bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Characterization of the Impedance and Spectral Content of Multistable Structural Responses During Dynamic Bifurcations
Authors: Goodpaster Benjamin A. , Harne Ryan L.
Published: March 2018

The ability to predict multistable structural dynamics challenges the development of future high-performance air vehicles that will be subjected to extreme multiphysics loads. To aid in the establishment of methodologies that characterize the response states of harmonically excited multistable structures, a catalog of empirical and practical evidence is necessary. Recent research has suggested that evolving aspects of mechanical impedance metrics may be correlated with measurable quantities, although their relation to bifurcations of the dynamic response remains incompletely understood. Motivated to begin establishing such knowledge base, this research seeks to construct a library of experimental evidence from which to draw generalized insights on the impedance- and spectral-changing trends of multistable structures undergoing severe nonlinear response due to harmonic loading. A connection between vanishing real and imaginary components of impedance and dynamic bifurcations is uncovered. In the process, a technique to forecast dynamic bifurcations is articulated, which utilizes mechanical impedance measurements in real-time to monitor the susceptibility of postbuckled structural components to undergo dynamic bifurcations. An examination of higher-order harmonics of the dynamic responses further illuminates the nearness to bifurcations and may help classify the precise response regime. Thus, by correlating the real-time impedance and spectral response with analytical predictions, a future tool may be established for condition monitoring and diagnosis.
Voltage-Induced Snap-Through of an Asymmetrically Laminated, Piezoelectric, Thin-Film Diaphragm Micro-Actuator—Part 1: Experimental Studies and Mathematical Modeling
Authors: Tai W. C. , Luo Chuan , Yang Cheng-Wei , Cao G. Z. , Shen I. Y.
Published: March 2018

A piezoelectric thin-film microactuator in the form of an asymmetrically laminated diaphragm is developed as an intracochlear hearing aid. Experimentally, natural frequencies of the microactuator bifurcate with respect to an applied bias voltage. To qualitatively explain the findings, we model the lead-zirconate-titanate (PZT) diaphragm as a doubly curved, asymmetrically laminated, piezoelectric shallow shell defined on a rectangular domain with simply supported boundary conditions. The von Karman type nonlinear strain–displacement relationship and the Donnell–Mushtari–Vlasov theory are used to calculate the electric enthalpy and elastic strain energy. Balance of virtual work between two top electrodes is also considered to incorporate an electric-induced displacement field that has discontinuity of in-plane strain components. A set of discretized equations of motion are obtained through a variational approach.
Three-Body Heat Transfer Between Anisotropic Magneto-Dielectric Hyperbolic Metamaterials
Authors: Song Jinlin , Lu Lu , Cheng Qiang , Luo Zixue
Published: March 2018

We investigate the near-field (NF) radiative heat transfer of the three-body system consisting of anisotropic magnetodielectric hyperbolic metamaterials (AMDHMs), which can support coupled surface phonon polaritons (SPhPs) and hyperbolic modes for both p and s polarizations. We numerically demonstrate that the NF heat transfer between two AMDHMs bodies can be further enhanced by inserting an AMDHMs slab. Due to the loss in AMDHMs, there exists an optimum thickness of the intermediate slab to maximize the NF heat flux flowing to the receiver for a fixed gap distance. Results obtained from this work will facilitate investigations of the NF heat transfer involving magnetic hyperbolic metamaterials.
Analysis of a Vortexing Circulating Fluidized Bed for Process Intensification Via High-G Flows
Authors: Bobek Michael , Rowan Steve , Yang Jingsi , Weber Justin , Shafer Frank , Breault Ronald W.
Published: March 2018

Fluidized beds are used in many industries where gas–solid reactions are present for their favorable characteristics of good solids mixing, high heat, and mass transfer rates, and large throughputs. In an attempt to increase throughput, reduce reactor footprints, and reduce costs, process intensification by unconventional reactor designs is being pursued. Specifically, this work focuses on the development of high-G reactors where the particles are experiencing a centripetal force typically on the order of ten times the force of gravity. This operating regime provides intensified gas–solids contact providing higher mass transfer, heat transfer, and gas throughput than a typical fluidized bed. This work focuses analysis of a cold flow vortexing circulating fluidized bed (CFB). Through mapping the pressure distributions in the riser, insights into the behavior of the system were made and compared to CPFD Barracuda computational fluid dynamic models. The simulation results outlined the working envelope of the system and provided a baseline to compare the experimental results. The experimental pressure data determined angular velocities of the gas in the range of 30–40 m/s, with corresponding particle velocities around 15 m/s.
Comparison of Single and Multiple Injection Strategies in a Butanol Diesel Dual Fuel Engine
Authors: Yadav Jaykumar , Ramesh Asvathanarayanan
Published: March 2018

