共查询到20条相似文献，搜索用时 266 毫秒
1.
Laboratory experiments were conducted to investigate the evolution of interfacial internal solitary waves(ISWs) incident on a triangular barrier. ISWs with different amplitudes were generated by gravitational collapse. The ISW energy dissipation and turbulence processes were calculated as waves passed over the triangular barrier. Experimental results showed that ISWs were reflecting back off the triangular barrier, and shoaling ISWs led to wave breaking and mixing when waves propagated over the obstacle. Wave instability created the dissipation of energy as it was transmitted from waves to turbulence. The rate of ISW energy dissipation, the maximum turbulent dissipation, and the buoyancy diffusivity linearly increased with the increase in the incident wave energy. 相似文献
2.
Many observations show that in the Yellow Sea internal tidal waves (ITWs) possess the remarkable characteristics of internal Kelvin wave, and in the South Yellow Sea (SYS) the nonlinear evolution of internal tidal waves is one of the mechanisms producing internal solitary waves (ISWs), which is different from the generation mechanism in the case where the semidiurnal tidal current flows over topographic drops. In this paper, the model of internal Kelvin wave with continuous stratification is given, and an elementary numerical study of nonlinear evolution of ITWs is made for the SYS, using the generalized KdV model (GKdV model for short) for a continuous stratified ocean, in which the different effects of background barotropic ebb and flood currents are considered. Moreover, the parameterization of vertical turbulent mixing caused by ITWs and ISWs in the SYS is studied, using a parameterization scheme which was applied to numerical experiments on the breaking of ISWs by Vlasenko and Hutter in 2002. It is found that the vertical turbulent mixing caused by internal waves is very strong within the upper layer with depth less than about 30m, and the vertical turbulent mixing caused by ISWs is stronger than that by ITWs. 相似文献
3.
Large amplitude internal solitary waves (ISWs) often exhibit highly nonlinear effects and may contribute significantly to
mixing and energy transporting in the ocean. We observed highly nonlinear ISWs over the continental shelf of the northwestern
South China Sea (19°35′N, 112°E) in May 2005 during the Wenchang Internal Wave Experiment using in-situ time series data from
an array of temperature and salinity sensors, and an acoustic Doppler current profiler (ADCP). We summarized the characteristics
of the ISWs and compared them with those of existing internal wave theories. Particular attention has been paid to characterizing
solitons in terms of the relationship between shape and amplitude-width. Comparison between theoretical prediction and observation
results shows that the high nonlinearity of these waves is better represented by the second-order extended Korteweg-de Vries
(KdV) theory than the first-order KdV model. These results indicate that the northwestern South China Sea (SCS) is rich in
highly nonlinear ISWs that are an indispensable part of the energy budget of the internal waves in the northern South China
Sea. 相似文献
4.
Internal solitary waves (ISWs) always happen in marginal seas, where stable stratification exists. ISWs may carry large energy when they propagate and affect marine engineering constructions such as marine drilling platforms. Previous studies, including a large number of mooring observations and laboratory experiments, show the speed of ISWs will change when they pass by shelf slopes. Korteweg-de Vries (KdV) theory explain this phenomenon. In the paper, we use a laboratory experiment and a numerical model experiment to verify this theory. In the laboratory experiment, we injected two layers of water of different densities in a tank to simulate marine stratification and make ISWs. We use a CCD camera to record the whole process. The camera can take 16 photos per second. In the numerical experiment, we input the same original conditions as the laboratory one. The results of 18 different original conditions show the dimensionless factor d plays a key role in deciding the amplitudes and shapes of ISWs. The main conclusion also contains that small-amplitude waves match well with KdV theory while mKdV is better for largeamplitude waves. Whether the laboratory experiment or numerical experiment shows results with a high agreement. In future studies, we may use a numerical model with higher resolution to get analysis about phase speed and energy of ISWs. 相似文献
5.
Internal solitary waves(ISWs) are frequently observed in the area between Dongsha Island(DI) and Taiwan Island. However, there have been few in-situ observations southwest of DI. To improve our knowledge of ISWs in this area, we observed the ISWs over the continental shelf(115.4°E, 20.3°N) from Aug. 29 to Oct. 10, 2011 with temperature sensors and an acoustic Doppler current profiler(ADCP). The observations showed that the a fully developed ISW produced a current whose maximum westward velocity was 0.92 m/s and maximum northward velocity was 0.47 m/s. During the 41-day observation period the ISWs appeared for three periods with about 7-day gaps between each period. During each day, two types of ISWs were observed. The first type of wave arrived regularly diurnally at the same time each day, with a similar pattern to that of the type- a wave identified by Ramp et al.(2004). The second type arrived about 12 h after the first type and was delayed about 1 hour each day; this wave type was related to the type- b wave. Thus, our observations confirmed that both type- a and type- b waves can reach the area southwest of the DI. Moreover, the waves observed by the mooring propagated toward the directions of 270°–315° clockwise from true north, indicating obvious refraction from uneven topography around DI. 相似文献
6.
