bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel association of Psychrobacter and Pseudomonas with malodour in bloodhound dogs, and the effects of a topical product composed of essential oils and plant‐derived essential fatty acids in a randomized, blinded, placebo‐controlled study
Authors: Meason‐Smith Courtney , Older Caitlin E. , Ocana Roxanna , Dominguez Brandon , Lawhon Sara D. , Wu Jing , Patterson Adam P. , Rodrigues Hoffmann Aline
Published: September 2018

Background

The pathogenesis and treatment of cutaneous malodour in dogs have not been investigated previously. Staphylococcus and Corynebacterium spp. are associated with human axillary malodour.

Hypothesis

Staphylococcus and Corynebacterium spp. are associated with cutaneous malodour in dogs, and treatment with a topical essential oil‐based product will improve malodour and reduce the abundance of odour‐causing bacteria.

Animals

Twenty seven bloodhound dogs from a south Texas boarding facility were enrolled in this study.

Methods and materials

Skin swabs were taken from the axilla and dorsum of 27 dogs at initiation of the study. Mean malodour scores were used to assign dogs to control or malodour groups. The malodourous dogs were randomly assigned to a treatment or placebo group, received four weekly topical applications of the spot‐on or placebo, and samples were recollected. Next‐generation sequencing (NGS) and real‐time quantitative PCR (qPCR) were performed on all swabs.

Results

Psychrobacter and Pseudomonas spp. were significantly more abundant (P < 0.001, P = 0.006; respectively), and overall bacterial diversity was reduced (P = 0.0384) on the skin of malodourous dogs. Staphylococcus and Corynebacterium spp. were not associated with malodour. The topical essential oil‐based product significantly (P = 0.0078) improved malodour in the treatment group and shifted their bacterial community structure.

Conclusions and clinical importance

A novel association of bacterial genera with malodour in bloodhound dogs, identified by NGS, highlights future targets for odour control. The topical treatment significantly reduced malodour. The interaction between the topical treatment and cutaneous microbiota should be further investigated and may be useful in other dermatological conditions involving microbiota.
Comparison of the tube test and column agglutination techniques for anti‐A/‐B antibody titration in healthy individuals
Authors: Matsuura Hideaki , Akatsuka Yoshiki , Matsuno Takahiro , Sugiura Yukari , Arakawa Shoko , Oikawa Shota , Yoshida Jumpei , Kosugi Mitsuaki , Emi Nobuhiko
Published: September 2018

Background and Objectives

Determination of the anti‐A/‐B titre pre‐ and post‐transplantation is beneficial for treatment selection. Currently, the recommended method for antibody titration is the tube test (TT) assay. Dithiothreitol (DTT) is used for IgM antibody inactivation. Recently, a fully automated antibody titration assay using the column agglutination technique (CAT) was developed (auto‐CAT). Our aim was to compare the auto‐CAT and TT techniques for ABO antibody titration, to evaluate the effectiveness of DTT‐treated plasma for use with auto‐CAT and to define the cut‐off value for antibody titration by auto‐CAT.

Materials and Methods

We enrolled 30 healthy individuals, including 10 each for blood types A, B and O. We performed antibody titre measurement using the TT technique and auto‐CAT simultaneously. Auto‐CAT uses the bead column agglutination technology.

Results

With the auto‐CAT cut‐off value set to weak (w)+ with DTT treatment plasma, the concordance rate was 45%, and the weighted kappa value between TT and auto‐CAT results was 0·994 in all subjects. Furthermore, there was a significant positive correlation between the anti‐A/‐B titre results obtained using the TT technique and auto‐CAT in all blood types. Moreover, a positive bias (falsely elevated end‐points due to agglomeration of A/B cells) was not observed in auto‐CAT testing using DTT‐treated plasma.

Conclusion

Our results show that 1+ agglutination using the TT technique is equivalent to w+ agglutination obtained using auto‐CAT. We recommend that DTT may be used with auto‐CAT to measure antibody titres. Thus, we suggest that auto‐CAT is useful for antibody titration in routine examination.
Effect of implementation of a surgical safety checklist on perioperative and postoperative complications at an academic institution in North America
Authors: Cray Megan T. , Selmic Laura E. , McConnell Briana M. , Lamoureux Lorissa M. , Duffy Daniel J. , Harper Tisha A. , Philips Heidi , Hague Devon W. , Foss Kari D.
Published: September 2018

Objective

To evaluate the efficacy of a surgical safety checklist (SSC) in reducing perioperative and postoperative complications.

Study design

Before‐and‐after intervention study.

Animals

Client‐owned dogs (n = 633) and cats (n = 44).

Methods

Consecutive surgeries were enrolled in the study. The “before” phase consisted of 267 surgeries performed without an SSC (SSC−) followed by 75 SSC− surgeries in which a trained observer was in the operating room to detect possible complications. An SSC was then implemented in the operating rooms during 1 week. The “after” phase consisted of 58 surgeries in which a safety checklist (SSC+) and an observer were used and 277 SSC+ surgeries without an observer. Complications were prospectively recorded when witnessed by the observer, and all other perioperative complications were retrospectively recorded from veterinary records and client telephone communication.

