Author: Ian M. Hutchings
Publisher: John Wiley & Sons
ISBN: 1118452933
Category : Science
Languages : en
Pages : 417
Book Description
Whilst inkjet technology is well-established on home and small office desktops and is now having increasing impact in commercial printing, it can also be used to deposit materials other than ink as individual droplets at a microscopic scale. This allows metals, ceramics, polymers and biological materials (including living cells) to be patterned on to substrates under precise digital control. This approach offers huge potential advantages for manufacturing, since inkjet methods can be used to generate structures and functions which cannot be attained in other ways. Beginning with an overview of the fundamentals, this bookcovers the key components, for example piezoelectric print-heads and fluids for inkjet printing, and the processes involved. It goes on to describe specific applications, e.g. MEMS, printed circuits, active and passive electronics, biopolymers and living cells, and additive manufacturing. Detailed case studies are included on flat-panel OLED displays, RFID (radio-frequency identification) manufacturing and tissue engineering, while a comprehensive examination of the current technologies and future directions of inkjet technology completes the coverage. With contributions from both academic researchers and leading names in the industry, Inkjet Technology for Digital Fabrication is a comprehensive resource for technical development engineers, researchers and students in inkjet technology and system development, and will also appeal to researchers in chemistry, physics, engineering, materials science and electronics.
Inkjet Technology for Digital Fabrication
Author: Ian M. Hutchings
Publisher: John Wiley & Sons
ISBN: 1118452933
Category : Science
Languages : en
Pages : 417
Book Description
Whilst inkjet technology is well-established on home and small office desktops and is now having increasing impact in commercial printing, it can also be used to deposit materials other than ink as individual droplets at a microscopic scale. This allows metals, ceramics, polymers and biological materials (including living cells) to be patterned on to substrates under precise digital control. This approach offers huge potential advantages for manufacturing, since inkjet methods can be used to generate structures and functions which cannot be attained in other ways. Beginning with an overview of the fundamentals, this bookcovers the key components, for example piezoelectric print-heads and fluids for inkjet printing, and the processes involved. It goes on to describe specific applications, e.g. MEMS, printed circuits, active and passive electronics, biopolymers and living cells, and additive manufacturing. Detailed case studies are included on flat-panel OLED displays, RFID (radio-frequency identification) manufacturing and tissue engineering, while a comprehensive examination of the current technologies and future directions of inkjet technology completes the coverage. With contributions from both academic researchers and leading names in the industry, Inkjet Technology for Digital Fabrication is a comprehensive resource for technical development engineers, researchers and students in inkjet technology and system development, and will also appeal to researchers in chemistry, physics, engineering, materials science and electronics.
Publisher: John Wiley & Sons
ISBN: 1118452933
Category : Science
Languages : en
Pages : 417
Book Description
Whilst inkjet technology is well-established on home and small office desktops and is now having increasing impact in commercial printing, it can also be used to deposit materials other than ink as individual droplets at a microscopic scale. This allows metals, ceramics, polymers and biological materials (including living cells) to be patterned on to substrates under precise digital control. This approach offers huge potential advantages for manufacturing, since inkjet methods can be used to generate structures and functions which cannot be attained in other ways. Beginning with an overview of the fundamentals, this bookcovers the key components, for example piezoelectric print-heads and fluids for inkjet printing, and the processes involved. It goes on to describe specific applications, e.g. MEMS, printed circuits, active and passive electronics, biopolymers and living cells, and additive manufacturing. Detailed case studies are included on flat-panel OLED displays, RFID (radio-frequency identification) manufacturing and tissue engineering, while a comprehensive examination of the current technologies and future directions of inkjet technology completes the coverage. With contributions from both academic researchers and leading names in the industry, Inkjet Technology for Digital Fabrication is a comprehensive resource for technical development engineers, researchers and students in inkjet technology and system development, and will also appeal to researchers in chemistry, physics, engineering, materials science and electronics.
