bluuebunny/crossref_metadata_2025 huggingface dataset:
Associational refuge in practice: can existing vegetation facilitate woodland restoration?
Authors: Stutz Rebecca S. , Banks Peter B. , Dexter Nicholas , McArthur Clare
Published: November 2014

Herbivores can dramatically diminish revegetation success, but associational refuge theory predicts that neighbouring plants could hinder browsing of planted seedlings. The key to strategic restoration using associational refuge is to define which patch variables are effective against the appropriate herbivores, at multiple scales, and to understand which stages of the foraging process these variables disrupt. Our study aimed to test the capacity of existing vegetation to act as associational refuge for planted seedlings by affecting search, detection and consumption decisions, and more generally influence herbivore foraging patterns. We conducted a field trial with free‐ranging, mammalian herbivores and nursery‐raised, native tree seedlings. We quantified seedling browsing damage over time in relation to a suite of existing patch variables at two spatial scales (100 m2 and 4 m2). After two months, 78% of seedlings were browsed, suffering mean foliage loss of 90.5%. Focal seedlings were almost exclusively consumed by swamp wallabies Wallabia bicolor, an abundant generalist browser. Once a swamp wallaby investigated a seedling, the probability of consumption was high (86%). At the large scale, browsing of seedlings was delayed in patches with lower canopy cover and fewer browsed plant species. Seedlings in fern‐dominated patches escaped browsing for longer than those in grass‐dominated patches. At the small scale, browsing was delayed with higher cover of understorey vegetation. Associational refuge was provided by vegetation with characteristics, and at spatial scales, consistent with disrupted search and detection of focal seedlings by herbivores. Thus strategic placement of seedlings in existing vegetation – based on understanding which herbivore species is responsible and how it responds to vegetation – can take advantage of associational refuge during restoration. However, given rapid seedling detection by herbivores, associational refuge may be inadequate in the long‐term under high browsing pressure unless high absolute numbers of seedlings are planted among refuge.
Stressor‐induced biodiversity gradients: revisiting biodiversity–ecosystem functioning relationships
Authors: Mensens Christoph , De Laender Frederik , Janssen Colin R. , Sabbe Koen , De Troch Marleen
Published: November 2014

Biodiversity–ecosystem functioning experiments typically inspect functioning in randomly composed communities, representing broad gradients of taxonomic richness. We tested if the resulting evenness gradients and evenness–functioning relationships reflect those found in communities facing evenness loss caused by anthropogenic stressors. To this end, we exposed marine benthic diatom communities to a series of treatments with the herbicide atrazine, and analysed the relationship between the resulting gradients of evenness and ecosystem functioning (primary production, energy content and sediment stabilization). Atrazine exposure resulted in narrower evenness gradients and steeper evenness–functioning relations than produced by the design of random community assembly. The disproportionately large decrease in functioning following atrazine treatment was related to selective atrazine effects on the species that contributed most to the ecosystem functions considered. Our findings demonstrate that the sensitivity to stress and the contribution to ecosystem functioning at the species level should be both considered to understand biodiversity and ecosystem functioning under anthropogenic stress.

Synthesis

Biodiversity loss affects ecosystem functioning, yet biodiversity–ecosystem functioning relations have mainly been investigated using communities with random species loss. In nature however, species are lost according to their sensitivity to environmental stress. In the present study, biodiversity loss and biodiversity–ecosystem functioning relations in randomly composed diatom communities were compared to those induced by the pesticide atrazine. Stress exposure resulted in smaller biodiversity loss but steeper decrease in functioning than in randomly composed communities, due to selective atrazine effects on the best performing species. Therefore, species‐specific sensitivity and contribution to ecosystem functioning need to be considered to predict biodiversity and ecosystem functioning under anthropogenic stress.
Evolutionary irony: evidence that ‘defensive’ plant spines act as a proximate cue to attract a mammalian herbivore
Authors: Kohl Kevin D. , Miller Aaron W. , Dearing M. Denise
Published: November 2014

Many plants produce structural defenses to deter feeding by herbivores. However, many previous studies testing whether spines are effective at defending against mammalian herbivores have produced equivocal results. These ambiguous results are hypothesized to be due to herbivore counter‐adaptations. We investigated potential counter‐adaptations in a population of white‐throated woodrats Neotoma albigua that specialize on cactus by investigating feeding behavior and preference for cacti varying in spinescence. Neotoma albigula exhibited a unique behavior of clipping cactus spines, which renders these defenses ineffective. Strikingly, these woodrats chose to collect spiny cacti over experimentally de‐spined cacti, demonstrating that spines act as a proximal cue that attracts woodrats. This attraction is likely due to the higher protein and lower fiber content of spiny cacti compared to naturally non‐spiny cacti. Thus, the ‘defensive’ spines of cacti are ineffective against a specialist herbivore and instead serve as an indicator of nutritional quality that promotes herbivory. Our results support the ‘rule‐of‐thumb’ hypothesis of foraging, which states that herbivores forage according to obvious visual cues that are indicative of nutritional content, rather than sampling nutrient composition of plants. We propose that specialist herbivores are unique systems in which to study other counter‐adaptations to structural defenses and ‘rule‐of‐thumb’ foraging strategies.
Hypothyroidism Affects Differentially the Cell Size of Epithelial Cells Among Oviductal Regions of Rabbits
Authors: Anaya‐Hernández A , Rodríguez‐Castelán J , Nicolás L , Martínez‐Gómez M , Jiménez‐Estrada I , Castelán F , Cuevas E
Published: November 2014

