车用发动机轴瓦烧损的原因及预防措施

分析了轴瓦的烧损机理,介绍了发动机烧瓦抱轴的几种常见故障及原因,并提出了防止发动机烧瓦的措施。     

基于有机肥料新标准的有机质测定方法分析

选取不同种类的有机肥料,分别用灼烧法、NY 525-2002和NY 525-2012中的重铬酸钾氧化法测定有机质含量,比较不同检测方法测得有机质结果,分析了检测影响因素及有机肥料新标准与旧标准在测量结果上的差异,并做了加标回收率试验。结果表明,有机肥料新标准中,重铬酸钾溶液浓度虽然从原来的0.3 mol/L提高到0.4 mol/L,但随着浓硫酸浓度的大幅降低(从65%降低至49%),其氧化能力也随之减弱,在不乘氧化校正系数的前提下,测得有机质均小于旧标准所测值,下降幅度为1.08%～14.47%。根据肥料所含还原物质的量及氧化难易程度差别,不同种类有机肥料氧化校正系数范围为1.24～1.54,计算结果统一乘以1.5,会导致一部分有机质数据偏高,甚至超过100%。     

The dynamics of Themeda Triandra tillers in relation to burning in the natal Drakensberg

Abstract

Marked tillers of Themeda triandra were sampled regularly over a two year period in Highland Sourveld burnt annually in winter, biennially in spring and after a single summer and early winter burning treatment. Parameters recorded were height of shoot apex, tiller mass, number of new lateral tillers and time of flowering. Monitoring of marked tillers before and after each burn enabled the life history of populations of tillers to be followed.

There were no significant differences in survivorship between tillers in the annual winter and biennial spring burn treatments but winter burning stimulated the development of a greater number of daughters per parent. Both populations exhibited a constant death rate over the two year period. Only 8% of the marked T. triandra tillers survived the single summer burning treatment.     

Leucosidea sericea — control in southern Lesotho

Tebuthiuron chemical treatments were effective in controlling Leucosidea sericea shrubs upon rangelands of the Quthing sheep stud station in southern Lesotho. Cutting treatments were also effective but more labour intensive. Repeated applications of 2,4,5‐T and fire resulted in less mortality of the shrubs and lower vigour of Eragrostis chloromelas grass than Tebuthiuron treatments.     

Effect of crop rotation and residue management on properties of cracking clay soils under irrigated cotton-based farming systems of new south wales

The effects of planting cereal or leguminous crops in rotation with irrigated cotton (Gossypium hirsutum L.) on the properties of cracking clay (swelling) soils in the Macquarie and Namoi Valleys of New South Wales, Australia were evaluated during the summer of 1992–3. The observations were made on commercial farmers' fields. The soil properties evaluated were the particle size distribution, the dispersion index, the plastic limit, the percentage of coarse (particle diameter 212–2000 μm) and fine (particle diameter 53-212 μm) particulate soil organic matter, soil respiration rate, soil reactivity, soil aggregate density, pH, nitrate-N and exchangeable Ca, Mg, K and Na. In general, the planting of rotation crops decreased the dispersion index, plastic limit and soil aggregate density, and increased the amount of coarse particulate organic matter. Planting rotation crops also resulted in significantly higher clay and lower silt contents in the Macquarie Valley, and significantly higher soil respiration in the Namoi Valley. Soil pH, nitrate-N and exchangeable cation concentrations were not significantly affected by planting rotation crops in the Macquarie Valley, whereas exchangeable Na was increased in the Namoi Valley. The retention of crop residues in situ, compared with burning crop residues, decreased the dispersion index, plastic limit and aggregate density, and increased the amount of coarse particulate soil organic matter at all measured depths of the Macquarie Valley. The retention of crop residues in the Namoi Valley decreased the plastic limit and dispersion index only in the 0–50 mm depth range, whereas burning crop residues increased exchangeable K at all depths. In general, planting rotation crops and the retention of crop residues had greater beneficial effects on the soil physical properties in the Macquarie Valley than in the Namoi Valley, and in the topsoil compared with the subsoil. These differences are attributed to a shorter rotation interval in the Namoi Valley, smaller amounts of coarse particulate soil organic matter in the subsoil, and differing soil types in the two valleys. In the Namoi Valley the coarse organic matter produced by leguminous crops appeared to be more effective in promoting structural stability than that from non-leguminous crops, although no such difference was observed in the Macquarie Valley.     

