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APES (Amplitude and Phase EStima- tion) is an adaptive FIR filtering approach intro- duced recently for complex spectral estimation. For stationary signals, APES can yield more accurate spectral estimates than the widely used Capo...
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APES (Amplitude and Phase EStima- tion) is an adaptive FIR filtering approach intro- duced recently for complex spectral estimation. For stationary signals, APES can yield more accurate spectral estimates than the widely used Capon and FFT estimators. The authors present a recursive APES algorithm for time-varying spectral analysis, which is computationaly effi- cient and only involves FFT and simple matrix operations. The recursive APES algorithm is applied to ISAR (inverse synthetic aperture radar) imaging and feature extraction of targets with complex manoeuvring motion. Both numeri- cal and experimental examples are provided to demonstrate the performance of the proposed method.
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Asymptotic crack tip stress fields are developed for a plane strain crack located on the interface between two incompressible, elastic--perfectly plastic solids, with matching elastic properties, but mismatched yield strengths. Th...
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Asymptotic crack tip stress fields are developed for a plane strain crack located on the interface between two incompressible, elastic--perfectly plastic solids, with matching elastic properties, but mismatched yield strengths. The complete range of normal versus shear tractions on the interface at the crack tip is analyzed. In the limit as the yield strength mismatch vanishes the asymptotic stress fields for the interface crack approach established crack tip fields for homogeneous bodies. The crack tip stress fields are assembled from combinations of centered fans, constant stress sectors and elastic sectors. All the stresses within each material region are continuous while traction continuity is maintained across the interface. These asymptotic stress fields are verified by comparison with small-scale yielding finite element solutions obtained for various remote load mixity using boundary layer formulations (Rice, l967).
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The smoke-filling process in atra of local shopping malls was studied. The scenario of smoke spreading form a shop located adjacent to an atrium was considered. A two-layer zone model, CL-Atrium, was developed with balcony spill p...
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The smoke-filling process in atra of local shopping malls was studied. The scenario of smoke spreading form a shop located adjacent to an atrium was considered. A two-layer zone model, CL-Atrium, was developed with balcony spill plume. Three plume expressions due to Thomas et al. [13], Poreh et al. [12] and NFPA-92B[11] were used and assessed. Comparison was made with simulations due to CFAST. It is found that a condition has to be satisfied for the plume expression due to Thomas et al. [13]. Further, the results on the smoke layer temperature and interface height in the atrium are similar while using the plume expressions by Poreh et al. [12] and Thomas et al. [13].
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This paper presents two complementing algorithms for remote sensing based coal fire research and the results derived thereof. Both are applicable on Landsat, ASTER and MODIS data. The first algorithm automatically delineates coal ...
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This paper presents two complementing algorithms for remote sensing based coal fire research and the results derived thereof. Both are applicable on Landsat, ASTER and MODIS data. The first algorithm automatically delineates coal fire risk areas from multispectral satellite data. The second automatically extracts local coal fire related thermal anomalies from thermal data. The presented methods aim at the automated, unbiased retrieval of coal fire related information. The delineation of coal fire risk areas is based on land cover extraction through a knowledge based spectral test sequence. This sequence has been proven to extract coal fire risk areas not only in time series of the investigated study areas in China, but also in transfer regions of India and Australia. The algorithm for the extraction of thermal anomalies is based on a moving window approach analysing sub-window histograms. It allows the extraction of thermally anomalous pixels with regard to their surrounding background and therefore supports the extraction of very subtle, local thermal anomalies of different temperature. It thus shows clear advantages to anomaly extraction via simple thresholding techniques. Since the thermal algorithm also does extract thermal anomalies, which are not related to coal fires, the derived risk areas can help to eliminate false alarms. Overall, 50% of anomalies derived from night-time data can be rejected, while even 80% of all anomalies extracted from daytime data are likely to be false alarms. However, detection rates are very good. Over 80% of existing coal fires in our first study area were extracted correctly and all fires (100%) in study area two were extracted from Landsat data. In MODIS data extraction depends on coal fire types and reaches 80% of all fires in our study area with hot coal fires of large spatial extent, while in another region with smaller and 'colder' coal fires only the hottest ones (below 20%) can be extracted correctly. The success of the synergetic application of the two methods has been proven through our detection of so far unknown coal fires in Landsat 7 ETM + remote sensing data. This is the first time in coal fire research that unknown coal fires were detected in satellite remote sensing data exclusively and were validated later subsequently during in situ field checks.
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The concept of using a time constant, a parameter describing the smoke filling process including atrium geometry and design of the fire, is further reviewed. Time constants of 138 local atria were investigated. The smoke filling t...
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The concept of using a time constant, a parameter describing the smoke filling process including atrium geometry and design of the fire, is further reviewed. Time constants of 138 local atria were investigated. The smoke filling time required to fill 80/100 of the space volume of 69 atria to satisfy the criteria for applying the NFPA smoke filling equation was evaluated with a slow t~2-fire. The two-layer zone model ASET was used to calculate the smoke filling time for all 138 atria. The time for the smoke front to reach the ceiling is included to modify the calculation.
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The Ting Kau Bridge in Hong Kong is a cable-stayed bridge comprising two main spans and two side spans. The bridge deck is supported by three towers, an end pier and an abutment. Each of the three towers consists of a single reinf...
