An Evaluation of Four Different Wavelet Decomposition Procedures for Spatial Feature Discrimination in Urban Areas   总被引：2，自引：0，他引：2  

Soe Win Myint  Nina Lam  & John Tyler 《Transactions in GIS》2002,6(4):403-429

Texture or spatial arrangement of neighborhood objects and features plays an important role in the human visual system for pattern recognition and image classification. The traditional spectral–based image processing techniques have proven inadequate for urban land use and land cover mapping from images acquired by the current generation of fine–resolution satellites. This is because of the high frequency spatial arrangements or complex nature of urban features. There is a need for an effective algorithm to digitally classify urban land use and land cover categories using high–resolution image data. Recent studies using wavelet transforms for texture analysis have generally reported better accuracy. Based on a high–resolution ATLAS image, this study illustrates four different wavelet decomposition procedures – the standard, horizontal, vertical, and diagonal decompositions – for urban land use and land cover feature extraction with the use of 33×33 pixel samples. The standard decomposition approach was found to be the most efficient approach in urban texture analysis and classification. For comparison purposes and to better evaluate the accuracy of wavelet approaches in image classification, spatial autocorrelation techniques (Moran's I and Geary's C ) and the spatial co–occurrence matrix method were also examined. The results suggest that the wavelet transform approach is superior to all other approaches.  相似文献   

珠江口地区海陆风系的研究   总被引：12，自引：3，他引：12  

张立凤  张铭  林宏源 《大气科学》1999,23(5):581-589

选取香港、澳门、广州三站为珠江口地区的指标站，对三站多年的观测资料进行统计分析，得到了珠江口地区海陆风现象的一些特征。并用细网格Mass模式对该地区的海陆风风系作诊断研究，得到了该地区海陆风风系的细致分布特征，在指标站该诊断结果与观测资料相一致。  相似文献   

Mathematical modeling of PCB bioaccumulation in Perna viridis     

Yu KN  Lam PK  Cheung CC  Yip CW 《Marine pollution bulletin》2002,45(1-12):332-338

In the present work, we built a mathematical model of polychlorinated biphenyl (PCB) bioaccumulation in Perna viridis, namely, a one-compartment model with a time dependent incorporation rate R (μg g⁻¹ lipid per ppb water per day), with positive substrate cooperativity as the underlying physical mechanism. The temporal change of the PCB concentration Q (μg g⁻¹ lipid) in the soft tissues of the mussel depends on the competition of the input rate RW and the output rate kQ, where W is the concentration of PCB in water (ppb water) and k is the elimination rate (per day). From our experimental data, k=0.181±0.017 d⁻¹. The critical concentration in water W_c for positive substrate cooperativity was found to be 2.4 ppb. Below W_c, R is a constant. For a water concentration of 0.5 ppb Aroclor 1254, R=24.0±2.4 μg g⁻¹ lipid ppb⁻¹ d⁻¹. Above W_c, positive substrate cooperativity comes into effect and R becomes a function of time and dependent on the concentration Q in a form R=γQ/(Q+δ). This is the case for a water concentration of 5 ppb Aroclor 1254, where γ=15.1 μg g⁻¹ lipid ppb⁻¹ d¹ and δ≈200 μg g⁻¹ lipid. From this model, the uptake is exponentially increasing when the PCB concentration in the mussel is small compared to 200 μg g⁻¹ lipid, and hyperbolically increasing when the concentration is large compared to 200 μg g⁻¹ lipid, which are consistent with the experimental data. The model is useful for understanding the true processes taking place during the bioaccumulation and for risk assessment with higher confidence. Future experimental data which challenge the present model are anticipated and in fact desirable for improvement and perfection of the model.  相似文献   

A spatial dynamic model of population changes in a vulnerable coastal environment     

Kenan Li  Nina S. N. Lam 《International journal of geographical information science》2018,32(4):685-710

This study developed a spatial dynamic model to examine the coupled natural–human responses in the form of changes in population and associated developed land area in the Lower Mississippi River Basin region. The goal was to identify key socioeconomic factors (utility) and environmental factors (hazard damages, elevation, and subsidence rate) that affected population changes, as well as to examine how population changes affected the local utility and the local environment reciprocally. We first applied areal interpolation techniques with the volume-preserving property to transform all the data at Year 2000 into a unified 3 km by 3 km cellular space. We then built an Elastic Net model to extract 12 variables from a set of 33 for the spatial dynamic model. Afterward, we calibrated the neighborhood effects with a genetic algorithm and use the spatial dynamic model to simulate population and developed land area in 2010. Furthermore, we took a Monte Carlo approach for analyzing the uncertainty of the model outcome. Our accuracy assessment shows that the model on average slightly overpredicts the number of population and the developed land percentage at 2010, as indicated by the low values of mean absolute deviation (MAD) due to quantity. On the other hand, the MADs due to allocation are larger than the MADs due to quantity, with most outliers found in the New Orleans region where population and urban development declined significantly during 2000–2010 after Hurricane Katrina. The proposed model sheds light on the complex relationships between coastal hazards and human responses and provides useful insights to strategic development for coastal sustainability.  相似文献   

