Fortifying a Buffer Region:

2021 ◽  
pp. 55-62
Author(s):  
Elke Richter
Keyword(s):  
Buffer Region

scholarly journals The Equilibrium Phase Formation and Thermodynamic Properties of Functional Tellurides in the Ag–Fe–Ge–Te System

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1314
Author(s):  
Mykola Moroz ◽  
Fiseha Tesfaye ◽  
Pavlo Demchenko ◽  
Myroslava Prokhorenko ◽  
Nataliya Yarema ◽  
...  
Keyword(s):  
Electromotive Force ◽  
Equilibrium Phase ◽  
Stoichiometric Composition ◽  
Negative Electrode ◽  
Electrochemical Cells ◽  
Thermodynamic Quantities ◽  
Positive Electrodes ◽  
Gibbs Energies ◽  
Buffer Region ◽  
First Time

Equilibrium phase formations below 600 K in the parts Ag2Te–FeTe2–F1.12Te–Ag2Te and Ag8GeTe6–GeTe–FeTe2–AgFeTe2–Ag8GeTe6 of the Fe–Ag–Ge–Te system were established by the electromotive force (EMF) method. The positions of 3- and 4-phase regions relative to the composition of silver were applied to express the potential reactions involving the AgFeTe2, Ag2FeTe2, and Ag2FeGeTe4 compounds. The equilibrium synthesis of the set of phases was performed inside positive electrodes (PE) of the electrochemical cells: (−)Graphite ‖LE‖ Fast Ag+ conducting solid-electrolyte ‖R[Ag+]‖PE‖ Graphite(+), where LE is the left (negative) electrode, and R[Ag+] is the buffer region for the diffusion of Ag+ ions into the PE. From the observed results, thermodynamic quantities of AgFeTe2, Ag2FeTe2, and Ag2FeGeTe4 were experimentally determined for the first time. The reliability of the division of the Ag2Te–FeTe2–F1.12Te–Ag2Te and Ag8GeTe6–GeTe–FeTe2–AgFeTe2–Ag8GeTe6 phase regions was confirmed by the calculated thermodynamic quantities of AgFeTe2, Ag2FeTe2, and Ag2FeGeTe4 in equilibrium with phases in the adjacent phase regions. Particularly, the calculated Gibbs energies of Ag2FeGeTe4 in two different adjacent 4-phase regions are consistent, which also indicates that it has stoichiometric composition.

Derivatives of isatin in aqueous solution. I. Kinetics of ring opening of Isatin-5-sulfonate

1981 ◽  
Vol 34 (2) ◽  
pp. 365 ◽  
Author(s):  
H Stunzi
Keyword(s):  
Ring Opening ◽  
Rate Of Change ◽  
Spectroscopic Methods ◽  
Ph Values ◽  
Buffer Region ◽  
Pka Value ◽  
Back Titration ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Sulfonate Anion

The reactions of isatin-5-sulfonate anion (si-) which cause a hysteresis in pH titrations were studied by pH-metric and n.m.r, spectroscopic methods. Rapid alkalimetric titrations [I 0.15 M (KNO3),37�] gave the pKa value corresponding to the addition of OH- to si- [pKa(ring) 9.55]. The slow ring opening to the sulfonatoisatate dianion (sia2-) led to a drift of the pH values towards an equilibrium buffer region. Its pKa, value [pKa(eq) 3.44] corresponds to the reaction si-+H2O ↔ sia 2-+H+ Rapid back-titration gave the pKa value of the ring-opened species Hsia- [pKa(open) c. 1.3]. The rate law for the ring opening d[sia]/dt=k2 [siOH](OH)+k1*[si] was obtained from the rate of change of pH. N-Methylisatin-5-sulfonate behaves analogously.

Oval Flow Mode Between Two Corotating Disks With Stationary Shroud

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Ching Min Hsu ◽  
Jia-Kun Chen ◽  
Min Kai Hsieh ◽  
Rong Fung Huang
Keyword(s):  
Flow Structure ◽  
Solid Body ◽  
Circumferential Velocity ◽  
Body Rotation ◽  
Flow Core ◽  
Core Flow ◽  
Node Point ◽  
Solid Body Rotation ◽  
Characteristic Flow ◽  
Buffer Region

The characteristic flow behavior, time-averaged velocity distributions, phase-resolved ensemble-averaged velocity profiles, and turbulence properties of the flow in the interdisk midplane between shrouded two corotating disks at the interdisk spacing to disk radius aspect ratio 0.2 and rotation Reynolds number 3.01 × 105 were experimentally studied by flow visualization method and particle image velocimetry (PIV). An oval core flow structure rotating at a frequency 60% of the disks rotating frequency was observed. Based on the analysis of relative velocities, the flow in the region outside the oval core flow structure consisted of two large vortex rings, which move circumferentially with the rotation motion of the oval flow core. Four characteristic flow regions—solid-body-rotation-like region, buffer region, vortex region, and shroud-influenced region—were identified in the flow field. The solid-body-rotation-like region, which was featured by its linear distribution of circumferential velocity and negligibly small radial velocity, was located within the inscribing radius of the oval flow core. The vortex region was located outside the circumscribing radius of the oval flow core. The buffer region existed between the solid-body-rotation-like region and the vortex region. In the buffer region, there existed a “node” point that the propagating circumferential velocity waves diminished. The circumferential random fluctuation intensity presented minimum values at the node point and high values in the solid-body-rotation-like region and shroud-influenced region due to the shear effect induced by the wall.