A turbocharged three cylinder automotive common rail diesel engine was modified to operate in the n-butanol diesel dual fuel mode. The quantity of butanol injected by the port fuel injectors and the rail pressure, injection timing, and number of injection pulses of diesel were varied using open engine controllers. Experiments were performed in the dual fuel mode at a constant speed of 1800 rpm at varying brake mean effective pressure (BMEPs). Butanol to diesel energy share was varied, and the injection timing of diesel was always set for highest brake thermal efficiency (BTE). Single pulse injection (SPI) and two pulse injection (TPI) of diesel were evaluated. In SPI, with increase in the butanol to diesel energy share, the BTE remained unchanged. At high loads and high amounts of butanol, the heat release rate (HRR) variation indicated that butanol auto ignited before diesel with both SPI and TPI of diesel. NO emission always decreased because of reduced temperatures due to evaporation of butanol. Butanol also reduced the smoke levels except at high loads. HC levels were always higher. With optimized injection parameters, TPI of diesel resulted in lower NO, similar smoke, and BTE with lesser rate of pressure rise as compared to SPI of diesel in the dual fuel mode at high loads. On the whole, the SPI mode is suitable for low to medium outputs and the TPI mode is suitable for high outputs.
Performance Degradation and Poison Build-Up of an Oxidation Catalyst in Two-Stroke Natural Gas Engine Exhaust
Authors: Baumgardner Marc E. , Olsen Daniel B.
Published: March 2018

Due to current and future exhaust emissions regulations, oxidation catalysts are increasingly being added to the exhaust streams of large-bore, two-stroke, natural gas engines. Such catalysts have a limited operational lifetime, primarily due to chemical (i.e., catalyst poisoning) and mechanical fouling resulting from the carry-over of lubrication oil from the cylinders. It is critical for users and catalyst developers to understand the nature and rate of catalyst deactivation under these circumstances. This study examines the degradation of an exhaust oxidation catalyst on a large-bore, two-stroke, lean-burn, natural gas field engine over the course of 2 years. Specifically, this work examines the process by which the catalyst was aged and tested and presents a timeline of catalyst degradation under commercially relevant circumstances. The catalyst was aged in the field for 2-month intervals in the exhaust slipstream of a GMVH-12 engine and intermittently brought back to Colorado State University for both engine testing and catalyst surface analysis. Engine testing consisted of measuring catalyst reduction efficiency as a function of temperature as well as the determination of the light-off temperature for several exhaust components. The catalyst surface was analyzed via scanning electron microscope (SEM)/energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) techniques to examine the location and rate of poison deposition. After 2 years online, the catalyst light-off temperature had increased ∼55 °F (31 °C) and ∼34 wt % poisons (S, P, Zn) were built up on the catalyst surface, both of which represent significant catalyst deactivation.
A Study on the Generalized Thermoelastic Problem for an Anisotropic Medium
Authors: Ghosh Debkumar , Lahiri Abhijit
Published: March 2018

A vector–matrix differential equation is formulated using normal mode analysis from the governing equations of a three-dimensional anisotropic half space in presence of heat source and gravity. The corresponding solution is obtained with the help of eigenvalue approach. Numerical computations for displacement, thermal strain and stress component, temperature distribution are evaluated and presented graphically.
Consolidation-Driven Defect Generation in Thick Composite Parts
Authors: Belnoue J. P.-H. , Nixon-Pearson O. J. , Thompson A. J. , Ivanov D. S. , Potter K. D. , Hallett S. R.
Published: March 2018

Fiber waviness is one of the most significant defects that occurs in composites due to the severe knockdown in mechanical properties that it causes. This paper investigates the mechanisms for the generation of fiber path defects during processing of composites prepreg materials and proposes new predictive numerical models. A key focus of the work was on thick sections, where consolidation of the ply stack leads to out of plane ply movement. This deformation can either directly lead to fiber waviness or can cause excess fiber length in a ply that in turn leads to the formation of wrinkles. The novel predictive model, built on extensive characterization of prepregs in small-scale compaction tests, was implemented in the finite element software abaqus as a bespoke user-defined material. A number of industrially relevant case studies were investigated to demonstrate the formation of defects in typical component features. The validated numerical model was used to extend the understanding gained from manufacturing trials to isolate the influence of various material, geometric, and process parameters on defect formation.
Dynamic Tensile Behavior of Fiber Bundles Isolated From Spinal Neve Roots: Effects of Anatomical Site and Loading Rate on Mechanical Strength
Authors: Tamura Atsutaka , Sakaya Mizuki
Published: March 2018

We found a significant difference (P < 0.05) between the linear portion of the elastic modulus (∼20 MPa) and tensile strength (∼2 MPa) at the 0.2 mm/s (low: 0.01 s−1), 2 mm/s (medium: 0.11 s−1), and 20 mm/s (high: 1.11 s−1) loading rates by performing a series of uniaxial stretching tests. However, the mechanical properties of the neural fiber bundles were resultantly of the same magnitude, indicating that their mechanical responses were relatively insensitive to a given strain rate regardless of a 100-fold increase in the applied stretching velocities. We also confirmed that a “spinal level effect” exists in the nerve roots, i.e., a fiber bundle isolated from the lumbar spinal level is weaker in mechanical strength compared to that from the cervical and thoracic spinal levels (P < 0.05), suggesting that closer attention should be paid to an anatomical site from which test samples are excised.
A Backlash Compensator for Drivability Improvement Via Real-Time Model Predictive Control
Authors: Rostiti Cristian , Liu Yuxing , Canova Marcello , Stockar Stephanie , Chen Gang , Dourra Hussein , Prucka Michael
Published: March 2018

