ABSTRACT
TLS is nowadays often used for deformation monitoring. As it is not able to scan identical points in different time epochs, mathematical models of objects derived from point clouds have to be used. The most common geometric form to describe built objects is a plane, which can be described by four parameters. In this study, we aimed to find out how small changes in the parameters of the plane can be detected by TLS. We aimed to eliminate all possible factors that influence the scanning. Then, we shifted and tilted a finite physical representation of a plane in a controlled way. After each controlled change, the board was scanned several times and the parameters of the plane were calculated. We used two different types of scanning devices and compared their performance. The changes in the plane parameters were compared with the actual change values and statistically tested. The results show that TLS detects shifts in the millimetre range and tilts of 150â³ (for a 1 m plane). A robotic total station can achieve twice the precision of TLS despite lower density and slower performance. For deformation monitoring, we strongly recommend repeating each scan several times (i) to check for gross errors and (ii) to obtain a realistic precision estimate.
ABSTRACT
Objective To understand the emission rate and the attenuation rule of formaldehyde in the artificial woodiness boards for sell in China and to study the efficiency of formaldehyde-eliminator. Methods With the small Climate-Chamber and 4160 formaldehyde-analyzer, quantity of formaldehyde released from some kinds of woodiness boards was analyzed under the different condition of temperature, relative humidity and ventilation cycle. Results The emission rate of formaldehyde in most veneers was over 1.2 mg/(m2?h), in most of moderate density fibreboard, it was 0.7～1.0 mg/(m2?h) and in the veneer for medical application, it was 0.3～0.9 mg/(m2?h). Formaldehyde emission rates of all the three kinds of woodiness boards investigated in the present study showed a fall of 75% in a period of time after made, and met the National Standard of China. The formaldehyde eliminator could reduce the emission rate of formaldehyde remarkably, however the effect perhaps weakened in a short time. Conclusion The formaldehyde emission rates in all kinds of woodiness boards investigated in the present paper are different, they exceed the National Standard of China while the boards made immediately and will reduce after 10-15 days in a given condition. The formaldehyde eliminator used in the study shows a remarkable effect but lasts only a short time.
