Porosity of closed carbon nanotubes compressed using hydraulic pressure

Experimental data of nitrogen adsorption (T = 77.3 K) from gaseous phase measured on commercial closed carbon nanotubes are presented. Additionally, we show the results of N2 adsorption on compressed (using hydraulic press) CNTs. In order to explain the experimental observations the results of GCMC simulations of N2 adsorption on isolated or bundled multi-walled closed nanotubes (four models of bundles) are discussed. We show that the changes of the experimental adsorption isotherms are related to the compression of the investigated adsorbents. They are qualitatively similar to the theoretical observations. Taking into account all results it is concluded that in the "architecture" of nanotubes very important role has been played by isolated nanotubes

The Einsteinian T(3)-Gauge Approach and the Stress Tensor of the Screw Dislocation in the Second Order: Avoiding the Cut-off at the Core

A translational gauge approach of the Einstein type is proposed for obtaining the stresses that are due to non-singular screw dislocation. The stress distribution of second order around the screw dislocation is classically known for the hollow circular cylinder with traction-free external and internal boundaries. The inner boundary surrounds the dislocation's core, which is not captured by the conventional solution. The present gauge approach enables us to continue the classically known quadratic stresses inside the core. The gauge equation is chosen in the Hilbert--Einstein form, and it plays the role of non-conventional incompatibility law. The stress function method is used, and it leads to the modified stress potential given by two constituents: the conventional one, say, the `background' and a short-ranged gauge contribution. The latter just causes additional stresses, which are localized. The asymptotic properties of the resulting stresses are studied. Since the gauge contributions are short-ranged, the background stress field dominates sufficiently far from the core. The outer cylinder's boundary is traction-free. At sufficiently moderate distances, the second order stresses acquire regular continuation within the core region, and the cut-off at the core does not occur. Expressions for the asymptotically far stresses provide self-consistently new length scales dependent on the elastic parameters. These lengths could characterize an exteriority of the dislocation core region.Comment: 34 pages, LaTe

Identification of systems reliability

A purpose of the article is discussing the method of technical systems reliability modelling. The most important methods used for constructing realist models of the physical world, i.e. the method of the experimental modelling and the method of the probabilistic modelling, were presented. The particular attention was focussed on the method of the probabilistic modelling allowing for taking into account uncertainty in functioning of systems. An example of using the proposed method to the modelling of the reliability of the air-traffic-control-system was quoted

The scalarization approach for multi-objective optimization of network resource allocation in distributed systems

The paper presents a multi-objective optimization framework to the network resource allocation problem, where the aim is to maximize the bitrates of data generated by all agents executed in a distributed system environment. In the proposed approach, the utility functions of agents may have different forms, which allows a more realistic modeling of phenomena occurring in computer networks. A scalarizing approach has been applied to solve the optimization problem

Symulacyjna metoda szacowania efektywności systemów rozproszonych

Artykuł jest poświęcony omówieniu symulacyjnej metody szacowania efektywności systemów rozproszonych opartych na przesyłaniu komunikatów. Do modelowania matematycznego tych systemów wykorzystano dwa paradygmaty, tj. paradygmat modelowania eksperymentalnego i paradygmat modelowania probabilistycznego. W pracy zaproponowano miary efektywności rozpatrywanej rodziny systemów. Przedstawiono algorytm symulacji stochastycznej szacowania efektywności systemów rozproszonych.This paper presents a simulation method for evaluating the effectiveness of distributed systems based on passing messages. For mathematical modelling of these systems, two paradigms were used, i.e. the paradigm of experimental modelling and the paradigm of probabilistic modelling. The paper proposes effectiveness measures of the considered family of systems. An algorithm of stochastic simulation for effectiveness evaluation of distributed systems was presented

Simulation modeling of stationary systems reliability

A purpose of the article is describing the methodology of the simulation modeling of systems reliability. At the work is assumed that the process of the use of the studied system is stationary. An algorithm of the simulation applying the technique of discrete-event was presented. An example of using the proposed methodology to the reliability analysis of the air traffic control system was quoted

Waves in elastic materials and structures

The mathematical description of waves propagation in elastic materials and structures is presented. Particularly, the considerations concern the water as a transmission medium for acoustic waves. The following issues are discussed: discontinuity, reflection, and propagation speed, among others

Probabilistic Modeling of the Message Passing Process in Distributed Systems

W artykule omówiono zagadnienia modelowania probabilistycznego oraz analizy statystycznej procesu przesyłania komunikatów w systemach rozproszonych. Przyjęto, że modelami probabilistycznymi przepływności linków sieciowych są niestacjonarne ze względu na wartość oczekiwaną procesy stochastyczne. Analizy statystyczne prowadzi się na podstawie danych generowanych przez symulator stochastyczny procesu przepływów danych w sieciach komputerowych. Dane generowane przez symulator są interpretowane jako realizacje niestacjonarnych procesów stochastycznych. Przytoczono przykład wykorzystania proponowanego podejścia do badania procesu przesyłania danych w prostym systemie rozproszonym.The article discusses an issue of the probabilistic modeling of the message passing process in distributed systems. It has been assumed that the probabilistic models of bitrates in network links are non-stationary due to the expected value of stochastic processes. Statistical analysis is carried out on the basis of data generated by the stochastic simulator of the data flow process in computer networks. The data generated by the simulator have been interpreted as realizations of stochastic processes. The paper includes an example of the application of the presented approach to research the message passing process in a simple distributed system

Simulation of operation of systems

W artykule zaproponowano wykorzystanie metody symulacji stochastycznej do oceny niezawodności systemów stacjonarnych w szerszym sensie. Przyjęto, że modelami ewolucji czasowej stanów niezawodnościowych systemu są zmienne losowe o dodatnio skoncentrowanych wartościach. Przedstawiono metodologię modelowania niezawodnościowego i metodologię modelowania symulacyjnego. Przytoczono przykład wykorzystania metody symulacyjnej do oceny niezawodności systemu rozproszonego.In the paper the use of stochastic simulation method for evaluation of the reliability of weak stationary systems have been proposed. It is assumed that models of the time evolution of the system reliability states are random variables with positively concentrated values. Methodology for reliability modeling and methodology for simulation modeling have been presented. An example of using the simulation method for the distributed system reliability evaluation has been quoted