bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sliding Mode Analysis of a Counterbalance Valve Induced Instability in an Electrohydraulic Drive
Authors: Zagar Philipp , Scheidl Rudolf 
Published: December 2021

Abstract
This paper analyzes the dynamic effects of an electrohydraulic drive that uses a counterbalance valve for rod volume compensation. It shows that local stability analysis is not sufficient in this particular case to get general statements of the system's chattering properties. A reduced-order switched system is proposed to gain deeper insights in system dynamics with saturation effects such as the end-stop of a valve poppet and solutions are compared numerically to the full-system dynamics which incorporates pressure built-up, piston, and valve dynamics as well as motor dynamics. It is shown that in cases of, e.g., fast valves with small cracking pressures undesirable chattering of the full system exists which can be easily understood in terms of the reduced-order system in form of sliding mode solutions. The paper also describes under which conditions such sliding modes exist, how they behave, and how they can be interpreted in terms of the full system.
Momentum Preserving Simulation of Cooperative Multirotors With Flexible-Cable Suspended Payload
Authors: Kaya Uluhan Cem , Subbarao Kamesh 
Published: December 2021

Abstract
In this paper, a momentum-preserving integration scheme is implemented for the simulation of single and cooperative multirotors with a flexible-cable suspended payload by employing a Lie group–based variational integrator (VI), which provides the preservation of the configuration manifold and geometrical constraints. Due to the desired properties of the implemented VI method, e.g., symplecticity, momentum preservation, and the exact fulfillment of the constraints, exponentially long-term numerical stability, and good energy behavior are obtained for more accurate simulations of aforementioned systems. The effectiveness of Lie group VI method with the corresponding discrete systems are demonstrated by comparing the simulation results of two example scenarios for the single and cooperative systems in terms of the preserved quantities and constraints, where a conventional fixed-step Runge–Kutta 4 (RK4) and variable-step integrator are utilized for the simulation of continuous-time models. It is shown that the implemented VI method successfully performs the simulations with a long-time stable behavior by preserving invariants of the system and the geometrical constraints, whereas the simulation of continuous-time models by RK4 and variable step are incapable of satisfying these desired properties, which inherently results in divergent and unstable behavior in simulations.
Investigating the Effect of Real-Time Center of Pressure Feedback Training on the Swing Phase of Lower Limb Kinematics in Transfemoral Prostheses With SACH Foot
Authors: Tiwari Ashutosh , Kujur Abhijeet , Kumar Jyoti , Joshi Deepak 
Published: December 2021

Abstract
Transfemoral amputee often encounters reduced toe clearance resulting in trip-related falls. Swing-phase joint angles have been shown to influence the toe clearance; therefore, training intervention that targets shaping the swing phase joint angles can potentially enhance toe clearance. The focus of this study was to investigate the effect of the shift in the location of the center of pressure (CoP) during heel strike on modulation of the swing-phase joint angles in able-bodied participants (n = 6) and transfemoral amputees (n = 3). We first developed a real-time CoP-based visual feedback system such that participants could shift the CoP during treadmill walking. Next, the kinematic data were collected during two different walking sessions-baseline (without feedback) and feedback (shifting the CoP anteriorly/posteriorly at heel strike to match the target CoP location). Primary swing-phase joint angle adaptations were observed with feedback such that during the midswing phase, posterior CoP shift feedback significantly increases (p &lt; 0.05) the average hip and knee flexion angle by 11.55 deg and 11.86 deg, respectively, in amputees, whereas a significant increase (p &lt; 0.05) in ankle dorsiflexion, hip and knee flexion angle by 3.60 deg, 3.22 deg, and 1.27 deg, respectively, compared to baseline was observed in able-bodied participants. Moreover, an opposite kinematic adaptation was seen during anterior CoP shift feedback. Overall, results confirm a direct correlation between the CoP shift and the modulation in the swing-phase lower limb joint angles.
Singularity-Free Lie Group Integration and Geometrically Consistent Evaluation of Multibody System Models Described in Terms of Standard Absolute Coordinates
Authors: Müller Andreas 
Published: December 2021