Nonlinear dynamics in the transmission and drive shafts of automotive powertrains, such as backlash, induce significant torque fluctuations at the wheels during tip-in and tip-out transients, deteriorating drivability. Several strategies are currently present in production vehicles to mitigate those effects. However, most of them are based on open-loop filtering of the driver torque demand, leading to sluggish acceleration performance. To improve the torque management algorithms for drivability and customer acceptability, the powertrain controller must be able to compensate for the wheel torque fluctuations without penalizing the vehicle response. This paper presents a novel backlash compensator for automotive drivetrain, realized via real-time model predictive control (MPC). Starting from a high-fidelity driveline model, the MPC-based compensator is designed to mitigate the drive shaft torque fluctuations by modifying the nominal spark timing during a backlash traverse event. Experimental tests were conducted with the compensator integrated into the engine electronic control unit (ECU) of a production passenger vehicle. Tip-in transients at low-gear conditions were considered to verify the ability of the compensator to reduce the torque overshoot when backlash crossing occurs.
Forced and Mixed Convection Heat Transfer at High Pressure and High Temperature in a Graphite Flow Channel
Authors: Valentín Francisco I. , Artoun Narbeh , Kawaji Masahiro , McEligot Donald M.
Published: March 2018

High pressure/high temperature forced and mixed convection experiments have been performed with helium and nitrogen at temperatures and pressures up to 893 K and 64 bar, respectively. The test section had a 16.8 mm ID flow channel in a 108 mm OD graphite column. Flow regimes included turbulent, transitional, and laminar flows with the inlet Reynolds numbers ranging from 1500 to 15,000. Due to strong heating, the local Reynolds number decreased by up to 50% over the 2.7 m test section. In addition, heat transfer degradation and flow laminarization caused by intense heating led to Nusselt numbers 20–50% lower than the values given by the modified Dittus–Boelter and modified Gnielinski correlations. Flow laminarization criteria were considered based on a dimensionless acceleration parameter (Kv) and buoyancy parameter (Bo*). Upward turbulent flows displayed higher wall temperatures than downward flows, due to the impact of flow laminarization which is not expected to affect buoyancy-opposed flows. Laminar Reynolds number flows presented an opposite behavior due to the enhancement of heat transfer for buoyancy-aided flows. At low Reynolds numbers, downward flows displayed higher and lower wall temperatures in the upstream and downstream regions, respectively, than the upward flow cases. In the entrance region of downward flows, convection heat transfer was reduced due to buoyancy leading to higher wall temperatures, while in the downstream region, buoyancy-induced mixing caused higher convection heat transfer and lower wall temperatures.
Investigation of Parametric Effects on Geometrical Inaccuracies in Deformation Machining Process
Authors: Singh Arshpreet , Agrawal Anupam
Published: March 2018

Deformation machining (DM) is a combination of thin structure machining and single-point incremental forming/bending (SPIF/SPIB). This process enables the creation of complex structures and geometries, which are probably difficult or sometimes impossible to manufacture employing conventional manufacturing techniques. Geometrical discrepancies in thin structure or sheet metal bending and forming are a major obstacle in manufacturing quality components. These discrepancies are more prevalent and complex in nature in incremental or generative manufacturing. In the present work, a comprehensive experimental and numerical study on the parametric effects on various geometrical inaccuracies in DM process has been performed. This study would help in giving an insight in providing necessary geometrical compensation, ensuring a quality product over a wide range of process parameters.
Experimental and Numerical Investigation of Forming Limit Differences in Biaxial and Dome Test
Authors: Nikhare Chetan P.
Published: March 2018

For centuries, metals and materials have been characterized using a traditional method called a uniaxial tension test. The data acquired from this test found to be adequate for operations of simple forming where one axis stretching is dominant. Currently, due to the demand of lightweight component production, multiple individual parts eliminated by stamping a single complex shape, which also further reduces many secondary operations. This change is driving by the new fuel-efficiency requirement by corporate average fuel economy of 55.8 miles per gallon by 2025.1 Due to complex part geometry, this forming method induces multiaxial stress states, which are difficult to predict using conventional tools. Thus, to analyze these multiaxial stress states limiting dome height tests and bulge tests were recommended in many research publications. However, these tests limit the possibilities of applying multiaxial loading and rather a sample geometry changes are required to imply multiaxial stresses. Even this capability is not an option in bulge test due to leakage issue. Thus, a test machine called a biaxial test was devised that would provide the capability to test the specimen in multiaxial stress states by varying the independent load or displacement on two independent axis. In this paper, two processes, limiting dome tests and biaxial tests were experimented, modeled, and compared. For the biaxial tests, a cruciform test specimen was utilized, and conventional forming limit specimens were used for the dome tests. Variation of sample geometry in limiting dome test and variation of loading in biaxial test were utilized to imply multiaxial stress states in order to capture the limit strain from uniaxial to equibiaxial strain mode. In addition, the strain path, forming, and formability investigated and the differences between the tests provided. From the results, it was noted that higher limit strains were acquired in dome tests than in biaxial tests due to contact pressure from the rigid punch. The literature shows that the contact pressure (which occurs when the rigid tool contacts the deformed body), increases the deformation and thus increases the limit strains to failure. This contact pressure parameter is unavailable in biaxial test, and thus, a pure material behavior can be obtained. However, limit strains from biaxial test cannot be considered for a process where rigid tool is processing the metal, and thus, calibration is necessary.
A Novel In Vitro Testing Approach for the Next Generation of Transvenous Cardiac Leads: Buckling Behavior
Authors: Walsh Donna L. , Williams Ashok , Vesnovsky Oleg , Timmie Topoleski L. D. , Duraiswamy Nandini
Published: March 2018

