bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns of tree diversity and composition in Amazonian floodplain paleo‐várzea forest
Authors: Assis Rafael L. , Haugaasen Torbjørn , Schöngart Jochen , Montero Juan C. , Piedade Maria T.F. , Wittmann Florian
Published: September 2014

Question

In a recent re‐classification of Amazonian floodplain types, a new category was established for paleo‐várzea. Although the geological basis for this classification is sound, a key question is whether it can be supported by botanical criteria, where floodplain paleo‐várzea forests contain distinct tree assemblages compared to other major floodplain types.

Location

Central Amazonian floodplains, Brazil.

Methods

We used 41 tree inventories from floodplain paleo‐várzea, várzea and igapó forests to perform a meta‐analysis. Diversity and richness estimators were applied at the level of genus and the examination of floristic composition was performed at family and generic levels. Generic composition across the three floodplain types was investigated using GNMDS and cluster analysis. Similarity coefficients and ANOSIM were applied to quantify floristic resemblance at the generic level between forest types. Indicator species analysis (ISA) was used to identify any indicator genera for the forest types evaluated.

Results

Alpha diversity and generic richness in paleo‐várzea forest was similar to várzea. Igapó forest was clearly the least diverse. Family composition was similar across the three forest types; Fabaceae was the dominant family on all three floodplains. Pouteria, Licania and Eschweilera presented the highest importance values in paleo‐várzea, but these genera were also important in várzea and igapó. Nevertheless, ANOSIM analyses show that generic composition differed significantly between the three forest types, and a GNMDS ordination and cluster analysis portrays paleo‐várzea tree composition as intermediate between várzea and igapó. ISA revealed that Euterpe, Dipteryx and Goupia were the most important indicator genera of paleo‐várzea.

Conclusions

We conclude that paleo‐várzea floodplain tree assemblages are dissimilar to those of várzea and igapó, but contain components typical of both these floodplain types, explaining their intermediate positioning in our analyses. This floral mix probably allows paleo‐várzea alpha diversity to be similar to that of várzea.
Candida nivariensis in comparison to different phenotypes of Candida glabrata
Authors: Swoboda‐Kopeć Ewa , Sikora Magdalena , Golas Marlena , Piskorska Katarzyna , Gozdowski Dariusz , Netsvyetayeva Irina
Published: September 2014

The purpose of the study was to establish the prevalence of new Candida glabrata complex species: Candida nivariensis and Candida bracarensis isolated from clinical material, evaluate their phenotypes and the prevalence of gene family encoding extracellular glycosylphosphatidylinositol‐linked aspartyl proteases, crucial for C. glabrata virulence. Study material included 224 C. glabrata clinical strains. Candida glabrata phenotypes were identified using CHROMagar Candida medium. Strains were analysed by using C. glabrata‐specific PCR for the internal transcribed spacer region to confirmed the identification. To identify C. nivariensis and C. bracarensis strains, the D1/D2 region of 26S rRNA was sequenced. The prevalence of YPS‐family proteases genes was detected using standard PCR method. Candida nivariensis amounted about 6% among the total number of C. glabrata strains. Candida nivariensis strains had a white phenotype on chromogenic agar media and assimilated two sugars – trehalose and glucose. Among the 13 C. nivariensis strains, 10 did not present any YPS‐family protease genes. Coexistence of all detected YPS‐family protease genes was specific for C. glabrata species. This study identified C. nivariensis strains; however, no C. bracarensis strains were identified. The white phenotype of C. nivariensis was confirmed. Most strains of the new species do not present any of the tested YPS genes.
Free to Be Human: Thomas Aquinas's Discussion of Liberum Arbitrium
Authors: Mitchell Louise A.
Published: September 2014

Thomas Aquinas's use of the terms libero, libertas, and liberum arbitrium in the Summa theologiae gives us a wealth of information about free will and freedom. Human beings have free will and are masters of themselves through their free will. Free will can be impeded by obstacles or ignorance but naturally moves toward God. According to Servais Pinckaers, our freedom can be that of indifference (the morality of obligation) or that of excellence (the morality of happiness). The difference is that of free will moving reason versus reason moving free will. The freedom of indifference is the power to choose between good and evil. The will is inclined toward neither and freely chooses between them. The freedom for excellence is the power to be the best human being we can be. Here the rules, or what makes for a good human being, are the grounding for freedom. One who observes these rules has the freedom to become excellent. According to Aquinas, intellect and will have command over free will. This then is true freedom, and on this Aquinas and Pinckaers agree. We do not have freedom of indifference, we have freedom for excellence. Anything else makes us slaves.
Infection by a foliar endophyte elicits novel arabidopside‐based plant defence reactions in its host, Cirsium arvense
Authors: Hartley Susan E. , Eschen Rene , Horwood Julia M. , Gange Alan C. , Hill Elizabeth M.
Published: September 2014

Endophytic fungi live asymptomatically within plants. They are usually regarded as nonpathogenic or even mutualistic, but whether plants respond antagonistically to their presence remains unclear, particularly in the little‐studied associations between endophytes and nongraminoid herbaceous plants.

