基于驻波与ZigBee实时监测雾滴蒸发系统设计与试验

雾滴在叶面上蒸发时间长短,会改变叶面对农药的吸收效率.为了阐述药液在叶面的蒸发情况,该文设计了基于驻波与Zig Bee无线传输的雾滴蒸发实时监测装置.该装置以STM32为核心搭建Zig Bee网络,雾滴采集传感器信号由RS232串口传至基于Lab View2014设计的远程终端,并通过波形图实时在线监测雾滴蒸发状况.试验证明该装置能够准确测量药液在叶面的蒸发散失量并显示雾滴面积铺展的波动曲线,较图像处理方法误差小,易操作,更具实用性.试验还表明:1)蒸发时间与粒径大小呈正相关,随粒径增大而增长,但当粒径超过242.3μm时,蒸发时间随粒径增大而增长的趋势更为明显.2)蒸发时间与面积铺展率呈负相关,随面积铺展率的变大而减少.当有机硅体积分数由0.025%增到0.050%时,雾滴面积铺展率呈变大趋势,但当由0.050%增到0.100%时,雾滴铺展率增长幅度相对缩小.3)该装置不仅能够实现远程检测,避免接触药液,而且实时分析雾滴在叶面的蒸发时间与面积铺展率,合理选择有机硅体积分数与雾滴粒径,有助于改善叶面对药液的吸收效率.     

Transitions of water‐drop impact behaviour on hydrophobic and hydrophilic particles

Extreme soil water repellency can have substantial implications for soil hydrology, plant growth and erosion, including enhanced splash erosion caused by raindrop impact. Previous studies of water droplet impact behaviour on man‐made super‐hydrophobic surfaces, with which water‐repellent soil shares similar characteristics, revealed three distinct modes of splash behaviour (rebound, pinning and fragmentation) distinguished by two transition velocities: rebound‐to‐pinning (v_min) and pinning‐to‐fragmentation (v*). By using high‐speed videography of single water droplet impacts we show that splash behaviour is influenced by the hydrophobicity of immobile particles, with hydrophobic glass spheres exhibiting all three modes of splash behaviour in the hydrophobic state but hydrophilic spheres exhibiting solely pinning behaviour. We found that increasing the particle size of fixed glass spheres increases v_min. A study of droplet impact on hydrophobic sand shows that the increased roughness of the immobile particles makes impacting droplets more likely to fragment at slower impact velocities. The mobility of the particles influenced droplet impact behaviour, with loose, hydrophobic particles displaying significantly greater v_min values than their fixed analogues. The surface tension of the water droplet also lifted loose, hydrophobic particles from the surface, forming highly mobile ‘liquid marbles'. Water‐repellent soil was also shown to form ‘liquid marbles' at both the slow (approximately 0.3–2.1 m s^?1) and fast (about 7 m s^?1) droplet impact velocities studied. The observation of very mobile liquid marbles upon water droplet impact on water‐repellent soil is significant as this provided a mechanism that may enhance erosion rates of water‐repellent soil.     

Front-face fluorescence spectroscopy study of globular proteins in emulsions: displacement of BSA by a nonionic surfactant

The displacement of a globular protein (bovine serum albumin, BSA) from the surface of oil droplets in concentrated oil-in-water emulsions by a nonionic surfactant (polyoxyethylene sorbitan monolauarate, Tween 20) was studied using front-face fluorescence spectroscopy (FFFS). This method relies on measurement of the change in intensity (I(MAX)) and wavelength (lambda(MAX)) of the maximum in the tryptophan emission spectrum. A series of oil-in-water emulsions (21 wt % n-hexadecane, 0.22 wt % BSA, pH 7.0) containing different molar ratios of Tween 20 to BSA (R = 0-131) were prepared. As the surfactant concentration was increased, the protein was progressively displaced from the droplet surfaces. At R > or = 66, the protein was completely displaced from the droplet surfaces. There was an increase in both I(MAX) and lambda(MAX) with increasing Tween 20 concentration up to R = 66, which correlated with the increase in the ratio of nonadsorbed to adsorbed protein. In contrast, there was a decrease in I(MAX) and lambda(MAX) with Tween 20 concentration in protein solutions and for R > or = 66 in the emulsions, which was attributed to binding of the surfactant to the protein. This study shows that FFFS is a powerful technique for nondestructively providing information about the interfacial composition of droplets in concentrated protein-stabilized emulsions in situ. Nevertheless, in general the suitability of the technique may also depend on protein type and the nature of the physicochemical matrix surrounding the proteins.     

