Based on the absolute and relative gravity observations in North China from 2009 to 2014,spatial dynamic variations of the regional gravity field are obtained. We employed the Euler deconvolution method and the theore...Based on the absolute and relative gravity observations in North China from 2009 to 2014,spatial dynamic variations of the regional gravity field are obtained. We employed the Euler deconvolution method and the theoretical model to get the best estimates of parameters. Gravity field change caused by the depth and distribution in North China is calculated by back analysis. The results show the structural index that equals 1 is suitable for inversion of the gravity variation data. The inversion results indicate that the depths of anomaly field sources are spread over the Hetao fault. The research method of this paper can be used in the quantitative study on the field source and may shed new light on the interpretations of gravity change, and also provide quantitative basis for earthquake prediction index criterions based on the gravity change.展开更多
Background: To increase ecosystem resilience and biodiversity, the maintenance and improvement of structural and compositional diversity of forests has become an important goal in forest management for many forest own...Background: To increase ecosystem resilience and biodiversity, the maintenance and improvement of structural and compositional diversity of forests has become an important goal in forest management for many forest owners and jurisdictions. At the same time, future harvesting intensity (HI) may increase to meet the demand for woody biomass by an increasing bioeconomy sector. Yet, the influence of HI on forest structural diversity is largely unknown. Here, we address this issue by analyzing the relationship between HI and structural diversity based on large-scale national forest inventory (NFI) data, where the latter is quantified using a previously developed Forest Structure Index and HI is expressed as wood volume removal during the period 2002-2012 for the same inventory plots. Results: Our results show a surprisingly small impact of harvesting intensity on changes in structural diversity for most of the analysed types of forests. Only intense harvesting (> 80%-90% of initial growing stock) led to a significant reduction in structural diversity. At low to moderate HI most aspects of structural diversity were positively influenced. Only the quadratic mean DBH and the volume of large trees (≥ 40 cm DBH) were substantially negatively influenced at HI > 60% and 70% of initial growing stock, respectively. Conclusions: In several forest types, HI could be increased without a reduction in overall structural diversity. Hence, structural diversity in these selectively managed forests appears to be a very resistant forest property in relation to HI. Other indicators at stand and landscape scale may be needed to adjust levels of HI that are suited to maintain forest biodiversity.展开更多
Numerous approaches have been developed to quantify forest structure modules.A variety has measured each as part of stand attributes.This study was carried out in managed mixed stands in northern Iran.The objective wa...Numerous approaches have been developed to quantify forest structure modules.A variety has measured each as part of stand attributes.This study was carried out in managed mixed stands in northern Iran.The objective was to quantify stand structure and its variation before and after tree marking through the Gini index and structural triangle method.A full sampling inventory was taken in 2004 and 2014 at the beginning and end of a period,before and after tree marking operations in five stands.The results indicate that the Gini index was 39.5,62.2,43.0,82.0 and 74.0%forⅠ,Ⅱ,Ⅲ,ⅣandⅤstands respectively.Furthermore,approximate structural diameters were determined as a large category forⅠ,Ⅱ,ⅢandⅤstands while standⅡhad an intermediate-large class pre-tree marking to an intermediate-small class post-tree marking.The paired t-test results were not significant for tree numbers and growing stock changes for all species,and for beech,hornbeam,and velvet maple before and after tree harvesting in the whole stand.Therefore,the Gini index and the structural triangle method can be used for natural stand modeling,structural diversity designation,and for management practices in nature-oriented forestry strategies.展开更多
In the case of composite girders, an effective cooperation of both parts of the section is influenced by deformability of connectors. Limited flexural stiffness of welded studs, used commonly in bridge structures, doe...In the case of composite girders, an effective cooperation of both parts of the section is influenced by deformability of connectors. Limited flexural stiffness of welded studs, used commonly in bridge structures, does not provide full interaction of a steel beam and a concrete slab. This changes strain distribution in cross-sections of a composite girder and results in redistribution of internal forces in steel and concrete element. In the paper partial interaction index defined on the basis of a neutral axis position, which can be used for verification of steel-concrete interaction in real bridge structures rather than in specimens is proposed. The range of the index value changes, obtained during load testing of a typical steel-concrete composite beam bridge, is presented. The investigation was carried out on a motorway viaduct, consisting of two parallel structures. During the testing values of strains in girders under static and quasi-static loads were measured. The readings from the gauges were used to determine the index, characterizing composite action of the girders. Results of bridge testing under movable load, changing position along the bridge span is presented and obtained in-situ influence functions of strains and index values are commented in the paper.展开更多
A novel coupled quantum well structure - quasi-symmetric coupled quantum well （QSCQW） is proposed. In the case of low applied electric field （F = 25 kV/cm） and low absorption loss （a ≈ 100 cm^-1）, a large field...A novel coupled quantum well structure - quasi-symmetric coupled quantum well （QSCQW） is proposed. In the case of low applied electric field （F = 25 kV/cm） and low absorption loss （a ≈ 100 cm^-1）, a large field-induced refractive index change （for TE mode, △n = 0.0106; for TM mode, △n = 0.0115） is obtained in QSCQW structure at operating wavelength λ = 1550 nm. The value is larger by over one to two order of magnitude compared to that in a rectangular quantum well （RQW） and about 50% larger than that of five-step asymmetric coupled quantum well （FACQW） structure under the above work conditions.展开更多
基金funded by the Natural Science Foundation of China(61627824,41274083)the Youth Foundation of Earthquake Prediction(2017010227)
文摘Based on the absolute and relative gravity observations in North China from 2009 to 2014,spatial dynamic variations of the regional gravity field are obtained. We employed the Euler deconvolution method and the theoretical model to get the best estimates of parameters. Gravity field change caused by the depth and distribution in North China is calculated by back analysis. The results show the structural index that equals 1 is suitable for inversion of the gravity variation data. The inversion results indicate that the depths of anomaly field sources are spread over the Hetao fault. The research method of this paper can be used in the quantitative study on the field source and may shed new light on the interpretations of gravity change, and also provide quantitative basis for earthquake prediction index criterions based on the gravity change.
