bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simple Spring-Loaded Inverted Pendulum (SLIP) Model of a Bio-Inspired Quadrupedal Robot Over Compliant Terrains
Authors: Hayati Hasti , Walker Paul , Brown Terry , Kennedy Paul , Eager David
Published: January 2019

To study the impact of compliant terrains on the biomechanics of rapid legged movements, a well-known spring loaded inverted pendulum (SLIP) model is deployed. The model is a three-degrees-of-freedom system (3 DOF), inspired by galloping greyhounds competing in a racing condition. A single support phase of hind-leg stance in a galloping gait is taken into consideration due to its primary function in powering the greyhounds locomotion and higher rate of musculoskeletal injuries. To obtain and solve the nonlinear second-order differential equation of motions, the Lagrangian method and MATLABb R2017b (ode45 solver), which is based on the Runge-Kutta method, has been used, respectively. To get the viscoelastic behavior of compliant terrains, a Clegg hammer test was developed and performed five times on each sample. The effective spring and damping coefficients of each sample were then determined from the hysteresis curves. The results showed that galloping on the synthetic rubber requires more muscle force compared with wet sand. However, according to the Clegg hammer test, wet sand had a higher impact force than synthetic rubber which can be a risk factor for bone fracture, particularly hock fracture, in greyhounds. The results reported in this paper are not only useful for identifying optimum terrain properties and injury thresholds of an athletic track, but also can be used to design control methods and shock impedances for legged robots performing on compliant terrains.
Printed and 360 Head-Mounted Display Rendering: A Cross-Cultural Study Comparing Utility, Spatial Representation and Emotional Capabilities
Authors: Rojas Juan-Carlos , Higuera-Trujillo Juan Luis , Mora-Salinas Roberto , Galindo Jessica , Abad Susana Iñarra
Published: January 2019

Environmental simulations through rendering has an important role to play in the design process of and communication regarding the built environment. Technological advances allow for widely used printed renders with 360° panoramic representations to be displayed through head-mounted devices (HMD). However, the adoption of this technology should be done with caution, due to the possible effects of the user’s context relative to his or her expertise and geographic–cultural level. This study compared printed and 360° HMD-render setup capacities for experts and nonexperts in Architecture, from different geographic–cultural contexts of Mexico and Spain. To tackle this, a broad spectrum of 15 components addressing aspects of utility, spatial representation, and the emotional and general capabilities of environmental simulations were assessed using bipolar scales by a total of 120 participants. Analyses showed differences in all aspects for all contexts of the study. The greatest differences were general, with non-experts of an indistinct geographic–cultural context showing the least perception of the capabilities. This indicates a strong conditioning, generated by experience acquired in different geographical–cultural contexts, supporting the idea of incorporating context–aware reasoning into the representation of novel rendering. Hence, our results will have interest for both professionals and instructors.
Numerical Investigation of Velocity Coefficient for Organic Turbine Nozzles Using MM As Working Fluid
Authors: Zhuang Laihe , Xu Guoqiang , Wen Jie , Dong Bensi
Published: January 2019

Organic Rankine cycle (ORC) has gained an increasing worldwide attention due to its high efficiency in converting low-grade thermal energy into electricity. The expander is the most critical component in the ORC system. Among the influential factors that define the performance of the expander, the velocity coefficient of the nozzle is crucial. This work numerically investigates the effects of the nozzle height, length, surface roughness, outlet geometric angle, and expansion ratio, on the velocity coefficient of the nozzle in the ORC turbine with hexamethyldisiloxane (MM) as working fluid. In the 3-D viscous numerical analysis, the shear stress transports k-ω turbulence model is employed and the numerical method is verified by the experimental data of the nozzle with pressured air based on hotwire technology. The numerical results show that the velocity coefficient is almost independent of expansion ratio compared to other factors due to the relatively small flow boundary layer and high Reynolds number. Since the existing correlations for the gas nozzle cannot well predict the velocity coefficient of the organic nozzle, an empirical equation is proposed according to the numerical results with the maximum deviation of 3.0%.
The Positive Effects on Student Performance of Using Social Networks in Courses of Applied Mechanics
Authors: Rodríguez-Paz Miguel X. , González-Mendivil Jorge A. , Zárate-García J. Asunción , Peña-Ortega Luis O.
Published: January 2019

Digital Social Networks such as Facebook, Twitter, Instagram and Youtube are part of the lives of most students nowadays. Generally, lecturers and teachers do not allow the use of mobile devices during class time. In this work, some results are shown of the positive effects that the allowance of such devices, as well as the interaction between professor-students through social networks can have on students grades compared to previous semesters where no use of social networks was included in class. The main objective of this work is to show that, if digital social networks interaction between professor and class is included, the overall confidence of the group increases as well as the grade results in their examinations versus previous groups of similar sizes where there was no such interaction. Feedback from students is analyzed to show the perception of students on the use of the Youtube channel and how it has positively affected their performance in the course by increasing the reviewing options they get before an exam.

