bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Frequency Domain Seakeeping Analysis of a Fast Monohull in Regular Head Waves
Authors: Schellin Thomas E. , Beiersdorf Christian , Chen Xiao-Bo , Maron Adolfo
Published: March 2009

Two sets of seakeeping computations and comparative model teats were performed for a fast monohull in regular waves. The first set of computations used an existing three-dimensional frequency domain panel code that formulates the potential flow problem by means of the zero-speed Green function. The second set used a modified version of this code that implemented an advanced software module, newly developed within the European research project WAVELOADS, where the free-surface forward-speed Green function method based on the Fourier-Kochin formulation accounts for forward speed effects. Although this formulation provided a solid mathematical basis for obtaining robust and accurate numerical predictions, numerical inaccuracies prevented obtaining satisfactory results. For nearly all cases investigated, predictions from the original (zero-speed Green function) code correlated more favorably with test data than those from the modified (forward-speed Green function) code. For the fast monohull investigated here, practically relevant global load predictions based on the zero-speed Green function correlated favorably with measurements.
A Numerical Study on Hydrodynamic Pressure and Structural Response of Stiffened Plates Under Water Body Collision Considering Fluid-Structure Interaction
Authors: Sano Atsushi , Ikebuchi Tetsuro , Okada Hiroo , Masaoka Koji
Published: March 2009

In damage examples of hatch covers under green seas and bow flare subjected to slamming, external force where causes the structure damage comes from collision between hull structure and water around it. And the structural deformation and hydrodynamic pressure are so closely related with each other that a fluid-structure dynamics interaction must be considered. In this paper, we briefly introduce a computer program for fundamental study of these phenomena considering fluid-structure dynamics interaction, which is combined with SOLA-VOF developed by Hirt and et al and DYNA3D developed by Hallquist and et al. Next, we discuss some calculation results carried out for collision of 2-D flat plates and stiffened plates with cylindrical water body, compared with experimental results presented by Faltinsen and et al. Finally, effects of stiffness of stiffened plate and water body shape on pressure and structural response are investigated.
Fully-Nonlinear Spectral/BEM Solution for Irregular Wave Interactions With a 3D Body
Authors: Ferrant Pierre , Le Touze´ David
Published: March 2009

An original method for simulating the interaction of irregular long crested waves with a 3D body is described. Incident waves are modeled using a recently developed pseudo-spectral method for fully-nonlinear free surface waves in water of finite depth. The wave generation process is based on submerged dipoles. The dipoles strengths and orientations are combined in such a way that waves are generated in a single direction. Furthermore, the wave generation transfer function is predetermined analytically, so that sea states of given energy spectrum are easily generated. The interaction of these waves with a 3D body is modeled using the 3D fully nonlinear BEM solver XWAVE, based on a formulation for the nonlinear diffracted flow. The effective coupling of both models is illustrated by simulating the diffraction of 2D wave packets as well as different realizations of ITTC wave spectra, by a vertical bottom-mounted cylinder.
Free Surface Flow Past Ships in Shallow Water
Authors: Ganguly A. , Shigunov V. , Turan O.
Published: March 2009

A finite volume method with a multiphase type free surface description is employed to calculate the flow around ships in shallow and restricted channels. The flows at critical and supercritical depth Froude numbers (Fnd = 1.0 and Fnd = 1.18) are calculated for Series–60 monohull and a medium speed catamaran. A steady state solution for Reynolds-averaged Navier-Stokes equations with a k-ε turbulence model is obtained by time marching. Computed wave profiles are in good agreement with model tests in the near field of the ship. The computed and measured resistance agree fairly well.
A Spectral Response Surface Method for Calculating Crest Elevation Statistics
Authors: Tromans Peter S. , Vanderschuren Luc
Published: March 2009

The statistics of wave crest elevation in a random, directionally spread sea are calculated using a novel approach. The non-linearity of steep waves is modelled to second order using Sharma and Dean kinematics and a spectral response surface method is used to deduce the crest elevation corresponding to a given probability of exceedance. The spectral response surface method works in the probability domain, making it several times faster than conventional time domain simulation of random waves. However, the results from the two methods show good agreement. As expected, non-linearity makes extreme crests higher than the corresponding linear ones.
Coupled Dynamic Analysis of a Mini TLP: Comparison With Measurements
Authors: Chen Xiaohong , Zhang Jun , Liagne Pierre-Yves F. , Niedzwecki John M. , Teigen Per
Published: March 2009

A numerical code (COUPLE) was recently developed for computing 6 Degree-Of-Freedom (DOF) motions of a moored floating structure dynamically interacting with its mooring/riser/tendon system. The computation of hydrodynamic forces on the moored structure can be conducted based on a diffraction wave theory model, e.g. WAMIT, and/or the Morison Equation based upon a slender body assumption. Wave kinematics up to the free surface, used in the Morison Equation, is computed using nonlinear deterministic Hybrid Wave Models, and is accurate up to second order in wave steepness. Experimental data from the model tests of a mini TLP was used as the basis for investigation of the numerical computation. Using COUPLE and its alternatives, coupled as well as quasi-static analyses were conducted for the mini TLP model that incorporates four risers and four tendons. Two different methods for computing hydrodynamic loads, namely, WAMIT and Morison Equation, were used, respectively. Through the comparison between the numerical results and the corresponding measurements, dynamic interactions between the riser/tendon system and the hull were examined. Findings made in this study, though based upon a mini TLP may have valuable applications to the design and simulation of a wide range of compliant deep-water structures.
Future Directions in the Study of Non-Conservative Water Wave Systems
Authors: Tulin Marshall P.
Published: March 2009

