bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developing a Proactive Environmental Management System (PEMS) in Offshore West Africa
Authors: Ogunsanya B. O. , Ifebajo A. J. 
Published: April 2020

Abstract
Every industry that seeks to remain efficient and relevant in this millennium should constantly be looking for ways of becoming more environmentally responsible — no business may call itself efficient if it threatens the environment within which it operates. As the quest for hydrocarbons intensifies in our deeper waters, we see environmental performance quality playing an increasingly critical role in every company’s business performance.
In the last couple of years, reports from onshore E&P activities in Nigeria have shown that operating in the Niger Delta region poses some of the toughest challenges in the world. This region has witnessed a spate of attacks on oil and gas facilities, staff and contractors. Consequently, major oil and gas players have to contend with complex operational uncertainties due to increased pressures from the local communities for improved environmental control measures.
In this project, we have outlined safe and effective plans, actions, and procedures to help pre-empt these pressures; maintain harmony with local communities, and effectively manage operational uncertainties within complex environmental settings like the Nigerian Niger Delta area. A proactive environmental management style based on continuous consultation, goal-oriented monitoring, as well as a continuous improvement attitude (CIA) are some of the various solutions proposed in this work.
Finally, we are confident that this kind of environmental management system will undoubtedly enhance the economic viability, as well as the global competitiveness of our deep-water fields in offshore West Africa.
Multiphase Flow Wax Deposition Modeling
Authors: Matzain Ahmadbazlee , Apte Mandar S. , Zhang Hong-Quan , Volk Michael , Redus Clifford L. , Brill James P. , Creek Jeff L. 
Published: April 2020

Abstract
Results are presented from two-phase flow wax deposition tests using a state-of-the-art, high pressure, multiphase flow test facility. Wax deposition was found to be flow pattern dependent and occurs only along the pipe wall in contact with the waxy crude oil. The deposition buildup trend at low mixture velocities is similar to that observed in laminar single-phase flow tests. The buildup trend at high mixture velocities is similar to that observed in turbulent single-phase flow tests. Thinner and harder deposits at the bottom than at the top of the pipe were observed in horizontal intermittent flow tests. Thicker and harder deposits were observed at low liquid superficial velocity than at high liquid superficial velocity annular flow tests. No wax deposition was observed along the upper portion of the pipe in stratified flow tests.
A semi-empirical kinetic model tailored for the wax deposition tests predicted wax thickness with an acceptable accuracy, especially at high oil superficial velocity. Deposition rate reduction due to shear stripping and rate enhancement due to entrapment of oil and other mechanisms not accounted for by the classical Fick’s mass diffusion theory were incorporated through the use of dimensionless variables and empirical constants derived from the wax deposition data. The kinetic model, although semi-empirical, provides an insight for future model development.
Real-Time Multiphase Metering Using Non-Intrusive Microwave Sensor
Authors: Hogan B. , Al-Shamma’a A. I. , Lucas J. 
Published: April 2020

Abstract
At the University of Liverpool we have developed a real-time, non-intrusive multiphase dielectric meter capable of measuring the dielectric properties of different mixtures of oil, gas and water in full well stream flow. The design of such a microwave cavity using a range of rf and microwave is described. The experimental results with a wide range of multiphase mixtures from 0 to 100% are reported. In this paper we also present the implementation of a neural network to simulate the response of the meter under all conceivable conditions. Other parameters including pump speed, temperature, salt and sand are also discussed.
Global Optimization of Gas Allocation to a Group of Wells in Artificial Lift Using MATLAB
Authors: Alarcón Gabriel A. , Torres-Monzón Carlos F. , Gonzalo Nellyana , Gómez Luis E. 
Published: April 2020

Abstract
Continuous flow gas lift is one of the most common artificial lift method in the oil industry and is widely used in the world. A continuous volume of gas is injected at high pressure into the bottom of the tubing, to gasify the oil column and thus facilitate the extraction. If there is no restriction in the amount of injection gas available, sufficient gas can be injected into each oil well to reach maximum production. However, the injection gas available is generally insufficient. An inefficient gas allocation in a field with limited gas supply also reduces the revenues, since excessive gas injection is expensive due to the high gas prices and compressing costs. Therefore, it is necessary to assign the injection gas into each well in optimal form to obtain the field maximum oil production rate. The gas allocation optimization can be considered as a maximization of a nonlinear function, which models the total oil production rate for a group of wells. The variables or unknowns for this function are the gas injection rates for each well, which are subject to physical restrictions. In this work a MATLAB™ nonlinear optimization technique with constraints was implemented to find the optimal gas injection rates. A new mathematical fit to the “Gas-Lift Performance Curve” is presented and the numeric results of the optimization are given and compared with results of other methods published in the specialized literature. The optimization technique proved fast convergence and broad application.
Numerical Computations of Higher Class Solutions for 2D Polymer Flows Using PTT Constitutive Model
Authors: Surana K. S. , Nayak H. Vijayendra 
Published: April 2020

