Study of time-domain digital pulse shaping algorithms for nuclear signals

With the development on high-speed integrated circuit,fast high resolution sampling ADC and digital signal processors are replacing analog shaping amplifier circuit.This paper firstly presents the numerical analysis and simulation on R-C shaping circuit model and C-R shaping circuit model.Mathematic models are established based on 1st order digital differential method and Kirchhoff Current Law in time domain,and a simulation and error evaluation experiment on an ideal digital signal are carried out with Excel VBA.A digital shaping test for a semiconductor X-ray detector in real time is also presented.Then a numerical analysis for Sallen-Key(S-K) low-pass filter circuit model is implemented based on the analysis of digital R-C and digital C-R shaping methods.By applying the 2nd order non-homogeneous differential equation,the authors implement a digital Gaussian filter model for a standard exponential-decaying signal and a nuclear pulse signal.Finally,computer simulations and experimental tests are carried out and the results show the possibility of the digital pulse processing algorithms.

Improvement of digital S-K filter and its application in nuclear signal processing

On the basis of preliminary studies,a novel duo-parameter model consisting of amplitude filter factor and frequency filter factor for low-pass S-K filter is presented in this paper.The model is established by applying numerical differentiation method.Some simulation experiments and real data tests are carried out to verify the feasibility and superiority of the new algorithm.The results show that this duo-parameter model of low-pass S-K filter can be used to achieve high performance in signal processing and nuclear spectrum smoothing.

基于Sallen-Key滤波器的数字高斯成形方法的仿真

详细阐述了一种指数信号数字高斯成形技术的计算机仿真方法。首先,以Sallen-Key滤波器为基础,建立了指数输入信号和高斯输出信号之间的数学关系模型。该模型是一个二阶微分方程。其次,模型解算过程中利用数值微分算法得到一个数值递推解。通过计算机仿真该数值递推解实现了指数信号的数字高斯成形。最后,将成形模型应用于实际核脉冲信号分析系统中,通过计算机仿真确定了成形参数。

Gaussian shaper for nuclear pulses based on multilevel cascade convolution

For nuclear measurements,it is necessary to obtain accurate information from nuclear pulses,which should be obtained by first shaping the pulses outputted by the detectors.However,commonly used pulse-shaping algorithms have certain problems.For example,certain pulse-shaping algorithms have long dead-times in high-counting-rate environments or are difficult to achieve in digital systems.Gaussian signals are widely used in analog nuclear instruments owing to their symmetry and completeness.A Gaussian signal is usually implemented by using a multilevel S–K filter in series or in parallel.It is difficult to construct a real-time digital Gaussian filter for the complex Gaussian filtering algorithm.Based on the multilevel cascade convolution,a pulse-shaping algorithm for double exponential signals is proposed in this study,which,in addition to double exponential signals,allows more complex output signal models to be used in the new algorithm.The proposed algorithm can be used in high-counting-rate environments and has been implemented in an FPGA with fewer multipliers than those required in other traditional Gaussian pulse-shaping algorithms.The offline processing results indicated that the average peak base width of the output-shaped pulses obtained using the proposed algorithm was reduced compared with that obtained using the traditional Gaussian pulse-shaping algorithm.Experimental results also demonstrated that signal-to-noise ratios and energy resolutions were improved,particularly for pulses with a low energy.The energy resolution was improved by 0.1–0.2%while improving the counting rate.

棉织物新型涂料数码喷墨印花应用性能研究

针对传统涂料数码喷墨印花工艺中喷涂织物处理液和高温固色的环节,通过使用新型涂料数码喷墨印花工艺可省去上述环节,以达到缩短工艺流程、节能环保、减少废气排放、降本增效的目的。通过对新型涂料数码喷墨印花技术和传统涂料数码喷墨印花技术进行对比研究,将使用两种喷墨印花工艺的棉织物分别进行颜色特征值、色牢度、pH值、硬挺度、折皱回复角的测试。结果表明,新型涂料数码喷墨印花工艺在绿色节能、降低成本的同时,其耐摩擦色牢度、硬挺度和折皱回复角方面的表现优于传统涂料数码印花工艺;在颜色特征值、pH值和耐皂洗色牢度方面与传统涂料数码印花工艺性能相当。总体来说,新型涂料数码喷墨印花工艺符合绿色印染的发展方向,降低了企业生产成本,对企业实际的生产有一定的参考意义,具有广阔的应用前景和发展潜力。

数控机床XY工作台插补中滤波技术

在插补过程中,程序段与程序段之间在衔接处的转向,导致在程序段衔接处产生加速度突变,容易引起机床震动,为平滑加速度,对各轴速度进行低通滤波,对各轴速度进行低通滤波即是对各轴的速度曲线进行平滑,从而消除加速度突变,使得机床运行平稳。基于数控机床XY工作台进行研究,采用有限脉冲响应(FIR)数字滤波器进行轴滤波,证明了对轴位置点滤波卷积运算,即是对速度进行滤波,并且对滤波产生的轮廓误差进行分析,并且结合实际数控机床加工情况,对滤波后产生的进给量过小问题进行分析并做补偿处理。该方法应用于数控激光切割系统,结果证明该方案能改善系统性能,提升系统加工的平稳度。

