288 research outputs found
Ground Improvement for Increasing Lateral Pile Group Resistance
Lateral load tests were performed on a full-scale pile cap in untreated clay along with pile groups involving (a) excavation and replacement with sand backfill, (b) a soilcrete wall along the side of the pile group, and (c) a jet grouted zone below the pile cap. The average compressive strength of the soft, plastic clay increased from an average of 50 kPa to an average of about 1000 kPa with soil mixing (10% cement) and to 3000 kPa with jet grouting (20% cement). Excavation and replacement only increased resistance by about 20%; however, the soil mixed wall increased resistance by 60%, and jet grouting increased resistance by 160%. For the soil mixed wall, essentially all of the increased resistance can be explained due to passive pressure and side/base shear against the soil mixed wall. However, for the jet grout treatment, additional resistance can also be attributed to increased structural resistance of the composite soilcrete volume under the cap. Soil mixing and jet grouting provide a means to significantly increase the lateral resistance of existing pile group foundations with relatively little investment of time, effort, and expense relative to the addition of more piles
MAC-Oriented Programmable Terahertz PHY via Graphene-based Yagi-Uda Antennas
Graphene is enabling a plethora of applications in a wide range of fields due
to its unique electrical, mechanical, and optical properties. In the realm of
wireless communications, graphene shows great promise for the implementation of
miniaturized and tunable antennas in the terahertz band. These unique
advantages open the door to new reconfigurable antenna structures which, in
turn, enable novel communication protocols at different levels of the stack.
This paper explores both aspects by, first, presenting a terahertz
Yagi-Uda-like antenna concept that achieves reconfiguration both in frequency
and beam direction simultaneously. Then, a programmable antenna controller
design is proposed to expose the reconfigurability to the PHY and MAC layers,
and several examples of its applicability are given. The performance and cost
of the proposed scheme is evaluated through full-wave simulations and
comparative analysis, demonstrating reconfigurability at nanosecond granularity
with overheads below 0.02 mm and 0.2 mW.Comment: Accepted for presentation in IEEE WCNC '1
SIMPLIFIED PARAMETERS FOR THE EVALUATION OF SITE EFFECTS IN THE
After the 2002 earthquakes, that struck the southern Italy provinces of Campobasso (Molise) and Foggia
(Apulia), the safety assessment of buildings has allowed to evaluate, for different building typologies, the
damage level caused by the seismic event; in particular, the survey of the damaged cultural heritage was carried
out by the Task Cultural Heritage of the Mixed Operating Centre (COM) in Larino (a village in the epicentral
area), coordinated by the “Working Group for the Safeguard of the Cultural Heritage from Natural Risks”
(Italy’s Gazzetta Ufficiale n. 116, 21 May 2001 - PCM-DPC Decree, 3 May 2001)”.
For this survey activity, the churches were investigated with a specific form proposed by the same Working
Group (Ministerial Decree n. 133, 23th January 2001), adopting different forms for other kinds of buildings. The
surveyors were organized in teams, called NOPSA (Nuclei Operativi Patrimonio Storico Artistico), composed by
officials of the Regional board of the Ministry of Cultural Heritage and Environmental Conservation (architects
and art historians), an engineer and a Fire Brigade technician. The first phase of the safety assessment has been developed on the basis of the warnings received by the Larino COM, and most of the surveyed buildings were
churches. The damage assessment of public or private buildings began, initially, near the earthquake epicentre
(area 1 - IMCS between 6 and 8.5) and subsequently was carried out for all the villages from which inspection
requests arrived. At the same time a vulnerability survey was carried out for the churches, using the II level form
(Lagomarsino et al., 2004) proposed in the SAVE Project (“Updated Tools for the Seismic Vulnerability
Evaluation of the Italian Real Estate and of Urban Systems” – http://gndt.ingv.it). The damage and vulnerability
survey has allowed to verify and optimize the procedures for damage assessment immediately after a seismic
event (emergency phase) and to obtain useful indications for the reconstruction phase. On the whole 379
monumental buildings in 101 Molise villages and 207 monumental buildings in 44 Apulia villages were
investigated. Figure 1 shows the number of monumental buildings surveyed after the earthquakes for each
Molise village, subdividing the region according to the seismic classification proposed by the recent Italian
Seismic Code (OPCM n. 3274, 2003 – http://zonesismiche.mi.ingv.it)
Heat to Electricity Conversion by a Graphene Stripe with Heavy Chiral Fermions
A conversion of thermal energy into electricity is considered in the
electrically polarized graphene stripes with zigzag edges where the heavy
