bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Method for Performance Measurement of PPV Fans for Fire Fighting Under Realistic Conditions
Authors: Steppert Michael , Epple Philipp , Steber Michael , Gast Stefan 
Published: February 2021

Abstract
PPV Fans (Positive Pressure Ventilation Fans) are used in firefighting to remove smoke from a burning building, so that fire fighters can have a clear view inside the house and injured people do not have to breathe toxic smoke. This can be done by placing a PPV fan in a distance of about two meters in front of a door of the burning building. On another, carefully chosen position in the building, e. g. a window, a door or at the roof an opening has to be created, where the smoke can leave the building. The same volumetric flow rate of gas that is blown into the building by the PPV fan has to leave the building at a chosen opening. Because the gas entering the building is air and the gas leaving the building is a mixture of smoke and air, the smoke concentration in the building can be reduced.
To test the performance of such PPV fans, a test building with a door in the first floor and a window in the 3rd floor has been built. To measure the volumetric flow rate of the smoke and air mixture through the window in the 3rd floor that is leaving the building, a flow meter nozzle was designed. The design process was done using the commercial Navier Stokes solver Star CCM+, where three nozzle designs, such as a nozzle with constant velocity increase, a quarter circle nozzle and a non-curved nozzle were investigated for different volumetric flow rates. Also, a rounding at the window, where the nozzle is placed, was investigated to prevent flow detachment and shock losses at the inlet of the nozzle.
The volumetric flow rate through the nozzle can be calculated, by measuring the pressure at the nozzle wall (before the contraction) and applying Bernoulli’s law, the continuity equation and assuming atmospheric pressure at the free jet flow at the end of the nozzle. The so calculated volumetric flow rate was compared with the actual flow rate, given by the numerical CFD simulations. With these values, the nozzle specific coefficient of discharge for several volumetric flow rates has been calculated and a function fitting was done to get obtain analytical relation between pressure and volumetric flow rate.
The detailed design process of the three nozzles, the numerical results of the CFD studies and the determination of the nozzle specific coefficients of discharge are shown and discussed in detail in this work.
Effect of Air Release Agents on Performance Results of Fabric Lined Bushings
Authors: Sahay Chittaranjan , Ghosh Suhash , Mormino Mathew 
Published: February 2021

Abstract
A configuration of a plain (sliding) bearing system is the use of a reinforced fabric comprising a woven structure of polytetrafluoroethylene (PTFE) and other fibers integrated with a phenolic resin system used to both encapsulate the fibrous materials and provide adhesion to metallic and other substrates. This construction promotes dimensional stability and improves thermal conductivity. These PTFE linings offer exceptionally low coefficient friction. The bushing is recommended for high loads when combined with low surface speeds. These fully self-lubricating bushings offer good contamination resistance, no stick-slip and excellent cold flow resistance. This technique has shown longer life of 7 to 10 times that of standard steel-backed, bronze-sintered and PTFE overlay. Proprietary self-lubricating PTFE fibers are applied directly to the steel. This polytetrafluoroethylene is woven onsite and applied directly to the steel. The woven liner is compressible and able to absorb distortions in mating surfaces. PTFE fabrics processed with phenolic resins can entrap air within the cured fabric liner. The entrapped air has the potential to affect bearing performance by reduction of bonding area and reduction in load carrying capabilities. Air release agents can be used to limit the amount of air entrapment within the liner system.
The intent of this research is to determine what, if any, affect the addition of commercially available air release agents would have on PTFE bearing performance. Experimental wear testing at various static and dynamic bearing conditions with and without contamination (de-ice fluid), including at high temperature (325°F) were conducted on eighteen specimens. Peel strength test were also conducted. All these tests were conducted based on prevalent industry standards. Parameters of static load resistance (deflection and permanent set) and loaded torque were found to be unaffected by the use of an air release agent when compared to baseline articles manufactured without such air releasing agents. Results showed that by integration of a commercially available air release agent into the processing of a PTFE based, phenolic resin bearing liner system, one can reduce variability and help stabilize wear performance. Specimens prepared with air release agent showed improved oscillation (fatigue) test results. Further, air release agent also resulted in a 35% increase in peel strength performance when tested per industry standard methods. Contamination with de-ice fluid showed no negative performance results. While the investigations here used only one ratio of additive among all tested bearings, but other concentrations are possible. Authors would like to pursue additional studies in future to determine the amount of air release agent that can reliably be added to remove the maximum air release without affecting the overall bearing performance. By finding this, a threshold of additive can also be determined.
Efficient Residual and Matrix-Free Jacobian Evaluation for Three-Dimensional Tri-Quadratic Hexahedral Finite Elements With Nearly-Incompressible Neo-Hookean Hyperelasticity Applied to Soft Materials on Unstructured Meshes in Parallel, With PETSc and libCEED
Authors: Mehraban Arash , Brown Jed , Barra Valeria , Tufo Henry , Thompson Jeremy , Regueiro Richard 
Published: February 2021

