bluuebunny/crossref_metadata_2025 huggingface dataset:
Breeding and genomics status in faba bean (Vicia faba)
Authors: Maalouf Fouad , Hu Jinguo , O'Sullivan Donal M. , Zong Xuxiao , Hamwieh Aladdin , Kumar Shiv , Baum Michael
Published: September 2018

Faba bean is an important legume crop because of its high‐yield potential and nutrition‐dense grains. There have been significant achievements in faba bean improvement in the last four decades, which led to the doubling of the global yield average. This study reviews the genetic diversity, the breeding methodologies, major achievement on biotic and abiotic traits, and the recent molecular approaches. The high genetic diversity among faba bean accessions has been useful for increasing yield potential of the crop. Substantial increase in yield potential can be gained through the development of cultivars in open pollinated conditions. In the past, many faba bean varieties that are tolerant to abiotic and biotic stresses were released worldwide. The average yield gains varied from 1.65% per year in Syria to 4.17% per year in Ethiopia. The recent advances in molecular technologies will be used to develop more coherent genetic maps, which would also facilitate assembling and ordering genomic scaffolds in a future genome‐sequencing effort and molecular‐breeding approach.
Assessing variability for disease resistance and nutritional quality traits in an interspecific collection of groundnut (Arachis hypogaea)
Authors: Bera Sandip K. , Manohar Surendra S. , Variath Murali T. , Chaudhari Sunil , Yaduru Shasidhar , Thankappan Radhakrishnan , Narayana Manivannan , Kurapati Sadaiah , Pandey Manish K. , Sudini Hari K. , Shanmugavel Saravanan , Kulandaivelu Ganesamurthy , Varshney Rajeev K. , Pasupuleti Janila
Published: September 2018

Rust and late leaf spot (LLS) resistance sources involving Arachis batizocoi, A. duranensis, A. cardenasii and A. sps Manfredi‐5 were identified from field evaluation of interspecific derivatives (IDs) of groundnut in a disease nursery for two seasons. Although the sources displayed low levels of resistance compared to currently cultivated lines, they contribute allele diversity in groundnut breeding that has so far relied on alleles contributed from A. cardenasii for disease resistance. Multiple disease‐resistant and agronomically superior IDs, ICGVs 11379, 10121, 10179, 05097, 02411 and 00248 involving A. batizocoi, A. duranensis and A. cardenasii can be used in breeding for groundnut improvement. Genetic variability for resistance to rust and LLS, yield and nutritional quality traits was influenced by genotype, environment and genotype × environment interaction effects in individual and pooled analyses. In case of FAD (fatty acid desaturase)‐mutant alleles that govern high oleic trait, allele mining of IDs (110) showed that frequency of mutation in ahFAD2B is rare, whereas of ahFAD2A is common. High oleic lines were not detected among the IDs.
Selection of inbred soybean progeny (Glycine max): an approach with population effect
Authors: Volpato Leonardo , Simiqueli Guilherme Ferreira , Alves Rodrigo Silva , Rocha João Romero do Amaral Santos de Carvalho , Del Conte Murilo Viotto , Resende Marcos Deon Vilela de , Carneiro Pedro Crescêncio Souza , Silva Felipe Lopes da
Published: September 2018

To meet the growing demand of the soybean consumer market, cultivars increasingly early, productive and resistant to biotic and abiotic stress are sought. Several populations are obtained in soybean breeding programmes, but progeny are selected without being weighted for their respective population effect. As a consequence, progeny originating from high‐merit populations may be discarded too early. Given this scenario, this study proposes to employ the selection index with progeny and population effect via best linear unbiased prediction (SIPP‐BLUP) for the genetic selection of early and productive soybean progeny. A total of 180 progeny derived from three populations were evaluated for yield‐related traits. Genetic gains from selection, Spearman correlation and coincidence index were used to check the efficiency of the models with and without the population effect. The SIPP‐BLUP index achieved greater selection accuracy and was efficient in the identification and future selection of early soybean progeny. Therefore, this study demonstrates that soybean breeding programmes should consider the population effect via SIPP‐BLUP in progeny selection to obtain future lines that really contribute to genetic gain.
Lacosamide in bipolar disorder: A 30‐day comparison to a retrospective control group treated with other antiepileptics
Authors: Cuomo Ilaria , Piacentino Daria , Kotzalidis Georgios D. , Lionetto Luana , De Filippis Sergio
Published: September 2018

Aim

Bipolar disorder (BD) is often treated with anticonvulsants. Lacosamide has not been tested in BD. We assessed its effects in a hospital setting in patients with BD without epilepsy.

Methods

We treated 102 consecutive hospitalized patients with acute BD with lacosamide 50–300 mg/day. We compared this sample with a retrospective sample treated with other antiepileptics (OAE). We rated patients after 3, 7, 15, and 30 days of treatment with the Brief Psychiatric Rating Scale, Young Mania Rating Scale, Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale, Clinical Global Impressions – Severity, and Global Assessment of Functioning.

