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Tytuł:
Models for survey nonresponse and bias adjustment techniques
Autorzy:
Ayhan, H. Öztaş
Powiązania:
https://bibliotekanauki.pl/articles/18105172.pdf
Data publikacji:
2023-06-13
Wydawca:
Główny Urząd Statystyczny
Tematy:
response rate
nonresponse bias
nonresponse rate
sample survey
survey error
Opis:
Survey statisticians have been dealing with the issues of nonresponse in sample surveys for many years. Due to the complex nature of the mechanism, so far it has not been easy to find a general solution to this problem. In this paper, several aspects of this topic will be elaborated on: the survey unit nonresponse bias has been examined alternatively by taking response amounts which are fixed initially and also by taking the response amounts as random variables. An overview of the components of the bias due to nonresponse will be performed. Nonresponse bias components are illustrated for each alternative approach and the amount of bias was computed for each case.
Źródło:
Statistics in Transition new series; 2023, 24, 3; 139-149
1234-7655
Pojawia się w:
Statistics in Transition new series
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling Macro-Financial Linkages: Combined Impulse Response Functions in SVAR Models
Autorzy:
Serwa, Dobromił
Wdowiński, Piotr
Powiązania:
https://bibliotekanauki.pl/articles/2119956.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
vector autoregression
Cholesky decomposition
combined impulseresponse
banking sector
real economy
Opis:
We estimated a structural vector autoregressive (SVAR) model describing the links between a banking sector and a real economy. We proposed a new method to verify robustness of impulse-response functions to the ordering of variables in an SVAR model. This method applies permutations of orderings of variables and uses the Cholesky decomposition of the error covariance matrix to identify parameters. Impulse response functions are computed and combined for all permutations. We explored the method in practice by analyzing the macro- financial linkages in the Polish economy. Our results indicate that the combined impulse response functions are more uncertain than those from a single model specification with a given ordering of variables, but some findings remain robust. It is evident that macroeconomic aggregate shocks and interest rate shocks have a significant impact on banking variables.
Źródło:
Central European Journal of Economic Modelling and Econometrics; 2017, 4; 323-357
2080-0886
2080-119X
Pojawia się w:
Central European Journal of Economic Modelling and Econometrics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Evaluation of Some Machine Learning Algorithms as Tools for Predicting Soil Characteristics Based on Their Spectral Response in the Vis‑NIR Range
Autorzy:
Gruszczyński, Stanisław
Powiązania:
https://bibliotekanauki.pl/articles/1838007.pdf
Data publikacji:
2021
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
machine learning
soil properties
near infrared spectral response
stacked regression models
Opis:
Using the Land Use and Coverage Frame Survey (LUCAS) database of European soil surface layer properties, statistical and machine learning predictive models for several key soil characteristics (clay content, pH in CaCl2 , concentration of organic carbon, calcium carbonates and nitrogen and exchange cations capacity) were compared on the basis of processing their spectral responses in the visible (Vis) and near infrared (NIR) parts. Standard methods of relationship modeling were used: stepwise regression, partial least squares regression and linear regression with input data obtained from principal components analysis. Using the inputs extracted by statistical algorithms various machine learning algorithms were used in the modeling. The usefulness of the models was analyzed by comparison with the values of the determination coefficients, the root mean square error and the distribution of residual values. The mean square error of estimation in the cross validation procedure for the stack mod el using the multilayer perceptron and the distributed random forest were as follows: for clay content – ca. 4.5%; for pH – ca. 0.35; for SOC – ca. 7.5 g/kg (0.75% by weight); for CaCO3 content – ca. 19 g/kg; for N content – ca. 0.50 g/kg; and for CEC – ca. 3.5 cmol(+)/kg.
