The paper presents a proposal for the assessment of the reliability of steel truss (both statically determinate and indeterminate) in the persistent and accidental design situation. In the analysis, a probabilistic approach was used. The global Hasofer-Lind reliability index was employed, computed in successive time steps for the whole structure, not for individual elements. The statically determinate truss was modelled as a serial system from the reliability standpoint. For the statically indeterminate truss, kinematically admissible failure mechanisms were determined by means of the examination of the singularity of the stiffness matrix of the structure, converting the truss into a geometrically variable system. For the problem thus formulated, a serial-parallel reliability model was constructed. Monitoring the reliability index in the successive minutes of the fire makes it possible to estimate the probability of the structure failure, and to decide whether the required safety level is maintained.
The term Pakoszówka-Bessów type pottery is used to describe a specific kind of wheelmade pottery with easily abradable surfaces mostly dated to the 3rd century AD. Site 3 in Bessów, Bochnia Commune, Lesser Poland, is located in the dense Przeworsk culture settlement micro-region occupying the right bank of the lower reaches of the Raba River. The most characteristic feature of locally produced artefacts from Bessów, and to a lesser extent from other sites in the region, is the presence of enormous amounts of this pottery. The aim of laboratory analyses carried out on Pakoszówka-Bessów type pottery from Bessów was to verify the hypothesis that abradability of sherd surfaces is attributable to the alteration effect.
The paper concerns the accuracy of determining particle size distributions of the fine-grained materials by means of laser diffraction method. Selection of measuring method for determination of materials granulation depends on various properties of the sample, but mainly on the range of particle size in the sample. It must be taken into consideration that each of the measurement methods inherently generate different information about particle size distribution. The applied measurement method generates the main impact on the results of research because it uses various material properties, like: geometric properties, density or type of the surface (porosity).
Influence of density and particle shape on the results of measurements by laser diffraction was studied in the paper. This method becomes a standard for measuring particle size of mineral powders. Analysis of raw materials particle size distribution was performed using a laser particle-meter Analysette 22. Investigations included measurements of particle size of raw materials characterized by various densities (coal, porphyry, barite) and the shape of the particles (copper shale ore, fly ash from coal combustion). The density of raw materials was determined by helium pycnometer, while the particle shape was expressed by coefficient which was calculated on the basis of particles geometric parameters. Geometry of the grains was measured using an optical microscope with a digital record of images by means of image analysis method. The accuracy of laser granulometric analyzes was expressed by variation coefficient of narrow particle fractions contents. Results of analyzes confirmed that the laser granulometric analysis provides accurate information about the finestparticle size distribution. No significant effect of the material density on the accuracy of granulometric analysis was observed. Effect of particle shape of the tested materials caused more stable values of the variation coefficient for particles of more spherical shape what is related to the applied method of laser measurement. The accuracy of laser granulometric analyzes varies dependably on the measured particle size range of particles. The most accurate analyzed materials are these ones being the part of narrow particle fractions.
The selection of the formwork system for high rise building affects the entire construction project duration and cost. The study reports the factors influencing the selection of different formwork system in the construction of high rise buildings through structural questionnaire survey from the client, contractor, consultant, and interviews with expert members. Total of 40 technical factors was identified from the literature and 220 filled questionnaires were received from the respondent. Relative Importance Index method is used to find the topmost factors affecting the selection of formwork system. Additionally, from factor analysis 22 factors were identified to have a correlation with one another. Regression analysis reveals that duration of the project, maintenance cost, adaptability, and safety have impact on formwork selection across time, cost and quality. These findings could potentially increase the construction company’s existing knowledge in relation to formwork selection.
Thermodynamics deals with irreversible transformations of substances. Every thermodynamic property of a substance, as a function of two parameters describing its state, can be illustrated as a simply connected manifold. The term manifold stands for the Methods of Geometrical Representation of Thermodynamic Properties of Substances by Means of Surfaces. Generally, every transformation of a substance changes its energy (or enthalpy) by heat transfer and work done on it. All such changes (transformations) are considered to be irreversible and can be described using appropriate manifolds. Studies show that every transformation is associated with the degradation of energy. Such relations (between heat, work and other forms of energy or enthalpy) can be described by the Pfaff formulas and their integrations.
This article discusses the issue of irreversible energy degradation in heat transfer between two fluids. Irreversible heat transfer between separated fluids most often occurs through surface heat exchangers. All such processes are determined by convective heat transfer in thermal boundary layers and conduction through the wall. Consequently, entropy changes of fluids in heat and mass transfer can be observed in these layers. While the entropy rate of the heating fluid is negative and that of the heated medium is positive, the sum of entropy changes of all substances involved in the heat transfer process is always positive. These sums, known as entropy increase (entropy generation), can be interpreted as the measure of irreversible degradation of energy in heat transfer processes. The consequence of this degradation is that an arbitrary engine powered by the degraded (lower-temperature) heat flux will operate at a lower efficiency. The significance of this discussion relates especially to cases in power plants and cooling systems where surface heat exchangers are used. In the discussion proposed is the entropy increase as a criterion of irreversible energy degradation in heat transfer. Such introduced measure of effectiveness leads to an analysis of local overall heat transfer coefficient optimization on the cone-shaped manifold.