Rates of foliar penetration of chelated Fe(III): role of light, stomata, species, and leaf age

Rates of foliar penetration of Fe(III) chelates of imidodisuccinic acid (IDHA), ligninsulfonic acid (Natrel), and citric acid (ammonium ferric citrate) were studied at 20 degrees C using a leaf disk method. After drying of the donor droplets, the humidity over the donor residues was maintained at 100% because Fe(III) chelates deliquesce only when humidity is higher than 90%. The wetting agent Glucopon 215 CSUP was added at a concentration of 0.2 g L(-1) to all donor solutions. With fully expanded stomatous broad bean leaves, penetration of Fe-IDHA followed first-order kinetics and rate constants of penetration were higher in light (0.073 h(-1)) than in the dark (0.042 h(-1)). Permeability of broad been leaves to CaCl2 was about 8 times higher than to Fe-IDHA. Doubling the Fe-IDHA concentration in the donor from 2.5 to 5 mmol L(-1) decreased rate constants of Fe-IDHA penetration by a factor of 2.2. Adding the silicon surfactant Break Thru S240 at 10 g L(-1) to the donor induced infiltration of open stomata and about 80% of the applied Fe-IDHA penetrated during droplet drying, while with Glucopon 215 CSUP stomatal infiltration was not observed. With broad bean leaves, penetration of Natrel and ammonium ferric citrate also followed first-order kinetics and rate constants were also higher in light than in the dark. Adaxial astomatous surfaces of fully expanded pear, apple, and grapevine leaves were practically impermeable to Fe-IDHA while stomatous abaxial leaf surfaces were permeable, but rate constants of penetration decreased with time and differed greatly among species. Astomatous surfaces of young unfurling grapevine and peach leaves were permeable to Fe-IDHA, but permeability of stomatous surfaces was much higher. The effect of light on permeability of stomatous leaf surfaces is attributed to the presence of aqueous pores in cuticles over guard cells, and it is suggested that permeability of these pores increases as stomata open. Consequences of these results for foliar applications of Fe chelates are discussed.     

致病菌基因组岛的研究进展

细菌基因组岛是细菌基因组上的特定区域,和水平基因转移相关,具有一定的结构特点,常携带致病、耐药及与适应性等功能相关的基因。通过基因组岛在细菌间的移动,可以造成相关基因在细菌间的传播,在细菌生存和致病等过程中具有重要作用。目前已经可通过生物信息和分子生物学实验等方法对基因组岛进行预测和验证。通过对致病菌基因组岛的研究,可以阐释细菌致病性和耐药等重要功能的获得,对疾病进行溯源,在传染病预防控制中具有重要意义。     

Surfactants and soil water evaporation and migration

1. Water evaporation from soil and sand columns is smaller when the surfactant is placed on the surface, and larger when it is located at the bottom. Water evaporation from soil and sand mixed with the surfactant is as high as without the surfactant. 2. The fact that water evaporation from soil and sand depends on the location of the surfactant in the column is accounted for by the dominant role of migration but not by the suppressive action of the surfactant film on water evaporation. 3. Water migration from sites with surfactant towards sites without surfactant is caused by two pressures: the capillary and the additional pressure arising from the spreading of the surfactant. 4. The importance of the additional pressure on water migration is shown by experiments which rule out the existence of a capillary pressure difference.     

