bluuebunny/crossref_metadata_2025 huggingface dataset:
Calibration of a Time-Domain Hydrodynamic Model for A 12 MW Semi-Submersible Floating Wind Turbine
Authors: Silva de Souza Carlos Eduardo , Fonseca Nuno , Berthelsen Petter Andreas , Thys Maxime
Published: October 2021

Design optimization of mooring systems is an important step towards the reduction of costs for the floating wind turbine (FWT) industry. Accurate prediction of slowly-varying horizontal motions is needed, but there are still questions regarding the most adequate models for low-frequency wave excitation, and damping, for typical FWT concepts. To fill this gap, it is fundamental to compare existing load models against model tests results. This paper describes a calibration procedure for a three-columns semi-submersible FWT, based on adjustment of a time-domain numerical model to experimental results in decay tests, and tests in waves. First, the numerical model and underlying assumptions are introduced. The model is then validated against experimental data, such that the adequate load models are chosen and adjusted. In this step, Newman’s approximation is adopted for the second-order wave loads, using wave drift coefficients obtained from the experiments. Calm-water viscous damping is represented as a linear and quadratic model, and adjusted based on decay tests. Additional damping from waves is then adjusted for each sea state, consisting of a combination of a wave drift damping component, and one component with viscous nature. Finally, a parameterization procedure is proposed for generalizing the results to sea states not considered in the tests.
A Well-Based Field Development Redefinition of Unconventional Reservoirs Through Unconventionality Index: Utilizing Machine Learning
Authors: Aldhuhoori Mohammed , Belhaj Hadi , Ghosh Bisweswar , Alkuwaiti Hamda , Qaddoura Rabab
Published: October 2021

The intriguing aspect of this study is to include illustrative and realistic well-based matrix to efficiently evaluate, characterize and develop Unconventional reservoirs (UCRs). This research targets a newly assessment in redefining UCRs, and developing a well-based tool to evaluate, characterize and predict the performance of tight UCRs. In this study, permeability and viscosity are used to develop the Unconventionality Index (UI) to reflect the combined causes of low mobility from UCRs. Machine learning is applied to synthesize a novel comprehensive understanding of UCRs modeling. A distinct pattern is developed for to distinguish between UCRs and CRs to show the Recovery Factor (RF) / UI dependency. Consequently, to establish such relationship, data from major UCRs producers were examined and utilized. In addition, UCRs classification matrix has been developed utilizing actual UCRs data from different reservoirs. Furthermore, a unique Unconventionality Index has been established to classify UCRs, determine reasons of unconventionality and ascertain efficient method/s of development. Subsequently, a correlation between different rock and fluid properties incorporating UI and recovery factor has been attained.
Wave Impact Loads on the Bottom of Flat Decks
Authors: de Oliveira Costa Daniel , Perim Julia Araújo , Camargo Bruno Guedes , Sena Sales Junior Joel , Fernandes Antonio Carlos , Corrêa Rodrigo dos Santos
Published: October 2021

Slamming events due to wave impact on the underside of decks might lead to severe and potentially harmful local and/or global loads in offshore structures. The strong nonlinearities during the impact require a robust method for accessing the loads and hinder the use of analytical models. The use of computation fluid dynamics (CFD) is an interesting alternative to estimate the impact loads, but validation through experimental data is still essential.

The present work focuses on a flat-bottomed model fixed over the mean free surface level submitted to regular incoming waves. The proposal is to reproduce previous studies through CFD and model tests in a different reduced scale to provide extra validation and to identify possible non-potential scale effects such as air compressibility. Numerical simulations are performed in both experiments’ scales.

The numerical analysis is performed with a marine dedicated flow solver, FINE™/Marine from NUMECA, which features an unsteady Reynolds-averaged Navier-Stokes (URANS) solver and a finite volume method to build spatial discretization. The multiphase flow is represented through the Volume of Fluid (VOF) method for incompressible and nonmiscible fluids. The new model tests were performed at the wave channel of the Laboratory of Waves and Currents (LOC/COPPE – UFRJ), at the Federal University of Rio de Janeiro.
Corrosion Products and Surface Morphology for Coated, Uncoated, and Insulated A333 Steel Pipelines in Marine Harsh Environment
Authors: Hillier Alan , Khan Faisal , Caines Susan
Published: October 2021

