Research on pitch cone design for beveloid gears with crossed axes

Based on the spatial gearing theory, the mathematical model for working pitch cone design of crossed beveloid gears is created. The formulas to determine the transition from point contact to line contact are derived. The direct and in direct methods for pitch cone design of crossed beveloid gears are proposed. The effects of gearing parameters on the angle between the first principle directions are analyzed. The loaded tooth contact analysis is performed using FEM theory. The conclusion indicates that: the angle between the first principle directions is more sensitive to cone angles than to the helix angle. The increase of the angle between the first principle directions can obtain smaller contact area, higher transmission error and lower mesh stiffness. A practical tooth bearing test is conducted to demonstrate the proposed design procedure and the experimental result compared well with the simulation. For the matching design and optimization of beveloid gears, it has both the theoretical and project practical significance.     

影响根寄生植物列当种子萌发因素的研究

列当是对农业危害性较大的根寄生植物,其种子须经预培养并在萌发刺激物作用下才能萌发.本文阐述了温度、渗透势、预培养时间、生长调节物质及光照等因素对列当种子萌发的影响,为科学防治列当提供有益的探索依据.     

农作物新品种新技术的微观需求及影响因素分析——以油菜为例

基于我国主要油菜种植区600个农户的调查数据,通过统计分析,得出以下结论:农户普遍重视油菜新品种的潜在产量和抗性,认为现场示范和定期咨询的技术推广方式效果最佳。通过交叉表分析得出:年龄在50~60岁之间、户种植规模在1334m2以下和家庭收入处于中等水平的油菜种植户接受新品种新技术的积极性较强。油菜新品种新技术研发及推广部门可参照这些依据,采取针对性的改进措施推进油菜产业的发展。     

农业市场信息传播主体选择和影响因素分析

在当前我国农业信息化建设中,如何解决信息的供给者与需求者之间的信息传播问题是关键。本文从农户的视角来探析农业市场信息传播主体的需求状况,并用最优尺度回归方法分析影响农户期望选择的原因。研究发现当前农业市场信息传播以非正式传播主体为主,但农户满意度评价却较低,组织化传播主体较少但农户评价较高,农户期望选择更多的是政府服务部门和科技部门等正式组织。研究发现农户背景特征中年龄、区域分布、务农年限是农户期望选择的前三大显著性影响因素,而不同主体传播特征中政策优惠、价格合理和服务及时是影响农户选择变化的最重要的三个因素,并相应地提出了有关政策建议。     

Fine root and root hair morphology of cotton under drought stress revealed with RhizoPot

Fine roots (roots with a diameter of less than 2 mm) and root hairs are the primary absorbers of water and nutrients; however, the morphology of cotton fine roots and root hairs in response to drought stress has not yet been defined. To solve this problem, this study characterized a self-made in situ root observation device (RhizoPot) with a scanner with a resolution of up to 4,800 DPI was used to observe the roots of cotton plants grown indoors under both well-watered and drought stress conditions. RhizoPot provided healthy growth conditions for cotton, and fine roots as well as root hairs were successfully observed. Root length density increased significantly under drought stress, whereas the average root diameter decreased gradually with the extension of treatment time. Drought stress accelerated fine root death, and the diameter of the fine roots was positively correlated with root lifespan. Additionally, the root hair lifespan was negatively regulated by soil drought stress and was associated with the growth stage. This result suggests that cotton developed more slender fine roots and longer root hairs under drought stress, which accelerated the death process of both, in order to develop new fine roots. This process helps cotton absorb as much water as possible under drought stress.     

