Design and Implementation of Asymptotically Optimal Mesh Slicing Algorithms Using Parallel Processing

Mesh slicing is the process of taking a three dimensional model and reducing it to 2.5 dimensional layers that together create a layered representation of the model. The process is used in layered additive manufacturing, three dimensional voxelization, and other similar problems in computational geometry. The slicing process is computationally expensive, and the time required to slice an object can inhibit the viability of layered manufacturing in some industries. We designed and developed a fast implementation of the slicing process, called Sunder, that uses new asymptotically optimal algorithms and takes advantage of parallel processing platforms. To our knowledge, no other slicing implementation leverages massive parallel execution hardware, such as graphics processing units (GPUs), leaving significant potential for improvement. Furthermore, no published set of slicing algorithms completes all three major steps in the slicing process (preprocessing, slicing, and contour assembly) in linear time complexity, which our design achieves. Therefore, our implementation improves the current state of the art in mesh slicing

From 3D Models to 3D Prints: an Overview of the Processing Pipeline

Due to the wide diffusion of 3D printing technologies, geometric algorithms for Additive Manufacturing are being invented at an impressive speed. Each single step, in particular along the Process Planning pipeline, can now count on dozens of methods that prepare the 3D model for fabrication, while analysing and optimizing geometry and machine instructions for various objectives. This report provides a classification of this huge state of the art, and elicits the relation between each single algorithm and a list of desirable objectives during Process Planning. The objectives themselves are listed and discussed, along with possible needs for tradeoffs. Additive Manufacturing technologies are broadly categorized to explicitly relate classes of devices and supported features. Finally, this report offers an analysis of the state of the art while discussing open and challenging problems from both an academic and an industrial perspective.Comment: European Union (EU); Horizon 2020; H2020-FoF-2015; RIA - Research and Innovation action; Grant agreement N. 68044

Solid modelling for manufacturing: from Voelcker's boundary evaluation to discrete paradigms

Herb Voelcker and his research team laid the foundations of Solid Modelling, on which Computer-Aided Design is based. He founded the ambitious Production Automation Project, that included Constructive Solid Geometry (CSG) as the basic 3D geometric representation. CSG trees were compact and robust, saving a memory space that was scarce in those times. But the main computational problem was Boundary Evaluation: the process of converting CSG trees to Boundary Representations (BReps) with explicit faces, edges and vertices for manufacturing and visualization purposes. This paper presents some glimpses of the history and evolution of some ideas that started with Herb Voelcker. We briefly describe the path from “localization and boundary evaluation” to “localization and printing”, with many intermediate steps driven by hardware, software and new mathematical tools: voxel and volume representations, triangle meshes, and many others, observing also that in some applications, voxel models no longer require Boundary Evaluation. In this last case, we consider the current research challenges and discuss several avenues for further research.Project TIN2017-88515-C2-1-R funded by MCIN/AEI/10.13039/501100011033/FEDER‘‘A way to make Europe’’Peer ReviewedPostprint (published version

Sweep encoding: Serializing space subdivision schemes for optimal slicing

Slicing a model (computing thin slices of a geometric or volumetric model with a sweeping plane) is necessary for several applications ranging from 3D printing to medical imaging. This paper introduces a technique designed to compute these slices efficiently, even for huge and complex models. We voxelize the volume of the model at a required resolution and show how to encode this voxelization in an out-of-core octree using a novel Sweep Encoding linearization. This approach allows for efficient slicing with bounded cost per slice. We discuss specific applications, including 3D printing, and compare these octrees’ performance against the standard representations in the literature.This work has been partially funded by the Spanish Ministry of Science and Innovation (MCIN / AEI / 10.13039/501100011033) and FEDER (‘‘A way to make Europe’’) under grant TIN2017- 88515-C2-1-R.Peer ReviewedPostprint (published version

