bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer and Flow Phenomena in a Swirl Chamber Simulating Turbine Blade Internal Cooling
Authors: Hedlung C. R. , Ligrani P. M. , Moon H.-K. , Glezer B.
Published: April 2010

Heat transfer and fluid mechanics results are given for a swirl chamber whose geometry models an internal passage used to cool the leading edge of a turbine blade. The Reynolds numbers investigated, based on inlet duct characteristics, include values that are the same as in the application (18,000–19,400). The ratio of absolute air temperature between the inlet and wall of the swirl chamber ranges from 0.62 to 0.86 for the heat transfer measurements. Spatial variations of surface Nusselt numbers along swirl chamber surfaces are measured using infrared thermography in conjunction with thermocouples, energy balances, digital image processing, and in situ calibration procedures. The structure and streamwise development of arrays of Go¨rtler vortex pairs, which develop along concave surfaces, are apparent from flow visualizations. Overall swirl chamber structure is also described from time-averaged surveys of the circumferential component of velocity, total pressure, static pressure, and the circumferential component of vorticity. Important variations of surface Nusselt numbers and time-averaged flow characteristics are present due to arrays of Go¨rtler vortex pairs, especially near each of the two inlets, where Nusselt numbers are highest. Nusselt numbers then decrease and become more spatially uniform along the interior surface of the chamber as the flows advect away from each inlet.
Education Committee Best Paper of 1995 Award: Methods of Classical Mechanics Applied to Turbulence Stresses in a Tip Leakage Vortex
Authors: Moore J. G. , Schorn S. A. , Moore J.
Published: April 2010

Moore et al. measured the six Reynolds stresses in a tip leakage vortex in a linear turbine cascade. Stress tensor analysis, as used in classical mechanics, has been applied to the measured turbulence stress tensors. Principal directions and principal normal stresses are found. A solid surface model, or three-dimensional glyph, for the Reynolds stress tensor is proposed and used to view the stresses throughout the tip leakage vortex. Modeled Reynolds stresses using the Boussinesq approximation are obtained from the measured mean velocity strain rate tensor. The comparison of the principal directions and the three-dimensional graphic representations of the strain and Reynolds stress tensors aids in the understanding of the turbulence and what is required to model it.
Time-Accurate Euler Simulation of Interaction of Nozzle Wake and Secondary Flow With Rotor Blade in an Axial Turbine Stage Using Nonreflecting Boundary Conditions
Authors: Fan S. , Lakshminarayana B.
Published: April 2010

The objective of this paper is to investigate the three-dimensional unsteady flow interactions in a turbomachine stage. A three-dimensional time-accurate Euler code has been developed using an explicit four-stage Runge–Kutta scheme. Three-dimensional unsteady nonreflecting boundary conditions are formulated at the inlet and the outlet of the computational domain to remove the spurious numerical reflections. The three-dimensional code is first validated for two-dimensional and three-dimensional cascades with harmonic vortical inlet distortions. The effectiveness of the nonreflecting boundary conditions is demonstrated. The unsteady Euler solver is then used to simulate the propagation of nozzle wake and secondary flow through the rotor and the resulting unsteady pressure field in an axial turbine stage. The three-dimensional and time-dependent propagation of nozzle wakes in the rotor blade row and the effects of nozzle secondary flow on the rotor unsteady surface pressure and passage flow field are studied. It was found that the unsteady flow field in the rotor is highly three dimensional and the nozzle secondary flow has significant contribution to the unsteady pressure on the blade surfaces. Even though the steady flow at the midspan is nearly two dimensional, the unsteady flow is three dimensional and the unsteady pressure distribution cannot be predicted by a two-dimensional analysis.
Modeling Tip Clearance Effects in Multistage Axial Compressors
Authors: Baghdadi S.
Published: April 2010

A variety of techniques for simulating the effects of rotor tip clearances in multistage axial compressors is discussed. Proper recognition of stage coupling and rematching effects is shown to be key to successful modeling of the overall behavior of actual engine compression systems. The application of a relatively simple one-dimensional unsteady row-by-row systems analysis is presented and shown to compare well to test data from several engine compressors.
The Effects of Adverse Pressure Gradients on Momentum and Thermal Structures in Transitional Boundary Layers: Part 1—Mean Quantities
Authors: Mislevy S. P. , Wang T.
Published: April 2010

The effects of adverse pressure gradients on the thermal and momentum characteristics of a heated transitional boundary layer were investigated with free-stream turbulence ranging from 0.3 to 0.6 percent. The acceleration parameter, K, was kept constant along the test section. Both surface heat transfer and boundary layer measurements were conducted. The boundary layer measurements were conducted with a three-wire probe (two velocity wires and one temperature wire) for two representative cases, K1 = −0.51 × 10−6 and K2 = −1.05 × 10−6. The surface heat transfer measurements were conducted for K values ranging from −0.045 × 10−6 to −1.44 × 10−6 over five divergent wall angles. The Stanton numbers of the cases with adverse pressure gradients were greater than that of the zero-pressure-gradient turbulent correlation in the low-Reynolds-number turbulent flow, and the difference increased as the adverse pressure gradient was increased. The adverse pressure gradient caused earlier transition onset and shorter transition length based on Rex, Reδ*, and Reθ in comparison to zero-pressure-gradient conditions. As expected, there was a reduction in skin friction as the adverse pressure gradient increased. In the U+−Y+ coordinates, the adverse pressure gradients had a significant effect on the mean velocity profiles in the near-wall region for the late-laminar and early transition stations. The mean temperature profile was observed to precede the velocity profile in starting and ending the transition process, opposite to what occurred in favorable pressure gradient cases in previous studies. A curve fit of the turbulent temperature profile in the log-linear region for the K2 case gave a conduction layer thickness of Y+ = 9.8 and an average Prt = 0.71. In addition, the wake region of the turbulent mean temperature profile was significantly suppressed.
Effects of Streamwise Pressure Gradient on Turbulent Spot Development
Authors: Gostelow J. P. , Melwani N. , Walker G. J.
Published: April 2010