Fused Deposition Modeling Based 3D Printing
Author: Harshit K. Dave
Publisher: Springer Nature
ISBN: 303068024X
Category : Technology & Engineering
Languages : en
Pages : 517
Book Description
This book covers 3D printing activities by fused deposition modeling process. The two introductory chapters discuss the principle, types of machines and raw materials, process parameters, defects, design variations and simulation methods. Six chapters are devoted to experimental work related to process improvement, mechanical testing and characterization of the process, followed by three chapters on post-processing of 3D printed components and two chapters addressing sustainability concerns. Seven chapters discuss various applications including composites, external medical devices, drug delivery system, orthotic inserts, watertight components and 4D printing using FDM process. Finally, six chapters are dedicated to the study on modeling and optimization of FDM process using computational models, evolutionary algorithms, machine learning, metaheuristic approaches and optimization of layout and tool path.
Publisher: Springer Nature
ISBN: 303068024X
Category : Technology & Engineering
Languages : en
Pages : 517
Book Description
This book covers 3D printing activities by fused deposition modeling process. The two introductory chapters discuss the principle, types of machines and raw materials, process parameters, defects, design variations and simulation methods. Six chapters are devoted to experimental work related to process improvement, mechanical testing and characterization of the process, followed by three chapters on post-processing of 3D printed components and two chapters addressing sustainability concerns. Seven chapters discuss various applications including composites, external medical devices, drug delivery system, orthotic inserts, watertight components and 4D printing using FDM process. Finally, six chapters are dedicated to the study on modeling and optimization of FDM process using computational models, evolutionary algorithms, machine learning, metaheuristic approaches and optimization of layout and tool path.
High-Performance Composite Structures
Author: A. Praveen Kumar
Publisher: Springer Nature
ISBN: 9811673772
Category : Technology & Engineering
Languages : en
Pages : 306
Book Description
This book covers advanced 3D printing processes and the latest developments in novel composite-based printing materials, thus enabling the reader to understand and benefit from the advantages of this groundbreaking technology. The rise in ecological anxieties has forced scientists and researchers from all over the world to find novel lightweight materials. Therefore, it is necessary to expand knowledge about the processing, applications, and challenges of 3D printing of composite materials to expanding the range of their application. This book presents an extensive survey on recent improvements in the research and development of additive manufacturing technologies that are used to make composite structures for various applications such as electronic, aerospace, construction, and biomedical applications. Advanced printing techniques including fused deposition modeling (FDM), selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), inkjet 3D printing (3DP), stereolithography (SLA), and 3D plotting will be covered and discussed thoroughly in this book. This book also focuses the recent advances and challenges in polymer nanocomposite and introduces potential applications of these materials in various sectors.
Publisher: Springer Nature
ISBN: 9811673772
Category : Technology & Engineering
Languages : en
Pages : 306
Book Description
This book covers advanced 3D printing processes and the latest developments in novel composite-based printing materials, thus enabling the reader to understand and benefit from the advantages of this groundbreaking technology. The rise in ecological anxieties has forced scientists and researchers from all over the world to find novel lightweight materials. Therefore, it is necessary to expand knowledge about the processing, applications, and challenges of 3D printing of composite materials to expanding the range of their application. This book presents an extensive survey on recent improvements in the research and development of additive manufacturing technologies that are used to make composite structures for various applications such as electronic, aerospace, construction, and biomedical applications. Advanced printing techniques including fused deposition modeling (FDM), selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), inkjet 3D printing (3DP), stereolithography (SLA), and 3D plotting will be covered and discussed thoroughly in this book. This book also focuses the recent advances and challenges in polymer nanocomposite and introduces potential applications of these materials in various sectors.
