Modelling spatial variability in as-laid embedment for high pressure and high temperature (HPHT) pipeline design

2016 ◽  
Vol 53 (11) ◽  
pp. 1853-1865 ◽  
Author(s):  
Z.J. Westgate ◽  
W. Haneberg ◽  
D.J. White
Keyword(s):  
Spatial Variability ◽  
Mitigation Measures ◽  
Physical Mechanisms ◽  
Lateral Resistance ◽  
Project Costs ◽  
Seabed Interaction ◽  
Subsea Pipelines ◽  
Design Analyses ◽  
Pipeline Design ◽  
The Impact

Subsea pipelines are being designed to accommodate higher temperatures and pressures. Current modelling approaches that adopt constant lateral seabed resistance along the pipeline do not capture the high spatial variability in as-laid pipeline embedment from field observations, which strongly affects the lateral resistance. Ignoring spatial variability when designing pipelines with engineered buckles leads to higher predictions of axial force along the pipeline, with reduced likelihood of buckle formation. This can result in excessive mitigation measures being adopted, such as sleepers or counteract structures, which significantly increase project costs. Spatial variability of pipeline embedment is not currently handled rationally in design because an understanding of the physical mechanisms that cause as-laid embedment and methods for accurately predicting it have only recently emerged. This paper illustrates how the influence of these physical mechanisms that drive embedment can be extracted from field survey data and then modelled synthetically in design analyses. The impact of embedment variability and the resulting variation in lateral seabed resistance on the lateral buckling response is illustrated. The framework represents an improvement in the way geotechnical uncertainty and variability is handled in pipeline–seabed interaction analyses for use in pipeline design, and has already begun to be implemented in practice.

On the Calibration of Coefficients of Friction for Pipeline-Seabed Interaction

2010 ◽  
Author(s):  
Deepak V. Datye
Keyword(s):  
Contact Interaction ◽  
Variable Coefficients ◽  
Rational Representation ◽  
Interaction Behavior ◽  
Seabed Interaction ◽  
Subsea Pipelines ◽  
Pipeline Design ◽  
Resistance Data ◽  
Underlying Soil ◽  
3D Problem

Subsea pipelines placed on the seabed can buckle due to thermal and mechanical loads. This buckling, and the associated pipe walking phenomena, can lead to large stresses in the pipe sections and at the pipe end attachments. These high stresses need to be accounted for in pipeline design. An accurate simulation of pipeline buckling for design purposes requires a rational representation of the nonlinear large deformations of the underlying soil, which entails a large 3D problem to be solved with repeated remeshing in the Lagrangian setting. However, it is possible to reduce this effort and forgo the direct modeling of the underlying soil by modeling the pipe as a beam, the seabed as a surface, and the resistance offered by the soil to the pipe through an appropriate contact interaction behavior between the pipe and the seabed. This contact interaction behavior can be expressed through variable coefficients of friction between the pipeline and the seabed. In this paper the Coupled Eulerian-Lagrangian technique is used to evaluate the resistance offered by the plastic soil to the pipeline; the resistance data are then used to calibrate these coefficients of friction, which are in turn used in an implicit dynamic analysis for simulating the buckling deformations of a representative pipeline, modeled as a beam, in contact with the seabed, which is modeled as a surface.

Characterizing the effectiveness of COVID-19 mitigation measures: A data-centric approach (Preprint)

2020 ◽  
Author(s):  
Lukman Olagoke ◽  
Ahmet E. Topcu
Keyword(s):  
Control Measure ◽  
Control Measures ◽  
World Health ◽  
Mitigation Measures ◽  
Effective Control ◽  
The World ◽  
Decision Making Processes ◽  
And Performance ◽  
Health Organization ◽  
The Impact

