bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Investigation of a Failed Lock-Pin
Authors: Poursaeidi E. , Pirmohammadi A. A. , Arhani M. R. Mohammadi
Published: April 2009

This paper presents the outcomes of computational mechanics applied in the root-cause investigation on hot section failure of a 25 MW gas turbo generator in the domestic power plant after 2228 start-stops and 52,586 h operation. The failure includes the complete damage of the first and the second stage of nozzles, blades, seals, shroud segments, and also a peripheral damage on the disk of first stage. Several reported cases from the different power plants with similar events evidenced that the failure is a serious common type in the mentioned gas turbine engine. A previous study on complete metallurgical analysis of disk, moving blades, and lock-pins, was done by Poursaeidi and Mohammadi (2008, “Failure Analysis of Lock-Pin in a Gas Turbine Engine,” Eng. Fail. Anal., 15(7), pp. 847–855), which concluded that the mechanical specification of applied materials had been satisfied. Nevertheless, some problems were found in the fractographic results of lock-pins: the typical fatigue fracture surfaces in the neck of failed lock-pins and frankly localized pitting signs near the head of lock-pin. The lock-pins are kinds of small devices that lock the buckets after inserting them into disk grooves. In this work, a 3D finite element model (FEM) of a blade, a disk, and a lock-pin are made and analyzed by the ANSYS software. The results of the FEM showed a reasonable agreement between the analysis and position of fracture on lock-pins. Also, the results showed that the second vibrational mode of the bucket is a possible cause of failure because in this mode the peak stress occurs on the head of the lock-pin. However, inadequate design and long time service reduced the performance of lock-pins for sustaining a severe hot condition in the first stage of the turbine section.
Sensor Thermal Barrier Coatings: Remote In Situ Condition Monitoring of EB-PVD Coatings at Elevated Temperatures
Authors: Steenbakker Rémy J. L. , Feist Jörg P. , Wellman Richard G. , Nicholls John R.
Published: April 2009

Thermal barrier coatings (TBCs) are used to reduce the actual working temperature of the high pressure turbine blade metal surface. Knowing the temperature of the surface of the TBC and at the interface between the bondcoat and the thermally grown oxide (TGO) under realistic conditions is highly desirable. As the major life-controlling factors for TBC systems are thermally activated, therefore linked with temperature, this would provide useful data for a better understanding of these phenomena and to assess the remaining lifetime of the TBC. This knowledge could also enable the design of advanced cooling strategies in the most efficient way using minimum amount of air. The integration of an on-line temperature detection system would enable the full potential of TBCs to be realized due to improved precision in temperature measurement and early warning of degradation. This, in turn, will increase fuel efficiency and reduce CO2 emissions. The concept of a thermal-sensing TBC was first introduced by Choy, Feist, and Heyes (1998, “Thermal Barrier Coating With Thermoluminescent Indicator Material Embedded Therein,” U.S. Patent U.S. 6974641 (B1)). The TBC is locally modified so it acts as a thermographic phosphor. Phosphors are an innovative way of remotely measuring temperatures and also other physical properties at different depths in the coating using photo stimulated phosphorescence (Allison and Gillies, 1997, “Remote Thermometry With Thermographic Phosphors: Instrumentation and Applications,” Rev. Sci. Instrum., 68(7), pp. 2615–2650). In this study the temperature dependence of several rare earth doped EB-PVD coatings will be compared. Details of the measurements, the influence of aging, the composition, and the fabrication of the sensing TBC will be discussed in this paper. The coatings proved to be stable and have shown excellent luminescence properties. Temperature detection at ultrahigh temperatures above 1300°C is presented using new types of EB-PVD TBC ceramic compositions. Multilayer sensing TBCs will be presented, which enable the detection of temperatures below and on the surface of the TBC simultaneously.
An Understanding of the Mechanism That Promotes Adhesion Between Roughened Titanium Implants and Mineralized Tissue
Authors: Shim Jaewoo , Nakamura Hiromi , Ogawa Takahiro , Gupta Vijay
Published: April 2009

A previously developed laser spallation technique to determine the tensile strength of thin film interfaces was successfully adopted to study the effect of microsurface roughness of titanium disks on the adhesion strength of mineralized bone tissue. The study demonstrated that mineralized tissue has about 25% higher interfacial strength when it is cultured on the acid-etched titanium surface than on its machined counterpart. Specifically, interfacial tensile strength of 179±4.4 MPa and 224±2.6 MPa were measured when the mineralized tissue was processed on the machined titanium and acid-etched titanium surfaces, respectively. Since in the laser spallation experiment, the mineralized tissue is pulled normal to the interface, this increase is attributed to the stronger interfacial bonding on account of higher surface energy associated with the acid-etched surface. This enhanced local chemical bonding further enhances the roughness-related mechanical interlocking effect. These two effects at very different length scales—atomic (enhanced bonding) versus continuum (roughness-related interlocking)—act synergistically and explain the widely observed clinical success of roughened dental implants.
A Theoretical Study of Mechanical Stability of Arteries
Authors: Rachev Alexander
Published: April 2009

