Feature fusion for facial landmark detection: A feature descriptors combination approach

Facial landmark detection is a crucial first step in facial analysis for biometrics and numerous other applications. However, it has proved to be a very challenging task due to the numerous sources of variation in 2D and 3D facial data. Although landmark detection based on descriptors of the 2D and 3D appearance of the face has been extensively studied, the fusion of such feature descriptors is a relatively under-studied issue. In this report, a novel generalized framework for combining facial feature descriptors is presented, and several feature fusion schemes are proposed and evaluated. The proposed framework maps each feature into a similarity score, combines the individual similarity scores into a resultant score, used to select the optimal solution for a queried landmark. The evaluation of the proposed fusion schemes for facial landmark detection clearly indicates that a quadratic distance to similarity mapping in conjunction with a root mean square rule for similarity fusion achieves the best performance in accuracy, efficiency, robustness and monotonicity

Advanced Antenna System for 5G enabled CubeSats

Satellite mega constellations in Low Earth Orbit are becoming increasingly popular. Starlink (by Space X) and OneWeb are two but recent examples of the ongoing race to provide seamless global connectivity. Having thousands or and potentially tens of thousands of small satellites orbiting the Earth could enable the migration of terrestrial communication and internet-based services to outer space. One of these communication services is the fifth generation (5G) communication technology. The appearance of 5G in the terrestrial infrastructure happened in 2019 but there is an increasing trend to consider how 5G can be enabled from space. This trend is supported by the recent initiatives of 3GPP and the European Space Agency on Non-Terrestrial Networks (NTN) for 5G Systems and Satellites for 5G (S45G) respectively. As a matter of fact, the progress of Low Earth Orbit (LEO) mega constellations and 5G technologies is simultaneous and will be interleaved under the new Satellite-Terrestrial (S-T) hybrid paradigm. 5G enabled LEO constellations will complement the existing terrestrial cellular infrastructure as they offer many benefits. For example, coverage of remote areas, adaptability to diverse traffic, seamless handovers, global coverage and line of sight communication links which are crucial in the mm-Wave 5G frequencies. A promising platform that could accommodate such a system is a class of nanosatellites called CubeSats. CubeSats are another emerging technology and are known for their small size, low cost, ease of deployment and their suitability for mega constellations in LEO. One of the main challenges of CubeSats with 5G capabilities will be faced during the design and integration of a suitable antenna system to achieve high data rate downlink communications. In particular, a hybrid antenna system must be devised that provides high gain, increased throughput, must work in mm-Wave bands and can adapt to the high traffic demands of 5G. In this thesis, we propose a Reflectarray antenna system to meet the aforementioned needs. Reflectarrays are a hybrid of reflector and phased array antennas. Reflectarrays have an abundant of potentials such as high gain, beam shaping, beam scanning, reconfigurability and multi-beam characteristics. On the other hand, reflectarrays present certain limitations regarding their bandwidth, polarization diversity and cost. Moreover, the technology of reconfigurable reflectarrays at mmWave started in 2012, hence limited knowledge and implementations are available. Reflectarrays have been proposed for a variety of satellite applications mainly based on Geostationary Orbit while limited work exists on designs of CubeSats equipped with this type of antenna. Due to the aforementioned research gaps, this work studies reflectarrays as candidates for future 5G enabled CubeSat constellations with a focus on architectures that can achieve high gain that can be maintained over a wide frequency band. To that end, in this thesis, CubeSat missions are first surveyed from an antenna perspective in order to understand the requirements that each mission type poses to the antenna system of CubeSats. Based on this survey, an antenna selection guide is designed, which is used to select a suitable antenna type for 5G enabled CubeSats. It was found that for CubeSat missions, such as 5G from Space, where high data rates are important, reflectarrays that operate in X and Ka-bands are a suitable antenna solution. On the other hand, a limiting performance metric of relfectarrays is their gain-bandwidth which indicates the frequency range that a reflectarray can maintain a stable and high gain. Hence, in this thesis, wideband reflectarrays are studied and categorized according to four wideband phase tuning mechanisms, namely, multi resonance, angular rotation, true time or phase delay lines and subwavelength periodicity approach. The bandwidth is studied both from a unit cell and reflectarray system perspective with emphasis on the gain-bandwidth performance. From this study, several design guidelines are formed that can be followed to design low profile and low cost reflectarrays suitable for 5G enabled CubeSats. Based on these guidelines four wideband reflectarray unit cells operating in X and Ka-band frequencies are designed and optimized. The unit cells utilize the multi-resonance and subwavelength periodicity strategies. From these unit cells, the two with the best bandwidth performance are selected and are used to design and optimize a high-gain X-band reflectarray and a high-gain Ka-band reflectarray, surpassing the performance of existing state-of-the-art wideband reflectarrays in terms of the 1-dB gain bandwidth. Moreover, considering the real estate limitations of CubeSats and small satellite platforms, these two aforementioned reflectarrays are integrated into a single aperture. Consequently, a dual-band reflectarray, achieving a wide 1-dB gain bandwidth at both X and Ka-bands, is designed. Notably, the presented reflectarray is the first dual-band wideband reflectarray proposed for CubeSat applications in the current literature

