Wyniki wyszukiwania - Biblioteka Nauki

1

On Fisher-type inequalities for designs on regular graphs

100%

Mielniczuk J.

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2008

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tom 38

2

Wavelets for time series analysis - a survey and new results

63%

Mielniczuk J. , Wojdyłło P.

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tom Vol. 34, no 4

1093-1125

EN

In the paper we review stochastic properties of wavelet coefficients for time series indexed by continuous or discrete time. The main emphasis is on decorrelation property and its implications for data analysis. Some new properties are developed as the rates of correlation decay for the wavelet coefficients in the case of long-range dependent processes such as the fractional Gaussian noise and the fractional autoregressive integrated moving average processes. It is proved that for such processes the within-scale covariance of the wavelet coefficients at lag k is O(k^2(H-N)-2), where H is the Hurst exponent and N is the number of vanishing moments of the wavelet employed. Some applications of decorrelation property are briefly discussed.

3

Constitutive Relations in the Process of Hot Wood Rolling

63%

Malujda I. , Mielniczuk J.

Machine Dynamics Problems

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2004

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tom Vol. 28, No. 4

35-40

EN

While process modelling of plasticization of wood layer the factor of principal importance is the critical effort of material when its plastic flow occurs. The value of this stress depends on the thermomechanical properties of the material and, in particular, on three parameters of the process: roller temperature, strength and duration of the force exerted on the surface of the plasticized material. This paper attempts to formulate constitutive equations of the yield condition of porous and anisotropic medium taking into account the influence of temperature. This problem is analysed on the basis of plasticization of a thin layer of wood during hot rolling.

4

Elementy powierzchniowe o strukturze porowatej w konstrukcji dachów pojazdów szynowych

51%

Mielniczuk J. , Malinowski M. , Kuligowski P.

Pojazdy Szynowe

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2006

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tom nr 2

1-5

PL

Na przykładzie konstrukcji dachu omówiono możliwości zastosowania w budowie pojazdów szynowych elementów powierzchniowych o strukturze porowatej. Przedstawiono założenia modelu takich elementów. Przeprowadzono analizę wytrzymałościową fragmentu dachu z poszyciem o tradycyjnej konstrukcji stalowej i o strukturze porowatej oraz zestawiono porównanie wyników.

EN

On example of the construction of roof the possibilities of application in building of the rail vehicles surface elements with the porous structure are discussed. The assumptions of the model of those elements are presented. The strength analysis of the fragment of the roof with the sheathing with traditional steel construction and with the porous structure is carried out and the result comparison is drawn up.

5

Analiza wybranych metod optymalizacyjnych w transporcie drogowym

51%

Woźniak W. , Stryjski R. , Mielniczuk J. , Wojnarowski T.

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tom z. 120

447--458

PL

W artykule przedstawiono praktyczne rozwiązania problemu przydziału zleceń transportowych do dostępnych środków transportowych w transporcie drogowym. W tym celu dokonano analizy porównawczej wybranej metody optymalizacyjnej stosowanej w branży TSL z rozwiązaniem własnym. Zaproponowany algorytm do efektywnego przydziału wybranych zleceń transportowych opracowano na podstawie metod heurystycznych. Zaproponowano wykorzystanie algorytmu jako narzędzia wspomagającego pracę spedytorów do pozyskiwania opłacalnych zleceń transportowych z elektronicznych giełd transportowych.

EN

The article presents practical solutions to the problem of allocation of transport orders to available transport means in road transport. For this purpose, a comparative analysis of the selected optimization method used in the TSL industry with the own solution was made. The proposed algorithm for effective allocation of selected transport orders was developed based on heuristic methods. It was proposed to use the algorithm as a tool to support the work of shippers to obtain cost-effective transport orders from electronic transport exchanges.

6

Limit load of orthotropic porous materials under conditions of variable humidity

51%

Dudziak M. , Matyjaszczyk M. , Mielniczuk J.

