bluuebunny/crossref_metadata_2025 huggingface dataset:
Applicability of Quasi-3D Blade Design Methods to Profile Shape Optimizaton of Turbine Blades
Authors: Gezork Tobias , Völker Stefan
Published: November 2013

The performance of gas turbine airfoils is continually improved by creating advanced aerodynamic and thermal designs. Optimization methods are used to handle the increasing complexity of such a design. However, optimization is expensive when performed based on 3D CFD calculations. Therefore, an optimization strategy based on simpler, less expensive analysis methods is desirable.

Oftentimes, a so-called quasi-3D (Q3D) approach is used, where 2D calculations are carried out on multiple, radially stacked meridional blade sections. This paper investigates the applicability of such an approach for optimization with regard to blade profile loss.

Obviously, certain physical effects are neglected using this approach, leading to errors in the predicted blade performance. Still, optimization based on Q3D calculations might be possible if the error is consistent, i.e. not random.

For this purpose, a design of experiment (DOE) was carried out to compare and correlate loss predictions from Q3D calculations and high-fidelity 3D CFD calculations for gas turbine blades. It is shown that the total pressure loss coefficients found with both the Q3D and 3D calculations correlate well (75–90%) to warrant the use of a Q3D method for profile shape optimization. Subsequently, an optimization is performed to demonstrate the applicability of the method.
Optimization of a Centrifugal Compressor Impeller Design for Robustness to Manufacturing Uncertainties
Authors: Javed A. , Pecnik R. , van Buijtenen J. P.
Published: November 2013

Compressor impellers for mass-market turbochargers are die-casted and machined with an aim to achieve high dimensional accuracy and acquire specific performance. However, manufacturing uncertainties result in dimensional deviations causing incompatible operational performance and assembly errors. Process capability limitations of the manufacturer can cause an increase in part rejections, resulting in high production cost. This paper presents a study on a centrifugal impeller with focus on the conceptual design phase to obtain a turbomachine that is robust to manufacturing uncertainties. The impeller has been parameterized and evaluated using a commercial computational fluid dynamics (CFD) solver. Considering the computational cost of CFD, a surrogate model has been prepared for the impeller by response surface methodology (RSM) using space-filling Latin hypercube designs. A sensitivity analysis has been performed initially to identify the critical geometric parameters which influence the performance mainly. Sensitivity analysis is followed by the uncertainty propagation and quantification using the surrogate model based Monte Carlo simulation. Finally a robust design optimization has been carried out using a stochastic optimization algorithm leading to a robust impeller design for which the performance is relatively insensitive to variability in geometry without reducing the sources of inherent variation i.e. the manufacturing noise.
Special Challenges in the CFD Modeling of Transonic Turbo-Expanders
Authors: Rubechini Filippo , Marconcini Michele , Arnone Andrea , Del Greco Alberto Scotti , Biagi Roberto
Published: November 2013

High pressure ratio turbo-expanders often put a strain on CFD modeling. First of all, the working fluid is usually characterized by significant departures from the ideal behavior, thus requiring the adoption of a reliable real gas model. Moreover, supersonic flow conditions are typically reached at the nozzle vanes discharge, thus involving the formation of a shock pattern, which is in turn responsible for a strong unsteady interaction with the wheel blades. Under such circumstances, performance predictions based on classical perfect gas, steady-state calculations can be very poor. While reasonably accurate real gas models are nowadays available in most flow solvers, unsteady real gas calculations still struggle to become an affordable tool for investigating turbo-expanders. However, it is emphasized in this work how essential the adoption of a time-accurate analysis can be for accurate performance estimations. The present paper is divided in two parts. In the first part, the computational framework is validated against on-site measured performance from an existing power plant equipped with a variable-geometry nozzled turbo-expander, for different nozzle positions, and in design and off-design conditions. The second part of the paper is devoted to the detailed discussion of the unsteady interaction between the nozzle shock waves and the wheel flow field. Furthermore, an attempt is made to identify the key factors responsible for the unsteady interaction and to outline an effective way to reduce it.
Small Wind Turbines in the Built Environment: Influence of Flow Inclination on the Potential Energy Yield
Authors: Bianchi Serena , Bianchini Alessandro , Ferrara Giovanni , Ferrari Lorenzo
Published: November 2013

Increasing interest is being paid by architects, project developers and local governments to understand where small wind turbines can effectively be exploited to provide delocalized power in the built environment.

The wind conditions in the rooftop area of buildings in urban locations are, however, very complex and the real adaptability of wind turbines to these environments is not yet tested both in terms of real producibility and of structural compatibility with the building themselves. In these installations, in particular, the flow which incomes on the rotors is often inclined with respect to the horizontal direction due to the interaction with the building façade and the roof.

A correct estimation of the impact of an inclined flow on the performance of horizontal-axis wind turbines therefore becomes a very relevant issue to correctly predict the potential energy yield of a machine.

