bluuebunny/crossref_metadata_2025 huggingface dataset:
Rehabilitation following hospitalization in patients with COPD: Can it reduce readmissions?
Authors: Maddocks Matthew , Kon Samantha S.C. , Singh Sally J. , Man William D.‐C.
Published: December 2014

Exacerbations of chronic obstructive pulmonary disease (COPD) are one of the commonest causes of emergency hospital admission and are associated with high rates of readmission. Rehabilitation in the peri‐ and early post‐hospitalization setting may counteract the deleterious consequences of an acute hospital admission and target modifiable risk factors for readmission such as physical inactivity, reduced exercise capacity and impaired physical function. Pulmonary rehabilitation in the peri‐hospitalization period can improve exercise capacity and health‐related quality of life and can also reduce rates of readmission. Consequently, guidelines have recommended the provision of pulmonary rehabilitation in the acute setting. However, recent trials showing less positive results and observational data questioning acceptability may challenge prevailing enthusiasm. This review examines the role of pulmonary rehabilitation in the peri‐ and early post‐hospitalization setting, considering the modifiable risk factors for readmission, the latest evidence regarding rehabilitation in the acute setting, issues around acceptability and uptake, and alternative strategies to help deliver rehabilitation to more patients. The acceptability and effectiveness of pulmonary rehabilitation offered that post‐exacerbation could be improved by overcoming issues around the setting, timing and format of rehabilitation approaches, including their integration with self‐management interventions.
Development of quality indicators to evaluate antibiotic treatment of patients with community‐acquired pneumonia in Indonesia
Authors: Farida Helmia , Rondags Angelique , Gasem M. Hussein , Leong Katharina , Adityana A. , van den Broek Peterhans J. , Keuter Monique , Natsch Stephanie
Published: December 2014

Objective

To develop an instrument for evaluating the quality of antibiotic management of patients with community‐acquired pneumonia (CAP) applicable in a middle‐income developing country.

Method

A previous study and Indonesian guidelines were reviewed to derive potential quality of care indicators (QIs). An expert panel performed a two‐round Delphi consensus procedure on the QI's relevance to patient recovery, reduction of antimicrobial resistance and cost containment. Applicability in practice, including reliability, feasibility and opportunity for improvement, was determined in a data set of 128 patients hospitalised with CAP in Semarang, Indonesia.

Results

Fifteen QIs were selected by the consensus procedure. Five QIs did not pass feasibility criteria, because of inappropriate documentation, inefficient laboratory services or patient factors. Three QIs provided minor opportunity for improvement. Two QIs contradicted each other; one of these was considered not valid and excluded. A final set of six QIs was defined for use in the Indonesian setting.

Conclusion

Using the Delphi method, we defined a list of QIs for assessing the quality of care, in particular antibiotic treatment, for CAP in Indonesia. For further improvement, a modified Delphi method that includes discussion, a sound medical documentation system, improvement of microbiology laboratory services, and multi‐center applicability tests are needed to develop a valid and applicable QI list for the Indonesian setting.
Implementing WHO hospital guidelines improves quality of paediatric care in central hospitals in Lao PDR
Authors: Gray Amy Zigrida , Soukaloun Douangdao , Soumphonphakdy Bandith , Duke Trevor
Published: December 2014

Objectives

To evaluate the impact of implementing a multifaceted intervention based on the WHO Pocketbook of Hospital Care for Children on the quality of case management of common childhood illnesses in hospitals in Lao PDR.

Methods

The quality of case management of four sentinel conditions was assessed in three central hospitals before and after the implementation of the WHO Pocketbook as part of a broader mixed‐methods study. Data on performance of key steps in case management in more than 600 admissions were collected by medical record abstraction pre‐ and post‐intervention, and change was measured according to the proportion of cases which key steps were performed as well as an overall score of case management for each condition.

Results

Improvements in mean case management scores were observed post‐intervention for three of the four conditions, with the greatest change in pneumonia (53–91%), followed by diarrhoea and low birthweight. Rational drug prescribing, appropriate use of IV fluids and appropriate monitoring all occurred more frequently post‐intervention. Non‐recommended practices such as prescription of antitussives became less frequent.

Conclusions

A multifaceted intervention based on the WHO Pocketbook of Hospital Care for children led to better paediatric care in central Lao hospitals. The degree of improvement was dependent on the condition assessed.
FEASIBILITY FOR DETECTING LIVER METASTASES IN DOGS USING GADOBENATE DIMEGLUMINE‐ENHANCED MAGNETIC RESONANCE IMAGING
Authors: Louvet Arnaud , Duconseille Anne‐Carole
Published: December 2014