In situ studies with CUI and corrosion under coating is rare, especially for full scale tests in marine harsh environment. A333 low temperature carbon steel is selected for its versatile use in cold environments. This material is not widely studied in marine environment. Therefore, this work reports corrosion type, products, morphology and mechanism for thirty-six model pipelines (insulated, uninsulated, coated and uncoated) placed at Argentia, NL. Corrosion products were identified using x-ray diffraction (XRD). The detection and semi-quantification of elements on pipe surfaces was performed using energy disruptive spectroscopy (EDS) which was coupled to a scanning electron microscope (SEM). SEM images confirmed the formation of characteristic morphological structures such as sandy crystal (lepidocrocite γ-FeOOH), cotton ball (goethite α-FeOOH), and small grain (akageneite β-FeOOH) structures. For insulated uncoated pipes, the main phases were goethite, akageneite, and hematite(α-Fe2O3). For uncoated uninsulated pipes, akageneite, goethite, and hematite were detected as main phases. For coated pipes, goethite was the main phase. When ferrihydrite was detected with akageneite, there was less lepidocrocite and goethite than when ferrihydrite was not present. Uncoated pipes had deepest pits and highest corrosion rates as previously reported in [1]. Magnetite (Fe3O4) was present in these samples only in year two. Magnetite is a passive oxide formed on the iron surface but can also be a product of microbial reduction of ferrihydrite in certain conditions. A proposed mechanism for the high corrosion rate and pits in uncoated pipes is due to the increased localized corrosion from akageneite due to excess chloride and moisture from seawater spray as well as stabilized ferrihydrite limiting goethite formation, thus reducing steel pipe surface passivity.
Examination on Flaw Interactions in a Plate Subjected to Tensile and Bending Loads
Authors: Im Yeong Cheol , Kim Myung Hyun
Published: October 2021

Engineering Critical Assessment (ECA) procedure, which is a method to evaluate the integrity of various structures with embedded crack, surface crack and multiple cracks and so on. In BS7910, the acceptability of flaws in metallic structures is typically dealt with in terms of stress intensity factor solution. For the case with more than two flaws, BS7910 provides various flaw interaction rules. While such flaw interaction rules are developed based on many parametric studies, it is generally known to lead to very conservative results. In this study, the stress intensity factor solutions in a plate with multiple cracks are evaluated. Target structure is a simple plate subjected to tensile and bending loads, and a series of finite element analysis is carried out using ABAQUS. In addition, the results are validated against previous studies available in literatures. Based on the study, the distance criteria for multiple cracks in PD6493 and BS 7910 are found to be overly conservative. Therefore, a parametric investigation regarding the distance between multiple cracks is examined to reduce the overly conservative estimation in existing standards.
Reliability and Cost Estimation for Maintenance Planning of Oil and Gas Assets
Authors: Nithin Anu Hanish , Obisesan Abayomi , Sriramula Srinivas , Ebinum Terry
Published: October 2021

Safety and reliability of the assets in the Oil and Gas sector is considered critical to maximize availability and minimize downtime in production and operations. The industry, due to ageing assets, are re-visiting the maintenance planning of critical equipment through Reliability-Centered Maintenance (RCM). The RCM process comprises of the hierarchical structuring of technical objects according to their functional locations and further dividing them into their maintainable items and components. Generally, a criticality matrix is developed that would identify the highly critical assets based on criteria such as cost, production, safety, and environment. The Failure Modes and Effects Analysis (FMEA) is then performed for the identified functions, functional failures, and likely failure modes of each component of the asset. The failure modes can be identified from first principles and historical failure data from the asset owner or databases such as the Offshore Reliability Database (OREDA). The failure modes, mechanisms and causes are defined in accordance with International Standards such as ISO14224. The failure characteristics such as the hidden or evident nature of the failure modes, along with the occurrence of the failure within the bathtub curve, would help in deciding the right maintenance strategies such as condition-based, fixed-time, fault-finding intervals, run to failure or redesign. The maintenance tasks are then developed as a mitigation against each failure mode. Efficient and effective asset management strategies are achieved through the allocation of resources such as the labor, tools and materials required to execute the maintenance task. The maintenance tasks are grouped together based on the maintenance time intervals and the resulting maintenance plans are fed into the Computerized Maintenance Management System (CMMS) to manage the maintenance process and track the implementation of the maintenance tasks on site. The maintenance time intervals are allocated mainly based on the current industrial practices and may be qualitative in nature. This paper aims to quantitatively determine the right maintenance intervals by analyzing the historical failure data and determining the Mean Time Between Failures (MTBF) and Mean Time to Repair (MTTR). Cost and reliability analysis of the maintenance scenarios based on best industry practices and statistical analysis is determined. This helps with the decision-making process by improving the maintenance task intervals based on planned and unplanned maintenance downtime. A case study of an asset from the Oil and Gas sector is provided for demonstrating the proposed approach.
Seismic Design for Offshore Wind Farms – Lessons Learnt From the ACE Joint Industry Project
Authors: Klose Marcus , Wang Junkan , Ku Albert
Published: October 2021

