bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on Life Extension of Aged RPV Material Based on Probabilistic Fracture Mechanics: Japanese Round Robin
Authors: Yagawa G. , Yoshimura S. , Handa N. , Uno T. , Watashi K. , Fujioka T. , Ueda H. , Uno M. , Hojo K. , Ueda S. 
Published: February 2008

AbstractThis paper is concerned with round-robin analyses of probabilistic fracture mechanics (PFM) problems of aged RPV material. Analyzed here is a plate with a semi-elliptical surface crack subjected to various cyclic tensile and bending stresses. A depth and an aspect ratio of the surface crack are assumed to be probabilistic variables. Failure probabilities are calculated using the Monte Carlo methods with the importance sampling or the stratified sampling techniques. Material properties are chosen from the Marshall report, the ASME Code Section XI, and the experiments on a Japanese RPV material carried out by the Life Evaluation (LE) subcommittee of the Japan Welding Engineering Society (JWES), while loads are determined referring to design loading conditions of pressurized water reactors (PWR). Seven organizations participate in this study. At first, the procedures for obtaining reliable PFM solutions with low failure probabilities are examined by solving a unique problem with seven computer programs. The seven solutions agree very well with one another, i.e., by a factor of 2 to 5 in failure probabilities. Next, sensitivity analyses are performed by varying fracture toughness values, loading conditions, and pre and in-service inspections. Finally, life extension simulations based on the PFM analyses are performed. It is clearly demonstrated from these analyses that failure probabilities are so sensitive to the change of fracture toughness values that the degree of neutron irradiation significantly influences the judgment of plant life extension.
Normal Mode Theory as a Tool in Finite Element
Substructuring
Authors: Sebert K. A. , Scavuzzo R. J. 
Published: February 2008

Abstract
Two methods of substructuring finite element models are examined. Each method uses normal mode theory as the basis for selecting the appropriate modes for the substructure and the properties of the modes. One of the substructuring procedures uses component mode synthesis to attach the substructure to the residual structure, while the other method uses direct connection. The resulting combined models are evaluated for shock input using NASTRAN, and the results are compared to the analysis of the original model in each case.
A Technique to Distinguish the Primary and Secondary
Stresses
Authors: Eslami M. R. , Shariyat M. 
Published: February 2008

Abstract
A technique is developed which can be used to distinguish the primary and secondary stresses in pressure vessels. The general definition of the two types of stresses stated by the ASME Code is used; a simple viscoelastic model is proposed for each stress category. The proposed model can be extended to elastic as well as plastic regions of strain-hardening materials and can include the mechanical as well as thermal loads. The proposed viscoelastic models are used to judge the nature of elastic stresses and the effective stress-strain curve is used to simulate the state of stress at any stage of loading and the percentage of primary to secondary stresses at any radius of the vessel. It is found that thermal stresses cannot always be categorized as secondary stress, and in the case of thermoplastically loaded vessels they can contribute partly to the primary stress in the vessel.
Experiment of Chaotic Vibration of Loosely Supported Tube Rows in
Cross-Flow
Authors: Chen S. S. , Zhu S. , Cai Y. 
Published: February 2008

Abstract
A tube array supported by baffle plates in cross-flow may be subjected to fluidelastic instability in the tube-support-plate-inactive mode. An experimental study is presented to characterize the tube motion. Three series of tests were performed to measure tube displacements as a function of flow velocity for differing clearances. The motion was examined by root-mean-square values of tube displacements, power spectral densities, phase planes, Poincare´ maps, and Lyapunov exponents. The experimental data agree reasonably well with an analytical model based on the unsteady flow theory.
Fatigue Life Analyses and Tests for Thick-Wall Cylinders Including
Effects of Overstrain and Axial Grooves
Authors: Underwood J. H. , Parker A. P. 
Published: February 2008