Abstract
Soft materials such as rubber, elastomers, and soft biological tissues mechanically deform at large strain isochorically for all time, or during their initial transient (when a pore fluid, typically incompressible such as water, does not have time to flow out of the deforming polymer or soft tissue porous skeleton). Simulating these large isochoric deformations computationally, such as with the Finite Element Method (FEM), requires higher order (typically quadratic) interpolation functions and/or enhancements through hybrid/mixed methods to maintain stability. Lower order (linear) finite elements with hybrid/mixed formulation may not perform stably for all mechanical loading scenarios involving large isochoric deformations, whereas quadratic finite elements with or without hybrid/mixed formulation typically perform stably, especially when large bending or folding deformations are being simulated. For topology-optimization design of soft robotics, for instance, the FEM solid mechanics solver must run efficiently and stably. Stability is ensured by the higher order finite element formulation (with possible enhancement), but efficiency for higher order FEM remains a challenge. Thus, this paper addresses efficiency from the perspective of computer science algorithms and programming. The proposed efficient algorithm utilizes the Portable, Extensible Toolkit for Scientific Computation (PETSc), along with the libCEED library for efficient compiler optimized tensor-product-basis computation to demonstrate an efficient nonlinear solution algorithm. For preconditioning, a scalable p-multigrid method is presented whereby a hierarchy of levels is constructed. In contrast to classical geometric multigrid, also known as h-multigrid, each level in p-multigrid is related to a different approximation polynomial order, p, instead of the element size, h. A Chebyshev polynomial smoother is used on each multigrid level. Algebraic MultiGrid (AMG) is then applied to the assembled Q1 (linear) coarse mesh on the nodes of the quadratic Q2 (quadratic) mesh. This allows low storage that can be efficiently used to accelerate the convergence to solution. For a Neo-Hookean hyperelastic problem, we examine a residual and matrix-free Jacobian formulation of a tri-quadratic hexahedral finite element with enhancement. Efficiency estimates on AVX-2 architecture based on CPU time are provided as a comparison to similar simulation (and mesh) of isochoric large deformation hyperelasticity as applied to soft materials conducted with the commercially-available FEM software program ABAQUS. The particular problem in consideration is the simulation of an assistive device in the form of finger-bending in 3D.
Dry Reforming of Biogas to Syngas: An Eco-Friendly Renewable Fuel for I C Engines
Authors: Sabnis Sandeep P. , Seethamraju Srinivas 
Published: February 2021

