scholarly journals Evolution of simple multicellular life cycles in dynamic environments

2019 ◽  
Author(s):  
Yuriy Pichugin ◽  
Hye Jin Park ◽  
Arne Traulsen
Keyword(s):  
Natural Selection ◽  
Reproductive Strategies ◽  
Population Growth Rate ◽  
Dynamic Environment ◽  
Dynamic Environments ◽  
Life Cycles ◽  
Matrix Population Model ◽  
Bet Hedging ◽  
Reproduction Mode ◽  
Natural Response

AbstractThe mode of reproduction is a critical characteristic of any species, as it has a strong effect on its evolution. As any other trait, the reproduction mode is subject to natural selection and may adapt to the environment. When the environment varies over time, different reproduction modes could be optimal at different times. The natural response to a dynamic environment seems to be bet hedging, where multiple reproductive strategies are stochastically executed. Here, we develop a framework for the evolution of simple multicellular life cycles in a dynamic environment. We use a matrix population model of undifferentiated multicellular groups undergoing fragmentation and ask which mode maximizes the population growth rate. Counterintuitively, we find that natural selection in dynamic environments generally tends to promote deterministic, not stochastic, reproduction modes.

scholarly journals Evolution of simple multicellular life cycles in dynamic environments

2019 ◽  
Vol 16 (154) ◽  
pp. 20190054 ◽  
Author(s):  
Yuriy Pichugin ◽  
Hye Jin Park ◽  
Arne Traulsen
Keyword(s):  
Natural Selection ◽  
Reproductive Strategies ◽  
Population Growth Rate ◽  
Dynamic Environment ◽  
Dynamic Environments ◽  
Life Cycles ◽  
Matrix Population Model ◽  
Bet Hedging ◽  
Reproduction Mode ◽  
Natural Response

The mode of reproduction is a critical characteristic of any species, as it has a strong effect on its evolution. As any other trait, the reproduction mode is subject to natural selection and may adapt to the environment. When the environment varies over time, different reproduction modes could be optimal at different times. The natural response to a dynamic environment seems to be bet hedging, where multiple reproductive strategies are stochastically executed. Here, we develop a framework for the evolution of simple multicellular life cycles in a dynamic environment. We use a matrix population model of undifferentiated multicellular groups undergoing fragmentation and ask which mode maximizes the population growth rate. Counterintuitively, we find that natural selection in dynamic environments generally tends to promote deterministic, not stochastic, reproduction modes.

Multi-Robot SLAM in Dynamic Environments with Parallel Maps

2021 ◽  
pp. 2150011
Author(s):  
Sajad Badalkhani ◽  
Ramazan Havangi ◽  
Mohsen Farshad
Keyword(s):  
Large Scale ◽  
Dynamic Environment ◽  
Dynamic Environments ◽  
Extensive Literature ◽  
Real World Data ◽  
Data Set ◽  
Cooperative Approach ◽  
Localization And Mapping ◽  
Multi Robot

There is an extensive literature regarding multi-robot simultaneous localization and mapping (MRSLAM). In most part of the research, the environment is assumed to be static, while the dynamic parts of the environment degrade the estimation quality of SLAM algorithms and lead to inherently fragile systems. To enhance the performance and robustness of the SLAM in dynamic environments (SLAMIDE), a novel cooperative approach named parallel-map (p-map) SLAM is introduced in this paper. The objective of the proposed method is to deal with the dynamics of the environment, by detecting dynamic parts and preventing the inclusion of them in SLAM estimations. In this approach, each robot builds a limited map in its own vicinity, while the global map is built through a hybrid centralized MRSLAM. The restricted size of the local maps, bounds computational complexity and resources needed to handle a large scale dynamic environment. Using a probabilistic index, the proposed method differentiates between stationary and moving landmarks, based on their relative positions with other parts of the environment. Stationary landmarks are then used to refine a consistent map. The proposed method is evaluated with different levels of dynamism and for each level, the performance is measured in terms of accuracy, robustness, and hardware resources needed to be implemented. The method is also evaluated with a publicly available real-world data-set. Experimental validation along with simulations indicate that the proposed method is able to perform consistent SLAM in a dynamic environment, suggesting its feasibility for MRSLAM applications.

