Radim Briš - Academia.edu (original) (raw)

Papers by Radim Briš

Research paper thumbnail of Survival analysis on data of different surgery tech niques to evaluate risk of postoperative complications

Journal of Polish Safety and Reliability Association, 2011

Medical survival censored data of about 850 patients are evaluated to compare two basic surgery t... more Medical survival censored data of about 850 patients are evaluated to compare two basic surgery techniques. Data comes from patients who underwent colectomy in the University Hospital of Ostrava. The data has been screened into three general groups: all patients (data from both rectum and colon operations), data from rectum operations, data from colon operations. Two basic surgery techniques are used for the colectomy: either classical (open) or laparoscopic operation. Basic question which arises at the colectomy operation is which type of operation to choose to guarantee longer overall survival time. Two methodological approaches have been used to answer this relevant question. First is the non-parametric approach which results from Kaplan-Meier estimates of the survival function. For each data group two survival curves are constructed, i.e. for both open and laparoscopic type of operation. Final survival curves are compared and evaluated using advanced methods of statistical inference (e.g. log-rank test). Second is parametric approach which results from modelling of survival time. It is based on Maximum Likelihood Estimation method to estimate parameters of probability distribution of overall survival time. Moreover, two Weibull models are used to compare the two surgery techniques. Mean survival times assigned to particular types of operation are compared.

Research paper thumbnail of Structural reliability assessment using Direct Optimized Probabilistic Calculation with respect to the statistical dependence of input variables

The paper is focused on the newly developed probabilistic method of Direct Optimized Probabilisti... more The paper is focused on the newly developed probabilistic method of Direct Optimized Probabilistic Calculation – DOProC, which seems to be very effective for solving a number of probabil-istic tasksand probabilistic reliability assessments. The calculation, which does not use any of simulation techniques, solve the resulting probability purely numerical way using optimized numerical integration. Computational procedure of DOProC method is based on the basic concepts of probability theory. The accuracy of the solution is only influenced by numerical errors and error arising from the discretization of input and output variables. For application of DOProC method can currently use the program system so-called ProbCalc, which is still being developed. Using ProbCalc is possible to implement relatively easy analytical and numerical transformation model of the probabilistic tasks under the solution. The input random quantities (such as load, geometry, material properties, or imperfections) can be in the DOProC method as with the other probabilistic calculations expressed by histograms with nonparametric (empirical) or parametric probability distribution. Statistical correlation of random input statistically dependent variables can be expressed in the DOProC method using the so-called multidimensional histograms, which can be used to determine the numerical correlation index for characterization of the dependence not only for the linear relationship between two variables, but also for nonlinear dependence, or even for more than two random variables.

Research paper thumbnail of MLE versus MCMC estimators of the mixture of failure rate model

Safety and Reliability – Safe Societies in a Changing World

Research paper thumbnail of The effective iterative algorithm to solve a maintenance optimization problem of a highly reliable system

Reliability, Risk, and Safety, 2009

Research paper thumbnail of Highly reliable systems simulation accelerated using CPU and GPU parallel computing

Applied Mathematics in Engineering and Reliability, 2016

Research paper thumbnail of Bayesian approach to estimate the mixture of failure rate model

Research paper thumbnail of Applied mathematics in reliability engineering: Bayesian methods, Bayesian reliability

Applied Mathematics in Engineering and Reliability, 2016

Research paper thumbnail of Parallel computing for system availability and applications

Safety and Reliability: Methodology and Applications, 2014

Research paper thumbnail of Expression and 7-day time course of circulating microRNAs in septic patients treated with nephrotoxic antibiotic agents

BMC Nephrology, 2022

Background Through regulation of signaling pathways, microRNAs (miRNAs) can be involved in sepsis... more Background Through regulation of signaling pathways, microRNAs (miRNAs) can be involved in sepsis and associated organ dysfunction. The aims of this study were to track the 7-day time course of blood miRNAs in patients with sepsis treated with vancomycin, gentamicin, or a non-nephrotoxic antibiotic and miRNA associations with neutrophil gelatinase-associated lipokalin (NGAL), creatinine, procalcitonin, interleukin-6, and acute kidney injury (AKI) stage. Methods Of 46 adult patients, 7 were on vancomycin, 20 on gentamicin, and 19 on another antibiotic. Blood samples were collected on days 1, 4, and 7 of treatment, and miRNAs were identified using quantitative reverse transcription PCR. Results The results showed no relationship between miRNA levels and biochemical variables on day 1. By day 7 of gentamicin treatment miR-15a-5p provided good discrimination between AKI and non-AKI (area under curve, 0.828). In patients taking vancomycin, miR-155-5p and miR-192-5p positively correlated ...

