An experiment study of the realization of diesel engine emission standard of Euro IV

This paper calibrates the advanced injector angle and EGR of a four-in-line pressure engine on the specialized test stand, which makes the NOx achieved the standard of Euro IV. Then an experiment study of the diesel oxidation catalyst (DOC) and the particulate oxidation catalyst (POC) are made. Both make the diesel engine emission achieving the Standard of Euro IV. This experiment study shows a kind of method that realizing diesel engine emission standard of Euro IV, and concludes the character and law of the method.     

基于交角的林木竞争指数

建立基于交角的林木竞争指数(u_a_CIi),该指数能够同时表达出竞争木对对象木的上方遮盖和侧翼挤压。该指数取值范围为[0,1),无量纲,指数值越大,表明树体越小,所承受的竞争压力越大,清晰直观地表达林木在林分中所处的相对竞争态势。从理论上阐明大的竞争邻体比小的竞争邻体对对象木有更大影响,不仅反映在上方的遮盖也体现在侧方的挤压中。该指数与林木大小的相关性明显高于常用的HEGYI竞争指数。在测量技术飞速发展的今天,该竞争指数将具有很大的应用前景。     

水稻叶面积分布构成因子的数值模拟

叶面积分布是水稻株型研究的重要内容.通过机理分析建立了叶面积指数和叶面积分布模型,利用田间试验数据检验模型,通过数值模拟探讨节间距对叶面积分布影响的机理.模型检验效果良好,数值模拟结果可信,能为叶面积分布的优化提供理论基础.     

Variation in selected solid wood properties of young Pinus patula from diverse sites in the Mpumalanga escarpment area in South Africa

Regression analyses identified ‘Growth Days’ (an index expressing site moisture availability) as the only site variable contributing significantly to the prediction to wood density (R² = 0.57), whereas the model predicting grain angle included only ‘Altitude’ (R² = 0.60). These results surfaced during an investigative study to quantify various sources of variation in wood properties and to quantify the effect of a number of site factors on wood properties of Pinus patula grown in the Mpumalanga escarpment area of South Africa. For this purpose, 10 trees were sampled from each of 17 diverse sites for wood property analyses. The effects of site, distance from the pith and differences between trees within site on wood density, transverse shrinkage, grain angle and dynamic modulus of elasticity were investigated. The site factors considered included a wide variety of soil and climatic factors. The effect of radial distance from the pith and differences between individual trees within sites were highly significant, accounting for most of the variation in wood properties. Although the effects of a number of site factors were statistically significant, they generally explained relatively small but important variation in wood properties among sites. The study not only quantified the effects of important sources of variation on a few key wood properties, but it also revealed that the extent of differences between sites can be explained in terms of some specific site factors. It is envisaged that the results will contribute significantly towards the refinement of current forest site classification systems for improved decision-making with respect to wood quality in intensively managed plantation systems.     

Inclination Angle Affects Ozone Injury in the Flag Leaf of Rice

Abstract

To evaluate the effect of inclination angle of the leaf on the leaf injury of rice by O₃, we examined the effect of a 5-hr exposure to 0, 0.1, 0.3 cm³ m-³ O₃, abbreviated as O⁰, O^0.1 and O^0.3, respectively, of the flag leaf using natural-light gas-exposure chambers. The middle portion of the flag leaf was set horizontally using lead weights (H plant) and it was compared with a non-treated, erect leaf (E plant). Gas exchange and chlorophyll fluorescence were measured immediately before, immediately after, and 1 and 3 d after the start of the exposure. The net photosynthetic rate, stomatal conductance and operating quantum efficiency of photosystem II (F_q’/F_m’) were decreased by the exposure to O₃. Furthermore, the inhibitory effects of O^0.1 and O^0.3 on the H plants were severer than those on the E plants. The maximum quantum efficiency of photosystem II (F_v/F_m) in the leaf of H plants decreased immediately after exposure to O₃. These results indicate that the weaker inhibitory effect of O₃ on the erect leaf depends on the lower light intensity at the leaf surface, rather than the horizontal leaf position.

Key words: Ascorbic acid, Chlorophyll fluorescence, Gas exchange, Leaf inclination angle, Oryza sativa, O₃, Quantum efficiency.     

