bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring Situational Factors and Attitudes Affecting Sustainable Electric Kettle Usage
Authors: Engelking Kimberly Elisabeth , Irie Kanako , Thorup Rasmus Velling , Ramanujan Devarajan
Published: November 2019

This paper explores situational factors and attitudes affecting sustainable electric kettle usage. We conducted a two-week long field study with five residents in Denmark who self-reported their electric kettle usage data, purpose of usage, and situations of usage, over the study period. A follow-up interview was also conducted after the field study to explore reasons behind the observed behaviors. Results show, the amount of excess water heated significantly varied by usage purpose as well as the time sensitivity of the usage purpose. There was no observable effect of the minimum fill level marker on the amount of excess water heated. Participants’ considerations for purchasing a specific kettle and their usage behaviors were not influenced by sustainability-related concerns. We identified four important factors that influenced the amount of excess water heated and participants’ decision to retain or dispose it. They included, (1) uncertainty in the need for hot water in the near future, (2) flexibility in the needed volume for a usage purpose, (3) forgetting to use heated water, and (4) concerns about limescale build up.
Environmental and Economic Evaluation of the Sheet Metal Stamping Process Using Alternative Lubricants
Authors: Landi Daniele , Germani Michele , Mandolini Marco , Marconi Marco , Favi Claudio
Published: November 2019

Sheet metal forming of tribologically difficult materials (e.g. stainless steel) or forming in tribologically difficult conditions (e.g. ironing, punching, deep drawing) require the use of environmentally hazardous lubricants, such as chlorinated paraffin oils in order to avoid galling. The present paper describes an environmental and economic evaluation of two alternative sheet metal stamping processes. The forming of a sheet metal component for boiler burners has been taken as case study for the analyses. In particular, two different lubricants (standard mineral versus polymer matrix-based lubricant) have been tested and compared. However, the differences among the two processes involves not only the lubrication phase, but also the electric energy consumption during the stamping and degreasing, as well as the typology of solvent (perchloroethylene versus water). Results obtained with the economic analysis show that the use of the alternative lubricant leads to a 16% reduction of the total manufacturing cost, mainly due to the optimization of the degreasing. Concerning environmental results, instead, no relevant differences can be observed for almost all the considered impact categories (ReCiPe midpoint and endpoint), since the optimized phases are not the most critical ones.
Topology Design With Conditional Generative Adversarial Networks
Authors: Sharpe Conner , Seepersad Carolyn Conner
Published: November 2019

Deep convolutional neural networks have gained significant traction as effective approaches for developing detailed but compact representations of complex structured data. Generative networks in particular have become popular for their ability to mimic data distributions and allow further exploration of them. This attribute can be utilized in engineering design domains, in which the data structures of finite element meshes for analyzing potential designs are well suited to the deep convolutional network approaches that are being developed at a rapid pace in the field of image processing. This paper explores the use of conditional generative adversarial networks (cGANs) as a means of generating a compact latent representation of structures resulting from classical topology optimization techniques. The constraints and contextual factors of a design problem, such as mass fraction, material type, and load location, can then be specified as input conditions to generate potential topologies in a directed fashion. The trained network can be used to aid concept generation, such that engineers can explore a variety of designs relevant to the problem at hand with ease. The latent variables of the generator can also be used as design parameters, and the low dimensionality enables tractable computational design without analytical sensitivities. This paper demonstrates these capabilities and discusses avenues for further developments that would enable the engineering design community to further leverage generative machine learning techniques to their full potential.
Deep Active Subspaces: A Scalable Method for High-Dimensional Uncertainty Propagation
Authors: Tripathy Rohit , Bilionis Ilias
Published: November 2019

A problem of considerable importance within the field of uncertainty quantification (UQ) is the development of efficient methods for the construction of accurate surrogate models. Such efforts are particularly important to applications constrained by high-dimensional uncertain parameter spaces. The difficulty of accurate surrogate modeling in such systems, is further compounded by data scarcity brought about by the large cost of forward model evaluations. Traditional response surface techniques, such as Gaussian process regression (or Kriging) and polynomial chaos are difficult to scale to high dimensions. To make surrogate modeling tractable in expensive high-dimensional systems, one must resort to dimensionality reduction of the stochastic parameter space. A recent dimensionality reduction technique that has shown great promise is the method of ‘active subspaces’. The classical formulation of active subspaces, unfortunately, requires gradient information from the forward model — often impossible to obtain. In this work, we present a simple, scalable method for recovering active subspaces in high-dimensional stochastic systems, without gradient-information that relies on a reparameterization of the orthogonal active subspace projection matrix, and couple this formulation with deep neural networks. We demonstrate our approach on challenging synthetic datasets and show favorable predictive comparison to classical active subspaces.
Bio-Inspired Modeling Approaches for Human Networks With Link Dissipation
Authors: Panyam Varuneswara , Layton Astrid
Published: November 2019

