果园开沟施肥机机架优化设计与试验

为提高果园开沟施肥机的动态作业性能,避免共振的发生,同时保证作业时开沟一致性及施肥稳定性,对其机架进行多目标优化设计。首先,建立果园开沟施肥机机架的参数化模型及有限元模型。其次,通过模态分析,得出机架的固有频率及振型,研究其对整机动态性能的影响,将一阶模态频率设定为目标函数。通过机架灵敏度分析,得到各杆件厚度对一阶模态频率的灵敏度,将灵敏度杆件的厚度设定为设计变量,将其厚度变化范围设定为约束条件。根据现代农机结构轻量化设计的要求,将机架的质量也作为目标函数。以目标函数、设计变量、约束条件为基础,构建机架多目标优化的数学模型。然后,基于Hammersley抽样方法,按约束条件选取42组试验样本进行试验设计,并计算其对应的目标值。根据试验设计结果,选用移动最小二乘法并拟合出对应响应面。其中,一阶模态频率响应面模型的决定系数R2=0.9974,质量响应面模型的决定系数R2=0.9999,均大于拟合模型要求的精度0.9,拟合精度较高,满足设计要求。最后,基于响应面以及多目标遗传算法对果园开沟施肥机机架进行结构优化设计。优化结果表明：优化后的果园开沟施肥机机架一阶模态频率由原来的35.39Hz提高到38.31Hz,提高了8.25%,且远离拖拉机的输入频率35Hz;优化后质量为389kg,满足在提升一阶模态频率下,质量最小的要求。优化后果园开沟施肥机作业的开沟一致性系数和施肥稳定性系数比优化前分别提高3.72%、3.57%,提升效果明显,满足果园开沟施肥生产要求。     

基于模态分析的立式香蕉秸秆粉碎还田机机架优化

利用ANSYS Workbench软件对立式香蕉秸秆粉碎还田机机架的三维参数模型进行模态分析,检验立式香蕉秸秆粉碎还田机的作业可靠度。为了防止共振的发生,采用错开激励源频率的方法,对机架结构分两个阶段进行优化。优化结果表明:增加机架后挡板的钢板厚度或减少机架侧挡板及盖板的钢板厚度皆可提高机架的固有频率;机架在质量减小9%的情况下,1阶固有频率将增加28%,作业可靠度将得到显著提高。     

Comparative efficacy of trash fish versus compounded commercial feeds in cage aquaculture of Asian seabass (Lates calcarifer) (Bloch) and tiger grouper (Epinephelus fuscoguttatus) (Forsskål)

Trash fish/low valued fish is still the most commonly used feed in marine cage culture in Asia. Use of trash fish is controversial with regard to the sustainability of the farming practices, and related issues on environmental degradation. In this study, the results of farm based trials on Asian seabass (Lates calcarifer) and tiger grouper (Epinephelus fuscoguttatus) to evaluate the efficacies of the use of commercial pellet feed in comparison to trash fish/low valued fish in marine cages in Thailand are presented. In spite of the variations observed in each of the farm sites, the results indicate that the overall growth performances and fish survival rates between the two feed types were similar, for both species. However, better cost‐benefit and resource use were recorded for fish reared on trash fish/low valued fish. No significant differences were observed in water quality parameters, dissolved oxygen, transparency and ammonia, between sites where pellet or trash fish were used, inside and outside the cages and for both species. The results of the present study are discussed in the light of the current controversies on the use of trash fish/low valued fish in marine cage culture.     

Environmental consequences of land degradation in coastal drainage basins of north Queensland,Australia: Influence of farming practices

Views expressed by sugar cane farmers in the Johnstone Rivers system, north Queensland, are consistent with the broader community concern about the potentially adverse ecological effects of point source discharges to the Great Barrier Reef lagoon. the main link between agricultural land use and the deterioration of surface and groundwater quality in the region is perceived by the farmers to be a consequence of the influence exerted by new farm management strategies and economic constraints on local environmental variables, particularly soils. the effectiveness of the land use practices in relation to land capability and productivity thresholds is considered by farmers to be essential for developing new farm management strategies and for improving water quality in the north Queensland coastal regions. as a result of increasing inhomogeneity of land use practices involving the application of chemicals, catchment based investigation, including systematic interviews with the land users, is needed for the development of reliable databases on problems related to the discharge of agricultural chemicals to coastal waters.     