Threats to dragonflies on land islands can be as great as those on oceanic islands

We ask whether oceanic islands and equivalent-sized continental blocks, which we call here ‘land islands’, are similar or not in their species richness, number of range-restricted species, and in number of threatened species. We used sites in southern Africa and islands in the Western Indian Ocean. We chose dragonflies as they are taxonomically tractable, well surveyed, and provide a range of characteristics from narrow-range endemics to widely-spread and vagile opportunists. We then selected as many oceanic islands as possible where there were sufficient data to make comparisons with land islands of a similar area in African savanna, grassland and mountains rich in endemic species. Generalized Linear Mixed Models were used to analyse the overall, range-restricted and threatened species richness for all islands (both oceanic and land) and then for the two types of island separately. Species richness increased with island size, with oceanic and land island size relationships being similar. Land islands overall had significantly more range-restricted species. Species on land islands were as threatened as those on oceanic islands. However, the land islands of the Western Cape were under a higher level of threat than oceanic islands of comparative size. The large islands of Madagascar and Sri Lanka were outliers with very high levels of threat. Translated into conservation, the results illustrate that over-generalizations about island faunas being more threatened than continental ones are not necessarily valid. While not wishing to draw attention away from the urgent conservation action needed on many tropical islands, we argue that comparisons of oceanic versus land islands detract from the more urgent task of local conservation action based on the special needs of any particular area, whether land or oceanic. It is more meaningful to establish how threats operate and how to mitigate them on small populations rather than focusing purely on any particular island type per se.     

Enzymatic assay method for evaluating the lipase activity in complex extracts from transgenic corn seed

A colorimetric method was established to determine the activity of recombinant lipase in extracts from transgenic corn seed. The system was an oil-in-water emulsion that was stabilized by a surfactant to accommodate the organic phase substrate and aqueous phase enzyme. The lipase activity was measured by monitoring the release of nitrophenol at 346 nm from the substrate, 4-nitrophenyl butyrate. Emulsions prepared with various surfactant types and concentrations were tested. For each surfactant, the measured activity was greatest when the surfactant concentration was close to the critical micelle concentration, consistent with the changing trend of oil droplet size as a function of surfactant concentration. The optimal system, with 0.01% (w/w) Tween 80, demonstrated good reproducibility, high sensitivity, robustness, and a linear response to lipase concentration.     

植保无人机施药喷嘴的发展现状及其施药决策

农药的低利用率是影响农业生态环境和农产品品质安全的重要原因之一,优化农药喷施技术是提高农药利用率的有效手段。无人机植保喷施作业作为航空施药领域的重要组成部分,因其应对突发灾害能力强、不受作业地点限制等优势,具有巨大的发展潜力。喷嘴作为植保无人机喷施系统中的关键部件,主要分为液力雾化喷嘴和离心雾化喷嘴两大类,良好的喷嘴性能能够大大提升航空施药喷洒的均匀性,提高农药的利用效率。该文总结了各类植保无人机常用喷嘴的原理、特点以及应用场合,提出了喷嘴性能评价指标并总结了三大类常用的雾滴粒径、沉积量、分布、速度等指标的测量手段,包括雾滴收集方法,雾滴沉积量测试方法以及仪器测量法。最后,针对目前无人机施药缺乏专业的指导,农药喷施效果有待提升的现状,该文提出合理的施药决策是结合靶标作物、喷药需求以及喷施环境三方面因素共同作用的结果,并从喷嘴喷雾角、防堵塞性、喷嘴压力与流量以及最佳作业粒径4个方面分析了喷嘴选型的思路,从专业喷嘴选型决策系统的建立以及无人机植保专用喷嘴的研发两方面对今后的研究进行展望。     

蒸发式过冷水制冰液滴蒸发结晶的模拟

蒸发式过冷水制冰系统中液滴传热传质特性研究具有重要意义。为了分析蒸发式过冷水制冰系统中液滴的热质传输特性,该文将单个液滴冷却结晶过程分为全液相区、固-液两相区和全固相区3个不同区域,建立液滴在大空间内蒸发降温结晶过程的数学模型,通过数值求解方法研究其在大空间蒸发室内降温结晶过程的温度变化特性,进一步分析液滴和空气的入口参数与液滴整个蒸发结晶特性的关系,为蒸发式过冷水制冰系统的结构优化设计和运行管理提供参考依据。     

