Validity ranges of interfacial wave theories in a two-layer fluid system

In the present paper, we endeavor to accomplish a diagram, which demarcates the validity ranges for interfacial wave theories in a two-layer system, to meet the needs of design in ocean engineering. On the basis of the available solutions of periodic and solitary waves, we propose a guideline as principle to identify the validity regions of the interfacial wave theories in terms of wave period T, wave height H, upper layer thickness dl, and lower layer thick-ness d2, instead of only one parameter-water depth d as in the water surface wave circumstance. The diagram proposed here happens to be Le Mehaute＇s plot for free surface waves if water depth ratio r= d1/d2 approaches to infinity and the upper layer water density p1 to zero. On the contrary, the diagram for water surface waves can be used for two-layer interfacial waves if gravity acceleration g in it is replaced by the reduced gravity defined in this study under the condition of σ=（P2 - Pl）/P2 → 1.0 and r 〉 1.0. In the end, several figures of the validity ranges for various interfacial wavetheories in the two-layer fluid are given and compared with the results for surface waves.

Eco-environment range in the source regions of the Yangtze and Yellow rivers

Based on geographical and hydrological extents delimited, four principles are identified, as the bases for delineating the ranges of the source regions of the Yangtze and Yellow rivers in the paper. According to the comprehensive analysis of topographical characteristics, climate conditions, vegetation distribution and hydrological features, the source region ranges for eco-environmental study are defined. The eastern boundary point is Dari hydrological station in the upper reach of the Yellow River. The watershed above Dari hydrological station is the source region of the Yellow River which drains an area of 4.49×10 4 km 2 . Natural environment is characterized by the major topographical types of plateau lakes and marshland, gentle landforms, alpine cold semi-arid climate, and steppe and meadow vegetation in the source region of the Yellow River. The eastern boundary point is the convergent site of the Nieqiaqu and the Tongtian River in the upstream of the Yangtze River. The watershed above the convergent site is the source region of the Yangtze River, with a watershed area of 12.24×10 4 km 2 . Hills and alpine plain topography, gentle terrain, alpine cold arid and semi-arid climate, and alpine cold grassland and meadow are natural conditions in the source region of the Yangtze River.

Increasing the range accuracy of three-dimensional ghost imaging ladar using optimum slicing number method

The range accuracy of three-dimensional（3D） ghost imaging is derived. Based on the derived range accuracy equation, the relationship between the slicing number and the range accuracy is analyzed and an optimum slicing number（OSN）is determined. According to the OSN, an improved 3D ghost imaging algorithm is proposed to increase the range accuracy. Experimental results indicate that the slicing number can affect the range accuracy significantly and the highest range accuracy can be achieved if the 3D ghost imaging system works with OSN.

IMAGING ANALYSIS OF FREQUENCY MODULATION CONTINUOUS WAVE SYNTHETIC APERTURE RADAR IN NEAR RANGE MODE

Frequency-Modulation Continuous-Wave Synthetic Aperture Radar(FMCW SAR)has shown great potential in the applications of civil and military fields because of its easy deployment and low cost.However,most of these work and analysis are concentrated on airborne FMCW SAR,where the characteristics of the imaging geometry and signal are much similar to that of traditional pulsed-SAR.As a result,a series of test campaigns of automobile-based FMCW SAR were sponsored by Institute of Electronics,Chinese Academy of Sciences(IECAS)in the autumn of 2012.In this paper,we analyze the imaging issues of FMCW SAR in automobile mode(named as near range mode),where a vehicle is used as moving platform and a large looking angle is configured.The imaging geometry and signal properties are analyzed in detail.We emphasize the difference of the near range mode from the traditional airborne SAR mode.Based on the analysis,a focusing approach is proposed in the paper to handle the data focusing in the case.Simulation experiment and real data of automobile FMCW SAR are used to validate the analysis.

