bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of the Canine Atopic Dermatitis Extent and Severity Index (CADESI)‐4, a simplified severity scale for assessing skin lesions of atopic dermatitis in dogs
Authors: Olivry Thierry , Saridomichelakis Manolis , Nuttall Tim , Bensignor Emmanuel , Griffin Craig E. , Hill Peter B.
Published: January 2014

Background

Severity scales are used to grade skin lesions in clinical trials for treatment of dogs with atopic dermatitis (AD). At this time, only two scales have been validated, namely the Canine Atopic Dermatitis Extent and Severity Index (CADESI)‐3 and the Canine Atopic Dermatitis Lesion Index (CADLI). However, the high number of assessed sites makes the CADESI‐3 impractical.

Hypothesis/Objectives

The aim of this study was to develop and validate a fourth version of the CADESI that is simpler and quicker to administer.

Methods

Body sites, lesions and severity grades were revised by members of the International Committee on Allergic Diseases of Animals (ICADA). The newly designed CADESI‐4 was tested for its validity (i.e. content, construct and criterion), reliability (i.e. inter‐ and intra‐observer reliability and internal consistency), responsiveness (i.e. sensitivity to change) and time to administer. Disease severity benchmarks were chosen using receiver operating characteristic methodology.

Results

The CADESI‐4 was simplified in comparison to its previous version to comprise 20 body sites typically affected in atopic dogs. Three lesions (erythema, lichenification and alopecia/excoriation) were scored from 0 to 3 at each site. The CADESI‐4 had satisfactory validity, reliability and sensitivity to change. On average, the time to administer a CADESI‐4 was one‐third that of a CADESI‐3. Proposed benchmarks for mild, moderate and severe AD skin lesions are 10, 35 and 60, respectively.

Conclusions and clinical importance

The CADESI‐4 is simpler to use and quicker to administer than its previous version. The ICADA recommends the CADESI‐4 instead of the CADESI‐3 to score skin lesions of AD in dogs enrolled in clinical trials.
Ophraella communa, the ragweed leaf beetle, has successfully landed in Europe: fortunate coincidence or threat?
Authors: Müller‐Schärer H , Lommen S T E , Rossinelli M , Bonini M , Boriani M , Bosio G , Schaffner U
Published: January 2014

We report the occurrence of the North American ragweed leaf beetle Ophraella communa in Europe. During our surveys to monitor populations of the invasive alien plant Ambrosia artemisiifolia in Europe, we found the beetle south of the Alps, in more than 130 sites in southern Switzerland (Ticino) and northern Italy (Lombardia, Piemonte and Emilia‐Romagna). At sites where O. communa was present, up to 100% of the plants were attacked with damage levels high enough to completely defoliate and prevent flowering and seed set of most ragweed plants. That in its first year of discovery, O. communa was already found over a large area of c. 20 000 km2 and in all habitat types occupied by A. artemisiifolia reflects its great dispersal potential and wide habitat suitability. This oligophagous beetle is a successful biological control agent against A. artemisiifolia in China, but despite extensive host specificity tests, the risk of attack and the level of damage of sunflower under field conditions remain unclear. The recently launched COST Action on ‘Sustainable management of Ambrosia artemisiifolia in Europe (SMARTER)’ offers an ideal framework to respond quickly to the recent establishment of O. communa in Europe and to collect data that can help determine whether this event should be considered a troublesome introduction or whether it is likely to become the first case of a successful biological control of an invasive weed in continental Europe.
The combined influence of fat consumption and repeated mental stress on brachial artery flow‐mediated dilatation: a preliminary study
Authors: Poitras Veronica J. , Slattery David J. , Levac Brendan M. , Fergus Stevenson , Gurd Brendon J. , Pyke Kyra E.
Published: January 2014

New Findings

What is the central question of this study?

Both a high‐fat meal and acute mental stress can impair conduit artery endothelial function. The objective of this study was to determine whether the combination of a high‐fat meal and repeated postprandial stressful tasks would exacerbate dysfunction versus either stimulus alone.

What is the main finding and its importance?

Endothelial function was modestly greater when the postprandial state was accompanied by mental stress. Thus, in healthy subjects acute stress may confer protection from a negative impact of food consumption, possibly due in part to a stress‐induced reduction in plasma phosphorus levels. These findings challenge the position of acute mental stress as universally detrimental to endothelial function.

