Bibliografie tematiche / Back-of-the-envelope calculations

Letteratura scientifica selezionata sul tema "Back-of-the-envelope calculations"

Autore: Grafiati

Pubblicato: 26 luglio 2024

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Articoli di riviste sul tema "Back-of-the-envelope calculations"

Denning, Peter J. "Back of the envelope". Communications of the ACM 64, n. 9 (settembre 2021): 35–37. http://dx.doi.org/10.1145/3473612.

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Aspinall, R. J., J. A. Miller e J. Franklin. "Calculations on the back of a climate envelope: Addressing the geography of species distributions". Proceedings of the National Academy of Sciences 106, n. 16 (15 aprile 2009): E44. http://dx.doi.org/10.1073/pnas.0809891106.

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Arora, A., T. DebRoy e H. K. D. H. Bhadeshia. "Back-of-the-envelope calculations in friction stir welding – Velocities, peak temperature, torque, and hardness". Acta Materialia 59, n. 5 (marzo 2011): 2020–28. http://dx.doi.org/10.1016/j.actamat.2010.12.001.

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Löfgren, Karl-Gustaf. "A back of the envelope calculation method for calculations of the gains from genetic progress in forestry with some theoretical underpinning". Ecological Modelling 92, n. 2-3 (dicembre 1996): 245–52. http://dx.doi.org/10.1016/0304-3800(95)00174-3.

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Dessus, Sébastien, Santiago Herrera e Rafael de Hoyos. "The impact of food inflation on urban poverty and its monetary cost: some back-of-the-envelope calculations". Agricultural Economics 39 (novembre 2008): 417–29. http://dx.doi.org/10.1111/j.1574-0862.2008.00348.x.

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Davis, E. "Order of Magnitude Comparisons of Distance". Journal of Artificial Intelligence Research 10 (1 gennaio 1999): 1–38. http://dx.doi.org/10.1613/jair.520.

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Order of magnitude reasoning - reasoning by rough comparisons of the sizes of quantities - is often called `back of the envelope calculation', with the implication that the calculations are quick though approximate. This paper exhibits an interesting class of constraint sets in which order of magnitude reasoning is demonstrably fast. Specifically, we present a polynomial-time algorithm that can solve a set of constraints of the form `Points a and b are much closer together than points c and d.' We prove that this algorithm can be applied if `much closer together' is interpreted either as referring to an infinite difference in scale or as referring to a finite difference in scale, as long as the difference in scale is greater than the number of variables in the constraint set. We also prove that the first-order theory over such constraints is decidable.

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Chang, Tom, Joshua Graff Zivin, Tal Gross e Matthew Neidell. "Particulate Pollution and the Productivity of Pear Packers". American Economic Journal: Economic Policy 8, n. 3 (1 agosto 2016): 141–69. http://dx.doi.org/10.1257/pol.20150085.

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We study the effect of outdoor air pollution on the productivity of indoor workers at a pear-packing factory. Increases in fine particulate matter (PM2.5), a pollutant that readily penetrates indoors, leads to significant decreases in productivity, with effects arising at levels below air quality standards. In contrast, pollutants that do not travel indoors, such as ozone, have little, if any, effect on productivity. This effect of outdoor pollution on indoor worker productivity suggests an overlooked consequence of pollution. Back-of-the-envelope calculations suggest the labor savings from nationwide reductions in PM2.5 generated a sizable fraction of total welfare benefits. (JEL D24, J24, L66, Q13, Q51, Q53)

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Sanders, Nicholas J., e Alan I. Barreca. "Adaptation to Environmental Change: Agriculture and the Unexpected Incidence of the Acid Rain Program". American Economic Journal: Economic Policy 14, n. 1 (1 febbraio 2022): 373–401. http://dx.doi.org/10.1257/pol.20190060.

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The Acid Rain Program (ARP) cut sulfur dioxide (SO2) emissions from power plants in the United States, with considerable benefits. We show this also reduced ambient sulfate levels, which lowered agriculture productivity through decreased soil sulfur. Using plant-level SO2 emissions and an atmospheric transport model, we estimate the relationship between airborne sulfate levels and yields for corn and soybeans. We estimate crop revenue losses for these two crops at around $1–$1.5 billion per year, with accompanying decreases in land value. Back-of-the-envelope calculations of the costs to replace lost sulfur suggest producer responses were limited and suboptimal. (JEL Q15, Q24, Q53, Q58)

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Marcus, Michelle. "Going Beneath the Surface: Petroleum Pollution, Regulation, and Health". American Economic Journal: Applied Economics 13, n. 1 (1 gennaio 2021): 72–104. http://dx.doi.org/10.1257/app.20190130.

