bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparing actual and perceived causes of fever among community members in a low malaria transmission setting in northern Tanzania
Authors: Hertz Julian T. , Munishi O. Michael , Sharp Joanne P. , Reddy Elizabeth A. , Crump John A.
Published: October 2013

Objective

To compare actual and perceived causes of fever in northern Tanzania.

Methods

In a standardised survey, heads of households in 30 wards in Moshi, Tanzania, were asked to identify the most common cause of fever for children and for adults. Responses were compared to data from a local hospital‐based fever aetiology study that used standard diagnostic techniques.

Results

Of 810 interviewees, the median (range) age was 48 (16, 102) years and 509 (62.8%) were women. Malaria was the most frequently identified cause of fever, cited by 353 (43.6%) and 459 (56.7%) as the most common cause of fever for children and adults, respectively. In contrast, malaria accounted for 8 (2.0%) of adult and 6 (1.3%) of paediatric febrile admissions in the fever aetiology study. Weather was the second most frequently cited cause of fever. Participants who identified a non‐biomedical explanation such as weather as the most common cause of fever were more likely to prefer a traditional healer for treatment of febrile adults (OR 2.7, P < 0.001). Bacterial zoonoses were the most common cause of fever among inpatients, but no interviewees identified infections from animal contact as the most common cause of fever for adults; two (0.2%) identified these infections as the most common cause of fever for children.

Conclusions

Malaria is perceived to be a much more common cause of fever than hospital studies indicate, whereas other important diseases are under‐appreciated in northern Tanzania. Belief in non‐biomedical explanations of fever is common locally and has important public health consequences.
Non‐specific sex‐differential effect of DTP vaccination may partially explain the excess girl child mortality in Ballabgarh, India
Authors: Krishnan A. , Srivastava R. , Dwivedi P. , Ng N. , Byass P. , Pandav C. S.
Published: October 2013

Objective

To test the hypothesis that a gender differential exists in the effect on child mortality of BCG, DTP, measles vaccine as administered under programme conditions in Ballabgarh HDSS area.

Methods

All live births in 28 villages of Ballabgarh block in North India from 2006 to 2011 were followed until 31 December 2011 or 36 months of age whichever was earlier. The period of analysis was divided into four time periods based on eligibility for vaccines under the national immunisation schedule (BCG for tuberculosis, primary and booster doses of diphtheria–tetanus–pertussis and measles). Cox proportional hazards regression was used to assess the association between sex and risk of mortality by vaccination status using age as the timescale in survival analysis and adjusting for wealth index, access to health care, the presence of a health facility in the village, parental education, type of family, birth order of the child and year of birth.

Results

702 deaths (332 boys and 370 girls) occurred among 12 142 children in the cohort in the 3 years of follow‐up giving a cumulative mortality rate of 57.5 per 1000 live births with 35% excess girl child mortality. Age at vaccination for the four vaccines did not differ by sex. There was significant excess mortality among girls after immunisation with DTP, for both primary (HR 1.65; 95% CI:1.17–2.32) and DTPb (2.21; 1.24–3.93) vaccinations. No significant excess morality among girls was noted after exposure to BCG 1.06 (0.67–1.67) or measles 1.34 (0.85–2.12) vaccine.

Conclusion

This study supports the contention that DTP vaccination is partially responsible for higher mortality among girls in this study population.
The relevance of non‐technical skills in obstetrics and gynaecology
Authors: Jackson K Suzanne , Hayes Kevin , Hinshaw Kim
Published: October 2013

Key content

The non‐technical skills (NTS) as identified in the literature.

Developments in NTS training.

Current assessment practices and approaches to skills assessment in obstetrics and gynaecology.

Potential use of assessments of NTS in obstetrics and gynaecology.

Objectives

Describe the NTS required in obstetrics and gynaecology and their relationship to performance.

Develop an awareness of how these skills may be formally assessed and the potential role of NTS feedback.

Ethical issues

What are the ethical issues relating to the involvement of trainees in education research at the same time as performing an assessment?

Is another assessment feasible within the constraints of our training programme?
SMG1 is an ancient nonsense‐mediated mRNA decay effector
Authors: Lloyd James P. B. , Davies Brendan
Published: October 2013

