National Technical University of Athens

The study investigated the potential use of expanded perlite microspheres as fillers in ABS composite filaments for 3d printing application, with a focus on the effect of the filler size and density on the major properties of the filament and printed objects. A Vertical Electrical Furnace (VEF) prototype was employed for the preparation of filler grades of varying bulk densities (250, 375 and 500 kg/m³) and size distributions (D90 of 200 to 250 μm), which were used for the preparation of composite filaments, incorporating them in the ABS matrix under constant volume fraction of 20% using a screw extruder. The characterization campaigns focused on the physical and mechanical properties of the filaments, and on the microstructure, mechanical properties, rheology and printing quality of the printed objects. Results from the characterization campaigns revealed that the addition of microspheres’ filler improved shrinkage and warpage deformation of ABS polymer, with a parallel reduction of ductility and melt flow index. However, these changes, did not affect the melt extrusion process during printing. Particles survival rate increases by increasing the bulk density and decreasing size, with bulk density of 350 kg/m³ or higher being beneficial due to the higher strength. Overall, expanded perlite microspheres present adequate performance as a filler in ABS for 3D printing applications, provided the appropriate grade is used, while as inorganic, non-toxic and natural material can improve the environmental footprint of ABS and potentially of other conventional thermoplastics used for the filament preparation.

This study explores the Fourth International Congress of Modern Architecture (CIAM IV), focusing on Athens’ selection as the host city for the 1933 meeting. While recent research has uncovered complex frameworks and hidden narratives within CIAM’s inner circles, the reasons for holding the congress aboard a cruise ship traveling the Marseilles-Athens-Marseilles route remain enigmatic. Investigating the factors influencing CIAM IV’s planning and location choice, set against the backdrop of interwar modernity, reveals overlooked dynamics; Greece’s modernization efforts, which leveraged its diaspora to enhance cultural identity and tourism potential, played a crucial role in Athens’ selection — a perspective often neglected in post-CIAM IV narratives. An analysis of CIAM’s internal networks and power dynamics offers a reassessment of Greece’s position within the CIAM discourse, providing new insights into the decision-making processes of this influential architectural movement.

This is the third part of a short series of paper, revisiting some classical concepts of Linear Elastic Fracture Mechanics. Based on the solution for the single edge notched strip, discussed in Part-II, the present study deals with the stress field developed in a stretched finite strip, weakened by two symmetric edge notches. The notches are of parabolic shape, approximating the configuration of a rounded V-notch, varying from almost semicircular edge cavities to “mathematical” edge cracks of zero distance between their lips. The solution is obtained combining Muskhelishvili’s complex potentials technique with a procedure for “stress-neutralization” of specific areas of the loaded strip. To simplify the procedure, the notches are assumed to be “shallow” (short) so that they do not affect each other. Once the complex potentials are obtained, the stress field variations are plotted along strategic loci of the strip and along the periphery of the notches. Attention is paid to the stress field developed around the bases (tips or crowns) of the two notches, providing relatively simple formulae for the critical tensile stress. In addition, the respective stress concentration factor k is obtained for blunt notches, while in the case the edge discontinuities become “mathematical” cracks, a simple expression is given for the mode-I stress intensity factor KI at the tip of the crack. It is revealed that the assumption of “shallow” notches suffices a quite efficient solution for the overall stress field in finite strips.

In this study, silicon phthalocyanine dichloride (SiCl 2 Pc) was successfully encapsulated in β-cyclodextrin (β-CD) and hydroxy-propyl-β-cyclodextrin (HP-β-CD) using the kneading method. Dynamic Light Scattering (DLS) demonstrated complexes of various hydrodynamic diameters with moderate stability in aqueous solutions. Their structural characterization by Infrared Spectroscopy (FT- IR) indicated that a part of phthalocyanine is located inside the cyclodextrin cavity. Both photophysical and photochemical studies showed that phthalocyanine’s encapsulation in cyclodextrins increased its aqueous solubility. The photodynamic studies against A431 cancer cell line indicated that the complexes are more effective than pure SiCl 2 Pc. Pure SiCl 2 Pc’s photodynamic effect is characterized as dose-dependent, whereas both complexes presented a biphasic dose-response photodynamic effect. For the highest energy dose of 3.24 J/cm ² , pure SiCl 2 Pc induced mild cell toxicity. SiCl 2 Pc-β-CD complex was the most promising photosensitizer, exhibiting the highest photodynamic effect when irradiated at 2.16 J/cm ² .