Early detection of liver metastases may improve the prognosis for successful treatment in dogs with primary tumors. Hepatobiliary‐specific contrast agents have been shown to allow an increase in magnetic resonance imaging (MRI) detection of liver metastases in humans. The purpose of this prospective study was to test the feasibility for using one of these agents, gadobenate dimeglumine, to detect liver metastases in dogs. Ten consecutive dogs known to have a primary tumor were recruited for inclusion in the study. All dogs were scanned using the same protocol that included a T2‐weighted respiratory‐triggered sequence, T1 VIBE, diffusion‐weighted imaging, and 3D‐FLASH before and after dynamic injection of gadobenate dimeglumine contrast medium. Delayed imaging was performed less than 30 min after injection and up to 60 min in two cases. Histological analysis of liver lesions identified in delayed phases was performed for each case and confirmed metastatic origin. In all cases, lesion number detected in hepatobiliary contrast‐enhanced sequences was statistically higher than in other sequences. Optimal lesion detection occurred with a 3D‐FLASH sequence acquired in the transverse plane and less than 30 min after injection. Findings indicated that gabobenate dimeglumine enhanced MRI is a feasible technique for detecting liver metastases in dogs.
A large‐scale molecular survey ofClinostomum(Digenea, Clinostomidae)
Authors: Locke Sean A. , Caffara Monica , Marcogliese David J. , Fioravanti Maria L.
Published: December 2014

Members of the genusClinostomumLeidy, 1856 are parasites that mature in birds, with occasional reports in humans. Because morphological characters for reliable discrimination of species are lacking, the number of species considered valid has varied by an order of magnitude. In this study, sequences from theDNAbarcode region of cytochrome c oxidase I (CO1) and/or internal transcribed spacer (ITS) from specimens from Mexico, Bolivia, Peru, Brazil, Kenya, China and Thailand were analysed together with published sequences from Europe, Africa, Indonesia and North America. AlthoughITSandCO1 distances among specimens were strongly correlated, distance‐based analysis of each marker yielded different groups. Putative species indicated byCO1 distances were consistent with available morphological identifications, while those indicated byITSconflicted with morphological identifications in three cases. There was little overlap in sequence variation within and between species, particularly forCO1. AlthoughITSandCO1 distances tended to increase in specimens that were further apart geographically, this did not impair distance‐based species delineation. Phylogenetic analysis suggests a deep division between clades ofClinostomuminhabiting the New World and Old World, which parallels the distribution of their principal definitive hosts, the Ardeidae.
Effective limit distribution of the Frobenius numbers
Authors: Li Han
Published: December 2014

The Frobenius number$F(\boldsymbol{a})$of a lattice point$\boldsymbol{a}$in$\mathbb{R}^{d}$with positive coprime coordinates, is the largest integer which cannotbe expressed as a non-negative integer linear combination of the coordinates of$\boldsymbol{a}$. Marklof in [The asymptotic distribution of Frobenius numbers, Invent. Math.181(2010), 179–207] proved the existence of the limit distribution of the Frobenius numbers, when$\boldsymbol{a}$is taken to be random in an enlarging domain in$\mathbb{R}^{d}$. We will show that if the domain has piecewise smooth boundary, the error term for the convergence of the distribution function is at most a polynomial in the enlarging factor.
Involvement of multiple taste receptors in umami taste: analysis of gustatory nerve responses in metabotropic glutamate receptor 4 knockout mice
Authors: Yasumatsu Keiko , Manabe Tomohiro , Yoshida Ryusuke , Iwatsuki Ken , Uneyama Hisayuki , Takahashi Ichiro , Ninomiya Yuzo
Published: December 2014

Key points

The taste receptor T1R1 + T1R3 heterodimer and metabotropic glutamate receptors (mGluR) may function as umami taste receptors.

Here, we used mGluR4 knockout (mGluR4‐KO) mice and examined the function of mGluR4 in peripheral taste responses of mice.

The mGluR4‐KO mice showed reduced responses to glutamate and l‐AP4 (mGluR4 agonist) in the chorda tympani and glossopharyngeal nerves without affecting responses to other taste stimuli.

Residual glutamate responses in mGluR4‐KO mice were suppressed by gurmarin (T1R3 blocker) and AIDA (group I mGluR antagonist).

The present study not only provided functional evidence for the involvement of mGluR4 in umami taste responses, but also suggested contributions of T1R1 + T1R3 and mGluR1 receptors in glutamate responses.

Umami taste is elicited by l‐glutamate and some other amino acids and is thought to be initiated by G‐protein‐coupled receptors. Proposed umami receptors include heterodimers of taste receptor type 1, members 1 and 3 (T1R1 + T1R3), and metabotropic glutamate receptors 1 and 4 (mGluR1 and mGluR4). Accumulated evidences support the involvement of T1R1 + T1R3 in umami responses in mice. However, little is known about the in vivo function of mGluR in umami taste. Here, we examined taste responses of the chorda tympani (CT) and the glossopharyngeal (GL) nerves in wild‐type mice and mice genetically lacking mGluR4 (mGluR4‐KO). Our results indicated that compared to wild‐type mice, mGluR4‐KO mice showed significantly smaller gustatory nerve responses to glutamate and l‐(+)‐2‐amino‐4‐phosphonobutyrate (an agonist for group III mGluR) in both the CT and GL nerves without affecting responses to other taste stimuli. Residual glutamate responses in mGluR4‐KO mice were not affected by (RS)‐alpha‐cyclopropyl‐4‐phosphonophenylglycine (an antagonist for group III mGluR), but were suppressed by gurmarin (a T1R3 blocker) in the CT and (RS)‐1‐aminoindan‐1,5‐dicarboxylic acid (an antagonist for group I mGluR) in the CT and GL nerve. In wild‐type mice, both quisqualic acid (an agonist for group I mGluR) and l‐(+)‐2‐amino‐4‐phosphonobutyrate elicited gustatory nerve responses and these responses were suppressed by addition of (RS)‐1‐aminoindan‐1,5‐dicarboxylic acid and (RS)‐alpha‐cyclopropyl‐4‐phosphonophenylglycine, respectively. Collectively, the present study provided functional evidences for the involvement of mGluR4 in umami taste responses in mice. The results also suggest that T1R1 + T1R3 and mGluR1 are involved in umami taste responses in mice. Thus, umami taste would be mediated by multiple receptors.
Permeabilization of brain tissue in situ enables multiregion analysis of mitochondrial function in a single mouse brain
Authors: Herbst Eric A.F. , Holloway Graham P.
Published: December 2014