This study proposes a mathematical model for studying stability of arteries subjected to a longitudinal extension and a periodic pressure. An artery was considered as a straight composite beam comprised of an external thick-walled tube and a fluid core. The dynamic criterion for stability was used, based on analyzing the small transverse vibrations superposed on the finite deformation of the vessel under static load. In contrast to the case of a static pressurization, in which buckling is only possible if the load produces a critical axial compressive force, a loss of stability of arteries under periodic pressure occurs under many combinations of load parameters. Instability occurs as a parametric resonance characterized by an exponential increase in the amplitude of transverse vibrations over several bands of pressure frequencies. The effects of load parameters were analyzed on the basis of the results for a dynamic and static stability of a rabbit thoracic aorta. Under normal physiological loads the artery is in a stable configuration. Static instability occurs under high distending pressures and low longitudinal stretch ratios. When the artery is subjected to periodic pressure, an independent increase in the mean pressure, amplitude of the periodic pressure, or frequency, most often, but not always, increases the risk of stability loss. In contrary, an increase in longitudinal stretch ratio most likely, but not certain, stabilizes the vessel. It was shown that adaptive geometrical remodeling due to an increase in mean pressure and flow does not affect artery stability.
Development of High-Temperature Transport Technologies for Liquid Cadmium in Pyrometallurgical Reprocessing
Authors: Hijikata Takatoshi , Koyama Tadafumi
Published: April 2009

Pyrometallurgical reprocessing is one of the most promising technologies for the advanced fuel cycle with favorable economic potential and intrinsic proliferation-resistance. The feasibility of pyrometallurgical reprocessing has been studied through many laboratory-scale experiments. Hence the development of the engineering technology necessary for pyrometallurgical reprocessing is a key issue for its industrialization. The development of high-temperature transport technologies for molten salt and liquid cadmium is crucial for pyrometallurgical processing; however, there have been a few transport studies on high-temperature fluids. In this study, a metal transport test rig was installed in an argon glove box with the aim of developing technologies for transporting liquid cadmium at approximately 773 K. The transport of liquid Cd using gravity was controlled by adjusting the valve. The liquid Cd was transported by a suction pump against a 0.93 m head and the transport amount of Cd was well controlled with the Cd amount and the position of the suction tube. The transportation of liquid cadmium at approximately 700 K could be controlled at a rate of 0.5–2.5 dm3/min against a 1.6 m head using a centrifugal pump.
Peripapillary and Posterior Scleral Mechanics—Part I: Development of an Anisotropic Hyperelastic Constitutive Model
Authors: Girard Michaël J. A. , Downs J. Crawford , Burgoyne Claude F. , Suh J.-K. Francis
Published: April 2009

The sclera is the white outer shell and principal load-bearing tissue of the eye as it sustains the intraocular pressure. We have hypothesized that the mechanical properties of the posterior sclera play a significant role in and are altered by the development of glaucoma—an ocular disease manifested by structural damage to the optic nerve head. An anisotropic hyperelastic constitutive model is presented to simulate the mechanical behavior of the posterior sclera under acute elevations of intraocular pressure. The constitutive model is derived from fiber-reinforced composite theory, and incorporates stretch-induced stiffening of the reinforcing collagen fibers. Collagen fiber alignment was assumed to be multidirectional at local material points, confined within the plane tangent to the scleral surface, and described by the semicircular von Mises distribution. The introduction of a model parameter, namely, the fiber concentration factor, was used to control collagen fiber alignment along a preferred fiber orientation. To investigate the effects of scleral collagen fiber alignment on the overall behaviors of the posterior sclera and optic nerve head, finite element simulations of an idealized eye were performed. The four output quantities analyzed were the scleral canal expansion, the scleral canal twist, the posterior scleral canal deformation, and the posterior laminar deformation. A circumferential fiber organization in the sclera restrained scleral canal expansion but created posterior laminar deformation, whereas the opposite was observed with a meridional fiber organization. Additionally, the fiber concentration factor acted as an amplifying parameter on the considered outputs. The present model simulation suggests that the posterior sclera has a large impact on the overall behavior of the optic nerve head. It is therefore primordial to provide accurate mechanical properties for this tissue. In a companion paper (Girard, Downs, Bottlang, Burgoyne, and Suh, 2009, “Peripapillary and Posterior Scleral Mechanics—Part II: Experimental and Inverse Finite Element Characterization,” ASME J. Biomech. Eng., 131, p. 051012), we present a method to measure the 3D deformations of monkey posterior sclera and extract mechanical properties based on the proposed constitutive model with an inverse finite element method.
Peripapillary and Posterior Scleral Mechanics—Part II: Experimental and Inverse Finite Element Characterization
Authors: Girard Michaël J. A. , Downs J. Crawford , Bottlang Michael , Burgoyne Claude F. , Suh J.-K. Francis
Published: April 2009