Nonsense‐mediated mRNA decay (NMD) is a eukaryotic process that targets selected mRNAs for destruction, for both quality control and gene regulatory purposes. SMG1, the core kinase of the NMD machinery in animals, phosphorylates the highly conserved UPF1 effector protein to activate NMD. However, SMG1 is missing from the genomes of fungi and the model flowering plant Arabidopsis thaliana, leading to the conclusion that SMG1 is animal‐specific and questioning the mechanistic conservation of the pathway. Here we show that SMG1 is not animal‐specific, by identifying SMG1 in a range of eukaryotes, including all examined green plants with the exception of A. thaliana. Knockout of SMG1 by homologous recombination in the basal land plant Physcomitrella patens reveals that SMG1 has a conserved role in the NMD pathway across kingdoms. SMG1 has been lost at various points during the evolution of eukaryotes from multiple lineages, including an early loss in the fungal lineage and a very recent observable gene loss in A. thaliana. These findings suggest that the SMG1 kinase functioned in the NMD pathway of the last common eukaryotic ancestor.
ELASTOGRAPHIC CHARACTERISTICS OF THE METACARPAL TENDONS IN HORSES WITHOUT CLINICAL EVIDENCE OF TENDON INJURY
Authors: Lustgarten Meghann , Redding W. Rich , Labens Raphael , Morgan Michel , Davis Weston , Seiler Gabriela S.
Published: October 2013

Tendon and ligament injuries are common causes of impaired performance in equine athletes. Gray‐scale ultrasonography is the current standard method for diagnosing and monitoring these injuries, however this modality only provides morphologic information. Elastography is an ultrasound technique that allows detection and measurement of tissue strain, and may provide valuable mechanical information about equine tendon and ligament injuries. The purpose of this study was to determine the feasibility, reproducibility, and repeatability of elastography; and to describe elastographic characteristics of metacarpal tendons in sound horses. Nineteen legs for 17 clinically sound horses without evidence of musculoskeletal pathology were included. Elastographic images of the superficial and deep digital flexor tendons and the branches of the suspensory ligament (tendon of the interosseous muscle) were described quantitatively and qualitatively. There was no statistically significant difference between operators (P = 0.86) nor within operators (P = 0.93). For qualitative assessments, reproducibility (0.46) was moderate and repeatability (0.78) was good. Similar to human Achilles tendons, equine tendons were classified as predominantly hard using elastography. There was no statistically significant difference in stiffness of the flexor tendons (P = 0.96). No significant difference in stiffness was found with altered leg position during standing (P = 0.84) and while nonweight bearing (P = 0.61). The flexor tendons were softer when imaged in longitudinal versus transverse planes (P < 0.01) however, the suspensory branches were not (P = 0.67). Findings supported future clinical application of elastography as a noninvasive “stall‐side” imaging modality for evaluation of the tendons and ligaments of the distal forelimb in horses.
IMAGING DIAGNOSIS—MENINGOENCEPHALITIS SECONDARY TO SUPPURATIVE RHINITIS AND MENINGOENCEPHALOCELE INFECTION IN A DOG
Authors: Rosenblatt Alana J. , Scrivani Peter V. , Caserto Brian G. , Ruby Rebecca E. , Loftus John P. , de Lahunta Alexander , Noden Drew M.
Published: October 2013

Nasal encephaloceles (meningoceles or meningoencephaloceles) are rare and not reported to be infected or coupled with a facial deformity in dogs. This report describes an older dog with acute worsening of seizures due to suppurative meningoencephalitis with coexisting suppurative rhinitis and infection of a meningoencephalocele. Additionally, the dog had a facial deformity for at least 5 years. The results of necropsy, computed tomography, and postmortem magnetic resonance imaging are compared. The development of nasal encephaloceles is discussed, including the potential role of early trauma, and whether separation of neural ectoderm from the surface ectoderm is part of the pathogenesis.
Ultra Fast Cooling and Its Effect on the Mechanical Properties of Steel
Authors: Mohapatra Soumya S. , Ravikumar Satya V. , Ranjan Ravi , Pal Surjya K. , Brat Singh Shiv , Chakraborty Sudipto
Published: October 2013

The objective of this work is to study about the ultrafast cooling of a hot static 6 mm thick steel plate (AISI-1020) by air assisted spray cooling. The study covers the effect of air flow rate and the water impingement density on the cooling rate. The initial temperature of the plate, before the cooling starts, is kept at 900 °C. The spray was produced from a full cone high mass flux and low turn down ratio air atomizer at a fixed nozzle to plate distance. The cooling rate shows that low turn down ratio air atomized spray can generate ultra fast cooling (UFC) rate for a 6 mm thick steel plate. After cooling, the tensile strength and hardness of the cooled steel plate were examined. The surface heat flux and surface temperature calculations have been performed by using INTEMP software. The result of this study could be applied in designing of fast cooling system especially for the run-out table cooling.
Predicting Thermal System Performance and Estimating Parameters for Systems Burdened With Uncertainties and Noise Using Hierarchical Bayesian Inference
Authors: Emery A. F. , Bardot D.
Published: October 2013

The precision of estimates of system performance and of parameters that affect the performance is often based upon the standard deviation obtained from the usual equation for the propagation of variances derived from a Taylor series expansion. With ever increasing computing power it is now possible to utilize the Bayesian hierarchical approach to yield improved estimates of the precision. Although quite popular in the statistical community, the Bayesian approach has not been widely used in the heat transfer and fluid mechanics communities because of its complexity and subjectivity. The paper develops the necessary equations and applies them to two typical heat transfer problems, measurement of conductivity with heat losses and heat transfer from a fin. Because of the heat loss the probability distribution of the conductivity is far from Gaussian. Using this conductivity distribution for the fin gives a very long tailed distribution for the heat transfer from the fin.
Modeling Bicortical Screws Under a Cantilever Bending Load
Authors: James Thomas P. , Andrade Brendan A.
Published: October 2013

