基于改进忆阻器的高通滤波器设计与仿真

针对传统的忆阻器模型存在不能很好地与HP实验室提出的忆阻器物理模型中忆阻器的阻值变化特点相符的问题,提出了一种改进的带有阈值电压的忆阻器模型,该模型能很好地模拟忆阻器的"激活"现象,其特性与HP实验室的忆阻器物理模型相符;基于该改进模型设计了一种高通滤波器电路,该电路通过改变忆阻器阻值控制电路的输出信号来改变忆阻器的阻值,从而实现了滤波器截止频率的调节。SPICE仿真结果验证了设计的正确性。     

Minimal quadrature formulae for the spaces H 2 R and L 2 R . A unified interpolatory approach

We consider minimal quadrature formulae for the Hilbert spacesH ₂ ^R andL ₂ ^R consisting of functions which are analytical on the open disc with radiusR and centre at the origin; the inner products are the boundary contour integral forH ₂ ^R and the area integral over the disc forL ₂ ^R . Such formulae can be viewed as interpolatory, generalizing—in two ways—Markoff's idea to construct the classical Gaussian quadratur formulae. This can be done simultaneously for both spaces using the same Hermitian interpolating operator. The advantage of this approach to minimal formulae is that we get a nonlinear system of equations for the nodes of the minimal formulae alone, in contrast to the coupled system for nodes and weights which arises from the minimality conditions. The uncoupled system that we obtain is numerically solvable for reasonable numbers of nodes and numerical tests show that the resulting minimal formulae are very well suited for the integration of functions with boundary singularities.     

Fabrication and characterization of a thermal switch

The development of a thermal switch based on arrays of liquid–metal micro-droplets is presented. Prototype thermal switches are assembled from a silicon substrate on which is deposited an array of 1600 30-μm liquid–metal micro-droplets. The liquid–metal micro-droplet array makes and breaks contact with a second bare silicon substrate. A gap between the two silicon substrates is filled with either air at 760 Torr, air at of 0.5 Torr or xenon at 760 Torr. Heat transfer and thermal resistance across the thermal switches are measured for “on” (make contact) and “off” (break contact) conditions using guard-heated calorimetry. The figure of merit for a thermal switch, the ratio of “off” state thermal resistance over “on” state thermal resistance, R_off/R_on, is 129 ± 43 for a xenon-filled thermal switch that opens 100 μm and 60 ± 17 for an 0.5 Torr air-filled thermal switch that opens 25 μm. These thermal resistance ratios are shown to be markedly higher than values of R_off/R_on for a thermal switch based on contact between polished silicon surfaces. Transient temperature measurements for the liquid–metal micro-droplet switches indicate thermal switching times of less than 100 ms. Switch lifetimes are found to exceed one-million cycles.     

Improving active Mealy machine learning for protocol conformance testing

Using a well-known industrial case study from the verification literature, the bounded retransmission protocol, we show how active learning can be used to establish the correctness of protocol implementation I relative to a given reference implementation R. Using active learning, we learn a model M _R of reference implementation R, which serves as input for a model-based testing tool that checks conformance of implementation I to M _R . In addition, we also explore an alternative approach in which we learn a model M _I of implementation I, which is compared to model M _R using an equivalence checker. Our work uses a unique combination of software tools for model construction (Uppaal), active learning (LearnLib, Tomte), model-based testing (JTorX, TorXakis) and verification (CADP, MRMC). We show how these tools can be used for learning models of and revealing errors in implementations, present the new notion of a conformance oracle, and demonstrate how conformance oracles can be used to speed up conformance checking.     