Contents

Oviductal regions show particular histological characteristics and functions. Tubal pathologies and hypothyroidism are related to primary and secondary infertility. The impact of hypothyroidism on the histological characteristics of oviductal regions has been scarcely studied. Our aim was to analyse the histological characteristics of oviductal regions in control and hypothyroid rabbits. Hypothyroidism was induced by oral administration of methimazole (MMI) for 30 days. For both groups, serum concentrations of thyroid and gonadal hormones were determined. Sections of oviductal regions were stained with the Masson's trichrome technique to analyse both epithelial and smooth muscle layers. The percentage of proliferative epithelial cells (anti‐Ki67) in diverse oviductal regions was also quantified. Data were compared with Student t‐test, Mann–Whitney U‐test, or Fischer's test. In comparison with the control group, the hypothyroid group showed: (i) a low concentration of T3 and T4, but a high level of TSH; (ii) similar values of serum estradiol, progesterone and testosterone; (iii) a large size of ciliated cells in the ampulla (AMP), isthmus (IST) and utero‐tubal junction (UTJ); (iv) a large size of secretory cells in the IST region; (v) a low percentage of proliferative secretory cells in the fimbria‐infundibulum (FIM‐INF) region; and (vi) a similar thickness of the smooth muscle layer and the cross‐sectional area in the AMP and IST regions. Modifications in the size of the oviductal epithelium in hypothyroid rabbits could be related to changes in the cell metabolism that may impact on the reproductive functions achieved by oviduct.
A Comment on the Appellate Body Report in EC‐Seal Products in the Context of the Trade and Environment Debate
Authors: Marceau Gabrielle
Published: November 2014

The Appellate Body (AB) Report in EC‐Seal Products has potential ramifications for the environmental or social concerns in the World Trade Organization. It refines the jurisprudence on the balance between members' market access obligations and their right to give priority consideration to non‐trade concerns under the General Agreement on Tariffs and Trade (GATT) and the Agreement on Technical Barriers to Trade (TBT). This article outlines the main points of the AB Report, particularly related to what measures constitute technical regulations within the scope of the TBT Agreement, and the relationship between the GATT and TBT Agreement in the context of the pursuit of legitimate non‐trade concerns. It further highlights one of the issues raised in the report concerning processes and production methods (PPMs). In particular, it offers comments on what could constitute product‐related and non‐product related PPMs – a categorization that has emerged in the trade‐environment doctrine over the last 40 years and that should now be informed by the AB's interpretation of the TBT Agreement in this case.
Trade Measures to Address Environmental Concerns in Faraway Places: Jurisdictional Issues
Authors: Young Margaret A.
Published: November 2014

States sometimes restrict imports to address environmental concerns that arise from conduct outside of their territory: common examples include deforestation in foreign places or illegal fishing in the high seas. Apart from the need to comply with the agreements of the World Trade Organization (WTO), the adoption of such trade measures gives rise to two jurisdictional issues: first, the importing State might be alleged to be engaging in extraterritorial jurisdiction; and second, the importing State may affect the economic interests of indigenous communities. This article analyzes WTO jurisprudence and other international instruments. It shows that jurisdictional issues are underpinned by sovereignty – of the importing State, the exporting State and even other groups. If there is a need for a nexus between the importing State and the relevant product or measure in order to fall within any jurisdictional limitations of the WTO agreements (which remains uncertain), it will be more easily satisfied if environmental problems impact upon the ‘public morals’ of citizens or consumers, as was found in the recent challenge to the European Union's ban on seal products. However, the complex needs and interests of other States must also be considered, especially if the trade measures impact on the interests of indigenous peoples, and on the established or emerging legal arrangements between indigenous peoples and domestic governments. The design and application of trade measures to address environmental concerns requires flexibility and a commitment to seeking international consensus as well as an openness to rights and norms from outside the trade regime.
Focused and Model Average Estimation for Regression Analysis of Panel Count Data
Authors: Wang Haiying , Li Yang , Sun Jianguo
Published: November 2014

