引入地形因子的黑土区大豆干生物量遥感反演模型及验证

为了对田块尺度农作物地上干生物量进行估测,提高大豆地上干生物量反演模型的精度和稳定性,该文获取了研究区地块2016年7、8月份的SPOT-6多光谱数据,并测定不同地形坡位的大豆地上干生物量,以归一化植被指数(normalized difference vegetation index,NDVI)和增强型植被指数(enhanced vegetation index,EVI)为输入量,建立田块尺度大豆地上干生物量一元线性回归模型;加入与地上干生物量相关的地形因子,建立逐步多元回归和神经网络多层感知反演模型.结果表明:1)使用传统的单一植被指数模型预测大豆地上干生物量有可行性,但模型精度和稳定性不高.2)加入地形因子(海拔、坡度、坡向)的神经网络多层感知器模型,有较高的精度和可靠性,模型准确度达到90.4％,验证结果显示预估精度为96.2％.反演结果与地块的地形、地貌、气温和降水特征基本吻合,反映了作物长势的空间分布特征,可以为田块尺度大豆地上干生物量动态监测和精准管理,提供借科学依据.     

4LZ-0.8型水稻联合收割机清选装置气固两相分离作业机理

为解决小型水稻联合收割机脱净率和损失率问题,提高脱粒清选质量,利用两相流动力学理论,分析了4LZ-0.8型水稻联合收割机脱粒清选分流筒中气流和杂物颗粒两相流动的规律。建立了杂物颗粒流的运动微分方程,导出了分离筒中杂物漂浮速度计算的一种方法,通过比较不同粒径、密度的物料的悬浮速度,得到了杂物颗粒最高速度与气流速度之比随气流速度变化的关系曲线,气流和杂物在分流筒及吸风管中运动时的压力损失随气流速度变化呈现先降后升的规律,压力损失中以加速损失和摩擦损失为主,各约占30%和26%。压力损失曲线存在最小值,此时的气流速度定义为经济气流速度。在喂入量为0.8 kg/s,谷草比为3:1脱粒条件下的经济的清选气流速度9.2 m/s,压力损失为630 Pa。该研究为4LZ-0.8型水稻联合收割机脱粒清选部件的参数优化设计及风机的选择提供了理论依据。     

微酸性电解水结合壳聚糖对水蜜桃护色保鲜的效果

为了防止水蜜桃(Prunus persicaL.Batsch)采后的果肉颜色变化而严重影响其商品价值。该研究以南汇水蜜桃为材料,分别利用自制羧甲基壳聚糖复合保鲜剂,以及微酸性电解水对水蜜桃进行护色保鲜处理,并对冷藏条件下(2℃)水蜜桃果肉颜色及与颜色品质变化相关的指标进行了检测,同时还利用核磁共振成像(MRI)合成T2-MAP图研究了冷藏开始和结束后水蜜桃内部变化的规律。结果表明,在贮藏结束后,对照组果肉颜色的L*值、H*值、C*值分别是羧甲基壳聚糖复合保鲜剂和微酸性电解水处理组的85%～91%、85%～93%和114%～122%(p<0.05)。显然,羧甲基壳聚糖复合保鲜剂和微酸性电解水由于可以抑制水果自身乙烯的产生,减少水果的细胞膜透性和T2-MAP图中T2弛豫常数的变化,降低了多酚氧化酶(PPO)活性的增加速度,减少了酚类物质的累积,进而延缓了果肉的变色。另外,与仅用电解水处理相比,结合羧甲基壳聚糖处理具有较好的护色保鲜效果。通过该研究,可以为提高采后南汇水蜜桃的果肉护色保鲜效果提供参考。     

Environmentally friendly slow-release nitrogen fertilizer

To sustain the further world population, more fertilizers are required, which may become an environmental hazard, unless adequate technical and socioeconomic impacts are addressed. In the current study, slow-release formulations of nitrogen fertilizer were developed on the basis of natural attapulgite (APT) clay, ethylcellulose (EC) film, and sodium carboxymethylcellulose/hydroxyethylcellulose (CMC/HEC) hydrogel. The structural and chemical characteristics of the product were examined. The release profiles of urea, ammonium sulfate, and ammonium chloride as nitrogen fertilizer substrates were determined in soil. To further compare the release profiles of nitrogen from different fertilizer substrates, a mathematical model for nutrient release from the coated fertilizer was applied to calculate the diffusion coefficient D. The influence of the product on water-holding and water-retention capacities of soil was determined. The experimental data indicated that the product can effectively reduce nutrient loss, improve use efficiency of water, and prolong irrigation cycles in drought-prone environments.     