Źródło:
Geomatics and Environmental Engineering; 2021, 15, 1; 63-95
1898-1135
Pojawia się w:
Geomatics and Environmental Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Odpowiedź dynamiczna drogi szynowej jako struktury dwuwarstwowej w kierunku wzdłużnym
Dynamic response of rail track as two layer structure in longitudinal direction
Autorzy:
Czyczuła, Włodzimierz
Kozioł, Piotr
Powiązania:
https://bibliotekanauki.pl/articles/2055649.pdf
Data publikacji:
2020
Wydawca:
Stowarzyszenie Inżynierów i Techników Komunikacji Rzeczpospolitej Polskiej
Tematy:
hamowanie/rozpędzanie pociągu
modele analityczne toru
przemieszczenia wzdłużne szyn i podkładów
droga szynowa
rail track
braking/accelerating of train
analytical track models
rail and sleepers longitudinal displacements
Opis:
Praca przedstawia analizę liniowych modeli odpowiedzi toru przy obciążeniach wzdłużnych, wynikających z rozpędzania/hamowania pociągu. Przedstawiono zarówno strukturę jednowarstwową (szyny), jak i dwuwarstwową, gdzie wyodrębniono także warstwę podkładów. Analizę przeprowadzono przy założeniu, że – w krótkich przedziałach czasu – prędkość pociągu nie zmienia się istotnie; dlatego rozważana jest stacjonarna odpowiedź drogi szynowej. Elementem nowości w stosunku do poprzednich prac autorów jest wprowadzenie do modelu dynamicznego drugiej warstwy drogi szynowej, tzn. podkładów.
The paper presents an analysis of linear models for track response under longitudinal loads due to a braking/accelerating of a train. The one-layer (for rails only) and two-layer (for rails and sleepers) structures are considered. Analysis is carried out under assumption that – in a sufficiently short period of time – the train speed does not change significantly. Therefore a stationary response of rail track is considered. The main novelty of this paper is an introduction of a second layer (i.e. sleepers) in the developed previously more simplified model.
Źródło:
Zeszyty Naukowo-Techniczne Stowarzyszenia Inżynierów i Techników Komunikacji w Krakowie. Seria: Materiały Konferencyjne; 2020, 2 (121); 7--15
1231-9171
Pojawia się w:
Zeszyty Naukowo-Techniczne Stowarzyszenia Inżynierów i Techników Komunikacji w Krakowie. Seria: Materiały Konferencyjne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Causal Link Between the Polish Stock Market and Selected Macroeconomic Indicators
Związek przyczynowy między polskim rynkiem akcji i wybranymi wskaźnikami makroekonomicznymi
Autorzy:
Urjasz, Szczepan
Powiązania:
https://bibliotekanauki.pl/articles/1922362.pdf
Data publikacji:
2019-07-10
Wydawca:
Uniwersytet Warszawski. Wydawnictwo Naukowe Wydziału Zarządzania
Tematy:
stock market
industrial production
interest rate
impulse response function
VAR models
rynek akcji
produkcja przemysłowa
stopa procentowa
funkcja odpowiedzi na impuls
modele VAR
Opis:
This article proposes a study of dynamics in the bi-directional relationship between macroeconomic factors and the stock market in Poland. In order to verify Granger’s causality and analyse the course of the impulse response function, a model of vector autoregression was used. The analysis is based on monthly data and covers the period from January 2004 to December 2018. The results of the investigation show that the stock exchange index is a significant guide for the industrial production index and the relation is positive. At the same time, interest rates are not one of the most important variables that affect stock prices.
W niniejszym artykule zaproponowano badanie dynamiki w dwukierunkowej relacji między czynnikami makroekonomicznymi a rynkiem akcji w Polsce. W celu weryfikacji przyczynowości Grangera oraz analizy przebiegu funkcji odpowiedzi na impuls wykorzystano model wektorowej autoregresji. Analiza opiera się na danych miesięcznych i obejmuje okres od stycznia 2004 roku do grudnia 2018 roku. Wyniki badania wskazują, że indeks giełdowy znacząco przewodzi indeksowi produkcji przemysłowej i związek ten jest pozytywny. Równocześnie stopy procentowe nie są jedną z najważniejszych zmiennych, które oddziałują na ceny akcji.