A survey on discrete space and continuous space facility layout problems

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Irappa Basappa Hunagund ◽  
V. Madhusudanan Pillai ◽  
Kempaiah U.N.
Keyword(s):  
Literature Review ◽  
Facility Layout ◽  
Dynamic Environment ◽  
Dynamic Environments ◽  
Structure Design ◽  
Discrete Space ◽  
Content Type ◽  
Continuous Space ◽  
Complete Problems ◽  
Flexible Bay Structure

Purpose The purpose of this paper is to review, evaluate and classify the academic research that has been published in facility layout problems (FLPs) and to analyse how researches and practices on FLPs are. Design/methodology/approach The review is based on 166 papers published from 1953 to 2021 in international peer-reviewed journals. The literature review on FLPs is presented under broader headings of discrete space and continuous space FLPs. The important formulations of FLPs under static and dynamic environments represented in the discrete and continuous space are presented. The articles reported in the literature on various representations of facilities for the continuous space Unequal Area Facility Layout Problems (UA-FLPs) are summarized. Discussed and commented on adaptive and robust approaches for dynamic environment FLPs. Highlighted the application of meta-heuristic solution methods for FLPs of a larger size. Findings It is found that most of the earlier research adopted the discrete space for the formulation of FLPs. This type of space representation for FLPs mostly assumes an equal area for all facilities. UA-FLPs represented in discrete space yield irregular shape facilities. It is also observed that the recent works consider the UA-FLPs in continuous space. The solution of continuous space UA-FLPs is more accurate and realistic. Some of the recent works on UA-FLPs consider the flexible bay structure (FBS) due to its advantages over the other representations. FBS helps the proper design of aisle structure in the detailed layout plan. Further, the recent articles reported in the literature consider the dynamic environment for both equal and unequal area FLPs to cope with the changing market environment. It is also found that FLPs are Non-deterministic Polynomial-complete problems, and hence, they set the challenges to researchers to develop efficient meta-heuristic methods to solve the bigger size FLPs in a reasonable time. Research limitations/implications Due to the extremely large number of papers on FLPs, a few papers may have inadvertently been missed. The facility layout design research domain is extremely vast which covers other areas such as cellular layouts, pick and drop points and aisle structure design. This research review on FLPs did not consider the papers published on cellular layouts, pick and drop points and aisle structure design. Despite the possibility of not being all-inclusive, the authors firmly believe that most of the papers published on FLPs are covered and the general picture presented on various approaches and parameters of FLPs in this paper are precise and trustworthy. Originality/value To the best of the authors’ knowledge, this paper reviews and classifies the literature on FLPs for the first time under the broader headings of discrete space and continuous space representations. Many important formulations of FLPs under static and dynamic environments represented in the discrete and continuous space are presented. This paper also provides the observations from the literature review and identifies the prospective future directions.

Modified Newton's method applied to potential field based navigation for nonholonomic robots in dynamic environments

Robotica ◽  
2008 ◽  
Vol 26 (3) ◽  
pp. 285-294 ◽  
Author(s):  
Jing Ren ◽  
Kenneth A. McIsaac ◽  
Rajni V. Patel
Keyword(s):  
Newton’S Method ◽  
Potential Field ◽  
Newton's Method ◽  
Dynamic Environment ◽  
Dynamic Environments ◽  
Field Methods ◽  
Control Laws ◽  
Nonholonomic Robots ◽  
Modified Newton’S Method ◽  
Speed Up

SUMMARYThis paper is to investigate inherent oscillations problems of Potential Field Methods (PFMs) for nonholonomic robots in dynamic environments. In prior work, we proposed a modification of Newton's method to eliminate oscillations for omnidirectional robots in static environment. In this paper, we develop control laws for nonholonomic robots in dynamic environment using modifications of Newton's method. We have validated this technique in a multirobot search-and-forage task. We found that the use of the modifications of Newton's method, which applies anywhere C2 continuous navigation functions are defined, can greatly reduce oscillations and speed up robot's movement, when compared to the standard gradient approaches.

