bluuebunny/crossref_metadata_2025 huggingface dataset:
Unravelling migratory connections: the next level
Authors: Veen Thor
Published: August 2013

Migration is widespread among birds, and the strength of the link between the breeding and wintering grounds, migratory connectivity, influences many ecological and evolutionary processes. Despite its importance, migratory connectivity is poorly estimated for most species. Traditionally, visual observations and bird ringing have been used to monitor migration, but these methods require more effort for relatively little return. Genetic markers and stable isotope signatures have increasingly been used to study connectivity. Each approach has its distinct strengths and weaknesses, and as is often the case, a combination may yield the most insight. In this issue of Molecular Ecology, Rundel and colleagues (2013) present a novel Bayesian statistical framework in which genetics and stable isotope data can be combined to improve the assignment of individuals to different winter or breeding regions. The development of such new statistical methods combined with the increasing number and ease of access of isotopic and genetic data sets will greatly enhance our understanding of migratory connectivity. Add to this the developments of miniature devices to track movements of individuals, and the field is destined to make major progression in the decades to come.
COMBINING SOCIAL CAPITAL AND TECHNOLOGY FOR DROUGHT RESILIENCE IN AGRICULTURE
Authors: RANJAN RAM
Published: August 2013

In water‐scarce regions of the world, water‐saving technology adoption augments farm productivity. But so does social capital. In this paper, the issue of ensuring livelihood for farmers through the combined use of social capital and water‐saving technology is modeled in the context of repeated droughts. The model presented here derives optimal resource conservation and accumulation strategies when the farmer must ensure minimum consumption during a set of repeated drought events in the future. Findings indicate that the path to drought resilience presents a complex trade‐off between accumulating one form of capital over another and is influenced by farmers’ wealth and water endowments, level of risk associated with the repeated droughts and the duration of the repeated drought event that the farmer plans to survive. A higher risk of repeated droughts leads to an increase in groundwater conservation efforts but delays technology adoption. Lower water endowments may also delay adoption and reduce social capital, however, a lower social capital or a slow rate of its growth is not a hindrance to adopting water‐saving technology earlier. Finally, social capital evolves to higher levels when farmer is simultaneously faced with a higher level of risks and a longer span of drought events.
Constitutive expression of cell wall invertase genes increases grain yield and starch content in maize
Authors: Li Bei , Liu Hua , Zhang Yue , Kang Tao , Zhang Li , Tong Jianhua , Xiao Langtao , Zhang Hongxia
Published: August 2013

Grain size, number and starch content are important determinants of grain yield and quality. One of the most important biological processes that determine these components is the carbon partitioning during the early grain filling, which requires the function of cell wall invertase. Here, we showed the constitutive expression of cell wall invertase–encoding gene from Arabidopsis, rice (Oryza sativa) or maize (Zea mays), driven by the cauliflower mosaic virus (CaMV) 35S promoter, all increased cell wall invertase activities in different tissues and organs, including leaves and developing seeds, and substantially improved grain yield up to 145.3% in transgenic maize plants as compared to the wild‐type plants, an effect that was reproduced in our 2‐year field trials at different locations. The dramatically increased grain yield is due to the enlarged ears with both enhanced grain size and grain number. Constitutive expression of the invertase‐encoding gene also increased total starch content up to 20% in the transgenic kernels. Our results suggest that cell wall invertase gene can be genetically engineered to improve both grain yield and grain quality in crop plants.
The Institutional Collective Action Framework
Authors: Feiock Richard C.
Published: August 2013

Institutional collective action (ICA) dilemmas arise from the division or partitioning of authority in which decisions by one government in one or more specific functional area impacts other governments and/or other functions. The focus on externalities of choice in fragmented systems integrates multiple research traditions into a conceptual system to understand and investigate collective dilemmas ubiquitous in contemporary governance arrangements. The mechanisms for mitigatingICAdilemmas are classified according to their scope and enforcement. Incentives to participate in a mechanism are hypothesized to favor mechanisms that provide the greatest gain for the least cost under different conditions of collaboration risk as determined by the nature of the underlyingICAproblem, the compositions of affected jurisdictions, and institutional contexts. After reviewing empirical applications of the framework, an agenda to advance the theoretical and empirical development of theICAapproach is advanced.
An Angel on the Wind: How Heroic Policy Narratives Shape Policy Realities
Authors: Shanahan Elizabeth A. , Jones Michael D. , McBeth Mark K. , Lane Ross R.
Published: August 2013

