bluuebunny/crossref_metadata_2025_split huggingface dataset:
Active expiratory oscillator regulates nasofacial and oral motor activities in rats
Authors: de Britto Alan A. , Magalhães Karolyne S. , da Silva Melina P. , Paton Julian F. R. , Moraes Davi J. A. 
Published: December 2019

New Findings
What is the central question of this study?
Does the parafacial respiratory group (pFRG), which mediates active expiration, recruit nasofacial and oral motoneurons to coordinate motor activities that engage muscles controlling airways in rats during active expiration.
What is the main finding and its importance?
Hypercapnia/acidosis or pFRG activation evoked active expiration and stimulated the motoneurons and nerves responsible for the control of nasofacial and oral airways patency simultaneously. Bilateral pFRG inhibition abolished active expiration and the simultaneous nasofacial and oral motor activities induced by hypercapnia/acidosis. The pFRG is more than a rhythmic oscillator for expiratory pump muscles: it also coordinates nasofacial and oral motor commands that engage muscles controlling airways.
AbstractActive expiration is mediated by an expiratory oscillator located in the parafacial respiratory group (pFRG). Active expiration requires more than contracting expiratory muscles as multiple cranial nerves are recruited to stabilize the naso‐ and oropharyngeal airways. We tested the hypothesis that activation of the pFRG recruits facial and trigeminal motoneurons to coordinate nasofacial and oral motor activities that engage muscles controlling airways in rats during active expiration. Using a combination of electrophysiological and pharmacological approaches, we identified brainstem circuits that phase‐lock active expiration, nasofacial and oral motor outputs in an in situ preparation of rat. We found that either high chemical drive (hypercapnia/acidosis) or unilateral excitation (glutamate microinjection) of the pFRG evoked active expiration and stimulated motoneurons (facial and trigeminal) and motor nerves responsible for the control of nasofacial (buccal and zygomatic branches of the facial nerve) and oral (mylohyoid nerve) motor outputs simultaneously. Bilateral pharmacological inhibition (GABAergic and glycinergic receptor activation) of the pFRG abolished active expiration and the simultaneous nasofacial and oral motor activities induced by hypercapnia/acidosis. We conclude that the pFRG provides the excitatory drive to phase‐lock rhythmic nasofacial and oral motor circuits during active expiration in rats. Therefore, the pFRG is more than a rhythmic oscillator for expiratory pump muscles: it also coordinates nasofacial and oral motor commands that engage muscles controlling airways in rats during active expiration.
Degeneración subaguda combinada secundaria a infección crónica por Helicobacter pylori. Reporte de caso
Authors: Márquez Juan Camilo , De Valencia Catalina , Ramírez Sandra Milena , Uribe Vargas Mario 
Published: December 2019

La degeneración subaguda combinada es una patología poco frecuente. El diagnóstico se establece correlacionando el cuadro clínico, los resultados de laboratorio y los hallazgos en la resonancia magnética. Se presenta el caso de una mujer con síntomas neurológicos característicos de mielopatía con nivel sensitivo C5, con imágenes de resonancia magnética cervical que revelan una afectación desmielinizante exclusivamente en los cordones posteriores de la médula espinal. Clínicamente se documentó anemia, gastritis crónica e infección por Helicobacter pylori, además de déficit paraclínico de cianocobalamina.
Meningioma selar gigante y síndrome frontal
Authors: Escudero Siosi Alexa José , Muñoz Ramírez Dalia Isadora , Chirveches Calvache María Alejandra 
Published: December 2019

