一种改进的ALOHA防碰撞算法

针对现有动态帧时隙ALOHA防碰撞算法在射频识别系统中的标签识别效率最高只能达36.8%的问题,利用标签码元序列的唯一性,改进经典的动态帧时隙ALOHA防碰撞算法中随机选择时隙的方式,提出一种基于标签码元的碰撞序列进行时隙选择的方法,有效降低了标签碰撞的概率,从而提高系统识别效率。仿真结果表明改进的ALOHA标签防碰撞算法识别效率最低为37.5%,随着实际标签数目与碰撞位序列所能确定的标签数目越接近,识别效率越高,最高能达到100%,明显优于现有的动态帧时隙ALOHA算法。     

熔池中液态金属自由表面温度分布与液面形状研究

根据Ｙｏｕｎｇ－Ｌａｐｌａｃｅ方程对液态铀溶池的自由表面进行了数值计算。得到了表面凹陷与表面温度分布的关系。阐明了电子枪加热金属表面时出现的凹陷是由于原子蒸汽对液态金属表面反冲压力所引起的，而不是电子束的冲量造成的观点。对不同最高温度及不同熔池宽度的液态铀熔池表面凹陷形状进行了计算。     

Highly Organized Porous Gelatin-Based Scaffold by Microfluidic 3D-Foaming Technology and Dynamic Culture for Cartilage Tissue Engineering

A gelatin-based hydrogel scaffold with highly uniform pore size and biocompatibility was fabricated for cartilage tissue engineering using microfluidic 3D-foaming technology. Mainly, bubbles with different diameters, such as 100 μm and 160 μm, were produced by introducing an optimized nitrogen gas and gelatin solution at an optimized flow rate, and N₂/gelatin bubbles were formed. Furthermore, a cross-linking agent (1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide, EDC) was employed for the cross-linking reaction of the gelatin-based hydrogel scaffold with uniform bubbles, and then the interface between the close cells were broken by degassing. The pore uniformity of the gelatin-based hydrogel scaffolds was confirmed by use of a bright field microscope, conjugate focus microscope and scanning electron microscope. The in vitro degradation rate, mechanical properties, and swelling rate of gelatin-based hydrogel scaffolds with highly uniform pore size were studied. Rabbit knee cartilage was cultured, and its extracellular matrix content was analyzed. Histological analysis and immunofluorescence staining were employed to confirm the activity of the rabbit knee chondrocytes. The chondrocytes were seeded into the resulting 3D porous gelatin-based hydrogel scaffolds. The growth conditions of the chondrocyte culture on the resulting 3D porous gelatin-based hydrogel scaffolds were evaluated by MTT analysis, live/dead cell activity analysis, and extracellular matrix content analysis. Additionally, a dynamic culture of cartilage tissue was performed, and the expression of cartilage-specific proteins within the culture time was studied by immunofluorescence staining analysis. The gelatin-based hydrogel scaffold encouraged chondrocyte proliferation, promoting the expression of collagen type II, aggrecan, and sox9 while retaining the structural stability and durability of the cartilage after dynamic compression and promoting cartilage repair.     

Frequency-dependent dynamic effective properties of porous materials

The frequency-dependent dynamic effective properties (phase velocity, attenuation and elastic modulus) of porous materials are studied numerically. The coherent plane longitudinal and shear wave equations, which are obtained by averaging on the multiple scattering fields, are used to evaluate the frequency-dependent dynamic effective properties of a porous material. It is found that the prediction of the dynamic effective properties includes the size effects of voids which are not included in most prediction of the traditional static effective properties. The prediction of the dynamic effective elastic modulus at a relatively low frequency range is compared with that of the traditional static effective elastic modulus, and the dynamic effective elastic modulus is found to be very close to the Hashin-Shtrikman upper bound.     

单一水文站洪水波计算方法

本文介绍应用水力学方法计算洪水波绳套曲线。应用动力波模式的格戈夫方法,精度较高,特别适用于洪水期流量涨落变幅较大的场合,应用扩散波模式的琼斯方法,易于掌握和计算。以上两种方法都只需要用一个水文站的资料即可计算。对两种方法计算所得结果,用实测原型资料进行了验证。本文还对影响绳套曲线变化的惯性项进行了分析、探讨。     

Dynamic Decoupling for Combined Shape and Gauge Control System in Wide Strip Rolling Process

The precision of profile and thickness is the most important target for wide strip rolling,but the coupling of profile control and thickness control is ignored in rolling schedule,which holds down the simultaneous quality improvement of profile and thickness.A cross-coupled process control model for combined shape and gauge control was developed on the basis of the fact that both controls for profile and thickness are realized by controlling the rolling gap.A dynamic decoupling controller was then proposed to decouple the model.Both the simulation results and the online production data are valid and ensure the quality of the decoupling controller.     

DSP系统动态电源管理在血流监测仪中的设计与实现

本文介绍了DSP系统动态电源管理在便携式超声多普勒血流监测仪设计中的实现,包括DSP动态频率调整、DSP低功耗模式的应用以及自动关机功能的实现等方面,详细阐述了DSP系统低功耗设计的软、硬件方法。     

一种大动态检测输入前端设计

一种基于小信号处理、无源网输入、数字化处理、智能化操作的方法,以求获得较好的灵敏度和极大的测量动态范围的测量前端电路设计。     

改善低压大电流变换器动态性能的新方案

提出一种新颖的采用DRC(DynamicLoadTransientResponseCircuit)辅助电路来改善低电压大电流变换器动态响应性能。通过一个小容量的能量存储电容和一个快速反应的误差放大器,可达到提高动态响应的效果。与传统方法相比,该法有成本低、空间小、效率高的特点。实验证明,DRC电路对提高动态响应有良好的效果。