3-D vertical ray shooting and 2-D point enclosure, range searching, and arc shooting amidst convex fat objects

We present a new data structure for a set of n convex simply-shaped fat objects in the plane, and use it to obtain efficient and rather simple solutions to several problems including (i) vertical ray shooting—preprocess a set of n non-intersecting convex simply-shaped flat objects in 3-space, whose xy-projections are fat, for efficient vertical ray shooting queries, (ii) point enclosure—preprocess a set C of n convex simply-shaped fat objects in the plane, so that the k objects containing a query point p can be reported efficiently, (iii) bounded-size range searching— preprocess a set C of n convex fat polygons, so that the k objects intersecting a “not-too-large” query polygon can be reported efficiently, and (iv) bounded-size segment shooting—preprocess a set C as in (iii), so that the first object (if exists) hit by a “not-too-long” oriented query segment can be found efficiently. For the first three problems we construct data structures of size O(λ_s(n)log³n), where s is the maximum number of intersections between the boundaries of the (xy-projections) of any pair of objects, and λ_s(n) is the maximum length of (n, s) Davenport-Schinzel sequences. The data structure for the fourth problem is of size O(λ_s(n)log²n). The query time in the first problem is O(log⁴n), the query time in the second and third problems is O(log³n + klog²n), and the query time in the fourth problem is O(log³n).

We also present a simple algorithm for computing a depth order for a set as in (i), that is based on the solution to the vertical ray shooting problem. (A depth order for , if exists, is a linear order of , such that, if K₁, K₂ and K₁ lies vertically above K₂, then K₁ precedes K₂.) Unlike the algorithm of Agarwal et al. (1995) that might output a false order when a depth order does not exist, the new algorithm is able to determine whether such an order exists, and it is often more efficient in practical situations than the former algorithm.     

Direct Shooting Method for the Numerical Solution of Higher-Index DAE Optimal Control Problems

A method for the numerical solution of state-constrained optimal control problems subject to higher-index differential-algebraic equation (DAE) systems is introduced. For a broad and important class of DAE systems (semiexplicit systems with algebraic variables of different index), a direct multiple shooting method is developed. The multiple shooting method is based on the discretization of the optimal control problem and its transformation into a finite-dimensional nonlinear programming problem (NLP). Special attention is turned to the mandatory calculation of consistent initial values at the multiple shooting nodes within the iterative solution process of (NLP). Two different methods are proposed. The projection method guarantees consistency within each iteration, whereas the relaxation method achieves consistency only at an optimal solution. An illustrative example completes this article.     

New general guidance method in constrained optimal control,part 2: Application to space shuttle guidance

The application and the performance of the neighboring optimal feedback scheme presented in Part 1 of this paper is demonstrated for the heating-constrained cross-range maximization problem of a space-shuttle-orbiter-type vehicle. This problem contains five state variables, two control variables, and a state variable inequality constraint of order zero.This research was supported in part by the Deutsche Forschungsgemeinschaft under the Schwerpunktprogramm Anwendungsbezogene Optimierung und Steuerung.The authors wish to express their sincere and grateful appreciation to Professor Roland Bulirsch who encouraged this work.     

一种基于实例语义图的屏幕反窃照识别算法

目前防窃照技术手段主要依靠图像采集设备实时采集视频流,对拍照行为进行识别检测,但受复杂环境影响,现有识别方法存在精确度低、实时性差等问题。针对上述问题,提出了一种基于实例语义图的屏幕反窃照识别算法。该算法首先通过图像分割模型U²-Net提取原图像的显著视觉目标后生成实例语义图,然后通过微调单阶段的目标检测模型YOLO-v5实现对语义图中感兴趣对象的目标检测,最后通过设计的基于Inception-ResNet的拍照识别二分类模型实现对屏幕窃照行为的识别。实验结果表明,该算法在实际场景下的平均识别准确率达到95%以上。     

Back-and-forth shooting method for solving two-point boundary-value problems

The paper proposes a special iterative method for a nonlinear TPBVP of the form (t)=f(t, x(t),p(t)), (t)=g(t, x(t),p(t)), subject toh(x(0),p(0))=0,e(x(T),p(T))=0. Certain stability properties of the above differential equations are taken into consideration in the method, so that the integration directions associated with these equations respectively are opposite to each other, in contrast with the conventional shooting methods. Via an embedding and a Riccati-type transformation, the TPBVP is reduced to consecutive initial-value problems of ordinary differential equations. A preliminary numerical test is given by a simple example originating in an optimal control problem.     

Analytical and numerical solution for viscous dissipation effect on the heat transfer in a deformable channel

In this paper, shooting method and homotopy perturbation technique are applied for the flow analysis of temporal energy transport in a deformation channel with isothermal walls. An incompressible viscous fluid fills the space inside the channel. Analytical and numerical solutions are developed for the momentum and energy equations. The viscous dissipation effects are taken into account. Graphs for pertinent flow parameters are sketched and discussed. Comparison between the analytical and numerical solutions indicates an excellent agreement. It is noticed that behaviors of Prandtl and Eckert numbers on the temperature are qualitatively similar. Copyright © 2011 John Wiley & Sons, Ltd.     

Travelling wave mathematical analysis and efficient numerical resolution for a one-dimensional model of solid propellant combustion

We investigate a model of solid propellant combustion involving surface pyrolysis coupled to finite activation energy gas-phase combustion. Existence and uniqueness of a travelling wave solution are established by extending dynamical system tools classically used for premixed flames, dealing with the additional difficulty arising from the surface regression and pyrolysis. An efficient shooting method allows to solve the problem in phase space without resorting to space discretisation nor fixed-point Newton iterations. The results are compared to solutions from a CFD code developed at ONERA, assessing the efficiency and potential of the method, and the impact of the modelling assumptions is evaluated through parametric studies.     

圆形阵列光电探测系统双目标识别方法

针对双弹丸同时着靶情况下的立靶坐标测量问题,提出一种圆形阵列光电探测系统的双目标识别方法.采用光电探测器件组成1个圆形的探测阵列,并将3个发光角度均为60°的扇形一字线激光器均匀设置于圆形探测阵列上组成探测光幕.当2发弹丸同时穿过探测光幕时,会在圆形探测阵列上产生6个弹丸投影,通过信号处理电路识别6个弹丸投影的中心位置...     

双向多波长泵浦喇曼光纤放大器的优化算法

在变步长的龙格库塔法的基础上,提出利用打靶法,通过先猜测再修正的逐渐逼近的方法来确定计算初始值,进而求解双向泵浦喇曼放大器的功率耦合方程。并利用此算法对三泵浦波长的喇曼放大器进行优化设计,选择泵浦波长分别为1427nm、1445nm和1466nm时进行数值模拟,得到了1dB带宽35nm左右的较好的增益平坦度。     

舰载摄像稳定平台的结构设计

舰载摄像稳定平台为舰艇在高速及恶劣海况下摄像侦察提供了基础条件。介绍了舰载摄像稳定平台的结构形式,并阐述了其结构特点,论述了舰载摄像稳定平台的驱动方式及电机的选择。