We investigated the effects of the endophyte Chaetomium cochlioides on leaf chemistry in Cirsium arvense. Plants were sprayed with spores; leaf material from both subsequent new growth and the sprayed leaves was analysed 2 wk later. Infection frequency was 91% and 63% for sprayed and new growth, respectively, indicating that C. cochlioides rapidly infects new foliage.

Metabolomic analyses revealed marked changes in leaf chemistry with infection, especially in new growth. Changes in several novel oxylipin metabolites were detected, including arabidopsides reported here for the first time in a plant species other than Arabidopsis thaliana, and a jasmonate‐containing galactolipid.

The production of these metabolites in response to endophyte presence, particularly in newly infected foliage, suggests that endophytes elicit similar chemical responses in plants to those usually produced following wounding, herbivory and pathogen invasion. Whether endophytes benefit their hosts may depend on a complex series of chemically mediated interactions between the plant, the endophyte, other microbial colonists and natural enemies.
A systematic review of behavioural techniques used in nutrition and weight loss interventions among adults with mobility‐impairing neurological and musculoskeletal conditions
Authors: Plow M. A. , Moore S. , Husni M. Elaine , Kirwan J. P.
Published: September 2014

Obesity is a common comorbidity in adults with mobility‐impairing neurological and musculoskeletal conditions, such as stroke and arthritis. The interaction between mobility impairments and environmental factors often compromises motivation and ability to engage in healthy behaviours. Such difficulties to engage in healthy behaviours can result in energy imbalance, weight gain and a cycle of functional declines; i.e. obesity can exacerbate mobility impairments and symptoms and increase the likelihood of other comorbid conditions, all of which make it more difficult to engage in healthy behaviours. To help disrupt this cycle, there is a need to identify strategies to optimize energy balance. Thus, this review summarizes clinical trials of nutrition and weight loss interventions in adults with mobility‐impairing conditions. Although adults with osteoarthritis were represented in large rigorous clinical trials, adults with neurological conditions were typically represented in studies characterized by a small number of participants, a short‐term follow‐up and high attrition rates. Studies varied greatly in outcome measures, description and implementation of the interventions, and the strategies used to promote behaviour change. Nutrition and weight loss research in adults with mobility‐impairing conditions is still in its formative stages, and there is a substantial need to conduct randomized controlled trials.
Anesthesia‐related neurotoxicity and the developing animal brain is not a significant problem in children
Authors: Hansen Tom G.
Published: September 2014

A multitude of animal studies have shown that virtually all general anesthetics used in clinical practice possibly during a vulnerable period of brain development (i.e., brain growth spurt, peak of synaptogenesis) may lead to neurodegeneration (particularly apoptosis) and abnormal synaptic development with functional deficits in learning and behavior later in life. Initial studies were mainly performed in immature rodent pups, but more recent studies have included nonhumans primates (rhesus monkeys). Given the number of neonates, infants, and young children anesthetized annually worldwide, these findings could have significant public health implications. So far, relatively few human (cohort) studies focusing on this topic have been published with inconsistent results. While some studies have indicated an association between exposure to anesthesia and surgery, other studies have indicated no such association. Prospective studies are underway, but the result will not be available for several years. This paper reviews some of the preclinical background behind anesthesia‐related neurotoxicity but focuses mainly on the human studies so far. It is concluded that although disturbing, the animal data lack verification in humans. Fortunately, the humans studies performed so far have been unable to confirm these animal data. A single brief anesthetic seems safe in infants. Multiple anesthetic and surgical exposures on the other hand are different. But there may be other reasons for this than merely the anesthetics. Currently, there is no need to change current anesthetic clinical practice or to postpone or cancel truly urgent surgeries in young children.
Opsin Expression in Human Epidermal Skin
Authors: Haltaufderhyde Kirk , Ozdeslik Rana N. , Wicks Nadine L. , Najera Julia A. , Oancea Elena
Published: September 2014

Human skin is constantly exposed to solar light containing visible and ultraviolet radiation (UVR), a powerful skin carcinogen. UVR elicits cellular responses in epidermal cells via several mechanisms: direct absorption of short‐wavelength UVR photons by DNA, oxidative damage caused by long‐wavelength UVR, and, as we recently demonstrated, via a retinal‐dependent G protein‐coupled signaling pathway. Because the human epidermis is exposed to a wide range of light wavelengths, we investigated whether opsins, light‐activated receptors that mediate photoreception in the eye, are expressed in epidermal skin to potentially serve as photosensors. Here we show that four opsins—OPN1‐SW, OPN2, OPN3 and OPN5—are expressed in the two major human epidermal cell types, melanocytes and keratinocytes, and the mRNA expression profile of these opsins does not change in response to physiological UVR doses. We detected two OPN3 splice variants present in similar amounts in both cell types and three OPN5 splice isoforms, two of which encode truncated proteins. Notably, OPN2 and OPN3 mRNA were significantly more abundant than other opsins and encoded full‐length proteins. Our results demonstrate that opsins are expressed in epidermal skin cells and suggest that they might initiate light–induced signaling pathways, possibly contributing to UVR phototransduction.
Service Systems with Experience‐Based Anecdotal Reasoning Customers
Authors: Huang Tingliang , Chen Ying‐Ju
Published: September 2014

