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  • Author: Krzysztof Zieliński x
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Open access

Jerzy Łukaszewicz and Krzysztof Zieliński

Durability and narrow pore size distribution (PSD) of carbons fabricated from Salix viminalis wood

Microporous carbon molecular sieves of extremely narrow pore size distribution were obtained by carbonization of a novel raw material (Salix viminalis). The precursor is inexpensive and widely accessible. The pore capacity and specific surface area are upgradable by H3PO4 treatment without significant change of narrowed PSD. The dominating pore size indicates that these molecular sieves are a potential competitor to other nanoporous materials such as opened and purified carbon nanotubes.

Open access

Tomasz Zieliński and Krzysztof Duda

Frequency and Damping Estimation Methods - An Overview

This overview paper presents and compares different methods traditionally used for estimating damped sinusoid parameters. Firstly, direct nonlinear least squares fitting the signal model in the time and frequency domains are described. Next, possible applications of the Hilbert transform for signal demodulation are presented. Then, a wide range of autoregressive modelling methods, valid for damped sinusoids, are discussed, in which frequency and damping are estimated from calculated signal linear self-prediction coefficients. These methods aim at solving, directly or using least squares, a matrix linear equation in which signal or its autocorrelation function samples are used. The Prony, Steiglitz-McBride, Kumaresan-Tufts, Total Least Squares, Matrix Pencil, Yule-Walker and Pisarenko methods are taken into account. Finally, the interpolated discrete Fourier transform is presented with examples of Bertocco, Yoshida, and Agrež algorithms. The Matlab codes of all the discussed methods are given. The second part of the paper presents simulation results, compared with the Cramér-Rao lower bound and commented. All tested methods are compared with respect to their accuracy (systematic errors), noise robustness, required signal length, and computational complexity.

Open access

K. Zieliński

Abstract

Each bitumen has a slightly different group composition, thus bitumen modification with the SBS copolymer gives slightly different results in each case. Both in the industry and construction practice there is still no simple method available which would allow the evaluation of the impact of SBS content and the group composition of bitumen on the structural and rheological properties of the polymer bitumen mix. The article presents the results of the dynamic viscosity tests of three bitumen types. Based on the analysis of the results obtained, it was found that changes in the rheological properties caused by SBS additive are characteristic for each of the bitumens tested and their chemical and group composition. They are also proportionate to the amount of the modifier added. In order to have a possibility to measure this impact, three coefficients rheologically characterizing polymer and bitumen mixes were applied.

Open access

K. Zieliński and M. Babiak

Abstract

Hard bitumens are used in the construction industry primarily in it’s unmodified form, for instance for the production of the so-called traditional roofing felt. Due to the low price of these types of membranes, the use of a popular but expensive modifying agent, SBS copolymer, is not justified economically. Research carried out by the authors has shown that chemical organic compounds belonging to a group of imidazolines may potentially be used as much cheaper bitumen modifier. It was demonstrated that a new type of modifier based on oleic imidazoline, developed by the authors, has a significant impact on improving the physical properties of bitumen. The use of this modifier results in a significant increase in the bitumen plasticity range, both before and after laboratory ageing. In addition, there was a considerable increase of bitumen’s resistance to aging. Its use can help improve the quality and durability of popular waterproofing products manufactured with the use of hard bitumen.

Open access

Mariusz Zieliński, Krzysztof Fortuniak and Włodzimierz Pawlak

Abstract

The primary aim of this paper was to present the results of turbulent sensible heat flux (QH) measurements with Scintillometer Scintec BLS900 (LAS). The theoretical background of scintillation method has been presented as well as two different ways of sensible heat flux computation from LAS. The measurements presented here were conducted from April to December 2011. Diurnal and partially annual variability of QH has been analyzed, moreover the mean diurnal course of QH in considered months has been prepared. In order to choose the optimal method of QH computation from LAS the results obtained with three different Monin-Obuchov similarity theory functions as well as free convection assumption has been compared. In first case it has been proved that sensible heat flux differs significantly depending on chosen universal function. In turn in case of free convection assumptions it has been revealed that it is valid only for very unstable conditions. Therefore it does not apply to long-time heat flux measurement in case of Łódź. Nevertheless, this study has shown that scintillation method is valuable and reasonable source of path-averaged QH estimates in considered city.

Open access

Krzysztof Pałko, Andrzej Rogalski, Krzysztof Zieliński, Jarosław Glapiński, Maciej Kozarski, Tadeusz Pałko and Marek Darowski

RC Model-based Comparison Tests of the Added Compliance Method with Computer Simulations and a Standard Method

Ventilation of the lungs involves the exchange of gases during inhalation and exhalation causing the movement of respiratory gases between alveolars and the atmosphere as a result of a pressure drop between alveolars and the atmosphere. During artificial ventilation what is most important is to keep specific mechanical parameters of the lungs such as total compliance of the respiratory system Cp (consisting of the lung and the thorax compliances) and the airway resistance Rp when the patient is ventilated. Therefore, as the main goal of this work and as the first step to use our earlier method of added lung compliance in clinical practice was: 1) to carry out computer simulations to compare the application of this method during different expiratory phases, and 2) to compare this method with the standard method for its accuracy.

