bluuebunny/crossref_metadata_2025 huggingface dataset:
MusaATAF2 like protein, a stress‐related transcription factor, induces leaf senescence by regulating chlorophyll catabolism and H2O2 accumulation
Authors: Bhakta Subham , Negi Sanjana , Tak Himanshu , Singh Sudhir , Ganapathi Thumbali R.
Published: November 2021

NAC transcription factors are known for their diverse role in plants. In this study, we have demonstrated the role of MusaATAF2, a banana NAC transcription factor, in leaf senescence. Its expression gets strongly up‐regulated during the early stress responses of drought and high salinity exposure and down‐regulated under ABA application, which suggests MusaATAF2 is a stress‐related NAC transcription factor. To study the role of MusaATAF2 in banana, we have transformed the banana embryogenic cells with MusaATAF2 coding region and generated transgenic banana plants. Overexpression of MusaATAF2 in banana plants caused yellow leaf phenotype under control condition, suggesting its role as a senescence‐associated transcription factor. Transgenic banana leaves exhibited low chlorophyll content and high H2O2 accumulation. Hormone analysis of the leaves demonstrated a higher accumulation of ABA in the transgenic plants than the controls. Transgenic plants overexpressing MusaATAF2 have a higher transcript abundance of two chlorophyll catabolic pathway genes (PAO and HCAR) and lower transcript abundance of ROS scavenging enzymes (TDP, THIO, CAT, APX, and PRXDN) than control. Together, all these analyses indicate that MusaATAF2 induces senescence by inducing chlorophyll degradation and H2O2 accumulation in banana plants and controls its own expression using an ABA‐dependent feedback loop.
Uncle Tom’s Garden: Color, Culture, and Racialization in Garden Plants
Authors: Smith Gabriella V.
Published: November 2021

The structure of our racial hierarchy depends on the power of color, particularly skin color, to signify racial difference and justify stratification. Color is an important element of culture, capable of communicating multivocal meanings. Dark colors have sets of cultural meanings like evil, magic, and night, but they are also associated with skin color and race. This article seeks to understand how material objects act as vehicles for ideas about color and race, particularly Blackness, in the absence of bodies or images of people, by examining the phenomenon of named varieties of dark‐colored plants. My data included interviews with daylily breeders and an online database of over 90,000 named daylily varieties. Systematic analysis showed that dark plants were frequently, though not exclusively, given names referencing Blackness. White or light‐colored flowers did not receive racialized names. Findings demonstrate that color carries racial connotations even in areas of activity and cultural production that appear to have little or no connection with race, human bodies, or human identities. I suggest that color plays an important and underexamined role in the process of racialization and the perpetuation of White supremacy.
Prevalence and outcomes of Clostridioides difficile infection in liver transplant recipients
Authors: Kortt Nicholas C. , Santhakumar Cositha , Davis Rebecca J. , Strasser Simone I. , McCaughan Geoffrey W. , Liu Ken , Majumdar Avik
Published: November 2021

Background and aim

Data are limited on whether Clostridioides difficile infection (CDI) in the first year after liver transplantation (LT) is associated with increased mortality. In an Australian setting without hypervirulent strain of C. difficile we investigated the prevalence, risk factors, and patient survival associated with CDI in LT.

Methods

Consecutive patients who underwent deceased‐donor LT from 2007 to 2017 were studied retrospectively. Prevalence and long‐term outcomes of LT recipients with and without CDI were examined in the entire LT cohort. A case–control study was performed to investigate risk factors associated with CDI.

Results

Six hundred and forty‐nine patients underwent LT, of which 32 (4.9%) were diagnosed with CDI within the first 12 months post‐LT. There was no difference in patient survival in the overall LT cohort on Kaplan–Meier analysis when stratified by CDI status (log‐rank test, p = .08). Furthermore, age was the only predictor of mortality on Cox regression (hazard ratio (HR) 1.06, 95% confidence interval (CI) 1.00–1.13, p = .03). On multivariable logistic regression, rifaximin pre‐LT reduced risk (odds ratio (OR) 0.22, 95% CI 0.65–0.74, p = .01) whereas antibiotics pre‐LT (OR 7.02, 95% CI 1.26–39.01, p = .03) and length of hospital stay after LT (OR 1.03, 95% CI 1.01–1.06, p = .02) were associated with increased risk of CDI.

Conclusions

Within the local setting of our study, CDI within 12 months post‐LT is of low severity, associated with pre‐LT antibiotic exposure and longer hospital stay but no survival impact after LT. Rifaximin use pre‐LT reduced the risk of CDI post‐LT.
Powassan virus: What is the risk to the blood supply?
Authors: Bloch Evan M. , Tobian Aaron A. R. , Katz Louis M.
Published: November 2021

Powassan virus (POWV) is an emerging tick‐borne arbovirus that is found widely in Canada, the Northeastern and Northcentral United States, and the Russian Far East. While still rare, there has been an increase in reported cases of POWV disease over the last decade; most (>90%) cases have been neuroinvasive and the associated fatality rate is high (>10%). Transfusion‐associated risk of POWV remains uncertain; while no intervention is likely indicated, one probable case of transfusion‐transmitted POWV in the context of an increase in the incidence of POWV and other tick‐borne infections, merits vigilance.
Evidence for impaired chronotropic responses to and recovery from 6‐minute walk test in women with post‐acute COVID‐19 syndrome
Authors: Baranauskas Marissa N. , Carter Stephen J.
Published: November 2021

New Findings

What is the central question of this study?

