Results 1 - 10 of 27
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[en] We propose a general method to obtain approximation of the first passage time distribution for the birth–death processes. We rely on the general properties of birth–death processes, Keilson’s theorem and the concept of Riemann sum to obtain closed-form expressions. We apply the method to the three selected birth–death processes and the sophisticated order-book model exhibiting long-range memory. We discuss how our approach contributes to the competition between spurious and true long-range memory models. (paper: interdisciplinary statistical mechanics)
[en] Nutrients from a flowering plant are shared by its pollinators, giving rise to competition in the latter. Such exploitative competition of pollinators can limit their abundance and affect the global organization of the mutualistic partnership in the plant-pollinator mutualistic community. Here we investigate the effects of the exploitative competition between pollinators on the structure and the species abundance of the mutualistic networks which evolve by changing mutualistic partnership towards higher abundance of species. Simulations show different emergent network characteristics between plants and animals; hub plants connected to many pollinators are very rare while a few super-hub pollinators appear with the exploitative competition included, in contrast to equally many hubs of both types without the exploitative competition. More interestingly, the abundance of plant species increases with increasing the exploitative competition strength. We analyze the inverse of the generalized interaction matrix in the weak-interaction limit to identify the leading structural factors relevant to the species abundance, which are shown to be instrumental in optimizing the network structure to increase the mutualistic benefit and lower the cost of exploitative competition. (paper: biological modelling and information)
[en] This article studies the price competition and cooperation in a duopoly that is subjected to carbon emissions cap. The study assumes that in a departure from the classical Bertrand game, there is still a market for both firms’ goods regardless of the product price, even though production capacity is limited by carbon emissions regulation. Through the decentralized decision making of both firms under perfect information, the results are unstable. The firm with the lower maximum production capacity under carbon emissions regulation and the firm with the higher maximum production capacity both seek market price cooperation. By designing an internal carbon credits trading mechanism, we can ensure that the production capacity of the firm with the higher maximum production capacity under carbon emissions regulation reaches price equilibrium. Also, the negotiation power of the duopoly would affect the price equilibrium.
[en] Studying the competitive behavior of a crowd moving through an exit under extreme conditions has become an area of high interest for scientists in recent years. Conventional wisdom is that the flow rate of a crowd passing through an exit is dependent on exit width alone. This study investigated the impact of exit position on the flow rate using test mice under competition while driven by smoke produced from burning incense sticks. Prior to the test, the mice were trained to be familiar with the location of the exit. Exits with identical dimensions were placed at five different exit locations: at the center, the corner, 2 cm away from the sidewall, 10 cm away from the sidewall, and 20 cm away from the sidewall. Tests were subsequently repeated for each exit location. The time interval between the passage of two consecutive mice was 4.7 ± 0.3 s while the exit was located at the center position, and was reduced to 3.3 ± 0.1 s when the exit was moved to the corner position. Further study was again conducted by moving the exit to distances of 2 cm, 10 cm, and 20 cm away from the corner position. The minimal time interval was 2.9 ± 0.3 s when the exit was set to 2 cm away from the sidewall, which is a reduction of around 38% in comparison to scenarios which placed the exit in a central position. This study shows that the flow rate of mice passing through an exit under competition is in fact significantly affected by the location of exit. (paper: interdisciplinary statistical mechanics)
[en] Energy sector as a lever for Sustainable Development - Goals: Create competition in generation and commercialization through the creation of the Wholesale Electricity Market. Promote private investment in transmission and distribution through contracts with the Government. Speed up the energy transition towards a low carbon economy: improving the use of clean energies and more energy efficiency. Democratize access to energy.
