bluuebunny/crossref_metadata_2025 huggingface dataset:
Do wind and brass players snore less? A cross‐sectional study of snoring and daytime fatigue in professional orchestral musicians
Authors: Wardrop P.J.C. , Ravichandran S. , Hair M. , Robertson S.M. , Sword D.
Published: March 2011

Clin. Otolaryngol. 2011, 36, 134–138

Objectives:  To determine whether playing a wind or brass musical instrument is associated with reduced snoring or daytime fatigue.

Design:  Cross‐sectional, controlled, anonymous, questionnaire‐based observational study.

Setting:  Rehearsal and performance halls.

Participants:  Three hundred and forty musicians from Scotland’s five professional orchestras.

Main outcome measures:  Snore Outcomes Survey questionnaire and the Epworth Sleepiness Score.

Statistical method:  Hierarchical linear regression analysis.

Results:  No significant difference was found between the snoring severity (Snore Outcomes Survey score) or daytime sleepiness (Epworth score) of wind/brass and other professional musicians. A regression model with snoring severity (Snore Outcomes Survey score) as the dependent variable and the three covariates of gender, age and body mass index as independent variables was significant [F(3, 206) = 28.77, P < 0.01, adjusted r2 = 0.285]. Increasing age, body mass index and male gender were all significantly associated with lower Snore Outcomes Survey scores (i.e. worse snoring).The addition of instrument type did not significantly increase the fit of the model, and the regression coefficient for instrument type was not significant. There were similar results when the Epworth Sleepiness Score was used as the dependent variable.

Conclusions:  This study demonstrated no significant difference between the snoring severity or daytime sleepiness of brass/wind players and other professional orchestral musicians. This result may have been attributed to comparatively low levels of snoring/daytime sleepiness in the population studied. The findings contrast with previous studies examining the effects of singing and didgeridoo playing but concur with a recent similar study of orchestral musicians. A prospective interventional study would be required to determine whether playing a wind or brass instrument improves these variables in patients complaining of disruptive snoring.
Sociology and Human Rights in the Post‐Development Era
Authors: Frezzo Mark
Published: March 2011

This article explores the dilemmas of the sociology of human rights – a growing field of academic research. Sociologists are increasingly conceptualizing poverty, global economic inequality, and social inequalities of race, class, gender, and sexual orientation not as social problems, but rather as human rights abuses. The shift of emphasis from the social problems perspective to the human rights perspective demands a different set of remedies from IGOs, national governments, and local authorities. Whereas in the past sociologists tended either to recommend modifications to social policies or to propose large‐scale social transformation, they now find themselves advocating the implementation of human rights on the global, national, and local levels. This has brought sociologists into the area of global governance. The process of delineating an explicitly sociological perspective on human rights is impeded by two overlapping dilemmas: (1) the tension between an approach that emphasizes the analysis of ‘rights effects’ on the global, national, and local levels and an approach that stresses the advocacy of rights as a palliative for social inequalities; and (2) the tension between an interdisciplinary vision, in which sociology would join other disciplines in illuminating human rights and a unidisciplinary vision, in which sociologists and their allies would push for a unified social science founded on human rights.
GFC or KFC?: How Standard Setters Were Battered and Fried
Authors: Howieson Bryan
Published: March 2011

The Global Financial Crisis (GFC) has exposed the fragility of both the alleged independence of the International Accounting Standards Board (IASB) and the Financial Accounting Standards Board (FASB) and their agreement to work together on major projects such as accounting for financial instruments. This paper outlines the events that have dogged the IASB and FASB in their attempts to respond to the GFC and explores the implications of the recent political pressures on accounting standard setting for the likelihood of ultimately achieving one global set of accounting standards.
The Performance of Equity Analysts During the Global Financial Crisis
Authors: Sidhu Baljit , Tan Hwee Cheng
Published: March 2011

This paper investigates the response of equity analysts following Australian and US listed stocks to the onset of the 2007 Global Financial Crisis. Both groups of analysts reacted quickly by adjusting their forecasts downwards, and initially tending towards being overly pessimistic. Relative to pre‐crisis data, the authors identify sharp declines in earnings forecasts, an increase (decrease) in downward (upward) revisions, and a downward (upward) trend in sell (buy) recommendations. Forecast errors are larger, and dispersion of earnings forecasts is higher. Finally, the most accurate analysts in the pre‐crisis period continue to be significantly more accurate during the crisis period than their peers.
Carbon Management Accounting: Explaining Practice in Leading German Companies
Authors: Burritt Roger L. , Schaltegger Stefan , Zvezdov Dimitar
Published: March 2011

