共查询到20条相似文献，搜索用时 171 毫秒
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基于Geodatabase与CASE工具的林地保护利用规划数据库设计 总被引：1，自引：0，他引：1
林地保护利用规划数据具有多源、海量的特点。针对Geodatabase手动建模费时的特点,利用Geodatabase与CASE工具（Visio）进行UML建型,建立林地保护利用规划数据库模型。该模型实现了林地保护利用规划空间与属性数据的一体化存储,缩短了开发周期。 相似文献
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张清 《林业机械与木工设备》2001,29(1):26-27
可编程序控制器（ＰＬＣ）是一种数字运算的电子系统，其可靠性高、编程简单、操作方便、信号输入及输出清晰、整体线路简洁、紧凑．因此，我们对本厂胶合板车间一台早期生产的１０层下压式热压机继电器控制线路采用ＰＬＣ进行了改进．１改进前电路存在的问题１．１无精确二次保压功能 改进前的热压机采用手动阀卸荷，操作工在出板前因把握不准确，只能凭感觉拉动手动阀卸掉部分压力，然后再关闭手动阀，进行二次保压．由于压力控制不精确，易导致胶合板出现鼓泡现象，增加了次品率．１．２无保压时间显示 在压板过程中，因电路中无保压时间… 相似文献
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在模拟物流生产线控制系统中,要求能够可靠控制倍速链上物品的通行,并能够实现自动、手动控制。而应用PLC(可编程序控制器)的逻辑控制功能可以方便、灵活地实现生产线装配过程控制,其是一种简便、易行、有效的控制手段。 相似文献
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Different vegetation management practices implemented during the establishment of a Eucalyptus hybrid clone (GC304) in the coastal Zululand region of KwaZulu-Natal, South Africa, resulted in significant improvements in final volume when grown on a short pulp-wood rotation of 7 years, with a 42.5% higher underbark volume for the manually weeded control over that of the weedy control. This occurred despite the absence of competitive vegetation after the first growing season, due to reduced light following crown canopy closure. Interspecific and intra-genotypic competition were evident in the weedy control at different stages of tree development, but only intra-genotypic competition occurred in the manually weeded treatment. Interspecific competition resulted in greater variability between the trees in the weedy control by the time canopy closure had occurred. The differentiation in tree size was further enhanced by asymmetric intra-genotypic competition once the trees had become established. The onset of intra-genotypic competition was first detected 995 days (2 years and 9 months) after planting for the manually weeded treatment and 1641 days (4 years and 6 months) after planting for the weedy control. The presence of asymmetric intra-genotypic competition between different tree size classes was detected for both the weedy control and manually weeded treatment. 相似文献
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Two heuristic techniques, the genetic algorithm (GA) and Tabu search (TS), both with an embedded linear programming routine for earthwork allocation, were compared to a manually designed forest road profile. The manually designed road length was 345.7m and its average gradient was 14.1%. The best costs of the profiles designed by GA and TS, without changing the placement of control points, were less than that designed manually. The best cost found by GA was almost the same as the global optimum solution. While TS could not find a better solution than GA, it usually found a good solution in less time. It was not possible to search all alternatives by changing the placement of control points and find the global optimum solution within a reasonable time. However, it can be concluded from the results that both GA and TS found good solutions within a reasonable time. Since it is not possible to manually evaluate many alternatives, road designers should find heuristic techniques helpful for design of the road profile. Moreover, the effect of the number of control points on construction costs was examined. The results indicated that increasing the number of control points reduces the construction costs. However, driving safety and comfort might be decreased. 相似文献
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长期大量使用化学农药有两大弊端：一是污染环境,药的有效作用日益减少。通过生物防治、无污染化学防治、术等手段可减少使用化学农药防治植物病虫害。破坏生态平衡;二是病虫害的抗药性日益加强。化学农物理防治等方法,如人工捕捉、诱杀、栽培园艺控制技 相似文献
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赵怀久 《林业机械与木工设备》2011,39(2)
数控无卡轴旋切机的刀台进给系统通过丝杠螺母的传动可实现刀体座的进退,传动丝杠螺母都是依靠人工润滑,如果润滑不及时就会出现粘牙现象而导致整个设备不能工作。介绍了一种自动润滑装置,其可实现对丝杠螺母的自动润滑。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(7):605-616
