bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation Study of Permanent Magnetic Actuation for a Hydraulic Valve With Hysteresis Response Behavior
Authors: Scherrer Matthias , Hauser Erwin , Scheidl Rudolf 
Published: October 2020

Abstract
For the realization of compact and lightweight digital hydraulic cylinder drives for exoskeleton actuation the hydraulic binary counter concept was proposed. This counter principle is based on hydraulically piloted switching valves which feature a hysteretic response with respect to the pilot pressure. In first prototypes of that counter bistable mechanical buckling beams realized the hysteretic response. Their performance suffered from high friction in the hinges and high local stresses. Furthermore, they require tight manufacturing tolerances not only of themselves but also of their bearing structure. In this paper, the usage of a permanent magnet concept to realize the hysteresis function in an alternative way is studied. The valve spool is made of a ferromagnetic material and is attracted or repelled by a permanent magnet made of a Neodymium-Iron-Bor. The expected benefits are lower friction, lower demands on manufacturing tolerances, and an easier assembly of the valve. To find an advantageous embodiment of this functioning principle ring or disc shaped magnets of different sizes are analyzed. The magnetic forces exhibited by these different magnetic circuit designs are simulated with the Magnetic Finite Element code ‘FEMM’. The quasi-static magnetic forces at different spool positions are computed. Magnetic saturation and remanence are considered in this analysis. The aim is to achieve the required force on the piston and, thus, ensure the valve’s functionality. At the same time, however, the valve should be designed as compact and light as possible. The Finite element simulations are compared with an analytical model which provides a compact understanding of the influence of the design parameters on the functional and non functional performance criteria.
New Design Concepts for the Tribological Contact of Cylinder Block and Valve Plate
Authors: Geffroy Stefan , Wegner Stephan , Gels Stefan , Murrenhoff Hubertus , Schmitz Katharina 
Published: October 2020

Abstract
Axial piston machines are the most widely used type of hydraulic displacement machines and are characterized by their high reliability and efficiency. However, in order to ensure the high efficiency, the tribological contacts have to be precisely optimized. One of the three essential contacts in axial piston machines is the contact of valve plate and cylinder block, which is the subject of this paper. In a previous research project, a simulation model was built up specifically for the tribological contact of valve plate and cylinder block. A test rig was developed and installed for the validation of the simulation results. Both, the experimental and the simulation results show that the cylinder block tilts to the high-pressure side. It holds this preferred position nearly constantly for the different load situations over one revolution with four or five pistons pressurized with high pressure at the same time. The tilting increases the danger of solid body contact in the area of minimum gap height. In addition, it leads to temperature hot spots. Both effects necessitate the use of coatings as alternatives to the commonly used leaded alloys. This paper presents new design concepts for the optimization of the tribological contact of valve plate and cylinder block. Additional pressure pockets in the valve plate’s high-pressure kidney generate a torque and thus reduce the tilt angle of the cylinder block. By implementing additional pressure pockets at the cylinder block an imbalance results, which prevents a constant preferred position. Both concepts have the aim to reduce the heat concentration and improving the overall behavior of the tribological contact. The development and comparison of these concepts are based on a numerical analysis.
Study on an Underwater Flexible Manipulator Based on Hydraulic Drive
Authors: Li Xin , Xu He , Yang Chen , Wang Haihang , Yu Fengshu 
Published: October 2020

Abstract
The underwater flexible robot is a field of continuous exploration and innovation. An underwater flexible manipulator with the functions of bending and grasping is presented in this paper, which is driven by the water hydraulic. The flexible manipulator is consisted mainly of three sets of transverse and three sets of longitudinal Mckibben artificial muscles (MAM) equidistantly arranged. The motions of the manipulator were driven by accurately controlling the length of each MAM that was changed by controlling the internal pressure, which was provided by the hydraulic power subsystem. The flexible manipulator was controlled remotely by the control subsystem. The inverse kinematics of the flexible manipulator was studied based on the neural network in this paper. The feasibility of the neural network inverse kinematics was proved by the data analysis. The three-dimensional virtual model of the flexible manipulator was projected into the captured real scene by the augmented reality (AR) technology to judge the bending degree of the manipulator operation, which could be seen in the experiment image.
Methodology for the Evaluation of Gear Pump Performance
Authors: Williams Logan T. 
Published: October 2020