This paper explores carbon management accounting (CMA) by examining the practices of leading German companies with pronounced policies and histories. Using interview data, field notes, documentary evidence, and questionnaires, this research identifies the CMA behaviour of 10 companies and grounds it in a theoretical framework to categorise the practices. With climate change to the forefront CMA provides an opportunity to (re)gain competitive advantage by exceeding the legislative requirements for reporting on carbon and carbon‐equivalent emissions, CMA, when properly understood and contextualised, provides an ability to increase both effectiveness and efficiency of information collection and dissemination, and may assist in overcoming the currently uncoordinated approaches evident in the sample companies, and thus contribute to improved carbon management performance.
Management Controls in Public–Private Partnerships: An Analytical Framework
Authors: Appuhami Ranjith , Perera Sujatha , Perera Hector
Published: March 2011

Drawing on transaction cost economics and organisational theory, this paper proposes a framework to analyse management controls in Public–Private Partnerships (PPPs). The paper contributes to the related literature at a conceptual level by showing how three control archetypes, namely market, bureaucratic and clan, in conjunction with two control strategies, namely performance evaluation and trust‐based strategies, could be used by public partners to minimise relational and performance risk, thereby achieving value for money. Practitioners could also use the linkages identified in this paper to develop management control systems for PPPs.
Nonlinear Multiple Points Gas Turbine Off-Design Performance Adaptation Using a Genetic Algorithm
Authors: Li Y. G. , Ghafir M. F. Abdul , Wang L. , Singh R. , Huang K. , Feng X.
Published: March 2011

Accurate gas turbine performance models are crucial in many gas turbine performance analysis and gas path diagnostic applications. With current thermodynamic performance modeling techniques, the accuracy of gas turbine performance models at off-design conditions is determined by engine component characteristic maps obtained in rig tests and these maps may not be available to gas turbine users or may not be accurate for individual engines. In this paper, a nonlinear multiple point performance adaptation approach using a genetic algorithm is introduced with the aim to improve the performance prediction accuracy of gas turbine engines at different off-design conditions by calibrating the engine performance models against available test data. Such calibration is carried out with introduced nonlinear map scaling factor functions by “modifying” initially implemented component characteristic maps in the gas turbine thermodynamic performance models. A genetic algorithm is used to search for an optimal set of nonlinear scaling factor functions for the maps via an objective function that measures the difference between the simulated and actual gas path measurements. The developed off-design performance adaptation approach has been applied to a model single spool turbo-shaft aero gas turbine engine and has demonstrated a significant improvement in the performance model accuracy at off-design operating conditions.
Compensating Random Time Delays in a Feedback Networked Control System With a Kalman Filter
Authors: Probst Alexander C. , Magaña Mario E. , Sawodny Oliver
Published: March 2011

This paper presents procedures to handle time delays in a feedback control loop in which both measurement and control signals are sent through a network, where random time delays occur. Even when time stamps are utilized, for example, the control signal time delay still must be estimated. Using a Padé approximation and a Kalman filter, we can estimate the mean time delay. Furthermore, methods are described to estimate the time delay of every packet instead of the mean for the measurement channel, which greatly enhances the performance of the Padé approximation approach. This is done by matching the measurements to the expected measurements provided by the filter with maximum likelihood. The methods are applied to an inverted pendulum to assess performance.
An Artificial Neural Network Approach to Cooling Analysis of Electronic Components in Enclosures Filled With Nanofluids
Authors: Kargar A. , Ghasemi B. , Aminossadati S. M.
Published: March 2011

Computational fluid dynamics (CFD) and artificial neural network (ANN) are used to examine the cooling performance of two electronic components in an enclosure filled with a Cu-water nanofluid. The heat transfer within the enclosure is due to laminar natural convection between the heated electronic components mounted on the left and right vertical walls with a relatively lower temperature. The results of a CFD simulation are used to train and validate a series of ANN architectures, which are developed to quickly and accurately carry out this analysis. A comparison study between the results from the CFD simulation and the ANN analysis indicates that the ANN accurately predicts the cooling performance of electronic components within the given range of data.
Forward and Inverse Analyses of an SMA Actuated Compliant Link
Authors: Banerjee A. , Bhattacharya B. , Mallik A. K.
Published: March 2011

This paper presents forward and inverse analyses of the response of a compliant link actuated by a discretely attached shape memory alloy (SMA) wire subjected to a time-varying input voltage. The framework for a constrained recovery of the shape memory alloy wire is developed from a robust numerical model. The model for the large deflection of a beam element due to follower forces resulting from discrete actuation using a SMA wire is coupled with the proposed framework. Thus, the response of the link is correlated with the input voltage. The algorithm for implementing this framework has been demonstrated along with some numerical examples. Experiments have also been conducted on a SMA actuated cantilever beam, and the results are compared with those of the simulations. A qualitative agreement between the two is observed. It is concluded that the theoretical results can provide a reference signal for active control of the link to achieve higher accuracy.
Transient Thermal Response of Pin-Fin Sandwich Panels to Hot Jet Impingement
Authors: Feng S. S. , Lu T. J. , Kim T.
Published: March 2011