To this purpose, a simulation code based on a Blade Element Momentum (BEM) approach was developed and validated by means of experimental data found in the literature. The code was then used to evaluate the energetic suitability of a small-size wind turbine installation in the rooftop of a building in a conventional European city.

A numerical CFD analysis was carried out to characterize the flow field in the rooftop area of different buildings. The flow velocity modulus and direction were calculated for several oncoming wind profiles: the results were projected into an available wind power curve in the rooftop of the building.

The effective energy-yield capabilities were then corrected using the model for the flow inclination as a function of the specific flow conditions in the rooftop area.

The results were finally exploited to analyze the energy-oriented feasibility of an installation in a similar context.
Numerical Investigation of the Unsteady Interaction Within a Close-Coupled Centrifugal Compressor Used in an Aero Engine
Authors: Wilkosz Benjamin , Zimmermann Markus , Schwarz Philipp , Jeschke Peter , Smythe Caitlin
Published: November 2013

The present work forms part of a research project of the Institute of Jet Propulsion and Turbomachinery at the RWTH Aachen University in collaboration with GE Aviation. The subject is the detailed numerical analysis of the unsteady flow field focusing on the interaction between the impeller and the passage diffuser of a close-coupled transsonic centrifugal compressor used in an aero engine.

The centrifugal compressor investigated is characterized by a close-coupled impeller and passage diffuser with a radial gap of only 3.6%. The close coupling tends to provide a high aerodynamic efficiency but simultaneously cause a high unsteady interaction between the impeller and the diffuser. These unsteady effects can have a significant impact on the performance of both components [1,2] and present a challenge to state-of-the-art numerical methods. With increasing compressor efficiency, the more important it is to have a understanding of the detailed unsteady flow physics. Experimental data was obtained from a state-of-the art centrifugal compressor test rig located at the Institute of Jet Propulsion [3]. Steady and unsteady pressure measurements within the impeller and diffuser are used to gain detailed information on the temporal, time-averaged and spectral pressure distributions within the stage to validate the CFD.

The work presented shows the unsteady phenomena caused by the interaction as well as the location and propagation of these phenomena within the centrifugal stage. Within the impeller, the exducer is in first order excited by the BPF of the diffuser, whereas in the diffuser both the BPF, as well as the PPF, are present up until the end of the pipe-diffuser. Significant effects on the integral component performance could only be identified for the impeller. Special focus is paid to evaluate the diffuser upstream pressure field, since this is the major source of unsteadiness within the impeller. The performance of the rotor decreases due to the unsteady interaction. This effect is traced back to the unsteady tip-clearance flow, in which the time-averaged mass transport decreases, whereas the specific entropy production increases in a nonlinear way. Within the diffuser, local effects counteracting with respect to the integral performance are found. In front of the throat, there is less decay in total pressure, as a result of tangentially expanding pressure waves. Within the passage an decrease in flow uniformity in the unsteady flow is identified as the reason for the lower diffusion up until the throat and higher losses within the downstream diffuser passage.
Forced Response Analysis of a Steam Turbine Shrouded Blade: Numerical Analysis and Experiments
Authors: Piraccini Francesco , Lorusso Salvatore , Maceli Nicola , Ryman John
Published: November 2013

Faced with the present transformation of the world economy, steam turbine manufacturers are seeking ways to remain competitive in their respective markets.

Having longer Low Pressure (LP) blades and seeking for higher rotating speeds have always been two effective methods to improve the Steam Turbine efficiency, therefore to reduce steam consumption and related plant costs.

Both trends have increased the risk of failure for forced response due to the occurrence of resonance or to the decrease of alternating stress margins.

Because of large uncertainties in the estimation of friction damping and aerodynamic excitation, the prediction of dynamic response of the long blades in the LP section is still a challenge for the analytical tools; therefore, expensive activities for experimental validation are usually required.

In order to reduce design costs and time, a set of tools has been developed and validated using the test data collected during a full-scale test vehicle campaign in steam (Low Pressure Development Turbine - LPDT). In this study, the validation activity related to the blade response due to nozzle stimulus is reported.

As a first step, a steady state CFD analysis was performed at the operating conditions where significant response was observed, caused by the resonance with the Nozzle Passing Frequency (NPF). Then, an unsteady CFD analysis of the bucket blade was conducted considering the perturbation due to the nozzles. Subsequently, the computed unsteady pressure distribution on the blade airfoil was mapped onto a finite element model and forced response analyses were performed to estimate the bucket dynamic response. The predicted response was compared against measured test data and good correlation was found.
Excited Blade Vibration for Aeroelastic Investigations of a Rotating Blisk Using Piezo-Electric Macro Fiber Composites
Authors: Belz Joachim , May Markus , Siemann Jan , Seume Joerg R. , Voigt Christian , Böhmer Heiko , Grüber Björn
Published: November 2013

Experimental investigations of the aerodynamic damping of compressor blades are usually performed by forcing the blades externally to a motion that is similar to a given mode shape and inter-blade phase angle (IBPA) while measuring the motion-induced unsteady pressure distribution. Evaluating this to an aerodynamic work entry from the fluid to the blade, at least a local contribution to the flutter (in-)stability can be determined. Test rigs are usually non-rotating linear or rotating annular cascade wind tunnels. In the latter case, besides measuring in and transmitting data out of the rotating system, the excitation of the blades themselves is still a challenge.

