bluuebunny/crossref_metadata_2025_split huggingface dataset:
Buckling of Concentric String Pipe-in-Pipe
Authors: Li Changning , Samuel Robello 
Published: October 2017

Abstract
During the design stage of concentric tubular strings, the outer string is always considered to be rigid. However, in reality, the outer string can become displaced through contact with an inner buckled string. An analytical mathematical model was developed that includes this interaction effect and predicts the post-buckling behavior of a dual-string system in vertical wells. Case studies were conducted to compare the prediction results with previous models.
The post-buckling configurations are divided into two pre-assumed scenarios: sinusoidal buckling and helical buckling. An analytical mathematical model was developed to describe the post-buckling behavior of dual-string systems based on the minimum energy theory. The effect of contact interaction is considered in this model and evaluated during analysis. Variations of pitch, bending moment, bending stress, and total length change caused by buckling along the tubular can be evaluated using the new model. The model was verified with existing literature before application. A case study was performed to evaluate the improved prediction accuracy of the model during certain scenarios.
Two models exist for dual-string buckling—namely, the Christman (1976) and Mitchell (2012) models. The case study in this research determined that the Christman model tends to overestimate the stiffness of a dual-string system, thus leading to an unsafe design. The Mitchell model assumes an unrealistic space configuration for helical buckling, where the buckling is self-balanced and a dual-string system is independent of the wellbore. As a result, the Mitchell model cannot properly explain the influence of wellbore clearance on the buckling configuration. The new model properly solves these issues and provides a reliable prediction as a design reference. It is also observed that the outer string in a dual-string system tends to withstand more moments because of greater stiffness. Proper application of this new dual-string buckling model design can help reduce costs.
A Robust Finite Element Simulator for Black-Oil and Fully Compositional Compressible Flow in Hydrocarbon Reservoirs
Authors: Amooie Mohammad Amin 
Published: October 2017

Abstract
We present a unified numerical simulator for reservoir engineering problems of the highest complexity: fully compositional and black-oil, three-phase, compressible flow on three-dimensional unstructured grid.
In the context of black-oil modeling, where hydrocarbon components are lumped into a gas and an oil component with only the gas component being allowed to transfer between oil and gas phases, study cases may involve treating a variable bubble point pressure throughout the reservoir (e.g., in water flooding into saturated reservoirs, or introducing gas into an undersaturated grid cell). Traditionally, a primary variable switching strategy for phase appearance or disappearance has been proposed, which inherits convergence and phase identification issues. In this study, we adopt an overall molar composition-based framework that can self-consistently take care of such complications. We compute the black-oil properties from tables initially constructed through fully compositional phase split calculations. Phase properties across a broad range of pressures for different black-oil compositions are interpolated to correctly model the transitions between saturated and undersaturated states. While maintaining the accuracy, we are able to gain considerable speed-up in black-oil model -more pronounced in saturated reservoirs- as compared to the fully compositional model.
In addition, previous black-oil models are mostly limited to low order numerical schemes. Here finite element (FE) methods are adopted, which are well suited to parallelization and provide flexibility in discretizing the geometry. Mass transport is updated explicitly by a locally mass conserving discontinuous Galerkin method. Globally continuous pressure and velocity fields are obtained through an implicit mixed hybrid FE scheme. The robustness and accuracy of our FE simulator are demonstrated in several complex problems, where we have attained considerable speed-up and maintained the accuracy by means of the new black-oil model, specifically for phase split computations.
Identifying the Optimum Zone for Reducing Drill String Vibrations
Authors: Christian Etaje Darlington 
Published: October 2017

