Oligopoly can be defined as a market model of the imperfect competition type, assuming the existence of only a few companies in a sector or industry, from which at least some have a significant market share and can therefore influence the production prices in the market. Many models of oligopoly that differ from one another mostly in the nature of the competitive companies' behaviour can be found through the study of oligopolistic structures. Some models describe only the behaviour of two companies in the monitored market (duopoly), others describe several companies of the same power (cartel), still others assume that one of the companies has a dominant position in the market, etc. The text of this article deals with oligopolistic competition in the food market in the terms of the behaviour of grocers and with the impact of this competition upon the market competition in the sector. First, it mentions the agreements on common cooperation and procedure, when cartel market structure originates. It also analyzes the examples of behaviour of oligopoly with a dominant firm on the market with products in the food sector, with the goal of detecting whether the market with these products is significantly influenced by the oligopolistic behaviour of companies.

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Abstract-Existing localization approaches are divided into two groups: range-based and range-free. The range-free schemes often suffer from poor accuracy and low scalability, while the range-based localization approaches heavily depend on extra hardware capabilities or rely on the absolute RSSI (received signal strength indicator) values, far from practical. In this work, we propose a mobileassisted localization scheme called Perpendicular Intersection (PI), setting a delicate tradeoff between range-free and range-based approaches. Instead of directly mapping RSSI values into physical distances, by contrasting RSSI values from the mobile beacon to a sensor node, PI utilizes the geometric relationship of perpendicular intersection to compute node positions. We have implemented the prototype of PI with 100 TelosB motes and evaluate PI in both indoor and outdoor environments. Through comprehensive experiments, we show that PI achieves high accuracy, significantly outperforming the existing range-based and the mobile-assisted localization schemes.

Underwater acoustic sensor networks (UWA-SNs) are envisioned to perform monitoring tasks over the large portion of the world covered by oceans. Due to economics and the large area of the ocean, UWA-SNs are mainly sparsely deployed networks nowadays. The limited battery resources is a big challenge for the deployment of such long-term sensor networks. Unbalanced battery energy consumption will lead to early energy depletion of nodes, which partitions the whole networks and impairs the integrity of the monitoring datasets or even results in the collapse of the entire networks. On the contrary, balanced energy dissipation of nodes can prolong the lifetime of such networks. In this paper, we focus on the energy balance dissipation problem of two types of sparsely deployed UWA-SNs: underwater moored monitoring systems and sparsely deployed two-dimensional UWA-SNs. We first analyze the reasons of unbalanced energy consumption in such networks, then we propose two energy balanced strategies to maximize the lifetime of networks both in shallow and deep water. Finally, we evaluate our methods by simulations and the results show that the two strategies can achieve balanced energy consumption per node while at the same time prolong the networks lifetime.