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This paper quantifies the health impacts of petroleum leaks from underground storage tanks, the effectiveness of tank regulation, and the role of information as a policy tool in the same setting. Exposure to a leaking underground storage tank during gestation increases both the probability of low birthweight and preterm birth by 7–8 percent. Compliance with regulations requiring the adoption of preventative technologies mitigated the entire effect of leak exposure on low birthweight, and information increased avoidance and moving among highly educated mothers. Back-of-the-envelope calculations suggest the health benefits of preventative regulations exceed the upgrade cost to facilities. (JEL I12, K32, L71, L78, Q35, Q51, Q53)

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Hungerman, Daniel M. "Substitution and Stigma: Evidence on Religious Markets from the Catholic Sex Abuse Scandal". American Economic Journal: Economic Policy 5, n. 3 (1 agosto 2013): 227–53. http://dx.doi.org/10.1257/pol.5.3.227.

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This paper considers substitution between charitable activities in the context of religious practice by examining the Catholic Church sex abuse scandal's impact on both Catholic and non-Catholic religiosity. I find a fall in the Catholic population compensated by increases in non-Catholic participation and nonaffiliation. Back-of-the-envelope calculations suggest the scandal generated about $3 billion dollars in donations to non-Catholic faiths. Those leaving Catholicism frequently chose dissimilar alternatives: Baptist churches gained significantly while the Episcopal Church did not. These results challenge several theories of religiosity and suggest that policies or shocks specific to one religious group could have effects on other groups. (JEL D64, Z12)

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Tesi sul tema "Back-of-the-envelope calculations"

Dragani, Lorenzo. "Winning ways for your learning days - Analisi di libri di testo in fisica". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21062/.

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Lo scopo di questo lavoro è analizzare testi che hanno avuto un grande successo nel mondo dell’insegnamento della Fisica a livello Universitario utilizzando concetti provenienti dalla psicologia per tentare di capire se e quali siano le caratteristiche che li contraddistinguono come efficaci strumenti didattici. I testi sono stati selezionati analizzando e confrontando sia i tassi di adozione di questi presso prestigiosi Dipartimenti di Fisica sia le valutazioni e le recensioni su riviste specializzate, siti di e-commerce e rating di libri. L’analisi è stata inoltre complementata da interviste agli autori, i quali hanno spiegato come hanno sviluppato i loro libri e l’approccio didattico che li caratterizza.

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Libri sul tema "Back-of-the-envelope calculations"

Back of the Envelope. Dorrance Pub Co, 2000.

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Dessus, Sebastien, Santiago Herrera e Rafael de Hoyos. The Impact Of Food Inflation On Urban Poverty And Its Monetary Cost: Some Back-Of-The-Envelope Calculations. The World Bank, 2008. http://dx.doi.org/10.1596/1813-9450-4666.

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Reinert, Kenneth A. No Small Hope. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190499440.003.0012.

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This concluding chapter reviews the basic goods approach, its intellectual sources, and its practical importance. It emphasizes the role of basic goods as basic rights and connects these basic subsistence rights to the tradition of moral minimalism in political philosophy. It questions the claims of technological optimists and calls for a “rational pessimism” in the setting of global policy priorities. It also proposes a set of ten basic development goals to replace the current and often criticized sustainable development goals. It considers the feasibility of basic goods provision using back-of-the-envelope calculations, concluding that the goal of universal basic goods provision is indeed feasible.

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Cook, PG, e AL Herczeg. Groundwater Chemical Methods for Recharge Studies - Part 2. CSIRO Publishing, 1998. http://dx.doi.org/10.1071/9780643105348.

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These notes are restricted to those geochemical methods which have been used to quantify rates of groundwater recharge. There have been two main approaches. The first involves the use of mass balances and mixing cell models, mainly using conservative (non-reacting) dissolved species. The methods range in complexity from simple back-of-the-envelope calculations (zero-dimensional chloride mass balance), to complex three-dimensional computer models. The second approach seeks to estimate the age or residence time of the groundwater by measuring compounds which are radioactive, or whose input to the aquifer has been changing over time (chlorofluorocarbons). In this report, the methodology and case examples are described. References to further information on the techniques are also provided.

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Capitoli di libri sul tema "Back-of-the-envelope calculations"

"The Use of Linked DNA Markers". In Introduction to Risk Calculation in Genetic Counseling, a cura di Ian D. Young, 93–119. Oxford University PressNew York, NY, 2006. http://dx.doi.org/10.1093/oso/9780195305272.003.0005.