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tom Nr 60

49-52

EN

Softwood is a typical orthotropic and porous material. In a dry state the unit volume of wood consists of the so-called wood skeleton and of the air-filled pores. The variable humidity produces the internal forces within the loaded material bulk loading to destruction. In the paper the mathematical model of the transition of the softwood into the plastic state is formulated and discussed. The outset of yielding is examined for anisotropy with various ratios of humidity. The case of particular deformation is used as an example for which the material constants are identified and the limit load determined.

PL

W pracy przedstawiono matematyczny model uplastycznienia ortotropowego materiału • porowatego (drewna sosny) w warunkach zmiennej wilgotności. Wskazano na możliwość określenia nośności i wilgotności granicznej obciążonych elementów.

7

Metodyka badań właściwości mechatronicznych kości

51%

Habdas P. , Mielniczuk J. , Uklejewski R. , Winiecki M.

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tom Nr 60

61-66

PL

W pracy przedstawiono kość działającą jako przetwornik mcchalroniczny podczas obciążeń mechanicznych towarzyszących codziennej aktywności fizycznej organizmu. Podkreślono znaczenie badań potencjałów deforrnacyjnych kości SGPs dla współczesnej chirurgii ortopedycznej i rehabilitacji. Przedstawiono koncepcję badań osteopotencjałów opracowaną na podstawie badań literaturowych. Zaprezentowano projekt stanowiska badawczego, proces przygotowania próbek kości oraz oczekiwane wyniki.

EN

The paper describes porous bone matrix filled with intraosseous ionic fluid as mechatronic transducer. Authors present conception of experimental investigation of strain generated osteopotentials SGPs in bone developed on the basis of [6]. There was presented the m testing equipment, the method of preparation of specimens and the experiments results.

8

Habitat conditions of the endangered species Salix myrtilloides in Eastern Poland

51%

Serafin A. , Pogorzelec M. , Banach B. , Mielniczuk J.

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tom 73

EN

Changes in habitat conditions in the area of Eastern Poland (Polesie Podlaskie), often associated with anthropopressure, cause a reduction in the number of locations and population size of valuable and rare bog plant species, including a Pleistocene boreal relict, Salix myrtilloides. The aim of this study was to determine the current conditions of occurrence of this species based on the physico-chemical parameters of peatland piezometric groundwater. The results confirm the declining trend in the number of locations and abundance of this species in the past few decades, but at the same time they confirm the wide range of amplitude of the many investigated factors. Among the groundwater parameters studied, the low level of nitrogen fractions, phosphorus fractions, cations, and DOC can be considered to be a set of conditions promoting the preservation of the Salix myrtilloides population. The higher concentrations of phosphates, sulfates, Na, Ca, and Mg as well as higher pH and electrolytic conductivity can be considered to be presumably unfavorable. The lack of significant differences in the values of the piezometric water factors investigated for the sites with different population sizes of the studied species requires the identification of other limiting factors and the implementation of programs for its active protection in Poland.

9

Structural Bone-Implant Compatibility in Design of the Needle-Palisade Fixation System for Total Hip Resurfacing Arthroplasty Endoprosthesis

51%

Rogala P. , Uklejewski R. , Winiecki M. , Mielniczuk J.

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tom Vol. 32, No. 2

57-62

EN

The paper presents results of the experimental investigations on the structural compatibility in bone-implant fixation on the needle-palisade fixation system prototype of the cementless THRA (total hip resurfacing arthroplasty) endoprosthesis (Rogala's patents, 1999, Rogala, Uklejewski, 2006, Rogala, Uklejewski et al., 2006,). The main purpose of this research was to design the geometrical constructional properties of the needle-palisade fixation system for the prototype of the THRA endoprosthesis assigned for pre-clinical in vivo tests on animals. The most advantageous needle variant in aspect of its fit to the porosity of the inter-trabecular space of animal bone was proposed on the base of SEM observations and measurements of microstructure of trabecular bone from femoral head. There are also presented results of the needle-palisade fixation system optimization. The optimization was performed with the use of "the trabecular bone marrow lacunae and needles coincidence index" defined as number of needle's peaks covering the pores of the inter-trabecular porosity compartment of bone to total number of needles in the needle-palisade fixation system reproduced on the SEM micrographs of the trabecular bone from animal femur head.

