福建柏优树选择及种实表型变异研究

在调查研究福建柏资源基础上,制定了福建柏优树选择方法,于1998年6～11月和1999年7～11月在福建省福建柏自然分布区和栽培区以及湖南省道县福建柏天然林中选择出优树175株,其中从天然林中选出57株,从人工林中选出118株。这些优树总体表现较好,生长量大,平均树高、胸径、材积分别为15 49m、28 6cm和0 51263m3,树干通直圆满,树体健康,无病虫害,平均树龄为35 3a。1999年10～11月,采集到129株优树的球果,测定了各优树的种子千粒重、球果出籽率、球果重、球果长、球果宽、球果长×球果宽、球果长/球果宽和苞鳞数等8个指标,结果表明各优树在种实性状上差异比较大,差异最大的是球果重,平均单果重2 757g,变幅为1 342～4 748g,变异系数为27 86%;平均千粒重为6 378g,变幅为3 647～11 349g;平均出籽率为2 56%,变幅为1 62%～4 79%;球果大小相差较大,球果近球形但略长些。相关分析表明,优树各种实性状间的相关性大都达到极显著水平,千粒重与球果重量、大小呈密切的正相关,与出籽率、苞鳞数及球果形状关系不大;出籽率与其他种实性状间相关性很小,可能是个独立的性状;单果重与苞鳞数及球果大小呈高度的正相关关系,与球果形状没有关系。收集选出的175株优树中的162株,在福建省安溪白濑国有林场建成了全国第一个福建柏种?     

柳杉雄球花散粉方式及花粉结构特征

[目的]为柳杉良种繁育提供一定的理论依据。[方法]以100年以上的柳杉为试料,采用数码拍照来研究柳杉雄球花散粉方式,扫描电镜观察柳杉雄球花的花粉结构特征。[结果]雄球花的苞片在雨天对花粉具有保护功能。花粉的散发受降水、气温、风速、气压和相对湿度的综合影响。柳杉花粉远极面具一个明显的乳头状突起。[结论]该研究有利于柳杉良种生产。     

基于Android和Openlayers的旅游导览系统

为给游客提供全面的旅游信息,完善旅游服务体系,提升景区的服务和管理水平,本文以开源的Android和Openlayers为技术核心,以轻型数据库SQLite为数据支撑,开发出了具有导航、线路规划、定位、景点查询等众多功能的旅游导览系统.经检验,系统运行良好,证明了将Android和Openlayers用于地理信息开发时具有高效性和低成本性.     

导苗管式烟草移栽机的设计

为保证烟草实时移栽,提高移栽质量,减少劳动力投入,降低移栽成本,实现烟草移栽机械化、规模化,设计了一种导苗管式烟草移栽机.整机主要由悬挂架、地轮、仿形装置、投苗装置、导苗管、送苗装置、覆土压实轮、开沟器、动力传动链等组成.采用转盘式投苗机构把烟苗投入导苗管;采用曲柄摇杆机构、摆杆机构的可靠协调配合,把烟苗推入开沟器开好的沟中;曲柄摇杆机构摆动时把浇水阀门打开,实现移栽、浇水的同步;推入沟中的烟苗由覆土压实轮完成覆土和挤压;通过改变向投苗机构、送苗机构输送动力的链轮齿数实现株距的调整.该机具由拖拉机牵引,作业时地轮的转动经链传动、齿轮传动驱动转盘式投苗装置、曲柄摇杆机构、摆杆机构动作完成烟苗的移栽.该机具可完成移栽株距(500~650 mm)、移栽深度(80~120 mm)、灌水量(300~500 mL)可调以及效率高的目标,同时具有结构合理紧凑、维护方便、操作简单等优点.     

非线性四阶两点积分边值问题正解的存在性

研究非线性四阶微分方程两点积分边值问题解的存在性.利用一些分析技巧及锥上不动点定理,给出该问题存在一个及两个正解的充分条件.     