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Abstract Developments in molecular genetics have greatly enhanced the diagnostic repertoire of the clinical geneticist. If a specific pathogenic mutation can be identified in a family, then carrier detection, preclinical detection, and prenatal diagnosis become relatively straightforward. However, situations can still arise in which a specific mutation cannot be identified, possibly because a sample cannot be obtained from an affected individual or because the relevant gene has not been isolated even though the disease has been mapped to a particular chromosome region. In both of these situations, a compromise solution involves the use of polymorphic DNA marker loci that have been shown to be genetically linked to the disorder in question. Genetic linkage is a complex subject, and the use of linked DNA markers can generate some very difficult calculations. Sometimes these issues are best resolved with the help of one of the computer packages that have been developed (Lathrop and Lalouel, 1984). Simple calculations can usually be managed using pencil and paper, and even in situations where this is not possible, it is useful to understand the basic principles involved so that an attempt can be made to assess whether the answer provided by the computer program is plausible. This chapter offers an approach to the solution of some of the less complex linkage calculations that can be carried out on the back of the proverbial envelope (sometimes a rather large envelope is needed!).

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"The Product Operator Formalism". In Essential Mathematics for NMR and MRI Spectroscopists, 561–97. The Royal Society of Chemistry, 2016. http://dx.doi.org/10.1039/bk9781782627975-00561.

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Density matrix calculations are very powerful but also very time-consuming and error-prone when done by hand. The product operator formalism provides a compact way of doing “back-of-the-envelope” density matrix operations. In order to contrast the density operator method with the product operator method and to make clear the genesis of the product operator formalism a short discussion of a density matrix calculation is performed. The Cartesian product operator method is then presented and the rules for its use are developed. Multiple quantum coherence is defined and its genesis and evolution in time are explored. Helpful visualisations of product operator evolutions are presented as rotation diagrams. Several NMR pulse sequences are analysed and a visual operator-tree approach to analysis is presented. Single-transition product operators are discussed in preparation for the treatment of coherence transfer and relaxation.

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Polillo, Simone. "Winners and Losers in Financial Economics, or Fama versus Black". In The Ascent of Market Efficiency, 90–118. Cornell University Press, 2020. http://dx.doi.org/10.7591/cornell/9781501750373.003.0004.

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This chapter looks at the conflict between the exponents of two different and incompatible ways of conducting financial research by Fischer Black and Eugene Fama. It contrasts the trajectory of the efficient-market hypothesis with that of the Capital Asset Pricing Model (CAPM). Financial economists ultimately relegated CAPM to the status of one among many competing methods of portfolio selection, while market practitioners continue using it to make quick, back-of-the-envelope calculations. The chapter discusses how CAPM is recognized as the “centerpiece of modern financial economics” and how it is mainly explained in terms of historical significance, practical implications, and empirical shortcomings. The heart of the matter is that CAPM could be framed as one of the auxiliary assumptions that tests of the joint hypothesis of market efficiency relied on.

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Speller, Susannah. "Levitation Magic". In A Materials Science Guide to Superconductors, 52–71. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780192858344.003.0004.

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Abstract This chapter starts by outlining magnetic levitation and why superconductors are so much more practical than normal magnets for this application. The concept of flux pinning - which is arguably the most important aspect of applied superconductivity for all applications including levitation - is explained. The materials science of how we design superconductors to optimise flux pinning is introduced, and this becomes a recurring theme through the rest of the book. The chapter ends by showing how superconductors with good flux pinning can be made into permanent magnets. In the “Under the Lens” sections, back of the envelope calculations for estimating the strength of the levitation force and the strength of permanent magnets that can be created from superconducting pellets are given. A “Wider View” section explores how the same kind of crystal defects that are used for flux pinning can also affect mechanical properties of materials by solid solution strengthening.

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Yadav, Sarita, Nitanshu Chauhan, Shobhit Tyagi, Arvind Sharma, Shashank Banchhor, Rajiv Joshi, Rajendra Pratap e Bulusu Anand. "Supply Voltage Scaling for Energy Efficient FinFET Logic". In Nanoscale Field Effect Transistors: Emerging Applications, 68–88. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815165647123010007.