Results

There were more perioperative and postoperative complications when surgeries were performed without an SSC (140/342 [40.9%; 95% CI, 35.7%‐46.4%]) than there were when surgeries were performed with an SSC (98/335 [29.3%; 95% CI, 24.4%‐34.4%]; P = .002). Surgical checklist use, presence of an observer, American Society of Anesthesiologists score, and anesthesia time were all independently associated with the odds of complications.

Conclusion

Implementation of an SSC in an academic teaching hospital decreased the odds of perioperative and postoperative surgical complications.

Clinical significance

This study supports the use of an SSC to prevent surgical complications in veterinary teaching hospitals.
Youth Self-Report Factor Structure: Detecting Sex and Age Differences in Emotional and Behavioral Problems among Spanish School Adolescent Sample
Authors: Zubeidat Ihab , Dallasheh Waleed , Fernández-Parra Antonio , Sierra Juan Carlos , Salinas José María
Published: September 2018

The Youth Self-Report (YSR/11-18) is a widely used child-report measure that assesses problem behaviors along two “broadband scales”: internalizing and externalizing. It also scores eight empirically based syndromes and DSM-oriented scales and provides a summary of total problems. Although the YSR was designed for youths ages 11-18, no studies have systematically evaluated whether youths under the age of 11 can make valid reports using the YSR broad-band, syndrome and DSM-oriented scales. It is a parallel form to the caretaker-completed Child Behavior Checklist (CBCL) and teacher-completed Teacher Report Form (TRF). Few studies related to YSR/11-18 (Achenbach, & Rescorla, 2000, 2001) factor structure were carried out in Spanish children and adolescent population. This study analyses the factor structure of this assessment tool, in 961 Spanish adolescents attending school from 13 to 18 years old. A principal components method was used to extract the factors followed by a Varimax rotation. According to current research, each sex was treated separately, and only items referred to misbehavior (105 out of 119) were included. Seven first-order common factors were found in both, boys and girls: Anxious/Depressed, Somatic Complaints, Delinquent Behavior, Aggressive Behavior, Attention Problems, Thought Problems and Relational Problems. Factoring of these seven syndromes led to a single second-order factor in younger males. Older males and females showed labeled internalize and externalize symptoms. These results resembled that obtained in former studies with Spanish population.
Online Visibility, Social Networks and Glamorous Scientific Publications
Authors: Ferreira Carlos Miguel , Serpa Sandro
Published: September 2018

In a context of transformation of the higher education institutions’ mission, there is a growing need for the academy to respond to the needs placed both at the political and social levels, which has implications for the scholar’s expected activity. The purpose of this paper is to analyse the growing importance, besides publishing and being cited, of having visibility in the digital world. We conclude that this new dimension, which is being added to the success and legitimacy of the scholar and his/her institution, will have probable direct consequences both on the form and on the contents of future publications. The willingness of scholars to produce publications worthy of social visibility may foster a growing number of publications that are attractive, perhaps less complex and more accessible to the “uninitiated”, what we call glamorous publications.
Determining Levels of 8th Grade Students of Secondary School to Understand Cognitive Structures and Concepts Concerning Concepts of Fundamental Citizenship
Authors: Kılıçoğlu Gökçe
Published: September 2018

Purpose of this study is to determine cognitive structures, conceptual knowledge and misconceptions of the 8th grade students concerning concepts of citizenship through a word association test. In direction of this purpose, a word association test consisting of democracy, sovereignty, independency, freedom, right and responsibility concepts have been applied to 175 8th grade students who studied at 3 secondary schools in Trabzon province during 2017-2018 school years. Conceptual networks have been formed in direction of responses of the students to these concepts, and cognitive structures of the students have been demonstrated. It has been concluded as a result of the study that students associate concept of democracy mostly with equality, right, justice concepts. They associate concept of sovereignty with freedom, nation, independence concepts and concept of independency with freedom, flag and liberty concepts. They also associate concept of freedom with independency, justice, liberty concepts and concept of right with freedom, nation and sovereignty concepts. They associate again concept of responsibility with task, duty and work concepts. It has been determined as a result of the study that a good part of the students can make sentences involving scientific information about freedom, independency and responsibility concepts and they have no misconceptions about these concepts. It has been determined that a limited number of students have misconceptions about the concept of right. As for one of the important results of the study, most of the students have misconceptions about the concept of sovereignty.
Mechatronics for Humanitarian Explosive Ordnance Disposal in Cambodia
Authors: Clayton Garrett M.
Published: September 2018

