Multi-layer quasi-zero-stiffness meta-structure for high-efficiency vibration isolation at low frequency

An easily stackable multi-layer quasi-zero-stiffness(ML-QZS)meta-structure is proposed to achieve highly efficient vibration isolation performance at low frequency.First,the distributed shape optimization method is used to design the unit cel,i.e.,the single-layer QZS(SL-QZS)meta-structure.Second,the stiffness feature of the unit cell is investigated and verified through static experiments.Third,the unit cells are stacked one by one along the direction of vibration isolation,and thus the ML-QZS meta-structure is constructed.Fourth,the dynamic modeling of the ML-QZS vibration isolation metastructure is conducted,and the dynamic responses are obtained from the equations of motion,and verified by finite element(FE)simulations.Finally,a prototype of the ML-QZS vibration isolation meta-structure is fabricated by additive manufacturing,and the vibration isolation performance is evaluated experimentally.The results show that the vibration isolation performance substantially enhances when the number of unit cells increases.More importantly,the ML-QZS meta-structure can be easily extended in the direction of vibration isolation when the unit cells are properly stacked.Hence,the ML-FQZS vibration isolation meta-structure should be a fascinating solution for highly efficient vibration isolation performance at low frequency.

Underwater cylindrical sandwich meta-structures composed of graded semi re-entrant zero Poisson’s ratio metamaterials with pre-strained wave propagation properties

Zero Poisson’s ratio(ZPR)mechanical metamaterials can yield no transverse displacements when unidi-rectionally compressed,and cylindrical sandwich meta-structures composed of semi re-entrant(SRE)ZPR metamaterials are thus explored for applications on cylindrical shells of underwater equipment or sub-mersible structures.A group of ZPR unit cells with specified pre-strained wave propagation characteristics and adequate load-bearing capabilities is optimally designed based on the periodic boundary condition(PBC)and Bloch’s Theorem.The sound transmission and pressure-resistant performance of cylindrical sandwich meta-structures comprising the homogeneous and graded SRE ZPR unit cells are then investi-gated.The results show that the designed meta-structures can perfectly yield better vibroacoustic atten-uation behavior within the specified frequency regions corresponding to the pre-strained band gaps and safely bear the hydrostatic pressure equivalent to 1000 m depth with low weight-bulk ratios.In addition,the functionally graded metamaterial core can boost vibroacoustic performance within broader frequency ranges.

3D direct printing of mechanical and biocompatible hydrogel meta-structures

Direct Ink Writing(DIW)has demonstrated great potential as a versatile method to 3D print multifunctional structures.In this work,we report the implementation of hydrogel meta-structures using DIW at room temperature,which seamlessly integrate large specific surface areas,interconnected porous characteristics,mechanical toughness,biocompatibility,and water absorption and retention capabilities.Robust but hydrophobic polymers and weakly crosslinked nature-origin hydrogels form a balance in the self-supporting ink,allowing us to directly print complex meta-structures without sacrificial materials and heating extrusion.Mechanically,the mixed bending or stretching of symmetrical re-entrant cellular lattices and the unique curvature patterns are combined to provide little lateral expansion and large compressive energy absorbance when external forces are applied on the printed meta-structures.In addition,we have successfully demonstrated ear,aortic valve conduits and hierarchical architectures.We anticipate that the reported 3D meta-structured hydrogel would offer a new strategy to develop functional biomaterials for tissue engineering applications in the future.

Predicting CircRNA-Disease Associations Based on Improved Weighted Biased Meta-Structure

Circular RNAs(circRNAs)are RNAs with a special closed loop structure,which play important roles in tumors and other diseases.Due to the time consumption of biological experiments,computational methods for predicting associations between circRNAs and diseases become a better choice.Taking the limited number of verified circRNA-disease associations into account,we propose a method named CDWBMS,which integrates a small number of verified circRNA-disease associations with a plenty of circRNA information to discover the novel circRNA-disease associations.CDWBMS adopts an improved weighted biased meta-structure search algorithm on a heterogeneous network to predict associations between circRNAs and diseases.In terms of leave-one-out-cross-validation(LOOCV),10-fold cross-validation and 5-fold cross-validation,CDWBMS yields the area under the receiver operating characteristic curve(AUC)values of 0.9216,0.9172 and 0.9005,respectively.Furthermore,case studies show that CDWBMS can predict unknow circRNA-disease associations.In conclusion,CDWBMS is an effective method for exploring disease-related circRNAs.

RM-structure alignment based statistical machine translation model

A novel model based on structure alignments is proposed for statistical machine translation in this paper. Meta-structure and sequence of meta-structure for a parse tree are defined. During the translation process, a parse tree is decomposed to deal with the structure divergence and the alignments can be constructed at different levels of recombination of meta-structure （RM）. This method can perform the structure mapping across the sub-tree structure between languages. As a result, we get not only the translation for the target language, but sequence of meta-stmctu .re of its parse tree at the same time. Experiments show that the model in the framework of log-linear model has better generative ability and significantly outperforms Pharaoh, a phrase-based system.