June 2018, Volume 18, Number 4
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Uroš ČIBEJ - Jurij MIHELIČ SEARCH-TREE SIZE ESTIMATION FOR THE SUBGRAPH ISOMORPHISM PROBLEM [full paper]
This article addresses the problem of finding patterns in graphs. This is formally defined as the subgraph isomorphism problem and
is one of the core problems in theoretical computer science. We consider the counting variation of this problem. The task is to count all
instances of the pattern G occurring in a (usually larger) graph H. The vast majority of algorithms for this problem use a variation of
backtracking. Most commonly they exhaustively search through the space of all possible monomorphisms between G and H. The size
of the search tree depends heavily on the choice of the ordering of vertices of G, which are systematically assigned to the vertices of H.
We use a method called heuristic sampling to estimate the size of the search tree for each ordering in advance. We use this estimation
to select the most suitable order of vertices of G which minimizes the expected tree size. This approach is empirically evaluated on a
set of instances, showing the practical potential of the method.
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Samuel ŽUK - Alena PIETRIKOVÁ - Igor VEHEC POSSIBILITIES OF PLANAR CAPACITIVE RAIN SENSOR MANUFACTURING BY THICK FILM TECHNOLOGY [full paper]
In this paper, characterization and realisation of planar thick film rain sensor based on capacitive principle is presented. By using
three different pastes (inks) for realisation of capacitive sensor it was found out that sensor produced by carbon ink is not suitable for
use in this application because it shows no change in measured capacitance when temperature or humidity level varies. The best
characteristics were obtained by using silver conductive paste. Capacity of capacitive sensor realized by polymer silver paste shows
rising tendency when temperature and humidity values rises.
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Tomaž DOBRAVEC JAVA BYTECODE INSTRUCTION USAGE COUNTING WITH ALGATOR [full paper]
Development of algorithms for solving various kinds of computer related problems consists of several consecutive and possibly
repetitive phases. The final and very important step in this process is to implement the developed algorithm in a selected programming
language, to test its behavior on some real-world test cases and to compare the results with the results of other algorithms. This
evaluation can be done by comparing different execution indicators among which the time consumption is usually considered to be the
most relevant. On the other hand, timing the algorithms in practice is very difficult since it is hard to ensure a fair and reproducible
environment in which algorithm’s implementations can be compared. To overcome this barrier, we introduce a system called ALGATOR
that was developed to facilitate the algorithm evaluation process. Besides the time complexity and the project-specific indicators,
ALGATOR also measures the counters of Java code and Java bytecode usage. The measurement of the former is implemented by using
special tags that are to be inserted in the appropriate lines of Java code while the measurement of the latest is enabled by using an
adapted Java virtual machine, which counts the Java bytecode usage and reports the statistics. By using this counters new timingindependent
criteria for algorithm assessment can be derived. In this paper we present some basic concepts of the ALGATOR system
and give some examples of how to use the system in practice. We show the distribution of the usage of Java bytecode instruction for the
sorting problem and the usage of the Java bytecode indicators in the time-complexity prediction for the matrix multiplication algorithm.
The examples presented in this article show how the classic time measurement methods can be replaced by measuring some other more
reliable indicators, and how this measurements can help to asses the quality of our algorithms.
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Michal VARGA - Ján JADLOVSKÝ EVALUATION OF DEPTH MODALITY IN CONVOLUTIONAL NEURAL NETWORK CLASSIFICATION OF RGB-D IMAGES [full paper]
This paper investigates the value of depth modality in object classification in RGB-D images. We use a simple model based on a
multi-layered convolutional neural network which we train on a dataset of segmented RGB-D images of household and office objects.
We evaluate and quantify the benefit of additional depth modality and its effect on classification accuracy on this dataset. Also, we
compare the benefit of depth channel against the addition of color to grayscale image. Our experimental results support a conclusion,
that for these categories of objects the depth modality provides a significant benefit to classification, which also outweighs the benefit
of color information. Similar supporting evidence found in recent research is shown in comparison along with the resulting quantified
benefit of depth modality.
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Petr KADLEC - Radek POLANSKÝ INFLUENCE OF UV RADIATION ON DIELECTRIC ABSORPTION AND DIELECTRIC STRENGTH OF HALLOYSITE NANOTUBES FILLED POLYETHYLENE COMPOSITES [full paper]
This paper deals with the evaluation of the amount of filler influence and the ultraviolet (UV) radiation influence on selected
dielectric properties of the innovative type of composites. These composites consist of a linear low-density polyethylene matrix and
a clay filler (with different filling levels) that contains halloysite nanotubes (HNT) primarily. The intended application of tested
composites in the field of electrical engineering is in insulating systems of power cables. Attention is paid to the analysis of the
behaviour of composites in their charging, which is caused by the connection with the direct voltage source. The volume resistivity and
polarization indexes are determined based on this analysis. Analysis of charging based on the measurement of the current, which flows
through the sample under constant applied voltage, is supplemented with the short evaluation of the material behaviour after the
disconnecting of the voltage source and after the electrode shorting when the material is discharged. Furthermore, the measurement
of dielectric strength under an alternating electric field as another key parameter of electrical insulating materials is determined.