Are chronotropic responses to a 6‐minute walk test different in women with post‐acute coronavirus disease 2019 (COVID‐19) syndrome compared with control subjects?

What is the main finding and its importance?

Compared with control subjects, the increase in heart rate was attenuated and recovery delayed after a 6‐minute walk test in participants after infection with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). Women reporting specific symptoms at time of testing had greater impairments compared with control subjects and SARS‐CoV‐2 participants not actively experiencing these symptoms. Such alterations have potential to constrain not only exercise tolerance but also participation in free‐living physical activity in women during post‐acute recovery from COVID‐19.

The short‐term cardiopulmonary manifestations of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) are well defined. However, the implications of cardiopulmonary sequelae, persisting beyond acute illness, on physical function are largely unknown. Herein, we characterized heart rate responses to and recovery from a 6‐minute walk test (6MWT) in women ∼3 months after mild‐to‐moderate SARS‐CoV‐2 infection compared with non‐infected control subjects. Forty‐five women (n = 29 SARS‐CoV‐2; n = 16 controls; age = 56 ± 11 years; body mass index = 25.8 ± 6.0 kg/m2) completed pulmonary function testing and a 6MWT. The SARS‐CoV‐2 participants demonstrated reduced total lung capacity (84 ± 8 vs. 93 ± 13%; P = 0.006), vital capacity (87 ± 10 vs. 93 ± 10%; P = 0.040), functional residual capacity (75 ± 16 vs. 88 ± 16%; P = 0.006) and residual volume (76 ± 18 vs. 93 ± 22%; P = 0.001) compared with control subjects. No between‐group differences were observed in 6MWT distance (P = 0.194); however, the increase in heart rate with exertion was attenuated among SARS‐CoV‐2 participants compared with control subjects (+52 ± 20 vs. +65 ± 18 beats/min; P = 0.029). The decrease in heart rate was also delayed for minutes 1–5 of recovery among SARS‐CoV‐2 participants (all P < 0.05). Women reporting specific symptoms at the time of testing had greater impairments compared with control subjects and SARS‐CoV‐2 participants not actively experiencing these symptoms. Our findings provide evidence for marked differences in chronotropic responses to and recovery from a 6MWT in women several months after acute SARS‐CoV‐2 infection.
Free Vibration of Sandwich Flat Panels With Laminated Anisotropic Face Sheets
Authors: Hause Terry , Librescu Liviu
Published: November 2021

A study of the effect of anisotropy of face-sheets and of other physical/geometrical parameters on eigenfrequency characteristics of flat sandwich panels is presented. The study is carried out in the context of an advanced model of sandwich structures. A detailed analysis of the influence of a large number of parameters associated with the panel geometry, fiber orientation and stacking sequence in the face sheets, and material properties of the core is accomplished, and pertinent conclusions are outlined. Validations of frequency predictions obtained within the present structural model against the few ones available in the specialized literature are accomplished, and excellent agreements are reported.
Analysis of a New Paper Feeder Design
Authors: Shaw Dein , Chi Wei-Hsiang
Published: November 2021

A new paper feeder design of an apparatus that need a sheet of paper is proposed in this study. The weak point of a patented paper feeder was point out in this study. To improve that weak point, a new design including two arms, four gears and a slider was developed. The paper feeding mechanism of this study depends on the buckling of the paper sheet. Therefore, the buckling of a paper sheet is a very important parameter of designing the paper feeder. To make the design correct, a theoretical buckling model of the paper was developed. The analysis results were compared with the experiment results. Finally, the new design of best performance was presented.
Damage Evolution and Failure Modeling in Unidirectional Graphite/Epoxy Composite
Authors: Tandon G. P. , Kim R. Y.
Published: November 2021

A study is conducted to examine and predict the micromechanical failure modes in a unidirectional composite when subjected to tensile loading parallel to the fibers. Experimental observations are made at some selected stress levels to identify the initiation and growth of micro damage during loading. The axisymmetric damage model of a concentric cylinder is then utilized to postulate and analyze some failure scenarios.
Impact-Induced Damage Progression in 2-D and 3-D Woven Composite Systems
Authors: Baucom Jared N. , Zikry Mohammed A.
Published: November 2021