Another aspect also discussed in this work, is the importance of the personal branding the professor should develop so that he/she gets easily recognized across the different social networks.
Parametric Instability of Planetary Gear Transmission Mounted on Discrete Support Struts With Minimum Ring Gear Rim Thickness Design
Authors: Guan Peng , DeSmidt Hans
Published: January 2019

This research explores parametric instabilities of the PGT driveline system and a stability-based method for ring gear rim thickness design. Parametric excitation of a planetary gear transmission (PGT) driveline system arises from two sources: 1) gear mesh stiffness variation, 2) Interaction between moving planets, flexible ring gear and boundary struts. Many researchers have studied the parametric instability of planetary gear transmissions due to gear mesh stiffness variation, however, the effect of interaction between moving planets, flexible ring and discrete boundary struts on parametric instabilities has not been fully studied before. Especially, for sufficiently thin ring gears, this kind of effect becomes even more significant. To illustrate the novel PGT rim design proposal, firstly, a structural dynamics model of a complete PGT driveline system with elastic ring gear supported by discrete boundary struts is established. Secondly, by applying Floquet method, the parametric instability behavior due to the second parametric excitation source is fully investigated. Lastly, the design guidelines for planetary gear transmission ring gear rim thickness are proposed based on system stability from a dynamical viewpoint. The analysis and results provide new and important insights into dynamics and design of lightweight planetary gear transmission ring gear rim.
A Model Based Framework for Wheel Lock Simulation in a Brake Dynamometer Towards Heavy Road Vehicle Safety
Authors: Lanka Indeevar Shyam , Challa Akhil , Sridhar Nithya , Subramanian Shankar C. , Sankaralingam Sankarganesh , Vivekanandan Gunasekaran
Published: January 2019

This work proposes a method to simulate wheel lock of a Heavy Commercial Road Vehicle (HCRV) using pneumatic brake circuit on a brake dynamometer. The proposed methodology lumps the effects of wheel slip and load transfer during straight-line braking into ‘equivalent inertia’ on the wheels. This inertia profile could then be imported on a dynamometer interface and realized using suitable inertia discs and an electric motor. Equivalent inertia was computed from test datasets obtained from a Hardware-in-Loop (HiL) experimental system consisting of an air brake system and IPG TruckMaker®, a vehicle dynamic simulation software. These datasets were obtained for various road, vehicle load and braking conditions. This framework would facilitate the evaluation of wheel slip regulation algorithms using a brake dynamometer by capturing necessary dynamics of HCRVs during braking. It is expected that such testing can be placed between HiL and on-road tests, and would provide greater confidence in Active Safety Systems (ASSs) before their deployment on vehicles.
Robotic Polishing of Free-Form Surfaces With Controlled Force and Effective Path Planning
Authors: Mohsin Imran , He Kai , Du Ruxu
Published: January 2019

Industrial robots are widely used in many industries for different jobs. With the specific goal to limit the expensive process of polishing due to unhealthy conditions, trained workers requirement and human mistakes, it is an attractive idea to automate the surface polishing by machines. The important job in robotic polishing process is path planning and force control. This research work is with the objective to systematize and optimize the path planning for free-form surfaces under the regulated force. Robotic polishing based on CAD models of the workpiece is presented in this paper. A new technique of path planning for symmetrical free-form surfaces is used. The proposed method is tested for the polishing of a glasses frame. Finally, the optimized path planning idea for the symmetrical free-form surfaces is compared with other path planning methods in terms of quality and productivity.
Broadening the Bandgaps of Sonic Crystals by Varying Shapes, Sizes and Orientations of the Scatterers
Authors: Panda Debasish , Mohanty A. R.
Published: January 2019

Sonic Crystals are noise barriers wherein the incident sound waves are scattered multiple times by the periodically arranged scatterers placed inside a host fluid. Used as sound attenuators, sonic crystals attenuate sound over frequency bands known as bandgaps. Broadening and lowering the bandgaps is the primary objective of this work. Effect of changing the shape, size and orientations of the scatterers on the band characteristics have been reported here. Different shapes of the scatterers are found to affect the band characteristics of the sonic crystals. Adding local resonance to the scatterers introduce a new attenuation mechanism due to local acoustic resonances. A new type of double circle split-ring resonator is also proposed which use acoustic resonance to produce additional bandgaps. Size and orientation of the scatterers are also found to affect the bandwidth and center frequency of the bandgaps. The band diagram, transmission loss, eigenmodes are computed using finite element method. COMSOL Multiphysics, a commercially available finite element software has been used to implement FEM and model the two-dimensional unit cells and the sonic crystal arrays. Due to the large difference in impedance of the steel scatterer embedded in air, the scatterers are assumed to be sound hard (sound rigid) which imposes a condition where normal component of acceleration is zero.
Efficient Variation Simulation of Spot-Welded Assemblies
Authors: Lorin Samuel , Lindau Björn , Sadeghi Tabar Roham , Lindkvist Lars , Wärmefjord Kristina , Söderberg Rikard
Published: January 2019