The transient thermal response of a sandwich panel with pin-fin core subjected to nonuniform impinging jet heating was investigated theoretically and experimentally. Forced convection flow passing through the sandwich channel was employed to remove heat imposed nonuniformly on the pin-fin sandwich. A semi-empirical model was developed to predict the transient thermal fields in the front and back facesheets of the sandwich, in the pin-fins, and in the forced convective flow. Transient heat transfer measurements were conducted to validate the model with hot air impinging jet heating. The temperature history of the sandwich was predicted under two different boundary conditions: (1) continuous and (2) cyclic heating from a flame impinging jet. Heating by the flame impinging jet was modeled by prescribing heat flux distribution expressed with an exponential function. For continuous heating, systematic parametrical studies were carried out to examine the effects of convection Reynolds number, fin pitch, fin thickness, and facesheet thickness on the maximum facesheet temperature. For cyclic heating, the thermal performance of the sandwich as a function of heat flux intensity was quantified. It was demonstrated that pin-fin sandwiches are capable of thermally managing nonuniformly distributed heat fluxes having high intensities, either continuously or cyclically imposed.
Comparisons of Pins/Dimples/Protrusions Cooling Concepts for a Turbine Blade Tip-Wall at High Reynolds Numbers
Authors: Xie Gongnan , Sundén Bengt , Zhang Weihong
Published: March 2011

The blade tip region encounters high thermal loads because of the hot gas leakage flows, and it must therefore be cooled to ensure a long durability and safe operation. A common way to cool a blade tip is to design serpentine passages with a 180 deg turns under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase blade tip lifetime. Pins, dimples, and protrusions are well recognized as effective devices to augment heat transfer in various applications. In this paper, enhanced heat transfer of an internal blade tip-wall has been predicted numerically. The computational models consist of a two-pass channel with 180 deg turn and arrays of circular pins, hemispherical dimples, or protrusions internally mounted on the tip-wall. Inlet Reynolds numbers are ranging from 100,000 to 600,000. The overall performance of the two-pass channels is evaluated. Numerical results show that the heat transfer enhancement of the pinned-tip is up to a factor of 3.0 higher than that of a smooth tip while the dimpled-tip and protruded-tip provide about 2.0 times higher heat transfer. These augmentations are achieved at the cost of an increase of pressure drop by less than 10%. By comparing the present cooling concepts with pins, dimples, and protrusions, it is shown that the pinned-tip exhibits best performance to improve the blade tip cooling. However, when disregarding the added active area and considering the added mechanical stress, it is suggested that the usage of dimples is more suitable to enhance blade tip cooling, especially at low Reynolds numbers.
Some Analytical Results on Transmission Errors in Narrow-Faced Spur and Helical Gears: Influence of Profile Modifications
Authors: Velex P. , Bruyère J. , Houser D. R.
Published: March 2011

Some theoretical developments are presented, which lead to approximate analytical results on quasi-static transmission errors valid for low and high contact ratio spur and helical gears. Based on a multidegree-of-freedom gear model, a unique scalar equation for transmission error is established. The role of profile relief is analyzed by using Fourier series and it is shown that transmission error fluctuations depend on a very limited number of parameters representative of gear geometry and profile relief definition. An original direct solution to the optimum relief minimizing transmission error fluctuations is presented, which is believed to be helpful for designers. The analytical results compare well with the numerical results provided by a variety of models and it is demonstrated that some general laws of evolution for transmission error fluctuations versus profile modifications can be established for spur and helical gears.
On the Design of Adaptive Cable-Driven Systems
Authors: Rosati Giulio , Zanotto Damiano , Agrawal Sunil K.
Published: March 2011

Several systematic approaches have been developed for the optimal design of cable-based systems. Global indices are usually employed to quantify the effectiveness of a specific design inside a reference region of the workspace. The performances at the moving platform are strictly related to cable configuration, which, in turn, depends on the pose of the moving platform. As a result, traditional designs are characterized by the high variability of performances within the workspace and are often badly tailored to the design goals. The motivation behind this paper is to formalize a new design methodology for cable-driven devices. Based on a total or partial decoupling between cable disposition and end-effector pose, this methodology allows us to achieve well-tailored design solutions for a given design requirement. The resulting systems are here defined as adaptive cable-driven systems. Two simple design problems are presented and solved with both the traditional and the novel approaches, and the advantages of the latter are emphasized by comparing the resulting design solutions.
Workspace Analysis of Multibody Cable-Driven Mechanisms
Authors: Rezazadeh Siavash , Behzadipour Saeed
Published: March 2011

A systematic approach is proposed to determine the tensionable workspace of multibody cable-driven mechanisms. The method is also capable of finding analytical descriptions for the boundaries of the tensionable regions for any number of redundant cables used. The presented approach builds upon the available methods for conventional (rigid body) cable-driven mechanisms, i.e., null space analysis and supporting/separating hyperplanes. It extends these methods to the case of a multibody driven by cables. For this purpose, the notion of generalized forces and Lagrange’s method is used to eliminate the constraint forces/moments from the equilibrium equations. This has resulted in a more compact equation form with fewer unknowns. The method is then applied to several one- and two-DOF mechanisms with various cable distributions. Analytical descriptions for the boundaries of their workspaces are found. These boundaries and the resulting regions are then used to improve the design for larger tensionable workspaces.
Compound Triple Jets Film Cooling Improvements via Velocity and Density Ratios: Large Eddy Simulation
Authors: Farhadi-Azar R. , Ramezanizadeh M. , Taeibi-Rahni M. , Salimi M.
Published: March 2011

