bluuebunny/crossref_metadata_2025 huggingface dataset:
INFLUENCE OF CUT AND PACKAGING FILM ON SENSORY QUALITY OF FRESH‐CUT BUTTERHEAD LETTUCE (LACTUCA SATIVAL., CV. WANG)
Authors: MARTÍNEZ INÉS , ARES GASTÓN , LEMA PATRICIA
Published: February 2008

The purpose of the present work was to study the influence of cut (manual and using a sharp knife) and packaging film (bioriented polypropylene and polyolefin PD‐961) on the sensory quality of fresh‐cut butterhead lettuce stored under passive modified atmosphere at 5C. Results showed that lettuce cut by hand had a lower respiration rate and deterioration rate than those cut with a knife. This difference could be attributed to a difference in the level of wounding, which can be explained by the fact that cutting by hand caused the tear to follow the naturally weaker areas of the lettuce, leading to less tissue damage than that engendered by the use of a sharp knife.

PRACTICAL APPLICATIONS

Results suggest that lettuce leaves cut by hand showed a lower sensory deterioration rate than those cut with a sharp knife. While not industrially applicable, the cutting of lettuce by hand might be appealing to small ventures such as buffets, restaurants and catering services. The sensory analysis carried out suggests that the use of polyolefin PD‐961 is preferred over bioriented polypropylene for packaging fresh‐cut lettuce, in view of achieving a better quality of the produce.
PHYSICOCHEMICAL AND NUTRITIONAL ATTRIBUTES IN 20 BLACK SOYBEAN LINES (GLYCINE MAX L.) OF HIMALAYAN REGION, INDIA
Authors: SAHA SUPRADIP , GUPTA ARUN , MAHAJAN V. , KUNDU S. , GUPTA H.S.
Published: February 2008

The physicochemical compositions of 20 black‐seeded soybean lines were analyzed for different nutritional and cooking quality parameters. The range of variation for different characteristics was 1.04–1.20 g/mL for density, 17.34–30.20 kg for hardness, 72.7–214.4 µg/seed for hydration capacity, 1.06–1.24 for hydration index, 75.6–203.4 µL/seed for swelling capacity, 0.99–1.58 swelling index, 32.1–39.8% for protein, 10.8–19.6% for oil, 3.93–6.15% for total minerals, 131–205 mg/100 g for phosphorus, 6.4–13.9 mg/100 g for iron, 0.49–0.89 mg/g for trypsin inhibitor, 2.1–6.4 mg/g for phytic acid and 60.4–13.4 µg/g for polyphenols. Based on 18 physicochemical and nutritional attributes, 20 black soybean germplasm lines were grouped into four clusters using nonhierarchical Euclidean cluster analysis. The DARL‐BK‐615 and VRB‐PS‐1453 were found to be more diverse than others. The DARL‐BK‐615 was found best for low trypsin inhibitor and high mineral contents (Zn, Mn, Cu), while VRB‐PS‐1453 was found best for protein content and required the lowest time for cooking. The selection for the improvement of physicochemical nutritional attributes and antinutritional factors can be independently effective in black soybean genotypes.

PRACTICAL APPLICATIONS

This study has shown that sufficient variability for cooking quality, protein, oil, micronutrients and antinutritional factors exist in black soybean germplasm lines of the Himalayan region of India, which can be independently improved by the breeders. Different genotypes in four diverse groups may be used to develop improved lines with better nutritional and cooking quality coupled with low antinutritional factors for consumption as pulses. Germplasm lines with high protein, low levels of antinutrients and superior nutritional and cooking quality are useful materials for the improvement of quality in high‐yielding soybean lines.
EXTERNAL VALIDATION AND TRANSFERABILITY OF NIRS MODELS DEVELOPED FOR DETECTING AND QUANTIFYING MBM IN INTACT COMPOUND FEEDING STUFFS
Authors: PÉREZ MARÍN D.C. , GARRIDO‐VARO A. , GUERRERO J.E. , GÓMEZ A. , SOLDADO A. , DE LA ROZA B.
Published: February 2008

The ban on the use of animal‐origin by‐products such as meat and bone meal (MBM) in compound feeds was one of the measures implemented in the European Union to stop the spread of bovine spongiform encephalopathy (BSE) and to prevent its reoccurrence. It is now clear that the blanket ban will only be lifted if reliable analytical methods are available that ensure the detection of animal by‐products. Near‐infrared spectroscopy (NIRS) is likely to be the most rapid method for testing feedingstuffs, enabling a substantial increase in the number of samples tested and providing instant detection of adulteration, especially when samples are analyzed in intact form. This study aimed to demonstrate the feasibility of NIRS predictive models for detecting and quantifying MBM in intact compound feedingstuffs, and to demonstrate the transferability of calibration models between two NIRS instruments.

