基于改进快速幂次趋近律的永磁同步电机滑模控制

针对永磁同步电机(PMSM)滑模控制指数趋近律中趋近速度与抖振之间的矛盾问题,基于快速幂次趋近律提出一种幂次项系数自适应调节的新型趋近律。所提趋近律将系统状态引入幂次项系数中,实现了系统状态由较远处到滑模面附近的趋近过程中加入幂次项的作用,在保证幂次项特点的前提下,动态响应过程的收敛速度大大提高。负载转矩是滑模速度控制器中的一个扰动项,设计了带有幂次项的滑模观测器,将观测值作为转矩前馈补偿。仿真结果表明,与快速幂次趋近律相比,所提趋近律具有更快的收敛速度,负载观测器能准确跟踪负载变化,提升了系统抗扰性能。     

中美法学教育之比较

当代中国的法学教育发展很快，但由于起步晚，至今在很多方面仍有不足。为便于借鉴美国法学教育之长，特从教育管理、教育目标、教育层次、教育方法、师资等方面进行比较，以探索一条有中国特色的法学教育之路。     

多元靶碰撞级联中的粒子能量

用一种推广的幂指数散射截面求解了溅射输运方程，获得更加一般的渐近解，这个渐近解不但以Urbassek等人几年前所给出的两个解为其特殊情况，而且还为作者提出的SC解提供了新的证据，此外通过计算并分析了Vicanek等人发表的新的输运理论，发现他们所提出的转换理论结果与Monte Carlo模拟结果一致是不正确的。     

车铣加工中心刀塔结构的动力学建模

由于车铣加工中心刀塔结构的复杂性和多结合面性，本文将其分解为四个子系统，结合面用等效弹簧和等效阻尼代替，利用一个柔性结合点可以用二个刚性结合点和一个子结构替换的原理，并运用机械阻抗凝聚法和子结构综合法建立了刀塔结构的动力学模型。     

Derivation of the multisymplectic Crank–Nicolson scheme for the nonlinear Schrödinger equation

The Crank–Nicolson scheme as well as its modified schemes is widely used in numerical simulations for the nonlinear Schrödinger equation. In this paper, we prove the multisymplecticity and symplecticity of this scheme. Firstly, we reconstruct the scheme by the concatenating method and present the corresponding discrete multisymplectic conservation law. Based on the discrete variational principle, we derive a new variational integrator which is equivalent to the Crank–Nicolson scheme. Therefore, we prove the multisymplecticity again from the Lagrangian framework. Symplecticity comes from the proper discrete Hamiltonian structure and symplectic integration in time. We also analyze this scheme on stability and convergence including the discrete mass conservation law. Numerical experiments are presented to verify the efficiency and invariant-preserving property of this scheme. Comparisons with the multisymplectic Preissmann scheme are made to show the superiority of this scheme.     

强化环保设计,促进水泥工业的可持续发展

从烟(粉)尘排放总量控制、大气污染物排放标准、清洁生产、中水回用、环境绿化和加强环境法制观念等方面,提出强化水泥建设项目环保设计和建设、促进水泥工业可持续发展的想法和建议。     

Pressure drop for single and two‐phase flow of non‐newtonian liquids in helical coils

New experimental results on pressure loss for the single and two‐phase gas‐liquid flow with non‐Newtonian liquids in helical coils are reported. For a constant value of the curvature ratio, the value of the helix angle of the coils is varied from 2.56° to 9.37°. For single phase flow, the effect of helix angle on pressure loss is found to be negligible in laminar flow regime but pressure loss increases with the increasing value of helix angle in turbulent flow conditions. On the other hand, for the two‐phase flow, the well‐known Lockhart‐Martinelli method correlates the present results for all values of helix angle (2.56‐9.37°) satisfactorily under turbulent/laminar and turbulent/turbulent conditions over the following ranges of variables as: 0.57 ≤ n′ ≤ 1; Re′ < 4000; Re_l < 4000; Re_g < 8000; 8 ≤ x ≤ 1000 and 0.2 ≤ De′ ≤ 1000.     

Rheological properties and compatibility of NR/EPDM and NR/brominated EPDM blends

Ethylene–propylene–diene terpolymer (EPDM) was modified by bromination reaction. Blending the resulting brominated EPDM with natural rubber (STR5L) and blending the unmodified EPDM with STR5L at various compositions were carried out. The rheological properties of the blends were investigated using a capillary extrusion. Shear flow curves of the pure rubbers and their blends illustrated the pseudoplastic property as shear thinning behavior with a power law index n < 1. True shear viscosity of all blends showed the negative deviation in relation to their additive values. Rheological behavior and two T_g's found from the DSC thermograms at all blend compositions indicated blend incompatibility for both sets of blends. The incompatibility of the vulcanized blends was also found by measuring the spin–spin relaxation time T₂ by pulsed NMR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 837–847, 2003     

Teeth segmentation of dental periapical radiographs based on local singularity analysis

Teeth segmentation for periapical raidographs is one of the most critical tasks for effective periapical lesion or periodontitis detection, as both types of anomalies usually occur around tooth boundaries and dental radiographs are often subject to noise, low contrast, and uneven illumination. In this paper, we propose an effective scheme to segment each tooth in periapical radiographs. The method consists of four stages: image enhancement using adaptive power law transformation, local singularity analysis using Hölder exponent, tooth recognition using Otsu's thresholding and connected component analysis, and tooth delineation using snake boundary tracking and morphological operations. Experimental results of 28 periapical radiographs containing 106 teeth in total and 75 useful for dental examination demonstrate that 105 teeth are successfully isolated and segmented, and the overall mean segmentation accuracy of all 75 useful teeth in terms of (TP, FP) is (0.8959, 0.0093) with standard deviation (0.0737, 0.0096), respectively.     

4-(α-吡啶甲酰基)-PMP的合成与谱学特性研究

合成了新吡唑啉酮类试剂1-苯基-3-甲基-4-(α-吡啶甲酰基)-吡唑啉-5-酮(简称4-(α-吡啶甲酰基)-PMP,下同)。在表征分子结构的同时,对其红外、紫外吸收光谱,核磁共振氢谱、碳谱,质谱等谱学特性和质谱裂解规律进行了分析与研究。