Experimental Evaluation of CT Number Changes in 320-Row CBCT Volume Scan for Proton Range Calculation

We investigated the longitudinal positional dependence of CT number in 320-row Cone Beam Computed Tomography (CBCT) volume scan (320-row volume scan) using a simple geometric phantom (SGP) and a chest simulation phantom (CSP) in order to evaluate its effect on proton range calculation. The SGP consisted of lung substitute material (LSM) and a cylindrical phantom (CP) made of high-density polyethylene. The CSP was an anthropomorphic phantom similar to the human chest. The two phantoms were scanned using 320-row volume scan in various longitudinal positions from the central beam axis. In experiments using the SGP, an image blur at the boundary of the two materials became gradually evident when the LSM was placed far away from the beam central axis. The image blur of the phantom was consistent with the gradation in CT number. The maximum difference in CT numbers between the 64-row helical scan and 320-row volume scan at the boundary of the two materials was consistent with approximately 50% of the relative proton stopping power. In contrast, the CT number profile in each longitudinal position was fairly consistent and longitudinal positional dependence rarely occurred in the CSP experiments. Pass lengths of CT beams through areas with widely different electron densities were shorter, and thus did not significantly impact CT numbers. Based on findings from the CSP experiments, we considered 320-row volume scan to be feasible for proton range calculation in clinical settings, although the relatively large longitudinal positional dependence of CT number should be accounted for when doing so.

Fatigue Behaviour of Tubular Joints Made of China-Made Platform Steel

In China, a nationwide research program on fatigue behaviour of tubular joints made of China-made platform steel was carried out from 1983 to 1990, which was set by the Tubular Joint Research Committee for Offshore Structures (TJCOS) of China. This paper gives an outline of the basic properties of the China-made platform steel and fatigue test of tubular joints, including test specimens, test particulars and test results. A p-S-N curve based on the test results was established which reveals that the fatigue strength of tubular joints is fairly good. The thickness effect and effect of corrosion on fatigue strength in sea water are briefly discussed.

Evolution and breaking of a propagating internal wave in stratified ocean

The evolution and breaking of a propagating internal wave are directly numerically simulated using a pseudo-spectral method. The mechanism of PSI （ parametric subharmonic instability） involved in the evolution is testified clearly. It dominates gradually in nonlinear resonant interactions. As a consequence, the energy cascades to a second plant wave packet which has lower frequencies and higher wavenumbers than that of the primary wave. With the growth of this wave packet, wave breaking occurs and causes strongly nonlinear regime, i.e. stratified turbulence. The strong mixing and intermittent of the turbulence can be learned from the evolution of the total energy and kurtosis of vorticity vs. time. Some statistic properties of the stratified turbulence are also analyzed, including the spectra of KE （kinetic energy） and PE （potential energy）. The results show that the PE spectra display a wavenumber range scaling as 0. 2 N^4ky^-3 （N is the Brunt - Vaisala frequency, k, is the vertical wavenumber）, which is called buoyancy sub-range. However, the KE spectra cannot satisfy the negative cubic law of vertical wavenumber, which have a much larger downtrend than that of the PE spectra, for the potential energy is transferred more efficiently toward small scales than the kinetic energy. The Cox number of diapycnal diffusivity is also calculated, and it shows a good consistency with the observations and deductions in the ocean interior, during the stage of the stratified turbulence maintaining a fairly active level.

Statistical Mechanics Model of Liquid Binary Alloy（Ⅱ）─Parameters of Liquid Binary Alloy

Some parameters of liquid binary alloy were investigated , and the calculation formulae were proposed.According to the formulae for calculating coordination number, the accordination numbers of Cu-Zr , Fe-B, Ni-B, Co-P, Fe-P systems were calculated, the results agree well with those in literature and in experiments ofthis study.