Abstract
A fracture mechanics-based fatigue life analysis was developed for overstrained, pressurized thick-wall cylinders with one or several semi-elliptical-shaped axial grooves at the inner diameter. The fatigue life for a crack initiating at the root of the groove was calculated for various cylinder, groove, and crack configurations and for different material yielding conditions. Comparisons were made with fatigue crack growth and laboratory life results from A723 thick-wall cylinders, in which cannon firing tests were first performed to produce axial erosion grooves, followed by cyclic hydraulic pressurization to failure in the laboratory. The life analysis, with an initial crack size based on the expected preexisting defects, gave a good description of the crack growth and fatigue life of the tests for cylinders with and without grooves. General fatigue life calculations summarized important material and configurational effects on the fatigue life design of overstrained cylinders, including effects of material yield strength, cylinder diameter ratio, stress concentration factor, and initial crack size.
The Effect of Water Flow Rate Upon the Environmentally Assisted
Cracking Response of a Low-Alloy Steel
Authors: James L. A. , Wire G. L. , Cullen W. H. 
Published: February 2008

Abstract
The effect of water flow rate upon the environmentally assisted cracking (EAC) response of a high-sulfur ferritic steel was studied at a temperature of 243°C. In contrast to earlier studies which employed compact-type specimens, this study employed relatively large tight semi-elliptical surface cracks tested under generally linear-elastic conditions. Flow velocities parallel to the crack as low as 1.58–1.84 m/s were effective in mitigating EAC.
Stress-Strain and Failure Analyses of Composite Pipe Under
Torsion
Authors: Zhao Y. , Pang S. S. 
Published: February 2008

Abstract
An analytical and experimental study was conducted to investigate the elastic and failure behavior of composite laminated pipe under torsion. The analytical model was developed based on the mechanics of composite materials and the maximum strain failure criterion. Five composite pipe samples were tested on a specially designed pipe torsional tester. A finite element analysis was also performed to be compared with the analytical and experimental results. The relationship between applied torque and shear strain and between torque and torsional angles was obtained by all three methods. The effects of fiber angle and its deviation were also studied.
B31.3 Appendix X Rules for Expansion Joints
Authors: Becht C. 
Published: February 2008

Abstract
In 1988, ASME B31.3 added Appendix X containing requirements for Metallic Bellows Expansion Joints into the Chemical Plant and Petroleum Refinery Piping Code. These have been revised and improved in subsequent addenda to the Code. This paper describes some of the salient features of this Appendix, as well as the revisions and the background behind them.
Experimental Fretting-Wear Studies of Steam Generator
Materials
Authors: Fisher N. J. , Chow A. B. , Weckwerth M. K. 
Published: February 2008

Abstract
Flow-induced vibration of steam generator tubes results in fretting-wear damage due to impacting and rubbing of the tubes against their supports. This damage can be predicted by computing tube response to flow-induced excitation forces using analytical techniques, and then relating this response to resultant wear damage using experimentally derived wear coefficients. Fretting-wear of steam generator materials has been studied experimentally at Chalk River Laboratories for two decades. Tests are conducted in machines that simulate steam generator environmental conditions and tube-to-support dynamic interactions. Different tube and support materials, tube-to-support clearances, and tube support geometries have been studied. The effect of environmental conditions, such as temperature, oxygen content, pH and chemistry control additive, have been investigated as well. Early studies showed that damage was related to contact force as long as other parameters, such as geometry and motion, were held constant. Later studies have shown that damage is related to a parameter called work-rate, which combines both contact force and sliding distance. Results of short and long-term fretting-wear tests for CANDU steam generator materials at realistic environmental conditions are presented. These results demonstrate that work-rate is an appropriate correlating parameter for impact-sliding interaction.
A Practical Method Based on Stress Evaluation
(σd Criterion) to Predict Initiation of
Crack Under Creep and Creep-Fatigue Conditions
Authors: Moulin D. , Drubay B. , Acker D. , Laiarinandrasana L. 
Published: February 2008