PRACTICAL APPLICATIONS

This study shows the potential of near infrared spectroscopy (NIRS) as a fast screening method for detecting the adulteration of compound feedingstuffs with animal‐origin meals, useful for the feed industry and the inspection bodies. NIRS could provide the first line of defense of the food chain, allowing a large‐scale analysis and making more costly methods to be used more productively on suspect specimens.
Microbiological Response to Well Pumping
Authors: Kwon Man Jae , Sanford Robert A. , Park Jungho , Kirk Matthew F. , Bethke Craig M.
Published: February 2008

To better constrain sampling strategies for observing biologically sensitive parameters in ground water, we vigorously pumped for 120 h a lightly pumped well completed in a confined glacial aquifer while observing how various physical and chemical parameters evolve in the water produced. The parameters commonly monitored when sampling a well stabilized within about an hour, after 5 wellbore volumes were produced; these parameters include temperature, pH, dissolved oxygen, oxidation‐reduction potential (Eh), and electrical conductivity. The concentrations of ferrous iron, sulfide, and sulfate and various biological or biologically sensitive parameters, including the concentrations of dissolved hydrogen and methane, direct cell counts, and the microbial community profile, in contrast, required more than 8 h or 36 well volumes to stabilize. We interpret this result to mean that the zone of influence of the wellbore on biologic processes in the aquifer extends beyond the commonly recognized zone where physical properties are affected. A second period of adjustment of these biologically sensitive parameters began after about 50 h of pumping, following displacement of 230 wellbore volumes, and continued to the end of the experiment. During this period, the cell density and the composition of the microbial community suspended in the water samples changed. This finding indicates that the microbial community in and near the wellbore changed in response to pumping and the changes affected aspects of the composition of water produced from the well. The study demonstrates the importance of allowing adequate pumping time when sampling ground water for the analysis of biologically sensitive parameters.
Assessment of sustainable forest management in New Zealand indigenous forest
Authors: Gillman Len N.
Published: February 2008

Abstract:  There has been considerable international progress towards sustainable forest management (SFM) of temperate and boreal forest. However, the effectiveness of SFM legislation in providing for the protection of natural forest values has been largely undemonstrated. In this study, all the SFM Plans in the North Island, New Zealand, approved under the Forests Amendment Act (1993) are assessed. It is concluded that the requirements in the plans for assessing, monitoring and maintaining natural values are inadequate with the lack of public participation, and associated appeal rights over decisions, viewed as the key gap in the legislation.
L'univers du secteur public dans le système de la comptabilité nationale
Authors: Bélanger Gérard
Published: February 2008

Sommaire: L'implantation généralisée des comptes nationaux fut une importante réussite de l'après‐guerre. Ce texte étudie les problèmes que posent l'étendue du secteur public et l'nterprétation des données des administrations publiques dans ces comptes. Comme toute classification implique une part d'arbitraire, puisqu'il s'agit de placer ce qui se présente sous forme de continuum, le système canadien montre des incohérences dans le traitement des institutions sans but lucratif majoritairement financées et contrôlées par les organismes gouvernementaux. Des institutions sont rangées dans le groupe des ménages et d'autres tout à fait comparables sont incluses dans l'administration. Des ambiguités semblables existent à l'intérieur de la catégorie des activités marchandes et non marchandes et dans les sous‐catégories de l'administration.

Les niveaux élevés des déficits des gouvernements centraux au cours des dernières années ont accru l'intérêt pour les problèmes de mesure et d'interprétation des déficits. Ils sont nombreux: règles comptables utilisées, déficits actuariels des assurances sociales et des régimes de retraite, garantie de prêts et primes à l'inflation. Deux problèmes majeurs demeurent présents dans l'estimation du volume des activités gouvernementales: la mesure des services et leur classification comme produits finals.

Abstract: The generalized introduction of national accounts was a major statistical success of the postwar years. This article examines the problems involved in establishing the scope of the public sector and in interpreting the public administration data in those accounts. Since any classification involves arbitrary elements because it means subdividing data presented as a continuum, the Canadian system displays inconsistencies in its treatment of non‐profit institutions largely financed and controlled by government agencies. Some institutions come under the household heading, while other quite comparable entities are included under administration. Similar ambiguities exist in categorizing commercial/non‐commercial activities and subcategorizing the administration.

In recent years, large central government deficits have heightened interest in the problems of deficit measurement and interpretation. The problems are many: accounting principles used, actuarial deficits of social insurance and pension plans, loan guaranties and cost‐of‐living allowances. Two major problems remain in estimating the volume of government activities: measuring services, and their classification as final products.
Enriched Engagement Through Assistance to Systems’ Change: A Proposal
Authors: Graen George B.
Published: February 2008

Top management teams (TMTs) of postmodern multinational corporations are increasingly confronted by new multiple context shifts defining our advancing global knowledge era (Grant, 2000). These include seven major context changes, not the least of which is knowledge becoming the new driver, not labor, machine, or money (Graen, in press). In addition, some complicating elements are the dysfunctions of human psychology under drastic changes in contexts (Snowden & Stanbridge, 2004). Clearly our 20th-century organizational designs and processing engineering systems are in need of continuous improvement to remain competitive. What TMTs seek are new practical ways to bring about needed changes in corporate structures and systems (Graen, 2007).
On the Methodology of the Race Debate: Conceptual Analysis and Racial Discourse
Authors: GLASGOW JOSHUA
Published: February 2008