植物化感作用影响因素的探讨

化感作用在自然界普遍存在,生态系统中合理利用化感作用,潜力巨大。本文着眼于影响植物化感作用的因素,从植物的遗传因子及生长发育状况、化感物质的种类和数量、植物所处环境条件（土壤养分及质地、光照、温度、水分、生物）等方面进行探讨,以期为合理有效开发和利用化感作用提供参考价值。     

论品种利润及影响因素

利润是企业生存和发展的根本前提,整个产业链如何认识和合理分配利润非常关键。本文旨在阐述品种利润以及影响品种利润的因素等方面的问题,期望给种业同仁提供一些新的视觉。     

SBBR反应器SND脱氮的影响因素分析及响应曲面优化

采用活性炭涂层改性悬浮填料,在连续曝气的条件下,考察了SBBR反应器脱氮性能。结果表明,SBBR反应器表现出良好的同步硝化反硝化(SND)脱氮性能,对NH₃-N和TN的去除率分别为80.7%和63.1%。典型周期内反应器同步硝化反硝化率可达82.7%。单因素试验发现,脱氮率随着曝气时间t的增加而增加,随着溶解氧质量浓度ρ_DO和填料投加量δ增大而先增大后减小。同时,以溶解氧质量浓度、填料投加量和曝气时间为考察因素,脱氮率为评价指标,采用响应曲面法建立了二次多元回归模型。通过模型求解得出最佳工况:溶解氧浓度为2.37 mg/L,填料投加量为40.10%,曝气时间为5.17 h,此时,脱氮率得到最大值为69.28%。验证试验表明,回归模型的预测值与实测值偏差率为1.57%。     

contact stress and steady thermal analysis of herringbone gears in a gas turbine

To obtain the distribution characteristic of contact stress and the bulk temperature on the surface of herringbone gears, parameter modeling of gears was carried out by parametric design language. A numerical simulation was given to calculate the contact stress field and the steady thermal field by combining heat transfer theory, tribology theory, and mesh theory. The distribution of contact stress, the bulk temperature and heat flux also were analyzed. The analysis results show that the distribution of the load along the contact line possesses regularity. The heat flux along the tooth depth direction decreases first and then increases. The effect of thermal conduction of the tooth is stronger than that of convective heat transfer. The conclusion indicates that the finite element emulation method can be used to estimate the transmission performance of herringbone gears.     

String top fast measurement method of the more teeth and small modulus cycloidal gears

According to the self geometric characteristics of the cycloidal gear, string top method, one kind of fast measurement method which fits to the cycloidal gears that own the characters of small modulus and more teeth, is put forword. The calculating formulas of the distance between the sting and the top of the cycloidal gears’ theoretical tooth surface are given,furthermore, the distance of the modified profile of the cycloidal gears under the conditions that moving distance, equal distance and rotating angle are also discussed. The calculating program is written, sting top method of the cycloidal gear’s fast measurement software is developed, calculation and measurement example is given.     

Three-dimensional crack propagation simulation and life prediction in tooth root of cylindrical gear

Based on the theory of linear elastic fracture mechanics,a three-dimensional boundary element model of cylindrical gear with crack in tooth root is established and the stress intensity factor of crack tip is calculated. Then,through the automatic propagation analysis of initial crack,the growth trajectory and the propagation life of the crack at tooth root are obtained. Based on the obtained result,the influence of load magnitude,crack size,crack location and crack orientation on the crack propagation life is discussed. The results indicate that the tooth root crack expands slowly at first and then faster and faster;the crack propagates more easily along the tooth width than along the tooth thickness;the crack propagation life decreases with the increase of load magnitude or crack size,the effects of load magnitude on propagation life is significantly and the propagation life is more sensitive to initial crack depth than width;the propagation life is longer when crack is closer to the gear end-face and is shortest when crack has an initial direction about -30 degrees.     

