bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Multiaxial Fatigue Damage Using Polar Equations
Authors: Albinmousa Jafar , Iftikhar Syed Haris , Al-Samkhan Mustafa 
Published: January 2018

It is estimated that more than 70% of failures in engineering components are associated with fatigue loading. Therefore, fatigue is a major design tool for mechanical components. These components are usually subjected to multiaxial cyclic loading. In fact, multiaxial state is very common as tension specimen is under triaxial strain state even though its stress state is uniaxial.
There are three approaches to modeling fatigue damage: stress, strain and energy. Critical plane concept is established based on the fact that fatigue cracks initiate at specific plane(s), therefore, multiaxial fatigue damage parameter is evaluated at these plane(s). Critical plane fatigue models such as Fatemi-Socie is among the popular strain-based models. Because it was shown to provide estimation mostly within two factors of life for different materials and different multiaxial loading conditions.
This paper presents a new method for analyzing critical plane damage parameters. Using plane stress-strain transformation, maximum values of normal and shear stresses and strains from hysteresis loops are obtained at 360 planes. Plotting these values on polar diagrams shows that multiaxial cyclic responses represent polar curves that can successfully be fitted with definitive known polar equations. In principle, this means that both critical plane and fatigue damage can be determined analytically for a given loading path. However, fitting constants must first be determined.
A systematic analysis is performed on different experimental data that were obtained by testing two extruded magnesium alloys at proportional and 90° out of phase loading paths. A closed-form solution for Fatemi-Socie damage parameter is presented for these two loading paths.
Damage Accumulation Modeling and Rate Dependency of Spinal Dura Mater
Authors: Ramo Nicole L. , Shetye Snehal S. , Puttlitz Christian M. 
Published: January 2018

As the strongest of the meningeal tissues, the spinal dura mater plays an important role in the overall behavior of the spinal cord-meningeal complex (SCM). It follows that the accumulation of damage affects the dura mater’s ability to protect the cord from excessive mechanical loads. Unfortunately, current computational investigations of spinal cord injury etiology typically do not include post-yield behavior. Therefore, a more detailed description of the material behavior of the spinal dura mater, including characterization of damage accumulation, is required to comprehensively study spinal cord injuries.
Continuum mechanics-based viscoelastic damage theories have been previously applied to other biological tissues, however the current work is the first to report damage accumulation modeling in a SCM tissue. Longitudinal samples of ovine cervical dura mater were tensioned-to-failure at one of three strain rates (quasi-static, 0.05/sec, and 0.3/sec). The resulting stress-strain data were fit to a hyperelastic continuum damage model to characterize the strain-rate dependent sub-failure and failure behavior. The results show that the damage behavior of the fibrous and matrix components of the dura mater are strain-rate dependent, with distinct behaviors when exposed to strain-rates above that experienced during normal voluntary neck motion suggesting the possible existence of a protective mechanism.
Effective Tools to Learn Lean Thinking and Gather Together Academic and Practice Communities
Authors: Alves Anabela C. , Flumerfelt Shannon , Moreira F. , Leão Celina P. 
Published: January 2018

Lean Engineering learning should be compulsory on engineering curricula, and, particularly, on the Industrial Engineering field. Prior to the integration on the Industrial Engineering curriculum, Lean Engineering was already implemented by many organizations and, often, fostered by consulting companies. For this reason, if engineering students were taught about Lean Engineering, they would be better prepared to assume a leadership role in their organizations and/or to better communicate with Lean consultants.
Based on a literature review and on the authors’ practice, this paper discuss some approaches that have been used for Lean Engineering learning. Some learning experiences implemented in an engineering master’s degree are presented which make use of effective educational tools based on active methodologies, such as hands-on simulation, Problem or Project-Based Learning (PBL), Conceive-Design-Implement and Operate (CDIO) initiative, among others. This paper also presents these tools and how they address Lean Engineering learning through the lens of Lean Thinking principles. Their advantages in Lean Engineering learning are discussed by gathering the academic and practitioners’ communities opinions. These are based on final year projects’ reports, feedback from students and from organization supervisors.
Identification of Non-Linear Parameters of a Nuclear Fuel Rod
Authors: Ferrari Giovanni , Le Guisquet Stanislas , Balasubramanian Prabakaran , Amabili Marco , Painter Brian , Karazis Kostas 
Published: January 2018

