bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Piezoelectric Vibration Control of Subscale Composite Fan Blades
Authors: Duffy Kirsten P. , Choi Benjamin B. , Provenza Andrew J. , Min James B. , Kray Nicholas
Published: December 2013

As part of the Fundamental Aeronautics program, researchers at NASA Glenn Research Center (GRC) are investigating new technologies supporting the development of lighter, quieter, and more efficient fans for turbomachinery applications. High performance fan blades designed to achieve such goals will be subjected to higher levels of aerodynamic excitations which could lead to more serious and complex vibration problems.

Piezoelectric materials have been proposed as a means of decreasing engine blade vibration either through a passive damping scheme, or as part of an active vibration control system. For polymer matrix fiber composite blades, the piezoelectric elements could be embedded within the blade material, protecting the brittle piezoceramic material from the airflow and from debris.

To investigate this idea, spin testing was performed on two General Electric Aviation (GE) subscale composite fan blades in the NASA GRC Dynamic Spin Rig Facility. The first bending mode (1B) was targeted for vibration control. Because these subscale blades are very thin, the piezoelectric material was surface-mounted on the blades. Three thin piezoelectric patches were applied to each blade — two actuator patches and one small sensor patch. These flexible macro-fiber-composite patches were placed in a location of high resonant strain for the 1B mode. The blades were tested up to 5000 rpm, with patches used as sensors, as excitation for the blade, and as part of open- and closed-loop vibration control. Results show that with a single actuator patch, active vibration control causes the damping ratio to increase from a baseline of 0.3% critical damping to about 1.0% damping at 0 RPM. As the rotor speed approaches 5000 RPM, the actively controlled blade damping ratio decreases to about 0.5% damping. This occurs primarily because of centrifugal blade stiffening, and can be observed by the decrease in the generalized electromechanical coupling with rotor speed.
Combination Axial and Radial Active Magnetic Bearing With Improved Axial Bandwidth
Authors: Filatov Alexei V. , Hawkins Lawrence A.
Published: December 2013

Homopolar Permanent-Magnet-Biased Combination Axial and Radial Electromagnetic Actuators used in Active Magnetic Bearings (AMBs) have several advantages over arrangements of separate axial and radial actuators including shorter length, lower part count, lower cost and better rotordynamic response. However, these actuators may require higher-order compensators in applications with significant dynamic axial loads due to somewhat lower axial bandwidth.

One of the reasons for a lower axial bandwidth is having the axial magnetic control flux flowing through an opening in a radial actuator assembled from insulated electrical-steel laminations stacked axially. Whenever this flux changes in time, it induces an electrical current in each lamination which is responsible for the dynamic axial force reduction and an additional phase lag.

In an improved actuator design, a current path in each lamination is interrupted by a single slot located between two radial control poles. In order to maintain structural integrity of the stack and magnetic conductivity between the radial poles, the slot position is rotated by 90 degrees between each subsequent lamination in the stack.

The solution has been evaluated in a test actuator with 3000N axial and 1200N radial load capacities. 7dB gain improvement and 15 degrees phase improvement at 30Hz have been demonstrated.
Turbomachinery for Supercritical CO2 Power Cycles
Authors: Fuller Robert , Preuss Jason , Noall Jeff
Published: December 2013

Supercritical CO2 (S-CO2) power cycles offer high plant efficiencies and beneficial economics for variety of heat sources. Nuclear, solar, waste heat, energy storage, and clean coal combustion are some of the applications under consideration for S-CO2 power production. Different types of cycles, topping and bottoming, have been conceptualized based on the heat source. These cycles have the possibility of being economically beneficial and competitive against incumbent steam cycles, primarily due to reduced material costs. Often the turbo-machinery capabilities are overlooked during the cycle design process, or are not well understood.

A method and guideline for turbo machinery selection is offered. Several examples are offered to give the S-CO2 cycle designer to judge the compatibility of the turbo-machinery with the overall system including type, size, and efficiency. The guideline includes turbo machinery design limitations. Understanding the turbo machinery implications relative to cycle design will allow the system designer to optimize the plant for efficiency and positive economic outcome.
Experimental Investigations of Active Air Bearings
Authors: Morosi Stefano , Santos Ilmar F.
Published: December 2013

