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Dr. Niko Lukač
University of Maribor

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0 Computer Science
0 Parallel Algorithms
0 Remote Sensing Applications
0 Modelling and Simulation
0 Environmental simulations

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Journal article
Published: 21 March 2021 in Information
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Question-answering systems based on knowledge graphs are extremely challenging tasks in the field of natural language processing. Most of the existing Chinese Knowledge Base Question Answering(KBQA) can only return the knowledge stored in the knowledge base by extractive methods. Nevertheless, this processing does not conform to the reading habits and cannot solve the Out-of-vocabulary(OOV) problem. In this paper, a new generative question answering method based on knowledge graph is proposed, including three parts of knowledge vocabulary construction, data pre-processing, and answer generation. In the word list construction, BiLSTM-CRF is used to identify the entity in the source text, finding the triples contained in the entity, counting the word frequency, and constructing it. In the part of data pre-processing, a pre-trained language model BERT combining word frequency semantic features is adopted to obtain word vectors. In the answer generation part, one combination of a vocabulary constructed by the knowledge graph and a pointer generator network(PGN) is proposed to point to the corresponding entity for generating answer. The experimental results show that the proposed method can achieve superior performance on WebQA datasets than other methods.

ACS Style

Shuang Liu; Nannan Tan; Yaqian Ge; Niko Lukač. Research on Automatic Question Answering of Generative Knowledge Graph Based on Pointer Network. Information 2021, 12, 136 .

AMA Style

Shuang Liu, Nannan Tan, Yaqian Ge, Niko Lukač. Research on Automatic Question Answering of Generative Knowledge Graph Based on Pointer Network. Information. 2021; 12 (3):136.

Chicago/Turabian Style

Shuang Liu; Nannan Tan; Yaqian Ge; Niko Lukač. 2021. "Research on Automatic Question Answering of Generative Knowledge Graph Based on Pointer Network." Information 12, no. 3: 136.

Journal article
Published: 15 February 2021 in Journal of Visual Communication and Image Representation
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A new method for encoding a sequence of integers, named Binary Adaptive Sequential Coding with Return to Bias, is proposed in this paper. It extends the compressing pipeline for chain codes’ compression consisting of Burrows Wheeler Transform, Move-To-Front Transform, and Adaptive Arithmetic Coding. We also explain when to include the Zero-Run Transform into the above-mentioned pipeline. The Zero-Run Transform generates a sequence of integers corresponding to the number of zero-runs. This sequence is encoded by Golomb coding, Binary Adaptive Sequential Coding, and the new Binary Adaptive Sequential Coding with Return to Bias. Finally, a comparison is performed with the two state-of-the-art methods. The proposed method achieved similar compression efficiency for the Freeman chain code in eight directions. However, for the chain codes with shorter alphabets (Freeman chain code in four directions, Vertex Chain Code, and Three-OrThogonal chain code), the introduced method outperforms the referenced ones.

ACS Style

Borut Žalik; Domen Mongus; Krista Rizman Žalik; David Podgorelec; Niko Lukač. Lossless chain code compression with an improved Binary Adaptive Sequential Coding of zero-runs. Journal of Visual Communication and Image Representation 2021, 75, 103050 .

AMA Style

Borut Žalik, Domen Mongus, Krista Rizman Žalik, David Podgorelec, Niko Lukač. Lossless chain code compression with an improved Binary Adaptive Sequential Coding of zero-runs. Journal of Visual Communication and Image Representation. 2021; 75 ():103050.

Chicago/Turabian Style

Borut Žalik; Domen Mongus; Krista Rizman Žalik; David Podgorelec; Niko Lukač. 2021. "Lossless chain code compression with an improved Binary Adaptive Sequential Coding of zero-runs." Journal of Visual Communication and Image Representation 75, no. : 103050.

