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Number of results: 68
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Abstract

This paper discusses the challenges faced by the empirical macroeconomist and methods for surmounting them. These challenges arise due to the fact that macroeconometric models potentially include a large number of variables and allow for time variation in parameters. These considerations lead to models which have a large number of parameters to estimate relative to the number of observations. A wide range of approaches are surveyed which aim to overcome the resulting problems. We stress the related themes of prior shrinkage, model averaging and model selection. Subsequently, we consider a particular modelling approach in detail. This involves the use of dynamic model selection methods with large TVP-VARs. A forecasting exercise involving a large US macroeconomic data set illustrates the practicality and empirical success of our approach.
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Abstract

Convective and radiation heat transfer take place between various objects placed in open air space and their surroundings. These phenomena bring about heat losses from pipelines, building walls, roofs and other objects. One of the main tasks in energy auditing is the reduction of excessive heat losses. In the case of a low sky temperature, the radiation heat exchange is very intensive and the temperature of the top part of the horizontal pipelines or walls is lower than the temperature of their bottom parts. Quite often this temperature is also lower than the temperature of the surrounding atmospheric air. In the case of overhead heat pipelines placed in open air space, it is the ground and sky that constitute the surroundings. The aforementioned elements of surroundings usually have different values of temperature. Thus, these circumstances bring about difficulties during infrared inspections because only one ambient temperature which represents radiation of all surrounding elements must be known during the thermovision measurements. This work is aimed at the development of a method for determination of an equivalent ambient temperature representing the thermal radiation of the surrounding elements of the object under consideration placed in open air space, which could be applied at a fairly uniform temperature of the sky during the thermovision measurements as well as for the calculation of radiative heat losses.
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Abstract

Recently, there has been research on high frequency dissipative mufflers. However, research on shape optimization of hybrid mufflers that reduce broadband noise within a constrained space is sparse. In this paper, a hybrid muffler composed of a dissipative muffler and a reactive muffler within a constrained space is assessed. Using the eigenvalues and eigenfunctions, a coupling wave equation for the perforated dissipative chamber is simplified into a four-pole matrix form. To efficiently find the optimal shape within a constrained space, a four-pole matrix system used to evaluate the acoustical performance of the sound transmission loss (STL) is evaluated using a genetic algorithm (GA). A numerical case for eliminating a broadband venting noise is also introduced. To verify the reliability of a GA optimization, optimal noise abatements for two pure tones (500 Hz and 800 Hz) are exemplified. Before the GA operation can be carried out, the accuracy of the mathematical models has been checked using experimental data. Results indicate that the maximal STL is precisely located at the desired target tone. The optimal result of case studies for eliminating broadband noise also reveals that the overall sound power level (SWL) of the hybrid muffler can be reduced from 138.9 dB(A) to 84.5 dB(A), which is superior to other mufflers (a one-chamber dissipative and a one-chamber reactive muffler). Consequently, a successful approach used for the optimal design of the hybrid mufflers within a constrained space has been demonstrated.
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Abstract

The unbalance of the neutral point voltage is an inherent problem of three-level neutral-point-clamped (NPC) inverter, the effect of neutral point voltage balancing which is caused by voltage vector is analyzed, and the relationship of the voltage offset and neutral point voltage is studied in this paper. This paper proposes a novel neutral point balance strategy for three-level NPC inverter based on space vector pulse width modulation (SVPWM). A voltage offset is added to the modulation wave, and a closed-loop neutral point voltage balance control system is designed. In the control system, the dwelling time of synthesis voltage vectors for SVPWM is varied to solve the problem of the unbalance of the neutral point voltage, the sequence of the voltage vectors maintains unchanging. Simulation and experimental results show the neutral point voltage balancing control strategy based on SVPWM is effective.
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Abstract

The matrix rectifier modulated by the classical space vector modulation (SVM) strategy generates common-mode voltage (CMV). The high magnitude and high du/dt of the CMV causes serious problems such as motor damage, electromagnetic noise and many others. In this paper, an improved SVM strategy is proposed by replacing the zero vectors with suitable couple of active ones that substantially eliminate the CMV. Theoretical analysis proves that the proposed strategy can reduce the amplitude of the CMV to half of the original value. In addition, the quality of the input and output waveforms is not affected by extra active vectors. Simulation and experimental results demonstrate the feasibility and effectiveness of the proposed strategy are shown.
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Abstract

