bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Behavior Change Due to Rock Deformation in Shale Reservoirs: A Compositional Modeling Approach
Authors: Uzun Ilkay , Eker Erdinc , Kazemi Hossein , Rutledge Jeffrey M.
Published: October 2017

Pore diameters for shale reservoirs are on the order of few nanometers which become even smaller during production because of rock deformation. This dynamic interaction between pore fluid pressure and rock stress affects the phase behavior in unconventional reservoirs. In this paper, a new mathematical formulation of fully-coupled geomechanics and compositional dual-porosity model was used to determine the impact of rock deformation and confinement on the nanopore fluids as well as their effect on the production performance of Eagle Ford formation. The formulation presented was derived from our multiphase poroelasticity model which was an extension to the single-phase, single-porosity Biot's linear poroelasticity theory allowing to characterize the rock deformation and pore diameter reduction using the bulk modulus of the matrix-fracture system.

Changes in reservoir pore pressure and rock deformation that cause the pore diameter to reduce increases the capillary pressure in the pores which affects the bubble-point pressure suppression and significant shift in the phase envelope, favoring longer period of single-phase production. It was observed that not taking rock deformation into account will lead to over estimation of production, whereas ignoring the effect of pore confinement would underestimate the production forecast. In an example field study based on Eagle Ford reservoir, an increase of around eight percent in cumulative oil production was achieved when the effect of rock deformation and confinement was included in the compositional model compared to the case where only the rock deformation was included. On the other hand, if only pore confinement effect was included in the simulation runs, four percent of increase was achieved.
Real-Time Bit Wear Prediction Using Adaptive Data Analytics
Authors: Lakhanpal Vikrant , Samuel Robello
Published: October 2017

As the oil and gas well geometry becomes more complex, identifying the locations of critical bit wear becomes increasingly difficult. The analytical models currently used in the drilling industry are incapable of completely realizing the downhole dynamics and thus, are incapable of bit wear prediction. Current models either overestimate or are too conservative, while some models necessitate too many parameters, constants, and coefficients. There is no acceptable universal mathematical model that describes bit wear; thus, this paper proposes a method that does not use a model at all. This study focuses on harnessing the impact of real-time downhole dynamics on drilling parameters to predict bit wear using adaptive data analysis techniques.

This paper identifies a parameter that demonstrates the impact of downhole dynamics with a high degree of functionality. Though other parameters can also be used, real-time rate of penetration (ROP) is the basic parameter always available. Depending on the parameters available, different parameters can be combined and entered into the algorithm. For example, ROP and gamma ray data can be convoluted in an appropriate manner to predict bit wear and whether the bit wear is caused by formation change.

This work proposes an adaptive data analytics algorithm. This algorithm decomposes the continuously entered incremental ROP data that come in the form of wellsite information transfer standard markup language (WITSML), at each depth into its intrinsic mode functions (IMFs) using empirical mode decomposition (EMD). The trend of the final IMF at each depth is continuously monitored to predict bit wear. For the practical purpose of making the entire process fast and straightforward, the energy of the final IMF (IMF energy) is also continuously computed. This algorithm can be implemented using incremental depth analysis and incremental depth interval analysis. The depth interval analysis can be used during the preplanning stage of the drilling operations to identify the intervals in which the field personnel should be more cautious. The incremental depth analysis can be used during drilling operations.

The proposed workflow was tested on historical wells, and the results were compared with analytical models [Rashidi et al. 2010 (more conservative) and Liu et al. 2014] used in the industry. The results were also verified using the daily drilling reports (DDRs) from the field to confirm the algorithm predictions. The predicted results were synchronous. A warning was generated well before the actual failure caused by bit wear occurred. There were no false results recorded.
Challenges and Lessons from Implementing a Real-Time Drilling Advisory System
Authors: Spivey Benjamin J. , Payette Gregory S. , Wang Lei , Bailey Jeffrey R. , Sanderson Derek , Lai Stephen W. , Charkhand Behtash , Eddy Aaron
Published: October 2017

This paper discusses the technical challenges related to implementing a rig-site, real-time drilling advisory system and current solutions to these challenges. The system uses a data-driven response surface model based on physics-based calculations to optimize rate of penetration (ROP) while minimizing drilling vibration dysfunction with regards to lateral (whirl) and torsional (stick-slip) vibrational modes. Minimizing these vibrations is important to mitigate bit damage that can lead to reduced ROP and bit trips. By incorporating drilling vibrations with ROP optimization, the system helps operations identify drilling limiters and support the bit and BHA redesign process to improve drilling on subsequent wells.