The primary tests of the added-compliance method of the main lung parameters measurement have been made using the RC mechanical model of the lungs.

Open access

Piotr Reymer, Andrzej Leski, Wojciech Zieliński and Krzysztof Jankowski

Abstract

This article presents a concept of the full scale fatigue test of a Su-22 fighter bomber. The authors define the general concept and goals of the test as well as the tasks to be accomplished in the preparation stage. The current work status is summarized and future tasks are defined.

Open access

Michał Dziendzikowski, Wojciech Zieliński, Łukasz Obrycki, Marta Woch, Piotr Synaszko, Krzysztof Dragan and Andrzej Leski

Abstract

Knowledge about loads occurring in the structure during aircraft operation is vital from the point of view of the damage tolerance approach to aircraft design. In the best-life scenario, such information could be available from a network of sensors, e.g. strain gauges, installed in the aircraft structure to measure local stresses. However, operational loads monitoring (OLM) systems are still not widely applied. Instead, what is available is a set of flight parameters, which by the laws of inertia and aerodynamics help determine the dominant part of loads acting on a given element. This paper discusses the canonical correlation analysis (CCA) as a method for selecting the flight parameters used to predict aircraft loads. CCA allows for the identification of both different modes of stress distribution as well as flight parameters which are best suited for their prediction. The paper presents the application of this method to identify loads acting on the vertical stabilizer of an aircraft.

Open access

Romuald Olszański, Zbigniew Dąbrowiecki, Dorota Niewiedział, Krzysztof Gadomski and Ewa Zieliński

Abstract

Allergic rhinitis occurs in various regions of the world and affects from 10 to 40% of the population. The skin prick test is the “gold standard” for the detection of type I allergic diseases according to the Gella and Coombs classification, which is mediated by IgE. For our experiment, skin prick tests were performed on 60 divers aged between 30 and 40 years of age. The following tests for airborne allergens were used: tests for pollen from trees, grasses, cereals, weeds, proteins from house dust mites, animal hair and epidermis, and moulds. On the basis of an interview and a positive skin prick test allergic rhinitis was diagnosed in 17 divers.

Conclusions:

  1. Allergic rhinitis can cause health problems in divers and be the cause of diving accidents.

  2. The application of the skin prick test during the health qualification in the Military Maritime Health Commission, would allow the exclusion of diver candidates suffering from allergies.

Open access

Krzysztof Bieda, Fryderyk Pukacki, Maciej Zieliński, Paweł Sobczyński, Grzegorz Oszkinis, Roma Hartman-Sobczyńska and Wacław Majewski

Utility of Measurements of Abdominal Perfusion Pressure as a Measure of Isovolemic Status and Intestinal Perfusion in Patients with Ruptured Aortic Aneurysm

Ruptured abdominal aorta aneurysm of ten results in intraabdominal hypertension (IAH). When IAH exceeds 20 mm Hg, intestinal ischemia can result that is a common cause of severe postoperative complications, including death.

The aim of the study was to evaluate utility of measurement of abdominal perfusion pressure (APP) to estimate intestinal perfusion and isovolemic status in patients undergoing surgical treatment for ruptured abdominal aorta aneurysm.

Material and methods. A group of 40 patients of either sex, aged 47 - 93 years (average age 70 ± 10) was treated at an Intensive Care Unit after surgical reconstruction of abdominal aorta due to ruptured aortic aneurysm. The study was prospective. The following were measured: parameters of intraabdominal pressure (intraabdominal pressure - IAP, abdominal perfusion pressure - APP); parameters of intestinal perfusion - tonometric (intramucosal gastric carbon dioxide partial pressure PgCO2, intramucosal-arterial difference in carbon dioxide partial pressure - Pg-aCO2); hemodynamic parameters (mean arterial pressure - MAP, central venous pressure - CVP).

Results. A statistically significant correlation was demonstrated between parameters of visceral perfusion and abdominal perfusion pressure. Pearson correlation coefficient for APP/PgCO2 and APP/Pg-aCO2 was negative and was - 0.4664 and - 0.3498, respectively.

Conclusions. Abdominal perfusion pressure is an useful parameter in the evaluation of intestinal perfusion in IAH patients after surgical treatment of ruptured aortic aneurysm. MAP reflects current physiological body reserves at a critical stage of the disease, informing about possibility to provide visceral perfusion and indirectly, about adequacy of fluid replacement therapy. In intraabdominal hypertension, CVP is falsely elevated, making it of low utility in the evaluation of volemic status and intestinal perfusion.