BACKGROUND COVID-19 represents a serious threat to both national health and economic systems. To curb this pandemic, the World Health Organization (WHO) issued a series of COVID-19 public safety guidelines. Different countries around the world initiated different measures in line with the WHO guidelines to mitigate and investigate the spread of COVID-19 in their territories. OBJECTIVE The aim of this paper is to quantitatively evaluate the effectiveness of these control measures using a data-centric approach. METHODS We begin with a simple text analysis of coronavirus-related articles and show that reports on similar outbreaks in the past strongly proposed similar control measures. This reaffirms the fact that these control measures are in order. Subsequently, we propose a simple performance statistic that quantifies general performance and performance under the different measures that were initiated. A density based clustering of based on performance statistic was carried out to group countries based on performance. RESULTS The performance statistic helps evaluate quantitatively the impact of COVID-19 control measures. Countries tend show variability in performance under different control measures. The performance statistic has negative correlation with cases of death which is a useful characteristics for COVID-19 control measure performance analysis. A web-based time-line visualization that enables comparison of performances and cases across continents and subregions is presented. CONCLUSIONS The performance metric is relevant for the analysis of the impact of COVID-19 control measures. This can help caregivers and policymakers identify effective control measures and reduce cases of death due to COVID-19. The interactive web visualizer provides easily digested and quick feedback to augment decision-making processes in the COVID-19 response measures evaluation. CLINICALTRIAL Not Applicable

scholarly journals Detection of Unknown DDoS Attacks with Deep Learning and Gaussian Mixture Model

2021 ◽  
Vol 11 (11) ◽  
pp. 5213
Author(s):  
Chin-Shiuh Shieh ◽  
Wan-Wei Lin ◽  
Thanh-Tuan Nguyen ◽  
Chi-Hong Chen ◽  
Mong-Fong Horng ◽  
...  
Keyword(s):  
Deep Learning ◽  
Gaussian Mixture Model ◽  
Mixture Model ◽  
Denial Of Service ◽  
Gaussian Mixture ◽  
Mitigation Measures ◽  
Distribution Model ◽  
Ddos Attacks ◽  
Open Set ◽  
The Impact

DDoS (Distributed Denial of Service) attacks have become a pressing threat to the security and integrity of computer networks and information systems, which are indispensable infrastructures of modern times. The detection of DDoS attacks is a challenging issue before any mitigation measures can be taken. ML/DL (Machine Learning/Deep Learning) has been applied to the detection of DDoS attacks with satisfactory achievement. However, full-scale success is still beyond reach due to an inherent problem with ML/DL-based systems—the so-called Open Set Recognition (OSR) problem. This is a problem where an ML/DL-based system fails to deal with new instances not drawn from the distribution model of the training data. This problem is particularly profound in detecting DDoS attacks since DDoS attacks’ technology keeps evolving and has changing traffic characteristics. This study investigates the impact of the OSR problem on the detection of DDoS attacks. In response to this problem, we propose a new DDoS detection framework featuring Bi-Directional Long Short-Term Memory (BI-LSTM), a Gaussian Mixture Model (GMM), and incremental learning. Unknown traffic captured by the GMM are subject to discrimination and labeling by traffic engineers, and then fed back to the framework as additional training samples. Using the data sets CIC-IDS2017 and CIC-DDoS2019 for training, testing, and evaluation, experiment results show that the proposed BI-LSTM-GMM can achieve recall, precision, and accuracy up to 94%. Experiments reveal that the proposed framework can be a promising solution to the detection of unknown DDoS attacks.

