Autor: Walkowiak, T. - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Web server performance and availability model for simulation
Autorzy:: Walkowiak, T.
Powiązania:: https://bibliotekanauki.pl/articles/2069132.pdf
Data publikacji:: 2012
Wydawca:: Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:: performance
availability
simulation
web system
Opis:: The paper presents an approach to modelling and simulation of web systems. The systems are being modelled from the point of view of services realized by them. The formal model of a system, accompanied with a model of a request realization is presented. The main aspect of the paper is a simulation model of client-server interactions that adequately describes the relationship between the server response time, its availability and resource utilization. The model was constructed based on the the results of multiple experiments presented in a paper. Moreover, it was implemented in the simulation tool and its accuracy verified against testbed web servers. Apache and IIS servers were analysed.
Źródło:: Journal of Polish Safety and Reliability Association; 2012, 3, 2; 189--196
2084-5316
Pojawia się w:: Journal of Polish Safety and Reliability Association
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: A repair time model of a web based system including administrator working hours
Autorzy:: Walkowiak, T.
Powiązania:: https://bibliotekanauki.pl/articles/2069173.pdf
Data publikacji:: 2016
Wydawca:: Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:: reliability
web based system
repair time
working hours
Opis:: The paper presents a web based system reliability analysis. We propose to model different types of faults (hardware one, software and security incidents) taking consideration only the effect of the failure, not the source of the fault. It is assumed that failure events are independent and the time to failure is exponential. Whereas the time to repair is not exponential since repair actions are taken only when administrators are at work. We assume that administrators are not working 24/7. The paper presents an algorithmic model of the repair time including administrator working hours. The model is used to estimate reliability parameters (mean time, standard deviation and 90th percentile of yearly down time) by a use of Monte-Carlo simulation. The numerical results are compared with results from the analytical model (Markov one) that assumes exponential distribution of all repair times. Results for two web exemplar web systems (with reliability model consisting of two and five states) show the range of error caused by the exponential distribution assumption.
Źródło:: Journal of Polish Safety and Reliability Association; 2016, 7, 1; 233--240
2084-5316
Pojawia się w:: Journal of Polish Safety and Reliability Association
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Fuzzy quality analysis of web services implemented in virtualised environment
Autorzy:: Walkowiak, T.
Powiązania:: https://bibliotekanauki.pl/articles/2069094.pdf
Data publikacji:: 2015
Wydawca:: Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:: virtualization
web service
quality
availability
state-transitional model
fuzzy number
Opis:: The paper describes the quality analysis of web services implemented in virtualised environment. It takes into account the reliability and performance aspects of software and hardware elements of the web service. The presented state-transitional model considers the reconfiguration process to maintain the continuity of business services. The reconfiguration is based in on the redeployment of virtual machines so for some time the system operates in a degraded state. Author propose two quality measures based on the web service availability and maximum handled requests calculated at each of degradation levels. Moreover, authors proposed to model the web service reliability parameters by fuzzy numbers. A method for calculating fuzzy membership functions of quality measures are also presented.
Źródło:: Journal of Polish Safety and Reliability Association; 2015, 6, 2; 147--152
2084-5316
Pojawia się w:: Journal of Polish Safety and Reliability Association
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Simulation approach to Web system dependability analysis
Autorzy:: Walkowiak, T.
Powiązania:: https://bibliotekanauki.pl/articles/2069527.pdf
Data publikacji:: 2011
Wydawca:: Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:: dependability
performance
availability
reliability
failures
Web system
simulation
Opis:: The paper is concerned with the analysis of under-keel clearance of ships based on real data from Szczecin Maritime Office. Using probabilistic method for UKC assessment give it possibility to create the distribution of under-keel clearance in several ship’s passages and in further step to determine the probability of ship’s grounding accident during the port approach. The results of using this type of model could be used in risk assessment of ships entering to the ports, therefore it is possible to used probabilistic model in Maritime Office employees’ everyday decision making practice. Research results present verification of probabilistic model, based on data from Vessel Traffic Service database and probability of touching the bottom during ships’ passages on Swinoujscie – Szczecin waterway. Moreover there are presented examples of these situations when entering to the port for analysed ships is not allowed according to the model.
Źródło:: Journal of Polish Safety and Reliability Association; 2011, 2, 1; 197--204
2084-5316
Pojawia się w:: Journal of Polish Safety and Reliability Association
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Dependability aspects of language technology infrastructure
Autorzy:: Walkowiak, T.
