Coexistence of electron whispering-gallery modes and atomic collapse states in graphene/WSe2 heterostructure quantum dots

The relativistic massless charge carriers with a Fermi velocity of about c/300 in graphene enable us to realize two distinct types of resonances (c, the speed of light in vacuum). One is electron whispering-gallery mode in graphene quantum dots arising from the Klein tunneling of the massless Dirac fermions. The other is atomic collapse state, which has never been observed in experiment with real atoms due to the difficulty of producing heavy nuclei with charge Z > 170, however, can be realized near a Coulomb impurity in graphene with a charge Z ≥ 1 because of the “small” velocity of the Dirac excitations. Here, unexpectedly, we demonstrate that both the electron whispering-gallery modes and atomic collapse states coexist in graphene/WSe2 heterostructure quantum dots due to the Coulomb-like potential near their edges. By applying a perpendicular magnetic field, evolution from the atomic collapse states to unusual Landau levels in the collapse regime are explored for the first time.

Kootenay Lake kokanee (Oncorhynchus nerka) collapse into a predator pit

Kootenay Lake is a large, oligotrophic waterbody in southern British Columbia renowned for recreational fisheries for piscivorous rainbow trout (Oncorhynchus mykiss) and bull trout (Salvelinus confluentus). Long-term datasets showed a build-up of large-bodied (>2 kg) piscivore abundance followed by a collapse of the kokanee (Oncorhynchus nerka) prey population in 2013 and subsequent decline of large-bodied piscivores. An unprecedented post-collapse state formed in 2015-2018, characterized by low kokanee spawner abundance and biomass and high catch rates for small-bodied (<2 kg), slow growing piscivores. Bioenergetics model estimates of average historic (1961-2008) piscivore consumption was 29.3% of the average historic (1993-2008) kokanee prey supply (biomass and production), but increased to 78.7% in 2011, immediately preceding kokanee collapse. From 2015-2018, kokanee did not recover due to persistently poor juvenile survival; estimated piscivore consumption relative to prey supply remained high (73.0%), suggesting that kokanee were trapped in a predator pit. Although the ultimate and interacting causes of the initial predator build-up remain uncertain, overcoming current depensatory dynamics may be aided by kokanee stocking or increasing harvest on still-abundant, unsatiated piscivores.

Seismic Assessment of Asymmetric Single-storey R/C Buildings by Two New Methodologies: Enforced Displacement-Based and Forced-Based Pushover Procedures

Τwo new documented non-linear static (pushover) procedures on asymmetric single-storey R/C buildings are presented in detail herein, aiming directly at the Near Collapse state. Both procedures apply relative to the “Capable Near Collapse Principal reference system” of the single-storey building. The main objective of the two proposed procedures is to fully consider the coupling between torsional and translational vibrations of the floor-diaphragm under translational seismic excitation of the building’s base. The first pushover procedure, which is a Direct Displacement-Based one, uses floor enforced-displacements as action. In the second pushover procedure, which is a Force-Based one, the floor lateral static forces are applied eccentrically to centre of mass using suitable inelastic design eccentricities (dynamic plus accidental ones). The floor enforced-translations/rotation and the appropriate inelastic dynamic eccentricities used in the two proposed procedures derive from extensive parametric non-linear response history analysis and are given by figures or equations. In order to clarify in detail and evaluate the new pushover procedures, a torsionally-flexible, double-asymmetric, single-storey R/C building is seismically assessed. The validation of both procedures relative to the results of non-linear response history analysis shows that both predict with safety the in-plan displacements of the building.

Assessment of Reinforced Concrete Building for Disaster Reduction Strategy in Padang City, West Sumatra, Indonesia

Padang City, West Sumatra province is one of the most vulnerable cities in the west coast of Indonesia. Together with the increase in population in Padang City, the number of the building is also increasing. Meanwhile, researchers predicted that Padang City is facing the impendence of mega-earthquake with magnitude more than 8 in scale Richter (SR). The last Earthquake with magnitude 7.6 SR caused fatality with more than 1200 people died and almost 3000 others were injured. Most of the victims injured due to the collapse and damage of buildings, especially the Reinforced Concrete (RC) structure. To reduce the damage due to seismic load as the preparation for the future earthquake, the assessment of the element at risk subjected to the seismic load in Padang City is essential. The predominant building typology in Padang City is RC building. Using the Applied Element Method that can show structural response till collapse state, has been simulated typical low-rise RC infilled wall building in Padang City with the consideration of its different on concrete quality based on local concreting workmanship. Incremental Dynamic Analysis (IDA) by using some ground motion has been used to observe the structural response. The damage states and damage pattern has been judged based on HAZUS criteria. The results show that local compaction method affected the concrete compression quality, that also influences the building performance which is subjected to earthquake loads.

