旅游流距离衰减现象演绎研究

以旅游系统空间结构模型为依托,通过绘制旅游流距离衰减曲线,对旅游流距离衰减现象进行演绎研究。结果发现,高斯分布型和指数分布型是旅游流距离衰减曲线的基本类型,旅游系统中客源地结点的空间分布格局是旅游流距离衰减曲线类型的决定性因素,到访率距离衰减速率是曲线形状的修饰性因素,距离衰减曲线的绘制方法不同,距离衰减曲线的类型也不同。最后,以井冈山和庐山为案例进行了实证分析。     

Effects of episodic fluid flow on hydrocarbon migration in the Newport‐Inglewood Fault Zone,Southern California

Fault permeability may vary through time due to tectonic deformations, transients in pore pressure and effective stress, and mineralization associated with water‐rock reactions. Time‐varying permeability will affect subsurface fluid migration rates and patterns of petroleum accumulation in densely faulted sedimentary basins such as those associated with the borderland basins of Southern California. This study explores the petroleum fluid dynamics of this migration. As a multiphase flow and petroleum migration case study on the role of faults, computational models for both episodic and continuous hydrocarbon migration are constructed to investigate large‐scale fluid flow and petroleum accumulation along a northern section of the Newport‐Inglewood fault zone in the Los Angeles basin, Southern California. The numerical code solves the governing equations for oil, water, and heat transport in heterogeneous and anisotropic geologic cross sections but neglects flow in the third dimension for practical applications. Our numerical results suggest that fault permeability and fluid pressure fluctuations are crucial factors for distributing hydrocarbon accumulations associated with fault zones, and they also play important roles in controlling the geologic timing for reservoir filling. Episodic flow appears to enhance hydrocarbon accumulation more strongly by enabling stepwise build‐up in oil saturation in adjacent sedimentary formations due to temporally high pore pressure and high permeability caused by periodic fault rupture. Under assumptions that fault permeability fluctuate within the range of 1–1000 millidarcys (10^?15–10^?12 m²) and fault pressures fluctuate within 10–80% of overpressure ratio, the estimated oil volume in the Inglewood oil field (approximately 450 million barrels oil equivalent) can be accumulated in about 24 000 years, assuming a seismically induced fluid flow event occurs every 2000 years. This episodic petroleum migration model could be more geologically important than a continuous‐flow model, when considering the observed patterns of hydrocarbons and seismically active tectonic setting of the Los Angeles basin.     

Thermal springs and heat flow in North America

Thermal springs are commonly thought to be an indicator of geothermal resource potential. However, there have been few analyses of the relationship between thermal springs and the underlying thermal regime. An examination of temperature and discharge rates for a large database of thermal springs in North America demonstrates that there is not a simple relationship between these measurements made at the surface and subsurface heat flow. Hydrogeological factors appear to exert strong controls on the temperature and discharge at these springs and should be carefully considered in geothermal resource assessments.     

Mineral precipitation associated with vertical fault zones: the interaction of solute advection,diffusion and chemical kinetics

This article is concerned with chemical reactions that occur between two interacting parallel fluid flows using mixing in vertical faults as an example. Mineral precipitation associated with fluid flow in permeable fault zones results in mineralization and chemical reaction (alteration) patterns, which in turn are strongly dependent on interactions between solute advection (controlled by fluid flow rates), solute diffusion/dispersion and chemical kinetics. These interactions can be understood by simultaneously considering two dimensionless numbers, the Damköhler number and the Z‐number. The Damköhler number expresses the interaction between solute advection (flow rate) and chemical kinetics, while the Z‐number expresses the interaction between solute diffusion/dispersion and chemical kinetics. Based on the Damköhler and Z‐numbers, two chemical equilibrium length‐scales are defined, dominated by either solute advection or by solute diffusion/dispersion. For a permeable vertical fault zone and for a given solute diffusion/dispersion coefficient, there exist three possible types of chemical reaction patterns, depending on both the flow rate and the chemical reaction rate. These three types are: (i) those dominated by solute diffusion and dispersion resulting in precipitation at the lower tip of a vertical fault and as a thin sliver within the fault, (ii) those dominated by solute advection resulting in precipitation at or above the upper tip of the fault, and (iii) those in which advection and diffusion/dispersion play similar roles resulting in wide mineralization within the fault. Theoretical analysis indicates that there exists both an optimal flow rate and an optimal chemical reaction rate, such that chemical equilibrium following focusing and mixing of two fluids may be attained within the fault zone (i.e. type 3). However, for rapid and parallel flows, such as those resulting from a lithostatic pressure gradient, it is difficult for a chemical reaction to reach equilibrium within the fault zone, if the two fluids are not well mixed before entering the fault zone. Numerical examples are given to illustrate the three possible types of chemical reaction patterns.     

