基于AABB包围盒的碰撞检测算法的研究

利用虚拟空间中对象运动的特性和AABB包围盒的构造特性,改进了基于AABB层次包围盒的碰撞检测算法。传统的该类算法分为两个检测过程,在初步检测过程中,基于运动对象碰撞行为的局部性,改进了原来的排序方法,采用希尔排序。为了提高检测效率,在相交测试之前将检测对象细分,划分测试区域,避免了不必要的相交测试;在对可能相交的对象进行精确检测过程中,基于AABB包围盒的构造特性,对可能碰撞对象的层次包围盒树进行压缩存储,通过减少算法的存储空间来提高算法的检测速度。对算法的两个检测过程同时进行改进,实验表明在检测对象较多的情况下减少了算法所需的执行时间。     

基于Backstepping方法的MIMO过程分散PID控制器设计

A novel decentralized PID controller design procedure based on backstepping principles is presented to operate multiple-input multiple-output (MIMO) dynamic processes. The first key feature of the design procedure is that a whole MIMO control system is decomposed into multiple control loops, therefore the sub-controllers can be efficiently flexibly designed in parallel prototype. The second key feature is that the decentralized controller has equivalency to those designed by backstepping approach. As a complementary support to the design procedure, the sufficient condition of the whole closed-loop system stability is analyzed via the small gain theorem and it can be proven that the process tracking performance is improved. The simulation results of the Shell benchmark control problem are provided to verify the effectiveness and practicality of the proposed decentralized PID control.     

Shell煤气化工艺中甲烷化副反应的控制研究

考察了低水气比条件下空速和床层热点温度等对Shell粉煤加压气化制氨工艺中甲烷化副反应的影响。结果表明提高空速、降低床层热点温度均可以减少出口甲烷含量,从而避免甲烷化副反应带来的不利影响。     

壳式电炉变压器故障分析与修复

介绍了壳式电炉变压器绕组绝缘故障的检查、判断与修复过程,对相关问题进行了简要探讨。     

Shell finite element of reinforced concrete for internal pressure analysis of nuclear containment building

This paper describes a 9-node degenerated shell finite element (FE), an analysis program developed for ultimate pressure capacity evaluation and nonlinear analysis of a nuclear containment building. The shell FE developed adopts the Reissner-Mindlin (RM) assumptions to consider the degenerated shell solidification technique and the degree of transverse shear strain occurring in the structure. The material model of the concrete determines the level of the concrete stress and strain by using the equivalent stress-equivalent strain relationship. When a crack occurs in the concrete, the material behavior is expressed through the tension stiffening model that takes adhesive stress into account and through the shear transfer mechanism and compressive strength reduction model of the crack plane. In addition, the failure envelope proposed by Niwa is adopted as the crack occurrence criteria for the compression-tension region, and the failure envelope proposed by Yamada is used for the tension-tension region. The performance of the program developed is verified through various numerical examples. The analysis based on the application of the shell FE developed from the results of verified examples produced results similar to the experiment or other analysis results.     

充气膜承冰壳结构形态设计及其建造实践

充气膜承冰壳结构是通过对充气 膜喷溅液体材料,待其凝结成型后撤除充气 膜形成的冰壳结构,该技术始于20世纪40年 代的充气膜承薄壳混凝土结构。文章通过比 对混凝土薄壳和冰壳的差异性,梳理充气膜 承薄壳结构的发展主线,对其形态设计方法 进行总结。结合“2017哈尔滨国际冰雪建造 节”相关建造实践,从施工方案的拟定与实 践、施工材料的选择与工艺以及施工工法的 对比与分析三方面对充气膜承冰壳结构形态 设计与建造实践进行总结与备忘,并对其后 期维护相关条件与技术进行讨论。     

Energy consumption mode identification and monitoring method of process industry system under unstable working conditions

