bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutrient pathways regulating the nuclear maturation of mammalian oocytes
Authors: Downs Stephen M.
Published: March 2015

Oocyte maturation is defined as that phase of development whereby a fully grown oocyte reinitiates meiotic maturation, completes one meiotic division with extrusion of a polar body, then arrests at MII until fertilisation. Completion of maturation depends on many different factors, not the least of which is the proper provision of energy substrates to fuel the process. Interaction of the oocyte and somatic compartment of the follicle is critical and involves numerous signals exchanged between the two cell types in both directions. One of the prominent functions of the cumulus cells is the channelling of metabolites and nutrients to the oocyte to help stimulate germinal vesicle breakdown and direct development to MII. This entails the careful integration and coordination of numerous metabolic pathways, as well as oocyte paracrine signals that direct certain aspects of cumulus cell metabolism. These forces collaborate to produce a mature oocyte that, along with accompanying physiological changes called cytoplasmic maturation, which impart subsequent developmental competence to the oocyte, can be fertilised and develop to term. This review focuses on nuclear maturation and the metabolic interplay that regulates it, with special emphasis on data generated in the mouse.
Cytoskeletal alterations associated with donor age and culture interval for equine oocytes and potential zygotes that failed to cleave after intracytoplasmic sperm injection
Authors: Ruggeri Elena , DeLuca Keith F. , Galli Cesare , Lazzari Giovanna , DeLuca Jennifer G. , Carnevale Elaine M.
Published: March 2015

Intracytoplasmic sperm injection (ICSI) is an established method to fertilise equine oocytes, but not all oocytes cleave after ICSI. The aims of the present study were to examine cytoskeleton patterns in oocytes after aging in vitro for 0, 24 or 48 h (Experiment 1) and in potential zygotes that failed to cleave after ICSI of oocytes from donors of different ages (Experiment 2). Cytoplasmic multiasters were observed after oocyte aging for 48 h (P < 0.01). A similar increase in multiasters was observed with an increased interval after ICSI for young mares (9–13 years) but not old (20–25 years) mares. Actin vesicles were observed more frequently in sperm-injected oocytes from old than young mares. In the present study, multiasters appeared to be associated with cell aging, whereas actin vesicles were associated with aging of the oocyte donor.
Exploring big educational learner corpora for SLA research
Authors: Alexopoulou Theodora , Geertzen Jeroen , Korhonen Anna , Meurers Detmar
Published: March 2015

We consider the opportunities presented by big educational learner corpora for Second Language Acquisition (SLA). In particular, we focus on the EF Cambridge Open Language Database (EFCAMDAT), an open access database of student writings submitted to Englishtown, the online school of EF Education First. EFCAMDAT stands out for its size (33 million words, 85 thousand learners) and a range of 128 writing tasks covering all CEFR levels with data from learners from varying nationalities. We discuss methodological issues arising from analyzing big data resources generated in educational contexts and argue that Natural Language Processing (NLP) is essential for the automated processing of such datasets. As a study case, we follow the developmental trajectory of relative clauses, a construction that necessitates deeper syntactic analysis. We consider specific issues that can affect the developmental trajectory, including task effects, formulaic language and national language effects.
Caddoan Languages
Authors: Grant Anthony
Published: March 2015

The Caddoan languages were traditionally spoken in various locations in the Great Plains. In his article on Caddoan, which appears in The Languages of Native America: Historical and Comparative Assessment (1979), edited by Lyle Campell and Marianne Mithun, Wallace L. Chafe suggests that they were originally spoken in the area where Texas, Arkansas, and Louisiana now converge, and this remained the area where Caddo was spoken until well into the nineteenth century. When first contacted, speakers of Wichita and Kitsai were living in central Oklahoma, Pawnees in Kansas and Nebraska, and Arikaras were semi-sedentary and living in the Dakotas. The Caddos, Wichitas, and Pawnees were each actually groups of smaller bands or tribes who shared a common language. The late nineteenth century was the period of Indian Removal, when thousands of Native Americans living in the Plains saw their lands expropriated to be made available for homesteaders, and many were moved into Oklahoma, which constituted “Indian Territory.” As a result, speakers of all these languages, apart from Arikara, ended up in rural parts of northern or central Oklahoma. Arikaras found themselves at the Fort Berthold Reservation, North Dakota, where, with the Siouan-speaking Mandans and Hidatsas, they constituted the Three Affiliated Tribes. The Caddoan languages have relatively simple phonological systems of three to five oral vowels that developed from /i a u/, which distinguish short from long forms, and (apart from Caddo) fewer than a dozen consonants, including usually only one nasal, /n/. Wichita and Caddo also have a distinctive pitch accent, and Wichita and Pawnee, at least, have some three or four-element consonantal clusters (these are simplified in Arikara). Nouns are lightly inflected though they exhibit an absolutive suffix, the form of which varies from one language to another. Verbs are heavily inflected, marking aspect, plurality of arguments, direction of action (instead of using adpositions), and many other features, and verb roots are often discontinuous with each part consisting of just a few segments (or even only one). The Caddoan languages are polysynthetic in structure, incorporating noun elements within their complex verbs. Word-coinage is favored over borrowing for expressing new items of acculturation. Caddoan languages are highly endangered and it is likely that no one uses them today as their means of everyday conversation. As of 2013 Wichita had one remaining fluent speaker. Kitsai died out about 1940. Only partially fluent speakers of Arikara or Pawnee apparently remain, and fluent speakers of Caddo are few, though all of these groups have language revitalization programs in place.
SumVg: Total heritability explained by all variants in genome-wide association studies based on summary statistics with standard error estimates
Authors: So Hon-Cheong , Sham Pak C.
Published: March 2015

