bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of Transient Heat Transfer Models for the Coupled 3-D Moving Piston Assembly-Liner System
Authors: Jiang Yankun , Liu Zhien , Reitz Rolf D. , Dong Zheling , Ye Xiaoming
Published: May 2009

A transient heat transfer model for the coupling 3-D moving piston assembly-liner system has been successfully improved for predicting temperature distributions in the components of internal combustion engine chamber. In the model the effect of the 3-D friction heat generated at the piston ring/cylinder liner interfaces and the multi-dimensional lubricant film thickness between the piston rings and the liner has been taken into account. A directly coupled finite element method (FEM) is employed in the model for establishing the heat transfer relation among the moving piston assembly-cylinder liner components. A 3-D discrete model of the coupling system is formulated, which includes the piston rings, piston, liner and cylinder. Due to the complexity of the temperature stiffness matrix, a sparse matrix data structure is employed in the model to save the memory and calculation time. Finally, the 3-D coupling heat transfer model has been used to analyze heat transfer processes in a gasoline engine.
Experimental and Finite Element Analysis of Large-Strain Indentation of Polymeric Solids
Authors: Lu Y. C. , Shinozaki D. M.
Published: May 2009

The large-strain indentation test has been examined using experimental testing and finite element simulation on various engineering polymers. Cylindrical, flat-ended tips with diameter range from 10μm–100μm are used. In the large-strain region, the indentation stress-displacement curve shows linear response from which the mean indentation stress is extrapolated. The mechanism of large-strain indentation has been investigated through optical microscope and finite element simulations. Once a critical indentation depth is reached, the plastic zone surrounding the indenter remains constant.
A Numerical Investigation of the Effect of End-Wall Boundary Layer Skew on the Aerodynamic Performance of a Low Aspect Ratio, High Turning Compressor Cascade
Authors: Boehle M. , Stark U.
Published: May 2009

The paper reports on a numerical investigation into the effects of inlet boundary layer skew on the aerodynamic performance of a high turning 50 deg, 2D compressor cascade. The cascade geometry is representative of stator hub sections in highly loaded single-stage axial-flow low-speed compressors. 2D blades with NACA 65 thickness distribution on circular arc camber lines were used. The blade aspect ratio was 1.0, the space/chord ratio 0.5 and the stagger angle 25 deg. The simulations were done with a commercially available, steady three-dimensional RANS solver with the Spalart-Allmaras turbulence model. The incoming end-wall boundary layers were assumed to be collateral or skewed. In both cases the profile boundary layers were fully turbulent. The Reynolds-number was fixed at 600000 and the thickness of the incoming end-wall boundary layer was 0.1. Results are shown for an inlet-air angle of 50 deg, representing the impact free inlet-air angle of a hypothetical cascade with zero-thickness blades. Contrary to what has been expected, the results do not show (hub) corner stall, neither with nor without end-wall boundary layer skew. Flow reversal happens to occur almost exclusively on the suction surface of the blades, not on the end-walls. The end-wall flow is highly overturned, when the incoming boundary layer is collateral and is much less curved when the incoming boundary layer is skewed and (re)energized. This in turn leads to an interaction between the end-wall and blade suction surface flow which is much stronger in the first than in the second case with corresponding higher and lower losses, respectively.
Blast Response Analysis of Composite Plate by Multi-Domain Hermite Differential Quadrature Method (MD-HDQ)
Authors: Cheng Jinquan , Li Guoqiang
Published: May 2009

Blast response of armor composite plate is a complex process, which strongly depends on the form of the blast loading, materials properties of the target, structure boundary conditions, etc. The blast response of composite targets is also a time-dependent process. In order to better solve the time dependent non-linear governing equations of the composite plate under blast loading, a new multi-domain Hermite Differential Quadratue (MD-HDQ) method is developed to obtain the numerical results. In the proposed numerical method, the time-dependent unknown function is directly interpolated in both time domain and spatial domain, which is easy to implement and saves computation time. After the developed MD-HDQ method is numerically validated, the detailed numerical analyses about the effects of the boundary conditions and pressure pulse loading shapes are conducted and the influence of the transverse shear force on the dynamic response is discussed.
Thermal Interaction in Free Convection From Two Unequally Powered Discrete Heat Sources With Various Orientations and Separation Distances on a Vertical Plate
Authors: Kirby Patrick , Fleischer Amy
Published: May 2009

The purpose of this study is to examine the thermal interactions through both conduction and convection between two unequally powered discrete heat sources in free convection on a vertical plate. The sources are positioned at steadily increasing separation distances. The role of the thermal wake from the downstream component is quantified and is found to have competing influences that can either help or hinder the heat transfer from the upstream component depending on conditions.
Information Driven Product Development: A Framework for Product Design and Analysis Integration
Authors: Xiao Angran
Published: May 2009