The posterior sclera likely plays an important role in the development of glaucoma, and accurate characterization of its mechanical properties is needed to understand its impact on the more delicate optic nerve head—the primary site of damage in the disease. The posterior scleral shells from both eyes of one rhesus monkey were individually mounted on a custom-built pressurization apparatus. Intraocular pressure was incrementally increased from 5 mm Hg to 45 mm Hg, and the 3D displacements were measured using electronic speckle pattern interferometry. Finite element meshes of each posterior scleral shell were reconstructed from data generated by a 3D digitizer arm (shape) and a 20 MHz ultrasound transducer (thickness). An anisotropic hyperelastic constitutive model described in a companion paper (Girard, Downs, Burgoyne, and Suh, 2009, “Peripapillary and Posterior Scleral Mechanics—Part I: Development of an Anisotropic Hyperelastic Constitutive Model,” ASME J. Biomech. Eng., 131, p. 051011), which includes stretch-induced stiffening and multidirectional alignment of the collagen fibers, was applied to each reconstructed mesh. Surface node displacements of each model were fitted to the experimental displacements using an inverse finite element method, which estimated a unique set of 13 model parameters. The predictions of the proposed constitutive model matched the 3D experimental displacements well. In both eyes, the tangent modulus increased dramatically with IOP, which indicates that the sclera is mechanically nonlinear. The sclera adjacent to the optic nerve head, known as the peripapillary sclera, was thickest and exhibited the lowest tangent modulus, which might have contributed to the uniform distribution of the structural stiffness for each entire scleral shell. Posterior scleral deformation following acute IOP elevations appears to be nonlinear and governed by the underlying scleral collagen microstructure as predicted by finite element modeling. The method is currently being used to characterize posterior scleral mechanics in normal (young and old), early, and moderately glaucomatous monkey eyes.
Thin Film Nitinol Microstent for Aneurysm Occlusion
Authors: Chun Youngjae , Levi Daniel S. , Mohanchandra K. P. , Vinuela Fernando , Vinuela Fernando , Carman Gregory P.
Published: April 2009

Thin film nitinol produced by sputter deposition was used in the design of microstents intended to treat small vessel aneurysms. Thin film microstents were fabricated by “hot-target” dc sputter deposition. Both stress-strain curves and differential scanning calorimetry curves were generated for the film used to fabricate stents. The films used for stents had an Af temperature of approximately 36°C allowing for body activated response from a microcatheter. The 10 μm film was only slightly radio-opaque; thus, a Td marker was attached to the stents to guide fluoroscopic delivery. Thin film microstents were tested in a flow loop with and without nitinol support skeletons to give additional radial support. Stents could be compressed into and easily delivered with <3 Fr catheters. Theoretical frictional and wall drag forces on a thin film nitinol small vessel vascular stent were calculated, and the radial force exerted by thin film stents was evaluated theoretically and experimentally. In vivo studies in swine confirmed that thin film nitinol microstents could be deployed accurately and consistently in the swine cranial vasculature.
Hemodynamics of the Mitral Valve Under Edge-to-Edge Repair: An In Vitro Steady Flow Study
Authors: Shi Liang , He Zhaoming
Published: April 2009

Edge-to-edge repair (ETER) is a mitral valve repair technique that restores valvular competence by suturing together the free edges of two leaflets. This repair technique alters mitral valve inflow and thus left ventricle hemodynamics during diastole. Our objective was to investigate fluid mechanics immediately downstream of the mitral valve under ETER during diastole. Fresh porcine mitral valves of the annulus size M32 with chordae removed were installed into a steady flow loop simulating a peak diastolic inflow through the mitral valve. Digital particle image velocimetry was used to measure the velocity field immediately downstream of the mitral valve under normal and ETER conditions. First, to study the suture length effect, suture was applied in the central position of the leaflet edge with suture lengths of 3 mm, 6 mm, and 9 mm, respectively. Then, 3 mm suture was set in the central, lateral, and commissural positions of the leaflet edge to study the suture position effect. Flow rate was 15 l/min. Velocity, Reynolds shear stress (RSS), and effective orifice area were assessed. A total of five mitral valves were tested. The normal mitral valve without the ETER had one jet downstream of the valve, but the mitral valve with the central or lateral sutures under the ETER had two jets downstream of the valve with a recirculation region downstream of the suture. The maximum velocity, the maximum RSS in the jets, the pressure drop across the mitral valve, and the jet deflection angle increased with the increase in suture length in the central position. When the suture position effect was investigated with the 3 mm suture, the maximum velocity, the maximum RSS, and the pressure drop across the valve in the central suture position were greater than those of the lateral and the commissural suture positions. The lateral suture demonstrated major and minor jets with the greater maximum velocity and maximum RSS in the major jet. When the suture was in the commissural position, the flow field downstream of the mitral valve was similar to that of the normal mitral valve without the ETER. The effective orifice area was smallest when the suture was applied in the central position as compared with other suture positions. Both suture length and position have an important impact on fluid mechanics downstream of the mitral valve under the ETER in terms of flow pattern, maximum velocity, and RSS distribution. The altered hemodynamics of the mitral valve and thus of the left ventricle by the ETER may change mitral valve and left ventricle function.
Sex and limb differences in hip and knee kinematics and kinetics during anticipated and unanticipated jump landings: implications for anterior cruciate ligament injury
Authors: Brown T N , Palmieri-Smith R M , McLean S G
Published: April 2009

Objectives:

In this study, the effects of temporal changes in unanticipated (UN) prelanding stimuli on lower limb biomechanics and the impact of sex and limb dominance on these variables during single-leg landings were determined. It was hypothesised that reductions in the time of prelanding UN stimuli, female sex, and the non-dominant limb would significantly increase high-risk landing biomechanics during UN jump landings.

