Volume 71 (2020): Issue 2 (April 2020)

The article analyzes available methods for preventing acoustic resonance of high pressure lamps. A new method is proposed, the main idea of which is the filing of a high-voltage lamp modulated by a pseudo-random signal. An analysis of the spectral characteristics of the signal entering the lamp is made, the mathematical modeling of the set of a “discharge lamp - prototype of the device” - is implemented, which implements the proposed control method of the lamp. The results of simulation and oscillograms, taken from the prototype, which confirms the results of theoretical research, are presented.

Quality of speech synthesis is a crucial issue in comparison of various text-to-speech (TTS) systems. We proposed a system for automatic evaluation of speech quality by statistical analysis of temporal features (time duration, phrasing, and time structuring of an analysed sentence) together with standard spectral and prosodic features. This system was successfully tested on sentences produced by a unit selection speech synthesizer with a male as well as a female voice using two different approaches to prosody manipulation. Experiments have shown that for correct, sharp, and stable results all three types of speech features (spectral, prosodic, and temporal) are necessary. Furthermore, the number of used statistical parameters has a significant impact on the correctness and precision of the evaluated results. It was also demonstrated that the stability of the whole evaluation process is improved by enlarging the used speech material. Finally, the functionality of the proposed system was verified by comparison of the results with those of the standard listening test.

The paper presents the concept of installation of an electricity generator and en energy store inside a roller of belt or roller conveyor. Accordingly, the use of a generator-pulley does not require any structural changes to be made to an existing conveyor. In addition, the user will be able to power distributed sensors network for monitoring the operation of the belt conveyor anywhere on its route.

To detect the number of agents needed to serve customers, it is necessary to consider the call centre as a mass service system. Then it is possible to asses the convenient number of agents according to the probability of the system receiving a request and the time in which the request is serviced by employing a Markov chain and the Erlang model. In an archetypal call centre, the incoming calls are added to a waiting queue and subsequently they are assisted by an agent. In case all agents are occupied, the customer has to wait in the queue until one of the agents becomes available. It is, therefore, important to compromise on the number of agents and the time the customers spend waiting in the queue. The result should be that there are enough agents in the call centre to serve the customers in the time required. This article focuses on solving this problem.

A mobile users’ network with power control on traffic channels, as it is GSM, is considered in this paper. It is analyzed the influence of busy channels reallocation on the necessary emission power. The main principle in reallocation is that users who need greatest power for their connections take traffic channels of the first carrier where power is always maximum. It is assessed that reallocation process is not more complicate than the simplest handover processes. It is proved that this method may be used to decrease emission power of carriers after the second one. Power saving depends on number of carriers, environmental propagation coefficient and users’ density distribution in the cell. The results are verified by originally developed simulation program.

A hairpin shaped DGS, consisting of two tilted slots with a separation angle, is studied as a unit cell in this contribution. It is further served as a microwave resonator for microstrip lowpass filter applications. Two prototype filters that respectively cascade the same unit cells and the scaled cells with a different scale ratio are analyzed. For demonstration purposes, the two prototype filters are optimally developed, fabricated and examined both from numerical simulations and from experimental validations. Results show the cascaded scaled type demonstrator features a high stopband suppression level within a wide frequency band.

This paper presents the design and control of power electronic synchronous buck converter. Even though a synchronous buck converter is more popular and more widely available, it is not always efficient as nonsynchronous. Firstly, the inputoutput linearization from the state space averaging of the converter is studied, after which a small AC signal analysis is introduced to obtain the dynamic transfer function. All the parameters of the converter are calculated based on the output voltage, current ripples as well as the input voltage. For robustness, the controller is implemented by comparing the response of integer order with non-integer (fractional) order controller, simply known as fractional order controller (FOC). The fractional order derivative is implemented from the Oustaloup approximation and the controller parameters are being tuned using Nelder Mead approximation bases on a system model. It is shown that the FOC performance is comparatively better in presence of the load disturbances and parameter variations. The experimental study with the real-time fractional PI is possible to make for a stand-alone embedded application using FPAA. The proposed technique does not require any digitization of the signal, so it can be easy to implement with improved performance. The effectiveness of the analog controller is discussed, giving some future directions to adopt the new fractional controller.

A single inverted pendulum on a cart (SIPC) is designed and modeled physically using SolidWorks. The model is then exported to the Simulink environment to form a Simscape model for simulation and test purposes. This type of modeling uses a physical grid tactic to model mechanical structures. It requires connection of the physical elements with physical signal converter to define the implicit system dynamics to be modeled. The integration between the SolidWorks and Simscape eliminates the need of deriving the mathematical model and provides a platform for the rapid controller design for the system. State feedback control scheme is proposed, designed, and tuned aiming to maintain the pendulum in the upright place while tracking the desired cart position. Several simulation cases are studied to prove the controller abilities. In order to examine the controller robustness, disturbance rejection and noise attenuation capabilities are also discovered.

The paper describes the development and production of a nano-optical device consisting of a nano-perforated layer of silicon nitride stretched in a single-crystal silicon frame using electron beam lithography (EBL) and reactive ion etching (RIE) techniques. Procedures for transferring nanostructures to the nitride layer are described, starting with the preparation of a metallic mask layer by physical vapor deposition (PVD), high-resolution pattern recording technique using EBL and the transfer of the motif into the functional layer using the RIE technique. Theoretical aspects are summarized including technological issues, achieved results and application potential of patterned silicon nitride membranes.

The 5G cellular network technology, in collaboration with Internet of Things (IoT), is envisaged to connect the world together through a flawless Internet connection between devices and sensors. The things in IoT term can be of any smart devices or Internet-enabled sensors that can share information in order to perform a task collectively or individually. On the other hand, Cognitive Internet of Things plays a vital role in utilizing available spectrum for 5G networks. Addition of cognitive feature to the things can allow decision making capability, thereby reducing the overall traffic congestion and improving the efficiency of the whole IoT system. Therefore, it is of great concern to develop an intelligent network to address a few challenges such as heterogeneity and volume of devices in 5G. The aim of this article is to provide a critical review of existing IoT communication Technologies and highlight several challenges and their potential solutions associated with Cognitive IoT based 5G networks.