Vol. 15, No. 1, February 2018


Dejan B. Popović, Tadej Bajd
Pendulum Test: Quantified Assessment of the Type and Level of Spasticity in Persons with Central Nervous System Lesions
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Abstract: The development of a comprehensive computational model of the pendulum test which is appropriate for the analysis of the pathologic behavior of the leg in humans with the central nervous system (CNS) lesion is presented in this review. The model relates to the pendulum movement of the lower leg (shank and the foot) in the lateral plane due to the gravity and involuntary contractions of the muscles. The viscous damping and elastic stiffness reflect the soft tissues and friction in the knee joint. To quantify the pathologic activity of paralyzed muscles a reflex torque was added to the gravity generated knee joint torque. The knee joint encoder, accelerometers and gyroscopes positioned along the shank and thigh, and EMG amplifiers were used to acquire data for the illustration of the validity of the model. We show that the linear model of the movement of the lower leg is not a good representation of the motor impairment. We show that the model expanded with the reflex torque affecting the movement is well suited for the pendulum analysis. The timing of the reflex torques can be determined from the EMG recordings.
Keywords: Pendulum test, Spasticity, Three-component muscle model, Nonlinear pendulum model.

Stefan Mirković, Dragan Pejić, Marjan Urekar, Bojan Vujičić, Đorđe Novaković
Improvement of an Existing Method of Asynchronous Sampling for Determining RMS Value
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Abstract: Measuring a value by definition seems to be the best solution for getting the most precise results. In this paper, it is shown that by changing the general definition of root mean square (RMS) and average value of a periodic signal, their measurement can be improved. When measuring RMS with asynchronous sampling, it was observed that results were scattered around two values, and it was found that the main cause for this was initial sampling time. Redefining the RMS value has been proposed in order to increase the efficiency of the asynchronous method. After comparing the results based on general and proposed definition for RMS value, it was observed that there was significantly less scattering of results and higher accuracy. The simulation proved that the application of the proposed definition of RMS gives more accurate and precise results than the general definition for analog to digital (AD) converters with both lower and higher resolution.
Keywords: Root mean square, Average, Asynchronous sampling, Measurements, Metrology.

Antonina Aleksić, Stevica Graovac, Lana Popović Maneski, Dejan B. Popović
The Assessment of Spasticity: Pendulum Test Based Smart Phone Movie of Passive Markers
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Abstract: The pendulum test is the method for quantification of the level of spasticity in persons with spinal cord and brain injuries/diseases. The data for the assessment comes from the analysis of lower leg rotation in the sagittal plane while sitting caused by gravity. We built a simple instrument that uses the smart phone and passive markers for studying the pendulum movement of the leg. We compared the results of the new device with the results acquired with the conventional apparatus which uses a knee joint angle encoder and inertial sensors mounted on the upper and lower leg. The differences of parameters estimated from the test between the two systems are in the range of 5%, which is in the same range as the precision of the positioning of the pendulum apparatus on the leg. The new system is simple for the application (donning, doffing, setup time, accuracy, repeatability) and allows a straightforward interpretation to a clinician.
Keywords: Spasticity assessment, Pendulum test, Image processing, Smartphone.

Igor Jovanović, Uglješa Jovanović, Dragan Mančić
A Matlab/Simulink 3D Model of Unsymmetrical Ultrasonic Sandwich Transducers
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Abstract: Ultrasonic sandwich transducer is a half-wave resonant structure which oscillates in thickness direction. This paper presents a new Matlab/ Simulink model of a prestressed unsymmetrical ultrasonic sandwich transducer, which is modeled by applying three-dimensional (3D) Matlab/Simulink models of piezoceramic rings and metal endings derived from the piezoceramic ring model. With the cascade connection of the piezoceramic rings model with metal endings model, a complete model of ultrasonic transducer is obtained. Using this model one may determine any transducer transfer function, whereat is taken into the account the external medium influence, as well as the influence of the thickness and radial modes of each transducer component. The electro¬mechanical equivalent circuit of the hammer transducer, which represents one-dimensional (1D) model, is also derived and presented in this paper. The comparisons between experimental and theoretical results are quite good and validate the new analytical 3D design approach.
Keywords: Matlab/Simulink Model, Analytical 3D Model, Electrical Impedance Characteristics, Ultrasonic Sandwich Transducer.