The propagation and fission process of internal solitary waves (ISWs) with amplitudes of about 170 m are simulated in the northeast of the South China Sea (NSCS) by using the generalized Korteweg-de Vries (KdV) equation under continuous stratification. More attention is paid to the effects of the ebb and flood background currents on the fission process of ISWs. This kind of background current is provided by the composed results simulated in terms of monthly mean baroclinic circulation and barotropic tidal current. It is found that the obtained relation of the number of fission solitons to the water depth and stratification is roughly in accordance with the fission law derived by Djordjevic and Redekopp in 1978; however, there exists obvious difference between the effects of the ebb and flood background currents on the wave-lengths of fission solitons (defined as the distance between two neighboring peaks of ISWs). The difference in nonlinearity coefficient α between the ebb and flood background currents is a main cause for the different wave-lengths of fission solitons. 相似文献
7.
Depression and elevation internal solitary waves in a two-layer fluid and their forces on cylindrical piles 总被引：1，自引：0，他引：1
Both large amplitude depression and elevation internal solitary waves (ISWs) were observed on the continental shelf of the northwest South China Sea (SCS) during the Wenchang Internal Wave Experiment. In this study, we investigate the characteristics of depression and elevation ISWs based on comparisons between observational results and internal wave theories. It is suggested that the large amplitude depression wave is better represented by the extended Korteweg-de Vries (EKdV) theory than by the KdV model, whereas the large amplitude elevation wave is in better agreement with the KdV equation than with the EKdV theory. Wave-induced forces on a supposed small-diameter cylindrical pile by depression and elevation waves are also estimated using the internal wave theory and Morison formula. The wave-induced force by elevation ISWs is rarely reported in the literature. It is found that the force induced by the elevation wave differs significantly from that by the depression wave, and the elevation wave generally produces greater force on the pile in the lower water column than the depression wave. These results show that ISWs in the study area can present a serious threat to ocean engineering structures, and should not be ignored in the design of oil platforms and ocean operations. 相似文献
8.
Zhi-wei Wang Qian Wang Lin Zhao Xiao-dong Wu Guang-yang Yue De-fu Zou Zhuo-tong Nan Guang-yue Liu Qiang-qiang Pang Hong-bing Fang Tong-hua Wu Jian-zong Shi Ke-qin Jiao Yong-hua Zhao Le-le Zhang 《山地科学学报》2016,13(6):1035-1046
In this paper,an updated vegetation map of the permafrost zone in the Qinghai-Tibet Plateau(QTP) was delineated.The vegetation map model was extracted from vegetation sampling with remote sensing(RS) datasets by decision tree method.The spatial resolution of the map is 1 km×1 km,and in it the alpine swamp meadow is firstly distinguished in the high-altitude areas.The results showed that the total vegetated area in the permafrost zone of the QTP is 1,201,751 km~2.In the vegetated region,50,260 km~2 is the areas of alpine swamp meadow,583,909 km~2 for alpine meadow,332,754 km~2 for alpine steppe,and 234,828 km~2 for alpine desert.This updated vegetation map in permafrost zone of QTP could provide more details about the distribution of alpine vegetation types for studying the vegetation mechanisms in the land surface processes of highaltitude areas. 相似文献
9.
城镇是创造物质和精神财富的主要空间载体,划定城镇开发边界,是推动城镇化发展由外延扩张式向内涵提升式转变重要手段.第三次国土调查是以土地资源为基础的调查,是国土空间规划的底图底数.通过梳理,第三次国土调查对城镇开发边界底数支撑包括土地利用现状、土地管理、土地成片开发以及耕地保护等方面.具体研究方法为运用Arcgis 10... 相似文献
10.
加强目标观测,服务防灾减灾 总被引：3，自引：0，他引：3
以深入浅出的方式介绍了目标观测的定义、历史、确定目标观测敏感区的方法,以及实施目标观测与防灾减灾的关系;并以欧洲中期天气预报中心目标观测业务化为例,简明地概括了目标观测的实施过程;结合国内目标观测研究现状,对中国目标观测的未来提出了看法。 相似文献
11.
SUNJilin WANGDongxiao 《中国海洋大学学报(英文版)》2004,3(1):17-22
1 Introduction TheindicesfortheAsianmonsoonhavebeenstud iedinmanyworks .Recently ,thechoiceofpropermonsoonindiceshasreceivedexceptionalattentionandraisedcontroversy (WebsterandYang ,1 992 ;Goswa mietal.,1 999;Goswami,2 0 0 0 ;Wang ,2 0 0 0 ) .Us ingzona… 相似文献
12.
党的执政能力建设是党建工作的重中之重,是促进中国特色社会主义事业发展的关键所在。基于高等教育在中国特色社会主义事业中的重要地位和高校党建对全党工作的重要性,探讨了党的执政能力建设与高校党建的关系,阐述党的执政能力建设思想对高校党建的指导意义,强调用党的执政能力建设思想指导高校党建实践的若干环节。高校以提高执政能力为重点推进党的建设关键是提高主体素质,核心是提高办学能力,目的是发展高等教育。 相似文献
13.