Along with traditional oil lubrication, increasing demand for high-speed applications has renewed attention to gas bearings technology. Traditional aerostatic and aerodynamic gas lubrication has been widely used in a variety of applications, ranging from high-speed spindles to micro and meso-scale turbo-machinery. The present paper deals with experimental rotordynamic testing of a flexible rotor supported by hybrid aerostatic-aerodynamic gas journal bearing equipped with an electronic radial air injection system. From a rotordynamic point of view there are two phenomena that limit the widespread of traditional gas lubrication: 1) Low damping makes operation across critical speed dangerous, as even low level of unbalance can generate large vibration responses. This is especially problematic for gas bearing applications, which often operate in the supercritical region. Moreover, 2) An upper bound to supercritical operation is determined by the appearance of subsynchronous whirl instability. Due to the sudden increase in amplitude with respect to speed, this most often corresponds to the maximal attainable rotational speed of the system. Postponing the onset speed of instability poses therefore one of the greatest challenges in a high-speed gas bearing design. A great deal of research is devoted to attack such issues, where most propose passive designs such as compliant foil bearings, tilting pad and flexure pivot gas bearings. These solutions proved to be effective in improving static and dynamic properties of the bearings, however issues related to the manufacturing and accuracy of predictions has so far limited their applications. Another drawback is that passive bearings offer a low degree of flexibility, meaning that an accurate optimization is necessary for each application. The developed prototype active bearing offers several promising performance enhancements. Synchronous vibrations can be effectively addressed ensuring safe operation across the critical speeds; whirling instability is suppressed; intervening on the software, rather than the hardware can modify the response of the system. Implementing active lubrication adds however a considerable number of parameters and variables. The performance of a good control system lays most importantly on a good choice of control gains, which in general are different depending on the goal of the controller. Optimum tuning of the control loop is addressed experimentally, showing dependency on the supply pressure and, less prominently, the rotational velocity.
Aerodynamic and Mechanical Optimization of CF/PEEK Blades of a Counter Rotating Fan
Authors: Goerke Daniel , Le Denmat Anne-Laure , Schmidt Thomas , Kocian Frank , Nicke Eberhard
Published: December 2013

Since the development of the CRISP [1–3], a counter rotating integrated shrouded propfan, within a MTU-DLR program between 1985 and 2000, huge improvements in fan technologies have been made. In 2010 DLR launched an initiative to redesign the existing fan blades, taking advantage the latest developments in the field of material and manufacturing technology as well as numerical methods.

The new fan blades will be made of a carbon fiber reinforced PEEK material. Compared to the so called “onion skin configuration” of CRISP-1m, the layers of the CRISP2 lamina setups are parallel to each other. In contrast to metals, carbon fiber reinforced plastics have an orthotropic material behavior and a higher stiffness mass ratio, which have to be taken into account. The existing shaft and bearing system of the CRISP-1m-model [1–3] will be reused. The blades are mounted in titanium clevises by bolting.

To achieve an optimal design, it is necessary to optimize the aerodynamic performance together with the mechanical behavior within a multidisciplinary automated optimization process.

The optimization featured approximately one hundred free design variables, two objective functions (maximal displacement for respectively Rotor 1 and Rotor 2), as well as a high number of aerodynamic and mechanical constraints (efficiency, total pressure ratio, axial Mach number, stress, strain, eigenfrequencies, etc.).

This work shows how the challenge to integrate the modeling of CF/PEEK blades in a multidisciplinary design process were met in terms of the methods and optimization strategies involved. The major results of this optimization will be presented.

This design approach will give a new CRISP blade design ready for a planned rig test in the axial compressor test rig at the DLR in Cologne.
Effect of Non-Proportional Loading on Fatigue Crack Initiation and Growth Behavior of Maraging Steel
Authors: Nakamura Hiroshi , Takanashi Masahiro , Masaki Tatsuya , Zhang Shengde , Sakane Masao
Published: December 2013

This paper deals with multiaxial low cycle fatigue (LCF) crack behavior of maraging steel under non-proportional loading. Strain controlled LCF tests under proportional and non-proportional loading with 90° out-of-phase shift between the axial and shear strains were carried out on tube specimens at room temperature. In the correlation with Mises strain, LCF lives under non-proportional loading were underestimated by a factor of 10 from those under proportional loading. Observation of the specimen surface during fatigue tests showed that a large number of cracks were initiated in shear loading and non-proportional loading compared with uniaxial loading. Finite element analyses for estimating the stress concentration around inclusions revealed that the inclusion under shear loading and non-proportional loading had more locations to initiate cracks than the inclusion under uniaxial loading. The crack initiation life under proportional loading did not significantly differ from that under non-proportional loading. Fatigue cracks under non-proportional loading, however, propagated faster than those under proportional loading. The faster fatigue crack propagation under nonproportional loading presumably results from higher strain intensity at crack tips than that under proportional loading. The fatigue lives were predicted from the crack propagation analysis. Most calculated lives were within a factor of 2 scatter band so that the correlation of the test results appears satisfactory. Therefore, the main cause of shorter fatigue life under non-proportional loading resulted from the faster crack growth due to the higher strain intensity.
Meanline Modeling of Radial Inflow Turbine With Twin-Entry Scroll
Authors: Fredriksson Carl F. , Qiu Xuwen , Baines Nick C. , Müller Markus , Brinkert Nils , Gutmann Cornel
Published: December 2013

Twin entry turbines are widely used in turbocharging as a means of using the exhaust pulse energy of multi-cylinder engines. For modern engines where high levels of EGR are required, an asymmetric twin-entry turbine has been shown to have considerable advantages. Such turbines require a more developed approach to analysis and design than usual. A meanline model for a radial inflow turbine with twin-entry scroll has been developed. Different total pressures and total temperatures may be specified at each entry. Each volute passage is solved separately from the inlet to the splitter location, where the static pressures of both passages are assumed to be the same. From the volute splitter to the rotor inlet, the two streams mix into one uniform flow following conservation laws of continuity, momentum and energy. Experiments have been conducted on a test stand with a radial turbine with an asymmetric twin-entry scroll, where the inlet conditions can be varied independently for each entry. The test results are compared with the model prediction. A good accuracy of prediction is achieved with a realistic set of modeling coefficients. In the future, insights gained from test data and CFD analysis will be used to develop further the volute mixing model and include explicit partial admission losses in the rotor.
New Methods for Automated Fatigue Crack Growth and Reliability Analysis
Authors: McClung R. Craig , Lee Yi-Der , Enright Michael P. , Liang Wuwei
Published: December 2013

