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On the Foundations of Computing. Computing as the Fourth Great Domain of Science
Get PDFThis review essay analyzes the book by Giuseppe Primiero, On the foundations of computing. Oxford: Oxford University Press (ISBN 978-0-19-883564-6/hbk; 978-0-19-883565-3/pbk). xix, 296 p. (2020). It gives a critical view from the perspective of physical computing as a foundation of computing and argues that the neglected pillar of material computation (Stepney) should be brought centerstage and computing recognized as the fourth great domain of science (Denning)
Procurement\u27s role in resolving demand–supply imbalances: an\ua0information processing theory perspective
No full textPurpose: Drawing on information processing theory, the linkage between buffering and bridging and the ability on the part of procurement to resolve demand–supply imbalances is investigated, as well as contexts in which these strategies may be particularly useful or detrimental. Buffering may be achieved through demand change or redundancy, while bridging may be achieved by the means of collaboration or monitoring. Design/methodology/approach: This study employs a hierarchical regression analysis of a survey of 150 Finnish and Swedish procurement and sales and operations planning professionals, each responding from the perspective of their own area of supply responsibility. Findings: Both the demand change and redundancy varieties of buffering are associated with procurement\u27s ability to resolve demand–supply imbalances without delivery disruptions, but not with cost-efficient resolution. Bridging is associated with the cost-efficient resolution of imbalances: while collaboration offers benefits, monitoring seems to make things worse. Dynamism diminishes, while the co-management of procurement in S&OP improves procurement\u27s ability to resolve demand–supply imbalances. The most potent strategy for tackling problematic contexts appears to be buffering via demand change. Practical implications: The results highlight the importance of procurement in the S&OP process and suggest tactical measures that can be taken to resolve and reduce the effects of supply and demand imbalances. Originality/value: The results contribute to the procurement and S&OP literature by increasing knowledge regarding the role and integration of procurement to the crucial process of balancing demand and supply operations
Advances in the application of an early and selective recovery of lithium from spent lithium-ion batteries via hydrometallurgical methods
Get PDFIn 2020 alone, the use of electric vehicles (EVs) contributed to more than 50 Mt CO2-eq of savings in GHG emissions globally. Given their performance in terms of energy and power density, Lithium-ion batteries (LiBs) are the technology of choice for the success of rapid EV growth. The demand for elements such as cobalt, nickel, copper, and lithium has increased widely. The concern regarding the availability of lithium is growing, and countries are rushing to establish policies to ensure a stable supply of critical minerals for EV battery supply chains. Lithium was added to a list of critical raw materials in 2020, and new regulations are pushing towards the recycling of more materials. The recovery target for lithium is set at 70% by 2030. Current recycling systems do not have a high lithium recovery rate. Pyrometallurgy does not allow its recycling, while the current hydrometallurgy processes exhibit lithium losses. Traditional flowcharts are very complex. Usually disregarded, there has not been a major push to develop a recycling process centred around lithium. New recycling strategies are trying to lift its importance by recovering lithium in the first step. Early selective and more efficient recovery of lithium from spent lithium-ion batteries is the main objective of the research. The focus of this study was the investigation of early and complete lithium recovery. Two promising methods are considered: acombination of a thermal treatment followed by water leaching and a full hydrometallurgical route involving the use of oxalic acid as a leaching agent. The experiments were carried out using real LiB waste. The use of thermal treatment on spent batteries presents many advantages. It allows for safer handling of the battery cell and the reduction of waste volume. Moreover, the metal oxides undergo a reduction forming more leachable species. At the same time, the reaction between lithium dioxide and carbon dioxide form lithium carbonate, a water-soluble species. The highest lithium recovery (62%) is achieved after pyrolysis at 700\ub0C for 1h and water leaching at 25\ub0C for 1h with a solid-to-liquid ratio of 20 g/L. Aluminium is the only co-dissolved element. On the other hand, the use of oxalic acid led to a 98.8% leaching yield for lithium, while less than 0.5 % of cobalt and nickel, and 1.5% of manganese were leached when applying leaching at 60\ub0C, 1h, 0.6 M oxalic acid. Moreover, aluminium is completely leached, which is one of the novel findings in this field. Nickel, cobalt, and manganese oxalates are insoluble and remain in the solid residue, while lithium oxalate is dissolved in the solution
Resolving the Emission Regions of the Crab Pulsar’s Giant Pulses. II. Evidence for Relativistic Motion
