bluuebunny/crossref_metadata_2025 huggingface dataset:
Assistive Technologies: Addressing the Divide Between the Developed and Developing World
Authors: Chakraborty Stuti
Published: May 2020

Assistive technologies are used to enhance the day-to-day functionality of people with disabilities by improving their quality of life and by reducing the impact of disability in their lives. Various socio-economic, cultural, contextual, medical, personal, and family-related factors determine the feasibility and outcomes of using assistive technologies. While various forms of assistive technologies are being widely used for rehabilitation, recreational, or personal purposes around the world many still remain inaccessible and vastly unaffordable in countries around the world. Literature suggests that, when comparing high income countries with low and lower-middle income countries, differences among the longevity, availability, ease of users, affordability and, most importantly, the recognition of the need for an assistive technology, are common, with those measures lagging in low and lower-middle income countries. Certain targeted interventions have been suggested to provide insight into how discrepancies in promoting the use of assistive technologies between developed and developing nations can be minimised with the goal of reducing the global impacts of disability.
INVESTIGATING FACTORS AFFECTING ROAD FREIGHT OVERLOADING THROUGH THE INTEGRATED USE OF BLR AND CART: A CASE STUDY IN CHINA
Authors: Chen Yikai , Wang Kai , Zhang Yu , Luo Renjia , Yu Shujun , Shi Qin , Hu Wenting
Published: May 2020

Overloading of road freight vehicles accelerates road damage, creates unfair competition
in the transport market, and increases safety risk. There is a dearth of research on the mining of data of
highway Freight Weight (FW), and this paper therefore aims to discover factors affecting road freight overloading
based on highway FW data, with a view of developing strategies to mitigate such occurrences. A comprehensive
sampling survey of road freight transportation was conducted in Anhui Province (China). Vehicle Characteristics
(VC), Operation Mode (OM), and transportation information from a total of 3248 trucks were collected. In order
to take advantage of the strengths associated with both statistical modelling techniques and non-parametric methods,
a Classification And Regression Tree (CART) technique was integrated with Binary Logistic Regression (BLR) to reveal
the factors affecting road freight overloading. The classification efficacy test shows that the BLR–CART method
outperformed the BLR method in term of accuracy. It is also revealed that the factors affecting overloading of
freight vehicles are the Type of Transportation (ToT), Rated Load (RL), OM, FW during the investigation period,
interaction between RL and FW, and interaction among RL, FW, and Average Haul Distance (AHD). Road transport
authorities should pay greater attention to these factors in order to improve efficiency and effectiveness of
overloading inspection.
The Planetary Luminosity Problem: “Missing Planets” and the Observational Consequences of Episodic Accretion
Authors: Brittain Sean D. , Najita Joan R. , Dong Ruobing , Zhu Zhaohuan
Published: May 2020

The high occurrence rates of spiral arms and large central clearings in protoplanetary disks, if interpreted as signposts of giant planets, indicate that gas giants commonly form as companions to young stars (10 Myr) have yielded few successes. This discrepancy could be explained if most giant planets form by “cold start,” i.e., by radiating away much of their formation energy as they assemble their mass, rendering them faint enough to elude detection at later times. In that case, giant planets should be bright at early times, during their accretion phase, and yet forming planets are detected only rarely through direct imaging techniques. Here we explore the possibility that the low detection rate of accreting planets is the result of episodic accretion through a circumplanetary disk. We also explore the possibility that the companion orbiting the Herbig Ae star HD 142527 may be a giant planet undergoing such an accretion outburst.
Resolving the Soft X-Ray Ultrafast Outflow in PDS 456
Authors: Reeves J. N. , Braito V. , Chartas G. , Hamann F. , Laha S. , Nardini E.
Published: May 2020

Past X-ray observations of the nearby luminous quasar PDS 456 (at z = 0.184) have revealed a wide-angle accretion disk wind with an outflow velocity of ∼−0.25c, as observed through observations of its blueshifted iron K-shell absorption line profile. Here we present three new XMM-Newton observations of PDS 456: one in 2018 September where the quasar was bright and featureless and two in 2019 September, 22 days apart, occurring when the quasar was five times fainter and where strong blueshifted lines from the wind were present. During the second 2019 September observation, three broad (σ = 3000 km s−1) absorption lines were resolved in the high-resolution Reflection Grating Spectrometer spectrum that are identified with blueshifted O viii Lyα, Ne ix Heα, and Ne x Lyα. The outflow velocity of this soft X-ray absorber was found to be v/c = −0.258 ± 0.003, fully consistent with an iron K absorber with v/c = −0.261 ± 0.007. The ionization parameter and column density of the soft X-ray component (log ξ = 3.4, N
H = 2 × 1021 cm−2) outflow was lower by about 2 orders of magnitude when compared to the high-ionization wind at iron K (log ξ = 5, N
H = 7 × 1023 cm−2). Substantial variability was seen in the soft X-ray absorber between the 2019 observations, declining from N
H = 1023 to 1021 cm−2 over 20 days, while the iron K component was remarkably stable. We conclude that the soft X-ray wind may originate from an inhomogeneous wind streamline passing across the line of sight that, due to its lower ionization, is located further from the black hole, on parsec scales, than the innermost disk wind.
Measurement of the Rate Distribution of the Population of Repeating Fast Radio Bursts: Implications for Progenitor Models
Authors: James C. W. , Osłowski S. , Flynn C. , Kumar P. , Bannister K. , Bhandari S. , Farah W. , Kerr M. , Lorimer D. R. , Macquart J.-P. , Ng C. , Phillips C. , Price D. C. , Qiu H. , Shannon R. M. , Spiewak R.
Published: May 2020

