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Number of results: 20
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Abstract

The aim of the presented paper is to show the results of shape optimization of railway polynomial transition curves (TCs) of 5th, 7th, and 9th degrees through the use of the full vehicle model and new criteria of assessement concerning the jerk value. The search for the proper shape of TCs means that in this work, the evaluation of TC properties is based on select quantities and the generation of such a shape through the use of mathematically understood optimization methods. The studies presented have got a character of the numerical tests. For this work, advanced vehicle models describing dynamical track-vehicle and vehicle-passenger interactions as well as optimization methods were exploited. In the software vehicle model of a 2-axle freight car, the track discrete model, non-linear descriptions of wheel-rail contact are applied. This part of the software, the vehicle simulation software, is combined with a library optimization procedure into the final computer program.
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Abstract

Early recognition of altered lactate levels is considered a useful prognostic indicator in dis- ease detection for both human beings and animals. It is reasonable therefore to hypothesize that a portable, point of care (POC) spectrophotometric device for analysis of lactate levels, may have an application for field veterinarians across a range of conditions and diagnostic procedures. In this study, a total of 72 cattle in the transition period underwent POC spectrophotometric lactate measurement with a portable device (The Vet Photometer) in the field, with a small portion of blood used for comparative ELISA evaluation. Lactate measurements were compared using a of Passing-Bablok regression analysis and Bland-Altman plots. The Vet Photometer lactate mea- surement results were in agreement with those generated by the ELISA method. Values for the agreement were derived, in a 95% CI between -1.3 and 0.99, and a positive correlation (r=0.71) between the two measurements. The equation y= 0.68x + 0.60 was achieved using a Pass- ing-Bablok regression analysis. There were no statistical differences in mean values between the measurement methods. In conclusion, a novel veterinary POC spectrophotometric device “Vet Photometer” is an accurate device for evaluation of lactate levels in healthy transition cows.
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Abstract

Deep seismic sounding measurements were performed in the continent-ocean transition zone of north-western Spitsbergen , during the expedition ARKTIS XV/2 of the RV Polarstern and the Polish ship Eltanin in 1999. Profile AWI-99200 is 430 km long and runs from the Molloy Deep in the Northern Atlantic to Nordaustlandet in north-eastern Svalbard . Profile AWI-99400 is 360 km long and runs from the Hovgĺrd Ridge to Billefjorden. Seismic energy (airgun and TNT shots) was recorded by land (onshore) seismic stations (REF) and ocean bottom seismometers (OBS) and hydrophone systems (OBH). Good quality refracted and reflected P waves were recorded along the two profiles providing an excellent data base for a detailed seismic modelling along the profile tracks. Clear seismic records from airgun shots were obtained up to distances of 200 km at land stations and 50 km at OBSs. TNT explosions were recorded even up to distances of 300 km . A minimum depth of about 6 km of the Moho discontinuity was found east of the Molloy Deep. Here, the upper mantle exhibits P-wave velocity of about 7.9 km/s, and the crustal thickness does not exceed 4 km . The continent–ocean transition zone to the east is characterised by a complex seismic structure. The zone is covered by deep sedimentary basins. The Moho interface dips down to 28 km beneath the continental part of the 99200 profile, and down to 32 km beneath the 99400 profile. The P-wave velocity below the Moho increases up to 8.15 km/s. The continental crust consists of two or three crystalline layers. There is a lowermost crustal continental layer, in the 99400 profile’s model, with the P-wave velocity in order of 7 km/s, which does not exist in the continental crust along the 99200 profile. Additionally, along the 99200 profile, we have found two reflectors in the lower lithosphere at depths of 14–42 and 40–50 km dipping eastward, with P-wave velocity contrasts of about 0.2 km/s. The characteristics of the region bears a shear-rift tectonic setting. The continent–ocean transition zone along the 99200 profile is mostly dominated by extension, so the last stage of the development of the margin can be classified as rifting. The uplifted Moho boundary close to the Molloy Deep can be interpreted as a south-western end of the Molloy Ridge. The margin in the 99400 profile area is of transform character.
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Abstract

In this paper some issues of the transition process from air- to oxy-combustion were investigated. Advantages of flexible combustion were described. Flexible combustion tests carried out at four European plants and five plants outside Europe of different scales of process and test parameters were presented. An analysis of the transition time from air to oxy-combustion of different laboratory and pilot scale processes was carried out. The “first-order + dead time” approach was used as a model to describe transition process. Transitional periods between combustion modes and characteristic parameters of the process were determined. The transition time depends not only on the facility’s capacity but also it is impacted by specific operational parameters.
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Abstract