A pressure distribution representative of a controlled diffusion compressor blade suction surface is imposed on a flat plate. Boundary layer transition in this situation is investigated by triggering a wave packet, which evolves into a turbulent spot. The development from wave packet to turbulent spot is observed and the interactions of the turbulent spot with the ongoing natural transition and the ensuing turbulent boundary layer are examined. Under this steeply diffusing pressure distribution, strong amplification of primary instabilities prevails. Breakdown to turbulence is instigated near the centerline and propagates transversely along the wave packet until the turbulent region dominates. An extensive calmed region is present behind the spot, which persists well into the surrounding turbulent layer. Celerities of spot leading and trailing edges are presented, as is the spanwise spreading half-angle. Corresponding measurements for spots under a wide range of imposed pressure gradients are compiled and the present results are compared with those of other authors. Resulting correlations for spot propagation parameters are provided for use in computational modeling of the transition region under variable pressure gradients.
Validation of Three-Dimensional Euler Methods for Vibrating Cascade Aerodynamics
Authors: Gerolymos G. A. , Vallet I.
Published: April 2010

The purpose of this work is to validate a time-nonlinear three-dimensional Euler solver for vibrating cascades aerodynamics by comparison with available theoretical semi-analytical results from flat-plate cascades. First the method is validated with respect to the purely two-dimensional theory of Verdon (for supersonic flow) by computing two-dimensional vibration (spanwise constant) in linear three-dimensional cascades. Then the method is validated by comparison with the theoretical results of Namba and the computational results of He and Denton, for subsonic flow in a linear three-dimensional cascade with three-dimensional vibratory mode. Finally the method is compared with results of Chi from two subsonic rotating annular cascades of helicoi¨dal flat plates. Quite satisfactory agreement is obtained for all the cases studied. A first code-to-code comparison is also presented.
Unsteady Numerical Simulations of Radial Temperature Profile Redistribution in a Single-Stage Turbine
Authors: Dorney D. J. , Schwab J. R.
Published: April 2010

Experimental data taken from gas turbine combustors indicate that the flow exiting the combustor can contain both circumferential and radial temperature gradients. A significant amount of research recently has been devoted to studying turbine flows with inlet temperature gradients, but no total pressure gradients. Less attention has been given to flows containing both temperature and total pressure gradients at the inlet. The significance of the total pressure gradients is that the secondary flows and the temperature redistribution process in the vane blade row can be significantly altered. Experimental data previously obtained in a single-stage turbine with inlet total temperature and total pressure gradients indicated a redistribution of the warmer fluid to the pressure surface of the airfoils, and a severe underturning of the flow at the exit of the stage. In a concurrent numerical simulation, a steady, inviscid, three-dimensional flow angle distribution, In the current research program, a series of unsteady two-and three-dimensional Navier–Stokes simulations have been performed to study the redistribution of the radial temperature profile in the turbine stage. The three-dimensional analysis predicts both the temperature redistribution and the flow underturning observed in the experiments.
The Design and Performance of a High Work Research Turbine
Authors: Vlasic E. P. , Girgis S. , Moustapha S. H.
Published: April 2010

This paper describes the design and performance of a high work single-stage research turbine with a pressure ratio of 5.0, a stage loading of 2.2, and cooled stator and rotor. Tests were carried out in a cold flow rig and as part of a gas generator facility. The performance of the turbine was assessed, through measurements of reaction, rotor exit conditions and efficiency, with and without airfoil cooling. The measured cooled efficiency in the cold rig was 79.9 percent, which, after correcting for temperature and measuring plane location, matched reasonably well the efficiency of 81.5 percent in the gas generator test. The effect of cooling, as measured in the cold rig, was to reduce the turbine efficiency by 2.1 percent. A part-load turbine map was obtained at 100, 110, and 118 percent design speed and at 3.9, 5.0, and 6.0 pressure ratio. The influence of speed and the limit load pattern for transonic turbines are discussed. The effect of the downstream measuring distance on the calculated efficiency was determined using three different locations. An efficiency drop of 3.2 percent was measured between the rotor trailing edge plane and a distance four chords downstream.
Film Cooling With Compound Angle Holes: Heat Transfer
Authors: Sen B. , Schmidt D. L. , Bogard D. G.
Published: April 2010

