SLANT SUBMANIFOLDS OF A RIEMANNIAN PRODUCT MANIFOLD

In this article, the geometry of the slant submanifolds of a Riemannian product manifold is studied. Some necessary and sufficient conditions on slant, bi-slant and semi-slant submanifolds are given. We research fundamental properties of the distributions which are involved in definitions of semi- and bi-slant submanifolds in a Riemannian product manifold.

一种基于Slant变换和SVD的稳健性数字水印算法

针对奇异值分解(SVD)存在的虚警错误和水印隐蔽性与鲁棒性的矛盾问题,提出了一种基于Slant变换和SVD的稳健性数字水印算法。对二值水印图像进行Arnold置乱和Logistic映射双因子加密预处理,增强水印信息安全性;将原始载体图像分成8×8不重叠子块分别对其进行Slant变换和块奇异值分解;然后将水印图像SVD后的左奇异矩阵和奇异值矩阵相乘作为水印主成分嵌入到每个子块的最大奇异值中。仿真实验结果表明,该算法不仅有效解决了传统SVD水印算法的虚警问题,提升了运行速度和水印安全性,在具有较好隐蔽性的同时,对JPEG压缩、噪声、滤波、几何攻击等也有较好的稳健性。

基于方向小波与Slant变换的鲁棒水印算法

设计了一种基于内容的数字水印算法。算法以方向小波变换提取的独立分块图像正则方向作为水印信息,根据图像噪声可见函数将水印信息量化嵌入分块图像Slant变换中频系数之中。实验结果显示,算法对于常见图像处理和几何攻击均具有很强的鲁棒性,与基于DCT和PST变换的算法相比,该算法能够更有效地抵抗一些恶意和非恶意操作同时实施的操作。

Modeling of multi-depth slanted airgun source for deghosting

To obtain high-resolution of the subsurface structure, we modeled multidepth slanted airgun sources to attenuate the source ghost. By firing the guns in sequence according to their relative depths, such a source can build constructive primaries and destructive ghosts. To evaluate the attenuation of ghosts, the normalized squared error of the spectrum of the actual vs the expected signature is computed. We used a typical 680 cu.in airgun string and found via simulations that a depth interval of 1 or 1.5 m between airguns is optimum when considering deghosting performance and operational feasibility. When more subarrays are combined, preliminary simulations are necessary to determine the optimum depth combination. The frequency notches introduced by the excess use of subarrays may negatively affect the deghosting performance. Two or three slanted subarrays can be combined to remove the ghost effect. The sequence combination may partly affect deghosting but this can be eliminated by matched filtering. Directivity comparison shows that a multi-depth slanted source can significantly attenuate the notches and widen the energy transmission stability area.

结合图像归一化与Slant变换的鲁棒图像哈希

为了提高图像哈希算法抵抗几何攻击的性能,提出了一种结合图像归一化和Slant变换的图像哈希算法。使用几何不变矩将原始图像进行归一化操作得到仿射不变图像,仿射不变图像分块并进行Slant变换,根据用户密钥选择Slant变换中频系数极性并生成最终的图像哈希序列。实验结果表明该算法对常见图像操作处理和常见几何攻击鲁棒,对原始图像内容和用户密钥敏感,是一种有效的图像哈希算法。

与Slant矩阵相关的多通道滤波器的构造

为了构造多通道滤波器,研究了Slant矩阵各行元素和的特性.由该矩阵的第一行构造了一个低通滤波器,其它各行构造了一组高通滤波器.同时借助多相位分解,证明了多通道低通滤波器满足完全重构条件.给出了分解实例,验证了构造的多通道分解滤波器的有效性.

A Note on the Operator Equation Generalizing the Notion of Slant Hankel Operators

The operator equation λMz^-X = XMzk, for k ≥ 2,λ∈ C, is completely solved. Further, some algebraic and spectral properties of the solutions of the equation are discussed.

SLANT IMMERSIONS OF COMPLEX SPACE FORMS AND CHEN'S INEQUALITY

A submanifold in a complex space form is called slant if it has constant Wirtinger angles. B. Y. Chen and Y. Tazawa proved that there do not exist minimal proper slant surfaces in CP2 and CH2. So it seems that the slant immersion has some interesting properties. The authors have great interest to consider slant immersions satisfying some additional conditions, such as unfull first normal bundles or Chen’s equality holding. They prove that there do not exist n-dimensional Kaehlerian slant immersions in CPn and CHn with unfull first normal bundles. Next, it is seen that every Kaehlerian slant submanifold satisfying an equality of Chen is minimal which is similar to that of Lagrangian immersions. But in contrast, it is shown that a large class of slant immersions do not exist thoroughly. Finally, they give an application of Chen’s inequality to general slant immersions in a complex projective space, which generalizes a result of Chen.