3D and 4D Printing of Polymer Nanocomposite Materials
Author: Kishor Kumar Sadasivuni
Publisher: Elsevier
ISBN: 0128173025
Category : Technology & Engineering
Languages : en
Pages : 594
Book Description
3D and 4D Printing of Polymer Nanocomposite Materials: Processing, Applications, and Challenges covers advanced 3D and 4D printing processes and the latest developments in novel polymer-based printing materials, thus enabling the reader to understand and benefit from the advantages of this groundbreaking technology. The book presents processes, materials selection, and printability issues, along with sections on the preparation of polymer composite materials for 3D and 4D printing. Across the book, advanced printing techniques are covered and discussed thoroughly, including fused deposition modeling (FDM), selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), inkjet 3D printing (3DP), stereolithography (SLA), and 3D plotting. Finally, major applications areas are discussed, including electronic, aerospace, construction and biomedical applications, with detailed information on the design, fabrication and processing methods required in each case. - Provides a thorough, clear understanding of polymer preparation techniques and 3D and 4D printing processes, with a view to specific applications - Examines synthesis, formation methodology, the dispersion of fillers, characterization, properties, and performance of polymer nanocomposites - Explores the possibilities of 4D printing, covering the usage of stimuli responsive hydrogels and shape memory polymers
Publisher: Elsevier
ISBN: 0128173025
Category : Technology & Engineering
Languages : en
Pages : 594
Book Description
3D and 4D Printing of Polymer Nanocomposite Materials: Processing, Applications, and Challenges covers advanced 3D and 4D printing processes and the latest developments in novel polymer-based printing materials, thus enabling the reader to understand and benefit from the advantages of this groundbreaking technology. The book presents processes, materials selection, and printability issues, along with sections on the preparation of polymer composite materials for 3D and 4D printing. Across the book, advanced printing techniques are covered and discussed thoroughly, including fused deposition modeling (FDM), selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), inkjet 3D printing (3DP), stereolithography (SLA), and 3D plotting. Finally, major applications areas are discussed, including electronic, aerospace, construction and biomedical applications, with detailed information on the design, fabrication and processing methods required in each case. - Provides a thorough, clear understanding of polymer preparation techniques and 3D and 4D printing processes, with a view to specific applications - Examines synthesis, formation methodology, the dispersion of fillers, characterization, properties, and performance of polymer nanocomposites - Explores the possibilities of 4D printing, covering the usage of stimuli responsive hydrogels and shape memory polymers
3D Printing for Energy Applications
Author: Albert Tarancón
Publisher: John Wiley & Sons
ISBN: 1119560764
Category : Technology & Engineering
Languages : en
Pages : 400
Book Description
3D PRINTING FOR ENERGY APPLICATIONS Explore current and future perspectives of 3D printing for the fabrication of high value-added complex devices 3D Printing for Energy Applications delivers an insightful and cutting-edge exploration of the applications of 3D printing to the fabrication of complex devices in the energy sector. The book covers aspects related to additive manufacturing of functional materials with applicability in the energy sector. It reviews both the technology of printable materials and 3D printing strategies itself, and its use in energy devices or systems. Split into three sections, the book covers the 3D printing of functional materials before delving into the 3D printing of energy devices. It closes with printing challenges in the production of complex objects. It also presents an interesting perspective on the future of 3D printing of complex devices. Readers will also benefit from the inclusion of: A thorough introduction to 3D printing of functional materials, including metals, ceramics, and composites An exploration of 3D printing challenges for production of complex objects, including computational design, multimaterials, tailoring AM components, and volumetric additive manufacturing Practical discussions of 3D printing of energy devices, including batteries, supercaps, solar panels, fuel cells, turbomachinery, thermoelectrics, and CCUS Perfect for materials scientists, 3D Printing for Energy Applications will also earn a place in the libraries of graduate students in engineering, chemistry, and material sciences seeking a one-stop reference for current and future perspectives on 3D printing of high value-added complex devices.
Publisher: John Wiley & Sons
ISBN: 1119560764
Category : Technology & Engineering
Languages : en
Pages : 400
Book Description
3D PRINTING FOR ENERGY APPLICATIONS Explore current and future perspectives of 3D printing for the fabrication of high value-added complex devices 3D Printing for Energy Applications delivers an insightful and cutting-edge exploration of the applications of 3D printing to the fabrication of complex devices in the energy sector. The book covers aspects related to additive manufacturing of functional materials with applicability in the energy sector. It reviews both the technology of printable materials and 3D printing strategies itself, and its use in energy devices or systems. Split into three sections, the book covers the 3D printing of functional materials before delving into the 3D printing of energy devices. It closes with printing challenges in the production of complex objects. It also presents an interesting perspective on the future of 3D printing of complex devices. Readers will also benefit from the inclusion of: A thorough introduction to 3D printing of functional materials, including metals, ceramics, and composites An exploration of 3D printing challenges for production of complex objects, including computational design, multimaterials, tailoring AM components, and volumetric additive manufacturing Practical discussions of 3D printing of energy devices, including batteries, supercaps, solar panels, fuel cells, turbomachinery, thermoelectrics, and CCUS Perfect for materials scientists, 3D Printing for Energy Applications will also earn a place in the libraries of graduate students in engineering, chemistry, and material sciences seeking a one-stop reference for current and future perspectives on 3D printing of high value-added complex devices.
