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Wyszukujesz frazę "total volume" wg kryterium: Temat


Wyświetlanie 1-14 z 14
Tytuł:
Comparison of Total Tumor Volume, Size and Number of Colorectal Liver Metastases in Prediction of Survival in Patients after Liver Resection
Autorzy:
Hołówko, Wacław
Grąt, Michał
Wronka, Karolina Maria
Stypułkowski, Jan
Roszkowski, Rafał
Studnicki, Paweł
Krawczyk, Marek
Powiązania:
https://bibliotekanauki.pl/articles/1395543.pdf
Data publikacji:
2015-02-01
Wydawca:
Index Copernicus International
Tematy:
colorectal liver metastases
liver resection
total tumor volume
Opis:
Liver is the most common location of the colorectal cancer metastases occurrence. Liver resection is the only curative method of treatment. Unfortunately it is feasible only in 25% of patients with colorectal liver metastases, often because of the extensiveness of the disease. The aim of the study was to evaluate the predictive value of total tumor volume, size and number of colorectal liver metastases in patients treated with right hemihepatectomy. Material and methods. A retrospective analysis was performed in a group of 135 patients with colorectal liver metastases, who were treated with right hemihepatectomy. Total tumor volume was estimated based on the formula (4/3)πr3. Moreover, the study included an analysis of data on the number and size of tumors, radicality of the resection, time between primary tumor resection and liver resection, pre-operative blood serum concentration of carcinoembryonal antigen (CEA) and carcinoma antigen Ca19-9. The predictive value of the factors was evaluated by applying a Cox proportional hazards model and the area under the ROC curve. Results. The univariate analysis has shown the predictive value of size of the largest tumor (p=0.033; HR=1.065 per each cm) on the overall survival, however no predictive value of number of tumors (p=0.997; HR=1.000) and total tumor volume (p=0.212; HR=1.002) was observed. The multivariate analysis did not confirm the predictive value of the size of the largest tumor (p=0.141; HR=1.056). In the analysis of ROC curves, AUROC for the total tumor volume, the size of the largest tumor and the number of tumors were 0.629, 0.608, 0.520, respectively. Conclusions. Total tumor volume, size and number of liver metastases are not independent risk factors for the worse overall survival of patients with colorectal liver metastases treated with liver resection, therefore increased values of these factors should not be a contraindication for surgical treatment
Źródło:
Polish Journal of Surgery; 2015, 87, 2; 53-58
0032-373X
2299-2847
Pojawia się w:
Polish Journal of Surgery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance evaluation of unreliable system with infinite number of servers
Autorzy:
Tikhonenko, O.
Ziółkowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/201519.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
queueing systems with non-homogeneous customers
unreliable queueing systems
total volume
loss probability
Laplace–Stieltjes transform
Opis:
In the paper, we investigate queueing system M/G/∞ with non-homogeneous customers. By non-homogeneity we mean that each customer is characterized by some arbitrarily distributed random volume. The arriving customers appear according to a stationary Poisson process. Service time of a customer is proportional to his its volume. The system is unreliable, which means that all its servers can break simultaneously and then the repair period goes on for random time having an arbitrary distribution. During this period, customers present in the system and arriving to it are not served. Their service continues immediately after repair period termination. Time intervals of the system in good repair mode have an exponential distribution. For such system, we determine steady-state sojourn time and total volume of customers present in it distributions. We also estimate the loss probability for the similar system with limited total volume. An analysis of some special cases and some numerical examples are attached as well.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2020, 68, 2; 289-297
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ocena przyrostu całkowitej objętości nerek u dzieci i młodych dorosłych z wielotorbielowatością nerek o autosomalnie dominującym typie dziedziczenia w trakcie 12-miesięcznej obserwacji – doniesienie wstępne
