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Papers by Demetrios Kazakos
International Conference on Signal Processing, May 27, 2008
instantaneous rates of regional migration and mortality from conventional tagging data
We use the disproportion statistic to quantify the differences among ethnic groups and school set... more We use the disproportion statistic to quantify the differences among ethnic groups and school settings. Patterns of disciplinary actions in four school settings, Non–Title I Non–Charter, Non–Title I Charter, Title I Non–Charter, and Title I Charter schools are examined. Analysis is based on the most recent data provided by the U. S. Office of Civil Rights. The importance of this research is that it is one of the first studies to show that not only are there differences in disparities due to zero tolerance policies among ethnic groups, but there exists statistically significant differences in disparities among school settings as well.
The British journal of ophthalmology, Jan 11, 2017
Corneal graft (CG) surgery is the most common and successful tissue transplant worldwide. A small... more Corneal graft (CG) surgery is the most common and successful tissue transplant worldwide. A small and important group of patients are operated in emergency situations, typically to save a perforated eye. Our knowledge of the indications and outcomes of emergency corneal graft (eCG) is limited. Retrospective, multifactorial analysis of all CGs registered by the UK Transplant Service from April 1999 to March 2005. A total of 12 976 CGs were performed. 1330 (11.4%) were eCGs including 433 regrafts. Actual perforation occurred in 876 (65.9%) patients. 420 (31.5%) grafts were for tectonic purposes alone and 217 (16.3%) were also grafted for visual rehabilitation. The main diagnostic categories were infection (39.4%), non-infectious ulcerative keratitis (32.2%) and other causes (ectasias, previous ocular surgery, injury, dystrophies and opacification). Graft survival of first eCG at 1, 2 and 5 years was 78%, 66% and 47%, respectively. Best-corrected visual acuity of surviving grafts at 1 ...
Abstract : In many applications there appears the need to represent a set of raw data by fitting ... more Abstract : In many applications there appears the need to represent a set of raw data by fitting to them a smooth function or set of functions. A great amount of theoretical work has been done within the framework of approximation theory in studying properties of curve fitting for various families of approximating functions. One of the most attractive and well structured families of approximating functions are the splines. They have been extensively studied in the mathematical literature. Splines have been very useful in statistics. In the engineering literature, spline functions have been used as approximating tools, in the areas of Systems and Pattern Recognition. In this paper the authors concentrate on a fast, parallel computation technique for fitting a spline to n equispaced data points. Existing techniques can fit splines in 0(n) time, with recursive (serial) processing of the data. The new technique is based on the use of Fast Fourier Transform, and its parallel processing capability. As a result, our technique achieves the fitting of a spline in 0(log sub 2 n) time. The n data points must be equispaced.
1980 19th IEEE Conference on Decision and Control including the Symposium on Adaptive Processes, 1980
In this paper we derive recursive expression for certain distance measures between time-continuou... more In this paper we derive recursive expression for certain distance measures between time-continuous, stationary, vector Gaussian processes, and then utilize them to derive upper bounds to the mean square error performance of the Bayes and Maximum Likelihood estimate of a parameter, when only a finite-valued parameter set is utilized. The question of convergence when the true parameter value does not belong to the finite set is also answered.
Signal Processing, 1983
Abstract A random signal is observed in independent random noise. We are addressing the problem o... more Abstract A random signal is observed in independent random noise. We are addressing the problem of finding the optimum signal estimate that is constrained to lie in a given linear subspace. The optimality is defined in the sense of weighted mean square error. In the second step, we find the optimum linear subspace of given dimensionality. It is shown to be the linear manifold spanned by the eigenvectors of the simultaneous diagonalization of the signal and noise covariance, that correspond to the largest eigenvalues. The result is valid for both discrete and continuous time. For large observation time and stationary signals, it is shown that the constrained optimal estimate is determined by the two spectral densities and a weighted Fourier Transform of the noise observations. The above result applies to both discrete time and continuous time signals. The Wiener filter emerges as a special case of the constrained filtering estimate, when the linear subspace is enlarged to coincide with the total measurement space.