Narrative Policy Framework (NPF) is a new and maturing theory of the policy process that takes a systematic, scientific approach to understanding the social construction of policy realities. As such, NPF serves as a bridge between postpositivists, who assert that public policymaking is contextualized through narratives and social construction, and positivists, who contend that legitimacy is grounded in falsifiable claims. The central questions of NPF are: What is the empirical role of policy narratives in the policy process and do policy narratives influence policy outcomes? First, the contributions of NPF scholarship at three levels of analysis—micro, meso, and macro—are examined. Next, necessary conditions of a policy narrative are specified, accompanied by detailed discussion of the narrative components: narrative elements, narrative strategies, and policy beliefs. Finally, an empirical illustration of NPF—a case study of Cape Wind's proposal to install wind turbines off Nantucket—is presented. Although intercoalitional differences have long been studied in the NPF scholarship, this is the first study to examine intracoalitional cohesion or the extent to which a coalition tells the same story across narrative elements, narrative strategies, and policy beliefs. NPF is a new approach to the study of the policy process that offers empirical pathways to better speculating the role of narrative in the policy process.
Robustness of Social‐Ecological Systems: Implications for Public Policy
Authors: Anderies John M. , Janssen Marco A.
Published: August 2013

We conceptualize social‐ecological systems (SESs) as complex adaptive systems where public policy affects and is affected by the biophysical system in which it is embedded. The study of robustness ofSESscombines insights from various disciplines including economics, political science, ecology, and engineering. In this paper we present an approach that can be used to explore the implications for public policy when viewed as a component of a complex adaptive system. Our approach leverages theInstitutionalAnalysis andDevelopment framework to provide a platform for interdisciplinary research that focuses on system‐wide outcomes of the policy process beyond just policy change. The main message is that building robustness can create new vulnerabilities. Fail‐free policies cannot be developed, and instead of a focus on the “right” policy, we need to think about policy processes that stimulate experimentation, adaptation, and learning.
Governing Institutional Complexity: The Ecology of Games Framework
Authors: Lubell Mark
Published: August 2013

This paper provides an overview of our adaptation ofNortonLong's concept of the “ecology of games” into a theoretical framework for analyzing institutional complexity. I discuss the basic concepts of the framework, discuss hypotheses related to fundamental questions in governance and policy, and outline some basic analytical approaches. The conclusion assesses the future prospects of the ecology of games framework, including future research needs for theoretical and empirical development.
The Adoption and Abandonment of Council‐Manager Government
Authors: Choi Cheon Geun , Feiock Richard C. , Bae Jungah
Published: August 2013

What accounts for patterns of city adoption and abandonment of council‐manager government? Despite dozens of empirical studies, we lack a systematic understanding of these forces over time because previous work has relied on cross‐sectional designs or analysis of change over short periods. This article begins to fill this lacuna by constructing a historical data set spanning 75 years for the 191 largest cities with either mayor‐council or council‐manager governments in 1930. Event history analysis is applied to isolate adoption and abandonment trends and to provide new evidence revealing the forces that have shaped the trajectory of institutional change in U.S. cities. This analysis reveals that social context factors—in particular, economic conditions—generate both adoptions and abandonments.
A Systematic Review of Studies Performing the Hypo‐Osmotic Swelling Test to Evaluate the Quality of Canine Spermatozoa
Authors: Karger S , Arlt S , Haimerl P , Heuwieser W
Published: August 2013

Contents

The hypo‐osmotic swelling test (HOS test) is a simple and inexpensive test to evaluate the functional integrity of sperm cell membranes. According to the existing literature, its simple applicability has turned it into a valuable additional parameter to standard canine semen analysis. In the recent years, much research has been conducted in this field. The aim of this systematic review was to evaluate the quality of published literature in canine reproduction concerning the HOS test. Using two distinguished databases, 38 articles were detected and analysed subsequently according to various aspects, for example study design, population, semen sampling and implementation concerning the HOS test. Although there are numerous articles available, the diagnostic value of the HOS test remains ambiguous. Until now, neither a recognized test protocol nor reliable reference values have been defined. Most of the trials evaluated show serious methodological flaws and therefore do not permit drawing reliable conclusions. According to our results, approximately half of the studies (n = 20) included a sample size of five or less animals. None of the studies examined the inter‐ or intraobserver agreement for the HOS test. Further research is warranted including appropriate statistical methods and a sufficient number of animals to establish a standardized test protocol as well as reliable reference values. Most importantly, it is required to clarify a correlation between the HOS test and the fertilizing capacity to determine the diagnostic value of the HOS test.
Fitting Multilevel Multivariate Models with Missing Data in Responses and Covariates that May Include Interactions and Non-Linear Terms
Authors: Goldstein Harvey , Carpenter James R. , Browne William J.
Published: August 2013

The paper extends existing models for multilevel multivariate data with mixed response types to handle quite general types and patterns of missing data values in a wide range of multilevel generalized linear models. It proposes an efficient Bayesian modelling approach that allows missing values in covariates, including models where there are interactions or other functions of covariates such as polynomials. The procedure can also be used to produce multiply imputed complete data sets. A simulation study is presented as well as the analysis of a longitudinal data set. The paper also shows how existing multiprocess models for handling endogeneity can be extended by the framework proposed.
Re-Engaging with Survey Non-Respondents: Evidence from Three Household Panels
Authors: Watson Nicole , Wooden Mark
Published: August 2013

