Papers by Calin Enachescu
Computing in Cardiology, Sep 1, 2012
This study is aimed to present the development phases of hypoxia and anoxia using the dynamic Luo... more This study is aimed to present the development phases of hypoxia and anoxia using the dynamic Luo-Rudy II (LR) ventricular cell model. This task involves the robustness analysis of the selected cell model in low oxygen level circumstances that alter the ionic conductance properties of the cellular membrane and partially or totally inhibit the ionic pump functionality. We investigated hypoxia and its effect on activation potential, ionic currents, pumps, exchangers, and ionic concentrations involved in the LR model. To simulate non-pathologic cases we used Na + 132-148 mmol/L, K + 3.5-5 mmol/L, Ca 2+ 2 mmol/L extra-cellular and Na + 8-11.4 mmol/L, K + 130-175 mmol/L, Ca 2+ 0.11-0.16 μmol/L intra-cellular ionic concentrations. The presence of hypoxia has reduced the ionic pump functionality. Decreasing ionic pump power for 2-minute duration by 10%,
Procedia Technology, 2014
We consider an active supervised learning scenario in which the supervisor (trainer) can make dec... more We consider an active supervised learning scenario in which the supervisor (trainer) can make decisions regarding the possibility to choose new examples for learning. In the classical forms of supervised learning, the training set is chosen according to some known or random given distribution. The supervisor is a passive agent in the sense that he is not able to interact with the training set in order to improve the performances of the learning process of the neural network. We will introduce in a formal manner the terms of "difficult learning" and "easy learning" related to the training data set. We will investigate some possibilities that allow the trainer to become active and we will analyse the performances of such supervised learning. An active supervised learning algorithm is presented and also we have performed some simulation in order to prove our theoretical results.
American Institute of Physics Inc. eBooks, May 26, 2009
Google, Inc. (search). ...
ABSTRACT Because of its simplicity and speed, RC4 is one of the most widely used stream cipher. I... more ABSTRACT Because of its simplicity and speed, RC4 is one of the most widely used stream cipher. In this paper we advance a cryptanalytic attack based on Tabu search algorithm which tries to reconstruct the internal state of RC4. Our attack relies on the cryptanalytic algorithm presented by Knudsen et al. in, the tree representation of the output word Zt and the tree of general conditions presented by Tomaševic et al. in. Although the results of analitical calculations are slightly better than those given in and, the attack remains impractical due to the high complexity.
Procedia Technology, 2015
Nucleation and Atmospheric Aerosols, 2007
ABSTRACT Computers solve problems by using algorithmic approaches consisting of a set of rules th... more ABSTRACT Computers solve problems by using algorithmic approaches consisting of a set of rules that guides them to eventual solution of problems. This approach is different from neural computation that is based on neural networks and solves problems by learning and absorbing experience through the modification of their internal structure to accomplish a problem solution. The neural network's learning implies that the available information is usually divided into two categories: examples of function values otherwise known as training data and their corresponding prior information. This paper presents our approach to improve the learning performances of neural networks by using some additional information from the training data set through regression analysis. We discuss the theoretical foundation leading to the derivation of the prior information and also consider some experiments conducted to confirm our theoretical results based on the computation of Learning Error and Generalization Error metrics.
The Industrial Internet of Things (IIoT) combines industrial systems, the Internet of Things (IoT... more The Industrial Internet of Things (IIoT) combines industrial systems, the Internet of Things (IoT), and Cloud Computing. Consequently, IIoT enables a more agile and efficient automation, control and orchestration of future industrial systems, while improving the energy efficiency in smart factories. Unfortunately, while the benefits of IIoT are undeniable, their pervasive adoption as key enablers for future industries also paved the way for new security risks. As a response to newly emerging threats and disruptive cyber attacks, this paper documents a methodology for detecting cyber stealth attacks against IIoT. Cyber stealth attacks denote the ability of the attacker to remain in a stealth state (i.e., not to be detected) during the execution of a cyber attack. The developed methodology leverages a two-tiered approach, where the first tier uses individual anomaly detection engines implemented with the help of artificial neural networks, while the second tier adopts Dempster-Shafer's “Theory of Evidence” in order to aggregate the evidence from a distributed set of detection engines. Experimental results against a continuous stirred-tank reactor (CSTR) model demonstrate the applicability to IIoT.