In the present case a blisk rotor with realistic fan blade geometries and flow conditions was investigated aeroelastically. For the excitation of the 1st bending (1F) mode shape of the blading a sector of five blades was chosen. In this sector the natural vibration of the blading, represented by constant vibration amplitudes and a given IBPA should be simulated. Therefore the blades were equipped with Macro Fiber Composites (MFC). These foils of piezoelectric material expand and contract due to the applied high voltage. A control system was developed to adjust the amplitude and the IBPA of the blade vibration. For the transmission of the high voltage, a separate data transmission system on the base of liquid metals was chosen. The blade vibration was measured by strain gauges and additionally monitored by a specific rig system.

The aeroelastic investigations were carried out in the compressor test facility M2VP of the DLR Institute of Propulsion Technology in Cologne. During the measurement, the MFCs were able to excite the blades to a certain extent. The paper will present the technique to excite the blades of a compressor blisk by means of MFCs as well as achieved vibration amplitudes and limitations under engine-like operating conditions.
Numerical Investigation of an Additively Manufactured Compressor Casing: The Effect of Auxetic Structures on the Tip Clearances
Authors: Rockel David , Weihard Stefan , Hachmann Andreas , Hupfer Andreas , Kau Hans-Peter
Published: November 2013

A new approach for a compressor casing design has been developed using new design possibilities offered by additive manufacturing technologies. Tip clearance behaviour is a serious problem in compressor design leading to increased aerodynamic losses and limiting the operating range of a compressor through a decrease in surge margin. Efforts are necessary to minimise the tip clearance in the load cycle of an engine.

The approach presented in this work uses auxetic structures in a double-walled compressor casing with the aim to force the radial expansion behaviour of the inner casing wall in order to adapt the casing to the rotor. The studies of the casing and the calculations of the transient rotor displacement are carried out by using coupled-temperature-displacement calculations using commercial FEM-tools.

Elements which influence the radial expansion of the casing are identified with the aim of generating a modular system for future compressor casing developments. So the casing elements are adaptable to the radial expansion of a certain rotor. An improved tip clearance behaviour in relevant operating points is achieved. In the latter part of the paper, practical design considerations are made as the auxetic structures are integrated into the CAD model of an existing compressor casing. Design challenges are also briefly discussed.

This paper presents a new potential application of additive manufacturing technologies in future aero engine design. The focus of this paper is on the practical implementation of the new design freedom using the example of a compressor casing. The advantages for the overall engine performance as well as identified problems are also discussed qualitatively.
Aerodynamic Design and Analysis of Centrifugal Turbine Cascades
Authors: Persico G. , Pini M. , Dossena V. , Gaetani P.
Published: November 2013

The centrifugal turbine architecture represents a promising solution for Organic Rankine Cycle (ORC) Systems, in the small-to-medium power range. The large volumetric expansion ratios occurring in ORC turbines complicate the design of the turbo-expander, making the centrifugal arrangement worth of interest with respect to conventional architectures. A new-concept centrifugal turbine has been recently proposed by the authors, based on the design of Ljungström but implementing a stator-rotor arrangement, which allows for multi-stage assembly without compromising compactness.

To properly evaluate the potential of the centrifugal turbine solution, reliable data on cascade aerodynamic performances are required, but they are still lacking in the open literature. In this paper the aerodynamics of radial-outward turbine cascades is discussed, on the basis of Computational Fluid-Dynamics (CFD) simulations. A weakly transonic operating condition is selected and for that different classes of profiles are tested.

Results show that the intrinsic diverging shape of the radial-outward configuration complicates the blade design; if the flow deflection is not properly controlled along the streamwise direction, the bladed duct can result in a converging-diverging channel, leading to unexpected chocked flows and shocks even in weakly transonic configurations. The indications achieved by the comparison between different blade profiles are gathered to define guidelines for the design of novel elliptic profiles, which allow to control the flow acceleration process, providing high aerodynamic efficiency. Off-design performances of the elliptic profiles are finally addressed by studying the response of the cascade to different expansion ratios and high incidence angles.
Modal H∞-Control in the Context of a Rotor Being Subject to Unbalance Excitation and Gyroscopic Effect
Authors: Schittenhelm Rudolf Sebastian , Riemann Bernd , Rinderknecht Stephan
Published: November 2013

H∞-optimal controllers are designed for a rotor being subject to unbalance excitation and gyroscopic effect. The system possesses two unbalance-induced resonances within its operating range. The presence of gyroscopic effect is challenging for linear time invariant controller design because of the associated dependence of the system dynamics on the rotational frequency of the rotor. Controllers thus have to be robust against deviation of the actual system behavior from the controller design point model.

For vibration control purposes, there are two piezoelectric actuators installed in one of the two supports of the rotor. The signals of four inductive sensors measuring the displacements of the two discs of the rotor are used for controller design.

