Lower Bounds of Decay Rates for Solution to the Single-Layer Quasi-Geostrophic Model

In this paper, we study the long-time behavior of solutions of the single-layer quasi-geostrophic model arising from geophysical fluid dynamics. We obtain the lower bound of the decay estimate of the solution. Utilizing the Fourier splitting method, under suitable assumptions on the initial data, for any multi-index α, we show that the solution Ψ satisfies .

Improved algorithm of atmospheric refraction error in Longley-Rice channel model

Longley-Rice channel model modifies the atmospheric refraction by the equivalent earth radius method, which is simple calculation but is not accurate. As it only uses the horizontal difference, but does not make use of the vertical section information, it does not agree with the actual propagation path. The atmospheric refraction error correction method of the Longley-Rice channel model has been improved. The improved method makes use of the vertical section information sufficiently and maps the distance between the receiver and transmitter to the radio wave propagation distance, It can exactly reflect the infection of propagation distance for the radio wave propagation loss. It is predicted to be more close to the experimental results by simulation in comparison with the measured data. The effectiveness of improved methods is proved by simulation.

Study on Model of Atmospheric Refraction in GPS Measurement

In precise GPS measurement, one of the largest error sources is the correction for atmospheric refraction. It has become important to study the atmospheric refraction theory, to establish a more practical model, and to derive a precise correction formula. In this paper the theory of atmospheric refraction was studied in depth, a new atmospheric model was established, and a new and more precise correction formula for refraction was derived.

Combined refraction and diffraction models for sea waves over complicated topography and with currents in shallow water

-Combined refraction and diffraction models in the form of linear parabolic approximation are derived through smallparameter method. More strictly theoretical basis and more accuracy in the models than Lozano's (1980) are obtained. Some theoretical defects in Liu's model (1985) with consideration of current are not only found but also eliminated. More strict and accurate models are, therefore, presented in this paper.The calculation results and analysis in applying the models to actual wave field with consideration of bottom friction will be given in the following paper.

Cavity effect on Rayleigh wave dispersion and P-wave refraction

Sinkholes and cavities can represent serious hazards to human safety and urban infrastructures,cause roadbed subsidence,and so on.It is therefore essential to evaluate various sinkholes in different depths and sizes to assess the risk of collapse.This paper evaluates the effect of different cavities on Rayleigh-wave propagation and body(P)wave refraction.Rayleigh(R)wave propagation is analyzed according to the classical multi-channel analysis of surface waves(MASW)method also considering the R-wave backscattering.Synthetic seismic traces are computed by means of finite element modeling(FEM)for cavity and intrusion at different depths and sizes.Furthermore,field acquisition data is used to verify the detection effect of a cavity on R-and P-waves.The results show that the presence of backscattered R-waves and the changes in the R-wave velocity spectrum can help in cavity identification.Additional possible evidence is represented by significant changes in the refraction travel times over the cavity location.It can be concluded that the field data are in good agreement with the synthetic,and it could be effective to consider the results of both R-and P-wave analysis in order to efficiently identify the cavities.

“Refractivity-from-clutter” based on local empirical refractivity model

Constructing sophisticated refractivity models is one of the key problems for the RFC(refractivity from clutter)technology. If prior knowledge of the local refractivity environment is available, more accurate parameterized model can be constructed from the statistical information, which in turn can be used to improve the quality of the local refractivity retrievals. The validity of this proposal was demonstrated by range-dependent refractivity profile inversions using the adjoint parabolic equation method to the Wallops’ 98 experimental data.

High Resolution in Seismic Refraction Tomography for Environmental Study

Seismic refraction tomography (SRT) involves more complex mathematic algorithms to fit more flexible model. In the field procedure SRT in generally needs more shot points than standard seismic refraction survey to obtain high resolution profile. In this seismic refraction study, we have used 9 shot-points for inline and 10 shot-points for offset in purpose to obtaine high resolution of seismic refraction tomography. During a recent geophysical test site, the subsurface material was mapped along survey line using seismic refraction method. Analyses of the site investigation data revealed that the studied site was made up of two layers of the subsurface. The upper layer has velocity values with range of 500 m/s to1500 m/s which can be classified as unconsolidated surface deposits and mixtures of unsaturated sands and gravels. Meanwhile the lower layer has velocity values with range of2000 m/s to5500 m/s which is classified as compacted fine’s soil due to high pressure of the overburden. Analysis of seismic refraction data demonstrated that refraction tomography software systems are able to reveal subsurface material which represented by their seismic velocity value. Furthermore, the velocity model obtained in this study is agreed with its synthetic modelling result as initial model. This validity and reasonable results was able to assist in interpretation of the seismic refraction method for the environmental study.