The role of fabric architecture on the impact-induced damage progression and perforation resistance of glass-fiber reinforced vinyl-ester resin panels under dynamic loading condition is investigated. Three fabric preforms are considered: a 2-dimensional, plain-woven laminate, a commercially available biaxially reinforced warp-knit, and a 3-dimensional, orthogonally woven preform. Composite samples are subjected to multiple impacts, until perforation, and the impactor position and acceleration are monitored throughout each event, resulting in a visualization of dynamic energy dissipation. Failure modes of the various material systems are characterized. The radial damage expansion was smallest for the 2-d laminate, larger for the biaxially-reinforced warp-knit, and largest for the 3-d orthogonal woven composite. The 3-d composite survived more hits and dissipated more total energy than the other systems. The difference may be due to the additional energy absorption mechanisms, which involve the crimped portion of z-tows in the 3-d composites. This implies that failure may be controlled by manipulation of the properties of the z-tows. It also indicates that the surface condition of 3-d orthogonally woven composites can strongly affect the progression of impact-induced damage.
On Delamination Branching of Anisotropic Bimaterials
Authors: Li R. , Kardomateas G. A.
Published: November 2021

The phenomena of delamination branching/kinking from the interface of general anisotropic bimaterials are investigated based on the elegant Stroh’s sextic formulism of dislocation theory in matrix notation. A set of compact form of Green’s functions for two kinds of dislocation — an interface dislocation and a dislocation in one medium of the bimaterial elastic solid is obtained. Using these Green’s functions, the whole delamination including the interface part and the part branching into either one of the dissimilar anisotropic materials is modeled as a continuous distribution of the two kinds of dislocations. An interesting observation from this method is that the traction along the dislocation line when the dislocation is inside one medium, mathematically has similar form as the traction on the interface surface due to an interface dislocation. Thus a non-homogeneous Hilbert problem with discontinuous coefficients for this anisotropic bimaterials is formulated and a general solution to this problem is obtained. Consequentially, a preferable value of the branching angle for a given pair of anisotropic bimaterial media can be obtained by maximizing the energy release rate of the kinking-cracked solid. The comparison of other approaches which have appeared in the literature are discussed.
On Predicting the Dynamic Failure in Composite Materials Under Compressive and Tensile Loads
Authors: Vinson Jack R. , Xiao Shengkuan
Published: November 2021

Simple polynomial equations are presented for the ultimate strength and the modulus of elasticity as a function of strain rate for various unidirectional and quasi-isotropic composite materials used by government and industrial organizations. Included are several glass, graphite and aramid fiber composites. These are in various thermoset and thermoplastic polymeric matrices. Also included are stitched composites as well as one silicon carbide aluminum metal matrix composite. In addition, tensile properties are modeled for two woven composite materials. Through these equations, dynamic material properties may be used easily in the design and analysis of structures employing these materials rather than using the usual static properties. In all, the dynamic properties of fourteen different composite materials are characterized.
Experimental Characterization and Numerical Simulation of Impact Damage in Composite Laminates
Authors: Minnaar K. , Zhou M.
Published: November 2021

A new experimental technique is developed to determine the onset and evolution of delamination in fiber-reinforced composites. The configuration uses a split-Hopkinson bar for low-velocity impact loading and two Polytec laser vibrometer systems for real-time monitoring of the initiation and progression of delamination. The experiment allows the histories of load, displacement, and velocity of impacted specimens to be recorded and analyzed. Numerical simulations are conducted using a cohesive finite element method. The method employs a cohesive zone model to simulate in-ply cracking and interlaminar delamination and a transversely isotropic, elastic model to characterize the bulk behavior of each ply. The simulations provide time-resolved characterization of damage during the impact loading. The time at which delamination is detected decreases as the impact velocity is increased, and delamination is detected at similar surface displacements. The progression of damage changes as the bonding strength between plies is increased. The speed of delamination decreases as the bonding strength is increased.
Ballistic Impact Response of Foam-Filled Sandwich Composites
Authors: Vaidya Uday K. , Mathew Biju , Ulven Chad A. , Sinn Brent , Velazquez Marian
Published: November 2021

Sandwich composites find increasing use as flexural load bearing lightweight sub-elements rail / ground transportation and marine bodies. In recent year, alternatives to traditional foam and honeycomb cores are being sought. One such development includes filling the cells of the honeycomb core with foam. The increased surface area allows stress forces to dissipate over a larger area than that offered by the honeycomb alone. This allows for use of lowering the cost of the honeycomb cells, and thereby making the design extremely cost-effective. In the present research, phenolic impregnated honeycomb / corrugated cells with polyurethane foam filling has been considered. The intermediate and high velocity impact response of these types of sandwich constructions has been studied. The applications for such cores would be in rail and ground transportation, where impacts in the form of flying debris are common.
Modeling of Joints and Effect on Crash Simulation
Authors: Tyan Tau , Guimberteau Thierry , Faruque Omar
Published: November 2021

This paper reports the findings of a study that was conducted to evaluate the effect of joints and their proper modeling technique in the crash analysis. Joints such as universal joints, lower control arm connections, etc. are generally not characterized in details in the current CAE models used for crash simulation. In the past, assumption was that crash is a short duration event and therefore accurate modeling of the joint kinematics is relatively less important for crash simulation. However, review of many recent crash tests have shown that some of the critical joints in the vehicle may undergo severe joint motion during crash affecting the crash modes and the responses in a significant way. Especially, in some offset crash tests, tire was found to rotate inward and caused significant toe-board intrusion. Improper modeling of the mechanical joints sometimes can lead to inaccurate prediction and jeopardize the design verification process.

