bluuebunny/crossref_metadata_2025 huggingface dataset:
The RAND Health Insurance Experiment, Three Decades Later
Authors: Aron-Dine Aviva , Einav Liran , Finkelstein Amy
Published: February 2013

Between 1974 and 1981, the RAND health insurance experiment provided health insurance to more than 5,800 individuals from about 2,000 households in six different locations across the United States, a sample designed to be representative of families with adults under the age of 62. More than three decades later, the RAND results are still widely held to be the “gold standard” of evidence for predicting the likely impact of health insurance reforms on medical spending, as well as for designing actual insurance policies. On cost grounds alone, we are unlikely to see something like the RAND experiment again. In this essay, we reexamine the core findings of the RAND health insurance experiment in light of the subsequent three decades of work on the analysis of randomized experiments and the economics of moral hazard. First, we re-present the main findings of the RAND experiment in a manner more similar to the way they would be presented today. Second, we reexamine the validity of the experimental treatment effects. Finally, we reconsider the famous RAND estimate that the elasticity of medical spending with respect to its out-of pocket price is – 0.2. We draw a contrast between how this elasticity was originally estimated and how it has been subsequently applied, and more generally we caution against trying to summarize the experimental treatment effects from nonlinear health insurance contracts using a single price elasticity.
The Case Against Patents
Authors: Boldrin Michele , Levine David K
Published: February 2013

The case against patents can be summarized briefly: there is no empirical evidence that they serve to increase innovation and productivity, unless productivity is identified with the number of patents awarded—which, as evidence shows, has no correlation with measured productivity. Both theory and evidence suggest that while patents can have a partial equilibrium effect of improving incentives to invent, the general equilibrium effect on innovation can be negative. A properly designed patent system might serve to increase innovation at a certain time and place. Unfortunately, the political economy of government-operated patent systems indicates that such systems are susceptible to pressures that cause the ill effects of patents to grow over time. Our preferred policy solution is to abolish patents entirely and to find other legislative instruments, less open to lobbying and rent seeking, to foster innovation when there is clear evidence that laissez-faire undersupplies it. However, if that policy change seems too large to swallow, we discuss in the conclusion a set of partial reforms that could be implemented
Adsorption of CO2 on C,N–TiO2 Surfaces
Authors: Janus Magdalena
Published: February 2013

Modification of the TiO2 surface by carbon and nitrogen results in the formation of photocatalysts that have high sorption capacity for CO2. The photocatalysts were obtained as follows: approximately 1 g of bare TiO2 was placed in a furnace and kept for 1 hour at a temperature from 100 to 600 °C. The sample was first placed under argon atmosphere, following which it was placed under an atmosphere of carbon and nitrogen, achieved by passing ammonia via a washer with n-hexane. This treatment is continued for 1 hour, following which the sample was cooled down to room temperature under argon atmosphere. The photocatalysts thus obtained were characterized by Fourier transform-infrared/diffuse reflectance spectroscopy, UV–Vis/diffuse reflectance, X-ray diffraction and Brunauer, Emmett and Teller surface area measurements. In addition, the zeta potential of the surface of photocatalysts was measured. Sorption tests were conducted in a special reactor using the following conditions: temperature: 20 °C, gas flow rate: 100 cm3/minute; CO2 concentration: 1000 ppm. Our results show that the best sorbent was TiO2 modified at 100 °C for 1 hour. Its sorption capacity amounted to 6.63 mg of CO2 on 1 g of C,N–TiO2 photocatalyst.
Preparation and Characterization of Calcium Silicate for CO2 Sorption
Authors: Kale Kishor B. , Raskar Reshma Y. , Rane Vilash H. , Gaikwad Abaji G.
Published: February 2013

An attempt has been made to develop different samples of calcium silicate and to screen these samples for CO2 sorption and alkalinity in order to achieve maximum CO2 sorption. The CO2 sorption capacity of these samples was examined at different temperatures. Various methods such as solid–solid fusion, sol-gel, molten salt and templates (CTAB, cetyltrimethylammonium bromide or Aliquat 336, tricaprylmethylammonium chloride) were used to prepare the calcium silicate samples. The solid mass of calcium silicate samples were obtained by calcining the solid product obtained in an atmosphere of air or helium at 900 °C for 3 hours. The calcium silicate samples were characterized for surface area, alkalinity, scanning electron microscopic images and X-ray diffraction patterns. The temperature profile of CO2 sorption by calcium silicate was studied in the temperature range of 40–850 °C. Our results showed that the alkalinity and surface area of calcium silicate were in the range from 2.35 to 20 mmol g−1 and 1.4 to 10 m2 g−1, respectively. The sorption of CO2 at 500 °C over calcium silicate for the different Ca/Si mol ratio (range: 1–6) was found to be in the range from 3.12 to 29.96 wt%. Addition of a promoter such as sodium, potassium, caesium and lanthanum was found to enhance the sorption of CO2 by calcium silicate. Several samples of different mol ratios of Ca/Si prepared by different methods were tested for the sorption of CO2 at 500 °C.
Turbulence Modeling Advances and Validation for High Speed Aeropropulsive Flows
Authors: Dash Sanford M. , Brinckman Kevin W. , Ott James D.
Published: February 2013