Los meningiomas representan los tumores meníngeos benignos más comunes, cuya expresión clínica se encuentra directamente relacionada con su dimensión, ubicación y subsecuente compresión del tejido neural contiguo. Generalmente, el diagnóstico es un hallazgo incidental. Las alternativas de tratamiento pueden variar de paciente a paciente y, en algunos casos, el manejo quirúrgico puede ser un desafío. El presente reporte de caso corresponde al de un paciente atendido en el servicio de urgencias del Hospital Universitario San Ignacio en el 2012, a quien se le descubrió un meningioma selar gigante asociado con un síndrome frontal florido secundario.
Síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) y su relación con complicaciones perioperatorias: revisión de la literatura
Authors: Ruiz Morales Álvaro , Hidalgo Martínez Patricia , Sánchez Mejía Sandra I. , Perea Bello Ana H. , Segura Salguero Juan Camilo , Chavarriaga Soto Julián , Valencia Peña Maury , Rodríguez Salazar Catalina , Ruiz Delgado Julio A. , Chaparro de Reyes Laura Catalina 
Published: December 2019

El objetivo de este artículo es revisar la importancia del síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) en la población que va a ser llevada a cirugía y cómo detectar en el preoperatorio a pacientes con riesgo elevado de complicaciones en el perioperatorio mediante el cuestionario STOP-BANG. Para lo anterior, se realizó una búsqueda en las bases Pubmed, Science y SciELO. El SAHOS es un problema médico importante con prevalencia variable (hasta el 26 % en la población general dependiendo del centro donde se evalúe). Es una enfermedad de inicio insidioso y progresivo, en la que hay episodios recurrentes de apneas o hipopneas causadas por obstrucción de la vía aérea superior durante el sueño que produce un deterioro significativo de la calidad de vida. Se quiere evaluar si el cuestionario STOP-BANG es útil para identificar, en el preoperatorio, a pacientes que tengan complicaciones perioperatorias, probablemente porque identifica pacientes con SAHOS no diagnosticado.
Systematic Methodology for Reliability Analysis of Components in Axial Piston Units
Authors: Baus Ivan , Rahmfeld Robert , Schumacher Andreas , Pedersen Henrik C. 
Published: December 2019

Abstract
This paper covers a reliability analysis as a qualitative method, especially focused on axial piston units. The method is based on Fault Tree Analysis (FTA) and results in risk and reliability assessment at the components level. Especially, the development of the reliability assessment as a methodical tool is the core of the paper. Moreover, the FTA is combined with the industrial standard method known as Design Failure Mode Effects Analysis (DFMEA) which is typically used in the development phase of the design. The evaluation and the usability of the FTA methodology is analyzed in connection with field data. Thus, the deviation of the theoretical valuation from the field data was utilized as a success indicator of the method. The analysis of the fault spreading covers the assessment of component faults and links failure states with unit effects. The analysis of the axial piston unit as a system is made on idealized/theoretical design and functional behavior only. Hence, the failure rating and the effect is subsequently applied to determine the fault risk in form of the Risk Priority Number (RPN). The failure modes and effects are based on engineering experience of past decades, supported by existing DFMEAs of axial piston units. Thus, the assessment of the risk priority number is based on previous data, yielding the given severity, occurrence and detection quantification. This approach opens new opportunities of design assessment and the results show a good agreement to the damage accumulation seen in real field data. Furthermore, the connection between theoretical design assessment and field data do support the failure ranking improvement of the DFMEA.
A Hybrid Hydraulic-Electric Architecture (HHEA) for High Power Off-Road Mobile Machines
Authors: Li Perry Y. , Siefert Jacob , Bigelow David 
Published: December 2019

Abstract
Traditionally, off-road mobile machines such as excavators and wheel loaders are primarily powered by hydraulics and throttling valves are used to control their work circuits. In recent years, two general trends are towards more energy efficient systems and electrification. With electrification, both efficiency and control performance can be improved by the elimination of throttling losses and the use of high-bandwidth inverter control. Electrification is generally accomplished with Electro-hydraulic actuators (EHA) but they are limited to lower powered systems due to the high cost of electric machines capable of high power or high torque. This paper presents preliminary results of a new system architecture for off-road vehicles to improve efficiency and control performance. The architecture combines hydraulic power and electric power in such a way that the majority of power is provided hydraulically while electric drives are used to modulate this power. The hybrid hydraulic-electric architecture (HHEA) and its rationale are described. In addition, a case study is presented to illustrate its operation, its potential for energy saving, and its benefits of component downsizing. The case study indicates that compared to a baseline load sensing system, the HHEA has the potential to reduce energy consumption by more than 50%. Furthermore, the torque capability of the electrical components need only be ∼ 28% of what is required for the direct application of EHA.
Physically Motivated Simulation of Dynamic Hydraulic Seals
Authors: Angerhausen Julian , Murrenhoff Hubertus , Persson Bo N. J. , Schmitz Katharina 
Published: December 2019

