Constraint-based beautification and dimensioning of 3D polyhedral models reconstructed from 2D sketches

3D models reconstructed from 2D sketches are inaccurate because of the inherent inaccuracies in the input and the reconstruction method. It is therefore necessary to “beautify” them before use in CAD systems. We present a method that detects geometric constraints, such as parallel and orthogonal faces, present in the reconstructed model and then selects a subset that constrains the object sufficiently and consistently. The subset selection algorithm first prioritizes the constraints depending on their type and then uses a novel method, based on quasi-Newton optimization, to detect and eliminate redundant and inconsistent constraints. The remaining constraints then define the dimensions of the model fully and consistently. Results from our implementation show that the method can beautify and dimension recovered 3D models correctly at acceptable speed.     

分偏移距动校正方法的改进

在地震资料处理中，速度分析和动校正对资料品质的影响很大。由于动校正速度是随偏移距变化而变化的，而常规速度分析并没有考虑这一因素，动校正效果往往不是很理想，从而影响资料的叠加和成像效果。分偏移距动校方法是在不同偏移距上采用不同的速度进行动校正。但由于是在不同偏移距组上分别独立进行速度分析和动校正，因此不能将不同偏移距组的同一反射同相轴校正到同一to层位上。这样就需要进行繁琐的后续处理，而且还会降低同相轴的连续性和平滑性。为此，对该方法进行了一些改进，即固定to在不同的分偏移距段进行速度扫描，段与段之间的衔接问题采用平滑处理解决。理论模型分析表明，采取上述改进措施后，动校正效果得到了一定提高，改善了同相轴的连续性和平滑性。     

Optimal control of nonlinear systems to given orbits

Using optimal control techniques we derive and demonstrate the use of an explicit single-step control method for directing a nonlinear system to a target orbit and keeping it there. We require that control values remain near the uncontrolled settings. The full nonlinearity of the problem in state space variables is retained. The “one-step” of the control is typically a composition of known or learned maps over (a) the time required to learn the state, (b) the time to compute the control and (c) the time to apply the control. No special targeting is required, yet the time to control is quite rapid. Working with the dynamics of a well-studied nonlinear electrical circuit, we show how this method works efficiently and accurately in two situations: when the known circuit equations are used, and when control is performed only on a Poincaré section of the reconstructed phase space. In each case, because the control rule is known analytically, the control strategy is computationally efficient while retaining high accuracy. The target locations on the selected target trajectory at each control stage are determined dynamically by the initial conditions and the system dynamics, and the target trajectory is an approximation to an unstable periodic orbit of the uncontrolled system. A linear stability analysis shows that dissipation in the dynamical system is essential for reaching a controllable state.     

提高海水温度对锌合金和铝合金牺牲阳极电化学性能的影响

研究了提高海水温度对锌合金和铝合金牺牲阳极电化学性能的影响。结果表明，锌合金和铝合金牺牲阳级的电化学性能都随着海水温度的提高而变劣；凡是发生晶间腐蚀的合金，其晶间腐蚀程度都随着海水温度的提高而加剧。低含铝量的锌－铝－镉合金阳极在７０℃海水介质中，工作电位仍负于－１．０１０Ｖ，电流效率＞８０％，阳极工作表面溶解均匀，且不产生晶间腐蚀。     

微粒混凝土受压应力应变全曲线试验研究

采用一种特制的刚性辅助装置,进行了微粒混凝土和普通混凝土的应力应变全曲线试验研究,得到一系列应力应变曲线。对微粒混凝土和普通混凝土的立方体抗压强度与棱柱体抗压强度的关系、棱柱体抗压强度与峰值应力所对应应变的关系及棱柱体抗压强度与初始弹性模量的关系进行了分析,虽然微粒混凝土的力学性能与普通混凝土的力学性能存在一定的差别,但主要力学性能还是相似的,在模型试验中微粒混凝土是可以用来代替普通混凝土进行结构试验的。同时也验证了刚性辅助装置在测量微粒混凝土和普通混凝土的应力应变全曲线时的有效性。     

用载文南定理计算感应电机和变压器的特性曲线

感应电机和变压器激磁电路的参数是非线性的.为准确求取它们的特性曲线,需要的计算量很大.应用本文引入的方法可以避免大的计算量又可得到准确的特性曲线.     

粘合剂流变特性的研究(待续)

本文从流变学的观点出发,分析粘合剂在配制及粘结过程中,反映出不同的流变特性,而粘合剂本身的流动、粘度、触变性与涂胶及其粘合的质量关系重大。     

固定床吸附器透过曲线参数优化方法

开发了一种固定床吸附器透过曲线参数估值的优化方法，用Ｂａｓｉｃ语言编制了运算程序，并在普及型２８６微机上考核了该法的可靠性，相对误差在１％以下，运算机时７．５ｍｉｎ。     

衰减曲线分析的诺模图

基于Arps递减方程,建立了衰减曲线分析的诺模图。应用该诺模图,可以方便地确定油气田的可采储量。     

虚拟肝脏的规则和非规则手术切除技术

为了提高肝癌手术治疗计划的可靠性,在利用腹部CT图像数据进行肝脏三维重建的基础上,实现了任意角度对虚拟肝脏进行平面切割和切割面结构的显示;通过构造可以调节大小、位置的球体模型,实现了球体切除;通过在肝脏三维模型表面上勾画不规则封闭区域,实现了任意曲面肝脏切除;并依据肝内血管结构进行肝段划分,实现了解剖性肝段切除.临床实验结果表明,文中所述的技术能够满足虚拟手术的需求,有利于医生制定安全可靠的术前计划,提高手术成功率.