北洋海軍「平遠」艦考釋

中法甲申戰爭時，慘澹經營多年，後世喻為中國海軍搖籃的福州船政 局 (簡稱閩廠)，連同閩江沿線的防衛設備，於 1884年8月23-29 日的閩江之戰遭法人嚴重破壞。閩廠經費向非豐裕，戰後得修復與創新兼顧已非易事，更何況支用日益拮据，苟有所成，自屬難得。在這段非常時期，閩廠確有特殊的表現。這成就歸功於在甲申戰爭結束後不久便出掌閩廠的福建按察使蘇人裴蔭森(1823-1895)

Ultrasonic Monitoring of the Early-Age Hydration of Mineral Admixtures Incorporated Concrete using Cement-Based Piezoelectric Composite Sensors

The early-age hydration processes of concretes with mineral admixtures have been monitored and evaluated by a newly developed ultrasonic method based on embedded cement-based piezoelectric composite sensors. With the embedded ultrasonic (P-wave) measurement system, the waveform, wave velocity, attenuation coefficient index, and frequency-domain spectrum of detected ultrasonic waves during hydration can be recorded. The mineral admixtures examined include fly ash, slag, and silica fume, which replace part of the cement in concrete mixtures. It is found that the ultrasonic transmission parameters can be related to the microstructure changes of the concrete. Both the acceleration effects of silica fume and the retardation effects of fly ash and slag on the early hydration of concrete can be determined and explained through the analysis and comparison of the characteristics of the velocity curves. The attenuation coefficient index curve provides additional observation for the study of hydration kinetics. Moreover, the function of fresh concrete in filtering the high-frequency component of the wave varies with time, and concrete can be considered as low-pass frequency spectral filter. Frequency spectra analysis at different ages of fresh concrete provides useful information to reveal the early-age hydration process