Resistive Wall Research Articles

The theory of kinetic effects on resistive wall mode stability in tokamaks

Tokamak fusion plasmas benefit from high pressures but are then susceptible to modes of instability. These magnetohydrodynamic (MHD) modes are macroscopic distortions of the plasma, but certain collective motions of individual particles can provide stabilizing effects opposing them. The presence of a resistive wall slows the mode growth, converting a kink to a resistive wall mode (RWM). A kinetic MHD model includes Maxwell's equations, ideal MHD constraints, and kinetic effects included through the pressure tensor, calculated with the perturbed drift-kinetic distribution function of the particles. The kinetic stabilizing effects on the RWM arise through resonances between the plasma rotation and particle drift motions: precession, bounce, and transit. A match between particle motions and the mode allows efficient transfer of energy that would otherwise drive the growth of the mode, thus damping the growth. The first approach to calculating RWM stability is to write a set of equations for the complex mode frequency in terms of known quantities and then to solve the system. The “energy principle” approach, which has the advantage of clarity in distinguishing the various stabilizing and destabilizing effects, is to change the force balance equation into an equation in terms of changes of kinetic and potential energies, and then to write a dispersion relation for the mode frequency in terms of those quantities. These methods have been used in various benchmarked codes to calculate kinetic effects on RWM stability. The theory has illuminated the important roles of plasma rotation, energetic particles, and collisions in RWM stability.

Structural performance of balloon mass timber shear walls under in-plane lateral loads

Balloon-type mass timber shear walls are one of the most efficient structural systems to resist lateral loads induced by earthquakes or high winds. They are a viable solution for high-rise buildings, since they endure several key advantages, such as reducing connections and avoiding accumulating compression perpendicular to grain in the floors. This system, however, is not included in the 2020 National Building Code of Canada and has no design guidelines in the 2019 Canadian Standard for Engineering Design in Wood, so it is out of reach of most designers. A multi-year research project has been initiated at FPInnovations to quantify the system performance and develop the necessary technical information to codify balloon-type mass timber shear walls. This paper presents results of an analytical study on the structural performance of balloon-type CLT shear walls. A mechanics-based analytical model was updated to predict the CLT panel resistance, in addition to predicting the deflection and resistance of balloon type CLT shear walls. The influence of specific key parameters such as wall length and thickness, aspect ratio, vertical loads, and vertical joints, on the structural performance of this wall system under lateral loads was investigated using the updated model. The results of this study will give a valuable insight into the seismic performance of balloon type CLT shear walls.

Experimental clarification of the lateral performance of squat mud infill walls in the timber frames of traditional Japanese residential houses

This paper presents the experimental results of squat mud infill walls with three different height aspect ratios in the timber frames of traditional Japanese residential houses. The deformation and failure characteristics, lateral load-carrying mechanism, and influence of the height aspect ratio on the lateral behavior of squat mud walls are investigated. We observed that when the height aspect ratio of the mud wall is less than 0.5, the initial failure is dominated by corner crushing rather than by shear failure. The lateral stiffness of the squat mud wall is positively correlated with the wall height, whereas the drift angle corresponding to the bearing capacity exhibits an inverse relationship with the wall height. For a height aspect ratio less than 0.3, the internal deformation of the squat mud wall is primarily driven by the deformation angle related to corner crushing and sliding. However, when the height aspect ratio increases to 0.5, the rotation angle increases significantly. The transformation of the deformation characteristics and internal force distribution of the squat mud wall depends on the interplay between the wall height aspect ratio and friction coefficient between the mud wall and timber frame. Drawing from comparative experiments and internal force analysis, the lateral resistance of the squat mud infill wall can be separated into two groups of elements: Qc and Qc’, stemming from the corner compression between the mud wall and adjacent timber frame or internal timber laths, respectively, which exhibits a significant positive correlation with the wall height; Qf and Qg, attributed to the frictional force of the protruding ends of bamboo laths and the gravitational force of the squat mud wall, respectively, which exhibit a consistent behavior unaffected by alterations in the wall height.

