To investigate the influence of shape memory alloys (SMAs) on the dynamic properties (mainly refers to the frequency
and the damping ratio) of concrete columns, the vibration curves of the concrete column reinforced with steel wire and
SMA wires with different phase were measured through initial displacement method. In this study, the experiment
included two parts. One is the free vibration test, which utilized the active property tuning (APT) principle, i.e. the
passive damping, of SMAs to change the vibration performance of the concrete columns. The results show that SMAs
can increase the damping ratio of the concrete column due to its high damping and decrease the frequency owing to its
lower stiffness. The other is the vibration test with electrical current activation, the active strain energy tuning (ASET)
principle, i.e. the active damping, was applied to alternate the vibration performance of the concrete columns. In this test,
martensitic SMA wires were strained up to 4% and were heated with a current of 40A. The test results show that with
increasing of the temperature, the frequency of the concrete column decreases, while its damping ratio increases.
Comparing the results of these two tests, the influence of two tuning principles, APT principle and ASET principle, on
the damping ratio of concrete columns is almost the same. However, for the frequency of the concrete columns, the
influence of ASET principle is larger than that of APT principle.
In order to detect the plant's nitrogen content in real-time, a wireless crop growth monitor is developed. It is made up of
a sensor and a controller. The sensor consists of an optical part and a circuit part. The optical part is made up of 4 optical
channels and 4 photo-detectors. 2 channels receive the sunlight and the other 2 receive the reflected light from the crop
canopy. The intensity of sunlight and the reflected light is measured at the wavebands of 610 nm and 1220 nm
respectively. The circuit part is made up of power supply unit, 4 amplifiers and a wireless module. The controller has
functions such as keyboard input, LCD display, data storage, data upload and so on. Both hardware and software are
introduced in this report. Calibration tests show that the optical part has a high accuracy and the wireless transmission
also has a good performance.
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