Responses of a Noisy Excitable System to External Signals with Different Periods

The behaviour of an excitable system under Gaussian white noise and external periodic forcing is systematically studied. In a large range of noise intensity, the n:l phase locking patterns are obtained for certain ranges of the input periods, where n input periods give one spike. In the phase locking regimes, the system presents low noise-to-signal ratios and shows better regularities. Out of the regimes the system behaves less regularly and the relations between the noise-to-signal ratio and the noise intensity exhibit typical stochastic resonance phenomena.At a higher noise level, the system shows the characteristic behaviour of the noise.     

节理表面波纹度对其闭合性质的影响

节理的表面形貌中普遍含有波纹度。本文分析了含波纹度节理闭合模型的性质，探讨了其接触变形机理，研究了波纹度幅值、频率及不规则度方差对节理闭合性质的效应，最后与将波纹度分量作为随机分量处理的以往的节理闭合模型进行了比较。     

基于近红外反射光谱的番茄糖分快速检测模型研究

番茄是一种营养丰富且深受人们喜爱的果蔬,在全球都得到了广泛的种植,而我国番茄产销量稳居全球首位。番茄不仅在人们的生活中扮演了一个重要的角色,在工业生产中也占据了举足轻重的位置,我国番茄的出口也在不断增加。番茄的糖分、酸度、维生素C及可溶性固形物含量是反映番茄内部品质的重要评价指标,而可溶性固形物含量是这些内部品质的总和,能够较好地表征番茄的内部品质。因此,实现对番茄可溶性固形物含量的快速检测对番茄的工业生产和日常生活有着巨大的帮助。基于化学原理的传统检测方法会对番茄样品产生不可逆的破坏,且耗时耗力,难以应对我国现代工业生产的需要。因此,寻求番茄内部品质的快速无损检测技术成为了亟待解决的问题。近年来,近红外光谱分析在多个领域得到了广泛的应用;基于近红外光谱检测方法对反映番茄甜度的可溶性固形物含量进行了相关性建模和预测研究。实验搭建了近红外光谱检测平台,选择了255个不同成熟度和品种的番茄样本,每个样本采集了光谱数据和可溶性固形物含量值。研究对比了SNV, MSC, NOR和SG等光谱数据预处理方法,并采用K-S算法划分建模校正集和验证集。同时,为提高检测可靠度和建模效率,研究对比了CAR...     

Exploring the Critical Sensitivity in Small-World Networks

Catastrophic phenomena such as earthquakes, avalanches, and critical points in the stock market are hard to predict. Recently, Xia et al. [Pure Appl. Geophys. 159 (2002)2491] showed that a geometrical system near catastrophic rupture presents a general critical sensitivity: the system becomes significantly sensitive near the catastrophe transition. Here we report that the phenomenon of critical sensitivity also exists in small-world network systems. With the increase of the small-world rewiring probability p, from the regular network p=0 to the random one p=1, the system performs more sensitively before the critical point while remaining in better organization through the evolutional progress, and the prediction threshold P8 performs more in advance. The concept of critical sensitivity can be applied to other complex network systems.     

两种锥形脉管制冷机的数值模拟及其实验验证

本文对所提出的新型结构的脉管制冷机进行了数值模拟分析和实验研究。研究表明：锥形脉管制冷机存在一最佳锥度;在最佳锥度下,采用锥形脉管制冷机对改善制冷机的性能,进一步降低制冷温度、提高相同制冷温度下的制冷量是有利的。     

Frequency sensitivity of sub-excitable systems coupled with different topology

We have investigated numerically the behaviours of identical FitzHugh－Nagumo systems, which are coupled into topologies of regular one-dimensional lattice, small-world network and scale-free network, and driven by white noise and an external signal. We found that when a number of uniform systems are coupled into a network, the system's signal-to-noise ratio remains at a high level in a wider frequency range than in the case of a single oscillator. Different architectures manifest different impact, with the scale-free network being the most remarkable. Results presented here suggest a possible approach to improve the sensitivity of a system to external signals and are helpful for designing communication equipments.     

缝隙回热器式脉管制冷机的数值分析

提出一种缝隙回热器式脉管制冷机,并进行了计算机模拟.运用有限差分数值计算方法,对其进行了较全面的热力分析,着重讨论了一些运行参数和结构参数的影响.     

Pattern Formation in the Turing-Hopf Codimension-2 Phase Space in a Reaction-Diffusion System

We systematicaily investigate the behaviour of pattern formation in a reaction-diffusion system when the system is located near the Turing-Hopf codimension-2 point in phase space. The chloride-iodide-malonic acid （CIMA） reaction is used in this study. A phase diagram is obtained using the concentration of polyvinyl alcohol （PVA ） and malonic acid （MA） as control parameters. It is found that the Turing-Hopf mixed state appears only in a small vicinity near the codimension-2 point, and has the form of hexagonal pattern overlapped with anti-target wave; the boundary line separating the Taring state and the wave state is independent of the concentration of MA, only relies on the concentration of PVA. The corresponding numerical simulation using the Lengyel-Epstein （LE） model gives a similar phase diagram as the experiment; it reproduces most patterns observed in the experiment. However, the mixed state we obtain in simulation only appears in the anti-wave tip area, implying that the 3-D effect in the experiments may change the pattern forming behaviour in the codimension-2 regime.     

液体定压比热容的理论推算

液体定压比热容的理论推算赵小明，刘志刚，王文，陈钟颀（西安交通大学能源与动力工程学院西安７１００４９）关键词聚集理论，循环，比热容１前言物质的比热容不仅是其重要的热物性参数之一，而且是与物质结构密切相关的特征数据，它对物理学和化学的理论研究及许多化工...