检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

农业机器的随动控制导航

电子机械工程 2000年第5期16卷 30-33页

作者：应火冬 carr-west M Matin P 杭州市中国水稻研究所 310006 英国Writtle农学院

在一台试验用拖拉机上设计了一个由机械、液压和电子控制器组成的、以实现农业田间环境下机器自动引导行走为目标的随动控制系统。模拟试验和田间试验表明 ,这一控制系统具有容忍来自断续、不匀称引导基准的噪声干扰的能力 ,可以比较精... 详细信息

在一台试验用拖拉机上设计了一个由机械、液压和电子控制器组成的、以实现农业田间环境下机器自动引导行走为目标的随动控制系统。模拟试验和田间试验表明 ,这一控制系统具有容忍来自断续、不匀称引导基准的噪声干扰的能力 ,可以比较精确地引导试验车沿植物边界运动 ,也可以边界错位后自动跟随新边界 ;通过调低系统增益和优选死区大小 ,可以提高随动控制性能。

关键词：拖拉机随动控制系统农业机器导航

Effects of site productivity on individual tree maximum basal area growth rates of Eucalyptus pilularis in subtropical Australia

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2023年第6期34卷 1659-1668页

作者： P.W.west Forest Research Centre Southern Cross UniversityLismoreNSW 2480Australia

Inventory data were available from 96 plots of even-aged,monoculture,tall-open forests of Eucalyptus pilularis Smith,aged 2-63 years,growing in sub-tropical regions along the east coast of Australia.A model was developed relating the maximum possible stem basal area growth rate of individual trees to their stem basal *** any tree size,this maximum increased as site productivity ***,the size at which this maximum occurred decreased as productivity *** research has shown that,at any stand age,trees of a particular stem basal area are taller on more productive sites than on less productive *** trees incur greater respiratory costs to ensure maintenance of the photo synthetic capacity of their canopies;this reduces their growth *** was concluded that trees with larger basal areas will have the maximum possible growth rate on a less productive site,whilst trees with smaller basal areas will have the maximum possible on a more productive *** model developed may constitute the first stage of a complete individual tree growth model system to predict wood yields from these forests.

关键词： Growth model Individual tree Maximum growth rate Eucalyptus pilularis Physiological eff ects

Do increasing respiratory costs explain the decline with age of forest growth rate?

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2020年第3期31卷 693-712页

作者： P.W.west Forest research centre southern cross universitylismorensw 2480australia

Once forests have achieved a full canopy, their growth rate declines progressively with age. This work used a global data set with estimates from a wide range of forest types, aged 20-795 years, of their annual photosynthetic production(gross primary production, GPP) and subsequent above-plus below-ground biomass production(net primary production, NPP). Both GPP and NPP increased with increasing mean annual temperature and precipitation. GPP was then unrelated to forest age whilst NPP declined progressively with increasing age. These results implied that autotrophic respiration increases with age. It has been proposed that GPP should decline in response to increasing water stress in leaves as water is raised to greater heights as trees grow taller with age. However, trees may make substantial plastic adjustment in mor phology and anatomy of newly developing leaves, xylem and fi ne roots to compensate for this stress and maintain GPP with age. This work reviews the possibilities that NPP declines with age as respiratory costsincrease progressively in, any or all of, the construction and maintenance of more complex tissues, the maintenance of increasing amounts of live tissue within the sapwood of stems and coarse roots, the conversion of sapwood to hear twood, the increasing distance of phloem transport, increased turnover rates of fine roots, cost of supporting very tall trees that are unable to compensate fully for increased water stress in their canopies or maintaining alive competitively unsuccessful small trees.

关键词： Primary production Photosynthesis Respiration Biomass growth Ageing

Problems with models assessing influences of tree size and inter-tree competitive processes on individual tree growth:a cautionary tale

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2022年第2期33卷 565-577页

作者： P.W.west D.A.Ratkowsky Forest Research Centre Southern Cross UniversityLismoreNSWAustralia Tasmanian Institute of Agriculture University of TasmaniaHobartTASAustralia

In forest growing at any one site, the growth rate of an individual tree is determined principally by its size, which reflects its metabolic capacity, and by competition from neighboring trees. Competitive effects of a tree may be proportional to its size;such competition is termed ‘sym-metric’ and generally involves competition below ground for nutrients and water from the soil. Competition may also be ‘asymmetric’, where its effects are disproportionate to the size of the tree;this generally involves competition above ground for sunlight, when larger trees shade smaller, but the reverse cannot occur. This work examines three model systems often seen as exemplars relating individual tree growth rates to tree size and both competitive processes. Data of tree stem basal area growth rates in plots of even- aged, monoculture forest of blackbutt (Eucalyptus pilularis Smith) growing in sub-tropical eastern Australia were used to test these systems. It was found that none could distin-guish between size and competitive effects at any time in any one stand and, thus, allow quantification of the contribution of each to explaining tree growth rates. They were prevented from doing so both by collinearity between the terms used to describe each of the effects and technical problems involved in the use of nonlinear least-squares regression to fit the models to any one data set. It is concluded that quite new approaches need to be devised if the effects on tree growth of tree size and competitive processes are to be quantified and modelled successfully.