Abstract
Currently, most performance curves of gear pumps present volumetric efficiency as a function of one or more operating conditions. However, the nature of gear pumps is that volumetric efficiency is dependent on pump speed, pump pressure rise, and fluid viscosity. This dependency on multiple parameters impedes direct comparisons between pumps tested at disparate operating conditions or on different testbeds. A new method has been developed that formulates the volumetric efficiency as a function of a single parameter that captures pump speed, pressure, and fluid viscosity. The characteristics of the pump is then captured by curve fitting two constants to empirical data. This method allows extrapolation of pump performance beyond empirical data and direct comparison of the volumetric efficiency curves of two pumps tested under disparate conditions within a single plot. This work describes the analytical derivation of the methodology and the empirical data used for validations. Additionally, several possible applications of this method are presented.
Impact of Dynamics on the Losses at Radial Ball Piston Pump Interfaces
Authors: Bohach Garrett , Nahin Md Minal , Severson Eric , Van de Ven James D. 
Published: October 2020

Abstract
This paper presents a mathematical model of a radial ball piston pump/motor. The specific application of the pump is for direct integration with a high speed electric motor for use in off highway vehicles. The pump/motor must operate across all four quadrants with high flow rates at a low pressure differential. The model captures the major mechanical and volumetric losses within the hydraulic machine with specific attention given to the ball-cylinder interface and the pintle-rotor interface. The leakage and shear at the ball piston interface are dependent on the position of the ball piston in the cylinder; therefore, the dynamics of the ball piston are calculated. The pintle-rotor model includes the port geometry, which influences the flow rates into and out of the pump/motor. Leakage and shear at the interface are dependent on the gap height between the two surfaces; consequently, the model calculates the radial forces acting on the rotor and uses journal bearing theory to predict the eccentricity. This eccentricity balances the other forces and is necessary to determine the interface losses. Lastly, the importance of these dynamics is evaluated to determine which are needed in a future optimization framework. It is shown that considering the dynamics of both interfaces captures significantly more losses and results in a more accurate model than an earlier simplified one.
Development of a Physical Analog Excavator for Studies in Interactions Between Hydraulic Equipment and Human Operators
Authors: Wiens Travis , Klarkowski Madison , Zahabi Nima 
Published: October 2020

Abstract
This paper presents a scale model excavator intended to allow for studies on human-machine interactions. In the past, this work has been performed on full-scale equipment which can be dangerous and costly to acquire and operate, or fully in simulation, which requires high precision models of complex effects such as soil forces (e.g. using the Discrete Element Method, DEM, simulating thousands of particles). Also simulation models with scenes projected on computer monitors or in virtual reality may not be realistic enough for the human operator to be fully immersed and behave in a realistic manner. The motion of the small-scale excavator presented here is directed by a digital model of a hydraulic machine given inputs of operator commands and actuator forces, allowing it to mimic the behavior of various hydraulic architectures (e.g. pressure compensated load sensing vs open center vs closed center systems). The excavator is used to dig in physical soils, generating realistic soil-tool interaction forces (which are fed back into the digital machine model) without the need for computationally expensive DEM models. This allows for rapid, low-cost evaluation of various hardware modifications as well as human-machine interaction effects. We also present some preliminary data from a pilot study investigating energy efficiency.
On/Off Valves Synchronization and Reliability Evaluation of a Digital Hydraulic Actuator
Authors: Mantovani Ivan J. , Kagueiama Heitor A. , Gama Artur T. de C. , Dell' Amico Alessandro , Krus Petter , De Negri Victor J. 
Published: October 2020

