Effect of tool angles on the chips generated during milling of wood by straight router-bits

 The effect of tool angles on the shapes of chips generated by parallel-to-grain and end-grain milling was explored for China fir and maple under fixed spindle and feed speeds and cutting depth. The milling path was up-milling by straight router-bits with a diameter of 12 mm. The chip shapes could be distinguished as five types: spiral, splinter, flow, thin, and granules or powder. The flow and thin chips were generated most often (on a weight percentage basis) for all tool angles investigated for parallel-to-grain and end-grain milling of China fir and maple. More granule chips were produced with parallel-to-grain milling than with end-grain milling for both woods. The measured chip thickness (t′) was thicker than the calculated thickness (t _max). Thicker and longer maple chips were produced by end-grain milling than by parallel-to-grain milling. The tool geometries of 40°/15° (sharpness of the angle–rake angle), 50°/15°, and 60°/15° for China fir and 40°/25°, 50°/5°, and 60°/5° for maple produced relatively more flow chips with parallel-to-grain milling. Furthermore, the tool geometries of 40°/5°, 50°/15° and 60°/25° produced more flow chips (weight percentage) by end-grain milling of China fir and maple. Received: May 23, 2001 / Accepted: June 28, 2002 Acknowledgment This study was supported by a grant from the National Council of Science, Taiwan (NSC89-2313-B-415-011).     

突出本质功能崇尚简约自然——城市绿化新理念在北京奥运绿化中的实践

同一个世界,同一个梦想。北京奥运会圆满落下帷幕,实现了"有特色、高水平"的目标,向世界展示了中国和北京的风采。在奥运会成功举办的时空里,北京的奥运绿化也向世界悄然展示了一幅碧树繁花、生机盎然、美丽恢宏的画卷!       

The contribution of structural indices to the modelling of Sitka spruce (Picea sitchensis) and birch (Betula spp.) crowns

Crown dimensions are important for the quantification of tree interactions in some growth models. This study investigates the potential for structural indices and other spatial measures to improve the prediction of crown radius and crown length for birch (Betula spp.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) in forests in Wales. Crown dimensions were measured for 125 birch and 154 spruce in six fully stem-mapped research plots. These data were used to test the performance of a crown radius model and a crown length model which estimated crown dimensions on the basis of allometric relationships with stem dimensions. Spatial data from the six plots were used to calculate the structural indices mean directional index, diameter correlation index, species mingling, dbh and height dominance, and dbh differentiation, as well as the Hegyi competition index, and basal area of neighbours and larger neighbours, for each crown measurement sample tree, using various numbers of nearest neighbours. Two non-spatial indices, BAL and BALMOD, were also calculated for all sample trees for comparison. These spatial and non-spatial variables were then incorporated into modified crown dimension models. Model performances, in terms of efficiency and relative bias, were compared to determine whether the inclusion of spatial or non-spatial variables resulted in any improvements over models using tree dimensions alone. Crown length and radius were found to be correlated with most of the spatial measures studied. Models incorporating spatial variables gave improvements in performance over allometric models for every data set, and performed more consistently than models containing non-spatial variables. The greatest improvements were achieved for suppressed birch in unthinned forests which had irregularly shaped and strongly displaced crowns. The spatial variable contributing to the most efficient model for each data set varied widely. This points to the complexity of tree spatial interactions and indicates that there is a great deal of scope for investigating other structural indices and crown dimension model forms.     

因地制宜建设特色城市森林——以无锡市城市森林建设总体规划为例

以无锡市城市森林总体规划为例,探讨因地制宜的特色城市森林规划建设战略;以创建特色森林城市为目标,以无锡市自然、文化和城市发展3方面为重要内容,提出依水建林、森林生态建设、森林生态网络建设和森林生态文化景观区建设4大规划战略。       

北京西山两种特色植物

杠柳(Periploca sepium Bunge)属萝摩科杠柳属落叶木质藤本,是一种蔓生缠绕灌木,又名羊奶子、北五加皮等。分布黄河流域及北方各省,北京西山亦有广泛分布。杠柳耐干旱瘠薄土壤,喜光,根蘖性强,常丛生成团,初期生长茎直立,后渐匍匐或缠绕,为优良的水土保持树种。       

娘子关下绿色煤都——山西阳泉森林城建设规划

阳泉市位于山西省东部,太行山中段西麓,总面积4570km2,总人口124.26万人,其中建城区面积42km2,人口46.13万人。境内大部分属于土石区,山谷纵横,地形复杂,山地和丘陵占总面积的80%,仅有西烟、盂县、洗马堰等几块盆地。       

芒果

别名:番蒜(台湾),天桃木(广西)。大乔木,株高25m,直径可达80cm,冠幅20m。       

北方城市垂直绿化攀缘植物的选择

城市水平绿化面积越来越少,垂直绿化凸现其重要性。进行垂直绿化材料的选择时,首先要考虑垂直绿化植物的生物学特性、速生性和是否常绿,还要根据环境、功能、绿化方式和目的等选择适合的品种。       

广州市市花——木棉

岭南三月,春风荡漾,绿树丛中,一株株高大的乔木,未叶先花,花红如火,尽染长空,浓墨重彩地向人们报道着春天的消息,这种树名叫木棉。       

江苏、安徽城市森林建设

城市森林工程以现代城市森林建设理论为指导,把城市地域内的建成区、近郊区、远郊区等地的森林生态环境建设作为一个整体,进行系统布局设计,建立相对稳定而多样化的城市森林生态系统,有效控制和改善城市的大气污染、热岛效应、粉尘污染,解决城市居民游憩休闲、生态保健等实际需要,全面提高城市人居环境质量,实现城市社会经济可持续发展。