bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anisotropic Multicomponent Topology Optimization for Additive Manufacturing With Build Orientation Design and Stress-Constrained Interfaces
Authors: Zhou Yuqing , Nomura Tsuyoshi , Saitou Kazuhiro 
Published: November 2019

Abstract
This paper presents a multicomponent topology optimization method for designing structures assembled from additively-manufactured components, considering anisotropic material behavior for each component due to its build orientation and distinct material behavior and stress constraint at component interfaces (i.e., joints). Based upon the multicomponent topology optimization (MTO) framework, the simultaneous optimization of structural topology, its partitioning, and the build orientations of each component is achieved that maximizes an assembly-level structural stiffness performance, subject to a maximum stress constraint at component interfaces. The build orientations of each component are modeled by its orientation tensor that avoids numerical instability often experienced by the angular representation. A new joint model is introduced at component interfaces, which enables identifying the interface region, assigning a distinct tensor for the region, and imposing a maximum stress constraint in the region during optimization. Both 2D and 3D numerical examples are presented to illustrate the effect of the build orientation anisotropy and the component interface behavior on the resulting multicomponent assemblies. The example 3D assembly, optimized for a multi-load condition, is fabricated for the purpose of demonstration.
Compact Tensegrity Robots Capable of Locomotion Through Mass-Shifting
Authors: Rhodes Tyler , Vikas Vishesh 
Published: November 2019

Abstract
Robustness, compactness, and portability of tensegrity robots make them suitable candidates for locomotion on unknown terrains. Locomotion is achieved by breaking symmetry and altering the position of center-of-mass to induce “tip-over”. The design of curved links of tensegrity mechanisms allows continuous change in the point of contact (along the curve) as compared to discontinuities in the traditional straight links (point contact) which induces impulse reaction forces during locomotion. The illustrated curve-link tensegrity robot achieves smooth locomotion through internal mass-shifting. Additionally, this tensegrity robot displays folding and unfolding. Introduced is a design methodology for fabricating tensegrity robots of varying morphologies with modular components created using rapid prototyping techniques, including 3D printing and laser-cutting. The techniques are utilized to fabricate simple tensegrity structures, followed by locomotive tensegrity robots in icosahedron and half-circle arc morphologies.
A Method to Detect Head Media Spacing Change in a Hard Disk Drive Using an Embedded Contact Sensor
Authors: Rai Rahul , Bhargava Puneet , Knigge Bernhard , Murthy Aravind N. 
Published: November 2019

Abstract
Growth in the demand for higher capacity hard disk drives (HDD) has pushed the requirement for head-media spacing (HMS) to sub-nanometer levels. The drop in operational clearance makes a head-disk interface (HDI) more susceptible to potential head-wear and contamination related issues. Such degradation processes are often accompanied by a noticeable shift in the head-disk clearance. Hence monitoring an interface for a spacing change can be helpful in early detection of its imminent failure. In this paper, we present a method to detect the change in head-disk spacing using an embedded contact sensor (ECS). This technique involves the analysis of ECS dynamic response for an interface that is subjected to heater induced spacing modulations. As the head moves closer to the disk surface, the magnitude of the ECS frequency components can be used to determine the ‘characteristic spacing’ which can be used as a metric to detect any physical change for a given interface.
Achieving Sensing Precision of 0.5nA in Pixel With 7µs Settling Time by a New External Current Sensing Circuit for AMOLED Displays
Authors: Pandey Rajeev , Huang Tzu Hao , Ho Wei-Hsuan , Chao Paul C.-P. , Pribadi Eka Fitrah 
Published: November 2019