Results

Patients receiving lacosamide were significantly younger and had fewer mixed episodes at intake, and less substance use disorder comorbidity than those receiving OAE. Both groups showed positive effects on all measures. The two groups did not differ on any clinical measure at baseline, but from the 3rd day on, lacosamide patients fared better than OAE patients on the Young Mania Rating Scale and Clinical Global Impressions – Severity and worse on the Hamilton Anxiety Rating Scale. From the 15th day, OAE patients scored better on the Brief Psychiatric Rating Scale. Global Assessment of Functioning scores were significantly more improved in the lacosamide patients. Age, substance use disorder comorbidity, episode type, and educational level significantly affected results. No interactions were found amongst these parameters.

Conclusion

Lacosamide was effective in reducing psychopathology, mania, depression, and anxiety and in improving global functioning in patients with BD‐I/II disorder in the short term, with few side‐effects. Lacosamide improved mania, clinical severity, and global functioning better than OAE at doses lower than those used in epilepsy.
Stress‐driven increase in proline levels, and not proline levels themselves, correlates with the ability to withstand excess salt in a group of 17 Italian rice genotypes
Authors: Forlani G. , Bertazzini M. , Cagnano G.
Published: September 2018

In most plant species, a rapid increase in free proline content occurs following exposure to hyperosmotic stress conditions. However, inconsistent results were reported concerning the role of such an increase on the plant response to water shortage or excess salt. Therefore, the possibility that proline accumulation may help the cell to withstand stress conditions, or that it simply represents a stress marker, is still a matter of debate. A possible relationship between proline accumulation and salt tolerance was investigated in a set of 17 Italian rice varieties.

Rice seedlings were exposed to increasing salt concentrations during germination and early growth. The resulting levels of free proline were measured separately in shoots and roots and compared to those in untreated controls. Results were related to the corresponding ability of a given genotype to tolerate stress conditions.

Neither absolute proline levels in untreated or in salt‐stressed seedlings showed a straightforward relationship to the relative tolerance to salt, estimated as conductivity values able to reduce growth by 10 or 50%. Conversely, a highly significant correlation was found between the increase in proline levels in shoots and the ability to withstand stress.

The results strengthen a recent hypothesis suggesting than an increase in proline metabolic rates, more than the resulting proline content, may help the cell to counteract the effects of abiotic stress conditions.
Hard thresholding regression
Authors: Sun Qiang , Jiang Bai , Zhu Hongtu , Ibrahim Joseph G.
Published: September 2018

In this paper, we propose the hard thresholding regression (HTR) for estimating high‐dimensional sparse linear regression models. HTR uses a two‐stage convex algorithm to approximate the ℓ0‐penalized regression: The first stage calculates a coarse initial estimator, and the second stage identifies the oracle estimator by borrowing information from the first one. Theoretically, the HTR estimator achieves the strong oracle property over a wide range of regularization parameters. Numerical examples and a real data example lend further support to our proposed methodology.
Considering multiple methods for differentiating conceptually close constructs: Examples from the field of positive psychology
Authors: Hill Patrick L. , Allemand Mathias , Burrow Anthony L.
Published: September 2018

The field of positive psychology has sparked significant interest for researchers, in part given the apparent potential for individuals higher on “positive” dispositions to experience better health and well‐being. However, as the field has grown, so too have the number of conceptually similar dispositions identified by researchers as important to study. As such, there is an increasing need for researchers to understand whether and how conceptually similar “positive” dispositions are actually unique, an issue that may not be unique to positive psychology but has worsened with the field's prominence. The current manuscript provides a roadmap for one approach to differentiating conceptually close constructs in psychology, with examples couched within positive psychology. We will discuss the importance of combining quantitative and qualitative inquiries, as well as the adoption of techniques from multiple psychology disciplines, in order to better distinguish characteristics frequently studied in positive psychology.
Validation of a diagnostic tool for the diagnosis of lumpy skin disease
Authors: Mwanandota Julius J. , Macharia Mercy , Ngeleja Chanasa M. , Sallu Raphael S. , Yongolo Mmeta G. , Mayenga Charles , Holton Timothy A.
Published: September 2018

Background

Lumpy skin disease (LSD) is caused by LSD virus which is a member of the Capripoxvirus (CaPV) genus. Although PCR provides for a rapid and sensitive diagnosis, it has limited use due to its complexity in terms of cost, time and equipment. Loop‐mediated isothermal amplification (LAMP) is a simple, specific and cost‐effective method with a diagnostic accuracy similar to PCR.

Objectives/Hypothesis

To compare the detection rate (DR) of two LAMP assays versus PCR for the detection of CaPV.

Animals

This study used 105 apparently health animals (AHA) and 59 clinically sick animals (CSA).