In this article, H∞-optimal controllers are designed on the basis of input and output weighting as well as weighting of modal degrees of freedom and modal excitations. It is shown that superior control performance is achieved using modal weighting since a more accurate problem description of rotors excited by unbalance is incorporated in controller design. Results in this article show furthermore that it is possible to design well performing H∞-optimal controllers for a gyroscopic rotor by means of iterative controller design without taking model uncertainty directly into account via weighting of certain FRFs of the system to be controlled.
Rotor Drop Simulations and Validation With Focus on Internal Contact Mechanisms of Hybrid Ball Bearings
Authors: Anders Jens , Leslie Peter , Stacke Lars-Erik
Published: November 2013

Active Magnetic Bearings technology is becoming more and more a standard in Oil and Gas turbo machinery. Touchdown bearings are an important element of all machines levitated by magnetic bearings. Frequently implemented as hybrid ball bearings, they constitute the only mechanical link between the rotor spinning at high peripheral speed and the stator. Since both sides carry fragile parts, any uncontrolled contact must be avoided.

Extensive testing has been done in industry. When unplanned down-time would have a high system impact or when repair options are limited (upstream equipment, subsea operation), elaborate testing campaigns are common. A complement, if not an alternative, are computer based transient rotor drop simulations. They allow reducing uncertainties and help qualifying designs. In most cases, simulations use rotor dynamics models combined with contact models allowing an estimation of shaft behavior during a drop. We present a new approach for transient rotor drop simulations, where detailed calculation of the interior ball bearing mechanics is at the center of the model. This is possible by using a multiple-bodies simulation code, which was initially developed for pure ball bearing calculations and implements contact models including lubrication, wear, and geometry imperfections. Here, the same code is used to model entire shaft systems, associated with preloaded touchdown bearings. This technique allows not only to understand and to analyze failure patterns that determine bearing lifetime (contact stress, heat, and deformation), but also to take into account interactions of the bearing itself with the rest of the system.

After a feasibility study for validating the capability of simulating rotor drops, three models were realized for three different types of machines of increasing complexity that were all validated by actual drop tests. The last model is a supercritical horizontal shaft system (200kg) representing an actual Oil and Gas application in reduced scale. Simulated shaft behavior was successfully compared to drop test recordings. The output was analyzed for internal bearing mechanics (contact pressures and contact angle, sliding or rolling friction) and could be correlated with evidence found on the bearings from the drop tests.
Modeling Off-Design and Part-Load Performance of Supercritical Carbon Dioxide Power Cycles
Authors: Dyreby John J. , Klein Sanford A. , Nellis Gregory F. , Reindl Douglas T.
Published: November 2013

Continuing efforts to increase the efficiency of utility-scale electricity generation has resulted in considerable interest in Brayton cycles operating with supercritical carbon dioxide (S-CO2). One of the advantages of S-CO2 Brayton cycles, compared to the more traditional steam Rankine cycle, is that equal or greater thermal efficiencies can be realized using significantly smaller turbomachinery. Another advantage is that heat rejection is not limited by the saturation temperature of the working fluid, facilitating dry cooling of the cycle (i.e., the use of ambient air as the sole heat rejection medium). While dry cooling is especially advantageous for power generation in arid climates, the reduction in water consumption at any location is of growing interest due to likely tighter environmental regulations being enacted in the future. Daily and seasonal weather variations coupled with electric load variations means the plant will operate away from its design point the majority of the year. Models capable of predicting the off-design and part-load performance of S-CO2 power cycles are necessary for evaluating cycle configurations and turbomachinery designs.

This paper presents a flexible modeling methodology capable of predicting the steady state performance of various S-CO2 cycle configurations for both design and off-design ambient conditions, including part-load plant operation. The models assume supercritical CO2 as the working fluid for both a simple recuperated Brayton cycle and a more complex recompression Brayton cycle.
Uncertainty in Computed Time Average Gas-Side Temperatures for an HPT Rotor With Purge Cavities
Authors: Ratzlaff Jon , Orkwis Paul D. , Noll Christopher , Steuber Gary , Saeidi Rob , Athans Rob
Published: November 2013