Abstract
This study proposes a new push-pull transient current feedforward (PPTCF) based pixel current sensing circuit for active matrix organic light emitting diode (AMOLED) displays with precision within 0.5nA. A finite state machine (FSM) based digital control circuit is designed and developed for the baseline compensation. In order to achieve high accuracy, the digital baseline compensation circuit also incorporates the current digital-to-analog converter (CDAC) and successive approximation current analog-to-digital converter (CADC). The minimum LSB current for the CADC is 10nA. The readout circuit is implemented in the integrated chip with chip area of 125μm × 46μm and fabricated via TSMC T18 process. With standard 3.3V supply, the experimental result shows that the overall power consumption of the chip is 990μW watt. Despite of all parasitic capacitances of the panel display, experimental results show that the proposed circuit can sense 0.5nA current within 7μs of settling time. The sensing precision of 0.5nA within 7μs are the best among all reported literature to date.
Elementary Loading Processes and Scale Effects Involved in Wave-in-Deck Type of Loading: A Summary of the BreaKin JIP
Authors: Scharnke Jule 
Published: November 2019

Abstract
To quantify the loading due to breaking waves, model tests are currently the option of choice. However, it is suspected that scale effects lead to an overestimation of the prototype loading. As such, a typical question in impact load assessment is how conservative load measurements are. To understand how realistic model testing is in this respect, it is necessary to quantify scale effects in the measured loading due to breaking waves as well as to investigate to which extent entrapped air in the wave and during the wave impact is involved. To do so, the BreaKin Joint Industry Project was started in 2016. The objective of the BreaKin JIP was to get more insight into scale effects involved in wave-in-deck model tests and to take first steps towards linking wave kinematics with measured impact loads.
During this JIP wave-in-deck model tests were carried out in MARIN’s Depressurized Wave Basin (DWB) at two scales (25 and 50) in atmospheric and depressurized condition. This paper gives an overview of the results of the BreaKin JIP regarding loading processes involved in wave-in-deck type of impacts, effects of depressurization on measured loads and possible sources of scale effects.
Piston-Modal Resonance in a Box-Wall System
Authors: Huang Yu-xin , Geng Bao-lei , Jiang Sheng-chao 
Published: November 2019

Abstract
Hydrodynamic behavior of wave responses and wave forces induced by piston-modal resonance in the narrow gap formed by a ship section in front of a bottom mounted terminal is investigated based on the OpenFOAM® package. Numerical simulations suggested that the free surface piston-modal oscillations in the narrow gap have closely relationship with the vertical velocity along the gap bottom, implying the velocity flow around the gap bottom is able to affect the wave amplitude in the narrow gap, significantly. The horizontal wave forces can be decomposed into static water forces due to the difference of water level besides the box and the dynamic water forces due to the velocity flow. The amplitudes of static water forces are larger than that of horizontal wave forces, implying that the dynamic water forces can counteract part action of the static water forces. The dynamic wave forces approach to the maximal values at resonant frequencies, indicating that the extreme flow velocity around resonant frequency is useful for reducing the horizontal wave forces.
Design and Inclusion of a Desalination System in a Floating Offshore Wind Farm
Authors: Miriello Davide , Walker Michael , Canizares Loris , Smith Aaron , Roddier Dominique 
Published: November 2019

Abstract
This paper investigates the techno-economic feasibility of integrating a desalination system to an offshore wind farm.
The first part of the paper involves a proposal for the design of a desalination system fitted inside the WindFloat Atlantic hull. Taking into account of the power, footprint, volume and weight requirements of the desalination system, the desalination capacity is chosen to be 10,000 m3/d per platform2. A 3D model of the system is also presented.
The second part of the paper focuses on the development of an economic model that gives as output the levelized cost of water (LCOW) for the studied technology. At first, a methodology to estimate capital expenditure (Capex) and operational expenditure (Opex) of an offshore desalination system with the above-mentioned characteristics is presented. Then, three locations with high wind speeds and with frequent exposure to droughts (Gran Canaria, California and South Africa) are chosen and the model is applied. Particularly interesting results are found for Gran Canaria, isolated system with favorable conditions (high electricity price, high water production cost and good offshore wind resource).
Analytical Study for Lateral Buckling of Imperfect Pipelines With Distributed Buoyancy Section
Authors: Wang Zhenkui , van der Heijden G. H. M. , Tang Yougang 
Published: November 2019