Cyclic loading of surgical plating constructs can precipitate bone screw failure. As the frictional contact between the plate and the bone is lost, cantilever bending loads are transferred from the plate to the head of the screw, which over time causes fatigue fracture from cyclic bending. In this research, analytical models using beam mechanics theory were developed to describe the elastic deflection of a bicortical screw under a statically applied load. Four analytical models were developed to simulate the various restraint conditions applicable to bicortical support of the screw. In three of the models, the cortical bone near the tip of the screw was simulated by classical beam constraints (1) simply supported, (2) cantilever, and (3) split distributed load. In the final analytical model, the cortices were treated as an elastic foundation, whereby the response of the constraint was proportional to screw deflection. To test the predictive ability of the new analytical models, 3.5 mm cortical bone screws were tested in a synthetic bone substitute. A novel instrument was developed to measure the bending deflection of screws under radial loads (225 N, 445 N, and 670 N) applied by a surrogate surgical plate at the head of the screw. Of the four cases considered, the analytical model utilizing an elastic foundation most accurately predicted deflection at the screw head, with an average difference of 19% between the measured and predicted results. Determination of the bending moments from the elastic foundation model revealed that a maximum moment of 2.3 N m occurred near the middle of the cortical wall closest to the plate. The location of the maximum bending moment along the screw axis was consistent with the fracture location commonly observed in clinical practice.
The Gas Turbine Hybrid Vehicle LETHE™ at UDR1: The On-Board Innovative ORC Energy Recovery System — Feasibility Analysis
Authors: Capata Roberto , Sciubba Enrico , Toro Claudia
Published: October 2013

A GTHV (gas turbine hybrid vehicle) is an electric vehicle with traction entirely electric on 1 or 2 axles, equipped with a small turbogas whose only function is that of recharging the battery pack and possibly other energy storage devices present on board. After a brief review of the history of the GTHV technology, a complete feasibility assessment of a prototype configuration of a GTHV designed by the University of Roma 1 is presented. All issues related to the system and component design, packaging, identification of the “optimal” hybridization ratio, performance of the (gas turbine + batteries + electrical motor) conversion system, braking energy recovery systems (KERS), mechanical and electric storage devices (flywheels, capacitors, advanced batteries), monitoring and control logic, compliance with the European vehicular ECE emission regulations, have been already discussed in previous papers. The present study analyzes the feasibility to insert “on-board” an innovative and patented ORC (Organic Rankine Cycle) recovery system. In fact, the thermal source on the LETHE© vehicle is a turbogas of suitable power (10 to 30 kW depending on the vehicle class). The sensible heat of the exhaust gases is an ideal thermal source for an ORC system that can feed the car conditioning system and other auxiliaries.
The Solution of a Heat Transfer Problem With Change of State Inside a Spherical Shell
Authors: de Oliveira Danillo Silva , Ribeiro Fernando Brenha
Published: October 2013

The heat transfer problem is solved for the case of cooling, below the freezing temperature, an initially liquid material inside a spherical shell. The shell is limited by a fixed inner surface and by an outer surface, free to radially expand or contract. As boundary conditions it is imposed that the inner surface is kept constant below the freezing temperature of the liquid and the outer surface is maintained constant above it. The solution represents the formation of a solidified layer that expands outward, separated from the liquid by a spherical surface kept constant at the freezing temperature. The problem is solved in the form of two closed form solutions, written in non-dimensional variables: one for the heat conduction equation in the solid layer and the second for the heat conduction – advection equation in the liquid layer. The solutions formally depend of and are linked by the time dependent radius of the spherical solid–liquid interface and its time derivate, which are, at first, unknown. A differential equation describing the solid–liquid interface radius as function of time is obtained imposing the conservation of energy through the interface during the heat exchange process. This equation is non-linear and has to be numerically solved. Substitution of the interface radius and its time derivate for a particular instant in the heat transfer equations solutions furnishes the temperature distribution inside the spherical shell at that moment. The solution is illustrated with numerical examples.
Novel Formulations for Higher-Order Bounds on Effective Transverse Elastic Moduli of Three-Phase Cylindrical Fiber Reinforced Composites
Authors: Ko Yu-Fu , Ju J. W.
Published: October 2013