Variation simulation for assembled products is one important activity during product development. Variation simulation enables the designer to understand not only the features of the nominal product but also how uncertainty will affect production, functions and the aesthetic properties of the final product. For parts that are able to deform during assembly, compliant variation simulation is needed for accurate prediction. For this the Finite Element Method (FEM) is used. Despite many effective efforts to decrease simulation times for compliant variation simulation, simulation time is still considered an obstacle for full scale industrial use. In this paper, a new formulation for compliant variation simulation of assemblies that are joined in sequential spot-welding will be presented. In this formulation the deformation in the intermediate springback steps during the simulation of a spot-weld sequence do not have to be calculated. This is one of the most time consuming steps in sequential spot-welding simulation. Furthermore, avoiding the intermediate springback calculation will reduce the size of memory of the computer models since the number of sensitivity matrices is reduced. The formulation is implemented using the latest developments in compliant variation simulation, that is the Method of Influence Coefficients (MIC) where the Sherman-Morrison-Woodbury-formula is used to update the resulting sensitivity matrices and the contact- and weld forces are solved using a Quadratic Programme (QP). Industrial cases are used to demonstrate the reduced simulation time. It is believed that the reduction in simulation times will have future implications on sequence optimization for spot-welded assemblies.
ODS Coating for Critical Turbine Components Using DED Additive Manufacturing
Authors: Chia Eric , Kang Bruce S. , Zheng Min , Li Yang , Chyu Minking
Published: January 2019

A method to fabricate high temperature protective structural coating on top of critical gas turbine components by additive manufacturing (AM) technique using oxide dispersion strengthening (ODS) powder is presented. A novel combined mechanochemical bonding (MCB) plus ball milling (BM) process is utilized to produce ODS powders with nano-crystalline gamma prime phase. AM-assisted ODS coating by direct energy deposition (DED) method on MAR-247 substrate, with laser powers from 100W to 200W were carried out. The ODS coated samples were then subjected to cyclic thermal loadings for over 2000 cycles. Depth-profiling x-ray photoelectric spectroscopy (DP-XPS) was applied for detailed oxide formation analyses through the ODS coating layer at various thermal cycles. Corresponding mechanical properties such as Young’s modulus, yield strength and hardening component of ODS coating samples at various thermal cycles were measured at room temperature using an in-house developed non-destructive spherical micro-indentation testing method. Correlation of the measured mechanical properties with evolution of the ODS microstructures are studied. In particular, stability of gamma prime phase in the ODS coating after thermal cycles is analyzed. Test results revealed a thin steady durable alpha alumina oxide layer on ODS coating surface. After 2,200 thermal cycles, strong bonding at ODS/substrate interface is maintained for ODS coated samples with 200W laser power. Test results also showed stable substrate microstructures due to the protective ODS coating even after 2,200 thermal cycles.
Numerical Study of Two-Phase Flow in a Horizontal Pipeline Using an Unconditionally Hyperbolic Two-Fluid Model
Authors: de Freitas Raphael V. N. , Sondermann Carina N. , Patricio Rodrigo A. C. , Figueiredo Aline B. , Bodstein Gustavo C. R. , Rachid Felipe B. F. , M. Baptista Renan
Published: January 2019

Numerical simulation is a very useful tool for the prediction of physical quantities in two-phase flows. One important application is the study of oil-gas flows in pipelines, which is necessary for the proper selection of the equipment connected to the line during the pipeline design stage and also during the pipeline operation stage. The understanding of the phenomena present in this type of flow is more crucial under the occurrence of undesired effects in the duct, such as hydrate formation, fluid leakage, PIG passage, and valve shutdown. An efficient manner to model two-phase flows in long pipelines regarding a compromise between numerical accuracy and cost is the use of a one-dimensional two-fluid model, discretized with an appropriate numerical method. A two-fluid model consists of a system of non-linear partial differential equations that represent the mass, momentum and energy conservation principles, written for each phase. Depending on the two-fluid model employed, the system of equations may lose hyperbolicity and render the initial-boundary-value problem illposed. This paper uses an unconditionally hyperbolic two-fluid model for solving two-phase flows in pipelines in order to guarantee that the solution presents physical consistency. The mathematical model here referred to as the 5E2P (five equations and two pressures) comprises two equations of continuity and two momentum conservation equations, one for each phase, and one equation for the transport of the volume fraction. A priori this model considers two distinct pressures, one for each phase, and correlates them through a pressure relaxation procedure. This paper presents simulation cases for stratified two-phase flows in horizontal pipelines solved with the 5E2P coupled with the flux corrected transport method. The objective is to evaluate the numerical model capacity to adequately describe the velocities, pressures and volume fraction distributions along the duct.
Mechanical Property Determination of a Stereolithographic Resin Subjected to Compressive Loading
Authors: Fry Christian , Mihalko Adam , Michael Robert , Piovesan Davide
Published: January 2019