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A number of ultra-low power applications that don't need high performance can gain power from running at the lowest supply voltage possible. Scaling the supply voltage is a useful technique for cutting the energy needed by digital circuitry. Based on Shannon's channel capacity theorem, the fundamental limit for supply voltage for planar CMOS circuits has been determined to be 36 mV. FinFET devices fit ultra-low voltage applications better than planar devices because of their nearly excellent sub-threshold properties. For the first time, the fundamental supply voltage limit for logic circuits using FinFETs has been defined in this work. It is discovered that this theoretical limit is considerably lower than the limit for planar CMOS devices. On this fundamental limit, the impact of temperature variations and device design characteristics is also investigated. Other logic gates, such as the NAND gate, are included in the analysis. To determine this fundamental limit for a FinFET device, a novel physics-based, semi-empirical current equation valid for supply voltage below 100 mV has been proposed. This is because the operation of a FinFET device in the ultra-low voltage domain differs significantly from that of its planar counterpart. A circuit designer values a current model like this because it makes calculations for back of the envelope calculations simple. The proposed model is then used to study the logic gates functioning in this regime.

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"Calculating on the back of an envelope". In Common Sense Mathematics, 1–25. Providence, Rhode Island: American Mathematical Society, 2021. http://dx.doi.org/10.1090/text/063/01.

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Scarani, Valerio. "Dimensions And Boundaries". In Quantum Physics A First Encounter, 24–36. Oxford University PressOxford, 2006. http://dx.doi.org/10.1093/oso/9780198570479.003.0003.

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Abstract I am of the opinion that experimental physics is not given the credit it deserves in our society. Applied physics, ultimately industrial physics, is conveniently praised because it directly affects our lives. As for the high repute of theoretical physics, just stop and list five renowned physicists on the back of an envelope: I predict that the five names you have written down are those of five theoreticians (you can easily verify it on the internet). Experimentalists are those people who work in academic laboratories, confirming theories that they are (wrongly) supposed not to have understood, and making claims on possible applications that seldom attract the interest of industry. Of course, any physicist knows the truth: without the genius and the hard work of the experimentalists, there would simply be no physics at all. The laser is a striking example20: the basic equations had been written down by Einstein himself in 1917, but it required some brilliant experimentalists to make it real – against the scepticism of many colleagues, and without having any particular application in mind. In this and the following chapters, while discussing, as promised, some deeper questions raised by quantum physics, I hope to also provide a convenient description of what a real experiment looks like – still, leaving aside the most thankless tasks: purchase of materials, days and nights spent making adjustments, error calculations

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"1 Calculating on the Back of an Envelope". In Common Sense Mathematics, 1–22. Providence, Rhode Island: American Mathematical Society, 2019. http://dx.doi.org/10.1090/text/051/01.

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"Scaling – and the neglected art of back-of-the-envelope calculation". In The Air Engine. CRC Press, 2007. http://dx.doi.org/10.1201/9781439824160.pt4.

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Organ, Allan J. "Scaling – and the neglected art of back-of-the-envelope calculation". In The Air Engine, 211–25. Elsevier, 2007. http://dx.doi.org/10.1533/9781845693602.4.211.

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Atti di convegni sul tema "Back-of-the-envelope calculations"

Cobb, Corie L., e Alice M. Agogino. "Case-Based Reasoning for the Design of Micro-Electro-Mechanical Systems". In ASME 2006 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/detc2006-99120.

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Although Micro-Electro-Mechanical Systems (MEMS) are forming the basis for a rapidly growing industry and fields of research, many MEMS designers still rely on back-of-the-envelope calculations due to a lack of efficient computer-aided design (CAD) tools that can assist with the initial stages of design exploration. This paper introduces case-based reasoning (CBR) techniques to the design of MEMS, as part of a larger MEMS synthesis framework currently under development at UC Berkeley. Having the ability to draw upon past design knowledge is advantageous to the MEMS designer, allowing reuse and modification of previous successful designs to help deal with the complexities of a new design problem. CBR utilizes past successful MEMS designs and sub-assemblies as building blocks stored in an indexed library. Reasoning tools find cases in the library with solved problems similar to the current design problem in order to propose promising conceptual designs. This paper discusses case representation and case library design as well as the results of case retrieval studies, focusing on MEMS resonant structures. The paper recommends strategies for integrating the MEMS case library with evolutionary computation when parameter optimization over the retrieved conceptual designs is not sufficient or there are gaps of knowledge in the case library.

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Mal, Anwesha, Sven Inge Oedegaard, Stig Helgeland, Josef Navabi, Jan Ole Skogestad, Knut Steinar Bjoekevoll, Morten Lien, Tore Weltzin e Bjørn Rudshaug. "Drilling Parameter Optimization in Real-Time". In SPE/IADC International Drilling Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/212484-ms.