A new methodology has been developed for automated fatigue crack growth (FCG) life and reliability analysis of components based on finite element (FE) stress and temperature models, weight function stress intensity factor (SIF) solutions, and algorithms to define idealized fracture geometry models. The idealized fracture geometry models are rectangular cross-sections with dimensions and orientation that satisfactorily approximate an irregularly-shaped component cross-section. The fracture model geometry algorithms are robust enough to accommodate crack origins on the surface or in the interior of the component, as well as finite component dimensions, curved surfaces, arbitrary stress gradients, and crack geometry transitions as the crack grows. Stress gradients are automatically extracted from multiple load steps in the FE models for input to the fracture models. The SIF solutions accept univariant stress gradients and have been optimized for both computational efficiency and accuracy. The resulting calculations are used to automatically construct FCG life contours for the component and to identify hot spots. Finally, the new algorithms are used to support automated probabilistic assessments that calculate component reliability considering variability in the size, location, and occurrence rate of the initial anomaly; applied stress magnitudes; material properties; probability of detection; and inspection time. The methods are particularly useful for determining the probability of component fracture due to fatigue cracks forming at material anomalies that can occur anywhere in the volume of the component. The automation significantly improves the efficiency of the analysis process while reducing the dependency of the results on the individual judgments of the analyst. The automation also facilitates linking of the life and reliability management process with a larger integrated computational materials engineering (ICME) context, which offers the potential for improved design optimization.
Multiaxial Creep-Fatigue Life Prediction on the Rotor of a 1000MW Supercritical Steam Turbine
Authors: Mao Jianfeng , Wang Weizhe , Liu Yingzheng , Zhang Junhui
Published: December 2013

Damage of a high temperature rotor subjected to the creep-fatigue interaction was numerically investigated. Toward that end, a high temperature rotor of a 1000MW supercritical steam turbine was chosen for the study. A continuum damage mechanics model (CDM), which depicts the fatigue-creep interaction, was developed in the present paper. During the practical startup and shutdown processes, the influence of the multiaxial creep-fatigue interaction on strength of the rotor was analyzed in terms of stress, strain and damage. Comparison of the results from linear damage accumulation model (LDA) and CDM demonstrated that CDM was more reasonable to predict the lifetime of the rotor due to the multiaxial creep-fatigue interaction.
Performance Optimization of Wind Turbine Rotors With Active Flow Control: Part 2—Active Aeroelastic Simulations
Authors: Weinzierl G. , Pechlivanoglou G. , Nayeri C. N. , Paschereit C. O.
Published: December 2013

This paper presents the continuation of the research efforts of the authors in the direction of the development of “smart blades” for the wind turbines of the future. Results from previous research work is further in combination with a newly developed simulation code in order to assess the performance of Active Flow Control (AFC) elements implemented on modern wind turbine blade structures. Parametric investigations have been conducted in order to identify the optimal configuration of various AFC elements. These are tested under identical boundary conditions to define an overall optimal solution. The results of the research project show that the Active Gurney Flap is the element with a highest probability for the fastest implementation on wind turbine blades for load alleviation purposes. The most promising however overall solution is the Flexible Trailing Edge Flap. With its high control authority and relatively high regulation speed is able to significantly vary the aerodynamic performance of wind turbines.
Vibration Dissipation Characteristics of Symmetrical Piezoelectric Networks With Passive Branches
Authors: Fan Yu , Li Lin
Published: December 2013

In this paper, a new vibration reduction approach by means of symmetric piezoelectric network is proposed, combining energy harvesting and vibration reduction. The system could be constructed by several individual structures with identical mechanical parameters, such as blades of rotor machinery. Two basic forms of network-connection are studied, in which dissipation of both mechanical and electric field is considered. Dynamic models are established by the Lumped Parameter approach and Kirchhoff’s Circuit Theorem, and the normalizing process is used to make the models more general. Subsequently, the modal information and harmonic response of piezoelectric networks with an arbitrary number of components are obtained. Based on the dynamic characteristics of piezoelectric networks, the mechanism of vibration-suppression behavior of such systems is studied. Design guidelines of these vibration reduction systems are established via parameter studies. Eventually, the optimized parameters of each network-connection form are obtained analytically. It is shown that the symmetric piezoelectric network can suppress the response of the given frequency to zero, and also perform better than pure passive piezoelectric shunts in resonant frequency band.
Housing Stiffness Influence on Gearbox Dynamic Loading for Wind Turbine Applications
Authors: Jauregui Juan Carlos , Torres Ignacio , Garcia Ricardo , Leon Alejandro
Published: December 2013

The design of wind turbine gearboxes must consider particular conditions such as wind speed variations, load changes, and they must be as light as possible. Although there are enough field data, their life prediction lacks of good estimation. It is common to find gearboxes with bearing or gear premature failures. The housing can dissipate noise and vibrations in a positive manner; but in wind turbines it can increase the synchronization among nonlinear elements. This phenomenon adds an additional dynamic load on the gears and rolling bearings.