Image Steganography by Pixel-Value Differencing Using General Quantization Ranges

A new steganographic method by pixel-value differencing(PVD)using general quantization ranges of pixel pairs’difference values is proposed.The objective of this method is to provide a data embedding technique with a range table with range widths not limited to powers of 2,extending PVD-based methods to enhance their flexibility and data-embedding rates without changing their capabilities to resist security attacks.Specifically,the conventional PVD technique partitions a grayscale image into 1×2 non-overlapping blocks.The entire range[0,255]of all possible absolute values of the pixel pairs’grayscale differences in the blocks is divided into multiple quantization ranges.The width of each quantization range is a power of two to facilitate the direct embedding of the bit information with high embedding rates.Without using power-of-two range widths,the embedding rates can drop using conventional embedding techniques.In contrast,the proposed method uses general quantization range widths,and a multiple-based number conversion mechanism is employed skillfully to implement the use of nonpower-of-two range widths,with each pixel pair being employed to embed a digit in the multiple-based number.All the message bits are converted into a big multiple-based number whose digits can be embedded into the pixel pairs with a higher embedding rate.Good experimental results showed the feasibility of the proposed method and its resistance to security attacks.In addition,implementation examples are provided,where the proposed method adopts non-power-of-two range widths and employsmultiple-based number conversion to expand the data-hiding and steganalysis-resisting capabilities of other PVD methods.

ON THE RANGE OF RANDOM WALKS IN RANDOM ENVIRONMENT

The range of random walk on Z￣d in symmetric random environment is investigated. As results, it is proved that the strong law of large numbers for the range of random walk on Zdin some random environments holds if d≥ 3, and a weak law of large numbers holds for d= 1.

基于DCS-惯性权重组合的柔性机械臂运动轨迹控制系统研究

为了有效调控机械臂运动幅度,避免柔性机械臂实际运动轨迹与目标轨迹发生较大的偏差,设计一种基于分散控制系统(DCS)-惯性权重组合的柔性机械臂运动轨迹控制系统,它是一个集合了计算机、通信、显示和控制的计算机系统,该系统由过程控制和过程监控。通过DCS算法控制监测对象行为幅度并计算柔性机械臂惯性权重,利用DCS-惯性权重组合求解素数控制指标的具体数值,实现了对柔性机械臂运动轨迹控制系统的软件设计。实验结果表明,DCS-惯性权重组合算法作用下的机械臂末端坐标在横轴、纵轴、空间轴方向上的运动幅值均可以被控制在10个单位长度之内,并且在0.52 s内进入机械臂运动轨迹最佳控制状态,运动轨迹差值最大仅为0.01 rad,验证了该系统具备可行性和有效性。

基于ABAQUS的气动潜孔锤球齿碎岩及布齿优化

为提高坚硬地层大直径潜孔锤的破岩效率与使用寿命,运用ABAQUS软件建立了球齿碎岩仿真模型,对比分析?18 mm球齿在不同钻进参数下冲击切削碎岩过程中的破碎比功、侵入深度、破碎范围与应力影响范围等曲线,优选钻进参数和布齿。分析结果表明:当钻压为1.2 kN、冲击功为30 J时,对岩石的破碎效率较高,球齿入岩的位移可达0.67 mm,并对岩石进行应力界限划分,得出应力影响范围为43.4 mm;通过双齿冲击切削模拟确定了较为优秀的圈距与间距:圈距取47.4 mm,间距取43.4~51.4 mm;考虑到球齿的磨损,利用圈距与间距对?711 mm大直径潜孔锤进行了优化布齿。

基于光循环移频环的可重构微波光子滤波器

基于光循环移频环的频域多载波特性和时间延迟特性构建了一种结构简单、高可重构性的微波光子滤波器。光循环移频环的等间隔时间延迟特性可用于在不同抽头之间引入时间延迟。另外,由于光循环移频环所产生的多个光载波之间的频率差较大,因而可以避免由于光载波的高相干性所导致的强度干扰,可实现稳定的频谱响应。利用可编程光滤波器对光循环移频环的输出光谱进行整形,可实现不同抽头的筛选和每个抽头权重的调节,从而获得微波光子滤波器抽头数和自由频谱范围的有效调谐。实验展示了自由频谱范围为3.85 MHz情况下抽头数在2、5、10之间的切换,以及抽头数为2的情况下,自由频谱范围在3.85 MHz、1.925 MHz以及770 kHz之间的切换。通过光谱整形技术,实现了微波光子滤波器抽头数和自由频谱范围的可重构。

