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71.
以宁蒙沿黄地带为案例,基于城镇用地和最小交通时间成本划分城市影响区,分区统计影响区人口,将其与城市行政区非农人口的增速差进行统计分析。结果表明:基于城镇用地和最小交通时间成本的城市影响区划分边界更接近于行政区界;考虑城镇用地后大城市影响区扩展,考虑最小交通时间成本后小城市影响区相对扩展;以东胜区-伊旗为中心的地区非农人口增速始终显著高于潜在服务人口增速,这类城市应增强对周边县的扩散作用;以大武口-惠农区为中心的地区非农人口增速始终显著低于潜在服务人口增速,这类城市应加速产业与非农人口集聚。 相似文献
72.
Wave effects on ascending and descending motions of the autonomous underwater vehicle 总被引:1,自引:0,他引:1
In the paper, a hydrodynamic model including the characteristics of maneuvering and seakeeping is developed to simulate the six-degree of freedom motions of the underwater vehicle steering near the sea surface. The corresponding wave exciting forces on the underwater vehicle moving in waves are calculated by the strip theory, which is based on the source distribution method. With the hydrodynamic coefficients relevant to the maneuvering and seakeeping, the fourth-order Runge–Kutta numerical method is adopted to solve the equations of motions and six-degrees of freedom of the motions for the underwater vehicle steering near the free surface can be obtained. The wave effect on the corresponding motions of the underwater vehicle is investigated and some interesting phenomena with respect to different wave frequencies and headings are observed. The hydrodynamic numerical model developed here can be served as a valuable tool for analyzing the ascending and descending behaviors of the underwater vehicle near the sea surface. 相似文献
73.
74.
The sensitivity of the added mass coefficients of a typical autonomous underwater vehicle (AUV) to changes in geometric parameters was investigated. Qualitative deductions were made concerning the effect of geometric variations. Then the added mass coefficients for several configurations of body geometry were generated for the Canadian Self-Contained Off-the-shelf Underwater Testbed (C-SCOUT) vehicle using the computer program Estimate Submarine Added Mass (ESAM). The changes in the added mass coefficients have direct relationships to the varied parameter. The results presented here are specific to the C-SCOUT, but may be extended to similar axisymmetric bodies. 相似文献
75.
Nonlinear path-following control of an AUV 总被引:3,自引:0,他引:3
A new type of control law is developed to steer an autonomous underwater vehicle (AUV) along a desired path. The methodology adopted for path-following deals explicitly with vehicle dynamics. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path-following control strategies described in the literature. Controller design builds on Lyapunov theory and backstepping techniques. The resulting nonlinear feedback control law yields convergence of the path-following error trajectory to zero. Simulation results illustrate the performance of the control system proposed. 相似文献
76.
Jenny Brunnegrd Sibylle Grandel Henrik Sthl Anders Tengberg Per O.J. Hall 《Progress in Oceanography》2004,63(4):159-181
Rates of transformation, recycling and burial of nitrogen and their temporal and spatial variability were investigated in deep-sea sediments of the Porcupine Abyssal Plain (PAP), NE Atlantic during eight cruises from 1996 to 2000. Benthic fluxes of ammonium (NH4) and nitrate (NO3) were measured in situ using a benthic lander. Fluxes of dissolved organic nitrogen (DON) and denitrification rates were calculated from pore water profiles of DON and NO3, respectively. Burial of nitrogen was calculated from down core profiles of nitrogen in the solid phase together with 14C-based sediment accumulation rates and dry bulk density. Average NH4 and NO3-effluxes were 7.4 ± 19 μmol m−2 d−1 (n = 7) and 52 ± 30 μmol m−2 d−1 (n = 14), respectively, during the period 1996–2000. During the same period, the DON-flux was 11 ± 5.6 μmol m−2 d−1 (n = 5) and the denitrification rate was 5.1 ± 3.0 μmol m−2 d−1 (n = 22). Temporal and spatial variations were only found in the benthic NO3 fluxes. The average burial rate was 4.6 ± 0.9 μmol m−2 d−1. On average over the sampling period, the recycling efficiency of the PON input to the sediment was 94% and the burial efficiency hence 6%. The DON flux constituted 14% of the nitrogen recycled, and it was of similar magnitude as the sum of burial and denitrification. By assuming the PAP is representative of all deep-sea areas, rates of denitrification, burial and DON efflux were extrapolated to the total area of the deep-sea floor (>2000 m) and integrated values of denitrification and burial of 8 ± 5 and 7 ± 1 Tg N year−1, respectively, were obtained. This value of total deep-sea sediment denitrification corresponds to 3–12% of the global ocean benthic denitrification. Burial in deep-sea sediments makes up at least 25% of the global ocean nitrogen burial. The integrated DON flux from the deep-sea floor is comparable in magnitude to a reported global riverine input of DON suggesting that deep-sea sediments constitute an important source of DON to the world ocean. 相似文献
77.
