1,293 research outputs found
On the PSPACE-completeness of Peg Duotaire and other Peg-Jumping Games
Peg Duotaire is a two-player version of the classical puzzle called Peg Solitaire. Players take turns making peg-jumping moves, and the first player which is left without available moves loses the game. Peg Duotaire has been studied from a combinatorial point of view and two versions of the game have been considered, namely the single- and the multi-hop variant. On the other hand, understanding the computational complexity of the game is explicitly mentioned as an open problem in the literature. We close this problem and prove that both versions of the game are PSPACE-complete. We also prove the PSPACE-completeness of other peg-jumping games where two players control pegs of different colors
Sequential Formation of CO2 Hydrates in a Confined Environment: Description of Phase Equilibrium Boundary, Gas Consumption, Formation Rate and Memory Effect
Since 1980, one of the most promising solutions for the exploitation of natural gas hydrate
reservoirs was found to be the replacement of methane with carbon dioxide in order to improve the
efficiency of methane recovery and, at the same time, permanently store carbon dioxide. However,
the process efficiency is still too low and far from reaching technical maturity and becoming eco nomically competitive. In this sense, studying the intrinsic properties of CO2 hydrates formation
and dissociation processes may help in better defining the reasons for this low efficiency and finding
feasible solutions. This work deals with carbon dioxide hydrates formation in a natural silica-based
porous medium and in fresh water. A lab-scale apparatus was used for experiments, which were
carried out consecutively and with the same gasâwater mixture in order to detect the possible oc currence of the âmemory effectâ. Six tests were carried out: the quantity of gas available for the
formation of hydrates led to an initial pressure equal to 39.4 bar within the reactor (the initial pres sure was 46 bar; however, the dissolution of CO2 in water during the first test caused a reduction in
the quantity of gas available for the process). Each experiment started and ended at temperatures
equal or higher than 20 °C. Considering the local pressures, these temperatures ensured the com plete dissociation of hydrates. Besides thermodynamic parameters, the gas consumption and the
rate constant were evaluated throughout the whole of the experiments. Conversely to what is as serted in the literature, the results demonstrated the weak persistence of the memory effect at a
temperature slightly above 25 °C. As expected, ice formation competed with hydrates; however,
during tests, it caused the partial release of carbon dioxide previously trapped into hydrates or dis solved in water. Finally, the rate constant completely agreed with the labile Cluster Theory and
proved that primordial clusters and hydrate crystals formed and dissociated during the whole test.
The first phenomenon was predominant during the formation phase, while the opposite occurred
during the following step. The rate constant was found to be an effective parameter to quantify
differences between measured and real equilibrium conditions for the system
Experimental investigation on CO2methanation process for solar energy storage compared to CO2-based methanol synthesis
The utilization of the captured CO2 as a carbon source for the production of energy storage media offers a technological solution for overcoming crucial issues in current energy systems. Solar energy production generally does not match with energy demand because of its intermittent and non-programmable nature, entailing the adoption of storage technologies. Hydrogen constitutes a chemical storage for renewable electricity if it is produced by water electrolysis and is also the key reactant for CO2 methanation (Sabatier reaction). The utilization of CO2 as a feedstock for producing methane contributes to alleviate global climate changes and sequestration related problems. The produced methane is a carbon neutral gas that fits into existing infrastructure and allows issues related to the aforementioned intermittency and non-programmability of solar energy to be overcome. In this paper, an experimental apparatus, composed of an electrolyzer and a tubular fixed bed reactor, is built and used to produce methane via Sabatier reaction. The objective of the experimental campaign is the evaluation of the process performance and a comparison with other CO2 valorization paths such as methanol production. The investigated pressure range was 2â20 bar, obtaining a methane volume fraction in outlet gaseous mixture of 64.75% at 8 bar and 97.24% at 20 bar, with conversion efficiencies of, respectively, 84.64% and 99.06%. The methanol and methane processes were compared on the basis of an energy parameter defined as the spent energy/stored energy. It is higher for the methanol process (0.45), with respect to the methane production process (0.41â0.43), which has a higher energy storage capability