Fractal analysis is one of the rapidly evolving branches of mathematics and finds its application in different analyses such as pore space description. It constitutes a new approach to the issue of their natural irregularity and roughness. To be properly applied, it should be encompassed by an error estimation. The article presents and verifies uncertainties along with imperfections connected with image analysis and expands on the possible ways of their correction. One of key aspects of such research is finding both appropriate place and the number of photos to take. A coarse- grained sandstone thin section was photographed and then pictures were combined into one, bigger image. Fractal parameters distributions show their change and suggest that the accurately gathered group of photos include both highly and less porous regions. Their amount should be representative and adequate to the sample. The resolution influence on the fractal dimension and lacunarity values was examined. For SEM limestone images obtained using backscattered electrons, magnification in the range of 120x to 2000x was used. Additionally, a single pore was examined. The acquired results point to the fact that the values of fractal dimension are similar to a wide range of magnifications, while lacunarity changes each time. This is connected with changing homogeneity of the image. The article also undertakes a problem of determining fractal parameters spatial distribution based on binarization. The available methods assume that it is carried out after or before the image division into rectangles to create fractal dimension and lacunarity values for interpolation. An individual binarization, although time consuming, provides better results that resemble reality to a closer degree. It is not possible to define a single, correct methodology of error elimination. A set of hints has been presented that can improve results of further image analysis of pore space.
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Abstract

In the 20th century toponymy of the Kłodzko Land underwent serious changes, which with no doubt can be called a revolution. After 1945 and the displacement of the German population all the pre-war names were substituted with Polish ones, which, unfortunately, only rarely were connected with the former tradition, in some cases as old as the middle ages. Most of new names were introduced by a special commission whose main aim was to mark that the new areas gained by Poland after the World War II (the so called Regained Territories) were successfully taken into possession. However, many places and objects (some mountain tops, rock formations, springs, parts of villages) did not receive a name. In the next decades, new local communities started to accustom the mountainous landscape and independently gave names to various nameless (in Polish) places. Unfortunately, due to the depopulation of rural areas in the Kłodzko Land and other formal reasons, the process was quite slow. The main aim of the paper is not only to analyse those changes, but also to compare the numbers of names in chosen moments of the 20th century. For this purpose three types of maps in 1 : 25 000 scale were used: pre-war (German) “Meßtischblatt”, a Polish topographic map representing the situation at the beginning of the 1970s and, finally, the “Army topographic map” from the end of the 20th century. On the first map 531 geographical names were marked, on the second — only 225, and on the third — 277, which is still approximately half of the number before 1945.
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Abstract

The paper gives an evidence that construction of contemporary objects at the interface with the historic urban space, may be a way to renew and revitalize areas which require it. Such action may be a strong and valuable catalyst for the functional and visual transformation of a given fragment of urban space. It can also contribute to the increase of social activity within it. Research shows that public facilities from the turn of the 20th and 21st century, which were built using innovative architectural technologies and constructional solutions, are the buildings which provide great opportunities to contrast with historical architecture. This can be achieved due to their significant scale and rank in the urban space. The analyzes show that design based on the principle of contrast is the right solution for the degraded historic urban space. The replenishment of the old tissue should be carried out with the emphasis on the identity of the times in which we live, without creating architecture which could literally imitate historical objects or compete with them. Because of this contrast and diversity, new fragments of the city can become a counterweight or a valuable background to the existing historical tissue. Contemporary buildings located in a historical context are not only enhancing the values of cultural heritage but can also become a grateful element of the urban space and a strong accent of modernity and innovation in the city.
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Abstract

The presence of art in historic representative buildings is widespread and common. It is not surprising, therefore, that it is a frequent tool used in the transformation processes of these structures. A surprise, however, may be a situation where, instead of the art from the period of the creation of a given monument, the contemporary, multimedia or engaging the viewer cultural activities occur. Therefore, the key questions are the role of such forms of intervention in the historical representative interiors and the possibility of co-existing old and new. It is not without significance for objects under conservator’s protection that there are special requirements that the intervention must fulfill to be installed. The subject of considerations in this work are case studies of the application of contemporary multimedia art in the representative spaces of historical objects. The purpose of the article is to examine types of such artistic interventions resulting from the relationship between a work of art and exhibition space and their mutual influence.
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Abstract