Pol, M.
Powiązania:: https://bibliotekanauki.pl/articles/2068758.pdf
Data publikacji:: 2018
Wydawca:: Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:: dependability
language technology infrastructure
natural language processing
micro-service architecture
CLARIN-PL
Opis:: The paper presents dependability analysis of CLARIN-PL Centre of Language Technology (CLT). It describes infrastructure, high availability aspects and micro-service architecture used in CLARIN-PL applications. Microservices architecture improves dependability in respect to availability and reliability and to some extent safety. It is comprised of the mechanisms of reliable communication of applications, replication, recovery, and transaction processing. CLT has also a set of components for failure detection, monitoring and autonomic management, and distributed security policy enforcement.
Źródło:: Journal of Polish Safety and Reliability Association; 2018, 9, 3; 101--108
2084-5316
Pojawia się w:: Journal of Polish Safety and Reliability Association
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: The impact of administrator working hours on the reliability of the Centre of Language Technology
Autorzy:: Walkowiak, T.
Pol, M.
Powiązania:: https://bibliotekanauki.pl/articles/2068897.pdf
Data publikacji:: 2017
Wydawca:: Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:: reliability
repair time
working hours
language technology infrastructure
natural language processing
CLARIN-PL
Opis:: The paper presents reliability analysis of CLARIN-PL Centre of Language Technology (CLT). The CLT is a Polish part of the language technology infrastructure developed by CLARIN project. The main goal of which is to support researchers in humanities and social sciences. The infrastructure is a complex computer system that enables combining language tools with language resources into processing chains. Authors present the system structure, analyse types of faults and define the CLT reliability model. The model takes into account the fact the time gap, between the failure and the repair of the system is not exponential since repair actions are taken only when administrators are at work (assuming that administrators are not working 24/7). The model is used to estimate reliability metrics (mean time and 90th percentile of relative down time and relative partial operational time) by a use of Monte-Carlo simulation. Moreover, analysis of possible improvement in the CLT organisation and its influence on the estimated metrics is given.
Źródło:: Journal of Polish Safety and Reliability Association; 2017, 8, 1; 167--174
2084-5316
Pojawia się w:: Journal of Polish Safety and Reliability Association
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Risk in systems with virtualization : test case analysis
Autorzy:: Stanclik, M.
Walkowiak, T.
Powiązania:: https://bibliotekanauki.pl/articles/2069148.pdf
Data publikacji:: 2013
Wydawca:: Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:: virtualization
risk analysis
threats
Opis:: The paper presents an approach to risk analysis of exemplar test case information systems. Authors point out the common practice to implement virtualization and put away security considerations for future[5]. The overview of virtualization techniques, focusing on server virtualization is given. Next, authors present risk analysis of exemplar GIS system. First of all identification of threats is taken out focusing on virtualization aspects, but it also includes common threats for both that could have a significant impact on safety when using a virtualization. The risk assessment for the test case system was performed using qualitative method. Assessment of the likelihood and magnitude of impact of identified risks was performed on the basis of the expert’s knowledge and experience. The obtained results were used to develop risk rankings, which indicate the risks that need special attention when designing and managing a virtual system.
Źródło:: Journal of Polish Safety and Reliability Association; 2013, 4, 2; 249--258
2084-5316
Pojawia się w:: Journal of Polish Safety and Reliability Association
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Critical situations and human resources in discrete transportation systems analysis
Autorzy:: Walkowiak, T.
Mazurkiewicz, J.
Powiązania:: https://bibliotekanauki.pl/articles/2069570.pdf
Data publikacji:: 2011
Wydawca:: Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:: discrete transportation system
system dependability
critical situations analysis
Monte-Carlo simulation
Opis:: The paper presents an approach to critical situations analysis related to discrete transportation systems (DTS). The critical situation is understood as sudden shortage of some system recourses resulting in the transportation system performance degradation. The analysis is realized based on availability calculation of DTS. The system is described by the formal model, which includes reliability and functional parameters of DTS as well as human resources – drivers and management system. The availability and average availability of the system, defined in a functional way, is discussed as a function of different essential parameters of DTS. The proposed analysis is based on the modelling and simulating of the system behaviour using Monte-Carlo approach. The paper presents some exemplar systems – based on real Polish Post DTS – modelling and results.