Methods and materials

PCR and LAMP assays (LAMP1 and LAMP 2) were compared for detection of CaPV from AHA and CSA using blood and tissue samples. The detection was confirmed by sequencing of PCR positive samples. Analytical sensitivity and specificity of LAMP assays also were assessed.

Results

The DR in CSA was 13.6% for PCR whereas for LAMP it was 39.0% and 25.4% for LAMP 1 and 2 methods, respectively. In AHA, the LAMP assay DR was 14.3% and 1.9% for LAMP 1 and 2, respectively. Phylogenetic tree analysis confirmed the identity of CaPV. Analytic sensitivity showed a detection limit of 8 copies/μL. The analytic specificity test showed no cross detection with other infectious agents.

Conclusion and clinical importance

Good sensitivity and specificity results for LAMP assay support its application in the routine diagnosis of LSD, whereas its ability to detect LSDV in apparently healthy animals shows its usefulness in identifying populations at risk of LSD.
Aristotle on Economics and Ethics
Authors: Kahya Emel , Kim Sungsoo
Published: September 2018

Over the last several decades, we have witnessed seismic changes in corporate America: the increasingly myopic perspective of American managers, the relentless pursuit of short-term paper profit, reckless disregard for the interests of the non-shareholder community, a rise in hedge fund activism, and an ever-increasing use of incentive compensation, which arguably motivates managers to take on riskier investments. By revisiting Aristotle’s properties of ethics and economics, and considering their implications for accounting and finance, we try to learn guiding principles of economics, and by extension accounting and finance, from a great philosopher. We then discuss whether we have made progress, stood still, or even retreated from the philosopher’s propositions of more than two millenniums ago.
Can You Repair What You Own?
Authors: Shah Agam
Published: September 2018

Farmers could save time and money if they could troubleshoot tractors themselves, but have no access to the built-in software diagnostic tools that are accessible only to authorized servicepeople. The problem is so widespread that Nebraska farmers have taken it up with their state legislators, hoping to gain the legal right to access these diagnostic tools. These farmers are the latest members of a grassroots movement that is lobbying for what they call the “right to repair.” The movement’s goal is to give consumers the legal right to acquire parts and fix machines or devices that they have purchased, Right-to-repair activists want to break that monopoly with a healthy repair ecosystem so consumers can get repairs and parts at reasonable cost. This article takes a closer look at the current status of the movement.
Teaching Undergraduate Courses on Robotics and Control in Prison
Authors: Bretl Timothy
Published: September 2018

There is growing public consensus that the system of mass incarceration in the United States needs reform. More than 2.2 million residents (0.73%) of the United States were held in state or federal prisons or in local jails at the end of year 2010 [1]. This incarceration rate is the highest in the world, and disproportionately affects racial and ethnic minorities: 4.35% of black males were held in custody compared to 0.68% of white males in 2010.
Analysis of Displacement-Controlled Fretting Between a Hemisphere and a Flat Block in Elasto-Plastic Contacts
Authors: Yang Huaidong , Green Itzhak
Published: September 2018

This work employs a three-dimensional (3D) finite element analysis (FEA) to investigate the fretting metallic contact between a deformable hemisphere and a deformable flat block. Fretting is governed by displacement-controlled action where the materials of the two contacting bodies are set to have identical properties; studied first is steel-on-steel and then copper-on-copper. At contact onset, a normal interference (indentation) is applied, which is then followed by transverse cyclic oscillations. A large range of coefficients of friction (COFs) is imposed at the interface. The results show that the maximum von Mises stress is confined under the contacting surface for small COFs; however, that maximum reaches the contacting surface when the COFs are sufficiently large. It is also shown that fretting under sufficiently large COFs forms large plastic strains in “ring” like patterns at the contacting surfaces. Junction growth is found where the contacting region is being stretched in the direction of the fretting motion. At large COFs, pileups show up at the edges of the contact. The fretting loops of the initial cycles are found along with the total work invested into the system. At certain interference, there exists a certain COF, which results in the largest work consumption. The magnitude of the COF is found to produce either partial slip (prone for fretting fatigue) or gross slip (prone for fretting wear). A scheme of normalization is proposed, and it is shown to be effective for the two said materials that have vastly different material properties. Hence, the normalized results may well characterize a range of contact scales (from micro to macro) of various ductile material pairs that behave in an elastic–plastic manner with strain hardening.
Strain Hardening From Elastic–Perfectly Plastic to Perfectly Elastic Flattening Single Asperity Contact
Authors: Ghaednia Hamid , Brake Matthew R. W. , Berryhill Michael , Jackson Robert L.
Published: September 2018