铅胁迫对蔬菜根系形态的影响研究

通过营养液培养试验,铅胁迫对三种蔬菜根系生物量及根系形态影响表现为低浓度下（≤1 mg/L）的促进作用,随着处理浓度的提高（﹥2mg/L）,根系生物量及根长,根表面积,根体积均随之下降,抑制了根系的生长与发育。     

中国种子行业影响因素的探讨和发展对策

我国作为农业大国,种子行业具有巨大稳定的市场需求,农业生产用种构成种子市场的直接需求。据统计,全国年粮棉油用种量高达125亿kg,而目前种子基地的供种量仅为80亿kg左右,潜在市场巨大。2000年我国种子产业年销售额约为200亿元人民币,位居世界第2,本行业实现增值额约有150亿元     

棉花种子活力及其影响因素探讨

本文以作者多年来对棉种活力和质量控制的研究工作为基础，参考了国内外有关种子活力和棉花种子研究的文献资料，根据棉花种子的特点，探讨了种子活力的概念，指出各种种子活力测定方法对棉子的适用范围；提出种子相对活力的概念，为比较品种间的种子活力提供了可行性；指出用Ｋ＋渗出量和游离脂肪酸含量作为检验棉花种子活力的指标为佳；分析了棉种活力与种子营养品质、播种品质的相关性，以及与多逆抗性选择和棉子加工处理的关系；提出酸脱绒棉种的质量控制程序，为保证我国棉种加工质量的标准化提供了依据。     

Analysis of distribution characteristics of surface ozone and its influencing factors in summer in Chongqing

Based on the observation data of ozone and its precursor compounds and meteorological factors in near surface layer of Chongqing urban area,this paper emphatically analyzes the temporal and spatial distribution characteristics of ozone in summer. Meanwhile,the correlation between ozone and its precursor compounds,such as NO,NO2,CO,and some related meteorological factors are analyzed. Results show that the concentration of ozone in urban area is lower than that in the surrounding regions. Only one peak of ozone concentration appeared in about 4 p.m. The ozone concentration has an obvious negative correlation with precursor compounds,and has obvious positive correlation with meteorological factors,such as solar radiation and temperature. The appearance of high ozone concentrations resulted from the high pressure weather conditions,especially for the high intensity of solar radiation,breeze,low relative humidity and high temperature. Elevated ozone concentration is closely related to the decrease amplitude of atmospheric pressure. Higher ozone concentrations appear when the decrease amplitude is 0.4 kPa.     

Experiments of the influencing factors on dissolution rate of rock salt

The influence of different factors on dissolution rate of rock salt is studied by a series of experiments, such as dissolution obliquity, solution concentrations, solution temperatures and solution flows. The laws of rock salt dissolution shown in the experiments are as follows: it isn’t obvious that the effect of the dissolution rate on different dissolution area. Temperature, velocity of flow and dissolution obliquity is in an exponential relationship with rock salt dissolution. Dissolution rate decreases with the increase of solution concentration of rock salt. Gray correlation analysis is adopted to study the dissolution obliquity, solution concentration, temperature and solution flow rate. It is found that solution temperature is the main factor, followed by dissolution obliquity, solution flow rate, and solution concentration. The findings can provide theoretical foundation and experimental basis for rapidly create cavity.     

影响我国种业竞争力的关键性因素及对策研究

中国入世承诺5年期限刚过不久，国内种业发展面临的竞争更趋激烈。本文从国内种业市场规模、种业生产体系、种业贸易和植物新品种保护四个方面阐述我国种业发展现状，分析影响我国种业竞争力提升的关键性因素，并给出相应的对策建议。     

多参数冬小麦估产模型研究及产量影响因素分析

产量估算研究对制定粮食政策和经济计划,科学地进行粮食宏观调控有着重要意义。针对以往线性遥感估产模型中多是基于NDVI和LAI的研究,且参数间存在多重共线性等问题,该研究以河北省南部石家庄、保定、邯郸、邢台、衡水、沧州六市为研究区,选用2000—2008 年的种植区最佳时相NDVI、LAI累加值,并引入与小麦生物量积累密切相关的不同月份地表温度作为原始估产指标,针对参数累加值存在的误差,提出一个修正公式对NDVI、LAI 进行修正,再对选用参数进行主成分分析,将结果与冬小麦产量数据建立出4 个多参数综合作用的冬小麦遥感估产模型。结果表明,利用2009 年数据对模型进行验证,结果表明4 个模型的R2介于0.714~0.818 之间,估产精度均在93.0%以上,其中,综合所有遥感参数的模型拟合效果最好,R2为0.818,估产精度达95%,而且引入温差主成分的模型精度高于仅用NDVI、LAI作参数的模型,另外深入分析各参数对产量估测的影响可知4 月中旬和5 月中旬的地表昼夜温差对冬小麦的后期产量具有较大影响。     