Kadıköy is a central district of Istanbul and a public transportation hub located on the shores of the Marmara Sea. It has been highly affected by recent developments in Istanbul. The triggers of change in Kadıköy are both planned (developments in transportation facilities and redevelopment of old buildings) and unplanned (i.e. proliferating cafes, bars, and cultural facilities). It is also affected by metropolitan scale dynamics (changes in Beyoğlu, the culture and entertainment center of Istanbul). These changes in Kadıköy have inevitable eff ects on the inhabitants and users. This article discusses the positive and negative aspects of both planned and unplanned development on public life and spaces in Kadıköy. Vitality of public spaces seems increased. The main changes are increasing population and building densities, changes in public space usage, and a proliferation of cultural facilities led by recently opened theatre halls.
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Abstract

This paper presents the qualitative and quantitative characteristics of microstructures of Neogene clays from Warsaw, Poland. Scanning Electron Microscope (SEM) studies were used for the microstructural analysis of natural clays and clay pastes. Qualitative microstructural changes were observed: from a honeycomb microstructure for the initial clay paste to a turbulent microstructure for the dried paste. It was also noticed that water loss caused by the increase of the suction pressure had a significant impact on the microstructural transformations. Significant changes in the quantitative values of the pore space parameters were also observed. Increase of suction pressure and water loss caused a decrease in porosity and changes in the values of morphometric parameters, such as pore distribution; for example, a significant increase of the number of pores of 0−10 μm size and changes in the geometric parameters of the pore space were noticed with the increase of suction pressure. The pore space with larger isometric pores was modified into a pore space with the dominance of small anisometric and fissure-like pores. The increased degree of anisotropy from a poorly-oriented to a highly-oriented microstructure was also observed. After rapid shrinkage the reduction in the number of pores, maximum pore diameter, and total pore perimeter was recorded. The process of rapid water loss induced the closure of very small pores. A similar effect was observed during the increase of the suction pressure, where the closure of pore space of the clay pastes was observed very clearly.
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Abstract

Participatory budgeting has become an important element of empowerment of the residents in the process of spatial planning in Polish cities. The citizens gained the right and a concrete tool to implement their ideas on how to change the city spaces. Many of the projects of participatory budgeting are the results of serious negligence in basic infrastructure in the cities. On the other hand, some of them are an expression of great ingenuity and innovative approach of the citizens to the modernization and arrangements in urban spaces. The civic projects improve quality of life and increase the utility value of public spaces. The main aim of the paper is to review and classify tasks changing public spaces under the formula of participatory budgeting. The research in a form of diagnosis enables to present the directions of participatory budgeting. It helps to monitor and evaluate the social impacts in the process of city space transformations. The subject of analysis are participatory budgets in Łódź and Katowice based on editions in 2015/2016 and 2016/2017.
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Abstract

The post-mining areas due to the difficulties of those, often associated with expensive activities, usually take the form of wasteland. In contrast, unavailable, unused and alien areas the mentality of residents, are identified with empty space. The purpose of the authors was to answer the question: Are post-mining areas becoming empty spaces? Her research basis was changes in the functioning of post-mining areas and empty spaces in Katowice – a city with a long-standing mining tradition. Using GIS tools, a spatial analysis was carried out to determine the empty spaces functions and the perceiving of the post-mining areas by residents or users of a given district nearby.
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Abstract

The motion planning problem consists in finding a control function which drives the system to a desired point. The motion planning algorithm derived with an endogenous configuration space approach assumes that the motion takes place in an arbitrary chosen time horizon. This work introduces a modification to the motion planning algorithm which allows to reach the destination point in time, which is shorter than the assumed time horizon. The algorithm derivation relies on the endogenous configuration space approach and the continuation (homotopy) method. To achieve the earlier destination reaching a new formulation of the task map and the task Jacobian are introduced. The efficiency of the new algorithm is depicted with simulation results.
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Abstract

The article presents issues related to designing recreational and green areas and spatial planning of public areas in the context of physical disability. It gives exemplary proposals of public space development and spatial solutions for people with disabilities. It also discusses issues related to the designing and construction of selected items of landscape architecture for physically disabled people, which were created as part of the education of landscape architects.
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Abstract