Abstract
This paper presents formulations, computations and investigations of the solutions of classes C00 and C11 for two dimensional viscoelastic fluid flows in u, v, p, τijp, τijs with Phan-Thien-Tanner (PTT) constitutive model using p-version least squares finite element formulation (LSFEF). The main thrust of the research work presented in the paper is to employ ‘right classes of interpolations’ and the ‘best computational strategy’ 1) to obtain numerical solutions of governing differential equations (GDEs) for increasing Deborah numbers 2) investigate the nature of the computed solutions with the aim of establishing limiting values of the flow parameters beyond which the solutions may be possible to compute, but may not be meaningful.
The investigations presented in this paper reveal the following: a) The manner in which the stresses are non-dimensionalized significantly influences the performance of the iterative procedure of solving non-linear algebraic equations. b) Solutions of the class C00 are always the wrong class of solutions of GDEs in variables u, v, p, τijp and τijs and thus spurious. c) C11 class of solutions are the right class of solutions of the GDEs in variables u, v, p, τijp and τijs. d) In the flow domains, containing sharp gradients of the dependent variables, conservation of mass is difficult to achieve at lower p-levels (worse for coarse meshes). e) An augmented form of GDEs are proposed that always ensure conservation of mass at all p-levels regardless of the mesh and the nature of the solution gradients. f) Stick-slip problem is used as a model problem. We demonstrate that converged solutions are possible to compute for all flow rates reported and that the detailed examination of the solution characteristics reveals them to be in agreement with all the physics of the flow, g) Numerical studies with graded meshes and high p-levels presented in this paper are aimed towards establishing and demonstrating detail behavior of local as well as global nature of the computed solutions, h) Various norms are proposed and tested to judge local and global dominance of elasticity or viscous behavior i) New definitions are proposed for elongational (extensional) viscosity. The proposed definitions are more in conformity and agreement with the flow physics compared to currently used definitions j) A significant aspect and strength of our work is that we utilize straightforward p-version LSFEF with C00 and C11 type interpolations without linearizing GDEs and that SUPG, SUPG/DC, SUPG/DC/LS operators are neither needed nor used.
Computations of Solutions of Higher Classes of Gasdynamics Equations in Lagrangian Frame of Reference Using a New Theoretical and Computational Framework
Authors: Surana K. S. , Ahmadi Ali R. 
Published: April 2020

Abstract
In this paper we present and utilize a new theoretical and computational framework for computing solutions of higher classes of one dimensional transient Navier-Stokes partial differential equations in Lagrangian frame of reference using ρ, u, T variables. The approach utilizes ‘strong form’ of the governing differential equations (GDEs) and least squares method in constructing integral form. The currently used finite element approaches seek convergence of a solution in a fixed order space by h, p, or hp-adaptive processes. The fundamental point of departure in the proposed approach is that we seek the convergence of the computed converged solution over the spaces of different orders containing the basis functions. With this approach, dramatically higher convergence rates than those obtained for h, or hp-processes are achievable and the sequence of progressively converged solutions over the spaces of progressively increasing order in fact converge to the strong solution (analytical or theoretical) of the partial differential equation. It is demonstrated using one-dimensional transient Navier-Stokes equations for compressible fluid flow in Lagrangian frame of reference in ρ, u, T that in the presence of physical diffusion and dissipation, our computed converged solutions have exactly the same characteristics as the strong solutions. Compression of air in a rigid cylinder is used as the model problem.
Separation in Flat Indentation of Orthotropic Laminated Beams
Authors: Chen Chun-Fu 
Published: April 2020

Abstract
Problems of indentation of orthotropic laminated beams due to flat punches arc solved. Exact solution methods for a subsidiary problem are developed first for both the simply-supported and clamped-ended cases. A numerical iteration algorithm is then employed to assess the possible separation and the real contact area and the contact stresses for a given punch width and a beam span. The contact stresses and separation results for the beams of a typical span reveal various contact conditions that depend only upon the punch width but not the magnitude of the applied load. For a symmetric lamination of the beam, a wide range of punch widths and beam spans are implemented to detect the critical punch widths rendering the onset of separation between the punch and the beam and to establish the threshold curve for the critical aspect ratio of the beam versus the relative punch width. The effects of both the end support condition and slacking sequence of the beam upon the contact and separation scenarios as well as the threshold behavior are thoroughly evaluated.
Analysis of the Charge Movements in Barrel Finishing
Authors: Boschetto A. , Marchetti E. , Veniali F. 
Published: April 2020