This paper presents the findings of destructive compression testing on Formlabs© CLEAR Resin FLGPCL02 and TOUGH Resin FLTOTL03. Compression testing ASTM D695-15 was chosen because of the extreme fragility of the Clear Resin which did not allowed proper tensile testing with our equipment. The material was subjected to a steadily increasing compressive load until complete failure occurred. Five mechanical properties were extracted from stress versus strain curves. The five experimental properties, of Formlabs© CLEAR resin, found were young’s modulus (1.52 GPa) (std = 71 MPa), yield strength (39.6 MPa) (std = 2 MPa), ultimate strength (255 MPa) (std = 35 MPa), strain at fracture (0.509 m/m) (std = 0.0159 m/m), and toughness (49.1 J/m−3) (std = 3.9 J/m−3). The five experimental properties, of Formlabs© TOUGH resin, found were secant modulus (73.9 MPa) (std = 0.87 MPa), yield strength (42.8 MPa) (std = 3.03MPa), ultimate strength (587 MPa) (std = 61 MPa), strain at fracture (0.686 m/m) (std = 0.0097 m/m), and toughness (65 J/m−3) (std = 6 J/m−3). These were then compared to Formlabs© public released values.
High Voltage Plasma Reactor for Treatment of Carbon Dioxide and Oxygen Generation
Authors: Wright Kamau
Published: January 2019

High voltage plasma-based technologies have the ability to impact multiple fields from medicine to engineering. The goal of the most recent study was to investigate the efficacy of a novel high voltage plasma system to generate oxygen (O2) from carbon dioxide (CO2) through dissociation. The general endothermic plasma-chemical process of CO2 decomposition is presented, with CO2 destruction accompanying production of oxygen (and carbon monoxide) at a mole ratio of 2 to 1. A high voltage plasma reactor was developed for this purpose. SEM analysis was conducted on electrodes used for plasma discharges, to better elucidate characteristics of the plasma. CO2 gas samples were analyzed using an FTIR spectrometer. Baseline scans were taken of CO2 inside the reactor before plasma power was turned on; subsequent scans were taken after 10 min of plasma treatment. Results of FTIR analysis presented here have indicated a 30% decrease in CO2 concentration upon application of the developed plasma reactor. This paper reports on various aspects of the instrumented high voltage plasma reactor; and experimental results which further explore the capability to decrease CO2 concentrations in various environments, while also generating O2.
Future Scenarios for Emissions From Energy and Power Production in the Rocky Mountain Region
Authors: Nsanzineza Rene , Milford Jana
Published: January 2019

Across the U.S., electricity production from coal-fired generation is declining while use of renewables and natural gas is increasing. This trend is expected to continue in the future. In the Rocky Mountain region, this shift is expected to reduce emissions from electricity production while increasing emissions from the production and processing of oil and gas, with significant implications for the level, location, and timing of the air pollution emissions that are associated with these activities. In turn, these emissions changes will affect air quality in the region, with impacts on ground-level ozone of particular concern. This study aims to evaluate the tradeoffs in emissions from both power plants and oil and gas basins resulting from contrasting scenarios for shifts in electricity and oil and gas production through the year 2030. The study also incorporates federal and state-level regulations for CH4, NOx, and VOC emissions sources. These regulations are expected to produce significant emissions reductions relative to baseline projections, especially in the oil and gas production sector. Annual emissions from electricity production are estimated to decrease in all scenarios, due to a combination of using more natural gas power plants, renewables, emissions regulations, and retiring old inefficient coal power plants. However, reductions are larger in fall, winter, and spring than in summer, when ozone pollution is of greatest concern. Emissions from oil and gas production are estimated to either increase or decrease depending on the location, scenario, and the number of sources affected by regulations. The net change in emissions thus depends on pollutant, location, and time of year.
Using Multiple-Model Adaptive Estimation and System Identification for Fault Detection in Nuclear Power Plants
Authors: Farber Jacob A. , Cole Daniel G.
Published: January 2019

One challenge in nuclear power plant operation is the detection and identification of system faults and plant transients. Timely and accurate identification will reduce operational costs and increase plant safety. This paper describes a combined model-based and data-driven approach to identifying faults in nuclear power plants. Faults are detected for a GSES Generic Pressurized Water Reactor simulator using the multiple-model adaptive estimation (MMAE) technique. In this technique, multiple input-output system models are used that represent different operating conditions. The models predict sensor measurements for both normal and faulted operating conditions simultaneously. The predicted measurements are then compared to the sensor measurements to determine the most likely operating condition. The system models are obtained using system identification techniques for a specific set of faulted conditions. This technique uses sensor measurements from the simulation to identify appropriate parameters for the system models. The MMAE technique is then used to detect similar faults using the identified model. This combination of model-based and data-driven techniques can ultimately be used to create robust fault models that take advantage of both the models created during the design and validation process and real plant data.
Shape Memory Alloy Based Rotational Actuator
Authors: Hofmann Nick , Hennessey Michael P.
Published: January 2019

Due to recent technological developments in advanced materials, the integration of shape memory alloys (SMAs) into new machines and mechanisms is becoming more common and it offers tremendous potential for the future. Using currently available properties of common SMA materials, the paper’s contribution is to: Study through dynamic simulation the potential offered by SMA springs to serve as the basis for rotary actuation. In the process, the SMA displaces a rocker arm rotating about an axis to induce rotational motion of a driveshaft, in effect converting a force into rotational motion. When embedded in a cycle with heating & cooling phases and a resetting mechanism, unidirectional rotational motion can be achieved.