Experienced separately, both acute mental stress and high‐fat meal consumption can transiently impair endothelial function, and the purpose of the present study was to investigate their combined impact. On four separate days, 10 healthy men (23 years old) underwent brachial artery flow‐mediated dilatation (FMD) tests, before and hourly for 4 h post‐consumption of a high‐fat (HFM; 54 g fat) or low‐fat meal (LFM; 0 g fat; each meal ∼1000 calories), with hourly mental stress (mental arithmetic, speech) or control (counting) tasks (conditions HFM+S, LFM+S, HFM and LFM). Data are presented as means ± SD. Plasma triglycerides increased and remained elevated after the high‐fat but not the low‐fat meal (P = 0.004) and were not affected by mental stress (P = 0.329). Indices of stress reactivity increased during mental stress tasks (mean arterial pressure, ∼∆20 mmHg; heart rate, ∼∆22 beats min−1; salivary cortisol, ∼∆2.37 nmol l−1; and plasma noradrenaline, ∼∆0.17 ng ml−1) and were not influenced by meal (P > 0.05). There was no effect of the type of meal on FMD (P = 0.562); however, FMD was 4.5 ± 0.5% in the control conditions and 5.8 ± 0.6% in the mental stress conditions (P = 0.087), and this difference was significant when normalized for the shear stress stimulus (FMD/area under the curve of shear stress, P = 0.045). Overall, these preliminary data suggest that postprandial FMD was augmented with mental stress irrespective of meal type. These results are contrary to previous reports of impaired endothelial function after mental stress or fat consumption independently and highlight the need to further investigate the mechanisms underlying the interactions between these factors.
Effect of acute moderate exercise on induced inflammation and arterial function in older adults
Authors: Ranadive Sushant Mohan , Kappus Rebecca Marie , Cook Marc D. , Yan Huimin , Lane Abbi Danielle , Woods Jeffrey A. , Wilund Kenneth R. , Iwamoto Gary , Vanar Vishwas , Tandon Rudhir , Fernhall Bo
Published: January 2014

New Findings

What is the central question of this study?

The aim of the study was to evaluate the effect of acute induced systemic inflammation on endothelial function, wave reflection and arterial function in older adults.

What is the main finding and its importance?

Acute inflammation induced by influenza vaccination did not affect endothelial function in older adults. These findings have never been shown in older adults, and they emphasize the importance of vascular function during systemic arterial inflammation.

Acute inflammation reduces flow‐mediated vasodilatation and increases arterial stiffness in young healthy individuals. However, this response has not been studied in older adults. The aim of this study, therefore, was to evaluate the effect of acute induced systemic inflammation on endothelial function and wave reflection in older adults. Furthermore, an acute bout of moderate‐intensity aerobic exercise can be anti‐inflammatory. Taken together, we tested the hypothesis that acute moderate‐intensity endurance exercise, immediately preceding induced inflammation, would be protective against the negative effects of acute systemic inflammation on vascular function. Fifty‐nine healthy volunteers between 55 and 75 years of age were randomized to an exercise or a control group. Both groups received a vaccine (induced inflammation) and sham (saline) injection in a counterbalanced crossover design. Inflammatory markers, endothelial function (flow‐mediated vasodilatation) and measures of wave reflection and arterial stiffness were evaluated at baseline and at 24 and 48 h after injections. There were no significant differences in endothelial function and arterial stiffness between the exercise and control group after induced inflammation. The groups were then analysed together, and we found significant differences in the inflammatory markers 24 and 48 h after induction of acute inflammation compared with sham injection. However, flow‐mediated vasodilatation, augmentation index normalized for heart rate (AIx75) and β‐stiffness did not change significantly. Our results suggest that acute inflammation induced by influenza vaccination did not affect endothelial function in older adults.
Cell Growth Models Using Reaction Schemes: Batch Cultivation
Authors: Markov Svetoslav Marinov
Published: January 2014

Simple structured mathematical models of bacterial cell growth are proposed. The modelsВ  involve fractions of bacterial cells relatedВ  toВ  their physiological phases. Reaction schemes involving the biomass of theВ  cell fractions, the substrate and the product are proposed in analogy to reaction schemes in enzyme kinetics. Applying the mass action law these reaction schemesВ  lead toВ  dynamical models represented byВ  systems of ODE's. All parameters of the modelsВ  are rate constants with clear biological or biochemical meaning.В  The proposed models generalizeВ  classical bacterial growth models and offer more flexible tools for modelling and control of biotechnological processes. In this paper the study is focused on batch cultivation models.
Multiscale Analysis of Ionic Transport in Periodic Charged Media
Authors: Timofte Claudia
Published: January 2014

A macroscopic model for describing the ion transport in periodic charged porous media is rigorously derived. Our results can serve as a tool for biophysicists to analyze the ion transport through protein channels. Also, such a model is useful for describing the flow of electrons and holes in a semiconductor device.
An Inverse Dynamic Model of Over-Constrained Parallel Kinematic Machine Based on Newton–Euler Formulation
Authors: Bi Z. M. , Kang Bongsu
Published: January 2014

