Characterization of preferential flow paths between boreholes in fractured rock using a nanoscale zero-valent iron tracer test     

Po-Yu Chuang  Yeeping Chia  Ya-Hsuan Liou  Mao-Hua Teng  Ching-Yi Liu  Tsai-Ping Lee 《Hydrogeology Journal》2016,24(7):1651-1662

Recent advances in borehole geophysical techniques have improved characterization of cross-hole fracture flow. The direct detection of preferential flow paths in fractured rock, however, remains to be resolved. In this study, a novel approach using nanoscale zero-valent iron (nZVI or ‘nano-iron’) as a tracer was developed for detecting fracture flow paths directly. Generally, only a few rock fractures are permeable while most are much less permeable. A heat-pulse flowmeter can be used to detect changes in flow velocity for delineating permeable fracture zones in the borehole and providing the design basis for the tracer test. When nano-iron particles are released in an injection well, they can migrate through the connecting permeable fracture and be attracted to a magnet array when arriving in an observation well. Such an attraction of incoming iron nanoparticles by the magnet can provide quantitative information for locating the position of the tracer inlet. A series of field experiments were conducted in two wells in fractured rock at a hydrogeological research station in Taiwan, to test the cross-hole migration of the nano-iron tracer through permeable connected fractures. The fluid conductivity recorded in the observation well confirmed the arrival of the injected nano-iron slurry. All of the iron nanoparticles attracted to the magnet array in the observation well were found at the depth of a permeable fracture zone delineated by the flowmeter. This study has demonstrated that integrating the nano-iron tracer test with flowmeter measurement has the potential to characterize preferential flow paths in fractured rock.  相似文献   

Seasonal variations of wind and waves over Taiwan waters     

Beng-Chun Lee  Li-Chung Wu  Dong-Jiing Doong  Chia Chuen Kao 《Marine Geophysical Researches》2007,28(3):183-190

We here investigate the frequency and intensity of oscillations in oceanographic data within intraseasonal time scales using spectral analysis of surface wind and wave time-series data collected at off-island weather stations or moored buoys around Taiwan. Data from marine weather stations were used to trace atmospheric conditions, while we used buoy data to examine sea states. The spectra and wavelet scalogram of the wind fields revealed oscillations with a period of around 20–33 days, and the energy density of the wind field at the off-island stations was stronger than that at the data buoy stations. However, the wavelet scalogram of the wave height measured at the buoy stations was stronger than its associated wind field. This long-period oscillation is consistent with the wavelet scalogram of the wind field calculated from the off-island weather stations. About 20–33 day oscillations exist within intraseasonal variations, which are closely linked to the atmospheric environment and to wind and ocean wave fields. Oscillations with a period of 5–10 days are a pronounced feature over northeastern Taiwan waters during the winter season and can be interpreted as the wave pattern following synoptic weather systems.  相似文献   

Data quality check procedures of an operational coastal ocean monitoring network     

Dong Jiing Doong  Shen Hsien Chen  Chia Chuen Kao  Beng Chun Lee  Sun Pei Yeh 《Ocean Engineering》2007,34(2):234-246

Field oceanographic and meteorological data are required for ocean engineering. In response to the requirement of field data, an operational coastal ocean monitoring network was established around Taiwan coast, including nine deep-water data buoys, one shallow-water pile station, 10 coastal weather stations and 10 tide stations. Data quality check procedures are necessary to ensure the accuracy of measurements. This paper presents the data quality check procedures on ocean wave data which includes automatic and manual check procedures. The checking criteria are derived using statistical theory in this paper. In addition, a sea-state-dependent algorithm is presented in this study in order to derive checking criteria of time-continuity check. It is showed to have better performance of picking up suspicious data than using fixed threshold process. This data quality check program is now used on the operational monitoring network.  相似文献   

GPS RTK positioning via Internet-based 3G CDMA2000/1X wireless technology     

George?Chia?LiuEmail author 《GPS Solutions》2004,7(4):222-229

The latest evolution in digital wireless technology, third-generation (3G) Code Division Multiple Access/Single Carrier (CDMA2000/1X) wireless network, is applicable for transmitting real-time kinematic (RTK) GPS correction messages. Fast and reliable, publicly available wireless networks, combined with highly accessible Internet connectivity, allows the multicasting of messages to mobile users, who are no longer restricted to traditional private UHF wireless networks. Nationwide public wireless network systems continue to expand and can provide an inexpensive infrastructure for the emerging multi-reference network system. Transmission performance via the Internet-based CDMA2000/1X outperforms UHF technology in transmission throughput and latency, as well as in the RTK initialization time and positional accuracy.  相似文献   