The accurate prediction of wall temperatures in modern turbomachines is extremely important as firing temperatures increase to achieve ever higher efficiency. Many factors affect these predictions, including variations in the inlet profile, purge and cooling flows, tip clearances and geometry-specific unsteady flow physics. This paper explores the statistical behavior of gas-side near-wall temperature predictions to demonstrate the prediction uncertainty associated with solution time averaging. Gas-side temperatures have been obtained by time-averaging unsteady CFD solutions of a single-stage commercial HPT rotor. Forced unsteady calculations are performed for a cooled vane and an uncooled rotor with purge cavities. The presence of the vane coolant induces a significant circumferential temperature variation for the flow entering the rotor. For select regions within the rotor passage, this circumferential gradient, combined with the influence of the purge cavities, produces near-wall variations dominated by frequency content lower than blade passing. This content directly affects the uncertainty of the time average. Traditional CFD averaging approaches consider data over a single blade passing or some multiple associated with the blade counts, but often assume start time/position to be immaterial. In this work the variation in predicted average near-wall gas-side temperature at select points in the flow field is explored as both the averaging window (number of blade passings) and the averaging start time are varied. Time histories of gas-side temperature are taken at select near-wall locations around the passage in and away from regions heavily influenced by purge flows. Simulation results are examined for 120 blade passings after an initial transient period. These values are used to identify and discuss regions in this geometry with large predicted average temperature uncertainty. It was found that as the window size is increased the variation in predicted temperatures is reduced everywhere in the flow. Possible unsteadiness sources driving problem areas are discussed and convergence trends for the average temperature of each surface of interest are presented.
Forced Response of a Flexible Rotor With Squeeze Film Damper Under Parametric Change
Authors: He Feng , Allaire Paul E. , Dousti Saeid , Untaroiu Alexandrina
Published: November 2013

Squeeze film dampers play an important role in the dynamics of modern turbomachinery by improving vibrational response and stability. The present paper develops an effective tool for evaluating the forced response of these systems under parametric changes. A flexible rotor with multiple masses supported on a squeeze film damper at one end is investigated. The forced response of this asymmetrically supported system is obtained using the harmonic balance method with a predictor-corrector procedure. This response is examined with various parameters including unbalance forces with and without fluid inertia effects, unidirectional loads, stiffness of centering spring of the damper and the gyroscopic effects of the disks. The developed tool predicts the nonlinear jump phenomenon of the damper with large unbalance forces, indicates the present of multiple harmonics within the response with high damper eccentricity and shows the insensitivity of the damper to surrounding gyroscopic variation.
Gas Turbine Engine Health Management: Past, Present and Future Trends
Authors: Volponi Allan J.
Published: November 2013

Engine diagnostic practices are as old as the gas turbine itself. Monitoring and analysis methods have progressed in sophistication over the past 6 decades as the gas turbine evolved in form and complexity. While much of what will be presented here may equally apply to both stationary power plants and aero-engines, the emphasis will be on aero propulsion.

Beginning with primarily empirical methods centering around monitoring the mechanical integrity of the machine, the evolution of engine diagnostics has benefited from advances in sensing, electronic monitoring devices, increased fidelity in engine modeling and analytical methods. The primary motivation in this development is, not surprisingly, cost. The ever increasing cost of fuel, engine prices, spare parts, maintenance and overhaul, all contribute to the cost of an engine over its entire life cycle. Diagnostics can be viewed as a means to mitigate risk in decisions that impact operational integrity. This can have a profound impact on safety, such as In-Flight Shut Downs (IFSD) for aero applications, (outages for land based applications) and economic impact caused by Unscheduled Engine Removals (UERs), part life, maintenance and overhaul and the overall logistics of maintaining an aircraft fleet or power generation plants.

This paper will review some of the methods used in the preceding decades to address these issues, their evolution to current practices and some future trends. While several different monitoring and diagnostic systems will be addressed, the emphasis in this paper will be centered on those dealing with the aero-thermodynamic performance of the engine.
A Tool for the Structural Integrity Assessment of Turbine Disks: Probabilistic and Numerical Background
Authors: Madia M. , Beretta S. , Foletti S. , Cavalleri E. A.
Published: November 2013

Rotor disks for gas turbines are heavy components and are usually designed following a safe-life approach, where the low-cycle fatigue analysis is carried out referring to design life curves with suitable probabilistic margins. However, in the case of such a heavy component there is the possibility of rare occurrence of undetected defects or, better, the need to identify the defect acceptability for the different rotor regions (considering stress, temperature, mission profile).

In order to carry out such calculations for a turbine rotor disk a software named AStrID (Assessment of the Structural Integrity of Disks) has been developed in close cooperation between Politecnico di Milano and Ansaldo Energia (AEN). This paper summarizes its background and some of the relevant features.
Restoration of the Unfolded Protein Response in Pancreatic β Cells Protects Mice Against Type 1 Diabetes
Authors: Engin Feyza , Yermalovich Alena , Nguyen Truc , Hummasti Sarah , Fu Wenxian , Eizirik Decio L. , Mathis Diane , Hotamisligil Gökhan S.
Published: November 2013

Preservation of insulin-producing pancreatic β cells in type 1 diabetes requires an intact UPR, and treatment with tauroursodeoxycholic acid can restore UPR defects.
It Takes Two to Make a RAF Signal Right
Authors: Margolin Adam A.
Published: November 2013

A new technology allows single molecule–resolution imaging of RAS multimer formation.
Trojan siRNA Opens the Door to Chemotherapy
Authors: Artzi Natalie
Published: November 2013

