Evaluation method of cracking resistance of lightweight aggregate concrete

The cracking behavior of lightweight aggregate concrete(LWAC) was investigated by mechanical analysis, SEM and cracking-resistant test where a shrinkage-restrained ring with a clapboard was used. The relationship between the ceramsite type and the cracking resistance of LWAC was built up and compared with that of normal-weight coarse aggregate concrete(NWAC). A new method was proposed to evaluate the cracking resistance of concrete, where the concepts of cracking coefficient ζt(t) and the evaluation index Acr(t) were proposed, and the development of micro-cracks and damage accumulation were recognized. For the concrete with an ascending cracking coefficient curve, the larger Acr(t) is, the lower cracking resistance of concrete is. For the concrete with a descending cracking coefficient curve, the larger Acr(t) is, the stronger the cracking resistance of concrete is. The evaluation results show that in the case of that all the three types of coarse aggregates in concrete are pre-soaked for 24 h, NWAC has the lowest cracking resistance, followed by the LWAC with lower water absorption capacity ceramsite and the LWAC with higher water absorption capacity ceramsite has the strongest cracking resistance. The proposed method has obvious advantages over the cracking age method, because it can evaluate the cracking behavior of concrete even if the concrete has not an observable crack.

An enhanced landscape aggregation index

The aggregation index (AI) is a classical ecology calculation method, which has been widely used for measuring the aggregation level of spatial patterns within a landscape scale in landscape ecological studies. However, it has certain limitions. For instance, identical results can be obtained by AI even when the shape and number of landscape patches are totally different in two landscape units. Furthermore, the value of AI approaches to 1 if the landscape patch is large enough. To solve these problems, a logical limitation of the original AI equation was revised firstly. Secondly, an improved AI-J was developed based on the awareness of the effects of spatial distribution characteristics of patches and changing spatial scale on AI operation. Finally, the accuracy of AI and AI-J results were evaluated through a case study of city green patches in Chengdu, P. R. China. The results show that the calculated result of AI-J is more precise than that of AI and AI-J can be used to compare a certain landscape class under different spatial scales.

Spatial pattern of dominant tree species of the secondary monsoon rain forest in Lianjiang, Guangdong Province

Based on the summed dominance ratios of species in sample plots, the first three dominant species (Litchi chinensis, Elaeocarpus sylvestris and Canarium album) of the secondary monsoon rain forest of Mt. Royal Shoe in Lianjiang City, western Guangdong, were chosen for analyzing their spatial distribution pattern with the analysis methods such as frequency models of Poisson Distribution, Two Negative Items Distribution, Neyman Distribution, aggregate indexes, Taylor exponential equation and Iwao’s equation modeling. The results showed that these three species distributed in the congregate spatial pattern. Litchi chinensis and Elaeocarpus sylvestris had the characteristic of basic congregate population and attractive characteristic between their plants. The patterns for Canarium album may change and become more evenly distributed with the increase of density. The overall species spatial pattern also depended on the conservation of the secondary monsoon rain forest besides it was affected by the species reproduction characteristics and its growing environment. The congregate spatial patterns of three dominant species showed that it is important to conserve forest urgent conservation of the forest.

Preliminary Study on Spatial Distribution Pattern of Endoclyta signifer Walker Larva

[ Objective ] The paper was to study the spatial distribution of Endoclyta signifer Walker Larva. [ Method] The larvae distribution in eucalyptus planta- tion in Beiliu and Luchuan counties of Guangxi province were investigated. Ten standard plots were set, and the spatial distribution pattern of E. signifer larva was confirmed using six different aggregation indexes and regression model analysis method. [ Result] The larvae mainly distributed in the base of tnmk lower than 1 m, and its spatial distribution pattern was mainly aggregated distribution, which was caused by the enviromnental factors. The optimum sampling formula of E. signifer larva under different population densities was n = t2 （ 1.1/m ＋ 0. 674 4）/D2, and limited sequential sampling decision model was T＇0（n）, T＇0（n） = n ＋ 1. 332√n（ m0 = 1 ）. [ Conclusion] The result provided scientific basis for sampling and forecasting of E. signifier.

An Evaluation Approach for Operational Effectiveness of Anti-radiation Weapon

With the development of anti-radiation weapons,the effectiveness evaluation of anti-radiation weapons has been turned from the simple accuracy index to the integrated countermeasure capability.The research priority is how to access the combat effectiveness of anti-radiation weapons in a complex countermeasure environment.For the present situation of range test of anti-radiation weapons,a combat effectiveness assessment model based on non-linear index aggregation is proposed for anti-radiation weapons.And the corresponding index system model,index aggregation methods,index marking method and index weight determination are given.Finally,the simulation results verify the efficiency and feasibility of the proposed method.

Accumulation and relationship of metals in different soil aggregate fractions along soil profiles

Different aggregates vary in their ability to retain or adsorb metals in soil.Five soil profiles were sampled from different soil horizons and grouped,and the concentrations of Al,Mg,Ca,Fe,Mn,Cd,Cu and Pb were determined in six sizes of aggregates(>2,2-1,1-0.6,0.6-0.25,0.25-0.053,<0.053 mm).Significantly high(p<0.05)structural stability indexes(SSI)and ag-gregate stability indexes(ASI)were recorded in the topsoil horizon,which may be attributed to the high soil organic matter(SOM)content in aggregates from topsoil.In addition,ASI and SSI were positively correlated(r=0.569,p<0.05)with each other,which indicated that the stability of soil aggregates could contribute to the structural stability of bulk soil.Moreover,accumulation factors(AF),principal component analysis(PCA)and Pearson's correlation co-efficients were used for metal element assessment.The results indicated that SOM was not a key factor affecting the accumulation of Ca,Mg,Al,Fe,Mn,Pb,Cd and Cu in soil aggre-gates.In general,AF values for metal elements in microaggregates(<0.25 mm)were high,which showed that metals preferred to accumulate in fine soil aggregates.The PCA and Pearson's correlation coefficients indicated that soil parent materials primarily controlled the distribution of Al,Ca,Fe,Mg and Mn,while materials derived from technogenic sources have important impacts on the distribution of Cd,Cu and Pb in soil aggregates along the soil profile.