10

On some property of cyclic designs related to crop rotation experiments

51%

Przybysz T. , Bronowicka-Mielniczuk U. , Mielniczuk J.

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1999

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tom 29

11

Koncepcja usprawnienia wybranych algorytmów rozwiązujących zagadnienie transportowe

51%

Woźniak W. , Stryjski R. , Mielniczuk J. , Wojnarowski T.

Prace Naukowe Politechniki Warszawskiej. Transport

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2016

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tom z. 111

599--610

PL

W artykule zaprezentowano własną koncepcję algorytmu optymalizacyjnego, rozwiązującego zagadnienie transportowe w aspekcie złożoności czasowej. Prezentowany algorytm skraca czas wykonywania obliczeń związanych z przydziałem zleceń transportowych do dostępnych środków transportowych. Proponowane rozwiązanie może być wykorzystywane do szybkiego pozyskiwania wybranych (np. najbardziej zyskownych) zleceń transportowych z giełd transportowych.

EN

The paper presents the results of the optimisation algorithms, used in the solving of transport issues. In the present case, one such representative algorithm was the so-called "Hungarian Method". The algorithms were then compared with one’s own, proposed solution in the optimisation of transport orders, that is, compared with the "Improvement" algorithm, for the available means of transport as a function of search time reduction and the obtainment of feedback.

12

Testing for a difference between conditional variance functions of nonlinear time series

51%

Ćwik J. , Koronacki J. , Mielniczuk J.

Control and Cybernetics

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2000

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tom Vol. 29, no 1

33-50

EN

In this report, the problem of testing for a difference between conditional variance fnuctions (or volatilites) of two independent nonlinear time series is investigated by means of an extensive simulation study. Empirical results on the properties of the test proposed confirm the test's validity, at least for some types of heteroscedasticity as contrasted with homnoscedastic erroos as well as for some types of differences in heteooscedasticity. Moreover, interesting properties of several estimators of conditional mean, variance and fourth moment functions are empirically found too.

13

Prototype of minimally invasive hip resurfacing endoprosthesis - bioengineering design and manufacturing

51%

Uklejewski R. , Rogala P. , Winiecki M. , Mielniczuk J.

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2009

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tom Vol. 11, nr 2

65-70

EN

The resurfacing arthroplasty (RA) has become at present the most developed minimally invasive kind of all total arthroplasties, which is a result of the progress in biomaterials engineering, biomechanical design and surgical fixation methods achieved over the past decade. Despite the raising popularity of RA, which undergoes at present its renaissance, it still causes several clinical complications. In this paper, we present the most important result our research project (4T07C05629), finished in February 2008, which is the prototype of original minimally invasive endoprosthesis for total hip resurfacing arthroplasty (THRA). We propose the essential innovation in fixation technique of the RA endoprosthesis components in trabecular bone by means of the multi-spiked connecting scaffold, offering the possibility of totally cementless fixation and the physiological blood supply in trabecular bone of femoral head, which is not possible in contemporary used cemented RA endoprostheses. Moreover, the femoral component is designed to preserve the femoral neck and head blood vessels. The prototype of the new kind of hip resurfacing endoprosthesis was CAD-designed in the frames of the Rogala's international patent general assumptions (1)-(3), optimized on the basis of the preliminary biomechanical tests on the pre-prototypes, and manufactured in the Selective Laser Melting (SLM) of both CoCrMo powder and Ti6Al7Nb powder.

14

Experimental Determination of Anisotropy Coefficients for a Wood

51%

Berdychowski M. , Matyjaszczyk M. , Mielniczuk J.