Abstract
A laboratory scale barrel has been designed and constructed in order to achieve information about the charge movements in tumbling operation. The charge has been evidenced to be moving for almost the whole time with the same speed than the barrel. The velocity gradients are thus present mainly in the active layer of the charge and depend upon the rotational speed of the barrel. Also the relative speed of the work-piece with respect to the charge depends on the rotational speed.
An Experimental Study of Controlled Gas-Phase Combustion in Porous Media for Enhanced Recovery of Oil and Gas
Authors: Sanmiguel Javier E. , Mehta S. A. (Raj) , Moore R. Gordon 
Published: April 2020

Abstract
Gas-phase combustion in porous media has many potential applications in the oil and gas industry. Some of these applications are associated with: air injection based improved oil recovery (IOR) processes, formation heat treatment for remediation of near well-bore formation damage, downhole steam generation for heavy oil recovery, in situ preheating of bitumen for improved pumping, increased temperatures in gas condensate reservoirs, and improved gas production from hydrate reservoirs. The available literature on gas-phase flame propagation in porous media is limited to applications at atmospheric pressure and ambient temperature, where the main application is in designing burners for combustion of gaseous fuels having low calorific value. The effect of pressure on gas-phase combustion in porous media is not well understood.
Accordingly, this paper will describe an experimental study aimed at establishing fundamental information on the various processes and relevant controlling mechanisms associated with gas-phase combustion in porous media, especially at elevated pressures. A novel apparatus has been designed, constructed and commissioned in order to evaluate the effects of controlling parameters such as operating pressure, gas flow rate, type and size of porous media, and equivalence ratio on combustion characteristics. The results of this study, concerned with lean mixtures of natural gas and air and operational pressures from atmospheric (88.5 kPa or 12.8 psia) to 433.0 kPa (62.8 psia), will be presented. It will be shown that the velocity of the combustion front decreases as the operating pressure of the system increases, and during some test operating conditions, the apparent burning velocities are over 40 times higher than the open flame laminar burning velocities.
Carbonate platform production during the Cretaceous
Authors: Pohl Alexandre , Donnadieu Yannick , Godderis Yves , Lanteaume Cyprien , Hairabian Alex , Frau Camille , Michel Julien , Laugie Marie , Reijmer John J.G. , Scotese Christopher R. , Borgomano Jean 
Published: April 2020

AbstractPlatform carbonates are among the most voluminous of Cretaceous deposits. The production of carbonate platforms fluctuated through time. Yet, the reasons for these fluctuations are not well understood, and the underlying mechanisms remain largely unconstrained. Here we document the long-term trend in Cretaceous carbonate platform preservation based on a new data compilation and use a climate-carbon cycle model to explore the drivers of carbonate platform production during the Cretaceous. We show that neritic carbonate preservation rates followed a unimodal pattern during the Cretaceous and reached maximum values during the mid-Cretaceous (Albian, 110 Ma). Coupled climate-carbon cycle modeling reveals that this maximum in carbonate deposition results from a unique combination of high volcanic degassing rates and widespread shallow-marine environments that served as a substrate for neritic carbonate deposition. Our experiments demonstrate that the unimodal pattern in neritic carbonate accumulation agrees well with most of the volcanic degassing scenarios for the Cretaceous. Our results suggest that the first-order temporal evolution of neritic carbonate production during the Cretaceous reflects changes in continental configuration and volcanic degassing. Geodynamics, by modulating accommodation space, and turnovers in the dominant biota probably played a role as well, but it is not necessary to account for the latter processes to explain the first-order trend in Cretaceous neritic carbonate accumulation in our simulations.
Effect of long-term rigid gas-permeable contact lens wear on keratoconus progression
Authors: Araki Satoko , Koh Shizuka , Kabata Daijiro , Inoue Ryota , Morii Daichi , Maeda Naoyuki , Shintani Ayumi , Jhanji Vishal , Nishida Kohji 
Published: April 2020