0~3岁婴幼儿Cariostat龋活跃性、唾液生化指标调查及其与婴幼儿患龋情况的关系

目的调查0~3岁婴幼儿Cariostat龋活跃性、唾液生化指标水平及其与婴幼儿患龋情况的关系。方法选取2021年1月至2022年12月在该院进行口腔健康检查的186例0~3岁婴幼儿作为研究对象。所有婴幼儿均接受Cariostat龋活跃性、唾液生化指标[pH值、氯离子(Cl^(-))、氨离子(NH_(4)^(+))、硝酸根离子(NO_(3)^(-))、溴离子(Br^(-))、镁离子(Mg^(2+))、钙离子(Ca^(2+))]检查,分析不同年龄段、性别婴幼儿患龋情况[患龋率、龋坏牙数(dt)、龋失补指数(dmft)]。根据是否患龋将婴幼儿分为患龋组和健康组,比较两组婴幼儿Cariostat龋活跃性、唾液生化指标水平。采用Pearson相关对Cariostat值、Cl^(-)、NH_(4)^(+)、Br^(-)、NO_(3)^(-)与dt、dmft的相关性进行分析。结果不同年龄段婴幼儿患龋率、dt、dmft比较,差异均有统计学意义(P<0.05);不同性别婴幼儿患龋率、dt、dmft比较,差异均无统计学意义(P>0.05)。患龋组婴幼儿Cariostat值、Cl^(-)、NH_(4)^(+)、Br^(-)、Mg^(2+)、Ca^(2+)水平均高于健康组,pH值、NO_(3)^(-)水平均低于健康组,差异均有统计学意义(P<0.05)。Pearson相关分析结果显示,Cariostat值、Cl^(-)、NH_(4)^(+)、Br^(-)水平与dt、dmft均呈正相关(P<0.05),NO_(3)^(-)水平与dt、dmft呈负相关(P<0.05)。结论0~3岁婴幼儿患龋率整体偏高,并且随着年龄增长患龋率明显上升。Cariostat龋活跃性、唾液生化指标水平与婴幼儿dt、dmft密切相关,可用于临床辅助评估0~3岁婴幼儿的患龋情况。

中国社区老年人咀嚼能力与虚弱的相关性研究

目的探讨中国社区老年人咀嚼能力与虚弱的相关性。方法选取2018年中国老年健康和家庭幸福调查研究(CLHLS-HF)数据中12678例社区老年人为研究对象。采用多因素Logistic回归分析探讨社区老年人咀嚼能力与虚弱的关系,并采用基于Logistic回归分析的限制性立方样条(RCS)方法分析中国社区老年人牙齿数量与虚弱罹患风险的剂量-反应关系。结果12678例社区老年人年龄为65~117岁,平均(83.62±11.16)岁;男5848例(46.1%),女6830例(53.9%)。多因素Logistic回归分析结果显示,调整协变量性别、年龄、婚姻状况、居住地、民族、居住安排、受教育年限、医疗卫生可及性、60岁以前的职业、自评经济状况、体质量指数(BMI)、吸烟状况、饮酒状况、运动状况、自评健康状况变量、是否参与年度体检后,社区老年人咀嚼能力与虚弱患病风险有相关性(P<0.05)。RCS图显示,天然牙齿数量与虚弱罹患风险呈线性相关,当天然牙齿数量<10颗时,老年人罹患虚弱的风险增加,且随着牙齿数量的减少,老年人罹患虚弱的风险逐渐增大。结论中国社区老年人咀嚼能力与虚弱患病风险相关,天然牙齿数量与义齿使用对老年人虚弱的发生具有重要意义。

多颗恒牙迟萌的病因学研究进展

恒牙迟萌是指恒牙萌出时间显著晚于正常萌出期的现象,不仅可引起患儿错(牙合)畸形,还可进一步影响患儿的咀嚼、发音功能与面容美观,严重时将损害患儿正常生长发育及心理健康,给家长带来负担。其发生以个别恒牙较常见,但部分患儿出现多颗恒牙迟萌。多颗恒牙迟萌病因复杂,除局部机械因素外,还可能与环境(如疾病、营养、感染、放射、药物)、遗传等因素具有相关性,本文就以上因素作一综述,以期为多颗恒牙迟萌的病因学研究及临床诊断提供思路。