The work presented here is a method for estimating the influence of the housing stiffness on the dynamic synchronization of wind turbine gearbox elements. The analysis estimates a dynamic load factor that affects both gears and rolling bearings. The analysis takes into account the gearbox nonlinear elements, as well as the turbine blades excitations.
Dynamic Effects Caused by the Non-Linear Behavior of Oil-Film Journal Bearings in Rotating Machines
Authors: Vania A. , Pennacchi P. , Chatterton S.
Published: December 2013

Many common faults and malfunctions in rotating machines mainly cause synchronous vibrations (1X). Very high 1X vibration levels can occur, in case of severe faults. Large journal orbits inside oil-film journal bearings may generate non-linear effects in the oil-film forces, whose presence can be detected by means of the appearance of not negligible super-synchronous vibrations of the shafts.

In this paper, a model-based method has been used to study the effects of non-linear oil-film forces on the machine dynamic behavior that may occur during runups and rundowns.

In general, it is possible to suppose that the importance of the non-linear behavior of oil-film journal bearings, and then the level of the super-synchronous vibrations, increases with the amplitude of the 1X vibrations caused by the primary fault. However, the numerical results of this study and the experimental evidences found in the monitoring data of a real machine have shown that the super-synchronous harmonic components of the oil-film forces may excite resonances of the shaft-train causing unexpected amplifications of the super-synchronous vibrations. This may make difficult the recognition of the presence of non-linear effects in the machine dynamic behavior and the identification of the actual cause of abnormal vibrations.
Numerical Investigation of Three-Dimensional Wet Steam Flows in an Exhaust Diffuser With Non-Uniform Inlet Flows From the Turbine Stages in a Steam Turbine
Authors: Tanuma Tadashi , Sasao Yasuhiro , Yamamoto Satoru , Niizeki Yoshiki , Shibukawa Naoki , Saeki Hiroshi
Published: December 2013

The purpose of this paper is to present a numerical evaluation method for the aerodynamic design and development of high-efficiency exhaust diffusers in steam turbines, as well as to present the comparison between the numerical results and measured data in an actual real scale development steam turbine. This paper presents numerical investigation of three-dimensional wet steam flows in a down-flow-type exhaust diffuser that has non-uniform inlet flows from a typical last turbine stage. This stage has long transonic blades designed using recent aerodynamic and mechanical design technologies, including superimposed leakages and blade wakes from several upstream low pressure turbine stages. The present numerical flow analysis showed detail three-dimensional flow structures considering circumferential flow distributions caused by the down-flow exhaust hood geometry and the swirl velocity component from the last stage blades, including flow separations in the exhaust diffuser. The results were compared with experimental data measured in an actual development steam turbine. Consequently, the proposed aerodynamic evaluation method was proved to be sufficiently accurate for steam turbine exhaust diffuser aerodynamic designs.
Development and Assessment of Coatings for Future Power Generation Turbines
Authors: Alvin M. A. , Zhu D. , Klotz K. , McMordie B. , Warnes B. , Gleeson B. , Kang B. , Tannenbaum J.
Published: December 2013

The NETL-Regional University Alliance (RUA) continues to advance technology development critical to turbine manufacturer efforts for achieving DOE Fossil Energy (FE’s) Advanced Turbine Program Goals. In conjunction with NETL, Coatings for Industry (CFI), the University of Pittsburgh, NASA GRC, and Corrosion Control Inc., efforts have been focused on development of composite thermal barrier coating (TBC) architectures that consist of an extreme temperature coating, a commercially applied 7-8 YSZ TBC, a reduced cost bond coat, and a diffusion barrier coating that are applied to nickel-based superalloys or single crystal airfoil substrate materials for use at temperatures ≥1450°C (≥ 2640°F). Additionally, construction of a unique, high temperature (∼1100°C; ∼2010°F), bench-scale, micro-indentation, nondestructive (NDE) test facility at West Virginia University (WVU) was completed to experimentally address in-situ changes in TBC stiffness during extended cyclic oxidation exposure of coated single crystal coupons in air or steam-containing environments. The efforts and technical accomplishments in these areas are presented in the following sections of this paper.
Wind Resource Assessment Using a Mesoscale Model: The Effect of Horizontal Resolution
Authors: Jafari S. , Sommer T. , Chokani N. , Abhari R. S.
Published: December 2013

Prospecting for wind farm sites and pre-development studies of wind energy projects require knowledge of the wind energy resource over large areas (that is, areas of the order of 10’000 km2 and greater). One approach to detail this wind resource is the use of mesoscale numerical weather prediction models. In this paper, the mesoscale Weather Research and Forecasting (WRF) model is used to examine the effect of horizontal grid resolution on the fidelity of the predictions of the wind resource. The simulations are made for three test cases, Switzerland (land area 39’770 km2), Iowa (land area 145,743 km2) and Oregon (land area 248’647 km2), representing a range of terrain types, from complex terrain to flat terrain, over the period from 2006–2010. On the basis of comparisons to the data from meteorological masts and tall communication towers, guidelines are given for the horizontal grid required in the use of mesoscale models of large area wind resource assessment, especially over complex terrain.
Development of an Internally Cooled Centrifugal Compressor for Carbon Capture and Storage Applications
Authors: Moore J. Jeffrey , Lerche Andrew , Allison Timothy , Moreland Brian , Pacheco Jorge
Published: December 2013

