ALBERT

Description: A new di-mannitol adipate ester-based zinc metal alkoxide (DMAE-Zn) was synthesized as a bi-functional poly(vinyl chloride) (PVC) thermal stabilizer for the first time. The materials were characterized with Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). Characterization results confirmed the formation of Zn–O bonds in DMAE-Zn, and confirmed that DMAE-Zn had a high decomposition temperature and a low melting point. The thermal stability of DMAE-Zn on PVC also was tested by a conductivity test, a thermal aging test, and a UV-visible spectroscopy (UV-VIS) test. PVC stabilized by DMAE-Zn had a good initial color and excellent long-term stability. UV-VIS also showed that the conjugated structure in PVC stabilized by DMAE-Zn was almost all of the triene, suggesting that the addition of DMAE-Zn would suppress the formation of conjugated structures above tetraene. The dynamic processing performance of PVC samples tested by torque rheometer indicated that, having a good compatibility with PVC chains in the amorphous regions, DMAE-Zn contributed a good plasticizing effect to PVC. DMAE-Zn thus effectively demonstrates bi-functional roles, e.g., thermal stabilizers and plasticizers to PVC. Furthermore, FT-IR, a HCl absorption capacity test, and a complex ZnCl2 test were also used to verify the thermal stability mechanism of DMAE-Zn for PVC.

Description: Femtosecond laser ranging has drawn great interest in recent years, particularly based on an asynchronous optical sampling implementation where a pair of femtosecond lasers are used. High precision absolute ranging either relies on tightly-phase-locked optical frequency combs (a dual-comb setup) or multiple averaging of the measurements from two free-running femtosecond lasers. The former technique is too complicated for practical applications, while the latter technique does not apply to moving targets. In this report, we propose a new route to utilizing a powerful singular spectrum analysis (SSA) filtering method to improve femtosecond laser ranging precision for moving targets with acceleration. The SSA method is capable of separating complex patterns in signals without a priori knowledge of the dynamical model. Here, we utilize the basic SSA filter to extract the target trajectory in the presence of measurement noise both in numerical simulation and in the absolute ranging experiment based on a pair of free-running femtosecond lasers. The experimentally-achieved absolute ranging uncertainty of a moving target is well below 110 nm at a 200-Hz update rate by applying the basic SSA filter. This method paves the way to the practical applications of femtosecond absolute ranging for dynamic objects.

Description: The TanDEM-X (TDX) mission launched by the German Aerospace Center delivers unprecedented global coverage of a high-quality digital elevation model (DEM) with a pixel spacing of 12 m. To examine the relationships of terrain, vegetation, and building elevations with hydrologic, geologic, geomorphologic, or ecologic factors, quantification of TDX DEM errors at a local scale is necessary. We estimated the errors of TDX data for open ground, forested, and built areas in a coastal urban environment by comparing the TDX DEM with LiDAR data for the same areas, using a series of error measures including root mean square error (RMSE) and absolute deviation at the 90% quantile (LE90). RMSE and LE90 values were 0.49 m and 0.79 m, respectively, for open ground. These values, which are much lower than the 10 m LE90 specified for the TDX DEM, highlight the promise of TDX DEM data for mapping hydrologic and geomorphic features in coastal areas. The RMSE/LE90 values for mangrove forest, tropical hardwood hammock forest, pine forest, dense residential, sparse residential, and downtown areas were 1.15/1.75, 2.28/3.37, 3.16/5.00, 1.89/2.90, 2.62/4.29 and 35.70/51.67 m, respectively. Regression analysis indicated that variation in canopy height of densely forested mangrove and hardwood hammock was well represented by the TDX DEM. Thus, TDX DEM data can be used to estimate tree height in densely vegetated forest on nearly flat topography next to the shoreline. TDX DEM errors for pine forest and residential areas were larger because of multiple reflection and shadow effects. Furthermore, the TDX DEM failed to capture the many high-rise buildings in downtown, resulting in the lowest accuracy among the different land cover types. Therefore, caution should be exercised in using TDX DEM data to reconstruct building models in a highly developed metropolitan area with many tall buildings separated by narrow open spaces.

Description: Low water use efficiency and soil salinization are two main factors limiting cotton production in southern Xinjiang. A field experiment was conducted to investigate the effects of brackish water irrigation levels on cotton growth, yield and soil water–salt dynamics in southern Xinjiang, so as to provide a theoretical and experimental basis for the development and utilization of brackish water. There were three irrigation levels: W1 (75 mm + 80%ETc), W2 (150 mm + 80%ETc) and W3 (240 mm + 80%ETc) at the seeding stage (S1), seeding stage + budding stage (S2) and seeding stage + budding stage + flowering stage (S3), with an irrigation amount of 450 mm during spring as the CK (the local reference level) (10 treatments in total). The salt of the local brackish water used was 3 g·L−1. Film-mulched drip irrigation experiments were conducted to observe cotton growth, aboveground dry matter, cotton yield, soil water and salt distribution, as well as other indicators. The results showed that the irrigation applications of S3 can improve the soil moisture and salt distribution of the root zone. The salt accumulation at the harvest stage of W3S3 was reduced by 39.5% and 2.8% compared with W3S1 and W3S2, respectively. More frequent irrigation applications can reduce a soil’s total dissolved solids (TDS), avoid exceeding the salt tolerance threshold of 4.8 g kg−1 and lead to higher aboveground dry matter and cotton yields. W3S3 obtained the highest yield of 5685 kg ha−1, which was increased by 39.59%, 7.85% and 11.25% compared with W3S1, W3S2 and CK, respectively. The higher the irrigation amount, the less water use efficiency (WUE), following the order of S3 〉 S2 〉 S1 〉 CK at various growth stages. W3S1 obtained the lowest WUE of 0.64 kg·m−3. Comprehensively considering the effects of soil moisture retention and salt suppression, cotton growth, yield and water use efficiency, an irrigation amount of 240 mm brackish water at three growth stages, with 80%ETc for irrigation, is recommended for the sustainable production of cotton in southern Xinjiang.