Over the past six years, researchers at Villanova University (VU) and the Golden West Humanitarian Foundation (GWHF) have developed an integrated research and educational program focused on the use of mechatronics and robotics in humanitarian explosive ordnance disposal (EOD) and mine action. In the following article, I will talk about this program, discuss two ongoing projects - a low-cost EOD robot and an automated ordnance identification system - and talk about how we have successfully integrated students in the work. There are many opportunities for the DSCD community to get involved in this area and hopefully this article will pique your interest.
Reliability Simulation for Offshore Structures Based on Fault Tree Analysis
Authors: Guo Yongjin , Wang Hongdong , Yi Hong
Published: September 2018

Offshore structures are large-scale and multifunctional products with high requirements for reliability. In this paper, the reliability simulation method based on fault tree analysis for offshore structures is studied. For non-repairable systems, the Weibull distribution is used to fit the failure distribution function of the bottom events of fault trees. The Monte Carlo method is used to sample the lifetime of bottom events, and the unreliability of the top event is calculated through the structure function of the fault tree. For repairable systems, the time arrays of state changes are generated through sampling failure and maintenance time of the components. The system failure time of each simulation is calculated based on minimal cut sets of the fault tree. The method is applied in the reliability analysis of the electrical power system of offshore platforms to prove its feasibility and effectiveness.
Data Collection and Analysis for the Creation of a Digital Shadow During the Production of Thermoplastic Composite Layers in Unbonded Flexible Pipes
Authors: Schäkel Martin , McNab John , Dodds Neville , Peters Tido , Janssen Henning , Brecher Christian
Published: September 2018

Unbonded flexible pipes present a mature technology for the efficient recovery and transport of hydrocarbons offshore. The substitution of metallic reinforcement layers in the multi-layered structure by thermoplastic fiber-reinforced polymer (FRP) presents a solution for self-weight issues of especially long pipes, as FRP materials display high specific strength and modulus while being resistant to external pressure and corrosion.

The production of these layers is automated by the laser-assisted tape winding process without the need of additional curing steps. During the manufacturing process, several data like process temperature and consolidation pressure are continuously monitored by non-contact sensors to ensure process stability without interfering in the consolidation process. To gain additional information about the temperature distribution within the multi-layered laminate, contact temperature sensors were introduced in the tape winding process. By this method the temperature of subjacent tapes can be assessed during the continued winding process.

Additionally, this paper features a new approach of utilizing winding path data for relating the time-dependent sensor data to the exact position on the produced part. The visualization of path-dependent sensor data opens up possibilities of linking quality monitoring results to manufacturing insufficiencies and potential part defects.
Processing of Ambient Vibration Response for Modal Parameters Identification of a Jacket-Type Offshore Platform: Sea Test Study
Authors: Bao Xingxian , Liu Zhihui , Shi Chen
Published: September 2018

Modal parameters identification of offshore structures is important for many engineering applications, such as damage detection, structural health monitoring, etc. Operational modal analysis has been widely used for large structures. However, measured signals are inevitably contaminated with noise and may not be clean enough for identifying the modal parameters with proper accuracy. The traditional methods to estimate modal parameters in noisy situation are based on over-determined system to absorb the “noise modes” firstly, and then using the stability diagrams to distinguish the true modes from the “noise modes”. However, it is difficult to sort out true modes when the signal noise ratio is low, especially, the “noise modes” will also tend to be stable as the model order increases. This study develops a noise reduction procedure for polyreference complex exponential (PRCE) modal analysis based on ambient vibration responses. In the procedure, natural excitation technique (NExT) is firstly applied to get free decay responses (auto- and cross-correlation functions) from measured (noisy) ambient vibration data, and then the noise reduction method based on solving the partially described inverse singular value problem (PDISVP) is implemented to reconstruct a filtered data matrix from the measured data matrix. In our case, the measured data matrix is block Hankel structured, which is constructed based on the free decay responses. The filtered data matrix should maintain the block Hankel structure and be lowered in rank. When the filtered data matrix is obtained, the PRCE method is applied to estimate the modal parameters. The proposed NExT-PDISVP-PRCE scheme is applied to field test of a jacket type offshore platform. Results indicate that the proposed method can improve the accuracy of operational modal analysis.
Basic Characteristics of the Primary Conversion of an OWC Type WEC Installed on a Wave Dissipating Double-Caisson
Authors: Ikoma Tomoki , Masuda Koichi , Eto Hiroaki , Shibuya Shogo
Published: September 2018

Several types of oscillating water column (OWC) type wave energy converters (WECs) are researched and developed in the world. They are floating types and fixed types. In case of a fixed type, wave dissipating caissons could be replaced to WECs of an OWC type. On OWC types, installation of the projecting-walls (PWs) is useful in order to improve PTO performance. In this study, it was considered that a double dissipating caisson was used as an OWC type WEC with PWs. A front caisson of the double caisson seems the area surrounded by PWs and a back caisson can be seen as an OWC. The paper studied basic property of the primary conversion from wave power to power of air from model tests in a wave tank. As a result, wave height strongly effects on behaviours of OWC motion as well as air pressure. Finally, the primary conversion was affected by wave height. Besides, the concept of use of a double caisson was useful from the primary conversion over 80 % evaluated using test data.
Corrosion Margins for Redundant Ship Structures
Authors: Garbatov Yordan , Guedes Soares C.
Published: September 2018