Abstract
Seals are crucial machine elements, for example in hydraulic cylinders. However, especially in regard to dynamic seals, the theoretical understanding of the sealing mechanism is still insufficient. A physically motivated simulation can help to gain a more detailed understanding. In this contribution a elastohydrodynamic (EHD) seal simulation is presented. It is directly implemented in the commercial Software ABAQUS. The fluid film is considered by implementing the Reynolds equation. For a physically motivated simulation Persson’s theory of contact mechanics and rubber friction is used to calculate the solid contribution to the total friction of a hydraulic seal. Simulations for an oscillating motion of a cylinder rod, sealed by an O-ring seal, are carried out for different velocities and pressures. A qualitative comparison between measurement and simulation is provided. Hysteresis effects and the contributions from both, adhesive and viscoelastic friction to the total solid friction are investigated. The physical origin of these effects is discussed in order to provide a detailed understanding of the dynamic sealing mechanism.
Experimentally Validated Models for Switching Energy of Low Pressure Drop Digital Valves for Lightweight Portable Hydraulic Robots
Authors: Hashemi Saeed , Mitchell Hannah , Durfee William K. 
Published: December 2019

Abstract
The most critical factors for a switching valve in a lightweight, portable hydraulic systems are low pressure drop, low power consumption, fast response time, and small size and weight. In this paper, experimentally validated models are proposed for switching energy required by two valve architectures with minimum pressure drop (ball and butterfly valves). The orifice in a hydraulic valve creates a pressure drop across the valve that needs to be minimized especially for low-pressure passive applications. The ideal switching valve for a hydraulic device is one with an opening diameter that is the same as the hose diameter. Several valve architectures with low pressure drop can be motorized to be used as a digital valve. The valve operation mechanism determines the power consumption of the valve. In this paper, the energy to switch state was modeled for two rotary valve types: butterfly and ball. The model was being used to find the best valve configuration for low-pressure digital hydraulics. The model was validated through experiments on a low-pressure ball valve, a high-pressure ball valve, and a low-pressure butterfly valve. The butterfly valve has the lowest switching energy for the same geometry; however, this valve has a small pressure drop due to the presence of the disc in the open position. We conclude that either ball or butterfly valves are suitable for low-pressure, small-scale hydraulic applications.
Definition of Performance Requirements and Test Cases for Offshore/Subsea Winch Drive Systems With Digital Hydraulic Motors
Authors: Nordås Sondre , Ebbesen Morten K. , Andersen Torben O. 
Published: December 2019

Abstract
A subsea crane is normally mounted on a floating vessel and equipped with a winch system. The crane can operate in water down to 3000 m. The vessel tends to move up and down due to waves. This heave motion makes offshore lifting operations challenging. In order to ease the winch operation in rough sea, the winch can be equipped with additional systems like active heave compensation and constant tension. In active heave compensation and constant tension system, both motion and force control of the winch are important. This paper presents a digital displacement winch drive system and gives a description of challenges related to subsea lifting operations. The operation challenges are used to design a set of test cases for evaluating the performance of the digital displacement winch drive system.
Efficiency Optimized Pneumatic Pressure Booster
Authors: Reinertz Olivier , Schmitz Katharina 
Published: December 2019