Throughout development, the team has identified and managed challenges related to estimating drilling performance from data, making optimization trade-offs, guiding the driller to characterize performance, and handling formation variability. Surface sensors provide real-time drilling data measurements to an electronic drilling recorder which converts data into Wellsite Information Transfer Specification (WITS) records. These measurements often require filtering, averaging, and transformation with physical models to estimate drilling performance with suitable accuracy for driller guidance. Improving drilling performance involves a tradeoff between optimizing ROP and avoiding drilling dysfunction. The system currently uses a drilling efficiency term, such as mechanical specific energy (MSE),to incorporate whirl and other energy losses, and it computes an absolute estimate of bit stick-slip with the torsional severity estimate (TSE). This drilling optimization tradeoff requires comparing relative measures of performance, such as ROP and MSE, with an absolute measure of performance as TSE. A drill-off test involving changing the drilling parameters and observing performance is central to create performance trends versus the drilling parameters. A method for guiding the driller to conduct a drill-off test should accommodate driller human factors, capture sufficient data to provide an accurate trend, and complete the drill-off test in a sufficient amount of time to use the test results to optimize the current formation. Data-driven trends should be relevant for the formation the bit is currently drilling. Formation changes may occur with varying magnitude and frequency, and the system addresses aspects of formation change.

This paper discusses these drilling challenges using field and simulation data and provides results from recent North America land operations targeting unconventional oil and gasdevelopments. Field feedback has been incorporated for continuous improvement to algorithms. This deployment demonstrates the benefit of using the rig-site system for real-time drilling set point decisions and post-well drillstring redesign decisions.
Subsea Spares Analysis: Using Reliability, Production Impact and Cost Data to Deliver Optimum Value
Authors: Bonini C. , Clarke Y.
Published: October 2017

Subsea spares are expensive to procure and store; however, the potential consequences of having spares unavailable when required can be even worse. The main objective of this study is to create a tool to assist with the evaluation of the optimal number of spares for each subsea equipment, considering item cost, maintenance requirements, lead time and production impact.

The first step of the spares analysis process is to understand how reliable/unreliable the equipment is. This is carried out by following FMEA (failure modes and effects analysis), i.e. identifying failure modes, failure frequencies, failure consequences and repair scenarios (such as mean time to repair) based on asset specific performance data and industry historical data. The maximum number of spares depends on the cost associated with maintaining that item in storage and performing preventive maintenance. The minimum number of spares is determined by probabilistic analysis, based on Poisson distribution functions.

A Spares Analysis Tool was developed: it uses Poisson probability distribution and a cost-benefit analysis to calculate the ideal number of spares. This Excel based tool allows the subsea team working on the Frade project to be able to quickly evaluate the proper stock level of key components and ensure continuity of operations in a reliable and cost efficient manner. It also allows adjustments to be made according to changes in the oil price (which affects the criticality of the spare in terms of total Lost Production Opportunity, or LPO), and in case changes in failure rate are observed for a specific component over a long period of time. Failure rates can vary significantly depending on equipment operating conditions, and because of that, industry historical data may not always reflect the reality of every single project.

The results obtained by using this tool also assist with communicating with management and justifying expenditures in a scenario where costs need to be reduced.

No previous information related to the development of a tool to determine the optimal number of spares was found. In the current oil price environment, this tool can bring an important contribution by assisting teams to make informed decisions based on statistical information and field-specific failure data.

The strategy provides a reliability and risk based approach in the decision-making process.
The Study on Expandable Tubulars Collapse Performance and the Development of Risk Based Design Collapse Strength
Authors: Long X. , Roggeband S. M. , Pasaribu H. , Jabs M. , Klever F. J.
Published: October 2017

Solid Expandable Technology (SET) is helping the industry to reach more challenging wells. The objective of this study is to comprehensively investigate the effects of the expansion process on the pipe mechanical properties and collapse performance, and to develop a risk based design collapse strength for the expandables with a desired reliability level.

Full size expanded and unexpanded pipes with various D/t ratios were collapse tested. Detailed material properties were measured, such as large deformation material tension and compression test, X-Ray diffraction residual stresses measurement and detailed pipe geometry and wall thickness mapping. An FEA model was also developed to simulate the collapse performance of the expanded tubulars. A power law fitting formula and the Klever-Tamano formula were used to obtain the best fit mean (average) collapse strength of the test data. Then a risk based statistical approach was employed to develop the design collapse strength.

It was found that the expanded tubulars generally have 10-30% lower collapse performance than unexpanded tubulars depending on the pipe D/t ratios. This is due largely to the Bauschinger effect of the material caused by the expansion process. Other factors, such as pipe residual stresses development, and pipe geometry variations may play a secondary role. Traditional API collapse formulas may not be sufficient for the design collapse strength determination of expanded tubulars. A statistical approach was successfully employed to develop the collapse strength for expanded tubulars at 99.5% reliability level. Thus it leads to a reliable and safe application of expandable tubulars in well design and drilling operations.
Application of New Interpretation Workflows that Improve Cement Evaluation in Presence of Microannulus
Authors: Issabekov Yerlan , Kalyanaraman Ram Sunder , Haoua Taha Ben , Benaicha Hani , Gout Olivier J.
Published: October 2017

In many cases when using traditional cement evaluation techniques, we observe disagreement between the ultrasonic and sonic measurements on the quality of cement sheath. In some instances, both measurements can lead to a pessimistic assessment of the cement sheath in spite of a well-executed cementing job. To improve the robustness of the cement evaluation, new interpretation workflows were tested in North Africa to investigate if the apparent "disagreement" can be explained and result in an improved cement evaluation.

