bluuebunny/crossref_metadata_2025 huggingface dataset:
An Empirical Study on the Relationship between Urban Spatial Form and CO2 in Chinese Cities
Authors: Yi Yanchun , Ma Sisi , Guan Weijun , Li Ke
Published: April 2017

Although several studies have explained the effect of urbanization on China’s carbon emissions, most have focused on population urbanization, while ignoring the urban spatial form. This study investigates the impact of urban spatial form, measured by residential density, on the evolution of carbon emissions of 108 cities from 2003 to 2013 in China. The main results are as follows: (1) although urbanization significantly increases CO2 emissions, urban spatial form measured by residential density produces a negative effect on CO2 emissions in China.; (2) China has not become the “pollution haven” of foreign direct investment (FDI), instead, green FDI has reduced carbon emissions significantly; (3) the environmental dividends of low-carbon transformation have been observed in eastern and middle cities, but not in western ones. Therefore, establishing compact cities and traversing a low-carbon path is both feasible and necessary.
Effective Gravitational “Constant” in Scalar-(Curvature)Tensor and Scalar-Torsion Gravities
Authors: Järv Laur
Published: April 2017

In theories where a scalar field couples nonminimally to gravity, the effective gravitational “constant” becomes dependent on the value of the scalar field. This note first gives a brief review on how the cosmological evolution provides a dynamical stabilization for the gravitational “constant” as the system relaxes towards general relativity in matter dominated and potential dominated regimes for scalar-(curvature)tensor and scalar-torsion gravities. Second part summarizes the radius dependence of the gravitational “constant” around a point mass in the parametrized post-Newtonian formalism for scalar-tensor and multiscalar-tensor gravity.
Deep Sequencing Analysis of RNAs from Citrus Plants Grown in a Citrus Sudden Death-Affected Area Reveals Diverse Known and Putative Novel Viruses
Authors: Matsumura Emilyn , Coletta-Filho Helvecio , Nouri Shahideh , Falk Bryce , Nerva Luca , Oliveira Tiago , Dorta Silvia , Machado Marcos
Published: April 2017

Citrus sudden death (CSD) has caused the death of approximately four million orange trees in a very important citrus region in Brazil. Although its etiology is still not completely clear, symptoms and distribution of affected plants indicate a viral disease. In a search for viruses associated with CSD, we have performed a comparative high-throughput sequencing analysis of the transcriptome and small RNAs from CSD-symptomatic and -asymptomatic plants using the Illumina platform. The data revealed mixed infections that included Citrus tristeza virus (CTV) as the most predominant virus, followed by the Citrus sudden death-associated virus (CSDaV), Citrus endogenous pararetrovirus (CitPRV) and two putative novel viruses tentatively named Citrus jingmen-like virus (CJLV), and Citrus virga-like virus (CVLV). The deep sequencing analyses were sensitive enough to differentiate two genotypes of both viruses previously associated with CSD-affected plants: CTV and CSDaV. Our data also showed a putative association of the CSD-symptomatic plants with a specific CSDaV genotype and a likely association with CitPRV as well, whereas the two putative novel viruses showed to be more associated with CSD-asymptomatic plants. This is the first high-throughput sequencing-based study of the viral sequences present in CSD-affected citrus plants, and generated valuable information for further CSD studies.
The Paradox of Water Management Projects in Central Asia: An Institutionalist Perspective
Authors: Chatalova Lioudmila , Djanibekov Nodir , Gagalyuk Taras , Valentinov Vladislav
Published: April 2017

After the disintegration of the Soviet Union, the Central Asian countries have been faced with numerous development challenges in agriculture, especially those related to water use. Well-intentioned foreign donors and development agencies have stepped in to support local farmers, research centers, and public authorities in devising innovative solutions. Yet, development aid projects have borne fruit only partially. Paradoxically, innovative and apparently useful technologies proposed by foreign donors have rarely and only partially succeeded in taking root in the local institutional contexts. To explain this paradox, this paper draws on the institutional approach which shows the possibility of technological innovations being encapsulated by dysfunctional institutions. Reviewing recent studies of water-related projects in Central Asia, the paper shows this encapsulation to be at the core of the development project failures pervasive both in the Soviet period and today. If the concept of encapsulation is valid, then the current development efforts can be made more effective by detecting and counteracting the structures of vested interest on the part of all the actors involved, such as foreign donors, public authorities, research centers and local farmers.
High photocatalytic activity of Fe2O3/TiO2nanocomposites prepared by photodeposition for degradation of 2,4-dichlorophenoxyacetic acid
Authors: Lee Shu Chin , Lintang Hendrik O , Yuliati Leny
Published: April 2017