The traditional debate about whether race should be eliminated from public discourse is often conducted in significant part by examining whether race is real. Whether race is real, in turn, often comes down to whether racial discourse purports to refer to social or natural kinds, which means that analysis of racial concepts is crucial to the question of racial eliminativism. The dominate theory of conceptual analysis in the race debate is that racial concepts should be analyzed according to how those terms have been used by historical experts. It is argued here that this dominant theory is misguided, and that we should therefore analyze racial concepts according to how they are used in contemporary, folk discourse. In addition, and in contrast to the main rival to the dominant theory, I argue that we should analyze folk racial discourse not from the armchair, but instead through empirical research.
BMO from dyadic BMO on the bidisc
Authors: Pipher Jill , Ward Lesley A.
Published: February 2008

We generalize to the bidisc a theorem of Garnett and Jones relating the space BMO of functions of bounded mean oscillation to its martingale counterpart, dyadic BMO. Namely, translation‐averages of suitable families of dyadic BMO functions belong to BMO. As a corollary, we deduce a biparameter version of a theorem of Burgess Davis connecting the Hardy space H1 to martingale H1. We also prove the analogs of the theorem of Garnett and Jones in the one‐parameter and biparameter VMO spaces of functions of vanishing mean oscillation.
Low protein diet fed exclusively during mouse oocyte maturation leads to behavioural and cardiovascular abnormalities in offspring
Authors: Watkins Adam J. , Wilkins Adrian , Cunningham Colm , Perry V. Hugh , Seet Meei J. , Osmond Clive , Eckert Judith J. , Torrens Christopher , Cagampang Felino R. A. , Cleal Jane , Gray William P. , Hanson Mark A. , Fleming Tom P.
Published: February 2008

Early embryonic development is known to be susceptible to maternal undernutrition, leading to a disease‐related postnatal phenotype. To determine whether this sensitivity extended into oocyte development, we examined the effect of maternal normal protein diet (18% casein; NPD) or isocaloric low protein diet (9% casein; LPD) restricted to one ovulatory cycle (3.5 days) prior to natural mating in female MF‐1 mice. After mating, all females received NPD for the remainder of gestation and all offspring were litter size adjusted and fed standard chow. No difference in gestation length, litter size, sex ratio or postnatal growth was observed between treatments. Maternal LPD did, however, induce abnormal anxiety‐related behaviour in open field activities in male and female offspring (P < 0.05). Maternal LPD offspring also exhibited elevated systolic blood pressure (SBP) in males at 9 and 15 weeks and in both sexes at 21 weeks (P < 0.05). Male LPD offspring hypertension was accompanied by attenuated arterial responsiveness in vitro to vasodilators acetylcholine and isoprenaline (P < 0.05). LPD female offspring adult kidneys were also smaller, but had increased nephron numbers (P < 0.05). Moreover, the relationship between SBP and kidney or heart size or nephron number was altered by diet treatment (P < 0.05). These data demonstrate the sensitivity of mouse maturing oocytes in vivo to maternal protein undernutrition and identify both behavioural and cardiovascular postnatal outcomes, indicative of adult disease. These outcomes probably derive from a direct effect of protein restriction, although indirect stress mechanisms may also be contributory. Similar and distinct postnatal outcomes were observed here compared with maternal LPD treatment during post‐fertilization preimplantation development which may reflect the relative contribution of the paternal genome.
Hydroxyl radical and glutathione interactions alter calcium sensitivity and maximum force of the contractile apparatus in rat skeletal muscle fibres
Authors: Murphy R. M. , Dutka T. L. , Lamb G. D.
Published: February 2008

Studies on intact muscle fibres indicate that reactive oxygen species (ROS) produced during muscle activity, or applied exogenously, can cause decreased force responses primarily by reducing the Ca2+ sensitivity of the contractile apparatus. Identification of the molecular basis of this effect is complicated by the fact that studies on skinned muscle fibres in general have not observed reduced contractile Ca2+ sensitivity when applying ROS, predominantly H2O2. Here, using skinned fibres from rat extensor digitorum longus (EDL) and soleus muscle, it is shown that although H2O2 (≥ 100 μm) has little effect by itself, when added in the presence of myoglobin it causes marked reduction in the Ca2+ sensitivity of the contractile apparatus, probably due to production of hydroxyl radicals (OH•). Maximum force production is also reduced, but only with larger or more prolonged treatments. The effects are not prevented by tempol, a potent superoxide scavenger. Dithiotreitol (DTT) produces little reversal of the sensitivity change if applied afterwards, but it does substantially reverse all the changes if applied before the fibre undergoes an activation sequence. When glutathione (GSH, 5 mm) is present, exposure of EDL fibres to H2O2 and myoglobin causes an increase in Ca2+ sensitivity, with longer treatments causing a subsequent decrease, whereas in soleus fibres it causes only decreases in sensitivity and maximum force. The increased Ca2+ sensitivity in EDL fibres is evidently due to the summed actions of (i) a potentiating effect of glutathionylation, which can be reversed by DTT and only occurs in fast‐twitch fibres, and (ii) a less reversible reduction in sensitivity. Western blotting showed that reductions in Ca2+ sensitivity were not due to loss of troponin‐C. The present findings help provide a mechanistic basis for diverse findings on the effects of ROS in muscle fibres and implicate OH• radicals and glutathione as likely mediators of the effects.
Stresses in a Multilayer Thin Film/Substrate System Subjected to Nonuniform Temperature
Authors: Feng X. , Huang Y. , Rosakis A. J.
Published: February 2008