Assessing the Preparedness of Healthcare Facilities for Disasters and Emergencies in Damghan, Iran

2021 ◽  
pp. 1-7
Author(s):  
Behrad Pourmohammadi ◽  
Ahad Heydari ◽  
Farin Fatemi ◽  
Ali Modarresi
Keyword(s):  
Health Care ◽  
Cross Sectional Study ◽  
Health Care Facilities ◽  
Mitigation Measures ◽  
Health Staff ◽  
Cross Sectional ◽  
Healthcare Facilities ◽  
Wide Range ◽  
Care Facilities ◽  
The Impact

Abstract Objectives: Iran is exposed to a wide range of natural and man-made hazards. Health-care facilities can play a significant role in providing life-saving measures in the minutes and hours immediately following the impact or exposure. The aim of this study was to determine the preparedness of health-care facilities in disasters and emergencies. Methods: This cross-sectional study was conducted in Damghan, Semnan Province, in 2019. The samples consisted of all the 11 health-care facilities located in Damghan County. A developed checklist was used to collect the data, including 272 questions in 4 sections: understanding threatening hazards, functional, structural, and nonstructural vulnerability of health-care facilities. The data were analyzed using SPSS 21. Results: The results revealed that the health-care facilities were exposed to 22 different natural and man-made hazards throughout the county. The total level of preparedness of the health-care centers under assessment was 45.8%. The average functional, structural, and nonstructural vulnerability was assessed at 49.3%, 31.6%, and 56.4%, respectively. Conclusions: Conducting mitigation measures is necessary for promoting the functional and structural preparedness. Disaster educational programs and exercises are recommended among the health staff in health-care facilities.

scholarly journals Effect of snow microstructure variability on Ku-band radar snow water equivalent retrievals

2019 ◽  
Vol 13 (11) ◽  
pp. 3045-3059 ◽  
Author(s):  
Nick Rutter ◽  
Melody J. Sandells ◽  
Chris Derksen ◽  
Joshua King ◽  
Peter Toose ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Layer Thickness ◽  
Snow Water Equivalent ◽  
Estimation Accuracy ◽  
Snow Layer ◽  
Data Set ◽  
Snow Water ◽  
Retrieval Errors ◽  
Snow Microstructure ◽  
The Impact

Abstract. Spatial variability in snowpack properties negatively impacts our capacity to make direct measurements of snow water equivalent (SWE) using satellites. A comprehensive data set of snow microstructure (94 profiles at 36 sites) and snow layer thickness (9000 vertical profiles across nine trenches) collected over two winters at Trail Valley Creek, NWT, Canada, was applied in synthetic radiative transfer experiments. This allowed for robust assessment of the impact of estimation accuracy of unknown snow microstructural characteristics on the viability of SWE retrievals. Depth hoar layer thickness varied over the shortest horizontal distances, controlled by subnivean vegetation and topography, while variability in total snowpack thickness approximated that of wind slab layers. Mean horizontal correlation lengths of layer thickness were less than a metre for all layers. Depth hoar was consistently ∼30 % of total depth, and with increasing total depth the proportion of wind slab increased at the expense of the decreasing surface snow layer. Distinct differences were evident between distributions of layer properties; a single median value represented density and specific surface area (SSA) of each layer well. Spatial variability in microstructure of depth hoar layers dominated SWE retrieval errors. A depth hoar SSA estimate of around 7 % under the median value was needed to accurately retrieve SWE. In shallow snowpacks <0.6 m, depth hoar SSA estimates of ±5 %–10 % around the optimal retrieval SSA allowed SWE retrievals within a tolerance of ±30 mm. Where snowpacks were deeper than ∼30 cm, accurate values of representative SSA for depth hoar became critical as retrieval errors were exceeded if the median depth hoar SSA was applied.

Case Studies Highlighting Rapid Repair Methods of Pressurised Pipelines Damaged by Anchors

2018 ◽  
Author(s):  
Dale Millward
Keyword(s):  
Case Studies ◽  
Health And Safety ◽  
Cost Effective ◽  
Pipeline System ◽  
Subsea Pipeline ◽  
Damage Scenarios ◽  
Fail Safe ◽  
Subsea Pipelines ◽  
Marine Vessels ◽  
Pipeline Design