Abstract
A classical approach to the multibody systems (MBS) modeling is to use absolute coordinates, i.e., a set of (possibly redundant) coordinates that describe the absolute position and orientation of the individual bodies with respect to an inertial frame (IFR). A well-known problem for the time integration of the equations of motion (EOM) is the lack of a singularity-free parameterization of spatial motions, which is usually tackled by using unit quaternions. Lie group integration methods were proposed as an alternative approach to the singularity-free time integration. At the same time, Lie group formulations of EOM naturally respect the geometry of spatial motions during integration. Lie group integration methods, operating directly on the configuration space Lie group, are incompatible with standard formulations of the EOM, and cannot be implemented in existing MBS simulation codes without a major restructuring. The contribution of this paper is twofold: (1) A framework for interfacing Lie group integrators to standard EOM formulations is presented. It allows describing MBS in terms of various absolute coordinates and at the same using Lie group integration schemes. (2) A method for consistently incorporating the geometry of rigid body motions into the evaluation of EOM in absolute coordinates integrated with standard vector space integration schemes. The direct product group SO(3)×ℝ3 and the semidirect product group SE(3) are used for representing rigid body motions. The key element is the local-global transitions (LGT) transition map, which facilitates the update of (global) absolute coordinates in terms of the (local) coordinates on the Lie group. This LGT map is specific to the absolute coordinates, the local coordinates on the Lie group, and the Lie group used to represent rigid body configurations.
A Numerically Stable Algorithm for Analytic Inverse Kinematics of 7-Degrees-of-Freedom Spherical-Rotational-Spherical Manipulators With Joint Limit Avoidance
Authors: Wang Junchen , Lu Chunheng , Zhang Yinghao , Sun Zhen , Shen Yu 
Published: December 2021

AbstractThis article presents a numerically stable algorithm for analytic inverse kinematics of 7-DoF S-R-S manipulators with joint limit avoidance. The arm angle is used to represent the self-motion manifold within a global arm configuration. The joint limits are analytically mapped to the arm angle space for joint limit avoidance. To profile the relation between the joint angle and arm angle, it is critical to characterize the singular arm angle for each joint. In the-state-of-the art methods, the existence of the singular arm angle is triggered by comparing a discriminant with zero given a threshold. This leads to numerical issues since the threshold is inconsistent among different target poses, leading to incorrect range of the arm angle. These issues are overcome by associating indeterminate joint angles of tangent joints with angles of 0 or ±π of cosine joints, rather than using an independent threshold for each joint. The closed-form algorithm in c++ code to perform numerically stable inverse kinematics of 7-DoF S-R-S manipulators with global arm configuration control and joint limit avoidance is also given.
The Mixed-Body Model: A Method for Predicting Large Deflections in Stepped Cantilever Beams
Authors: Sargent Brandon S. , Ynchausti Collin R. , Nelson Todd G. , Howell Larry L. 
Published: December 2021

AbstractThis paper presents a method for predicting endpoint coordinates, stress, and force to deflect stepped cantilever beams under large deflections. This method, the mixed-body model or MBM, combines small deflection theory and the pseudo-rigid-body model for large deflections. To analyze the efficacy of the model, the MBM is compared to a model that assumes the first step in the beam to be rigid, to finite element analysis, and to the numerical boundary value solution over a large sample set of loading conditions, geometries, and material properties. The model was also compared to physical prototypes. In all cases, the MBM agrees well with expected values. Optimization of the MBM parameters yielded increased agreement, leading to average errors of &lt;0.01 to 3%. The model provides a simple, quick solution with minimal error that can be particularly helpful in design.
Toward the Design of Kresling Tower Origami As a Compliant Building Block
Authors: Berre J. , Geiskopf F. , Rubbert L. , Renaud P. 
Published: December 2021