Cultural heritage is expressed through monuments and temples that are sometimes isolated and constructed on steep rocky slopes, with limited access to visitors. Frequently, the adjacent environment suffers from geological changes and presents instability phenomena of the rocky slopes, mainly rockfalls or rockslides. It is well known that rockfalls are related to substantial incidents of fatalities, independently of their volume especially in areas characterized as “areas with highly touristic concentration”. In this study, a rockfall risk rating system for rock slopes which are adjacent to monuments is proposed, as part of rockfall risk management system, which is based on geological, geomorphological criteria and human behavior under dangerous situations (i.e., rockfalls). This rating system was applied to distinct sections along a pedestrian road at the base of a slope at Nisyros Island, Greece demonstrating the variability of rockfall risk for tourists and pedestrians. This study has considered, for the formulation of the rockfall risk management system more detailed governing parameters such as interference with vehicles, visibility of the entire slope, existence of forest, structural and discontinuities index, pedestrian or tourist concentration and behavior etc. Moreover, in quantitative point of view, the application of the aforementioned system indicates that the probability of injury to pedestrians in summertime is considerable, thus protection measures should be applied, in order to reduce the pedestrians’ risk. In addition, the velocity of the rocks when a rockfall occurs estimated to be in the order of magnitude of 0.6 ms−1, which is capable of causing serious injuries.

Realistic implementation of wave energy converters (WEC) must account for the effects of the surrounding bathymetry on the WEC performance. However, most modelling tools do not introduce this element into the design process. Thus, giving rise to unrealistic predictions of the overall WEC performance. This problem is quite relevant in WECs operating in intermediate water depths, where bathymetry effects affect the whole wave hydrodynamics. In this article, the performance of breakwater integrated U-oscillating water column wave energy systems is analysed. A Boundary Element Method (BEM) model, accounting for variable bathymetry effects, is developed and combined with a nonlinear U-OWC dynamic model for estimating the hydrodynamic quantities involved. The developed models are used for determining the impact of the water depth variability on both the U-OWC response and energy performance. As demonstrative examples, the case of a system operating in the Natural Ocean Engineering Laboratory of Mediterranea University of Reggio Calabria (NOEL) and the breakwater of the port of Salerno in Italy are examined. It is shown that bathymetry effects may play a constructive role in the U-OWC dynamics, as they may lead to higher converted energies. Furthermore, they may change the power output peak frequency.

Purpose Wounds from assault rifles and their commercial offspring have been encountered with increasing frequency in civilian practice. Our aim is to summarize wound ballistics related to the main injury patterns that can also affect management strategies. Methods An online search of the PubMed was conducted for research and review articles published after 2000 in English, using the MeSH terms “gunshot wounds”, “mass casualty incidents”, “war-related injuries”, “soft tissue injuries”, “vascular system injuries”, “colon injuries”, “wound infection”, “antibiotic prophylaxis”, “debridement”, “hemorrhage”, “penetrating head injuries”, “pneumothorax” and additional free-text terms. Other academic databases were also searched for relevant articles and book chapters. Results Consensus regarding recognition of high energy wounds from assault rifle projectiles is largely based on war experience. Studies of such wounds inflicted by expanding projectiles suggest that their wounding effects significantly increase tissue damage and adverse outcomes following injury, as a result of the temporary cavity and bullet fragmentation. The use of assault rifles in mass shootings has prompted utilization of tourniquet for control of life-threatening hemorrhage, also derived from military experience, while limited evidence indicates that tension pneumothorax rather than extremity wounds is the leading cause of potentially preventable death in these incidents. Conclusions Wound ballistics provides a system for evaluation of injuries from assault rifles and risk analysis of shooting incidents. Lessons learned from armed conflicts can improve the management of victims, with due consideration given to characteristics of civilian injuries. Further research is required to define the impact on survival by key life-saving procedures in the prehospital setting, in order to prioritize these interventions.