Genome-wide association studies (GWAS) have become increasingly popular these days and one of the key questions is how much heritability could be explained by all variants in GWAS. We have previously proposed an approach to answer this question, based on recovering the “true”z-statistics from a set ofobserved z-statistics. Only summary statistics are required. However, methods for standard error (SE) estimation are not available yet, thereby limiting the interpretation of the results. In this study we developed resampling-based approaches to estimate the SE and the methods are implemented in an R package. We found that delete-d-jackknife and parametric bootstrap approaches provide good estimates of the SE. Methods to compute the sum of heritability explained and the corresponding SE are implemented in the R package SumVg, available athttps://sites.google.com/site/honcheongso/software/var-totalvg

Contact

pcsham@hku.hk,hcso85@gmail.com
Simulation of X-ray diffraction profiles for bent anisotropic crystals
Authors: Sanchez del Rio Manuel , Perez-Bocanegra Nicolas , Shi Xianbo , Honkimäki Veijo , Zhang Lin
Published: March 2015

The equations for calculating diffraction profiles for bent crystals are revisited for both meridional and sagittal bending. Two approximated methods for computing diffraction profiles are treated: multilamellar and Penning–Polder. A common treatment of crystal anisotropy is included in these models. The formulation presented is implemented in theXOPpackage, completing and updating the crystal module that simulates diffraction profiles for perfect, mosaic and now distorted crystals by elastic bending.
Quantitative X-ray phase contrast waveguide imaging of bacterial endospores
Authors: Wilke R. N. , Hoppert M. , Krenkel M. , Bartels M. , Salditt T.
Published: March 2015

Quantitative waveguide-based X-ray phase contrast imaging has been carried out on the level of single, unstained, unsliced and freeze-dried bacterial cells ofBacillus thuringiensisandBacillus subtilisusing hard X-rays of 7.9 keV photon energy. The cells have been prepared in the metabolically dormant state of an endospore. The quantitative phase maps obtained by iterative phase retrieval using a modified hybrid input–output algorithm allow for mass and mass density determinations on the level of single individual endospores but include also large field of view investigations. Additionally, a direct reconstruction based on the contrast transfer function is investigated, and the two approaches are compared. Depending on the field of view and method, a resolution down to 65 nm was achieved at a maximum applied dose of below 5 × 105 Gy. Masses in the range of about ∼110–190 (20) fg for isolated endospores have been obtained.
Nested Kirkpatrick–Baez (Montel) optics for hard X-rays
Authors: Resta Giacomo , Khaykovich Boris , Moncton David
Published: March 2015

A comprehensive description and ray-tracing simulations are presented for symmetric nested Kirkpatrick–Baez (KB) mirrors, commonly used at synchrotrons and in commercial X-ray sources. This paper introduces an analytical procedure for determining the proper orientation between the two surfaces composing the nested KB optics. This procedure has been used to design and simulate collimating optics for a hard-X-ray inverse Compton scattering source. The resulting optical device is composed of two 12 cm-long parabolic surfaces coated with a laterally graded multilayer and is capable of collimating a 12 keV beam with a divergence of 5 mrad (FWHM) by a factor of ∼250. A description of the ray-tracing software that was developed to simulate the graded multilayer mirrors is included.
The fast azimuthal integration Python library:pyFAI
Authors: Ashiotis Giannis , Deschildre Aurore , Nawaz Zubair , Wright Jonathan P. , Karkoulis Dimitrios , Picca Frédéric Emmanuel , Kieffer Jérôme
Published: March 2015

pyFAIis an open-source software package designed to perform azimuthal integration and, correspondingly, two-dimensional regrouping on area-detector frames for small- and wide-angle X-ray scattering experiments. It is written in Python (with binary submodules for improved performance), a language widely accepted and used by the scientific community today, which enables users to easily incorporate thepyFAIlibrary into their processing pipeline. This article focuses on recent work, especially the ease of calibration, its accuracy and the execution speed for integration.
Natural gas stakeholders during price growth: a case of Ukraine
Authors: Goncharuk Anatoliy G.
Published: March 2015

Purpose

– The purpose of this paper is to establish groups of stakeholders who win and lose from changes in natural gas prices and to develop practical recommendations for a state regulator for the optimal setting natural gas prices in the domestic market through an example of Ukraine.