A few future directions and challenges in wave research are briefly discussed including Numerical Experiments as in the treatment of splashing waves, and topics in the Mechanics of Ocean Waves, especially in their non-linear, non-conservative reality. Breaking waves are featured.
Effect of Dynamic Behaviour of Piles on Offshore Towers Response
Authors: Mostafa Yasser E. , El Naggar M. Hesham
Published: March 2009

Pile foundations supporting offshore platforms and marine structures are required to resist dynamic lateral loading due to wind and wave forces. The response of a jacket offshore tower is affected by the foundation flexibility and the nonlinear behaviour of the supporting piles. In the present study, the soil resistance to the pile movement is modeled using dynamic p-y curves and t-z curves to account for soil nonlinearity and energy dissipation through radiation damping. The model also allows separation at the pile soil interface. The wave forces on the tower members and the tower response are calculated in the time domain using a finite element package (ASAS). The tower response is calculated with emphasis placed on the effects of dynamic pile-soil interaction on the tower performance and the forces acting on the piles for a range of wave conditions.
Review of Defect Distributions for Probabilistic Structural Integrity Assessment
Authors: Zhao W. , Stacey A.
Published: March 2009

The defect distribution is a particularly important parameter in the application of probabilistic defect assessment methods to the integrity assessment of welded structures. However, the subject is complex and, despite considerable research efforts in this area and the availability of a significant body of data, this defect distribution is subject to considerable variability and uncertainty. This paper reviews the data in the literature, providing a status review of defect distributions and the identification of areas requiring further investigation, with a view to assisting with the future development of probabilistic defect assessment methods.
Dry Tree Semisubmersible Options for Deepwater Production
Authors: Steen Atle , Tognarelli Mike , Xu Lixin , Banon Hugh
Published: March 2009

Recent deep water field developments have made increasing use of dry tree completions from floating production units, principally spars and TLPs. There are a number of development efforts underway to include dry tree semi-submersibles in deep water. The use of dry tree semis requires some form of heave suppression as well as a means for limiting pitch motions. Two concepts using this principle include the DPS 2001 and the TPG 3300. Both of these concepts consist of a deck supported on columns and, in the case of the DPS-2001, pontoons. In each case there is a submerged heave plate to trap mass and to dampen the heave motions. Risers must pass through this heave plate. This paper will present the results of study of options supporting top tensioned risers from these platforms, with a focus on the DPS-2001. Air Cans and tensioners have both been investigated. Air cans have been used on all spar platforms to date, but in this case the cans are shielded by the spar hull and are not exposed to wave kinematics or current loads. Tensioners have been used on all the TLPs, but their stroke is less than would be required for a semi-submersible, even one that is heave compensated. The tensioners used in this study had a relatively high stiffness in order to reduce stroke. This results in a coupling of the motions of the hull with the risers and results in some increase in the peak tensions. It also results in a lower heave period and higher heave motions. The paper will discuss the technical and economic tradeoffs for these options.
Large-Scale Model Tests With Wave Loading on Offshore Platform Deck Elements
Authors: Sterndorff Martin J.
Published: March 2009

The present paper concerns a detailed large-scale experimental study of wave loading on offshore platform decks. A series of model tests with wave loading on different types of deck elements have been performed in the large wave channel (GWK) at Forschungszentrum Kiiste in Hannover, Germany. The following types of deck elements have been considered: tubular elements, plate profiles, and HEB beam profiles. The tests have been performed with individual elements and arrays of elements. Tests have also been performed with an array of beam elements covered with deck plating. A large range of different wave types, air gaps, and inundation’s have been tested. Regular waves with wave height ranging from 1.4 m to 1.8 m, irregular waves and wave packages with crest heights ranging from 0.9 m to 1.6 m have been tested. During the tests the following parameters were measured: wave elevations, deck element inundation’s, wave kinematics profile, and wave forces on the individual deck elements. The model test results will be analysed to provide hydrodynamic load coefficients to a wave-in-deck load programme based on the concept of change of fluid momentum. The results will also be used to verify a CFD code based on the Volume of Fluid method.
Interaction Between Drillstring and Ice-Protection Pipe While Drilling Deepwater Wells in Water Basins With Ice Sheets
Authors: Tikhonov Vadim S. , Surkov Dmitry V. , Safronov Alexander I. , Gelfgat Michael Ya.
Published: March 2009

