bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonlinear optical properties related to intersubband transitions in asymmetrical double δ-doped GaAs; effects of an applied electric field
Authors: Rodríguez-Magdaleno K. A. , Martínez-Orozco J. C. , Rodríguez-Vargas I. , Mora-Ramos M. E. , Duque C.A. 
Published: February 2013

ABSTRACTIn this work, we calculated the ground and first excited states of an electron confined in an asymmetric double DDQW system within a Gallium Arsenide (GaAs) matrix. The two-dimensional impurities density (N2d) considered in our calculation are within the range of 1012 to 1013 cm−2. We obtain the linear and nonlinear optical properties related to intersubband transitions as a function of the spacing between δ-doped wells, two-dimensional impurities concentrations as well as in presence of electric field. We reported results for the linear and nonlinear optical absorption coefficient and in the relative refractive index changes. Our results show that the asymmetry induced in the double δ-doped well system gives rise to values that are several orders of magnitude higher in the resonant peaks intensity.
Electrodeposited Cobalt Alloys as Materials for Energy Technology
Authors: Glushkova Maryna , Bairachna Tetiana , Ved Maryna , Sakhnenko Mykola 
Published: February 2013

ABSTRACTThe influence of electrodeposition parameters on chemical composition, morphology and functional properties of such binary cobalt alloys as CoAg, CoW, and CoFe has been investigated. The alloys are shown to possess catalytic properties. Catalytic activity was preliminary estimated in the electrolytic hydrogen evolution reaction and tested by CO to CO2 conversion during the catalytic benzene oxidation.
Oligothiophene-Based Organic Thin-Film Transistors: A Kelvin Probe Force Microscopy Study of the Electronic Properties
Authors: Afsharimani N.S. , Nysten B. 
Published: February 2013

ABSTRACTIn the past decades organic thin film transistors (OTFTs) have been notably studied due to their interesting properties. Not only they can be processed by simple methods such as inkjet printing but also open the doors to new applications for cheap plastic electronics including electronic tags, biosensors, flexible screens,… However, the measured field-effect mobility in OTFTs is relatively low compared to inorganic devices. Generally, such low field-effect mobility values result from extrinsic effects such as grain boundaries or imperfect interfaces with source and drain electrodes. It has been shown that reducing the number of grain boundaries between the source and drain electrodes improves the field effect mobility.1-3 Therefore, it is important to understand the transport mechanisms by studying the structure of organic thin films and local electrical properties within the channel and at the interfaces with source and drain electrodes in order to improve the field-effect mobility in OTFTs. Kelvin probe force microscopy (KPFM) is an ideal tool for that purpose since it allows to simultaneously investigation of the local structure and the electrical potential distribution in electronic devices. In this work, the structure and the electrical properties of OTFTs based on dioctylterthiophene (DOTT) were studied. The transistors were fabricated by spin-coating of DOTT on the transistor structures with treated (silanized) and untreated channel oxide. The potential profiles across the channel and at the metal-electrode interfaces were measured by KPFM. The effect of surface treatment on hysteresis effects was also studied. Smaller crystals and a lower threshold voltage were observed for the silanized devices. Hysteresis effects appeared to be less important in modified devices compared to the untreated ones.
Transparent Conductive Oxide Less Flexible Dye-sensitized Solar Cells with Flat and Cylinder Shapes
Authors: Usagawa Jun , Park Byung-wook , Ogomi Yuhei , Pandey Shyam S. , Hayase Shuzi 
Published: February 2013

ABSTRACTTransparent conductive oxide less flexible dye-sensitized solar cells (TCO-less DSC) with flat and cylinder shapes are reported. The cell consists of a plastic cover, a flexible titania/dye sheet back contacted with a metal mesh sheet, a gel electrolyte sheet, and Pt layer on a Ti sheet. How to increase the efficiency were discussed. We concluded that making a titania/dye layer on a metal mesh sheet thinner and using a thinner electrolyte layer were effective for increasing the efficiency. A flat TCO-less DSC with 6.1 % efficiency and a cylindrical TCO-less DSC with 5.1 % efficiency are reported.
Investigation of Nanometric Thin-Film Bismuth Piezoresistors Deposited on Silicon Substrates
Authors: Estrada Horacio V. 
Published: February 2013