基于超混沌和Slant变换的鲁棒水印算法

为进一步提高水印算法的安全性和抗攻击能力,结合超混沌和Slant变换的优点,提出一种基于超混沌和Slant变换的鲁棒水印算法。首先,在隐藏水印之前采用超混沌系统对水印图像进行加密,提高了待隐藏图像的安全性;其次,将原始载体图像划分成大小为8×8的不重叠分块并对各个分块分别进行Slant变换;最后,将加密后的水印图像隐藏到Slant变换后的直流系数和中频系数中。大量的仿真结果表明,本文算法具有较好的隐蔽性,对JPEG压缩、噪声、滤波、缩放、对比度调整等攻击具有较好的抗攻击能力。与相似算法相比,本文算法具有更好的鲁棒性能。

Rock deformation equations and application to the study on slantingly installed disc cutter

At present the mechanical model of the interac- tion between a disc cutter and rock mainly concerns indentation experiment, linear cutting experiment and tunnel boring machine （TBM） on-site data. This is not in line with the actual rock-breaking movement of the disc cutter and impedes to some extent the research on the rock-breaking mechanism, wear mechanism and design theory. Therefore, our study focuses on the interaction between the slantingly installed disc cutter and rock, developing a model in accordance with the actual rock-breaking movement. Displacement equations are established through an analysis of the velocity vector at the rock-breaking point of the disc cutter blade; the func- tional relationship between the displacement parameters at the rock-breaking point and its rectangular coordinates is established through an analysis of micro-displacement vectors at the rock-breaking point, thus leading to the geometric equations of rock deformation caused by the slantingly installed disc cutter. Considering the basically linear relationship between the cutting force of disc cutters and the rock deformation before and after the leap break of rock, we express the constitutive relations of rock deformation as generalized Hooke＇s law and analyze the effect of the slanting installa- tion angle of disc cutters on the rock-breaking force. This will, as we hope, make groundbreaking contributions to the development of the design theory and installation practice of TBM.

An efficient algorithm to compute transient pressure responses of slanted wells with arbitrary inclination in reservoirs

Compared with vertical and horizontal wells, the solution and computation of transient pressure responses of slanted wells are more complex. Vertical and horizontal wells are both simplified cases of slanted wells at particular inclination, so the model for slanted wells is more general and more complex than other models for vertical and horizontal wells. Many authors have studied unsteady-state flow of fluids in slanted wells and various solutions have been proposed. However, until now, few of the published results pertain to the computational efficiency. Whether in the time domain or in the Laplace domain, the computation of integration of complex functions is necessary in obtaining pressure responses of slanted wells, while the computation of the integration is complex and time-consuming. To obtain a perfect type curve the computation time is unacceptable even with an aid of high-speed computers. The purpose of this paper is to present an efficient algorithm to compute transient pressure distributions caused by slanted wells in reservoirs. Based on rigorous derivation, the transient pressure solution for slanted wells of any inclination angle is presented. Assuming an infinite-conductivity wellbore, the location of the equivalent-pressure point is determined. More importantly, according to the characteristics of the integrand in a transient pressure solution for slanted wells, the whole integral interval is partitioned into several small integral intervals, and then the method of variable substitution and the variable step-size piecewise numerical integration are employed. The amount of computation is significantly reduced and the computational efficiency is greatly improved. The algorithm proposed in this paper thoroughly solved the difficulty in the efficient and high-speed computation of transient pressure distribution of slanted wells with any inclination angle.

Characteristics of a partially coherent Gaussian Schell-model beam propagating in slanted atmospheric turbulence

On the basis of the extended Huygens-Fresnel principle and the model of the refractive-index structure constant in the atmospheric turbulence proposed by the International Telecommunication Union-Radio Communication Sector,the characteristics of the partially coherent Gaussian Schell-model（GSM） beams propagating in slanted atmospheric turbulence are studied.Using the cross-spectral density function（CSDF）,we derive the expressions for the effective beam radius,the spreading angle,and the average intensity.The variance of the angle-of-arrival fluctuation and the wander effect of the GSM beam in the turbulence are calculated numerically.The influences of the coherence degree,the propagation distance,the propagation height,and the waist radius on the propagation characteristics of the partially coherent beams are discussed and compared with those of the fully coherent Gaussian beams.

