Analysis and design of an improved servo system for rubidium atomic frequency standard

In this paper, we analyze and design a new type of servo system with noninteger voltage controlled crystal oscillator (VCXO) for rubidium atomic frequency standard (RAFS), which does not require fractional frequency synthesizer. By the establishment of the loop equations with noises and drifts, we prove that all the components of the loop can affect its performance index, and in which, RAFS long-term frequency stability is mainly determined by frequency multiplier, quantum system, and servo amplifier; the short-term one is mostly decided by VCXO. Owing to the elimination of the frequency synthesizer and its additive mixing unit, we can reduce phase noise and stray of the servo system, and it is favorable for miniaturizing the RAFS system. In addition, we adopt some targeted optimization measures to improve the frequency stability index. The good short-term fre-quency stability index is also validated by the test results.     

Integrated extremum seeking control method and its application to the suppression of combustion instabilities

The suppression of combustion instabilities using the extremum seeking algorithm （ESA） is analyzed. A function model of the pressure oscillation and the mean fuel-air ratio in the combustion chamber is derived and implies an extremum relation between the oscillation amplitude of the pressure and the mean fuel-air ratio. Hence, the control system of combustion instabilities can be considered as an extremum seeking control system （ESCS）. All traditional ESCSs employ a separate design method, which divides the design of the ESA from the controller design. It is thus difficult for traditional ESCSs to achieve optimal performance of the control system. To solve this problem, an integrated extremum seeking control method for ESCSs is proposed. Using this integrated control, the minimal oscillation amplitude of the pressure is realized by adaptively seeking the optimal mean fuel-air ratio. Hence, this design method can effectively suppress combustion instabilities in aeroengines. By comparing simulation results, the effectiveness of the proposed method is validated.     

An improved potential field method for mobile robot navigation

In order to overcome the inherent oscillation problem of potential field methods ( PFMs) for au-tonomous mobile robots in the presence of obstacles and in narrow passages, an enhanced potential field method that integrates Levenberg-Marquardt ( L-M ) algorithm and k-trajectory algorithm into the basic PFMs is proposed and simulated.At first, the mobile robot navigation function based on the basic PFMs is established by choosing Gaussian model.Then, the oscillation problem of the nav-igation function is investigated when a mobile robot nears obstacles and passes through a long and narrow passage, which can cause large computation cost and system instability.At last, the L-M al-gorithm is adopted to modify the search direction of the navigation function for alleviating the oscilla-tion, while the k-trajectory algorithm is applied to further smooth trajectories.By a series of compar-ative experiments, the use of the L-M algorithm and k-trajectory algorithm can greatly improve the system performance with the advantages of reducing task completion time and achieving smooth traj-ectories.     

Randomness in the Hybrid Modeling and Simulation of Insulin Secretion Pathways in Pancreatic Islets

Insulin secreted by pancreatic islet ˇ-cells is the principal regulating hormone of glucose metabolism.Disruption of insulin secretion may cause glucose to accumulate in the blood, and result in diabetes mellitus.Although deterministic models of the insulin secretion pathway have been developed, the stochastic aspect of this biological pathway has not been explored. The first step in this direction presented here is a hybrid model of the insulin secretion pathway, in which the delayed rectifying KCchannels are treated as stochastic events. This hybrid model can not only reproduce the oscillation dynamics as the deterministic model does, but can also capture stochastic dynamics that the deterministic model does not. To measure the insulin oscillation system behavior, a probability-based measure is proposed and applied to test the effectiveness of a new remedy.     

A new complex Duffing oscillator used in complex signal detection

In view of the fact that complex signals are often used in the digital processing of certain systems such as digital communication and radar systems,a new complex Duffing equation is proposed.In addition,the dynamical behaviors are analyzed.By calculating the maximal Lyapunov exponent and power spectrum,we prove that the proposed complex differential equation has a chaotic solution or a large-scale periodic one depending on different parameters.Based on the proposed equation,we present a complex chaotic oscillator detection system of the Duffing type.Such a dynamic system is sensitive to the initial conditions and highly immune to complex white Gaussian noise,so it can be used to detect a weak complex signal against a background of strong noise.Results of the Monte-Carlo simulation show that the proposed detection system can effectively detect complex single frequency signals and linear frequency modulation signals with a guaranteed low false alarm rate.     