Following the Money: Corruption,Conflict, and the Winners and Losers of Suburban Land Acquisition in China

Land acquisition in suburban China is not merely the administrative means through which land is transferred from collectively owned rural land to state‐owned urban land; it is also a process of unlawful profit grabbing by rent‐seeking stakeholders. This licentiousness has been the source of intense controversy in recent years, becoming a major source of social unrest in contemporary China. Although standards of compensation are legally governed by strict policies, these standards are rarely followed as prescribed. As a result, we know very little about how revenue from land acquisition is shared in practice. This is because, as a contentious political issue rife with corrupt practices, accurate data are extremely difficult to obtain. This paper aims to address this vast empirical gap by tracing the flow of profit proliferation and distribution in a land acquisition case, using a suburban village in Shandong province, China, as an example. To expedite the drawn‐out acquisition process, the local government permits the corrupt behaviour of the village party secretary, who exploits his position to amass a great personal fortune. In contrast to previous research, which emphasises low compensation standards or excessive profit grabbing by local government, we find that villagers' protests are triggered by the corrupt practices of the village party secretary.     

Modelling the Lost City hydrothermal field: influence of topography and permeability structure

The Lost City hydrothermal field (LCHF) is hosted in serpentinite at the crest of the Atlantis Massif, an oceanic core complex close to the mid‐Atlantic Ridge. It is remarkable for its longevity and for venting low‐temperature (40–91°C) alkaline fluids rich in hydrogen and methane. IODP Hole U1309D, 5 km north of the LCHF, penetrated 1415 m of gabbroic rocks and contains a near‐conductive thermal gradient close to 100°C km^?1. This is remarkable so close to an active hydrothermal field. We present hydrothermal modelling using a topographic profile through the vent field and IODP site U1309. Long‐lived circulation with vent temperatures similar to the LCHF can be sustained at moderate permeabilities of 10^?14 to 10^?15 m² with a basal heatflow of 0.22 W m^?2. Seafloor topography is an important control, with vents tending to form and remain in higher topography. Models with a uniform permeability throughout the Massif cannot simultaneously maintain circulation at the LCHF and the near‐conductive gradient in the borehole, where permeabilities <10^?16 m² are required. A steeply dipping permeability discontinuity between the LCHF and the drill hole is required to stabilize venting at the summit of the massif by creating a lateral conductive boundary layer. The discontinuity needs to be close to the vent site, supporting previous inferences that high permeability is most likely produced by faulting related to the transform fault. Rapid increases in modelled fluid temperatures with depth beneath the vent agree with previous estimates of reaction temperature based on geochemical modelling.     

Estimating Antebellum Passenger Costs: A Hub-and-Spoke Approach

Abstract

Over 30,000 miles of railroad and 4,000 miles of canals were constructed in the United States between 1815 and 1861. However, the lack of data has prevented the study of this “transportation revolution” for most cities. This article thus enables a closer study of antebellum travel improvements by constructing a hub-and-spoke network that is capable of estimating the cost of passenger travel from New York City and Philadelphia to any U.S. city in 1836, 1850, 1856, 1859, and 1867. The semi-parametric approach provides an accurate cost estimate by using available historical information to determine the travel cost to all other cities.     

Experimental study of the effect of variation in in‐situ stress on capillary residual trapping during CO2 geo‐sequestration in sandstone reservoirs

During a geo‐sequestration process, CO₂ injection causes an increase in reservoir pore pressure, which in turn decreases the reservoir net effective stress. Changes in effective stress can change all the reservoir and cap‐rock properties including residual saturations. This article presents the results of an experimental work carried out to understand the potential change in the volumes of residually trapped CO₂, while the porous medium tested underwent change in the net effective stress under in‐situ reservoir conditions of pore pressure and temperature. The experimental results obtained show that an initial 1725 psi (11.9 MPa) decrease in the net effective pressure caused 1.4% reduction in the volumes of residually trapped CO₂, while another 1500 psi (10.3 MPa) reduction caused a further 3.2% drop in the residual saturation of CO₂.     

Large-scale Debris Flow Disasters: Hazard-Risk-Vulnerability Analysis Approach in Taiwan

Catastrophic disasters may cause irreversible damage to cultural heritage. This study identified the risk to cultural heritage sites in Taiwan posed by large-scale debris flow disasters. The cultural heritage sites that may be affected by debris flows were identified through risk identification and by using GIS. Subsequently, an on-site field survey was conducted to confirm the cultural heritage sites that are potentially vulnerable to debris flow disasters. The research findings are as follows: (a) the top three cultural heritage sites that are most affected by debris flows are municipal, county, and city monuments, historical buildings, and historical sites; (b) the number of cultural heritage sites affected is related to environmental exploitation; (c) the cultural heritage sites at high risk of being affected by disasters were primarily located in Taitung and Chiayi Counties.