12-month assessment of increase in total kidney volume in children and young adults with autosomal dominant polycystic kidney disease – a pilot study
Autorzy:
Pawlak-Bratkowska, Monika
Afshari, Susan
Grzelak, Piotr
Podgórki, Michał
Wosiak, Agnieszka
Młudzik, Agnieszka
Michalak, Krzysztof
Kostrzewa, Marta
Faltin, Kamil
Tkaczyk, Marcin
Powiązania:
https://bibliotekanauki.pl/articles/1036277.pdf
Data publikacji:
2017
Wydawca:
Śląski Uniwersytet Medyczny w Katowicach
Tematy:
dzieci
adpkd
całkowita objętość nerek
torbielowatość
progresja choroby
children
total kidney volume
polycystic
disease progression
Opis:
WSTĘP: Autosomalna dominująca wielotorbielowatość nerek (ADPKD – autosomal dominant polycystic kidney disease) to najczęstsza z dziedziczonych monogenowo chorób nerek. Stanowi przyczynę schyłkowej niewydolności nerek u 5–10% dorosłych leczonych nerkozastępczo. Dawniej uważana była za chorobę ludzi dorosłych, lecz od czasu upowszechnienia badań ultrasonograficznych zaczęto obserwować jej występowanie także u dzieci. MATERIAŁ I METODY: Grupę badaną stanowiło 19 pacjentów z prawidłową czynnością nerek (w wieku 1,8–18,8 roku w trakcie kontroli, 12 dziewczynek, 7 chłopców) chorujących na ADPKD. Spośród pacjentów 15 spełniało ultrasonograficzne kryteria rozpoznania choroby, a 4 nie spełniało kryteriów, przy czym były to dzieci z dodatnim wywiadem rodzinnym w kierunku ADPKD, a w USG stwierdzono minimum 2 torbiele. Całkowita objętość nerek (TKV), określona jako suma objętości obu nerek, została odniesiona do powierzchni ciała pacjenta (TKV/BSA). Dzieci badane były średnio co 12 miesięcy. WYNIKI: W badanej grupie stwierdzono istotny statystycznie roczny przyrost całkowitej objętości nerek (w 2015 r. 296,71 ± 178,67 cm3 vs. 350,38 ± 195,86 cm3 w 2016 r.; p = 0,019) oraz także TKV w odniesieniu do powierzchni ciała (w 2015 r. 191,23 ± 86,29 cm3/m2 vs. 221,15 ± 96,99 cm3/m2 w 2016 r.; p = 0,037). Nie uwidoczniono różnic w tempie przyrost całkowitej objętości nerek w zależności od płci (dziewczynki 32,45 ± 51,88 cm3/m2/rok vs. chłopcy 25,56 ± 71,00 cm3/m2/rok; p = 0,81) oraz ze względu na zaawansowanie choroby, ocenianej jako liczba stwierdzonych w badaniu ultrasonograficznym torbieli w obrębie nerek (< 5 torbieli 30,77 ± 61,6 cm3/m2/rok vs. ≥ 5 torbieli 29,41 ± 58,22 cm3/m2/rok; p = 0,96). WNIOSKI: U dzieci i młodych dorosłych z ADPKD można zaobserwować zwiększenie względnej całkowitej objętości nerek (w odniesieniu do BSA) już w trakcie 12-miesięcznej obserwacji.
INTRODUCTION: Autosomal dominant polycystic kidney disease (ADPKD) is the most common type of monogenic kidney disease. It is the cause of ESRD in 5–10% of adult patients who undergo renal replacement therapy. Owing to the increasing use of ultrasonography, occurrence of the disease has been observed among children. MATERIAL AND METHODS: The research group consisted of 19 patients with normal kidney function (12 girls and 7 boys aged 1.8–18.8 at the moment of examination) who suffered from ADPKD. 15 patients met the ultrasonographic criteria of the diagnosis. Although the remaining 4 patients did not meet the criteria, they had a strong family history of ADPKD and underwent USG which revealed at least 2 cysts. For each patient, the Total Kidney Volume (TKV), defined as the sum volume of both kidneys, was juxtaposed with BSA. The children underwent the examination approximately every 12 months. RESULTS: The members of the research group manifested a statistically significant annual increase in TKV (in 2015, 296.71 ± 178.67 cm3 versus 350.38 ± 195.86 cm3 in 2016, p = 0.019), as well as TKV in relation to body surface (in 2015, 191.23 ± 86.29 cm3/m2 versus 221.15 ± 96.99 cm3/m2 in 2016, p = 0.037). There were no apparent differences in the rate of total TKV increase which would depend either on the patient's gender (girls 32.45 ± 51.88 cm3/m2/year versus boys 25.56 ± 71.00 cm3/m2/year, p = 0.81), or on the number of renal cysts revealed by USG (< 5 cysts 30.77 ± 61.6 cm3/m2/year versus ≥ 5 cysts 29.41 ± 58.22 cm3/m2/year, p = 0.96). CONCLUSION: In children and young adults with ADPKD, the increase in total kidney volume (in relation to BSA) can be observed after a 12-month observation.