Investigating the Depth and the Geometry of the Quarzitic Panafrican Basement Using Near-Surface 3D Seismic Refraction Tomography: Case Study of the Locality of Bakel (Senegal)

Seismic refraction investigations have been carried out in Bakel, Eastern Senegal. The purpose was to map geometrical relationship between the existing rock types and the Panafrican quarzitic basement, which is valuable information for the project of the Bakel fluviatile port construction. Four seismic refraction profiles were acquired. The obtained data have been processed by inversion. The obtained four seismic P-wave velocity profiles have been integrated to obtain a 3D model. By comparing the outcropping geological formations with the observed seismic data at the surface, it was possible to identify the lithology corresponding to each measured range of seismic velocity for the alluvium, the weathered bed rock, and the fresh rock. The results showed that the depth of the fresh rock of the basement varies from 0 to 18 meters above the sea level, with a deepening toward the Senegal River and toward the Northern part of the studied area. The presence of alluviums and their thickness are linked to the existence of bays and gulfs. The results of this study give valuable information for the river bed dredging cost assessment prior to the port construction phase.

一种光波大气折射率剖面模型构建方法

根据经典光波折射率计算公式和ITU-R建议书中水汽密度经验公式,给出了一种新的光波大气折射率计算公式;借鉴Hopfield折射率静力项剖面模型和ITU-R建议书中水汽密度剖面模型,给出了一种基于历史气象探空数据构建光波大气折射率剖面模型的方法。以青岛地区为例,通过对1986—1995年历史气象探空数据的处理并结合参考标准大气,建立了适合当地的光波大气折射率剖面模型;统计剖面模型预测折射率剖面与实测折射率剖面的均方根误差,结果表明:构建的剖面模型具有较好的预测精度,这对光学外测设备的折光修正数据处理具有很好的参考价值。

层析+折射约束迭代反演近地表建模方法及应用探索

塔西南山前带是塔里木盆地重要的勘探接替领域之一,其地表为巨厚黄土覆盖,黄土厚度可达500 m以上,速度在纵、横向上变化快,表层结构复杂。为改善地震成像效果,针对复杂地表区表层模型精度难以满足需求的问题,开展了拟合时深曲线量板、层析反演及折射反演等方面研究工作。结果表明:多种表层建模方法综合运用是提高近地表模型精度的有效途径;黄土曲线量板可反映连续介质区近地表速度变化规律;层析+折射约束迭代反演近地表建模方法能够将模型精度误差控制在5%以内;逐级递进约束层析反演可拓展可信速度场深度约1500 m。以上成果认识,对类似探区构建高精度近地表模型及提高地震成像精度具有指导意义。

聚苯基甲基硅氧烷分子量-折射率模型研究

聚硅氧烷是应用广泛的一种特种有机硅材料,折射率是衡量聚硅氧烷性能的重要指标。应用基团贡献法建立了适用于聚苯基甲基硅氧烷体系的分子量-折射率模型,结合自由体积理论对模型进行了修正。修正后的模型能够根据分子量和温度有效地预测聚苯基甲基硅氧烷的折射率,相对误差在±0.2%范围内。根据修正后的模型阐述了分子量、温度对折射率的影响:折射率随着分子量的增大而升高,最终趋于一定值;折射率随着温度的升高明显下降。研究结果可为高折射率聚硅氧烷的设计与合成提供参考。

