Trends to determine fracture intiation and propagation of a pipe under service pressure

A fracture toughness transferability curve has been established for the X52 pipe steels described by a linear relationship between the notch critical stress intensity factor and the average value of T stress over the opening stress distribution. This curve is used to determine the fracture toughness associated with the structure. the characteristic length of the fracture process. Crack extension modelled by Finite Element method using CTOA criterion coupled with the the node release technique is used to predict the crack velocity, the arrest pressure and crack length. This method is compared with the different Two Curves Methods Batelle, HLP and HLP-Sumitom

Comparison between using longitudinal and shear waves in ultrasonic stress measurement to investigate the effect of post-weld heat-treatment on welding residual stresses

ABSTARCT: Fusion welding is a joining process widely used in the industry. However, undesired residual stresses are produced once the welding process is completed. Post-weld heat-treatment (PWHT) is extensively employed in order to relieve the welding residual stresses. In this study, effect of PWHT time and temperature on the residual stresses of a ferritic stainless steel is investigated. Residual stress distributions in eight welded specimens were measured by using an ultrasonic method. Ultrasonic stress measurement is a nondestructive method based on acoustoelasticity law, which correlates mechanical stresses with velocity of an ultrasonic wave propagating within the subject material. The ultrasonic wave employed could be longitudinal or shear wave produced by the longitudinal (normal) or transverse (shear) transducers, respectively. Ultrasonic stress measurements based on longitudinal waves use longitudinal critically refracted (LCR) waves in this direction, while shear wave methods use an ultrasonic birefringence phenomenon. The results show that the effect of PWHT can be successfully inferred by both longitudinal and shear wave methods, but the former is found to be more sensitive to stress variation. Furthermore, the distribution of subsurface residual stresses is found to be more distinguishable when the LCR method is employed

Incorporating Physical Knowledge into Machine Learning for Planetary Space Physics

Recent improvements in data collection volume from planetary and space physics missions have allowed the application of novel data science techniques. The Cassini mission for example collected over 600 gigabytes of scientific data from 2004 to 2017. This represents a surge of data on the Saturn system. Machine learning can help scientists work with data on this larger scale. Unlike many applications of machine learning, a primary use in planetary space physics applications is to infer behavior about the system itself. This raises three concerns: first, the performance of the machine learning model, second, the need for interpretable applications to answer scientific questions, and third, how characteristics of spacecraft data change these applications. In comparison to these concerns, uses of black box or un-interpretable machine learning methods tend toward evaluations of performance only either ignoring the underlying physical process or, less often, providing misleading explanations for it. We build off a previous effort applying a semi-supervised physics-based classification of plasma instabilities in Saturn's magnetosphere. We then use this previous effort in comparison to other machine learning classifiers with varying data size access, and physical information access. We show that incorporating knowledge of these orbiting spacecraft data characteristics improves the performance and interpretability of machine learning methods, which is essential for deriving scientific meaning. Building on these findings, we present a framework on incorporating physics knowledge into machine learning problems targeting semi-supervised classification for space physics data in planetary environments. These findings present a path forward for incorporating physical knowledge into space physics and planetary mission data analyses for scientific discovery.Comment: 25 pages, 7 figures, accepted for publication in Frontiers in Astronomy and Space Sciences for the Research Topic of Machine Learning in Heliophysics at https://www.frontiersin.org/articles/10.3389/fspas.2020.0003

Chiropractic treatment of older adults with neck pain with or without headache or dizziness: Analysis of 288 Australian chiropractors' self-reported views