Two series of Fe2O3/TiO2samples were prepared via impregnation and photodeposition methods. The effect of preparation method on the properties and performance of Fe2O3/TiO2for photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under UV light irradiation was examined. The Fe2O3/TiO2nanocomposites prepared by impregnation showed lower activity than the unmodified TiO2, mainly due to lower specific surface area caused by heat treatment. On the other hand, the Fe2O3/TiO2nanocomposites prepared by photodeposition showed higher photocatalytic activity than the unmodified TiO2. Three times higher photocatalytic activity was obtained on the best photocatalyst, Fe2O3(0.5)/TiO2. The improved activity of TiO2after photodeposition of Fe2O3was contributed to the formation of a heterojunction between the Fe2O3and TiO2nanoparticles that improved charge transfer and suppressed electron–hole recombination. A further investigation on the role of the active species on Fe2O3/TiO2confirmed that the crucial active species were both holes and superoxide radicals. The Fe2O3(0.5)/TiO2sample also showed good stability and reusability, suggesting its potential for water purification applications.
AN INTEGRATED FUZZY AHP AND ARAS MODEL TO EVALUATE MOBILE BANKING SERVICES
Authors: ECER Fatih
Published: April 2017

Mobile banking (M-banking) which integrates software, hardware, and human is a new platform for banks. Determining the performance of M-banking services helps bank practitioners identify better policy to improve their positions. The aim of this study is to develop an integrated model for evaluating M-banking services by two methods, namely the Fuzzy Analytic Hierarchy Process (FAHP) with an extent analysis approach and ARAS (Additive Ratio ASsessment). In this study, the priority weights obtained through the FAHP are combined with the ARAS method to as­sess and rank the M-banking services. Moreover, in order to verify the applicability of this proposed model, a case study in Turkey is offered. The findings indicate that facilitating conditions play the most determining role in the adoption of the M-banking, followed by self-efficacy, privacy risk, and security risk. Consequently, the proposed model helps to overcome difficulties in M-banking service evaluation process and increases the efficiency of the M-banking service activities. Besides, the case study validates that the proposed model is an effective and efficient decision making tool for the evaluation of M-banking services under fuzzy environments.
Uniform Silicon Isotope Ratios Across the Milky Way Galaxy
Authors: Monson Nathaniel N. , Morris Mark R. , Young Edward D.
Published: April 2017

We report the relative abundances of the three stable isotopes of silicon, 28Si, 29Si, and 30Si, across the Galaxy using the

transition of silicon monoxide. The chosen sources represent a range in Galactocentric radii (

) from 0 to 9.8 kpc. The high spectral resolution and sensitivity afforded by the Green Bank Telescope permit isotope ratios to be corrected for optical depths. The optical-depth-corrected data indicate that the secondary-to-primary silicon isotope ratios

and

vary much less than predicted on the basis of other stable isotope ratio gradients across the Galaxy. Indeed, there is no detectable variation in Si isotope ratios with

. This lack of an isotope ratio gradient stands in stark contrast to the monotonically decreasing trend with

exhibited by published secondary-to-primary oxygen isotope ratios. These results, when considered in the context of the expectations for chemical evolution, suggest that the reported oxygen isotope ratio trends, and perhaps those for carbon as well, require further investigation. The methods developed in this study for SiO isotopologue ratio measurements are equally applicable to Galactic oxygen, carbon, and nitrogen isotope ratio measurements, and should prove useful for future observations of these isotope systems.
The Correlation between Halo Mass and Stellar Mass for the Most Massive Galaxies in the Universe
Authors: Tinker Jeremy L. , Brownstein Joel R. , Guo Hong , Leauthaud Alexie , Maraston Claudia , Masters Karen , Montero-Dorta Antonio D. , Thomas Daniel , Tojeiro Rita , Weiner Benjamin , Zehavi Idit , Olmstead Matthew D.
Published: April 2017

We present measurements of the clustering of galaxies as a function of their stellar mass in the Baryon Oscillation Spectroscopic Survey. We compare the clustering of samples using 12 different methods for estimating stellar mass, isolating the method that has the smallest scatter at fixed halo mass. In this test, the stellar mass estimate with the smallest errors yields the highest amplitude of clustering at fixed number density. We find that the PCA stellar masses of Chen et al. clearly have the tightest correlation with halo mass. The PCA masses use the full galaxy spectrum, differentiating them from other estimates that only use optical photometric information. Using the PCA masses, we measure the large-scale bias as a function of

for galaxies with

, correcting for incompleteness at the low-mass end of our measurements. Using the abundance matching ansatz to connect dark matter halo mass to stellar mass, we construct theoretical models of

that match the same stellar mass function but have different amounts of scatter in stellar mass at fixed halo mass,

. Using this approach, we find

. This value includes both intrinsic scatter as well as random errors in the stellar masses. To partially remove the latter, we use repeated spectra to estimate statistical errors on the stellar masses, yielding an upper limit to the intrinsic scatter of 0.16 dex.
A Comprehensive Library of X-Ray Pulsars in the Small Magellanic Cloud: Time Evolution of Their Luminosities and Spin Periods
Authors: Yang J. , Laycock S. G. T. , Christodoulou D. M. , Fingerman S. , Coe M. J. , Drake J. J.
Published: April 2017

