198,276 research outputs found
Study of high strain rate effect on sheet formability based on Nakazima test
No full textThe knowledge of the sheet metals formality is important for the success of the manufacturing processed based on plastic deformation. Even though many industrial processes take place at relatively high speeds, higher than the quasi-static regime ones, few studies are present in the literature on the evaluation of the formability at high speed. In this framework, the present paper aims at studying the effect of the high strain rate on the formability of AA6082 aluminium alloy, characterized by a thickness of 1 mm. An experimental equipment, based on the Nakazima test, mounted on a direct tension-compression Split Hopkinson Bar, has been developed in order to define the formability under dynamic loading conditions. The high strain rate behaviour of the alloy has been compared with the one obtained in quasi-static condition
Identification of constitutive model parameters in Hopkinson bar tests
No full textIn this work, tension and compression tests have been carried out on aluminium samples at low and high strain rate, the latter performed by means of a direct tension Hopkinson bar equipment. The parameters of the Johnson-Cook constitutive model have been identified using different approaches; the first method consists in the classical Finite Element Model Updating, where numerical simulations are repeated with different material parameters until the mismatch between the experimental and numerical load–displacement curves falls below an acceptable threshold. The second method is based on the analysis of the digital images acquired by a fast camera during the tests; this permitted to calibrate the JC model by an analytical minimization procedure, without any FE simulation. A third inverse technique was also implemented, consisting in applying the FE model updating but using an enriched cost function, where also the mismatch between the numerical and acquired specimen shape profiles is included and minimized. The advantages and drawbacks of the different techniques are assessed and compared
Preface to Tectonophysics, 347, 1-3 (2002)
No full textAntarctica is the most poorly understood region of our planet. It, however, maintains an important geologic record of the Gondwana and Rodinia evolution and therefore is a center of extensive scientific inquiry.
Magnetic data provide a critical window for geological studies due to the nearly ubiquitous snow and ice cover of this forbidding region. Consequently, numerous
magnetic surveys have been carried out for site-specific geologic objectives since the International Geophysical Year 1957/1958.
Plans for an international project to process and combine these disparate data sets into a single magnetic anomaly map were formulated at the 1993 meeting of the International Association of Geomagnetism and Aeronomy (IAGA) in Buenos Aires, Argentina.
Both IAGA and the Scientific Committee on Antarctic Research (SCAR) passed resolutions of encouragement (Johnson et al., 1996; Chiappini et al., 1999). At a 1995 workshop at the British Antarctic Survey in Cambridge, UK, it became clear that these individual
magnetic surveys could indeed be combined into a regional synthesis to further enhance their utility for geological studies (Johnson et al., 1996, 1997; Chiappini et al., 1998, 1999).
Accordingly, the Antarctic Digital Magnetic Anomaly Project (ADMAP) was launched at this first workshop (ADMAP I) to compile and integrate into a digital database existing near-surface and satellite magnetic anomaly data of Antarctica and the surrounding oceans
south of 60jS. An international working group of 32 scientists from eight countries that operate magnetic programs in the Antarctic was established. The working group adopted protocols for making existing and future magnetic data sets available to this international effort. In particular, existing Antarctic magnetic data holdings will be deposited in the world data centers by the end of this first phase of the project in 2002.Published1-23.2. Tettonica attiva3.4. GeomagnetismoJCR Journalreserve
High Strain Rate Tests by a 90 m Long Tension-Torsion Hopkinson Bar
No full textThis work describes the design, construction, and first experimental results of an innovative device of the Hopkinson bar type with a length of 90 m for performing high strain rate tests on metals in a combined tension-torsion state. Analogously to the classic split Hopkinson bar technique, the system configuration consists of three bars: a pre-stressed bar, an input bar, and an output bar; the measurement is also based on the classical three-wave method, where the incident, transmitted, and reflected waves are measured. The length of the bars is designed so that the tensile wave reaches the sample from the output bar side at the same time as the torsion wave comes from the input bar. A successful test has been conducted on a hollow aluminum sample; it has been possible to measure the tension-torsion stress-strain curves; in addition, the dynamic equivalent stress-equivalent strain curves have been evaluated
The oldest stars of the bulge: new information on the ancient Galaxy
No full textRecently the search for the oldest stars have started to focus on the Bulge region. The Galactic bulge hosts extremely old stars, with ages compatible with the ages of the oldest halo stars. The data coming from these recent observations present new chemical signatures and therefore provide complementary constraints to those already found in the halo. So, the study of the oldest bulge stars can improve dramatically the constraints on the nature of first stars and how they polluted the pristine ISM of our Galaxy. We present our first results regarding the light elements (CNO) and the neutron capture elements. Our findings in the oldest bulge stars support the scenario where the first stellar generations have been fast rotators
CHIAPPINI, L.; MARTINS, M. H.; PESAVENTO, S. J. (Orgs.) Pampa e Cultura: de Fierro a Netto.