Fundamentals of Fibre Reinforced Composite Materials
Author: A.R. Bunsell
Publisher: CRC Press
ISBN: 9781420056969
Category : Science
Languages : en
Pages : 418
Book Description
Fiber reinforced composite materials encompass a wide range of material classes from reinforced glasses, plastics, and rubbers through to more recently developed metals and ceramics. Fundamentals of Fibre Reinforced Composite Materials is a comprehensive and authoritative book that introduces the topic with a brief history of composite development, a review of composite applications, the types of fibre used, and their respective indiviual properties. An entire chapter considers organic matrices and their behavior, reviewing all of the most commonly encountered polymer matrix systems. Composite manufacturing techniques are then discussed, including those methods employed in the production of advanced metal and ceramic matrix composites. The remaining chapters are devoted primarily to theoretical treatments of composite behavior, with emphasis on the understanding of damage mechanisms such as cracking, delamination, and fibre breakage. Where a mathematical approach is required, an attempt is made to relate the sometimes rather abstract notions back at the structure of the material being discussed. With extensive sets of sample problems accompanying each chapter, Fundamentals of Fibre Reinforced Composite Materials is ideally suited to undergraduate and graduate students of materials science, structural, mechanical, and aeronautical engineering, polymer science, metallurgy, physics and chemistry. It will also be of use as a reference to researchers working with composite materials and material scientists in general.
Publisher: CRC Press
ISBN: 9781420056969
Category : Science
Languages : en
Pages : 418
Book Description
Fiber reinforced composite materials encompass a wide range of material classes from reinforced glasses, plastics, and rubbers through to more recently developed metals and ceramics. Fundamentals of Fibre Reinforced Composite Materials is a comprehensive and authoritative book that introduces the topic with a brief history of composite development, a review of composite applications, the types of fibre used, and their respective indiviual properties. An entire chapter considers organic matrices and their behavior, reviewing all of the most commonly encountered polymer matrix systems. Composite manufacturing techniques are then discussed, including those methods employed in the production of advanced metal and ceramic matrix composites. The remaining chapters are devoted primarily to theoretical treatments of composite behavior, with emphasis on the understanding of damage mechanisms such as cracking, delamination, and fibre breakage. Where a mathematical approach is required, an attempt is made to relate the sometimes rather abstract notions back at the structure of the material being discussed. With extensive sets of sample problems accompanying each chapter, Fundamentals of Fibre Reinforced Composite Materials is ideally suited to undergraduate and graduate students of materials science, structural, mechanical, and aeronautical engineering, polymer science, metallurgy, physics and chemistry. It will also be of use as a reference to researchers working with composite materials and material scientists in general.
Carbon Nanotubes and Graphene
Author: Kazuyoshi Tanaka
Publisher: Newnes
ISBN: 0080982689
Category : Science
Languages : en
Pages : 458
Book Description
Carbon Nanotubes and Graphene is a timely second edition of the original Science and Technology of Carbon Nanotubes. Updated to include expanded coverage of the preparation, purification, structural characterization, and common application areas of single- and multi-walled CNT structures, this work compares, contrasts, and, where appropriate, unitizes CNT to graphene. This much expanded second edition reference supports knowledge discovery, production of impactful carbon research, encourages transition between research fields, and aids the formation of emergent applications. New chapters encompass recent developments in the theoretical treatments of electronic and vibrational structures, and magnetic, optical, and electrical solid-state properties, providing a vital base to research. Current and potential applications of both materials, including the prospect for large-scale synthesis of graphene, biological structures, and flexible electronics, are also critically discussed. - Updated discussion of properties, structure, and morphology of biological and flexible electronic applications aids fundamental knowledge discovery - Innovative parallel focus on nanotubes and graphene enables you to learn from the successes and failures of, respectively, mature and emergent partner research disciplines - High-quality figures and tables on physical and mathematical applications expertly summarize key information – essential if you need quick, critically relevant data
Publisher: Newnes
ISBN: 0080982689
Category : Science
Languages : en
Pages : 458
Book Description