In the past, most of the offshore wind farms have been installed in European countries. In contrast to offshore wind projects in European waters, it became clear that the impact from earthquakes is expected to be one of the major design drivers for the wind turbines and their support structures in other areas of the world. This topic is of high importance in offshore markets in the Asian Pacific region like China, Taiwan, Japan, Korea as well as parts of the United States. So far, seismic design for wind turbines is not described in large details in existing wind energy standards while local as well as international offshore oil & gas standards do not consider the specifics of modern wind turbines. In 2019, DNV GL started a Joint Industry Project (JIP) called “ACE -Alleviating Cyclone and Earthquake challenges for wind farms”. Based on the project results, a Recommended Practice (RP) for seismic design of wind turbines and their support structures will be developed. It will supplement existing standards like DNVGL-ST-0126, DNVGL-ST-0437 and the IEC 61400 series. This paper addresses the area of seismic load calculation and the details of combining earthquake impact with other environmental loads. Different options of analysis, particularly time-domain simulations with integrated models or submodelling techniques using superelements will be presented. Seismic ground motions using a uniform profile or depth-varying input profile are discussed. Finally, the seismic load design return period is addressed.
Iceberg Load Software Update Using 2019 Iceberg Profile Dataset
Authors: Stuckey Paul , Fuglem Mark , Younan Adel , Shayanfar Hamid , Huang Yujian , Liu Lei , King Tony
Published: October 2021

The Iceberg Loads Software (ILS) was developed initially to determine design iceberg loads for the Hebron Gravity Base Structure (GBS). The ILS framework has since been adapted for assessing iceberg loads on other structures such as the West White Rose Platform, subsea protection structures, pipelines laid on the seabed and floating production structures (spars and FPSOs). When the ILS was developed, the available iceberg geometry dataset (collected in the 1980s) was relatively limited, which required certain assumptions (i.e., flat wall interaction) and parametrizations (i.e., length distribution, length/draft/mass relationships, eccentricity, etc.) in the formulation of the interaction model. Renewed iceberg profile collection began in 2012, with ongoing improvements in the data collection methodology such that, of the 200 iceberg profiles collected from 2012 onwards, 134 were collected in 2019. The profile data were collected using LiDAR for the iceberg sail and multibeam sonar for the keel. The ILS has been updated using the recent three dimensional (3D) profiles, and a comparison of original versus updated iceberg load distributions for a generic structure show a decrease in loads. Updated ILS loads are compared with another iceberg load analysis tool that directly incorporates iceberg profile data rather than relying on some of the assumptions and parametrizations used in the original ILS formulation. This comparison shows some differences, particularly for extreme loads, which are the subject of on-going investigation.
Buckling Analysis of Torpedo’s Cylindrical Shell
Authors: Siva Sankara Rao Yemineni , Mallikarjuna Rao Kutchibotla , Subba Rao V. V.
Published: October 2021

Torpedo is a self-propelled weapon. It can be launched above or below the water surface. Torpedo’s different internal parts are housed in cylindrical, conical and spherical shell structures. Underwater applications require the minimization of the structural weight of shell structure for increased buckling strength, speed, and operating distance. To serve this purpose lightweight material such as Al-Cu alloy is preferred for the manufacturing of torpedo’s cylindrical shell. Here in the present investigation, unstiffened cylindrical shell structural member of the torpedo is considered for the evaluation of its linear buckling strength when the torpedo is subjected to hydro-static pressure under the sea water. Linear buckling analysis which is also called Eigen buckling analysis is done on unstiffened cylindrical shell geometry by using ANSYS R14.5 software. The values obtained for linear buckling strength from empirical equations mentioned in British Standards Institution, BS 5500 (now superseded by PD 5500) ‘Unfired Fusion Welded Pressure Vessels’ are validated with those results from ANSYS R14.5 and are observed to be closer to each other. The variation of the failure stress of an unstiffened cylindrical shell due to buckling for the variation of its thickness is also observed using both the empirical and simulation using ANSYS R14.5 approaches and are compared using the corresponding plots. And also, the critical buckling pressures of an unstiffened cylindrical shell with a constant thickness for the formation of different number of lobes for the simply supported boundary conditions are calculated by using empirical relations and this variation is observed using the corresponding plot. For these analyses numerical examples are considered.
Effects of Hull Geometry and Tightness of Turns on Ship Maneuverability: An OSIS-IHI Simulation
Authors: Lau Michael
Published: October 2021

OSIS-IHI (Ocean Structure Interaction Simulator – Ice-Hull Interaction) is a ship maneuvering in ice modeling software developed at OCRE for a marine simulator and ship performance assessment applications. A series of OSIS-IHI simulations is conducted to explain the maneuvering behavior observed of the USCGC Polar Icebreaker indicative design previously tested at the centre. The simulation is conducted with the original and a modified version of the USCGC Icebreaker Healy. The Icebreaker USCGC Healy was equipped with doublescrew conventional propellers. The hull geometry of the OSIS-Healy model is appropriately modified to mimic the hull form of two indicated design versions in question and its propulsion units replaced by twin pods prior to studying its maneuverability in order to shed light on the apparently poor maneuvering performance of the podded version of the indicative design. The modified version extends the mid-body leaving just 7.5 % of hull that constitutes the stern section. It is hypothesized that the extended mid-section cost large resisting moment against turning due to the increase of ice breaking at the aft shoulder and mid-body. This hypothesis is validated numerically to explain the poor maneuverability exhibited by the extended mid-body design, based on consideration of ice-hull interaction geometry and basic mechanics of ice breaking as well as existing anecdotal test evidences. This paper presents result of the simulation to explore effects of hull geometry and tightness of turns on ship maneuverability. Important insights gained are summarized and recommendation for further work given.
Investigation of Gas-Liquid Flow Using Electrical Resistance Tomography and Wavelet Analysis Techniques for Early Kick Detection
Authors: Barooah Abinash , Khan Muhammad Saad , Rahman Mohammad Azizur , Hasan Abu Rashid , Manikonda Kaushik , Abdelrazeq Motasem , Sleiti Ahmad Khalaf , El-Naas Muftah , Hascakir Berna
Published: October 2021