Journal article
Published: 26 January 2021 in Sustainability
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When it comes to the proliferation of photovoltaic (PV) systems, technological solutions have to go hand in hand with optimized policy approaches and regulatory frameworks. This paper proposes a new application of state-of-the-art PV potential estimation method based on Light Detection And Ranging (LiDAR) data targeted toward individual household self-supply. The performance of the proposed general approach is demonstrated in the case of Slovenian PV based self-supply (yearly net self-sufficient energy supply) scheme and related policy. The results obtained by PV potential assessment method show drawbacks of the current policy solution in Slovenia, which limits the installed peak power of the PV systems to 80% of the rated power supply. The paper proposes to change the policy in a way that increases the yearly energy production of the PV system and assures proper voltage profiles in the electricity network. The paper is novel in terms of considering PV potential over LiDAR data by also considering self-sustainability, in using such techno-economic analysis to validate the merits and demerits of a policy approach and is the first such case study used in the context of Slovenian self-supply policy. The proposed PV potential estimation method is generally applicable for any location and can be easily adjusted to the local regulatory framework.

ACS Style

Luka Tomažič; Niko Lukač; Gorazd Štumberger. A New Regulatory Approach for PV-Based Self-Supply, Validated by a Techno-Economic Assessment: A Case Study for Slovenia. Sustainability 2021, 13, 1290 .

AMA Style

Luka Tomažič, Niko Lukač, Gorazd Štumberger. A New Regulatory Approach for PV-Based Self-Supply, Validated by a Techno-Economic Assessment: A Case Study for Slovenia. Sustainability. 2021; 13 (3):1290.

Chicago/Turabian Style

Luka Tomažič; Niko Lukač; Gorazd Štumberger. 2021. "A New Regulatory Approach for PV-Based Self-Supply, Validated by a Techno-Economic Assessment: A Case Study for Slovenia." Sustainability 13, no. 3: 1290.

Journal article
Published: 21 November 2020 in Energy and Buildings
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Increasing population and urbanisation threaten sustainable urban development due to increased resource consumption and emissions. As buildings are one of the largest energy consumers, it is crucial that their thermal load can be inspected on a large scale and at the highest resolution possible. The proposed method is performed in two stages. First, the LiDAR data and buildings’ metadata are preprocessed to generate high-resolution 3D building models that are represented by a triangle mesh. Thermal load of buildings throughout the year is then calculated per-triangle in a parallelised manner, while considering local micro-climate and shadowing from surroundings. Parallel design of the estimation enables significant speed-up of large-scale workloads, while maintaining accurate shadowing estimation. In experiments, the method was applied over a part of the city of Maribor, where heating and cooling loads were inspected in addition to other factors of thermal load estimation. Yearly thermal load calculation with an hourly time-step for 4,817 buildings with over 9.17 million triangles took about 8 min on a modern GPU. When comparing the run-times using a GPU and a modern CPU, the GPU was more than 60-times faster than a CPU for a million triangles. The speed-up grew with the number of triangles.

ACS Style

Marko Bizjak; Borut Žalik; Gorazd Štumberger; Niko Lukač. Large-scale estimation of buildings’ thermal load using LiDAR data. Energy and Buildings 2020, 231, 110626 .

AMA Style

Marko Bizjak, Borut Žalik, Gorazd Štumberger, Niko Lukač. Large-scale estimation of buildings’ thermal load using LiDAR data. Energy and Buildings. 2020; 231 ():110626.

Chicago/Turabian Style

Marko Bizjak; Borut Žalik; Gorazd Štumberger; Niko Lukač. 2020. "Large-scale estimation of buildings’ thermal load using LiDAR data." Energy and Buildings 231, no. : 110626.

Journal article
Published: 28 March 2020 in Information Sciences
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Burrows-Wheeler Transform, followed by Move-To-Front Transform, are often used transformation techniques in data compression. They may reduce the information entropy of the input sequence, which becomes more compressible in this way. This paper suggests an alternative, a Prediction-based Move-To-Front Transform, which may replace the aforementioned transformations. According to the context, consisting of a few already seen symbols, the Prediction-based Move-To-Front Transform selects an appropriate ordered domain of symbols to achieve a better match with the currently transforming symbol. Freeman chain code in four and eight directions, Three-Orthogonal chain code, and Vertex Chain Code were used for experiments. We confirmed that the proposed approach, when using an appropriate length of context, reduces the information entropy to a similar extent as the Burrows-Wheeler Transform followed by the Move-To-Front Transform on chain code data. Both approaches led to a very similar compression efficiency on 32 testing shapes when an arithmetic coder was used in the final stage. The proposed approach turned out to be more efficient when longer chain code sequences were used, obtained by merging all the testing chain codes of the same type.

