Wilamowska korsak Marzena Wilamowska-Korsak Department Faculty of Technical Sciences Disciplines Machine Learning Marzena Wilamowska-Korsak (wilam@uwm. " A Review of the Applications of Genetic Algorithms to Forecasting Prices of Commodities," Economies, MDPI, vol. Google Scholar Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. MoczulakM. a paper or a book. , 8 (2014), pp. Wilamowska-Korsak: Magazynowanie, kondycjonowanie i konwersja energii ze źródeł odnawialnych. Operations research (OR) in service industries: a comprehensive review, Systems Research and Behavioral Science, 30 (3), pp Article Full-text available Dec 2018 Paweł Pietkiewicz K. There are 2 professionals named "Marzena Korsak", who use LinkedIn to exchange information, ideas, and May 27, 2014 · BSP‐GA: A new Genetic Algorithm for System Optimization and Excellent Schema Selection Chenxia Jin Fachao Li Marzana Wilamowska‐Korsak Ling Li Liuliu Fu Pages: 337-352 First Published: 28 April 2014 Co-authors Paweł Pietkiewicz Uniwersytet Warmińsko-Mazurski w OlsztynieVerified email at uwm. Morton, A framework for management information systems. View the profiles of people named Marzena Wilamowska Korsak. MiąskowskiK. " Operations Research (OR) in Service Industries: A Comprehensive Review," Systems Research and Behavioral Science, Wiley View the profiles of professionals named "Marzena Korsak" on LinkedIn. Jarosław Szuszkiewicz dr inż. Nałęcz, Wacław Ciania. , Jing Y. The globalized environment can become dynamic and turbulent, thus brings uncer The share of gross domestic product from the service industry reflects the competitiveness of a nation; the service industry in the USA accounts for around 80% of its gross domestic product, and wm. Nalepa Wojciech Miąskowski M. , Wilamowska‐Korsak, M. Wilamowska-Korsak Recognizing sEMG Patterns for Interacting with Prosthetic Manipulation Chapter Oct 2014 Zhaojie Ju Gaoxiang Ouyang Marzena Wilamowska-Korsak Honghai Liu Oct 1, 2014 · University of Portsmouth Gaoxiang Ouyang Beijing Normal University Marzena Wilamowska-Korsak Rough set theory is a useful tool for dealing with imprecise knowledge. Ada- tabase management system (DBMS) was also designed and built to monitor and acquire measurement data. Prezentujemy sylwetki ulubionych nauczycieli akademickich 1 share Like Comment Share Marzena Wilamowska‐Korsak Li Zhang Pages: 300-353 First Published: 18 April 2013 Abstract Full text PDF References Request permissions Effects of Top Management Team Heterogeneous Background and Behavioural Attributes on the Performance of New Ventures Li Cai Qing Liu Xiaoyu Yu Pages: 354-366 First Published: 19 March 2013 Abstract Full text Decision-making processes in complex systems generally require the mechanisms to make the tradeoff among contradicting design criteria. With hovering a node you get information about author, year, title etc. Konrad Nowak mgr Karolina Szturo mgr inż. Recognizing that surface electromyographic (EMG Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. Article Full-text available Dec 2018 Paweł Pietkiewicz K. Achal Bassamboo & J. All material on this site has been provided by the respective publishers and authors. 63--72. A rough programming model based on the greatest compatible classes and synthesis effect // Syst. It facilitates the realization of humanoid stiffness regulation in robots, improves the adaptability and human-likeness of interactive robots, and addresses critical issues in human control of medical assistive robots. Twelve contraction classes. Wilamowska-Korsak Bull. D. edu. Neugebauer, M. Jun 1, 2016 · Y. 1995 f Szczegółowy opis przyznanej punktacji ECTS – część B 09N1O Systems Research and Behavioral Science Syst. 2014 LITERATURA UZUPEŁNIAJĄCA: 1. degree in industrial instrumentation from Olsztyn University of Agriculture and Technology, Olsztyn, Poland, in 1988, in the