A layer-by-layer nanoparticle assembly allows timed combination therapy against triple-negative breast cancer in mice.
A Retrograde Trafficking Inhibitor of Ricin and Shiga-Like Toxins Inhibits Infection of Cells by Human and Monkey Polyomaviruses
Authors: Nelson Christian D. S. , Carney Dan W. , Derdowski Aaron , Lipovsky Alex , Gee Gretchen V. , O’Hara Bethany , Williard Paul , DiMaio Daniel , Sello Jason K. , Atwood Walter J.
Published: November 2013

Polyomaviruses are ubiquitous pathogens that cause severe disease in immunocompromised individuals. JC polyomavirus (JCPyV) is the causative agent of the fatal demyelinating disease progressive multifocal leukoencephalopathy (PML), whereas BK polyomavirus (BKPyV) causes polyomavirus-induced nephropathy and hemorrhagic cystitis. Vaccines or antiviral therapies targeting these viruses do not exist, and treatments focus on reducing the underlying causes of immunosuppression. We demonstrate that retro-2
cycl
, an inhibitor of ricin and Shiga-like toxins (SLTs), inhibits infection by JCPyV, BKPyV, and simian virus 40. Retro-2
cycl
inhibits retrograde transport of polyomaviruses to the endoplasmic reticulum, a step necessary for productive infection. Retro-2
cycl
likely inhibits polyomaviruses in a way similar to its ricin and SLT inhibition, suggesting an overlap in the cellular host factors used by bacterial toxins and polyomaviruses. This work establishes retro-2
cycl
as a potential antiviral therapy that broadly inhibits polyomaviruses and possibly other pathogens that use retrograde trafficking.

IMPORTANCE
The human polyomaviruses JC polyomavirus (JCPyV) and BK polyomavirus (BKPyV) cause rare but severe diseases in individuals with reduced immune function. During immunosuppression, JCPyV disseminates from the kidney to the central nervous system and destroys oligodendrocytes, resulting in the fatal disease progressive multifocal leukoencephalopathy. Kidney transplant recipients are at increased risk of BKPyV-induced nephropathy, which results in kidney necrosis and loss of the transplanted organ. There are currently no effective therapies for JCPyV and BKPyV. We show that a small molecule named retro-2
cycl
protects cells from infection with JCPyV and BKPyV by inhibiting intracellular viral transport. Retro-2
cycl
treatment reduces viral spreading in already established infections and may therefore be able to control infection in affected patients. Further optimization of retro-2
cycl
may result in the development of an effective antiviral therapy directed toward pathogens that use retrograde trafficking to infect their hosts.
Successful revision of polyethylene only, after delayed presentation of a dislocated bearing in an Oxford unicompartmental knee replacement
Authors: Gul Syed Firzoque Fahad , Davies Andrew Paul
Published: November 2013

We present the case of a 79-year-old man who dislocated the mobile bearing of a well-functioning Oxford unicompartmental knee replacement in a fall. The diagnosis was delayed by 14 days during which time the patient remained fully mobile. At the time of arthrotomy, there was some visible burnishing of the femoral articular surface where it had been rubbing on the tibial component. Both components were soundly fixed and had been functioning well for 7 years. The decision was made to leave the components in situ and simply replace the mobile meniscal bearing. The patient returned to full normal activity and has been followed-up for 3.5 years. Serial X-rays reveal no evidence of polyethylene wear and the knee remains pain free and fully functional. We conclude that it is safe to retain the components of an Oxford unicompartmental knee replacement despite some evidence of surface damage. Replacing just the mobile meniscus gave a good result in our patient.
Morphologic and hemodynamic analysis of paraclinoid aneurysms: ruptured versus unruptured
Authors: Liu Jian , Xiang Jianping , Zhang Ying , Wang Yang , Li Haiyun , Meng Hui , Yang Xinjian
Published: November 2013

Background

In order to determine the risk factors related to aneurysm rupture, we studied the aneurysms at the paraclinoid segment of the internal carotid artery by applying morphologic and hemodynamic numerical analyzes.

Methods

107 patients with 110 paraclinoid aneurysms (26 ruptured, 84 unruptured) were analyzed using computational fluid dynamics based on patient-specific three-dimensional geometrical models. A series of morphologic and hemodynamic parameters were evaluated to find the potential indicators of aneurysm rupture.

Results

Aneurysms with an irregular shape accounted for 23.1% of the ruptured group and only 8.3% of the unruptured group. The difference was statistically significant (p=0.042, χ2test). Ruptured paraclinoid aneurysms were found to be significantly smaller than unruptured aneurysms (p=0.041), which is different from the results of most previous studies. Energy loss (EL) and inflow concentration showed a level of statistical significance to assess the risk of rupture in paraclinoid aneurysms. By multivariate logistic regression analysis, aneurysm shape (regular or irregular), EL and inflow concentration were retained as independently significant parameters. The odds of rupture were increased by 1.65 times for a 10% increase in EL, by 4.88 times for an aneurysm with an irregular shape and by 2.91 times for an aneurysm with concentrated inflow jet.

