bluuebunny/crossref_metadata_2025 huggingface dataset:
Visual features of microwave ignition of methane-air mixture in a constant volume cylinder
Authors: Wang Qiang , Zhang Guixin , Liu Yongxi , Hou Lingyun , Liu Cheng , Wang Zhi , Huang Jian
Published: November 2013

In this paper, the visual features of microwave ignition process were investigated. To realize microwave ignition under high pressure, a 2.45 GHz cylinder microwave resonator was designed. The electric field in the resonator and the quality factor were theoretically calculated. A needle-like coupling antenna was introduced to further enhance the maximum electric field to ensure the reliability of discharge. We ignited stoichiometric methane-air mixture at 10 bars by a 2 ms, 1 kW, 2.45 GHz microwave pulse. The photography images and pressure history of the ignition were obtained and analyzed. These results were compared with spark plug ignition under identical conditions.
Effect of electric field on the spray deposited poly (3,4-ethylenedioxythiophene): poly(styrenesulfonate) layer and its use in organic solar cell
Authors: Chaturvedi Neha , Alam Firoz , Kumar Swami Sanjay , Dutta Viresh
Published: November 2013

Spray process under different applied voltages (0 V to 700 V) is used for the deposition of poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL). The deposition of PEDOT:PSS film by spray process under the effect of electric field results in smoother film morphology, increase in conductivity and reduction in the sheet resistance. The improvement in surface morphology and conductivity enhancement of PEDOT: PSS films are the key to the improvement in the J–V characteristics of ITO/PEDOT:PSS/P3HT:PCBM/Al solar cell structures. The XPS peak height for PEDOT at 164.4 eV increased by 47% and that for PSS at 169.0 eV decreased by 30%, showing that the enhancement in the conductivity of the films deposited under electric field is due to the change in the PEDOT: PSS ratio. The organic solar cell using the electric field (created using 700 V) assisted spray deposited PEDOT:PSS film exhibit 42% and 69% improvement in the short circuit current density(Jsc) and power conversion efficiency, respectively, in comparison to the cells having PEDOT:PSS films deposited without the electric field.
Well-posedness, regularity and exact controllability for the problem of transmission of the Schrödinger equation
Authors: Allag I. , Rebiai S.
Published: November 2013

In this paper, we shall study the system of transmission of the Schrödinger equation with Dirichlet control and colocated observation. Using the multiplier method, we show that the system is well-posed with input and ouput spaceU=L2(Γ)U=L^{2}(\Gamma )and state spaceX=H−1(Ω).X=H^{-1}(\Omega ).The regularity of the system is also established, and the feedthrough operator is found to be zero. Finally, the exact controllability of the open-loop system is obtained by proving the observability inequality of the dual system.
Grapevine Trunk Diseases in British Columbia: Incidence and Characterization of the Fungal Pathogens Associated with Esca and Petri Diseases of Grapevine
Authors: Úrbez-Torres J. R. , Haag P. , Bowen P. , O'Gorman D. T.
Published: November 2013

Esca and Petri disease are two economically important grapevine diseases worldwide. This study reports for the first time the occurrence of both diseases on grapevines in British Columbia (BC) and subsequently in Canada. Visual assessment of 55,699 vines in 118 vineyards revealed a low incidence of esca with only 104 (0.2%) vines showing foliar symptoms. Young vine decline (YVD) was observed in 1,910 (7.8%) of 24,487 monitored young vines and in 52 (8%) of 654 young vines used as re-plants in mature vineyards. In 8 of 51 monitored young vineyards, YVD-affected vines ranged between 15 and 55%. Morphological studies along with DNA analyses of the ITS1-5.8S-ITS2, and part of the β-tubulin, actin, and translation elongation factor 1-α gene regions, allowed us to identify Cadophora luteoolivacea, Phaeomoniella chlamydospora, Phaeoacremonium iranianum, Togninia fraxinopennsylvanica, Togninia minima, and the novel species Phaeoacremonium canadense and Phaeoacremonium roseum from esca and Petri disease infected vines in BC. This study includes for the first time the EF1-α DNA marker in Phaeoacremonium spp. delineation. Pathogenicity studies showed all seven fungi to cause vascular symptoms similar to those observed in esca and Petri disease infected vines. Additionally, the “tiger-stripes” foliar symptom of esca was successfully reproduced when healthy potted vines were inoculated with BC isolates of Pa. chlamydospora, Pm. canadense, Pm. iranianum, T. fraxinopennsylvanica, and T. minima.
Comparing effective population sizes of dominant marine alphaproteobacteria lineages
Authors: Luo Haiwei , Swan Brandon K. , Stepanauskas Ramunas , Hughes Austin L. , Moran Mary Ann
Published: November 2013