In this article, the classification of underground space types is analyzed. It is established that there are objects that are taxed in the tax code of Ukraine and there are those that are not taxed. The results of the research are justified by the lack of mechanisms and technical solutions of three-dimensional objects of commercial space taxation, which have been intensively developing in Ukraine. The ways of solving legal conflicts regarding registration and taxation of real estate objects are suggested. Based on the study of the legislative base and normative legal documents in the sphere of land relations, a classifier of three-dimensional space objects, which today are fully or partially used for commercial purposes in various types of economic activity has been proposed. The analysis of the regulatory and legal framework regarding the taxation of underground space facilities has been carried out. Objects for which the taxation of land is charged and those objects for which there is no charge for the use of underground space have been identified. A methodology for the justified calculation of a decreasing percentage ratio for calculating a normative monetary evaluation (NME) is developed for the cases where the object of an underground commercial space is located at a distance from the center in one of the proposed zones.
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Abstract

The paper presents the possibilities of quantitative analysis of results obtained from CT examination of organs and anatomical structures of the upper respiratory tract. The presented results of the analysis were obtained using proprietary software developed in the MATLAB 2018b environment (Image Processing toolbox). The software enables to visualize the original results of CT scan and, after evaluating the visible structures, enables to select the area to be subjected to quantitative analysis. After the initial identification of an area of interest requiring detailed diagnostics, its volume and the surface areas of individual cross-sections are calculated in the area separated for examinations. A graphical presentation of the analysis results – the surface areas of selected cross-sections possible to visualize in two- and three-dimensional space – enables quick analysis of changes in the examined region.
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Abstract

The article presents state of work in technology of free-space optical communications (Free Space Optics − FSO). Both commercially available optical data links and their further development are described. The main elements and operation limiting factors of FSO systems have been identified. Additionally, analyses of FSO/RF hybrid systems application are included. The main aspects of LasBITer project related to such hybrid technology for security and defence applications are presented.
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Abstract

This study presents the indoor soundscape framework in detail by describing the variables and factors that form an indoor soundscape study. The main objective is to introduce a new indoor soundscaping framework and systematically explain the variables that contribute to the overall evaluation of an indoor soundscape. Hence, the dependencies of physical and psychoacoustical factors of the sound environment and the spatial factors of the built entity are statistically tested. The new indoor soundscaping framework leads to an overarching evaluation perspective of enclosed sound environments, combining objective room acoustics research and noise control engineering with architectural analysis. Therefore, it is hypothesised that case spaces with certain plan organisations, volumetric relations, and spatial referencing lead to differentiated sound pressure level (SPL) and loudness (N) values. SPL and N parametric variances of the sound environments are discussed through the statistical findings with respect to the architectural characteristics of each library case space. The results show that the relation between crowd level variances and sound environment parametric values is statistically significant. It is also found that increasing the atrium height and atrium void volume, the atrium’s presence as a common architectural element, and its interpenetrating reference and domain containment results in unwanted variances and acoustic formations, leading to high SPL and N values.
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Abstract

Public space in geographical and social aspects. Space as a scientific and social term has many interpretations. Work organizes mutual relations between various kinds of spaces. The paper focuses on the contemporary determinants of shaping a public space in cities regarding the popularization of information and communication technologies. Attention was also paid to the metric feature of social spaces because it is usually neglected while constructing such spaces.
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Abstract

We study the autocovariance structure of a general Markov switching second-order stationary VARMA model.Then we give stable finite order VARMA(p*, q*) representations for those M-state Markov switching VARMA(p, q) processes where the observables are uncorrelated with the regime variables. This allows us to obtain sharper bounds for p* and q* with respect to the ones existing in literature. Our results provide new insights into stochastic properties and facilitate statistical inference about the orders of MS-VARMA models and the underlying number of hidden states.
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Abstract

In the flexible road pavement design a mechanistic model of a multilayered half-space with linear elastic or viscoelastic layers is usually used for the pavement analysis. This paper describes a domain selection for the purpose of a FE model creating of the linear elastic layered half-space and boundary conditions on borders of that domain. This FE model should guarantee that the key components of displacements, stresses and strains obtained using ABAQUS program would be in particular identical with those ones obtained by analytical method using VEROAD program. It to achieve matching results with both methods is relatively easy for stresses and strains. However, for displacements, using FEM to obtain correct results is (understandably) highly problematic due to infinity of half-space. This paper proposes an original method of overcoming these difficulties.
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Abstract

The article is devoted to the development of technogenic risk management models and formalization of the process of support in making decision in the sphere of industrial safety. The structural, informative and mathematical models, used to process information in the technological risks management, as well as a formal model of the process of support of making decision in achieving an acceptable level of technical risk are presented and analyzed.
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