bluuebunny/crossref_metadata_2025 huggingface dataset:
TGF‐β1 and TNF‐α differentially regulate Twist1 mediated resistance towards BRAF/MEK inhibition in melanoma
Authors: Menon Dinoop R. , Wels Christian , Bonyadi Rad Ehsan , Joshi Shripad , Knausz Heike , Lade‐Keller Johanne , Brandner Johanna M. , Schaider Helmut
Published: July 2013

Resistance to BRAF and MEK inhibition is a common phenomenon in melanoma. Cytokines and transcription factors have been attributed to contribute to the loss of sensitivity towards these inhibitors. Here, we show that transforming growth factor (TGF)‐β1 if combined with PLX4032, a BRAF inhibitor, or GSK1120212, a MEK inhibitor, substantially increased cell death in BRAF‐mutant melanoma cell lines. This increase was based on the combined regulatory decrease in Twist1, an antiapoptotic protein. Overexpression or silencing of Twist1 attenuated or aggravated induction of apoptosis through PLX4032 or GSK1120212, respectively. Exposure to tumour necrosis factor (TNF)‐α, however, led to increased Twist1 levels and oppositional decrease in cell death if exposed to PLX4032 or GSK1120212. This increase in drug resistance again depended on Twist1 levels. Our studies suggest that Twist1 as a common downstream target of multiple signalling cascades plays a crucial role in mediating drug resistance to BRAF‐ and MEK‐targeted molecular inhibitors.
‘Seeing is Believing’; the use of novel imaging approaches towards creating a greater understanding of parasite: host interactions
Authors: Mountford A. P.
Published: July 2013

This editorial highlights some of the key points made in the six invited reviews in this special issue of Parasite Immunology on the use of contemporary imaging technologies to investigate the parasite: host interface. Three of the reviews deal with the protozoa Trypanosoma, Leishmania, and Plasmodium, whilst the remainder focus on helminth parasites particularly Schistosoma. The reviews cover aspects related to how the development of transgenic parasites has vastly advanced our understanding of how parasites interact with host cells, particularly as a cause of pathology. Imaging technologies have also been exploited in revealing parasite localisation within host tissues and identifying novel therapeutic targets. Combined the reviews show how ‘state of the art’ imaging technologies have resulted in a seismic advance in our understanding of parasite biology and how this has the potential to develop new, and improved, strategies to combat disease caused by parasite infections.
Induction of appropriate Th‐cell phenotypes: cellular decision‐making in heterogeneous environments
Authors: van den Ham H.‐J. , Andeweg A. C. , de Boer R. J.
Published: July 2013

Helper T (Th)‐cell differentiation is a key event in the development of the adaptive immune response. By the production of a range of cytokines, Th cells determine the type of immune response that is raised against an invading pathogen. Th cells can adopt many different phenotypes, and Th‐cell phenotype decision‐making is crucial in mounting effective host responses. This review discusses the different Th‐cell phenotypes that have been identified and how Th cells adopt a particular phenotype. The regulation of Th‐cell phenotypes has been studied extensively using mathematical models, which have explored the role of regulatory mechanisms such as autocrine cytokine signalling and cross‐inhibition between self‐activating transcription factors. At the single cell level, Th responses tend to be heterogeneous, but corrections can be made soon after T‐cell activation. Although pathogens and the innate immune system provide signals that direct the induction of Th‐cell phenotypes, these instructive mechanisms could be easily subverted by pathogens. We discuss that a model of success‐driven feedback would select the most appropriate phenotype for clearing a pathogen. Given the heterogeneity in the induction phase of the Th response, such a success‐driven feedback loop would allow the selection of effective Th‐cell phenotypes while terminating incorrect responses.
Structuring Work Distribution for Global Product Development Organizations
Authors: Tripathy Anshuman , Eppinger Steven D.
Published: July 2013

This study describes (through an application) a novel approach toward organizing work distribution across globally distributed design and development centers of a product development (PD) organization. While there exist several studies (and modeling applications) for work distribution and allocation for manufacturing and supply chain networks, those related to product development organizations are limited to qualitative suggestions such as offshoring of modular tasks. However, most PD efforts are characterized by significant complexity in information sharing and information dependency among PD tasks (represented by coupling in the system architecture of the firm), thus preventing the identification of modular tasks. Also, redesigning the architecture to introduce modularity has associated risks of costs and product integrity. We demonstrate a methodology to organize work distribution globally in an industrial setting, utilizing the design structure matrix to quantify the system architecture of the firm. Our optimization results show significant cost savings through a restructured PD organization. On analysis of the results, we make two significant observations: (a) while offshoring based on modularity is generally appropriate, it is not the whole answer, as there exists a trade‐off between the efficiency of performing specific PD tasks at the offshore location and the modularity of the task; and (b) firms should successively increase work allocation to the offshore location, benefiting from capability improvements through learning effects.
Hierarchical Multi‐skill Resource Assignment in the Telecommunications Industry
Authors: Barz Christiane , Kolisch Rainer
Published: July 2013