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Abstract There is an increased demand for contactless and/or low touch activities as well as a requirement for most product delivery and services to be such. This paper aims to demonstrate how drilling parameter optimisation in real-time provides a drilling team with an Edge based solution that can continuously improve performance and avoid problems without the need of subject matter experts. Results from testing the Edge-System on multiple wells from several operators are presented related to auto-calibration of real-time prediction models and for optimization of drilling parameters. This system based on cloud technology with Model based reasoning in Artificial Intelligence (AI) is able to give real-time and forward advice for operational parameters, ref SPE-204074-MS The key enabler for such system is "automatic" auto-calibration of models which is used for multiple forward-looking and what-if calculations to find optimal drilling parameters within the well envelope ahead. A simplified configuration has been made so that the rig-team can operate and maintain the system without the need for subject matter experts. "Automatic" Auto-calibration at stable conditions and/or during ramping conditions removes the need for subject matter experts. Such a system helps reduce operational costs as the rig-team can operate the system without the need of back-office support. Comparison will be made to document operational improvements.

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Lee, Gary Y. H., Ohgeon Kwon, Zuwairi Ramli e Zaki Mohamad Afifi. "Crude Furnace Creep Assessment and High Temperature Degradation". In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65046.

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Creep calculations indicate a crude furnace radiant section carbon steel tubes exceeding their life fraction due to flame impingement reaching up to 700°C for a year. The ambiguity of the temperature and material data means the life fraction of creep calculations were based on limited inspection data and infra-red scanning giving a conservative indication of end of life. Due to unavailable tubes in stock, a planned pit stop cannot be arranged due to economic and safety reasons as the furnace may not be started back up safely. To safeguard the integrity of the furnace until the planned outage, the temperature on the furnace tube was stabilized to a current limit of 540°C through improvements in burner operations. The crude diet was also maintained within the crude acceptance envelope. Visual checks at every shift were done to ensure no observation from tube bulging or uneven flame pattern. A decision tree was created to facilitate quick decision making using a go/no go criteria of which tubes to replace during the August 2015 planned turnaround. The criteria set for the decision tree required tube wall thickness, surface hardness test, tube outer diameter ring gauge to be examined. Failing any of the criteria will require the tube to be replaced. The replaced tubes (one worst and one representative) will also be lab tested through destructive examination to identify the degradation mechanism and high temperature properties of the worst tubes to quantitatively define the high temperature properties and life fraction of the tubes that are left in the furnace. The lab test will provide results after a year of creep testing and can give assurance of continued furnace operation for 4 more years until the next outage. The final decision after the examination based on the decision tree was made required 17 tubes to be replaced in this turnaround. The worst degraded tubes were found to be at the vicinity of the initial observed location around the flame impingement zone.

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Forshaw, Matthew J., Rafael A. Madeira e Pedro J. Arévalo. "Tripping Optimisation for Drilling Systems Automation: Potential of Digital Twins, Transient Models and Control Systems to Reduce Invisible Lost Time in Well Construction". In SPE Canadian Energy Technology Conference. SPE, 2022. http://dx.doi.org/10.2118/208961-ms.

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Abstract Tripping, the process whereby a string is moved in either axial direction makes up 30% of the well construction time and is therefore responsible for a significant portion of capital expenditure by operators. Typically, the focus in the industry in optimizing this segment of the operation has centered on minimizing the slips-to-slips connection time. This references the time taken to swing in and make-up, or breakout and rack-back a stand before engaging elevators to either run-in or pull-out with the next component. This required both human-process optimization through training and technological development of topside equipment, first in isolation and then through systems automation. This paper recognizes these optimization efforts but identifies additional potential to significantly reduce invisible-lost-time (ILT) during tripping operations even further by reducing out-of-slips running time in tripping operations, all while keeping wellbore pressures within the safe operating envelope. Physics-based steady-state fluid dynamics models have been in use for decades to define boundary conditions for these operations. These swab and surge calculations output a velocity limit for moving pipe. Models that are more complex have begun to diffuse into the commercial environment over the last decade and enhance borehole protection by providing a coupled acceleration limit. Acceleration and velocity are inherently linked so an optimization must be performed to arrive at the optimum velocity-time curve. In this paper we present real-time engineering simulations to create a digital twin of the downhole environment and calculate optimum tripping parameters for every stand. The parameters are then passed as set-points to automated rig control systems. The paper summarizes the physics-based modelling as well as the mathematical optimization. The system, including interfaces required to implement control in the context of drilling systems automation is also described. Field examples are presented whereby exposing actual real-time measurements and derived tripping boundary conditions in an intuitive, accessible user interface can lead to performance improvements. The ability to calculate the optimum velocity-time curve is the essential ingredient in gaining efficiency while out-of-slips during tripping operations, and simultaneously staying within a safe operating envelope. The resulting reduction in invisible-lost-time demonstrated, and associated reduction in rig time has obvious financial implications for operators and increasingly more important, helps achieve critical ESG targets. Finally, the paper will touch the need, and applicability of such technology in the energy transition new frontiers, specifically geothermal.