Integrated assessment modelling as a positive science: private passenger road transport policies to meet a climate target well below 2 <Superscript>∘</Superscript>C     

J.-F. Mercure  A. Lam  S. Billington  H. Pollitt 《Climatic change》2018,151(2):109-129

Transport generates a large and growing component of global greenhouse gas emissions contributing to climate change. Effective transport emissions reduction policies are needed in order to reach a climate target well below 2 ^°C. Representations of technology evolution in current integrated assessment models (IAM) make use of systems optimisations that may not always provide sufficient insight on consumer response to realistic policy packages for extensive use in policy-making. Here, we introduce FTT: transport, an evolutionary technology diffusion simulation model for road transport technology, as an IAM sub-component, which features sufficiently realistic features of consumers and of existing technological trajectories that enables to simulate the impact of detailed climate policies in private passenger road transport. Integrated to the simulation-based macroeconometric IAM E3ME-FTT, a plausible scenario of transport decarbonisation is given, defined by a detailed transport policy package, that reaches sufficient emissions reductions to achieve the 2 ^°C target of the Paris Agreement.  相似文献   

Variation of initial Th/Th and limits of high precision U-Th dating of shallow-water corals     

Chuan-Chou Shen  Kuei-Shu Li  Danny Natawidjaja  Xianfeng Wang  Doan Dinh Lam  Tung-Yung Fan  Fred W. Taylor  Hong-Wei Chiang 《Geochimica et cosmochimica acta》2008,72(17):4201-4223

One hundred eighty U-Th data, including 23 isochrons on 24 pristine modern and Holocene corals and 33 seawater samples, were analyzed using sector-field mass spectrometry to understand the variability of initial ²³⁰Th/²³²Th (²³⁰Th/²³²Th₀). This dataset allows us to further assess the accuracy and precision of coral ²³⁰Th dating method. By applying quality control, including careful sampling and subsampling protocols and the use of contamination-free storage and workbench spaces, the resulting low procedural blanks give an equivalent uncertainty in age of only ±0.2-0.3 yr for 1-2 g of coral sample. Using site-specific ²³⁰Th/²³²Th₀ values or isochron techniques, our study demonstrates that corals with an age less than 100 yrs can be ²³⁰Th-dated with precisions of ±1 yr. Six living subtidal coral samples were collected from two continental shelf sites, Nanwan off southern Taiwan in the western Pacific and Son Tra off central Vietnam in the South China Sea; one coral core was drilled from an open-ocean site, Santo Island, Vanuatu, in the western tropical Pacific; and modern and fossil intertidal coral slabs, 17 in total, were cut from six sites around the islands of Simeulue, Lago, North Pagai and South Pagai of Sumatra in the eastern Indian Ocean. The results indicate that the main source of thorium is the dissolved phase of seawater, with variation of ²³⁰Th/²³²Th₀ depending on local hydrology. With intense input of terrestrial material, low ²³⁰Th/²³²Th₀ atomic ratios of 4.9 × 10⁻⁶ and 3.2 × 10⁻⁶ with a 10% variation are observed in Nanwan and Son Tra, respectively. At the Santo site, we find a value of 5.6 × 10⁻⁶ at 4 horizons and one high value of 24 × 10⁻⁶ in a sample from AD 1974.6 ± 0.5, likely due to the upwelling of cold water during a La Niña event between AD 1973 and 1976. The natural dynamics of ²³⁰Th/²³²Th₀ recorded in the intertidal corals at sites in the Sumatran islands are complicated so that this value varies significantly from 3.0 to 9.4 × 10⁻⁶. Three of the 141 modern coral ²³⁰Th ages differ from their true ages by −23 to +4, indicating the presence of detrital material with anomalous ²³⁰Th/²³²Th values. Duplicate measurement of coeval subsamples is therefore recommended to verify the age accuracy. This improved high precision coral ²³⁰Th dating method raises the prospects of refining the age models for band-counted and tracer-tuned chronologies and of advancing coral paleoclimate research.  相似文献   