scholarly journals Optimal strategies to protect a sub-population at risk due to an established epidemic

2021 ◽  
Author(s):  
Elliott H. Bussell ◽  
Nik J. Cunniffe
Keyword(s):  
National Park ◽  
Optimal Strategies ◽  
The Elderly ◽  
Phytophthora Ramorum ◽  
Limited Budget ◽  
Redwood National Park ◽  
Buffer Region ◽  
The Face ◽  
Test Robustness

AbstractEpidemics can particularly threaten certain sub-populations. For example, for SARS-CoV-2, the elderly are often preferentially protected. For diseases of plants and animals, certain sub-populations can drive mitigation because they are intrinsically more valuable for ecological, economic, socio-cultural or political reasons. Here we use optimal control theory to identify strategies to optimally protect a “high value” sub-population when there is a limited budget and epidemiological uncertainty. We use protection of the Redwood National Park in California in the face of the large ongoing state-wide epidemic of sudden oak death (caused by Phytophthora ramorum) as a case study. We concentrate on whether control should be focused entirely within the National Park itself, or whether treatment of the growing epidemic in the surrounding “buffer region” can instead be more profitable. We find that, depending on rates of infection and the size of the ongoing epidemic, focusing control on the high value region is often optimal. However, priority should sometimes switch from the buffer region to the high value region only as the local outbreak grows. We characterise how the timing of any switch depends on epidemiological and logistic parameters, and test robustness to systematic misspecification of these factors due to imperfect prior knowledge.

On the dynamical relevance of coherent vortical structures in turbulent boundary layers

2010 ◽  
Vol 648 ◽  
pp. 325-349 ◽  
Author(s):  
SERGIO PIROZZOLI ◽  
MATTEO BERNARDINI ◽  
FRANCESCO GRASSO
Keyword(s):  
Viscous Sublayer ◽  
Momentum Balance ◽  
Substantial Contribution ◽  
Vortex Sheets ◽  
Vortical Structures ◽  
Buffer Region ◽  
Non Local ◽  
Low Speed Streaks ◽  
Vortex Tubes ◽  
Stream Direction

The dynamical relevance of vortex tubes and vortex sheets in a wall-bounded supersonic turbulent flow at Mach numberM= 2 and Reynolds numberReθ≈ 1350 is quantitatively analysed. The flow in the viscous sublayer and in the buffer region is characterized by intense, elongated vorticity tongues forming a shallow angle with respect to the wall, whose characteristic length isO(200) wall units and whose size in the cross-stream direction isO(50) wall units. The formation of vortex tubes takes place starting fromy+≈ 10, and it is mainly associated with the roll-up and the interaction of vortex sheets. The analysis of the non-local dynamical effect of tubes and sheets suggests that the latter have a more important collective effect, being closely associated with low-speed streaks, and being responsible for a substantial contribution to the mean momentum balance and to the production of turbulence kinetic energy and enstrophy.

Prediction and investigation of the turbulent flow over a rotating disk

2000 ◽  
Vol 418 ◽  
pp. 231-264 ◽  
Author(s):  
XIAOHUA WU ◽  
KYLE D. SQUIRES
Keyword(s):  
Boundary Layer ◽  
Rotating Disk ◽  
Shear Stresses ◽  
Normal Velocity ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Velocity Fluctuations ◽  
Buffer Region ◽  
The Mean ◽  
Good Agreement

