倾斜地表下隧道开挖引起的三维地表沉降计算

为研究倾斜地表下隧道开挖引起的地表沉降计算方法,考虑倾斜地表对隧道埋深的影响,建立了倾斜地表下隧道开挖模型和三维情况下单元体开挖计算模型.采用随机介质理论,推导出三维倾斜地表下隧道开挖引起的地表沉降计算公式,并结合工程实例选取监测数据和计算数据对比验证,证明了计算方法的准确性.最后针对地表倾斜角度进行对比分析,表明地表斜面倾角越大,地表不均匀沉降越明显.该倾斜地表沉降计算方法对隧道开挖地表沉降预测有一定的工程价值和指导意义.     

暴雨条件下紫色土区玉米季坡耕地氮素流失特征

【目的】研究暴雨条件下,川中丘陵紫色土区坡耕地玉米全生育期土壤侵蚀及氮素流失规律,为研究区氮素流失预测和有效防控提供科学依据。【方法】采用人工模拟降雨与径流小区相结合的方法,在玉米苗期（5月1日）,拔节期（5月26日）,抽雄期（6月27日）和成熟期（8月4日）进行模拟降雨,结合川中丘陵紫色土区夏季暴雨多的特点,开展降雨强度为1.5 mm·min^-1,坡度为15°条件下地表径流、壤中流和侵蚀泥沙中氮素流失特征的研究。【结果】（1）玉米各生育时期地表径流产流率和产沙率总体表现为随降雨时间延长而呈增加的变化趋势,地表径流产流率和产沙率均表现苗期最高,抽雄期最低;壤中流产流率则表现为抽雄期最高,成熟期最低。（2）玉米各生育时期地表径流中总氮流失率随降雨时间延长而呈增加,在降雨36 min后基本趋于稳定,总氮和可溶性总氮流失率均在玉米苗期最大,平均值分别为5.24和4.74 mg·m^-2·min^-1;玉米全生育期地表径流中硝态氮流失率则在降雨30 min后基本稳定,铵态氮流失率呈现波动性,硝态氮和铵态氮流失率均在玉米拔节期最大,平均值分别为3.90和0.14 mg·m^-2·min^-1。在玉米全生育期地表径流中总氮,可溶性总氮和硝态氮流失量与地表径流量呈现极显著线性关系。（3）壤中流中总氮流失率在玉米各生育时期随降雨时间延长缓慢增加,壤中流中可溶性总氮和硝态氮流失率在玉米苗期、拔节期和成熟期变化趋势与总氮一致,而铵态氮流失率在玉米全生育期呈现波动性;总氮,可溶性总氮,硝态氮和铵态氮流失率均在玉米拔节期最大,平均值分别为25.04、20.34、16.20和0.22 mg·m^-2·min^-1。在玉米全生育期壤中流中总氮,可溶性总氮和硝态氮流失量与壤中流量呈现显著线性关系,且均在玉米拔节期表现为斜率最大。（4）玉米各生育时期侵蚀泥沙中氮素流失率均随降雨时间延长而增加,但在玉米苗期表现为增幅最大,平均值为0.92 mg·m^-2·min^-1。在玉米全生育期,侵蚀泥沙中氮素流失量与侵蚀泥沙量呈现极显著线性关系。（5）地表径流中不同形态氮素流失量均在玉米苗期和拔节期最大,壤中流中总氮流失量则在玉米拔节期和抽雄期最大,侵蚀泥沙中氮素流失量在玉米苗期最大。壤中流为研究区坡耕地氮素流失的主要途径,占氮素流失总量的64.07%-83.39%。可溶性总氮为径流中氮素流失主要形态,以硝态氮为主要形态。【结论】1.5 mm·min^-1降雨强度下,地表径流和壤中流中总氮流失量分别在玉米苗期和拔节期最高,可溶性总氮和硝态氮流失量均在拔节期最高,存在水体富营养化潜在风险,控制苗期地表径流量和拔节期壤中流量可减少该区域氮素流失量。     

芥菜籽中异硫氰酸酯提取工艺的优化

以芥菜籽为试材,异硫氰酸酯提取率为考察指标,采用超声提取法,分别设超声温度(40、50、60、70、80℃),超声时间(20、30、40、50、60 min)和乙醇体积分数(65%、75%、85%、95%、100%)3个单因素试验,再在单因素试验的基础上进行响应面试验,优化芥菜籽中异硫氰酸酯的提取工艺。结果表明:乙醇体积分数为70%,超声温度为50℃、超声时间为40 min时,芥菜籽中异硫氰酸酯提取率较高,为2.199%。     

W-HE生物表面活化剂对玉米产量及产量性状的影响

为了明确W-HE生物表面活化剂的使用效果,经过3a试验,调查其对玉米产量及植株素质的影响。结果表明:使用W-HE生物表面活化剂能促进玉米前期的生长发育,促进根系的生长和干物质的积累,植株生长加快,果穗变大,百粒重提高,双穗率提高,增产幅度达10%以上。     

Factors affecting the virulence of Ralstonia solanacearum and its colonization on tobacco roots

Tobacco bacterial wilt caused by Ralstonia solanacearum is a serious disease affecting tobacco cultivation in southwest China. The response surface methodology was employed to evaluate the optimal conditions of tobacco bacterial wilt, and green fluorescent protein gene (gfp) labelling was applied to monitor the location and survival dynamics of R. solanacearum (Rs::gfp) on tobacco roots and in soil under these optimal conditions. The results showed that the highest wilt incidence was 91.13%, which occurred when the population reached 6.6 × 10⁶ CFU/g soil, the temperature was 30.55 °C, and the humidity was >81.42%. The Rs::gfp densely colonized the root tips and root hairs, and cells of Rs::gfp were observed intermittently in the elongation zone or at the point of the emerging lateral roots. The Rs::gfp number in the rhizosphere soil was 10.75‐, 73.13‐ and 74.86‐times higher than that in the bulk soil at 10, 15 and 20 days after transplantation, respectively. Increased colonization by Rs::gfp was related to the population of the pathogen, the environmental temperature and the humidity in the soil. These three conditions determined whether R. solanacearum would induce tobacco wilt. This is the first study to investigate factors affecting the virulence of a tobacco wilt bacterial pathogen, which is important for conducting field diagnosis and biocontrol of tobacco bacterial wilt.     

