bluuebunny/crossref_metadata_2025 huggingface dataset:
Predictions of Rotordynamic Performance for Electric Turbocompound
Authors: Ryu Keun , Cavagnaro Augustine
Published: December 2013

An electric turbocompound (ETC) system for heavy duty diesel engines offers significant system level benefits, such as improved fuel efficiency and reduced NOx emissions with a lower CO2 footprint. Presently, a high speed switched reluctance type motor/generator is integrated into a turbocharger shaft between the turbine and compressor wheels. The motor assists rapid acceleration of the turbocharger shaft, thereby rendering faster transient response. At steady or over-boost operating conditions, the generator provides electric power which can be used directly or stored in an on-board storage device. ETCs operate at high rotational speeds and, if equipped with fluid film bearings, use pressurized engine oil to lubricate the bearings (journal and thrust). This paper presents comprehensive predictions of the linear and nonlinear shaft motions of an ETC supported on floating ring bearings. A rotor structural finite element model integrates the floating ring bearing model for prediction of the rotor-bearing system (RBS) linear and nonlinear forced responses under actual operating conditions. Predictions show a complex rotordynamic behavior of the RBS with large amplitude subsynchronous motions over a wide speed range. However, the subsynchronous whirl motions reach a limit cycle enabling continuous operation without system failure. Most importantly, stiffness of the lamination stack mounted on the shaft has a significant effect on the amplitude and frequency content of the shaft motion. The present analysis effectively aids to accelerate ETC prototype development with increased reliability and product troubleshooting.
Magnetoelastic Torquemeter System for LCAC Hovercraft Turboshaft Engine Monitoring and Control
Authors: Kari Ryan J. , Patel Tej , Canilang Benjamin , Bonafede Americo , Bitar Sami , Garshelis Ivan J.
Published: December 2013

This paper presents the development of a magnetoelastic torque-meter for use on the Landing Craft Air Cushion (LCAC) hovercraft’s high speed gas turbine engines. As the gas turbine can produce in excess of the nominal torque limit of the right angle gearbox, torque limiting is required. Limiting torque based on torque tables (as is done currently) penalizes the overall performance of the majority of the fleet due to a significant variance in engine output horsepower. This sub-optimal operation of the craft could be overcome by measuring actual torque produced by each engine with a torque-meter; however conventional torque-meter designs were deemed impractical to retrofit due to the design requirements, and issues with integration and reliability / maintainability. An in-depth search by the US Navy identified a torque-meter concept utilizing magnetoelastic polarized band technology. The aim of this paper is to: (i) outline the general architecture of the system, (ii) highlight the performance of the torque-meter developed for the LCAC, (iii) describe the efforts that helped to mature this technology to Technology Readiness Level 8 and to transition it from motorsport applications to use on the LCAC, and (iv) summarize the initial results of the torque-meter system validation obtained through dynamometer tests on the engine and craft tests on the LCAC.
A Nonlinear Vibration Absorber Based on Nonlinear Shunted Piezoelectrics
Authors: Zhou Biao , Thouverez Fabrice , Lenoir David
Published: December 2013

In this research, a nonlinear shunted piezoelectric is proposed for practical realization of nonlinear vibration absorbers. The main advantage of the electro-mechanical system is that non-linearity can be readily achieved by proper circuit design. First, the dynamics of a SDOF linear mechanical oscillator coupled to a nonlinear shunted piezoelectric attachment is studied. Both the nonlinear normal modes and the nonlinear forced response of the electro-mechanical system are investigated. Numerical simulation reveals that under certain condition, a fast, passive energy transfer from the mechanical oscillator to the piezoelectric attachment is observed. The essentially nonlinear absorber is also able to work over broad frequency band under periodic excitation with a smaller inductance requirement compared with the linear piezoelectric vibration absorber. The application of piezoelectric vibration absorbers to simplified blade-disk structures is also taken into consideration. It is shown that when blades become mistuned, the nonlinear vibration absorber yields better vibration mitigation performance than the linear shunt circuit does. Namely, the blade mistuned vibration could be reduced by the nonlinear effect in the piezoelectric absorber. However, to improve the performance of piezoelectric-based vibration absorber, a systematic and rigorous study of the optimal tuning design deserves further investigation.
Full-Size Rotordynamic Test Rig for Magnetic and Auxiliary Bearing Testing and Initial Results
Authors: De Santiago Oscar , Solórzano Víctor , Díaz Sergio
Published: December 2013

Recent challenges in turbocompresor design include applications in subsea installations as well as remote operation in unmanned floating platforms. These applications benefit from oil-free operation which solves technical hurdles while being environmentally friendly. The most mature oil-free rotor support technology today is the magnetic bearing which is being used by several manufacturers as their standard solution to these advanced applications. These systems require auxiliary bearings to contain the rotor in case of a power failure to the magnetic bearings or a transient event. In general, there exists the need to develop commercial solutions for auxiliary bearings to extend its life, in particular regarding cumulative damage associated to drop events.

