Ondrej Kovac

Ultra-wearable capacitive coupled and common electrode-free ECG monitoring system

Nowadays, transfer of the health care from ambulance to patients home needs higher demand on patients mobility, comfort and acceptance of the system. Therefore, the goal of this study is to proof the concept of a system which is ultra-wearable, less constraining and more suitable for long term measurements than conventional ECG monitoring systems which use conductive electrolytic gels for low impedance electrical contact with skin. The developed system is based on isolated capacitive coupled electrodes without any galvanic contact to patients body and does not require the common right leg electrode. Measurements performed under real conditions show that it is possible to acquire well known ECG waveforms without the common electrode when the patient is sitting and even during walking. Results of the validation process demonstrate that the system performance is comparable to the conventional ECG system while the wearability is increased.

Investigation of nano-inks’ behaviour on flexible and rigid substrates under various conditions

Purpose This paper aims to find the optimal deposition conditions for achieving the homogenous structure of the silver layers onto three types of polymeric substrates as well as on the rigid substrates. For this reason, the detailed investigation of the silver-based layers deposited at different technological conditions by microscopic methods is presented in this paper. Design/methodology/approach The special test pattern has been designed and deposited at different substrate temperatures by using two types of generally available silver-based nano-inks. Cross-sections and 3D profiles of the deposited silver layers have been profoundly analysed by using the optical profiler Sensofar S Neox on the generally used polymeric (PI, PET and PEN) and rigid substrates (951 and 9K7 LTCC, glass and alumina). Findings The results prove the strong correlation between the substrate temperature during the deposition process and the final shape of the created structure which has the a direct impact on the layers’ homogeneity. The results also prove the theory of the coffee ring effect creation in the inkjet printing technology. Originality/value The main benefit of this paper lies in the possibility of the homogeneity achievement of the deposited silver-based layers on the several polymeric and rigid substrates by managing the temperature during the deposition. The paper also offers the comparative study of nano-inks’ behaviour on several polymeric and rigid substrates.

Image steganography with using QR code and cryptography

This paper is focused on proposal of image steganographic method that is able to embedding of encoded secret message using Quick Response Code (QR) code into image data. Discrete Wavelet Transformation (DWT) domain is used for the embedding of QR code, while embedding process is additionally protected by Advanced Encryption Standard (AES) cipher algorithm. In addition, typical characteristics of QR code was broken using the encryption, therefore it makes the method more secure. The aim of this paper is design of image steganographic method with high secure level and high non-perceptibility level. The relation between security and capacity of the method was improved by special compression of QR code before the embedding process. Efficiency of the proposed method was measured by Peak Signal-to-Noise Ratio (PSNR) and achieved results were compared with other steganographic tools.

Influence of firing profile on microstructural and dielectric properties of LTCC substrates

Purpose The purpose of this paper is to analyse the influence of various firing profiles on microstructural and dielectric properties of low-temperature, co-fired ceramic (LTCC) substrates in a GHz frequency range. According these analyses, sintering process can be controlled and modified to achieve better performance of devices fabricated from LTCC substrates. Design/methodology/approach Samples from LTCC substrates GreenTape 951 and GreenTape 9K7 were sintered by four firing profiles. Basic firing profile recommended by the manufacturer was modified by increasing the peak temperature or the dwell time at the peak temperature. The influence of firing profile on microstructural properties was analysed according to measurements by X-ray diffractometer (application of the Cu K-alpha radiation and the Bragg-Brentano method), and the influence on dielectric properties (dielectric constant and dielectric losses) was analysed according to measurements by split cylinder resonator method at 9.7 and 12.5 GHz. Findings Rising of the peak temperature or extension of dwell time at this temperature has influence on all analysed properties of LTCC substrates. Size of crystallites can be changed by modification of firing profile as well as microdeformation. In addition, dielectric properties can be changed too by modification of the firing profile. Correlation between microdeformation and dielectric losses was observed. Originality/value The novelty of this work lies in finding the mutual relationship between changes in microstructural (size of grains and microdeformation) and dielectric properties (dielectric constant and dielectric losses) caused by different firing profiles.

Improvement of the evaluation of inkjet printed silver based layers’ adhesion

Abstract This paper presents the improved method of analysis and evaluation of the silver layers’ adhesion printed by inkjet printing technology. The generally known method for adhesion measurement of layers and coatings according to the standards ASTM D3359 and ISO 2409 has been improved by development of the automatic evaluation software of achieved results from cross cut tests. The developed evaluation tool offers the possibilities of calculation the detached area, rotation of the image, setting the threshold and the automatic classification according to the mentioned standards. The inaccuracy caused by samples’ assessment by humans is mainly eliminated by using of this tool. The developed evaluation tool has been applied to experimental works oriented to analysis of the adhesion of two commercially available silver based nano-inks on two polymeric based substrates (PI and PET). For this purpose, different sintering conditions have been applied to analysed samples. The achieved results show the differences between the investigated nano-inks’ adhesion on two types of polymeric substrates. The adhesion of silver layers can be optimized by controlling the sintering conditions. By developing the software tool the simple and inaccurate method of adhesion analysis has been upgraded to the appropriate technique to the silver layers’ adhesion testing. The improved method for adhesion measurements can serve as a tool for fast and relatively simple technique for technologist.

Convolution implementation with a novel approach of DGHM multiwavelet image transform

Abstract The purpose of this paper is to develop convolution implementation of DGHM (Donovan, Geronimo, Harding, Massopust) multiwavelet image transform using a new approach of ordering wavelet coefficients at the second and higher levels. Firstly, the method of implementation of one-dimensional discrete multiwavelet transform (1D DMWT) for DGHM multiwavelet using discrete convolution and scalar filters is presented. Then, convolution implementation of DGHM multiwavelet image transform by application of 1D DMWT for two dimensions (2D) in a separable way is proposed. Next, the second level of 2D DMWT is performed in three possible ways. The novelty of the proposed implementation is in reordering of L subband wavelet coefficients at the first level into one subimage. The results are evaluated as the energy ratios between the transformed images in L subband at the second level and the input original image. According to the experimental results, the developed implementation of 2D DMWT is approximately 5% more effective in energy compression than the ones most commonly mentioned in the literature. This paper shows a possibility of convolution implementation of 2D DMWT with higher energy compression.

Influence of accelerating ageing on LTCC and PCB substrates' dielectric properties in GHz area

This paper is focused on investigating stability of dielectric properties, dielectric constant and loss tangent, after exposing dielectric materials to accelerated ageing tests. Two types of Low Temperature Co-fire Ceramics (LTCC) substrates and four types of printed circuit boards (PCB) substrates were exposed to temperature loads. DuPont GreenTape 951 and DuPont GreenTape 9K7 represent LTCC substrates and Rogers 3003C, Rogers 4003, Rogers RT/duroid 5880 and Rogers RT/duroid 6010/LM represent PCB substrates. Thermal shock chamber and temperature humidity chambers provided two types of accelerating ageing test, temperature cycling and High Temperature Operation Life (HTOL) tests. Dielectric properties of these LTCC and PCB substrates were measured by combination of Vector Network Analyzer (VNA) and split cylinder resonator. This measuring method provided dielectric properties at two frequencies, which depend on concrete material, the first frequency is around 10 GHz and second about 12.5 GHz. Preliminary results show better stability of LTCC substrates after accelerating ageing test. It is caused by composition of these substrates which minimalizes moisture absorption, because moisture has major impact on degradation of dielectric properties.