螺旋气道变截面进气的缸内充量分层模拟研究

构建了YN33共轨柴油机螺旋气道-气门-气缸的CAD模型,划分螺旋气道的进气口为不同进气截面,并通过在各个截面分区进气,以及时序分区进气实现缸内的充量分层。研究表明:变截面进气时,进气截面下半部进气量比上半部进气量多7%,而右下区的进气会在缸内形成较为均匀的分布,其它区域进气则会形成浓度场各异的分布特性。三段时序进气条件下,4个区域进气对缸内进气总量贡献的差异由前段进气与后段进气所决定,且后段进气影响更大;在分布特性上,进气截面右上区和右下区的前段进气会在缸内形成明显的上稀、下浓分布特点,而后段进气均会在缸内形成上浓、下稀的分布。     

Ameliorating acidity of an extensively‐managed permanent pasture soil

Acid soil amelioration was measured annually over an 11 year experiment. Lime, and superphosphate were surface‐applied under combinations of three rates of lime, viz. nil, lime to raise pH_{C a} of 0–10 cm to 5.0 (low rate) and 5.5 (high rate) respectively, two rates of superphosphate (125 kg/ha every 2 to 3 yr, 250 kg/ha/yr) and two sheep stocking rates. Soils were sampled at 0–2.5, 2.5–5, 5–7.5, 7.5–10, 10–15 and 15–20 cm. Soil pH stratification developed after lime application. By 11 yr lime had not raised pH_{C a} to either 5.0 or 5.5 in the 5–10 cm profile. However, pH_{C a} >5.0 or >5.5 were observed in the 0–5 cm profile. Under high P, low lime application, soil pH_{C a} was higher in the 0–2.5 cm profile at low stocking rate. Effects of applied lime on pH_{C a} declined with time and depth under low lime and the relationship with Al_ex which increased as pH_{C a} declined, was modelled. A rarely reported relationship showed that as soil C increased the apparent solubility of Al decreased. At the lowest pH_{C a} considered, there was a strong negative association between Al_ex and total C, becoming weaker with positive pH_{C a} increments. Higher P rates increased pH_{C a} under low lime contrasting with lesser effects on pH_{C a} under low P at the same lime rate. Slow and limited lime movement means that farmers growing acid sensitive plants must apply lime early enough and at rates and frequencies sufficient to ensure downward movement.     

Organic Farming Affects C and N in Soils Under Olive Groves in Mediterranean Areas

Under semiarid climatic conditions, intensive tillage increases soil organic matter losses, reduces soil quality, and contributes to climate change due to increased CO₂ emissions. There is a need for an agricultural management increasing soil organic matter. This paper presents the organic carbon (OC) and nitrogen (N) stocks, C:N ratio and stratification ratios (SRs) of these properties for olive groves soils under long‐term organic farming (OF), and conventional tillage (CT) in Los Pedroches valley, southern Spain. The results show that OF increased C and N stocks. The soil organic carbon (SOC) stock was 73·6 Mg ha⁻¹ in OF and 54·4 Mg ha⁻¹ in CT; and the total nitrogen (TN) stock was 7·1 Mg ha⁻¹ and 5·8 Mg ha⁻¹ for OF and CT, respectively. In the surface horizon (A: 0–16·9 cm in OF and Ap: 0–21·8 cm in CT) and Bw horizon (16·9–49·6 cm in OF and 21·8–56 cm in CT), SOC and TN concentrations and C:N ratios were higher in OF than in CT. Soil properties stratification in depth, expressed as a ratio, indicates the soil quality under different soil management systems. The SR of SOC ranged from 2·2 to 3·1 in OF and from 2·1 to 2·2 in CT. However, only SR2 (defined by Ap‐A/C) showed significant differences between CT and OF. The SR of TN showed similar trends to that of the SR of SOC. Organic farming contributes to a better soil quality and to increased carbon sequestration. Copyright © 2013 John Wiley & Sons, Ltd.     