Abstract
The development of actuators for flight control surfaces based on electrical technologies had a breakthrough in the last decade. Nevertheless, servo-hydraulic systems are still widely used. Servo Hydraulic Actuators (SHA) have the advantages of precise positioning, high dynamic response and being a jam-free solution in case of failures, but they present low energy efficiency. Digital hydraulics has become a topic of interest in improving energy efficiency in the fluid power community. A Digital Hydraulic Actuator (DHA) for aircraft is being developed to be used in primary flight control surfaces. The DHA concept is based on secondary control with multi-chamber cylinders and shows an energy efficiency gain with a similar response when compared to SHA. However, the opening and closing times of on/off valves are different and uncertain. These aspects may result in short circuits, bringing energy losses, or in blocked chambers, which may cause pressure peaks or cavitation. Consequently, the DHA system may have a lower energy efficiency or presents vibration due to fluid blocking. The present paper presents a solution for these issues and the reliability evaluation of the DHA. The opening and closing times issues are addressed using the synchronization between on/off valves through a method to find the correct time for valve opening control. As a result, the synchronization of pressure shifting without knowledge of the response times of on/off valves was accomplished. Moreover, when used periodically, this method can estimate future failures in valves due to a change of the required time delay. In order to evaluate the system reliability, FTA models were developed considering valve and pressure line failures, modelling how the failures affect force availability to move the control surfaces. The resulting FTAs were reduced to the minimum cut-sets that lead to force profiles that are insufficient for a safe flight and also may lead to an aircraft crash. Considering that the on/off valves have similar failure rates to those of servo valves, the results show that DHA and SHA have comparable reliability levels.
Valve Timing and Area Profile Selection for Hydraulic Pumps and Motors
Authors: Boyce-Erickson Grey C. , Chase Thomas R. , Van de Ven James D. 
Published: October 2020

Abstract
A significant amount of research has been conducted to select valve timing and area profiles that create efficient and quiet hydraulic pumps and motors. Numerous active valve architectures have been modeled and optimized, but the rationale for the final solution is often unclear. The solution is usually highly dependent on the modeled valve geometry constraints and the duty cycle of the pump or motor for which the valve was optimized. In contrast, this paper proposes a methodology for designing efficient valving that is not constrained to any specific valve geometry, operating point, parameterization, or physical system limitation. An idealized valve area profile is formulated using a piston-cylinder model with variable valve openings. A working fluid that has a pressure dependent bulk modulus is utilized in the model. The valve timing is idealized by constraining it to produce a specified constant pressure drop across the valve. The idealized area profile is synthesized by modeling the piston-cylinder as a pump with passive (check) valves. A representation of the idealized timing is demonstrated for positive pressure differential and positive rotation direction, also known as the first quadrant. The effect of varying pressure on valve timing is shown for the first quadrant, but the trend can be extrapolated for all quadrants of operation. The idealized valve area profile is implemented as fixed valve timing in a pump-motor, meaning the valve area is only a function of the timing angle of the rotating group. Fixed valve timing is preferred to variable valve timing as it can often be implemented mechanically, increasing reliability. The pump-motor is simulated in one rotation direction through a pressure range. Performance is high in pumping operation, but when the pressure differential is reversed, cylinder pressure spikes ensue. Two strategies to modify an idealized valve area profile are presented: timing grooves and a pressure shifted valve timing. Timing grooves reduce pressure spikes and cavitation in the cylinder but generally increase throttling losses. A pressure shifted valve timing has lower throttling energy losses, making it the favored solution.
A Design Procedure for Multistage External Gear Pumps
Authors: Guerra Davide , Polastri Marco , Battarra Mattia , Suman Alessio , Mucchi Emiliano , Pinelli Michele 
Published: October 2020

Abstract
In this work, the authors present a robust and integrated procedure for the design of multi-stage gear pumps to be used in dry sump system applications. Based on the target delivery flow rate, rotational speed and fluid properties, the developed iterative method enables to directly obtain the geometrical features and the working parameters of the pump components, such as gearpair specifics, shaft and journal bearing dimensions, clearance values. The methodology is then applied to a case study in order to highlight its features and detail the achievable outcomes. Quality of the results is assessed by means of a CFD analysis, demonstrating the capability to obtain the expected volumetric efficiency.
Fast Calculation of Stiff Hydraulic Models Using the Modified Pseudo-Dynamic Solver
Authors: Malysheva Julia , Handroos Heikki 
Published: October 2020