A remote sensing-based agricultural drought indicator and its implementation over a semi-arid region,Jordan

The objective of the study was to develop a remote sensing(i.e., Landsat-8 and MODIS)-based agricultural drought indicator(ADI) at 30-m spatial resolution and 8-day temporal resolution and also to evaluate its performance over a heterogeneous agriculture dominant semi-arid region in Jordan. Firstly, we used principal component analysis(PCA) to evaluate the correlations among six commonly used remote sensing-derived agricultural drought related variables. The variables included normalized difference water index(NDWI), normalized difference vegetation index(NDVI), visible and shortwave drought index(VSDI), normalized multiband drought index(NMDI), moisture stress index(MSI), and land surface temperature(LST). Secondly, we integrated the relatively less correlated variables(that were found to be NDWI, VSDI, and LST) to generate four agricultural drought categories/conditions(i.e., wet, mild drought, moderate drought, and severe drought). Finally, we evaluated the ADI maps against a set of 8-day ground-based standardized precipitation index values(i.e., SPI-1, SPI-2, …, SPI-8) by use of confusion matrices and observed the best results for SPI-4(i.e., overall accuracy and Kappa-values were 83% and 76%, respectively) and SPI-5(i.e., overall accuracy and Kappa-values were 85% and 78%, respectively). The results demonstrated that the method would be valuable for monitoring agricultural drought conditions in semi-arid regions at both a reasonably high spatial resolution(i.e., 30-m) and a short time period(i.e., 8-day).     

A proposed surface resistance model for the Penman-Monteith formula to estimate evapotranspiration in a solar greenhouse

Greenhousing is a technique to bridge season gap in vegetable production and has been widely used worldwide. Calculation of water requirement of crops grown in greenhouse and determination of their irrigation schedules in arid and semi-arid regions are essential for greenhouse maintenance and have thus attracted increased attention over the past decades. The most common method used in the literature to estimate crop evapotranspiration(ET) is the Penman-Monteith(PM) formula. When applied to greenhouse, however, it often uses canopy resistance instead of surface resistance. It is understood that the surface resistance in greenhouse is the result of a combined effect of canopy restriction and soil-surface restriction to water vapor flow, and the relative dominance of one restriction over another depends on crop canopy. In this paper, we developed a surface resistance model in a way similar to two parallel resistances in an electrical circuit to account for both restrictions. Also, considering that wind speed in greenhouse is normally rather small, we compared three methods available in the literature to calculate the aerodynamic resistance, which are the r_a~1 method proposed by Perrier(1975a, b), the r_a~2 method proposed by Thom and Oliver(1977), and the r_a~3 method proposed by Zhang and Lemeu(1992). We validated the model against ET of tomatoes in a greenhouse measured from sap flow system combined with micro-lysimeter in 2015 and with weighing lysimeter in 2016. The results showed that the proposed surface resistance model improved the accuracy of the PM model, especially when the leaf area index was low and the greenhouse was being irrigated. We also found that the aerodynamic resistance calculated from the r_a~1 and r_a~3 methods is applicable to the greenhouse although the latter is slightly more accurate than the former. The proposed surface resistance model, together with the r_a~3 method for aerodynamic resistance, offers an improved approach to estimate ET in greenhouse using the PM formula.     

红松阔叶混交林林隙0cm地温的地统计学分析

[目的]揭示小兴安岭红松阔叶混交林林隙0 cm地面温度的时空变化规律。[方法]以小兴安岭原始红松阔叶混交林林隙为研究对象,采用网格法布点,通过对生长季内林隙各样点0 cm地面温度的连续观测,利用基本统计学和地统计学的方法研究林隙0 cm地面温度的时空分布格局。[结果]林隙地面温度不同,空间样点之间存在异质性,且异质性的强度、尺度和空间结构组成随时间的延长而改变,各月0 cm平均地面温度斑块形状复杂,林隙0 cm地面温度从大到小依次为6、7、8、9月,月平均0 cm地温的最大值和最小值分布位置不固定,同一月份地面温度从大到小为空旷地、林隙、郁闭林分。[结论]该研究可为红松阔叶混交林的可持续经营提供基础数据和理论参考。     

酶法提取啤酒糟中水溶性膳食纤维的研究

[目的]采用响应面法优化啤酒糟中水溶性膳食纤维的提取工艺,以期提高啤酒糟的综合利用价值。[方法]采用酶法提取啤酒糟中水溶性膳食纤维。在单因素试验基础上,以温度、纤维素酶量、固液比3个因素为自变量,水溶性膳食纤维得率为响应值,进行响应面分析,确定最佳工艺参数。[结果]啤酒糟中水溶性膳食纤维最佳提取条件:温度为50.8℃、纤维素酶量为6.7%、固液比(g∶m L)为1∶14。当满足最佳提取条件时,验证值为5.16%。根据最佳提取条件进行验证试验,水溶性膳食纤维的实际得率为5.09%,相对误差为1.36%。[结论]酶法提取提高了水溶性膳食纤维得率,且操作简单、可重复性强,适用于啤酒糟中水溶性膳食纤维的提取。