bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soft Spherical Tensegrity Robot Design Using Rod-Centered Actuation and Control
Authors: Chen Lee-Huang , Kim Kyunam , Tang Ellande , Li Kevin , House Richard , Agogino Alice M. , Agogino Adrian , Sunspiral Vytas , Jung Erik 
Published: December 2016

This paper presents the design, analysis and testing of a fully actuated modular spherical tensegrity robot for co-robotic and space exploration applications. Robots built from tensegrity structures (composed of pure tensile and compression elements) have many potential benefits including high robustness through redundancy, many degrees of freedom in movement and flexible design. However to fully take advantage of these properties a significant fraction of the tensile elements should be active, leading to a potential increase in complexity, messy cable and power routing systems and increased design difficulty. Here we describe an elegant solution to a fully actuated tensegrity robot: The TT-3 (version 3) tensegrity robot, developed at UC Berkeley, in collaboration with NASA Ames, is a lightweight, low cost, modular, and rapidly prototyped spherical tensegrity robot. This robot is based on a ball-shaped six-bar tensegrity structure and features a unique modular rod-centered distributed actuation and control architecture.
This paper presents the novel mechanism design, architecture and simulations of TT-3, the first untethered, fully actuated cable-driven six-bar tensegrity spherical robot ever built and tested for mobility. Furthermore, this paper discusses the controls and preliminary testing performed to observe the system’s behavior and performance.
Design of Self-Supported 3D Printed Parts for Fused Deposition Modeling
Authors: Lischke Fabian , Tovar Andres 
Published: December 2016

One of the primary challenges faced in Additive Manufacturing (AM) is reducing the overall cost and printing time. A critical factor in cost and time reduction is post-processing of 3D printed (3DP) parts, of which removing support structures is one of the most time consuming steps. Support is needed to prevent the collapse of the part or certain areas under its own weight during the 3D printing process. Currently, the design of self-supported 3DP parts follows a set of empirical guide lines. A trial and error process is needed to produce high quality parts by Fused Depositing Modeling (FDM). The usage of chamfer angle with a max 45° angle form the horizontal for FDM is a common example. Inclined surfaces with a smaller angle are prone to defects, however no theoretical basis has been fully defined, therefore a numerical model is needed. The model can predict the problematic areas at a print, reducing the experimental prints and providing a higher number of usable parts.
Physical-based models have not been established due to the generally unknown properties of the material during the AM process. With simulations it is possible to simulate the part at different temperatures with a variety of other parameters that have influence on the behavior of the model. In this research, analytic calculations and physical tests are carried out to determine the material properties of the thermoplastic polymer Acrylonitrile - Butadiene - Styrene (ABS) f or FDM at the time of extrusion. This means that the ABS is going to be extruded at 200°C to 245°C and is a viscous material during part construction.
Using the results from the physical and analytical models, i.e., Timoshenko’s modified beam theory for micro-structures, a numerical material model is established to simulate the filament deformation once it is deposited onto the part. Experiments were also used to find the threshold for different geometric specifications, which could then be applied to the numerical model to improve the accuracy of the simulation. The result of the finite element analysis is compared to experiments to show the correlation between the prediction of deflection in simulation and the actual deflection measured in physical experiments.
A case study was conducted using an application that optimizes topology of complex geometries. After modeling and simulating the optimized part, areas of defect and errors were determined in the simulation, then verified and and measured with actual 3D prints.
Energy Harvesting From Arterial Blood Pressure for Embedded Brain Sensing
Authors: Nanda Aditya , Karami M. Amin 
Published: December 2016

