Risks pertaining to construction work relate to situations in which various events may randomly change the duration and cost of the project or worsen its quality. Because of possible significant changes of random events, favorable, moderate, and difficult conditions of construction work are considered. It is the first stage of the construction risk analysis. The probabilistic parameters of construction are identified and described by using the design characteristics model of the structure and the construction technology model. The first describes the probabilistic properties of the structure execution's technology. The second describes the probabilistic properties of the works execution. Both models contain basic probabilistic data for scheduling, cost estimating, and risk assessment of the construction.
Buckling and postbuckling response of thin-walled composite plates investigated experimentally and determinated analytically and numerically is compared. Real dimension specimens of composite plates weakened by cut-out subjected to uniform compression in laboratory buckling tests have been modelled in the finite element method and examined analytically based on P-w2 and P-w3 methods. All results were obtained during the experimental investigations and the numerical FEM analysis of a thin-walled composite plate made of a carbon-epoxy laminate with a symmetrical eight-layer arrangement of [90/-45/45/0]s. The instrument used for this purpose was a numerical ABAQUS® program.
The paper presents a method of priority scheduling that is useful during the planning of multiple-structure construction projects. This approach is an extension of the concept of interactive scheduling. In priority scheduling, it is the planner that can determine how important each of the technological and organisational constraints are to them. A planner's preferences can be defined through developing a ranking list that defines which constraints are the most important, and those whose completion can come second. The planner will be able to model the constraints that appear at a construction site more flexibly. The article presents a general linear programming model of the planning of multiple-structure construction projects, as well as various values of each of the parameters that allow us to obtain different planning effects. The proposed model has been implemented in a computer program and its effectiveness has been presented on a calculation example.
Considering concrete nonlinearity, the wave height limit between small and large amplitude sloshing is defined based on the Bernoulli equation. Based on Navier-Stokes equations, the mathematical model of large amplitude sloshing is established for a Concrete Rectangle Liquid-Storage Structure (CRLSS). The results show that the seismic response of a CRLSS increases with the increase of seismic intensity. Under different seismic fortification intensities, the change in trend of wave height, wallboard displacement, and stress are the same, but the amplitudes are not. The areas of stress concentration appear mainly at the connections between the wallboards, and the connections between the wallboard and the bottom.
In this paper, the authors present a robot for pipe inspection and exploration, which has in its structure a module for the maintenance of a constant pressure force between the robot's wheels and the inside diameter of the pipe. The paper starts with a short introduction about necessity of the presented solution followed by design aspects and finalizing with the test of the developed compliant module.
The protection of Polish architectural heritage in the former eastern borderlands, accomplished through the conservation and technical securing of historical structures, constitutes one of the main programmes that are implemented by the Ministry of Culture and National Heritage. Currently, many Polish historical buildings in the former eastern borderlands are in a very bad technical condition. The load-bearing systems of these elements, as well as elements of their finish, require immediate emergency securing work. The basic steps that precede conservation work are emergency structural works, which guarantee the durability and stability of the entire historical substance. The specifics and complexity of the problem of the failure of historical buildings often demands an in-depth analysis of a series of factors that are difficult to measure and which are responsible for the cause and effect relationship during the early stage of the technical evaluation of a structure. The analyses of failures of numerous historical structures, for instance that were carried out by the authors, have become the inspiration for the search for effective methods of analysis that would allow for an in-depth analysis of the causes and effects of the failures in question. The DEMATEL method (Decision Making Trial and Evaluation Laboratory) that has been presented in this work, and its fuzzy extension, has lately become one of the more popular methods used in the cause-and-effect analysis of various phenomena. The authors demonstrated how this method works on the example of the evaluation and securing of the load-bearing system of the XVII Collegiate church of the Holy Trinity in the town of Olykha in the Volhynskiy Oblast, Ukraine.
In Part I of this article, two-stage solidification model was presented. In this part we use our model to simulate solidification of the Al 7% Si alloy for two cooling rates and . Simulations have been performed for two eutectic transformation modes, typical for modified and unmodified alloys. Obtained cooling curves are qualitatively consistent with the typical cooling curves for modified and unmodified alloys. Moreover, evolution of cooling-curve characteristics is compared with the analytical model and found to be in close agreement.
The paper presents adaptation problem of lamellar/rod growth of eutectic. The transformation of eutectic microstructure was investigated systematically. A interpretation of the eutectic growth with theory minimum entropy production was presented.
The paper presents a new numerical model of solidification processes in hypoeutectic alloys. The model combines stochastic elements, such as e.g. random nucleation sites and orientation of dendritic grains, as well as deterministic methods e.g. to compute velocity of dendritic tips and eutectic grains. The model can be used to determine the temperature and the size of structure constituents (of both, the primary solid phase and eutectics) and the arrangement of individual dendritic and eutectic grains in the consecutive stages of solidification. Two eutectic transformation modes, typical to modified and unmodified hypoeutectic alloys, have been included in the model. To achieve this, cellular automata and Voronoi diagrams have been utilized.