Front-face fluorescence spectroscopy study of globular proteins in emulsions: influence of droplet flocculation

Measurement of the intensity (I(MAX)) and/or wavelength (lambda(MAX)) of the maximum in the tryptophan (TRP) emission spectrum using front-face fluorescence spectroscopy (FFFS) can be used to provide information about the molecular environment of proteins in nondiluted emulsions. Many protein-stabilized emulsions in the food industry are flocculated, and therefore, we examined the influence of droplet flocculation on FFFS. Stock oil-in-water emulsions stabilized by bovine serum albumin were prepared by high-pressure valve homogenization (30 wt % n-hexadecane, 0.35 wt % BSA, pH 7). These emulsions were used to create model systems with different degrees of droplet flocculation, either by changing the pH, adding surfactant, or adding xanthan. Emulsions (21 wt % n-hexadecane, 0.22 wt % BSA) with different pH (5 and 7) and molar ratios of Tween 20 to BSA (R = 0-131) were prepared by dilution of the stock emulsion. As the surfactant concentration was increased, the protein was displaced from the droplet surfaces, which caused an increase in both I(MAX) and lambda(MAX), because of the change in TRP environment. The dependence of I(MAX) and lambda(MAX) on surfactant concentration followed a similar pattern in emulsions that were initially flocculated (pH 5) and nonflocculated (pH 7). Relatively small changes in FFFS emission spectra were observed in emulsions (21 wt % n-hexadecane, 0.22 wt % BSA, pH 7) with different levels of depletion flocculation induced by adding xanthan. These results suggested that droplet flocculation did not have a major impact on FFFS. This study shows that FFFS is a powerful technique for nondestructively providing information about the molecular environment of proteins in concentrated and flocculated protein-stabilized emulsions. Nevertheless, in general the suitability of the technique may also depend on protein type and the nature of the physicochemical matrix surrounding the proteins.     

表面活性剂对老化土壤中PAHs的生物有效性的影响

采用聚2,6-二苯基对苯醚(poly(2,6-diphenyl-p-phenylene oxide),Tenax-TA)提取和蚯蚓(Eisenia Fetida)富集实验研究曲拉通-100(聚乙二醇辛基苯基醚,Triton X-100)、吐温-80(聚氧乙烯脱水山梨醇油酸酯,Tween-80)和羟丙基-β环糊精(HPCD)表面活性剂对老化农田土壤中多环芳烃(PAHs)可提取组分以及生物有效性的影响。结果显示,表面活性剂可以显著增加PAHs的可提取性和在蚯蚓体内的蓄积浓度;和对照相比,增加可提取性42.3%~269%,蚯蚓体内的蓄积量增加10%~340%。研究表明在使用表面活性剂进行土壤修复时老化PAHs类污染物可能重新释放到环境中并带来环境风险。     

Influence of surfactant charge on antimicrobial efficacy of surfactant-stabilized thyme oil nanoemulsions

Thyme oil-in-water nanoemulsions stabilized by a nonionic surfactant (Tween 80, T80) were prepared as potential antimicrobial delivery systems (pH 4). The nanoemulsions were highly unstable to droplet growth and phase separation, which was attributed to Ostwald ripening due to the relatively high water solubility of thyme oil. Ostwald ripening could be inhibited by incorporating ≥75% of corn oil (a hydrophobic material with a low water solubility) into the nanoemulsion droplets. The electrical characteristics of the droplets in the nanoemulsions were varied by incorporating ionic surfactants with different charges after homogenization: a cationic surfactant (lauric arginate, LAE) or an anionic surfactant (sodium dodecyl sulfate, SDS). The antifungal activity of nanoemulsions containing positive, negative, or neutral thymol droplets was then conducted against four strains of acid-resistant spoilage yeasts: Zygosaccharomyces bailli, Saccharomyces cerevisiae, Brettanomyces bruxellensis, and Brettanomyces naardenensis. The antifungal properties of the three surfactants (T80, LAE, SDS) were also tested in the absence of thymol droplets. Both ionic surfactants showed strong antifungal activity in the absence of thymol droplets, but no antimicrobial activity in their presence. This effect was attributed to partitioning of the antimicrobial surfactant molecules between the oil droplet and microbial surfaces, thereby reducing the effective concentration of active surfactants available to act as antimicrobials. This study shows oil droplets may decrease the efficacy of surfactant-based antimicrobials, which has important consequences for formulating effective antimicrobial agents for utilization in emulsion-based food and beverage products.     