Structural similarities between human networks and biological ecosystems have inspired biomimetic design of human networks. The approach requires the networks to be represented as graphs, where the actors are nodes and the connections between actors are links. A major oversight in the application of ecosystem-based modeling to human networks thus far has been in the selection of actors and links. Transfers between species in a biological ecosystem are direct, happening when the species are co-located. Human networks often require a physical aid to complete the transaction, such as power transmission lines, pipelines, or vehicles. These exchange methods experience dissipation, which is not captured in current applications of ecosystem-based human network modeling. Human networks modeled as ecosystems thus far simply categorize exchanges as links in the graph, effectively forcing dissipation during material/energy transport to be neglected. This dissipation can sometimes be high relative to the total energy/material exchanged and thus is a potentially large oversight. Three hypothetical power grids and three Italian urban water distribution networks are used to quantify the impact of modeling interaction aids — power lines and water pipelines — as actors (and thus including any dissipation) in an ecosystem model. Ecological structural and flow metrics previously applied to human networks are evaluated between the two modeling methods. The comparison shows that the impact of this overlooked aspect is potentially significant and warrants consideration.
Design and Biological Simulation of 3D Printed Lattices for Biomedical Applications
Authors: Egan Paul F.
Published: November 2019

There is great potential for using 3D printed designs fabricated via additive manufacturing processes for diverse biomedical applications. 3D printing offers capabilities for customizing designs for each new fabrication that could leverage automated design processes for personalized patient care, but there are challenges in developing accurate and efficient assessment methods. Here, we conduct a sensitivity analysis for a biological growth simulation for evaluating 3D printed lattices for regenerating bone and then use these simulations to identify performance trends. Four design topologies were compared by generating varied unit cells. Biological growth was modeled in a voxel environment by simulating the advancement of a tissue front by calculating its local curvature. Designs were generated with properties suitable for bone tissue engineering, namely 50% porosity and microscale pores. The sensitivity analysis determined trade-offs between prediction consistency and computation time, suggesting calculating curvature within a radius of 7.5 voxels is sufficient for most cases. Topologies were compared in bulk with design variations. All topologies had similar tissue growth rates for a given surface-volume ratio, but with differing unit cell sizes. These findings inform future optimization for selecting unit cells based on volume requirements and other criteria, such as mechanical stiffness. A fitted analytical relationship predicted tissue growth rate based on a design’s surface-volume ratio, which enables design evaluation without computationally expensive simulations. Lattices were 3D printed with biocompatible materials as proof-of-concepts, demonstrating the feasibility of the approach for future computational design methods for personalized medicine.
On the Friction Isolator for Precision Motion Control and its Dynamics
Authors: Dong Xin , Okwudire Chinedum , Wang Jiamin , Barry Oumar
Published: November 2019

Motion stages are widely used for precision positioning in manufacturing and metrology applications. However, they suffer from nonlinear pre-motion (i.e., “static”) friction which adversely affects their precision and motion speed. Existing friction compensation methods are not robust enough to handle the highly nonlinear and variable dynamic behavior of pre-motion friction. Therefore, the first two authors have proposed the concept of a friction isolator as a simple and robust solution to mitigate the undesirable effects of pre-motion friction in precision motion stages. They experimentally demonstrated that a motion stage with friction isolator can achieve significantly improved precision, speed and robustness to variations in pre-motion friction. However, a theoretical study was not carried out to fundamentally understand the dynamic phenomena associated with using a friction isolator on a motion stage. This introductory paper investigates the dynamics of a PD-controlled motion stage with friction isolator. The influence of the friction isolator on the response and stability of the system is examined through theoretical and numerical analysis. It is shown, using a case study, that the addition of a friction isolator shrinks the range of P and D gains that can stabilize the motion stage. Several other case studies that include the effects of external excitation and integral controller are carried out to motivate deeper dynamic analyses of the friction isolator for precision motion control.
Reference Governors Based on Online Learning of Maximal Output Admissible Set
Authors: Lanchares Manuel , Kolmanovsky Ilya , Girard Anouck , Rizzo Denise
Published: November 2019

Reference governors are add-on control schemes that modify the reference commands, if it becomes necessary, in order to avoid constraint violations. To implement a reference governor, explicit knowledge of a model of the system and its constraints is typically required. In this paper, a reference governor which does not require an explicit model of the system or constraints is presented. It constructs an approximation of the maximal output admissible set, as the system operates, using online neural network learning. This approximation is used to modify the reference command in order to satisfy the constraints. The potential of the algorithm is demonstrated through simulations for an electric vehicle and an agile positioning system.
Energy Optimization of Lateral Motions for Autonomous Ground Vehicles With Four-Wheel Steering Control
Authors: Wang Fengchen , Xu Peidong , Li Ao , Chen Yan
Published: November 2019