3D Facial landmark detection under large yaw and expression variations

A 3D landmark detection method for 3D facial scans is presented and thoroughly evaluated. The main contribution of the presented method is the automatic and pose-invariant detection of landmarks on 3D facial scans under large yaw variations (that often result in missing facial data), and its robustness against large facial expressions. Three-dimensional information is exploited by using 3D local shape descriptors to extract candidate landmark points. The shape descriptors include the shape index, a continuous map of principal curvature values of a 3D object’s surface, and spin images, local descriptors of the object’s 3D point distribution. The candidate landmarks are identified and labeled by matching them with a Facial Landmark Model (FLM) of facial anatomical landmarks. The presented method is extensively evaluated against a variety of 3D facial databases and achieves state-of-the-art accuracy (4.5-6.3 mm mean landmark localization error), considerably outperforming previous methods, even when tested with the most challenging data

Achaiki Iatriki : official publication of the medical society of western Greece and Peloponnesus

In the current issue, the editorial by Cauchi et al. argues for eco-friendly measures in endoscopy and emphasies the role of healthcare providers in reducing waste. The editorial adeptly employs the three Rs (Reduce, Reuse, Recycle) framework to tackle waste management, offering practical solutions. The editorial by Milionis et al. focuses on the reverse cascade screening for paediatric familial hypercholesterolaemia (FH), which is an upcoming tool for public health. Advantages, practices, and challenges regarding FH are thoroughly discussed. Lastly, the editorial by Fousekis et al. presents the main aspects of a chronic immune-mediated cutaneous disease, dermatitis herpetiformis (DH), which constitutes an extraintestinal manifestation of celiac disease, including its diagnosis, pathogenesis, and management. Moreover, this issue includes three review articles. The review article by Krontira et al. discusses the evolving data on the epidemiology, diagnostic approach and appropriate management of foreign body and caustic substance ingestion, based on updated guidelines published by gastroenterological and endoscopic societies. The review by Halliasos et al. provides data on the clinical presentation, diagnosis, and management of metastatic acute spinal cord compression, focusing on the importance of a multidisciplinary team approach, including spine surgeons, radiation oncologists, medical oncologists, palliative care clinicians, physiotherapists, and psychologists. Lastly, the review by Schinas et al. outlines the potential of immune modulation in the treatment of infections and the need for individualised approaches in the modern world of personalised medicine by examining some of the key strategies and immune-based therapies being developed to combat infectious diseases.peer-reviewe

A Printed Yagi Antenna for CubeSat with Multi-Frequency Tilt Operation

In this paper, a printed Yagi antenna with an integrated balun is proposed for CubeSat communications. The printed antenna is mechanically adjustable to realize three functional states at different operating frequencies in the L‐band and S‐band respectively. Three different angle deployments are proposed at 10°, 50° and 90°, so that the antenna operates at three different operating frequencies, namely 1.3 GHz (L‐band), 2.4 GHz (S‐band) and 3 GHz (S‐band). The measured results of the fabricated antenna are well matched with the simulation, having frequencies of 2.82–3.07 GHz, 1.3–1.4 GHz and 2.38–2.57 GHz, with similar radiation patterns. The measured gain of the antenna is 8.167 dBi at 2.4 GHz, 5.278 dBi at 1.3 GHz and 6.120 dBi at 3 GHz. Keeping within the general theme of cheap off the shelf components for CubeSats, this antenna design allows the CubeSat designers to choose from three popular frequencies, through a simple angle configuration. The main contribution of this work lies with the reconfigurable frequency, relatively high gain and simplicity of design