盐碱胁迫对海岛棉种子萌发及幼苗根系生长的影响

为明确海岛棉种子萌发及幼苗根系对盐胁迫的响应,并筛选出耐盐能力较高的海岛棉品种。以新疆阿克苏地区主推海岛棉品种新海31号、新海35号、新海43号和新海48号为试材,采用NaCl、Na2SO4以及NaCl、NaHCO3以物质的量1∶1混合分别模拟中性盐混合盐(中性盐)和碱性盐混合盐(碱性盐)两种盐类型,胁迫处理总盐浓度(Na+)为0、120、180、240、300、360 mmol L~(–1),研究了盐胁迫下海岛棉种子萌发和幼苗根系生长参数。结果表明,在两种盐类型下,随着盐浓度的增加,海岛棉种子的萌发参数、生物量、根冠比、盐敏感指数、盐耐受指数、根系长度、根系表面积及根系体积均呈下降趋势;高盐浓度下,海岛棉株高、根系生物量及茎叶生物量与盐浓度呈显著负相关,说明高盐环境抑制了棉种发芽及幼苗的正常生长。120 mmol L~(–1)浓度下,中性盐处理的新海48号的根系总长度比对照无显著增加,其余品种均有显著增加,各品种根系总体积与总表面积均无显著差异,低盐促进了各品种细根(d≤0.5 mm)的伸长及生长,新海43号的中根(0.5d≤2.0 mm)长度比CK增加显著,导致此品种根系的总体积与总表面积有显著增加;碱性盐处理的根系总长度、表面积及体积除新海31号与对照差异不显著外,其余品种均有显著降低。180～240mmolL~(–1)浓度下,中性盐处理的根系总长度、表面积及体积与对照相比除新海43号有显著下降外,各品种均差异不显著;碱性盐处理的各品种均是下降显著,其中新海35号的根系总长度下降幅度比其余品种缓慢。300～360mmolL~(–1)浓度下,两种盐处理的各品种的根系总长度、体积与表面积均急剧下降。碱性盐胁迫比中性盐胁迫下降的趋势更为显著。本试验条件下,海岛棉幼苗正常生长所能承受的盐浓度为240 mmol L~(–1),但碱性盐对于海岛棉幼苗的伤害远大于中性盐,供试品种耐盐碱程度为新海35号新海43号新海31号新海48号。     

Effect of pollinator on haploid production in durum wheat crossed with maize and pearl millet

The aim of this work was to analyse the influence of the male parent on the production of embryos and haploid plants in durum wheat crossed with maize and pearl millet, to find a proper trait to identify the most efficient pollinators and to evaluate the mixtures of pollen. Two genotypes of durum wheat, low and high responding, were crossed with eight pollen samples: (i) three maize hybrids, (ii) three pearl millet inbred lines, (iii) a mixture of maize pollen and (iv) another mixture of pearl millet pollen. No significant differences on embryos and haploid plant production were observed among the four samples of maize pollen, but there were clear genotypic differences for the production of haploids between genotypes of pearl millet. The best pearl millet genotype produced significantly more haploid plants than the other two and the mixture of pollen. There was no correlation between the production of embryos and haploid plants. Therefore, the production of haploid plants must be the criterion to identify superior pollinators. In addition, a mixture of pollen is inappropriate except when using genotypes previously identified as good pollinators.