A fundamental question in marine microbial ecology is how microbes adapt to ocean environments. Although numerically dominant populations are typically considered more successful, higher census population sizes (Nc) do not equate directly to a greater capability for adaptation. Instead, effective population size (Ne) determines the fate of deleterious and favourable mutations, and thus is a key parameter for determining the adaptive potential of a population. In the case of the SAR11 and Roseobacter lineages, two abundant heterotrophic bacteria in ocean surface waters with contrasting life history strategies, culture‐independent population surveys suggest that SAR11s have greater Nc than Roseobacters. To determine relative Ne, we compared the ratio of nonsynonymous to synonymous substitution rates (ω) of recently diverged lineages of these taxa. Values of ω associated with several of the Roseobacter subclades were lower than for SAR11 subclades, suggesting greater Ne in these cases. Most Roseobacter lineages also had smaller ω values compared with an atypical basal Roseobacter lineage with a large Nc. This finding provides insight into variability in Ne across two important marine bacterial lineages, and provides an evolutionary context for considering how heterotrophic marine bacteria may differ in their ability to adapt to changing ocean habitats.
Barriers to Patient‐Centered Care: A Thematic Analysis Study
Authors: Esmaeili Maryam , Ali Cheraghi Mohammad , Salsali Mahvash
Published: November 2013

Purpose

To explore nurses’ attitudes and experience toward the barriers to achieving patient‐centered care in the critical care setting.

Methods

A qualitative exploratory design with thematic analysis approach was used to collect and analyze data, and identify barriers to patient‐centered care. Data collection was based on in‐depth semi‐structured interviews.

Findings

Data analyses resulted in the identification of three themes: (a) lack of common understanding of teamwork, (b) individual barriers, and (c) organizational barriers.

Conclusion

This study goes beyond reporting problems with patient‐centered care to try to understand why patients do not always receive high‐quality care.

Implication for Nursing Practice

For achieving patient‐centered care, not only nurses’ individual efforts in following up‐to‐date evidence‐based practice and having a holistic view are necessary, but also team coordination, organizational support, and elimination of nursing job problems.
Review of the impact of presbyopia on quality of life in the developing and developed world
Authors: Goertz Ariana D. , Stewart William C. , Burns William R. , Stewart Jeanette A. , Nelson Lindsay A.
Published: November 2013

Purpose

To examine the public health impact of presbyopia regarding its effect on quality of life (QoL) and society in both the developed and developing worlds.

Methods

A database was created from articles found on PubMed, the Cochrane Library and Science Direct using the following search terms: presbyopia, QoL, accommodation, impact, cost, prevention, treatment and public health. Articles were accepted into the database if they addressed presbyopia and public health.

Results

This study showed in the developed world presbyopic subjects treated with reading glasses suffered a reduction in QoL parameters compared with those who were younger and emmetropic. A small minority of subjects were assessed to be a candidate for additional non‐spectacle treatment measures. In undeveloped areas, the manifestations of presbyopia were similar to the developed world in symptoms, age and reduced QoL. However, there was inadequate treatment of this condition, even with reading glasses. The availability of reading glasses ranged from 6 to 45%. Activities of daily living could not be accomplished as easily without near correction of reading. Reasons described for the lack of correction included: lack of access to medical care, poor awareness of decreased near vision, lack of motivation and cost. Overall scant data exist regarding presbyopia and its impact and how treatment affects QoL.

Conclusions

This review suggests that the effect of presbyopia and its treatments on QoL remain poorly described and incompletely treated, especially in developing areas of the world.
Professor John Scott, folate and neural tube defects
Authors: Hoffbrand A. Victor
Published: November 2013

John Scott (1940–2013) was born in Dublin where he was to spend the rest of his career, both as an undergraduate and subsequently Professor of Biochemistry and Nutrition at Trinity College. His research with the talented group of scientists and clinicians that he led has had a substantial impact on our understanding of folate metabolism, mechanisms of its catabolism and deficiency. His research established the leading theory of folate involvement with vitamin B12 in the pathogenesis of vitamin B12 neuropathy. He helped to establish the normal daily intake of folate and the increased requirements needed either in food or as a supplement before and during pregnancy to prevent neural tube defects. He also suggested a dietary supplement of vitamin B12 before and during pregnancy to reduce the risk of neural tube defects. It would be an appropriate epitaph if fortification of food with folic acid became mandatory in the UK and Ireland, as it is in over 70 other countries.
The association between children's contact with people with disabilities and their attitudes towards disability: a systematic review
Authors: MacMillan Megan , Tarrant Mark , Abraham Charles , Morris Christopher
Published: November 2013

Aim

The aim of this review was to systematically review and synthesize observational evidence of associations between children's naturally varying contact with people with disabilities and their attitudes towards disability.

Method

A comprehensive search was conducted across multiple databases. Studies were included if they measured children's contact with people with disabilities and their attitudes towards disability. Qualitative research and studies that experimentally varied the amount of contact children had were excluded. Data were synthesized in a narrative review.

Results

There were 35 studies that met the inclusion criteria: 22 of these reported a statistically significant association between contact with people with disabilities and more positive attitudes towards disability; two studies reported a negative association between contact and attitudes; and 11 studies reported no association. Incomplete reporting of the methods and results across studies limited the conclusions that could be drawn.