Branka Stojanović, Saša Milićević, Srđan Stanković
Improved Dehazing Techniques for Maritime Surveillance Image Enhancement
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Abstract: The subjective quality of images (human interpretation) is very important in long-range imaging systems, where the presence of haze directly influences visibility of the scene, by reducing contrast and obscuring objects. Image enhancement techniques – dehazing techniques, are usually required in such systems. This paper compares the most significant single image dehazing approaches, proposes three additional enhancement steps in dehazing algorithms, compares performance of the algorithms and additional enhancement steps, and presents test results on maritime surveillance images, which represent one special case of long-range images.
Keywords: Dehazing, Image enhancement, Surveillance imaging, Long-range imaging.

Đorđe Pešić, Marko Mišić, Jelica Protić, Milena Vujošević Janičić
Prototype Implementation of Segment Assembling Software
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Abstract: IT education is very important and a lot of effort is put into the development of tools for helping students to acquire programming knowledge and for helping teachers in automating the examination process. This paper describes a prototype of the program segment assembling software used in the context of making tests in the field of algorithmic complexity. The proposed new program segment assembling model uses rules and templates. A template is a simple program segment. A rule defines combining method and data dependencies if they exist. One example of program segment assembling by the proposed system is given. Graphical user interface is also described.
Keywords: Time complexity, Automated source code assembling, XML technologies.

Dragan Brkin, Branislav Kordić, Miroslav Popović
A Simulation of Distributed STM
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Abstract: This paper presents an extension of the IaaS Cloud simulator CloudSim. Computational tasks are modeled in the form of a transaction on a transactional memory and communication between the data center is based on the Two-Phase Commit protocol. The model of the distributed STM prototype is implemented using the extended CloudSim simulator. The obtained results are as expected and in accordance with desired system behavior. The presented results are positive and they stimulate future work in development of distributed STM.
Keywords: CloudSim, Software Transactional Memory, Distributed Systems, Two phase commit protocol.

Danilo Stanojević, Boban Bondžulić, Boban Pavlović1, Vladimir Petrović
The Impact of Quality of Service Parameters to the Subjective and Objective Video Quality Assessment
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Abstract: This paper deals with the delay, delay variation – jitter, packet loss rate and bandwidth as quality of service parameters, in the form of four types of video quality degradations. The impact of defined levels of degradation on subjective impressions (given as mean opinion scores) is analyzed. ReTRiEVED video dataset with publicly available subjective scores is used in the analysis. Three full-reference measures are used for objective assessment of video quality. The degree of consistency of subjective and objective quality scores is shown through scatter plots and quantitative measures (linear correlation coefficient and correlation of the ranks). Based on the interpolation functions, quality of service parameters are mapped to subjective experience. We show that jitter is a much more destructive effect than other degradation types.
Keywords: Jitter, Packet loss rate, Quality of service, Subjective and objective video quality assessment.

Aleksandar M. Stanisavljević, Vladimir A. Katić, Boris P. Dumnić, Bane P. Popadić
A Brief Overview of the Distribution Test Grids with a Distributed Generation Inclusion Case Study
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Abstract: The paper presents an overview of the electric distribution test grids issued by different technical institutions. They are used for testing different scenarios in operation of a grid for research, benchmarking, comparison and other purposes. Their types, main characteristics, features as well as application possibilities are shown. Recently, these grids are modified with inclusion of distributed generation. An example of modification and application of the IEEE 13-bus for testing effects of faults in cases without and with a distributed generator connection to the grid is presented.
Keywords: Distribution test grids, IEEE test grids, Distributed generation, Distributed energy resources (DERs).

©2018 Serbian Journal of Electrical Engineering