This paper investigates energy harvesting from arterial blood pressure via the piezoelectric effect for the purpose of powering embedded micro-sensors in the brain. Blood flow is highly dynamic and arterial blood pressure varies, in the average human blood vessel, from 120 mm of Hg to 80 mm of Hg and we look at transduction of this pressure variation to electric energy via the piezoelectric effect. We propose two different geometries for this purpose. Initially, we look at the energy harvested by a cylinder, coated with PVDF (Polyvinylidene fluoride) patches, placed inside an artery acted upon by blood pressure. The arrangement is similar to that of a stent which is a cylinder placed in veins and arteries to prevent obstruction in blood flow. The governing equations of the harvester are obtained using Hamilton’s principle. Pressure acting in arteries is radially directed and this is used to simplify the governing equations. Specifically, radial pressure directed on the inner wall of the cylinder is assumed to excite only the radial breathing mode of vibration. Using this, the transfer function relating pressure to the induced voltage across the surface of the harvester is derived and the power harvested by the cylindrical harvester is obtained for different shunt resistances.
However, the natural frequency of the radial breathing mode (RBM) is found to be very high and the harvested power at the frequencies of interest (3 Hz – 20 Hz) is very low. To decrease the natural frequency, we propose a novel streaked cylinder design that involves cutting the cylinder along the length, transforming it to a curved beam with an opening angle of 360 deg.. The governing equations corresponding to a circular curved beam, with PVDF patches on top and bottom surfaces, are derived using Hamilton’s principle and modal analysis is used to obtain the transfer function relating radial pressure to induced voltage. We validate the derived transfer function by evaluating the harvested power for a beam with very large radius of curvature; in which case, the curved beam becomes a straight beam and the harvested power is compared with the same for a straight beam (which exists in the literature). Further, we conduct design analyses and obtain the power as the geometric parameters of the harvester are varied for the purpose of optimizing the dimensions of harvester for maximal power generation. The power harvested by the harvester, at lower frequencies is deemed to be satisfactory.
Multiphase Effects in Dynamic Systems Under Vibration
Authors: O’Hern Timothy J. , Torczynski John R. , Clausen Jonathan R. 
Published: December 2016

Analysis, simulations, and experiments are performed for a piston in a vibrated liquid-filled cylinder, where the damping caused by forcing liquid through narrow gaps depends almost linearly on the piston position. Adding a little gas completely changes the dynamics of this spring-mass-damper system when it is subject to vibration. When no gas is present, the piston’s vibrational response is highly overdamped due to the viscous liquid being forced through the narrow gaps. When a small amount of gas is added, Bjerknes forces cause some gas to migrate below the piston. The resulting pneumatic spring enables the liquid to move with the piston so that little liquid is forced through the gaps. This “Couette mode” thus has low damping and a strong resonance near the frequency given by the pneumatic spring constant and the piston mass. Near this frequency, the piston response is large, and the nonlinearity from the varying gap length produces a net force on the piston. This “rectified” force can be many times the piston’s weight and can cause the piston to compress its supporting spring.
A surrogate system in which the gas regions are replaced by upper and lower bellows with similar compressibility is studied. A recently developed theory for the piston and bellows motions is compared to finite element simulations. The liquid obeys the unsteady incompressible Navier-Stokes equations, and the piston and the bellows obey Newton’s 2nd Law. Due to the large piston displacements near resonance, an Arbitrary Lagrangian Eulerian (ALE) technique with a sliding-mesh scheme is used to limit mesh distortion. Theory and simulation results for the piston motion are in good agreement.
Experiments are performed with liquid only, with gas present, and with upper and lower bellows replacing the gas. Liquid viscosity, bellows compressibility, vibration amplitude, and gap geometry are varied to determine their effects on the frequency at which the rectified force makes the piston move down. This critical frequency is found to depend on whether the frequency is increased or decreased with time.
Motion of Active Fluids: Diffusion Dynamics of Cyanobacteria
Authors: Vourc’h Thomas , Léopoldès Julien , Méjean Annick , Peerhossaini Hassan 
Published: December 2016