Methods:

26 (13 men and 13 women) had initial contact (IC) and peak stance (0–50%) phase (PS) lower limb joint kinematics and kinetics quantified during anticipated (AN) and UN single-leg (left and right) landings. Postlanding jump direction was governed via one of two randomly ordered light stimuli, presented either before initiation of the jump (AN), or 600 ms (UN1), 500 ms (UN2) or 400 ms (UN3) immediately before ground contact.

Results:

Statistically significant (p<0.05) differences in IC hip posture and PS hip and knee internal rotation moments occurred in UN compared with AN landings. Differences were not observed, however, among UN conditions for any biomechanical comparisons. Significant (p<0.05) differences in specific IC and PS hip and knee postures and loads occurred between sexes and limbs. Neither of these factors, however, influenced movement condition effects.

Conclusion:

UN landings induce modifications in landing biomechanics that may increase anterior cruciate ligament injury risk in both men and women. These modifications, however, do not appear overly sensitive to the timing of the UN stimulus, at least within a temporal range affording a successful movement response. Expanding UN training to include even shorter stimulus-response times may promote the additional central control adaptations necessary to manoeuvre safely within the random sports setting.
Video analysis of trunk and knee motion during non-contact anterior cruciate ligament injury in female athletes: lateral trunk and knee abduction motion are combined components of the injury mechanism
Authors: Hewett T E , Torg J S , Boden B P
Published: April 2009

Background:

The combined positioning of the trunk and knee in the coronal and sagittal planes during non-contact anterior cruciate ligament (ACL) injury has not been previously reported.

Hypothesis:

During ACL injury female athletes demonstrate greater lateral trunk and knee abduction angles than ACL-injured male athletes and uninjured female athletes.

Design:

Cross-section control-cohort design.

Methods:

Analyses of still captures from 23 coronal (10 female and 7 male ACL-injured players and 6 female controls) or 28 sagittal plane videos performing similar landing and cutting tasks. Significance was set at p⩽0.05.

Results:

Lateral trunk and knee abduction angles were higher in female compared to male athletes during ACL injury (p⩽0.05) and trended toward being greater than female controls (p = 0.16, 0.13, respectively). Female ACL-injured athletes showed less forward trunk lean than female controls (mean (SD) initial contact (IC): 1.6 (9.3)° vs 14.0 (7.3)°, p⩽0.01).

Conclusion:

Female athletes landed with greater lateral trunk motion and knee abduction during ACL injury than did male athletes or control females during similar landing and cutting tasks.

Clinical relevance:

Lateral trunk and knee abduction motion are important components of the ACL injury mechanism in female athletes as observed from video evidence of ACL injury.
Cold-season patterns of reserve and soluble carbohydrates in sugar maple and ice-damaged trees of two age classes following drought
Authors: Wong B. L. , Baggett K. L. , Rye A. H.
Published: April 2009

This study examines the effects of summer drought on the composition and profiles of cold-season reserve and soluble carbohydrates in sugar maple ( Acer saccharum Marsh.) trees (50–100 years old or ∼200 years old) in which the crowns were nondamaged or damaged by the 1998 ice storm. The overall cold season reserve carbohydrate profiles in twig wood tissue of drought-stressed (DS) trees and non-drought-stressed (NDS) trees were generally similar, although differences were observed in the amount of reserve carbohydrates in DS and NDS trees. The cold-season level of starch stored in DS trees in early autumn in the wood tissue was about one-third to one-fifth that in NDS trees. The cold season sugar content in the DS trees was significantly greater than can be attributed to degradation of stored starch, only. The level of sucrose in DS trees remained high throughout the winter until termination of dormancy and dehardening. The concentrations of winter glucose and fructose in DS trees attained peak levels at the time of dormancy termination and declined during dehardening. The profiles of glucose and fructose in DS and damaged DS trees were generally different from that of sucrose throughout the leafless phase. In contrast, profiles of glucose and fructose in NDS trees closely paralleled that of sucrose. Elevated levels of sucrose, glucose, and fructose in DS sugar maple trees during the cold season may function as osmoregulators for freeze protection. Low sugar level or lack of increase in sugar level following dehardening in DS trees may suggest limited change in cellular constituents in adapting to low temperatures.
Experimental crosses within EuropeanSilene latifolia(Caryophyllaceae): intraspecific differentiation, distance effects, and sex ratio
Authors: Hathaway Louise , Andersson Stefan , Prentice Honor C.
Published: April 2009

The dioecious weed Silene latifolia Poiret is thought to have spread northwards through Europe from separate southern source populations and shows a pronounced east–west pattern of differentiation in seed morphology. We used crossing experiments to investigate whether patterns of interfertility in S. latifolia are consistent with a scenario of ongoing speciation (reflected by outbreeding depression in crosses between the seed races), a scenario involving local inbreeding (reflected by heterosis in interpopulations crosses), or a combination of both scenarios. The experiments involved three western and three eastern populations, which were crossed reciprocally in all possible inter- and intra-population combinations. Inter-race cross-progenies did not have lower fitness than those from intra-racial crosses, and the results are not consistent with a scenario of incipient speciation. A pattern of overall heterosis was found in three variables, indicating the expression of inbreeding depression in progeny from intrapopulation crosses. For two fitness variables, negative relationships between interpopulation distance and heterosis, together with signs of outbreeding depression in the longest-distance crosses, suggest that there may be significant levels of genetic differentiation between geographically distant populations. The sex ratio was female-biased in most progenies, especially in those from the longest-distance crosses.
Glomus achrumandG. bistratum,two new species of arbuscular mycorrhizal fungi (Glomeromycota) found in maritime sand dunes
Authors: Błaszkowski Janusz , Ryszka Przemysław , Oehl Fritz , Koegel Sally , Wiemken Andres , Kovács Gábor M. , Redecker Dirk
Published: April 2009

