3D Printing: La polvere di ottone prende forma

RIASSUNTO: Il presente lavoro si colloca all’interno delle attività di studio del settore della prototipazione rapida (RP) e si prefigge lo scopo di realizzare semplici componenti metallici (in particolare in ottone), con la tecnica del three dimensional printing (3DP). Il lavoro si articola nelle seguenti parti principali: caratterizzazione dei materiali, polvere di ottone e liquido legante realizzazione di una postazione di lavoro e progettazione dell’interfaccia di controllo tuning dei parametri del processo di printing La prima parte ha per oggetto l’analisi della granulometria della polvere di ottone (per la prima volta impiegata in esperienze di 3DP), lo studio della bagnabilità con il liquido legante selezionato (silice colloidale in glicole etilenico) e la valutazione dell’interazione locale polvere-colla con esperienze preliminari alla stampa inkjet. Il secondo punto riguarda l’assemblaggio di una struttura con guide motorizzate per permettere la movimentazione della testina sul piano di lavoro, lo sviluppo di un circuito con microcontrollore per il pilotaggio (con onda quadra) dell’ugello selezionato, e di un programma che coordina gli spostamenti della testina con il controllo dell’accensione dell’ugello in modo da realizzare la geometria di ciascuna sezione del componente 3D. La parte finale coinvolge le numerose esperienze sperimentali sul perfezionamento del sistema e sull’ottimizzazione dei parametri in particolare prima con stampe con inchiostro su carta e metallo per studiare l’influenza del segnale elettrico sulle caratteristiche (forma, dimensioni, velocità) delle goccioline espulse dall’orifizio, successivamente con stampe con liquido legante sul letto di polvere in modo da caratterizzare la linea primitiva, la sezione, il modello 3D. SUMMARY: This work has been carried out within the framework of the rapid prototyping (RP) systems studies and has the aim to build simple metal components (particularly brass) with the technique of the three dimensional printing (3DP). The thesis is divided into the following main parts: characterization of the materials (brass powders and binder) realization of a workbench and developing of a control interface tuning of the printing parameters The first part is related to the particle-size analysis of brass powders (for the fist time employed in 3DP experiences), the study of the wet ability of the selected binder fluid (Colloidal silica in Ethylene glycol) and the evaluation of the interaction grain-binder with preliminary tests before printing with the inkjet-head. The second part regards the assembly of a structure with motorized guides in manner to consent the moving of the head on the workspace, the development of a circuit with microcontroller for the activation (with PWM signal) of the selected nozzle, and of the control program to coordinate the moving of the inkjet-head with the control of the firing of the nozzle in order to realize the desired geometry of each section of the 3D component. The final part deals with the several experimental experiences about the improvement of the system and the optimization of the parameters in particular before with ink printing on paper and metal to study the influence of the PWM signal on the characteristics (size, form, speed) of the droplets produced by the orifice, next with printing with binder on the powderbed in order to characterize the primitive line, the section, the 3D model

Compensatory Relationship Between Exonic Splicing Enhancer, Splice Site and Protein Function

The process of pre-mRNA splicing involves the removal of intronic sequences from the pre-mRNA and it is directed by intronic cis acting elements know as the 5’ and 3’ splice sites that mark the boundaries of the exons. Over the two decades, however, it has become clear that exons encode for auxiliary splicing signals that either enhance or perturb their inclusion in the final mRNA product. It is possible that the evolution of mRNA sequences could be conditioned by the presence of these exonic cis-acting splicing regulatory elements and not mainly by the selection of optimal protein function. To explore this hypothesis, I have investigated how the need for ESE influences the gene evolution of a paralogous gene family, specifically the human Alkaline Phosphatases (ALPs). In this work, I have identified in correspondence to a weak 3’splice site, two ESE sequences in the placental ALP exon 4, and demonstrate that the ESE are necessary for the exon inclusion in the mRNA due to the weak 3’splice sites. Furthermore, I show that they are absent in the corresponding exon of the non-tissue specific ALP transcript, specifically exon 5 that carries a strong 3’ splice site. Most importantly, the localization of the ESEs correspond to an area that in the paralogous non-tissue specific ALP gene differs in amino acid composition with respect, not only to the placental ALP where I mapped the ESEs but also to the other members of the family, where this area is well conserved. These amino acid changes may represent a possible evolutionary constraint on enzymatic activity, in keeping with this hypothesis, substituting the amino acids in the region of the ESE for those of the paralogous non-tissue specific ALP gene increases the enzymatic activity. Thus splicing-related constraints challenge the primacy of biochemical function in rates of protein evolution

