共查询到20条相似文献，搜索用时 225 毫秒
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<正>位于安徽蒙城的佰世达木业年产22万m~3中高密度板生产线已进入全线调试和试生产阶段,该条生产线采用的电子测量设备全部为德国EWS公司产品,包括:在线厚度测量、在线鼓泡探测、在线含水率测量和实验室剖面密度仪等。EWS的在线厚度测量,是当今欧洲最高技术等级的产品之一,与国产优秀人造板装备供应商——亚联的2500 mm/s高速超薄板生产线完美匹配。EWS在线测厚设备,采用非接触式传感器,无机械磨损,设备占用空间小,无需维护且便于升级。 相似文献
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基于DSP2407a的爬壁饥器人控制系统硬件电路设计 总被引：1，自引：0，他引：1
介绍一种以TI公司TMS320Ⅱ2407a为核一心处理器的无线爬壁机器人嵌入式控制系统硬件电路，该系统实现了对爬壁机器人的运动控制、真空吸盘内的负压控制、对锂电池的电压检测和与上位机的无线通信。 相似文献
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采用由计算机，模数转换板（A／D板），激光传感器等组成的木材表面粗糙度在线检测系统，在CNC数控加工中心上对铣削加工的针叶材花旗松和阔叶材山毛榉进行了表面粗糙度RZ的在线检测。实验结果表明，该系统的检测数据是准确的，并具有高速在线测量等特点。 相似文献
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介绍一种以TI公司TMS320LF2407a为核心处理器的无线爬壁机器人嵌入式控制系统硬件电路.该系统实现了对爬壁机器人的运动控制、真空吸盘内的负压控制、对锂电池的电压检测和与上位机的无线通信. 相似文献
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介绍了两个微型电机对角驱动能实现精密移动定位的微小型移动机器人。该机器人具有直线运动、任意半径圆周运动两种运动方式，能实现大范围内的快速移动定位，定位精度可达毫米级。 相似文献
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基于单片机的木材表面粗糙度激光在线检测系统 总被引：1，自引：0，他引：1
介绍一种用单片机控制激光位移传感器进行在线检测木材机械加工表面粗糙度的新方法.该系统由单片机、模数转换器和激光传感器测量系统(激光头及激光控制器)等组成,试验在木材加工CNC装置上进行.文中给出了硬件结构及软件程序设计流程图. 相似文献
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概述了拱泥机器人主要组成及工作原理。在无障碍运动过程分析的基础上,分析了拱泥机器人避障运动过程的基本规律,建立了避障运动过程的数学模型,可用于避障运动过程计算机仿真研究的仿真模型,也可以作为实际工作中路径规划的重要依据。 相似文献
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为了提高木片远距离高压压送计算的准确性,采用一种国际上流行的新的当量长度计算法,这种算法涵盖水平管段,垂直管段和所有弯头的压力损失计算,利用连续方程的质量守恒定律和等温过程的状态方程可以得到管道起点（供料器下的B点）和管道终点C（卸料点）的绝对静压力之差,即为BC管段的压力损失,加上其他损失即可得到该系统所耗损功率。 相似文献
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We tested the hypotheses that freezing-induced embolism is related to conduit diameter, and that conifers and angiosperms with conduits of equivalent diameter will exhibit similar losses of hydraulic conductivity in response to freezing. We surveyed the freeze-thaw response of conifers with a broad range of tracheid diameters by subjecting wood segments (root, stem and trunk wood) to a freeze-thaw cycle at -0.5 MPa in a centrifuge. Embolism increased as mean tracheid diameter exceeded 30 microm. Tracheids with a critical diameter greater than 43 microm were calculated to embolize in response to freezing and thawing at a xylem pressure of -0.5 MPa. To confirm that freezing-induced embolism is a function of conduit air content, we air-saturated stems of Abies lasiocarpa (Hook.) Nutt. (mean conduit diameter 13.7 +/- 0.7 microm) by pressurizing them 1 to 60 times above atmospheric pressure, prior to freezing and thawing. The air saturation method simulated the effect of increased tracheid size because the degree of super-saturation is proportional to a tracheid volume holding an equivalent amount of dissolved air at ambient pressure. Embolism increased when the dissolved air content was equivalent to a mean tracheid diameter of 30 microm at ambient air pressure. Our centrifuge and air-saturation data show that conifers are as vulnerable to freeze-thaw embolism as angiosperms with equal conduit diameter. We suggest that the hydraulic conductivity of conifer wood is maximized by increasing tracheid diameters in locations where freezing is rare. Conversely, the narrowing of tracheid diameters protects against freezing-induced embolism in cold climates. 相似文献
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The development of high-resolution remote sensing imaging technology provides a new way to the large-scale estimation of forest canopy density. The traditional inversion methods for canopy density only use spectral or topographical features of remote sensing images.However,due to the existence of the different thing with same spectrum and the same thing with different spectrum phenomena,it is difficult to improve the estimation accuracy of canopy density.Based on spectrum and other traditional features,this paper combines texture features of remote sensing images to estimate canopy density.Firstly,the gray level co-occurrence matrix (GLCM) texture features are computed using objectbased method.Then,the principal component analysis (PCA) method is applied in correlation analysis and dimension reduction of texture features.Finally, spectrum and topographical features together with texture features are introduced into stepwise regression model to estimate canopy density.The experimental results showed that compared with the traditional method only based on spectrum or topographical features,the method combined with texture features greatly improved the estimation accuracy.The coefficient of determination(adjusted R~2 ) increased from 0.737 to 0.805.The estimation accuracy increased from 81.03%to 84.32%. 相似文献
