Damian Ledziński

Assessing Measurements of QoS for Global Cloud Computing Services

Many global distributed cloud computing applications and services running over the Internet, between globally dispersed clients and servers, will require certain levels of Quality of Service (QoS) in order to deliver and give a sufficiently smooth user experience. This would be essential for real-time streaming multimedia applications like online gaming and watching movies on a pay as you use basis hosted in a cloud computing environment. However, guaranteeing or even predicting QoS in global and diverse networks supporting complex hosting of application services is a very challenging issue that needs a stepwise refinement approach to be solved as the technology of cloud computing matures. In this paper, we investigate if latency in terms of simple Ping measurements can be used as an indicator for other QoS parameters such as jitter and throughput. The experiments were carried out on a global scale, between servers placed in universities in Denmark, Poland, Brazil and Malaysia. The results show some correlation between latency and throughput, and between latency and jitter, even though the results are not completely consistent. As a side result, we were able to monitor the changes in QoS parameters during a number of 24-hour periods. This is also a first step towards defining QoS parameters to be included in Service Level Agreements for cloud computing in the foreseeable future.

Using latency as a QoS indicator for global cloud computing services

Many globally distributed cloud computing (CC) applications and services running over the Internet, between globally dispersed clients and servers, will require certain levels of QoS in order to deliver and give a sufficiently smooth user experience. This would be essential for real‐time streaming multimedia applications such as online gaming and watching movies on a pay as you use basis hosted in a CC environment. However, guaranteeing or even predicting QoS in global and diverse networks that are supporting complex hosting of application services is a very challenging issue that needs a stepwise refinement approach to be solved as the technology of CC matures. In this paper, we investigate if latency in terms of simple ping measurements can be used as an indicator for other QoS parameters such as jitter and throughput. The experiments were carried out on a global scale, between servers placed in universities in Denmark, Poland, Brazil, and Malaysia. The results show the correlation between latency and throughput, and between latency and jitter, even though the results are not completely consistent. As a side result, we were able to monitor the changes in QoS parameters during a number of 24‐hour periods. This is also a first step toward defining QoS parameters to be included in service level agreements for CC at the global scale in the foreseeable future. Concurrency and Computation: Practice and Experience, 2013.© 2013 Wiley Periodicals, Inc.

Evaluation of modified degree 5 chordal rings for network topologies

In this paper an analysis of modified degree 5 chordal rings is presented. First modified graphs and reference graphs (ideal and optimal) have been defined, and it is shown that the reference graphs are useful for estimation of average path length and diameter in both original and modified graphs. Then the comparison of basic graph parameters, diameter and average path length, is given for original and modified graphs. Our finding shows that the modified graphs contain shorter distances than the original graphs, and thus can be good candidates for network topologies.

Molecular Dynamic Analysis of Hyaluronic Acid and Phospholipid Interaction in Tribological Surgical Adjuvant Design for Osteoarthritis

Tribological surgical adjuvants constitute a therapeutic discipline made possible by surgical advances in the treatment of damaged articular cartilage beyond palliative care. The purpose of this study is to analyze interactions between hyaluronic acid and phospholipid molecules, and the formation of geometric forms, that play a role in the facilitated lubrication of synovial joint organ systems. The analysis includes an evaluation of the pathologic state to detail conditions that may be encountered by adjuvants during surgical convalescence. The synovial fluid changes in pH, hyaluronic acid polydispersity, and phospholipid concentration associated with osteoarthritis are presented as features that influence the lubricating properties of adjuvant candidates. Molecular dynamic simulation studies are presented, and the Rouse model is deployed, to rationalize low molecular weight hyaluronic acid behavior in an osteoarthritic environment of increased pH and phospholipid concentration. The results indicate that the hyaluronic acid radius of gyration time evolution is both pH- and phospholipid concentration-dependent. Specifically, dipalmitoylphosphatidylcholine induces hydrophobic interactions in the system, causing low molecular weight hyaluronic acid to shrink and at high concentration be absorbed into phospholipid vesicles. Low molecular weight hyaluronic acid appears to be insufficient for use as a tribological surgical adjuvant because an increased pH and phospholipid concentration induces decreased crosslinking that prevents the formation of supramolecular lubricating forms. Dipalmitoylphosphatidylcholine remains an adjuvant candidate for certain clinical situations. The need to reconcile osteoarthritic phenotypes is a prerequisite that should serve as a framework for future adjuvant design and subsequent tribological testing.

