Dariusz Czerwinski

Analysis of Alternating Overcurrent Response of 2G HTS Tape for SFCL

The scope of this article was to find the transient response of the 2G high-temperature superconducting (HTS) tape under alternating overcurrent. The authors performed a series of measurements for the SF12050 HTS tape produced by SuperPower Inc. The tape was fed by a 50-Hz ac voltage source with adjustable amplitude. The temporal dependences of the tape current and voltage drops in each test segment were recorded simultaneously. The measurements were performed for the current amplitudes exceeding the critical value specified by the manufacturer ( Ic = 270 A @77 K, self-field). The instantaneous values of the tape temperature during overcurrent transient period were also determined. Additionally, the numerical analysis of the SF12050 tape was performed. A numerical model was built using PSPICE environment. The model assumes the nonlinear dependence of tape parameters in the function of temperature, as well as the variable cooling conditions during transient state. The constructed model was verified with measurement results.

Influence of the VM Manager on Private Cluster Data Mining System

In this paper the comparative analysis of the impact of the virtual machine manager on the Private Cluster Data Mining System performance was shown. The idea of the research is comparison of the performance of Data Mining System under different VM’s and different operating systems. In this article the results obtained in a test environment, based on the Ubuntu Desktop 13.10 x64 used as host OS and Cloudera Hadoop distribution used as personal cluster guest OS, were shown. The main focus of the research is the hypervisor impact on the typical operations in data mining system, such as parallelized calculation, file system operations and the use of CPU resources.

Digital Filter Implementation in Hadoop Data Mining System

Paper presents Savitzky-Golay digital filter implementation using the R software environment in private Hadoop Data Mining System. The idea of the research was the implementation of the digital filter to handle big data came from measurements. The study focused on proper filter implementation and comparison of the results with National Instruments Diadem – enterprise class system for data management and mining.

Resource Management in Grid Systems

The management of resources in the grid networks becomes complex task. The reason for this is that grids are heterogeneous, distributed and owned by different organizations environments. Each solution has own policies of resource management and different cost models. This paper contains a discussion of the issues related to resource management in grid systems on the basis of XtreemOS grid. The purpose of this study is the analysis of cost model of network management in distributed environments. The results of performed tests demonstrate how the Resource Management System (RMS) behaves under different operating conditions.

Numerical Performance in the Grid Network Relies on a Grid Appliance

The author of this paper will introduce the issues related to performance of the numerical calculations carried out on non-homogeneous Grid network. Created Grid Network is running the Grid Appliance, which is based on a network operating system Ubuntu 9.04. The author performed the series of tests of this system. Performed tests demonstrated how the single node is working under different Grid configurations as well as what is the efficiency of the numerical calculations in a Grid network.

Path Loss Model for a Wireless Sensor Network in Different Weather Conditions

The paper presents path loss model for a WSN in an open space on the basis of measurements. The measurements were performed in different weather conditions i.e. temperature and humidity in agricultural area. Theoretical path loss models are always flawed because of their exponential relationship. This causes an increase in error during the localization process. Thus, the determination of the path loss exponent constant based on measurement results become so important. The study focused on designation of the path loss model for different weather conditions. The influence of the temperature and the humidity on the RSSI distribution was analysed.

Comparison of Overcurrent Responses of 2G HTS Tapes

In this paper, the comparison of transient responses of second-generation (2G) high-temperature superconducting (HTS) tapes under alternating overcurrent was presented. The authors performed the series of measurements of the SF4050 and SCS4050 HTS tapes produced by Superpower Co. The measurements were carried out for various amplitudes of current exceeding a critical value given by the manufacturer (Ic = 100 A, dc, @77 K, self-field). Seven measuring probes were soldered to each tape, which allow for simultaneous recording of the supplying current and voltage in each test segment. Tapes were immersed in liquid nitrogen bath under atmospheric pressure and supplied from the 50-Hz voltage source with adjustable amplitude. Numerical models of SF4050 and SCS4050 tapes were build using PSPICE environment. The models assume the nonlinear dependence of tape parameters in the function of temperature and the variable cooling conditions during transient state. The numerical results were compared with the measurements, and good correlation was achieved. Elaborated models allow for the calculation of the overcurrent responses of 2G HTS tapes with and without copper shunts.

RSSI-Based Localisation of the Radio Waves Source by Mobile Agents

The paper presents a practical realisation of the localisation of a radio wave source. The system is based on the RSSI principle and uses a set of blind mobile agents. The main goal of the research was to implement the localisation system of the root node in WSN on the low-cost autonomous mobile embedded platform. This platform has a limited ability for complex mathematical operations, therefore more easy algorithms should be used. The study focused on implementation of movement algorithms and exchanging the knowledge between blind agents. In the solution described the gradient search path algorithm was implemented.

QoE-Oriented Fairness Control for DASH Systems Based on the Hierarchical Structure of SVC Streams

Nowadays, multimedia content is the basis of most popular network services. At the same time, adaptive video streaming is becoming more widely used method for delivering such content to end users. The main purpose of the mechanisms of adaptation is to maximize the usage of network resources while ensuring the best quality of transmitted video. The implementation of adaptation, however, has a serious drawback of not considering the mutual influence of simultaneous transmission of multiple video streams. In this article, we propose a method of the QoE-oriented fairness control for DASH systems which uses a new utility function. This function based on a hierarchical structure of a SVC video stream. The properties of this solution were evaluated in a test environment that uses SDN principles. Functional features of the proposed control method were compared with standard algorithm of the adaptation used by DASH supported devices.

Evaluation of the Jammers Performance in the WiFi Band

The paper presents evaluation of the performance of two different jammers in an open space on the basis of measurements. The measurements were performed with the use of Fluke AirMagnet Spectrum XT analyser in agricultural area. Signal power heat maps were prepared and analysed. Theoretical path loss models of different jammers’ configurations were worked out. The determination of the path loss models parameters allow to calculate the theoretical heat maps and compare them with measurements. The study focused on designation of the performance of the jammers in open space. This allows to estimate the area of effective signal jamming. The influence of channel frequency in WiFi 2.4 GHz band on the jammer performance was analysed.