感应式线圈靶半径分布对区截信号的影响

水下弹丸测速常采用感应式线圈靶作为区截装置。以点磁偶极子作为磁化弹丸的物理模型 ,运用电磁学理论 ,导出了弹丸穿越线圈靶时的感应电动势表达式 ,分析了线圈靶半径对区截信号的影响 ,得出了具有指导意义的结论     

内融冰式蓄冰桶数学模型的改进

介绍内融冰式蓄冰桶改进的数值计算模型.将盘管分成许多小段进行研究,考虑了蓄冷时冰层和释冷时水层间的连通现象及蓄冷期冰的温度变化和释冷期水温的变化.所得结果可为设计选用提供依据.     

用于头盔瞄准具的电磁敏感系统误差的校正

分析了用于头盔瞄准具的电磁敏感系统的系统误差,提出了一种校正方法。该方法可一次校正由于工作环境不良引起的电磁场畸变以及由于三轴天线轴不正交所产生的系统误差,其可行性已被计算机模拟和实验所证明。     

Synthesis,characterization, and self‐assembly of ion‐bonded A2B rod‐coil copolymer with oligo(para‐phenyleneethynylene) as rod segment

Supramolecular A₂B rod‐coil copolymer, composed of two polystyrene (PSt) arms and one oligo(para‐phenyleneethynylene) (OPE) arm linked via ionic bond, has been designed and successfully synthesized. First, a trifunctional initiator, methyl 1,3‐bis(bromomethyl)benzonate, was prepared and used to initiate the polymerization of styrene under atom transfer radical polymerization (ATRP) condition to provide polystyrene (PSt) carrying monoester group at the middle of polymer chain. Then, the ester group was transferred into tertiary amino group to give amino‐functionalized PSt, (PSt)₂? N(CH₃)₂. Subsequently, the ion‐bonded rod‐coil copolymer, (PSt)₂? OPE, was obtained by the reaction of (PSt)₂? N(CH₃)₂ with carboxy‐terminated OPE (OPE? COOH). The resulting copolymer was characterized by nuclear magnetic resonance (NMR), Fourier transformer infrared (FTIR), and gel permeation chromatography (GPC) techniques. Vesicles and spherical micelles were generated from this supramolecular rod‐coil copolymer through the manipulation of the initial polymer concentration in toluene. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7667–7676, 2008     

一种基于变频器PID控制的卷料匀拉力输送装置的应用

通过对卷料输送能力和材料拉伸强度的分析,应用变频器内置的PID控制功能,设计了一种卷料匀拉力输送装置,该装置采用变频器PID控制、卷心驱动的方式,实时跟踪主驱动线速度,同步精度高,同时保证材料不会因拉伸变形、拉断,图案不失真.该装置已在烟草包装机械上验证,使用方便,性能可靠.     

Acoustic noise simulation and measurement of a gradient insert in a 4 T MRI

High speed switching of current in gradient coils within high magnetic field strength magnetic resonance imaging (MRI) scanners results in high acoustic sound pressure levels (SPL) in and around these machines. Many studies have already been conducted to characterize the sound field in and around MRIs and various methods have been investigated to attenuate the noise generated. In the work presented here a computational vibro-acoustic model was developed based on an iteratively modified and validated finite element (FE) model to characterize the acoustic noise properties of the gradient coil. The simulation results from the computational model were verified through experimental noise measurement for the gradient coil insert in a 4 T MRI scanner by using swept sinusoidal time waveform inputs. Comparisons show that the computational model predicts the noise characteristic properties extremely accurately. There are three dominant frequency bands where the SPL is much higher than those at other frequencies. The SPL in the horizontal direction is much higher than that in the vertical direction due to the excitation to the horizontally placed X coil. The SPL to the inner surface of the coil is higher than far from the inner surface, which proves that the acoustic noise is radiated from the inner surface and primarily caused by the normal vibration of the inner surface. Further verification was conducted by using two types of trapezoidal sequence inputs usually used, which is to simulate real scanning sequences for small animals. Again the accuracy of the developed model is verified. The validated acoustic computational model could be used as an effective method to predict the noise that would be produced by a coil in the design stage. Modification of the structural design or the excitation pulse could be performed to reduce the acoustic noise when the gradient coil is in scanning.     