To study the effect of joints on crash responses, detailed models for the major joint types in the vehicle were developed. Four types of joints — spherical, revolute, cylindrical and universal joints, have been identified and investigated since they are used extensively in the design of vehicle’s chassis. In particular, attention was focused on accurately simulating the kinematics of the joints under various loading and impact conditions. Component modeling of the four joints was investigated first to ensure the proper motion of the different joints individually. A number of analyses were conducted with the models for different impact conditions. The joint models, thus verified, were incorporated into sub-system models to verify the responses of multiple components and joints. Finally full vehicle simulations, with and without these joints, were performed and compared with physical test to prove out the joint modeling methodologies. Both car and truck chassis were included in the full system study to examine the robustness of the models. The results showed that the inclusion of the joints in the CAE models can affect the simulated responses significantly.
Teaching MEMS to Mechanical Engineering Students: A Paradigm Shift From Macro to Micro World
Authors: Kao Imin
Published: November 2021

This paper presents pedagogical issues and experience in teaching the introduction to MEMS (Micro Electro-Mechanical System) course to a group of engineering students, primarily Mechanical Engineering students. The paper draws upon the author’s experience in teaching the MEMS course. Since MEMS is highly inter-disciplinary, the presentation of various relevant topics in MEMS, which may or may not be familiar to a mechanical engineering student, is of critical importance. These topics vary from physics, electrochemistry, materials, and electronic engineering, to various areas in mechanical engineering. An integrated approach for the presentation of subjects, especially in design and fabrication, was found to be very helpful. Moreover, the paradigm shift from the macro world, that most students are familiar and comfortable with, to the micro world is significant and needs to be emphasized. The author found the concept of scaling law, when shifting to the micro world, to be essential in the presentation of MEMS to engineering students in order for them to comprehend the size factor in MEMS. In addition, understanding and appreciation of the strengths and limitations of MEMS are also critical in learning MEMS. Finally, a good textbook will facilitate the learning process of such vast subject. A bibliography of useful textbooks and reference books used by the author will be listed at the end of this paper.
MEMS Design Education by Case Studies
Authors: Pryputniewicz Ryszard J.
Published: November 2021

Advances in microelectromechanical systems (MEMS) technology are based on understanding of the issues involved in design, analysis, fabrication, characterization, and use of the finished products. Although this understanding is being developed “on the job” to satisfy immediate needs of rapid advances in the emerging MEMS technology, there is also growing demand for “academic” education in MEMS. Whether on-the-job or academic, development of the required understanding is no easy task because the MEMS field is very multidisciplinary. Those involved should be able to work simultaneously with topics relating to physics, chemistry, materials, computer science, engineering, as well as other relevant disciplines. To facilitate preparation of future engineers for work with MEMS, we have developed undergraduate and graduate courses addressing some of the crucial issues relating to MEMS. These courses are based on case studies that we have developed in our laboratories. The courses include lectures, laboratory experiments, student projects, and presentations. This paper describes selected case studies used in our courses as they relate to design education with MEMS.
Wilbur and Orville Wright and the Evolution of Efficient Aircraft Propellers
Authors: Ash Robert L. , Miley Stanley J. , Landman Drew , Hyde Kenneth W.
Published: November 2021

Four Wright brothers’ propellers have been carefully reproduced by The Wright Experience for the purpose of measuring their performance using modern instrumentation. Reproductions of a 1903 Flyer propeller, a 1904 ‘Le Mans’ propeller, and two circa 1910 ‘bent end’ propellers have been manufactured, duplicating materials, construction and dimensional geometry. As evidenced by the correlation between static thrust measurements reported originally by the Wright brothers and our recent measurements in Old Dominion University’s Langley Full Scale Tunnel, the propeller reproductions match the static thrust performance of the original propellers to within experimental accuracy. Using modern instrumentation, it has been possible to measure the overall performance of these propeller reproductions covering their full speed ranges. Our tests have shown that the 1903 Wright propeller had a peak efficiency greater than 80 percent (Wilbur appears to have estimated its efficiency to be 66 percent) and the 1904 and 1910 propellers had peak efficiency levels approaching 90 percent. Not only did the Wright brothers’ propellers exhibit systematic increases in static thrust, but their propeller designs were extraordinary because they produced efficiencies approaching the levels found on modern-day human-powered flying machines. Our measurements have shown that the Wright brothers’ use of large-diameter, slowly rotating propellers enabled them to achieve propulsive efficiencies that were unsurpassed for nearly 20 years.
A Study of Early Stage Self-Loosening of Bolted Joints
Authors: Jiang Yanyao , Huang Bin , Zhao Hua , Lee Chu-Hwa
Published: November 2021

