基于二维声子晶体第一带边态的声学定向辐射

采用多重散射方法研究二维四方钢/水声子晶体中线源的辐射问题。数值结果表明利用声子晶体ΓΜ方向的第一带边态可以实现声定向辐射。利用文中设计的三角形晶体结构既可以实现声波的单束定向辐射,还能够得到传播方向互相垂直的双束定向辐射。该研究对声子晶体功能器件的设计具有一定的意义。     

Effects of periodic modulation on the nonlinear Landau--Zener tunneling

We study the Landau-Zener tunneling of a nonlinear two-level system by applying a periodic modulation on its energy bias. We find that the two levels are splitting at the zero points of the zero order Bessel function for high-frequency modulation. Moreover, we obtain the effective coupling constant between two levels at the zero points of the zero order Bessel function by calculating the final tunneling probability at these points. It seems that the effective coupling constant can be regarded as the approximation of the higher order Bessel function at these points. For the low-frequency modulation, we find that the final tunneling probability is a function of the interaction strength. For the weak inter-level coupling case, we find that the final tunneling probability is more disordered as the interaction strength becomes larger.     

Design and implementation of a programming circuit in radiation-hardened FPGA

We present a novel programming circuit used in our radiation-hardened field programmable gate array （FPGA） chip.This circuit provides the ability to write user-defined configuration data into an FPGA and then read it back.The proposed circuit adopts the direct-access programming point scheme instead of the typical long token shift register chain.It not only saves area but also provides more flexible configuration operations.By configuring the proposed partial configuration control register,our smallest configuration section can be conveniently configured as a single data and a flexible partial configuration can be easily implemented.The hierarchical simulation scheme, optimization of the critical path and the elaborate layout plan make this circuit work well.Also,the radiation hardened by design programming point is introduced.This circuit has been implemented in a static random access memory（SRAM）-based FPGA fabricated by a 0.5μm partial-depletion silicon-on-insulator CMOS process.The function test results of the fabricated chip indicate that this programming circuit successfully realizes the desired functions in the configuration and read-back.Moreover,the radiation test results indicate that the programming circuit has total dose tolerance of 1×10⁵ rad（Si）,dose rate survivability of 1.5×10¹¹ rad（Si）/s and neutron fluence immunity of 1×10¹⁴ n/cm².     

平板二维声子晶体声波能带结构研究

利用超元胞法,研究由钢板上生长有限长度的钢柱体形成的散射体嵌入环氧树脂基体中所构成的平板二维声子晶体的声波能带结构,分析散射体的几何参数如柱体的高、半径和板的厚度对声波带隙的影响。研究结果表明:(1)这种新型的声子晶体具有很宽的带隙,且带隙出现在低频范围内;(2)散射体的几何参数对带隙的宽度有很大的影响,它们是控制带隙宽度的主要因素。     

饱和两相介质动力固结问题时域求解的精细时程积分方法

针对u-p形式的饱和两相介质波动方程,采用精细时程积分方法计算固相位移u,采用向后差分算法求解流体压力p,建立了饱和两相介质动力固结问题时域求解的精细时程积分方法。针对标准算例,对该方法的计算精度进行了校核。开展了该方法相关算法特性的研究,对采用不同数值积分方法计算非齐次波动方程特解项计算精度的差异进行了对比研究,并对采用不同积分点数目的高斯积分法计算特解项条件下计算精度的差异进行了对比研究。研究结果表明,(1)该方法具有良好的计算精度。(2)计算非齐次波动方程特解项的数值积分方法中,梯形积分法的计算精度最差,高斯积分法、辛普生积分法和科茨积分法都具有较好的计算精度。(3)增加高斯积分点数目对于提高计算精度的作用并不显著。     

多层波导中矢量波动的时域人工边界条件

本文提出了一种近似的时域人工边界条件(artificial boundary condition,ABC)用来模拟含有瑞利阻尼的线弹性多层波导平面内的矢量波动,该ABC是时域稳定的,且能与有限元法无缝耦合.建立ABC的思路是,首先将多层波导的矢量波动方程简化为x方向和y方向解耦的两个标量波动方程;其次基于比例边界有限元...     

辐射加固SOI工艺FPGA的设计与验证

进行了一款辐射加固SRAM基VS1000 FPGA的设计与验证。该芯片包含196个逻辑模块、56个IO模块、若干布线通道模块及编程电路模块等。每个逻辑模块由2个基于多模式4输入查找表的逻辑单元组成,相对传统的4输入查找表,其逻辑密度可以提高12%;采用编程点直接寻址的编程电路,为FPGA提供了灵活的部分配置功能;通过对编程点的完全体接触提高了全芯片的抗辐射能力。VS1000 FPGA基于中电集团第58所0.5μm部分耗尽SOI工艺进行辐射加固设计并流片,样片的辐照试验表明,其抗总剂量水平达到1.0×105rad(Si),瞬态剂量率水平超过1.5×1011rad(Si)/s,抗中子注量水平超过1.0×1014n/cm2。     

一种抗辐射加固FPGA 编程电路的设计与实现

本文介绍了抗辐射加固SOI-SRAM基FPGA编程电路的设计与实现。该电路完成FPGA配置数据的下载与回读。该编程电路采用编程点直接寻址的方式,相对典型的移位寄存器链寻址方式不仅能够节约面积开销而且可以提供更为灵活的配置选择。通过对本电路提出的部分配置控制寄存器的配置,该编程电路可以实现的最小配置单元仅包含1位数据,FPGA更为灵活的部分重配置功能得以方便实现。层次化的仿真策略,对关键路径的优化及精密的版图布局保证了该电路的性能。此外对编程点进行了抗辐射加固设计。该电路在基于0.5μm部分耗尽SOI工艺SRAM基的FPGA中实现。功能测试结果表明, 该编程电路成功实现FPGA配置数据的下载与回读,且抗辐照实验结果表明,抗总剂量水平超过1x105Krad(Si), 抗瞬态剂量率水平超过1.5x1011 rad(Si)/s,抗中子注入量水平达到1x1014 n/cm2。     

音叉型声子晶体能带结构研究

利用超元胞法研究音叉型散射体构成的声子晶体的声波带结构,分析音叉型散射体的几何参数(板的厚度,圆柱体的半径和高)对能带结构的影响.研究结果表明:这种新型的声子晶体比传统声子晶体具有更优的带隙,而且带隙的调节机制更为简单,结果还表明超元胞法是研究这一类声子晶体能带结构的一种有效方法.     

Bias Voltage Controlled Positive Magnetoresistance of Fe0.05-C0.95/Si Heterostructures

Fe-doped amorphous carbon films of about lOOnm in thickness are deposited on n-type silicon substrates by pulsed laser deposition （PLD）, and positive magnetoresistance （MR） is observed for these Fe-doped amorphous carbon/n-Si heterostructures under current-perpendicular-to-plane configuration at forward bias. Two MR peaks are observed in the temperature range 40-120 K and the positive MR varies with applied bias voltage. This bias voltage controlled MR may be related to the maguetic-field-controlled freeze out effect and recombination through the deep trapping states in the Fe-doped carbon films.