Gas kick is a well control problem and is defined as the sudden influx of formation gas into the wellbore. This sudden influx, if not controlled, may lead to a blowout problem. An accidental spark during a blowout can lead to a catastrophic oil or gas fire. This makes early gas kick detection crucial to minimize the possibility of a blowout. The conventional kick detection methods such as the pit gain and flow rate method have very low sensitivity and are time-consuming. Therefore, it is required to identify an alternative kick detection method that could provide real-time readings with higher sensitivity. In this study, Electrical Resistance Tomography (ERT) and dynamic pressure techniques have been used to investigate the impact of various operating parameters on gas volume fraction and pressure fluctuation for early kick detection. The experiments were conducted on a horizontal flow loop of 6.16 m with an annular diameter ratio of 1.8 for Newtonian fluid (Water) with varying pipe inclination angle (0–10°) and annulus eccentricity (0–30%), liquid flow rate (165–265 kg/min), and air input pressure (1–2 bar). The results showed that ERT is a promising tool for the measurement of in-situ gas volume fraction. It was observed that the liquid flow rate, air input pressure and inclination has a much bigger impact on gas volume fraction whereas eccentricity does not have a significant influence. An increase in the liquid flow rate and eccentricity by 60% and 30% decreased the gas volume fraction by an average of 32.8% and 5.9% respectively, whereas an increase in the inclination by 8° increased the gas volume fraction by an average 42%. Moreover, it was observed that the wavelet analysis of the pressure fluctuations has good efficacy for real-time kick detection. Therefore, this study will help provide a better understanding of the gas-liquid flow and potentially provide an alternative method for early kick detection.
Three-Dimensional Effects on Slamming Loads
Authors: Wang Shan , Guedes Soares C.
Published: October 2021

Three-dimensional effects on slamming loads predictions of a ship section are investigated numerically using the unsteady incompressible Reynolds-Average Navier-Stokes (RANS) equations and volume of fluid (VOF) method, which are implemented in interDyMFoam solver in open-source library OpenFoam. A convergence and uncertainty study is performed considering different resolutions and constant Courant number (CFL) following the ITTC guidelines. The numerical solutions are validated through comparisons of slamming loads and motions between the CFD simulations and the available experimental values. The total slamming force and slamming pressures on a 2D ship section and the 3D model are compared and discussed. Three-dimensional effects on the sectional force and the pressures are quantified both in transverse and longitudinal directions of the body considering various entry velocities. The non-dimensional pressure coefficient distribution on the 3D model is presented.
Analysis of Square Wave Characteristic Based on Viscous Flow CFD
Authors: Wu Yuanhao , Liu Liwei , Wang Luqun , Ma Yongyan , Zhang Zhiguo
Published: October 2021

When two waves in different directions meet due to different weather patterns, a cross wave pattern will be generated, which will finally result in the spread of square waves on the sea surface. The emergence of square waves will threaten the navigation performance of a ship and may lead to capsizing of a ship in severe cases. In this paper, the numerical square wave tank is developed by using the in-house CFD software HUST-Ship. In the process of simulation, by means of solving the unsteady RANS equation of incompressible fluid, the analytical solution of the corresponding regular wave is generated at the inlet boundary, and the free surface is captured by level-set method. Square wave is generated by superimposing two vertical regular waves with the same wave length, wave height and phase. Through analyzing the CFD model of square wave, the uncertainty analysis of wave height and length are performed. The verification and validation procedures of grid and time-step are performed to ensure the credibility of simulation results. Moreover, a detecting point is set at the origin to get the time history curve of the wave height. The linear solution and second-order Stokes solution of waves are used to fit the wave height time-history curve respectively.
Advanced Reservoir Monitoring Technologies for IOR/EOR: An Overview
Authors: Al-Qasim Abdulaziz S. , Kokal Sunil
Published: October 2021

Monitoring and surveillance (M&S) is one of the key requisites for assessing the effectiveness and success of any Improved Oil Recovery (IOR) or Enhanced Oil Recovery (EOR) project. These projects can include waterflooding, gas flooding, chemical injection, or any other types. It will help understand, track, monitor and predict the injectant plume migration, flow paths, and breakthrough times. The M&S helps in quantifying the performance of the IOR/EOR project objectives. It provides a good understanding of the remaining oil saturation (ROS) and its distribution in the reservoir during and after the flood.