Heat transfer coefficients have been measured for film cooling injection from a single row of holes laterally directed with a compound angle of 60 deg. Two hole configurations were tested, round holes and holes with a diffusing expansion at the exit. Streamwise-directed round holes were also tested as a basis for comparison. All the holes were inclined at 35 deg with respect to the surface. The density ratio was 1.0, momentum flux ratios ranged from I = 0.16 to 3.9, and mass flux ratios ranged from M = 0.4 to 2.0. Results are presented in terms of hf/ho, the ratio of film cooling heat transfer coefficient to the heat transfer coefficient for the undisturbed turbulent boundary layer at the same location. Results indicate that for the streamwise directed holes, the heat transfer rates are close to the levels that exist without injection. Similarly, at low momentum flux ratio, holes with a large compound angle had little effect on heat transfer rates. However, at high momentum flux ratios, holes with a large compound angle had significantly increased heat transfer levels. The results were combined with adiabatic effectiveness results to evaluate the overall performance of the three geometries. It is shown that for evaluation of film cooling performance with compound angle injection, especially at high momentum flux ratios, it is critical to know the heat transfer coefficient, as the adiabatic effectiveness alone does not determine the performance. Compound angle injection at high momentum flux ratios gives higher effectiveness values than streamwise-directed holes, but the higher heat transfer levels result in poorer overall performance.
Novel Electrode-Supported Honeycomb Solid Oxide Fuel Cell: Design and Fabrication
Authors: Yamaguchi Toshiaki , Suzuki Toshio , Fujishiro Yoshinobu , Awano Masanobu , Shimizu Sota
Published: April 2010

We have developed a novel and highly effective electrode-supported solid oxide fuel cell (SOFC) with honeycomb structure for intermediate temperature operation. Honeycomb-supported SOFC is known as one of the most compact SOFCs due to the large electrode area per unit volume, which is attractive with regard to space saving and cost reduction. In this study, we summarized the design of the channel shape, size, and sequence using numerical simulation and technologies to realize the designed honeycomb SOFC fabrication. The calculation results showed that the wall thickness and the channel size of the honeycomb had to be less than 0.22 mm and more than 0.3 mm, respectively, for the sufficient net channel surface and the acceptable pressure drop. Also, a cathode-honeycomb-supported SOFC can be the more efficient form with lower current collection resistance, as compared with the anode-supported type. The actual fabricated honeycomb SOFC exhibited a high volumetric power density above 1 W/cm3 at 650°C under wet H2 fuel flow.
The Effect of Inlet Parameters on Fluid Flow and Cell Performance at Cathode of a Proton Exchange Membrane Fuel Cell
Authors: Gulan Utku , Turkoglu Hasmet , Ar Irfan
Published: April 2010

In this study, the fluid flow and cell performance in cathode side of a proton exchange membrane (PEM) fuel cell were numerically analyzed. The problem domain consists of cathode gas channel, cathode gas diffusion layer, and cathode catalyst layer. The equations governing the motion of air, concentration of oxygen, and electrochemical reactions were numerically solved. A computer program was developed based on control volume method and SIMPLE algorithm. The mathematical model and program developed were tested by comparing the results of numerical simulations with the results from literature. Simulations were performed for different values of inlet Reynolds number and inlet oxygen mole fraction at different operation temperatures. Using the results of these simulations, the effects of these parameters on the flow, oxygen concentration distribution, current density and power density were analyzed. The simulations showed that the oxygen concentration in the catalyst layer increases with increasing Reynolds number and hence the current density and power density of the PEM fuel cell also increases. Analysis of the data obtained from simulations also shows that current density and power density of the PEM fuel cell increases with increasing operation temperature. It is also observed that increasing the inlet oxygen mole fraction increases the current density and power density.
Proton Exchange Membrane Fuel Cell Air Management in Automotive Applications
Authors: Blunier Benjamin , Miraoui Abdellatif
Published: April 2010

This paper deals with the state-of-the-art of air management in proton exchange membrane fuel cell (PEMFC), which is a challenge because commercial compressors and humidification systems are not suitable for automotive applications. Major tasks and requirements for compression and humidification subsystems have been introduced, showing that compression and humidification subsystems cannot be decoupled. A higher working pressure around 2.5 bar is recommended because it permits the PEMFC to have a higher efficiency, as well as a lighter stack and a lower volume than an equivalent PEMFC working at a lower pressure; moreover, the water necessary for humidifying the membrane decreases, resulting in a simple management. For high pressure fuel cells, centrifugal compressors or positive displacement compressors with internal compression have to be preferred than those with external compression because they offer a better efficiency. The built-in compression ratio has to be as close as possible to the fuel cell working pressure to ensure maximum efficiency. Downstream or integrated direct water injection has shown many advantages for air humidification compared with other methods because of its controllability, low power consumption, and compactness.
The Effect of Mechanical Fatigue on the Lifetimes of Membrane Electrode Assemblies
Authors: Pestrak Michael , Li Yongqiang , Case Scott W. , Dillard David A. , Ellis Michael W. , Lai Yeh-Hung , Gittleman Craig S.
Published: April 2010