The flow hydrodynamic effects and film cooling effectiveness placing two small coolant ports just upstream the main jet (combined triple jets) were numerically investigated. Cross sections of all jets are rectangular and they are inclined normally into the hot cross-flow. The finite volume method and the SIMPLE algorithm on a multiblock nonuniform staggered grid were applied. The large-eddy simulation approach with three different subgrid scale models was used. The obtained results showed that this flow configuration reduces the mixing between the freestream and the coolant jets and hence provides considerable improvements in film cooling effectiveness (both centerline and spanwise averaged effectiveness). Moreover, the effects of density and velocity differences between the jets and cross-flow and between each of the jets were investigated. The related results showed that any increase in density ratio will increase the penetration of the jet into the cross-flow, but increasing the density ratio also increases the centerline and spanwise average film cooling effectiveness. Increasing the smaller jet velocity ratios, compared with the main jet, significantly improve the cooling effectiveness and uniform coolant distribution over the surface by keeping the main jet coolant fluid very close to the wall.
An Archive of Skin-Layer Thicknesses and Properties and Calculations of Scald Burns With Comparisons to Experimental Observations
Authors: Johnson N. N. , Abraham J. P. , Helgeson Z. I. , Minkowycz W. J. , Sparrow E. M.
Published: March 2011

A numerical model has been constructed to assess the depth of injury incurred when skin is exposed to heated water. The model includes an extended duration that occurs when clothing, saturated with hot water, is kept in contact with the skin after the direct exposure has ended. The model takes data from a broad summary of literature, which examines the ranges of reported tissue thicknesses, tissue thermophysical properties, and blood perfusion. Water temperatures ranging from 60°C to 90°C and total exposure durations up to 110 s were modeled. As expected, longer durations and elevated temperatures lead to a greater extent of tissue injury. For lower values of temperatures (60°C), burns range from mild (0.1 mm) to severe (2.2 mm) depending on the exposure duration. On the other hand, for higher exposure temperatures (90°C), all durations led to burns that extended at least halfway through the dermal layer. As expected, burn depths with intermediate temperatures fell between these ranges. Calculated values of tissue injury were compared with prior injury reports. These reports, taken from literature, reinforce the present calculations. It is seen that numerical models can accurately predict burn injury as assessed by clinical observations; in fact, the calculations of burn injury presented here provide more information for the appropriate treatment of burn injuries compared with visual observation. Finally, literature values of a number of skin-layer thicknesses, thermophysical properties, and burn-injury parameters were collected and presented as an archival repository of information.
Mathematical Analysis for Off-Design Performance of Cryogenic Turboexpander
Authors: Ghosh Subrata K. , Sahoo R. K. , Sarangi Sunil K.
Published: March 2011

A study has been conducted to determine the off-design performance of cryogenic turboexpander. A theoretical model to predict the losses in the components of the turboexpander along the fluid flow path has been developed. The model uses a one-dimensional solution of flow conditions through the turbine along the mean streamline. In this analysis, the changes of fluid and flow properties between different components of turboexpander have been considered. Overall, turbine geometry, pressure ratio, and mass flow rate are input information. The output includes performance and velocity diagram parameters for any number of given speeds over a range of turbine pressure ratio. The procedure allows any arbitrary combination of fluid species, inlet conditions, and expansion ratio since the fluid properties are properly taken care of in the relevant equations. The computational process is illustrated with an example.
Parametric Study of an Autothermal Micro Surface Reactor for Hydrogen Production
Authors: Akbari M. H. , Sharafian Ardakani A. H. , Andisheh Tadbir M.
Published: March 2011

Hydrogen production through autothermal reforming (ATR) of hydrocarbons, such as methane, is one option of interest for mobile applications of hydrogen fuel cells. In the present study, a numerical investigation of catalytic autothermal reforming of methane in a surface microreactor is presented. A three-dimensional ATR reactor model is developed to simulate the flow and surface reactions in a microchannel of rectangular cross section with 340-μm sides, and total length of 8.5 mm. A four-reaction mechanism is implemented to simulate the surface reactions on a Ni/Al2O3 catalyst. The governing equations in the model include conservations of mass, momentum, energy and chemical species. A CFD code based on the finite-volume method has been developed in-house to solve the governing equations. Validation of the results against available data confirms the accuracy of the numerical approach. The simulation results reveal the dependency of hydrogen yield on space velocity (SV), air/fuel molar ratio (A/F), water/fuel molar ratio (W/F), and the gas feed temperature.
Experimental Investigation of Air-Water Two Phase Flow Regime in Vertical Mini Pipe
Authors: Hanafizadeh Pedram , Ghanbarzadeh Soheil , Nouri Gheimasi Arash , Saidi Mohammad Hassan
Published: March 2011