Źródło:
Problemy Zarządzania; 2019, 3/2019 (83); 179-196
1644-9584
Pojawia się w:
Problemy Zarządzania
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modele działań realizacyjnych i pielęgnacyjnych wdrażanych w ogrodzie wilanowskim w odpowiedzi na współczesne wyzwania rewaloryzacyjne ogrodów historycznych
Models of implementation and maintenance activities implemented in the Wilanów garden in response to contemporary restoration challenges of historical gardens
Autorzy:
Przybylak, Łukasz
Powiązania:
https://bibliotekanauki.pl/articles/1927082.pdf
Data publikacji:
2019
Wydawca:
Narodowy Instytut Dziedzictwa
Tematy:
konserwacja
krajobraz
muzeum
ogród
rewaloryzacja
Wilanów
conservation
landscape
museum
garden
restoration
Opis:
Intensywność czynników środowiskowych, społecznych i legislacyjnych sprawia, iż mimo wzrastającej popularności działań rewaloryzacyjnych prowadzonych w obiektach stanowiących nasze dziedzictwo ogrodowe, jest to dziedzina konserwacji przeżywająca poważny kryzys. Walka z nim wymaga nie tylko podjęcia złożonych i długoletnich prac u podstaw kształcenia i podnoszenia świadomości społecznej, ale także obrania modeli postępowania pozwalających na plastyczne reagowanie na zmieniające się uwarunkowania. Podejmowanie działań zaradczych mających na celu sprostanie współczesnym wyzwaniom rewaloryzacyjnym na poziomie zarządczym i realizacyjnym można obserwować na przykładzie Muzeum Pałacu Króla Jana III w Wilanowie, które od 2015 r. wdraża nowe modele postępowania.
The intensity of environmental, social and legislative factors means that despite the growing popularity of restoration activities carried out in facilities constituting our garden heritage, it is a field of conservation experiencing a serious crisis. The fight against it requires not only undertaking complex and long-term work at the grassroots of education and raising social awareness, but also choosing models of conduct that allow for a plastic response to the changing conditions. Undertaking remedial actions aimed at meeting contemporary restoration challenges at the management and implementation level can be observed on the example of the Museum of King Jan III’s Palace at Wilanów, which has been implementing new models of conduct since 2015.
Źródło:
Ochrona Zabytków; 2019, 2; 93-119
0029-8247
Pojawia się w:
Ochrona Zabytków
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Osteoblasts response to novel chitosan/agarose/hydroxyapatite bone scaffold – studies on MC3T3-E1 and hFOB 1.19 cellular models
Autorzy:
Kazimierczak, Paulina
Vivcharenko, Vladyslav
Truszkiewicz, Wiesław
Wójcik, Michał
Przekora, Agata
Powiązania:
https://bibliotekanauki.pl/articles/284277.pdf
Data publikacji:
2019
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
Tematy:
bone tissue engineering
biocompatibility
osteoconductivity
cell growth
osteogenic differentiation
Opis:
Since it is known that various cell lines may ex-press different behaviours on the scaffolds surface, a comprehensive analysis using various cellular mo-dels is needed to evaluate the biomedical potential of developed biomaterials under in vitro conditions. Thus, the aim of this work was to fabricate bone scaffolds composed of a chitosan-agarose matrix reinforced with nanohydroxyapatite and compare the biological response of two cell lines, i.e. mouse calvarial preosteoblasts (MC3T3-E1 Subclone 4) and human foetal osteoblasts (hFOB 1.19). Within this study, the osteoblasts number on the scaffold surface and the osteogenic markers level produced by MC3T3-E1 and hFOB 1.19 cells were determined. Furthermore, changes in calcium and phosphorous ions concentrations in the culture media dedicated for MC3T3-E1 and hFOB 1.19 were estimated after the biomaterial incubation. The obtained results proved that the fabricated biomaterial is characterized by biocompatibility and osteoconductivity since it favours osteoblasts attachment and growth. It also supports the production of osteogenic markers (collagen, bALP, osteocalcin) by MC3T3-E1 and hFOB 1.19 cells. Interestingly, the developed biomaterial exhibits different ion reactivity values in the two culture media dedicated for the mentioned cell lines. It was also revealed that mouse and human osteoblasts differ in the cellular response to the fabricated scaffold. Thus, the use of at least two various cellular models is recommended to carry out a reliable biological characterization of the novel biomaterial. These results demonstrate that the tested bone scaffold is a promising biomaterial for bone regeneration applications, however further biological and physicochemical experiments are essential to fully assess its biomedical potential.