In this paper, a hierarchical optimal four-wheel steering (4WS) controller is proposed to enhance the energy saving for vehicle lateral motions. By the integration of the four-wheel vehicle dynamics, wheel dynamics, and tire model, the vehicle propulsion power consumption is derived with respect to the front and rear wheel steering angles as control inputs. In the high level of the proposed controller, an autonomous path following control is developed to provide virtual control inputs including the lateral forces and yaw moment via the dynamic sliding mode control design. In the low level, the high-level virtual control inputs are distributed to the front and rear steering angles, in which the energy optimization problem is solved. The objective function of the optimization problem aims to minimize the vehicle propulsion power consumption and virtual control tracking error. Furthermore, the requirements of the vehicle stability and the path following accuracy are considered in the constraints. Verified by CarSim® and MATLAB/Simulink® co-simulation, the proposed 4WS hierarchical energy optimization controller can successfully reduce the power loss for vehicle lateral motions.
Gaussian-Based Kernel for Multi-Agent Aerial Chemical-Plume Mapping
Authors: He Xiang , Steiner Jake A. , Bourne Joseph R. , Leang Kam K.
Published: November 2019

This paper presents a multi-vehicle chemical-plume mapping process that incorporates onboard wind speed and direction estimation. A Gaussian plume model is exploited to develop the kernel for extrapolating the measured data. Compared to the uni- or bi-variate kernels, the proposed kernel uses the estimated wind information to refine the chemical concentration prediction downwind of the source. This new approach, compared to previous mapping methods, relies on fewer parameters and provides 30% reduction in the mapping mean-squared error. Simulation and experimental results are presented to validate the approach. Specifically, outdoor flight tests show three aerial robots with chemical sensing capabilities mapping a real propane gas leak to demonstrate feasibility of the approach.
A Preliminary Study on a Physical Model Oriented Learning Algorithm With Application to UAVs
Authors: Zheng Minghui , Chen Zhu , Liang Xiao
Published: November 2019

This paper provides a preliminary study for an efficient learning algorithm by reasoning the error from first principle physics to generate learning signals in near real time. Motivated by iterative learning control (ILC), this learning algorithm is applied to the feedforward control loop of the unmanned aerial vehicles (UAVs), enabling the learning from errors made by other UAVs with different dynamics or flying in different scenarios. This learning framework improves the data utilization efficiency and learning reliability via analytically incorporating the physical model mapping, and enhances the flexibility of the model-based methodology with equipping it with the self-learning capability. Numerical studies are performed to validate the proposed learning algorithm.
Generic On-Board Decision Support System Framework for Marine Operations
Authors: Skjong Stian , Kyllingstad Lars T. , Reite Karl-Johan , Haugen Joakim , Ladstein Jarle , Aarsæther Karl Gunnar
Published: November 2019

In this work, we present a generic framework for designing on-board decision support systems for marine operations. We discuss different technologies and methods for obtaining and analysing data and providing relevant information to on-board personnel. In particular, we focus on combining and integrating simulators with measurements, both live and stored historical data, in on-board systems for both pre-operational planning and live situation observers that might have predictive functionalities. To exemplify, we present four case studies: The first two are concerned with development of an on-board decision support system for offshore crane operations. Here, vessel motion measurements and numerical models are combined for both on-board surveillance applications and on-board pre-operational planning applications, where the latter include historical vessel characteristics. In the third, we combine simulations, measurements and automatic control in an application aimed at triple-trawl fishing operations. Finally, we present a data-driven decision support system for energy-efficient operation of hybrid propulsion systems.
Evaluation of Flow Field in the Layouts of Cross-Shaped Artificial Reefs
Authors: Tang Yanli , Hu Qi , Wang Xinxin , Zhao Fenfang , Huang Liuyi , Xie Tao
Published: November 2019

Artificial reefs (ARs) are purposely submerged in natural aquatic environments to provide additional habitat for fish. The reasonable layout of ARs on the sea floor can effectively enhance and support important marine species. This research involves a three-dimensional numerical simulation to analyze the flow effect of three types of AR layouts based on computational fluid dynamics. Through numerical simulation of the flow past the reefs, we can determine the scale of the upwelling and back-eddy flow. Based on the simulation data, the rational transverse distance between two cross-shaped artificial reefs (CSARs) is 6L (L is the length of the single reef), which is used to design the layouts of CSARs. Five indicators have been used to evaluate the flow field effect of these three layouts. According to the comparison of five indications for different layouts of CSAR, it is more reasonable to divide the AR layouts into two categories: upwelling layout and back eddy layout. Finally, the sphere of influence of the AR layouts on the fisheries resource is also discussed.
Numerical Simulation of Solitary Wave Breaking With Adaptive Mesh Refinement
Authors: Zhang Yunxing , Duan Wenyang , Liao Kangping , Ma Shan , Xia Guihua
Published: November 2019

The numerical simulation of wave breaking problem is still a tough challenge, partly due to the large grid number and CPU time requirement for capturing the multi-scale structures embedded in it. In this paper, a two-dimensional two-phase flow model with Adaptive Mesh Refinement (AMR) is proposed for simulating solitary wave breaking problems. Fractional step method is employed for the velocity-pressure decoupling. The free surface flow is captured with the Volume-of-Fluid (VOF) method combined with Piecewise Linear Interface Calculation (PLIC) for the reconstruction of the interface. Immersed boundary (IB) method is utilized to account for the existence of solid bodies. A geometric multigrid method is adopted for the solution of Pressure Poisson Equation (PPE).