Źródło:
Annales Academiae Medicae Silesiensis; 2017, 71; 109-115
1734-025X
Pojawia się w:
Annales Academiae Medicae Silesiensis
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multiline queueing system with random time limitations and limited buffer space
Autorzy:
Tikhonenko, O.
Zając, P.
Powiązania:
https://bibliotekanauki.pl/articles/122703.pdf
Data publikacji:
2018
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
total demands volume
system buffer capacity
loss probability
Stieltjes convolution
system kolejkowy
splot Stieltjesa
pojemność bufora
Opis:
In the paper, we investigate multi-server queueing systems with demands of random space requirements (volumes), in which buffer space is limited by constant value and queueing ore (and) service time are limited by exponentially distributed random variables. For such systems, stationary demands number distribution and loss probability are determined. Some numerical results are attached as well.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2018, 17, 4; 99-106
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Queueing systems with random volume customers and a sectorized unlimited memory buffer
Autorzy:
Tikhonenko, Oleg
Ziółkowski, Marcin
Kempa, Wojciech M.
Powiązania:
https://bibliotekanauki.pl/articles/2055163.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
queueing system
random volume customers
sectorized memory buffer
total volume vector
Laplace transform
Laplace–Stieltjes transform
multivariate L’Hospital rule
system kolejkowania
wektor objętości
transformata Laplace'a
transformata Laplace'a-Stieltjesa
Opis:
In the present paper, we concentrate on basic concepts connected with the theory of queueing systems with random volume customers and a sectorized unlimited memory buffer. In such systems, the arriving customers are additionally characterized by a non-negative random volume vector. The vector’s indications can be understood as the sizes of portions of information of a different type that are located in the sectors of memory space of the system during customers’ sojourn in it. This information does not change while a customer is present in the system. After service termination, information immediately leaves the buffer, releasing its resources. In analyzed models, the service time of a customer is assumed to be dependent on his volume vector characteristics, which has influence on the total volume vector distribution. We investigate three types of such queueing systems: the Erlang queueing system, the single-server queueing system with unlimited queue and the egalitarian processor sharing system. For these models, we obtain a joint distribution function of the total volume vector in terms of Laplace (or Laplace-Stieltjes) transforms and formulae for steady-state initial mixed moments of the analyzed random vector, in the case when the memory buffer is composed of two sectors. We also calculate these characteristics for some practical case in which the service time of a customer is proportional to the customer’s length (understood as the sum of the volume vector’s indications). Moreover, we present some numerical computations illustrating theoretical results.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2021, 31, 3; 471--486
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Expected volumes of requests in systems of the queueing network with a limited number of waiting places
Autorzy:
Zając, P.
Matalytski, M.
Powiązania:
https://bibliotekanauki.pl/articles/121834.pdf
Data publikacji:
2017
Wydawca:
Uniwersytet Humanistyczno-Przyrodniczy im. Jana Długosza w Częstochowie. Wydawnictwo Uczelniane
Tematy:
sieci HM
sieci kolejkowe
system kolejkowy
bezprzewodowy punkt dostępu
HM-networks
queueing network
single-line queueing system
queueing system
queuing time
limited queue
demands total volume
wireless access point
volume of requests
Opis:
We present a method of finding the expected volume of requests in HM-network with homogeneous requests and bypass of the queueing systems of requests. The case was considered when the volume changes associated with the transitions between the states of the network are deterministic functions, depending on the state of the network and time, and the systems are single line. It is assumed that the probability of the states of the network systems, the parameters of the entrance flow of the requests and the service depend on the time.
