Critical Drift Research Articles

Au-delà du miroir : Signe, référentialité et interprétation dans le roman francophone

At the origins of this study, we find an assessment of a problematic, implied relationship between the representation of the world in Francophone novels and the Francophone socio, historical-political reality. The proximity between the literary text and reality is assumed by too many critics and reduces the essentially interpretative function of literary texts, particularly fiction texts. This approach treats the text as a document without always realising that the dual language of the text acts as an invisible and distorting screen. Of course, this critical drift is certainly the result of the beginning of a relationship between reality, experience, praxis and representation. This relationship is important to be approached from a more holistic perspective in order to understand its inner workings, its structure. By necessity, the postcolonial Francophone text is a text in translation that invites translating reading. The question of interpretation and hermeneutical tools arises within the very textual production. This methodologically feeds a practice that escapes the philological frameworks imposed by the various political bodies that control the text. It is a fact that the reference world deployed by authors does not always correspond to that of the receiver of the text. This is particularly the case in texts which, without being explicitly translated, undergo constraints. To clarify our subject and approach, we must remember that the function of this dimension of the translator depends on the informal mother language and its visibility in the text. Using extracts from Francophone Maghrebi novels, we demonstrate the function of the linguistic sign and its referentiality in a very particular literary language.

Seismic behavior of unreinforced and confined masonry walls using innovative sintered insulation shale blocks under cyclic in-plane loading

An innovative masonry unit, sintered insulation shale block, is produced with excellent thermal insulation performance and high compressive strength. In order to provide comprehensive understanding of the seismic behavior of sintered insulation shale masonry wall and promote the application in the severe cold region, seven prototype single leaf wall specimens test under the cyclic in-plane loading corresponding with the constant vertical load, including the unreinforced masonry and confined masonry walls. Previous research has indicated the tie-columns could enhance the seismic behavior of common masonry walls, and we further set out thin reinforced concrete bonds to connect the end tie-columns and hinder the brittle destruction of masonry. The main investigated parameters are axial load ratio, comprehensive effect of construction measures and aspect ratio. Thereafter, the failure mechanism, hysteretic behavior, deformation and strength capacity comparatively conducted between the tested specimens. The axial load ratio significantly impacts the failure modes. Moreover, the higher axial load would result in severe brittle destruction presenting crushed webs and shells for shear effect, which also causes the relatively fast decrease of strength after the maximum strength. The tie-columns corresponding to reinforced concrete bonds play a crucial role to improve the seismic behavior, in particular the maximum strength and ultimate deformation. Nevertheless, the effective constraint would not reverse the brittle destruction failure induced by the SIS masonry. Finally, the formulas propose to predict the critical stress and drift in the skeleton hysteresis curves. For example, the reinforcement yield strength and ductility use as the main parameters to determine the maximum stress and ultimate drift, respectively. Moreover, the formula results are in agreement with the experimental results.

Linear theory of current driven ion acoustic instability at the distance 0.3 to 1 AU from the Sun

Several kinds of instabilities are often observed in the solar wind. We studied the linear theory of the current-driven electrostatic ion acoustic instability at frequencies near the ion cyclotron frequency at distances from the Sun over 0.3 to 1 AU. The properties of current driven electrostatic ion-acoustic instability are investigated. The instability parameters, such as angular wave frequency, the critical drift velocity and the growth rate are calculated. We used the dispersion relation in hot magnetized plasma to calculate the current driven ion acoustic instability properties. To determine the critical drift velocity and the growth rate a full numerical solution of the dispersion relation equation is carried out. Since the growth rate of instability depends on the wave normal angle, the drift velocity of the electron along the magnetic field and the ion thermal cyclotron radius, the calculation is carried out for ranging of the wave normal angles, drift velocities and ion thermal cyclotron radius. The results show that the growth rate of instability increases with increasing distance from the Sun. The growth rate of instability increases with decreasing the wave normal angle, but the critical drift velocity decreases with decreasing the wave normal angle.

