控制汽油机排放污染物的技术措施

１汽油机排污物的组成及影响因素１．１污染物的组成 通过测试，汽油机排气中的污染物主要是ＣＯ、ＨＣ和ＮＯｘ。三者的浓度主要与过量空气系数有关。另外，汽油机排气中还含有铅，其主要来源于汽油中的含铅抗爆添加剂。１．２污染物形成的影响因素 在稳定运转状态时，除循环变动外，每个相连的工作循环基本相同，这时对污染物的形成影响不是很大。在非稳定运转状态，内燃机零部件的温度以及每个工作循环的气体浓度组成和压力规律不断地变化。在此种情况下，当冷启动、加速和减速时，排污物各有特点，分述如下。 ①冷启动汽油机在冷启动时…     

可燃混合气浓度对汽油机性能影响的分析

汽油机是营林生产的主要动力。汽油机性能的好坏与林业生产有着密切关系。影响汽油机性能的因素很多,其中,可燃混合气浓度对汽油机性能的关系是最主要的。浓混合气可以使汽油机具有良好的动力性,而稀混合气能使汽油机获得较好的经济性。如何兼顾动力性与经济性,要视汽油机的具体工作情况而定。     

农用小型汽油机燃用沼气技术措施的实验研究

介绍沼气的成分和特性,分析压缩比、点火能量和点火提前角等因素对火花点燃式沼气汽油机的影响,针对上述因素对小型165F 汽油机进行改装,并采用蓄电池点火装置提高点火能量,对改装后的汽油机进行运行试验,比较汽油机在不同参数下的运行状况,试验结果表明沼气应用于改装后的汽油机上,性能接近于改装前的性能,验证沼气在小型汽油机上燃用的可行性。     

小型汽油机点火提前角的检查与调整

营林作业中常用的小型营林机械,如弥雾喷粉机、割灌机、油锯及风力灭火机等,均是以单缸二冲程汽油机为配套动力。单缸二冲程汽油机的点火系统为磁电机式,其工作好坏直接影响到机器的功率、油耗及使用寿命,定期地检查和调整点火提前角,是一项不可忽视的工作。 1、点火提前角及其对汽油机的影响。     

便携式汽油机综合故障分析

通过对便携式汽油机综合故障现象和产生的原因分析,介绍其故障排除方法。     

手扶旋刀式草坪机起动不着火的原因分析

近年来 ,我国草坪面积增加很快 ,手扶旋刀式草坪机的拥有量也与日俱增 ,成为草坪养护中不可或缺的机具。这些机具绝大部分是进口产品 ,其汽油机的构造与制造工艺不同于国内原来生产的机器 ,加上操作人员往往是新手 ,所以起动不着火的情况经常发生。尽管汽油机使用说明书上列举了一些常见故障 ,但只是一些简单故障 ,实际情况要复杂得多。笔者在多年实际工作中取得一些经验 ,借此文与同行交流。目前国内使用的手扶旋刀式草坪机上安装的都是立轴式单缸四冲程风冷汽油机 ,其中美国Ｂ＆Ｓ公司产品占一大半。现以Ｂ＆Ｓ汽油机为例进行分析。汽油与…     

汽车使用醇燃料的技术探讨

随着对汽车排放与环境保护的要求,清洁燃料的研究已逐步得到世界各国的重视。作为清洁燃料之一的醇燃料,其使用方式有很多,文章主要对汽油机及柴油机使用醇燃料技术进行了探讨。     

谈汽车强制怠速的断油节油系统

我们仔细考察汽车的行驶过程,认真分析汽车行驶中每个阶段里发动机所做的功和油耗量,就可以发现在装有汽油机的汽车上,特别是那些不带超越传动装置的汽车,无论在什么时候,不管需不需要发动机输出功率,只要发动机运转,就会不断地消耗燃料。这显然是一种燃料浪费现象,本文就如何克服这一浪费现象做如下论述。     

弥雾喷粉机故障的诊断与排除

JMP—1型背负式机动弥雾喷粉机是用于农田、苗圃灭虫的机具。它经常发生的故障是:不易启动,发动机功率不足和运转时有熄火现象。一、启动困难该机具是用1E40F汽油机作动力的。如发生启动困难,按如下方法查找原因。 1.先检查油路,看油箱是否有油,油路是否畅通,化油器各部分是否工作正常。排除异常情况,正确操作,即可启动。     

浅谈通用汽油机排气系统降低成本的一种方法

通过对通用汽油机排气系统进行分析,在不影响其排放性能的前提下,通过合理的改变排气系统的内部结构,可有效地降低通用发动机的生产成本,并在实践中得到了验证。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.