Deposition of thick and thin nanocrystalline diamond films by microwave plasma enhanced chemical vapor deposition

Thick (around 3 μm) and thin (48-310 nm) nanocrystalline diamond (NCD) films have been produced from Ar-rich CH4/Ar/H2 (1/89/10 %) and H2-rich CH4/H2 (1/99 %) microwave plasmas, respectively. The thick NCD films were obtained with and without an initial buffer layer (BL). The BL is easily obtained under typical microcrystalline diamond growth conditions (CH4/H2 mixtures). The effect of the deposition temperature (TD, 630-900°C) was investigated on the morphology, the surface roughness and the bonding characteristics of the films grown with and without BL. The thin NCD films were grown on Si substrates treated by two different methods, i.e. ultrasonic agitation in a suspension of diamond powders of 40-60 μm or combinatorial approach in a suspension of mixed diamond powders of 250 nm and 40-60 μm. The present experimental results show that the buffer layer procedure allows a good preservation of the surface of treated Si substrate and the combinatorial approach promotes effectively the seeding of the Si surface

Photoemission tuning of nanodiamond particles treated in variable percentages of H2H_2-N2N_2 plasmas

This work deals with photochatodes (PCs) based on as-received and treated nanodiamond (ND) particles, 250 nm in size. The aim of this study is the hydro-, hydro-/nitro- and nitro-genation of NDs performed in microwave plasmas adding different $N_2$ percentages (0, 50 and 100 %) to pure $H_2$ gas. Untreated and treated NDs are dispersed in solvents such as 1,2-dichloroethane and deionized water, and then deposited, as continuous layers, on p-Si and kapton substrates by the pulsed spray technique. The produced layers are characterized by Raman, photoluminescence spectroscopies and photoemission measurements. The quantum efficiency (QE), a merit figure for photocathodes, is assessed in the UV spectral range from 146 to 210 nm. The results show an enhancement of the photoemission for PCs based on hydro-, hydro-/nitro- and nitro-genated NDs that exhibit at 146 nm QE values of about 23, 21 and 13 %, respectively. The advantage of nitrogenated PCs is the good stability to air exposure against their lowest QE values

Telling faults from cyber-attacks in a multi-modal logistic system with complex network analysis

We investigate the properties of systems of systems in a cybersecurity context by using complex network methodologies. We are interested in resilience and attribution. The first relates to the system's behavior in case of faults/attacks, namely to its capacity to recover full or partial functionality after a fault/attack. The second corresponds to the capability to tell faults from attacks, namely to trace the cause of an observed malfunction back to its originating cause(s). We present experiments to witness the effectiveness of our methodology considering a discrete event simulation of a multimodal logistic network featuring 40 nodes distributed across Italy and daily traffic roughly corresponding to the number of containers shipped through in Italian ports yearly averaged daily

Hybrid metal/polymer filaments for fused filament fabrication (FFF) to print metal parts

The exploitation of mechanical properties and customization possibilities of 3D printed metal parts usually come at the cost of complex and expensive equipment. To address this issue, hybrid metal/polymer composite filaments have been studied allowing the printing of metal parts by using the standard Fused Filament Fabrication (FFF) approach. The resulting hybrid metal/polymer part, the so called “green”, can then be transformed into a dense metal part using debinding and sintering cycles. In this work, we investigated the manufacturing and characterization of green and sintered parts obtained by FFF of two commercial hybrid metal/polymer filaments, i.e., the Ultrafuse 316L by BASF and the 17-4 PH by Markforged. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS) analyses of the mesostructure highlighted incomplete raster bonding and voids like those observed in conventional FFF-printed polymeric structures despite the sintering cycle. A significant role in the tensile properties was played by the building orientation, with samples printed flatwise featuring the highest mechanical properties, though lower than those achievable with standard metal additive manufacturing techniques

Biomedical prostheses coated by tailored MWPECVD nanocrystalline diamond films

Different aspects concerning the use of nanocrystalline diamond (NCD) film, as coating for biomedical prostheses, is discussed. An overview is done on diamond implementation in prostheses, on the NCD mechanical properties and on the technological aspects concerning the NCD growth process i.e. Microwave Plasma Enhanced Chemical Vapor deposition. Then, the attention is focused on a possible improvement of NCD growth on titanium (Ti) substrate. Further, a theoretical study by finite element method is discussed in order to model the adhesion properties of a NCD layer on Ti and Ti/Titanium Carbide (TiC) substrates. The goal of the proposed work is to provide a study about the use of thin NCD coating on Ti based prostheses. The function of the NCD coating on Ti material is to improve the implanted prosthesis with a long duration time, thus decreasing the total costs and the invasive surgery treatments