The existing queueing literature typically assumes that customers either perfectly know the expected waiting time or are able to form rational expectations about it. In contrast, in this article, we study canonical service models where customers do not have such full information or capability. We assume that customers lack full capability or ample opportunities to perfectly infer the service rate or estimate the expected waiting time, and thus can only rely on past experiences and anecdotal reasoning to make their joining decisions. We fully characterize the steady‐state equilibrium in this service system. Compared with the fully rational benchmark, we find that customers with anecdotal reasoning are less price‐sensitive. Consequently, with a higher market potential (higher arrival rate), a revenue‐maximizing firm may increase the price if the service rate is exogenous, and it may decrease the price if the service rate is at the firm's discretion. Both results go against the commonly accepted pricing recommendations in the fully rational benchmark. We also show that revenue maximization and welfare maximization lead to fundamentally different pricing strategies with anecdotal reasoning, whereas they are equivalent in the fully rational benchmark.
Split‐Award Procurement Auctions—Can Bayesian Equilibrium Strategies Predict Human Bidding Behavior in Multi‐Object Auctions?
Authors: Bichler Martin , Guler Kemal , Mayer Stefan
Published: September 2014

We analyze if and when symmetric Bayes Nash equilibrium predictions can explain human bidding behavior in multi‐object auctions. We focus on two sealed‐bid split‐award auctions with ex ante split decisions as they can be regularly found in procurement practice. These auction formats are straightforward multi‐object extensions of the first‐price sealed‐bid auction. We derive the risk‐neutral symmetric Bayes Nash equilibrium strategies and find that, although the two auction mechanisms yield the same expected costs to the buyer, other aspects of the two models, including the equilibrium bidding strategies, differ significantly. The strategic considerations in these auction formats are more involved than in single‐lot first‐price sealed‐bid auctions, and it is questionable whether expected utility maximization can explain human bidding behavior in such multi‐object auctions. Therefore, we analyzed the predictive accuracy of our equilibrium strategies in the laboratory. In human subject experiments we found underbidding, which is in line with earlier experiments on single‐lot first‐price sealed‐bid auctions. To control for regret, we organize experiments against computerized bidders, who play the equilibrium strategy. In computerized experiments where bid functions are only used in a single auction, we found significant underbidding on low‐cost draws. In experiments where the bid function is reused in 100 auctions, we could also control effectively for risk aversion, and there is no significant difference of the average bidding behavior and the risk‐neutral Bayes Nash equilibrium bid function. The results suggest that strategic complexity does not serve as an explanation for underbidding in split‐award procurement auctions, but risk aversion does have a significant impact.
An Integrated Text Analytic Framework for Product Defect Discovery
Authors: Abrahams Alan S. , Fan Weiguo , Wang G. Alan , Zhang Zhongju (John) , Jiao Jian
Published: September 2014

The recent surge in the usage of social media has created an enormous amount of user‐generated content (UGC). While there are streams of research that seek to mine UGC, these research studies seldom tackle analysis of this textual content from a quality management perspective. In this study, we synthesize existing research studies on text mining and propose an integrated text analytic framework for product defect discovery. The framework effectively leverages rich social media content and quantifies the text using various automatically extracted signal cues. These extracted signal cues can then be used as modeling inputs for product defect discovery. We showcase the usefulness of the framework by performing product defect discovery using UGC in both the automotive and the consumer electronics domains. We use principal component analysis and logistic regression to produce a multivariate explanatory analysis relating defects to quantitative measures derived from text. For our samples, we find that a selection of distinctive terms, product features, and semantic factors are strong indicators of defects, whereas stylistic, social, and sentiment features are not. For high sales volume products, we demonstrate that significant corporate value is derivable from a reduction in defect discovery time and consequently defective product units in circulation.
Fairness Among Servers When Capacity Decisions Are Endogenous
Authors: Geng Xin , Huh Woonghee Tim , Nagarajan Mahesh
Published: September 2014

We look at a simple service system with two servers serving arriving jobs (single class). Our interest is in examining the effect of routing policies on servers when they care about fairness among themselves, and when they can endogenously choose capacities in response to the routing policy. Therefore, we study the two‐server game where the servers’ objective functions have a term explicitly modeling fairness. Moreover, we focus on four commonly seen policies that are from one general class. Theoretical results concerning the existence and uniqueness of the Nash equilibrium are proved for some policies. Further managerial insights are given based on simulation studies on servers’ equilibrium/off‐equilibrium behaviors and the resulting system efficiency performance under different policies.
Characterization of mating type (MAT) alleles differentiated by a natural inversion in Sclerotinia minor
Authors: Chitrampalam P. , Pryor B. M.
Published: September 2014