Źródło:: Journal of Polish Safety and Reliability Association; 2011, 2, 1; 205--216
2084-5316
Pojawia się w:: Journal of Polish Safety and Reliability Association
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Fuzzy approach to complex system analysis
Autorzy:: Mazurkiewicz, J.
Nowak, K.
Walkowiak, T.
Powiązania:: https://bibliotekanauki.pl/articles/2069196.pdf
Data publikacji:: 2012
Wydawca:: Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:: dependability
modelling
complex systems
fuzzy logic
Opis:: The paper presents a new approach to reliability and functional analysis of sophisticated complex systems using fuzzy logic. We propose to use such methodology since dependability parameters of the system are mostly approximated by experts instead of classical sources of data. Presented approach show different idea – modeling system using the unified structure – in functional sense. We assess the reliability of the system by accumulated down time. Fuzzy logic based reliability analysis, as well as Computer Information System and Discrete Transport System modeling and simulation are presented. Moreover, results of numerical experiment performed on a test case scenario related to the economic and functional aspects using proposed methodology are given. Fuzzy approach allows reducing the problem of assumptions of reliability distributions and – this way – seems to be very interesting for real systems management and tuning.
Źródło:: Journal of Polish Safety and Reliability Association; 2012, 3, 2; 169--178
2084-5316
Pojawia się w:: Journal of Polish Safety and Reliability Association
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: The role of the origin (automatic vs. reflective) of affective state for the effectiveness of persuasion based on strong vs. weak arguments
Autorzy:: Walkowiak, Magdalena T.
Imbir, Kamil K.
Powiązania:: https://bibliotekanauki.pl/articles/2127064.pdf
Data publikacji:: 2019-04-08
Wydawca:: Katolicki Uniwersytet Lubelski Jana Pawła II. Towarzystwo Naukowe KUL
Tematy:: Elaboration Likelihood Model
persuasion
Emotion Duality Model
reflective emotions
automatic emotions
information processing
Opis:: Previous research has focused on the influence of emotional valence on the effectiveness of per-suasion via the central route or the peripheral route. The purpose of this study was to answer the question of whether other dimensions of emotion, such as the origin of emotional charge (auto-matic vs. reflective) may also influence the effectiveness of persuasion. It was expected that reflective emotions would increase susceptibility to strong arguments, while automatic emotions would result in a lack of sensitivity to the quality of arguments. Emotional words of proven emotional quality were used to elicit affective states. They were chosen in order to contrast the different levels of emotional valence (negative, neutral, and positive) and the origin of emotion (automatic and reflective). It turned out that in the case of reflective conditions, a significantly higher effectiveness of persuasion was observed for strong arguments than for weak ones. In the case of automatic conditions, there was no difference in the effectiveness of persuasion depending on the quality of the arguments. There were also no differences related to emotional valence; however, the manipulation of affective states on emotional valence dimension turned out not to be effective. This suggests that the origin of emotion can be considered a factor influencing processing via the central or peripheral route to persuasion.
Źródło:: Roczniki Psychologiczne; 2018, 21, 1; 9-33
1507-7888
Pojawia się w:: Roczniki Psychologiczne
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 11.

Tytuł:: Evaluation of susceptibility of phytopathogenic fusarium culmorum strain on selected essential oils
Ocena wrażliwości fitopatogennego szczepu Fusarium culmorum na wybrane olejki eteryczne
Autorzy:: Krzyśko-Łupicka, T.
Walkowiak, W.