In order to reduce the amount of carbon dioxide (CO2) released into the atmosphere, significant progress has been made into capturing and storing CO2 from power plants and other major producers of greenhouse gas emissions. The compression of the captured carbon dioxide stream requires significant amounts of power and can impact plant availability, and increase operational costs. Preliminary analysis has estimated that the CO2 compression process reduces plant efficiency by 8% to 12% for a typical power plant. This project supports the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL) objective of reducing energy requirements for carbon capture and storage in electrical power production. The primary objective of this study is to boost the pressure of CO2 to pipeline pressures with the minimal amount of energy required. Previous thermodynamic analysis identified optimum processes for pressure rise in both liquid and gaseous states. Isothermal compression is well known to reduce the power requirements by minimizing the temperature of the gas entering subsequent stages. Intercooling is typically accomplished using external gas coolers and integrally geared compressors. For large scale compression, use of straight through centrifugal compressors, similar to those used in oil and gas applications including LNG production, is preferred due to the robustness of the design. However, intercooling between each stage is not feasible. The current research develops an internally cooled compressor diaphragm that removes heat internal to the compressor. Results documenting the design process are presented including 3D conjugate heat transfer CFD studies. Experimental demonstration of the design is performed on a sub scale centrifugal compressor closed loop test facility for a range of suction pressures.
Influence of Wetness on Efficiency of the Full Scale Size Low Pressure Turbines
Authors: Tsukuda Tomohiko , Kawagishi Hiroyuki , Shibukawa Naoki , Hashidate Tadayuki , Goto Koichi , Tashima Tsuguhisa
Published: December 2013

Efficiencies of 60Hz full size test turbines were measured in various wet steam conditions to reveal the wetness impact on the performance. We changed the wetness and stage load conditions independently under the condition of constant steam mass flow rate in the low pressure turbine. The test results told that the stage efficiency decreases with the increasing of wetness as many studies showed, furthermore, the stage efficiency decreases more in smaller load conditions than in the design point. In addition, blade length effects were examined by comparing two types of LP turbine to be found that the longer case got more deficits at the same wetness. Some theoretical evaluations were tried and a combination of some simple loss models explained the tendencies above, qualitatively. The evaluation showed that absolute value of mechanical wet loss such as braking loss remained unchanged regardless of load conditions, so in low load condition, ratio of mechanical loss to stage load increased, resulting decrease of stage efficiency. It also showed that increasing wet loss at the longer blade was mainly because higher circumferential velocity caused larger mechanical wet loss such as braking loss.
Supercritical CO2 Cycle Development at Pratt and Whitney Rocketdyne
Authors: Johnson Gregory A. , McDowell Michael W. , O’Connor George M. , Sonwane Chandrashekhar G. , Subbaraman Ganesan
Published: December 2013

Pratt & Whitney Rocketdyne’s extensive experience in both the rocket engine and energy industries, provides an effective underpinning for work in supercritical CO2 power cycle development. Our current thrusts are supercritical CO2 power conversion for a LMR, a solar power system using molten salt energy storage, and a zero emission coal power system. Key observations from our nuclear power application work is that large, highly-effective heat exchangers will need to be developed, system architecture is driven by start-up operations, etc. along with steady-state full-power operations, and the large volumetric flow rates associated with this cycle coupled with the desire to keep pressure losses low will lead to parallel runs of large diameter pipe. Our solar power work is focused on developing a system architecture that can take advantage of the full thermal storage temperature spectrum while maintaining the high-efficiency and low-cost potential of this cycle. And in the fossil-fuel arena, the efficiency improvements derived from supercritical CO2 are particularly interesting as a way to make up the losses that are caused by CO2 sequestration.
Vibration Investigation for Low Pressure Turbine Last Stage Blade Failure in Steam Turbines of a Power Plant
Authors: Sinha Jyoti K. , Hahn W. , Elbhbah K. , Tasker G. , Ullah I.
Published: December 2013

West Burton Power Plant, UK owned by EDF energy has 4 steam turbo-generator (TG) units for power generation. These units were installed and commissioned between 1967 and 1969 and have since operated smoothly without any major problems up to 2007. In 1995 and 1996, two TG sets, namely units 2 and 3, were retrofitted with the new design LP rotors and in 2005, retrofitting of HP rotor for all four TG units was commenced. The retrofitting was done without changing the foundation, but only with the aim to enhance the power output by 20MW (10 MW through LP retrofit and 10MW through HP retrofit). Cracking of the last stage blades of LP1 and LP2 turbine, steam-end blades has been observed in TG units 2 and 3 only. Hence the in-situ vibration measurements have been carried out on TG unit 3 and compared with healthy TG unit 1 to understand the dynamics of both units. This paper presents observations made on the dynamics of TG units 1 and 3, and results from the root cause analysis which may possibly lead to the solution to the blade failure problem in TG units 2 and 3.
High Pressure CO2 Compressor Testing for Tupi 1, Tupi 2, and Tupi 3
Authors: Colby Gary M. , Griffin Timothy R. , Gupta Manoj K. , Miller Harry F. , Nove Steven E. , Sehlstedt Niklas H.
Published: December 2013

