bluuebunny/crossref_metadata_2025 huggingface dataset:
The longitudinal association between weight change and health‐related quality of life in adults and children: a systematic review
Authors: Hayes M. , Baxter H. , Müller‐Nordhorn J. , Hohls J. K. , Muckelbauer R.
Published: October 2017

This systematic review examined longitudinal associations between weight change (weight gain and loss) and both physical and mental aspects of health‐related quality of life (HRQOL) compared with stable weight in adults and children of the general population. MEDLINE, EMBASE, PsycINFO and PubMed databases were searched. Longitudinal observational studies measuring HRQOL with six predefined instruments were synthesized according to type of association: weight change and change in HRQOL (change‐on‐change association) and weight change and HRQOL at follow‐up (predictive association). Twenty studies of adults (n = 15) or children (n = 5) were included. Fifteen studies used the SF‐12 or SF‐36. Results of nine studies in adults examining the change‐on‐change association were combined through a tallying of 606 analyses. Weight gain was most often associated with reduced physical, but not mental HRQOL, across all baseline body mass index categories and in both men and women. Weight loss may be associated with improved physical, but not mental HRQOL, among adults with overweight and obesity. Weight gain was more strongly associated with HRQOL than weight loss, implicating a greater need for preventative strategies to tackle obesity. Results in children and for the predictive association generally reflected these findings but require further research.
Muscle fiber diameter assessment in cleft lip using image processing
Authors: Khan MFJ , Little J , Abelli L , Mossey PA , Autelitano L , Nag TC , Rubini M
Published: October 2017

Objective

To pilot investigation of muscle fiber diameter (MFD) on medial and lateral sides of the cleft in 18 infants with cleft lip with or without cleft palate (CL/P) using image processing.

Material and Methods

Formalin‐fixed paraffin‐embedded (FFPE) tissue samples from the medial and lateral sides of the cleft were analyzed forMFDusing an image‐processing program (ImageJ). For within‐case comparison, a paired Student'sttest was performed. For comparisons between classes, an unpairedttest was used.

Results

Image processing enabled rapid measurement ofMFDwith majority of fibers showing diameter between 6 and 11 μm. There was no significant difference in meanMFDbetween the medial and lateral sides, or betweenCLandCLP. However, we found a significant difference on the medial side (p = .032) between males and females.

Conclusion

The image processing onFFPEtissues resulted in easy quantification ofMFDwith finding of a smallerMFDon the medial side in males suggesting possible differences in orbicularis oris (OO) muscle between the two sexes inCLthat warrants replication using larger number of cases. Moreover, this finding can aid subclinical phenotyping and potentially in the restoration of the anatomy and function of the upper lip.
Acceptance and commitment therapy for psychosis and trauma: Improvement in psychiatric symptoms, emotion regulation, and treatment compliance following a brief group intervention
Authors: Spidel Alicia , Lecomte Tania , Kealy David , Daigneault Isabelle
Published: October 2017

Objectives

Acceptance and Commitment Therapy (ACT) has shown effectiveness for individuals with psychosis and individuals with a history of childhood trauma, but has not been investigated with people with psychosis who also have a history of childhood trauma. This study aims at determining the efficacy of a mindfulness‐based ACT with this clientele in diminishing psychiatric symptoms, trauma‐related symptoms, as well as in improving treatment adherence.

Design and Methods

Fifty participants meeting our inclusion criteria were recruited and randomized to take part in either 10 sessions of ACT group, or Treatment as Usual (TAU).

Results

Using RCT it was found that symptom severity, for both overall symptoms (BPRS) and anxiety (GAD), decreased over the course of the treatment, and participants' ability to regulate their emotional reactions (i.e., accept them) increased. The study also found that treatment engagement increased with regards to help‐seeking for those in the ACT group, compared with the TAU controls.

Conclusions

Acceptance and Commitment Therapy offered in a group appears a promising treatment for those with psychosis and history of trauma.

Practitioner points

To understand the benefits of ACT with those who suffer from psychosis and a history of trauma.

To further the understanding of the effectiveness of ACT.
Lessons of a day hospital: Comprehensive assessment of patients with albinism in a European setting
Authors: Marti Aurélie , Lasseaux Eulalie , Ezzedine Khaled , Léauté‐Labrèze Christine , Boralevi Franck , Paya Clément , Coste Valentine , Deroissart Vincent , Arveiler Benoit , Taieb Alain , Morice‐Picard Fanny
Published: October 2017

