Synthetic on-line signature generation. Part I: Methodology and algorithms

The theoretical framework and algorithms of a novel method for the generation of synthetic on-line signatures are presented. This model-based approach combines the spectral analysis of real signatures with the Kinematic Theory of rapid human movements in order to generate totally synthetic specimens. Two different algorithms are also described in order to produce duplicated samples from the synthetic master signatures, so that the generation scheme as a whole is able to produce in a complete automatic fashion huge synthetic databases. Typical examples of synthetic specimens are presented to highlight their human-like appearance. The validation protocol and the test results are presented and discussed in a companion paper.     

Relational consistency in on-line signature validation

An input signature is validated by elastic matching with a reference specimen signature. The matching algorithm is based on checking relational consistency only to an extent that is practicable in a low-cost real-time system.     

Newton methods for parametric surface registration. Part II. Experimental validation

The first part of this paper introduced a new freeform surface registration algorithm whereby sets of points measured from a physical surface are aligned to the computer-aided design model of the surface. The algorithm is based on traditional Newton minimization techniques with the benefit of analytic formulas for derivatives. In the past, these techniques have been abandoned due to the inability to efficiently compute derivative information of the registration objective function. The result is a new method for parametric surface registration.In the second part, more specific implementation details are given such as the various types of Newton methods employed. In addition, experimental results are provided that compare these new methods to existing registration techniques such as ICP [IEEE Trans Pattern Anal Mach Intell 14 (1992) 239]. The results reveal the advantages and disadvantages characteristic of these new techniques.     

HMM-based on-line signature verification: Feature extraction and signature modeling

A function-based approach to on-line signature verification is presented. The system uses a set of time sequences and Hidden Markov Models (HMMs). Development and evaluation experiments are reported on a subcorpus of the MCYT bimodal biometric database comprising more than 7000 signatures from 145 subjects. The system is compared to other state-of-the-art systems based on the results of the First International Signature Verification Competition (SVC 2004). A number of practical findings related to feature extraction and modeling are obtained.     

An alternative structure for next generation regulatory controllers. Part II: Stability analysis,tuning rules and experimental validation

We recently developed, as an alternative to the PID controller, a novel 4-mode control scheme that takes full advantage of modern electronic hardware components, and whose tuning parameters are directly related to controller performance attributes (robustness, set-point tracking, and disturbance rejection); its achievable performance is better than that of the PID controller, and it can be designed and implemented much more directly and transparently. In this companion paper we present robust stability results for the proposed controller, for any given plant/model mismatch; these results are then used to generate simple tuning rules for the controller. The effect of noise on controller performance is explicitly considered and modified tuning rules are proposed for excessively noisy processes. The controller tuning results and procedure are then illustrated via experimental testing and validation. First, water level control in a simple laboratory scale process is used to illustrate the design, tuning, and implementation of the RTDA controller. We use this process primarily to evaluate the controller performance and illustrate how the tuning parameters influence, directly and independently, the controller performance attributes. The controller is then implemented on a pilot-scale physical vapor deposition process to demonstrate its performance on a more complicated process that is prototypical of 21st century manufacturing. We demonstrate that the proposed controller achieves improved performance with minimal tuning effort.     

Logical form generation as abduction: Part II. A dual-route parsimonious covering approach

Abductive inferences are commonplace during natural language processing. Having identified some limitations of an existing parsimonious covering model of abductive diagnostic inference, we developed an extended, dual-route version to address issues in word sense disambiguation and logical form generation. the details of representing knowledge in this framework and the syntactic route of covering are described in a companion article [V. Dasigi, Int. J. Intell. Syst., 9 , 571-608 (1994)]. Here, we describe the semantic covering process in detail. A dual-route algorithm that integrates syntactic and semantic covering is given. Taking advantage of the “transitivity” of irredundant syntactic covering, plausible semantic covers are searched for, based on some heuristics, in the space of irredundant syntactic covers. Syntactic covering identifies all possible candidates for semantic covering, which in turn, helps focus syntactic covering. Attributing both syntactic and semantic facets to “open-class” linguistic concepts makes this integration possible. an experimental prototype has been developed to provide a proof-of-concept for these ideas in the context of expert system interfaces. the prototype has at least some ability to handle ungrammatical sentences, to perform some nonmonotonic inferences, etc. We believe this work provides a starting point for a nondeductive inference method for logical form generation, exploiting the associative linguistic knowledge. © 1994 John Wiley & Sons, Inc.     