The discovery of many repeating fast radio bursts (FRBs) by the Canadian Hydrogen Intensity Mapping Experiment, the high rate of individual bursts, and the observation of repeat bursts from a bright FRB initially detected by the Australian Square Kilometre Array Pathfinder (ASKAP) suggest a significant population of repeating FRBs. Here, we analyze the rate distribution of this population using results from follow-up observations of the Commensal Real-time ASKAP Fast Transients Survey. Characterizing a repeating FRB by its burst rate R
0 above an energy of 1038 erg, we consider a volumetric density Φ(R
0) with rate distribution

. We use maximum-likelihood methods to constrain ζ < −1.94 at 90% confidence. We discuss how this constraint can be used to limit different classes of progenitor models for repeating FRBs: it excludes FRBs with burst rate proportional to neutron star spin-down power with braking index n ≤ 14, i.e., magnetic dipole radiation (n = 3); and it excludes some scenarios for FRB emission from magnetars, and the magnetic field interactions of compact binaries.
CMB Shadows: The Effect of Interstellar Extinction on Cosmic Microwave Background Polarization and Temperature Anisotropy
Authors: Nashimoto Masashi , Hattori Makoto , Chinone Yuji
Published: May 2020

We evaluate the degradation of the accuracy of the component separation between the cosmic microwave background (CMB) and foreground components caused by neglect of absorption of the CMB’s monopole component by the galactic interstellar matter. The amplitude of the temperature anisotropy caused by the CMB shadow, due to dust components, is about 1 μK. This value is comparable to the required noise level necessary to probe non-Gaussianity studies with upcoming CMB experiments. In addition, the amplitude of the polarization caused by the CMB shadow due to dust is comparable to or larger than the rms value of the CMB B-mode polarization, imprinted by primordial gravitational waves. We show that applying a single-power-law model as the dust spectrum to observed multifrequency data introduces systematic errors, which are comparable to or larger than the required noise level for forthcoming CMB B-mode polarization experiments. Deducing the intrinsic spectrum of dust emission from the submillimeter wave band data reduces the systematic error to below the required noise level. However, this method requires dust temperature measurements with an accuracy of better than a few percent. We conclude that the CMB shadow due to dust must be considered in future CMB missions for achieving their targeted sensitivity. Our results will be important to detect the primordial CMB B-mode polarization, with the amplitude of the tensor-to-scalar ratio of r = 10−3.
Tearing Instability and Periodic Density Perturbations in the Slow Solar Wind
Authors: Réville Victor , Velli Marco , Rouillard Alexis P. , Lavraud Benoit , Tenerani Anna , Shi Chen , Strugarek Antoine
Published: May 2020

In contrast with the fast solar wind, which originates in coronal holes, the source of the slow solar wind is still debated. Often intermittent and enriched with low first ionization potential elements—akin to what is observed in closed coronal loops—the slow wind could form in bursty events nearby helmet streamers. Slow winds also exhibit density perturbations that have been shown to be periodic and could be associated with flux ropes ejected from the tip of helmet streamers, as shown recently by the WISPR white-light imager on board Parker Solar Probe (PSP). In this work, we propose that the main mechanism controlling the release of flux ropes is a flow-modified tearing mode at the heliospheric current sheet (HCS). We use magnetohydrodynamic simulations of the solar wind and corona to reproduce realistic configurations and outflows surrounding the HCS. We find that this process is able to explain long (∼10–20 hr) and short (∼1–2 hr) timescales of density structures observed in the slow solar wind. This study also sheds new light on the structure, topology, and composition of the slow solar wind, and could be, in the near future, compared with white light and in situ PSP observations.
Dynamics of ionic flows via Poisson-Nernst-Planck systems with local hard-sphere potentials: Competition between cations
Authors: W. Bates Peter ,   Department of Mathematics, Michigan State University, East Lansing, MI 48824, USA, Chen Jianing , Zhang Mingji ,   Department of Mathematics, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA
Published: May 2020

We study a quasi-one-dimensional steady-state Poisson-Nernst-Planck type model for ionic flows through a membrane channel with three ion species, two positively charged with the same valence and one negatively charged. Bikerman's local hard-sphere potential is included in the model to account for ion sizes. The problem is treated as a boundary value problem of a singularly perturbed differential system. Under the framework of a geometric singular perturbation theory, together with specific structures of this concrete model, the existence and uniqueness of solutions to the boundary value problem for small ion sizes is established. Furthermore, treating the ion sizes as small parameters, we derive an approximation of individual fluxes, from which one can further study the qualitative properties of ionic flows and extract concrete information directly related to biological measurements. Of particular interest is the competition between two cations due to the nonlinear interplay between finite ion sizes, diffusion coefficients and boundary conditions, which is closely related to selectivity phenomena of open ion channels with given protein structures. Furthermore, we are able to characterize the distinct effects of the nonlinear interplays between these physical parameters. Numerical simulations are performed to identify some critical potentials which play critical roles in examining properties of ionic flows in our analysis.
Diffusion of Innovations Among Mexico
Authors: Valle-Cruz David , Sandoval-Almazan Rodrigo
Published: May 2020