Albinism is a rare genetic disease, comprising syndromic and non‐syndromic forms. We assessed clinical and genetic characteristics in a prospective evaluation of 64 patients (33 children and 31 adults) seen at a specialized day hospital. Causative genetic mutations were found in TYR (23/64, 35.9%), OCA2 (19/64, 29.7%), TYRP1 (1/64, 1.6%), SLC45A2 (12/64, 18.7%), C10orf11 (1/64, 1.6%), HPS1 (3/64, 4.7%), HPS5 (1/64, 1.5%), HPS6 (1/64, 1.6%) and GPR143 (2/64, 3.1%). Causative mutations remained undetermined for one patient (1.6%). Heterogeneity for hair and skin phenotype was noted across and within the different genotypes. Skin and hair hypopigmentation did not correlate with visual impairment. The diagnosis of unrecognized syndromic forms and of cases of ocular albinism in this prospective and comprehensive series of patients with albinism in a European setting is remarkable. Photoprotection was overall good but not optimal.
Epigenetics of skin cancer: Interventions by selected bioactive phytochemicals
Authors: Penta Dhanamjai , Somashekar Bagganahalli S. , Meeran Syed Musthapa
Published: October 2017

The prevalence and risk of skin cancer have been increasing over past three decades. Two major types of skin cancer observed in humans are melanoma and nonmelanoma. Nonmelanoma further subdivided into basal cell carcinoma and squamous cell carcinoma. Melanoma arises from melanocyte which locates at the bottom layer of skin epidermis, which primarily protects the skin from being exposed to external factors. Melanoma is less common among all other types of skin cancers but causes higher mortality. Epigenetic regulation associated with the transcriptional activation and inactivation of genes plays a major role in various disease progression including skin cancer. The major epigenetic changes observed at cellular level include DNA methylation, histone modifications, and miRNA‐mediated gene regulation. The aberrant pattern in these epigenetic processes leads to altered expression of several genes involved in cell cycle, cell proliferation, cell motility, and apoptosis. Several natural bioactive phytochemicals have been shown to exhibit epigenetic modulatory capability and act as chemopreventive as well as therapeutic agents. In this review, we mainly discuss the major epigenetic modifications observed in melanoma and the epigenetic modulatory role of selected bioactive phytochemicals against the skin cancer.
Characteristics of Cu–Mo Mineralization in the Chatree Mining Area, Central Thailand
Authors: Tangwattananukul Ladda , Ishiyama Daizo
Published: October 2017

Cu–Mo mineralization occurs in southern part of the Chatree Au–Ag deposit, central Thailand. Quartz veins of Cu–Mo mineralization are divided into five types: Types A, B, C, D and E. Quartz veins of Types A, B and C are hosted in altered granodiorite porphyry, and quartz veins of Types D and E occur in altered andesite lava. Mineral assemblages of Types A, B and C quartz veins are composed of qz–chl–ilt–mol–py–ccp, qz–chl–ilt–ccp–py and qz–chl–ilt–ccp–py–sp–po, respectively. Types D and E quartz veins consist of qz–chl–py–ccp–sp–po and qz–ep, respectively. Fluid inclusions of quartz veins are divided into liquid‐rich two‐phases fluid inclusion, vapor‐rich two‐phases fluid inclusion and multiphase solid‐bearing fluid inclusion. Coexistence of a halite‐bearing fluid inclusion having salinity of 37 equiv. wt.% NaCl and a vapor‐rich two‐phases fluid inclusion having salinity of 1 equiv. wt.% NaCl suggests that the Cu–Mo‐bearing quartz veins were formed at temperature of 450°C and pressure of 250 bars (depth of approximately 1.5 km from the paleosurface). Based on the formation temperature of 450°C of quartz veins and the δ18O values of quartz of the quartz veins, the δ18O value of fluid responsible for the Cu–Mo‐bearing quartz vein is estimated to be +9.9‰. The origin of fluid forming the Cu–Mo‐bearing quartz veins in the N prospect of the Chatree mining area would be magmatic water. Based on the characteristics of geology, age, mineral assemblage and the formation environment, Cu–Mo mineralization would be different from the epithermal Au–Ag mineralization of the Chatree mining area.
A Spatiotemporal Multispecies Model of a Semicontinuous Response
Authors: Jones-Todd Charlotte M. , Swallow Ben , Illian Janine B. , Toms Mike
Published: October 2017

As accessible and potentially vulnerable species high up in the food chain, birds are often used as indicator species to highlight changes in ecosystems. This study focuses on multiple spatially dependent relationships between a raptor (sparrowhawk), a potential prey species (house sparrow) and a sympatric species (collared doves) in space and time. We construct a complex spatiotemporal latent Gaussian model to incorporate both predator–prey and sympatric relationships, which is novel in two ways. First, different types of species interactions are represented by a shared spatiotemporal random effect, which extends existing approaches to multivariate spatial modelling through the use of a joint latent modelling approach. Second, we use a delta–gamma model to capture the semicontinuous nature of the data to model the binary and continuous sections of the response jointly. The results indicate that sparrowhawks have a localized effect on the presence of house sparrows, which could indicate that house sparrows avoid sites where sparrowhawks are present.
Platelets in liver regeneration
Authors: Meyer J. , Balaphas A. , Fontana P. , Sadoul K. , Morel P. , Gonelle‐Gispert C. , Bühler L.
Published: October 2017

Background and Objectives

Loss of liver tissue leading to impairment of liver function represents a major cause of mortality. Understanding the mechanism of liver regeneration and developing therapies to sustain liver regeneration are of high therapeutic relevance. In this regard, platelets are considered as potential candidates for stimulating liver regeneration.