Two new arbuscular mycorrhizal fungal species, Glomus achrum sp. nov. and Glomus bistratum sp. nov. (Glomeromycota), are described and illustrated. Both species produce small, hyaline spores in aggregates formed in the soil and inside roots. Glomus achrum was associated with roots of Ammophila arenaria (L.) Link colonizing maritime dunes of the Vistula Bar in northern Poland, and G. bistratum occurred among vesicular-arbuscular mycorrhiza of Xanthium cf. spinosum growing in dunes of the Mediterranean Sea adjacent to Veriko, Greece. Spores of G. achrum are globose to subglobose, (25–)43(–55) µm in diameter, rarely egg-shaped, oblong to irregular, 15–45 µm × 55–65 µm. Their wall consists of three hyaline layers: a mucilaginous, short-lived outermost layer; a laminate middle layer composed of loose sublayers; and a flexible innermost layer. The outermost and the innermost layers stain deeply red in Melzer’s reagent. Spores of G. bistratum are globose to subglobose, (20–)29(–50) µm in diameter, and have a wall composed of two permanent, hyaline layers. The outer layer is unit, smooth, and the inner one laminate. Only the inner layer stains yellow in Melzer’s reagent. Both species formed vesicular-arbuscular mycorrhiza in single-species cultures with Plantago lanceolata  L. as the host plant. Phylogenetic analyses of partial 18S rDNA subunit and internal transcribed spacer (ITS) region sequences placed G. achrum and G. bistratum into Glomus group A, but did not reveal any closely related described species. Environmental sequences from the public databases suggested that G. achrum occurred in at least two other plant species from geographically distant regions. No such evidence could be obtained for G. bistratum, which is currently known only from the type location.
Species richness of both native and invasive aquatic plants influenced by environmental conditions and human activity
Authors: Capers Robert S. , Selsky Roslyn , Bugbee Gregory J. , White Jason C.
Published: April 2009

Invasive plants alter community structure, threatening ecosystem function and biodiversity, but little information is available on whether invasive species richness responds to environmental conditions in the same way that richness of native plants does. We surveyed submerged and floating-leaved plants in 99 Connecticut (northeast USA) lakes and ponds, collecting quantitative data on abundance and frequency. We used multiple linear and logistic regression to determine which environmental conditions were correlated with species richness of invasive and native plants. Independent variables included lake area, maximum depth, pH, alkalinity, conductivity, phosphorus concentration, productivity, and dominance (the proportional abundance of the most abundant and frequently found species), plus two estimates of human activity. Species richness of both native and invasive richness was correlated with alkalinity and human activity. Native richness also increased with water clarity, lake area, and productivity; invasive species richness also rose with pH. We found no evidence that richness of one group affected richness of the other. We also investigated patterns of dominance and found that native plants were as likely to become dominant as invasive species. Dominance occurred overwhelmingly in shallow lakes with high productivity.
Pollen limitation and reproduction varies with population size in experimental populations ofSabatia angularis(Gentianaceae)
Authors: Spigler Rachel B. , Chang Shu-Mei
Published: April 2009

Individuals in large plant populations are expected to benefit from increased reproductive success relative to those in small populations because of the facilitative effects of large aggregations on pollination. As populations become small, the inability to attract sufficient numbers of pollinators can reduce reproduction via pollen limitation. This study experimentally tested whether such trends occur for the herbaceous biennial Sabatia angularis (L.) Pursh (Gentianaceae). We created artificial populations of varying size consisting of potted S. angularis plants in two field sites to determine whether population size affected mean fruit and seed set. We also examined whether population size affected the degree of pollen limitation using a supplemental pollination design in one of the sites. Our results showed that, on average, seed set was lower in large populations, not small populations, of S. angularis and that this result may be due to increased pollen limitation in large populations. We suggest that in certain contexts, small populations may enjoy reproductive advantages over large populations by escaping intraspecific competition for pollinators.
Background to seismic design provisions in CSA A23.3–04 for high-strength concrete
Authors: Paultre Patrick , Mitchell Denis
Published: April 2009