Design/methodology/approach

– In this study, to identify groups of stakeholders with gains and losses from the pricing of natural gas, the author used traditional methods of correlation and statistical regression analysis, including the ordinary least squares (OLS) method.

Findings

– The main profit from natural gas remains in the extraction sector. The remaining profit is distributed among the various stakeholders. The consumers during rapidly rising gas prices have to rely on energy efficiency and switching to alternative, less costly resources. The existing system of unified natural gas price for all industrial consumers is inefficient and leads to the losses of the largest industrial sectors in Ukraine – metallurgy and chemical industry. With the help of the developed models, the author determined the critical levels of natural gas prices for these two industries.

Research limitations/implications

– The study is limited by data about activity of eight key manufacturing companies, four gas distribution companies, and main state gas companies from two country only.

Practical implications

– Defined levels can be used by a state regulatory authority as a boundary, above which these industries will be unprofitable and their fate along with hundred thousands of workers will be questionable.

Originality/value

– This is the first paper that set the critical levels of natural gas prices for two manufacturing industries in Ukraine.
Power-saving localization techniques for mobile devices
Authors: Narzt Wolfgang
Published: March 2015

Purpose

– This paper aims to develop generic strategies for improving energy consumption for location sensing on smartphones and compares the results of iOS and Android implementations. Mobile smartphone applications utilizing localization sensors (e.g. Global Positioning System) collectively face the problem of battery draining. Energy consumption is at a peak when applications permanently and stolidly use those sensors, even if their excessive exploitation is avoidable (e.g. when the user carrying the device is not moving).

Design/methodology/approach

– Considering contextual parameters affecting localization of mobile devices (i.e. incorporating movement probability, speed, etc.) is the basic idea for developing a strategy capable of reducing energy consumption for location determination on mobile devices. This paper explains the paradigm and draws the architecture for a generic context-based energy saving strategy for mobile location-based services.

Findings

– The paper reveals the positive implications in terms of energy consumption measured in the course of exhaustive tests for iOS and Android devices and discusses accuracy issues and potential workarounds, especially focusing on Apple’s M7 motion co-processor for consuming accelerometer data on a low energy level.

Originality/value

– The paper identifies and measures energy issues for location determination on smartphones and presents a generic and heuristic concept for saving energy.
An optimized travelling time estimation mechanism for minimizing handover failures and unnecessary handovers from cellular networks to WLANs
Authors: Mahmood Adnan , Zen Hushairi , Othman Al-Khalid
Published: March 2015

Purpose

– The paper aims to propose an optimized handover necessity estimation scheme for a mobile terminal (MT) traversing from a third-generation (3G) cellular network into the wireless local area network (WLAN) cell for reducing the number of handover failures and unnecessary handovers.

Design/methodology/approach

– The proposed optimized handover necessity estimation scheme comprises of two algorithms – a “travelling time prediction” reliant on consecutive received signal strength (RSS) measurements and MT’s velocity, and a “time threshold estimation” depending on the handover latency, WLAN’s cell radius, tolerable handover failure probability and the tolerable unnecessary handover probability.

Findings

– Our performance analysis reveals that the suggested mechanism effectively minimizes the number of handover failures and unnecessary handovers by 60 per cent as compared to the already proposed schemes in the literature.

Originality/value

– The convergence of Internet and wireless mobile communication accompanied by a massive increase in the number of cellular subscribers has led mobility management to emerge as a significant and challenging domain for wireless mobile communication over the Internet. Mobility management enables serving networks to locate roaming terminals for the call delivery (location management) and ensures a seamless connection as MT enters into the new service area (handover management). In this manuscript, an optimized handover necessity estimation scheme has been envisaged for reducing the probability of handover failures and unnecessary handovers from 3G cellular networks to WLANs to provide optimal network utilization along with an enhanced user satisfaction. Performance analysis reveals that the suggested scheme yields enhanced results as compared to the schemes already proposed in the literature.
Switchable dual band equilateral triangular microstrip patch antenna using pin diode
Authors: Pratap Prabal , Bhatia Ravinder Singh , Kumar Binod
Published: March 2015

Purpose

– The purpose of this paper is to study and calculate the electrical characteristic of an equilateral triangular microstrip patch antenna that is proposed for dual frequency operation using the pin diode. The electrical characteristic of an equilateral triangular microstrip patch antenna is proposed for dual-frequency operation. Spur lines and ON/OFF condition of the pin diode are utilized to switch the resonant frequency of the patch. The presence of spur lines excites the surface current of the patch which is dependent on the resonant frequency of an equilateral triangular microstrip patch. Insertion of the diode in the spur lines gives a better result and compactness in patch design, which improves the miniaturization in size of patch.