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 1996
IEEE Transactions on Communications, 1992
IEEE Transactions on Automatic Control, 1980
We derive new necessary and sufficient conditions for exponentially convergent discrimination bet... more We derive new necessary and sufficient conditions for exponentially convergent discrimination between two stationary vector Gaussian processes, and relate them to previously studied conditions for parameter identifiability and consistent discrimination.
We consider discrete-time detection with dynamical modeling, where the data generating processes ... more We consider discrete-time detection with dynamical modeling, where the data generating processes are represented through state-variable tech- niques. Given the modeling above, one computation- ally effective method of calculating the likelihood ratio functions is due to Schweppe. In this paper, we study the asymptotic properties of Schweppe's likeli- hood ratio detector, and evaluate the power probabil- ity within a Bayesian framework.
Complex sample survey data are obtained through multistage sampling designs that involve clusteri... more Complex sample survey data are obtained through multistage sampling designs that involve clustering, stratification, and non–responce adjustments. Standard statistical methods such as empirical likelihood are typically not applicable to complex samples because independent, identically distributed observations seldom result from such data. Hence, we derive pseudo empirical likelihood confidence intervals for stratified single–stage and stratified multistage sampling designs. Use of such designs include national health data sets.
Inthisnote, a revenue schemebased onthechannelreservation schemeinawireless system isinvestigated... more Inthisnote, a revenue schemebased onthechannelreservation schemeinawireless system isinvestigated. Here, therevenue function isconsidered tobe aweighted function fortheactual call connection time (ACCT)([5] [6])of incomplete call andtheACCT of thecomplete call, whichisachallenge method inthe updated uireless networks. We numerically showthat thestrategy ofreserving asmall numbers ofthechannelsisbetter thanthatofreserving alarger numberof channels forthis revenue structure. Theideaandthe technique areexpected tobeapplied toother advanced communications systems.
AIMS Mathematics, 2017
Statistical analysis of the connectivity of real world networks have revealed interesting feature... more Statistical analysis of the connectivity of real world networks have revealed interesting featuressuch as community structure, network motif and as on. Such discoveries tempt us to understandthe dynamics of a complex network system by studying those of its subnetworks. This approach isfeasible only if the dynamics of the subnetwork systems can somehow be preserved or partially preservedin the whole system. Most works studied the connectivity structures of networks while very fewconsidered the possibility of translating the dynamics of a subnetwork system to the whole system. Inthis paper, we address this issue by focusing on considering the relations between cycles and fixedpoints of a network system and those of its subnetworks based on Boolean framework. We proved thatat a condition we called agreeable, if X0 is a fixed point of the whole system, then X 0 restricted to thephase-space of one of the subnetwork systems must be a fixed point as well. An equivalent statementon cycles follows from this result. In addition, we discussed the relations between the product of thetransition diagrams (a representation of trajectories) of subnetwork systems and the transition diagramof the whole system.
Eurasip Journal on Wireless Communications and Networking, Apr 2, 2006
Proceedings of the First US/Japan Conference on the Frontiers of Statistical Modeling: An Informational Approach, 1994
The problem of estimating the location parameter Θ of a set of independent random variables with ... more The problem of estimating the location parameter Θ of a set of independent random variables with common cummulative distribution function F(t-Θ) when F(t-Θ) is approximately known, was extensively studied by Huber [Huber (1964), (1981)]. He was concerned with the model of indeterminacy F=(1-e) Ф + eH where 0≤e≤1 is a known number, Ф(t) is a known cumulative distribution function and H(t) is an unknown contaminating distribution.