Źródło:
Scientific Issues of Jan Długosz University in Częstochowa. Mathematics; 2017, 22; 141-160
2450-9302
Pojawia się w:
Scientific Issues of Jan Długosz University in Częstochowa. Mathematics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Single-server queueing system with external and internal customers
Autorzy:
Tikhonenko, O.
Ziółkowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/199838.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
single-server queueing system with non-homogeneous customers
random volume customers
loss probability
total volume distribution
Laplace transform
Laplace-Stieltjes transform
RAM memory space
prawdopodobieństwo straty
transformacja Laplace'a
transformata Laplace'a-Stieltjesa
pamięć RAM
Opis:
In the paper, we investigate a single-server queueing system with unlimited memory space and non-homogeneous customers (calls) of the two following types: 1) external customers that are served by the system under consideration, 2) internal customers that arrive and interrupt the service process only when an external customer is being served. The external customers appear according to a stationary Poisson process. Customers of each of the above-mentioned types are characterized by some random volume. The customer service time depends arbitrarily on its volume. Two schemes of customer service organization are analyzed. The non-stationary and stationary distributions of the total volume of customers present in the system are determined in terms of Laplace and Laplace-Stieltjes transforms. The stationary first and second moments of total customers volume are also calculated. The obtained results are used to approximate loss characteristics in analogous systems with limited buffer space. Numerical examples illustrating theoretical results are attached as well.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2018, 66, 4; 539-551
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
M/G→ /n/0 Erlang queueing system with heterogeneous servers and non-homogeneous customers
Autorzy:
Ziółkowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/199840.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
multi-server queueing systems
queueing systems with non-homogeneous customers
queueing systems with heterogeneous servers
total volume distribution
Laplace–Stieltjes transform
system kolejkowania
transformata Laplace'a-Stieltjesa
dystrybucja
Opis:
In the present paper, we investigate a multi-server queueing system with heterogeneous servers, unlimited memory space, and non-homogeneous customers. The arriving customers appear according to a stationary Poisson process. Service time distribution functions may be different for every server. Customers are additionally characterized by some random volume. On every server, the service time of the customer depends on their volume. The number of customers distribution function is obtained in the classical model of the system. In the model with non-homogeneous customers, the stationary total volume distribution function is determined in the term of Laplace–Stieltjes transform. The stationary first and second moments of a total customers volume are calculated. An analysis of some special cases of the model and some numerical examples are also included.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2018, 66, 1; 59-66
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance evaluation of an M/G/n-type queue with bounded capacity and packet dropping
Autorzy:
Tikhonenko, O.
Kempa, W. M.
Powiązania:
https://bibliotekanauki.pl/articles/331288.pdf
Data publikacji:
2016
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
AQM algorithm
finite buffer
loss probability
total packet volume
queue size distribution
aktywne zarządzanie kolejką
prawdopodobieństwo straty
rozkład wielkości kolejki
Opis:
A queueing system of the M/G/n-type, n ≥ 1, with a bounded total volume is considered. It is assumed that the volumes of the arriving packets are generally distributed random variables. Moreover, the AQM-type mechanism is used to control the actual buffer state: each of the arriving packets is dropped with a probability depending on its volume and the occupied volume of the system at the pre-arrival epoch. The explicit formulae for the stationary queue-size distribution and the loss probability are found. Numerical examples illustrating theoretical formulae are given as well.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2016, 26, 4; 841-854
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Juvenile wood volume and its proportion to stem volume vs. selected biometric features of Scots pine [Pinus sylvestris L.] trees
Autorzy:
Pazdrowski, W
Tomczak, A.
Kupczyk, G.
Jelonek, T.
