罗汉果采摘装置的设计仿真与试验

为了改善罗汉果采摘条件、提高采摘效率,基于罗汉果生长特性和采摘实际需求,设计了一种罗汉果采摘装置.通过UG建立装置模型并进行优化设计,并通过Adams和Ansys进行了运动学和有限元分析,验证了所设计装置的合理性.最后,制造样机并进行试验,结果表明:采摘装置大大提高了采摘效率,满足使用要求.     

森林生态采伐评价指标计量方法

运用层次分析和模糊评价建立了森林生态采伐评价指标模型,并参考已被广泛承认的公式及德尔菲法量化森林生态采伐作业指标,给出了生态采伐的森林活力、森林组织结构、森林恢复力和森林生态效益、经济效益、社会效益等各个评价指标的计量方法。     

坡面集雨补灌对玉米生育中后期干物质积累和分配的影响

本文讨论了半干旱地区坡面集雨不同补灌条件下,玉米一生干物质积累与其在各器官中分配的动态及其差异,结果表明,集雨补灌可加速玉米的生育进程,增加生育前中期营养器官和中后期雌穗的干物质积累量,并从灌浆期开始各器官中的干物质迅速向雌穗转移,使雌穗占单株总干重的比重不断增加;不补灌的处理前期干物质积累比补灌的要慢,根冠比大,在当地后期雨水充足的情况下,干物质积累快,但成熟推后,产量降低;不同补灌方式中以覆膜坐水和前中期补灌2次的效果最佳,特别是拔节期补灌增产效果最为明显.     

自走式穗茎兼收型玉米联合收获机的设计与试验

为了解决玉米茎秆回收利用,提出立式摘穗茎秆切碎单元体结构,设计了玉米收获、茎秆切碎、根茬破碎于一体的玉米收获工艺,并用于4YQZ-3自走式穗茎兼收型玉米联合收获机,通过生产试验和检测证明,符合国家相关标准规定。为解决玉米穗茎兼收关键技术提供了技术方案和应用实例。     

基于彩色信息的树上柑橘识别研究

为正确识别自然环境中的树上水果,从而为机械手的运动提供参数并完成水果的自动采摘,研究了基于彩色信息的树上柑橘识别方法。在对53幅含有各种背景情况的可见光彩色图像进行颜色特征提取和理解的基础上,建立了利用柑橘、树叶、树枝在R-B颜色指标上的差异进行树上柑橘识别的颜色模型,并利用动态阈值法,根据图像特征动态产生阈值T,将柑橘从背景中分割出来。分别在顺光条件和逆光条件下进行了试验分析,试验结果表明该识别模型可以实现对树上可见的柑橘的识别,并适用于单个和多个果实的识别,正确识别率较高。     

Atlantic cod recovery from the Allee effect zone: contrasting ecological and evolutionary rescue

The ability of a population to recover from disturbances is fundamental for its persistence. Impaired population recovery might be associated with a demographic Allee effect. Immigration from adjacent populations could accelerate the recovery not only by promoting population growth beyond the Allee effect threshold but also by bringing in advantageous genotypes. We explore the nature and role of ecological and evolutionary rescue in an Atlantic cod (Gadus morhua Gadidae) population fished below its Allee effect threshold. We utilize an eco‐evolutionary model and simulate scenarios, where the target population evolves in response to selective fishing and sample immigrants from (a) a source population similarly adapted to fishing (post‐fishing genotypes) or (b) an unexploited source population with natural genetic and phenotypic diversity (pre‐fishing genotypes). Immigration of pre‐fishing genotypes enhances the recovery due to the larger body sizes and the flow of associated genes. Post‐fishing immigrants can also promote the population abundance recovery, but they increase uncertainty about recovery times as compared to pre‐fishing immigrants and do not promote evolutionary recovery. Our results stress the importance of maintaining genetic and phenotypic diversity and suggest that marine protected areas can serve as an important source of immigrants to promote both the demographic and evolutionary recovery of exploited populations.     