Powiązania:: https://bibliotekanauki.pl/articles/389303.pdf
Data publikacji:: 2014
Wydawca:: Towarzystwo Chemii i Inżynierii Ekologicznej
Tematy:: Fusarium culmorum
thyme oil
lemongrass oil
Litsea cubeba oil
cajeput oil
tea tree oil
verbena oil
grapefruit oil
antifungal activity
olejek tymiankowy
olejek lemongrasowy
olejek Litsea cubeba
olejek kajeputowy
olejek z drzewa herbacianego
olejek verbenowy
olejek grejpfrutowy
antyfungistatyczna aktywność
Opis:: The prevalence in environment, high pathogenicity, toxigenicity and acquisition of resistance to used fungicides by Fusarium culmorum leads to a search for alternative methods to combat them. The solution to this problem may be essential oils. The aim of the study was to evaluate the sensitivity of the phytopathogenic Fusarium culmorum 187 (Mart.) Sacc. strain on selected essential oils such as thyme, lemongrass, Litsea cubeba, cajeput, tea tree, verbena and grapefruit in comparison to Funaben T seed preparation. The research material was a species of Fusarium culmorum 187 (Mart.) Sacc., isolated from infected cereals. The tested essential oils such as thyme, lemongrass, Litsea cubeba, cajeput, tea tree, verbena and grapefruit oils were introduced into the substrate at concentrations of 0.025; 0.05; 0.125; 0.25; 0.5; 1.00, 2.0 %, while Funaben T at concentrations of 0.125; 0.25; 0.5 %. The control was the development of the fungus in a medium free from these substances. Biotic activity of essential oils in reducing the linear growth of F. culmorum 187 (Mart.) Sacc. was assessed using the method of poisoned substrates. The activity of oils in reducing the linear growth of mycelium was evaluated by measuring the growth of fungal colonies (growth rate index) while the fungistatic activity was evaluated on the basis of the percentage growth inhibition of fungal colony calculated according to Abbott’s formula. The susceptibility of Fusarium culmorum 187 strain was differentiated and depended on the type and concentration of tested oils. Thyme oil at all concentrations tested (0.025–2.0 %) completely inhibited the growth of mycelia while other oils caused a total inhibition of growth at concentrations of 0.5–2.0 %. The effect of essential oils was similar to that of Funaben T preparation.
Rozpowszechnienie w środowisku, wysoka patogenność i toksynotwórczość oraz nabywanie oporności na stosowane fungicydy przez grzyby Fusarium culmorum prowadzi do poszukiwania alternatywnych metod ich zwalczania. Rozwiązanie problemu mogą stanowić olejki eteryczne. Celem pracy była ocena wrażliwości fitopatogennego szczepu Fusarium culmorum 187 na wybrane olejki eteryczne, takie jak: tymiankowy, z trawy cytrynowej, z Litsea cubeba, kajeputowy, z drzewa herbacianego, werbenowy i grejpfrutowy w porównaniu do zaprawy nasiennej Funaben T. Materiał badawczy stanowił gatunek grzyba Fusarium culmorum 187 (Mart) Sacc., wyizolowany z porażonych zbóż. Testowane olejki eteryczne, takie jak: tymiankowy z trawy cytrynowej, z Litsea cubeba, kajeputowy, z drzewa herbacianego, werbenowy i grejpfrutowy, wprowadzano do podłoża w stężeniach: 0.025; 0.05; 0.125; 0.25; 0.5; 1.00; 2.0 %. Natomiast Funaben T w stężeniach; 0.125; 0.25; 0.5. Kontrolę stanowił rozwój grzyba w podłożu wolnym od tych substancji. Aktywność biotyczną olejków w ograniczaniu wzrostu liniowego grzyba F. culmorum 187 Mart.(Sacc.) oceniano metodą zatrutych podłoży. Aktywność olejków w ograniczaniu wzrostu liniowego grzybni oceniano na podstawie pomiarów przyrostu kolonii grzybów (indeks tempa wzrostu), a fungistatyczną – na podstawie procentu zahamowania wzrostu kolonii grzyba obliczonego zgodnie ze wzorem Abbotta. Evaluation of Susceptibility of Phytopathogenic Fusarium culmorum 365 Wrażliwość szczepu Fusarium culmorum 187 była zróżnicowana i zależała od rodzaju i zastosowanego stężenia testowanych olejków. Olejek tymiankowy we wszystkich badanych stężeniach (0.025–2.0 %) całkowicie hamował rozwój grzybni, a pozostałe olejki całkowite zahamowanie wzrostu wywoływały w stężeniach 0.5–2.0 %. Efekt działania olejków eterycznych był zbliżony do działania zaprawy Funaben T
Źródło:: Ecological Chemistry and Engineering. A; 2014, 21, 3; 355-366
1898-6188
2084-4530
Pojawia się w:: Ecological Chemistry and Engineering. A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 12.

Tytuł:: Prediction of additive genetic effects based on the multitrait mixed model
Autorzy:: Molinski, K.
Szwaczkowski, T.
Walkowiak, R.
Powiązania:: https://bibliotekanauki.pl/articles/68090.pdf
Data publikacji:: 1993
Wydawca:: Polska Akademia Nauk. Instytut Genetyki Roślin PAN
Tematy:: doswiadczalnictwo
addytywne efekty genetyczne
statystyka matematyczna
genetyka zwierzat
wielocechowy model mieszany
doswiadczenia wielocechowe
Źródło:: Genetica Polonica; 1993, 34, 1; 47-55
0016-6715
Pojawia się w:: Genetica Polonica
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 13.