Previous research into the correlates and determinants of non-response in longitudinal surveys has focused exclusively on why it is that respondents at one survey wave choose not to participate at future waves. This is very understandable if non-response is always an absorbing state, but in many longitudinal surveys, and certainly most household panels, this is not so. Indeed, in these surveys it is normal practice to attempt to make contact with many non-respondents at the next wave. This study differs from previous research by examining re-engagement with previous wave non-respondents. Drawing on data from three national household panels it is found that the re-engagement decision is indeed distinctly different from the decision about continued participation. Further, these differences have clear implications for the way that panel surveys should be administered given the desire to enhance overall response rates.
Optimal Bayesian Sequential Sampling Rules for the Economic Evaluation of Health Technologies
Authors: Pertile Paolo , Forster Martin , Torre Davide La
Published: August 2013

We present a Bayes sequential economic evaluation model for health technologies in which an investigator has flexibility over the timing of a decision to stop carrying out research and to conclude that one technology is preferred to another on cost-effectiveness grounds. We implement the model by using an evaluation of the treatment of bacterial sinusitis and derive approximations of the optimal stopping rule as a function of accumulated sample size. We compare the performance of the model with existing frequentist and Bayes sequential designs and investigate the sensitivity of the stopping rule to changes in the parameters of the model. Our results suggest that accounting for the dynamic nature of experimentation, together with its economic parameters, should lead to greater efficiency in resource allocation within healthcare systems.
A pragmatic approach to embedding patient blood management in a tertiary hospital
Authors: Leahy Michael F. , Roberts Heather , Mukhtar S. Aqif , Farmer Shannon , Tovey Julie , Jewlachow Val , Dixon Tracy , Lau Peter , Ward Michael , Vodanovich Matthew , Trentino Kevin , Kruger Paul C. , Gallagher Trudi , Koay Audrey , Hofmann Axel , Semmens James B. , Towler Simon ,   Western Australian Patient Blood Management Program
Published: August 2013

Background

We describe the implementation and impact of a patient blood management program (PBMP) in an Australian teaching hospital.

Study Design and Methods

A PBMP was introduced at a single tertiary care hospital in 2009 as a pilot for the Western Australian Health Department statewide PBMP. The first 3 years of interventions aimed to make effective use of preoperative clinics, manage perioperative anemia, improve perioperative hemostasis, reduce blood sample volumes, and implement restrictive transfusion triggers and a single‐unit transfusion policy.

Results

Between 2008 and 2011, admissions to Fremantle Hospital and Health Services increased by 22%. Using 2008 as a reference year, the mean number of red blood cell (RBC) units per admission declined 26% by 2011. Use of fresh‐frozen plasma and platelets showed 38 and 16% declines, respectively. Cryoprecipitate increased 7% over the 4‐year period. For elective admissions between 2008 and 2011, the leading decline in RBC transfusion rate was seen in cardiothoracic surgery (27.5% to 12.8%). The proportion of single RBC unit use increased from 13% to 28% (p < 0.001), and the proportion of double units decreased from 48% to 37% (p < 0.001).

Conclusion

This is the first tertiary hospital in Australia to establish a multidisciplinary multimodal PBMP. Interventions across disciplines resulted in decreased use of RBC units especially in orthopedic and cardiothoracic surgery. Continuing education and feedback to specialties will maintain the program, improve patient outcomes, and decrease the transfusion rate.
The effect of salt stress on Arabidopsis thaliana and Phelipanche ramosa interaction
Authors: Demirbas S , Vlachonasios K E , Acar O , Kaldis A
Published: August 2013

Salinity and Orobanche or Phelipanche spp. infection are important crop stress factors in agricultural areas. In this study, we investigated the effect of salt stress on Phelipanche ramosa seed germination and its attachment onto Arabidopsis thaliana roots. We also evaluated the effect of both stresses on the expression of genes regulated by abiotic and biotic stresses. According to our results, high concentration of NaCl delayed P. ramosa seed germination in the presence of a strigolactone analogue (GR24). A similar pattern was observed in the presence of A. thaliana plants. Furthermore, we found that salt‐treated A. thaliana seedlings were more sensitive to P. ramosa attachment compared with the untreated plants, indicating that there was a positive correlation between salt sensitivity and the ability of P. ramosa to infect A. thaliana plants. At the molecular level, a synergystic effect of both salt and P. ramosa stresses was observed on the cold‐regulated (COR) gene expression profile of treated A. thaliana seedlings. Our data clarify the interaction between parasitic plants and their hosts under abiotic stress conditions.
Retracted: Risks of Avian Influenza (H5) in Duck Farms in the Ayeyarwaddy Delta Region, Myanmar
Authors: Win H. H. , Mon C. C. Su , Aung K. M. , Oo K. N. , Sunn K. , Htun T. , Tiensin T. , Maclean M. , Kalpravidh W. , Amonsin A.
Published: August 2013