The work presented here analyses the structural corrosion degradation of two sets of corrosion depth measurements collected with a one-decade difference. The corrosion degradation process is associated to a first order system, subjected to a sudden disturbance, where a step function is used as an input to define the solution of the differential equation of this system leads to the exponential corrosion degradation model as developed earlier. Corrosion margins of redundant ship structures with serious consequences of failure are derived and several conclusions related to the new trend in the ageing structures are presented and discussed. Partial safety factors with respect to the corrosion environment and corrosion margins are developed that can be used in the design, avoiding a complex probabilistic analysis.
Onset and Post Buckling of Pipe-in-Pipe’s Helical Buckling Using Improved Energy Method
Authors: Gong Lixin
Published: September 2018

The purpose of this paper is to present theoretical solutions based on an improved energy method for predicting the helical buckling (HB) behavior of pipes in vertical, inclined, and horizontal wells.

The energy method has been applied to solve the pipe-in-pipe’s (PIP) helical buckling behavior since Lubinski, et al [2] in the 1950’s. However, in the preceding studies, the energy methods are not yet completely correct because the pipe’s potential energy of the distributed contact normal force induced by the helical buckling was considered to be negligible. This deficiency caused improper deductive procedures.

In this paper, the energy method is improved by adding the term of the potential energy of the distributed contact normal force. With this improvement, not only can the PIP’s critical helical buckling forces be successfully derived, but it also provides a deeper insight on the PIP’s helical buckling onset, as well as the post helical buckling behavior.

For inclined and horizontal wells, equations are provided to determine the critical forces required to initiate the helical buckling mode for both “long” and “short” pipes. In addition, the post buckling behavior is also described, and a new concept of helical buckling zone (HBZ) for “short” pipes is introduced based on the force-pitch plots as an area in-between the helical buckling’s onset curve and the classical Lubinski curve.

Finite element ABAQUS models have also been utilized to confirm the analysis using the improved energy method. And the ABAQUS results show remarkable agreement with the theoretical solutions.
Study on Resistance Performance of Ice-Breaking Tanker According to Ship’s Length
Authors: Cho Seong-Rak , Jang Jinho , Kim Cheol-Hee , Oh Eun-Jin , Kang Kuk-Jin , Lee Sungsu , Lee Yong-Chul
Published: September 2018

In this paper, ice model tests with different lengths of parallel middle-body were conducted to estimate accurate resistance performance of ice-breaking merchant vessels. Totally, three model ships were manufactured: The standard vessel is 90,000 DWT tanker to transport oil in the ARC7 condition, and two vessels have only different lengths of parallel middle-ship compared to the standard vessel. Ice breaking, ice friction, ice buoyancy, and open-water resistances were classified and measured in experiments, and each resistance component according to change of ship’s length is analyzed. In addition, the resistance formula of ice-breaking tanker is developed by a regression analysis.
Retrofitting of Floating Bridges With Perforated Outer Cover for Mitigating Wave-Induced Responses
Authors: Vijay K. G. , Sahoo T.
Published: September 2018

An investigation has been carried out based on multi-domain boundary element method to analyze the mitigation of wave-induced hydrodynamic loads on a pair of floating rectangular bridges by retrofitting the structures with external porous plates. The study is based on the assumptions of small amplitude water wave theory in finite water depth with the characteristics of wave-body interactions remain unaltered along the bridge. Wave past porous structure is modelled using Darcy’s law. Various hydrodynamic characteristics are studied by analyzing the wave forces acting on the floating bridges and the retrofitted porous structures for different wave and structural parameters. With the introduction of a retrofit, the horizontal force on the bridge reduces irrespective of wave and structural parameters, whilst vertical force increases under certain conditions. Moreover, when the distance between the bridges is an integer multiple of half of the wavelength of the incident waves, both the bridges experience optima in horizontal and vertical wave forces, with both these forces being 180° out of phase. The present study is expected to be useful in the design of efficient bridge structures which will reduce wave-induced hydrodynamics loads on the structure and thus enhance the service life of floating bridges.
On Bending Performance of Additively Manufactured Steel Catenary Riser (SCR): Effect of Welding Residual Stress on Bending Strain Capacity
Authors: Ebrahimi Alireza , Kenny Shawn , Mohammadi Mohsen
Published: September 2018

Additive manufacturing (AM) also known as 3D printing is defined as a bottom-up layer on layer process of joining materials to make objects from 3D CAD models. Of particular interest in this paper is a powder bed fusion technique, namely Direct Metal Laser Sintering (DMLS) method to sinter metal powders. The advantages of metal 3D printing, e.g. high strength-to-density ratio, rapid prototyping, etc. are the motivations to employ this new disruptive technology in the marine sector, besides its current applications in medical, defense, aerospace, and automotive industries.