Efficient privacy enhanced software registration with ID-based blind signatures

In existing software registration schemes, the privacy of users is not taken into account and may be in the risks of abuses. In this paper, we proposed a novel software registration system which can greatly reduce unauthorized use of software while keeping the privacy of users. To the best of our knowledge, this is the first system that the privacy of users is guaranteed in software registration. Our system enjoys a modular design and can be implemented by any secure ID-based partially blind signature scheme. Furthermore, the proposal allows flexible registration information definition. This feature makes our scheme flexible and practical for more software registration applications.     

Oscillating chemiluminescence in rhodamine B-induced Belousov-Zhabotinsky reaction catalyzed by Ce（IV）

It was found that rhodamine B could induce oscillating chemiluminescence （OCL） from the Ce4＋-catalyzed Belousov-Zhabotinsky reaction. This new OCL system, i.e., rhodamine B-malonic acid-bromate- Ce（IV）-sulfuric acid, exhibited two clearly distinguished emission peaks in each oscillation period. The initial concentrations of the reactants strongly influenced the oscillation pattern. For the study of the CL mechanism, a platform for a versatile and simultaneous potential and CL measurement was estab- lished to compare the potential oscillation with the CL oscillation behavior of this system. The CL spectra, UV-visible absorption spectra and time-resolved fluorescence spectra of this OCL system were studied. A possible, simplified mechanism for the OCL is proposed. It is suggested that the generation of the two CL peaks is likely due to the oxidation of the intermediate of rhodamine B by Ce（IV） and Br2, respectively. This work provided a new method and platform to research the complex chemical oscilla- tions.     

An Intrusion Alarming System Based on Self-Similarity of Network Traffic

Intrusion detection system can make effective alarm for illegality of network users, which is absolutely necessarily and important to build security environment of communication base service. According to the principle that the number of network traffic can affect the degree of self-similar traffic, the paper investigates the variety of self-similarity resulted from unconventional network traffic. A network traffic model based on normal behaviors of user is proposed and the Hurst parameter of this model can be calculated. By comparing the Hurst parameter of normal traffic and the self-similar parameter, we can judge whether the network is normal or not and alarm in time.     

Cognitive information metrics for cognitive wireless networks

Considering the dynamic changes and uncer- tainty features of the radio environment in cognitive wireless networks （CWNs）, the environment cognition ability is critical for the performance evaluation of CWNs design and optimization. However, there are no effective metrics to evaluate the ability and gain of information cognition in CWNs from an information theory perspec- tive. Therefore, the novel cognitive information concept is proposed and defined as a metric to evaluate the uncer- tainty of both the internal and external environments of one system that can be removed by other systems or nodes using cognitive radio techniques. As an intelligent wireless communication system that is aware of its surrounding radio, network, and user multi-domains environment, the more cognitive information it achieves, the higher level cognitive capability it is. In this paper, we define and analyze the mathematical features of cognitive informa- tion. Results reveal that the increase of cognitive infor- mation can improve the spectrum efficiency and reduce the interference probability simultaneously in CWNs. Thus cognitive information can be regarded as a metric for CWNs optimization. Finally, we apply the theory of cog- nitive information in the parameters optimization in energy detection and cooperative spectrum sensing.     

COMPUTER DYNAMIC SIMULATION FOR PRISMATIC PARTS MANUFACTURED ON MACHINING CENTER

This paper describes a dynamic simulation system for manufacturing prismatic components on machining centers named NCDSS. It is a subsystem of CAD/CAPP/NC integrated system for prismatic parts that we are working on. Based on the system of CAD and CAPP, it can automati. cally generate NC program used on machining centers and can simulate the machining process in the sequence of technology. Techniques of automatically producing NC program for prismaic parts and the method of dynamic simulation are also discussed.     

