变化树方法及应用

变化树适用于情况复杂的作业场所中复杂事件的分析。用链式依赖或汇合依赖或分叉依赖关系分析先行事件与事件之间的关系,绘制变化树;用手臂压伤事故说明了建立变比树的步骤。

会变化的树

一位父亲带着四个儿子生活在一个气候炎热的国家，这里的树木总是郁郁葱葱的。一天，父亲带着儿子们搬迁到另外一个不同的地方。这里一年有四个季节。来后不久，四个兄弟就听说当地有一种被称为紫荆的漂亮的树。他们非常想亲眼看看这种树。

基于过程蓝图的基本树变换操作研究

在过程蓝图工作已有的基础上,提出一些新的基本树变化操作,不变量和重构操作。这些工作更好地发挥了过程蓝图的树形结构优势,弥补了原有工作的不足,使过程蓝图的重构理论更加丰富。

基于GPS区域法的表面形貌分析方法研究

基于Maxwell的地貌学理论及GPS(geometrical product specification)区域法表面结构要素的规范特点,深入研究应用于表面形貌分析中的变化树及Wolf修剪技术;进一步规范区域、线、点等要素的Wolf修剪标准及表征表面结构的量化参数;并以实例阐述其在工程实践中的可行性。该表面分析技术不仅能便捷地实现微观表面形貌特定几何形状的提取和表面结构参数的量化,为微观表面几何形貌的分析开辟一条可行之路;同时也为新一代GPS区域标准的贯彻实施提供重要的技术支撑。

一种基于带权CAT的DDoS分布式检测方法

针对DCD(distributed change-point detection)方案存在受害端开销大、检测率低等问题,提出了一种基于带权CAT(change aggregation trees)的检测方案.采用分布式分级体系结构,将检测任务分布到互联网源端、中间网络和受害端,实现攻击的早期检测;利用CUSUM算法对微小变化的敏感性,在源端主机和中间网络的路由器处进行基于到达目标数据包数量的检测以及基于超级流聚合变化的检测;受害端进行基于域树权重的检测.实验和分析表明,CAT方案对UDP攻击的检测率从DCD的最高0.72提高到0.94,TCP攻击检测率也略有提高;网络的通信开销和受害端的存储开销从o(mnk)降为o(mk),受害端的计算开销从o(mn)降为o(m).系统在实现检测的同时,获得了攻击路径和攻击的准确位置,实现了DDoS攻击的分布式追踪.

村镇供水管网优化设计探讨

如何合理确定村镇供水管网敷设方案,关系到整个供水系统的安全性和可靠性。通过生成树变化法,将环状管网转化成树状管网,确定供水管网中最短供水路线,再计算最短供水路线下的最低综合费用、供水系统的经济管径,以确定最优管道敷设方案。根据该方法对四川省某镇供水系统进行了设计。

STUDY OF FLOW AND TEMPERATURE IN RESIN TRANSFER MOLDING PROCESS BY NUMERICAL MODEL

A mathematical model of resin flow and temperature variation in the filling stage of the resin transfer molding (RTM) is developed based on the control volume/finite element method (CV/FEM). The effects of the heat transfer and chemical reaction of the resin on the flow and temperature are considered. The numerical algorithm of the resin flow and temperature variation in the process of RTM are studied. Its accuracy and convergence are analyzed. The comparison of temperature variations between experimental results and model predictions is carried out for two RTM cases. Result shows that the model is efficient for evaluating the flow and temperature variation in the filling stage of RTM and there is a good coincidence between theory and experiment.

Changes in spatial variations of sap flow in Korean pine trees due to environmental factors and their effects on estimates of stand transpiration

It is difficult to scale up measurements of the sap flux density(J_S) for the characterization of tree or stand transpiration(E) due to spatial variations in J_S and their temporal changes.To assess spatial variations in the sap flux density of Korean pine(Pinus koraiensis) and their effects on E estimates,we measured the J_S using Granier-type sensors.Within trees,the J_S decreased exponentially with the radial depth,and the J_S of the east aspects were higher than those of the west aspects.Among trees,there was a positive relationship between J_S and the tree diameter at breast height,and this positive relationship became stronger as the transpiration demand increased.The spatial variations that caused large errors in E estimates(i.e.,up to 110.8 % when radial variation was ignored) had varied systematically with environmental factors systematic characteristics in relation to environmental factors.However,changes in these variations did not generate substantial errors in the E estimates.For our study periods,the differences in the daily E(E_D) calculated by ignoring radial,azimuthal and tree-to-tree variations and the measured E_D were fairly constant,especially when the daily vapor pressure deficit(D_D)was higher than 0.6 k Pa.These results imply that the effect of spatial variations changes on sap flow can be a minor source of error compared with spatial variations(radial,azimuthal and tree-to-tree variations) when considering E estimates.