Interpretation

Studies identified in this review generally indicate that children's contact with people with disabilities is associated with more positive attitudes towards disability. There is a need for more rigorous research to examine the effect of children's contact with people with disabilities on their attitudes towards disability.
Evaluation of Left Ventricular Diastolic Function by Global Strain Rate Imaging in Patients with Obstructive Hypertrophic Cardiomyopathy: A Simultaneous Speckle Tracking Echocardiography and Cardiac Catheterization Study
Authors: Chen Shi , Yuan Jiansong , Qiao Shubin , Duan Fujian , Zhang Jiafen , Wang Hao
Published: November 2013

Background

Impaired left ventricular (LV) diastolic function is a common pathophysiological feature of patients with hypertrophic cardiomyopathy (HCM). The noninvasive evaluation of diastolic function in these patients remains a challenge. Speckle tracking echocardiography (STE) provides direct information on intrinsic myocardial function and may improve the diagnostic of diastolic dysfunction in HCM patients.

Methods and Results

We retrospectively analyzed 51 patients with obstructive HCM (HOCM). Strain rate (SR) curves were obtained for 18 different segments of the LV myocardium. The peak SR during the isovolumic relaxation period (SRIVR) and the peak early diastolic strain rate (SRE) were measured for each segment. Cardiac catheterization was performed within 24 hours after echocardiographic analysis. LV end‐diastolic pressure (LVEDP) was measured and time constant of myocardial relaxation (τ) was calculated. We therefore correlated STE‐derived with invasive indices and compared it with flow and tissue Doppler measurements. SRIVR and SRE were significantly reduced in all 51 HOCM patients (0.16 ± 0.09%/sec and 0.71 ± 0.25%/sec).The ratio of peak early mitral inflow velocities to SRIVR and SRE (E/SRIVR and E/SRE) correlated well with LVEDP (r = 0.760, P < 0.001; r = 0.401, P = 0.004). Receiver operating characteristic analysis shown E/SRE ratio had the largest under curve area in predicting HOCM patients with seriously elevated LVEDP. In addition, SRIVR and SRE significantly related with τ (r = −0.611, P < 0.001; r = −0.369, P = 0.008).

Conclusions

Diastolic function was seriously impaired in HOCM patients. The E/SRE ratio can be used to predict LVEDP with acceptable accurate in HOCM patients. In addition, SRIVR is a reliable parameter to assess LV relaxation in patients with HOCM.
Impact of short‐term exposure to low subzero temperatures on egg hatch in the hemlock looper, Lambdina fiscellaria
Authors: Delisle Johanne , Labrecque Alain , Royer Lucie , Bernier‐Cardou Michèle , Bauce Éric , Charest Martin , Larrivée Sandra
Published: November 2013

The frequency of extreme events, such as cold spells, is expected to increase under global warming. Therefore, the ability of insects to survive rapid changes in temperature is an important aspect to investigate in current population ecology. The hemlock looper (HL), Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae), a defoliator of boreal balsam fir forests in eastern Canada, overwinters at the egg stage on tree trunks and branches where eggs can be exposed to very low subzero air temperatures. Using eggs from the island of Newfoundland (NL) and Quebec mainland (QC), we undertook field and laboratory experiments to determine: (1) their supercooling point (SCP) in mid‐January and mid‐February; (2) overwintering mortality; (3) cold tolerance to various combinations of subzero temperatures (−25, −30, −33, −35, or −37 °C) and exposure durations (2, 4, 8, 12, or 16 h); and (4) potential causes of death at subzero temperatures above the SCP. Regardless of population or sampling date, eggs supercooled on average at −40.1 °C. In the field, 59% of eggs from either population that overwintered in Sainte‐Foy (QC) and Corner Brook (NL) hatched successfully, whereas none did in Armagh (QC) or Epaule (QC). In the laboratory, 50% of eggs survived after 4 h at −34.4 °C or after 14 h at −32.9 °C. In contrast, regardless of exposure duration, >50% of eggs hatched at temperatures ≥−33 °C, but <50% did so at ≤−35 °C, suggesting high pre‐freeze mortality. However, when eggs were attached to thermocouples and exposed to temperatures ranging from −25 to −37 °C for 16 h, 69% froze at temperatures of −35 to −37 °C, but only 2% did at −25 or −30 °C. Time to freeze decreased as subzero temperatures declined, and this was more evident in island eggs than in mainland eggs. Overall, eggs can freeze after a brief exposure to subzero temperatures higher than the standard SCP, and are thus highly vulnerable to cold spells.
Thai nurses’ perspectives on the use of complementary and alternative medicine among Thai breast cancer survivors in northern Thailand
Authors: Wanchai Ausanee , Armer Jane M , Stewart Bob R
Published: November 2013

Breast cancer survivors are more likely to seek complementary and alternative medicine (CAM) for their health and well‐being than other cancer patients. The purpose of the study was to describe how Thai nurses perceive the use of CAM in Thai breast cancer survivors. An ethno‐nursing research method was used. Fifteen Thai nurses who had experience in taking care of Thai breast cancer survivors who used CAM from a tertiary care referral and resource centre in the lower northern part of Thailand were interviewed. Two major themes emerged from this study: Meaning of care practices in CAM was seen as: (i) an additional beneficial choice for health; and (ii) emotional and psychological healing. Nurses should be concerned about CAM use in Thai breast cancer survivors. Open communication about CAM helps ensure that safe and holistic care is provided. Further research to enhance integration of CAM into health care is needed.
Evaluating temporal variation in Citizen Science Data against temporal variation in the environment
Authors: Snäll Tord , Forslund Pär , Jeppsson Tobias , Lindhe Anders , O’Hara Robert B.
Published: November 2013