A recent study on fungal mating type genes revealed two MAT alleles within homothallic Sclerotinia sclerotiorum differentiated by an inversion, Inv− (inversion negative) and Inv+ (inversion positive). An analysis of mating type in closely related S. minor was conducted to shed light on the evolution of this MAT inversion. Inv− and Inv+ MAT alleles were identified in S. minor and were characterized. Both MAT alleles in S. minor were flanked by APN2 and SLA2, and consisted of two idiomorphs fused as in other homothallic ascomycetes. However, in the Inv+ MAT, the 3·6 kb MAT region was inverted relative to the Inv− MAT. Except for the inversion, both Inv− and Inv+ MAT in S. minor were equal in size and identical in nucleotide sequence. The MAT inversion in Inv+ S. minor was at exactly the same place as in Inv+ S. sclerotiorum and affected three of four MAT genes: MAT1‐1‐1 was truncated and MAT1‐2‐4 and MAT1‐2‐1 were inverted. Unlike S. sclerotiorum, expression of MAT genes did not differ between Inv− and Inv+ S. minor. The 250 bp inverted repeat motif that flanked the inverted MAT region in S. sclerotiorum and believed responsible for the MAT inversion was also found in S. minor, but was 256 bp. Depending on the MAT genes, 93–96% nucleotide identity was observed between Sclerotinia species. Both Inv+ and Inv− MAT S. minor and S. sclerotiorum isolates were commonly found in lettuce fields of Arizona along with MAT heterokaryons.
Small Area Estimation of Labour Force Indicators Under a Multinomial Model with Correlated Time and Area Effects
Authors: López-Vizcaíno Esther , Lombardía María José , Morales Domingo
Published: September 2014

The aim of the paper is the estimation of small area labour force indicators like totals of employed and unemployed people and unemployment rates. Small area estimators of these quantities are derived from four multinomial logit mixed models, including a model with correlated time and area random effects. Mean-squared errors are used to measure the accuracy of the estimators proposed and they are estimated by analytic and bootstrap methods. The methodology introduced is applied to real data from the Spanish Labour Force Survey of Galicia.
Climatic fluctuations and orogenesis as motors for speciation in East Africa: case study on ParepistaurusKarsch, 1896 (Orthoptera)
Authors: HEMP CLAUDIA , KEHL SIEGFRIED , SCHULTZ OLIVER , WÄGELE JOHANN W. , HEMP ANDREAS
Published: September 2014

Mechanisms of speciation of flightless grasshoppers in mountainous and coastal East Africa are inferred considering (i) phylogenies estimated with a combination of molecular markers (16S rRNA locus, COI and H3), (ii) ecological data and (iii) the geographic distribution of Parepistaurus species. The study suggests that coastal taxa of Parepistaurus belong to ancestral lineages from which evolved the high diversity of species found in the Eastern Arc Mountains of Tanzania and Kenya, which are geologically ancient mountain formations. Network analyses and a molecular clock approach, calibrated with the geological age of the volcanoes, suggested that speciation was boosted by climatic fluctuations affecting large areas of East Africa. With the aridification beginning 2.8 Ma, forest taxa were isolated due to forest fragmentation and populations were separated by extended grasslands, which are avoided by Parepistaurus species. However, a humid period between 2.7 and 2.5 Ma triggered a spread of coastal taxa along the Eastern Arc Mountains. Forests expanded again and riparian vegetation along rivers draining into the Indian Ocean probably served as corridors for the dispersal of coastal taxa to the hinterland. The inland volcanoes such as Mount Kilimanjaro are therefore good time markers because their geological age is known, limiting the available time for speciation processes of mountainous Parepistaurus in the area to a maximum of about 1–2 Ma. A third humid but cold period between 1.1 and 0.9 Ma probably further boosted the spread of several flightless and montane‐adapted Orthoptera taxa.
Faculty Perception of the Effectiveness of EBP Courses for Graduate Nursing Students
Authors: Zeleníková Renáta , Beach Michael , Ren Dianxu , Wolff Emily , Sherwood Paula
Published: September 2014

Background

Effective teaching is key in preparing students to become successful evidence‐based healthcare professionals. The effectiveness of graduate evidence‐based practice (EBP) pedagogy is not often a subject of research studies.

Purpose

The purpose of this study was to determine how faculty from the 50 top graduate nursing schools in the United States perceived the effectiveness of EBP courses for graduate nursing students.

Methods

A descriptive cross‐sectional design was used to explore faculty perception of the effectiveness of EBP courses. A web‐based survey was used for data collection. A total of 45 questionnaires were subjected to statistical analysis.

