关于HLA研究的几个问题

With the requh-ement of actual simulation application and the development of simulation standards, this pa-per analyzes HLA/RTI services characteristics, and then summaries the advantage and disadvantage of HLA. It is pointed out that RTI performance measurement and RTI to RTI communication protocol are urgent research projects of HLA/RTI.     

一种扩展任意波形发生器输出带宽的设计

增加输出带宽和降低输出噪声是关系任意波形发生器发展的两个重要方面.本文在论述任意波形发生器工作特点的基础上,提出了一种多路组合的任意波形发生器设计方案.它能在不降低输出信噪比的条件下,用较低速的波形存储器和数-模转换器实现较高速率的波形输出.论文着重介绍了这种电路结构的设计思想和实现这种设计所要解决的关键技术,并给出了四路组合的任意波形发生器实验系统及测试结果.     

Study and application of X radiation sampling technique

The physical bases of a X radiation sampling technique are investigated.Three technical problems of unevenness,matrix and heterogeneous mineralization effects,are considered and successfully resolved.This new technique was appled to three sites of Au,Sn and Cu deposits(representing higher,medial and lower atomic number minerals)in different exploration stages in China and satisfactory results are obtained.     

A nuclear spectrum generator for semiconductor X-ray detectors

A nuclear spectrum generator for semiconductor X-ray detectors is designed in this paper. It outputs step ramp signals with random distribution in amplitude and time according to specified reference spectrum. The signals are similar to the signals from an actual semiconductor X-ray detector, and can be use to check spec- trum response characteristics of an X-ray fluorometer. This helps improving energy resolution of the X-ray fluorometer. The spectrum generator outputs step ramp signals satisfying the probability density distribution function of any given reference spectrum in amplitude through sampling on the basis of 32-bit randomizer. The system splits 1024 interval segmentation of the time that the step ramp signals appear, and calculates the ap- pearance probability of step ramp signals in different intervals and the average time between the time intervals, by random sampling. The step ramp signals can meet the rule of exponential distribution in time. Test results of the spectrum generator show that the system noise is less than 2.43 mV, the output step ramp signals meet the Poisson distribution in counting rate and the probability density distribution function of the reference spectrum in amplitude. The counting rate of the output step ramp signals can be adjusted. It meets the rule of the output signals from semiconductor X-ray detectors, such as Si-pin detector and silicon drift detector.     

基于3D双流卷积神经网络的异常行为检测

随着科技的不断发展,越来越多的人工智能技术应用于社会生活.依据这一现实,本文运用当前较为热门的图像处理技术进行能识别视频中异常行为并给出预测值的系统开发.首先,我们利用双流膨胀3D卷积网络(Two-Stream-I3D)特征提取技术对视频进行特征提取.其次,运用Python对特征进行处理,转化为深度学习网络所能识别的特征,最后进行GRNN广义回归网络训练,最终达到能对特征值进行良好的异常概率回归的效果.实验表明,运用本系统针对测试集近50例的视频的检测下,系统的平均准确率达74％,具有良好的性能.     

Pulse Pile-up Correction by Particle Swarm Optimization with Double-layer Parameter Identification Model in X-ray Spectroscopy

In X-ray spectrum analysis, the pulse pile-up is a long-standing issue which deteriorates the energy resolution and count rates of the radiation detection systems. In this study, a novel pulse pile-up identification method based on particle swarm optimization and double-layer parameter identification model (PSO-DLPIM) is proposed. Different Gaussian pile-up waveforms are realized by exponential pulse through Sallen-Key (S-K) low-pass filtering. Then, the proposed model recognizes the parameters of each sub-Gaussian pulse. Especially, it can be used to modelling the pulse indirectly without a certain model parameter and overcomes the model mismatch troubles. Finally, computer simulations and experimental tests are carried out and the results show that this method has higher accuracy for the recognition of pile-up pulses. The example shows that the minimum distance between pulses that can be identified by this method is 0.05 μs. And when the pulse generation time is known and the environmental noise is low, the relative error of the amplitude of pulse pile-up recognition is as low as 0.15%. Therefore, this method can greatly improve the resolution of the X-ray spectrum.

     

Implementation of a cusp-like for real-time digital pulse shaper in nuclear spectrometry

Pulse shaping,which improves signal-to-noise ratio excellently,has been extensively used in nuclear signal processing.This paper presents a cusp-like pulse-shaping technique developed through the recursive difference equation in time domain.It can be implemented in field programmable gate array hardware system.Another fiat-topped cusp-like shaper is developed to optimize the time constant of pulse shaping and reduce the influence of ballistic deficit.The methods of both baseline restoration and pile-up rejection are described.The 137Cs energy spectra measured with the digital cusp-like shaper are 6.6％ energy resolution,while those by traditional analog pulse shaper are 7.2％ energy resolution,under the same conditions.This technique offers flexibility,too,in adjusting the pulse shaper parameters.     

Verification of a self-developed CFD-based multi-physics coupled code MPC-LBE for LBE-cooled reactor

To perform an integral simulation of a pool-type reactor using CFD code, a multi-physics coupled code MPC-LBE for an LBE-cooled reactor was proposed by integrat...     

不同贮藏时间琯溪蜜柚果肉营养及香气成分研究

目的 探讨琯溪蜜柚贮藏过程中果肉香气成分及果实营养品质的变化特征。方法 利用气相色谱-质谱法(gas chromatography-mass spectrometry, GC-MS)测定其品质变化关键时期的香气成分, 解析琯溪蜜柚果肉在贮藏过程中营养和香气成分的动态变化规律。结果 采后琯溪蜜柚果实失重率上升、淀粉含量增加、维生素C含量降低、糖酸比下降。贮藏后期琯溪蜜柚果肉的木质素、纤维素、半纤维素含量显著增加, 出现了明显的粒化现象。随贮藏时间延长, 部分醛类和醇类物质呈下降趋势, 对应的似果香味和花香味香气逐渐逸散, 正戊醛、2,4-二甲基苯甲醛、β-环柠檬醛等物质增加, 似发酵面包味、苦杏仁味和大蒜味等较难闻的味道增加。结论 在室内常温贮藏条件下, 随着贮藏时间的延长会使琯溪蜜柚果肉水分逐渐减少、风味慢慢变劣、营养不断流失、粒化日趋严重, 建议琯溪蜜柚采摘后在30 d内食用最佳, 超过60 d不建议鲜食, 并尽量采取一些保鲜措施以减少风味营养成分的损失。     

A new digital Gaussian pulse shaping algorithm based on bilinear transformation

Nuclear pulse signal needs to be transformed to a suitable pulse shape to remove noise and improve energy resolution of a nuclear spectrometry system. In this paper, a new digital Gaussian shaping method is proposed.According to Sallen-Key analog Gaussian shaping filter circuits, the system function of Sallen-Key analog Gaussian shaping filter is deduced on the basis of Kirchhoff laws. The system function of the digital Gaussian shaping filter based on bilinear transformation is deduced too. The expression of unit impulse response of the digital Gaussian shaping filter is obtained by inverse z-transform. The response of digital Gaussian shaping filter is deduced from convolution sum of the unit impulse response and the digital nuclear pulse signal. The simulation and experimental results show that the digital nuclear pulse has been transformed to a pulse with a pseudo-Gaussian, which confirms the feasibility of the new digital Gaussian pulse shaping algorithm based on bilinear transformation.