Assessment of critical parameters affecting the behaviour of bearing reinforced concrete walls under fire exposure

PurposeThis research paper aims to investigate reinforced concrete (RC) walls' behaviour under fire and identify the thermal and mechanical factors that affect their performance.Design/methodology/approachA three-dimensional (3D) finite element (FE) model is developed to predict the response of RC walls under fire and is validated through experimental tests on RC wall specimens subjected to fire conditions. The numerical model incorporates temperature-dependent properties of the constituent materials. Moreover, the validated model was used in a parametric study to inspect the effect of the fire scenario, reinforcement concrete cover, reinforcement ratio and configuration, and wall thickness on the thermal and structural behaviour of the walls subjected to fire.FindingsThe developed 3D FE model successfully predicted the response of experimentally tested RC walls under fire conditions. Results showed that the fire resistance of the walls was highly compromised under hydrocarbon fire. In addition, the minimum wall thickness specified by EC2 may not be sufficient to achieve the desired fire resistance under considered fire scenarios.Originality/valueThere is limited research on the performance of RC walls exposed to fire scenarios. The study contributed to the current state-of-the-art research on the behaviour of RC walls of different concrete types exposed to fire loading, and it also identified the factors affecting the fire resistance of RC walls. This guides the consideration and optimisation of design parameters to improve RC walls performance in the event of a fire.

“Making Peace With Oneself”: Internal Conflict in Addictions and Its “Resolution” in Therapeutic Group Interactions

"Counselors and therapists on addictions and recovery from addictions are employing a variety of methods and techniques to break through the wall of denial and resistance. Accordingly, new methods of research are needed in order to describe and eventually understand the phenomenon of addictions and the ways of recovery from addictions. The paper attempts to define and describe the internal conflict and the way it is brought to the surface and “resolved” (processed and eventually transformed) in therapeutic group interactions. For that, we are using a phenomenological approach to conceptualize addiction in terms of connectedness and methods inspired by the analysis of interactions in order to document the transformative experience necessary for the recovery from addiction. Keywords: addiction; recovery from addictions transformative experience; internal conflict; therapeutic group; phenomenological approach; analysis of interactions. "

Design and manufacturing of resistive wall mode control coil of JT-60SA

Resistive wall mode control coils (RWMCs) will be installed in the vacuum vessel of JT-60SA. Since 200 °C baking of vacuum vessel on JT-60SA is performed to remove the impurity in the plasma facing components, in-vessel components must be made with heat-resistant materials such as metal and ceramic or must be cooled with water. We looked for the heat-resistant organic insulator for JT-60SA RWMC and performed the heat resistant test for several resins. However, no resin passed the test (Sukegawa et al., 2015). We again performed the heat resistant test of several organic insulator in the circumstances without air and finally found that the some Bismaleimide–Triazine (BT) resin has enough heat resistance without air. We designed the eight-turn RWMC with the BT resin. Based on this design, the specification of RWMC and power supply requirement are decided. For the design of RWMC, the finite element (FEM) analysis of electromagnetic force during disruption and thermal stress during baking and operation were performed. Manufacturing of the RWMC has already launched.

Interplay of plasma resistivity and rotation on β limits in free boundary diverted tokamaks

A plasma resistivity-β driving mechanism aimed at explaining the appearance of long wavelength global instabilities in free boundary high-β tokamak plasmas with a divertor is presented. These perturbations resemble very closely the resistive wall mode phenomenon. Performing a proper toroidal analysis, we show that the magnetohydrodynamic stability is worsened by the interplay of plasma β and resistivity. By modelling the effect of a magnetic separatrix through a careful positioning of the resonant surfaces, we find that in an ideal plasma wall effects are effectively screened, so that the ideal β limit becomes independent of the wall position/physics. A lower wall dependent critical β is found if plasma resistivity is allowed. We find that global stability can be improved with a toroidal flow, small enough not to induce equilibrium modification. The rotation stabilisation effectiveness depends upon the proximity of the plasma equilibrium parameters to the resistive marginal boundary.

IMPACT RESISTANCE ASSESSMENT OF INTERLOCKING COMPRESSED EARTH BRICKS (ICEB) INCORPORATING CRUMB RUBBER

Interlocking compressed earth bricks (ICEB) are a cleaner and sustainable alternative to conventional fired bricks and it has comparable strength to other masonry systems, making it feasible for both cladding and load-bearing purposes. However, it tends to be brittle and has poor performance under impact loading. Impact resistance of masonry walls are important as one of the main purposes of cladding is to protect its occupants from external projectiles. This study was commissioned to investigate the feasibility incorporating both crumb rubber (CR) and treated CR into ICEBs in place of sand to improve its impact resistance. The drop weight impact tests carried out concluded that ICEBs containing CR have better impact resistance and this was further improved with heat-treated CR. Heat-treated CR ICEBs also had less catastrophic failure compared to untreated CRs which had pieces of materials spalling off. Mechanical tests also show that this improvement in impact resistance comes at the expense of a minor loss in compressive and flexural strength at replacement levels higher than 7.5 %. Heat-treated CRs also showed higher losses of mechanical strength compared to untreated CRs.