Estimation of Gaussian overlapping nuclear pulse parameters based on a deep learning LSTM model

A long short-term memory(LSTM)neural network has excellent learning ability applicable to time series of nuclear pulse signals.It can accurately estimate parameters associated with amplitude,time,and so on,in digitally shaped nuclear pulse signals—especially signals from overlapping pulses.By learning the mapping relationship between Gaussian overlapping pulses after digital shaping and exponential pulses before shaping,the shaping parameters of the overlapping exponential nuclear pulses can be estimated using the LSTM model.Firstly,the Gaussian overlapping nuclear pulse(ONP)parameters which need to be estimated received Gaussian digital shaping treatment,after superposition by multiple exponential nuclear pulses.Secondly,a dataset containing multiple samples was produced,each containing a sequence of sample values from Gaussian ONP,after digital shaping,and a set of shaping parameters from exponential pulses before digital shaping.Thirdly,the Training Set in the dataset was used to train the LSTM model.From these datasets,the values sampled from the Gaussian ONP were used as the input data for the LSTM model,and the pulse parameters estimated by the current LSTM model were calculated by forward propagation.Next,the loss function was used to calculate the loss value between the network-estimated pulse parameters and the actual pulse parameters.Then,a gradient-based optimization algorithm was applied,to feedback the loss value and the gradient of the loss function to the neural network,to update the weight of the LSTM model,thereby achieving the purpose of training the network.Finally,the sampled value of the Gaussian ONP for which the shaping parameters needed to be estimated was used as the input data for the LSTM model.After this,the LSTM model produced the required nuclear pulse parameter set.In summary,experimental results showed that the proposed method overcame the defect of local convergence encountered in traditional methods and could accurately extract parameters from multiple,severely overlapping Gaussian pulses,to achieve optimal estimation of nuclear pulse parameters in the global sense.These results support the conclusion that this is a good method for estimating nuclear pulse parameters.

十字型接头k因子的有限元分析

本文用有限单元法计算了十字型接头工作焊缝的ｋ因子，为十字型接头的设计提供了另一组参考依据．

真丝绸活性染料喷墨印花预处理工艺研究

将混合糊料HC应用到真丝绸数码印花的浆料中,通过正交试验确定了常规上浆助剂碳酸氢钠、硫酸钠、尿素等对真丝绸数码印花效果的影响;为了提高织物的防渗化性能,研究了吸附剂在上浆前处理中的应用,测试了印花织物的K/S值、渗化度及色牢度。结果表明,合适的预处理工艺提高了真丝绸数码印花的印花效果,得到了轮廓清晰、得色量高、色牢度好的花纹图案。

基于数字图像处理的土石混合体细观结构

为了研究土石混合体这类复杂的岩土体的内部细观结构特征,利用现代数字图像处理技术对研究区选取的土石混合体断面图像进行了分析,获得了其中所包含的丰富信息,建立了其各自相应的细观结构的"概念模型"。并在此基础上对研究区分布的土石混合体的粒度、块体表面分维、块体定向性分维及形态特征等内部细观结构进行了相应的统计分析研究。其结果表明土石混合体的"混乱"状态只是其外在表现,其内部块体的分布具有良好的统计自相似性特点。

X荧光光谱仪脉冲成形电路的设计

对设计应用在X荧光光谱仪上的成形电路进行了详细的电路分析,改进了经典的S-K滤波器,并给出了电路原理图和试验总结。试验测试结果表明,设计电路完全达到设计指标要求,并具有移植性和通用性。

基于双参数模型核脉冲信号数字高斯成形技术

阐述了一种基于脉宽和幅度双参数的新型核脉冲信号数字高斯成形模型的研究方法。以Sallen-Key滤波器(以下简称S-K滤波器)为基础,运用基尔霍夫电流定律建立输入信号Vi和输出信号Vo之间的数学关系方程。方程解算过程中,引入脉宽和幅度双因子进行参数替代,并运用数值微分算法迭代得到一个核脉冲信号数字高斯成形的数值递推模型。通过标准指数衰减信号和实际核信号仿真验证了该模型的正确性,也进行了成形参数的确定。最后,实测55Fe核素标准谱线的结果显示在能量色散X荧光分析系统中应用数字高斯成形技术,提升了系统能量分辨率和计数通过率等性能指标,收到了良好效果。

羊毛织物数码印花前处理的研究

对羊毛织物数码印花前处理条件进行了探讨,分析前处理液的上浆量、低温染色助剂TCEP对羊毛织物数码印花效果的影响。结果表明,前处理中上浆量的多少对印花表面表观深度有较大影响,低温染色助剂有助于提高印花得色量。