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We studied the effect of tree architecture on xylem anatomy in three Betula pendula Roth., three Picea abies (L.) H. Karst. and three Pinus sylvestris (L.) trees (mean age 35 years). First, the analysis of conduit anatomy in different tree parts showed that conduits tapered and their frequency increased from roots (≥ 2 mm) to stem, from stem to branches and further to leaf petioles in B. pendula. Conduit anatomy in lateral and main roots, as well as lateral and main branches, significantly differed from each other in all the studied species. The increase in conduit diameter and decrease in frequency from the pith to the bark were clear aboveground, but variable patterns were observed belowground. In the leaf petioles of B. pendula, conduit diameter increased and conduit frequency decreased with increasing individual leaf area. Second, the results concerning the scaling of conduit diameter were compared with the predictions of the general vascular scaling model (WBE model) and Murray's law. The scaling parameter values at the tree level corresponded with the predictions of the WBE model in all the studied trees except for one tree of both conifer species. However, the scaling parameter values changed from one tree compartment to another rather than remaining uniform inside a tree, as assumed by the WBE model. The assumptions of the WBE model of a constant conductivity ratio, constant tapering and an unchanged total number of conduits were not fulfilled. When the conductivity ratio and relative tapering were plotted together, the results aboveground corresponded quite well with Murray's law: the conductivity ratio increased when relative tapering decreased. Our results support the theory that trees adjust both their macro- and microstructure to maximize their water transport efficiency, but also to prevent embolism and ensure mechanical safety. 相似文献
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In plants, water flows from roots to leaves through a complex network of xylem conduits. The xylem architecture is characterized by the conduit enlargement towards the stem base and the multiplication of conduits near the apices of lateral branches. The xylem architecture of a small ash tree was analysed by measuring the vessel hydraulic diameter (Dh) and number (N) at different heights along the stem and branches. Along the stem, Dh and N increased from the apex to the point of crown insertion. Below, Dh and N decreased and remained constant, respectively. In branches, the Dh and N of apices increased with distance from the ground (PL) (P < 0.001 and P < 0.0001, respectively), indicating that apical resistance (R(APEX)) becomes lower in the most peripheral branches (P < 0.0001). At the level of branch nodes along the stem, the total conductive area (AC) of the stem and branches just above the node was 11% higher than that of the stem just below the node (P = 0.024), whereas the conductivity (Kh) remained invariant above and below (P = 0.76). The difference in AC (ΔAC) between the branches and stem above each node increased with the distance of the node position from the stem apex (L). The xylem architecture of the analysed tree was characterized by anatomical modifications likely aimed at equilibrating the different path length effects on the hydraulic resistance of the different branches. Conduit tapering and multiplication seem to play a crucial role for the achievement of equal hydraulic resistance of all the leaves in the crown. 相似文献
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We evaluated whether patterns in hydraulic architecture increase transport efficiency. Five patterns are identified: area-preserving branching; variable trunk versus twig sap velocity; distally decreasing leaf specific conductivity (K(L)) and conduit diameter; and a decline in leaf specific conductance (k(L)) of the entire plant with maturation. These patterns coexist in innumerable combinations depending on the ratio of distal/proximal conduit number (F). The model of West and colleagues does not account for this diversity, in part by specifying F = 1 and requiring a specific conduit taper derived from the incorrect premise that k(L) is constant with plant size. We used Murray's law to identify the conduit taper that maximizes k(L)for a given vascular investment. Optimal taper requires the ratio of distal/proximal conduit diameter to equal the ratio of distal/proximal K(L). The smaller these ratios, the greater the k(L). Smaller ratios are achieved by an increase in F. Conductivity and diameter ratios < 1 and F >/= 1 in plants are therefore consistent with maximizing conducting efficiency. However, the benefit of increasing F requires area-increasing conduit branching, potentially leading to mechanical instability of trees. This trade-off may explain why tree stems were relatively inefficient with F near 1 and limited conduit taper compared with vine stems or compound leaves with F > 1 and greater taper. Within trees, the anatomies of a coniferous and a diffuse-porous species were less efficient than that of a ring-porous species, presumably because the latter allows conduit area to increase distally without also increasing total xylem area. This is consistent with decelerating sap velocities from trunk to twigs in ring-porous trees versus accelerating velocities in other types. In general, the observed architectural patterns are consistent with the maximization of transport efficiency operating within mechanical constraints. 相似文献