V. Groza

Polytechnic University of Timisoara, Freidorf, Timiş, Romania

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Publications (122)14.68 Total impact

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    ABSTRACT: Physicians' understanding of biosignals as measured with medical instruments becomes the foundation of their decisions and diagnoses of patients, as they rely strongly on what the instruments show. Thus, it is critical and very important to ensure that the instruments' recordings exactly reflect what is happening in the patient's body so that the acquired signal is the real one or at least as close to the real in-body signal as possible. This is such an important issue that sometimes physicians use invasive measurements to obtain the real biosignal. Generating an in-body signal from what a measurement device shows is called “signal purification” or “reconstruction” and can be done only when we have adequate information about the interface between the body and the monitoring device. In this paper, first, we present a device that we developed for electrocardiogram (ECG) acquisition and transfer to PC. To evaluate the performance of the device, we use it to measure ECG and apply conductive textile as our ECG electrode. Then, we evaluate ECG signals captured by different electrodes, specifically traditional gel Ag/AgCl and dry golden plate electrodes, and compare the results, allowing us to investigate if ECG measured with the device is proper for applications where no skin preparation is allowed, such as ECG-assisted blood pressure monitoring devices. Next, we propose a method to reconstruct the ECG signal from the signal acquired by our device, with respect to the interface characteristics and their relation to the ECG. The interface in this paper is skin–electrode interface for conductive textiles. In the last stage of this paper, we explore the effects of pressure on skin–electrode interface impedance and its parametrical variation.
    IEEE Transactions on Instrumentation and Measurement 01/2014; 63(6):1412-1422. · 1.71 Impact Factor
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    ABSTRACT: Oscillometry is a popular technique for automatic estimation of blood pressure (BP). However, most of the oscillometric algorithms rely on empirical coefficients for systolic and diastolic pressure evaluation that may differ in various patient populations, rendering the technique unreliable. A promising complementary technique for automatic estimation of BP, based on the dependence of pulse transit time (PTT) on cuff pressure (CP) (PTTCP mapping), has been proposed in the literature. However, a theoretical grounding for this technique and a nonparametric BP estimation approach are still missing. In this paper, we propose a novel coefficient-free BP estimation method based on PTTCP dependence. PTT is mathematically modeled as a function of arterial lumen area under the cuff. It is then analytically shown that PTTCP mappings computed from various points on the arterial pulses can be used to directly estimate systolic, diastolic, and mean arterial pressure without empirical coefficients. Analytical results are cross-validated with a pilot investigation on 10 healthy subjects where 150 simultaneous ECG and oscillometric BP recordings are analyzed. The results are encouraging whereby the mean absolute errors of the proposed method in estimating systolic and diastolic pressures are 5.31 mmHg and 4.51 mmHg, respectively, relative to the Food and Drug Administration (FDA)-approved Omron monitor. Our work thus shows promise towards providing robust and objective BP estimation in a variety of patients and monitoring situations.
    IEEE transactions on bio-medical engineering 01/2013; · 2.15 Impact Factor
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    ABSTRACT: Localization techniques are of key interest for mobile robot groups. A certain node is usable by the system when its position is known and it can communicate (one-way or two-ways). Ideally, the localization should be quick, precise and with low resource consumption. For this, the possibilities to keep track of the node should be seen as parameters and modified to obtain the best results. To study such a localization case of a group of robots we developed a simulation environment based on the hardware configuration from our previous work (mobile robots with wireless communication and ultrasound based location system). This paper aims to show the impact certain parameters and situations have on the localization problem.
    Robotic and Sensors Environments (ROSE), 2013 IEEE International Symposium on; 01/2013
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    ABSTRACT: Sleep apnea is a common condition that poses serious health risks. Current state-of-the-art technology for diagnosing and assessing sleep apnea is obtrusive, expensive, and lacks integration/analysis of important cardiovascular and respiratory parameters. This paper evaluates a novel unobtrusive multiparameter sleep apnea monitor, namely, the Biopeak chest belt monitor, and describes a collection of associated algorithms for the detection of sleep apnea and assessment of the extent of the resulting physiological disturbance. The system uses dry electrodes to acquire electrocardiogram, respiratory, and stroke volume data and analyzes multiple physiological parameters from it. In a pilot investigation on eight healthy subjects simulating a total of 66 obstructive sleep apnea (OSA) events with Mueller maneuvers, the proposed system achieves an accuracy of 95.6%, a specificity of 97.2%, and a sensitivity of 93.8% for identifying these events. Moreover, the response of the simulated OSA events on the multiple physiological parameters conforms to earlier published work. We thus conclude that the proposed chest belt system has potential to be used for reliable sleep apnea detection and comprehensive evaluation of cardiovascular and respiratory parameters in sleep apnea.