Both experimental investigation and finite element analysis were conducted to explore the mechanisms of the early stage self-loosening of bolted joints under transverse cyclic loading. The nuts were glued to the bolts using a strong thread locker in the self-loosening experiments to ensure that no backing-off of the nut occurred. Depending on the loading magnitude, the clamping force reduction ranged from 10% to more than 40% of the initial preload after 200 loading cycles. Three-dimensional elastic-plastic finite element analysis was conducted with the implementation of an advanced cyclic plasticity model. The finite element results revealed that the local cyclic plasticity occurring near the roots of the engaged threads resulted in cyclic strain ratchetting. The localized cyclic plastic deformation caused the stresses to redistribute in the bolt, and the result was the gradual loss of clamping force with loading cycles. The finite element results agreed with the experimental observations quantitatively. Both experiments and finite element simulations suggested that the friction between the clamped plates has an insignificant influence on self-loosening.
Noninvasive Measurements and Computational Modeling of SMT Assemblies
Authors: Pryputniewicz Ryszard J. , Rosato David , Furlong Cosme
Published: November 2021

Differential thermal expansions cause strains in the interconnection structures, during functional operation of active devices. To evaluate these strains, temperature profiles of the interconnected components must be known. In this paper, a methodology for developing thermal models of surface mount technology (SMT) assemblies is presented using thermal analysis system (TAS) and its application is demonstrated by simulating thermal fields of a representative package. Thermomechanical deformations of the package are measured quantitatively using state-of-the-art laser-based optoelectronic holography (OEH) methodology. Results of TAS simulation show good correlation with noninvasive full-field-of-view OEH measurements of thermomechanical field effects of the SMT assembly under actual operating conditions.
DSC, TMA, DMA, and TGA of Epoxies for Fiber-Optic Transceiver Applications
Authors: Lau John , Erasmus Steve , Sporon-Fiedler Fred , Chang Chris
Published: November 2021

The curing conditions (such as temperature and time) and material properties such as the TCE (thermal coefficient of expansion), Tg (glass transition temperature), storage modulus, tangent delta (tan δ), and moisture absorption of two different epoxy materials from two different vendors are measured. Emphasis is placed on specimen preparations, experimental procedures, and data analyses. The methods and results presented herein should be useful for evaluating epoxies for fiber-optic transceiver applications.
Periodic Homogeneization Techniques As a Way to Account for Surface Roughness in a Confined Air Flow
Authors: Bourgin Patrick , Boutaous M’hamed , Woehl Pierre
Published: November 2021

The motivation of the study is concerned with high speed winding of plastic films (i.e. PET). During this process, some air is entrapped between the first wrap and the roll being wound. It is well known that the residual air layer between the plastic layers has a strong influence on the internal stress state within the roll. The surface roughness of the film plays an important role on these aerodynamic effects and consequently on the internal stress. Nevertheless, the mechanisms involved are not clarified yet.

As a first step, an experimental study was conducted with the aim of characterizing the global flow kinetics of an air layer squeezed between a plastic film sample and a smooth substrate. In so doing, a new parameter was defined: some sort of a “dynamic roughness coefficient”. Nevertheless, the correlation between this parameter and those which describe the topography of a film surface (static) needed to be established.

Using the tools of 3D roughness measurements, it was observed that the heights of the peaks and the mean distances between them are of the same order of magnitude as the average distance between the opposite surfaces. We therefore assimilated the surface topography to a periodic array of cylinders of known dimensions, their spatial period and their height being of the same order as the interlayer distance. In such conditions, the air flow squeezed in the space confined between the two surfaces is studied by using an approach based on periodic homogeneization techniques.

The first tendencies indicate that a good qualitative agreement exists between the global experimental data and the theoretical results.
Recirculating Turbulent Flows of Thixotropic Fluids
Authors: Pereira Américo S. , Pinho Fernando T.
Published: November 2021

An aqueous suspension of 1% by weight laponite was investigated in terms of its rheology and hydrodynamic behaviour in a sudden expansion flow. The fluid was shear-thinning, thixotropic and had an yield stress which was measured by direct and indirect methods. The oscillatory tests showed that the elasticity of the 1% Laponite suspension was very small.

The high Reynolds number turbulent flow downstream of a sudden expansion, with fully-developed inlet conditions, showed no major difference in relation to the flow of water. There were no differences between the laponite and water mean and turbulent flow characteristics upstream and downstream of the expansion plane, except for a small anticipation of the loci of maximum Reynolds stresses with the suspension, but this had no further consequence.

In conclusion, although the laponite suspension was thixotropic, shear-thinning and viscoplastic, its hydrodynamic behaviour in a sudden expansion was akin to that of water, a result which could not be anticipated.
Instabilities of Numerically Computed Thermocapillary Flows in Liquid Bridges at Medium Prandtl Numbers
Authors: Hirsch Charles , Dinescu Cristian
Published: November 2021

The instabilities of the thermocapillary flows in cylindrical liquid bridges are investigated numerically by employing a finite volume approach to solve the complete Navier-Stokes equations accompanied by appropriate boundary conditions on the free surface, which model the surface tension effects.