Key points

Mitochondrial function in the brain is traditionally assessed through analysing respiration in isolated mitochondria, a technique that possesses significant tissue and time requirements while also disrupting the cooperative mitochondrial reticulum.

We permeabilized brain tissue in situ to permit analysis of mitochondrial respiration with the native mitochondrial morphology intact, removing the need for isolation time and minimizing tissue requirements to ∼2 mg wet weight.

The permeabilized brain technique was validated against the traditional method of isolated mitochondria and was then further applied to assess regional variation in the mouse brain with ischaemia–reperfusion injuries.

A transgenic mouse model overexpressing catalase within mitochondria was applied to show the contribution of mitochondrial reactive oxygen species to ischaemia–reperfusion injuries in different brain regions.

This technique enhances the accessibility of addressing physiological questions in small brain regions and in applying transgenic mouse models to assess mechanisms regulating mitochondrial function in health and disease.

Mitochondria function as the core energy providers in the brain and symptoms of neurodegenerative diseases are often attributed to their dysregulation. Assessing mitochondrial function is classically performed in isolated mitochondria; however, this process requires significant isolation time, demand for abundant tissue and disruption of the cooperative mitochondrial reticulum, all of which reduce reliability when attempting to assess in vivo mitochondrial bioenergetics. Here we introduce a method that advances the assessment of mitochondrial respiration in the brain by permeabilizing existing brain tissue to grant direct access to the mitochondrial reticulum in situ. The permeabilized brain preparation allows for instant analysis of mitochondrial function with unaltered mitochondrial morphology using significantly small sample sizes (∼2 mg), which permits the analysis of mitochondrial function in multiple subregions within a single mouse brain. Here this technique was applied to assess regional variation in brain mitochondrial function with acute ischaemia–reperfusion injuries and to determine the role of reactive oxygen species in exacerbating dysfunction through the application of a transgenic mouse model overexpressing catalase within mitochondria. Through creating accessibility to small regions for the investigation of mitochondrial function, the permeabilized brain preparation enhances the capacity for examining regional differences in mitochondrial regulation within the brain, as the majority of genetic models used for unique approaches exist in the mouse model.
RuSe Electrocatalysts and Single Wall Carbon Nanohorns Supports for the Oxygen Reduction Reaction
Authors: Morawa Eblagon Katarzyna , Brandão Lúcia
Published: December 2014

Selenium modified ruthenium electrocatalysts supported on carbon black were synthesized using NaBH4 reduction of the metal precursor. Prepared Ru/C electrocatalysts showed high dispersion and very small averaged particle size. These Ru/C electrocatalysts were subsequently modified with Se following two procedures: (a) preformed Ru/carbon catalyst was mixed with SeO2 in xylene and reduced in H2 and (b) Ru metal precursor was mixed with SeO2 followed by reduction with NaBH4. The XRD patterns indicate that a pyrite-type structure was obtained at higher annealing temperatures, regardless of the Ru:Se molar ratio used in the preparation step. A pyrite-type structure also emerged in samples that were not calcined; however, in this case, the pyrite-type structure was only prominent for samples with higher Ru:Se ratios. The characterization of the RuSe/C electrocatalysts suggested that the Se in noncalcined samples was present mainly as an amorphous skin. Preliminary study of activity toward oxygen reduction reaction (ORR) using electrocatalysts with a Ru:Se ratio of 1:0.7 indicated that annealing after modification with Se had a detrimental effect on their activity. This result could be related to the increased particle size of crystalline RuSe2 in heat-treated samples. Higher activity of not annealed RuSe/C catalysts could also be a result of the structure containing amorphous Se skin on the Ru crystal. The electrode obtained using not calcined RuSe showed a very promising performance with a slightly lower activity and higher overpotential in comparison with a commercial Pt/C electrode. Single wall carbon nanohorns (SWNH) were considered for application as ORR electrocatalysts' supports. The characterization of SWNH was carried out regarding their tolerance toward strong catalyzed corrosion conditions. Tests indicated that SWNH have a three times higher electrochemical surface area (ESA) loss than carbon black or Pt commercial electrodes.
Oxygen Reduction Activity on a Nanosized Perovskite-Type Oxide Prepared by Polyvinyl Pyrrolidone Method
Authors: Nagai Tsukasa , Fujiwara Naoko , Kitta Mitsunori , Asahi Masafumi , Yamazaki Shin-ichi , Siroma Zyun , Ioroi Tsutomu
Published: December 2014

