Volume 67 (2016): Issue 6 (December 2016)

In this paper we analyze the influence of users’ density distribution in one cell of CDMA mobile network (ie adjusted power control on the forward link) on base station emission power. This influence is analyzed for different circles radii around base station within which same emission power is generated for all mobile users, and for different values of propagation loss coefficient. It is proved that emission power in this cell must be increased comparing to the similar cell, which uses complete power control. The power increase is greater when greater number of users are situated near base station, and for greater values of propagation loss coefficient. The results are presented, illustrated by numerical examples and verified by simulation for three users’ density distributions: uniform, decreasing and increasing density from the base station to the cell rim. The simulation process, which is based on random traffic process, is presented briefly.

The first step in the transformer design process is to find the active part’s key design parameters. This is a non-linear mathematical optimisation task, which becomes more complex if the economic conditions are considered by the capitalisation of the losses. Geometric programming combined with the method of branch and bound can be an effective and accurate tool for this task even in the case of core-form power transformers, when formulating the short-circuit impedance in the required form is problematic. Most of the preliminary design methods consider only the active part of the transformer and the capitalised costs in order to determine the optimal key design parameters. In this paper, an extension of this meta-heuristic transformer optimisation model, which takes the cost of the insulating oil and the cooling equipment into consideration, is presented. Moreover, the impact of the new variables on the optimal key design parameters of a transformer design is examined and compared with the previous algorithm in two different economic scenarios. Significant difference can be found between the optimal set of key-design parameters if these new factors are considered.

This article deals with non-destructive evaluation of austenitic stainless steels, which are used as the biomaterials in medical practice. Intrinsic magnetic field is investigated using the fluxgate sensor, after the applied plastic deformation. The three austenitic steel types are studied under the same conditions, while several values of the deformation are applied, respectively. The obtained results are presented and discussed in the paper.

PDMS (polydimethylsiloxane) collapse method is a simple and low cost approach for micronanochannel fabrication. However, the bonding pressure which influences the size of the final PDMS micro/nanochannels has not yet been studied. In this study, the effect of the bonding pressure on the size and maximum local stress of the PDMS micronanochannels was investigated by both experimental and numerical simulation method. The results show that when the bonding pressure is lower than 0.15 MPa the experiment results can agree well with the simulation results. The fluorescent images demonstrate that there is no blocking or leakage over the entire micro/nanochannels.

In this paper, the analysis of ice-shedding from ACSR conductors to its swing up height and vibration using Finite Element Method (FEM) is presented. For the numerical simulations the effective material properties of the ACSR conductor are calculated using the homogenisation method. Numerical analysis concerning vibration of one and triple-bundle conductors with icing for a whole range or on their certain parts are performed. The impact of ice-shedding to the mechanical tension in the conductors at the points of attachment is investigated and evaluated. Identification of the impact of ice-shedding from the ACSR conductors on its mechanical state may contribute to increasing the safety and quality of an electrical transmission system.

A detailed numerical study on structure of symmetric tilt grain boundaries in α-iron is presented. The study is focused on structural and energetic optimization of 〈100〉 grain boundaries Σ5(210), Σ5(310), Σ17(410) and Σ13(510). Particular attention is given to grain boundary reconstruction, which is characterized by increased atomic density in grain boundary plane compared to bulk. The results of our numerical experiments significantly improved our knowledge about the migration of atoms between planes perpendicular as well as parallel to GB plane as an essential part of grain boundary reconstruction.

In this paper a new structure of digital clock recovery — DCR circuit is presented. The main features of this DCR are: low complexity design, low power consumption and a single system clock operation. Thus, multiple instantiation of this type of DCR on a single chip is not complex. Due to this, such DCR can target application in energy-efficient cognitive radio systems with carrier aggregation. For performance evaluation, we have derived Markov chain based mathematical model for peak-to-peak and root mean square jitter performance analysis. The stability problem of this model, rising from the fact that some phase error states have several orders of magnitude lower probabilities than the others, is solved using mathematical apparatus for symbolic analysis. The mathematical model validity is examined by laboratorial measurements of proposed DCR for 4-PAM signal. The measurement methodology and results are described in details.

To improve the performance of inverse synthetic aperture radar (ISAR) imaging based on compressed sensing (CS), a new algorithm based on log-sum minimization is proposed. A new interpretation of the algorithm is also provided. Compared with the conventional algorithm, the new algorithm can recover signals based on fewer measurements, in looser sparsity condition, with smaller recovery error, and it has obtained better sinusoidal signal spectrum and imaging result for real ISAR data. Therefore, the proposed algorithm is a promising imaging algorithm in CS ISAR.

The duality transformation was used to define the polarization mechanisms that arise from magnetic monopoles. Then, a dimensional analysis was conducted to describe the displacement and magnetic intensity vectors (constitutive equations) in SI units. Finally, symmetric Maxwell equations in a material medium with new field quantities were introduced. Hence, the Lorentz force and the Poynting theorem were defined with these new field quantities, and many possible definitions of them were constructed.

In this paper a tuning structure for a MOSFET?RC filters is presented. The proposed tuning structure is composed of switched resistor banks with voltage controlled transistors. The voltage controlled transistors use active feedback with extended control range for continuous filter parameter tuning, without degrading the total linearity performance of the filter. The proposed tuning structure is tested by implementing it in a second order low pass biquadratic filter cell in 65 nm CMOS technology. The designed filter has a highly reconfigurable response, ranging from Chebyshev to Bessel, a tuneable -3 dB bandwidth from 10 MHz to 100 MHz and can be used for multiple standard wireless solutions. Filter IIP3 performance is not degraded when the bandwidth is continuously tuned by 40 % with a 1 V pp input. The maximum power dissipation, including active feedback circuits, is 17.2 mW from a 1.2 V source when the filter is tuned to 100 MHz bandwidth.

Patterning of metal oxide nanostructures with different shapes and well-defined size may play an important role in the improvement of MEMS systems, sensors and optical devices. We investigated the effects of HSQ e-beam resist processing on the fabrication of sputtered TiO₂ nanostructures. They were patterned using direct write e-beam lithography combined with ICP-RIE etching in CF₄/Ar plasma. Experimental results confirmed that the HSQ resist with a thickness of about 600 nm is suitable as a masking material for optimal etching process and allows patterning of the dots array in TiO₂ sputtered films with a thickness up 150 nm. TiO₂ arrays with a minimal dots diameter of 180 nm and spacing of 1000 nm were successfully developed.

This paper deals with pulse signals influenced by loss of energy in high frequency band. Five types of pulses were tested and evaluated under various conditions. Achieved results can be helpful for some specific tasks in signal transmission. An example presents highest frequency of periodic pulse signals processed on printed circuit board.