This paper describes an architecture for a compact real-time time-delay sonar beamformer. The design is based on a time-domain interpolation concept, and includes shading, interpolation, and time-delay functions for up to 64 sensor data inputs. A one card per beam configuration has been achieved. The digital interpolation technique used improves the effective sampling rate by a factor of 128. The beamformer design features 16-bit arithmetic precision, up to approximately a 5-kHz sampling rate for each of the 64 sensor input channels, and adaptability to any type of array, e.g., linear, circular, or arrays with nonequal interelement spacings. A 31-beam beamformer system, performing more than 620-million arithmetic operations a second, is discussed. 相似文献
Dim and small target detection is one of the most challenging issues based on space-based detector. Original space-based detector only uses infrared bands, and the target information is limited in one-band image, so that detection error rate is high. In order to increase the target information, we suppose spectral imaging technology can be applied to the space-based detection system. Use bands of stronger radiation of targets than that of background as detection bands theoretically; the detection bands also can be called as the characteristic bands of targets. On these bases, the paper proposes methods of fuzzy fusion and fusion segmentation to achieve the target detection. Fusion is a combination of images from the characteristic bands, which can eliminate background, restrain noise, and enhance the target. Threshold segmentation and fuzzy algorithm assisted fusion algorithm to complete the final detection. In the simulation experiment, missile plume is considered as the detection target, atmosphere, cloud and jet plume is considered as the detection background, and the advantages of the characteristic spectrum detection and the proposed algorithm are verified from SNR, SCR, ROC curve, and time. 相似文献
Surveys in Geophysics - In 2D anisotropic media, non-stationary filters and low-rank approximation methods are classical strategies to compute the decomposition operators, but they suffer from... 相似文献
Toppling is the foremost failure pattern of anaclinal rock slopes, and deep-seated toppling deformations (DSTDs) are common on high anaclinal slopes on the sides of gorges in western China. The DSTDs can develop to depths of more than 200 m, and may show distinct signs of zonal failure. Many DSTDs undergo transformation to large landslides involving rock volumes of more than 106 m3. However, the conditions for the formation and the basic evolving processes of DSTDs remain unclear. This study seeks to develop an inventory to classify the distribution, and the conditioning factors which govern the formation and deformation modes of DSTDs in western China and to analyze the effect of the geological and geomorphological variables on the toppling intensities. To this end, forty-nine DSTDs were analyzed. The results indicate that DSTDs in western China are commonly distributed along large deeply incised rivers in the southeastern margin of the Qinghai-Tibet plateau. The steep-dip anaclinal metamorphic soft or soft-hard-interbedded strata with near parallel strikes in the river channel, V-shaped deeply incised river channels, and convex slopes are favorable conditions for the formation of DSTDs in these settings. The dip angle, the gradient, and the height of most slopes which develop DSTDs are 60–90°, 30–50°, and 200–800 m, respectively. There is a highly positive relationship between the depth of toppling and the height of the slope. The toppled rock masses can be classed as extremely intense, intense, moderate, and weak toppling zones characterized by complete block detachment, tensile-shear fracture, tensile fracture, and reverse slip along foliations, respectively. Each zone corresponds to a specific range of the dip angle of the toppled strata, the aperture of the tensile cracks, the P-wave velocity, the state of rock weathering, and the degree of unloading. The extremely intense and the intense toppling zones tend to evolve into sliding failures. Overall, 94% of the DSTDs were derived from flexural toppling and 33% have developed into large landslides.
The Beijing-Tianjin-Hebei (BTH) region is an important engine for China’s socioeconomic development. Timely and effectively assessing constraint factors of resources and environment is of great significance for the sustainability assessment and the sustainable development of this region. However, comprehensive assessment research considering key resource and environmental constraints are still lacking. In this study, therefore, the limiting factors of resources and the environment in the BTH region were assessed based on the framework of landscape sustainability science. First, we chose five limiting factors, including topographic condition, geological environment, water resource, land resource, and atmospheric environment, to assess the constraints of resources and the environment using the single-factor evaluation method and the multi-factor comprehensive evaluation method. Based on the results, we divided the whole region into five subregions, i.e., the ecological conservation subregion, the geological disaster subregion, the water resource scarcity subregion, the atmospheric pollution subregion, and the cropland protection subregion. The results revealed that the northern BTH region was highly constrained by topographic conditions, the central BTH region was strongly constrained by geological environment and water resources, whereas the southern BTH region was constrained mainly by land resources and atmospheric environment. In addition, water resource was the main limiting factor for regional population growth and economic development. In 2010, the water resource scarcity subregion had a total population of 39.59 million, an urban population of 76.90%, and a gross domestic product of 2 455.57 billion yuan. We argue that the sustainable development of the BTH region should explicitly consider the resource and environmental limiting factors, implement land use optimization according to local conditions, maintain multiple land use types and diverse management strategies, based on the perspective of “strong sustainability”, so as to promote the regional sustainable development. 相似文献
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