Research paper thumbnail of Methodological Overview of Prospensity Score Matching Methods demonstrated on Colorectal Data

2023 International Conference on Information and Digital Technologies (IDT)

Research paper thumbnail of Maintenance Optimization of Dormant Systems Submitted to Failure Based PM and Imperfect CM

2023 International Conference on Information and Digital Technologies (IDT)

Research paper thumbnail of Assessment of the Availability of an Offshore Installation by Stochastic Petri Net Modeling

Communications - Scientific letters of the University of Zilina, 2014

The purpose of this article is to illustrate the combination of stochastic Petri nets and Monte C... more The purpose of this article is to illustrate the combination of stochastic Petri nets and Monte Carlo simulation approach for the evaluation of the production availability of a multi-state, multi-output offshore installation with operational loops. The presented test case comprises a great number of the problems encountered when dealing with probabilistic studies. The reason for using Petri net modeling is that it provides the necessary flexibility to describe the complexity of the plant and the realistic aspects of system behavior, such as a degradation and standby of components, maintenance, etc. Different production levels of the system are assessed and evaluated from both reliability and production efficiency point of view. Four selected configurations of the system are analyzed to investigate how the production efficiency and average availability are influenced by applying a preventive maintenance and an additional cold standby of component.

Research paper thumbnail of Simulation approach for modeling of dynamic reliability using time dependent acyclic graph

The dynamic reliability approach takes into account changes (evolution) of the system structure (... more The dynamic reliability approach takes into account changes (evolution) of the system structure (hardware). For instance, the dynamic reliability allows modeling a human operator (or an electronic control system) naturally. In these cases, the structure of the system is usually changed in order to keep the functionality and/or safety of the system. The main purpose of the paper is to illustrate, by means of a model example, the ability of acyclic oriented graph, terminal nodes of which are programmable components, to model simple dynamic system and to assess its performance via Monte-Carlo simulations. To demonstrate the availability of our framework a test case study with the deterministic evolution is presented. The here presented numerical results are in agreement with the exact analytical solution.

Research paper thumbnail of Optimization of High Voltage Substation Model

The real system from practice is selected for optimization purpose in this paper. We describe the... more The real system from practice is selected for optimization purpose in this paper. We describe the real scheme of a high voltage (HV) substation in different work states. Model scheme of the HV substation 22 kV is demonstrated within the paper. The scheme serves as input model scheme for the maintenance optimization. The input reliability and cost parameters of all components are given: the preventive and corrective maintenance costs, the actual maintenance period (being optimized), the failure rate and mean time to repair MTTR.

Research paper thumbnail of Coloured Petri nets and a dynamic reliability problem

Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability, 2008

ABSTRACT One of the major problems of the system reliability calculation is an implementation of ... more ABSTRACT One of the major problems of the system reliability calculation is an implementation of a dynamic behaviour. One way to show a possible representation of dynamic systems is by using coloured stochastic Petri nets (CSPNs). In this paper this approach is applied to one benchmark on the dynamic reliability taken from the literature. The system consists of a tank containing some liquid where the liquid level is controlled by suitable detectors acting on three hardware components that work independently. The modelled system is consequently used as an input for the calculation of the cumulative distribution functions and other characteristics (e.g. reliability of the system). As the next step, this benchmark will be modified. The first system modification is the maintenance action inclusion. The second one is the enhancement of the system by adding another process variable (the liquid temperature within the tank that is dependent on time). The CSPN approach is used to find a suitable representative scheme of these modifications.