Abstract
Distributed buoyancy method is one of the buckle initiation techniques used to trigger controlled lateral buckling at planned locations for subsea pipelines operating under high temperature and high pressure (HT/HP) conditions. Deviations from a straight profile for pipelines may be introduced by the pipe-laying vessel’s sway motion during the installation process. In this study, analytical solutions of lateral buckling are deduced for imperfect unburied subsea pipelines with a distributed buoyancy section. The effect of initial imperfections on buckled configurations and typical post-buckling behaviours is illustrated and analysed. The results show that, compared to the case without initial imperfection, lateral displacement amplitude becomes larger when initial imperfection exists. Maximum compressive stress increases when wavelength of initial imperfection is smaller than buckled length of pipeline. However, maximum compressive stress decreases when wavelength of initial imperfection is larger than buckled length of pipeline. So it’s better to introduce longer wavelength of initial imperfection.
Study of Extreme Waves Propagating Over Reefs in Large Wave Flume
Authors: Chen Songgui , Wang Zeming , Zheng Jinhai , Zhang Chi , Hu Ke 
Published: November 2019

Abstract
Waves propagating over reefs have been studied by many researchers. However due to limitation of small wave flume, most experiments focused on the normal waves. Extreme waves are the input parameters for structure design on reefs. Thus, experiments of extreme waves propagating over reefs were conducted in the large wave flume of the Tianjin Research Institute of Water Transport Engineering. Extreme wave hydrodynamic within surf zone will be focused on. Tests with different wave heights Hi, wave periods T and water levels on reefs h have been carried out. The model scale is set to be 1:15, then Hi from 4.5m to 12m, T from 9s to 17s, hr from 0 to 3m are generated in the test. Wave breaking points are observed by high speed camera. Wave breaking points move offshore as Hi and T increase and h decrease. Wave setups and wave-induced flows along the reef are measured at different locations. It can be found that wave setups increase with increasing Hi and T and decreasing water level h. Wave-induced flows increase with increasing Hi and h and decreasing T. As waves propagate towards landside, wave setups and wave-induced flows have a local extremum at the middle of surf zone. Compared with our test, Gourlay’s formulas overestimate wave setup while underestimate wave induced flow within extreme wave surf zone.
Analytical Methods for Preliminary Design of Anchor Flanges for Subsea Structures
Authors: Rajaratnam Sabesan , Sriskandarajah T. , Clayton Daryl , Roberts Graeme , Loentgen Vincent , Charnaux Carlos 
Published: November 2019

Abstract
Anchor flanges are interface items which are used to connect pipelines to subsea in-line and end termination structures. They are forged and tend to be long-lead items; therefore, the design of an anchor flange should be completed at a very early project stage, possibly even during the tender phase. An optimised, analytical method for preliminary design would result in reduced design time overall and have beneficial cost implications.
The analytical notch methods (i.e. Neuber’s and Glinka’s) that are presented utilise linear-elastic stress concentration factors to make realistic predictions of the ultimate load carrying capacity of an anchor flange in the non-linear regime.
The linear-elastic stress concentration factor values are calculated with simple analytical formulae and graphs. The analytical notch methods are deployed to predict the anchor flange limit load and peak plastic strain and thereby ensure that the plastic strain remains within the allowable limits of design codes.
The cost and time saving associated with the analytical notch methods, and the accuracy that is maintained, are assessed by comparison with the predictions results obtained from detailed finite element analyses.
Variability in Encountered Waves During Deterministically Repeated Seakeeping Tests at Forward Speed
Authors: van Essen Sanne 
Published: November 2019

