Specific Modeling Issues on an Adaptive Winglet Skeleton

Morphing aeronautical systems may be used for a number of aims, ranging from improving performance in specific flight conditions, to keeping the optimal efficiency over a certain parameters domain instead of confining it to a single point, extending the flight envelope, and so on. An almost trivial statement is that traditional skeleton architectures cannot be held as a structure modified from being rigid to deformable. That passage is not simple, as a structure that is able to be modified shall be designed and constructed to face those new requirements. What is not marginal, is that the new configurations can lead to some peculiar problems for both the morphing and the standard, supporting, elements. In their own nature, in fact, adaptive systems are designed to contain all the parts within the original geometry, without any “external adjoint”, such as nacelles or others. Stress and strain distribution may vary a lot with respect to usual structures and some particular modifications are required. Sometimes, it happens that the structural behavior does not match with the common experience and some specific adjustment shall be done to overcome the problem. What is reported in this paper is a study concerning the adaptation of the structural architecture, used to host a winglet morphing system, to make it accomplish the original requirements, i.e., allow the deformation values to be under the safety threshold. When facing that problem, an uncommon behavior of the finite element (FE) solver has been met: the safety factors appear to be tremendously dependent on the mesh size, so as to raise serious questions about the actual expected value, relevant for the most severe load conditions. On the other side, such singularities are more and more confined into single points (or single lines), as the mesh refines, so to evidence somehow the numerical effect behind those results. On the other side, standard engineering local methods to reduce the abovementioned strain peaks seem to work very well in re-distributing the stress and strain excesses to the whole system domain. The work does not intend to give an answer to the presented problem, being instead focused on describing its possible causes and its evident effects. Further work is necessary to detect the original source of such inconsistencies, and propose and test operative solutions. That will be the subject of the next steps of the ongoing research.

Time matters: Early-phase multiple sclerosis is accompanied by considerable impairments across multiple domains

Impairments across multiple domains are a disabling consequence of multiple sclerosis (MS). Originating from preventive medical strategies, the “time matters”-perspective has become a focal point when treating MS. In particular, early detection of physical and cognitive deficits, along with deficits in patient-reported outcomes seems crucial to further optimize both pharmacological and non-pharmacological MS treatment strategies. Therefore, this topical review investigates the level of impairments across multiple domains (physical function, cognitive function, and patient-reported outcomes) in the early stage of MS (⩽5 years since diagnosis, including clinically isolated syndrome (CIS)), when compared to matched healthy controls. Even at early disease stages, studies show impairments corresponding to 8%–34% and small-to-large numerical effect sizes (0.35–2.85) in MS/CIS patients across domains. This evidence call for early screening programs along with early interventions targeting the multiple impaired domains. This further highlights the importance of preventive initiatives preserving and/or restoring physical and cognitive reserve capacity if possible.

Impact of the Hall effect in star formation and the issue of angular momentum conservation

We present an implementation of the Hall term in the non-ideal magnetohydrodynamics equations into the adaptive-mesh-refinement code RAMSES to study its impact on star formation. Recent works show that the Hall effect heavily influences the regulation of the angular momentum in collapsing dense cores, strengthening or weakening the magnetic braking. Our method consists of a modification of the two-dimensional constrained transport scheme. Our scheme shows convergence of second order in space and the frequency of the propagation of whistler waves is accurate. We confirm previous results, namely that during the collapse, the Hall effect generates a rotation of the fluid with a direction in the mid-plane that depends on the sign of the Hall resistivity, while counter-rotating envelopes develop on each side of the mid-plane. However, we find that the predictability of our numerical results is severely limited. The angular momentum is not conserved in any of our dense core-collapse simulations with the Hall effect: a large amount of angular momentum is generated within the first Larson core, a few hundred years after its formation, without compensation by the surrounding gas. This issue is not mentioned in previous studies and may be correlated to the formation of the accretion shock on the Larson core. We expect that this numerical effect could be a serious issue in star formation simulations.

Reducing scale dependence in TOPMODEL using a dimensionless topographic index

This paper stems from the fact that the topographic index used in TOPMODEL is not dimensionless. In each pixel i in a catchment, it is defined as xi=ln(ai/Si), where ai is the specific contributing area per unit contour length and Si is the topographic slope. In the SI unit system, ai/Si is in meters, and the unit of xi is problematic. We propose a simple solution in the widespread cases where the topographic index is computed from a regular raster digital elevation model (DEM). The pixel length C being constant, we can define a dimensionless topographic index yi=xi-lnC. Reformulating TOPMODEL equations to use yi instead of xi helps giving the units of all their terms and emphasizes the scale dependence of these equations via the explicit use of C outside from the topographic index, in what can be defined as the transmissivity at saturation per unit contour length T0/C. The term lnC defines the numerical effect of DEM resolution, which contributes to shift the spatial mean x of the classical topographic index when the DEM cell size C varies. A key result is that both the spatial mean y of the dimensionless index and T0/C are much more stable with respect to DEM resolution than their counterparts x and T0 in the classical framework. This shows the importance of the numerical effect in the dependence of the classical topographic index to DEM resolution, and reduces the need to recalibrate TOPMODEL when changing DEM resolution.

COMPLETE BREMSSTRAHLUNG CORRECTIONS TO THE FORWARD–BACKWARD ASYMMETRIES IN b→Xsℓ+ℓ-

In a recent paper we presented a calculation of NNLL virtual corrections to the forward–backward asymmetries in b→Xsℓ+ℓ- decay. That result does not include bremsstrahlung corrections which are free from infrared and collinear singularities. In the present paper we include the remaining [Formula: see text] bremsstrahlung corrections to the forward–backward asymmetries in b→Xsℓ+ℓ- decay. The numerical effect of the calculated contributions is found to be below 1%.

On the waiting time of a two-stage queueing system with blocking

An analysis is given of the first-come-first-served waiting-time process in stages 1 and 2 of a two-stage service system with k and n parallel service channels in the first and second stages respectively, and m intermediate waiting places (k, n ≧ 1, m ≧ 0).Although the method of analysis is straightforward the details are intricate and require careful study of the location of the zeros of a high-degree polynomial.The analysis paves the way for an extensive study of the numerical effect on waiting time of blocking in commonly encountered systems of this nature. ‘Effective service time' in stage 1, defined so as to include blocked time, is considered separately.

On the waiting time of a two-stage queueing system with blocking

An analysis is given of the first-come-first-served waiting-time process in stages 1 and 2 of a two-stage service system with k and n parallel service channels in the first and second stages respectively, and m intermediate waiting places (k, n ≧ 1, m ≧ 0). Although the method of analysis is straightforward the details are intricate and require careful study of the location of the zeros of a high-degree polynomial. The analysis paves the way for an extensive study of the numerical effect on waiting time of blocking in commonly encountered systems of this nature. ‘Effective service time' in stage 1, defined so as to include blocked time, is considered separately.