We have collected and analyzed the complete archive ofXMM-Newton(116),Chandra(151), andRXTE(952) observations of the Small Magellanic Cloud (SMC), spanning 1997–2014. The resulting observational library provides a comprehensive view of the physical, temporal, and statistical properties of the SMC pulsar population across the luminosity range oferg s−1. From a sample of 65 pulsars we report ∼1654 individual pulsar detections, yielding ∼1260 pulse-period measurements. Our pipeline generates a suite of products for each pulsar detection: spin period, flux, event list, high time-resolution light curve, pulse profile, periodogram, and spectrum. Combining all three satellites, we generated complete histories of the spin periods, pulse amplitudes, pulsed fractions, and X-ray luminosities. Some pulsars show variations in pulse period due to the combination of orbital motion and accretion torques. Long-term spin-up/spin-down trends are seen in 12/11 pulsars, respectively, pointing to sustained transfer of mass and angular momentum to the neutron star on decadal timescales. Of the sample, 30 pulsars have a relatively very small spin period derivative and may be close to equilibrium spin. The distributions of pulse detection and flux as functions of spin period provide interesting findings: mapping boundaries of accretion-driven X-ray luminosity and showing that fast pulsars (P < 10 s) are rarely detected, which as of yet are more prone to giant outbursts. Accompanying this paper is an initial public release of the library so that it can be used by other researchers. We intend the library to be useful in driving improved models of neutron star magnetospheres and accretion physics.
HALOGAS Observations of NGC 4559: Anomalous and Extraplanar H i and its Relation to Star Formation
Authors: Vargas Carlos J. , Heald George , Walterbos René A. M. , Fraternali Filippo , Patterson Maria T. , Rand Richard J. , Józsa Gyula I. G. , Gentile Gianfranco , Serra Paolo
Published: April 2017

We use new deep 21 cm H i observations of the moderately inclined galaxy NGC 4559 in the HALOGAS survey to investigate the properties of extraplanar gas. We use TiRiFiC to construct simulated data cubes to match the H i observations. We find that a thick-disk component of scale height ∼2 kpc, characterized by a negative vertical gradient in its rotation velocity (lag) of ∼13 ± 5 km s−1 kpc−1 is an adequate fit to extraplanar gas features. The tilted ring models also present evidence for a decrease in the magnitude of the lag outside R
25, and a radial inflow of ∼10 km s−1. We extracted lagging extraplanar gas through Gaussian velocity profile fitting. From both the 3D models and extraction analyses we conclude that ∼10%–20% of the total H i mass is extraplanar. Most of the extraplanar gas is spatially coincident with regions of star formation in spiral arms, as traced by Hα and GALEX FUV images, so it is likely due to star formation processes driving a galactic fountain. We also find the signature of a filament of a kinematically “forbidden” H i feature, containing ∼1.4 × 106
M
⊙ of H i, and discuss its potential relationship to a nearby H i hole. We discover a previously undetected dwarf galaxy in H i located ∼0.°4 (∼58 kpc) from the center of NGC 4559, containing ∼4 × 105
M
⊙. This dwarf has counterpart sources in SDSS with spectra typical of H ii regions, and we conclude that it is two merging blue compact dwarf galaxies.
H-atmospheres of Icy Super-Earths Formed In Situ in the Outer Solar System: An Application to a Possible Planet Nine
Authors: Levi A. , Kenyon S. J. , Podolak M. , Prialnik D.
Published: April 2017

We examine the possibility that icy super-Earth mass planets, formed over long timescales (0.1–1 Gyr) at large distances (∼200–1000 au) from their host stars, will develop massive H-rich atmospheres. Within the interior of these planets, high pressure converts CH4 into ethane, butane, or diamond and releases H2. Using simplified models that capture the basic physics of the internal structure, we show that the physical properties of the atmosphere depend on the outflux of H2 from the mantle. When this outflux is

molec cm−2 s−1, the outgassed atmosphere has a base pressure of ≲1 bar. Larger outflows result in a substantial atmosphere where the base pressure may approach 103–104 bar. For any pressure, the mean density of these planets, 2.4–3 g cm−3, is much larger than the mean density of Uranus and Neptune, 1.3–1.6 g cm−3. Thus, observations can distinguish between a Planet Nine with a primordial H/He-rich atmosphere accreted from the protosolar nebula and one with an atmosphere outgassed from the core.
Root Cause Analysis and Actions for the Prevention of Medical Errors: Quality Improvement and Resident Education
Authors: Charles Ryan , Hood Brandon , DeRosier Joseph M. , Gosbee John W. , Bagian James P. , Li Ying , Caird Michelle S. , Biermann J. Sybil , Hake Mark E.
Published: April 2017

The quality of care delivered by orthopedic surgeons continues to grow in importance. Multiple orthopedic programs, organizations, and committees have been created to measure the quality of surgical care and reduce the incidence of medical adverse events. Structured root cause analysis and actions (RCA
2
) has become an area of interest. If performed thoroughly, RCA
2
has been shown to reduce surgical errors across many subspecialties. The Accreditation Council for Graduate Medical Education has a new mandate for programs to involve residents in quality improvement processes. Resident engagement in the RCA
2
process has the dual benefit of educating trainees in patient safety and producing meaningful changes to patient care that may not occur with traditional quality improvement initiatives. The RCA
2
process described in this article can provide a model for the development of quality improvement programs. In this article, the authors discuss the history and methods of the RCA
2
process, provide a stepwise approach, and give a case example. [
Orthopedics.
2017; 40(4):e628–e635.]
Slovenian exonyms in North America
Authors: Perko Drago , Kladnik Drago
Published: April 2017