Feasibility Study on Additive Manufacturing of Dielectrics in Antenna Structures

The advancements in additive manufacturing in the past decade has not gone unnoticed in the field of wireless communication. Using 3D printing, it is possible to manufacture complex shapes that cannot be achieved through conventional means. Furthermore, antennas commonly make use of different dielectrics, which can be 3D printed. In this thesis, three essential techniques for 3D printing a variable-permittivity antenna are analyzed. First, the theory behind material mixing is studied, to be able to control the permittivity of a dielectric material. Second, the necessity to be able to perform measurements of dielectric materials, is addressed. Finally, the usefulness of a variable-permittivity in an antenna structure is demonstrated. To manufacture a 3D printed variable-permittivity material, the basic theory behind permittivity mixing is reviewed, and a model based on spherical inclusions is designed. To prove the viability of the material, samples are manufactured and measured. It was found that the inclusion radius of the variable material is limited by the accuracy of the 3D printer, and larger inclusions provide more reliable results. To verify that the variable-permittivity material works as intended, a measurement kit for dielectric measurements is designed based on the transmission/reflection line measurement method. The measurement kit consists of a 3D printed and metalized waveguide section. The associated TRL-calibration and the parameter extraction algorithms are also reviewed. The measurement process and data processing algorithms are verified both in simulations and in practice. To demonstrate the benefits of a variable-permittivity dielectric in an antenna system, a simulated case study was conducted. In the case study, the performance of a variable-permittivity antenna array is compared to two reference antennas: a free space reference antenna, and a reference antenna with a homogeneous dielectric loading. The variable dielectric antennas showed to provide several advantages over the reference models, such as reduced element height, and wider bandwidths, and higher polarization purity.Framstegen inom friformsframställning har under det senaste decenniet inte gått obemärkt inom trådlös kommunikation. 3D-printning möjliggör tillverkningen av komplexa former som inte går att producera på konventionella sätt. Dielektriska material för bruk i antenner kan även produceras med hjälp av 3D-printning. I denna avhandling analyseras tre väsentliga tekniker som behövs för att utarbeta en antenn med variabel permittivitet genom att utnyttja 3D-printning. Först studeras teorin bakom materialblandning för att kunna kontrollera permittiviteten hos ett dielektriskt material, och sedan framställs en mätsats i syftet att kunna utföra mätningar av dielektriska material. Slutligen kommer ändamålsenligheten av en antennstruktur med variabel permittivitet att motiveras. För att kunna tillverka ett 3D-printat material med variabel permittivitet granskas den grundläggande teorin bakom materialblandning, och en modell baserad på sfäriska ihåligheter utformas. För att bevisa att materialet fungerar som avsett tillverkas det prover vilka mäts. Det visar sig att ihåligheternas radie i det variabla materialet begränsas av 3D-skrivarens noggrannhet, och att större ihåligheter åstadkommer mer tillförlitliga resultat. En mätsats framställs i syftet att mäta permittiviteten på de dielektriska proven, vilket är grundläggande för att kunna verifiera att materialen fungerar som avett. Mätningsmetoden baserar sig på transmission och reflektion av radiovågor i en 3D-printad vågledarsektion, som framställs genom att insidan metalliseras. Den tillhörande TRL-kalibreringen, samt och algoritmen för framställningen av permittiviteten uppvisas även också. Mätprocessen verifierades både genom simuleringar och tillämpades praktisk. Fördelarna med ett dielektriskt material med variabel permittivitet i ett antennsystem undersöktes i formen av en simulerad fallstudie. I studien jämförs prestandan hos en antennuppsättning med variabel permittivitet med två referensantenner: en referensantenn för fritt utrymme och en referensantenn med en homogen dielektrisk belastning. De variabla dielektriska antennerna uppvisade förbättrad prestanda jämfört med referensmodellerna, bland annat genom bredare bandbredder, högre polarisationsrenhet, och reducerad elementhöjd

Suspension Near-Field Electrospinning: a Nanofabrication Method of Polymer Nanoarray Architectures for Tissue Engineering

Chapter 1. This chapter is divided into six sections. The first will discuss the issue of nerve tissue loss, and the strategies of therapy (1.1). The second describes the role of nanofabrication in tissue engineering (1.2). The third section details the theoretical background of electrospinning in terms of solution and process parameters (1.3). The fourth section introduces near-field electrospinning (NFES), recent advances in this field and the principles of NFES techniques (1.4). The fifth section details objectives for a tissue engineered construct for neural cell therapy, and presents possible viable solutions (1.5). The sixth summarizes the aims and structure of this thesis (1.6)..

