The article presents a comparative analysis of various classifi cations of both sciences’ and management sciences’ paradigms in terms of their pragmatism and adequacy regarding organization research. Furthermore, the aim of the article is also to justify the thesis about the high usefulness of research model proposed by Keneth D. Strang. Strang’s model, based on the concept of researcher’s socio-cultural philosophy, allows on the one hand to overcome the theoretical incommensurability and on the other hand makes it possible for representatives of various paradigms to cooperate with each other. The article contains also refl ections on the paradigm as a key factor affecting both the development of management sciences and the practice of management. The choice of a specifi c paradigm, i.e. research ideology, has a decisive impact on the results of research, as well as the generalization of practice. The paradigm defi nes the research strategy, selection of research methods and inference rules. Furthermore, it infl uences the education process, and thus has an impact on shaping the worldview of scientists, entrepreneurs as well as managers.
Technology advancements entail a necessity to remove huge amounts of heat produced by today’s electronic devices based on highly integrated circuits, major generators of heat. Heat transfer to boiling liquid flowing through narrow minichannels is a modern solution to the problem of heat transfer enhancement. The study was conducted for FC-72 boiling in a rectangular, vertical and asymmetrically heated minichannel that had depths of 0.5-1.5 mm, a width of 20 mm and a length of 360 mm. The heat flux increased and decreased within the range of 58.3-132.0 kWm−2, the absolute pressure ranged from 0.116 to 0.184 MPa and the mass flux was 185-1139.2 kgm−2s−1. The boiling process took place on a flat vertical heating surface made of Haynes-230 0.1 mm thick acid-proof rolled plate with the surface roughness of 121 μm.
In this study, the influences of different parameters at performance two-phase closed thermosiphon (TPCT) was presented. It has been confirmed that the working fluid, as well as operating parameters and fill ratio, are very important factors in the performance of TPCT. The article shows characteristics of gravitational tube geometries, as well as the technical characteristic of the most important system components, i.e., the evaporator/condenser. The experiment’s plan and the results of it for the two-phase thermosiphon for both evaluated geometries with varying thermal and fluid flow parameters are presented. Experiments were performed for the most perspective working fluids, namely: water, R134a, SES36, ethanol and HFE7100. Obtained research proves the possibility to use TPCT for heat recovery from the industrial waste water.
Heat exchangers of different types find application in power systems based on solid oxide fuel cells (SOFC). Compact plate fin heat exchangers are typically found to perfectly fit systems with power output under 5 kWel. Micro-combined heat and power (micro-CHP) units with solid oxide fuel cells can exhibit high electrical and overall efficiencies, exceeding 85%, respectively. These values can be achieved only when high thermal integration of a system is assured. Selection and sizing of heat exchangers play a crucial role and should be done with caution. Moreover, performance of heat exchangers under variable operating conditions can strongly influence efficiency of the complete system. For that reason, it becomes important to develop high fidelity mathematical models allowing evaluation of heat exchangers under modified operating conditions, in high temperature regimes. Prediction of pressure and temperatures drops at the exit of cold and hot sides are important for system-level studies. Paper presents dedicated mathematical model used for evaluation of a plate fin heat exchanger, operating as a part of micro-CHP unit with solid oxide fuel cells.
Cold-formed structure connections utilizing gusset plates are usually semi-rigid. This paper investigates the behaviours of rectangular gusset plates in cold-formed connections of elements whose columns and beams are made with lipped back-to-back C-sections. Methods of calculating strength and stiffness are necessary for such semi-rigid joints. The main task of this paper is to determine a method capable of calculating these characteristics. The proposed analytical method could then be easily adapted to the component method that is described in part 1993-1-8 of the Eurocode. This method allows us to calculate both the strength and stiffness of rectangular gusset plates, assuming that the joint deforms only in plane. This method of design moment resistance calculation was presented taking into account that an entire cross-section shall reach its yield stress. A technique of stiffness calculation was presented investigating the sum of deformations acquired at the bending moment and from shear forces which are transmitted from each beam bolt group. Calculation results according to the suggested method show good agreement of laboratory experimental results of specimens with numerical simulations. Two specimens of beam-to-column connections were tested in the laboratory. Lateral supports were used on the specimens to prevent lateral displacements in order to better investigate the behaviour of the rectangular gusset plate in plane. Experiments were simulated by modelling rectangular gusset plates using standard finite element software ANSYS Workbench 14.0. Three-dimensional solid elements were used for modelling and both geometric and material nonlinear analysis was performed.
Per- and polyfl uoroalkyl substances (PFASs) are human-invented chemicals that were created in the middle of the 20th century. They were synthesized for the fi rst time in 1949, and because of their exceptional surfactant properties, they have been widely used in many industrial applications and daily life products. The common use of PFASs resulted in their worldwide dissemination in natural environment. PFASs are reported to be ubiquitous in surface and drinking waters, but also may be present in soils, animals, milk and milk-products, plants, food. Contaminated drinking water and food are the most signifi cant exposure sources to these chemicals. Ingested PFASs are bio-accumulative and have adverse eff ect on health of humans as well as animal organisms. This paper reviews the most signifi cant information on the origin, properties, distribution, environmental fate, human exposure, health eff ects, and the environmental regulations on PFASs and summarizes the latest advances in the development of novel methods for the eff ective removal of these chemicals from the aqueous environment. Recognized (reverse osmosis, adsorption on activated carbon) and most promising developing removal methods such as adsorption on biomaterials (plant proteins, chitosan beds), mineral adsorbents (LDHs, hydrotalcite), ionexchange resins, and photocatalytic degradation have been emphasized.
Samples for the study were collected from, known from the literature, outcrop profiles in Zarzecze, Radymno, Dybawka, Tarnawce and Pikulice-Nehrybka, situated at the Carpathian border, in the vicinity of the Przemyśl town, close to the San River valley (SE Poland). They represent the Vistulian loess-palaeosol sequences. Carbonates occur mainly in the loesses representing OIS 2 and 3. Pollen analysis, carried out for two profiles (Tarnawce, Radymno), throws light on palaeoecological conditions of loess cover formation and transformation.Isotopic analysis of authigenic carbonates was carried out on carbonate cemented bodies dispersed throughout the loess in forms of nodule, rhizolith and rhizocretion and on bioclasts, mainly snail shells, ostracod valves, and sparse globules (probably the internal shells of the naked snails).In the successions studied, the upper Vistulian loess deposited in environment with poor vegetation, contains rhizo- liths and rhizocretions mainly, while in the middle and lower Vistulian loess with well developed soils, gley horizons, and intercalations of subaqueous sediments, remains of snail shells and ostracod valves prevail. The two main forms of carbonates differ markedly in isotopic composition from one another. These differences seem to be more important than those between samples of one form of carbonates along particular sections. That is the result of numerous factors affecting the fractionation of carbon and, in particular, oxygen stable isotopes in the environment of precipitation of authigenic calcite. The isotopic composition of carbonates cementing sediments is controlled mainly by biominerali- zation of organic matter and local climatic parameters which were rather slightly differentiated during the formation of the studied sediments. The d13C values for bioclasts vary in a broader range than for calcitic cements. Usually the snail shell carbonate is more enriched with heavier carbon isotope than that from ostracod valves, resulting from the isotopic equilibrium with precipitation and with surface waters, respectively. Basing on our study we can conclude that fluctuations of isotope composition of authigenic carbonates make it hard to apply as a paleoclimatic indicator. However, the general trend of d18O variation in analysed carbonate fractions from leoss-palaeosol sequences displays some connections with climatic fluctuations.