Panel count data arise in many fields and a number of estimation procedures have been developed along with two procedures for variable selection. In this paper, we discuss model selection and parameter estimation together. For the former, a focused information criterion (FIC) is presented and for the latter, a frequentist model average (FMA) estimation procedure is developed. A main advantage, also the difference from the existing model selection methods, of the FIC is that it emphasizes the accuracy of the estimation of the parameters of interest, rather than all parameters. Further efficiency gain can be achieved by the FMA estimation procedure as unlike existing methods, it takes into account the variability in the stage of model selection. Asymptotic properties of the proposed estimators are established, and a simulation study conducted suggests that the proposed methods work well for practical situations. An illustrative example is also provided. © 2014 Board of the Foundation of the Scandinavian Journal of Statistics
Serological diagnosis of canine visceral leishmaniasis in Brazil: systematic review and meta‐analysis
Authors: Peixoto Henry Maia , de Oliveira Maria Regina Fernandes , Romero Gustavo Adolfo Sierra
Published: November 2014

Objective

To evaluate the quality and accuracy of serological diagnosis of canine visceral leishmaniasis in the Americas.

Methods

A systematic review found original studies in the databases MEDLINE, EMBASE and LILACS up to November 2012 and in complementary sources up to February 2013. Studies were evaluated in accordance with QUADAS 2 and STARD parameters and recommended in accordance with GRADE parameters. Meta‐analysis was carried out with Meta‐DiSc software, using the random‐effect model.

Results

Two hundred and eighty‐four studies were identified, of which 25 met the inclusion criteria, comprising the final synthesis. All but one was conducted in Brazil, and only two were judged to be of good quality. 15 studies involving immuno‐enzymatic tests with crude antigens (cELISA), 11 studies on indirect immunofluorescence tests (IFAT) and three on the immunochromatographic dual‐path platform (DPP) test were meta‐analysed. The combined results for sensitivity and specificity were cELISA: 0.89 (CI 95% 0.87–0.91) and 0.87 (CI 95% 0.86–0.88); IFAT: 0.88 (CI 95% 0.85–0.91) and 0.63 (CI 95% 0.61–0.65); and DPP: 0.83 (CI 95% 0.78–0.88) and 0.73 (CI 95% 0.70–0.75).

Conclusion

Enzyme‐linked immunosorbent assay with crude antigens and DPP tests have moderate accuracy for the diagnosis of canine visceral leishmaniasis, and the quality of the design, implementation and analysis of validation studies on diagnostic tests for this disease urgently require improvement. The recommendation for use of the evaluated tests is based on evidence that is scarce and restricted to Brazil.
ERNEST BECKER'S PSYCHOLOGY OF RELIGION FORTY YEARS ON: A VIEW FROM SOCIAL COGNITIVE PSYCHOLOGY
Authors: Jong Jonathan
Published: November 2014

This article distinguishes between three projects in Ernest Becker's (1924–1974) later work: his psychology of “religion,” his psychology of religion, and his psychology of Religion (with a capital R). The first is an analysis of culture and civilization as immortality projects, means by which to deny death. The second, which overlaps with the first, is a characterization of religion‐as‐practiced (e.g., by adherents of the world religions) as a particularly effective immortality project vis‐à‐vis death anxiety. The third is less social scientific and more theological; Becker argues for a view of God that is in the tradition of Søren Kierkegaard and Paul Tillich (and, arguably, Pseudo‐Dionysius, Augustine, and Thomas Aquinas). Focusing on the second of these projects—as much has already been written on the first, and little can be said about the third—this article evaluates Becker's claims about religion‐as‐practiced in light of recent developments in social cognitive psychology.
What is Heat?
Authors: Beretta Gian Paolo , Gyftopoulos Elias P.
Published: November 2014

We define heat as a particular kind of nonwork interaction that involves only energy and entropy transfers, and that is entirely distinguishable from work. The existence of heat interactions is a consequence of the first and second laws of thermodynamics. The requirement that heat be entirely distinguishable from work implies strict conditions on the end states of the interacting systems, and guarantees a definite relation between such states and the energy and entropy transfers. We illustrate these conditions by using energy versus entropy graphs. Many experiences can be represented as heat interactions, including the exchanges between two black bodies at temperatures that differ infinitesimally. We discuss the latter point in a companion paper at this conference.
Biophysical Analysis of Dystrophic and Osteogenic Models of Valvular Calcification
Authors: Chen Joseph , Peacock Jon R. , Branch Janelle , David Merryman W.
Published: November 2014

Calcific aortic valve disease (CAVD) is a significant cardiovascular disorder characterized by the formation of calcific nodules (CN) on the valve. In vitro assays studying the formation of these nodules were developed and have led to many significant mechanistic findings; however, the biophysical properties of CNs have not been clearly defined. A thorough analysis of dystrophic and osteogenic nodules utilizing scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and atomic force microscopy (AFM) was conducted to describe calcific nodule properties and provide a link between calcific nodule morphogenesis in vitro and in vivo. Unique nodule properties were observed for dystrophic and osteogenic nodules, highlighting the distinct mechanisms occurring in valvular calcification.
A Rolling 8-Bar Linkage Mechanism
Authors: Tian Yaobin , Yao Yan-An , Wang Jieyu
Published: November 2014