2,4-二羟基苯乙酮缩三羟基甲基氨基甲烷的合成及其在稀土矿样中铽的痕量荧光分析中的应用

合成了一种新的席夫碱配体2,4-二羟基苯乙酮缩三羟基甲基氨基甲烷.该配体与铽(Ⅲ)的配合物的荧光强度在磷酸钠或六次甲基四胺的存在下可增强18或26倍.有机溶剂CH3CN,DMF,丙酮,THF,DMSO,CH3OH,C2H5OH的添加可使其荧光强度进一步增加3～19倍.其中,用CH3CN作溶剂时荧光增加倍数最大,Tb-HL-HMTM体系荧光最强.pH=6.0时,激发和发射波长分别是355和545 nm.在理想情况下,荧光强度与Tb3+离子浓度成正比.对于HL-Na3PO4-CH3CN体系,线性范围2.3×10-10～5.8×10-5 mol/L,检测限2.0×10-10 mol/L,对于HL-HMTM-CH3CN体系,线性范围9.8×10-11～7.2×10-5 mol/L,检测限9.0×10-11 mol/L.基于此对Tb3+进行定量测定,该分析方法简单、快速、灵敏、干扰小.同时对荧光增强的机理进行了分析和讨论.     

利用聚钙黄绿素薄膜修饰电极测定阿司匹林

利用聚钙黄绿素薄膜修饰电极(PCALE)对阿司匹林(AS)的电催化作用,建立了对AS含量进行定量分析的方法.在0.05 mol/L KH2PO4-Na2HPO4(pH=6.8)+0.2 mol/L KNO3体系中,AS的浓度在4.5×10 7～1.2×10 5mol/L范围内与峰电流呈良好的线性关系,线性回归方程和线性相关系数分别为:ip=1.75×105C 1.51;γ=0.997 7,检出限可达9.1×10 8mol/L.利用该法对阿司匹林样品进行定量分析,得到满意结果.八次样品分析结果的相对标准偏差为2.0%,样品回收率为98.4%～100.4%,完全满足微量分析的要求.     

流动注射化学发光法研究PAN对鲁米诺-亚铁氰化钾反应的催化性能

1-(2-吡啶偶氮)-2-萘酚(PAN)对鲁米诺-亚铁氰化钾化学发光反应有良好的催化性能,实验结果表明:在1.0×10-5-1.0×10-7mol/L范围内,发光强度与PAN的浓度之间有良好的线性关系,检测极限为5.6×10-8mol/L。同时发现一些金属对此化学发光反应有强的抑制作用,为此建立了用此反应测定这此金属离子的新方法,测定Ni2+,Cr3+,Zn2+,Co2+和Cu2+的检测极限分别为1.0×10-9mol/L、1.0×10-8mol/L、1.0×10-8mol/L、5.0×10-9mol/L和6.0×10-9mol/L,相对标准偏差在1.28-3.10%(n=11)范围内。     

高锰酸钾—鲁米诺化学发光体系测定香草醛

为了拓展流动注射化学发光法在食品检测中的应用,利用草醛能够增敏NaOH介质中高锰酸钾—鲁米诺化学发光体系的发光信号的特点,建立了化学发光测定香草醛的方法。文中考察了介质浓度、发光试剂浓度等因素对发光体系信号的影响,确定了测定香草醛的最佳条件:介质NaOH浓度为0.20 mol/L,高锰酸钾浓度为3.0×10-5mol/L,鲁米诺浓度为7.0×10-5mol/L。在优化实验条件下,体系的发光强度与香草醛浓度在5.0×10-8～3.0×10-6 g/mL内呈线性关系,标准曲线:ΔI=7.188 3×108C(g/mL)+71.767 4(r=0.994 2)。对5.0×10-7g/mL的香草醛平行测定11次,相对偏差为1.3%,其检出限为1.1×10-8g/mL。建立了测定香草醛的流动注射化学发光法新方法,并成功地测定了片剂中香草醛的含量,回收率为98%～104%。     

流动注射-鲁米诺-铁氰化钾化学发光体系测定环境水体中痕量2,4-二氯苯酚

基于中性介质中,2,4-二氯苯酚对鲁米诺-铁氰化钾化学发光体系有明显的增敏作用,提出了流动注射化学发光法测定痕量2,4-二氯苯酚的方法.在优化的试验条件下,2,4-二氯苯酚的化学发光强度与其浓度在1.0×10-7~1.0×10-5 mol/L范围内呈线性关系,方法的检出限(3S/N)为1.060×10-8 mol/L.对浓度为1.0×10-5mol/L2,4-二氯苯酚溶液连续测定11次,测定值的相对标准偏差为2.1%.取工业废水水样,经固相萃取后用该法测定其中痕量2,4-二氯苯酚含量,同行业推荐标准方法对比,结果相近.     