Abstract
Biogas, a promising alternative fuel, a substitute for fossil fuels, is predominantly a mixture of methane and carbon dioxide. Both are major greenhouse gases. Methane has a long-term effect on the environment while carbon dioxide is recycled by the plants. Hence, capture and burning of biogas to consume methane as a fuel is desired both from energy and environmental outlook. The presence of a large amount of carbon dioxide in biogas, however, impairs combustion in engines resulting into slow burning and higher hydrocarbon and carbon monoxide emissions.
Dry reforming, a conversion process of biogas to synthesis gas (syngas), a mixture of hydrogen and carbon monoxide, is a catalytic process that has the potential to greatly improve biogas combustion in engines. The researchers’ focus in dry reforming, however, has been for the generation of hydrogen for fuel cells and reactants for Fischer Tropsch process in industry — this approach aims towards maximum conversion of methane and carbon dioxide. The work presented here investigates the possibility of partial conversion of biogas to harness maximum energy and reduce emissions from I.C. Engines. The published research on dry reforming of biogas has examples of high concentrations of methane in the syngas with calorific values suitable for I.C. Engine application. For example, a 50:50 v/v CH4/CO2 composition biogas has calorific value of 13.33 MJ/kg which when converted to a syngas at 550°C results in a gas with 18:42:14:26 v/v CO2/CH4/H2/CO and a calorific value of 19.96 MJ/kg). Such compositions have moderate percentage of hydrogen to act as combustion enhancer and the carbon dioxide present helps to control NOx emissions. The major contributors of energy are methane and carbon monoxide in these cases.
The dry reforming reaction is an endothermic reaction, which produces hydrogen. The side reactions that happen are the reverse water gas shift reaction, which reduces hydrogen yield and the Bouduard reaction which results in carbon deposition on the catalyst surface. The reactor conditions need to be chosen appropriately, especially the reactor temperature. Simulation of dry reforming reaction using a process simulation software (Aspen Plus) is carried out to find the extent of conversion and exit syngas composition for different biogas compositions. The endothermic heat for the reactor can be provided by the heat of the engine exhaust — therefore, an opportunity exists to use waste heat recovery from the engine exhaust. However, there is a tradeoff between the reactor temperature, syngas composition going to engine inlet and the engine exhaust heat — which is investigated in this study.
A Theoretical Study of Sensor-Artery Interaction in Noninvasive Arterial Pulse Signal Measurement Using Tactile Sensors
Authors: Roxas Roman Carlo B. , Harnish Adam T. , Johnson Dylon N. , Stewart Camrie M. , Nguyen Dieu , Osbourne Erika , Wolbert Joshua A. , Vahala Linda , Hao Zhili 
Published: February 2021

Abstract
This paper presents a theoretical study of sensor-artery interaction in arterial pulse signal measurement using a tactile sensor. A measured pulse signal is a combination of the true pulse signal in an artery, the arterial wall, its overlying tissue, and the sensor, under the influence of hold down pressure exerted on the sensor and motion artifact. The engineering essence of sensor-artery interaction is identified as elastic wave propagation in the overlying tissue and pulse signal transmission into the sensor at the skin surface, and different lumped-element models of sensor-artery interaction are utilized to examine how the involved factors affect a measured pulse signal. Achieving ideal sensor-artery conformity is the key for acquiring a measured pulse signal with minimum distortion. Hold-down pressure, sensor design, and overlying tissue collectively contribute to ideal sensor-artery conformity. Under ideal sensor-artery conformity, both the sensor and overlying tissue cause an increase in the measured stiffness of the arterial wall; damping and inertia of the sensor and overlying tissue also affects a measured pulse signal. The theoretical study shows the need to tailor the sensor design for different arteries and individual, and interpret estimated arterial indices with consideration of individual variations as well as instruments used.
Momentum Analysis of Vehicles With Disparate Masses
Authors: Eichaker Lauren , Eiselstein Nicholas , Buczek Sean , Panoff Stephen , Wiechel John , Guenther Dennis 
Published: February 2021

