bluuebunny/crossref_metadata_2025 huggingface dataset:
Porous Wall Gas Lubricated Journal Bearings: Theoretical Investigation
Authors: Gargiulo E. P.
Published: November 2010

A model has been developed to compute the dynamic stiffness and damping properties of externally pressurized, porous-wall, gas journal bearings which includes the effects of journal rotation and eccentricity. This paper presents the derivation of the governing equations and the perturbation analysis used to find the unsteady characteristics. Typical nondimensional performance curves are found and the influences of seven governing parameters are discussed. A companion paper describes an experimental investigation of porous journal bearings.
Steady State Performance of a Hydrodynamic Journal Bearing With a Pseudoplastic Lubricant
Authors: Rajalingham C. , Prabhu B. S. , Rao B. V. A.
Published: November 2010

Starting from the general shear stress-shear strain relation of the odd cubic polynomial type considering correlation effect for pseudoplastic (shear thinning) lubricant, a modified form of Reynolds’ equation (nonlinear) is derived under conventional hydrodynamic lubrication approximations. The finite difference technique with successive over relaxation is used adopting the solution of the associated linear equation as a first approximation to obtain the pressure distribution of a finite cylindrical journal bearing incorporating Reynolds’ boundary conditions. Steady state performance characteristics such as load capacity, attitude, friction and flow rate are obtained for various values of nonlinear parameter and bearing slenderness ratio. The results presented in nondimensional form are compared with established results for Newtonian lubricants. The investigation shows a significant effect of correlation on the bearing load capacity and flow rate.
High Stiffness Bearing
Authors: Brzeski Lech , Kazimierski Zbyszko
Published: November 2010

A new type of high stiffness gas or liquid lubricated bearing is presented. The general principle and bearing configuration are explained. The theoretical model of the bearing is given for a case of gas journal bearing. Load versus displacement data were determined both theoretically and experimentally. The results obtained confirmed the very high stiffness of the bearing. The experimental investigation of the bearing demonstrated its stable operation.
Simulation of Resonances and Instability Conditions in Pinion-Gear Systems
Authors: Benton M. , Seireg A.
Published: November 2010

This paper describes a computer simulation procedure based on the phase-plane method for predicting the steady-state response, resonances and instabilities of pinion-gear systems subjected to sinusoidal excitation. An experimental technique is also presented which is capable of checking the accuracy of the simulation under different operating conditions. The experimental set-up which utilizes a shaker for producing variations of mesh stiffness without complete rotation of the gear pair provides a relatively simple and convenient means for investigating this class of problems.
Stress Condition, Vibrational Exciting Force, and Contact Pattern of Helical Gears with Manufacturing and Alignment Error
Authors: Kubo A.
Published: November 2010

The general calculating method of load sharing to every tooth pair in meshing, load distribution, and contact pattern on tooth flank of helical gears with manufacturing and alignment error is shown, for which some parts of tooth flanks on the geometrical line of contact can separate from each other due to the errors. For such gears, stiffness of meshing tooth pair, exciting force of gear vibration, and total composite error (single flank) under loaded condition is derived. Using this calculating method, tooth stiffness, vibration excitation, tooth fillet stress, and contact pattern are calculated for some helical and spur gears, and they are compared with measured results.
Load Distribution in Timing Belts
Authors: Gerbert G. , Jo¨nsson H. , Persson U. , Stensson G.
Published: November 2010

A theory is presented for determining the distribution of the belt tension and the tooth load in timing belts. It appears that the distribution of both loads is of exponential character and one important parameter is the ratio between the spring constant of the tooth and the spring constant of the cord (a nondimensional number). Friction between the belt and the top of the pulley is also considered. This mostly influences the tooth load distribution. A criterion is presented for maximum tension ratio with respect to correct tooth action. Two belts are examined experimentally (steel cord-urethane and glass fiber cord-neoprene rubber). The spring constant of the tooth is determined both experimentally (a test procedure is presented) and theoretically (using the finite element method) and the agreement is good. The distribution of the belt tension in timing belt drives has been measured. The agreement between theory and experiment for the belts examined is satisfactory. Some discrepancies were observed. These will be the subject for further research.
Analysis of Performance of Pneumatic Impact Absorbers
Authors: Hundal M. S.
Published: November 2010

Performance of impact absorbers employing a pneumatic damper and a linear spring in parallel is analyzed. The governing nonlinear differential equations are derived and converted to nondimensional form. For case of a damper with fixed area orifice the equations are numerically integrated. Performance charts are presented in terms of three dimensionless parameters: mass, spring stiffness and orifice area ratio. Then, a second case is considered in which the damper orifice area is made to vary in two stages. During an initial portion of the stroke the orifice is closed and the air pressure rises to a certain value. In the second stage the orifice area varies in such a manner that a constant deceleration of the mass is achieved. A closed form solution of the governing equations is presented for the second case. The design and performance are compared with that of an impact absorber consisting of a spring only, and with those employing hydraulic dampers.
Optimization of Pneumatic Vibration Isolation System for Vehicle Suspension
Authors: Esmailzadeh E.
Published: November 2010