Implantation-free edge termination structures in vertical GaN power diodes

Gallium nitride (GaN) is a promising candidate for power applications, due to its superior electrical properties such as high critical breakdown field and saturation drift velocity. The recent emergence of GaN substrates with low defect densities has made it feasible to develop efficient vertical GaN power diodes. However, the breakdown voltage of these diodes is far from the theoretical value, due to the lack of suitable edge termination techniques in GaN such as junction termination extension (JTE). This is attributed to the processing challenges in fabricating GaN power diodes where it is difficult to form p-type regions through implantation. This work addresses this challenge and proposes the design, optimization, and a comprehensive design methodology for implantation-free, edge termination techniques such as field plate (FP), single and multi-etch JTE, and a hybrid FP-JTE structure, suitable for vertical GaN diodes. The proposed approaches demonstrate that close to theoretical breakdown voltages (>80%) are achievable, with greater area efficiency, simple processing, and high tolerance in process variation.

A New Method for Seismic Collapse Assessment of Mid-Rise Concrete Buildings

Collapse is the most critical performance level of seismic assessment of concrete buildings. Most of the conventional collapse assessment methods employ incremental dynamic analysis (IDA) for an equivalent single degree of freedom system. Meanwhile, the ambiguity about the stories, where the maximum engineering demands (such as drifts) occur, has raised grave doubts about the efficiency of the IDA for the conventional collapse assessment approach. This study proposes a new method to overcome this shortcoming by improving the existing IDA-based technique. For this purpose, a matrix is made up of drifts resulted from a pushover analysis of a multi-degree of freedom frame. This matrix of critical drifts is employed in the interpretation of the IDA results. Therefore, those stories, that experience partial collapse, are identified. To illustrate how the proposed methodology is implemented, two sets of 7- and 10-story typical building frames are modeled. It is assumed that they would fail in the flexural mode, and also the premature failure of the joints would never occur under seismic excitations. This new methodology results in a more conservative assessment of the collapse capacity in comparison with the IDA-based conventional method. Therefore, the proposed method is reliable enough to predict the building collapse possibility. In this method, the uncertainty associated with the estimated collapse limit state is lower than the conventional approach evaluation.

Stochastic differential equations with critical drifts

We establish the well-posedness of SDE with the additive noise when a singular drift belongs to the critical spaces. We prove that if the drift belongs to the Orlicz-critical space Lq,1([0,T],Lxp) for p,q∈(1,∞) satisfying 2q+dp=1, then the corresponding SDE admits a unique strong solution. We also derive the Sobolev regularity of a solution under the Orlicz-critical condition.

Исследование взаимосвязи между теоретическим и фактическим радиусами поворота гусеничной машины с помощью математического моделирования

Introduction. Determination of the traction force and power required in a turn by a tracked ve-hicle is based on analytical dependencies given in classical literary sources. In this case, the de-pendence of the theoretical and actual turning radius is usually not described accurately enough. Subject of study. A study of the dependence of the theoretical and actual turning radius and the influence of the parameters of the undercarriage of the tracked vehicle, the characteristics of the support base and the mode of movement on it was made. Methodology and methods. The study was carried out using a specially developed stationary rotation tracked vehicle (TV) model, which differs by taking into account the redistribution of nor-mal reactions and implementation, allowing one to quickly carry out multifactorial experiments. The rotation of the TV in the model is described as a plane motion of a rigid body. In contrast to the classical approaches, the model allows one to study the rotation of the TV at a speed close to the critical drift. Results and scientific novelty. During computational experiments, the parameters of the chassis of the TV, the properties of the support base, as well as the speed of movement and the actual turn-ing radius were varied. It was found that the classical dependences of the actual and theoretical turning radius need to be refined when driving at a speed close to the critical drift, while the form of the dependence is determined by the height of the center of mass of the TV. Practical significance. These features should be taken into account both when assessing the speed of the vehicle and determining the required thrust-to-weight ratio, and when working on the development of active safety systems for tracked vehicles.