Current methodologies used for the inference of thin film stress through curvature measurements are strictly restricted to uniform film stress and system curvature states over the entire system of a single thin film on a substrate. By considering a circular multilayer thin film/substrate system subjected to nonuniform temperature distributions, we derive relations between the stresses in each film and temperature, and between the system curvatures and temperature. These relations featured a “local” part that involves a direct dependence of the stress or curvature components on the temperature at the same point, and a “nonlocal” part, which reflects the effect of temperature of other points on the location of scrutiny. We also derive relations between the film stresses in each film and the system curvatures, which allow for the experimental inference of such stresses from full-field curvature measurements in the presence of arbitrary nonuniformities. These relations also feature a “nonlocal” dependence on curvatures making full-field measurements of curvature a necessity for the correct inference of stress. The interfacial shear tractions between the films and between the film and substrate are proportional to the gradient of the first curvature invariant, and can also be inferred experimentally.
Angular Velocity Estimation From the Angular Acceleration Matrix
Authors: Cardou Philippe , Angeles Jorge
Published: February 2008

Computing the angular velocity ω from the angular acceleration matrix is a nonlinear problem that arises when one wants to estimate the three-dimensional angular velocity of a rigid-body from point-acceleration measurements. In this paper, two new methods are proposed, which compute estimates of the angular velocity from the symmetric part WS of the angular acceleration matrix. The first method uses a change of coordinate frame of WS prior to performing the square-root operations. The new coordinate frame is an optimal representation of WS with respect to the overall error amplification. In the second method, the eigenvector spanning the null space of WS is estimated. As ω lies in this space, and because its magnitude is proportional to the absolute value of the trace of WS, it is a simple matter to obtain ω. A simulation shows that, for this example, the proposed methods are more accurate than those existing methods that use only centripetal acceleration measurements. Moreover, their errors are comparable to other existing methods that combine tangential and centripetal acceleration measurements. In addition, errors of 2.15% in the accelerometer measurements result in errors of approximately 3% in the angular-velocity estimates. This shows that accelerometers are competitive with angular-rate sensors for motions of the type of the simulated example, provided that position and orientation errors of the accelerometers are accounted for.
Stiff-String Basis Functions for Vibration Analysis of High Speed Rotating Beams
Authors: Gunda Jagadish Babu , Ganguli Ranjan
Published: February 2008

A new rotating beam finite element is developed in which the basis functions are obtained by the exact solution of the governing static homogenous differential equation of a stiff string, which results from an approximation in the rotating beam equation. These shape functions depend on rotation speed and element position along the beam and account for the centrifugal stiffening effect. Using this new element and the Hermite cubic finite element, a convergence study of natural frequencies is performed, and it is found that the new element converges much more rapidly than the conventional Hermite cubic element for the first two modes at higher rotation speeds. The new element is also applied for uniform and tapered rotating beams to determine the natural frequencies, and the results compare very well with the published results given in the literature.
Vibrations of Double-Walled Carbon Nanotubes With Different Boundary Conditions Between Inner and Outer Tubes
Authors: Xu Kai-Yu , Aifantis Elias C. , Yan Yong-Hua
Published: February 2008

Free vibrations of a double-walled carbon nanotube (DWNT) are studied. The inner and outer carbon nanotubes are modeled as two individual elastic beams interacting each other by van der Waals forces. An original method is proposed to calculate the first seven order resonant frequencies and relative vibrational modes. Detailed results are demonstrated for DWNTs according to the different boundary conditions between inner and outer tubes, such as fixed-free, cantilever-free, fixed-simple and fixed-fixed (reduced form) supported ends. Our results indicate that there is a special invariable frequency for a DWNT that is not affected by different combinations of boundary conditions. All vibrational modes of the DWNT must be coaxial when the resonant frequency is smaller than this frequency. Some noncoaxial vibrations will occur when their resonant frequencies exceed the frequency. Especially, the first noncoaxial resonant frequency is still invariable for all different boundary conditions. A change of resonant frequency for various lengths of DWNTs is discussed in detail. In addition, our model predicts a new coaxial-noncoaxial vibrational mode in fixed-simple supports for inner and outer tubes of a DWNT.
Moving Load and Prestress Identification Using Wavelet-Based Method
Authors: Law S. S. , Wu S. Q. , Shi Z. Y.
Published: February 2008

