The magnetic exchange parameters and anisotropy of the quasi-two dimensional antiferromagnet NiPS3_3

Neutron inelastic scattering has been used to measure the magnetic excitations in powdered NiPS$_3$, a quasi-two dimensional antiferromagnet with spin $S = 1$ on a honeycomb lattice. The spectra show clear, dispersive magnons with a $\sim 7$ meV gap at the Brillouin zone center. The data were fitted using a Heisenberg Hamiltonian with a single-ion anisotropy assuming no magnetic exchange between the honeycomb planes. Magnetic exchange interactions up to the third intraplanar nearest-neighbour were required. The fits show robustly that NiPS$_3$ has an easy axis anisotropy with $\Delta = 0.3$ meV and that the third nearest-neighbour has a strong antiferromagnetic exchange of $J_3 = -6.90$ meV. The data can be fitted reasonably well with either $J_1 < 0$ or $J_1 > 0$, however the best quantitative agreement with high-resolution data indicate that the nearest-neighbour interaction is ferromagnetic with $J_1 = 1.9$ meV and that the second nearest-neighbour exchange is small and antiferromagnetic with $J_2 = -0.1$ meV. The dispersion has a minimum in the Brillouin zone corner that is slightly larger than that at the Brillouin zone center, indicating that the magnetic structure of NiPS$_3$ is close to being unstable.Comment: 21 pages, 7 figures, 33 reference

Low yield metals and perforated steel shear walls for seismic protection of existing RC buildings

In the field of the seismic protection of buildings, the use of steel plate shear walls (SPSWs) may be particularly profitable in the seismic retrofitting interventions of existing RC buildings designed for gravity loads only. Some past researches have shown that when traditional full SPSWs are used as bracing devices of framed buildings, they may induce excessive design forces to the surrounding frame members. Therefore, low yield steels (LYS) could be a valuable option to overcome this applicability limit. Nevertheless, the scarce availability on the market of these steels suggests the employment of aluminium alloys and perforated steel plates, which have the benefit of incurring excursions in plastic range already for low stress levels. In this paper, a parametric analysis concerning the use of perforated metal plate shear walls (MPSWs) for seismic upgrading of existing RC framed structures represents a novelty of the research in the retrofitting interventions field. To this purpose, first, some experimental tests have been considered to calibrate a finite element model of the panel devices by using the SeismoStruct software. Subsequently, the proposed FEM model has been used to design the retrofitting systems with either full MPSWs or perforated SPSWs of an existing RC residential five-storey building, designed between the 1960s and 1970s of the last century. Finally, the different retrofitting panel systems examined have been compared to each other in terms of both structural and economic viewpoints, allowing to select the best intervention strategy

Perforated Shear Panels for Seismic Rehabilitation of Existing Reinforced Concrete Buildings

In the field of the seismic protection of buildings, the use of steel plate shear walls (SPSWs) may be particularly appropriate for the intervention of seismic retrofitting of existing reinforced concrete (RC) buildings designed for gravity loads only. Some past research has shown that, when traditional full SPSWs are used as bracing devices for framed buildings, they may induce excessive design forces to the surrounding frame members. Therefore, low yield steel could be a valuable option to overcome this applicability limit. Nevertheless, the scarce availability in the market of these steels suggests the employment of aluminium alloys and perforated steel plates, which have the benefit of incurring behaviour in the plastic range for low stress levels. In this paper, in order to conduct a parametric analysis concerning the use of full and perforated SPSWs for seismic upgrading of existing RC framed structures, first some experimental tests have been numerically calibrated using the SeismoStruct software. Subsequently, the proposed finite element model has been used to design the retrofitting systems with either full or perforated SPSWs of an existing RC residential five-storey building. Finally, the differences in the use of these solutions, in terms of both structural and economic viewpoints, have been demonstrated