Dust-ion-acoustic modes at comet 67P/Churyumov-Gerasimenko

The dynamics of dust-ion-acoustic (DIA) modes at Comet 67P/Churyumov-Gerasimenko, where H2O+ ions with warm and cold electrons as well as dust grains were detected, are investigated within the two-electron-temperature dusty plasmas model by the kinetic theory. In terms of current-driven DIA waves, the bulk electron drift is assumed to overcome Landau damping due to resonance interaction of DIA waves with cometary ions. The results show that the presence of charged dust grains lowers the critical drift velocity of bulk electrons and the Landau damping rates, and inversely enhances the growth rates of DIA instabilities. Consequently, the presented dust grains make the DIA modes more easily excited. The present results indicate that the DIA wave may be a possible candidate to interpret the wave observation of the European Space Agency's spacecraft “Rosetta” at comet 67P/Churyumov-Gerasimenko.

Concrete panel thickness demand for the design of composite steel plate shear wall

SummaryComposite steel plate shear walls (C‐SPWs) are composed of an infill steel plate and reinforced concrete encasements. With an adequate thickness, the concrete encasement can effectively prevent the premature buckling of the infill steel plate. Researchers have provided nonconservative concrete thickness demands through analyses of approximate elastic buckling, for which the analytical model is too simplistic to simulate C‐SPW buckling. In this paper, the buckling of C‐SPW is addressed using a nonlinear finite element method. To assist this method, a formula for the buckling strength of C‐SPW is theoretically developed. Utilizing the results of nonlinear finite element analysis on C‐SPW, the effects of concrete panel thickness, concrete elastic modulus, infill steel plate thickness, panel aspect ratio, and stud spacing on the infill steel plate buckling are analyzed, and the critical drift ratio corresponding to the buckling of the infill steel plate is obtained. According to the criterion that the C‐SPW will not buckle until its drift ratio achieves the drift limit (0.4%), the minimum concrete panel thicknesses demands are captured from finite element analysis. Fitting these predicted minimum concrete thicknesses, an available formula is proposed for the concrete thickness demand in the design of C‐SPW.

The frog model on trees with drift

We provide a uniform upper bound on the minimal drift so that the one-per-site frog model on a $d$-ary tree is recurrent. To do this, we introduce a subprocess that couples across trees with different degrees. Finding couplings for frog models on nested sequences of graphs is known to be difficult. The upper bound comes from combining the coupling with a new, simpler proof that the frog model on a binary tree is recurrent when the drift is sufficiently strong. Additionally, we describe a coupling between frog models on trees for which the degree of the smaller tree divides that of the larger one. This implies that the critical drift has a limit as $d$ tends to infinity along certain subsequences.

Stochastic ODEs and stochastic linear PDEs with critical drift: regularity, duality and uniqueness

In this paper linear stochastic transport and continuity equations with drift in critical $L^{p}$ spaces are considered. In this situation noise prevents shocks for the transport equation and singularities in the density for the continuity equation, starting from smooth initial conditions. Specifically, we first prove a result of Sobolev regularity of solutions, which is false for the corresponding deterministic equation. The technique needed to reach the critical case is new and based on parabolic equations satisfied by moments of first derivatives of the solution, opposite to previous works based on stochastic flows. The approach extends to higher order derivatives under more regularity of the drift term. By a duality approach, these regularity results are then applied to prove uniqueness of weak solutions to linear stochastic continuity and transport equations and certain well-posedness results for the associated stochastic differential equation (sDE) (roughly speaking, existence and uniqueness of flows and their $C^\alpha$ regularity, strong uniqueness for the sDE when the initial datum has diffuse law). Finally, we show two types of examples: on the one hand, we present well-posed sDEs, when the corresponding ODEs are ill-posed, and on the other hand, we give a counterexample in the supercritical case.