The suspension system of a vehicle provides the means by which forces and movements are transferred from the body to the wheels and vice versa. While the general outline of vehicle suspension behavior is fairly well known, little interest has been shown in the detailed dynamic performance of the various components. Air springs are perhaps the most versatile and adaptable type of suspension element. They provide practically frictionless action, adjustable load capacity and simplicity of height control. Initially, a vehicle suspension system with a pneumatic isolator connected to a fixed volume tank via parallel plate restrictor is considered. Here the damping is provided by the flow of air through the restricted passage which has an advantage over the conventional viscous shock absorber. Body movements are only considered to be vertical harmonic displacement. An optimization technique is applied to evaluate the optimum values of many parameters involved for which the maximum transmitted motion to the body would be minimum over the broad frequency range. Theoretical expressions for the transmissibility of the body and the wheel, optimum values of mass ratio, stiffness ratio and damping ratio are presented. Design data are presented nondimensionally for parameter variations which are sufficiently broad to encompass a wide range of practical engineering problems.
Nonlinear Analysis of the Lateral Response of Columns to Periodic Loads
Authors: Tezak E. G. , Mook D. T. , Nayfeh A. H.
Published: November 2010

Parametrically excited transverse oscillations of columns are studied. The amplitude of the response is taken to be small, but finite; hence, stretching of the neutral axis is significant. Nonlinear strain-displacement relationships are used. A general method of analysis is first described and then used to solve two numerical examples—one without and one with internal resonances. The results show that jump phenomena exist, that the same excitation can produce two rather different responses, and that, when there is an internal resonance, two rather different excitations can produce practically the same response.
Dynamic Accuracy of Hybrid Profiling Mechanisms in Cam Manufacturing
Authors: Sankar S. , Osman M. O. M.
Published: November 2010

Dynamic accuracy in cam production using hybrid profiling mechanisms in turning with a single point cutting tool is investigated. A profiling mechanism consisting of a four-way, critical-centered spool valve and a symmetrical volume power cylinder with a fixed piston is mathematically modeled and simulated on a hybrid computer to study its dynamic behavior. The model includes the dynamic cutting forces and their interaction with the velocity response of the mechanism, the nonlinear dry friction in the copying slide, and the dynamic behavior of the copying slide, control valve, and the stylus. The kinematic displacement of the stylus in time domain is formulated from the cam profile characteristic and is used as the input function for the simulation. The response of the mechanism to this input describes the shape of the manufactured cam profile in time domain. Based on the results of this investigation, it can be concluded that for a minimum manufacturing error in cam profiling, hybrid profiling mechanisms should be designed with low stylus inertia and high stylus stiffness. Operating a profiling mechanism with high supply pressure, low exhaust pressure, smaller depth of cut, and low angular velcoity of master cam also give high dynamic accuracy. The influence of dry friction in the copying slide and the copy-slide angle γ on the manufacturing error is also presented. Plots are also developed to be used as a guide in the design and operation of these hybrid profiling mechanisms.
Analysis of Roller/Ball Bearing Vibrations
Authors: Braun S. , Datner B.
Published: November 2010

Described is a vibration based diagnostic method aimed at detecting localized defects developing in roller/ball bearings. The signature is decomposed into generalized periodic functions and a search strategy for the various components developed and implemented. The method is shown to be applicable for cases where spectral analysis fails to give results.
Analysis and Simulation of Planar Mechanism Systems Using Bond Graphs
Authors: Karnopp D. , Margolis D.
Published: November 2010

A method is presented for incorporating planar mechanisms into dynamic system models using bond graphs. Through the use of stiff coupling springs at the mechanism joints, the nonlinear geometrical relationships are uniformly and simply described by displacement modulated transformers and the system state equations can be written with no algebraic complications. In contrast to the more elegant kinematic techniques for describing mechanism dynamics, the present method results in higher order systems of equations but the equations themselves are simpler and not densely coupled. In addition, coupling forces are available at the joints. An example demonstrates that the extra eigenvalues associated with the coupling springs can readily be found for any configuration so that the spring constants can be chosen to minimize computation time.
A Compendium of Line-Symmetric Four-Bars
Authors: Baker J. Eddie
Published: November 2010

Geometrical properties of linkages, such as parallelism of joint axes and symmetries, have previously been used to establish mobility. Because it was not until very recently that all relevant four-bar linkages had been isolated, it had not been possible to investigate the extent to which line-symmetry is significant in linkage mobility. In this paper, the concurrence or otherwise of line-symmetry and mobility is comprehensively studied as it applies to four-bar loops, resulting in the specification of the five distinct line-symmetric four-bars. Finally, a conclusion is drawn concerning the relationship between symmetries and linkage mobility.
Principles and Criteria of Vibration Isolation of Machinery
Authors: Rivin E. I.
Published: November 2010