1986 25th IEEE Conference on Decision and Control, 1986
ABSTRACT
26th IEEE Conference on Decision and Control, 1987
ABSTRACT
International Conference on Signal Processing, May 27, 2008
instantaneous rates of regional migration and mortality from conventional tagging data
We use the disproportion statistic to quantify the differences among ethnic groups and school set... more We use the disproportion statistic to quantify the differences among ethnic groups and school settings. Patterns of disciplinary actions in four school settings, Non–Title I Non–Charter, Non–Title I Charter, Title I Non–Charter, and Title I Charter schools are examined. Analysis is based on the most recent data provided by the U. S. Office of Civil Rights. The importance of this research is that it is one of the first studies to show that not only are there differences in disparities due to zero tolerance policies among ethnic groups, but there exists statistically significant differences in disparities among school settings as well.
The British journal of ophthalmology, Jan 11, 2017
Corneal graft (CG) surgery is the most common and successful tissue transplant worldwide. A small... more Corneal graft (CG) surgery is the most common and successful tissue transplant worldwide. A small and important group of patients are operated in emergency situations, typically to save a perforated eye. Our knowledge of the indications and outcomes of emergency corneal graft (eCG) is limited. Retrospective, multifactorial analysis of all CGs registered by the UK Transplant Service from April 1999 to March 2005. A total of 12 976 CGs were performed. 1330 (11.4%) were eCGs including 433 regrafts. Actual perforation occurred in 876 (65.9%) patients. 420 (31.5%) grafts were for tectonic purposes alone and 217 (16.3%) were also grafted for visual rehabilitation. The main diagnostic categories were infection (39.4%), non-infectious ulcerative keratitis (32.2%) and other causes (ectasias, previous ocular surgery, injury, dystrophies and opacification). Graft survival of first eCG at 1, 2 and 5 years was 78%, 66% and 47%, respectively. Best-corrected visual acuity of surviving grafts at 1 ...
Abstract : In many applications there appears the need to represent a set of raw data by fitting ... more Abstract : In many applications there appears the need to represent a set of raw data by fitting to them a smooth function or set of functions. A great amount of theoretical work has been done within the framework of approximation theory in studying properties of curve fitting for various families of approximating functions. One of the most attractive and well structured families of approximating functions are the splines. They have been extensively studied in the mathematical literature. Splines have been very useful in statistics. In the engineering literature, spline functions have been used as approximating tools, in the areas of Systems and Pattern Recognition. In this paper the authors concentrate on a fast, parallel computation technique for fitting a spline to n equispaced data points. Existing techniques can fit splines in 0(n) time, with recursive (serial) processing of the data. The new technique is based on the use of Fast Fourier Transform, and its parallel processing capability. As a result, our technique achieves the fitting of a spline in 0(log sub 2 n) time. The n data points must be equispaced.
1980 19th IEEE Conference on Decision and Control including the Symposium on Adaptive Processes, 1980
In this paper we derive recursive expression for certain distance measures between time-continuou... more In this paper we derive recursive expression for certain distance measures between time-continuous, stationary, vector Gaussian processes, and then utilize them to derive upper bounds to the mean square error performance of the Bayes and Maximum Likelihood estimate of a parameter, when only a finite-valued parameter set is utilized. The question of convergence when the true parameter value does not belong to the finite set is also answered.
Signal Processing, 1983
Abstract A random signal is observed in independent random noise. We are addressing the problem o... more Abstract A random signal is observed in independent random noise. We are addressing the problem of finding the optimum signal estimate that is constrained to lie in a given linear subspace. The optimality is defined in the sense of weighted mean square error. In the second step, we find the optimum linear subspace of given dimensionality. It is shown to be the linear manifold spanned by the eigenvectors of the simultaneous diagonalization of the signal and noise covariance, that correspond to the largest eigenvalues. The result is valid for both discrete and continuous time. For large observation time and stationary signals, it is shown that the constrained optimal estimate is determined by the two spectral densities and a weighted Fourier Transform of the noise observations. The above result applies to both discrete time and continuous time signals. The Wiener filter emerges as a special case of the constrained filtering estimate, when the linear subspace is enlarged to coincide with the total measurement space.