chiral fermion (HCF) states are formed. The stripes are characterized by a high
electric conductance Ge and by a significant Seebeck coefficient S. The
electric current in the stripes is induced due to a non-equilibrium thermal
injection of "hot" electrons. This thermoelectric generation process might be
utilized for building of thermoelectric generators with an exceptionally high
figure of merit Z{\delta}T \simeq 100 >> 1 and with an appreciable electric
power densities \sim 1 MW/cm2.Comment: 8 pages, 3 figure
Correlation between local amplification effects and damage mechanism for monumental buildings
The damage and vulnerability survey of the monumental buildings, damaged by the 2002 earthquake in the Molise Region, has allowed singling out of a correlation between the observed damage of the churches and their morphological site conditions. The vulnerability model connected to the survey methodology provides an evaluation of the expected mean damage. Comparison with the observed damage determined the introduction of a local morphological behaviour modifier, able to take into account the vulnerability increase due to the site effects. In order to validate the previous results, a numerical 2-D analysis of the seismic local response has been performed. In particular, a numerical code, working with boundary elements, has been applied to the analyzed situations. The results, in terms of pseudo-acceleration response spectra and amplification factors, allow one to compare the numerical and the observed analyses. This comparison shows good agreement and allows one to find some correlations between the geometric characteristics of the sites, the values of the amplification coefficients and the damage mechanism activated
Correlation between local amplification effects and damage mechanisms for monumental buildings
The damage and vulnerability survey of the monumental buildings, damaged by the 2002 earthquake in the Molise Region, has allowed singling out of a correlation between the observed damage of the churches and their morphological site conditions. The vulnerability model connected to the survey methodology provides an evaluation of the expected mean damage. Comparison with the observed damage determined the introduction of a local morphological behaviour modifier, able to take into account the vulnerability increase due to the site effects. In order to validate the previous results, a numerical 2-D analysis of the seismic local response has been performed. In particular, a numerical code, working with boundary elements, has been applied to the analyzed situations. The results, in terms of pseudo-acceleration response spectra and amplification factors, allow one to compare the numerical and the observed analyses. This comparison shows good agreement and allows one to find some correlations between the geometric characteristics of the sites, the values of the amplification coefficients and the damage mechanism activated
Effetti di amplificazione topografica osservati sul patrimonio monumentale
La ricerca ha avuto l’obiettivo di indagare gli effetti di amplificazione sismica, per cause topografiche, che possono aver interessato le chiese danneggiate
da alcuni terremoti storici italiani. La novità di questo studio consiste nell’aver messo a punto una metodologia di analisi che, partendo dall’osservazione
degli effetti del terremoto sull’edificio, confronta il danno osservato ed il danno atteso, calcolato attraverso modelli basati su dati statisticamente
affidabili, prevede una fase di rilevo delle caratteristiche geologiche, geomorfologiche, geotecniche e geofisiche dei siti di ubicazione delle chiese, arriva
a quantificare, anche attraverso modellazioni numeriche della risposta sismica locale, l’influenza che la morfologia di questi siti può aver avuto nel
determinare l’incremento dell’input sismico e conseguentemente del danno osservato
Abundances of Molecular Species in Barnard 68
Abundances for 5 molecules (C18O, CS, NH3, H2CO, and C3H2) and 1 molecular
ion (N2H+) and upper limits for the abundances of 1 molecule (13CO) and 1
molecular ion (HCO+) are derived for gas within the Bok globule Barnard 68
(B68). The abundances were determined using our own BIMA millimeter
interferometer data and single-dish data gathered from the literature, in
conjunction with a Monte Carlo radiative transfer model. Since B68 is the only
starless core to have its density structure strongly constrained via extinction
mapping, a major uncertainty has been removed from these determinations. All
abundances for B68 are lower than those derived for translucent and cold dense
clouds, but perhaps only significantly for N2H+, NH3, and C3H2. Depletion of CS
toward the extinction peak of B68 is hinted at by the large offset between the
extinction peak and the position of maximum CS line brightness. Abundances
derived here for C18O and N2H+ are consistent with other, recently determined
values at positions observed in common.Comment: 16 pages, 1 figure, accepted by AJ, typo corrected, reference removed
in Section 4.
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