Design/methodology/approach

– Antenna Design Aspects: A basic structure of an equilateral triangular microstrip antenna (ETMA) having two spur lines and one pin diode positioned in between the spur line is considered in this paper. The design parameters are chosen on the basis of substrate materials having relative permittivity less than three. Specification of the antenna is given in Table I. Substrate material used is RT Duroid 5,880; relative permittivity of the substrate er is 2.2; thickness of dielectric substrate h is 1.5 mm; sides of equilateral triangular patch a are 10 mm, spur width s is 0.5 mm; and spur length b is 2.0 mm.

Findings

– This paper gives an account of achieving polarization swiftness with coplanar waveguide (CPW) feed. The miniaturized size of the antenna is 35 × 30 mm2. Switchable microstrip equilateral triangular antenna has been demonstrated for dual-frequency operations. The resonant frequency of an ETMA can be adjusted by setting the diode in an ON and OFF state. The design improves the miniaturization in size with a discussion of radiation density. The excited patch surface current is limited to flow around just the mid of the patch in simple ETMA with a single slit cut. It is observed that for an ETMA, when the diode is in the ON state at 9.16 GHz, the excited patch surface current is highly distributed in the patch compared to when the diode is in the ON state at 11 GHz. Similarly, it is observed that the excited surface patch current is highly distributed when the diode is in the OFF state in both frequencies (9 and 11.96 GHz). The mode is changed by the use of a switch at time and it is suitable for wireless communication applications.

Originality/value

– Spur lines and the ON/OFF condition of the pin diode are utilized to switch the resonant frequency of the patch. The presence of spur lines excites the surface current of the patch which is dependent on the resonant frequency of an equilateral triangular microstrip patch. Insertion of the diode in spur lines gives a better result and compactness in patch design, which improves the miniaturization in size of the patch.
Resource heterogeneity and its effects on interaction and integration in customer-supplier relationships
Authors: Abrahamsen Morten H. , Håkansson Håkan
Published: March 2015

Purpose

– The purpose of this paper is to study the phenomenon of customer-supplier interaction and integration from a resource perspective. In economic terms, a fish may be seen as a more or less homogeneous resource. If the herring is seen as a homogeneous resource, a market should be the best way to handle the selling and buying. However, if the herring is seen as a heterogeneous resource, a more extensive type of interaction is needed. One interesting aspect with herring is that different business actors apparently see this resource in different ways. Thus, the authors will have a mixed situation, creating possible difficulties for the actors involved.

Design/methodology/approach

– The authors start this study in Germany, one of the most important export markets for Norwegian herring. Today, Norwegian legislation hinders the possibility of vertical integration and cooperation at the supply side of the network. However, the industry sees opportunities for growth and integration on the marketing side. To examine this issue, the study uses a qualitative design methodology, incorporating personal in-depth interviews with selected respondents in Norway and Germany. Secondary data is also used. To analyse the data, the authors introduce five interaction and integration patterns termed pure exchange – no integration; limited interaction and integration; extensive interaction and developed integration and; indirect interaction and structural integration; and full integration.

Findings

– The findings suggest that there is a link between how the actors perceive herring as a resource and how they interact with counterparts. The authors find that the actors who see the resource as homogeneous have limited interaction and little or no integration, whereas the actors who see the resource as heterogeneous have a much more extensive interaction and closer ties.

Originality/value

– The paper is an investigation of the link between the resource heterogeneity and the patterns of customer-supplier integration.
Is extra care housing in England care-neutral?
Authors: Mayagoitia Ruth , Van Boxstael Els , Wojgani Hedieh , Wright Fay , Hanson Julienne , Tinker Anthea
Published: March 2015

Purpose

– Extra care housing (ECH) is housing for older people that aims to provide flexible care while fostering independence. The purpose of this paper is to examine the impact that some of the successes and failures in improving accessibility during remodelling had on care provision, in order to offer advice to social housing providers planning to remodel existing properties into ECH.

Design/methodology/approach

– The data consisted of an inventory of accessibility features and assistive technology (AT) items in flats and common areas. The data were drawn from ten ECH schemes in different regions of England.

Findings

– Most of the AT found was low-technology supporting independence, such as grabbers; some was specific to care provision, such as hoists. Even after remodelling, the design and layout of most buildings did not fully comply with accessibility standards, leading to increased provision of care for some tenants: a care-negative situation.

Research limitations/implications

– This multidisciplinary, original research on remodelling into ECH presents successful examples of accessibility, AT and care integration that required active tenant involvement and creative design input from care staff, architects and builders who were AT and accessibility aware. It is argued that for new and remodelled ECH buildings to be care-neutral, designers need to work towards the most inclusive model of ECH.

Originality/value

– This is original research that has produced guidance for builders, developers, policy makers and other stake holders.
Regulatory change in Australia and New Zealand following the global financial crisis
Authors: Brown Christine Ann , Davis Kevin , Mayes David
Published: March 2015

Purpose

– The purpose of this study is to explain rationale for regulatory change in Australia and New Zealand after the global financial crisis.

Design/methodology/approach

– Outline regulatory changes and relate to crisis experience and regulatory shortcomings exposed.

