bluuebunny/crossref_metadata_2025 huggingface dataset:
An Educational Game in Collaborative Logistics
Authors: D'Amours Sophie , Rönnqvist Mikael
Published: February 2013

We describe an educational game in collaborative logistics. The game is based on an award-winning application in cost allocation in transportation. The purpose of the game is to acquire an understanding of negotiation, coalition building, and cost/profit sharing when the players have different powers and hold different levels of information. The game is played with each player representing a single company. The challenge for the players is to find an efficient coalition and to share the benefits and costs of the collaboration. We describe the underlying case study, review basic concepts in game theory, outline the teaching case, and discuss experiences from running the game in several countries and with students in business, engineering, and forestry.
Call for Papers—Focused Issue of Transportation Science on Maritime Transportation and Port Logistics
Authors: Psaraftis Harilaos N.
Published: February 2013

Submission Deadline: May 31, 2013
Call for Papers—Focused Issue of Transportation Science on Facility Logistics
Authors: Koster René de , Gue Kevin , Vis Iris
Published: February 2013

Submission Deadline: April 30, 2013
New methods for the localization of discontinuities of the first kind for functions of bounded variation
Authors: Ageev Alexandr L. , Antonova Tatyana V.
Published: February 2013

We construct and study methods for approximating the positions (localization) of discontinuities of the first kind of a one-dimensional function.
Instead of the exact function, its approximation in and the perturbation level are known; smoothness conditions are imposed on the function outside
the discontinuities.
The number of discontinuities is countable, and all the discontinuities are divided into two sets: with the absolute value of the jump greater than some
positive and discontinuities satisfying a smallness condition for the value of the jump. It is required to find the number of discontinuities in the first
set and localize them using the approximately given function and the perturbation level. Since the problem is ill-posed, regularization algorithms should be used for its solution.
Under additional conditions on the exact function, we construct regular methods for the localization
of discontinuities and obtain estimates for the accuracy of localization and for the separability threshold, which is another important characteristic of the method.
The order optimality of the constructed methods on classes of functions with discontinuities is established.
An inverse problem for the quadratic pencil of non-self-adjoint matrix operators on the half-line
Authors: Bondarenko Natalia , Freiling Gerhard
Published: February 2013

We consider a pencil of non-self-adjoint matrix Sturm–Liouville
operators on the half line and study the inverse problem of constructing this pencil
by its Weyl matrix. A uniqueness theorem is proved, and a constructive algorithm for the solution
is obtained.
Variational smoothness assumptions in convergence rate theory—an overview
Authors: Flemming Jens
Published: February 2013

Variational smoothness assumptions are a concept for measuring abstract
smoothness of solutions to operator equations. Such assumptions are useful
for analyzing regularization methods, especially for proving convergence
rates in Banach spaces and in more general settings. We collect results from different papers published by several
authors during the last five years. The aim is to present an overview of
this relatively new concept to the interested reader without going too
deep into the details.
On the smoothness and convexity of Besov spaces
Authors: Kazimierski Kamil S.
Published: February 2013

In this paper we deal with Besov spaces . We show that generalized
forms of the polarization identity hold for the wavelet-characterization
of the Besov space norm. In particular we show that these spaces are
smooth of power type and convex of power type for .
A Laboratory Study to Predict the Rutting and Fatigue Behavior of Asphalt Concrete Using the Indirect Tensile Test
Authors: Wen Haifang , Bhusal Sushanta
Published: February 2013

Rutting, fatigue, moisture susceptibility, and thermal cracking are the primary distresses of asphalt pavement. Currently several test methods are used to predict the rutting and fatigue behavior of asphalt concrete. This study uses the indirect tensile (IDT) test to evaluate both the rutting and fatigue behavior of asphalt. Recycled concrete aggregate (RCA) and virgin aggregate are blended at different percentages (0 %, 20 %, 40 %, 60 %, 80 %, and 100 %) to produce mixes with a variety of fatigue and rutting performance. The IDT rutting test was performed by running high temperature IDT flow time and strength tests. In addition, flow number tests were performed using an asphalt mixture performance tester (AMPT). A strong correlation is observed between the high temperature IDT flow time/strength and flow number from AMPT. The test results show that IDT tests can be used to predict the rutting behavior of asphalt concrete at high temperatures. To characterize fatigue, cyclic IDT and monotonic fracture energy tests were performed at intermediate temperatures. At intermediate temperatures, good correlation is found between the fatigue life obtained from cyclic IDT test results and the fracture energy obtained from monotonic fracture test results. Based on the laboratory test results, the IDT test can be used to evaluate both the fatigue and rutting behavior of asphalt concrete. Considering that IDT testing has been used to characterize thermal cracking and moisture susceptibility, the IDT test has the potential to serve as a single performance test for fatigue, rutting, thermal cracking and moisture damage. Validation of the findings with more materials and field performance are recommended.
Stress-Relaxation Cracking Test for Welded Joints
Authors: Kuhn B. , Ullrich C. , Tschaffon H. , Beck T. , Singheiser L.
Published: February 2013

