Friction plays a pivotal role in the sliding-mode triboelectric energy harvester(TEH),which not only enables the charge transfer between two dielectrics,but also influences the energy harvesting performance by affecti...Friction plays a pivotal role in the sliding-mode triboelectric energy harvester(TEH),which not only enables the charge transfer between two dielectrics,but also influences the energy harvesting performance by affecting the dynamic response of the TEH.How to evaluate the effects of the friction on TEHs is important for optimizing TEHs in engineering practices.In order to analyze the effects of the friction on the dynamic response and evaluate the energy harvesting performance ofTEHs,the paper models the friction of a devised non-linear TEH based on the Coulomb friction model and the Macro-slip friction theory.The TEH equips a pair of magnets,rendering a switching between the bistability and the monostability by tuning the distance between two magnets.The dynamic model of the non-linear TEH is established by the extended Hamilton principle.The effects of friction in slidingmode TEH are dissected in detail.The influences of parameters on both the mechanical and electrical responses are also systemically studied to explore an optimal energy harvesting performance in the low-frequency range.This work provides a guideline for designing and accurately analyzing a sliding-mode TEH.展开更多
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 us...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.展开更多
A gradient metamaterial with varying-stiffness local resonators is proposed to open the multiple bandgaps and further form a broad fusion bandgap.First,three local resonators with linearly increasing stiffness are per...A gradient metamaterial with varying-stiffness local resonators is proposed to open the multiple bandgaps and further form a broad fusion bandgap.First,three local resonators with linearly increasing stiffness are periodically attached to the spring-mass chain to construct the gradient metamaterial.The dispersion relation is then derived based on Bloch's theorem to reveal the fusion bandgap theoretically.The dynamic characteristic of the finite spring-mass chain is investigated to validate the fusion of multiple bandgaps.Finally,the effects of the design parameters on multiple bandgaps are discussed.The results show that the metamaterial with a non-uniform stiffness gradient pattern is capable of opening a broad fusion bandgap and effectively attenuating the longitudinal waves within a broad frequency region.展开更多
Mulberries(Morus alba L.cv.Longsang 1),rich in various nutrients and bioactive compounds.Fermentation can improve the nutritional value of fruit juice processed from mulberries,making it easier to absorb,and can also ...Mulberries(Morus alba L.cv.Longsang 1),rich in various nutrients and bioactive compounds.Fermentation can improve the nutritional value of fruit juice processed from mulberries,making it easier to absorb,and can also improve the taste and aroma,thus promoting further development.this study investigates the differences in aroma and sensory attributes between Pichia kudriavzevii and Weissella confusa mixed bacterial fermentation(PWF)and sequentially fermented(MLF)mulberry juices.Headspace solid phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS)analysis was employed to examine the volatile metabolites in fermentation juice,while high performance liquid chromatography(HPLC)-MS analysis quantified the free amino acid and organic acid content.additionally,electronic nose and electronic tongue technologies were utilized for sensory evaluation.Results from HS-SPME-GC-MS analysis revealed a notable 61.06%increase in esters in MLF juice,imparting fruity and floral aromas.HPLC-MS analysis indicated a 52.69%increase in sour amino acids in MLF juice,with umami amino acids being 2.23 times higher compared to PWF,resulting in a more pronounced taste profile.additionally,succinic acid,citric acid,lactic acid,tartaric acid,and malic acid exhibited reductions of 20%,50%,12.66%,75%,and 43.18%,respectively.Electronic tongue and electronic nose analyses demonstrated elevated response values for aromatic components and decreased astringency and bitterness in MLF juice.this research presents a novel fermentation approach to enhance the sensory attributes of fermented mulberry juice.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11972152,12002122,and 12122206)Natural Science Foundation of Hunan Province(Grant Nos.2021JJ40092,and 2020JJ4208)Natural Science Foundation of Chongqing and China Postdoctoral Science Foundation(Grant No.2020M672476).