Cyanobacteria are photosynthetic micro-organisms colonizing all aquatic and terrestrial environments. The motility of such living micro-organisms should make their diffusion distinct from typical Brownian motion. This diffusion can be investigated in terms of global behavior (Fickian or not) and in terms of displacement probabilities, which provide more detail about the motility process. Using cyanobacterium Synechocystis sp. PCC 6803 as the model micro-organism, we carry out time-lapse video microscopy to track and analyze the bacteria’s trajectories, from which we compute the mean-squared displacement (MSD) and the distribution function of displacement probabilities.
We find that the motility of Synechocystis sp. PCC 6803 is intermittent: high-motility “run” phases are separated by low-motility “tumble” phases corresponding to trapped states. However, this intermittent motility leads to a Fickian diffusive behavior, as shown by the evolution of the MSD with time.
Numerical Investigations on Intake Tube Design of Micro Kaplan Hydro-Turbine System
Authors: ElGammal Tarek , Yen Yi-Hsin , Amano Ryoichi S. , Millevolte Joseph , Mueller Randal J. , Lequesne Bruno 
Published: December 2016

In this context, a numerical study was conducted to predict the performance of a small axial Kaplan hydro-turbine of 30 cm diameter that can be manufactured and installed vertically on a low head water level of less than 3 m. As a CFD simulation scheme, Large Eddy Simulation was selected to solve for the variables of turbulent flow due to its high fidelity performance for capturing time-variable turbulence wakes and eddies.
Turbine intake tube dimensioning was primarily studied as an affecting element to maximize energy extraction with the set of initial design parameters. The intake tube was tested at six angles (3, 6, 9, 12, 15, 18 degrees) and four lengths (50, 60, 75, 90 cm). The simulations were performed on a pre-determined water height, one diffuser design, and one set of stator-rotor having a rotational speed of 750 rpm. Maximizing the efficiency of a system with less material cost was the primary goal of the comparative study. After that, bellmouth profile was adopted to find out its influence on the system performance. Outcomes have proven the merit of higher slope per side length in enhancing output power with an average of 2.7 percent by full expansion from minimum to the maximum angle. Moreover, a corresponding marginal efficiency raise was observed by increasing intake slope, while it was found that the system acts poorly with longer intake tubes as both power and efficiency go down. Bellmouth profiles, based on the guidelines of the best straight design, significantly improved system output to reach 81 percent efficiency.
Numerical Optimization of Micro Kaplan Hydro Turbine System
Authors: Yen Yi-Hsin , ElGammal Tarek , Amano Ryoichi S. , Millevolte Joseph , Lequesne Bruno , Mueller Randal J. 
Published: December 2016

Micro hydro turbines with capacity ranging from 5–100 kW can provide a source of renewable energy which has high potential to grow due to the sheer number of available sites with a relatively small head difference and flow rate. Such systems would complement existing conventional large-scale hydro installations.
The paper presents a study of a 30 cm diameter Kaplan hydroturbine geometry with performance optimization through Computational Fluid Dynamics (CFD) method based on Large Eddy Simulation (LES) of transient turbulence modeling. The work under this study include: selection of horizontal or vertical setup, tail water head test, draft tube length test, draft tube angle test, intake tube geometry test and blade geometry combination test. All of these geometric parameters will be tested and compared based on power output, mass flow rate and efficiency. The optimized geometry was selected for system manufacturing and experimenting by Cadens LLC in a project site in Sullivan, WI.
Coupled 3-D CFD-DDPM Numerical Simulation of Turbulent Swirling Gas-Particle Flow Within Cyclone Suspension Preheater of Cement Kilns
Authors: Cristea Eugen-Dan , Conti Pierangelo 
Published: December 2016

The paper presents a three-dimensional (3-D), time-dependent Euler-Lagrange multiphase approach for high-fidelity numerical simulation of strongly swirling, turbulent, heavy dust-laden flows within large-sized cyclone separators, as components of the state-of-art suspension preheaters (SPH) of cement kilns.
The case study evaluates the predictive performance of the coupled hybrid 3-D computational fluid dynamics–dense discrete phase model (CFD-DDPM) approach implemented into the commercial general purpose code ANSYS-Fluent R16.2, when applied to industrial cyclone collectors used to separate particles from gaseous streams. The gas (flue gases) flow is addressed numerically by using the traditional CFD methods to solve finite volume unsteady Reynolds-averaged Navier-Stokes (FV-URANS) equations. The multiphase turbulence is modeled by using an option of Reynolds stress model (RSM), namely dispersed turbulence model. The motion of the discrete (granular) phase is captured by DDPM methodology.
The twin cyclones of SPH top-most stage have been analyzed extensively both for the overall pressure drop and global collection efficiency, and for the very complex multiphase flow patterns established inside this equipment. The numerical simulation results have been verified and partially validated against an available set of typical industrial measurements collected during a heat and mass balance (H&MB) of the cement kiln.
Optimization of Anastomotic Geometry for Vascular Access Fistula
Authors: Bao Guangyu , Chen Xiaomin , Agarwal Ramesh K. 
Published: December 2016