Research paper thumbnail of Inovační metody pro ocenění spolehlivosti prvků a systémů /

Research paper thumbnail of Unavailability calculations within the limits of computer accuracy

The paper presents a new analytical algorithm which is able to carry out direct and exact reliabi... more The paper presents a new analytical algorithm which is able to carry out direct and exact reliability quantification of highly reliable systems with maintenance (both preventive and corrective). A directed acyclic graph is used as a system representation. The algorithm is based on a special new procedure which permits only summarization between two or more non-negative numbers that can be very different. If the summarization of very small positive numbers transformed into the machine code is performed effectively no error is committed at the operation. Reliability quantification is demonstrated on a real system from practice.

Research paper thumbnail of Critical software defects are located in important source code

Software reliability is the most important problem of software development. Therefore it is im- p... more Software reliability is the most important problem of software development. Therefore it is im- portant to predict and monitor occurrences of software defects. This report shows how to compute evolution of importance of source code fragments by using PageRank algorithm. It has been empirically proven that there exists a correlation between severity of defects and importance of source code fragments. The severe defects are located in important code.

Research paper thumbnail of Maintenance optimization of highly reliable systems — Linear model

The Proceedings of 2011 9th International Conference on Reliability, Maintainability and Safety, 2011

This paper describes a new iterative numerical algorithm for optimal reliability design based on ... more This paper describes a new iterative numerical algorithm for optimal reliability design based on maintenance. The algorithm quantifies the time-dependent unavailability characteristics in full machine accuracy. It stems from the previous author's research work which brings a new direct analytical method that enables exact reliability quantifications of highly reliable systems with maintenance (both preventive and corrective). The method takes into account systems with highly reliable and maintained components, including repairable components undergoing to hidden failures. It will be used to solve a cost-optimization problem based on maintenance. The new algorithm results from linear approximation of total system cost that is supposed to be a linear function of frequency of maintenance (both preventive and corrective). The optimization method is demonstrated on practical system - selected part of a real power distribution network.

Research paper thumbnail of Reliability, Risk, and Safety, Three Volume Set

Reliability, Risk, and Safety, Three Volume Set, 2009

Research paper thumbnail of Survival analysis on data of different surgery tech niques to evaluate risk of postoperative complications

Journal of Polish Safety and Reliability Association, 2011

Medical survival censored data of about 850 patients are evaluated to compare two basic surgery t... more Medical survival censored data of about 850 patients are evaluated to compare two basic surgery techniques. Data comes from patients who underwent colectomy in the University Hospital of Ostrava. The data has been screened into three general groups: all patients (data from both rectum and colon operations), data from rectum operations, data from colon operations. Two basic surgery techniques are used for the colectomy: either classical (open) or laparoscopic operation. Basic question which arises at the colectomy operation is which type of operation to choose to guarantee longer overall survival time. Two methodological approaches have been used to answer this relevant question. First is the non-parametric approach which results from Kaplan-Meier estimates of the survival function. For each data group two survival curves are constructed, i.e. for both open and laparoscopic type of operation. Final survival curves are compared and evaluated using advanced methods of statistical inference (e.g. log-rank test). Second is parametric approach which results from modelling of survival time. It is based on Maximum Likelihood Estimation method to estimate parameters of probability distribution of overall survival time. Moreover, two Weibull models are used to compare the two surgery techniques. Mean survival times assigned to particular types of operation are compared.

Research paper thumbnail of Structural reliability assessment using Direct Optimized Probabilistic Calculation with respect to the statistical dependence of input variables

The paper is focused on the newly developed probabilistic method of Direct Optimized Probabilisti... more The paper is focused on the newly developed probabilistic method of Direct Optimized Probabilistic Calculation – DOProC, which seems to be very effective for solving a number of probabil-istic tasksand probabilistic reliability assessments. The calculation, which does not use any of simulation techniques, solve the resulting probability purely numerical way using optimized numerical integration. Computational procedure of DOProC method is based on the basic concepts of probability theory. The accuracy of the solution is only influenced by numerical errors and error arising from the discretization of input and output variables. For application of DOProC method can currently use the program system so-called ProbCalc, which is still being developed. Using ProbCalc is possible to implement relatively easy analytical and numerical transformation model of the probabilistic tasks under the solution. The input random quantities (such as load, geometry, material properties, or imperfections) can be in the DOProC method as with the other probabilistic calculations expressed by histograms with nonparametric (empirical) or parametric probability distribution. Statistical correlation of random input statistically dependent variables can be expressed in the DOProC method using the so-called multidimensional histograms, which can be used to determine the numerical correlation index for characterization of the dependence not only for the linear relationship between two variables, but also for nonlinear dependence, or even for more than two random variables.