The current study is part of a series of collaborative work initiated by Marine Additive Manufacturing Center of Excellence (MAMCE) in which the bending strain capacity of two welded linepipes at the most critical failure point of SCR (i.e. touch-down zone) was examined. This paper comprises two main sections; in the first part a continuum finite element model was developed to simulate welding induced residual stresses and the results were calibrated with existing data in published literature; and the last part is dedicated to examination of bending strain capacity of the welded pipe. The methodology is used for two different model; a conventional stainless steel pipe; and a hybrid (i.e. Maraging steel-stainless steel) riser made using 3D metal printing technique in existence of welding induced residual stresses (i.e. section one). A comparison between the hybrid SCR model and conventional carbon steel one under similar conditions was presented providing valuable perspective over bending performance of each kind. The major outcomes of this paper are the residual stress pattern and bending moment-curvature graphs for both types of the pipe configurations, which comparatively demonstrate the significance of the type of manufacturing (AM and conventional methods), and existence of welding residual stress and internal pressure on bending behavior of SCR.
Can Titanium and Copper Oxide Commercial Nanoparticles Be Used for HP/HT Applications? A Comparison With the Very Well Performing Fe3O4 NP
Authors: Vryzas Zisis , Kelessidis Vassilios C. , Nalbandian Lori , Zaspalis Vassilios
Published: September 2018

Smart drilling fluids, which can change their properties according to the flow environment, must be carefully designed so that they can handle the difficult challenges of HP/HT drilling successfully. Due to their unique physico-chemical properties, nanoparticles (NP) are considered as very good candidates for the formulation of these smart drilling fluids. This study presents filtration and rheological results of newly developed high-performance water-based drilling fluid systems containing different nanoparticles, commercial (C) titanium oxide (TiO2) and commercial (C) copper oxide (CuO) NP and compares them with results from using custom-made (CM) iron oxide (Fe3O4) NP and commercial (C) iron oxide (Fe3O4) NP, previously reported.

Novel nano-based drilling fluids were made of de-ionized water, 7 wt% commercial Na-bentonite (base fluid), and NP were added at 0.5 wt%. The rheological properties of the produced suspensions were measured at temperatures up to 60°C and at atmospheric pressure with a Couette-type viscometer. Filtration characteristics were determined at elevated pressures and temperatures in a HP/HT filter press (500 psi/176°C) using ceramic discs as filter media, of permeability, k = 775 mD.

The results of this study showed that the samples containing 0.5 wt% C TiO2 caused a reduction in the fluid loss by 23%, while C CuO NP resulted in 16% reduction, when compared to that of the base fluid, at these HPHT conditions. This should be compared to the 47% and 34% reduction in fluid loss of 0.5% CM Fe3O4 NP and of 0.5% of C Fe3O4 NP, reported previously.

Analysis of rheological data revealed shear-thinning behavior for all the tested novel drilling fluids. The samples containing TiO2 and CuO NP exhibited a yield stress less than that of the base fluid, compared to the increased yield stress observed for the C and CM Fe3O4 NP. This behavior can be attributed to the fact that TiO2 and CuO NP may also act as deflocculants and prevent the gelation of bentonite suspensions.

This study shows that commercial nanoparticles of TiO2 and CuO do not perform as well as the Fe3O4 NP on filtration but provide drilling fluids with lower yield stresses, thus they could be considered as alternatives to Fe3O4 in situations where the rheological properties are critical.
Experimental Measurements of WindFloat 1 Prototype Responses and Comparison With Numerical Model
Authors: Cermelli Christian , Leroux Charlotte , Díaz Domínguez Sandra , Peiffer Antoine
Published: September 2018

This paper presents experimental results of WindFloat 1 platform and comparisons with the numerical model developed by Principle Power. The WindFloat platform is designed to support multi-megawatt wind turbines. A full-scale prototype was installed offshore Portugal from 2011 to 2016, and produced 17GWh into the Portuguese grid. An extensive monitoring system was installed, including a wave rider buoy, 6-degrees of freedom measurement devices, anemometers, strain gauges, turbine monitoring instruments. Important results obtained during the measurement campaign are described in this paper. These include power predictions, turbine and tower loads, and platform motions. Comparison with numerical simulations are also provided. The numerical analysis methodology includes fully coupled simulations, based on Orcaflex, a commercially available state-of-the-art software to compute the hydrodynamic response of floating systems, combined in the time-domain with FAST, a well-established numerical tool for the design of wind turbines. Results of these comparisons show that the numerical tools are fit for purpose, and were used to calibrate some hydrodynamic coefficients that cannot be obtained accurately with numerical analysis or scaled model tests.
Analytical Formulation of Nonlinear Froude-Krylov Forces for Surging-Heaving-Pitching Point Absorbers
Authors: Giorgi Giuseppe , Ringwood John V.
Published: September 2018

Accurate and computationally efficient mathematical models are fundamental for designing, optimizing, and controlling wave energy converters. Wave energy devices are likely to exhibit significant nonlinear behaviour, over their full operational envelope, so that nonlinear models may become indispensable.