收缩喷嘴内部流道型线对射流流场的影响

为研究收缩喷嘴内部流道形成对射流流场的气体动特性参数的影响 ,根据可压缩流体轴对称N—S方程 ,采用非结构网格和二阶精度的有限体积法 ,对不同内部流道形线的喷嘴自由射流进行数值模拟。亚声速射流采用RNGk_ε湍流模型 ,超声速射流采用S—A湍流模型 ,计算结果与实验较吻合。在亚声速流动中 ,收缩喷嘴的收缩角大小会影响其对射流的阻滞效果 ,内部流道形线设计为维多辛斯基曲线可以获得更好的流场动特性参数 ,有利于提高喷嘴的工作效率。在超声速流动中 ,喷嘴流道型线对出口膨胀波的角度与强弱影响较大 ,要根据射流的有效作用区域选择合适的喷嘴 ,才能使能量的损失最小。若要获得较佳的外部流场参数 。

纯棉织物活性染料数码印花上浆工艺研究

为提高棉织物织物喷墨印花产品质量为目的,对棉织物活性染料数码印花上浆工艺进行了研究,分析上浆配方工艺参数对棉织物数码印花效果的影响。测试了不同参数条件下产品喷墨印花效果。结果表明:海藻酸钠用量3%、碳酸氢钠用量4%、硫酸钠用量2%、尿素用量4%,此上浆工艺在喷墨印花色彩得色量,精细度,稳定性上都有较好体现。

涂料数码印花得色量和色牢度提升工艺研究

采用预处理液DM-8814对棉织物进行预处理,探讨了预处理工艺、固色柔软一浴法整理工艺对涂料数码印花效果的影响,测试了整理后K/S值、白度、色牢度及手感。结果表明:采用预处理度DM-8814 50 g/L,烘干温度100℃,喷墨印花后,焙烘温度160℃,与空白相比,得色深度能提高20%~30%,耐摩擦色牢度提高1级;通过后整理可进一步改善耐摩擦色牢度、手感和得色深度,优化工艺为固色剂DM-2589 30 g/L,增深剂0115 10 g/L或单独使用增深剂0115 20 g/L,经后整理处理后,得色深度能提高30%,耐摩擦色牢度能达到3~4级,使涂料数码印花实现颜色鲜艳、得色较深、轮廓清晰、手感优良、耐摩擦色牢度优异等性能。

数码热升华直喷印花涤纶地毯的开发

涤纶地毯数码印花存在色深值低及耐摩擦色牢度差等问题,文中选用(50.0~66.7)tex/192 f涤纶低弹丝为面组织,33.3 tex/96 f的涤纶低弹丝为地组织,开发了涤纶地毯数码热升华直喷印花面料。介绍了原料选择、织造方法、涤纶地毯数码喷墨印花的设备及数码印花的工艺流程及工艺参数,探讨了分散染料颗粒大小及分散剂对墨水性能的影响。结果表明,墨水中超细化染料的粒径为125 nm时,选用分散剂NNO进行分散染料热升华墨水进行印花,能够有效提高印花图案的深色效应和耐摩擦色牢度,耐摩擦色牢度达到4级,K/S值为13.4。

箭体壳段结构数字散斑相关测量方法研究

针对复杂大型箭体壳段结构静力试验采用电测法获取相关试验数据存在的测点有限以及空间局限性等问题,提出了基于数字散斑相关的光学测量方法,可以有效的获取全场应变,从而指导和修正壳段结构的设计。

双面法兰绒数码热转移印花的探讨

文中对比了4种不同的数码喷墨打印机设备、工艺参数及印花效果,不同品牌转移纸的性能,分析并测试了3种不同染料墨水的K/S值、色牢度,探讨了热转移印花中温度、转速对双面法兰绒热转移印花效果的影响。指出了双面法兰绒印花可根据客户要求选择不同机型,J-next Subly JXS 65热转移分散墨水的K/S值较高,耐皂洗牢度和耐升华牢度一致都在4级及以上,全佳的热转印纸防渗性能好,打印更稳定;确定大生产热转印温度为215~230℃、速度12~14 r/min,但由于双面法兰绒面料布面较厚,图案无法渗透到毛根部位,易产生毛根露白问题。

Numerical investigation on the “S” characteristics of a reduced pump turbine model

The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to predict the S-shaped curve accurately and develop a reliable tool for design improvement, a shear stress transport model (SST) with various numerical schemes for pressure term in the governing equation was investigated in a whole pump turbine including spiral casing, stay vanes, guide vanes, runner and draft tube. Through the computation, it was shown that different zones in the curve should employ different schemes to get the solution converged. Comparison of discharge-speed performance showed that good correspondence is got between experimental data and CFD results. Based on this, internal flow analysis was carried out at three typical operating points representing turbine mode, shut-off mode and reversible pump mode, respectively. According to the flow field concerned, the mechanism for the speed-no-load instability was explained, which provides good guidelines to take countermeasures in future design.