Long-term durability of the membrane electrode assembly (MEA) in proton exchange membrane (PEM) fuel cells is one of the major technological barriers to the commercialization of fuel cell vehicles. The cracks in the electrode layers of the MEA, referred to as mud-cracks, are potential contributors to the failure in the PEM. To investigate how these mud-cracks affect the mechanical durability of the MEA, pressure-loaded blister tests are performed at 90°C to determine the biaxial fatigue strength of Gore-Primea® series 57 MEA. In these volume-controlled tests, leaking rate is determined as a function of fatigue cycles. The failure is defined to occur when the leaking rate exceeds a specified threshold. Postmortem characterization using bubble point testing and field emission scanning electron microscopy (FESEM) was conducted to provide visual documentation of leaking failure sites. The analysis of the experimental leaking data indicates that the MEA has much shorter lifetimes at the same nominal stress levels than membrane samples without the electrode layers. FESEM photomicrographs of leaking locations identified via the bubble point testing show cracks in the membrane that are concentrated within the mud-cracks of the electrode layer. These two pieces of information indicate that the mud-cracks within the electrode layers contribute to the leaking failures of the MEA assembly. For the fuel cell industry, this study suggests there is an opportunity to reduce the likelihood of membrane pinhole failures by reducing the size and occurrence of the mud-cracks formed during the MEA processing or by increasing the fatigue resistance (including the notch sensitivity) of the membrane material within the MEA.
Development of a Reference Electrode for a PEMFC Single Cell Allowing an Evaluation of Plate Potentials
Authors: Andre Johan , Guillet Nicolas , Petit Jean-Pierre , Antoni Laurent
Published: April 2010

Increasing lifetime and performance is critical for proton exchange membrane fuel cell (PEMFC) using stainless steel plates. A good compromise between passivity and electrical contact resistance of the plate material is required. Measuring the potential of each plate during fuel cell operation is of paramount importance to lead to relevant ex situ tests in order to investigate new materials. From a review on methods used for potential measurements, the present work focused on the realization and use of a dynamic hydrogen electrode (DHE) device as a reference electrode in a PEMFC single cell and its evaluation in terms of accuracy and drift. With classic reference electrodes introduced into the flow field, measurements were shown to be irrelevant because of the impossibility to ensure good and stable ionic conductivity between the reference electrode and the plate when operating the cell. Several examples of DHE found in the literature were reviewed and used to realize a DHE, which showed correct accuracy and stability of its potential under fully humidified conditions. The experimental device was shown to be reliable and easily adaptable for different single cells. It was used to investigate transient phenomena while cycling a cell, but needs some improvement when the cell is operated with unsaturated gases.
Kinetic Analysis of C4 Alkane and Alkene Pyrolysis: Implications for SOFC Operation
Authors: Al Shoaibi Ahmed , Dean Anthony M.
Published: April 2010

Pyrolysis experiments of isobutane, isobutylene, and 1-butene were performed over a temperature range of 550–750°C and a pressure of ∼0.8 atm. The residence time was ∼5 s. The fuel conversion and product selectivity were analyzed at these temperatures. The pyrolysis experiments were performed to simulate the gas-phase chemistry that occurs in the anode channel of a solid-oxide fuel cell (SOFC). The experimental results confirm that molecular structure has a substantial impact on pyrolysis kinetics. The experimental data show considerable amounts of C5 and higher species (∼2.8 mole % with isobutane at 750°C, ∼7.5 mole % with isobutylene at 737.5°C, and ∼7.4 mole % with 1-butene at 700°C). The C5+ species are likely deposit precursors. The results confirm that hydrocarbon gas-phase kinetics have substantial impact on a SOFC operation.
Synchronous breast cancer and lymphoma: a case series and a review of the literature
Authors: Cuff Katharine E , Dettrick Andrew J , Chern Boris
Published: April 2010

Four patients with synchronous breast cancer and lymphoma are described. In all cases, the lymphoma was an unexpected finding in the histopathology of the axillary lymph-node dissection. The diagnosis of synchronous malignancies poses challenges for both the diagnosing pathologist and the treating clinicican.
Methylation of cyclin-dependent kinase inhibitors, XAF1, JUNB, CDH13 and soluble Wnt inhibitors in essential thrombocythaemia
Authors: Chim C S , Fung T K , Liang R
Published: April 2010

Background

Methylation of genes regulating cell-cycle check-point (INK4 cyclin-dependent kinase inhibitors), apoptosis (XAF1), adhesion (CDH13), JUNB and Wnt signalling (soluble Wnt inhibitors) has been implicated in pathogenesis of haematological and epithelial cancers.

Method

The authors studied the methylation status of CDKN2A, CDKN2B, XAF1, CDH13, JUNB and a panel of soluble Wnt inhibitors includingWIF1, DKK3, APC, SFRP1, SFRP2, SFRP4andSFRP5by methylation-specific PCR in 31 bone marrow and 21 peripheral blood samples of patients with essential thrombocythaemia.

Results and discussion

There was no evidence of hypermethylation of all these genes in both the BM and PB samples. Therefore, in contrast to myeloid leukaemias, methylation of these genes regulating the cell cycle, apoptosis, adhesion and Wnt signalling does not play an important role in the pathogenesis of myeloproliferative diseases. Whether differential methylation may occur in the progenitor or mature blood cell compartments remains to be verified. Our study contributes to the literature on methylation in chronic myeloproliferatve diseases.
Pelvic lymph nodes: distribution and nodal tumour burden of urothelial bladder cancer
Authors: Seiler Roland , von Gunten Michael , Thalmann George N , Fleischmann Achim
Published: April 2010

Aims

To evaluate the number of lymph nodes and the lymph node tumour burden in different anatomical pelvic regions to better asses the impact of variations in the extent of lymphadenectomy on reported LN parameters and pelvic tumour clearance.

