Neighbourhood redevelopment and the making of a housing middle class: Can gentrification explain China’s spatial and social changes?     

Chung  Him 《GeoJournal》2021,86(3):1375-1388

GeoJournal - This paper addresses the relationship between spatial change and social process in China. Studies in Anglo-American and European cities usually suggest middle classes move into a...  相似文献   

Time series analyses of hydrological parameter variations and their correlations at a coastal area in Busan,South Korea     

Sang Yong Chung  Venkatramanan Senapathi  Selvam Sekar  Tae Hyung Kim 《Hydrogeology Journal》2018,26(6):1875-1885

Monitoring and time-series analysis of the hydrological parameters electrical conductivity (EC), water pressure, precipitation and tide were carried out, to understand the characteristics of the parameter variations and their correlations at a coastal area in Busan, South Korea. The monitoring data were collected at a sharp interface between freshwater and saline water at the depth of 25 m below ground. Two well-logging profiles showed that seawater intrusion has largely expanded (progressed inland), and has greatly affected the groundwater quality in a coastal aquifer of tuffaceous sedimentary rock over a 9-year period. According to the time series analyses, the periodograms of the hydrological parameters present very similar trends to the power spectral densities (PSD) of the hydrological parameters. Autocorrelation functions (ACF) and partial autocorrelation functions (PACF) of the hydrological parameters were produced to evaluate their self-correlations. The ACFs of all hydrologic parameters showed very good correlation over the entire time lag, but the PACF revealed that the correlations were good only at time lag 1. Crosscorrelation functions (CCF) were used to evaluate the correlations between the hydrological parameters and the characteristics of seawater intrusion in the coastal aquifer system. The CCFs showed that EC had a close relationship with water pressure and precipitation rather than tide. The CCFs of water pressure with tide and precipitation were in inverse proportion, and the CCF of water pressure with precipitation was larger than that with tide.  相似文献   

DEM modeling of hydraulic fracturing in permeable rock: influence of viscosity,injection rate and in situ states     

Kang Duan  Chung Yee Kwok  Wei Wu  Lu Jing 《Acta Geotechnica》2018,13(5):1187-1202

Hydraulic fracturing in permeable rock is a complicated process which might be influenced by various factors including the operational parameters (e.g., fluid viscosity, injection rate and borehole diameter) and the in situ conditions (e.g., in situ stress states and initial pore pressure level). To elucidate the effects of these variables, simulations are performed on hollow-squared samples at laboratory scale using fully coupled discrete element method. The model is first validated by comparing the stress around the borehole wall measured numerically with that calculated theoretically. Systematic parametric studies are then conducted. Modeling results reveal that the breakdown pressure and time to fracture stay constant when the viscosity is lower than 0.002 Pa s or higher than 0.2 Pa s but increases significantly when it is between 0.002 and 0.2 Pa s. Raising the injection rate can shorten the time to fracture but dramatically increase the breakdown pressure. Larger borehole diameter leads to the increase in the time to fracture and the reduction in the breakdown pressure. Higher in situ stress requires a longer injection time and higher breakdown pressure. The initial pore pressure, on the other hand, reduces the breakdown pressure as well as the time to fracture. The increase in breakdown pressure with viscosity or injection rate can be attributed to the size effect of greater tensile strength of samples with smaller infiltrated regions.  相似文献   

Uncertainties Monitoring Groundwater Levels in Exploratory Wells     

J. David Rogers  Jae‐Won Chung 《Ground water》2013,51(1):2-4

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Dynamic factor analysis and artificial neural network for estimating pan evaporation at multiple stations in northern Taiwan     

F.J. Chang  W. Sun  C.H. Chung 《水文科学杂志》2013,58(4):813-825

Abstract

Evaporation is an important reference for managers of water resources. This study proposes a hybrid model (BD) that combines back-propagation neural networks (BPNN) and dynamic factor analysis (DFA) to simultaneously precisely estimate pan evaporation at multiple meteorological stations in northern Taiwan through incorporating a large number of meteorological data sets into the estimation process. The DFA is first used to extract key meteorological factors that are highly related to pan evaporation and to establish the common trend of pan evaporation among meteorological stations. The BPNN is then trained to estimate pan evaporation with the inputs of the key meteorological factors and evaporation estimates given by the DFA. The BD model successfully inherits the advantages from the DFA and BPNN, and effectively enhances its generalization ability and estimation accuracy. The results demonstrate that the proposed BD model has good reliability and applicability in simultaneously estimating pan evaporation for multiple meteorological stations.