Results

The mean perception of the effectiveness of EBP courses for the whole sample, on a scale from 1 to 7, was 5.58 (min. 4.29; max. 6.73), a higher score signifying higher perceived effectiveness. The highest rated item concerned a school's access to different databases. The strongest correlations were found between the total score and the scores for items describing students’ opportunities to strengthen and apply their EBP skills (rs = .66). The internal consistency of the Perception of Effectiveness of EBP Courses scale, based on standardized Cronbach's alpha, was .84, which signifies strong internal consistency. Faculty perceived themselves as most competent at the following EBP skills: (a) “Asking questions regarding patients’ care” (6.56), (b) “Considering patient preferences when implementing EBP” (6.40), and (c) “Critically appraising the relevant body of evidence to address clinical questions” (6.40).

Discussion

To strengthen the effectiveness of EBP courses, students should have more opportunities to implement their EBP knowledge and skills after completing EBP courses.

Linking Evidence to Action

Evaluation of faculty perceptions of the effectiveness of EBP courses can help to guide the development of nursing school curricula that better integrate EBP. Further evaluation of the psychometric properties of the instrument used to measure perception of the effectiveness of EBP courses is required along with objective measures of faculty knowledge and skills in teaching EBP.
An Evaluation of the Semi-Coupled Scheme for the Analysis of Floating Production Systems
Authors: Cruces Girón Aldo Roberto , Nogueira Corrêa Fabrício , Pinheiro Jacob Breno
Published: September 2014

Analysis techniques and numerical formulations are available in a variety for mooring and riser designers. They are applied in the different stages of the design processes of floating production systems (FPS) by taking advantage of both the accuracy of results and the computational costs. In early design stages, the low computational cost is more valued with the aim of obtaining fast results and taking decisions. So in these stages it is common to use uncoupled analysis. On the other hand, in more advanced design stages, the accuracy of results is more valued, for which the use of coupled analysis is adequate. However, it can lead to excessive computing times.

To overcome such high computational costs, new formulations have been proposed with the aim of obtaining results similar to a coupled analysis, but with low computational costs. One of these formulations is referred as the semi-coupled scheme (S-C). Its main characteristic is that it combines the advantages of uncoupled and coupled analysis techniques. In this way, analyses can be performed with very fast execution times and results are superior to those obtained by the classical uncoupled analysis.

This work presents an evaluation of the S-C scheme. The evaluation is made by comparing their results with the results of coupled analyses. Both type of analysis were applied in a representative deep water platform. The results show that the S-C scheme have the potentially to provide results with appropriate precision with very low computational times. In this way, the S-C scheme represents an attractive procedure to be applied in early and intermediate stages of the design process of FPS.
Hyperbaric Testing of an Alternative Approach to Remove Carbon Dioxide From Underwater Life Support Equipment
Authors: Nuckols M. , Kolaczkowski S. , Awdry S. , Smith T. , Thomas D.
Published: September 2014

Traditional CO2 absorption methods for underwater life support equipment use alkali metal hydroxide chemical beds — mostly calcium hydroxide — that have been shown to have poor absorption efficiencies at cold temperatures, and must be replaced at considerable trouble and expense on a frequent basis. With chemical utilizations as low as 20% in water temperatures of 2°C, these hydroxides do not lend themselves to applications requiring extended durations in cold water due to the inability to carry sufficient quantities of expendables. A joint research effort between Duke University and the University of Bath has verified the feasibility in laboratory trials of an alternative carbon dioxide removal method that intimately mixes seawater with breathing circuit gases within a packed bed of Dixon rings. Based on the results of these laboratory trials, two multi-path scrubber prototypes were designed and fabricated for unmanned testing. In March 2013, the hyperbaric performance of these prototype scrubbers was characterized over a wide range of gas and water flow rates when operating the scrubbers in counter-current (water flowing in the opposite direction as gas flow) and co-current (water flowing in the same direction as gas flow) fashion. Significant findings from these tests included the following:

• Both scrubber prototypes were found to be capable of delivering exit CO2 levels below 0.5 vol% (surface equivalent) at respiratory rates up to 22.5 liters per minute and at depths ranging from 0 to 40 meters of seawater (MSW).

• Negligible collateral O2 absorption was observed at surface pressure (exit O2 levels were typically above 20.2 vol%), and exit O2 levels were typically above 18.4% during testing at 10 MSW.

• At surface pressure, both prototypes had significantly lower breathing resistances than design goals established by the U. S. Navy.
On the Tidal Stream Resource of Two Headland Sites in the English Channel: Portland Bill and Isle of Wight
Authors: Adcock Thomas A. A. , Draper Scott
Published: September 2014

There are various candidate sites for tidal stream energy extraction in the English Channel. In this paper we examine the tidal stream resource at Portland Bill and the south coast of the Isle of Wight. A depth-averaged numerical model is developed and compared to field measurements. The presence of rows of tidal turbines is simulated using a line-discontinuity to represent the head loss across the turbines. The head loss is given by linear momentum actuator disc theory. At each site the length of the turbine rows, the local blockage ratio, and the location of the turbines are varied. For Portland Bill the presence of an array with multiple rows of turbines is also considered. We find that it is likely that (based purely on the hydrodynamics) power could viably be extracted at each site, with the mean power produced by each site being in the order of 10s MW.
Advantages of Using a Time-Domain Approach for Dynamic Positioning (DP) Pipelay Studies
Authors: Armaoğlu Evren , Monti Paolo
Published: September 2014

Normally, the DP capability of a vessel is calculated through the use of static force equilibrium programs in which the dynamic effects are either not taken into account or taken into account by empirical load amplification factors. However, competitive and safe S-laying of large diameter pipelines in deep waters lead to large and long pipe lay vessels for which DP requirements are demanding. The power/propulsion requirement of the vessel needs to be considered from an early stage especially when accounting for the pipe laying equipment demands. This imposes a need for detailed dynamic analysis of the lay vessel. This analysis needs to include the slow drift oscillations counteracted by DP and the analysis in entirety needs to ensure the pipe string integrity is maintained.