    IEEE Transactions on Instrumentation and Measurement 01/2013; 62(10):2751-2762. · 1.71 Impact Factor
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    ABSTRACT: This paper focuses on the problem of relative location management in a robotic systems starting from the previous developed methods, techniques and algorithms. We discuss about inter-robot alignment, distance measurement and localization using the triangulation and trilateration methods. We will show the importance of the confidence number of the robotic nodes in the system, to the relative localization approaches. The measurement results, performed on the CORE-TX case study, show that the proposed solutions meet the design requirements previously specified.
    Instrumentation and Measurement Technology Conference (I2MTC), 2013 IEEE International; 01/2013
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    ABSTRACT: The subject paper presents new approach to response data compaction of multi-output digital circuits using two-input nonlinear logic with the objective of designing zeroaliasing (aliasing-free) space compression hardware for single stuck-line faults, extending well-known concept of conventional switching theory, viz. that of compatibility relation as used in the minimization of incompletely specified sequential machines. For a pair of response data outputs of the circuit under test (CUT), the method introduces the notion of fault detection compatibility and conditional fault detection compatibility (conditional upon some other pair of response data outputs being simultaneously fault detection compatible) with respect to two-input AND/NAND and/or OR/NOR logic. The process is illustrated with the design details of space compressors for the International Symposium on Circuits and Systems or ISCAS 85 combinational and ISCAS 89 full-scan sequential benchmark circuits using simulation programs ATALANTA, FSIM and COMPACTEST, though, because of space constraints, only some partial results on simulation on ISCAS 89 full-scan sequential benchmark circuits using ATALANTA are provided here.
    Instrumentation and Measurement Technology Conference (I2MTC), 2013 IEEE International; 01/2013
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    ABSTRACT: In this work we evaluated the quality of the ECG signals obtained from conductive fabric dry electrodes. The purpose of this work was to evaluate if lead I ECG collected with dry conductive fabric electrodes is suitable for applications where no special preparation of electrodes specific for ECG monitoring is allowed. An example of such application is ECG-assisted blood pressure (BP) monitoring device where the user of the BP device should only follow standard procedures of BP measurements. In this paper, we present a system that we developed for the acquisition of ECG signals and their transfer to the PC, and we evaluate the quality of the ECG signals from different electrodes placed at biceps and wrist or touched by fingers. In our experiments we compared signals obtained using gel Ag/AgCl, dry contact electrodes made of golden plates and conductive fabric-based electrodes. Conductive fabric-based electrodes are capable of collecting ECG with accuracy comparable to the accuracy of the signal collected by gel electrodes.
    Medical Measurements and Applications Proceedings (MeMeA), 2013 IEEE International Symposium on; 01/2013
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    ABSTRACT: An adaptive compressed domain watermarking method is proposed in the paper. In this technique, multiple binary images derived from a single watermark image are first embedded in a video sequence. The spatial spread spectrum watermark is directly incorporated in the compressed bit streams by modifying the wavelet coefficients. Experimental evidence demonstrates that the developed approach is efficient and also robust against spatial attacks such as scaling and frame averaging, and temporal attacks like frame dropping and shifting.
    Instrumentation and Measurement Technology Conference (I2MTC), 2013 IEEE International; 01/2013
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    ABSTRACT: The distributed energy resources (DER) contains several technologies, such as diesel engines, small wind turbines, photovoltaic inverters, etc. The control of DER components with storage devices and (controllable) loads, such as batteries, capacitors, dump loads, are central to the concept of the Micro Grids (MGs). A MG can operate interconnected to the main distribution grid or in islanded mode. This paper presents experimental tests for static and dynamic stability analysis carried out in a dedicated laboratory for research in distributed control and micro-grid with a high share of renewable energy production. Moreover to point out, on a laboratory scale, the coupling between DR and storage and to effectively compensate wind fluctuations a number of tests have been done. In order to find out the parameters of various types of DER components for dynamic simulation models a number of tests are required under different operation modes and loads. The testing reporting here includes three modes of operation: stand alone, parallel/hybrid and grid connection.
