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1.
针对严寒地区线性菲涅尔聚光集热器末端损失严重的问题,该文以呼和浩特地区小型线性菲涅尔聚光集热系统为研究对象,根据不同季节太阳位置的变化,理论分析并计算了沿水平南北轴放置的线性菲涅尔集热器自东向西跟踪过程的末端损失,得到其变化规律及补偿方法,并进行了试验验证。结果表明,一天中末端损失随时间的变化趋势与太阳高度角的变化趋势相同,与太阳方位角变化趋势相反,正午时刻末端损失最大,早晨和傍晚时刻末端损失最小;不同季节相同时间段内的末端损失,冬季最大,夏季最小,春季和秋季几乎相等;镜场调节试验结果表明,增大反射镜北端与水平面的夹角可以补偿末端损失,在夏至前后正午,当镜场北端抬高20°时,末端损失减少至集热器长度的1/10左右,瞬时集热效率达到65.9%,与反射镜调节前相比,正午瞬时集热效率提高54.5%,下午时间段内瞬时集热效率提高20%左右。研究结果可为减小严寒地区小型线性菲涅尔聚光集热器末端损失提供理论参考。 相似文献
2.
食用菌温室温度具有时变、非线性、多耦合特性,准确预测对稳定食用菌生产具有重要意义。本研究从挖掘温室历史温度数据时序信息角度出发,提出一种MA-ARIMA-GASVR组合方法建立温度预测模型,利用移动平均方法将历史温度序列分解成线性序列和残差序列,然后采用移动平均差分自回归模预测线性序列的趋势,再将移动平均差分自回归预测值、历史残差数据、历史温度数据作为支持向量回归模型的输入,并结合遗传算法优化支持向量回归模型参数改善其性能,从而获得更符合实际情况的温度预测值。最后选取实测温度数据作为训练集,对未来2d的温度进行预测验证。结果显示,MA-ARIMA-GASVR组合方法能更好地拟合原始温度数据,间隔1h的均方误差、平均绝对误差和平均绝对百分误差分别为0.18、0.36和1.34,均显示本研究方法预测精度优于支持向量回归、遗传算法优化的支持向量回归单一模型,也优于未经移动平均以及未经遗传算法优化的组合模型;此外,间隔6h的均方误差、平均绝对误差和平均绝对百分误差为0.29、0.52和1.95,说明本研究方法还能满足6 h以内的多步预测,为食用菌生产者预留更多调整时间。 相似文献
3.
基于K-means 聚类和ELM神经网络的养殖水质溶解氧预测 总被引：8，自引：5，他引：3
为解决养殖水质溶解氧预测传统方法引入不良样本、精度低等问题,该文以2014、2015年江苏常州养殖基地水质和气象数据为基础,提出了一种基于K-means聚类和ELM神经网络（extreme learning machine,ELM）的溶解氧预测模型。采用皮尔森相关系数法确定环境因素与溶解氧的相关系数,自定义相似日的统计量－相似度,通过K-means聚类方法将历史日样本划分为若干类,然后分类识别获得与预测日最相似的一类历史日样本集,将其与预测日的实测环境因素作为预测模型的输入样本建立ELM神经网络溶解氧预测模型。试验结果表明,该模型均具有较快的计算速度和较高的预测精度,在常规天气下,平均绝对百分误差和均方根误差分别达到1.4%、10.8%;在突变天气下,平均绝对百分误差和均方根误差分别达到2.6%和11.6%,有利于水产养殖水质精准调控。 相似文献
4.
采用改进长短时记忆神经网络的水产养殖溶解氧预测模型 总被引：5，自引：4，他引：1
为了精确预测水产养殖溶解氧变化趋势,该研究提出了基于K-means聚类和改进粒子群优化(Improved Particle Swarm Optimization,IPSO)的长短时记忆(Long Short-term Memory,LSTM)神经网络预测模型。根据环境因子间的相似度,应用改进的K-means聚类算法将环境数据划分为若干类。在此基础上,基于LSTM神经网络算法构建改进的水产养殖溶解氧预测模型,并引入改进粒子群优化算法对模型参数进行优化,以减少经验选取参数的盲目性。在不同天气状况下利用该模型对溶解氧进行预测。试验结果表明,在良好天气情况下,该模型预测误差曲线波动较小,预测精度更高。当天气发生突变时,溶解氧预测模型评价指标平均绝对百分误差、均方根误差、平均绝对误差和纳什系数分别为0.129 5、0.645 3、0.461 3和0.902 2。该模型一定程度改善了天气突变状况下的数据缺失、鲁棒性差等问题。 相似文献
5.