It has been known that redundant constrains in a mechanism can improve the rigidity and stiffness of the mechanism. Some Parallel Kinematic Machines (PKMs) have adopted redundant constraints to enhance their performance and stability. However, limited studies have been conducted on the dynamics of over-constrained mechanisms. While a dynamic model is not essential to machine control, a clear understanding of the dynamic behavior of the system can be useful in identifying the weakest components, optimizing the overall structure, and improving the quality of control. In this paper, the dynamic characteristics of an over-constrained PKM are investigated for the first time. The Newton–Euler formulation is extended to develop the dynamic model of the machine. It is shown that the compliance of deformations of the redundant constraints needs to be taken into account to build a complete and solvable dynamic model since the number of equations derived from the force and moment equilibrium of the PKM components is insufficient to determine all unknown variables. The proposed approach is generic in sense that it can be applied to model dynamic behaviors of other over-constrained machines with a combination of the Newton–Euler formulation and compliance conditions. Its effectiveness has been verified by the dynamic model established for Exechon PKM. The developed dynamic model has its potential to be integrated with control systems to improve accuracy and dynamic performance of real-time control.
Real-Time Hybrid Switching Control of Automotive Cold Start Hydrocarbon Emission
Authors: Salehi Rasoul , Shahbakhti Mahdi , Karl Hedrick J.
Published: January 2014

Reduction of cold start hydrocarbon (HC) emissions requires a proper compromise between low engine-out HC emission and fast light-off of the three way catalytic converter (TWC). In this paper, a hybrid switching system is designed and optimized for reducing HC emissions of a mid-sized passenger car during the cold start phase of FTP-75 (Federal Test Procedure). This hybrid system has the benefit of increasing TWC temperature during the early stages of the driving cycle by switching between different operational modes. The switching times are optimized to reduce the cumulative tailpipe HC of an experimentally validated automotive emission model. The designed hybrid system is tested in real-time on a real engine control unit (ECU) in a model-in-the-loop structure. The results indicate the new hybrid controller reduces the HC emissions over 6.5% compared to nonswitching cold start controller designs.
Experimental Evaluation of Hydrodynamic Bearings for a High Speed Turbocharger
Authors: Kirk Robley G.
Published: January 2014

Many high speed turbochargers are known to operate with limit cycle vibration as a result of fluid-film instability. The goal of this research was to achieve a stable synchronous response with a minimum of self-excited nonsynchronous contribution. Those vibration components excited by the engine harmonics and exhaust pressure pulsations were not the target of this research. This paper will review the experimental results of the fixed geometry fluid-film bearing designs selected to replace the standard stock floating-ring design. In addition, the paper documents a novel radial tilting pad bearing concept that was designed to replace the fixed geometry bearings, with a minimum of modification to the stock bearing housing. A summary of the on-engine testing over the past seven years is documented in this paper.
Forced Response Analysis of a Mistuned Compressor Blisk
Authors: Beirow Bernd , Giersch Thomas , Kühhorn Arnold , Nipkau Jens
Published: January 2014

The forced response of an E3E-type high pressure compressor (HPC) blisk front rotor is analyzed with regard to varying mistuning and the consideration of the fluid-structure interaction (FSI). For that purpose, a reduced order model is used in which the disk remains unchanged and mechanical properties of the blades, namely stiffness and damping, are adjusted to measured as well as intentional blade frequency mistuning distributions. The aerodynamic influence coefficient technique is employed to model the aeroelastics. Depending on the blade mode, the exciting engine order, and aerodynamic influences, it is sought for the worst mistuning distributions with respect to the maximum blade displacement based on optimization analyses. Genetic algorithms using blade-alone frequencies as design variables are applied. The validity of the Whitehead limit is assessed in this context. In particular, the question is addressed if and how far aeroelastic effects, mainly caused by aerodynamic damping, combined with mistuning can even cause a reduction of the forced response compared to the ideally tuned blisk. It is shown that the strong dependence of the aerodynamic damping on the interblade phase angle is the main driver for a possible response attenuation considering the fundamental as well as a higher blade mode. Furthermore, the differences to the blisk vibration response without a consideration of the flow and an increase of the disk's stiffness are discussed. Closing, the influence of pure damping mistuning is analyzed again using optimization.
Thermal Analysis of Air-Cooled Electronic Units With Integrated Offset Strip-Fin Heat Sink
Authors: Sundén Bengt , Xie Gongnan
Published: January 2014

This short communication addresses a numerical investigation of the thermal behavior of an electronic unit. The unit consists of several parallel planes and on the top and bottom planes heat is generated by a number of electronic chips. The heat is transported by conduction through plastic and copper-invar layers. Finally, the heat is rejected by a forced air stream in the center of the unit. The channel system for the cooling air is designed as an offset strip fin surface. A three-dimensional numerical method based on a thermal resistance or conductance network has been developed. The grid points on the cooling air side are staggered compared to the grid points in the solid materials. Details of the numerical method as well as some temperature distributions on the chip planes are provided.
Startup and Operation of a Supercritical Carbon Dioxide Brayton Cycle
Authors: Clementoni Eric M. , Cox Timothy L. , Sprague Christopher P.
Published: January 2014