ACS Style

Borut Žalik; Domen Mongus; Niko Lukač; Krista Rizman Žalik. Can burrows-Wheeler transform be replaced in chain code compression? Information Sciences 2020, 525, 109 -118.

AMA Style

Borut Žalik, Domen Mongus, Niko Lukač, Krista Rizman Žalik. Can burrows-Wheeler transform be replaced in chain code compression? Information Sciences. 2020; 525 ():109-118.

Chicago/Turabian Style

Borut Žalik; Domen Mongus; Niko Lukač; Krista Rizman Žalik. 2020. "Can burrows-Wheeler transform be replaced in chain code compression?" Information Sciences 525, no. : 109-118.

Journal article
Published: 12 February 2020 in Applied Energy
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The availability of high-resolution LiDAR (Light Detection And Ranging) geospatial data has increased immensely, providing new opportunities to solve challenges in the field of spatial energy planning. This paper presents a new method for large-scale placement of photovoltaic arrays over buildings’ rooftops in an optimal manner by using the global optimisation approach. The position, aspect and slope are the ey geometrical parameters being optimised for each photovoltaic array. The predicted energy generation (i.e. photovoltaic potential) is simulated by using state-of-the-art hourly shadowing estimation from the surroundings, anisotropic diffuse, reflected, and direct irradiances that are based on a Typical Meteorological Year, and non-linear efficiency characteristics of a considered photovoltaic system configuration. The optimisation performs multiple simulation scenarios throughout an entire year for each photovoltaic array, in order to maximise its photovoltaic potential. The method was tested over three LiDAR datasets with different landscape topographies and urban densities. In comparison to the methods for photovoltaic arrays’ fixed optimal slope estimation, the proposed method is substantially more suitable for application in urban environments.

ACS Style

Niko Lukač; Denis Špelič; Gorazd Štumberger; Borut Žalik. Optimisation for large-scale photovoltaic arrays’ placement based on Light Detection And Ranging data. Applied Energy 2020, 263, 114592 .

AMA Style

Niko Lukač, Denis Špelič, Gorazd Štumberger, Borut Žalik. Optimisation for large-scale photovoltaic arrays’ placement based on Light Detection And Ranging data. Applied Energy. 2020; 263 ():114592.

Chicago/Turabian Style

Niko Lukač; Denis Špelič; Gorazd Štumberger; Borut Žalik. 2020. "Optimisation for large-scale photovoltaic arrays’ placement based on Light Detection And Ranging data." Applied Energy 263, no. : 114592.

Journal article
Published: 07 May 2019 in Computers & Electrical Engineering
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A lossless chain code compression algorithm consisting of Burrows-Wheeler Transform, Move-To-Front Transform, and a modified interpolative coding is presented in this paper. The interpolative coding divides a strictly increasing array of integers and encodes the middle element recursively, where the required number of bits is obtained from the difference of the array’s border values. In this paper, it is shown that, for some intervals, Golomb coding is more efficient than the interpolative coding. This fact was used to construct a hybrid approach that yields slightly better compression results than the state-of-the-art while compressing Three OrThogonal chain code, Freeman chain code in four and eight directions, and Vertex Chain Code.

ACS Style

Borut Žalik; Krista Rizman Žalik; Eva Zupančič; Niko Lukač; Mitja Žalik; Domen Mongus. Chain code compression with modified interpolative coding. Computers & Electrical Engineering 2019, 77, 27 -36.

AMA Style

Borut Žalik, Krista Rizman Žalik, Eva Zupančič, Niko Lukač, Mitja Žalik, Domen Mongus. Chain code compression with modified interpolative coding. Computers & Electrical Engineering. 2019; 77 ():27-36.