While drilling deepwater stratigraphic wells in the water basins with ice sheets, drillers usually encounter the problem of a drillstring protecting from ice loads. One of the methods of the drillstring protection from ice impact provides for clearance installation of an ice pipe in the drilling vessel unit moonpool with the pipe bottom several meters below the keel. The paper suggests the numerical-analytical method of the stress-deformated state calculation for the drillstring and the ice-protection pipe with allowance for contact interaction between the drillstring, the ice protection pipe and the moonpool wall. The ice load value is determined based on the condition of equality between the kinetic energy of a moved ice floe and the elastic energy of the “drillstring – ice-protection pipe” system. The principle of the minimum potential elastic energy is used for calculating the system equilibrium configuration, with account to constraints of the system element displacement. The method of coordinate-by-coordinate descent is used to find a solution for the conditional minimization problem. The developed method is employed to evaluate the efficiency of the ice pipe design to be used while drilling deepwater stratigraphic wells from the Botnica multi-function icebreaker in the Arctic region under the International Ocean Drilling Program (IODP). The study showed that the suggested ice pipe design was capable of withstanding impacts of ice floes moving at 1.5 m/sec with thickness of 1 m and with diameter up to 3.5 m.
Feasibility of a Cold Seawater Facility
Authors: Rojas Raymond , Gregory Todd
Published: March 2009

The students who participated in the Fall 2000 “design class” offered by the Department of Ocean and Resource Engineering at the University of Hawaii performed a preliminary design of a cold seawater facility at Kekaha, Hawaii. The course imparted a great deal of design experience, but more importantly it introduced the classmates to cold seawater as a developing resource with high potential. As the two students who participated in the design class, we were particularly impressed with this resource and convinced that cold seawater can feasibly be developed as a valuable resource for island communities. We collaborated to combine, condense and generalize the reports in an effort to familiarize other ocean engineers and island planners to this technology and its potential. This paper discusses several uses for cold seawater in tropical island settings and the site characteristics required to feasibly develop a land-based cold seawater facility. The preliminary design of a cold seawater facility at Kekaha is presented along with an economic analysis of its capital and operating costs.
Effects of Modeling Assumptions on the Accuracy of Spectrum Fatigue Lifetime Predictions for a Fiberglass Laminate
Authors: Wahl Neil , Samborsky Daniel , Mandell John , Cairns Douglas
Published: March 2009

This paper presents an extension of the work described in Reference 1, which dealt only with tensile fatigue loads spectra. Experimental results and modeling have now been extended to simple spectra which cover a full range of loads including compression and reversed tension-compression, as well as WISPERX and other spectra representative of wind turbines, containing a full range of R-values. Experimental fatigue data (over 1100 tests) have been generated for a fiberglass laminate which is typical of wind turbine blade construction, tested under a variety of loads spectra. Constant amplitude data typical of the DOE/MSU fatigue database are then used with various modeling schemes to predict the lifetime under spectrum loading. Several areas of current concern in blade lifetime prediction are explored. First, it is demonstrated that the Miner’s Rule cumulative damage law results in significantly non-conservative lifetime predictions for most loads spectra. Linear and nonlinear residual strength models are easily applied and are more accurate in predicting lifetime; they also provide a prediction of remaining strength as a function of the history of loading prior to failure. Prediction accuracy is also sensitive to the model (exponential or power law) used to represent and extrapolate the constant amplitude S-N fatigue data. A power law representation appears to provide more accurate predictions of lifetime under spectral loading for longer lifetime cases.
Alternative Materials, Manufacturing Processes, and Structural Designs for Large Wind Turbine Blades
Authors: Griffin Dayton A.
Published: March 2009

As part of the U.S. Department of Energy’s Wind Partnerships for Advanced Component Technologies program, Global Energy Concepts LLC (GEC) has performed a study concerning innovations in materials, processes and structural configurations for application to wind turbine blades in the multi-megawatt range. Constraints to cost-effective scaling-up of the current commercial blade designs and manufacturing methods are identified, including self-gravity loads, transportation, and environmental considerations. A trade-off study is performed to evaluate the incremental changes in blade cost, weight, and stiffness for a wide range of composite materials, fabric types, and manufacturing processes. Fiberglass/carbon hybrid blades are identified as having a promising combination of cost, weight, stiffness and fatigue resistance. Vacuum-assisted resin transfer molding, resin film infusion, and pre-impregnated materials are identified as having benefits in reduced volatile emissions, higher fiber content, and improved laminate quality relative to the baseline wet lay-up process. Alternative structural designs are identified, including jointed configurations to facilitate transportation. Based on the study results, recommendations are developed for further evaluation and testing to verify the predicted material and structural performance.
Concepts for Adaptive Wind Turbine Blades
Authors: Ashwill Thomas D. , Veers Paul S. , Locke James , Contreras Ivan , Griffin Dayton , Zuteck Mike D.
Published: March 2009

Bend-twist coupling in wind turbine blades has been shown to reduce both fatigue and extreme operating loads, especially when applied in conjunction with a pitch-controlled rotor. This type of coupling has been used in other industries, implemented either through biased lay-ups of fiber-reinforced materials, or with swept wings. The critical issues restricting the widespread implementation of this technology to wind turbines lies in the detailed design, manufacturing, and durability of the bend-twist-coupled blades. A series of industry contracts were initiated to evaluate/study these issues. The results of three of these studies are summarized in this paper. Global Energy Concepts (GEC) studied design issues from the perspective of traditional wind turbine blade conceptual design. Wichita State University investigated the use of braided composites with a multi-cellular blade structure. Finally, MDZ Consulting studied the possibilities of using sweep alone to achieve the desired bend-twist coupling. A common result of all the studies is that a higher stiffness fiber, such as carbon, has tremendous benefits in this application.
Rotational Augmentation of Horizontal Axis Wind Turbine Blade Aerodynamic Response
Authors: Schreck S. , Robinson M.
Published: March 2009