A comprehensive and advanced monitoring and surveillance (M&S) program has to be developed for any given IOR/EOR project. The best practices of any such M&S program should include conventional, advanced and emerging novel technologies for wellbore and inter-well measurements. These include advanced time-lapse pulsed neutron, resistivity, diffusion logs, and bore-hole gravity measurements, cross-well geophysical measurements, water and gas tracers, geochemical, compositional and soil gas analyses, and 4D seismic and surface gravity measurements.

The data obtained from the M&S program provide a better understanding of the reservoir dynamics and can be used to refine the reservoir simulation model and fine tune its parameters. This presentation reviews some proven best practices and draw examples from on-going projects and related novel technologies being deployed. We will then look at the new horizon for advanced M&S technologies.
Numerical Simulation of ONRT Turning Motion in Regular Waves
Authors: Ye Bin , Yu Jiawei , Liu Liwei , Wang Qing , Zhang Zhiguo
Published: October 2021

Numerically simulating a ship with six-degrees-of-freedom response motions of an unsteady maneuver in a wave environment is very important in seakeeping characteristics of ship design. This paper presents the simulation studies of the turning motion in regular waves of the ONRT model. Numerical simulations were performed using viscous CFD code HUST-Ship to solve the RANS equation coupled with six degrees of freedom (6DOF) solid body motion equations and dynamic overset grids designed for ship hydrodynamics. RANS equations are solved by the finite difference method (FDM) and PISO arithmetic. The level-set method is used to simulate the free surface flow. Before the turning circle simulation, a V&V study is conducted for the total towed resistance. The real propeller was replaced by a description body force method in the process of turning motion. The constant rate of the revolution was applied throughout the simulation. The rotation of the propeller corresponds to the self-propulsion point of the model speed. The control of rudders was controlled by the following autopilot. The maximum rudder rate was assigned to 35.0 [deg/s]. The ship was released when a wave crest is passing the midship. The study focused on the parameters of the trajectories for turning circle, roll, pitch, velocity, etc, it is helpful to judge the influence of the wave on the turning motion. The simulation results match well with test data from IIHR.
Model Test of a Novel Floating Vertical-Axis Wind Turbine Under Wind and Wave Joint Loads
Authors: Zheng Hua-Dong , Zheng Xiang Yuan , Lei Yu
Published: October 2021

Recently a floating vertical-axis wind turbine (VAWT) concept that integrates a VAWT with a steel fishing cage has been developed by leading authors. In order to fathom the kinetic characteristics and performance of this floater under wind and wave joint loads, a series of model tests have been carried out in the ocean basin located at Tsinghua Shenzhen International Graduate School. The wind generation system of this facility allows turbulent wind to be produced such that examination of wind-wave joint actions can be extended to a number of stochastic scenarios. With a scale of 1/40th, the physical models of the floating VAWT and the platform of a steel fishing cage are introduced first. Details are also given to instrumentations and measurement methods. Then, thrust-wind speed tests, free-decay tests, and basin wind-wave tests are respectively carried out to probe the primary dynamic performance of the floating system. The second-order hydrodynamic effects are observed in tests, but they play a secondary role in the response of VAWTs as compared to aerodynamic effects. The aerodynamic loads can induce the obvious low-frequency response at surge and pitch eigen-frequencies, while for heave motion response its contribution is smaller. Additionally, test results reveal that third-per-revolution (3P) effects are insignificant in the platform’s surge, pitch and heave dynamic responses.
Dynamic Response and Flow Field Variation of a Floating Collar Under Extreme Wave Condition Using Computational Fluid Dynamics
Authors: Yu Songchen , Li Peng , Qin Hongde , Xu Lingyun
Published: October 2021

An innovation in aquaculture fisheries around the world is in progress. More and more fish cages have been put into use to meet the needs of human for protein. However, the fish cage shows violent dynamic response and structural destruction while suffering to unpredictable marine environment. As the main component of the cage, floating collar plays an important role in providing buoyancy and ensuring the shape of cage. Thus, the dynamic response of the floating collar and the variation of flow field around the floating collar under extreme wave condition were studied in this paper. Referring to the previous literature, considering the motion form of the floating collar under waves, only the heave and pitch motions of the floating collar were obtained. Results obtained by Computational Fluid Dynamics method were compared with that obtained by potential flow theory. We found that the viscosity of the water has greater influence on heave motion of the floating collar rather than the pitch motion. At the same time, the flow field surrounding the floating collar was analyzed, and an overtopping phenomenon on both sides of the floating collar along the wave propagation direction was observed when the wave was passing through the floating collar.
A temporal-spectral generative adversarial network based end-to-end packet loss concealment for wideband speech transmission
Authors: Wang Jie , Guan Yuansheng , Zheng Chengshi , Peng Renhua , Li Xiaodong
Published: October 2021