Findings

– Regulatory change was driven primarily by need, as capital importing nations, to comply with emerging global standards, and the different approaches in both nations are also related to domestic political considerations.

Research limitations/implications

– The process of regulatory change in response to the crisis is ongoing.

Practical implications

– A number of areas for further improvement in financial regulation are identified.

Social implications

– Costs of poor regulation and financial crises are identified.

Originality/value

– A comparison of regulatory approaches in two countries dominated by the same four large banks helps understand the challenges of cross-border financial regulation cooperation.
Pairs of quadrics in 11 variables
Authors: Munshi Ritabrata
Published: March 2015

For non-singular intersections of pairs of quadrics in 11 or more variables, we prove an asymptotic for the number of rational points in an expanding box.
An Efficient Dissipative Particle Dynamics-Based Algorithm for Simulating Ferromagnetic Colloidal Suspensions
Authors: Li Wuming , Ouyang Jie , Liu Qingsheng
Published: March 2015

In this paper, the algorithm, Euler scheme-the modified velocity-verlet algorithm (ES-MVVA) based on dissipative particle dynamics (DPD) method, is applied to simulate a two-dimensional ferromagnetic colloidal suspension. The very desirable aggregate structures of magnetic particles are obtained by using the above-mentioned algorithm, which are in qualitatively good agreement with those in the literature obtained by other simulation methods for different magnetic particle–particle interaction strengths. At the same time, the radial distribution functions of magnetic particles and the mean equilibrium temperatures of the system are also calculated. Next, the mean equilibrium velocities of magnetic and dissipative particles are calculated, by comparing the results obtained by ES-MVVA with those obtained by other algorithm for different time step sizes, it shows the validity and good accuracy of the present algorithm. So, the DPD-based algorithm presented in this paper is a powerful tool for simulation of magnetic colloidal suspensions.
Limitations of Additive Manufacturing on Microfluidic Heat Exchanger Components
Authors: Rua Yenny , Muren Russell , Reckinger Shanon
Published: March 2015

This work describes the testing of microfluidic components created using additive manufacturing. An Objet Eden 250 was used to create microfluidic channel test coupons with passages ranging from 0.5 to 3.0 mm and wall thicknesses ranging from 0.032 to 0.5 mm. Coupons were cleaned and tested under flow to examine structural integrity. Microfluidic channels with wall thicknesses down to 0.032 mm could be printed, cleaned, and tested successfully, although plastic deformation was observed in coupons with wall thicknesses below 0.1 mm. Given these limits, additive manufacturing based microfluidic heat exchangers (HXs) offer cost and performance benefits in natural convection HX applications.
Large-Scale Needfinding: Methods of Increasing User-Generated Needs From Large Populations
Authors: Schaffhausen Cory R. , Kowalewski Timothy M.
Published: March 2015

Understanding user needs and preferences is increasingly recognized as a critical component of early stage product development. The large-scale needfinding methods in this series of studies attempt to overcome shortcomings with existing methods, particularly in environments with limited user access. The three studies evaluated three specific types of stimuli to help users describe higher quantities of needs. Users were trained on need statements and then asked to enter as many need statements and optional background stories as possible. One or more stimulus types were presented, including prompts (a type of thought exercise), shared needs, and shared context images. Topics used were general household areas including cooking, cleaning, and trip planning. The results show that users can articulate a large number of needs unaided, and users consistently increased need quantity after viewing a stimulus. A final study collected 1735 needs statements and 1246 stories from 402 individuals in 24 hr. Shared needs and images significantly increased need quantity over other types. User experience (and not expertise) was a significant factor for increasing quantity, but may not warrant exclusive use of high-experience users in practice.
Worm Gear Drives With Adjustable Backlash
Authors: Kacalak Wojciech , Majewski Maciej , Budniak Zbigniew
Published: March 2015

This article presents the design of patented worm gear drives, which allow backlash adjustment or elimination by using specially designed worms and worm wheels. Many of the presented solutions allow backlash adjustment without disassembling the drive. The proposed solutions allow reduction of both backlash and its standard deviation to as little as 7.5% and 5% of their initial values, respectively. The presented solutions are a good alternative to harmonic drives and conventional precise drives, which are currently in use. The presented drives can successfully find their application in mechanisms for precise positioning of test benches, as well as in precise technological equipment, technological instrumentation, and in the case of miniaturization—in mechanisms resistant to severe working conditions.
A Fast Interactive Two-Dimensional Blade-to-Blade Profile Design Method
Authors: Willis G. D. , Goulas A.
Published: March 2015