Mustang Daily, September 29, 1999

Student newspaper of California Polytechnic State University, San Luis Obispo, CA.https://digitalcommons.calpoly.edu/studentnewspaper/6479/thumbnail.jp

Towards vocal-behaviour and vocal-health assessment using distributions of acoustic parameters

Voice disorders at different levels are affecting those professional categories that make use of voice in a sustained way and for prolonged periods of time, the so-called occupational voice users. In-field voice monitoring is needed to investigate voice behaviour and vocal health status during everyday activities and to highlight work-related risk factors. The overall aim of this thesis is to contribute to the identification of tools, procedures and requirements related to the voice acoustic analysis as objective measure to prevent voice disorders, but also to assess them and furnish proof of outcomes during voice therapy. The first part of this thesis includes studies on vocal-load related parameters. Experiments were performed both in-field and in laboratory. A one-school year longitudinal study of teachers’ voice use during working hours was performed in high school classrooms using a voice analyzer equipped with a contact sensor; further measurements took place in the semi-anechoic and reverberant rooms of the National Institute of Metrological Research (I.N.Ri.M.) in Torino (Italy) for investigating the effects of very low and excessive reverberation in speech intensity, using both microphones in air and contact sensors. Within this framework, the contributions of the sound pressure level (SPL) uncertainty estimation using different devices were also assessed with proper experiments. Teachers adjusted their voice significantly with noise and reverberation, both at the beginning and at the end of the school year. Moreover, teachers who worked in the worst acoustic conditions showed higher SPLs and a worse vocal health status at the end of the school year. The minimum value of speech SPL was found for teachers in classrooms with a reverberation time of about 0.8 s. Participants involved into the in-laboratory experiments significantly increased their speech intensity of about 2.0 dB in the semi-anechoic room compared with the reverberant room, when describing a map. Such results are related to the speech monitorings performed with the vocal analyzer, whose uncertainty estimation for SPL differences resulted of about 1 dB. The second part of this thesis was addressed to vocal health and voice quality assessment using different speech materials and devices. Experiments were performed in clinics, in collaboration with the Department of Surgical Sciences of Università di Torino (Italy) and the Department of Clinical Science, Intervention and Technology of Karolinska Institutet in Stockholm (Sweden). Individual distributions of Cepstral Peak Prominence Smoothed (CPPS) from voluntary patients and control subjects were investigated in sustained vowels, reading, free speech and excerpted vowels from continuous speech, which were acquired with microphones in air and contact sensors. The main influence quantities of the estimated cepstral parameters were also identified, which are the fundamental frequency of the vocalization and the broadband noise superimposed to the signal. In addition, the reliability of CPPS estimation with respect to the frequency content of the vocal spectrum was evaluated, which is mainly dependent on the bandwidth of the measuring chain used to acquire the vocal signal. Regarding the speech materials acquired with the microphone in air, the 5th percentile resulted the best statistic for CPPS distributions that can discriminate healthy and unhealthy voices in sustained vowels, while the 95th percentile was the best in both reading and free speech tasks. The discrimination thresholds were 15 dB (95\% Confidence Interval, CI, of 0.7 dB) and 18 dB (95\% CI of 0.6 dB), respectively, where lower values indicate a high probability to have unhealthy voice. Preliminary outcomes on excerpted vowels from continuous speech stated that a CPPS mean value lower than 14 dB designates pathological voices. CPPS distributions were also effective as proof of outcomes after interventions, e.g. voice therapy and phonosurgery. Concerning the speech materials acquired with the electret contact sensor, a reasonable discrimination power was only obtained in the case of sustained vowel, where the standard deviation of CPPS distribution higher than 1.1 dB (95\% CI of 0.2 dB) indicates a high probability to have unhealthy voice. Further results indicated that a reliable estimation of CPPS parameters is obtained provided that the frequency content of the spectrum is not lower than 5 kHz: such outcome provides a guideline on the bandwidth of the measuring chain used to acquire the vocal signal

Sistema multiagente para el análisis de interacciones entre usuarios en medios sociales