Chicago/Turabian Style

Borut Žalik; Krista Rizman Žalik; Eva Zupančič; Niko Lukač; Mitja Žalik; Domen Mongus. 2019. "Chain code compression with modified interpolative coding." Computers & Electrical Engineering 77, no. : 27-36.

Conference paper
Published: 27 February 2019 in 7th Symposium on Applied Electromagnetics SAEM`18: Conference Proceedings
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The International Symposium on Applied Electromagnetics is aimed at the presentation of research work results in various areas of Applied Electromagnetics. The Symposium is devoted to exchanging ideas, presenting achievements and results, providing the forum for researchers and academics. Open and friendly atmosphere, which our conferences are known for, encourages especially young researchers to present their achievements and ideas, even at an early stage of their research work. The Symposium continues the tradition of joint conferences, organised in previous years by the organisers from Macedonia, Poland, Slovenia and Hungary. The symposium is open for participants from all over the world. This year’s symposium took place between 17th and 20th June 2018 in Podčetrtek, Slovenia. We would like to thank all the participants for their participation at the International Symposium on Applied Electromagnetics and wish them a successful academic career. Mednarodni Simpozij o Aplikativni Elektromagnetiki je namenjen predstavitvi rezultatov raziskovalnega dela na različnih področjih aplikativne elektromagnetike. Simpozij je namenjen izmenjavi idej, predstavitvi dosežkov in rezultatov, zagotavljanju foruma za raziskovalce in akademike. Naše konference so znane po odprtem in prijaznem vzdušju, ki spodbuja zlasti mlade raziskovalce, da predstavijo svoje dosežke in ideje še v zgodnji fazi njihovega raziskovalnega dela. Simpozij nadaljuje tradicijo skupnih konferenc, ki so bile v preteklih letih organizirane v Makedoniji, Poljski, Sloveniji in Madžarski. Simpozij je odprt za udeležence iz vsega sveta. Letošnji simpozij je potekal med 17. in 20. junijem 2018 v Podčetrtku, Slovenija. Vsem udeležencem se zahvaljujemo za sodelovanje na mednarodnem simpoziju o Aplikativni elektromagnetiki in jih želimo uspešno akademsko kariero.

ACS Style

Nevena Srećković; Niko Lukač; Borut Žalik; Gorazd Štumberger. Minimization of Distribution Network Losses Using Optimal PV Installation, Reactive Power Generation and Network Reconfiguration. 7th Symposium on Applied Electromagnetics SAEM`18: Conference Proceedings 2019, 1 .

AMA Style

Nevena Srećković, Niko Lukač, Borut Žalik, Gorazd Štumberger. Minimization of Distribution Network Losses Using Optimal PV Installation, Reactive Power Generation and Network Reconfiguration. 7th Symposium on Applied Electromagnetics SAEM`18: Conference Proceedings. 2019; ():1.

Chicago/Turabian Style

Nevena Srećković; Niko Lukač; Borut Žalik; Gorazd Štumberger. 2019. "Minimization of Distribution Network Losses Using Optimal PV Installation, Reactive Power Generation and Network Reconfiguration." 7th Symposium on Applied Electromagnetics SAEM`18: Conference Proceedings , no. : 1.

Journal article
Published: 01 May 2018 in Information Sciences
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This paper considers the use of interpolative coding for lossless chain code compression. The most popular chain codes are used, including Freeman chain code in eight (F8) and four directions (F4), Vertex Chain Code (VCC), and three-orthogonal chain code (3OT). The whole compression pipeline consists of the Burrows–Wheeler transform, Move-To-Front transform and the interpolative coding, which was improved by FELICS and new Ψ-coding. The approach was compared with the state-of-the-art chain code compression algorithms. For VCC, 3OT and F4, the obtained results are slightly better than the existing approaches. However, an important improvement was achieved with F8 chain code, where the presented approach is considerably better.

ACS Style

Borut Žalik; Domen Mongus; Niko Lukač; Krista Rizman Žalik. Efficient chain code compression with interpolative coding. Information Sciences 2018, 439-440, 39 -49.