Process industry systems under unstable working conditions are prone to potential anomalies, deviating from the original transition trajectory, and taking longer than expected to return to stability due to persistent disturbances from uncertainties and experience-based regulation errors. The energy waste caused by this situation has not received sufficient attention, and cannot be addressed by existing energy consumption monitoring methods. Herein, an energy consumption mode (ECM) identification and monitoring method under unstable working conditions is proposed, consisting of ECM identification model and multi-mode dynamic monitoring model, focusing on the variation rules of the correlation between energy consumption and other states of the system. In the ECM identification stage, the ECM correlation parameters that reflect the comprehensive production information are selected. Then, given the transfer characteristics of ECM, a Hidden Semi-Markov Model (HSMM) is constructed to fit the migration between modes and the duration within modes. The Variational Bayesian Gaussian Mixture Model is introduced to improve the HSMM, which solves the problem of lacking prior knowledge of ECM and achieves the automatic classification and online identification of ECM. In the dynamic monitoring stage of multi-ECMs, a series of dynamic kernel principle component analysis models are established, and the corresponding monitoring thresholds are set for each ECM. By calculating the maximum of the posteriori probability and the mode thresholds, the ECMs under unstable conditions can be accurately identified and automatically monitored. Compared with previous methods, the proposed method reduces the false detection rate and missed detection rate of abnormal ECM identification to 1.04% and 1.31% in the actual slag grinding production process, which proves its effectiveness.     

Spatially Resolved Temperature Measurements during Condensation in Presence of a Non-Condensable Gas

Axial temperature profiles of the vapor phase can provide valuable indication of the condensation process along the heat transfer path and highlight the impact of non-condensable gases on a unit's performance. The local measurements at moderate vacuum conditions for condensation of a binary mixture are presented alongside the implementation and assessment of optical sensors in a heat transfer process. The results show a good depiction of the characteristic temperature behavior during the condensation process. The relation between temperature, partial pressure and mole fractions are shown.     

High Performance Carbon‐Supported Core@Shell PdSn@Pt Electrocatalysts for Oxygen Reduction Reaction

In this report, a low‐cost and high performance PdSn@Pt/C catalyst with core–shell structure is prepared by two‐stage route. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) examinations show that the composite catalyst particles distribution is quite homogeneous and has a high surface area and the PdSn@Pt/C catalyst has an average diameter of ca. 5.6 nm. The oxygen reduction reaction (ORR) activity of PdSn@Pt/C was higher than commercial Pt/C catalyst. Catalytic activity is studied by cyclic voltammetry. High electrocatalytic activities could be attributed to the synergistic effect between Pt and PdSn.     

Composite beads of alginate and biological hydroxyapatite from poultry and mariculture for hard tissue repair

Synthesizing materials that stimulate the natural growth of living tissues and restore damaged parts of the body is one of the most challenging problems in regenerative medicine. Despite being the most commonly used biomaterial, synthetic hydroxyapatite is a calcium phosphate with a relatively low rate of bioresorption related to new tissue growth. For specific applications, the speed of resorption is essential, and synergy between polymer and hydroxyapatite composite materials from natural sources can be developed. Therefore, this study attempts to synthesize hydroxyapatite from poultry and mariculture by-products and produce spheres with alginate for use as biomaterials for tissue repair. Shells different shellfish and eggs were used as sources of CaCO₃ and added to a phosphoric acid solution as precursors in wet synthesis. The powders were dried, thermally treated and characterized. Structural analysis revealed hydroxyapatite in nanometric crystallites (61–72 nm) with high crystallinity (86–89%). The calcium phosphate obtained from Mozambique shellfish acquired the best characteristics. Beads with various sizes and porosities were produced through changes in the process parameters, including the type and size of the dripper, speed of agitation of the solution, and type of drying. The results show that the type of dripper strongly influences the size of the beads and that the rotation speed influences the sphericity. The styling directly influenced the fluid absorption, demonstrating that the spheres dried by lyophilization can absorb up to 223% of their weight. In comparison, samples dried in a desiccator could absorb only 112% of their weight in body fluids. The porosity of the optimized beads was up to 90%, which is similar to that of human bone, and they did not show cytotoxicity. Therefore, the beads composed of alginate and hydroxyapatite produced here have the potential for application in tissue repair.