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Pehlke, Trent, Greer Simpson, Tamara Maxwell, Charles Bourgeois e Joshua Stibbs. "On Track for Refrac: Targeting Under-Stimulated Stages and Assessing Casing Integrity Defects with High-Resolution Acoustic Imaging". In SPE Hydraulic Fracturing Technology Conference and Exhibition. SPE, 2024. http://dx.doi.org/10.2118/217768-ms.

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Abstract Fracturing technology and industry knowledge garnered over the past decade have unlocked the viability and value of refracturing wells originally stimulated using legacy methods. Refracturing wells plays a vital role in the overall pad-level production strategy and prevents losing parent wells when fracturing child wells. High-resolution acoustic imaging technology has become commonplace for assessing all aspects of the refracture operation. In a single run, this technology captures detailed corrosion and wall loss information to de-risk subsequent refracture injection pressures and rates. While new casing can be assumed to be within API specification of 12.5% from nominal thickness, legacy wells may be up to 20 years old bring no such guarantee, and assets are often exposed to corrosive environments some containing H2S, mechanical wear, and were previously exposed to high-rate slurry. Based on the submillimetric datasets collected, this diagnostic imaging technology informs the critical decisions of whether to run a protective tie-back string, what depth the liner hanger can be safely set at, where Fracture-Driven-Interactions (FDI) communication between neighboring wellbores may have taken place through casing and liner deformation analysis, and provides perforation erosion analysis of the initial stimulations proppant placement. This provides operators with the insight needed to efficiently tailor the refracture program to target undrained reservoir, de-risk any corrosion or deformation concerns from the original casing and reduce the likelihood of total loss of parent wells due to FDI's. This paper details how high-resolution acoustic imaging is used to assess pre-refracture well integrity, optimize refracture designs, and increase production rates. From a well-integrity perspective, the asset is inspected for corrosion, ovality, mechanical wear, and connection defects. Using the submillimetric defect dimensions for wall loss events, Effective Area, RSTRENG, Modified B31G, and Barlow burst pressure calculations are conducted to determine the safe pressure envelope of the existing casing. This enables a definitive decision on whether to run a costly tie-back string to protect a damaged or corroded casing from failure during the subsequent stimulation. From a refracture design perspective, the novel imaging technology enables operators to target under-depleted zones for restimulation. Outlying stages with low or non-uniform perforation growth are identified by capturing submillimetric measurements of the initially stimulated perforations. Once identified, these under-stimulated stages can be selectively targeted in the refracture design by adjusting proppant poundage, selecting appropriate diverters, defining mesh sizing, optimizing slurry rates, or altering exit hole area and phase by adding perforations in the same or new orientation phase. Lastly, this paper contains two field-based case studies outlining real-world deployments of this technology to provide operators with a single-pass evaluation of well integrity and optimize production rates.

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Edwards, Kristen M., Vaishnavi L. Addala e Faez Ahmed. "Design Form and Function Prediction From a Single Image". In ASME 2021 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/detc2021-71853.

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Abstract Estimating the form and functional performance of a design in the early stages can be crucial for a designer for effective ideation Humans have an innate ability to guess the size, shape, and type of a design from a single view. The brain fills in the unknowns in a fraction of a second. However, humans may struggle with estimating the performance of designs in the early stages of the design process without making prototypes or doing back-of-the-envelope calculations. In contrast, machines need information about the full 3D model of a design to understand its structure. Machines can estimate the performance using pre-defined rules, expensive numerical simulations, or machine learning models. In this paper, we show how information about the form and functional performance of a design can be estimated from a single image using machine learning methods. Specifically, we leverage the image-to-image translation method to predict multiple projections of an image-based design. We then train deep neural network models on the predicted projections to provide estimates of design performance. We demonstrate the effectiveness of our method by predicting the aerodynamic performance from images of aircraft models. To estimate ground truth aero-dynamic performance, we run CFD simulations for 4045 3D aircraft models from the ShapeNet dataset and use their lift-to-drag ratio as the performance metric. Our results show that single images do carry information for both form and functional performance. From a single image, we are able to produce six additional images of a design in different orientations, with an average Structural Similarity Index score of 0.872. We also find image-translation methods provide a promising direction in estimating the performance of design. Using multiple images of a design (gathered through image-translation) to predict design performance yields a recall value of 47%, which is 14% higher than a base guess, and 3% higher than using a single image. Our work identifies the potential and provides a framework for using a single image to predict the form and functional performance of a design during the early-stage design process. Our code and additional information about our work are available at http://decode.mit.edu/projects/formfunction/.