为了进一步提高日光温室内主动蓄放热的热能利用效率,该研究在日光温室内的顶部空间,构建了基于曲面菲涅尔透镜的直散分离系统,该系统对顶部区域的空间利用率为25.8%。利用光学仿真软件对不同入射角的太阳光进行追踪,并对该曲面菲涅尔透镜在典型日条件下的接收效率和焦斑分布进行分析,得到一日内的变化规律。在直射光集热测试方面,正午时段内,该系统的集热效率可以达到45%。对比散射光环境对温室的影响,发现试验区全天光照度减小约为10%~40%。该文以主动集热土垄加温系统提升栽培土垄温度作为试验组,并与不加温对照组进行了比较。试验结果表明,系统可提高土垄温度4.5~5.0℃。连续晴天情况下,土垄加温系统的COP(coefficient of performance)为1.5~1.9。研究表明此新型温室集热方式可提高空间利用率,改善温室内光热环境,同时利用午间强直射光集热,实现太阳能综合利用。 相似文献
6.
《农业工程学报》2020,(4)
为了进一步提高日光温室内主动蓄放热的热能利用效率,该研究在日光温室内的顶部空间,构建了基于曲面菲涅尔透镜的直散分离系统,该系统对顶部区域的空间利用率为25.8%。利用光学仿真软件对不同入射角的太阳光进行追踪,并对该曲面菲涅尔透镜在典型日条件下的接收效率和焦斑分布进行分析,得到一日内的变化规律。在直射光集热测试方面,正午时段内,该系统的集热效率可以达到45%。对比散射光环境对温室的影响,发现试验区全天光照度减小约为10%～40%。该文以主动集热土垄加温系统提升栽培土垄温度作为试验组,并与不加温对照组进行了比较。试验结果表明,系统可提高土垄温度4.5～5.0℃。连续晴天情况下,土垄加温系统的COP(coefficient of performance)为1.5～1.9。研究表明此新型温室集热方式可提高空间利用率,改善温室内光热环境,同时利用午间强直射光集热,实现太阳能综合利用。 相似文献
7.
基于灰色模型和ARMA模型的猪瘟月新发生次数预测比较 总被引：1，自引：1，他引：0
对猪瘟月新发生次数(每个月的新发生次数)的定量预测可以为当地动物疫病防控部门提供依据,使其针对猪瘟发病风险有选择性地采取防控措施.该文分别选用灰色预测模型和ARMA预测模型对贵州省猪瘟月新发生次数进行了预测.灰色模型和ARMA模型以2005-2008年兽医公报中统计的贵州省猪瘟发病数据为预测依据,以2009年的统计数据评价比较预测效果.灰色模型和ARMA模型预测平均绝对误差分别为1.84和1.48,平均绝对百分误差为0.272和0.229.预测结果表明,ARMA预测模型的预测精度更高,对贵州省猪瘟发病的预测是可行有效的. 相似文献
8.
菲涅尔高倍聚光PV/T系统热电输出性能模拟与试验 总被引：1，自引：1，他引：0
该文基于直通式微通道冷却的菲涅尔高倍聚光PV/T系统热电输出性能的仿真和试验进行研究,结果表明,太阳辐照度、聚光元件间的装配距离、入射角及热对流等对系统热电性能的影响较大;太阳直接辐照度为226 W/m2时,菲涅尔透镜与聚光元件间距离增大2 mm后,功率和电效率分别下降0.98 W和7.4%,对于确定的菲涅尔高倍聚光PV/T系统,存在最佳聚光元件装配参数范围;当太阳直接辐照度一定时,冷却工质流量越大,电池表面温度下降越快,但在较高流量时,随着流量持续增大,电池表面温度下降趋势减小;当入射角由0°增大至1°后,系统得热量下降0.25 MJ,在太阳辐照度达到500 W/m2时,输出功率下降6.35 W;试验系统输出性能稳定,且适用于大型系统,该文研究为系统实际运行参数调控提供理论和试验依据。 相似文献
9.