Counter-Doped Multizone Junction Termination Extension Structures in Vertical GaN Diodes

GaN is an attractive wide bandgap semiconductor for power applications, owing to its superior electrical properties, such as high critical electric field and saturation drift velocity. Recent advancements in developing native GaN substrates has drawn attention toward exploring vertical GaN power diodes with high breakdown voltages (VBR). In practice, effective edge terminations techniques, such as junction termination extension (JTE) structures, play a crucial role in realizing high-voltage devices. Though certain challenges in fabricating GaN diodes, such as difficulty in forming p-type region, makes it difficult to realize edge termination, hence impeding the development and adoption of such devices. This paper aims to address these challenges by presenting the design and methodology of forming multi-zone, counter-doped JTE structures in vertical GaN diodes, which attains close to theoretical breakdown voltage for a wide range of tolerance in implant dose variation. Extensive device simulations using experimental data and including the effects of surface charges and implant profiles, are performed to present realistic results. The results suggest that >80% of ideal VBR is achievable for a wide range of doping concentration ( $2.4\times 10^{17}$ cm $^{-3}$ ) with a maximum VBR reaching 96% of the ideal value. This paper serves as the first step toward leveraging the current challenges in the fabrication of GaN diodes, by proposing optimum design techniques for realizing vertical GaN diodes with high breakdown voltages.

Nonintersecting Brownian bridges on the unit circle with drift

Nonintersecting Brownian bridges on the unit circle form a determinantal stochastic process exhibiting random matrix statistics for large numbers of walkers. We investigate the effect of adding a drift term μ to walkers on the circle conditioned to start and end at the same position. For each return time T<π2 we show there exists a critical drift μc(T) such that if |μ−2πm/T|<μc(T) for some integer m then the expected winding number for each walker is asymptotically m. In addition, we compute the asymptotic distribution of total winding numbers in the double-scaling regime in which the expected number of walkers with winding number not equal to m is finite. The method of proof is Riemann–Hilbert analysis of a certain family of discrete orthogonal polynomials with varying complex exponential weights. This is the first asymptotic analysis of such a class of polynomials. We determine asymptotic formulas for these polynomials as the degree of the polynomial grows large and demonstrate the emergence of a second band of zeros by a mechanism not previously seen for discrete orthogonal polynomials with real weights.

Current-Driven Low-Frequency Electrostatic Waves in a Collisional Strongly Coupled Magnetized Dusty Plasma

Current-driven low-frequency electrostatic waves are studied in a collisional strongly coupled magnetized dusty plasma. The theoretical model for the longitudinal and transverse modes is developed in the regime $\omega \tau _{m} \ll 1$ for the collisional strongly coupled magnetized dusty plasma in the presence of drifting currents. It is observed that the dispersion properties of low-frequency electrostatic waves are modified under the effect of magnetic field-aligned drifting ion currents in a strongly coupled collisional magnetized dusty plasma. The frequency rate and growth rate of longitudinal and transverse modes increase with normalized wave number. Moreover, the growth rate of unstable waves is destabilized with normalized drift velocity of ions for both longitudinal and transverse modes. The critical drift velocity of ions decreases with normalized wave number but increases with increase in the strong correlation parameter $\Gamma $ . The effect of strong coupling parameter on the frequency and growth rate of low-frequency electrostatic modes in the presence of current drift and collisions is also investigated.

Effects of Ground Motion Directionality on the Seismic Behavior of Mid-rise Concrete Buildings with Considering Unequal Live-Load Distribution in Height

The incident angle of ground motion is one of the sources of uncertainty in the seismic response of buildings. Moreover, understanding the structural response to the impose ground motion may cause significant changes in the maximum response of buildings. In order to investigate the influence of the spatial distribution of orthogonal components of earthquake strong motion on the structural responses, three 15-story buildings were analyzed in this study using the time-history method. A significant live load (750 kg/m2) is imposed at different vertical levels of the structures. The imposed load was combined with ground motion excitations in the range of 0 to 90 degrees. The response of structure was investigated using roof drift index and inter-story drift ratio. Results demonstrate the orientation of seismic excitation and considering the maximum values of roof drift index, which correspond to the critical direction increase roof drift index between 8 to 12 percent. Furthermore, the inter-story drift ratio increased between 30 to 33 percent due to the orientation of excitation and considering the maximum values of the inter-story drift ratio, which correspond to the critical direction.