Results of analyses of absorption and resorption processes and the dielectric strength measurement of materials in the delivered state
prove a significant effect of the filler percentage in the composite. Subsequently, markedly different values of selected parameters
because of material exposure to UV radiation are also determined. Observed changes in dielectric properties caused by UV irradiation
are supported by the analysis of the chemical structure of materials via Fourier transform infrared spectroscopy.
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Ľuboš PAVLOV - Ľuboš SKURČÁK NEW METHODS FOR SPECIFICATION LATENT LOSSES FOR ELECTRICITY TRANSMISSION BY OVERHEAD LINES [full paper]
The submitted contribution is devoted to the issue of the existence of latent losses on the overhead lines. Quantification of latent
losses of electricity is a very complicated task, which has been solved in practice for several years. In their assessment, however,
often appear some inconsistencies which cause is often unknown. The magnitude of these losses in some cases cannot be negligible.
From the point of view of maintaining an efficient and reliable operation of distribution and transmission systems in the future,
attention will still need to be paid to the problem of latent loss analysis.
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Mutiu Adesina ADEGBOYE - Lukman Adewale AJAO - Taofeeq Alabi BADMUS PERFORMANCE EVALUATION OF MULTIPLE TRANSFORM WATERMARKING SYSTEM FOR PRIVACY PROTECTION OF MEDICAL DATA USING PSNR AND NC [full paper]
This paper presents the performance evaluation of a developed multiple transform watermarking system for privacy protection of
medical data using Peak Signal to Noise Ratio (PSNR) and Normalized Cross-Correlation (NC). The PSNR was used to evaluate the
imperceptibility of the system, while the NC was used to evaluate the robustness of the system under the various attacks include:
Gaussian noise, pepper and salt noise, sharp enhancing, image cutting, image compression, low pass filter and image rotation. The
obtained result showed that the similarity between original image and watermarked image has PSNR of 52.4595dB as compared to
the existing system of 50.0285dB. This indicates that the proposed scheme can conceal the watermark better, and as well retains the
image quality.
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Ondrej KOVÁČ - Iveta GLADIŠOVÁ - Matej ŠUĽA - Volodymyr PALAHIN COMPARISON COMPRESSION PROPERTIES DWT WITH FB 5/3 AND FB 9/7 [full paper] The suitability of 2-dimensional Discrete Wavelet Transform (2D DWT) as a tool in image and video compression is nowadays
indisputable. Wavelet based techniques such as JPEG2000 for image compression has a lot more to offer than conventional methods
in terms of compression ratio. This paper presents DWT and the use of its compression properties in image processing and briefly
describes convolutional implementation of the discrete wavelet transform. More specifically, it deals with lifting implementations of
the discrete wavelet transform (LDWT). The main feature of the lifting scheme is that all constructions are derived in the spatial
domain. LDWT does not require complex mathematical calculations unlike traditional methods and does not depend on Fourier
transforms. The lifting scheme is used to generate second-generation wavelets, which are not necessarily translation and dilation of
one particular function. This paper compares two most common types of implementation of LDWT, which are LDWT using a filter
banks (FB) 5/3 and 9/7. Within the experiment, the compression properties of the LDWT implementations are compared.
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Miroslava MUCHOVÁ - Ján PARALIČ - Barbora NAGYOVÁ DATA ANALYSIS OF THE LOGISTICS COMAPANY’S DATA BY MEANS OF BUSINESS INTELLIGENCE [full paper] The aim of this article is to present how we processed and analysed data from a logistics company using various Business
Intelligence tools. The theoretical part of the article is therefore focused on defining Business Intelligence concepts and data
warehouses that are relevant to the issue. The practical part of the article focuses on editing data, creating dimension tables and facts.
The data were collected from the Dynafleet system and originated from a shipping company. The data provided are for the period from
2013 to 2016. We design user scenarios to help the company's manager in making an efficient assignment of drivers to planned delivery
routes. The research is focused on design and creation of a logistics system based on data analytics that can continuously analyze the
incoming data and generate current decision support reports. The created user scenarios have a wide range of uses and can also be
helpful in assessing the performance of individual drivers and their workloads. Using a logistics system, the logistics manager can get
the valuable and useful information needed to effectively operate the business.
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