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Wong, Daniel Lorng Yon, e Peter Alastair Adam. "Carbon Capture and Storage in Depleted Hydrocarbon Reservoirs: Lessons Learned from Projects in Asia Pacific". In SPE Asia Pacific Oil & Gas Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210784-ms.

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Abstract Carbon Capture and Storage (CCS) is a lot harder than it seems. Storage capacity can be far lower than a back-of-the-envelope calculation would suggest and keeping Carbon Dioxide (CO2) in the desired phase requires careful engineering. As the adoption of carbon pricing mechanisms increase in Asia Pacific, more CCS projects are expected to be developed. In this paper, we share some technical lessons learned while working on several of these projects. The paper provides an overview of factors that should be considered for CO2 storage in depleted hydrocarbon reservoirs, primarily concerning capacity, injectivity and containment. We further discuss some of the challenges faced while assessing these factors. Firstly, we highlight the impact that regional geothermal gradients have on storage site selection. Particularly, we show that higher geothermal gradients due to the proximity to the ring of fire affects CO2 capacity negatively and CO2 injectivity positively. Building on this lesson, we propose a graphical approach which provides improved insights when screening depleted reservoirs for CO2 storage; the approach combines both density and viscosity data to screen reservoirs for capacity and injectivity. Next, challenges surrounding the dynamic modelling of CO2 injection into depleted reservoirs are discussed. We compare the use of large and small scale models, and their implications on simulation accuracy and well placement optimization. We also discuss simulation stopping techniques, and how the incorrect application of a stopping criterion may result in capacity overestimation and risk of CO2 leakage. Finally, we demonstrate the need for careful engineering at injection sites to accommodate complicated CO2 phase transitions. Two approaches were compared – injecting CO2 in liquid or supercritical state versus injecting CO2 in gas state. The trade-offs between both approaches suggested that neither options should be ruled out by default, and that both options should be evaluated against project specific constraints.

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Chang Li Si, Claire, Fedawin Johing, Yoon Chiang Wong, Nur Melatee Binti Mohd Fauzi, Ahmad Muzakkir Bin Mohamad, Kwang Chian Chiew e Kit Teng Chaw. "A Case Study on Field F Multiphase Flow Meter: How is it Better than a Conventional Test Separator?" In SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205557-ms.

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Abstract Multiphase flow meters (MPFM) have been known save costs for new installations, are compact and as effective as a test separator. Field "F" is a green field with 2 wells and has been producing since 2018 from the same reservoir. The test facilities consist of an MPFM, and F flows to a hub called Field "G". Towards Q2 of 2019, there was a significant increase in production rates from both wells without any changes to surface choke size and without enhancement jobs performed. Added to that, reservoir pressure showed steady depletion. Daily production allocation for F showed lower than usual reconciliation factor when combined with G hub production. This suboptimal allocation raised doubts about the MPFM well test readings which launched a full investigation into the accuracy of the meter. From the offshore remote monitoring system, the first suspect was the increased inlet pressure causing parameters to be out of the MPFM operating envelope range. However, after further checking, there were other pressing issues such as faulty transmitter, and low range sensors. As these issues were being dealt with amidst the COVID-19 pandemic, the process to fix the meter was longer than usual. Rectification involved troubleshooting the MPFM post performing Multi Rate Tests, back allocation check to hub production and PROSPER/GAP model matching to check on the credibility of the well tests. These efforts were made due to budget cuts, as there was no advantage to bring onboard an entire well test package (separator) to test the F wells. Post several rectifications, the liquid, gas and oil rates were within 10% difference from allocation meter back allocation and PROSPER model calculation. Reconciliation factor for field G has also increased to normal range of 0.92 to 0.95. However, the rectification also showed a significant drop in metered rates, proving that the MPFM was indeed generating incorrect well tests since Q2 2019. The drop was higher than 30% in gross production rates which lead to a better understanding of the reservoir, and corrections to be made to dynamic models for any future development projects. This hence proves that even with the similar reservoir properties in both wells, the MPFM well tests still require vigorous checking and should not be treated in the same way as a test separator. This paper will describe the efforts by surface and subsurface faculties to ensure the quality of well tests from the MPFM. For future projects considering the MPFM installation, best to frequently quality check the MPFM well test figures with a test separator. However, if that option is not feasible, the efforts in this paper can act as a guide for the field.