The data acquired in wells in North Africa was processed and interpreted with traditional workflows and compared with new interpretation workflows that were recently made available. The new workflows include a) an ultrasonic workflow that improves the discrimination of lightweight solids and through its detection of the presence of a microannulus also provides the ability to discriminate a dry microannulus situation and b) a novel way of comparing sonic and ultrasonic measurements in the acoustic impedance space. The workflows have been applied in many wells and have been seen to improve the robustness of the cement evaluation that is consistent with the expectation for a cementing operation. In case studies from data acquired in two wells in North Africa, we observed that presence of a wet or dry microannulus affected the ultrasonic and sonic responses differently, which the traditional evaluation techniques failed to address adequately—in some cases resulting in a pessimistic assessment of the cement sheath. The new workflows enable not only the detection of the presence of a microannulus but also allow discriminating between a wet microannulus and a dry microannulus.

This improved ability to diagnose debonded cement behaviour in situ has helped us arrive at consistent, robust, and reliable evaluation of the cement sheath. The examples presented in this paper demonstrate the successful application of new interpretation workflows for ultrasonic and sonic measurements that improve the confidence of cement evaluation, especially when cement has debonded from casing. This ability also has the potential to reduce unwanted and costly cement remediation work.
Retrievable Inflatable Bridge Plug used as Solution Product for Through Tubing Intervention in Deepwater GoM
Authors: Ramnath Lawrence , Pocza James , Reynolds Andrew
Published: October 2017

This paper discusses how the application of a Retrievable Inflatable Bridge Plug (RIBP) helped overcome the challenges encountered in a subsea deepwater intervention operation. The technical details of the challenges are first outlined, followed by the salient features of the RIBP that facilitated its successful use.

The RIBP was used to isolate the reservoir prior to change-out of the upper completion tubing as per the intervention scope of work. The monobore completion for which the intervention was planned did not have any nipple profiles to allow for reservoir isolation using a traditional lock and plug. Therefore, through-tubing Mechanical Bridge Plug (MBP) technologies had to be considered. Only the RIBP was able to provide the functionality for the intervention operation. This RIBP technology was applied successfully to two different wells with identical scopes of work.

The inflatable technology provided a robust solution to the compound challenges faced during the planned intervention operation. Since these challenges are common to the industry, especially in the deepwater subsea environment, the successful RIBP application discussed in this paper increases confidence in the future use of such technology.
Predicting Dead-End Pore-Volume in a Reservoir from Single Tracer Experiment
Authors: Phirani Jyoti , Roy Shantanu , Pant Harish J.
Published: October 2017

Tracer studies are used to characterize the porous media for pore volume occupied by different phases and flow trajectories and velocity of the phases. When a tracer is injected as a pulse into a liquid stream flowing in a porous media, the stagnant or the dead-end pore volume in the porous media interacts with the tracer leading to a tailing effect in the outlet tracer curve. The tailing-effect impacts the determination of the flow path or the phase saturations in the porous media using the outlet tracer concentration. Generally, history matching of the effluent concentration profile is used to determine and separate the effect of dead-end pore volume from other tracer behavior in the reservoir such as dispersion or convection. History matching is computationally expensive and many simulation runs are required to match the exit concenetration profile. In the present work we have used the method of moments of the Residence Time Distribution (RTD) of the tracer to determine dead-end pore volume and parameters associated with it. We are able to describe from the method deviced, which parameters can be determined and which cannot be determined in different flow scenarios in the porous media. We also use numerical experiments of the tracer transport in porous media and compare the results with the method of moments. In the end, we delineate general guidelines for estimation of the parameters, especially the dead-end pore volume.
An Enhanced Pseudo-3D Model of Hydraulic Fracture in Multi-Layered Formation
Authors: Budennyy Semen
Published: October 2017

The manuscript presents the development of hydraulic fracturing simulation tool based on cell-based pseudo-3D model. The model was upgraded up to enhanced P3D model that accounts for viscous dissipation in lateral growth implicitly. In addition to P3D model enhancement the aim of present paper is to explore crucial effects and processes taking place during hydraulic fracturing simulation: proppant particles settling, tip-screen out, interaction between several fractures in multi-stage treatment. To achieve the goal we developed the mathematical model that is able to simulate the fracture growth in highly non-uniform geological lithology, the flow of non-Newtonian liquid and proppant particles in the fracture channel, interaction between fractures. All of these effects are investigated separately, the impact of each process on the fracture shape is discussed, possible solutions are suggested.
Profitability Calculations of Abandoned Mine Methane Production in the Upper Silesian Coal Basin
Authors: Labuda Wojciech
Published: October 2017

The aim of the paper is to identify whether and to what extent an exploitation of abandoned mine methane (AMM) is economically viable in the Upper Silesian Coal Basin (USCB).