Dynamic Characteristics of Rotor System with a Slant Crack Based on Fractional Damping

The traditional modeling method of rotor system with a slant crack considers only integer-order calculus.However,the model of rotor system based on integer-order calculus can merely describe local characteristics,not historical dependent process.The occur of fractional order calculus just makes up for the deficiency in integer-order calculus.Therefore,a new dynamic model with a slant crack based on fractional damping is proposed.Here,the stiffness of rotor system with a slant crack is solved by zero stress intensity factor method.The proposed model is simulated by Runge-Kutta method and continued fraction Euler method.The influence of the fractional order,rotating speed,and crack depth on the dynamic characteristics of rotor system is discussed.The simulation results show that the amplitude of torsional excitation frequency increases significantly with the increase of the fractional order.With the increase of the rotating speed,the amplitude of first harmonic component becomes gradually larger,the amplitude of the second harmonic becomes smaller,while the amplitude of the other frequency components is almost invariant.The shaft orbit changes gradually from an internal 8-type shape to an ellipse-type shape without overlapping.With the increase of the slant crack depth,the amplitude of the transverse response frequency in the rotor system with a slant crack increases,and the amplitude in the second harmonic component also increases significantly.In addition,the torsional excitation frequency and other coupling frequency components also occur.The proposed model is further verified by the experiment.The valuable conclusion can provide an important guideline for the fault diagnosis of rotor system with a slant crack.

Propagation of partially coherent beams carrying an edge dislocation through atmospheric turbulence along a slant path

This paper derives the explicit expressions for the average intensity, beam width and angular spread of Gaussian Schell-model （GSM） beams with edge dislocation propagating through atmospheric turbulence along a slant path. The propagation of GSM beams with edge dislocation through horizontal atmospheric turbulence can be treated as a special case through a slant one. The propagation properties of GSM beams with edge dislocation through slant atmospheric turbulence are studied, where the influence of edge dislocation parameters including the slope p and off-axis distance d on the spreading of GSM beams with edge dislocation in atmospheric turbulence is stressed. It shows that the spreading of the intensity profile of GSM beams with edge dislocation along a slant path is smaller than that along a horizontal path in the long-distance atmospheric propagation. The larger the slope ｜p｜ and the smaller the off-axis distance ｜d｜ are, the less the beam-width spreading and angular spread of GSM beams with edge dislocation are affected by turbulence. The CSM beams with edge dislocation is less affected by turbulence than that of GSM beams without edge dislocation. The results are illustrated numerically and their validity is interpreted physically.

Slant Range Distribution Characteristics of Submarine Launch Mobile Mine

With the bias between the predetermined planting location and the fact mine position,slant range of SLMM(submarine launch mobile mine)appears randomly scattered.The normal distribution model of slant range was proposed by the distribution theory of multivariate random variables,and the simplified model based on key parameters was present,and the laws of slant range distribution parameters such as mean and variance were given,which were affected by key parameters.The conclusions ensure that slant range of SLMM can be controlled when laying mines and provide the basis for tactical decision-making.

Wind-Driven Slanting Profile Wave Derived from the Unified Variational Principle of Water Gravity Wave

Considering that at present the regular waves in common use have the profile symmetrized to a vertical axis, which are different from actual wind-driven sea waves, and based on deriving linear wave, solitary wave, fifth order Stokes wave and stream function wave by using Unified Variational Principle of Water Gravity Wave (UVPWGW), this paper derives wind-driven slanting profile wave by using UVPWGW. Its feature is that under the action of wind pressure, the wave profile is not symmetrized to a vertical axis, but that it is in the forward slanting form.

拟齐次符号Slant H-Toeplitz算子的交换性

刻画了拟齐次符号的Slant H-Toeplitz算子在Bergman空间上的交换性,当不同次拟齐次符号Slant H-Toeplitz算子满足交换性,则必有一符号函数为0;相同非负次拟齐次符号Slant H-Toeplitz算子满足交换性,两符号函数线性相关.这与Bergman空间上具有相同符号的Toeplitz算子的交换性不同.

OPTIMIZING THE CUTTER FOR SLANTING KNIFE CUTTING OPERATION AND ITS BLANKING FORCE

The cutting force under a slanting cutter is discussed.It is not only related to the sheet to be cut and the slanting cutter height,but also to the shape of the cutter.It is from this point of view that the question of optimizing the cutter for slanting knife cutting operation is addressed.Then the general differential equations for the optimum cutter are obtained,and analytic solutions for the workpiece,the contour of which consists of straight lines and arcs,are obtained.A method for solving the general equations is also presented.The cutting force and breaking noise will be minimized for a given slanting cutter height and workpiece if the optimum cutter is employed.

к-order Slant Toeplitz Operators on the Bergman Space

In this paper k-order slant Toeplitz operator on the Bergman space is defined. Some properties like spectrum, commuting are discussed.

Workover String Mechanical Model and Calculation of Slanted and Horizontal Well

Force analysis and calculation of workover string in the slanted and horizontal well are the basis of designing and checking string strength, selecting tools and determining operation parameters, which determine the operation safety and success of engineering accidence treatment. In this paper, by comprehensive consideration of wellbore structure, string assembly, string load and workover operation conditions, the workover string mechanical model has been built under three kinds of working states of lifting, lowering and rotating. The downhole string mechanics has been analyzed and calculated. By field verification, the string assembly, tool selection and operation parameter optimization can be achieved, which can improve the safety and success rates of workover engineering accident treatment.