Normal Form (normal + form)

Distribution by Scientific Domains


Selected Abstracts


Grammatical Inference Techniques and Their Application in Ground Investigation

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 1 2008
Ian Morrey
The data obtained from trial pits can be coded into a form that can be used as sample observations for input to a grammatical inference machine. A grammatical inference machine is a black box, which when presented with a sample of observations of some unknown source language, produces a grammar which is compatible with the sample. This article presents a heuristic model for a grammatical inference machine, which takes as data sentences and non-sentences identified as such, and is capable of inferring grammars in the class of context-free grammars expressed in Chomsky Normal Form. An algorithm and its corresponding software implementation have been developed based on this model. The software takes, as input, coded representations of ground investigation data, and produces as output a grammar which describes and classifies the geotechnical data observed in the area, and also promises the possibility of being able to predict the likely configuration of strata across the site. [source]


Neural Network Adaptive Robust Control Of Siso Nonlinear Systems In A Normal Form

ASIAN JOURNAL OF CONTROL, Issue 2 2001
J.Q. Gong
ABSTRACT In this paper, performance oriented control laws are synthesized for a class of single-input-single-output (SISO) n -th order nonlinear systems in a normal form by integrating the neural networks (NNs) techniques and the adaptive robust control (ARC) design philosophy. All unknown but repeat-able nonlinear functions in the system are approximated by the outputs of NNs to achieve a better model compensation for an improved performance. While all NN weights are tuned on-line, discontinuous projections with fictitious bounds are used in the tuning law to achieve a controlled learning. Robust control terms are then constructed to attenuate model uncertainties for a guaranteed output tracking transient performance and a guaranteed final tracking accuracy. Furthermore, if the unknown nonlinear functions are in the functional ranges of the NNs and the ideal NN weights fall within the fictitious bounds, asymptotic output tracking is achieved to retain the perfect learning capability of NNs. The precision motion control of a linear motor drive system is used as a case study to illustrate the proposed NNARC strategy. [source]


An artificial neural network satisfiability tester

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 12 2001
Tatiana Tambouratzis
An artificial neural network tester for the satisfiability problem of propositional calculus is presented. Satisfiability is treated as a constraint satisfaction optimization problem and, contrary to most of the existing satisfiability testers, the expressions are converted into disjunctive normal form before testing. The artificial neural network is based on the principles of harmony theory. Its basic characteristics are the simulated annealing procedure and the harmony function; the latter constitutes a measure of the satisfiability of the expression under the current truth assignment to its variables. The tester is such that: (a) the satisfiability of any expression is determined; (b) a truth assignment to the variables of the expression is output which renders true the greatest possible number of clauses; (c) all the truth assignments which render true the maximum number of clauses can be produced. © 2001 John Wiley & Sons, Inc. [source]


Feedback stabilization of bifurcations in multivariable nonlinear systems,Part II: Hopf bifurcations

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 4 2007
Yong Wang
Abstract In this paper we derive necessary and sufficient conditions of stabilizability for multi-input nonlinear systems possessing a Hopf bifurcation with the critical mode being linearly uncontrollable, under the non-degeneracy assumption that stability can be determined by the third order term in the normal form of the dynamics on the centre manifold. Stabilizability is defined as the existence of a sufficiently smooth state feedback such that the Hopf bifurcation of the closed-loop system is supercritical, which is equivalent to local asymptotic stability of the system at the bifurcation point. We prove that under the non-degeneracy conditions, stabilizability is equivalent to the existence of solutions to a third order algebraic inequality of the feedback gains. Explicit conditions for the existence of solutions to the algebraic inequality are derived, and the stabilizing feedback laws are constructed. Part of the sufficient conditions are equivalent to the rank conditions of an augmented matrix which is a generalization of the Popov,Belevitch,Hautus (PBH) rank test of controllability for linear time invariant (LTI) systems. We also apply our theory to feedback control of rotating stall in axial compression systems using bleed valve as actuators. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Normal form representation of control systems