[en] In this paper, a new evolutionary algorithm, the well-known imperialist competition algorithm, is proposed for optimizing the optical thin-films. In this method, the process is modeled of the competition between countries as imperialists and their colonizing of others as colonies. This algorithm could be an appropriate alternative to some of the more popular algorithms for optimizing the optical thin-films for good performance. The polarizer and edge filter for example are designed by using the imperialist competition algorithm method and the results are compared with those from two optimization high-performance methods: the genetic algorithm and differential evolutionary algorithm. Based on these results, the performance of the imperialist competition algorithm method shows that this algorithm is not sensitive to the change of its parameters and it can be an important advantage for quickly achieving a global optimal point. On the other hand the results show a better ratio of P-polarization transmittance to S-polarization transmittance in the design of a 1540-nm polarizer, which is more appropriate than the results from the other two methods. In the second design, an edge filter with a lower number of layers and more uniform bandpass spectrum than the counterparts of those methods is obtained. These results indicate that the imperialist competition algorithm is a robust method for optical thin-film designs. (paper)
[en] We study a mixture of s-bosons and like-nucleon pairs with the standard pairing interaction outside an inert core. Competition between the nucleon-pairs and s-bosons is investigated in this scenario. The robustness of the BCS-BEC coexistence and crossover phenomena are examined through an analysis of pf-shell nuclei with realistic single-particle energies, in which two configurations with Pauli blocking of nucleon-pair orbits due to the formation of the s-bosons is taken into account. When the nucleon-pair orbits are considered to be independent of the s-bosons, the BCS-BEC crossover becomes smooth, with the number of the s-bosons noticeably more than that of the nucleon-pairs near the half-shell point, a feature that is demonstrated in the pf-shell for several values of the standard pairing interaction strength. As a further test of the robustness of the BCS-BEC coexistence and crossover phenomena in nuclei, results are given for B(E2; 01+ → 21+) values of even-even 102-130 Sn with 100Sn taken as a core and valence neutron pairs confined within the 1d5/2, 0g7/2, 1d3/2, 2s1/2, 1h11/2 orbits in the nucleon-pair orbit and the s-boson independent approximation. The results indicate that the B(E2) values are reproduced well. (authors)
[en] Whereas there is not yet any offshore wind turbine farm along the French coast, three out of the eleven European factories producing wind turbines are located in France (in Saint-Nazaire, Cherbourg and Le Havre). They belong to different actors, General Electric and Siemens Gamesa which are represented by their subsidiaries (Alstom Energie and Areva Wind). These factories are briefly presented. The situation of the whole French sector is discussed: it nearly covers the whole range of activities, but some components still come from abroad, notably from China. The high level of competition in Europe is outlined. A second article focuses on a specific aspect of the floating wind energy sector to notice that oil companies are interested in entering this sector because technologies are close to those of oil offshore platforms
[en] In Brazil, as it has been occurring worldwide, the number of procedures using radiopharmaceuticals are increasing. The production and selling of short half-life radioisotopes are monopolized by the Brazilian Government. In 2006, a Constitutional Amendment revoked the state monopoly due to the need for the use of short half-life radioisotopes in nuclear medicine centres very far from government production facilities. The aim of this study is to describe the current status of radioisotope production and sales in Brazil and discuss some licensing process. Currently, there are 14 radiopharmaceuticals production facilities and 4 radiopharmacies operating in Brazil. The type of licensing process conducted in Brazil does not take into account the population density of each state, with a free competition model being adopted. Because of this, there are a lot of equipment concentrated in the Southeast while no cyclotrons or radiopharmacy operating in the Northern part of the country. One of the biggest obstacles during the licensing process is the designation of qualified personnel in radiopharmacy or accelerator for radiopharmaceutical production as operation workers and radiation safety officers. Currently, there are only 17 qualified workers in these fields. Regarding regulatory inspection in Brazil, during the facilities licensing process two types of inspections are usually performed: one to monitor the radiopharmaceutical production (usually overnight) and another to verify records and to test security systems. The number of facilities for radiopharmaceuticals production and sales are increasing. However, several external factors such as the distance from the nuclear medicine centres, and qualified personnel have proved crucial for the economic viability of this type of facility, and a rigorous licensing process is necessary to ensure radiological protection. (author)
[en] The organization of the electricity market as we know it today in Europe and in a number of other countries has its intellectual roots in issues of thirty years ago. The first European directive that initiates the opening to competition of the electricity sector in Europe will celebrate this year its twenty-three years. The Electricity Act in the United Kingdom, which dismantles and privatizes the integrated electricity monopoly and establishes a mandatory exchange exchange, will be thirty years this summer. The theoretical sources of this movement are even older: the founding economic work of Paul Joskow and Richard Schmalensee (Joskow, 1983) was published more than thirty-five years ago. Thus, the architecture and organization of our electrical systems in Europe is based on an intellectual landscape of more than a quarter of a century (Mistral, 2019).