Fabric covering is often used by designers, as it can easily mask acoustic structures that do not match an interior. However, in the case of sound diffusers based on change in the phase of the reflected wave, the use of fabric covering is not without its effect on acoustics. It reduces the effectiveness of these structures and raises acoustic absorption. In the paper, the authors analyzed the acoustical properties of a selected fabric used to cover sound diffusers. Sound absorption and scattering coefficients for a system composed of sound diffusers and a fabric situated at different distances d were measured. The results were compared to the sound absorption predicted on the basis of Kuttruff’s and Mechel’s theoretical models. Analysis of the results indicates that the fabric has a significant influence on the system’s acoustic parameters. It is also observed, that fabric applied directly on a phase grating diffuser, produces higher absorption than when it is at some distance from it.
Water is essential for plant growth and development, and the degree of its availability significantly shapes ecosystems in different climate zones. How does an overabundance or deficiency of water affect the flora in Poland and different parts of the world?
The application of hardfacing is one of the ways to restore the functional properties of worn elements. The possibility of using filler materials rich in chrome allows for better wear resistance than base materials used so far. The paper presents the results of research on the use of 3 different grades of covered electrodes for the regeneration of worn track staves. The content of the carbon in the covered electrodes was from 0,5% to 7% and the chromium from 5% to 33%. The microscopic and hardness tests revealed large differences in the structure and properties of the welds. The differences in the hardness of the welds between the materials used were up to 150 HV units. The difference in wear resistance, in the ASTM G65 test, between the best and worst materials was almost 12 times big.
Properties of a snow cover in the vicinity of Arctowski Station, King George Island (West Antarctica) were studied in 1991. Variations of snow quality and physical transformations were analysed against changes of atmospheric parameters, basing on water equivalent index and repeatable examination of snow pits. Essential dependence of snow cover distribution and snow structure from local climatic features and terrain morphology was found. Thawing occurs in the whole mass of snow, with its contribution of both liquid and gas water phases.
The paper presents experimental research carried out to determine the possible actions to reduce the noise generated by trams in a highly urbanised area. A few design strategies affecting tram ride quality have been presented – especially in the aspect of the acoustic phenomena. Main sources of the noise in trams were characterised. The paper includes selected results of comprehensive studies of tram noise in the pass-by test based on the authors’ research methodology. The tests were carried out on various types of trams to recognise the acoustic phenomena characteristic for the rolling stock in a selected tram system. The results of the measurements were analysed both in the field of amplitudes based on noise maps and in respect to frequencies based on noise spectra. The results indicated the rolling noise as important issue demanding taking some actions in order to reduce its level. In this area, elements for the application of individual attenuation solutions, i.e. at the source and during propagation, were presented. The results of the measurements were used as input data to the assumptions of the noise attenuation passive system, which was the final outcome of the study. Dedicated external dampers were used in the case of wheel and rail pairs, where the dominant power of the noise is emitted. The acoustic properties of the bogie area and the bogie side covers were redeveloped to hamper the noise propagation, which is a novel application. The presented results indicate measurable benefits from the applied solutions on the tram noise reduction.
Recently, Google Earth Engine (GEE) provides a new way to effectively classify land cover utilizing available in-built classifiers. However, there have a few studies on the applications of the GEE so far. Therefore, the goal of this study is to explore the capacity of the GEE platform in terms of land cover classification in Dien Bien Province of Vietnam. Land cover classification in the year of 2003 and 2010 were performed using multiple-temporal Landsat images. Two algorithms – GMO Max Entropy and Classification and Regression Tree (CART) integrated into the Google Earth Engine (GEE) plat-form – were applied for this classification. The results indicated that the CART algorithm performed better in terms of mapping land use. The overall accuracy of this algorithm in the year of 2003 and 2010 were 80.0% and 81.6%, respective-ly. Significant changes between 2003 and 2010 were found as an increase in barren land and a reduction in forest land. This is likely due to the slash-and-burn agricultural practice of ethnic minorities in the province. Barren land seems to occur more at locations near water sources, reflecting the local people’s unsuitable farming practice. This study may provide use-ful information in land cover change in Dien Bien Province, as well as analysis mechanisms of this change, supporting en-vironmental and natural resource management for the local authorities.