Background/aimsTo investigate the chronological corneal changes associated with long-term rigid gas-permeable contact lens (RGP-CL) wear in patients with keratoconus (KC).MethodsClinical records of 405 patients with KC or with KC suspect were retrospectively reviewed. Patients with mild-to-moderate KC and uneventful follow-up were classified into the CL (RGP-CL wear) and non-CL (without CL wear) groups. Inclusion criteria were (1) at least 3-year follow-up and (2) Scheimpflug-based corneal imaging examination at each visit. The anterior (ARC) and posterior (PRC) radius of curvature obtained in a 3.0 mm optical zone, the thinnest pachymetry reading of the corneal thickness (Tmin), and maximum keratometry values (Kmax) were investigated as tomographic parameters.ResultsTwenty-two and 15 patients who met the inclusion criteria were included in the CL and non-CL groups, respectively (31 and 20 eyes, respectively). The mean observation periods were 75 (CL group) and 63 (non-CL group) months. A multivariable non-linear regression analysis to assess the change in tomographic parameters over the follow-up period and difference of the trend between the two groups demonstrated no significant differences in the chronological change in ARC, PRC and Tmin between the CL and non-CL groups (p=0.318, p=0.280 and p=0.874, respectively).ConclusionBased on corneal tomographic evaluation over 5–6 years, the effects of long-term RGP-CL wear had no effect on KC progression.
Conceptual model for pluralistic healthcare behaviour: results from a qualitative study in southwestern Uganda
Authors: Sundararajan Radhika , Mwanga-Amumpaire Juliet , King Rachel , Ware Norma C 
Published: April 2020

IntroductionMedical pluralism, or concurrent utilisation of multiple therapeutic modalities, is common in various international contexts, and has been characterised as a factor contributing to poor health outcomes in low-resource settings. Traditional healers are ubiquitous providers in most regions, including the study site of southwestern Uganda. Where both informal and formal healthcare services are both available, patients do not engage with both options equally. It is not well understood why patients choose to engage with one healthcare modality over the other. The goal of this study was to explain therapeutic itineraries and create a conceptual framework of pluralistic health behaviour.MethodsIn-depth interviews were conducted from September 2017 to February 2018 with patients seeking care at traditional healers (n=30) and at an outpatient medicine clinic (n=30) in Mbarara, Uganda; the study is nested within a longitudinal project examining HIV testing engagement among traditional healer-using communities. Inclusion criteria included age ≥18 years, and ability to provide informed consent. Participants were recruited from practices representing the range of healer specialties. Following an inductive approach, interview transcripts were reviewed and coded to identify conceptual categories explaining healthcare utilisation.ResultsWe identified three broad categories relevant to healthcare utilisation: (1) traditional healers treat patients with ‘care’; (2) biomedicine uses ‘modern’ technologies and (3) peer ‘testimony’ influences healthcare engagement. These categories describe variables at thehealthcare provider,healthcare systemandpeerlevels that interrelate to motivate individual engagement in pluralistic health resources.ConclusionsPatients perceive clear advantages and disadvantages to biomedical and traditional care in medically pluralistic settings. We identified factors at the healthcare provider, healthcare system and peer levels which influence patients’ therapeutic itineraries. Our findings provide a basis to improve health outcomes in medically pluralistic settings, and underscore the importance of recognising traditional healers as important stakeholders in community health.
Ecological study of the association between mental illness with human development, income inequalities and unemployment across OECD countries
Authors: Barbalat Guillaume , Franck Nicolas 
Published: April 2020

ObjectivesRecent studies have demonstrated worsened mental health in relatively highly developed countries impacted by social inequalities and unemployment. Here, we investigate (1) whether mental health issues are differently or similarly affected by these social factors and (2) whether their effects on mental health are related or unrelated to each other.SettingAnalysis at the country level among Organization for Economic Cooperation and Development (OECD) countries (n=36). Data on social indicators were collected from OECD and the United Nations Development Programme databases. Data on the prevalence of mental issues were obtained from the Institute for Health Metrics and Evaluation’s Global Burden of Disease study 2017.ParticipantsNo involvement of participants.Primary and secondary outcome measuresUsing linear regression models, we investigated the relative contribution played by human development (as measured by the Human Development Index (HDI)), social inequalities (Gini index) and unemployment (unemployment rate) on the prevalence of 10 mental health issues. We then measured the relationship between the socioeconomic factors’ effects on mental issues using 2×2 Pearson’s correlation test and principal component analysis.ResultsFirst, the overall effect of each socioeconomic factor on a combination of mental health disorders was large (r range: 0.51 to 0.76; p<0.002). However, the influence of social factors on mental health was relative to each mental issue (r range: −0.34 to 0.74). Second, the socioeconomic factors’ effects on mental health showed strong interdependence (rHDI-Gini=0.93, rHDI-unemploy=0.81, runemploy-Gini=0.84; p<0.001. Principal component analysis demonstrated that the first principal component of the three variables (rHDI, rGini, runemploy) explained 91.5% of the variance.ConclusionThese results implore a reanalysis of the socioeconomic determinants of mental health where (1) the heterogeneity of mental health issues would be taken into account and (2) each socioeconomic indicator’s effect would be analysed and interpreted in conjunction with the others.