量子电压标定的噪声温度计系统设计

针对传统噪声温度计2个噪声源的功率和阻抗不能同时匹配的问题,为实现热力学温度自动化准确测量,以量子电压任意波形合成技术为基础,合成频率、幅度已知的赝噪声源作为参考端信号,并以高精度数字分析仪PXI—5922为数据采集平台,完成量子电压标定的噪声温度计系统设计。初步实验结果表明:此系统运行良好,可以实现水三相点热力学温度的准确测量。     

正交相位输出压控振荡器的低相位噪声优化设计

分析了负阻结构 LC 压控振荡器各组成部分对相位噪声的贡献途径及优化方法;介绍了利用两独立 VCO 核心输出正交相位信号的原理及其相位噪声优化方法;利用所得结论设计出工作于 ISM波段2.4GHz 的 QVCO,相位噪声在100kHz、1MHz 和3MHz 频偏处分别达到-103.3、-121.1和-125.9dBc/Hz,仅消耗功率3.8 mW;所设计电路利用 HJTC0.18μm工艺制造,占用芯片面积0.75mm×1mm。     

Using Vmax to estimate changes in the sodium membrane conductance in cardiac cells

Relative changes in the sodium conductance of the resting cardiac cell membrane are often estimated from relative changes in the maximum rate of rise of the action potential (Vmax). This approach has given rise to some controversy and it has not been possible so far to test it directly on an experimental basis. We have examined here the validity of this estimation using three different Hodgkin-Huxley representations of the cardiac membrane sodium current. The two basic requirements are a constant membrane capacitance and a negligible relative value of the nonsodium membrane currents at the time of Vmax. It is shown further that the approach leads to a satisfactory estimation only when the latency of Vmax is kept constant and a correction factor for the sodium driving force is applied to Vmax measurements. This conclusion applies either to a nonpropagated action or to an action potential propagated at constant velocity, provided that the membrane is not too strongly depolarized. It is valid for a wide range of sodium equilibrium potentials and a range of maximum sodium conductances limited to about 50% of the nominal value.     

Mathematical modeling of fluctuations of the neuronal membrane potential during activation of exciting and inhibiting synapses

A probabilistic model of impulse activation of single neurons is proposed. The mean membrane potential and its limiting values are determined for the case when the impulses reaching the exciting and inhibiting synapses form a Poisson input or an arbitrary renewal process.Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 139–152, July–August, 1991.     

The kinetics of the IPSC, the heterogeneity and the noise affect the firing coherence of a population of inhibitory interneurons

The Fast Spiking interneurons are coupled by both inhibitory and electrical synapses and the experimental findings suggest they operate as clockworks affecting the neural information processing. At present, the functional role of the electrical synapses in a network of inhibitory interneurons is not well understood. In this paper, this issue is investigated by using a single compartment biophysical interneuron model of a Fast Spiking cell. In particular, the parameter values leading to the emergence of synchronous regimes in a network model of inhibitory interneurons coupled by chemical and electrical synapses are determined theoretically in the weak-coupling limit. Moreover, the effects on the firing coherence, arising from heterogeneity and noise, are studied by means of numerical simulations, both for a pair of Fast Spiking cells and for larger size networks.     

An extended analytic expression for the membrane potential distribution of conductance-based synaptic noise

Synaptically generated subthreshold membrane potential (Vm) fluctuations can be characterized within the framework of stochastic calculus. It is possible to obtain analytic expressions for the steady-state Vm distribution, even in the case of conductance-based synaptic currents. However, as we show here, the analytic expressions obtained may substantially deviate from numerical solutions if the stochastic membrane equations are solved exclusively based on expectation values of differentials of the stochastic variables, hence neglecting the spectral properties of the underlying stochastic processes. We suggest a simple solution that corrects these deviations, leading to extended analytic expressions of the Vm distribution valid for a parameter regime that covers several orders of magnitude around physiologically realistic values. These extended expressions should enable finer characterization of the stochasticity of synaptic currents by analyzing experimentally recorded Vm distributions and may be applicable to other classes of stochastic processes as well.     

Computation of phase and noise characteristics of the playback by taking fluctuations of the sawtooth transition in digital magnetic recording into account

A model of the sawtooth magnetization transition in thin-film environment with random distribution of parameters is proposed. An expression of the playback signal is obtained taking fluctuations of the magnetization transition into account. A computation of phase, amplitude, and noise characteristics of the quantity of the sawtooth transition parameters is performed.     