Nowadays coal mining in many countries is in a crisis because of imposing decarbonization policy on one hand, and displacement of energy based on hard coal by energy based on renewables on the other. It turns out that methane accumulates in significant amounts in abandoned underground coal mines’ pathways, galleries and gobs. Hence, both electricity and heat production (combined heat and power – CHP) from AMM could improve the economic situation of post-mining areas and provide clean energy. Moreover, utilization of AMM exploited by boreholes drilled from surface could increase safety in neighboring working hard coal mines. However, existence of these advantages is determined by economic calculation.

Firstly, I identified the factors influencing the level of investment costs and the size of revenues. In both cases I left the popular deterministic assessment and I decided to use stochastic approach, which allows a better reflection of reality by taking into account the variability and unpredictability of the future price of electricity, heat, drilling and other factors. Calculation is based on real data acquired from the local electric power industry. The analysis was possible by using the Monte Carlo method and @Risk program from the Palisade’s package – Decision Tools. Eventually, I prepared sensitivity and scenario analysis to identify which factors have the greatest impact on the profitability of such projects.

Abandoned mine methane may soon become a valuable source of income for the mining areas struggling with many socio-economic problems and become a bridge between coal-based energy system and clean energy resources.
Pore-Scale Experimental Study of Matrix-Fracture Interactions during Tertiary Gas Injection in Carbonates Using X-Ray Microtomography
Authors: Sabti Mohammad
Published: October 2017

Fractured oil reservoirs, which are among the most technically complicated oil and gas reservoirs, often trap significant amounts of recoverable oil within the matrix. Extraction of this oil requires a better insight of the main displacement physics controlling matrix-fracture interactions. Immiscible gas injection, for example, is one of the common techniques used to improve oil recovery from fractured reservoirs. However, the presence of fractures in such reserves as a high permeable path impacts the displacement physics and consequently the oil recovery, especially where three phases (i.e., brine, oil, and gas) coexist.

In this study, I performed a set of two- and three-phase experiments under tertiary gas injection using spreading oil on a fractured 10-mm diameter limestone rock sample by utilizing micro-CT imaging technique. The aim is to compare pore fluid occupancies under a wide range of oil saturations within the pore space and the fracture openings. Interpretation of the micro-scale images helps to capture a detailed map of the fluid arrangements within the pore space in the matrix and the fracture. These maps clearly demonstrated the relevance of spreading phenomena to fluid displacements in the fracture undergoing three-phase flow processes.

The saturation profile over the course of the gas injections showed that brine was predominately produced first since it was the most well-connected phase. After increasing the gas flow rate, the gas obtained sufficient capillary pressure to invade areas containing trapped oil at which point oil layers began to form and re-connect the oil phase. The oil layers allowed the further production of oil with each incremental increase in gas flow rate. Oil layers were seen to be thicker at lower flow rates and became progressively thinner with increased capillary number. Overall, it was found that, at higher oil saturations, the displacement of oil was predominantly achieved by the connectivity of the bulk oil after the evolution of the reconnected trapped oil blobs in the matrix, whereas at lower oil saturations, the displacement of oil was governed by the stability and the hydraulic connectivity of the spreading oil layers that maintained the continuity of the oil phase from the matrix to the fracture.
Improved Method of Moments to Determine Mobile Phase Saturations With Single Well Chemical Tracer Test
Authors: Tian Wei
Published: October 2017

The residual oil saturation obtained from SWCTT is critical for designing enhanced oil recovery (EOR). However, a key assumption in conventional SWCTT is that only single phase (water) is mobile. In reality, this is often not the case, and significant error can occur if the conventional SWCTT analysis method is used when multiple phases flow at the same time. The objective of this study is to improve the accuracy and precision of SWCTT interpretation in multi-phase flow condition.

In this paper, we propose an innovative procedure of modified SWCTT and the method of moment (MoM), aiming at the two-mobile-phase condition. In the development of the algorithm, a ratio parameter is introduced to adjust the calculated swept volume difference between the conservative tracer and partitioning tracer. In addition, a mixture injection of oil and water is required, instead of pure water injection in SWCTT.