A higher-order multiscale structure for three-phase composites containing randomly located yet unidirectionally aligned circular fibers is proposed to predict effective transverse elastic moduli based on the probabilistic spatial distribution of circular fibers, the pairwise fiber interactions, and the ensemble-area multi-level homogenization method. Specifically, the two inhomogeneity phases feature distinct elastic properties and sizes. In the special event, two-phase composites with same elastic properties and sizes of fibers are studied. Two non-equivalent micromechanical formulations are considered to derive effective transverse elastic moduli of two-phase composites leading to new higher-order bounds. Furthermore, the effective transverse elastic moduli for an incompressible matrix containing randomly located and identical circular rigid fibers and voids are derived. It is demonstrated that significant improvements in the singular problems and accuracy are achieved by the proposed methodology. Numerical examples and comparisons among our theoretical predictions, available experimental data, and other analytical predictions are rendered to illustrate the potential of the present method.
Estimating the ‘In-Service’ Modulus of Elasticity and Length of Polyester Mooring Lines via a Non Linear Viscoelastic Model Governed by Fractional Derivatives
Authors: Evangelatos Georgios I. , Spanos Pol D.
Published: October 2013

In this paper a non linear viscoelastic model governed by fractional derivatives is presented for modeling the in-service behavior of polyester mooring lines. In the formulation an iterative approach utilizing the Gauss-Newton minimization algorithm in conjunction with the catenary equations used to determine the static modulus of elasticity and the effective length of polyester mooring lines corresponding to calm sea conditions. Upon establishing the accuracy of the static modulus via comparison with field data, the catenary equations and the offshore platform’s position versus time are used to identify the polyester strain under developed-sea conditions. In this manner, time histories of stress and strain for polyester ropes in service conditions are obtained. Then, a non linear viscoelastic model involving fractional derivative terms is used to capture the in service polyester line behavior. For this, the tension of the proposed model corresponding to the actual polyester strain is compared at each time step to the tension obtained from the field data. Finally, the parameters of the proposed model are derived by minimizing the error in the least-squares sense over a large number of data points using the Levenberg-Marquardt algorithm. The numerically derived force-strain relationship is found to be in reasonable agreement with supplementary field and laboratory experimental data, the field data pertain to an offshore structure moored in position using polyester mooring lines operated in the Gulf of Mexico during Hurricane Katrina (August of 2005).
Determination of Dynamic Fracture Toughness at High Loading Rates
Authors: Mayer Uwe
Published: October 2013

To determine fracture mechanics values at high loading rates from force and displacement signals requires the influences of inertia and the propagation of elastic waves to be taken into account. This paper shows how measurement technique requirements can be fulfilled for determination of key values for a testing time below 100μs for 1T C(T) specimens. Results using this method are given for specimens of 22 NiMoCr 3 7 steel (A 508 C1.2) from a project on correlation between dynamic crack initiation and crack arrest.
Velocity Field Computation in Plastic Flow in Non-Circular Tubes Using Natural Coordinates
Authors: Letelier Mario F. , Stockle Juan S.
Published: October 2013

A numerical method to determine the velocity field, and related variables, in plastic flow in non-circular straight ducts is presented. The method is an extension of previous work of the senior author related to modeling laminar flow in pipes of arbitrary cross-sectional contours using natural coordinates. In this case the concept of “natural coordinates” is applied to the system of orthogonal curves determined by the plane isovels and their normal counterparts. The momentum equation for the axial velocity is expressed in natural coordinates in which one relevant variable is the radius of curvature of isovels. The method is applied to a selected set of shapes when the fluid is a Bingham plastic.

Isovels and plug zones are determined drawing on the properties of the isolvels and normal curves. Computations start at the pipe perimeter and advance toward the center.
Numerical Simulation of Condensation in a Rectangular Minichannel Using VOF Model
Authors: Liu Zhenyu , Sunden Bengt , Yuan Jinliang
Published: October 2013

The understanding of two-phase flow and heat transfer with phase change in minichannels is needed for the design and optimization of heat exchangers and other industrial applications. In this study a three-dimensional numerical model has been developed to predict filmwise condensation heat transfer inside a rectangular minichannel. The Volume of Fluid (VOF) method is used to track the vapor-liquid interface. The modified High Resolution Interface Capture (HRIC) scheme is employed to keep the interface sharp. The governing equations and the VOF equation with relevant source terms for condensation are solved. The surface tension is taken into account in the modeling and it is evaluated by the Continuum Surface Force (CSF) approach. The simulation is performed using the CFD software package, ANSYS FLUENT, and an in-house developed code. This in-house code is specifically developed to calculate the source terms associated with phase change. These terms are deduced from Hertz-Knudsen equation based on the kinetic gas theory. The numerical results are validated with data obtained from the open literature. The standard k-ω model is applied to model the turbulence through both the liquid and vapor phase. The numerical results show that surface tension plays an important role in the condensation heat transfer process. Heat transfer enhancement is obtained due to the presence of the corners. The surface tension pulls the liquid towards the corners and reduces the average thermal resistance in the cross section.
A Protective Structure, Saver During Structural Collapse
Authors: Heidari Alireza , Galishnikova Vera V. , Kani Iradj Mahmoudzadeh
Published: October 2013

In this paper a new protective structure is presented to save human life, in the case of building collapse, caused by an earthquake, a terrorist attack or other catastrophic events. It is well-known that the number of casualties after major earthquakes during night time far exceeds the corresponding number of those events of similar magnitudes occurring that of the day times.

