bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical Investigation on Hydrodynamic Interaction Coefficients for a Group of Truncated Composite Cylinders Floating in Waves
Authors: Ali Mir Tareque
Published: October 2021

When a group of bodies are floating closely in waves, the fluid loading on these bodies will be influenced due to the presence of the neighboring bodies. The wave loading on each of these bodies are affected, because of the sheltering or wave-reflection effects due to the presence of surrounding floating bodies, while additional loads are exerted by the radiated waves produced by the motions of the nearby floating bodies. For a multiple floating body system, it is important to precisely compute the hydrodynamic interaction coefficients, since these parameters will be used later to solve the 6xN simultaneous equations to predict the motion responses (where N is the number of freely floating bodies in the multi-body system). On the other hand, the hydrodynamic interaction coefficients are absent for an isolated floating body case. This paper investigates the hydrodynamic interaction coefficients for a group of three dimensional (3-D) bodies floating freely in each other’s vicinity. Since the nature of hydrodynamic interaction is rather complex, it is usually recommended to study this complicated phenomenon using numerically accurate scheme. A computer code developed using 3-D source distribution method which is based on linear three-dimensional potential theory is used and the validation of the computer code has been justified by comparing the present results with that of the published ones for the hydrodynamic interaction coefficients of multiple bodies. The agreement between the calculated results with those of the published ones is quite satisfactory. Numerical simulations are further conducted for a group of identical truncated composite circular cylinders floating vertically at close proximity in regular waves. During the computations of hydrodynamic interaction coefficients of this multi-body model for different groups, the number of members in the group as well as the gap width among them has been varied. The paper also examines the occurrence of hydrodynamic resonances in the gap among the floating bodies and the presence of spikes with rapid fluctuation in the results of the diagonal and coupling terms for interaction coefficients. Finally, some conclusions are drawn on the basis of the present analysis.
An Experimental Investigation of Nonlinear Wave Generation by Flap Wavemakers
Authors: Fouques Sébastien , Laflèche Sébastien , Akselsen Andreas , Sauder Thomas
Published: October 2021

It is well known that flap wavemakers behave in a nonlinear way when either the flap angle or the flap velocity becomes large. Moreover, the hinge depth should be adapted to the period of the generated waves in order to minimize linear evanescent modes, which may contribute to the formation of nonlinear spurious waves. For example, imposing a sinusoidal motion with a relatively long period and a large amplitude to a short flap will result in a surface elevation composed of a regular wave with the same period as the flap motion, but also of a variety of harmonics with higher frequencies. Second-order harmonics can be predicted theoretically for regular and irregular waves, and they can be corrected by modifying the control signal of the wavemaker. However, there is no theory that can describe nor mitigate effects of orders higher than two. The design of the wavemaker is then essential to generate extreme sea states with good quality and predictability in a laboratory.

In this paper, the nonlinearities of flap wavemakers are investigated experimentally for regular and irregular waves generated in SINTEF Ocean’s laboratories. Nonlinearities of order two and three are estimated from times series of the surface elevation measured at different locations by an array of wave probes. Particular focus is put on identifying the effects of the classical second-order correction on the second- and third-order harmonics.
An Adaptive Method to Further Improve the Tolerance of an ANN-Based Detection System for Mooring Line Failure
Authors: Sidarta Djoni E. , Tcherniguin Nicolas , Lim Ho-Joon , Bouchard Philippe , Kang Mengchen , Leridon Aurelien
Published: October 2021

The use of an Artificial Neural Network (ANN) for detection of mooring line failure has been a growing subject of discussion over the past several years. Sidarta et al. [6, 8, 12] have presented papers on the detection of mooring line failure of a moored vessel by monitoring shifts in the low frequency periods, mean yaw angles as a function of vessel positions, mass and added mass.

An ANN model has been trained using MLTSIM hydrodynamic simulations based on information from the early stages of the project. The restoring forces and moments from mooring lines, risers and umbilicals have been solved using catenary equations to significantly reduce the computational time to generate the ANN training data. This paper presents the evaluation of this ANN model using fully coupled OrcaFlex hydrodynamic simulations, based on the latest information of the project. The results of this evaluation demonstrate the tolerance of the trained ANN model as it can properly function when tested using time series of vessel motions from the fully coupled OrcaFlex hydrodynamic simulations. Furthermore, although the ANN model has been trained using simulations with a completely removed line, the trained model can still function when tested with simulations of a line broken at the bottom. These give affirmation that the ANN model can tolerate the differences that exist between the test and training data.

Sensitivity of the polyester line stiffness has also been performed using fully coupled OrcaFlex hydrodynamic simulations, and the computed time series of vessel motions have been used to test the ANN model. The ANN model can deal with some level of differences between the sensitivity tests and training data. However, sensitivity tests of the polyester line stiffness to model aging lines has posed a real challenge to the ANN model as its prediction accuracy has decreased significantly. This paper presents an adaptive method that can be implemented such that the ANN model can adapt to relatively new conditions that are quite different from the training data and maintain the accuracy of its prediction. With this approach, an existing ANN model that has been trained under certain assumptions of the system can still function although the behavior of the system has drifted away from those assumptions.