The proposed approach is verified through numerical simulation on synthetic cases with known input parameters. The simulated models consist of a radial flow regime with a single vertical well in the center. The input oil saturation varies from 0.1 (immobile oil saturation) to 0.9. Our results show that the saturation estimated from modified MoM matched the simulation input data, which indicates that our approach is able to capture the saturations under two-mobile-phase condition. Moreover, the modified MoM can also be applied in single-mobile-phase condition and improved accuracy of conventional MoM.
Dynamic analysis of different business failure process
Authors: Flores-Jimeno Rocío , Jimeno-García Inmaculada
Published: October 2017

This work is framed in the research of business failure. We examine a method of analyzing the dynamics of financial failure. The authors examine a method of analyzing the dynamics of financial failure, because our goal is to analyze how the economic and financial indicators show the risk of failure in a group of companies. Using a sample of 163 companies declared bankrupt or dissolved, the authors show how to depict company trajectories of behavior and movement to terminal failure. They analyze these trajectories to find and describe empirical evidence of the different dynamics of bankruptcy. The authors also show that the estimation of failure risk is more accurate when these different failure trajectories are defined. In conclusion, the authors can see that there are different failure trajectories. One can use these different trajectories to identify more efficiently the indicators warning of the failure risk of the companies analyzed.
Effect of underbody structure on aerodynamic drag and optimization
Authors: Yuan Zhiqun , Wang Yiping
Published: October 2017

The numerical simulation and wind tunnel experiment are employed to investigate the aerodynamic characteristics of automobile. The object is to investigate the sensibility of aerodynamic characteristic to the underbody, and summarize the influence of aerodynamic attachments on the aerodynamic drag, which can provide more useful date as a reference to underbody design of automobile. In the wind tunnel experiments, the aerodynamic drag of automobile with simplified flat underbody is measured. The realizable k-ε model is employed to compute the aerodynamic drag. The computational results show a good agreement with the experimental date, which proving the accuracy of the numerical calculation method. Then the numerical calculation model with real underbody structure is established on this basis. Calculation results show that there are many separation vortexes in the automotive underbody and with a great influence on the aerodynamic characteristics, which is the main reason for the formation of aerodynamic drag and make the aerodynamic drag increased by 23.4 %. In order to reduce drag, A kind of wheel spoiler and three kinds of underbody spoiler are designed, and the influence of the key parameters on aerodynamic drag is analyzed, which both had effective influence for reducing aerodynamic drag, and the largest drop of drag coefficient are 4.86 % and 7.05 % with the reasonable structure designs. The results of calculation and analysis can give suggestion for vehicle designing.
Numerical simulation for optimizing the nozzle of moist-mix shotcrete based on orthogonal test
Authors: Chen Lianjun , Li Pengcheng , Liu Guoming , Wang Fei
Published: October 2017

The nozzles of moist-mix shotcrete are the key parts of forming a steady jet flow field and ensuring the uniform mixing of water and other ingredients. In this paper, for optimizing the nozzle of moist-mix shotcrete, both the internal and external field of a variety of spray nozzles were simulated and analyzed by adopting orthogonal test method with Fluent simulation software combined. Then the phase volume fraction and single-phase velocity of the outlet section of flow field inside the nozzles and cloud pictures including single-phase velocity and volume of different sections lengthways in the external flow field of nozzle were obtained. The results demonstrated that the change of different factors and different levels of the same factor affected the shotcreting performance of spray nozzle, but the effect degree is different. Additionally, compared with the traditional nozzle, the rationality of new-type nozzle structure was verified, which provided a basis for the improvement and optimization of the nozzle structure in the future.
Effect of counter-rotating fan’s speed matching on stall inception and characteristics of tip clearance flow
Authors: Luan Hengxuan , Chen Qingguang , Weng Liyuan , Luan Yuanzhong , Chen Peng
Published: October 2017

In order to study the effect of speed matching on behavior of tip clearance flow and its possible link to stall inception in counter-rotating fan, the Reynolds-averaged Navier-Stokes equations are solved by the numerical method in conjunction with a SST turbulence model, the effect of speed matching on performance and stability margin are investigated, so are the difference of the tip clearance flow in different speed matching. Furthermore, the effect of speed matching on behavior of tip clearance flow and its possible link to stall inception are investigated. Research results show that: when the rotational speed of Rotor 2 is less than that of Rotor 1, with the decrease of rotational speed of Rotor 2 has no notable effect on tip clearance flow fields of the two rotors, therefore offset of stalling boundary is minor and strong blockage effect is observed in Rotor 1; when the rotational speed of Rotor 1 is less than that of Rotor 2, decrease of rotational speed of Rotor 1 show significant effect on the two rotors, which leads to major offset of stalling boundary, tip leakage flow performance of Rotor 1 improved, while that of Rotor 2 weakened and large blockage area occurs. By comparison, speed variation of Rotor 1 has more effect on stalling boundary of counter-rotating fan.
Influence of curing time on impact energy absorption characteristics of artificially cemented sand
Authors: Yuan Pu , Xu Ying
Published: October 2017