Methods

162 patients with lymph-node-positive urothelial carcinoma of the bladder were treated by cystectomy and extended pelvic lymphadenectomy. Various lymph node parameters were determined separately for the three pelvic regions (external iliac, obturator and internal iliac).

Results

Of 4080 evaluated lymph nodes (median 25 per patient, range 8–55) 39%, 35% and 26% (p<0.05) were found in the external iliac, obturator and internal iliac region, respectively. The distribution of the 625 lymph node metastases (median two per patient, range 1–35) was not significantly different between the regions (external iliac 33%, obturator 38%, internal iliac 29%). However, the median diameter of largest metastasis and total diameter of all metastases were smallest in the internal iliac region (external iliac 0.85 cm, 1.1 cm; obturator 0.8 cm, 1.0 cm; internal iliac 0.6 cm, 0.8 cm; p<0.03, p<0.05; for median diameter of largest metastasis and total diameter of all metastases, respectively). Metastases in only one region were found in 33% of patients (external iliac 13%, obturator 10%, internal iliac 10%); these three groups showed no significant difference in survival. No difference was detected in lymph node parameters between genders.

Conclusions

Lymph node counts and retrieval of metastases depends on the extent of pelvic lymphadenectomy. Dissection not including the internal iliac region misses 26% of all pelvic lymph nodes, 29% of metastases, and understages a substantial number of patients as pN0 (10%).
Evolution of a beach–dune system following a catastrophic storm overwash event: Greenwich Dunes, Prince Edward Island, 1936–2005
Authors: Mathew Sojan , Davidson-Arnott Robin G.D. , Ollerhead Jeff
Published: April 2010

Greenwich Dunes, Prince Edward Island National Park, is a sandy mainland and barrier spit beach–dune complex stretching for about 10 km along the northeast shore of Prince Edward Island, Canada. In October 1923, surge associated with an intense storm produced catastrophic overwash along the whole length of the study area. Subsequent evolution of the system was quantified from historic aerial photographs taken in 1936, 1953, 1971, 1997, and 2005. Orthophoto mosaics were generated for each photo set using PCI Geomatica OrthoEngine, a digital photogrammetric software. Linear changes in shoreline position and areal changes in geomorphic units were evaluated for each photo set. In addition, digital elevation models (DEMs) were extracted from the 1953, 1971, and 1997 aerial photos, enabling analysis of topographic and volumetric changes. The 1936 photos show complete destruction of all foredunes, with overwash and transgressive dunes extending 300 to 600 m inland. A descriptive model of the stages of evolution of the system is proposed based on the processes controlling overwash healing and dune stabilization. Detailed topographic and volumetric changes associated with the development of an extensive transgressive dunefield and subsequent stabilization as a result of reduced sand supply due to the growth of a new vegetated foredune complex and vegetation colonization are doccumented for each stage. It was nearly 40 years before a continuous foredune system was re-established and a further 30 years before the inland transgressive dunes became completely stabilized.
The Advocate ophiolite mantle, Baie Verte, Newfoundland: regional correlations and evidence for metasomatismGeological Survey of Canada, Earth Sciences Sector, Contribution 20090211.
Authors: Bédard Jean H. , Escayola Monica
Published: April 2010

Mantle rocks of the Advocate ophiolite near Flatwater Pond (Baie Verte, Newfoundland) are dominated by harzburgite tectonites, which are extensively converted to listvenite along the Baie Verte Road fault and represent a potential gold exploration target. Most Advocate harzburgites have forsteritic olivine (Fo90.5 to Fo93) and Cr-spinels, with Cr# (= 100Cr/(Cr + Al)) between 52 and 64 and Mg# (= 100Mg/(Mg + Fe2+)) between 56 and 68. These mineral chemical signatures, together with high whole-rock MgO (46%–48%), low Al2O3 (<1%), and TiO2 (<0.003%), imply the Advocate harzburgites are refractory residues after ca. 25%–35% melting. Cr-spinel compositions of Advocate mantle rocks overlap with Cr-spinels from the mantle rocks of the Point Rousse and Betts Cove ophiolites, with Mg# higher than those of Bay of Islands or Thetford Mines mantle Cr-spinels. Although refractory in terms of major elements and mineral chemistry, Advocate harzburgites contain high La–Ce–Pr–Pb–Nd–Sm–Zr contents suggestive of pervasive metasomatism. Similar geochemical signatures occur in all ophiolitic mantle rocks from the Baie Verte Peninsula examined so far. The enrichments are not consistent with supra-subduction zone syn-melting metasomatism as observed in other Appalachian ophiolites. The apparent absence of visible metasomatic channels in most outcrops suggests that metasomatism occurred before obduction by diffuse percolation, but the nature and origin of the metasomatic agent remain speculative. The similarities of mineral and whole-rock geochemistry imply that all mantle rocks from Baie Verte ophiolites are correlative and may represent remnants of a single obducted slab.
Detrital zircon characteristics of the Lower Cretaceous Isachsen Formation, Sverdrup Basin: source constraints from age and Hf isotope data
Authors: Røhr Torkil S. , Andersen Tom , Dypvik Henning , Embry Ashton F.
Published: April 2010

