分类: 农、林、牧、渔 >> 农业基础学科 提交时间: 2022-10-13 合作期刊: 《干旱区科学》
摘要:In order to cope with drought and water shortages, the working people in the arid areas of Northwest China have developed a drought-resistant planting method, namely, gravel-sand mulching, after long-term agricultural practices. To understand the effects of gravel-sand mulching on soil water evaporation, we selected Baifeng peach (Amygdalus persica L.) orchards in Northwest China as the experimental field in 2021. Based on continuously collected soil water stable isotopes data, we evaluated the soil evaporation loss rate in a gravel-sand mulching environment using the line-conditioned excess (lc-excess) coupled Rayleigh fractionation model and Craig-Gordon model. The results show that the average soil water content in the plots with gravel-sand mulching is 1.86% higher than that without gravel-sand mulching. The monthly variation of the soil water content is smaller in the plots with gravel-sand mulching than that without gravel-sand mulching. Moreover, the average lc-excess value in the plots without gravel-sand mulching is smaller. In addition, the soil evaporation loss rate in the plots with gravel-sand mulching is lower than that in the plots without gravel-sand mulching. The lc-excess value was negative for both the plots with and without gravel-sand mulching, and it has good correlation with relative humidity, average temperature, input water content, and soil water content. The effect of gravel-sand mulching on soil evaporation is most prominent in August. Compared with the evaporation data of similar environments in the literature, the lc-excess coupled Rayleigh fractionation model is better. Stable isotopes evidence shows that gravel-sand mulching can effectively reduce soil water evaporation, which provides a theoretical basis for agricultural water management and optimization of water-saving methods in arid areas.
分类: 生物学 >> 生态学 提交时间: 2022-06-17 合作期刊: 《干旱区科学》
摘要: Abstract: Caragana korshinskii Kom. and Tamarix ramosissima Ledeb. are pioneer shrubs for water and soil conservation, and for windbreak and sand fixation in arid and semi-arid areas. Understanding the water use characteristics of different pioneer shrubs at different ages is of great importance for their survival when extreme rainfall occurs. In recent years, the stable isotope tracing technique has been used in exploring the water use strategies of plants. However, the widespread 2H offsets of stem water from its potential sources result in conflicting interpretations of water utilization of plants in arid and semi-arid areas. In this study, we used three sets of hydrogen and oxygen stable isotope data (2H and 18O, corrected 2H_c1 based on SW-excess and 18O, and corrected 2H_c2 based on 8.1 and 18O) as inputs for the MixSIAR model to explore the water use characteristics of C. korshinskii and T. ramosissima at different ages and in response to rainfall. The results showed that 2H_c1 and 18O have the best performance, and the contribution rate of deep soil water was underestimated because of 2H offset. During the dry periods, C. korshinskii and T. ramosissima at different ages both obtained mostly water from deeper soil layers. After rainfall, the proportions of surface (010 cm) and shallow (1040 cm) soil water for C. korshinskii and T. ramosissima at different ages both increased. Nevertheless, there were different response mechanisms of these two plants for rainfall. In addition, C. korshinskii absorbed various potential water sources, while T. ramosissima only used deep water. These flexible water use characteristics of C. korshinskii and T. ramosissima might facilitate the coexistence of plants once extreme rainfall occurs. Thus, reasonable allocation of different plants may be a good vegetation restoration program in western Chinese Loess Plateau.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: In this paper, flexible Ag electrodes with a hexagonal micromesh structure were fabricated on PET substrate using a photolithography technique. The effect of film thickness on optical and electrical properties of Ag electrodes was investigated systematically. Furthermore, these flexible transparent Ag mesh electrodes were firstly applied to a polymer dispersed liquid crystal (PDLC) device and its performance was evaluated. All of the Ag electrodes exhibited a high average transmittance of about 80.2–85.0% in the visible range (400–800 nm), and the minimum sheet resistance value reached 8.2 U sq 1. The prepared Ag mesh also showed an excellent performance of adhesion and bending, demonstrating its superior durability. The PDLC device based on Ag mesh electrodes showed comparable performance with that using ITO electrodes, indicating that the Ag mesh film can be a good substitution for ITO electrodes in PDLC devices and may find practical application in large area flexible devices.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Flexible transparent conductive films (TCFs) are used in a variety of optoelectronic devices. However, their use is limited due to poor thermostability. We report hybrid TCFs incorporation in both aluminum-doped zinc oxide (AZO) and silver nanowires (AgNWs). The layered AZO/ AgNWs/AZO structure was deposited onto a transparent polyimide (PI) substrate and displayed excellent thermo- stability. When heated to 250 °C for 1 h, the change in resistivity (Rc) was less than 10% (Rc of pure AgNW film > 500) while retaining good photoelectric properties (Rsh = 8.6 Ohm/sq and T = 74.4%). Layering the AgNW network between AZO films decreased the surface roughness (Rrms < 8 nm) and enhances the mechanical flexibility of the hybrid films. The combination of these characteristics makes the hybrid film an excellent candidate for substrates of novel flexible optoelectronic devices which require high-temperature processing.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Hybrid transparent conductive films (TCFs) with a sandwich structure composed of aluminum-doped zinc oxide (AZO) and Ag nanowires (AgNWs) were deposited on polyethylene terephthalate (PET) substrates. The AZO layers were prepared at room temperature by RF magnetron sputtering. The AgNWs were synthesized by a modified polyol method and inserted into the AZO layers. The optical properties and conductivity can be modified by the number of spin-coating cycles of an AgNWs suspension. Typically, an AZO/AgNW/AZO hybrid film exhibited an optical transmittance of 80.5%, a sheet resistance of 27.6 U sq 1 and an optical haze of 14.9%. The increase in optical haze caused by the silver nanowires may be beneficial for applications in solar cells. The hybrid films presented excellent flexible stability, showing only minor resistance changes and no surface cracks compared with pure AZO films. The AZO layers acted as the protecting layers that enhanced the adhesive and thermal stability of the hybrid films. The resulting hybrid TCFs with an AZO/ AgNW/AZO sandwich structure show potential applications in flexible electronics, energy storage and photovoltaic devices.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: In this paper, Ga-doped ZnO (GZO) thin films are deposited on glass substrates by radio frequency magnetron sputtering for low loss plasmonic applications. The effects of Ga2O3 content in the target and substrate temperature on the electrical, structural and optical properties of GZO films are investigated. Film with the highest carrier concen- tration of 7.0 × 1020 cm− 3 was obtained at a Ga2O3 content of 5 wt% in the target under room temperature deposi- tion. With increasing deposition temperature, the lowest electrical resistivity of 3.8 × 10− 4 Ω cm was acquired at a deposition temperature of 200 °C. The values of plasmonic resonances wavelength could be changed from 1.35 to 2.39 μm by adjusting the carrier concentration. Material absorption losses in these GZO films are 10 times lower than that of conventional Ag films at telecommunication wavelengths. These results make GZO a promising low-loss plasmonic material operating at telecommunication wavelengths.
提交时间: 2017-05-02
摘要: Heterovalent Sn2O3 nanosheets were fabricated via an oxidation annealing process and the formation mechanism was investigated. The temperature required to complete the phase transformation from Sn3O4 to Sn2O3 was considered. Two contrasting experiments sh