The Ayeyarwaddy delta region in the south‐west of Myanmar is the main agricultural and rice‐growing area. The region has a high density of duck and backyard chicken populations with low biosecurity. The objective of this study was to analyse risk factors for avian influenza (H5) in the Ayeyarwaddy delta region, Myanmar. A case–control risk factor study was conducted from April to June 2010 by individual interviews including risk factor questionnaires given to duck farmers (n = 50) in five townships in the Ayeyarwaddy delta region, Myanmar. Risk factor analyses were conducted using univariate analysis and multivariate logistic regression model with backward stepwise (wald) method. The results showed significant risk factors for AI (H5) sero‐positivity in ducks were wooden egg box containers (OR = 52.7, 95% CI = 2.34–1188, P = 0.013) and water sourced from wetlands (OR = 30.7, 95% CI = 1.96–481.6, P = 0.015). Conversely, the cleaning of reusable egg containers was determined as a protective factor (OR = 0.03, 95% CI = 0.00–0.42, P = 0.01). In conclusion, this study identified risk factors for AI (H5) in duck farms and the importance of avian influenza prevention and control.
Excimer Laser Micromachining Using Binary Mask Projection for Large Area Patterning With Single Micrometer Features
Authors: Dayal Govind , Nadeem Akhtar Syed , Ramakrishna S. Anantha , Ramkumar J.
Published: August 2013

Excimer laser micromachining using binary mask projection has been investigated for rapid patterning of single micrometer features over large areas of various substrates. Simple limit for depth of focus that determines the depth to width aspect ratios is given and verified for different materials. Binary mask projection technique is found to conformally reproduce the mask features from the millimetre to the micrometer scale under proper focusing conditions. Large arrays of 1 μm and 15 μm holes on Kapton are made with high resolution and uniform periodicity. Material removal rate (MRR) for the laser machining of these holes are examined and the machining efficiency for these are found to have different dependence on the fluence. A saturation of hole-depth with increasing number of pulses is obtained.
Influence of Clearances and Thermal Effects on the Dynamic Behavior of Gear-Hydrodynamic Journal Bearing Systems
Authors: Fargère R. , Velex P.
Published: August 2013

A global model of mechanical transmissions is introduced which deals with most of the possible interactions between gears, shafts, and hydrodynamic journal bearings. A specific element for wide-faced gears with nonlinear time-varying mesh stiffness and tooth shape deviations is combined with shaft finite elements, whereas the bearing contributions are introduced based on the direct solution of Reynolds' equation. Because of the large bearing clearances, particular attention has been paid to the definition of the degrees-of-freedom and their datum. Solutions are derived by combining a time step integration scheme, a Newton–Raphson method, and a normal contact algorithm in such a way that the contact conditions in the bearings and on the gear teeth are simultaneously dealt with. A series of comparisons with the experimental results obtained on a test rig are given which prove that the proposed model is sound. Finally, a number of results are presented which show that parameters often discarded in global models such as the location of the oil inlet area, the oil temperature in the bearings, the clearance/elastic couplings interactions, etc. can be influential on static and dynamic tooth loading.
Development of Tightening Specification for Post Yield Angle Control Tightening Strategy
Authors: Housari Basil , Alkelani Ali , Yocum Grant
Published: August 2013

There are several tightening strategies used for bolted joints in the industry, such as torque control, angle control, yield control, and stretch control. The most common strategy is torque control due to the ease of use, simple tooling, and availability of tabulated torque and average corresponding clamp force values for common fastener sizes and classes.

For some special applications, angle controlled tightening strategy is used where maximum fastener strength utilization and more consistent clamp load are required. Unlike torque control tightening strategy, angle control tightening is more complicated and requires more advanced tooling. In addition, there are no tabulated values that provide the angle control tightening parameters for a specific fastener material and size. The tightening specification is rather developed on a case by case basis.

This paper provides a method for developing tightening specification for angle control tightening. It also provides a method to calculate the maximum expected final torque which can be used to select the proper tool size. The maximum expected final torques are tabulated in the paper for most commonly used fasteners. Finally, the paper provides a criterion for detecting parts and/or joint quality issues when angle control tightening is used.
Qualification of Nuclear Equipment Against Hydrogen Detonation Using Explicit and Implicit Finite Element Methods
Authors: Breach Michael R.
Published: August 2013

Conservative static load methodologies have been devised to design equipment against postulated hydrogen detonation. However, these methodologies do not address the dynamic response of the system. Moreover, dynamic response methodologies can be used in lieu of static analyses, if the moving pressure profile due to detonation corresponds to the Chapman-Jouguet pressure and velocity. This moving pressure profile can be applied to a finite element model (FEM) in several ways. One approach is to develop the moving pressure profile by combining the Chapman-Jouguet model of an ideal detonation with the Taylor-Zeldovich [6] similarity solution to obtain an analytic solution to the flow field behind a steadily propagating detonation in a tube. This approach is robust and forgoes modeling the complex physics associated with transitioning from deflagration to detonation and the specific chemical kinetics associated with the gaseous species involved. In another approach, a Lagrange-Arbitrary Lagrange Eulerian (ALE) Model can be used. This type of modeling uses both implicit and explicit constitutive equations that are suitable for simulating fluid structure interaction (FSI) and the disintegration of materials. The method can be exemplified as state variables from the motion of a Lagrange mesh being advected to that of the background ALE mesh. Parts that flow in the ALE mesh interact with the Lagrange structure. However, direct FSI is through specification of the ALE FSI projection card. The ensuing FSI is solved and the state variables of the Lagrange mesh are adjusted for the next iteration. In this scheme the chemical kinetics associated with the detonation of specific mixtures of gaseous species can be considered.
Standard Procedure to Test 2-1/4Cr-1Mo-V Saw Filler Material Reheat Cracking Susceptibility
Authors: Pillot Sylvain , Chauvy Cédric
Published: August 2013

