Autonomous exploration is an important application of multi-vehicle systems, where a team of networked robots are coordinated to explore an unknown environment collaboratively. This technique has ...earned significant research interest due to its usefulness in search and rescue, fault detection and monitoring, localization and mapping, etc. In this paper, a novel cooperative exploration strategy is proposed for multiple mobile robots, which reduces the overall task completion time and energy costs compared to conventional methods. To efficiently navigate the networked robots during the collaborative tasks, a hierarchical control architecture is designed which contains a high-level decision making layer and a low-level target tracking layer. The proposed cooperative exploration approach is developed using dynamic Voronoi partitions, which minimizes duplicated exploration areas by assigning different target locations to individual robots. To deal with sudden obstacles in the unknown environment, an integrated deep reinforcement learning based collision avoidance algorithm is then proposed, which enables the control policy to learn from human demonstration data and thus improve the learning speed and performance. Finally, simulation and experimental results are provided to demonstrate the effectiveness of the proposed scheme.
To examine whether comprehensive chromosome screening (CCS) for preimplantation genetic screening (PGS) has an effect on improving in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) ...outcomes compared to traditional morphological methods.
A literature search was conducted in PubMed, EMBASE, CNKI and ClinicalTrials.gov up to May 2015. Two reviewers independently evaluated titles and abstracts, extracted data and assessed quality. We included studies that compared the IVF/ICSI outcomes of CCS-based embryo selection with those of the traditional morphological method. Relative risk (RR) values with corresponding 95% confidence intervals (CIs) were calculated in RevMan 5.3, and subgroup analysis and Begg's test were used to assess heterogeneity and potential publication bias, respectively.
Four RCTs and seven cohort studies were included. A meta-analysis of the outcomes showed that compared to morphological criteria, euploid embryos identified by CCS were more likely to be successfully implanted (RCT RR 1.32, 95% CI 1.18-1.47; cohort study RR 1.74, 95% CI 1.35-2.24). CCS-based PGS was also related to an increased clinical pregnancy rate (RCT RR 1.26, 95% CI 0.83-1.93; cohort study RR 1.48, 95% CI 1.20-1.83), an increased ongoing pregnancy rate (RCT RR 1.31, 95% CI 0.64-2.66; cohort study RR 1.61, 95% CI 1.30-2.00), and an increased live birth rate (RCT RR 1.26, 95% CI 1.05-1.50; cohort study RR 1.35, 95% CI 0.85-2.13) as well as a decreased miscarriage rate (RCT RR 0.53, 95% CI 0.24-1.15; cohort study RR 0.31, 95% CI 0.21-0.46) and a decreased multiple pregnancy rate (RCT RR 0.02, 95% CI 0.00-0.26; cohort study RR 0.19, 95% CI 0.07-0.51). The results of the subgroup analysis also showed a significantly increased implantation rate in the CCS group.
The effectiveness of CCS-based PGS is comparable to that of traditional morphological methods, with better outcomes for women receiving IVF/ICSI technology. The transfer of both trophectoderm-biopsied and blastomere-biopsied CCS-euploid embryos can improve the implantation rate.
The present study aimed to undertake a review of available evidence assessing whether time-lapse imaging (TLI) has favorable outcomes for embryo incubation and selection compared with conventional ...methods in clinical in vitro fertilization (IVF).
Using PubMed, EMBASE, Cochrane library and ClinicalTrial.gov up to February 2017 to search for randomized controlled trials (RCTs) comparing TLI versus conventional methods. Both studies randomized women and oocytes were included. For studies randomized women, the primary outcomes were live birth and ongoing pregnancy, the secondary outcomes were clinical pregnancy and miscarriage; for studies randomized oocytes, the primary outcome was blastocyst rate, the secondary outcome was good quality embryo on Day 2/3. Subgroup analysis was conducted based on different incubation and embryo selection between groups.
Ten RCTs were included, four randomized oocytes and six randomized women. For oocyte-based review, the pool-analysis observed no significant difference between TLI group and control group for blastocyst rate relative risk (RR) 1.08, 95% CI 0.94-1.25, I2 = 0%, two studies, including 1154 embryos. The quality of evidence was moderate for all outcomes in oocyte-based review. For woman-based review, only one study provided live birth rate (RR 1,23, 95% CI 1.06-1.44,I2 N/A, one study, including 842 women), the pooled result showed no significant difference in ongoing pregnancy rate (RR 1.04, 95% CI 0.80-1.36, I2 = 59%, four studies, including 1403 women) between two groups. The quality of the evidence was low or very low for all outcomes in woman-based review.
Currently there is insufficient evidence to support that TLI is superior to conventional methods for human embryo incubation and selection. In consideration of the limitations and flaws of included studies, more well designed RCTs are still in need to comprehensively evaluate the effectiveness of clinical TLI use.
Flocking is a social animals’ common behaviour observed in nature. It has a great potential for real-world applications such as exploration in agri-robotics using low-cost robotic solutions. In this ...paper, an extended model of a self-organised flocking mechanism using heterogeneous swarm system is proposed. The proposed model for swarm robotic systems is a combination of a collective motion mechanism with obstacle avoidance functions, which ensures a collision-free flocking trajectory for the followers. An optimal control model for the leader is also developed to steer the swarm to a desired goal location. Compared to the conventional methods, by using the proposed model, the swarm network has less requirement for power and storage. The feasibility of the proposed self-organised flocking algorithm is validated by realistic robotic simulation software.
We report a Ni-Al layered double hydroxide (LDH)-graphene superlattice composite via alternating assembly of the exfoliated thin flakes with opposite charges that show stable high-rate performance ...for alkaline battery cathodes.