Methods

We aim to review the most recent evidence regarding the role of platelets in liver regeneration.

Results

Platelets stimulate liver regeneration in animal models of liver resection. In humans, platelets are independent predictors of postoperative mortality, liver function and volume recovery. One proposed mechanism by which platelets stimulate liver regeneration relies on their direct effect on hepatocytes. Following partial hepatectomy, platelets accumulate in the residual liver and release their granule content. Platelet‐containing molecules, such as HGF, VEGF, IGF‐1 and serotonin, stimulate hepatocyte proliferation. A putative additional mechanism involves the transfer of platelet mRNA to hepatocytes following platelet internalization. Recent studies have suggested that the effect of platelets relies on their interactions with LSEC. Platelets induce the secretion of IL‐6 from LSEC, a strong initiator of hepatocyte proliferation. Additionally, platelets convey molecules that may impact LSEC function and, by extension, liver regeneration. Platelets potentially interact with Kupffer cells, but the effect of that interaction on liver regeneration remains to be determined.

Conclusion

Platelets stimulate liver regeneration. Several mechanisms seem to be involved, acting on the level of hepatocytes, LSEC and potentially Kupffer cells. Identification of the platelet‐molecule(s) involved may lead to targeted therapies for patients with impairment of liver function.
Embarked Quad Flat Nonlead 16, 32, and 64 Electronic Devices Subjected to Free Convection: Influence of the Adhesive Paste on the Junction Temperature
Authors: Baïri Abderrahmane , Chanetz Bruno , Millán-García J. A.
Published: October 2017

The junction temperature of the quad flat nonlead (QFN) electronic devices equipping embarked assemblies may be controlled so that it does not exceed the maximum value recommended by the manufacturer. The packaging design is then important to ensure correct operation and high reliability, given the significant power generated during operation and the inclination angle of the packages during the flight. It is particularly important when thermoregulation is achieved by means of natural convection. The objective of this study is to examine the influence of the adhesive paste used to connect the Die of the QFN with its base. The study deals with three devices among the most used in the conventional arrangements: the QFN16, 32, and 64. A three-dimensional (3D) numerical solution based on the control volume formulation allows to determine their thermal behavior for generated power ranging from 0.1 to 1.0 W by steps of 0.1 W and inclination angle varying between 0 deg (horizontal position) and 90 deg (vertical position) by steps of 15 deg. A wide range of the paste’s thermal conductivity has been considered, varying between −80% and +100% of its average value, measured by means of the transient plane source (TPS) method. The numerical results confirmed by measurements show that the junction temperature strongly increases when the conductivity of the paste decreases. The temperature is moderately reduced when the paste is thermally more conductive. Relationships are proposed to calculate the junction temperature for the three considered devices, according to the generated power, the inclination angle, and the relative paste’s thermal conductivity.
Airflow Management on the Efficiency Index of a Container Data Center Having Overhead Air Supply
Authors: Wang Cheng-Hao , Tsui Yeng-Yung , Wang Chi-Chuan
Published: October 2017

Effect of airflow managements on the efficiency index of a small container data center having overhead air supply is reported in this study. Seventeen arrangements and configurations regarding the airflow and blockage arrangements are experimentally examined and compared. Test results indicate an appreciable hot air recirculation occurring for rack arrangement without any blockage, and the hot spot occurs at the second rack alongside the cold aisle. The hot spot had moved to the first rack when the blockage plate is installed on the rack top. Rack locations relative to air handler casts a negligible effect on the efficiency index, and it is comparatively more effective by sealing the trailing of the cold aisle. A smaller cold-aisle spacing helps to lower the temperature distribution, and an additional opening of the supplied vent will not help in removal of hot spot. Shutting off the grille in the center of cold aisle is also unable to fix the hot air recirculation and may even incur hot air reversal. The hot air reversal can be removed by adding additional blockage plate at the flow reversal section. Higher supplied air flow rate also improves the efficiency index considerably.
Influence of Stator Blade Geometry on Torque Converter Cavitation
Authors: Liu Cheng , Wei Wei , Yan Qingdong , Weaver Brian K. , Wood Houston G.
Published: October 2017