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Rapporti di organizzazioni sul tema "Back-of-the-envelope calculations"

Jamilov, Rustam, Hélène Rey e Ahmed Tahoun. The Anatomy of Cyber Risk. Institute for New Economic Thinking Working Paper Series, maggio 2023. http://dx.doi.org/10.36687/inetwp206.

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This paper employs computational linguistics to introduce a novel text-based measure of firm-level cyber risk exposure based on quarterly earnings conference calls of listed firms. Our quarterly measures are available for more than 13,000 firms from 85 countries over 2002-2021. We document that cyber risk exposure predicts cyber attacks, affects stock returns and profits, and is priced in the equity option market. The cost of option protection against price, variance, and tail risks is greater for more cyber-exposed firms. Cyber risks spill over across firms and persist at the sectoral level. The geography of cyber risk exposure is well approximated by a gravity model extended with cross-border portfolio flows. Back-of-the-envelope calculations suggest that the global cost of cyber risk is over $200 billion per year.

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Pecha, Camilo, e Diether Beuermann. Healthy to Work: The Impact of Free Public Healthcare on Health Status and Labor Supply in Jamaica. Inter-American Development Bank, novembre 2016. http://dx.doi.org/10.18235/0011773.

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This study examines whether Jamaica's free public healthcare policy affectedhealth status and labor supply of adult individuals. It compares outcomes of adults without health insurance versus their insured counterparts, before and after policy implementation. The study finds that the policy reduced both the likelihood of suffering illnesses with associated lost work days and the number of lost days due to illnesses by 28.6 percent and 34 percent, respectively. Consistent with the absence of "employment lock", no effects are found on employment at the extensive margin. However, consistent with a reduced number of days lost due to illnesses, there is a positive effect of 2.15 additional weekly labor hours. This is primarily a labor supply effect as the study shows that both reported and imputed hourly wages decreased by 0.15 and 0.06 log-points respectively. Back-of-the-envelope calculations suggest that the policy added a yearly average of US$PPP 26.6 million worth of net real production to the economy during the period 2008-12.

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Slacalek, Jiri, Oreste Tristani e Giovanni Violante. Household Balance Sheet Channels of Monetary Policy: A Back of the Envelope Calculation for the Euro Area. Cambridge, MA: National Bureau of Economic Research, gennaio 2020. http://dx.doi.org/10.3386/w26630.

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Schmid, Juan Pedro, e Xavier Malcolm. The Fear Factor: A Back-Of-The-Envelope Calculation on the Economic Risk of an Ebola Scare in the Caribbean. Inter-American Development Bank, dicembre 2014. http://dx.doi.org/10.18235/0008451.

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This brief presents simulations of an Ebola scare in the Caribbean, including three highly tourism-dependent economies, The Bahamas, Barbados, and Jamaica. On the basis of the experience of Mexico in 2009 with swine flu, we simulate a short but sharp drop in tourist arrivals resulting from tourists' worries about Ebola. The Caribbean is special in that tourism contributes directly and indirectly up to half of its GDP. The simulations indicate that the volatility of tourism combined with that dependence creates significant vulnerability for the region. Under the worst-case scenario, a noticeable impact could be expected even in countries with a smaller dependence on tourism. In addition, declines could also be expected for employment and revenues. However, 'pandemic scares' can be short-lived and the simulations indicate that the Caribbean would be able to absorb a short tourism drop. The intensity and duration of the outfall in tourism would depend on the real and perceived preparedness of the affected countries, highlighting that countries in the Caribbean need to not only avoid or minimize any Ebola cases but also ensure that tourists perceive these countries as safe places.

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Peña-Torres, Julio, Kailin Kroetz, James N. Sanchirico e David Corderi. Evaluation of the Chilean Jack Mackerel ITQ System. Inter-American Development Bank, marzo 2016. http://dx.doi.org/10.18235/0011723.

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The debate in commercial fishery management has evolved from whether well-defined rights are necessary for sustainability to measuring the impacts of different rights-based system designs. Most assessments are on developed world fisheries. Using a unique collection of datasets, we develop counterfactuals to evaluate the impacts of the Chilean Jack Mackerelcatch share program. We investigate vessel and trip characteristics, as well as trip costs and revenues, before and after the implementation of the program. We find an increase in higher value products and associated revenue, as well as consolidation of catch on larger vessels, vessels taking longer trips, and catching more per trip. Overall, we estimate that the program led to a measureable increase in fishing profits, mainly due to movement toward higher value products. A back-of-the-envelope calculation results in an implied annual quota rental rate on the order of ~15-19% of ex-vessel prices.

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