Information on stem quality of standing (broadleaf) timber is of great importance to the forestry sector to help optimise harvesting and marketing strategies. Manual assessment of such quality parameters in standing trees is extremely difficult, time consuming and costly. The objectives of this study were therefore to assess stem quality parameters such as taper, lean and sweep in ash (Fraxinus excelsior L.) stands, during leaves-on and leaves-off conditions, using terrestrial laser scanning technology, and to compare the estimated parameters with manually measured values in a mature and young stand. Diameter estimation was more accurate during the leaves-off condition in both stands, resulting in taper estimates that were closer to the manually obtained values as well. However, in general, the taper values did not match those obtained manually very closely. Given that the sample trees were chosen deliberately to include noticeable defects such as non-circularity, bending, swellings, knots resulting from the removal of branches and multiple leaders, this is not surprising. It probably is the case that the scanned data capture these defects more accurately than the manually collected data, especially when multi-scan data are used. 相似文献
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A PC-based line-scan machine vision system providing rapid measurement of bare-root seedling morphological features has been developed. Designed for quality control and morphological data acquisition by nursery personnel, the machine provides a user-friendly, menu-driven graphical interface. Individual seedlings are manually placed on a conveyor belt and inspected in less than 0.25 seconds.The machine automatically locates the root collar and measures stem diameter, shoot height, sturdiness ratio, root mass length, projected shoot and root area, shoot-root area ratio, and percent fine roots. Sample statistics are computed for each measured feature. Measurements for each seedling may be stored for later analysis. Feature measurements may be compared with multi-class quality criteria to determine sample quality or to perform multi-class sorting. Statistical summary and classification reports may be printed to facilitate the communication of quality concerns with grading personnel.Tests were conducted at a USDA Forest Service nursery to evaluate measurement precision. Four quality control personnel measured root collar diameter, shoot height, and root mass length on 100 2--0 Douglas fir and 100 2--0 Ponderosa pine seedlings. The same seedlings were inspected four times by the machine. Root collar diameter measurement standard deviation of the machine was 25% that of manual measurements. Machine and manual measurements had comparable precision for shoot height and root mass length. 相似文献
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Kazuhiro Aruga 《Journal of Forest Research》2005,10(4):275-284
This article describes a program for optimizing horizontal and vertical alignments of forest roads using Tabu search, a modern heuristic technique. Once a series of intersection points (IPs) is selected manually, the program generates alternative horizontal and vertical alignments. The program precisely generates ground profile and cross sections using a high-resolution digital elevation model (DEM) derived from light detection and ranging (LiDAR) data. It accurately calculates earthwork volumes for curved roadways using the Pappus-based method. The program also estimates construction and maintenance costs. Tabu search optimizes forest road alignments based on the total costs. The application of the program to part of Capitol State Forest in Washington State, USA, indicated that the program successfully found better alignments than manually selected initial alignments. The effect of initial solutions and the number of iterations on the Tabu search process was examined. The result showed that the solutions were improved using the best solutions with the smaller number of grade change points as the initial solutions. It also showed that a small number of iterations could be used to reduce computation time due to the fact that Tabu search is based on a gradient search technique. Finally, the Dijkstra method was examined to find initial solutions without manually initialized solutions. The program, when combined with the Dijkstra method, could find similar-quality solutions from manually initialized solutions. The program will become useful with further tests and verifications. 相似文献