Benchmark case of advection test is considered first to test the VOF method. Then the solitary wave propagation problem is utilized to validate the model on AMR grid as well as analyze the efficiency of AMR. Furthermore, the solitary wave past a submerged stationary stage problem is simulated to validate the combined IB-VOF-AMR model. All the numerical results are compared with analytic solutions, experimental data or other published numerical results, and good agreements are obtained. Finally, the influence of stage height on the occurrence of wave breaking is analyzed. The locations of wave breaking are summarized for different stage heights.
Fluid-Structure-Soil Interaction of a Moored Wave Energy Device
Authors: Tom Joe G. , Rijnsdorp Dirk P. , Ragni Raffaele , White David J.
Published: November 2019

This paper explores the response of a wave energy device during extreme and operational conditions and the effect of this response on the geotechnical stability of the associated taut moorings. The non-hydrostatic wave-flow model SWASH is used to simulate the response of a taut-moored wave energy converter. The predicted forces acting on the mooring system are used to compute the build-up of excess pore pressures in the soil around the mooring anchor and the resulting changes in strength and capacity. An initial loss of strength is followed by a subsequent increase in capacity, associated with long-term cyclic loading and hardening due to consolidation. The analyses show how cyclic loading may actually benefit and reduce anchoring requirements for wave energy devices. It demonstrates the viability of a close interdisciplinary approach towards an optimized and cost-effective design of mooring systems, which form a significant proportion of expected capital expenditures.
Optimal Methods for Estimating the JONSWAP Spectrum Peak Enhancement Factor From Measured and Hindcast Wave Data
Authors: Ewans Kevin , McConochie Jason
Published: November 2019

The specification of design wave spectra is based on spectral parameters estimated from available wave data. Measured data allow high-resolution estimates to be made, but they suffer from sampling variability and often do not contain a sufficient number of measurements in extreme sea states. Hindcast data can be used to examine spectral features associated with extreme sea states, but they can be limited by resolution and are dependent on how the physics are incorporated in the source terms of the wave model. We examine and compare the effects of estimating JONSWAP spectrum peak enhancement factor from measured and hindcast data for a range of sea states but particularly those with large significant wave heights. In the case of measured data, we build on earlier work and review effects associated with different methods for processing measured time series data, including the effect of sampling frequency, record length, and smoothing. These are then contrasted with estimates made from typical hindcast data, including the effect of the spectral shape associated with different source terms — in particular the four-wave interaction term. Finally, we provide recommendations on how best to estimate the peak enhancement factor of the JONSWAP spectrum for design purposes.
Baseline Design of the Deep Turbine Installation-Floating, a New Floating Wind Concept
Authors: Serret Jordi , Tezdogan Tahsin , Stratford Tim , Thies Philipp R. , Venugopal Vengatesan
Published: November 2019

This paper presents the preliminary design of the Deep Turbine Installation-Floating (DTI-F) concept. The DTI-F concept is a hybrid spar buoy-based floating offshore substructure capable of supporting a 7MW wind turbine with the uniqueness of being able to raise and lower the tower and nacelle, which simplifies construction, installation, maintenance, and decommissioning.

A relevant subset of design load cases (DLCs) derived from the International Electrotechnical Commission (ICE) standards is simulated with NREL-FAST software, and the aero-elastic loads are used for the structural assessment.

The paper presents the principal dimensions and crucial hydrostatic and hydrodynamic properties. The floating platform with three different mooring configurations is designed using ANSYS AQWA software, and the design is validated with experiments in laboratory conditions. The paper evaluates the design regarding the natural frequencies and the stability of the platform for a chosen site off the Scottish coast.

Further, a novel construction method, the materials chosen for the construction, and the installation and assembly processes are also outlined.
Big Data Analytics As a Tool to Monitor Hydrodynamic Performance of a Ship
Authors: Gupta Prateek , Steen Sverre , Rasheed Adil
Published: November 2019

A modern ship is fitted with numerous sensors and Data Acquisition Systems (DAQs) each of which can be viewed as a data collection source node. These source nodes transfer data to one another and to one or many centralized systems. The centralized systems or data interpreter nodes can be physically located onboard the vessel or onshore at the shipping data control center. The main purpose of a data interpreter node is to assimilate the collected data and present or relay it in a concise manner. The interpreted data can further be visualized and used as an integral part of a monitoring and decision support system. This paper presents a simple data processing framework based on big data analytics. The framework uses Principal Component Analysis (PCA) as a tool to process data gathered through in-service measurements onboard a ship during various operational conditions. Weather hindcast data is obtained from various sources to account for environmental loads on the ship. The proposed framework reduces the dimensionality of high dimensional data and determines the correlation between data variables. The accuracy of the model is evaluated based on the data recorded during the voyage of a ship.
Axial Resistance of Smooth Polymer Pipelines on Sand
Authors: Milewski Henry , Dietz Matt , Diambra Andrea , de Leeuw Lawrence W.
Published: November 2019