The purpose of this chapter is to describe the technological adoption by state governments, based on a longitudinal study of technology in Mexico for which the authors analyzed data from all the local governments from 2010 to 2018. With this data, they proposed a ranking to classify adoption technology, using the diffusion of the innovation theory. They included in the analysis other variables such as the percentage of households with a computer, internet, and other communication technology equipment. The results show that Mexico City is the innovator; Baja California, Sonora, and Nuevo Leon are early adopters, while Oaxaca, Chiapas, and Guerrero are laggards. The most influential variable in the adoption of information technologies is illiteracy, and there is an inverse relationship between technology and illiteracy. Future research will open several paths to understand different adoption behaviors between specific technologies in each state, such as big data, artificial intelligence, internet of things, and smart cities.
Mudamos
Authors: Konopacki Marco , Albu Debora , Cerqueira Diego , Tavares Thayane Guimarães
Published: May 2020

Brazil's Constitution established a few means of direct democracy including the possibility of any citizen to propose a draft bill at a legislative house given the support of a minimum of citizens expressed by their signature. Until today, citizens' initiative bills' signatures are paper based, which is not only costly, but also poses transparency and safety issues. Considering these challenges, the Institute for Technology and Society developed a mobile app called “Mudamos” (“We Change”) to prove it is possible to sign such bills electronically. However, despite its potential for changing citizen participation, technology by itself does not promote political and cultural changes. Thus, Mudamos became an integrated engagement framework, including the free application and also an offline legal draft-a-thon and advocacy for institutional change. In this chapter, the authors present this framework, connecting cutting-edge digital innovation on electronic signatures with social innovative methodologies, highlighting the importance of adopting a holistic approach to institutional change.
Impact of Dynamic Community Partnerships on STEM Education of Students of Color
Authors: Hargrave Constance P. , Rollins Anita D.
Published: May 2020

The Science Bound Model is an effective school-community partnership preparing precollege students of color to pursue college degrees and careers in STEM fields via a four-way partnership among school administrators and teachers, STEM corporations, students and families of color, and a land-grant university. For nearly 30 years, this partnership has been effective in bringing together the skill sets, resources, expertise, and opportunities necessary to support students' preparation for college and pursuit of technical degrees. The four-way partnership annually provides more than 400 students an average of 100 hours of out-of-school STEM learning experiences and mentorship by 50 teachers and 150 STEM professionals. Used in a rural community, a small city, and an urban community, the model establishes and maintains dynamic partnerships within and across partner groups. Five key factors that guide the four-way Science Bound partnership and a case example of how the model works are presented.
Make Use of the Difference of Failure and Exit to Improve the Operation Efficiency
Authors: Chen Yangyang , Dong Weiwei , Zhang Dixuan , Jin Mingwei
Published: May 2020

As business failure is a high probability event that influences the operation efficiency of the entrepreneurial ecosystem, it is necessary to know how to manage business failure experience to promote serial entrepreneurship and improve circulation in the ecosystem. While most scholars agree that it is different between failure and exit, DeTienne suggests that exit could be a way to avoid failure and protect the passion and financial condition of entrepreneurs. Therefore, this chapter analyzes the difference of failure and exit and conducts a model to help entrepreneurs decide whether to exit and how to choose a better way to exit entrepreneurship. In the meantime, this chapter analyzes why entrepreneurial exit can improve the operation efficiency of entrepreneurial ecosystem, and also it would give some ideas about how to bound from failure and benefit from failure to do better next time. After reading this chapter, entrepreneurs have the idea that failure is controllable and exit may be a restart to do business more successfully.
The Effects of Opportunity Alertness and Competitive Tension on Organizational Change Strategies
Authors: Zhang Ao , Cui Yuehui , Li Na , Li Sinan
Published: May 2020

Competitive dynamics theory emphasizes that entrepreneurs must be alert to the opportunities, perceiving the tension of competition between firms to implement organizational change strategy. However, empirical studies on the above aspects are very scarce. Based on the literature review, this chapter proposes a research model about opportunity alertness, competitive tension, and organizational change and uses 183 valid questionnaires from the northeast of China to test this model. The empirical results show that opportunity alertness and competitive tension have a significant impact on organizational change strategies respectively, and competitive tension moderates the relationship between opportunity alertness and organizational change strategies. The results show that facing fierce competition, entrepreneurs, who can exert the organizational strategies, should not only improve opportunity alertness, but also strengthen their understanding of the competitive situation among enterprises and the value of competitive tension. Finally, theoretical and practical implications are addressed.
Innovation or Imitation in New Ventures?
Authors: Chen Biao , Sun Yu , Ding Yuchao , Liu Yang
Published: May 2020

