bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hybrid Zero Dynamics Control of an Underactuated Lower-Limb Exoskeleton for Gait Guidance
Authors: Goo Anthony , Laubscher Curt A. , Sawicki Jerzy T. 
Published: February 2022

Abstract
Hybrid zero dynamics (HZD) control creates dynamically stable gaits by driving a hybrid robot model toward an optimally generated state-dependent reference signal. This paper presents the first application of HZD to an underactuated lower-limb exoskeleton for gait guidance. A phase-based reference gait is generated to follow a nominal walking pattern. Simulation results using a phase-based proportional-derivative (PD) controller validate that stable periodic gait similar to nominal gait is possible for the identified human-exoskeleton model. For hardware application, a bilateral mixing strategy is taken to accommodate the presence of the double support phase, which was assumed to be instantaneous in the hybrid model. A treadmill experiment is conducted with a healthy subject using the Indego Explorer exoskeleton. Comparing the recorded gait to the optimal phase-based reference, the root-mean-square joint tracking errors (RMSE) are 2.87 deg, 2.79 deg, 3.20 deg, and 11.0 deg at the stance hip, stance knee, swing hip, and swing knee, respectively. Similarly, compared to the commanded reference, the RMSE are 2.04 deg, 4.40 deg, 4.58 deg, and 6.83 deg, respectively. A second experiment was conducted wherein the treadmill speed varied from 0.3 to 0.5 m/s. The results show how the HZD controller exhibits remarkable flexibility and robustness for multiple walking speeds and grants the operator greater level of volitional control due to the time-invariant, phase-based nature of the implementation. Taken altogether, the presented results suggest that HZD control can serve as a rehabilitative control method capable of providing gait guidance in underactuated exoskeleton systems.
Performance Evaluation of an Improved Unglazed Photovoltaic and Thermal Hybrid System
Authors: Fang Hao , Ma Jinwei , Du Tao , Chen Qianqian , Chen Haifei , Tong Weiwei , Wang Yunjie 
Published: February 2022

Abstract
This paper proposes a novel unglazed photovoltaic/thermal (PV/T) system completely covered by photovoltaic (PV) cells, the system can significantly increase the power generation, and unglazed structure helps to improve the performance of the electricity. The variable flow experiment shows that the average value of the unglazed PV/T daily electrical and thermal efficiencies can reach 18.62% and 26.86%, respectively, and the corresponding exergy and energy saving efficiencies are 20.51% and 73.76%. Compared with PV module, the electrical efficiency of the PV/T module is increased by 11.54%. As for the large heat loss of unglazed PV/T, a series or parallel system composed of PV/T modules was built to improve heat collection capacity. The results show that the electrical and thermal energy of the series or parallel system increases significantly; temperature of water can be increased by 20 °C when the water volume is more than doubled. However, the electrical efficiency of the system is lower than that of the single PV/T, and the maximum value is 17.32%. Combined with economic analysis, the unglazed PV/T system with higher exergy efficiency and the cost is lower than that of glazed PV/T.
Fault Tolerant Robust Passivity-Based Control Design for a Proton Exchange Membrane Fuel Cell Power Supply
Authors: Zaidi Abdelaziz , Barambones Oscar , Charaabi Asma , Zanzouri Nadia 
Published: February 2022

Abstract
The proton exchange membrane fuel cell (PEMFC) best exploitation needs to be based on reliability and fault tolerant control. One of the issues to fulfill this objective is ensuring high reliability indexes of the associated DC/DC converter, which is indispensable in practice. Three-stage interleaved boost converter is proposed in this context with a reliability-based reconfiguration control. The proposed control approach is passivity based, it is robust against high-temperature variations and load perturbations. However, this article proposes a novel method that adapts the reference current by a linear transformation. The fault tolerant control manages the open circuit failure to adapt the control algorithm to two-stage converter reconfigured structure. The matlab/simulink-based simulations show the effectiveness of the proposed control scheme as well as the reconfiguration method, which can give a technical improvement in the exploitation of PEMFC power supplies in the presence of faults and perturbations.
Response of a Tandem-Staged Compressor to Circumferential Inflow Distortion
Authors: Kumar Amit , Pradeep A. M. 
Published: February 2022