In this paper, a rolling mechanism constructed by a spatial 8-bar linkage is proposed. The eight links are connected with eight revolute joints, forming a single closed-loop with two degrees of freedom (DOF). By kinematic analysis, the mechanism can be deformed into planar parallelogram or spherical 4-bar mechanism (SFM) configuration. Furthermore, this mechanism can be folded onto a plane at its singularity positions. The rolling capability is analyzed based on the zero-moment-point (ZMP) theory. In the first configuration, the mechanism can roll along a straight line. In the second configuration, it can roll along a polygonal region and change its rolling direction. By alternatively choosing one of the two configurations, the mechanism has the capability to roll along any direction on the ground. Finally, a prototype was manufactured and some experiments were carried out to verify the functions of the mechanism.
Integrated Design and Multi-objective Optimization of a Single Stage Heat-Pump Turbocompressor
Authors: Schiffmann J.
Published: November 2014

Small-scale turbomachines in domestic heat pumps reach high efficiency and provide oil-free solutions, which improve heat-exchanger performance and offer major advantages in the design of advanced thermodynamic cycles. An appropriate turbocompressor for domestic air based heat pumps requires the ability to operate on a wide range of inlet pressure, pressure ratios, and mass flows, confronting the designer with the necessity to compromise between range and efficiency. Further, the design of small-scale direct driven turbomachines is a complex and interdisciplinary task. Textbook design procedures propose to split such systems into subcomponents and to design and optimize each element individually. This common procedure, however, tends to neglect the interactions between the different components leading to suboptimal solutions. The author proposes an approach based on the integrated philosophy for designing and optimizing gas bearing supported, direct driven turbocompressors for applications with challenging requirements with regards to operation range and efficiency. Using experimentally validated reduced order models for the different components an integrated model of the compressor is implemented and the optimum system found via multi-objective optimization. It is shown that compared to standard design procedures, the integrated approach yields an increase of the seasonal compressor efficiency of more than 12 points. Further, a design optimization based sensitivity analysis allows to investigate the influence of design constraints determined prior to optimization such as impeller surface roughness, rotor material, and impeller force. A relaxation of these constrains yields additional room for improvement. Reduced impeller force improves efficiency due to a smaller thrust bearing mainly, whereas a lighter rotor material improves rotordynamic performance. A hydraulically smoother impeller surface improves the overall efficiency considerably by reducing aerodynamic losses. A combination of the relaxation of the three design constraints yields an additional improvement of six points compared to the original optimization process. The integrated design and optimization procedure implemented in the case of a complex design problem thus clearly shows its advantages compared to traditional design methods by allowing a truly exhaustive search for optimum solutions throughout the complete design space. It can be used for both design optimization and for design analysis.
The Effect of Internal Crossflow on the Adiabatic Effectiveness of Compound Angle Film Cooling Holes
Authors: McClintic John W. , Klavetter Sean R. , Winka James R. , Anderson Joshua B. , Bogard David G. , Dees Jason E. , Laskowski Gregory M. , Briggs Robert
Published: November 2014

In gas turbine engines, film cooling holes are often fed by an internal crossflow, with flow normal to the direction of the external flow around the airfoil. Many experimental studies have used a quiescent plenum to feed model film cooling holes and thus do not account for the effects of internal crossflow. In this study, an experimental flat plate facility was constructed to study the effects of internal crossflow on a row of cylindrical compound angle film cooling holes. There are relatively few studies available in literature that focus on the effects of crossflow on film cooling performance, with no studies examining the effects of internal crossflow on film cooling with round, compound angled holes. A crossflow channel allowed for coolant to flow alternately in either direction perpendicular to the mainstream flow. Experimental conditions were scaled to match realistic turbine engine conditions at low speeds. Cylindrical compound angle film cooling holes were operated at blowing ratios ranging from 0.5 to 2.0 and at a density ratio (DR) of 1.5. The results from the crossflow experiments were compared to a baseline plenum-fed configuration. This study showed that significantly greater adiabatic effectiveness was achieved for crossflow counter to the direction of coolant injection.
Performance/Condition Monitoring and Optimization for Fossil Power Plants
Authors: Sunder Raj Komandur
Published: November 2014

Increased competition and consolidation of plant ownership have created a need for power companies to leverage technological advances and tools as they attempt to maximize generating asset value by doing more efficiently with less. Legacy-based, labor-intensive systems are being supplanted with automated, standardized systems for fleet-wide data collection, analysis, diagnostics and reporting.

Focus is also shifting from monitoring the performance/condition of individual plants and components to entire fleets for maximum economic benefit. Today’s virtual environment allows an enterprise to monitor in real time the performance and health of individual plants as well as an entire fleet for continuous learning and to sustain optimum performance.