The number of Slovenian exonyms around the world decreases with distance from Slovenia. This applies less so to North America, where their density is twice as high as in South and Central America.Based on a comparative analysis of geographical names from all important world atlases in Slovenian, we prepared two spreadsheets of Slovenian exonyms. The extensive spreadsheet has 5,038 names and the concise spreadsheet has 3,819 names. Each exonym has thirty-five thematic fields.In North America, marine hydronyms (21.1%) are the most numerous semantic type of exonyms, and completely translated names (77.9%) are the most numerous Slovenianized type of exonyms. Among the original languages of exonyms, English completely prevails (97.1%).The most commonly used Slovenian exonyms from North America in Slovenian texts are Dolina smrti ‘Death Valley’, Veliki kanjon ‘Grand Canyon’, Niagarski slapovi ‘Niagara Falls’, Skalno gorovje ‘Rocky Mountains’, and Aleuti ‘Aleutian Islands’.
The Role of Institutionalized Corporate Communication Function on Good Governance
Authors: Menteş Süleyman Ahmet
Published: April 2017

Corporate communication practice contributes to the good governance of the corporations only if it is used as a strategic management tool. This requires an institutionalized and consistent communication management function in corporations. In this context the study empirically tests the influence of institutionalized corporate communication function on the good governance of firms listed at Borsa Istanbul 100 Index (BIST100). The study also explores the role of institutionalized corporate communication function on identifying the stakeholders of the firms. Findings reveal that there is statistical association not only between institutionalized corporate communication function and good governance but also between institutionalized corporate communication function and stakeholder identification process at BIST100 listed firms. This research is important in the sense that it is the first research that empirically exhibits the association between institutionalized corporate communication function and good governance in Turkey.
Psychosocial Health at Work
Authors: Vatansever Çiğdem
Published: April 2017

In today's 24/7 work life, mainly productivity demands and increasing work hours affect negatively employees' health and well-being. The negative qualities are called as psychosocial hazards they are defined as “new” and “increasing” risks of work environment. The job-demand-resources model explains the behavioral interactions at work environment that lead to psychosocial hazards and risks. This study aims to determine the demands of the working environment together with the degree of control given to the employees, the level of social support and how all these related to burnout. The subjects are 144 private security officers in a Turkish bank. Study confirmed the positive relation between job demands and burnout; on the otherhand the mediator role of control and supports are not validated.
Is the Web Site Well Structured?
Authors: Cui Tingru , Wang Xinwei , Teo Hock-Hai
Published: April 2017

Globalization has driven many organizations to develop an international presence on the web. Building a culturally-competent Web site is of paramount importance. This research investigates the effect of cultural cognitive style on user perception of Web site structure characteristics and performance on the Web site, and the subsequent user satisfaction towards the Web site. More specifically, we focus on the breadth versus depth of a Web site's structure. A laboratory experiment involving 125 participants from China and the United States was conducted to test the hypotheses. The results showed that cultural cognitive style and Web site structure indeed interact to affect user perception and performance. People with holistic and analytic cultural cognitive styles displayed different perceived navigability and user performance on “broad” and “deep” Web sites. This study extends Web site structure literature to the cross-cultural context. It also suggests pragmatic strategies for Web site design practitioners to improve website design in order to attract international audience.
Usage and Performance of Enterprise Micro-Blogging
Authors: Lv Zhepeng , Huang Jinghua , Li Yangfan , Zhang Yu-Jin
Published: April 2017

The increasing use of micro-blogging as a marketing tool has increased research attention on usage and performance of enterprise micro-blogging. Based on research on information system (IS) usage and resource-based view (RBV) theory, this study sets up a model to reveal the mechanism of business value creation of enterprise micro-blogging. The model consists of metrics on micro-blogging usage, marketing capability, micro-blogging operational performance, and firm performance. Questionnaires were distributed to firms that use micro-blogging on Weilbo of Sina. This study collects 241 valid responses for empirical analysis. The results suggest that the use of enterprise micro-blogging improves operational performance of enterprise micro-blogging directly and indirectly by increasing marketing capability, while operational performance of enterprise micro-blogging significantly affects firm performance. Furthermore, different use affects marketing capability and operational performance differently. This study extends the stream of research that combines IS usage and RBV theory.
Marketing Information System
Authors: Ekhlassi Amir , Alinaghian Ehsan
Published: April 2017