Advances made in extending a unified k–ε based RANS turbulence model to “more reliably” analyze high-speed aero-propulsive flows are discussed. The unified model solves additional scalar fluctuation model (SFM) equations to predict variations in turbulent Prandtl and Schmidt numbers, which can be quite substantial for these types of flows. The discussion includes a historical perspective of the developmental work performed as well as an overview of the current modeling status. RANS modeling still plays a dominant role in the “practical” analysis of aeropropulsive flows. It is used for preliminary design and design-optimization studies, where a large matrix of calculations must be performed, and, in the application of hybrid RANS/LES methodology, where the use of LES is often restricted to massively separated or jet/free shear regions of the flow. In extending the model, we have adhered to a “building-block” philosophy using data sets of increasing complexity and emphasizing high-speed applications where compressibility effects can play a dominant role. Fundamental laboratory data sets as well as benchmark LES/DNS solutions have been used for model calibration and validation, with several key comparisons presented in this article. Recent extensions described in this article include: low Re extensions to the SFM model improving near wall predictions; a compressibility/density gradient correction to the species fluctuation equation improving mixing predictions; and, a baroclinic torque correction to the kinetic energy equation improving predictions for angled jets. This article shows how these extensions serve to improve comparisons with data for a number of basic aeropropulsive flows, and it also discusses utilization of the unified RANS model in a hybrid RAN/LES DES modeling framework.
Effects of Jet Noise Source Distribution on Acoustic Far-Field Measurements
Authors: Kuo Ching-Wen , Veltin Jérémy , McLaughlin Dennis K.
Published: February 2013

Jet noise production is well known to be of a distributed nature along the jet, with high frequency noise components radiating from locations close to the nozzle exit and low frequency noise being produced farther downstream, around the end of the potential core. Such a distributed source implies that measurements need to be made at a significant distance from the source in order to be in the true geometric (acoustic) far field. The current study presents measurements of fully expanded Mj = 1.5 jets operating with cold air and heat simulated at TTR = 2.2 made at various positions in the acoustic field, some short of the minimum distance required to be in the true geometric far field. A close look is taken at the details of the noise generation region in order to better understand the mismatch between spectra measured at various acoustic field radial locations. A processing method is presented to correct for near-field effects and efficiently compare near and far field spectra with unprecedented accuracy. This technique is then further used to clarify the nonlinear propagation effects that can be observed at the high frequency end of high speed jets noise.
Aeroacoustics of Twin Supersonic Jets: A Review
Authors: Raman Ganesh , Panickar Praveen , Chelliah Kanthasamy
Published: February 2013

Interaction of twin supersonic jets can dramatically alter the dynamic pressures in the near-field and cause fatigue of aircraft structures. This review paper focuses on the twin jet coupling situation that is rich in fluid flow physics, requires sophisticated analysis tools and is of relevance to aircraft with closely spaced engines and other industrial situations involving multiple jet flows. The review consists of four sections: (i) a historical survey of twin jet exhaust coupling, (ii) rectangular twin jets with both spanwise uniform and non-uniform geometry, (iii) a description of multi-modes and mode jumps using higher order spectral analysis, and (iv) the suppression of twin jet coupling. The parameters that affect twin jet coupling include nozzle geometry, internozzle spacing and nozzle operating conditions. Certain modes of resonant coupling increase the dynamic pressures drastically in the inter-nozzle region, whereas other coupling modes can suppress unsteady pressure levels. Since coupled resonances can cause fatigue failure of components, mitigation approaches need to be considered. Successful techniques include nozzle inserts, beveled nozzles, water injection, and miniature pins and cavities.
Stock Prediction Based on Phase Space Reconstruction and Echo State Networks
Authors: Zhang Huaguang , Liang Jiuzhen , Chai Zhilei
Published: February 2013

In this paper a synthetic model for stock prediction is proposed based on phase space reconstruction, Echo State Networks (ESN) and Moving Average Convergence/Divergence (MACD). In this model, time series data is reconstructed in phase space before feeding to the ESN. Guided by the MACD strategy, stock prices are predicted and valuable trading advices are provided. The proposed model is tested by Microsoft Company stock price. The experiments are compared with those provided by other models such as BackPropagation Neural Networks (BNN), Support Vector Machine (SVM), Hidden Markov Model (HMM) and Procedural Neural Networks (PNN). The test results show that the proposed model is effective and efficient in stock price prediction.
Strategic Flexibility and International Venturing by Emerging Market Firms: The Moderating Effects of Institutional and Relational Factors
Authors: Liu Heng , Jiang Xu , Zhang Jianqi , Zhao Xinglu
Published: February 2013