Cavitation in torque converters may cause degradation in hydrodynamic performance, severe noise, or even blade damage. Researches have highlighted that the stator is most susceptible to the occurrence of cavitation due to the combination of high flow velocities and high incidence angles. The objective of this study is to therefore investigate the effects of cavitation on hydrodynamic performance as well as the influence of stator blade geometry on cavitation. A steady-state homogeneous computational fluid dynamics (CFD) model was developed and validated against test data. It was found that cavitation brought severe capacity constant degradation under low-speed ratio (SR) operating conditions and vanished in high-speed ratio operating conditions. A design of experiments (DOE) study was performed to investigate the influence of stator design variables on cavitation over various operating conditions, and it was found that stator blade geometry had a significant effect on cavitation behavior. The results show that stator blade count and leaning angle are important variables in terms of capacity constant loss, torque ratio (TR) variance, and duration of cavitation. Large leaning angles are recommended due to their ability to increase the cavitation number in torque converters over a wide range of SRs, leading to less stall capacity loss as well as a shorter duration of cavitation. A reduced stator blade count is also suggested due to a reduced TR loss and capacity loss at stall.
Extreme Loads on a Jacket Based on Joint Metocean Data
Authors: Bruserud Kjersti
Published: October 2017

In lack of simultaneous metocean data for wind, waves and currents, Norwegian design regulations recommend a combination of metocean parameters for estimation of extreme metocean loads on offshore structures assumed to be conservative. The possible conservatism in the design regulations and also the effect of currents in the estimation of extreme loads are considered. A simplified parametric load model for a jacket, based on waves and currents, is assumed. Both measured and hindcast wave data are combined with different measured current data into load time series and the extreme loads estimated. The extreme load according to the recommended approach is also estimated. This is done at four locations in the northern North Sea. When compared to the recommended approach, the other approaches yield a reduced estimated extreme metocean load. Current is found to have an effect on the total extreme load. The results are intended be illustrative and not suitable for use in design.
Quantifying Uncertainties in Phenomenological Model of Two-Dimensional VIV Using Multivariate Monte Carlo Simulations
Authors: Tagliaferri Francesca , Srinil Narakorn
Published: October 2017

Phenomenological modelling based on the use of coupled wake-cylinder oscillators has been implemented for several decades for vortex-induced vibration (VIV) response predictions of rigid circular cylinders and long flexible risers. Although such models can capture several VIV nonlinear phenomena, they still rely on empirical coefficients and parameters with some levels of uncertainties associated with fluid-structure interactions. Most of these are due to the variation in experimental test conditions giving rise to different benchmarking test data in the literature. A very few studies have quantified such model uncertainties.

To gain an insight into the relative contributions of these coefficients, this paper presents a sensitivity study based on a multivariate Sobol-Monte Carlo approach for a two-dimensional nonlinear coupled wake-cylinder oscillator model simulating combined cross-flow/in-line VIV. A preliminary investigation is carried out to identify the relative contribution to the model uncertainty of the geometrical, empirical wake and wake-cylinder coupling coefficients. The effect of Reynolds number (Re) in the subcritical flow regime is also taken into account through a lift, drag, Strouhal and wake coefficient depending on calibration with experimental data. A key challenge is the identification of suitable probability distribution function to model the scattering experimental datasets. A combination of Gaussian and uniform distributions are calibrated.

Parametric studies based on the combined Sobol-Monte Carlo simulations reveal the uncertainties due to the coupling of empirical coefficients and system parameters governing the two-dimensional lock-in and combined cross-flow/in-line VIV responses. The relative importance of the selected wake coefficients and geometric parameters appears to be strongly dependent on the system mass ratio as well as Re influencing the hydrodynamic properties including the lift and drag coefficients, the Strouhal number and stall parameter. For the cylinder with a lower mass ratio, greater uncertainties are found within the considered sub-critical Re range for both cross-flow/in-line VIV. This remark should also be recognized in the phenomenological VIV modelling of long flexible risers in offshore applications.
The Study on the Influence of Pipe-Soil Interaction on VIV for Different Free Span Types
Authors: Zhou Chongyao , Xu Gang , Huang Zhiming , Zhang Dagang , Ye Naiquan , Sævik Svein
Published: October 2017

Subsea pipeline laid on the seabed will experience free span when the lay path is long and seabed is rugged. Hydrodynamic loads caused by the currents around the pipeline can induce oscillations in both cross-flow and in-line directions. This phenomenon is called vortex-induced vibration (VIV) which is the most common case that could induce serious fatigue problems. The pipe-soil interaction is one of the main factors that influence the vibration.

In this paper, a study focusing on the effect of pipe-soil interaction on VIV for different types of free span is presented. The Milan wake oscillator is applied to calculate the dynamic response induced by VIV in Orcaflex, and the results are compared with experimental data to identify its validity. A sensitivity study is also performed to study the parameter influence of the Milan wake oscillator model.

Four types of free span (including the multiple free spans) are modeled in Orcaflex and time domain VIV analysis is carried out to study the influence of pipe-soil interaction. Comparison among different types of free span is discussed. The influence of structural damping is studied for flexible pipe only because its influence on steel pipe is negligible. The influence of structural damping on flexible pipe is studied by means of a predefined moment-curvature curve. In addition, several cases are studied to investigate the influence of tension on VIV by Milan wake oscillator.
An Integrated Analytical Tool on Predicting Structural Responses of Ships Under Collision and Grounding Scenarios
Authors: Song Zijie , Hu Zhiqiang
Published: October 2017

An integrated analytical tool is introduced in this paper, which can be used to predict the structural responses, including resistance, energy dissipation and structural damage, for the ships under accidental collision and grounding scenarios. On purpose of preventing the disastrous consequences due to ship collision and grounding from happening, it is necessary to predict the structural responses and the event consequences during the structure design stage, and mostly important, in a cost-effective and conveniently using way, that can be accepted by ship structure designers. Analytical prediction method has the advantages of cost-effective and fast-calculation. Therefore, an integrated analytical tool is built to predict ship structural response under collision and grounding accident scenarios.