Utilizing existing telecommunication cables for Distributed Acoustic Sensing (DAS) experiments has eased the collection of seismological data in previously difficult‐to‐access areas such as the ocean bottom. To assess the potential of submarine DAS for monitoring seismic activity, we conducted an experiment from mid‐October to mid‐December 2021 using a 45 km long dark fiber extending from the Greek island of Santorini along the ocean bottom to the neighboring island of Ios. This region is of great geophysical and public interest because of its historical and recent seismic and volcanic activity, especially along the Kolumbo volcanic chain. Besides recording anthropogenic noise and around 1,000 seismic events, we observe the primary and secondary microseisms in the submarine section, the latter inducing Scholte waves in a sediment layer where the cable is well‐coupled. By using the spectral element wave propagation solver Salvus, we compute synthetic strains for earthquakes with varying degrees of model complexity. Despite including topography, a water layer, and a heterogeneous velocity model, we are unable to reproduce the lack of coherence in our observed earthquake waveforms. Backpropagation simulations for four observed earthquakes indicate that clear convergence of the wavefield, and thus the ability to constrain a source region, is only possible when all model complexities are considered. We conclude that, despite the promising emergence of DAS, monitoring capabilities are limited by often unfavorable cable geometries, cable coupling, and the complexity of the medium. Interrogating multiple cables simultaneously or jointly analyzing DAS and seismometer data could help improve future monitoring experiments.

We consider a nonlinear Dirichlet eigenvalue problem driven by a general nonhomogeneous differential operator and a reaction that exhibits the combined effects of a singular term and a convective perturbation. Using truncations and comparison techniques, and eventually the Leray–Schauder alternative principle (fixed point theory), we show that for all small values of the parameter $\lambda >0$, the problem has a positive smooth solution.

An important parameter of the Hoek-Brown failure criterion for intact rock materials is mi, a dimensionless material constant that depends on the frictional characteristics of the component minerals. In this study a laboratory testing program was carried out in order to experimentally study the correlations between mi and two frictional parameters: (a) the sliding friction angle which is determined from direct shear tests on pre-fractured rock specimens and (b) the Mohr-Coulomb internal friction angle which is determined from triaxial compression strength tests conducted at low confining stresses. We carried out direct shear tests on rough tension joints of ten fresh, low porosity (< 5%) natural rocks, including two igneous, three sedimentary and five metamorphic under normal stresses ranged from 0 to 2 MPa and determined the sliding friction angle φnd using peak shear stress and dilation measurements. An independent series of triaxial compression tests was conducted on intact cylindrical specimens of the same rocks at various confining pressures up to 70 MPa and the values of the internal friction angle φi0 at low confining stresses were determined as well as the values of mi, σci and the principal stresses at the brittle-ductile transition. Our experimental results show that, within the used range of values of the parameters mi, φnd and φi0, mi increases linearly with decreasing sliding friction angle and increasing internal friction angle. Both correlations were found to be statistically significant at a significance level of 0.001.

The need for large-scale production of highly accurate simulated event samples for the extensive physics programme of the ATLAS experiment at the Large Hadron Collider motivates the development of new simulation techniques. Building on the recent success of deep learning algorithms, variational autoencoders and generative adversarial networks are investigated for modelling the response of the central region of the ATLAS electromagnetic calorimeter to photons of various energies. The properties of synthesised showers are compared with showers from a full detector simulation using geant4. Both variational autoencoders and generative adversarial networks are capable of quickly simulating electromagnetic showers with correct total energies and stochasticity, though the modelling of some shower shape distributions requires more refinement. This feasibility study demonstrates the potential of using such algorithms for ATLAS fast calorimeter simulation in the future and shows a possible way to complement current simulation techniques.