Evolutionary characteristics of morbilliviruses during serial passages in vitro: Gradual attenuation of virus virulence

The genus Morbillivirus is classified into the family Paramyxoviridae, and is composed of 6 members, namely measles virus (MV), rinderpest virus (RPV), peste-des-petits-ruminants virus (PPRV), canine distemper virus (CDV), phocine distemper virus (PDV) and cetacean morbillivirus (CeMV). The MV, RPV, PPRV and CDV have been successfully attenuated through their serial passages in vitro for the production of live vaccines. It has been demonstrated that the morbilliviral virulence in animals was progressively attenuated with their consecutive passages in vitro. However, only a few reports were involved in explanation of an attenuation-related mechanism on them until many years after the establishment of a quasispecies theory. RNA virus quasispecies arise from rapid evolution of viruses with high mutation rate during genomic replication, and play an important role in gradual loss of viral virulence by serial passages. Here, we overviewed the development of live-attenuated vaccine strains against morbilliviruses by consecutive passages in vitro, and further discussed a related mechanism concerning the relationship between virulence attenuation and viral evolution.     

Day-blindness in three dogs: clinical and electroretinographic findings

A 6-month-old Rhodesian ridgeback-cross, a 6-year-old Chihuahua and a 12-month-old Australian cattle dog were presented to the authors with a history of colliding with obstacles in daylight. Ophthalmic examination was normal and all three dogs successfully negotiated obstacle courses in dim light. In daylight the dogs became suddenly blind and repeatedly collided with obstacles. Elecroretinography (ERG) revealed no retinal activity to high frequency (30 Hz), bright intensity blue light retinal stimulation by any dog, confirming cone dysfunction. Achromatopsia has previously been recorded in Alaskan malamutes and miniature poodles. This clinical case series illustrates the characteristic behavioral presentation and the electroretinographic findings of severe day-blindness and demonstrates that this condition may exist in other breeds of dogs.     

Simultaneous measurement of soil water and soil hardness using a modified time domain reflectometry probe and a conventional cone penetrometer

Soil strength and water content are important indices for assessing soil resistance to root growth and soil compaction both of which affect other soil properties. Therefore, simultaneous measurement of soil penetration resistance (PR) and soil water content can aid agricultural land management. We measured PR with a conventional cone penetrometer, followed immediately by determining water content using a modified TDR probe inserted into the penetrometer hole. From the results of a field feasibility test, soil water content was measured satisfactorily and correlated well with data obtained by the gravimetric method, except for those data from near the surface owing to soil disturbance when the cone penetrometer was extracted after the PR measurements. Field results demonstrate that PR and soil water content have three‐dimensional variability, with a markedly different distribution pattern between cultivated and subsoil layers at the field scale. Overall, the variability in the PR and soil water data is similar to that reported in previous studies. We conclude that our method produces results helpful to field management of soil and water because it is based on a simple and easy technique for the simultaneous measurement of soil water content and PR.     

前置导叶对畜禽舍轴流风机性能的影响

畜禽养殖过滤除臭装置对传统轴流风机负压抽吸能力提出了更高的要求。为提高传统轴流风机的气动性能，扩大其有效工作区间，该研究以550型农用轴流风机为对象，结合试验和数值模拟研究了前置导叶对轴流风机性能的影响。通过单因素和响应面分析方法，对前置导叶的导叶安装角（α）、轴向间距（L）、导叶个数（n）对风机性能和流场的影响进行研究，分析各因素对风机性能的影响，求解出最佳参数组合。通过3D打印制作前置导叶并进行样机试验。结果表明，增设前置导叶后，风机内部区域涡流得到削弱，降低了流动损失，静压效率提高，流动剧烈程度降低，流场更稳定，叶片静压差增大，风机叶片的做功能力增强，与传统结构相比，增设前置导叶后风机通风量和能效比均明显提升，通风量提升幅度在5.7%～10.39%，能效比提升幅度在6.62%～10.89%；在静压50 Pa下，通风量提升6.76%，能效比提升7.75%。研究结果证明了增设前置导叶提升轴流风机负压抽吸能力的可行性。     

建构观下教师角色的定位

在建构主义理论的指导下,教师必须改变机械的和静态的数学教学观,向动态的、易谬(经验主义和似经验主义)的数学观念转化。要重新认识教师在教学过程中的主导作用,教师不再是简单的知识传授者,而应是数学建构活动的激励者、组织者、参与者和导向者。