We formulate a discrete time Markov decision process for a resource assignment problem for multi‐skilled resources with a hierarchical skill structure to minimize the average penalty and waiting costs for jobs with different waiting costs and uncertain service times. In contrast to most queueing models, our application leads to service times that are known before the job is actually served but only after it is accepted and assigned to a server. We formulate the corresponding Markov decision process, which is intractable for problems of realistic size due to the curse of dimensionality. Using an affine approximation of the bias function, we develop a simple linear program that yields a lower bound for the minimum average costs. We suggest how the solution of the linear program can be used in a simple heuristic and illustrate its performance in numerical examples and a case study.
Detection of quantitative resistance loci associated with resistance to rice false smut (Ustilaginoidea virens) using introgression lines
Authors: Zhou Y.‐L. , Xie X.‐W. , Zhang F. , Wang S. , Liu X.‐Z. , Zhu L.‐H. , Xu J.‐L. , Gao Y.‐M. , Li Z.‐K.
Published: July 2013

False smut, caused by Ustilaginoidea virens, is a rice disease of increasing importance worldwide, with no source of high‐level resistance in the existing rice germplasm. To facilitate breeding varieties with good levels of field resistance to false smut, quantitative resistance loci (QRL) were identified using 213 introgression lines (ILs) from a cross between Teqing (recipient) and Lemont (donor) evaluated using natural infection at two hotspots of false smut in northeast China. Ten QRL affecting percentages of diseased hills, diseased panicles and diseased spikelets were detected and mapped to rice chromosomes 2, 3, 4, 6, 8, 10, 11 and 12. The Lemont alleles at all QRL increased false smut resistance. Four QRL (qFSR‐6‐7, qFSR‐10‐5, qFSR‐10‐2 and qFSR‐11‐2) had relatively larger and consistent effects across the two testing sites. Promising resistant ILs were identified, most of which had multiple QRL, suggesting that pyramiding multiple QRL by marker‐assisted selection would be an effective strategy for improving rice resistance to false smut. The identified QRL and their linked DNA markers will facilitate this breeding effort in the future.
Screening Corymbia populations for resistance to Puccinia psidii
Authors: Pegg G. S. , Brawner J. T. , Lee D. J.
Published: July 2013

The exotic rust pathogen Puccinia psidii is now widespread along the east coast of Australia from temperate Victoria to tropical far north Queensland, with a current host range exceeding 200 species from 37 myrtaceous genera. To determine the threat P. psidii poses to plantation and native eucalypts, artificial inoculation was used to screen germplasm of spotted gum (Corymbia spp.) for resistance to the biotype of P. psidii that has become established in Australia. The objective was to characterize resistance to P. psidii within the Corymbia species complex so that management strategies for the deployment of germplasm from existing breeding programmes of these spotted gum species could be developed. Symptom development initiated 7 days after inoculation, with resistant and susceptible seedlings identified within all species, provenances and families. Inter‐ and intraspecific variability in rust resistance was observed among spotted gum species. There was no apparent relationship between climatic conditions at the provenance origin and disease resistance. The heritability estimates for all assessments are moderate to high and indicate a significant level of additive genetic variance for rust resistance within the populations. The results of this study clearly identify potential to select for resistance at the family level within the tested populations. While the potential for P. psidii to detrimentally impact upon Corymbia in the nursery and in young plantations was demonstrated, estimations of the heritability of resistance suggest that efforts to enhance this trait through breeding have reasonable prospects for success.
Endowment Differences and the Composition of Intra‐Industry Trade
Authors: Cabral Manuel , Falvey Rod , Milner Chris
Published: July 2013

The empirical relationship between differences in endowments and different types of trade is investigated in this paper. Although net trade (NT) and vertical intra‐industry trade (IIT) are both broadly viewed as reflecting endowment differences, we suggest that there will be systematic differences in the way their shares of trade adjust as endowment differences become larger. Empirical evidence for European Union trade with its 52 major trading partners confirms this. The share of horizontal IIT (net trade) decreases (increases) for all increases in absolute endowment differences, but the share of vertical IIT can both increase and decrease with increases in endowment differences.
The “Impossible Trinity” Hypothesis in an Era of Global Imbalances: Measurement and Testing
Authors: Aizenman Joshua , Chinn Menzie David , Ito Hiro
Published: July 2013

We outline new metrics for measuring the trilemma aspects: exchange rate flexibility, monetary independence, and capital account openness, taking into account substantial international reserve accumulation that has taken place since the 2000s. Since 1990, the trilemma variables in emerging markets have converged towards intermediate levels, characterizing by managed flexibility, using sizable international reserves as a buffer while retaining some degree of monetary autonomy. We test the linearity of the trilemma, and find that the weighted sum of the three trilemma variables adds up to a constant. Thus, a rise in one trilemma variable should be traded‐off with a drop of the weighted sum of the other two.
An Economic Evaluation of Model Risk in Long‐term Asset Allocations
Authors: Boucher Christophe , Jannin Gregory , Kouontchou Patrick , Maillet Bertrand
Published: July 2013