78.
Roberto Furfaro Jeffrey S. Kargel Wolfgang Fink Michael P. Bishop 《Planetary and Space Science》2010,58(5):761-779
Future planetary exploration of Titan will require higher degrees of on-board automation, including autonomous determination of sites where the probability of significant scientific findings is the highest. In this paper, a novel Artificial Intelligence (AI) method for the identification and interpretation of sites that yield the highest potential of cryovolcanic activity is presented. We introduce the theory of fuzzy cognitive maps (FCM) as a tool for the analysis of remotely collected data in planetary exploration. A cognitive model embedded in a fuzzy logic framework is constructed via the synergistic interaction of planetary scientists and AI experts. As an application example, we show how FCM can be employed to solve the challenging problem of recognizing cryovolcanism from Synthetic Aperture Radar (SAR) Cassini data. The fuzzy cognitive map is constructed using what is currently known about cryovolcanism on Titan and relies on geological mapping performed by planetary scientists to interpret different locales as cryovolcanic in nature. The system is not conceived to replace the human scientific interpretation, but to enhance the scientists’ ability to deal with large amounts of data, and it is a first step in designing AI systems that will be able, in the future, to autonomously make decisions in situations where human analysis and interpretation is not readily available or could not be sufficiently timely. The proposed FCM is tested on Cassini radar data to show the effectiveness of the system in reaching conclusions put forward by human experts and published in the literature. Four tests are performed using the Ta SAR image (October 2004 fly-by). Two regions (i.e. Ganesa Macula and the lobate high backscattering region East of Ganesa) are interpreted by the designed FCM as exhibiting cryovolcanism in agreement with the initial interpretation of the regions by Stofan et al. (2006). Importantly, the proposed FCM is shown to be flexible and adaptive as new data and knowledge are acquired during the course of exploration. Subsequently, the FCM has been modified to include topographic information derived from SAR stereo data. With this additional information, the map concludes that Ganesa Macula is not a cryovolcanic region. In conclusion, the FCM methodology is shown to be a critical and powerful component of future autonomous robotic spacecraft (e.g., orbiter(s), balloon(s), surface/lake lander(s), rover(s)) that will be deployed for the exploration of Titan. 相似文献
79.
准苏吉花敖包铜多金属矿控矿因素分析 总被引:1,自引:0,他引:1
准苏吉花敖包铜多金属矿区位于东乌旗-二连浩特多金属成矿带西段,地质情况复杂.因部分地层中含有碳质板岩,对地球物理工作的结果产生了一定的影响.通过结合地质、地球物理、地球化学特征分析,总结出了该区的找矿方向. 相似文献
80.
将内蒙古已知金矿划分为5大类型20个矿床亚类:即重熔岩浆热液金矿、变质热液金矿、沉积变质热液金矿、火山-次火山热液金矿、砂金矿。对各类型金矿床的地质成因特征进行了初步探讨。 相似文献