VIRTUAL HULL MONITORING: CONTINUOUS FATIGUE ASSESSMENT WITHOUT ADDITIONAL INSTRUMENTATION

2021 ◽  
Vol 160 (A3) ◽  
Author(s):  
I M Thompson
Keyword(s):  
Transfer Functions ◽  
Stress Transfer ◽  
Short Term ◽  
Naval Vessel ◽  
Wave Data ◽  
Calculated Stress ◽  
Fatigue Damage Accumulation ◽  
Stress States ◽  
Strain Gauge Measurements ◽  
Using Data

A novel technique to monitor hull stresses using data currently collected on most ships is explored. This technique, referred to herein as virtual hull monitoring, uses global position signals, measured or numerically-modelled wave data, and a database of calculated stress transfer functions. This enables monitoring of short-term stress states and corresponding fatigue damage accumulation for many structural locations, either onboard or at a central location, for an entire fleet. The components, benefits, and limitations of this proposed technique are discussed. Wave buoy and strain gauge measurements from a full-scale naval vessel trial are used in comparisons with hindcast wave data and the calculated stress spectra for one structural location. Close agreement between the wave data sources and corresponding stress spectra warrants further examination of virtual hull monitoring. 

Virtual Hull Monitoring: Continuous Fatigue Assessment Without Additional Instrumentation - Technical Note

2018 ◽  
Vol Vol 160 (A3) ◽  
Author(s):  
I M Thompson
Keyword(s):  
Transfer Functions ◽  
Stress Transfer ◽  
Technical Note ◽  
Naval Vessel ◽  
Wave Data ◽  
Calculated Stress ◽  
Fatigue Damage Accumulation ◽  
Stress States ◽  
Strain Gauge Measurements ◽  
Using Data

Technical Note - A novel technique to monitor hull stresses using data currently collected on most ships is explored. This technique, referred to herein as virtual hull monitoring, uses global position signals, measured or numerically-modelled wave data, and a database of calculated stress transfer functions. This enables monitoring of short-term stress states and corresponding fatigue damage accumulation for many structural locations, either onboard or at a central location, for an entire fleet. The components, benefits, and limitations of this proposed technique are discussed. Wave buoy and strain gauge measurements from a full-scale naval vessel trial are used in comparisons with hindcast wave data and the calculated stress spectra for one structural location. Close agreement between the wave data sources and corresponding stress spectra warrants further examination of virtual hull monitoring.

Calibration of Stress Transfer Functions for Wellhead Fatigue

2015 ◽  
Author(s):  
Dara Williams
Keyword(s):  
Real Time ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Transfer Functions ◽  
Stress Transfer ◽  
Element Model ◽  
Soil Conditions ◽  
System Response ◽  
Fatigue Damage Accumulation ◽  
Fatigue Loads

In many harsh environment or high current regions (e.g. West of Shetlands, East Africa and GoM) wellhead fatigue during drilling or workover activities can be a major concern. As a result extensive wellhead and conductor fatigue assessments are required in order to predict likely fatigue damage prior to landing the BOP on to the wellhead. These pre-drilling or predictive studies are based on a number of assumptions regarding actual environmental and soil conditions. In addition the uncertainty associated with the input data requires safety factors of 10 and 20 for wave and VIV effects respectively. As a result of these assumptions the predicted levels of fatigue damage to the wellhead may be highly conservative. In cases where wellhead and conductor fatigue life is a concern the operator may choose to deploy motion monitoring systems on the BOP stack so that actual fatigue loads recorded during drilling can be calculated. These systems can be configured to provide ‘real-time’ updates on fatigue damage accumulation or can be used to record data for ‘post-drilling’ assessment. In each case the methodology applied to calculate stresses at fatigue hotspots is critical to the calculation of overall fatigue damage. The calculation of fatigue loads based on measured data is typically carried out by applying the measured BOP motions to a global finite element model of the drilling riser and wellhead system. However due to the large amounts of data involved this can be a very time consuming exercise and is not conducive to ‘real-time’ presentation of results (e.g. for on-board systems). A proposed solution to this problem is to develop stress transfer functions (STFs) that relate BOP motion to stresses at critical fatigue hotspots. Thus ‘real-time’ BOP motions and be instantly converted to ‘real-time’ stresses. However, as is outlined in this paper, the frequency content of the system response can have a significant impact on the levels of stress calculated. If frequency dependent response is not accounted for a significant under-prediction in fatigue loads may occur. The objective of this paper is to outline a detailed methodology to derive STFs for critical fatigue hotspots in the wellhead and conductor. This methodology accounts for capturing the non-linear frequency dependence of the system and incorporating this into the STFs. In addition a methodology for rapidly calculating ‘real-time’ fatigue damage accumulation in the wellhead and conductor system and presenting this data on-board is also outlined.