Emerging market (EM) firms adopt international venturing strategies as they seek global opportunities, yet research to date has not fully explored the factors driving this phenomenon. Adopting the dynamic capability theory, this study investigates how strategic flexibility affects EM firms in their international venturing efforts and considers critical institutional and relational assets that act as moderators. Data from a sample of 135 Chinese firms with two key informants each indicate that strategic flexibility is positively related to EM firms’ international venturing. In addition, high levels of domestic institutional support and strong ties with foreign organizations further enhance this positive linkage. This study adds a dynamic capability view to the explanations for this new phenomenon. The authors conclude with a discussion of contributions, implications, and future directions.
Technological Capability Growth and Performance Outcome: Foreign versus Local Firms in China
Authors: Ju Min , Zhou Kevin Zheng , Gao Gerald Yong , Lu Jiangyong
Published: February 2013

This study examines the growth and performance impact of technological capability (TC) in China. The authors posit that foreign and local firms exhibit different TC growth patterns and that TC has differential performance effects for these two types of firms. From a multilevel analysis of five-year panel data of 448 technology-oriented firms, they find that, in general, foreign firms possess higher levels of TC, whereas local firms can develop their TC faster than foreign firms. Furthermore, compared with foreign firms, local firms experience a stronger performance return from their TC; however, foreign firms have a higher growth rate in the contribution of TC to their performance over time. Moreover, firms can develop TC faster in regions with better intellectual property protection, and TC exerts a stronger effect on performance when industrial uncertainty is higher.
Nerve growth factor reduces myocardial ischemia/reperfusion injury in rat hearts
Authors: Strande Jennifer L. , Routhu Kasi V. , Lecht Shimon , Lazarovici Philip
Published: February 2013

Background: Nerve growth factor (NGF) is a neurotrophin that supports the survival and differentiation of sympathetic neurons, and its increased expression after myocardial infarct was correlated with cardiac sympathetic hyperinnervation and arrhythmias. However, it is unclear whether NGF protects the heart during infarct. In this study, we sought to address this issue in rat heart exposed to ischemia/reperfusion injury (IRI).

Methods: NGF was administered intravenously (IV), 15 min before ischemia, at different concentrations in the absence or presence of inhibitors of phosphatidylinositol-3 kinase (PI3K) or nitric oxide synthase (NOS) in different groups of rats (n=6) with left coronary occlusion for 30 min followed by 120-min reperfusion. The area at risk and infarct to risk ratios were determined from sections stained with 1% 2,3,5-triphenylterazolium chloride.

Results: NGF treatment at doses of 0.015–15 μg/kg, with an optimal dose of 0.15 μg/kg given IV before ischemia, reduced the infarct size from about 60% at the area of risk to about 25%, indicating cardioprotection by about 60%. The infarct-sparing effects of NGF were partially abolished by the inhibition of PI3K and NOS using wortmannin and N(G)-monomethyl-l-arginine, respectively.

Conclusions: We have demonstrated for the first time that NGF attenuates myocardial infarct damage in an in vivo rat model of myocardial regional IRI. This cardioprotective effect is proposed to be related to the activities of PI3K and NOS. This suggests that NGF has a potential therapeutic role in the treatment of IRI.
Rate- and Temperature-Dependent Fracture Characteristics of Asphaltic Paving Mixtures
Authors: Im Soohyok , Kim Yong-Rak , Ban Hoki
Published: February 2013

Cracking in asphaltic pavement layers causes primary failure of the roadway structure, and the fracture resistance and characteristics of asphalt mixtures significantly influence the service life of asphaltic roadways. A better understanding of the fracture process is considered a necessary step to the proper development of design-analysis procedures for asphaltic mixtures and pavement structures. However, such effort involves many challenges because of the complex nature of asphaltic materials. In this study, experiments were conducted using uniaxial compressive specimens to characterize the linear viscoelastic properties and semi-circular bending (SCB) specimens to characterize fracture behavior of a typical dense-graded asphalt paving mixture subjected to various loading rates and at different temperatures. The SCB fracture test was also incorporated with a digital image correlation (DIC) system and finite-element model simulations including material viscoelasticity and cohesive-zone fracture to effectively capture local fracture processes and resulting fracture properties. The test results and model simulations clearly demonstrate that: (1) the rate- and temperature-dependent fracture characteristics need to be identified at the local fracture process zone, and (2) the rate- and temperature-dependent fracture properties are necessary in the structural design of asphaltic pavements with which a wide range of strain rates and service temperatures is usually associated.
The Culture of Dysthanasia: Attempting CPR in Terminally Ill Children
Authors: Clark Jonna D. , Dudzinski Denise M.
Published: February 2013

