共查询到20条相似文献，搜索用时 140 毫秒
1.
2.
从我国现阶段公路发展情况及使用状况入手,介绍公路的主要病害,并分析病害产生的原因。另外还从我国公路养护与维修的决策、分类以及存在的问题等三方面阐述了我国现阶段的公路养护现状;并对今后公路养护的发展趋势做了展望。 相似文献
3.
4.
园林绿化工程可以提升城市环境品质,要保证园林树木的健康成长,需要做好养护管理工作。本文在对城市园林绿化工程中树木养护管理的主要内容进行系统梳理的基础上,从浇水施肥、修剪、防冻、病害防治等几个方面,详细论述了养护管理的主要措施。 相似文献
5.
近年来,交通量日益增长,很多公路沥青路面出现了不同程度的病害,比如车辙、裂缝、坑槽等。我国公路建设已进入了大规模养护时期,养护里程占全国公路总里程的99%以上。在有限的养护资金条件下,如何提高公路质量和沥青路面耐久性成了人们必须思考的问题。在全面掌握沥青路面常见病害类型的基础上,分析了沥青路面病害的成因,并结合具体案例,提出养护施工对策,以供参考。 相似文献
6.
7.
从林区公路自身特点入手,介绍林区公路的主要病害,并分析病害的产生原因;同时还从林区公路养护与维修的决策、分类及存在的问题等方面分别阐述林区公路养护的现状。 相似文献
8.
屋顶绿化是城市绿化的重要组成部分,在养护过程中,有害生物的识别与防控是十分重要的环节。以广州节约型屋顶绿化中常见的主要有害生物为研究对象,调查并记录了多种病虫害种类,在病害方面鉴定了叶斑病、根腐病、炭疽病等病原物,对其病症与病征进行了描述;在虫害方面,确定了千足虫、粉蚧及蚜虫的危害症状和识别特点。同时对以上各类病虫害进行了防治方法的初探,筛选出高效、低毒、低残留的安全化学药剂,并确定了最佳使用浓度和方法。本研究为节约型屋顶绿化的有害生物防治工作提供了理论依据,使屋顶绿化的养护和管理更加规范化和合理化。 相似文献
9.
本文就北京地区冷地型草坪草上常见病害及其危害进行了调查研究,综合了各种栽培养护措施和化学防治措施对病害的控制作用。北京地区城市绿地中冷地型草坪草主要以草地早熟禾为主,每年发生的病害主要有锈病、褐斑病、腐霉枯萎病和夏季斑枯病等。每种病害在草坪上的发生时间有所不同,表现症状也存在差异。病害防治采取的主要措施有:培育措施、化学防治措施和病害预测预报。 相似文献
10.
阐述了宿根花卉的特点及其在南京江宁科学园绿地中的应用,探讨了宿根花卉养护管理中存在的问题,对宿根花卉应用前景进行了展望。 相似文献
11.
Identification of defect position in a wooden beam from the power spectrum of longitudinal vibration
The inverse solution procedure that enables the identification of the defect position in a beam from the resonance frequency
was exploited. Resonance frequency shifts of a power spectrum due to defects in a longitudinally vibrating beam when both
ends are free were investigated by both numerical and experimental analysis. Calculation by a transfer matrix method showed
that the frequency shift was large when the defect position coincides with a node of vibration and that no shift occurs when
it coincides with a loop of vibration. The frequency shift could be approximated by a sinusoidal curve. Calculation results
agreed well with those of the experiment in which artificial round holes were drilled as the defect model. Experimental equations
predicting the amount of the frequency shift in function of the defect position were obtained. In the inverse procedure, the
defect position was determined by comparing the resonance frequencies between the experimental and estimated power spectra
so that the coincidence factor S(x) became a minimum. The results showed the validity of the proposed method to identify the defect positions of fewer than
two predominant defects. 相似文献
12.
13.
14.
基于OTSU算法与数学形态学的木材缺陷图像分割 总被引：3，自引：0，他引：3
在木材分选过程中,图像缺陷分割技术占有重要的地位,能否精确提取缺陷轮廓会直接影响到分选的准确率.本文讨论提取木材表面缺陷图像的方法,应用OTSU算法与数学形态学相结合的方法对缺陷图像进行分割,最终提取出缺陷边缘.实验表明,经过OTSU算法和数学形态学进行图像分割,最后得到的木材缺陷图像更加清晰、连贯,提高了图像的可视性和准确性. 相似文献
15.
