Burke and Teng introduced a two-player combinatorial game Atropos based on Sperner's lemma, and showed that deciding whether one has a winning strategy for Atropos is PSPACE-complete. In the original Atropos game, the players must color a node adjacent to the last colored node. Burke and Teng also mentioned a variant Atropos-k in which each move is at most of distance k of the previous move, and asked a question on determining the computational complexity of this variant. In this paper, we answer this question by showing that for any fixed integer k (k>=2), Atropos-k is PSPACE-complete by reduction from True Quantified Boolean Formula (TQBF).
Human fault detection plays an important role in the industrial assembly process. In the current unstructured industrial workspace, the definition of human faults may vary over a long sequence, and this vagueness introduces multiple issues when using traditional detection methods. A method which could learn the correct action sequence from humans, as well as detect the fault actions based on prior knowledge, would be more appropriate and effective. To this end, we propose an end-to-end learning model to predict future human actions and extend it to detect human faults. We combined the auto-encoder framework and recurrent neural network (RNN) method to predict and generate intuitive future human motions. The convolutional long short-term memory (ConvLSTM) layer was applied to extract spatio-temporal features from video sequences. A score function was implemented to indicate the difference between the correct human action sequence and the fault actions. The proposed model was evaluated on a model vehicle seat assembly task. The experimental results showed that the model could effectively capture the necessary historical details to predict future human actions. The results of several fault scenarios demonstrated that the model could detect the faults in human actions based on corresponding future behaviors through prediction features.
This paper focuses on the undecidability of translational tiling of $n$-dimensional space $\mathbb{Z}^n$ with a set of $k$ tiles. It is known that tiling $\mathbb{Z}^2$ with translated copies with a set of $8$ tiles is undecidable. Greenfeld and Tao gave strong evidence in a series of works that for sufficiently large dimension $n$, the translational tiling problem for $\mathbb{Z}^n$ might be undecidable for just one tile. This paper shows the undecidability of translational tiling of $\mathbb{Z}^3$ with a set of $6$ tiles.
Most robots are programmed to carry out specific tasks routinely with minor variations. However, more and more applications from SMEs require robots work alongside their counterpart human workers. To smooth the collaboration task flow and improve the collaboration efficiency, a better way is to formulate the robot to surmise what kind of assistance a human coworker needs and naturally take the right action at the right time. This paper proposes a prediction-based human-robot collaboration model for assembly scenarios. An embedded learning from demonstration technique enables the robot to understand various task descriptions and customized working preferences. A state-enhanced convolutional long short-term memory (ConvLSTM)-based framework is formulated for extracting the high-level spatiotemporal features from the shared workspace and predicting the future actions to facilitate the fluent task transition. This model allows the robot to adapt itself to predicted human actions and enables proactive assistance during collaboration. We applied our model to the seats assembly experiment for a scale model vehicle and it can obtain a human worker's intentions, predict a coworker's future actions, and provide assembly parts correspondingly. It has been verified that the proposed framework yields higher smoothness and shorter idle times, and meets more working styles, compared to the state-of-the-art methods without prediction awareness.
Posterior capsule opacification (PCO) compromises vision development in infants after cataract surgery and lead to amblyopia. To observe the effects of curcumin on PCO in infant rabbits, curcumin was injected under the capaule and into the anterior chamber during phacoemulsification.Seventy-five 1-month-old healthy New Zealand white rabbits were randomized into 3 groups, one eye of each rabbit was randomly selected to be operated. The operation involved continuous circular capsulorhexis, followed by hydrodissection with 0.6 ml each of balanced salt solution (BSS, group A), hydroxypropyl-β-dodextrin (HP-β-CD, 90 µg/ml, group B) or CUR-HP-β-CD (123 µg/ml, group C), respectively. After phacoemulsification, 0.4 ml of each drug solution was injected into the anterior chamber via an incision. The extent of corneal edema and the inflammatory response within the anterior chamber were considered as measures PCO and observed postoperatively. All eyes were examined 1 and 2 months postoperative by slit lamp microscopy and photography after pupil dilation. On the third day postoperative, 6 rabbits from each group were executed. Paraffin-embedded sections were stained with hematoxylin-eosin (HE) or terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL, indicative of apoptosis). Stained sections were observed under light microscopy. Proliferation of lens epithelial cells (LECs) was observed microscopically on day 3, day 7, month 1 and month 2 after the operation with HE staining.The remission of cornea edema occurred earlier in group C than in groups A and B (P < 0.05); there were no significant differences between groups A and B. The remission of anterior chamber exudation in group C was earlier than those in groups A and B (P < 0.05). No significant difference in the times when PCO occurred, was observed among groups. Compared to groups A and B, the extent of PCO was less severe (P < 0.05). Three days after the operation, LECs aggregated at the orbit. Meanwhile, minor apoptosis was observed in all groups. One month after the operation transparent, cortex and proliferating LECs were observed near the orbit in groups A and B. Two months postoperative, heavy cortex proliferation was observed in all groups: epithelial cells migrated and aggregated at the posterior capsule and rearranged under the anterior capsule in the control group. Proliferation was also observed in group C, but to a less severe extent than in the other two groups.CUR-HP-β-CD exerts an inhibitory effect on PCO.
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