This paper presents the design of a configurable test rig that can accommodate different rotor sizes, up to 1200 mm in bearing span, and 711 mm diameter wheels. The rig can also accommodate bearing sizes up to 229 mm. Rig pedestals can fit different bearing types such as magnetic bearings and/or auxiliary bearings independently, including oil bearings for comparison purposes. Misalignment and support flexibility effects are also possible. A 15.5 kW, variable speed electric motor drives the test rotor up to a speed limit of 10,000 rpm.

Initial experiments on auxiliary bearings are shown for a 5-impeller, 57.8 kg, subcritical compressor rotor without drop events to study the baseline dynamic behavior of roller-element bearings (with inner clearance) on soft supports (o-rings). These experiments are presented to illustrate non-linear vibration regimes present during rotor-stator interaction with a highly unbalanced rotor. Experimental evidence presented can be used to fine-tune current auxiliary bearingmodels to improve rotordynamic predictive codes.
Optimization of a High-Pressure Steam Turbine Stage for a Wide Flow Coefficient Range
Authors: Bellucci Juri , Rubechini Filippo , Arnone Andrea , Arcangeli Lorenzo , Maceli Nicola , Dossena Vincenzo
Published: December 2013

In this paper a multi-objective, aerodynamic optimization of a high-pressure steam turbine stage is presented. The overall optimization strategy relies on a neural-network-based approach, aimed at maximizing the stage’s efficiency, while at the same time increasing the stage loading. The stage under investigation is composed of prismatic blades, usually employed in a repeating stage environment and in a wide range of operating conditions. For this reason, two different optimizations are carried out, at high and low flow coefficients. The optimized geometries are chosen taking into account aerodynamic constraints, such as limitation of the pressure recovery in the uncovered part of the suction side, as well as mechanical constraints, such as root tensile stress and dynamic behavior. As a result, an optimum airfoil is selected and its performance are characterized over the whole range of operating conditions. Parallel to the numerical activity, both optimized and original geometries are tested in a linear cascade, and experimental results are available for comparison purposes in terms of loading distributions and loss coefficients. Comparisons between measurements and calculations are presented and discussed for a number of incidence angles and expansion ratios.
RR4500 Auxiliary Turbine Generator Proposed Predictive and Condition Based Maintenance
Authors: Moore Greg
Published: December 2013

Past and current Navy maintenance philosophy in military systems is to perform maintenance at scheduled intervals based on manufacturer maintenance recommendations. For example, if a manufacturer recommends that lube oil filters require replacement every 300 operating hours, maintenance personnel replaced oil filters regardless of condition. The Rolls Royce Naval Marine INC (RRNMI) designed, RR4500 Auxiliary Turbine Generator (ATG) program has designed advanced system monitoring capable of indicating out of specified conditions warning shipboard personnel to take maintenance action. Using a variety of sensors and state-of-the-art micro-processing, the RR4500 ATG utilizes a combination of audible and visual alarms alerting operators of out of condition parameters. The warning system allows maintenance personnel to investigate potential system problems before more serious damage occurs. However, maintenance personnel rely on alarms rather than performance trending to commence maintenance actions which requires an unscheduled system shutdown to correct the problem. Condition Based and Predictive Maintenance utilizes trending of data, already captured by the Full Authority Digital Control (FADC), to predict a potential failure prior to the onset of an alarm or system shutdown. This maintenance philosophy is called Condition Based Maintenance (CBM). Maintenance actions are based on the condition of the hardware or system rather a scheduled maintenance plan. The proposed application of CBM and Predictive Maintenance for the RR4500 ATG will be presented.
A Comparison of Two Load Transferring Methods in an Unsteady One-Way Fluid-Structure Interaction Analysis
Authors: Drewczynski Marcin , Solinski Marek , Rzadkowski Romuald
Published: December 2013

A full two-way aeroelasticity coupling analysis of rotating machinery and their main components requires considerable computational analysis and CPU time. This is why the most common methodology for this type of problem is a one-way coupling between fluid and structure. In this case, forces acting on rotor blades that result from a flow are introduced into a structural model of a blade as a local spot load in the centre of gravity or a series of local spot points deployed along the blade length. However, this method does not take into account how the forces change in a chordwise direction (along chord).

An alternative way is to use the method of directly transferring the pressure field as a surface load from the CFD analysis to a structural model of a blade. In this case various interpolation methods are needed to transfer the results from the CFD mesh on to the structural mesh nodes.