Citizen Science Data (CSD) is increasingly contributing to the assessment of biodiversity and ecosystems. However, there is a need to evaluate the usefulness of CSD for different purposes. Ideally, CSD from populations should be evaluated against independent population data collected using a proper sampling design, but such data are lacking for almost all species. We propose an approach for evaluating CSD against environmental data. First, an evaluation model is formulated based on knowledge of how environmental variables affect population dynamics. Second, the hypotheses of the evaluation model are tested statistically. Support for the evaluation model is interpreted as support for the CSD. We applied the approach to six longhorn beetle species using Swedish data from 1930–2000. The evaluation model assumed that early summer temperature affects larval development time. We found support for the evaluation model in two species, and some evidence in its favour in one species. This suggests that the CSD from these species reflect true inter‐annual variation. We also found statistical evidence for population trends in three to four species. In two of these, the evaluation model was supported thus providing particular support for the trend estimates. Lack of support for the evaluation model may be due to biological inaccuracy, the general characteristics of CSD, or low resolution of the environmental evaluation data. We also discuss alternative environmental data for evaluating CSD.
Changes of community composition at multiple trophic levels due to hunting in Nigerian tropical forests
Authors: Effiom Edu O. , Birkhofer Klaus , Smith Henrik G. , Olsson Ola
Published: November 2013

Hunting in tropical forests decimates large mammals, and this may have direct and indirect effects on other trophic levels and lead to trophic cascades. We compared replicated sites of hunted and protected forests in southeastern Nigeria, with respect to community composition of primates, other mammals, birds, plant seedlings, and mature trees. We make predictions regarding the community composition at the different trophic levels. In forests where large primates are rare, we hypothesize that their ecological role will not be fully compensated for by small frugivores. We apply multivariate methods to assess changes in community composition of mammals, birds, and seedlings, controlling for any differences between sites in the other groups, including mature trees. Medium and large (4–180 kg) primates were much rarer in hunted sites, while porcupine and rock hyrax increased in abundance with hunting. In contrast, the community composition of birds was similar in both types of forests. Seedling communities were significantly related to the community composition of mammals, and thus strongly affected by hunting. In protected forests primate dispersed plant seedling species dominated, whereas in hunted forests the seedling community was shifted towards one dominated by abiotically dispersed species. This was probably both a consequence of reduced seed dispersal by primates, and increased seed predation by rodents and hyrax. Hence we found no evidence for buffering effects on tree regeneration through functional compensation by non‐hunted animals (such as birds). Our results highlight how seedling communities are changed by the complex plant–animal intera ctions, triggered by the loss of seed dispersers. The results predict a rarity of primate‐dispersed trees in future tropical forest canopies; a forest less diverse in timber and non‐timber resources.
Interspecific scaling patterns of talar articular surfaces within primates and their closest living relatives
Authors: Yapuncich Gabriel S. , Boyer Doug M.
Published: November 2013

The articular facets of interosseous joints must transmit forces while maintaining relatively low stresses. To prevent overloading, joints that transmit higher forces should therefore have larger facet areas. The relative contributions of body mass and muscle‐induced forces to joint stress are unclear, but generate opposing hypotheses. If mass‐induced forces dominate, facet area should scale with positive allometry to body mass. Alternatively, muscle‐induced forces should cause facets to scale isometrically with body mass. Within primates, both scaling patterns have been reported for articular surfaces of the femoral and humeral heads, but more distal elements are less well studied. Additionally, examination of complex articular surfaces has largely been limited to linear measurements, so that ‘true area’ remains poorly assessed. To re‐assess these scaling relationships, we examine the relationship between body size and articular surface areas of the talus. Area measurements were taken from microCTscan‐generated surfaces of all talar facets from a comprehensive sample of extant euarchontan taxa (primates, treeshrews, and colugos). Log‐transformed data were regressed on literature‐derived log‐body mass using reduced major axis and phylogenetic least squares regressions. We examine the scaling patterns of muscle mass and physiological cross‐sectional area (PCSA) to body mass, as these relationships may complicate each model. Finally, we examine the scaling pattern of hindlimb musclePCSAto talar articular surface area, a direct test of the effect of mass‐induced forces on joint surfaces. Among most groups, there is an overall trend toward positive allometry for articular surfaces. The ectal (= posterior calcaneal) facet scales with positive allometry among all groups except ‘sundatherians’, strepsirrhines, galagids, and lorisids. The medial tibial facet scales isometrically among all groups except lemuroids. Scaling coefficients are not correlated with sample size, clade inclusivity or behavioral diversity of the sample. Muscle mass scales with slight positive allometry to body mass, andPCSAscales at isometry to body mass.PCSAgenerally scales with negative allometry to articular surface area, which indicates joint surfaces increase faster than muscles' ability to generate force. We suggest a synthetic model to explain the complex patterns observed for talar articular surface area scaling: whether ‘muscles or mass’ drive articular facet scaling is probably dependent on the body size range of the sample and the biological role of the facet. The relationship between ‘muscle vs. mass’ dominance is likely bone‐ and facet‐specific, meaning that some facets should respond primarily to stresses induced by larger body mass, whereas others primarily reflect muscle forces.
Controls on methane emissions from Alnus glutinosa saplings
Authors: Pangala Sunitha R. , Gowing David J. , Hornibrook Edward R. C. , Gauci Vincent
Published: November 2013