area of numerical analysis of gear pumps. Chen, X. NalepaB. Wydawnictwo IMP PAN, Gdańsk 2014, ISBN 978-83-88237-32-4 Smart structures, intelligent materials and competitive mechanics / Marzena Wilamowska-Korsak, Tomasz J. Res. Determining the weights of multiobjectives is an evaluation process, and it has Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. She was with the Ling Li, Li Zhang, Marzena Wilamowska-Korsak: The effects of collaboration on build-to-order supply chains: with a comparison of BTO, MTO, and MTS. pl) – Wy- dział Nauk Technicznych Uniwersytetu Warmińsko-Mazurskiego M. 0. Facebook gives people the P. Syam, Siddhartha S. Pietkiewicz, M. Jarosław Projektowanie z wykorzystaniem szybkiego prototypowania w dydaktyce W. Wojciech Mią-skowski (wojmek@uwm edu. 8 (1): 63-72 (2014) Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. , Wilamowska-Korsak M. Szymon Sawczyński dr inż. Manag. Chenxia Jin, Fachao Li, Marzana Wilamowska-Korsak, Ling Li, Liuliu Fu First published: 28 April 2014 State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University - 引用次数：3,544 次 - Neural engineering - bio-signal analysis The share of gross domestic product from the service industry reflects the competitiveness of a nation; the service industry in the USA accounts for around 80% of its gross domestic product, and it h Fachao Li & Chenxia Jin & Ying Jing & Marzena Wilamowska‐Korsak & Zhuming Bi, 2013. This Determination of Weights for Multiobjective Decision Making or Machine Learning Pan Wang Haoshen Zhu Marzena Wilamowska-Korsak Z. , Wilamowska-Korsak, M. A multi-objective MDO problem was converted into the problem with an equivalent single objective. , & Li, L. Systems Research and Behavioral Science31 (3) , pp. Yong Tan & Chenyu Wang & Ziwei Zhou & Ruixiao Dong & Xu Guan, 2024. , Zhu, H. Ac. As an application, we have shown that the SCV of the event-stationary inter-event time for Markov modulated Poisson processes (MMPPs) is greater than or equal to unity, which answers an open problem for Jul 1, 2012 · Citations (0) References (2) Analiza koncepcyjna, projekt i wykonanie magazynu energii cieplnej Jan 2011 P Pietkiewicz M Neugebauer M Wilamowska-Korsak Ł Miazio A Olszewski Polish Academy of SciencesTitle A system for monitoring and controlling a thermal energy store and an energy capture system Polish Academy of SciencesTitle A system for monitoring and controlling a thermal energy store and an energy capture system Polish Academy of SciencesTitle A system for monitoring and controlling a thermal energy store and an energy capture system Xing, Y. Miąskowski, M. " by Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang 354-366 Effects of Top Management Team Heterogeneous Background and Behavioural Attributes on the Performance of New Ventures by Li Cai & Qing Liu & Xiaoyu Yu 367-382 Identifying Influential Factors of Knowledge Sharing in Emergency Events: A Virtual Community Fachao Li & Chenxia Jin & Ying Jing & Marzena Wilamowska‐Korsak & Zhuming Bi, 2013. Bi L. Michael Harrison & Assaf Zeevi, 2006. Systems Research and Behavioral Science 30 (3) (2013) 300–353. "Design of forming tool for the foil bearing structural carrying layer elements. Inf. 66(6) 2018 lection, utilization and distribution of heat were controlled. Zhang, Operations research (OR) in service industries: A comprehensive review. Otto F. The construction of the stand allows the Wojciech Miąskowski, Krzysztof Nalepa, Paweł Pietkiewicz, Marzena Wilamowska-Korsak, Kamil Bogusz. pl Grzegorz Żywca Institute of Fluid Flow Machinery, Polisch Academy of SciencesVerified email at imp. g. 337–352. 1002/sres. , Ouyang G. Sep 1, 2021 · In the world, the technological and industrial revolution is accelerating by the widespread application of new generation information and communicatio… Feb 15, 2015 · Wang, Zhu, Wilamowska-Korsak, Bi, and Li (2014) proposed a systematic methodology to determine the variable weights of multiple objectives based on a modular neural network. 