This phenomenon may have similarity with a possible reality that measured behavior in the field can be somewhat different from numerical simulations. This adaptive method has a potential for addressing this issue such that a simulation trained ANN model can maintain its expected accuracy although dealing with different conditions from the training data. If successful, this is a good cost saving scenario that an ANN model adapts to some degree to relatively new and different conditions before the differences become too much to handle and the only solution is to retrain the model.
Load Coefficients and Dimensions of Raschel Knitted Netting Materials in Fish Farms
Authors: Moe Føre Heidi , Endresen Per Christian , Bjelland Hans V.
Published: October 2021

New types of fish farms are often larger and structurally more complex than conventional fish farming structures, and associated challenges concerning safety and costs increase correspondingly. Thus, increased precision in structural design is required, with estimation of hydrodynamic loads on nets as an important topic. Today, both load coefficients for nets and measured netting dimensions are given with relatively high uncertainties. New knowledge for netting materials with high solidities as well as scaled netting commonly applied in model tests are included in the presented study. Results from towing tests and the development of a new mathematical expression for local drag coefficients (for netting twines) indicate that drag coefficients are not only dependent on solidity and Reynolds number, but may also be affected by the velocity reduction and the local velocity at the twines.
Ground Effect on Current Energy Harvesting From a Freely-Oscillating Circular Cylinder at Low Reynolds Number
Authors: Hamada Ahmed A. , Fürth Mirjam
Published: October 2021

This paper investigates the potential of current energy harvesting from a freely-oscillating circular cylinder, with a focus on near-ground effects. Energy can be harvested by converting the oscillatory motion of a cylinder excited by water current into electricity. The boundary shear layer, created by the ground surface, interacts with the cylinder vortices and consequently affects the force behavior and power harvesting performance. The problem is simulated in a two-dimensional turbulent flow, using the Finite Volume (FV) solver and the dynamic motion module, inherited in OpenFOAM. Ground effects on the power generation capacity of an oscillating cylinder operating in river current velocity at Reynolds number of 3 × 104 are studied at varying depths. Vortex-induced vibration is studied to observe the ground boundary layer influence on the structural response, vortex structure, hydrodynamic forces, and gained power. The results shed physical insight into the understanding of the flow behavior of the oscillating cylinder near the ground. Simulations show that the ground effect appears when the distance between the cylinder and the ground is less than three times the cylinder’s diameter. Decreasing the gap distance between the cylinder and the ground suppresses the vortices behind the oscillating cylinder, causing an increase in the harvested energy. Further, the optimal-power harvesting distance between the ground and the freely-oscillating cylinder is two and half times the cylinder’s diameter, because of the high oscillating frequency, causing higher power relative to shorter distances.
IOR/EOR Methods Adapted to High Water Production Zones of Heavy and Extra-Heavy Oil Reservoirs in La Faja Petrolifera Del Orinoco-Venezuela: State of the Art
Authors: Rodriguez M. Fernancelys
Published: October 2021

Venezuela is well known for its immense reserves of heavy and extra heavy crude oils located in La Faja Petrolífera Del Orinoco (La FPO), in the east of the country, with certified reserves of up to 235 billion barrels. The main production methods that have been applied in La FPO are Cold Production with sand through vertical and horizontal wells, and the application of Thermal IOR/EOR methods (e.g. steam injection, In-situ Combustion, SAGD, etc.) and Chemical EOR methods (e.g. polymer flooding).

One of the main challenges in La FPO is the increase in the recovery factor (with < 10% of recovery factor to date), due to the low mobility of crude oil at reservoir conditions, and the presence of local and regional bodies of water (flushed zones and aquifers) where conventional cold production methods are not efficient. The presence of these bodies of water negatively affects the production profiles and the quality of crude oil, observing high water cuts due to the adverse mobility ratio and the formation of complex emulsions that affect the crude lifting and separation systems.

Due to the current dramatic decline in production of conventional reservoirs in Venezuela and the vital role of La FPO to support Venezuelan oil production, it is important to identify methods and new technologies that allow for the increase in recovery factors in these complex reservoirs. This paper presents a literature review of the applied production methods and those that could be envisaged, including horizontal and dewatering wells as well as reported research work (e.g. Chemical EOR methods), to increase the oil recovery in flushed zones and/or reservoir zones with high water cuts in La FPO.
Application of Fracture Mechanics to Structural Fatigue Assessment Based on Spectral Method
Authors: Samaria Sagar , Kyoung Johyun , O’Donnell Jeffrey , Zhang Bob
Published: October 2021

The spectral fatigue methodology is a widely accepted methodology to compute the fatigue life of an offshore platform. The ever-increasing demand for life extension of the existing floating platforms worldwide continues to grow. ABS Guide for Fatigue Assessment of Offshore Structures and DNVGL-RP-C203 have established guidelines for employing finite element analysis (FEA) to calculate fatigue lives using the spectral fatigue method.