A nanosized perovskite-type oxide supported on carbon black (perovskite/C) was prepared by the polyvinyl pyrrolidone (PVP) addition method and subsequent mechanical milling with carbon black. Transmission electron microscope (TEM) observation and scanning transmission electron microscope (STEM)–energy dispersive X-ray (EDX) mapping clearly revealed that the oxide prepared by the PVP method was small (ca. 20 nm) and highly dispersed on the carbon support. The oxygen reduction reaction (ORR) activity on the perovskite/C catalyst was investigated with rotating ring-disk electrode (RRDE) measurement in an alkaline solution at 25 °C. The prepared perovskite/C catalyst showed enhanced activity compared to catalysts obtained by the conventional solid state reaction and citrate process; i.e., a positive shift of the onset potential and increased ORR current at a disk electrode. The present catalyst was also associated with decreased ring current.
Collagen Structure and Mechanical Properties of the Human Sclera: Analysis for the Effects of Age
Authors: Coudrillier Baptiste , Pijanka Jacek , Jefferys Joan , Sorensen Thomas , Quigley Harry A. , Boote Craig , Nguyen Thao D.
Published: December 2014

The objective of this study was to measure the collagen fiber structure and estimate the material properties of 7 human donor scleras, from age 53 to 91. The specimens were subjected to inflation testing, and the full-field displacement maps were measured by digital image correlation. After testing, the collagen fiber structure was mapped using wide-angle X-ray scattering. A specimen-specific inverse finite element method was applied to calculate the material properties of the collagen fibers and interfiber matrix by minimizing the difference between the experimental displacements and model predictions. Age effects on the fiber structure and material properties were estimated using multivariate models accounting for spatial autocorrelation. Older age was associated with a larger matrix stiffness (p = 0.001), a lower degree of fiber alignment in the peripapillary sclera (p = 0.01), and a lower mechanical anisotropy in the peripapillary sclera (p = 0.03).
Characterizing Granular Mixing Homogeneity at Various Dimensionless Mixing Lengths in a Double Screw Mixer
Authors: Kingston Todd A. , Heindel Theodore J.
Published: December 2014

Granular mixing processes are commonly used to increase product homogeneity in many industrial applications involving pharmaceuticals, food processing, and energy conversion. Determining the appropriate granular mixing length is necessary to avoid over/under mixing and unnecessary power consumption. The goal of this study is to experimentally characterize the granular mixing process and determine, under various operating conditions, the needed mixing length to achieve adequate mixing in a laboratory-scale double screw mixer. Nine different combinations of screw rotation speeds and dimensionless screw pitches are used to investigate the rate of mixing at dimensionless mixing lengths of L/D = 2, 5, and 10. Composition and statistical analysis methods are employed to assess mixing effectiveness, and it is determined that the dimensionless mixing length is the most influential parameter in terms increasing granular homogeneity. For all the conditions tested, the granular mixture approaches an acceptable level of mixing for all testing conditions when the dimensionless mixing length is L/D = 10. However, the segregation rate throughout the screw mixer is vastly different for various combinations of screw rotation speed and dimensionless screw pitch, and is partly attributed to the influence of entrance effects caused by the material injection process.
Experimental and Numerical Investigation Into Turbulent High Reynolds Number Flows Through a Square Duct With 90-Degree Streamwise Curvature: II — Numerical Methods
Authors: Ondore Faustin
Published: December 2014

A square duct with a 90-degree streamwise curvature is representative of complex flow domains. Such flow domains are encountered in the designs of fluids engineering systems, especially in the aerospace turbo-machinery components. Examples include the gas turbine engine axial compressor interstage spaces, where the rise in air pressure (and hence compressor efficiency) is dependent on suppression of turbulence. In the case of the centrifugal compressor, pressure rise in the U-shaped diffuser assembly where the suppression of turbulence is critical to the attainable pressure ratio. The results obtained from numerical calculations are analysed and discussed along with the corresponding hot-wire measurements and flow visualization result from a wind-tunnel of identical configuration. Calculations are implemented in four turbulent models, i.e. Standard k-e Module, Algebraic Stress Model (ASM), Non-linear Renormalization Group (RNG) - k-e Model and Differential Stress Model (DSM). The discretization up-winding scheme is the Quadratic Up-winding with Interpolation Kinematics (QUICK). Two high Reynolds number turbulent flows are investigated, with mainstream velocities of 12.3 m/s and 20.4 m/s, representing Re=3.56×105 and Re=6.43×105 respectively. Generally strong correlation between theory and experimental data are recorded. Further, as reported in similar studies, the turbulence modules that are formulated to account for turbulence anisotropy return results that more closely match experimental measurements. Uniquely for this configuration, a massive flow detachment is predicted along the convex wall at about the 90° position. Also, the core of the fluid flow is observed to shift from the outer to the inner areas of the bend in proportion to the secondary (recirculating) flow generated by the bend.
A Focus on the Literature Review of Nanorefrigerants
Authors: Dalkılıç Ahmet Selim , Aktaş Melih , Celen Ali , Çebi Alican , Mahian Omid , Wongwises Somchai
Published: December 2014