文摘Friction plays a pivotal role in the sliding-mode triboelectric energy harvester(TEH),which not only enables the charge transfer between two dielectrics,but also influences the energy harvesting performance by affecting the dynamic response of the TEH.How to evaluate the effects of the friction on TEHs is important for optimizing TEHs in engineering practices.In order to analyze the effects of the friction on the dynamic response and evaluate the energy harvesting performance ofTEHs,the paper models the friction of a devised non-linear TEH based on the Coulomb friction model and the Macro-slip friction theory.The TEH equips a pair of magnets,rendering a switching between the bistability and the monostability by tuning the distance between two magnets.The dynamic model of the non-linear TEH is established by the extended Hamilton principle.The effects of friction in slidingmode TEH are dissected in detail.The influences of parameters on both the mechanical and electrical responses are also systemically studied to explore an optimal energy harvesting performance in the low-frequency range.This work provides a guideline for designing and accurately analyzing a sliding-mode TEH.
基金supported by the National Natural Science Foundation of China(Nos.12122206 and 12272129)the Natural Science Foundation of Hunan Province of China(No.2024JJ4004)the Zhejiang Provincial Natural Science Foundation of China(No.LQ24A020006)。
文摘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.
基金supported by the National Natural Science Foundation of China(Nos.12122206,52175125,12272129,12304309,and 12302039)the Zhejiang Provincial Natural Science Foundation of China(No.LQ24A020006)+1 种基金the Hong Kong Scholars Program of China(No.XJ2022012)the Natural Science Foundation of Hunan Province of China(No.2024JJ4004)。
文摘A gradient metamaterial with varying-stiffness local resonators is proposed to open the multiple bandgaps and further form a broad fusion bandgap.First,three local resonators with linearly increasing stiffness are periodically attached to the spring-mass chain to construct the gradient metamaterial.The dispersion relation is then derived based on Bloch's theorem to reveal the fusion bandgap theoretically.The dynamic characteristic of the finite spring-mass chain is investigated to validate the fusion of multiple bandgaps.Finally,the effects of the design parameters on multiple bandgaps are discussed.The results show that the metamaterial with a non-uniform stiffness gradient pattern is capable of opening a broad fusion bandgap and effectively attenuating the longitudinal waves within a broad frequency region.
基金supported by the Natural Science Foundation of Heilongjiang Province(LH2022C075)Key Laboratory of Functional inorganic Material Chemistry(Heilongjiang University),Ministry of Education.
文摘Mulberries(Morus alba L.cv.Longsang 1),rich in various nutrients and bioactive compounds.Fermentation can improve the nutritional value of fruit juice processed from mulberries,making it easier to absorb,and can also improve the taste and aroma,thus promoting further development.this study investigates the differences in aroma and sensory attributes between Pichia kudriavzevii and Weissella confusa mixed bacterial fermentation(PWF)and sequentially fermented(MLF)mulberry juices.Headspace solid phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS)analysis was employed to examine the volatile metabolites in fermentation juice,while high performance liquid chromatography(HPLC)-MS analysis quantified the free amino acid and organic acid content.additionally,electronic nose and electronic tongue technologies were utilized for sensory evaluation.Results from HS-SPME-GC-MS analysis revealed a notable 61.06%increase in esters in MLF juice,imparting fruity and floral aromas.HPLC-MS analysis indicated a 52.69%increase in sour amino acids in MLF juice,with umami amino acids being 2.23 times higher compared to PWF,resulting in a more pronounced taste profile.additionally,succinic acid,citric acid,lactic acid,tartaric acid,and malic acid exhibited reductions of 20%,50%,12.66%,75%,and 43.18%,respectively.Electronic tongue and electronic nose analyses demonstrated elevated response values for aromatic components and decreased astringency and bitterness in MLF juice.this research presents a novel fermentation approach to enhance the sensory attributes of fermented mulberry juice.