Mechanism of two rapid and long-runout landslides in the 16 April 2016 Kumamoto earthquake using a ring-shear apparatus and computer simulation (LS-RAPID)   总被引：3，自引：3，他引：0  

Khang Dang  Kyoji Sassa  Hiroshi Fukuoka  Naoki Sakai  Yuji Sato  Kaoru Takara  Lam Huu Quang  Doan Huy Loi  Pham Van Tien  Nguyen Duc Ha 《Landslides》2016,13(6):1525-1534

Around hundred landslides were triggered by the Kumamoto earthquakes in April 2016, causing fatalities and serious damage to properties in Minamiaso village, Kumamoto Prefecture, Japan. The landslides included many rapid and long-runout landslides which were responsible for much of the damage. To understand the mechanism of these earthquake-triggered landslides, we carried out field investigations with an unmanned aerial vehicle to obtain DSM and took samples from two major landslides (Takanodai landslide and Aso-ohashi landslide) to measure parameters of the initiation and the motion of landslides. A series of ring-shear tests and computer simulations were conducted using a measured Kumamoto earthquake acceleration record from KNet station KMM005, 10 km west of Aso-ohashi landslide. The research results supported our assumed mechanism of sliding-surface liquefaction for the rapid and long-runout motion of these landslides.  相似文献   

The variability of heat flow both regional and with depth in southern Alberta, Canada: Effect of groundwater flow?     

J.A. Majorowicz  F.W. Jones  H.L. Lam  A.M. Jessop 《Tectonophysics》1984,106(1-2)

Detailed studies of terrestrial heat flow in southern and central Alberta estimated on the basis of an order of magnitude larger data base than ever used before (33653 bottom-hole temperature data from 18711 wells) and thermal conductivity values based on detailed rock studies and measured rock conductivities show significant regional and local variations and variations with depth. Heat flow values were estimated for each 3 × 3 township/range area (28.8 × 28.8 km). A difference in heat flow exists between Paleozoic and Mesozoic strata. Generally lower heat flow values are observed in the strata above the Paleozoic erosional surface (20–75 mW m⁻²). Much higher values are estimated for the Younger Paleozoic formations, with large local and regional variations between 40 and 100 mW m⁻².Average heat flow values based on heat flow determinations below and above the Paleozoic surface that agree within 20% show an increase from values less than 40 mW m⁻² in southern and southwestern Alberta to values as high as 70 mW m⁻² in central Alberta. The predominance of regional downward groundwater flows in Mesozoic strata seem to be responsible for the generally observed heat flow increase with depth.The results show that the basin heat flow pattern is influenced by water movement and even careful detailed heat flow measurements will not give correct values of background steady-state heat flow within the sedimentary strata.  相似文献   

An inverse problem approach to modelling coastal effluent plumes     

D. C. L. Lam  C. R. Murthy  K. C. Miners 《Advances in water resources》1981,4(4):185-190

Formulated as an inverse problem, the diffusion parameters associated with length-scale dependent eddy diffusivities can be viewed as the unknowns in the mass conservation equation for coastal zone transport problems. The values of the diffusion parameters can be optimized according to an error function incorporated with observed concentration data. Examples are given for the Fickian, shear diffusion and inertial subrange diffusion models. Based on a new set of dyeplume data collected in the coastal zone off Bronte, Lake Ontario, it is shown that the predictions of turbulence closure models can be evaluated for different flow conditions. The choice of computational schemes for this diagnostic approach is based on tests with analytic solutions and observed data. It is found that the optimized shear diffusion model produced a better agreement with observations for both high and low advective flows than, e.g., the unoptimized semi-empirical model, K_y=0.075 σ_y^1.2, described by Murthy and Kenney.  相似文献   

On the Issues of Scale,Resolution, and Fractal Analysis in the Mapping Sciences*   总被引：1，自引：0，他引：1  

Nina Siu-Ngan Lam  Dale A. Quattrochi 《The Professional geographer》1992,44(1):88-98

Scale and resolution have long been key issues in geography. The rapid development of analytical cartography, GIS, and remote sensing (the mapping sciences) in the last decade has forced the issues of scale and resolution to be treated formally and better defined. This paper addresses the problem of scale and resolution in geographical studies, with special reference to the mapping sciences. The fractal concept is introduced, and its use in identifying the scale and resolution problem is discussed. The implications of the scale and resolution problem on studies of global change and modeling are also explored.  相似文献