Measurements of the ion-depletion zone evolution in a micro/nano-channel

Ion-depletion and ion-enrichment are the most important phenomena found in a hybrid micro/nano-channel. This depletion process significantly decreases the ion concentration at the anodic end of the nano-channels and lower concentration propagation in the microchannel. The present paper focuses on measurement and analyzes the extension of the depletion zone with time and propagation of concentration perturbation. The systemic experiments were conducted using the nano-porous membranes with different pore diameters (ϕ15 nm, ϕ50 nm), the applied electric voltages (20–100 V) and the buffer solution pH values (pH 5.4, 9.2). According to dimensionless analysis, the extension of the depletion boundary was initially found to be independent of time and to have a non-linear variation for larger times. Based on Nernst–Planck equation, a one-dimensional wave equation is obtained under certain hypothesis, which also shows the propagation of concentration perturbation in depletion zone with constant speed at the initial time.     

ε-Descending Support Vector Machines for Financial Time Series Forecasting

This paper proposes a modified version of support vector machines (SVMs), called ε-descending support vector machines (ε-DSVMs), to model non-stationary financial time series. The ε-DSVMs are obtained by incorporating the problem domain knowledge – non-stationarity of financial time series into SVMs. Unlike the standard SVMs which use a constant tube in all the training data points, the ε-DSVMs use an adaptive tube to deal with the structure changes in the data. The experiment shows that the ε-DSVMs generalize better than the standard SVMs in forecasting non-stationary financial time series. Another advantage of this modification is that the ε-DSVMs converge to fewer support vectors, resulting in a sparser representation of the solution. This revised version was published online in June 2006 with corrections to the Cover Date.     

A search for laws in the results of gravitational constant measurements

A spectral analysis has been performed on time series of the results of gravitational constant G measurements in the period of 1985–2003. A manifestation of cosmic rhythmics in the measurement results can be connected with the effects of terrestrial mediators, among which the most probable are microseisms and temperature variations. Talk given at the International Conference RUSGRAV-13, June 23–28, 2008, PFUR, Moscow.     

Passive-state generation mechanisms and stabilization of dynamic systems

Conclusion In the models of passive-state formation considered above we have assumed for simplicity constant control parameters. In reality, the control parameters are functions of time, environmental factors, and the values of the “active” variables [7, 8]. These functions are “reasonably” constructed: under “bad” conditions the variables shift to a passive state, and when “good” conditions are restored, the variables switch back to active state. It is relevant to develop and analyze the corresponding model circuits. Here we can expect to observe even stronger stabilization effects in the behavior of complex systems. In conclusion, I would like to thank an anonymous referee for useful comments. The study is financed by the Russian Foundation of Basic Research. Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 103–112, November–December, 1995.     

Exact Sampling from Perfect Matchings of Dense Regular Bipartite Graphs

We present the first algorithm for generating random variates exactly uniformly from the set of perfect matchings of a bipartite graph with a polynomial expected running time over a nontrivial set of graphs. Previous Markov chain results obtain approximately uniform variates for arbitrary graphs in polynomial time, but their general running time is Θ(n¹⁰ (ln n)²). Other algorithms (such as Kasteleyn's O(n³) algorithm for planar graphs) concentrated on restricted versions of the problem. Our algorithm employs acceptance/rejection together with a new upper limit on the permanent of a form similar to Bregman's theorem. For graphs with 2n nodes, where the degree of every node is γn for a constant γ, the expected running time is O(n^{1.5 + .5/γ}). Under these conditions, Jerrum and Sinclair showed that a Markov chain of Broder can generate approximately uniform variates in Θ(n^{4.5 + .5/γ} ln n) time, making our algorithm significantly faster on this class of graphs. The problem of counting the number of perfect matchings in these types of graphs is # P complete. In addition, we give a 1 + σ approximation algorithm for finding the permanent of 0–1 matrices with identical row and column sums that runs in O(n^{1.5 + .5/γ} (1/σ²) log (1/δ))$, where the probability that the output is within 1 + \sigma$ of the permanent is at least 1 – δ.     

Effects of planar inlet plenums on the hydrodynamically developing flows in rectangular microchannels of complementary aspect ratios

The effects of planar inlet plenum geometry on the developing flow fields in two rectangular microchannels of reciprocal aspect ratios (H/W ∼2.75 and ∼0.40) were investigated for Re _D =  1–100 using micro particle image velocimetry (μPIV). These two microchannels were made by a precision sawing and silicon microfabrication techniques. Both the velocity profiles and centerline velocity developments were clearly resolved and extracted along the axial distance from μPIV results. The entrance lengths were found from the centerline velocities using a decaying exponential fitting function where the centerline velocity reaches 99% of the fully developed centerline velocity. The proposed fitting function showed excellent agreement with the experimental results. The planar plenum was shown to cause an upstream predevelopment resulting in the significant reductions in the entrance lengths. Two entrance length correlations were proposed in the forms of Atkinson et al.’s (AIChE J 15:548–553, 1969) and Chen’s (J Fluids Eng 95:153–158, 1973) correlations. The proposed entrance length correlations showed that acquired constant portion and slope of the entrance lengths showed 23–27 and 70–81% reductions for H/W =  2.75 while the entrance length correlation for H/W =  0.40 showed 69–73% increase and 41–63% decrease in the constant portion and slope, respectively.     