Abstract
In the scope of this paper, a novel efficiency optimized supply pressure adaptive concept of pneumatic pressure boosters is presented. It is deduced from a profound analysis of state of the art components. The working cycle of the pump chambers can be divided into a filling, compression, pumping and decompression phase. A promising solution for efficiency improvements, which is further analyzed in the scope of this paper, is to adapt the required force of the compression chambers by nonlinear mechanics. Thus, a smaller force at the end of the stroke is required and a reduced air consumption of the driving chamber occurs. As the force demand of the compression chamber and therewith the load distribution over the stroke changes with the operational pressures, an adaptive concept needs to be implemented.
The novel device and its parameterization are deduced by means of an analytical description of state of the art pressure boosters. Subsequently, it is investigated by one-dimensional simulation in DSHplus. The results show broad applicability of the method in relevant applications and huge energy saving potentials compared to state of the art products.
Mechanical and Hydraulic Actuation Strategies for Mainstage Spool Valves in Hydraulic Motors
Authors: Boyce-Erickson Grey C. , Fulbright Nathaniel J. , Voth John A. F. , Chase Thomas R. , Li Perry Y. , Van de Ven James D. 
Published: December 2019

Abstract
A large variety of options for the internal valves of a hydraulic motor are available. Poppet valves, rotary valves, and port plates are common options, but each have drawbacks such as actuation force, complexity, leakage, or friction. An alternative type that is also common is spool valves. Spool valves require minimal actuation force and have low throttling losses if sized correctly. This paper compares two drive options for a mainstage spool valve: a hydraulic pilot from a rotary valve and mechanical actuation. Dynamic models of the two valve configurations are created to carry out design studies and evaluate the performance of the motor. Compressibility effects, viscous drag, and flow forces are included in the model. Simulations show that the rotary valve pilot operation causes an unacceptable lag in the motion of the spool that cannot be corrected without reducing performance when running in reverse. Furthermore, the rotary pilot stage drive results in the motor timing becoming retarded at higher operating speeds. For these reasons, mechanically actuated valves are preferred over pilot operated valves for hydraulic motors operated bi-directionally or across a wide speed range.
H
2-Optimal Low Order Transmission Line Models
Authors: Manhartsgruber Bernhard 
Published: December 2019

Abstract
Transmission line modeling has played a crucial role in understanding the dynamics of fluid power systems. A vast body of literature exists from simple lumped parameter approaches to fully coupled three-dimensional fluid structure interaction models. When it comes to computationally efficient, yet physically sound low order models needed for fast computations iteratively called by optimization codes or for the purpose of model based control design, there is still room for improvement. Modal approximations of the input-output behaviour of liquid transmission lines have been around for decades. The basic idea of tuning the parameters of a canonical linear time invariant state space model to fit the transfer functions of a transmission line model in the H2-optimal sense under passivity constraints has been published by the author of the present paper in the past. However, the method so far was barely usable due to numerical difficulties in the underlying optimization process. A new implementation of the method employing quadruple-precision floating point numbers has recently been found to resolve the convergence problems and is reported in the present paper. The new version of the method is based on analytic computation of the cost and constraint functions as well as their gradients in the computer algebra package Maple and automatic code generation for compilation in FORTRAN. Results are very promising because both the entire low frequency behaviour and the first three eigenmodes of a transmission line model can be accurately covered by a model of order eight only.
Series, Parallel, and Hybrid Series-Parallel Hydrostatic Transmission Architectures for Ground Locomotion
Authors: Martelli Massimo , Marani Pietro , Gessi Silvia 
Published: December 2019

Abstract
Ground locomotion of wheeled vehicles, in all-wheel drive configuration, is subject to unique, generally highly variable and not predictable, loading conditions on the driveline subsystem. Any sensible design must cope at least with the effects induced by slope changes, asymmetrical losses of adherence and cornering maneuvers.
When severe constraints on the driveline layout make the implementation of standard mechanical transmissions unfeasible, a typical option is given by compound hydrostatic transmission architectures, with multiple dedicated motor-wheels.
Requirements are then defined on two different levels: at vehicle level, traction functionality must never be lost; at hydraulic circuit level, all components must work within their nominal operating ranges and hydraulic stresses must be limited.
Common standard topologies for motor connection, viz. series and parallel, come with different strengths and weaknesses, often requiring the implementation of auxiliary highly dissipative compensation components and/or complex electronic control, while a hybrid series-parallel concept, derived from a patented application, based on three-port motors allows the implementation of an effective, purely hydraulic system.
In the present work, a general comparison of the above-mentioned architectures is provided, by means of numerical simulation, over a wide set of virtual experiments. Each architecture is analyzed: its specific features are described and the correlation between hydraulic performance/specifications and vehicle traction performance is pointed out.
Experimental Testing of a Variable Displacement Pump/Motor That Uses a Hydro-Mechanically Timed Digital Valving Mechanism to Achieve Partial-Stroke Piston Pressurization (PSPP)
Authors: Montzka Alissa , Epstein Nathan , Rannow Michael , Chase Thomas R. , Li Perry Y. 
Published: December 2019