基金supported by a grant from the Ministry of Science,Research and the Arts of Baden-Württemberg(7533-10-5-78)to Jürgen Bauhussupport through the BBW For Werts Graduate Program
文摘Background: To increase ecosystem resilience and biodiversity, the maintenance and improvement of structural and compositional diversity of forests has become an important goal in forest management for many forest owners and jurisdictions. At the same time, future harvesting intensity (HI) may increase to meet the demand for woody biomass by an increasing bioeconomy sector. Yet, the influence of HI on forest structural diversity is largely unknown. Here, we address this issue by analyzing the relationship between HI and structural diversity based on large-scale national forest inventory (NFI) data, where the latter is quantified using a previously developed Forest Structure Index and HI is expressed as wood volume removal during the period 2002-2012 for the same inventory plots. Results: Our results show a surprisingly small impact of harvesting intensity on changes in structural diversity for most of the analysed types of forests. Only intense harvesting (> 80%-90% of initial growing stock) led to a significant reduction in structural diversity. At low to moderate HI most aspects of structural diversity were positively influenced. Only the quadratic mean DBH and the volume of large trees (≥ 40 cm DBH) were substantially negatively influenced at HI > 60% and 70% of initial growing stock, respectively. Conclusions: In several forest types, HI could be increased without a reduction in overall structural diversity. Hence, structural diversity in these selectively managed forests appears to be a very resistant forest property in relation to HI. Other indicators at stand and landscape scale may be needed to adjust levels of HI that are suited to maintain forest biodiversity.
基金conducted by support of research credit(No:89034)from the University of Tehran
文摘Numerous approaches have been developed to quantify forest structure modules.A variety has measured each as part of stand attributes.This study was carried out in managed mixed stands in northern Iran.The objective was to quantify stand structure and its variation before and after tree marking through the Gini index and structural triangle method.A full sampling inventory was taken in 2004 and 2014 at the beginning and end of a period,before and after tree marking operations in five stands.The results indicate that the Gini index was 39.5,62.2,43.0,82.0 and 74.0%forⅠ,Ⅱ,Ⅲ,ⅣandⅤstands respectively.Furthermore,approximate structural diameters were determined as a large category forⅠ,Ⅱ,ⅢandⅤstands while standⅡhad an intermediate-large class pre-tree marking to an intermediate-small class post-tree marking.The paired t-test results were not significant for tree numbers and growing stock changes for all species,and for beech,hornbeam,and velvet maple before and after tree harvesting in the whole stand.Therefore,the Gini index and the structural triangle method can be used for natural stand modeling,structural diversity designation,and for management practices in nature-oriented forestry strategies.
文摘In the case of composite girders, an effective cooperation of both parts of the section is influenced by deformability of connectors. Limited flexural stiffness of welded studs, used commonly in bridge structures, does not provide full interaction of a steel beam and a concrete slab. This changes strain distribution in cross-sections of a composite girder and results in redistribution of internal forces in steel and concrete element. In the paper partial interaction index defined on the basis of a neutral axis position, which can be used for verification of steel-concrete interaction in real bridge structures rather than in specimens is proposed. The range of the index value changes, obtained during load testing of a typical steel-concrete composite beam bridge, is presented. The investigation was carried out on a motorway viaduct, consisting of two parallel structures. During the testing values of strains in girders under static and quasi-static loads were measured. The readings from the gauges were used to determine the index, characterizing composite action of the girders. Results of bridge testing under movable load, changing position along the bridge span is presented and obtained in-situ influence functions of strains and index values are commented in the paper.
基金This work was supported by the National NaturalScience Foundation of China under Grant No. 60277034,60436020.
文摘A novel coupled quantum well structure - quasi-symmetric coupled quantum well （QSCQW） is proposed. In the case of low applied electric field （F = 25 kV/cm） and low absorption loss （a ≈ 100 cm^-1）, a large field-induced refractive index change （for TE mode, △n = 0.0106; for TM mode, △n = 0.0115） is obtained in QSCQW structure at operating wavelength λ = 1550 nm. The value is larger by over one to two order of magnitude compared to that in a rectangular quantum well （RQW） and about 50% larger than that of five-step asymmetric coupled quantum well （FACQW） structure under the above work conditions.