The axial resistance of pipelines is an important design input, influencing a variety of analyses such as buckling and axial walking. As such, accurate assessment of the frictional behaviour of the soil-pipeline interface is necessary to properly model axial behaviour. Smooth polymer coated pipelines are commonly used subsea, yet despite their common application, limited guidance exists in the main governing standards concerning the expected level of axial friction to be used in design. Related guidance that does exist (e.g. BSI, 2016) suggests a minimum friction coefficient of 0.55 for sand-pipeline interfaces. This paper reviews various aspects of sand-polymer direct shear interface testing that must be considered and presents the results of some experimental research TechnipFMC have undertaken in collaboration with the University of Bristol. These results indicate that a sand-pipeline friction coefficient of 0.55 is often unrealistic for smooth polymer coated pipelines and in many design scenarios a lower frictional coefficient is more appropriate.

The experimental test program considered the main factors believed to influence axial friction of smooth polymers on sand including D50 grain size, sand density and a range of stress levels (including the low stresses expected for subsea pipelines). All tests were conducted fully saturated to mimic subsea conditions and the roughness of the pipe coating samples was thoroughly characterised. TechnipFMC project experience has found that use of lower axial friction is sometimes beneficial (e.g. axial feed-in to trigger buckle initiation). In other cases, a higher axial friction may be better for design (e.g. limiting axial walking). Being able to better characterise the friction range is therefore important to ensure a robust design and to assist in avoiding more costly mitigation measures where they may not actually be needed.
Surge Response Control of FPSO Using Multiple Tuned Liquid Dampers: A Study on Effect of Multiple Frequencies in TLD
Authors: Gurusamy Saravanan , Kumar Deepak
Published: November 2019

Industries rely mostly on off-shore resources to fulfill the increase in demand for oil and gas. In general, for oil extraction and various other refinery processes, fixed or floating structures are being utilized. Floating Production Storage and Offloading (FPSO) system is one of the floating systems which have advantage of storing the crude oil and, if required, it can be easily moved to other places. Also, in deep Ocean where sub-sea pipeline infrastructures are often not possible and so the FPSOs give alternate option of storing and processing the crude oil. Being moored-systems, FPSOs are very flexible structures having high surge natural period and hence they may undergo larger surge displacement. Excessive displacement may cause damage for the riser system also it may affect the workability under extreme sea condition. Therefore, there is a need for investigating the issues of safety, efficiency and response control of FPSO systems under different sea-state conditions. Ocean wave loads on FPSO causes dynamic interaction between FPSO vessel and liquid in the oil storage containers. The liquid motion in containers disturbs the dynamics of the vessel significantly. Hence, it is essential to study the surge response control of FPSO in detail.

An easy way to control the response is to use the existing cargo containers of FPSO as passive damping devices. If the natural frequency of liquid oscillation is tuned to the natural frequency of FPSO, these cargo tanks can act as Multiple Tuned Liquid Dampers (MTLDs). In case of simple linear model, Tuned liquid damper (TLD) can be idealized as a Single Degree of Freedom (SDOF) system, namely Tuned Mass Damper (TMD). The present study attempts to model a TLD using three different TMD systems to account the effects of shallow water sloshing.
Port Channel Navigation Subjected to Environmental Conditions Using Reinforcement Learning
Authors: Amendola José , Tannuri Eduardo A. , Cozman Fabio G. , Reali Costa Anna H.
Published: November 2019

This paper proposes a machine learning agent for automatically navigating a vessel in a confined channel subject to environmental conditions. The agent is trained and tested using a Ship Maneuvering Simulator and is responsible for commanding the rudder, so as to keep the vessel inside the channel with minimum distance from the center line, and to reach the final part of the channel with a prescribed thruster rotation level. The algorithm is based on deep reinforcement learning method and uses an efficient state-space representation. The advantage of using reinforcement learning is that it does not require any expert to directly teach the agent how to behave under particular conditions. The novelty of this work is that: it does not require previous knowledge on the vessel dynamic model and the maneuvering scenario; it is robust against fluctuations of environmental forces such as wind and current; it considers discrete actions of rudder commands emulating the pilot actions in a real maneuver. The developed method is convenient for simulations in scenarios or areas that were never navigated before, in which no previous navigation data can be used to train a conventional supervised learning agent. One direct application for this work is the integration with a realistic fast-time maneuvering simulator for new ports or operations. Both training and validation experiments focused on the unsheltered approach channel of the Suape Port, in Brazil; these experiments were run in a SMH-USP maneuvering simulator (real environmental conditions measured on-site were employed in simulations).
Frequency Domain Analysis of a Hybrid Aquaculture-Wind Turbine Offshore Floating System
Authors: Abhinav K. A. , Collu Maurizio , Ke Sun , Binzhen Zhou
Published: November 2019

The aquaculture industry is being pushed into deeper waters, to accommodate the increasing demand for seafood worldwide and the lack of nearshore sites: aquaculture systems for farther, harsher conditions are now being proposed. The Blue Growth initiative by the European Union is also tuned in the same direction, with the focus being on developing ocean based resources, including energy and aquaculture, and finding synergies among them.