Both dying children and their families are treated with disrespect when the presumption of consent to cardiopulmonary resuscitation (CPR) applies to all hospitalized children, regardless of prognosis and the likely efficacy of CPR. This “opt-out” approach to CPR fails to appreciate the nuances of the special parent–child relationship and the moral and emotional complexity of enlisting parents in decisions to withhold CPR from their children. The therapeutic goal of CPR is not merely to resume spontaneous circulation, but rather it is to provide circulation to vital organs to allow for treatment of the underlying proximal and distal etiologies of cardiopulmonary arrest. When the treating providers agree that attempting CPR is highly unlikely to achieve the therapeutic goal or will merely prolong dying, we should not burden parents with the decision to forgo CPR. Rather, physicians should carry the primary professional and moral responsibility for the decision and use a model of informed assent from parents, allowing for respectful disagreement. As emphasized in the palliative care literature, we recommend a directive and collaborative goal-oriented approach to conversations about limiting resuscitation, in which physicians provide explicit recommendations that are in alignment with the goals and hopes of the family and emphasize the therapeutic indications for CPR. Through this approach, we hope to help parents understand that “doing everything” for their dying child means providing medical therapies that ameliorate suffering and foster the intimacy of the parent–child relationship in the final days of a child’s life, making the dying process more humane.
Role of pediatricians in the diagnosis and therapy of	dyslexia, dysgraphia and dyscalculia
Authors: Gergely Katalin , Lakos Renáta
Published: February 2013

Pediatricians play an important role in the diagnosis and therapy of children with dyslexia, dysgraphia or dyscalculia. These syndromes strongly affect children’s school performance. Children with dyslexia, dysgraphia or dyscalculia show a significant underachievement in reading, writing or counting and their failure to meet the school requirements undermines their self confidence and positive self-concept. As a result, children with learning problems often become aggressive, frustrated or play the clown in the classroom. According to the Hungarian law children with any learning difficulties have the right to get special education by their specific symptoms. In the realisation of the law and equity the pediatrician’s expertise is essential and has an important role in the therapeutical procedures. However, the pediatrician’s role is more complex than writing an opinion. Pediatricians can help by giving a detailed description about these syndromes and explain them how they can help their child, what are the main difficulties during the child’s studies, what kind of therapies can be efficient and how they can make their child’s school years easier. During the assessment most of the parents ask the following questions: What does dyslexia, dyscalculia or dysgraphia exactly mean? Is it a handicap or a learning difficulty? Could the child live a normal life? With the proper answer and with an inclusive attitude pediatricians can help both the parents and the children to create a liveable lifestyle and make their children’s schoolwork more successful. The authors’ opinions are to close the medical and the pedagogical view, because without the cooperation of these two scientific fields, the theme affected parents, children and teachers cannot get proper help to find better solution and support for their problems. In the survey the authors intend to give a complex view about the symptoms of these syndromes and try to give useful advice for pediatricians how they can support their patients emphasizing the key role of pediatricians and clinical expertises in the early recognition and therapy. Orv. Hetil., 2013, 154, 209–218.
The use of Integra dermal regeneration matrix in the	surgical treatment of a recurrent, extensive malignant skin lesion in the	temporal region
Authors: Halmy Csaba , Nádai Zoltán , Csőre Krisztián , Vajda Adrienne , Tamás Róbert
Published: February 2013

Authors report on the use of Integra dermal regeneration template after excision of an extended, recurrent skin tumor in the temporal region. The area covered with Integra was 180 cm2. Skin grafting to cover Integra was performed on the 28th day. Both Integra and the skin transplant were taken 100%. Integra dermal regeneration template can provide good functional and aesthetic result in the surgical management of extended skin tumors over the skull. Orv. Hetil., 2013, 154, 225–227.
Practical electrical contact resistance measurement method for bulk thermoelectric devices
Authors: Gupta Rahul P. , McCarty Robin , Bierschenk Jim , Sharp Jeff
Published: February 2013

As thermoelectric (TE) element length decreases, the impact of contact resistance on TE device performance grows more significant. In fact, for a TE device containing 100-μm tall Bi2Te3TE elements, the figure of merit ratio (ZTDevice/ZTMaterial) drops from 0.9 to 0.5 as the contact resistivity increases from 5 x 10-07 to 5 x 10-06 Ω-cm2. To understand the effects of contact resistance on bulk TE device performance, a reliable experimental measurement method is needed. There are many popular methods to extract contact resistance such as Transmission Line Measurements (TLM) and Kelvin Cross Bridge Resistor method (KCBR), but they are only well-suited for measuring metal contacts on thin films and do not necessarily translate to measuring contact resistance on bulk thermoelectric materials. The authors present a new measurement technique that precisely measures contact resistance (on the order of 5 x 10-07 Ω-cm2) on bulk thermoelectric materials by processing stacks of bulk, metal-coated TE wafers using TE industry standard processes. One advantage of this technique is that it exploits realistic TE device manufacturing techniques and results in an almost device-like structure, therefore representing a realistic value for electrical contact resistance in a bulk TE device. Contact resistance measurements for metal contacts to n- and p-type Bi2Te3 alloys are presented and an estimate of the accuracy of the measurements is discussed.
Enhancement in Thermoelectric Figure-of-merit of n-type Si-Ge Alloy Synthesized Employing High Energy Ball Milling and Spark Plasma Sintering
Authors: Bathula Sivaiah , Jayasimhadri M. , Dhar Ajay , Saravanan M. , Misra D. K. , Singh Nidhi , Srivastava A. K. , Budhani R. C.
Published: February 2013