Genetic Variation and Differentiation of Larix decidua Populations in Swiss Alps

Genetic diversity within and among six subpopulations of Larix decidua Mill. from two altitudinal transects of Swiss Alps was investigated using 6 enzyme systems coding for 8 loci. Globally, the mean proportion of polymorphic loci was 22.9%, the average number of alleles per locus was 1.3, and the mean expected heterozygosity was 0.095. Only 5.8% of the genetic variation resided among populations. The mean genetic distance was 0.006. Several significant differences of gene frequencies were found between different age classes. Positive values of the species mean fixation index observed in this study suggested a considerable deficit of heterozygotes in the populations of L. decidua of Swiss Alps. At one of the sites (Arpette), the highest subpopulation in elevation gave the lowest level of genetic diversity (as evidenced by the lowest proportion of polymorphic loci and the lowest mean expected heterozygosity) and the largest value of genetic distance when compared to other subpopulations. The genetic differences between the highest subpopulation and the other ones suggest that the founder effect may be an important factor influencing genetic differentiation of L. decidua populations at Arpette transect.

NDVI Variation of Tree Rings between March and May since 1915 in the Eastern Part of the Qilian Mountains of China

[Objective] The aim was to analyze the correlation between tree-ring width of Picea crassifolia in the east of Qilian Mountains and the precipitation, temperature and the normalized difference vegetation index (NDVI). [Method] The correlation analysis and the regression analysis were used in this study. [Result] The tree-ring width was significantly correlated with the autumn precipitation and the spring average NDVI. The conversion equation between tree-ring width and spring NDVI (R2 = 48.5% , R2adj =46.2% , F =21.627, P <0.001) was developed and NDVI sequence was reconstructed during the period 1915 -2007. The drought in the 1920s was pronounced. Vegetation cover in the Qilian Mountains increased during the period 1922-1934, 1940-1957, 1965-1969, 1984-1988 and 1995-1997, but decreased during 1935 -1939, 1958 -1964, 1970 -1983, 1989 -1994 and 1998 -2005. [Conclusion] The reconstructed NDVI showed the drought evolution in the study area.

Curing mechanism of TDE-85/MeTHPA epoxy resin modified by polyurethane

Diglycidyl 4,5-epoxy tetrahydro phthalate/methyl tetrahydrophthalic anhydride （TDE-85/MeTHPA） epoxy resin modified by polyurethane （PU） was prepared with 1,4-butanediol （1,4-BDO）, trimethylol propane （TMP） and polyurethane prepolymer synthesized by polypropylene glycol and toluene diisocynate. Chemical reaction and curing mechanism of this system were discussed by incorporating the results of infra spectrum analysis. The results indicate that the epoxy polymeric network I is obtained by the curing reaction between TDE-85 and MeTHPA, while the PU polymeric network II is obtained by the chain-extended and crosslinking reaction between 1,4-BDO, TMP and polyurethane prepolymer（PUP）. The graft chemical bonds are formed between polymer networks I and II that therefore increase the degree of blend and compatibility between epoxy polymer and PU.

One-step process for production of biodiesel from Jatropha curcas L. seeds： Optimization using Response Surface Methodology （RSM）

Jatropha curcas L. （JCL） seeds were extracted and transesterified in-situ using supercritical methanol extraction in the absence of catalyst at different temperatures （200-280℃） and pressures （8-12 MPa）, and at a fixed reaction time of 30 min with seeds-to-methanol ratio of 1：40 w/v. Design of experiment approach using five-level-two-factors design of Response Surface Methodology （RSM） was used to observe the effect of two independent variables i.e. temperature and pressure and the percent of biodiesel yield which required 13 runs. For optimization of the variables, Central Composite Rotatable Design （CCRD） was used for regression analysis and analysis of variance （ANOVA）. The optimize conditions suggested by RSM were at T = 280℃ and P = 12.04 MPa. The predicted and experimental biodicsel yields were found to be 56.8% and 59.9%, respectively, with relatively small deviation errors of 1.59%.