Abstract
Drilling operators witness significant lost time due to early failure of bottomhole equipment resulting from vibration and shock. This eventually leads to cumulative losses of millions of dollars for the industry. Increase in applied weight on bit (WOB) at low angular velocity (RPM) can trigger instabilities leading to stick slip. Potentially, compression and stretch that occurs along the BHA during drilling operations could lead to whirling and buckling. The complexity of the whirling motion causes lateral shifts, shocks and friction against the borehole walls.
The driller has limited options. If stick-slip is identified, the driller decreases weight-on-bit (WOB) but whirling may occur from increasing revolutions per minute (RPM). Since the overall goal is to optimize drilling then reducing both WOB and ROB would not be an option since that would results in decrease in rate of penetration (ROP). This puts the driller in a tough situation where both severe vibrations and low ROP could occur simultaneously during drilling operations.
There is an optimum zone where drilling parameters – RPM and WOB -- improve BHA/bit stability. A machine learning methodology is described which is able to (a) identify the zone of stability through the use of supervised and unsupervised learning and (b) anticipate an upcoming optimum for safe drilling by merging historic data with real time analysis through the use of online learning. A comparison is presented which compares supervised and unsupervised machine learning in identifying and updating the optimum zone. From this zone, a parameter set of permissible combinations of WOB and RPM can be estimated. The methodology described is then applied to data derived from several hours of drilling in a highly tortuous zone with persistent vibration problems.
Single-Phase Flow of Aqueous Polymer Solutions Used in Enhanced Oil Recovery: An Experimental and Numerical Approach
Authors: Long Marjohny Lorene 
Published: October 2017

Abstract
Chemical Enhanced Oil Recovery with polymer flooding allows to decrease the mobility ratio between oil and water and therefore increase the sweep efficiency in the reservoir through different mechanisms that take place, such as: pressure drops and viscosity changes of the injected fluid. The main objective of this work is to assess the friction factor coupled with the pressure drop evaluation, to define its impact in the polymer injection through porous media. The evaluation will allow the determination of the drag enhancement and drag reduction zones of the polymer solutions, which contributes to understand the additional oil recovery.
A total of 12 polymer solutions were selected for this investigation and to establish numerical and experimental comparisons. Two types of commercial hydrolyzed polymers (Flopaam 6035S and Hengfloc 63023) were used at three different concentrations (500, 1000 and 1500 ppm). The polymer solutions were prepared using two different approaches (induced mechanical degradation and non-sheared). Experiments were performed injecting the polymer solutions in Bentheimer core samples. The evaluation was performed using a fourfold approach: 1) Three different rheological models were applied (Ergun (1949), Tiu et al. (1997) y Al Fariss (1990)), to determine mechanical parameters such as friction factor, Reynolds number and Weissenberg number. 2) Detailed relationship between viscosity as a function of pressure drop. 3) Defining correlations between the viscoelastic behavior of polymeric solutions and pressure drop associated to each experiment. 4) Numerical analysis using CMG Stars simulator, allowing Absolute Average Error (AAE) calculation.
The additional increase in differential pressure indicates that shear and frictional forces are not the main determinants during the flooding process. The results indicate that the polymer viscoelasticity is the main reason of this increase while polymer undergo deformation. The work provides a comprehensive evaluation to characterize the pressure observed during the flow of polymer in porous media.
Application of Artificial Neural Network to Estimate Permeability From Nuclear Magnetic Resonance Log
Authors: Olayiwola Teslim 
Published: October 2017

Abstract
Many oil reservoirs have heterogeneity in rock properties. Understanding the form and spatial distribution of these heterogeneities is fundamental to the success of reservoir description. Permeability is one of the fundamental rock properties to characterize flow potentials of reservoir when subjected to applied pressure gradients. A number of mathematical models have been suggested in the literature to simulate and quantify this property. However, common to them is difficulties in being able to model appropriately various geological variations associated with any reservoir. This study explores the benefits of using artificial neural network and NMR log in the permeability predictive model development. ANN was used to capture the non-linearity issues between the dependent and independent variables while the transversal relaxation times (T2) data is capable of capturing intrinsic rock properties at pore scale level. Out of verified datasets available, 60% of the datasets were used for the training process and the remainder for testing and validation. The input data was transverse relaxation time data, its mean value of the bins, mean square value of the bins and the maximum value of the bins. The developed ANN was trained, tested and validated using MATLAB Neural network toolbox trained with backward propagation scheme. The result shows a very good performance of ANN when compared with other existing empirical correlations adopted in this study.
Flywheel micro-vibration characters of a high resolution optical satellite
Authors: Li Lin , Tan Luyang , Kong Lin , Yang Hongbo , Wang Dong 
Published: October 2017