A novel moving force and prestress identification method based on finite element and wavelet-based method for bridge-vehicle system is developed. A two-axle vehicle model and simple-supported beam with prestressing force are studied. Finite element method is flexible in modeling structures with complex boundaries while the wavelet-analysis method has the characteristic of multiresolution and the ability to detect abrupt changes. Both methods are used in this work to identify the moving loads and prestressing force from the “measured” bridge responses, which may be strain or acceleration. Numerical simulations demonstrate the efficiency of the method under the effects of measurement noise, road roughness, sampling rate, and the arrangement of sensors with good accuracy. Results indicate that the proposed method has the advantages of both high computational performance and fine identification resolution.
Simulation and Nonlinear Dynamics Analysis of Planing Hulls
Authors: Hicks J. D. , Troesch A. W. , Jiang C.
Published: February 2008

The high speeds, small trim angles, and shallow drafts of planing hulls produce large changes in vessel wetted surface which, in turn, lead to significant hydrodynamic and dynamic nonlinearities. Due to the complex nonlinearities of this type of craft, naval architects and planing boat designers tend to rely upon experimental tests or simulation for guidance. In order for simulation to be an effective design tool, a fundamental understanding of the system’s dynamic characteristics is required. This paper describes a developing methodology by which the necessary insight may be obtained. A demonstration of the combined use of modern methods of dynamical system analysis with simulation is given in the evaluation of the vertical motions of a typical planing hull. Extending the work of Troesch and Hicks (1992) and Troesch and Falzarano (1993), the complete nonlinear hydrodynamic force and moment equations of Zarnick (1978) are expanded in a multi-variable Taylor series. As a result, the nonlinear integro-differential equations of motion are replaced by a set of highly coupled, ordinary differential equations with constant coefficients, valid through third order. Closed-form, analytic expressions are available for the coefficients (Hicks, 1993). Numerical examples for all first-order and some second-order terms are presented. Once completely determined, the coefficient matrices will serve as input to path following or continuation methods (e.g., Seydel, 1988) where heave and pitch magnification curves can be generated, allowing the entire system response to be viewed. The branching behavior of the solutions resulting from a variation of the center of gravity is examined in detail. These studies of the second-order accurate model show the potential of the method to identify areas of critical dynamic response, which in turn can be verified and explored further through the use of the simulator.
Numerical Stress Analysis of Internal Ring-Stiffened Tubular
T-Joints
Authors: Nwosu D. I. , Swamidas A. S. J. , Munaswamy K.
Published: February 2008

In order to design a tubular joint to carry a larger load and to possess a longer life, the prime objective of design would be to reduce stress concentration factor at the intersection of the joint; one method to achieve the same is to stiffen the joint with internal ring stiffeners. This paper presents results of the stress analysis for stress distribution, along the intersection of internally ring-stiffened tubular T-joints, under the action of axial and in-plane/out-of-plane (bending) loads, using degenerate shell elements. The stress analyses results are obtained using the general-purpose finite element package called ABAQUS. Post-processing of results has been facilitated by other small programs developed for the purpose. The nominal brace stress and the maximum principal stress values have been used for stress concentration factor computations. The effects of stiffener size, location, number, thickness (τ) and thinness (γ) ratios have been investigated, and the results validated with known analytical and experimental investigations. A comparison of the results obtained from finite element analysis, and experimental results of the Canadian Cooperative Fatigue Studies Program, carried out at Memorial University and University of Waterloo, is also made. The results obtained indicate that stiffening can considerably reduce the stress concentration in joints, and thus increase the load-carrying capacity of tubular T-joints.
A Method to Calculate Pack Ice Driving Forces
Authors: Evgin E. , Zhan C. , Frederking R. M. W.
Published: February 2008

A method is proposed to calculate pack ice driving forces. In order to develop the method, stress distributions in a circular ice floe are calculated for various boundary loading conditions. The analysis is carried out using a special-purpose finite element program in which Sinha’s creep equation is used to model the behavior of ice. Charts relating pack ice driving forces to stresses in the ice floe are produced for both linear elastic and creep equations for ice behavior. The results indicate that, for a short period of loading time and at low stress levels, a linear elastic analysis can be used to calculate the pack ice driving forces. However, when the stress levels in the ice floe are high or the time span of load application is long, linear and nonlinear analyses produce much different values for pack ice driving forces.
Loading on a Vertical Cylinder in Multidirectional Waves
Authors: Chaplin J. R. , Subbiah K. , Irani M.
Published: February 2008