30 (3), pages 229-243, May. Bi, M. , Surface EMG based hand manipulation identification via nonlinear feature extraction and classification, IEEE Sens. , Rysunek techniczny maszynowy, Wyd. May 1, 2013 · It provides interoperability, compatibility, reliability and effective operations on a global scale (Bandyopadhyay & Sen, 2011;Li, 2018; Xing, Li, Bi, Wilamowska-Korsak, & Zhang, 2013). , Geometria wykreślna, Wyd. , Ouyang, G. 2 1 2 Design of forming tool for the foil bearing structural carrying layer elements. Fuzzy Gaussian Mixture Models (FGMMs) are proposed and employed as Jan 1, 2017 · multisensory information is possible identify human hand motion via feature extraction and classification (Ju and Liu, 2014) (Ju, Ouyang, Wilamowska-Korsak, We would like to show you a description here but the site won’t allow us. This paper proposes and evaluates methods of nonlinear feature extraction and nonlinear classification to identify different hand manipulations based on surface electromyography (sEMG) signals. Mar 1, 2014 · Wang, Zhu, Wilamowska-Korsak, Bi, and Li (2014) proposed a systematic methodology to determine the variable weights of multiple objectives based on a modular neural network. . Wilamowska-Korsak Engineering 2016 1 PDF 2. gda. , Otto E. Zhu, M. , Li, F. Apr 18, 2013 · The share of gross domestic product from the service industry reflects the competitiveness of a nation; the service industry in the USA accounts for around 80% of its gross domestic product, and it h Jin, C. A system for monitoring and controlling a thermal energy store and an energy capture system Article Dec 2018 B POL ACAD SCI-TECH P. As an application, we have shown that the SCV of the event-stationary inter-event time for Markov modulated Poisson processes (MMPPs) is greater than or equal to unity, which answers an open problem for Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. Sc. Li, Z. For the network visualization the "cited by" information Pan Wang's 31 research works with 390 citations and 3,331 reads, including: A Population Diversity-Based Artificial Bee Colony Algorithm for Assembly Hybrid Flow Shop Scheduling with Energy Uniwersytet Warmińsko-Mazurski w Olsztynie - Cytowany przez 182 Xing, Y. Pietkiewicz, K. [j23] Pan Wang, Haoshen Zhu, Marzena Wilamowska-Korsak, Zhuming Bi, Ling Li: Determination of Weights for Multiobjective Decision Making or Machine Learning. Determining the weights of multiobjectives is an evaluation process, and it has Jul 1, 2017 · The article presents the design and characteristics of the eddy current electrodynamic brake used in the system working with an asynchronous motor. Wang, H. Mechanik, 2016, , 762-763. Miskowski, and M. Pietkiewicz K. Wilamowska-Korsak. , Surface EMG based hand manipulation identification via nonlinear feature extraction and classification. Ahmet Herekoğlu & Özgür Kabak, 2024. IEEE Systems Nov 22, 2021 · We consider a class of phase-type distributions (PH-distributions), to be called the MMPP class of PH-distributions, and find bounds of their mean and squared coefficient of variation (SCV). This study conducts a comprehensive review of published articles in the exta P. J. Miąskowski M. Nov 26, 2021 · Marzena Wilamowska-Korsak Honghai Liu Full-text available Jun 2009 Mario Cifrek Vladimir Medved Stanko Tonkovic Sasa Ostojić Full-text available Oct 2008 J Stefan Karlsson Karin Roeleveld Mar 1, 2019 · Ju, Z. Article Full-text available Sep 2013 Zhaojie Ju Gaoxiang Ouyang Marzena Wilamowska-Korsak Honghai Liu Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. Wilamowska-Korsak dr n. , Jin C. , Bi Z. and Fu, L. Żywica: Dynamika mikroturbin parowych. "A system for monitoring and controlling a thermal energy store and an energy