Bechtel Marine Propulsion Corporation (BMPC) is testing a supercritical carbon dioxide (S-CO2) Brayton system at the Bettis Atomic Power Laboratory. The 100 kWe integrated system test (IST) is a two shaft recuperated closed Brayton cycle with a variable speed turbine driven compressor and a constant speed turbine driven generator using S-CO2 as the working fluid. The IST was designed to demonstrate operational, control, and performance characteristics of an S-CO2 Brayton power cycle over a wide range of conditions. Initial operation of the IST has proven a reliable method for startup of the Brayton loop and heatup to normal operating temperature (570 °F). An overview of the startup process, including initial loop fill and charging, and heatup to normal operating temperature is presented. Additionally, aspects of the IST startup process which are related to the loop size and component design which may be different for larger systems are discussed.
Room Level Modeling of Air Flow in a Contained Data Center Aisle
Authors: Arghode Vaibhav K. , Joshi Yogendra
Published: January 2014

Cold aisle containment is used in air cooled data centers to minimize direct mixing between cold and hot air. Here, we present room level air flow field investigation for open, partially and fully contained cold aisles. Our previous investigation for rack level modeling has shown that consideration of momentum rise above the tile surface, due to acceleration of air through the pores, significantly improves the predictive capability as compared to the generally used porous jump model. The porous jump model only specifies a step pressure loss at the tile surface without any influence on the flow field. The momentum rise could be included by either directly resolving the tile's pore structure or by artificially specifying a momentum source above the tile surface. In the present work, a modified body force model is used to artificially specify the momentum rise above the tile surface. The modified body force model was validated against the experimental data as well as with the model resolving the tile pore geometry at the rack level and then implemented at the room level. With the modified body force model, much higher hot air entrainment and higher server inlet temperatures were predicted as compared to the porous jump model. Even when the rack air flow requirement is matched with the tile air flow supply, considerable hot air recirculation is predicted. With partial containment, where only a curtain at the top of the cold aisle is deployed and side doors are opened, improved cold air delivery is suggested.
Effective Mitigation of Shock Loads in Embedded Electronic Packaging Using Bilayered Potting Materials
Authors: Meguid S. A. , Zhuo Chen , Yang Fan
Published: January 2014

Shock loads which are characterized by high intensity, short duration, and vibration at varied frequencies can lead to the failure of embedded electronics typically used to operate/control numerous devices. Failure of electronics renders these devices ineffective, since they cannot carry out their intended function. It is therefore the objective of this work to determine the behavior of a typical electronic board assembly subject to severe shock loads and the means to protect the electronics. Specifically, three aspects of the work were considered using 3D finite element (FE) simulations in supercomputer environment. The first was concerned with the dynamic behavior of selected electronic devices subject to shock loads. The second with the ability of different potting materials to attenuate the considered shock loads. The third was with the use of a new bilayer potting configurations to effectively attenuate the shock load and vibration of the electronic board. The shock loads were delivered to the Joint Electron Device Engineering Council (JEDEC) standard board using simulated drop impact test. The effectiveness of different protective potting designs to attenuate the effect of shock loads was determined by considering the two key factors of electronics reliability: the stress in the interconnection and deformation of the printed circuit board. Our results reveal the remarkable effectiveness of the bilayer potting approach over the commonly adopted single potting attenuation strategy.
Effects of the Radial Gap Between Impeller Tips and Volute Tongue Influencing the Performance and Pressure Pulsations of Pump as Turbine
Authors: Yang Sun-Sheng , Liu Hou-Lin , Kong Fan-Yu , Xia Bin , Tan Lin-Wei
Published: January 2014

The radial gap between the impeller tips and volute tongue is an important factor influencing the overall performance and unsteady pressure fields of the pump as turbine (PAT). In this paper, a numerical investigation of the PAT's steady performance with different radial gaps was first performed. The results show that there is an optimal radial gap for a PAT to achieve its highest efficiency. An analysis of the PAT's unsteady pressure fields indicates that the rotorstator interaction of a rotating impeller and stationery volute would cause high frequency unsteady pulsation within the volute and low frequency unsteady pressure pulsation within the impeller. The high frequency unsteady pressure pulsation would propagate through the PAT's flow channel. Thus, the unsteady pressure field within the impeller is the combined effect of these two kinds of pressure pulsations. The unsteady pressure pulsation within the outlet pipe is mainly caused by the propagation of unsteady pressure formed within the volute. With the increase of the radial gap, the amplitude of high frequency unsteady pressure pulsation within the volute caused by the rotor-stator interaction is decreased, while the amplitude of the low frequency unsteady pressure pulsation caused by the rotor-stator interaction within the impeller remains unchanged.
Stochastic Characteristics in Microgrinding Wheel Static Topography
Authors: Kunz Jacob A. , Rhett Mayor J.
Published: January 2014