AMA Style

Borut Žalik, Domen Mongus, Niko Lukač, Krista Rizman Žalik. Efficient chain code compression with interpolative coding. Information Sciences. 2018; 439-440 ():39-49.

Chicago/Turabian Style

Borut Žalik; Domen Mongus; Niko Lukač; Krista Rizman Žalik. 2018. "Efficient chain code compression with interpolative coding." Information Sciences 439-440, no. : 39-49.

Journal article
Published: 01 January 2018 in Building and Environment
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ACS Style

Marko Bizjak; Borut Žalik; Gorazd Štumberger; Niko Lukač. Estimation and optimisation of buildings' thermal load using LiDAR data. Building and Environment 2018, 128, 12 -21.

AMA Style

Marko Bizjak, Borut Žalik, Gorazd Štumberger, Niko Lukač. Estimation and optimisation of buildings' thermal load using LiDAR data. Building and Environment. 2018; 128 ():12-21.

Chicago/Turabian Style

Marko Bizjak; Borut Žalik; Gorazd Štumberger; Niko Lukač. 2018. "Estimation and optimisation of buildings' thermal load using LiDAR data." Building and Environment 128, no. : 12-21.

Conference paper
Published: 01 January 2018 in Proceedings of the 2018 International Conference on Distance Education and Learning
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ACS Style

David Jesenko; Matej Brumen; Niko Lukač; Borut Žalik; Domen Mongus. Visualization and Analytics Tool for Multi-dimensional Data. Proceedings of the 2018 International Conference on Distance Education and Learning 2018, 11 -15.

AMA Style

David Jesenko, Matej Brumen, Niko Lukač, Borut Žalik, Domen Mongus. Visualization and Analytics Tool for Multi-dimensional Data. Proceedings of the 2018 International Conference on Distance Education and Learning. 2018; ():11-15.

Chicago/Turabian Style

David Jesenko; Matej Brumen; Niko Lukač; Borut Žalik; Domen Mongus. 2018. "Visualization and Analytics Tool for Multi-dimensional Data." Proceedings of the 2018 International Conference on Distance Education and Learning , no. : 11-15.

Journal article
Published: 01 November 2017 in Energy
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ACS Style

Sebastijan Seme; Niko Lukač; Bojan Štumberger; Miralem Hadžiselimović. Power quality experimental analysis of grid-connected photovoltaic systems in urban distribution networks. Energy 2017, 139, 1261 -1266.

AMA Style

Sebastijan Seme, Niko Lukač, Bojan Štumberger, Miralem Hadžiselimović. Power quality experimental analysis of grid-connected photovoltaic systems in urban distribution networks. Energy. 2017; 139 ():1261-1266.

Chicago/Turabian Style

Sebastijan Seme; Niko Lukač; Bojan Štumberger; Miralem Hadžiselimović. 2017. "Power quality experimental analysis of grid-connected photovoltaic systems in urban distribution networks." Energy 139, no. : 1261-1266.

Journal article
Published: 01 November 2017 in Journal of Visual Communication and Image Representation
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ACS Style

Borut Žalik; Domen Mongus; Krista Rizman Žalik; Niko Lukač. Boolean operations on rasterized shapes represented by chain codes using space filling curves. Journal of Visual Communication and Image Representation 2017, 49, 420 -432.

AMA Style

Borut Žalik, Domen Mongus, Krista Rizman Žalik, Niko Lukač. Boolean operations on rasterized shapes represented by chain codes using space filling curves. Journal of Visual Communication and Image Representation. 2017; 49 ():420-432.

Chicago/Turabian Style

Borut Žalik; Domen Mongus; Krista Rizman Žalik; Niko Lukač. 2017. "Boolean operations on rasterized shapes represented by chain codes using space filling curves." Journal of Visual Communication and Image Representation 49, no. : 420-432.