Multi-walled carbon nanotubes co-doped with sulfur and nitrogen (S–N-MWCNTs) were produced onto silicon/silicon oxide by means of chemical vapor deposition (CVD) upon decomposition of dimethyl sulfoxide (DMSO) and acetonitrile (ACN) in the presence of ferrocene (FeCp2). The synthesized S–N-MWCNTs were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and electrochemical impedance spectroscopy (EIS). The electrochemical response of S–N-MWCNTs towards oxidation of ascorbic acid (AA), dopamine (DA), uric acid (UA), and glucose (GL) was investigated in phosphate buffer solution (PBS) (pH 7.4) by means of cyclic voltammetry (CV). Strong dependence of electrochemical quality of S–N-MWCNTs on the concentration of decomposed DMSO precursor was observed. Namely, upon increasing the percentage of decayed DMSO from 1.0 up to 2.0% wt., the electrocatalytic activity of S–N-MWCNTs tends to improve. The separations of oxidation waves between AA-DA, DA-UA, and AA-UA reached their maximum values on S–N-MWCNTs-3, fabricated upon decomposition of 2.0% wt. DMSO precursor, permitting their individual and simultaneous electrochemical determination. Strong interference of GL in the analysis of DA was observed, and consequently, simultaneous analysis of AA, DA, and UA can be only carried out in the absence of GL. A great influence of concentration of decomposed DMSO precursor on the sensitivity of S–N-MWCNTs was also observed. Specifically, upon increasing the percentage of decayed DMSO from 1.0 up to 2.0% wt., the sensitivity and detection capability of S–N-MWCNTs towards AA, DA, UA, and GL analytes tend to enhance.

In 2015, all United Nations Member States adopted 17 Sustainable Development Goals (SDGs) for the 2030 agenda. Addressing the issue of employing alternative data sources for exploring aspects of utilizing said goals, this paper explores the Circular Economy dimension within the SDG12 score, focusing on responsible production and consumption and the broader SDG index. Data from LinkedIn are collected, examining profiles, companies, job postings, and services using the keywords ‘Sustainable Development Goals’ and ‘Circular Economy’. Furthermore, the SDG index (including the SDG12 score) for the United States is integrated in the analysis; SDG is a published metric evaluating the progress of sustainable communities within each state. Finally, data on the past five US general elections are retrieved, in order to explore the relationship between SDGs, Circular Economy, and voting behavior. Regression analyses incorporating PCA components and state election data reveal that the LinkedIn-derived SDG and circular economy components exhibit positive impacts on the corresponding indices. Notably, a state’s political inclination toward the Republican or the Democratic parties highlights contrasting effects on the SDG and SDG12 indices, indicating divergent trends based on electoral choices. Overall, this study underscores LinkedIn’s potential as a valuable source for assessing SDG and Circular Economy position in the US, and highlights the interplay between political factors and sustainable communities at state level.

This article presents a Visual Servoing Nonlinear Model Predictive Control (NMPC) scheme for autonomously tracking a moving target using multirotor Unmanned Aerial Vehicles (UAVs). The scheme is developed for surveillance and tracking of contour-based areas with evolving features. NMPC is used to manage input and state constraints, while additional barrier functions are incorporated in order to ensure system safety and optimal performance. The proposed control scheme is designed based on the extraction and implementation of the full dynamic model of the features describing the target and the state variables. Real-time simulations and experiments using a quadrotor UAV equipped with a camera demonstrate the effectiveness of the proposed strategy.

Carbon nanomaterials exhibit unique morphological and physical properties. When used as fillers in various matrices such as polymers, they can provide enhanced electrical, thermal and mechanical characteristics. The emerging field of sensing technologies has witnessed remarkable advancements, resulting from the integration of carbon-based nanocomposites. This paper presents a comprehensive review of the latest a developments in key carbon-based nanocomposite sensors. First, the unique properties of carbon nanomaterials are reviewed covering the full dimensional spectrum, followed by main synthesis routes addressing critical aspects such as morphology, surface functionalization, and doping strategies. Later, the synergistic effects arising from the combination of carbon nanomaterials with other components, such as polymers, are explored in detail, emphasizing the role of percolation levels in the overall sensing performance. The different sensing applications presented in this review cover a broad range, including strain, temperature, gas and biosensing. The mechanisms and principles governing the sensing capabilities of carbon-based nanocomposites are provided, shedding light on the interactions between analytes and nanocomposite surfaces. A critical analysis of current challenges and prospects is also presented, outlining potential avenues for further research and innovation. Finally, this review aims to serve as a valuable resource for researchers interested in carbon-based nanocomposites and their evolving role in advancing sensing technologies.