Abstract
In this paper, the use of the Kresling tower origami as a building block for compliant mechanism design is considered. To help building systems using this origami, models are derived to link the origami pattern geometry to the Kresling tower characteristics. This includes the position of stable configurations, the helical trajectory describing the motion and the orientation of panels during the tower deployment. The provided analytical expressions are helpful to adjust the tower geometry according to desired specification. In addition, an original modification of fold geometry is introduced to modify the tower stiffness. Material removal at specific locations, where maximum fold deformations occur, aims at reducing the actuation force without affecting the kinematics. Experimental evaluation is conducted to assess the relevance of the proposed models and evaluate the impact of fold line modification. The proposed simplified models are precise enough for the synthesis. The capacity to strongly reduce the actuation force, due to the fold line modification, is observed.
Tracing fluid evolution in sedimentary basins with calcite geochemical, isotopic and U-Pb geochronological data: Implications for petroleum and mineral resource accumulation in the Nanpanjiang Basin, South China
Authors: Ge Xiang , Shen Chuanbo , Zhou Renjie , He Peng , Zhao Jianxin , Feng Yuexing 
Published: December 2021

AbstractFluid migration in sedimentary basins enable mass and energy transport and play critical roles in geochemical and geodynamical evolution of sedimentary basins. Moreover, reconstructing sedimentary basin fluid evolution from the geological record aids in constraining the evolution of associated petroleum and mineralization systems. As a relict of fluid flow activity, calcite is often a record of fluid flow and therefore can be used to characterize the fluids responsible for its precipitation.Here we study the Nanpanjiang Basin in South China where petroleum reservoirs and Carlin-type gold deposits spatially coincide. Through in situ U-Pb dating and geochemical analysis (87Sr/86Sr, δ18OVienna standard mean ocean water, δ13CVienna Peedee belemnite, rare earth elements) of calcite, this work constrains the key times related to petroleum migration/accumulation and Carlin-type gold mineralization, defines the basin fluid evolution, and proposes a genetic model for petroleum accumulation and gold mineralization within the Nanpanjiang Basin. The U-Pb age (ca. 241.4 Ma) for the gray/black calcite related to bitumen indicates the petroleum migration/accumulation occurred during the Triassic. The U-Pb date (ca. 106–121 Ma) of the white calcite associated with the gold-bearing pyrite, realgar, and fluorite record the lower timing limit of the Carlin-type gold systems. The geochemical data suggest both calcite types are cogenetic but suffered complex evolution with the gray/black calcite precipitating under low temperatures related to the continuous basin burial and the white calcite affected by post formation alteration related to both hydrothermal and meteoric fluids. Combined with the regional tectonic history, the Early Triassic petroleum migration/accumulation and the Early Cretaceous secondary Carlin-type gold mineralization events are considered to be related to the collision between the Indo-China and South China blocks, and the subduction between the Paleo-Pacific and Eurasian plates, respectively.
Nothing But Depopulation? Lateral Rural Migration In The Old-Developed Forest Non-Chernozem Territories
Authors: Averkieva K. V. 
Published: December 2021

Abstract—In the article, the author poses the question of what migration processes took place in the post-Soviet period at the intraregional level against depopulation and spatial polarization inherent to areas of the old-developed Non-Chernozem Region, and how this influenced the current state of populated areas and the overall rural settlement pattern. Totemsky district of Vologda Oblast was chosen as the research site for the study. Field research materials and analysis of local-level statistics made it possible to trace the rural population dynamics and identify the resettlement of rural residents within the district. The territorial units considered by the author were administrative rural units (sel’sovets) within the old borders, before the municipal reform and consolidation of the 2010s, which corresponded to individual rural clusters or large logging centers. Territories with different geographic positions and economic conditions were selected. Depopulation in the post-Soviet period proceeded unevenly, but its territorial projection did not just obey the center–periphery logic. The rural population grew in size both in district center and village near gas compressor stations, as well as in a number of other settlements with different characteristics. The post-Soviet dynamics of population numbers and transformation of the economy of the settlements were influenced by the peculiarities of their microlocation, buildings development, neighborhoods, and other local and almost nonparameterizable factors. They also often affect the attractiveness of rural settlements for the seasonal population, which fosters temporary support of the historical settlement network and generates some small potential for the redevelopment of certain territories.
Evaluation of retinal nerve fibre layer thickness as a possible measure of diabetic retinal neurodegeneration in the EPIC-Norfolk Eye Study
Authors: Zafar Sidra , Staggers Kristen A , Gao Jie , Liu Yao , Patel Praveen J , Foster Paul J , Frankfort Benjamin J , Abramoff Michael , Minard Charles G , Warwick Alasdair , Khawaja Anthony P , Channa Roomasa 
Published: December 2021