Manufacturers are constantly seeking to design new, better performing transvenous cardiac leads to prevent perforation of the heart by the lead tip. Currently, there is no standardized test method to measure the buckling load of leads, a major factor in the propensity of the lead to perforate the heart. This study further investigates the effect of boundary conditions on buckling loads at the lead tip of different transvenous cardiac leads achieved using different variations of our initial physiologically relevant test method. The goals of the test are to create the maximum buckling load with high repeatability and the simplest possible design. A buckling test was performed to capture maximum buckling load using three leads of each model (five currently available cardiac lead models) and were tested in each of six test setups. The buckling test methodology had a substantial effect on the load-displacement profiles, regardless of whether the lead was a pacemaker or defibrillator lead. By adding the right ventricular (RV) constraint, the buckling load more than doubled for most leads. The use of a lubricant reduced friction between the lead body and the RV surface, and thereby subsequently lowered the buckling load in those setups that used the RV constraint. In addition, the use of the lubricant reduced the variability in the results. The addition of both the RV constraint and the lubricant substantially influences the mechanical behavior of transvenous cardiac leads and is recommended for buckling testing of transvenous cardiac leads.
Numerical Investigation of Convective Heat Transfer to Supercritical Pressure Hydrogen in a Straight Tube
Authors: Ji Yu , Sun Jun , Shi Lei
Published: March 2018

Hydrogen is adopted as coolant for regenerative cooling nozzle and reactor core in nuclear thermal propulsion (NTP), which is a promising technology for human space exploration in the near future due to its large thrust and high specific impulse. During the cooling process, the hydrogen alters its state from subcritical to supercritical, accompanying with great variations of fluid properties and heat transfer characteristics. This paper is intended to study heat transfer processes of supercritical pressure hydrogen under extremely high heat flux by using numerical approach. To begin with, the models explaining the variation of density, specific heat capacity, viscosity, and thermal conductivity are introduced. Later on, the convective heat transfer to supercritical pressure hydrogen in a straight tube is investigated numerically by employing a computational model, which is simplified from experiments performed by Hendricks et al. During the simulation, the standard k–ε model combining the enhanced wall treatment is used to formulate the turbulent viscosity, and the results validates the approach through successful prediction of wall temperature profile and bulk temperature variation. Besides, the heat transfer deterioration which may occur in the heat transport of supercritical fluids is also observed. According to the results, it is deduced that the flow acceleration to a flat velocity profile in the near wall region due to properties variation of hydrogen contributes to the suppression of turbulence and the heat transfer deterioration, while the “M-shaped” velocity profile is more often correlated to the starting of a recovery phase of turbulence production and heat transfer.
Enhancement in Exergoeconomic and Enviroeconomic Parameters for Single Slope Solar Still by Incorporating N Identical Partially Covered Photovoltaic Collectors
Authors: Singh Desh B. , Kumar Navneet , Kumar Sanjay , Dwivedi Vijay K , Yadav Jeetendra K , Tiwari Gopal N
Published: March 2018

This paper deals with the enhancement in exergoeconomic and enviroeconomic parameters for single-slope solar still by incorporating N identical partially covered photovoltaic thermal (PVT) collectors. Three cases: (a) single slope solar still incorporating N identical partially covered PVT flat plate collectors (FPC) (N-PVT-FPC-SS), (b) single slope solar still incorporating N identical partially covered PVT compound parabolic concentrator collectors (N-PVT-CPC-SS), and (c) conventional single slope solar still (CSSSS) have been taken to assess the improvement in various parameters. The various parameters have been computed at 0.14 m water depth, selected values of mass flow rate, and number of collectors considering four climatic conditions of New Delhi for each month of year. It has been concluded that N-PVT-FPC-SS performs best followed by N-PVT-CPC-SS and CSSSS on the basis of exergoeconomic and enviroeconomic parameters; however, CSSSS performs better than N-PVT-FPC-SS and N-PVT-CPC-SS on the basis of productivity measured in terms of ratio of monetary value of output and input. The kWh per unit cost based on exergoeconomic parameter is higher by 45.11% and 47.37%; environmental cost is higher by 65.74% and 90.02%; however, the output per unit input based on productivity is higher by 12.09% and lower by 26.83% for N-PVT-FPC-SS than N-PVT-CPC-SS and CSSSS, respectively.
Enhanced Seismic Fragility Analysis of Unanchored Steel Storage Tanks Accounting for Uncertain Modeling Parameters
Authors: Phan Hoang Nam , Paolacci Fabrizio , Alessandri Silvia
Published: March 2018