Abstract
The behavior of defects like cracks in nuclear components operating at high temperature, where creep is significant, must be under control. There exists the need to have a practical method of analysis, which can be used by engineers, to calculate the time of initiation for defects existing at the start of life of nuclear components. This study presents the background, the development, the application, and results concerning validation work made for a simplified method named σd of prediction of initiation for nuclear structures made of 316L austenitic steel and operating at temperature where creep is significant. This method relies on the evaluation of real stress-strain history on a small distance d (d = 0.05 mm) close to the crack front and material characteristics (limiting stresses) that are available in nuclear codes like ASME Code cases or RCC-MR.
Ramberg-Osgood Strain-Hardening Characterization of an ASTM A302-B
Steel
Authors: James L. A. 
Published: February 2008

Abstract
The Ramberg-Osgood strain-hardening exponents and coefficients are characterized for an unirradiated ASTM A302-B steel over a wide range of temperatures from −129 to 260°C. The strain-hardening exponent increases only slightly with temperature over this range, while the coefficient decreases with increasing temperature. Tensile specimens irradiated to 0.002, 0.029, and 0.046 dpa exhibited significant increases in the strain-hardening exponent with increasing neutron irradiation level.
Alternative Method of RTNDT Determination
for Some Reactor Vessel Weld Metals Validated by Fracture Toughness
Data
Authors: Yoon K. K. 
Published: February 2008

Abstract
The fracture toughness curves used for nuclear power plant operation pressure-temperature limits and for pressurized thermal shock evaluations are dependent on the reference temperature for nil-ductility transition (RTNDT). The original method to determine the RTNDT was formulated more than 20 yr ago when Section III of the ASME Code was adopted. At that time, there were insufficient data to judge whether some of the weld metals used in reactor vessel fabrication were unsuitable for this procedure. Presently, this causes a compliance problem for some weld metals used in nuclear reactor vessels, whereas there is no technical problem in meeting required safety margins. The RTNDT is a parameter to index degrees of irradiation embrittlement to adjust the Code reference fracture toughness curves to represent the actual degraded fracture toughness at a given fluence of a reactor vessel beltline region. When there is a problem determining RTNDT value for unirradiated material where Charpy transition temperature is the dominating criterion, an alternative RTNDT based solely on a drop-weight test was investigated for some of the weld metals. Using a new test method for fracture toughness in the transition range (ASTM, 1993), a fracture toughness curve was directly generated from a set of compact tension test data and used for validating the nil-ductility temperature (TNDT) from drop-weight test data as the sole mean for determining initial RTNDT value.
IDENTIFICATION AND MANAGEMENT OF SESSIONS GENERATED BY INSTANT MESSAGING AND PEER-TO-PEER SYSTEMS
Authors: CHEN ZHONGQIANG , DELIS ALEX , WEI PETER 
Published: February 2008

Sessions generated by Instant Messaging and Peer-to-Peer systems (IM/P2Ps) not only consume considerable bandwidth and computing resources but also dramatically change the characteristics of data flows affecting both the operation and performance of networks. Most IM/P2Ps have known security loopholes and vulnerabilities making them an ideal platform for the dissemination of viruses, worms, and other malware. The lack of access control and weak authentication on shared resources further exacerbates the situation. Should IM/P2Ps be deployed in production environments, performance of conventional applications may significantly deteriorate and enterprise data may be contaminated. It is therefore imperative to identify, monitor and finally manage IM/P2P traffic. Unfortunately, this task cannot be easily attained as IM/P2Ps resort to advanced techniques to hide their traces including multiple channels to deliver services, port hopping, message encapsulation and encryption. In this paper, we propose an extensible framework that not only helps to identify and classify IM/P2P-generated sessions in real time but also assists in the manipulation of such traffic. Consisting of four modules namely, session manager, traffic assembler, IM/P2P dissector, and traffic arbitrator, our proposed framework uses multiple techniques to improve its traffic classification accuracy and performance. Through fine-tuned splay and interval trees that help organize IM/P2P sessions and packets in data streams, we accomplish stateful inspection, traffic re-assembly, data stream correlation, and application layer analysis that combined will boost the framework's identification precision. More importantly, we introduce IM/P2Ps "plug-and-play" protocol analyzers that inspect data streams according to their syntax and semantics; these analyzers render our framework easily extensible. Identified IM/P2P sessions can be shaped, blocked, or disconnected, and corresponding traffic can be stored for forensic analysis and threat evaluation. Experiments with our prototype show high IM/P2Ps detection accuracy rates under diverse settings and excellent overall performance in both controlled and real-world environments.
Cortical Differentiation for Nouns and Verbs Depends on Grammatical Markers
Authors: Tyler L. K. , Randall B. , Stamatakis E. A. 
Published: February 2008