New paradigms and accompanying software systems are necessary to support the integration of system level design and discipline level analysis activities for the implementation of product lifecycle management. In this paper, we present an information driven product development method for the integration in the context of multidisciplinary product realization. The method contains three constituents: product information model which represents the associativities among design requirements, product components, and design parameters; compromise Decision Support Problem which maps the information model directly into design problems; and knowledge based Finite Element Analysis which generates analysis model automatically from the information model. Information driven product development uses product information model as a communication media between design and analysis activities, hence provides an effective way to trace the impact of design changes, facilitates the reuse of analyses models, and supports collaborative decision-making. An electronic chip package design and analysis scenario is presented to illustrate and demonstrate this method.
Implementation of Magnetic Suspension Control With FPGA
Authors: Lei Shuliang , Provenza Andy , Palazzolo Alan , Beach Raymond
Published: May 2009

This paper presents a methodology for an alternative implementation of DSP-based controllers typically used for magnetic bearing (MB) levitation and control on FPGA hardware. The approach takes s-domain transfer functions of the controller components and discretizes them using z-transform conversions into discrete time domain expressions. These expressions, which are essentially digital IIR filters, are synthesized and implemented to obtain downloadable bit-stream using Xilinx ISE software packages. In the example presented, the executable code was sent to configure the two FPGAs for control. An equivalent PD with notch filter FPGA-based controller was constructed to replicate an existing two-axis DSP controller used to control a radial magnetic bearing on a vertical rotor in the Dynamic Spin Rig Facility at NASA Glenn Research Center. The FPGA controller was successfully demonstrated on the NASA hardware.
Thermo-Fluid Mechanics of Fluid Injection and Refrigeration System Performance Improvement
Authors: Shiva Prasad B. G. , Moeller Philip , Sheridan John
Published: May 2009

Injecting a fluid into a flowing stream is a common and powerful flow control technique to improve the flow process or performance of downstream components and machinery. This paper presents an application of such a technique to scroll compressors for improving the cooling capacity and efficiency of refrigerators and other heat pumps. It provides some insights into the physics of fluid injection and suggests methods for maximizing the benefits. Further, it discusses the need for CFD in system design and optimization and illustrates its application.
Static Power Consumption: Silicon on Insulator Metal Oxide Semiconductor Field Effect Transistor
Authors: Raju Uthaman , Pandojirao-S. Praveen , Sivakumar Niraja , Agonafer Dereje
Published: May 2009

The static power consumption due to leakage current plays a significant part in semiconductor devices, as the device dimensions continue to shrink. Low power dissipation is one of the critical factors needed to achieve high performance in a chip. New methods are continuously being implemented for reduction of leakage current in deep sub micron ultra thin SOI MOSFET using device simulator tools. In this paper, an 18nm gate length ultra thin SOI MOSFET is simulated for different silicon body thicknesses and the leakage current is determined by using the device simulator, MEDICITM. It is demonstrated that MEDICI™ device simulations is a good tool that can effectively be used for ultra thin SOI MOSFET devices to study the effect of design parameters on the leakage current. Ultra thin SOI MOSFET with 18nm gate length of different Silicon body thickness is simulated and the leakage current as determined by using MEDICI™ shows that the leakage current decreases by 10–15% as the silicon body thickness reduces by 2 nm.
Single Hole Film Cooling on a Turbine-Blade Leading-Edge Model
Authors: Mishra Suman , Wanchoo Rohan , Ghia Urmila , Ghia Kirti N.
Published: May 2009

The present study numerically investigates the effectiveness of film cooling on a turbine blade leading-edge model through a single-hole coolant exit. The model used in this study has the same dimensions as that of an experimental investigation done earlier by Ekkad et al [1]. The cylindrical model, a half cylinder and a flat after-body attached to it, well represents the leading edge of a turbine blade. The half-cylinder is 88.9 mm in diameter with a length of 364 mm. The flat after-body is attached to it to constitute the model of a turbine blade leading edge. The coolant hole is situated approximately at the center of the cylindrical model along the spanwise direction. The coolant hole makes an angle of 21.5 degrees to the true leading edge and 20 degrees to the spanwise direction. A multi-block grid is generated using GridGen, and the flow is simulated using the flow solver Fluent. The highly clustered structured C-grid is developed around the leading edge of the model with an initial Δy corresponding to a y+ value of 1 and a growth ratio of 1.1 till 10d from the surface. The outer unstructured domain imitates the wind-tunnel as used in the experimental study of Ekkad et al. [1], and the leading-edge model is placed at the center of the domain. Simulations are carried out for different blowing ratios M, ranging from 0.25 to 1.0, with the k-ε realizable turbulence model and κ-ω SST model. The flow is assumed to have a free-stream turbulence intensity of 0.75%. Additionally, the enhanced wall function approach is used as the near-wall treatment in the computational model for the simulation with k-ε realizable turbulence model. Results obtained indicate an increased film-effectiveness for low blowing ratio in the far downstream region. Also, in the vicinity of coolant jet exit, it is observed that increase in blowing ratio increases the film cooling effectiveness.
Practical Issues in Ground Testing of Pulsed Detonation Engines
Authors: Panicker Philip K. , Lu Frank K. , Wilson Donald R.
Published: May 2009