Short Stress State Questionnaire

2015 ◽  
Vol 31 (1) ◽  
pp. 20-30 ◽  
Author(s):  
William S. Helton ◽  
Katharina Näswall
Keyword(s):  
Stress State ◽  
Factor Structure ◽  
Human Performance ◽  
Self Report ◽  
Confirmatory Factor ◽  
Stress States ◽  
Related Stress ◽  
Using Data ◽  
Task Conditions ◽  
Multiple Samples

Conscious appraisals of stress, or stress states, are an important aspect of human performance. This article presents evidence supporting the validity and measurement characteristics of a short multidimensional self-report measure of stress state, the Short Stress State Questionnaire (SSSQ; Helton, 2004 ). The SSSQ measures task engagement, distress, and worry. A confirmatory factor analysis of the SSSQ using data pooled from multiple samples suggests the SSSQ does have a three factor structure and post-task changes are not due to changes in factor structure, but to mean level changes (state changes). In addition, the SSSQ demonstrates sensitivity to task stressors in line with hypotheses. Different task conditions elicited unique patterns of stress state on the three factors of the SSSQ in line with prior predictions. The 24-item SSSQ is a valid measure of stress state which may be useful to researchers interested in conscious appraisals of task-related stress.

scholarly journals Higher Handgrip Strength Is Linked to Better Cognitive Performance in Chinese Adults with Hypertension

2021 ◽  
Vol 11 (8) ◽  
pp. 985
Author(s):  
Shenghua Lu ◽  
Fabian Herold ◽  
Yanjie Zhang ◽  
Yuruo Lei ◽  
Arthur F. Kramer ◽  
...  
Keyword(s):  
Cognitive Performance ◽  
Short Term Memory ◽  
Handgrip Strength ◽  
Adult Health ◽  
Linear Regression Models ◽  
Chinese Adults ◽  
Short Term ◽  
Term Memory ◽  
Using Data ◽  
The Relationship

Objective: There is growing evidence that in adults, higher levels of handgrip strength (HGS) are linked to better cognitive performance. However, the relationship between HGS and cognitive performance has not been sufficiently investigated in special cohorts, such as individuals with hypertension who have an intrinsically higher risk of cognitive decline. Thus, the purpose of this study was to examine the relationship between HGS and cognitive performance in adults with hypertension using data from the Global Ageing and Adult Health Survey (SAGE). Methods: A total of 4486 Chinese adults with hypertension from the SAGE were included in this study. Absolute handgrip strength (aHGS in kilograms) was measured using a handheld electronic dynamometer, and cognitive performance was assessed in the domains of short-term memory, delayed memory, and language ability. Multiple linear regression models were fitted to examine the association between relative handgrip strength (rHGS; aHGS divided by body mass index) and measures of cognitive performance. Results: Overall, higher levels of rHGS were associated with higher scores in short-term memory (β = 0.20) and language (β = 0.63) compared with the lowest tertiles of rHGS. In male participants, higher HGS was associated with higher scores in short-term memory (β = 0.31), language (β = 0.64), and delayed memory (β = 0.22). There were no associations between rHGS and cognitive performance measures in females. Conclusion: We observed that a higher level of rHGS was associated with better cognitive performance among hypertensive male individuals. Further studies are needed to investigate the neurobiological mechanisms, including sex-specific differences driving the relationship between measures of HGS and cognitive performance in individuals with hypertension.

scholarly journals Long-Term Development of Urban Agriculture: Resilience and Sustainability of Farmers Facing the Covid-19 Pandemic in Japan

2021 ◽  
Vol 13 (8) ◽  
pp. 4316
Author(s):  
Shingo Yoshida ◽  
Hironori Yagi
Keyword(s):  
Urban Agriculture ◽  
Food Systems ◽  
Direct Marketing ◽  
Farming System ◽  
Long Term Effects ◽  
Short Term ◽  
Short Supply ◽  
Using Data ◽  
Urban People