Abstract
The work addresses the problem of the fast and accurate calculation of the mathematically stiff hydraulic models using the modified pseudo-dynamic solver (PDS). In particular, it studies which of the numerical integration methods inside the modified PDS ensure efficient calculation of the stiff hydraulic model. In the work, the operating principle of the modified PDS is described. The effect of the three different fixed-step integration methods (Euler, Runge-Kutta of fourth order, and modified Heun’s method) are considered. The numerical stability of the modified Heun’s method is improved by substituting the purely turbulent orifice model with the two-regime orifice model. The two-regime orifice accounts for both the turbulent and laminar flows and thus allows to avoid the numerical problems related to the small pressure drops. As a numerical example of the mathematically stiff hydraulic model a hydraulic circuit with the two-way flow control valve which contains small volume is employed. As the implementation environment for the developed simulation models the compiled C language that supports the real-time simulation is chosen. The solutions obtained for the numerical example using the modified PDS based on the three integration methods, their accuracies and calculation speeds are presented in comparison with the solution obtained using conventional integration procedure. The obtained results show that, in general, the modified PDS allows to solve numerically stiff hydraulic models in a very efficient way ensuring accelerated simulation with the high solution accuracy. It is also shown that the simulation speed-up can be obtained not only by the complexity reduction of the numerical integration method employed inside the modified PDS but also by increasing its numerical stability.
Additive effects of green tea and coffee on all-cause mortality in patients with type 2 diabetes mellitus: the Fukuoka Diabetes Registry
Authors: Komorita Yuji , Iwase Masanori , Fujii Hiroki , Ohkuma Toshiaki , Ide Hitoshi , Jodai-Kitamura Tamaki , Yoshinari Masahito , Oku Yutaro , Higashi Taiki , Nakamura Udai , Kitazono Takanari 
Published: October 2020

IntroductionThe impact of consuming green tea or coffee on mortality in patients with diabetes is controversial. We prospectively investigated the impact of each beverage and their combination on mortality among Japanese patients with type 2 diabetes.Research design and methodsIn all, 4923 patients (2790 men, 2133 women) with type 2 diabetes (mean age, 66 years) were followed prospectively (median, 5.3 years; follow-up rate, 99.5%). We evaluated the amount of green tea and coffee consumed using self-administered questionnaires.ResultsDuring the follow-up period, 309 participants died. The consumption of green tea, coffee, and a combination of the beverages was associated with reduced all-cause mortality. Multivariable-adjusted hazard ratios (95% CIs) for green tea were as follows: none 1.0 (referent); 0.85 (0.60–1.22) for ≤1 cup/day; 0.73 (0.51–1.03) for 2–3 cups/day; 0.60 (0.42–0.85) for ≥4 cups/day; and P for trend, 0.002. For coffee, they were: none 1.0 (referent); 0.88 (0.66–1.18) for <1 cup/day; 0.81 (0.58–1.13) for 1 cup/day; 0.59 (0.42–0.82) for ≥2 cups/day; P for trend, 0.002. With the combination they were 1.0 (referent) for no consumption of green tea and coffee; 0.49 (0.24–0.99) for 2–3 cups/day of green tea with ≥2 cups/day of coffee; 0.42 (0.20–0.88) for ≥4 cups/day of green tea with 1 cup/day of coffee; and 0.37 (0.18–0.77) for ≥4 cups/day of green tea with ≥2 cups/day of coffee.ConclusionsHigher consumption of green tea and coffee was associated with reduced all-cause mortality: their combined effect appeared to be additive in patients with type 2 diabetes.
Artificial intelligence-enabled screening for diabetic retinopathy: a real-world, multicenter and prospective study
Authors: Zhang Yifei , Shi Juan , Peng Ying , Zhao Zhiyun , Zheng Qidong , Wang Zilong , Liu Kun , Jiao Shengyin , Qiu Kexin , Zhou Ziheng , Yan Li , Zhao Dong , Jiang Hongwei , Dai Yuancheng , Su Benli , Gu Pei , Su Heng , Wan Qin , Peng Yongde , Liu Jianjun , Hu Ling , Ke Tingyu , Chen Lei , Xu Fengmei , Dong Qijuan , Terzopoulos Demetri , Ning Guang , Xu Xun , Ding Xiaowei , Wang Weiqing 
Published: October 2020