改进小脑模型网络的干式变压器卷线机跑偏信号谐波分析

提出一种基于改进的小脑模型控制器（CMAC）神经网络的干式变压器卷线机跑偏信号谐波分析方法．该方法在检测到干式变压器卷线机跑偏信号的基础上，对不同频率的谐波进行了分析、推论，将常规CMAC网络的学习因子改成随学习误差的变化动态调整，然后采用基于改进的CMAC神经网络对跑偏各谐波分别辨识，再取主次非线性谐波叠加．辨识结果表明，这种方法不仅能方便地识别出最大跑偏信号谐波基频的最小频率范围，而且比在相同情况下采用常规反向传播（BP）的网络辨识的精度高，学习速度提高20％，同时得到了最大跑偏信号谐波的最简单模型．     

ABA‐type liquid crystalline triblock copolymers via nitroxide‐mediated radical polymerization: Design,synthesis, and morphologies

We have designed and synthesized rod–coil–rod triblock copolymers of controlled molecular weight by two‐step nitroxide‐mediated radical polymerization, where the rod part consists of “mesogen‐jacketed liquid crystalline polymer” (MJLCP). The MJLCP segment examined in our studies is poly{2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene} (MPCS) while the coil part is polyisoprene (PI). Characterization of the triblock copolymers by GPC, ¹H and ¹³C NMR spectroscopies, TGA, DSC confirmed that the triblock copolymers were comprised of microphase‐separated low T_g amorphous PI and high T_g PMPCS blocks. Analysis of POM and 1D, 2D‐WAXD demonstrated that the triblock copolymers formed nematic liquid crystal phase. Morphological studies using TEM indicated the sample formed lamellar structure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5949–5956, 2007     

ToF‐SIMS depth profiling of a complex polymeric coating employing a C60 sputter source

A complex poly(vinylidene difluoride) (PVdF)/poly(methyl methacrylate) (PMMA)‐based coil coating formulation has been investigated using time‐of‐flight SIMS (ToF‐SIMS). Employing a Bi₃⁺ analysis source and a Buckminsterfullerene (C₆₀) sputter source, depth profiles were obtained through the polymeric materials in the outer few nanometres of the PVdF topcoat. These investigations demonstrate that the PVdF coating's air/coating interface is composed principally of the flow agent included in the formulation. Elemental depth profiles obtained in the negative ion mode demonstrate variations in the carbon, oxygen and fluorine concentrations within the coating with respect to depth. All three elemental depth profiles suggest that the PVdF coating bulk possesses a constant material composition. The oxygen depth profile reveals the presence of a very thin oxygen‐rich sub‐surface layer in the PVdF coating, observed within the first second of the sputter/etch profile. Retrospectively, extracted mass spectra (from the elemental depth profile raw data set) of the PVdF coating sub‐surface and bulk layers indicates this oxygen‐rich sub‐surface layer results from segregation of the acrylic co‐polymers in the formulation towards the PVdF coating air/coating interface. Molecular depth profiles obtained in both the positive and negative secondary ion modes provide supporting evidence to that of the elemental depth profiles. The molecular depth profiles confirm the presence of a sub‐surface layer rich in the acrylic co‐polymers indicating segregation of the co‐polymers towards the PVdF topcoats air‐coating surface. The molecular depth profiles also confirm that the PVdF component of the topcoat is distributed throughout the coating but is present at a lower concentration at the air‐coating interface and in the sub‐surface regions of the coating, than in the coating bulk. Copyright © 2007 John Wiley & Sons, Ltd.     

微硬盘驱动器的时变线性模型及其跟踪控制研究

引入磁头臂转动角度变量，建立音圈马达驱动器的时变线性系统模型，利用Lyapunov稳定性理论及线性矩阵不等式凸优化技术，通过设计状态观测器和反馈控制器，解决了该系统的跟踪控制问题。将此控制器与复合非线性控制器分别用于音圈马达驱动器的基本模型及本文的定常线性模型进行仿真比较，获得其优越性；最后将设计的控制器用于所设计的音圈马达驱动器的时变线性系统，获得跟踪速度快、跟踪精度高的效果。