Recent studies have confirmed significant tree‐mediated methane emissions in wetlands; however, conditions and processes controlling such emissions are unclear. Here we identify factors that control the emission of methane from Alnus glutinosa.

Methane fluxes from the soil surface, tree stem surfaces, leaf surfaces and whole mesocosms, pore water methane concentrations and physiological factors (assimilation rate, stomatal conductance and transpiration) were measured from 4‐yr old A. glutinosa trees grown under two artificially controlled water‐table positions.

Up to 64% of methane emitted from the high water‐table mesocosms was transported to the atmosphere through A. glutinosa. Stem emissions from 2 to 22 cm above the soil surface accounted for up to 42% of total tree‐mediated methane emissions. Methane emissions were not detected from leaves and no relationship existed between leaf surface area and rates of tree‐mediated methane emissions. Tree stem methane flux strength was controlled by the amount of methane dissolved in pore water and the density of stem lenticels.

Our data show that stem surfaces dominate methane egress from A. glutinosa, suggesting that leaf area index is not a suitable approach for scaling tree‐mediated methane emissions from all types of forested wetland.
Neonatal pain
Authors: Walker Suellen M.
Published: November 2013

Effective management of procedural and postoperative pain in neonates is required to minimize acute physiological and behavioral distress and may also improve acute and long‐term outcomes. Painful stimuli activate nociceptive pathways, from the periphery to the cortex, in neonates and behavioral responses form the basis for validated pain assessment tools. However, there is an increasing awareness of the need to not only reduce acute behavioral responses to pain in neonates, but also to protect the developing nervous system from persistent sensitization of pain pathways and potential damaging effects of altered neural activity on central nervous system development. Analgesic requirements are influenced by age‐related changes in both pharmacokinetic and pharmacodynamic response, and increasing data are available to guide safe and effective dosing with opioids and paracetamol. Regional analgesic techniques provide effective perioperative analgesia, but higher complication rates in neonates emphasize the importance of monitoring and choice of the most appropriate drug and dose. There have been significant improvements in the understanding and management of neonatal pain, but additional research evidence will further reduce the need to extrapolate data from older age groups. Translation into improved clinical care will continue to depend on an integrated approach to implementation that encompasses assessment and titration against individual response, education and training, and audit and feedback.
Optimisation and standardisation of an immunoagglutination assay for the diagnosis of Trypanosoma cruzi infection based on latex‐(recombinant antigen) complexes
Authors: Garcia Valeria S. , Gonzalez Verónica D. G. , Marcipar Ivan S. , Vega Jorge R. , Gugliotta Luis M.
Published: November 2013

Objective

To determine the conditions under which the immunoagglutination assay to detect Chagas disease, obtained from a novel latex‐(chimeric recombinant antigen) complex, shows greater discrimination between the responses of a positive control serum and a negative control serum.

Methods

The following variables were determined: (i) the sensitisation mechanism, (ii) the emulsifier employed for protein desorption, (iii) the reaction time, (iv) the ionic strength of the reaction medium, (v) the particle concentration, (vi) the presence of blocking agents, (vii) the presence of polyethyleneglycol as potentiator of reaction and (viii) the antigen and antibody concentrations. The search of optimal conditions was investigated by varying one variable at a time. To this effect, monodisperse latex particles sensitised with a recombinant chimeric protein (CP1) were subjected to different conditions. The agglutination reaction was followed by measuring the changes in the optical absorbance by turbidimetry.

Results

The maximum discrimination between negative and positive sera was obtained at a reaction time of 5 min, when latex complexes with a concentration of covalently coupled protein of 2.90 mg/m2 were put in contact with undiluted sera in buffer borate pH 8–20 mm containing glycine (0.1 m) and polyethyleneglycol 8000 (3% w/v). Finally, the latex–protein complex was tested under the obtained optimal conditions, with a panel of Trypanosoma cruzi‐positive sera, leishmaniasis‐positive sera and ‐negative sera for both parasites.