Research paper thumbnail of MLE versus MCMC estimators of the mixture of failure rate model

Safety and Reliability – Safe Societies in a Changing World

Research paper thumbnail of The effective iterative algorithm to solve a maintenance optimization problem of a highly reliable system

Reliability, Risk, and Safety, 2009

Research paper thumbnail of Highly reliable systems simulation accelerated using CPU and GPU parallel computing

Applied Mathematics in Engineering and Reliability, 2016

Research paper thumbnail of Bayesian approach to estimate the mixture of failure rate model

Research paper thumbnail of Applied mathematics in reliability engineering: Bayesian methods, Bayesian reliability

Applied Mathematics in Engineering and Reliability, 2016

Research paper thumbnail of Parallel computing for system availability and applications

Safety and Reliability: Methodology and Applications, 2014

Research paper thumbnail of Expression and 7-day time course of circulating microRNAs in septic patients treated with nephrotoxic antibiotic agents

BMC Nephrology, 2022

Background Through regulation of signaling pathways, microRNAs (miRNAs) can be involved in sepsis... more Background Through regulation of signaling pathways, microRNAs (miRNAs) can be involved in sepsis and associated organ dysfunction. The aims of this study were to track the 7-day time course of blood miRNAs in patients with sepsis treated with vancomycin, gentamicin, or a non-nephrotoxic antibiotic and miRNA associations with neutrophil gelatinase-associated lipokalin (NGAL), creatinine, procalcitonin, interleukin-6, and acute kidney injury (AKI) stage. Methods Of 46 adult patients, 7 were on vancomycin, 20 on gentamicin, and 19 on another antibiotic. Blood samples were collected on days 1, 4, and 7 of treatment, and miRNAs were identified using quantitative reverse transcription PCR. Results The results showed no relationship between miRNA levels and biochemical variables on day 1. By day 7 of gentamicin treatment miR-15a-5p provided good discrimination between AKI and non-AKI (area under curve, 0.828). In patients taking vancomycin, miR-155-5p and miR-192-5p positively correlated ...

Research paper thumbnail of Methodological Overview of Prospensity Score Matching Methods demonstrated on Colorectal Data

2023 International Conference on Information and Digital Technologies (IDT)

Research paper thumbnail of Maintenance Optimization of Dormant Systems Submitted to Failure Based PM and Imperfect CM

2023 International Conference on Information and Digital Technologies (IDT)

Research paper thumbnail of Assessment of the Availability of an Offshore Installation by Stochastic Petri Net Modeling

Communications - Scientific letters of the University of Zilina, 2014

The purpose of this article is to illustrate the combination of stochastic Petri nets and Monte C... more The purpose of this article is to illustrate the combination of stochastic Petri nets and Monte Carlo simulation approach for the evaluation of the production availability of a multi-state, multi-output offshore installation with operational loops. The presented test case comprises a great number of the problems encountered when dealing with probabilistic studies. The reason for using Petri net modeling is that it provides the necessary flexibility to describe the complexity of the plant and the realistic aspects of system behavior, such as a degradation and standby of components, maintenance, etc. Different production levels of the system are assessed and evaluated from both reliability and production efficiency point of view. Four selected configurations of the system are analyzed to investigate how the production efficiency and average availability are influenced by applying a preventive maintenance and an additional cold standby of component.