In the present study, we report the enhancement in figure-of-merit (ZT) of nanostructured n-type Silicon-Germanium (Si80Ge20) thermoelectric alloy synthesized using high energy ball milling followed by spark plasma sintering (SPS). After 90 h of ball milling of elemental powders of Si, Ge and P (2 at.%), a complete dissolution of Ge in Si matrix has been observed forming the nanostructured n-type Si80Ge20 alloy powder. X-ray diffraction analysis (XRD) confirmed the crystallite size of the host matrix (Si) to be ∼7 nm and also indicated the formation of an additional phase of SiP nano-precipitates after SPS. HR-TEM analysis revealed that the nano-grained network was retained post-sintering with a crystallite size of size of 9 nm and also confirmed the SiP precipitates formation with a size of 4 to 6 nm. As a result, a very low thermal conductivity of ∼2.3W/mK at 900°C has been observed for Si80Ge20 alloy primarily due to scattering of phonons by nanostructured grains and nano-scaled SiP precipitates which further contribute to this scattering mechanism. Electrical conductivity values of SiGe sintered alloy are slightly lower to that of reported values in literature. This was attributed to the formation of SiP which creates a compositional difference between the grain boundary region and the grain region, leading to a chemical potential difference at interface and the grain region. Figure-of-merit (ZT) of n-type Si80Ge20 nanostructured alloy was found to be ≈1.5 at 900°C, which is the highest reported so far at this temperature.
Coupling In-Situ Techniques to Analyze Zinc Deposition and Dissolution for Energy Storage Applications
Authors: Keist Jayme , Orme Christine , Ross Frances , Steingart Dan , Wright Paul , Evans James
Published: February 2013

This investigation describes preliminary results of in-situ analysis of zinc deposition within an ionic liquid electrolyte utilizing electrochemical atomic force microscopy (EC AFM). From the AFM analysis, the morphology of the zinc deposition was analyzed by quantifying the surface roughness using height-height correlation functions. These results will be used to analyze the scattering data obtained from zinc deposition analysis utilizing an electrochemical ultra-small angle x-ray scattering (EC USAXS). The goal of this research is to link the early nucleation and growth behavior to the formation of detrimental morphologies.
Inkjetted Organic Transistors using a Novel Pentacene Precursor
Authors: Volkman Steven K. , Molesa Steven , Mattis Brian , Chang Paul C. , Subramanian Vivek
Published: February 2013

Pentacene is one of the most promising organic materials for organic transistor fabrication, since it offers higher mobility, better on-off ratio, improved environmental stability, and better reliability than most other organic semiconductors. However, its severe insolubility renders it useless for the solution-based fabrication of electronic devices. Solution-based processing is the key to enabling ultra-low-cost circuit fabrication, since it eliminates the need for lithography, subtractive processing, and vacuum-based film deposition. Using a recently developed soluble pentacene precursor, we demonstrate the first inkjet-printed pentacene transistor fabricated to date. This is achieved using a substrate-gated transistor structure in conjunction with an inkjetprinted pentacene precursor active layer. After deposition, the precursor is converted to pentacene via heating, through the decomposition of the Diels-Alder product. As the anneal temperature increases above 120°C, performance increases dramatically. The process is therefore compatible with numerous low-temperature plastics. As the anneal time is increased to several minutes, performance likewise increases through increased precursor decomposition. However, exposure to excess temperatures or times tends to degrade performance. This is caused by morphological and chemical changes in the pentacene film. Optimization of the anneal process alone has resulted in the demonstration of transistors with an on-off ratio of >105 and field-effect mobility of >0.01cm2/V-s, attesting to the great promise of this material.
Broadening the ecological context of ungulate–ecosystem interactions: the importance of space, seasonality, and nitrogen
Authors: Murray Bryan D. , Webster Christopher R. , Bump Joseph K.
Published: February 2013

Spatial heterogeneity of soil resources, particularly nitrogen availability, affects herbaceous‐layer cover and diversity in temperate forest ecosystems. Current hypotheses predict that ungulate herbivores influence nitrogen availability at the stand scale, but how ungulates affect nitrogen availability at finer spatial scales that are relevant to the herb layer is less understood. We tested the hypothesis that ungulate exclusion reduces the spatial complexity of nitrogen availability at neighborhood scales (1–26 m) apart from mean stand scale effects. This outcome was expected due to a lack of ungulate nitrogenous waste deposition within exclosures and seasonally variable ungulate habitat use. To test this hypothesis we examined spatial patterning of ammonium and nitrate availability, herb‐layer cover and diversity, and under‐canopy solar radiation using geostatistical models. Our study sites included six stands of eastern hemlock (Tsuga canadensis) forest: three where white‐tailed deer (Odocoileus virginianus) were excluded and three that were accessible to deer. Where deer were present, patch sizes of ammonium availability, cover, and diversity were smaller compared to deer exclosures, whereas mean site‐level effects were not significant. Within deer exclosures cover and solar radiation were more similar in patch size than were cover and nitrogen availability. Our results suggest that browsing ungulates affect spatial patterns of herb‐layer cover and diversity through the excretion of nitrogenous wastes in small, discrete patches. Ungulate‐excreted nitrogen deposition and herbivory were concentrated in the dormant season, allowing herb‐layer plants a greater opportunity to benefit from nitrogen additions. Therefore, the impact of ungulates on nitrogen cycling in forest ecosystems varies with spatial scale and the seasonal timing of ungulate impacts. In this way, ungulates may function as a seasonally dependent link between fine‐scale and landscape‐level ecological processes.
Using Computational Fluid Dynamics to Accurately Determine Ball Drop Times and Velocities in Fracturing Systems
Authors: De Mas Carolina , Pitts Michael J. , Jamieson David
Published: February 2013

