Worldwide Approximations of Current Profiles for Steel Riser Design: The WACUP Project

2012 ◽  
Author(s):  
Marc Prevosto ◽  
George Z. Forristall ◽  
Gus Jeans ◽  
Christelle Herry ◽  
Gavin Harte ◽  
...  
Keyword(s):  
Best Practice ◽  
Data Sets ◽  
Current Profile ◽  
Self Organizing Maps ◽  
Steel Catenary Riser ◽  
Large Current ◽  
Riser Design ◽  
Comparison Of The Results

This paper describes the objectives and methodology of the WACUP (Worldwide Approximations of Current Profiles) Joint Industry Project. The project goal is to establish best practice for reducing large current profile databases into a smaller, representative set of profiles for riser design. We studied the use of the following three techniques for comparing and reducing measured in-situ databases: Empirical Orthogonal Function (EOF), Self Organizing Maps (SOM) and classical Current Profile Characterisation (CPC). We evaluated the skill of these three techniques in estimating Vortex Induced Vibration (VIV) fatigue damage to a Steel Catenary Riser (SCR). Our measure of skill was the comparison of the results from the reduced data sets with results from the original complete database. The standard techniques were modified and accuracy was improved. The role of numerical current models to complement in-situ measurements in riser design was also assessed.

Strength Performance of Steel Catenary Riser Using Short Term and Long Term Analysis Methodologies

2016 ◽  
Author(s):  
Feng Wang ◽  
Roger Burke ◽  
Anil Sablok ◽  
Kristoffer H. Aronsen ◽  
Oddgeir Dalane
Keyword(s):  
Bending Moment ◽  
Current Profile ◽  
Short Term ◽  
Sea State ◽  
Strength Performance ◽  
Steel Catenary Riser ◽  
Analysis Methodology ◽  
Riser Design ◽  
Term Analysis

Strength performance of a steel catenary riser tied back to a Spar is presented based on long term and short term analysis methodologies. The focus of the study is on response in the riser touch down zone, which is found to be the critical region based on short term analysis results. Short term riser response in design storms is computed based on multiple realizations of computed vessel motions with various return periods. Long term riser response is based on vessel motions for a set of 45,000 sea states, each lasting three hours. The metocean criteria for each sea state is computed based on fifty six years of hindcast wind and wave data. A randomly selected current profile is used in the long term riser analysis for each sea state. Weibull fitting is used to compute the extreme riser response from the response of the 45,000 sea states. Long term analysis results in the touch down zone, including maximum bending moment, minimum effective tension, and maximum utilization using DNV-OS-F201, are compared against those from the short term analysis. The comparison indicates that the short term analysis methodology normally followed in riser design is conservative compared to the more accurate, but computationally more expensive, long term analysis methods. The study also investigates the important role that current plays in the strength performance of the riser in the touch down zone.

The Use of Empirical Orthogonal Functions for Deriving Response Based Extreme Current Profiles

2012 ◽  
Author(s):  
Gus Jeans ◽  
Liam Harrington-Missin ◽  
Andrew Watson ◽  
Jon Upton
Keyword(s):  
Surface Current ◽  
Empirical Orthogonal Functions ◽  
Current Profile ◽  
Orthogonal Functions ◽  
Data Set ◽  
Near Surface ◽  
Orthogonal Function ◽  
Large Current ◽  
Traditional Assumption

Coherent extreme current profiles are derived to reduce the over-conservatism associated with the traditional assumption that extreme currents occur at all depths through the water column simultaneously. Empirical Orthogonal Function (EOF) analysis has proven effective for derivation of coherent extreme current profiles in regions where it effectively captures the dominant characteristics of the flow regime. This is despite the questionable suitability of EOF for Current Profile Characterisation, which reduces a large current profile data set into a much smaller set of profiles for riser fatigue studies. EOF Mode 1 and 2 are used to represent six years of in-situ current profiles accounting for 97.75% of the original variance. With the assumption that depth integrated speed squared is proportional to drag on a simple riser, three sets of extreme current profiles were derived. A) Profiles associated with extreme near surface current speeds, B) Profiles associated with extreme mid-depth current speeds and C) Profiles associated with extreme drag on a riser.

scholarly journals Cryocrystallography in capillaries: critical glycerol concentrations and cooling rates

2008 ◽  
Vol 41 (4) ◽  
pp. 791-797 ◽  
Author(s):  
Matthew Warkentin ◽  
Valentina Stanislavskaia ◽  
Katherine Hammes ◽  
Robert E. Thorne
Keyword(s):  
Crystal Growth ◽  
High Resolution ◽  
Structure Determination ◽  
Best Practice ◽  
Ice Formation ◽  
Data Sets ◽  
Glycerol Concentration ◽  
Cooling Rates ◽  
X Ray

Capillary tubes have many advantages over multi-well plates for macromolecular crystal growth and handling, including the possibility ofin situstructure determination. To obtain complete high-resolution X-ray data sets, cryopreservation protocols must be developed to prevent crystalline ice formation and preserve macromolecular crystal order. The minimum glycerol concentrations required to vitrify aqueous solutions during plunging into liquid nitrogen and liquid propane have been determined for capillary diameters from 3.3 mm to 150 µm. For the smallest diameter, the required glycerol concentrations are 30%(w/v) in nitrogen and 20%(w/v) in propane, corresponding to cooling rates of ∼800 and ∼7000 K s−1, respectively. These concentrations are much larger than are required in current best practice using crystals in loops or on microfabricated mounts. In additon, the relation between the minimum cooling rate for vitrification and glycerol concentration has been estimated; this relation is of fundamental importance in developing rational cryopreservation protocols.