Procedia. Economics and finance, 2012
Many difficult problem solving require computational intelligence. One of the major directions in... more Many difficult problem solving require computational intelligence. One of the major directions in artificial intelligence consists in the development of efficient computational intelligence algorithms, like: evolutionary algorithms, and neural networks. Systems, that operate in isolation or cooperate with each other, like mobile robots could use computational intelligence algorithms for different problems/tasks solving, however in their behavior could emerge an intelligence called system s intelligence, intelligence of a system. The traveling salesman problem TSP has a large application area. It is a well-known business problem. Maximum benefits TSP, price collecting TSP have a large number of economic applications. TSP is also used in the transport logic Raja, 2012. It also has a wide range of applicability in the mobile robotic agent path planning optimization. In this paper a mobile robotic agent path planning will be discussed, using unsupervised neural networks for the TSP solving, and from the TSP results the finding of a closely optimal path between two points in the agent working area. In the paper a modification of the criteria function of the winner neuron selection will also be presented. At the end of the paper measurement results will be presented.
IEEE Access, 2019
The Industrial Internet of Things (IIoT) have been designed to perform a more agile and efficient... more The Industrial Internet of Things (IIoT) have been designed to perform a more agile and efficient automation, control, and orchestration of future industrial systems while improving the energy efficiency in smart factories. Unfortunately, while the benefits of the IIoT are undeniable, their pervasive adoption as key enablers for future industries also paved the way for new security risks. In fact, the damaging effects of exploiting vulnerable IIoT have been repeatedly demonstrated and publicly reported. The Mirai botnet, various reports on hackable and invasive devices, alongside the infamous Stuxnet malware, constitute significant proof on the undisputed and disruptive effect of the malware-targeting IIoT systems. As a response, a plethora of solutions has been developed to address the issue of securing IIoT systems in specific sectors. Nevertheless, we believe that the gradual decay of the IIoT's physical dimension (e.g., the physical process), also called aging, is a natural component of the IIoT's life cycle, which has not received sufficient attention from the scientific community. This paper develops a methodology for detecting abnormal behavior in the context of aging IIoT. The approach leverages multivariate statistical analysis [e.g., principle component analysis (PCA)], alongside the Hotelling's T 2 statistics, and the univariate cumulative sum in order to detect abnormal process events. An innovative feature of the developed approach is the detection of stealth attacks attempting to influence the dataset in each age. The extensive experimental results on a continuous stirred-tank reactor (CSTR) model demonstrate its applicability to the IIoT and its superior performance to the recently reported techniques. INDEX TERMS Anomaly detection systems, Industrial Internet of Things, aging processes, multivariate statistical analysis.
IEEE Transactions on Smart Grid, Sep 1, 2017
We formulate two Intrusion Detection System (IDS) design problems for Smart Grids. The first one ... more We formulate two Intrusion Detection System (IDS) design problems for Smart Grids. The first one optimally places IDS devices on communication paths, while the second one addresses the resilient communications requirement and enhances the first problem with the provisioning of K distinct backup paths and additional IDS devices. The developed problems harmonize real-time communication requirements with the infrastructure's resource limitations (e.g., bandwidth), detection requirements, and the available budget. A heuristic approach is developed based on the column-generation model to reduce the computation time. Experimental results comprising the Romanian 440kV and 220kV power transmission networks, the Romanian Educational communication Network (RoEduNet), alongside synthetic topologies demonstrate the effectiveness and applicability of the heuristic methodology on large problem instances.
IFAC Proceedings Volumes, 2012
In this study we investigated hypoxia effect on activation potential and ionic currents of a vent... more In this study we investigated hypoxia effect on activation potential and ionic currents of a ventricular cell using the ionic-based theoretical Beeler-Reuter model. We simulated hypoxia and anoxia phenomena at the level of individual ionic currents and ionic concentrations. We compared the obtained results with several published works on the effects of hypoxia on fast and late sodium current, calcium current and delayed potassium current. Although quite often hypoxia alone induces small modification in the shape of activation potential, in several cases the anoxia dependent opening of potassium channels may induce prolongation of the action potential and early after-depolarizations that can develop dangerous spontaneous tachycardia. The Beeler-Reuter model is most sensitive at the modification of potassium and calcium currents. Several times a relatively small alteration of an internal voltagedependent parameter in the ionic current equation induces a serious modification of the resulting activation potential function. Compared with several quite complex ventricular models, the investigated relatively simple Beeler-Reuter model used with parameterized voltage-dependent parameters yields good results in hypoxia study.
