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.     

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.     

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.     

UTILIZATION OF FOREST PRODUCTS WITH SPECIAL REFERENCE TO TIMBER-FRAMED HOUSING

The history of professional forestry education in South Africa is shortly outlined, with emphasis on the last few years. Information is presented on syllabus and staff, and on the numbers and scholastic standard of the forestry students.     

楠木种子处理办法初探

由于楠木种质资源有限,如何充分利用现有的种质资源进行珍稀树种扩繁,是本次试验的主要目的。在恒温条件下(24℃),利用不同浓度的赤霉素溶液处理经过不同层积天数的楠木种子,然后进行发芽试验。结果表明:900 mg/L的赤霉素溶液浸泡层积时间为50 d的种子,其发芽率最高达到92%,与对照相比差异很大,因此适宜的楠木种子处理方法可以显著提高其发芽率。     

筒仓中入粮自动分级的动力学分析及缓解措施研究

简述了自动分级在筒仓储粮中的危害。依据动力学原理,建立了颗粒下落的动力学方程,并推导出颗粒下落深度与飘移距离之间的关系方程。通过计算得出颗粒的水平飘移距离随着下落深度的增加而增加;在筒仓内的同一下落深度,颗粒水平飘移距离随着密度的增加而减小;在筒仓内的同一下落深度,颗粒水平飘移距离随着半径的增加而增加。针对颗粒飞行的动力学特性,提出了几种缓解自动分级的措施。     

太阳能蓄热水箱内置隔板开孔方式对蓄热性能的影响

为研究太阳能蓄热水箱内具有相同开孔面积、不同开孔数量的隔板对热分层及蓄热性能的影响,该文对安装有不同开孔方式隔板的不同流动参数条件下水箱内换热过程进行数值分析。结果表明:热水和冷水入口温度分别为333和303 K、热水和冷水入口流速分别为0.05和0.5 m/s情况下,开孔面积为0.007 9 m~2的1个开孔隔板水箱热分层效率最高,理查森数为2.341;与相同开孔面积的1个开孔隔板相比,开孔面积为0.031 4 m~2的5个开孔隔板使得水箱内高温水的容积得到显、著扩展,开孔数量对水箱冷热水出口温差的影响很微弱,开孔面积越大,开孔数量对理查森数的影响越明显。当用户端用水量在一定范围内变化时,理查森数随用户用水量的增大而减小,在冷水入口流速低于0.3 m/s范围内增大该流速破坏热分层的可能性更大。热水入口温度分别为333和343K对应的热水出口温度最大相对偏差为0.22%,但这2种工况对冷水出口温度几乎没有影响。研究结果可为液体分离设备中的孔板结构优化设计提供一定的理论参考。     

江苏海门市药用植物资源调查与研究

目的：深入了解江苏省南通市海门市野生药用植物资源现状,探究海门地区药用植物开发利用前景。方法：采取样地、样线调查与空间分层随机抽样相结合的方法对海门市野生药材资源展开了大量调查,比较第三次中药普查的数据,分析其所蕴藏的药用植物多样性。结果：记录了海门市药用植物220种,隶属于74科182属,列为国家重点调查品种的有32种,在第三次中药普查的基础上,发现新分布药用植物共108种,但原记录的269种此次普查并未发现。结论：显示海门市中药资源种类有较丰富的多样性,但总体种类较少,分布点较散。这与第三次中药普查相比,变化较大,建议应合理地开发利用当地的药用植物资源,适当地发展中药材种植与养殖产业。     

黑樱桃种子休眠机理及处理方法的研究

对黑樱桃种子处理方法进行研究的结果表明,生理后熟和抑制物质的存在是造成黑樱桃种子休眠的主要原因,暖温层积90天后再冷温层积120天可以有效打破种子的休眠,其中暖温层积是种胚后期发育的主要时期,而冷温层积是消除抑制物抑制作用的关键。