    IEEE I2MTC-International instrumentation & measurement technology conference; 05/2012
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    ABSTRACT: For protecting the authenticity of multimedia objects, watermarking plays a vital role, since, they are much easier to get copied, exchanged and modified these days. Conventional watermarking techniques as available are not always competent enough to protect the authenticity of multimedia objects as they are usually applied in the uncompressed domain. To address this deficiency, the subject paper presents a new compressed domain video watermarking scheme. The method proposed herein embeds several binary images decomposed from a single watermarked image into different scenes in a video sequence. The spatial spread spectrum watermark is embedded directly into the compressed bit streams by modifying the discrete cosine transform coefficients. In order to embed the watermark with minimum loss in image fidelity, a visual mask based on local image characteristics is incorporated. Simulation experiments demonstrate that the developed technique yields effective and robust protection against conventional spatial strikes, viz. scaling and frame averaging besides temporal attacks.
    Instrumentation and Measurement Technology Conference (I2MTC), 2012 IEEE International; 01/2012
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    ABSTRACT: Synthesizing aliasing-free space compactor for built-in self-testing of very large scale integration circuits and systems is of great importance, especially because of the design paradigm shift in recent years from system-on-board to system-on-chip. This paper investigates and provides additional results on a recently developed approach to designing aliasing-free space compaction hardware targeting particularly embedded cores-based system-on-chips for single stuck-line faults, extending well-known concept from conventional switching theory, viz. that of compatibility relation as used in the minimization of incomplete sequential machines. For a pair of response outputs of the circuit under test, the method introduces the notion of fault detection compatibility and conditional fault detection compatibility (conditional upon some other response output pair being simultaneously fault detection compatible) with respect to two-input XOR/XNOR logic. The process is illustrated with design details of space compactors for the International Symposium on Circuits and Systems (ISCAS 85) combinational (and ISCAS 89 full-scan sequential) benchmark circuits using simulation programs ATALANTA and FSIM, attesting to the importance of the technique from the viewpoint of simplicity, resultant low area overhead and full fault coverage for single stuck-line faults, thereby making it an appropriate choice in commercial design environments.
    Instrumentation and Measurement Technology Conference (I2MTC), 2012 IEEE International; 01/2012
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    ABSTRACT: The conventional design of home security systems typically monitors only the property and lacks physical control aspects of the house itself. Also, the term security is not well defined because there is a time delay between the alarm system going on and actual arrival of the security personnel. This paper discusses the development of a home security and monitoring system that works where the traditional security systems that are mainly concerned about curbing burglary and gathering evidence against trespassing fail. The paper presents the design and implementation details of this new home control and security system based on field programmable gate array (FPGA) The user here can interact directly with the system through a web-based interface over the Internet, while home appliances like air conditioners, lights, door locks and gates are remotely controlled through a user-friendly web page. An additional feature that enhances the security aspect of the system is its capability of monitoring entry points such as doors and windows so that in the event any breach, an alerting email message is sent to the home owner instantly.
    Instrumentation and Measurement Technology Conference (I2MTC), 2012 IEEE International; 01/2012
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    L. Mihet-Popa, V. Groza
    International Review of Modelling and Simulations-IREMOS. 12/2011; 4(11):1410-1418.
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    ABSTRACT: Robotic collectives have been a very popular research topic in the last years. Also, applying emergent behavior patterns to such collectives has been similarly popular. This article introduces a mathematical model for resource gathering applications which is based on the study of ant colonies and validates it by simulating it inside Microsoft Robotics Studio simulator. The model is based on the implementation of a new emergent pattern, called “patrol”. During the course of the simulations, another emergent behavior pattern, called “Foodball”, is studied.
    Robotic and Sensors Environments (ROSE), 2011 IEEE International Symposium on; 10/2011
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    Lucian Mihet-Popa, Voicu Groza
    07/2011; , ISBN: 978-953-307-467-2