Carbon Nanotubes and Graphene is a timely second edition of the original Science and Technology of Carbon Nanotubes. Updated to include expanded coverage of the preparation, purification, structural characterization, and common application areas of single- and multi-walled CNT structures, this work compares, contrasts, and, where appropriate, unitizes CNT to graphene. This much expanded second edition reference supports knowledge discovery, production of impactful carbon research, encourages transition between research fields, and aids the formation of emergent applications. New chapters encompass recent developments in the theoretical treatments of electronic and vibrational structures, and magnetic, optical, and electrical solid-state properties, providing a vital base to research. Current and potential applications of both materials, including the prospect for large-scale synthesis of graphene, biological structures, and flexible electronics, are also critically discussed. - Updated discussion of properties, structure, and morphology of biological and flexible electronic applications aids fundamental knowledge discovery - Innovative parallel focus on nanotubes and graphene enables you to learn from the successes and failures of, respectively, mature and emergent partner research disciplines - High-quality figures and tables on physical and mathematical applications expertly summarize key information – essential if you need quick, critically relevant data
Introduction to Aerospace Materials
Author: Adrian P Mouritz
Publisher: Elsevier
ISBN: 0857095153
Category : Technology & Engineering
Languages : en
Pages : 637
Book Description
The structural materials used in airframe and propulsion systems influence the cost, performance and safety of aircraft, and an understanding of the wide range of materials used and the issues surrounding them is essential for the student of aerospace engineering.Introduction to aerospace materials reviews the main structural and engine materials used in aircraft, helicopters and spacecraft in terms of their production, properties, performance and applications.The first three chapters of the book introduce the reader to the range of aerospace materials, focusing on recent developments and requirements. Following these introductory chapters, the book moves on to discuss the properties and production of metals for aerospace structures, including chapters covering strengthening of metal alloys, mechanical testing, and casting, processing and machining of aerospace metals. The next ten chapters look in depth at individual metals including aluminium, titanium, magnesium, steel and superalloys, as well as the properties and processing of polymers, composites and wood. Chapters on performance issues such as fracture, fatigue and corrosion precede a chapter focusing on inspection and structural health monitoring of aerospace materials. Disposal/recycling and materials selection are covered in the final two chapters.With its comprehensive coverage of the main issues surrounding structural aerospace materials,Introduction to aerospace materials is essential reading for undergraduate students studying aerospace and aeronautical engineering. It will also be a valuable resource for postgraduate students and practising aerospace engineers. - Reviews the main structural and engine materials used in aircraft, helicopters and space craft in terms of their properties, performance and applications - Introduces the reader to the range of aerospace materials, focusing on recent developments and requirements, and discusses the properties and production of metals for aerospace structures - Chapters look in depth at individual metals including aluminium, titanium, magnesium, steel and superalloys
Publisher: Elsevier
ISBN: 0857095153
Category : Technology & Engineering
Languages : en
Pages : 637
Book Description
The structural materials used in airframe and propulsion systems influence the cost, performance and safety of aircraft, and an understanding of the wide range of materials used and the issues surrounding them is essential for the student of aerospace engineering.Introduction to aerospace materials reviews the main structural and engine materials used in aircraft, helicopters and spacecraft in terms of their production, properties, performance and applications.The first three chapters of the book introduce the reader to the range of aerospace materials, focusing on recent developments and requirements. Following these introductory chapters, the book moves on to discuss the properties and production of metals for aerospace structures, including chapters covering strengthening of metal alloys, mechanical testing, and casting, processing and machining of aerospace metals. The next ten chapters look in depth at individual metals including aluminium, titanium, magnesium, steel and superalloys, as well as the properties and processing of polymers, composites and wood. Chapters on performance issues such as fracture, fatigue and corrosion precede a chapter focusing on inspection and structural health monitoring of aerospace materials. Disposal/recycling and materials selection are covered in the final two chapters.With its comprehensive coverage of the main issues surrounding structural aerospace materials,Introduction to aerospace materials is essential reading for undergraduate students studying aerospace and aeronautical engineering. It will also be a valuable resource for postgraduate students and practising aerospace engineers. - Reviews the main structural and engine materials used in aircraft, helicopters and space craft in terms of their properties, performance and applications - Introduces the reader to the range of aerospace materials, focusing on recent developments and requirements, and discusses the properties and production of metals for aerospace structures - Chapters look in depth at individual metals including aluminium, titanium, magnesium, steel and superalloys