Catastrophic failure of the above ground steel storage tanks was observed during past earthquakes, which caused serious economic and environmental consequences. Many of the existing tanks were designed in the past with outdated analysis methods and with underestimated seismic loads. Therefore, the evaluation of the seismic vulnerability of these tanks, especially ones located in seismic prone areas, is extremely important. Seismic fragility functions are useful tools to quantify the seismic vulnerability of structures in the framework of probabilistic seismic risk assessment. These functions give the probability that a seismic demand on a given structural component meets or exceeds its capacity. The objective of this study is to examine the seismic vulnerability of an unanchored steel storage tank, considering the uncertainty of modeling parameters that are related to material and geometric properties of the tank. The significance of uncertain modeling parameters is first investigated with a screening study, which is based on nonlinear static pushover analyses of the tank using the abaqus software. In this respect, a fractional factorial design and an analysis of variance (ANOVA) have been adopted. The results indicate that the considered modeling parameters have significant effects on the uplift behavior of the tank. The fragility curves of two critical failure modes, i.e., the buckling of the shell plate and the plastic rotation of the shell-to-bottom plate joint, are then developed based on a simplified model of the tank, where the uplift behavior is correctly modeled from the static pushover analysis. The uncertainty associated with the significant parameters previously identified are considered in the fragility analysis using a sampling procedure to generate statistically significant samples of the model. The relative importance of different treatment levels of the uncertainty on the fragility curves of the tank is assessed and discussed in detail.
Comparison of Natural Convection Around a Circular Cylinder With Different Geometries of Cylinders Inside a Square Enclosure Filled With Ag-Nanofluid Superposed Porous-Nanofluid Layers
Authors: Hussain Salam Hadi , Rahomey Mustafa Salah
Published: March 2018

Numerical simulations are carried out for fluid flow and natural convection heat transfer induced by a temperature difference between a hot inner cylinder with different geometries (i.e., circular; triangular; elliptic; rectangular; and rhombic) and a cold outer square enclosure filled with nanofluid superposed porous-nanofluid layers. The Darcy–Brinkman model is applied for the saturated porous layer with nanofluid. Moreover, the transport equations (mass, momentum, and energy) are solved numerically using the Galerkin weighted residual method by dividing the domain into two sets of equations for every layer with incorporating a nonuniform mesh size. The considered domains in this investigation are closely examined over a wide range of Rayleigh number (103 ≤ Ra ≤ 106), Darcy number (10−5 ≤ Da ≤ 10−1), the thickness of porous layer (0% ≤ Xp ≤ 100%), thermal conductivity ratio (1 ≤ Rk ≤ 20), and nanoparticle volume fraction (0 ≤ φ ≤ 0.1), respectively. The nanofluid is considered to be composed of Ag-nanoparticle and water as a base fluid. The results showed that the obtained total surfaces-averaged Nusselt numbers of the enclosure, in all cases, at the same operating conditions, the rate of heat transfer from the outer enclosure which the triangular cylinder is located inside is better. Also, as the thickness of the porous layer is increased from 20% to 80%, the free convection performance will decrease significantly (to about 50%) due to the hydrodynamic properties of the porous material.
Natural Convection and Surface Radiation in a Heated Wall, C-Shaped Fracture
Authors: Lugarini Alan , Franco Admilson T. , Junqueira Silvio L. M. , Lage José L.
Published: March 2018

The present study considers the coupled natural convection and surface radiation process through an open fracture of a solid wall facing a reservoir containing isothermal quiescent fluid (air). The fracture is modeled as a regular, C-shape path through the wall, with the vertical surface being heated and the horizontal ones adiabatic. The solid center section of the fracture is thermally participant inasmuch it can be heated or cooled by the natural convection process and by the radiation effect from the other surfaces of the fracture. The convection-radiation phenomenon is mathematically modeled and numerically simulated in a systematic parametric study of the thermal process as affected by changes in the fracture channel size, via changes in the size of the solid center section 0 < D < 1.0, surface emissivity 0 ≤ ε ≤ 1.0, Rayleigh number 105 ≤ Ra ≤ 108, and Pr = 0.71. Attention is given to the radiation shadowing effect caused by the center section of the fracture and of the interference effect, as the fracture channel changes in size, affecting the natural convection process through the fracture. An analytical prediction of the interference effect and an empirical correlation for predicting the total Nusselt number, both validated against the numerical results, are presented.
Grinding Characteristics, Material Removal, and Damage Formation Mechanisms of Zirconia Ceramics in Hybrid Laser/Grinding
Authors: Xu Sheng , Yao Zhenqiang , He Jiawei , Xu Jian
Published: March 2018