Regarding heating and cooling cycles, forced air convection is used to reduce thermal cycle cooling and is calculated via transient thermal analyses. Using typical parameter values for the representative design considered, through forced air convection, cooling cycles are reduced from approximately 30 seconds (natural) to 5.5 seconds (forced) and as a result, a complete system cycle can occur in 10 seconds, with the applied inertial load of 2.0 kg-m2.

Using MATLAB and Simulink, a nonlinear 3rd order dynamic system model was created and simulations were performed. One complicating factor concerned angular limits and the necessary thermal cycling, which was solved through appropriate sequencing and resetting of integrators for different phases. Simulation results for the design considered show that a peak torque of 1.72 N-m is possible and that relatively smooth motion and approximately constant torque output is also possible through the addition of a few more rocker arm systems, properly commutated. Lastly, the design analysis framework and results may inspire future realization of actual devices.
A Computational Fluid Dynamics (CFD) Study of Material Transport and Deposition in Aerosol Jet Printing (AJP) Process
Authors: Salary Roozbeh (Ross) , Lombardi Jack P. , Weerawarne Darshana L. , Rao Prahalada K. , Poliks Mark D.
Published: January 2019

The objective of this work is to forward a 3D computational fluid dynamics (CFD) model to explain the aerodynamics behind aerosol transport and deposition in aerosol jet printing (AJP). The CFD model allows for: (i) mapping of velocity fields as well as particle trajectories; and (ii) investigation of post-deposition phenomena of sticking, rebounding, spreading, and splashing. The complex geometry of the deposition head was modeled in the ANSYS-Fluent environment, based on a patented design as well as accurate measurements, obtained from 3D X-ray CT imaging. The entire volume of the geometry was subsequently meshed, using a mixture of smooth and soft quadrilateral elements, with consideration of layers of inflation to obtain an accurate solution near the walls. A combined approach — based on the density-based and pressure-based Navier-Stokes formation — was adopted to obtain steady-state solutions and to bring the conservation imbalances below a specified linearization tolerance (10−6). Turbulence was modeled, using the realizable k-ε viscose model with scalable wall functions. A coupled two-phase flow model was set up to track a large number of injected particles. The boundary conditions were defined based on experimental sensor data. A single-factor factorial experiment was conducted to investigate the influence of sheath gas flow rate (ShGFR) on line morphology, and also validate the CFD model.
Discovery and Development of a Fast Charging Li-Ion Battery
Authors: Liu Teng , Yang Xiao-Guang , Wang Chao-Yang
Published: January 2019

Enabling fast charging of Li-ion batteries (LiB) is essential for mainstream adoption of electric vehicles (EVs). A critical challenge to fast charging is lithium plating, which can lead to drastic capacity loss and safety risks. Fundamentally, fast charging is restricted by anode surface reaction kinetics, lithium diffusion in anode solid particles and Li+ diffusion and conduction in electrolyte. In this work, we present an analysis of the contributions of these different physicochemical processes to the total overpotential during fast charging, using an electrochemical-thermal (ECT) coupled model. Special attention is paid to the effect of increasing electrode thickness, a common approach for raising energy density of EV cells, on fast charging capability. It is found that lithium plating is more prone to occur in thicker anodes due to larger electrolyte transport resistance. Furthermore, we present a novel approach of thermal stimulation to enable 10-minutes (6C rate) fast charging of an EV cell with 170Wh/kg energy density.
A Scalabale Microfluidic Device for Switching of Microparticles Using Dielectrophoresis
Authors: Waheed Waqas , Alazzam Anas , Mathew Bobby , Abu Nada Eiyad , Al Khateeb Ashraf N.
Published: January 2019

In this paper, we have introduced a negative Dielectrophoresis based microfluidic system using a novel arrangement of microelectrodes to perform switching of micro objects. Both the experimental and numerical results are presented. Two sets of interdigitated electrodes, extending slightly into the microchannel from each sidewall, are embedded on the bottom of the microchannel. A finite element model in COMSOL Multiphysics 5.2a was developed to demonstrate switching of Red Blood Cells in the microchannel followed by multiple parametric studies to study the effect of several parameters on cell trajectories and optimize the design parameters. To verify numerical results, a PDMS-based microfluidic device on glass wafer was fabricated. The switching of Red Blood Cells in the microfluidic device with a single inlet and three outlets was also demonstrated.
A Clinical Experiment on Infant Applied Pressures During Breastfeeding
Authors: Jiang Lin , Alatalo Diana L. , Geddes Donna T. , Hassanipour Fatemeh
Published: January 2019