Superabrasive grind wheels are used for the machining of brittle materials such as tungsten carbide. Stochastic modeling of the wheel topography can allow for statistical bounding of the grind force characteristics allowing improved surface quality without sacrificing productivity. This study utilizes a machine vision method to measure the wheel topography of diamond microgrinding wheels. The results showed that there are large variances in wheel specifications from the manufacturer and that microgrinding wheels suffer from statistical scaling effects that increase wheel-to-wheel variability in the topography. Analysis of the static grit density values measured on the microgrinding wheels showed that the distributions provided by both analytic stochastic and numerical simulation models accurately predicted the static grit density within a significance level of 5%. Utilizing only manufacturer-supplied specifications caused the models to predict the static grit density with errors as large as 25.3% of the predicted value leading to a need for improved wheel tolerancing and in situ wheel measurement. The spacings between the grits on the wheel surface were shown to be independent of direction and can best be described by a loglogistic distribution.
Research on the Dynamic Calibration of Thermocouple and Temperature Excitation Signal Generation Method Based on Shock-Tube Theory
Authors: Yang Zhaoxin , Meng Xiaofeng
Published: January 2014

This paper introduces the equipment for generating an excitation signal during the process of thermocouple dynamic calibration in air medium, with the objective of dealing with the problems existing extensively in the excitation signal of incapable assessment of the rising time and inaccuracy in the traceability for the step amplitude. Based on the shock-tube theory, the step-temperature excitation signal that is suitable for the dynamic calibration of the thermocouple with appreciable rising time, wide-frequency bandwidth, and traceable step amplitude can be generated by means of the improvement in the structure of the traditional shock tube as well as the compensation of the shock-tube parameters. Through on-site assessment experimentation and dynamic modeling of the thermocouple, the time constant of the thermocouple can be obtained and the dynamic response of the thermocouple can be modified and compensated, the calibration result of which shows that the dynamic calibration method of the thermocouple proposed in this paper can be implemented for different ranges of frequencies and different phases of the temperature sensor with high reliability; moreover, the calibration equipment is miniaturized.
Turbojet Engine Performance Tuning With a New Map Adaptation Concept
Authors: Alberto Misté Gianluigi , Benini Ernesto
Published: January 2014

Gas turbine off design performance prediction is strictly dependent on the accuracy of compressor and turbine map characteristics. Experimental data regarding component maps are very difficult to find in literature, since it is undisclosed proprietary information of the engine manufacturers. To overcome this limitation, gas turbine engineers use available generic component maps and modify them to reach the maximum adherence with the experimental measures. Different scaling and adaptation techniques have been employed to this aim; these methodologies are usually based upon analytic regression models which minimize the deviation from experimental data. However, since these models are built mainly for a specific compressor or turbine map, their generalization is quite difficult: in fact, regression is highly shape-dependent and, therefore, requires a different model for each different specific component. This paper proposes a solution to the problem stated above: a new method for map adaptation is investigated to improve steady-state off design prediction accuracy of a generic gas turbine component. The methodology does not employ analytical regression models; its main principle relies in performing map modifications in an appropriate neighborhood of the multiple experimental points used for the adaptation. When using gas turbine simulation codes, component maps are usually stored in a data matrix and are ordered in a format suitable for 2D interpolation. A perturbation of the values contained in the matrix results in component map morphing. An optimization algorithm varies the perturbation intensity vector in order to minimize the deviation between experimental and predicted points. The adaptation method is integrated inside TSHAFT, the gas turbine prediction code developed at the University of Padova. The assessment of this methodology will be exposed by illustrating a case study carried out upon a turbojet engine.
Experimental Investigation of a Hollow Cone Spray Using Laser Diagnostics
Authors: Das Mithun , Chatterjee Souvick , Mukhopadhyay Achintya , Sen Swarnendu
Published: January 2014

Atomization of fuel is a key integral part for efficient combustion in gas turbines. This demands a thorough investigation of the spray characteristics using innovative and useful spray diagnostics techniques. In this work, an experimental study is carried out on a commercial hollow cone nozzle (Lechler) using laser diagnostics techniques. A hollow cone spray is useful in many applications because of its ability to produce fine droplets. But apart from the droplet diameter, the velocity field in the spray is also an important parameter to monitor and has been addressed in this work. Kerosene is used as the test fuel, which is recycled using a plunger pump providing a variation in the injection pressure from 100 to 300 psi. An innovative diagnostic technique used in this study is through illumination of the spray with a continuous laser sheet and capturing the same with a high speed camera. A ray of a laser beam is converted to a planer sheet using a lens combination which is used to illuminate a cross section of the hollow cone spray. This provides a continuous planar light source which allows capturing high speed images at 285 fps. The high speed images thus obtained are processed to understand the nonlinearity associated with disintegration of the spray into fine droplets. The images are shown to follow a fractal representation and the fractal dimension is found to increase with rise in injection pressure. Also, using PDPA, the droplet diameter distribution is calculated at different spatial and radial locations at a wide range of pressure.
An Automated Process Sequence Design and Finite Element Simulation of Axisymmetric Deep Drawn Components
Authors: Fazli Ali , Arezoo Behrooz , Hasanniya Mohammad H.
Published: January 2014