In this study the flow patterns of air-water two phase flows have been investigated experimentally in a vertical mini pipe. The flow regimes observed by 1200 fps high speed video recorder in the pipe with diameters of 2, 3 and 4 mm having the length of 27, 31 and 25cm, respectively. The comprehensive visualization of air water two phase flow in a vertical mini pipe has been performed to realize the physics of such two phase flow. Different flow patterns of air–water flow were observed simultaneously in the mini pipe at different values of air and water flow rates. Consequently the flow pattern map proposed for flow in mini-pipe in terms of superficial velocities of liquid and gas phases. The resulted flow pattern map is compared with those of other researchers in the existing literatures.
A Finite Element Model for Predicting the Collapse of Short and Large Two-Line Patterns During Drying Process in Photolithography
Authors: Chini Seyed Farshid , Amirfazli Alidad
Published: March 2011

Photolithography is one of the main mass nano-production processes. Smaller devices are always aimed to save material and energy. Manufacturing small devices by photolithography is a challenge, due to the risk of collapse of patterns during the drying of rinse liquid. One of the main pattern shapes is the two-line parallel. In our previous study, an analytical model was developed for predicting the collapse of large (L/d, LAR>20; see Fig. 1) two-line parallel patterns [1]. This model assumes the rinse interface shape is cylindrical. Knowledge of the rinse interface shape is needed to define the forces contribute to collapse, i.e. Laplace pressure and surface tension force at the three-phase line. In the current study, a Finite Element (FE) model is developed to predict the collapse of short (LAR<20) and large (LAR>20) two-line parallel patterns. Rinse liquid shape and its curvature are found using Surface Evolver (an interactive program for the study of surfaces shaped by surface tension, gravitational and other energies). Another finite element method (i.e. ANSYS 11.0) is used to find the pattern deformation. It was found that the pattern deformation decreases by decreasing the LAR value. It is important as for the cases that due to the design specifications, selection of the pattern material and rinse liquid is restricted, by changing the LAR value one may resolve the collapse problem.
Parallel Computation for Particle-Grid Hybrid Method
Authors: Guo Yun , Ishiwatari Yuki , Ikejiri Satoshi , Oka Yoshiaki
Published: March 2011

In this paper, parallel computational technology is used in the numerical analysis code of particle-grid hybrid method. Particle-grid hybrid method is a rising solution method to analyze two-phase flow problem. It has shown its ability in several two-dimensional simulations. However, when this method was used to predict the droplet entrainment ratio of annulus flow the calculation time was insufferable. When the droplet occurs in the gas core, the density field varying near the droplet is strenuous. The pressure correction equations are very hard to be convergence. Hence, the MPI (Message Passing Interface) library is chosen as the parallel technology to decrease the calculation time. The grid and particle calculation parts are paralleled, separately. Jacobi point iteration method and ADI (alternating direction implicit) combined with divide and flow line programming techniques for grid calculation are discussed. All the particles are divided into several groups depending on the processor number. Then several cases are set for testing the parallel efficiency. Generally, with four processors the efficiency is about 60%. If the processor number is more than four the parallel efficiency will decrease rapidly. This method can accelerate the hybrid method; however, it still needs improving. Finally, some droplet entrainment cases calculated by parallel code are summarized.
An Immersed Boundary Method Based on Navier-Stokes Equations in Discrete Stream Function Formulation
Authors: Zhang Xing , Wang Shizhao , He Guowei
Published: March 2011

A new variant of Immersed Boundary method is proposed in the framework of discrete stream function approach for the Navier-Stokes equations. A parallelized flow solver is developed to simulate two and three-dimensional flow problems involving complex and moving boundaries. The parallel performance of the present flow solver is tested by varying the number of processors used in the simulation. Code validations and applications are also presented, in an order of increasing complexity.
Thermodynamic Analysis of Temperature and Pressure on Carbon Deposition for Methane Reforming at Low Temperature in Micro-Combustor
Authors: Ran Jing-yu , Zhao Liu-jie
Published: March 2011

Aimed at problems caused by carbon deposition in the micro-combustor, such as catalyst deactivation and channel block, based on the technology of methane-wet air autothermal reforming and the effects of hydrogen and methane conversion, the influences of temperature and pressure on carbon deposition below 973K are discussed with thermodynamic analysis method in this paper. Results show that for a definite feed gas composition, carbon deposition adds with increasing temperature firstly, and then decreases. Reaction pressure is suitable to maintain at 1atm. Moreover, the increasing methane mass flow, decreasing air and steam mass flow can lead to expansion of carbon deposition temperature region exists, also lead to the amount of carbon deposition increase and the temperature peak of carbon deposition shift to higher temperature segment. Under the research conditions that methane mass flow is 6.6g/h, reaction pressure is 1atm, air-methane ratio and steam-methane ratio are respectively 2 and 1 in the micro-combustor, the temperature range of carbon deposition production is at 680∼850K. The largest carbon deposition is occurred and its mass fraction is 0.66% when the reaction temperature is at 785K, also the methane conversion rate and the mass fraction of hydrogen are approximately 53.43% and 2.37% respectively.
Loss Coefficients in Laminar Flows: Indispensable for the Design of Micro Flow Systems
Authors: Herwig H. , Schmandt B. , Uth M.-F.
Published: March 2011

