3,753 research outputs found
Secondary yaw control to improve curving vs. stability trade-off for a railway vehicle
No full textActive primary / secondary suspensions have been proposed to solve the trade-off between curving and stability in railway vehicles. One concept is known as Secondary Yaw Con-trol (SYC), which consists of applying a controllable yaw torque between the carbody and the two bogies. This has been studied in the past mainly to enhance the vehicle’s curving ability, but this paper extends the idea by examining the implications of designing a bogie with soft yaw stiffness between the bogie frame and the wheelsets and using SYC to provide active stabilisation. To this aim, a state feedback control law is designed according to the LQR technique. The paper presents the general concept of the active suspension control to be investigated and the specific control strategies applied. Then the effectiveness of the proposed actuation concept is investigated by means of numerical simulations performed on mathematical models of the passive and actively controlled vehicles implemented in a fully nonlinear multi-body simulator.</p
The 2D/3D dynamics of wall-bounded low-Rm magnetohydrodynamic (MHD) turbulence
No full textWith this experimental study, we give evidence that the dynamics of low-Rm MHD turbulence depends on the diffusion length l_z, which corresponds to the distance over which the Lorentz force is able to diffuse momentum before it is balanced by inertia
Triangular Constellations in Flows
No full textParticles advected on the surface of a fluid can exhibit fractal clustering. The local structure of a fractal set is described by its dimension , which is the exponent of a power-law relating the mass in a ball to its radius : . It is desirable to characterise the {\em shapes} of constellations of points sampling a fractal measure, as well as their masses. The simplest example is the distribution of shapes of triangles formed by triplets of points, which we investigate for fractals generated by chaotic dynamical systems. The most significant parameter describing the triangle shape is the ratio of its area to the radius of gyration squared. We show that the probability density of has a phase transition: is independent of and approximately uniform below a critical flow compressibility , which we estimate. For the distribution appears to be described by two power laws: when , and when
Exact two-dimensionalization of low-magnetic-Reynolds-number flows subject to a strong magnetic field
No full textWe investigate the behavior of flows, including turbulent flows, driven by a horizontal body-force and subject to a vertical magnetic field, with the following question in mind: for very strong applied magnetic field, is the flow mostly two-dimensional, with remaining weak three-dimensional fluctuations, or does it become exactly 2D, with no dependence along the vertical? We restrict attention to low-magnetic-Reynolds number (Rm) flow. Because liquid metals have low magnetic Prandtl number, such low- flows can have a kinetic Reynolds number as large as one million and therefore be strongly turbulent. We first focus on the quasi-static approximation, i.e. the asymptotic limit of vanishing magnetic Reynolds number Rm << 1: we prove that the flow becomes exactly 2D asymptotically in time, regardless of the initial condition and provided the interaction parameter N is larger than a threshold value. We call this property absolute two-dimensionalization: the attractor of the system is necessarily a (possibly turbulent) 2D flow. We then consider the full-magnetohydrodynamic equations and we prove that, for low enough Rm and large enough N, the flow becomes exactly two-dimensional in the long-time limit provided the initial vertically-dependent perturbations are infinitesimal. We call this phenomenon linear two-dimensionalization: the (possibly turbulent) 2D flow is an attractor of the dynamics, but it is not necessarily the only attractor of the system. Some 3D attractors may also exist and be attained for strong enough initial 3D perturbations. These results shed some light on the existence of a dissipative anomaly for magnetohydrodynamic flows subject to a strong external magnetic field
The Decay of Wall Bounded MHD Turbulence at Low RM
No full textWe have developed a new spectral method to simulate flows with very fine boundary layers present. We apply it to calculate the evolution of freely decaying MHD turbulence between isolating walls. By comparison them with results obtained in fully periodic domain we quantify the influence of the channel walls on the character of freely decaying MHD turbulence
MiRNA-205 modulates cellular invasion and migration via regulating zinc finger E-box binding homeobox 2 expression in esophageal squamous cell carcinoma cells