A computer-aided design (CAD) system is developed for automatic process design and finite element (FE) modeling of axisymmetric deep drawn components. Using the theoretical and experimental rules, the system initially designs the process sequence of the component. The obtained process sequence is automatically modeled in abaqus software and the system tests whether failure occurs. The failure is supposed to happen when the fracture is predicted in FE simulation. If failure is predicted, the system changes the appropriate process parameters and carries out the simulation process again until all drawing stages are successful. The system returns the requested parameters for die design such as part geometries in middle stages, drawing forces, blank-holder forces, die, and punch profiles radii. The system is successfully tested for some components found in industry and handbooks.
First Principles and Finite Element Predictions of Radiative Properties of Nanostructure Arrays: Single-Walled Carbon Nanotube Arrays
Authors: Sisto Aaron , Ruan Xiulin , Fisher Timothy S.
Published: January 2014

Recent advances in nanofabrication technology have facilitated the development of arrays of nanostructures in the classical or quantum confinement regime, e.g., single-walled carbon nanotube (SWCNT) arrays with long-range order across macroscopic dimensions. So far, an accurate generalized method of modeling radiative properties of these systems has yet to be realized. In this work, a multiscale computational approach combining first-principles methods based on density functional theory (DFT) and classical electrodynamics simulations based on the finite element method (FEM) is described and applied to the calculations of optical properties of macroscopic SWCNT arrays. The first-principles approach includes the use of the GW approximation and Bethe–Salpeter methods to account for excited electron states, and the accuracy of these approximations is assessed through evaluation of the absorption spectra of individual SWCNTs. The fundamental mechanisms for the unique characteristics of extremely low reflectance and high absorptance in the near-IR are delineated. Furthermore, opportunities to tune the optical properties of the macroscopic array are explored.
On Multilayer Modeling of Radiative Transfer for Use With the Multisource k-Distribution Method for Inhomogeneous Media
Authors: Tencer John , Howell John R.
Published: January 2014

A nonisothermal medium is modeled using the multilayer approach in which the continuous temperature distribution in a one-dimensional system as modeled as being piecewise constant. This has been shown to provide accurate results for a surprisingly small number of layers. Analysis is performed on a nonisothermal gray medium to attempt to characterize the ways in which the errors introduced by the multilayer modeling change with various physical parameters namely, the optical thickness and the temperature or emissive power gradient. A demonstration is made of how the multisource k-distribution method is capable of evaluating the heat flux within a one-dimensional system with piecewise constant temperature distribution with line-by-line accuracy with a significant decrease in computational expense. The k-distribution method for treating the spectral properties of an absorbing–emitting medium represents a powerful alternative to line-by-line calculations by reducing the number of radiative transfer equation (RTE) evaluations from the order of a million to the order of 10 without any significant loss of accuracy. For problems where an appropriate reference temperature can be defined, the k-distribution method is formally exact. However, when no appropriate reference temperature can be defined, the method results in errors. The multisource k-distribution method extends the k-distribution method to problems with piecewise constant temperature and optical properties.
Energy Harvester Synthesis Via Coupled Linear-Bistable System With Multistable Dynamics
Authors: Wu Z. , Harne R. L. , Wang K. W.
Published: January 2014

In this research we study the dynamics of a coupled linear oscillator-bistable energy harvester system. The method of harmonic balance and perturbation analysis are used to predict the existence and stability of the bistable device interwell vibration. The influences of important parameters on tailoring the coupled system response are investigated to determine strategies for improved energy harvesting performance. We demonstrate analytically that for excitation frequencies in a bandwidth less than the natural frequency of the uncoupled linear oscillator having net mass that is the combination of the bistable and linear bodies, the bistable harvester dynamics may be substantially intensified as compared to a single (individual) bistable harvester. In addition, the linear-bistable coupled system may introduce a stable out-of-phase dynamic around the natural frequency of the uncoupled linear oscillator, enhancing the performance of the harvester by providing a second interwell response not possible when using a single bistable harvester. Key analytical findings are confirmed through numerical simulations and experiments, validating the predicted trends and demonstrating the advantages of the coupled system for energy harvesting.
Temperature Effect on Phase-Transition Radiation of Water
Authors: Brewster M. Q. , Wang K.-T. , Wu W.-H. , Khan M. G.
Published: January 2014