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 5 2002
Daizhan Cheng
Abstract This paper is to investigate the normal form representation of control systems. First, as numerical tools we develop an algorithm for normal form expression and the matrix representation of the Lie derivative of a linear vector field over homogeneous vector fields. The concept of normal form is modified. Necessary and sufficient conditions for a linear transformation to maintain the Brunowsky canonical form are obtained. It is then shown that the shift term can always be linearized up to any degree. Based on this fact, linearization procedure is proposed and the related algorithms are presented. Least square linear approximations are proposed for non-linearizable systems. Finally, the method is applied to the ball and beam example. The efforts are focused on the numerical and computer realization of linearization process. Copyright © 2002 John Wiley & Sons, Ltd. [source]


The dynamical stability of a Kuiper Belt-like region

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2007
A. Celletti
ABSTRACT The dynamics of the Kuiper Belt region between 33 and 63 au is investigated just taking into account the gravitational influence of Neptune. Indeed the aim is to analyse the information which can be drawn from the actual exoplanetary systems, where typically physical and orbital data of just one or two planets are available. Under this perspective we start our investigation using the simplest three-body model (with Sun and Neptune as primaries), adding at a later stage the eccentricity of Neptune and the inclinations of the orbital planes to evaluate their effects on the Kuiper Belt dynamics. Afterwards we remove the assumption that the orbit of Neptune is Keplerian by adding the effect of Uranus through the Lagrange,Laplace solution or through a suitable resonant normal form. Finally, different values of the mass ratios of the primary to the host star are considered in order to perform a preliminary analysis of the behaviour of exoplanetary systems. In all cases, the stability is investigated by means of classical tools borrowed from dynamical system theory, like Poincaré mappings and Lyapunov exponents. [source]


Neural Network Adaptive Robust Control Of Siso Nonlinear Systems In A Normal Form

ASIAN JOURNAL OF CONTROL, Issue 2 2001
J.Q. Gong
ABSTRACT In this paper, performance oriented control laws are synthesized for a class of single-input-single-output (SISO) n -th order nonlinear systems in a normal form by integrating the neural networks (NNs) techniques and the adaptive robust control (ARC) design philosophy. All unknown but repeat-able nonlinear functions in the system are approximated by the outputs of NNs to achieve a better model compensation for an improved performance. While all NN weights are tuned on-line, discontinuous projections with fictitious bounds are used in the tuning law to achieve a controlled learning. Robust control terms are then constructed to attenuate model uncertainties for a guaranteed output tracking transient performance and a guaranteed final tracking accuracy. Furthermore, if the unknown nonlinear functions are in the functional ranges of the NNs and the ideal NN weights fall within the fictitious bounds, asymptotic output tracking is achieved to retain the perfect learning capability of NNs. The precision motion control of a linear motor drive system is used as a case study to illustrate the proposed NNARC strategy. [source]


Aneuploidy in spermatozoa of infertile men with teratozoospermia

INTERNATIONAL JOURNAL OF ANDROLOGY, Issue 4 2001
Kati HÄrkönen
Recent studies have shown that aneuploidy in spermatozoa of infertile men with poor semen quality is increased. The purpose of this study was to determine whether poor sperm morphology is associated with the incidence of spermatozoa with numerical chromosome abnormalities. Semen samples from 20 infertile teratozoospermic men were studied using multicolour fluorescence in situ hybridization (FISH). Men were divided into four groups according to the proportion of normal sperm morphology: infertile men with <10% (group A, n=7), 10,19% (group B, n=6), and 20,29% (group C, n=7) of morphologically normal spermatozoa, and controls (group D, n=5) with ,30% normal forms. Two hybridizations were performed. All the samples were analysed using probes for chromosomes 1 and 7 and, in addition, in group A and in controls with normal semen parameters probes for chromosomes X, Y and 18 were also used. Ten thousand spermatozoa were scored per hybridization. Severely teratozoospermic men (<10% normal forms) had significantly higher frequency of disomy 7, 18, YY, XY and diploidy in their spermatozoa when compared with controls. The results suggest that poor sperm morphology is associated with numerical chromosome abnormalities of spermatozoa. Severely teratozoospermic men may be at an increased risk of producing aneuploid offspring. [source]


Can a cumulus cell complex be used to select spermatozoa for assisted reproduction?