Conclusions

Irregular shape, larger EL and concentrated inflow jet were independently associated with the rupture status of paraclinoid aneurysms. These findings need to be further confirmed based on large multicenter and multipopulation data.
Linearized sloshing model for 2D tuned liquid dampers with modified bottom geometries
Authors: Love J.S. , Tait M.J.
Published: November 2013

This study presents a new model for predicting the response of a two-dimensional tuned liquid damper (TLD) tank with a variable fluid depth. A simple finite element method is presented, which is used to calculate the sloshing mode shapes. From the mode shapes, the equivalent mechanical properties of the sloshing fluid are estimated. Three tanks (flat-bottom, triangular-bottom, and circular-bottom), which have closed-form expressions for their equivalent mechanical properties are used to evaluate the model. The proposed model is in agreement with the closed-form expressions. Subsequently, a parametric study is conducted on tanks with a chamfered-bottom, boxed-bottom, and ramped-bottom to assess how their properties change as the shape of the tank bottom is altered. The model provides TLD designers with greater flexibility when selecting a tank shape. Moreover, the model could be used to optimize the shape of a TLD tank to maximize its performance for a given liquid mass, allowing construction cost savings to be realized.
Activation of PI3K–Akt through taurine is critical for propofol to protect rat cardiomyocytes from doxorubicin-induced toxicity
Authors: Sun Xuechao , Gu Jing , Chi Meng , Li Mingming , Lei Shi , Wang Guonian
Published: November 2013

Myocardial toxicity is one of the major side effects of many chemotherapeutics. It has been shown that propofol can ameliorate the cardiotoxicity of chemotherapeutic agents. In this study, we intend to investigate the role of the PI3K–Akt–Bad signaling pathway in propofol relief of doxorubicin-induced oxidative stress and apoptosis in rat cardiomyocytes. Cultured neonatal rat cardiomyocytes were treated with vehicle, doxorubicin, propofol, or propofol plus doxorubicin in the presence or absence of the PI3K inhibitor LY294002. Cells were harvested 20 h post-exposure to doxorubicin followed by analysis of their cellular taurine content, oxidative/nitrative stresses, and cellular apoptosis. The activation of the PI3K–Akt pathway was analyzed by immunoblotting. FACS, TUNEL, and LDH assays showed that the viability of cardiomyocytes was markedly reduced by doxorubicin, but was improved by propofol. Doxorubicin treatment significantly elevated cellular reactive oxygen and nitrogen contents while lowering the levels of taurine, Akt, and phosphorylated Akt and Bad. The abovementioned doxorubicin-induced changes were reversed by propofol. The protective effects of propofol were abrogated by simultaneous treatment with LY294002. In conclusion, the PI3K–Akt–Bad pathway plays a critical role in conferring the protective effects of propofol against myocardial toxicity from doxorubicin.
Near-Field Representations of the Acoustic Green's Function in a Shallow Ocean with Infinite Elastic Seabed
Authors: Gilbert Robert , Ou Miao-Jung Yvonne
Published: November 2013

In this paper, we show how to construct acoustic Green's functions for a water column atop an infinite elastic seabed using a generalization of the method by Ahluwalia and Keller.6Our goal is to obtain a representation of the acoustic Green's function which is valid in the near field. Such a representation is useful in the investigation of the inverse shape problem using the methodology we pioneered for waveguides with reflecting seabeds.
Damage Characterization of Polypropylene Honeycomb Sandwich Panels Subjected to Low-Velocity Impact
Authors: Amir Freeda A. , Othman A. R. , Akil H. Md.
Published: November 2013

The post-test deformation and failures of sandwich composites may involve complex interactions between various failure mechanisms. In this study, the extent of impact damages and response of the thermoplastic honeycomb sandwich are analysed through energy profile diagrams and associated load history curves. The degree of the postimpact damages of the sandwich is further characterized using an optical surfaces metrology analysis. The thickness of the honeycomb was found to influence the extent of the damage which occurred following the low-velocity impact. Thicker core was able to sustain a higher load as well as the energy absorption before total failure occurred.
Sex Hormone Receptor Repertoire in Breast Cancer
Authors: Higa Gerald M. , Fell Ryan G.
Published: November 2013

Classification of breast cancer as endocrine sensitive, hormone dependent, or estrogen receptor (ER) positive refers singularly to ERα. One of the oldest recognized tumor targets, disruption of ERα-mediated signaling, is believed to be the mechanistic mode of action for all hormonal interventions used in treating this disease. Whereas ERαis widely accepted as the single most important predictive factor (for response to endocrine therapy), the presence of the receptor in tumor cells is also of prognostic value. Even though the clinical relevance of the two other sex hormone receptors, namely, ERβand the androgen receptor remains unclear, two discordant phenomena observed in hormone-dependent breast cancers could be causally related to ERβ-mediated effects and androgenic actions. Nonetheless, our understanding of regulatory molecules and resistance mechanisms remains incomplete, further compromising our ability to develop novel therapeutic strategies that could improve disease outcomes. This review focuses on the receptor-mediated actions of the sex hormones in breast cancer.
Equivalent Representation Form of Oscillators with Elastic and Damping Nonlinear Terms
Authors: Elías-Zúñiga Alex , Olvera Daniel , Ferrer Real Inés , Martínez-Romero Oscar
Published: November 2013