According to the pictures of a sub-meter resolution optical satellite which were acquired on orbit, there is a phenomenon of jitter in the process of taking pictures. As the main attitude control component of the satellite, the flywheel will produce the disturbance in its normal work, which has great influence on the high resolution optical satellite. This paper has respectively researched the flywheel components’ disturbance mechanism from four parts, including uneven rotator, rotator friction, bearing disturbance, foundation loose, and builds the mathematical model of disturbance to analyze the characteristics of disturbance. We have simulated and tested the flywheel components’ disturbance. The disturbance force of flywheel components is 2 N magnitude and the torque of disturbance is 1.5 N·m magnitude in time domain. The flywheel's infrastructure should be more inflexible especially around 90-100 Hz. For this target high resolution optical satellite, there should be effective damping measures around 48.6 Hz, 190.4 Hz and 285.4 Hz to decrease the flywheel disturbance to guarantee the high precision of the satellite. The result would offer guidance for system optimization design and vibration isolation compensation of the later type of improved satellite or other same type of satellites.
Multi-objective optimization for the aerodynamic noise of the high-speed train in the near and far field based on the improved NSGA-II algorithm
Authors: Yuan Chun Yan , Li Ming Qing 
Published: October 2017

With the increased running speed of trains, the aerodynamic noise of trains becomes increasingly obvious. Reducing aerodynamic noises has become one of keys to controlling the noise of high-speed trains. This paper conducted a numerical simulation on the aerodynamic noise of head of the high-speed train. Firstly, this paper established a mathematical-physical model for the three-dimensional turbulent flow field of a high-speed train, adopted standard k-ε equation turbulent model and broadband noise source model to compute the aerodynamic noise sources of the high-speed train and applied three-dimensional transient large eddy simulation (LES) to compute the external unsteady flow field of the high-speed train after obtaining noise sources. Based on the unsteady flow field, then this paper applied FW-H equations to compute the far-field aerodynamic noise of the high-speed train. After obtaining the unsteady fluctuation pressure on the surface of the train, this paper computed the radiation characteristics of aerodynamic noises around the high-speed train based on the boundary element method (BEM). Researched results showed: The main aerodynamic noise sources of the high-speed train were at the nose tip of head train; fluid separation and recombination were main reasons for the aerodynamic noise of the high-speed train; vortexes in the position of head train were striped and horseshoe-shaped or hairpin vortexes were mainly in the area of tail train; in addition, vortexes were symmetrically distributed along the longitudinal symmetry plane of train; dipole noises were mainly distributed in the area of head train, whose main energy was decreased with the increased frequency; the quadrupole noise of aerodynamic noises of the high-speed train was mainly distributed in the wake flow area of tail train; when the high-speed train ran at the speed of 300 km/h, the maximum sound pressure level of far-field observation points was 76.8 dB; additionally, aerodynamic noises in the far field were mainly a broadband noise, whose main energy was within the frequency range of 1250 Hz to 3150 Hz. Finally, the improved NSGA-II algorithm was used to conduct a multi-objective optimization for the head shape. The aerodynamic drag of the high-speed train could be most reduced by 6.74 %, and the dipole aerodynamic noise source could be most reduced by 8.34 dB. The improved NSGA-II algorithm has an obvious effect on the multi-objective optimization of the head shape.
Pollution risk evaluation of regional groundwater based on sources apportionment of pollution
Authors: Zuo Rui , Chen Xiaojuan , Wang Bin , Shan Dan , Yang Jie , Li Xianbo , Wang Jinsheng , Teng Yanguo 
Published: September 2017

Abstract
Pollution sources are determined by source apportionment, and are used as human-influenced factors to calculate the pollution risk of regional groundwater. In this case study, 266 samples of shallow groundwater were collected from the Lower Liaohe River Plain in northeastern China. Hydrochemical indexes of NH4+, Ca2+, Cl−, F−, HCO3−, Pb, Mg2+, NO3−, NO2−, K+, Na+, SO42−, total Cr, chemical oxygen demand, total dissolved solids, and total hardness of each sample were determined. Factor analysis method was used to identify potential pollution sources. Five common factors (agricultural activities, groundwater extraction, industrial activities, river pollution, and sewage discharges) represented 77.10% of the total variance. The results showed that the relatively high pollution risk mainly occurred in the west, with 19.91% of the area. The southeastern area showed a low risk of pollution, covering only 1.07% of the study area. Clearly, human activities have significantly changed the distribution of regional groundwater pollution risk in the study area.
Co-Occurrence of Plasmid-Mediated AmpC β-Lactamase Activity Among Klebsiella pneumoniae and Escherichia Coli
Authors: Zorgani Abdulaziz , Daw Hiyam , Sufya Najib , Bashein Abdullah , Elahmer Omar , Chouchani Chedly 
Published: October 2017

Introduction:
Extended-spectrum β-lactamases (ESBLs), including the AmpC type, are important mechanisms of resistance among Klebsiella pneumoniae and Escherichia coli isolates.