For complex structural details, the FE models with 2-D elements may not be able to capture the actual geometric details accurately. Hence, detailed FE models with solid (3-D) elements are utilized to capture geometric SCF’s (stress concentration factors) for these locations. The fatigue lives thus obtained using SCF approach with 2-D elements can be highly conservative or inaccurate. To overcome unreliable fatigue results for such complex locations that need using 3-D elements for a better definition of the local structure, this paper presents an extension to the defined guidelines by employing spectral fatigue methodology to 3-D solid elements. The paper also illustrates the applicability of Engineering Criticality Assessment (ECA) using stress-histogram based Fracture Mechanics Evaluation (FME) approach.

A comparative study is performed for a critical weld location on an offshore platform using solid 3-D and shell 2-D FE models. First, FEA is performed for both the models to calculate fatigue lives using the S-N curve-based approach. In addition, FME is also performed for the same critical weld location in order to provide a more accurate and reliable solution that will enable clients to plan their in-service inspections and maintenance programs. Also, presented is a comparison of fatigue lives based on the solid and shell element FME.
Estimation of Cuttings Concentration and Frictional Pressure Losses During Drilling Using Data-Driven Models
Authors: Ozbayoglu Murat , Ozbayoglu Evren , Ozdilli Baris Guney , Erge Oney
Published: October 2021

Drilling practice has been evolving parallel to the developments in the oil and gas industry. Current supply and demand for oil and gas dictate search for hydrocarbons either at much deeper and hard-to-reach fields, or at unconventional fields, both requiring extended reach wells, long horizontal sections, and 3D complex trajectories. Cuttings transport is one of the most challenging problems while drilling such wells, especially at mid-range inclinations. For many years, numerous studies have been conducted to address modeling of cuttings transport, estimation of the concentration of cuttings as well as pressure losses inside the wellbores, considering various drilling variables having influence on the process. However, such attempts, either mechanistic or empirical, have many limitations due to various simplifications and assumptions made during the development stage. Fluid thixotropy, temperature variations in the wellbore, uncertainty in pipe eccentricity as well as chaotic motion of cuttings due to pipe rotation, imperfections in the wellbore walls, variations in the size and shape of the cuttings, presence of tool joints on the drillstring, etc. causes the modeling of the problem extremely difficult. Due to the complexity of the process, the estimations are usually not very accurate, or not reliable. In this study, data-driven models are used to address the estimation of cuttings concentration and frictional loss estimation in a well during drilling operations, instead of using mechanistic or empirical methods. The selected models include Artificial Neural Networks, Random Forest, and AdaBoost. The training of the models is determined using the experimental data regarding cuttings transport tests collected in the last 40 years at The University of Tulsa – Drilling Research Projects, which includes a wide range of wellbore and pipe sizes, inclinations, ROPs, pipe rotation speeds, flow rates, fluid and cuttings properties. The evaluation of the models is conducted using Root Mean Square Error, R-Squared Values, and P-Value. As the inputs of the data-driven models, independent drilling variables are directly used. Also, as a second approach, dimensionless groups are developed based on these independent drilling variables, and these dimensionless groups are used as the inputs of the models. Moreover, performance of the data-driven model results are compared with the results of a conventional mechanistic model. It is observed that in many cases, data-driven models perform significantly better than the mechanistic model, which provides a very promising direction to consider for real time drilling optimization and automation. It is also concluded that using the independent drilling variables directly as the model inputs provided more accurate results when compared with dimensional groups are used as the model inputs.
Investigation of Flowzan as Non-Newtonian Cutting Transport Fluid in Directional Drilling Applications via Electrical Resistance Tomography Method
Authors: Khan Muhammad Saad , Barooh Abinash , Rahman Mohammad Azizur , Hassan Ibrahim , Hasan Rashid
Published: October 2021

In-situ cutting transport measurement is essential to understand the hydrodynamics and operational parameters required for efficient annulus cleaning. Electrical resistance tomography (ERT) has been a promising method in many industrial applications. This study aimed to provide comprehensive information on the use of a non-invasive ERT method to examine the volume fraction of solids in the presence of non-Newtonian fluid (0.5 wt percent of Flowzan) in a directional drilling annulus (80–90° from vertical orientation). The experiments were performed in a horizontal flow loop system where the annulus segment was 240 (6.16 m) inch long with an inner and outer diameter of 2.5 inches (6.4 cm) and 4.5 inches (11.4 cm), respectively. The results obtained indicated that the ERT device could effectively detect the volume fraction of the solids in the presence of non-Newtonian fluid (Flowzan) under different drilling conditions. Results also showed that the annulus’ successful cleaning was observed with an increase in fluid mass flow rates indicated the relative increase in cuttings volumes (AVF = 7 to 9%). Besides, the rotation of the drill pipe often had a beneficial effect on cutting transport. Furthermore, it was observed that both (30%) eccentricity and inclination (80–85 °) cause a reduction in cutting volume fraction. Therefore, this study will provide an avenue for the industrial implementation of in situ ERT measurement technology in directional drilling operations, particularly in the case of non-Newtonian drilling fluids.
Advances on Reduced-Order Modeling of Floating Offshore Wind Turbines
Authors: Lemmer Frank , Yu Wei , Steinacker Heiner , Skandali Danai , Raach Steffen
Published: October 2021