© 2019 The Author(s). Background: Neck pain is a leading cause of individual and societal burden worldwide, affecting an estimated 1 in 5 people aged 70 years and older. The nature and outcomes of chiropractic care for older adults with neck pain, particularly those with co-morbid headaches, remains poorly understood. Therefore, we sought to ascertain: What proportion of Australian chiropractors' caseload comprises older adults with neck pain (with or without headache); How are these conditions treated; What are the reported outcomes? Methods: An online survey examining practitioner and practice characteristics, clinical patient presentations, chiropractic treatment methods and outcomes, and other health service use, was distributed to a random nationally representative sample of 800 Australian chiropractors. Quantitative methods were used to analyze the data. Results: Two hundred eighty-eight chiropractors (response rate = 36%) completed the survey between August and November 2017. Approximately one-third (M 28.5%, SD 14.2) of the chiropractors' patients were older adults (i.e. aged ≥65 years), of which 45.5% (SD 20.6) presented with neck pain and 31.3% (SD 20.3) had co-morbid headache. Chiropractors reported to combine a range of physical and manual therapy treatments, exercises and self-management practices in their care of these patients particularly: manipulation of the thoracic spine (82.0%); activator adjustment of the neck (77.3%); and massage of the neck (76.5%). The average number of visits required to resolve headache symptoms was reported to be highest among those with migraine (M 11.2, SD 8.8). The majority of chiropractors (57.3%) reported a moderate response to treatment in reported dizziness amongst older adults with neck pain. Approximately 82% of older adult patients were estimated to use at least one other health service concurrently to chiropractic care to manage their neck pain. Conclusion: This is the first known study to investigate chiropractic care of older adults living with neck pain. Chiropractors report using well-established conservative techniques to manage neck pain in older adults. Our findings also indicate that this target group of patients may frequently integrate chiropractic care with other health services in order to manage their neck pain. Further research should provide in-depth investigation of older patients' experience and other patient-reported outcomes of chiropractic treatment

Identifying the process of national knowledge creation and learning and evaluating its impact on gross domestic product, considering the mediating role of national intelligencee

Background and Objectives: The economic growth of a country depends on several factors, among which the role of knowledge is undeniable. Many studies have shown that countries' GDP is often affected by the country's knowledge infrastructure. A knowledge-based economy is an economy that is directly based on the production, distribution and consumption of knowledge, and investment in knowledge and knowledge-based industries is given special attention. In this economy, where a significant share of GDP is from knowledge-based and knowledge-creating activities, knowledge generates more production than traditional factors such as labor and capital, and the value of many software and biotechnology companies arises from non-physical capitals, i.e. their knowledge and scientific privileges. Accordingly, knowledge creation is an essential weapon in today's world and without a continuous process of knowledge creation, any society is doomed to destruction. Knowledge creation and learning is the creation of new knowledge, or the replacement and improvement of the existing knowledge through social relations and organizational partnerships. The creation and application of knowledge has a major role in increasing wealth in a knowledge-based economy. The problem is that knowledge creation and learning has not been investigated at the national level yet. Methods: By applying qualitative-quantitative methods, based on Delphi technique, the procedure of identifying and explaining the processes of national knowledge creation and learning has been discussed first. Then by using exploratory and confirmatory factor analysis, a significant t-value of more than 1.96, between the identified dimensions and the variable national knowledge creation and learning, was obtained that was acceptable. Findings: Additionally, the impact of the process of national knowledge creation and learning on GDP was measured through conducting a survey and using a questionnaire, while taking the mediating role of national intelligence into account by using Sobel test. It was found that by including the mediating variable of national intelligence, the standardized beta for the relationship between national knowledge creation and learning, and gross domestic product was reduced from 0.80 to 0.18, but it is significant. Conclusion: Therefore, the variable national intelligence plays the role of a partial mediator; in other words, while the impact of national knowledge creation and learning, as the main variable, is maintained, the mediating role of national intelligence also affects GDP. This research had some limitations. One of these limitations was the stereotyped thinking about the process of knowledge creation. In this study, only one dimension of knowledge management, namely ‘knowledge creation’ was used. While we can pay attention to all the processes of the knowledge management cycle in society, instead of just thinking about the creation of knowledge at the national level, in order to promote national performance. Based on this, it is suggested that other researchers consider other dimensions of the knowledge management cycle and go one step further. Researchers can also examine the existing challenges and potential barriers to the national knowledge creation process or the requirements for knowledge creation at the national level. Alternatively, researchers can study international knowledge creation processes by considering cultural differences and provide solutions to increase the likelihood of knowledge creation globally. It is suggested that future researchers make a comparative study of the national knowledge creation model with other models of measuring intellectual capital in the world and examine the strengths and weaknesses of each model and prioritize these models based on their applicability in similar countries. It is also suggested that researchers use fuzzy logic theory to make relative measurements of each of the constructs of the national knowledge creation process and conduct field and academic research in this regard. As another suggestion, researchers can conduct this research on a specific industry and compare its results with the results of this study.   ===================================================================================== COPYRIGHTS  ©2020 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.  ====================================================================================