Structure and property of metal melt Ⅰ:The number of residual bonds after solid-liquid phase changes

Based on the mechanism of metal solid-liquid phase change and the theory of liquid metal's micro-inhomogeneity,a physical model is established between latent heats of fusion and vaporization and the numbers of residual bonds and short-range ordered atoms at the melting point inside a metal melt.Meanwhile,the mathematical derivation and proof are also offered.This model produces the numbers of residual bonds and short-range ordered atoms after the solid-liquid phase change only by using basic parameters and thermophysical properties of the crystal structure.Therefore,it presents a more effective way to analyze the melt's structural information.By using this model,this study calculates the numbers of residual bonds and short-range ordered atoms in Al and Ni melts.The calculated results are consistent with the experimental results.Simultaneously,this study discusses the atomic number's influence on the numbers of residual bonds and short-range ordered atoms in the melts within the first(ⅠA) and second main group(ⅡA) elements.

3自由度球齿轮齿盘设计与啮合分析

提出一种与球齿轮啮合的3自由度齿盘结构,该齿盘由两个环形齿条齿面和两个弧形齿面组成,能够实现平面和球面之间运动和动力的转换,且理论上没有传动误差。根据球齿轮齿盘的啮合原理,利用空间变换理论,推导出齿盘的齿面方程和啮合方程;根据齿盘结构特点,由球齿轮和齿盘弧形齿的正确啮合条件推导出与球齿轮啮合时齿盘每一层的齿数,并对球齿轮-齿盘结构进行了运动学仿真,计算了齿盘各层啮合时的啮合效率。验证说明,球齿轮-齿盘结构能够稳定地传递动力。齿盘的参数化设计提供了一种能实现平面和球面之间运动和动力转换的结构。

下前牙区多生牙发生率75例回顾性研究

目的:探讨下前牙区多生牙的发生率和临床特征。方法:对2019年1月至2022年10月来苏州口腔医院就诊的患者进行回顾性分析,观察记录下前牙区多生牙的发生情况。应用SPSS24.0统计学软件分析所得的数据。查阅电子病例,记录下前牙区多生牙患者的口腔诊疗内容。结果:最终纳入下前牙区多生牙患者75例,下前牙区多生牙的发生率为0.99‰(75/75465),男性(31例)少于女性(44例),性别间差异无统计学意义(P>0.05)。本组病例多生牙特征:混合牙列患者占48.00%、1颗多生牙患者占92.00%、牙根未发育完成占65.43%、多生牙未萌出占65.43%、垂直正置生长占90.12%。多生牙在形态上类似下颌切牙、尖牙或前磨牙。多生牙的存在伴发下前牙区拥挤占52.00%;伴发邻近恒牙阻生、迟萌、乳牙滞留等占12.00%。本组研究病例还伴发乳牙列多生牙、乳恒牙先天缺失、乳恒牙融合牙、其他部位多生牙、含牙囊肿。75例患者中有35例在我院接受下前牙区多生牙拔除和/或正畸治疗。结论:下前牙区多生牙临床上虽不多见,但会影响美观和口腔功能,应引起口腔医师重视,常需要行多学科联合治疗,才能达到满意的效果。

橡胶密炼机转子强度评估及传动参数小型化的优化

为进一步提升橡胶密炼机的性能以保证所制造橡胶的质量满足实际生产的要求,在对橡胶密炼机总体结构进行综合分析的基础上,基于UG和ANSYS软件构建的有限元仿真分析模型,重点对前转子在实际工况下的应变和应力进行综合分析,验证其转子强度是否满足生产要求;最后,针对传动过程中稳定性不佳的问题基于MATLAB软件对橡胶密炼机前后转子的传动参数进行了优化设计,在保证其刚度和强度满足要求的基础上达到减小传动机构体积,提升传动系统小型化的目的。