To help with the design of axial flow steam turbine blading a suite of flow analysis programs has been adapted and developed. Effort has been concentrated on improving the blade-to-blade analysis and developing a two-dimensional blade-to-blade profile design method. The development and verification of the analysis program have already been reported in detail (Willis, 1987 and Willis and Goulas, 1987). This paper presents the design or inverse solution. The analysis method uses an inviscid stream function solution coupled with an integral boundary layer calculation. In the design program the required changes in the blade geometry are effected via a transpiration type model. It is therefore a ‘profile refinement’, rather than an ‘original’ design procedure, and is necessarily an iterative solution. A required velocity distribution may be specified over only part of the blade surface. Two examples are presented in this paper to illustrate the capability of the design program.
Secondary Flow, Separation and Losses in the NACA 48-Inch Centrifugal Impeller at Design and Off-Design Conditions
Authors: Moore John , Moore Joan G.
Published: March 2015

An elliptic flow calculation procedure has been used to model 3-D flow in the NACA 48–inch centrifugal impeller. The results demonstrate that fully elliptic steady flow calculations can be performed at design and off-design conditions. The calculations reproduce the measured overall performance and most of the features of the loss distributions observed in the NACA flow study. They give further insight into the complex 3-D flow with leading-edge separation and tip leakage.

The calculated secondary flow patterns are presented and used to explain the convection of vortices in a more recent laser anemometry study of a centrifugal compressor impeller.
Development of a Variable Area Radial Turbine for Small Turbochargers
Authors: Okazaki Yoichiro , Matsuo Eito , Matsudaira Nobuyasu , Busch Paul
Published: March 2015

This paper summarizes the development of variable area radial turbines for small turbochargers, intended for passenger car applications. Comparisons of aerodynamic performance of several different kinds of variable radial inflow turbines are discussed.

The results of comparative performance evaluations indicate the scroll area control type (VI) is the most suitable design for small turbochargers, where performance, cost and durability are the major design considerations.
Design Optimization of Gas Turbine Blades With Geometry and Natural Frequency Constraints
Authors: Cheu Tsu-Chien , Wang Bo Ping , Chen Ting-Yu
Published: March 2015

In this paper an automated procedure is presented to obtain the minimum weight design of gas turbine blades with geometry and multiple natural frequency constraints. The objective is achieved using a combined finite element-sequential linear programming, FEM-SLP technique. Thickness of selected finite elements are used as design variables. Geometric constraints are imposed on the thickness variations such that the optimal design has smooth aerodynamic shape. Based on the natural frequencies and mode shapes obtained from finite element analysis an assumed mode reanalysis technique is used to provide the approximate derivatives of weight and constraints with respect to design variables for sequential linear programming. The results from SLP provide the initial design for the next FEM-SLP process. An example is presented to illustrate the interactive system developed for the optimization procedure.
The Effect of Unsteady Compression and Expansion Waves on a Compressible Boundary Layer
Authors: Wilson Dennis , Sheller Michael R.
Published: March 2015

This abstract summarizes the results of an investigation into the effects of finite amplitude acoustic disturbances or weak compression and expansion waves on compressible boundary layers. Specifically, the goal is to provide a theoretical model which predicts the increased heat transfer and skin friction associated with unsteady pressure disturbances. These pressure disturbances, which are produced by combustion instabilities, are present in most combustors. The magnitude of the fluctuating component relative to the stagnation pressure varies from the low acoustic range (0.05 %) to the weak shock range (5 %). The frequencies range from a few hundred Hz. for the longitudinal mode to a few thousand Hz. for the transverse mode. A simple but accurate theoretical model which predicts the enhanced heat transfer and skin friction for a wide range of frequencies and magnitudes is presented. The formulation yielded an unexpected result in that an approximate analytical solution is possible for the laminar flow case.
A Unified Method for Solving Aerodynamic Cascade Design Problems on an Arbitrary Surface of Revolution
Authors: Sun X. Y. , Guo Y. , Zhao Y. Q. , Xu J. Z.
Published: March 2015

A method for solving various aerodynamic problems of transonic cascade design is developed, in which the coordinates equation is derived directly by inverting the stream function and the principal equation of the stream function. The corresponding “boundary conditions are obtained similarly. The coordinates equation has the same type property as that of the original equation and the only difference for various aerodynamic problems is the change of the boundary conditions on the cascade surfaces. Numerical results show that this unified method offers a useful tool for transonic cascade design.
Coal Fueled Aero-Derivative Gas Turbine: Design Approach
Authors: Horner M. W. , Sabla P. E. , Kimura S. G.
Published: March 2015

The direct use of coal as a gas turbine fuel offers the opportunity to burn coal in an environmentally sound manner at a competitive cost of energy. A development program is underway to verify the feasibility of using coal water mixture to fuel an aero-derivative gas turbine. This paper presents the overall program approach, required gas turbine design modifications, and reports the results from small-scale combustor test facilities.