Scientific and technological research concerning the underlying damage mechanism and the evaluation of adequate countermeasures of so called strain-age (SAC), stress-relaxation (SRC), or ductility-dip cracking (DDC) of service exposed base materials and welded joints suffers a lack of specialized testing methods, that are able to detect the most cracking susceptible area of the weld and result in a definite “pass or fail” distinction for every single experiment without leaving ambiguity in the interpretation of testing results. For these reasons an advanced four-point-bending technique was developed on the basis of the three-point-bending test established by van Wortel. The proposed method was applied for evaluating the cracking susceptibility of Alloy617B welded joints. The technique proved to be suitable for the base metal as well as for welded joints. All as-welded joints failed by interdentritic fracture within the weld and the site of fracture corresponded well with the maximum hardness location (HV10) evaluated after the bending tests. The proposed testing method distinctively provided evidence for reduced cracking susceptibility of welded joints caused by a post-weld heat treatment (980°C, 3 h, air). All heat treated joints surpassed the bending test without cracking underlining the unambiguity of the proposed testing technique.
Advances in the Understanding of Gelation in the Framework of the Test ASTM D5133
Authors: Maroto-Centeno J. A. , Pérez-Gutiérrez T. , Quesada-Pérez M.
Published: February 2013

This work presents a theoretical survey that sheds light on the physical meaning of the gelation index, that is, the main parameter involved in ASTM D5133. More specifically, it is proved that the pulse-shaped region of the gelation curve can be explained as the relief of the supersaturation of the solution, which is a nucleation process that finishes when the saturation ratio takes a value equal to 1. Comparison between experiments and the theoretical approach put forward in this work reveals qualitative agreement. This work also confirms the poor reproducibility of ASTM D4684, which is an alternative test for the evaluation of gelation in engine oils. Particularly, it is shown that the poor reproducibility of this test can be attributed to a systematic error made during the measurements. The lack of accuracy of the temperature, in particular the final test temperature, could be the main cause for discrepancies between laboratories. Finally, it is shown that in order to predict gelation within ASTM D5133, not only must the gelation index be considered, but the gelation index temperature also plays an important role.
Improved Digital Image Correlation Method for Eliminating Pixel Shape-Induced Errors in Shear-Strain Calculations
Authors: Peng Bei , Huang Chengcheng , Zhou Wu , Yu Huijun , Zeng Zhi
Published: February 2013

Digital image correlation is widely used in non-contact displacement/strain measurements for numerous engineering applications. Under rigid body rotation or shear deformation, however, the calculated surface strain of specimens is unreliable when camera pixels are characterized by non-square geometry, that is, the width-to-height ratio of pixels is not 1. This study analyzes the computational errors introduced by cameras, and proposes a modified least-squares method that eliminates such errors when the strain field is calculated. Experimental results confirm that the algorithm validly and effectively computes shear strain.
Computation and Uncertainty Evaluation of Offset Yield Strength
Authors: Matusevich Ariel E. , Massa Julio C. , Mancini Reinaldo A.
Published: February 2013

This paper presents computer procedures for the calculation of offset yield strength (Sy) and for the evaluation of the uncertainty in its computation. Offset yield strength is obtained from the plot of stress-strain data recorded in a tension test, as the stress that corresponds to the intersection between the stress-strain curve and a line parallel to its proportional region (offset by a prescribed strain). In the proposed method, the problem is reduced to finding the point of intersection between two straight lines, one that fits the curve in the neighborhood of the intersection and the offset line. For the fitting of each line, we propose the use of a weighted total least-squares algorithm that takes into account uncertainties in both ordinates and abscissas. The evaluation of the uncertainty associated with Sy, in accordance with the Guide to the Expression of Uncertainty in Measurement, considers the correlation between the parameters involved in its calculation. The implementation of these procedures motivated the development of dedicated software for the computation of tensile parameters from tension-test raw data and for the estimation of their associated uncertainties. To validate the program, developed in MATLAB as a standalone application, we used a set of ASCII data curves that have agreed values for the tensile parameters and which are publicly available at the web site of the National Physical Laboratory of the United Kingdom. Using these curves we demonstrate the validity of the proposed method for the computation of Sy; to validate the uncertainty-evaluation procedure, we use the law of propagation of probability distributions through Monte Carlo simulation. The computational tool, whose capabilities are presented in this work, is currently being used at the Laboratory of Mechanical Testing of the National Institute of Industrial Technology (INTI), in Córdoba, Argentina.
Failure Analysis of a Set of Flapper Valves Under ALT With Alternative Test Device
Authors: Martins J. A. , Ferreira I. , Leite D. , Romão E. C.
Published: February 2013