This paper describes the mechanical and aerodynamic testing of the high-pressure CO2 compressors for the Tupi I, Tupi II, and Tupi III projects. This includes the results of the API 617 mechanical test and a special magnetic bearing exciter test to demonstrate rotordynamic stability at design operating conditions, as well as the results of the ASME PTC-10 Type 2 inert gas performance test and the ASME PTC-10 Type 1 full load–full pressure test on a CO2–hydrocarbon gas mixture equivalent to the actual process gas. A brief description of the compressor design and manufacture is also presented.
Contour identification with pitch and loudness cues using cochlear implants
Authors: Luo Xin , Masterson Megan E. , Wu Ching-Chih
Published: December 2013

Different from speech, pitch and loudness cues may or may not co-vary in music. Cochlear implant (CI) users with poor pitch perception may use loudness contour cues more than normal-hearing (NH) listeners. Contour identification was tested in CI users and NH listeners; the five-note contours contained either pitch cues alone, loudness cues alone, or both. Results showed that NH listeners' contour identification was better with pitch cues than with loudness cues; CI users performed similarly with either cues. When pitch and loudness cues were co-varied, CI performance significantly improved, suggesting that CI users were able to integrate the two cues.
Interferon-γ Resets Muscle Cell Fate by Stimulating the Sequential Recruitment of JARID2 and PRC2 to Promoters to Repress Myogenesis
Authors: Londhe Priya , Davie Judith K.
Published: December 2013

Too much interferon-γ, produced in response to inflammation, represses genes needed for muscle repair.
Science Signaling
Podcast: 10 December 2013
Authors: Davie Judith K. , VanHook Annalisa M.
Published: December 2013

Although interferon-γ is required for muscle repair, too much of this inflammatory cytokine inhibits the differentiation of muscle cells.
Light Turns the Array
Authors: Hines Pamela J.
Published: December 2013

A self-organizing system makes the microtubule array in plants rearrange in order for the shoot to turn toward blue light.
Command and Control
Authors: Ash Caroline
Published: December 2013

Soluble lymphotoxin plays a paracrine role in controlling immunoglobulin A responses and regulating gut microbiota.
An “A tZ” for Shoots, Not Roots
Authors: Ferrarelli Leslie K.
Published: December 2013

A hydroxyl side chain on
trans
-zeatin (tZ) specifies its role in promoting shoot growth in plants.
Failure of Clindamycin To Eradicate Infection with Beta-Hemolytic Streptococci Inducibly Resistant to Clindamycin in an Animal Model and in Human Infections
Authors: Lewis James S. , Lepak Alex J. , Thompson George R. , Craig William A. , Andes David R. , Sabol-Dzintars Kathryn E. , Jorgensen James H.
Published: December 2013

Inducible clindamycin resistance in beta-hemolytic streptococci remains an underrecognized phenomenon of unknown clinical significance. We performed an evaluation of inducible clindamycin resistance using an animal model as well as retrospectively reviewing the charts of patients treated with clindamycin monotherapy who were infected with beta-hemolytic streptococci inducibly resistant to clindamycin. The neutropenic mouse thigh model of infection was used to evaluate the
in vivo
activity of clindamycin against beta-hemolytic streptococci, including isolates susceptible, inducibly resistant, or constitutively resistant to clindamycin. The clinical microbiology laboratory information system and pharmacy databases were cross-referenced to identify patients with infections due to inducibly clindamycin-resistant beta-hemolytic streptococci who were treated with clindamycin monotherapy. Medical records of these patients were reviewed to evaluate microbiologic and clinical outcomes. Inducible clindamycin resistance resulted in impaired killing of beta-hemolytic streptococci in the animal model. Though suppressed initially, compared to those with constitutive resistance (
P
= 0.0429), by 48 h, colony counts of inducibly clindamycin-resistant organisms were similar to those of constitutively resistant isolates (
P
= 0.1142). In addition, we identified 8 patients infected with inducibly clindamycin-resistant beta-hemolytic streptococci who experienced clinical and microbiologic failure when treated with clindamycin monotherapy. These patients either improved initially and subsequently failed or never responded to clindamycin therapy. We have demonstrated in a murine model of infection and from human cases that inducible clindamycin resistance in beta-hemolytic streptococci is clinically significant. Routine testing and reporting by clinical laboratories should be encouraged and alternative antimicrobial agents considered when these organisms are encountered in clinical care.
Susceptibility of Multiresistant Gram-Negative Bacteria to Fosfomycin and Performance of Different Susceptibility Testing Methods
Authors: Perdigão-Neto L. V. , Oliveira M. S. , Rizek C. F. , Carrilho C. M. D. M. , Costa S. F. , Levin A. S.
Published: December 2013