Atypical reproduction in a syllid worm: the stolon of Syllis rosea (Annelida, Syllidae) takes care of its offspring

2020 ◽  
Vol 100 (2) ◽  
pp. 221-227
Author(s):  
Joachim Langeneck ◽  
Michela Del Pasqua ◽  
Margherita Licciano ◽  
Adriana Giangrande ◽  
Luigi Musco
Keyword(s):  
Parental Care ◽  
Sexual Reproduction ◽  
Reproductive Strategy ◽  
Reproductive Strategies ◽  
Congeneric Species ◽  
Reproduction Mode ◽  
Laboratory Rearing ◽  
Larval Stages ◽  
The Family ◽  
Reproductive Cycles

AbstractThe family Syllidae, aside from representing the most species-rich family in Annelida, is characterized by a number of sexual and asexual reproductive strategies. With the exception of a few viviparous species, the subfamily Syllinae is characterized by schizogamous reproduction with pelagic larval stages and without parental care. Laboratory rearing of ripe specimens of Syllis rosea showed a different reproductive strategy, hitherto unknown in this subfamily. While male stolons rapidly degenerated after fertilization, female ones released large eggs in a gelatinous cluster attached to the middle-posterior chaetigers. The gel mass progressively compacted as a cocoon wrapped by the stolon body; 7 days after the deposition the larvae hatched out from the cocoon at the metatrochophore stage and the female stolon died after a few days. After hatching the larvae remained associated to the stolon, and young specimens of S. rosea survived up to the 3-chaetiger stage. Until now cocoon brooding by the stolon has only been reported for some Autolytinae. The production of gelatinous egg masses and parental care are known in basally branching clades within Syllidae, suggesting that this reproduction mode might retain some ancestral features. The scarce knowledge about reproductive cycles in Syllinae does not allow clarification whether this strategy is unique for S. rosea, or it occurs in other congeneric species. Further research is needed to understand possible relationships between sexual reproduction and phylogeny, stolon morphology and its adaptation to parental care, and ultimately between reproductive strategies and ecology.

Technological innovation in libraries

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Pei-Chun Lee
Keyword(s):  
United States ◽  
Organizational Learning ◽  
Technological Innovation ◽  
Dynamic Environment ◽  
Patent Citation ◽  
Life Cycles ◽  
Knowledge Source ◽  
Content Type ◽  
Demand Pull ◽  
Library Technology

PurposeThe purpose of this study was to identify technological innovation in libraries and further examine the knowledge source and their effects during the technology life cycle (TLC).Design/methodology/approachThis paper discusses the technological innovation taking place in libraries. Patent citation analysis was used to capture the trend of technological innovation associated with libraries.FindingsThe findings are as follows: (1) library technologies are now in the ascent phase of their life cycles; (2) private companies from the United States, Germany, France, Japan and the United Kingdom are the top-five owners of intellectual property rights associated with library technology and (3) patent data along with knowledge and technology indicators can be interpreted in the light of library development. The knowledge source with the highest degree of scientific and technological orientation was identified as basic material chemistry. The major technological categories that have received the greatest knowledge effect from library-associated technological innovation are chemistry, electrical engineering, instruments, mechanical engineering, with other fields (civil engineering and furniture, games) being subject to less effect.Research limitations/implicationsThere are two research limitations in this study. First, the results use single informants, patents retrieved from United States Patent and Trademark Office, as the source of data. Second, this study uses patent citation measures for exploring the knowledge source and effect of technological innovation, these measures are only subjective for those new invention highly based technological advances. This study concludes that technological innovation for libraries will be characterized by an increasing role for science-intensive and interdisciplinary areas. This study also suggests that organizational learning facilitates innovation. Therefore, a library hoping to co-evolve with dynamic environment through technological innovation should improve its organizational learning processes.Practical implicationsTheories of technology-push and demand-pull were examined in relation to technological innovation taking place in libraries. The TLC analysis indicated that library technology is mainly in the ascent stage, suggesting that libraries have not achieved the strongest technological transformation. The findings suggest that the importance of demand-pull and technology-push vary over the TLC of libraries.Social implicationsTo survive in a dynamic environment library must be able to cope with increasing complexity and high-speed technological change. It is pivotal to integrate the views of users (as customers), software houses or design companies (as suppliers) as well as other libraries (as communities) into the sustainable development strategy of a library. In these contexts, libraries with the capacity to innovate will be able to respond to new demands faster and to invent and provide new services better than noninnovative libraries.Originality/valueAnalysis based on the technological innovation perspective to identify the future development of libraries is still lacking. This paper seeks to identify the technological innovation employed in libraries to accommodate the 21st century model of information-seeking behavior. This study identifies a variety of factors that have influenced the transformation of library services, and these include technology developments and new demands from library users. To illustrate the driving forces of technology-push in libraries, this paper examines holistic-patented technologies invented for libraries.