Surface pressure data were acquired using the NREL Unsteady Aerodynamics Experiment, a full-scale horizontal axis wind turbine, which was erected in the NASA Ames 80 ft × 120 ft wind tunnel. Data were collected first for a stationary blade, and then for a rotating blade with the turbine disk at zero yaw. Analyses compared aerodynamic forces and surface pressure distributions under rotating conditions against analogous baseline data acquired from the stationary blade. This comparison allowed rotational modifications to blade aerodynamics to be characterized in detail. Rotating conditions were seen to dramatically amplify aerodynamic forces, and radically alter surface pressure distributions. These and subsequent findings will more fully reveal the structures and interactions responsible for these flow field enhancements, and help establish the basis for formalizing comprehension in physics based models.
Bubble Induced Unsteadiness on Wind Turbine Airfoils
Authors: Mayda E. A. , van Dam C. P. , Duque Earl P. N.
Published: March 2009

The effect of laminar separation bubbles on the surface pressure distribution and aerodynamic force characteristics of two quite different airfoils is studied numerically. The low-Reynolds-number Eppler E387 airfoil is analyzed at a chord Reynolds number of 1.0×105 whereas the NREL S809 airfoil for horizontal-axis wind turbines is analyzed at 1.0×106. For all cases in the present study, bubble induced vortex shedding is observed. This flow phenomenon causes significant oscillations in the airfoil surface pressures and, hence, airfoil generated aerodynamic forces. The computed time-averaged pressures compare favorably with wind-tunnel measurements for both airfoils.
The Nebulous Art of Using Wind-Tunnel Airfoil Data for Predicting Rotor Performance
Authors: Tangler James L.
Published: March 2009

The objective of this study was threefold: to evaluate different two-dimensional S809 airfoil data sets in the prediction of rotor performance; to compare blade-element momentum rotor predicted results to lifting-surface, prescribed-wake results; and to compare the NASA Ames combined experiment rotor measured data with the two different performance prediction methods. The S809 airfoil data sets evaluated included those from Delft University of Technology, Ohio State University, and Colorado State University. The performance prediction comparison with NASA Ames data documents shortcomings of these performance prediction methods and recommends the use of the lifting-surface, prescribed-wake method over blade-element momentum theory for future analytical improvements.
A Study of a Wind Farm Power System
Authors: Muljadi E. , Wan Y. , Butterfield C. P. , Parsons B.
Published: March 2009

A wind power system differs from a conventional power system. In a conventional power plant, the operator can control the plant’s output. The output of a wind farm cannot be controlled because the output fluctuates with the wind. In this study, we investigated only the fixed-frequency induction generator, often used with wind turbines. We adopted the worst-case scenario and conducted a per-phase, per-turbine analysis. Our analysis showed a strong interaction among the wind farm, the utility grid, and the individual generator. In this paper, we investigate the power-system interaction resulting from power variations at wind farms using steady-state analysis. We use the characteristic of a real windsite on a known weak grid. We present different types of capacitor compensations and use phasor diagrams to illustrate the characteristics of these compensations. The purpose of our study is to provide wind farm developers with somc insights on wind farm power systems.
Diatom-inferred pH calibration of lakes near Wawa, Ontario
Authors: Dixit Sushil S.
Published: March 2009

In the absence of long-term pH records for lakes, sedimentary diatoms have often been used to detect the extent of recent lake acidification. Although various methods have been used to relate surface-sediment diatom remains to contemporary lake-water pH, their usefulness and selection criteria have not been clearly defined for Canadian lakes. Surface-sediment diatoms of 28 lakes (pH 4.0–8.13) located northeast of Lake Superior were identified and enumerated. Lake-water pH estimates were made using multiple regression analyses of selected diatom taxa and Hustedt's pH indicator groups, as well as by index α and index B. Multiple regression, using the abundance of pH indicator assemblages, appears to be the most suitable method for the studied lake region. Discrepancies associated with other methods are discussed in details.
The effects of blue and red light on Acetabularia mediterranea after a long dark period: recovery of the endogenous rhythms of transcellular electrical potential and chloroplast velocity
Authors: Borghi Hélène , Puiseux-Dao Simone , Dazy Anne-Catherine
Published: March 2009