In late 2007 and early 2008, 2 1/4Cr1MoV heavy reactors fabrication has undergone some weld metal reheat cracking issues that became a serious situation as roughly 25 large vessels were affected. Strong efforts from the whole production chain were put in trying to isolate the root cause of the crack appearance and solve this particular matter. Many investigations were conducted by independent laboratories in the first months of 2008.

In particular, a hot tensile Gleeble® test indicated a decrease in ductility in the critical temperature range of Intermediate Stress Relieving (ISR) treatment (650–680 °C) of the affected welding consumables compared to those that did not cause cracking. This mechanical test was successfully combined with high sensitivity chemical analyses (Glow Discharge Mass Spectroscopy – GDMS) to find the root cause of such batch-to-batch differences in ductility. A chemical composition factor, called Kfactor, was defined and statistically linked to the Gleeble® test in July 2008. Altogether, it permitted to solve the issue.

Even if reliable and well documented, the Gleeble® test was originally developed to understand the root cause of the cracking. But due to lack of other solutions, its role was largely extended and it became a kind of standard test to qualify 2 1/4Cr1MoV SAW filler material. It was decided to optimize this test, keeping its general philosophy but making it feasible by a larger number of laboratories. In order to do that, a one-year Joint Industrial Program (JIP) was proposed to the community, accepted, sponsored and launched at the beginning of 2010. The target was to create a new test protocol able to discriminate batches of filler material.

The objective of this paper is to summarize the investigations performed and the optimization of the original Gleeble® test during the project that led to the definition of a new hot tensile mechanical test successfully benchmarked by independent laboratories and now balloted to be incorporated in American Petroleum Institute (API) recommended practice API RP 934-A as a new appendix.
Effects of Base Uplifting on the Seismic Response of Unanchored Liquid Storage Tanks
Authors: Vathi Maria , Karamanos Spyros A.
Published: August 2013

Unanchored liquid storage tanks under strong earthquake loading tend to uplift. In the present study, the effects of base uplifting on the seismic response of unanchored tanks are presented with emphasis on elephant’s foot buckling, base plate strength and shell-to-base connection capacity. Towards this purpose, base uplifting mechanics is analyzed through a detailed simulation of the tank using non-linear finite elements, and a static pushover analysis is conducted that considers the hydrodynamic pressure distribution due to seismic loading on the tank wall and the base plate. The uplifting provisions from EN 1998-4 and API 650 Appendix E standards are briefly described. Numerical results for a typical 27.8-meter-diameter steel tank are compared with the above design provisions.
Design, Simulation and Testing of Overpack Encapsulation Vessels
Authors: Towse A. , Dodds J.
Published: August 2013

The paper presents an overpack designed to contain nuclear product cans which may become pressurised or contaminated. The overpack provides a protective barrier to an inner product can, and due to the possibility of leakage of gas from the contents, the overpack must also function as a pressure vessel. Furthermore, the overpack is required to provide physical protection to the inner can and proof of containment was therefore necessary under a number of different impact scenarios, both pre-pressurised and also with the simulation of pressurisation at the moment of impact. Additionally, the inner product can was to be maintained in a central position during the deceleration at impact.

This paper focuses on the analytical design and substantiation of the impact of the system which was performed using an explicit dynamic solver for a number of impact orientations. The design of the overpack to satisfy the relevant pressure vessel Code are not discussed in detail. The potential failure modes of the overpack during impact were assessed and design improvements made over a number of iterations. Following completion of the design and simulation phase, prototypes were built and tested to verify the engineering design and analysis. The testing showed that simulation driven design in conjunction with a pressure vessel design by rule approach was successful in creating a solution for the product can encapsulation. A comparison between the analytical simulation and high-speed video footage of the testing was also made.
Crack-Tip Constraint and Fracture Toughness of an Inner-Surface Crack Under Thermal Shock
Authors: Meshii Toshiyuki
Published: August 2013

This paper considered the crack-tip constraint and fracture toughness of a semi-elliptical surface crack inside a hollow cylinder that experiences loss of coolant accident (LOCA). The magnitude of the crack-tip constraint was measured by evaluating the in and out of plane T-stress; i.e., T11. Results showed that T11 was negative at the deepest point, and that conservatism can be expected in using the fracture toughness obtained from standard fracture toughness test specimens. Finally, this conservatism was estimated quantitatively by applying a framework to correlate test specimen crack depth effect on fracture toughness with T-stresses.
NESC VII: A European Project for Application of WPS in RPV Assessment Including Biaxial Loading
Authors: Moinereau Dominique , Chapuliot Stéphane , Marie Stéphane , Gilles Philippe
Published: August 2013

The Reactor Pressure Vessel (RPV) is an essential component liable to limit the lifetime duration of pressurized water reactor (PWR) plants. The assessment of defects in RPV subjected to PTS (pressurized thermal shock) transients made at an European level does not necessarily take into account the beneficial effect of load history (warm pre-stress WPS) on the resistance of RPV material regarding the risk of brittle failure. Numerous experimental, analytical and numerical results are available, which confirm the beneficial effect of warm pre-stress on RPV steels, with an effective increase of the material resistance regarding the risk of brittle failure.