No full textCHIAPPINI, L.; MARTINS, M. H.; PESAVENTO, S. J. (Orgs.) Pampa e Cultura: de Fierro a Netto. PortoAlegre: Editora da UFRGS / Instituto Estadual do Livro, 2004. 285p.Resenhado por: Andrea Cristiane Kahman
Forward magnetic models across the southern Apennines: implications for the basement setting
No full textWe discuss here the forward magnetic modeling, along a southern
Apennines transect, of the new magnetic map of Italy (CHIAPPINI
et alii, 2000a). This map has been realized through an integrated
digital magnetic anomaly database built for the Italian territory and
the surrounding sea. For the first time, all the magnetic observations
made onshore and offshore the Italian peninsula have been compiled
into a new digital database, that gives a complete regional scale
view of the magnetic anomaly crustal field over the area. The new
magnetic map shows a low-amplitude (~20 nT), long-wavelength
positive anomaly along the external southern Apennines, and negative
anomalies over both the Tyrrhenian margin of southern Italy
and the Apulian foreland. South of the Vulture volcano (~41° N), the
positive magnetic anomaly is elongated and exactly parallel to the
external belt. Furthermore, the eastern anomaly margin is exactly
parallel to the belt front, and located few tens of kilometers southwest
of it. The negative pattern of the Tyrrhenian Sea and margins is
likely due to the high thermal flow, which significantly reduces the
thickness of the susceptive crustal layer. A magnetic modeling was
performed along a selected southern Apennines transect (located ca.
50 km south of the CROP04 profile), where the shallow crustal setting
(down to 5-6 km depth) is well-known by seismic and drill-hole
data. Seismic data and oil wells suggest that the top of the magnetic
basement cannot be shallower in the belt than in the Apulian foreland,
where it was reached at ~6 km depth by the Puglia 1 well.
Therefore, the positive signature of the external southern Apennines
requires a strongly magnetic body beneath the belt. This source
must be definitely more susceptive than the basement of the Apulian
foreland. Since the solution of magnetic modeling is not unique, we
show here three different settings that are able to bring into coincidence
the observed and modeled residuals. First, we speculate that,
within the belt, the basement located beneath the Apulian carbonates
(Apulian basement) is differentiated and contaminated at depth
by susceptive magmas or mantle fluids. Then, we explore the possibility
that a very magnetic composite internal crustal wedge is tectonically
interposed between the Apulian carbonates and basement.
Two possible settings of such composite wedge are modeled and
discussed. The uniformity of the magnetic anomaly pattern along
250 km of the belt, the remarkable parallelism between the southern
Apennine positive residuals and the superficial belt front, associated
with the gravity data, the estimates of Moho depth, and the flexural
behavior of the Apulian lithosphere beneath the belt, support the
two latter models.Published13-203.4. GeomagnetismoJCR Journalreserve
High Strain Rate Tests by a 90 m Long Tension-Torsion Hopkinson Bar
No full textThis work describes the design, construction, and first experimental results of an innovative device of the Hopkinson bar type with a length of 90 m for performing high strain rate tests on metals in a combined tension-torsion state. Analogously to the classic split Hopkinson bar technique, the system configuration consists of three bars: a pre-stressed bar, an input bar, and an output bar; the measurement is also based on the classical three-wave method, where the incident, transmitted, and reflected waves are measured. The length of the bars is designed so that the tensile wave reaches the sample from the output bar side at the same time as the torsion wave comes from the input bar. A successful test has been conducted on a hollow aluminum sample; it has been possible to measure the tension-torsion stress-strain curves; in addition, the dynamic equivalent stress-equivalent strain curves have been evaluated
Enhancing Efficiency in Sustainable Markets
No full textInterest in sustainable finance—and any other investment supporting the creation of positive social and environmental effects—has grown over the last ten years. Following the global financial crisis, investors and policy makers reconsidered common financial schemes, business models and products through the lens of sustainability issues. Policy makers intercepted the growing trend and moved on with a set of new regulatory proposals. This was particularly true in the European Union where several regulations were proposed by the European Commission. Many of these issues are still open on both the theoretical and practical side.
This chapter aims to summarize some of the main trends, opportunities and risks linked with sustainability and, in turn, with sustainable finance. The chapter is structured as follows. Section 11.2 outlines recent trends in sustainable finance. Section 11.3 discusses some of the main opportuni- ties and risks linked with sustainable finance
Introduction
No full textThe aim of this chapter is to introduce the aim and structure
of the book. Speci!cally, the aim of the book is to build a bridge between
corporate social responsibility (CSR) and sustainable !nance in !nancial markets. Classic CSR topics have been investigated in the light of a
modern conception of sustainability. The book is organized in two main
blocks. The !rst block emphasizes four relevant topics in the CSR panorama of !nancial institutions: banks remuneration practices; human capital disclosure; the impact of environmental performance on banks, and
!nally, the institutional investors’ attitude towards socially responsible
investments (SRIs). The second block looks to CSR practices within the
!nancial markets and discusses risk-return pro!les of SRI and non-SRI
indexes in different time frames; it investigates whether thematic social
responsible funds obtain different risk-return than traditional funds,
and !nally, assesses whether equity crowdfunding could foster social
innovation
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