Tytuł:: Biofilm formation under anaerobic conditions on biomaterial’s surface
Autorzy:: Jakubowski, W.
Biela, T.
Kamińska, M.
Walkowiak-Przybyło, M.
Walkowiak, B.
Powiązania:: https://bibliotekanauki.pl/articles/284942.pdf
Data publikacji:: 2009
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
Tematy:: biofilms
surface
biomaterials
Opis:: Investigations of the biofilm formation processes on biomaterials surfaces are focused on typical physiologic conditions - aerobic condition. In experimental works onto model strains, and also in the clinical reports there is a lack of the information related to the mechanisms engaged in biofilm grown under conditions of limited access to oxygen or in entirely anaerobic environment. Presented results show the colonization of medical steel 316L surface and creation of biofilm structures by E. coli bacteria’s, under oxygen deficit conditions or its total lack. In studied arrangement the change of the dynamics of bacterium growth was observed, which led to considerable slowdown of the biofilm development. Bacteria were observed with use of the combination of fluorescent dyes - bis-benzimide and propidium iodide – which makes it possible the distinction of live/death bacteria. In oxygen deficiency and in anaerobic conditions multiplication of death bacteria level in comparison to standard conditions was observed (suitably 34% and 41% dead cells, oxygenic conditions - 1%). The limitation of oxygen utilization possibility by the bacteria, which colonized investigated surfaces also resulted in decreased sizes reached by the cells.
Źródło:: Engineering of Biomaterials; 2009, 12, no. 89-91; 254
1429-7248
Pojawia się w:: Engineering of Biomaterials
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 14.

Tytuł:: Corrosion behaviour of polished and sandblasted titanium alloys in PBS solution
Autorzy:: Burnat, B.
Walkowiak-Przybyło, M.
Błaszczyk, T.
Klimek, L.
Powiązania:: https://bibliotekanauki.pl/articles/306724.pdf
Data publikacji:: 2013
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:: corrosion
PBS solution
polishing
sandblasting
titanium alloys
korozja
stop tytanu
piaskowanie
Opis:: In this work, we performed comparative studies of the effect of surface preparation of Ti6Al4V and Ti6Al7Nb biomedical alloys and the influence of endothelial cells on their corrosion behaviour in PBS (Phosphate Buffered Saline). Two different methods of surface modification were applied – polishing and sandblasting. The polished Ti6Al7Nb alloy was found to have the best resistance against general corrosion in PBS. It was characterized by the lowest corrosion rate, the widest passive range and the lowest reactivity. Both alloys prepared by sandblasting exhibited worse corrosion properties in comparison to the polished ones. This can be associated with a greater development of their surface and the presence of Al2O3 grains which caused an increase of corrosion potential but might also influence the weakening of the passive layer. Results of potentiodynamic anodic polarization indicated that more resistant to pitting corrosion was Ti6Al7Nb alloy regardless of the method of surface preparation. In those cases, anodic polarization caused only an increase of passive layer, while in the case of sandblasted Ti6Al4V alloy it caused a pitting corrosion. The results obtained allowed us to conclude that the niobium-titanium alloys had higher corrosion resistance than titanium alloys with vanadium. Moreover, it was stated that endothelial cells improved the corrosion resistance of all the titanium alloys examined.
Źródło:: Acta of Bioengineering and Biomechanics; 2013, 15, 1; 87-94
1509-409X
2450-6303
Pojawia się w:: Acta of Bioengineering and Biomechanics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 15.

Tytuł:: Design and manufacture of customized medical implants
Autorzy:: Elgalal, M.
Komorowski, P.
Makowski, K.
Styczyński, A.
Ulański, P.
Kubiak, T.
Sawicki, J.
Domżalski, M.
Walkowiak, B.
Powiązania:: https://bibliotekanauki.pl/articles/285113.pdf
Data publikacji:: 2018
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
Tematy:: implants
patient anatomy
manufacturing
Źródło:: Engineering of Biomaterials; 2018, 21, 148; 36
1429-7248
Pojawia się w:: Engineering of Biomaterials
Dostawca treści:: Biblioteka Nauki

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