Abstract
Here we address the contentious issue of how nouns and verbs are represented in the brain. The co-occurrence of noun and verb deficits with damage to different neural regions has led to the view that they are differentially represented in the brain. Recent neuroimaging evidence and inconsistent lesion–behavior associations challenge this view. We have suggested that nouns and verbs are not differentially represented in the brain, but that different patterns of neural activity are triggered by the different linguistic functions carried by nouns and verbs. We test these claims in a functional magnetic resonance imaging study using homophones—words which function grammatically as nouns or verbs but have the same form and meaning—ensuring that any neural differences reflect differences in grammatical function. Words were presented as single stems and in phrases in which each homophone was preceded by an article to create a noun phrase (NP) or a pronoun to create a verb phrase (VP), thus establishing the word's functional linguistic role. Activity for single-word homophones was not modulated by their frequency of usage as a noun or verb. In contrast, homophones marked as verbs by appearing in VPs elicited greater activity in the left posterior middle temporal gyrus (LpMTG) compared to homophones marked as nouns by occurring in NPs. Neuropsychological patients with grammatical deficits had lesions which overlapped with the greater LpMTG activity found for VPs. These results suggest that nouns and verbs do not invariably activate different neural regions; rather, differential cortical activity depends on the extent to which their different grammatical functions are engaged.
Age-related Differences in Brain Activity during True and False Memory Retrieval
Authors: Dennis Nancy A. , Kim Hongkeun , Cabeza Roberto 
Published: February 2008

AbstractCompared to young adults, older adults show not only a reduction in true memories but also an increase in false memories. We investigated the neural bases of these age effects using functional magnetic resonance imaging and a false memory task that resembles the Deese–Roediger–McDermott (DRM) paradigm. Young and older participants were scanned during a word recognition task that included studied words and new words that were strongly associated with studied words (critical lures). During correct recognition of studied words (true memory), older adults showed weaker activity than young adults in the hippocampus but stronger activity than young adults in the retrosplenial cortex. The hippocampal reduction is consistent with age-related deficits in recollection, whereas the retrosplenial increase suggests compensatory recruitment of alternative recollection-related regions. During incorrect recognition of critical lures (false memory), older adults displayed stronger activity than young adults in the left lateral temporal cortex, a region involved in semantic processing and semantic gist. Taken together, the results suggest that older adults' deficits in true memories reflect a decline in recollection processes mediated by the hippocampus, whereas their increased tendency to have false memories reflects their reliance on semantic gist mediated by the lateral temporal cortex.
The Key Locus of Common Response Inhibition Network for No-go and Stop Signals
Authors: Zheng Dongming , Oka Tatsuro , Bokura Hirokazu , Yamaguchi Shuhei 
Published: February 2008

