Full Collapse Research Articles

Experimental investigation of a partial collapse during the sawtooth instability in EAST

ABSTRACT In this article, partial and full collapses of sawtooth activity are investigated with the high-resolution two-dimensional electron cyclotron emission (ECE) Imaging diagnostic in EAST. The partial collapse in normal sawtooth behavior is detected during the precursor phase of an L-mode plasma heated by ICRF. The electron heat diffusivity is determined with the time-to-peak analysis. The experimental results revealed that heat diffusivity suppresses at the time of the partial collapse. As a result, the partial collapse process interrupts and the small amount of heat releases outward. The hot core survives and is enclosed by the cold magnetic island. The inversion radii are estimated with the help of sawtooth and the only single inversion radius is found during the entire collapse process.

Abstract P563: Prognosis Driven Definition of Carotid Near-Occlusion With Full Collapse

Introduction: Carotid near-occlusion is a severe carotid stenosis causing distal artery collapse of varying degree. Near-occlusion is often divided into a “full collapse” group with a threadlike distal lumen, and the often overlooked “without full collapse” group with a normal-appearing, albeit small, distal lumen. By this division by appearance, symptomatic near-occlusion with full collapse has been reported to have worse short-term prognosis than those without full collapse, no other division has been assessed for prognosis. The aim of this study was to assess if a measurement based definition of full collapse might improve prognostic discrimination. Methods: 99 consecutive patients with symptomatic near-occlusion diagnosed on CT-angiography were included. The risk of preoperative recurrent ipsilateral ischemic stroke within 28 days of presenting event was assessed with Kaplan-Meier analysis, censoring at revascularization. We assessed residual stenosis diameter, distal ICA diameter, ICA-ratio (side-to-side), and ICA-ECA ratio as risk markers. Results: By appearance, the 28-day risk of stroke tended to be higher for full collapse (27%, 11/42) than without full collapse (11%, 6/57), p=0.054 (figure). The best new definition of full collapse was distal ICA diameter ≤2.0 mm and/or ICA ratio ≤0.47. 10 patients were reclassified by this new definition compared to appearance definition, 5 in each direction. By the new definition, 28-day risk of stroke was higher in full collapse (34%, 14/42) than without full collapse (5%, 3/57), p<0.001 (fig 1B). Conclusions: Compared to the appearance based definition, our new definition of separating near-occlusions into with and without full collapse yields similar groups sizes but better prognostic discrimination. This new definition could be used as inclusion criteria in future treatment trials.

Commentary

Commentary

Research on design of the real-time monitoring system for full hall steel tubular scaffolds

Full tubular scaffolds are widely used in substation engineering. However, full hall steel tubular scaffolds collapse can lead mass casualties without effective safety management. The real-time monitoring system for full hall steel tubular scaffolds can prevent collapse accidents. Aiming at the monitoring demand of full hall steel tubular scaffolds, research on design of real-time monitoring system is carried out. This paper mainly discusses system design principle, system function design and system formwork design. The function design part refines the different function permissions of users in different roles, and the framework design part analyzes the composition of the system and the way of data transmission.

Investigating the Current Collapse Mechanisms of p-GaN Gate HEMTs by Different Passivation Dielectrics

In this letter, the dynamic R on degradation mechanisms of the p-GaN gate HEMTs induced by off -state stress are investigated with different passivation dielectrics AlON and SiN. The degradation mechanisms are twofold, including V TH shift and surface trapping in the gate-to-drain access region, whose impacts are successfully distinguished. Surface trapping by SiN passivation is evidently proved to be the dominant factor that can almost induce a full current collapse. The V TH positive shift diminishes the drain current by shrinking the overdrive V GS, which however, can be compensated by a higher V GS overdrive in applications. SiN passivation can effectively suppress the positive bias temperature instability effect, probably by passivating the p-GaN fast traps with hydrogen during passivation. Last, the transient measurements unveil that both the surface trapping and V TH shift have a very slow recovery process.