In this study, modification of the AZ91 magnesium alloy surface layer with a CO2 continuous wave operation laser has been taken on. The
extent and character of structural changes generated in the surface layer of the material was being assessed on the basis of both macro- and
microscopy investigations, and the EDX analysis. Considerable changes in the structure of the AZ91 alloy surface layer and the
morphology of phases have been found. The remelting processing was accompanied by a strong refinement of the structure and a more
uniform distribution of individual phases. The conducted investigations showed that the remelting zone dimensions are a result of the
process parameters, and that they can be controlled by an appropriate combination of basic remelting parameters, i.e. the laser power, the
distance from the sample surface, and the scanning rate. The investigations and the obtained results revealed the possibility of an effective
modification of the AZ91 magnesium alloy surface layer in the process of remelting carried out with a CO2 laser beam.
The academic environment of Wrocław emerged and developed in particularly difficult conditions of the post WWII era. Thanks to continuation of the tradition, experience and contributions of leading scientists from the former Jan Kazimier University of Lwów, it quickly achieved an important, internationally recognized position in particular in mathematics and chemistry. Two different sociological concepts of relations within the scientific community have developed simultaneously: (1) partnership between leaders and research team members, (2) hierarchical structure based on authority of a leader. History proved that both may be effective. Wrocław became a modern center of research management comparable to leading western universities. The general approach based on relationship „between master and a follower” has been replaced by the more effective relatioship „between a school and a follower”. Similarly to the Lwów tradition the Wrocław Scientific Society has played an integrative role in relations among scientists of different disciplines.
The objective of the article is to examine the approximative and adjustive uses of the verb dire, which is mostly regarded as an assertive and eventful verb; hence nonapproximative. Meanwhile, in many expressions, in an impersonal use, in negation when the subjunctive mode is used, in the conditional forms, its evidence value is weakened and the verb dire can express approximation. The study is situated in light of the enunciation theory, notably it refers to a notion of modalisation. The corpus was established on the basis of dictionaries, which are representative for normative uses, but we will refer as well to press texts, particularly interviews, where the verb say is frequently used as a marker of the position of the speaker.
One of the challenges of modern crystallography of complex systems (complex metallic alloys, proteins, aperiodic crystals and quasicrystals) is to properly describe the disorder in these systems and discuss correctly the refinement results in terms of the structural disorder. In this paper we briefly discuss a new approach to phasons and phonons in quasicrystals and focus on the new theory of phonons in these materials. A newly derived correction factor for phonons in the form of the Bessel function is the approximated way of describing optic modes in the phonon spectra of quasicrystals. It is applied to a real decagonal quasicrystal in the Al-Cu-Rh system with 56/38 atoms per thick/thin structural unit, based on 2092 unique reflections selected from the collected diffraction data, significantly improving the refinement results. The final R-factor value is 7.24%, which is over 0.5% better result comparing to originally reported. We believe our work will open a broader discussion on the disorder in quasicrystals (and other aperiodic systems) and motivate to develop new approaches to treat the diffraction data influenced by different types of disorder in the new way.
The studies were carried out in Wielkopolska region (western Poland) in oat and winter rye cultures. Density and species structure of Thysanoptera were studied. Average density of adult Thysanoptera on oat reached 371.4 individuals/m2, and was higher than on rye, where it reached 107.5 individuals/m2. Limothrips cerealium Haliday was a dominant species on oat as well as on winter rye.
The dominance, diversity and activity density of rove beetles were studied in Central European apple and pear orchards. Altogether 6 877 individuals, belonging to 271 species and 11 subfamilies were collected. Thirteen species presented a relative abundance from 9 to 2% and amounted to almost 56% of all staphylinids recorded. In dominance order they were: Dinaraea angustula (Gyllenhal), Omalium caesum Gravenhorst, Drusilla canaliculata (F.), Sphenoma abdominale Mannerheim, Palporus nitidulus (F.), Xantholinus linearis (Olivier), Dexiogya corticina (Erichson), Coprochara bipustulata L., Mocyta orbata (Erichson), Oligota pumilio Kiessenwetter, Xanthlinus longiventris (Olivier), Tachyporus hypnorum (F.) and Pycnota vicina (Kraatz). The alpha diversity of staphylinids for different environmental conditions was relatively similar but the Shannon-Weiner Index (H`) was higher than of other similar studies. However, the activity density was higher in pear, in sand and in abandoned plantations; under different environmental conditions this could not be considered uniform in time. After the cumulative studies on the population dynamics, one can conclude that the highest number of species can be found in spring and in summer. Species D. canaliculata and P. nitidulus presented the similar seasonal dynamics in orchards located in different environmental areas, while O. caesum had the same activity density both in apple and pear orchards.
A numerical algorithm is presented for the filling process of a cylindrical column with equilateral cylinders. The process is based on simplified mechanics - the elements are added one by one until the mechanical equilibrium is reached. The final structure is examined with respect to the global and local porosity distribution. Oscillating radial porosity profile is obtained in accordance with experimental data.