After a long dark period (2 – 8 weeks), the transcellular electrical potential along the cell of Acetabularia mediterranea has almost disappeared and cytoplasmic streaming is at a stop. Irradiation with continuous blue light (450 nm) induces the transcellular electrical potential to increase and oscillate. After two shorter oscillations, the rhythm becomes firmly established with a period around 23 h. This behaviour is similar to that observed in white light, where the final period is around 26 h. White light and blue light induce the appearance of endogenous diurnal oscillations in the velocity of the cytoplasmic streaming which resumes following a periodicity pattern similar to that of the transcellular electrical potential. Irradiation with continuous red light (650 nm) causes a strong increase of transcellular electrical potential and recovery of cytoplasmic streaming but seldom induces these two processes to resume with the typical oscillations. However, after irradiation with blue light, the rhythm of transcellular electrical potential persists for some time in red light but disappears progressively. When blue light is given after red light, the transcellular electrical potential rhythm resumes immediately. Blue light may be considered as a "Zeitgeber."
The influence of phosphorus fertilization, drought, fungal species, and nonsterile soil on mycorrhizal growth response in tall grass prairie plants
Authors: Hetrick B. A. Daniels , Kitt D. Gerschefske , Wilson G. Thompson
Published: March 2009

In a series of experiments, factors effecting mycorrhizal growth response in prairie plants were examined. Two prairie grasses (Andropogon gerardii Vitman and Sorghastrum nutans (L.) Nash) and two forb species (Petalostemum purpureum (Venten) Rydb. and Liatris punctata Hook) benefited significantly from Glomus etunicatum Becker & Gerd. inoculation in fumigated or steamed soil. This benefit from mycorrhizae is probably related to phorphorus availability, since addition of 100 ppm phosphorus overcame the mycorrhizal growth response. No stimulation of growth occurred from additional vesicular–arbuscular, mycorrhizal inoculum to nonsterile soil. Neither was growth in nonsterile soil comparable to that achieved in inoculated, sterilized soil, suggesting a suppression of mycorrhizal growth response in nonsterile soil. In a related experiment addition of 1 or 10% nonsterile soil to sterilized, inoculated soil resulted in significantly reduced plant growth and greatly diminished mycorrhizal root colonization. Thus, soil microorganisms may suppress mycorrhizal growth responses, explaining the lack of mycorrhizal growth response observed in nonsterile soil. Of the four mycorrhizal fungi compared (Gigaspora rosea Nicol. & Schenk, Glomus deserticolum Trappe, Bloss & Menge, Glomus etunicatum Becker & Gerd., and Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe), the two indigenous species most stimulated plant growth. Under severe moisture stress (−4500 kPa) a significant mycorrhizal growth response was evident for G. etunicatum, but not for G. deserticolum inoculated plants. Growth response does not necessarily suggest drought tolerance, since the magnitude of response was similar in adequately watered and severely draughted plants.
Spindle pole body fusion in the smut fungus Tilletia foetida
Authors: Goates Blair J. , Hoffmann James A.
Published: March 2009

Fusion of double-structured, interphase spindle pole bodies (SPBs) occurred before nuclear fusion in heterokaryotic secondary sporidia. The SPBs of two separate nuclei were juxtaposed with their long axes perpendicular to each other. Also, SPBs were observed oriented with their long axes parallel and fused to each other at both ends. Fusion apparently continued toward the midportion of the SPBs. Nuclei were observed joined together in a narrow region. These nuclei appeared to share a single SPB that was located opposite to a protuberance on both nuclei. Following fusion, the SPB apparently returned to an interphase structure.
The role of root nutrient reserves in regrowth of two savanna shrubs
Authors: Miyanishi Kiyoko , Kellman Martin
Published: March 2009

The critical nutrient(s) limiting vegetative regrowth following shoot destruction by burning or cutting were identified in two neotropical savanna shrubs, Miconia albicans and Clidemia sericea, growing in the Mountain Pine Ridge Forest Reserve, Belize. Only starch, and not Ca, Mg, K, or P, was significantly depleted in the roots of these shrubs after both a single burn and repeated annual burns. Phosphorus was depleted only after repeated burns, while the other mineral nutrients showed no significant decline. In roots that failed to sprout following repeated shoot cuttings at 2-month intervals, phosphorus was reduced by 35–45% and starch was reduced by 97–98% compared with unburned roots. Therefore, root starch was indicated as a critical nutrient that limited resprouting ability. Root starch reserves were replenished to preburn levels within 2 years following a burn, suggesting that a cumulative net decline would occur only with annual burning. The decline in root starch was paralleled by a decline in growth of 1-year-old shoots under annual burning.
MOLECULAR DYNAMICS STUDY OF THE COALESCENCE OF EQUAL AND UNEQUAL SIZED Cu NANOPARTICLES
Authors: KART H. H. , WANG G. , KARAMAN I. , ÇAĞIN T.
Published: March 2009

Molecular dynamics simulations technique is used to study the consolidation of two nanoparticles of Cu element. We have studied sintering processes of two nanoparticles at different temperatures. Two model systems with 4 and 10 nm diameter of particles are selected to study the sintering process of the two nanoparticles. Orientation effects on the physical properties of consolidation of two nanoparticles with respect to each other are investigated. Temperature effects on the consolidation of two nanoparticles are also studied. The order of the values obtained in the simulation for the constant volume heat capacity and latent heat of fusion is good agreement with the bulk results. Moreover, we have investigated the size effects on the consolidation of two different sizes of nanoparticles, that is, one particle of diameter with 10 nm is fixed while the other one is changing from 1 to 10 nm. Melting temperatures of the copper nanoparticles are found to be decreased as the size of the particle decreases. It is found that simulation results are compatible with the other theoretical calculations.
MODELING THE INTERACTION BETWEEN MOTORIZED VEHICLE AND BICYCLE BY USING CELLULAR AUTOMATA MODEL
Authors: LI XIN-GANG , GAO ZI-YOU , JIA BIN , ZHAO XIAO-MEI
Published: March 2009