Following the recent crisis and the revealed weakness of risk management practices, regulators of developed markets have recommended that financial institutions assess model risk. Standard risk measures, such as the value‐at‐risk (VaR), emerged during the 1990s as the industry standard for risk management and become today a key tool for asset allocation. This paper illustrates and estimates model risk, and focuses on the evaluation of its impact on optimal portfolios at various time horizons. Based on a long sample of US data, the paper finds a non‐linear relation between VaR model errors and the horizon that impacts optimal asset allocations.
US Ethanol Trade Policy: Pollution Reduction or Domestic Protection
Authors: Devadoss Stephen , Bayham Jude
Published: July 2013

To mitigate dependence on fossil fuel and reduce pollution, the US government has undertaken several policies—an import tariff, tax credit, and mandate—to augment domestic ethanol production and increase ethanol in the fuel supply. This study uses a general equilibrium model to analyze the effects of the US ethanol import tariff on welfare by internalizing the externality and incorporating US fuel and ethanol policies and to determine the optimal tariff. The results show that because of the environmental benefits of imported ethanol, the adverse effects of domestic ethanol on the environment, the need for the imported ethanol to boost the blended gasoline production, and the economy‐wide interactions of various markets, the optimal trade policy may call for subsidizing rather than taxing ethanol imports.
Tendinopathies around the Elbow Part 1: Lateral Elbow Tendinopathy
Authors: Donaldson Oliver , Vannet Nicola , Gosens Taco , Kulkarni Rohit
Published: July 2013

Tendinopathies of the elbow and in particular of the common extensor origin are a common cause of elbow pain. Part one of this two part review of tendinopathies of the elbow will focus on the pathophysiology and management of lateral elbow tendinopathy, frequently referred to as tennis elbow. Lateral elbow tendinopathy is a common condition with an incidence of 1 – 2%. The pathology arises from the origin of extensor carpi radialis brevis where changes, consistent with all tendinopathies, of angiofibroblastic hyperplasia occur secondary to repetitive micro trauma. It is not an inflammatory condition. Clinical history and examination is usually sufficient for diagnosis although MRI and ultrasound can be used. The many treatment options that have been proposed have a mixed quality of supporting evidence. Thus management protocols are difficult to define. Treatment depends on the length of symptoms. Acute presentation is managed through conservative measures including activity modification, topical NSAIDs and physiotherapy. For patients with recalcitrant symptoms, injection therapy with, for example, platelet rich plasma can be used. Alternatively surgical excision of the diseased tissue can be performed. This review article will consider the available evidence in order to identify both treatments that are effective and those that are not.
Sediment geochemistry as a provenance indicator: Unravelling the cryptic signatures of polycyclic sources, climate change, tectonism and volcanism
Authors: Zhang Yuanyuan , Pe‐Piper Georgia , Piper David J.W.
Published: July 2013

Interpretation of bulk‐sediment geochemistry is one of several approaches for determining sediment provenance. This study investigates the value added by bulk‐sediment geochemical analysis in interpreting provenance in a passive margin clastic basin, the Upper Jurassic–Lower Cretaceous deltaic sediments of the Scotian Basin. Provenance studies in this basin are challenging because source tectonic terranes are parallel to the basin margin and polycyclic sediment sources are abundant. More than 400 samples of mudstone and sandstone representing the geographical and stratigraphic range of interest were analysed for 57 elements. Diagenetic processes added calcium to many samples and removed potassium in rocks buried below 3 km, thus impacting principal component analysis and published weathering indices. However, multiple geochemical approaches to assessing the degree of weathering showed climatically controlled changes in weathering in the Tithonian and Barremian, and changes in supply from major tectonic events, such as the top‐Aptian uplift in the Labrador rift. Covariance of elements in heavy minerals demonstrates the varying magnitude of polycyclic supply and stratigraphic changes in sources. Geochemical analyses revealed a previously unsuspected Tithonian alkali volcanic sediment source, characterized by high niobium and tantalum. The lack of highly contrasting sources means that geochemistry alone is inadequate to determine sediment provenance. Published discrimination diagrams are of limited value. Statistical analysis of geochemical data is strongly influenced by diagenetic processes, episodic volcanic inputs and polycyclic concentration of resistant heavy minerals in sandstones. Single indicator elements for particular sources are generally lacking. Nevertheless, careful consideration of geochemical variability on a case by case basis, integrated with detrital mineral studies, provides new insights into palaeoclimate, sediment provenance and, hence, regional tectonics. Although there is no simple template for such analysis, this study demonstrates an approach that can be used for other basins.
Lactate dehydrogenase and Haemolysis Index as quality control markers of haemolysis in intra‐operative cell salvage
Authors: Sullivan I. J. , Faulds J. N.
Published: July 2013

Objectives

The aim of this investigation was to explore the potential use of the tests lactate dehydrogenase (LDH) and Haemolysis Index as haemolysis markers in intra‐operative cell salvage (ICS) blood in comparison to plasma free haemoglobin levels.