On the numerical solution of nonlinear systems of Volterra integro-differential equations with delay arguments

Particular cases of nonlinear systems of delay Volterra integro-differential equations (denoted by DVIDEs) with constant delay τ > 0, arise in mathematical modelling of ‘predator–prey’ dynamics in Ecology. In this paper, we give an analysis of the global convergence and local superconvergence properties of piecewise polynomial collocation for systems of this type. Then, from the perspective of applied mathematics, we consider the Volterra’s integro-differential system of ‘predator–prey’ dynamics arising in Ecology. We analyze the numerical issues of the introduced collocation method applied to the ‘predator–prey’ system and confirm that we can achieve the expected theoretical orders of convergence.      

Choosing the parameter of a modified additive-averaged splitting algorithm

The problem-solving time and the solution accuracy are expressed as functions of a parameter. An optimization problem of choosing the parameter using a “time cost–solution accuracy” criterion is considered. A Pareto-optimal set of solutions is obtained. The best value of the parameter is chosen by the ideal-point method. Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 98–105, July–August 2009.     

Systemintegration of microsystems/chip elements in miniaturized automata for high-throughput synthesis and screening in biology, biochemistry and chemistry

 Microsystems recently have been introduced as tools for screening in modern chemistry, biochemistry and biology. It has been shown that new microsystems can be implemented in the biomedical laboratory by using the microsystemic approach for the sample carrier – the miniaturized microtiter plate (“the nanotiter plate”) – or the production of nanodroplets with ink jetters and to integrate those systems in macrodevices like xyz tables and detection devices like CCD-cameras. We show in this paper that decisive problems of the approach – the evaporation problem and the problem of chemical/biochemical/biological compatibility of the assays and the used materials can be solved successfully. It is possible to realize chemical synthesis in miniaturized flow systems and to perform isothermal amplification of RNA in silicon wafers. Furthermore real high throughput screening with in vivo systems can be performed and all relevant parameters as evaporation, pipetting and detection can be controlled on reasonable time scales. Received: 27 May 1997/Accepted: 2 June 1997     

Stability of an equilibrium state in a multiinfectious-type SIS model on a truncated network

In a homogeneous constant population, the basic SIS model potentially has an epidemic equilibrium state with global asymptotic stability since it can be reduced to the logistic equation. On the basic SIS model with a nonhomogeneous constant population, viewed as a multitype SIS model, the global or local asymptotic stability of an epidemic equilibrium state has also been studied.^1–4 However, this kind of analysis in other models with nonhomogeneous populations has rarely been developed, even though the corresponding models with homogeneous populations are well known. In addition, recent studies of complex networks have revealed that heterogeneity of the link number of vertices drastically changes the epidemic thresholds.^5–9 For these reasons, figuring out the roles of heterogeneity is a major topic in epidemic modeling. Here, we consider a multiinfectious-type SIS model on a network, and show the (local or global) asymptotic stability of an epidemic equilibrium state whenever it exists. This work was presented in part at the 11th International Symposium of Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

Econometric Effects of Utility Order-Preserving Transformations in Discrete Choice Models

In the random utility modelling context, choice probabilities are unaffected by increasing linear transformations of the systematic utility; hence its empirical specification is derived on the basis that only differences in utility matters and that the scale of utility is arbitrary. We argue that choice probabilities remain unchanged if these linear transformations are made under the deterministic perspective of a single individual choosing several times. But, in the random utility setting, parameter estimates might be significantly affected by these transformations. In particular we focus on the effect of two order-preserving transformations usually applied in the derivation of the representative utility from the conditional indirect utility function: adding a constant to the utility of all alternatives and multiplying each alternative utility by a constant. We concentrate on the two most popular specifications in transport mode choice: the “wage rate” (Train and McFadden Transport Res 12:349–353, 1978) and the “expenditure rate” (Jara-Díaz and Farah Transport Res 22B:159–171, 1987) specifications. Using a collection of synthetic datasets generated in a new fashion directly from the conditional indirect utility function, i.e. before applying any expansion or transformation, we demonstrate how taking this class of order-preserving transformations could lead to misinterpretation of the econometric results, such as detecting randomly distributed and correlated parameters and/or income and time effects which are in fact not present.     