The present work proposes a novel multi-purpose platform (MPP), by retrofitting a feed barge with a small wind turbine and energy storage system, able to provide sustainable energy to a reference offshore aquaculture farm. The requirements and constraints for such hybrid system are defined, as well as a set of keys load cases, and its performance are analysed in the frequency domain. Wave loads are modelled using linear potential theory, while from an aerodynamic point of view, only the maximum thrust at the wind turbine hub level is considered in the static stability analysis. With reference to stability criteria and dynamic analysis in frequency domain, the suitability of the proposed MPP to act as a source of feed storage and energy supply is established, showing this as a potentially suitable solution.
A Benchmarking Exercise on Estimating Extreme Environmental Conditions: Methodology and Baseline Results
Authors: Haselsteiner Andreas F. , Coe Ryan G. , Manuel Lance , Nguyen Phong T. T. , Martin Nevin , Eckert-Gallup Aubrey
Published: November 2019

A wide range of methods have been proposed for the derivation of environmental contours for marine structures that must meet reliability targets. An environmental contour is a set of joint extremes of environmental conditions associated with a target return period. In general, environmental contour methods help with the prediction of some future critical combinations of environmental conditions (e.g., wind, waves, current) at a location of interest based on a limited dataset, thus allowing designers to ensure a prescribed structural reliability. In fact, some of these contour methods are specifically recommended by technical specifications and standards as part of a design process. This paper outlines the rules and procedures for a collaborative benchmarking exercise — focused on open comparison — in which researchers are invited to develop and present their own contour derivation approaches based on common datasets that will be available to all. Hindcast and observational datasets are considered and two exercises are planned: One focuses on applying environmental contour methods to a wide range of datasets and the other focuses on uncertainty characterization. Besides describing the benchmark’s methodology, this paper presents baseline results of computed contours following current recommendations. The overall goals of this endeavor are: (i) to work towards the development of more robust statistical models and contour construction methods, (ii) to encourage increased discussion in the international research community and among practitioners, and (iii) to support ongoing efforts to improve technical specifications and standards.
Experimental Study of Pipe Pulling Through Settled Barite
Authors: Taghipour Ali , Vrålstad Torbjørn , Skorpa Ragnhild , Bhuiyan Mohammad Hossain , Ytrehus Jan David , Stroisz Anna
Published: November 2019

Wells are essential in oil and gas production and construction of them is one of the main cost drivers for field development. It is normally needed to drill and construct new wells from existing fields during most of the production time. In order to reduce costs one can re-use parts of existing wells when they are no longer efficient. This is done in offshore fields also when there is limitation for new wells due to capacity of the subsea template. Through tubing drilling is a method to drill a side track through the wellbore tubulars. However, this will normally result in a smaller and less effective well completion.

Removing parts of the casing section and drill a larger size sidetrack is an option to provide a new full-size wellbore. Removing the 9 5/8” casing through the settled particle in the annulus can be challenging. The wellbore annulus is normally filled with old drilling fluid, displacing fluid and/or cement slurry. The solid particles of these annular fluids are settled during years of shut-in and make it difficult to move the casing sections. There are several techniques for pulling the casing section, but there is a lack of knowledge of some of the key mechanism causing the resistance in these operations.

In order to study and address the dominating effects in these operations, down-scaled laboratory tests are performed. The experiments reported here are performed by pulling steel pipes through the settled barite in the annulus. The pipes used in the tests are down-scaled from typical casing sizes with and without collars. The barite slurry compacted inside the annulus have different hydrostatic and pore pressures. When the pipe is pulled the required mechanical force is measured.

Results show that the single most significant factor causing resistance when pulling the tubulars is the collars outside the pipe. Furthermore, it is identified that the pore pressure improves the mobility of the settled particle around the collar. In total these results provide improved understanding on the dominating factors during pulling pipes from a packed annulus.
Eigen-Solution for Flow Induced Oscillations (VIV and Galloping) Revealed at the Fluid-Structure Interface
Authors: Bernitsas Michael M. , Ofuegbe James , Chen Jau-Uei , Sun Hai
Published: November 2019