细胞壁微纤丝角和结晶区对木材物理力学性能影响研究进展

木材是由不同种类的细胞组成的天然材料,其实体物质是组成其结构的各类型细胞的细胞壁。细胞壁的超微构造主要包括微纤丝和结晶区,微纤丝角能表征纤维素微纤丝的取向,纤维素大分子链排列的有序程度及排列形态决定其结晶程度和微晶形态等结晶区特征。基于前人的研究,系统概述了细胞壁微纤丝和结晶区对木材物理力学性能影响的研究进展,重点围绕微纤丝角和结晶度2个方面,分别归纳了二者对木材密度、尺寸稳定性、木材声学等物理性质以及弹性模量、强度等力学性质的影响作用,同时阐述了微纤丝角与木材硬度和刚度以及结晶度与冲击韧性等的相互关系,并概述了细胞壁微晶形态对木材润湿性和纤维强度影响方面的研究进展,最后对今后的研究方向进行了展望。     

西藏原始林芝云杉林空间结构参数分布特征

以藏东南波密岗乡自然保护区原始林芝云杉林为研究对象,应用空间结构参数角尺度、混交度和大小比数,建立空间结构参数的三元分布,揭示林分的空间结构特征。结果表明,从一元分布看,林木整体属于随机分布,林分强度混交,树种的优劣程度参差不齐,整体处于中庸状态;在混交度和角尺度分布中,以随机分布和强度混交林木株数最多,大小比-角尺度组合中,均以随机分布轴线和中庸轴线两侧基本对称;三元结构参数组合为强度混交、随机分布、亚优势状态林木分布较多。主要树种的混交程度较高,呈现强度和极强度混交状态;其中林芝云杉和华山松为该群落的优势树种随机分布,其他主要树种都为轻度聚集分布;树种间大小比数差异明显,其中林芝云杉最低,<0.252,处于亚优势状态。全面分析原始林芝云杉林的空间结构,为林芝云杉林结构优化调整提供重要参考,为藏东南天然林可持续发展提供科学依据。     

深松铲减阻性及耕作阻力影响因素研究——基于LS-DYNA

为研究不同触土曲面深松铲的减阻效果及不同工作参数对深松铲耕作阻力的影响,设计了5种典型准线的深松铲结构,并通过ANSYS/LS-DYNA软件对深松铲切削土壤过程进行了仿真,对比分析了不同结构深松铲切削土壤时所受到的阻力,选择出减阻性能最好的深松铲结构。以优选的深松铲作为研究对象,对入土角、工作速度及工作深度等因素进行单因素试验,研究上述因素对耕作阻力的影响。试验结果表明:仿生变曲率深松铲的减阻性能最好,其耕作阻力最小(601 N);入土角为24°时,深松铲耕作阻力最小;耕作阻力随工作速度和工作深度的增加而增大。该文可为深松铲结构的设计以及工作参数的选择提供一定的技术支持。     

汽油发动机进排气凸轮匹配对性能影响分析及试验研究

以小排量汽油机作为性能提升开发分析及试验研究对象,主要从小排量汽油发动机的进、排配气机构方面进行方案的研究与讨论并提出了优化方案试验结果表明,在满足发动机裸机排放标准的前提下,该方案既能使发动机性能得到大幅提升,又能使怠速稳定性得到良好改善。     

基于角度指数的油菜叶片等效水厚度估算研究

叶片等效水厚度(EWT)是评估油菜生长状态的一个重要参数。为快速准确估算油菜叶片EWT,选择9个常用的植被水分指数(WI、PRI、NDVI、NDII、NDWI、MSI、PWI、GVMI、NDMI),在6个已有角度指数(β_SWIR1、SANI、SASI、ANIR、NANI、NASI)基础上,提出2种角度比值指数(SARI、NARI),并根据油菜叶片水吸收谷峰高光谱特征,提出基于水吸收谷1 450 nm和1 930 nm的8种改进型角度指数,利用以上25种角度指数估算不同施氮水平下苗期、蕾薹期以及不区分苗期、蕾薹期情况下的油菜叶片EWT。结果表明,苗期ANI₁₄₅₀、ASI₁₄₅₀、MSI、GVMI、NDII估算效果较好,R^2均达到0.81以上;蕾薹期ANI₁₉₃₀、ASI₁₉₃₀、NASI、SANI、GVMI、SARI效果最好,R^2均达到0.71以上;在不区分苗期、蕾薹期的情况下,改进型角度指数ANI₁₄₅₀、ASI₁₄₅₀效果最好,R^2均达到0.832,可以在不区分苗期、蕾薹期情况下对油菜叶片EWT进行估算,适用性更广。本研究提出的改进型角度指数不仅丰富了已有角度指数,且提高了其反演油菜叶片EWT的精度,为快速精确估计油菜叶片EWT提供了新的研究思路。