Choral singers are among intensive voice users whose excessive vocal effort puts them at risk of developing voice disorders. The aim of the work was to assess voice quality for choral singers in the choir at the Polish-Japanese Academy of Information Technology. This evaluation was carried out using the acoustic parameters from the COVAREP (A Collaborative Voice Analysis Repository For Speech Technologies) repository. A prototype of a mobile application was also prepared to allow the calculation of these parameters.
The study group comprised 6 male and 19 female choir singers. The control group consisted of healthy non-singing individuals, 50 men and 39 women. Auditory perceptual assessment (using the RBH scale) as well as acoustic analysis were used to test the voice quality of all the participants. The voice quality of the female choir singers proved to be normal in comparison with the control group.
The male choir singers were found to have tense voice in comparison with the controls. The parameters which proved most effective for voice evaluation were Peak Slope and Normalized Amplitude Quotient.
Monitoring the solidification process is of great importance for understanding the quality of the melt, for controlling it, and for predicting the true properties of the alloy. Solidification is accompanied by the development of heat, the magnitude of which depends on the different phases occurring during solidification. Thermal analysis is now an important part of and tool for quality control, especially when using secondary aluminium alloys in the automotive industry. The effect of remelting on the change of crystallization of individual structural components of experimental AlSi9Cu3 alloy was determined by evaluation of cooling curves and their first derivatives. Structural analysis was evaluated using a scanning electron microscope. The effect of remelting was manifested especially in nucleation of phases rich in iron and copper. An increasing number of remelts had a negative effect after the fourth remelting, when harmful iron phases appeared in the structure in much larger dimensions.
The aim of this study was to compare computer assisted sperm analysis (CASA) results of frozen thawed bull semen using three different chambers. Sixty bull frozen semen samples were thawed (37°C; 30 sec), extended in PBS (30×106 spermatozoa/mL; 37°C) and incubated (37°C; 2 min). Each semen sample was analyzed by CASA [total motility, progressive (pro)/ non-progressive/rapid/medium/slow movement spermatozoa, VCL, VSL, VAP, ALH, BCF, LIN, STR, WOB and hyperactive spermatozoa] using three different chambers: a Makler® chamber (MC; 10 μm); a Leja 4 chamber slide (LC; 20 μm); and a Glass slide covered with a coverslip (GSC; 10.3 μm). The Makler chamber gave higher values compared to both the LC and GSC for almost all examined parameters. No systematic effect was evident between LC and GSC for VCL, VSL, VAP, LIN, STR, WOB, ALH, and BCF. Method agreement between MC and LC was generally moderate, between MC and GSC poor and between LC and GSC moderate to good. In general, narrower limits of agreement were found in samples with lower values. In conclusion, the CASA outcomes could be influenced by the analysis chambers. This finding should be taken into consideration when comparing results from different laboratories.
The progress of additive manufacturing technology brings about many new questions and challenges. Additive manufacturing technology allows for designing machine elements with smaller mass, but at the same time with the same stiffness and stress loading capacity. By using additive manufacturing it is possible to produce gears in the form of shell shape with infill inside. This study is carried out as an attempt to answer the question which type of infill, and with how much density, is optimal for a spur gear tooth to ensure the best stiffness and stress loading capacity. An analysis is performed using numerical finite element method. Two new infill structures are proposed: triangular infill with five different densities and topology infill designed according to the already known results for 2D cantilever topology optimization, known as Michell structures. The von Mises stress, displacements and bending stiffness are analyzed for full body gear tooth and for shell body gear tooth with above mentioned types of infill structure.
The main objective of this work is to present an innovative method of numerical modeling of anchored piles system acting as a road protection against landslide, called the “2D/3D method”. Firstly, short description of the problem and “state of the art” review are included. An effective methodology of the design supported by the numerical analysis, solving the problem of interaction of a periodic system of piles and the unstable soil mass is presented, for which some detailed information about proposed numerical approach is given. The key idea of 2D/3D method is to join the pile with the 2D plane strain continuum by fictitious connectors of Winkler type with P-Y properties identified during the analysis of a subsidiary 3D problem. Practical example of usage of proposed approach to a real case of a road endangered by a landslide then protected by the piles system is presented. On the base of this example, a discussion about important design issues like internal forces in piles (mainly bending moments) and anchors (tensile forces) or overall stability of the soil-structure system is done.
The dynamic analyses are of key importance in the cognitive process in terms of the correct operation of structures loaded with time alternating forces. The development of vehicle industry, which directly results in an increase in the speed of moving vehicles, forces the design of engineering structures that ensure their safe use. The authors of the paper verified the influence of speed and vehicle parameters such as mass, width of track of wheels and their number on the values of displacements and accelerations of selected bridge elements. The problem was treated as the case study, because the analyses were made for one bridge and the passage of three types of locomotives. The response of the structure depends on the technological solutions adopted in the bridge, its technical condition, as well as the quotient of the length of the object and vehicle. A new bridge structure was analyzed and dynamic tests were carried out for trainsets consisting of one and two locomotives. During the actual dynamic tests, the structure was loaded with a locomotive moving at a maximum speed of 160 km/h.