This paper provides an overview of performance/condition monitoring and optimization for fossil power plants. It examines performance and condition monitoring models, their capabilities and benefits in analyzing plant issues and, some of the results that might be achieved. It discusses the key features and benefits of on-line monitoring systems and provides examples of key performance/condition data, parameters and indicators to monitor and diagnose operation, performance, health, economics, integrity, reliability and environmental issues. The paper also examines current performance/condition monitoring initiatives in the power industry.
The Thermal and Mechanical Considerations for the Replacement of Existing Condenser Tubes (Either by Retubing or Modular Replacement), Tubesheets and Waterboxes to Ensure Plant Optimization
Authors: Nightingale Darren M. , Proud Earl
Published: November 2014

Degraded performance of a steam surface condenser will directly affect the availability and operational efficiency of any power plant, and this in turn will always impact plant optimization. Results of eddy current testing, loss of surface area through excessive numbers of plugged tubes or turbine blade failure, life extension studies, extended power uprates, the general effects of erosion and corrosion, etc. — these are all examples of issues that may lead to the replacement of tubes, tubesheets and/or waterboxes at some point during the operational life of a power plant steam surface condenser.

Retubing, and the modular replacement of existing condenser tube bundles, are two options available to power plant owners & operators that can help to regain lost performance, and even in some cases improve on the original unit design. However, the use of different tube materials and wall thickness for retubing, as well as different tube diameters and quantities for modular replacements; means that these changes must be accompanied by the necessary detailed evaluation of the impact to the original design.

In addition to Tubes, it may also be necessary to replace existing Tubesheets and/or even Waterboxes. This work scope should always include a detailed review of the possible impacts of any changes due to these replacements. Failure to perform the necessary thermal and mechanical evaluations can lead to additional operational issues that may also impact unit performance & longevity.
Case Studies: Nueces Bay, Unit #7 and Barney M. Davis, Unit #2 for Topaz Power: The Successful Turnkey Repowering of Existing Steam Surface Condensers From Traditional Rankine to a 2x1 Combined Cycle Configuration
Authors: Nightingale Darren M. , Powers Vincent , Proud Earl , Johnson Barry
Published: November 2014

The turnkey repowering conversion of any existing steam surface condenser, from operation within a traditional steam plant Rankine cycle to that of Combined Cycle configuration, includes a great number of detailed and complex thermal & mechanical design, modification, installation and operational challenges to be considered and overcome. Indeed, it may not always be possible to even consider the reuse and conversion of an existing steam surface condenser from a traditional Rankine cycle to Combined Cycle operation due to one, or more, existing limitations. The purpose of this paper, through case studies, is to showcase the entire process of the determination and subsequent implementation of the minimum requirements for the modification and refurbishment of two steam surface condensers at existing power plant facilities.
Development of a Full-Scale-Lab-Validated Dynamic Simulink© Model for a Stand-Alone Wind-Powered Microgrid
Authors: Janssen Nicholas T. , Peterson Rorik A. , Wies Richard W.
Published: November 2014

Isolated hybrid wind microgrids operate within three distinct modes, depending on the wind resources and the consumer grid demand: diesel-only (DO), wind-diesel (WD) and wind-only (WO). Few successful systems have been shown to consistently and smoothly transition between wind-diesel and wind-only modes. The University of Alaska – Fairbanks Alaska Center for Energy and Power (ACEP) has constructed a full scale test bed of such a system in order to evaluate technologies that facilitate this transition. The test bed is similar in design to the NREL Power Systems Integration Laboratory (PSIL) and sized to represent a typical off-grid community. The objective of the present work is to model the ACEP test bed in DO and WD modes using MATLAB™ SIMULINK© and then validate the model with actual full-scale laboratory measurements. As will be shown, the frequency responses are grouped into three classifications based on their behavior. The model is shown to be successful in describing the frequency response of relatively small (0.15 per unit) steps in load. Modifications to the excitation system model are discussed which could improve the accuracy for larger steps in load. The ACEP test bed and associated SIMULINK© model are to be used in future work to support investigating WO operation.
Numerical Investigation of Rotating Stall Characteristics and Active Stall Control in Centrifugal Compressors
Authors: Halawa Taher , Alqaradawi Mohamed , Badr Osama , Gadala Mohamed S.
Published: November 2014

This paper focuses on providing better view for the understanding of rotating stall phenomenon in centrifugal compressors by using numerical simulations and presents a study of the role of air injection method in delaying stall inception by using different injection parameters aiming at increasing the efficiency of this method. Results showed that the formation of stall begins at the impeller inlet due to early flow separation at low mass flow rates and due to the increase of the turbulence level and the absence of fluid orientation guidance at the vaneless region. The flow weakness causes back flow that results in the formation of the tip leakage flow which causes stall development with time. Results also showed that using air injection at specified locations at the vaneless shroud surface at injection angle of 20° and with injection mass flow rate of 1.5% of the inlet design mass flow rate, can delay the stall onset to happen at lower mass flow rate about 3.8 kg/s comparing with using injection with angle of 10° with different injection mass flow rates and also comparing with the case of no injection.
Numerical Simulation of Stall Development Into Surge and Stall Control Using Air Injection in Centrifugal Compressors
Authors: Halawa Taher , Alqaradawi Mohamed , Badr Osama , Gadala Mohamed S.
Published: November 2014