This paper presents the background experimental and analytical research that was carried out to develop the provisions for the seismic design of high-strength concrete structures in the 2004 Canadian standard CSA A23.3–04. It is noted that the 1994 Canadian standard CSA A23.3–94 limited the concrete compressive strength to 55 MPa for the seismic design of nominally ductile and ductile structures, while the 1995 New Zealand Standard limited the concrete compressive strength to 70 MPa. In contrast, the 2008 American Concrete Institute (ACI) code ACI 318M has no upper limit on concrete strength, even for the seismic design of ductile structural elements. This tremendous variation in these limits indicated that more experimental evidence was needed. This paper presents experimental results of reversed cyclic loading tests on large-scale structural components as well as simulated seismic loading tests of a frame structure constructed with high-strength concrete. The goal of this collaborative research program at the University of Sherbrooke and McGill University was to determine the seismic design and detailing requirements for high-strength concrete structures to achieve the desired level of ductility and energy dissipation. The experimental programs include full-scale testing of the following: columns subjected to a pure axial load (square and circular columns); columns subjected to flexure and axial loads; beam-column subassemblages (square and circular columns); coupling beams in coupled wall structures; shear walls and a two-storey, three-dimensional frame structure. The results of the responses of the high-strength concrete structural specimens are compared with the responses of companion specimens constructed with normal-strength concrete.
Interval-parameter robust optimization for environmental management under uncertainty
Authors: Li Y.P. , Huang G.H.
Published: April 2009

In this study, an interval-parameter robust optimization (IPRO) method is developed through incorporating techniques of interval-parameter programming and robust optimization within a two-stage stochastic programming framework. The IPRO improves upon the two-stage stochastic programming methods by allowing uncertainties presented as both intervals and random variables to be handled in the optimization system. Moreover, in the modeling formulation, penalties are exercised with the recourse against any infeasibility, and robustness measures are introduced to examine the variability of the second-stage costs that are above the expected level. The IPRO is generally suitable for risk-aversive planners under high-variability conditions. The developed method is applied to a case of long-term waste management under uncertainty. Interval solutions under different robustness levels have been generated. They cannot only be used for analyzing various policy scenarios that are related to different levels of economic penalties when the pre-regulated waste allocation allowances are violated, but also help decision makers to analyze the interrelationships between the penalties and their variabilities.
Lessons learned about the impacts of size and weight regulations on the articulated truck fleet in the Canadian prairie region
Authors: Regehr Jonathan D. , Montufar Jeannette , Clayton Alan
Published: April 2009

Three highway engineering policies directed at improving truck productivity by increasing size and weight limits have been implemented in the Canadian prairie region within the last 35 years: the 1974 Western Canada Highway Strengthening Program, the 1988 Roads and Transportation Association of Canada Memorandum of Understanding on Heavy Vehicle Weights and Dimensions, and special permitting of longer combination vehicles. As policies change, the trucking industry adjusts its fleets to take advantage of available efficiencies. Evidence of these changes and the lessons learned from the adoption of these policies are provided. Ultimately, as a result of these policies, articulated trucks now carry heavier and larger payloads, have different axle configurations, and have higher axle weight limits than they did 35 years ago. The threefold to fivefold increase in articulated truck volumes that occurred during this period would have been more dramatic had these policies not been implemented. Further research is necessary to understand the interactions among policies, vehicles, and infrastructure.
Electrochemical treatment of wastewaters containing 4-nitrocathecol using boron-doped diamond anodesA paper submitted to the Journal of Environmental Engineering and Science.
Authors: Bensalah Nasr , Ahmadi Mohamed F. , Gadri Abdelatif
Published: April 2009

The electrochemical oxidation of aqueous wastes polluted with 4-nitrocathecol has been studied on boron-doped diamond electrodes in an acidic medium. The voltammetric results showed that 4-nitrocathecol is oxidized in the potential region where the supporting electrolyte is stable. Galvanostatic electrolysis study showed that the oxidation of these wastes in a single-compartment electrochemical flow cell with boron-doped diamond anodes results in the complete mineralization of the organics. Cathecol, benzoquinone, 4-aminocathecol, maleic and oxalic acids have been detected as soluble organics, polymeric product as solid product at the cathode surface and NO3– as mineral product during the electrolysis of 4-nitrocathecol. The electrochemical oxidation of 4-nitrocathecol consists of a sequence of steps: release of NO2 and (or) hydroxylation of the aromatic ring; formation of quinonic compounds; oxidative opening of aromatic ring to form carboxylic acids; and oxidation of carboxylic acids to carbon dioxide. Both direct and mediated oxidation processes are involved in these stages.
Détection des cavités sous les pavages par l’analyse modal des ondes de Rayleigh (MASW)
Authors: Karray Mourad , Lefebvre Guy
Published: April 2009

Le problème de cavités sous les pavages au voisinage des ponceaux est relié à l’érosion du sol à travers des ponceaux défectueux. Ceci se traduit par le développement d’une cheminée jusqu’à provoquer un affaissement jusqu’à la surface, créant ainsi un cratère dans le pavage routier. L’apparence de cratère dans le pavage constitue un danger pour les usagers, en particulier dans le cas des routes et autoroutes achalandées (circulation à fréquence élevée). L’utilisation des ondes de surface pour la caractérisation des sols de fondation sous un pavage est problématique compte tenu de la difficulté d’exciter le sol à travers un pavage rigide. La méthode « modal analysis of surface waves (MASW) » permet de placer les capteurs à la surface du pavage et d’exciter le sol à l’extérieur de celui-ci. Cette configuration a été testée au moyen de simulations numériques qui montrent qu’il est possible de caractériser le sol en dessous d’une structure de pavage relativement rigide. Des essais « MASW » ont également été réalisés à un site, où des cavités de dimensions connues ont été réalisées en pratiquant des ouvertures dans le toit d’un ponceau routier. L’analyse de ces relevés a permis d’élaborer une méthode d’interprétation rapide et adaptée à la détection des cavités ou zones de faiblesse sous les pavages routiers.
Foliar morphology and chemistry of upland oaks, red maple, and sassafras seedlings in response to single and repeated prescribed fires
Authors: Alexander H.D. , Arthur M.A.
Published: April 2009