High-fidelity modeling of MEMS resonators. Part II. Coupled beam-substrate dynamics and validation

A computational multiphysics model of the coupled beam-substrate-electrostatic actuation dynamics of MEMS resonators has been developed for the model-based prediction of Q-factor and design sensitivity studies of the clamped vibrating beam. The substrate and resonator beam are modeled independently and then integrated by enforcing their interface compatibility condition and the force equilibrium to arrive at the multiphysics model. The present model has been validated with several reported single-beam clamped resonators. The validated model indicates that: the anchor loss is primarily engendered through coupling between the resonant modes and the waves propagating through the substrate inner layers; the resonant frequency of the beam decreases up to 5% due to substrate flexibilities interacting with beam at the anchors; and, for a given design the beam mass and its relative compliance with respect to the substrate are key parameters that influence the Q-factor degradation. In addition, the coupled model has also been used to predict the Q-factor of a paired-beam mechanical filter device with high fidelity when compared with the experimentally observed Q-factor.     

Model validation for control and controller validation in a prediction error identification framework—Part II: illustrations

In this paper, we illustrate our new results on model validation for control and controller validation in a prediction error identification framework, developed in a companion paper (Gevers et al., Automatica (2003) 39(3) pii: S005-1098(02)00234-0), through two realistic simulation examples, covering widely different control design applications. The first is the control of a flexible mechanical system (the Landau benchmark example) with a tracking objective, the second is the control of a ferrosilicon production process with a disturbance rejection objective.     

SUSIG: an on-line signature database, associated protocols and benchmark results

We present a new online signature database (SUSIG). The database consists of two parts that are collected using different pressure-sensitive tablets (one with and the other without an LCD display). A total of 100 people contributed to each part, resulting in a database of more than 3,000 genuine signatures and 2,000 skilled forgeries. The genuine signatures in the database are real signatures of the contributors. In collecting skilled forgeries, forgers were shown the signing process on the monitor and were given a chance to practice. Furthermore, for a subset of the forgeries (highly skilled forgeries), this animation was mapped onto the LCD screen of the tablet so that the forgers could trace over the mapped signature. Forgers in this group were also informed of how close they were to the reference signature, so that they could improve their forgery quality. We describe the signature acquisition process and several verification protocols for this database. We also report the performance of a state-of-the-art signature verification system using the associated protocols. The results show that the highly skilled forgery set is significantly more difficult compared to the skilled forgery set, providing researchers with challenging forgeries. The database is available through .     

SAS: semantics aware signature generation for polymorphic worm detection

String extraction and matching techniques have been widely used in generating signatures for worm detection, but how to generate effective worm signatures in an adversarial environment still remains a challenging problem. For example, attackers can freely manipulate byte distributions within the attack payloads and thus inject well-crafted noisy packets to contaminate the suspicious flow pool. To address these attacks, we propose SAS, a novel Semantics Aware Statistical algorithm for automatic signature generation. When SAS processes packets in a suspicious flow pool, it uses data flow analysis techniques to remove non-critical bytes. We then apply a hidden Markov model (HMM) to the refined data to generate state-transition-graph-based signatures. To our best knowledge, this is the first work combining semantic analysis with statistical analysis to automatically generate worm signatures. Our experiments show that the proposed technique can accurately detect worms with concise signatures. Moreover, our results indicate that SAS is more robust to the byte distribution changes and noise injection attacks compared to Polygraph and Hamsa.     

Application of finitized power series distributions to accelerated variate generation. Part II: the case of the logarithmic distribution

The method of aliasing vastly expands the palette of discrete random variate generation methodologies while providing excellent speed. However, its application is limited to finitely supported distributions. We demonstrate that an application of moment preserving finitization called the Negative Taylor Series Finitization (NTSF) method for the power series family of discrete distributions, when coupled with the method of aliasing, can greatly improve infinitely supported discrete random variate generation speed with certain limitations. We illustrate this with the logarithmic power series distribution, and we compare four published algorithms designed to generate random variates from a logarithmic distribution to the aliasing method of random variate generation from an NTSF version of the same distribution. We compare the accuracy and speed (user‐time) of these various methods for generating variates from a logarithmic distribution.     

On flowchart theories: Part II. The nondeterministic case

We give a calculus for nondeterministic flowchart schemes similar to the calculus of polynomials. It uses a formal representation of flowchart schemes and a natural equivalence on these formal representations. The algebraic structure involved is a matrix theory endowed with an axiomatized repetition.     