It is shown that heat energy transfer from the source to the medium is accompanied by rheological transitions. Physical parameters of the medium change in the rheological transition zone due to heat energy flow transfer at a certain speed. It is shown that use of linear gradient laws during description of heat energy transfer processes leads to great differences between theoretical and experimental results, as well as the paradox of infinite spreading speed of disturbances of temperature fields. For mathematical description of heat energy transfer processes in mediums, it is proposed to use the method of irreversible rheological transitions and zero gradient, thus providing solutions of nonlinear differential equations in analytical form.
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Abstract

This study examines the causal links between improvements in economic freedom and changes in GDP per capita of new EU members in transition in the period 2000‒2009. The empirical results suggest significant causality running from changes in monetary and fiscal freedom, trade openness, regulation of credit, labour, and business, legal structure and security of property rights, and access to sound money to movements in GDP per capita, especially in less and moderately developed CEE transition countries. Moreover, we find evidence that improvements in economic freedom are one of the main factors stimulating the convergence of these economies towards rich EU members. The evidence of causality in the opposite direction is much weaker.
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Abstract

This article examines the ontological and spatial character of the waterfront and its influence on perception and design, with particular focus on the process of reproduction of space (Lefebvre) through the generation of mental maps. The convergence of land and water holds in itself an inherent tension between the accessible and the unattainable: the unconscious can be projected on the unknowable underwater space; the unseen domain beyond the horizon can hold a promise of a better world. Another polarity is that of the familiar and the unknown/exotic, off ering a new perspective, a reevaluation of the familiar through the process of ‘ostranenie’ (Shklovsky),’verfremdung’ (Brecht) or ‘estrangement’. The impact of these polarities reaches beyond the spectacle of urban life, the cinematic experience or the theatrum mundi: it enables the reevaluation of the preconceptions of beauty and utility, as exemplifi ed by Futurist Manifesto (Marinetti). These polarities manifest themselves in the hierarchy and dynamics of a waterfront community: physical impermanence of water dwellings foregrounds the contingent nature of human relationships. The waterfront community inhabits superimposed yet separate networks of land and water. First, mental maps have to be generated for each of these separately, then they have to be reconciled in a coherent whole in a separate process. That mapping of the separate networks necessitates a physical transition, a spatial translation that also has linguistic consequences: a different semantic field is assigned to the vocabulary of the everyday, for the significance of the basic terms like ‘home’ or ‘street’ need a modifi ed definition. All the aforementioned processes and phenomena infl uence the ability to perceive, design and reproduce waterfront areas of cities.
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Abstract

This paper discusses the influence of the direction of applied deformation on the ability to gelation of thermosensitive chitosan hydrogels. The application of the shear rate equal in value to the classically performed oscillatory measurements leads to significantly different shapes of experimental curves. It was found that the type of mechanically applied deformation has a significant impact on the gelation ability of colloidal chitosan solutions and conditions of sol-gel phase transition. Simple shear leads to a phase transition at a lower temperature or in a shorter time compared to oscillatory tests. Moreover, based on the final values of dynamic viscosity in rotational measurements, it was found that stronger crosslinking of the polymer structure was observed.
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Abstract

A review of the contemporary mainstream literature on exchange rate modelling clearly indicates that the rational expectations hypothesis (RE) is almost invariably taken as a point of reference in empirical investigations. This paper tests the RE hypothesis for the Polish foreign exchange market within the Roman Frydman and Michael Goldberg model that builds on the hypothesis of imperfect knowledge economics (IKE). The employed modelling strategy consists in the formulation of assumptions about the persistence of nominal rate, prices and interest rates and of the verification of competing scenarios congruent with RE and IKE. As a result of the analysis, the RE hypothesis is rejected in favour of the IKE alternative.
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Abstract

Owing to the dramatic change in the thermal conductivity of 4He when its temperature crosses the transition of superfluid (HeI) and normalfluid (HeII), a sealed-cell with a capillary is used to realize the lambda transition temperature, Tλ. A small heat flow is controlled through the capillary of the sealed-cell so as to realize the coexistence of HeI and HeII and maintain the stay of HeI/HeII interface in the capillary. A stable and flat lambda transition temperature "plateau" is obtained. Because there is a depression effect of Tλ caused by the heat flow through the capillary, a series of heat flows and several temperature plateaus are made and an extrapolation is applied to determine Tλ with zero heat flow. A rhodium-iron resistance thermometer with series number A34 (RIRT A34) has been used in 24 Tλ -realization experiments to derive Tλ with a standard deviation of 0.022mK, which proves the stability and reproducibility of Tλ.
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Abstract

This paper presents numerical two-dimensional results for fine-grained concrete under quasi-static three-point bending at meso-scale. Concrete was modelled as a random heterogeneous three-phase material. The simulations for notched concrete beams were carried out with the standard finite element method using an isotropic damage constitutive model enhanced by a characteristic length of micro-structure by means of a non-local theory. The effect of the volume fraction, shape, size, statistical distribution and stiffness of aggregate was analysed. Moreover, the effect of the bond thickness, notch size and characteristic length of micro-structure on the material behaviour was numerically investigated. The FE results were compared with own laboratory test results and other meso-scale calculations for three-phase concrete elements.
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Abstract