Participant recruitment and data collection through Facebook: the role of personality factors

2017 ◽  
Author(s):  
Sean Chandler Rife ◽  
Kelly L. Cate ◽  
Michal Kosinski ◽  
David Stillwell
Keyword(s):  
Data Collection ◽  
Social Research ◽  
Personality Factors ◽  
The Internet ◽  
Data Sets ◽  
Social Networking Service ◽  
Participant Recruitment ◽  
Conducting Research ◽  
Promising Avenue

As participant recruitment and data collection over the Internet have become more common, numerous observers have expressed concern regarding the validity of research conducted in this fashion. One growing method of conducting research over the Internet involves recruiting participants and administering questionnaires over Facebook, the world’s largest social networking service. If Facebook is to be considered a viable platform for social research, it is necessary to demonstrate that Facebook users are sufficiently heterogeneous and that research conducted through Facebook is likely to produce results that can be generalized to a larger population. The present study examines these questions by comparing demographic and personality data collected over Facebook with data collected through a standalone website, and data collected from college undergraduates at two universities. Results indicate that statistically significant differences exist between Facebook data and the comparison data-sets, but since 80% of analyses exhibited partial η2 < .05, such differences are small or practically nonsignificant in magnitude. We conclude that Facebook is a viable research platform, and that recruiting Facebook users for research purposes is a promising avenue that offers numerous advantages over traditional samples.

{10-12} Twinning Mechanism During In Situ Micro-Tensile Loading of Pure Mg: Role of Basal Slip and Twin-Twin Boundary Interaction

2020 ◽  
Author(s):  
Nicolò Maria della Ventura ◽  
Szilvia Kalácska ◽  
Daniele Casari ◽  
Thomas Edward James Edwards ◽  
Johann Michler ◽  
...  
Keyword(s):  
Twin Boundary ◽  
Basal Slip ◽  
Tensile Loading ◽  
Boundary Interaction

The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface

1999 ◽  
Vol 39 (7) ◽  
pp. 91-98 ◽  
Author(s):  
Ryan N. Jordan ◽  
Eric P. Nichols ◽  
Alfred B. Cunningham
Keyword(s):  
Mass Transfer ◽  
Cell Membrane ◽  
Substrate Concentration ◽  
Water Interface ◽  
Industrial Systems ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Surfactant Sorption

Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.

THE ROLE OF BACTERIAL COMMUNITIES ON IN-SITU ARSENIC AND IRON CYCLING IN RIVERBANKS ALONG THE MEGHNA RIVER, BANGLADESH

2020 ◽  
Author(s):  
Kimberly D. Myers ◽  
◽  
Katrina Lee Jewell ◽  
P.S.K. Knappett ◽  
Mehtaz M. Lipsi ◽  
...  
Keyword(s):  
Bacterial Communities ◽  
Iron Cycling

How Artefacts Do Leadership: A Ventriloquial Analysis

2021 ◽  
pp. 089331892199807
Author(s):  
Jonathan Clifton ◽  
Fernando Fachin ◽  
François Cooren
Keyword(s):  
Organizational Communication ◽  
Recent Work ◽  
Distributed Leadership ◽  
Network Theory ◽  
Actor Network Theory ◽  
Fine Grained ◽  
Naturally Occurring ◽  
Human Actors

To date there has been little work that uses fine-grained interactional analyses of the in situ doing of leadership to make visible the role of non-human as well as human actants in this process. Using transcripts of naturally-occurring interaction as data, this study seeks to show how leadership is co-achieved by artefacts as an in-situ accomplishment. To do this we situate this study within recent work on distributed leadership and argue that it is not only distributed across human actors, but also across networks that include both human and non-human actors. Taking a discursive approach to leadership, we draw on Actor Network Theory and adopt a ventriloquial approach to sociomateriality as inspired by the Montreal School of organizational communication. Findings indicate that artefacts “do” leadership when a hybrid presence is made relevant to the interaction and when this presence provides authoritative grounds for influencing others to achieve the group’s goals.

scholarly journals Phosphorylation of GAPVD1 Is Regulated by the PER Complex and Linked to GAPVD1 Degradation

2021 ◽  
Vol 22 (7) ◽  
pp. 3787
Author(s):  
Hussam Ibrahim ◽  
Philipp Reus ◽  
Anna Katharina Mundorf ◽  
Anna-Lena Grothoff ◽  
Valerie Rudenko ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Transcriptional Repression ◽  
Small Gtpase ◽  
Main Role ◽  
Interacting Proteins ◽  
Casein Kinase 1 ◽  
Bona Fide ◽  
Kinetics Of

Repressor protein period (PER) complexes play a central role in the molecular oscillator mechanism of the mammalian circadian clock. While the main role of nuclear PER complexes is transcriptional repression, much less is known about the functions of cytoplasmic PER complexes. We found with a biochemical screen for PER2-interacting proteins that the small GTPase regulator GTPase-activating protein and VPS9 domain-containing protein 1 (GAPVD1), which has been identified previously as a component of cytoplasmic PER complexes in mice, is also a bona fide component of human PER complexes. We show that in situ GAPVD1 is closely associated with casein kinase 1 delta (CSNK1D), a kinase that regulates PER2 levels through a phosphoswitch mechanism, and that CSNK1D regulates the phosphorylation of GAPVD1. Moreover, phosphorylation determines the kinetics of GAPVD1 degradation and is controlled by PER2 and a C-terminal autoinhibitory domain in CSNK1D, indicating that the regulation of GAPVD1 phosphorylation is a novel function of cytoplasmic PER complexes and might be part of the oscillator mechanism or an output function of the circadian clock.

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