For elastic contact, an exact analytical solution for the stresses and strains within two contacting bodies has been known since the 1880s. Despite this, there is no similar solution for elastic–plastic contact due to the integral nature of plastic deformations, and the few models that do exist develop approximate solutions for the elastic–perfectly plastic material model. In this work, the full transition from elastic–perfectly plastic to elastic materials in contact is studied using a bilinear material model in a finite element environment for a frictionless dry flattening contact. Even though the contact is considered flattening, elastic deformations are allowed to happen on the flat. The real contact radius is found to converge to the elastic contact limit at a tangent modulus of elasticity around 20%. For the contact force, the results show a different trend in which there is a continual variation in forces across the entire range of material models studied. A new formulation has been developed based on the finite element results to predict the deformations, real contact area, and contact force. A second approach has been introduced to calculate the contact force based on the approximation of the Hertzian solution for the elastic deformations on the flat. The proposed formulation is verified for five different materials sets.
Analysis of a New Structure for Offshore Waste Landfill: Contaminant Transport Characteristics Affected by Tidal Fluctuations
Authors: Chae Kwangseok , Lee Jongsub , Jin Hyunsik , Oh Myounghak
Published: September 2018

The paper deals with water cut-off walls for offshore waste landfill facilities that are used to prevent leakage of toxic substances to the surrounding water. A new type of a widely used water cut-off wall called Steel Pipe Sheet Piles (SPSP) is investigated with experimental measurements as well as numerical simulations. The main objective is to found out the influence of tidal fluctuations in the sea on the outflow of the contaminant and the results show that the outflow of contaminants is lower when tidal fluctuations are present compared to the case with only a mean water level. The influence of different filler materials on this behavior is also investigated.
Comparison of Methods to Find the Weibull Stress Parameters
Authors: Coppejans O. J. , Walters C. L.
Published: September 2018

The Weibull stress (Beremin, 1983) relates the local first principal stress and plastically strained volume to the probability of fracture. It requires two constants (m, σu) as input, which are generally regarded as material parameters. As the Beremin approach is used in the background to structural analysis rules, the Beremin parameters are now being used in other situations, including engineering analysis. However, the currently accepted way to find the Beremin constants requires twenty tests, which is considered to be unacceptably expensive for industrial application. Less expensive ways of finding the Beremin parameters have been published in the literature, but they have never been compared to the de facto standard. In this paper, the Beremin parameters were found by the de facto standard method and two other ways, and a comparison is made. It was found that the Beremin parameters can be estimated with reasonable accuracy with a method that uses on just two sets (six specimens) of fracture specimens by careful application of the method of Andrieu (2012). Also, a proposal is made for another method which is based only on the Master Curve temperature T0.
Numerical Analysis of Steep Wave-Induced Seabed Response and Liquefaction Around Gravity-Based Offshore Foundations
Authors: Li Yuzhu , Ong Muk Chen , Gudmestad Ove Tobias , Hjertager Bjørn Helge
Published: September 2018

Gravity-based offshore foundations generally consist of a bottom slab and one or more cylindrical shafts on top of it. The geometry of the structure can strongly affect the flow pattern, dynamic wave pressure and further soil response and the liquefaction risk in the vicinity of the foundation. In this work, gravity-based foundations with bottom slabs of cylindrical shape and hexagonal prismatic shape are investigated. An integrated wave-structure-seabed interaction model applied in this work is developed in Open-FOAM, incorporating a nonlinear wave solver, a linear elastic structure solver and an anisotropic Biot’s poroelastic soil solver consisting of consolidation and liquefaction modules.

Soil consolidation behavior in the presence of the foundations is investigated. It is found that the corners of the hexagonal foundation cause stress concentration in the soil. Therefore the initial effective stress around the hexagon corners is relatively high. Then, fully nonlinear waves modelled by fifth-order stream functions are simulated. Wave-induced pressure distributions and momentary liquefaction depths around the foundations are predicted.
Long-Term Extreme Response Prediction of Mooring Lines Using Subset Simulation
Authors: Leong Darrell , Low Ying Min , Kim Youngkook
Published: September 2018

Rigorous methods of probabilistic evaluations on long-term extremes are integral components in reliability research of offshore structures against overload events. Assessment across all conceivable sea states requires accounting for variabilities of long-term environmental loads and short-term stochastics, traditionally captured through extensive sampling or numerical expectation integration. The amount of environmental load variables render numerical integrations across high dimensions computationally prohibitive, while industry requirements of high return periods demand large Monte Carlo samples of timedomain dynamic analyses. Subset simulation offers a promising alternative to classic methods of statistical analysis, dividing ultra-low probability problems into subsets of intermediate probabilities. The methodology is uniquely advantageous for the assessment of heavy-tail overload events, which are unpredictably severe and occur at exceedingly rare frequencies. Subset simulation is experimented on a mooring case study situated in the hurricane-prone Gulf of Mexico, with the structure exposed to a joint-probabilistic description of wave, wind and current loads. The devised methodology is found to successfully evaluate hurricane-stimulated extreme events at ultra-low probabilities, beyond the feasible reach of Monte Carlo simulation at reasonable lead times.
Damage Detection of Offshore Platform Mooring Line Using Artificial Neural Network
Authors: Sidarta Djoni E. , O’Sullivan Jim , Lim Ho-Joon
Published: September 2018

Station-keeping using mooring lines is an important part of the design of floating offshore platforms, and has been used on most types of floating platforms, such as Spar, Semi-submersible, and FPSO. It is of great interest to monitor the integrity of the mooring lines to detect any damaged and/or failures.