Pulsed detonation engines can potentially revolutionize aerospace propulsion and they are the subject of intense study. However, most of the studies involve single shot and very short duration test runs. Some of the practical issues in developing PDEs are discussed from the viewpoint of developing ground-based demonstrators. This represents only the beginning of a roadmap toward the successful development of flightweight engines. Viable solutions are offered that may help overcome the difficulties posed by the high temperature and pressures on the test rig and instrumentation. Commercial solenoid valves and electronic fuel injectors are presented as means to achieving higher operational frequencies. Issues concerning data acquisition, such as proper implementing procedures for pressure transducers and choosing the appropriate sampling rates are discussed. Methods for mitigating electromagnetic interference are discussed.
Design of Acoustic Metamaterials for Super-Resolution Ultrasound Imaging
Authors: Zhang Shu , Yin Leilei , Fang Nicholas
Published: May 2009

We report the numerical design and preliminary experiment of 2-D acoustic metamaterials composed of a planar network of subwavelength Helmholtz resonators. The considerably smaller size of the Helmholtz resonator to the corresponding resonant wavelength, allows a compact and light weight design for kilohertz frequency applications. Based on transmission line model to describe the acoustic wave propagation inside such ultrasonic metamaterials, we derived the acoustic parameters such as effective density and compressibility. Extremely large or even negative value of effective density and compressibility can be designed in this acoustic metamaterial. Our simulation demonstrates the focusing and imaging of sound sources through different lenses made of this novel acoustic metamaterial, which may have great potential application in ultrasound imaging. The influences of frequency and source position on the property of the focused image are also investigated.
Thermal Analysis of Plastic Serpentine-Type Microchannel Evaporators
Authors: Kosoy Boris , Arik Mehmet
Published: May 2009

Recently, microchannel liquid cooling technology showed very high heat transfer coefficients enabling high heat fluxes at allowable wall temperatures. It promises to be a potential solution to high flux electronics. This paper presents result of two related areas in the field of microchannel heat transfer. First, experimental results of serpentine-type fluoroplastic evaporated thermosyphons for microchannel applications are presented. R11 and R113 were used as working fluid, and it was shown that R11 has higher heat removal rate than R113. Flow distribution and flow characteristics (liquid, vapor, mixture etc) are discussed. Later discussion is extended towards key issues in mini and micro channels, and proposed correlations will be discussed. It is our great honor to contribute to Prof. Sadik Kakac symposium to celebrate his 75th birthday. We feel privileged knowing him and learning from his scientific books, papers, and personal discussions. We wish him a happy, healthy, and long life.
Study of the Homogenization Technique in a Two-Layer Cylindrical Material
Authors: Taher Bilal , Abboudi Said , Youness Rafik
Published: May 2009

The objective of this study is to analyze the thermo-mechanical behavior of a two-layer cylindrical material, subjected to variable thermal solicitations. The thermo-mechanical coupling is done by the consideration of the spatiotemporal variations of the temperature in the mechanical problem on one hand, and by means of the variations of the thermal and mechanical properties on the other hand. The study is led in two dimensions (r, z) on a cylindrical multi-material consisting of two layers subjected to a periodic or constant heat flux on one face, and to an exchange condition on the opposite face. Other faces are supposed to be insulated. We compare two approaches of the problem, the first one is a local approach based on a theoretical study of the thermal and mechanical fields (thermal transfer and constraints) and the second approach is based on the notion of equivalence of the thermo-physical properties of both layers to only one. Thus, this second approach is a homogenization of the multi-material in a single fictitious material possessing the same thermo-mechanical behavior.
Thermal Measurement of Harsh Environments Using Indirect Acoustic Pyrometry
Authors: Schmidt P. L. , Walker D. G. , Yuhas D. E. , Mutton M. J.
Published: May 2009

The inversion of a composite governing equation for the estimation of a boundary heat flux from ultrasonic pulse data is presented. The time of flight of the ultrasonic pulse is temperature dependent and can be used to predict the boundary heat flux. Sensitivities of the approach are examined, results from fabricated data are presented, and example solutions are provided with actual ultrasonic temperature measurement data. The results indicate that compared to the canonical inverse heat conduction problem, the additional step of resolving the time-of-flight data to temperature degrades the sensitivities. Nevertheless, sampling the entire temperature distribution and enhances the results. This method of using ultrasonic pulses to remotely determine heat fluxes is comparable in terms of accuracy to more common heat flux estimation methods.
Building Gaussian Process Based Metamodels Using Variable-Fidelity Experiments for Dynamic Analysis of Mechanical Systems
Authors: Negrut Dan , Qian Z. G. Peter , Khude Naresh
Published: May 2009