Large-eddy simulation (LES) has been used to predict the statistically three-dimensional turbulent boundary layer (3DTBL) over a rotating disk. LES predictions for six parameter cases were compared to the experimental measurements of Littell & Eaton (1994), obtained at a momentum thickness Reynolds number of 2660. A signal-decomposition scheme was developed by modifying the method of Spalart (1988) to prescribe time-dependent boundary conditions along the radial direction, entrainment towards the disk surface was prescribed by satisfying global mass conservation. Predictions of the mean velocities and r.m.s. fluctuations are in good agreement with data, with the largest discrepancy occurring in the prediction of the wall-normal intensities. The primary and two secondary shear stresses are also in good agreement with the measurements and one-dimensional energy spectra of the velocity fluctuations agree well with established laws, i.e. a −1 slope in the buffer region and −5/3 slope near the edge of the boundary layer.Conditionally averaged velocities provide new evidence in support of the structural model of Littell & Eaton (1994) concerning the interaction of mean-flow three-dimensionality and shear-stress producing structures. Inside the buffer region under strong ejections, the conditionally averaged crossflow (radial) velocity is larger than the unconditioned mean, and the profile conditioned on strong sweeps is smaller than the mean. This is consistent with the notion that streamwise vortices having the same sign as the mean streamwise vorticity, and beneath the peak crossflow location, are mostly responsible for strong sweep events; streamwise vortices with opposite sign as the mean streamwise vorticity promote strong ejections. Comparison of two-point spatial correlations with previous measurements in two-dimensional turbulent boundary layers (2DTBLs) indicates interesting structural similarities, e.g. the correlation of wall pressure and surface-normal velocity fluctuations is an odd function of streamwise separation, being positive downstream and negative upstream. These similarities offer quantitative indirect support to the hypothesis advanced by Littell & Eaton (1994) and Johnston & Flack (1996) that structural models describing 2DTBLs may be employed as a baseline in (equilibrium) 3DTBL structural studies.

Geo-fencing to secure airport perimeter against sUAS

2017 ◽  
Vol 5 (4) ◽  
pp. 102-116 ◽  
Author(s):  
Chris Boselli ◽  
Jason Danis ◽  
Sandra McQueen ◽  
Alex Breger ◽  
Tao Jiang ◽  
...  
Keyword(s):  
Unmanned Aircraft ◽  
Unmanned Aircraft Systems ◽  
Controlled Environment ◽  
Security Threat ◽  
Commercial Aircraft ◽  
Content Type ◽  
Buffer Region ◽  
The Usa ◽  
Critical Regions ◽  
Runway Incursion

Purpose Small unmanned aircraft systems (sUAS) are becoming increasingly popular among hobbyists, and with this popularity there comes the risk of runway incursion between a commercial aircraft and sUAS around airports. To keep airports safe and secure, the purpose of this paper is to propose a module, called the Airport Secure Perimeter Control System, that can be attached to every hobbyist’s sUAS for the purpose of notification and prevention. Design/methodology/approach Upon startup, the module connects to a database containing the central coordinates of every airport in the USA. A five-mile critical radius plus an additional one-mile buffer region is established around each point. The buffer region is created in order to inform the user that he/she is approaching a safe airspace and needs to take corrective action. Once the five-mile zone has been breached, autopilot software takes over the manual controls, and the sUAS is landed in a controlled manner, while the user still has lateral control of the vehicle in order to avoid any potential hazards below it. Then, both operator and airport receive messages about the event. Findings To demonstrate the proposed design, a prototype was developed that successfully implemented this system, and was formally tested within a controlled environment. Originality/value This solution would drastically reduce the security threat of sUAS breaching the critical regions surrounding airports, and its implementation is relatively simple.

scholarly journals The turbulence boundary of a temporal jet

2013 ◽  
Vol 739 ◽  
pp. 254-275 ◽  
Author(s):  
Maarten van Reeuwijk ◽  
Markus Holzner
Keyword(s):  
Average Distance ◽  
One Dimensional ◽  
Entrainment Velocity ◽  
Buffer Region ◽  
Close Proximity ◽  
Reynolds Number Effects ◽  
Integral Rate ◽  
Plane Jet ◽  
Viscous Transport ◽  
Good Agreement

AbstractWe examine the structure of the turbulence boundary of a temporal plane jet at$\mathit{Re}= 5000$using statistics conditioned on the enstrophy. The data is obtained by direct numerical simulation and threshold values span 24 orders of magnitude, ranging from essentially irrotational fluid outside the jet to fully turbulent fluid in the jet core. We use two independent estimators for the local entrainment velocity${v}_{n} $based on the enstrophy budget. The data show clear evidence for the existence of a viscous superlayer (VSL) that envelopes the turbulence. The VSL is a nearly one-dimensional layer with low surface curvature. We find that both its area and viscous transport velocity adjust to the imposed rate of entrainment so that the integral entrainment flux is independent of threshold, although low-Reynolds-number effects play a role for the case under consideration. This threshold independence is consistent with the inviscid nature of the integral rate of entrainment. A theoretical model of the VSL is developed that is in reasonably good agreement with the data and predicts that the contribution of viscous transport and dissipation to interface propagation have magnitude$2{v}_{n} $and$- {v}_{n} $, respectively. We further identify a turbulent core region (TC) and a buffer region (BR) connecting the VSL and the TC. The BR grows in time and inviscid enstrophy production is important in this region. The BR shows many similarities with the turbulent–non-turbulent interface (TNTI), although the TNTI seems to extend into the TC. The average distance between the TC and the VSL, i.e. the BR thickness is about 10 Kolmogorov length scales or half a Taylor length scale, indicating that intense turbulent flow regions and viscosity-dominated regions are in close proximity.

Sign in / Sign up

Export Citation Format

Share Document