ABSTRACTThin film bismuth piezoresistors, defined on oxidized silicon wafers, are investigated as a function of their orientation for their eventual integration on micro-electro-mechanical (MEMS) microsensors. Bismuth’s piezoresistance (or elasto-resistance) is experimentally investigated to accurately determine its longitudinal and transverse strain sensitivities. Whisker-shaped resistive elements defined on different orientations (from 0o, the beam’s main strain axis, to 90o, perpendicular to that axis) undergo changes of resistance (ΔR), associated with the induced strains on silicon cantilevers beam’s surface when these are mechanically loaded under pure bending stress conditions. For Bi-resistors, the traditional gage factor concept, (ΔR/Ro)/εl, is found to be equal to +16 and +33, for elements oriented along 0 and 90o, respectively, considerably larger than those for metals or metal alloys. These high sensitivity values and the “unusual” positive, higher value for the 90o (perpendicular) resistors can be of considerable interest for microsensors applications. The results of this study enable us to precisely determine the bismuth’s longitudinal and transverse strain sensitivities that are calculated to be equal to +26 and +40.5 respectively. This experimental study is extended to explore the Bi-films’ response to bi-axial strain fields.
Sputtered Bismuth thin films as trace metal electrochemical sensors
Authors: Baron J. , Silva-Bermudez P. , Rodil S.E. 
Published: February 2013

ABSTRACTThis work studies the performance of sputtered bismuth films as disposable working electrodes for stripping voltammetry. The electrodes were produced by coating a glass substrate with a bismuth film using DC magnetron sputtering under different conditions of power and time. The Bi-based sensors were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. Electrochemical evaluation included linear sweep voltammetry using different buffer solution and pHs to observe the effect of the deposition conditions and thickness on the potential window accessible for stripping analysis. Subsequently, the electrodes were tested for the detection of low concentrations of trace metals (Cd(II) and Pb(II)) by square wave anodic stripping voltammetry (SWASV). Clear and reproducible stripping peaks were observed for trace concentrations in the 50 - 450 ppb range of the target analytes. The detection limit of the Bi electrodes were quantitatively estimated from the analyses of SWASV, demonstrating that even using simple sensor geometry, detection limits in the 14-20 ppb range could be obtained. The reproducibility of the measurements is good (relative standard deviations about 4%) after 10 consecutive measurements which define the maximum number of times that the sensor can be used.
Piezoresponse Force Microscopy Studies of pc-BiFeO3 Thin Films Produced by the Simultaneous Laser Ablation of Bi and FeO3
Authors: Enriquez-Flores C. I. , Gervacio-Arciniega J. J. , Flores-Ruiz F. J. , Cardona D. , Camps E. , Muñoz-Saldaña J. , Espinoza-Beltrán F.J. 
Published: February 2013

ABSTRACTBismuth iron oxide BFO films were produced by the pulsed laser deposition technique. These films are a mixture of BiFeO3 ferroelectrical and Bi25FeO40 piezoelectrical phases. The ferroelectrical domain structure of these films was studied via contact resonance piezoresponse force microscopy (CR-PFM) and resonance tracking PFM (RT-PFM). The proportions of area of these BFO phases were derived from the PFM images. The ferroelectrical domain size corresponds to the size of the BiFeO3 crystals. The CR-PFM and RT-PFM techniques allowed us to be able to distinguish between the ferroelectric domains and the piezoelectric regions existing in the polycrystalline films.
Thermoelectrical properties of α phase and γ phase NaxCo2O4 ceramics prepared by spark plasma sintering method
Authors: Mikami Natsuko , Nishio Keishi , Arai Koya , Sakamoto Tatsuya , Minowa Masahiro , Nakamura Tomoyuki , Hirayama Naomi , Kogo Yasuo , Iida Tsutomu 
Published: February 2013