Zirconia ceramics which are sometimes called “ceramic steel” have gained significant interest because of their excellent properties. However, it is desired to maintain the surface quality while increasing the economics of ceramics grinding process. A hybrid laser/grinding (HLG) process was utilized to grind zirconia ceramics which was irradiated with continuous wave laser before grinding in the hybrid process. The feasibility of hybrid laser/grinding of zirconia ceramics was investigated in terms of grinding force and energy, material removal, and damage formation mechanisms. The results show that laser irradiation can induce lateral cracks, which can help material removal and prevent further crack propagating into the base. The results of grinding tests indicate that grinding force and energy decrease significantly as compared with conventional grinding of ceramics. The combinations of the fractured area, the plowing striations, and seldom debris on the ground surfaces in this work indicate the combined material removal mechanism of both brittle mode and ductile mode.
Particle Dynamics Modeling of the Creping Process in Tissue Making
Authors: Pan Kui , Srikantha Phani A. , Green Sheldon
Published: March 2018

The manufacturing of low-density paper such as tissue and towel typically involves a key operation called creping. In this process, the wet web is continuously pressed onto the hot surface of a rotating cylinder sprayed with adhesive chemicals, dried in place, and then scraped off by a doctor blade. The scraping process produces periodic microfolds in the web, which enhance the bulk, softness, and absorbency of the final tissue products. Various parameters affect the creping process and finding the optimal combination is currently limited to costly full-scale experiments. In this paper, we apply a one-dimensional (1D) particle dynamics model to systematically study creping. The web is modeled as a series of discrete particles connected by viscoelastic elements. A mixed-mode discrete cohesive zone model (CZM) is embedded to describe the failure of the adhesive layer. Self-contact of the web is incorporated in the model using a penalty method. Our simulation results delineate three typical stages during the formation of a microfold: interfacial delamination, web buckling, and post-buckling deformation. The effects of key control parameters on creping are then studied. The creping angle and the web thickness are found to have the highest impact on creping. An analytical solution for the maximum creping force applied by the blade is derived and is found to be consistent with the simulation. The proposed model is shown to be able to capture the mechanism of crepe formation in the creping process and may provide useful insights into the manufacturing of tissue paper.
Virtual Model of Gear Shaping—Part II: Elastic Deformations and Virtual Gear Metrology
Authors: Katz Andrew , Erkorkmaz Kaan , Ismail Fathy
Published: March 2018

Elastic deflection of cutting tools relative to the workpiece is one of the major factors contributing to dimensional part inaccuracies in machining. This paper examines the effect of tool deflection in gear shaping and its effect on the gear's profile form error, which can cause transmission error and noise during gear operation. To simulate elastic tool deflection in gear shaping, the tool's static stiffness is estimated from impact hammer testing. Then, based on simulated cutter-workpiece engagement and predicted cutting forces, the elastic deflection of the tool is calculated at each time-step. To examine the effect of tool deflection on the profile error of the gear, a virtual gear measurement module is developed and used to predict the involute profile deviations in the virtually machined part. Simulated and measured profile deviations were compared for a one-pass external spur gear process and a two-pass external spur gear process. The simulated profile errors correlate very well with the measured profiles on the left flanks of the workpiece teeth, which are cut by the leading edges of the cutter teeth. However, additional research is needed to improve the prediction of the right flanks, which are cut by the trailing edges of the cutter teeth.
Control of Final Part Dimensions in Polymer Extrusion Using a Variable-Geometry Die
Authors: Funke Lawrence W. , Schmiedeler James P.
Published: March 2018

Parts made via polymer extrusion are currently limited to a constant cross section. Additionally, the process is difficult to control, so desired final part dimensions are often achieved via a manual trial-and-error approach to parameter adjustment. This work seeks to increase the capability of polymer extrusion by using iterative learning control (ILC) to regulate the final width of a rectangular part through changing the width of a simple variable-geometry die. Simulation results determine the appropriateness of the learning algorithm and gains to be used in experiment. A prototype die on a production extruder was used to demonstrate the effectiveness of the approach. These experiments achieved automated control over both gross change in shape and final part dimension when the puller speed was held constant, which has not been seen previously in the literature.
Performance Prediction and Assessment of Energy Conservation Potential for a Light Pipe System in Indian Composite Climate of New Delhi
Authors: Patil K. N. , Kaushik S. C. , Garg S. N.
Published: March 2018

Light pipes are popularly used for transporting outdoor sunlight into deep spaces of the building, and hence, use of artificial lighting could be substantially reduced. Performance prediction of a light pipe is an essential step before its use in buildings, so that energy saving potential of the light pipe could be quantified. This paper deals with experimental validation of three existing semi-empirical models for light pipes with different aspect ratios, installed on a windowless test room, at IIT Delhi, New Delhi. Two new semi-empirical models based on the existing correlations are developed. The new model found to perform better with mean bias error (MBE) and root-mean-squared error (MSE) of 0.076 and 0.01, respectively. The better performing new model is used for the evaluation of hourly internal illuminance by the light pipe in a typical meteorological year (TMY) in New Delhi. From hourly internal illuminance in a typical meteorological year, the energy saving potential and CO2 mitigation potential of light pipe system for the test room are evaluated. Monthly average energy saving potentials of the light pipe-fluorescent tube light system are found to be 50% for continuous dimming control and 38% for three-step on–off control. Results show that the light pipe-fluorescent tube light system, with different lighting controls, could reduce CO2 emissions to 15–50%.
Skin Modeling Analysis of a Force Sensing Instrument-Assisted Soft Tissue Manipulation Device
Authors: Alotaibi Ahmed M. , Anwar Sohel , Terry Loghmani M.
Published: March 2018