This project proposes a system for extraction and analysis of structural properties generated from user interactions on Twitter networks. The test will be conducted at two levels: social level (complete network) and individual (nodes). Its implementation will be carried out in a distributed manner using the technology of multi-agent systems, graph analysis measures and tools for managing large volumes of data.El presente proyecto propone un sistema para la extracción y el análisis de propiedades estructurales de redes generadas a partir de las interacciones de usuarios en Twitter. Al análisis se realizará a dos niveles: nivel social (red completa) e individual (nodos). Su implementación se llevará a cabo de manera distribuida utilizando la tecnología de los sistemas multiagente, medidas de análisis de grafos y herramientas para la gestión de grandes volúmenes de datos. El present projecte proposa un sistema per a l'extracció i l'anàlisi de propietats estructurals de xarxes generades a partir de les interaccions d'usuaris a Twitter. A l'anàlisi es realitzarà a dos nivells: nivell social (xarxa completa) i individual (nodes). La seva implementació es durà a terme de manera distribuïda utilitzant la tecnologia dels sistemes multiagent, mesures d'anàlisi de grafs i eines per a la gestió de grans volums de dades.Martínez Poveda, C. (2016). Sistema multiagente para el análisis de interacciones entre usuarios en medios sociales. http://hdl.handle.net/10251/76836TFG

Standard spacecraft procurement analysis: A case study in NASA-DoD coordination in space programs

The Space Test Program Standard Satellite (STPSS), a design proposed by the Air Force, and two NASA candidates, the Applications Explorer Mission spacecraft (AEM) and the Multimission Modular Spacecraft (MMS), were considered during the first phase. During the second phase, a fourth candidate was introduced, a larger, more capable AEM (L-AEM), configured by the Boeing Company under NASA sponsorship to meet the specifications jointly agreed upon by NASA and the Air Force. Total program costs for a variety of procurement options, each of which is capable of performing all of the Air Force Space Test Program missions during the 1980-1990 time period, were used as the principal measure for distinguishing among procurement options. Program cost does not provide a basis for choosing among the AEM, STPSS, and MMS spacecraft, given their present designs. The availability of the L-AEM spacecraft, or some very similar design, would provide a basis for minimizing the cost of the Air Force Space Test Program

Valutazione e controllo del danneggiamento per fatica nei ponti ferroviari in acciaio

La corretta pianificazione degli interventi di manutenzione delle infrastrutture di trasporto come i ponti ferroviari ha assunto nel corso degli anni un’importanza sempre maggiore a causa delle perdite economiche connesse all’interruzione del regolare servizio. Tale aspetto risulta inoltre amplificato dal fatto che sia i ponti già esistenti che quelli di nuova costruzione saranno inclusi nella nuova rete di trasporto Europea. In particolare la fatica risulta essere la causa di degrado più diffusa nei ponti in acciaio ed in soluzione composta acciaio – calcestruzzo, causando circa 80-90% dei danneggiamenti nei componenti metallici. I ponti ferroviari sopportano milioni di cicli di carico durante la vita di esercizio ed sono particolarmente soggetti a questo tipologia di danno. Molte ricerche sono state realizzate per la valutazione del comportamento a fatica dei ponti in acciaio e composti acciaio – calcestruzzo; tali studi hanno fornito la base per l’elaborazione delle attuali Normative di progettazione. Tuttavia la corretta stima dei fenomeni di fatica nelle nuove strutture ed in quelle esistenti rimane un problema particolarmente complesso, determinato da fattori di incerta valutazione come gli spettri di traffico realmente presenti sulle linee ferroviarie, il comportamento dinamico effettivo degli impalcati in acciaio ed in soluzione composta acciaio-calcestruzzo, l’influenza dei fenomeni di interazione dinamica treno-struttura sull’intensità e l’andamento delle tensioni interne, l’effettiva resistenza alla fatica di dettagli strutturali di incerta classificazione. La presente tesi illustra una metodologia innovativa per la valutazione globale del comportamento a fatica di ponti e viadotti ferroviari metallici. L’approccio si basa su un’opportuna interconnessione delle più moderne tecniche di analisi sperimentali e numeriche al fine di ottenere una valutazione realistica ed affidabile degli indici di danneggiamento per fatica dei componenti principali e dei dettagli critici. Tali tecniche di analisi riguardano i diversi aspetti che contribuiscono alla valutazione del comportamento in esercizio degli impalcati metallici ed in particolare riguardano: i) la modellazione meccanica delle strutture mediante modelli numerici; ii) l’identificazione dinamica globale e/o locale; iii) l’aggiornamento dei modelli numerici mediante algoritmi di ottimizzazione; iv) il monitoraggio strutturale e l’identificazione del traffico ferroviario; v) la caratterizzazione sperimentale del comportamento a fatica di dettagli critici. La metodologia proposta è stata calibrata su due casi studio fornendo indicazioni importanti circa l’effettivo comportamento in esercizio delle opere analizzate e, più in generale, dimostrando la propria validità nel valutare in modo realistico ed affidabile i principali parametri che contribuiscono a definire il comportamento a fatica degli impalcati metallici, confermandosi come strumento particolarmente utile e versatile per la stima dei fenomeni di fatica nelle strutture di nuova realizzazione ed in quelle già esistenti