Increasingly, business leaders are viewing market information not only as an input for making better decisions but also as an important strategic asset. Marketing Information may prove to a business's chief competitive advantage in many business sectors. Competitors can copy each other's products, processes, procedures, and technologies, but they cannot duplicate the marketing information and intellectual capital. Marketing Information System primarily serves the company's marketing and top level managers, but it may also provide information to external partners, such as suppliers, partners, distributors, or marketing services agencies. A good Marketing Information System balances the information users would like to have against what they really need and what is feasible to offer and the cost of obtaining. This chapter explains how a Marketing Information system can be developed in a business? What are the subsystems of a Marketing Information system and their functions?
Comparison of Technology Qualification Approaches
Authors: Ye Joanna , D`Angelo Luis , Viteri Martha , Weston Robert , Caires Luis
Published: April 2017

New concepts and technology are vital for the Oil & Gas industry to meet ever more challenging requirements for drilling and production in deep and ultra-deep waters. When new technology is deployed, whether with novel equipment or standard equipment in novel applications, it is critical to build confidence in ts safety and reliability before implementation. Given that current industry standards and codes might not address all potential modes of failure for new technologies, a systematic technology qualification process can be used to identify and mitigate any potential threats. Compliance with the required functionality and reliability requirements can be demonstrated through qualification methods such as testing and analyses, and the uncertainty or risks associated with the technology, system and interfaces can be eliminated or minimized.

Several recognized technology qualification methodologiesare currently available to the industry that completely or partially address qualification of new technology: ISO 20815 Petroleum, Petrochemical and Natural Gas Industries - production assurance and reliability management [1], NASA technology readiness level assessment system [2], DOE G 413.3-4A technology readiness assessment guide [3], Technology Readiness Assessment (TRA) Guidance, United States Department of Defense [4], , API RP 17N Recommended Practice for Subsea Production Systems Reliability and Technical Risk Management [5], API RP 17Q Subsea Equipment Qualification [6], and DNV RP A203 Technology Qualification [7].

Two of the widely accepted technology qualification (TQ) methodologies in the offshore Oil & Gas industry are API 17N [5] and 17Q [6] and DNV RP A203 [7]. Although both methodologies are quite similar, the differences may confuse technology developers, this paper addresses differences including the circumstances under which one might be more efficient/cost-effective than the other, how new technology is defined, and how much rigor is needed to address potential threats.

In summary, this paper reviews and examines the similarities and differences that are presented in the two widely accepted TQ methodologies. Further, this paper provides insights on how to employ these methodologies to meet specific end user needs. In addition, a case study is included to demonstrate the comparisons between the methodologies.
Estimation of BOP Stack Drag and Added Mass Using Computational Fluid Dynamics
Authors: Lopez Carlos F. , Pordal Harbinder , Bhalla Kenneth , Stahl Matthew J.
Published: April 2017

The hydrodynamic drag and added mass of a blowout preventer (BOP stack) influences the resonant amplitudes and frequencies of a drilling riser system during connected (low amplitude oscillations) and disconnected (high amplitude oscillation) conditions. The prediction of hydrodynamic loads on a BOP stack at resonant frequencies is of importance for analyzing wellhead and casing fatigue and ensuring well integrity. Accurate prediction of dynamic hook load fluctuation is also of significant importance, particularly in determining feasibility for deploying and hanging-off drilling riser systems in ultra-deep water.

A predictive technique based on computational fluid dynamics (CFD) methods is developed to estimate hydrodynamic forces exerted on a BOP stack. This method is applied to analyze the flow behavior during steady-state flow, connected oscillation, and disconnected hang-off oscillation to characterize the stack added mass and drag properties. This study considers four scenarios:

Steady-state drag over the BOP stack,

Lateral oscillations of the BOP stack in stationary water,

Lateral oscillations of the BOP stack under nominal current conditions and

Coupled axial and lateral oscillations in stationary water.

This paper describes the use of CFD coupled with analytical methods to obtain key characteristic parameters associated with an oscillating BOP stack.

The analysis shows that the steady-state drag coefficient significantly under predicts the drag coefficient for an oscillating BOP stack. The drag coefficient of an oscillating BOP stack in stationary water is significantly higher than the corresponding steady-state drag coefficient. The added mass coefficient shows dependence on oscillation amplitude and frequency; however, the dependence is not as significant as that observed for the drag coefficient. The combined lateral and axial oscillations show similar values of drag coefficient and added mass as the uncoupled lateral or axial oscillations. A study of BOP stack added mass and drag under nominal background current shows changes to the drag and added mass computed with stationary water conditions for an oscillating BOP stack.

