铸件新型修复工艺与技术

铸件新型修复工艺与技术（４１２００６）中南林学院罗佑新铸件在铸造过程中经常产生气孔、渣孔、夹砂、缩孔、裂缝等缺陷，造成铸件使用寿命缩短或无法满足使用要求。为了消除这些缺陷，通常采用焊补工艺修复，但焊补修复工艺复杂、成本高，而且若缺陷在铸件内部时就无法...     

铸件新型焊补工艺

铸件新型焊补工艺（１５８４０２）黑龙江省东方红林业局机电厂徐海波铸件在铸造过程中经常产生气孔、渣孔、夹砂、缩孔、裂缝等缺陷，加之使用过程中，由于超负荷、机械事故以及自然损坏等原因，造成许多铸件机体损坏．过去，铸件焊补多采用含镍生铁焊条或铸件加热气焊补...     

广东省雨雪冰冻灾害森林生态修复工程规划与技术

文章通过对广东省雨雪冰冻灾害受灾现状调查统计,对受灾林木和林分划分轻、中、重度受灾等级,提出生态公益林、商品林的清理和造林技术要点,选择全面造林、补植套种、封育管护等森林修复技术和修复方式进行森林生态修复,重现广东省生物多样性丰富、抗逆能力强的地带性森林植被。     

广东省雨雪冰冻灾森林生态修复工程规划与技术

文章通过对广东省雨雪冰冻灾害受灾现状调查统计,对受灾林木和林分划分轻、中、重度受灾等级,提出生态公益林、商品林的清理和造林技术要点,选择全面造林、补植套种、封育管护等森林修复技术和修复方式进行森林生态修复,重现广东省生物多样性丰富、抗逆能力强的地带性森林植被。     

辽东地区退化蚕场修复技术

在调查分析辽东地区柞蚕场的现状的基础上,确定了蚕场分类特征和退化蚕场标准,提出了退化蚕场修复可分为以放养柞蚕为主导利用方向和改造为红松果材林为主导利用方向的两种修复技术措施。其中,二类蚕场可采取补植加密柞树、中刈放拐扩冠、延长根刈周期等措施修复;三类蚕场可采取补植5年生红松一级苗,嫁接后改造为红松果材林的措施修复。     

关帝山林区退化防护林成因及修复技术

笔者对关帝林区退化防护林现状进行了阐述,分析了其退化原因为人工林树种单一、部分天然林为杨桦萌生林、成过熟林衰退、病虫害及其他自然灾害、人工林密度大。并结合不同林分的实际状况,提出了补植补造、林冠下造林、皆伐更新、择伐更新、抚育间伐、封禁保护、综合修复7项退化防护林修复措施,以期为培育结构稳定、功能完善、优质高效的森林生态系统提供技术支撑。     

发动机机体裂纹修复工艺

发动机机体材料为铸铁,由于工作中热应力及变载荷的作用,以及使用、维修不当都会导致发动机机体损坏,其中,常见的损坏是发动机机体出现裂纹。因发动机机体上裂纹大小及部位不同,故通常采用粘补、裁丝、补板和焊修四种方法修复。1粘补法修复裂纹在进行粘补修复前,应用丙酮、汽油     

六盘山围栏封育区人工补植中药材自然修复效果分析

2006—2009年,以宁夏隆德县六盘山补植中药材的围栏封育退耕还林地为研究对象,开展了以封禁、围栏、人工补植、人工抚育等多项技术措施有机结合的中药材人工补植技术研究;并对围栏封育区和对照区内主要中药材的盖度、密度、频度、高度以及地上生物量及植物物种多样性进行了调查和研究。结果表明,围栏封育下退耕还林地人工补植中药材可有效地增加植被覆盖度,保护生物多样性,促进生态环境修复,并且具有显著的经济、生态和社会效益,有较高的推广应用价值。     

压铸壳体试漏机的改进

压力铸造由于具有铸件的尺寸精度高、组织致密、生产率高、易于实现自动化生产等特点，在批量生产中被广泛应用。但在压铸生产中，由于液态金属充型速度高，压力大，气体难以完全排出，在铸件内常存在皮下针孔；另外，铸件凝固快，补缩困难，易产生缩松。上述缺陷的存在，严重影响压铸件的内在质量，特别是对铸     

退化草地植被修复研究进展

为了研究草地植被退化以及治理修复技术,该文对草地退化和治理相关文章进行整理与归纳,总结了近年来退化草地植被修复的案例,对如何应对退化草地展开了对策讨论,为退化草地生态修复提供一定的理论依据.自然因素以及人为因素引起草地植被的退化,超载过牧是草地植被退化的主要原因;围栏封育、补播、施肥、灌溉以及鼠害防治等是主要常见的草地...     

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.