Journal article
Published: 12 September 2017 in ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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Information about the 3D structure of understory vegetation is of high relevance in forestry research and management (e.g., for complete biomass estimations). However, it has been hardly investigated systematically with state-of-the-art methods such as static terrestrial laser scanning (TLS) or laser scanning from unmanned aerial vehicle platforms (ULS). A prominent challenge for scanning forests is posed by occlusion, calling for proper TLS scan position or ULS flight line configurations in order to achieve an accurate representation of understory vegetation. The aim of our study is to examine the effect of TLS or ULS scanning strategies on (1) the height of individual understory trees and (2) understory canopy height raster models. We simulate full-waveform TLS and ULS point clouds of a virtual forest plot captured from various combinations of max. 12 TLS scan positions or 3 ULS flight lines. The accuracy of the respective datasets is evaluated with reference values given by the virtually scanned 3D triangle mesh tree models. TLS tree height underestimations range up to 1.84 m (15.30 % of tree height) for single TLS scan positions, but combining three scan positions reduces the underestimation to maximum 0.31 m (2.41 %). Combining ULS flight lines also results in improved tree height representation, with a maximum underestimation of 0.24 m (2.15 %). The presented simulation approach offers a complementary source of information for efficient planning of field campaigns aiming at understory vegetation modelling.

ACS Style

M. Hämmerle; N. Lukač; K.-C. Chen; Zs. Koma; Chi-Kuei Wang; K. Anders; B. Höfle. SIMULATING VARIOUS TERRESTRIAL AND UAV LIDAR SCANNING CONFIGURATIONS FOR UNDERSTORY FOREST STRUCTURE MODELLING. ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2017, IV-2/W4, 59 -65.

AMA Style

M. Hämmerle, N. Lukač, K.-C. Chen, Zs. Koma, Chi-Kuei Wang, K. Anders, B. Höfle. SIMULATING VARIOUS TERRESTRIAL AND UAV LIDAR SCANNING CONFIGURATIONS FOR UNDERSTORY FOREST STRUCTURE MODELLING. ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2017; IV-2/W4 ():59-65.

Chicago/Turabian Style

M. Hämmerle; N. Lukač; K.-C. Chen; Zs. Koma; Chi-Kuei Wang; K. Anders; B. Höfle. 2017. "SIMULATING VARIOUS TERRESTRIAL AND UAV LIDAR SCANNING CONFIGURATIONS FOR UNDERSTORY FOREST STRUCTURE MODELLING." ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W4, no. : 59-65.

Journal article
Published: 01 September 2017 in Environmental Modelling & Software
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ACS Style

Niko Lukač; Gorazd Štumberger; Borut Žalik. Wind resource assessment using airborne LiDAR data and smoothed particle hydrodynamics. Environmental Modelling & Software 2017, 95, 1 -12.

AMA Style

Niko Lukač, Gorazd Štumberger, Borut Žalik. Wind resource assessment using airborne LiDAR data and smoothed particle hydrodynamics. Environmental Modelling & Software. 2017; 95 ():1-12.

Chicago/Turabian Style

Niko Lukač; Gorazd Štumberger; Borut Žalik. 2017. "Wind resource assessment using airborne LiDAR data and smoothed particle hydrodynamics." Environmental Modelling & Software 95, no. : 1-12.

Journal article
Published: 22 February 2017 in IEEE Transactions on Smart Grid
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This paper proposes a parallelized online optimization of low voltage distribution network (LVDN) operation. It is performed on a graphics processing unit (GPU) by combining the optimization procedure with the load flow method. In the case study, performed for the test LVDN with distributed generators (DGs) and controllable loads, differential evolution optimization based on a backward-forward sweep load flow method was parallelized on GPU. The goal of online optimization is to keep the LVDN voltage profile within the prescribed limits, to minimize LVDN losses, and to enable demand response functionality. This is achieved by the optimization determined reference values for the controllable load's operation, and the reactive power generation, and active power curtailment of DGs. The results show that the parallelized GPU implemented optimization can be significantly faster than similar implementation on a central processing unit, and is, therefore, suitable for the online optimization of the presented LVDN.