Evaluating remotely sensed live fuel moisture estimations for fire behavior predictions in Georgia, USA

Research has shown that remote sensing techniques can be used for assessing live fuel moisture content (LFMC) from space. The need for dynamic monitoring of the fire risk environment favors the use of fast, site-specific, empirical models for assessing local vegetation moisture status, albeit with some uncertainties. These uncertainties may affect the accuracy of decisions made by fire managers using remote sensing derived LFMC. Consequently, the analysis of these LFMC retrieval uncertainties and their impact on applications, such as fire spread prediction, is needed to ensure the informed use of remote sensing derived LFMC measurements by fire managers. The Okefenokee National Wildlife Refuge, one of the most fire-prone regions in the southeastern United States was chosen as our study area. Our study estimates the uncertainties associated with empirical site specific retrievals using NDWI (Normalized Difference Water Index; (R_0.86 − R_1.24) / (R_0.86 + R_1.24)) and NDII (Normalized Difference Infrared Index; (R_0.86 − R_1.64) / (R_0.86 + R_1.64)) that are simulated by coupled leaf and canopy radiative transfer models. In order to support the findings from those simulations, a second approach estimates uncertainties using actual MODIS derived indices over Georgia Forestry Commission stations that provide NFDRS model estimates of LFMC. Finally, we used the FARSITE surface fire behavior model to examine the sensitivity of fire spread rates to live fuel moisture content for the NFDRS high pocosin and southern rough fuel models found in Okefenokee. This allowed us to evaluate the effectiveness of satellite based LFMC estimations for use in fire behavior predictions. Sensitivity to LFMC (measured as percentage of moisture weight per unit dry weight of fuel) was analyzed in terms of no-wind no-slope spread rates as well as normalized spread rates. Normalized spread rates, defined as the ratio of spread rate at a particular LFMC to the spread rate at LFMC of 125 under similar conditions, were used in order to make the results adaptable to any wind-slope conditions. Our results show that NDWI has a stronger linear relationship to LFMC than NDII, and can consequently estimate LFMC with lesser uncertainty. Uncertainty analysis shows that 66% of NDWI based LFMC retrievals over non-sparsely vegetated regions are expected to have errors less than 32, while 90% of retrievals should be within an error margin of 56. In pocosin fuel models, under low LFMC conditions (< 100), retrieval errors could lead to normalized spread rate errors of 6.5 which may be equivalent to an error of 47 m/h in no-wind no-slope conditions. For southern rough fuel models, when LFMC < 175, LFMC retrieval errors could amount to normalized spread rate errors of 0.6 or an equivalent error of 9.3 m/h in no-wind no-slope conditions. These spread rate error estimates represent approximately the upper bound of errors resulting from uncertainties in empirical retrievals of LFMC over forested regions.     

A legal information flow (LIF) scheduler based on role-based access control model

Information systems have to be consistent and secure in presence of multiple conflicting transactions. The role-based access control (RBAC) model is widely used to keep information systems consistent and secure. A role shows a job function in an enterprise and is a set of access rights (permissions). Here, a subject s is allowed to issue a method op to an object o only if an access right 〈o, op〉 is included in the roles granted to the subject s. A subject is granted one or more than one role and issues a transaction to multiple objects. The transaction is assigned with some roles of the subject which is referred to as purpose. Even if every access request issued by every subject is authorized in the roles, illegal information flow might occur as well known confinement problem. In this paper, we define a legal information flow (LIF) relation (R₁ ?^I R₂) among a pair of role families R₁ and R₂ to prevent illegal information flow. Here, an LIF relation R₁ ?^I R₂ shows that no illegal information flow occur if a transaction T₁ with a role family R₁ is performed prior to another transaction T₂ with a role family R₂. In addition, it is significant to discuss which transaction to be performed prior to another transaction if the both transactions manipulate the same object in a conflicting way. In this paper, we define a significantly precedent relation R₁ ?^s R₂ among role families R₁ and R₂ which implies that the role family R₂ is more significant than R₁. Suppose a pair of transactions T₁ and T₂ with role families R₁ and R₂ issue conflicting methods op₁ and op₂, respectively, to an object o. If R₁ ?^s R₂, op₂ is performed on the object o prior to op₁. The more significant a transaction is, the more prior it is performed. We discuss a legal information flow (LIF) scheduler to synchronize transactions so as to prevent illegal information flow and to serialize conflicting methods from multiple transactions in terms of significancy and information flow relation of roles families. We evaluate the LIF scheduler in terms of how much illegal information flow can be prevented compared with the other scheduler.     