Objective:
The aim of the study was to investigate the occurrence of AmpC-type β-lactamase producers isolated from two hospitals in Tripoli, Libya.

Methods:
All clinical isolates (76 K. pneumoniae and 75 E. coli) collected over two years (2013-2014) were evaluated for susceptibility to a panel of antimicrobials and were analyzed phenotypically for the ESBL and AmpC phenotype using E-test and ESBL and AmpC screen disc test. Both ESBL and AmpC-positive isolates were then screened for the presence of genes encoding plasmid-mediated AmpC β-lactamases by polymerase chain reaction (PCR).

Results:
Of the K. pneumoniae and E. coli tested, 75% and 16% were resistant to gentamicin, 74% and 1.3% to imipenem, 71% and 12% to cefoxitin, 80% and 12% to cefepime, 69% and 22.6% to ciprofloxacin, respectively. None of the E. coli isolates were multidrug resistant compared with K. pneumoniae (65.8%). K. pneumoniae ESBL producers were significantly higher (85.5%) compared with (17.3%) E. coli isolates (P <0.0001, OR=4.93). Plasmid-mediated AmpC genes were detected in 7.9% of K. pneumoniae, and 4% E. coli isolates. There was low agreement between phenotypic and genotypic methods, phenotypic testing underestimated detection of AmpC enzyme and did not correlate well with molecular results. The gene encoding CMY enzyme was the most prevalent (66.6%) of AmpC positive isolates followed by MOX, DHA and EBC. Only one AmpC gene was detected in 5/9 isolates, i.e, blaCMY (n=3), bla
MOX (n=1), blaDHA (n=1). However, co-occurrence of AmpC genes were evident in 3/9 isolates with the following distribution:
bla
CMY and blaEBC (n=1), and blaCMY and blaMOX (n=2). Neither blaFOX nor blaACC was detected in all tested isolates. All AmpC positive strains were resistant to cefoxitin and isolated from patients admitted to intensive care units.

Conclusion:
Further studies are needed for detection of other AmpC variant enzyme production among such isolates. Continued surveillance and judicious antibiotic usage together with the implementation of efficient infection control measures are absolutely required.
Prevalence and Correlates of Metabolic Syndrome Among Adults Attending Healthcare Facilities in Eastern Cape, South Africa
Authors: Owolabi Eyitayo Omolara , Ter Goon Daniel , Adeniyi Oladele Vincent , Adedokun Aanuoluwa O. , Seekoe Eunice 
Published: October 2017

Background and Aim:Urbanisation and westernisation have greatly influenced the metabolic health of individuals in South Africa, with resultant increase in metabolic syndrome (METs) components. This study aimed to determine the prevalence and factors associated with METs among adults in Buffalo City Municipality, East London, South Africa.Methods:This was a healthcare facility-based cross-sectional, descriptive study. The World Health Organisation STEPwise demographic and lifestyle behavioural questionnaire was used to collect relevant data from 998 participants. Anthropometric measurements, blood pressure and fasting blood glucose were measured using standardised protocols. Metabolic syndrome was diagnosed using the International Diabetes Federation criteria.Results:The prevalence of metabolic syndrome was 21.8%; 15.6% and 24.8% among males and females, respectively. The prevalence of METs was higher among participants who were aged 56 years and above, with low level of education (grade 1 – 7), married and retired. After adjusting for confounders, only age 26 and above (AOR=4.1, CI=2.0-8.4), marriage (AOR=2.3 CI=1.6-3.3), female sex (AOR=1.6, CI=1.1-2.4), alcohol use (AOR=2.0, CI= 1.3-3.1), unemployment (AOR=1.8, CI= 1.2-2.6) and earning an income below ZAR1200 (AOR= 1.1, CI= 1.1-2.4) were significant and independent predictors of METs. Participants aged 26 and above were four times more likely to have METs. Married non-alcohol users and unemployed participants were two times more likely to have METs than unmarried alcohol users and employed individuals.Conclusion:There was a high prevalence of metabolic syndrome among the participants which indicates a high risk for cardiovascular diseases; a leading cause of premature morbidity and mortality.
Natural resistance of four Amazon woods submitted to xylophagous fungal infection under laboratory conditions
Authors: Reis Alisson Rodrigo Souza , Reis Luciane Pereira , Alves Júnior Miguel , Carvalho Josiane Celerino de , Silva Jhonata Ribeiro da 
Published: September 2017