ACS Style

Ernest Belic; Niko Lukac; Klemen Dezelak; Borut Zalik; Gorazd Stumberger. GPU-based Online Optimization of Low Voltage Distribution Network Operation. IEEE Transactions on Smart Grid 2017, 8, 1 -1.

AMA Style

Ernest Belic, Niko Lukac, Klemen Dezelak, Borut Zalik, Gorazd Stumberger. GPU-based Online Optimization of Low Voltage Distribution Network Operation. IEEE Transactions on Smart Grid. 2017; 8 (3):1-1.

Chicago/Turabian Style

Ernest Belic; Niko Lukac; Klemen Dezelak; Borut Zalik; Gorazd Stumberger. 2017. "GPU-based Online Optimization of Low Voltage Distribution Network Operation." IEEE Transactions on Smart Grid 8, no. 3: 1-1.

Journal article
Published: 01 July 2016 in Journal of Visual Communication and Image Representation
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This paper introduces a new chain code named Unsigned Manhattan Chain Code – UMCC. Although it exploits a pixel’s neighbourhood of 8-connectivity, only two coding symbols are used for navigating through the geometric shape’s boundary pixels. For this, the movements in the xx- and yy-coordinate direction are separated, whilst the sign of the moving direction is controlled by two flags – one for each coordinate direction. UMCC is insensitive to rotation and mirroring and enables shape magnification. However, the more unique property is the UMCC’s ability to explicitly separate the monotonic parts of the geometric shape. UMCC’s properties have been compared against the properties of other chain codes including the Freeman chain code in eight and four directions, the Vertex Chain Code, and the Three OrThogonal chain code. It has been shown that the UMCC has superior properties in regards to the up-to-date chain codes.

ACS Style

Borut Žalik; Domen Mongus; Yong-Kui Liu; Niko Lukač. Unsigned Manhattan chain code. Journal of Visual Communication and Image Representation 2016, 38, 186 -194.

AMA Style

Borut Žalik, Domen Mongus, Yong-Kui Liu, Niko Lukač. Unsigned Manhattan chain code. Journal of Visual Communication and Image Representation. 2016; 38 ():186-194.

Chicago/Turabian Style

Borut Žalik; Domen Mongus; Yong-Kui Liu; Niko Lukač. 2016. "Unsigned Manhattan chain code." Journal of Visual Communication and Image Representation 38, no. : 186-194.

Journal article
Published: 01 July 2016 in Energy
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Within the last few years, the increase of the world's energy consumption has substantially impacted the environment. Solar energy initiative is more than ever involved to tackle this issue, especially when deploying PV (photovoltaic) systems over large-scale residential areas. However, not all surfaces in these areas are economically suitable, while some surfaces have low CO2 mitigation. With the availability of high-resolution remote sensing data, the estimation of suitable rooftops for PV systems installation can be performed automatically by estimating the PV potential. This paper presents a novel method for estimating NPV (net present value) of the potential PV systems installed on rooftops by using LiDAR (Light Detection And Ranging) data and PV systems' nonlinear efficiency characteristics. More importantly, the environmental impact is estimated for each rooftop through EPBT (energy payback time) and GGER (greenhouse gas emission rate), based on the life-cycle of a specific PV system. This is combined with NPV in order to find rooftops that are both economically and environmentally viable candidates for PV systems deployment. Results demonstrate a case study LiDAR data for predicting each building's economical and environmental impact, as well as providing an overall view of resulting cumulative CO2 mitigation over large residential area.

ACS Style

Niko Lukač; Sebastijan Seme; Katarina Dežan; Borut Žalik; Gorazd Štumberger. Economic and environmental assessment of rooftops regarding suitability for photovoltaic systems installation based on remote sensing data. Energy 2016, 107, 854 -865.

AMA Style

Niko Lukač, Sebastijan Seme, Katarina Dežan, Borut Žalik, Gorazd Štumberger. Economic and environmental assessment of rooftops regarding suitability for photovoltaic systems installation based on remote sensing data. Energy. 2016; 107 ():854-865.