Fosfomycin may be a treatment option for multiresistant Gram-negative bacteria. This study compared susceptibility methods using 94 multiresistant clinical isolates. With agar dilution (AD), susceptibilities were 81%, 7%, 96%, and 100% (CLSI) and 0%, 0%, 96%, and 30% (EUCAST), respectively, for
Acinetobacter baumannii
,
Pseudomonas aeruginosa
,
Klebsiella pneumoniae
, and
Enterobacter
spp. Categorical agreement between Etest and AD for
Enterobacteriaceae
and
A. baumannii
was ≥80%. Disk diffusion was adequate only for
Enterobacter
. CLSI criteria for urine may be adequate for systemic infections.
Moxifloxacin Pharmacokinetics and Pleural Fluid Penetration in Patients with Pleural Effusion
Authors: Chatzika Kalliopi , Manika Katerina , Kontou Paschalina , Pitsiou Georgia , Papakosta Despina , Zarogoulidis Konstantinos , Kioumis Ioannis
Published: December 2013

The aim of this study was to evaluate the pharmacokinetics and penetration of moxifloxacin (MXF) in patients with various types of pleural effusion. Twelve patients with empyema/parapneumonic effusion (PPE) and 12 patients with malignant pleural effusion were enrolled in the study. A single-dose pharmacokinetic study was performed after intravenous administration of 400 mg MXF. Serial plasma (PL) and pleural fluid (PF) samples were collected during a 24-h time interval after drug administration. The MXF concentration in PL and PF was determined by high-performance liquid chromatography, and main pharmacokinetic parameters were estimated. Penetration of MXF in PF was determined by the ratio of the area under the concentration-time curve from time zero to 24 h (AUC24) in PF (AUC24PF) to the AUC24in PL. No statistically significant differences in the pharmacokinetics in PL were observed between the two groups, despite the large interindividual variability in the volume of distribution, clearance, and elimination half-life. The maximum concentration in PF (CmaxPF) in patients with empyema/PPE was 2.23 ± 1.31 mg/liter, and it was detected 7.50 ± 2.39 h after the initiation of the infusion. In patients with malignant effusion, CmaxPFwas 2.96 ± 1.45 mg/liter, but it was observed significantly earlier, at 3.58 ± 1.38 h (P< 0.001). Both groups revealed similar values of AUC24PF(31.83 ± 23.52 versus 32.81 ± 12.66 mg · h/liter). Penetration of MXF into PF was similarly good in both patient groups (1.11 ± 0.74 versus 1.17 ± 0.39). Despite similar plasma pharmacokinetics, patients with empyema/parapneumonic effusion showed a significant delay in achievement of PF maximum MXF levels compared to those with malignant effusion. However, in both groups, the degree of MXF PF penetration and the on-site drug exposure, expressed by AUC24PF, did not differ according to the type of pleural effusion.
Two-Photon Intravital Imaging of Lungs during Anthrax Infection Reveals Long-Lasting Macrophage-Dendritic Cell Contacts
Authors: Fiole Daniel , Deman Pierre , Trescos Yannick , Mayol Jean-François , Mathieu Jacques , Vial Jean-Claude , Douady Julien , Tournier Jean-Nicolas
Published: December 2013

The dynamics of the lung immune system at the microscopic level are largely unknown because of inefficient methods of restraining chest motion during image acquisition. In this study, we developed an improved intravital method for two-photon lung imaging uniquely based on
a posteriori
parenchymal tissue motion correction. We took advantage of the alveolar collagen pattern given by the second harmonic generation signal as a reference for frame registration. We describe here for the first time a detailed dynamic account of two major lung immune cell populations, alveolar macrophages and CD11b-positive dendritic cells, during homeostasis and infection by spores of
Bacillus anthracis
, the agent of anthrax. We show that after alveolar macrophages capture spores, CD11b-positive dendritic cells come in prolonged contact with infected macrophages. Dendritic cells are known to carry spores to the draining lymph nodes and elicit the immune response in pulmonary anthrax. The intimate and long-lasting contacts between these two lines of defense may therefore coordinate immune responses in the lung through an immunological synapse-like process.
Interleukin-17A Enhances Host Defense against Cryptococcal Lung Infection through Effects Mediated by Leukocyte Recruitment, Activation, and Gamma Interferon Production
Authors: Murdock Benjamin J. , Huffnagle Gary B. , Olszewski Michal A. , Osterholzer John J.
Published: December 2013

Infection of C57BL/6 mice with the moderately virulent
Cryptococcus neoformans
strain 52D models the complex adaptive immune response observed in HIV-negative patients with persistent fungal lung infections. In this model, Th1 and Th2 responses evolve over time, yet the contribution of interleukin-17A (IL-17A) to antifungal host defense is unknown. In this study, we show that fungal lung infection promoted an increase in Th17 T cells that persisted to 8 weeks postinfection. Our comparison of fungal lung infection in wild-type mice and IL-17A-deficient mice (IL-17A
−/−
mice; C57BL/6 genetic background) demonstrated that late fungal clearance was impaired in the absence of IL-17A. This finding was associated with reduced intracellular containment of the organism within lung macrophages and deficits in the accumulation of total lung leukocytes, including specific reductions in CD11c
+
CD11b
+
myeloid cells (dendritic cells and exudate macrophages), B cells, and CD8
+
T cells, and a nonsignificant trend in the reduction of lung neutrophils. Although IL-17A did not alter the total number of CD4 T cells, decreases in the total number of CD4 T cells and CD8 T cells expressing gamma interferon (IFN-γ) were observed in IL-17A
−/−
mice. Lastly, expression of major histocompatibility complex class II (MHC-II) and the costimulatory molecules CD80 and CD86 on CD11c
+
CD11b
+
myeloid cells was diminished in IL-17A
−/−
mice. Collectively, these data indicate that IL-17A enhances host defenses against a moderately virulent strain of
C. neoformans
through effects on leukocyte recruitment, IFN-γ production by CD4 and CD8 T cells, and the activation of lung myeloid cells.
Confluence: A Seminar Series as a Teaching Tool
Authors: Dewsbury Bryan M. , Reid Amy , Weeks Ophelia
Published: December 2013