The heat transfer performance of various thermal devices can be augmented by active and passive techniques. One of the passive techniques is the addition of nanoparticles had the size of 1 and 100 nanometers to the common heat transfer so that the thermal transport properties of the prepared suspension called nanofluid will be enhanced compared to the base fluid. Nanorefrigerants as a special type of nanofluids which are mixtures of nanoparticles and refrigerants have a wide range of applications in diverse fields such as refrigeration, air conditioning systems and heat pumps. In this study, the missing points on this new method are also indicated regarding the lack of studies on the determination of physical properties of nanorefrigerants and the flow of nanoparticles.
A Computational Fluid Study of Falling Film Behavior on Flat Plate
Authors: Yu Yiqi
Published: December 2014

In this paper, the 3D numerical simulations on falling film behaviour on flat plate with and without interfacial gas-liquid shear stress are carried out. The film thickness and velocity distribution of water film flow with different Reynolds numbers are studied. The results agree well with the experimental and theoretical data. The influence of the surface wave on film velocity is revealed. The calculations also investigate the effect of gas-liquid shear stress on solitary waves of falling film.
Effects of Particle Density on Gas-Liquid-Solid Flows in Bubble Columns
Authors: Zhang Xinyu , Ahmadi Goodarz
Published: December 2014

A numerical simulation is performed to study the effects of particle density on gas-liquid-solid flows in bubble columns. An Eulerian-Lagrangian model is used where the liquid flow is modeled by a volume-averaged system of governing equations and motions of particles and bubbles are modeled by Lagrangian trajectory method. Interactions between particle-particle, bubble-bubble, bubble-liquid and particle-liquid are included in the study. The drag, lift, buoyancy, and virtual mass forces are evaluated for the particles and bubbles. Particle-particle and bubble-bubble interactions are accounted for by a hard sphere model. The bubble coalescence is also included in this study. The predicted results were compared with the experimental data in a previous work, and satisfied agreement was obtained. Particles with various density are used in different cases. A parcel method is used to account for particle load. The effects of particle density on gas-liquid-solid three-phase flows are discussed based on the comparison of the transient flow characteristics of these gas-liquid-solid three-phase flows. The simulations show that large particle density may result in weak phase mixing in gas-liquid-solid three-phase flows in bubble columns.
Numerical Simulation on Rupture Behavior and Selection of Safety Membranes
Authors: Sheng Chen , Jian Zhang , Yu Xiaodong
Published: December 2014

This present study deals with a new mechanical device consisting of a set of safety membranes, which has been successfully applied in several middle and small hydropower stations in China instead of a surge tank. Safety membranes are installed on the penstock near the powerhouse as controlled weak points. When the pressure caused by load rejection rises to the preset explosive value, one or more membranes rupture, protecting the penstock and the unit from damage. The device is simple, reliable and economical. The method of characteristics is employed to establish numerical model of safety membranes to simulate their rupture behavior, which is then introduced to investigate how to determine the number and diameter of membranes from two aspects, large fluctuation and hydraulic disturbance. The results show that the diameter of the membranes depends on the negative pressure along pipeline under hydraulic disturbance while the number of the membrane depends on the maximum water hammer pressure under large fluctuation during load rejection of the unit. The conclusion of membrane selection can perfect the present theory of safety membranes, and provide the theoretical guidance and practical basis for membrane device design and safety operation.
Mass Transfer From Single Carbon Dioxide Bubbles in Contaminated Water
Authors: Aoki Jiro , Hayashi Kosuke , Hosoda Shogo , Hosokawa Shigeo , Tomiyama Akio
Published: December 2014

Mass transfer from single carbon dioxide bubbles rising through contaminated water in a vertical pipe of 12.5 mm diameter was measured to investigate effects of surfactant. The bubble diameter was widely varied to cover various bubble shapes such as spheroidal, wobbling, cap and Taylor bubbles. The gas and liquid phases were 99.9 % purity carbon dioxide and a surfactant solution made of purified water and Triton X-100. Comparison of mass transfer rates between contaminated and clean bubbles made clear that the surfactant decreases the mass transfer rates of small bubbles. The Sherwood number of small bubbles in the extreme cases, i.e. zero and the highest surfactant concentrations, is well correlated in terms of the bubble Reynolds number, Schmidt number and the ratio, λ, of the bubble diameter to pipe diameter. The Sherwood numbers at intermediate surfactant concentration, however, are not well correlated using available correlations. The mass transfer rates of Taylor bubbles also decrease with increasing the surfactant concentration. They however increase with the diameter ratio and approaches that of clean Taylor bubbles as λ increases. The main cause of this tendency was revealed by interface tracking simulations, i.e. the surfactant adsorbs only in the bubble tail region and the nose-to-side region is almost clean at high λ.
Computational Modeling of the Condensed Phase Aerosol Based Fire Extinguisher
Authors: Sharma Himanshu , Damodaran Murali , Gandhi Pravinray
Published: December 2014