a library for the simulation of smart energy systems the case of the campus of the university of parma
Abstract Smart energy systems are complex systems (i.e. composed of windmills, PV panels, solar collectors, heat pumps, CHP systems, etc) in which synergies rise through the ICT (Information and Communications Technology) based management and control of the whole system. In the development of efficient smart energy systems, a fundamental step is the optimization of total energy conversion, transmission and utilization processes within the whole system. To this extent, mathematical models can represent very useful tools for the simulation of the behavior of the system. In this paper, a library for the dynamic simulation of smart energy systems is presented. The library is implemented in Matlab Âź /Simulink Âź and each component (i.e. the energy conversion and distribution systems and the end-users) is developed through a modular approach. Therefore, the modules are designed by considering a standardized input/output and causality structure. Finally, the capabilities of this approach are evaluated through the application to the district heating and cooling network of the Campus of the University of Parma. The case study is based on a branch which feeds twelve buildings with a total heating volume of about 150 000 m 3 and peak thermal power demand of about 8 MW. Results reported in the paper demonstrate the effectiveness of this approach and the capability in term of system optimization
Dipping prism modelling of subduction plates in view of an improved GOCE Global Moho: The Tonga example
The study of subduction zones, i.e. the process occurring at convergent boundaries by which one tectonic plate moves under another and sinks into the mantle, is a fundamental topic in many Earthârelated sciences. Since usually important density variations occur in the corresponâ dence of subduction zones, a proper modelling of these regions is fundamental when studying the Earth crust from gravity field observations. In the present work, we investigate the possibility to characterize a subduction zone by exploiting GOCE gravity gradients. The main obâ jective of the work is to find a simple way to model subducting plates in view of a global inversion of the gravity field to recover the main features of the Earth crust. In particular, GOCE alongâorbit filtered data are firstly reduced for the effects of the bathymetry, upperâsediâ ments, middleâsediments, and lowerâsediments. After that, the residual signal is further reduced for the effect of a âregular crustâ by means of a Kriging procedure, isolating, in this way, the gravitational effect of the subducting plate. The signal is thus fitted, by means of a simâ ulated annealing (SA) procedure, with the gravitational effect of a dipping prism, characterized by a set of parameters that define the prism position, size, density, and its strike and dipping angles. The methodology has been firstly assessed in a closedâloop experiment to test the performance of the SA algorithm in detecting the parameâ ters used to best fit the isolated gravitational signal of the subduction plate. Then, the Tonga subduction plate has been chosen as a natural labâ oratory to perform some numerical experiments. The closedâloop simulations have shown the capability of the proposed approach to estimate the parameters with a relative error smaller than 10%, even in the presence of observation noise. As for the Tonga subduction, the estimated model wellâfit the observed gravitational signal and its geometric parameters are highlyâconsistent with the values available in the literature
Origin, evolution, and distribution of the molecular machinery for biosynthesis of sialylated lipooligosaccharide structures in Campylobacter coli
Campylobacter jejuni and Campylobacter coli are the most common cause of bacterial gastroenteritis worldwide. Additionally, C. jejuni is the most common bacterial etiological agent in the autoimmune Guillain-Barre syndrome (GBS). Ganglioside mimicry by C. jejuni lipooligosaccharide (LOS) is the triggering factor of the disease. LOS-associated genes involved in the synthesis and transfer of sialic acid (glycosyltranferases belonging to family GT-42) are essential in C. jejuni to synthesize ganglioside-like LOS. Despite being isolated from GBS patients, scarce genetic evidence supports C. coli role in the disease. In this study, through data mining and bioinformatics analysis, C. coli is shown to possess a larger GT-42 glycosyltransferase repertoire than C. jejuni. Although GT-42 glycosyltransferases are widely distributed in C. coli population, only a fraction of C. coli strains (1%) are very likely able to express ganglioside mimics. Even though the activity of C. coli specific GT-42 enzymes and their role in shaping the bacterial population are yet to be explored, evidence presented herein suggest that loss of function of some LOS-associated genes occurred during agriculture niche adaptation.Peer reviewe
- âŠ