Abstract
Tandem rotor, as a concept, promises a higher diffusion capacity than a single rotor. However, it is reported to have a lower operating range than the conventional rotor. Inflow distortion can lead to significant changes in the flow dynamics of the axial-flow compressor. Further, a highly loaded tandem blade is likely to be severely affected due to the inflow distortions. In this study, circumferential distortion is imposed at the inlet of a tandem stage and its response is studied, using steady and unsteady probes. The performance characteristics and other aerodynamics parameters under the circumferential distortion are compared with the clean inflow case. As expected, the tandem stage experiences a significant drop in the total pressure rise and operating range under circumferential distortion. A large deficit in the total pressure, efficiency, and axial velocity is observed in the distorted region. The casing pressure traces, Morlet wavelet analysis, and Fast Fourier Transform techniques are used to analyze the unsteady data. The stall is incepted in the form of a low-intensity spike, which later evolved into a fully grown stall within 2.5 rotor revolutions. Further, the amplitude of the stall cell under the circumferential distortion is found to be higher than the clean flow.
Lid-Driven Butterfly Cavity for a Controllable Viscous Flow
Authors: Turkyilmazoglu Mustafa 
Published: February 2022

Abstract
The theme of current effort is to numerically analyze physical aspects of the flow triggered by a lid-driven cavity of butterfly cross section. The main goal is to search how the butterfly shape adds to the mixing phenomenon and its stationary flow solution. To achieve the aim, numerical simulations are performed from the scaled equations employing a conventional finite element technique. The induced pressure and velocity field topologies are elucidated through visualizing the contour plots and stream flows for varying Reynolds numbers. The present results reveal that the amount of flow and its mixing process can be controlled by adjusting the nonparallel walls of the butterfly in such a manner that fast mixing and slow mixing can take place in different sections of the cavity. This permits us decomposition of particles during separation process of chemical substances in industrial applications.
Scattering of Water Waves by Very Large Floating Structure in the Presence of a Porous Box
Authors: Singla S. , Behera H. , Martha S. C. , Sahoo T. 
Published: February 2022

Abstract
We investigate the effectiveness of a porous box in attenuating the structural response of a very large floating structure (VLFS). Assuming the water depth to be finite and small amplitude water wave theory, the physical problem is formulated by employing Darcy’s law for flow past a porous structure. The boundary value problem is reduced to a system of linear algebraic equations with the aid of matched eigenfunction expansion method. Further, these simultaneous equations are solved numerically to compute physical quantities. The mathematical model is validated through a comparison with the theoretical results available in the literature. The reflection, transmission, and dissipation coefficients, elastic plate deflection, forces acting on the box, and free-surface elevation are computed. The reflection, transmission, and dissipation coefficients exhibit an oscillatory pattern for large values of wavenumber irrespective of the structural parameters of the box. It is highlighted that a porous box with moderate values of the porous-effect parameter is effective in reducing strain and shear force on the VLFS. Further, the results on elevation and VLFS deflection depict that the suitable porous-effect parameter values for the box reduce the resultant wave amplitude of the elastic plate deflection as well as the amplitude in the lee side of the VLFS. The study reveals that the width and height of the porous box are critical toward the trapping of incident waves inside the box and dissipating the maximum amount of incident wave energy in reduction of wave transmission in the lee side of the structure and thereby attenuating the structural response of the VLFS.
Performance Determinants in Trail-Running Races of Different Distances
Authors: Pastor Frederic Sabater , Besson Thibault , Varesco Giorgio , Parent Audrey , Fanget Marie , Koral Jérôme , Foschia Clément , Rupp Thomas , Rimaud Diana , Féasson Léonard , Millet Guillaume Y. 
Published: February 2022