This paper presents laboratory measurements of local and total loading on an isolated vertical cylinder in irregular unidirectional and multidirectional waves. Maximum Keulegan-Carpenter numbers in individual waves were about 16, and maximum Reynolds numbers about 3 × 104. It is shown that in these conditions, existing theoretical and numerical models underestimate the reduction in loading on a cylinder due to wave spreading. Besides the changes that are predicted when Morison’s equation is used with constant coefficients, there are hydrodynamic influences that contribute further force reductions. Comparisons with Dean’s (1977) hybrid approach suggest that in the present conditions these reductions are in the region of 3 and 6 percent for a spreading function cos2s θ, with s = 8 and s = 2, respectively. Larger reductions can be expected at higher Keulegan-Carpenter numbers, though scale effects are likely to become more important in the drag-dominated regime.
A Two-Dimensional Weibull Distribution and Its Application to
Rolling
Authors: Myrhaug D. , Dahle E. Aa. , Rue H.
Published: February 2008

A two-dimensional Weibull distribution is presented which is obtained by transforming a two-dimensional Rayleigh distribution. The emphasis herein is on its application to describe the statistics of successive wave periods, and the results are illustrated by discussing the rolling of smaller vessels in beam seas in a simplified manner. Reference is also made to the related subjects on the joint correlation of successive high waves and on the joint statistics of wave steepness parameters for two successive waves, where the wave steepness parameters considered are the crest front steepness and the total wave steepness.
Fatigue Testing of Metric Bolts Fitted With Lip-Type Nuts
Authors: Dragoni E.
Published: February 2008

The paper addresses the effect of the external shape of lip-type nuts on the fatigue strength of commercial M10 bolts loaded in tension. Evolving from the standard configuration, six nut geometries are compared, characterized by lips of different shape (cylindrical or tapered) and length. Testing and statistical treatment of the data are performed in accordance with a JSME standard involving 14 specimens for each geometry. Within the class of merely cylindrical lips, only limited advantages over the standard assembly are detected. In particular, the bolt strength remains mostly unaffected by lengthening of the lip beyond one-third of the nut height. Conversely, tapering of the lip end so as to thin its wall around the entry section of the bolt results in substantial improvements. In this case, the strength increase is roughly proportional to the taper length. Adoption of a tapered lip covering two-thirds of the nut height enhances the bolt strength by about one-fourth with respect to the standard geometry.
Horizontal Motions of an SPM Tanker Under Alternative Mooring Configurations
Authors: Jiang T. , Schellin T. E. , Sharma S. D.
Published: February 2008

Horizontal motions of a tanker single point moored in current, wind, and waves were numerically investigated under four alternative configurations, namely, buoy mooring (SBM), articulated tower mooring (ATM), bow turret mooring (BTM), and internal turret mooring (ITM). The analysis was based on a previously validated, comprehensive mathematical model of the equations of motion in three degrees of freedom (surge, sway, and yaw) that considers five sets of forces: 1) nonlinear quasi-steady hydrodynamic response and control forces; 2) linear memory effects due to radiated waves; 3) nonlinear mooring restoring force characteristics; 4) empirical wind actions; and 5) first-order wave forces and wave drift forces. Locally linearized stability analyses showed that restoring characteristics have no influence on static bifurcations (typical for BTM and ITM) and only minor influence on dynamic bifurcations (typical for SBM and ATM). However, nonlinear time domain simulations revealed that they do affect the form of asymptotic motion trajectories as well as line tension amplitudes. It was found that turret position is a significant parameter and motion behavior is sensitive to the direction of wind and waves relative to current. Comparison of simulated time histories between autonomous and nonautonomous modes indicated that the traditional spectral analysis treating high-frequency and low-frequency responses separately may not be valid for locally unstable cases.
Parameter Identification of Nonlinear Ocean Mooring Systems Using the
Hilbert Transform
Authors: Gottlieb O. , Feldman M. , Yim S. C. S.
Published: February 2008

We introduce and demonstrate the applicability of a parameter identification algorithm based on the Hilbert transform to nonlinear ocean mooring systems. The mooring dynamical system consists of a submerged small body and includes a geometrically nonlinear restoring force and a nonlinear dissipation function incorporating both viscous and structural damping. By combining a recently developed methodology with a generalized averaging procedure, parameter estimation from the slowly varying envelope dynamics is enabled. System backbone curves obtained from data generated by numerical simulation are compared to those obtained analytically and are found to be accurate. An example large-scale experiment is also considered.
Freezing of a Salt Solution in a Packed Bed
Authors: Chellaiah S. , Singh H.
Published: February 2008