Breastfeeding provides both nutrients and immunities necessary for infant growth. Understanding the biomechanics of breastfeeding requires capturing both positive and negative pressures exerted by infants on the breast. This clinical experimental work utilizes thin, flexible pressure sensors to capture the positive oral pressures of 7 mother-infant dyads during breastfeeding while simultaneously measuring vacuum pressures and imaging of the infants oral cavity movement via ultrasound. Methods for denoising signals and evaluating ultrasound images are discussed. Changes and deformations on the nipple are evaluated. The results reveal that pressure from the infant’s maxilla and mandible are evenly distributed in an oscillatory pattern corresponding to the vacuum pressure patterns. Variations in nipple dimensions are considerably smaller than variations in either pressure but the ultrasound shows positive pressure dominates structural changes during breastfeeding. Clinical implications for infant-led milk expression and data processing are discussed.
Seismic Probabilistic Risk Assessment of Nuclear Power Plants: 10 CFR 50.69 Assumptions and Sources of Uncertainty
Authors: Lyons Sara , Vasavada Shilp
Published: January 2019

The U.S. Nuclear Regulatory Commission (NRC) promulgated Part 50.69 to Title 10 of the Code of Federal Regulations (CFR), “Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors,” in November 2004 (hereafter referred to as 10 CFR 50.69). The rule provides a voluntary alternative to compliance with many regulations which require “special treatment,” or regulatory requirements which go beyond industrial controls, including: specific inspection, testing, qualification, and reporting requirements. The voluntary alternative includes a process for categorization of structures, systems, and components (SSCs) as having either low safety significance (LSS) or high safety significance (HSS). The categorization process can result in increased requirements for HSS SSCs which were previously treated as non-safety-related, and reduced requirements for LSS SSCs which were previously treated as safety-related.

The categorization process includes plant-specific risk analyses which are used in combination with an integrated decision-making panel (IDP) to determine whether the SSC has a low or high safety significance. Seismic probabilistic risk assessment (SPRA) is one of the risk analyses options to account for the seismic risk contribution. Because the 10 CFR 50.69 rule has currently not been implemented widely, the significance of various SPRA assumptions and sources of uncertainty to the categorization process has had limited evaluation for a broad spectrum of U.S. nuclear power plants.

This paper will assess the importance of certain aspects of the seismic risk contribution to the categorization process. NRC Standardized Plant Analysis Risk (SPAR) models will be used to perform sensitivity studies to quantify the impact of various assumptions and sources of uncertainty on the outcome of the categorization process.
Locating and Quantifying Through Circular Damage in CNT/GFRP Composite Panel Using Gaussian Fit
Authors: Ikikardaslar Kerim T. , Delale Feridun , Ardebili Mahmoud K. , Yildiz Salih , Gollins Kenneth
Published: January 2019

Previously published articles on detecting damage in electrically conductive panels mainly concentrate on electrical impedance tomography methods (EIT) which are based on using surface bounded boundary electrodes and taking advantage of an electrically conductive layer on the surface of the panel or of a conductive matrix material. In this study instead, embedded electrodes in glass fiber reinforced epoxy panels are used to locate and quantify the artificial damage inflicted on the panel. The panel was manufactured using vacuum infusion method. It consisted of 10 (S-2) glass fabric plies, where copper electrodes were embedded below the top layer and then vacuum infused with carbon nanotube (CNT) mixed epoxy. During all measurements, a constant electrical current was supplied from two outer electrodes (the source and sink) and changes in voltage from the two inner probes were recorded. In contrast to EIT methods, no complicated algorithm is used to solve the conductivity distribution of the panel but instead, a simple algorithm that fits Gaussian curves to the data obtained using a four-probe measurement technique. Using the fitted curves, we are able to detect location and magnitude of the damages within a confidence bound. This practical method reduces computational cost and also enables the use of embedded electrodes which could provide more durability for the sensors. The experimental data is in very good agreement with the finite element simulations. Comparison of relative voltage change before and after the damages is consistent and sensitive enough to detect damages down to 1/8” diameter hole inside an area of 33 in2. As expected, accuracy is higher for larger diameter holes.
Numerical Analysis of the Contribution of Shot Peening in the Fatigue Strength of Multipass Welded Joints
Authors: Etxeberria U. , Esnaola J. A. , Ulacia I. , Ugarte D. , Llavori I. , Larrañaga M. , Lopez-Jauregi A.
Published: January 2019

Tensile residual stress (RS) peaks near the weld toe accelerate crack generation and propagation stages reducing dramatically the life of welded components. In order to relief RS, components are typically heat-treated. However, heat treatments can affect the microstructure compromising mechanical properties. In addition, their application in big structures is complex due to size limitations. As an alternative, mechanical treatments such as shot peening can be locally applied. Moreover, they generate local compressive stresses in the treated surfaces, which present beneficial effect in the fatigue strength of treated components.