In search of further understanding and continuous improvement of mechanical products which suffer dynamics loading, several methods of analysis have been applied, among them, computational simulations and laboratorial experiments. This paper aims to describe the failure mechanics of a regular flapper valve and valve reed used on Hermetic Compressors when tested under accelerated test conditions by a special device, created for testing purpose. The results obtained from the valve reed were plotted on a graph, which reveals the endurance under fatigue, versus the device speed/load change. These curves represent the obtained valve reed lifetime by Weibull ALT (accelerated life test) (statistical analysis). The values obtained were analysed using the normality and the probability approaches beyond t-student. The Weibull ALT graph (fatigue lifetime), microscopic analysis by SEM (scanning electron microscope) and EDS (energy dispersive spectroscopy) were performed on the failed valve reed surface as well as on the valve plate seat utilised throughout the tests.
Compressive Behavior of Square-Cell Titanium Honeycomb
Authors: Parsons Ryan , Frink Elizabeth , Lease Kevin , Dubnicka Suzanne
Published: February 2013

The purpose of this study was to experimentally characterize the compressive behavior of square-cell titanium honeycomb cores according to the American Society of Testing and Materials Standard C365-05. By varying the honeycomb cell size and height, as well as the foil thickness, many configurations of titanium honeycomb were manufactured utilizing a laser welding and expansion method. The test matrix consisted of 1080 compression specimens. The compression specimens were split evenly into stabilized and bare tests. At the conclusion of the characterization, a comprehensive statistical analysis was performed on the data. It was determined that the compressive behavior has a strong dependence on the relative density of the honeycomb. The compressive strength was found to be slightly affected by the presence of a stabilizing face sheet, and largely unaffected by specimen core height. The compressive modulus was affected by both the core height and the presence of a face sheet. The compression behavior of the honeycomb was compared with experimental results of honeycomb from existing publications and found to be consistent.
Serious Air Leak Syndrome Complicating High-Flow Nasal Cannula Therapy: A Report of 3 Cases
Authors: Hegde Satyanarayan , Prodhan Parthak
Published: February 2013

Despite the absence of clinical safety data, heated, humidified high-flow nasal cannula (HHFNC) therapy is increasingly being used as an alternative to positive-pressure ventilation in pediatrics. This use of HHFNC is “off label” because the US Food and Drug Administration’s approval for these devices was only for air humidification and not as a modality to provide positive distending pressure. For the first time we describe 3 cases who developed serious air leaks related to HHFNC therapy. The first child was a previously healthy 2-month-old male infant with respiratory syncytial virus bronchiolitis who developed a right pneumothorax on day 5 of his illness at 8 liters per minute (lpm). He subsequently required intubation and ventilation for 14 days. The second case involved an otherwise healthy 16-year-old boy with cerebral palsy who developed pneumomediastinum and died of its complications. He was receiving 20 lpm HHFNC therapy when he developed pneumomediastinum. The third case involved a 22-month-old, previously healthy boy who developed subdural hematoma secondary to abuse. He developed a right pneumothorax while receiving HHFNC at a flow of 6 lpm, requiring chest tube placement. These cases emphasize the need for extreme caution while using HHFNC for the off-label indication of providing positive distending pressure in children, especially at flows higher than the patient’s minute ventilation. A more detailed study to specifically look at the serious adverse events related to HHFNC is urgently needed.
A Novel Strategy for Hemolytic Uremic Syndrome: Successful Treatment With Thrombomodulin α
Authors: Honda Takashi , Ogata Shohei , Mineo Eri , Nagamori Yukako , Nakamura Shinya , Bando Yuki , Ishii Masahiro
Published: February 2013

Hemolytic uremic syndrome (HUS) is a life-threatening infectious disease in childhood for which there is no confirmed therapeutic strategy. Endothelial inflammation leading to microthrombosis formation via complement activation is the main pathology of HUS. Thrombomodulin is an endothelial membrane protein that has anticoagulation and anti-inflammatory effects, including the suppression of complement activity. Recombinant human soluble thrombomodulin (rTM) is a novel therapeutic medicine for disseminated intravascular coagulation. We administered rTM to 3 patients with HUS for 7 days and investigated the outcomes in view of the patients’ prognoses, changes in biochemical markers, complications, and adverse effects of rTM. Symptoms and laboratory data improved after initiation of rTM in all 3 patients. Abnormal activation of complements was also dramatically suppressed in 1 patient. The patients recovered without any complications or adverse effects of rTM. They were discharged having normal neurologic status and with no renal dysfunction. To our knowledge, this is the first report of rTM being used to treat HUS. These case reports show the positive effect of rTM in patients with HUS. Randomized controlled studies should be performed to assess the efficacy and safety of rTM for children with HUS.
Stressing Lipid Membranes: Effects of Polymers on Membrane Structural Integrity
Authors: Wang Jia-Yu , Cheng Chi-Yuan , Kausik Ravinath. , Chin Jaemin , Han Songi. , Marks Jeremy D. , Lee Ka Yee C.
Published: February 2013

