Jugoslav Jokovic

Neural network based optical character recognition system

This paper presents an application of a neural network in the optical character recognition (OCR) system. It introduces general architecture of modern OCR systems, discussing each module in detail. Specific contribution of this paper is novelty of the character extraction and segmentation, by considering them as image features. MSER (Maximally Stable Extremal Regions) feature detector is applied, discussing numerical and practical restrictions for character segmentation and recognition. The neural network is trained for character recognition and applied on the appropriate example.

TLM analysis of the inverted microstrip patch antenna in a cylindrical grid

3-D TLM approach based on the cylindrical grid and enhanced with the compact wire model has been used for modelling of an inverted circular microstrip patch (IMCP) antenna with the coaxial feed. The simulated results have been compared with the measured results and rectangular grid based TLM results. Additional, the influence of the air gap height on the resonant frequency of the IMCP antenna has been explored.

Scene cut detection in video by using combination of spatial-temporal video characteristics

For the mainstream hard cut scene detection algorithm based on the color-histogram difference new criteria are added to increase precision and improve computational efficiency. This approach utilizes additional detection criterion based on spatial distribution of luminance blocks difference during scene cut. Also, in order to improve computational efficiency, time sampling at larger time resolutions and detection at smaller time resolutions is used. On the different video examples the results in precision and reliability are given.

Analysis of real feed probe influence to the resonant frequencies and field distribution in the cylindrical metallic cavity using 3D TLM method

For the example of the cylindrical metallic cavity with circular cross-section, the real excitation modeling, using TLM wire node, is presented. The small wire conductor, as an excitation form, is used according to the wanted type of mode in the cavity. The modeling process is described and the obtained TLM numerical results are compared with the experimental ones, to the aim of verification of the method. Besides, the influence of length and radius of real feed probe to the resonant frequencies of TM and TE modes in frequency range f=[1.5-3.5] GHz is analysed. TLM results, in the case of empty cavity with real excitation probe, are compared with results calculated by using the theoretical approach, that is TLM simulator with impulse excitation. Finally, field strength versus length of real feed probe are investigated and the appropriate conclusions are given.

Advantages of using integral cylindrical TLM method for modelling of coax-fed microstrip circular antenna

The purpose of this paper is to investigate accuracy and advantages of the TLM method in a cylindrical grid enhanced with the compact wire model when the subject of modelling is a circular patch antenna with a coaxial feed. Obtained results representing S11 parameter are compared with corresponding results reached by the rectangular grid based TLM method for different mesh resolutions as well as with referenced measured results.

TLM cylindrical model of a coaxially loaded cylindrical cavity

This paper explores the effectiveness of the TLM method based on the cylindrical grid for the purpose of an analysis of a cavity with a circular cross-section and coaxial load. To consider the advantages of the cylindrical over rectangular TLM grid, coaxial inner load with different dielectric properties and dimensions have been used. Obtained numerical results have been verified comparing with corresponding analytic and measured results.

EM field monitoring in circular cavity using wire compact model implemented in cylindrical TLM mesh

This paper presents the procedure of compact wire model implementation in the 3-D TLM cylindrical mesh. It is based on the wire structures parameters calculation in conditions of variable cross-section of the TLM nodes through which wire conductor passes due to nature of cylindrical grid along the wire path. Efficiency of the wire model adapted to cylindrical mesh has been carried out on the example of a circular cylindrical metallic cavity when an EM field is excited and detected via wire probes. Obtained numerical results representing reflection and transmission characteristics have been compared with the results reached by TLM method based on a rectangular grid and experimental results. Model advantages in terms of analysis of cavity resonant frequency dependence of a feed probe radius have been considered.

Real excitation modeling in a loaded cylindrical metallic cavity using 3-D TLM method

The example of a cylindrical metallic cavity with a rectangular cross section loaded with a dielectric slab placed on the bottom of the cavity, real excitation modeling, using the transmission-line modeling (TLM) wire node, is presented. We use a small wire conductor, as an excitation form, according to the wanted type of mode in the cavity. Also, a small wire conductor as a receiving probe is modeled. Water at a temperature of 20/spl deg/, is used as a dielectric layer. Its relative dielectric constant is calculated from Debbys formula. The modeling process is described and the numerical results obtained are compared with the results calculated by using the theoretical approach based on the transverse resonance (TR) method, and the experimental results and the appropriate conclusions are given.

Efficient Modeling of a Circular Patch-Ring Antenna Using the Cylindrical TLM Approach

This letter addresses the ability of the TLM method with an incorporated compact wire model, both adjusted to the cylindrical grid, to accurately model a coaxially fed patch-ring antenna together with an investigation of the computational efficiency in a modeling procedure. Design of the antenna has included an optimization of the coaxial feed location to achieve a wider bandwidth. A prototype of the antenna was fabricated and measured. It has been shown that the patch-ring antenna exhibits more than three times wider bandwidth than the classic circular patch antenna. Advantages of the cylindrical-grid-based TLM approach related to a better conformity of the orthogonal polar mesh with the structure being modeled and a better efficiency associated with a number of TLM cells in the modeling procedure have been demonstrated with regards to the rectangular-grid-based TLM method. Also, a limitation of the rectangular solver related to an inadequate modeling of narrow slots that is dependent on the mesh resolution applied has been accentuated and proved.

Characterization of EM field in the probe-coupled cavity resonator using the cylindrical TLM solver

This paper investigates applicability of the in-house solver based on the TLM method adapted to the cylindrical grid and improved with the compact wire model for the purpose of EM field characterization using a number of radially placed wire probes within cylindrical cavity resonator. Both an empty and a coaxially loaded cavity have been investigated.