含噪声驱动阵的相关噪声卡尔曼滤波及稳定性

探讨相关噪声下离散时变线性系统的卡尔曼滤波模型。借助广义逆和最小模最小二乘解的思想,在Frobenius范数意义下,获得基于偏差最优估计的转换系数矩阵,将相关噪声系统转化为不相关噪声系统,获得相应的卡尔曼滤波模型。理论上,在误差协方差矩阵有界前提下,获证该滤波模型是全局渐近稳定的,数值实验获该模型的合理性。理论和实验结果表明,该模型是稳定的,且可有效解决含相关噪声和时变量测噪声驱动阵的离散时变系统的状态估计问题。     

Comment on "Characterization of subthreshold voltage fluctuations in neuronal membranes," by M. Rudolph and A. Destexhe

In two recent articles, Rudolph and Destexhe (2003, 2005) studied a leaky integrator model (an RC-circuit) driven by correlated ("colored") gaussian conductance noise and Gaussian current noise. In the first article, they derived an expression for the stationary probability density of the membrane voltage; in the second, they modified this expression to cover a larger parameter regime. Here we show by standard analysis of solvable limit cases (white noise limit of additive and multiplicative noise sources; only slow multiplicative noise; only additive noise) and by numerical simulations that their first result does not hold for the general colored-noise case and uncover the errors made in the derivation of a Fokker-Planck equation for the probability density. Furthermore, we demonstrate analytically (including an exact integral expression for the time-dependent mean value of the voltage) and by comparison to simulation results that the extended expression for the probability density works much better but still does not exactly solve the full colored-noise problem. We also show that at stronger synaptic input, the stationary mean value of the linear voltage model may diverge and give an exact condition relating the system parameters for which this takes place.     

On-line learning with malicious noise and the closure algorithm

We investigate a variant of the on-line learning model for classes of \0,1\-valued functions (concepts) in which the labels of a certain amount of the input instances are corrupted by adversarial noise. We propose an extension of a general learning strategy, known as “Closure Algorithm”, to this noise model, and show a worst-case mistake bound of m + (d+1)K for learning an arbitrary intersection-closed concept class C, where K is the number of noisy labels, d is a combinatorial parameter measuring C's complexity, and m is the worst-case mistake bound of the Closure Algorithm for learning C in the noise-free model. For several concept classes our extended Closure Algorithm is efficient and can tolerate a noise rate up to the information-theoretic upper bound. Finally, we show how to efficiently turn any algorithm for the on-line noise model into a learning algorithm for the PAC model with malicious noise. This revised version was published online in June 2006 with corrections to the Cover Date.     

Analysis of the Hodgkin-Huxley equations with noise: the effects of noise on chaotic neurodynamics

The chaotic behavior of Hodgkin-Huxley equations modulated by noise was studied by power spectra, correlation exponents, and information entropies by changing noise amplitude and components. The power spectra of the membrane potential calculated by the equations showed two major peaks at 105 and 115Hz. The noise component of compressing dynamics (CDN) enhanced the amplitude of the 105Hz component and also increased its frequency. The correlation exponent of the correlation integral, which was calculated with a scale size below the noise amplitude, was almost the same as the degree of freedom of the system (=4) when CDN was applied. Contrary to this, the noise component of extending dynamics (EDN) increased the exponent only up to 2.5–3.0. The information entropy shows that both CDN and EDN produced noise-induced order (NIO). The effect of EDN was slightly larger than that of CDN. When comparing the effects of noise imposed on the variables of the Hodgkin-Huxley equations, V and m appeared to be related to CDN, while h and n appeared to be related to EDN. These results suggest that the fluctuations induced by EDN were restricted within some parts of submanifolds comprising the strange attractor, while those induced by CDN shook the orbit away from the submanifolds. This shake-out mechanism may have a significant role on real neurodynamics.This work was presented, in part, at the 8th International Symposium on Artificial Life and Robitics, Oita, Japan, January 24–26, 2003     