To this purpose Saipem developed in-house a time-domain simulator (FIPLA – Fully Integrated Pipe LAying) that employs all environmental forces (i.e. wind, wave, current) as well as the pipe tension on the vessel. It is used to assess the DP performances and laying capabilities of pipe lay vessels in harsh dynamic environments as well as critical areas for operations. The software can also be used to assess the performance of the vessel in case of failure of thrusters, power generators or bus bars, study DP Control System improvements, and assess the interaction between vessel, tensioner and pipe in deep and shallow waters.

This paper focuses on the advantages of using dynamic simulations as an enhancement to the static DP capability charts, to produce detailed information for the DP Operator (DPO) in terms of setting of the DP parameters and to analyze critical laying events. This information can be used together with the weather forecast and can help getting the best performance out of the DP system in harsh environments, reducing downtime, improving operability and ensuring a safe operation.
Monohull Dynamics During Heavy Lift
Authors: Vu Khac Kien , Zhang Yang , Deng Xiaofang , Yang Zhibin
Published: September 2014

The dynamics of offshore heavy lift remains complex due to the interaction between the monohull construction vessel and the lifting object under the challenging environmental loads. This system becomes even more difficult to judge by common sense as the lifting weight offshore is usually above the motion reference point (the center of flotation of vessel), which makes the coupled system more unstable than the vessel without the lifting weight. This study proposes an analytical formula using the double pendulum, based on the Euler-Lagrangian equations, to explore the insight of the heavy lift dynamics. The effect of initial lifting condition is investigated to explain different possible outcomes for lifting similar weights. A range of vessel stiffness (GM), lifting heights and weights are considered in the parametric study for a better understanding of the coupled dynamic behaviour. While such analytical model is convenient for the understanding of the system mechanism, it is difficult to capture the effect from the wave loading. Therefore numerical models are used for this purpose. A comparison between the analytical model and the numerical model, performed in the frequency domain, evaluates the quality of ship motion response analysis performed by the numerical model. Results of these works will be useful in development of offshore crane curves for heavy lift offshore.

Apart from the theoretical formulation, several real time ship instrumentation records including the ship motion and the crane hook load have been collected and investigated in this paper. The offshore instrumentation records provide a valuable benchmark to calibrate the numerical model or to accumulate “experience” for future projects. Challenges in such process are depicted and possible solutions are discussed. To make the comparison a fair “apple to apple”, the major difficulty arises from the “unknown” environment itself, where wave is not always measured and operation relies heavily on weather forecast and “experience”. There are also limitations in offshore measurement itself. Possibility of using the ship motion as the indicator is explored for decision making (to lift or not to lift). The paper develops a practical approach for obtaining reasonable numerical results in the engineering office and investigates scientifically sound interpretation of the ship motion time history onboard towards a safe offshore heavy lift.
Prediction of Irregular Motions of Free-Fall Lifeboats During Drops From Damaged FPSO
Authors: Tregde Vidar , Nestegård Arne
Published: September 2014

A Free Fall Lifeboat (FFLB) which is evacuating from a damaged host in storm conditions must to be able to safely run away from the host. For a safe evacuation, the FFLB must first of all avoid irregular motion (“log dive”), and secondly resurface at a sufficient distance away from host (headway) to be able to run away. The design standard [1] requires a controlled motion trajectory for the FFLB in waves.

A drop simulator for random drops of FFLBs from a floating host in storm conditions, intact or damaged has been developed. Time histories of the host motions are generated and random drops of the FFLBs are done during three hour duration of each sea state. The FFLB point of impact in the wave is identified and the local wave height, wave length and hit point in the wave cycle is found for each of the impact points.

A structured database with results from a large number of Computational Fluid Dynamics (CFD) simulations has been made for a specific FFLB. In this CFD screening process the lifeboat has been dropped with variations in wind and waves, as well as varying conditions of host during launch. This database forms the basis for a regression analysis used to estimate responses for each drop of free fall lifeboat found from the drop simulator.