This analytical tool contains two modules, one is ship collision module and the other is ship grounding module. In ship collision module, the scenario of head on striking in a right angle is adopted as the most critical scenario. The major structural properties of the striking vessel and those of the struck vessel can be defined, including ship hull scantling, plate thickness, scantling of stiffeners, striking positions, striking velocity and material property. The shape of the striking ship’s bow can be defined as bulbous bow or raked bow. In ship grounding module, powered grounding is defined as the critical grounding scenario. Scantling of ship bottom structure, plate thickness, scantling of stiffeners, material property, ship grounding velocity, shape of the indenter and the grounding positions are the mandatory input parameters.

With the application of the analytical tool, structural resistance, energy dissipation and structural damage can be calculated by a series of analytical equations. These analytical expressions on resistance and energy dissipation come from the related work conducted in SJTU within the past few years.

Furthermore, numerical simulations were also conducted with code LS_DYNA, to prove the feasibility of the analytical tool. This integrated analytical tool can tell the structural designer the crashworthiness of the ship under collision and grounding scenario during the structural design stage.
Evaluation of Conventional Methods of Establishing Extreme Mooring Design Loads
Authors: Stanisic Dunja , Efthymiou Michalakis , Kimiaei Mehrdad , Zhao Wenhua
Published: October 2017

A key aspect in the design of a mooring system for a floating production unit is the estimation of the extreme mooring line loads for a specified short-term sea state of typical duration equal to 3 hours. Commonly used design approaches today are based on time-domain simulations whereby each 3 hour sea state is run a number of times (typically 10–30 times) to represent the randomness of the sea. A maximum response is recorded from each simulation. Particular statistic of the maxima data (e.g. mean, most probable maximum or a percentile) is used to represent the extreme mooring load for which the lines are designed.

This paper studies and assesses the accuracy of obtaining design value from a population of maxima with reference to the mooring line load of a large ship-shaped floating production vessel. A coupled model, including all mooring lines and risers, has been developed, validated and used to generate responses for 100yr extreme condition and 10,000yr survival condition. To establish an accurate benchmark against which the results are compared, the time-domain analyses (duration 3 hours) are repeated 170 times, for each sea state, to represent different random realisations of each environment. It is examined how the accuracy of predicting the design mooring line load, from a sample of response maxima, improves as the number of simulations is increased progressively from 10 through to 170. The assessment is performed across different statistics of maxima that are usually chosen to represent the design response. Besides the mooring line load, other response parameters such as heave and turret excursion, are examined in this paper. The paper examines whether the severity of the response (100yr vs 10,000yr storm) or the response variable affect the number of maxima required to achieve statistical stability. The results indicate fitting a Gumbel distribution to the maxima from about 30–40 simulations can yield results that are statistically stable and accurate and are recommended as preferred methods of estimating the design response.
Prediction of Relative Vertical Motion Between Cargo and HTV During Offshore Loading and Discharge
Authors: Peters Onno A. J. , Huijsmans René H. M.
Published: October 2017

In Heavy Marine Transport, it is common practice to dry-transport large and heavy floating offshore structures. In general, loading and discharge of these floating cargoes on- and from heavy transport vessels is done at sheltered locations, like harbors, where sea-state and swell conditions are insignificant. Often these locations are at large distance from operating fields of the offshore structures, which means that the structures need to be towed from- or to these fields. To save time and costs, it is beneficial to perform the loading and discharge operations in the field. This necessitates a reconsideration of the maximum allowable wave conditions such as to perform the loading- and discharge operations within specified time frame whilst ensuring safety of crew, cargo and heavy transport vessel. Therefore accurate prediction tools to determine the relative motions between heavy transport vessel and cargo are required. In the past, studies have shown that standard prediction tools over-estimate relative vertical motions compared to model tests and practical experience.

This paper discusses the prediction of relative vertical motion, which is dominated by the phenomenon squeeze flow. From model tests and CFD calculations non-linear hydrodynamic loads related to squeeze flow are recognized. Standard linearized solutions do not cover the non-linear loads and therefore result in a lack of accuracy in predicting the relative vertical motions. Linearized solutions assume small motion amplitudes with respect to characteristic dimensions of the flow problem; in the case of squeeze flow this assumption is not valid as the motion amplitude may be in the same order as the gap between cargo bottom and the deck of the heavy transport vessel. With linearized potential solvers it is found that the added mass is strongly dependent on the gap height, which verifies the analytical work of Molin et al. [1]. Following the work of Molin, the change in added mass due to changing gap height gives a large contribution to the non-linear hydrodynamic load. Additionally, a second important contribution is related to the relative vertical velocity, recognized as a drag component. As such, a non-linear formulation is found which can be used in a time-domain approach. This formulation requires gap-height dependent added mass as found using the linearized potential solver. As potential solvers are known to have difficulty dealing with the small gap, different methods have been investigated.