ABSTRACTThe thermoelectrical properties of α and γ phases of NaxCo2O4 having different amounts of Na were evaluated. The γ NaxCo2O4 samples were synthesized by thermal decomposition in a metal-citric acid compound, and the α NaxCo2O4 samples were synthesized by self-flux processing. Dense bulk ceramics were fabricated using spark plasma sintering (SPS), and the sintered samples were of high density and highly oriented. The thermoelectrical properties showed that γ NaxCo2O4 had higher electrical conductivity and lower thermal conductivity compared with α NaxCo2O4 and that α NaxCo2O4 had a larger Seebeck coefficient. These results show that γ NaxCo2O4 has a larger power factor and dimensionless figure of merit, ZT, than α NaxCo2O4.
Prediction of SRV and Optimization of Fracturing in Tight Gas and Shale Using a Fully Elasto-Plastic Coupled Geomechanical Model
Authors: Nassir M. , Settari A. , Wan R. 
Published: February 2013

Abstract
Hydraulic fracturing is essential for economical development of tight gas and shale gas reservoirs. Current techniques are unable to predict the SRV dependence on frac job and rock mechanics parameters, which precludes any meaningful optimization. In our previous work on the SRV propagation prediction by means of combined tensile/shear fracturing model, the applications showed relatively narrow, focused SRV that resembled behavior dominated by a single fracture. In this work, we significantly improved the model by implementing rigorous full Newton elasto-plastic solution of fracturing problems by pseudo-continuum technique. The results reveal interesting features of complex fracturing occurring in tight formations, which are in broad agreement with the shapes of SRV’s obtained from microseismic imaging.
Flexibility of the code to select either tensile or shear fracturing mechanism or combination of both allows various scenarios to be examined. Different cases of 2-D and 3-D simulations will be presented which demonstrate some important features of the process. First, it is found that a wide SRV can result in cases where initial reservoir conditions are close to shear fracturing point such as in formations with microfractures, partially cemented natural fractures and abnormally high initial pore pressure. The SRV width is found to depend on the horizontal stress contrast as expected. Second, wide SRV growth is associated with constant or increasing pumping pressure for further failed zone growth due to the loss of elastic coupling by off-planar failure propagation. Further, under high injection pressure, an efficient fracture elasto-plastic constitutive model developed can drive both maximum and minimum effective stresses to zero or tensile and therefore creation of tensile fracture can be predicted simultaneously with shear fracturing. This will then provide means of modeling proppant transport. The new model is a significant step towards development of an integrated predictive tool for the optimization of shale gas development.
Interpretation of Closure Stress in the Montney Shale Using PTA Based Techniques
Authors: Hawkes Robert V. , Anderson Irene , Bachman R. C. , Settari A. 
Published: February 2013