Instrument-assisted soft tissue manipulation (IASTM) is a form of manual therapy which is performed with rigid cast tools. The applied force during the IASTM process has not been quantified or regulated. Nor have the angle of treatment and strokes frequency been quantified which contribute to the overall recovery process. This paper presents a skin modeling analysis used in the design of a novel mechatronic device that measures force in an IASTM application with localized pressures, similar to traditional, nonmechatronic IASTM devices that are frequently used to treat soft tissue dysfunctions. Thus, quantifiable soft tissue manipulation (QSTM) represents an advancement in IASTM. The innovative mechatronic QSTM device is based on one-dimensional (1D) compression load cells, where only four compression force sensors are needed to quantify all force components in three-dimensional (3D) space. Here, such a novel QSTM mechatronics device is simulated, analyzed, and investigated using finite element analysis (FEA). A simplified human arm was modeled to investigate the relationship between the measured component forces, the applied force, and the stress and strain distribution on the skin surface to validate the capability of the QSTM instrument. The results show that the QSTM instrument as designed is able to correlate the measured force components to the applied tool-tip force in a straight movement on the skin model.
The effect of sentential context on phonetic categorization is modulated by talker accent and exposure
Authors: Schertz Jessamyn , Hawthorne Kara
Published: March 2018

Higher-level factors, including the contextual plausibility of competing word candidates, interact with lower-level phonetic cues to influence how listeners interpret the speech signal. This work shows that listeners' phonetic categorization (e.g., coat versus goat) is more heavily influenced by sentential context when listening to a non-native versus native talker. Further, the effect of context on phonetic categorization decreases as the listener becomes familiar with the talker's phonetic characteristics, for both native and non-native talkers. Overall, results suggest that listeners adjust their perceptual strategies to optimize accurate perception of a talker's message.
Temperature effect on phase state and reactivity controls atmospheric multiphase chemistry and transport of PAHs
Authors: Mu Qing , Shiraiwa Manabu , Octaviani Mega , Ma Nan , Ding Aijun , Su Hang , Lammel Gerhard , Pöschl Ulrich , Cheng Yafang
Published: March 2018

Atmospheric refrigerator increases the global transport and health risks of carcinogenic PAHs.
Metamorphic records of multiple seismic cycles during subduction
Authors: Viete Daniel R. , Hacker Bradley R. , Allen Mark B. , Seward Gareth G. E. , Tobin Mark J. , Kelley Chris S. , Cinque Gianfelice , Duckworth Andrew R.
Published: March 2018

Garnets record subduction earthquakes.
An EVolving approach to directed enzyme prodrug therapy for cancer
Authors: Jay Steven M.
Published: March 2018

Gene-directed enzyme prodrug therapy for cancer is made more specific via targeted extracellular vesicle-mediated mRNA delivery.
Complete Genome Sequence of Human Coronavirus NL63 CN0601/14, First Isolated in South Korea
Authors: Kim Jeong-Min , Kim Seung-Tae , Yang Jeong-Sun , Kim Sung Soon , Cheong Hyang-Min
Published: March 2018

We report here the complete genome sequence of the human coronavirus NL63 CN0601/14 strain, first isolated from South Korea. It contains 18-nucleotide discontinuous deletions of the open reading frame 1a (ORF1a) and spike regions. This study will aid in our understanding of the complete genome sequences of isolated coronaviruses in South Korea.
Clinical features of patients with diabetic anterior uveitis
Authors: Watanabe Takayo , Keino Hiroshi , Nakayama Kyoko , Taki Wakako , Echizen Nariaki , Okada Annabelle A
Published: March 2018

Aim

To describe clinical features and outcomes of new-onset anterior uveitis associated with poorly controlled or undiagnosed diabetes mellitus.

Methods

Retrospective analysis of 25 eyes of 18 patients (14 men, 4 women; mean age 44 years) who presented between December 2001 and October 2016 to the Kyorin Eye Center.

Results

Ocular findings at presentation included posterior synechiae (15 eyes, 60%), anterior chamber fibrin (13 eyes, 52%), keratic precipitates (10 eyes, 40%), Descemet membrane folds (7 eyes, 28%) and hypopyon (3 eyes, 12%). Seven cases were bilateral. Intraocular pressure >21 mm Hg (7 eyes, 28%) and diabetic retinopathy (7 eyes, 28%, all non-proliferative) were also noted. The mean random blood glucose was 332 mg/dL (range 135–604 mg/dL) and the mean haemoglobin A1c was 12.6% (range 9.7%–16.7%). Seven patients (39%) were unaware of their hyperglycaemic state, and the remainder had either poor glucose control or had discontinued their diabetes treatment. Systemic examination and ancillary testing ruled out other possible causes of the uveitis. The ocular inflammation was managed in all cases using local corticosteroid therapy (drops and subconjunctival injections) in addition to internal medicine intervention for the diabetes. The best-corrected visual acuity (BCVA) was improved or maintained in all eyes at 3 months. The BCVA was ≤0.5 in two eyes due to both cataract and diabetic macular oedema.