This paper presents a method to train an Artificial Neural Network (ANN) model for damage detection of mooring lines based on a patented methodology that uses detection of subtle shifts in the long drift period of a moored floating vessel as an indicator of mooring line failure, using only GPS monitoring. In case of an FPSO, the total mass or weight of the vessel is also used as a variable. The training of the ANN model employs a back-propagation learning algorithm and an automatic method for determination of ANN architecture.

The input variables of the ANN model can be derived from the monitored motion of the platform by GPS (plus vessel’s total mass in case of an FPSO), and the output of the model is the identification of a specific damaged mooring line. The training and testing of the ANN model use the results of numerical analyses for a semi-submersible offshore platform with twenty mooring lines for a range of metocean conditions. The training data cover the cases of intact mooring lines and a damaged line for two selected adjacent lines.

As an illustration, the evolution of the model at various training stages is presented in terms of its accuracy to detect and identify a damaged mooring line. After successful training, the trained model can detect with great fidelity and speed the damaged mooring line. In addition, it can detect accurately the damaged mooring line for sea states that are not included in the training. This demonstrates that the model can recognize and classify patterns associated with a damaged mooring line and separate them from patterns of intact mooring lines for sea states that are and are not included in the training.

This study demonstrates a great potential for the use of a more general and comprehensive ANN model to help monitor the station keeping integrity of a floating offshore platform and the dynamic behavior of floating systems in order to forecast problems before they occur by detecting deviations in historical patterns.
Optimized Bolt Tightening Sequences in Bolted Joints Using Superelement FE Modeling Technique
Authors: Coria Ibai , Martín Iñigo , Bouzid Hakim , Heras Iker , Aguirrebeitia Josu
Published: September 2018

A lot of effort is put to achieve bolt preload uniformity during the assembly process of offshore bolted joint connections resulting in potentially high economic costs and project delays. The complexity of this operation is due to the effect of the elastic interaction between the different joint elements which causes load variations of adjacent bolts whenever a bolt is tightened. As a consequence, it is difficult to achieve a uniform target load in the bolts.

In order to avoid this phenomenon, tightening sequences of a large number of passes are usually carried out until a uniform target load is achieved. This solution is neither practical nor efficient when treating hundreds or even thousands of bolted joints due to the large assembly time needed. Several methods were developed to study the effect of the elastic interaction and minimize the assembly time. These methods usually predict the loss of load of every bolt during the tightening sequence, and thus calculate the tightening loads that will provide a uniform final load at the end of the sequence. As a result, an optimized tightening sequence is achieved, which provides a uniform final load distribution in only one or two tightening passes. However, several complex and costly analyses are previously necessary for such purpose.

Based on these traditional methods, this paper presents a new and more efficient optimization methodology to achieve assembly bolt load uniformity. The method is based on the use of superelement technique and is capable of producing similar results with computational costs reduced by 30 times as compared to the more conventional Finite Element (FE) modeling. The results were satisfactorily validated with the latter as well as with tests conducted on a NPS 4 class 900 bolted joint.
Strength Assessment of Jacket Offshore Wind Turbine Support Structure Accounting for Rupture
Authors: Yeter Baran , Garbatov Yordan , Guedes Soares C.
Published: September 2018

The objective of the present work is to carry out the strength assessment of jacket offshore wind turbine support structures subjected to progressive rupture. A defect existing in a structure made during the fabrication may turn into a small-scale rupture and because of the high-stress concentration and low-cycle fatigue load. Therefore, the ultimate load-carrying capacity of the support structure is analysed accounting for the progress of the rupture until the leg component experiences a full rupture along its circumference. The effect of the severity of the imperfection is also investigated through 3 case studies that are created by varying the amplitude of the waves. The moment-curvature relationship of the structure with respect to the studied cases is presented. Furthermore, the jacket support structures, at different water depths, are also analysed and discussed. Finally, some of the leg components are removed one by one to study the redundancy of the jacket support structure at 80-m water depth.
Verification of Twistlock Simulations for Modular Use in the Arctic
Authors: Kistner Josefine , Backhaus Eldor , Kaeding Patrick
Published: September 2018

The University of Rostock has generated dimensioning equations to calculate the strength of twistlock systems under non-standard loading conditions on offshore platforms in the POLAR project in the last years. These dimensioning equations have been presented on previous OMAE conferences. In this paper ultimate strength analyses are conducted to assess the safety margin between elastic design and final rupture. The validation of the local system is shown and the results of the experiment and the simulation are analyzed and compared. In these experiments twistlock systems are subjected to cyclic loads, long-term tensile load at design level and ultimate loads. The experiments are conducted with a heavy duty hydraulic test rig. The results show agreement between experiment and simulation with regard to the rupture behavior and the force-displacement relationship.
Drilling Riser Disconnection Challenges in Ultra-Deep Water
Authors: Diezel Alexandre , Venero Germain , Gomes Victor , Muniz Leandro , Fachini Rafael , Corrignan Hugues
Published: September 2018