The coronavirus disease 2019 (Covid-19) pandemic has forced global food systems to face unprecedented uncertain shocks even in terms of human health. Urban agriculture is expected to be more resilient because of its short supply chain for urban people and diversified farming activities. However, the short-and long-term effects of the Covid-19 pandemic on urban farms remain unclear. This study aims to reveal the conditions for farm resilience to the Covid-19 pandemic in 2020 and the relationship between short-term farm resilience and long-term farm development using data from a survey of 74 farms located in Tokyo. The results are as follows. First, more than half of the sample farms increased their farm sales during this period. This resilience can be called the “persistence” approach. Second, short-term farm resilience and other sustainable farm activities contributed to improving farmers’ intentions for long-term farm development and farmland preservation. Third, the most important resilience attributes were the direct marketing, entrepreneurship, and social networks of farmers. We discussed the necessity of building farmers’ transformative capabilities for a more resilient urban farming system. These results imply that support to enhance the short-term resilience of urban farms is worth more than the short-term profit of the farms.

Determinants of Treasury-LIBOR Swap Spreads

2005 ◽  
Vol 08 (04) ◽  
pp. 687-705 ◽  
Author(s):  
D. K. Malhotra ◽  
Vivek Bhargava ◽  
Mukesh Chaudhry
Keyword(s):  
Interest Rate ◽  
Interest Rates ◽  
Default Risk ◽  
Yield Curve ◽  
Short Term ◽  
Long Run ◽  
Interest Rate Volatility ◽  
Short Run ◽  
Using Data ◽  
Swap Spreads

Using data from the Treasury versus London Interbank Offer Swap Rates (LIBOR) for October 1987 to June 1998, this paper examines the determinants of swap spreads in the Treasury-LIBOR interest rate swap market. This study hypothesizes Treasury-LIBOR swap spreads as a function of the Treasury rate of comparable maturity, the slope of the yield curve, the volatility of short-term interest rates, a proxy for default risk, and liquidity in the swap market. The study finds that, in the long-run, swap spreads are negatively related to the yield curve slope and liquidity in the swap market. We also find that swap spreads are positively related to the short-term interest rate volatility. In the short-run, swap market's response to higher default risk seems to be higher spread between the bid and offer rates.

scholarly journals Studies of the Movement of Coastal Sea Ice Near Prudhoe Bay, Alaska, U.S.A.

1977 ◽  
Vol 19 (81) ◽  
pp. 533-546 ◽  
Author(s):  
W. F. Weeks ◽  
A. Kovacs ◽  
S. J. Mock ◽  
W. B. Tucker ◽  
W. D. Hibler ◽  
...  
Keyword(s):  
Prediction Models ◽  
Stress Transfer ◽  
Short Term ◽  
Laser Measurements ◽  
A Value ◽  
Pack Ice ◽  
Ice Drift ◽  
Coastal Sea ◽  
Fast Ice ◽  
Prudhoe Bay

Abstract During March-May 1976, a combination of laser and radar ranging systems was used to study the motion of both the fast ice and the pack ice near Narwhal and Cross Islands, two barrier islands located 16 and 21 km offshore in the vicinity of Prudhoe Bay, Alaska. Laser measurements of targets on the fast ice near Narwhal Island indicate small net displacements of approximately 1 m over the period of study (71 d) with short-term displacements of up to 40 cm occurring over 3 d periods. The main motion was outward normal to the coast and was believed to be the result of thermal expansion of the ice. The radar records of fast-ice sites farther offshore show a systematic increase in the standard deviation of the displacements as measured parallel to the coast, reaching a value of ±6.6 m at 31 km. The farthest fast-ice sites show short-term displacements of up to 12 m. There are also trends in the records that are believed to be the result of the general warming of the fast ice with time. Radar targets located on the pack ice showed large short-term displacements (up to 2.7 km) but negligible net ice drift along the coast. There was no significant correlation between the movement of the pack and the local wind, suggesting that coastal ice prediction models can only succeed if handled as part of a regional model which incorporates stress transfer through the pack. The apparent fast-ice-pack-ice boundary in the study area was located in 30-35 m of water.