The life-saver device discussed here is a bolted-moment-resisting 3-D steel frame that encapsulates a single or double-bed sleeping area at home. The frame consists of a number of beam-columns of angle cross-section, bolted together by gusset plates and topped with a thin steel plate or a rectangular rebar mesh. The collapse of walls and ceilings of the building on top of this structure will result in large plastic deformations in various sections of the frame, whereby the energy of the falling debris is dissipated. Despite these large deflections, no harm is inflicted upon the people sleeping inside the frame.

The physical behavior of this new life-saving device, under real situation of structural collapse, is modeled in the ANSYS LS-DYNA software. Combined nonlinear analysis of the frame is performed under dynamic loads developed. It is assumed that the angle members of the frame are stiffened by welding triangular gusset plates at appropriate intervals along their length, so that they behave in a compact manner without local buckling. The discussion of this phenomenon is the subject of another paper and is not presented here. The behavior of the protective structure shows that the people resting or taking refuge inside, will be safe in the event of the collapse of the building.

Austenitic twinning induced plasticity (TWIP) steel which has a good combination of both strength and ductility also has been used for modeling and designing this structure and the results has been compared with ordinary steels. The design is verified for the emergency limit state considering the safety of people inside the protective structure.
A New Trajectory Control of a Car-Like Wheeled Robot
Authors: Lee Ho-Hoon
Published: October 2013

This paper proposes a trajectory control scheme for a car-like four-wheeled mobile robot. The proposed control scheme consists of a trajectory generator, a motion control law, and a steering control law. First, a real-time trajectory generator is designed based on the nonholonomic kinematic constraints of the robot, in which the reference driving speed and time rate of heading angle are computed in real time for a given desired trajectory of the robot. Next, motion and steering control laws are designed based on the dynamic model of the robot. The motion and steering control laws are used to control the robot speed and steering angle. Finally, the validity of the proposed control scheme is shown by realistic computer simulations with one sampling time delay in the control loop. In this study, the Lyapunov stability theorem and the loop shaping method are used as mathematical design tools. The proposed control guarantees asymptotic stability of the trajectory control while keeping all internal signals bounded. The proposed method of control design is much simpler than the back-stepping method.
Analysis and Control of Chaotic Responses of a Cantilever Beam Subjected to Sinusoidal Excitation
Authors: Dai Liming , Sun Lin
Published: October 2013

With employment of a modified Fuzzy Sliding Mode Control (FSMC) approach, in the present research a methodology is developed to control the chaotic responses of a laminated composite cantilever beam subjected to an external sinusoidal excitation. The 3rd order shearing effect on the responses of the beam is considered in the model establishment. The modified FSMC approach has shown significant advantages on effectively suppressing the chaotic responses of the investigated system.
Dynamic Response of a Steel-Concrete Hybrid Frame to Support 15MW Compressor
Authors: Shin Seunghoon , Sun Guangyoung , Lee Juwon , Kim Kangboo
Published: October 2013

In this paper, the structural dynamics study of the frame to support 15MW compressor is suggested. This study used the steel-concrete hybrid frame to support a large compressor system. This paper provided experimental and analytical method to structural design the hybrid frame by considering in rotordynamics and aerodynamics. Dynamic characteristics of the frame have to be identified to tune the finite element model’s boundary condition and to avoid resonance. Therefore modal testing of the frame is performed and boundary conditions are modified applying to the previously obtained modal parameters. While compressor is operated, multiple dynamic loads of compressor, motor and expander may excite on the frame. The total dynamic load is derived by axial aerodynamic load of impeller, radial load of gear and unbalance load of rotor. After dynamic analysis completion, the analysis result is compared with test result to verify the accuracy of analysis. Through this structural dynamic analysis, structural vibration response of hybrid frame can be estimated.
Enhanced Forced Convection in a Square Channel With Two-Stage Corona Wind Generator
Authors: Mazumder A. K. M. Monayem H. , Lai F. C.
Published: October 2013

In this study, enhancement in forced convection inside a square channel by a two-stage electrohydrodynamic (EHD) gas pump has been examined by numerical simulations. The EHD gas pump with 28 emitting electrodes in each stage has been evaluated for a wide range of operating voltages starting from the corona threshold voltage up to 28 kV for further improvement in its performance over that of a single-stage. To achieve the maximum enhancement in heat transfer, the emitting electrodes of the corona wind generator are flush mounted on the channel walls so that the corona wind produced directly perturbs the boundary layer. The results show that EHD technique has a great potential for applications in thermal management.
Analysis of Electrohydraulic Shock Wave Generation
Authors: Carden Arnold E.
Published: October 2013