In 2007 Florida International University (FIU) received NIH, NSF, and internal support to create a curriculum that was quantitative in nature, and that incorporated some of the most contemporary approaches to the classroom. The QBIC (Quantifying Biology In the Classroom; http://qbic. fiu.edu) Program is a specialized program in the Department of Biology specifically set up to implement ‘vision and change’ principles in the department’s overall approach to students. It is now an optional track within the Department of Biological Sciences. We discuss the major objectives of this series, the affect areas that it addresses, as well as how students incorporate the series’ lessons for their own professional development. It became apparent to us anecdotally that our undergraduates were making career choices without the awareness of the many other viable career options in biology. This is not an issue unique to our institution and other authors (1) have discussed steps to address career choice and exposure. At our institution, we created a number of career development initiatives, one of which was a seminar series called “Confluence: where life and science meet.” For this series we invite science professionals from around the country to give a seminar, mostly to undergraduates, not only on the technical specifics of their field, but also on their personal life story, and how that story informed their career choice. After the seminar, the speaker sits down with a QBIC faculty member for a half-hour interview where he or she is able to go into more specifics about the themes from the seminar. The interview is videotaped in front of a live student-only audience in a film studio on campus. The recording is published on the series’ website (http://qbic.fiu. edu/confluence). In this article we discuss using the series to address issues of identity, and how our video blog can be used in other classrooms to achieve similar objectives for science students nationally.
Observing Chemotaxis in
Vibrio fischeri
Using Soft Agar Assays in an Undergraduate Microbiology Laboratory
Authors: DeLoney-Marino Cindy R.
Published: December 2013

Chemotaxis, the directed movement of cells towards or away from a chemical, is both an exciting and complicated behavior observed in many bacterial species. Attempting to adequately visualize or demonstrate the chemotaxic response of bacteria in the classroom is difficult at best, with good models to illustrate the concept lacking. The BSL-1 marine bacterium
Vibrio fischeri
(a.k.a.
Aliivibrio fischeri
) is easy to culture, making it an ideal candidate for experiments in an undergraduate microbiology course. A number of chemoattractants for
V. fischeri
have been identified, including a variety of sugars, nucleosides, and amino acids (1, 2). Below presents how the soft agar-based chemotaxis assay can be implemented in the undergraduate laboratory. As bacterial cells migrate towards one or more attractants in soft agar, students can directly observe the chemotaxic behavior of
V. fischeri
without the need to learn complicated techniques or use specialized equipment. Once the bands of bacterial cells are observed, the migration can then be disrupted by the addition of excess attractant to the soft agar, thereby visualizing what happens once cells are no longer in a gradient of attractant. In addition, soft agar plates lacking attractants can be used to visualize the random movements of bacterial cells that are non-chemotaxing. These exercises can be used in the microbiology laboratory to help students understand the complex behavior of bacterial chemotaxis.
Using Scientific Abstracts to Measure Learning Outcomes in the Biological Sciences
Authors: Giorno Rebecca , Wolf William , Hindmarsh Patrick L. , Yule Jeffrey V. , Shultz Jeff
Published: December 2013

Educators must often measure the effectiveness of their instruction. We designed, developed, and preliminarily evaluated a multiple-choice assessment tool that requires students to apply what they have learned to evaluate scientific abstracts. This examination methodology offers the flexibility to both challenge students in specific subject areas and develop the critical thinking skills upper-level classes and research require. Although students do not create an end product (performance), they must demonstrate proficiency in a specific skill that scientists use on a regular basis: critically evaluating scientific literature via abstract analysis, a direct measure of scientific literacy. Scientific abstracts from peer-reviewed research articles lend themselves to in-class testing, since they are typically 250 words or less in length, and their analysis requires skills beyond rote memorization. To address the effectiveness of particular courses, in five different upper-level courses (Ecology, Genetics, Virology, Pathology, and Microbiology) we performed pre- and postcourse assessments to determine whether students were developing subject area competence and if abstract-based testing was a viable instructional strategy. Assessment should cover all levels in Bloom’s hierarchy, which can be accomplished via multiple-choice questions (2). We hypothesized that by comparing the mean scores of pre- and posttest exams designed to address specific tiers of Bloom’s taxonomy, we could evaluate the effectiveness of a course in preparing students to demonstrate subject area competence. We also sought to develop general guidelines for preparing such tests and methods to identify test- and course-specific problems.