In this paper the authors compare how both methods of load transfer affect rotor blade stress and displacement levels during one period of rotation. Calculations were carried out for the first stage compressor blade of an aircraft engine. Ansys 12.1 was used to calculate the entire structure. Unsteady CFD calculations were carried out using Fluent for a 1.5 stage axial compressor model. For the numerical calculations a non-viscous flow was used. The unsteady forces were calculated on 10 control cross-sections of a rotor blade. The transient results obtained from the CFD calculations were transferred onto a structural rotor blade model using APDL language script. For both methods of load transference, transient displacements and transient stresses for the rotor blade were calculated. The harmonic analysis results were compared. Mesh sensivity analysis was also carried out for the structural model.
An Experimental Flow Investigation of Low Pressure Turbine Stages With Various Wet Conditions
Authors: Shibukawa Naoki , Tsukuda Tomohiko , Hashidate Tadayuki , Kawagishi Hiroyuki , Uchida Tatsuro , Goto Koichi
Published: December 2013

Detail flow characteristics of an actual size low pressure steam turbine stages under real operating conditions were examined in this paper. The main purpose of the experimental work was to obtain the radial distribution of the velocity triangles in the wet flow of the large size turbine, so that a series of tests were carried out with various wet conditions. Some particular changes of the flow pattern were observed at the exit of both the stator and the blade rows which would not predicted by steam turbine design tools.

A kind of flow coefficient was defined and investigated as well as the steam velocities. With an assumption of the steam wetness distribution along the blade span, a tendency of the flow coefficient was appeared which was similar to previous work [7]. The wetness assumption was qualitatively verified by bore-scope observation of the water concentration on the stator surface and the fog condition of the steam path.
Non-Linear Dynamics of Steam Turbine Blades With Shroud: Numerical Analysis and Experiments
Authors: Zucca Stefano , Gola Muzio M. , Piraccini Francesco
Published: December 2013

The prediction of the aeromechanical behavior of low-pressure blades represents one of the main challenges in the Steam Turbine Industry. The evaluation of forced response and damping is critical for the reliability of new designs and usually requires expensive validation campaigns such as Wheel Box Tests (WBT).

A WBT consists of one or more blade rows assembled on a rotor and spun at the desired rotating speed in a vacuum cell, with synchronous excitation provided by various sources. The WBT provides accurate information about the blade modes frequency, the alternating response level, and allows the evaluation of the mechanical damping.

Given the large effort in terms of costs and time associated to the experimental activity, the possibility to rely on the output of a numerical code either during the first steps of a new design or to investigate the effect of minor changes to a current design would be extremely beneficial to the development of future products.

In order to compute the non-linear forced response of shrouded blades of steam turbines, custom numerical solvers must be developed, since commercial finite element (FE) solvers do not perform this kind of analysis in the frequency domain.

In this paper, the forced response of a blade with shrouds of a low pressure steam turbine is computed and numerical results are compared with the experimental Wheel Box Tests performed at GE Oil & Gas. The calculations require a three-step procedure: in the first step, a non-linear static analysis is performed in ANSYS® in order to compute the actual contact area on the shroud surface and the distribution of static normal loads, then a reduced order model of the blade is generated in ANSYS® taking into account the stiffening effect on the blade of the pre-stress due to the centrifugal force, finally the reduced model is imported in a numerical code and the non-linear forced response of the blade is computed.

The numerical code solves the balance equations of the system in the frequency domain, by means of the Harmonic Balance Method, imposing cyclic symmetry boundary conditions of the system. An interpolation procedure is implemented in order to manage the non-perfectly matching meshes of the shroud contact surfaces, while the tangential and normal contact stiffness is computed with a numerical model based on the contact mechanics principles.

The numerical and the experimental results around some of the critical resonances of the system are compared in order to assess the reliability and accuracy of the numerical tool for its future implementation in the mechanical design practice of the blades.
Performance Analysis of Cogenerative and Trigenerative Plant With Microgas-Turbine
Authors: Brandoni Caterina , Comodi Gabriele , Pelagalli Leonardo , Caresana Flavio
Published: December 2013

The paper reports on the performance analysis of cogenerative and trigenerative plants based on Micro Gas Turbines. The core of the system is a natural-gas-fuelled Turbec T100 operating on a regenerated open-air cycle.

A code specifically developed by the authors to simulate the micro gas turbine in cogeneration plants, and already checked against experimental data, has been upgraded to simulate the unit’s behavior when facing also a cooling demand (trigenerative case).

For this purpose the model of a water-LiBr single-effect absorption chiller driven by hot water has been used.

The analysis cover all the unit’s application range and represent a start for its economic evaluation.
Decreasing Bladed Disk Response With Dampers on a Few Blades: Part II—Nonlinear and Blade-Blade Dampers Applications
Authors: Murthy Raghavendra , Mignolet Marc P.
Published: December 2013

This two part paper focuses on the optimum placement of a limited number of dampers, i.e. fewer than the number of blades, on a bladed disk to induce the smallest possible amplitude of blade response with or without involuntary, random mistuning. Intentional mistuning is also considered as an option to reduce the amplitude of blade response and the pattern of two blade types (referred to as A and B blades) is then part of the optimization effort in addition to the location of the dampers on the disk.