Electrohydraulic Shock Wave Generation is an energy conversion process. Electrical energy stored at high voltage in a capacitor is discharged through a set of electrodes under water. The arc heats a small volume of water to a high temperature and pressure in the shock regime. This paper analyzes the relationship of the significant variables from an energy conversion perspective. The expanding pressure wave is able to fracture rock, kidney stones (lithotripsy), and resin bonded sand cores in castings. Experimental results are presented.
Dynamic Analysis of Vehicle-Guideway Interaction in a Maglev Cargo Transportation System
Authors: Buth Bun , Lu Bei
Published: October 2013

The dynamic response of a magnetic levitation (maglev) transportation system has important consequences for guideway design and system costs. The objective of this research is to develop a framework to analyze the dynamic interaction between a flexible guideway structure and a maglev vehicle named Electric Cargo Conveyor (ECCO). Different from other maglev vehicles, which use either electromagnetic or electrodynamic suspension technologies, the ECCO is the only system utilizing the Inductrack levitation technology, where the permanent magnets are arranged as so-called Halbach arrays to create a levitating force. The theoretical dynamic model of the ECCO system is derived in this paper. The guideway structure is modeled as a simply supported beam based on Bernoulli-Euler beam theory. The vehicle is modeled as a two-degree-of-freedom mass-damper-spring system. They are coupled with each other through nonlinear magnetic forces. To investigate the dynamic interaction between the vehicle and guideway, a finite element model of the ECCO system is created in COMSOL Multiphysics using its equation-based modeling interface. Numerical simulations are conducted to examine the effects of different factors such as the cargo weight and the vehicle speed.
Use of Modified Balje Maps in the Design of Low Reynolds Number Turbocompressors
Authors: Capata Roberto , Sciubba Enrico
Published: October 2013

The design of micro and ultra-micro turbomachinery introduces severe challenges due to the absence of a reliable and sufficiently extended database, so that the phenomenological differences among micro-turbomachines and between micro- and commercial-scale devices must be semi-empirically modelled from case to case. Scope of this study is to verify the possibility of extending the usual design correlations and maps to such small scales: specifically, this paper presents a procedure to conveniently modify the standard performance Balje map so that it can be adopted “as is” in the design of a micro and ultra-micro machines. The results of a systematic comparison with the general Stodola-like formula allow extending the applicability of Re-corrected Balje and Smith charts to the range of Re ≤ 105.
Heat Transfer Coefficients and Lifetimes of Micro-Droplet Evaporation in the Transition Regime
Authors: Hanchak Michael S. , Briones Alejandro M. , Ervin Jamie S. , Byrd Larry W.
Published: October 2013

The goal of the present work is to determine the heat transfer characteristics of evaporating micro-droplets of water from a hot surface. To accomplish this, a one-dimensional, finite-difference model is used to simulate the transport of water vapor and energy from the droplet’s liquid-vapor interface toward and inside the hemispherical, gaseous region surrounding the droplet. The model incorporates a transition regime correction to the kinetic theory evaporative mass flux. The transition regime correction, a multiplier applied to the kinetic flux, is a function of the Knudsen number, the ratio of molecular mean free path to the droplet radius. The transition regime encompasses droplet sizes for which neither the kinetic model of evaporation nor the hydrodynamic continuum theory is entirely appropriate. The model simulates the liquid phase as one-dimensional conduction between the hot surface and the liquid-vapor interface. Previously, we validated our model against measured volume data as a function of time for several evaporating droplets. Using the model, overall heat transfer coefficients and total evaporation times are determined. Linear fits of both are provided against dimensional groupings of initial droplet volume and surface temperature superheat.
Optimal Power Generation Unit Sizing for Base-Loaded Combined Heat and Power Systems Using Monthly vs. Hourly Time-Steps
Authors: Thomas Robert , Luck Rogelio , Mago Pedro J.
Published: October 2013

In many applications combined heat and power (CHP) systems provide both cost and environmental benefits when used in place of traditional grid utility systems. The benefits of CHP systems, however, are very sensitive to the proper selection of the system’s components for given loading conditions, especially the power generation unit (PGU). The PGU size should be selected based on the facility’s electrical and thermal loading conditions to generate the maximum cost savings. Many researchers have presented methods for selecting the optimal PGU size using hourly load data. However, hourly load data is seldom available for a facility. For this reason, this paper provides a series of calculations that determine the optimal PGU size based on annual cost savings for a base-loaded CHP system using monthly load data, which is representative of a facility’s utility bills that are always available. Furthermore, because resale of excess electricity to the grid is widely available in the United States and other countries, this capability is included in the equations presented in this paper. Unfortunately, in some cases monthly-based calculations do not provide enough information to properly determine the optimal size of the PGU. A case study is performed to compare the results of monthly-based and hourly-based calculations for sixteen benchmark buildings in Albuquerque, NM and Baltimore, MD to investigate when monthly-based calculations can be used. It is noted that resale of excess electricity is considered in Baltimore, but not considered in Albuquerque for this study. A statistical analysis of the results uncovers that the magnitude of the coefficient of variation of the building’s heating demand indicates whether monthly-based calculations can be used, and furthermore, whether annual cost savings are possible. Results indicate that the proposed monthly-based calculations can determine the optimal PGU size, and calculate annual cost savings for approximately half of the facilities in Albuquerque and Baltimore. Further studies must be performed to determine a broader range of locations where this monthly-based calculation strategy is valid.
Chaos in Non-Newtonian Rotational Flow With Axial Flow
Authors: Ashrafi N. , Hazbavi A. , Forghani F.
Published: October 2013

