基于非可加测度的一致性变异测度

建立在经典概率测度理论体系下的风险测度理论已经有了不少的研究成果,但在金融、保险市场中存在着许多的非可加风险,针对传统风险测度理论分析非可加风险的缺陷,研究了在Choquet积分理论基础上的风险变量空间为非可加测度空间的变异测度问题,证明了这种测度是共单调可加一致性的变异测度,给出了在Chance空间共单调可加一致性变异测度的表示定理,这些结论是对风险变异测度理论在非可加条件下的发展,对于分析非可加风险具有重要的理论价值与现实意义。

Effect of Water Salinity on the Spatial Variability of Soil and Plant Parameters

Spatial pattern and interdependence of different soil and plant parameters were examined in green bean field experiment carried out at the Mediterranean Agronomic Institute of Bari （MAIB）, Italy. The study aimed to identify the spatial distribution of soil and plant parameters and their relationship at transects scale. The experiment consisted of three transects of 30 m length and 4.2 m width, irrigated with three different salinity levels （1 dSm＂1, 3 dSm1, 6 dSml）. Soil measurements （electrical conductivity and soil water content） were monitored along each transect in 24 sites, using TDR probe installed vertically at soil surface. Water storage was measured by using Diviner sensor for calculating directly the evapotranspiration fluxes along the whole soil profile under the different salinity levels imposed during the experiment. In the same 24 sites, crop monitoring involved measurements of Leaf Area Index （LAI）, Osmotic Potential （OP）, Root length Density （RID） and Evapotranspiration fluxes （ET）. Soil and plant properties were analyzed using both classical and geostatistical methods which included descriptive statistics, semivariograms and cross-semivariograms. Results indicated that moderate to large spatial variability existed across the field for soil and plant parameters, especially under the 6 dSm1 salinity treatment. A relatively satisfactory fit of the experimental cross-semivariogram was obtained for the 6 dS1, thus indicating similar spatial structures of the pairs of compared variables. By contrast, the experimental cross-semivariograms observed under the 3 dS~ treatment indicated no significant correlation structure between the compared variables. Overall, the results observed in the 3 dSm-1 were not significantly different from those obtained in the 1 dSm-1 transect and suggested a general insensitivity of the crop response to those levels of salinity.

Effect of Soil Sampling Density on Detected Spatial Variability of Soil Organic Carbon in a Red Soil Region of China

Spatial variability of soil organic carbon (SOC) of different land use patterns and soil types was examined in a county-wide red soil region of South China,using six sampling densities,14,34,68,130,255,and 525 samples designed by the method of grid sampling in 6 different grid sizes,labeled as D14,D34,D68,D130,D255,and D525,respectively.The results showed that the coefficients of variation (CVs) of SOC decreased gradually from 62.8% to 47.4% with the increase in soil sampling densities.The SOC CVs in the paddy field change slightly from 30.8% to 28.7%,while those of the dry farmland and forest land decreased remarkably from 58.1% to 48.7% and from 99.3% to 64.4%,respectively.The SOC CVs of the paddy soil change slightly,while those of red soil decreased remarkably from 82.8% to 63.9%.About 604,500,and 353 (P < 0.05) samples would be needed a number of years later if the SOC change was supposedly 1.52 g kg-1,based on the CVs of SOC acquired from the present sampling densities of D14,D68,and D525,respectively.Moreover,based on the same SOC change and the present time CVs at D255,the ratio of samples needed for paddy field,dry farmland,and forest land should be 1:0.81:3.33,while the actual corresponding ratio in an equal interval grid sampling was 1:0.74:0.46.These indicated that the sampling density had important effect on the detection of SOC variability in the county-wide region,the equal interval grid sampling was not efficient enough,and the respective CV of each land use or soil type should be fully considered when determining the sampling number in the future.

HEART RATE VARIABILITY DURING HIGH-INTENSITY EXERCISE

The aim of this paper is to describe and analyse the behaviour of heart rate variability(HRV)during constant-load,high-intensity exercise using a time frequency analysis(Wavelet Transform).Eleven elite cyclists took part in the study(age:18.6±3.0 years;VO_(2max):4.88±0.61 litres·min^(-1)).Initially,all subjects performed an incremental cycloergometer test to determine load power in a constant load-test(379.55±36.02 W;89.0%).HRV declined dramatically from the start of testing(p<0.05).The behaviour of power spectral density within the LF band mirrored that of total energy,recording a significant decrease from the outset LF peaks fell rapidly thereafter,remaining stable until the end of the test.HF-VHF fell sharply in the first 20 to 30 seconds.The relative weighting(%) of HF-VHF was inverted with the onset of fatigue,[1.6%at the start,7.1(p<0.05) at the end of the first phase,and 43.1%(p<0.05) at the end of the test].HF-VHF_(peak) displayed three phases:a moderate initial increase,followed by a slight fall,thereafter increasing to the end of the test.The LF/HF-VHF ratio increased at the start,later falling progressively until the end of the first phase and remaining around minimal values until the end of the test.