Background

Quality control (QC) should be seen as a fundamental part of any ICS blood conservation programme, however, due to lack of available knowledge, familiarity and experience, QC is still a comparatively new subject. A QC pilot scheme is currently being undertaken by the Royal Cornwall Hospital in association with the UK Cell Salvage Action Group to explore potential markers that can be used to assess the quality of blood obtained from ICS. This test list should be available to all ICS users and achievable within financial budgets. Currently this proposed test list includes a full blood count, a protein marker such as urine albumin/microalbumin and heparin monitoring. Haemolysis testing is another key marker.

Methods/Materials

Samples were collected from ICS processed blood and allogeneic SAGM leucodepleted red cell units and processed for plasma free haemoglobin, LDH and Haemolysis Index.

Results

There was a very strong correlation between plasma free haemoglobin and LDH (0·960), and plasma free haemoglobin and the Haemolysis Index (0·944).

Conclusion

We have shown that the LDH and Haemolysis Index tests are suitable and reliable alternatives for measuring haemolysis from samples obtained from ICS or allogeneic blood. We have incorporated the LDH test into our Hospital's ICS QC package and recommend that this test is considered for all ICS QC samples.
An APETALA3 homolog controls both petal identity and floral meristem patterning in Nigella damascena L. (Ranunculaceae)
Authors: Gonçalves Beatriz , Nougué Odrade , Jabbour Florian , Ridel Céline , Morin Halima , Laufs Patrick , Manicacci Domenica , Damerval Catherine
Published: July 2013

Flower architecture mutants provide a unique opportunity to address the genetic origin of flower diversity. Here we study a naturally occurring floral dimorphism in Nigella damascena (Ranunculaceae), involving replacement of the petals by numerous sepal‐like and chimeric sepal/stamen organs. We performed a comparative study of floral morphology and floral development, and characterized the expression of APETALA3 and PISTILLATA homologs in both morphs. Segregation analyses and gene silencing were used to determine the involvement of an APETALA3 paralog (NdAP3–3) in the floral dimorphism. We demonstrate that the complex floral dimorphism is controlled by a single locus, which perfectly co‐segregates with the NdAP3–3 gene. This gene is not expressed in the apetalous morph and exhibits a particular expression dynamic during early floral development in the petalous morph. NdAP3–3 silencing in petalous plants perfectly phenocopies the apetalous morph. Our results show that NdAP3–3 is fully responsible for the complex N. damascena floral dimorphism, suggesting that it plays a role not only in petal identity but also in meristem patterning, possibly through regulation of perianth organ number and the perianth/stamen boundary.
MULTIPASS, a rice R2R3‐typeMYBtranscription factor, regulates adaptive growth by integrating multiple hormonal pathways
Authors: Schmidt Romy , Schippers Jos H. M. , Mieulet Delphine , Obata Toshihiro , Fernie Alisdair R. , Guiderdoni Emmanuel , Mueller‐Roeber Bernd
Published: July 2013

Growth regulation is an important aspect of plant adaptation during environmental perturbations. Here, the role ofMULTIPASS(OsMPS), an R2R3‐typeMYBtranscription factor of rice, was explored.OsMPSis induced by salt stress and expressed in vegetative and reproductive tissues. Over‐expression ofOsMPSreduces growth under non‐stress conditions, while knockdown plants display increased biomass.OsMPSexpression is induced by abscisic acid and cytokinin, but is repressed by auxin, gibberellin and brassinolide. Growth retardation caused byOsMPSover‐expression is partially restored by auxin application. Expression profiling revealed that OsMPS negatively regulates the expression ofEXPANSIN(EXP) and cell‐wall biosynthesis as well as phytohormone signaling genes. Furthermore, the expression of OsMPS‐dependent genes is regulated by auxin, cytokinin and abscisic acid. Moreover, we show that OsMPS is a direct upstream regulator ofOsEXPA4,OsEXPA8,OsEXPB2,OsEXPB3,OsEXPB6and the endoglucanase genesOsGLU5andOsGLU14. The multiple responses ofOsMPSand its target genes to various hormones suggest an integrative function of OsMPSin the cross‐talk between phytohormones and the environment to regulate adaptive growth.
On the Differential Behaviour of National and Multinational Firms: A Within‐ and Across‐sectors Approach
Authors: Latorre María C.
Published: July 2013

This paper looks for different patterns of behaviour of national firms and multinational enterprises (MNEs). Its main contribution is the use of a computable general equilibrium perspective to analyse firms’ performance. The model is calibrated for the case of theCzechRepublic, which has been a very attractive foreign direct investment location in the last three decades. We replicate the arrival ofMNEs to different sectors of this country in turn and analyse the responses of both types of firms across the 20 different sectors in which theCzech economy has been split. Our results grasp the short‐run impact. The higher labour intensity of national firms leads them to different patterns of production and labour demand, compared withMNEs operatingwithinthe same sector. The demand side of the model (particularly, exports and private consumption) drives the evolution of production and labour demandacrosssectors. Regarding prices, we also find a differential pattern between both types of firmswithinandacrosssectors. Our analysis offers detailed evidence on how the impact ofMNEs will differ depending on the sector to which they arrive. Finally, the aggregate results suggest that a completely different microeconomic panorama may underlie rather similar macroeconomic outcomes.
Raman and Infrared Thermometry for Microsystems
Authors: Phinney Leslie M. , Lu Wei-Yang , Serrano Justin R.
Published: July 2013