This second part of the investigation focuses on the application of the optimization algorithms developed in Part I to nonlinear dampers, more specifically friction dampers, as well as to the consideration of blade-blade dampers, linear or nonlinear (underplatform dampers). Additionally, the optimization of blade-only and blade-blade linear dampers will be extended to include uncertainty/variability in the damper properties that arise during the manufacturing and/or inservice. It is found that the optimum achieved without considering such uncertainty/variability is robust with respect to it.
Improving Tilting-Pad Journal Bearing Predictions: Part II—Comparison of Measured and Predicted Rotor-Pad Transfer Functions for a Rocker-Pivot Tilting-Pad Journal Bearing
Authors: Wilkes Jason C. , Childs Dara W.
Published: December 2013

As described in Part I [1], most analytical models for TPJBs are based on the assumption that explicit dependence on pad motion can be eliminated by assuming harmonic rotor motion such that the amplitude and phase of pad motions resulting from radial and transverse rotor motions are predicted by rotor-pad transfer functions (TFs). In short, these transfer functions specify the amplitude and phase of pad motion (angular, radial, translational, etc.) in response to an input rotor motion.

Direct measurements of pad motion during test excitation were recorded to produce measured transfer functions between rotor and pad motion, and a comparison between these measurements and predictions is given. Motion probes were added to the loaded pad (having the static load vector directed through its pivot) of a 5-pad TPJB to obtain accurate measurement of pad radial and tangential motion, as well as tilt, yaw, and pitch. Strain gages were attached to the side of the loaded pad to measure static and dynamic bending strains, which were then used to determine static and dynamic changes in pad curvature (pad clearance).
Impact of Secondary Flow on the Accuracy of Simplified Design Methods for Steam Turbine Stages
Authors: Schumann Jan , Harbecke Ulrich , Sahnen Daniel , Polklas Thomas , Jeschke Peter , Schwarz Mark André
Published: December 2013

The subject of the presented paper is the validation of a design method for HP and IP steam turbine stages. Common design processes have been operating with simplified design methods in order to quickly obtain feasible stage designs. Therefore, inaccuracies due to assumptions in the underlying methods have to be accepted. The focus of this work is to quantify the inaccuracy of a simplified design method compared to 3D Computational Fluid Dynamics (CFD) simulations.

Short computing time is very convenient in preliminary design; therefore, common design methods work with a large degree of simplification. The origin of the presented analysis is a mean line design process, dealing with repeating stage conditions. Two features of the preliminary design are the stage efficiency, based on loss correlations, and the mechanical strength, obtained by using the beam theory. Due to these simplifications, only a few input parameters are necessary to define the primal stage geometry and hence, the optimal design can easily be found. In addition, by using an implemented law to take the radial equilibrium into account, the appropriate twist of the blading can be defined.

However, in comparison to the real radial distribution of flow angles, this method implies inaccuracies, especially in regions of secondary flow. In these regions, twisted blades, developed by using the simplified radial equilibrium, will be exposed to a three-dimensional flow, which is not considered in the design process. The analyzed design cases show that discrepancies at the hub and shroud section do exist, but have minor effects. Even the shroud section, with its thinner leading-edge, is not vulnerable to these unanticipated flow angles.
Forced Response Analysis of a Transonic Fan
Authors: Vasanthakumar Parthasarathy , Ebel Paul-Benjamin
Published: December 2013

The forced response of turbomachinery blades is a primary source of high cycle fatigue (HCF) failure. This paper deals with the computational prediction of blade forced response of a transonic fan stage that consists of a highly loaded rotor along with a tandem stator. In the case of a transonic fan, the forced response of the rotor due to the downstream stator assumes significance because of the transonic flow field. The objective of the present work is to determine the forced response of the rotor induced as a result of the unsteady flow field due to the downstream stator vanes. Three dimensional, Navier-Stokes flow solver TRACE is used to numerically analyse the forced response of the fan. A total of 11 resonant crossings as identified in the Campbell diagram are examined and the corresponding modeshapes are obtained from finite element modal analysis. The interaction between fluid and structure is dealt with in a loosely coupled manner based on the assumption of linear aerodynamic damping. The aerodynamic forcing is obtained by a nonlinear unsteady Navier-Stokes computation and the aerodynamic damping is obtained by a time-linearized Navier-Stokes computation. The forced response solution is obtained by the energy method allowing calculations to be performed directly in physical space. Using the modal forcing and damping, the forced response amplitude can be directly computed at the resonance crossings. For forced response solution, the equilibrium amplitude is reached when the work done on the blade by the external forcing function is equal to the work done by the system damping (aerodynamic and structural) force. A comprehensive analysis of unsteady aerodynamic forces on the rotor blade surface as a result of forced response of a highly loaded transonic fan is carried out. In addition, the correspondence between the location of high stress zones identified from the finite element analysis and the regions of high modal force identified from the CFD analysis is also discussed.
Energy-Yield-Based Optimization of an H-Darrieus Wind Turbine
Authors: Bianchini Alessandro , Ferrari Lorenzo , Magnani Sandro
Published: December 2013

Small-size H-Darrieus wind turbines are gaining more popularity in the wind energy market, thanks to some particular benefits (simplicity, reliability and low noise emissions) and to the efforts of industrial manufacturers to propose new exterior solutions coupled with tempting rated-power offers. The actual operating conditions of a rotor over a year can be, however, very different from the nominal one and strictly dependent on the features of the installation site. Based on these considerations, a turbine optimization oriented to maximize the annual energy yield, instead of the maximum power, is thought to represent a more interesting solution.