In this paper, the cellular automata models for motorized vehicle flow and that for bicycle flow are combined to modeling the interactions between the right-turning motorized vehicle and the driving ahead bicycle at intersection. We introduce the probability that the cross point is taken up by the same kind of vehicle during two successive time steps to describe the complex behaviors when conflict happens. The flux of both motorized vehicle and bicycle depending on the inflow rates are investigated and the spatiotemporal diagrams are also presented to show different traffic states as the inflow rates change. The simulation results show that the model can describe the interactions between motorized vehicle and bicycle. It makes foundations for future research on mixed traffic flow.
THE STUDY OF PHASE TRANSITION BY PERIODIC DISTRIBUTION OF BIMODAL BONDS IN 2D POTTS MODEL
Authors: YAŞAR FATIH , DILAVER MEHMET
Published: March 2009

We have studied the influence of the distribution of bimodal bonds on the phase transition in two-dimensional 8-state Potts model by the recently proposed Wang–Landau (WL) and the Swendsen–Wang (SW) algorithm. All simulations and measurements are done for r = 0.5. Physical quantities such as energy density and specific heat are evaluated at all temperatures. We have also obtained the probability distributions of the energy in order to monitor the transitions. We have observed that some cases of the periodically arranged bond distributions show a single peak, and some cases show double or triple peaks in the specific heat. Besides, it seems that the appearing of these peaks in the specific heat relates to a blocking procedure for periodicity. When the number of interaction pairs between the bimodal bonds is increased on the lattice with the blocking procedure, one can observe a single peak, otherwise, one can observe a double or triple peaks in the specific heat. From the point of view of simulation methods, the WL algorithm also works efficiently in the simulation of the system for a periodically arranged bond distribution as well as the SW algorithm.
STABILITY AND CONTROLLABILITY OF ASYMMETRIC COMPLEX DYNAMICAL NETWORKS: EIGENVALUE ANALYSIS
Authors: XIANG LINYING , CHEN ZENGQIANG , LIU ZHONGXIN , CHEN FEI , YUAN ZHUZHI
Published: March 2009

The stability and controllability of asymmetric complex dynamical networks are investigated in detail based on eigenvalue analysis. Pinning control is suggested to stabilize the homogenous stationary state of the whole coupled network. The complicated coupled problem is reduced to two independent problems: clarifying the stable regions of the coupled network and specifying the eigenvalue distribution of the asymmetric coupling and control matrices. The dependence of the controllability on both pinning density and pinning strength is studied.
GEOMETRIC RANDOM INNER PRODUCT TEST AND RANDOMNESS OF π
Authors: SEZGIN FATIN
Published: March 2009

The Geometric Random Inner Product (GRIP) is a recently developed test method for randomness. As a relatively new method, its properties, weaknesses, and strengths are not well documented. In this paper, we provide a rigorous discussion of what the GRIP test measures, and point out specific classes of defects that it is able to diagnose. Our findings show that the GRIP test successfully detects series that have regularities in their first- or second-order differences, such as the Weyl and nested Weyl sequences. We compare and contrast the GRIP test to some of the existing conventional methods and show that it is particularly successful in diagnosing deficient random number generators with bad lattice structures and short periods. We also present an application of the GRIP test to the decimal digits of π.
COSMIC CONSTRAINTS ON DECELERATION PARAMETER WITH Sne Ia AND CMB
Authors: XU LIXIN , LU JIANBO
Published: March 2009

In this paper, a parametrized deceleration parameter q(a) = q0+q1(1-a) is constrained by using the current cosmic observational data from type Ia Supernova (Sne Ia) and Cosmic Microwave Background Radiation (CMB). When the CMB dataset is added as a strong constraint, it is found that the 1σ error is largely reduced. The values of transition redshift zT from decelerated expansion to accelerated expansion and current deceleration parameter q0 are larger than that obtained from the case where Sne Ia dataset is used alone. With comparison to the case of Sne Ia 182 dataset used,15 it is found that the value of transition redshift is smaller than that in Sne 192 dataset case. This is the so-called dataset dependence.
BOUNCES/DYONS IN THE PLANE WAVE MATRIX MODEL AND SU(N) YANG–MILLS THEORY
Authors: POPOV ALEXANDER D.
Published: March 2009