Źródło:
Engineering of Biomaterials; 2019, 22, 151; 24-29
1429-7248
Pojawia się w:
Engineering of Biomaterials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The use of mathematical experiments planning in building materials quality research
Autorzy:
Dvorkin, Leonid
Prokopski, Grzegorz
Marchuk, Vitaliy
Huts, Andriy
Powiązania:
https://bibliotekanauki.pl/articles/947637.pdf
Data publikacji:
2019
Wydawca:
Politechnika Rzeszowska im. Ignacego Łukasiewicza. Oficyna Wydawnicza
Tematy:
mathematical planning of experiment
polynomial models
response surface
regression equations
variation levels
planowanie eksperymentu
modele matematyczne
modele wielomianowe
równanie regresji
Opis:
The issue of ensuring the construction of materials and products, necessary quality characteristics and durability, is associated with the solution of many problems arising both in the construction industry enterprises and in the conditions of a construction site. Most of these (construction-technological) problems are solved due to the rational choice of raw materials, changes in the ratio between the main components, as well as production modes. The method of solving such problems assumes simultaneous consideration of many factors (composition, consumption of components, formation conditions, hardening, etc.) and providing many parameters (workability, strength, frost resistance, water resistance, etc.), which in practice is difficult to implement by traditional methods of experimentation because of high labor intensity of the work and the need for complex analysis. The article considers using methods of system analysis and mathematical planning of experiments in the study of building materials quality. Methods of obtaining mathematical models of various types, their interpretation and analysis, as well as the basic principles of using system analysis for solving the problems of building materials technology are presented. The technique of mathematical planning of experiments is presented. The main types of tasks solved with this method are analyzed, optimization criteria for solving problems of concrete technology are formulated. Methods for constructing linear and nonlinear models, their statistical analysis, and typical plans for carrying out experiments are presented.
Źródło:
Czasopismo Inżynierii Lądowej, Środowiska i Architektury; 2019, 66, 4; 5-16
2300-5130
2300-8903
Pojawia się w:
Czasopismo Inżynierii Lądowej, Środowiska i Architektury
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The use of mathematical experiments planning in building materials quality research
Autorzy:
Dvorkin, Leonid
Prokopski, Grzegorz
Marchuk, Vitaliy
Huts, Andriy
Powiązania:
https://bibliotekanauki.pl/articles/2065749.pdf
Data publikacji:
2019
Wydawca:
Politechnika Rzeszowska im. Ignacego Łukasiewicza. Oficyna Wydawnicza
Tematy:
mathematical planning of experiment
polynomial models
response surface
regression equations
variation levels
planowanie eksperymentu
modele matematyczne
modele wielomianowe
równanie regresji
Opis:
The issue of ensuring the construction of materials and products, necessary quality characteristics and durability, is associated with the solution of many problems arising both in the construction industry enterprises and in the conditions of a construction site. Most of these (construction-technological) problems are solved due to the rational choice of raw materials, changes in the ratio between the main components, as well as production modes. The method of solving such problems assumes simultaneous consideration of many factors (composition, consumption of components, formation conditions, hardening, etc.) and providing many parameters (workability, strength, frost resistance, water resistance, etc.), which in practice is difficult to implement by traditional methods of experimentation because of high labor intensity of the work and the need for complex analysis. The article considers using methods of system analysis and mathematical planning of experiments in the study of building materials quality. Methods of obtaining mathematical models of various types, their interpretation and analysis, as well as the basic principles of using system analysis for solving the problems of building materials technology are presented. The technique of mathematical planning of experiments is presented. The main types of tasks solved with this method are analyzed, optimization criteria for solving problems of concrete technology are formulated. Methods for constructing linear and nonlinear models, their statistical analysis, and typical plans for carrying out experiments are presented.
Źródło:
Czasopismo Inżynierii Lądowej, Środowiska i Architektury; 2019, 66, 4; 5--16
2300-5130
2300-8903
Pojawia się w:
Czasopismo Inżynierii Lądowej, Środowiska i Architektury
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
3D Simulation of Chlorine Dispersion in Rrural Area
Symulacja 3D dyspersji chloru w terenie wiejskim
Autorzy:
Polanczyk, A.
Salamonowicz, Z.
Majder-Lopatka, M.
Dmochowska, A.
Jarosz, W.
Matuszkiewicz, R.
Makowski, R.