Aero-hydro-servo-elastic modeling of Floating Offshore Wind Turbines (FOWTs) is a key component in the design process of various components of the system. Different approaches to order reduction have been investigated with the aim of improving structural design, manufacturing, transport and installation, but also the dynamic behavior, which is largely affected by the blade pitch controller. The present work builds on previous works on the SLOW (Simplified Low-Order Wind Turbine) code, which has already been used for the above purposes, including controller design. While the previous rigid rotor model gives good controllers in most cases, we investigate in the present work the question if aero-elastic effects in the design model can improve advanced controllers. The SLOW model is extended for the flap-wise bending and coupled to NREL’s AeroDyn, linearized and verified with the OlavOlsen OO-Star Wind Floater Semi 10MW public FOWT model. The results show that the nonlinear and linear reduced-order SLOW models agree well against OpenFAST. The state-feedback Linear Quadratic Regulator (LQR) applied with the same weight functions to both models, the old actuator disk, and the new aero-elastic model shows that the LQR becomes more sensitive to nonlinear excitation and that the state feedback matrix is significantly different, which has an effect on the performance and potentially also on the robustness. Thus modeling uncertainties might even be more critical for the LQR of the higher-fidelity model.
A Joint-Industry Effort to Develop and Verify CFD Modeling Practice for Vortex-Induced Motion of a Deep-Draft Semi-Submersible
Authors: Jang Hyunchul , Kim Dae-Hyun , Agrawal Madhusuden , Loubeyre Sebastien , Lee Dongwhan , Huang Jerry , Law Yun Zhi , Magee Allan , Koop Arjen
Published: October 2021

Platform Vortex Induced Motion (VIM) is an important cause of fatigue damage on risers and mooring lines connected to deep-draft semi-submersible floating platforms. The VIM design criteria have been typically obtained from towing tank model testing. Recently, computational fluid dynamics (CFD) analysis has been used to assess the VIM response and to augment the understanding of physical model test results. A joint industry effort has been conducted for developing and verifying a CFD modeling practice for the semi-submersible VIM through a working group of the Reproducible Offshore CFD JIP. The objectives of the working group are to write a CFD modeling practice document based on existing practices validated for model test data, and to verify the written practice by blind calculations with five CFD practitioners acting as verifiers.

This paper presents the working group’s verification process, consisting of two stages. In the initial verification stage, the verifiers independently performed free-decay tests for 3-DOF motions (surge, sway, yaw) to check if the mechanical system in the CFD model is the same as in the benchmark test. Additionally, VIM simulations were conducted at two current headings with a reduced velocity within the lock-in range, where large sway motion responses are expected,. In the final verification stage, the verifiers performed a complete set of test cases with small revisions of their CFD models based on the results from the initial verification. The VIM responses from these blind calculations are presented, showing close agreement with the model test data.
Qualification Criteria for the Verification of Numerical Waves – Part 1: Potential-Based Numerical Wave Tank (PNWT)
Authors: Fouques Sébastien , Croonenborghs Eloïse , Koop Arjen , Lim Ho-Joon , Kim Jang , Zhao Binbin , Canard Maxime , Ducrozet Guillaume , Bouscasse Benjamin , Wang Weizhi , Bihs Hans
Published: October 2021

There is an increasing trend towards using numerical wave simulations for the design of offshore structures, especially for the stochastic prediction of nonlinear wave loads like those related to air-gap and wave impact. Unlike experimental facilities, where the complex nonlinear physics of wave propagation is simply enforced by the laws of nature, numerical wave tanks (NWTs) rely on assumptions and simplifications to solve the propagation equations in a reasonable amount of time. It is therefore important to verify the quality of the waves generated by NWTs in terms of realistic physical properties.

As part of the effort to develop reliable numerical wave modeling practices in the framework of the “Reproducible Offshore CFD JIP”, qualification criteria are formulated for the wave solutions generated from either potential-flow based or CFD-based codes. The criteria have been developed based on experiences from physical wave tank tests and theoretical/numerical studies. They are being evaluated using results from several numerical models and available benchmark data. This paper presents the proposed qualification criteria and on-going evaluation efforts by comparing results from different codes.
Numerical Simulation of Full-Scale Ship Self-Propulsion for Japan Bulk Carrier
Authors: Xu Jing , Zhou Yujie , Yu Jiawei , Deng Weihua , Feng Dakui
Published: October 2021