To investigate the influence of curing time on impact energy absorption characteristics of artificially cemented sand in geomechanical model experiments, aluminium split Hopkinson pressure bar apparatus with bar diameter of 37 mm has been developed to conduct impact uniaxial compression tests under various striker velocities. The curing times of artificially cemented sand are 7 days, 14 days, and 21 days, respectively. Then test results have been analyzed from the energy point of view. Test results show that only a small amount of energy goes through the specimen and passes into transmitted bar in impact uniaxial compression tests, while most of incident energy is reflected back to incident bar for relatively low wave impedance of artificially cemented sand. With striker velocity increasing, there is an obviously positive linear relation between specific energy absorption (SEA) of artificially cemented sand specimens and squared striker velocity. As the bonding, mechanical behaviors between sand particles are gradually strengthened with curing time growing, the impact energy absorption characteristics of artificially cemented sand increases with curing time growing under certain striker velocity condition. And the increasing rate from 7 days to 14 days is slower, while it is faster from 14 days to 21 days. With respect to the SEA of artificially cemented sand cured 7 days, the impact energy absorption increase factor (IEAIF) of artificially cemented sands cured 14 days and 21 days are 1.19 and 1.48, respectively.
Iterative response surface joint algorithm analysis of optimization arrangement on mistuned blades
Authors: Pan Honggang , Zhao Tianyu , Yuan Huiqun , Li Bobo
Published: October 2017

This paper presents a test method to measure vibration characteristics of mistuned bladed disk system. Modal analysis for the disk is to verify the precision of test bench. Further mistuned parameter identification method is proposed to introduce stiffness detuning. From this the samples can be obtained. On the other hand, the joint optimization analysis system is applied which consists of iterative response surface method and particle swarm optimization algorithm. At the same time, it is proved to have higher accuracy and better generalization ability than standard polynomial response surface method for the problem in this paper. The research results indicate that the amplitudes of optimal solution are smaller than that with random arrangement. The vibration response can be improved obviously, especially for resonance region. So, this paper has a certain universality and application value for blade arrangement based on iterative response surface joint algorithm.
Effect of drilling pipe rotation on vortex induced vibration response of drilling riser
Authors: Mao Liangjie , Liu Qingyou , Wang Guorong , Zhou Shouwei
Published: October 2017

An experiment was carried out in a basin to investigate rotation of drilling pipe on vortex induced vibration response of drilling riser. Vibration displacement time-history and frequency are obtained. Results show that dominant vibration frequency in the in-line direction is almost twice as high as that in the cross-flow direction. The vibration amplitudes in both the cross-flow and in-line direction increase with an increase in rotation speed of drilling pipe under the experimental conditions. However, the influence of rotation speed drilling pipe on drilling riser vibration amplitude is insignificant. Dominant frequencies are invariant with variation of drilling pipe rotation under experimental conditions.
Ultrasound spectral analysis-based assessment of macular areas in patients with age related macular degeneration
Authors: Būdienė Brigita , Sakalauskaitė Ieva , Mikalauskaitė Rasa , Stanislovaitienė Daiva , Trumpaitis Jurgis , Žaliūnienė Dalia
Published: October 2017

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in people aged 50 and older in the developed world. Early detection and treatment of AMD play the key role in helping patients at high risk for developing exudative to maintain their vision or slow down the progression of the disease. In this paper, the new technique for AMD evaluation using ultrasound spectral analysis is presented. Our aim was to compare B scan ultrasound signals backscattered from healthy tissues of macular area with signals from nonexudative and exudative AMD areas. In case-control study of 64 patients (144 tissues) we compared 82 cases of healthy tissue of macular area (I group) with 35 cases of nonexudative AMD (II group) and 30 cases of exudative AMD (III group) using B scan ultrasound. Estimated results showed that B scan amplitude and spectral intercept are informative to distinguish healthy tissues of macular area from AMD and spectral slope spectral, momentary bandwidth allow us to distinguish forms of AMD (nonexudative and exudative).We suggest that ultrasound spectral analysis is noninvasive, widely available, easy-to-use and less expensive method which can be used as an additional diagnostic tool in AMD detecting and differentiating when there are no possibilities to use more specific examination.
Road profile estimation for suspension system based on the minimum model error criterion combined with a Kalman filter
Authors: Wang Zhen Feng , Dong Ming Ming , Qin Ye Chen , Gu Liang
Published: October 2017

This paper presents a novel approach for improving the estimation accuracy of the road profile for a vehicle suspension system. To meet the requirements of road profile estimation for road management and reproduction of system excitation, previous studies can be divided into data-driven and model based approaches. These studies mainly focused on road profile estimation while seldom considering the uncertainty of parameters. However, uncertainty is unavoidable for various aspects of suspension system, e.g., varying sprung mass, damper and tire nonlinear performance. In this study, to improve the estimation accuracy for a varying sprung mass, a novel algorithm was derived based on the Minimum Model Error (MME) criterion and a Kalman Filter (KF). Since the MME criterion method utilizes the minimum value principle to solve the model error based on a model error function, the MME criterion can effectively deal with the estimation error. Then, the proposed algorithm was applied to a 2 degree-of-freedom (DOF) suspension system model under ISO Level-B, ISO Level-C and ISO Level-D road excitations. Simulation results and experimental data obtained using a quarter-vehicle test rig revealed that the proposed approach achieves higher road estimation accuracy compared to traditional KF methods.
Rotating machinery fault diagnosis for imbalanced data based on decision tree and fast clustering algorithm
Authors: Zhang Xiaochen , Jiang Dongxiang , Long Quan , Han Te
Published: October 2017