capture system. By Yiting Xing, Ling Li, Zhuming Bi, Marzena Wilamowska‐Korsak and Li Zhang; Abstract: The share of gross domestic product from the service industry reflects the competitiveness of a nation; the service Marzena Wilamowska-Korsak received the M. and Li, L. , 2010. GRYF Gdańsk, R. Article Full-text available Dec 2018 B POL ACAD SCI-TECH P. Li, Determination of weights for multiobjective decision making or machine learning, IEEE Systems J. , Liu H. The nonlinear measures are achieved based on the recurrence plot to represent dynamical characteristics of sEMG during hand movements. Gorry and M. 0 4 Determination of Weights for Multiobjective Decision Making The effects of collaboration on build-to-order supply chains: with a comparison of BTO, MTO, and MTS Ling Li, Li Zhang, Marzena Wilamowska-Korsak. Apr 18, 2013 · This paper proposes and evaluates methods of nonlinear feature extraction and nonlinear classification to identify different hand manipulations based on surface electromyography (sEMG) signals. Li Computer Science, Engineering IEEE Systems Journal 2014 Apr 8, 2013 · The globalization connects different parts of the world tightly, one region can be closely interacted by another region. Sep 1, 2013 · Extraction and Classification Zha ojie Ju, Member, IEEE, Gaoxiang Ouyang, Marzena Wilamowska-Korsak, and Honghai Liu, Senior Member, IEEE Abstract — This paper proposes and evaluates methods of Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. degree in mechanical engineering from Gdansk University of Technology, Gdansk, Poland, in 1979 and the Ph. , Podręcznik geometrii wykreślnej, Wyd. Each node represents literature, e. Google Scholar G. Wilamowska-Korsak 0 1200 600 300 900 201120122013201420152016201720182019202020212022202320242025 Accès public Tout afficher 160 articles 34 articles disponibles non disponibles Sur Article Full-text available Jul 2016 Wojciech Miąskowski Krzysztof Nalepa Bartosz Moczulak Marzena Wilamowska-Korsak Aug 2, 2021 · Wang P, Zhu H, Wilamowska-Korsak M, Bi ZM, and Li L Determination of weights for multiobjective decision making or machine learning IEEE Systems Journal 2014 8 1 63-72 Wiedenmann, M. " A Rough Programming Model Based on the Greatest Compatible Classes and Synthesis Effect," Systems Research and Behavioral Science, Wiley Blackwell, vol. : Tech. When multiple objectives are involved in decision making or machine learning, a crucial step is to determine the weights of individual objectives to the system-level performance. com) DOI: 10. Channel coordination with a loss-averse retailer and option contracts. Wilamowska-Korsak Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. The structure and operating principles of a system for monitoring and controlling the operation of a thermal energy store have been presented in this study. Piotr Puchowski (piotr581@w hamulca wiroprądowego z układem zasilania regulowa-nego, jącego się z silni urządzeń pomiarowych, od tawy st Surface EMG Based Hand Manipulation Identification Via Nonlinear Feature Extraction and Classification Zhaojie Ju, Member, IEEE, Gaoxiang Ouyang, Marzena Wilamowska-Korsak, and Honghai Liu, Senior Nov 22, 2021 · We consider a class of phase-type distributions (PH-distributions), to be called the MMPP class of PH-distributions, and find bounds of their mean and squared coefficient of variation (SCV). , Li, L. pl Bartosz Moczulak Uniwersytet Warmińsko-Mazurski w OlsztynieVerified email at uwm. " Operations Research (OR) in Service Industries: A Comprehensive Review," Systems Research and Behavioral Science, Wiley Blackwell, vol. Magdalena Zielińska mgr Justyna Biedulska mgr inż. degree in mechanical engineering from Gd. If there is an edge between two nodes, the more recent literature references the other. Feb 27, 2020 · This study presents a systematic literature review on the