The authors examine the effects of innovation and imitation strategies on new venture competitive advantage during both technological and market turbulence. In turn, they test the moderating effects of dysfunctional competition in these settings. Using data collected from 153 new ventures in China, they find that innovation and imitation strategies have positive effects on new venture competitive advantage. Furthermore, they find that dysfunctional competition increases the positive relationship between imitation strategies and new venture competitive advantage in these settings. However, the negative moderating effects of dysfunctional competition are partly verified. And they find that the consumption attitudes of the younger generation in China may explain why the theory is inconsistent with the empirical results. The theoretical and practical implications of the findings are discussed.
Performance Comparison between Polyurethane Foam and Cement Grouting Slab Replacement for Soft Ground Improvement at Shallow Depth Using Finite Element Model
Authors: Che Lat Diana , Jais Ismacahyadi Bagus Mohamed , Ali Nazri , Baharom Bahardin , Salleh Saleha Md , Omar Aslina
Published: May 2020

Two methods of ground improvement have been proposed to overcome excessive and differential settlement problem of soft ground foundation for infrastructure such as road, highway and parking space namely polyurethane (PU) foam and cement grouting slab. It has been executed by excavating and replacing the soft soil at shallow depth with the proposed ground improvement methods. The ground improvement methods able to minimise the excessive and differential settlement as the shallow depth of soft soil is removed and replaced by the stiff materials, thus the load can be distributed evenly to the underlying soil. The comparison of performance between both methods are evaluated in this study by carried out finite element analysis for soft ground problem namely PLAXIS. The results show that the settlement can be reduced significantly to the tolerable amount by applying PU foam instead of cement grouting slab as the increase in thickness of cement grouting slab cause the increase in settlement. On the other hand, the increase in PU foam thickness has not contributed to further settlement as the PU foam is lightweight, however, the soil may experience upward displacement due to insufficient overburden load to counter uplift.
Manganese Sinter Production with Wood Biomass Application
Authors: Kieush Lina , Boyko Maksym , Koveria Andrii , Yaholnyk Maksym , Poliakova Natalia
Published: May 2020

A large amount of finely dispersed manganese ore left after benefication operations or blown out from the furnaces is unsuitable for direct use in electric furnaces and blast furnaces, therefore it is necessary to granulate it in order to have the efficient use of its fine ore particles in metallurgy. To make our research more of practical use, we found it is reasonable not only work over manganese fines sintering but also to attempt mitigating the negative effect on the environment produced by the further sintering and apply the biofuel within the total fuel mass. Under laboratory conditions, the studies have been carried out with the objective to obtain manganese sinter, in which wood biomass is applied, namely initial and pre-pyrolyzed, at temperatures of 673, 873, 1073 and 1273 K. The amount of biofuel in the sinter blend was 25 wt.%. It has been established that the biomass use causes the decrease in the specific capacity of the sintering plant. However, for the efficient manganese ores sintering process, the biofuel of high pyrolysis temperature of 1273 K is required. To achieve the specific capacity and the yield to be as high as those when coke breeze is only used, the amount of the biofuel for manganese ore sintering should be less than 25 wt.% of the solid fuel. Additionally, it has been revealed that the further increase in the biofuel ratio in the total fuel amount is possible on condition that its reactivity is decreased, or larger particles of the biofuel are used.
Improvement of Stamping by Rolling Processes of Pipe and Cylindrical Blades on Experimental Research
Authors: Shtuts Andrii , Kolisnyk Mykola , Vydmysh Andrii , Voznyak Oleksandr , Baraban Serhii , Kulakov Pavlo
Published: May 2020

During the experimental study, a pronounced beating and sealing of the side surface of the tubular, cylindrical blanks was recorded. It is established that cracks appear and develop in the central part of the lateral surface, i.e., it are destroyed. This fact confirms the claim that the destruction of tubular, cylindrical blanks of some materials begins on the side surface. It is established that the bases of analytical dependencies between the components of deformations describe the obtained results of the experimental study of SR tubular, cylindrical blanks within the error of the experimental data, which made it possible to construct a number of mathematical models for the purpose of further study of the SDS and the method of their determination.
Conditions of Suitability of Coal Seams for Underground Coal Gasification
Authors: Pivnyak Gennadiy , Falshtynskyi Volodymyr , Dychkovskyi Roman , Saik Pavlo , Lozynskyi Vasyl , Cabana Edgar , Koshka Oleksandr
Published: May 2020

Results of evaluating the suitability of certain sections of Western Donbas coal seams, based predominately on properties of coal material, for their further experimental development by means of underground gasification method are represented. Criteria to evaluate both expediency of underground gasification and specific conditions of that process are substantiated basing upon the methodology developed at the National Mining University (Dnipro, Ukraine) together with representatives from National University of Saint Augustine (Arequipa, Peru). The methodology has been industrially approved with the confirmation of its efficiency while developing technical documentation for underground gasification projects: “Project of experimental section of Pidzemgaz station of Pavlogradvuhillia association”, “Feasibility study of the expediency of the construction of Pidzemgaz station” FS 3858-PZ”, Synelnykovo deposit; “Project on experimental underground gas generator”, Monastyryshche deposit, FS of experimental module of UCG station of Solenovske coal-mining area, Donbas. Also, they contain the researches, which were conducted within the project GP – 489, financed by Ministry of Education and Science of Ukraine.
Results of Research into the Content of Rare Earth Materials in Man-Made Phosphogypsum Deposits
Authors: Malanchuk Zynovii , Moshynskyi Viktor , Malanchuk Yevhenii , Korniienko Valerii , Koziar Mykola
Published: May 2020