Given the highly nonlinear attribute of the underlying dynamics associated with the time evolution of multibody systems, an open question in mechanical system simulation is how one can reliably replace a model whose simulation is time consuming with a more expeditious one. Pushing this idea to the limit one can all together eliminate the dynamics of the problem using a set of simulations that train a predictor that is later used to provide the time evolution of the dynamic system. This paper investigates a Gaussian Random Function (GRF) based approach that attempts to address these questions. It relies on a framework recently proposed in the Statistical Analysis community that largely deals with the issues of model validation, calibration, and data integration. The approach investigated has several steps that are illustrated with a slider-crank mechanical systems whose time evolution is governed by a nonlinear set of index 3 Differential Algebraic Equations (DAEs). The paper concludes with a set of remarks on the potential of GRFs in the context of time domain analysis of mechanical systems.
Direct Numerical Simulation (DNS) of Suspensions in Spatially Varying Electric Fields
Authors: Janjua M. , Nudurupati S. , Singh P. , Fischer I. , Aubry Nadine
Published: May 2009

We have developed a numerical scheme to simulate the motion of dielectric particles in uniform and nonuniform electric fields. The particles are moved using a direct simulation scheme in which the fundamental equations of motion of fluid and solid particles are solved without the use of models. The motion of particles is tracked using a distributed Lagrange multiplier method (DLM) and the electric force acting on the particles is calculated by integrating the Maxwell stress tensor (MST) over the particle surfaces. One of the key features of the DLM method is that the fluid-particle system is treated implicitly by using a combined weak formulation where the forces and moments between the particles and fluid cancel, as they are internal to the combined system. The flow inside the particles is forced to be a rigid-body motion using the distributed Lagrange multiplier method. The MST is obtained from the electric potential, which, in turn, is obtained by solving the electrostatic problem. In our numerical scheme the Marchuk-Yanenko operator-splitting technique is used to decouple the difficulties associated with the incompressibility constraint, the nonlinear convection term, and the rigid-body motion constraint. A comparison of the DNS results with those from the point-dipole approximation shows that the accuracy of the latter diminishes when the distance between the particles becomes comparable to the particle diameter, the domain size is comparable to the diameter, and also when the dielectric mismatch between the fluid and particles is relatively large.
Electrostatic Forces on Particles Floating Within the Interface Between Two Immiscible Fluids
Authors: Aubry Nadine , Singh Pushpendra
Published: May 2009

The objective of this paper is to study the dependence of the electrostatic force that act on a particle within the interface between two immiscible fluids on the parameters such as the dielectric properties of the fluids and particles, the particle’s position within the interface, and the electric field strength. It is shown that the component of electrostatic force normal to the interface varies as a2, where a is the particle radius, and since in equilibrium it is balanced by the vertical capillary force, the interfacial deformation caused by the particle changes when an external electric field is applied. In addition, there are lateral electrostatic forces among the particles due to the dipole-dipole interactions which, when the distance between two particles is O(a), vary as a2, and remain significant for submicron sized particles.
Effects of Large Scale High Freestream Turbulence, and Exit Reynolds Number on Turbine Vane Heat Transfer in a Transonic Cascade
Authors: Nasir S. , Carullo J. S. , Ng W. F. , Thole K. A. , Wu H. , Zhang L. J. , Moon H. K.
Published: May 2009

This paper experimentally and numerically investigates the effect of large scale high freestream turbulence intensity and exit Reynolds number on the surface heat transfer distribution of a turbine vane in a 2-D linear cascade at realistic engine Mach numbers. A passive turbulence grid was used to generate a freestream turbulence level of 16% and integral length scale normalized by the vane pitch of 0.23 at the cascade inlet. The baseline turbulence level and integral length scale normalized by the vane pitch at the cascade inlet were measured to be 2% and 0.05, respectively. Surface heat transfer measurements were made at the midspan of the vane using thin film gauges. Experiments were performed at exit Mach numbers of 0.55, 0.75 and 1.01 which represent flow conditions below, near, and above nominal conditions. The exit Mach numbers tested correspond to exit Reynolds numbers of 9 × 105, 1.05 × 106, and 1.5 × 106, based on true chord. The experimental results showed that the large scale high freestream turbulence augmented the heat transfer on both the pressure and suction sides of the vane as compared to the low freestream turbulence case and promoted slightly earlier boundary layer transition on the suction surface for exit Mach 0.55 and 0.75. At nominal conditions, exit Mach 0.75, average heat transfer augmentations of 52% and 25% were observed on the pressure and suction side of the vane, respectively. An increased Reynolds number was found to induce earlier boundary layer transition on the vane suction surface and to increase heat transfer levels on the suction and pressure surfaces. On the suction side, the boundary layer transition length was also found to be affected by increase changes in Reynolds number. The experimental results also compared well with analytical correlations and CFD predictions.
A Scenario for a Secure Transportation System Based on Fuel From Biomass
Authors: West Ronald E. , Kreith Frank
Published: May 2009

This article presents a scenario to meet the future fuel needs of the US ground transportation system that does not require hydrogen, can use existing technology and eventually transition to ethanol from biomass. This scenario is based on a combination of reduction of liquid fuel use by means of plug-in hybrid electric vehicles and generation of ethanol from biomass. The article also demonstrates the reduction in CO2 generation with this technology and the urgency of initiating a strategy for reducing gasoline consumption as soon as possible.
The Development of a Pneumatic Stepping Motor Concept for Valve Based Flow Control During Injection Molding
Authors: Tantrapiwat Akapot , Coulter John P.
Published: May 2009