针对作物生产碳排放预测较为困难的实际问题,提出基于BP神经网络算法的玉米生产碳排放预测模型。选择地处河西走廊石羊河下游的民勤绿洲246家农户,面对面调查玉米种植户农场内生产投入数据,将玉米生产投入数据作为神经网络输入层;查阅和梳理国内外相似区域玉米生产环节碳排放系数,运用碳足迹生命周期法计算得到的碳排放值作为神经网络输出层;基于BP人工神经网络算法,运用试凑法确定网络隐含层节点个数,建立河西绿洲玉米生产碳排放预测模型,选择多元线性回归模型、多元非线性回归模型,对该模型有效性进行评估。研究结果表明,3层且各层节点数9、10、1的神经网络结构能够准确预测河西绿洲玉米生产碳排放,其碳排放预测值为0.763 kg(CO_2-eq)·kg~(-1)(DM);9-10-1结构的神经网络预测模型的相关系数(R~2=0.984 7)高于多元线性和非线性回归模型,该神经网络结构模型的均方根误差(RMSE=0.069 1)、平均绝对误差(MAE=0.051 3)均低于其他模型,BP神经网络算法预测性能明显优于其他预测模型。该研究为准确预测农业生产碳排放提供了新思路和可操作方法。 相似文献
10.
为精准把控并及时调节葡萄大棚棚内小气候,利用清徐县葡萄大棚农田小气候站观测数据及气象站、辐射站、土壤水分站资料,建立以棚外气温、相对湿度、风速、总辐射、土壤湿度为输入变量,棚内气温、相对湿度、土壤温度为输出变量的基于BP神经网络葡萄大棚小气候预测模型。为了对比分析BP神经网络的精确度和稳定性,同时建立多元线性回归模型。结果表明,基于BP神经网络建立的预测模型,其训练值和实测值之间的绝对误差分别为1.55 ℃、4.46%、0.77 ℃,标准误差分别为2.18 ℃、5.94%、1.00 ℃;预测值和实测值之间的绝对误差分别为1.37 ℃、2.84%、0.42 ℃,标准误差分别为1.96 ℃、4.60%、0.53 ℃。预测效果明显优于多元线性回归模型,预测精度满足棚内小气候要素预报要求。 相似文献
11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响 总被引：2，自引：2，他引：0
【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。 相似文献
12.
Aleš Lebeda Ivana Doležalová Eva Křístková Barbora Mieslerová 《Genetic Resources and Crop Evolution》2001,48(2):153-164
Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions. 相似文献
13.
Kyle Devey Michael Mucalo Gordon Rajendram Joseph Lane 《Communications in Soil Science and Plant Analysis》2015,46(4):72-80
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing. 相似文献
14.
Thomas Larsen Jesper Luxhøi Jakob Magid Lars Stoumann Jensen Paul Henning Krogh 《Biology and Fertility of Soils》2007,44(1):59-68
We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization
and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition
with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the
decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots
with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass,
soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration,
N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially
(<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation
in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils,
indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but
the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation
for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community
performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea. 相似文献
15.
《中国生态农业学报》2014,(6)
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
16.
《中国生态农业学报》2014,(7)
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
17.
I.L. Boyd 《Biological conservation》2010,143(7):1664-1674
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options. 相似文献
18.
Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage 总被引：1，自引：0，他引：1
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate. 相似文献
19.
《中国生态农业学报》2014,(8)
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
20.
M.A. Callaham Jr. J.M. BlairT.C. Todd D.J. KitchenM.R. Whiles 《Soil biology & biochemistry》2003,35(8):1079-1093
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils. 相似文献