This paper reports and compares Raman and infrared thermometry measurements along the legs and on the shuttle of a SOI (silicon on insulator) bent-beam thermal microactuator. Raman thermometry offers micron spatial resolution and measurement uncertainties of ±10 K. Typical data collection times are a minute per location leading to measurement times on the order of hours for a complete temperature profile. Infrared thermometry obtains a full-field measurement so the data collection time is on the order of a minute. The spatial resolution is determined by the pixel size, 25 μm by 25 μm for the system used, and infrared thermometry also has uncertainties of ±10 K after calibration with a nonpackaged sample. The Raman and infrared measured temperatures agreed both qualitatively and quantitatively. For example, when the thermal microactuator was operated at 7 V, the peak temperature on an interior leg is 437 K ± 10 K and 433 K ± 10 K from Raman and infrared thermometry, respectively. The two techniques are complementary for microsystems characterization when infrared imaging obtains a full-field temperature measurement and Raman thermometry interrogates regions for which higher spatial resolution is required.
Heat Transfer Scaling Close to the Wall for Turbulent Channel Flows
Authors: Srinivasan Chiranth , Papavassiliou Dimitrios V.
Published: July 2013

This work serves a two-fold purpose of briefly reviewing the currently existing literature on the scaling of thermal turbulent fields and, in addition, proposing a new scaling framework and testing its applicability. An extensive set of turbulent scalar transport data for turbulent flow in infinitely long channels is obtained using a Lagrangian scalar tracking approach combined with direct numerical simulation of turbulent flow. Two cases of Poiseuille channel flow, with friction Reynolds numbers 150 and 300, and different types of fluids with Prandtl number ranging from 0.7 to 50,000 are studied. Based on analysis of this database, it is argued that the value and the location of the maximum normal turbulent heat flux are important scaling parameters in turbulent heat transfer. Implementing such scaling on the mean temperature profile for different fluids and Reynolds number cases shows a collapse of the mean temperature profiles onto a single universal profile in the near wall region of the channel. In addition, the profiles of normal turbulent heat flux and the root mean square of the temperature fluctuations appear to collapse on one profile, respectively. The maximum normal turbulent heat flux is thus established as a turbulence thermal scaling parameter for both mean and fluctuating temperature statistics.
Dynamic Models of Piled Foundations
Authors: Kuo Kirsty A. , Hunt Hugh E. M.
Published: July 2013

The vibration behavior of piled foundations is an important consideration in fields such as earthquake engineering, construction, machine-foundation design, offshore structures, nuclear energy, and road and rail development. This paper presents a review of the past 40 years' literature on modeling the frequency-dependent behavior of pile foundations. Beginning with the earliest model of a single pile, adapted from those for embedded footings, it charts the development of the four pile-modeling techniques: the “dynamic Winkler-foundation” approach that uses springs to represent the effect of the soil; elastic-continuum-type formulations involving the analytical solutions for displacements due to a subsurface disk, cylinder, or other element; boundary element methods; and dynamic finite-element formulations with special nonreflecting boundaries. The modeling of pile groups involves accounting for pile-soil-pile interactions, and four such methods exist: interaction factors; complete pile models; the equivalent pier method; and periodic structure theory. Approaches for validating pile models are also explored.
Active Outer Ring Cooling of High Loaded and High Speed Ball Bearings
Authors: Flouros Michael , Hirschmann Markus , Cottier Francois , Gloeckner Peter , Dullenkopf Klaus
Published: July 2013

Bearings for aero engine applications are subjected to a high thermal impact because of the elevated speeds and loads. The high rate of heat generation in the bearing cannot be sustained by the materials used and in the absence of lubrication will fail within seconds. For this reason aero engine bearings have to be lubricated and cooled by a continuous oil stream. The heat which is generated in the bearings through friction is transferred into the oil. Oil itself has not unlimited capabilities and can only remove heat as long as its temperature does not reach critical limits. When the critical limits have been reached or even exceeded the oil will suffer chemical decomposition (coking) with loss of its properties and subsequently causing a detrimental impact on the rotating machinery. Oil is normally transferred into the bearings through holes in the inner ring thus taking advantage of the centrifugal forces due to the rotation.

In its way through the bearing the oil continuously removes heat from the inner ring, the rolling elements and the bearing cage until it reaches the outer ring. Since the oil has already been heated up its capability to remove heat from the outer ring is considerably reduced. The idea to provide the bearing with an “unlimited” quantity of oil to ensure proper cooling cannot be considered since an increase in the oil quantity leads to higher parasitic losses (churning) in the bearing chamber and increased requirements on the engine’s lubrication system in terms of storage, scavenging, cooling, weight, etc, not mentioning the power needed to accomplish all these.