Transferencia de calor y masa durante la formación de escarcha en superficies horizontales con flujo paralelo

La formación de escarcha es un fenómeno muy común que ocurre cuando se tiene una superficie a baja temperatura en un ambiente con aire húmedo. Este fenómeno ocurre debido a que el vapor de agua contenido en el aire cambia de fase, depositándose sobre la superficie fría. El estudio de este fenómeno es de gran importancia debido a que el espesor y las propiedades termof´ısicas (i.e. conductividad térmica y densidad) de la capa de escarcha afectan considerablemente a la transferencia de calor que ocurre entre el aire húmedo y la superficie fría. Debido a esto, en los ´últimos 20 años se han realizado diversos estudios numéricos y experimentales para poder conocer las condiciones bajo las cuales se favorece la formación de la escarcha, además de conocer la variación de sus propiedades y el efecto que tiene esta variación a la transferencia de calor. Para poder predecir el crecimiento de la capa de escarcha sobre superficies planas a bajas temperaturas en condiciones de convección forzada, en este trabajo de investigación se desarrolló un código numérico empleando el Método de los volúmenes finitos. Para lograr esto, fue necesario resolver las ecuaciones que gobiernan dicho fenómeno, es decir, las ecuaciones de conservación de masa, conservación de cantidad de movimiento, conservación de la energía y transporte de especies para todo el dominio, mismo que incluía la capa de escarcha y el aire húmedo. Para calcular la tasa de crecimiento se realizó un balance de masa en la interfaz escarcha-aire en donde se estimó la diferencia entre los flujos de masa que provenían del lado del aire y los flujos de masa que se difundían dentro de la capa de escarcha, y esta diferencia correspondía a la masa que contribuye al crecimiento de la escarcha. Además de esto, se calculó la variación de las propiedades termof´ısicas dentro de la capa de escarcha considerando que ´esta es un medio poroso. Para validar el código numérico, se realizó un estudio experimental en un calorímetro tipo túnel de viento en el que es posible tener controladas las variables involucradas en el fenómeno (i.e. temperatura, humedad relativa, velocidad del aire). El parámetro que se valido fue el espesor de la capa de escarcha. Se realizaron tres casos de estudio, con el fin de poder comparar los resultados numéricos a diferentes condiciones y se encontró una diferencia relativa menor del 10 % en la mayoría de los puntos en donde se midió el espesor, siendo que al final de la placa el error fue mayor, de entre 12 % y 22 %, presumiblemente por la transición al régimen turbulento

Estudio del efecto de las propiedades de mezclas ternarias de combustibles en el proceso de mezcla en un motor diésel

En este capítulo se presentan, en primer lugar, la motivación para la realización de este estudio. A continuación, se detallan los antecedentes del campo de conocimiento en que se enmarca la investigación. Por ´último, se expone la hipótesis junto con los objetivos, tanto de carácter general como específico, planteados para la realización de la investigación

Development of New Methodologies for Prediction of Performances of Asphalt Mixtures

This thesis proposes the use of new methodologies for prediction of performances of asphalt mixtures. Recent improvements in technology make it possible to adopt new methods of investigation with the dual objective of improving the performance in the survey of the parameters and investigate new properties so far not analyzed. In particular, the image analysis and the tyre/surface interaction belong to an innovative framework, which is next to flank, if not replace, the classic measurements so far employed. The thesis deals with the use of these technologies for the analysis of three rubberized stone mastic asphalts, which were laid on a stretch of road close to Bologna, Italy. Three different surveys were carried out on site during the first year of service. The surveys included the change in texture and skid resistance due to the traffic, along with the acoustic properties of the pavement. Local as well as dynamic continuous measurements were carried out, involving the use of a profilometer and a skiddometer. A second phase involved the prediction of the surface parameters with different stages of simulated trafficking on Road Test Machine. At each stage change in macrotexture, skid resistance, adhesion between bitumen and aggregates, contact pressures and areas were assessed. The image analysis is used for the assessment of the adhesion between the bitumen and the aggregate. The images are then processed in order to create 3D models of the asphalt specimens and investigate the surface and volume properties. The tyre/pavement interaction is another fundamental phenomena that received little considerations from the research, given its importance. A final discussion summarizes these investigations by separately review three different simulated periods, i.e. the early life, the in-service equilibrium and the end of life. In order to accelerate the distress, one slab was subjected to Immersion Wheel Track test