Infrared radiation associated with vapor-liquid phase transition of water is investigated using a suspension of cloud droplets and mid-infrared (IR) (3–5 μm) radiation absorption measurements. Recent measurements and Monte Carlo (MC) modeling performed at 60 °C and 1 atm resulted in an interfacial radiative phase-transition probability of 5 × 10−8 and a corresponding surface absorption efficiency of 3–4%, depending on wavelength. In this paper, the measurements and modeling have been extended to 75 °C in order to examine the effect of temperature on water's liquid-vapor phase-change radiation. It was found that the temperature dependence of the previously proposed phase-change absorption theoretical framework by itself was insufficient to account for observed changes in radiation absorption without a change in cloud droplet number density. Therefore, the results suggest a strong temperature dependence of cloud condensation nuclei (CCN) concentration, i.e., CCN increasing approximately a factor of two from 60 °C to 75 °C at near saturation conditions. The new radiative phase-transition probability is decreased slightly to 3 × 10−8. Theoretical results were also calculated at 50 °C in an effort to understand behavior at conditions closer to atmospheric. The results suggest that accounting for multiple interface interactions within a single droplet at wavelengths in atmospheric windows (where anomalous IR radiation is often reported) will be important. Modeling also suggests that phase-change radiation will be most important at wavelengths of low volumetric absorption, i.e., atmospheric windows such as 3–5 μm and 8–10 μm, and for water droplets smaller than stable cloud droplet sizes (<20 μm diameter), where surface effects become relatively more important. This could include unactivated, hygroscopic aerosol particles (not CCN) that have absorbed water and are undergoing dynamic evaporation and condensation. This mechanism may be partly responsible for water vapor's IR continuum absorption in these atmospheric windows.
Effect of formalin fixation on thermal conductivity of the biological tissue
Authors: Bauserman Steven C. , Valvano Jonathan W.
Published: January 2014

Effect of formalin fixation on thermal conductivity of the biological tissues is presented. A self-heated thermistor probe was used to measure the tissue thermal conductivity. The thermal conductivity of muscle and fatty tissue samples was measured before the formalin fixation and then 27 hours after formalin fixation. The results indicate that the formalin fixation does not cause a significant change in the tissue thermal conductivity of muscle and fatty tissues. In the clinical setting, tissues removed surgically are often fixed in formalin for subsequent pathological analysis. These results suggest that, in terms of thermal properties, it is equally appropriate to perform in vitro studies in either fresh tissue or formalin-fixed tissue.
Planar Shock Focusing Through Perfect Gas Lens: First Experimental Demonstration
Authors: Biamino Laurent , Mariani Christian , Jourdan Georges , Houas Lazhar , Vandenboomgaerde Marc , Souffland Denis
Published: January 2014

When a shock wave crosses an interface between two materials, this interface becomes unstable and the Richtmyer–Meshkov instability develops. Such instability has been extensively studied in the planar case, and numerous results were presented during the previous workshops. But the Richtmyer–Meshkov (Richtmyer, 1960, “Taylor Instability in Shock Acceleration of Compressible Fluids,” Commun. Pure Appl. Math., 13(2), pp. 297–319; Meshkov, 1969, “Interface of Two Gases Accelerated by a Shock Wave,” Fluid Dyn., 4(5), pp. 101–104) instability also occurs in a spherical case where the convergence effects must be taken into account. As far as we know, no conventional (straight section) shock tube facility has been used to experimentally study the Richtmyer–Meshkov instability in spherical geometry. The idea originally proposed by Dimotakis and Samtaney (2006, “Planar Shock Cylindrical Focusing by a Perfect-Gas Lens,” Phys. Fluid., 18(3), pp. 031705–031708) and later generalized by Vandenboomgaerde and Aymard (2011, “Analytical Theory for Planar Shock Focusing Through Perfect Gas Lens and Shock Tube Experiment Designs,” Phys. Fluid., 23(1), pp. 016101–016113) was to retain the flexibility of a conventional shock tube to convert a planar shock wave into a cylindrical one through a perfect gas lens. This can be done when a planar shock wave passes through a shaped interface between two gases. By coupling the shape with the impedance mismatch at the interface, it is possible to generate a circular transmitted shock wave. In order to experimentally check the feasibility of this approach, we have implemented the gas lens technique on a conventional shock tube with the help of a convergent test section, an elliptic stereolithographed grid, and a nitrocellulose membrane. First experimental sequences of schlieren images have been obtained for an incident shock wave Mach number equal to 1.15 and an air/SF6-shaped interface. Experimental results indicate that the shock that moves in the converging part has a circular shape. Moreover, pressure histories that were recorded during the experiments show pressure increase behind the accelerating converging shock wave.
Large Eddy Simulation of a Free Circular Jet
Authors: Gohil Trushar B. , Saha Arun K. , Muralidhar K.
Published: January 2014