In Pressurized Water Reactors (PWR), fuel assemblies are made up of fuel rods, long slender tubes filled with uranium pellets, bundled together using spacer grids. These structures are subjected to fluid-structure interactions, due to the flowing coolant surrounding the fuel assemblies inside the core, coupled with large-amplitude vibrations in case of external seismic excitation. Therefore, understanding the nonlinear response of the structure, and, particularly, its dissipation, is of paramount importance for the choice of safety margins, in the design of fuel assemblies, to ensure their functionality and safety in the worst external condition scenarios.
To model the nonlinear dynamic response of fuel rods, the identification of the nonlinear stiffness and damping parameters is required. A tool based on harmonic balance method was developed to identify these parameters from the experimentally obtained force-response curves, considering one-to-one internal resonance phenomenon present in axisymmetric structures such as cylindrical tubes and shells. To validate the tool, it was applied to the reference case of circular cylindrical shell filled with water, which revealed an increase of damping with the excitation amplitude.
In the following paper, the more realistic case of a single fuel rod with clamped-clamped boundary condition was investigated by applying harmonic excitation at various force levels. The nonlinear parameters including damping were extracted from experimental results by means of the adapted tool. An increase in damping with excitation amplitude has been shown according to earlier studies.
Performance Assessment of a Cooling Tower and a Ground Source Heat Pump for Heat Dissipation
Authors: Moreira Daniel , Zabala Gonzalo , Villanueva Rubén , Soriano Guillermo 
Published: January 2018

An experimental comparison between two heat sinks systems has been performed. The area of the study is Guayaquil, Ecuador with an average annual temperature of 27 °C and an average annual relative humidity of 77% (UTM 0621517/09749485) where typical large HVAC systems with cooling towers are used. As a result of the high relative humidity in the area, the thermal efficiency of this type of heat exchanger is reduced. A geothermal heat exchanger cooling water using the constant and relatively low soil temperature is considered as a viable alternative for HVAC systems in this location. In this project, a prototype geothermal heat exchanger is built and experimentally compared with a cooling tower system.
Through previous research, it was determined that the soil at this borehole consist of 5 % of landfill material; 86 % several strata of low plasticity silt, alternating silt; and 5 % sand. This location corresponds to the estuarine deposits of the Guayas River. The average soil temperature is 27 ° C, associated with a thermal conductivity of 1.87 W / m K and a thermal diffusivity of 0.085 m2 / day obtained from a Thermal Response Test of the soil.
An experiment for the comparison of these two types of heat exchangers under a uniform heat load is designed and built. The cooling tower water installed has a capacity of 5 Tons of Refrigeration with a flow of 15 Gallons per minute. The geothermal heat exchanger consisting of four drilled to 42 meters deep vertical holes and connected in a parallel circuit. Both systems operate in periods of 8 and 12 hours during the hours of daylight. To simulate the thermal load in both cases, water is heated using two identical electric boilers with a nominal power of 9 kW each. Data from the energy consumption, and energy dissipation from each system is collected and analyzed.
The Energy Efficiency Rating obtained for each system is on the order of 10.61 for the cooling tower water, and on the order of 14.78 for the geothermal heat exchanger, with savings of 61.7% in energy consumption and CO2 emissions by the system of geothermal cooling through better efficiency.
We have also projected the costs of installation, operation and maintenance of both systems. Results suggest that despite the high cost of installation, a geothermal sink is a valid option for HVAC systems in cities or regions that have high temperatures and high humidity.
Organization and Compaction of Composite Filler Material Using Acoustic Focusing
Authors: Chai Lauren A. , Anthony Brian W. 
Published: January 2018