The influences of Marangoni number, aspect ratio A and gravity on the computed spatio-temporal structures of the thermocapillary flow are emphasized.

The structures associated with high Marangoni number regimes are analyzed by using specific tools of the nonlinear dynamics: temperature signal, power spectrum, first return maps and Poincare maps.
The Application of PIV in the Study of Impeller-Diffuser Interaction in Centrifugal Fan: Part I — Impeller-Vaneless Diffuser Interaction
Authors: Mekhail Tarek , Li Zhang , Zhaohui Du , Jansen Willem , Hanping Chen
Published: November 2021

The PIV (Particle Image Velocimetry) technology is a brand-new technique of measuring velocity. It started in the 1980’s with the development of high-speed photography and the image processing technique of computers. This article deals with PIV applied to the study of unsteady impeller-vaneless diffuser interaction in centrifugal fen. Experiments were carried out at The Turbomachinery Laboratory of Shanghai Jiaotong University. The test rig consists of a centrifugal, shrouded impeller, diffuser and volute casing all made of plexiglass. A series of performance measurements were carried out at different speeds and different vaneless diffuser widths. PIV measurements were applied to measure the unsteady flow at the exit part of the impeller and the inlet part of the diffuser for the case of the same width vaneless diffuser. The absolute flow field is measured at medium flow rate and at maximum flow rate. It is informative to capture the whole flow field at the same instant of time, and it might be more revealing to observe the unstable flow in real time.
The Application of PIV in the Study of Impeller-Diffuser Interaction in Centrifugal Fan: Part II — Impeller-Vaned Diffuser Interaction
Authors: Mekhail Tarek , Li Zhang , Zhaohui Du , Jansen Willem , Hanping Chen
Published: November 2021

The real flow inside a turbomachinery passage is unsteady and strongly affected by wakes between stator and rotor. The aim of this study was to help our understanding of the complex unsteady flow associated with the interaction between the impeller and its vaned diffuser of a centrifugal plexiglass fan where the number of impeller and diffuser blades are 13 for each. The purpose of this paper is to present the first trial of measuring the instantaneous whole field in a part of the impeller and diffuser together at different relative locations between them. The velocity measurements utilizing a PIV system from Dantec Measurement Technology were performed. The measurements were performed at medium, maximum and minimum flow rate, near the hub, the middle and near the shroud. The Laser sheet is adjusted to go through the outer casing, the diffuser and to reach the impeller blades. The instantaneous whole field velocity measurements were taken at the exit half of the impeller and the inlet half of the diffuser including the vaneless space before the diffuser blades. The absolute radial and circumferential velocities are measured. The unsteady interaction between the impeller and vaned diffuser was measured at different relative positions between the impeller and diffuser. Further analyses concerning the relative velocity, streamlines and vorticity are also presented.
On Dynamic Pressure Measurement of Hydraulic Return Line
Authors: Koivula Timo S. , Ellman Asko U. , Vilenius Matti J.
Published: November 2021

Rapidly fluctuating flow conditions exist in various fluid power applications. Particularly, in return lines of fast on-off valves, circumstances are very demanding as rapidly changing flow rate causes large pressure variations and cavitation downstream from the valve. Pressure measurement of such flow conditions is diverse. In order to exploit the measured data, the measurement equipment and methods have to be reliable.

In this paper, several aspects affecting on dynamic pressure measurement in hydraulic return lines are dealt with. Suitability of several transducer types for such dynamic measurements is studied. The effects of various mounting methods and transducer orientations are studied as well.

Considerable differences in pressure responses were found with various transducer types. In addition, mounting method and restrictors in mounting fittings were found to be significant. Cavitation was found to be present in the return line and it affected measured responses. In the paper, pressure responses acquired with various pressure transducers and mounting scenarios are presented. The effects of mounting scenarios and orientation of transducers are discussed and measured responses are presented.
Simulation of Fluid Power Components Using DSHplus and ADAMS
Authors: Deeken Michael , Murrenhoff Hubertus
Published: November 2021

Efficiency improvement of an axial piston pump or motor is an important part in the design and development process. The behaviour of an axial piston pump or other displacement machines is a complex interaction between tribology of sliding contacts, pressure gradient in hydraulic volumes and dynamics and kinematics. Simulation programs are useful development tools to design these fluid power components on digital computers. At present all these programs are stand-alone tools and specialised to calculate a specific behaviour or effect of an axial piston pump or motor. To reproduce and to solve all this physical effects numerically in one program is impractical. Since the opportunity exists to couple standardised products, this is a promising approach.

The paper presents a simulation approach of a displacement machine (axial piston pump in swash plate design) using two different kinds of simulation programs. The tribology, e.g. surface roughness, mixed lubrication and contact pressure, and the hydraulic, e.g. the computed pressure gradient and flows, are calculated numerically by means of DSHplus. The integration of all kind of forces and torque, e.g. mass moment of inertia and pressure forces, to solve the equation of motion is calculated with a multiple body simulation program, in this case ADAMS by Mechanical Dynamics.