To diagnose rotating machinery fault for imbalanced data, a kind of method based on fast clustering algorithm and decision tree is proposed. Combined with wavelet packet decomposition and isometric mapping (Isomap), sensitive features of different faults can be obtained so the imbalanced fault sample set is constituted. Then the fast clustering algorithm is applied to search core samples from the majority data of the imbalanced fault sample set. Consequently, the balanced fault sample set consisted of the clustered data and the minority data is built. After that, decision tree is trained with the balanced fault sample set to get the fault diagnosis model. Finally, gearbox fault data set and rolling bearing fault data set are used to test the fault diagnosis model. The experiment results show that proposed fault diagnosis model could accurately diagnose the rotating machinery fault for imbalanced data.
A hydraulic fault diagnosis method based on sliding-window spectrum feature and deep belief network
Authors: Wang Xinqing , Huang Jie , Ren Guoting , Wang Dong
Published: October 2017

The vibration signal of hydraulic system contains abundant state information, so vibration testing technology is an effective way to realize the fault diagnosis of hydraulic system. However, the mapping relation between signal characteristic and system state is complex and the expression meaning of characteristic is obscure, which brings a great challenge to the hydraulic fault diagnosis. The DBN, a newly proposed deep learning model, has an advantage of autonomously learning and reasoning. And it is good at studying the concealed representation of data and highlighting the feature expression. So, it is contributive to deal with the problems of large capacity data like high dimension, redundancy, and nonlinear etc. Therefore, DBN is chosen as the fault diagnosis method in this paper. Meanwhile, given that the difficulty in feature extraction of hydraulic vibration signal and the important influence of input feature vector to the diagnosing of DBN, a fast and effectively feature extraction method based on sliding-window spectrum feature (SWSF) is proposed. It is effective in remaining the integrity of feature, avoiding the risking of relative shifting of characteristic spectrum, and decreasing the dimensions of feature vector. The experimental results demonstrate that the combination of SWSF and DBN is a fast and effective approach to realize the fault diagnosis of hydraulic system.
Geometry, kinematics, paleostress analysis and tectonic model of the extensional fault system deforming the Plio-Pleistocene reefal limestone in southeastern Dominican Republic
Authors: García-Senz J. , Escuder-Viruete J. , Pérez-Estaún A.
Published: October 2017

This paper describes a system of extensional faults oriented NW-SE, NNW-SSE, and ENE-WSW responsible for the tectonic relief of semi-grabens in southeastern Dominican Republic. These faults constitute the natural extension of a previously recognized fault system in western Puerto Rico and the Mona Passage. Paleostress analysis carried out on the faults and fractures in the Pliocene limestone results in a minimum NE-SW stress axis, changing to SSW in the faults that affect the Pleistocene limestone. In contrast, the inversion of focal mechanisms of deep, intermediate, and shallow earthquakes provides a mechanism characteristic of pure thrust, oblique thrust, strike-slip, and normal. Extension in the upper part of the Caribbean crust is accompanied by vertical movements of uplift and subsidence that deform the Plio-Pleistocene coral platform. These movements have been modeled as a broken elastic plate flexed to the trench and incorporated in a more general model of necking in the subducted Atlantic slab. Nevertheless, the flexural mechanism alone can hardly explain the regional extension observed, which is better explained as diffuse rifting, maybe due to the continuity at low rate of the counterclockwise rotation of Puerto Rico.
Study of fibers and colours in Dominican Larimar
Authors: Espí J. A.
Published: October 2017

The origin of the blue pectolite has hardly been studied. Now this BGM special issue is devoted to this unusual stone. Thus the reader is referred to the two accompanying papers. As we were unable to recognize the crystallization sequences and relationships with their environment of the coloured pectolite (Larimar) in the Dominican Republic, we decided to scan the polished surface without any intermediaries, and then expand the image to enhance the desired effect. Thus the defining traits have been achieved in the history of its complex formation, such as deposition sequences based on their colour, display input channels, the organizational structure that it sometimes supports, features of movements and deformations and, above all, fitness with the model previously deduced.
Evaluation of Technology-Enhanced Learning Programs for Health Care Professionals: Systematic Review (Preprint)
Authors: Nicoll Pam , MacRury Sandra , van Woerden Hugo C , Smyth Keith
Published: October 2017

BACKGROUND

Technology-enhanced learning (TEL) programs are increasingly seen as the way in which education for health care professionals can be transformed, giving access to effective ongoing learning and training even where time or geographical barriers exist. Given the increasing emphasis on this mode of educational support for health care practitioners, it is vital that we can effectively evaluate and measure impact to ensure that TEL programs are effective and fit for purpose. This paper examines the current evidence base for the first time, in relation to the evaluation of TEL programs for health care professionals.