箱式通风干燥机小麦干燥试验研究

为了解小麦平床通风干燥特性,该文以某型号箱式通风干燥机为试验设备,开展小麦收获后干燥试验研究,测试分析了干燥床风场分布、干燥床层含水率分布、温度分布及耗能等特性。研究表明,该设备在水平面和垂直面均存在较明显的干燥速度差异;在干燥6h结束时整个小麦床层的最大含水率差异超过3%,影响整批物料的干燥效率和干燥成本;干燥5h后整批物料含水率达到小麦贮藏要求,每1kg物料含水率下降5%的能耗成本为0.09元。根据试验研究结果,提出在入风口增加导风栅格、干燥仓体4个角采用圆弧过渡处理、采用气流换向机构和交替换向通风干燥工艺等改进措施来改善该设备干燥均匀性。研究结果为该类型干燥机的小麦干燥工艺优化及设备改进设计提供了依据。     

微孔曝气流量与曝气管长度对水体增氧性能的影响

为了探究曝气流量与曝气管长度对增氧性能的影响,在不同曝气流量、不同曝气管长度条件下进行了室内水体底部微孔曝气增氧试验。分析了曝气流量与曝气管长度对氧体积传质系数、增氧量和氧利用率的影响。研究结果表明,当曝气流量为0.27~0.55 m3/s、曝气管长为0.9~1.5 m时,所对应的氧体积传质系数在0.63~1.1 h-1变化,增氧量在6.8~12.9 g/h变化,氧利用率在6.87%~9.28%变化,且在一定的曝气管长度下,氧体积传质系数、增氧量均与曝气流量成正比,而氧利用率则与其成反比关系;在一定的曝气流量下,曝气管长度对氧体积传质系数产生的影响表现为先高后低再高的趋势;氧体积传质系数与修正的饱和溶解氧浓度是否作为增氧量的主要影响因子取决于曝气管长度;曝气流量对氧利用率较曝气管长度更为敏感。研究还发现,微孔曝气系统中存在着最优曝气管长度,使得增氧性能最佳,并建立了最优曝气管长度与曝气流量、水深、输入压力、最优初始气泡直径的相关关系式,为低碳经济下微孔曝气系统的设计和运行提供了理论依据。     

适宜气调包装延缓冷藏鲳鱼品质变化延长货架期(英文)

该文主要研究了不同气体比例组分的气调包装处理对冷藏鲳鱼贮藏期间品质变化及货架期的影响,从中找出能使鲳鱼冷藏货架期延长的适宜气体比例。将新鲜鲳鱼以冰藏方式快速运至实验室,将样品经去头、去尾、去内脏处理后,分别置于3种气体组分条件(MAP1:20%CO2/80%N2,MAP2:50%CO2/50%N2,MAP3:80%CO2/20%N2)的气调包装袋内冷藏(4±1)℃保鲜,以空气包装样品作为冷藏对照组(AIR),其中包装袋内的气体与样品体积比为3∶1,在12 d内隔天测定各组样品的感官指标、微生物指标(菌落总数)与化学指标(挥发性盐基氮值、K值、三甲胺值与p H值)变化。冷藏后的第4天,对照组与气调处理组的感官分值、菌落总数、挥发性盐基氮值与三甲胺值差异显著(P0.05),冷藏对照组样品的各项指标首先达到新鲜限值,其冷藏货架期仅为4-5d。经过气调处理后的鲳鱼样品,其菌落总数达到二级鲜度的速度明显缓于冷藏对照组,其他各项指标的变化也证实了气调包装的潜在优点。其中,80%CO2+20%N2处理组能明显延缓样品p H值、挥发性盐基氮值、菌落总数、三甲胺值与K值的升高(P0.05),较冷藏对照组相比,其冷藏货架期能延长6~8 d。同时,气调处理组贮藏期间的p H值未呈现先降后升的变化规律,表明p H值不适用于评价气调包装鲳鱼贮藏期间的品质变化。气调包装样品的菌落总数在贮藏前期略有下降,表明CO2对样品菌落总数的升高有较好的抑制作用。在CO2≤80%条件下,各项微生物与理化指标的测定结果显示出不同气体比例的气调包装处理对冷藏鲳鱼的保鲜效果,CO2浓度越高,其保鲜效果越显著,气调处理能使鲳鱼样品的冷藏保鲜期由4 d延长至6-12 d,其中80%CO2+20%N2的气调处理组对鲳鱼样品的冷藏货架期延长效果较佳。     