Conclusion

The immunoagglutination test based on the latex‐CP1 complex could be used as a screening method for detecting Chagas disease. This test is rapid, easy to implement and could be used under field conditions; but its results should be confirmed by reference techniques like ELISA, HAI, and IFI.
Mass Transfer in Single Bends Under Annular Two Phase Flow Conditions
Authors: Mazhar H. , Ewing D. , Cotton J. S. , Ching C. Y.
Published: November 2013

The distributions of the mass transfer coefficient in horizontal 90 deg bends were measured under a range of two phase annular flow conditions. A dissolving wall technique at a high Schmidt number (Sc = 1280) is used for the measurements. The maximum mass transfer occurred on the centerline of the bend outer wall at an angle of approximately 50 deg from the bend inlet under all tested conditions. The area of maximum mass transfer rate was found to span approximately 30 deg in the circumferential direction. A second region of enhanced mass transfer occurred on the latter part of the bend with a local maximum occurring slightly off the bend centerline in some cases. Changing the air and water superficial velocities (Jv = 22–30 m/s, JL = 0.17–0.41 m/s) showed that the air velocity had a larger effect on the mass transfer rates than the water velocity; however, the effect of the water velocity on the mass transfer was not insignificant.
Molecular Dynamics Studies of Homogeneous and Heterogeneous Thermal Bubble Nucleation
Authors: Chen Min , Yang Juekuan , Gao Yandong , Chen Yunfei , Li Deyu
Published: November 2013

Thermal bubble nucleation was studied using molecular dynamics for both homogeneous and heterogeneous argon systems using isothermal-isobaric (NPT) and isothermal-isostress (NPzzT) ensembles. Unlike results using NVE and NVT ensembles, no stable nanoscale bubble exists in the NPT ensembles, but instead, the whole system changes into vapor phase. In homogeneous binary systems, reducing the interaction strength between alien atoms and argon atoms significantly decreases the nucleation temperature; however, enhancing the interaction strength only increases the nucleation temperature marginally. For nanoconfined heterogeneous NPzzT ensembles with liquid argon between two solid plates, the nucleation temperature increases as the channel height decreases if the channel height is less than ∼7.63 nm. More interestingly, in this regime, the bubble nucleation temperature could be significantly higher than the corresponding homogeneous nucleation temperature. This observation is different from the common expectation that homogeneous thermal bubble nucleation, as a result of fundamental thermodynamic instability, sets an upper limit for thermal bubble nucleation temperature under a given pressure. However, the result can be understood physically based on the more ordered arrangement of atoms, which corresponds to a higher potential energy barrier.
On the Unsteady Formation of Secondary Flow Inside a Rotating Turbine Blade Passage
Authors: Schneider C. M. , Schrack D. , Kuerner M. , Rose M. G. , Staudacher S. , Guendogdu Y. , Freygang U.
Published: November 2013

This paper addresses the unsteady formation of secondary flow structures inside a turbine rotor passage. The first stage of a two-stage low pressure turbine is investigated at a Reynolds Number of 75 000. The design represents the third and the fourth stages of an engine representative low pressure turbine. The flow field inside the rotor passage is discussed in the relative frame of reference using the streamwise vorticity. A multi-stage URANS prediction provides the time-resolved data set required. It is supported by steady and unsteady area traverse data acquired with five-hole probes and dual-film probes at rotor inlet and exit. The unsteady analysis reveals a non-classical secondary flow field inside the rotor passage of this turbine. The secondary flow field is dominated by flow structures related to the upstream nozzle guide vane. The interaction processes at hub and casing appear to be mirror images and have characteristic forms in time and space. Distinct loss zones are identified which are associated with vane-rotor interaction processes. The distribution of the measured isentropic stage efficiency at rotor exit is shown which is reduced significantly by the secondary flow structures discussed. Their impacts on the steady as well as on the unsteady angle characteristics at rotor exit are presented to address the influences on the inlet conditions of the downstream nozzle guide vane.
Inlet Condition Effects on the Tip Clearance Flow With Zonal Detached Eddy Simulation
Authors: Riéra William , Castillon Lionel , Marty Julien , Leboeuf Francis
Published: November 2013

In the present study, the influence of the inlet condition on the tip clearance flow of an axial compressor is investigated. Two different ZDES computations are carried out and compared to RANS and URANS computations as well as to experimental data. A rotating distortion map of the flow cartography is set as inlet condition for the first ZDES computation. An azimuthally averaged inlet condition is used for the second one and uncouples the rotor tip-leakage vortex flutter phenomenon, which stems from the arrival of the Inlet Guide Vane wake, from the behaviour inherent to the rotor tip-leakage vortex. In the studied configuration, the Inlet Guide Vane tip vortex reveals to lower the effects from double leakage on the rotor. The topology of the rotor tip-leakage vortex is described and its development is analysed.
Unsteady Work Processes Within a Low Pressure Turbine Vane Passage
Authors: Marx Martin , Lipfert Martin , Rose Martin G. , Staudacher Stephan , Korte Detlef
Published: November 2013