In this work we consider the nonlinear equivalent representation form of oscillators that exhibit nonlinearities in both the elastic and the damping terms. The nonlinear damping effects are considered to be described by fractional power velocity terms which provide better predictions of the dissipative effects observed in some physical systems. It is shown that their effects on the system dynamics response are equivalent to a shift in the coefficient of the linear damping term of a Duffing oscillator. Then, its numerical integration predictions, based on its equivalent representation form given by the well-known forced, damped Duffing equation, are compared to the numerical integration values of its original equations of motion. The applicability of the proposed procedure is evaluated by studying the dynamics response of four nonlinear oscillators that arise in some engineering applications such as nanoresonators, microresonators, human wrist movements, structural engineering design, and chain dynamics of polymeric materials at high extensibility, among others.
Cost Effectiveness of TNF-αInhibitors in Rheumatoid Arthritis
Authors: Said Cynthia , Coleiro Bernard , Zarb Adami Maurice , Azzopardi Lilian M. , Serracino Inglott Anthony
Published: November 2013

Background.TNF-αinhibitors have shown to be effective in reducing disease activity and improving the quality of life. Due to the high costs associated with acquisition of this treatment, this study was undertaken to evaluate the ICER of TNF-αantagonists (etanercept, adalimumab, and infliximab) in improving the quality of life.Methods.The HAQ and SF-36 were administered at phases 1, 2, and 3, in order to assess the improvement in the QOL. Suppression of disease activity was assessed through the DAS-28.Results.Statistically significant improvements (P<0.05) were noted for the SF-36 and HAQ after 3 months and for the DAS-28 after 6 months of TNF-αinhibitor therapy. The mean ICER per 10% improvement in the HAQ, DAS-28, and SF-6D were €1976.5, €2086.5, and €2316.4, respectively, following 6 months of TNF-αintervention. Most favorable ICERs were reported from a patient who had to undergo surgical intervention whilst on DMARD therapy.Conclusion.Significant improvement was observed in patients’ quality of life, after a short timeframe of 6 months. Such data is useful information in the light of convincing policy makers, in terms of providing access to the medications to individual patients on national health service schemes.
Weak and Strong Convergence of an Algorithm for the Split Common Fixed-Point of Asymptotically Quasi-Nonexpansive Operators
Authors: Dang Yazheng , Gao Yan
Published: November 2013

Inspired by the Moudafi (2010), we propose an algorithm for solving the split common fixed-point problem for a wide class of asymptotically quasi-nonexpansive operators and the weak and strong convergence of the algorithm are shown under some suitable conditions in Hilbert spaces. The algorithm and its convergence results improve and develop previous results for split feasibility problems.
Performance Analysis for Priority-Based Broadcast in Vehicular Networks
Authors: Woo Rinara , Song Jung-Hoon , Han Dong Seog
Published: November 2013

Transportation safety is one of the most important applications of vehicular ad hoc networks which is based on IEEE 802.11p. When a vehicle is in an emergency situation, a safety-related message is transmitted to the neighboring vehicles and infrastructures. Vehicles and infrastructures exchange periodic messages on vehicle position, traffic information, and so forth to provide various services. When the traffic load is very high, the emergency message cannot be delivered immediately. To overcome this situation, a priority-based transmission scheme is considered to guarantee the transmission of the emergency message. In this paper, the performance of vehicular communication networks is analyzed in two perspectives. Firstly, an analytical Markov chain model for vehicle-to-vehicle (V2V) ad hoc communication networks is proposed for broadcasting messages with priority based on the IEEE 802.11p wireless access for vehicular environments (WAVE) standard. Secondly, an analytic queuing model for vehicular communication networks is proposed to evaluate the network performance to deal with safety and nonsafety messages.
A Dynamic Topology Reformation Algorithm for Power Saving in ZigBee Sensor Networks
Authors: Wang Reen-Cheng , Chang Ruay-Shiung , Yen Jei-Hsiang , Lee Pu-I
Published: November 2013

ZigBee is a protocol suite based upon IEEE standard 802.15.4 for the construction of low-rate wireless personal area networks. Since most of ZigBee devices are powered by battery, the power saving is an important issue. In the past several years, many solutions are proposed to extend battery life by reducing device transmitting and receiving time. However, few studies have noticed that most energy is consumed in sensing and monitoring rather than communicating activities, since the data rates in most ZigBee networks are low. Besides, energy will consume the most of those nodes which act as routers or are orphans that cannot join the network. In order to extend the life time of network, we proposed a dynamic topology reformation algorithm. The algorithm consists of a cluster reformation scheme for enhancing connectivity and a self-swapping method for averaging the loading of router nodes and end devices. As the experimental result shows, compared with the ZigBee standard, our method gains 6.02% to 15.13% improvement in network join ratio. And the role swapping balances the power consumption which makes the lifetime of the whole network 1.3 to 1.375 times longer.