Abstract
This work describes an efficient means to adjust the power level of an axial piston hydraulic pump/motor. Conventionally, the displacement of a piston pump is varied by changing the stroke length of each piston. Since the losses do not decrease proportionally to the displacement, the efficiency is low at low displacements. Here, with partial-stroke piston pressurization (PSPP), displacement is varied by changing the portion of the piston stroke over which the piston is subjected to high pressure. Since leakage and friction losses drop as the displacement is decreased, higher efficiency is achieved at low displacements with PSPP. While other systems have implemented PSPP with electric or cam-actuated valves, the pump described in this paper is unique in implementing PSPP by way of a simple, robust hydro-mechanical valve system. Experimental testing of a prototype PSPP pump/motor shows that the full load efficiency is maintained even at low displacements.
Designing an Improved Controller for a Pump Direct Driven Electro-Hydraulic System Using a Nonlinear Flow Mapping
Authors: Helian Bobo , Chen Zheng , Yao Bin , Yang Can 
Published: December 2019

Abstract
Pump control systems are widely used, because of their energy saving properties and their high efficiency. Nevertheless, pump control systems generally have a low accuracy, because of the nonlinear pump flow and other nonlinearities of hydraulic systems. Furthermore, due to the underlaying high order dynamics, pump control systems have low response times, which is one of the main drawbacks. Servo motor-pump direct driven systems are commonly used in today’s industry. The application of servo motor pumps allow a reliable performance with quick response times. For low speeds, however, servo motor pumps do not achieve a high accuracy due to the pump flow deviation. The goal of this paper is to present a controller for a servo motor-pump direct driven system, which improves the accuracy especially at low pump speeds. For that purpose, the controller uses a nonlinear flow mapping, which maps the desired pump flow and pump pressure to the voltage input for the motor-pump. Additionally, the controller uses a backstepping method, which tracks the position as a first step and regulates the pressure as a second step. Comparison experiments to a controller without nonlinear flow mapping show that the controller designed in this paper has improved performances and tracking accuracy.
2D CFD Analysis of Servovalve Main Stage Internal Leakage
Authors: Tamburrano Paolo , Plummer Andrew R. , Elliott Phil , Morris William , Page Sam , Distaso Elia , Amirante Riccardo , De Palma Pietro 
Published: December 2019

Abstract
This paper presents research aimed at understanding the effects of geometrical imperfections and tolerances upon the internal leakage occurring around null in the main stages of servovalves. Specifically, a two-dimensional (2D) computational fluid dynamic analysis was used to predict the direct leakage flow as a function of the overlap and clearance between the spool and bushing sleeve, as well as the roundness on the edges of the spool and bushing sleeve. Predictions of direct leakage flow against edge overlap, which have general validity, are provided in the paper for three selected values of the pressure drop. For different values of the pressure drop, analytical correlations can be applied using the data retrieved from these graphs. The analysis shows that the leakage flow is highly affected by the above-mentioned geometrical parameters. As expected, for given values of overlap and radial clearance, the greater the roundness of the edges caused by manufacturing processes or wear, the higher the leakage flow. For low leakage and hence low power loss requirement, the radii on the spool and bushing sleeve as well as the clearance must be maintained as low as possible. In addition, it is well-known that overlap between the spool and its bushing sleeve can help to reduce the leakage flow at null, and the effect of edge roundness on this reduction is now revealed.