Packet loss concealment (PLC) aims to mitigate speech impairments caused by packet losses so as to improve speech perceptual quality. This paper proposes an end-to-end PLC algorithm with a time-frequency hybrid generative adversarial network, which incorporates a dilated residual convolution and the integration of a time-domain discriminator and frequency-domain discriminator into a convolutional encoder-decoder architecture. The dilated residual convolution is employed to aggregate the short-term and long-term context information of lost speech frames through two network receptive fields with different dilation rates, and the integrated time-frequency discriminators are proposed to learn multi-resolution time-frequency features from correctly received speech frames with both time-domain waveform and frequency-domain complex spectrums. Both causal and noncausal strategies are proposed for the packet-loss problem, which can effectively reduce the transitional distortion caused by lost speech frames with a significantly reduced number of training parameters and computational complexity. The experimental results show that the proposed method can achieve better performance in terms of three objective measurements, including the signal-to-noise ratio, perceptual evaluation of speech quality, and short-time objective intelligibility. The results of the subjective listening test further confirm a better performance in the speech perceptual quality.
When less is more
Authors: Kaiser Jocelyn
Published: October 2021

Some cancer therapies may work better if doses are timed to thwart tumor evolution.
Trans-Pacific Alliance Draws Up Ecology Plan
Authors: Stone Richard
Published: October 2021

Vladivostok and Khabarovsk, Russia—Last month, a group of American, Chinese, and Russian environmental scientists finished a draft report that lays out an unprecedented plan for balancing economic development with the preservation of key ecosystems in the biologically rich Ussuri-Wusuli river watershed that spans the border between China and Russia. The report, which designates areas for development, preservation and monitoring, and ecosystem restoration, is the fruit of a 2-year trilateral collaboration involving 150 scientists—the largest joint study since much of Russia's Far East was opened to foreigners in 1990.
Genes, Junctions, and Disease at Cell Biology Meeting
Authors: Pennisi Elizabeth
Published: October 2021

San Francisco—Recent work by several teams, some of which reported their results at the Congress on Cell Biology and at the annual meeting of the American Society for Cell Biology here, has linked defects in connexins, the proteins that form the cell-to-cell communication channels known as gap junctions, to conditions ranging from heart malformations to infertility and cataracts. Although most of the work has been done in mice, researchers hope the findings will lead to a better understanding of similar conditions in humans.
Synaptic Substrates of the Implicit and Explicit Self
Authors: Davidson Richard J.
Published: October 2021

Synaptic Self
How Our Brains Become Who We Are. Joseph LeDoux. Viking, New York, 2002. 416 pp. $29.95, C$43.99. ISBN 0-670-03028-7.

LeDoux combines perspectives from neuroscience, philosophy, literature, and the history of science to explain how human personalities are created by our brains (and, in particular, by the synaptic connectivity within them).
A skin-inspired tactile sensor for smart prosthetics
Authors: Wu Yuanzhao , Liu Yiwei , Zhou Youlin , Man Qikui , Hu Chao , Asghar Waqas , Li Fali , Yu Zhe , Shang Jie , Liu Gang , Liao Meiyong , Li Run-Wei
Published: October 2021

A skin-inspired tactile sensor achieved transduction of digital-frequency signals by an inductance-capacitance oscillation mechanism.
Incidentally identified coronary artery calcium on non-contrast CT scan of the chest predicts major adverse cardiac events among hospital inpatients
Authors: Yu Christopher , Ng Austin C C , Ridley Lloyd , Anjaria Mekhala , Meier Silvan , Yiannikas John , Kritharides Leonard , Naoum Christopher
Published: October 2021

Background

Coronary artery calcium (CAC) identified on non-gated CT scan of the chest is predictive of major adverse cardiac events (MACE) in multiple studies with guidelines therefore recommending the routine reporting of incidental CAC. These studies have been limited however to the outpatient setting. We aimed to determine the prognostic utility of incidentally identified CAC on CT scan of the chest among hospital inpatients.

Methods and results

Consecutive patients (n=740) referred for inpatient non-contrast CT scan of the chest at a tertiary referral hospital (January 2011 to March 2017) were included (n=280) if they had no known history of coronary artery disease, active malignancy or died within 30 days of admission. Scans were assessed for the presence of CAC by visual assessment and quantified by Agatston scoring. Median age was 69 years (IQR: 54–82) and 51% were male with a median CAC score of 7 (IQR 0–205). MACE occurred in 140 (50%) patients at 3.5 years median follow-up including 98 deaths. Half of all events occurred within 18 months. Visible CAC was associated with increased MACE (HR) 6.0 (95% CI: 3.7 to 9.7) compared with patients with no visible CAC. This finding persisted after adjusting for cardiovascular risk factors HR 2.4 (95% CI: 1.3 to 4.3) and with both absolute CAC score and CAC score ≥50th percentile.

Conclusion

Incidental CAC identified on CT scan of the chest among hospital inpatients provides prognostic information that is independent of cardiovascular risk factors. These patients may benefit from aggressive risk factor modification given the high event rate in the short term.
Impaired autonomic function after incomplete revascularisation
Authors: Armstrong Richard , Wheen Peter , Brandon Lisa , Finucane Ciarán , Kenny Rose Anne , Maree Andrew
Published: October 2021

Introduction

Incomplete cardiac revascularisation (ICR) assessed by residual SYNTAX score (rSs) is associated with increased 5-year mortality. Furthermore, in the general population, our group has demonstrated that impaired autonomic function determined by heart rate recovery time between 10 and 20 s (HRR10–20) following an active stand is associated with increased all-cause mortality.