Fundamentals of SIGLA,an interval computing system over the completed set of intervals

The SIGLA System has been designed to obtain an Interval Computing System working with the whole surrounding structure of the standard interval setI (R) (see [9]), that is, the lattice completion ofI (R) with the ordinary algebraic operations extended onto it. A statistical component associating intervals to Bounded Fuzzy Distributions is added. Rounding semantics onI ^* (R) is considered, and bounding theorems directing programming are given. Improper intervals are shown to mean “control-band-like variables”, in contrast to the classical “autonomous random variables” represented by proper intervals. An outline of the SIGLA language is given.     

Numerical solution for the Cauchy problem in nonlinear 1-D-thermoelasticity

We approximate the Cauchy problem by a problem in a bounded domain Ω _R =(?R,R) withR>0 sufficiently large, and the boundary conditions on ?Ω _R are imposed in terms of the far field behavior of solutions to the Cauchy problem. Then we solve this approximate problem by the finite element method for the spatial variable and the difference method for the time variable. Moreover a coupled numerical scheme for the Cauchy problem is presented. The error estimates are established.     

Fuzzy measures for a correlation coefficient of fuzzy numbers under TW(the weakest t-norm)-based fuzzy arithmetic operations

Recently, the sup-min convolution based on Zadeh’s extension principle has been used by Liu and Kao [Fuzzy measures for correlation coefficient of fuzzy numbers, Fuzzy Sets and Systems 128 (2002) 267-275], to calculate a fuzzy correlation coefficient. They used a mathematical programming approach to derive fuzzy measures based on the classical definition of the correlation coefficient. It is well known that T_W (the weakest t-norm)-based addition and multiplication preserve the shape of L-R fuzzy numbers. In this paper, we consider the computational aspect of the T_W-based extension principle when the principle is applied to a correlation coefficient of L-R fuzzy numbers. We give the exact solution of a fuzzy correlation coefficient without programming or the aid of computer resources.     

High performance concrete compressive strength forecasting using ensemble models based on discrete wavelet transform

This paper investigates the use of wavelet ensemble models for high performance concrete (HPC) compressive strength forecasting. More specifically, we incorporate bagging and gradient boosting methods in building artificial neural networks (ANN) ensembles (bagged artificial neural networks (BANN) and gradient boosted artificial neural networks (GBANN)), first. Coefficient of determination (R²), mean absolute error (MAE) and the root mean squared error (RMSE) statics are used for performance evaluation of proposed predictive models. Empirical results show that ensemble models (R²_BANN=0.9278, R²_GBANN=0.9270) are superior to a conventional ANN model (R²_ANN=0.9088). Then, we use the coupling of discrete wavelet transform (DWT) and ANN ensembles for enhancing the prediction accuracy. The study concludes that DWT is an effective tool for increasing the accuracy of the ANN ensembles (R²_WBANN=0.9397, R²_WGBANN=0.9528).     

Fuzzy approach to select machining parameters in electrical discharge machining (EDM) and ultrasonic-assisted EDM processes

Condition monitoring of the machining process is very important in today's precision manufacturing, especially in the electrical discharge machining (EDM). This paper introduces a fuzzy-based algorithm for prediction of material removal rate (MRR), tool wear ratio (TWR), and surface roughness (R_z, R_k) in the EDM and ultrasonic-assisted EDM (US/EDM) processes. In this system, discharge current, pulse duration, and ultrasonic vibration of tool are the input variables and outputs are MRR, TWR, R_z, and R_k. The proposed fuzzy model in this study provides a more precise and easy selection of EDM and US/EDM input parameters, respectively for the required MRR, TWR, R_z, and R_k, which leads to better machining conditions and decreases the machining costs. The fuzzy modeling of EDM and US/EDM were able to predict the experimental results with accuracies more than 90%.     