NESC VII (Network for Evaluating Steel Components), a new project dealing with WPS, has been launched in 2008 (in link with the European Network of Excellence NULIFE) with the participation of international organizations (involving R&D and Technical support, Utilities, Manufacturers, Safety & Regularory organizations). Based on experimental, analytical and numerical tasks, the project is focussed on topics generally non covered by past experience on WPS : biaxiality of loading on small and large-scale specimens, influence and effect of irradiation, applicability to intergranular fracture, modeling (including analytical and numerical models) … Among these tasks, new original WPS experiments are conducted on small, medium and large scale specimens to study the influence of biaxial loading on WPS effect, using a fully representative RPV steel (18MND5 steel similar to A533B steel).

A full description of NESC VII project, including the present status, is presented in this paper.
Alignment of Stress Intensification and Flexibility Factors for the B31 Book Sections
Authors: Creates David H. , Côté Daniel P.
Published: August 2013

It has been recognized for some time that the current B31 Codes are inconsistent in the values they use for stress intensification factors for piping design. ASME has undertaken a project to align the Stress Intensification and Flexibility Factors in the various B31 book sections via the ASME ST-LLC 07-02 Project which is being managed by the Paulin Research Group. The intent is neither to decrease nor to increase conservatism but rather to improve the accuracy of piping analysis as it attempts to model the real world. The supporting research is based on literature reviews, recent testing (within the last 25 years), new testing, advanced analysis techniques and interviews with industry and research personnel. The results are intended to be eventually included in a non-mandatory appendix to ASME B31J.

In this paper the scope of the changes and visual representation of some of the current information from the Project is provided to acquaint the piping analysts in general terms. Since flexibility changes are more fundamental to piping analysis, some discussion is provided as to how to incorporate them and some of the possible effects on piping design.
Risk-Based Operations Assessment of a Multilayered Vessel Under Cyclic Loading Conditions
Authors: Zhao Mingxin , Parkinson Richard
Published: August 2013

Operational risks have been evaluated for a multilayered vessel through the fitness-for-service (FFS) assessment. The vessel has been in service for more than four decades and is subjected to cyclic mechanical and thermal loads during normal operations. Leakage has been found over the years by inspections, which led to safety concerns for continued operation. FFS assessment was used to evaluate the condition of the vessel to determine if the vessel was fit for continued operation and the associated risks for a catastrophic type failure or burst of all layers of the vessel. Finite element analysis and fatigue evaluation, with associated partial probability, were conducted for the assessment per API 579. The operational risks were evaluated on the combined basis of FFS assessment results, failure modes, and field inspection findings. It was concluded that, despite of the problems found during inspections, risks for the catastrophic type failure of the multilayered vessel are very low and continued operation with appropriate monitoring and maintenance is recommended.
Comparison of Analysis Methods for Transient Forces
Authors: Kim Byung Jo
Published: August 2013

Fluid transients have been a major topic of research due to its possible fatal consequence. For example, the sudden closure of valves or operation of pumps can create pressure waves. High pressure pulses propagate through pipelines and generate huge unbalanced forces, known as waterhammer. A lack of consideration of fluid transient forces can even lead to pipe ruptures. The increasing interest in dynamic safety demands the necessity of deep considerations for fluid transients. An assessment process is required that includes the internal unbalanced forces and the dynamic system response in the pipework. This paper presents the comparison between a simplified method and time history analysis, which are analytical methods for transient forces. A simplified method is manual calculation based on the conservation of mass and momentum equations, and the impact loading theory. Time history analysis is computer simulation for transient analysis and piping structural analysis. The paper illustrates the deviations of result which contain waterhammer force, displacements and resultant stresses for the piping system by applying both analytical methods.
Analysis of Venting of a Resin Slurry
Authors: Laurinat James E. , Hensel Steve J.
Published: August 2013

A resin slurry venting analysis was conducted to address safety issues associated with overpressurization of ion exchange columns used in the Purex process at the Savannah River Site (SRS). If flow to these columns were inadvertently interrupted, an exothermic runaway reaction could occur between the ion exchange resin and the nitric acid used in the feed stream. The nitric acid-resin reaction generates significant quantities of noncondensable gases, which would pressurize the column. To prevent the column from rupturing during such events, rupture disks are installed on the column vent lines.