The present study proposes a definition and a method to identify irregular motions for FFLBs, and this definition is used as a motion indicator in the regression analysis. By using the proposed motion indicator, the regression analysis provides percentage of acceptable vs. non-acceptable motion trajectories for a given intact or damaged host during a storm condition. The worst conditions are found, and can be used for further analysis of headway, i.e. the ability of the FFLB to escape from the host after resurfacing.
Influence of the Waterline Integral on the Solution of the Frequency-Domain Forward-Speed Radiation-Diffraction Problem of a Ship Advancing in Waves
Authors: Hong D. C. , Hong S. Y. , Lee G. J. , Shin M. S.
Published: September 2014

The radiation-diffraction potential of a ship advancing in waves is studied using the three-dimensional frequency-domain forward-speed free-surface Green function (Brard 1948) and the forward-speed Green integral equation (Hong 2000). Numerical solutions are obtained by making use of a second-order inner collocation boundary element method which makes it possible to take account of the line integral along the waterline in a rigorous manner (Hong et al. 2008). The present forward-speed Green integral equation includes not only the usual free surface condition for the potential but also the adjoint free surface condition for the forward-speed free-surface Green function as indicated by Brard (1972). Comparison of the present numerical results of the heave-heave wave damping coefficients and the experimental results for the Wigley ship models I, II and III (Journee 1992) has been presented. These coefficients are compared with those calculated without taking into account of the line integral along the waterline in order to show the forward speed effect represented by the waterline integral when it is properly included in the free-surface Green integral equation. Comparison of the present numerical results and the equivalent time-domain results (Hong et al. 2013) has also been presented.
The Effect of Coverage Length and Density on the Performance of Fairings
Authors: Allen Don W. , Liapis Stergios
Published: September 2014

While the application of fairings can both increase a tubular’s fatigue life and decrease a tubular’s drag, it is not always possible or economical to fully cover a tubular with fairings. Aside from the desire to minimize the cost of VIV suppression by only covering the necessary portion of a tubular’s span, the presence of connectors, anodes, and other appurtenances can restrict the ability to install fairings over the entire tubular’s length. The result is that it is critical to understand how much of a tubular’s span should be covered with fairings and the effect of partial coverage on the overall suppression performance, and drag reduction, of the fairings system.

This paper utilizes data from a two similar test programs to examine the effects of coverage length and density on the performance of fairings. The results show that the location of the fairings has a substantial effect on both the local and global response of the tubular. In practical terms, having fairings present in the high current region can suppress VIV in both the high current and low current regions of the tubular.
Development and Application of a New Style Low Dosage Hydrate Inhibitors
Authors: Pang Weixin , Li Qingping , Sun Fujie
Published: September 2014

The hydrate is an important issue that the flow assurance has to face in the oil and gas industry, especially in the deepwater area. With high pressure and low temperature, the hydrate formation is easily happened and leads to plug in the pipeline. In addition to the traditional thermodynamic inhibitor, the low dosage hydrate inhibitors (LDHI) has been increasing used as a costly effective technology for gas hydrate control. The LDHI include kinetic hydrate inhibitor (KHI) and anti-agglomerant (AA), the former can inhibit the hydrate formation in the pipeline, and the latter can prevent the agglomeration and plug of hydrate particles. According to the properties of oil and gas of South China Sea, a new KHI and AA were developed, a field test of the KHI has been undertaken and the results indicate that it can prevent the hydrate formation and plug in the pipeline well, the lab evaluation of the developed AA is in progress and the field test will be performed by the next year.
Determination of the Effect of Second Order Motions of Moored MODU on Wellhead Fatigue
Authors: Williams Dara , Ashton Patrick
Published: September 2014

As has been noted in industry publications and conferences in the recent past the use of more modern deepwater capable 5th and 6th generation semisubmersible drilling rigs in relatively shallow water applications (when compared to design water depth) is likely to become more commonplace. Water depths of 500m or less will necessitate the use of mooring systems in order to maintain position close to the well centre whilst drilling. For fatigue assessments of moored MODUs, the current industry practice to estimate fatigue damage in the drilling riser and the wellhead, using global riser analysis techniques, is to consider both wave and VIV fatigue effects. Standard wave fatigue analysis considers two key response parameters, firstly the impact of the hydrodynamic loading on the riser joints due to drag forces, inertia and added mass effects, and secondly the effects of vessel motions on the riser system and wellhead loading. Standard practice for wave fatigue analysis is to consider only first order motion effects as described by the vessel RAO (response amplitude operator). However, for a moored MODU low frequency (100s-200s period) vessel response can have a significant impact on the overall vessel motions.

The actual response and magnitude of MODU motion will be influenced by the size and displacement of the vessel in addition to the configuration of the mooring system. First order lateral motions for a semisubmersible tend to increase as wave period is increased and therefore at lower periods first order motions can be quite low. However, the opposite can be said of wave drift forces that contribute to second order response. Although the wave drift forces are largest for lower wave periods, these low period drift forces have a significant influence on the resulting long period second order response of a moored MODU. This has important implications for drilling riser and wellhead fatigue analysis as in many cases the critical seastates for fatigue damage are low period seastates with a large number of occurrences. Thus the current global analysis techniques for fatigue calculations may lead to an underestimation of fatigue damage contribution from low period seastates.