Structure of binary solution droplets: Continuum theory and Monte Carlo simulation

To calculate the formation energy of a binary mixture droplet out of the gas phase in classical ‘heteromolecular’ nucleation theory, one has to take into account that the concentration of the solution near the droplet surface can be different from the composition in the droplet interior (‘surface enrichment’, Gibbs adsorption equation). This problem is solved in a simple picture where the composition varies spatially but where one has a sharp liquid-gas surface. In a material independent continuum theory, the variation of the composition is assumed to give a free energy contribution proportional to the square of the concentration gradient. This treatment of the surface enrichment gives a formation energy contribution smaller (for large droplets) by a factor 1 ^?1/√3 than previous theories (Döring and Neumann, 1940; Stauffer and Kiang, 1974), which therefore overestimated the surface enrichment for large droplets. This continuum theory is tested by Monte Carlo methods on a particularly symmetric mixture, the magnetic spin 1/2 Ising model. Here up-spins are identified with one type of molecule and down spins with another type. Reasonable agreement with the continuum theory is found, even for parameter ranges where the assumptions of the continuum theory are no longer valid. The results show clearly a strong but smooth variation of the concentration within the droplet. They constitute to our knowledge the first computer simulations of mixture microclusters.     

Influence of pH and iota-carrageenan concentration on physicochemical properties and stability of beta-lactoglobulin-stabilized oil-in-water emulsions

The influence of pH and iota-carrageenan concentration on the properties of beta-lactoglobulin (beta-Lg)-stabilized oil-in-water emulsions was investigated by measuring the particle charge, particle size distribution, and creaming stability. Emulsions containing droplets stabilized by beta-Lg were produced by homogenization, and then, iota-carrageenan was added. At pH 3, the droplet charge did not change for iota-carrageenan concentrations 相似文献   

Influence of rhamnolipids and triton X-100 on the biodegradation of three pesticides in aqueous phase and soil slurries.

The effect of surfactants on the biodegradation of trifluralin and atrazine (by Streptomyces PS1/5) and coumaphos (by degrading consortia from a contaminated cattle dip) in liquid cultures and soil slurries was tested at different concentrations of a rhamnolipid mixture (Rh-mix) and Triton X-100 (TX-100). The extent of trifluralin biodegradation in liquid culture was improved at high concentrations of both surfactants. The extent of atrazine degradation dropped in the presence of either surfactant. Coumaphos biodegradation improved slightly at Rh-mix dosages >3000 microM; however, it was readily inhibited by TX-100 at amounts above the critical micelle concentration. In soil slurries, the extent of both trifluralin and atrazine biodegradation was higher in Hagerstown A (HTA) soil than in Hagerstown B (HTB) soil and was not significantly affected by the presence of either surfactant. The onset of trifluralin biodegradation was retarded at higher concentrations of surfactants. In the absence of surfactant, up to 98% of coumaphos in both soil slurries was transformed. At increasing dosages of Rh-mix, the onset of coumaphos biodegradation was retarded, but the removal efficiency of the pesticide increased. Rh-mix and TX-100 depletion was observed during Streptomyces PS1/5 growth in liquid cultures. Rh-mix concentration also decreased during coumaphos biodegradation, whereas TX-100 concentration was not affected. These results suggest that surfactants, added for the purpose of increasing the apparent water solubility of hydrophobic organic compounds, may have unintended effects on both the rate and extent of biodegradation of the target compounds if the surfactants can also be degraded by the microorganisms in the system.     