The Structural Model of National Knowledge Creation Processes: An Interpretative Structural Modeling Approach

and organizations, each of which in turn is moving toward becoming a foundational science because incompatibility with global developments leads to failure. So organizations need to have the flexibility to change their structure, goals, strategies, and vision. One of the tools used to create a knowledge-based organization is to create the process of knowledge creation to gain a competitive advantage. As a result creation of the concept of the process of creating national knowledge will is not out of the reach. Today, countries need management of knowledge resources and, in particular, the knowledge creation for knowledge development. There are lots of studies in the field of organizational knowledge creation and so various models have been developed for this purpose. But, the important point is that the creation of knowledge has so far been at the organizational level and in some cases cross-organization and among the subset of a parent organization. The innovation of this article is identifying the process of knowledge creation at the national level. Methods: For this purpose, based on the literature review and analyzing the research gap, using the Delphi method and a survey of experts, possible processes at the national knowledge creation has been addressed. The panel of experts includes seven professors and experts in the field of knowledge management, who are both theoretically and experimentally familiar with this concept. Findings: The results of Delphi technique show that the processes of socialization, externalization, combination, culture creation, application, and internalization can be referred to as the processes of national knowledge creation. Using interpretive structural modeling, it was revealed that the processes of socialization, internalization and externalization are at level 1, the processes of culture and combination are in the second level and the process of application is at the third level of the model. Conclusion: The results of the National Knowledge Creation Model indicate that socialization, externalization, and internalization are the cornerstones of the model. This means that in order to successfully implement the creation of knowledge at the national level, one must first invest in these issues. According to the results obtained it is clearly seen that the processes of combination and culture making are independent dimensions and planning for combining knowledge among different organizations and organizational programming for culture building at organizational level can be done independent of other processes. It should be noted that the identification of the structures of the process of creating the national knowledge process has been achieved based on theoretical foundations and receiving the opinions and of a limited number of academic and experimental experts. Therefore, the scope for future research is the application of factor analysis method, path analysis and structural equation modeling approach to test the research model to examine the validity of the obtained model.   ===================================================================================== COPYRIGHTS  ©2019 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.  ====================================================================================

On the sensitivity of local flexibility markets to forecast error : A bi-level optimization approach

The large-scale integration of intermittent distributed energy resources has led to increased uncertainty in the planning and operation of distribution networks. The optimal flexibility dispatch is a recently introduced, power flow-based method that a distribution system operator can use to effectively determine the amount of flexibility it needs to procure from the controllable resources available on the demand side. However, the drawback of this method is that the optimal flexibility dispatch is inexact due to the relaxation error inherent in the second-order cone formulation. In this paper we propose a novel bi-level optimization problem, where the upper level problem seeks to minimize the relaxation error and the lower level solves the earlier introduced convex second-order cone optimal flexibility dispatch (SOC-OFD) problem. To make the problem tractable, we introduce an innovative reformulation to recast the bi-level problem as a non-linear, single level optimization problem which results in no loss of accuracy. We subsequently investigate the sensitivity of the optimal flexibility schedules and the locational flexibility prices with respect to uncertainty in load forecast and flexibility ranges of the demand response providers which are input parameters to the problem. The sensitivity analysis is performed based on the perturbed Karush-Kuhn-Tucker (KKT) conditions. We investigate the feasibility and scalability of the proposed method in three case studies of standardized 9-bus, 30-bus, and 300-bus test systems. Simulation results in terms of local flexibility prices are interpreted in economic terms and show the effectiveness of the proposed approach.</p