Citation Chang, F.J., Sun, W., and Chung, C.H., 2013. Dynamic factor analysis and artificial neural network for estimating pan evaporation at multiple stations in northern Taiwan. Hydrological Sciences Journal, 58 (4), 813–825.  相似文献   

Modeling and assessment of bridge structure for seismic hazard prevention   总被引：7，自引：7，他引：0  

Jeng-Wen Lin  Cheng-Wu Chen  Shang-Heng Chung 《Natural Hazards》2012,61(3):1115-1126

This study uses data from Mao-Luo-Hsi Bridge to model the bridge structure and a set of developed alarm and action values to formulate guidelines for bridge maintenance and seismic hazard prevention. The bridge model is improved by incorporating on-site ambient vibration measurement to perform modal analyses. Dynamic analyses of the bridge are implemented using the established 3D model subjected to uniform loading and seismic force, with or without consideration of soil interaction with the structure. The maximum displacements for different sections of the bridge are compared, and statistical regression analyses are used to explore their correlation. Information for bridge safety assessment is proposed, which can mitigate loss of property and lives due to bridge failure. Regression analyses of the maximum displacements between abutments D and E of the considered bridge in the axial, horizontal, and vertical directions under various seismic intensities are conducted, giving R ² values of 0.9462, 0.9352, and 0.9010, respectively. The developed maintenance guidelines are reliable since all parameters from regression analyses have a 95% confidence interval excluding the zero value. The bridge alarm value and action value are determined for this bridge site at earthquake intensity scales of 4 and 5, respectively.  相似文献   

Geostatistical techniques to evaluate groundwater contamination and its sources in Miryang City,Korea     

Senapathi Venkatramanan  Sang Yong Chung  Tae Hyung Kim  Byung-Woo Kim  Sekar Selvam 《Environmental Earth Sciences》2016,75(11):994

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Identification of saline water intrusion in part of Cauvery deltaic region,Tamil Nadu,Southern India: using GIS and VES methods     

G. Gnanachandrasamy  T. Ramkumar  S. Venkatramanan  S. Y. Chung  S. Vasudevan 《Marine Geophysical Researches》2016,37(2):113-126

We use electrical resistivity data arrayed in a 2715 km² region with 30 locations to identify the saline water intrusion zone in part of Cauvery deltaic region, offshore Eastern India. From this dataset we are able to derive information on groundwater quality, thickness of aquifer zone, structural and stratigraphic conditions relevant to groundwater conditions, and permeability of aquifer systems. A total of 30 vertical electrode soundings (VES) were carried out by Schlumberger electrode arrangement to indicate complete lithology of this region using curve matching techniques. The electrical soundings exhibited that H and HK type curves were suitable for 16 shallow locations, and QH, KQ, K, KH, QQ, and HA curves were fit for  other location. Low resistivity values suggested that saline water intrusion occurred in this region. According to final GIS map, most of the region was severely affected by seawater intrusion due to the use of over-exploitation of groundwater.The deteriorated groundwater resources in this coastal region should raise environmental and health concerns.  相似文献   

On the weak turbulent motions of an isothermal dry granular dense flow with incompressible grains: part I. Equilibrium turbulent closure models   总被引：1，自引：1，他引：0  

Chung Fang  Wei Wu 《Acta Geotechnica》2014,9(5):725-737

The weak turbulent motions of a dry granular dense flow and the influence of the turbulent fluctuations caused by the minor short-term elastic/inelastic instantaneous collisions and the major long-term enduring frictional contacts among the grains on the mean flow characteristics are investigated. To this end, the conventional Reynolds-averaging process is applied to obtain the balance equations for the mean primitive fields associated with turbulent closure models. The thermodynamic analysis, based on the Mueller–Liu entropy principle, is carried out to derive the equilibrium formulations of the closure models. It shows that the effect of the turbulent fluctuations on the mean flow characteristics as well as the turbulent kinetic energy and dissipation can be taken into account by the granular coldness: a phenomenological measure of the fluctuating kinetic energy intensity. The implementation of the complete thermodynamically consistent turbulent closure models and the simulation of a gravity-driven stationary flow down an inclined moving plane compared with the experimental outcomes are provided in Part II of the present study.  相似文献   

Marine-Derived Fungi in Korea     

Kwon  Yong Min  Bae  Seung Sub  Choi  Grace  Lim  Ji Yeon  Jung  Yoon-Hee  Chung  Dawoon 《Ocean Science Journal》2021,56(1):1-17

Ocean Science Journal - Studies on marine fungi (termed as ‘marine-derived fungi’ in this paper) have been significantly increasing worldwide because of the critical role displayed by...  相似文献