Background/aimsMarkers to clinically evaluate structural changes from diabetic retinal neurodegeneration (DRN) have not yet been established. To study the potential role of peripapillary retinal nerve fibre layer (pRNFL) thickness as a marker for DRN, we evaluated the relationship between diabetes, as well as glycaemic control irrespective of diabetes status and pRNFL thickness.MethodsLeveraging data from a population-based cohort, we used general linear mixed models (GLMMs) with a random intercept for patient and eye to assess the association between pRNFL thickness (measured using GDx) and demographic, systemic and ocular parameters after adjusting for typical scan score. GLMMs were also used to determine: (1) the relationship between: (A) glycated haemoglobin (HbA1c) irrespective of diabetes diagnosis and pRNFL thickness, (B) diabetes and pRNFL thickness and (2) which quadrants of pRNFL may be affected in participants with diabetes and in relation to HbA1c.Results7076 participants were included. After controlling for covariates, inferior pRNFL thickness was 0.94 µm lower (95% CI −1.28 µm to −0.60 µm), superior pRNFL thickness was 0.83 µm lower (95% CI −1.17 µm to −0.49 µm) and temporal pRNFL thickness was 1.33 µm higher (95% CI 0.99 µm to 1.67 µm) per unit increase in HbA1c. Nasal pRNFL thickness was not significantly associated with HbA1c (p=0.23). Similar trends were noted when diabetes was used as the predictor.ConclusionSuperior and inferior pRNFL was significantly thinner among those with higher HbA1c levels and/or diabetes, representing areas of the pRNFL that may be most affected by diabetes.
Advanced portal venous access techniques for transjugular intrahepatic portosystemic shunt placement
Authors: Partovi Sasan , Li Xin , Shwaiki Omar , Rashwan Basem , Ruff Christer , Grozinger Gerd , Gadani Sameer , Szaflarski Diane , Thompson Dustin , D'Amico Guiseppe , Levitin Abraham , Kapoor Baljendra 
Published: December 2021

IntroductionTransjugular intrahepatic portosystemic shunt (TIPS) placement is a well-established but technically challenging procedure for the management of sequelae of end-stage liver disease. Performed essentially blindly, traditional fluoroscopically guided TIPS placement requires multiple needle passes and prolonged radiation exposure to achieve successful portal venous access, thus increasing procedure time and the risk of periprocedural complications. Several advanced image-guided portal access techniques, including intracardiac echocardiography (ICE)-guided access, cone-beam CT (CBCT)-guided access and wire-targeting access techniques, can serve as alternatives to traditional CO2portography-based TIPS creation.MethodsA literature search was performed on the electronic databases including MEDLINE and Embase, from 2000 to the present to identify all relevant studies. The reference list also included studies identified manually, and studies referenced for other purposes.FindingsThe main benefit of these advanced access techniques is that they allow the operator to avoid essentially blind portal punctures, and the ability to visualise the target, thus reducing the number of required needle passes. Research has shown that ICE-guided access can decrease the radiation exposure, procedure time and complication rate in patients undergoing TIPS placement. This technique is particularly useful in patients with challenging portal venous anatomy. However, ICE-guided access requires additional equipment and possibly a second operator. Other studies have shown that CBCT-guided access, when compared with traditional fluoroscopy-guided access, provides superior visualisation of the anatomy with similar amount of radiation exposure and procedure time. The wire-targeting technique, on the other hand, appears to offer reductions in procedure time and radiation exposure by enabling real-time guidance. However, this technique necessitates percutaneous injury to the liver parenchyma in order to place the target wire.ConclusionAdvanced portal access techniques have certain advantages over the traditional fluoroscopically guided TIPS access. To date, few studies have compared these advanced guided access options, and further research is required.
Association between egg consumption and metabolic syndrome in Chinese population: a cross-sectional study
Authors: Wang Haochen , Wang Wanchun , Shen Minren , Yang Zidan , Wang Ning , Zhu Zhenglei , Wu Ziying , Xie Dongxing 
Published: December 2021