Dynamic Optical Networks for Data Centres and Media Production

This thesis explores all-optical networks for data centres, with a particular focus on network designs for live media production. A design for an all-optical data centre network is presented, with experimental verification of the feasibility of the network data plane. The design uses fast tunable (< 200 ns) lasers and coherent receivers across a passive optical star coupler core, forming a network capable of reaching over 1000 nodes. Experimental transmission of 25 Gb/s data across the network core, with combined wavelength switching and time division multiplexing (WS-TDM), is demonstrated. Enhancements to laser tuning time via current pre-emphasis are discussed, including experimental demonstration of fast wavelength switching (< 35 ns) of a single laser between all combinations of 96 wavelengths spaced at 50 GHz over a range wider than the optical C-band. Methods of increasing the overall network throughput by using a higher complexity modulation format are also described, along with designs for line codes to enable pulse amplitude modulation across the WS-TDM network core. The construction of an optical star coupler network core is investigated, by evaluating methods of constructing large star couplers from smaller optical coupler components. By using optical circuit switches to rearrange star coupler connectivity, the network can be partitioned, creating independent reserves of bandwidth and resulting in increased overall network throughput. Several topologies for constructing a star from optical couplers are compared, and algorithms for optimum construction methods are presented. All of the designs target strict criteria for the flexible and dynamic creation of multicast groups, which will enable future live media production workflows in data centres. The data throughput performance of the network designs is simulated under synthetic and practical media production traffic scenarios, showing improved throughput when reconfigurable star couplers are used compared to a single large star. An energy consumption evaluation shows reduced network power consumption compared to incumbent and other proposed data centre network technologies

High Performance Optical Transmitter Ffr Next Generation Supercomputing and Data Communication

High speed optical interconnects consuming low power at affordable prices are always a major area of research focus. For the backbone network infrastructure, the need for more bandwidth driven by streaming video and other data intensive applications such as cloud computing has been steadily pushing the link speed to the 40Gb/s and 100Gb/s domain. However, high power consumption, low link density and high cost seriously prevent traditional optical transceiver from being the next generation of optical link technology. For short reach communications, such as interconnects in supercomputers, the issues related to the existing electrical links become a major bottleneck for the next generation of High Performance Computing (HPC). Both applications are seeking for an innovative solution of optical links to tackle those current issues. In order to target the next generation of supercomputers and data communication, we propose to develop a high performance optical transmitter by utilizing CISCO Systems®\u27s proprietary CMOS photonic technology. The research seeks to achieve the following outcomes: 1. Reduction of power consumption due to optical interconnects to less than 5pJ/bit without the need for Ring Resonators or DWDM and less than 300fJ/bit for short distance data bus applications. 2. Enable the increase in performance (computing speed) from Peta-Flop to Exa-Flops without the proportional increase in cost or power consumption that would be prohibitive to next generation system architectures by means of increasing the maximum data transmission rate over a single fiber. 3. Explore advanced modulation schemes such as PAM-16 (Pulse-Amplitude-Modulation with 16 levels) to increase the spectrum efficiency while keeping the same or less power figure. This research will focus on the improvement of both the electrical IC and optical IC for the optical transmitter. An accurate circuit model of the optical device is created to speed up the performance optimization and enable co-simulation of electrical driver. Circuit architectures are chosen to minimize the power consumption without sacrificing the speed and noise immunity. As a result, a silicon photonic based optical transmitter employing 1V supply, featuring 20Gb/s data rate is fabricated. The system consists of an electrical driver in 40nm CMOS and an optical MZI modulator with an RF length of less than 0.5mm in 0.13&mu m SOI CMOS. Two modulation schemes are successfully demonstrated: On-Off Keying (OOK) and Pulse-Amplitude-Modulation-N (PAM-N N=4, 16). Both versions demonstrate signal integrity, interface density, and scalability that fit into the next generation data communication and exa-scale computing. Modulation power at 20Gb/s data rate for OOK and PAM-16 of 4pJ/bit and 0.25pJ/bit are achieved for the first time of an MZI type optical modulator, respectively

Process–Structure–Properties in Polymer Additive Manufacturing

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