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    ABSTRACT: Battery-powered embedded systems have known a rapid evolution in recent years, as nickel-metal hydride (Ni-MH) battery technology has enabled important reductions in size and proportional increases in total capacity over the older nickel-cadmium (Ni-Cd) and lead-acid battery types. This paper addresses the problem of state-of-health (SoH) estimation and prediction for use in resource-constrained Ni-MH-battery-powered embedded systems. We propose a novel SoH prediction methodology, presenting both a theoretical analysis of the estimation algorithm and the detailed description of hardware and software implementation. Two versions of estimation algorithms are proposed, along with the analysis of their performances in terms of prediction accuracy and required processing power, as the SoH prediction is designed to run online, being part of an embedded battery management system.
    IEEE Transactions on Instrumentation and Measurement 07/2011; · 1.71 Impact Factor
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    ABSTRACT: Responding to more demand in coming years, the task of the small wind energy industry requires progress on several fronts—the public policy initiatives, technology development, and market growth. One important issue of the wind energy utilization is the conversion efficiency of the usable energy into productive power. Enhanced technologies such as contrarotating blades, gearbox and lubrication, airfoils, generators, and power electronics will lower cost and increase energy production. The purpose of this paper is, therefore, to reinforce the effectiveness of employing contrarotating system to enhance the performance of a small wind energy converter (SWEC). With this concept, the SWEC works more efficiently and therefore produces more energy in a unit turbine area. To verify the SWEC performance, a research model has been built and tested over a range of operating conditions. Wind tunnel tests were carried out to ascertain the overall performance of the contrarotating SWEC. Results are presented for cases of different wind speeds and Reynolds number. The results demonstrated a significant increase in wind energy conversion efficiency and capability of operation at lower wind speeds while keeping up performance compared to a single-rotor system of the same type.
    ISRN Mechanical Engineering. 06/2011; 2011.
  • L. Mihet-Popa, V. Groza
    IEEE I2MTC-International instrumentation & measurement technology conference; 05/2011
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    ABSTRACT: Responding to more demand in coming years, the task of the small wind energy industry requires progress on several fronts-from public policy initiatives, to technology development, to market growth. Enhanced technologies such as contra-rotating blades, transmission systems, lubrication, airfoils, generators, and power electronics will lower cost and increase energy production. This paper mainly considers two key technological points of a small wind energy converter (SWEC) namely, the performance of the rotor system and induction generator. Small-scale prototypes have been built to experimentally verify the performance of the SWEC. Wind tunnel tests of the power output, power coefficient, and turbine speed were carried out to ascertain the aerodynamic power conversion and the operation capability at lower wind speeds. The results demonstrated a significant increase in performance compared to a single-rotor system of the same type. Another aspect of development and test is to present a comparative performance evaluation between a standard induction generator and an efficient but with modified design (TRIAS Generator) as a realistic solution of clean power for grid-connected SWECs. The paper also discusses issues related to control and monitoring of SWEC.
    Electronic Design, Test and Application (DELTA), 2011 Sixth IEEE International Symposium on; 02/2011
  • A. Hossain, V. Groza, S.R. Das
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    ABSTRACT: Designing aliasing-free space support hardware for built-in self-testing in very large scale integration circuits and systems is of immense significance, specifically due to the design paradigm shift in recent years from system-on-board to system-on-chip. This paper develops an approach to designing aliasing-free space compaction hardware targeting particularly embedded cores-based system-on-chips for single stuck-line faults, extending well known concept from conventional switching theory, viz. that of compatibility relation as used in the minimization of incompletely specified sequential machines. For a pair of response outputs of the circuit under test, the method introduces the notion of fault detection compatibility and conditional fault detection compatibility (conditional upon some other response output pair being simultaneously fault detection compatible) with respect to two-input OR/NOR logic. The process is illustrated with design details of space compactors for the International Symposium on Circuits and Systems or ISCAS 85 combinational (and ISCAS 89 full-scan sequential) benchmark circuits using simulation programs ATALANTA and FSIM, attesting to the importance of the technique from the viewpoint simplicity, resultant low area overhead and full fault coverage for single stuck-line faults, thereby making it an appropriate choice in commercial design environments.
    Electronic Design, Test and Application (DELTA), 2011 Sixth IEEE International Symposium on; 02/2011

Publication Stats

180 Citations
14.68 Total Impact Points

Institutions

  • 2005–2011
    • Polytechnic University of Timisoara
      • Department of Automation and Applied Informatics
      Freidorf, Timiş, Romania
  • 1997–2010
    • University of Ottawa
      • School of Electrical Engineering and Computer Science
      Ottawa, Ontario, Canada
  • 2008
    • West University of Timisoara
      • Department of Computer Science
      Timişoara, Judetul Timis, Romania