The self-propulsion simulations of JBC (Japan Bulk Carrier) were performed in model and full scale with two approach: one is the body force method using steady blade element theory (lift lines theory) and infinite blade propeller, the other is 3-D discretized propeller method. All simulations were investigated using an in-house CFD code which is based on the finite difference method to discretize the governing equations. A dynamic overset technique was used and any revolutions of the propeller can be achieved in the simulation. In order to obtain the self-propulsion point, a PI speed controller was utilized to adjust the rate of revolutions of the propeller. To obtain self-propulsion factors, resistance and open water tests are also computed. Thrust identity method was used to obtain wake fraction. The full scale total resistance coefficient was obtained according two extrapolation methods: the first is the ITTC 1978 recommended procedure, while the second is the extrapolation method based on Grigson friction line. Wake fraction was revised following ITTC recommended procedures in full scale. All the results of the simulation have a reasonable agreement with experimental results. The computational results presented in this paper also provide evidence to the full scale self-propulsion prediction ability of the in-house code.
Dynamic Responses of the State-of-the-Art Floating System Integrating a Wind Turbine With a Steel Fish Farming Cage: Model Tests vs. Numerical Simulations
Authors: Lei Yu , Zheng Xiang Yuan , Zheng Hua-dong
Published: October 2021

This work is dedicated to comparing the experimental and numerical results of the dynamic responses of a novel floating system integrating a floating offshore wind turbine with a steel fish farming cage (FOWT-SFFC) under wind and wave loadings. The patents of this floating system have been successfully licensed recently in China and USA.

The experimental study is carried out in the Ocean Basin of Tsinghua Shenzhen International Graduate School, with a Froude scaling of 1:30. A small commercial wind turbine is used to produce the scaled wind loads on FOWT-SFFC in terms of the similarity of thrust force.

In this paper, the setup of model tests is described first. Second, a numerical model of prototype FOWT-SFFC is built in the software OrcaFlex. Then, this numerical model is calibrated and updated by the results of free decay tests and static offset tests in the basin. The numerical model also adopts three sets of drag coefficients. Finally, the experimental results of FOWT-SFFC under a variety of load cases are presented and compared with the numerical simulation results. They include seakeeping tests for hydrodynamic motion response amplitude operators (RAOs) and dynamic responses corresponding to normal operating and survival conditions. The numerical simulation results show that, though they are in good agreement with model test data especially on time records of dynamic responses, they are sensitive to the selection of drag coefficients particularly on extreme values and low-frequency spectral contents. Appropriate drag coefficients are suggested to be used in the numerical model for a specific environmental condition. Drag coefficients benchmarked from the free decay tests may not be suitable for moderate and harsh wave conditions.
Cement Sheath Integrity During High Temperature Geothermal Well Operations
Authors: Vrålstad Torbjørn , Skorpa Ragnhild , Opedal Nils , Todorovic Jelena , Agofack Nicolaine , Hoang Nguyen-Hieu
Published: October 2021

Development of geothermal energy sources is an important contribution to ensure the “green shift” from fossil fuels to more sustainable sources of energy. Currently, most geothermal wells operate at temperature range of 150–300° C, but development of super-high temperature geothermal reservoirs may be needed to increase power production. However, the high temperature conditions to be found in such wells, up to 400–500 °C, are very challenging and may be detrimental for the integrity of well cement.

In this paper, several cement integrity challenges for high temperature geothermal wells are reviewed, such as mechanical failures during well start-up and potential shut-in periods, and long-term issues caused by chemical alterations of the cement during high temperature exposure. Experimental tests have been performed with two different, potential geothermal well cement systems: a Portland-based system with silica flour and MicroSilica as additives, and a non-Portland, calcium aluminate cement system. For both cement systems, high temperature ageing tests have been performed at 500 °C for 8 weeks, where unconfined mechanical properties were determined before and after exposure. Furthermore, down-scaled tests of radial crack formation in casing-cement-rock samples have been performed, as simplified functions tests of cement sheath integrity during well start-up.
Well Integrity Enabled by Digital Workflow
Authors: Brechan (Wellviz) B. , Teigland A. , Dale S. , Sangesland S.
Published: October 2021

Emerging technologies are expected to provide step changes in many areas within planning, making and production of wells. The main topic of this paper covers in a digital workflow, where the different disciplines contributions to well integrity are expected to be on a fully digital format. All phases in the lifecycle of wells are integrated into one digital process, where possible improvements are enabled by the transition from a human oriented work process to a software oriented (human supported) process. This transition has taken place in several other comparable energy and capital-intensive industries.

Today, some wells have the new fiber optics that enables a range of opportunities for improvement of well integrity. Distributed Acoustic Sensing (DAS) has measurements for every meter, which provides new aspects such as in situ measurements during cement jobs and drilling. Other applications of the new fiber optic technology are monitoring of gas migration, source of sustained casing pressure and other measurements which have the potential to develop into standard procedures or even regulatory requirements. With gas migration, corrosion and other changes affecting the integrity of the well construction, integrity can be re-modelled and updated automatically in a fully digital workflow to understand the safety margins. A part of this digital process is automating the risk level for each well and the entire asset. These processes and the prototype of the automated risk assessment are possible in a fully digital process, where planning and well construction commence with support from modern well planning and integrity software.
Non-Linear Response Analysis of Jacket Supported Offshore Wind Turbine under Seismic Loads using Hilbert-Huang Transform
Authors: Kashyap Subham , Saha Nilanjan , Abhinav K. A.
Published: October 2021