Powiązania:
https://bibliotekanauki.pl/articles/1813729.pdf
Data publikacji:
2018
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
chlorine dispersion
CFD
dense gas dispersion models
turbulent flow
emergency response model
dyspersja chloru
model dyspersji gazu ciężkiego
przepływ turbulentny
model awaryjnej odpowiedzi
Opis:
Prediction of hazardous substances dispersion resulting from accidental leakage in environment is essential for risk analysis and emergency response. Different numerical tools are applied for description of dispersion process. Development of numerical algorithms has enabled the computational fluid dynamics (CFD) models to be used extensively in indoor dispersion studies. Numerical methods based on computational fluid dynamics (CFD) may facilitate the precise investigation of the hazardous substances dispersion. Therefore, the aim of the study was to prepare a transient CFD model describing the phenomena of chlorine dispersion in a dynamic setup including different environmental factors. Reliable computational description of dispersion process still represents one of the most challenging applications. Therefore, we aimed to prepare a transient 2D and 3D numerical models of chlorine dispersion from a ground source in a dynamic setup. For 2D simulation a Degadis model was used, while for 3D approach a multiphase Volume of Fluid model (VOF) was applied. For both analyzed cases area of investigation was equal to 0.1 km2. Furthermore, for 3D simulations height was equal to 50 m. For the reconstruction of atmospheric conditions Pasquill stability classes and one-direction wind were applied. Analysis of chlorine concentration in function of wind intensity indicated extension of chlorine cloud with decrease of concentration. Moreover, comparison of constant and dynamic setup indicated high impact of wind. In case of windless conditions circular profile of chlorine concentration around dispersion source was noticed. Wind directed the chloride cloud which dispersed accordingly to the wind direction. As expected chloride concentration decreased with altitude. 2D model allowed prediction of polluted cloud in horizontal direction, while 3D model allowed description of horizontal and vertical distribution of chlorine. It was observed that with increase of Pasquill stability class the area of chlorine dispersion had similar character for horizontal model as well as for horizontal and vertical model (3D). For the windless case circular profile of chlorine concentration around dispersion source was observed. Additionally, for the wind application the main chlorine concentration moved ahead the source of dispersion. Analysis of chlorine concentration in function of height resulted in decrease of chlorine appearance in upper level of mathematical domain.
Predykcja dyspersji substancji niebezpiecznych z przypadkowych wycieków jest niezbędna w analizie ryzyka. W tym celu do opisu procesu dyspersji stosowane są różne numeryczne narzędzia. Rozwój matematycznych algorytmów umożliwia stosowanie m.in. techniki CFD na szeroką skalę. Tym samym celem niniejszej pracy było opracowanie dwuwymiarowego i trójwymiarowego modelu opisującego zjawisko dyspersji chloru z naziemnego źródła. Dla dwuwymiarowego podejścia zastosowano model Degadisa. Natomiast dla trójwymiarowego podejścia wielofazowy model VOF. Dla obu przypadków powierzchnia analizowanego obszaru wynosiła 0.1 km2. Co więcej, dla trójwymiarowego podejścia wysokość analizowanej domeny obliczeniowej wynosiła 50 m. W celu rekonstrukcji parametrów atmosferycznych uwzględniono klasy stabilności Pasquilla oraz wpływ wiatru. Dwuwymiarowy model umożliwiał analizę procesu dyspersji w płaszczyźnie poziomej, podczas gdy model trójwymiarowy umożliwiał analizę zarówno w płaszczyźnie poziomej jak i pionowej. Analiza obu modeli wskazuje, iż wzrost intensywności wiatru wydłuża zasięg chmury chloru, z jednoczesnym spadkiem jego stężenia. Co więcej, w przypadku nieuwzględnienia przepływu wiatru obserwowano kołowy profil stężenia chloru dookoła źródła dyspersji. Natomiast przepływający wiatr powodował zmniejszenie koncentracji chloru wraz z wysokością. Również zaobserwowano, iż uwzględnienie klas stabilności Pasquilla miało porównywalny efekt w przypadku podejścia dwuwymiarowego i trójwymiarowego. Uwzględnienie wiatru powodowało przemieszczenie maksymalnej wartości stężenia chloru znad źródła dyspersji. Co więcej, analiza stężenia chloru w funkcji wysokości wskazuje na zmniejszenie zawartości chloru w górnej części domeny matematycznej.