This study presents a numerical simulation of the formation of rotating stall and the initiation of surge in order to study the connection between stall and surge in centrifugal compressors. Also, the current paper introduces an optimization of the air injection method as a way to increase the surge margin. Results showed that during stall, the compressor is exposed to velocity and pressure fluctuations varying with time, and these fluctuations are increased suddenly and causing surge initiation. The major part which is responsible for the sudden increase in fluctuations is the vaneless region because it was found that the problem starts at the impeller exit near the shroud surface and then transfers to the impeller inlet. Results also showed that during surge, forces on the impeller blades increase to nearly double of its initial value and then decrease again. By using air injection at the vaneless region with different injection angles, it was found that injection with angle of 30° has a good effect on preventing surge and minimizing the pressure fluctuations comparing to other injection angles results. Results showed finally that the surge margin can be increased by using the injection with angle of 30° and with injection mass flow rate of 1% of the design inlet mass flow rate and this causes the surge limit to shift from 4 kg/s to 3.9 kg/s.
Earthquake Experience Data Point to Benefit of Diverse Backup Power
Authors: Calhoun David J. , Gake Mark A.
Published: November 2014

Operating nuclear power plants typically have backup electrical power supplied by diesel generators. Although backup power systems are designed with redundant trains, each capable of supplying the power requirements for safe shutdown equipment, there is a common-mode seismic failure risk inherent in these customary backup power arrangements. In an earthquake, multiple equipment trains with similar, if not identical, components located side-by-side are exposed to inertial forces that are essentially identical. In addition, because of their similar subcomponent configurations, seismic fragilities are approximately equal. In that case, the probability of multiple backup power system failures during an earthquake is likely to be dependent on, and nearly the same as, the individual seismic failure probability of each equipment train.

Post-earthquake inspections at conventional multiple unit power stations over the last 40 years identified this common-mode seismic failure risk long before the tsunami-related common-mode failures of diesel generators at Fukushima Daiichi in March 2011. Experience data from post-earthquake inspections also indicate that failure probabilities of diverse sets of power generation equipment are independent and inherently less susceptible to common-mode failures.

This paper demonstrates that employing diverse backup power designs will deliver quantifiable improvements in electrical system availability following an earthquake. These improvements are illustrated from available literature of post-earthquake inspection reports, along with other firsthand observations. A case study of the seismic performance of similarly configured electrical power generation systems is compared to the performance of diverse sets of electrical power systems. Seismic probabilistic risk analyses for several system configurations are presented to show the benefit of improved post-earthquake availability that results from designing new backup power systems with greater diversity.
Experimental Investigation of Film Cooling Performance for a New Shaped Hole at the Leading Edge
Authors: Elnady Tarek , Hassan Ibrahim
Published: November 2014

An experimental investigation has been performed to study the film cooling performance of a smooth expansion exit at the leading edge of a gas turbine vane. A two-dimensional cascade has been employed to measure the cooling performance of the proposed expansion using the transient Thermochromatic Liquid Crystal technique. One row of cylindrical holes, located on the stagnation line, is investigated with two expansion levels, 2d and 4d, in addition to the standard hole. The air is injected at 90° and 60° inclination angle relative to the vane surface at four blowing ratios ranging from 1 to 2 at a 0.9 density ratio. The Mach number and the Reynolds number based on the cascade exit velocity and the axial chord are 0.23 and 1.4E5, respectively. The detailed local heat transfer coefficient over both the pressure side and the suction side are presented in addition to the lateral-averaged normalized heat transfer coefficient. The proposed expansion provides a lower heat transfer coefficient compared with the standard cylindrical hole over the investigated blowing ratios. Combining the heat transfer coefficient with the corresponding cooling effectiveness, previously presented, the smooth expansion shows a significant reduction in the heat load with more uniform distribution of the coolant over the leading edge region. The strong confrontation between the coolant jet and the mainstream, in case of 90° injection, yields a strong dispersion of the coolant with higher heat transfer coefficient and high thermal load over the vane surface.
Investigation on Solar-Powered Turbines Using Refrigerant R-134A
Authors: Rishmany Jihad , Daaboul Michel , Tawk Issam , Saba Nicolas
Published: November 2014

Renewable energy has become a promising solution to substitute fossil fuels in power generation. In particular, the use of solar energy is stretched to a wide range of applications, e.g. photovoltaic cells, solar water heaters, solar space heating, solar thermal plants. However, the combination of solar energy with the Rankine cycle is limited to few applications only. In this context, this study aims in investigating the practicality of employing solar heaters to operate a Rankine cycle for small scale power generation. The working fluid in this study is refrigerant R-134a. Sizing and calculations of the various components of the system are carried out based on a net output power of 1 kW. In comparison with available electricity sources in Lebanon, it was found that the proposed system is currently more expensive than public electricity. However, it can compete with private generators that currently fill the gap in electricity shortage. The main advantage herein lies in the friendly environmental load due to the absence of combustion gases.
Syngas Combustion Analysis Using an Experimental and Numerical Approach
Authors: Teixeira André F. L. , Couto Nuno T. D. , Teixeira Sandra C. F.
Published: November 2014