基于水下机器人的水下混凝土结构表观病害三维重建方法

利用水下机器人进行水下结构病害检测能大幅提升检测效率、降低检测成本,然而利用水下机器人拍摄得到的水下结构平面图像仅包含结构表面的有限信息。通过对水下结构三维重构可以直观地显示结构的空间构形和特征,可以多视角、全方位获取结构的表观缺陷信息。该文提出了基于水下机器人拍摄平面图像的水下混凝土结构三维重建方法,通过水下折射摄像机成像模型、SIFT特征提取和匹配算法以及点云重建的方式对水下带病害的混凝土结构表面进行三维重建。实验表明:该文提出的水下混凝土结构三维重建方法能实现病害三维立体展示,从多视角清晰获取水下结构表面病害信息。

基于线激光三维视觉的燃料组件水下在位变形测量方法

为了解决燃料组件弯曲与扭曲变形水下在位测量难题,提出了基于线激光三维视觉的燃料组件水下在位变形测量方法。通过基于单层折射的水下相机标定、基于平面约束的光平面标定算法研究解决单个测量单元的标定问题;研究基于三维标定工装的10组测量单元在位快速标定方法,解决测量系统全局坐标统一问题,并利用激光跟踪仪测量标定工装的弯扭精度,进行测量精度对比试验验证。研究表明,研制的基于线激光三维视觉的燃料组件水下在位变形测量系统扭曲测量误差限为0.15°,弯曲测量误差限为0.3 mm,且整个测量时间约在1 s,测量效率和测量误差限优于现有的测量系统。

FS-LASIK矫正中高度近视术后1年屈光回退危险因素及其预测模型构建

目的:探讨飞秒激光辅助准分子激光原位角膜磨镶术(FS-LASIK)矫正中高度近视术后1 a屈光回退的危险因素并构建预测模型。方法:回顾性分析2017-06/2018-11于西安高新医院行FS-LASIK手术矫正中高度近视患者400例800眼临床资料,将患者按照3∶1的比例随机分为建模组(n=300例)和验证组(n=100例),依照患者术后1 a屈光回退发生情况将建模组分为回退组与未回退组两个亚组,观察其角膜曲率和角膜厚度变化情况,采用Logistic回归分析筛选FS-LASIK矫正中高度近视患者术后1 a屈光回退的危险因素,基于回归系数构建预测模型,采用受试者工作特征曲线(ROC)评估模型区分度。结果:建模组44眼、验证组15眼于术后1 a发生屈光回退。建模组中未回退组术后6、12 mo时角膜前表面曲率低于回退组(均P<0.05);术后1、3、6、12 mo时回退组角膜增生程度大于未回退组(均P<0.05);FS-LASIK矫正中高度近视患者术后1 a屈光回退发生概率值回归方程为:P=1/[1+e^(-(-5.989+0.127×年龄+2.019×术前屈光度-0.022×术前角膜中央厚度+0.043×切削深度-1.569×切削光学区直径))],Hosmer-Lemeshow检测回归方程拟合优度(P=0.818),利用建模组数据进行内部验证,ROC曲线下面积为0.890(95%CI 0.843-0.937),灵敏度为81.82%,特异度为84.71%;利用验证组数据进行外部验证,ROC曲线下面积为0.838(95%CI 0.717-0.959),灵敏度为80.00%,特异度为87.57%。结论:构建的风险模型判别效度良好,可用于识别中高度近视患者行FS-LASIK术后1 a屈光回退高危人群。

The estimation of lower refractivity uncertainty from radar sea clutter using the Bayesian-MCMC method

The estimation of lower atmospheric refractivity from radar sea clutter（RFC） is a complicated nonlinear optimization problem.This paper deals with the RFC problem in a Bayesian framework.It uses the unbiased Markov Chain Monte Carlo（MCMC） sampling technique,which can provide accurate posterior probability distributions of the estimated refractivity parameters by using an electromagnetic split-step fast Fourier transform terrain parabolic equation propagation model within a Bayesian inversion framework.In contrast to the global optimization algorithm,the Bayesian-MCMC can obtain not only the approximate solutions,but also the probability distributions of the solutions,that is,uncertainty analyses of solutions.The Bayesian-MCMC algorithm is implemented on the simulation radar sea-clutter data and the real radar seaclutter data.Reference data are assumed to be simulation data and refractivity profiles are obtained using a helicopter.The inversion algorithm is assessed（i） by comparing the estimated refractivity profiles from the assumed simulation and the helicopter sounding data;（ii） the one-dimensional（1D） and two-dimensional（2D） posterior probability distribution of solutions.