Abstract
Numerical seakeeping codes for ships at forward speed in waves are often validated or tuned based on experiments, which makes knowledge about the experimental variability essential. This variability was evaluated using repeat tests during a state-of-the-art seakeeping campaign.
A steep wave condition over the longitudinal basin axis (waveA) and a less steep oblique wave condition (waveB) were studied. Overall similarity as well as individual crest height, steepnesses and timing variability are discussed, because ship response is not equally sensitive for every point in the wave time series. The variability of the measured incoming wave crests and their timing increases with distance from the wave generator for waveA. The crest height variability for waveB is lower and more constant over the basin length (because the propagation distance to the model is constant in oblique waves and wave breaking is less likely).
It was shown that only a small part of the variability close to the wave generator is caused by ‘input’ uncertainties such as the accuracy of the wave generator flap motions, measurement carriage position, their synchronisation and measurement accuracy. The rest of the variability is caused by wave and basin effects, such as wave breaking instabilities and small residual wave-induced currents from previous tests. The latter depend on previous wave conditions, which requires further study.
Further work on the influence of the wave variability on the variability of ship motions, relative wave elevation along a ship and impact loads on deck of a ship at forward speed will be presented in a next publication.
Mean Load Impact on Mooring Chain Fatigue Capacity: Lessons Learned From Full Scale Fatigue Testing of Used Chains
Authors: Gabrielsen Øystein , Larsen Kjell , Dalane Oddgeir , Lie Hans B. , Reinholdtsen Svein-Arne 
Published: November 2019

Abstract
Fatigue of mooring chain is for many floating offshore installations a limiting factor in design. With aging installations and the need for field life extension beyond the original design life, questions on mooring chain endurance are raised. Current SN curves utilized in fatigue limit state (FLS) calculation are based on full scale testing of new chain, performed at a high mean load level (20% of the chains minimum breaking load (MBL)). The high mean load level in the tests do not correspond to the conditions for many chains in operation, as mean load in fatigue relevant seastates are often significantly less than mean load used in the new chain fatigue tests. Mooring chains in operation also experience different degree of corrosion, both general corrosion and pitting. Surface roughness and corrosion pits contribute to crack initiations, and thus reduce fatigue capacity. Fatigue tests with new chain condition cannot be assumed representative for corroded chains.
As part of mooring integrity programs, Equinor has been replacing mooring chains since year 2000. To assess actual fatigue capacity, many chain segments have been full scale fatigue tested. First tests started in 2011, and the tests cover different degrees of corrosion. The tests have been performed at typical mean load levels relevant for operation of the installations, which for most cases are less than 20%MBL. From these tests it is observed that fatigue capacity in some cases are better than expected for new chain, even for chain segments with significant corrosion. Fatigue test results show a large effect of the mean load. For test cases with significant corrosion and high mean load (20%MBL), a significant reduction in fatigue capacity compared to new chains is found.
This paper presents some of the fatigue test results on used chain, highlighting the effect of the mean load for the given chain conditions. Effect of corrosion at mean load of 20%MBL is also included. The paper discusses some of the underlaying causes for the mean load dependency.
State of the Art and Knowledge Gaps on Modelling Structures in Cold Regions
Authors: von Bock und Polach R. U. Franz , Klein Marco , Kubiczek Jan , Kellner Leon , Braun Moritz , Herrnring Hauke 
Published: November 2019