Consistent rather than heuristic nondimensionalization of the fluid and oscillator dynamics in fluid-structure interaction, leads to decoupling of amplitude from frequency response. Further, recognizing that the number of governing dimensionless parameters should decrease, rather than increase, due to the fluid-structure synergy at the interface, an eigen-relation is revealed for a cylinder in Flow Induced Oscillations (FIO), including VIV and galloping: mA/mbod = CA/m* = 1/f*2-1. It shows that, for a given dimensionless oscillation frequency f*, the ratio of real added-mass to oscillating-mass is fully defined. Amplitude decoupling and the eigen-relation, lead to explicit expressions for coefficients, phases, and magnitudes of total, added-mass, and in-phase-with-velocity forces; revealing their dependence on the generic Strouhal number (Stn = fn*), damping, and Reynolds. Heuristic dimensionless parameters, (mass-damping, reduced velocity, mass-ratio, force coefficients) used in VIV data presentation are not needed. Theoretical derivations and force reconstruction match nearly perfectly with extensive experimental data collected over a decade in the Marine Renewable Energy Laboratory (MRELab) at the University of Michigan using four different oscillator test-models. Beyond the single frequency response model, the residuary force is derived by comparison to experiments. Established facts regarding VIV and galloping and new important observations are readily explained: (1) The effects of Strouhal, damping-ratio, mass-ratio, Reynolds, reduced velocity, and stagnation pressure. (2) The cause of expansion/contraction of the VIV range of synchronization. (3) The corresponding slope-change in oscillation frequency with respect to the Strouhal frequency of a stationary-cylinder. (4) The critical mass-ratio m* implying perpetual VIV. (5) The significance of the natural frequency of the oscillator in vacuo. (6) The effect of vortices on VIV and galloping. (7) The magnitude of vortex forces. (8) The indirect and direct vortex effects. (9) The unification of VIV and galloping onset. (10) Defining the next step in higher order theories for VIV and galloping beyond the eigen-relation.
Environmentally Assisted Fatigue Data From the INCEFA-PLUS Project
Authors: Bruchhausen Matthias , McLennan Alec , Cicero Roman , Huotilainen Caitlin , Mottershead Kevin , le Roux Jean-Christophe , Vankeerberghen Marc
Published: November 2019

The European project INCEFA-PLUS characterises environmentally assisted fatigue in light water reactor conditions. The project aims at developing a new procedure to assess environmentally assisted fatigue damage susceptibility in nuclear power plant components.

The basis for the development of a new fatigue assessment procedure is a major test campaign carried out in eleven different laboratories across Europe which will deliver approximately 200 fatigue tests. The test campaign is based on a common test matrix that was optimized by means of the Design of Experiments method. The initial focus of the project is on the effects and interactions between the factors strain range, environment (air and light water reactor environment), surface finish, hold time, and mean strain. Whereas the bulk of the test program is carried out on a single heat of 304L austentic steel, some tests on different heats of 304L or other austenitic steels allow studying the influence of material variability.

To guarantee the quality of the data, the tests are performed according to commonly agreed specifications based on ISO 12106 and each test is validated by a group of experts from within the project.

The paper presents the test procedures, provides an overview of the data that has been acquired so far, and gives an outlook on the tests that will be carried out during the final stage of the project.
Hydrogen Effects on Fracture Toughness of Additively Manufactured Type 304L Stainless Steel
Authors: McWilliams Anthony , Morgan Michael , Korinko Paul
Published: November 2019

Rectangular blocks of Type 304L stainless steel were additively manufactured (AM) using the directed energy deposition process. These samples were characterized using tensile, fracture toughness, fractography, and metallography and compared to forged Type 304L steel. The AM materials exhibited high density, tensile properties consistent with mechanically deformed stainless steel, and acceptable fracture toughness properties (> 100 Mpam) in the as fabricated and hydrogen charged (approximately 2500 appm) conditions.
Optical, electrical, and structural properties of single-phase Ti2 − xN films deposited by cathodic cage
Authors: Verbeno C. H. , Kröhling A. C. , Miranda M. C. , Freitas T. C. , Nascimento V. P. , Passamani E. C. , Gontijo L. C.
Published: November 2019

Cathodic cage, operating in the plasma nitriding mode, has been widely applied to improve the mechanical properties of steel surfaces. This paper investigated the use of this method for the deposition of titanium nitride films on a glass substrate, demonstrating its promising application in nanostructured materials with good electrical and optical properties. 300 nm thick films were grown varying the N2/H2 gas ratio for a fixed working pressure of 1 Torr and a cage temperature of 460 °C. The formation of a single-phase tetragonal δ'-Ti2 − xN structure was shown possible by means of controlling the N2/H2 gas ratio flux. The Ti2 − xN films have shown modified electrical and optical properties, such as a different charge carrier density, resistivity, transmittance, and gap energy.
A PVC Geodesic Dome Planetarium
Authors: Regester Jeff , McGahee Courtney
Published: November 2019

A planetarium is an invaluable tool for teaching introductory astronomy, but one that few astronomy educators have ready access to. Here we describe a do-it-yourself planetarium that can be built with modest funding. There have been other planetarium construction projects described in the literature and online, most of which use cardboard to make multiple faces, which are then fastened together to form a dome that serves as the planetarium projection surface. Our design uses a skeletal dome that supports a hemispherical cloth projection screen. A computer LCD projector, reflecting off a diverging half-dome security mirror on the interior edge of the dome base, serves as the starfield projector. The open-source sky simulation software Stellarium has the necessary features to pre-distort the sky image appropriately so that, after reflection from the diverging mirror, the dome is properly filled.
The multistep morphing of beetle horns
Authors: Nijhout H. Frederik
Published: November 2019