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tom Vol. 34, No. 1

14-22

EN

A special form of the yield condition of porous anisotropic materials, such as a wood containing the wood humidity, is a function of the modulus of elasticity, the modulus of humidity and anisotropy coefficients. It is necessary to determine anisotropy coefficients to develop this equation for engineers. A measuring laboratory and a methodology of experimental determination of anisotropy coefficients for a wood are given in the paper.

15

Propozycja algorytmu redukującego operacje przeładunkowe w intermodalnym węźle kolejowo-drogowym

51%

Woźniak W. , Stryjski R. , Mielniczuk J. , Wojnarowski T.

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2017

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tom z. 115

203--212

PL

W artykule przedstawiono koncepcję algorytmów optymalizujących ilość operacji przeładunkowych urządzeń dźwigowych w kolejowo-drogowym węźle intermodalnym. Opracowane algorytmy zostały zaimplementowane do zintegrowanego systemu informatycznego wspomagającego zarządzanie procesami magazynowymi.

EN

The article presents the concept of algorithms to optimize the number of transshipment operations of cargo- lifting equipment in an intermodal transport node. Algorithms have been implemented in an integrated system to support management of warehouse process.

16

Soil carbon accumulation as affected by tillage and crop systems in Southern Brazil

51%

Mielniczuk J. , Bayer C. , Amado T. J. C. , Fernandes S. B. V.

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tom 2B

17

The poroaccessibility parameters for three-dimensional characterization of orthopaedic implants porous coatings

45%

Uklejewski R. , Winiecki M. , Mielniczuk J. , Rogala P. , Auguściński A.

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2008

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tom Vol. 15, nr 2

215-226

EN

The ability of formation of the proper bone-porous implant fixation depends, among others, on the structural-osteoinductive properties of the porous coating covering the orthopaedic implant surface. These properties, describing the poroaccessibility of porous biomaterial, are one of co-factors conditioning the promotion of bone tissue ingrowth into pore space of implant porous coating. So far the structural-osteoinductive properties of implants porous coatings are described by the traditional two-dimensional roughness parameters obtained with contact or non-contact roughness profile measurement (mostly standard surface roughness amplitude parameters e.g.: Ra, Rq, Rmax) or with the average pore size, which is, in the authors opinion, inadequate and unsatisfactory for porous coating characterization in respect of its poroaccessibility. The lack of proper directives on porous structure characterization of titanium and hydroxyapatite coatings on orthopaedic implants is the reason to work them out. In connection with the development of methods for surface texture analysis in three dimensions, the authors have perceived new possibilities for porous coatings microstructure analysis and on this base a set of parameters of poroaccessibility of implant porous coating for bone tissue ingrowth has been proposed: the effective volumetric porosity ΦVef, the index of the porous coating space capacity VPM, the representative surface porosity ΦSrep, the representative pore size pSrep, the representative angle of the poroaccessibility Ωrep and the bone-implant interface adhesive surface enlargement index Ψ. With this set of parameters one can characterize the structural-osteoinductive properties of porous biomaterial. In this paper a new set of poroaccessibility parameters of implant porous coatings and a method of calculation of these parameters on the basis of three-dimensional roughness measurements are presented.

18

The Concept and Geometrical Model of Modern Endoprosthesis Concerning Minimal Invasive Total Hip Resurfacing Arthroplasty (THRA)

45%

Rogala P. , Uklejewski R. , Winiecki M. , Mielniczuk J. , Auguściński A.