Dry coniferous forest restoration and understory plant diversity: The importance of community heterogeneity and the scale of observation

Maintaining understory plant species diversity is an important management goal as forest restoration and fuel reduction treatments are applied extensively to dry coniferous forests of western North America. However, understory diversity is a function of both local species richness (number of species in a sample unit) and community heterogeneity (beta diversity) at multiple spatial scales, while studies of restoration treatment effects often only examine local species richness at one or two spatial scales. We studied experimental thinning and prescribed fire treatment effects on understory plant species richness and community heterogeneity at three spatial scales using additive diversity partitioning. We also evaluated treatment effects on understory plant species colonization and extirpation at two spatial scales. There was no evidence that active restoration treatments reduced species richness or increased local extirpation of species. Restoration treatments significantly increased herbaceous species richness at the treatment-unit level primarily by increasing community heterogeneity among sampling points within the units. The combination of thinning and burning produced the greatest increase in community heterogeneity, and increased colonization by species that were not sampled prior to treatment. These results suggest that restoration treatments designed primarily to reduce fire hazard and promote sustainable conditions in these fire-adapted ecosystems can also increase community heterogeneity and facilitate colonization by new understory species without significant local extirpation of extant species.     

Testing prescribed fire as a tool to promote Scots pine <Emphasis Type="Italic">Pinus sylvestris</Emphasis> regeneration

Techniques for encouraging natural tree regeneration are of increasing interest to managers of Scots pine Pinus sylvestris forests. We tested prescribed fire at a management scale, with deer present or excluded, as a means of increasing rates of Scots pine forest expansion on heathland. At a semi-natural pinewood in Scotland, ten experimental blocks were established, within range of pine seed-fall. Each block comprised four, 100 m² plots. Two plots at each site were burnt and two fenced, allowing the effects of burning on pine regeneration to be measured at two levels of deer abundance. We monitored pine seedlings, seed-fall, deer dung and vegetation for 5 years following treatment. Differences in seedling detection rates between treatments were quantified using dummy seedlings, and analyses corrected accordingly. Mean new pine seedling establishment was 9.8 times higher on burnt ground than unburnt ground (confidence intervals 3.2–30). Differences were even more pronounced in a year of high seed-fall, and following fires with low rates of spread. Establishment rates varied strongly between experimental blocks. Exclusion of deer increased establishment rates, but only in the first 2 years after fire. There was evidence that both seedling survival, and cumulative recruitment of older (over 12 months) seedlings, were improved by prescribed burning. Our results support the use of prescribed fire as a tool to promote increased Scots pine seedling establishment. This technique is likely to give strong fine-scale variation in seedling densities, and so would most suit areas where a variable spatial pattern of regeneration is sought, for landscape or naturalness reasons. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Temperature and stubble management influence microbial CO2-C evolution and gross N transformation rates

Few studies have examined the kinetics of gross nitrogen (N) mineralization, immobilization, and nitrification rates in soil at temperatures above 15 °C. In this study, ¹⁵N isotopic pool dilution was used to evaluate the influence of retaining standing crop residues after harvest versus burning crop residues on short-term gross N transformation rates at constant temperatures of 5, 10, 15, 20, 30, and 40 °C. Gross N mineralization rates calculated per unit soil organic carbon were between 1 and 7 times lower in stubble burnt treatments than in stubble retained treatments. In addition, significant declines in soil microbial biomass (P=0.05) and CO₂-C evolution (P<0.001) were associated with stubble burning. Immobilization rates were of similar magnitude to gross N mineralization rates in stubble retained and burnt treatments incubated between 5 and 20 °C, but demonstrated significant divergence from gross N mineralization rates at temperatures between 20 and 40 °C. Separation in the mineralization immobilization turnover (MIT) in soil at high temperatures was not due to a lack of available C substrate, as glucose-C was added to one treatment to test this assumption. Nitrification increased linearly with temperature (P<0.001) and dominated over immobilization for available ammonium in soil incubated at 5 °C, and above 20 °C indicating that nitrification is often the principal process controlling consumption in a semi-arid soil. These findings illustrate that the MIT at soil temperatures above 20 °C is not tightly coupled, and consequently that the potential for loss of N (as nitrate) is considerably greater due to increased nitrification.     

大兴安岭三种森林类型地表可燃物燃烧气体排放量的研究

以大兴安岭林区兴安落叶松林、樟子松林和杨桦林中的草本、枯枝和半分解层为研究对象,采取外业调查取样及室内控制环境燃烧实验相结合的方法,分析了不同林型、不同可燃物燃烧过程CO2、CO、CxHy、NO和SO2释放量的差异。结果表明,草本燃烧CO2排放量阔叶林(杨桦林)大于针叶林(兴安落叶松林、樟子松),针叶林(兴安落叶松林、樟子松)枯枝CO2排放量大于阔叶林(杨桦林),而半分解层兴安落叶松林CO2排放量大于杨桦林和樟子松林。兴安落叶松林半分解层除NO释放量以外,其它四种气体与草本、枯枝无显著的差异。     

绵阳市城市生活垃圾处理现状及发展分析

以绵阳作为四川省的典型城市,对其垃圾产生及处理情况进行了调查,并在此基础上结合绵阳市城市总体规划,对绵阳市城市生活垃圾的热值和产生量进行预测。结果表明,绵阳市城市生活垃圾特性未来变化特点为产生量不断增加,热值不断升高,适合采用焚烧处理。