The influence of axial flow on the vortex formation of pseudoplastic rotating flow between cylinders is explored. The fluid is assumed to follow the Carreau-Bird model and mixed boundary conditions are imposed. The four-dimensional low-order dynamical system, resulted from Galerkin projection of the conservation of mass and momentum equations, includes additional nonlinear terms in the velocity components originated from the shear-dependent viscosity. In absence of axial flow the base flow loses its radial flow stability to the vortex structure at a lower critical Taylor number, as the pseudoplasticity increases. The emergence of the vortices corresponds to the onset of a supercritical bifurcation which is also seen in the flow of a linear fluid. However, unlike the Newtonian case, pseudoplastic Taylor vortices lose their stability as the Taylor number reaches a second critical number corresponding to the onset of a Hopf bifurcation. Existence of an axial flow, manifested by a pressure gradient appears to further advance each critical point on the bifurcation diagram. In addition to the simulation of spiral flow, the proposed formulation allows the axial flow to be independent of the main rotating flow. Complete transient flow field together with viscosity maps are also presented.
Design, Construction and Calibration of an Instrument for Measuring the Production of Chilled Water by the Combined Effects of Evaporation and Night Sky Radiation
Authors: Al-Zubaydi Ahmed Y. Taha , Dartnall John , Dowd Annette
Published: October 2013

This paper presents the design and mathematical modeling of thermal radiator panels to be used primarily to measure night sky radiation from dry and wet coated surfaces. Three panels may be used in conjunction as a combined measuring system. One panel consists of an upper dry surface coated aluminum sheet laminated to an ethylene vinyl acetate foam backing block having a pattern of parallel flow water channels and header channels milled into its mating surface prior to lamination to the aluminum sheet. This configuration provides a fin and channel radiator instrument whereby circulating water may be used to measure the heat loss from this panel to night sky radiation. In a second configuration, the surface of a panel without buried water channels but otherwise identical may be wetted in order to study and compare the night sky radiation from its wet surface. In this case, the measuring water is circulated over the upper face of this panel. In a third configuration, water is sprayed onto the surface of the second panel (or a similar panel) so that an evaporative cooling effect is gained in addition to the radiation effect. Initial TRNSYS simulations for the performance of all three configurations are presented and it is planned to use the panels as calibrated instruments for discriminating between the cooling effects of night sky radiation and evaporation.
A Novel Magnetically-Levitated Flywheel Energy Storage Alternative to Lithium-Ion Battery Packs for Oilfield Service
Authors: Saeed Ahmed , Palazzolo Alan , Ahmed Shehab
Published: October 2013

In this study, a novel concept for a downhole flywheel energy storage module to be embedded in a bottom-hole-assembly (BHA) is presented and modeled, as an alternative power source to existing lithium-ion battery packs currently deployed in drilling operations. Lithium-ion batteries disadvantages include deteriorated performance in high temperature, limited lifetime that necessitates frequent replacement which elevates operation costs, and environmental hazards associated with its proper disposal. Extreme and harsh downhole conditions necessitate that the flywheel module withstands temperatures and pressures exceeding 300 °F and 20 kpsi, respectively, as well as violent vibrations encountered during drilling. Moreover, the flywheel module should adhere to the geometric constraints of the wellbore and the BHA in which it is embedded. A five-axis magnetic levitation control system was designed and tuned to maintain continuous suspension of the flywheel under the harsh lateral, axial and torsional drilling vibrations of the BHA. This necessitated complete identification and modeling of the drill string dynamics and the sources of vibrations excitation that include stick-slip, bit-bounce, and whirling. Thus, an integrated finite element model was developed that included the rotordynamic behavior of the flywheel and the BHA, the component dynamics of the magnetic levitation control system, and the drillbit cutting dynamics. The model also included a newly developed model for coupling between lateral, axial and torsional vibrations. It was demonstrated through numerical simulations that the active magnetic bearings (AMB) successfully maintain continuous flywheel suspension due to all different types of external vibration as well as its own lateral vibration due to mass imbalance.
Dynamics and Controller Design of a Screw Wheel Drive Holonomic Rescue Robot
Authors: Kececi Emin Faruk
Published: October 2013