Results of model tests and CFD calculations are shown, which are used to tune the non-linear formulation. Tuning is done by adapting the drag component. Furthermore, results of a multi-body problem based on standard linear hydrodynamics and the non-linear formulation are compared.
In-Line Vibrations of Flexible Pipes
Authors: Ulveseter Jan V. , Sævik Svein
Published: October 2017

A semi-empirical prediction tool for pure in-line vortex-induced vibrations is under development. The long-term goal is to be able to realistically model the dynamic behavior of free spanning pipelines exposed to arbitrary time dependent external flows at low velocities. Most VIV programs operate in frequency domain, where only steady currents and linear structural models can be simulated. In contrast, the proposed model predicts hydrodynamic forces as function of time, enabling a time integration scheme to solve the equation of motion. Non-linear time domain simulations allow for modelling of excitation from non-steady currents. In addition, non-linear effects such as soil-pipe interaction, varying tension, and response dependent material, stiffness and damping properties may be included in the analysis, when combining the hydrodynamic force model with a structural non-linear finite element model. Hydrodynamically, the proposed prediction tool consists of the general Morison equation plus two vortex shedding forcing terms. The latter two are able to synchronize with the structural motion for a given frequency band, to induce vibrations in lock-in regimes.

In this paper, the proposed pure in-line VIV model is compared to the frequency domain model VIVANA and DNV Recommended Practice, simulating experiments with a model-scale flexible pipe exposed to current velocities at which cross-flow vibrations have not yet developed. A few experimental data points are included in verifying the performance of the newly developed time domain model. The effect of changing empirical coefficients in the vortex shedding forcing terms, and allowing only one of the terms to excite structural vibrations during a simulation, is numerically investigated. A goal is to obtain increased understanding of how the proposed time domain model performs when simulating VIV of a flexible pipe, which is more complex than that of an elastically mounted rigid cylinder since several natural frequencies and corresponding modes might be excited.
Consolidation of Empirics for Calculation of VIV Response
Authors: Voie Per , Wu Jie , Resvanis Themistocles L. , Larsen Carl M. , Vandiver J. Kim , Triantafyllou Michael , Baarholm Rolf
Published: October 2017

The present paper consolidates available experimental results for both sub-critical and critical Reynolds numbers and varying surface roughness and formulates a coefficient excitation model that aims at unbiased response estimates when using semi-empirical VIV prediction programs. A simplified procedure is suggested to account for higher order effects when relevant.

The paper discusses the use of a modified coefficient excitation model with the objective of capturing or correctly reflecting certain specific features that have been observed in sub-critical and supercritical VIV experiments.

The first part of this paper shows how the available low Reynolds number hydrodynamic data that currently forms the basis for most semi-empirical prediction software needs to be modified to correctly reflect the available experimental observations at sub-critical Reynolds numbers.

The latter part of this paper looks at the available high Reynolds experimental data and suggests ways whereby the previously identified force coefficient database might be modified to reflect what is currently known about the VIV response of smooth and rough surfaced cylinders in the critical and super-critical Reynolds regimes.
Numerical Modeling of Dynamic Response of Water Tank in Collision
Authors: Liang Qiyu , Zhu Ling , Zhang Shengming , Chen Mingsheng
Published: October 2017

A simplified model is developed to analyse the interaction between the liquid motion and structural dynamic response of the side plate of a water tank. A mathematical model is established to simulate a knife-edged indenter impacting the side plate of a partially-filled water tank. The minimum potential energy principle is used to simulate the structural deformation and the kinematic equation is established to describe the two-dimensional ideal-fluid motion in the water tank. Considering the structural displacement as a connection between the water motion and dynamic response of the side plate, there is a displacement-pressure exchange between the water and the side plate for every time step. With increase of time, the water will finally become still and the plate will arrive at its final deformation. The numerical results based on the present simplified model are compared with the results from numerical simulations of an empty tank under the same impact condition, so as to investigate the effect of the water motion on the structural dynamic response of the side plate.
Influence of a Seabed Trench on a Taut Mooring Line
Authors: Xiong Lingzhi , Yang Jianmin , Tian Xinliang
Published: October 2017