Powiązania:
https://bibliotekanauki.pl/articles/57743.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Botaniczne
Tematy:
breast height diameter
tree height
Scotch pine
total stem volume
determination coefficient
juvenile wood
Pinus sylvestris
tree
wood
forest site type
Opis:
The aim of the study was to determine whether there is a correlation between breast height diameter, tree height and stem total volume of Scots pines, on the one hand, and volume and proportion of juvenile wood, on the other. The investigations comprised pure pine stands of the IInd, IIIrd, IVth and Vth age classes developed in conditions of fresh mixed coniferous forest. A distinct curvilinear correlation was found between volume and proportion of juvenile wood in tree stems and breast height diameter, height and stem total volume. Because of high values of determination coefficients (R2), which characterised the above-mentioned correlations, it seems appropriate to use these regularities to assess the quality of the timber raw material regarding the proportions of its volume and juvenile wood in stems of Scots pine trees.
Źródło:
Acta Societatis Botanicorum Poloniae; 2005, 74, 4
0001-6977
2083-9480
Pojawia się w:
Acta Societatis Botanicorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Single–server queueing system with limited queue, random volume customers and unlimited sectorized memory buffer
Autorzy:
Ziółkowski, Marcin
Tikhonenko, Oleg
Powiązania:
https://bibliotekanauki.pl/articles/2173725.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
single-server queueing system
queueing systems with random volume customers
sectorized memory buffer
total volume vector
Laplace-Stieltjes transform
system kolejkowy z jednym serwerem
system kolejkowy z losowymi klientami
bufor pamięci sektorowany
wektor objętości całkowity
transformata Laplace'a-Stieltjesa
Opis:
In the present paper, we analyze the model of a single–server queueing system with limited number of waiting positions, random volume customers and unlimited sectorized memory buffer. In such a system, the arriving customer is additionally characterized by a non– negative random volume vector whose indications usually represent the portions of unchanged information of a different type that are located in sectors of unlimited memory space dedicated for them during customer presence in the system. When the server ends the service of a customer, information immediately leaves the buffer, releasing resources of the proper sectors. We assume that in the investigated model, the service time of a customer is dependent on his volume vector characteristics. For such defined model, we obtain a general formula for steady–state joint distribution function of the total volume vector in terms of Laplace-Stieltjes transforms. We also present practical results for some special cases of the model together with formulae for steady–state initial moments of the analyzed random vector, in cases where the memory buffer is composed of at most two sectors. Some numerical computations illustrating obtained theoretical results are attached as well.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2022, 70, 6; art. no. e143647
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Energetyczne określenie twardości Brinella
Energy-based determination of Brinell hardnes
Autorzy:
Zatorski, Z.
Biernat, R.
Powiązania:
https://bibliotekanauki.pl/articles/221917.pdf
Data publikacji:
2014
Wydawca:
Akademia Marynarki Wojennej. Wydział Dowodzenia i Operacji Morskich
Tematy:
twardość Brinella
energie właściwe odkształceń
materiały sprężysto-plastyczne
odkształcenia całkowite sprężyste
Brinell hardness
proper energies of strains
materials elastic-plastic
volume of total
Opis:
W artykule zweryfikowano energetycznie twardość Brinella materiałów konstrukcyjnych. Badania realizowano w Akademii Marynarki Wojennej w Gdyni przy użyciu oprzyrządowanych maszyn wytrzymałościowych MTS 810.12 i FU 1000. Analiza wykresów siła — głębokość odcisku służyła do wyznaczenia energii właściwych odkształceń sprężystych, plastycznych i całkowitych absorbowanych przez materiał. Energie właściwe wyznaczono przez podzielenie odpowiednich wartości energii przez objętość odkształceń całkowitych, sprężystych oraz plastycznych odcisku.
This article presents energy-based verification of Brinell hardness in construction materials. The investigations were conducted at the Naval Academy in Gdynia using testing machines MTS 810.12 and FU 1000. The analysis of force-indentation depth diagrams was used to determine proper energies of elastic, plastic and total strains being absorbed by the material. In order to determine the proper energies the appropriate energy values were divided by the volume of total, elastic and plastic strains of the indentation.
Źródło:
Zeszyty Naukowe Akademii Marynarki Wojennej; 2014, R. 55 nr 4 (199), 4 (199); 103-116
0860-889X
Pojawia się w:
Zeszyty Naukowe Akademii Marynarki Wojennej
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Repetitive apneas reduce nonlinear dynamical complexity of the human cardiovascular control system
Autorzy:
Trzebski, A.
