一种对称非均匀细分曲面算法

为了得到能更好应用于CAD系统的细分曲面造型方法,提出一种基于B-样条的对称非均匀细分算法,其中的思想和均匀Lane-Riesenfeld节点插入算法相似。基于B-样条的节点插入算法,以Blossoming为工具,计算出细分后的新控制顶点。细分后得到的极限曲面由张量积样条曲面组成,在奇异点达到2C连续。与传统的细分曲面算法相比,该细分曲面算法具有良好的局部支撑性,大大降低了算法的复杂度,而且该算法是对称的,不用考虑定向问题。     

Electrochemical insertion of sodium into hard carbons

The electrochemical insertion of sodium ions into different types of hard carbons was achieved in electrolytes composed of ethylene carbonate as the solvent and NaClO₄ as the salt. For all the materials studied the sodium uptake increases when the carbon highest heat treatment temperature (HTT) decreases. PAN-based carbon fibres appear to be suitable structures to allow significant sodium insertion. Thus, T650 ex-PAN fibres lead to a reversible capacity close to 209 mAh g⁻¹. In that case, sodium insertion occurs in two main ways: one is the adsorption on the single graphene layers and the other is the concomitant insertion into the porosity that occurs below 0.1 V versus Na⁺/Na. This second mechanism, which is indicated by a low-voltage plateau on the electrochemical curves, allows significant insertion. The compared electrochemical study of two saccharose-coke samples corresponding to different regions of Dahn's classification underlines the importance of the carbon precursor and of the manufacture process. The reversible capacity is equal to 184 mAh g⁻¹ for the sample heat treated at 800 °C which presents a high hydrogen content whereas it is close to 145 mAh g⁻¹ for the one characterized by a HTT of about 1500 °C and a low hydrogen content. The best electrochemical performances are obtained for pyrolyzed cellulose carbons. Indeed, the reversible capacity is about 279 mAh g⁻¹. Outgassing these carbons at 950 °C results in such a decrease of the reversible capacity down to 145 mAh g⁻¹. That can be related either to the thermal elimination of heteroelements or to modifications of the pore size distribution. Consequently, the most suitable hard carbon material for anodic applications in rechargeable sodium-ion batteries should both present a high residual hydrogen content and a significant microporosity.     

Synthesis and electrode performance of layered nickel dioxide containing alkaline ions

Several polymorphs of layered nickel dioxide were prepared by using the chemical insertion of alkaline ions into Li_0.10NiO₂. We used aqueous AOH (A = Li, Na, K) solutions as reducing agents. Sodium and potassium insertion resulted in hydrated layered compounds that can be classified as γ-NiOOH with high crystallinity, while lithium insertion occurred without hydration. We discuss the coordination environment around the A⁺ ions for these inserted compounds. The thermal behavior, analyzed using high temperature (HT) X-ray diffraction (XRD) and thermogravimetric (TG) measurements, indicated that heating the hydrate at 150 °C yielded its dehydrate. The electrode performance of the nickelate was studied in lithium cells. We discuss the effect of interlayer water on cell rechargeability and the similarity between these nickelate and hydrated manganese dioxide (birnessite).     

Insertion/removal kinetics of lithium ion in spinel LiCuxMn2-xO4

The insertion/removal processes of lithium ion in spinel lithium manganese oxide（LiMn204） and copper doped spinel lithium manganese oxide （LiCuxMn2-xO4） on a powder microelectrode were studied by electrochemical impedance spectroscopy（EIS）, cyclic voltammetry（CV） and X-ray diffractometry（XRD）. The insertion/removal process of lithium ion in the spinel oxides consists of three steps： charge transfer of lithium ion on the surface of the spinel oxides, diffusion and occupation of lithium ion in the lattice of the spinel oxide. Similar to chromium, the doping of copper in spinel lithium manganese oxide results in the increase of the charge transfer resistance and the double layer capacitance for lithium insertion or removal, and the decrease of the diffusion coefficient of lithium ion in the lattice of spinel oxide. However, the insertion capacitance, a parameter reflecting the occupation of lithium ion in the lattice of the spinel oxide, is hardly influenced by the doping of copper. The influence of the doped copper on the kinetic process of lithium insertion/removal in spinel lithium manganese oxide is related to the contraction of spinel lattice.     