The Hodge decomposition of shell current on the Keda Torus eXperiment device

The Hodge decomposition is a valuable tool for uniquely decomposing total currents on the composite shell into three types: inductive current, halo current, and harmonic current, each with its specific physical meaning. During plasma disruptions, halo currents appear, essential for studying the wall’s thermal load and electromagnetic force. Furthermore, understanding halo currents is crucial for improving the existing methodologies by removing their effects on equilibrium reconstructions and instability analyses based on boundary magnetic probe data. On the Keda Torus eXperiment (KTX) device, radial and tangent halo currents can be simultaneously provided to locate the contact region during a minor disruption experimentally. Additionally, experimental results demonstrate that, in addition to the occurrence of halo current during minor disruption events, halo current is already present simultaneously with the generation of inductive current when a resistive wall mode exists. For devices that lack the capability to measure the two-dimensional shell current distribution on the entire shell, we propose a method to estimate inductive and halo currents only using a set of shell currents along the toroidal direction. This technique is demonstrated on the KTX device and provides an overall good approximation of the inductive and halo current distribution.

Ferroelectric Domain Wall p-n Junctions.

We have used high-voltage Kelvin probe force microscopy to map the spatial distribution of electrical potential, dropped along curved current-carrying conducting domain walls, in x-cut single-crystal ferroelectric lithium niobate thin films. We find that in-operando potential profiles and extracted electric fields, associated with p-n junctions contained within the walls, can be fully rationalized through expected variations in wall resistivity alone. There is no need to invoke additional physics (carrier depletion zones and space-charge fields) normally associated with extrinsically doped semiconductor p-n junctions. Indeed, we argue that this should not even be expected, as inherent Fermi level differences between p and n regions, at the core of conventional p-n junction behavior, cannot occur in domain walls that are surrounded by a common matrix. This is important for domain-wall nanoelectronics, as such in-wall junctions will neither act as diodes nor facilitate transistors in the same way as extrinsic semiconducting systems do.

Development of KER-012, a modified ActRIIB ligand trap, for the treatment of pulmonary arterial hypertension

Abstract Background Pulmonary Arterial Hypertension (PAH) is a debilitating disorder characterized by elevated pulmonary vascular resistance (PVR) due to severe constriction obliteration of pulmonary vessels (Tielemans 2019). The pathology of PAH is driven by endothelial dysfunction and vascular remodeling that leads to increased wall thickening and resistance to blood flow. Dysregulated TGF-β, specifically SMAD signaling, is a key molecular defect in proliferative thickening of pulmonary arterioles in PAH leading to increased arterial pressure and compensatory right ventricular hypertrophy, ultimately resulting in decompensated right heart failure. Increased levels of activin A, a TGF-β superfamily ligand, have been found in PAH patients, and in the lungs of hypoxia-induced pulmonary hypertensive mice (Yndestad 2009). KER-012 is an investigational modified ActRIIB ligand trap designed to bind and inhibit activin A, activin B, GDF8 and GDF11 to maximally inhibit SMAD2/3 (pro proliferative), while permitting SMAD1/5/9 (anti-proliferative) signaling. This profile is expected to rebalance defective SMAD signaling in PAH and potentially delay or reverse disease progression. Aim To evaluate safety and tolerability of KER-012 in healthy post-menopausal women (PMW) and present the planned design of a Phase 2 trial in participants with PAH. Methods A two-part Phase 1 study has been conducted with KER-012 in healthy PMW. Participants received either placebo or a single dose of KER-012 ranging between 0.75 and 5.0 mg/kg in Part 1 or multiple doses between 0.75 and 4.5 mg/kg in Part 2 subcutaneously once every 4 weeks over a 12-week period. Safety, PK and biomarkers of activin target engagement were assessed. Results KER-012 was generally well tolerated at dose levels up to 5 mg/kg as a single dose and at dose levels up to 4.5 mg/kg administered Q4W for a total of 3 doses (Table 1). Maximal target engagement of KER-012, as demonstrated by changes in biomarkers of activin inhibition, namely follicle stimulating hormone (FSH) and bone specific alkaline phosphatase (BSAP), was observed in this study. As previous studies with activin receptor type II ligand traps have shown a potentially dose-limiting increase in erythropoiesis, changes in red blood cells (RBC) were closely monitored in this study. KER-012 did not elicit any changes in hemoglobin or RBC count in the Phase 1 study (Figure 1). Summary KER-012 was generally well tolerated in healthy participants. The observed biomarker changes are consistent with inhibition of activins, suggestive of a balance shift in favor of signaling via the anti-proliferative SMAD 1/5/9 pathway. Based on this mechanism, administration of KER-012 could potentially result in reverse vascular remodeling and clinical cardiopulmonary improvements in patients with PAH, without targeting erythropoietic pathways. Given this profile, KER-012 is being advanced for development in patients with PAH in an upcoming Ph2 clinical trial (Figure 2).