The venting analysis models accelerating rate calorimeter (ARC) tests and data from tests that were performed in a vented test vessel with a rupture disk. The tests showed that the pressure inside the test vessel continued to increase after the rupture disk opened, though at a slower rate than prior to the rupture. Calculated maximum discharge rates for the resin venting tests exceeded the measured rates of gas generation, so the vent size was sufficient to relieve the pressure in the test vessel if the vent flow rate was constant. The increase in the vessel pressure is modeled as a transient phenomenon associated with expansion of the resin slurry/gas mixture upon rupture of the disk. It is postulated that the maximum pressure at the end of this expansion is limited by energy minimization to approximately 1.5 times the rupture disk burst pressure. The magnitude of this pressure increase is consistent with the measured pressure transients. The results of this analysis demonstrate the need to allow for a margin between the design pressure and the rupture disk burst pressure in similar applications.
Study on the Effect of Axial Flaw Length on Limit Bending Load of Wall Thinned Straight Pipes by Large Strain Finite Element Analyses
Authors: Ito Yoshiaki , Meshii Toshiyuki
Published: August 2013

In this paper, we examined the effect of axial flaw length δz (Fig. 1) on limit bending load Mc of wall-thinned straight pipes by large strain finite element analysis (FEA). In the past, Han et al. [1] studied the effect of axial flaw length δz on limit bending load Mc of wall-thinned straight pipes by limit-load analyses. Han et al.’s [1] results indicated the trend which the Mc monotonically decreased with the increase in δz. If this finding is accepted, the Mc for a crack is larger than that for a non-planar flaw (wall thinning), and as a result, using the crack model for a non-planar flaw would be non-conservative. In contrast, Tsuji and Meshii [2] demonstrated by their tests that the Mc showed the maximum for a small δz. They estimated that this inconsistency was mainly due to the fact that Han et al. [1] and other researchers always assumed the fracture mode as the collapse, but the cracking was observed in Tsuji’s [2] experiment for small δz.

Therefore in this work, we examined the effect of axial flaw length δz on limit bending load Mc of wall-thinned straight pipes by large strain FEA and applying Domain Collapse Criterion (DCC) [3] (which can predict fracture mode and the Mc accurately) to FEA results. In concrete, we attempted to reproduce Tsuji and Meshii’s experimental results [2] by FEA that the Mc showed the maximum for a small δz. In addition, we tried to understand the reason why limit-load analysis failed to predict this tendency.

The results showed that large strain FEA with DCC [3] reproduced the Mc-δz relationship observed in the experiments. The inconsistency of Mc-δz relationship between Tsuji and Meshii’s experiment [2] and Han et al.’s limit-load analysis [1] and others analysis was estimated on due to the limit-load analysis failed to predict the failure for the flaw with a small δz, in which the failure mode is governed by the local stress (cracking) and not by the plastic deformation in a large volume (collapse).
Residual Stress Evaluation of Hydraulically Expanded Tube-to-Tubesheet Joint
Authors: Otani Yoshihiro , Sakakibara Yohei , Tsunori Mitsuyoshi , Ohtake Yasuhiro , Shutto Nobuyuki
Published: August 2013

An evaluation of a residual stress of hydraulically expanded tube-to-tubesheet joints is important in strength evaluation of certain devices such as heat exchangers, steam generators, etc. In this study, we carried out the analytical and experimental investigation in order to develop a model for the prediction of residual stress.

The experiment of the tube expansion was carried out with nickel-base alloy tubes and a low-alloy steel tubesheet. The residual stress of each tube was evaluated by sectioning method where the released strain was measured after each tube was cut into thin strips. As a result, the tensile residual stress was detected at the transition zone between the expanded zone and the non-expanded zone on each tube. A finite element analysis was also performed with a three dimensional model for the tube-to-tubesheet joint. The accuracy of the analysis, however, needed to be improved. Therefore FEM models were developed where the following factors were considered: (i) work-hardened layer on the tube before expansion, (ii) friction between the inner surface of the tube and the mandrel used for hydraulic expansion. The accuracy improvement of the analysis was confirmed through the comparison of the numerical and experimental results.
Simulation of Ductile Crack Propagation in Pipeline Steels Using Cohesive Zone Modeling
Authors: Dunbar Andrew , Wang Xin , Tyson Bill (W. R. ) , Xu Su
Published: August 2013

This paper presents recent results of numerical studies on stable crack extension of high toughness steels typical of those in modern gas pipelines using cohesive zone modeling. Two sets of materials are modeled. The first material set models a typical structural steel, with variable toughness described by four traction-separation (TS) laws. The second set models an X70 pipe steel, with three different TS laws. For each TS law, there are three defining parameters: the maximum cohesive strength, the final separation and the work of separation. The specimens analyzed include a crack in an infinite plate (small-scale yielding, SSY) and a standard drop-weight tear test (DWTT). Fracture propagation characteristics and values of crack-tip opening angle (CTOA) are obtained from these two types of specimens. It is shown that cohesive zone models can be successfully used to simulate ductile crack propagation and to numerically measure CTOAs. The ductile crack propagation characteristics and CTOAs obtained from SSY and DWTT specimens are compared for each set of steels. In addition, the CTOA results from numerical cohesive zone modeling of DWTT specimens of X70 steel are compared with those from laboratory tests.
Bench-KJ: Benchmark on Analytical Calculation of Fracture Mechanics Parameters KI and J for Cracked Piping Components
Authors: Marie S. , Faidy C.
Published: August 2013