Carbon nanofibers in polymer-based composites reduce the electrical resistivity of the composite but can be up to 100 times more expensive than the bulk polymer. This work uses acoustic focusing to organize and compact carbon nanofibers in a mineral oil mixture. The result is a decrease in the composite electrical resistivity without an increase in the global volume fraction of the fibers in the composite and associated material cost.
The composite consisted of Pyrograf PR-19-LHT carbon nanofibers mixed in light mineral oil at 1.6% volume fraction carbon nanofibers. The mixture was contained in a 1 cm × 1 cm × 4 cm glass cuvette. A PZT-4 piezoelectric transducer, epoxied to the external face of one of the sidewalls, generated the acoustic radiation forces in the container. A 1.179 MHz sinusoidal signal powered the transducer, producing a standing wave with 27 nodes and 13 antinodes in the container. A digital multimeter performed the 2-wire resistance measurement before, during and after focusing.
Settling of the filler due to gravity resulted in an initial drop in the electrical resistance. Once the mixture reached steady state, toggling the signal power off and on also toggled the approximate electrical resistance between the 19.2 MOhms and 11.5 MOhms respectively. This work also presents a simple volume fraction model, which predicted that the focused resistance would be 34% of the unfocused value. In the experiment, acoustic focusing reduced the electrical resistance to 60% of the resistance in the unfocused mixture, demonstrating acoustic focusing as a method for reducing electrical conductivity within a composite.
Modal Analysis and Experimental Testing of Air-Inflated Drop-Stitch Fabric Structures Used in Marine Applications
Authors: Hulton Andrew W. , Cavallaro Paul V. , Hart Christopher J. 
Published: January 2018

Rapid deployment of marine structures is of growing importance to U.S. naval forces. Surface-based inflatable structures including Rigid Inflatable Boats (RIBs), inflatable causeways and bridging, and launch and recovery systems provide unique solutions for temporary structures during sea-based missions. When performance specifications demand minimal weight and stowage, rapid deployability and temporary rigidity, solutions are limited to inflatable structures constructed of flexible materials. Driven by air pressure, today’s inflatables provide significant load-carrying capacities per unit weight (or stowed volume) utilizing technical textiles, elastomers or “soft” composites. Overloading of inflatable structures produces unique fail-safe behaviors (reversible wrinkling) that allow the structures to assume rigidity and load-carrying capacity upon load removal.
Design standards are virtually nonexistent for inflatable structures involving shapes constructed of spheres, beams, arches and most recently flat panels using 3D woven drop-stitch panels. Predictive performance tools (analytical and numerical) for static applications lag significantly behind those for conventional structures. Nonlinear system behaviors (material and geometric), thermo-mechanical coupling and fluid-structure interactions (FSI’s) pose significant challenges when applying existing design tools to inflatable structures. This gap is further exacerbated for dynamic applications as inflatable structures exhibit pressure-dependent natural frequencies and mode shapes. Surface-based structures must be designed with consideration given to operational sea state frequencies and wave periods so that the onset of structural instabilities (wrinkling, buckling) and loss of load-carrying capacities can be prevented.
The present research establishes the validity of physics based models using the Ideal Gas Law as an equation of state (EOS) to predict the natural frequencies and corresponding mode shapes of air-inflated drop-stitch fabric panels as functions of inflation pressure. Particular concern is given to the breathing modes for inflation pressures ranging from 5.0 to 30.0 psig. The presence of breathing modes can negatively impact the riding performance of RIBs vessels constructed with drop-stitch fabric hulls by amplification of the panel’s skin separation displacements and vertical accelerations, and are not seen in this material system for the pressures considered. Both numerical and experimental methods are pursued; the results of laboratory modal experiments are used to validate the numerical models. Predicted and experimental natural frequencies and mode shapes are compared and excellent correlation was observed. Increasing inflation pressures produced increasing in-plane and through-thickness normal stresses and modal frequencies of the drop-stitch fabric panels.
Microfluidic Systems for Studying Chemical Reactions, Mixing, and Heat Transfer
Authors: Chiou Richard Y. , Mauk Michael G. , Varapula Dharma T. , Wang Senyu , Ruiz Carlos , Tseng Tzu-Liang (Bill) 
Published: January 2018