Machine Dynamics Problems

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2006

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tom Vol. 30, No. 4

89-96

EN

The needle-palisade fixation for total resurfacing arthroplasties of hip and other joints (e.g. knee joint) and the implantation method are presented. The needles are symmetrically spaced on the terminal surfaces of the endoprothesis up to a resistance edge on one portion of the endoprothesis and up to a resistance surface on a second portion of the endoprothesis. The area between multilateral needles will be filled up by new bone formation to the terminal surfaces. The endoprothesis also includes a glenoid cavity and a head which have round terminal surfaces with the multilateral needles placed. The projected multilateral needles have different lengths and mutually parallel axes which are perpendicular to the planes in which the round resistance edge of the glenoid cavity and resistance plane of the head are located. Each of needles is pyramidal. The total surface area of the needle-palisade fixation system is at least seven times greater than total surface area of head external surface and it is when the relation between radius and height of pyramid is about 1 to 5. The implantation method involves the successive introduction of multilateral needles into the spongy bone. The concept of the needle-palisade system for total hip replacement fixation presents: 1) safer operative procedure-press-fit technique, 2) easier revision arthroplasty, 3) good adhesion system (important for example in case of osteoporosis), 4) cortical and cancellous load transmission system, 5) "biological-like" fixation, expectable "life performance" solution, 6) uniform distribution of biomechanical forces. The geometrical model of the new concept of the endoprosthesis for total hip resurfacing arthroplasty created in Autodesk Inventor CAD system is presented. The model is assigned for further experimental researches, i.e.: FEM analysis, virtual simulation of endoprosthesis insertion and the productions of prototypes for biomechanical experiments and pre-clinical investigations.

19

Experimental Investigations on the Structural-Osteoinductive Properties of Porous Coatings on Orthopaedic Implants

45%

Uklejewski R. , Winiecki M. , Mielniczuk J. , Auguściński A. , Rogala P.

Machine Dynamics Problems

|

2006

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tom Vol. 30, No. 4

171-180

EN

The adaptive bone tissue ingrowth into the pore space of a porous coating on orthopaedic implants is influenced by the structural-osteoinductive properties of this coating. The effective bone tissue ingrowth determines the proper fixation of the porous implant in its bony surroundings. The adequate evaluation of the structural-adaptive compatibility of bone-implant interface can be performed on the basis of the two-phase poroelastic biomechanical model of bone tissue and of implant porous coatings with the set of original parameters characterizing the poroaccessibility of implant porous coatings: the effective volumetric porosity φVef, the index of the porous coating space capacity VPM, the effective pore depth ρdef, the representative surface porosity φSrep, the representative pore size ρSrep, the representative angle of the poroaccessibility Ωrep, the index of the enlargement of the adhesive surface of bone-implant interface Ψ, which is proposed in (Mielniczuk et al., 2006; Winiecki et al., 2006; Uklejewski et al., 2005a and 2005b; Winiecki, 2006) to the biostructural evaluation of the porous coated orthopedic implants. This paper presents the results of experimental investigations of the microgeometrical properties of implants porous coatings made with contact profile measurement on the representative examples of endoprostheses stems.

20

Physico-chemical groundwater conditions at Salix lapponum stands in Eastern Poland

45%

Serafin A. , Pogorzelec M. , Banach B. , Szczurowska A. , Mielniczuk J.

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tom 73

EN

A subarctic-boreal relict species, Salix lapponum, found within the area of the Łęczna-Włodawa Lakeland (Eastern Poland), is particularly threatened with extinction due to the southern limit of its range and the specific conditions of its occurrence. This conclusion is evidenced by a systematic reduction in the number of its locations, which is accompanied by a decrease in the numbers of individuals making up its populations. The aim of the present study was to determine habitat conditions of the occurrence of Salix lapponum populations on the basis of an analysis of physico-chemical factors of groundwater at the sites associated with various stages of succession taking place in small peatland water bodies. The results of this study confirm the trend that the stands and population numbers of this species are decreasing with the intensification of ecological succession and the degree of its progress and at the same time show that this species exhibits a wide amplitude of many of the investigated factors. Among the groundwater parameters under investigation, the low level of total nitrogen, phosphorus fraction and DOC as well as the high level of Ca, pH and electrolytic conductivity can be considered to be a set of conditions that promote the maintenance of Salix lapponum populations. On the other hand, in the case of nitrates, nitrites, sulphates as well as the Na, K and Mg ions, the Kruskal-Wallis statistical test showed that the distribution of their values was invariant in relation to the studied habitats, which is probably evidence that they do not determine the development or extinction of the investigated populations in these habitats.