The viability of using computational methods for determining drag and added mass coefficients for a BOP stack under various conditions is established. Hydrodynamic coefficients that have been determined by this approach can be used to improve the accuracy of dynamic global drilling riser and wellhead fatigue analysis.
The Importance of Periodic Reassessment of Operational Strategies for Wax Management
Authors: Lavenson David M. , Venkatesan Rama , Young Michelle K. , Kebert Neal
Published: April 2017

Periodic reassessment of flow assurance risks is a critical topic for greenfield and brownfield projects hoping to ensure an optimal risk management strategy in addition to efficient operations. Greenfield projects must understand the value of flow assurance risk monitoring in order to operate efficiently and reliably throughout the asset life to ensure maximum value is captured. Brownfield operations, in the current market, are continuously looking for methods to reduce cost while maintaining operational excellence. Recently, a comprehensive field optimization of an offshore brownfield application was conducted that focused on a re-evaluation of incumbent wax management strategies for pipelines and flowlines. Balancing pigging schedules with chemical injection is the most common wax mitigation, yet over time drivers for risk management plans can change – specifically for activities like regular pigging of flowlines. The team reviewed extensive laboratory testing of current and potential wax inhibitor chemicals to determine expected performance. The lab results, coupled with operational constraints and recent pigging campaign results, led to a recommendation for a new wax management strategy. Results of the campaign were successful; a dramatic reduction in the wax chemicals required to maintain a manageable wax deposition, and an optimized pigging schedule which resulted in a reduction in operating expenses exceeding $5 million per year. This value creation was a direct result of emphasizing a reassessment of flow assurance risks – specifically waxes – of operating assets. This work will emphasize that flow assurance risks must be continually monitored – to ensure the risk profile has not changed for better or worse, and to identify opportunities to adjust mitigation methods to capture cost savings and/or added value.
Experimental Investigation of Propellant Fracturing in a Large Sandstone Block
Authors: Malhotra Sahil , Rijken Peggy , Sanchez Alicia
Published: April 2017

Propellants have been utilized in oil and gas wells to assist with perforating and creating near wellbore stimulation. Propellants are electrically ignited in the wellbore at the perforated interval. Upon ignition they rapidly create a large amount of gas and the pressurization leads to breakdown of the formation. It has been postulated that the pressurization leads to creation of multiple fractures in the formation. This paper describes an experimental study with a new propellant and aims to understand the pattern of fracture creation with these propellants. The results are also compared to an older generation of propellant tested by Wieland et al. 2006 (SPE 102907).

A large scale laboratory test was performed in a sandstone block (30″ × 30″ × 54″) with a 2″ diameter vertical centralized wellbore extending the full block height. The block was loaded in a poly-axial stress frame. A proppellant cartridge was positioned in the center of the wellbore. Small holes were drilled in the rock to intersect the expected primary fracture and instrumented with high resolution pressure gauges to enable fracture timing and growth rate analysis. Anisotropic stresses representative of field conditions were applied on the block and the wellbore was pressurized prior to ignition.

The propellant ignition produced an initial peak pressure of 5,790psi in 1.4 milliseconds followed by saw tooth pattern of pressure increase to a maximum pressure of 6,600psi before decaying due to fracture growth and gas leak-off. The block was removed from the test frame and cut vertically and horizontally to examine the fracture pattern generated by the propellant. A dominant planar fracture was observed on either side of the wellbore which propagated in the direction perpendicular to the minimum horizontal stress direction. It was verified that the propellant had much higher burn rate than the propellant tested by Wieland et al. (2006).

The large block test provides critical insights and data which can serve as important inputs to calibrate physics based models utilized for modeling propellant ignition and stimulation. The results help in understanding the benefits and limitations of using propellants for stimulation.
Preparing Offshore Facilities for Seismic Events
Authors: Sheppard Robert , Carson Patrick
Published: April 2017

Seismic design approaches for offshore assets focus on structural response, with the ultimate goal of preventing catastrophic collapse under intense ground motions. This is a prudent approach and places the emphasis on life safety. However, it does not address the operational and safety aspects of nonstructural component response. It is possible that a facility can survive an earthquake with little or no structural damage but be unsafe to man or unable to operate due to damage to the equipment and systems supported by the structure.

After the Gulf of Mexico hurricanes, Ivan, Katrina, Rita, and Ike, in the 2000s, it was recognized that topsides damage to permanent equipment was a significant problem for offshore assets, and guidance was produced by the industry to proactively address the issue. While there have been no significant earthquake impacts on offshore assets in seismic regions, there is still a need to prepare for their occurrence so that damage can be prevented.

This paper addresses the seismic vulnerabilities of mechanical, piping and electrical systems and equipment on offshore facilities and how operators can prepare their assets to safely withstand earthquakes with limited interruption to operations. The approaches presented build on the experience of the onshore power generation industry and field investigations of earthquakes impacts on industrial and commercial facilities going back over 40 years. Emphasis is placed on practical investigation of vulnerabilities, and mitigations to limit the kind of damage that is known to occur for various equipment types.
Applying Real Time Data Analytics to Early Detect Underreamer Failure During Hole Enlargement While Drilling at Deepwater Gulf of Mexico
Authors: Wu Xianping , Liu Yu , Martinez Manny
Published: April 2017

Deepwater drilling often requires simultaneously hole-enlargement-while-drilling (HEWD) to improve project economics and preserve hole size for reaching deep reservoirs. The challenge of having two active cutting structures (drill bit and expandable underreamer) in one BHA is improving ROP performance of entire drilling system while preventing premature failure of the underreamer, which is susceptible to vibration induced damages. From an operational standpoint, one potentially disastrous scenario is when underreamer has been severely damaged, but the drill bit is still in good condition. If such situation is not detected promptly and drilling continues, HEWD operation could potentially create a significantly undergauge hole section whose diameter is similar to drill bit. Such consequence can cause enormous difficulty for running/cementing the casing string, and often result in costly remedial operations, or in severe cases, hole abandonment.