Net and gross mineral N production rates at three levels of forest canopy retention: evidence that NH<Subscript>4</Subscript><Superscript>+</Superscript> and NO<Subscript>3</Subscript><Superscript>−</Superscript> dynamics are uncoupled

Alternative silvicultural systems were introduced in Coastal Western Hemlock forests of British Columbia, Canada, to reduce disturbance incurred by conventional clear-cutting and to maintain the forest influence on soil nutrient cycling. As we hypothesized, in situ pools and net mineralization of NH₄ ⁺ were lower under no and low disturbance (old-growth forest and shelterwood) compared to clear-cuts (high disturbance); in situ pools and net production of NO₃ ⁻ were very low across all treatments. Gross transformation rates of NH₄ ⁺ increased while those of NO₃ ⁻ decreased with increasing disturbance, suggesting that these processes were uncoupled. We conclude that shelterwood harvesting reduces the impact on forest floor NH₄ ⁺ cycling compared to clear-cutting, and that neither low nor high disturbance intensity results in substantial NO₃ ⁻ accumulation, as what occasionally occurs in other ecosystems. We hypothesize that the uncoupling of NH₄ ⁺ and NO₃ ⁻ dynamics may be due to the predominance of heterotrophic nitrification by lignin-degrading fungi that oxidize organic N rather than NH₄ ⁺–N, and whose activities are suppressed at high NH₄ ⁺ concentrations.     

Stress responses of carp pond fish stock upon hunting activities of the great cormorant(Phalacrocorax carbo sinensis L.)

In addition to direct predation, cormorants can affect carp pond fish stock through disturbance and wounding of the fish. Fish stress response was evaluated by catch per unit effort (CPUE) using lift‐net sampling. A significantly higher (P<0.001) CPUE was recorded in the littoral region of ponds affected by cormorant visits (43.6 ± 39.6) in comparison with a control pond (CP) without their occurrence (0.9 ± 1.1). Stress indices, spleen somatic index (SSI) and Fulton's condition coefficient (FCC) were evaluated for fish subject to two stress factors, hunting cormorants (HC) and pond harvesting (PH), and compared with levels in fish from the CP. Both SSI and FCC decreased significantly (P<0.05) in PH and HC fish in comparison with the control group, while non‐significant differences were observed in both SSI and FCC indices among the HC and PH groups. Plasma biochemical indices (cortisol, glucose and lactate concentrations) were significantly higher (P<0.01) in the PH group as compared with the HC and CP groups. Concentrations in the HC and CP groups did not differ significantly. Total plasma protein levels were significantly higher (P<0.01) in HC fish compared with CP fish, but did not differ significantly from PH fish.     

Effects of selective harvesting and claw ablation of all‐male freshwater prawn (Macrobrachium rosenbergii ) on water quality,production and economics in polyculture ponds

The effects of selective harvesting (SH) and claw ablation (CA) of blue‐clawed (BC) prawns on an all‐male freshwater prawn–finfish polyculture system were compared with control (Co) in quadruplicate. Ponds were stocked with all‐male freshwater prawn Macrobrachium rosenbergii, silver carp Hypophthalmichthys molitrix, catla Catla catla and mola Amblypharyngodon mola at 12 000, 2000, 500 and 20 000 ha^?1 respectively. Prawns were fed with pelleted feed. Ponds were fertilized regularly with urea, triple super phosphate and cow‐dung. SH of BC prawns in treatment SH and CA in treatment CA started on the 60th day during a 137‐day culture and continued at 15‐day intervals until the final harvest. Water quality parameters and plankton abundance did not vary significantly (P>0.05) among the treatments. Treatment SH resulted in a higher (P<0.05) net production of freshwater prawn (437 kg ha^?1), with better survival and mean weight, followed by CA (354 kg ha^?1) and Co (322 kg ha^?1). The combined net production of prawn plus finfish was also higher in SH (1244 kg ha^?1) as compared with CA (1161 kg ha^?1) and Co (1137 kg ha^?1), although the finfish production did not differ significantly. The periodic SH of BC prawns showed a better economic return with a BCR of 1.71.     

不同土壤对甘蔗入土切割负载压力影响的研究

针对甘蔗收获机入土切割系统负载压力的预测适应性差、准确性低的问题,通过正交试验探究在不同土壤类型下切割系统的负载压力与入土切割深度、土壤含水率、甘蔗密度及土壤硬度等因素之间的关系并对各影响因素的显著性进行排序;根据试验结果搭建基于BP神经网络的负载切割压力的预测模型并进行验证.试验及验证结果表明:各土壤中入土深度、土壤...