The present study addresses SYNGAS combustion in static chamber, using both experimental and numerical approaches, in order to derive the quenching distance and heat flux in laminar syngas–air flames. Three typical mixtures of H2, CO, CH4, CO2 and N2 are considered as representative of the syngas coming from wood gasification, and its laminar combustion will be performed in a static spherical vessel. A two dimensional CFD model is used and validated under experimental runs. The classical Woschni model based on the hypotheses of forced convection and the Rivère model based on kinetic theory of gases are included in the CFD approach. The paper considers two different approaches for chemical reactions: the use of eight reactions and the multizone model. Temperature and pressure analysis is also being carried out. The numerical results are in good agreement with experimental ones. This study could be very useful in predicting the physical conditions of the quenching distance where the measurement is not possible such as in engines and the possibility of using this model in internal combustion engines.
Effect of Vertical Mini-Fins on External Condensation Heat Transfer
Authors: Martínez Andrés , Chiroy Caleb
Published: November 2014

The purpose of this research is to experimentally study how vertical mini-fins affect the overall heat transfer on a solid surface under external condensation conditions. Filmwise condensation is a major factor when designing steam condensers for thermoelectric power plants. These plants currently account for 40% of freshwater withdrawal and 3% of freshwater usage in the United States. Filmwise condensation averages five times lower heat transfer coefficients than those present in dropwise condensation. Due to the elevated nucleation rates in thermoelectric power plant condensers, filmwise condensation is the dominant condensation regime. The film thickness is directly proportional to the condenser’s overall thermal resistance on a surface under filmwise condensation. This research investigates the potential of mini-fins to mitigate the onset and effect of filmwise condensation, thus reducing thermal resistance and maximizing heat transfer. The overall heat transfer is determined by measuring the temperature gradient across aluminum test sections. The experimental setup was designed to control the cooling load, pressure, and steam quality in order to measure the temperature gradient under steady state conditions. By comparing the overall heat transfer of surfaces with different mini-fins, the optimal surface geometries can be found. Preliminary results show that mini-fins can improve the overall heat transfer ratios. Future work will introduce other mini-fin shapes, as well as focus on investigating the most efficient heat fluxes for each mini-fin.
Oxy-Fuel Turbine Through-Flow Design
Authors: Sammak Majed , Deshpande Srikanth , Genrup Magnus
Published: November 2014

The objective of the paper is to present the through-flow design of a twin-shaft oxy-fuel turbine. The through-flow design is the subsequent step after the turbine mean-line design. The through-flow phase analyses the flow in both axial and radial directions, where the flow is computed from hub to tip and along streamlines. The parameterization of the through-flow is based on the mean-line results, so principal features such as blade angles at the mean-line into the through-flow phase should be retained. Parameters such as total inlet pressure and temperature, mass flow, rotation speed and turbine geometries are required for the through-flow modelling.

The through-flow study was performed using commercial software — AxCent(™) from Concepts NREC. The rotation speed of the twin-shaft power turbine was set to 7200 rpm, while the power turbine was set to 4800 rpm. The mean-line design determined that the twin-shaft turbine should be designed with two compressor turbine stages and three power turbine stages.

The through-flow objective was to study the variations in the thermodynamic parameters along the blade. The power turbine last-stage design was studied because of the importance of determining exit Mach number distribution of the rotor tip. The last stage was designed with damped forced condition. The term ‘damped’ is used because the opening from the tip to the hub is limited to a certain value rather than maintaining the full concept of forced vortex.

The study showed the parameter distribution of relative Mach number, total pressure and temperature, relative flow angle and tangential velocity. Through-flow results at 50% span and mean-line results showed reasonable agreement between static pressure, total pressure, reaction degree and total efficiency. Other parameters such as total temperature and relative Mach number showed some difference which can be attributed to working fluid in AxCent being pure CO2. The relative tip Mach number at rotor exit was 1.03, which is lower than the maximum typically allowed value of 1.2. The total pressure distribution was smooth from hub to tip which minimizes the spanwise gradient of total pressure and thus reduces the strength of secondary vortices. The reaction degree distribution was presented in the paper and no problems were revealed in the reaction degree at the hub. Rotor blades were designed to produce a smooth exit relative flow angle distribution. The relative flow angle varied by approximately 5° from hub to tip. The tangential velocity distribution was proportional to blade radius, which coincided with forced vortex design. Through-flow design showed that the mean-line design of a twin-shaft oxy-fuel turbine was suitable.
The Effect of Different Designs on Performance of a Fluid Power Control System
Authors: Sadak Tahany W. , Fouly Ahmed
Published: November 2014