Computational Fluid Dynamics (CFD) has been used as a means of accurately determining the time and displacement volume of balls used to activate multiple ports in a multi-zone fracturing system that is 18,000 feet long.

Hydraulic fracturing techniques are complex and highly evolving. In such processes, ball-operated sliding sleeves are a means to access multiple zones in the formation, creating fractures into which proppant is pumped. The success of placement in such systems depends upon accurate calculation of the time required for a ball to be pumped from the topside to the multiple ball seats over distances of tens of thousands of feet. It is vital that any treatment is not over displaced and thus accurate volume and timing is essential.

Using CFD unsteady simulations for validation, a simple mathematical model was created that allowed an accurate, quick-response evaluation of the time taken for a ball to be pumped through a completion. These simulations involved the use of Dynamic Fluid Body Interaction (DFBI), morphing and overset computational meshes as well as lagrangian particle-based physics. A number of challenges were met with innovative solutions; the completion followed a complex path and was over 18,000 ft in length, the duration of the study was very short, the fluid within which the ball was immersed was non-Newtonian and the particle-based fluid-particle interaction models used required validation.

This study brought together many applications areas including completion string design, the formation fracture process, CFD numerical methods, simulation management, external aerodynamics and CFD software development. Results of the simulations were compared to full-sized testing and field data.
Competition Between Transverse And Axial Hydraulic Fractures In Horizontal Wells
Authors: Lecampion Brice , Abbas Safdar , Prioul Romain
Published: February 2013

Most horizontal wells in unconventional reservoirs are drilled in the direction of the minimum stress. The preferred far-field fracture orientation thus favors hydraulic fractures transverse to the wellbore. The near-wellbore stress concentration, however, sometimes favors the initiation of fractures in a plane defined by the well axis. Transverse and axial hydraulic fractures can thus both initiate in some situations and cause significant near-wellbore tortuosity. We investigate the competition between these two types of fractures by comparing their energy requirement during hydraulic fracture initiation and propagation. First, we investigate the limiting cases of slow and fast pressurization where fluid flow and fracture mechanics uncouple. We then use recently developed numerical models for the initiation and propagation of hydraulic fractures from an open hole accounting for fluid flow in the newly created crack, wellbore stress concentration and injection system compressibility.

Compared to a simple tensile stress analysis, the methodology described here provides a way to quantify the occurrence of only transverse or both transverse and axial hydraulic fractures as well as the maximum length of the axial fractures in the latter case. Based on dimensional analysis and numerical simulations for a range of relevant formation properties and far-field stress conditions, our results show that the critical defect length that favors transverse fracture over longitudinal is less than a borehole radius in the slow pressurization limit. For realistic injection conditions, if the initial defect length favors axial fractures, the distance over which transverse fractures become energetically favorable can become much larger than its slow pressurization value, especially for large dimensionless viscosity. Smaller pressurization rate and less viscous fluid ultimately favor the propagation of transverse fractures compared to axial ones.
Application of Multivariate Analysis and Geographic Information Systems Pattern-Recognition Analysis to Production Results in the Bakken Light Tight Oil Play
Authors: LaFollette Randy F. , Izadi Ghazal , Zhong Ming
Published: February 2013

Even after the drilling of several thousand horizontal Bakken wells in Montana and North Dakota, geologists and engineers question whether their companies are using the appropriate completion and stimulation parameters for their reservoir in their particular location. Answers to this fundamental question can be difficult to come by using univariate statistical techniques. Thus, more advanced and integrated methods of analysis may be needed to achieve sound interpretations. The purpose of this paper is to apply multivariate statistical modeling in conjunction with Geographic Information Systems (GIS) pattern recognition work to update and expand previous Bakken data-mining efforts.

The investigation began by updating Bakken Formation data using both proprietary and public information. The different data sets were loaded into a common database and put through quality control sanity checks. Production proxies, such as maximum oil rate in the first 12 producing months, were selected and merged with the other data. Final data sets were then subjected to analysis in both an open-source statistical analysis environment and a commercial (GIS) application.

The integration of the two analysis and interpretation methods highlighted the importance of using well location as a proxy for reservoir quality when working with data sets that lack such measurements. The use of multivariate statistical analysis allowed modeling the impact of particular completion and stimulation parameters on the production outcome by averaging out the impact of all other variables in the system.