The computational modeling of a novel condensed phase aerosol based fire extinguisher is considered in this study to assess its operational details and performance. A solid propellant is present inside the canister which is ignited using piezoelectric actuators producing hot fire extinguishing gases. The cooling of these hot gases is facilitated by a matrix of chemically active cooling pellets placed along the canister which condenses hot gas and discharges solid aerosol particulates. The initial experimental investigation of the extinguisher carried out at the premises of an industrial partner showed that improper cooling of the hot gases by pellets can lead to high temperature of the effluent gases and sparks at the exit. A decision was made to use modeling to develop better understanding of the physics of the extinguisher performance and develop improved experimental procedure using computational fluid dynamics model. A one dimensional computation has been established initially in the study by solving Euler’s equations using the Finite Volume Method. Based on the results obtained, high fidelity three-dimensional computation of the problem, by solving the multi-component combustion gas flow inside the extinguisher, using Navier Strokes equations has been done. While detailed chemical kinetics are not accounted for in the process, initial experimental estimates of these processes are used in the simulations to account for the effects on dynamics of the process. The computed results show how improper cooling by the pellet region may lead to hot spots in the extinguisher. These results will be used in the improved experimental design.
Numerical Study of Dielectric Barrier Discharge Plasma Actuation
Authors: Shan Hua , Lee Yu-Tai
Published: December 2014

There has been an increasing interest in dielectric barrier discharge (DBD) plasma actuation for flow control in the past decade. Compared to other means of active flow controls, the DBD plasma actuations have several advantages, including absence of moving parts, a fast time response for unsteady applications, a very low mass of the device, no cavities or holes on control surfaces, and possibly low energy consumption. These features are especially important for applications with high g-loads, such as turbomachinery blades rotating at high speed.

A computational method has been developed to couple a DBD electro-hydrodynamic (EHD) body force model with the Reynolds averaged Navier-Stokes (RANS) model for incompressible flows. The EHD body force model is based on solving the electrostatic equations for the electric potential due to applied voltage and the net charge density due to ionized air. The boundary condition for charge density on the dielectric surface is obtained from a Space-Time Lumped-Element (STLE) circuit model that accounts for time and space dependence of the air ionization on the input voltage amplitude, frequency, electrode geometry, and dielectric properties. Alternatively, an empirical formulation representing a Gaussian distribution of charge density on the dielectric surface can also be used. The EHD body force is calculated using the solutions obtained from solving the electric potential and the net charge density equations. As a comparison, a much simpler Linearized Electric Body Force (LEBF) model is also used to directly specify the spatial distribution of the averaged EHD body force. The coupled computational models have been implemented using a multiple-domain approach. The electric potential equation, the net charge density equation, and the flow equations are solved in separate computational domains. All equations are discretized in space using a cell-centered finite volume method. Parallel computation is implemented using domain-decomposition and message passing interface (MPI). Due to a large disparity in time scales between the electric discharge and the flow, a multiple sub-cycle technique is used in coupling the plasma solver and the flow solver.

The DBD plasma induced flow in quiescent air is used as a test case and the computational results are validated against experimental measurement. A comparison between different EHD body force models is also presented. Then, the effect of driving duty-cycles with different waveforms and input voltage amplitudes is investigated in terms of electrical power, EHD thrust, and kinetic energy of induced flow.
Radially and Circumferentially Oriented Vortices in Axial Flow Compressors
Authors: Gill Andrew , von Backström Theodor W. , Harms Thomas M.
Published: December 2014

This study relates in general to accident scenarios in a closed cycle, nuclear powered, three-shaft, helium gas turbine, and in particular to finding explanations for the high energy dissipation rates at certain compressor operating modes on a four quadrant compressor map. A four quadrant compressor map allows the presentation of all combinations of positive and negative pressure rise and flow direction for positive or negative direction of rotation.

The paper presents measured velocity profiles between blade rows, and computed particle path lines in blade passages. They reveal radially oriented vortices between the blades in a blade row when operating at low positive and negative flow rates. These vortices almost completely block the flow, and flow passing through the blade passage has to follow a helical path from casing to hub or vice versa around the vortex. The flow paths through these vortices are linked to the flow paths around circumferential ring vortices near the hub or near the casing in the blade free passages between blades rows. When operating as a turbine under high flow rates the vortices associated with negative incidence stall may be sheltered by the stator blade concave surfaces and deflect the flow in addition to blocking it.