In this sense, the authors have developed a method which would enable active cooling of the outer ring. Similar to fins which are used for cooling electronic devices, a spiral groove engraved in the outer ring material would function as a fin body with oil instead of air as the cooling medium. The number of “threads” and the size of the groove design characteristics were optimized in a way that enhanced heat transfer is achieved without excessive pressure losses.

An experimental set up was created for this reason and a 167.5mm PCD (Pitch Circle Diameter) ball bearing was investigated. The bearing was tested with and without the outer ring cooling. A reduction of 50% of the lubricant flow through the inner ring associated with a 30% decrease in heat generation was achieved.
Numerical Research on Flow Characteristics of Inlet Flow-Path for Ram-Rotor
Authors: Kang Weijia , Liu Zhansheng , Cao Zhixuan , Wang Le , Wang Gangwei
Published: July 2013

A design method of ram-rotor inlet flow-path with shock wave compression is proposed with consideration of shock wave angle, plane turning angle, the inlet flow-path throat, and subsonic diffuser. A 3D model of the inlet flow path for ram-rotor is established by applying this design method. Effects of the back pressure, rotational speed and flow-path structure on the structure of shock wave and flow-path field distribution are numerically analyzed. The simulation results indicate that the inlet compression efficiency and thermal efficiency of rotating ramjet engine are improved with the increment of exit back pressure when the inlet flow-path operates normally. But along with the increase of rotational speed, the change trends of pressure ratio and compression efficiency are opposite. Reasonable compromise is needed in improving the rotating speed of ram-rotor. In addition, the constant length should also be guaranteed in the throat of inlet flow-path, where a relatively stable shock train forms.
Research on Flow Characteristics of Pulverized Coal in a High Pressure Blow Tank
Authors: Pu Wenhao , Lu Peng , Yue Chen , Han Dong
Published: July 2013

In the present study, the flow characteristics of a top discharge blow tank at high pressure were investigated. Experiments on discharge properties of pulverized coal in dense-phase pneumatic conveying system with a high pressure blow tank were carried out. The influences of fluidizing velocity, pressurizing velocity, transporting differential pressure, sending pressure in the blow tank and pulverized coal diameter on the solid mass flow rate were studied. The experimental results indicated that the ratio of fluidizing velocity to pressurizing velocity was of great importance on the solid mass flow rate and there existed an optimum range. The solid mass flow rate increased as the transporting differential pressure and sending pressure increased. The increase of particle diameter led to the decrease of the solid mass flow rate. A model for determining the solid mass flow rate has been formulated using dimensional analysis. It was found that the calculation results were in good agreement with the experimental data. Finally, a kinetic–frictional model, which treated the kinetic and frictional stresses in an additive manner, was incorporated into the two fluid model based on the kinetic theory of granular flow to simulate the transient behaviors of the high pressure blow tank.
Physics and Chemistry of Ash in Gas Turbines: The HVOF Technique as a Powerful Simulation Tool
Authors: Verdy C. , Coddet C. , Montavon G. , Molière M. , Vierling M. , Sokolov D.
Published: July 2013

In a real gas turbine the fluid dynamics and the thermal conditions that prevail in the hot gas path and near hot parts walls are rather complex. This type of machine features indeed a very specific set of operating conditions, including: high gas temperatures and velocities, complex gas streamlines combined with a wide range and fast variability of operation load. The artifacts caused by internal cooling devices and thermal barriers or anti-corrosion coatings add to this complexity. For these reasons, predicting the fate of ash particles approaching or impinging a hot part represents a real challenge.

In addition the particular conditions that prevail in the combustors, especially: the pressurized and very oxidizing flames, the high temperature but short residence time, make the chemistry of ash formation fairly complex as well.

A work recently undertaken by GE Energy and LERMPS shows that HVOF (High Velocity Oxy-Fuel) facilities represent interesting tools to simulate the “in-flame generation” of ash particles and their fate when impinging on a part wall, provided the test conditions, especially the thermal and velocity fields, are properly adjusted and controlled.

The paper summarizes the development of HVOF experiments specifically devised to study the formation of ash particles with controlled chemistry and their deposition onto hot parts.
Techniques for Supersonic Turbojet Noise Reduction
Authors: Munday David , Cuppoletti Dan , Perrino Michael , Gutmark Ephraim , Burak Markus O. , Eriksson Lars-Erik
Published: July 2013

Observations and simulations are presented of a supersonic jet from a nozzle representative of high-performance military aircraft such as the Saab Gripen. The nozzle has a design Mach number of 1.56 and is examined at its design condition with a surrounding secondary flow at Mach numbers of 0.0, 0.1 and 0.3. Chevrons and internal fluidic injection by microjets each reduce the noise generated by the main jet.
A Critical Evaluation of Turbulence Modeling in a Model Combustor
Authors: Jiang Leiyong
Published: July 2013