This paper considers a complex of problems connected with the systematic approach to vibration isolation of production machinery. After general classification of machinery and the formulation of typical features of a dynamic vibroisolation system of machinery, criteria of effective isolation for main groups of machinery are derived. Designs of isolators complying with these criteria are described.
On the Prototype Testing and Computer Simulation of St. Lawrence Seaway Hydro-Mechanical Lock Gate Drives
Authors: Sankar S. , Proszanski A.
Published: November 2010

This paper presents the computer simulation and the prototype testing of hydro-mechanical drives for mitre gates in St. Lawrence Seaway navigation locks. For the computer simulation, the technique of Power Bond Graph is adopted to obtain the mathematical model of the lock gate drive. A digital computer is used to predict the performance of the lock gate under the actual operating environment. The model takes into account the friction load, wind load, load due to water surging, inertia load and water resistance load. Dynamic performance measurements on a prototype hydro-mechanical mitre gate drives in St. Lawrence Seaway while in operation were carried out. Good correlation exists between the simulation and prototype test results for pressure and torque transients and also in the operating time for gate opening and closing. Based on this investigation, recommendations are made on a single constant power hydraulic drive of 25 HP for operating St. Lawrence Seaway lock gates most economically.
Large Deflection Elastic-Plastic Dynamic Response of Stiffened Shells of Revolution
Authors: Stricklin J. A. , Haisler W. E. , Von Riesemann W. A.
Published: November 2010

This paper presents the formulation and check-out problems for a computer code DYNAPLAS, which analyzes the large deflection elastic-plastic dynamic response of stiffened shells of revolution. The formulation for spacial discretization is by the finite element method with finite differences being used for the evaluation of the pseudo forces due to material and geometric nonlinearities. Time integration is by the Houbolt method or central differences. The stiffeners may be due to concentrated or distributed eccentric rings and spring supports at arbitrary angles around the circumference of the elements. Check-out problems include the comparison of solutions from DYNAPLAS with experimental and other computer solutions for rings and conical and cylindrical shells. A hypothetical submarine including stiffeners and missile tube is studied under a combination of hydrostatic and dynamically applied asymmetrical pressure loadings.
A Solids Mesh Generator and Result Display Package
Authors: Kamel H. A. , Shanta P. J.
Published: November 2010

The paper describes a three-dimensional mesh generator aimed at complex solids, using a mini-computer in conjunction with interactive graphics. The principles of operation are: 1 – The solid is divided into subregions, each generated from key point coordinates. 2 – Interfacing of the subregions can easily be accomplished by the user. 3 – Numerical information may be obtained regarding any of the nodes or elements. 4 – The generator is attached to a standard Unified Data Base to enable interfacing with analysis packages. 5 – Different materials may be used and stored as part of the data base. 6 – Provisions are made for substructures and reduced substructures. 7 – Graphics display is based on minimizing screen information for best effectiveness. 8 – Software rotation and perspective including depth. 9 – It is possible to display arbitrary sections based on topological or geometrical considerations. 10 – Stresses and deflections may be displayed and screened.
Stresses in a Spherical Shell With a Circular Elastic Inclusion
Authors: Prakash P. , Rao K. P.
Published: November 2010

The problem of a circular elastic inclusion in a thin pressurized spherical shell is considered. Using Reissner’s differential equations governing the behavior of a thin shallow spherical shell, the solutions for the two regions are obtained in terms of Bessel and Hankel functions. Particular cases of a rigid circular inclusion free to move with the shell and a clamped rigid circular inclusion are also considered. Results are presented in nondimensional form which will greatly facilitate their use in the design of spherical shells containing a rigid or an elastic inclusion.
Elastic-Plastic Fracture Toughness: A Comparison of J-Integral and Crack Opening Displacement Characterizations
Authors: Griffis C. A.
Published: November 2010

The geometry dependence of the J-integral and crack opening displacement at fracture initiation, Ji and (COD)i, is examined for HY-80 steel using precracked bend specimens having thicknesses ranging from 1.6 to 53mm. The amount of crack growth at selected points on the load-deflection diagram was delineated using an unload-heat tint procedure. Resistance curves of J and COD versus crack extension were constructed to determine critical values of these parameters at incipient crack movement. Results are interpreted in terms of previously proposed minimum size requirements for valid Ji measurement. The adequacy of the Rice-Srawley J-integral formula for the bend specimen and the utility of J and COD values at maximum load are also considered.
Design Philosophy of Pressure Vessels for Service Above 10 ksi (70 MPa)
Authors: Witkin D. E. , Mraz G. J.
Published: November 2010