scholarly journals Navigation in Unknown Dynamic Environments Based on Deep Reinforcement Learning

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 3837 ◽  
Author(s):  
Junjie Zeng ◽  
Rusheng Ju ◽  
Long Qin ◽  
Yue Hu ◽  
Quanjun Yin ◽  
...  
Keyword(s):  
Reinforcement Learning ◽  
Domain Knowledge ◽  
Moving Objects ◽  
Dynamic Environment ◽  
Dynamic Environments ◽  
Continuous Control ◽  
Complex Environments ◽  
Reward Function ◽  
Knowledge Based ◽  
Task Architecture

In this paper, we propose a novel Deep Reinforcement Learning (DRL) algorithm which can navigate non-holonomic robots with continuous control in an unknown dynamic environment with moving obstacles. We call the approach MK-A3C (Memory and Knowledge-based Asynchronous Advantage Actor-Critic) for short. As its first component, MK-A3C builds a GRU-based memory neural network to enhance the robot’s capability for temporal reasoning. Robots without it tend to suffer from a lack of rationality in face of incomplete and noisy estimations for complex environments. Additionally, robots with certain memory ability endowed by MK-A3C can avoid local minima traps by estimating the environmental model. Secondly, MK-A3C combines the domain knowledge-based reward function and the transfer learning-based training task architecture, which can solve the non-convergence policies problems caused by sparse reward. These improvements of MK-A3C can efficiently navigate robots in unknown dynamic environments, and satisfy kinetic constraints while handling moving objects. Simulation experiments show that compared with existing methods, MK-A3C can realize successful robotic navigation in unknown and challenging environments by outputting continuous acceleration commands.

Reproductive Strategies of Demersal and Pelagic Spawning Fish

1984 ◽  
Vol 41 (11) ◽  
pp. 1565-1569 ◽  
Author(s):  
T. C. Lambert ◽  
D. M. Ware
Keyword(s):  
Growth Rate ◽  
Reproductive Strategies ◽  
Larval Growth ◽  
Clupea Harengus ◽  
Time Interval ◽  
Bet Hedging ◽  
Atlantic Mackerel ◽  
Larval Growth Rate ◽  
Mouth Size ◽  
The Relationship

The spawning tactic of herring (Clupea harengus) wherein batches of eggs are deposited leading to a succession of larval cohorts is elaborated. We found the time interval between cohorts to be a function of larval growth rate as well as larval mouth size. In view of the relationship with growth rate we suggest a continuum of reproductive strategies with "bet hedging" by herring at one extreme and an "all at once" egg release by Atlantic mackerel (Scomber scombrus) at the other.

Research on Mobile Robot SLAM in Dynamic Environment

2011 ◽  
Vol 130-134 ◽  
pp. 232-238
Author(s):  
Bai Fan Chen ◽  
Zi Xing Cai
Keyword(s):  
Mobile Robot ◽  
Experimental Test ◽  
Data Association ◽  
Dynamic Environment ◽  
Dynamic Environments ◽  
Target Model ◽  
Dynamic Objects ◽  
Objects Detection

A SLAMiDE（SLAM in Dynamic Environments) system is designed and realized in the paper, which supplies a holistic framework and a series of implementation methods for mobile robot SLAM in dynamic environments. A uniform target model is proposed in SLAMiDE system. The dynamic targets and static targets and the mobile robot pose are estimated simultaneously, by synthesized the research of the data association and dynamic targets detection and static SLAM based on local maps. Finally, the results of the experimental test prove that the SLAMiDE system can realize dynamic objects detection and mapping and location correctly.

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