Purpose

We hypothesised that ICR would be associated with impaired autonomic function determined by HRR10–20.

Methods

After ethical approval and informed consent, consecutive patients attending cardiac rehabilitation in a tertiary referral centre were enrolled. All patients had percutaneous coronary revascularisation. During an active stand, real-time heart rate, blood pressure and ECG recordings were taken using non-invasive digital photoplethysmography and HRR10–20determined. Assessment of autonomic function was performed by determining speed of HRR10–20post-orthostatic challenge.

Patients with an rSs >0 were considered incompletely revascularised and those with an rSs of 0 fully revascularised. Demographic data were recorded and statistical analysis performed.

Results

Patients (n=53) comprised those with complete revascularisation (CR) (n=37) and ICR (n=16). In the ICR group, mean rSs was 9.4.

HRR10–20was impaired in the ICR group (−3±0.60) compared with the CR cohort (−6.56±0.52) (p<0.0001). Completeness of revascularisation was strongly associated with HRR10–20(Pearson’s correlation coefficient 0.529; p<0.0001). Baseline demographics did not differ significantly. Use of rate-limiting medication was similar between cohorts (beta blockers, calcium channel blockers, ivabradine).

Conclusions

Our data confirm significant correlation between ICR and impaired autonomic function determined by speed of heart rate recovery. Thus, determining autonomic dysfunction post-ICR may identify those at increased mortality risk.
Impact of interruption probability of the current optimal velocity on traffic stability for car-following model
Authors: Li Xiaoqin , Zhou Yanyan , Peng Guanghan
Published: October 2021

Traffic interruption is one of the important factors resulting in traffic jam. Therefore, a new optimal velocity model is established involving the traffic interruption probability for self-expected velocity. Linear stable condition and mKdV equation are deduced with regard to the self-interruption probability of the current optimal velocity from linear stable analysis and nonlinear analysis, respectively. Moreover, numerical simulation reveals that the traffic self-interruption probability of the current optimal velocity can increase traffic stability, which certifies that the traffic self-interruption probability of the current optimal velocity plays important influences on traffic system.
Tau and Galerkin operational matrices of derivatives for treating singular and Emden–Fowler third-order-type equations
Authors: Abd-Elhameed W. M. , Ahmed H. M.
Published: October 2021

In this paper, our target is to implement and analyze numerical algorithms for the numerical solutions of initial and boundary third-order singular-type equations, and in particular the Emden–Fowler-type equations. Both linear and nonlinear equations are investigated. Two kinds of basis functions in terms of the shifted Chebyshev polynomials of the second kind are employed. Regarding the initial value problems, a new Galerkin operational matrix of derivatives is established and utilized, while in the case of boundary value problems (BVPs), the operational matrix of derivatives of the shifted Chebyshev polynomials of the second kind is employed. Convergence and error estimates of the two proposed expansions are given. The obtained solutions are spectral and they are consequences of the application of tau and collocation methods. These methods serve to convert the problems governed by their initial/boundary conditions into systems of linear or nonlinear algebraic equations which can be solved via suitable numerical solvers. Finally, we support our theoretical study by presenting several examples to ensure the accuracy and efficiency of the proposed algorithms.
Learning Target Class Feature Subspace (LTC-FS) Using Eigenspace Analysis and N-ary Search-Based Autonomous Hyperparameter Tuning for OCSVM
Authors: Sonbhadra Sanjay Kumar , Agarwal Sonali , Nagabhushan P.
Published: October 2021

Existing dimensionality reduction (DR) techniques such as principal component analysis (PCA) and its variants are not suitable for target class mining due to the negligence of unique statistical properties of class-of-interest (CoI) samples. Conventionally, these approaches utilize higher or lower eigenvalued principal components (PCs) for data transformation; but the higher eigenvalued PCs may split the target class, whereas lower eigenvalued PCs do not contribute significant information and wrong selection of PCs leads to performance degradation. Considering these facts, the present research offers a novel target class-guided feature extraction method. In this approach, initially, the eigendecomposition is performed on variance–covariance matrix of only the target class samples, where the higher- and lower-valued eigenvectors are rejected via statistical analysis, and the selected eigenvectors are utilized to extract the most promising feature subspace. The extracted feature-subset gives a more tighter description of the CoI with enhanced associativity among target class samples and ensures the strong separation from nontarget class samples. One-class support vector machine (OCSVM) is evaluated to validate the performance of learned features. To obtain optimized values of hyperparameters of OCSVM a novel [Formula: see text]-ary search-based autonomous method is also proposed. Exhaustive experiments with a wide variety of datasets are performed in feature-space (original and reduced) and eigenspace (obtained from original and reduced features) to validate the performance of the proposed approach in terms of accuracy, precision, specificity and sensitivity.
ON NONLINEAR FRACTIONAL-ORDER MATHEMATICAL MODEL OF FOOD-CHAIN
Authors: NISAR KOTTAKKARAN SOOPPY , RAHMAN MATI UR , LAOUINI GHAYLEN , SHUTAYWI MESHAL , ARFAN MUHAMMAD
Published: October 2021