Froude-Krylov nonlinearities are of great importance in point absorbers but, in general, their calculation requires an often unacceptable increase in model complexity and computational time. However, if the body is assumed to be axisymmetric, it is possible to describe the whole geometry analytically, thereby allowing faster calculation of nonlinear Froude-Krylov forces.

In this paper, a convenient parametrization of axisymmetric body geometries is proposed, applicable to devices moving in surge, heave, and pitch. In general, the Froude-Krylov integrals must be solved numerically. Assuming small pitch angles, it is possible to further simplify the problem, and achieve an algebraic solution, which is considerably faster than numerical integration.
Effects of Misaligned Wave and Wind Action on the Response of the Combined Concept WindWEC
Authors: Karimirad Madjid , Michailides Constantine
Published: September 2018

In the present paper, the effects of misaligned wave and wind action on the dynamic response of the WindWEC combined concept are evaluated and presented. WindWEC is a recently proposed combined wind and wave energy system; a hybrid offshore energy system that consists of: (a) a 5MW floating wind turbine supported by a spar-type substructure (e.g. Hywind), a Wave Energy Converter (WEC) that is of heaving buoy type (e.g. Wavestar), (c) a structural arm that connects the spar with the WEC and (d) a common mooring system. Hybrid offshore platforms are combining wave and wind energy systems and are designed in order to gain the possible synergy effects and reduce the cost of generated electrical power while increasing the quality of delivered power to grids. During the lifetime of a combined concept, wave and wind can be misaligned which may affect the dynamic response and as a result the functionality of it. In particular, for asymmetric configurations, the misalignment of the wave and wind may result in unexpected behaviour and significant effects that may reduce the produced power. For the case of the WindWEC concept, the relative motion of the spar platform and WEC buoy results to the produced power. In this paper, the dynamic response and power production of the buoy type WEC and wind turbine are examined for different loading conditions where the wave and wind are misaligned. Integrated/coupled aero-hydro-servo-elastic time-domain dynamic simulations considering multi-body analyses are applied. The motion, structural and tension responses as well as power production are examined. The misalignment of wave and wind results to higher loads that affect the mooring line system and motion responses of the spar. It is found that the produced power of wind turbine is not significantly affected.
Energy Extraction of Pontoon-Type Wave Energy Converter
Authors: Tay Zhi Yung , Wei Yanji , Vakis Antonis I.
Published: September 2018

Presented herein is the performance of a pontoon-type wave energy converter (WEC) similar to that of the ‘Floater Blanket’ WEC, which consists of a grid of interconnected floating elements. The current WEC design takes into account the elastic deformation of the structure under wave action and investigates its efficiency in generating wave energy as compared to its counterparts that achieve this via rigid body motions. The power take off (PTO) systems are installed at the seabed and attached to the WEC to generate energy via the vertical motions of the WEC’s structural modules. Three types of pontoon-type WEC designs are investigated, i.e. with hinges, with a reduced number of hinges and without hinges. In addition, the influence of the flexibility of the structural modules towards the energy generation is also investigated in order to assess its performance when behaving like an elastic material. The pontoon-type WEC’s structural modules with fewer or without hinge connections are preferable due to their ease in installation, while allowing for flexible deformation in the structural design would yield savings in material cost.
Development of Parametric Simulation Models for Metal Forming Processes of Plate Structures
Authors: Wurzler Tom , Lindemann Thomas , Kistner Josefine , Kaeding Patrick
Published: September 2018

During the process of workpiece productions in metal forming industries, it is necessary to control the results of the reshaped piece to ensure its quality. A common procedure of metal plate forming processes is given by the application of an upper and lower die. Therefore, ribbed die configurations can be used. To simulate the forming process of metal workpieces, the Finite Element Method (FEM) is a feasible tool. In this paper, a parametric model of a ribbed die structure is developed with the specification that only small imperfections on the workpiece surfaces will appear after the forming process. The workpieces in this paper are plates with thickness values equal and greater than 20mm. Furthermore, the springback behaviour of the different workpieces will be in the main focus of the proposed analyses. The results of the simulations are used to developed different types of holder configurations instead of the lower die. This concept might further reduce the costs of forming processes of large metal plates.
Virtual Subsea Flow Metering Technology for Gas Condensate Fields and its Application in Offshore China
Authors: Cheng Bing , Li Qingping , Wang Jue , Wang Qing
Published: September 2018

Due to the inconvenient maintenance and high costs of subsea flowmeters, virtual subsea flow metering technology is developed for subsea gas condensate fields, especially for marginal fields. In this paper, virtual subsea flow metering technology is introduced, the advantages are summarized, and international virtual metering products are listed. For a typical gas field virtual subsea flow metering system, the configuration, input and output data, as well as flow models and calculation methodology is explained. A virtual flow metering field application case in a subsea tieback gas condensate field in offshore China is introduced, from the project background to the application execution and finally the results. The virtual metering results met well with gas field data and showed great robustness by continuously working on the site.
Vortex Shedding From Hulls in Close Proximity With Relative Motion
Authors: Milne Ian A. , Graham J. Michael R.
Published: September 2018