The present work studies the performance of an offshore wind turbine system in an earthquake coupled with wave and wind loading. The NREL 5 MW offshore wind turbine, supported on the OC4 jacket [14], has been analysed within a finite element framework. A coupled model of hydrodynamics and soil-structure interaction has been implemented. The structure-foundation system is analysed under earthquakes recorded close to offshore waters and at sites with shear-wave velocities, classified under Site-Class D or Site-Class E as per API RP: 2EQ [8]. The soil conditions emulate characteristics of a prospective offshore wind turbine site along the west coast of India, which falls within the Site-Class D classification mentioned above. The geotechnical modelling is done as per the soil curves prescribed by the non-linear Winkler springs along the pile’s length. The complete analysis has been processed in a finite-element framework through the commercial program USFOS [16]. The Hilbert-Huang transform [29] of the tower-responses suggests the increased vulnerability to the resonance phenomenon with 1P and 3P loading. It also suggests an involvement of higher modes in the tower-response. The change in the frequency of the structure-foundation system during and post-earthquake has also been studied.
40Ca+ optical clocks in China
Authors: Guan Hua , Zhang Baolin , Zhang Huaqing , Huang Yao , Hao Yanmei , Zeng Mengyan , Gao Kelin
Published: October 2021

In this review, the improvements made in the past two decades for 40Ca+ optical clocks in China are presented. Uncertainty of below 1.3×10−17 was achieved by applying the “magic” RF trapping frequency and introducing a generalized Ramsey excitation scheme. The stability of 40Ca+ optical clocks has been improved to 2.5×10−15/τ with an uptime rate of 93.8% by implementing two ameliorated lock algorithms in the Ramsey excitation scheme. A long-term clock frequency comparison shows a clock stability of 6.3 × 10−18 in an averaging time of 524 000 s. A robust and transportable clock installed in an air-conditioned car trailer can achieve almost the same performance of laboratory clocks. A height difference between transportable and laboratory clocks was measured with an uncertainty of 0.33 m and the absolute frequency of 40Ca+ optical clock transitions was remeasured as 411 042 129 776 400.41(23) Hz, with a fractional uncertainty of 5.6×10−16 based on a Cs fountain clock in the National Institute of Metrology after the transportable clock was transported from Wuhan to Beijing. The author predicts that transportable single-ion optical clocks especially based on the 40Ca+ will make a significant contribution to the construction of a world-wide optical clock network and the redefinition of the unit of time in the future.
Splitting of the 520-Kilometer Seismic Discontinuity and Chemical Heterogeneity in the Mantle
Authors: Saikia Ashima , Frost Daniel J. , Rubie David C.
Published: October 2021

Seismic studies indicate that beneath some regions the 520-kilometer seismic discontinuity in Earth's mantle splits into two separate discontinuities (at ∼500 kilometers and ∼560 kilometers). The discontinuity near 500 kilometers is most likely caused by the (Mg,Fe)
2
SiO
4
β-to-γ phase transformation. We show that the formation of CaSiO
3
perovskite from garnet can cause the deeper discontinuity, and by determining the temperature dependence for this reaction we demonstrate that regional variations in splitting of the discontinuity arise from variability in the calcium concentration of the mantle rather than from temperature changes. This discontinuity therefore is sensitive to large-scale chemical heterogeneity. Its occurrence and variability yield regional information on the fertility of the mantle or the proportion of recycled oceanic crust.
Investigation of Antiparasitic Activity of 10 European Tree Bark Extracts on Toxoplasma gondii and Bioguided Identification of Triterpenes in
Alnus glutinosa
Barks
Authors: Darme Pierre , Spalenka Jérémy , Hubert Jane , Escotte-Binet Sandie , Debelle Laurent , Villena Isabelle , Sayagh Charlotte , Borie Nicolas , Martinez Agathe , Bertaux Benjamin , Voutquenne-Nazabadioko Laurence , Renault Jean-Hugues , Aubert Dominique
Published: October 2021

Toxoplasmosis is a worldwide parasitosis that affects one-third of the population. People at risk, such as immunocompromised patients (AIDS, chemotherapy treatment) or fetuses (maternal-fetal transmission) can develop severe forms of the disease.
In Vitro
Antifungal Combination of Terbinafine with Itraconazole against Isolates of
Trichophyton
Species
Authors: Bidaud Anne-Laure , Schwarz Patrick , Chowdhary Anuradha , Dannaoui Eric
Published: October 2021