Thermal and optical investigations of various transparent wall configurations and building integrated photovoltaic for energy savings in buildings

The growing global attention on energy consumption in buildings, along with the harmful effects of carbon dioxide emissions on climate change, has recently heightened efforts on sustainability and energy savings in buildings. As a result, the search for high thermal resistance walls, as well as the development of integrated photovoltaic technology with front glass walls to save energy in buildings, is an important and promising topic. The current study investigates and compares the energy-saving capabilities of four building transparent wall configurations: basic glass, facade, basic glass integrated with photovoltaics, and facade integrated with photovoltaics at different ambient temperatures, wind speeds, and solar radiation. The study also introduces a comprehensive three-dimensional heat transfer and electrical model that combines a Steady-State Thermal solution with the ANSYS mechanical solver and a fluid flow solution with the ANSYS Fluent solver to simulate the full layers of Cadmium Telluride solar cells, transparent walls, and the air conditioning room. Each model was subjected to a full-day simulation using Egypt weather conditions in the summer season to evaluate the efficacy in terms of saving artificial lighting loads, thermal loads for air conditioning, daily electricity generation from Cadmium Telluride solar cells, and total energy savings throughout the day. According to the findings, the facade integrated with photovoltaics and basic glass integrated with photovoltaics configurations deliver about 394 Wh/m2 of electrical energy to the building daily. Furthermore, when air conditioning and lighting loads, as well as solar cell productivity, are considered, the facade, basic glass integrated with photovoltaics, and facade integrated with photovoltaics configurations save 46.9%, 31.5%, and 79.3% of total electricity consumption, respectively, when compared to the basic glass wall.

Models of resistive wall tearing mode disruptions

Disruptions are a serious issue in tokamaks. In a disruption, the thermal energy is lost by means of an instability which could be a resistive wall tearing mode (RWTM). During precursors to a disruption, the plasma edge region cools, causing the current to contract. Model sequences of contracted current equilibria are given, and their stability is calculated. A linear stability study shows that there is a maximum value of edge qa≈3 for RWTMs to occur. This also implies a minimum rational surface radius normalized to plasma radius from RWTMs to be unstable. Nonlinear simulations are performed using a similar model sequence derived from an equilibrium reconstruction. There is a striking difference in the results, depending on whether the wall is ideal or resistive. With an ideal wall, the perturbations saturate at moderate amplitude, causing a minor disruption without a thermal quench. With a resistive wall, there is a major disruption with a thermal quench, if the edge qa≤3. There is a sharp transition in nonlinear behavior at qa=3. This is consistent with the linear model and with experiments. If disruptions are caused by RWTMs, then devices with highly conducting walls, such as the International Tokamak Experimental Reactor will experience much milder, tolerable, disruptions than presently predicted.

Design errors during major repairs of apartment buildings

The main design errors during the overhaul of the heating system of apartment buildings on the example of a 5-storey building made of expanded clay concrete panels are considered and analyzed. A comparative analysis of the values of the heat transfer resistance of external walls obtained by calculation and based on the results of experimental data is performed. Based on the obtained values of the heat transfer resistance of the exterior walls, the calculation of the heat losses of the building was performed. As a result of the identified shortcomings, the amount of thermal energy that the residents of the surveyed house located on the territory of the city of Samara did not receive was calculated.

High thermal storage capacity phase change microcapsules for heat transfer enhancement through hydroxylated-silanized nano-silicon carbide

In this study, nano-silicon carbide (SiC) doped tetradecyl octadecanoate (TO) phase change microcapsules with enhanced thermal energy transfer and storage capacity were prepared through interfacial polymerization. Besides, a series of experiments were performed to comparatively investigate the effects of SiC, hydroxylated SiC (H–SiC), and hydroxylated-silanized SiC (Si–H–SiC) on the morphology, chemical structure, thermal storage performance, thermal stability, cyclic thermal stability, thermal conductivity, and exudation stability of prepared phase change microcapsules. The findings show that phase change microcapsules containing 1 wt% Si–H–SiC exhibit the best performance, as evidenced by their large thermal storage capacity (161.54 J/g) and high encapsulation efficiency (69.03 %). The thermal conductivity of Si–H–SiC-doped phase change microcapsules is up to 0.1167 W/m·k, being 17.6 % higher than that of SiC-doped ones. In addition, they show favorable thermal stability and reliability as no leakage is found after 300 thermal cycles, and they barely leak the core material TO after being kept at 120 °C for 2 h. The reason behind this phenomenon is that Si–H–SiC is doped into the shell of phase change microcapsules through chemical bonds and gets evenly distributed, which greatly improves the interfacial thermal resistance and capsule wall strength of phase change microcapsules.