Based on the previous benchmark studies on combustion, scalar transfer and radiation models, a critical evaluation of turbulence models in a propane-air diffusion flame combustor with interior and exterior conjugate heat transfers has been performed. Results obtained from six turbulence models are presented and compared in detail with a comprehensive database obtained from a series of experimental measurements. It is found that the Reynolds stress model (RSM), a second moment closure, is superior over the five popular eddy-viscosity two-equation models. Although the main flow patterns are captured by all six turbulence models, only the RSM is able to successfully predict the lengths of both recirculation zones and give fairly accurate predictions for mean velocity, temperature, CO2 and CO mole fractions, as well as turbulence kinetic energy in the combustor chamber. In addition, the realizable k-ε (Rk-ε) model illustrates better performance than four other two-equation models and can provide comparable results to those from the RSM for the configuration and operating conditions considered in the present study.
Determination of Steady State Gas Turbine Operation
Authors: Davison Craig R.
Published: July 2013

Repeatable measurement of engine performance requires the system to be near steady state. A technique is presented to assess how close engine operation is to steady state. It estimates the rate of change of the assessed parameter across the sample time and provides an associated confidence interval. This allows a minimum amount of test time to characterize performance and provides consistent criteria to assess steady state.

The technique can either be used online to determine when to take a steady state point or to find the optimal sample from a given data set. To make the technique feasible during testing a recursive method is developed to minimize the computational time.

The technique is demonstrated on known functions with random noise to benchmark its capabilities. This is followed by a demonstration on test data from a small turbo jet engine operated in an altitude facility, a turboprop on an outdoor test stand and an after-burning turbofan in an indoor test cell.
Application of an Optical Pyrometer to Newly Developed Industrial Gas Turbine
Authors: Taniguchi Tomoki , Tanaka Ryozo , Shinoda Yuji , Ryu Masanori , Moritz Norbert , Kusterer Karsten
Published: July 2013

Kawasaki Heavy Industries, Ltd (KHI) have developed a new industrial gas turbine, L30A. The turbine section composed of two-stage high pressure turbine and three-stage low pressure turbine. In the development period, a commercial pyrometer system was employed to measure blade temperatures under real engine condition. The pyrometer was equipped with an updated detector module and could measure lower temperature compared to the conventional one. Thus it could be used to measure all stages of blades with one pyrometer. The validity of the result was demonstrated by comparing the result with data obtained with other conventional techniques. With the pyrometer system the temperature distribution on the blade surface was easily available and cooling capabilities of blades were evaluated without taking much time.

This paper describes the detail of measurement and evaluation process.
Study of Gas/Liquid Behaviour Within an Aeroengine Bearing Chamber
Authors: Chandra Budi , Simmons Kathy , Pickering Stephen , Collicott Steven H. , Wiedemann Nikolas
Published: July 2013

Aeroengine bearing chambers typically contain bearings, seals, shafts and static parts. Oil is introduced for lubrication and cooling and this creates a two phase flow environment that may contain droplets, mist, film, ligaments, froth or foam and liquid pools. Some regions of the chamber contain a highly rotating air flow such that there are zones where the flow is gravity dominated and zones where it is rotation dominated.

The University of Nottingham Technology Centre in Gas Turbine Transmission Systems, is conducting an ongoing experimental program investigating liquid and gas flow behavior in a relevant highly rotating environment. Previously reported work by Chandra et al [1, 2] has investigated film thickness and residence volume within a simplified chamber consisting of outer cylindrical chamber, inner rotating shaft and cuboid off-take geometry (termed the generic deep sump).

Recently a more aeroengine relevant bearing chamber offtake geometry has been studied. This geometry is similar to one investigated by Chandra [3] at Purdue University and consists of a “sub-sump” region approached by curved surfaces linked to the bearing chamber.

The test chamber consists of an outer, stationary cylinder with an inner rotating shaft. The rig runs at ambient pressure and the working fluid (water) is introduced either via a film generator on the chamber wall or through holes in the shaft. In addition to visual data (high speed and normal video), liquid residence volume within the chamber and film thickness were the two numerical comparators chosen. Data was obtained for a number of liquid supply rates, scavenge ratios and shaft rotation speeds.

The data from the current model is compared to that from the earlier studies [1, 2, & 3]. The data shows that in contrast to the previously reported generic deep sump study, the residence volume of the curved wall deep sump (CWDS) designs is far less sensitive to shaft speed, liquid supply rate and scavenge ratio. The method of liquid supply only makes a significant difference at the lowest scavenge ratios. Residence volume data for the Nottingham CWDS is comparable, when appropriately scaled, to that for the Purdue design.

The film thickness data shows that at the lower shaft speeds investigated the flow is gravity dominated whereas at higher shaft speeds shear dominates.
Model of a Combined Cycle Steam Section for Use in an On-Line Fuzzy-Based Diagnosis System
Authors: Barbosa Rafael , Ferreira Sandro , Duarte Raphael , Ribeiro Pinto Paula , Paula e Silva Marília
Published: July 2013

In recent years, combined cycle power plants showed remarkable progress in the safe operation and reliability of their equipment, mostly because of the reliable control and instrumentation systems available today. However, these systems cannot detect and evaluate inconsistencies in the behaviour of equipment due to failures and avoid trips caused by catastrophic events. Computer models developed to simulate the power plant equipment are often employed in diagnosis tools in order to provide accurate healthy parameters that are compared to the field measured parameters.