Growth Analysis of Nyssa yunnanensis Saplings

The growth of Nyssa yunnanensis saplings in Guanping area was monitored in 2011, 2013 and 2015. The results showed that the average basal diameter growth rate during 2013-2015 was higher than that during 2011-2013, and that during 2009-2011 was lowest; the average height growth rates in the durations of 2011-2013 and 2013-2015 were basically the same, and that during 2009-2011 was relatively slow; the growth of diameter at breast height（DBH） in the duration of 2013-2015 was significantly higher than that in the duration of 2011-2013. Comprehensive and better nature-returning work, as well as long-term and stable funding, is required for the protection of Nyssa yunnanensis.

Vegetation and Community Changes of Elm (Ulmus pumila) Woodlands in Northeastern China in 1983-2011

Elm （Ulmus pumila）, widely distributed in the north temperate zone, contributes to a special savanna-like woodland in typical grassland region in the northeastern China. This woodland performs a variety of ecological functions and environmental signifi- cance, such as decreasing soil erosion, stabilizing sand dunes, preserving species diversity. However, in the last approximate 30 years, the species composition, productivity and distribution area of elm woodland has decreased severely. A series of studies have been carried out to find out whether the climate changes or human disturbances caused the degradation of elm woodland and how these factors af- fected elm woodland. In this study, undisturbed, plowing and grazing elm woodland were investigated in 1983 and 2011 by using Point-Centered Quarter method. The relationship between vegetation changes and environmental factors was analyzed by Bray-Curtis ordination. The results show that in 2011, species diversity and understory productivity of undisturbed elm woodland decrease slightly compared to those of undisturbed elm woodland in 1983. However, nearly 60% of the species is lost in the plowing and grazing elm woodland relative to the species undisturbed elm woodland in 1983. Interestingly, plowing stimulates the growth of elm and certain understory species through furrowing soil and accelerating soil nutrient turnover rate. Grazing disturbance not only leads to species loss and productivity decrease, but also induces changes in elm growth （small, short and twisted）. The mean age of the elm was 29 -4- 2 yr in undisturbed and plowing elm woodland, while only 15 yr in the grazing elm woodland. The results of Bray-Curtis ordination analysis show that all sample stands clustered to three groups： Group I including the undisturbed sample stands of 83UE （undisturbed elm wood- land in 1983） and l lUE （undisturbed elm woodland in 2011）; Group II including sample stands of PE （elm woodland disturbed by plowing）; Group III including samples stands of GE （elm woodland disturbed by grazing）. The results indicate that the long time distur- bance of the plowing and grazing have converted elm woodland to different community types. Climate change is not the primary reason causing the degradation of elm woodland, but plowing and grazing disturbance. Both plowing and grazing decrease the vegetation composition and species diversity. Grazing further decreases vegetation productivity and inhibits the growth of elm tree. Therefore, we suggest that reasonable plowing and exclusive grazing would be favorable for future regeneration of degraded elm woodland.

Characteristics of Cyanate Ester and Fluorenyl Epoxy-Based Polymer-Ceramic Composites

In the field of highly integrated printed circuit board （PCB）, the heat resistant substrate with low water absorption is very important material. To get the resin composition for the high functional substrate material with low moisture absorption and high glass transition temperature （Tg） simultaneously, a fluorenyl ＂Cardo＂ epoxy was incorporated into novolac cyanate ester resin. As an optimum curing agent for the fiuorenyl epoxy, methyl nadic anhydride （MNA） was selected. Silica powders as fillers were added into the resin composition. The partial replacement of the cyanate ester resin with the fluorenyl epoxy could reduce the moisture absorption with keeping high glass transition temperature over 300 ℃. The laminate, which was fabricated from prepregs made with 40 wt% silica-filled resin composition and glass fabric, showed high Tg of 317 ℃ and low moisture absorption of 0.57%.

Performance of Tree Species Growing on Tailings Dam Soils in Zambia： A Basis for Selection of Species for Re-vegetating Tailings Dams

To facilitate the development of the basis for the selection of plants for re-vegetating tailings in Zambia, an as sessment of the performance of tree species growing on tailings dams was conducted. The performance of species was determined in terms of relative density, frequency and importance value for each species. The study reveals variations in performance of species; for example in terms of importance values, Acacia polyacantha （33.5%）, Toona ciliata （21.4%）, Acacia sieberana （9.9%）, Bauhinia thonningii （9.1%） and Peltophorum africanum （8.3%） were the most dominant species. The dominance of these species on tailings dams demonstrates tolerance to railings dams conditions. The study recommends that emphasis must be placed on these species in re-vegetating tailings dams.