Influence of the Convection over the South China Sea on the Summer Precipitation of Shandong Province 总被引：2，自引：0，他引：2
1 Introduction ShandongProvince ,whichislocatedintheeastofChina ,consistspartlyofpeninsulaandpartlyofinlandwithatotalareaofabout 1 5 0 0 0 0km2 .Lyingfrom34°2 0′Nto 38°2 0′Nandfrom 1 1 4°4 0′Eto 1 2 2°4 0′E ,alltheareabelongstothemoderateregionandtothetypicalAsianmonsoonclimate .SoShandong’ssum merprecipitationaccountsforover 6 0 %oftheannualrainfall,andaccordinglyflood droughtdisastersmain lyoccurinsummer.Moreover,becauseitisgeographi callylocatedinthetransitionalareabetweenthe… 相似文献
14.
15.
傅学良 《广东海洋大学学报》2006,26(2):41-43
当今社会正面临日趋严重且类型众多的灾害,构成生态环境安全的巨大威胁。运用刑法武器维护环境安全成为各国普遍采用的法制手段,但是我国刑法在环境刑事责任的归责陈述、承担主体、归责因果关系以及环境刑事责任的实现等诸方面,并没有体现出与实践相适应的环境刑事责任理论。鉴于此,立足于环境安全视角,评述环境刑事责任的现状及发展。 相似文献
16.
傅学良 《广东海洋大学学报》2006,26(2):41-43
当今社会正面临日趋严重且类型众多的灾害，构成生态环境安全的巨大威胁。运用刑法武器维护环境安全成为各国普遍采用的法制手段，但是我国刑法在环境刑事责任的归责陈述、承担主体、归责因果关系以及环境刑事责任的实现等诸方面。并没有体现出与宴践相适应的环境刑事责任理论。鉴于此，立足于环境安全视角，评述环境刑事责任的现状及发展。 相似文献
17.
Studying the mechanical properties of the soil-root interface using the pullout test method 总被引：4，自引：0，他引：4
It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mechanical properties can be obtained through the pullout force and root slippage curve(F-S curve). About 120 Pinus tabulaeformis single roots whose diameters ranged from 1 mm to 10 mm divided into 6 groups based on different root embedment length(50 mm, 100 mm and 150 mm) and different load velocity(10 mm·min~(-1), 50 mm·min~(-1), 100 mm·min~(-1) and 300 mm·min~(-1)) were investigated using the pullout method. This study aims to explore the mechanical properties of the soil-root interface in the real conditions using the pullout test method. The results showed two kinds of pullout test failure modes during the experimental process: breakage failure and pullout failure. The results showed that the roots were easier to be broken when the root diameter was smaller or the loading speed was larger. The relationship between the maximum anchorage force and root diameter was linear and the linearly dependent coefficient(R~2) was larger than 0.85. The anchorage force increased with the root embedment length. An increase of 10%~(-1)5% for the maximumanchorage force was found when load speed increased from 10 to 300 mm.min~(-1). The mean peak slippage of the root was from 13.81 to 35.79 mm when the load velocity varied from 10 to 300 mm.min~(-1). The study will be helpful for the design of slopes reinforced by vegetation and in predicting risk of uprooting of trees, and will have practical benefits for understanding the mechanism of landslide. 相似文献
18.
Assessment of the ecological security in the three gorges reservoir area by using the ecological footprint method 总被引：3，自引：1，他引：2
Haiming Wang Hai’e Wang Hongyang Sun Xiaolan Wang Xiaoyong Liao Zhijian Chen Xianwei Li 《山地科学学报》2012,9(6):891-900
The ecological footprint concept and its calculation models are useful for the measurement of the sustainable level of social and economic development.The ecological security situation of the Three Gorges Reservoir Area(TGRA) was evaluated using this concept in this study.The construction of the Three Gorges Reservoir has led to the change in the ecology and immigration status of TGRA.The ecological footprint method is an important means to study the regional ecological security.Our results suggested that,by excluding the areas for biodiversity conservation(12% of the total land),the ecological footprint per capita was 0.57895 ha,which exceeded the ecological carrying capacity in TGRA.The total ecological deficit was found to be 11,522,193.34 ha,accounting for 95.02% of the ecological carrying capacity.These findings suggested that the ecological security of TGRA was not good.In order to compensate for the ecological deficit,it was essential to introduce natural resources from other regions. 相似文献
19.
20.
研究利用GPS观测资料解算ERP参数的方法。首先,利用全球近100个均匀分布、站址稳定的IGS测站的GPS观测数据解算地球自转参数,并将其与IGS相应产品进行比较,结果显示该解算方案可靠。其次,从实验数据和数理表示方面分析ERP参数解算过程中的轨道约束方案、先验ERP信息、站坐标数量对解算精度的影响,给出一些提高ERP参数解算精度的建议：对ECOM光压模型9参数中径、法向（D、Y）4个周期项采取相对宽松约束、随机脉冲参数采取紧约束,解算效果更佳;降低ERP先验信息对解算精度的影响,重点在于提高UT1-UTC的预报值精度;利用100个跟踪站数据解算,可达到解算效率和解算质量均最佳的效果。 相似文献