Rates of cuticular penetration of chelated Fe(III): role of humidity, concentration, adjuvants, temperature, and type of chelate

Time courses of cuticular penetration of FeCl3 and Fe(III) complexes of citric acid, EDTA, EDDHA (Sequestrene 138Fe), imidodisuccinic acid (IDHA), and ligninsulfonic acid (Natrel) were studied using astomatous cuticular membranes (CMs) isolated from Populus x canescens leaves. At 100% relative humidity, the Fe(III) chelates disappeared exponentially with time from the surface of the CMs; that is, penetration was a first-order process that can be described using rate constants or half-times of penetration (t(1/2)). Half-times ranged from 20 to 30 h. At 90% humidity, penetration rates were insignificant with the exception of Natrel, for which t(1/2) amounted to 58 h. Rate constants were independent of temperature (15, 25, and 35 degrees C). Permeability decreased with increasing Fe chelate concentration (IDHA and EDTA). At 100% humidity, half-times measured with FeIDHA were 11 h (2 mmol L(-1)), 17 h (10 mmol L(-1)) and 36 h (20 mmol L(-1)), respectively. In the presence of FeEDTA, penetration of CaCl2 was slowed greatly. Half-times for penetration of CaCl2, which were 1.9 h in the absence of FeEDTA, rose to 3.12 h in the presence of an equimolar concentration of EDTA and 13.3 h when the FeEDTA concentration was doubled. Hence, Fe chelates reduced permeability of CMs to CaCl2 and to the Fe chelates themselves. It is suggested that Fe chelates reduced the size of aqueous pores. This view is supported by the fact that rate constants for calcium salts were about 5 times higher than for Fe chelates with the same molecular weights. Adding Tween 20 (5 g L(-1)) as a humectant did not increase permeability to FeIDHA at 90% humidity and below, while addition of glycine betaine did. Penetration of FeCl3 applied at 5 g L(-1) (pH 1.5) was not a first order process as rate constants decreased rapidly with time. Only 2% of the dose penetrated during the first 2 h and less than that in the subsequent 8 h. Recovery was only 70%. This was attributed to the formation of insoluble Fe hydroxide precipitates on CMs. These results explain why in the past foliar application of Fe compounds had limited success. Inorganic Fe salts are instable and phytotoxic because of low pH, while Fe chelates penetrate slowly and 100% humidity is required for significant penetration rates. Concentrations as low as reasonably possible should be used. These physical facts are expected to apply to stomatous leaf surfaces as well, but absolute rates probably depend on leaf age and plant species. High humidity in stagnant air layers may favor penetration rates across stomatous leaf surfaces when humidity in bulk air is below 100%.     

Effects of tropical forest fragmentation on aerial insectivorous bats in a land-bridge island system

Habitat fragmentation causes drastic changes in the biota and it is crucial to understand these modifications to mitigate its consequences. While studies on Neotropical bats have mainly targeted phyllostomid bats, impacts of fragmentation on the equally important aerial insectivores remain largely unexplored. We studied species richness, composition, count abundance and feeding activity of aerial insectivorous bats in a system of land-bridge islands in Panama with acoustic sampling. We predicted negative effects of fragmentation on forest species while bats foraging in open space should remain essentially unaffected. Rarefaction analyses indicated higher species richness for islands than mainland sites. For forest species, multivariate analyses suggested compositional differences between sites due to effects of isolation, area and vegetation structure. Contrary to our expectations, count abundance of forest species was similar across site categories. Feeding activity, however, was curtailed on far islands compared to near islands. As expected, bats hunting in open space did not reveal negative responses to fragmentation. Interestingly, they even displayed higher abundance counts on far and small islands. On the species level, two forest bats responded negatively to size reduction or site isolation, respectively, while a forest bat and a bat hunting in open space were more abundant on islands, irrespectively of island isolation or size. Our findings suggest that small forest remnants are of considerable conservation value as many aerial insectivores intensively use them. Hence high conservation priority should be given to retain or re-establish a high degree of forest integrity and low levels of isolation.     