No full textBackground: Esophageal squamous cell carcinoma (ESCC) is often diagnosed at later stages until they are incurable. MicroRNA (miR) is a small, non-coding RNA that negatively regulates gene expression mainly via translational repression. Accumulating evidence indicates that deregulation of miR is associated with human malignancies including ESCC. The aim of this study was to identify miR that could be specifically expressed and exert distinct biological actions in ESCC. Methods: Total RNA was extracted from ESCC cell lines, OE21 and TE10, and a non-malignant human esophageal squamous cell line, Het-1A, and subjected to microarray analysis. Expression levels of miR that showed significant differences between the 2 ESCC and Het-1A cells based on the comprehensive analysis were analyzed by the quantitative reverse transcriptase (RT)-PCR method. Then, functional analyses, including cellular proliferation, apoptosis and Matrigel invasion and the wound healing assay, for the specific miR were conducted. Using ESCC tumor samples and paired surrounding non-cancerous tissue obtained endoscopically, the association with histopathological differentiation was examined with quantitative RT-PCR. Results: Based on the miR microarray analysis, there were 14 miRs that showed significant differences (more than 2-fold) in expression between the 2 ESCC cells and non-malignant Het-1A. Among the significantly altered miRs, miR-205 expression levels were exclusively higher in 5 ESCC cell lines examined than any other types of malignant cell lines and Het-1A. Thus, miR-205 could be a specific miR in ESCC. Modulation of miR-205 expression by transfection with its precursor or anti-miR-205 inhibitor did not affect ESCC cell proliferation and apoptosis, but miR-205 was found to be involved in cell invasion and migration. Western blot revealed that knockdown of miR-205 expression in ESCC cells substantially enhanced expression of zinc finger E-box binding homeobox 2, accompanied by reduction of E-cadherin, a regulator of epithelial mesenchymal transition. The miR-205 expression levels were not associated with histological differentiation of human ESCC. Conclusions: These results imply that miR-205 is an ESCC-specific miR that exerts tumor-suppressive activities with EMT inhibition by targeting ZEB2.Kayoko Matsushima... Gregory J Goodall... et al
The IFCC reference measurement system for HbA(1)C: A 6-year progress report
No full textBACKGROUND: The IFCC Reference Measurement System for hemoglobin (Hb)A(1)c (IFCC-RM) has been developed within the framework of metrologic traceability and is embedded in a network of 14 reference laboratories. This paper describes the outcome of 12 intercomparison studies (periodic evaluations to control essential elements of the IFCC-RM). METHODS: Each study included: unknown samples (to test individual network laboratories); known samples (controls); recently manufactured calibrators (to check calculated assigned value); stored calibrators (to test stability) and a calibration-set (to calibrate the IFCC-RM). The unknown samples are measured by use of the IFCC-RM and the designated comparison methods [DCMs; the National Glycohemoglobin Standardization Program (NGSP) in the US, Japanese Diabetes Society/Japanese Society for Clinical Chemistry (JDS/ JSCC) in Japan, and Mono-S in Sweden] are used to investigate the stability of the Master Equation (ME), the relationship between IFCC-RM and DCMs. RESULTS: A total of 105 IFCC-RM data sets were evaluated: 95 were approved, 5 were not, and for 5 no data were submitted. Trend analysis of the MEs, expressed as change in percentage HbA(1)c per year, revealed 0.000% (NGSP, not significant), -0.030%, (JDS/JSCC; significant) and -0.016% (Mono-S; not significant). Evaluation of long-term performance revealed no systematic change over time; 2 laboratories showed significant bias, 1 poor reproducibility. The mean HbA(1)c determined by laboratories performing mass spectrometry (MS) was the same as the mean determined by laboratories using capillary electrophoresis (CE), but the reproducibility at laboratories using CE was better. One batch of new calibrators was not approved. All stored calibrators were stable. CONCLUSION: A sound reference system is in place to ensure continuity and stability of the analytical anchor for HbA(1)c
A basis of a certain module for the hyperalgebra and some applications
No full textIn the hyperalgebra of the -th Frobenius kernel of the algebraic group , we construct a basis of the
-module generated by a certain element which was given by the
author before. As its applications, we also prove some results on the
-modules and the algebra .Comment: 30 page
Borromini tuscolano
No full textLa pubblicazione propone, in versione ampliata e aggiornata, la chiave di lettura già avanzata dall’autore alcuni anni or sono in relazione all’intervento seicentesco voluto dalla famiglia Falconieri sulla più antica delle Ville Tuscolane, la Rufina, ritenendone valida la consolidata attribuzione al Borromini.
Nel volume viene data un’ampia dimostrazione dell’efficacia dell’interazione “documenti storici-rilievo architettonico”, nella ricostruzione delle fasi evolutive di una fabbrica e di come questo momento d’analisi, ove insufficientemente approfondito, possa indurre a considerazioni erronee.
Infatti, l’ipotesi diffusa in vari contributi sull’argomento riguardo alla forma dell’originario Casino della Rufina – e in particolare alla posizione della loggia verso Roma – è suffragata soltanto da incisioni d’epoca e non è mai stata scientificamente comprovata dal riscontro di un rilievo, né dal confronto attento con la pianta del nucleo originario della fabbrica conservata nelle Carte Strozzi presso l’Archivio di Stato di Firenze, ignorata o considerata – con una certa superficialità – come inattendibile.
L’ipotesi qui sostenuta valuta la “logica” dell’addizione alla Villa Rufina basandosi su considerazioni relative sia ai vari documenti iconografici sia all’attendibilità di ciascuno; il tutto è inoltre riferito al completo rilevamento dell’opera nel suo stato attuale.