香菇菌棒在架注水机的设计与试验

针对香菇菌棒在出菇环节需要多次对多层菌架上的菌棒逐一进行补水操作时传统人工补水劳动强度大、效率低且无法精准控制注水量的问题,设计了一种香菇菌棒在架注水机,该机主要由夹持装置、注水装置、升降装置、旋转装置、驱动装置和定位装置六部分组成,由夹持装置和注水装置组成注水单元,一次可同时完成3层共15个菌棒的夹持注水工作,在升降装置带动下实现多层菌棒的补水作业,再通过旋转装置完成另一侧菌架的菌棒在架补水作业。理论计算结果显示,夹持装置的最大加持力F_jmax为4 750 N,注水装置的最小推力F_tmin为2 455 N,旋转装置需先加速2 s后再匀速旋转3.5 s。样机试验结果显示,补水后菌棒的破损率为0,平均质量比为84.8%,平均工作效率为230个/h。     

高层货架货格数目整数规划模型

分析了货架结构和组成部分,将货架建设费用细分为货架基本材料费用、紧固件费用、加工费用三部分,并配合堆垛机的运行参数,提出了建设费用与运行费用之和最低为目标函数,以货架货格数量、水平分布、垂直分布为离散控制变量,建立了高层货架最佳货格整数规划模型,编写了相应的计算机数值分析程序,进行了算例的实证分析,完善了斯麦霍夫模型.     

Distortional Buckling Formulae of Cold-Formed Thin-Walled Rack Members Upright with Rear Flange and Additional Lip Stiffeners

According to the generalised beam theory based on the exist studies, the aim of this paper is to derive the distortional buckling formulae of pined or fixed cold-formed thin-walled rack members upright with rear flanges and additional lip stiffeners. The formulae is adopted to calculate the distortional buckling load and the buckling half-wave length of the member subjected to axial compression or minor and major axis bending. Meanwhile, the results are compared to those of finite strip program CUFSM and other analytical formulae. The derived formulae is proved to be accurate enough. As a result, it may be directly used in practical design as well as further study.     

基于高架库模式的打叶复烤均质化加工技术研究

[目的]研究不同的配方打叶过程成品片烟烟叶内在质量均匀性的变化规律,为利用高架库实现均质化配方打叶提供参考。[方法]选用福建产区多个产地等级的烟叶为试验原料,选择烟叶烟碱含量为参数,将50%原料作为试验组利用高架库自动控制功能实现均质化配方打叶,另外50%作为对照组,不做控制,通过标准偏差、变异系数分析评价2种方法片烟烟碱含量的波动情况。[结果]试验组利用高架库自动控制功能能够实现均质化配方打叶,使成品片烟烟碱含量的标准偏差和变异系数分别降至0.07%和2.53%;对照组利用高架库随机投料,成品片烟烟碱含量的标准偏差和变异系数分别降至0.10%和3.60%;试验组与对照组相比,成品片烟的标准偏差和变异系数分别降低了0.03和1.07个百分点。[结论]打叶复烤过程利用高架库自动控制功能可实现均质化配方打叶,提升成品片烟内在质量的均匀性。     

庙头泵站拦污栅工程设计

工程设计采用两根地梁平行布置,将闸墩底板联成一块,使底板形成方格式的整体结构,较好地解决了拦污栅工程的抗滑稳定问题。     

2BF-9型小麦播种机的研制

摘要：为了满足朝阳地区农业生产的需要，设计了一种小麦播种机，可以一次性完成开沟、施肥、播种和覆土作业，经田间试验测试，播种深度40mm，行距120mm,苗带宽度70mm,效率0.43hm2/h；其创新点是链轮通过链轮定位板限位，在后横梁上交错设置后开沟器架和前开沟器架；优势是苗带宽，结构简单调整方便。