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 1996
IEEE Transactions on Communications, 1992
IEEE Transactions on Automatic Control, 1980
We derive new necessary and sufficient conditions for exponentially convergent discrimination bet... more We derive new necessary and sufficient conditions for exponentially convergent discrimination between two stationary vector Gaussian processes, and relate them to previously studied conditions for parameter identifiability and consistent discrimination.
We consider discrete-time detection with dynamical modeling, where the data generating processes ... more We consider discrete-time detection with dynamical modeling, where the data generating processes are represented through state-variable tech- niques. Given the modeling above, one computation- ally effective method of calculating the likelihood ratio functions is due to Schweppe. In this paper, we study the asymptotic properties of Schweppe's likeli- hood ratio detector, and evaluate the power probabil- ity within a Bayesian framework.
Complex sample survey data are obtained through multistage sampling designs that involve clusteri... more Complex sample survey data are obtained through multistage sampling designs that involve clustering, stratification, and non–responce adjustments. Standard statistical methods such as empirical likelihood are typically not applicable to complex samples because independent, identically distributed observations seldom result from such data. Hence, we derive pseudo empirical likelihood confidence intervals for stratified single–stage and stratified multistage sampling designs. Use of such designs include national health data sets.
Inthisnote, a revenue schemebased onthechannelreservation schemeinawireless system isinvestigated... more Inthisnote, a revenue schemebased onthechannelreservation schemeinawireless system isinvestigated. Here, therevenue function isconsidered tobe aweighted function fortheactual call connection time (ACCT)([5] [6])of incomplete call andtheACCT of thecomplete call, whichisachallenge method inthe updated uireless networks. We numerically showthat thestrategy ofreserving asmall numbers ofthechannelsisbetter thanthatofreserving alarger numberof channels forthis revenue structure. Theideaandthe technique areexpected tobeapplied toother advanced communications systems.
AIMS Mathematics, 2017
Statistical analysis of the connectivity of real world networks have revealed interesting feature... more Statistical analysis of the connectivity of real world networks have revealed interesting featuressuch as community structure, network motif and as on. Such discoveries tempt us to understandthe dynamics of a complex network system by studying those of its subnetworks. This approach isfeasible only if the dynamics of the subnetwork systems can somehow be preserved or partially preservedin the whole system. Most works studied the connectivity structures of networks while very fewconsidered the possibility of translating the dynamics of a subnetwork system to the whole system. Inthis paper, we address this issue by focusing on considering the relations between cycles and fixedpoints of a network system and those of its subnetworks based on Boolean framework. We proved thatat a condition we called agreeable, if X0 is a fixed point of the whole system, then X 0 restricted to thephase-space of one of the subnetwork systems must be a fixed point as well. An equivalent statementon cycles follows from this result. In addition, we discussed the relations between the product of thetransition diagrams (a representation of trajectories) of subnetwork systems and the transition diagramof the whole system.
Eurasip Journal on Wireless Communications and Networking, Apr 2, 2006
Proceedings of the First US/Japan Conference on the Frontiers of Statistical Modeling: An Informational Approach, 1994
The problem of estimating the location parameter Θ of a set of independent random variables with ... more The problem of estimating the location parameter Θ of a set of independent random variables with common cummulative distribution function F(t-Θ) when F(t-Θ) is approximately known, was extensively studied by Huber [Huber (1964), (1981)]. He was concerned with the model of indeterminacy F=(1-e) Ф + eH where 0≤e≤1 is a known number, Ф(t) is a known cumulative distribution function and H(t) is an unknown contaminating distribution.
1986 25th IEEE Conference on Decision and Control, 1986
ABSTRACT
26th IEEE Conference on Decision and Control, 1987
ABSTRACT