温度分层均质压燃发动机燃烧和排放数值模拟

通过修改SENKIN程序,建立起一个有质量交换和缸壁传热的9区化学反应动力学模型.以SKLE正庚烷简化模型作为燃烧反应动力学机理,利用该模型计算了发动机的主要燃烧参数和排放物含量.结果表明,该多区模型能够准确地模拟温度分层均质压燃发动机的燃烧和排放特性.在温度分层均质压燃发动机中,外核心区、壁面边界层和缝隙是CO和HC的主要来源.其中,在外核心区产生CO和HC是由于壁面边界层和缝隙内的未燃混合气在膨胀过程中流入该区被部分氧化或没有被继续氧化.NO_x主要来源于高温的内核心区.要同时获得高效燃烧和超低排放,应适当提高壁面温度.     

黄土高原不同土地利用方式分层植被的盖度差异

[目的] 分析不同土地利用方式黄土高原植被的覆盖状况,为监测该区植被特别是非绿色植被盖度的变化提供数据支持,为遥感估算植被覆盖度(FVC)在土壤侵蚀预测中的应用提供可靠依据。[方法] 选择黄土高原不同土地利用类型的7块植被样地,采用样带法进行逐半月的分层植被盖度调查,分析了绿色植被盖度(f_PV)和非绿色植被盖度(f_NPV)在不同类型以及不同层次结构下的年内变化,为侵蚀过程模型中植被因素的获取提供参数。[结果] ①沙地、草地、人工柠条林地、人工油松林地、黄陵和秦岭的天然林地等6个样地中,植被的年内投影总盖度变化不大。投影f_PV和其所占投影总盖度的比例年内均随时间先逐渐增加,7—9月达到最大值,其后迅速减小。而投影f_NPV随时间的变化趋势与f_PV相反。受耕作制度影响,耕地投影f_PV和f_NPV年内变化剧烈。②7—9月,在黄陵和秦岭的天然林样地,投影f_PV比例可达100%,其他4种样地分别可达60.6%,70.5%,58.8%和84.9%,意味着仅考虑投影f_PV,将忽略占总盖度39.4%,29.5%,41.2%和15.1%的f_NPV的生态效益。③人工柠条、人工油松林地,黄陵、秦岭的天然林地等4种具有明显植被垂直结构的样地中,乔木层、灌木层和地表层的f_PV与f_NPV的年内变化与投影f_PV与f_NPV的变化趋势基本一致;4种样地植被的投影总盖度与地表层总盖度呈线性关系,其相关性可达0.85(R²)。[结论] 黄土高原不同土地利用方式耕地投影f_PV和f_NPV年内变化剧烈,其他样地年内投影f_PV先增加后减小,投影f_NPV与其相反。占总投影盖度的15.1%～41.2%的投影f_NPV,在该区是不可忽略的地被组成。不同层次的f_PV和f_NPV年内变化趋势与投影f_PV和f_NPV一致,地表层总盖度与投影总盖度也存在显著的线性相关性。在区域监测时应重点关注耕地植被盖度的提取季节与地表总盖度。     

北方农牧交错带(武川县)土壤微生物数量分布及层化比率研究

采用田间采样及室内培养方法，对内蒙古武川县耕地、退耕还灌地和放牧草原3种类型土地土壤微生物各类群的数量分布和层化比率进行了研究。结果表明：在土壤耕作层（0～30cm）土壤微生物数量呈逐层下降趋势，3种类型土地的土壤微生物总数相差不大，3种类型土地土壤微生物层化比率存在明显差异。同时提出了土壤微生物层化比率的概念，并认为土壤微生物层化比率可能是一个比较好的指示动态土壤质量（土壤演替方向）的指标，当一个区域土壤微生物层化比率大于2时，土地一般不会发生退化现象。在研究的3块实验区域中，耕地存在较高的退化风险．退耕还灌地正处于逐步恢复的阶段，放牧草原依然存在逐步退化的趋势。     