Effective pipeline design and regular maintenance can assist in prolonging the lifespan of subsea pipelines, however the presence of marine vessels can significantly increase the risk of pipeline damage from anchor hazards. As noted in the Health and Safety Executive – Guideline for Pipeline Operators on Pipeline Anchor Hazards 2009. “Anchor hazards can pose a significant threat to pipeline integrity. The consequences of damage to a pipeline could include loss of life, injury, fire, explosion, loss of buoyancy around a vessel and major pollution”. This paper will describe state of the art pipeline isolation tooling that enables safe modification of pressurised subsea pipelines. Double Block and Bleed (DBB) isolation tools have been utilised to greatly reduce downtime, increase safety and maximise unplanned maintenance, providing cost-effective solutions to the end user. High integrity isolation methods, in compliance with international subsea system intervention and isolation guidelines (IMCA D 044 / IMCA D 006), that enable piggable and unpiggable pipeline systems to be isolated before any breaking of containment, will also be explained. This paper will discuss subsea pipeline damage scenarios and repair options available to ensure a safe isolation of the pipeline and contents in the event of an incident DNV GL type approved isolation technology enables the installation of a fail-safe, DBB isolation in the event of a midline defect. The paper will conclude with case studies highlighting challenging subsea pipeline repair scenarios successfully executed, without depressurising the entire pipeline system, and in some cases without shutting down or interrupting production.

scholarly journals Numerical Study of Hydrodynamic Impact on Bubbly Water

2015 ◽  
Author(s):  
Mehdi Elhimer ◽  
Aboulghit El Malki Alaoui ◽  
Kilian Croci ◽  
Céline Gabillet ◽  
Nicolas Jacques
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Numerical Data ◽  
Void Volume Fraction ◽  
Bubbly Liquid ◽  
Impact Loads ◽  
Hydrodynamic Impact ◽  
Physical Mechanisms ◽  
The Impact ◽  
The Relationship

The phenomenon of slamming on a bubbly liquid has many occurrences in marine and costal engineering. However, experimental or numerical data on the effect of the presence of gas bubbles within the liquid on the impact loads are scarce and the related physical mechanisms are poorly understood. The aim of the present paper is to study numerically the relationship between the void volume fraction and the impact loads. For that purpose, numerical simulations of the impact of a cone on bubbly water have been performed using the finite element code ABAQUS/Explicit. The present results show the diminution of the impact loads with the increase of the void fraction. This effect appears to be related to the high compressibility of the liquid-gas mixture.

scholarly journals Regionalized Terrestrial Ecotoxicity Assessment of Copper-Based Fungicides Applied in Viticulture

2018 ◽  
Vol 10 (7) ◽  
pp. 2522 ◽  
Author(s):  
Ivan Viveros Santos ◽  
Cécile Bulle ◽  
Annie Levasseur ◽  
Louise Deschênes
Keyword(s):  
Spatial Variability ◽  
Soil Properties ◽  
Regression Models ◽  
Management Practices ◽  
Metal Speciation ◽  
Agricultural Systems ◽  
Geographical Variability ◽  
Terrestrial Ecotoxicity ◽  
The Impact ◽  
Growing Region

