No abstract

No abstract

The chlorophyll, pheophytin, and their proportions are critical factors to evaluate the sensory quality of green tea. This research aims to establish an effective method to determine the quantification of chlorophyll and pheophytin in green tea, based on Fourier transform infrared (FT–IR) spectroscopy. First, five brands of tea were collected for spectral acquisition, and the chlorophyll and pheophytin were measured using the reference method. Then, a relation between these two pigments and FT–IR spectroscopy were developed based on chemometrics. Additionally, the characteristic IR wavenumbers of these pigments were extracted and proved to be effective for a quantitative determination. Successively, non-linear models were also built based on these characteristic wavenumbers, obtaining coefficients of determination of 0.87, 0.80, 0.85 and 0.89; and relative predictive deviations of 2.77, 2.62, 2.26 and 3.07 for the four pigments, respectively. These results demonstrate the feasibility of FT–IR spectroscopy for the determination of chlorophyll and pheophytin.

No abstract

A tuned mass damper (TMD) is a widely used vibration reduction measure in bridge engineering, whose design is based on the modal property of bridge structure. As a consequence, bridge vibrations in certain frequencies are reduced, while vibrations in some other frequencies may be amplified according to the design methodology of the TMD. This paper systematically investigates the influence of these amplified frequencies on the dynamic performance of running trains subject to earthquake loads. Primarily, the design methodology of bridge-based designed TMD (BBD-TMD) is introduced. On this basis, a detailed train–track–bridge coupled dynamic model with attached BBD-TMD is established based on the multi-body dynamics theory and the finite element method. Finally, aiming at a practical engineering problem in China, the influence of BBD-TMD on running trains subject to earthquake loads is investigated. The results indicate that, for the bridge structure adopted in this study, the amplified frequency bands are similar to the natural frequencies of the car body in the train system. To design TMDs for railway bridges, the dynamic performance of running trains caused by these external installations should be seriously considered.

No abstract

No abstract

Near-infrared (NIR) spectroscopy was investigated to determine the total amino acids (TAA) in oilseed rape (Brassica napus L.) leaves under a new herbicidepropyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273)-stress. In full-spectrum partial least squares (PLS) models, direct orthogonal signal correction (DOSC) was the best preprocessing method. Successive projections algorithm (SPA) was used to select the relevant variables. Multiple linear regression (MLR), PLS, and least squares-support vector machine (LS-SVM) were used for calibration. The DOSC-SPA-LS-SVM model achieved the best prediction performance with correlation coefficients r=0.9968 and root mean squares error of prediction (RMSEP) =0.2950 comparing all SPA-MLR, SPA-PLS, and SPA-LS-SVM models. Some parsimonious direct functions were also developed based on the DOSC-SPA wavelength (1,340 nm) such as linear, index, logarithmic, binominal, and exponential functions. The best performance was achieved by direct exponential function with r=0.9968 and RMSEP=0.2943. The overall results indicated that NIR was able to determine the TAA in herbicide-stressed oilseed rape leaves, and the DOSC-SPA was quite helpful for the development of detection sensors and the monitoring of the growing status and herbicide effect on field crop oilseed rape.