一种EEPROM中高压产生电路的设计与实现

设计了一种应用于EEPROM的低电源电压的片内升压电路。基于电压倍乘电路,获得两倍于电源电压的驱动电压,用来驱动高压电荷泵电路得到EEPROM擦写用的15 V高压,实现EEPROM在1.3 V电压下稳定的工作。同时,基于负温度特性的电压分压电路实现电荷泵输出高压的负温度特性,提升了存储器在整个工作温度范围(-40℃~85℃)内的可靠性。设计的高压产生电路在0.13μm Embedded EEPROM CMOS工艺实现,工作电压为1.3 V~1.75 V,面积大小为600μm×80μm。     

Optimizing a production system with rework and equal sized batch shipments

In several cases producing new or recovering defective products takes place on a common facility, with these activities are carried out in lots. Consequently, there is a necessity to coordinate the production and rework activities with respect to the timing of operations and also with regard to appropriate lot sizes for both processes while completely satisfying a given demand. Thereby, a decision has to be made on how to assign units completed at one stage to partial lots—called batches—for shipment to the next operation. In this paper we present a lot size model which addresses all of these aspects. Based on total relevant costs per unit time, an optimization method is developed to determine the economic production and rework quantity as well as the corresponding batch sizes for both activities. The algorithm is illustrated by a numerical example followed by a sensitivity analysis of the models behavior under different problem parameters.     

Vehicle noise and the passenger

Little effort has been put into studying the noise climate inside passenger vehicles. This paper shows that noise levels in motor cars and heavy goods vehicles are unacceptable to the passenger at typical cruising speeds. It is suggested that one factor responsible for this state of affairs is the lack of criteria for acceptable noise levels. Research into the subjective response to noise in motor vehicles, both on the road and in the laboratory, is described. The importance of very low frequencies is shown in determining levels of comfort, as well as the difficulties in accurately reproducing in-vehicle noise in the laboratory. A tentative criterion is given for acceptable noise levels in passenger vehicles and work is described which, it is hoped, will lead to a more precise measure of subjective rating.     

On the computer generation of the Erlang and negative binomial distributions with shape parameter equal to two

We provide closed-form expressions for the quantile functions of the Erlang and negative binomial distributions with shape parameter equal to two. These expressions are related to the Lambert W function.     

Salt and pepper noise filtering with fuzzy-cellular automata

A new image denoising algorithm is proposed to restore digital images corrupted by impulse noise. It is based on two dimensional cellular automata (CA) with the help of fuzzy logic theory. The algorithm describes a local fuzzy transition rule which gives a membership value to the corrupted pixel neighborhood and assigns next state value as a central pixel value. The proposed method removes the noise effectively even at noise level as high as 90%. Extensive simulations show that the proposed algorithm provides better performance than many of the existing filters in terms of noise suppression and detail preservation. Also, qualitative and quantitative measures of the image produce better results on different images compared with the other algorithms.     

A closed-form optimal control for linear systems with equal state and input delays

This paper presents the optimal regulator for a linear system with equal delays in state and input and a quadratic criterion. The optimal regulator equations are obtained using the maximum principle. Performance of the obtained optimal regulator is verified in the illustrative example against the best linear regulators available for the linear system without delays and for a rational approximation of the original time delay system. Simulation graphs demonstrating better performance of the obtained optimal regulator are included.     

利用LM2678实现遥控和本地调压的直流电源

给出了一种简单的电源调压方法,介绍了LM2678芯片的功能结构、调压系统的硬件和软件设计,最后给出了实验结果和分析,证明了该方法的可行性和实用性。     

Curvature correction to vacuum fluctuations and cosmic evolution with cosmological duality

The curvature correction to the Lagrangian of vacuum fluctuations is studied. After a brief tour through the vacuum expectation value of the energy–momentum tensor 〈T _μν 〉 and comparing this with the semiclassical averaging value of T _μν , it is found that vacuum polarization due to curvature determines the effective cosmological constant and the gravitational constant in such a way that the quantum corrections of order R ² are inevitable in the high curvature regime. Considering the asymptotic past and future as vacuum states of the Universe, a Cosmological Duality Conjecture (CDC) is put forward that “if there are terms proportional to R ⁿ (n > 0), there are also terms proportional to R ^?m (m >0) in the gravitational Lagrangian.” The CDC indicates a cyclic cosmological evolution where the late-time dark energy phase comes to an end and a collapsing phase begins with reversal of the arrow of time.