共查询到20条相似文献，搜索用时 803 毫秒
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71型索道即承载索松紧式索道,在无荷与有荷状态时,都可以用抛物线法求解,线型同样符合两端固定式索道承载索遵循的定律,设计方法很多,但以钢索最大拉力为依据调整统盘机制动力矩的方法最为简便、安全。 相似文献
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以缆索吊装理论为基础,对缆索在桥梁施工中的吊装作业情况进行分析,建立缆索吊装设计数学模型,利用Visual Basic6．0实现系统设计。系统界面友好,操作简便,改变了繁琐的人工计算过程。实现了给定参数输入,通过计算可以得到主索、起重索、牵引索、风缆索、塔架、地垄及绞盘机功率等精确的设计结果,可为缆索吊装设计提供科学依据。 相似文献
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Cable-based technologies have been a backbone for harvesting on steep slopes. The layout of a single cable road is challenging because one must identify intermediate support locations and heights that guarantee structural safety and operational efficiency while minimizing set-up and dismantling costs. Our study objectives were to (1) develop an optimization approach for designing the best possible intermediate support layout for a given ground profile, (2) compare optimization procedures between linearized and nonlinear analyses of a cable structure and (3) investigate the effect of simplifying a multi-span representation. Our results demonstrate that the computational effort is 30–60 times greater for an optimization approach based on nonlinear cable mechanical assumptions than when considering linear assumptions. Those nonlinear assumptions also stipulate lower heights for intermediate supports and a larger span length. Finally, compared with the unloaded case, tensile force in the skyline is increased by as much as 80% under load for a single-span skyline configuration. Our approach provides additional value for cable operations because it ensures greater structural safety at a lower cost for installation. Improvements are still needed in developing a stand-alone application that can be easily distributed. Moreover, our rather simple assumptions regarding set-up and dismantling costs must be refined. 相似文献
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结合对黑河电信塔及电缆线路工程地质勘察的工作实际,介绍了该项工程的任务、目的及要求,结合当地的实际地形、地貌条件,提出评价和建议,并且制定出比较科学合理的工程地质勘察方案。 相似文献
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The four-line model of the Triangular Running Skyline (TRS) system is the theory generalized from the previous TRS theory
to treat the main and slack-pulling lines separately. The previous theory,i.e., the three-line model, treated the main and slack-pulling lines as a single line to simplify the solution. The first part
of this study developed numerical procedures for the four-line model. In this paper, to empirically ascertain the accuracy
of the four-line model theory, a series of static equilibrium tests was carried out using a reduced scale model of the TRS
system. The result proved that the theory of the four-line model has the same accuracy as that of the three-line model. However,
the result also proved that the carriage may have to be located lower than the designated height. Thus, it has been proved
that the development of a certain adjusting method is necessary to move the carriage of the TRS system closer to the designated
point.
A part of this paper was orally presented at the Second Annual Meeting of the Japanese Forest Engineering Association, November
18, 1995, Tokyo.
This English title is a tentative translation from the original Japanese by the authors of this paper. 相似文献
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采用牛顿切线法求解公式既简单又可以利用计算机进行程序计算,提高了全悬式缆索起重机承载索张力计算的精度和速度。从而解决了全悬式缆索起重机承载索设计中的问题。 相似文献
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本文在半悬空集材索道设计的数学模型及其理论推导的基础上,用高级BASIC语言编程.该系统能对单跨半悬空集材索道的三种类型(两端固定式、松紧式、运行式)分别进行完整的设计计算.并绘制索道纵断面图。 相似文献
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We inventoried plant regeneration and soil compaction along mule trails to evaluate damage to forest stands and regeneration follow-ing mule hauling before and after operations in Kheyrud Forest in the... 相似文献
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The generalized static solution of the Triangular Running Skyline (TRS) system has been derived. A pair of tail spars with
a haulback line enables the carriage of the TRS system to move around over the triangular area formed by connecting the bases
of the three spars with each other,i.e., the two tail spars and one head spar. From the head spar, the main and slack-pulling lines stretch toward the carriage to
move up and down the load. The theory derived in this paper separately evaluates the line lengths and line tensions of the
main and slack-pulling lines (the four-line model), while the previous theory treats these two lines as a single equivalent
line (the three-line model). Four numerical examples provided in this paper ascertained the accuracy of the two procedures
of the four-line model.
A part of this paper was orally presented at the Second Annual Meeting of the Japanese Forest Engineering Association, November
18, 1995, Tokyo.
This English title is a tentative translation form the original Japanese by the authors of this paper. 相似文献
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单圣涤 《中南林业科技大学学报(自然科学版)》1988,(1)
索系是指索道各工作索相互关联的配置系统,主要包括索道各工作索相互关联而成的各种承载方式、起重方式、牵引方式和落勾方式。而索道的起重方式基本上包含了索道的承载方式,牵引方式基本上包含了落勾方式。本文根据索道工作索的总根数及其起重方式和牵引方式,对林用索道的索系进行了分类,并编制了代号。 相似文献
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Hans R. Heinimann 《Journal of Forest Research》1998,3(1):1-9
Road spacing on slpes depends on the underlying off-road transportation technology. One major decision in road network planning
is to determine under what terrain conditions ground- or cable based extraction systems should be applied. The present investigation
aims to develop a road spacing model for steep slope conditions and to implement a total cost model for skidder and cableyarder
based road network concepts. The study analyzes transportation and road geometry to specify the relationship between road
density, slope gradient, and road spacing. Production functions for skidder and yarder-systems make it possible to derive
transportation cost as a function of road density and slope gradient. A total cost function integrates road building cost,
harvesting strategy, and production economics to derive optimal road density for the two network concepts. The difference
between the cost levels at optimum road density is an indicator for differentiating cable and skidder-based extraction systems.