Terbinafine is used as the first-line therapy for dermatophytosis, but the incidence of terbinafine resistance is increasing. A combination of terbinafine with itraconazole was tested using the checkerboard method based on the EUCAST methodology for antifungal susceptibility testing against 9 terbinafine-susceptible and 7 terbinafine-resistant clinical isolates of
Trichophyton
spp. from India.
RNA Sequencing Elucidates Drug-Specific Mechanisms of Antibiotic Tolerance and Resistance in Mycobacterium abscessus
Authors: Schildkraut Jodie A. , Coolen Jordy P. M. , Burbaud Sophie , Sangen Jasper J. N. , Kwint Michael P. , Floto R. Andres , op den Camp Huub J. M. , te Brake Lindsey H. M. , Wertheim Heiman F. L. , Neveling Kornelia , Hoefsloot Wouter , van Ingen Jakko
Published: October 2021

Mycobacterium abscessus
is an opportunistic pathogen notorious for its resistance to most classes of antibiotics and low cure rates.
M. abscessus
carries an array of mostly unexplored defense mechanisms. A deeper understanding of antibiotic resistance and tolerance mechanisms is pivotal in development of targeted therapeutic regimens.
Time-dependent propensity-matched general population study of the effects of statin use on cancer risk in an interstitial lung disease and pulmonary fibrosis cohort
Authors: Yeh Jun-Jun , Lai Jung-Nien , Lin Cheng-Li , Hsu Chung-Y , Kao Chia-Hung
Published: October 2021

Objective

To determine the effect of statins on risk of cancer in patients with interstitial lung disease (ILD) and pulmonary fibrosis.

Setting

We retrospectively enrolled patients with ILD and pulmonary fibrosis and divided them into two cohorts by statin use (statin users (n=10 036) and statin non-users (n=10 036)).

Participants

We selected patients with ILD and pulmonary fibrosis (N=53 862) from Taiwan’s National Health Insurance Research Database. Time-dependent Cox models were used to compare risk of cancer of propensity-matched statin users and non-users. Cumulative cancer incidence was analysed through Cox proportional regression. We calculated adjusted HRs (aHRs) and their 95% CIs for cancer after adjusting for sex, age, comorbidities, and use of inhaled corticosteroids, oral steroids and statins.

Results

Compared with statin non-users, the aHRs (95% CIs) for statin users were 0.60 (0.55 to 0.65) for cancer, 0.52 (0.35 to 0.78) for haematological malignancy, 0.52 (0.38 to 0.72) for cancer of the head and neck, 0.73 (0.59 to 0.89) for colorectal cancer, 0.34 (0.26 to 0.43) for liver cancer, 0.39 (0.23 to 0.67) for pancreatic cancer, 0.40 (0.17 to 0.96) for skin cancer, 0.67 (0.52 to 0.87) for breast cancer, 0.27 (0.14 to 0.54) for cervical cancer, 0.37 (0.30 to 0.46) for other immunological cancers, 0.73 (0.54 to 0.98) for bladder/kidney cancer and 0.88 (0.71 to 1.09) for lung cancer.

Conclusion

Statin use is associated with lower risk of cancer in the ILD and pulmonary fibrosis cohort.
Women’s perceptions and self-reports of excessive bleeding during and after delivery: findings from a mixed-methods study in Northern Nigeria
Authors: Yargawa Judith , Fottrell Edward , Hill Zelee
Published: October 2021

Objectives

To explore lay perceptions of bleeding during and after delivery, and measure the frequency of self-reported indicators of bleeding.

Setting

Yola, North-East Nigeria.

Participants

Women aged 15–49 years who delivered in the preceding 2 years of data collection period (2015–2016), and their family members who played key roles.

Methods

Data on perceptions of bleeding were collected through 7 focus group discussions, 21 in-depth interviews and 10 family interviews. Sampling was purposive and data were analysed thematically. A household survey was then conducted with 640 women using cluster sampling on postpartum bleeding indicators developed from the qualitative data; data were analysed descriptively.

Results

Perceptions of excessive bleeding fell under four themes: quantity of blood lost; rate/duration of blood flow; symptoms related to blood loss and receiving birth interventions/hearing comments from birth attendants. Young and less educated rural women had difficulty quantifying blood loss objectively, including when shown quantities using bottles. Respondents felt that acceptable blood loss levels depended on the individual woman and whether the blood is ‘good’ or ‘diseased/bad.’ Respondents believed that ‘diseased’ blood was a normal result of delivery and universally took steps to help it ‘come out.’ In the quantitative survey, indicators representing less blood loss were reported more frequently than those representing greater loss, for example, more women reported staining their clothes (33.6%) than the bed (18.1%) and the floor (6.2%). Overall, indicators related to quantity and rate of blood flow had higher frequencies compared with symptom and intervention-related/comment-related indicators.

Conclusion

Women quantify bleeding during and after delivery in varied ways and some women do not see bleeding as problematic. This suggests the need for standard messaging to address subjectivity. The range of indicators and varied frequencies highlight the challenges of measuring excessive bleeding from self-reports. More work is needed in improving and testing validity of questions.
Protocol of a systematic review and network meta-analysis for the prevention and treatment of perinatal depression
Authors: Smith Robert David , Hung Sze Chai , Goh Joyce , Ip Hoi Lam , Fong Daniel Yee Tak , Ali Shehzad , Wilson Claire Anna , Lok Kris Yuet-Wan
Published: October 2021

Introduction

Perinatal depression is common and can often lead to adverse health outcomes for mother and child. Multiple pharmacological and non-pharmacological treatments have been evaluated against usual care or placebo controls in meta-analyses for preventing and treating perinatal depression compared. It is not yet established which of these candidate treatments might be the optimal approach for prevention or treatment.