A Roy Model of Social Interactions

We develop a Roy model of social interactions in which individuals sort into peer groups based on comparative advantage. Two key results emerge: First, when comparative advantage is the guiding principle of peer group organization, the effect of moving a student into an environment with higher-achieving peers depends on where in the ability distribution she falls and the effective wages that clear the social market. In this sense our model may rationalize the widely varying estimates of peer effects found in the literature without casting group behavior as an externality in agents’ objective functions. Second, since a student’s comparative advantage is typically unobserved, the theory implies that important determinants of individual choice operate through the error term and may, even under random assignment, be correlated with the regressor of interest. As a result, linear in means estimates of peer effects are not identified. We show that the model’s testable prediction in the presence of this confounding issue–an individual’s ordinal rank predicts her behavior, ceteris paribus–is borne out in two data setssocial interactions; peer effects; roy model; idenitification

Kinetic Study of the Thermal Dehydration of SiO2 and SiO2-ZrO2 composites prepared by Sol-Gel route

Abstract. SiO2, ZrO2 and SiO2-ZrO2 composites at different percentage of zirconia were synthesized by the solgel method and spectroscopically characterized by Fourier Transformed Infrared (FTIR) spectroscopy. Different series of composites were prepared and analysed, as it is and with a postpreparation conditioning at 600 and 1000°C respectively. The calcination were carried out to verify the changing in composite structure and if these treatments will affect the subsequently analyses. The synthesized samples were subjected to the thermogravimetric analysis (TGA) to investigate the kinetics of dehydration process. To this purpose, TGA data were treated by the Kissinger method to calculate the apparent activation energy (Ea) of dehydration. The obtained kinetics parameters are discussed and compared with each other and with those obtained for the control material

Kinetic Study of the Thermal Dehydration of Fly Ash Filled Geopolymers

Metakaolin-based geopolymers at different percentage of fly ash (namely 25, 50, and 70% wt) are prepared by using recycled fly ash, aiming at reducing the amount of waste to be treated or disposed in landfills. The synthesized samples are subjected to the thermogravimetric analysis (TGA) to investigate the kinetics of dehydration process. To this purpose, TGA data are treated by the Kissinger method to calculate the apparent activation energy (Ea) of dehydration. The obtained kinetics parameters are discussed and compared with each other and with those obtained for the control geopolymer. A decrease in Ea values of the filled geopolymers is found, showing the effect of the fly ash in reducing the dehydration rate. A classification among the samples at different percentage of fly ash is also drawn up, showing the reaching of a plateau at percentage above the 50 wt%

Formalizing the Execution Context of Behavior Trees for Runtime Verification of Deliberative Policies

In this paper, we enable automated property verification of deliberative components in robot control architectures. We focus on formalizing the execution context of Behavior Trees (BTs) to provide a scalable, yet formally grounded, methodology to enable runtime verification and prevent unexpected robot behaviors. To this end, we consider a message-passing model that accommodates both synchronous and asynchronous composition of parallel components, in which BTs and other components execute and interact according to the communication patterns commonly adopted in robotic software architectures. We introduce a formal property specification language to encode requirements and build runtime monitors. We performed a set of experiments, both on simulations and on the real robot, demonstrating the feasibility of our approach in a realistic application and its integration in a typical robot software architecture. We also provide an OS-level virtualization environment to reproduce the experiments in the simulated scenario

A Roy Model of Social Interactions

We develop a Roy model of social interactions in which individuals sort into peer groups based on comparative advantage. Two key results emerge: First, when comparative advantage is the guiding principle of peer group organization, the effect of moving a student into an environment with higher-achieving peers depends on where in the ability distribution she falls and the effective wages that clear the social market. In this sense our model may rationalize the widely varying estimates of peer effects found in the literature without casting group behavior as an externality in agents' objective functions. Second, since a student's comparative advantage is typically unobserved, the theory implies that important determinants of individual choice operate through the error term and may, even under random assignment, be correlated with the regressor of interest. As a result, linear in means estimates of peer effects are not identified. We show that the model's testable prediction in the presence of this confounding issue–an individual's ordinal rank predicts her behavior, ceteris paribus–is borne out in two data sets.