For the private and public sector in any particular country it is crucial to know, which industries may exhibit comparative advantages, that for some reasons are not realized. This can efficiently help all current and potential actors to improve their economic strategy both at the micro- and macroeconomic level. In this paper we propose an approach of forecasting comparative advantages dynamics in foreign trade. The instrument is based on relative price differences and is efficient for countries in the process of economic liberalization. An empirical analysis based on the example of Central and East European countries confirms a good performance in the sense of predictive power of this instrument. On the example of Russia, experiencing a period of economic liberalization and with the prospect to join the WTO agreements, we demonstrate which sectors are most likely to contain comparative advantages in the near future.
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Abstract

The transition effect between different track-foundation systems is examined from the point of view of energy that is produced during the passage of load. Analytical solution is given. A model of beam on elastic foundation with damping is used as the base model. It is developed into a model composed of two parts that represent the track-subgrade system with an abrupt change in mechanical parameters: bending stiffness, foundation stiffness, damping, and mass. Several calculations are carried out including examples of comparative calculations with the Finite Difference Model and the Finite Element Model. Transient rail deflections and energy are determined, which may serve to estimate the rate of track-subgrade deterioration.
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Abstract

Being more sensitive to economic fluctuations, childbearing postponement increased during the second demographic transition and was accompanied by a moderate decline in the number of children per woman and the progressive rise of mother’s age at first birth. Under the hypothesis that recessions have a marked influence on population dynamics, the present study investigates spatial changes in mother’s age at birth in Greece with the aim to assess the differential impact of economic crisis along the urban-rural gradient. The percent composition of births by mother's age class – considered a gross indicator of fertility under a changing socioeconomic context – was studied at 4 spatial scales (the whole country, administrative regions, prefectures and metropolitan areas or specific economic districts) over an economic cycle from expansion to recession (1980–2016). While stimulating childbearing postponement observed since the early 1980s, empirical results of this study indicate that the 2007 recession was quite neutral on fertility trends in Greece, consolidating the traditional divide between urban and rural areas.
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Abstract

This paper investigates the life cycle profiles of income and consumption and relative income mobility in Poland – a transition economy facing rapid structural economic and social changes. According to my results, and in line with the empirical evidence for advanced economies, the age-profiles of average income and consumption in Poland exhibit a hump. The inequality of income over the life cycle is found to flatten relatively quickly in Poland, which contrasts with the approximately linear shape observed in the US. When individual income process is fitted to match the Polish inequality profile, it exhibits less persistence than in the US. Past earnings turn out to affect current income more strongly for the group of more educated individuals. Moreover, and in contrast to the permanent income hypothesis as well as findings for other economies, no evidence of an increase in consumption inequality for households older than 30 years is found. Finally, the obtained estimates of relative income mobility in Poland are higher than those for developed countries.
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Abstract

The purpose of this paper is to model daily returns of the WIG20 index. The idea is to consider a model that explicitly takes changes in the amplitude of the clusters of volatility into account. This variation is modelled by a positive-valued deterministic component. A novelty in specification of the model is that the deterministic component is specified before estimating the multiplicative conditional variance component. The resulting model is subjected to misspecification tests and its forecasting performance is compared with that of commonly applied models of conditional heteroskedasticity.
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Abstract

Changes in the size and the age structure of a population have a great impact on an economy, especially on national savings and capital flows. Poland’s population, although still relatively young when compared to other developed countries, is expected to experience accelerated ageing and decline in forthcoming decades. In this paper, we assess the effects of these processes for Polish economy. Using an open-economy OLG model with demographic shocks and a variable retirement age, we simulate dynamics of real interest rates, main macro aggregates as well as net foreign assets to GDP. We show that rapid ageing will reduce the interest rate gap between Poland and the developed countries by 1.3-2 p.p. We also document a strong positive relationship between interest rates and the retirement age and find that the decline in the interest rate in Poland is primarily driven by the surviving probability shock
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Abstract

Over the years laser welding has evolved as a fabrication process capable of overcoming the limitations of conventional joining methodologies. It facilitates the welding of diverse range of materials like metals, non-metals, polymers etc. Laser transmission welding is a technique employed for fabricating intricate shapes/contours in polymers with better precision compared to the other conventional processes. Nylon6, a synthetic semi-crystalline polymer is utilized as an engineering thermoplastic due to its high strength and temperature resistant properties. In the earlier researches, various welding techniques were employed for the fabrication of polymers and metals keeping the laser beam stagnant, and much emphasis was given only to temperature distribution along the different axes and limited attention was given to residual stress analysis. Therefore, in this research work, a three-dimensional time-dependent model using a moving laser beam is used to fabricate unreinforced Nylon6 specimens.
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