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Search Results: 1 - 10 of 1113 matches for " Pawel Gburzynski "
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On Reliable Transmission of Data over Simple Wireless Channels
Pawel Gburzynski,Bozena Kaminska,Ashikur Rahman
Journal of Computer Networks and Communications , 2009, DOI: 10.1155/2009/409853
Abstract: Standard protocols for reliable data transmission over unreliable channels are based on various Automatic Repeat reQuest (ARQ) schemes, whereby the sending node receives feedback from the receiver and retransmits the missing data. We discuss this issue in the context of one-way data transmission over simple wireless channels characteristic of many sensing and monitoring applications. Using a specific project as an example, we demonstrate how the constraints of a low-cost embedded wireless system get in the way of a workable solution precluding the use of popular schemes based on windows and periodic acknowledgments. We also propose an efficient solution to the problem and demonstrate its advantage over the traditional protocols.
The Internet Inter-Orb Protocol Security Bridge
Pawel Pietras,Pawel Slowikowski
Computer Science , 1999,
Abstract: In this paper, we present a security bridge for the Internet protocol of interoperability amongst CORBA objects and the Internet inter-ORB Protocol (IIOP). The bridge helps in making accessible objects in the Internet and makes possible the access control to them. The bridge was realized in the popular request broker the Visigenic's VisiBroker under Windows 95/NT and Solaris 2.X operating systems. We describe two ways of locating the bridge in the request broker. The first means uses one name domain of broker and is not transparent for client. The second one uses two name domains and provides objects protection on the level of the Naming Service and is transparent lor the client. We also describe the variant ofthe second means with using GateKeeper server to support IIOP tunneling within HTTP. We emphasize the importance of a firewall, cooperating with a bridge. which is required for the purpose of providing object protection. The paper presents an original conception of security managing, basing on the ideas of users, groups and resources defined using the standard terms of CORBA, IIOP and TCP/IP, that allows to control positively and negatively the access to classes (interfaces), objects and also to their individual methods. This conception was effectively implemented in a functioning bridge. Further chapters describe the foundations and some details of the bridge implementation sueli as the use ofthe Interface Repository, cache memory application, thread synchronization and the way of synchronization of the configuration applet with the bridge's objects. We discuss the influence of these solutions on the efficiency ofthe bridge and its source code portability. We also present the general structure of the component objects ofthe bridge with a scheme. ln the next part we characterize the implementation foundations ofthe bridge manager, realized as an applet in Java, with the stress on the possibility of the bridge configuration through the network. Later, we describe the functionality ofthe bridge manager, which allows the configuration of all the important parameters ofthe bridge and of the security management. The next chapter discusses the conclusions l`roin the eflieiency tests ofthe two main bridge layers the bridge manager and the bridge (proxy mechanism), the influence of the usage memory caching on its efficiency. We provide there also an overall evaluation of the obtained results The last chapter includes a summary and discusses the bridge advantages and limitations as well as its evolution possibilities.
Biochemical Bone Turnover Markers and Osteoporosis in Older Men: Where Are We?
Pawel Szulc
Journal of Osteoporosis , 2011, DOI: 10.4061/2011/704015
Abstract: In men aged less than 60, the association of serum and urinary levels of biochemical bone turnover markers (BTMs) and bone mineral density (BMD) is weak or not significant. After this age, higher BTM levels are correlated weakly, but significantly, with lower BMD and faster bone loss. Limited data from the cohort studies suggest that BTM measurement does not improve the prediction of fragility fractures in older men in comparison with age, BMD, history of falls and fragility fractures. Testosterone replacement therapy (TRT) decreases bone resorption. During TRT, bone formation markers slightly increase (direct effect on osteoblasts), then decrease (slowdown of bone turnover). Bisphosphonates (alendronate, risedronate, ibandronate, zoledronate) induce a rapid decrease in bone resorption followed by a milder decrease in bone formation. In men receiving antiresorptive therapy for prostate cancer, zoledronate, denosumab and toremifene decrease significantly levels of bone resorption and bone formation markers. Teriparatide induced a rapid increase in serum concentrations of bone formation markers followed by an increase in bone resorption. We need more studies on the utility of BTM measurement for the improvement of the persistence and adherence to the anti-osteoporotic treatment in men.