OBJECTIVE

We conducted a systematic review of the current literature relating to the evaluation of TEL programs for health care professionals and critically appraised the quality of the studies.

METHODS

This review employed specific search criteria to identify research studies that included evaluation of TEL for health care professionals. The databases searched included Medline Ovid, Cumulative Index of Nursing and Allied Health Literature Plus Advanced, Applied Social Sciences Index and Abstracts, ZETOC, Institute of Electrical and Electronics Engineers Explore Digital Library, Allied and Complementary Medicine, and Education Resources Information Center between January 2006 and January 2017. An additional hand search for relevant articles from reference lists was undertaken. Each of the studies identified was critically appraised for quality using the Crowe Critical Appraisal Tool. This approach produced a percentage total score for each study across specified categories. A proportion of the studies were independently assessed by an additional two reviewers.

RESULTS

The review identified 21 studies that met the inclusion criteria. The studies included scored totals across eight categories within a range of 37%-95% and an average score of 68%. Studies that measured TEL using learner satisfaction surveys, or combined pretest and posttest knowledge score testing with learner satisfaction surveys, were found to be the most common types of TEL evaluations evident in the literature. The studies reviewed had low scores across reporting on ethical matters, design, and data collection categories.

CONCLUSIONS

There continues to be a need to develop effective and standard TEL evaluation tools, and good quality studies that describe effective evaluation of TEL education for health care professionals. Studies often fail to provide sufficient detail to support transferability or direct future TEL health care education programs.
Recommendations for the Development of a Mobile HIV Prevention Intervention for Men Who Have Sex With Men and Hijras in Mumbai: Qualitative Study (Preprint)
Authors: Rawat Shruta , Wilkerson J Michael , Lawler Sylvia M , Patankar Pallav , Rosser BR Simon , Shukla Kanjani , Butame Seyram , Ekstrand Maria L
Published: October 2017

BACKGROUND

As Internet and mobile phone use expands in India, there is an opportunity to develop mobile health (mHealth) interventions for marginalized populations, including men who have sex with men (MSM) and hijras (transgender women), hesitant to access traditional health care systems.

OBJECTIVE

The purpose of this study was to determine if an mHealth intervention was acceptable to MSM and hijras living in Mumbai, and if so, what features would be useful in targeting the prevention of HIV acquisition and to increase the quality of life among persons living with HIV/AIDS.

METHODS

Data from 4 focus groups with MSM and interviews with 4 hijras, 10 health service providers, and 8 mHealth developers were thematically analyzed.

RESULTS

Once the need for an mHealth intervention was confirmed, comments about features were organized into 3 themes: content, interface, and retention. Content subthemes included providing sex education for younger community members, providing information about STIs, and providing information and social support for persons living with HIV. Interface subthemes included presenting content using pictures; using videos to present stories of role models; using push notifications for testing, appointment, and medication reminders; using geolocation to link to just-in-time services; and using telemedicine to increase access to health service providers and community services. The 5 retention subthemes included keeping it fun, using gaming mechanics, developing content in regional languages, protecting confidentiality, and linking to social networking apps.

CONCLUSIONS

These findings may help inform mHealth development in India.
Increase of the Durability of the Ni3Al-based alloy Piercing Plug on Account of Reinforcing Particles
Authors: Konovalov M S , Shenogin V P
Published: October 2017

В данной работе слитки изготавливались методом выплавки электродов в открытой индукционной электрической печи СЭЛТ-20С/20 с последующим их электрошлаковым переплавом как с добавлением армирующих частиц молибдена в кристаллизатор методом равномерной подсыпки во время переплава, так и без добавления. Для выплавки использовались чистые шихтовые материалы без добавления отходов. Армирующие частицы молибдена были получены измельчением заготовок молибдена марки МШ-1 (ТУ 48-19-73-86) в планетарной мельнице. В результате проведения работы методом открытой индукционной выплавки было получено четыре электрода сплава на основе Ni3Al. Первые два электрода (№ 1 и 2) были подвергнуты стандартному электрошлаковому переплаву (ЭШП), а вторые два электрода (№ 3 и 4) были подвергнуты ЭШП с добавлением в кристаллизатор во время переплава порошка молибдена. Из всех полученных слитков были изготовлены прошивные оправки, которые испытывались при прошивке прутков коррозионно-стойкой стали марки 08Х18Н10Т-Ш. При помощи оправок, изготовленных из слитков № 1 и 2, было прошито 7 и 6 прутков соответственно, а при помощи оправок из слитков № 3 и 4 было прошито 11 и 12 прутков соответственно. Полученные результаты показали, что возможно повысить стойкость оправок из сплава на основе интерметаллида Ni3Al при прошивке прутков из стали марки 08Х18Н10Т-Ш на 76 % за счет повышения жаропрочных характеристик сплава армирующими частицами из порошка молибдена, вводимыми в процессе проведения ЭШП.