This work is believed to be unique in its combination of multivariate statistics and GIS pattern recognition to address questions of well optimization in unconventional reservoirs and that is its application. It is significant in that it expands the scope of prior studies that did not take full advantage of multivariate statistical methods.
Electrical Resistivity for Characterization and Infiltration Monitoring beneath a Managed Aquifer Recharge Pond
Authors: Mawer Chloe , Kitanidis Peter , Pidlisecky Adam , Knight Rosemary
Published: February 2013

Efficiency of managed aquifer recharge (MAR) via surface infiltration ponds relies heavily on the properties and processes of the unsaturated zone. The spatial and temporal resolutions needed in data for monitoring such processes are higher than typical hydrologic data can provide. Recently developed direct‐push resistivity probes can be located in the base of a MAR pond and used to obtain vertical electrical conductivity profiles with high spatial and temporal resolutions. In this study, we developed an inversion algorithm that uses a vertical electrical conductivity profile and auxiliary hydrologic data to estimate the van Genuchten parameters and saturated hydraulic conductivity of a homogeneous unsaturated zone. Using a synthetic case, we analyzed the method's accuracy and sensitivity to temporal and spatial resolutions in data. We then derived a new relationship for using the parameter estimation and electrical conductivity data to estimate infiltration rates and pond bottom clogging in situ in real time, extending electrical resistivity as a method for gaining qualitative infiltration information to a tool for quantitative infiltration rate monitoring. We found that we were able to best estimate the logarithm of the saturated hydraulic conductivity, which was within 5% of the true value for all cases. The van Genuchten parameter α was the least accurately predicted parameter, deviating at most 22% from the true value. We found that we could estimate infiltration rates and pond bottom clogging with a level of accuracy appropriate for use in modeling and management decisions, in most cases to within 11% of the true value.
Effectiveness and potential environmental impact of a yeast-based deoxygenation process for treating ship ballast waters
Authors: de Lafontaine Y. , Chambers Y. , Despatie S.-P. , Gagnon C. , Blaise C.
Published: February 2013

We assessed the effectiveness and potential environmental impact of a yeast-based deoxygenation process considered for treating ship ballast waters to reduce the risk of aquatic species introduction. Laboratory experiments were conducted to test three treatment concentrations (0.33%, 0.67% and 1.0% v v−1) at five temperatures (4, 10, 15, 20 and 25 °C) in both fresh- and saltwater, with and without mixing. Complete anoxia (<0.3 mg L−1) was achieved in all experiments, and there were no significant differences in effectiveness between fresh- and saltwater or between mixing levels. Time to hypoxia was inversely related to temperature, ranging from half a day at 25 °C to nearly 7 days at 4–5 °C. The process can quickly generate and maintain anoxic conditions over a long enough period of time to effectively eliminate a wide variety of aquatic organisms. Results of six bioassays indicated that treated waters were not toxic at the end of experiments and would not pose a toxic risk to natural receiving waters. Increased concentrations of ammonia, organic carbon and particulate matter resulting from yeast production in treated waters may cause some potential adverse environmental effects. The practicality of implementing this process for treating ballast water in ships is discussed.
Methodology for extrapolation of rock mass deformability parameters in tunneling
Authors: Zafirovski Zlatko , Pesevski Igor , Papic Jovan
Published: February 2013

This article proposes one approach for extrapolation of necessary parameters
for numerical analyses in tunnelling. The approach is named as an empirical -
statical - dynamical method for extrapolation. The proposed methodology is
based on combination of empirical classification rock mass methods,
geophysical measurements and direct dilatometer deformability testing on a
field. The analyses are prepared for purposes of investigation and design for
several tunnels in Republic of Macedonia. One example for dividing of tunnel
length in quasi-homogenous zones, as a basis for forming of geotechnical and
numerical model that can be a basis for interaction analyses of rock -
structures system and stress-strain behaviour of rock massif, is also given.
The several original regressive models between rock mass quality,
deformability and velocity of longitudinal seismic waves are shown.
Energy efficiency of buildings with phase-change materials
Authors: Lukic Predrag , Tamburic Jasmina , Stojic Dragoslav
Published: February 2013

The construction of energy efficient buildings using innovative building
materials such as phase change materials, in addition to improving indoor
comfort, energy savings and costs, can be achieved by increasing their market
value. Because of its ability to absorb and release energy at predictable
temperatures, phase change materials are effective in controlling and
maintaining the thermal environment in the building. The use of phase
changing materials, materials stored latent energy storage is an effective
form of heat.
Proton therapy Monte Carlo SRNA-VOX code
Authors: Ilic Radovan
Published: February 2013