Arteriovenous fistula (AVF) is one type of vascular access which is a surgically created vein used to remove and return blood during hemodialysis [1]. It is a long-term treatment for kidney failure. Although clinical treatment and technology have both achieved great improvements in recent years, the vascular access for hemodialysis still has significant early failure rates after the insertion of AVF in patients [2]. Studies have shown that stenosis in the vascular access circuit is the single major cause for access morbidity. Majority of efforts to understand the mechanisms of stenosis formation, and its prevention and management have largely focused on understanding and managing this complication based on the pathophysiology, tissue histology and molecular biology; however these efforts have not resulted in significant progress to date. We believe that the major impact in this area will come from continued and accurate understanding of the hemodynamics, and by development of techniques of intervention to modulate factors such as flow rates, pressures and compliance of the circuit.
The goal of this paper is to study anastomotic models of AV access using Computational Fluid Dynamics (CFD) and optimize them to minimize the wall shear stress (WSS). In order to achieve this goal, the commercial CFD software FLUENT [3] is employed in conjunction with a single objective genetic algorithm [4].
Computations for two types of AVF currently in use in clinical practice are performed. AVF with 25° angle/3–4mm diameter and 90° angle/3–5mm diameter are selected to conduct the optimization. A single-objective genetic algorithm is employed in the optimization process and a k-kl-ω turbulence model is employed in CFD simulations; this model can accurately compute transitional/turbulent flows. In order to optimize for the same flow conditions, a fixed boundary condition is used during the optimization process. Computations for 16 to 20 generations of the selected AVFs are obtained from the genetic algorithm solver. The maximum WSS in the two AVFs considered are 6997.8 and 7750 dynes/cm2; however, the maximum WSS in the shape-optimized AVFs are reduced to 3511.2 and 4293.9 dynes/cm2 respectively, which have decreased by 49.82% and 44.59% respectively. Thus, the probability of the formation of stenosis in AVFs and early failure rates of vascular access are reduced by using the optimized AVFs.
Sand Flow Regimes in Slightly Upward Inclined Gas-Liquid Stratified Flow
Authors: Dabirian Ramin , Mohan Ram S. , Shoham Ovadia , Kouba Gene 
Published: December 2016

Sand particles are produced from the reservoir with low formation strength. A sand management system is required to be designed to keep the sand particles moving so as to prevent them from accumulating in the pipeline. Operating under unnecessarily high fluid velocities is not cost effective, moreover, it can lead to equipment failure; therefore, it is required to find the minimum velocity, known as critical sand deposition velocity, to keep the particles constantly moving.
In order to assess the critical sand deposition condition, a unique test facility was designed and constructed with 4-in ID PVC pipeline, which enables the pipe to be inclined 1.5° upward. Experiments were conducted with air-water-glass beads at low sand concentrations (< 10,000 ppm), and the air and water flow rates were selected to ensure stratified flow regime along the pipe. At constant superficial liquid velocity the gas velocity was reduced to find the critical sand deposition velocity.
The experimental results reveal that air-water flow regime plays an important role in particle transport; slug flow has high capability to transport particles at the pipe bottom, while the stratified flow has high risk of sand deposition. As long as the sand dunes are observed at the pipe bottom, the critical sand deposition velocities slightly increase with concentrations, while for stationary bed, the critical velocity increases exponentially with concentration.
Modeling Separation and Cavitation Behind a Blunt Body
Authors: Ma Jingsen , Hsiao Chao-Tsung , Wu Xiongjun , Chahine Georges L. 
Published: December 2016