Źródło:
Rocznik Ochrona Środowiska; 2018, Tom 20, cz. 2; 1035-1048
1506-218X
Pojawia się w:
Rocznik Ochrona Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of corneal and fatty tissues biomechanical response in dynamic tonometry tests by using inverse models
Autorzy:
Jannesari, M.
Kadkhodaei, M.
Mosaddegh, P.
Kasprzak, H.
Behrouz, M. J.
Powiązania:
https://bibliotekanauki.pl/articles/307551.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
biomechanika rogówki
okulistyka
tkanka tłuszczowa
tonometria
corneal biomechanics
fatty tissue
dynamic tonometry
inverse finite element method
Opis:
The assessment of corneal biomechanics is essential for studying ophthalmological operations, such as refractive surgeries, and for more accurate estimation of intraocular pressure. The chief aim of the current study is to characterize corneal and fatty tissues in order to construct a model to predict eye globe behavior during dynamic tonometry tests. Methods: In the present study, images from corneal deformation, acquired from Corvis ST tonometer, were processed. Then, corneal pure displacement and eye globe retraction were calculated. Utilizing inverse finite element method, corneal material properties were calculated in order to predict pure deformation obtained from Corvis ST. Using a similar approach, material parameters of fatty tissue were estimated in order to predict the eye globe retraction. The model used for fatty tissue was considered as corneal boundary condition in a forward finite element model to create a joint model, which could simulate corneal behavior in dynamic tonometry tests. Results: It was shown that an isotropic material model is accurate enough to predict corneal deformation in dynamic tonometry tests. Moreover, effects of IOP on the estimated material properties were investigated. Finally, utilizing the joint model, it was demonstrated that there is strong correlation between corneal stiffness and the biomechanical parameter introduced by Corvis ST. Conclusions: An eye globe model was constructed and characterized by two distinct inverse models for corneal and fatty tissue. This model can be utilized for predicting eye globe behavior during dynamic tonometry tests besides other ophthalmological operations.
Źródło:
Acta of Bioengineering and Biomechanics; 2018, 20, 1; 39-48
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cement Concrete Mixture Performance Characterization
Autorzy:
Chisala, Maxwell
Powiązania:
https://bibliotekanauki.pl/articles/390117.pdf
Data publikacji:
2018
Wydawca:
Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
Tematy:
response models
mixture-design
mixture-factors
mixture-strength
mixture-porosity
physical properties
Opis:
The cementitious composite nature of concrete makes very diffi cult directly ascertaining each mixture-factors’ contribution to a given concrete mixture performance characteristics but also doubly diffi cult to accurately balance mutually exclusive requirements for performance (workability, strength, durability) and sustainability (the economic and effi cient use of materials) for mixture proportioning based on recipes of previously produced concretes. This study sought to quantify individual mixture-factors’ contribution to a given concrete mixture’s performance characteristics. Proposed multi-parametric exponential mixture-response models were fi tted to available test-performance data sets of HPC mixtures proportioned based on the best combined grade aggregate (minimum void) to generate mixture-strength and mixture-porosity development (age-mixture response relationships) profi les of HPC mixtures and deemed robust enough to yield reliable determination of mixture-response rate-parameters So, Sp, Si and Po, Pp, Pi as functions of mixture-factors that permitted reliable quantifi cation of contributions to HPC mixture performance of individual mixture-factors and optimization of mixture properties under study over the study domain. Mixture-response sensitivity analysis models (or mixture response trace plots) to allow construction of mixture-factor envelopes and ultimately optimized mixture-response models to facilitate selection of optimal mixture-factors and optimal tailoring of HPC mixture requirements to HPC mixture performance were developed and used to obtain optimized adapted HPC mixtures from available high performance concrete (HPC) mixture design recipes investigated in the study over the study domain. Adapted HPC mixture design recipes yielded alternative mixture compositions with improved performance and effi ciency characteristics with statistical performance metrics MAPE, NMBE and RMSE values of 7.6%,–3.7% and 6.5 MPa, respectively.