16.
Laureano RG Lazo YO Linares JC Luque A Martínez F Seco JI Merino J 《Tree physiology》2008,28(11):1721-1728
We tested whether growth and maintenance costs of plant organs vary with environmental stress. Quercus ilex L. seedlings from acorns collected from natural populations in the northern Iberian Peninsula and in a lower elevation and putatively less stressful habitat in the southern Iberian Peninsula were grown in pots under the same conditions. Growth and maintenance respiration were measured by CO(2) exchange. Young leaves from 5-month-old seedlings of both populations had similar mean specific leaf areas, nitrogen and carbon concentrations and specific growth rates, and almost identical growth costs (1.26 g glucose g(-1)). Leaf maintenance cost was higher in northern than in the southern population (27.3 versus 22.4 mg glucose g(-1) day(-1), P < 0.01). In both populations, leaf maintenance cost decreased by 90% as leaves aged, but even in mature leaves, the maintenance cost was higher in the northern population than in the southern population (3.38 versus 2.53 mg glucose g(-1) day(-1), P < 0.01). The growth costs of fine roots < 1 mm in diameter were similar in the two populations (1.20 g glucose g(-1)), whereas fine root maintenance cost was higher in the northern population than in the southern population (9.86 versus 7.45 mg glucose g(-1) day(-1); P < 0.05). The results suggest that the cost of organ maintenance is related to the severity of environmental stress in the native habitat. Because the observed differences in both leaves and roots were constitutive, the two populations may be considered ecotypes. 相似文献
17.
杉木人工林不同造材方式的效果分析 总被引：1，自引：1，他引：1
以福建顺昌130株杉木人工林采伐样木资料为基础,采用7种不同的造材方式进行实际造材,对不同造材方式的出材率和平均销售单价进行比较,分析结果表明,不同造材方式出材率、平均销售单价之间均有显著差异。采用第7种造材方式(遇到根部有缺陷的,则截1 m段头,4 m段造材,根部无缺陷的,则不截头,4 m段造材)出材率和平均销售单价均最大,为最佳的造材方式。 相似文献
18.
传感器数量对应力波检测原木内部缺陷精度的影响 总被引：1，自引：0，他引：1
木材无损检测技术是高效利用木材的方法之一.该文阐述了应力波法检测木材缺陷的原理,分析了传感器数量对图像的拟合度和误差率两个指标的影响.结果表明,当原木直径在20～40cm范围内时,若需对原木缺陷进行精确测量,要求图像拟合度接近90%和误差率在0.1左右时,至少需12个传感器才能满足要求;当不需要对原木缺陷进行精确测量,只需确定缺陷的大致位置时,宜选用10个传感器进行测量;当仅仅需要判断原木是否存在缺陷时,选用6个传感器就能满足要求.图3表4参8. 相似文献
19.
Over a three-year period, CO(2) exchange rates were measured continuously on the aboveground parts of a 13-year-old hinoki (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.) tree in the field, using an open gas-exchange system tracking ambient temperature. The relationship between daily aerial respiratory consumption and daily gross production, which was analyzed monthly, closely resembled McCree's equation. The value of the coefficient of growth respiration ranged between 0.0 in winter and 0.16 in summer and increased with increasing monthly mean temperature. A clockwise loop was observed for monthly change in the relationship between the coefficient of growth respiration and temperature. Maintenance respiration could be formulated as a power function of aboveground dry weight. The exponent of the equation ranged from 0.3 to 1.1. A value of 1.1 in May and June, when trees were growing most actively, indicated that maintenance respiration was directly proportional to aboveground weight. In March, April, July, and August, maintenance respiration was not proportional to aboveground weight, but it was closely proportional to surface area. The exponent value exhibited seasonal change with a clockwise loop in response to monthly average temperature. During the dormant season, respiration was used only for maintenance purposes, whereas during the growing season both growth and maintenance respiration occurred. Annual growth and maintenance respiration increased with increasing tree age. The average annual contribution to total respiratory consumption was 21% for growth respiration and 79% for maintenance respiration. 相似文献