The flexible modelling of mechanical structures in ADAMS makes it possible to create various simulation models of motion, such as cylinders and valves. The mechanical simulation program is coupled with the hydraulic simulation program DSHplus. Both programs run simultaneously on PCs and exchange data in discrete simulation time intervals.
Modeling and Measurement of Pressure-Dependent Junction-Spreader Thermal Resistance for Integrated Circuits
Authors: Zhou Peng , Goodson Kenneth E.
Published: November 2021

The junction-spreader thermal resistance is an important part of the overall junction-ambient thermal resistance in electronic packages. Past research has provided theoretical models for contact thermal resistance between the thermal interface material (TIM) and the contacting rough solid surface. However, these models are based on steady-state assumptions and do not describe the evolution of the junction-spreader thermal resistance during the lifetime of an electronic package. This chapter presents a transient model for the junction-spreader thermal resistance based on classical theories for lubrication and surface wettability. This transient model provides a simple relationship for pressure-dependent junction-spreader thermal resistance and yields an optimum filler volume fraction for particle filled TIMs. An experimental approach developed in this chapter measures the pressure-dependence, as well as the spatial distribution of junction-spreader thermal resistance. The data agree reasonably well with the model predicting for the pressure-dependent junction-spreader thermal resistance. The theoretical and experimental approaches developed in this study are promising tools for thermal management and reliability engineering of electronic packaging.
Adaptation of Aerospace Cool-Suit Technology to Treatment of Multiple Sclerosis Symptoms
Authors: Emerton K. B. , Cooke W. H. , Nelson D. A.
Published: November 2021

Some symptoms of Multiple Sclerosis (MS) are mitigated by lowering the patient’s core temperature. Personal cooling garments, similar to those developed for cooling crewmembers in military aircraft, have been developed and marketed for the treatment of MS symptoms.

This study investigated the effectiveness of a water-cooled vest in reducing the skin surface and core (rectal) temperatures in healthy male subjects. Results show no effect on core temperature, and modest increases in skin temperature over a 30-min session. It is not known whether similar results would obtain with healthy female subjects, or with MS subjects of either gender.
Improvements for the Ford Mustang Braking System
Authors: Lambert Jon G. , Zahraee Mohammad , McIndoo Keith A.
Published: November 2021

Historically, the Ford Mustang is America’s favorite “Pony Car”. A Pony Car by definition means an economical sports car. However, this economical sports car is required to compete against automobiles like the Corvette and Viper in many racing circuits. In order to better compete; Mustangs must be modified, often heavily, from their showroom stock condition.

Modifications to the Mustang’s braking system are limited to what is available in the Mustang aftermarket. As such, the aftermarket has yet to address two common weaknesses in the Mustang’s braking system. They are: a lack of a front disk cooling device, and rear brakes that utilize disks larger than 11.65 inches in diameter.

This paper discusses the design, fabrication, and testing of prototype parts to eliminate these two weaknesses in the Mustang’s braking system.
Undergraduate Research Into Motorsports Safety at UNC Charlotte
Authors: Braun Edwin R.
Published: November 2021

The Mechanical Engineering Technology (MET) program at the University of North Carolina at Charlotte (UNC Charlotte) has encouraged industrial collaboration in its Senior Design capstone course. Very few projects have drawn the interest and enthusiasm as a recent set of projects in Motorsports Safety. The Senior Design course has dual purposes: to serve as an integrative capstone design experience, and to teach the basics of the engineering design process. Some of the process elements include: requirements capture, project planning and tracking, technical research, decision analysis, evaluation, and documentation.
Trends in NDE Using Thermal Inspection Methods
Authors: Meyendorf Norbert G. , Hoffmann Jochen , Shen Liming , Rösner Henrik
Published: November 2021

This paper gives a brief overview of present NDE techniques that use infrared cameras. Starting with physical basics, current state of the art and future trends are discussed. Two new methods for materials characterization that use heat dissipation and hot air for heat stimulation will be presented. A new technique called fan thermography, has high potential for corrosion detection under intact coatings. Using this technique, low-cost uncooled infrared cameras are sufficient for obtaining excellent, highly sensitive imaging results.
Calculations of Transport Phenomena in Solid-Oxide Fuel Cells
Authors: Beale S. B. , Dong W. , Zhubrin S. V. , Boersma R. J.
Published: November 2021

This paper presents the results of a collaborative research project of computer modeling of transport phenomena within the passages of solid-oxide fuel cells. From a mechanical design viewpoint, fuel cells may be considered to be similar to heat exchangers with internal heat generation due to ohmic heating. This is a function of load-driven factors. The thermomechanical design of the units is of paramount importance, as the reaction rates are a function of temperature, pressure, and species concentrations, i.e., the process is fully coupled. The design goal of the project is to ensure uniform flow and temperature distribution throughout the stack, to optimize performance and minimize the risk of failure.