Self-sensing for electromagnetic actuators. Part II: Position estimation

The second paper in a two part series presents the position estimation scheme for an 8-pole heteropolar active magnetic bearing (AMB). The integrated self-sensing assembly comprises a nonlinear MIMO parameter estimator together with a coupled reluctance network model (Part I), by which problems associated with magnetic cross-coupling and saturation are collectively addressed. The parameter estimator utilizes the first harmonic components of the current and voltage waveforms to determine estimates for the x and y rotor positions. Magnetic saturation is accounted for using a saturation factor, which scales the demodulated coil currents to ensure that the actuator with the lowest flux density contributes the most to the position estimate. Basic functionality and feasibility of the proposed self-sensing scheme are demonstrated via an experimentally validated transient simulation model (TSM). The TSM incorporates magnetic effects such as eddy currents, cross-coupling, and hysteresis. In the second part of this work, the static and dynamic performance of the self-sensing sensor is evaluated. The influence of magnetic cross-coupling, saturation, and duty cycle variation on the position estimate is documented. The results demonstrate the importance of including a mutual coupling term in the position estimation model in order to stably suspend the rotor. Furthermore, stability margin analyses indicate that the robustness of the magnetic bearing control is satisfactory for unrestricted long-term operation.     

Logical form generation as abduction: Part I. Representation of linguistic concepts

For some time, researchers have become increasingly aware that some aspects of natural language processing can be viewed as abductive inference. This article describes knowledge representation in dual-route parsimonious covering theory, based on an existing diagnostic abductive inference model, extended to address issues specific to logic form generation. the two routes of covering deal with syntactic and semantic aspects of language, and are integrated by attributing both syntactic and semantic facets to each “open class” concept. Such extensions reflect some fundamental differences between the two task domains. the syntactic aspect of covering is described to show the differences, and some interesting properties are established. the semantic associations are characterized in terms of how they can be used in an abductive model. A major significance of this work is that it paves the way for a nondeductive inference method for word sense disambiguation and logical form generation, exploiting the associative linguistic knowledge. This approach sharply contrasts with others, where knowledge has usually been laboriously encoded into pattern-action rules that are hard to modify. Further, this work represents yet another application for the general principle of parsimonious covering. © 1994 John Wiley & Sons, Inc.     

An automatic coarse and fine surface mesh generation scheme based on medial axis transform: Part II implementation

In this paper, we present implementation aspects of a surface finite element (FE) meshing algorithm described in Part I (this volume) [1]. This meshing scheme is based on the medial axis transform (MAT) [2] to interrogate shape and to subdivide it into topologically simple subdomains. The algorithm can be effectively used to create coarse discretization and fine triangular surface meshes. We describe our techniques and methodology used in the implementation of the meshing and MAT algorithms. We also present some running times of our experimental system. We finally report the results we have obtained from several design and analysis applications which include adaptive surface approximations using triangular facets, and adaptiveh- andp-adaptive finite element analysis (FEA) of plane stress problems. These studies demonstrate the potential applicability of our techniques in computer aided design and analysis.     

在线算法验证系统的设计与实现

针对远程教学练习环节中存在的问题,提出了一种利用ASP.NET技术构建在线算法验证系统的实现方法.系统用命令行编译和批处理技术实现对算法程序的自动编译;利用运行结果的捕获技术和数据库技术实现算法程序的自动测试;利用数据库技术、哈希表技术,算法相似度计算等技术实现算法练习的管理.实践运行结果表明,该系统有效解决了练习提交的及时性和练习批改及管理的自动化问题,大大地改善了教学手段、提高了教学效果.     

Modeling multibody systems with uncertainties. Part II: Numerical applications

This study applies generalized polynomial chaos theory to model complex nonlinear multibody dynamic systems operating in the presence of parametric and external uncertainty. Theoretical and computational aspects of this methodology are discussed in the companion paper “Modeling Multibody Dynamic Systems With Uncertainties. Part I: Theoretical and Computational Aspects”.In this paper we illustrate the methodology on selected test cases. The combined effects of parametric and forcing uncertainties are studied for a quarter car model. The uncertainty distributions in the system response in both time and frequency domains are validated against Monte-Carlo simulations. Results indicate that polynomial chaos is more efficient than Monte Carlo and more accurate than statistical linearization. The results of the direct collocation approach are similar to the ones obtained with the Galerkin approach. A stochastic terrain model is constructed using a truncated Karhunen-Loeve expansion. The application of polynomial chaos to differential-algebraic systems is illustrated using the constrained pendulum problem. Limitations of the polynomial chaos approach are studied on two different test problems, one with multiple attractor points, and the second with a chaotic evolution and a nonlinear attractor set.The overall conclusion is that, despite its limitations, generalized polynomial chaos is a powerful approach for the simulation of multibody dynamic systems with uncertainties.