This paper discusses design criteria for pressure vessels intended for service above 10 ksi (70 MPa). Since the ASME Boiler and Pressure Vessel Code cannot, in a practical sense, be applied to the construction of such vessels, suitable supplementary and alternative criteria are proposed to serve as a design basis for such vessels. It is hoped that they can also serve as the basis for development of Design Rules for High Pressure Vessels by the ASME. Topics considered include: Use of yield strength criteria; Use of alternative fatigue criteria; Use of burst and plastic flow criteria; Alternative hydrostatic test pressure criteria; Criteria for prestressing; Material quality standards. These show that suitable criteria for high pressure vessel design require a higher level of precision than now exists in the Code. Higher levels of material quality and testing are needed to insure required minimum levels of properties without the need to compensate (by elements of the factors of safety) for excessive variation. More detailed and comprehensive analysis, to make the mathematical models more truly reflect the actual stress conditions than are usually used in Section VIII of the Code, are found to be necessary.
Fracture Discontinuities and Structural Analysis in Resource Recovery Endeavors
Authors: Cleary M. P.
Published: November 2010

The need for redirection of investigative effort in the area of mineral and energy recovery is emphasized: more fundamental analytical descriptions must be linked to innovative design explorations if traditionally slow rates of methodology evolution are to accelerate reliably and ecologically toward a compensation for rapid depletion of readily available resources. An example of the problems to be resolved is provided in the form of a mechanism for failure by gradual fracture evolution: this involves substantial departure from predictions of conventional mechanics modelling and is traced to inherent instability among the constitutive features of representative geological materials. Major advances are needed, both in physically motivated formulations and tractable incorporation into computational schemes, before this unavoidable behavior can be confidently encompassed by standard design procedures; current trends indicate an excess desire to provide elaborate numerical solutions for superficially consistent models, although the essential physical mechanism is manifestly absent in the results. The practitioner can be encouraged to seek skilled scientific aid only if truly realistic simulations of his design application can actually be performed—development of that ability will require much logical rigor, engineering skill and ingenuity. Corresponding examples are suggested for other aspects of the general discipline, called thermomechanics, which is so central to the present resource crisis.
Mathematical and Experimental Investigation Into the Auto-Frettaging of High-Pressure Mudpump Fluid Ends
Authors: Van Der Krogt A. H.
Published: November 2010

The fluid ends on high-pressure triplex mud pumps are exposed to high cyclic internal pressures. These fluid ends should therefore have adequate elastic strength and fatigue life under operating conditions. A method for increasing the fatigue life of the fluid ends is the auto-frettage process. The elastico-plastic behavior of fluid ends manufactured with side bores subjected to internal pressure has been studied both mathematically and experimentally. The mathematical analysis was carried out using an elasto-plastic finite-element approach. The experimental study, using direct strain-gage measurements, confirmed the mathematical analysis.
Lower-Bound Limit Pressures for the Cylinder-Cylinder Intersection: A Parametric Survey
Authors: Robinson M.
Published: November 2010

Lower-bound limit pressures are presented for the case of a flush radial cylindrical nozzle in a cylindrical vessel under internal pressure. A comprehensive range of parameters has been covered and these lower-bound pressures are compared, where possible, with theoretical values by other authors, and also with a number of experimental results. It is shown that, because of uncertainty and ambiguity in interpreting the experimental data and an inadequate number of good upper-bound results, there is still a need for further work to be done on this problem.
The Effect of Stress Ratio on Fatigue Crack Growth in a Biaxial Stress Field
Authors: Zamrik S. Y. , Shabara M. A.
Published: November 2010

The effect of stress ratio (mean stress) on fatigue crack growth in a biaxial stress field was investigated. The biaxiality was introduced by means of anticlastic bending of rhombic plates. A crack initiator in the form of an EDM slot was embedded in the top surface of plate specimen. The crack tip was subjected, as a result of specimen bending, to two principal stresses, one tensile and normal to the crack and the other parallel to it but in a compressive direction. Three mean stress ratios of R = Kmin/Kmax were applied, one in a zero to tension mode, the second in a completely reversed cycling where the stress ratio R = −1, and the third in an intermediate ratio of R = −0.5. All stress ratios were imposed in an existing biaxial stress field. Uniaxial concepts such as Walker’s approach were analyzed and applied to biaxial stress system. Experimental results have shown that fatigue crack growth is influenced by both variables: mean stress ratio and stress biaxiality ratio. Each variable was isolated by using the concept of effective stress intensity range ΔK. The crack growth and the fracture mode under each type of loading are discussed and analyzed.
A Method for Analysis of a Prototype Articulated Multiline Marine Production Riser System
Authors: Caldwell J. B. , Gammage W. E.
Published: November 2010

This paper describes a newly developed nonlinear computer program that predicts internal reaction forces and motions of a multiline marine production riser exposed to wave and current forces. The paper also presents an analytical method that accounts for large geometric displacements and nonlinear wave forces. A simulation of the response of a prototype articulated multiline marine production riser during a mild tropical storm illustrates the program’s capability.
Arctic Transportation: Operational and Environmental Evaluation of an Air Cushion Vehicle in Northern Alaska
Authors: Abele G. , Brown J.
Published: November 2010

