Ileum of the Cephalotes ants: A specialized structure to harbor symbionts microorganisms

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Limitations of trust management schemes in VANET and countermeasures

Vehicular networks ensure that the information received from any vehicle is promptly and correctly propagated to nearby vehicles, to prevent accidents. A crucial point is how to trust the information transmitted, when the neighboring vehicles are rapidly changing and moving in and out of range. Current trust management schemes for vehicular networks establish trust by voting on the decision received by several nodes, which might not be required for practical scenarios. It might just be enough to check the validity of incoming information. Due to the ephemeral nature of vehicular networks, reputation schemes for mobile ad hoc networks (MANETs) cannot be applied to vehicular ad hoc networks (VANET). We point out several limitations of trust management schemes for VANET. In particular, we identify the problem of information cascading and oversampling, which commonly arise in social networks. Oversampling is a situation in which a node observing two or more nodes, takes into consideration both their opinions equally without knowing that they might have influenced each other in decision making. We show that simple voting for decision making, leads to oversampling and gives incorrect results. We propose an algorithm to overcome this problem in VANET. This is the first paper which discusses the concept of cascading effect and oversampling effects to ad hoc networks. © 2011 IEEE.

A social network approach to trust management in VANETs

In the past few years, vehicular ad hoc networks(VANETs) was studied extensively by researchers. VANETs is a type of P2P network, though it has some distinct characters (fast moving, short lived connection etc.). In this paper, we present several limitations of current trust management schemes in VANETs and propose ways to counter them. We first review several trust management techniques in VANETs and argue that the ephemeral nature of VANETs render them useless in practical situations. We identify that the problem of information cascading and oversampling, which commonly arise in social networks, also adversely affects trust management schemes in VANETs. To the best of our knowledge, we are the first to introduce information cascading and oversampling to VANETs. We show that simple voting for decision making leads to oversampling and gives incorrect results in VANETs. To overcome this problem, we propose a novel voting scheme. In our scheme, each vehicle has different voting weight according to its distance from the event. The vehicle which is more closer to the event possesses higher weight. Simulations show that our proposed algorithm performs better than simple voting, increasing the correctness of voting. © 2012 Springer Science + Business Media, LLC.

Mass occurrence of the cubomedusa Copula sivickisi (Cnidaria: Cubozoa) at Seto Harbor, Shirahama, Wakayama, Japan in summer of 2013, a recent example of global warming

More than 200 very young medusae of Copula sivickisi (Stiasny) were collected within totally 60 minutes at two nights in June, 2013 at the Seto Harbor, Shirahama, Wakayama, Japan. This mass occurrence might be related to recent global warming at Shirahama, known as the northernmost distributional locality of this cubozoan species. It is assumed that the polyp stage of this species may live in the surrounding areas, because there jellyfish were small size (most are less than 1.6 mm height) that was conceivable as the newly released one from the polyp.

Mitigation of the bullwhip effect considering trust and collaboration in supply chain management: a literature review

The aim of this paper is to provide results of trust and collaboration that lead to the mitigation of the bullwhip effect in supply chain management through a systematic literature review. The criterion for its inclusion in the sample of papers was that at least two reviews of the respective subfields were published in peer-reviewed journals between 1990 and 2014. A total of 24 articles were selected. The analysis found that few studies focused on addressing behavioral aspects to reduce the bullwhip effect. Most of them focused on operational and quantitative aspects. These results indicate the need for studies on behavioral aspects in mitigating the bullwhip effect, where trust and collaboration among those involved in the supply chain need to be developed and organized.