Refractivity estimations from an angle-of-arrival spectrum

This paper addresses the probability of atmospheric refractivity estimation by using field measurements at an array of radio receivers in terms of angle-of-arrival spectrum. Angle-of-arrival spectrum information is simulated by the ray optics model and refractivity is expressed in the presence of an ideal tri-linear profile. The estimation of the refractivity is organized as an optimization problem and a genetic Mgorithm is used to search for the optimal solution from various trial refractivity profiles. Theoretical analysis demonstrates the feasibility of this method to retrieve the refractivity parameters. Simulation results indicate that this approach has a fair anti-noise ability and its accuracy performance is mainly dependent on the antenna aperture size and its positions.

Modelling of Energy Storage Photonic Medium by Wavelength-Based Multivariable Second-Order Differential Equation

Wavelength-dependent mathematical modelling of the differential energy change of a photon has been performed inside a proposed hypothetical optical medium.The existence of this medium demands certain mathematical constraints,which have been derived in detail.Using reverse modelling,a medium satisfying the derived conditions is proven to store energy as the photon propagates from the entry to exit point.A single photon with a given intensity is considered in the analysis and hypothesized to possess a definite non-zero probability of maintaining its energy and velocity functions analytic inside the proposed optical medium,despite scattering,absorption,fluorescence,heat generation,and other nonlinear mechanisms.The energy and velocity functions are thus singly and doubly differentiable with respect to wavelength.The solution of the resulting second-order differential equation in two variables proves that energy storage or energy flotation occurs inside a medium with a refractive index satisfying the described mathematical constraints.The minimum-value-normalized refractive index profiles of the modelled optical medium for transformed wavelengths both inside the medium and for vacuum have been derived.Mathematical proofs,design equations,and detailed numerical analyses are presented in the paper.

Applications of A Numerical Model to Wave Propagation on Mild Slopes

Based on the mild slope equation that has heen deeomposed inlo three equations related to wave phase function, wave amplitude and wave approach angle, a refraction-diffraction model is developed. The finite difference method has been selected as the solution method. The model results are compared with experimental results and the model is applied to coastal waters of the Fethiye Bay, whieh is located at the Mediterranean Sea of Turkey.

Asymptotic Solution to Scattering Problem on a Set of Small Particles and Application to Creating the Materials with a Peculiar Refractive Index

The asymptotic solution to the scattering problem on a set of small particles, supplemented into homogeneous material, is used for modeling the materials with the desired refractive index. The consideration concerns the case of acoustic scalar scattering and the solution to initial scattering problem is built using an asymptotic approach. The closed form solution is reduced for the scattering problem. This is significant advantage of approach because there is no need to solve the respective system of boundary integral equations. High accuracy of solving the scattering problem is achieved by choosing the optimal parameters of the domain with small particles. The approach allows obtaining an explicit formula for the refractive index of the resulting inhomogeneous material. The numerical calculations show the possibility to get the specific values of refractive index including its negative values.

Refractive Features and Diffraction Scattering Patterns Observed in the Elastic Scattering of ¹²C from ¹²C at Various Energies

We have measured the angular distributions for 12C ion beam elastically scattered from 12C target of thickness 17.4 μg/cm2 at energies 15, 18 and 21 MeV which is close to the Coulomb barrier energy for 12C + 12C nuclear system. The elastic scattering of 12C beam on 12C was analysed also at different energies (139.5, 158.8, 180, 240, 288.6, 300, 360 and 420 MeV) from literature in order to obtain the global optical potential parameters, which could fairly reproduce the experimental data. The experimental results were analysed within the framework of both the optical model and the double folding potential obtained with different density-dependent NN interactions which give the corresponding values of the nuclear incompressibility K in the Hartree-Fock calculation of nuclear matter. The agreement between the experimental results and the theoretical predictions in the whole angular range is fairly good.