Traffic tests conducted near Barrow, Alaska with a 7-ton SK-5 Air Cushion Vehicle have shown that these types of vehicles can provide year-round high-speed transport capability over a variety of relatively level, low strength terrains. The ecological impact of ACV traffic over easily degradable tundra terrains is not nearly as significant as that of wheeled or tracked vehicle traffic.
Downhole Measurements Through Modified Drill Pipe
Authors: Denison E. B.
Published: November 2010

A modified, circuit-containing drill pipe has been developed which allows instantaneous data transmission from a borehole while drilling. The system sends 600 data samples/second and is capable of much more. Results of the first system field test are reported. System components are described; they include a downhole instrument, a special 3000-ft (900-m) drill string, a slip/ring, kelly assembly, uphole readout, and special cleaning equipment.
The Flexibility of Curved Pipes in Creep
Authors: Boyle J. T. , Spence J.
Published: November 2010

The redistribution of stress in a linear, thin shell model of a curved pipe creeping under the action of a constant applied in-plane bending moment is represented by an equation of evolution in time. Using finite differences, this continuous system is reduced to a finite set of initial value problems which are numerically integrated using a fifth order Runge-Kutta method. The flexibility of the curved pipe is compared to that of a similar elastic, and a similarly creeping, straight pipe. Results are compared with two simple approximate methods and with a previous-steady state analysis.
Local Flexibility Coefficients for the Built-in Ends of Beams and Plates Including the Effects of Foundation Fillet Radii
Authors: Gordon J. L. , Jones D. P.
Published: November 2010

The local deformations at the built-in end of a beam or plate re-entrant corner have considerable influence upon the redundant forces and moments at the juncture, and hence, upon the stresses. The effects of these local flexibilities are quite significant at nozzle-to-vessel intersections, head-to-shell junctures, tubesheet-to-heat exhanger shell junctures, and the like. Methods are available in the literature which permit the incorporation of the additional flexibility of the juncture into a structural analysis, but these methods do not adequately consider the influence of the transition fillet radius. Presented in this paper is the dependency on the fillet radius of the planar flexibility coefficients for the mean rotation and displacement due to bending and shear acting on a quarter-plane support. These relationships are obtained from elastic finite-element analyses of a quarter-plane support and are presented in a form that may be easily incorporated into design methodologies. Also, presented are the stress concentration factors in the fillet and a numerical example illustrating the significance of the results.
Enabling Unbalanced Fermentations by Using Engineered Electrode-Interfaced Bacteria
Authors: Flynn Jeffrey M. , Ross Daniel E. , Hunt Kristopher A. , Bond Daniel R. , Gralnick Jeffrey A.
Published: November 2010

Cellular metabolism is a series of tightly linked oxidations and reductions that must be balanced. Recycling of intracellular electron carriers during fermentation often requires substrate conversion to undesired products, while respiration demands constant addition of electron acceptors. The use of electrode-based electron acceptors to balance biotransformations may overcome these constraints. To test this hypothesis, the metal-reducing bacterium
Shewanella oneidensis
was engineered to stoichiometrically convert glycerol into ethanol, a biotransformation that will not occur unless two electrons are removed via an external reaction, such as electrode reduction. Multiple modules were combined into a single plasmid to alter
S. oneidensis
metabolism: a glycerol module, consisting of
glpF
,
glpK
,
glpD
, and
tpiA
from
Escherichia coli
, and an ethanol module containing
pdc
and
adh
from
Zymomonas mobilis
. A further increase in product yields was accomplished through knockout of
pta
, encoding phosphate acetyltransferase, shifting flux toward ethanol and away from acetate production. In this first-generation demonstration, conversion of glycerol to ethanol required the presence of an electrode to balance the reaction, and electrode-linked rates were on par with volumetric conversion rates observed in engineered
E. coli
. Linking microbial biocatalysis to current production can eliminate redox constraints by shifting other unbalanced reactions to yield pure products and serve as a new platform for next-generation bioproduction strategies.