We consider SU (N) Yang–Mills theory on the space ℝ × S3 with Minkowski signature (-+++). The condition of SO(4)-invariance imposed on gauge fields yields a bosonic matrix model which is a consistent truncation of the plane wave matrix model. For matrices parametrized by a scalar ϕ, the Yang–Mills equations are reduced to the equation of a particle moving in the double-well potential. The classical solution is a bounce, i.e. a particle which begins at the saddle point ϕ = 0 of the potential, bounces off the potential wall and returns to ϕ = 0. The gauge field tensor components parametrized by ϕ are smooth and for finite time, both electric and magnetic fields are nonvanishing. The energy density of this non-Abelian dyon configuration does not depend on coordinates of ℝ × S3 and the total energy is proportional to the inverse radius of S3. We also describe similar bounce dyon solutions in SU (N) Yang–Mills theory on the space ℝ × S2 with signature (-++). Their energy is proportional to the square of the inverse radius of S2. From the viewpoint of Yang–Mills theory on ℝ1,1 × S2 these solutions describe non-Abelian (dyonic) flux tubes extended along the x3-axis.
Learning styles of physiology students interested in the health professions
Authors: Breckler Jennifer , Joun David , Ngo Huy
Published: March 2009

Student learning may be classified according to the sensory modalities by which one prefers to take in information. One such classification scheme uses the VARK instrument, which categorizes learning preferences as visual (V), auditory (A), reading-writing (R), or kinesthetic (K). Many students have a single, strong preferences (“unimodal”), whereas others have multiple (“multimodal”) learning preferences. Although limited in scope and reliability, knowledge of student learning preferences is important for reasons of pedagogy. Teaching and student learning styles may also affect student academic success in science coursework and fulfillment of student career goals. In our study, we determined the learning preferences of upper-division students in a human physiology course during a 2-yr period at a public undergraduate institution in California. We also sought to determine the association between individual learning styles and stated career intentions. We found that the majority of students interested in the health professions have multimodal learning preferences. Furthermore, a greater percentage of premedical students had multimodal preferences compared with predental and prescientist students. When data were compared by gender, we found that more female than male students had multimodal learning preferences. We also observed some gender differences when separating student groups by career choice. For example, more premedical men had multimodal preferences compared with nonpremedical men. In contrast to men, women showed little differences in their learning style profiles whether premedical or not and also self-predicted their learning preferences more accurately. Thus, career choice may be an important consideration in determining whether or not there are gender differences among students.
The “core principles” of physiology: what should students understand?
Authors: Michael Joel , Modell Harold , McFarland Jenny , Cliff William
Published: March 2009

The explosion of knowledge in all of the biological sciences, and specifically in physiology, has created a growing problem for educators. There is more to know than students can possibly learn. Thus, difficult choices have to be made about what we expect students to master. One approach to making the needed decisions is to consider those “core principles” that provide the thinking tools for understanding all biological phenomena. We identified a list of “core principles” that appear to apply to all aspects of physiology and unpacked them into their constituent component ideas. While such a list does not define the content for a physiology course, it does provide a guideline for selecting the topics on which to focus student attention. This list of “core principles” also offers a starting point for developing an assessment instrument to be used in determining if students have mastered the important unifying ideas of physiology.
Learning our L.I.M.I.T.S.: less is more in teaching science
Authors: Hoskins Sally G. , Stevens Leslie M.
Published: March 2009

The rapid and accelerating pace of change in physiology and cell biology, along with the easy access to huge amounts of content, have altered the playing field for science students, yet most students are still mainly taught from textbooks. Of necessity, textbooks are usually broad in scope, cover topics much more superficially than do journal articles, and present the scientific process as a linear string of successful experiments, largely ignoring the reality of rejected hypotheses, unanticipated discoveries, or surprising findings that may shift paradigms. We suggest that a more narrow focus on scientific thinking, using a new method for reading a series of journal articles that track the evolution of a single project over a period of years, can more realistically convey the excitement and challenges of research science and perhaps stimulate some students to consider research careers for themselves. Our approach, termed “CREATE” (for Consider, Read, Elucidate hypotheses, Analyze data, and Think of the next Experiment), has proven successful at both demystifying the scientific literature and humanizing science/scientists in undergraduate biology courses ( 8 ), and we suggest that it could be profitably expanded to physiology courses.
Reviewing scientific manuscripts: how much statistical knowledge should a reviewer really know?
Authors: Morton James P.
Published: March 2009

In the sequel to their guidelines for reporting statistics in American Physiological Society journals, Curran-Everett and Benos highlighted that the initial guidelines of 2004 have had little effect on the statistical reporting practices of authors. In the present article, I suggest that the guidelines have also had little impact on both journal reviewers and editors. I present three cases of statistical reporting practices in which there appears to be considerable discrepancies between the author and reviewer and, moreover, inconsistencies between reviewers. I argue that for authors to comply with these guidelines, the initial challenge is to have a team of reviewers who are also willing to accept the unfamiliar. Indeed, the opinions of reviewers who are ill informed about relatively novel statistical methods and recommended reporting practices may have implications for the final editorial decision on the suitability of submitted manuscripts for publication.
Interleukin-6 activates arginine vasopressin neurons in the supraoptic nucleus during immune challenge in rats
Authors: Palin Karine , Moreau Marie L. , Sauvant Julie , Orcel Hélène , Nadjar Agnès , Duvoid-Guillou Anne , Dudit Jennifer , Rabié Alain , Moos Françoise
Published: March 2009