This paper reports a holonomic rescue robot where the robot is driven by screw wheels. The necessity of a such platform is explained and the mechanical design and the actual prototype are presented. In order to design an adaptive control algorithm to ensure the trajectory tracking, the dynamical model is constructed. The stability of the adaptive control algorithm is proven with Lyapunov stability analysis. The necessary electronics to implement the controller algorithm is explained and the conclusions and future work section reports the results of the study as well as the future research directions.
Application of an Advanced Simulation Model to a Micro-CHP ORC-Based System for Ultra-Low Grade Heat Recovery
Authors: Ziviani Davide , Beyene Asfaw , Venturini Mauro
Published: October 2013

This paper presents the results of the application of an advanced thermodynamic model developed by the authors for the simulation of Organic Rankine Cycles (ORCs). The model allows ORC simulation both for steady and transient analysis. The expander, selected to be a scroll expander, is modeled in detail by decomposing the behavior of the fluid stream into several steps. The heat source is coupled with the system through a plate heat exchanger, which is modeled using an iterative sub-heat exchanger modeling approach.

The considered ORC system uses solar thermal energy for ultra-low grade heat recovery. The simulation model is used to investigate the influence of ORC characteristic parameters related to the working medium, hot reservoir and component efficiencies for the purpose of optimizing the ORC system efficiency and power output. Moreover, dynamic response of the ORC is also evaluated for two scenarios, i.e. (i) supplying electricity for a typical residential user and (ii) being driven by a hot reservoir. Finally, the simulation model is used to evaluate ORC capability to meet electric, thermal and cooling loads of a single residential building, for typical temperatures of the hot water exiting from a solar collector.
Computational Studies of Droplet Dynamics in a Steady Electric Field
Authors: Yao Ye , Beussman Kevin M. , Wang Yechun
Published: October 2013

A three-dimensional spectral boundary integral algorithm has been developed to investigate the dynamics of a neutrally buoyant and initially uncharged droplet in another immiscible fluid subjected to a steady electric field. Good agreement has been found by comparing with analytical solutions and experimental results for droplets in a uniform electric field. Benefit from the fully three-dimensional algorithm that we have developed, the droplet deformation and migration induced by the nonuniform electric field created by a point charge has been investigated. We computationally predict the deformation and migration of the droplet under the influence of physical properties of the system: resistivities, permittivities and viscosities, as well as the electric capillary number. The numerical scheme developed by this study and computational results provide foundation for the computational investigation of droplet motion in digital microfluidics.
The Comparative Study of Two Frictional Theories for Monodisperse and Polydisperse Granular Flow From a Hopper
Authors: Caserta Alice Jordam , de Souza Braun Meire Pereira , Navarro Hélio Aparecido
Published: October 2013

The purpose of this paper is to analyze the granular material discharge from a hopper. For this study was used the modification of a frictional-kinetic model for the gas-particle flow proposed by Srivastava and Sundaresan [1] (S-S model) and compared it with the frictional model proposed by Syamlal et al. [2] (S-R-O model). The numerical simulations were performed using the source code MFIX (Multiphase Flow with Interphase eXchange) [2] developed at NETL (“National Energy Technology Laboratory”). The two frictional flow theories were studied for both monodisperse and polydisperse granular flow. For polydisperse flow, two different particle diameters were used, 0.05 cm and 0.1 cm. The influence of the particle diameter was presented and discussed. The results obtained from the comparison of the two frictional models showed that the lower values of the discharge rate were computed using the S-R-O frictional model as compared to the S-S model predictions. This was expected due to the fundamental difference between these two frictional models.
Nanoparticle Transport Through Boundaries of Nanoporous Structures
Authors: Mahadevan T. S. , Milosevic M. , Kojic M. , Hussain F. , Kojic N. , Ferrari M. , Ziemys A.
Published: October 2013

In transport phenomena involving colloidal nanoparticle (NP) suspensions in complex environments, the inter particle interactions play an important role especially when the sizes of the confining environments approaches the particle sizes. Specific examples of such systems are encountered in NP transport through nanochannels used in drug delivery and nanofluidic cooling[1–5]. In ionic colloidal suspensions like the ones encountered in the above applications, the NPs acquire characteristic surface charges which results in a surface potential and a double layer of co- and counter-ions from the solution. DLVO theory predicts the interaction energy resulting from the double layer to be [6]:(1)Wr=64πkBTRρ∞γ2κ2exp-κr where r is the separation between NP surfaces, and R is the radius of the NP, ρ∞ is the concentration of ions in the suspension, κ−1 is the Debye screening length (characteristic size of the double layer) and kB and T are the Boltzmann constant and the temperature. As κ−1 approaches the size range of the particles, the interactions amongst the particles may span several times the particle size and contributes to particle diffusion.