With the extension of the offshore drilling operations to water depths of 10,000 ft and beyond, the technical challenges involved also increased considerably. In this context, the management of the riser integrity through the application of computational simulations is capital to a safe and successful operation — particularly in harsh environments. One of the main challenges associated with keeping the system under safe limits is the recoil behavior in case of a disconnection from the well. The risk that an emergency disconnect procedure can take place during the campaign is imminent, either due to failure of the dynamic positioning system or due to extreme weather in such environments.

Recent work [1] in the field of drilling riser dynamic analysis has shown that the recoil behavior of the riser after a disconnection from the bottom can be one of the main drivers of the level of top tension applied. Tension fluctuations can be very large as the vessel heaves, especially in ultra-deep waters where the average level of top tension is already very high.

In order to be successful, a safe disconnection must ensure that the applied top tension is sufficient for the Lower Marine Riser Package (LMRP) to lift over the Blow-Out Preventer (BOP) with no risk of interference between the two. This tension should also not exceed a range in which the riser will not buckle due to its own recoil, that the telescopic joint will not collapse and transfer undesirable loads onto the drilling rig or that the tensioning lines will not compress. A good representation of such behavior in computational simulations is therefore very relevant to planning of the drilling campaign.

A case study is presented herein, in which a recoil analysis was performed for a water depth of 11,483ft (3,500m). Numerical simulations using a finite element based methodology are applied for solving the transient problem of the riser disconnection in the time domain using a regular wave approach. A detailed hydro-pneumatic tensioning system model is incorporated to properly capture the effect of the anti-recoil valve closure and tension variations relevant during the disconnection.

A reduction of conservativism is applied for the regular wave approach, where the maximum vessel heave likely to happen in every 50 waves is applied instead of the usual maximum in 1000 waves approach. ISO/TR 13624-2 [4] states that using the most probable maximum heave in 1000 waves is considered very conservative, as the event of the disconnection takes place in a very short period of time.

The challenges inherent to such an extreme site are presented and conclusions are drawn on the influence of the overall level of top tension in the recoil behavior.
Development and Testing of a Friction-Based Post-Installable Fiber-Optic Monitoring System for Subsea Applications
Authors: Seaman Calvin H. , Wilson J. Conrad , Kipp Robert M. , Hedengren John D. , Tang Henry H. , Bentley Nicole L. , Le Suy Q. , Brower David V.
Published: September 2018

This paper continues to document the design, development, and test of a friction-based (non-adhesive) post-installable fiber-optic strain sensing system for oil and gas applications — especially those that require deployment on existing subsea structures. (Ref: OMAE2017-61494 Development and Testing of a Friction-Based Post-Installable Sensor for Subsea Fiber-Optic Monitoring Systems [1]). The prototype fiber-optic monitoring system collects a wide range of real-time data, which can be used to determine structural loading, fatigue, temperature, pressure, and flow assurance on operational platforms.

The primary challenge of a post-installed instrumentation monitoring system is to ensure secure coupling between the sensors and the structure of interest for reliable measurements. Friction-based coupling devices have the potential to overcome installation challenges caused by marine growth and soil contamination on subsea structures, flowlines, or risers. This particular design solution is compatible with structures that are suspended in the water column and those that are resting on the seabed. In addition, the system can be installed by commercial divers in shallow depths or by remotely operated vehicles in deep-water applications.

Operational limitations of the initial design concept were identified in the previous series of tests (2016–2017), and several innovative enhancements have been implemented which resulted in significant improvements in sensor system coupling and strain measurement correlation with traditional strain measuring devices. This paper provides a summary of the notable prototype design changes, full-scale test article buildup, and detailed performance data recorded during tension and compression loading that simulated representative offshore conditions. The test results were positive and demonstrated the effectiveness of the design enhancements. Compromises made during mounting of the sensing elements resulted in better performance in tension than compression. These effects are well understood and are fully discussed, and do not influence the viability of the design changes.