Seismic Vulnerability Assessment of Steel Moment-Resisting Frames Based on Local Damage

This paper investigates the seismic vulnerability of steel moment-resisting frames (SMRFs) based on plasticity development in structural components. Pushover analyses with three different lateral load patterns are performed to identify the location of plastic hinges at the collapse state and IDA analysis is employed to find the seismic intensities causing the formation of the specified hinges. An ensemble of 30 near-fault pulse-like motions classified into three groups of short, medium and long period motions and ten ordinary ground motions are used for seismic loading on five sample frames with 3 to 15 stories. Employing this method, the interstory drift ratio coincident to the seismic collapse is evaluated. Then, the critical pulse period producing the most damage to the structures is estimated. Finally, fragility curves are developed for near- and far-fault excitations. The results indicate that maximum interstory drift ratio at the collapse state of the frames ranges from 1.5% to 10%. It is also found that the ratio of critical pulse period to natural period of SMRF structures is between 2.3 and 2.9. Moreover, the fragility analysis reveals that collapse intensity equivalent to 10% of exceedence for near-fault motions is 70% to 85% less than far-fault records.

Fictional States & Atomized Public Spheres: A Non-Western Approach to Fragility

This essay explains why political order in some places gives way to especially persistent conflict and prolonged state institutional collapse. State failure is rooted in decades of personalist rule, as leaders have sought to fragment and disorganize institutions and social groups that they thought would be possible bases of opposition. This problem was considered particular to sub-Saharan Africa, but now parts of the Middle East and Central Asia exhibit this connection between a particular type of authoritarian rule and state failure. State failure in these countries produces multisided warfare that reflects the fragmentation upon which prewar regimes relied for their protection. Policy-makers are thus faced with the dilemma of propping up personalist regimes that present themselves as bulwarks against disorder at the same time that their domestic strategies of governance play a central role in creating the conditions of protracted multisided warfare in the event that they fail.

Collapse State of Multi-Storey Masonry Walls Reinforced by Steel Ties Subjected to In-Plane Horizontal Loads

The determination of the seismic strength of masonry building is strictly connected to the in-plane strength of masonry walls under the action of horizontal forces. Simplified criteria are currently available in literature, based on modelling of the structure as loaded by dead loads and by a gradually increasing distribution of horizontal forces, proportional to the mass of the building. According to this approach, called push-over method, the seismic strength of the building corresponds to the intensity of these gradually increasing horizontal loads, leading the building to the failure condition. This paper moves in the framework of the Limit Analysis, based on the Heyman’s masonry model (1966), rigid in compression with no tensile strength. The resistant model refers to a multi-storey wall with openings arranged in regular patterns, along both vertical and horizontal directions, reinforced at floor levels by steel ties. The in-plane failure of the regular multi-storey walls can occur with the development of various kinematically admissible mechanisms, characterized by the attainment of the yielding state in the steel ties. The proposed methodology consists in the definition of the mechanism along which the failure effectively occurs and in a subsequent check of the statical admissibility of the internal stress state at the limit load. Only in this case, the corresponding kinematical multiplier is the effective collapse multiplier. The presence of the panels situated above the openings strongly conditions the in-plane failure of the wall, acting as diagonal struts, causing different horizontal displacements between the piers at the floor levels and consequently engaging the horizontal ties in the mechanism. In order to ensure the development of the global failure, avoiding local brittle failures, steel strengths of the ties have thus to be suitably defined. Finally, a parametric investigation is carried out considering different geometries of masonry walls and varying the position of the piers self-weights and the horizontal forces distribution, constant or proportional to the height of the masses from the foundation level.

The Research on the Affect of Collapse State and Bearing Capacity of the Soil Layer Properties Adjacent to the Bearing Plate of the Multi-Extruded-Expanded-Plates Pile

This paper introduces the research status and analysis of the Multi-Extruded-Expanded-Plates pile (the MEEP pile) at home and abroad, by studying when the plate of pile embedded in different characteristics soil layer, the thickness, physical properties of upper and lower soil layer adjacent to the soil with plate cause the influence on soil break and bearing capacity of the soil layer with plate, analyzing the work together with pile and soil in different soil layer, providing a theoretical basis to improve the calculation formula of bearing capacity of single pile, ensuring the rationality and reliability of the design of the MEEP pile.