Terahertz NDE for Metallic Surface Roughness Evaluation

Metallic surface roughness in a nominally smooth surface is a potential indication of material degradation or damage. When the surface is coated or covered with an opaque dielectric material, such as paint or insulation, then inspecting for surface changes becomes almost impossible. Terahertz NDE is a method capable of penetrating the coating and inspecting the metallic surface. The terahertz frequency regime is between 100 GHz and 10 THz and has a free space wavelength of 300 micrometers at 1 THz. Pulsed terahertz radiation, can be generated and detected using optical excitation of biased semiconductors with femtosecond laser pulses. The resulting time domain signal is 320 picoseconds in duration. In this application, samples are inspected with a commercial terahertz NDE system that scans the sample and generates a set of time-domain signals that are a function of the backscatter from the metallic surface. Post processing is then performed in the time and frequency domains to generate C-scan type images that show scattering effects due to surface non-uniformity

Terahertz NDE for Under Paint Corrosion Detection and Evaluation

Corrosion under paint is not visible until it has caused paint to blister, crack, or chip. If corrosion is allowed to continue then structural problems may develop. Identifying corrosion before it becomes visible would minimize repairs and costs and potential structural problems. Terahertz NDE imaging under paint for corrosion is being examined as a method to inspect for corrosion by examining the terahertz response to paint thickness and to surface roughness

Evaluation of Feasibility and Impact of Attacks against the 6top Protocol in 6TiSCH Networks

The 6TiSCH architecture has been gaining attraction as a promising solution to ensure reliability and security for communication in applications for the Industrial Internet of Things (IIoT). While many different aspects of the architecture have been investigated in literature, an in-depth analysis of the security features included in its design is still missing. In this paper, we assess the security vulnerabilities of the 6top protocol, a core component of the 6TiSCH architecture for enabling network nodes to negotiate communication resources. Our analysis highlights two possible attacks against the 6top protocol that can impair network performance and reliability in a significant manner. To prove the feasibility of the attacks in practice, we implemented both of them on the Contiki-NG Operating System and tested their effectiveness on a simple deployment with three Zolertia RE-Mote sensor nodes. Also, we carried out a set of simulations using Cooja in order to assess their impact on larger networks. Our results show that both attacks reduce reliability in the overall network and increase energy consumption of the network nodes

Daylight-Transfer Systems: Physiological And Energetic Advantages

Daylight-transfer systems are devices designed to operate according to the law of reflection: they collect and transfer it to rooms lacking in light. On the whole, possible applications can deal with rooms which do not communicate directly with the outside. For instance, it can be the case of both basements and large-sized buildings like those devoted to the service industry. In recent years, the considerable attention devoted to sustainable development has prompted planners to reconsider the use of daylighting in architecture. Current research, partly examined in this article, aims at producing a range of systematised products and techniques according to some specific characteristics in order to highlight the advantages of these systems in terms of energy conservation as for essential artificial lighting and, consequently, to contribute towards decreasing the use of non-renewable sources of energy and related problems about sustainability

Enamel fluorosis in rat’s incisor: S.E.M. and T.E.M. investigation

Findings on the alterations taking place in the enamel have demonstrated that they are generally caused by a daily use of highly fluoritic drinking waters.According to that, the Authors have carried out an ultrastructural study on lower incisors of albino rats after administering for 60 days water with a fluorine concentration five times the normal one.The samples, studied under the S.E.M., showed a general slowing of both the deposition and the maturation phase as well as the presence of some hypomineralized areas even after eruption.All this suggested the possibility that the damages observed were not due to the direct effect of fluorine on the enamel, but to the interaction between fluorine and ameloblasts.The Authors have then carried out an ultrastructural study on the enamel organ using the S.E.M.The results showed the presence of a well-evident endoplasmic reticulum, the lack in dense granules during the secretion phase, the lack in ruffle ended webs during the modulation phase, and the mitochondrial damage in the ameloblast.All this could justify the slowing of the enamel mineralization caused by fluorine effect on the ameloblasts.Il a été démontré que des altérations de l’émail sont généralement dues à l’absorption quotidienne d’eaux de boissons riches en fluor.Les auteurs ont entrepris une étude ultrastructurale des incisives inférieures du rat ayant reçu pendant 60 jours de l’eau dont la concentration en fluor est 5 fois supérieure à la normale.Les échantillons étudiés en microscopie électronique à balayage ont montré un ralentissement global de la déposition et de la phase de maturation ainsi que la présence de territoires hypominéralisés même après l’éruption.Toutes ces constatations suggèrent la possibilité que les dommages observés ne sont pas dus à l’effet direct du fluor sur l’émail, mais aux interactions entre le fluor et les améloblastes.Les auteurs ont mené une étude ultrastructurale de l’émail en utilisant le microscope électronique à balayage.Les résultats ont montré la présence d’un réticulum endoplasmique bien apparent, l’absence de grains denses au cours de la phase secrétoire, l’absence d’extrémités membranaires rugueuses au cours de la phase de modulation, et des altérations des mitochondries dans les améloblastes.Toutes ces constatations pourraient expliquer le ralentissement de la minéralisation de l’émail causé par les effets du fluor sur les améloblastes

Processing and Probability Analysis of Pulsed Terahertz NDE of Corrosion under Shuttle Tile Data

This paper examines data processing and probability analysis of pulsed terahertz NDE scans of corrosion defects under a Shuttle tile. Pulsed terahertz data collected from an aluminum plate with fabricated corrosion defects and covered with a Shuttle tile is presented. The corrosion defects imaged were fabricated by electrochemically etching areas of various diameter and depth in the plate. In this work, the aluminum plate echo signal is located in the terahertz time-of-flight data and a threshold is applied to produce a binary image of sample features. Feature location and area are examined and identified as corrosion through comparison with the known defect layout. The results are tabulated with hit, miss, or false call information for a probability of detection analysis that is used to identify an optimal processing threshold

Microbiological quality of drinking water from dispensers in Italy

<p>Abstract</p> <p>Background</p> <p>Water coolers are popular in office buildings and commercial stores and the quality of this source of drinking water has the potential to cause waterborne outbreaks, especially in sensitive and immunocompromised subjects. The aim of this study was to determine the quality of water plumbed in coolers from commercial stores in comparison with tap water in Italy.</p> <p>Methods</p> <p>For each sample, microbial parameters and chemical indicators of contamination were evaluated and information about the date of installation, time since last ordinary and extraordinary maintenance of water coolers was collected.</p> <p>Results</p> <p>In all samples the chemical parameters (nitrite, ammonium, free active chlorine residual) did not exceed the reference values of the drinking water regulation; the pH value in 86.8% samples of the carbonated waters was lower than the reference limit. The microbiological results indicated that the bacteria count at 22°C and 37°C was higher than the required values in 71% and 81% for the non-carbonated water and in 86% and 88% for the carbonated one, respectively. <it>Enterococcus </it>spp. and <it>Escherichia coli </it>were not detected in any of the water samples. <it>Pseudomonas aeruginosa </it>was found in only one sample of the tap water and in 28.9% and 23.7% of the non-carbonated and carbonated water samples, respectively. No statistically significant differences in bacterial counts at 22°C and 37°C have been found between the non-carbonated and carbonated water from the sampled coolers in relation with the time since the last filter was substituted. The bacteriological quality of tap water was superior to that of non-carbonated and carbonated water from coolers.</p> <p>Conclusion</p> <p>The results emphasize the importance of adopting appropriate routinely monitoring system in order to prevent or to diminish the chances of contamination of this water source.</p