Investigations of the snow cover at the end of the winter 1990/1991 were carried out in several areas in West Spitsbergen, namely, Lomonosovfonna, Kongsvegen, Fridtjovbreen, Amundsenisen and that north of the Hornsund Fjord. The physical properties and chemical nature of precipitation and the snow cover were determined. The studies revealed high variation in the precipitation and the thickness of the snow cover: 317 mm w.e. (water equivalent) in the Hornsund area, 659 mm w.e. at Lomonosovfonna, 1076 mm w.e. at Fridtjovbreen and 1716 mm w.e. at Amundsenisen. The salt loads deposited in the snow cover in different parts of West Spitsbergen were also calculated (2.8 t/km2 at Lomonosovfonna, 15.8 t/km2 at Kongsvegen and 43.2 t/km2 at Amundsenisen). An intensive process of demineralisation during the conversion of snow to firn was revealed, reaching as much as 90% during the first summer. An attempt to determine the anthropogenic element content using the pH values for the precipitation and snow cover was also made. A distinct correlation between the physico-chemical characteristic of snow layer and falling snow was found. On the basis of the quality of the precipitation and snow cover, West Spitsbergen has been classified into following provinces: (1) northern situated within Arctic High (Lomonosovfonna and Kongsvegen), (2) southern ndergoing mainly moving air masses from the Arctic High and Greenland Low (Amundsenisen and Hornsund region).
The aim of this study is to examine the importance of the decision in Engelhart CTP (US) LLC v Lloyd’s Syndicate 1221 with regard to the insurance of economic losses and non-existent goods in the context of all-risks cover. It also strives to analyse to what extent the principles of construction described in this decision are applicable to the interpretation of all risks cover in marine insurance disputes subject to Polish law. Assureds and beneficiaries of cargo policies are defrauded into taking up false documents for non-existent goods yet Polish law fails to address the questions which arise in such situations. It is thus important not only to investigate and evaluate the answers provided by English law but also to explore if and how Polish law may employ them. It follows from this study that Engelhart may be used in construction of all-risks policies subject to Polish law in most scenarios.
Effective use of energy in various branches of economy is one of world trends in development of power engineering. Relevant energy consumption occurs during exploitation of buildings, so there is still potential to diminish it as far as heating, ventilation, and air conditioning are concerned. Particularly in summer season, the choice of respective roofing colour can play a decisive role for the heat flux transferred to the inside of the object. Decrease of heat flux causes a lower heat burden to the building and lower power consumption by the air conditioning systems. In winter, on the contrary, heat flux transferred to building’s interior should be higher, as a result, demand of energy for heating will be lower. However, calculations of the heat flux require that energy balance must be made for the object. Unfortunately, not all producers of roofing covers inform about the values of reflectivity and thermal emissivity of their products, which is, in turn, necessary for calculations. In the present paper, research methodology elaborated by authors is proposed for determination of thermal emissivity of roofing covers. The paper presents test stand, methodology, and research results for roofing paper in blue colour (as an example) for which the thermal emissivity is an unknown parameter.
The subject of the article is a comparison of two types of concrete carbonation models: self-limited carbonation and infinite carbonation. The results of the research on the progress of carbonation during six years of sample exposure in natural atmospheric conditions were used to determine the detailed models for a set of concretes with different w/c and different types of cement, and two scenarios of initial curing. It has been established that the model of self-limiting carbonation (i.e. hyperbolic) is more adequate for describing laboratory tests results in natural conditions.
The aim of the research is laboratory investigation of aluminium brackets employed to fasten lightweight curtain walls to building facilities. Tensile loads perpendicular to end plates (vertical) were applied here. The author focused on the solutions intended to increase the load-carrying capacity of aluminium brackets applying the plain washer form A (DIN 125; ISO 7089), plain washer with an outer diameter about 3d (DIN 9021; ISO 7093) and additional cover plates (straps) in the location of bolt anchoring on the base plate. The aluminium brackets were tested on a steel base and concrete substrate. The flexibility of anchoring strongly affects the increase of the end plate middle point displacement and movable crosshead displacement.