Number of particles absorbed in a BBM on the extinction event

We consider a branching Brownian motion which starts from $0$ with drift $\mu \in \mathbb{R}$ and we focus on the number $Z_x$ of particles killed at $-x$, where $x>0$. Let us call $\mu_0$ the critical drift such that there is a positive probability of survival if and only if $\mu>-\mu_0$. Maillard \cite{maillard2013number} and Berestycki et al. \cite{berestycki2015branching} have study $Z_x$ in the case $\mu \leq -\mu_0$ and $\mu\geq \mu_0$ respectively. We complete the picture by considering the case where $\mu>-\mu_0$ on the extinction event. More precisely we study the asymptotic of $q_i(x):=\mathbb{P}\left(Z_x=i,\zeta_x \mu_c$.

The obstacle problem for the fractional Laplacian with critical drift

We study the obstacle problem for the fractional Laplacian with drift, $$\min \{(-\varDelta )^su + b \cdot \nabla u,\,u -\varphi \} = 0$$ in $$\mathbb {R}^n$$ , in the critical regime $$s = \frac{1}{2}$$ . Our main result establishes the $$C^{1,\alpha }$$ regularity of the free boundary around any regular point $$x_0$$ , with an expansion of the form where $$e \in \mathbb {S}^{n-1}$$ is the normal vector to the free boundary, $$\sigma >0$$ , and $$c_0> 0$$ . We also establish an analogous result for more general nonlocal operators of order 1. In this case, the exponent $$\tilde{\gamma }(x_0)$$ also depends on the operator.

Hölder estimates for fractional parabolic equations with critical divergence free drifts

This work focuses on drift-diffusion equations with fractional dissipation (−Δ)α in the regime α∈(1/2,1). Our main result is an a priori Hölder estimate on smooth solutions to the Cauchy problem, starting from initial data with finite energy. We prove that for some β∈(0,1), the Cβ norm of the solution depends only on the size of the drift in critical spaces of the form Ltq(BMOx−γ) with q>2 and γ∈(0,2α−1], along with the Lx2 norm of the initial datum. The proof uses the Caffarelli/Vasseur variant of De Giorgi's method for non-local equations.

Resolving critical dimension drift over time in plasma etching through virtual metrology based wafer-to-wafer control

As semiconductor devices are scaled down to sub-20 nm, process window of plasma etching gets extremely small so that process drift or shift becomes more significant. This study addresses one of typical process drift issues caused by consumable parts erosion over time and provides feasible solution by using virtual metrology (VM) based wafer-to-wafer control. Since erosion of a shower head has center-to-edge area dependency, critical dimensions (CDs) at the wafer center and edge area get reversed over time. That CD trend is successfully estimated on a wafer-to-wafer basis by a partial least square (PLS) model which combines variables from optical emission spectroscopy (OES), VI-probe and equipment state gauges. R2 of the PLS model reaches 0.89 and its prediction performance is confirmed in a mass production line. As a result, the model can be exploited as a VM for wafer-to-wafer control. With the VM, advanced process control (APC) strategy is implemented to solve the CD drift. Three σ of CD across wafer is improved from the range (1.3–2.9 nm) to the range (0.79–1.7 nm). Hopefully, results introduced in this paper will contribute to accelerating implementation of VM based APC strategy in semiconductor industry.

Analytical study of effects of positron density and temperature anisotropy on electrostatic ion cyclotron instability

The effects of the positron concentration and ion temperature anisotropy on the electrostatic ion cyclotron instability are studied analytically, in a magnetized electron-positron-ion plasma with temperature anisotropy, using the linear kinetic theory. Positrons and electrons are supposed to drift either in the same direction or in opposite directions relative to singly ionized stationary ions and parallel to the magnetic field. The dispersion relation of the electrostatic ion cyclotron waves is derived, and then the conditions for exciting the instability of the waves are investigated. Moreover, the condition for the marginally stable state is also studied. It is found that as the positron concentration and perpendicular ion temperature increase, the growth rate of the electrostatic ion cyclotron instability decreases, whereas the critical drift velocity increases. It is also found that for the chosen set of parameters, with electrons and positrons drifting in the same direction, the instability in the plasma is stronger than when the electrons and positrons drift in opposite directions. In addition, a comparison is made to the normal electron-ion plasma.