Chicago/Turabian Style

Niko Lukač; Sebastijan Seme; Katarina Dežan; Borut Žalik; Gorazd Štumberger. 2016. "Economic and environmental assessment of rooftops regarding suitability for photovoltaic systems installation based on remote sensing data." Energy 107, no. : 854-865.

Journal article
Published: 01 June 2016 in Digital Signal Processing
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This paper considers the suitability of string transformation techniques for lossless chain codes' compression. The more popular chain codes are compressed including the Freeman chain code in four and eight directions, the vertex chain code, the three orthogonal chain code, and the normalised directional chain code. A testing environment consisting of the constant 0-symbol Run-Length Encoding (RLE0L), Move-To-Front Transformation (MTFT), and Burrows–Wheeler Transform (BWT) is proposed in order to develop a more suitable configuration of these techniques for each type of the considered chain code. Finally, a simple yet efficient entropy coding is proposed consisting of MTFT, followed by the chain code symbols' binarisation and the run-length encoding. PAQ8L compressor is also an option that can be considered in the final compression stage. Comparisons were done between the state-of-the-art including the Universal Chain Code Compression algorithm, Move-To-Front based algorithm, and an algorithm, based on the Markov model. Interesting conclusions were obtained from the experiments: the sequential uses of MTFT, RLE0L, and BWT are reasonable only in the cases of shorter chain codes' alphabets as with the vertex chain code and the three orthogonal chain code. For the remaining chain codes, BWT alone provided the best results. The experiments confirm that the proposed approach is comparable against other lossless chain code compression methods, while in total achieving higher compression rates.

ACS Style

Borut Žalik; Domen Mongus; Krista Rizman Žalik; Niko Lukač. Chain code compression using string transformation techniques. Digital Signal Processing 2016, 53, 1 -10.

AMA Style

Borut Žalik, Domen Mongus, Krista Rizman Žalik, Niko Lukač. Chain code compression using string transformation techniques. Digital Signal Processing. 2016; 53 ():1-10.

Chicago/Turabian Style

Borut Žalik; Domen Mongus; Krista Rizman Žalik; Niko Lukač. 2016. "Chain code compression using string transformation techniques." Digital Signal Processing 53, no. : 1-10.

Journal article
Published: 01 February 2016 in Energy
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Proliferation of distributed generation units, integrated within the distribution network requires increased attention to their proper placements. In urban areas, buildings' rooftops are expected to have greater involvement in the deployment of PV (photovoltaic) systems. This paper proposes a novel procedure for determining roof surfaces suitable for their installation. The PV potential of roof surfaces is assessed based on Light Detection And Ranging (LiDAR) data and pyranometer measurements. Then, the time-dependent PV generation profiles, electricity distribution network configuration, and time-dependent loading profiles are used together over time-steps for selecting those roof surfaces with the highest PV potential, which would lead to the highest reduction of network losses per year. The presented procedure was implemented within a real urban area distribution network. The results obtained confirmed that PV potential assessment could be an insufficient criterion when selecting those roof surfaces suitable for the installation of PV systems. In order to obtain relevant results, network configuration and time-dependent loading and generation profiles must be considered as well.

ACS Style

Nevena Srećković; Niko Lukač; Borut Žalik; Gorazd Štumberger. Determining roof surfaces suitable for the installation of PV (photovoltaic) systems, based on LiDAR (Light Detection And Ranging) data, pyranometer measurements, and distribution network configuration. Energy 2016, 96, 404 -414.

AMA Style

Nevena Srećković, Niko Lukač, Borut Žalik, Gorazd Štumberger. Determining roof surfaces suitable for the installation of PV (photovoltaic) systems, based on LiDAR (Light Detection And Ranging) data, pyranometer measurements, and distribution network configuration. Energy. 2016; 96 ():404-414.

Chicago/Turabian Style

Nevena Srećković; Niko Lukač; Borut Žalik; Gorazd Štumberger. 2016. "Determining roof surfaces suitable for the installation of PV (photovoltaic) systems, based on LiDAR (Light Detection And Ranging) data, pyranometer measurements, and distribution network configuration." Energy 96, no. : 404-414.