Methods and analysis

A systematic review and Bayesian network meta-analyses will be conducted. Eight electronic databases shall be searched for randomised controlled trials that have evaluated the effectiveness of treatments for prevention and/or treatment of perinatal depression. Screening of articles shall be conducted by two reviewers independently. One network meta-analysis shall evaluate the effectiveness of interventions in preventing depression during the perinatal period. A second network meta-analysis shall compare the effectiveness of treatments for depression symptoms in women with perinatal depression. Bayesian 95% credible intervals shall be used to estimate the pooled mean effect size of each treatment, and surface under cumulative ranking area will be used to rank the treatments’ effectiveness.

Ethics and dissemination

We shall report our findings so that healthcare providers can make informed decisions on what might be the optimal approach for addressing perinatal depression to prevent cases and improve outcomes in those suffering from depression through knowledge exchange workshops, international conference presentations and journal article publications.

PROSPERO registration number

CRD42020200081.
Healthcare professionals in COVID-19-intensive care units in Norway: preparedness and working conditions: a cohort study
Authors: Lie Irene , Stafseth Siv , Skogstad Laila , Hovland Ingvild Strand , Hovde Haakon , Ekeberg Øivind , Ræder Johan
Published: October 2021

Objective

To survey the healthcare professionals’ background and experiences from work with patients with COVID-19 in intensive care units (ICUs) during the first wave of the COVID-19 pandemic in Norway.

Design

Observational cohort study.

Setting

COVID-ICUs in 27 hospitals across Norway.

Participants

Healthcare professionals (n=484): nurses (81%), medical doctors (9%) and leaders (10%), who responded to a secured, web-based questionnaire from 6 May 2020 to 15 July 2020.

Primary and secondary measures

Healthcare professionals’: (1) professional and psychological preparedness to start working in COVID-ICUs, (2) factors associated with high degree of preparedness and (3) experience of working conditions.

Results

The age of the respondents was 44.8±10 year (mean±SD), 78% were females, 92% had previous ICU working experience. A majority of the respondents reported professional (81%) and psychological (74%) preparedness for working in COVID-ICU. Factors significantly associated with high professional preparedness for working in COVID-19-ICU in a multivariate logistic model were previous ICU work experience (p<0.001) and participation in COVID-ICU simulation team training (p<0.001). High psychological preparedness was associated with higher age (p=0.003), living with spouse or partner (p=0.013), previous ICU work experience (p=0.042) and participation in COVID-ICU simulation team training (p=0.001). Working with new colleagues and new professional challenges were perceived as positive in a majority of the respondents, whereas 84% felt communication with coworkers to be challenging, 46% were afraid of being infected and 82% felt discomfort in denying access for patient relatives to the unit. Symptoms of sweating, tiredness, dehydration, headache, hunger, insecurity, mask irritation and delayed toilet visits were each reported by more than 50%.

Conclusions

Healthcare professionals working during the first wave of COVID-ICU patients in Norway were qualified and prepared, but challenges and potential targets for future improvements were present.

Trial registration number

NCT04372056.
Direct medical costs of type 2 diabetes mellitus in the Philippines: findings from two hospital databases and physician surveys
Authors: Jimeno Cecilia , Sy Rosa Allyn , De La Pena Pepito , Cipriano Chritopher , Tan Rima , Panelo Araceli , Ng Junice Yi Siu
Published: October 2021

Objective

To estimate the annual direct medical cost of type 2 diabetes mellitus (T2DM) in hospitals and outpatient care clinics from a healthcare payer perspective in the Philippines.

Design and participants

(1) A review of electronic hospital records of people with T2DM in two tertiary hospitals—Ospital ng Makati (OsMak) and National Kidney and Transplant Institute (NKTI) and (2) a cross-sectional survey with 50 physicians providing outpatient care for people with T2DM.

Setting

Primary, secondary and tertiary healthcare facilities in Metro Manila.

Outcome measures

Cost of managing T2DM and its related complications in US dollars (USD) in 2016.

Results

A total of 1023 and 1378 people were identified in OsMak and NKTI, with a complication rate of 66% and 74%, respectively. In both institutions, the average annual cost per person was higher if individuals were diagnosed with any complication (NKTI: US$3226 vs US$2242 and OsMak: US$621 vs US$127). Poor diabetes control was estimated to incur higher per person cost than good control in both public outpatient care (poor control, range: US$727 to US$2463 vs good control, range: US$614 to US$1520) and private outpatient care (poor control, range: US$848 to US$2507 vs good control, range: US$807 to US$1603).

Conclusion

The results highlight the high direct medical cost resulting from poor diabetes control and the opportunity for cost reduction by improving control and preventing its complications.