Disruption of cell membranes triggers rapid metabolic energy exhaustion, then acute cellular necrosis. Cell membrane dysfunction due to loss of structure integrity is the pathology of tissue death in trauma, muscular dystrophies, reperfusion injuries and common diseases. It is now established that certain PEG-based biocompatible polymers, such as Poloxamer 188, Poloxamine 1107 and PEG, are effective in sealing of injured cell membranes, and thus can prevent acute necrosis if delivered within a few hours after injury. Despite these broad applications of PEG-based polymers for human health, the fundamental mechanisms of how PEG-based polymers interact with cell membranes are still under debate. Here, the effects of PEG-based biocompatible polymers on phospholipid membrane integrity under external stimuli (osmotic stress and oxidative stress) were explored using giant unilamellar vesicles (GUVs) as model cell membranes. Through fluorescence leakage assays and time-lapse fluorescence microscopy, we directly observed that the surface-adsorbed P188 can efficiently inhibits the loss of structural integrity of giant unilamellar vesicles (GUVs) under hypo-osmotic stress. We propose that the adsorption of polymers on the membrane surface is responsible for the cell membrane resealing process, while the insertion of the hydrophobic portion of the polymers increases membrane permeability. To elucidate the mechanism by which hydrophilic polymers help restore membrane integrity while their hydrophobic counterparts disrupt it,1H Overhauser Dynamic Nuclear Polarization (ODNP)-NMR spectroscopy, a newly developed NMR technique that provides unprecedented resolution for differentiating weak surface adsorption versus translocation of polymers to membranes, was employed to sensitively detect polymer-lipid membrane interactions through the modulation of local hydration dynamics in lipid membranes. Our study shows that P188—the most hydrophilic poloxamer known as a membrane sealant—weakly adsorbs onto the membrane surface, yet effectively retards membrane hydration dynamics. Contrarily, P181—the most hydrophobic poloxamer known as a membrane permeabilizer—initially penetrates past lipid headgroups and enhances intrabilayer water diffusivity. Consequently, our results illustrate that the relative hydrophilic/hydrophobic ratio of the polymer dictates its functions. These findings gleaned from local hydration dynamics are well supported by our thermodynamics and fluorescence data.
Ion Implanted Dielectric Films for an Improved Optical and Electronic Silicon Photovoltaic Response
Authors: Shalav Avi , Henderson Christian , Ratcliff Tom , Thomson Andrew
Published: February 2013

Over the past few years, ion implanters specifically developed for the high throughput required by the silicon photovoltaic industry, have become commercially available. Recent research and development has focused on the formation of doped surface regions, particularly the formation of selective emitters. In this study we explore two effects of ion implantation into a thermal silicon dioxide passivating/antireflection dielectric. We show evidence that the electronic and optical performance of the layer can be improved via the incorporation of charges created within the dielectric film and the creation of a graded refractive index, minimizing the surface recombination and reflection losses respectively.
Determination of the Density of States on N-type Ptcdi-c13 Organic Thin-film Semiconductor
Authors: Puigdollers J. , Marsal A. , Galindo S. , Carreras P. , Voz C. , Bertomeu J. , Alcubilla R.
Published: February 2013

In this paper we study the density of states in n-type N,N’-ditridecylperylene-3,4,9,10-tetracarboxylic diimide organic semiconductor using two different methods. The first one is based on the temperature dependence of the channel conductance in field-effect transistors. The second one is based on the subgap optical absorption coefficient measured using the Photothermal Deflection Spectroscopy technique. Both techniques allow estimating the distribution of localized states in the band gap of the semiconductor.
Enhanced Electrocaloric Effect in Poly(vinylidene fluoride-trifluoroethylene)-based Composites
Authors: Chen Xiang-Zhong , Qian Xiao-Shi , Li Xinyu , Lu David Sheng-Guo , Gu Haiming , Lin Minren , Shen Qun-Dong , Zhang Qiming
Published: February 2013

The poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) based ferroelectric and relaxor materials have been proved to be good electrocaloric (EC) materials. To further enhance the EC effect in ferroelectric relaxor terpolymer poly(vinylidene fluoride–trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), composites such as polymer-polymer blends and nanocomposites filled with inorganic nanoparticles are fabricated and investigated. It is found that the addition of small amount of filler (such as P(VDF-TrFE) or nano-ZrO2) can increase terpolymer’s crystallinity and enhance its relaxor behavior through interface couplings. The increased crystallinity and enhanced relaxor behavior together result in enhanced electrocaloric effect. The results demonstrate the promise of composite approaches in tailoring and enhancing ECE in the relaxor terpolymers.
Precursor Investigation in the Synthesis of PtPb Nanocatalysts
Authors: Porter Nathan , Wu Hong , Kong Minji , Sun Kai , Kumbhar Amar , Fang Jiye
Published: February 2013

