Studio di fattibilità di braccio robotico R-P

Con questo elaborato si è eseguito lo studio di fattibilità di un banco didattico per il Corso di Laurea magistrale in Ingegneria meccanica - indirizzo Meccanica per l’automazione. Le specifiche per la progettazione del banco sono state dettate dall’esigenza di realizzare un meccanismo a più gradi di libertà controllato tramite opportuna scheda elettronica con l’obiettivo di avere un modello sperimentale sul quale approfondire alcuni aspetti di modellazione cinematica e dinamica, nonchè testare differenti strategie di controllo. Si è quindi pensato ad un braccio robotico a due gradi di libertà mobile in un piano verticale, controllato attraverso l’attuazione di una coppia rotoidale e di una prismatica, per la manipolazione di oggetti afferrati per mezzo di una ventosa ad attuazione pneumatica. Definita in prima istanza l’architettura di massima del sistema, grazie a opportuni calcoli di dimensionamento sono stati effettuati la scelta dei componenti commerciali ed il progetto delle parti da costruire. Si è quindi proposto un modello CAD in ambiente SolidWorks che ha permesso, fra l’altro, di definire le proprietà inerziali dei membri mobili. Queste ultime sono state sfruttate per eseguire simulazioni cinetostatiche con il software multibody Adams. Grazie ai risultati così ottenuti, è stato possibile eseguire il dimensionamento degli attuatori (motori brushless e relative trasmissioni) e la conseguente scelta a catalogo. Una volta selezionati gli azionamenti e gli altri componenti commerciali, si sono definiti i disegni costruttivi dei componenti da realizzare ad hoc ed è stata avviata la fase di approvvigionamento del materiale. Un possibile sviluppo del banco prova prevede l’introduzione di un’ulteriore coppia rotoidale attuata (da interporre con asse verticale fra il telaio e l’attuale primo membro), per ottenere un manipolatore dotato di moto spaziale

Mismatch distributions of D-loop haplotypes found in Germany.

<p>Expected distributions were modeled for stable populations and populations undergoing demographic expansion by using the parameters τ = 0.5, θ₀ = 0 and θ₁ = 99999.</p

Depiction of forward simulation models and key parameters considered.

<p>We model D-loop haplotype frequencies by random genetic drift in a neutrally evolving population with an effective population size (N_e0) of 10,000 for 250 years, assuming that the Norway rat colonized Europe at t₀∼1750 A.D. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone.0088425-Long1" target="_blank">[16]</a> and assuming 2 generations per year <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone.0088425-Geraldes1" target="_blank">[54]</a> (left). At t₁∼1950, or 400 generations later, we model the introduction of warfarin in form of a genetic bottleneck because initially rodent control induced high rates of mortality <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone.0088425-Greaves1" target="_blank">[55]</a> (middle and right). For the reduction to N_ei we introduced 4 levels of N_ei after rodent control (100, 500, 3,000, 7,000) to reflect the effectiveness of warfarin in controlling rats when warfarin was introduced in the 1950s, and we assumed that rodent control remained effective by keeping N_e reduced (middle). Finally, we evaluate a model that assumes that resistance has evolved within 10 years (t₁∼t₂) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone.0088425-Boyle1" target="_blank">[20]</a> and constant population size growth recovers to N_e0 (right); the evolution of resistance was modeled on one autosomal locus (representing Y139C), which freely recombines with mtDNA and is under balancing selection with coefficient of 0.3 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone.0088425-Greaves1" target="_blank">[55]</a>. Simulations were run for 1,000 replicates using a series of initial haplotype frequencies (<i>i</i>) for one most common haplotype (<i>i</i> = 0.04, 0.2, 0.4, 0.6 and 0.8) at the time rats settled in Germany, with the remaining haplotype frequencies equally shared by all the other haplotypes (here: 24). We assumed that a population colonized Europe that carried all 25 D-loop haplotypes detected in this study. Finally, we calculated the probability that the expected frequencies of all the 25 haplotypes are equal or greater than the observed frequency, which refers to the haplotype frequency of 0.72 for the most common haplotype (D1; see main text) in Germany.</p

The syntheses, crystal structures, and characterizations of two Mn^II/III-sandwiching polyoxometalate complexes based on [<i>α</i>-SeW₉O₃₃]⁸⁻ units