Purpose: While the physiological determinants of road running have been widely studied, there is a lack of research in trail-running racing performance. The aim of our study was to determine the physiological predictors of trail-running performance in races of different distances in similar terrain and weather conditions. Methods: Seventy-five trail runners participating in one of the races of the Ultra-Trail du Mont-Blanc were recruited. Previous to the race, each runner was evaluated with (1) an incremental treadmill test to determine maximal oxygen uptake, ventilatory thresholds, cost of running, and substrate utilization; (2) a power–force–velocity profile on a cycle ergometer; (3) maximal voluntary contractions of the knee extensors and plantar flexors; and (4) anthropometric characteristics. Neuromuscular fatigue was evaluated after the races. Twenty-four runners finished a SHORT (<55 km), 16 finished a MEDIUM (101 km), and 14 finished a LONG (>145 km) race. Correlations and multiple linear regressions were used to find the determinants of performance in each race distance. Results: Performance in SHORT was explained by maximal oxygen uptake and lipid utilization at 10 km/h (r2 = .825, P < .001). Performance in MEDIUM was determined by maximal oxygen uptake, maximal isometric strength, and body fat percentage (r2 = .917, P < .001). A linear model could not be applied in LONG, but performance was correlated to peak velocity during the incremental test. Conclusions: Performance in trail running is mainly predicted by aerobic capacity, while lipid utilization also influences performance in races <60 km and performance in approximately 100 km is influenced by muscle strength and body composition.
The continent-to-ocean transition in the Iberia Abyssal Plain
Authors: Grevemeyer Ingo , Ranero Cesar R. , Papenberg Cord , Sallares Valenti , Bartolomé Rafael , Prada Manel , Batista Luis , Neres Marta 
Published: February 2022

Abstract
Conceptual models of magma-poor rifting are strongly based on studies of the nature of the basement in the continent-to-ocean transition of the Iberia Abyssal Plain, and suggest that exhumed mantle abuts extended continental crust. Yet, basement has only been sampled at a few sites, and its regional nature and the transition to seafloor spreading inferred from relatively low-resolution geophysical data are inadequately constrained. This uncertainty has led to a debate about the subcontinental or seafloor-spreading origin of exhumed mantle and the rift-related or oceanic nature of magmatic crust causing the magnetic J anomaly. Different interpretations change the locus of break-up by &gt;100 km and lead to debate of the causative processes. We present the tomographic velocity structure along a 360-km-long seismic profile centered at the J anomaly in the Iberia Abyssal Plain. Rather than delineating an excessive outpouring of magma, the J anomaly occurs over subdued basement. Furthermore, its thin crust shows the characteristic layering of oceanic crust and is juxtaposed to exhumed mantle, marking the onset of magma-starved seafloor spreading, which yields the westward limit of an ~160-km-wide continent–ocean transition zone where continental mantle has been unroofed. This zone is profoundly asymmetric with respect to its conjugate margin, suggesting that the majority of mantle exhumation occurs off Iberia. Because the J anomaly is related to the final break-up and emplacement of oceanic crust, it neither represents synrift magmatism nor defines an isochron, and hence it poorly constrains plate tectonic reconstructions.
Properties and stratigraphy of polar ice patches in the Canadian High Arctic reveal their current resilience to warm summers
Authors: Davesne Gautier , Fortier Daniel , Domine Florent 
Published: February 2022

Ice patches are ubiquitous in polar regions and are a key element for landscape evolution. We present new insights into polar desert ice patch formation based on snow and ice properties at Ward Hunt Island (Canadian High Arctic, 83°N). Our results demonstrate that ice patches are composed of two distinct units. The upper unit is characterized by very fine granular and bubbly ice with a clear oblique layering. By contrast, the lower unit is strikingly different with coarse crystals, lower porosity, and a high frequency of fractures. For both units, superimposed ice formation at the base of the deep snowpack stands out as the primary ice aggradation process. The distinct properties of the lower unit likely result from a long period of kinetic ice crystal growth indicating a minimum age of several hundred years. A radiocarbon date of 3 487 ± 20 cal BP suggests that ice patches could potentially date back to the late Holocene. This old ice was recently truncated during warmer summers between 2008 and 2012, but the ice patch quickly recovered its volume during cooler summers. The old age of the ice patches and their rapid regeneration after melt events suggest their resilience to current warmer summers.
Altitude impacts body size but not age in the Asia Minor Thin-toed Gecko (Mediodactylus heterocercus)
Authors: Altunışık Abdullah , Yıldız Mehmet Zülfü , Üçeş Fatma , Bozkurt Mehmet Akif , Sömer Mehtap 
Published: February 2022