To develop the control over mold filling during polymer melt manipulation, an alternative way of driving rotary plug valves, which were placed on mold runners, was investigated in this study. During the present investigation, the pneumatic stepping motor concept was explored by designing, fabricating, and testing a specific motor for a target injection molding base application. In order to improve the actuator performance, which is used to drive the valves, a stepping motor driven by a sequence of digital solenoid valves utilizing pressurized air was designed to enhance torque capacity and reduce energy consumption, while maintaining a fixed position for a long period of time. Similar to electromagnetic stepping motors, this pneumatic stepping motor can be driven by a simple switching circuit, which only moves one step for each driving signal without a fading rotation. This mechanism yields an effective system for speed and position control. Although the speed of pressurized air switching is limited by the response time of air solenoid valves that cause a lower rotation output speed, the holding torque and efficiency of this actuator was found to be relatively higher. By using a set of circular pistons aligned so as to actuate on axial wobble gear, the motor produced a very unique motion between the gear and rotor, causing the beneficial characteristics. In this study, the performance of the new motor was tested and compared to a similar size of electromagnetic stepping motor, as well. Thus, this study provides fundamental concepts to develop a suitable actuator for control valves in injection molding at low cost.
Finite Element Modeling of a Highly Flexible Rotating Beam for Active Vibration Suppression With Piezoelectric Actuators
Authors: Gilardi Gabriele , Buckham Bradley J. , Park Edward J.
Published: May 2009

In this paper a new finite element model (FEM) is introduced for the analysis of a highly flexible beam undergoing large deformations due to fast slewing. The finite element model uses a novel absolute nodal coordinate formulation (ANCF) that employs a third order twisted cubic spline geometry. Galerkin’s method of weighted residuals is applied to discretize equations of motion derived for the beam continuum. The model exploits a synergy between the twisted spline geometry and the lumped mass approximation to halve the size of the matrix equations that must be solved on each time step. In the simulation of fast slewing maneuvers, a very slender beam is considered and the elastic deformations experienced are an order of magnitude larger than cases considered to date. Closed-loop control simulation results, using PD feedback for both hub and piezoelectric actuator control, show that the proposed schemes are effective in suppressing very large vibrations. These results show the potential of the proposed FEM as an effective design and simulation tool for analyzing a highly flexible beam undergoing fast slewing, and for synthesizing vibration controllers for piezoelectric actuators.
Constitutive Behavior of Sn3.8Ag0.7Cu and Sn1.0Ag0.5Cu Alloys at Creep and Low Strain Rate Regimes
Authors: Bhate D. , Chan D. , Subbarayan G. , Chiu T. C. , Gupta V. , Edwards D.
Published: May 2009

Constitutive models for SnAgCu solder alloys are of great interest at the present. Commonly, constitutive models that have been successfully used in the past for Sn-Pb solders are used to describe the behavior of SnAgCu solder alloys. Two issues in the modeling of lead-free solders demand careful attention: (i) Lead-free solders show significantly different creep strain evolution with time, stress and temperature, and the assumption of evolution to steady state creep nearly instantaneously may not be valid in SnAgCu alloys and (ii) Models derived from bulk sample test data may not be reliable when predicting deformation behavior at the solder interconnection level for lead-free solders due to the differences in the inherent microstructures at these different scales. In addition, the building of valid constitutive models from test data derived from tests on solder joints must deconvolute the effects of joint geometry and its influence on stress heterogeneity. Such issues have often received insufficient attention in prior constitutive modeling efforts. In this study all of the above issues are addressed in developing constitutive models of Sn3.8Ag0.7Cu and Sn1.0Ag0.5Cu solder alloys, which represent the extremes of Ag composition that have been mooted at the present time. The results of monotonic testing are reported for strain rates ranging from 4.02E-6 to 2.40E-3 s−1. The creep behavior at stress levels ranging from 7.8 to 52 MPa are also described. Both types of tests were performed at temperatures of 25°C, 75°C and 125°C. The popular Anand model and the classical time-hardening creep model are fit to the data and the experimentally obtained model parameters are reported. The test data are compared against other reported data in the literature and conclusions are drawn on the plausible sources of error in the data reported in the prior literature.
Microsatellites reveal clear genetic boundaries among Atlantic salmon (Salmo salar) populations from the Barents and White seas, northwest Russia
Authors: Tonteri Anni , Veselov Alexei Je. , Zubchenko Alexander V. , Lumme Jaakko , Primmer Craig R.
Published: May 2009