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The Ting Kau Bridge in Hong Kong is a cable-stayed bridge comprising two main spans and two side spans. The bridge deck is supported by three towers, an end pier and an abutment. Each of the three towers consists of a single reinforced concrete mast strengthened by transverse cables and struts. The bridge deck is supported by four inclined planes of cables emanating from anchorages at the tower tops. In view of the heavy traffic on the bridge, and threats from typhoons and earthquakes originated in areas nearby, the dynamic behaviour of long-span cable-supported bridges in the region is always an important consideration in their design. Baseline finite element models of various levels of sophistication have been built not only to match the bridge geometry and cable forces specified on the as-constructed drawings but also to be calibrated using the vibration measurement data captured by the Wind and Structural Health Monitoring System. This paper further describes the analysis of axle loading data, as well as the generation of random axle loads and simulation of vibrations of the bridge using the finite element models. Various factors affecting the vehicular loading on the bridge will also be examined.
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In this paper we investigate the use of radial basis functions for solving Poisson problems with a near-singular inhomogeneous source term. The solution of the Poisson problem is first split into two parts: near-singular solution ...
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In this paper we investigate the use of radial basis functions for solving Poisson problems with a near-singular inhomogeneous source term. The solution of the Poisson problem is first split into two parts: near-singular solution and smooth solution. A method for evaluating the near-singular particular solution is examined. The smooth solution is further split into a particular solution and a homogeneous solution. The MPS-DRM approach is adopted to evaluate the smooth solution.
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Urban stormwater has been identified as a significant source of phosphorus to Severn Sound and a potential source of bacterial contamination which can affect recreational bathing areas within the Sound. In order to develop an effe...
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Urban stormwater has been identified as a significant source of phosphorus to Severn Sound and a potential source of bacterial contamination which can affect recreational bathing areas within the Sound. In order to develop an effective remedial action plan, a cooperative study of urban stormwater impacts was initiated in the Severn Sound Area of Concern (AOC) through a joint partnership that included Environment Canada (Great Lakes 2000 Cleanup Fund), the Ontario Ministry of the Environment, the Simcoe County District Health Unit, and various municipalities in the Sound.
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Over the last several years, the US inland waterway transportation industry has significantly reduced its fuel consumption and improved its efficiency, with the side effect of less fuel tax collected per ton of cargo carried, desp...
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Over the last several years, the US inland waterway transportation industry has significantly reduced its fuel consumption and improved its efficiency, with the side effect of less fuel tax collected per ton of cargo carried, despite the increase in cargo traffic. Fuel tax revenues are used for rehabilitation and construction pro- jects in the inland waterway system, hence the US Army Corps of Engineers, providing us with relevant data over the interval in question, asked us to inves- tigate this surprising reduction, and determine the main technical and fleet man- agement improvements that caused it. Our research involved both visits with most major US inland waterway fleets, interviews with their engineers and managers, as well as statistical analysis of the above data. Technical improvements (such as engine plant efficiency increases), lighter, stronger building materials (such as light steel), and improved designs for better hydrodynamics, were not as important compared to management improvements (such as the use of computer-aided monitoring systems and advanced telecommunications, optimized tow configura- tion and speed, and increased triangular trips as opposed to simple round trips with returns empty). In addition, the demand for less expensive, imported steel for the US has resulted in an increased percentage of fully loaded return trips from New Orleans to the US Midwest, and hence also in increased fleet utilization.
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Solids cleanouts using coiled tubing (CT) remain a major part of total activity in the CT industry. Because of the multitude of parameters that influence solids transport, it can be very challenging to design and execute solids cl...
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Solids cleanouts using coiled tubing (CT) remain a major part of total activity in the CT industry. Because of the multitude of parameters that influence solids transport, it can be very challenging to design and execute solids cleanouts successfully with CT in highly deviated, larger wellbores with 7-in. production tubing, or even larger tubulars, installed.
Numerous papers have been written about the development of wiper-trip cleanout technology and associated engineering design tools, but this paper is focused instead on important practical issues that directly impact the effective implementation of wiper-trip technology in the field. This paper presents the results and lessons learned based on a database that was compiled from more than 100 solids cleanout operations using wiper-trip methodologies. Results will be presented showing how the wiper trip cleanout methodology has improved cleanout efficiency and success rate. Examples are presented showing how the effectiveness of cleanout bottom-hole assemblies (BHAs) involving positive-displacement motors (PDMs) and mills has been improved, while simultaneously reducing stress on surface equipment during the operation. Circulation rates higher than specified maximum rates for the PDM are being used without danger of damaging the PDM, while reducing the total volume pumped through the PDM during the cleanout by 80-90%. Larger outer diameter (OD) items in the BHA are kept clean of solids while wiper tripping, reducing the risk of stuck CT and protecting sensitive completion components from undesirable interactions with the PDM/mill BHA. Multiple wiper trips can be performed in one run without the use of drop balls, while having the ability to use selected functions of critical BHA components and full-size drifting of the wellbore for subsequent operations. Field-proven procedures are explained, allowing solids loading in the annulus to be controlled and reduced when necessary, and allowing estimates of solids volumes during the cleanout to be established, on the basis of feedback from the cleanout BHA before any solids have actually reached surface.
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