With this goal in mind, 5400 test cases of H-Darrieus rotors were compared on the basis of their energy-yield capabilities for different annual wind distributions in terms of average speed. To this purpose, the wind distributions were combined with the predicted performance maps of the rotors obtained with a specifically developed numerical code based on a Blade Element Momentum (BEM) approach. The limits related to the wind turbine start-up behavior and to the structural loads (i.e. maximum rotational speed and maximum wind velocity) were also taken into account.

The analysis, developed in terms of dimensionless parameters, highlighted the configurations which ensure the largest annual energy yield for each wind distribution. In addition, the differences between the results of a design process oriented to the maximum power output or to the maximum annual-energy-yield were analyzed; in particular, the comparison showed that a design oriented to the maximum energy-yield is assumed to provide a notable increase in the extracted energy (up to around 20%, with the selected design assumptions) whenever wind distributions with low average wind speeds are considered.
Leakage-Induced Compressor Blade Excitation due to Inter-Segment Gaps
Authors: Bladh Ronnie , Zhuang Qingyuan , Hu Jiasen , Hammar Johan
Published: December 2013

A comprehensive investigation is presented related to leakage-induced blade excitation from shrouded vane segments found in industrial gas turbine compressors. The focus of the investigation is to explore the excitation mechanism acting on downstream rotor blades that stem from the particularly complex leakage flows around the hub inter-segment gaps.

The aerodynamic forces are here determined using 3D nonlinear time-marching CFD simulations. The employed computational model encompasses the two rear-most stages in an existing industrial gas turbine compressor. The inter-segment gap is implemented in the next-to-last stator, varying from no gap to twice the nominal gap size.

Obtained results indicate that the excitation induced by the inter-segment gap leakage flows is distinctly multi-harmonic and unexpectedly strong. As much as five times the excitation strength of upstream wakes was observed already for the nominal gap. The induced unsteady forces were found to derive from two different sources: (i) a large separation producing local forcing in the hub region; and (ii) circumferentially varying flow speed resulting in distributed forcing over the entire blade.

The findings imply that the excitation induced by inter-segment gap leakage flows can be a significant contributor to blade vibratory responses in the intermediate engine order range, and thereby add to the knowledge base related to blade dynamic integrity.
Microturbine Powered Generator Technology Assessment: Direct-Drive High-Speed Versus Direct-Connected Low-Speed
Authors: Ebrahim Mohammed , Armstrong Jeffrey
Published: December 2013

An assessment of the different technologies reveals that the selection of the optimum generation/power-control technology for microturbine generators requires the consideration of a myriad of factors. The study presented is based on extensive experience with the design, manufacture, and field operation of a 250kW direct-connected, low-speed microturbine powered generator. High-speed generators and power electronics for the same engine are examined considering impact on performance, installed cost, reliability, and flexibility. Although general improvement is expected, there are certain challenges that must be addressed before the benefits of advanced power electronics and high speed machinery can be exploited. These challenges increase with increased power demand. Higher efficiencies are not only an energy/cost saving exercise, but essential due to increased thermal stress at larger power ratings and higher electrical frequencies. Future trends of technology, manufacturing, and materials are also presented. In the final analysis, it will be prudent to carefully select a technology which ensures that the advantages of microturbines are optimized rather than compromised.
Performance Analysis of Direct Steam Generation-Central Receiver Systems
Authors: Sanz-Bermejo Javier , Gonzalez-Aguilar José , Romero Manuel
Published: December 2013

This work presents a comparative study between direct steam generation central receiver solar power plants working at live steam conditions similar to those found in commercial plants. PS10 and PS20 by Abengoa Solar use a single-receiver, producing saturated steam, whereas Sierra SunTower by e-Solar and Ivanpah Solar Electric Generating System (ISEGS) by BrightSource use dual-receiver technology producing superheated steam.

The system analysis includes individual studies for each subsystem: solar field, receiver and Rankine power block; as well as the overall-analysis of a 66.7 MWth plant. PS10 working conditions were analysed with and without intermediate reheat step. It was assumed that Sierra SunTower-configuration has non-reheat turbine and Ivanpah-cycle includes an intermediate reheat step. The reheat process in PS10 configuration was performed using a fraction of live steam coming from the receiver; while for Ivanpah-configuration exhaust steam from high pressure turbine stage was sent back to the superheated steam section of the dual-receiver. These concepts make possible to avoid hybridisation and assure special regimes (such as Spanish feed-in tariff).