Detrital zircons from the Lower Cretaceous Isachsen Formation of the Sverdrup Basin, Canadian Arctic Archipelago, have been dated by the U–Pb method and analyzed for Hf isotopes by laser ablation microprobe – inductively coupled plasma – mass spectrometry (LAM–ICP–MS). Five samples from four locations on Ellesmere and Axel Heiberg islands display similar ranges of U–Pb ages, with significant zircon populations at 2.8–2.6, 1.9–1.8, 1.7–1.6, and 1.2–1.0 Ga. Major hiatuses occur between 2.4 and 2.0 Ga and from 0.96 to 0.5 Ga. Low initial εHfvalues indicating recycled crust components are significant in Palaeoproterozoic (1.9–1.8 Ga) and Neoarchaean (2.8–2.6 Ga) zircon populations. Other U–Pb age populations in the studied samples are dominated by zircon with positive εHfvalues, indicating a significant contribution from mantle-derived protoliths. The εHfvalues seen within a given U–Pb age population are generally consistent, with only minor scatter among the different samples. U–Pb and Hf data closely resemble previously published data from Lower Cretaceous rocks in northern Greenland, suggesting they have the same origin. The data are also largely consistent with the East Greenland Caledonides and the Precambrian basement of Greenland and northern Canada as predominant sources of zircon for the studied sandstones. However, based on the level of similarity between data from the Wandel Sea Basin and Sverdrup Basin sediments and on previous Nd isotope work in the Sverdrup Basin, it is likely that the sediments represent redeposited lower and middle Palaeozoic sediments.
Gap disturbance regime in an old-growthFagus–Abiesforest in the Dinaric Mountains, Bosnia-Herzegovina
Authors: Nagel Thomas A. , Svoboda Miroslav
Published: April 2010

Due to the scarcity of old-growth forests in much of Europe, there is little quantitative information on disturbance processes that influence forest dynamics. However, this information is crucial for forest management that tries to emulate patterns and processes in natural forests. We quantified the gap disturbance regime in an old-growth forest dominated by European beech ( Fagus sylvatica L.) and silver fir ( Abies alba Miller) in the Dinaric Mountains of Bosnia and Herzegovina. We sampled 87 gaps in four stands using line-intercept sampling. The percentages of forest area in canopy gaps and expanded gaps ranged from 12% to 17.2% and 35.5% to 39.7%, respectively. Although many of the gaps were small (<100 m2) and formed from a single gapmaker, large canopy openings >1000 m2with numerous gapmakers made up a disproportionate amount of the total gap area. More than half the gaps had more than one gapmaker and were often in separate decay classes, indicating gaps had expanded over time during separate disturbance events. Furthermore, 51% of all gapmakers were uprooted or wind-snapped, whereas only 22% died standing. These results suggest that wind disturbance plays an important role in creating intermediate to large canopy openings through both gap formation and gap expansion processes.
Density and distribution of advance regeneration in mountain pine beetle killed lodgepole pine stands of the Montane Spruce zone of southern British Columbia
Authors: Nigh Gordon D. , Antos Joseph A. , Parish Roberta
Published: April 2010

Insect outbreaks, such as the current mountain pine beetle ( Dendroctonus ponderosae Hopkins) outbreak in lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forests in British Columbia, are major disturbances in many forests. After an insect outbreak, the advance regeneration typically forms a new canopy, which may be adequate for timber objectives in some stands. Our purpose was to quantify and then model the abundance and spatial distribution of advance regeneration (trees <10.0 m tall). We sampled understory and overstory trees in 28 lodgepole pine stands in south-central British Columbia at two spatial scales: 0.1 ha plots and 25 m2 subplots. We developed models predicting advance regeneration abundance and spatial distribution. Density of advance regeneration averaged 2689 trees/ha (range 120 to 23 000 trees/ha), most of which were <1 m tall. Although advance regeneration was clumped, 75% of the subplots contained at least one individual. Models indicated negative relationships of advance regeneration abundance to overstory basal area and density. Over half the stands had enough advance regeneration to form new stands of adequate density, indicating that use of advance regeneration is a viable option in this mountain pine beetle outbreak and probably other insect disturbances.
Optimal on- and off-site forest carbon sequestration under existing timber supply constraints in northern New Brunswick
Authors: Neilson Eric T. , MacLean David A. , Meng Fan-Rui , Hennigar Chris R. , Arp Paul A.
Published: April 2010