IMPORTANCE
All reactions catalyzed by whole cells or enzymes must achieve redox balance. In rare cases, conversion can be achieved via perfectly balanced fermentations, allowing all electron equivalents to be recovered in a single product. In most biotransformations, organisms must produce a mixture of acids, gasses, and/or alcohols, and no amount of enzyme or strain engineering can overcome this fundamental requirement. Stoichiometric conversion of glycerol, a waste product from biodiesel transesterification, into ethanol and CO
2
with no side products represents such an impossible fermentation, due to the more reduced state of glycerol than of ethanol and CO
2
. The unbalanced conversion of glycerol to ethanol has been viewed as having only two solutions: fermenting glycerol to ethanol and potentially useful coproducts or “burning off” excess electrons via careful introduction of oxygen. Here, we use the glycerol-to-ethanol example to demonstrate a third strategy, using bacteria directly interfaced to electrodes.
Potential for domesticated–wild interbreeding to induce maladaptive phenology across multiple populations of wild Atlantic salmon (Salmo salar)
Authors: Fraser Dylan J. , Minto Cóilín , Calvert Anna M. , Eddington James D. , Hutchings Jeffrey A.
Published: November 2010

We report how aquaculture may negatively alter a critical phenological trait (developmental rate) linked to survival in wild fish populations. At the southern limit of the species range in eastern North America, the persistence of small Atlantic salmon ( Salmo salar ) populations may be constrained by interbreeding with farmed salmon that escape regularly from intensive aquaculture facilities. Using a common-garden experimental protocol implemented over an 8-year period, we show that embryos of farmed salmon and multigenerational farmed–wild hybrids (F1, F2, wild backcrosses) had slower developmental rates than those of two regional wild populations. In certain cases, our data suggest that hybrid developmental rates are sufficiently mismatched to prevailing environmental conditions that they would have reduced survival in the wild. This implies that repeated farmed–wild interbreeding could adversely affect wild populations. Our results therefore reaffirm previous recommendations that based on the precautionary principle, improved strategies are needed to prevent, or to substantially minimize, escapes of aquaculture fishes into wild environments.
Environmental drivers of fish functional diversity and composition in the Lower Colorado River Basin
Authors: Pool Thomas K. , Olden Julian D. , Whittier Joanna B. , Paukert Craig P.
Published: November 2010

Freshwater conservation efforts require an understanding of how natural and anthropogenic factors shape the present-day biogeography of native and non-native species. This knowledge need is especially acute for imperiled native fishes in the highly modified Lower Colorado River Basin (LCRB), USA. In the present study we employed both a taxonomic and functional approach to explore how natural and human-related environmental drivers shape landscape-scale patterns of fish community composition in the LCRB. Our results showed that hydrologic alteration, watershed land use, and regional climate explained 30.3% and 44.7% of the total variation in fish community taxonomic and functional composition, respectively. Watersheds with greater dam densities and upstream storage capacity supported higher non-native functional diversity, suggesting that dams have provided additional “niche opportunities” for non-native equilibrium life-history strategists by introducing new reservoir habitat and modifying downstream flow and thermal regimes. By contrast, watersheds characterized by greater upstream land protection, lower dam densities, and higher variation in spring and summer precipitation supported fish communities with a strong complement of native species (opportunistic–periodic strategists). In conclusion, our study highlights the utility of a life-history approach to better understand the patterns and processes by which fish communities vary along environmental gradients.
Genetic homogeneity of weathervane scallops (Patinopecten caurinus) in the northeastern Pacific
Authors: Gaffney Patrick M. , Pascal Carita M. , Barnhart Jeffery , Grant W. Stewart , Seeb James E.
Published: November 2010

We assessed genetic differentiation among populations of weathervane scallop ( Patinopecten caurinus ) in the northeastern Pacific, extending over 2500 km in the Gulf of Alaska and southeastern Bering Sea. Variability was surveyed at nuclear loci with allozyme, microsatellite, and single nucleotide polymorphism (SNP) methods, and at mitochondrial (mt)DNA loci with SNPs and nucleotide sequencing. High levels of gene diversity were detected for allozymes (H = 0.080), microsatellites (H = 0.734), and mtDNA (h = 0.781). Genotypes at nuclear loci generally fit Hardy–Weinberg proportions, except for some microsatellite loci, for which null-allele frequencies of 0.02 to 0.34 were estimated. No allele-frequency differences were detected among samples, except for the allozyme loci Gpi and Pep-4. Overall levels of differentiation ranged from FST= 0.0004 for allozymes, FST= 0.0008 for mtDNA to FST= 0.0004 for microsatellites. No isolation by distance was found for any of the markers. A unimodal mtDNA mismatch distribution and significant excesses of low-frequency variants for allozymes, microsatellites, and mtDNA may reflect a post-glacial population expansion. The lack of genetic differentiation measured by neutral markers does not preclude the existence of locally adapted, self-sustaining populations that are important in the harvest management of this species.
Management implications of the effects of marine-derived nutrients on salmon population dynamics
Authors: Adkison Milo D.
Published: November 2010