According to the materials of the Rivne exploration expedition in Rivne region more than 15.3 million tons of phosphogypsum materials in rock dumps are stored. For further use and recycling of waste, it is necessary to evaluate the content of rare earth elements in phosphogypsum, which are of considerable economic value. The possible recycling of this production will increase the level of environmental safety through the use of more reliable engineering systems for the environmentally safe storage of phosphogypsum rock dumps. The migration of phosphorus, fluorine, sulfur, copper, chromium, manganese, zinc, lead, cadmium, iron, nickel and cobalt along the profile of the artificial ground cross-section was investigated experimentally. The results of studies confirmed the increased accumulation of metal in the phosphogypsum rock dumps. Analyzing the content of nickel, lead, sulfur, manganese, cobalt and zinc in experimental samples, we observe the distribution pattern, the content of which in samples is 2 – 3 times higher than the content of trace elements of the above-mentioned groundwater deposits. The results of the sorption and desorption of nickel, lead, sulfur, manganese, cobalt and zinc indicate that the rock is not an obstacle to the migration of trace elements and its aggregates in the rock and is observed only in the zone of full water saturation due to the filling of pore space. The conducted researches established the presence of phosphogypsum in man-made wastes of nickel, lead, cobalt, zinc, iron with a percentage content up to 1% per ton of rock waste.
Techniques and Technology of Waste Disposal of Lignite Briquettes
Authors: Matsyuk Iryna , Krivoschokov Vyacheslav , Kushniruk Natalia , Skliar Liudmyla
Published: May 2020

Development of a waste-free technology for lignite slurry upgrading at briquetting factories, which provides for getting cleared water for closed-loop water supply and transportable product for burning or briquetting with sustainable equipment application. Detection and study of peculiarities of lignite coal and slurry of briquetting factories, as well as research on slurry surface properties for substantiating a separation ratio. Determination of the separation ratio of lignite coal slurry taking into account its surface properties to estimate technological efficiency of reagentless flotation separation. Research on kinetics of settling and influence of different flocculants on efficiency of the slurry thickening process for sludge collection and getting circulating water. Development of waste-free technology for lignite slurry upgrading with the purpose of slurry recycling based on the substantiation of rational technological parameters and appropriate equipment. Regularities of the process of reagentless flotation separation of lignite coal slurry, kinetics of settling are defined, which is the basis of technological solutions on separate briquetting waste treatment. A waste-free technology for upgrading lignite slurry and cinders with closed-cycle of water supply and transportable final product for burning and briquetting with moisture content of 26% ... 28 % is developed. Floating and sinking fractions of lignite slurry are studied and necessity of separate treatment of these fractions is substantiated. Kinetic regularities of deposition of heat-treated lignite particles are determined; rational modes which provide for efficient deposition of particles of the sinking fraction with minimum flow of a flocculant are defined. A phenomenon of hydrophobic behaviour of mineral particle surface after heat treating and briquetting of lignite coal is revealed, which is taken as a separation ratio; this allowed substantiating the waste-free technology for lignite slurry upgrading through reagentless flotation separation. The practical value of the results obtained involves development of a waste treatment technology at a briquetting factory (slurries and cinders) and its conversion into closed-loop water supply, which will allow obtaining 23 t/year of transportable final product additionally as well as decreasing consumption of pure water considerably and eliminating environment pollution.
Using ProCAST to Study the Effects of SEED Process Parameters on the Radial Temperature Distribution in Semi-Solid Slugs
Authors: Luo Min , Li Da Quan , Qu Wen Ying , Midson Stephen P. , Zhu Qiang , Fan Jian Zhong
Published: May 2020

The SEED (Swirled Enthalpy Equilibrium Device) process was used to produce semi-solid slurries. One of the factors that controls whether or not a slug can be used to produce high quality castings is the solid fraction distribution within the slug, and the solid fraction distribution is strongly dependent upon the temperature distribution. In this study, a model has been developed using ProCAST to investigate the relationship between process parameters and the temperature distribution within slugs. The parameters examined included the heat transfer coefficient between the crucible and slug, the heat transfer coefficient between the crucible and air, the slug diameter, and the initial melt temperature (pouring temperature). It was found that the most important parameters controlling the temperature distribution within slugs were the crucible size and the heat transfer coefficient between crucible and air. Adjustment of other parameters had little influence on the temperature distribution. Processing parameters will be discussed in order to allow the SEED process to be used for the production of large diameter slugs (>100 mm), and for narrow freezing range (0.3<fs<0.5, fs is fraction solid) alloys such as 6063.
First-Principles Study of Structural, Mechanical, and Thermodynamic Properties of Refractory Metals (Rh, Ir, W, Ta, Nb, Mo, Re, and Os)
Authors: Sun Ying Jie , Xiong Kai , Li Zong Bo , Zhang Shun Meng , Mao Yong
Published: May 2020