The safe and efficient offloading of liquid natural gas (LNG) in a side-by-side configuration has emphasised the need to accurately quantify the hydrodynamic responses of floating bodies when located in very close proximity. A new series of computational results are presented for the forced roll of a hull in the presence of a second body representative of a floating FLNG facility. The vortex shedding phenomenon which provides a significant contribution to the damping of an isolated hull, is demonstrated to be modified by the presence of the second body. The total damping coefficients were found to be significantly reduced by approximately 50 percent for the very small gap widths considered. It is shown that in addition to the modification of the local shedding dynamics, the variation in the pressure field owing to the presence of the second body also contributes significantly to the reduction in the damping. The findings will be of particular interest to the offshore industry for improving and optimising offloading practices.
Experimental and Numerical Investigation of Aluminum Alloy Plates With Initial Crack Under Repeated Dynamic Impact Loads
Authors: Duan Fangjuan , Liu Weiguang , Xie De , Liu Jingxi , Hu Zhiqiang
Published: September 2018

Ships and offshore structures are often exposed to various types of repeated impact loads, such as wave slamming, floating ice impacts and ship collisions which will cause large deformation or even fracture. With imperfections due to the process of construction or damage caused by accidents, the load carrying capacity of structures will decrease. This paper investigates the load carrying capacity of aluminum alloy plate with an initial crack under repeated impact loads by means of experiments and numerical simulations. In the experiments, the prepared specimens with crack and without crack are impacted repeatedly up to plate perforation by releasing a hemispherical-headed cylindrical hammer. Numerical simulations are carried out with ABAQUS/Explicit software. The numerical models are built according to the actual experimental conditions. Comparison of the numerical predictions with the experimental results shows reasonable agreement. It is found that aluminum alloy plates under repeated impacts are sensitive to initial cracks. The fracture mode and plastic deformation of aluminum alloy plates can also be affected.
Alternative Methodologies for Subsea Flexible Strength Analysis
Authors: Miranda Anskey A. , Turner Fred P. , Barltrop Nigel
Published: September 2018

This paper presents a study of the analysis methodologies used to predict the most likely response of flexibles in a subsea environment, with the aim of determining an efficient and reliable prediction methodology. The most accurate method involves simulating multiple wave realisations of a real world sea state, i.e. irregular waves, and post-processing the results to determine the most probable maximum (MPM). Due to the computationally intensive nature of this approach, however, regular wave analysis is typically used to determine flexible response. This approach considers the maximum wave within a design storm at a desired period; the choice of periods may leave room for uncertainty in the conservatism of the approach. With proper screening, regular wave analysis can be a valid yet overly conservative approach resulting in over design and additional cost. However, if screened incorrectly, there is a possibility that the choice of periods could give results that are under conservative. In addition to regular wave analysis, the paper presents two alternative methodologies to determine the most likely response, with the focus on reducing the computational resources required. The first alternative is an ‘Irregular Wave Screen’ approach in which the wave train is screened at areas of interest for waves within a user defined threshold of the maximum wave height, in addition to other user defined parameters. Only waves within these parameters are simulated to determine responses. The second alternative is the ‘New Wave’ approach, which models the most probable wave elevation around the maximum wave crest. The calculated new wave is then placed at the desired location to determine responses. The responses of the Regular, Irregular Wave Screen and New Wave methodologies are compared with the Irregular MPM approach to determine their feasibility to predict the response of flexibles in a real world irregular sea state with lower computational requirements.
A Method to Predict Embedded Trajectory Based on the Finite Element Analyses of Bearing Capacity of Drag Anchor
Authors: Qiao Dongsheng , Bao Muren , Yan Jun , Zhou Daocheng , Li Yugang
Published: September 2018

With the development of marine resources going to deeper water depth, the mooring system design becomes more important. Predicting the embedded trajectory of drag anchor during the installation process is very significant for calculating the ultimate pullout bearing capacity of drag anchor and the mooring system design. Firstly, the initial angle and embedded depth of drag anchor are assumed. Secondly, the drag anchor penetrates a unit displacement along the direction parallel to the anchor fluke at each incremental step, and the specific position information (horizontal, vertical, angle) could be obtained. Thirdly, the ultimate bearing capacity of drag anchor at this incremental step could be calculated using the two-dimensional and three-dimensional finite element model which considering the contact friction between the drag embedment anchor and seabed clay. And then, the new specific position information could be obtained according to the mechanical equilibrium equation of inverse catenary. Finally, the whole drag anchor embedded trajectory could be obtained when the drag angle between the anchor fluke and seabed tends to zero as a limit state. In this paper, a method of predicting embedded trajectory based on the finite element analyses of bearing capacity of drag anchor is established, which could be used as a reference for the practical engineering.
Comparison of In Situ Current Measurement Methods, the Accuracy Achieved in the Field and Recommendations for Engineering Design Applications
Authors: Bush Gregory , Nolan Carey
Published: September 2018