The purpose of this paper is to present the key conclusions and findings of a study carried out in order to determine the effects of low frequency moored MODU motions on wellhead fatigue. These results are derived from a case study of a moored 6th generation semi-submersible drilling vessel in 500m water depth.
Force in the Connection Line for a Wave Energy Converter: Simulation and Measurement Experimental Setup
Authors: Hai Ling , Svensson Olle , Castellucci Valeria , Lejerskog Erik , Waters Rafael , Leijon Mats
Published: September 2014

In order to capture ocean wave energy and transform it into electric energy, Uppsala University has developed a point absorber wave energy converter (WEC) for electricity production. For a better understanding of a torus shaped buoy’s performance, this paper conducts a force analysis under linear conditions, to investigate the hydrodynamic characteristic and line force differences between the torus buoy that is going to be deployed, and two similar cylindrical buoys. The result reveals the line force from this torus buoy is roughly 5% larger than from cylindrical buoys for the most energy dense wave climate in Lysekil test site, and negative added mass phenomena won’t have a significant impact for the line force.

To measure the line force, a force measurement system has been designed. A detailed description is given on the design of the 500 kN force measurement system, and the major differences compared with former force measurement systems. Onshore test result has also been presented. With the force measurement experiment, hydrodynamic analysis for torus buoy can be validated when the system performs linearly, and extreme force for storm weather can be monitored to provide information for future WEC structure’s mechanical design.
Estimation of Storm Peak and Intra-Storm Directional-Seasonal Design Conditions in the North Sea
Authors: Feld Graham , Randell David , Wu Yanyun , Ewans Kevin , Jonathan Philip
Published: September 2014

Specification of realistic environmental design conditions for marine structures is of fundamental importance to their reliability over time. Design conditions for extreme waves and storm severities are typically estimated by extreme value analysis of time series of measured or hindcast significant wave height, HS. This analysis is complicated by two effects. Firstly, HS exhibits temporal dependence. Secondly, the characteristics of HSsp are non-stationary with respect to multiple covariates, particularly wave direction and season.

We develop directional-seasonal design values for storm peak significant wave height (HSsp) by estimation of, and simulation under a non-stationary extreme value model for HSsp. Design values for significant wave height (HS) are estimated by simulating storm trajectories of HS consistent with the simulated storm peak events. Design distributions for individual maximum wave height (Hmax) are estimated by marginalisation using the known conditional distribution for Hmax given HS. Particular attention is paid to the assessment of model bias and quantification of model parameter and design value uncertainty using bootstrap resampling. We also outline existing work on extension to estimation of maximum crest elevation and total extreme water level.
Fatigue Failure Analysis of Fillet Welded Joints Used in Offshore Structures
Authors: Ringsberg Jonas W. , Anvari Majid , Djavit Djan Eirik , Strande Erik
Published: September 2014

This paper presents a comparison made of different fatigue calculation methods used in the maritime industry today, with the aim of having a higher control of a fatigue failure site. To provide an overview of the different fatigue calculation methods, a comparison study was performed, as well as a local weld parameter study for two typical fillet welded joints. The two methods used for this study were the structural hot spot and effective notch stress method. Two fillet welded joints were provided by Aker Solutions MMO AS, Bergen, Norway. The first joint is a rectangular hollow section from a davit, built as a truss. The second model is a part of a K-joint from a semi-submersible (Aker H3 design). Both joints were analysed using fine 3D finite element models.

The two different fatigue life calculation methods yielded different fatigue lives for the weld toe, with inconclusive results regarding their conservatism which is discussed in the paper. An increased weld toe radius gave a higher fatigue life for the weld toe, while the larger weld size increased the fatigue life in the weld root. Any weld size effect regarding fatigue life in the weld toe could not be established. Based on the effective notch stress method calculations, there was an indication of weld root failure for the K-joint of the drilling unit. Fatigue life improvement methods only increasing weld toe fatigue life are not recommended based on these results.
Reynolds Averaged Navier-Stokes Computational Solution for Experimentally Generated High Velocity Bore Impact on Vertical Walls
Authors: Paczkowski K. W. , Riggs H. R. , Robertson I. N. , Kobayashi M. H.
Published: September 2014

A set of computational model tests was carried out to simulate high velocity bore impact on a vertical wall. The results were compared to a series of experimental tests conducted at the O.H. Hinsdale Wave Research Laboratory, large wave flume (LWF) at Oregon State University (OSU) [1]. Experimental tests included scaled tsunami experimental bores that traveled over a flat bottom [2]. The experimental bores were generated by solitary waves propagating over a sloping beach and breaking onto a flat reef [3]. After traveling through the reef portion, the generated bore impacted a vertical wall. In the experiments the resulting forces and pressures on the wall were measured. The aim of the study was to computationally regenerate the experimental bore flow and its impact on the vertical wall. Two computational domain setups were tested: 1) a dam break [3–8,10–16] and 2) a new approach, in which constant height and velocity water inflow was defined at the inlet to the domain. The two numerical approaches were compared to the LWF experimental data [3].