We developed computer models to predict the performance of cells and stacks of cells, so as to minimize the development of expensive experimental protypes and test rigs. The standard techniques of heat transfer and computational fluid dynamics were substantially modified to be applicable in this context. Three distinct approaches were considered. In all cases two fluids; air and fuel, each containing different chemical species were considered. The equations for fluid flow, heat and mass transfer with electro-chemical reactions occurring were discretized and solved using a finite-volume method. Detailed numerical simulations of a single cell and stacks of up to 54 cells were performed using fine three-dimensional meshes of up to 4.6 million cells. Simplified models based on a distributed resistance (porous media) analogy, and also traditional presumed flow methods used in heat exchanger and furnace design, were also employed. These latter approaches have the advantage of being readily executable on small personal computers. The three methodologies are described and compared in detail.
Second Law Analysis of a Stirling Cryocooler With Optimal Design of the Regenerator and Losses
Authors: Rogdakis E. D. , Bormpilas N. A.
Published: November 2021

The aim of the research in this paper is a second law analysis of a Stirling cryocooler. A one-dimensional model is proposed for the simulation of the gas flow in the expansion space, the regenerator, the warm-end, the compression space and the compressor. Helium gas is selected as the working medium. An algorithm has been developed considering parametrically the most from the main operational tasks of the thermodynamic cycle.

Performance indices such as heat input, efficiency, external dimensions of the engine and technical requirements are taken into account as constraints. Engine operating parameters i.e. speed, external temperature, mean pressure are fixed. The regenerator loss has a critical influence on the cryocooler efficiency and the reduction of this kind of internal irreversibilities is extremely difficult due to the generator is subject to rapidly cycling flows accompanied by steep temperature gradients and large pressure variations.

The second flow analysis of the regenerator identifies two principal losses, the irreversible internal heat transfer into the solid matrix and the hydraulic resistance. An optimization technique leads to entropy generation charts, extremely useful for a good design of the regenerator.

Finally the main thermodynamic characteristics (net refrigeration, power input and the coefficient of performance) of the cryocooler are given both cases with and without external and internal irreversibilities.
Laying Modeling of Submarine Pipelines Using Contact Elements Into a Corotational Formulation
Authors: Martínez Cora , Goncalves Raúl
Published: November 2021

A new finite element formulation to analyze stresses and displacements in submarine pipelines during laying operations is presented in this paper. The method is based on the corotational formulation using Bernoulli non-linear beam elements to model the large displacements and rotations of the pipeline. The penalty method is used with spring-contact elements to accurately represent the actual boundary conditions. During the lay barge installation, the pipe rolls over the barge ramp and slides over the stinger before reaching the sea floor. The barge stinger is a ramp over floating supports that holds the pipeline in such a way that the pipe adopts an S-curve during the laying process. Since contact elements allow the pipeline to separate from the stinger at those points where the contact is lost, introducing these elements into the analysis makes it possible to accurately model the actual boundary conditions on the stinger. In addition, the use of contact elements allows the pipe to reach the sea floor at all those points, which naturally require this condition without imposing any displacement boundary condition during the convergence process. A real laying case of an oil transportation submarine pipeline is presented at the end of the paper to validate the results obtained with the developed formulation. A comparison with a finite element formulation introduced by the authors in a previous paper is also presented in order to verify the accuracy and computational effectiveness of the proposed method.
Clearance Considerations for Passenger Rolling Stock
Authors: Strong Philip M.
Published: November 2021

Passenger rolling stock often operates with a softer suspension than used in freight cars, in order to obtain good ride quality. In order to maximize seating, interior width forces exterior width to approach Plate C freight car dimensions. Close clearance to platforms is an important safety consideration for passenger entrance and egress. The associated rolling stock and platform designs need to be considered as clearance issues, especially in mixed passenger and freight traffic operations. Some passenger railroads that operate self-propelled cars use a third rail for power collection, which presents a clearance constraint on curves, particularly for the undercar equipment that is common on these cars. Maximum height at center of cars and locomotives is constrained by catenary clearance in some operations.

Clearance considerations for passenger rolling stock on new and/or existing properties are covered using a general approach. Examples are presented which illustrate some of the factors that need to be considered in clearance investigations.
Estimating minke whale relative abundance in the North Atlantic using passive acoustic sensors
Authors: Kiehbadroudinezhad Shahideh , Bruce Martin S. , Mills Flemming Joanna
Published: November 2021

Estimates of abundance and their changes through time are key elements of marine mammal conservation and management. Absolute marine mammal abundance in a region of the open ocean is often difficult to attain. However, methods of estimating their abundance based on passive acoustic recordings are becoming increasingly employed. This study shows that passive acoustic monitoring of North Atlantic minke whales with a single hydrophone provides sufficient information to estimate relative population abundance. An automated detector was developed for minke whale pulse trains and an approach for converting its output into a relative abundance index is proposed by accounting for detectability as well as false positives and negatives. To demonstrate this technique, a 2 y dataset from the seven sites of the Atlantic Deepwater Ecosystem Observatory Network project on the U.S. east coast was analyzed. Resulting relative abundance indices confirm pulse train-calling minke whale presence in the deep waters of the outer continental shelf. The minkes are present December through April annually with the highest abundance near the site offshore of Savannah, Georgia.