Hydraulic systems are characterized by their ability to import large forces at high speeds and are used in many industrial motion systems, also, in applications where good dynamic performance is important. This research concentrates on static and dynamic performance of a linear hydraulic system under different operating conditions in case of connecting an Electro Hydraulic Servo Valve (EHSV) and a Proportional Directional Flow Control Valve (PDFCV). High technology is used for measuring and recording the experimental results which achieves accurate evaluations. Experiments have been conducted in case of no-load and under load 5560 N. Supply pressure has been changed from 10 up to 50 bar. Effect of pressure and load variation on hydraulic system performance has been studied. It is concluded that increasing the load decreases the bandwidth frequency, but increasing the supply pressure increases the bandwidth frequency. Comparing the time lag of the system considering connecting the (EHSV) with that in case of connecting (PDFCV), it’s observed that in the present investigation the time lag improves by about 86.4% in case of free-load and by about 95.3% in case of system loaded.
Investigation of Particle Size on Gasification Process for Solid Waste Treatment
Authors: Ho T. C. , Fu S. C. , Chao Christopher Y. H.
Published: November 2014

Gasification is a technologically advanced and environmentally friendly process for solid waste treatment. The chemical reactions in the gasification process highly depend on the agents’ flow rates which, due to fluid dynamics and thermodynamics, are in fact functions of particle size and structure. Therefore, in order to obtain a better prediction model, it is important to determine the effect of particle size on the operation of a gasification system. The purpose of this research is to investigate the effect of particle size of some common solid waste on the gasification process. Specimens including starch and polyethylene of different sizes are investigated experimentally. To achieve the aim, the gasification processes are monitored by a thermal gravimetric analysis system. The mass change and the heat flow are measured in real time during the reaction. Comparison between the experimental results and different gasification models are made. Based on the experimental results, the effect of particle size was studied and the importance of the porous structure was revealed. The relationship between particle size and porous structure during gasification was developed.
Quantifying Correction Curve Uncertainty Through Empirical Methods
Authors: Bañares Christopher R. , Schmitt Thomas P. , Daigle Evan E. , Winterberger Thomas P.
Published: November 2014

The accuracy of a thermal performance test is typically estimated by performing an uncertainty analysis calculation in accordance with ASME PTC 19.1 or equivalent. The resultant test uncertainty estimate is often used as a key factor in the commercial contract, in that many contracts allow a test tolerance and define the test tolerance to be equal to the test uncertainty. As such, the calculated test uncertainty needs to accurately reflect all of the technical factors that contribute to the uncertainty. The test uncertainty is a measure of the test quality, and, in many circumstances, the test setup must be designed such that the uncertainty remains lower than test code limits and/or commercial tolerances.

Traditional uncertainty calculations have included an estimate of the measurement uncertainties and the propagation of those uncertainties to the test result. In addition to addressing measurement uncertainties, ASME PTC 19.1 makes reference to other potential errors of method, such as “the assumptions or constants contained in the calculation routines” and “using an empirically derived correlation”. Experience suggests that these errors of method can in some circumstances dominate the overall test uncertainty. Previous studies (POWER2011-55123 and POWER2012-54609) introduced and quantified a number of operational factors and correction curve factors of this type.

To facilitate testing over a range of boundary conditions, the industry norm is for the equipment supplier to provide correction curves, typically created using thermodynamic models of the power plant to predict the response of the system to changes in boundary conditions. As noted in various PTC codes (PTC-22, PTC-46, and PTC-6) it is advisable to run the test at conditions as close to the rated conditions as possible to minimize the influence of the correction curves. Experience suggests that large deviations from rated conditions, and the associated influence of the correction curves, can result in decreased accuracy in the final corrected result. A discussion of these types of situations via case studies is discussed, as well as a means by which to reduce the uncertainty contributions from correction curves considerably.
Modeling Climate-Water Impacts on Electricity Sector Capacity Expansion
Authors: Cohen Stuart M. , Averyt Kristen , Macknick Jordan , Meldrum James
Published: November 2014

Climate change has the potential to exacerbate water availability concerns for thermal power plant cooling, which is responsible for 41% of U.S. water withdrawals. This analysis describes an initial link between climate, water, and electricity systems using the National Renewable Energy Laboratory (NREL) Regional Energy Deployment System (ReEDS) electricity system capacity expansion model. Average surface water projections from Coupled Model Intercomparison Project 3 (CMIP3) data are applied to surface water rights available to new generating capacity in ReEDS, and electric sector growth is compared with and without climate-influenced water rights. The mean climate projection has only a small impact on national or regional capacity growth and water use because most regions have sufficient unappropriated or previously retired water rights to offset climate impacts. Climate impacts are notable in southwestern states, which experience reduced water rights purchases and a greater share of rights acquired from wastewater and other higher-cost water resources. The electric sector climate impacts demonstrated herein establish a methodology to be later exercised with more extreme climate scenarios and a more rigorous representation of legal and physical water availability.