Robot Actions Planning Algorithms in Multi-Agent System

In this paper, the basic information about multi-agent systems is given. The authors propose robot control algorithms for managing virtual autonomous warehouses, where the task performed by the robots is transportation between specific locations in the warehouse and a number of distribution points. Algorithms control the work of a single robot, including the cooperation with other robots in the environment as well as collisions avoidance. Different routing algorithms are evaluated through simulations focusing on service time and waiting time of executing tasks. The impact of the proposed algorithms on energy consumption was also checked, since this is important for the working time between battery charges.

Hyaluronan-Chondroitin Sulfate Anomalous Crosslinking Due to Temperature Changes

Glycosaminoglycans are a wide class of biopolymers showing great lubricating properties due to their structure and high affinity to water. Two of them, hyaluronic acid and chondroitin sulfate, play an important role in articular cartilage lubrication. In this work, we present results of the all-atom molecular dynamics simulations of both molecules placed in water-based solution. To mimic changes of the physiological conditions, especially temperature, of the synovial fluid in joints under successive load (e.g., walking, jogging, jumping), simulations have been performed at different physiological temperatures in the range of 300 to 320 Kelvin (normal intra-articular temperature is 305 K). The stability of the biopolymeric network at equilibrium (isothermal and isobaric) conditions has been studied. To understand the process of physical crosslinking, the dynamics of intra- and intermolecular hydrogen bonds forming and breaking have been studied. The results show that following addition of chondroitin sulfate, hyaluronan creates more intermolecular hydrogen bonds than when in homogeneous solution. The presence of chondroitin in a hyaluronan network is beneficial as it may increase its stability. Presented data show hyaluronic acid and chondroitin sulfate as viscosity modifiers related to their crosslinking properties in different physicochemical conditions.

Analysis of the Possibility of Emission Reduction for Complex WSN Networks by the Implementation of a Larger Number of Acquisition Nodes

Abstract The article presents the results of simulations conducted on the network which has been implemented in one of the cities with dense urban development. The simulations were conducted to verify how the lowering of the emission (this affected the topology of the network) of the network will affect the network reliability and time of the data collection.

Reliability in Low Emission Wireless Measurement Networks

Wireless sensor networks called WSN’s increasingly find their wide application in various distributed measurement systems. Currently, many manufacturers focus on implementation of these devices in energy meters. In addition these devices are increasingly being considered as a system that do not carry big financial effort to be implement as a measuring systems of key safety parameters in production environments. Such environments are becoming an important element to ensure reliable transmission between measuring devices broadcasting. Another challenge in the systems under consideration is to provide low emissivity in the network. The low emissivity provides less interference between operating devices. This premise has an important effect on networks with large numbers of nodes.

Task Scheduling Algorithms for Multi-Carrying Robots

In recent years, problem of task scheduling and allocation of resources has become the subject of many research. The interest of this issue, due to the necessity develop a perfect model, which properly mapped the many of logistical environment. Optimal appoint the path of robots, and also allocate the respective tasks and their order, is the key to solve this problem. For this purpose, was developed the virtual environment, which mapping the activities, taken in this area. Transport these resources is performed in real-time. The task is called by the transport of resources, performed by the robot, between the place of start point to point of distribution. Distribution point is called by the place for downloading and putting the resources by customers. In this article, presents the algorithms relates to aspects of the management of work and planning of task for robots. The results shows the times of the tasks, as well as the times of services the customers, via uses the different algorithms of working robot, and also the amount of consumed the energy, during the performed tasks.

Network Structures Constructed on Basis of Chordal Rings 4th Degree

In this paper, on analysis of the properties of modified chordal ring 4\(^\textrm{th}\) degree topologies has been presented. Two special types of these structures, namely optimal and ideal graphs, have been defined. The basic parameters (diameter and average path distance) were calculated and described by approximate formulas which makes possible to evaluate these parameters for any modified graph proposed by authors, and it gives possibility to model the properties of these networks without requiring any specific path calculation between pairs of nodes which may be time and resource consuming for large scale systems. In the last part of paper the comparison of the analyzing structures and reference graph has been carry out.