The analysis of the heliostat field for dual-receiver concepts reveals that the aiming strategy on the absorbers has not relevant influence on optical performances. However, receiver efficiency decreased from 91.9%, working with saturated steam, to 87.86–84.14% working with superheated steam related to operating temperatures and heat exchange surface area. This study reveals that the improvement achieved in the power block under Ivanpah configuration was able to compensate higher thermal losses at the receiver, increasing net power production by 25.5% compared with saturated steam conditions.
Advanced Chemical Vapor Aluminizing Technology: Co-Deposition Process and Doped Aluminized Coatings
Authors: Strakov Hristo , Papageorgiou Vasileios , Bonetti Renato , Lieberman Val , Scott Audie
Published: December 2013

Chemical Vapor Aluminizing (CVA) is used for more than 20 years to protect blades and vanes in the hot section of aero- and land based turbines against oxidation and hot corrosion [1]. Modern CVA is an advanced process capable of controlled alloying the coating with additional elements using metal chlorides and tight control of the coating composition. CVA processes offer a number of advantages over conventional pack and above-the-pack cementation. This paper deals with the industrial CVA technology to produce multi-component coatings using different metal chloride generating devices. Specific examples illustrate the influence of the coating parameters and base materials on the NiAl-based coatings microstructure and composition. Advanced co-deposition CVA processes with addition of different metal elements to the aluminide coatings are presented. Modified coating properties and structures of multiple metal coatings with elements like Al, Cr, Si, Co, Y and others will be discussed.
Clutter depth discrimination using the wavenumber spectrum
Authors: Benjamin Reeder D.
Published: December 2013

Clutter depth is a key parameter in mid-frequency active sonar systems to discriminate between sources of clutter and targets of interest. A method is needed to remotely discriminate clutter depth by information contained in the backscattered signal—without a priori knowledge of that depth. Presented here is an efficient approach for clutter depth estimation using the structure in the wavenumber spectrum. Based on numerical simulations for a simple test case in a shallow water waveguide, this technique demonstrates the potential capability to discriminate between a clutter source in the water column vs one on the seabed.
Accurate measurement of guided modes in a plate using a bidirectional approach
Authors: Moreau Ludovic , Minonzio Jean-Gabriel , Foiret Josquin , Bossy Emmanuel , Talmant Maryline , Laugier Pascal
Published: December 2013

Measuringguided wave propagation in long bones is of interest to the medical community. When an inclination exists between the probe and the tested specimen surface, a bias is introduced on the guided mode wavenumbers. The aim of this study was to generalize the bidirectional axial transmission technique initially developed for the first arriving signal. Validation tests were performed on academic materials such a bone-mimicking plate covered with either a silicon or fat-mimicking layer. For any inclination, the wavenumbers measured with the probe parallel to the waveguide surface can be obtained by averaging the wavenumbers measured in two opposite directions.
Phase Portraits of the Proliferation-Quiescence Decision
Authors: Zhang Tongli
Published: December 2013

The ON-OFF status of the CDK2-RB bistable switch, rather than a particular time point, defines the restriction point.
Resistance Through cAMP Signaling
Authors: Gough Nancy R.
Published: December 2013

Reactivation of a pathway associated with melanocyte lineage specification confers resistance to inhibition of the MAPK pathway in melanoma.
What’s Downstream? A Set of Classroom Exercises to Help Students Understand Recessive Epistasis
Authors: Knight Jennifer K. , Wood William B. , Smith Michelle K.
Published: December 2013

Undergraduate students in genetics and developmental biology courses often struggle with the concept of epistasis because they are unaware that the logic of gene interactions differs between enzymatic pathways and signaling pathways. If students try to develop and memorize a single simple rule for predicting epistatic relationships without taking into account the nature of the pathway under consideration, they can become confused by cases where the rule does not apply. To remedy this problem, we developed a short pre-/post-test, an in-class activity for small groups, and a series of clicker questions about recessive epistasis in the context of a signaling pathway that intersects with an enzymatic pathway. We also developed a series of homework problems that provide deliberate practice in applying concepts in epistasis to different pathways and experimental situations. Students show significant improvement from pretest to posttest, and perform well on homework and exam questions following this activity. Here we describe these materials, as well as the formative and summative assessment results from one group of students to show how the activities impact student learning.
Cooperative Learning through Team-Based Projects in the Biotechnology Industry
Authors: Luginbuhl Sarah C. , Hamilton Paul T.
Published: December 2013

We have developed a cooperative-learning, case studies project model that has teams of students working with biotechnology professionals on company-specific problems. These semester-long, team-based projects can be used effectively to provide students with valuable skills in an industry environment and experience addressing real issues faced by biotechnology companies. Using peer-evaluations, we have seen improvement in students’ professional skills such as time-management, quality of work, and level of contribution over multiple semesters. This model of team-based, industry-sponsored projects could be implemented in other college and university courses/programs to promote professional skills and expose students to an industry setting.
Engineering Your Own Superbug: A Useful Assignment to Evaluate Real Learning Comprehension in Microbiology Classes
Authors: Chen Yun-Chi
Published: December 2013