In the present work, the contribution of shot peening in the fatigue strength of multipass welded joints is numerically evaluated. For that purpose, first the RS stress pattern of a 3 pass butt weld of 10mm thick, 50mm length S275JR plates is calculated. Following, the application of shot peening in the tensile RS area is modelled and the evolution of RS pattern is analyzed. Finally, the fatigue strength of treated and non-treated butt welds is evaluated.
Effect of Speed on the Performance Characteristics of Non-Recessed Worn Hybrid Conical Journal Bearing for Different Semi Cone Angles
Authors: Phalle Vikas M. , Pawar Sanjay R. , Patil Sangram S.
Published: January 2019

The conical fluid film hybrid journal bearing may be developed as a modification to overcome the adverse effects of cylindrical journal bearing configuration. Hybrid bearing also have a capability to take advantage of simultaneous hydrodynamic and hydrostatic action. This paper aims to study analytically the performance characteristics of a non-recessed, worn hybrid conical journal bearing compensated with constant flow valve as restrictor. The Reynolds equation for conical bearing is developed in spherical coordinate system for governing the flow of iso-viscous incompressible fluid in the clearance space of conical journal and bearing and it is solved by finite element method together with restrictor flow equation. Numerically simulated results indicate that appreciable change in the performance characteristics of worn hybrid conical journal bearing with change in speed parameter and they are expected to be quite useful for the bearing designer.
Active Acoustic Metamaterials With Programmable Densities Using an H-∞ Controller
Authors: Baz Amr
Published: January 2019

Various types of acoustic metamaterials have been developed to control the flow of acoustical energy through these materials. Most of these metamaterials are passive in nature with pre-tuned and fixed material properties. In this paper, the emphasis is placed on the development of a class of one-dimensional acoustic metamaterials with programmable densities in order to enable the control the acoustic wave propagation in these media. With such unique capabilities, the proposed active acoustic metamaterials (AAMM) can be utilized to physically realize, for example, acoustic cloaks, wave shifters and focusers, tunable acoustic absorbers and reflectors, as well as non-reciprocal acoustic media.

The theoretical analysis of this class of AAMM with programmable effective dynamical densities is presented for an array of cavities separated by piezoelectric boundaries. These boundaries provide means for controlling the stiffness of the individual cavity and, in turn, its dynamical densities. In this regard, a disturbance rejection strategy is considered which is based on an H-∞ robust controller. The time and frequency response characteristics of a unit cell of the AAMM are investigated for various parameters of the controller in an attempt to optimize the performance characteristics.

Extension of this study to include active control capabilities of the bulk modulus of the metamaterials would enable the development of wide classes of AAMM that are only limited by our imagination.
Effect of Nano Silica on Compressive Strength of Concrete
Authors: Al-Rifaie Wail , Alawaneh Abdalmjeed , Al-Bajawi Mohammed , Ahmed Waleed
Published: January 2019

In the present work, the use of nano silica fume in developing a compressive strength of concrete that can lead to improvement in concrete construction is carried out in the present work. One of the parameters considered is a number of curing days for measuring the compressive strength. The measured results demonstrate the increase in compressive. To achieve our goals, concrete cubes were cast and tested for compressive strength, all concrete sample has the same mixing ratio and sub-classified to standard, and Silica fume added by weight of cement (5%, 10%, 15%, 20% and 30%). The results show that the recommended addition was 15% of Silica fumes for optimum compressive strength that reaches 74.8 MPa.
Motion Planning for Handspring Maneuver Using a Two Link Robot
Authors: Bhirangi Raunaq , Sangwan Vivek
Published: January 2019

Motion planning and control to generate human like walking with bipedal robots has been an active area of research for several decades. Besides walking, humans are capable of performing several other complex maneuvers using their limbs. A handspring is one such maneuver. During this acrobatic move, a person performs a complete revolution of the body by first placing her hands as if in a handstand, then pushing off of the floor with her hands to return to a standing position. Often, acrobats leverage the momentum from one handspring to perform a series of continuous back-to-back handsprings. In this paper, we present handspring trajectory planning for a simple two link robot using numerical optimization. We are able to generate near-periodic perpetual handspring-like maneuvers using two different actuation strategies (i) a constant torque at the hip joint, and (ii) an impulsive actuation to the imminent free leg.
Strategies to Address “Design Thinking” in Engineering Curriculum
Authors: Shetty Devdas , Xu Jiajun
Published: January 2019