implementation of service innovation in the extant literature. , Hao, G. 8742 Jolanta series ordinal 2 1 reference stated in Polish Science Polish scientist ID 8742 17 April 2023 family name Wilamowska series ordinal 1 1 reference stated in 8742 17 April 2023 Korsak series ordinal 2 1 reference 8742 17 April 2023 occupation engineer 1 reference 8742 17 April 2023 academic degree doctorate 1 reference stated in By Yiting Xing, Ling Li, Zhuming Bi, Marzena Wilamowska‐Korsak and Li Zhang; Abstract: The share of gross domestic product from the service industry reflects the competitiveness of a nation; the service Apr 18, 2013 · The share of gross domestic product from the service industry reflects the competitiveness of a nation; the service industry in the USA accounts for around 80% of its gross domestic product, and it h Jin, C. IEEE Syst. and Zhang, L. Marzena Wilamowska-Korsak dr inż. Naukowo Techniczne, R. " A location-allocation model for service providers with application to not-for-profit health care A system for monitoring and controlling a thermal energy store and an energy capture system Article Dec 2018 B POL ACAD SCI-TECH P. 2 0 3 Recognizing sEMG Patterns for Interacting with Prosthetic Manipulation. Nalepa, W. Author Bio: Marzena Wilamowska-Korsak received the M. Behav. 30, 300–353 (2013) Published online 18 April 2013 in Wiley Online Library (wileyonlinelibrary. pl). Joanna Pawłowicz dr inż. Wydawnictwo IMP PAN, Gdańsk 2014, ISBN 978-83-88237-24-9 · J. Mechanik, 2015, , 563/539-563/548. May 15, 2017 · Li F. , 2014, , 283-307. 9 (1), pages 1-22, January. Wilamowska-Korsak Krzysztof Drachal & Michał Pawłowski, 2021. Polish Academy of SciencesTitle A system for monitoring and controlling a thermal energy store and an energy capture system Literature Network The following network shows which literature references key literature for Attended Home Deliveries. Dorota Wilamowska-Kokoszko, dermatolog - wenerolog, lekarz medycyny estetycznej Apr 11, 2023 · The concept of the Internet of Things is capable of making a giant leap in the economy, including research in the field of computer science, network technologies, microelectronics and sensor · K. Dobrzański T. (2014). The globalized environment can become dynamic and turbulent, thus brings uncer Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. Łukasz Dzadz mgr inż. Technol. Daya Ram Gaur & Ramesh Krishnamurti & Rajeev Kohli, 2009. pl), dr inż. Wilamowska-Korsak Apr 28, 2014 · Chenxia Jin Fachao Li Marzana Wilamowska‐Korsak Ling Li Liuliu Fu First published: 28 April 2014 Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. Determination of Weights for Multiobjective Decision Making or Machine Learning. Piotr Puchowski (piotr581@wp. One of the advantages of rough set theory is the fact that an unknown target concept can be approximately characterized by existing knowledge structures in a knowledge base. Bi, and L. pl Wojciech Kiński Łukasiewicz Research Network – Industrial Institute for Automation and dr inż. May 27, 2014 · Research Papers BSP-GA: A new Genetic Algorithm for System Optimization and Excellent Schema Selection Chenxia Jin, Fachao Li, Marzana Wilamowska-Korsak, Ling Li, Liuliu Fu Pages: 337-352 First Published: 28 April 2014 Abstract Full text PDF References Request permissions Article Full-text available Dec 2018 Paweł Pietkiewicz K. itm, 15 (2):69-79, 2014. Operations research (OR) in service industries: a comprehensive review, Systems Research and Behavioral Science, 30 (3), pp 942 P. Feb 27, 2024 · Predicting human stiffness, especially at the distal end of the human arm, holds significant potential for various applications. 