Acoustical Properties of Acetylated Wood

Many of the traditional woods used for musical instruments have been selected not only for their natural beauty but for the high content of waxes and resins that help increase water repellency of the wood but have little or no effect on stabilizing dimensions or vibrational properties. Moisture changes have a great negative effect on both the musical quality of wooden musical instruments and limit the length of time they can be played without loss of musical quality. It is possible to stabilize both the wood and the vibrational properties by chemically modifying the wood. One technology that can do this is the reaction of wood with acetic anhydride. Acetylation of wood slightly increases density, and slightly （about 5%） reduces both sound velocity and sound absorption when compared to unreactedwood. Acetylation does not change the acoustic converting efficiency. Acetylation reduces the amount of moisture in the cell wall decreasing the effect of moisture on the viscose properties of wood. This allows a wooded musical instrument to be played longer without having to let it dry out. This gives an instrument made from acetylated wood a greater range of moisture conditions it can be played in without losing tone quality. Acetylation also greatly stabilizes the physical dimensions of the wood. The major effect of acetylation of wood, therefore, is to stabilize acoustic properties. The technology can be applied to almost any wood though more easily to permeable types so non-traditional wood species can be used. A violin, a piano soundboard, a guitar, a recorder, a bagpipe chanter, and trumpet and trombone mouthpieces have been made using acetylated wood with very positive results. Several more wooden instruments made from acetylated wood are presently being made for further testing and early market development.

Effects of climate change on potential habitats of the cold temperate coniferous forest in Yunnan province, southwestern China

We built a classification tree （CT） model to estimate climatic factors controlling the cold temperate coniferous forest （CTCF） distributions in Yunnan province and to predict its potential habitats under the current and future climates, using seven climate change scenarios, projected over the years of 2070-2099. The accurate CT model on CTCFs showed that minimum temperature of coldest month （TMW） was the overwhelmingly potent factor among the six climate variables. The areas of TMW〈-4.05 were suitable habitats of CTCF, and the areas of -1.35 〈 TMW were non-habitats, where temperate conifer and broad-leaved mixed forests （TCBLFs） were distribute in lower elevation, bordering on the CTCF. Dominant species of Abies, Picea, and Larix in the CTCFs, are more tolerant to winter coldness than Tsuga and broad-leaved trees including deciduous broad-leaved Acer and Betula, evergreen broad- leaved Cyclobalanopsis and Lithocarpus in TCBLFs. Winter coldness may actually limit the cool-side distributions of TCBLFs in the areas between -1.35℃ and -4.05℃, and the warm-side distributions of CTCFs may be controlled by competition to the species of TCBLFs. Under future climate scenarios, the vulnerable area, where current potential （suitable ＋ marginal） habitats （80,749 km^2） shift to non-habitats, was predicted to decrease to 55.91% （45,053 km^2） of the current area. Inferring from the current vegetation distribution pattern, TCBLFs will replace declining CTCFs. Vulnerable areas predicted by models are important in determining priority of ecosystem conservation.

Quantitative Changes in Main Parameters of Secondary Xylem during Aging Process in Pinus bugeana

Quantitative changes in main parameters of secondary xylem during aging process were studied in four trees of Pinus bungeana collected from two different sites.No marked difference was found in the width of heartwood, transition zone and sapwood at four cardinal directions and a wider sapwood and a narrower heartwood were noted in fast grown trees than in slowly grown ones. Earlywood generally showed a higher percentage of aspirated pits than latewood regardless of the age and growth conditions of the trees in addition , the earliest dead cells and the last living cells in the marginal cells were found a bit earlier than those in the central cells. It thus seems appropriate to conclude that the death of cells results largely from decrease of fluid permeability as the number of aspirated pits increases during aging process.

A HYDROGEN BONDING ASSISTED CATALYST SCREENED OUT VIA COMBINATORIAL CHEMISTRY STRATEGY

Possibilities for enhancement of catalytic reaction rate by combining phase transfer catalysis and hydrogen bonding of the catalyst with the substrate and reagent were studied. A phase transfer catalyst library with sixty polystyrene-supported quaternary ammonium salt catalysts was synthesized. The reduction of acetophenone by NaBH, was used as the probing reaction to select out the most active catalyst in the library by using iterative method, which was the gel-type triethanolamine aminating strongly basic anion exchange resin with the crosslinking degree of 2% A hydrogen bonding assisted catalytic mechanism was proposed to explain the high catalytic activity of the catalyst.