Biological evolution in a sequence space with random fitnesses is studied within Eigen's quasispecies model. A strong selection limit is employed, in which the population resides at a single sequence at all times. Evolutionary trajectories start at a randomly chosen sequence and proceed to the global fitness maximum through a small number of intermittent jumps. The distribution of the total evolution time displays a universal power law tail with exponent -2. Simulations show that the evolutionary dynamics is very well represented by a simplified shell model, in which the subpopulations at local fitness maxima grow independently. The shell model allows for highly efficient simulations, and provides a simple geometric picture of the evolutionary trajectories.Biological evolution often displays a punctuated dynamical pattern, in the sense that quiescent periods of stasis alternate with bursts of rapid change. A variety of mechanisms for punctuation have been proposed, which operate on different levels of the tree of life. On the largest scales of macroevolution, coevolutionary avalanches may play a role, which have been associated with self-organized criticality [1]. On the level of populations, punctuation due to rare, beneficial mutations has been observed in evolution experiments with bacteria [2]. Similar behavior has been found in simulations of RNA evolution, where stasis corresponds to diffusion on a neutral network, and a punctuation event marks the transition to another network of higher fitness [3].Possibly the simplest interpretation of punctuated evolution is in terms of a homogeneous population, represented by a localized distribution in some phenotypic or genotypic space, which evolves in a static, multipeaked fitness landscape [4]. Under conditions of strong selection and small mutation rate, such a population will rapidly climb a local fitness maximum, where it then resides for a long time, until a rare, large fluctuation allows it to cross the valley to a more favorable peak. At least in the limit of infinite population size [5], the mathematics of this process is closely related to physical problems such as noise-driven barrier crossing, tunneling [6] and variablerange hopping [7], and it is easy to show that the residence time at one peak can be vastly larger than the time required for the transition to the next [8]. In a rugged fitness landscape, the sequence of transitions forms an evolutionary trajectory, which probes the distribution of fitness peaks and the geometry of the landscape.In this Letter we investigate the statistics of such evolutionary trajectories in the framework of Eigen's quasispecies model [9,10]. We consider a population of individuals, each characterized by a binary genomic sequence σ of length N , which reproduce asexually and mutate in discrete time t. The total number of sequences is S = 2 N . An individual with genotype σ leaves A(σ) offspring in the next generation, and point mutations occur with probability µ per site and generation. In a mean field approximation, wh...
Background. The majority of bidding models, such as those developed by Friedman and Gates focus on the mark-up decision. Despite a large body of literature, particularly related to the construction industry, these bidding models largely ignore human behavior. Aim. This article has two aims. The first is to contribute to the potential use of business games to study the results of auction behavior in a construction business environment. The second is to investigate the winner’s curse and its effects on individual companies and the market. Method. The methodology for this study is rooted in game theory. The reasoning which leads to the winner’s curse is explored through a behavioral multi-actor experiment. I developed a database-driven, online multiplayer auction game which served as a laboratory experiment. The study included 42 participants. Data were collected during the game, and debriefing results were analyzed. Results. The results show that contractors suffer from the winner’s curse for a variety of reasons including their own bidding strategy, strong competition within the construction market, and inaccurate estimates of project costs. These reasons affect the behavior of contractors and the intention to win the project’s bid as well as their willingness to take risks. Conclusion and Recommendations. The approach outlined in this article contributes to decision-making research in the context of the ‘reverse’ auction low bid method. I recommend that future researchers consider second-price, sealed-bid auctions (Vickrey auctions); this type of auction is also easy to implement.
Robotic systems are increasingly becoming a relevant factor for so-called "made to order" production, as is the case in the construction industry. The aim of this contribution is to provide a basis for a cross-disciplinary discussion on the topic of robotics in the construction industry, in which both technical issues regarding the technical challenges of robotics in the construction industry and how automated building construction can be practically addressed in education and training. Based on case studies and lab experiments, the authors investigated upcoming transformations in shell production by comparing the conventional construction process with proposed processes involving cable-driven parallel robots. The focus is on bricklaying and working methods for the installation of prefabricated elements. Based on the prospective changes in construction the impact on vocational education and training will be discussed and influences in current educational frameworks based on automation and robotics will be introduced.
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