Age and size-related life-history traits of animals are influenced by a variety of factors. In connection with climate, the effect of altitude on demographic parameters may differ among different populations of the same species. In the present study, we analyzed how body size and longevity of the Asia Minor Thin-toed Gecko (Mediodactylus heterocercus (Blanford, 1874)) vary along an elevational gradient in Turkey. For this purpose, a total of 138 specimens of the species (52 males, 75 females, and 11 juveniles) from 11 different populations were analyzed. Populations at intermediate altitude had shorter lifespans compared with those at low and high altitudes (marginal environments). Furthermore, adult life expectancy (ESP), which indicates the expected lifespan of individuals having reached sexual maturity, was higher in high-altitude populations (ESP: 6.59 years) than in intermediate-altitude populations (ESP: 5.40 years) and low-altitude populations (ESP: 6.01 years). The results of the study suggest that the body size, but not age, of Asia Minor Thin-toed Geckos increases with altitude.
Acceptability conditions and relativistic anisotropic generalized polytropes
Authors: Suárez-Urango Daniel , Ospino Justo , Hernández Héctor , Núñez Luis A. 
Published: February 2022

AbstractThis paper explored the physical acceptability conditions for anisotropic matter configurations in General Relativity. The study considered a generalized polytropic equation of state $$P=\kappa {\rho }^{\gamma }+\alpha \rho -\beta $$

P
=
κ

ρ

γ

+
α
ρ
-
β

for a heuristic anisotropy. We integrated the corresponding Lane–Emden equation for several hundred models and found the parameter-space portion ensuring the physical acceptability of the configurations. Polytropes based on the total energy density are more viable than those with baryonic density, and small positive local anisotropies produce acceptable models. We also found that polytropic configurations where tangential pressures are greater than radial ones are also more acceptable. Finally, convective disturbances do not generate cracking instabilities. Several models emerging from our simulations could represent candidates of astrophysical compact objects.
Natriuretic Peptide Oligomers Cause Proarrhythmic Metabolic and Electrophysiological Effects in Atrial Myocytes
Authors: Yang Zhenjiang , Subati Tuerdi , Kim Kyungsoo , Murphy Matthew B. , Dougherty Owen P. , Christopher Isis L. , Van Amburg Joseph C. , Woodall Kaylen K. , Barnett Joey V. , Murray Katherine T. 
Published: February 2022

Background:
With aging, the human atrium invariably develops amyloid composed of ANP (atrial natriuretic peptide) and BNP (B-type natriuretic peptide). Preamyloid oligomers are the primary cytotoxic species in amyloidosis, and they accumulate in the atrium during human hypertension and a murine hypertensive model of atrial fibrillation susceptibility. We tested the hypothesis that preamyloid oligomers derived from natriuretic peptides cause cytotoxic and electrophysiological effects in atrial cells that promote arrhythmia susceptibility and that oligomer formation is enhanced for a mutant form of ANP linked to familial atrial fibrillation.

Methods:
Oligomerization was assessed by Western blot analysis. Bioenergic profiling was performed using the Seahorse platform. Mitochondrial dynamics were investigated with immunostaining and gene expression quantitated using quantitative reverse transcription polymerase chain reaction. Action potentials and ionic currents were recorded using patch-clamp methods and intracellular calcium measured using Fura-2.

Results:

Oligomer formation was markedly accelerated for mutant ANP (mutANP) compared with WT (wild type) ANP. Oligomers derived from ANP, BNP, and mutANP suppressed mitochondrial function in atrial HL-1 cardiomyocytes, associated with increased superoxide generation and reduced biogenesis, while monomers had no effects. In hypertensive mice, atrial cardiomyocytes displayed reduced action potential duration and maximal dV/dT of phase 0, with an elevated resting membrane potential, compared with normotensive mice. Similar changes were observed when atrial cells were exposed to oligomers. mutANP monomers produced similar electrophysiological effects as mutANP oligomers, likely due to accelerated oligomer formation, while ANP and BNP monomers did not. Oligomers decreased Na
+
current, inward rectifier K
+
current, and L-type Ca
++
current, while increasing sustained and transient outward K
+
currents, to account for these effects.