Pile contribution to slope stability: application to open quays

Foundation piles can contribute to the stability of a slope thorough which they are installed as they have to be sheared or fail in bending for the full collapse of the slope. The classical design of open quays, consisting of a piled platform with a slope beneath, can benefit from the consideration of the piles for its overall stability. The methods currently available for the consideration of piles are the limit equilibrium method (LEM) and the finite-element method. Although the former requires some side computations for the pile contributions, it has the advantage of identifying the failure mode. This can be used to make changes to the piling design in order to increase pile contribution to stability. The LEM approach, by Bishop's method, which considers circular slip surfaces, is particularly practical. A typical quay is studied with both approaches and the main parameters of such projects – pile density, slope angle and soil shear strength – are evaluated. The results of the analyses indicate that the consideration of the piles leads to an increase in the factor of safety of the slope. It is also suggested that the LEM approach can be used to advantage in everyday practice.

CAROTID ARTERY STENTING OF INTERNAL CAROTID ARTERY“NEAR OCCLUSION” STENOSIS – CASE REPORT

Carotid near-occlusion stenosis is distal luminal collapse of the internal carotid artery beyond a tight stenosis. In everyday practice, it is easily misdiagnosed as a conventional high degree stenosis. Because of the different stroke risk, proper differentiation of these two types of lesions is important for the correct treatment decision. Recent data showed no advantage of best medical therapy versus surgical endarterectomy or carotid artery stenting.We report a case of carotid artery stenting of symptomatic ICANO stenosis without full collapse, via transradial approach, in the presence of contralateral ICA (Internal Carotid Artery) “critical” stenosis.This case provides additional data about optimal treatment of these patients, who are often excluded from randomized control trials (RCT’s), but frequently encountered in the cardiovascular practice. Key words: carotid artery stenting, near occlusion stenosis, internal carotid artery

COVIDECONOMICS: The Evaluation of COVID-19 Economic Effects

COVIDECONOMICS: The Evaluation of COVID-19 Economic Effects

Properties of Concrete Containing Palm Oil Fuel Ash and Expanded Polystyrene Beads

This paper investigates the stress strain behaviour of concrete containing Palm Oil Fuel Ash and Expanded Polystyrene, axial compressive strength, tensile strength and modulus of elasticity. EPS-POFA concrete was prepared by substituting fine aggregates with EPS beads and cement replaced with POFA by 10%, 20% and 30%. Results of this study showed that EPS-POFA concrete exhibited low axial compressive strength, peak strain, tensile strength and elastic modulus when the EPS and POFA contents in concrete increased. However, the decrease in axial compressive strength of concretes with containing 10 to 20% EPS and POFA are suitable amount and acceptable to be applied on building structure as per stated in America Concrete Institute 318 with minimum specified compressive strength for structural concrete is 2500 psi (17 MPa). While, the failure of EPS-POFA concrete under axial compression gradually occurred and the concretes were able to retain the load after failure without full collapse. The slope of stress-strain curve of concretes with containing EPS and POFA was lower than that of normal concrete, demonstrating that the normal concrete more brittleness that EPS-POFA concretes.

Progressive geomorphic evolution of reservoir bank in coarse-grained soil in East China – Insights from long-term observations and physical model test

Reservoir bank collapse, as a typical geological hazard, severely affects the geomorphic evolution and safety of residential sites. In this study, a case of Tankeng Reservoir, which is a large reservoir in eastern China is used to analyze a three-dimensional evolution mechanism and deformation characteristics of reservoir bank collapse by years of field investigation, underwater topography measurements and monitoring and corresponding physical modeling experiment. The results show that 90% of the bank collapsed within six years, and a full collapse occurred within nine years for the coarse-grained soil bank. In addition, a three-dimensional progressive pattern for the bank collapse evolution process and a new parameter of stable angles were proposed for first time, and this parameter has practical significance for further scientific calculations of the width and length of bank collapse.

How Long More the World Economy Can Resist the COVID-19 Crisis Pressure?

This research is willing to evaluate how long the world economy can resist COVID-19 crisis pressure. In the present COVID-19 crisis looks unstoppable and uncertain its end. We try to make a serial of simulations using possible slight or extreme scenarios with different environments in the short and long run. The main objective is to offer a specific date until the world economy can likely resist COVID-19 crisis pressure. Finally, we try to evaluate how much developed and developing countries can resist the COVID-19 crisis pressure and find its critical point for recovery or full collapse, respectively.