龙胆酸对B-Z化学振荡反应的影响及其分析测定

利用龙胆酸对四氮杂大环铜催化的B-Z化学振荡体系(NaBrO3-H2SO4-苹果酸-[CuL](ClO4)2)的扰动建立测定龙胆酸的新方法.其分析结果表明龙胆酸的浓度在1.25×10-6～1×10-4mol.L-1之间时,振幅改变值与加入龙胆酸的浓度对数有良好的线性关系,其相关系数为0.99821.同时对各组分浓度的影响及其扰动机理进行了探讨.     

流动注射化学发光法测定棉酚

NaOH介质中,铁氰化钾可以氧化棉酚产生弱的化学发光,罗丹明6G有强的增敏作用.基于此,结合流动注射分析技术,建立了一种化学发光法测定棉酚的新方法.在最佳优化条件下,该方法测定棉酚的线性范围为2.0×10^-8mol/L～2.0×10^-6mol/L,检出限为1.4×10^-9mol/L（3σ）,相对标准偏差为2.0%.将该方法应用于棉籽油和血清中棉酚含量的测定,结果满意.     

Highly sensitive spectrofluorimetric determination of riboflavin based on the generation of active oxygen coupled with enzymatic reaction

A spectrofluorimetric method for the determining riboflavin (VB2) based on its enhancement on the fluorescence of hemoglobin-catalyzed enzymatic reaction was proposed. The proposed method consisted of two reactions. One was the photochemical reaction of VB2, the other was a hemoglobin-catalyzed enzymatic reaction. The optimal experimental conditions for the determinations were established. The linear range of the method was 5.0×10-9-1.0×10-7mol/L of VB2. The detection limit was calculated to be 3.65×10-9 mol/L. The relative standard deviation of this method was 2.3 % at 7.0×10-8 mol/L for 11 determinations.     

果糖(Frn)-KBrO3-MnSO4-H2SO4-丙酮(Act)体系及其在磷酸盐Na2HPO4-NaH2PO4中的振荡反应

研究了独立的Frn-KBrO3-MnSO4-H2SO4-Act体系及其在磷酸盐Na2HPO4·NaH2PO4中的振荡反应,考察了Na2HPO4-NaH2PO4对振荡反应的影响及反应过程的能量关系,发现[BrO-3]0=0.05mol/L时,磷酸盐起加速反应的作用,使振荡周期、振荡寿命变小,振荡频率增加,[BrO-3]0=0.035mol/L时,磷酸盐起延缓振荡反应的作用,使诱导期、振荡周期、振荡寿命增大.     

克林沙星的吸附伏安特性及其应用

在0．2mol·L^-1KH2PO4-K2HPO4（pH6．80）底液中,克林沙星（CF）在汞电极上有一线性扫描还原峰,峰电位Eρ=-1．46V（vs．Ag／AgCl）,该峰说明汞电极对克林沙星具有明显的吸附性。测得CF在汞电极上的饱和吸附量Гs=4．82×10^-11mol．cm^-2,每个CF分子所占电极面积为2．64nm^2,CF在汞电极上的吸附符合Langmuir吸附等温式。测得吸附系数β=1．06×10^6,25℃时的吸附自由能△G^θ=-32．13kJ·mol^-1,电极反应电子数n=2,不可逆体系动力学参量αnα=1．44,表面电极反应速率常量ks=0．26s^-1。建立了吸附溶出伏安法测定CF的最佳条件,方法的检出限为2．0×10^-8mol．L^-1。