关键词： Symmetric competition Asymmetric competition Tree growth rate Growth modeling Nonlinear modeling

Dynamic expression of Slit1–3 and Robo1–2 in the mouse peripheral nervous system after injury

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2020年第5期15卷 948-958页

作者： Bing Chen Lauren carr Xin-Peng Dun Department of Neurology The Affiliated Huaian No.1 People’s Hospital of Nanjing Medical UniversityHuai’anJiangsu ProvinceChina Plymouth University Peninsula Schools of Medicine and Dentistry PlymouthUK The Co-innovation Center of Neuroregeneration Nantong UniversityNantongJiangsu ProvinceChina

The Slit family of axon guidance cues act as repulsive molecules for precise axon pathfinding and neuronal migration during nervous system development through interactions with specific Robo *** we previously reported that Slit1–3 and their receptors Robo1 and Robo2 are highly expressed in the adult mouse peripheral nervous system,how this expression changes after injury has not been well ***,we constructed a peripheral nerve injury mouse model by transecting the right sciatic *** 14 days after injury,quantitative real-time polymerase chain reaction was used to detect mRNA expression of Slit1–3 and Robo1–2 in L4–5 spinal cord and dorsal root ganglia,as well as the sciatic *** analysis was performed to examine Slit1–3,Robo1–2,neurofilament heavy chain,F4/80,and vimentin in L4–5 spinal cord,L4 dorsal root ganglia,and the sciatic ***-expression of Slit1–3 and Robo1–2 in L4 dorsal root ganglia was detected by in situ *** addition,Slit1–3 and Robo1–2 protein expression in L4–5 spinal cord,L4 dorsal root ganglia,and sciatic nerve were detected by western blot *** results showed no significant changes of Slit1–3 or Robo1–2 mRNA expression in the spinal cord within 14 days after *** the dorsal root ganglion,Slit1–3 and Robo1–2 mRNA expression were initially downregulated within 4 days after injury;however,Robo1–2 mRNA expression returned to the control level,while Slit1–3 mRNA expression remained upregulated during regeneration from 4–14 days after *** the sciatic nerve,Slit1–3 and their receptors Robo1–2 were all expressed in the proximal nerve stump;however,Slit1,Slit2,and Robo2 were barely detectable in the nerve bridge and distal nerve stump within 14 days after ***3 was highly ex-pressed in macrophages surrounding the nerve bridge and slightly downregulated in the distal nerve stump within 14 days after ***1 was upregulated in vimentin-positive cells and migrating S

关键词： dorsal root ganglion nerve regeneration neural regeneration peripheral nerve Robo 1 Robo 2 sciatic nerve Slit1 Slit2 Slit3

SYNTHESIS AND CROSSLINKING OF LIQUID ORGANOSILANE POLYMERS

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 1986年第1期4卷 24-34页

作者：张兴华,Robert west Institute of Chemistry Academia Sinica Beijing Department of Chemistry University of Wisconsin Madison W1 53706 U.S.A.

Liquid organosilane polmers have been synthesized by sodium coupling of diorganodichloro-silanes with diphenylmethylchlorosilane in toluene. These polysilanes can be formed into desiredshape by potting, casting or coating and crosslinked under ultraviolet irradiation in the presenceof multifunctional vi?ylsilanes. The molecular weight distributions, infra-red, ultraviolet andnuclear magnetic resonance spectra for the organosilane polymers have been described.

关键词： Poly SYNTHESIS AND CROSSLINKING OF LIQUID ORGANOSILANE POLYMERS OC GPC

Feature-aligned segmentation using correlation clustering

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Computational Visual Media 2017年第2期3卷 147-160页

作者： Yixin Zhuang Hang Dou Nathan carr Tao Ju National Digital Switching System Engineering & Technological Research Center Washington University in St. Louis Adobe

We present an algorithm for segmenting a mesh into patches whose boundaries are aligned with prominent ridge and valley lines of the shape. Our key insight is that this problem can be formulated as correlation clustering(CC), a graph partitioning problem originating from the data mining *** formulation lends two unique advantages to our method over existing segmentation methods. First,since CC is non-parametric, our method has few parameters to tune. Second, as CC is governed by edge weights in the graph, our method offers users direct and local control over the segmentation result. Our technical contributions include the construction of the weighted graph on which CC is defined, a strategy for rapidly computing CC on this graph, and an interactive tool for editing the segmentation. Our experiments show that our method produces qualitatively better segmentations than existing methods on a wide range of inputs.

关键词： mesh segmentation correlation clustering(CC) feature lines

ORGANOSILANE POLYMERS: OXIDATION—CROSSLINKABLE CYCLOTETRAMETHYLENESILYLENE POLYMER AND COPOLYMERS

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 1987年第2期5卷 156-161页

作者：张兴华 Robert west Institute of Chemistry Academia Sinica Beijing China Department of Chemistry University of Wisconsin Madison U.S.A.

Polysilane polymers containing cyclotetramethylenesilylene units were synthesized by sodium coupling of diorganodichlorosilanes in toluene. These polymers are soluble in common solvents, can be formed into a variety of shapes by molding, castihg, coating or potting. They can be crosslinked by irradiation and oxidation at moderate or room temperature.

关键词： Polysilane polymers Cyclotetramethylenesilylene polymer

ORGANOSILANE POLYMERS: SYNTHESIS AND CROSSLINKING OF FORMABLE POLYMERS CONTAINING PHENYLSILYLENE UNITS

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 1987年第3期5卷 240-253页

作者：张兴华,Robert west Institute of Chemistry Academia Sinica Beijing) Department of Chemistry University of Wisconsin Madison U. S. A.

Polysilane polymers which contain silicon hydride units in the chain were synthesized by sodium coupling of PhHSiCl2with R1R2SiCl2in toluene （R1and R2alkyl, aryl or aralkyl）, followed by termination with a monochlorosilane and neutralization with sodium bicarbonate solution. These polymers are soluble in common solvents and can be formed into a variety of shapes by molding, casting, coating or potting. This class of polymers can be crosslinked by oxidation and irradiation, or by reaction with a multifunctional vinylsilane in th presence of platinum complexes.

关键词： Organosilane Polymer crosslinking phenylsilylene