To mitigate this risk, an advanced data analytics method was developed to early detect the failure of underreamer by utilizing the standard drilling mechanics data from both surface and downhole sensors. This patent-pending method includes the development of new performance metrics for underreamers based on rock cutting physics and cutter wearing mechanism. This new technology enables the operator to extract insights from similar tool failures in historical data and puts those insights into action on real-time data "in motion". A warning flag can be displayed immediately when the underlying failure pattern is detected by the new method. All relevant rig and office personnel are notified in real-time to promote timely discussion and facilitate decision making.

The operator working in Gulf of Mexico required hole-enlargement-while-drilling to open a pilot hole from 16.5″ to 20″ from 14,000′ MD to approximately 21,000′ MD. The new technology was utilized to monitor the underreamer performance in real-time for this challenging section. The technology provided a warning signal as soon as the algorithm detected the onset of a failure pattern from the underreamer at about the midpoint of the section. When it was pulled to surface, underreamer showed significant damage on cutting structure and had started becoming undergauge. This case study demonstrated the validity of this new method in detecting underreamer failure in real-time. Since then, this technology has been deployed on more than 10deepwaterwells to mitigate the risk of underreamer failure.
Meeting the Demand for Barrier Plug Integrity Assurance & Verification of Well Abandonment Barriers
Authors: Stein Arild
Published: April 2017

Well barrier installation practice is dictated by territoryspecific regulations which are largely based on historic practices. However, emerging technologies, tighteningnationalregulations, and demands from assetowners are gradually affecting the way we carry out our intervention operations. Driving the technology development is time saving but with a sharp eye on safety. Well documented verifications on temporary barriers and barriers installed for well suspension and future P&A barrier installation is expected. There are multiple issues involved in gaining proper verification of aninstalled barrier. One major issue appearing is the general condition and status of previously installed plugs and valve components in older wells, which canresult intwo wellbore barriers installed in close proximity. Othermajor issues are the well'sgeneral ability to support an inflow test, and the time it takes to get asegregating well stable.
Riserless Light Well Intervention Restores Production on Oyo - 8 Subsea Well
Authors: Adenipekun Adedokun , Marinho Gregory , Odeyemi Olushola , Ugboaja Chidi , Bassey Ayoge , Nnebocha Ezinne , Ade-Aina Oladeji
Published: April 2017

Producing hydrocarbons in a deepwater environment is quite challenging and the goal is always to sustain production for as long as possible. Any shutdown, whether intended or unintended, can prove costly. Such was the case on Oyo-8 when the down-hole safety valve failed to open after a planned production curtailment. The several attempts to open the valve were unsuccessful due to suspected loss of hydraulic communication to the operating mechanism or the malfunction of the mechanism. A well intervention was therefore deemed necessary to re-enter the well.

Well intervention in a deepwater environment is particularly expensive, risky and complex, whether it is rig based or rigless. A vessel based riserless light well intervention (RLWI) operation was determined as the optimal solution for Oyo-8. This entails a through-tubing operation to install a retrofit sub-surface controlled safety valve (velocity valve) assembly across the tubing-retrievable safety valve (TRSV) to permanently hold open its flapper and serve as a sub-surface controlled safety valve.

The notable advantages of a vessel based operation were the reduced personnel and reduced number of third-party service contractor interfaces to manage. The rig-up is significantly simpler than the requirements for rig-based completion/de-completion operations. The fact that it is riserless also eliminates the debris management issues usually associated with the marine risers of mobile drilling units. The key components of RLWI are the subsea well-control package, subsea wireline lubricator, subsea pressure-control head, a compensated winch mounted on a module-handling tower, compensated heavy-duty over-side crane, slickline unit, and two work-class ROVs.

The RLWI operation was completed within the budgeted time with less than 3% nonproductive time. The recovery of the horizontal tree crown plugs was uneventful, as the ROV high-pressure jetting tool was effective in flushing out debris from the top of the upper plug before installing the well control package and carrying out the slickline runs. The velocity valve assembly was installed hanging off the end of a thru-tubing packer set in blank tubing. A carefully planned combined operation with the FPSO ensured that control of Oyo-8 horizontal tree was maintained during well intervention from the production topside.

The intervention operation achieved the set objectives of restoring Oyo-8 to full production within allotted time and budget without any QHSE incidents. The RLWI operation was the first of its kind in Nigerian waters.
Nano-Enhanced Elastomers for Oilfield Applications
Authors: Dolog Rostyslav , Ventura Darryl , Khabashesku Valery , Darugar Qusai
Published: April 2017

The use of elastomers in oil industry extends over a broad range of applications including seals, packing elements, reactive rubber elements, stators, and pads. These applications require a variety of property requirements that may differ for dynamic and static applications or include a need for stimuli-responsive capabilities in certain tools.