There are many natural processes and technological applications that involve the solidification of a binary solution saturating a porous matrix. Some of them are: natural freezing and artificial freezing (for construction purposes) of soil, oil exploration in cold regions, and processing and preservation of food. This paper presents the results of a fundamental study of freezing of a binary salt solution saturating a packed bed. An aqueous sodium chloride solution (of noneutectic composition) constituted the binary solution and spherical glass beads constituted the packed bed. The freezing was initiated at one of the vertical walls of a rectangular cavity. The temperature distributions in the solid, mush, and liquid regions were recorded using thermocouples. The concentration of salt was determined using a sample withdrawal technique in conjunction with a refractometer and a calibration chart. There was buoyancy-driven convective flow generated and sustained by the thermal and solutal gradients. The effect of this flow on the freezing process was significant. The morphology of the freezing fronts, the temperature and salt concentration profiles, and the rate of freezing were all influenced by the flow. Even in experiments with an initial superheat of 10°C, it was found that the effect of flow was considerable. For even though the fluid flows through the interstitial spaces in the porous matrix, the permeability was large for balls of 0.5-in. diameter. With a superheat of 20°C, the convection was vigorous and the rate of freezing was retarded considerably. The salt rejected during freezing was redistributed by the flow. At later times, a stable solute-rich region formed at the bottom of test cell where the concentration decreased with height. The amount of salt rejected was directly influenced by the rate of freezing, which in turn was controlled by the superheat and the permeability of packed bed.
Optimum Control of a Floating Wave-Energy Converter With Restricted Amplitude
Authors: Eidsmoen H.
Published: February 2008

In this paper, the use of optimal control techniques for improving the energy absorption by a wave-energy converter (WEC) is investigated. A mathematical model is developed for a floating body, which is exposed to an irregular incident wave, and is moving relative to a fixed reference. This model includes a control force from the power take-off and control machinery, and a friction force which restricts the oscillation amplitude. This force models end-stop devices, which are necessary to protect the machinery. An optimal control strategy is determined, based on variations of a Lagrange functional. This gives a set of adjoint equations in addition to the state equations, as a necessary condition for optimum. An algorithm is given for solving the problem numerically by iteration, based on a gradient method. It is shown that the optimal motion in a sinusoidal wave is not sinusoidal when the excursion is constrained. Instead, the motion should be stopped in certain intervals. In irregular waves the constrained solution is close to the unconstrained solution when the excursion is small. Moreover, the timings of the extrema and of the zero crossings agree fairly well. When the excursion is constrained, the mean output power is reduced compared to the unconstrained case, but the ratio between the output energy and the total energy passing through the machinery is increased. This means that the conversion efficiency of the machinery is less critical.
Performance of the Biplane Wells Turbine
Authors: Gato L. M. C. , Curran R.
Published: February 2008

The paper describes the experimental investigation of the biplane Wells turbine for use on a wave power plant. The performance of the biplane turbine was tested in unidirectional steady air flow by varying the model configurations using solidity, gap-to-chord ratio, and rotor stagger angle. It was found that the gap-to-chord ratio and stagger considerably influenced the performance of the biplane turbine due to the mutual interference between the rotor planes.
Strain Concentrations in Pipelines With Concrete
Coating
Authors: Ness O. B. , Verley R.
Published: February 2008

This paper concerns the strain distribution, and in particular strain concentration in field joints, for concrete-covered pipelines during laying. A semi-analytical model, full-scale tests to verify the model, and results of a parameter study are described. The model is used to establish nonlinear moment-curvature curves at a number of cross sections on the concrete-coated pipe and in the field joint (FJ). These are used to establish a strain concentration factor (SCF) for the FJ, or characteristics for a varying stiffness model of a pipe for direct use in lay analyses. Constant moment, four-point bending tests have been conducted on 16-in and 20-in dia, concrete-coated pipes as well as material tests on the pipe steel, corrosion coating and concrete. The behavior of the pipe, and in particular the SCF at the field joints, is investigated and compared to predictions using the semi-analytical model. The model is found to give a good prediction of the SCF and strain distribution along the pipe joint, for both the steel and the concrete, and is suitable for use in lay analyses for the overbend of S-mode lay vessels.
Sum-Frequency Diffraction Loads on Tension-Leg Platforms in
Bidirectional Waves
Authors: Vazquez J. H. , Williams A. N.
Published: February 2008

Second-order diffraction theory is utilized to compute the sum-frequency diffraction loads on a deepwater tension-leg platform (TLP) in bidirectional waves. The linear diffraction solution is obtained utilizing a Green function approach using higher-order boundary elements. The second-order hydrodynamic loads explicitly due to the second-order potential are computed using the indirect, assisting radiation potential method. An efficient numerical technique is presented to treat the free-surface integral which appears in the second-order load formulation. Numerical results are presented for a stationary ISSC TLP in water of infinite depth. It is found that wave directionality may have a significant influence on the second-order hydrodynamic loads on a TLP and that the assumption of unidirectional waves does not always lead to conservative estimates of the sum-frequency loading.
A Two-Way Nesting Procedure for the WAM Model: Application to the
Spanish Coast
Authors: Gomez Lahoz M. , Carretero Albiach J. C.
Published: February 2008

The performance of the standard one-way nesting procedure for a regional application of a third-generation wave model is investigated. It is found that this nesting procedure is not applicable when the resolution has to be enhanced drastically, unless intermediate grids are placed between the coarse and the fine grid areas. This solution, in turn, requires an excess of computing resources. A two-way nesting procedure is developed and implemented in the model. Advantages and disadvantages of both systems are discussed. The model output for a test case is compared with observed data and the results are discussed in the paper.
Constraint Effect—How to Link Between Structural Integrity Assessment and Fracture Toughness Evaluation
Authors: Toyoda M.
Published: February 2008