This paper investigates the dynamical semi-analysis of the delayed food chain model under the considered fractional order. The food chain model is composed of three compartments, namely, population of the prey, intermediate predator and a top predator. By using the fixed point theorem approach, we exploit some conditions for existence results and stability for the considered system via Atangana–Baleanu–Caputo derivative with fractional order. Also, using the well-known Adam–Bashforth technique for numerics, we simulate the concerning results for the interference between the prey and intermediate predator. Graphical results are discussed for different fractional-order values for the considered model.
EVALUATION OF SCREWING CONFIGURATIONS IN CONVENTIONAL PLATING OF FEMORAL SHAFT FRACTURES USING FINITE ELEMENT ANALYSIS
Authors: Öztepe Burkay , Gök Kadir , Erdoğan Yasin , Inal Sermet , Gok Arif
Published: October 2021

Several fractures that occur in the human body depend on trauma or as a result of hormonal and bone fatigue. Fracture types that take place out of the neck area of the femoral bone are named femoral shaft fractures. Femoral shaft fractures are frequent conditions in orthopedics. Conventional plating method is a method that necessitates the fixation of the contact surface by contacting the epiphyses used in the treatment of such fractures. This method is known to be efficent in speeding up the healing process by reducing the movement between the epiphyses. In this study, femur models which are plated in various forms with fractures were analyzed with computer-aided finite element software and stresses on bone surfaces and fracture surfaces were determined. It is aimed to determine the best result by examining the relationship between the inputs such as the number of screws used during plating, the fixation area and material selection and the outputs obtained by finding the stresses on the bone surface and stresses on the broken surfaces.
Management of Resource-Saving and Energy-Saving Technologies as an Innovative Direction of Agri-Food Enterprise Restructuring
Authors: Markina Iryna , Diachkov Dmytro , Bodnarchuk Tetiana , Paschenko Polina , Chernikova Nataliia
Published: October 2021

The paper deals with the analysis of the resources and energy consumption at different levels of economic management. The most effective management tools are characterized. The quantitative and qualitative analysis of the use of different types of resources by agri-food enterprises is carried out. Using the results of the analysis, a model that takes into account the features of general and specific for agri-food enterprises’ types of resources is proposed. The practical significance of this model lies in accumulating the most effective resource-saving and energy-saving technologies of renewable and non-renewable resources of agro-sphere (according to experience in application by different countries).
Modeling of COVID-19 using an SEIR model with a saturated incidence rate
Authors: Nasir Hanis
Published: October 2021

Coronavirus disease 2019 (COVID-19) is a worldwide infectious disease and very contagious. A mathematical model using ordinary differential equations was introduced to study the dynamics of COVID-19. Local and global stability analysis was proved, which depends on the basic reproduction number [Formula: see text]. The value of parameters was estimated using the COVID-19 outbreak in China. Based on the index sensitivity results, an optimal control problem was formulated to represent the implementation of a movement control order. Finally, it is numerically shown that the spread of COVID-19 can be smothered viably by implementing an optimal control strategy.
Extending properties of exact projection invariant submodules
Authors: Tercan Adnan , Yücel Canan Celep
Published: October 2021

In this paper, on using a left exact preradical, we define a module [Formula: see text] to be EPD (EPG) if and only if each ep-submodule [Formula: see text] of [Formula: see text] is a direct summand (there exists a direct summand [Formula: see text] such that [Formula: see text] is essential in both [Formula: see text] and [Formula: see text]). We investigate structural properties of former new classes of modules and locate the implications between the other extending properties. We deal with decomposition theory as well as ring and module extensions for EPD and EPG-modules. We show that the EPD property is inherited by finite direct sums however we provide algebraic topological examples which show that direct summands do not enjoy the property. Moreover, we obtain that EPG property is closed under right essential overring and rational hull. We provide examples to illustrate some of the results by making special choices of left exact preradicals.
On approximating MIS over B1-VPG graphs*
Authors: Lahiri Abhiruk , Mukherjee Joydeep , Subramanian C. R.
Published: October 2021

In this paper, we present an approximation algorithm for the maximum independent set (MIS) problem over the class of [Formula: see text]-VPG graphs when the input is specified by a [Formula: see text]-VPG representation. We obtain a [Formula: see text]-approximation algorithm running in [Formula: see text] time. This is an improvement over the previously best [Formula: see text]-approximation algorithm [J. Fox and J. Pach, Computing the independence number of intersection graphs, in Proc. Twenty-Second Annual ACM-SIAM Symp. Discrete Algorithms (SODA 2011), 2011, pp. 1161–1165, doi:10.1137/1.9781611973082.87] (for some fixed [Formula: see text]) designed for some subclasses of string graphs, on [Formula: see text]-VPG graphs.