Pacific salmon ( Oncorhynchus spp.) populations transfer large quantities of nutrients from their marine habitats to their freshwater habitats, but the management implications of this nutrient import mechanism are not clear. I investigate whether the effects of these nutrient imports on salmon productivity can be detected, how well management strategies can perform if they ignore the effects of marine-derived nutrients when productivity is strongly dependent on nutrient levels, and under what circumstances nutrient-depleted stocks can recover. I find that stock-recruitment data do not usually permit the detection of the effects of nutrient imports. Some management strategies that ignore nutrient-related effects will, as they are updated, converge to policies that are similar to those that are optimal, given the nutrient effects. Constant harvest rate policies will approach optimal harvesting faster than constant escapement policies. Nutrient dependence can lead to multiple stable states for a population, so that a population subject to one harvest rate can be either maintained at high abundance or, if at low abundance and nutrient-depleted, driven to extirpation. While the importance of nutrient effects on a salmon stock may be difficult to ascertain, managers can employ harvest strategies that are robust to this possibility.
Predicting the vertical distributions of reef fish larvae in the Straits of Florida from environmental factors
Authors: Huebert Klaus B. , Sponaugle Su , Cowen Robert K.
Published: November 2010

Three seasons of vertically stratified ichthyoplankton sampling at the edge of the Florida Current revealed consistent accumulations of some coral reef fish larvae under taxon-specific environmental conditions. Environmental variability ranging from predictable (seasonal differences in temperature, diel changes in light, and vertical gradients in many variables) to stochastic (changes in wind-driven turbulence and patchiness of zooplankton) was used to model larval distributions. In five taxa, including the commercially important Epinephelini (groupers), relative larval densities were predicted with significant accuracy based entirely on sampling depth. Models yielding these predictions were cross-validated among all seasons, indicating that larval vertical distributions were remarkably unaffected by other environmental factors, while revealing strong behavioral preferences for specific ranges of hydrostatic pressure. Pomacentridae (damselfish) larvae consistently occupied shallower depths at night than during the day, demonstrating diel vertical migrations. At the community level, depth and season were two major factors structuring larval coral reef fish assemblages. Predictable vertical distributions of larvae in the Straits of Florida can facilitate modeling the same taxa elsewhere in the Western Central Atlantic.
Quantifying the research impact of the Sustainable Forest Management Network in the social sciences: a bibliometric study
Authors: Klenk Nicole L. , Dabros Anna , Hickey Gordon M.
Published: November 2010

This research note presents the results of a bibliometric analysis that was conducted to better understand the impact that Sustainable Forest Management Network (SFMN) funded research had in the forest-related social and Aboriginal research communities. We applied two indicators of research impact: (i) research outputs and (ii) citations. Our results suggest that the SFMN’s research outputs were highest in the fields of economics, sociology, and political science and law. The number of research articles that acknowledged the SFMN was 30% of the total research output of the SFMN-funded Principal Investigators. These articles represented 3% of the social science articles published in the Forestry Chronicle (the journal most frequently used by SFMN-funded Principal Investigators). Research output related to Aboriginal forestry indicated that the SFMN had a significant influence on the development of the field. Our citation analysis indicated that the average number of citations per SFMN-acknowledged publication in the social sciences was approximately the same as the international impact standard in the field. These results suggest that the SFMN-funded research in the social sciences compared very well with the international research standards in forest-related social sciences.
Estimating the consequences of wildfire for wildfire risk assessment, a case study in the southern Gulf Islands, British Columbia, Canada
Authors: Tutsch Matthew , Haider Wolfgang , Beardmore Ben , Lertzman Kenneth , Cooper Andrew B. , Walker Robert C.
Published: November 2010

Wildfire risk assessment research has made considerable progress towards estimating the probability of wildfires but comparatively little progress towards estimating the expected consequences of potential fires. One challenge with estimating wildfire consequences has been to identify a common metric that can be applied to consequences measured in different units. In this paper, we use the preferences of representatives of local fire management agencies as the common consequences metric and apply it to a case study in the southern Gulf Islands, British Columbia, Canada. The method uses an expert survey and a maximum-difference conjoint analysis to establish the relative importance of specific fire consequences. A fire with a major potential for loss of life was considered to be about three times worse than major damage to houses and 4.5 times worse than loss of a rare species. Risk ratings were very sensitive to changes in fire consequences ratings. As the complexity of values at risk and number of stakeholders increase, the most efficient allocation of wildfire prevention, protection, and suppression resources becomes increasingly challenging to determine. Thus, as the complexity of stakeholder representation and values at risk increases, we need to pay increasing attention to quantitative methods for measuring wildfire consequences.
A REVIEW STUDY OF THE 3-PARTICLE TODA LATTICE AND HIGHER-ORDER TRUNCATIONS: THE ODD-ORDER CASES — PART I
Authors: ZACHILAS LOUKAS
Published: November 2010

The numerical behavior of the truncated 3-particle Toda lattice (3pTL) is reviewed and studied in more detail (than in previous papers) and at higher energies (at odd-orders n ≤ 9). We further extended our study to higher truncations at odd-orders, n = 2k + 1, k = 1, …, 9. We have located the majority of the families of periodic orbits along with their main bifurcations. By using: (a) the method of Poincaré surface of section, (b) the maximum Lyapunov characteristic number and (c) the ratio of the families of ordered periodic orbits, we studied the topology of the nine odd-order Hamiltonians with respect to their order of truncation.
BIOINFORMATIC APPROACHES FOR PREDICTING SUBSTRATES OF PROTEASES
Authors: SONG JIANGNING , TAN HAO , BOYD SARAH E. , SHEN HONGBIN , MAHMOOD KHALID , WEBB GEOFFREY I. , AKUTSU TATSUYA , WHISSTOCK JAMES C. , PIKE ROBERT N.
Published: November 2010