Abstract
The environment in cold regions undergoes significant changes that manifest in rising temperatures and melting ice caps. These processes allow access to new areas for shipping and the installation of structures. However, the occurring changes are not solely a reduction of ice, but also waves increasingly occur in cold regions contributing to ice break up in the Marginal Ice Zone (MIZ) and the transport of ice towards the open sea. Much work has been done to combine the single topic disciplines: wave-hydrodynamics, ice mechanics and structure mechanics to wave-structure (WSI) and ice-structure interaction (ISI). The changing environment in cold regions and the increased wave activity form a new combined discipline: wave-ice-structure interaction (WISI). This paper addresses existing knowledge gaps of the future loading scenario WISI that need to be addressed in engineering to ensure safety for future operations in Polar Regions.
The knowledge gaps however, do not only refer to the discipline interfaces, i.e. challenges in combining them, but also to knowledge gaps within them.
Wave statistics and the cross-effect between wave and ice are widely unknown which limits the definition of a design wave-scenario. Structures in such environments are exposed to subzero temperatures and neither their impact on properties nor on fatigue life is fully understood. While most phenomena of these two disciplines and their implementation into numerical models are established the ice mechanics appear as the weakest link. Ice is a complex material and not all aspects of its mechanical behaviour are understood and if – the implementation into (numerical) models has not been successful yet. Ice pieces that are energetically charged by waves and collide with structures at high velocities and for such high impact loads the governing ice mechanics are hardly covered by the state of the art or not at all.
Hydrodynamics of Towed Vertical Surface-Piercing Cylinders
Authors: Potts Douglas A. , Binns Jonathan R. , Marcollo Hayden , Potts Andrew E. 
Published: November 2019

Abstract
This project investigates a cantilevered cylinder projecting down into the water column moving at high velocity through still water, as is applicable to submarine masts. Surface-piercing cylinders differ from fully submerged cylinders due to the generation of surface wakes and under increasing flow speeds the formation of a ventilated pocket in the lee of the cylinder, both of which grow with increasing velocity, with concomitant effects on the hydrodynamic loading. The relative length of submergence, or immersed aspect ratio (L/D) and end conditions of the cylinder with respect to tip vortex drag effects may also impact the hydrodynamic loads and wake formation. Laboratory testing of surface-piercing cylinders to date has predominantly been confined to characterising the wakes shed from a rigid cylinder cantilevered down into the water from a towing tank carriage, which under certain test conditions will also exhibit significant Vortex-Induced-Vibration (VIV), though not adequately identified and accounted for in its magnification of drag and wake.
Laboratory Investigation of Helical Strakes With Serrated and Twisted Fins to Suppress VIV
Authors: Assi Gustavo R. S. , Crespi Tommaso 
Published: November 2019

Abstract
Slender offshore structures of a cylindrical cross section, such as drilling and production risers, are susceptible to vortex-induced vibrations (VIV) when exposed to water currents. The present work presents an experimental investigation of the suppression of VIV of a circular cylinder by means of three different types of helical strakes: (i) a strake with continuous blades, (ii) a strake with serrated blades (or fins) and (iii) a strake with serrated blades individually twisted in relation to the incoming flow. By altering the blade geometry to produce the twisted-bladed strake, it was possible to keep the same level of suppression of the cross-flow vibration achieved by conventional strakes, but reducing drag in 15%. Experiments have been conducted in a recirculating water channel at moderate Reynolds numbers.
Making Effective WEC Design Choices Based on Simulation and Analysis
Authors: Vance Charlene , Ringsberg Jonas W. , Yang Shun-Han 
Published: November 2019

Abstract
The study presents analyses of key parameters that affect the performance of the point absorbing wave energy converter (WEC). Performance is assessed by running hydrodynamic and structural response simulations and calculating the power absorption of the WEC and fatigue damage in the mooring lines from the output data. The baseline model of the WEC input to the simulation is modelled after the WaveEL 3.0 device, designed by Waves4Power and installed in Runde, Norway. Simulations are run for single buoy and small array configurations, varying environmental conditions, mooring system, and WEC buoy shaft length. Environmental conditions are chosen to reflect locations studied as potential future installation sites. Select configurations are further analyzed through an analysis of LCOE and LCA. The results show that optimal mooring line geometry depends on water depth, and that optimal shaft length depends on the average sea conditions at the location. The array simulations show that small WEC separating distances will limit the mooring line length, which will result in lower power absorption and lower fatigue lives in the mooring lines. The LCOE shows that the four-buoy array configuration is the most profitable, and both the LCOE and LCA show that the main process contribution to climate change and the total product cost is the manufacturing of the WEC buoy itself. The research in this study demonstrates the importance of using simulations to make effective WEC design choices for a given environment.