Segmenting root systems in X-ray computed tomography images using level sets

The segmentation of plant roots from soil and other growing media in X-ray computed tomography images is needed to effectively study the root system architecture without excavation. However, segmentation is a challenging problem in this context because the root and non-root regions share similar features. In this paper, we describe a method based on level sets and specifically adapted for this segmentation problem. In particular, we deal with the issues of using a level sets approach on large image volumes for root segmentation, and track active regions of the front using an occupancy grid. This method allows for straightforward modifications to a narrow-band algorithm such that excessive forward and backward movements of the front can be avoided, distance map computations in a narrow band context can be done in linear time through modification of Meijster et al.'s distance transform algorithm, and regions of the image volume are iteratively used to estimate distributions for root versus non-root classes. Results are shown of three plant species of different maturity levels, grown in three different media. Our method compares favorably to a state-of-the-art method for root segmentation in X-ray CT image volumes.Comment: 11 page

Анализ методов построения объемных дистанционных карт

В статье рассмотрены и сопоставлены друг с другом по нескольким аспектам (точность, скорость, простота реализации, возможность распараллеливания) методы построения трехмерных дистанционных карт, в результате чего можно с определенной долей уверенности дать ответ на вопрос, в каком случае лучше использовать тот или иной метод.У статті розглянуті і зіставлені один з одним за декількома аспектами (точність, швидкість, простота реалізації, можливість розпаралелювання) методи побудови тривимірних дистанційних карт, в результаті чого можна з певною долею впевненості дати відповідь на питання, в якому випадку краще використовувати той або інший метод.Methods of distance map construction were examined and compared with each other in several aspects (accuracy, speed, ease of implementation, the possibility of paralleling) techniques for constructing three-dimensional distance. With some confidence you can give an answer to a question, in which case it is better to use one or another method

Multi-robot Automated Search for Non-Adversarial Moving Evaders in an Unknown Environment

In this paper, the problem of searching for moving evaders in unknown environment using group of mobile robots is investigated. The aim is to find the moving evaders as fast as possible. Three different search techniques are proposed and evaluated through extensive experimentation. In the first two techniques, robots do not cooperate or coordinate their actions. Alternatively, they implement simple movement strategies to locate the evaders. On the contrary, in the third technique, robots employ explicit coordination among each other and they implement a relatively complex algorithm based on voronio graph to find the evaders. In the later technique, each robot needs to be equipped with communication and localization capabilities. The results showed that graph-based technique led to shortest search time. However, it also showed that a reasonable performance is possible with cheap robots implementing simple and non-coordination techniques. Keywords: Search, Multi-Robot, Voronio Graph, Moving Target, Coordination