COMBINING METHODOLOGICAL TOOLS FOR THE OPTIMUM 3D MODELLING OF NTUA CAMPUS

Rapid urbanisation relates to increased space requirements above and below ground and the development of complex structures. This profound need attracted increasing interest for the collection, modelling, management, visualisation and dissemination of 3D objects through various application fields, such as: 3D Cadastre, 3D City Modelling and Building Information Modelling. Contemporary advances in GIS technology, Geo-Web services and computer graphics facilitate the development of such models accompanied by semantic, geometrical and topological information, while the use of international standards enables the communication and interoperability between the systems. The aim of this paper is to combine state-of-the art methodologies and technologies for the development of semantically enriched 3D models for the Campus of the National Technical University of Athens in Greece. The result is a web-based 3D Campus map that integrates these models as Web Services, providing access to management and navigation for the campus area and can also be used for maintenance purposes from the various NTUA Departments. To this end, the database schema has been designed compatible with CityGML, while attention was given to interoperability issues that arise from differently derived 3D models which had to be stored and visualised while retaining their characteristics

An internal combustion engine visualization physical prototype applying digital manufacturing

Nowadays computers have invaded all levels of production, thus improving the quality and quantity of products. Digital manufacturing involves all tools for design, simulate, and programming machine tools in order to manufacture prototypes or tools for production use. This project is a case study of digital manufacturing for prototyping of an internal combustion engine visualization model. Solidworks is used for 3D modeling of all parts of the engine. Fused filament fabrication (FFF) is used for physical modeling of the engine parts. Pros and cons of the manufacturing process are discussed. It is concluded that parameter optimization is needed in order to improve quality indicators of the 3D printed engine parts. © Published under licence by IOP Publishing Ltd

An experimental investigation of surface roughness in 3D-printed PLA items using design of experiments

This work investigates the effect of 3D-printing parameters on surface roughness in polylactic acid printed material by adopting Taguchi's design of experiments approach. The control parameters under study were: number of shells, printing temperature, infill rate, and printing pattern. As the response, mean surface roughness (Ra) was selected. The control parameters were assigned to an L9 orthogonal array to organize the experiments and obtain the mean surface roughness results. It is concluded that printing temperature is the dominant parameter that affects surface roughness when it comes to 3D printing of polylactic acid material followed by printing pattern, infill rate, and the number of shells. © IMechE 2021

Parallel Memory Accessing for FFT Architectures

The current paper introduces an efficient technique for parallel data addressing in FFT architectures performing in-place computations. The novel addressing organization provides parallel load and store of the data involved in radix-r butterfly computations and leads to an efficient architecture when r is a power of 2. The addressing scheme is based on a permutation of the FFT data, which leads to the improvement of the address generating circuit and the butterfly processor control. Moreover, the proposed technique is suitable for mixed radix applications, especially for radixes that are powers of 2 and straightforward continuous flow implementation. The paper presents the technique and the resulting FFT architecture and shows the advantages of the architecture compared to hitherto published results. The implementations on a Xilinx FPGA Virtex-7 VC707 of the in-place radix-8 FFT architectures with input sizes 64 and 512 complex points validate the results. © 2018, Springer Science+Business Media, LLC, part of Springer Nature

On the application of grey Taguchi method for benchmarking the dimensional accuracy of the PLA fused filament fabrication process

The dimensional accuracy of a simple benchmark specimen fabricated with fused filament fabrication (FFF) route is discussed in the present study. FFF is a low-cost 3D-printing process that builds complicated parts by extruding molten plastic. Experimental method was designed according to Taguchi robust design based on an orthogonal array with nine experiments (L9 orthogonal array). The printing material was the polylactic acid (PLA). First, Grey–Taguchi method was used for the identification of the optimal printing parameter levels which result in the best dimensional accuracy for the PLA FFF parts. The printing parameters selected included number of shells, printing temperature, infill rate and printing pattern; they were selected in accordance with relevant studies already published. Then, in the second phase, nine specimens were fabricated using the same optimal printing parameter values determined in the first phase. The tolerance of these specimens was characterized according to international tolerance grades (IT grades). Data analysis showed that nozzle temperature is the dominant parameter. Additionally, the parts printed using the optimized process parameter levels possess good dimensional accuracy, which is compatible with the IT grades specification. © 2020, Springer Nature Switzerland AG

Direct 3D Printing of a hand splint using Reverse Engineering

The present work is focused on the direct manufacturing of a hand splint using free-open access software and a low-cost three-dimensional printer (3DP). The hand digital model was created using panoramic photos by a common mobile phone camera. The photos were used as input to the "3DF-Zephyr"free software for creating the hand surface model. Then, the hand surface model was transferred into the "Autodesk fusion 360"free software and the surface model of the hand splint was generated and modified according to the design requirements. Sequentially, both hand and hand splint were translated to Stereolithography (STL) files and transferred to open access "MakerBot"3D printing software in order to prepare the G-codes for 3D printing. A low cost 3D printer was used for building the models while Polylactic acid (PLA) was the material of the customized 3D physical models. © Published under licence by IOP Publishing Ltd

Design of a Real-Time DSP Engine on RF-SoC FPGA for 5G Networks

5G advances the wireless communications by providing a significant improvement to the data rate, capability of connected devices and data volumes compared to the previous generations. While these advantages combine along with a wider range of applications to merit the end-user, the technologies to be used are not specified. Considering this problem and in order to efficiently support the 5G deployment researchers and engineers turned their attention on FPGA base band architectures that keep the implementation cost relatively low and at the same time they are reprogramable to provide solutions to the emerging requirements and their consequent modifications. Aiming at the contribution to the 5G technologies the current paper introduces the design of a base band DSP architecture that targets the required real time performance. Moreover, the proposed architecture is scalable by efficiently parallelizing and/or pipelining the corresponding data paths. The paper presents the pilot FPGA designs of the IFFT/FFT and Sampling Frequency Offset (SFO) functions that achieve a 500 Msps performance on a RF-SoC Xilinx ZCU111 board. © 2020, IFIP International Federation for Information Processing