Sustainability for 3D Printing
Author: Kamalpreet Sandhu
Publisher: Springer Nature
ISBN: 3030752356
Category : Technology & Engineering
Languages : en
Pages : 194
Book Description
With advancement in modern technology human life span in 21st century has significantly improved as compared to past centuries. Indeed, the manufacturing and household wastes have also boosted in the same era, presenting a hazardous condition to the various living beings. However, through smart methodologies, it can be possible to recycle/reuse of the different types of wastes as a feedstock convenient for specialized manufacturing technologies, such as 3D printing. This means that through proper facilities the waste can be used as the raw material for the printing technologies with characteristic at par with the virgin feedstock. Furthermore, producing the feedstock using waste materials will help to reduce the cost of the processing material, productivity and eco-friendliness of this manufacturing technology. This book will cover a boarder aspect of such efforts wherein various applications and state of art solutions will be discussed in a comprehensive way. This book will be much interest for academics, research and entrepreneur who are working in the field materials science, 3D printing, and manufacturing because of its coverage of state of art solution in the field of commercial, industrial and healthcare products.
Publisher: Springer Nature
ISBN: 3030752356
Category : Technology & Engineering
Languages : en
Pages : 194
Book Description
With advancement in modern technology human life span in 21st century has significantly improved as compared to past centuries. Indeed, the manufacturing and household wastes have also boosted in the same era, presenting a hazardous condition to the various living beings. However, through smart methodologies, it can be possible to recycle/reuse of the different types of wastes as a feedstock convenient for specialized manufacturing technologies, such as 3D printing. This means that through proper facilities the waste can be used as the raw material for the printing technologies with characteristic at par with the virgin feedstock. Furthermore, producing the feedstock using waste materials will help to reduce the cost of the processing material, productivity and eco-friendliness of this manufacturing technology. This book will cover a boarder aspect of such efforts wherein various applications and state of art solutions will be discussed in a comprehensive way. This book will be much interest for academics, research and entrepreneur who are working in the field materials science, 3D printing, and manufacturing because of its coverage of state of art solution in the field of commercial, industrial and healthcare products.
Process–Structure–Properties in Polymer Additive Manufacturing
Author: Swee Leong Sing
Publisher: MDPI
ISBN: 303651371X
Category : Technology & Engineering
Languages : en
Pages : 218
Book Description
Additive manufacturing (AM) methods have grown and evolved rapidly in recent years. AM for polymers is an exciting field and has great potential in transformative and translational research in many fields, such as biomedical, aerospace, and even electronics. Current methods for polymer AM include material extrusion, material jetting, vat polymerisation, and powder bed fusion. With the promise of more applications, detailed understanding of AM—from the processability of the feedstock to the relationship between the process–structure–properties of AM parts—has become more critical. More research work is needed in material development to widen the choice of materials for polymer additive manufacturing. Modelling and simulations of the process will allow the prediction of microstructures and mechanical properties of the fabricated parts while complementing the understanding of the physical phenomena that occurs during the AM processes. In this book, state-of-the-art reviews and current research are collated, which focus on the process–structure–properties relationships in polymer additive manufacturing.
Publisher: MDPI
ISBN: 303651371X
Category : Technology & Engineering
Languages : en
Pages : 218
Book Description
Additive manufacturing (AM) methods have grown and evolved rapidly in recent years. AM for polymers is an exciting field and has great potential in transformative and translational research in many fields, such as biomedical, aerospace, and even electronics. Current methods for polymer AM include material extrusion, material jetting, vat polymerisation, and powder bed fusion. With the promise of more applications, detailed understanding of AM—from the processability of the feedstock to the relationship between the process–structure–properties of AM parts—has become more critical. More research work is needed in material development to widen the choice of materials for polymer additive manufacturing. Modelling and simulations of the process will allow the prediction of microstructures and mechanical properties of the fabricated parts while complementing the understanding of the physical phenomena that occurs during the AM processes. In this book, state-of-the-art reviews and current research are collated, which focus on the process–structure–properties relationships in polymer additive manufacturing.