Conclusions:
These findings provide compelling evidence that natriuretic peptide oligomers are novel mediators of atrial arrhythmia susceptibility. Moreover, the accelerated oligomerization by mutANP supports a role for these mediators in the pathophysiology of this mutation in atrial fibrillation.
Everyday Migrant Accompaniment: Humanitarian Border Diplomacy
Authors: Churruca-Muguruza Cristina 
Published: February 2022

Summary
This article advances the notion of humanitarian border diplomacy, contributing to current academic discussions on humanitarian diplomacy and on the practice-theory nexus by conceptualising NGOs’ migrant accompaniment at borders as a form of everyday humanitarian diplomacy. The contention is that humanitarian diplomacy is similar to other diplomatic practices. Starting by rethinking humanitarian diplomacy, it discusses the emergence of humanitarian border diplomacy as a key component of everyday migrant accompaniment. Humanitarian border diplomacy focuses on advancing migrants’ rights, seeking to make helpful, empowering and transformational interventions in an attempt to resist and change the contemporary global governance of migration. The article presents the everyday diplomatic practices of the Servicio Jesuita a Migrantes in Melilla, on Spain’s southern border, as an example of humanitarian border diplomacy. At the border, as an alternative space for resistance, difference and otherness, the need for diplomatic culture as the symbolic mediation of estrangement is revealed.
الغيب ومفاتحه: مفهوم الغيب في القرآن وسؤال التنبؤ الجيني
Authors: حللي (Abdulrahman Helli) عبد الرحمن 
Published: February 2022

الخلاصة
‫تعترض التنبؤ الجيني في العلم الحديث تساؤلات عن مدى كونه يتعارض مع الموقف الإسلامي من الغيب، حيث وردت نصوص تحرم أنماطًا من التنبؤ بالغيب، فهل ينطبق على التنبؤ الجيني ما ينطبق على التنبؤ بالغيب؟ تناقش هذه الدراسة هذا الموضوع من خلال ثلاثة محاور، الأول: تحرير مفهوم الغيب في القرآن، والثاني: تحرير مفهوم مفاتيح الغيب الذي بنيت عليه القضايا المشكلة في الموضوع، والمحور الثالث: تحرير علة ما تم تحريمه أو السماح به من أنماط التنبؤ بالغيب، مع استعراض تاريخي لمواقف الفقهاء من القيافة وبناء الأحكام عليها كنموذج من نماذج التنبؤ، وانتهت الدراسة إلى أن مناط المنع أو الاباحة في التنبؤ يرتبط بعلمية الوسيلة وخلوها من التلبس بمعتقد ديني ينافي التوحيد، وأن ما ينطبق على التنبؤ بالغيب ينطبق على التنبؤ الجيني.‬
Protests in a Small Island State during the Year of covid-19: The Case of Malta
Authors: Briguglio Michael 
Published: February 2022

Abstract
This paper relies on protest event analysis (pea) to study protests held in Malta during 2020 and analyses specific features of those protests, namely issues, organisations, coalitions, venues, and types of protest. The study verifies how Malta’s status as a small state impacts protest, especially in terms of networks of activism and in the context of the covid-19 pandemic.
Findings show the environment as the most prominent issue, followed by the murder of Daphne Caruana Galizia and human rights, respectively. The most active actors were Repubblika and Occupy Justice on the Daphne Caruana Galizia issue; Movement Graffitti on the environment; and irregular migrants without organisational set-ups, who protested human rights violations. This study emphasizes the importance of considering the characteristics and opportunity structures of Malta as a small state. Such factors are not only reflected in the protest repertoire, but also in the way organisations and activists invest in social networks.
Despite certain trends regarding protest numbers, there was no correlation between covid-19 and the number of protests. Furthermore, the main issues characterising protests were similar to those of previous years.