In Situ Samplings and Remote Sensing Measurements to Characterize Aerosol Properties over Southeast Italy

Abstract Ground-based particulate matter (PM) samplers, an XeF Raman lidar operating in the framework of the European Aerosol Research Lidar Network (EARLINET), and a sun/sky radiometer operating in the framework of the Aerosol Robotic Network (AERONET) have been used to characterize vertical profiles, optical and microphysical properties, and chemical composition of aerosols during the 29 June–1 July 2005 dust outbreak that occurred over the central-eastern Mediterranean. Aerosol backscatter coefficient, total depolarization, and lidar ratio vertical profiles revealed that a well-mixed dust layer extending from ∼0.5 to 6 km was present over southeastern Italy on 30 June. Sun/sky radiometer measurements revealed a bimodal lognormal size distribution during all measurement days. The particle volume distribution was found to be well correlated either to the PM mass distribution measured at ground by a seven-stage cascade impactor and to the fine to total suspended PM mass ratio measured by ground-based PM samplers. Scanning electron microscopy and ion chromatography analyses on PM samples revealed that coarse-mode aerosols were mainly made of carbonate, aluminum-silicate, and sea salt particles. Carbon, sulfate, and nitrate particles were the main components of fine-mode aerosols representing more than 50% of the total aerosol load; the significant role of fine-mode anthropogenic particles during a dust event is highlighted. Finally, the potential capabilities of complementary measurements by passive and active remote sensing techniques and in situ observations to retrieve the vertical distribution of the particle number and mass concentration are analyzed and discussed

Predictivity of clinical, laboratory and imaging findings in diagnostic definition of palpable thyroid nodules. A multicenter prospective study

Abstract PURPOSE: To assess the role of clinical, biochemical, and morphological parameters, as added to cytology, for improving pre-surgical diagnosis of palpable thyroid nodules. METHODS: Patients with a palpable thyroid nodule were eligible if surgical intervention was indicated after a positive or suspicious for malignancy FNAC (TIR 4-5 according to the 2007 Italian SIAPEC-IAP classification), or two inconclusive FNAC at a 653 months interval, or a negative FNAC associated with one or more risk factor. Reference standard was histological malignancy diagnosis. Likelihood ratios of malignancy, sensitivity, specificity, negative (NPV), and positive predictive value (PPV) were described. Multiple correspondence analysis (MCA) and logistic regression were applied. RESULTS: Cancer was found in 433/902 (48%) patients. Considering TIR4-5 only as positive cytology, specificity, and PPV were high (94 and 91%) but sensitivity and NPV were low (61 and 72%); conversely, including TIR3 among positive, sensitivity and NPV were higher (88 and 82%) while specificity and PPV decreased (52 and 63%). Ultrasonographic size 653\u2009cm was independently associated with benignity among TIR2 cases (OR of malignancy 0.37, 95% CI 0.18-0.78). In TIR3 cases the hard consistency of small nodules was associated with malignity (OR: 3.51, 95% CI 1.84-6.70, p\u2009<\u20090.001), while size alone, irrespective of consistency, was not diagnostically informative. No other significant association was found in TIR2 and TIR3. CONCLUSIONS: The combination of cytology with clinical and ultrasonographic parameters may improve diagnostic definition of palpable thyroid nodules. However, the need for innovative diagnostic tools is still high

Experimental Uncertainty Evaluation in Optical Measurements of Micro-Injection Molded Products

Optical measurements are increasingly widely used as preferential techniques to evaluate dimensional and surface quantities in micro-products. However, uncertainty estimation is more critical on micro-products than macro, and it needs careful attention for evaluating the obtained quality, the requested tolerance, and the correct setting of experimental process settings. In this study, optical measurements characterized micro-injected products by linear and surface acquisition and considered all the sources contributing to uncertainties. The results show that the measure uncertainty could be underestimated if only the standard deviation on simple measurements is considered; this could cause a significant restriction of the estimated range covering the measured values. Furthermore, the findings confirm that the correct evaluation of the potential uncertainties contributes to accurately assessing the process behavior and improving product quality

Quality Definition in Micro Injection Molding Process by Means of Surface Characterization Parameters

