数值模拟受抑尘导流板影响的自由下落散料流流场特性

指出了属于气固两相流的自由下落散料流在降落点常产生大量粉尘,虽然高能耗通风除尘系统采用高扬程风机抽吸含尘空气,但依然有大量粉尘向周围散射,污染工作环境。研究设想在散料流与下部接收装置上安装可调倾斜角度抑尘导流板,人为控制由于散料流与接收设备发生碰撞所产生大量粉尘的散射方向,提高通风除尘系统吸尘口对吸收散射粉尘的效率,达到节能减排目的。通过数值模拟方法,采用计算流体软件模拟粉尘的运动轨迹及速度场,探索了物理参数和环境参数对除尘效果的影响,进而得到了导流板除尘的最优方案。     

一种新型生物质进料机构的研究

针对国内生物质给料系统容易出现卡塞、回火、给料不均匀等问题,设计了一种新型生物质给料系统,并搭建了试验平台,对落料、控料、送料等诸多环节进行试验,以确定最佳设计方案。     

3D仿真曲线受料靴设计及结构要点

指出了带式输送机在运行过程中,经常会出现撒料溢尘现象,存在较严重的环境污染。提出并阐述了3D仿真曲线图受料靴的设计原理及其结构与性能。通过优化头部漏斗、溜管设计,降低物流下落加速度,减少冲击,消除粉尘和物料溢出,保证良好的受料点避免胶带重载跑偏,延长输送系统各部件的使用寿命,保障系统出力和减少系统维护,提高胶带的输送效率。     

白僵菌粉碎及菌粉收集系统的研制

简述了白僵菌的性质、用途、对人的危害及系统研究背景、设计原则，着重研究了系统中的菌粉收集部分。通过对粉尘生产产生原因的分析，提出了防尘收尘措施及集尘点设置，并对菌粉收集部分所涉及的抽风量、阻力等因素进行了正确的计算，解决了白僵菌粉尘收集和对人体危害的问题。     

基于GSM网络的实验室安防报警系统设计

介绍了一种基于GSM网络的实验室安防报警系统,阐述了该系统的结构及其软硬件设计.报警系统采用GSM短信模块来发送接收短信,从而实现对实验室安全的监控.该系统结构简单、安装调试容易、使用方便.     

加强煤矿通风安全隐患管理的措施

煤矿生产集中在井下,这一区域瓦斯和粉尘容易积累,极易导致中毒和爆炸事件,当前煤矿企业一般应采用煤矿通风系统,利用煤矿通风设备实现井下生产过程中环境质量和空气质量的改善。而煤矿通风系统在运行中会出现各类问题,导致煤矿通风出现各种安全方面的隐患,不利于煤矿生产和安全目标的实现。文章列举了排除煤矿通风系统安全隐患的措施,提供了煤矿通风加强管理的方法,希望对煤矿通风系统安全运行有所帮助。     

白菌粉碎及菌粉收集系统的研制

简述了白僵菌的性质，用途对人的危害及系统研究背景，设计原则，着重研究了系统中的菌粉收集部分。通过对粉尘生产产生原因的分析，提出了防尘收尘措施及集尘点设置，并对菌粉收集部分所涉及的抽风量，阻力等因素进行了正确的计算，解决了白僵菌粉尘收集和对人体危害的问题。     

基于钾元素发射光谱的木粉尘火焰/火花检测装置

为提高粉尘火焰/火花检测的可靠性,基于钾元素发射光谱设计木粉尘火焰/火花检测装置。利用粉尘蕴含元素受热会激发光谱特征为理论依据,采用高精度光谱元件、高速数模转换和控制芯片搭建检测装置,通过网口协议稳定传输获取的实时光谱特征。结果表明:采用上述方法能够获得明显的钾元素光谱,具有显著的光谱特征,可作为检测装置的检测依据。所设计的装置能迅速准确获得实时粉尘光谱状态,且成本低、精度高、体积小,可为预防粉尘燃爆事故的发生提供技术支撑。     

刨花板生产中原料堵塞的成因及预防

1前言木材在经过削片、刨片制成刨花，再经过干燥、筛选、打磨、分选、施胶、成型、热压成刨花板的过程，有很多轻型颗粒状的物质──细小刨花和木粉尘生成。而轻型颗粒状的物质通常很容易凝聚。当它们自然降落并被存入料仓或在送料管道中时，既会聚集在一起而影响物料畅通流动。其结果，在送料管道或料仓中出现结块，使出料系统出现堵塞。特别管道潮湿时，轻型的颗粒状物质更易于胶结在一起，因而加强了凝块的趋向，造成原料堵塞。经过多年的生产实践，证明生产线中，刨花堵塞的现象，除了细小颗粒状物质凝聚结块造成塞料外，还有机械、刀…     

中纤板粉尘回收和除尘系统的改造

粉尘污染是大多数中密度纤维板厂存在的问题。广东威华梅州中纤板厂是一家年产6万m3的中密度纤维板厂,全套设备为国产设备,由于诸多方面的原因,该厂纤维回收利用和通风除尘系统运行效果极不理想,大量散失纤维,严重污染环境,不仅有害员工健康,而且浪费原材料。经研究设计,对该系统进行了一系列的改进,取得了明显的效果(本文所述只针对铺装工段的纤维回收系统,砂光粉尘另外配有一套独立设备)。     

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.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

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。