In recent years, platinum-based single crystalline nanoalloys as nanoscale catalysts, such as Pt-M (M = Ni, Co, Fe..etc.), have exhibited improved catalytic performance due to the increase in the surface-to-volume ratio. Some Pt-M nanopolyhedra such as nanocubes and nano-octahedra have been reported with enhanced activity when being used as electrocatalysts. In order to further establish a correlation between the exposed nanocrystal facets (shapes) and their corresponding activities, a pursuit of shape-controlled nanocatalyst synthesis is essential. Although PtPb nanoalloys have been prepared using solution-based methods, few studies have highlighted their catalytic activity as a function of the nanocrystal shape. This work focuses on a modified polyol synthesis technique and an adjustment of the Pb-metal precursor, which serves as a “buffer” in the nucleation stage of the shape-controlled nanoalloy development. Using this developed synthetic strategy, shape-controlled hexagonally close-packed PtPb nanoalloys can be prepared in a one-pot synthesis without additional post-treatment. The as-prepared PtPb nanocrystals demonstrate an improved anode electrocatalytic performance.
Over 12% Light to Hydrogen Energy Conversion Efficiency of Hydrogen Generation from Water: New System Concept, Concentrated Photovoltaic Electrochemical Cell (CPEC)
Authors: Fujii Katsushi , Nakamura Shinichiro , Watanabe Kentaroh , Bagheri Behgol , Sugiyama Masakazu , Nakano Yoshiaki
Published: February 2013

Energy storage is a key technology for establishing a stand-alone renewable energy system. Current energy-storage technologies are, however, not suitable for such an energy system. They are cost ineffective and/or are with low energy-conversion efficiency. Hydrogen generation and storage from water by sunlight is one of these technologies. In this study, a simple concept of hydrogen generation from water by using sunlight, “concentrated photovoltaic electrochemical cell (CPEC)” is proposed. It is experimentally shown that the CPEC operates stably and achieves conversion efficiency from light to hydrogen energy of over 12%.
Optical band-gap of TiO2 nanopowders doped with Al2O3
Authors: Yoshimura Keisuke , Hashimoto Tetsuya , Katsumata Hiroshi
Published: February 2013

Optical band-gap and cathode luminescence (CL) properties of anatase TiO2 nanopowders mixed with γ- Al2O3 powders by planetary ball mill were evaluated as a function of a powder mass ratio (x=Al2O3/TiO2) of 0 to 0.5 and their correlation with XRD spectra was also investigated. The optical band-gap of TiO2 increased from 3.36 eV to 3.41eV with increasing milling time (tm) up to 600 min, which was in good agreement with the blue shifts observed in the CL spectra with increasing tm and it was interpreted as a quantum size effect. In addition, the optical band-gap of TiO2 powders mixed with Al2O3 with tm=60min greatly increased from 3.36 eV to 3.48 eV with increasing x up to x=0.5. On the other hand, the optical band-gap of all the powders was decreased by annealing at temperatures above 600°C, which was evidenced by the XRD spectra to be due to the growth of grain size.
Intensity-Modulated Photovoltage Spectroscopy at Evaporated Bulk Heterojunctions of PcCu and C60to Determine the Average Effective Lifetime of Charge Carriers
Authors: Dragässer André , Schlettwein Derck
Published: February 2013

Organic solar cells consisting of Phthalocyaninatocopper (PcCu) as donor and the Buckminsterfullerene C60as acceptor molecule were prepared by physical vapor deposition as planar or bulk heterojunctions. The devices were studied by IV-characterization as well as intensity-modulated photovoltage spectroscopy to determine the average lifetime of charge carriers formed subsequent to light absorption. An increasing charge carrier lifetime was determined for an increasing PcCu-content in the films. Back transfer of electrons at the undesired contact of C60with PEDOT:PSS as well as recombination following hole trapping in interface states in the contact of PcCu with C60or in isolated domains of PcCu are discussed as possible origins.
Effect of Nitric Acid Concentration on Doping of Thin Film Single-walled Carbon Nanotubes for Electrode Application in Transparent, Flexible Dye Sensitized Solar Cells
Authors: Zhang Liling , Rao Manohar , Kochupurackal Jinesh , Mathews Nripan , Lam Yeng Ming , Mhaisalkar Subodh G.
Published: February 2013

A simple method is proposed for the chemical modification of carbon nanotubes (CNT) thin film counter electrodes (CE) for the replacement of fluorine-doped tin oxide (FTO) and platinum catalyst (Pt) while retaining light transparency. In order to decrease the sheet resistance, CNT thin films underwent various concentrations (≤10 M) and durations of HNO3 treatment prior to cell fabrication, and the effect on thin film properties was analyzed. P-doping was observed, and the maximum change in work function was found to be +0.35 eV with 4 M HNO3. Optimum sheet resistance reduction (50%) and work function increment were achieved after 1 h treatment with 4 M HNO3. Changes in optical transmittances for all samples were negligible (± 5%). Pristine and HNO3 treated films on plastic substrates were tested as CE in flexible bifacial dye sensitized solar cells (DSSC). Most significant improvements in conversion efficiencies were obtained when CNT on plastic substrates were pretreated with 8 M HNO3 (from 1.18% to 1.40% under roomlight, from 0.19% to 0.26% under 1 Sun).
High-temperature thermoelectric properties of W-substituted CaMnO3
Authors: Alfaruq Dimas S. , Eilertsen James , Thiel Philipp , Aguirre Myriam H , Otal Eugenio , Populoh Sascha , Yoon Songhak , Weidenkaff Anke
Published: February 2013