A two-stage low pressure turbine is tested within the co-operation project between the Institute of Aircraft Propulsion Systems (ILA) and MTU Aero Engines GmbH. With experimental data taken in the altitude test facility this study aims to analyze the origin and effect of unsteady pressure fluctuations causing unsteady work in the second stator vane. Measurements at aerodynamic design conditions cover steady and unsteady surface pressure data on the mid span streamline position. Unsteady pressure fluctuations are identified close to the throat plane area, which are influenced by both upstream and downstream events such as wake and potential field interaction. Upstream moving static pressure waves can be identified. To support the experimental results, URANS CFD predictions of the whole turbine configuration were performed. The numerical approach is suitable to reproduce the observed phenomena and allows a deeper investigation. The observed pressure pulsations influence the local unsteady work done to and by the fluid. An evaluation of particle paths in the second stator vane indicates an isentropic energy transfer from free stream to wake fluid. Due to this unsteady energy exchange the momentum deficit of the wake gets reduced, resulting in a potential benefit on the mixing loss.
Unsteady Vibration of a Gas Turbine Compressor Blade at Subsonic Near-Stall Conditions
Authors: Yamaguchi Kazuyuki , Takahashi Yasuo
Published: November 2013

Cascade wind tunnel tests were conducted to clarify unsteady blade vibration characteristics near stall conditions. An oscillating strain and pressure on a blade surface were measured. An aerodynamic damping ratio was also measured using the sweep excitation method and the operational modal analysis. Moreover, an unsteady blade vibration response and aerodynamic damping ratios were calculated using a three-dimensional computational fluid dynamics and a three-dimensional structural finite element method.

As a result of the experiments, the natural frequency component oscillated by the broadband frequency component of the fluid force was dominant in the stress, while the discrete low frequency components appeared in the pressure. The amplitudes of the stress and pressure increased when the Mach number or the incidence increased. As a result of the calculations, the discrete low frequency components appeared in the pressure, and those components and the natural frequency components appeared in the stress. The experimental and calculation results of the stress amplitude were generally in agreement.

The measured damping ratios increased when the Mach number increased. The dispersion of the measured damping ratio using the operational modal analysis was small. The calculated damping ratio was 1.3–1.8 times larger than the measured result.
Damping and Inertia Coefficients for Two End Sealed Squeeze Film Dampers With a Central Groove: Measurements and Predictions
Authors: San Andrés Luis , Seshagiri Sanjeev
Published: November 2013

Aircraft engine rotors, invariably supported on rolling element bearings with little damping, are particularly sensitive to rotor imbalance and sudden maneuver loads. Most engines incorporate Squeeze Film Dampers (SFDs) as means to dissipate mechanical energy from rotor motions and to ensure system stability. The paper quantifies experimentally the dynamic forced performance of two end sealed SFDs with dimensions and operating envelope akin to those in actual jet engine applications. The current experimental results complement and extend prior research conducted with open ends SFDs [21]. In the tests, two journals make for two SFD configurations, both with diameter D = 127 mm and nominal radial film clearance c = 0.127 mm. One short length damper has film lands with extent L = 12.7 mm, while the other has 25.4 mm (= 2L) land lengths. A central groove with length LG = L and depth at ¾ L separates the film lands. A light viscosity lubricant is supplied into the central groove via 3 orifices, 120° apart, and then flows through the film lands whose ends are sealed with tight piston rings. The oil pushes through the piston rings to discharge at ambient pressure. In the tests, a static load device pulls the damper structure to increasing eccentricities (max. 0.38c) and external shakers exert single-frequency loads, 50 Hz–250 Hz, inducing circular orbits with amplitudes equaling ∼5% of the film clearance. The lubricant feed and groove pressures and flow rates through the top and bottom film lands are recorded to determine the flow resistances through the film lands and the end seals. Measured dynamic pressures in the central groove are as large as those in the film lands thus demonstrating a strong flow interaction, further intensified by the piston ring end seals which are effective in preventing side leakage. Dynamic pressures and reaction loads are substantially higher than those recorded with the open ends dampers. Comparisons to test results for two identical damper configurations but open ended [21] demonstrate at least a thrice increase in direct damping coefficients and no less than a twice increment in added mass coefficients. Predictions from a physics based model that includes the central groove, the lubricant feed holes and the end seals’ flow conductances are in agreement with the test results for the short length damper. For the long damper, the predicted damping coefficients are in good agreement with the measurements while the added masses are under predicted by ∼25%.
Temperature-Based Optimization of Film Cooling in Gas Turbine Hot Gas Path Components
Authors: Viana Felipe A. C. , Madelone Jack , Pai Niranjan , Khan Genghis , Baik Sanghum
Published: November 2013

To achieve high efficiency, modern gas turbines operate at temperatures that exceed melting points of metal alloys used in turbine hot gas path parts. Parts exposed to hot gas are actively cooled with a portion of the compressor discharge air (e.g., through film cooling) to keep the metal temperature at levels needed to meet durability requirements. However, to preserve efficiency, it is important to optimize the cooling system to use the least amount of cooling flow. In this study, film cooling optimization is achieved by varying cooling hole diameters, hole to hole spacing, and film row placements so that the specified targets for maximum metal temperature are met while preserving (or saving) cooling flow. The computational cost of the high-fidelity physics models, the large number of design variables, the large number and nonlinearity of responses impose severe challenges to numerical optimization. Design of experiments and cheap-to-evaluate approximations (radial basis functions) are used to alleviate the computational burden. Then, the goal attainment method is used for optimizing of film cooling configuration. The results for a turbine blade design show significant improvements in temperature distribution while maintaining/reducing the amount of used cooling flow.
Modified Modal Domain Analysis of a Bladed Rotor Using Coordinate Measurement Machine Data on Geometric Mistuning
Authors: Vishwakarma Vinod , Sinha Alok , Bhartiya Yasharth , Brown Jeffery M.
Published: November 2013