Fourteen microsatellite loci were employed to study the genetic structure of 34 Atlantic salmon ( Salmo salar ) populations from the White and Barents seas area, the last major European region where the species has remained in its natural state. The populations were separated into four distinct clusters (Atlantic Ocean and western Barents Sea, Kola Peninsula, western White Sea, and eastern Barents Sea) within which genetic divergence varied between 0.02 and 0.10 as estimated with FST. When this structuring was contrasted with previously identified mtDNA-based groupings, a remarkable similarity was observed, implying that these four groups can be considered as a good starting point for defining management units in the region. Indeed, several approaches for assessing every population’s conservation value suggested that conservation of populations from each observed cluster would maximize preservation of the region’s genetic diversity. Furthermore, each unit may require differing management strategies, as distinct patterns of genetic diversity and divergence characteristics were detected. In addition, individual assignment success within a region was high (87%–96%), indicating that the data can be used as a baseline to differentiate individuals caught in offshore fisheries on a regional level with a relatively high degree of accuracy.
A novel statistical method for validating the periodicity of vertebral growth band formation in elasmobranch fishes
Authors: Okamura Hiroshi , Semba Yasuko
Published: May 2009

A simple age verification method is presented for centrum edge analysis (CEA) of elasmobranch species. In this method, a binomial model is linked with a von Mises distribution for circular data, taking the characteristics of the CEA data into account. The periodicity of growth band pairs is categorized as no cycle, an annual cycle, or a biannual cycle. Three models are then constructed according to different periodicities. We use the Akaike information criterion (AIC) to determine which model is the best. The models were applied to the shortfin mako shark ( Isurus oxyrinchus ) data collected in the North Pacific to identify the best periodicity model. The AIC best-fitting model was one involving an annual cycle. The general performance of the method was evaluated using simulated data of various sample sizes, formation times, and durations of growth band pairs. The simulation trials showed that the performance of the method was satisfactory with moderate sample sizes. This method should improve the accuracy of age determination and could be applied to all species that have periodic growth band pairs.
The importance of scale for fishing impact estimations
Authors: Piet G. J. , Quirijns F. J.
Published: May 2009

The impact of a bottom trawl fishery on fish or benthos is often determined by multiplying the frequency of the passing of the trawl by a factor for the effect (i.e., % mortality) of the singular passing of the gear. As fishing intensity in an area is not homogeneously distributed, it is necessary to determine the proportions of the area that are fished with different trawling frequencies, as these subareas together contribute to the overall species’ mortality. In this study, we show that the perceived proportion of the area fished with a specific trawling frequency depends upon the spatial and temporal scale used. A smaller spatial scale results in an increased perceived patchiness of the fishing intensity, while a longer time period does the opposite. The implication is that to determine the fishing-induced mortality of a particular species, the trawling frequency needs to be determined at those spatio-temporal scales that are appropriate considering the species’ spatial processes (e.g., dispersion) or temporal processes described by life history characteristics.
Comment on “Does the fall phytoplankton bloom control recruitment of Georges Bank haddock, Melanogrammus aeglefinus, through parental condition?”Appears in Can. J. Fish. Aquat. Sci. 65: 1076–1086.
Authors: Payne Mark R. , Dickey-Collas Mark , Nash Richard D.M.
Published: May 2009

In the paper “Does the fall phytoplankton bloom control recruitment of Georges Bank haddock, Melanogrammus aeglefinus , through parental condition?”, Friedland et al. (Can. J. Fish. Aquat. Sci. 65(6): 1076–1086, 2008) examine a sizable number of hypotheses aiming to explain the recruitment patterns observed in Georges Bank haddock. The authors focus on a correlation between the size of the autumnal phytoplankton bloom and the survivor ratio (recruitment), concluding this to be the main factor determining recruitment, via the mechanism of adult condition at the time of spawning. Here we examine this result in close detail and re-analyse some of the data presented in the paper. We show that the recruitment metric upon which Friedland et al. base their conclusions inadvertently biases the analysis in favour of high recruitment events and against low recruitments. As a consequence, Friedland et al. disregard correlations that are, in fact, significant. Furthermore, we show that the parental condition hypothesis hinges upon a single, highly uncertain data point, without which the correlation is no longer significant. We find that evidence for the parental condition hypothesis is weak, and that in performing the analysis in the chosen manner, Friedland et al. have overlooked alternative hypotheses.
Reply to the comment by Payne et al. on “Does the fall phytoplankton bloom control recruitment of Georges Bank haddock, Melanogrammus aeglefinus, through parental condition?”Appears in Can. J. Fish. Aquat. Sci. 65: 1076–1086.
Authors: Friedland Kevin D. , Hare Jonathan A. , Wood Grayson B. , Col Laurel A. , Buckley Lawrence J. , Mountain David G. , Kane Joseph , Brodziak Jon , Lough R. Gregory , Pilskaln Cynthia H.
Published: May 2009