Post-earthquake fire behavior and performance-based fire design of steel moment frame buildings

This paper presents an assessment of steel buildings subjected to post-earthquake fire, illustrated through the implementation of a ten-story case study building, which was designed in accordance with U.S. design codes. The building is located in a high seismic region (Los Angeles, CA), and designed for the associated seismic hazard levels using perimeter special moment frames (SMFs) to resist lateral (wind and seismic) loading and gravity interior frames with composite floor systems to resist gravity (dead and live) loading. The entire 3D building structure was idealized and analyzed using finite element models capable of modeling inelastic deformations, instability failures, and connection damage due to earthquakes and fire. The building models were subjected to eleven earthquakes followed by three different fire scenarios to simulate the effects of post-earthquake fires. The results from post-earthquake fire analyses were used to assess the impact of earthquake-induced damage on structural behavior and stability during fire. Assessments indicate that, for the type and design of structure considered in this research, earthquake-induced damage is generally limited to the perimeter moment frames and has limited influence on post-earthquake fire performance, which is governed by the strength and stability of gravity columns and floor systems. Analytical parametric studies were conducted to further assess and develop performance-based design guidelines for improving structural behavior and stability during post-earthquake fires. These studies indicate that partial or full collapse of the building structure can be prevented by sufficiently increasing the structural design (size) or fire protection (fireproofing thickness) of the critical gravity columns.

COVID-19 and the Restructuration of the International Trade in Century XXI

COVID-19 and the Restructuration of the International Trade in Century XXI

The Invisible Killer of the Market Economy: The COVID-19

The extensive damage of COVID-19 in the market economy is highly costly and painful worldwide. This research debates how COVID-19 can reduce the massive consumption considerably in the short run. We remark that the market economy's surviving mechanism directly depends on maintaining enormous consumption levels and generating many profits. On the other hand, this research attempts to introduce a new concept entitled "The Massive Constrictioness of Consumption." This new concept involves how a global pandemic such as COVID-19 can generate terror, psychosis, and massive abstentions amongst the buyers in getting goods or services from restaurants, large shopping malls, popular markets, or any plaza. Meanwhile, an enormous constrictioness of consumption can generate the partial or full collapse of business immediately. Finally, this research supports that the massive constrictioness of consumption cannot keep long because it can impact the market economy performance in the short run directly.

Sealing performance and mechanical behavior of PEMFCs sealing system based on thermodynamic coupling

The reliability of sealing system is closely related to the work performance of PEMFCs. The model of steel-strip PEMFCs is established in this paper, the stress-strain distribution of sealing system in single-cell and multi-cells structures under three different working temperature were investigated. Effects of compression ratio, fluid pressure, dislocation and dimension of gasket on the sealing performance and mechanical behavior of PEMFCs were studied. The results show that the sealing performances of single-cell and multi-cells structures are similar under different working temperatures. Temperature has a great influence on the von-Mises stress of sealing system and the deformation of MEA frame. The research results of single-cell can be extended to the multi-cells, but the influence of temperature can't be ignored. With the increasing of compression ratio, fluid pressure and dimension, the sealing performance also be improved. Excessive dislocation may aggravate the deformation of MEA frame. The high stress area appears inside cross section which is prone to cause seal failure and full cells collapse.

Variable area, constant force shock absorption motivated by traumatic brain injury prevention

Compact and efficient energy absorption is desirable for numerous applications including manufacturing, transportation, and protective equipment. An ideal shock absorber is a smart material or structure that can adapt its force-displacement properties to minimize the peak impact force regardless of the impact energy. While traditional shock absorbers can produce precisely-tuned ideal force profiles, they are rigid devices that only compress half of their total length, limiting utility in space-constrained applications. Energy absorbers that are soft and collapsible, such as foams, do not have ideal force profiles and generally have insufficient viscoelasticity to adapt to different impact energies. Here, we present a smart structure concept–variable area shock absorption (VASA)–that leverages a changing contact area in a hydraulically damped collapsible system to passively adapt the force to the minimum necessary to absorb the energy of an impact. Using an analytical fluid dynamics model, we derived the contact area as a function of compression to produce a constant force over the entire stroke of a fixed-orifice damper, and validate this concept experimentally using a preliminary 3D-printed prototype. The VASA prototype follows the constant force profile with a NRMSE between 0.02–0.25 at impact speeds between 2.3 and 4.3 m s−1. This new approach for absorbing energy is compatible with full collapse of the absorber, enabling soft devices for space-constrained applications in future work. Potential applications include helmets that must absorb energy at a near-minimum force level across multiple impact energy levels.