Managers increasingly use prescribed fire in oak forests to decrease fire-sensitive species, increase understory light, and improve oak ( Quercus spp.) regeneration. To better understand woody seedling response to burning, single and repeated (3×) prescribed fires were implemented over 6 years (2002–2007) in eastern Kentucky, and leaf traits of red ( Erythrobalanus spp.) and white oaks ( Leucobalanus spp.) were compared with competitors red maple ( Acer rubrum L.) and sassafras ( Sassafras albidum (Nutt.) Nees). Burned seedlings had higher total leaf area (TLA) because of two to three times higher TLA of sassafras. Leaf mass per area (LMA) and leaf N content per area (Narea) increased postfire but were independent of seedling identity. Canopy openness during 2006, which was lower on unburned sites (4%–8%) compared with those burned 1× (4%–16%) and 3× (7%–33%), was positively correlated with sassafras TLA, oak and sassafras Narea, and LMA of all seedling groups the subsequent year. In 2007, TLA, LMA, and Narea were positively correlated with basal diameter of all groups but most significantly for sassafras and red maple. These findings indicate that low-intensity, early growing season prescribed fire can alter seedling leaf characteristics, but not in a manner that enhances oak seedling leaf traits relative to their competitors red maple and sassafras.
Effect of application time on the efficacy of Chondrostereum purpureum treatment against the sprouting of birch in Finland
Authors: Vartiamäki Henna , Hantula Jarkko , Uotila Antti
Published: April 2009

To test the effect of application time on the efficacy of a biological control agent to prevent sprouting of cut stumps, birches ( Betula pendula Roth. and Betula pubescens Ehrh.) were cut and stumps treated with a decay fungus ( Chondrostereum purpureum (Pers. ex Fr.) Pouzar) at different times during one growing season. Applications were conducted at 2 week intervals. The presence of fruiting bodies was examined three times during the 2 years following treatment. Sprouting was measured twice. Fructification was most abundant 1 year after the treatment, and the frequency of stumps with fruiting bodies was highest when the stumps were treated between May and July. Treatment reduced the percentage of living stumps compared with controls, except if conducted in late autumn. The reduction was the highest on stumps treated in the middle of July; 2 years after the treatment, only 12.5% of treated stumps were resprouting compared with 74% of control stumps. Also, the number of living sprouts per stump decreased by the treatment, except if conducted in late autumn. Although the number of living sprouts per stump decreased owing to C. purpureum treatment, it had no effect on the maximum height of the sprouts.
Detrital carbon pools in temperate forests: magnitude and potential for landscape-scale assessment
Authors: Bradford John , Weishampel Peter , Smith Marie-Louise , Kolka Randall , Birdsey Richard A. , Ollinger Scott V. , Ryan Michael G.
Published: April 2009

Reliably estimating carbon storage and cycling in detrital biomass is an obstacle to carbon accounting. We examined carbon pools and fluxes in three small temperate forest landscapes to assess the magnitude of carbon stored in detrital biomass and determine whether detrital carbon storage is related to stand structural properties (leaf area, aboveground biomass, primary production) that can be estimated by remote sensing. We characterized these relationships with and without forest age as an additional predictive variable. Results depended on forest type. Carbon in dead woody debris was substantial at all sites, accounting for ∼17% of aboveground carbon, whereas carbon in forest floor was substantial in the subalpine Rocky Mountains (36% of aboveground carbon) and less important in northern hardwoods of New England and mixed forests of the upper Midwest (∼7%). Relationships to aboveground characteristics accounted for between 38% and 59% of the variability in carbon stored in forest floor and between 21% and 71% of the variability in carbon stored in dead woody material, indicating substantial differences among sites. Relating dead woody debris or forest floor carbon to other aboveground characteristics and (or) stand age may, in some forest types, provide a partial solution to the challenge of assessing fine-scale variability.
OPEN STRING IN pp-WAVE BACKGROUND WITH B-FIELD
Authors: CAO ZHEN-BIN , DUAN YI-SHI
Published: April 2009

The open string ending on a flat D-brane in the pp-wave background with a constant B-field is exactly solvable but will be controlled by a more mass parameter. In this paper we mainly quantize this open string theory canonically by employing the Faddeev–Jackiw symplectic quantization procedure, and find that the phase space of the string coordinate and canonical momentum becomes fully noncummutative, consistent with the results obtained previously.
ENERGY–MOMENTUM PRESCRIPTIONS IN GENERAL SPHERICALLY SYMMETRIC SPACETIMES
Authors: MIRSHEKARI SAEED , ABBASSI AMIR M.
Published: April 2009

In this paper we investigate Einstein, Landau–Lifshitz, Papapetrou, Weinberg, and Møller energy–momentum prescriptions in general spherically symmetric spacetimes. We show that for two special but not unusual classes of general spherically symmetric spacetimes, several energy–momentum prescriptions in Schwarzschild Cartesian coordinates lead to some coincidences in energy distribution. We also obtain that for a special class of spherically symmetric metrics Møller and Einstein energy–momentum prescriptions give the same result for energy distribution if and only if it has a specific dependence on radial coordinate.
ELECTROMAGNETIC FIELDS OF SLOWLY ROTATING MAGNETIZED GRAVASTARS
Authors: TURIMOV B. V. , AHMEDOV B. J. , ABDUJABBAROV A. A.
Published: April 2009