Quality evaluation of micro injection molded products is a complex task, in particular when instruments basing on contact methods are used and issues in measurements could arise due to the contact tool dimension not fitting well with extremely narrow features. Therefore, in these cases, optical methods may be preferred for the evaluation of molded products&rsquo; dimensions and surface quality, especially for parts devoted to applications requiring functional purposes. In this context, the present paper proposes the use of surface parameters as a quality index for the evaluation of both the micro injection molding process and the resulting products. To this aim, two experimental procedures were implemented to allow for: (i) the evaluation of the most suitable surface parameters identified in relation to the process parameters; (ii) comparisons of the surface parameters findings with those obtained by classic dimensional quantity via a designed experimental plan (DoE). The results show that the surface parameters, evaluated in critical areas of the components, can ensure reliable estimates for the surface quality of the molded parts and can be preferred in comparison to linear measurements

Replicating capability investigation of micro features in injection moulding process

Abstract Achieving high quality parts is a crucial task for the micro injection moulding process due to the sensitive nature of applications as medical and aerospace. In this work, simulation and an experimental study are performed to analyse the effect of four main parameters (injection speed, melt and mould temperature, and holding pressure) on replicating capability of a micro feature by injection moulding process that is the main focus of the present paper. This work also assesses the performance of a screwless-two plungers micro moulding machine in processing polyoximethilene (POM) and liquid crystal polymers (LCP). Results show that mould temperature and injection speed are the most effective parameters on replicating capability respectively for \POM\ and \LCP\ and high parameters setting improved the dimensions of the feature and thus the quality. For LCP, achieving process reproducibility is more difficult than for \POM\ even if the obtained replication fidelity is considerably higher

Replication capability of micro injection moulding process for polymeric parts manufacturing

Micro injection moulding process represents a key technology for realizing micro components and micro devices used in several fields: IT components, biomedical and medical products, automotive industry, telecommunication area and aerospace. The development of new micro parts is highly dependent on manufacturing systems that can reliably and economically produce micro components in large quantities. In this work, the authors investigate the process parameters on the overall quality of a miniaturised dog-bone-shaped specimen in order to determine the process constraints. The factors affecting parts aspects and mass are studied by experimentation designed using DoE methodology and then discussed. Two polymer materials (polyoxymethylene and liquid crystal polymer), particularly suitable for injection moulding applications due to their flowability and stability, are tested and evaluated in relation to the process replication capability. It has been found that the holding pressure and holding time for POM and holding pressure and injection velocity for LCP have the highest influence on achieving high part mass. Differently, melt temperature has the highest influence on minimising the process variability for both tested polymers. A further investigation has been carried out on the relationship between the holding pressure and the part mass and dimensions demonstrating the existence of a linear correlation between specimens mass and dimensions

Pulse-Type Influence on the Micro-EDM Milling Machinability of Si3N4–TiN Workpieces

In this paper, the effect of the micro-electro discharge machining (EDM) milling machinability of Si3N4&ndash;TiN workpieces was investigated. The material removal rate (MRR) and tool wear rate (TWR) were analyzed in relation to discharge pulse types in order to evaluate how the different pulse shapes impact on such micro-EDM performance indicators. Voltage and current pulse waveforms were acquired during micro-EDM trials, scheduled according to a Design of Experiment (DOE); then, a pulse discrimination algorithm was used to post-process the data off-line and discriminate the pulse types as short, arc, delayed, or normal. The analysis showed that, for the considered process parameter combinations, MRR was sensitive only to normal pulses, while the other pulse types had no remarkable effect on it. On the contrary, TWR was affected by normal pulses, but the occurrence of arcs and delayed pulses induced unexpected improvements in tool wear. Those results suggest that micro-EDM manufacturing of Si3N4&ndash;TiN workpiece is relevantly different from the micro-EDM process performed on metal workpieces such as steel. Additionally, the inspection of the Si3N4&ndash;TiN micro-EDM surface, performed by SEM and EDS analyses, showed the presence of re-solidified droplets and micro-cracks, which modified the chemical composition and the consequent surface quality of the machined micro-features

Mechanical characterisation and replication quality analysis of micro-injected parts made of carbon nanotube/polyoxymethylene nanocomposites