The learning comprehension of students in microbiology classes is not easy to evaluate, particularly when the student population is diverse in terms of backgrounds, majors, levels of training and preparedness, and the students’ expectations and enthusiasm for the class. It is difficult to design a one-size-fits-all exam that best suits a mixed student population; and most traditional assignments/case studies focusing on particular microbes or topics might not readily assess students’ overall understanding and learning comprehension. It is important to develop an assessment method that not only can engage students in active learning and deliberate practice but can also promote their imaginative and creative potential. The word “superbugs” often appears in the media and refers to some deadly or drug-resistant microbes. These superbugs possess special phenotypic and functional attributes that constitute their “superness.” It is predicted that more new surprising superbugs will emerge in the future and students should be challenged now with some mindstimulating ideas and exercises in their microbiology class. To develop a supplementary tool to evaluate students’ comprehension and to prepare them for the predicted superbugs unknown to us, a writing project entitled “Constructing Your Own Superbug” was designed to achieve these goals.
An Argument and Plan for Promoting the Teaching and Learning of Neglected Tropical Diseases
Authors: Bonney Kevin M.
Published: December 2013

Neglected tropical diseases constitute a significant public health burden, affecting over one billion people globally, yet this group of diseases is underrepresented in the appropriation of both monetary and intellectual capital for developing improved therapies and public health campaigns. The topic of neglected tropical diseases has been similarly marginalized in the biology classrooms of our nation’s high schools and colleges, despite offering an opportunity to teach and learn about a diverse area of microbiology with far-reaching public health, social, and economic implications. Discussed herein is an argument for increasing the representation of neglected tropical diseases in microbiology education as a means to generate increased interest in these diseases among the generation of future researchers and policy-makers, and to promote interdisciplinary learning, civic engagement, and critical thinking.
Benefits of Acupuncture for Diabetic Gastroparesis: A Comparative Preliminary Study
Authors: Danielli Miller Netanella , Schiff Elad , Ben-Arye Eran , Singer Joelle , Tsadok Perets Tsachi , Flaut Shlomit , Sahar Nadav , Niv Yaron , Dickman Ram
Published: December 2013

Objectives

The aim of this preliminary study was to compare the effectiveness of domperidone and acupuncture for the management of diabetic gastroparesis.

Methods

This was a preliminary, prospective non-randomised, unblinded case-crossover study conducted in patients with longstanding, uncontrolled diabetes mellitus and gastroparesis. All patients received domperidone (20 mg four times a day) for 12 weeks, followed by a 2–3 week washout period, and then biweekly acupuncture treatments for 8 weeks. Gastric emptying rate, glucose and glycated haemoglobin (HbA1C) levels were measured at start and end of each treatment period. At each of these timepoints patients completed the Gastroparesis Cardinal Symptom Index (GCSI), the Satisfaction with Life Scale (SWLS), and the Short-Form 36 Health Survey Update (SF-36).

Results

The trial was curtailed after only eight participants could be recruited in 3 years. The mean age of patients was 57.1±9.9 years, the male:female ratio was 1:7 and mean body mass index (kg/m2) was 25.2±1.2. There was no change in any of the outcome parameters after treatment with domperidone. Acupuncture was associated with a decrease in scores for almost all cardinal symptoms of the GCSI, as well as in increased total score on the SWLS (p=0.002) and the social functioning domain of the SF-36 (p=0.054). Acupuncture did not lead to an improvement in gastric emptying, or glucose control from baseline.

Conclusions

Acupuncture treatment may lead to symptomatic improvement in patients with diabetic gastroparesis. Within the limitations of this preliminary, non-randomised and unblinded study, it appears that this effect may be due to non-specific mechanisms.
Reversible cardiomyopathy after radiofrequency ablation of 30-year persistent atrial tachycardia
Authors: Suzuki Atsushi , Shiga Tsuyoshi , Arai Kotaro , Shoda Morio
Published: December 2013

Tachycardia-induced cardiomyopathy (TIC) is a reversible form of the left ventricular (LV) systolic dysfunction and is believed to be a relatively acute process. We report a TIC case with a 30-year history of long-lasting persistent atrial tachycardia involving a 44-year-old man previously diagnosed with dilated cardiomyopathy and a low LV ejection fraction (LVEF) of 20%. ECG revealed atrial tachycardia at 110–120 bpm. He was hospitalised with a worsening heart failure. His clinical status was New York Heart Association functional class III, and echocardiography revealed LV dilation and an LVEF of 9%. A two-dimensional speckle-tracking strain measurement revealed LV mechanical dyssynchrony. He underwent radiofrequency ablation for atrial tachycardia. After restoring sinus rhythm, his cardiac symptoms improved immediately. The LV mechanical dyssynchrony decreased a week after ablation, without changes in the LV dilation or LVEF. Thereafter, the LV dilation and systolic function gradually improved, and atrial tachycardia and heart failure remained absent.
Stridor in an 11-year-old child
Authors: Abraham Deepu , Karuvattil Rajesh , Fitzpatrick Maggie
Published: December 2013