T-resolution: refinements and model elimination

T-resolution is a binary rule, proposed by Policriti and Schwartz in 1995 for theorem proving in first-order theories (T-theorem proving) that can be seen - at least at the ground level - as a variant of Stickel's theory resolution. In this paper we consider refinements of this rule as well as the model elimination variant of it. After a general discussion concerning our viewpoint on theorem proving in first-order theories and a brief comparison with theory resolution, the power and generality of T-resolution are emphasized by introducing suitable linear and ordered refinements, uniformly and in strict analogy with the standard resolution approach. Then a model elimination variant of T-resolution is introduced and proved to be sound and complete; some experimental results are also reported. In the last part of the paper we present two applications of T-resolution: to constraint logic programming and to modal logic

Damage Probability Matrices and Empirical Fragility Curves From Damage Data on Masonry Buildings After Sarpol-e-zahab and Bam Earthquakes of Iran

The weakness of tensile strength and high weight in masonry structures under the dynamic loads of earthquakes has always led to structural damage, financial losses, injuries, and deaths. In spite of cheap and affordable masonry materials, their use has been very limited in constructions over the past three decades. However, common masonry materials are still found in monumental and historical structures, deteriorated texture, and rural buildings. Identifying the seismic behavior and the probability of the structural damage is vital for pre-earthquake seismic risk reduction of urban areas and the rapid post-earthquake assessment. The earthquake event that occurred in Ezgeleh on 2017 November 12 with Mw = 7.3 triggered the greatest damage in Sarpol-e-zahab city at a distance of about 37 km from the epicenter. Post-earthquake reconnaissance, microtremor analysis, and rapid visual inventory of structural damages in different zones were performed by research teams. In the present study, the strong ground motion and the peak ground acceleration, and its corresponding intensity distribution, which are based on the site response analysis in different parts of the city, are introduced. Afterward, damage probability matrices of different types of masonry buildings, namely unreinforced masonry and confined masonry buildings, are determined for both bins of peak ground accelerations and intensities. Finally, the fragility curves of two types of masonry structures are extracted based on the RISK-UE level 1 (LM1) method by assuming a beta distribution to estimate the probability distribution function of the damage. These curves are useful in assessing pre-earthquake possible damages in masonry structures with similar construction methods and similar materials to reduce seismic risks

Induced seismic-site effects on the vulnerability assessment of a historical centre in the molise Region of Italy: Analysis method and real behaviour calibration based on 2002 earthquake

The present research aims to estimate the influence of site amplification on the seismic vulnerability of the historical centre of the municipality of Baranello in the Molise Region of Italy. Firstly, a structural and typological characterization of the investigated area has been done according to the EMS-98 scale. Subsequently, the vulnerability assessment of the historical buildings located there has been carried out through an appropriate survey form in order to identify the buildings which are most susceptible to seismic damage. To this purpose, the seismic event occurring in October of 2002 has been selected as a reference earthquake. Moreover, according to the AeDES form implemented by the Italian Civil Protection Department to evaluate the usability of constructions after seismic events, the calibration of the typological vulnerability curves of the built-up area has been done, and a quantitative assessment of the local seismic response has been achieved, based on the seismic motions recorded after the 2002 Molise earthquake. Finally, the local amplification factor, which negatively influences the severity of the seismic damage on the structures, has been taken into account in order to more correctly foresee the expected damage of the inspected urban sector, so as to use more appropriately the achieved results for reliable seismic risk mitigation plans

Epistemic Logic Programs: a Novel Perspective and Some Extensions

Epistemic Logic Programs (ELPs), which propose an extension to Answer Set Programming (ASP) with epistemic operators, have their semantic defined, in various ways, in terms of world views, which are sets of belief sets. Several semantic approaches have in fact been proposed over time to characterize world views, and, recently, to also characterize semantic properties that should be met by any semantics for ELPs. We propose a new semantics, easy also from the computational point of view, but effective, also in order to compare the different semantic approaches. We also propose a significant extension to the ELP approach, by allowing epistemic atoms in rule heads

Epistemic Logic Programs: an Approach to Semantic Comparison

Epistemic Logic Programs (ELPs) extend Answer Set Programming (ASP) with epistemic operators. The semantics of such programs is provided in terms of world views, which are sets of belief sets. Several semantic approaches have been proposed over time to characterize world views. Recent work has introduced semantic properties that should be met by any semantics for ELPs. We propose a new method, easy but, we believe, effective, to compare the different semantic approaches