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The objective of this research was to evaluate the influence of vegetation control on the microclimate (light, air temperature, vapor-pressure deficit (VPD)) and on the growth of young planted, sessile oak seedlings. Three types of vegetation control, creating a range of above-ground interaction intensity, were compared. In the open treatment, vegetation was chemically controlled and was maintained at a low height; in the closed treatment, vegetation was manually controlled and a few dominant individuals that overtopped the oak seedlings were cut; and in the sheath treatment, the vegetation in a 0.5-m diameter circle around each seedling was manually cut to a height equal to three quarters of the total seedling height. In all treatments, a strong reduction of incoming radiation was observed, as well as an increase in air temperature and VPD during the day, and a decrease in daily PET, compared to the reference located 4 m above the vegetation. However, the neighboring vegetation did not modify the microclimate around the seedling to a level that could have induced a significant reduction in seedling photosynthesis and, thus, in seedling growth. Seven years after planting, seedlings were shortest in the open treatment and tallest in the closed treatment (334, 372, 378 cm in the open, sheath and closed treatments, respectively). Seedlings in the open treatment allocated proportionally more biomass to diameter increment than to height growth, compared to seedlings in the sheath and closed treatments. The seedlings averaged 1.77, 1.10 and 1.00 forks in the open, sheath and closed treatments, respectively, and the average height of the lowest fork was 171, 206 and 226 cm in the same treatments. The reduction of the number of forks per seedling was not related to a reduction of the appearance of new forks, but rather to a reduction in the persistence of the existing forks. These changes in stem allometry and in fork development seemed to be related to the lateral shade afforded by the vegetation. 相似文献
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In South Africa, commercial eucalypt stands may be regenerated through the stepwise reduction of coppice shoots following felling. The development of secondary coppice regrowth following these reduction operations results in competition with the remaining stems, possibly resulting in a reduction in growth. Currently, secondary coppice regrowth is controlled manually, or through spraying with glyphosate at 0.6% when ca. 0.75?m in height. No research has been conducted to determine whether alternative rates and/or timing of application are possible or cost-effective. In 2006 a trial was implemented in Zululand, South Africa on a recently coppiced stand of Eucalyptus grandis × Eucalyptus urophylla so as to optimise rates of glyphosate application (0.6%, 1.2% and 1.8%) for the control of secondary coppice regrowth at various heights (0.5, 1.0 and 1.5?m). Tree and secondary coppice regrowth variates were measured annually until rotation-end (9 years, 3 months). The volume of herbicide used, the number of occasions each treatment was sprayed and associated costs were combined to provide an indication of the most cost-effective treatment. Although there were no significant differences in final coppice yield for the various rates of glyphosate and timing of application (as assessed by the size of the secondary coppice regrowth) tested, treatment efficacy in terms of treating secondary coppice regrowth increased with an increase in the rate of glypho- sate applied (0% < 0.6% < 1.2% < 1.8%), especially when treated at either 1.0 or 1.5?m in height. The use of glypho- sate, irrespective of rate and/or timing of application (as assessed by secondary coppice regrowth height), proved to be more cost-effective compared with manual control or the spraying of the secondary coppice regrowth at 0.75?m height with 0.6% glyphosate. The most cost-effective treatment was 1.2% glyphosate applied when the secondary coppice regrowth was 1.5?m. If reduced herbicide use is a major criterion within a company portfolio, then the secondary coppice regrowth can be manually removed when 1.5?m. 相似文献
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福建省安溪云中山自然保护区植被资源及其垂直分布特征 总被引：1，自引：0，他引：1
在野外科学考察的基础上,分析总结了安溪云中山自然保护区植被资源的现状,系统介绍了该保护区主要植物群落类型及其物种组成。发现该保护区的植被类型分布呈现出一定的垂直分布特征,但其植被垂直带谱出现较为明显交错镶嵌现象,尤其常绿阔叶林和针叶林有着相同的垂直分布范围出现重叠,表明了地带性植被的优势地位正在被以人工经营的针叶林所取代。因此,以植被为主的生物多样性以及森林生态系统的结构与功能当成为今后保护区研究和建设的一项重点,使其特有的生产力得到充分发挥,产生良好的生态效益,社会效益和经济效益。 相似文献