Stridor in older children can be due to diverse aetiology that includes infections, anaphylaxis and rarely systemic conditions leading to hypocalcaemia. We report the case of a previously asymptomatic 11-year-old girl who presented to the casualty with stridor due to hypocalcaemia. The aetiological investigations for hypocalcaemia uncovered previously undetected chronic renal failure, possibly due to a rare autosomal recessive condition called nephronophthisis. We report this case to highlight the importance of widening the diagnostic focus for children presenting with stridor, especially when they fall outside the usual age group for infections like croup, or when the history is atypical.
SIMPLE SIMULATION SCHEMES FOR CIR AND WISHART PROCESSES
Authors: BALDI PAOLO , PISANI CAMILLA
Published: December 2013

We develop some simple simulation algorithms for CIR and Wishart processes. We investigate rigorously the square of a matrix valued Ornstein–Uhlenbeck process, the main idea being to split the generator and to reduce the problem to the simulation of the square of a matrix valued Ornstein–Uhlenbeck process to be added to a deterministic process. In this way, we provide a weak second-order scheme that requires only the simulation of i.i.d. Gaussian r.v.'s and simple matrix manipulations.
MECHANICAL PROPERTIES AND TOPOLOGICAL CHANGES IN A Fe-CRYSTAL WITH FIXED AND MIGRATING H-ATOM: A NUMERICAL STUDY
Authors: VINOGRADOV O.
Published: December 2013

A numerical study, within the framework of molecular statics, is conducted to assess the effect of a fixed and migrating hydrogen atom on the stress–strain data and the topological changes taking place in a 3D BCC α-iron crystal subjected to a tensile elongation. A pair-wise Morse potential is used to describe the interatomic forces. The results for a crystal with 2324 iron atoms show that the presence of a hydrogen atom, either migrating or fixed, produces relatively small effect on the stress–strain data within the elastic and some plastic range of loading. However, the topological changes, represented by the changes in the nearest neighbors for each atom within the cut-off distance after each displacement increment, are substantially different. Similarly, a comparison of the changes in the atomic potential energies when the sudden drop in stresses takes place shows differences between the two cases.
FIRST PRINCIPLES DENSITY FUNCTIONAL INVESTIGATION OF SUPPORTED TUNGSTEN CLUSTER (Wn; n = 1 TO 6) ON ANCHORED GRAPHITE (0001) SURFACE
Authors: BARMAN SONALI , DAS G. P. , KAWAZOE Y.
Published: December 2013

Size-selected Wn clusters can be deposited firmly on a graphite (0001) surface using a novel technique, where the positive ions (of the same metal atom species) embedded on the graphite surface by ion implantation, act as anchors. The size selected metal clusters can then soft land on this anchored surface m [Hayakawa et al., 2009]. We have carried out a systematic theoretical study of the adsorption of Wn (n = 1-6) clusters on anchored graphite (0001) surface, using state-of-art spin-polarized density functional approach. In our first-principles calculations, the graphite (0001) surface has been suitably modeled as a slab separated by large vacuum layers. Wn clusters bond on clean graphite (0001) surface with a rather weak Van-der-Waals interaction. However, on the anchored graphite (0001) surface, the Wn clusters get absorbed at the defect site with a much larger adsorption energy. We report here the results of our first-principles investigation of this supported Wn cluster system, along with their reactivity trend as a function of the cluster size (n).
Distortion is Fixed Parameter Tractable
Authors: Fellows Michael , Fomin Fedor V. , Lokshtanov Daniel , Losievskaja Elena , Rosamond Frances , Saurabh Saket
Published: December 2013

We study low-distortion embedding of metric spaces into the line, and more generally, into the shortest path metric of trees, from the parameterized complexity perspective. Let
M
=
M
(
G
) be the shortest path metric of an edge-weighted graph
G
, with the vertex set
V
(
G
) and the edge set
E
(
G
), on
n
vertices. We give the first fixed parameter tractable algorithm that for an
unweighted
graph metric
M
and integer
d
either constructs an embedding of
M
into the line with distortion at most
d
, or concludes that no such embedding exists. Our algorithm requires
O
(
nd
4
(2
d
+ 1)
2d
) time which is a significant improvement over the best previous algorithm that runs in time
O
(
n
4d+2
d
O(1)
). Because of its apparent similarity to the notoriously hard
Bandwidth Minimization
problem, we find it surprising that this problem turns out to be fixed parameter tractable.

We extend our results on embedding unweighted graph metric into the line in two ways. First, we give an algorithm to construct small-distortion embeddings of
weighted
graph metrics. The running time of our algorithm is
O
(
n
(
dW
)
4
(2
d
+ 1)
2dW
), where
W
is the largest edge weight of the input graph. To complement this result, we show that the exponential dependence on the maximum edge weight is unavoidable. In particular, we show that deciding whether a weighted graph metric
M
(
G
) with maximum weight
W
< |
V
(
G
)| can be embedded into the line with distortion at most
d
is NP-complete for every fixed rational
d
≥ 2. This rules out any possibility of an algorithm with running time
O
((
nW
)
h(d)
) where
h
is a function of
d
alone. Second, we consider more general host metrics for which analogous results hold. In particular, we prove that for any tree
T
with maximum degree
Δ
, embedding
M
into a shortest path metric of
T
is fixed parameter tractable, parameterized by (
Δ
,
d
).