<div><p>Two sandwich-type polyoxometalates (POM) based on [<i>α</i>-SeW₉O₃₃]⁸⁻ building blocks, K₈[{Mn^II(H₂O)}₂(WO)(SeW₉O₃₃)₂]·12H₂O (<b>1</b>) and K₆[{Mn^III(H₂O)}₂(WO)(SeW₉O₃₃)₂]·18H₂O (<b>2</b>), have been synthesized and characterized by elemental analyses, IR, diffuse reflectance UV–vis-NIR spectra, TG, X-ray photoelectron spectroscopy, and single-crystal X-ray diffraction. Electrochemical properties and photocatalytic activities have also been investigated. Single-crystal X-ray diffraction analysis shows that the polyoxoanions of <b>1</b> and <b>2</b> have similar sandwich structures composed of [<i>α</i>-SeW₉O₃₃]⁸⁻ units except for different oxidation states of Mn centers (II for <b>1</b>, III for <b>2</b>). Compound <b>2</b> is the first high-valent trinuclear-manganese (III)-substituted [<i>α</i>-SeW₉O₃₃]⁸⁻-based POM. Cyclic voltammograms of <b>1</b> and <b>2</b> show irreversible redox processes for Mn²⁺ and Mn³⁺, respectively. Compound <b>2</b> has better photocatalytic properties with photocatalytic degradation of Rhodamine-B (RhB) compared to <b>1</b>.</p></div

Analysis of <i>cyt-b</i> (first number) and D-loop (second number) genetic diversity measures.

<p>Number of different haplotypes (h) and private haplotypes (P-h), haplotype diversity (h.d.), nucleotide diversity (π) x10^-3, - not applicable (n.a.), not determined (n.d.)</p

Continents and countries (shaded in grey) sampled for wild Norway rats (circle size reflects sample size <i>N</i>; c.f.Tables 1 & 2) and observed frequencies of <i>cyt-b</i> haplotype groups (clades CI-CVI).

<p>The red star indicates the location where the earliest Norway rat fossils were found ∼1.2–1.6 Mya <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone.0088425-Jin1" target="_blank">[13]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone.0088425-Wu1" target="_blank">[14]</a>. The sampling sites (provinces) in China from north to south are Heilongjiang, Jilin, Liaoning, Inner Mongolian, Hebei, Shandong, Henan, Jiangsu, Hubei, Hunan, Fujian, Guangdong, Yunnan and Hainan. The figure was drawn using ArcMap using ArcGIS 10.1 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone.0088425-ESRI1" target="_blank">[53]</a></p

Ancestral area reconstruction based on <i>cyt-b</i> haplotypes.

<p>Pie charts on each node show the probability of each ancestral haplotype to have occurred at an inferred ancestral geographic location using the RASP method. Locations are shown in different colors and denoted with alphabetic letters A-H. Probabilities <5% were lumped together as “*”. Node numbers are shown along branches (red), indicating differences between methods (c.f. methods and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone.0088425.s002" target="_blank">Table S2</a>). Green arrows indicate possible dispersal events. Black thick branches indicate posterior possibilities ≥0.69. Red symbols mark haplotypes found in animals carrying Y139C, Y139F, and S56P mutations in <i>Vkorc1</i>. Estimated mean divergence times and 95% highest posterior densities (in parentheses) are shown next to each of clades CI-CVI and the node supporting monophyly of the Norway rat.</p

Results of neutrality tests and goodness-of-fit tests of demographic expansion for rats in selected continents based upon <i>cyt-b</i> sequences.

<p>D - Tajima's D.</p><p>Fs - Fu's Fs.</p><p>R2 - Ramos-Onsins & Rozas's R2.</p><p>SSD - the sum of squared deviations.</p><p>RI - Harpending's raggedness index.</p><p>Estimated demographic parameters τ, θ₀ and θ₁ shown as x10⁻³.</p><p>* (P<0.05) and ** (P<0.01).</p

The probability that the expected haplotype frequency for the most common haplotype is equal to or greater than the observed frequency of 0.72.

<p>Shown are the models described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone-0088425-g002" target="_blank">Fig. 2</a> left (L), middle (M) and right (R) considering various levels of population size reductions to N_ei = 100, 500, 3,000 and 7,000. The grey dashed line indicates the probability of 5% of the most common haplotype to reach a frequency ∼0.72 or higher.</p

Median-Joining (MJ) mtDNA <i>cyt-b</i> (A) and D-loop (B) haplotype networks and warfarin resistance.

<p>Figure details as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088425#pone-0088425-g004" target="_blank">Fig. 4</a>, except that here the relative frequency of resistant and susceptible rats is shown. Only animals for which resistance status is known from experimental evidence are included here.</p