6,314 research outputs found
Realizing the Promise
UNLVâs Science and Engineering Building is open for business â the business of conducting world-class research. Step inside and find out why some are calling it the most important structure built on campus since the university was established more than 50 years ago
Measuring Social Capital: Culture as an Explanation of Italy's Economic Dualism.
The paper presents a quantitative test of the oft-repeated view that Italy's backward and poor South suffered from low "social capital", a tendency to defect from co-operative engagements. The problem with such assertions is that they run the risk of taking as evidence in favour of the hypothesis the very observations that need to be explained. The analysis carried out in this work tries to break out of this impasse by analyzing the conditions under which it was ex ante welfare-improving for farmers in early 20th century Italy to join an unlimited liability rural co-operative bank which would give them access to cheaper credit but also exposed them to the risk of their neighbours' defection.POVERTY ; CULTURE ; SOCIAL CAPITAL
Risk in Tuscan Agriculture in the Late 19th and Early 20th Centuries
We analyse output risk in Italian agriculture over the period 1870- 1914. We use data on a set of 16 tenanted plots grouped into three farms comprising a single large estate. We estimate the degree of risk associated with each separate crop, with the portfolio of crops at the level of the plot, the farm and the estate. We highlight two particular features: the relatively high risk associated with tree crops (wine, oil and nuts); and the substantial scope for the landlord to reduce risk through crop diversification across plots. We discuss the implications of these for tenure contract theory.Output risk; agriculture; tenure contracts; Tuscany
Design and development of a smart panel with five decentralised control units for the reduction of vibration and sound radiation
This Technical Report discusses the design and the construction of a smart panel with five decentralised direct velocity feedback control units in order to reduce the vibration of the panel dominated by well separated low frequency resonances. Each control unit consists of an accelerometer sensor and a piezoelectric patch strain actuator. The integrated accelerometer signal is fed back to the actuator via a fixed negative control gain. In this way the actuator generates a control excitation proportional and opposite to the measured transverse velocity of the panel so that it produces active damping on the panel. First the open loop frequency response function between the sensor and the actuator of a single channel has been studied and an analogue controller has been designed and tested in order to improve the stability of this control system. Following the stability of all five control units has been assessed using the generalised Nyquist criterion. Finally the performances of the smart panel have been tested with reference to the reduction of the vibrations at the error positions and with reference to the reduction of the radiated sound. Finally in appendix to this Report, a parametric study is presented on the properties of sensor-actuator FRFs measured with different types of piezoelectric patch actuators. The results of this parametric study have been used in order to choose the actuators to be used for the construction of the smart pane
Modeling sea level changes and geodetic variations by glacial isostasy: the improved SELEN code
We describe the basic features of SELEN, an open source Fortran 90 program
for the numerical solution of the so-called "Sea Level Equation" for a
spherical, layered, non-rotating Earth with Maxwell viscoelastic rheology. The
Sea Level Equation was introduced in the 70s to model the sea level variations
in response to the melting of late-Pleistocene ice-sheets, but it can be also
employed for predictions of geodetic quantities such as vertical and horizontal
surface displacements and gravity variations on a global and a regional scale.
SELEN (acronym of SEa Level EquatioN solver) is particularly oriented to
scientists at their first approach to the glacial isostatic adjustment problem
and, according to our experience, it can be successfully used in teaching. The
current release (2.9) considerably improves the previous versions of the code
in terms of computational efficiency, portability and versatility. In this
paper we describe the essentials of the theory behind the Sea Level Equation,
the purposes of SELEN and its implementation, and we provide practical
guidelines for the use of the program. Various examples showing how SELEN can
be configured to solve geodynamical problems involving past and present sea
level changes and current geodetic variations are also presented and discussed
Effects of coupling between octahedral tilting and polar modes on the phase diagram of PbZr1-xTixO3 (PZT)
The results are presented of anelastic and dielectric spectroscopy
measurements on large grain ceramic PZT with compositions near the two
morphotropic phase boundaries (MPBs) that the ferroelectric (FE) rhombohedral
phase has with the Zr-rich antiferroelectric and Ti-rich FE tetragonal phases.
These results are discussed together with similar data from previous series of
samples, and reveal new features of the phase diagram of PZT, mainly connected
with octahedral tilting and its coupling with the polar modes. Additional
evidence is provided of what we interpret as the onset of the tilt instability,
when is initially frustrated by lattice disorder, and the long range order is
achieved at lower temperature. Its temperature T_IT(x) prosecutes the long
range tilt instability line T_T(x) up to T_C, when T_T. It is proposed that the
difficulty of seeing the expected 1/2 modulations in diffraction
experiments is due to the large correlation volume associated with that type of
tilt fluctuations combined with strong lattice disorder. It is shown that the
lines of the tilt instabilities tend to be attracted and merge with those of
polar instabilities. Not only T_IT bends toward T_C and then merges with it,
but in our series of samples the temperature T_MPB of the dielectric and
anelastic maxima at the rhombohedral/tetragonal MPB does not cross T_T, but
deviates remaining parallel or possibly merging with T_T. These features,
together with a similar one in NBT-BT, are discussed in terms of cooperative
coupling between tilt and FE instabilities, which may trigger a common phase
transition. An analogy is found with recent simulations of the tilt and FE
transitions in multiferroic BiFeO3. An abrupt change is found in the shape of
the anelastic anomaly at T_T when x passes from 0.465 to 0.48, possibly
indicative of a rhombohedral/monoclinic boundary.Comment: 15 pages, 11 figure
Piezoelectric softening in ferroelectrics: ferroelectric versus antiferroelectric PbZrTiO
The traditional derivation of the elastic anomalies associated with
ferroelectric (FE) phase transitions in the framework of the Landau theory is
combined with the piezoelectric constitutive relations instead of being
explicitly carried out with a definite expression of the FE part of the free
energy. In this manner it is shown that the softening within the FE phase is of
electrostrictive and hence piezoelectric origin. Such a piezoelectric softening
may be canceled by the better known piezoelectric stiffening, when the
piezoelectric charges formed during the vibration are accompanied by the
depolarization field, as for example in Brillouin scattering experiments. As
experimental validation, we present new measurements on Zr-rich PZT, where the
FE phase transforms into antiferroelectric on cooling or doping with La, and a
comparison of existing measurements made on FE PZT with low frequency and
Brillouin scattering experiments
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