Abstract
Response inhibition is one of the highest evolved executive functions of human beings. Previous studies revealed a wide variety of brain regions related to response inhibition, although some of them may not be directly related to inhibition but to task-specific effects or noninhibitory cognitive functions such as attention, response competition, or error detection. Here, we conducted event-related functional magnetic resonance imaging studies in which all subjects performed both stop-signal and go/no-go tasks in order to explore key neural correlates within the response inhibition network irrelevant to task designs and other cognitive processes. The successful inhibition in the stop-signal and go/no-go tasks, respectively, activated a set of predominantly right-lateralized hemispheric cortices. The common inhibitory regions across the two tasks included the right middle prefrontal cortex in addition to the right middle occipital cortex. Correlation analysis was carried out within these areas between intensity of activation and behavioral performance in the two tasks. Only the region located in the middle prefrontal cortex showed significant correlations in both tasks. We believe this region is the key locus for execution of response inhibition in the distributed inhibitory neural network.
Arousal and Attention: Self-chosen Stimulation Optimizes Cortical Excitability and Minimizes Compensatory Effort
Authors: Fischer Thomas , Langner Robert , Birbaumer Niels , Brocke Burkhard 
Published: February 2008

Abstract
Cortical excitability is assumed to depend on cortical arousal level in an inverted U-shaped fashion: Largest (optimal) excitability is usually associated with medium levels of arousal. It has been proposed that under conditions of low arousal, compensatory effort is exerted if attentional demands persist. People tend to avoid this resource-consuming top–down compensation by creating or selecting environmental conditions that provide sufficient bottom–up stimulation. These assumptions were tested in an attention-demanding dual-task situation: We combined a simulated driving task to induce three different arousal levels by varying stimulation (high vs. low vs. self-chosen) with a visual two-stimulus paradigm to assess cortical excitability by the initial contingent negative variation (iCNV) component of the event-related potential. Additionally, we analyzed the oscillatory power of the beta2 band of the electroencephalogram at anterior frontal sites, which is assumed to reflect low-arousal compensatory activity. The iCNV amplitude differed in all three arousal conditions as expected: It was highest in the condition of self-chosen stimulation and lowest in the low- and high-arousal conditions. Additionally, in the low-arousal condition, anterior frontal beta2 power was found to be significantly higher than in the other two conditions and correlated positively with subjective strain. This pattern of results suggests that subjects select medium levels of stimulation which optimize cortical excitability under attentional demand conditions. The elevated fronto-central beta2 power in the low-stimulation condition may indicate the involvement of the anterior cingulate cortex in compensating for reduced arousal by top–down stimulation of the noradrenergic arousal system.
Trait Aggressiveness Modulates Neurophysiological Correlates of Laboratory-induced Reactive Aggression in Humans
Authors: Krämer Ulrike M. , Büttner Sarah , Roth Gerhard , Münte Thomas F. 
Published: February 2008

Abstract
Reactive aggression following provocation is a frequent form of human social behavior. The neural basis of reactive aggression, especially its control, remains poorly understood, however. We conducted an event-related potential (ERP) study using a competitive reaction time task that elicits aggression through provocation. Participants were selected from a larger sample because of extreme scores in trait aggressiveness, yielding high and low trait aggressive groups. As each trial in the task is separated into a decision phase, during which the punishment level for the opponent is set, and an outcome phase, during which the punishment is applied or received, we were able to disentangle provocation-related and evaluation-related modulations of the ERPs during the aggressive interaction. Specifically, we observed an enhanced frontal negativity during the decision phase under high provocation that was positively correlated with the participants' ability to refrain from retaliation. This held true for high trait aggressive participants only, pointing to a higher need for inhibitory and control processes in these people when provoked. During the outcome phase, we detected a mediofrontal negativity in loss compared to win trials, resembling previous ERP findings to negative feedback stimuli, which have been linked to the evaluation of an outcome's valence. This mediofrontal negativity was differentially pronounced in aggressive and nonaggressive participants: Nonaggressive participants showed only a slightly smaller mediofrontal negativity in win than in loss trials, suggesting that for them punishing the opponent had a similar negative valence as being punished.