ObjectivesMetabolic syndrome (MS) comprises a constellation of symptoms that include abdominal obesity, hypertension, hyperglycaemia and dyslipidaemia. Dietary intake is a crucial environmental risk factor for MS, but the exact association between MS and egg consumption, which accounts for more than half of the daily total cholesterol intake in Chinese population, has not been previously studied. The aim of this study was to examine the correlation between dietary egg consumption and the prevalence of MS in the context of a large population.DesignA cross-sectional study.SettingsOur study was conducted in a health examination centre in China.ParticipantsParticipants who aged ≥40 years and received routine physical examinations were included for analyses.Main outcome measuresMS was diagnosed in accordance with the clinical diagnosis criteria specified in the American Heart Association Guidelines. Egg consumption was assessed by a validated semi-quantitative food frequency questionnaire.ResultsA total of 11 529 participants (46.2% women) were included in the present study. On the basis of multivariable logistic regression analysis, egg consumption was negatively associated with the prevalence of MS after adjusting for dietary energy intake (OR=0.84, 95% CI 0.76 to 0.93, p value for trend=0.001). The above findings did not change with further adjustment for other potential confounders: model 2 was further adjusted for age, body mass index and sex (based on model 1) and model 3 was further adjusted for education level, physical activity level, smoking status, alcohol use status, dietary fat intake, dietary fibre intake and nutritional supplementation (based on model 2). Consistent results were obtained from the analysis in the female subgroup but not in male subjects.ConclusionsA higher level of egg consumption was associated with a lower prevalence of MS in our study participants, and particularly in female subjects.
Melatonin for prevention of postoperative delirium after lower limb fracture surgery in elderly patients (DELIRLESS): study protocol for a multicentre randomised controlled trial
Authors: Sigaut Stéphanie , Couffignal Camille , Esposito-Farèse Marina , Degos Vincent , Molliex Serge , Boddaert Jacques , Raynaud-Simon Agathe , Durand-Zaleski Isabelle , Marcault Estelle , Jacota Madalina , Dahmani Souhayl , Paugam-Burtz Catherine , Weiss Emmanuel 
Published: December 2021

IntroductionPostoperative delirium (POD) is one of the most frequent complication after surgery in elderly patients, and is associated with increased morbidity and mortality, prolonged length of stay, cognitive and functional decline leading to loss of autonomy, and important additional healthcare costs. Perioperative inflammatory stress is a key element in POD genesis. Melatonin exhibits antioxidative and immune-modulatory proprieties that are promising concerning delirium prevention, but in perioperative context literature are scarce and conflicting. We hypothesise that perioperative melatonin can reduce the incidence of POD.Methods and analysisThe DELIRLESS trial is a prospective, national multicentric, phase III, superiority, comparative randomised (1:1) double-blind clinical trial. Among patients aged 70 or older, hospitalised and scheduled for surgery of a severe fracture of a lower limb, 718 will be randomly allocated to receive either melatonin 4 mg per os or placebo, every night from anaesthesiologist preoperative consultation and up to 5 days after surgery. The primary outcome is POD incidence measured by either the French validated translation of the Confusion Assessment Method (CAM) score for patients hospitalised in surgery, or CAM-ICU score for patients hospitalised in ICU (Intensive Care Unit). Daily delirium assessment will take place during 10 days after surgery, or until the end of hospital stay if it is shorter. POD cumulative incidence function will be compared at day 10 between the two randomised arms in a competing risks framework, using the Fine and Grey model with death as a competing risk of delirium.Ethics and disseminationThe DELIRLESS trial has been approved by an independent ethics committee the Comité de Protection des Personnes (CPP) Sud-Est (ref CPP2020-18-99 2019-003210-14) for all study centres. Participant recruitment begins in December 2020. Results will be published in international peer-reviewed medical journals.Trial registration numberNCT04335968, first posted 7 April 2020.Protocol version identifierN°3–0, 3 May 2021.