无人机旋翼风场作用下雾滴在水稻植株上的黏附量模型构建

为了探究植保无人机旋翼风场对雾滴在水稻植株上黏附量的影响规律,该研究以大疆T30植保无人机为施药平台,分别以清水、1%迈飞和0.5%迈图Target助剂溶液为喷洒溶液,基于航空风洞和粒子图像测速系统（Particle Image Velocimetry,PIV）测量了植保无人机旋翼风场作用下的雾流场、溶液的动态表面张力、黏度和密度以及雾滴在水稻叶片表面的动态接触角,分析了植保无人机旋翼风场对雾滴沉降速度的影响,以及飞防助剂对溶液性质参数、喷嘴雾化性能和雾滴在水稻叶片表面润湿铺展能力的影响规律。在此基础上,结合雾滴拦截模型和雾滴与作物叶片表面碰撞模型,建立了应用于植保无人机施药技术领域的雾滴黏附量预测模型,并对模型计算的准确率进行了田间验证试验。试验结果表明,助剂溶液对溶液性质、喷嘴雾化性能、雾滴在水稻叶片表面的润湿铺展能力以及雾滴在水稻植株上的黏附量方面均有不同程度的影响。与清水溶液相比,添加1%迈飞与0.5%迈图Target助剂溶液后,溶液表面张力分别降低了46.81%,62.21%;喷嘴雾化雾滴的粒径均呈增大趋势,约增大9.3%;雾滴在水稻叶片表面的接触角分别降低了27.74%,46.37%;雾滴在每公顷水稻植株上的黏附量分别增加了800.78%和1 051.49%。无人机旋翼风场对雾滴沉降速度和雾滴在水稻植株上的黏附量均有明显影响,旋翼系统开启后,雾滴沉降速度明显增加,且更快达到稳定运动状态,当无人机旋翼转速由0增加至1 000 r/min 再增加至1 800 r/min时,雾滴沉降速度分别增加了366.67%,64.29%。与旋翼关闭状态相比,旋翼系统开启后,1%迈飞和0.5%迈图Target助剂溶液在水稻植株上的黏附量分别降低了26.78%和29.75%。本文建立的黏附量模型预测清水、1%迈飞和0.5%迈图Target 3种溶液在水稻植株上黏附量的准确率分别为48.59%,79.07%和79.29%。该研究为植保无人机对水稻进行施药作业时筛选助剂提供理论参考与指导,并提供一个新的旋翼风场作用下雾滴在水稻植株上黏附量的预测模型。     

利用探地雷达低频天线监测滴灌棉田盐渍化土壤盐分迁移研究

盐渍化问题严重制约着新疆地区农业经济的发展,而掌握土壤盐分迁移情况是防治土壤盐渍化的前提。为更好地了解滴灌棉田盐渍化土壤盐分的迁移情况,本文选用一典型滴灌棉田为研究对象,采用探地雷达低频天线（250 MHz）进行土壤剖面的探测,由探地雷达图像中的信息,推测土壤盐分在垂直方向上的迁移情况,再用土壤剖面水盐动态、盐分通量变化等实际观测数据进行验证。结果表明:（1）当土壤盐分浓度具有一定梯度时,采用探地雷达低频天线收集的雷达图像中可以划分出盐分积累带、包气带和蒸发面。（2）在整个研究阶段盐分实际运移情况为先整体向上再整体向下。通过水盐动态和盐分通量等方式的验证,发现探地雷达图像中的蒸发面变化情况与实际盐分运移情况一致。因此,使用探地雷达低频天线监测滴灌棉田土壤盐分在垂直方向上的迁移情况是可行的,并且可以使用探地雷达中蒸发面的变化情况表征盐分的整体运移情况。探地雷达低频天线对蒸发面快速无损的识别,为防治盐分迁移导致的土壤盐渍化问题提供了新思路。