快速二维中值滤波算法及其FPGA硬件设计

针对数字图像噪声抑制过程中去噪性能要求较高、处理速度要求较快的问题,以常规中值滤波算法为基础,提出用归并插入排序算法来实现5×5快速中值滤波器的方案。通过对滤波窗口中行列像素点以及对角线上的像素点的归并插入排序,得到窗口的中值,在Xilinx的ISE10.0软件开发环境下成功完成该算法硬件设计。相比常规算法,该方案简单易行、运算速度快,能够满足实时性的要求,易在现场可编程门阵列（FPGA ）上实现,为实时性要求较高的图像去噪领域提供了可靠的技术支持。     

基于FPGA的喷气织机引纬控制系统设计

提出了一种新的以FPGA为控制核心的高精度引纬控制系统.以EP3C10F256C8芯片为核心,设计了控制系统的硬件电路和软件结构.利用FPGA程序并行执行实现实时参数调节、编码器检测、引纬控制信号产生等功能.实验结果表明:该引纬控制系统使喷气织机的车速达到1200 r/min,入纬率达到2000 m/min以上,满足喷气织机高速性和对引纬控制信号实时性、一致性的要求,显著提高了喷气织机引纬控制系统性能.     

Delaunay三角网动态更新算法的研究进展

通过对Delaunay三角网动态更新算法进行研究,综述了Delaunay三角网中插入和删除点、约束线算法以往研究.详细介绍点定位、LOP优化、对角线交换等关键技术的研究进展,并对比各种方法的优缺点,分析已解决的问题和仍存在的问题.最后对更新算法研究不足之处进行总结,并提出若干可能的研究方向.     

Almost strictly total positivity of NUAT B-spline basis

Total positivity of spline basis has been well known in the theory of computer aided geometry design, which is highly related with good shape preserving property. Almost strictly total positivity is stronger, which could determine the positive minors while the other is zero. In this paper, a geometrical approach is proposed to prove the collection matrices of NUAT B-spline basis are almost strictly totally positive. In this paper, knot insertion algorithm combined with coefficient variation of NUAT B-spline function, we put forward an intuitive and geometrical method.     

黄土地区隧道锁脚锚管作用机理分析研究

锁脚锚管在隧道施工中被广泛应用,而目前施工中锁脚锚管的长度、下插锚角度等几乎全部依靠工程经验来确定。通过有限元软件模拟了黄土隧道锁脚锚管在不同长度和角度下承担的最大内力和最大变形量,对比分析了锁脚锚管的长度、锚管下插角度与位移的关系。研究结果表明,锚管长度越长,变形越小,但最为经济的锚管长度为3 m左右;当所加锚管下插角在±30°时有利于支护内力的发挥。在研究结论基础上提出了隧道施工中应该采用的锁脚锚管合理长度及下插角度。     

Metal Ions versus Protons: Tracking of Charge-Carrier Insertion into a Cathode Oxide in Aqueous Rechargeable Batteries

Protons in aqueous electrolytes can perform as an additional type of charge carrier for insertion/extraction in addition to the primary carrier cations in aqueous rechargeable batteries. Despite many diverse claims regarding the effect of protons, mutually conflicting experimental results and their interpretations without direct evidence have been reported over the last decade. Systematic examinations and analyses are thus imperative to clarify the conditions of proton insertion in aqueous rechargeable batteries. Utilizing V₂O₅ as a model cathode and beaker-type cells with a sufficient amount of ZnSO₄ aqueous electrolytes in this work, it is demonstrated that protons are inserted into the cathode prior to Zn-ions in low-pH conditions (pH ≤ 3.0). In stark contrast, the influence of protons on the discharge voltage and capacity is insignificant, when either the pH becomes higher (pH ≥ 4.0) or the electrolyte volume is considerably low in coin-type cells. Similar behavior of pH-dependent proton insertion is also verified in Na–, Mg–, and Al-ion electrolytes. Providing a resolution to the controversy regarding proton insertion, the present study emphasizes that the influence of protons substantially varies depending on the pH and relative volume of electrolytes in aqueous batteries.