生物保鲜剂结合气调包装对带鱼冷藏货架期的影响

为了延长带鱼冷藏货架期,以空气包装组为对照,在（4±1）℃冷藏条件下,采用复合生物保鲜剂涂膜及保鲜剂结合气调包装对带鱼进行保鲜试验。以感官评分、细菌总数、挥发性盐基氮值（total volatile base nitrogen,TVB-N）、pH值、硫代巴比妥酸值（the 2-thiobarbituric acid,TBA）和汁液流失率为指标,测定带鱼冷藏过程中的品质变化。结果表明：空气包装组带鱼冷藏货架期为4 d,复合生物保鲜剂（1.0%壳聚糖＋0.4%茶多酚）具有良好的抑菌保鲜作用,高浓度CO2气调包装带鱼汁液流失较为严重,生物保鲜剂结合60%CO2＋10%O2＋30%N2气调包装组保鲜效果最为显著,冷藏贮存20 d,带鱼的细菌总数为5.59 lg(cfu/g),TVB-N值为19.39 mg/100 g,仍处在带鱼二级鲜度之内,可将冷藏带鱼货架期延长至20d,是对照组的5倍,且能较好地维持新鲜带鱼感官品质,以期为带鱼的保鲜提供一定的参考。     

脱氮功能菌去除市政废水中氮素的研究

为了探讨实验室筛选获得的氨氧化细菌CM-NR014和反硝化细菌CM-NRD3联合去除市政废水中氮素的应用价值,采用了两级A／O工艺进行菌株去除废水中氮素的小试实验,最后将菌株用于废水脱氮工程中。结果表明,脱氮功能菌实现了短程硝化-反硝化,氨氮去除率在98％以上,总氮去除率在75％以上,COD（化学需氧量）去除率大于90％,出水各项指标均低于城镇污水处理厂污染物排放一级（A）标准。脱氮功能菌在去除市政废水中氮素方面有很高的应用价值,可用于城镇污水处理厂提标改造等。     

Asymmetric warming effects on N dynamics and productivity in rice (Oryza sativa L.)

Climate warming exhibits strong diurnal variations, with higher warming rates being observed at nighttime, which significantly affects rice (Oryza sativa L.) growth and grain yield. The objective of this study was to determine the effects of asymmetric warming (all-day warming, AW; daytime warming from 07:00 to 19:00, DW; nighttime warming from 19:00 to 07:00, NW, and a control, CK) on rice nitrogen (N) dynamics and productivity. Two rice bucket warming experiments were performed in Nanjing in Jiangsu Province, China, using the free air temperature increase (FATI) technique. The daily mean temperatures in the rice canopy in the AW, DW and NW plots were 2.0, 1.1 and 1.3ºC higher than those in the rice canopy in the CK plots, respectively. The results indicated that the total N accumulation of rice was 8.27–40.53% higher in the warming treatment than in the control during the jointing, anthesis and maturity stages. However, there was no significant difference detected among the three warming treatments. The warming treatment substantially decreased N translocation efficiency, leading to the retention of more N in the plant stems during grain filling. The warming treatment also decreased the N harvest index, N utilization efficiency based on grain yield and N utilization efficiencies based on biomass in both growing seasons. The warming treatment significantly increased the aboveground biomass (9.26–16.18%) in the jointing stage but decreased it (2.75–9.63%) in the maturity stage. Although DW increased the carbon (C) gain by photosynthesis and NW increased the C loss by night respiration, the daytime higher-temperature treatment affected rice photosynthesis and reduced its photosynthetic rate and product. This effect may be one of the primary reasons for the insignificant difference in the aboveground biomass between the DW and NW treatments. In the AW, DW and NW plots, the grain yield was reduced by an average of 10.07, 5.05 and 7.89%, respectively, across both years. The effective panicles and grains per spike tended to decrease in the warmed plots, whereas irregular changes in the 1000-grain weight were observed. Our results suggest that under the anticipated climate warming, rice productivity would further decline in the Yangtze River Basin.