ANDROLOGIA, Issue 6 2009
D. R. Franken
Summary Since the onset of intracytoplasmic sperm injection, researchers have intensified the search for the ideal spermatozoa to be used for injection. The aim of this study was to record the functional role of cumulus cell interaction with human spermatozoa as far as capacitation, acrosome reaction, morphology, zona binding and chromatin packaging quality are concerned. Using a previously described cumulus oophorus model, we recorded specific sperm functional aspects of sperm populations that transverse a cumulus cells mass. Control spermatozoa were kept under similar experimental conditions in the culture media only. Results indicated cumulus cells to be beneficial to spermatozoa as far as functional and capacitational events are concerned. The mean percentage of morphologically normal spermatozoa in the control sample was 6.9%, while the spermatozoa that traversed the cumulus oophorus (test) had a significantly higher percentage of normal forms (mean 9.5%; P , 0.01). We observed a decline in the percentage of CMA3-positive spermatozoa when we compared the control population (49.1%) to the test, i.e. 38.4%, (P = <0.05), thus implying that the spermatozoa with good chromatin condensation increased during cumulus penetration. Significantly more (P , 0.01) acrosome-reacted spermatozoa were found in the penetrated spermatozoa (mean 23%) than in the control spermatozoa (mean 11%). The test spermatozoa had a higher zona binding capacity with significantly more (P , 0.01) tightly bound spermatozoa on the hemizona (61 ± 15) than the control spermatozoa (47 ± 18). In the absence of sophisticated and expensive sperm selection products, the use of a cumulus model to select spermatozoa for intracellular sperm injection seems to be an alternative method. [source]


Seminal reactive oxygen species-antioxidant relationship in fertile males with and without varicocele

ANDROLOGIA, Issue 2 2009
T. Mostafa
Summary The aim of this study was to assess seminal reactive oxygen species (ROS)-antioxidants relationship in fertile and infertile men with and without varicocele. One hundred and seventy six males were studied; fertile healthy volunteers (n = 45), fertile men with varicocele (n = 45), infertile oligoasthenozoospermia (OA, n = 44) without varicocele and infertile OA with varicocele (n = 42). In their seminal plasma, two ROS parameters (malondialdehyde, hydrogen peroxide) and five antioxidants (superoxide dismutase, catalase, glutathione peroxidase, vitaminE, vitaminC) were estimated. Compared with fertile healthy men, in all other studied groups, estimated seminal ROS were significantly higher and estimated antioxidants were significantly lower. Infertile men with varicocele showed the same relationship as infertile men without varicocele. Sperm concentration, total sperm motility as well as sperm normal forms were negatively correlated with seminal malondialdehyde and were positively correlated with vitaminC. It is concluded that varicocele has an oxidative stress (OS) in fertile normozoospermic bearing conditions. This may allow understanding that, within men with varicocele, there is a threshold value of OS over which male fertility may be impaired. [source]


Stepwise regression analysis to study male and female factors impacting on pregnancy rate in an intrauterine insemination programme

ANDROLOGIA, Issue 3 2001
M. Montanaro Gauci
Summary. The aim of this study was to evaluate the impact of male and female factors on the pregnancy rate in an intrauterine insemination (IUI) programme. Data on 522 cycles were retrospectively studied. All patients 39 years or younger were included in the study where data were available on male and female diagnosis, as well as on ovulation induction methodology. Regression analysis was possible on 495 cycles to study different factors affecting the pregnancy rate per treatment cycle. Logistic regression identified variables which were related to outcome and were subsequently incorporated into a statistical model. The number of follicles was found to have a linear association with the risk ratio (chance) of pregnancy. The age of the woman was also found to have a linear (negative) association with pregnancy. The percentage motility and percentage normal morphology (by strict criteria) of spermatozoa in the fresh ejaculate were the male factors that significantly and independently predicted the outcome. Percentage motility ,,50 was associated with a risk ratio of pregnancy of 2.95 compared to percentage motility < 50. Percentage normal sperm morphology > 14% was associated with a risk ratio of pregnancy of 1.8 compared to percentage normal morphology ,,14%. Female patients with idiopathic infertility were divided into three groups according to normal sperm morphology. The pregnancy rate per cycle was 2.63% (1/38) for the P (poor) pattern group (0,4% normal forms), 11.4% (17/149) for the G (good) pattern group (5,14%), and 24% (18/75) for the N (normal) pattern group (> 14% normal forms). A female diagnosis of endometriosis or tubal factor impacted negatively on the probability of pregnancy (risk ratio of 0.17), compared with other female diagnoses. Male and female factors contribute to pregnancy outcome, but the clinician can influence prognosis by increasing the number of follicles, especially in severe male factor cases. [source]