大型镁合金压铸机合模尾板的减重设计分析

尾板是压铸机合锁模机构中的关键零件,其刚度不仅关系到所加工零件的精度,而且直接影响到相关运动副乃至设备的寿命。为保证尾板在设汁过程中的合理性,文中对某30000kNJ压铸机尾板满载荷条件下的力学行为进行分析。利用有限元法比较原始和减承两种设汁方案的刚度以及应力等力学参量,根据计算结果对尾板加工制造中的要点给出相应的建议。整个分析结果表明,减重设计对尾板刚度将产生一定的影响,但目前的减重设计方案可以满足设计要求。     

基于Pro/E三维标准定位、夹紧元件库的建立

传统的专用夹具设计都是根据国标二维图样来完成的,随着CAD技术的日趋成熟,三维造型技术应用已越来越普及,采用Pro/E提前建立好三维标准定位、夹紧元件库,可大大缩短设计周期,降低产品开发及设计成本。     

CaAl2O4：Eu^2＋，Nd^3＋纳米粉体的合成与表征

采用溶胶一凝胶法制备了CaAl2O4：Eu^2＋，Nd^3＋纳米粉体发光材料。样品的XRD和SEM分析结果表明：800℃已形成CaAl2O4晶相；样品颗粒尺寸随灼烧温度升高而增加，平均粒径约为20nm～40nm。光谱分析表明：样品的激发光谱为240nm～400nm的宽带谱，在256．6nm和330．6nm处有激发峰。发光光谱是386nm～500nm的宽带谱，峰值位于440nm，与CaAl2O4：Eu^2＋，Nd^3＋粗晶材料相比，光谱发生了“蓝移”现象。样品的热释光峰值位于206℃，与粗晶材料相比，峰值向高温移动了96℃，热释发光峰曲线形状也变宽。样品的发光衰减是由初始的快衰减和随后的慢衰减构成，余辉时间为5h。     

Luminescent properties of Na2GdMg2(VO4)3:Eu3+ red phosphors for NUV excited pc-WLEDs

Herein, a series of novel Na₂GdMg₂(VO₄)₃:Eu³⁺ (NGMVO:Eu³⁺) red phosphors were elaborated by conventional solid-state reaction process. Their structural features, luminescent properties, energy transfer were researched at length. XRD patterns indicate that NGMVO:Eu³⁺ crystallized in single cubic garnet structure. Under the excitation of near ultraviolet light at 356 nm, the emission spectra of NGMVO host could be divided in two parts that resulted from ³T₂ → ¹A₁ and ³T₁ → ¹A₁ transitions of VO₄^3?. While NGMVO:Eu³⁺ phosphors show intense sharp red emission peaks including 590, 610, 652 and 706 nm that originated from ⁵D₀ → ⁷F_J (J = 1–4) transitions of Eu³⁺, respectively. The optimal concentration of Eu³⁺ is 0.7. Importantly, NGMVO:0.7Eu³⁺ sample presents high energy transfer efficiency (89 %) and high external quantum efficiency (48.3 %). Besides, its emission intensity remains 79 % at 420 K compared with that at 300 K, proving the good thermal stability of phosphors. All above results suggest that NGMVO:Eu³⁺ red phosphors have latent applications in white light emitting diodes.     

Parameter estimation method based on parameter function surface

By analyzing the structure of the objective function based on error sum of squares and the information provided by the objective function, the essential problems in the current parameter estimation methods are summarized: (1) the information extracted from the objective function based on error sum of squares is unreasonable or even wrong for parameter estimation; and (2) the surface of the objective function based on error sum of squares is more complex than that of the parameter function, which indicates that the optimal parameter values should be searched on the surface of the parameter function instead of the objective function. This paper proposes the concept of sample intersection and demonstrates the uniqueness theorem of intersection point (namely the uniqueness of optimal parameter values). According to the characteristics of parameter function surface and Taylor series expansion, a parameter estimation method based on the sample intersection information extracted from parameter function surface (PFS method) was constructed. The results of theoretical analysis and practical application show that the proposed PFS method can avoid the problems in the current automatic parameter calibration, and has fast convergence rate and good performance in parameter calibration.     

A low complexity algorithm of blind estimation of convolutional interleaver parameters

Interleaving plays an important role in many wireless communication systems,which is used to cope with burst errors and improve the reliability of data transmission.In this paper,we propose a new method to blindly estimate the parameters of convolutional interleaver in a non-cooperative context.The proposed method exploits both the property of interleaved stream and the deinterleaving technique.The product of the depth and width of the interleaver is firstly determined by analyzing interleaved data stream.Then the interleaved data stream is let to pass through a series of reconstructed deinterleavers.Thus the delay,the depth and width of the convolutional interleaver can be estimated by analyzing the deinterleaved data streams.Compared with other algorithms,the proposed method significantly reduces the searching scope and improves computational efficiency.Simulation results show that the algorithm has good performance even if errors exist.     

基于GIS的山地型城市用地适宜性评价

将GIS技术引入到城市用地适宜性评价中,可以利用已有的数据进行科学的分析评价,从而使后续的城市规划在综合分析基础上做出科学判断与决策。本文就ArcGIS软件在天水市区南北两山城市用地适宜性评价中的应用进行了论述,并将评价结果在三维视图中展现,使评价结果更加直观。     

CO_2加氢反应的基础研究进展

对通过CO_2加氢反应合成烃类和含氧化合物的研究近来获得重要进展,主要表现在催化剂的研制和反应动力学及反应机理方面的研究上。本文在大量有关文献的分析基础上概述了这些进展,为今后的进一步工作做了一些理论准备。     

单片机串行通讯技术在数据采集系统中的应用

能够完成异步通信的硬件电路称为UART,即通用异步接收器/发送器(Universal Asynchronous Receiver/Transmitter),本文介绍了应用8051单片机一主机多从机组成的串行异步通讯接口技术进行数据采集,采用RS-485标准接口通信,其抗干扰能力强,可与32台从机通讯,传输距离可达1200m,最大传送速率1Mb/S.     

防范网络内部威胁的动态安全模型的研究与设计

本文分析了外围安全环境、安全常规控制、技术控制和内部威胁之间的动态模型,揭示了内部信息安全各因素之间相互影响、相互制约的关系,并描述了内部信息安全控制的实现方法,对于防范内网威胁具有重要指导意义。