 MPa. The results are in accordance with the seismotectonic and geodynamic setting of Morocco as, for instance, the amount of slip along the faults with respect to the relative displacement of Nubia to Iberia (~4 mm·yr-1) determined from GPS data, taking into account the period of stress accumulation. However, some events show very variable corner frequency and low-frequency amplitude values which lead to considerably higher stress drop and fault slip values, especially at the nearest stations, which may reflect some site effects or uncertainties on depth and take-off angles.

盖州青石岭震群断层面参数的确定及构造应力场特征研究

根据之前学者的双差定位结果,使用Fit_Fault软件包计算盖州青石岭震群发震断层面走向为114.30°,倾角74.67°。收集2001年至2011年辽宁地区的震源机制解资料,采用全局网格搜索算法,反演该地区的构造应力场,其主压应力轴为NEE向,主张应力轴为NNW向,整体呈现拉张的应力状态。并据此确定出青石岭震群发震断层的滑动角是35.49°,为左旋走滑性质。模拟在辽宁地区构造应力体系下各种产状的断层面上可产生的相对剪应力和相对正应力分布情况,发现该震群发震断层面上的相对剪应力和相对正应力分别为0.513和0.576。分析认为盖州青石岭震群是一处地质薄弱带,背景构造应力场在其最近一期的活动中未起主导作用。

L_(5)/S_(1)椎间盘突出重吸收的腰骶矢状面参数改变

背景:以往有研究表明了腰骶矢状面参数与腰椎间盘突出重吸收现象的相关性,但腰骶矢状面参数包括了腰椎前凸角、腰骶关节角、骶骨倾斜角等众多参数,且各参数对椎间盘重吸收的影响具有差异性;另外目前对具体某一节段椎间盘突出重吸收的研究尚少,测量数据也多从数字化X射线摄影或CT中获取,而从MRI中测量的腰骶矢状面参数与L_(5)/S_(1)椎间盘突出后发生重吸收的相关性报道则较少见。目的:观察L_(5)/S_(1)椎间盘突出重吸收后腰椎矢状面参数的相应改变,筛选出椎间盘重吸收过程中变化最显著的腰骶矢状面参数。方法:选择具有完整MRI影像资料的57例腰椎间盘突出症患者,符合腰椎间盘突出症诊断标准,且单纯接受非手术治疗L_(5)/S_(1)突出节段发生重吸收现象。MRI测量冠状面上的最大突出层面的突出面积、腰骶矢状面参数,包括腰椎曲线指数、腰椎前凸角(α)、L_(5)/S_(1)椎间盘角(β)、椎间隙高度、腰骶关节角、骶骨平台角、骶骨倾斜角、下腰椎前凸角,将腰骶矢状面参数在R软件中采用随机森林模型进行变量重要性排序,再将显著的变量进行多元线性回归拟合,并通过配对样本t检验分析治疗前后各参数之间的变化。结果与结论:①共计57例L_(5)/S_(1)腰椎间盘突出症患者纳入研究,患者症状及影像学特征都在很大程度上较治疗前明显缓解;②治疗前的美国密歇根州立大学(MSU)分型为1级4例,2级29例,3级24例,经治疗后变为1级48例,2级9例;③随机森林模型提示椎间隙高度、腰椎曲线指数、骶骨倾斜角、下腰椎前凸角在L_(5)/S_(1)椎间盘突出重吸收中变化显著,而其变化显著性排序为腰椎曲线指数>椎间隙高度>骶骨倾斜角>下腰椎前凸角;④治疗后的腰椎曲线指数、腰椎前凸角、骶骨平台角较治疗前增大,差异均有显著性意义(P<0.05);椎间盘角、椎间隙高度、下腰椎前凸角、骶骨倾斜角、腰骶关节角治疗前后比较差异无显著性意义(P>0.05);⑤腰椎曲线指数是突出椎间盘重吸收中变化最显著的腰骶矢状面参数,而腰椎曲线指数、骶骨倾斜角、下腰椎前凸角是临床常用的描述腰椎曲度变化的参数,说明L_(5)/S_(1)椎间盘突出重吸收与腰椎曲度变化存在相关性,提示在腰椎间盘突出症治疗中可通过改善或恢复紊乱的腰椎曲度进而达到临床治愈的目的。

