浙江省自然保护区落叶阔叶林群落物种组成与结构比较研究

群落组成是影响森林演替方向的主要因素之一.浙江省地处我国东部,属典型亚热带气候,全省植被类型多样,物种组成丰富.为了更好地了解浙江省自然保护区内落叶阔叶林群落结构,于2012年在浙江清凉峰自然保护区（QLF）、浙江天目山自然保护区（TMS）、浙江龙王山自然保护区（LWS）、浙江九龙山自然保护区（JLS）、浙江大盘山自然保护区（DPS）5个自然保护区内选取并建立了12个30 m×30 m不同落叶阔叶群落样地,对样地中胸径（DBH）≥1 cm的木本个体进行了坐标定位和每木调查.结果表明,12个样地内木本植物共计218种,隶属于46科,103属,总计8 935株.各样地物种数由大到小依次为,LWS12、TMS31、QLF21、QLF22、JLS31、LWS22、TMS21、LWS31、JLS32、QLF12、DPS11、LWS11;从物种多度和重要值等指标来看,除DPS11群落具有比较明显的优势种以外,其余各群落内物种重要值分配较均匀;所有群落的区系成分以温带成分较多,原生林群落温带成分比例较次生林群落高,属的分布也更为相似;12个群落中除QLF22和DPS11中所有物种的径级分布分别呈“L”型和偏正态外,其余各群落的径级分布均呈倒“J”型,具有良好的更新性;相同树种在不同群落内的径级分布各不相同,表明群落类型与种群动态有密切关系.     

Simulation of magnetization behaviours of Sm（Co,Fe,Cu,Zr）z magnet with low Cu content

The effects of microstructure, cell orientation and temperature on magnetic properties and the coercivity mechanism in Sm(Co,Fe,Cu,Zr)z with low Cu content are studied by using the micromagnetic finite element method in this paper. The simulations of the demagnetization behaviours indicate that the pinning effect weakens gradually with the thickness of cell boundary decreasing and strengthens gradually with the cell size decreasing. Because of the intergrain exchange coupling, the coercivity mechanism is determined by the difference in magnetocrystalline anisotropy between the cell phase and the cell boundary phase. And the coercivity mechanism is related to not only the cells alignment but also temperature. With temperature increasing, a transformation of the demagnetization mechanism occurs from the domain pinning to the uniform magnetization reversal mode and the transformation temperature is about 650~K.     

n维广义IMBq方程的初边值问题

本文研究广义IMBq方程utt-2utt-2tu=2g(u)的初边值问题局部广义解和古典解的存在性、唯一性,并给出解爆破的充分条件.     

MAGNETIC VISCOSITY AND DEMAGNETIZATION BEHAVIOUR IN ISOTROPIC NANOCRYSTALLINE Pr12Fe82B6 RIBBONS

We present the experimental results of the magnetic viscosity, demagnetization curve and recoil loop for isotropic nanocrystalline Pr₁₂Fe₈₂B₆ ribbons prepared by melt-spinning. The thermal fluctuation field, activation volume and irreversible demagnetization are discussed. The coercivity mechanism is mainly determined by the inhomogeneous nucleation rather than a simple nucleation of reverse domain.     

Residual field suppression for magnetocardiography measurement inside a thin magnetically shielded room using bi-planar coil

For a magnetocardiography (MCG) system inside a magnetically shielded room (MSR), the residual field should be further suppressed to obtain high-quality MCG signals. In this paper, a compensation system has been developed based on the bi-planar coil and the proportional-integral-derivative (PID) controller. The bi-planar coil, derived from the target-field theory and the Tikhonov regularization method, is utilized to generate magnetic field with high uniformity in the pre-defined target region. And the PID controller is introduced to provide dynamic compensation current for the coil, according to the residual field change monitored by a reference SQUID magnetometer. The measurement results show that the noise suppression ratio (NSR) can reach above 20 dB in the low-frequency range from 0.1 Hz to 50 Hz. The DC component and the fluctuation of the residual field in time-domain can be respectively suppressed to 0 pT and 4 pT, indicating that this proposed compensation method is useful for the MCG measurement.     

一类具记忆项的非线性强阻尼双曲方程解的爆破性

利用一个特殊不等式得到一类具记忆项的非线性阻尼双曲方程解的爆破条件.方程描述了具记忆时滞的粘弹性梁问题.     

Syntheses and Crystal Structures of Mono- and Bis-3-pyridinyldiazo-dipyrromethane

Two azopyrrole compounds, 1 and 2, have been synthesized and characterized. The crystal of compound 1 is of triclinic, space group P1 with a = 6.5632(10), b = 7.0805(10), c = 17.436(3) A, α = 89.504(2), β = 79.460(2), γ = 84.2788(2)o, V = 792.6(2) A3, Z = 2, C18H21N5, Mr = 307.40, Dc = 1.288 g/cm, F(000) = 328 and μ(Mo Kα) = 0.080 mm-1. The crystal of compound 2 is of triclinic, space group P1 with a = 9.7324(8), b = 9.9779(8), c = 12.3817(11) A, α = 87.052(2), β = 71.766(2), γ = 70.968(2)o, V = 1077.86(16) A3, Z = 2, C23N24H8, Mr = 412.5, Dc = 1.271 g/cm, F(000) = 436 and μ(Mo Kα) = 0.081 mm-1. The molecules of compounds 1 and 2 prefer to form dimers through pairs of N–H···N hydrogen bonds between pyrrole NH groups and pyridine N atoms. In addition, in the crystal of compound 2, the dimers self-assemble into a layer structure through N–H···N hydrogen bonds between pyrrole NH groups and azo N atoms as well as C–H···N hydrogen bonds between the ethyl groups and pyridine N atoms.     

一类巴西列维奇函数的Fekete-Szeg问题

本文我们引入了一类巴西列维奇函数，讨论了该类函数上的Fekete－Szego问题，所获得的结论是准确的．一些已知的结论是本文的特例．     

雷达天线控制系统频域辨识与仿真方法研究

雷达天线控制系统仿真是雷达系统目标跟踪动态仿真中一个重要环节。为解决雷达天线控制系统仿真中滞后误差大、动态效果差等问题,依据某雷达天线控制系统性能实际测试结果,以典型系统模型作为研究对象,利用频域最小二乘法完成模型参数辨识,建立系统模型,并对辨识模型进行验证。在此基础上,采用基于时域的增广矩阵法对系统进行了数字快速仿真分析。结果表明,辨识模型满足精度,且增广矩阵法能够有效快速地完成系统数字仿真,对天线控制系统建模以及快速动态仿真研究具有一定的参考价值。     

火控雷达动态目标探测跟踪建模仿真

火控雷达目标探测跟踪是现代与未来防空作战的首要任务,也是火控系统的关键环节。针对火控雷达连续、自动、快速跟踪目标的特点,首先分析了火控雷达系统闭环连续探测跟踪工作流程,然后利用信号级建模方法,在信号层面上进行了雷达回波信号生成、信号处理与跟踪控制的一体化建模,并给出了各模块模型,最后完成动态火控雷达闭环目标距离、方位角与高低角三维探测跟踪测量过程仿真与分析。仿真结果不仅验证了建模方法与模型逼真有效,也对以后火控雷达跟踪性能评估、数据处理等仿真研究有着一定的参考价值。