The difference in the degree of plastic constraint in the vicinity of a pre-existing crack brings about difficulty in the evaluation of fracture performance of weldments when using fracture toughness obtained by conventional fracture toughness test results. The constraint controlling factors can be divided into two main areas, geometrical and material factors. The effect of both factors on the stress/strain behavior in the vicinity of a crack tip is discussed systematically based on previous research and numerical analyses. It is clarified that the common fracture parameters such as J and CTOD do not always represent material constants because of the change of stress/strain behavior as a result of the difference in plastic constraint. The possibility of evaluation based on the local approach is discussed in order to link between structural integrity assessment and fracture toughness evaluation.
Fatigue of Ship Critical Structural Details
Authors: Xu T. , Bea R. G.
Published: February 2008

During the past six years, a joint government-industry-sponsored project titled Ship Structural Maintenance Project (SMP) has been conducted at the University of California at Berkeley. As part of the SMP, fatigue of ship critical structural details (CSD) has been studied. This paper summarizes developments in the stress range—number of cycles to failure (SN) analysis developed during the SMP. Nominal stress and hot spot stress procedures were employed to evaluate fatigue damage to ship CSD. A “cracked SN curve” approach was developed based on a hybrid SN-FM (fracture mechanics) methodology to evaluate the residual life of cracked ship CSD. The fatigue durability characteristics of repaired CSD was studied. Numerical examples are presented to illustrate these developments.
Field Verification of Linear and Nonlinear Hybrid Wave Models for
Offshore Tower Response Prediction
Authors: Couch A. T. , Conte J. P.
Published: February 2008

Accuracy of the prediction of the dynamic response of deepwater fixed offshore platforms to irregular sea waves depends very much on the theory used to determine wave kinematics. A common industry practice consists of using linear wave theory, which assumes infinitesimal wave steepness, in conjunction with empirical wave stretching techniques to provide a more realistic representation of near-surface water kinematics. The current velocity field is then added to the wave-induced fluid velocity field and the wave-and-current forces acting on the structure are computed via Morison’s equation. The first objective of this study is to compare the predicted responses of Cognac, a deepwater fixed platform, obtained from several popular empirical wave models with the response Cognac predicted based on the hybrid wave model. The latter is a recently developed higher-order, and therefore more accurate, wave model which satisfies, up to the second-order in wave steepness, the local mass conservation and the linear free surface boundary conditions at the instantaneous wave surface. The second objective of this study is to correlate the various analytical response predictions with the measured response of Cognac. Availability of a set of oceanographic and structural vibration data for Cognac provides a unique opportunity to evaluate the prediction ability of traditional analytical models used in designing such structures. The results of this study indicate that (i) the use of the hybrid wave model provides predicted platform response time histories which overall are in better agreement with the measured response than the predictions based on the various stretched linear wave models; and (ii) the Wheeler stretching technique produces platform response time histories which overall are more accurate than those obtained by using the other stretching schemes considered here.
Bifurcations of a Nonlinear Small-Body Ocean-Mooring System Excited by Finite-Amplitude Waves
Authors: Gottlieb O.
Published: February 2008

We investigate the response of a nonlinear small-body ocean-mooring system excited by finite-amplitude waves. The system is characterized by a coupled geometrically nonlinear restoring force defined by a single elastic tether. The nonlinear hydrodynamic exciting force includes both dissipative and convective terms that are not negligible in a finite wave amplitude environment. Stability of periodic motion is determined numerically and the bifurcation structure includes ultrasubharmonic and quasi-periodic response. The dissipation mechanism is found to control stability thresholds, whereas the convective nonlinearity governs the evolution to chaotic system response.
Reliability-Based Design of the Primary Structure of Oil Tankers
Authors: Casella G. , Dogliani M. , Guedes Soares C.
Published: February 2008

The present paper describes a reliability analysis carried out for two oil tanker-ships having comparable dimensions, but different design. The scope of the analysis was to derive indications on the value of the reliability index obtained for existing, typical and well-designed oil tankers, as well as to apply the tentative “rule checking” formulation developed within the CEC funded SHIPREL Project. The checking formula was adopted to redesign the midships section of one of the considered ships, upgrading her in order to meet the target failure probability considered in the rule development process. The resulting structure, in view of an upgrading of the steel grade in the central part of the deck, leads to a convenient reliability level. The results of the analysis clearly showed that a large scatter exists presently in the design safety levels of ships, even when the Classification Societies’ unified requirements are satisfied. A reliability-based approach for the calibration of the rules for the global strength of ships is therefore proposed, in order to assist designers and Classification Societies in the process of producing ships which are more optimized, with respect to ensured safety levels. Based on the work reported in the paper, the feasibility and usefulness of a reliability-based approach in the development of ship longitudinal strength requirements has been demonstrated.