The concept of head loss coefficients K for the determination of losses in conduit components is discussed in detail. While so far it has mainly been applied to fully turbulent flows it is extended here to also cover the laminar flow regime. Specific numbers of K can be determined by integration of the entropy generation field (second law analysis) obtained from a numerical simulation. This general approach is discussed and illustrated for various conduit components.
Entering a New Era of Diagnosis
Authors: Ritzi-Lehnert Marion
Published: March 2011

Looking at the development of diagnostics from prehistorical days up to know and even further visioning into the future the shamans of the old days were slowly replaced by the early “all-round” doctor having first simple diagnostical and surgery possibilities, changing to nowadays specialized physicians doing the diagnoses based on analytical results provided by decentralized specialized labs. Future visions present doctors offices harboring small instruments that allow the physicians to do analyses directly as fast and as minimally or even non-invasive as possible advantageously combined with a connection to a smart health care database providing anamnesis and providing possible therapeutical measures. Already in the 1960s’ science fiction series Star Trek the spaceship crew used very small instruments for fast, non-invasive diagnosis and treatment. Although, such analyzers are future vision actual developments lead to less and less complex and small systems. Using micro- and nano-technologies manifold approaches addressing so-called “Lab-on-a-chip (LoC)” or “micro total analysis systems (μTAS)” where described during the last two decades. Huge progress can be seen in miniaturization not only of electronics but also of mechanics. While presently, table-top systems reach the market handheld systems providing complete analysis from sample taking to result are rare. Presently, often complex sample preparation methods have to be performed to reach the sensitivity and robustness needed for reliable results. In addition, specific disease markers are still missing that give clear conclusions about health status. In this field, intensive research is going on identifying new better and more specific markers for fast and easy reliable determination of diseases, infections, predispositions and more. Having markers available where each marker gives a non-misleading conclusion that a person will have or already has a certain disease, being able to determine these markers directly from the sample without complex sample preparation steps and having instruments available being preferably portable and applicable by non-specialists such a vision is getting closer. The actually developed miniaturized instruments are an important step towards the envisioned future systems demonstrating the basic proof of concept and thereby heralding a new era of diagnosis.
Fast Inertial Microfluidic Actuation and Manipulation Using Surface Acoustic Waves
Authors: Yeo Leslie Y. , Friend James R.
Published: March 2011

Though uncommon in most microfluidic systems due to the dominance of viscous and capillary stresses, it is possible to drive microscale fluid flows with considerable inertia using surface acoustic waves (SAWs), which are nanometer order amplitude electro-elastic waves that can be generated on a piezoelectric substrate. Due to the confinement of the acoustic energy to a thin localized region along the substrate surface and its subsequent leakage into the body of liquid with which the substrate comes into contact, SAWs are an extremely efficient mechanism for driving fast microfluidics. We demonstrate that it is possible to generate a variety of efficient microfluidic flows using the SAW. For example, the SAWs can be exploited to pump liquids in microchannels or to translate free droplets typically one or two orders of magnitude faster than conventional electroosmotic or electrowetting technology. In addition, it is possible to drive strong microcentrifugation for micromixing and bioparticle concentration or separation. In the latter, rich and complex colloidal pattern formation dynamics have also been observed. At large input powers, the SAW is a powerful means for the generation of jets and atomized aerosol droplets through rapid destabilization of the parent drop interface. In the former, slender liquid jets that persist up to centimeters in length can be generated without requiring nozzles or orifices. In the latter, a monodispersed distribution of 1–10 micron diameter aerosol droplets is obtained, which can be exploited for drug delivery and encapsulation, nanoparticle synthesis, and template-free polymer array patterning.
Statistical Characteristics in Water Jet Discharged From a Central-Body Nozzle
Authors: Kang Can , Zhang Feng , Liu Dong , Yang Minguan
Published: March 2011

As a special nozzle, central-body nozzle has attracted a lot of attention since its concept was proposed in 1980s. With Karman vortex street principle and phase-change theory, cavitation is expected to occur just after the central body. However, turbulent features in water jet flow discharged from central-body nozzle have not been illustrated by sufficient experimental data when water is ejected into ambient air. Under jet pressures of 11MPa, 13MPa and 17MPa, free water jet discharged from a central-body nozzle was experimentally studied. Phase Doppler particle anemometry (PDPA) was applied to measure non-intrusively the flow fields. Four traverse sections were selected for data visualization and representative description of the flow features. Control volumes at center and rim of the four sections were monitored for recording of every validated single droplet passing through. Experiment results indicate that pressure increase influences maximum velocity significantly. Obvious statistical characteristics exist at jet center and jet rim. The statistical feature of the droplet distribution varies slightly with pressure increase. Turbulent fluctuation is proved to be in reasonable relation to droplet behavior and droplet diameter distribution.
An Immersed Boundary Based Method for Studying Thermal Interaction of Particles in a Viscous Fluid
Authors: Feng Zhi-Gang , Paudel Basu D. , Zhang Xing
Published: March 2011