Cavitation flow behind a blunt body is modeled using a physics-based numerical model of cavitation initiation and transition to larger cavities. The calculations initiate from the dynamics of nuclei, then tracks the dispersed bubble phase with a two-phase viscous model. This solver includes a level set method to model coalescence of the nuclei into large cavities and to track the dynamics of the resulting free surfaces. A transition scheme enables collection of the bubbles into a large cavity and also enables breakup of a large cavity into a bubble cloud.
Using this model, simulations are conducted for different flow velocities and corresponding cavitation regimes. When the velocity is relatively small (i.e., large cavitation number), flow separation behind the body results in the shedding of vortices, which capture nuclei in their cores to form elongated vortical cavities. As the flow velocity increases (or as the ambient pressure decreases) the flow evolves into a separated flow with a large cavity behind the body. A reentrant jet may form and move upstream into the cavity towards the body. This jet periodically shears off portions of the cavity volume, resulting in large amounts of bubble clouds. These results are in good qualitative agreements with experimental observations.
A Study of the Effect of Various Recess Shapes on Hybrid Journal Bearing Using CFD and Response Surface Method
Authors: Fu Gen , Untaroiu Alexandrina 
Published: December 2016

Hybrid bearings are mostly used in high speed and load situations due to their better stability and loading capacity. They are typically designed with recess grooves to enhance both static and dynamic performance of the bearing. Previous theoretical studies on the influence of the recess geometrical shapes often utilize the Reynolds equation method and most of the research focuses on thrust bearings. The aims of this paper is to analytically study the influence of various recess geometrical shapes on hybrid journal bearings.
A 3-D CFD model of a hybrid journal bearing is built and a new method of response surface model is employed to determine the equilibrium position of the rotor. Based the response surface model, an optimization scheme is used to search around the equilibrium position to get a more accurate solution. The current analysis includes the recess geometry of rectangular, circular, triangular, elliptical and annular shapes. All these different shapes are studied assuming the same operating and loading conditions and bearing static properties are used as the indices of the bearing performance.
The flow rate, fluid film thickness and recess flow pattern are analyzed for various recess shapes. The CFD model for the baseline bearing is validated against experimental data. The results show that the response surface model method is fast and robust in determining the rotor equilibrium position even though a 3-D CFD model is utilized. The results suggest that recess shape is a dominant factor in hybrid bearing design. This study proposed a new design process for a 3-D CFD bearing model with the ability of calculating equilibrium position and is expected to be useful to bearing designers.
Ultrasonography as an integrated tool in clinical decision-making in the Emergency Department
Authors: Golea Adela C. , Mureșan Eugenia G.P. , Lăcan Sorin S. , Pasc Mihaela Gh. , Bolboacă Sorana D. 
Published: December 2016

The aim of this retrospective study was to identify the role of ultrasonography as a decision-making and screening tool in emergency patients with pathological changes. Material and method: The study was carried out for 28 months in the Emergency Department of the County Emergency University Hospital, Cluj-Napoca. An ultrasound examination was performed as part of the clinical algorithm within the first hour of treating non-critical patients after they had been triaged. The diagnostic decision based on the results of the ultrasound examination was compared with the final diagnosis on discharge from the Emergency Department. Results: In study were included 1565 patients with a mean age of 50.61±19.21 years. Ultrasound changes were detected in a statistically significant number of patients from all the examined subgroups (p≤0.002). The concordance between clinical and ultrasound findings was of 54.06%. Of all the examined patients, 20.63% were referred to surgery department based on the results of the ultrasound examination. Surgery was the final therapeutic decision in 5.06% of all the patients with normal ultrasound findings. Conclusions: Ultrasonography as an integrated tool in the clinical examination algorithm allowed the identification of non-critical patients who required emergency surgery (20.63%). The integration of point-of-care ultrasound into the clinical examination allows the management of emergency patients through the ranking of decisions: hospital admission for surgery and medical treatment, other diagnostic investigations, referral to outpatient care and family physician.