Accurate measurement of anchor rod length is crucial for ensuring structural safety in tunnel engineering,yet conventional destructive techniques face limitations in efficiency and adaptability to complex underground ...Accurate measurement of anchor rod length is crucial for ensuring structural safety in tunnel engineering,yet conventional destructive techniques face limitations in efficiency and adaptability to complex underground environments.This study presents a novel wireless instrument based on the standing wave principle to enable remote,non-destructive length assessment.The system employs a master-slave architecture,where a handheld transmitter unit initiates measurements through robust 433 MHz wireless communication,optimized for signal penetration in obstructed spaces.The embedded measurement unit,integrated with anchor rods during installation,utilizes frequency-scanning technology to excite structural resonances.By analyzing standing wave characteristics,anchor length is derived from a calibrated frequency-length relationship.Power management adopts a standby-activation strategy to minimize energy consumption while maintaining operational readiness.Experimental validation confirms the system effectively measures anchor lengths with high precision and maintains reliable signal transmission through thick concrete barriers,demonstrating suitability for tunnel deployment.The non-destructive approach eliminates structural damage risks associated with traditional pull-out tests,while wireless operation enhances inspection efficiency in confined spaces.Thiswork establishes a paradigmfor embedded structural healthmonitoring in tunneling,offering significant improvements over existing methods in safety,cost-effectiveness,and scalability.The technology holds promise for broad applications in mining,underground infrastructure,and geotechnical engineering.展开更多
The sound absorption coefficients of wood and wood boards for five eucalypt species (Eucalyptus urophylla, Euca-lyptus urophylla E. grandis, Eucalyptus urophylla E. tereticornis, Eucalyptus urophylla E. camaldulensis ...The sound absorption coefficients of wood and wood boards for five eucalypt species (Eucalyptus urophylla, Euca-lyptus urophylla E. grandis, Eucalyptus urophylla E. tereticornis, Eucalyptus urophylla E. camaldulensis and Eucalyptus cloeziana) that were collected from plantation in Dongmen Forestry Center of Guangxi Province, China were tested with stand-ing wave method and their sound absorption properties were also compared. The results showed that the sound absorption co-efficients of the five eucalypt wood species did not change evidently below 1000 Hz, but above 1000 Hz their sound absorption coefficients increased with the increasing frequency. The difference in sound absorption coefficient among five species of eucalypt wood is not evident at the tested frequency range (200-2000 Hz), but the sound absorption property of Eucalyptus urophylla at low frequency is better than that of other four species. The sound absorption coefficient of the tangential-sawn board is higher than that of the radial-sawn board. The sound absorption property of eucalypt wood of 0.5 cm in thickness is much better than that of 1.0 cm in thickness. It is concluded that wood sound absorption properties of eucalypts are affected by their board thickness and the type of sawn timber within the testing frequency, but the variance of wood sound absorption property among the five tested species is not significant.展开更多
基金supported in part by the Natural Science Foundation of Gansu Province(Nos.20JR10RA614,22YF7GA182,22JR11RA042,22JR5RA1006,24CXGA024)the National Natural Science Foundation of China under Grant 61804071.
文摘Accurate measurement of anchor rod length is crucial for ensuring structural safety in tunnel engineering,yet conventional destructive techniques face limitations in efficiency and adaptability to complex underground environments.This study presents a novel wireless instrument based on the standing wave principle to enable remote,non-destructive length assessment.The system employs a master-slave architecture,where a handheld transmitter unit initiates measurements through robust 433 MHz wireless communication,optimized for signal penetration in obstructed spaces.The embedded measurement unit,integrated with anchor rods during installation,utilizes frequency-scanning technology to excite structural resonances.By analyzing standing wave characteristics,anchor length is derived from a calibrated frequency-length relationship.Power management adopts a standby-activation strategy to minimize energy consumption while maintaining operational readiness.Experimental validation confirms the system effectively measures anchor lengths with high precision and maintains reliable signal transmission through thick concrete barriers,demonstrating suitability for tunnel deployment.The non-destructive approach eliminates structural damage risks associated with traditional pull-out tests,while wireless operation enhances inspection efficiency in confined spaces.Thiswork establishes a paradigmfor embedded structural healthmonitoring in tunneling,offering significant improvements over existing methods in safety,cost-effectiveness,and scalability.The technology holds promise for broad applications in mining,underground infrastructure,and geotechnical engineering.
文摘The sound absorption coefficients of wood and wood boards for five eucalypt species (Eucalyptus urophylla, Euca-lyptus urophylla E. grandis, Eucalyptus urophylla E. tereticornis, Eucalyptus urophylla E. camaldulensis and Eucalyptus cloeziana) that were collected from plantation in Dongmen Forestry Center of Guangxi Province, China were tested with stand-ing wave method and their sound absorption properties were also compared. The results showed that the sound absorption co-efficients of the five eucalypt wood species did not change evidently below 1000 Hz, but above 1000 Hz their sound absorption coefficients increased with the increasing frequency. The difference in sound absorption coefficient among five species of eucalypt wood is not evident at the tested frequency range (200-2000 Hz), but the sound absorption property of Eucalyptus urophylla at low frequency is better than that of other four species. The sound absorption coefficient of the tangential-sawn board is higher than that of the radial-sawn board. The sound absorption property of eucalypt wood of 0.5 cm in thickness is much better than that of 1.0 cm in thickness. It is concluded that wood sound absorption properties of eucalypts are affected by their board thickness and the type of sawn timber within the testing frequency, but the variance of wood sound absorption property among the five tested species is not significant.