We describe a procedure to maximize carbon (C) sequestration and apply it to a 428 000 ha industrial forest management area in northern New Brunswick, Canada. Stand-specific C yield tables and C residency periods in harvested wood products were used as inputs to a linear programming model to maximize on- and off-site C sequestration in forest land. Five management scenarios were evaluated. A scenario that maximized on-site forest C sequestration for 80 years, respecting “business-as-usual” harvest constraints, projected an extra 3 t C·ha–1 across the forest management area compared with the business-as-usual scenario, with net C storage potential (forest C + forest C in products – emissions produced from decayed wood products) resulting in approximately 1 Mt C. A scenario to double softwood harvest led to a projected decrease in the forest C pool by approximately 5 t C·ha–1 from 2007 to 2082 and overall storage decrease of almost 2 Mt C from the base run. Other scenarios to increase or decrease harvest volumes by 10% resulted in overall C storage increases of 1.6 Mt C and almost 2.7 Mt C, respectively, above the base run. All scenarios resulted in net sinks of C after the 80 year simulation.
Applying ant colony optimization metaheuristic to solve forest transportation planning problems with side constraints
Authors: Contreras Marco A. , Chung Woodam , Jones Greg
Published: April 2010

Forest transportation planning problems (FTPP) have evolved from considering only the financial aspects of timber management to more holistic problems that also consider the environmental impacts of roads. These additional requirements have introduced side constraints, making FTPP larger and more complex. Mixed-integer programming (MIP) has been used to solve FTPP, but its application has been limited by the difficulty of solving large, real-world problems within a reasonable time. To overcome this limitation of MIP, we applied the ant colony optimization (ACO) metaheuristic to develop an ACO-based heuristic algorithm that efficiently solves large and complex forest transportation problems with side constraints. Three hypothetical FTPP were created to test the performance of the ACO algorithm. The environmental impact of forest roads represented by sediment yields was incorporated into the economic analysis of roads as a side constraint. Four different levels of sediment constraints were analyzed for each problem. The solutions from the ACO algorithm were compared with those obtained from a commercially available MIP solver. The ACO solutions were equal to or slightly worse than the MIP solution, but the ACO algorithm took only a fraction of the computation time that was required by the MIP solver.
Contrasting downed woody debris dynamics in managed and unmanaged northern hardwood stands
Authors: Vanderwel Mark C. , Thorpe Hilary C. , Shuter Jennifer L. , Caspersen John P. , Thomas Sean C.
Published: April 2010

The reported effects of selection silviculture on downed woody debris (DWD) vary. To investigate the processes underlying potential management impacts on DWD stocks and fluxes, we conducted a repeated census of downed wood in selection-harvested, selectively harvested, and unmanaged (old-growth) stands in central Ontario. DWD was significantly more abundant in stands harvested within the last 20 years than in stands harvested earlier, and shifted towards more advanced decay classes over the first 20 years after harvest. These results are consistent with persistence of a harvest-related DWD pulse for up to two decades in managed stands. The transition of DWD from early and middle decay classes to more advanced decay classes proceeded more slowly in managed than unmanaged stands. Species type, identity of fungal fruiting bodies, presence of a cut surface, and plot moisture class were significant predictors of variation in decay dynamics within particular decay classes; however, these factors did not account for observed differences in decay-class transitions between managed and unmanaged stands. A decay class matrix model projected DWD half-lives of 19 years for unmanaged stands and 21 years for managed stands. Over the long term, slower decay dynamics may help somewhat in maintaining relatively high DWD abundances in stands managed under selection silviculture.
ON THE MINIMUM ABSOLUTE VALUE OF THE DISCRIMINANT OF ABELIAN FIELDS OF DEGREE p2
Authors: INTERLANDO J. CARMELO , LOPES JOSÉ OTHON DANTAS , NETO TRAJANO PIRES DA NÓBREGA , FLORES ANDRÉ LUIZ
Published: April 2010

Let p be a prime number. A formula for the minimum absolute value of the discriminant of all Abelian extensions of ℚ of degree p2is given in terms of p.
HIGHER-ORDER DISCONTINUOUS MODELING OF FRACTURING IN CONCRETE USING THE NUMERICAL MANIFOLD METHOD
Authors: KOUREPINIS DIMITRIOS , PEARCE CHRIS , BIĆANIĆ NENAD
Published: April 2010

This paper presents an overview of the numerical manifold method (NMM) as a unifying framework for modeling fracturing phenomena in quasi-brittle materials, and particularly in concrete. NMM is attractive due to its potential to provide an efficient framework for modeling the entire transition between continuum to discontinuum, from a continuum point of view, without remeshing. To achieve this, the following characteristics are employed: (1) discontinuities are introduced in a discrete manner, without remeshing; (2) the approximation is improved locally, for any arbitrary level, without remeshing. Furthermore, essential boundary conditions are enforced using projection matrices and higher-order boundary issues are identified.
SIMULATION OF TOPPLING FAILURE OF ROCK SLOPE BY NUMERICAL MANIFOLD METHOD
Authors: ZHANG GUOXIN , ZHAO YAN , PENG XIAOCHU
Published: April 2010

As one type of rock slope failures, topping failure can be accurately simulated only when several aspects are correctly calculated such as deformation and stress, contacts between blocks, contact stress, movement of blocks, open/close of contacts between blocks, development of failure plane, and crack generation and propagation. Current numerical methods encounter many difficulties in simulating toppling failure, especially for rock slope with lots of rock-bridges. Numerical manifold method (NMM) can deal with these highly discontinuous problems and be used to model the toppling failure of rock slopes. This paper first introduces the fundamental principles, modeling of contacts, calculation of contact force and stress, and modeling of failure in NMM. Then, several case studies are conducted to testify the accuracy and convergence of method; comparisons with method, based on limit equilibrium principle, which was proposed by Goodman and Bray (G–B method) and centrifuge test are conducted. Finally, the topping failure of left bank of one high dam is simulated. Results show that the NMM can be used to correctly calculate the toppling safety factor, simulate the failure process of slope toppling, and accurately model the whole failure process of rock slopes with many rock-bridges.
Arguments for an information-centric internetworking architecture
Authors: Trossen Dirk , Sarela Mikko , Sollins Karen
Published: April 2010