Research paper thumbnail of Simulation approach for modeling of dynamic reliability using time dependent acyclic graph

The dynamic reliability approach takes into account changes (evolution) of the system structure (... more The dynamic reliability approach takes into account changes (evolution) of the system structure (hardware). For instance, the dynamic reliability allows modeling a human operator (or an electronic control system) naturally. In these cases, the structure of the system is usually changed in order to keep the functionality and/or safety of the system. The main purpose of the paper is to illustrate, by means of a model example, the ability of acyclic oriented graph, terminal nodes of which are programmable components, to model simple dynamic system and to assess its performance via Monte-Carlo simulations. To demonstrate the availability of our framework a test case study with the deterministic evolution is presented. The here presented numerical results are in agreement with the exact analytical solution.

Research paper thumbnail of Optimization of High Voltage Substation Model

The real system from practice is selected for optimization purpose in this paper. We describe the... more The real system from practice is selected for optimization purpose in this paper. We describe the real scheme of a high voltage (HV) substation in different work states. Model scheme of the HV substation 22 kV is demonstrated within the paper. The scheme serves as input model scheme for the maintenance optimization. The input reliability and cost parameters of all components are given: the preventive and corrective maintenance costs, the actual maintenance period (being optimized), the failure rate and mean time to repair MTTR.

Research paper thumbnail of Coloured Petri nets and a dynamic reliability problem

Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability, 2008

ABSTRACT One of the major problems of the system reliability calculation is an implementation of ... more ABSTRACT One of the major problems of the system reliability calculation is an implementation of a dynamic behaviour. One way to show a possible representation of dynamic systems is by using coloured stochastic Petri nets (CSPNs). In this paper this approach is applied to one benchmark on the dynamic reliability taken from the literature. The system consists of a tank containing some liquid where the liquid level is controlled by suitable detectors acting on three hardware components that work independently. The modelled system is consequently used as an input for the calculation of the cumulative distribution functions and other characteristics (e.g. reliability of the system). As the next step, this benchmark will be modified. The first system modification is the maintenance action inclusion. The second one is the enhancement of the system by adding another process variable (the liquid temperature within the tank that is dependent on time). The CSPN approach is used to find a suitable representative scheme of these modifications.

Research paper thumbnail of Inovační metody pro ocenění spolehlivosti prvků a systémů /

Research paper thumbnail of Unavailability calculations within the limits of computer accuracy

The paper presents a new analytical algorithm which is able to carry out direct and exact reliabi... more The paper presents a new analytical algorithm which is able to carry out direct and exact reliability quantification of highly reliable systems with maintenance (both preventive and corrective). A directed acyclic graph is used as a system representation. The algorithm is based on a special new procedure which permits only summarization between two or more non-negative numbers that can be very different. If the summarization of very small positive numbers transformed into the machine code is performed effectively no error is committed at the operation. Reliability quantification is demonstrated on a real system from practice.

Research paper thumbnail of Critical software defects are located in important source code

Software reliability is the most important problem of software development. Therefore it is im- p... more Software reliability is the most important problem of software development. Therefore it is im- portant to predict and monitor occurrences of software defects. This report shows how to compute evolution of importance of source code fragments by using PageRank algorithm. It has been empirically proven that there exists a correlation between severity of defects and importance of source code fragments. The severe defects are located in important code.

Research paper thumbnail of Maintenance optimization of highly reliable systems — Linear model

The Proceedings of 2011 9th International Conference on Reliability, Maintainability and Safety, 2011

This paper describes a new iterative numerical algorithm for optimal reliability design based on ... more This paper describes a new iterative numerical algorithm for optimal reliability design based on maintenance. The algorithm quantifies the time-dependent unavailability characteristics in full machine accuracy. It stems from the previous author's research work which brings a new direct analytical method that enables exact reliability quantifications of highly reliable systems with maintenance (both preventive and corrective). The method takes into account systems with highly reliable and maintained components, including repairable components undergoing to hidden failures. It will be used to solve a cost-optimization problem based on maintenance. The new algorithm results from linear approximation of total system cost that is supposed to be a linear function of frequency of maintenance (both preventive and corrective). The optimization method is demonstrated on practical system - selected part of a real power distribution network.

Research paper thumbnail of Reliability, Risk, and Safety, Three Volume Set

Reliability, Risk, and Safety, Three Volume Set, 2009