Cross-ice acoustic information transmission is an effective means of communication in polar sea areas covered by ice.However,the channel is extremely complicated because of the combined influence of water,ice,and air....Cross-ice acoustic information transmission is an effective means of communication in polar sea areas covered by ice.However,the channel is extremely complicated because of the combined influence of water,ice,and air.Based on the normalmode theory,this paper establishes a cascade acoustic channel(CAC)model for the transmission of underwater acoustic waves across ice layer.The model can calculate the displacement response of the ice layer’s upper surface by separating the upward waves from normal modes in the water and multiplying it by a transmission coefficient matrix.The relationship between the displacement response of the upper surface of ice layer and the acoustic frequency is calculated by the finite-element method,and the calculation result was consistent with that of the CAC model.To verify the applicability of the model,a cross-ice acoustic communication experiment was conducted in Songhua River in January 2019.Experimental results show the energy of the acoustic signals received by geophones is closely related to sound frequency and crossice acoustic communication is feasible.The result of present research is important for understanding crossice acoustic channel characteristics and developing future cross-ice acoustic communication in polar sea areas.展开更多
Based on the results of multipurpose regional geochemical surveys of the Guizhou Province, geochemical characteristics of soil Se and Se-rich land resources in the central area of Guiyang City were studied and evaluat...Based on the results of multipurpose regional geochemical surveys of the Guizhou Province, geochemical characteristics of soil Se and Se-rich land resources in the central area of Guiyang City were studied and evaluated.Major conclusions are as follows:(1) the Se content in surface soil of the central area of Guiyang City was 0.17–2.89 mg kg^(-1), and the average was 0.78 mg kg^(-1), which were respectively 2.6 and 3.9 times of the national background value of soil and the world background value of soil.The Se content in deep soil was 0.11–1.48 mg kg^(-1), and the average was 0.44 mg kg^(-1), which were respectively 1.5 and2.2 times of the national background value of soil and the world background value of soil. The soil Se content decreased with the increase in the soil depth on the vertical profile, and the surface soil had a higher Se content.(2)Distribution of Se content was mainly affected by parent material, physicochemical properties of soil and other components, soil type, and land use type. Parent material played a key role, as the soil Se content was mainly originated from parent rock and increased with the background value of Se in parent rock, physicochemical properties of soil and other components had certain influences upon the Se content. Se was shown to have a significant linear positive correlation with S and organic carbon but no significant correlation with p H value. Se content varied with different types of soil as follows: skeleton soil > yellow soil > paddy soil > limestone soil > purple soil. Land use type also hadcertain influences upon the soil Se content as follows: dry land > construction land > garden plot > grassland =garden plot > forest land.(3) Taking 0.4 mg kg^(-1)B x(Se) <3.0 mg kg^(-1) as the standard for Se-rich soil, Se-rich soil of the study area covered an area of 2224 km^2 and 92.5% of the total area; the remaining is general soil. The study area had no Se-excess soil. Therefore, the central area of Guiyang City has a high proportion of Se-rich land, a large area of Serich land resources, and a moderate selenium enrichment strength, which have been rarely seen anywhere and provide advantageous resources for the development of Se-rich featured agriculture.展开更多
基金This research was funded by the National Key R&D Program of China(2018YFC1405900)The National Natural Science Foundation of China(Grant No.61631008 and No.51779061)+2 种基金the Fok Ying-Tong Education Foundation,China(Grant,No.151007)The Heilongjiang Province Outstanding Youth Science Fund(JC2017017)and the Innovation Special Zone of National Defense Science and Technology.
文摘Cross-ice acoustic information transmission is an effective means of communication in polar sea areas covered by ice.However,the channel is extremely complicated because of the combined influence of water,ice,and air.Based on the normalmode theory,this paper establishes a cascade acoustic channel(CAC)model for the transmission of underwater acoustic waves across ice layer.The model can calculate the displacement response of the ice layer’s upper surface by separating the upward waves from normal modes in the water and multiplying it by a transmission coefficient matrix.The relationship between the displacement response of the upper surface of ice layer and the acoustic frequency is calculated by the finite-element method,and the calculation result was consistent with that of the CAC model.To verify the applicability of the model,a cross-ice acoustic communication experiment was conducted in Songhua River in January 2019.Experimental results show the energy of the acoustic signals received by geophones is closely related to sound frequency and crossice acoustic communication is feasible.The result of present research is important for understanding crossice acoustic channel characteristics and developing future cross-ice acoustic communication in polar sea areas.
基金supported by outstanding science and technology education personnel special funds of Guizhou Province (Specific words in Guizhou Province (2012)No.27)National multipurpose regional geochemical survey Project (GZTR20070110)
文摘Based on the results of multipurpose regional geochemical surveys of the Guizhou Province, geochemical characteristics of soil Se and Se-rich land resources in the central area of Guiyang City were studied and evaluated.Major conclusions are as follows:(1) the Se content in surface soil of the central area of Guiyang City was 0.17–2.89 mg kg^(-1), and the average was 0.78 mg kg^(-1), which were respectively 2.6 and 3.9 times of the national background value of soil and the world background value of soil.The Se content in deep soil was 0.11–1.48 mg kg^(-1), and the average was 0.44 mg kg^(-1), which were respectively 1.5 and2.2 times of the national background value of soil and the world background value of soil. The soil Se content decreased with the increase in the soil depth on the vertical profile, and the surface soil had a higher Se content.(2)Distribution of Se content was mainly affected by parent material, physicochemical properties of soil and other components, soil type, and land use type. Parent material played a key role, as the soil Se content was mainly originated from parent rock and increased with the background value of Se in parent rock, physicochemical properties of soil and other components had certain influences upon the Se content. Se was shown to have a significant linear positive correlation with S and organic carbon but no significant correlation with p H value. Se content varied with different types of soil as follows: skeleton soil > yellow soil > paddy soil > limestone soil > purple soil. Land use type also hadcertain influences upon the soil Se content as follows: dry land > construction land > garden plot > grassland =garden plot > forest land.(3) Taking 0.4 mg kg^(-1)B x(Se) <3.0 mg kg^(-1) as the standard for Se-rich soil, Se-rich soil of the study area covered an area of 2224 km^2 and 92.5% of the total area; the remaining is general soil. The study area had no Se-excess soil. Therefore, the central area of Guiyang City has a high proportion of Se-rich land, a large area of Serich land resources, and a moderate selenium enrichment strength, which have been rarely seen anywhere and provide advantageous resources for the development of Se-rich featured agriculture.