Modified Modal Domain Analysis (MMDA), a reduced order modeling technique, is applied to a geometrically mistuned integrally bladed rotor to obtain its natural frequencies, mode shapes and forced response. The geometric mistuning of blades is described in terms of proper orthogonal decomposition (POD) of the coordinate measurement machine (CMM) data. Results from MMDA are compared to those from the full (360 degrees) rotor ANSYS model. It is found that the MMDA can accurately predict natural frequencies, mode shapes, and forced response. The effects of the number of POD features and the number of tuned modes used as bases for model reduction are examined. Results from frequency mistuning approaches, fundamental mistuning model (FMM) and subset of nominal modes (SNM), are also generated and compared to those from full (360 degree) rotor ANSYS model. It is clearly seen that FMM and SNM are unable to yield accurate results whereas MMDA yields highly accurate results.
Experimental Study on Lateral and Torsional Vibration of Cracked Rotor With Torsional Excitation
Authors: Liu Chao , Jiang Dongxiang
Published: November 2013

Crack failures in rotating machinery can result in catastrophic accidents, and they are are difficult to detect online. Condition monitoring is widely applied in field to detect changes of vibration, and form diagnostic features. However, effective features in vibration of the cracked rotor need more tests, especially validating the features with experiments. This work carried out an experimental study on cracked rotors in laboratory. The experiments are as following: (I) vibration of the rotor in normal condition is firstly tested, where lateral vibration and torsional vibration are measured; (II) torsional excitation is exerted on driven end of rotor system, and vibration characteristics of the rotor are tested; (III) cracked rotors are tested with transverse and slant cracks, respectively. With the measured signals, comparisons of vibrations in normal rotor and cracked rotors are carried out. The results show that, the transverse crack introduces more significant changes in 1X frequency and coupled frequency, while the slant crack employs larger changes in 2X frequency. And variation of phases of 1X frequency is presented. Also, the crack plays an impact on the torsional responses.
Structural Dynamic Analysis Approach Used in a GE Heavy Duty Gas Turbine Combustor for MTBM Enhancement
Authors: lal Jangid Bihari , Provenzale Michele , Del Puglia Eugenio
Published: November 2013

Gas turbine combustors are subjected to vibrations due to combustion dynamics pressure and rotor imbalance force which results in forced excitation of hardware. Such structural vibration leads to high cycle fatigue and wear out of contact interfaces of combustor, thus limiting hardware durability with reduced maintenance intervals. To have more realistic hardware life prediction for both failure modes, it is vital to understand structural dynamic behavior of combustor assembly in the presence of vibratory loads.

This paper describes the methodology used in developing MS5002D LHE combustor assembly linearized finite element dynamic models, the strategy to calibrate them with experimental data and the approach used to perform a forced responded analysis with harmonically varying combustion dynamics pressure and rotor imbalance force. Study shows that with adopted approach, an acceptable modal correlation between the model and the experimental test rig can be achieved. The forced dynamic response analysis results, in terms of dynamic stress distribution, interface sliding displacements and contact loads, represent the needed inputs for life prediction and for addressing the design improvements.
Localizing Unbalance Faults in Rotating Machinery
Authors: Walker R. B. , Perinpanayagam S. , Jennions I. K.
Published: November 2013

Excessive levels of unbalance in rotating machinery continue to contribute to machine downtime and unscheduled and costly maintenance actions. Whilst unbalance as a rotordynamic fault has been studied in great detail during the last century, the localization of unbalance within a complex rotating machine is today often performed in practice using little more than ‘rules of thumb’. In this work, localizing excessive unbalance has been studied from an experimental perspective through the use of two rotordynamic test rigs fitted with multiple disks. Sub-synchronous non-linear features in the frequency domain have been identified and studied as a method of aiding the localization of unbalance faults, particularly in situations where sensor placement options are limited. The results of the study are discussed from the perspective of next-generation Integrated Vehicle Health Management (IVHM) systems for rotating machines.
Simulation of the Compressor Stage of a Turbocharger: Validation of the Open Source Library OpenFOAM
Authors: Heinrich Martin , Schwarze Rüdiger
Published: November 2013

A segregated pressure-based solver for compressible flows for turbomachinery applications has been developed to investigate the flowfield the compressor side of a turbocharger. The solver is based on the open source CFD library OpenFOAM. Local time stepping is employed, the total energy equation is implemented and the multiple reference frame approach is utilized. The solver has been validated using two test cases for centrifugal compressors. The first case is the simlation of one blade passage of the DLR centrifugal compressor for highspeed subsonic flows. The complete compressor side of a turbocharger is used as second test case, including ported shroud and volute. The performance maps are calculated for several rotational speeds. In each case, numerical results and test bench measurements show a good similarity and the slopes are met well. The performance is overpredicted by up to 5 %, though.