It is suggested by many scholars that if the goal of engineering education is to produce engineers who can critically design and create, then providing students with early opportunities to engage in creative engineering design is important. While basic design is focused on the development of new products for the individual, working towards a more sustainable world demands greater attention to designing for and with communities. Improving design education and examining design-learning outcomes requires a kind of targeted approach that could match the best practices to personalize student learning. Design is complex and design includes balancing the needs of multiple stakeholders. However, there is a gap in the preparation of design education that will be needed in a challenging environment. This paper reviews the history of design thinking in the engineering curriculum. Design thinking education starts with an understanding of its importance with socioeconomic relevance. Through observation and empathy, mapping the designer uses the listening and learning tools for mapping users unarticulated needs, working in a team environment. The designer takes time to think carefully why a certain project is considered and details which aspects of machine learning application can be applied from functional to complete success for the end users. The availability of powerful virtual reality methodologies, have made it possible to consider the realistic needs and visualize scenarios and to explore the design alternatives with new ideas before full scale resource allocation on new ideas. Mid-to-advanced level courses with experimental assignments require that students apply through experimentation the principles and concepts learned in foundation courses. The basic design tools such as axiomatic thinking, theory of inventive problem solving, design iteration and simulation using hardware-in-the loop are discussed with case studies. Consideration of product sustainability with the thoughts of design for disassembly and disposal has emerged as a major part of design thinking. Senior engineering courses center on cross and interdisciplinary design and capstone experiences so that students experience fully guided practice of device design and problem solving, simulating what they are likely to experience in the world. This paper examines the critical issues of design thinking in a curriculum from observation, empathy mapping, validation of the idea, and improvement of idea by virtual reality and machine learning, optimization of the idea by tools such as axiomatic design, hardware in the loop simulation, and finally examining product sustainability causes.
Frequency Response for MEMS Circular Plate Resonators Under Superharmonic Resonance of the Second Order
Authors: Botello Martin , Beatriz Julio , Caruntu Dumitru I.
Published: January 2019

A nonlinear dynamics investigation is conducted on the frequency-amplitude response of electrostatically actuated micro-electro-mechanical system (MEMS) clamped plate resonators. The Alternating Current (AC) voltage is operating in the realm of superharmonic resonance of second order. This is given by an AC frequency near one-fourth of the natural frequency of the resonator. The magnitude of the AC voltage is large enough to be considered as hard excitation. The external forces acting on the MEMS resonator are viscous air damping and electrostatic force. Two proven mathematical models are utilized to obtain a predicted frequency-amplitude response for the MEMS resonator. Method of Multiple Scales (MMS) allows the transformation of a partial differential equation of motion into zero-order and first-order problems. Hence, MMS can be directly applied to obtain the frequency-amplitude response. Reduced Order Model (ROM), based on the Galerkin procedure, uses mode shapes of vibration for undamped circular plate resonator as a basis of functions. ROM is numerically integrated using MATLAB software package to obtain time responses. Also, ROM is used to conduct a continuation and bifurcation analysis utilizing AUTO 07P software package in order to obtain the frequency-amplitude response. The time responses show the movement of the center of the MEMS circular plate as a function of time. The frequency-amplitude response allows one to observe bifurcation and pull-in instabilities within the nonlinear system over a range of frequencies. The influences of parameters (i.e. damping and voltage) are also included in this investigation.
Experimental Characterization of Particle-Laden Air Flow Across Horizontal Pipe Junctions
Authors: Khan Tariq S. , Alshehhi Mohamed , Rumin Xu , Salam Saqib
Published: January 2019

There are several industrial applications in which two phase solid-gas flows are involved. At times, pipe junctions are involved where flow split takes place. Present study consists of experimental investigation of turbulent gas-solid two-phase flow through horizontal pipe junctions. The effects of air flow rate, branch diameter and pipe orientation at junctions are investigated on mass fraction, phase split and solid particles distribution across the junctions. Silica powder, in the monodispersed size of 15 μm was injected into the pipelines by a micro-feeder. The powder was entrained in an air flow which passed horizontally through a long straight channel of circular pipe with T and Y junctions. The main pipe was 51mm in diameter while the inlet superficial velocity of gas was varied from 5 m/s to 13.5m/s. The particles mass concentration was measured by the aerodynamic particle sizer (APS). Experimental results showed that solid phase split followed air flow split while decreasing the inlet air velocity caused major decrease in the mass fraction at junction pipe. The orientation of junction pipe has a significant effect on the flow behavior along the pipe. These results indicate that the behavior of solid particles is a complex phenomenon in pipe flows.
Effect of Geometric Configuration and Back Plate Addition in Minichannel Solar Collectors
Authors: Hota Sai Kiran , Perez Julio , Diaz Gerardo
Published: January 2019

Minichannel tubes have been successfully integrated into automotive, aerospace and HVAC due to their performance superiority and cost effectiveness. Recently, they have also been introduced in the solar thermal industry for similar reasons. Considering the indirect and limited contact area for heat exchange between absorber and fluid in a conventional solar collector, a minichannel tube has the advantage of providing an absorber surface with large heat transfer area and has less thermal resistance. Due to the method of construction, in many cases, minichannel tubes are separated by a few millimeters from each other, leaving a gap in between tubes that wastes collector area. The addition of a back plate to these minichannel-tube collectors will enhance the thermal output as they together provide a larger surface area for absorption. This effectively increases the thermal output. However, the balance between heat transfer and pumping power needs to be analyzed, thereby the need arises to optimize these geometric parameters. This paper attempts to determine these performance values while optimizing the minichannel-tube geometry and back plate width. From energy analysis, it is deduced that a back plate of 40mm width with the corresponding hydraulic diameter for a constant heat exchange width of 100mm maximizes the thermal performance. The exergy analysis further shows that when the back plate width was between 40mm–45mm, maximum of 73% exergy efficiency can be achieved.