Transient analysis of sliding contact of layered elastic/plastic solids with rough surfaces

 Based on the boundary element method (BEM) and a variational principle, a numerical model is developed to analyze the time – transient sliding contact of two layered elastic/plastic solids. Two cases are considered: one is the loading/sliding/unloading of a rough surface on a smooth surface, and the other is of two rough surfaces. Contact statistics, contact pressure profile and stress distribution are predicted at each time step with updated surface roughness. The results are used to study the effect of surface roughness, physical properties of the layer and the substrate, and lubricant film thickness on friction, stiction, and wear. Discussion on the integration of this contact model into advanced tribological models, e.g., wear model, is also presented. Received: 28 June 2002/Accepted: 23 October 2002 Currently at: Seagate Technology, Pittsburgh, PA Paper presented at the 13th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 17–18 June, 2002     

Lyapunov function method for investigation of stability of stochastic Ito random-structure systems with impulse Markov switchings. I. General theorems on the stability of stochastic impulse systems

The asymptotic stochastic stability on the whole and asymptotic p-stability on the whole are investigated with the help of Lyapunov functions and the concept of an infinitesimal operator over solutions to a system (to calculate this operator, it suffices to know only the coefficients of the system). The stability under constant perturbations is considered. Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 135–145, March–April 2009.     

Trial and Error

A pac-learning algorithm is -space bounded, if it stores at most examples from the sample at any time. We characterize the -space learnable concept classes. For this purpose we introduce the compression parameter of a concept class and design our Trial and Error Learning Algorithm. We show : is -space learnable if and only if the compression parameter of is at most . This learning algorithm does not produce a hypothesis consistent with the whole sample as previous approaches e.g. by Floyd, who presents consistent space bounded learning algorithms, but has to restrict herself to very special concept classes. On the other hand our algorithm needs large samples; the compression parameter appears as exponent in the sample size. We present several examples of polynomial time space bounded learnable concept classes: – all intersection closed concept classes with finite VC–dimension. – convex -gons in . – halfspaces in . – unions of triangles in . We further relate the compression parameter to the VC–dimension, and discuss variants of this parameter. Received May 24, 1994 / July 4, 1995     

A Gi/Hr/1/0 queue in which the longest job is lost

Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 180–182, March–April, 1994.     

New Results on Web Caching with Request Reordering

We study web caching with request reordering. The goal is to maintain a cache of web documents so that a sequence of requests can be served at low cost. To improve cache hit rates, a limited reordering of requests is allowed. Feder et al. (Proceedings of the 13th ACM–SIAM Symposium on Discrete Algorithms, pp. 104–105, 2002), who recently introduced this problem, considered caches of size 1, i.e. a cache can store one document. They presented an offline algorithm based on dynamic programming as well as online algorithms that achieve constant factor competitive ratios. For arbitrary cache sizes, Feder et al. (Theor. Comput. Sci. 324:201–218, 2004) gave online strategies that have nearly optimal competitive ratios in several cost models.     

Short term memory in recurrent networks of spiking neurons

We present in this paper a general model of recurrent networks of spiking neurons, composed of several populations, and whose interaction pattern is set with a random draw. We use for simplicity discrete time neuron updating, and the emitted spikes are transmitted through randomly delayed lines. In excitatory-inhibitory networks, we show that inhomogeneous delays may favour synchronization provided that the inhibitory delays distribution is significantly stronger than the excitatory one. In that case, slow waves of synchronous activity appear (this synchronous activity is stronger in inhibitory population). This synchrony allows for a fast ada ptivity of the network to various input stimuli. In networks observing the constraint of short range excitation and long range inhibition, we show that under some parameter settings, this model displays properties of –1– dynamic retention –2– input normalization –3– target tracking. Those properties are of interest for modelling biological topologically organized structures, and for robotic applications taking place in noisy environments where targets vary in size, speed and duration. This revised version was published online in June 2006 with corrections to the Cover Date.     

The best polynomial multidimensional-matrix regression

The problem of finding the best polynomial multidimensional-matrix regression is formulated. A system of equations is obtained to calculate the parameters of polynomial regression of any degree. Expressions for the parameters of constant linear and square regressions are derived as well. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 138–143, May–June 2007.     

Planck’s constant variation as a cosmological evolution test for the early universe

A conjecture on a hierarchical cosmological time evolution of Planck’s constant has been accepted. This presumed phenomenon might be responsible for the cosmological high redshifts as an alternative mechanism instead of the Doppler effect. The Bohr radius of a hydrogen atom and the probability of alpha decay of atomic nuclei have been estimated: both results are in sufficient consent with observational data concerning the light elements abundance in the early Universe. Talk given at the International Conference RUSGRAV-13, June 23–28, 2008, PFUR, Moscow.     

An earlier time for inserting and/or accelerating tasks

In a periodic real-time system scheduled by the EDF (Earliest Deadline First) algorithm (Liu and Layland, J. ACM 20(1), 40–61, 1973; Barauh, Proc. of the 27th IEEE International Real-Time Systems Symposium, 379–387, 2006; Buttazzo, J. Real-Time Syst. 29(1), 5–26, 2005), when new tasks have to be inserted into the system at run-time and/or current tasks request to increase their rates in response to internal or external events, the new sum of the utilizations after the insertion and/or acceleration should be limited, otherwise, one or more current tasks should usually be compressed (their periods being prolonged) in order to avoid overload. Buttazzo offered a time from which on this kind of adjustment can be done without causing any deadline miss in the system (Buttazzo et al., IEEE Trans. Comput. 51(3), 289–302, 2002). It is, however, not early enough. In this paper, an earlier time is given and formally proved.