Abstract
The Montney formation In NE British Columbia and NW Alberta is one of the largest economically feasible resource plays in North America. It contains both gas and liquids rich light ends. Horizontal multi-staged fracturing is the method for developing this vast resource. Prior to hydraulically fracturing the wellbore, the toe stage is frequently mini-fraced to obtain reservoir and geomechanical properties. Interpreting these mini-fracs, commonly referred to as DFIT’s (Diagnostic Fracture Injection Tests), has proved to be a challenge using traditional combination G Function and square root plots. It is always important to ensure that all data being analyzed is associated with a reservoir response and not wellbore behavior, surface operational interruptions or data quality issues. Some of these challenges can be overcome when using some new techniques for mini-frac Fall-off analysis, which will be discussed in this paper.
Various pressure transient analyses (PTA) based interpretation techniques have been introduced to the industry over the last couple of years for the determination of closure pressure (Bachman et al. 2012, Mohamed et al. 2011 and Marongiu-Porcu et al. 2011). From a theoretical viewpoint, unification of the fields of traditional PTA and mini-frac interpretation has been achieved.
We recommend that the standard PTA based log-log derivative plot using equivalent time is included in the analysis of mini-frac / fall-off tests. This plot is rarely, if ever, used in current interpretations. For mini-frac interpretation, the starting point should now be the standard PTA based log-log derivative plot. The primary pressure derivative (dp/dt) curve should also be added to the log-log derivative plot as an independent flow regime identification technique. This now gives two independent flow regime identification techniques in one plot. The power of the primary pressure derivative to enhance the interpretation of closure and flow regime identification will be illustrated. Subsequently, flow regime specific plots can be constructed to enhance the interpretation.
A number of field examples from the Montney formation in the Farrell Creek area of NE British Columbia are illustrated using a systematic PTA interpretation methodology demonstrating multiple closure events, high fracture extension pressure gradients of 34.0 kPa/m, non-Darcy pressure derivative diagnostics and observation of complex fracture orientation.
Breaking Up is Hard to Do: Creating Hydraulic Fracture Complexity in the Bakken Central Basin
Authors: Pearson C. Mark , Griffin Larry , Wright Chris , Weijers Leen 
Published: February 2013

Abstract
The Bakken drilling boom in North Dakota has seen a frenzy of activity over the past several years as operators sought to hold acreage and create value with the drill bit. This has been particularly true in the Central Basin portion of the Williston Basin where initial wells drilled prior to 2008 were uneconomic. However, advances in completion technology caused such a fundamental shift in economics that the whole Central Basin area of over 2500 square miles has been opened to economic development with ~100 rigs currently drilling in the region.
The most fundamental change in completion design has been the incorporation of "high-intensity" multi-stage fracturing. What makes Bakken completion design fundamentally different from recent shale gas developments has been the widespread use of uncemented liners with external packers in the open-hole lateral in order to create the multi-stage zonal isolation.
As operators have advanced the application of multi-stage completion techniques there has been a wide variety of completion equipment used and stimulation designs that have been pumped. This operator decided to employ a completion design that comprised: An open-hole "uncemented" liner section;Annular zonal isolation created by swell packers;The use of "plug and perf" technology to individually open successive zones to stimulation;The pumping of slickwater fracture treatment fluids at high rate;The use of high-quality ceramic proppant to generate the required fracture conductivity.
Production data are presented from 58 wells in which this completion and stimulation design has been conducted, which show that the use of this approach has resulted in well performance that is 25-45% superior to any other Bakken completion technique.
Development of the Brittle Shale Fracture Network Model
Authors: M. Nejad Amir , Shelley Robert F. , Lehman Lyle V. , Shah Koras , Gusain Deepak , Conway Matthew T. 
Published: February 2013

Abstract
This paper discusses the workflow for the development of a brittle shale model using a data mining approach. A database of more than 1,000 fracture stages and associated microseismic mapping results in the Barnett Shale was assembled. The fracture database is comprised of fracture design parameters including treatment volumes, rates, proppant mass and size, perforation length, fracture pressure, surface pressure trend and fracture dimensions on horizontal well bores. The goal of this analysis is to establish the relationship between frac design, pressure and frac network geometry. Data mining techniques are used on this complex database to find possible hidden relationships to explain the nature of the data. The outcome of this study is to develop a predictive model for fracture networks in shale. Also, using the predictive model, improvements in the current fracture design in Barnett shale are made.
Various aspects of this dataset are examined using data modeling and mining techniques including self-organizing maps (SOM). SOMs are unsupervised artificial neural networks that can cluster large amounts of data into two dimensional maps. Using SOM, frac design parameters are clustered and studied in depth. Then, a forward predictive neural network model is trained with fracture design parameters as inputs and fracture network length, width, height, and fracture volume as outputs. The network is trained with the help of genetic algorithm (GA). Sensitivity study on the trained network demonstrates the effect of different parameters on the fracture geometry. For example, an increase in slick-water volume will have a positive effect on fracture network width and length and negative effect on height. On the other hand, higher injection rates tend to accelerate height growth. Perforation length is also having a negative impact on the total stimulated or affected reservoir volume and tighter perforation designs are preferred. The results of this work potentially helps understanding of the development of fracture networks in shale reservoirs and the recommendations on improving stimulated reservoir volume. This will potentially help operators on more effective treatment designs and reducing the operational costs associated with fracturing in a brittle shale environment.
Impact of Liquid Loading in Hydraulic Fractures on Well Productivity
Authors: Agrawal Samarth , Sharma Mukul M. 
Published: February 2013