The increasing demand for small and cheap parts is boosting the development of reliable micro-system technologies. Fabrication process capabilities should expand to encompass a wider range of materials and geometric forms, which can satisfy the specific requirements of new emerging micro-products, and ensure the compatibility of new materials and processing technologies. Polymeric composites are very promising materials, since they offer new combinations of properties not available in traditional homogeneous materials. Because of their advantageous light weight, high strength, fatigue life, and corrosion resistance, they are forecast to replace conventional materials in several applications. Among the plastic process technologies, injection moulding is one of the key technologies for manufacturing miniaturised components due to its mass production capability and relatively low production cost. Micro-injection moulding allows to transfer micron and even submicron precision features to small products. Since final product properties strongly depend on materials and production processes and parameters, the process conditions of compounding as well as of product manufacturing have to be carefully studied and controlled. This is particularly important for the manufacturing of micro-products, since, at the micro-scale, some phenomena negligible at the macro-scale (as hesitation effect or capillarity forces for examples) can become important. However, only few studies concern the micro-injection of nanocomposites. Therefore, in this paper the micro-injection of two composites made of polyoxymethylene and carbon nanotubes has been studied. First, the electrical properties of the compounds have been measured; the fillers are dispersed in the matrix and form a network that dramatically increases the conductivity of the composites in comparison with the pristine resin. Then the compounds have been injected using a micro-injection machine and the components have been analysed. The mechanical analysis, based on tensile tests and dynamic-mechanical experiments on miniaturised dog-bone specimens, shows a slight reinforcing effect of the filler; however, the ductility is considerably reduced. This is likely due to a scarce adhesion of the carbon nanotubes and the polymer and the presence of some agglomerates. Moreover, as expected, the mould temperature affects the mechanical properties of the specimens, probably due to its effect on the internal structure of the solidified materials. The dimensional analyses carried out on micro-rib specimens show that replication capability is increased by the presence of the filler and using high values of the process parameters. Finally, microscopic analyses have been done in order to verify the dispersion and orientation of the fillers in the compounds. These effects have been observed only when high shear rates are involved

Micro Injection Molding of Thin Cavities Using Stereolithography for Mold Fabrication

At the present time, there is a growing interest in additive manufacturing (AM) technologies and their integration into current process chains. In particular, the implementation of AM for tool production in micro injection molding (µ-IM), a well-established process, could introduce many advantages. First of all, AM could avoid the need for the time-consuming and expensive fabrication of molds for small series of customized products. In this work, the feasibility, quality, and reliability of an AM/µ-IM process chain were evaluated by designing and fabricating mold inserts for µ-IM by stereolithography (SLA) technology; the mold inserts were characterized and tested experimentally. The selected geometry is composed of four thin cavities: This particular feature represents an actual challenge for both the SLA and µ-IM perspective due to the large surface-to-volume ratio of the cavity. Two different materials were used for the mold fabrication, showing sharply different performance in terms of endurance limit and cavity degradation. The obtained results confirm that the µ-IM process, exploiting an SLA fabricated mold insert, is feasible but requires great accuracy in material choice, mold design, fabrication, and assembly

How the Electrical Conductivity of Water Fluids Affects Micro-EDM in the Short-Pulse Regime

This work investigates micro-electro discharge machining (EDM) performance involving deionized and tap water. The chosen machining regime was semi-finishing, where open voltage (from 100 to 130 V) and current values (5–10 A) were applied using a 0.5 µs pulse-on time and a frequency of 150 kHz, i.e., a duty cycle of 25%. First, numerical analyses were performed via COMSOL Multiphysics and used to estimate the plasma channel distribution and melted material, varying the current, sparking gap, electrical conductivity, and permittivity of the two fluids. Then, experimentally, the micro-EDM of holes and channels in hardened thin steel plates were replicated three times for each considered fluid. The material removal rate (MRR), tool wear ratio (TWR), radius overcut, and surface roughness were plotted as a function of open voltage and electrical conductivity. The study proves that as voltage and current increase, the MRR and TWR decrease with electrical conductivity. Nonetheless, for higher electrical conductivity (tap water), the process did not proceed for lower open voltages and currents, and the radius overcut was reduced, contrary to what is commonly acknowledged. Finally, the crater morphology and size were evaluated using a confocal microscope and compared to simulated outcomes