The current Internet architecture focuses on communicating entities, largely leaving aside the information to be exchanged among them. However, trends in communication scenarios show that WHAT is being exchanged becoming more important than WHO are exchanging information. Van Jacobson describes this as moving from interconnecting machines to interconnecting information. Any change of this part of the Internet needs argumentation as to why it should be undertaken in the first place. In this position paper, we identify four key challenges, namely information-centrism of applications, supporting and exposing tussles, increasing accountability, and addressing attention scarcity, that we believe an information-centric internetworking architecture could address better and would make changing such crucial part worthwhile. We recognize, however, that a much larger and more systematic debate for such change is needed, underlined by factual evidence on the gain for such change.
Perspectives on tracing end-hosts
Authors: Joumblatt Diana , Teixeira Renata , Chandrashekar Jaideep , Taft Nina
Published: April 2010

There is an amazing paucity of data that is collected directly on user personal machines. One key reason for this is the perception among researchers that users are unwilling to participate in such a data collection effort. To understand the range of opinions on matters that occur with end-host data tracing, we conducted a survey of 400 computer scientists. In this paper, we summarize and share our findings.
Workshop on internet economics (WIE2009) report
Authors: claffy k. c.
Published: April 2010

On September 23, 2009, CAIDA hosted a virtual Workshop on Internet Economics [3] to bring together network technology and policy researchers, commercial Internet facilities and service providers, and communications regulators to explore a common goal: framing a concrete agenda for the emerging but empirically stunted field of Internet infrastructure economics. With participants stretching from Washington D.C. to Queensland, Australia, we used the electronic conference hosting facilities supported by the California In stitute of Technology (CalTech) EVO Collaboration Network. This report describes the workshop discussions and presents relevant open research questions identified by participants.
How to build a research system in your spare time
Authors: Mahajan Ratul
Published: April 2010

This paper is based on a talk that I gave at CoNEXT 2009. Inspired by Hal Varian's paper on building economic models, it describes are search method for building computer systems. I find this method useful in my work and hope that some readers will find it helpful as well.
The ambient Loo
Authors: Haddadi Hamed , Henderson Tristan , Crowcroft Jon
Published: April 2010

On numerous occasions, trips to the facilities coincide with an important mobile phone call. Due to the sleek and polished nature of modern phones, attempting to promptly deal with such calls can occasionally lead to the phone sliding through the owner's hands, surrendering to the force of gravity and flying down the hole. This is a disaster, and often an expensive incident. It can also be a health and safety hazard, with the owner desperately attempting to retrieve their phone and re-using it.

This paper provides a first attempt at a cell phone recovery system using the modern functionalities of Toto Japanese toilets. In our approach, the phone is calmly recovered, sanitized and retrieved by the user. This can all happen without the call even being dropped, with possibility of secure back-up of the user data by embedded sensor and Wi-Fi network connectivity in the toilet. We envision that such an approach will increase the collaboration between Japanese, European and American mobile operators, network researchers and hardware manufacturers.
Large Electric‐Field Modulation of Magnetic Properties in Fe Films on BiScO3‐PbTiO3 Ceramics
Authors: Wang Jing , Wang Han , Jiang He , Wang Xiaohui , Lin Yuanhua , Nan C. W.
Published: April 2010

Based on the magneto‐optical Kerr effect, we report the electric‐field modulation of the magnetic properties in Fe/BiScO3‐PbTiO3 (BSPT) film‐on‐ceramic substrate structure. The Fe films are directly grown on the fully‐poled BSPT ceramic substrates by magnetron sputtering. An electric field applied parallel to the prepolarization direction of the piezoelectric BSPT can induce a reversible increase in the coercive field Hc of about 30%, whereas an electric field antiparallel to the prepolarization direction can cause a persistent, tremendous decrease (as large as 97%) in Hc, and a small reversal electric field can resume it back. The strain induced by the inverse piezoelectric effect is the primary mechanism behind. This large modulation of the coercive field by the electric field could inspire further exploration of electric‐field‐controlled magnetic switching in multiferroic heterostructures.
Generalizations of the Nash Equilibrium Theorem in the KKM Theory
Authors: Park Sehie
Published: April 2010

The partial KKM principle for an abstract convex space is an abstract form of the classical KKM theorem. In this paper, we derive generalized forms of the Ky Fan minimax inequality, the von Neumann-Sion minimax theorem, the von Neumann-Fan intersection theorem, the Fan-type analytic alternative, and the Nash equilibrium theorem for abstract convex spaces satisfying the partial KKM principle. These results are compared with previously known cases for "Equation missing"-convex spaces. Consequently, our results unify and generalize most of previously known particular cases of the same nature. Finally, we add some detailed historical remarks on related topics.