This study is part of a continuing collaboration between the Houston-based NASA-Johnson Space Center and Astro Technology, Inc. within a study called Clear Gulf. The primary objective of the Clear Gulf study is to develop advanced instrumentation technologies that will improve operational safety and reduce the risk of hydrocarbon spillage. NASA provided unique insights, expansive test facilities, and technical expertise to advance these technologies that would benefit the environment, the public, and commercial industries.
Motion Simulation Analysis of the Cable-Body of the Deep Underwater Towed System
Authors: Zhang Dapeng , Bai Yong , Jing Biao , Zhu Keqiang , Sun Guowei
Published: September 2018

As the demand of marine resources is continuously growing, more and more people are focusing on the study of underwater towed system for marine survey, in which mastering and predicting the dynamic characteristic of the system is the key problem. Based on the parameters of a certain underwater system, combined with the lumped mass method, the underwater cable-body 3D motion mathematical model has been established by OrcaFlex, in which the variation of the tension of the towed cable and the variation of the depth of the towed body have been given and the effect of the towed speed on critical radius in the process of the 360° rotary motion has been discussed. The results show a good agreement with previous research results. At the same time, we also make a research on the effects of the change of the hydrodynamic coefficients and the parameters of towed cable on variation of the tension and towed depth. These studies can provide a basis for the selection of cable in the system.
On-Site Measurement and Numerical Modelling of a Lifting Operation for Caissons Using Floating Crane
Authors: Oh Sho , Utsunomiya Tomoaki , Saiki Kota
Published: September 2018

Floating cranes are often used for the installation and maintenance operations for offshore wind turbines when they are located in deep waters. As the motions of the vessel being easily affected by external environments, accurate prediction of the motion of the system is important. In this study, first a numerical system based on basic multibody dynamics system is developed for estimation of the behaviour of the lifting operations using floating cranes. Next, on-site measurements are carried out for a lifting operation of a caisson using floating crane. Two numerical models were built with flexible and fixed connectors and validation was performed for the static displacement during lifting operation and the dynamic characteristics of the caisson in the stand-by condition. The static displacements during the lifting operation calculated with de developed tool agreed well with the measurement. The peak frequency of the cargo acceleration in y direction calculated with the flexible model was lower than that calculated with the fixed model. Both models approximately agreed with the measurement. Calculated acceleration of the cargo in x direction largely underestimated the peak frequency of the measurement for both flexible and fixed models. The use of the linear spring to model the wire rope including friction at the end is a possible contributor to the difference.
LBM Simulation of Flow Around an Oscillating Cylinder and a Stationary Cylinder in Side-by-Side Arrangement
Authors: Zhang Yang , Sheng Li , Duan Jinlong , Chen Ke , You Yunxiang
Published: September 2018

Flow interference between two identical circular cylinders in side-by-side arrangement with one stationary and the other forced to oscillate in the transverse direction are studied. Direct numerical simulations are performed by Lattice Boltzmann Method (LBM) with a constant Reynolds number of 100. We consider four representative pitch ratios, T/D, ranging from 1.2 to 4, corresponding to four distinct flow patterns for two stationary side-by-side cylinders. The forced oscillation is fixed at a constant small amplitude of A/D = 0.1. A wide range of dimensionless oscillating frequency (fe/fs = [0.5, 2]) is examined. The results show that the response state of flow around two side-by-side cylinders when one cylinder is forced to vibrate is quite different from that of the corresponding stationary system. Four response states are identified according to the different characteristics on the power spectra and phase portrait of lift forces on cylinders. In addition, hydrodynamic forces on the cylinders are analyzed in terms of root-mean-square and time-averaged quantities. It is found that the pitch ratio, oscillating frequency and response state play different roles in determining the force quantities.
Application of Wave Devouring Propulsion Technology to Support Positioning of Floating Structure
Authors: Yoshida Hisafumi , Yamasaki Keiichi , Sunahara Shunji
Published: September 2018

It becomes one of the key issues to reduce capacity of generators for the dynamic positioning (DP) system on offshore structures for the reduction of Green House Gas emission. For the purpose, to decrease environmental forces, wave, wind and current forces, are very important for the DP system design. One of the concepts to reduce wave forces is the “wave devouring propulsion technology” (WDPT) installed vessels. WDPT employs wings attached to the vessel and they produce thrust in waves as a propulsor of vessel. WDPT concept seems to be applicable for offshore structures. In this paper, application of WDPT for three-column type offshore structure is experimentally investigated. Flat plate type wings are installed between columns, and vertical position of wings, frequency response of thrusts in waves and directional particulars of wave incident angle are studied.
Study on the Effects of Drilling Riser Attachments
Authors: Lee Sung-Je , Kang Chan-Hoe , Lee Jeong-Ho , Jang Chang-Hwan , Park Sung-Gun , Han Sung-Kon
Published: September 2018

A drilling riser is a conduit that provides a temporary extension of a subsea oil well to a surface drilling facility. The drilling risers are used with subsea BOP and generally used by floating drilling vessels. When used at deeper depths, the drilling riser must be tensioned to maintain stability. To reduce the capacity of the tensioner needed to maintain the riser’s stability, a buoyancy module is added to the riser to neutralize buoyancy when submerged. And as current flows over the drilling riser, VIV is generated by repeated vortex shedding. Designer can attach a VIV suppression device to prevent excessive fatigue loading by VIV. This attachment is necessary to ensure the stability of the drilling riser, but it also has side effects. In the design of the drilling riser, it is important that the riser offsets occur laterally along the depth when current is applied to the riser and that the clear distance from the moonpool is maintained. Drilling risers also require attention to fatigue and cost. In this paper, we investigated the influence of the attachment, such as the buoyancy and the VIV suppression devices.
Real Sea Testing of a Small Scale Weptos WEC Prototype
Authors: Kofoed Jens Peter , Tetu Amelie , Ferri Francesco , Margheritini Lucia , Sonalier Nathan , Larsen Tommy
Published: September 2018