The vortex structures appear to be fundamental in nature as they were evident in three quadrants and in two different compressors. The vortices play a role in the high energy dissipation rates in axial flow compressors at very low flow rates, where they operate effectively as flow mixers and not as compressors in possible accident scenarios. They also explain the poor performance as turbine in the fourth quadrant.
Microfluidics for Live-Cell Imaging Pancreatic Islets of Langerhans for Human Transplant
Authors: Mendoza-Elias Joshua E. , Oberholzer José , Wang Yong
Published: December 2014

Since the introduction of the Edmonton Protocol in 2000, islet transplantation has been emerging as promising therapy for Type I diabetes mellitus (T1DM) and currently is the only therapy that can achieve glycemic control without the need for exogenous insulin. Transplanting islet cells has several advantages over transplanting a whole pancreas in that it involves only a minor surgical procedure with low morbidity and mortality, and at a significantly lower cost. However, an obstacle to realizing this goal is a lack of an islet potency index as required by the U.S. Food and Drug Administration (FDA) biologics licensing, as well as a more complete understanding of the physiological mechanisms governing islet and β-cell physiology. Recently, the University of Illinois at Chicago (UIC) has developed a microfluidic platform that can mimic in vivo islet microenvironments through precise and dynamic control of perifusing culture media and oxygen culture levels; all while measuring functionally relevant factors including intracellular calcium levels, mitochondrial potentials, and insulin secretion. By developing an understanding of the physiology and pathophysiology of islets we can more effectively develop strategies that reduce metabolic stress and promote optimization in order to achieve improved success of islet transplantation and open new clinical avenues.

The presentation begins by introducing key issues in the field of pancreatic islet transplantation as a clinical therapy for T1DM. This is followed by brief review various technologies that have been developed to study islet cells. The presentation then describes the design, application, and evolution of UIC’s microfluidic-based multimodal islet perifusion and live-cell imaging system for the study of pancreatic islet and β-cell physiology. The article then concludes presenting initial findings from studies seeking to develop an islet potency test.
Numerical Study of Reactor Cooling Pumps Under Two-Phase Gas-Liquid Flow
Authors: Wang Peng , Yuan Shouqi , Wang Xiuli , Li Guidong , Zhou Banglun , Liu Janrui
Published: December 2014

In this paper, the unsteady pressure field and head-drop phenomenon caused by one of the most dangerous accidents in reactor plants known as Loss of Coolant Accident (LOCA) in its worse condition called small LOCA have been investigated numerically by computational fluid dynamics (CFD) in a nuclear reactor cooling pump. Five computational models with different blades had been calculated using Eulerian-Eulerian two fluid models using a multiphase approach. Simulation results show increasing gas volume fraction results in a sharp decline of the head pressure and pump efficiencies for each of 5 kinds of pumps modeled. This is especially evident for both the head pressure of impeller types C and impeller E. Here only have operating at half (58m and 54.9m)of the design condition when the gas volume fraction is 25%. The analysis of inner flow field of the five model pumps shown that the lower pressure area appeared at the inlet and outlet of the impeller as well as a small part distribution at the inlet of the diffuser, which is the main reason made the gas bubbles tend to concentrate at the impeller eye on the suction surface, the distribution of two phases appeared by non-linear increase and random located in whole passages. The experimental and simulation results are compared and are in good agreement with values obtained for the global performance at lower gas contents (below20%). When the gas contents increases to 25%, the bubbles occupy the passages, which effectively causes unsteady flow in the gas phase cannot be neglected for accurately predicting the inner flow of the pump. These results imply that this numerical method is suitable for the two-phase flow under certain gas contents (below 20%) in the reactor cooling pump.
Influencing Factors on Submicron Particle Movement Patterns in Supersonic Laminar Boundary Layers
Authors: Li Xing , Bai Bofeng
Published: December 2014

The process of submicron particle movement in laminar boundary layers is present in many practical applications such as the particles depositing on the turbine blade and mist droplets depositing on the surface of aircrafts. Although great progress has been made on this issue during the last decades, many underlying mechanisms still remain unclear. Here, we developed a theoretical model to understand how submicron particles will behave when they enter a supersonic laminar boundary layer above an adiabatic plate along with the main stream. In this model, we used the Lagrangian method to track the particles and calculate their trajectories, and the Eulerian method was used to calculate the flow field. Because of the large velocity and temperature gradient near the wall and the small size of the particle in this question, four forces (e.g., drag force, Saffman lift force, thermophoretic force and Brownian force) acting on the particle are considered. The effects of entering position, Mach number, the size and density of particles are investigated. We discovered that there are three particle movement patterns when they enter the supersonic boundary layer, and that the drag force and Saffman lift force play dominating roles on which pattern will happen in this process. Moreover, the results also reveal that the particle tends to move towards the wall as the diameter and the density of the particle and the Mach number of main flow increases. Finally, we suggested a dimensionless number to describe the three patterns of particle motion. This research provides a better understanding of the particle movement process in the supersonic laminar boundary layer, which can be a useful guidance for the industrial processes involving this phenomenon.
Numerical Modeling of Kites for Power Generation
Authors: Nejad Alireza Mahdavi , Olinger David J. , Tryggvason Gretar
Published: December 2014