Life cycle assessment has been recognized as an important decision-making tool to improve the environmental performance of agricultural systems. Still, there are certain modelling issues related to the assessment of their impacts. The first is linked to the assessment of the metal terrestrial ecotoxicity impact, for which metal speciation in soil is disregarded. In fact, emissions of metals in agricultural systems contribute significantly to the ecotoxic impact, as do copper-based fungicides applied in viticulture to combat downy mildew. Another issue is linked to the ways in which the intrinsic geographical variability of agriculture resulting from the variation of management practices, soil properties, and climate is addressed. The aim of this study is to assess the spatial variability of the terrestrial ecotoxicity impact of copper-based fungicides applied in European vineyards, accounting for both geographical variability in terms of agricultural practice and copper speciation in soil. This first entails the development of regionalized characterization factors (CFs) for the copper used in viticulture and then the application of these CFs to a regionalized life-cycle inventory that considers different management practices, soil properties, and climates in different regions, namely Languedoc-Roussillon (France), Minho (Portugal), Tuscany (Italy), and Galicia (Spain). There are two modelling alternatives to determine metal speciation in terrestrial ecotoxicity: (a) empirical regression models; and (b) WHAM 6.0, the geochemical speciation model applied according to the soil properties of the Harmonized World Soil Database (HWSD). Both approaches were used to compute and compare regionalized CFs with each other and with current IMPACT 2002+ CF. The CFs were then aggregated at different spatial resolutions—global, Europe, country, and wine-growing region—to assess the uncertainty related to spatial variability at the different scales and applied in the regionalized case study. The global CF computed for copper terrestrial ecotoxicity is around 3.5 orders of magnitude lower than the one from IMPACT 2002+, demonstrating the impact of including metal speciation. For both methods, an increase in the spatial resolution of the CFs translated into a decrease in the spatial variability of the CFs. With the exception of the aggregated CF for Portugal (Minho) at the country level, all the aggregated CFs derived from empirical regression models are greater than the ones derived from the method based on WHAM 6.0 within a range of 0.2 to 1.2 orders of magnitude. Furthermore, CFs calculated with empirical regression models exhibited a greater spatial variability with respect to the CFs derived from WHAM 6.0. The ranking of the impact scores of the analyzed scenarios was mainly determined by the amount of copper applied in each wine-growing region. However, finer spatial resolutions led to an impact score with lower uncertainty.

scholarly journals Iron-bound organic carbon in forest soils: quantification and characterization

2016 ◽  
Vol 13 (16) ◽  
pp. 4777-4788 ◽  
Author(s):  
Qian Zhao ◽  
Simon R. Poulson ◽  
Daniel Obrist ◽  
Samira Sumaila ◽  
James J. Dynes ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Spatial Variability ◽  
Forest Soils ◽  
The United States ◽  
Biogeochemical Cycles ◽  
Mean Annual Temperature ◽  
Aliphatic Carbon ◽  
A Site ◽  
The Impact ◽  
X Ray Absorption

Abstract. Iron oxide minerals play an important role in stabilizing organic carbon (OC) and regulating the biogeochemical cycles of OC on the earth surface. To predict the fate of OC, it is essential to understand the amount, spatial variability, and characteristics of Fe-bound OC in natural soils. In this study, we investigated the concentrations and characteristics of Fe-bound OC in soils collected from 14 forests in the United States and determined the impact of ecogeographical variables and soil physicochemical properties on the association of OC and Fe minerals. On average, Fe-bound OC contributed 37.8 % of total OC (TOC) in forest soils. Atomic ratios of OC : Fe ranged from 0.56 to 17.7, with values of 1–10 for most samples, and the ratios indicate the importance of both sorptive and incorporative interactions. The fraction of Fe-bound OC in TOC (fFe-OC) was not related to the concentration of reactive Fe, which suggests that the importance of association with Fe in OC accumulation was not governed by the concentration of reactive Fe. Concentrations of Fe-bound OC and fFe-OC increased with latitude and reached peak values at a site with a mean annual temperature of 6.6 °C. Attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) and near-edge X-ray absorption fine structure (NEXAFS) analyses revealed that Fe-bound OC was less aliphatic than non-Fe-bound OC. Fe-bound OC also was more enriched in 13C compared to the non-Fe-bound OC, but C ∕ N ratios did not differ substantially. In summary, 13C-enriched OC with less aliphatic carbon and more carboxylic carbon was associated with Fe minerals in the soils, with values of fFe-OC being controlled by both sorptive and incorporative associations between Fe and OC. Overall, this study demonstrates that Fe oxides play an important role in regulating the biogeochemical cycles of C in forest soils and uncovers the governing factors for the spatial variability and characteristics of Fe-bound OC.

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