The thermoelectric properties of W-substituted CaMn1-xWxO3-δ (x = 0.01, 0.03; 0.05) samples, prepared by soft chemistry, were investigated from 300 K to 1000 K and compared to Nb-substituted CaMn0.98Nb0.02O3-δ. All compositions exhibit both an increase in absolute Seebeck coefficient and electrical resistivity with temperature. Moreover, compared to the Nb-substituted sample, the thermal conductivity of the W-substituted samples was strongly reduced. This reduction is attributed to the nearly two times greater mass of tungsten. Consequently, a ZT of 0.19 was found in CaMn0.97W0.03O3-δ at 1000 K, which was larger than ZT exhibited by the 2% Nb-doped sample.
The Team Approach to Replacing the Congenitally Missing Lateral Incisor: Restorative and Periodontal Considerations
Authors: Clem Donald S. , Hinds Kenneth F.
Published: February 2013

Introduction: The replacement of congenitally missing maxillary lateral incisors can be a challenge from both a restorative and surgical perspective. The restorative dentist is limited in achieving esthetics by the surgical result not only by the implant position but by the surrounding periodontium of the site itself, as well as the adjacent teeth. The present case, replacing congenitally missing lateral incisors with an immediate provisional restoration, is important because it demonstrates the ideal team approach. By each clinician participating in stage I surgery, the restorative dentist and periodontist can work toward an optimal result. The combination of restorative expertise and regenerative enhancements simultaneously can result in a minimally invasive approach with fewer appointments and greater patient acceptance.

Case Presentation: This case report demonstrates the restorative and surgical considerations and techniques for prefabrication of screw‐retained provisional restorations placed at the time of surgery. Surgical considerations and techniques to support the restoration position, size, and screw retention connection are also presented.

Conclusions: Close communication between treatment team members is critical to achieving predictable esthetics and function for congenitally missing maxillary lateral incisors. The participation of the restorative dentist at stage I surgery is critical in demanding esthetic cases such as this. Periodontal hard and soft tissues respond well to prefabricated screw‐retained provisional restoration delivered at the time of surgery.
Self-Suspending Proppant
Authors: Mahoney R. P. , Soane D. , Kincaid K. P. , Herring M. , Snider P. M.
Published: February 2013

Presented here is a new approach to hydraulic fracturing, using proppants that self-suspend in water. To form these self-suspending proppants (SSP), conventional proppant particles are encapsulated with a thin layer of a high-molecular-weight hydrogel polymer, and then dried, yielding a free-flowing granular system that can be handled much like traditional proppants. Once the SSP contacts water, the hydrogel layer expands spontaneously and it forms a space-filling cushion around each granule. These SSPs were created to address the performance limitations that exist with traditional proppants. In contrast to traditional proppants, SSPs remain well suspended and evenly distributed within fracturing fluid. The new technology can be applied to a variety of proppant substrates.

Properties of the SSP arise from the hydrogel formulation used as their coating. Upon hydration in water, the hydrogel coating around the proppant particles imbibes water quickly and swells substantially, expanding the hydrodynamic radius of the polymer-enveloped solid core. In addition, any SSP particles that settle are easily resuspended upon restart of flow. The self-suspending proppant approach delivers proppants efficiently with the hydraulic fracturing fluid and results in no observable segregation/sedimentation. Conventional breakers are used to reverse the effect of the hydrogel layer, releasing the proppant into the fracture after transport.

Conventional proppants have a tendency to settle out of the carrier fluid, causing segregation during pumping. By contrast, the self-suspending proppant technology enables complete proppant suspension until deposition in the fracture. Moreover, using SSP can eliminate the need for the viscosity and suspension properties of a gel carrier entirely, thereby reducing the hydraulic pumping pressure for proppant transport. This self-suspending proppant technology offers a promising alternative to the proppant systems currently available for hydraulic fracturing applications. The major benefit of the SSP is better placement of proppant in the fracture, leading to lower water injection requirements, lower proppant usage, and improved well productivity.
Development and Use of High-TDS Recycled Produced Water for Crosslinked-Gel-Based Hydraulic Fracturing
Authors: Lebas R. , Lord P. , Luna D. , Shahan T.
Published: February 2013

Large quantities of high-total dissolved solids (TDS) produced water are generated during oil and gas production in Eddy County, New Mexico (more than 164 million bbl in 2011). Most of the high-saline produced water is reinjected into disposal wells at an average cost of USD 0.75 to USD 1.00 per bbl. Caused in part by the persistent drought conditions in New Mexico, beneficial use of produced water is receiving attention in the oil and gas industry. One alternative being considered is the use of produced water for hydraulic fracturing operations. Typically, wells in the Delaware basin require 40,000 to 60,000 bbl of fresh water each for hydraulic fracturing job during well development. As such, reclaiming produced water as the base fluid for fracturing not only helps alleviate the industry’s dependence on fresh water but can also lower the overall cost of the well stimulation treatment.

Using produced water exceeding TDS values of 270,000 ppm is key to reclamation and reuse programs in the Delaware basin. This paper discusses a project to (1) identify the critical parameters and the corresponding optimal ranges in the laboratory, that will allow use of treated produced water as a base fluid for crosslinked-gel-based hydraulic fracturing, and (2) evaluate the validity of the laboratory findings under actual field conditions.