Get PDFThe Crab Pulsar is the prime example of an emitter of giant pulses. These short, very bright pulses are thought to originate near the light cylinder, at ∼1600 km from the pulsar. The pulsar’s location inside the Crab Nebula offers an unusual opportunity to resolve the emission regions, using the nebula, which scatters radio waves, as a lens. We attempt to do this using a sample of 61,998 giant pulses found in coherently combined European VLBI network observations at 18 cm. These were taken at times of relatively strong scattering and hence good effective resolution. From correlations between pulse spectra, we show that the giant pulse emission regions are indeed resolved. We infer apparent diameters of ∼2000 and ∼2400 km for the main and interpulse components, respectively, and show that with these sizes the correlation amplitudes and decorrelation timescales and bandwidths can be understood quantitatively, both in our observations and in previous ones. Using pulse-spectra statistics and correlations between polarizations, we also show that the nebula resolves the nanoshots that comprise individual giant pulses. The implied diameters of ∼1100 km far exceed light-travel-time estimates, suggesting the emitting plasma is moving relativistically, with γ ≃ 104, as inferred previously from drifting bands during the scattering tail of a giant pulse. If so, the emission happens over a region extended along the line of sight by ∼107 km. We conclude that relativistic motion likely is important for producing giant pulses, and may be similarly for other sources of short, bright radio emission, such as fast radio bursts
Minimum parking requirements and car ownership: An analysis of Swedish municipalities
Get PDFTransportation is a major contributor to anthropogenic climate change driven primarily by private automobility and for nearly a century, cities have used a suite of policies and regulations that reinforce high rates of car ownership. One such regulation is minimum parking requirements, enacted to ensure that private properties can accommodate the storage of private vehicles. In recent years, cities have begun to reevaluate these parking requirements, with some municipalities reducing them, others providing opportunities for flexible parking, and some even removing parking requirements in part or all of the city. This article explores the relationship between parking requirements and car ownership by analyzing a survey of 56 municipalities across Sweden. In this paper, we develop two methods for comparing different parking metrics that municipalities use (parking spaces per apartment and parking spaces per building area). Our analysis examines variation between different sizes and classifications of municipalities. We find that across all municipalities, there is a positive relationship between minimum parking requirements and car ownership, meaning that higher minimum parking requirements are associated with higher rates of car ownership. City size is an important factor in rates of car ownership, but our analysis shows that even among similarly sized municipalities, minimum parking requirements tend to be associated with higher rates of car ownership. These findings show that reducing parking minimums can be an effective policy to reduce car ownership, but it is important to consider that these changes only impact new development and repurposing parking areas in existing housing areas may be an equally effective policy to curb car ownership
Marine yeast (Candida sake) cultured on herring brine side streams is a promising feed ingredient and omega-3 source for rainbow trout (Oncorhynchus mykiss)
Get PDFA major challenge for the aquaculture industry is the supply of sustainable feeds. A promising model to achieve this is to utilize circular flows where feed ingredients, such as single cell protein, are cultivated using side streams of the food industry. The aim of this study was to evaluate the marine yeast Candida sake, produced on herring brine side streams, as a source of protein and immune stimulant in feed for salmonid fish. The dry C. sake product contained 54% protein (3.3% lysine and 0.8% methionine) and 13% lipids (1.1% eicosapentaenoic, EPA, and 1% docosahexaenoic acid, DHA). Four experimental diets were designed and tested in a 9-week feeding trial using juvenile rainbow trout (Oncorhynchus mykiss). A control diet containing both fish and plant-based ingredients constituted the base feed to which 20% (to evaluate effects on digestibility, growth and intestinal physiology), 20% heat-treated (to evaluate effects of downstream processing) and 3% (to evaluate immune stimulatory properties, replacing 3% soy protein concentrate) C. sake was added. The apparent digestibility coefficient of C. sake for protein, fat and gross energy was above 80%, and for amino acids above 90% regardless of treatment, suggesting a high bioavailability of C. sake. All three yeast containing diets performed equally to the control regarding specific growth rate, feed conversion ratio and functional intestinal health. These results suggest that C. sake is a promising alternative protein source for circular feeds in the salmonid industry. The presence of EPA and DHA represents an added value. The heat treatment increased the apparent digestibility coefficient of dry matter by 8% but decreased amino acid digestibility by on average 3%, indicating that heat treatment may not be the optimal downstream processing technique. Furthermore, the inclusion of 3% C. sake increased the intestinal lamina propria width and TGF-β transcription, indicating an immune stimulating effect. Future research is needed to understand these immune modulatory effects of C. sake supplementation
Investigation of the dynamic airtightness coefficient of high-speed trains traveling through a tunnel: A field study