The most powerful feature of the Monte Carlo method is the possibility of
simulating all individual particle interactions in three dimensions and
performing numerical experiments with a preset error. These facts were the
motivation behind the development of a general-purpose Monte Carlo SRNA
program for proton transport simulation in technical systems described by
standard geometrical forms (plane, sphere, cone, cylinder, cube). Some of the
possible applications of the SRNA program are: (a) a general code for proton
transport modeling, (b) design of accelerator-driven systems, (c) simulation
of proton scattering and degrading shapes and composition, (d) research on
proton detectors; and (e) radiation protection at accelerator installations.
This wide range of possible applications of the program demands the
development of various versions of SRNA-VOX codes for proton transport
modeling in voxelized geometries and has, finally, resulted in the ISTAR
package for the calculation of deposited energy distribution in patients on
the basis of CT data in radiotherapy. All of the said codes are capable of
using 3-D proton sources with an arbitrary energy spectrum in an interval of
100 keV to 250 MeV.
Fair Value Accounting for Financial Instruments: Does It Improve the Association between Bank Leverage and Credit Risk?
Authors: Blankespoor Elizabeth , Linsmeier Thomas J. , Petroni Kathy R. , Shakespeare Catherine
Published: February 2013

Many have argued that financial statements created under an accounting model that measures financial instruments at fair value would not fairly represent a bank's business model. In this study we examine whether financial statements using fair values for financial instruments better describe banks' credit risk than less fair-value-based financial statements. Specifically, we assess the extent to which various leverage ratios, which are calculated using financial instruments measured along a fair value continuum, are associated with various measures of credit risk. Our leverage ratios include financial instruments measured at (1) fair value; (2) U.S. GAAP mixed-attribute values; and (3) Tier 1 regulatory capital values. The credit risk measures we consider are bond yield spreads and future bank failure. We find that leverage measured using the fair values of financial instruments explains significantly more variation in bond yield spreads and bank failure than the other less fair-value-based leverage ratios in both univariate and multivariate analyses. We also find that the fair value of loans and deposits appear to be the primary sources of incremental explanatory power.

Data Availability: All data are publicly available from the sources indicated in the paper.
Evidence that Market Participants Assess Recognized and Disclosed Items Similarly when Reliability is Not an Issue
Authors: Bratten Brian , Choudhary Preeti , Schipper Katherine
Published: February 2013

We provide evidence that disclosed items are not processed differently from recognized items when the disclosures are salient, not based on management estimates, and amenable to simple techniques for imputing as-if recognized amounts. For a sample of firms with both capital and operating leases, we find that as-if recognized amounts for leases are generally reliable and that both recognized lease obligations and disclosed lease obligations are associated with proxies for costs of debt and equity. The magnitudes of these associations are not statistically different across accounting treatments, suggesting that market participants impound as-if recognized operating lease obligations and recognized capital lease obligations similarly into costs of capital. Conditioning on the reliability of as-if recognized operating lease obligations, we find a difference in the association between recognized versus as-if recognized lease obligations and proxies for the costs of debt and equity when the operating lease disclosures are less reliable.

Data Availability: Data used are available from public sources identified in the study.
Extended Euclidean Algorithm and CRT Algorithm
Authors: Okazaki Hiroyuki , Aoki Yosiki , Shidama Yasunari
Published: February 2013

In this article we formalize some number theoretical algorithms, Euclidean Algorithm and Extended Euclidean Algorithm [9]. Besides the a gcd b, Extended Euclidean Algorithm can calculate a pair of two integers (x, y) that holds ax + by = a gcd b. In addition, we formalize an algorithm that can compute a solution of the Chinese remainder theorem by using Extended Euclidean Algorithm. Our aim is to support the implementation of number theoretic tools. Our formalization of those algorithms is based on the source code of the NZMATH, a number theory oriented calculation system developed by Tokyo Metropolitan University [8].
Products in Categories without Uniqueness of cod and dom
Authors: Korniłowicz Artur
Published: February 2013

The paper introduces Cartesian products in categories without uniqueness of cod and dom. It is proven that set-theoretical product is the product in the category Ens [7].
Schooling entrepreneurs: Entrepreneurship, governmentality and education policy in Sweden at the turn of the millennium
Authors: Dahlstedt Magnus , Hertzberg Fredrik
Published: February 2013

Departing from Michel Foucault’s concept of governmentality, the focus of this article is the introduction of entrepreneurial education in Swedish education policy at the turn of the millennium. We analyze the various meanings attached to the concepts of “entrepreneur” and “entrepreneurship” in education policy documents, as well as the main arguments for introducing entrepreneurial education. In policy documents, the “entrepreneur” is portrayed as being flexible, creative, enterprising and independent, as having the ability to take initiative, solve problems and make decisions. Here, there is an emphasis made on economical utility, and its priority over other values. With an increasing mobilization of entrepreneurship in school, previous pedagogical and educational doctrines - focusing on equality, universalism and redistribution - are challenged. Other visions, stating other educational purposes and goals emerge. In the vision of the entrepreneurial school, it becomes logical and natural to emphasize the value education has for the economic system. In conclusion, entrepreneurial education may be seen as a particular kind of governmentality, connecting students and their subjectivity to the rationality of the market - fostering subjects in line with the imperatives of the “advances liberal society”.