High-TDS produced water from a Brushy Canyon producing well near Carlsbad, New Mexico was used as the base fluid for the bench-scale experiments. Crosslinked gels were formulated with carboxymethyl hydroxypropyl guar gum (CMHPG), a zirconium-based crosslinker, sodium chlorite breakers, and other ingredients. The apparent viscosity of the gels was measured using Chandler Model 5550 high-pressure/high-temperature (HP/HT) viscometers. The bottomhole temperature simulated in the experiments was approximately 140°F. The rheological effects of several parameters, including pH, salinity, and scaling tendencies, were evaluated. Other factors, including organics and suspended solids, are included in the discussion. In addition, a field test performed following the bench-scale experiments to validate the laboratory findings under the actual stimulation conditions is discussed. Results indicate that the fracturing treatment using high-TDS produced water successfully created a fracture network and transported sand into that fracture network.
Production Forecasting of Hydraulically Fractured Conventional Low-Permeability and Unconventional Reservoirs Linking the More Detailed Fracture and Reservoir Parameters
Authors: Sierra Leopoldo , Mayerhofer Mike , Jin C. J.
Published: February 2013

Fracture stimulation and production forecasting are two important processes for conventional low-permeability or unconventional reservoirs. Fracture stimulation of either type of reservoir helps assure commercial production rates or maximize exploitation, while proper production forecasting informs the operator in advance of the potential short- and long-term value of the well and the area.

To provide more accurate recovery forecasts for conventional low-permeability or unconventional reservoirs, one must consider the key parameters of the generated hydraulic fracture, including effective fracture length (affected by filtrate clean-up and fracture damage), relative differences in fracture and formation flow capacity (e.g., dimensionless fracture conductivity), proppant distribution, tapered fracture conductivity, and stress dependence of the fracture conductivity. In addition, stress dependence of reservoir permeability and reservoir fluid properties also have a major impact. Non-darcy and multiphase flow effects inside the fracture have been extensively discussed in the literature and will not be discussed in this paper but can be indirectly included when considering the discussion on reduced fracture conductivity.

For the horizontal wellbore architecture commonly used to exploit unconventional reservoirs, the knowledge of the optimum number of fractures to maximize the recovery is very important. This paper uses a numerical reservoir simulation study to develop simple correlations that quantify what fracture spacing is necessary to optimize recovery factors in unconventional gas reservoirs and how various hydraulic fracture parameters and non-ideal reservoir behaviors affect the horizontal well completion design.

Because the reservoir simulation process can take significant time and effort, and analytical solutions are sometimes very complex, a simple "back of the envelope" methodology to estimate the optimum fracture spacing can be advantageous for everyday use and a starting point for completion optimization. This paper also discusses how deviations from ideal behavior, in terms of fracture and reservoir properties, can affect the well design.
Proppant Distribution in Multistage Hydraulic Fractured Wells: A Large-Scale Inside-Casing Investigation
Authors: Crespo Freddy , Aven Nevil Kunnath , Cortez Janette , Soliman M. Y. , Bokane Atul , Jain Siddharth , Deshpande Yogesh
Published: February 2013

Effectively stimulating multiple pay zones using separate fracturing treatments can be costly and time consuming. By contrast, multistage fracturing is a widely used technique that offers the advantage of stimulating significant portions of the reservoir by fracturing through multiple perforations simultaneously. While the multistage fracturing method known as "plug and perf" has been proven to be an effective method for developing unconventional resources, it presents the challenge of achieving even proppant distribution to all perforation clusters during each stimulation stage.

It is commonly assumed that the plug and perforate multistage fracturing technique provides the planned fluid and proppant distribution among the fractures that are simultaneously taking fluid during pumping a single stage. However, parameters, such as the reservoir properties, fluid rheology, and proppant characteristics have demonstrated a strong influence on the actual proppant and fluid distribution into the various perforations.

Field data indicates, in many cases, that some of the clusters do not contribute to production. This indication supports the hypothesis that actual proppant and fluid distribution along the stimulated clusters might be different from the assumed uniform distribution. Some believe that the amount of proppant appears to be heavily weighted toward the end of the perforated interval, which results in uneven proppant distribution. Empirical data as well as laboratory tests have yet to be challenged against the few studies that exist.

This paper presents a first- of-its-kind large-scale investigation that was conducted to study proppant distribution among separated perforations along a horizontal interval. These experiments closely simulate any single stage during the plug-and-perforate fracturing process. The effect of various fluid specific gravities, fluid viscosities, proppant specific gravities, proppant sizes, and slurry flow rates were investigated while keeping outside-casing parameters constant. The various aspects of proppant and fluid flow through a perforated interval are discussed. The experimental efforts discussed in this paper create a better understanding of fluid and proppant behavior in this widely used fracturing process to help achieve maximum efficiency.
Constraints on Simultaneous Growth of Hydraulic Fractures from Multiple Perforation Clusters in Horizontal Wells
Authors: Bunger A. P. , Jeffrey R. G. , Zhang X.
Published: February 2013