Genes that specify insect wings initiate horn development in dung beetles
Genetic Diversity, Compartmentalization, and Age of HIV Proviruses Persisting in CD4
+
T Cell Subsets during Long-Term Combination Antiretroviral Therapy
Authors: Jones Bradley R. , Miller Rachel L. , Kinloch Natalie N. , Tsai Olivia , Rigsby Hawley , Sudderuddin Hanwei , Shahid Aniqa , Ganase Bruce , Brumme Chanson J. , Harris Marianne , Poon Art F. Y. , Brockman Mark A. , Fromentin Rémi , Chomont Nicolas , Joy Jeffrey B. , Brumme Zabrina L.
Published: November 2019

The main barrier to HIV cure is the ability of a genetically diverse pool of proviruses, integrated into the genomes of infected CD4
+
T cells, to persist despite long-term suppressive combination antiretroviral therapy (cART). CD4
+
T cells, however, constitute a heterogeneous population due to their maturation across a developmental continuum, and the genetic “landscapes” of latent proviruses archived within them remains incompletely understood. We applied phylogenetic techniques, largely novel to HIV persistence research, to reconstruct within-host HIV evolutionary history and characterize proviral diversity in CD4
+
T cell subsets in five individuals on long-term cART. Participants varied widely in terms of proviral burden, genetic diversity, and age distribution between CD4
+
T cell subsets, revealing that proviral landscapes can differ between individuals and between infected cell types within an individual. Our findings expose each within-host latent reservoir as unique in its genetic complexity and support personalized strategies for HIV eradication.
Redox Regulation of a Light-Harvesting Antenna Complex in an Anoxygenic Phototroph
Authors: Fixen Kathryn R. , Oda Yasuhiro , Harwood Caroline S.
Published: November 2019

An essential aspect of the physiology of phototrophic bacteria is their ability to adjust the amount and composition of their light-harvesting apparatus in response to changing environmental conditions. The phototrophic purple bacterium
R. palustris
adapts its photosystem to a range of light intensities by altering the amount and composition of its peripheral LH complexes. Here we found that
R. palustris
regulates its LH4 complex in response to the cellular redox state rather than in response to light intensity
per se
. Relatively oxidizing conditions, including low light, semiaerobic growth, and growth under nitrogen-fixing conditions, all stimulated a signal transduction system to activate LH4 expression. By understanding how LH composition is regulated in
R. palustris
, we will gain insight into how and why a photosynthetic organism senses and adapts its photosystem to multiple environmental cues.
Draft Genome Sequence of an Acinetobacter baumannii Isolate Recovered from a Horse with Conjunctivitis in Germany
Authors: Wareth Gamal , Abdel-Glil Mostafa Y. , Schmoock Gernot , Steinacker Ulrike , Kaspar Heike , Neubauer Heinrich , Sprague Lisa D.
Published: November 2019

Here, we announce the draft genome sequence of
Acinetobacter baumannii
strain 161514, which was recovered from a horse with conjunctivitis, and determine the genetic basis of its antimicrobial resistance phenotype. The genome has a size of 3,839,365 bp and a G+C content of 38.93% and is predicted to contain 3,529 coding sequences. The isolate belongs to sequence type 462 (ST462) according to the Oxford scheme (Abaumannii1) and to ST46 according to the Pasteur scheme (Abaumannii2).
Complete Genome Sequence of the Carotenoid-Producing
Deinococcus
sp. Strain AJ005
Authors: Choi Jun Young , Lee Kunjoong , Lee Pyung Cheon
Published: November 2019

The novel species
Deinococcus
sp. strain AJ005, isolated from King George Island, synthesizes a red carotenoid. Its complete genome is made up of a single circular chromosome (3,380,712 bp, 64.2% G+C content) and four circular plasmids.
Rapid Bladder Interleukin-10 Synthesis in Response to Uropathogenic Escherichia coli Is Part of a Defense Strategy Triggered by the Major Bacterial Flagellar Filament FliC and Contingent on TLR5
Authors: Acharya Dhruba , Sullivan Matthew J. , Duell Benjamin L. , Goh Kelvin G. K. , Katupitiya Lahiru , Gosling Dean , Chamoun Michelle N. , Kakkanat Asha , Chattopadhyay Debasish , Crowley Michael , Crossman David K. , Schembri Mark A. , Ulett Glen C.
Published: November 2019

Interleukin-10 is part of the immune response to urinary tract infection (UTI) due to
E. coli
, and it is important in the early control of infection in the bladder. Defining the mechanism of engagement of the immune system by the bacteria that enables the protective IL-10 response is critical to exploring how we might exploit this mechanism for new infection control strategies. In this study, we reveal part of the bacterial flagellar apparatus (FliC) is an important component that is sensed by and responsible for induction of IL-10 in the response to UPEC. We show this response occurs in a TLR5-dependent manner. Using infection prevention and control trials in mice infected with
E. coli
, this study also provides evidence that purified FliC might be of value in novel approaches for the treatment of UTI or in preventing infection by exploiting the FliC-triggered bladder transcriptome.