Taut mooring systems have become a prospective solution for the station keeping of offshore floating facilities in deep water. In such scenario, the associated anchor foundations may withstand substantial uplift loads. To maximize the holding capacity, it is common to attach the anchor chain to the suction caisson at 60 to 70 % of the embedded depth. However, new phenomenon has been observed, which may be a challenge to the integrity of mooring systems, such as the trenching of the seabed near the suction caissons of floating systems. It is unclear whether trenching will induce significant effect on the integrity of mooring systems. To evaluate the influence of the seabed trenching, where existing commercial codes have not covered, a numerical model has been developed in this study. Based on this developed model, numerical simulations have been conducted with and without considering the trenching effect at the seabed. It is found that the seabed trench has a limited influence on the tension at fairlead but has a significant influence on both the tension and the inclination angle at padeye.
Simplifying Neural Network Based Model for Ship Motion Prediction: A Comparative Study of Sensitivity Analysis
Authors: Cheng Xu , Chen Shengyong , Diao Chen , Liu Mengna , Li Guoyuan , Zhang Houxiang
Published: October 2017

This paper presents a comparative study of sensitivity analysis (SA) and simplification on artificial neural network (ANN) based model used for ship motion prediction. Considering traditional structural complexity of ANN usually results in slow convergence, SA, as an efficient tool for correlation analysis, can help to reconstruct the ANN model for ship motion prediction. An ANN-Garson method and an ANN-EFAST method are proposed, both of which utilize the ANN for modeling but select the input parameters in a local and a global fashion, respectively. Through the benchmark tests, ANN-EFAST exhibits superior performance in both linear and nonlinear systems. Further test on ANN-EFAST via a case study of ship heading prediction shows its cost-effective and timely in compacting the ANN based prediction model.
Effect of Porous Baffle on Sloshing Pressure Distribution in a Barge Mounted Container Subjected to Wave Excitation
Authors: Thuvanismail Nasar , Surahonne Deepak J. , Shah Akshay P. , Annamalaisamy Sannasiraj S.
Published: October 2017

An experimental study has been carried out to assess the sloshing pressure expected on the tank walls. Three porosities of 15%, 20.2%, 25.2% and baffle wall placed at center of tank is considered. The sloshing tank is fitted into the freely floating barge of model scale 1:43.The barge is kept inside the wave flume in the beam sea conditions. The effects of wave excitation frequencies and on the sloshing pressure variation have been studied in detail and, the salient results are herein reported.
Extreme Wave Generation, Breaking and Impact Simulations With REEF3D
Authors: Bihs Hans , Kamath Arun , Alagan Chella Mayilvahanan , Arntsen Øivind A.
Published: October 2017

An accurate description of extreme waves is necessary in order to estimate maximum wave forces on offshore structures. On several occasions freak waves have been observed in the past, some causing severe damage. In order to model such extreme wave conditions with a computational fluid dynamics (CFD) model, emphasize needs to be put on the wave generation. One possibility is to use focused waves of first or second order based on irregular sea state wave spectra. For focused waves, the wave phase is chosen, so that the waves focus in a predetermined location at a specified time. Numerical tests have shown, that generating extreme waves based on this method is somewhat limited. The individual wave components are steep enough, that they start to break before the focus location. In the current paper, transient wave packets are used for extreme wave generation. This way, extreme waves can be generated that are higher, but only break at the concentration point. The transient wave packets method is implemented in the open-source CFD software REEF3D. This model uses the level set method for interface capturing. For the hydrodynamics, the Navier-Stokes equations are solved in three dimensions. The code employs a staggered Cartesian mesh, ensuring tight pressure-velocity coupling. Complex geometries are handled with a ghost cell immersed boundary method. High-performance computing is enabled through domain decomposition based parallelization. Convection discretization of the different flow variables is performed with the fifth-order WENO (weighted essentially non-oscillatory) scheme. For the explicit time treatment a third-order Runge-Kutta scheme is selected. In order to validate the extreme wave generation, numerical tests in an empty wave tank are performed and compared with experimental data. Then, the extreme wave breaking on a vertical circular cylinder is investigated.
Experimental and Numerical Investigation of Sloshing in Marine LNG Fuel Tanks
Authors: Grotle Erlend Liavåg , Æsøy Vilmar
Published: October 2017

In the last 15 years, there has been an increasing number of LNG-fuelled ships carrying C-type tanks, classified as pressure vessels. Experience have shown that vessel motion combined with low bunkering temperature can result in rapid pressure drop. The form of the tank heads has a spherical shape, and its influence on the sloshing requires further investigation. In this study, we look at the sloshing characteristics in a small cylindrical tank with 2:1 semi-elliptic heads undergoing a harmonic pitch motion with different filling levels and frequencies, but with constant amplitude. Results from numerical simulations are compared with laboratory experiments performed at NTNU in Ålesund. Numerical simulations are performed with the open-source CFD tool OpenFOAM. Both two- and three-dimensional simulations are compared to the experiments, but it is found that three-dimensional effects cannot be excluded in these tanks. Presented results are non-dimensional wave elevation in the tank as well as general description of the sloshing characteristics. The results show interesting wave patterns due to the spherical shape of the tank heads, and the agreement between the measured non-dimensional free-surface elevation and simulations is good. At higher filling, a violent jet is formed because the tank heads lead the water back with high speed.
Numerical Simulation of Single Thruster in Open Water
Authors: Zhang Qin , Ma Peifeng , Liu Jing , Kumar Jaiman Rajeev
Published: October 2017