Microsystems comprising microfluidic networks and miniaturized actuators, transducers, and sensors provide a convenient, revealing, and low-cost means for studying chemical reactions, separation processes such as filtration and extraction, phase changes, mixing, heat and mass transfer, and fluid flow phenomena. For instance, palm-sized plastic cartridges or cassettes (‘chips’) with channels, chambers, manifolds and other components for flow control and fluid actuation can be instrumented with embedded thermocouples and pressure sensors, and operated with small Peltier coolers/heaters and programmable syringe pumps or microrotary pumps. With proper design, the on-chip microfluidic processes can also be imaged with CCD cameras (especially using fluorescent dyes and particles), and infrared thermal cameras for temperature profiling. Such image (including video) capture and processing affords much more data compared to point sensors such as thermocouples and pressure transducers, and can be directly compared with finite element modeling. These systems are effective vehicles for project-based learning in fluid mechanics, heat transfer, chemical reaction engineering, separation processes and other unit operations, process control, and various biotechnical operations such as enzymatic digestion, nucleic acid amplification, and sample fractionation. The chips are made as bonded laminates from patterned acrylic, polycarbonate, thin metal sheet, and many other material types.
Students can quickly design (using CAD software such as SolidWorks™), simulate (using FEM programs such as Comsol) microfluidic platforms, that can be rapid prototyped with laser machining, 3D printing, CNC machining, soft lithography, engraving and printed circuit board fabrication methods with a turn-around time of 1 day. The chip is instrumented using LabView™ or an Arduino™ microcontroller for data acquisition and process control. These benchtop or desktop systems make only modest demands on the resources of educational institutions, due to their low cost and safety, and minimal waste generation and reagent consumption. Also, their multidisciplinary nature affords an excellent opportunity for students to integrate their knowledge of CAD, simulation, prototyping, instrumentation and microcontrollers, statistical data analysis, and image processing and analysis. Further, these experiments give students a high level of hands on interaction and visualization of important unit operation processes. We discuss in detail some representative systems for heat exchangers, mixers, chemical reactors, and crystal growth, and their use as educational, project-based modules in the undergraduate engineering curriculum.
Design of Portable Patient Lift System for Assistant Living Homes
Authors: Dong Janet , Cheek Karina , Duncan John , Kalnasy Alex 
Published: January 2018

The portable patient lift system is a Senior Capstone Design project that is defined through the collaboration between the University of Cincinnati and a retirement/assisted living community in Cincinnati. The objective of the project is to design, build, and test a lift system that is capable of safely lifting fallen elderly patients at assistant living homes out of tight spaces. Two student teams in 2015–2016 and 2016–2017 academic years had taken on this project. They applied the product development process which they learned from their senior year to develop a workable system. Their work started with survey, interviews, research, followed by developing alternative concept designs. The pros and cons of each concept were discussed, analyzed, and evaluated among peers, advisors, and Maple Knoll nurses. The final design of using inflatable method to lift patients was justified as the best option. Two final concept designs from each year were then manufactured or assembled in school. The testing of the final systems were conducted and demonstrated at Maple Knoll senior community. The expectations from nursing staff and senior residents were greatly satisfied.
This paper will describe our senior capstone design and product development process of such portable patient lift system, and discuss our experiential learning experience at Maple Knoll and lessons learned from design and making such system with focus on the consideration of seniors and their capabilities at settings of nursing homes.
On the Use of Gas Flow Models to Predict Leak Rates Through Sheet Gasket Materials
Authors: Bouzid Abdel-Hakim , Aweimer Ali Salah Omar 
Published: January 2018