There are many potential applications of swarm robotic systems in real-world scenarios. In this paper, formation-containment controller design for single-integrator and double-integrator swarm ...robotic systems with input saturation is investigated. The swarm system contains two types of robots—
leaders
and
followers
. A novel control protocol and an implementation algorithm are proposed that enable the leaders to achieve the desired formation via semidefinite programming (SDP) techniques. The followers then converge into the convex hull formed by the leaders simultaneously. In contrast to conventional consensus-based formation control methods, the relative formation reference signal is not required in the real-time data transmission, which provides greater feasibility for implementation on hardware platforms. The effectiveness of the proposed formation-containment control algorithm is demonstrated with both numerical simulations and experiments using real robots that utilize the miniature mobile robot, Mona.
The robotic shepherding problem has earned significant research interest over the last few decades due to its potential application in precision agriculture. In this article, we first modeled the ...sheep flocking behavior using adaptive protocols and artificial potential field methods. Then, we designed a coordination algorithm for robotic dogs. An occlusion-based motion control strategy was proposed to herd the sheep to the desired location. Compared to formation-based techniques, the proposed control strategy provides more flexibility and efficiency when herding a large number of sheep. Simulation and lab-based experiments, using real robots and a global vision-based tracking system, were carried out to validate the effectiveness of the proposed approach.
The precise evaluation of sensory perceptions during fabric-skin interactions is still poorly understood in neuroscience. This study aims to investigate the cortical sensory response to fabric ...stimuli with different textiles by Electroencephalographic (EEG) spectral intensities, and evaluate the relationships between EEG frequency bands, traditional subjective questionnaires, and the materials' physical properties. Twelve healthy adult participants were recruited to test three fabrics with different textile compositions of 1) cotton, 2) nylon, and 3) polyester and wool. The physical properties of the fabrics were quantitatively evaluated by a Fabric Touch Tester (FTT). Subjects were invited to rate the sensory perception of the fabric samples via a subjective questionnaire and objective EEG recording. Significant differences in the EEG relative spectral power of Theta and Gamma bands were acquired in response to the different fabric stimuli (P<0.05). The Theta and Gamma powers demonstrated a significant correlation with the most of the subjective sensations evaluated by questionnaire and the fabrics' physical properties by FTT (P<0.05). The EEG spectral analysis could feasibly be used for the discrimination of fabric stimuli with different textile compositions and further indicates sensory perceptions during fabric stimulation. This finding may provide evidence for further exploratory research of sensory perceptions via EEG spectral analysis, which could be applied to the study of brain generators of skin tactility in future prostheses and the automatic detection of sensory perception in industries.
During spermatogenesis, interconnected haploid spermatids segregate undesired cellular contents into residual bodies (RBs) before detaching from RBs. It is unclear how this differentiation process is ...controlled to produce individual spermatids or motile spermatozoa. Here, we developed a live imaging system to visualize and investigate this process in C. elegans. We found that non-muscle myosin 2 (NMY-2)/myosin II drives incomplete cytokinesis to generate connected haploid spermatids, which are then polarized to segregate undesired cellular contents into RBs under the control of myosin II and myosin VI. NMY-2/myosin II extends from the pseudo-cleavage furrow formed between two haploid spermatids to the spermatid poles, thus promoting RB expansion. In the meantime, defective spermatogenesis 15 (SPE-15)/myosin VI migrates from spermatids towards the expanding RB to promote spermatid budding. Loss of myosin II or myosin VI causes distinct cytoplasm segregation defects, while loss of both myosins completely blocks RB formation. We found that the final separation of spermatids from RBs is achieved through myosin VI-mediated cytokinesis, while myosin II is dispensable at this step. SPE-15/myosin VI and F-actin form a detergent-resistant actomyosin VI ring that undergoes continuous contraction to promote membrane constriction between spermatid and RB. We further identified that RGS-GAIP-interacting protein C terminus (GIPC)-1 and GIPC-2 cooperate with myosin VI to regulate contractile ring formation and spermatid release. Our study reveals distinct roles of myosin II and myosin VI in spermatid differentiation and uncovers a novel myosin VI-mediated cytokinesis process that controls spermatid release.
•A fully-distributed and robust secondary voltage and frequency control scheme for islanded microgrid.•Feedback linearization applied to suppress the structural heterogeneity of the DG units.•It ...reduces the bandwidth requirement and offers greater reliability and flexibility in operation.•It considers the effects due to parameter variation, model uncertainty and unmodelled dynamics.
This paper deals with the problem of designing a fully-distributed and robust secondary control scheme for voltage and frequency restoration of islanded microgrids along with real power sharing. Compared to the existing developments in this topic, the proposed multi-agent consensus-based secondary control scheme takes into account the effects of model uncertainty, parameter variation and unmodelled dynamics and thereby, offers a certain degree of robustness against all these factors. Due to virtue of the fully-distributed control configuration, each distributed generating (DG) unit in a microgrid requires only the information of its own and some of its neighbours but not of all other DG units attached to that microgrid. This helps in reducing the bandwidth requirement and cost of the underlying communication network and also causes enhanced flexibility and reliability of the overall microgrid operation. The proposed scheme counteracts any fluctuation in the terminal voltage and frequency of the DG units and also facilitates real power sharing among them at a pre-specified ratio despite the time-varying load disturbances, various power line faults, communication delays, etc. Finally, an exhaustive case study on a prototype IEEE 14-bus microgrid system containing five DG units has been accomplished to demonstrate the usefulness of the developed scheme.
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