A large eddy simulation (LES) of an incompressible spatially developing circular jet at a Reynolds number of 10,000 is performed. The shear-improved Smagorinsky model (Lévêque et al., 2007, “A Shear-Improved Smagorinsky Model for the Large-Eddy Simulation of Wall-Bounded Turbulent Flows,” J. Fluid Mech., 570, pp. 491–502) is used for the resolution of the subgrid stress tensor within the filtered three-dimensional unsteady Navier–Stokes equations. Higher-order spatial and temporal discretization schemes are used for capturing the details of the turbulent flow field. With the help of instantaneous and time-averaged flow data, the spatial transition from the laminar state to the turbulent is analyzed. Flow structures are visualized using isosurfaces of the Q-criterion. Instantaneous flow patterns show single tearing and multiple pairing processes. Tracing individual vortex rings over a longer time period, a detailed understanding of the vortex interaction is revealed. The observed trends and the length of the potential core are in conformity with the findings of earlier experiments. The time-averaged axial velocity profile shows that the jet attains self-similarity and the computed profile matches well with the experimental results of Hussein et al. (1994, “Velocity Measurements in a High-Reynolds-Number, Momentum-Conserving, Axisymmetric, Turbulent Jet,” J. Fluid Mech., 258, pp. 31–75). The centerline decay of the velocity and entrainment rate are in agreement with published experiments. The Reynolds stress components u'u'¯, v'v'¯, and u'v'¯ and the third-order velocity moment are in good agreement with thr experimental results, thus confirming the validity of the present simulation.
Gear Dynamics Analysis With Turbulent Journal Bearings Mounted Hybrid Squeeze Film Damper—Chaos and Active Control Analysis
Authors: Chang-Jian Cai-Wan
Published: January 2014

The hybrid squeeze film damper mounted turbulent journal bearing–gear system is proposed in this paper. The nonlinear dynamics of a gear pair supported by such bearing is studied. Numerical results show that, due to the nonlinear factors of lubricant film force, the trajectory of the pinion demonstrates a complex dynamics with dimensionless unbalance parameters. Poincaré maps and bifurcation diagrams are used to analyze the behavior of the pinion trajectory in the horizontal direction. The maximum Lyapunov exponent is used to determine if the system is in a state of chaotic motion. In order to avoid the nonsynchronous chaotic vibrations, an increased proportional gain kp = 0.1 is applied to control this system. It is shown that the pinion trajectory will leave chaotic motion to periodic motion in the steady state under control action.
A Formulation on the Special Euclidean Group for Dynamic Analysis of Multibody Systems
Authors: Sonneville Valentin , Brüls Olivier
Published: January 2014

This paper presents a finite element approach of multibody systems using the special Euclidean group SE(3) framework. The development leads to a compact and unified mixed coordinate formulation of the rigid bodies and the kinematic joints. Flexibility in the kinematic joints is also easily introduced. The method relies on local description of motions, so that it provides a singularity-free formulation and exhibits important advantages regarding numerical implementation. A practical case is presented to illustrate the method.
Dynamic Analysis of Cable-Driven Parallel Manipulators Using a Variable Length Finite Element
Authors: Du Jingli , Cui Chuanzhen , Bao Hong , Qiu Yuanying
Published: January 2014

Cable-driven parallel manipulator (CDPM) is a good solution to achieving large workspace. However, unavoidable vibrations of long cables can dramatically degrade the positioning performance in large workspace applications. Most work so far on cable-driven parallel manipulators (CDPMs) simply neglected the dynamics of the cables themselves. In this paper dynamic modeling of large CDPMs is addressed using a variable domain finite element method (FEM). A cable element with variable length is derived using the absolute nodal coordinate formulation to facilitate motion analysis of CDPMs. The effects of cable length variation and the resulting mass variation are also considered. Based on this element dynamics model of CDPMs can be readily obtained using the standard assembling operation in the FEM. Numerical results showed that the effect of the derivatives of cable length variation and that of the mass variation are trivial.
Optimal Sensor Placement for Substructural Response Reconstruction
Authors: Ye Q. , Law S. S.
Published: January 2014

In an existing substructural dynamic response reconstruction method (Li, J., and Law, S.S., 2011. “Substructural Response Reconstruction in Wavelet Domain,” ASME J. Appl. Mech., 78(4), p. 041010) developed by Law, two sets of sensors are needed for the reconstruction of dynamic responses at selected degrees-of-freedom. A method to find the optimal sensor placement is presented in this paper for the substructural response reconstruction. It is based on the effective independence method but in the time domain. Unlike previous methods on sensor placement, two sets of optimal sensor placement are needed with the first set for estimating the interface forces between substructures, and the second set for reconstructing the responses. Sensors that capture the most information of the interface forces will be selected into the first set, and the subsequently estimated interface forces are used to reconstruct the responses at the second set of selected degrees-of-freedom. The selection of the second set of sensors is based on the least measurement noise effect in the response reconstruction process. A box-section bridge deck is adopted in the simulation studies. Numerical simulations with the forward and backward sequential sensor placement methods show that the proposed method could give reasonable predictions with smaller error in the reconstructed responses, and sensor locations along the major directions of the interface forces should be selected into the first or the second set of sensor configuration.