The present study aimed to assess the natural resistance of four Amazon tropical wood species, used in the production of sawn timber, against infection with xylophagous fungi. Apuleia leiocarpa (amarelão), Dinizia excelsa (angelim vermelho), Vochysia maxima (quaruba), and Bagassa guianensis (tatajuba) were selected to perform the accelerated laboratory test. These species were exposed to white rot xylophagous fungi Pycnoporus sanguineus, Phanerochaete chrysosporium and Schizophyllum commune, and to the brown rot fungus Gloeophyllum abietinum. The laboratory test was performed following the methodology and classification of the natural resistance of wood according to ASTM D2017-86 (American Society for Testing Materials). All species were classified as highly resistant to fungal attack; however, V. maxima lost the highest percentage of weight. Therefore, we recommend that D. excelsa, A. leiocarpa, and B. guianensis be used in the production of sawn timber since they exhibited lower weight loss in the presence of all the fungi tested during a period of 12 weeks.
MANAJEMEN KESAN MELALUI FOTO SELFIE DALAM FACEBOOK: STUDI FENOMENOLOGI PADA MAHASISWA ILMU KOMUNIKASI UMS
Authors: Mala Puspa Aqirul 
Published: October 2017

This research explores about selfies phenomenon, especially how people managing their self-presentation through selfies on the Facebook. Computer Mediated Communications (CMC) and Erving Goffman’s Dramaturgi become basic theory in this research. Six informants were active uploaded their selfies and all of them are students of Communications Science in Muhammadiyah University of Surakarta. Phenomenology qualitative data result that informants are active managing their visual impression management on Facebook. They consider that Facebook is a stage and themself is an actor, so they can managing their selfies easily. Formed the charactheristic of CMC consist of: interactive, editable, de massified, and asynchronity.
MERANCANG DAN MENGIMPLEMENTASI MODUL PRAKTIKUM PEMBANGKIT LISTRIK TENAGA MIKRO HIDRO DI JURUSAN TEKNIK ELEKTRO DAN KOMPUTER UNIVERSITAS UDAYANA
Authors: Bahri Achmad , Jasa Lie , Sudarmojo Yanu Prapto 
Published: September 2017

Penelitian ini bertujuan untuk merancang suatu modul praktikum PLTMH kemudian mengimplementasi modul tersebut dengan menyusun petunjuk-petunjuk praktikum serta melakukan pengukuran. Data hasil pengukuran dalam pembahasan didapatkan dari prototipe praktikum Pembangkit Listrik Tenaga Mikro Hidro (PLTMH) yang di desain. Pengukuran dilakukan dengan menggunakan tiga jenis turbin, yaitu turbin sudu setengah lingkaran, turbin sudu segitiga, dan turbin sudu sirip. Hasil pengukuran tersebut dibahas dan dianalisis dengan menggunakan rumus dan program komputer Ms. Excel. Prosedur pengukuran dalam praktikum PLTMH dirancang untuk mengetahui prinsip kerja prototype PLTMH dengan mengukur Arus (I), Tegangan (V), Daya (P), Debit Air (Q), Putaran Turbin (nt), dan Putaran Generator (ng) dengan sudut nozzle 100, 150, 200, 250, 300, 350, dan 400 untuk setiap percobaan, dengan tiga macam jenis sudu turbin, serta dapat menentukan efisiensi dan regulasinya. Berdasarkan hasil pengukuran dari prototype PLTMH yang telah dirancang, efisiensi turbin pada masing-masing sudu mencapai titik tertinggi pada sudut 300. Pada sudut tersebut, efisiensi turbin sudu setengah lingkaran sebesar 0.26, turbin sudu segitiga sebesar 0.46 dan efisiensi turbin sudu sirip sebesar 0.38. Sehingga dari ketiga jenis sudu turbin tersebut, tingkat efisiensi turbin yang paling baik berdasarkan hasil pengukuran dari prototype yang telah dirancang adalah turbin sudu segitiga yang nilai efisiensinya sebesar 0.46 atau 46%.