Here we present a wealth of comparison data from acoustic backscatter current meters against current meters that use an active acoustic path (the RPS CM04). The data cover a wide range of environmental conditions. Very poor agreement between current meters frequently occurs, presenting as both bias and noise. The causes of the differences remain unproven, although for acoustic profilers deployed in deep water, failure of the assumption of the same flow in all beams is a possible source of significant error. As a result of decade’s worth of comparisons plagued with unexplained differences, we have reduced confidence in the accuracy of current data collected by acoustic backscatter sensors. We therefore avoid (where practical) using these instruments when the application of the current data is for engineering design, where uncertainty in accuracy can have significant cost or risk consequences.
Green Water Flow on a Fixed Model Structure in a Large Wave Basin Under Random Waves
Authors: Chuang Wei-Liang , Chang Kuang-An , Mercier Richard
Published: September 2018

Green water generated by random waves on a fixed, simplified geometry model structure was measured in a large wave basin. The velocity field of the flow that is aerated and highly turbulent was quantified using the bubble image velocimetry (BIV) technique. BIV utilizes shadow textures created by air-water interfaces as tracers in backlit images recorded by a high speed camera. The tracers in consecutive images are then cross-correlated to obtain the corresponding two-dimensional velocities. Random waves were generated by the JONSWAP spectrum with a significant wave height close to the freeboard. An image-based triggering method was employed to detect the green water events and trigger image acquisition. A total of 179 green water events were collected and categorized into three different types, based on the flow behavior. That includes the collapse of overtopping wave, fall of bulk water, and breaking wave crest. Statistical distributions of maximum green water velocities under random waves were developed, while the lognormal distribution was found as the best fit. By modeling the green water as a dam break flow, the Ritter solution was found to be able to capture the horizontal velocity distribution for the random green water events. A prediction equation for the green water velocity distribution under random waves was also obtained.
Alkaline Electrolysis at Sea for Green Hydrogen Production: A Solution to Electrolyte Deterioration
Authors: d’Amore-Domenech Rafael , Navarro Emilio , Mora Eleuterio , Leo Teresa J.
Published: September 2018

This article illustrates a novel method to produce hydrogen at sea with no carbon footprint, based on alkaline electrolysis, which is the cheapest electrolysis method for in-land hydrogen production, coupled to offshore renewable farms. The novelty of the method presented in this work is the solution to cope with the logistic problem of periodical renewal of the alkaline electrolyte, considered problematic in an offshore context. Such solution consists in the integration of a small chlor-alkali plant to produce new electrolyte in situ. This article describes a proposal to combine alkaline water electrolysis and chlor-alkali processes, first considering both in a separate manner, and then describing and discussing the combined solution, which seeks high efficiency and sustainability.
Simultaneous Stochastic Model of Waves and Currents for Prediction of Structural Design Loads
Authors: Bruserud Kjersti
Published: September 2018

Simultaneous data of metocean parameters, such as wind, waves and current, of sufficient quality and duration are necessary to establish reliable, joint models of metocean loads and load effects on marine structures. In lack of such joint models, the Norwegian design standard, NORSOK N-003, recommends combinations of metocean parameters for load estimations assumed to be conservative. However, the degree of conservatism is rather uncertain.

The possible conservatism in NORSOK N-003 for combinations of wave and current conditions in the northern North Sea has been assessed. To perform such an assessment, precise knowledge about the wave and current conditions is required, as well as simultaneous wave and current data of high quality and long duration.

Available measured wave and current data during nearly five years, at selected locations in the northern North Sea, are described. A thorough assessment of the current conditions at these locations is given, with the following important findings; (1) the quality of measured current data is poorer than anticipated, (2) the dominating current conditions at some locations is wind-generated inertial oscillations, (3) the seasonality of current conditions at these locations is very distinct due to the inertial oscillations and (4) significant inter-annual variations in current conditions is found.

For waves in the northern North Sea, both measured and hindcast data are found to be of appropriate quality and duration for joint considerations, but neither current measurements nor hindcast have the required quality or duration. To generate adequate current data, a simple model for wind-generated inertial oscillations is applied and validated at one location in the northern North Sea. With that, simultaneous wave and current data of sufficient quality and duration for joint modelling are available and a joint conditional model for waves and currents is proposed.

The anticipated conservatism in NORSOK N-003 for load estimations is assessed by a case study. A simplified model for a generic static load on a jacket, caused by waves and currents, is assumed. For the northern North Sea, metocean loads are estimated first according to the NORSOK N-003 recommendation, and then directly from a load times series. Comparison of the two different approaches gives a clear indication that the NORSOK recommendation is not necessarily conservative in the northern North Sea. Due to several simplifications in the steps leading up to the load estimations, this result is intended to be illustrative.