Abstract
One of the major challenges in fracturing low permeability gas formations is the loss of well productivity due to fluid entrapment in the matrix or fracture. Field results have indicated that only 15-30% of the frac fluid is recovered at the surface after flow back. Past studies have suggested that this water is trapped in the rock matrix near the fracture face and remains trapped due to the high capillary pressure in the matrix. Significant efforts have been made in the past to understand the impact of liquid blocking in hydraulically fractured conventional gas wells. This study shows that when considering hydraulic fractures in horizontal wells, the fluid may also be trapped within the fracture itself and may impact the cleanup as well as productivity. Under typical gas flow rates in tight / shale gas formations, liquid loading of both the fractures and the matrix is very likely to occur. This paper presents the results of 3D simulations of liquid loading in hydraulic fractures in horizontal wells, including gravity and capillary pressure effects. The impact of drawdown, fracture and reservoir properties on liquid loading and well productivity is presented. Results show that low drawdown, low matrix permeability or low initial gas rates aggravate the liquid loading problem inside the fracture and thereby impact the gas productivity during initial production.
Production Review of Current Stimulation Techniques in the Jonah Field
Authors: Paterniti Melanie , Kundert Donald , Ramurthy Muthukumarappan , Craig David 
Published: February 2013

Abstract
Since the discovery of the Jonah field in 1977, many styles of hydraulic fracturing treatments have been employed to stimulate the Lance formation. Commercial production was not established in the field until the early 1990s, and technological improvements have permitted increased production since that time. Further trials of fracturing techniques, including slickwater fracs, induced stress diversion, and flow-through composite fracture plugs, continued over time. Since March 2010, channel fracturing treatments have been employed in the Lance formation in conjunction with more traditional, conventional fracturing treatments.
For the purpose of this paper, conventional fracturing treatments consist of either crosslinked gel or slickwater fracturing treatments. The proppant is added in a continuous manner with an increasing proppant concentration. For crosslinked gel treatments, the typical proppant is 20/40 -mesh white sand added up to a maximum of 6 lbm/gal. For the slickwater treatments, the typical proppant is 40/70- or 30/50- mesh white sand added up to a maximum of 3 lbm/gal. The channel fracturing treatments use a pulsed method of adding the proppant to the fluid. Instead of adding the proppant continuously, the proppant is turned on and off in approximately 15-second time intervals. This concept is intended to provide high-conductivity, unpropped open flow paths through hydraulic fractures held open by the proppant pillars.
To assess the effectiveness of the channel fracturing method in the Jonah field compared to conventional fracturing treatments, a spatial sampling technique was used. Spatial sampling is a documented method for comparing large groups of wells with their direct offsets. The original intent of the spatial sampling method was to identify underperforming wells; however, the method has also been employed as a way to compare various completion or stimulation techniques. In this case, spatial sampling was applied in an attempt to evaluate the effectiveness of the channel fracturing technique compared to conventional fracturing techniques using continuous proppant addition during the treatment. Five discrete areas of the Jonah field were included in the study. Only wells completed in the same time frame as the channel fractured wells were included. The treatment and production data for all wells were obtained from public sources. There might also be differences in production among the conventionally fractured wells, depending on whether a crosslinked or slickwater treatment was used; however, the effect of slickwater treatments, as opposed to crosslinked treatments, was not considered in this study.