Average time behavior of distributive sorting algorithms

In this paper we investigate the expected complexityE(C) of distributive (“bucket”) sorting algorithms on a sampleX ₁, ...,X _n drawn from a densityf onR ¹. Assuming constant time bucket membership determination and assuming the use of an average timeg(n) algorithm for subsequent sorting within each bucket (whereg is convex,g(n)/n↑∞,g(n)/n ² is nonincreasing andg is independent off), the following is shown:

1. Iff has compact support, then ∫g(f(x))dx<∞ if and only ifE(C)=0(n).
2. Iff does not have compact support, then \(E(C)/n\xrightarrow{n}\infty \) .

No additional restrictions are put onf.     

An Efficient Algorithm for Processing Multi-Relation Queries in Relational Databases

After a relation scheme R is decomposed into the set of schemes ρ={R1，…，Rn},we may pose queries as if Rexisted in the database,taking a join of Ri‘s,when it is necessary to implement the query,Suppos a query involves a set of attributes S R，we want to find the smallest subset of ρ whose union includes.S.We prove that the problem is NP-complete and present a polynomial-bounded approximation algorithm.A subset of ρ whose union includes S and has a decomposition into 3NF with a lossless join and preservation of dependencies in given in the paper.     

Filament formation in lithium niobate memristors supports neuromorphic programming capability

Memristor crossbars are capable of implementing learning algorithms in a much more energy and area efficient manner compared to traditional systems. However, the programmable nature of memristor crossbars must first be explored on a smaller scale to see which memristor device structures are most suitable for applications in reconfigurable computing. In this paper, we demonstrate the programmability of memristor devices with filamentary switching based on LiNbO₃, a new resistive switching oxide. We show that a range of resistance values can be set within these memristor devices using a pulse train for programming. We also show that a neuromorphic crossbar containing eight memristors was capable of correctly implementing an OR function. This work demonstrates that lithium niobate memristors are strong candidates for use in neuromorphic computing.

     

Algorithms for multicommodity flows in planar graphs

This paper gives efficient algorithms for the muiticommodity flow problem for two classes C₁₂ and C₀₁ of planar undirected graphs. Every graph in C₁₂ has two face boundaries B₁ and B₂ such that each of the source-sink pairs lies on B₁ or B₂. On the other hand, every graph inC ₀₁ has a face boundaryB ₁ such that some of the source-sink pairs lie onB ₁ and all the other pairs share a common sink lying onB ₁. The algorithms run inO(kn +nT(n)) time if a graph hasn vertices andk source-sink pairs andT(n) is the time required for finding the single-source shortest paths in a planar graph ofn vertices.     

Geometric properties of linearizable control systems

In this paper the distributions associated with a non-linear system of the form $$\frac{{dx}}{{dt}} = f(x) + \sum\limits_{\alpha = 1}^m {u_\alpha (t)g_\alpha (x)} ,f(0) = 0andx \in U_0 \subset R^n$$ are studied in relation to nonlinear state feedback $$u(x,v) = \hat a(x) + \hat S(x)v$$ withâ, u, v ∈ R ^m and ? a nonsingularm×m matrix withâ, ? functions ofx. Bothf andg are vector fields onU ₀, generally assumed to be real analytic. Two nested families of distributions {G ^j } and {M ^j } associated with the system are examined with emphasis on generic points ofU ₀, where it is shown that the usual conditions for feedback linearizability contain some redundancy. A characterization of state linearizability in terms of invariant factors of the equivalent linear form are given, and a criterion in terms of the distributions for a type of partial linearization is found.     

Analogs of Gröbner Bases in Polynomial Rings over a Ring

In this paper we will define analogs of Gröbner bases forR-subalgebras and their ideals in a polynomial ringR[x₁,...,x_n] whereRis a noetherian integral domain with multiplicative identity and in which we can determine ideal membership and compute syzygies.The main goal is to present and verify algorithms for constructing these Gröbner basis counterparts.As an application, we will produce a method for computing generators for the first syzygy module of a subset of anR[x₁,...,x_n] where each coordinate of each syzygy must be an element of the subalgebra.