灌区降水量影响因子分析与集合降水预测

针对降水随机性较强、影响因素复杂、单一模型预测精度低的特点,采用集对分析法,研究降水量与气象影响因子的关系。将基于密度参数的径向基函数人工神经网络模型与灰色模型相结合,利用信息熵权重法计算2个单一模型的权重,构建基于信息熵的集合模型(Combing model based on information entropy,IE-CM),用于三江平原友谊农场的降水量预测。研究结果表明,与单一模型相比,IE-CM模型预测结果的决定系数、平均相对误差及均方根误差较单一模型均有所提高,分别为0.99、10.655%和3.03 mm,预测结果的合格率为83.3%,均满足水文预测要求。     

Collatz猜想探讨

定义了Collatz波集CWS及作用在其上的3-1映射triim,探讨了CWS在triim映射下的性质,从另一个角度对Collatz猜想进行了探讨,以期为最终证明Collatz猜想提供了一个全新的思路。     

灰色──马尔柯夫模型的建立及其在林业经济中的应用

本文介绍了灰色──马尔柯夫模型的建立方法，并利用我国林业系统工业企业全员价值劳动生产率资料（１９７１～１９８６年），按照灰色──马尔柯夫模型的建模步骤建立模型并进行预测，同时还进行了误差分析。结果表明，按照该法预测今后的林业系统工业企业全员价值劳动生产率是可行的，而且，在预测林业系统其他企业的多种经济指标方面，有较为广阔的应用前景。     

微灌用自清洗网式过滤器自清洗结构流场分析与优化研究

自清洗过滤器是灌溉节水系统关键设备,随着微灌系统自动化程度提高,对该设备要求也越来越高。为此,在概述了过滤器特点及原理的基础上,运用FLUENT流体软件对自动清洗结构进行流场分析,得出速度矢量分布图,在此基础上,根据吸管流速相对方差与相对极差的计算结果,改变排污管、吸管部位的直径,使各个吸管的流量基本保持一致,达到吸污...     

Gear-based management of a tropical artisanal fishery based on species selectivity and capture size

The population density, species composition and lengths of fish landed by artisanal fishermen using six types of gear: large and small traps, gill nets, hand lines, spears and beach seines were studied in the multi‐species fishery of southern Kenya. Selectivity and catch composition among gears were determined by studying the species richness, diversity, size and mean trophic level of the catches for each gear type, to develop gear‐based management recommendations for this artisanal reef lagoon fishery. One hundred and sixty‐three reef and reef‐associated species from 37 families were recorded in the catch. Beach seines and small traps accounted for the highest number of fish landed (34–35 individuals per fisherman per day). These gears also caught smaller fish than big traps, spears and gill nets. Beach seines caught the highest number of species (14 ± 7 species per day) while most other gears caught four to five species per day with no differences between gears. Predatory species with a mean trophic level of 3.6 dominated catches from hand lines, while the mean trophic level of the other gears was low and ranged from 2.6 to 2.9 with no differences between the gears. The high diversity and small size of fish caught in beach seines indicates that its selectivity overlapped most with large traps and gill nets. Spears and small traps also showed high similarity in species selectivity and small traps captured the smaller mean size of fish, indicating that they are likely to pre‐empt the resource of spears. Large traps, hand lines and spears catch the largest individuals and the species composition of the catch differed sufficiently such that their selectivity should overlap the least and may, therefore, be the preferred mix of gears. The elimination or reduction of beach seines and small traps should reduce the catch of small fish and overlap in selectivity among the existing gears.     

Survival Rates of Black Sea Turbot (Psetta maxima maeotica, L. 1758) Broodstock Captured by Gill Nets from Different Depths and their Adaptation Culture Conditions