基于钻孔摄像的岩体结构面参数快速提取研究

目的:岩体结构面决定着岩体强度和承载能力,直接影响着地下工程允许暴露面积和暴露时间。钻孔摄像是获取岩体深部结构面的重要方法。论文针对当前钻孔摄像获得岩体结构面参数自动提取难、精度差等问题开展研究。方法:分析了钻孔摄像中结构面的特征,研究了三维钻孔模型到二维平面展开过程中,钻孔图像中结构面与平面展开图上的节理轨迹的对应关系,提出了基于钻孔摄像图像信息反向重构三维空间钻孔和结构面的流程和参数提取方法。重点突破了基于钻孔图像信息的节理信息提取的坐标转换、结构面拟合和结构面倾向、倾角和迹宽等参数提取方法等三个关键技术(创新点),利用Python开发语言,基于PyCharm作为集成开发环境,使用PyQt5图形控件、Numpy数值计算库和SQLite数据库,开发了钻孔图像结构面参数自动提取软件,并成功应用于某矿山地下钻孔岩体结构面参数的提取。结果:应用结果表明本文设计的方法和开发的系统具有提取速度快、准确度高的特点。结论:本文研究为钻孔结构面参数快速提取提供了一套有益的方法。

磁场中受垂直激励非线性单摆的动力学分析

在结合能量采集等生活实际应用领域的基础上,构建了一个在磁场中的单摆模型,并深入分析了其动力学行为,旨在为工程摆设备的工作性能参数的优化选择提供理论支持。首先通过势能函数导出了势阱曲线,并探讨了势阱和势垒对系统动力特性的影响。然后采用Melnikov函数方法,不仅求解了系统的同宿轨迹和产生Smale意义上混沌的临界条件,还揭示了单摆系统振幅与系统频率之间的关系,并提出了计算同宿分岔曲线的数值方法,成功绘制了分岔曲线。最后通过综合运用单参数分岔、Lyapunov指数、相轨迹图、庞加莱截面图以及双参数平面上的分岔图等分析工具,展示了摆动系统演进至混沌的两种路径:倍周期分岔和鞍结分岔。此外,还揭示了这类单摆系统的全局运动规律,如倍周期分岔、吸引子倍增、鞍结分岔等,进一步明确了相关参数对工程系统工作性能的影响及其作用机制。

聚焦换能器声场特性的快速检验方法

高强度聚焦超声(HIFU)已在无创肿瘤治疗方面展示出巨大的应用潜力,而换能器聚焦性能的优劣对疗效起到至关重要的作用,因此声场的精确测量成为实际应用的重要保障.由于加工工艺和安装精度的限制,聚焦换能器的实际声场和理想声场可能存在一定偏差.针对传统三维扫描测量存在速度慢和精度低的问题,提出了一种基于双平面双精度测量的聚焦换能器声场特性快速检验方法.通过沿理想z轴的高精度一维扫描确定换能器倾斜角范围,在声压极值点所在横截面内利用低精度和高精度变邻域搜索法实现最大声压点的精准定位,进一步通过焦域内双平面最大声压点构建声场的实际轴线,完成实际声场焦点的精确定位,最后基于实际焦平面内轴向与径向的高精度测量结果,计算获得焦域尺寸、旁瓣大小、分布对称性和声功率等性能参数.利用构建的声场扫描实验系统对聚焦换能器声场进行三维扫描和快速测量,结果表明在相同的测量精度(0.1 mm)下可以有效提高测量速度百倍以上,具有测量速度快、测量精度易于调节和性能分析全面等优点.方法为聚焦换能器检验提供一种高精度的快速声场测量新技术,在超声治疗仪器的检验中具有重要的指导意义与应用价值.