ABSTRACT Vascular system recognition and spatial reconstruction using MR images consist an import... more ABSTRACT Vascular system recognition and spatial reconstruction using MR images consist an important element of modern health care. The developed reconstruction method successfully handles the intensity inhomogeneity or intensity non uniformity (INU), that is an undesired phenomenon during measurement and represents the main obstacle for MR image segmentation and registration methods. The segmentation is realized by a fuzzy c-means (FCM) algorithm together with the INU estimation. The proposed method determines the contours and using a medical knowledge base analysis determines the edges that are parts of the vascular system. Finally a spatial reconstruction is performed from the obtained data. Several MR databases were analyzed, and approximately a 98.5% recognition performance was obtained. The developed method can serve as excellent support for 3-D registration and visualization techniques.
Studies in Informatics and Control, Dec 25, 2012
The traveling salesman problem (TSP) has many applications in economy, transport logic [1] etc. I... more The traveling salesman problem (TSP) has many applications in economy, transport logic [1] etc. It also has a wide range of applicability in the mobile robot path planning optimization [2]. The paper presents research result of solving the path planning subproblem of the navigation of an intelligent autonomous mobile robotic agent. Collecting objects by a mobile robotic agent is the final problem that is intended to be solved. For the robotic mobile agent's path planning is used an unsupervised neural network that can find a closely optimal path between two points in the agent's working area. We have considered a modification of the criteria function of the winner neuron selection. Simulation results are discussed at the end of the paper. The next future development is the hardware implementation of the selforganizing map with real time functioning.
The main goal of the proposed project is to build real-time hardware implementations of Optical F... more The main goal of the proposed project is to build real-time hardware implementations of Optical Flow methods for tasks like egomotion estimation and/or obstacle avoidance. The current paper presents the theoretical foundations and the development and adaptation of appropriate algorithms needed for the motion detection task and the selection of the most suitable hardware/software design environments that aids the embedded implementation process. Using proper hardware/software co-design techniques, we present the development of a low-power, low resource-cost video data processing algorithm. The developed hardware efficient Optical flow extraction method is validated via software implementation and tested with standard video sequence inputs. We than present the architecture of the same method on an embedded, FPGA-based platform.
Proceedings of the ... International Conference on Recent Achievements in Mechatronics, Automation, Computer Sciences and Robotics, Mar 1, 2015
The expansion of Internet has led to a variety of directly accessible devices and services. Nowad... more The expansion of Internet has led to a variety of directly accessible devices and services. Nowadays, companies tend to increase the number of Internetfacing services in order to ensure higher visibility, and accessibility towards end-users. Nonetheless, this profound expansion towards an "Internet of Things" brings new opportunities to malicious actors. As a result, novel cyber-physical attacks bring new challenges to systems administrators in order to accommodate traditional user requests with security prerequisites. Therefore, in this paper we propose a novel approach for historical Internet connectivity assessment of services. The technique uses the output of the popular Shodan search engine to infer the lifetime of different Internet-facing services. Experimental results conducted on IP address blocks attributed to six different institutions distributed across four sectors (university, telecommunications, banking, and power) show different possible service lifetime patterns.
International Journal of Information Security Science, Sep 29, 2015
Nowadays, the increasing number of devices and services that require a direct Internet access, cr... more Nowadays, the increasing number of devices and services that require a direct Internet access, creates new security challenges. These challenges need to meet user feature-based requirements with the companies' restrictive security policies. Therefore, security administrators need to adopt novel tools in order to quickly and non-intrusively verify the degree of exposure of Internet-facing services. In this respect, we find tools such as Shodan and ZMap which enable scanning of services at an Internet-scale. This paper presents a methodology that expands the feature delivered by such tools with automated vulnerability assessment capabilities. The proposed methodology builds on the results returned by Shodan, which are analyzed in order to automatically identify known vulnerabilities from National Vulnerability Database. Experiments conducted on five university-type institutions revealed the effectiveness of the proposed approach and the high degree of service exposure which may require immediate, yet simple service sanitizing security measures.
Procedia Technology, 2014
We consider an active supervised learning scenario in which the supervisor (trainer) can make dec... more We consider an active supervised learning scenario in which the supervisor (trainer) can make decisions regarding the possibility to choose new examples for learning. In the classical forms of supervised learning, the training set is chosen according to some known or random given distribution. The supervisor is a passive agent in the sense that he is not able to interact with the training set in order to improve the performances of the learning process of the neural network. We will introduce in a formal manner the terms of "difficult learning" and "easy learning" related to the training data set. We will investigate some possibilities that allow the trainer to become active and we will analyse the performances of such supervised learning. An active supervised learning algorithm is presented and also we have performed some simulation in order to prove our theoretical results.
Procedia Technology, 2015
Procedia Technology, 2016
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Papers by Calin Enachescu