Abstract
It is well established that the law of conservation of momentum is applicable to all interactions between any two bodies during an impact. The law dictates that the total momentum before a collision is the same as the total momentum after the collision (for elastic collisions). This law has been accepted as a fundamental part of Newtonian physics since Newton incorporated Descartes’ work into his own. Scientists rarely question its applicability to kinematics of bodies in the non-quantum world. The law of conservation of momentum is regularly used in vehicle accident reconstruction to calculate a speed of one of the vehicles before or after the collision, assuming that the masses of the vehicles and sufficient other velocities are known. Collisions of vehicles with highly disparate masses pose an interesting dilemma. In such a collision, the speed of the higher mass vehicle will change very little in a collision with a vehicle of much smaller mass and the speed change of the smaller mass vehicle will be large. This is due to the ratio of the masses of the two vehicles which minimizes the effect of the smaller mass vehicle on the vehicle of larger mass. The lopsided nature of the speed change of this kind of collision can lead one to conclude that momentum is not applicable to collisions between vehicles of dramatically different masses. The objective of this work is to investigate the effect of dissimilar masses of vehicles on the effectiveness of momentum to accurately predict speed change. The mathematical formulation of the error associated with dissimilar mass vehicles is presented and quantified to give the reconstructionist guidance in when momentum can be used reliably and when the error resulting from the use of momentum may be larger than desired.
Numerical Simulation of Stress States in White Matter via a Continuum Model of 3D Axons Tethered to Glia
Authors: Pasupathy Parameshwaran , De Simone Robert , Pelegri Assimina A. 
Published: February 2021

Abstract
A new finite element approach is proposed to study the propagation of stress in axons in the central nervous system (CNS) white matter. The axons are embedded in an extra cellular matrix (ECM) and are subjected to tensile loads under purely non-affine kinematic boundary conditions. The axons and the ECM are described by the Ogden hyperelastic material model. The effect of tethering of the axons by oligodendrocytes is investigated using the finite element model. Glial cells are often thought of as the “glue” that hold the axons together. More specifically, oligodendrocytes bond multiple axons to each other and create a myelin sheath that insulates and supports axons in the brainstem. The glial cells create a scaffold that supports the axons and can potentially bind 80 axons to a single oligodendrocyte.
In this study, the microstructure of the oligodendrocyte connections to axons is modeled using a spring-dashpot approximation. The model allows for the oligodendrocytes to wrap around the outer diameter of the axons at various locations, parameterizing the number of connections, distance between connection points, and the stiffness of the connection hubs. The parameterization followed the distribution of axon-oligodendrocyte connections provided by literature data in which the values were acquired through microtome of CNS white matter. We develop two models: 1) multiple oligodendrocytes arbitrarily tethered to the nearest axons, and 2) a single oligodendrocyte tethered to all the axons at various locations. The results depict stiffening of the axons, which indicates that the oligodendrocytes do aid in the redistribution of stress. We also observe the appearance of bending stresses at inflections points along the tortuous path of the axons when subjected to tensile loading. The bending stresses appear to exhibit a cyclic variation along the length of the undulated axons. This makes the axons more susceptible to damage accumulation and fatigue. Finally, the effect of multiple axon-myelin connections in the central nervous system and the effect of the distribution of these connections in the brain tissue is further investigated at present.
Using Virtual Reality–Based Rehabilitation in Sarcopenic Older Adults in Rural Health Care Facilities—A Quasi-Experimental Study
Authors: Chen Guan-Bo , Lin Che-Wei , Huang Hung-Ya , Wu Yi-Jhen , Su Hung-Tzu , Sun Shu-Fen , Tuan Sheng-Hui 
Published: February 2021

Because of a shortage of health care providers, providing rehabilitation in health care facilities is difficult. Virtual reality–based rehabilitation is effective in older populations. There are only a few studies among patients with sarcopenia. This is a quasi-experimental, single-group, pretest–posttest design evaluating the clinical effectiveness of virtual reality–based progressive resistance training among residents aged over 60 years with sarcopenia in rural care facilities. The authors used Oculus Rift with headsets to provide the virtual reality–based progressive resistance training. The authors administered the program twice per week, 30 min per session, for 12 weeks. The primary outcomes were dominant handgrip strength, walking speed, and appendicular skeletal muscle mass index. Data from 30 participants were analyzed. Significant improvements in handgrip strength and walking speed were observed. Although an increasing trend in appendicular skeletal muscle mass index was observed, it did not reach statistical significance. The authors concluded that the virtual reality–based progressive resistance training is partially effective in older sarcopenic adults in health care facilities.
A Magnetic Resonance Imaging–Compatible Device to Perform In Vivo Anterior Knee Joint Loading
Authors: Park-Braswell Kyoungyoun , Shultz Sandra J. , Schmitz Randy J. 
Published: February 2021