The structural, mechanical, and thermodynamic properties of refractory metals Rh, Ir, W, Ta, Nb, Mo, Re, and Os have been systematically investigated by first-principles calculations based on density functional theory. Comparative studies reveal that Young's modulus (E= 636.42 GPa), shear modulus (G= 256.81 GPa), bulk modulus (B= 406.55 GPa), and microhardness (H= 44.69 GPa) of hexagonal Os are the highest, which reveals Os has the best overall mechanical properties. The body-centered cubic Nb has the smallest Young's modulus (E= 94.76 GPa), shear modulus (G= 33.62 GPa), bulk modulus (B= 174.50 GPa), and hardness (H= 2.04 GPa). Based on the ratio of bulk to shear modulus, it is judged that Rh, Ir, and Os are brittle materials (B/G< 1.75), and Nb, Ta, Mo, W, and Re exhibit ductile (B/G> 1.75). The elastic anisotropy has also been discussed by plotting both the 3D contours and the 2D planar projections of Young's modulus. For the face-centered cubic metals Rh and Ir and hexagonal close-packed metals Re and Os, the 3D contours of the Young's modulus are very similar, whereas body-centered cubic metals Ta, W, Nb, and Mo exhibit significant difference in elastic anisotropy. The thermodynamic calculations show that Debye temperature and minimum thermal conductivity decreases along Rh, Os, Mo, Ir, Re, W, Ta, Nb sequence. Furthermore, the results can be used as a general guidance for the design and development of high temperature refractory alloy system.
Thermodynamic Study of Equilibrium Phase in Quasicrystalline Strengthened Magnesium Alloys
Authors: Wang Jin San
Published: May 2020

In order to optimize the composition and microstructure of quasicrystalline strengthened Mg-based alloy, the equilibrium phases of Mg-Zn-Y-Zr alloys with three components were studied by using thermodynamic calculation. The calculated results showed that the equilibrium phases of the three alloys were mainly Liquid phase, α-Mg matrix phase, α-Zr dispersed phase, quasicrystalline strengthening I phase, W phase and Z phase. It was observed that the specific content and temperature range of these phases were different. Among them, alloy 3 had the highest quasicrystalline content. And alloys 1 and 2 contained dispersed phase α-Zr which can lead to grain refinement.
Corrosion Behavior of Cobalt Alloy Coating in NaCl Solution
Authors: Hou Yue , Chen Hai Yan , Fan Li , Xu Yu Rong , Cheng Qian , Dong Li Hua
Published: May 2020

Two kinds of Co-based coatings were obtained through the laser cladding (LC) and plasma transfer arc (PTA) process. The phase composition and microstructure of the coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The corrosion behaviour of the different Co-based alloy coatings in 3.5wt% NaCl solution were compared by means of open-circuit potential (OCP), polarization curve and electrochemical impedance spectroscopy (EIS). XRD and SEM measurements demonstrated that the microstructures of the two different Co-based coatings were composed of primary solid solution γ-Co and eutectic structure Cr23C6, whereas, fish-bone typed (CoCrW)6C was also detected in the coating produced by PTA. The polarization curves and EIS results showed that in 3.5wt% NaCl solution, the passivation zones of the two coatings occurred obviously, the self-corrosion potential of the two coatings shifted to the right, and the self-corrosion current density was much smaller than that of the substrate. In addition, the Co-based coating made by LC showed lower corrosion current density and larger diameter of a capacitive arc than that of Co-based coating produced by PTA, indicating the LC coating had the best corrosion resistance in the three samples.
Corrosion Resistance of Zinc Phosphate Conversion Coatings on AZ91D Surface
Authors: Yue Jian Hang , Lou Gui , Zhou Guo Rong , Leng Jin Feng , Feng Yun , Teng Xin Ying
Published: May 2020

Magnesium alloys have been widely applied in many fields, because of their high strength-to-weight ratio. However, magnesium alloys have high chemical activity and are easily corroded. The poor corrosion resistance of magnesium alloys greatly limits its further application. In this paper, the zinc phosphate conversion coatings were prepared on the surface of AZ91D magnesium alloys. Nano-zinc oxide was the source of zinc and the zinc phosphate conversion coatings were prepared by the given process: 1.25 g/L NaNO3, 3 g/L C6H8O7 H2O, 2.5 g/L NaF, 5.5 g/L ZnO, 12.5 mL/L H3PO4, reaction temperature 50°C, reaction for 30 minutes. The full immersion uniform corrosion test was conducted for the fabricated coatings. The morphology and composition of corrosion in different corrosion stages were characterized by XRD, SEM and other microscopies. The results showed that: (1) the corrosion process of the conversion coatings could be divided into three stages: the dissolution of the conversion coatings, the corrosion of the matrix and the deposition of insoluble matter; (2) XRD analysis and other methods found that the pine-needle magnesium oxychloride compounds were formed in the process of immersion firstly, and it was dissolved into Mg(OH)2 over time; (3) With the extension of immersion time, Mg(OH)2 increased continuously and played a major role in corrosion prevention. The deposited Mg(OH)2 was divided into two layers. In the initial deposition stage, it was mainly evenly dispersed on the surface of the alloy to form a tightly arranged inner layer. Afterwards, the crystals of Mg(OH)2 agglomerated and formed a sphere, becoming the outer layers.
Failure Analysis on Friction and Wear of Tool Joints
Authors: Liu Yong Gang , Zhang Xian Cai , Wang Xian Lin , Feng Chun , Li Rui Zhe
Published: May 2020