Discrete Model of Opinion Changes Using Knowledge and Emotions as Control Variables
Pawel Sobkowicz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0044489
Abstract: We present a new model of opinion changes dependent on the agents emotional state and their information about the issue in question. Our goal is to construct a simple, yet nontrivial and flexible representation of individual attitude dynamics for agent based simulations, that could be used in a variety of social environments. The model is a discrete version of the cusp catastrophe model of opinion dynamics in which information is treated as the normal factor while emotional arousal (agitation level determining agent receptiveness and rationality) is treated as the splitting factor. Both variables determine the resulting agent opinion, which itself can be in favor of the studied position, against it, or neutral. Thanks to the flexibility of implementing communication between the agents, the model is potentially applicable in a wide range of situations. As an example of the model application, we study the dynamics of a set of agents communicating among themselves via messages. In the example, we chose the simplest, fully connected communication topology, to focus on the effects of the individual opinion dynamics, and to look for stable final distributions of agents with different emotions, information and opinions. Even for such simplified system, the model shows complex behavior, including phase transitions due to symmetry breaking by external propaganda.
A stabilization method of inhomogeneous ladder networks with nonlinear elements
Pawel Skruch
Archives of Control Sciences , 2011, DOI: 10.2478/v10170-010-0046-z
Abstract: In the paper, different structures of electric ladder networks are considered: RC, RL, and RLC. Such systems are composed of resistors, inductors and capacitors connected in series. The elements of the network are not identical and have nonlinear characteristics. The network's dynamic behavior can be mathematically described by nonlinear differential equations. A class of robust feedback controls is designed to stabilize the system. The asymptotic stability of the closed-loop system is analyzed and proved by the use of Lyapunov functionals and LaSalle's invariance principle. The results of computer simulations are included to verify theoretical analysis and mathematical formulation.
Cs containing borosilicate waste glasses
Pawel Stoch
Optica Applicata , 2008,
Abstract: Vitrification has been recognized as the best method of the neutralization and immobilization of the radioactive and toxic waste. Toxic elements are introduced into the structure of chemically durable glasses (waste glass). SiO2–B2O3–Al2O3–Na2O glass is one of the most commonly used waste glass. Radioactive 137Cs is often a dangerous contaminant of hospital and laboratory waste. Incineration of these waste and vitrification of ash by its co-melting with borosilicate glass is the perspective method of immobilization of this nuclide for safety waste storing. The influence of the partial substitution of Na by Cs and of the introduction of CaO as the main waste incineration ash component in the SiO2–B2O3–Al2O3–Na2O waste glass on the change of its structure, crystallization ability, and physical properties were studied.
Influence of technological parameters on the properties of sol-gel silica films
Pawel Karasinski
Optica Applicata , 2005,
Abstract: The paper presents the influence of selected technological parameters on the properties of silica films produced in sol-gel processes using the dip-coating method. The influence of water content and catalyst content was investigated as well as the influence of aging time of sols. It was demonstrated that the conditions of film deposition and the content of catalyst have a great influence on the thickness of the films produced. The greatest influence on the refractive index is exerted by molar ratio TEOS:H2O. Together with the rise of aging time of the sol its properties are changing, and the changes depend on pH.
Influence of aging and annealing on the properties of silica films produced with sol-gel method
Pawel Karasinski
Optica Applicata , 2006,
Abstract: The paper presents the results of investigations involving the influence of aging and annealing of the sol films on the final parameters of the obtained silica films. Both technological process and measurement method were described. The changes of refractive index were presented as well as the changes of film thickness of sols deposited on glass substrates during their aging under ambient conditions. The influence of the annealing process of films on their final parameters was examined. Silica films on glass substrates were deposited using dip coating method.
Sol-gel derived optical waveguide films for planar sensors with phase modulation
Pawel Karasinski
Optica Applicata , 2004,
Abstract: The paper presents the results of investigation of the technology of optical waveguide films produced with the sol-gel technique. The silica-titania films were deposited on glass substrates by a deep coating method. The influence of withdrawal speed and aging time of sol on the refractive index and film thickness has been tested.
The Epistemological Status of Theoretical Models of Molecular Structure
Pawel Zeidler
Hyle : International Journal for Philosophy of Chemistry , 2000,
Abstract: For many decades, chemists regarded rigid models of molecular structure as representing structures of real molecules as their attributes. However, new experimental data required a new theoretical conceptualization. The rigid model has been replaced with a dynamic model in which molecular structure is changed under the influence of environmental conditions. The above case shows some problems connected with recognizing theoretical models as structural representations of real empirical systems. Owing to the fact that theoretical models of molecular structure obtain local interpretations with a procedural character, they can be carriers of specific information about structures of real molecules. Finally, I argue that, although theoretical models can be well corroborated empirically, they cannot be treated as representations of real empirical systems but can play a very important role in experimental practice.
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