For many design and ageing considerations fracture mechanics is needed to evaluate cracked components. The major parameters used are K and J. For that, the different codes (RSE-M appendix 5, RCC-MRx appendix A16, R6 rule, ASME B&PV Code Section XI, API, VERLIFE, Russian Code…) propose compendia of stress intensity factors, and for some of them compendia of limit loads for usual situations, in terms of component geometry, type of defect and loading conditions.

The benchmark bench-KJ, proposed in the frame of the OECD/IAGE Group, aims to compare these different estimation schemes by comparison to reference analyses done by Finite Element Method, for representative cases (pipes and elbows, mechanical or/and thermal loadings, different type and size of cracks). The objective is to have a global comparison of the procedures but also of all independent elements as stress intensity factor or reference stress.

The benchmark will cover simple cases with basic mechanical loads like pressure and bending up to complex load combinations and complex geometries (cylinders and elbows) including cladding or welds: these cases are classified into 6 tasks.

Twenty-eigth partners are involved in this benchmark. This paper gives a global overview of the different tasks of the benchmark and presents the analysis of the results for the first task, devoted on the elastic stress intensity factor calculation (task 1).
Specimen Orientation and Constraint Effects on the Creep Crack Growth Behaviour of 316H Stainless Steel
Authors: Mehmanparast A. , Davies C. M. , Dean D. W. , Nikbin K. M.
Published: August 2013

Pre-compression (PC) is found to have strong effects on the tensile, uniaxial creep rupture and creep crack growth (CCG) behaviour of type 316H stainless steel at 550 °C. In this work, blocks of 316H steel have been pre-compressed to 8% plastic strain at room temperature and compact tension, C(T), specimens are extracted from the pre-strained blocks with loading directions parallel and normal to the PC axis. The influence of specimen orientation and thickness on the CCG behaviour of the PC material is examined. The results are compared to short term and long term CCG behaviour of 316H steel at the same temperature. Higher CCG rates and shorter CCI times have been found in PC material with a loading direction normal to the PC axis compared to that parallel to the PC axis. These observations are discussed with respect to the microstructural effects.
Modified Fatigue Stress at Shell-to-Bottom Joint of Steel Tanks on Ring Walls
Authors: Sathyanarayanan Sridhar , Adluri Seshu M. R.
Published: August 2013

Shell-to-bottom joint of hydrocarbon storage tanks is a critical failure location which needs careful evaluation especially in the case of elevated temperature tanks. The fill/draw down cycle of the stored liquid causes low cycle fatigue near this joint and hence a fatigue evaluation is recommended. The peak alternating stress at this location, used to enter the fatigue curves is currently determined using a pseudo elastic stress that represents strain range due to inelastic deformations. For this, API 650 employs beam on elastic foundation theory. This theory is being used for tanks resting fully on earthen foundation as well as those on concrete ring wall. This paper studies the validity of using this theory for tanks with concrete ring wall foundation which are much more rigid compared to earthen foundations. Some of the difficulties in the current practice are highlighted. Alternatives to using the current model are derived to determine the stresses in such tanks. The results are validated using finite element analysis.
Development of Test on Sent Specimens to Study Geometry Effects
Authors: Le Delliou Patrick , El-Gharib Joumana
Published: August 2013

The accurate prediction of ductile fracture behaviour plays an important role in structural integrity assessments of critical engineering structures under fully plastic regime, including nuclear reactors and piping systems. Many structural steels and aluminium alloys generally exhibit significant increases in fracture toughness, characterized by the J-integral, over the first few mm of stable crack extension (Δa), often accompanied by large increases in background plastic deformation. Conventional testing programs to measure crack growth resistance (J-Δa) curves employ three-point bend, SEN(B), or compact, CT. However, laboratory testing of fracture specimens to measure resistance curves (J-Δa) consistently reveals a marked effect of absolute specimen size, geometry, relative crack size (a/W ratio) and loading mode (tension vs. bending) on R-curves. These effects observed in R-curves have enormous practical implications in defect assessments and repair decisions of in-service structures under low constraint conditions. Structural components falling into this category include pressurized piping systems with surface flaws that form during fabrication or during in-service operation.

This paper presents the on-going work to develop specimens and test procedures to study geometry effects (e.g., triaxiality effects) in the brittle to ductile transition of carbon-manganese steels, the basic idea being to compare the results obtained on these specimens with the results obtained on CT specimens. A clamped SENT specimen was chosen for this study. Finite element computations have been made to optimize the specimen shape and to develop the η-factor, the shape factor F (to compute K) and the normalized compliance μ. Preliminary tests have been conducted, showing that some adjustments of the test procedure should be made. Tests on new specimens are on-going.