黄河上游退耕地植被组成、结构及水保功能评价

 面对黄河上游地区生态失衡的严重现实,作为植被恢复重建重要手段的退耕还林还草工程,其水保功能研究不仅具有理论价值,而且有十分迫切的实践需要。退耕地人工植被的建立,是一种仿拟自然植被的过程,植物种数越多,垂直层次性越复杂,植被的水保功能也越高。在黄河上游脑山区,物种丰富度指数最高的阶段,往往为植物群落演替的中间阶段,此时植物层次较多,一般可达3～5层,种类繁杂,生物基因保存多;同时,多层次的植物群落结构,对降水的截留作用明显,水保功能突出,以青海云杉为主的针阔混交类型,就是其典型代表之一。退耕地植被随着林分年龄增加,其水保功能逐步提高。一些退耕20多年的人工植被类型,生物多样性高,垂直层次结构复杂,水保功能甚至超过一些天然植被类型,直逼水保功能表现最好的50多年生天然青海云杉针阔混交林。在退耕还林还草工作中,通过仿拟自然植被结构,建造复层、混交的植被类型,来实现稳定的退耕地人工植被水保功能的整体思路,是切实可行的。     

对新疆杨扦插生根机理的初探

本文研究了新疆杨插穗低温层积处理前后内源抑制物和部分酶类活性的变化,植物生长素和地膜育苗对插穗生根的影响,观察了插穗的形态解剖特征。为提高新疆杨扦插成活率找到了一些科学依据     

Physical variability in Prince William Sound during the SEA Study (1994–98)

From 1994 to 1998, a multidisciplinary ecosystem study (the Sound Ecosystem Assessment) examined the primary physical and biological factors that influence the production of pink salmon and Pacific herring in Prince William Sound (PWS), species that experienced population declines after the 1989 Exxon‐Valdez oil spill. Three physical processes are described that influence ecosystem processes: surface layer stratification; upper layer (<100 m) circulation; and exchange between PWS and the northern Gulf of Alaska (NGOA). Stratification formed first in the PWS nearshore regions in March, and subsequently in the northern central basin in April, primarily due to freshening. The northern stratified layer and the associated zonal density front persisted at least through June, but year‐to‐year differences occurred. In spring and summer, circulation in central PWS could be either cyclonic or anticyclonic. Drifter trajectories often linked central PWS to a nearshore bay or fjord, or one bay or fjord to another. September was characterized by a cyclonic circulation and isopycnal doming in central PWS, with little year‐to‐year variability. At Hinchinbrook Entrance, a main connection with the Gulf of Alaska, alternating inflows and outflows occurred in spring over all depths. In summer through early autumn (1995), in the absence of predominantly westward winds, the dominant exchange pattern was outflow above about 150 m and inflow below. In summer through early autumn (1996–98), there was also surface (<20 m) inflow at Montague Strait (the other main entrance). Northward transport at Hinchinbrook Entrance was maximum in late autumn through winter, with inflow above ~150 m and outflow below. Westward wind events over the shelf associated with the weather cycle drove inflow events at both Hinchinbrook Entrance and Montague Strait that may result in transport of zooplankton important to the PWS ecosystem.     

滇重楼种子内源激素含量与种胚长度和萌发的关系

[目的]通过研究滇重楼种子层积过程中不同阶段内源激素含量与种胚长度的动态变化情况来探讨种子休眠机理.[方法]应用酶联免疫吸附法测定不同阶段种子内激素含量.[结果]种子萌发过程中,脱落酸(ABA)含量由54.34 ng·g^-1·FW降至32.16 ng·g^-1·FW,赤霉素(GA)、玉米素核苷(ZR)显著升高,吲哚乙酸(IAA)含量波动较大,但整体呈逐渐升高趋势,随层积时间延长,未萌发种子中ABA含量持续降低,GA含量与GA/ABA值持续升高,仍显著低于已萌动种子中激素含量(p<0.05);种子在层积42天后,种胚开始膨胀,胚率快速增加;相关性分析结果,内源激素含量及比值与种胚生长呈显著相关(p<0.05),其中,GA/ABA值对种胚生长的影响最大.[结论]种子萌发过程中仅ABA含量降低不足以解除滇重楼种子休眠,同期GA含量升高和GA/ABA值达到某一阈值时能有效的解除滇重楼种子的休眠和促进胚的发育;种子在层积40天左右后,由于各项激素的综合作用,滇重楼种子由休眠状态逐步转变为破除休眠状态和萌发状态.