The GE LM500 gas turbine was selected for this program because of its high efficiency and size, which is appropriate for transportation and cogeneration markets. The LM500 gas turbine power system design will be modified to accommodate coal fuel and any required emissions control devices. The design for the modified annular combustor is complete and preparations for coal fired tests of a 140 degree annular sector combustor are in progress. The combustor design and test development are being supported by a component test program with a One Nozzle Segment Combustor and a single can combustor LM500 Turbine Simulator. These test facilities are providing results on coal water mixture handling and fuel nozzle design, air staging requirements, component metal temperatures, combustor temperature performance, ash deposition rates, and emissions abatement for NOx, SOx, and particulates.
Laser Diagnostics for Gas Turbine Combustion Research
Authors: Ballal D. R. , Chen T. H. , Schmoll W. J.
Published: March 2015

Gas turbine combustors pose many modeling and design difficulties. This has created an urgent need for experimental research using laser diagnostics to validate and refine computer design models of combustors. In this paper, key practical problems, limitations, and our operational experience with laser diagnostic systems for gas turbine combustion research are described.

It is found that unavailability of a good LDA seeder design and an unambiguous particle bias correction scheme present the main obstacles to using LDA in gas turbine combustor measurements. The practical problems of the Raman/Rayleigh system, particularly above 1200 K are high background luminosity, beam steering due to unmixedness, and high Poisson uncertainty in temperature and concentration measurements. The integration of LDA-Raman systems is beset by optical and data acquisition difficulties. Therefore, considerable work is still required to make the applications of advanced laser diagnostics to measurements in a practical gas turbine combustor a reality.
Base Pressure in Transonic Speeds: A Comparison Between Theory and Experiment
Authors: Motallebi F.
Published: March 2015

The problem of base pressure in the absence of base bleed has been investigated for a symmetrical model with a square-cut trailing edge. The model was mounted at zero angle of attack in a transonic wind tunnel covering a range of mainstream Mach number from 0.6 to 1.3. The role of vortex shedding was found to be of great importance in the prediction of base pressure. A semi-theoretical analysis for the prediction of base pressure in subsonic and transonic speeds which includes the effect of vortex shedding is proposed.
Correlation Between Sodium Sulfate Mass Transfer and Low-Temperature Hot Corrosion
Authors: Ahluwalia R. K. , Im K. H.
Published: March 2015

A mass transfer model is developed that considers diffusive and chemical aspects of sodium sulfate formation and deposition on cooled blades of coal-fired gas turbines. The roles of gas phase condensation of sodium sulfate and multicomponent diffusion across a chemically frozen thin boundary layer are elaborated. A rational procedure is presented for correlating material wastage with laboratory weight gain data obtained by exposing alloy specimens pre-coated with a thin film of salt to SO2-SO3 in an oxygen environment. The sodium sulfate mass transfer model is used in conjunction with the correlation to project blade corrosion and lifetime as a function of gas turbine inlet temperature, blade cooling, and sodium and sulfur contaminant concentration.
An Experimental Study of Streamwise Vortices in a Compressor Cascade
Authors: Fang Chen , Mao-Zhang Chen , Hao-Kang Jiang
Published: March 2015

An experimental study on the production and development of streamwise vortices in a compressor cascade is reported.

At four locations inside and one location outside the blade passage, the mean velocity components, three turbulent intensities and three Reynolds stresses were measured with a “x” hot wire probe. The results obtained describe the flow structure in the corner between the end-wall and blade suction surface in detail. Besides a passage vortex within the passage, there exist a shed corner vortex pair and a secondary vortex pair in the corner. The characteristics of two vortex pairs were different from that of the passage vortex.

The mechanism causing the shed corner vortex pair and secondary vortex pair and the effect of these vortices on the cascade losses are discussed.
Gas Turbine Heat Recovery Steam Generators for Combined Cycles Natural or Forced Circulation Considerations
Authors: Pasha Akber
Published: March 2015

In recent years the combined cycle has become a very attractive power plant arrangement because of its high cycle efficiency, short order-to-on-line time and flexibility in the sizing when compared to conventional steam power plants. However, optimization of the cycle and selection of combined cycle equipment has become more complex because the three major components, Gas Turbine, Heat Recovery Steam Generator and Steam Turbine, are often designed and built by different manufacturers.

Heat Recovery Steam Generators are classified into two major categories — 1) Natural Circulation and 2) Forced Circulation. Both circulation designs have certain advantages, disadvantages and limitations.

This paper analyzes various factors including; availability, start-up, gas turbine exhaust conditions, reliability, space requirements, etc., which are affected by the type of circulation and which in turn affect the design, price and performance of the Heat Recovery Steam Generator. Modern trends around the world are discussed and conclusions are drawn as to the best type of circulation for a Heat Recovery Steam Generator for combined cycle application.
Operating Characteristics of Heavy-Duty Gas Turbines in Utility Service
Authors: Rowen William I.
Published: March 2015

With the increasing utilization of gas turbines in industrial and cogeneration applications, they are taking on a greater role in base load service. Because of their inherent responsiveness, they also offer operating characteristics that can enhance their contribution to utility systems as a generator prime mover. This paper will describe these characteristics, particularly as they relate to the interaction of the gas turbine, the governor, and the temperature control system. Additional features, such as load control, variable inlet guide vanes, peaking operation and other unique characteristics are also discussed from this point of view.
Gas Turbine Heat Transfer With Alternate Cooling Fluids
Authors: Abuaf N. , Cohn A.
Published: March 2015