The model was implemented as a Visual Basic add-in for Microsoft Excel spreadsheet software. This flexible approach makes
future adaptations and changes very easy due to the modular concept. The validity of the model is limited to the production
functions of the underlying off-road transportation technologies. Future work needs to develop production functions for the
state-of-the-art technologies and to improve the road building cost model. 相似文献
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Simulation of soil water dynamics in a Caragana intermedia woodland in Huangfuchuan watershed 总被引：1，自引：0，他引：1
As vegetation coverage increases, soil water content can decrease due to water uptake and evapotranspiration. At a very high
level of plant density, poor growth and even mortality can occur due to the decrease of soil water content. Hence, a better
understanding of the relationship between soil water content and the density of plants is important to design effective restoration
projects. To study these relationships, we developed a soil water dynamic simulation model of a Caragana intermedia woodland under different slope gradient and slope aspect conditions in the Huangfuchuan watershed on the basis of the previous
studies and field experiments. The model took into account the major processes that address the relationships of plants and
the environment, including soil characteristics, precipitation, infiltration, vegetation transpiration, and soil evaporation.
Daily changes in soil water content, transpiration, and evaporation of the Caragana intermedia woodland with different vegetation coverage, slope gradient, and slope aspect were simulated from 1971 to 2000. Based on
the model simulations, we determined the functional relationships among soil water content, plant coverage and slope as well
as the optimal plant density on flat slopes. We also determined the effects of slope gradient and slope aspect on soil water
content. When slope gradient was less than 10°, the optimal plant density was sensitive to slope gradient. In the slope range
from 10° to 30°, plant density was not sensitive to slope gradient. Therefore, it is important to consider planting densities
on the hillsides with slope gradients less than 10° for reconstructing vegetation.
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Translated from Acta Phytoecologica Sinica, 2005, 29(6): 910–917 [译自: 植物生态学报] 相似文献
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Rostam Mousavi 《林业研究》2012,23(4):691-697
The performance of the skidder Timber jack 450 C was presented in timber skidding of non-coniferous trees in hilly and mountainous conditions.An empirical time study was conducted to evaluate the current skidding system in Hyrcanian forest in northern Iran for improving production rate of skidding and finding out the production cost for planning.Based on the identified elements of skidding work phase and 130 recorded cycles,we calculated the models for effective time consumption,total productivity,and unit cost.The validity of the model was tested at 95% confidence interval.The average load volume per cycle was 2.82 m 3,average one way skidding distance was 450 m,and the average slope was 18%.The average travel speed of unloaded skidder was 5.8 km·h-1,and the average speed of loaded skidder was 0.1 km·h-1 higher than the speed of the unloaded ones.The travel speed was predominantly affected by longitudinal slopes and types of strip roads.The average speed of pulling the cable was 1.16 km·h-1,and that of load winching was 0.74 km·h-1.The average outputs in skidding was 10.6 m 3 ·h-1 and the unit cost was 12.1 US$ per hour.The time consumption and productivity of skidding depends on distances and slope,number of logs per cycle,volume,log length,etc.However,the influence of variables is not the same. 相似文献
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After mechanized whole-tree harvesting at a clear cutting site, using a cable yarding system and a processor, piles of slash
remain at the landing areas near roads. This study examined the movement of slash piles and their effect on soil nutrients
in the ground below the pile. The profile of one pile was measured for three years. In order to investigate nutrient concentrations,
soil was sampled at two sites. The volume of the pile decreased by 6% per year. Piles placed on convex or uniform hillsides
are stable, and have a low risk of sliding on a slope. Analysis of the water-soluble nutrients in the soil suggests that water
carries nutrients from the pile into the soil up toca. 7 m from the pile. There is a reduction in soil acidity, and rainwater flow from the pile adds several minerals to the soil,
particularly Ca. Slash in a pile on a convex or uniform hillside does not have any impact on a forest, either positively or
negatively. We should try to return slash to stands or utilize it as a biomass resource.
This study was supported by a Grant-in-Aid of Scientific Research (No. 09660164) from the Ministry of Education, Science,
and Culture, of Japan. 相似文献
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钢丝绳弹性模量的研究 总被引：7，自引：0，他引：7
钢丝绳是不少机械的重要组成部分。钢丝绳属挠性体,负荷时不可避免出现弹性伸长,其关键参数弹性模量的取值问题关系到机械设计的精度与安全性。架空索道、缆索起重机等承载索挠度比较大的设备,弹性伸长更是不可忽视。通过综合考虑挠度引起弹性模量和弹性伸长引起弹性模量推导出等效弹性模量。 相似文献
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