Payne et al. (Can. J. Fish. Aquat. Sci. 66: 869–872, 2009) raised several points concerning the handling and interpretation of data that went into an analysis of the population dynamics of Georges Bank haddock that suggested a relationship between the fall phytoplankton bloom and recruitment (Can. J. Fish. Aquat. Sci. 65: 1076–1086, 2008). Their main points were the manner in which logarithmic transforms were applied, whether the 2003 year class was truly as large as estimated in a 2006 assessment, and if correlation analyses of zooplankton data should be reconsidered. The reply to these comments was aided by a new assessment which provided additional years of data and improved the quality of the recruitment time series. The reply analyses showed that the relationships were robust to the way the logarithmic transform was applied, the initial estimates of the size of the 2003 year class were correct, and relationships between recruitment and spring zooplankton biomass levels remain statistically insignificant. From these new analyses, the interpretations and conclusions reached in the original paper remain the same; the fall bloom has emerged as a candidate explanatory variable for the stock independent variation in haddock recruitment on Georges Bank.
Underground gas storage: An introduction and UK perspective
Authors: Evans D. J. , Chadwick R. A.
Published: May 2009

Rising demand and the depletion of its offshore reserves has resulted in the UK becoming a net importer of natural gas. An increased reliance on imports and limited current storage availability mean that the UK faces increasing energy bills and risk of disruption to supply. Because of this the UK government has set about ensuring security of energy supply. Steps taken include the construction of major new pipelines from Norway and Holland and improvements to interconnectors in the southern North Sea. The Government also recognizes that improvements to the gas supply infrastructure are required, including the need for significant increases in gas storage capacity; best met by the construction of underground storage facilities. Focus on energy security has also raised the likelihood of a new generation of coal-fired power-stations. For such a step to be environmentally viable, clean-coal technologies with near-zero greenhouse gas emissions will be required. Underground CO
2
storage will be a key element of this strategy. This volume reviews the technologies and issues involved in the underground storage of natural gas and CO
2
, by means of case-studies and examples from the UK and also from overseas. The potential for underground storage of other gases such as hydrogen, or compressed air linked to renewable sources is also reviewed.
Well integrity: An overlooked source of risk and liability for underground natural gas storage. Lessons learned from incidents in the USA
Authors: Miyazaki Brent
Published: May 2009

Safety is a primary concern at underground gas storage (UGS) sites. Thorough evaluation of all potential migration pathways is critical to ensure UGS containment and public safety. Substantial risk is directly associated with inaccurate technical evaluations, that may result in subsequent gas migration from a UGS facility.

Existing wellbores, including abandoned oil and gas wells, old dry exploration wells and water wells represent primary potential vertical gas migration conduits, which are not always thoroughly analysed during UGS site evaluation studies. Most abandoned oil and gas wells develop leaks over time, even when plugged in accordance with current (US) government regulations.

Leaking wells in urban areas represent significant health and safety hazards. Many cities including Los Angeles permit construction of new homes directly over abandoned wells, even though state agencies recommend against this practice, thus placing residents at risk. Explosions and fires, along with possible exposure to substances such as benzene and toluene, are possible when gas reaches the surface through leaking wells and accumulates inside building voids. These potential problems are amplified with UGS fields, where operating pressures, already raised above the declining pressures of the field, fluctuate when alternating gas injection and extraction induce cyclic stress on wellbores and caprock sequences.
Review of monitoring issues and technologies associated with the long-term underground storage of carbon dioxide
Authors: Chadwick R. A. , Arts R. , Bentham M. , Eiken O. , Holloway S. , Kirby G. A. , Pearce J. M. , Williamson J. P. , Zweigel P.
Published: May 2009

Large-scale underground storage of CO
2
has the potential to play a key role in reducing global greenhouse gas emissions. Typical underground storage reservoirs would lie at depths of 1000 m or more and contain tens or even hundreds of millions of tonnes of CO
2
. A likely regulatory requirement is that storage sites would have to be monitored both to prove their efficacy in emissions reduction and to ensure site safety. A diverse portfolio of potential monitoring tools is available, some tried and tested in the oil industry, others as yet unproven. Shallow-focused techniques are likely to be deployed to demonstrate short-term site performance and, in the longer term, to ensure early warning of potential surface leakage. Deeper focused methods, notably time-lapse seismic, will be used to track CO
2
migration in the subsurface, to assess reservoir performance and to calibrate/validate site performance simulation models. The duration of a monitoring programme is likely to be highly site specific, but conformance between predicted and observed site performance may form an acceptable basis for site closure.
Environmental and safety monitoring of the natural gas underground storage at Stenlille, Denmark
Authors: Laier T. , Øbro H.
Published: May 2009