A theoretical investigation on heat transport feature of Sutterby nanofluid flow above a conical surface

ABSTRACT Theoretical analysis is performed to examine the heat convection in hydromagnetic Sutterby nanofluid flow across a cone in the attendance of Darcy-Forchheimer and modified temperature flux effects. The enhanced heat transmission was investigated using Maxwell and interfacial layer (nanolayer) approaches by considering ethylene glycol (EG) based spherical copper (Cu) nanoparticles. An exact model is developed and verified numerically using the bvp5c MATLAB scheme. Simultaneous outcomes are obtained for Maxwell and nanolayer approaches. Pertinent parameters influence on momentum and energy fields is examined via plots and tables. The nanolayer approach reported higher thermal conductivity than the Maxwell approach. Also, modified heat flux commendably improves the heat diffusion rate of Sutterby nanofluid without affecting the wall resistance.

Anti-Malassezia Drug Candidates Based on Virulence Factors of Malassezia-Associated Diseases.

Malassezia is a lipophilic unicellular fungus that is able, under specific conditions, to cause severe cutaneous and systemic diseases in predisposed subjects. This review is divided into two complementary parts. The first one discusses how virulence factors contribute to Malassezia pathogenesis that triggers skin diseases. These virulence factors include Malassezia cell wall resistance, lipases, phospholipases, acid sphingomyelinases, melanin, reactive oxygen species (ROS), indoles, hyphae formation, hydrophobicity, and biofilm formation. The second section describes active compounds directed specifically against identified virulence factors. Among the strategies for controlling Malassezia spread, this review discusses the development of aryl hydrocarbon receptor (AhR) antagonists, inhibition of secreted lipase, and fighting biofilms. Overall, this review offers an updated compilation of Malassezia species, including their virulence factors, potential therapeutic targets, and strategies for controlling their spread. It also provides an update on the most active compounds used to control Malassezia species.

Modulated complexed stenosed region consequences under the electroosmotic stimulation

The present study analyzes the theoretical consequences of slip effects in a complex stenosed region. The flow of blood in a stenosed region is incorporated with hybrid nanofluid features which are being prepared with copper and copper oxide nanoparticles. The flow is also intensified by applying an electric field in the axial direction. The governing equations for the proposed paradigm are solved and the corresponding closed-form solutions are obtained for the cases of mild stenosis. Parameters such as Electro-osmotic, velocity slip and Helmholtz–Smoluchowski are specially focused in this study. The heat transfer, hemodynamic velocity, wall shear stress and resistance impedance for the flow are precisely determined. The various parameters that influence the physical characteristics of flow are plotted, and their effects are discussed in detail. The present model has the potential application in medical pumps for drug delivery systems.

Synthesis of vertically aligned and interconnected BN fiber skeleton for significantly improving thermal conductivity of PVDF

Seeking efficient thermal management materials for electronic components is urgent and important. BN has high thermal conductivity and good insulating properties, making it an ideal polymer filler for improving thermal conductivity. Currently, because of the weak interaction between BN and its high melting point, it is extremely difficult to construct a BN three-dimensional skeleton by direct sintering to achieve efficient heat transfer channels. In this work, vertically aligned BN three-dimensional skeletons with fiber walls were synthesized in one step by combining the in-situ conversion of precursor fibers and directional freeze-drying technology. The precursor fibers were expelled by the directionally grown ice crystals, forming vertically aligned fiber walls. Importantly, molten B2O3 produced during air calcination made the fibers bond to each other, thus obtaining the vertically aligned and interconnected BN fiber skeleton. Benefiting from the short-path fast heat transfer and low interfacial thermal resistance of the fiber walls, the obtained vertically aligned BN skeleton exhibited obvious structural advantages, resulting in composites with a unidirectional thermal conductivity of 1.372 W/(m·K) with the filling content of 25.7 wt% and high enhancement efficiency per unit volume of 32.6 %. This approach is expected to open a new avenue for developing highly thermally conductive composites with great potential.

Estimation of thermal resistance and capacitance of a concrete wall from in situ measurements: A comparison of steady-state and dynamic models

Estimation of thermal resistance and capacitance of a concrete wall from in situ measurements: A comparison of steady-state and dynamic models