Due to complex working conditions, such as deep wells, ultra-deep wells and extended reached horizontal wells, etc, the failures of friction and wear on tool joints often occur, which become one of the main failure models of tool joints. In this paper, some failure cases of the tool joint, including longitudinal crack, axial wash-out, necking deformation, and fracture were analyzed, and their macro profiles, micro characteristics and microstructure transformation were investigated. The results showed that since the material performances of tool joints met the requirements of product standard, the cracks, deformation and even strength degradation of tool joints can be caused by the heat generated by friction and wear between tool joint and the well wall, meanwhile, the heat didn't drain away in time. As a result, effective method to reduce friction heat generation, including improving quality of wellbore trajectory, reducing contact pressure, enhancing the stability of wellbore and so on, should be suggested in the field
Threaded Failure Analysis for Three-Dimensional Horizontal Wells Casing
Authors: Nan Rong Li , Sun Xin , Shu Bo Zhao , Wang Hang , Yang Shang Yu , Lu Cai Hong , Han Li Hong
Published: May 2020

In view of the external thread fracture during casing running in a well in Xinjiang Oilfield, the failure reasons of thread fracture were analyzed by combining the theory with experiment, and the casing safe service window with harsh working conditions was given. The operation of the failed casing and determined the actual working conditions of the casing threaded joints during the running process were investigated in this paper. According to the theoretical method, the boundary conditions and load conditions of the fracture casing joint in service were determined. With the aid of full-scale physical simulation test device, as well as the above boundary conditions and load conditions, the same batch casing tensile bearing characteristics were determined. Through nondestructive testing, the metallographic observation, scanning electron microscopy, spectral analysis and up-and-down test, the main controlling factors of casing thread fracture were determined. By the finite element analysis, the casing threads service state under axial tension and bending loads was established, the safety performance of threads under ideal working conditions was studied, and the fatigue mechanism of threads was revealed. Combined with the analysis results, the corresponding relationship between the casing tensile bearing characteristics and safety factor was given, which provides technical support for the safe service selection of casing body and thread under harsh conditions, saving cost and shortening the well construction period.
Investigations on the Hardness Distribution and Microstructure of Friction-Stir-Welded 6082 Aluminum Alloy
Authors: Gao Kun Yuan , Li Bo , Ding Yu Sheng , Huang Hui , Wen Sheng Ping , Wu Xiao Lan , Nie Zuo Ren
Published: May 2020

The hardness and microstructure of friction stir welded (FSW) 6082 aluminum alloy joint were investigated by Vickers microhardness test, optical microscopy (OM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The hardness distribution is in a W shape, and from the base metal to the heat affected zone (HAZ) the hardness decreases from 103 HV to 72 HV, then gradually increases to 84 HV at the nugget zone (NZ). The grains of base metal (BM) are elongated and composed of a great quantity of low-angle grain boundaries. The nugget zon was of quite fine recrystallized grains. For the thermomechanical affected zone (TMAZ), the grain size is a little smaller than that of base metal and some low-angle grain boundaries remain. In the heat affected zone, the grain size was similar to that of the base metal. The β'' phase (Mg5Si6) and Al-Mn-Si particles are dispersed in the base metal. . In the heat affected zone, β'' phase transforms to β' phase (Mg9Si5). The hardness distribution in a W-shape was discussed on the basis of grain size, density of low-angle grain boundary and secondary phases.
Leakage Failure Analysis of 80SS Tubing in Gas Field
Authors: Lu Cai Hong , Han Li Hong , Feng Chun , Xu Xin , Yang Shang Yu , Zhu Li Juan , Wang Xin Hu
Published: May 2020

During acidizing process in a gas field, leakage of 80SS anti-sulfur tubing occurred.The main reasons for failure of the tubing have been investigated based on analysis techniques of chemical composition analysis,Optical Microscopy (OM), Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) , X-ray Diffraction (XRD) and mechanical test. The results show that composition and mechanical properties of the tubing were all in accordance with the corresponding requirements of API Spec 5CT standards. Furthermore,leakage of tubing from inner wall was caused by combined impacts of acid corrosion, H2S corrosion, low PH value, high temperature and a certain pressure. Meanwhile, Low concentration of corrosion inhibitor was also one of the factors of corrosion perforation.
Analysis of Weld Cracking in a Low-Pressure Steam Pipe
Authors: Zhuang Fa Kun , Shi Jin , Liu Wen , Cao Luo Wei
Published: May 2020