A study was performed during Spring 2002 to determine the survival rates of Black Sea Turbot (Psetta maxima maeotica) broodstock captured by gill nets from different depths (20 m, 20–45 m, and 45 m) in Sinop Bay (Black Sea, Turkey) and their adaptation to culture conditions. The weight of captured females ranged between 1.6 and 5.5 kg, while males ranged between 1.1 and 3.7 kg. Within 23 h of capture the fish were transported to Çanakkale (Marmara Sea, Turkey). During transportation, the stocking density ranged from 19 to 40 kg/m³ and no mortality was recorded. At the end of the fishing operations, the survival rates were calculated for Group 1 (20 m), Group 2 (20–45 m), and Group 3 (45 m) as 24.9, 71.4, and 92%, respectively. There were significant differences (p < 0.05) between the survival rates of the groups. Eggs and sperms were obtained by hand-stripping. The mean fertilisation rate of the eggs was 3.19%. This low fertilisation rate was due to overripened eggs. At the end of adaptation period of 1 month, the survival rates of the broodstock were found to be 14.2, 45.4, and 48.3% for Groups 1, 2, and 3, respectively. No significant difference was found between the survival rates of the broodfish during the adaptation period (p > 0.05).     

丽蚜小蜂及配套措施联合控制技术对温室粉虱的防治效果

为明确丽蚜小蜂应用技术中一些配套措施的作用,在越冬番茄温室内,进行了丽蚜小蜂及配套措施联合使用控制温室粉虱效果的试验。以传统农药防治为对照(CK),研究了3项措施联合使用技术(释放丽蚜小蜂+温室安装防虫网+适时清除底部老叶)、未装防虫网(释放丽蚜小蜂+适时清除底部老叶)、未清除底部老叶(释放丽蚜小蜂+温室安装防虫网)对温室粉虱成虫数量的影响。结果表明:3项措施联合使用的温室11月~翌年6月粉虱数量持续低于2头/株,未装防虫网的温室(释放丽蚜小蜂+适时清除底部老叶)3月下旬~6月中旬粉虱数量从0.90头/株增加至11.99头/株,未及时清除底部老叶的温室(释放丽蚜小蜂+温室安装防虫网)2月底~4月中旬粉虱数量从0.25头/株迅速增长至8.93头/株,农药防治的温室(CK)自3月以后粉虱数量持续在3~5头/株。3项措施联合使用对温室粉虱的控制效果显著优于其他处理和农药防治。释放丽蚜小蜂、安装防虫网和适时清除底部老叶3项措施联合控制技术,能够较好地防治越冬番茄温室粉虱,且控制效果可持续作物整个生长期。     

旱作马铃薯配方肥配方制定过程分析

通过马铃薯田间“3414”试验结果和土壤氮、磷、钾土测值的分析,建立了氮、磷、钾肥料效应函数、养分丰缺指标、综合效应函数、不同养分丰缺指标下的最佳施肥量以及土壤养分测定值频率分布,从而进行了配方施肥量的确定、配方的计算以及施肥量的建议。     

基于集对分析-可变模糊集的地表水环境质量综合评价

基于集对分析原理,选取地表水环境质量监测指标中的10个指标建立了基于集对分析-可变模糊集的水环境质量评价模型,并采用该模型对北京市10大湖泊水库的水环境质量进行了评价。结果表明,北京市10大湖泊水库的水质较好,基本满足水质功能的要求;除密云水库、海子水库外,其余水库均受到不同程度的污染,其中官厅水库、沙河水库水质最差。该评价结果与单因子评价法、模糊数学综合评价法和SVM法的评价结果基本一致,说明采用集对分析-可变模糊集评价模型对地表水环境质量进行评价具有可操作性和实用性。     

芒果椰浆凝固型酸奶的发酵工艺研究

[目的]寻求芒果椰浆凝固型酸奶的最佳发酵工艺条件。[方法]以芒果与椰浆为原料,先通过单因素试验分别考察奶粉添加量、接种量、椰浆添加量等因素对芒果椰浆凝固型酸奶感官评价的影响,然后通过L9（3^4）正交试验,获得芒果椰浆凝固型酸奶的最佳工艺条件,最后对该产品进行感官评价。[结果]正交试验表明,4因素对该产品感官评价的影响由强到弱的顺序为：发酵温度〉发酵时间〉芒果添加量〉蔗糖添加量;芒果椰浆凝固型酸奶的最佳工艺条件为：奶粉添加量14%,接种量3%,蔗糖添加量8%,椰浆添加量10%,芒果添加量10%,发酵温度42℃,发酵时间4 h。[结论]该产品乳白色,具有芒果和椰浆特有的香气,风味协调,且有芒果果粒,口感丰富。