The increase of plasma arginin-vasopressin (AVP) release, which translates hypothalamic AVP neuron activation in response to immune challenge, appears to occur independently of plasma osmolality or blood pressure changes. Many studies have shown that major inflammatory mediators produced in response to peripheral inflammation, such as prostaglandin (PG)-E2 and interleukin (IL)-1β, excite AVP neurons. However, in vivo electrical activation of AVP neurons was still not assessed in relation to plasma AVP release, osmolality, or blood pressure or to the expression and role of inflammatory molecules like PG-E2, IL-1β, IL-6, and tumor necrosis factor-α (TNFα). This study aims at elucidating those factors that underlie the activation of AVP neurons in response to immune stimulation mimicked by an intraperitoneal injection of lipopolysaccharide (LPS) in male Wistar rats. LPS treatment concomittanlty decreased diuresis and increased plasma AVP as well as AVP neuron activity in vivo, and these effects occurred as early as 30 min. Activation was sustained for more than 6 h. Plasma osmolality did not change, whereas blood pressure only transiently increased during the first hour post-LPS. PG-E2, IL-1β, and TNFα mRNA expression were raised 3 h after LPS, whereas IL-6 mRNA level increased 30 min post-LPS. In vivo electrophysiological recordings showed that brain IL-6 injection increased AVP neuron activity similarly to peripheral LPS treatment. In contrast, brain injection of anti-IL-6 antibodies prevented the LPS induced-activation of AVP neurons. Taken together, these results suggest that the early activation of AVP neurons in response to LPS injection is induced by brain IL-6.
Mineralocorticoid receptor antagonism attenuates glomerular filtration barrier remodeling in the transgenic Ren2 rat
Authors: Whaley-Connell Adam , Habibi Javad , Wei Yongzhong , Gutweiler Alex , Jellison Jessica , Wiedmeyer Charles E. , Ferrario Carlos M. , Sowers James R.
Published: March 2009

Recent evidence suggests that mineralocorticoid receptor (MR) antagonism has beneficial effects on tissue oxidative stress and insulin metabolic signaling as well as reducing proteinuria. However, the mechanisms by which MR antagonism corrects both renin-angiotensin-aldosterone system (RAAS) impairments in renal insulin metabolic signaling and filtration barrier/podocyte injury remain unknown. To explore this potential beneficial interactive effect of MR antagonism we used young transgenic (mRen2)27 (Ren2) rats with increased tissue RAAS activity and elevated serum aldosterone levels. Ren2 and age-matched Sprague-Dawley (SD) control rats (age 6–7 wk) were implanted with a low dose of the MR antagonist spironolactone (0.24 mg/day) or vehicle, both delivered over 21 days. Albuminuria, podocyte-specific proteins (synaptopodin, nephrin, and podocin), and ultrastructural analysis of the glomerular filtration barrier were measured in relation to RAAS activation of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, reactive oxygen species (ROS), and the redox-sensitive Rho kinase (ROK). Insulin metabolic signaling was determined via measurement of insulin receptor substrate-1 (IRS-1) phosphorylation, IRS-1 ubiquitin/proteasomal degradation, and phosphorylation of Akt. Ren2 rats exhibited albuminuria, loss of podocyte-specific proteins, and podocyte foot process effacement contemporaneous with reduced renal IRS-1 and protein kinase B/Akt phosphorylation compared with SD control rats (each P < 0.05). Ren2 kidneys also manifested increased NADPH oxidase/ROS/ROK in conjunction with enhanced renal tissue levels of angiotensin II (ANG II), ANG-(1-12), and angiotensin type 1 receptor. Low-dose spironolactone treatment reduced albuminuria and tissue RAAS activity and improved podocyte structural and protein integrity with improvements in IRS-1/Akt phosphorylation. Thus, in this model of RAAS activation, MR antagonism attenuates glomerular/podocyte remodeling and albuminuria, in part through reductions in redox-mediated impairment of insulin metabolic signaling.
Unitary Recordings of TRP and TRPL Channels From Isolated Drosophila Retinal Photoreceptor Rhabdomeres: Activation by Light and Lipids
Authors: Delgado Ricardo , Bacigalupo Juan
Published: March 2009

Transient receptor potential (TRP) channels play key roles in sensory transduction. The TRP family founding members, the Drosophila light-dependent channels, were previously studied under voltage clamp, but had not been characterized in intact rhabdomeres at single-channel level. We report patch-clamp recordings from intact isolated photoreceptors of wt and mutant flies lacking TRP ( trp 343), TRPL ( trpl 302), or both channels ( trp 313 ; trpl 302). Unitary currents were activated by light in rhabdomere-attached patches. In excised rhabdomeral patches, the channels were directly activated by molecules implicated in phototransduction, such as diacylglycerol and polyunsaturated fatty acids. Currents recorded from trpl photoreceptors are blocked by external Ca2+, Mg2+ (1 mM), and La3+ (20 μM), whereas those from trp photoreceptors are not. Rhabdomeric patches lacked voltage-dependent activity. Patches from trp;trpl mutants were devoid of channels. These characteristics match the macroscopic conductances, suggesting that the unitary currents from Drosophila trpl and trp photoreceptors correspond to TRP and TRPL.