The prediction of leak rate through porous gaskets for different gases based on test conducted on a reference gas can prevent bolted joint leakage failure and save the industry a lot of money. This work gives a basic comparison between different gas flow models that can be used to predict leak rates through porous gasket materials. The ability of a model to predict the leak rate at the micro and nano levels in tight gaskets relies on its capacity to incorporate different flow regimes that can be present under the different working conditions. Four models based on Navier-Stokes equations and incorporate the boundary conditions of the appropriate flow regime considered. The first and second order slip, diffusivity and molecular flow models are used to predict and correlate leak rates of gases namely helium, nitrogen, SF6, methane, argon and air passing through three frequently used nanoporous gasket materials which are flexible graphite, PTFE and compressed fiber.
The methodology is based on the determination experimentally of the porosity parameter (N and R) of the micro channels assumed to simulate the leak paths present in the gasket using helium as the reference gas. The predicted leak rates of different gases at the different stresses and pressure levels are confronted to the results obtained experimentally by measurements of leak rates using pressure rise and mass spectrometry techniques. The results show that the predictions depend on the type of flow regime that predominates. Nevertheless the second order slip model is the one that gives better agreements with the measured leaks in all cases.
Whole-Genome Sequencing of Emerging Invasive Neisseria meningitidis Serogroup W in Sweden
Authors: Eriksson Lorraine , Hedberg Sara Thulin , Jacobsson Susanne , Fredlund Hans , Mölling Paula , Stenmark Bianca 
Published: January 2018

ABSTRACT

Invasive disease caused by
Neisseria meningitidis
serogroup W (MenW) has historically had a low incidence in Sweden, with an average incidence of 0.03 case/100,000 population from 1995 to 2014. In recent years, a significant increase in the incidence of MenW has been noted in Sweden, to an average incidence of 0.15 case/100,000 population in 2015 to 2016. In 2017 (1 January to 30 June), 33% of invasive meningococcal disease cases (7/21 cases) were caused by MenW. In the present study, all invasive MenW isolates from Sweden collected in 1995 to June 2017 (
n
= 86) were subjected to whole-genome sequencing to determine the population structure and to compare isolates from Sweden with historical and international cases. The increase of MenW in Sweden was determined to be due to isolates belonging to the South American sublineage of MenW clonal complex 11, namely, the novel U.K. 2013 lineage. This lineage was introduced in Sweden in 2013 and has since been the dominant lineage of MenW.
Smoking duration alone provides stronger risk estimates of chronic obstructive pulmonary disease than pack-years
Authors: Bhatt Surya P , Kim Young-il , Harrington Kathy F , Hokanson John E , Lutz Sharon M , Cho Michael H , DeMeo Dawn L , Wells James M , Make Barry J , Rennard Stephen I , Washko George R , Foreman Marilyn G , Tashkin Donald P , Wise Robert A , Dransfield Mark T , Bailey William C 
Published: January 2018

BackgroundCigarette smoking is the strongest risk factor for COPD. Smoking burden is frequently measured in pack-years, but the relative contribution of cigarettes smoked per day versus duration towards the development of structural lung disease, airflow obstruction and functional outcomes is not known.MethodsWe analysed cross-sectional data from a large multicentre cohort (COPDGene) of current and former smokers. Primary outcome was airflow obstruction (FEV1/FVC); secondary outcomes included five additional measures of disease: FEV1, CT emphysema, CT gas trapping, functional capacity (6 min walk distance, 6MWD) and respiratory morbidity (St George’s Respiratory Questionnaire, SGRQ). Generalised linear models were estimated to compare the relative contribution of each smoking variable with the outcomes, after adjustment for age, race, sex, body mass index, CT scanner, centre, age of smoking onset and current smoking status. We also estimated adjusted means of each outcome by categories of pack-years and combined groups of categorised smoking duration and cigarettes/day, and estimated linear trends of adjusted means for each outcome by categorised cigarettes/day, smoking duration and pack-years.Results10 187 subjects were included. For FEV1/FVC, standardised beta coefficient for smoking duration was greater than for cigarettes/day and pack-years (P<0.001). After categorisation, there was a linear increase in adjusted means FEV1/FVC with increase in pack-years (regression coefficient β=−0.023±SE0.003; P=0.003) and duration over all ranges of smoking cigarettes/day (β=−0.041±0.004; P<0.001) but a relatively flat slope for cigarettes/day across all ranges of smoking duration (β=−0.009±0.0.009; P=0.34). Strength of association of duration was similarly greater than pack-years for emphysema, gas trapping, FEV1, 6MWD and SGRQ.ConclusionSmoking duration alone provides stronger risk estimates of COPD than the composite index of pack-years.Trial registration numberPost-results; NCT00608764.