Proteases have central roles in "life and death" processes due to their important ability to catalytically hydrolyze protein substrates, usually altering the function and/or activity of the target in the process. Knowledge of the substrate specificity of a protease should, in theory, dramatically improve the ability to predict target protein substrates. However, experimental identification and characterization of protease substrates is often difficult and time-consuming. Thus solving the "substrate identification" problem is fundamental to both understanding protease biology and the development of therapeutics that target specific protease-regulated pathways. In this context, bioinformatic prediction of protease substrates may provide useful and experimentally testable information about novel potential cleavage sites in candidate substrates. In this article, we provide an overview of recent advances in developing bioinformatic approaches for predicting protease substrate cleavage sites and identifying novel putative substrates. We discuss the advantages and drawbacks of the current methods and detail how more accurate models can be built by deriving multiple sequence and structural features of substrates. We also provide some suggestions about how future studies might further improve the accuracy of protease substrate specificity prediction.
The impact of service demand variability on resource allocation strategies in a grid system
Authors: Zikos Stylianos , Karatza Helen D.
Published: November 2010

Scheduling and resource management play an important role in building complex distributed systems, such as grids. In this article we study the impact on performance of job service demand variability in a two-level grid architecture, given that the grid and local schedulers are unaware of each job's service demand. We examine two scheduling policies at grid level, which utilize site load information and three policies at local level. A simulation model is used to evaluate performance. Results show that service demand variability degrades performance, and thus a suitable local resource allocation policy is needed to reduce its impact.
Geodesic image and video editing
Authors: Criminisi Antonio , Sharp Toby , Rother Carsten , P'erez Patrick
Published: November 2010

This article presents a new, unified technique to perform general edge-sensitive editing operations on n-dimensional images and videos efficiently.

The first contribution of the article is the introduction of a Generalized Geodesic Distance Transform (GGDT), based on soft masks. This provides a
unified
framework to address several edge-aware editing operations. Diverse tasks such as denoising and nonphotorealistic rendering are all dealt with fundamentally the same, fast algorithm. Second, a new Geodesic Symmetric Filter (GSF) is presented which imposes contrast-sensitive spatial smoothness into segmentation and segmentation-based editing tasks (cutout, object highlighting, colorization, panorama stitching). The effect of the filter is controlled by two intuitive, geometric parameters. In contrast to existing techniques, the GSF filter is applied to real-valued pixel likelihoods (soft masks), thanks to GGDTs and it can be used for both interactive and automatic editing. Complex object topologies are dealt with effortlessly. Finally, the parallelism of GGDTs enables us to exploit modern multicore CPU architectures as well as powerful new GPUs, thus providing great flexibility of implementation and deployment. Our technique operates on both images and videos, and generalizes naturally to n-dimensional data.

The proposed algorithm is validated via quantitative and qualitative comparisons with existing, state-of-the-art approaches. Numerous results on a variety of image and video editing tasks further demonstrate the effectiveness of our method.
Cross-layer bandwidth management and optimization in TDMA based wireless mesh networks using network coding
Authors: Mogre Parag S.
Published: November 2010

Wireless Mesh Networks (WMNs) provide a novel network architecture to extend broadband network coverage with low costs. Additionally, we see an increased interest in supporting demanding multimedia applications in next-generation wireless mesh networks. Provision of Quality of Service (QoS) in wireless mesh networks requires end-to-end support for routing packets via a suitable multihop route to the destination. However, in wireless mesh networks, if the medium access control layer does not support mechanisms for QoS support at a per-link level, all efforts for providing end-to-end QoS are futile. Hence, we see a trend towards standards for wireless mesh networks which support QoS at the Medium Access Control (MAC) level on a per-link basis.
The Genetics of Lignin Biosynthesis: Connecting Genotype to Phenotype
Authors: Bonawitz Nicholas D. , Chapple Clint
Published: November 2010

The processes underlying lignification, which for many years have been the near-exclusive purview of chemists and biochemists, have more recently been approached using both classical forward genetic screens and targeted reverse genetic approaches such as antisense suppression, RNAi, and characterization of insertional mutants. In this review, we provide an overview of the current understanding of lignin biosynthesis and structure, with emphasis on mutant and transgenic plants that have contributed to this knowledge. We also discuss ongoing work aimed at elucidating the relationship between lignin structure and function in vivo, as well as the phenotypic consequences arising from genetic manipulation of the lignin biosynthetic pathway.