No full textDetermining the dynamic airtightness coefficient (τdyn) of train carriages using a high-accuracy and high-efficiency method is essential regarding the study of the dynamic airtightness performance of high-speed trains (HSTs) traveling through tunnels. This study set out to provide a systematic elaboration and investigation of the whole process of establishing the calculation methodology of τdyn of HST carriages. Moreover, the applicability of three different typical optimization algorithms in the calculation of τdyn was explored and compared. These were the traversal algorithm (TRAA), the trichotomy algorithm (TRIA), and the genetic algorithm (GA). Using the established calculation method, the values of τdyn of different HST carriages for tunnels with different lengths were calculated based on field test data of pressure outside and inside HST carriages. Results revealed that the selection of optimization algorithms had significant effects on the calculation process of τdyn because of their different optimization mechanisms. These three optimization algorithms were proven to be feasible for establishing the calculation method of τdyn and gave the same calculation result of τdyn for the calculation example within the expected accuracy. The elapsed time of the TRAA and GA were approximately 100 and 80 times that of the TRIA regarding the calculation example. The TRIA was the preferable choice for the calculation of τdyn among the three algorithms because of its uncomplicated implementation logic and high efficiency. Within the tunnel-length range involved, the tunnel length itself had no significant effect on τdyn of HST carriages. A significant increasing trend in τdyn of HST carriages was found along the train length. Compared to the head car, the increasing ratio of τdyn of the second car was varying from 0.2 to 0.5, while the increasing ratio of the seventh car was ranging from 0.8 to 1.7 considering different tunnel lengths. These findings provide a reference basis for the design of the calculation method of τdyn of HST carriages and also enhance understanding of τdyn of HST carriages under different operating circumstances
Counting rational points on projective varieties
Get PDFWe develop a global version of Heath-Brown\u27s p-adic determinant method to study the asymptotic behaviour of the number N(W; B) of rational points of height at most B on certain subvarieties W of Pn defined over Q. The most important application is a proof of the dimension growth conjecture of Heath-Brown and Serre for all integral projective varieties of degree d ≥ 2 over Q. For projective varieties of degree d ≥ 4, we prove a uniform version N(W; B) = Od,n,ε(BdimW+ε) of this conjecture. We also use our global determinant method to improve upon previous estimates for quasi-projective surfaces. If, for example, (Formula presented.) is the complement of the lines on a non-singular surface X ⊂\ua0P3 of degree d, then we show that (Formula presented.). For surfaces defined by forms (Formula presented.) with non-zero coefficients, then we use a new geometric result for Fermat surfaces to show that (Formula presented.) for B ≥ e
A full transit of v 2 Lupi d and the search for an exomoon in its Hill sphere with CHEOPS
Get PDFThe planetary system around the naked-eye star v2 Lupi (HD 136352; TOI-2011) is composed of three exoplanets with masses of 4.7, 11.2, and 8.6 Earth masses (M⊕). The TESS and CHEOPS missions revealed that all three planets are transiting and have radii straddling the radius gap separating volatile-rich and volatile-poor super-earths. Only a partial transit of planet d had been covered so we re-observed an inferior conjunction of the long-period 8.6 M⊕ exoplanet v2 Lup d with the CHEOPS space telescope. We confirmed its transiting nature by covering its whole 9.1 h transit for the first time. We refined the planet transit ephemeris to P = 107.13610.0022+0.0019 days and Tc = 2459009.77590.0096+0.0101 BJDTDB, improving by ~40 times on the previously reported transit timing uncertainty. This refined ephemeris will enable further follow-up of this outstanding long-period transiting planet to search for atmospheric signatures or explore the planet s Hill sphere in search for an exomoon. In fact, the CHEOPS observations also cover the transit of a large fraction of the planet s Hill sphere, which is as large as the Earth s, opening the tantalising possibility of catching transiting exomoons. We conducted a search for exomoon signals in this single-epoch light curve but found no conclusive photometric signature of additional transiting bodies larger than Mars. Yet, only a sustained follow-up of v2 Lup d transits will warrant a comprehensive search for a moon around this outstanding exoplanet
The discrete spectrum of the Neumann-Poincar\ue9 operator in 3D elasticity
Get PDFFor the Neumann-Poincar\ue9 (double layer potential) operator in the three-dimensional elasticity we establish asymptotic formulas for eigenvalues converging to the points of the essential spectrum and discuss geometric and mechanical meaning of coefficients in these formulas. In particular, we establish that for any body, there are infinitely many eigenvalues converging from above to each point of the essential spectrum. On the other hand, if there is a point where the boundary is concave (in particular, if the body contains cavities) then for each point of the essential spectrum there exists a sequence of eigenvalues converging to this point from below. The reasoning is based upon the representation of the Neumann-Poincar\ue9 operator as a zero order pseudodifferential operator on the boundary and the earlier results by the author on the eigenvalue asymptotics for polynomially compact pseudodifferential operators