Conclusions

We characterised new-onset anterior uveitis in 18 patients in association with poorly controlled or undiagnosed diabetes mellitus. The uveitis was managed in all cases with local corticosteroid therapy in addition to proper diabetes systemic treatment.
Comparison of baseline and postconcussion SCAT3 scores and symptoms in varsity athletes: an investigation into differences by sex and history of concussion
Authors: Hurtubise Johanna M , Hughes Cindy E , Sergio Lauren E , Macpherson Alison K
Published: March 2018

Objective

To investigate the use of the Sport Concussion Assessment Tool 3 (SCAT3) as an assessment tool in the varsity population, as well as the effects of sex and concussion history on both baseline and postconcussion scores.

Methods

A comparison between baseline and postconcussion SCAT3 scores of varsity level athletes was conducted through retrospective chart review. Differences in both baseline and postconcussion scores were further analysed by sex and history of concussion.

Results

The only clinically significant change on the SCAT3 elicited by a concussion was that of self-reported symptoms. There were no clinically significant differences based on sex or history of concussion.

Conclusion

The SCAT3 in its entirety may not be useful in this population. Additional research on sociocultural and sport aspects that may be affecting symptom reporting in this population is needed.
Emergency department overcrowding: a survey among European neurotrauma centres
Authors: Velt Kimberley Bernadette , Cnossen Maryse , Rood Pleunie P M , Steyerberg Ewout W , Polinder Suzanne , Lingsma Hester F
Published: March 2018

Background

ED overcrowding is an increasing problem worldwide that may negatively affect quality of care and patient outcomes. We aimed to study ED overcrowding across European centres.

Methods

Questionnaires on structure and process of care, including crowding, were distributed to 68 centres participating in a large European study on traumatic brain injury (Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury).

Results

Of the 65 centres included in the analysis, 32 (49%) indicated that overcrowding was a frequent problem and 28 (43%) reported that patients were placed in hallways ‘multiple times a day’; 27 (41%) stated that multiple times a day, there was no bed available when a patient needed to be admitted. Ambulance diversion rarely occurred in the participating centres.

Conclusion

Similar to reports from other parts of the world, ED crowding appears to be a considerable problem in Europe. More research is needed to determine effective ways to reduce overcrowding.
Guanylate cyclase-C as a therapeutic target in gastrointestinal disorders
Authors: Waldman Scott A , Camilleri Michael
Published: March 2018

Functional gastrointestinal disorders (FGIDs) and IBDs are two of the most prevalent disorders of the GI tract and consume a significant proportion of healthcare resources. Recent studies have shown that membrane-bound guanylate cyclase-C (GC-C) receptors lining the GI tract may serve as novel therapeutic targets in the treatment of FGIDs and IBDs. GC-C receptor activation by its endogenous paracrine hormones uroguanylin and guanylin, and the resulting intracellular production of its downstream effector cyclic GMP, occurs in a pH-dependent manner and modulates key physiological functions. These include fluid and electrolyte homeostasis, maintenance of the intestinal barrier, anti-inflammatory activity and regulation of epithelial regeneration. Studies of the GC-C paracrine signalling axis have revealed the therapeutic potential of these receptors in treating GI disorders, including chronic idiopathic constipation and irritable bowel syndrome–constipation. This review focuses on the evolving understanding of GC-C function in health and disease, and strategies for translating these principles into new treatments for FGIDs and IBDs.
Overloading among crash-involved vehicles in China: identification of factors associated with overloading and crash severity
Authors: Zhang Guangnan , Li Yanyan , King Mark J , Zhong Qiaoting
Published: March 2018

Objective

Motor vehicle overloading is correlated with the possibility of road crash occurrence and severity. Although overloading of motor vehicles is pervasive in developing nations, few empirical analyses have been performed on factors that might influence the occurrence of overloading. This study aims to address this shortcoming by seeking evidence from several years of crash data from Guangdong province, China.

Methods

Data on overloading and other factors are extracted for crash-involved vehicles from traffic crash records for 2006–2010 provided by the Traffic Management Bureau in Guangdong province. Logistic regression is applied to identify risk factors for overloading in crash-involved vehicles and within these crashes to identify factors contributing to greater crash severity. Driver, vehicle, road and environmental characteristics and violation types are considered in the regression models. In addition to the basic logistic models, association analysis is employed to identify the potential interactions among different risk factors during fitting the logistic models of overloading and severity.

Results

Crash-involved vehicles driven by males from rural households and in an unsafe condition are more likely to be overloaded and to be involved in higher severity overloaded vehicle crashes. If overloaded vehicles speed, the risk of severe traffic crash casualties increases. Young drivers (aged under 25 years) in mountainous areas are more likely to be involved in higher severity overloaded vehicle crashes.

Conclusions

This study identifies several factors associated with overloading in crash-involved vehicles and with higher severity overloading crashes and provides an important reference for future research on those specific risk factors.