Displacement-Based Simplified Seismic Loss Assessment of Italian Precast Buildings

ABSTRACT Economic losses associated with the structural and non-structural damage occurring after an earthquake are of particular importance in the case of industrial buildings due to the consequences of such losses on the local economy and employment level. The seismic sequences that hit the industrial area of Emilia-Romagna region of Italy in 2012 represent an emblematic example. In this earthquake event, major damage on poorly performing precast structures was recorded: many buildings were severely damaged and experienced partial or full collapse. The level of the recorded damage was related to a design lacking modern seismic detailing and to a non-up-to-date evaluation of the seismic hazard: in fact, several industrial buildings, typically one storey precast reinforced concrete (RC) structures, were designed to transfer horizontal loads (i.e. between roof elements and supporting beam or main girder and supporting columns) through either friction or under-designed mechanical connections. The aim of this paper is to provide insights on the evaluation of direct losses in the case of precast RC structures typical of the Italian industrial sector, particularly for buildings built before the enforcement of modern seismic codes. A simplified displacement-based seismic loss assessment procedure is proposed and applied to a selected case study and comparisons are made with the results obtained from non-linear time history analyses on simplified (i.e. single column models) and complete three-dimensional models. Retrofit solutions are proposed and their influence on the collapse probability of the structural elements and on the economic losses is evaluated.

Investigation of Progressive Collapse Resistance Mechanism in Reinforced Concrete Beam–Column Assembly

Progressive collapse is defined as the spread of an initial local failure of a structure. This phenomenon, caused by the removal of one or more load-bearing elements, is followed by a chain of failures through the structure and ultimately leads to partial or even full collapse of an entire structure. As a result, an accurate understanding of structural behavior subjected to large displacements, caused by progressive collapse, is essential to ensure a safe structural design. In this study, the behavior of the beam–column assembly subjected to progressive collapse was investigated by using finite element software. The results were compared to those of the results published in the literature, and model validation was ensured. The progressive collapse resistance mechanisms in RC beam–column assembly as well as the effectiveness of each mechanism in progressive collapse prevention were investigated. According to the results, the four resistance mechanisms, i.e., flexural action, compressive arch action, plastic hinge formation, and catenary action, have a significant effect on structural behavior.

Minor disruptions triggered by supersonic molecular beam injection on J-TEXT tokamak

Disruption mitigation experiments with supersonic molecular beam injection of argon gas on J-TEXT were conducted to explore the evolution process during multistage minor disruption. The corresponding numerical simulation was performed using a 3D magnetohydrodynamic (MHD) code, namely, NIMROD (Sovinec et al 2004 J. Comput. Phys. 195 355). The experimental and numerical simulation results are shown in the following. The central plasma temperature decreases to less than tens of electovolts after a relatively long period of multistage thermal collapse. Different MHD instability modes appear when the impurity cold front propagates toward the q = 2 surface. During the burst of MHD activity and central plasma thermal collapse, the heat flux is transferred from the core region to the plasma boundary. Further numerical simulation results show that the MHD process is accompanied by a significant increase in the core-oriented spread of impurities through the q = 2 surface. During the transition stage from the minor disruption to the major disruption, the high order modes play an important role and the magnitude of the n = 3 growth rate is even larger than that of the n = 1 or n = 2 mode. What seems to separate major from minor disruptions is that in a minor disruption, a single MHD crash is not sufficient to cause a full radiative collapse.

Axion structure formation – II. The wrath of collapse

ABSTRACT The first paper in this series showed that quantum chromodynamic axion dark matter, as a highly correlated Bose fluid, contains extra-classical physics on cosmological scales. The source of the derived extra-classical physics is exchange–correlation interactions induced by the constraints of symmetric particle exchange and interaxion correlations from self-gravitation. The paper also showed that the impact of extra-classical physics on early structure formation is marginal, as the exchange–correlation interaction is inherently non-linear. This paper continues the study of axion structure formation into the non-linear regime, considering the case of full collapse and virialization. The N-body method is chosen to study the collapse, and its algorithms are derived for a condensed Bose fluid. Simulations of isolated gravitational collapse are performed for both Bose and cold dark matter fluids using a prototype N-body code. Unique Bose structures are found to survive even the most violent collapses. Bose post-collapse features include dynamical changes to global structures, creation of new broad sub-structures, violations of classical binding energy conditions, and new fine structures. Effective models of the novel structures are constructed and possibilities for their observation are discussed.