In this work, the computer models built for the simulation of some of the main bottoming cycle equipment of a real power plant (steam turbine, HRSG, boiler feed water pumps and condenser) are described. These models were developed through characteristics maps and constitutive equations related to the fluid path analysis, implemented in Fortran language.

The results provided by the developed models for each equipment show good agreement with operational data at base and partial load in simulations that covered a good part of the load domain. Due to the good agreement between the measured parameters values and those calculated through simulation, these models are intended to be included in an on-line fuzzy-based diagnosis system.
Specifying and Benchmarking a Thin Film Model for Oil Systems Applications in ANSYS Fluent
Authors: Wang C. , Morvan H. P. , Hibberd S. , Cliffe K. A. , Anderson A. , Jacobs A.
Published: July 2013

A thin film model developed for calculating the oil film flow in aero-engine bearing chamber is described. The performance of the model, which has been implemented in the commercial computational fluid dynamics software product: ANSYS Fluent, is benchmarked by comparing the computational results obtained from a Nottingham UTC in-house code and a development version of Fluent. Both codes are used to solve thin film flow in a test case configuration and based on the same finite area method. With identified constraints, the two implementations agree well.
CFD Modeling of Pulverized Coal Combustion in an Industrial Burner
Authors: Torresi Marco , Fortunato Bernardo , Camporeale Sergio Mario , Saponaro Alessandro
Published: July 2013

The accurate prediction of pulverized coal combustion in industrial application still remains a great challenge. This is mainly due to the lack of high quality experimental data acquired during the operation of industrial plants.

This work describes the CFD model used in order to numerically simulate the pulverized coal combustion of a full scale, swirl stabilized, aerodynamically staged, industrial burner. In particular, two different combinations of devolatilization and char burnout models were investigated comparing the numerical results with available experimental data obtained during a burner test carried out, in full-scale configuration, in a 50 MWth, fully instrumented, test rig.

In order to avoid any unrealistic assumption on pulverized coal distribution at the burner inlet, the entire primary air duct for pulverized coal transportation has been considered. The main flow is computed solving the steady, incompressible, three-dimensional, Reynolds Averaged Navier-Stokes (RANS) equations, whereas the pulverized coal is simulated as a reacting discrete second phase in a Lagrangian frame of reference, computing the trajectories of the discrete phase entities, as well as heat and mass transfer.

The numerical analysis confirms the very good burner performance obtained during the tests with a very low percentage of fixed carbon left in the ashes.
On the Determination of the Transfer Function of Infinite Line Pressure Probes for Turbomachinery Applications
Authors: Van de Wyer Nicolas , Brouckaert Jean-François , Miorini Rinaldo L.
Published: July 2013

This paper deals with the use of the infinite line pressure probes (ILP) to measure fluctuating pressures in hot environments in turbomachinery applications. These probes, sometimes called waveguide measuring systems, and composed of a series of lines and cavities are using a remote pressure sensor. Ideally they should form a non-resonant system. This is however not always the case and the frequency response of these systems is of course limited by the tubing (diameter and length) but is also highly dependent on other geometrical parameters like sudden expansions or discontinuities in the tubing, or parasite cavities. The development of a new model for ILP simulation, based on the analogy between the propagation of the pressure waves in a line-cavity system and the electrical transmission line, is presented. Unlike the models based on the Bergh and Tijdeman equations, this approach allows the simulation of systems presenting parallel branches. This makes the model appropriate for the prediction of the frequency response of ILP. The model is validated by a comparison of the results with the theory of Bergh and Tijdeman, and with experimental results from the literature and from shock tube tests. Finally, the model is applied for the optimization of ILPs, representative of the systems used in the aeronautics industry, and compared to the experimental results performed on an axial compressor. In those tests, a typical ILP geometry is installed on the compressor casing to measure static pressure fluctuations in the rotor tip gap. Simultaneous measurements with a fast response flush-mounted sensor provided data for comparison and validation of the predicted transfer function.
Development of Fault Specific Soft Sensors With Application to Gas Turbine Diagnosis
Authors: Scheianu Dorin
Published: July 2013

The paper presents a method of diagnosis for a gas turbine installation monitored for a number of parameters by using tools specific to multivariate statistical analysis. Data is acquired periodically and organized as individual observation vectors. The objective is to detect the occurrence of a fault, to identify and discriminate the type of fault and eventually to find its cause. The author developed a new concept of soft sensor (similar to the sensor fusion in other works, see [1]) based on the intrinsic properties of the data historically acquired when the process was deemed to be in normal operating conditions, and on the current observation vector. This soft sensor was applied to an example of detecting the occurrence of a fault and characterizing it in the p-dimensional space of observation vectors associated with a proper metric.