scholarly journals Sex ratio effects on reproductive strategies in humans

2015 ◽  
Vol 2 (1) ◽  
pp. 140402 ◽  
Author(s):  
Ryan Schacht ◽  
Monique Borgerhoff Mulder
Keyword(s):  
Sexual Selection ◽  
Sex Ratio ◽  
Ethnic Group ◽  
Reproductive Strategies ◽  
Situational Factors ◽  
Male Mating ◽  
Mating Effort ◽  
Short Term ◽  
Adult Sex Ratio ◽  
Using Data

Characterizations of coy females and ardent males are rooted in models of sexual selection that are increasingly outdated. Evolutionary feedbacks can strongly influence the sex roles and subsequent patterns of sex differentiated investment in mating effort, with a key component being the adult sex ratio (ASR). Using data from eight Makushi communities of southern Guyana, characterized by varying ASRs contingent on migration, we show that even within a single ethnic group, male mating effort varies in predictable ways with the ASR. At male-biased sex ratios, men's and women's investment in mating effort are indistinguishable; only when men are in the minority are they more inclined towards short-term, low investment relationships than women. Our results support the behavioural ecological tenet that reproductive strategies are predictable and contingent on varying situational factors.

Comparison of Spar and Semisubmersible Floater Concepts of Offshore Wind Turbines Using Long-Term Analysis

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Hasan Bagbanci ◽  
D. Karmakar ◽  
C. Guedes Soares
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Transfer Functions ◽  
Probability Distributions ◽  
Offshore Wind ◽  
Short Term ◽  
Offshore Wind Turbines ◽  
Floating Wind Turbine ◽  
Offshore Floating Wind Turbine

The long-term probability distributions of a spar-type and a semisubmersible-type offshore floating wind turbine response are calculated for surge, heave, and pitch motions along with the side-to-side, fore–aft, and yaw tower base bending moments. The transfer functions for surge, heave, and pitch motions for both spar-type and semisubmersible-type floaters are obtained using the fast code and the results are also compared with the results obtained in an experimental study. The long-term predictions of the most probable maximum values of motion amplitudes are used for design purposes, so as to guarantee the safety of the floating wind turbines against overturning in high waves and wind speed. The long-term distribution is carried out using North Atlantic wave data and the short-term floating wind turbine responses are represented using Rayleigh distributions. The transfer functions are used in the procedure to calculate the variances of the short-term responses. The results obtained for both spar-type and semisubmersible-type offshore floating wind turbine are compared, and the study will be helpful in the assessments of the long-term availability and economic performance of the spar-type and semisubmersible-type offshore floating wind turbine.

scholarly journals Modeling the Peach Sugar Contents in Relation to Fruit Growth

1996 ◽  
Vol 121 (6) ◽  
pp. 1122-1131 ◽  
Author(s):  
Michel Génard ◽  
Michel Souty
Keyword(s):  
Growth Curve ◽  
Prunus Persica ◽  
Transfer Functions ◽  
Dry Weight ◽  
Fruit Growth ◽  
Data Sets ◽  
Weight Growth ◽  
Using Data ◽  
Good Agreement

The edible quality of peaches (Prunus persica L. Batsch) to a great extent depends on their sweetness, which is related to sugar composition. Our objective was to develop a model to predict carbon partitioning within fruit flesh and to predict the sucrose, sorbitol, glucose, and fructose contents. The model is dynamic and deterministic and was designed to be driven by the flesh dry-weight growth curve, flesh water content, and temperature data. It uses differential equations where the state of the system is defined by variables that describe how much carbon is present as each form of sugar and as other compounds (acids and structural carbohydrates). The rates of change of these amounts of carbon depend on the current values of corresponding variables and on the transfer functions between them. These functions are defined by rate constants or by functions of degree-days after full bloom. The model was calibrated and tested using data sets from treatments that covered several leaf: fruit ratios. The predictions of the model were in fairly good agreement with experimental data. A sensitivity analysis was performed to identify the most influential transfer function parameters. Carbon flows between sugar forms were analyzed. Sucrose, which was the most abundant sugar, and fructose, which is the sweetest, contributed most to fruit sweetness. Simulations were performed to study the effects of changes in fruit growth-curve parameters on sugar contents and concentrations.

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