A computational model of a massless kite that produces power in an airborne wind energy system (AWE) is presented. AWE systems use tethered kites at high altitudes to extract energy from the wind, and are being considered as an alternative to wind turbines since the kites can move in high-speed cross-wind motions over large swept areas to increase power production. In our model the kite completes successive power-retraction cycles where the kite angle of attack is altered as required to vary the resultant aerodynamic forces on the kite. The numerical simulation models the flow field in a two-dimensional domain near the flexible kite by solving the full Navier-Stokes equations. Eulerian grid points for the flow domain together with a Lagrangian representation of the kite are employed. The flow field is determined through a second-order finite difference projection method using a non-uniform mesh on a staggered grid. A corrector-predictor technique is employed to ensure the second-order accuracy in time of the numerical simulation. The two-dimensional kite shape is modeled as a slightly cambered immersed boundary that evolves with the flow. The flexible kite surface is modeled with a set of linear springs following Hooke’s law. The unstretched length of each elastic tether at a given time step is controlled using periodic triangular wave shapes to achieve the required power-retraction phases. A study was conducted in which the wave shape amplitude, frequency, and phase (between two tethers) was adjusted to achieve a suitably high net power output with very good agreement to predictions for Loyd’s simple kite in two-dimensional motion. Aerodynamic coefficients for the kite, tether tensions, tether reel-out and reel-in speeds, and vorticity flowfields in the kite wake are also determined.
Liquid-Gas Two-Phase Flow Simulation for Flat Fan Nozzles
Authors: Li Guibo , Lian Yongsheng , Mersch Matt , Omalley Chris , Hofmann Adam
Published: December 2014

This paper focuses on the numerical simulation of two-phase flow near the outlet of flat fan nozzles under low operating pressure. The moment-of-fluid (MOF) method is used for the representation of the liquid gas interface and the directional split method is used for the advection of the interface. A variable density pressure projection algorithm is used for the fluid solver and a block structured adaptive mesh refinement (AMR) method is used to locally increase the resolution near interface. The internal geometry of the nozzle is defined by three parameters: nozzle inlet diameter D, V-cut or U-cut width W and V-cut or U-cut offset H. The effects of these three parameters on the fan exit angle and pressure loss through the nozzles are studied. Experiments are conducted to validate our simulation results. Finally, we give some conclusions about the modeling of the flat fan nozzle under low operating pressure based on our study.
Near Field Pressure and Associated Coherent Structures of Excited Jets
Authors: Speth Rachelle L. , Gaitonde Datta V.
Published: December 2014

Large Eddy Simulations (LES) were performed for Mach 0.9 and 1.3 cold jets to associate the structures of the shear layer with near field pressure fluctuations. The jets were excited by Localized Arc Filament Plasma Actuators (LAFPAs) arranged around the periphery of the nozzle with the axisymmetric (m = 0) mode. Excitation frequencies of St = fD/Uj = 0.05 to 0.25 (close to the column mode frequency) were computed for each Mach number. The St = 0.05 produces one pulse that propagates downstream without interacting with previously emitted pulses. This is referred to as the the impulse response. The St = 0.25 frequency exhibits subsequent pulse interactions. Simulation data for both Mach numbers was collected along three arrays at different radial locations. Strong agreement was found for the near field response to excitation and the mean center-line axial velocity between the subsonic simulations and the experiments. The experiment and simulations depict a large hydrodynamic wave downstream of the exit moving at the speed of convection near the shear layer consisting of a large peak followed by a large trough after the actuator pulse. For the highest excitation frequency, the interaction between structures yields an almost sinusoidal wave in the near field. These hydrodynamic waves are associated to the phase-averaged flow structure which includes a series of rollers and ribs and the associated dilatation field. The structure interactions from subsequent pulses results in a quasi-linear superposition of the impulse jet response (St = 0.05) to actuation. Auto-correlations and two-point correlations describe the development and interaction between adjacent structures in time and space.
An Experimental Study of Reducing Back Pressure of Fine Air Diffuser Used in Wastewater Plants
Authors: Al Ba'ba'a Hasan B. , Prada Michael A. , Olson Christopher D. , Alkhalidi Ammar A. T. , Amano Ryoichi S. , Li Jin
Published: December 2014

Aeration is the process at which air is added to water, an essential stage in wastewater treatment plants, since most of organic compounds are being treated through such an aeration process. This process also helps aerobic bacteria to survive from oxygenation to proliferate and digest organic materials. However, aeration consumes around 60% of the total cost of remediation. Therefore, any improvement in aeration efficiency (AE) will save a considerable amount of energy consumption. One way of reducing the power required is to decrease the back pressure of the air diffuser itself. In this study, a new material for manufacturing of fine air diffuser is presented. Polypropylene (PP) membrane, which is the new material chosen, shows lower back pressure values in comparison with Silver Series 2 (SS2) membrane at relatively low flow rates. The main reason behind choosing Polypropylene (PP) is that it has lower material resistance than SS2 with maintaining the capability of operation at the same pressure ranges in the aeration process. Despite the fact that SS2 has better oxygen transfer efficiency (OTE), PP membranes have significantly lower back pressure at relatively low flow rates which resulted in higher AE. In addition, contact angle measurements were done for PP and compared with previous measurements for the contact angle of SS2.