Steam or gases other than air have been proposed as substitutes for cooling industrial turbine components positioned along the hot gas path. To check the effect of coolant gas physical properties on the internal passage heat transfer coefficients, tests were conducted with air, helium, carbon dioxide, and refrigerant-12 in a serpentine passage with turbulence promoters. For the fully developed turbulent flow regions, the correlation proposed by Han et al. (1985) properly accounts for the cooling gas property changes. With respect to the external heat transfer aspects with film cooling, tests were run in a wind tunnel with a two-dimensional slit injection geometry. The film cooling effectiveness results measured with the same gases injected as a secondary gas into the main flow of air show that the correlations proposed by Kutateladze and Leont’ev (1963) and Librizzi and Cresci (1964) agree with the present data for the air/air, air/helium, and air/carbon dioxide combinations. The air/refrigerant-12 results are lower than all the correlations proposed in the literature.
Spray Automated Balancing of Rotors: Concept and Initial Feasibility Study
Authors: Smalley Anthony J. , Baldwin Richard M. , Schick Wilbur R.
Published: March 2015

This paper describes a new balancing concept: Spray Automated Balancing Of Rotors (SABOR). The Fuel Air Repetitive Explosion (FARE) process of metal film deposition is used to apply discrete amounts of metallic or ceramic particles to a spinning rotor at a controlled angular location on the rotor. In this way, without stopping the rotor, its mass eccentricity is changed in a manner designed to reduce the vibration sensed by a balancing machine.

The system design and control for implementing SABOR are described. Preliminary results are presented from a demonstration rig which confirm the ability of the method to control both angle of application and rate of application to the extent necessary for effective automated balancing. The method is used to balance a spinning disk without stopping it.

Results are presented which show that the bond strengths of materials deposited by the FARE process for use in small gas turbine engines are acceptable for the level of centrifugal stresses expected. Fatigue tests of sprayed samples show the data to be indistinguishable from that available for specimens hand-ground according to current balancing practice.
Development Test of a Small Aero-Derived Gas Turbine Combustor for Medium Btu Gaseous Fuel
Authors: Hua-Fang Wang , Gao-En Liu
Published: March 2015

WZ-5 engine is a small aero gas turbine engine rated in 1200kw class. A development program was initiated in 1986 to develop the engine with some modifications to accommodate the medium or low Btu gaseous fuel for its industrial application. The test program was accordingly carried out for the modified engine and combustor to evaluate their ability to burn medium Btu gaseous fuel. The present investigation is a part of the program to justify whether or not the modified combustor is capable of burning the medium Btu gaseous fuel with satisfactory combustion performances. The medium Btu gaseous fuel used in the test contains 50% of H2 and 20% of CH4 and the rest of N2 as innert. That is the typical processing gas produced in chemical fertilizer production. The low heating value of the gas is 3002 kcal/nm3.

All the test results whowed that when burning the medium Btu gaseous fuel the modified combustor had quite good performances except one combustor which had the injectors with slot-shape opening at the injector end and had unacceptable combustor exit temperature profile, and also showed that the modified combustor had the potential ability to burn low Btu gaseous fuel which has lower calorific value but some amount of H2.
Effects of Free-Stream Turbulence and Wake Characteristics on the Heat Transfer Along a Cooled Gas Turbine Blade
Authors: Wittig S. , Schulz A. , Dullenkopf K. , Fairbank J.
Published: March 2015

Heat transfer measurements under steady, quasi-steady and unsteady flow conditions are discussed. In continuing measurements on the influence of a plane steady wake flow as well as on the effects of grid-produced free-stream turbulence, the present paper describes the effects of the superposition of the free-stream turbulence with the wake flow. Of special interest is a comparison of the wake produced by a leading airfoil with that of a cylindrical bar in cross flow. The similarity of the wakes as far as macrostructure of the turbulence and velocity is concerned is documented using LDV and heat transfer measurements. In extending the modeling concept, a rotating wake generator is employed simulating the wake of a blade with cylindrical bars in cross flow. The comparison of the theoretical and experimental results is presented.
The Feasibility, From an Installational Viewpoint, of Gas-Turbine Pressure-Gain Combustors
Authors: Kentfield J. A. C.
Published: March 2015

The principles of pressure-gain combustors based on the wave rotor and pulse-combustor concepts were reviewed briefly. A study, based on experimental data, in which current-technology pressure-gain combustors were applied to three aircraft-engine derivative industrial gas-turbines, covering a power range from 275 kW (370 hp) to 29 MW (39,000 hp), showed that engine power increased by 6.5% to 9.6% with corresponding reductions of equal magnitude in specific fuel consumption. It was concluded that pressure-gain combustors appear to offer sufficient improvements in performance without incurring crippling installational penalties, although decreases in engine power/weight ratios were noted, to warrant further research and development.