圆型腔零件粗铣削加工编程方法的探讨

为了提高加工效率,延长刀具寿命,改善工件表面质量,提出了一种新的加工方法--半圆渐进滚铣圆法,对该方法的工艺、编程、加工过程和特点进行了详细阐述,为圆型腔零件的数控铣削加工提供了新的参考.     

Vibrations of microscale circular plates induced by ultra-fast lasers

In this study, the vibration phenomena during pulsed laser heating of a microscale circular plate are investigated. The circular plate is made of silicon and is heated uniformly on the upper surface by a non-Gaussian laser beam with a pulse duration of 2 ps, which incites vibration due to the thermoelastic coupling effect. The coupling between the temperature field and stress field induces energy dissipation and converts mechanical energy into heat energy, which is irreversible. An analytical-numerical technique based on the Laplace transform is utilized to calculate the vibration of the deflection and thermal moment. The size effect is analyzed. Finally, the vibration behaviors of the circular plate under different environmental temperatures are compared.     

循环经济和科技进步是福建省连城锰矿持续发展的重要途径

论述了福建省连城锰矿在矿山地质、采矿、选矿、废弃物利用等方面实施循环经济、综合回收利用资源所采取的措施,提出了发展循环经济应解决的问题。     

Energy absorption of aluminium alloy circular and square tubes under an axial explosive load

The energy absorption of circular and square aluminium alloy tubes subjected to an axial explosive load, which is transmitted to a tube by a small attached mass, is discussed. Particular attention is paid to the interaction between the inertia of the attached mass and a tube when the importance of the initial compression phase is revealed. The effect of this phase on the mean load, which is characteristic of the energy absorption capacity of structural elements, is demonstrated. The influence of the material models on the prediction of the response of aluminium alloy circular and square tubes is also discussed in relation with the temperature effects caused by the high strain rates. The analysis shows that the material properties play an important role for the formation of the buckling pattern due to the finite duration of the initial compression phase when plastic stress waves at different speeds propagate along a shell.     

Phosphorus purification in a paddy field watershed using a circular irrigation system and the role of iron compounds

In a paddy field watershed using a circular irrigation system, it was clear that the watershed tended to purify phosphorus by an analysis on the mass balance of pollutants. A reasonable hypothesis was that the phosphorus precipitation with iron compounds in a river may affect the purification. To verify this, an investigation on phosphorus and iron in the river water and sediments were conducted. Total iron (T-Fe) concentration in the river ranged from 3 to 10 mg/L, and the concentration increased with the river flowing down, whereas dissolved iron (D-Fe) concentrations tended to decrease. The concentrations of total phosphorus (T-P) and phosphate phosphorus (PO4-P) also tended to decrease as the river flowing down. From the analysis of mass balance, the study watershed was considered to be a substantial iron source, having 307 and 206 kg/ha of annual outflow loads. In the sediment of the river, T-P ranged from 834 to 2440 microg/g, and most of the inorganic compound was Fe-P. In addition, The Bray No.2 phosphorus (441-1030 microg/g) was much higher than in paddy soils. Therefore, the sediment contained a large amount of phosphorus and was fertile. From the results of laboratory-based experiments, it can be said that iron compounds in the river were sufficient for the precipitation of phosphorus. Since the accumulated sediment in the river was conventionally dredged up and transported to adjacent paddy fields, it was considered to be that this operation played a significant role in phosphorus resource recycling.     

超前支护复合土钉的双圆弧破坏分析

对具有超前支护桩的复合土钉进行整体稳定性分析时,存在试算滑弧与桩身相交的问题,因而提出双圆弧破坏模式,可对桩底以上滑弧的稳定性进行分析。推导了适于编程计算的双圆弧稳定安全系数表达式。通过对工程实例的验算分析了这一方法的合理性。     

无粘结预应力技术在大型圆形仓池结构中的应用

本文以某一贮煤筒仓和某一圆形水池为例 ,对无粘结预应力技术在大型仓池结构中的应用进行了较详细的介绍 ,对该类工程的设计和施工提出了建议     

基于模式空间变换的宽带波束形成方法

由于均匀圆阵独特的空间分布使其比均匀线阵有许多优点,且均匀圆阵在模式空间变换可以转化为虚拟线阵,而转换后的虚拟线阵具有远场模式下与频率无关的特性,因此均匀圆阵可以处理宽带信号。在此分析基础上,针对均匀圆阵提出一种基于模式空间变换的宽带波束形成方法。设计出该方法的原理图并给出了该方法的具体操作步骤,还通过计算机仿真实验验证了方法的有效性。该方法只适用于均匀圆阵系统,因而针对性强,具有很好的应用前景。     

基于环形统计量和支持向量机的CPM信号调制识别

频率成形脉冲是CPM信号调制相位的度量,也是信号解调必需的调制参数,包括脉冲形状和关联长度。本文提出一种基于环形统计量和支持向量机(Support Vector Machines, SVM)的CPM信号调制识别技术。首先将基带采样信号的瞬时频率看作环形分布的随机变量,计算瞬时频率的三角矩;然后提取其统计量作为分类特征;最后利用支持向量机,实现了不同频率成形脉冲CPM信号的识别。仿真结果表明,该方法可以实现在不同调制参数类型情况下任意脉冲成形CPM信号的识别。仿真结果中给出了包括多指数CPM信号在内的,不同频率成形脉冲CPM信号间的识别率。由于本文采用基于SVM的分类器,不依赖于信噪比条件,因此具有很高的分类性能和良好的稳健性。      

Experimental investigation on flow characteristics in circular tube inserted with rotor-assembled strand using PIV

Rotor-assembled strand works as a typical tube insert to achieve heat transfer augmentation and scale inhibition in a heat exchanger. In this work, the PIV experiment regarding the flow fields in a circular tube inserted with rotor-assembled strand was conducted and the flow characteristics on transverse section and longitudinal section were analyzed. The results showed that swirling flow was produced in the tube inserted with rotors and it was particularly strong within the swing diameter of the rotor on the section that contains the rotor; the average turbulence intensity and the radial velocity were improved notably; the velocity vectors on the longitudinal section remained along the direction of a straight line; both the swirling flow and average turbulence intensity were higher for the rotor with three blades than for the rotor with two blades except that the radial velocity was approximate, but they were all reduced by enlarging the lead of the rotor. Characterization of the flow patterns in a circular tube contributes to understanding the heat transfer efficiency and scale inhibition performance of the rotor-assembled strand and provides guidance for its application.