In spite of the fact that multistage hydraulic fracturing from horizontal wells is the fastest growing and arguably the most economically important application for well stimulation, there remain a number of fundamental questions relevant to determining how long to make each isolated interval and how many perforation clusters to place within each interval. This paper provides new insights to this problem by predicting how many hydraulic fractures can be expected to grow simultaneously from multiple perforation clusters pressurized by a single injection stage. These predictions are obtained from a coupled mathematical model that includes the contributions of fluid flow, rock breakage, and pressure loss through the perforations to the total power requirements for growth of arrays of multiple hydraulic fractures. For typical shale gas stimulations, radial hydraulic fractures are predicted to grow from all perforation clusters, with progressive reduction in the number of hydraulic fractures so as to maintain a ratio of the radius to the spacing that is a bit less than one. If the hydraulic fractures are contained to a height H, then multiple PKN-like hydraulic fractures are predicted to continue growing, with the length of each hydraulic fracture increasing throughout the injection and with a spacing that is approximately 1.5H when perforation losses are strong and approximately 2.5H when perforation losses are negligible. These geometric predictions are consistent with previously published observations based on microseismicity associated with stimulations in the Barnett Shale.
Diagnostic Fracture Injection Testing Tactics in Unconventional Reservoirs
Authors: Cramer D. D. , Nguyen D. H.
Published: February 2013

To achieve optimal production from unconventional reservoirs, it is useful to determine the permeability, pore pressure, and state of stress of rock strata. Doing so will lead to properly designed treatments, realistic predictions of well performance, and a basis for normalizing reservoir contribution when evaluating completion and stimulation effectiveness.

An effective way to derive the necessary reservoir information is to conduct in-situ pressure transient tests. Since it is difficult to inject fluid into or withdraw fluid from the pore network of tight rock, diagnostic fracture injection tests (DFIT) have been employed to create an analyzable pressure decline response, as well as to derive the minimum horizontal stress via fracture closure identification.

This paper is a study of numerous DFITs conducted in unconventional reservoirs throughout the world to evaluate the reservoir and geomechanical characteristics of the pay zone and bounding intervals. Within this body of work, experiments were implemented to study the impact of testing methods on the test response and various types of analysis methods documented in the literature were implemented and compared. The paper summarizes findings and introduces tactics for planning/conducting tests and evaluating results in a variety of unconventional reservoir types.

Topics covered in the paper include:

Defining test objectives Test planning and strategies ○ Tactics for selecting injection rates and volumes ○ Downhole shut-in techniques for hastening fracture closure and radial flow regime development. ○ Vertical vs. horizontal wells ○ Multiple injection-falloff cycles. ○ Multi-interval tests ○ Multiple non-communicating pressure gauges. ○ Tactics for understanding test height Pre-test fracture modeling for selecting injection volumes and rates and test intervals. Procedure/execution Reservoir and geomechanical considerations ○ Sub-pressured reservoirs ○ Fracture closure ○ Impact of natural fractures ○ Near-wellbore fracture complexity
Evaluating the Impact of Mineralogy, Natural Fractures and In Situ Stresses on Hydraulically Induced Fracture System Geometry in Horizontal Shale Wells
Authors: Miller Camron , Hamilton Daniel , Sturm Stephen , Waters George , Taylor Thomas , Le Calvez Joel , Singh Manish
Published: February 2013

The objective of this study is to better understand the impact of mineralogy, in-situ stress and natural fractures on hydraulically-induced fracture system geometry within horizontal organic shale wells. Vertical heterogeneity within organic shale occurs at a much smaller scale than that in the lateral direction. Previous studies involving borehole image analyses suggest that the lateral variability observed in most horizontal shale wells is the result of the wellbore traversing multiple layers of different rock properties (i.e., vertical heterogeneity). Results have shown that a more efficient and effective hydraulic fracture stimulation is possible when this variability is addressed in the completion design.

Borehole micro -resistivity image data from horizontal wells in multiple U.S. shale basins are analyzed and compared to borehole -based micro -seismic data. Natural and drilling-induced fracture type, spacing and orientation are analyzed in order to reveal their impact on hydraulic fracture initiation and geometry. Natural fracture orientation relative to the maximum horizontal stress has been shown to influence hydraulically-induced fracture system geometry. Drilling-induced fractures are essentially miniature hydraulic fractures and provide information about near wellbore in-situ stresses that can be used to predict relative hydraulically -induced fracture initiation pressures and geometry. Previous studies have shown that fracture initiation pressure is directly proportional to clay content within organic shale reservoirs.

This study provides an improved understanding of factors that ultimately control the economics of horizontal shale wells. Horizontal measurements collected during drilling or post-drill allow for (i) understanding where the wellbore is in section (i.e., well placement), (ii) visualization of how the reservoir characteristics are changing along the lateral wellbore (i.e., heterogeneity) and, (iii) planning the stimulation accordingly (i.e., treatment design). These data allow operators to predict how certain reservoir properties impact reservoir stimulation. Such correlations should lead to improved operational efficiency and better well performance, thereby increasing return on investment.