The Stenlille natural gas underground storage is located 70 km SE of Copenhagen and has been in operation since 1989. For safety reasons and to protect the environment it is necessary to monitor the storage carefully. Natural gas is being stored in an anticlinal structure with an expected gas storage capacity of about 3 billion Nm
3
(volume under ‘normal’ conditions) in the upper Triassic Gassum Sandstone Formation 1500–1600 m below the surface; it replaces saline formation water. So far, nineteen deep wells have been drilled on and around the structure. The 300 m thick clay sequence of the Lower Jurassic Fjerritslev Formation above the gas storage reservoir has acted as an efficient seal, since no sign of gas leakage has been observed in the monitoring well located in a sand stringer 15 m above the gas reservoir. Other monitoring wells have been located in order to check for possible lateral escape of natural gas. A baseline study on naturally occurring hydrocarbons performed before the natural gas storage came into operation indicated the presence of only trace amounts hydrocarbon gases in the subsurface of the Stenlille area. Results of analysis by the headspace and sorbed gas methods on drill-cuttings suggest that low-temperature thermal generation of hydrocarbon gases (δ
13
C
1
: −47 to −42‰; δ
13
C
2
: −34 to −30‰) has taken place in organic-rich marine shale below 1300 m. Low concentrations of dissolved methane (<0.5 mg/l) of bacterial origin (δ
13
C
1
: −90 to −62‰) were found in shallow groundwater that is used for water supply in the Stenlille area. After the start of injection of natural gas in 1989 (C
1
:C
2
:C
3
= 91:6:2; δ
13
C
1
: −47‰), no increase in methane concentration and no higher hydrocarbon gases were observed during the regular analysis of groundwater from 10 shallow wells located above the underground natural gas storage. However, a sudden increase in dissolved methane concentration from 0.02 to 27 mg/l was measured in a 130 m deep observation well after a minor gas leakage had been detected at a new deep drilling into the natural gas storage in 1995. Nonetheless, no increase in methane was observed in shallow groundwater at the same locality. Occasional higher concentrations of dissolved methane (up to 15 mg/l) were encountered in shallow observation wells in low permeability layers. Stable isotope analyses (δ
13
C
1
: −69 to −52‰) and radiocarbon dating show that the gas does not originate from the underground gas storage because the methane was less than 300 years old, but it may have formed due to local microbial activity.
Design of salt caverns for the storage of natural gas, crude oil and compressed air: Geomechanical aspects of construction, operation and abandonment
Authors: Lux K.-H.
Published: May 2009

Salt cavities for the storage of natural gas in bedded or domal salt structures are an important element of current and future energy supply management. In Germany, the mechanical design of salt cavities has a history of more than 35 years. This paper gives a personal view of current salt cavity design. It discusses the geomechanical characteristics of storage cavities and principle safety demands for their design as well as recent design concepts and methods for providing geotechnical proof of safety with specialized criteria, limit values and safety margins. In view of the uncertainties inherent in the design of geotechnical mechanical structures, monitoring of excavation and operation are essential parts of underground geotechnical constructions. A new monitoring software code is presented that will help both to document that past and to plan future cavern operation. Cavern abandonment is an object of current research, especially the basic understanding of mechanisms acting or becoming active at elevated fluid pressures (gas or brine) at the level of primary (lithostatic) rock mass pressures. This paper presents some basic knowledge and a computer code for analysing the long-term behaviour of sealed liquid-filled salt cavities with simulation of pressure build-up, infiltration and following seepage flow.
On the origins of bisimulation and coinduction
Authors: Sangiorgi Davide
Published: May 2009

The origins of bisimulation and bisimilarity are examined, in the three fields where they have been independently discovered: Computer Science, Philosophical Logic (precisely, Modal Logic), Set Theory.

Bisimulation and bisimilarity are coinductive notions, and as such are intimately related to fixed points, in particular greatest fixed points. Therefore also the appearance of coinduction and fixed points is discussed, though in this case only within Computer Science. The paper ends with some historical remarks on the main fixed-point theorems (such as Knaster-Tarski) that underpin the fixed-point theory presented.
On the use of memory and resources in minority games
Authors: Araujo Ricardo M. , Lamb Luis C.
Published: May 2009

The use of resources in multiagent learning systems is a relevant research problem, with a number of applications in resource allocation, communication and synchronization. Multiagent distributed resource allocation requires that agents act on limited, localized information with minimum communication overhead in order to optimize the distribution of available resources. When requirements and constraints are dynamic, learning agents may be needed to allow for adaptation. One way of accomplishing learning is to observe past outcomes, using such information to improve future decisions. When limits in agents' memory or observation capabilities are assumed, one must decide on how large should the observation window be. We investigate how this decision influences both agents' and system's performance in the context of a special class of distributed resource allocation problems, namely dispersion games. We show by using several numerical experiments over a specific dispersion game (the Minority Game) that in such scenario an agent's performance is non-monotonically correlated with her memory size when all other agents are kept unchanged. We then provide an information-theoretic explanation for the observed behaviors, showing that a downward causation effect takes place.
System level hardware design and simulation with SystemAda
Authors: Mahani Negin , Mokri Parnian , Navabi Zainalabedin
Published: May 2009

Recent research in the system level design field has produced a number of techniques for structuring the understanding of systems. Many of these techniques produce design structures that are easily expressible in Ada language. Ada language has a structure which allows the design of systems to be expressed independently of its implementation and thus can be a good system design language for use with these techniques [1]. This paper describes how to use Ada as a system description language like SystemC, which will use Ada compilers (such as Gnat) to evaluate the written program as a system; we have named it, SystemAda. This paper reviews Ada programming language requirements for modeling behavior and structures at Transaction Level Modeling (TLM), and considers possible approaches for extending Ada to meet these requirements [2].