Smietanowski, M.
Zebrowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/70116.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Fizjologiczne
Tematy:
total peripheral resistance
arterial chemoreceptor
apnea
man
stroke volume
hypertension
cardiac output
nonlinear dynamics
cardiovascular control
blood pressure
Źródło:
Journal of Physiology and Pharmacology; 2001, 52, 1
0867-5910
Pojawia się w:
Journal of Physiology and Pharmacology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhancement of tribological properties and characteristic of polymer matrix composite (UHMWPE reinforced with short fibres of polyester) for Total Disc Replacement (TDR)
Autorzy:
Obaid, M. N.
Radhi, S. H.
Powiązania:
https://bibliotekanauki.pl/articles/1818822.pdf
Data publikacji:
2020
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
total disc replacement
UHMWPE
polyester fibres
tribological
contact angle
crystalline degree
roughness
melting temperature
volume loss
całkowita wymiana dysku
całkowita endoprotezoplastyka krążka międzykręgowego
włókna poliestrowe
tribologia
kąt zwilżania
stopień krystaliczności
chropowatość
temperatura topnienia
utrata objętości
Opis:
Purpose: The number of people suffering from Degenerative Disc Disease (DDD) is increasing. The disease causes heavy pain and restrict a number of day-to-day life activities. In extreme cases, the degraded disc is removed under total disc replacement which is usually made up of Ultra-High Molecular Weight Polyethylene (UHMWPE). The material has astounding biocompatible characteristics mechanical properties and wear resistance. However, these characteristics are insufficient in arthroplasty application. Therefore, research investigations are ongoing to improve tribological properties through reinforcement that may result in a composite material of UHMWPE. Thus the current study is aimed at reinforcing UHMWPE with short fibres of polyesters to enhance the tribological properties and surface characteristic so as to improve wear resistance and nourish the fibroblast cells on synthetic disc. Design/methodology/approach: The researcher prepared UHMWPE composite material, reinforced with different weight fractions of short polyester fibres (2, 4, 6, 8 and 10% following hot press method. Further pin-on-disc device was used to study the tribological properties (coefficient of friction and volume of wear). The study tested surface roughness and surface characteristics by atomic force microscopy (AFM) device, hardness by shore D device, contact angle to study the effect of polyester short fibres on wettability of UHMWPE surface and tested the thermal properties and crystalline degree using Differential Scanning Calorimetry measurement (DSC) device. Findings: The results infer that the wear resistance got improved when using 2% w.t polyester though it got decreased initially. However, the value was still more than neat UHMWPE. There was a decrease observed in coefficient of friction, but after 4 w.t% polyester, the coefficient of friction got increased due to increasing percentage of fibres which make it harder and stiff compared to UHMWPE. There was a decline observed in surface roughness due to alignment of the fibres with smooth surface. The contact angle got increased in a moderate range while the roughness enhanced the growth of fibroblast cell. The hardness of composite material got increased, because the fibres turned stiffer and harder than the matrix. DSC results infer the improvements in thermal stability due to high thermal properties of polyester fibres compared to UHMWPE. The degree of crystallinity got increased which in turn enhanced wear resistance, especially at 6 w.t % polyester fibres. There was a mild increase observed in density since the density of polyester is higher than polymer. Research limitations/implications: The major challenge was the dispersion of fibres. Uniform distribution of fibres within the matrix (UHMWPE) was achieved through two steps of mixing processes such as mechanical mixture and twin extruder. In future studies, fatigue tests must be conducted to study the behaviour of prepared composite materials under fatigue cycle. Practical implications: A significant objective is how to connect among different properties to obtain good improvement in tribological and surface properties so as to enhance wear resistance and growth of fibrolase cells. Originality/value: In this study, polymeric short fibres were used as reinforcement with polymeric matrix to enhance the wettability of fibres with matrix. In this way, the bonding among them got increased which supports the tribological, surface, and crystalline behaviour.
Źródło:
Journal of Achievements in Materials and Manufacturing Engineering; 2020, 102, 2; 55--65
1734-8412
Pojawia się w:
Journal of Achievements in Materials and Manufacturing Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-14 z 14

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