The Weptos wave energy converter (WEC) is Danish concept that has been investigated during the last decade in laboratory test campaigns. It is an A-shaped floating structure that absorbs wave energy through multiple wave absorbing bodies. These bodies are rotors, with their shape inspired by the Salter duck, of which its high efficiency has been proven already back in the 1970’s. The Weptos WEC has the ability to maximise power absorption in operational sea states and minimize structural loads in extreme conditions through adjustment of its width.

Launch of a small scale real sea prototype of the Weptos WEC was done in July 2017, with a location in Lillebælt between Jylland and Fyn in Denmark, north of the small island Brandsø, at a water depth of 10 m. The paper contains a detailed description of the prototype and its instrumentation, along with the test planning and preliminary data analyses for the evaluation of the device characterization.
Verification and Benchmarking Methodology for O&M Planning and Optimization Tools in the Offshore Renewable Energy Sector
Authors: Rinaldi Giovanni , Pillai Ajit C. , Thies Philipp R. , Johanning Lars
Published: September 2018

Lowering Operation and Maintenance (O&M) expenses is pivotal in order to increase the penetration of offshore renewables in the generation of electricity. The combined use of Monte Carlo simulation and optimization algorithms has been explored to support the assets management and propose improved solutions in an efficient and automated way. However, due to the lack of operational experience and historical data, validation of these models, intended in the commonly known sense of comparison against observed data is often not possible. This generates concern about their ability to fully grasp and interpret the complex dynamics of an offshore renewable energy system. This paper presents a method to effectively calibrate, verify and benchmark computational tools for O&M strategies and asset management of an offshore wind farm, as an alternative to validation in absence of real data. A case study is used to test the quality of the results and compare them against those provided by similar tools built for the same purpose. The evaluation functions for an optimization of the O&M strategies are then benchmarked against these outputs in order to ensure that the solutions are consistent within the overall characterization and optimization framework. The requirements for acceptability of the models performance, as well as guidelines for analogous verifications using similar models, are derived. Hence, this work provides a basis to benchmark future models and increase confidence and credibility in computational tools for the O&M planning of offshore renewables.
Qualification of Sealing System for Flexible Pipes Using a Self-Energized Gasket
Authors: Wang Christian , Halsteen Martin , Ries Jesper
Published: September 2018

In order to meet higher technical demands designing flexible pipes at higher pressures and higher temperatures for deeper water depths NOV has introduced and qualified a new sealing system that is self-energized. The sealing material has been qualified and tested in different fluids. The sealing system has shown good functionality at higher pressures as well as at lower pressures.

The qualification of the sealing system has been based on multiple full-scale and mid-scale tests according to Recommended Practice API 17B and small-scale tests on the elastomer material including long-term ageing tests and rapid gas decompression tests in high pressure CO2 up to 900 bar.

The recommendations of RP API 17B used in the industry has its limitation with regards to qualification of a new sealing system. This paper gives an overview how to qualify a new sealing system on an existing product range achieving different technology readiness levels according to Recommended Practice API 17N from TRL1 up to TRL5. TRL5 covers system integration testing by full-scale testing of flexible pipes such as burst test, tension-pressure test, tension-tension test and deep immersion performance test. All qualification tests have been witnessed by a third-party Bureau Veritas and the enhanced sealing system has archived a TRL5 statement within its current design envelope.
Scale Effects on Ship Maneuverability Using RANS
Authors: Araki Motoki
Published: September 2018

Predicting ship maneuverability is one of the important topics in ship engineering. However because of the huge difference between model and full scale Reynolds number (Re), it is almost impossible to predict full scale ship maneuverability using conventional methods such as model test. On the other hands, with the developments of computational technologies and computational fluid dynamics (CFD) techniques, CFD simulations are widely applied on ship maneuvering problems (e.g. Stern et al., 2011). Moreover some of the researchers start the CFD simulation with full scale Re especially on propulsion problems (e.g. Tezdogan et al., 2015) which showing reasonable results.

Therefore, in this paper, captive maneuvering simulations (rudder angle test) in model/full scale Re on KVLCC2 are carried out using Reynolds-averaged Navier–Stokes (RANS) solver NAGISA (Ohashi et al., 2014) with the overset gird method UP_GRID (Kodama et al., 2012). And the results between model and full scale simulations are compared in maneuvering coefficients and flow field to reveal the scale effect on ship maneuverability.