IntroductionEarly screening for diabetic retinopathy (DR) with an efficient and scalable method is highly needed to reduce blindness, due to the growing epidemic of diabetes. The aim of the study was to validate an artificial intelligence-enabled DR screening and to investigate the prevalence of DR in adult patients with diabetes in China.Research design and methodsThe study was prospectively conducted at 155 diabetes centers in China. A non-mydriatic, macula-centered fundus photograph per eye was collected and graded through a deep learning (DL)-based, five-stage DR classification. Images from a randomly selected one-third of participants were used for the DL algorithm validation.ResultsIn total, 47 269 patients (mean (SD) age, 54.29 (11.60) years) were enrolled. 15 805 randomly selected participants were reviewed by a panel of specialists for DL algorithm validation. The DR grading algorithms had a 83.3% (95% CI: 81.9% to 84.6%) sensitivity and a 92.5% (95% CI: 92.1% to 92.9%) specificity to detect referable DR. The five-stage DR classification performance (concordance: 83.0%) is comparable to the interobserver variability of specialists (concordance: 84.3%). The estimated prevalence in patients with diabetes detected by DL algorithm for any DR, referable DR and vision-threatening DR were 28.8% (95% CI: 28.4% to 29.3%), 24.4% (95% CI: 24.0% to 24.8%) and 10.8% (95% CI: 10.5% to 11.1%), respectively. The prevalence was higher in female, elderly, longer diabetes duration and higher glycated hemoglobin groups.ConclusionThis study performed, a nationwide, multicenter, DL-based DR screening and the results indicated the importance and feasibility of DR screening in clinical practice with this system deployed at diabetes centers.Trial registration numberNCT04240652.
Reusability of filtering facepiece respirators after decontamination through drying and germicidal UV irradiation
Authors: Vernez David , Save Jonathan , Oppliger Anne , Concha-Lozano Nicolas , Hopf Nancy B , Niculita-Hirzel Hélène , Resch Grégory , Michaud Véronique , Dorange-Pattoret Laurie , Charrière Nicole , Batsungnoen Kiattisak , Suarez Guillaume 
Published: October 2020

IntroductionDuring pandemics, such as the SARS-CoV-2, filtering facepiece respirators plays an essential role in protecting healthcare personnel. The recycling of respirators is possible in case of critical shortage, but it raises the question of the effectiveness of decontamination as well as the performance of the reused respirators.MethodDisposable respirators were subjected to ultraviolet germicidal irradiation (UVGI) treatment at single or successive doses of 60 mJ/cm2after a short drying cycle (30 min, 70°C). The germicidal efficacy of this treatment was tested by spiking respirators with two staphylococcal bacteriophages (vB_HSa_2002 and P66 phages). The respirator performance was investigated by the following parameters: particle penetration (NaCl aerosol, 10–300 nm), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry and mechanical tensile tests.ResultsNo viable phage particles were recovered from any of the respirators after decontamination (log reduction in virus titre >3), and no reduction in chemical or physical properties (SEM, particle penetrations <5%–6%) were observed. Increasing the UVGI dose 10-fold led to chemical alterations of the respirator filtration media (FTIR) but did not affect the physical properties (particle penetration), which was unaltered even at 3000 mJ/cm2(50 cycles). When respirators had been used by healthcare workers and undergone decontamination, they had particle penetration significantly greater than never donned respirators.ConclusionThis decontamination procedure is an attractive method for respirators in case of shortages during a SARS pandemic. A successful implementation requires a careful design and particle penetration performance control tests over the successive reuse cycles.