Źródło:
Budownictwo i Architektura; 2018, 17, 4; 103-120
1899-0665
Pojawia się w:
Budownictwo i Architektura
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Investigation and Multi-Response Optimization in Turning of Incoloy 800H Superalloy
Autorzy:
Palanisamy, A.
Selvaraj, T.
Sivasankaran, S.
Powiązania:
https://bibliotekanauki.pl/articles/356237.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
superalloy
microstructure
Taguchi-Grey approach
mathematical models
Opis:
This research work is focused on examining the turning behavior of Incoloy 800H superalloy by varying important cutting parameters. Incoloy 800H is an Iron-Nickel-Chromium based superalloy; it can withstand high temperature (810°C), high oxidization and corrosion resistance. But, it is difficult to turn in conventional machines and hence the present work was carried out and investigated. Experiments were conducted based on the standard L27 orthogonal array using uncoated tungsten inserts. The cutting force components, namely, feed force (Fx), thrust force (Fy) and cutting force (Fz); surface roughness (Ra) and specific cutting pressure (SCPR) were measured as responses and optimized using Taguchi-Grey approach. The main effects plots and analysis of mean (ANOM) were performed to check the effect of turning parameters and their significance on responses of cutting forces in all the direction (FX, FY, FZ), the surface roughness (Ra) and specific cutting pressure (SCPR). The tool wear and machined surfaces were also investigated using white light interferometer and SEM.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 4; 1683-1691
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Identification of financial and macroeconomic shocks in a VAR model of the Polish economy. A stability analysis
Autorzy:
Ulrichs, Magdalena
Powiązania:
https://bibliotekanauki.pl/articles/943099.pdf
Data publikacji:
2018-03-30
Wydawca:
Uniwersytet Ekonomiczny w Poznaniu
Tematy:
VAR models
impulse response functions
Markov‑Switching VAR models
structural changes
Opis:
Dynamic macroeconomic models (both VAR and DSGE) currently play a very significant role in macroeconomic modelling. But these types of models rarely take into account the impact of financial markets on the behaviour of economies, they are rather more focused on the monetary transmission mechanism. The financial crisis of 2007-2008 highlighted the impact of the financial market on the macroeconomy. In this context macroprudential policy and financial stability analysis has gained a stronger meaning. The main aim of the paper is to estimate a model that simultaneously explains the dynamics of macroeconomic and financial variables and to assess whether the identified relationships are stable over time. Therefore, based on the estimated empirical structural vector autoregression model explaining the interactions between the real economy, the financial system and monetary policy in Poland, financial and macroeconomic shocks were identified. It was shown that the impulse reaction functions changed after the financial crisis. On the basis of Markov‑Switching vector autoregression model probabilities of transitions between states of the economy and the regime-dependent impulse reaction functions were estimated.
Źródło:
Economics and Business Review; 2018, 4(18), 1; 29-43
2392-1641
Pojawia się w:
Economics and Business Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Item response theory models in the measurement theory with the use of LTM package in R
Analiza teorii odpowiedzi na pozycje testowe w teorii pomiaru z zastosowaniem pakietu LTM programu R
Autorzy:
Brzezińska, Justyna
Powiązania:
https://bibliotekanauki.pl/articles/424883.pdf
Data publikacji:
2018
Wydawca:
Wydawnictwo Uniwersytetu Ekonomicznego we Wrocławiu
Tematy:
Item Response Theory (IRT)
measurement theory
latent class analysis
R software
Opis:
Item Response Theory (IRT) is an extension of the Classical Test Theory (CCT) and focuses on how specific test items function in assessing a construct. They are widely known in psychology, medicine, and marketing, as well as in social sciences. An item response model specifies a relationship between the observable examinee test performance and the unobservable traits or abilities assumed to underlie performance on the test. Within the broad framework of item response theory, many models can be operationalized because of the large number of choices available for the mathematical form of the item characteristic curves. In this paper we introduce several types of IRT models such as: the Rasch, and the Birnbaum model. We present the main assumptions for IRT analysis, estimation method, properties, and model selection methods. In this paper we present the application of IRT analysis for binary data with the use of the ltm package in R.
Źródło:
Econometrics. Ekonometria. Advances in Applied Data Analytics; 2018, 22, 1; 11-25
1507-3866
Pojawia się w:
Econometrics. Ekonometria. Advances in Applied Data Analytics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 37

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