Discutendo ipotesi diverse (anche attributive) emerse nel frattempo e sviluppando le considerazioni precedentemente avanzate grazie anche a un nuovo apparato iconografico che vede sfruttate le potenzialità della modellazione 3D applicate ai criteri del rilievo filologico, il lavoro tende a ribadire l’efficacia di tale metodo d’indagine, basato sul rilievo delle attuali condizioni dell’opera in associazione all’imprescindibile analisi storico-documentale.
Attraverso il medesimo impianto scientifico procedurale è inoltre sviluppata la ricostruzione filologica del fronte settentrionale, basata anche su documentazione fotografica d’epoca parzialmente inedita. Si intende così offrire un iniziale – seppur parziale – contributo alla rilettura dell’ultima fase (quella novecentesca) che ha contrassegnato la fabbrica, vedendola già alterata ai primi del XX secolo, quindi compromessa dagli eventi bellici e infine trasformata dalle operazioni di restauro/ripristino del complesso, che hanno riproposto solo parzialmente e in modo generico la precedente morfologia del manufatto.This publication proposes, in an expanded and updated version, the key that the Author had already advanced in an earlier essay which was published ten years ago, concerning the 17th century intervention on the Villa Rufina: the first one of the Ville Tuscolane (summer residences for the papal circle that rose, in the late Renaissance, on the hills at the south of Rome). The Authors assumes also to be valid the well-established attribution of this work to Francesco Borromini.
In this volume a wide demonstration is offered of the efficacy, for the aim of a reliable reconstruction of the evolutionary phases of a certain building, of the interaction between the historical documents and the architectural survey, showing also how this time of analysis can lead to incorrect or misleading considerations, when it is not carried out enough deeply.
In the second phase (the expansion of the 17th century) which characterized all the Ville Tuscolane, the Rufina, at the time owned by the Falconieri (family), was the subject of an extensive renewal. With this intervention the first bulding that had initiated the “modern rediscovery” of building activity in these places (being, in fact, the originator of the Complex) was considerably transformed with regard to its material structure, appearance and relationship with the environment. For the devising of the general plan, it is commonly ascribed to Francesco Borromini, on the basis more of archive documents than of its style.
If the decoration of the Villa has been extensively and reliably studied, the same cannot be said about the transformations that the old building underwent, especially with regard to the lost loggia towards Rome. The hypothesis that has gradually taken root, about the location of this lodge, in the various papers published on the subject, is in fact supported only by some engravings of the time (in which the Villa is depicted in a pseudo-perspectival view and only as an element amongst the many others of the Complex). It has never been scientifically proved by the check of a survey, or by a careful comparison with the plan of the original nucleus of the original factory map stored in the “Carte Strozzi” at the State Archives of Florence, that has been ignored or considered – with some superficiality – as unreliable.
The hypothesis the Author suggested since the previous essay, evaluates the “logic” of the addition Borromini made to the Villa Rufina detaching itself from these assumptions and basing itself on some specific considerations concerning the iconographic documents that have been published over the years in various contributions, evaluating the reliability of each of them. These considerations were also related to a comprehensive survey of the work in its current state, as the so far published surveys are partial or were carried out on the structure as extensively damaged by the war.
In the volume are also discussed several different hypotheses that emerged in the meantime, also on the allocation of the project, as the attribution to Borromini – which in the past had seen ups and downs, from the header of the engraving by Alessandro Specchi to the evidences provided by Paolo Portoghesi and by Angela Negro, taken from the Falconieri-Carpegna archive – has recently been the subject of a new attempt of denial.
Developing the considerations already advanced before, and using a new display of subsidiary iconography that sees the exploitation of the potential of 3d modeling when applied to the criteria of the philological surveying, this study aims at a confirmation of the effectiveness of this method of investigation, which is based on a survey of the work in its positive state in conjunction with an unavoidable historical-documentary analysis.
On the basis of this same scientific procedural system, taking as well in account many historical photographic documents, so far unpublished, is also developed a philological reconstruction of the northern front, that is proposed in the last chapter. The aim is to provide a first – although partial – contribution to the re-reading of the last phase (the 20th century), which marked the building, that had already been altered in the early years of the 20th century, then compromised by the war and finally transformed by the restoration and rehabilitation of the complex, which reconstructed the pre-existing morphology only in a partial and general way
Convective Ripening and Rainfall
No full textThis paper discusses the evolution of the droplet size distribution for a liquid-in-gas aerosol contained in a Rayleigh-B\'enard cell. It introduces a non-collisional model for broadening the droplet size distribution, termed \lq convective ripening'. The paper also considers the initiation of rainfall from ice-free cumulus clouds. It is argued that while collisional mechanisms cannot explain the production of rain from clouds with water droplet diameters of , the non-collisional convective ripening mechanism gives a much faster route to increasing the size of the small fraction of droplets that grow into raindrops
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