The results of thermal interactions between a solid particle and a fluid have two folds: the motion of fluid affects the heat transfer and energy balance of a particle; and the heat transfer from particles influences the fluid motion. When the temperature of a particle and its surrounding fluid is not the same, heat is transferred between the particle and the fluid. The heat flux influences the properties of the surrounding fluid and changes the dynamics of the sedimentation of the particle. To study the effect of non-isothermal flows to the motion of a particle, we have developed a Direct Numerical Simulation (DNS) method that is capable of solving both the momentum equation and heat transfer equation for the computation of thermal interaction between particles and fluid. This numerical method makes use of a finite difference method in combination with the Immersed Boundary (IB) method for treating the particulate phase. In particular, the IB concept has been extended to treat thermal boundary condition at the particle surface. A regular Eulerian grid is used to solve the modified momentum and energy equations for the entire flow region simultaneously. In the region that is occupied by the solid particles, a second particle-based Lagrangian grid is used, which tracks particles, and a force density function or an energy density function is introduced to represent the momentum interaction or thermal interaction between particle and fluid. In this paper, the IB based DNS method has been applied to study the fluidization of 12,000 circular particles, the unsteady conduction of a sphere in a stagnant fluid, and the sedimentation of a non-isothermal sphere in a viscous fluid at different Grashof number. Our simulation results show that the sedimentation velocity of the particle depends strongly on the thermal interaction of particle and fluid due to the strong buoyancy force exerted on the particle.
KOH-Etched Nozzles for Monodisperse Bubble Generation in Microreactors
Authors: Lang Philipp , Bammesberger Stefan , Woias Peter
Published: March 2011

Monodisperse micro bubbles are a great benefit for the direct fluorination of organic compounds, which is done via a direct injection of gaseous fluorine into the liquid reaction partner. In this two-phase system the fluorination process is improved by the large interfacial area of a chain of micro bubbles compared to slug or jet flow. A predictable generation of micro bubbles with high frequencies will lead to a higher yield and improved selectivity. Moreover, perfluorination is achievable. Here we describe the design and characterisation of a novel potassium hydroxide (KOH) etched nozzle concept for the generation of monodisperse microbubbles in a silicon microreactor. The gas is injected through the KOH-nozzle apex into a perpendicular liquid flow shearing off the gas bubbles. This concept enables a controlled variation of the bubble formation frequency and the gas-liquid interface. The control factors are the aspect ratio and the orientation of the nozzle with respect to the cross flowing liquid.
On Eulerian Modeling of Microchannel Gas Flows Closing Higher Statistical Moments of Molecule Velocity
Authors: Groll Rodion , Rath Hans J.
Published: March 2011

High pressure gradient driven micro-channel flow modelling with very the high ratios of absolute pressure and temperature (see Agrawal et al. 2005 [1]) define the difference between physical and computational results using continuum approaches (see Maurer et al. 2003, Durst et al. 2006, Dongari et al. 2008 [3, 4, 8]). In the present paper this deviation of the computational results is explained by the statistical correlation of the molecular number density and the single molecule velocity inside a compressible gas flow. Classical solutions of Navier-Stokes equations do not satisfy the physical conditions of compressible, dilute molecular flows (see Brenner 2005, Greenshields and Reese 2007, Mizzi et al. 2008 [2, 6, 9]). Furthermore the consistent entropy production and the comparison between macroscopic physical values and the molecular diffusion closure are shown. Finally the computational results using this statistical model are compared with algebraic solutions verifying the thermodynamic consistence of the present statistical moment closure model.
Micro-Scale Flow Pattern Classification Based on the K-Means Clustering Algorithm
Authors: Sempe´rtegui Daniel , Ribastki Gherhardt
Published: March 2011

In the present work, an objective method to characterize two-phase flow pattern was developed and implemented. The method is based on the characteristics of the signals provided by transducers measuring local temperature and pressure plus the intensity of a laser beam crossing the two-phase flow. The statistical characteristics of these signals were used as input features for the k-means clustering method. In order to implement the method, experimental flow patterns were obtained during flow boiling of R245fa in a 2.32 mm ID tube. Experiments were performed for mass velocities from 100 to 700kg/m2s, saturation temperature of 31 °C and vapor qualities up to 0.99. The cluster classification was compared against flow patterns segregated based on high speed camera images (8000 images/s) and a reasonable agreement was obtained.
Analysis on the Static Characteristics of the New Type Externally Pressurized Spherical Air Bearings
Authors: Wang Fusheng , Bao Gang
Published: March 2011