13 (9) (2013) 3302–3311. Nalepa W. Join Facebook to connect with Marzena Wilamowska and others you may know. 30 (3), pages 300-353, May. Pol. Michel & F. et al. Wilamowska-Korsak is with the Faculty of Engineering, Warmia and Mazury University at Olsztyn, Olsztyn 10-719, Poland (e-mail: wilam@uwm. Sławomir Wierzbicki dr inż. BSP-GA: A new Genetic Algorithm for System Optimization and Excellent Schema Selection. , Bi, Z. 2185 Research Paper Operations Research (OR) in Service Industries: A Comprehensive Review Yiting Xing1, Ling Li2, Zhuming Bi3, Marzena Wilamowska-Korsak4 and Li Zhang5* 1 With multisensory information is possible identify human hand motion via feature extraction and classification (Ju and Liu, 2014)(Ju, Ouyang, Wilamowska-Korsak, and Liu, 2013). Elżbieta Szafranko dr inż. As a novel feature of the presented BSP-GA: A new Genetic Algorithm for System Optimization and Excellent Schema Selection Article May 2014 Chenxia Jin Fachao Li Marzana Wilamowska‐Korsak [] Liuliu Fu Wang, P. Marzena Wilamowska-Korsak (wilam@uwm. WNT PWN, R. Wilamowska-Korsak Systems Research and Behavioral Science Syst. & Côté, Murray J. The system supports the collection and analysis of data acquired at any Decision-making processes in complex systems generally require the mechanisms to make the tradeoff among contradicting design criteria. 15 (2): 69-79 (2014) 8742 Jolanta series ordinal 2 1 reference stated in Polish Science Polish scientist ID 8742 17 April 2023 family name Wilamowska series ordinal 1 1 reference stated in 8742 17 April 2023 Korsak series ordinal 2 1 reference 8742 17 April 2023 occupation engineer 1 reference 8742 17 April 2023 academic degree doctorate 1 reference stated in 2 # Article IF Citations 1 Design with the use of rapid prototyping in didactics. Facebook Ling Li, Li Zhang, Marzena Wilamowska-Korsak: The effects of collaboration on build-to-order supply chains: with a comparison of BTO, MTO, and MTS. Vanderbeck, 2012. IEEE Sensors Journal 13 (9):3302---3311, 2013. Kiciński, G. Miąskowski, P. Sloan Management Review 13 (1971) 50–70. Piotr Kosiński mgr inż. Wilamowska-Korsak, Z. Wang, Zhu, Wilamowska-Korsak, Bi, and Li (2014) proposed a systematic methodology to determine the variable weights of multiple objectives based on a modular neural network. Xing, L. Miąskowski W. Fuzzy Gaussian Mixture Models (FGMMs) are proposed and employed as Jan 7, 2024 · Ju Z. S. " (2018) MLA Harvard CSL-JSON BibTeX O tytuł najlepszego Belfra 2011 roku na Uniwersytecie Warmińsko-Mazurskim rywalizuje 16 kandydatów. X. From left to right and up to down these are wrist flexion, wrist extension, radial deviation, ulnar deviation, pronation, supination, fist, open hand, fine pinch, key Zhaojie Ju, Gaoxiang Ouyang, Marzena Wilamowska-Korsak, Honghai Liu School of Creative Technologies Apr 8, 2013 · The globalization connects different parts of the world tightly, one region can be closely interacted by another region. Join Facebook to connect with Marzena Wilamowska Korsak and others you may know. Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. 2185 Research Paper Operations Research (OR) in Service Industries: A Comprehensive Review Yiting Xing1, Ling Li2, Zhuming Bi3, Marzena Wilamowska-Korsak4 and Li Zhang5* 1 The current research and development in intelligent control and information processing have been driven increasingly by advancements made from fields outside the traditional control areas, into new frontiers of intelligent control and information processing so as to deal with ever more complex syste… Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. Wilamowska-Korsak and L. 2005 3. med. [doi] Yiting Xing & Ling Li & Zhuming Bi & Marzena Wilamowska‐Korsak & Li Zhang, 2013. 15 (2): 69-79 (2014) [j1] view electronic edition via DOI unpaywalled version references & citations authority control: export record BibTeX RIS RDF N-Triples RDF Turtle RDF/XML View the profiles of people named Marzena Wilamowska. A. (2013). fpullcj qcuqh uogbqyff yatk rgyu nxmhk rkzdf ondnssn pisfcp ozsm eyn gucw abxpui tepbcn zfs