This research details the effect of nanofillers on elastomer properties for oil and gas components. The effects include enhancement of mechanical properties, wear resistance, thermal conductivity and heat expansion properties. In addition, effects of nanofillers on rapid gas decompression (RGD) resistance, chemical resistance to downhole fluids, and resistance to chemical aging at downhole temperatures were investigated.

Advanced rubber nanocomposites formulations, based on Hydrogenated Nitrile Butadiene Rubber (HNBR) elastomers, were designed internally. Their properties were assessed using methods and techniques to qualify elastomers for downhole applications. Mechanical properties of elastomers were evaluated at room temperature and at 325° F, which is a maximum application temperature for HNBR elastomers. RGD testing was conducted according to ISO standards.

Results indicated that it is possible to control mechanical properties of elastomers with nanotechnology, including improving the abrasion resistance of the elastomers by more than 100% in dynamic, wear-intensive applications, when compared to commercial compounds typically used in the oil industry. Thermal conductivity was improved by up to 40%, while heat expansion decreased by 30%, providing more versatility for seal design in dynamic applications which are prone to localized heating. In addition, RGD resistance in nanocomposites was examined and compared it to control samples. The industrial scale feasibility for nano-enhanced elastomers was demonstrated by a scale-up study.
Recent Improvements in Subsea Wellhead Fatigue Monitoring Algorithm and Accuracy Using Verification and Calibration Techniques
Authors: Ge Michael Long , Kebadze Buba , Henderson John , Zakeri Arash
Published: April 2017

Current subsea wellhead fatigue monitoring systems typically measure subsea BOP stack response and convert accelerations directly to the stress on various critical wellhead components using transfer functions. The veracity of this process relies on the accuracy of input data and the numerical modelling of the riser, subsea stack and wellhead conductor system. Poor representation of a real system could potentially yield an inaccurate calculation of transfer functions and consequently, imprecise estimation of the stress levels and predicted fatigue damage. The transfer function is strongly influenced by subsea stack system stiffness, which depends on dynamic soil response, stack hydrodynamic added mass and drag, location of the subsea stack fixity point, and stack-conductor system characteristic frequency. The latter two can be measured in the field and compared with predictions from numerical models. This paper evaluates the subsea wellhead fatigue monitoring algorithm and accuracy using verification and calibration techniques with field measurements. Important considerations for verification and calibration (e.g. soil property) are also discussed.

The new approaches described are applicable to fatigue monitoring and analysis of subsea wellhead and conductor systems in both shallow and deep waters. The approaches presented herein could improve determination of the conductor fixity point and subsea stack characteristics, which in turn, would help in accurately determining wellhead fatigue and extracting displacements if needed. The good match between predicted and measured values of these parameters demonstrates that the numerical model and associated transfer functions are adequate for measured fatigue damage estimation.

The transfer functions for fatigue monitoring systems and the associated subsea wellhead fatigue results could be significantly affected by the accuracy of the modelling methods and input data, particularly the soil properties. An inacccurate representation of the distance between the sensor and wellhead hot spot locations from which the transfer functions are derived could affect the accuracy of the fatigue results. For the case presented herein, the hydrodynamic properties drag loads and added mass have a less significant effect on the accuracy of transfer function and fatigue results.
Gaseous Calibration Standards: Manufacturing, Stability, Traceability and Uncertainty
Authors: Jacksier A Tracey , Weterings Werner
Published: April 2017

This paper addresses some key analytical issues which affect the accuracy and precision of analytical measurements required by hydrocarbon processors, refineries and petrochemical plants. These issues include the use of appropriate calibration standards for specific applications.
Comparison of Current Measurements from Oceanographic Mooring and Unmanned Surface Vehicle
Authors: Yazarov Maxim , Pai Sudhir , Quiniou-Ramus Valerie
Published: April 2017

Monitoring of currents is of high importance for Oil and Gas industry, especially when it comes to design, offload and support to operations. Various monitoring techniques, existing nowadays, with each having their own pros and cons, are briefly discussed in the paper.

The objective of study was to compare current data acquired by Unmanned Surface Vehicle (USV), used offshore South America East Coast to support seismic acquisition survey in 2013, to the ones measured by conventional oceanographic mooring (COM) deployed in the same area. Consistency of these datasets was investigated. Efficiency, flexibility and applicability of "static" (mooring) versus "dynamic"(USV) solution for current monitoring applications are discussed.

Data analysis started with plotting time series of current speed at selected depth levels. The quick comparison made it possible to discuss data comparability and current speed and direction patterns. The analysis was followed by establishing scatter diagrams, directional distributions and Quantiles-Quantiles plots, which in turn made it possible to conclude on overall data representation, consistency and agreement.

USV are relatively new in Oil and Gas industry. Its advantageous feature of being a lowcost, autonomous and quite flexible solution makes them extremely promising for applications in the industry. Positive results from a comprehensive statistical comparison of the datasets showed that it is possible to accurately collect the current data by means of USV, meaning that USV can be considered alternative to conventional oceanographic mooring. Some recommendations on suitable use of each of the techniques are provided following the conclutions from the study.