We study the dipolar magnetic field configuration and present solutions of Maxwell equations in the internal background spacetime of a slowly rotating gravastar. The shell of gravastar where magnetic field penetrated is modeled as sphere consisting of perfect highly magnetized fluid with infinite conductivity. Dipolar magnetic field of the gravastar is produced by a circular current loop symmetrically placed at radius a at the equatorial plane.
A HARDWARE/SOFTWARE CO-DESIGN VERSUS HARDWARE-ONLY IMPLEMENTATION OF MODULAR EXPONENTIATION USING THE SLIDING-WINDOW METHOD
Authors: NEDJAH NADIA , MOURELLE LUIZA DE MACEDO
Published: April 2009

Modular exponentiation is a basic operation in cryptosystems. Generally, the performance of this operation has a tremendous impact on the efficiency of the whole application. The efficiency of the modular exponentiation, in turn, depends mainly on that of modular multiplications as the former is somehow a repetition of the latter. One of the methods that computes the modular power is the sliding-window method, which pre-processes the exponent into zero and nonzero partitions. Zero partitions allow for a reduction of the number of modular multiplications required in the exponentiation process. In this paper, we devise a novel System-on-Chip (SoC) implementation for computing modular exponentiation using the sliding-window method. We also propose a hardware-only implementation for that operation. The partitioning strategy used in both approaches allows constant-length nonzero partitions, which increases the average number of zero partitions and so decreases that of nonzero partitions. The partitioning strategy allows variable-length zero partitions. The hardware/software co-design implements the modular multiplication on hardware and the rest of the system in software. We provide a useful comparison of the SoC-based implementation against hardware-only implementation. Both of the proposed implementations can be used in any industrial embedded system that needs to secure the handled information.
AN EFFICIENT OVERLAPPING BLOCK SELECTION METHOD IN MULTI-FRAME SKIPPING TRANSCODING
Authors: ZHENG YAN , ZHENG SHIBAO
Published: April 2009

This paper presents an overlapping block selection method to determine the dominant macroblock (MB) in multi-frame skipping transcoding to improve picture quality. A non-intra MB in a non-skipped frame should be predicted by a block in another non-skipped frame. The re-constructed motion vector (MV) between two non-skipped frames accumulates prediction error. As the number of frames between two non-skipped frames is increased, such prediction error, or called mismatch error, is also increased. To reduce the impact on the transcoding quality caused by the prediction error, we improve the traditional overlapping block selection method, and propose a most approximate overlapping block to help to determine a dominant MB. In the proposed method, the location of an overlapping block is calculated by adding the accumulated MVs and the position of the current MB. The accumulated MVs are not the real MVs for MBs but the approximate vectors for 16 × 16 overlapping blocks. Simulation shows that the proposed method has a higher performance than the traditional method.
A LOW POWER CASCADED FEED-FORWARD DELTA-SIGMA MODULATOR FOR RF WIRELESS APPLICATIONS
Authors: NERURKAR SHAILESH B. , ABED KHALID H.
Published: April 2009

This paper presents a design of a novel cascaded third-order feed-forward delta-sigma analog-to-digital converter (ADC). This ADC is realized using fully differential switched capacitor architecture and produces a 12-bit resolution at a data output rate (DOR) of 2.5 MS/s for RF wireless applications. The delta-sigma modulator consists of a second-order single-bit feed-forward modulator cascaded with a multi-bit first-order modulator. The cascaded feed-forward third-order (2-1) ADC is simulated using Matlab and Simulink. The delta-sigma modulator was designed using Cadence Virtuoso in TSMC 0.18 μm CMOS technology. The power consumption of the designed modulator is 12.74 mW, and the resolution is 11.85 bits for an over-sampling ratio (M = 32). The figure of merit is 1.38 pJ at a sample rate of 80 MS/s. The proposed delta-sigma modulator is compared with other state-of-the-art low-pass delta-sigma modulators in terms of their speed, power, DOR, and the proposed modulator has one of the lowest power consumption.
NON-CYCLIC GRAPH ASSOCIATED WITH A GROUP
Authors: ABDOLLAHI A. , HASSANABADI A. MOHAMMADI
Published: April 2009

We associate a graph [Formula: see text] to a non locally cyclic group G (called the non-cyclic graph of G) as follows: take G\ Cyc (G) as vertex set, where Cyc (G) = {x ∈ G | 〈x,y〉 is cyclic for all y ∈ G} is called the cyclicizer of G, and join two vertices if they do not generate a cyclic subgroup. For a simple graph Γ, w(Γ) denotes the clique number of Γ, which is the maximum size (if it exists) of a complete subgraph of Γ. In this paper we characterize groups whose non-cyclic graphs have clique numbers at most 4. We prove that a non-cyclic group G is solvable whenever [Formula: see text] and the equality for a non-solvable group G holds if and only if G/ Cyc (G) ≅ A5 or S5.