A weld cracking of the outlet pipe occurred during the operation of a low-pressure steam super-heater in the purification device. It was found that many cracks were perpendicular to the weld, which affected the equipment safe operation. In order to investigate the failure cause, the samples containing weld and cracks in the outlet pipe were cut. The experiments, including chemical composition analysis, mechanical properties testing, scanning electron microscope observation, energy spectrum analysis and metallographic analysis, were performed. The results showed that the corrosion products had loose structure, mainly consisting of iron, sodium and phosphorus oxides. The metallographic results of the fracture section indicated that there existed a mixed cracks of trans-granular and inter-granular mode, along with stepped crack characteristics. Therefore, it is believed that the weld transverse cracking in the outlet pipe may be resulted by both of alkali stress corrosion cracking and the hydrogen induced cracking. According to the failure cause analysis, the corresponding suggestions are given, such as welding, operation process and inspection.
Casing Bearing Capacity with Shear Load for Shale Gas Wells
Authors: Yang Shang Yu , Wang Jian Jun , Han Jia Wen , Wang Hang , Han Li Hong
Published: May 2020

Casing radial deformation during complex fracturing process was seriously for shale gas wells in Sichuan district of China, and the average casing deformation rate in the region is of 50%. The bridge plug, perforating gun and other tools cannot successfully pass with deformed casing. Aiming at the 3-D logging morphology for deformed casing of shale gas wells, the failure modes and mechanisms were analyzed by using elasticity and theoretical mechanics. Many factors were evaluated and integrated to achieve quantitative evaluation model including geology feature, wellbore trajectory, cement property, casing material and hydrofracture process. With the aid of the self-developed unconventional oil and gas well casing simulation test equipment, the casing bearing capacity with shear load were carried out, established the relationship between shear load value and radial deformation, and further constructed the casing failure criterion with shear force. This work can provide technical support for casing design and selection in shale gas wells.
Challenge and Review of Hydrogen Sulfide Corrosion Resistance Steels for Oil Country Tubular Goods
Authors: Song Ya Cong , Feng Chun , Zhu Li Juan , Cao Ya Qiong , Ge Hong Jiang
Published: May 2020

Corrosion of oil country tubular goods not only causes huge economic loss, but also brings serious environmental pollution. Stress corrosion cracking of oil country tubular goods in the sulfur-containing environment is the principal corrosion failure form in the exploitation of oil and gas process. Therefore, extensive investigations on hydrogen sulfide corrosion of steels for oil country tubular goods have been carried out. The aim of this work is to review the research progress on the hydrogen sulfide corrosion performance of steels for oil country tubular goods. The influence of alloy elements, defects, environmental factors and mechanical factors on hydrogen sulfide corrosion resistance of steels for oil country tubular goods were discussed. The future work in hydrogen sulfide corrosion performance of oil country tubular good and new sulfur-resistant steels for oil country tubular goods development were prospected.
Test Analysis of Corrosion Perforation in a Crude Oil Gathering Pipeline
Authors: Tong Ke , Fan Zhi Hai , Qu Ting Ting , Bai Xiao Liang
Published: May 2020

The reason for perforation leakage of gathering pipeline in an oilfield was investigated by size measurement, mechanical properties, metallographic structure, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrum (EDS). The results showed that the failure form of the spirally submerged arc welded pipe (SAW) was the corrosion perforation caused by local corrosion. The main cause of corrosion perforation was due to the existence of chlorine ion, H2O and O2 in the pipeline transportation medium. A large cathode and small anode electrode corrosion formed in the pipe marking area and the base metal, which eventually led to the perforation of the steel pipe.
Analysis of Corrosion Causes in the Export of a Compressor in the Pipeline of Western China
Authors: Qu Ting Ting , Cong Shen , Tong Ke , Song En Peng , Ren Ji Cheng
Published: May 2020

The field investigation, macro-inspection, thickness measurement, chemical components examination, mechanical characters tests, microstructure, SEM, XRD analysis and soil composition test were carried out, in order to analysis the external corrosion of the L415 pipe line near the compressor outlet. The results showed that the frequent vibration of the compressor outlet could lead to the damage and failure of the anticorrosive layer, which made the steel pipe loses protection and further exposed to the external environment to cause oxygen corrosion. The content of Cl- in soil was higher in the western China, which accelerated the corrosion of pipe. The corrosion acceleration mainly depended on the pipeline temperature and the secondary external anticorrosive layer.
Leakage Failure Analysis of the ERW Steel Pipeline
Authors: Cong Shen , Tong Ke , Li Dong Feng , Chen Zhi Xin , Cai Ke
Published: May 2020

This paper provides a thorough investigation on the leakage reason of the ERW steel pipeline in an oil field. Through appearance inspection, physicochemical inspection, metallographic inspection and scanning electron microscope (SEM), it was found that the main reason of corrosions was caused by residual liquid at the bottom of the pipeline and O2 and CO2 in the air pressure test. The corrosion medium was large volume of O2 and CO2 forming continuously saturated corrosive aqueous solution in small volume of residual liquid, and the corrosion type was the under-deposit corrosion. It is recommended to conduct hot air purging on the pipelined before pressure test for building pipelines in the future, and if the pipeline is not put into use in time, it is recommended to use nitrogen to maintain pressure.