Context: Greater anterior knee laxity (AKL) is associated with impaired sensory input and decreased functional knee stability. As functional magnetic resonance imaging (MRI) is the gold standard for understanding brain function, methods to load the anterior cruciate ligament in the MRI environment could further our understanding of the ligament’s sensory role in knee joint stability. Objective: To design and validate an MRI-compatible anterior knee joint loading device. Design: Descriptive laboratory study. Setting: University laboratory study. Participants: Sixteen healthy and physically active females participated (age = 23.4 [3.7] y; mass = 64.4 [8.4] kg). Interventions: The AKL was assessed by a commercially available arthrometer. The AKL was also assessed with a custom-made, MRI-compatible device that produced anterior knee joint loading in a manner similar to the commercial arthrometer while obtaining dynamic structural MRI data. Main Outcome Measurements: The AKL (in millimeters) at 133 N of loading was assessed with the commercial knee arthrometer. Anterior displacement of the tibia relative to the femur obtained at 133 N of loading was measured from dynamic MRI data obtained during usage of the custom device. Pearson correlations were used to examine relationships between the 2 measures. The 95% limits of agreement compared the absolute differences between the 2 devices. Results: There was a 3.2-mm systematic difference between AKL (6.3 [1.6] mm) and anterior tibial translation (3.2 [1.0] mm) measures. There was a significant positive correlation between values obtained from the commercial arthrometer and the MRI-compatible device values (r = .553, P = .026). Conclusions: While systematic differences were observed, the MRI-compatible anterior knee joint loading device anteriorly translated the tibia relative to the femur in a similar manner to a commercial arthrometer design to stress the anterior cruciate ligament. Such a device may be beneficial in future functional magnetic resonance imaging study of anterior cruciate ligament mechanoreception.
Changes over time in quality of life of school-aged children born extremely preterm: 1991–2005
Authors: Peart Stacey , Cheong Jeanie Ling Yoong , Roberts Gehan , Davis Noni , Anderson Peter J , Doyle Lex W 
Published: February 2021

ObjectiveTo compare health-related quality of life (HRQOL) at 8 years in children born extremely preterm (EP) with contemporaneous term-born controls over three epochs: 1991–92, 1997 and 2005.DesignProspective recruitment of geographic cohorts across three distinct eras. Utilities were calculated from the parent-completed Health Utilities Index (HUI), version 2 (1991–92 and 1997 cohorts) and version 3 (2005 cohort). Differences in utilities >0.05 are clinically important.SettingThe state of Victoria, Australia.Patients475 EP (<28 weeks’ gestation) and 570 term controls.Main outcome measuresUtilities of children born EP compared with term controls within each era, and paired differences between an EP and matched controls compared across eras.ResultsOverall, 86% of survivors had utility data at 8 years of age; 475 EP and 570 controls. In all eras, parent-reported utilities were lower for children born EP compared with controls (difference in medians (95% CIs); 1991–92, −0.053 (–0.071 to –0.035); 1997, –0.053 (−0.072 to –0.034); 2005, –0.082 (−0.097 to –0.068)). Mean differences (MD) between EP children and matched controls within each era were lower in the 2005 cohort compared with both the 1991–92 cohort (MD −0.054, 95% CI −0.097 to –0.010) and the 1997 cohort (MD −0.053, 95% CI −0.097 to –0.009).ConclusionChildren born EP in the postsurfactant era have clinically important reductions in parent-reported HRQOL compared with controls, which may be worsening over time.