SAF 2507, a superduplex stainless steel, combines mechanical strength with high corrosion resistance. As a powder, it can be used in conjunction with the laser cladding deposition process (LCD), restoring damaged components by erosion and improving their properties, regarding surface hardness and resistance to corrosive environments. In the current study, a SAF 2507 powder was employed to fabricate various multi-pass clads on an austenitic 316L substrate via laser cladding deposition (LCD). Specimens were later subjected to heat treatment procedures, in order to restore the phase balance ratio. The attained microstructures were observed through light optical and scanning electron microscopy (LOM and SEM), coupled with energy-dispersive spectroscopy (EDS) analysis. Vickers hardness tests were also conducted in order to evaluate the hardness of every clad layer. Finally, X-Ray Diffraction (XRD) was employed in order to ascertain the experimental results, as well as investigate the existence of undesirable phases. While a mostly ferritic microstructure was anticipated after the LCD process, the resulting clads were characterized by a relatively balanced phase ratio, with austenite being the dominant phase instead. After heat-treating, further austenite growth occurred, leading to an overall decrease in hardness, although nitrides that had precipitated during the deposition were no were no longer present.

Nowadays social cohesion and humanity prosperity are the issues directly linked to the evolution of traditional humanitarian ethics and the rethinking of indigenous cultural morals. In this context, the investigation of the entities of Society 5.0 and Industry 5.0 can be reviewed in terms of improving humanitarian values and ensuring sustainable development at an Industry 4.0 meta-epoch. Subsequently, humans and machines symbiosis is actually considered as a debate of Industry 5.0 vs. (evolving from) Industry 4.0, or (shifting) Industry 4.0 vs. (towards) Society 5.0. In this review study, a critique has raised of how digital transformation could actually identify and characterize an unstable era of threatening social cohesion, being considered as a global human-centricity issue by adopting production planning and suitable control systems towards Industry 5.0. Additionally, in the study an integrated approach of Industry 4.0 and Society 5.0 was structured and valued in alignment with sustainable development goals’ (SDGs)-authorized/-driven sustainable societies. Conclusively, the main constraints, the prevalent challenges and the future research considerations of such a humanitarian (r)evolution towards a future well-being have been demonstrated.

In the city centre of Trikala, Greece, a real-life logistics service was operated with a fleet of 5 droids on a public route in the urban pedestrian area in the context of the SHOW project (GA No 875530). It took place from December 2022 to the end of February 2023. The droids are small automated vehicles missioned to carry out indoor and outdoor logistic services in pedestrian-centric environments. The logistics service that operated in Trikala was of two types: (a) a multi-stop parcel delivery service from the depot to the shops and (b) a parcel collection service from the shops to the depot. The current manuscript describes the solutions implemented and the challenges faced by the droids while performing last-mile deliveries. The manuscript concludes with suggestions from experience for new implementations of logistics services operated by automated vehicles. These include the advice to not underestimate the difficulty of integrating radically new vehicles into existing logistics services; the importance of having the trust and support of the population and the need for data network stability.

Within the SHOW project (GA No 875530), real-life urban demonstrations across 22 cities were conducted, exploring and validating the integration of Cooperative Connected and Automated Mobility (CCAM) in various public transport schemes. The project employs extensive traffic simulations using different tools and approaches. This chapter outlines the development of an integrated simulation suite that combines elements from the diverse simulations. The simulation suite is a web-based open access tool and offers guidelines, steps, and mathematical definitions for simulating CCAM. Designed for researchers, practitioners and even non-experts, while providing insights and results valuable to city planners. By emphasizing key findings from simulations, the application of the suite and its support for decision-making become more tangible.