The new type externally pressurized spherical air bearings used mass properties measuring instruments are studied which are particularly recommended for determining mass properties of rockets, satellites and ballistic objects. The air bearings are the key component of the mass properties measuring instruments. In order to provide some theoretical guideline for the structure design of the new type externally pressurized spherical air bearings, this paper analyzes static characteristics and the factors affecting the static characteristics of the new type air bearings. A finite volume method is adopted to discretize the three-dimensional steady-state compressible Navier-Stokes equations, and a modified SIMPLE algorithm for compressible fluid is applied to solve the discretized governing equations. The pressure field and velocity field of the air bearings are obtained, from which the carrying capacity, static stiffness and mass flow of the air bearings can be derived, and the factors and rules affecting the static characteristics are analyzed. The calculation method proposed in this paper fits well the general principle, which can be extended to the characteristics analysis of other air bearings.
Experimental and Numerical Investigations of Inlet Boundary Conditions for a Propeller Turbine Draft Tube
Authors: Gagnon Jean-Mathieu , Flemming Felix , Qian Ruixia , Deschenes Claire , Coulson Stuart
Published: March 2011

The flow at the draft tube inlet of a propeller turbine is investigated via numerical simulations and experimental measurements. Two (2) experimental tools are used in combination to measure the velocity field in this study: 3D-Stereoscopic particles images velocimetry and 2D-laser doppler velocimetry. The numerical simulations are performed with steady RANS as well as URANS with the SST turbulence model. The results show the comparison of the turbulence intensity between experiments and CFD. Further assessment of the draft tube inlet flow is made with LDV to assess the circumferential non-uniformity of the flow. Finally, a complete frequency analysis puts in evidence the helical vortex rope frequency at partial discharge among many other flow phenomena. This study considered three operating points of a propeller axial turbine.
PIV Measurements of the Turbulent Secondary Flow in a Three-Dimensional Wall Jet
Authors: Namgyal Lhendup , Hall Joseph W.
Published: March 2011

The lateral half width of the turbulent three-dimensional wall jet is typically five to eight times larger than the vertical half width normal to the wall. Although, the reason for this behavior is not fully understood, it is known to be caused by strong secondary flows that develop in the jet due to presence of the wall. The source of the secondary flow in the jet has been attributed previously with both mean vorticity reorientation and to anisotropy in the Reynolds normal stresses, but until now there have been no measurements of these quantities in this flow. Particle Image Velocimetry (PIV) measurements are used herein to measure the Reynolds stresses that contribute to the secondary flow in a turbulent three-dimensional wall jet formed using a circular contoured nozzle with exit Reynolds number of 250,000. In particular, the Reynolds shear stress, vw was found to be significantly smaller throughout the jet than the differences in the Reynolds normal stresses (v2 − w2).
Numerical Simulation of Monju Plant Dynamics by Super-COPD Using Previous Startup Tests Data
Authors: Yamada Fumiaki , Ohira Hiroaki
Published: March 2011

Flow network models of the upper plenum of reactor vessel and the primary inlet plenum of intermediate heat exchanger (IHX) of MONJU were advanced and each model was validated by the measured data obtained in the previous system start-up tests (SSTs). Then the whole plant dynamics in a plant trip transient of MONJU were simulated by incorporating these flow network models. The natural circulation in the primary and secondary heat transport systems were also validated by these test results. From these validations, we concluded that the plant dynamics model incorporated the advanced models in Super-COPD code could simulate the whole plant dynamics in good accuracy both in the transients and natural circulation conditions and that it was applicable to predict the next SSTs.
Use of Micro-CT Images to Reconstruct Porous Media for Pore Network Model
Authors: Bera Bijoyendra , Mitra Sushanta K.
Published: March 2011

The present study is an investigation on the multi-phase flow, specifically oil-water phase flow inside an oil-reservoir using pore network modeling. Pore network model can be effectively used in understanding the transport process of the multiphase flow within the pores of oil reservoirs, which are typically in the range of 2–5 μm. Pore network model consists of two main components: the description of the pore geometry inside a porous rock material and the simulation of micro-scale processes to calculate various fluid flow properties. In the present study, the realistic description of the pore space is obtained using a Berea Sandstone Core sample. A small core of suitable dimension of this core sample is extracted and micro CT images of this sample are taken at a resolution of 2.1 m. Series of images are obtained in the form of cross-sectional view of individual layers as well as its two-dimensional reconstructions. These images are processed to reveal the exact positions of the void and solid spaces inside the rock-structure according to the pixel-distribution. Maximal ball algorithm is chosen and its extended form is applied to the image data to give the three dimensional reconstruction of the rock sample. In the 3D reconstruction, pores and throats are defined separately in a deterministic way. Thus, realistic complete network is possible to extract from high-resolution micro CT images, instead working with an equi-spaced pore throat system, normally used for such modeling. Pore network model calculations of the physical properties are easier to apply on the well-defined network and the property values such as permeability or capillary pressure are matched well against the experimental data.