The flow interaction between a dynamic positioning (DP) thruster and a floating structure (semi-submersible) hull attracted quite a lot of attention in recent years. In this study, the Spalart-Allmaras RANS model has been evaluated to simulate single thruster rotated in the open water with OpenFOAM. The actual thruster geometry has been meshed with structured grid, and the gap between the blade tip and nozzle is carefully treated. The Moving Reference Frame (MRF) method is used for steady-state simulation, and the arbitrary mesh interface (AMI) method is applied to simulate the rotating blade for transient dynamic mesh simulation. The numerical results are compared with available experimental and numerical data, especially in the wake flow. Good agreement is shown in this study.
Vortex Induced Motion of a Dry Tree Semisubmersible
Authors: Tan Jaime Hui Choo , Teng Yih Jeng , Kiprawi Fathieah
Published: October 2017

The main challenge in the hydrodynamic design of a dry tree semisubmersible is in limiting its motion responses particularly heave motions to enable the use of riser tensioners. Deep draft semisubmersibles have low heave motions but are more susceptible to vortex induced motions (VIM) due to high slenderness ratios of the columns. A novel in-house developed semisubmersible design named the Heave and VIM Suppressed (HVS) semisubmersible has been designed to possess low VIM and low heave responses required for dry tree applications.

A case study of the feasibility of a dry tree HVS semisubmersible in South East Asian environment has been published separately [1]. This paper presents the VIM performance of the same hull, estimated using model testing and Computational Fluid Dynamics (CFD) analysis. From the model tests, VIM suppression is observed in the HVS semisubmersible due to the presence of the column steps. CFD simulations of the model tests show results comparable to the measured data for the HVS semisubmersible. Additional CFD analysis is performed to account for the external damping effect of the mooring lines and risers on the VIM performance of the HVS semisubmersible.

This paper together with the earlier publication [1] shows the robustness of the HVS semisubmersible design concept in addressing both the heave and VIM issues in semisubmersibles for dry tree applications.
How to Account for Short-Term and Long-Term Variability in the Prediction of the 100 Years Response?
Authors: Derbanne Quentin , de Hauteclocque Guillaume , Dumont Martin
Published: October 2017

Current practices in offshore unit design are based on the prediction of the 100 years response (tension, offset, stress...). The methodologies described in various standards (ISO, API...) are all very similar: several design environments are described with a combination of sea state, wind and current. Usually envelope contours are used, describing a set of environmental conditions corresponding to a 100 years return period. These design conditions are supposed to produce the highest responses. A time domain (or sometimes frequency domain) simulation is done on each of these short-term conditions, and the 3h most probable maximum (MPM) is computed for each. The highest MPM over all the design conditions is taken as the 100 years response. This approach completely neglects the short-term variability of the response.

This paper compares several design methods with the exact 100 years response. The exact 100 years response is computed by integrating the conditional short-term distributions with respect to the probability density function of the environmental conditions. The various design methods are all based on a simplification of an Inverse First Order Reliability Method (IFORM) approach, which requires computing one or several design conditions corresponding to one or several return periods, each of these conditions being associated with a given short-term quantile.

Computations are done using two datasets. At first realistic line tensions of 7 offshore units are used, based on a large number of simulations with a mooring software. On a second stage a more general parametric model using a Weibull distribution to describe the long-term variability and a Gumbel distribution to describe the short-term distribution of the 3h maximum is used. It is shown that the current methods are unconservative with respect to the exact 100 years response. A more accurate method is proposed, based on a 40 years return period associated with the quantile 90% and a correction factor of 1.04.
Prediction of Residual Stresses in Mooring Chains and its Impact on Fatigue Life
Authors: Martinez Perez Imanol , Bastid Philippe , Venugopal Vengatesan
Published: October 2017

This paper reports the results of a study conducted to investigate how residual stresses generated during the manufacturing process and subsequent proof loading may affect the fatigue life of mooring chains. The present paper shows the quantitative predictions of residual stress field obtained from finite element models of the fabrication process, and discusses their effect on the fatigue life of chain links depending on the loading mode. The models combine heat transfer analyses for the prediction of temperature histories during heat treatment (quenching and tempering), and stress analyses accounting for the thermo-mechanical history, including proof loading. The manufacturing conditions assumed for the models correspond to data obtained from a chain manufacturer. The predicted residual stress distribution is then combined with the fatigue stress range in service, due to either tension-tension loading or Out-of-Plane Bending (OPB). The effect of the residual stress distribution on the fatigue damage is discussed, and a sensitivity study on the assumptions used in the residual stress prediction is carried out. This determines for which loading conditions the modeling of the heat treatment stage can be neglected so that modeling of the proof loading step is sufficient for assessing the effect on fatigue life.