Two-dimensional continuous wavelet transform of simulated spatial images of waves on a slowly varying topography   总被引：1，自引：0，他引：1  

Laurence Zsu-Hsin Chuang  Li-Chung Wu  Dong-Jiing Doong  Chia Chuen Kao 《Ocean Engineering》2008,35(10):1039-1051

The wavelet transform (WT) is now recognized as a useful, flexible, and efficient technique to analyze intermittent, non-stationary and inhomogeneous signals as well as images which are obtained from experimental or in situ measurements. In this study, the two-dimensional continuous wavelet transform (2-D CWT) was introduced to analyze the spatial image of waves. The numerical algorithm of 2-D CWT was developed and testified in simulated wave field of regular and random waves. Some more simulated wave fields of various wave conditions and sea bed slopes were then assumed to verify the analytical accuracy of this new technique. The comparisons of estimations to theoretical values for several wave parameters show that the 2-D CWT is capable of identifying the directional spectra and wave properties in shallow water.  相似文献   

A general solution for tide‐induced groundwater fluctuation in an estuarine‐coastal confined and unconfined aquifer system          下载免费PDF全文

Hsi‐Ting Fang  Yih‐Chi Tan  Mo‐Hsiung Chuang  Kai‐Yuan Ke  Po‐Chia Chen 《水文研究》2018,32(14):2239-2253

This paper presents an analytical solution to tide‐induced head fluctuations in a two‐dimensional estuarine‐coastal aquifer system that consists of an unconfined aquifer and a heterogeneous confined aquifer extending under a tidal river with a semipermeable layer between them. This study considers the joint effects of tidal‐river leakage, inland leakage, dimensionless transmissivity between the tidal‐river and inland confined aquifer, and transmissivity anisotropic ratios. The analytical solution for this model is obtained via the separation of variables method. Three existing solutions related to head fluctuation in one‐ or two‐dimensional leaky confined aquifers are considered as special cases in the present solution. This study shows that there is a threshold of tidal‐river confined aquifer length. When the tidal‐river length is greater than the threshold length, the inland head fluctuations remain sensitive to the leakage effect but become insensitive to the tidal‐river width and dimensionless transmissivity. Considering leakage and transmissivity anisotropy, this study also demonstrates that at a location farther from the river–inland boundary, head fluctuations increase with increasing leakage and transmissivity anisotropy; the maximum head fluctuation occurs when leakage and transmissivity anisotropy are both at their maximum values. The combined action of the 3 effects of loading, tidal‐river aquifer leakage, and inland aquifer leakage differs significantly according to various aquifer parameters. The analytical solution in this paper can be applied to demonstrate the behaviours of the head fluctuations of an estuarine‐coastal aquifer system, and the head fluctuations can be clearly described when the tidal and hydrogeological parameters are derived from field measurement data or hypothetical cases.  相似文献   

Experimental verification of a wireless sensing and control system for structural control using MR dampers     

Chin‐Hsiung Loh  Jerome P. Lynch  Kung‐Chun Lu  Yang Wang  Chia‐Ming Chang  Pei‐Yang Lin  Ting‐Hei Yeh 《地震工程与结构动力学》2007,36(10):1303-1328

The performance aspects of a wireless ‘active’ sensor, including the reliability of the wireless communication channel for real‐time data delivery and its application to feedback structural control, are explored in this study. First, the control of magnetorheological (MR) dampers using wireless sensors is examined. Second, the application of the MR‐damper to actively control a half‐scale three‐storey steel building excited at its base by shaking table is studied using a wireless control system assembled from wireless active sensors. With an MR damper installed on each floor (three dampers total), structural responses during seismic excitation are measured by the system's wireless active sensors and wirelessly communicated to each other; upon receipt of response data, the wireless sensor interfaced to each MR damper calculates a desired control action using an LQG controller implemented in the wireless sensor's computational core. In this system, the wireless active sensor is responsible for the reception of response data, determination of optimal control forces, and the issuing of command signals to the MR damper. Various control solutions are formulated in this study and embedded in the wireless control system including centralized and decentralized control algorithms. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Nappe structure revealed by thermal constraints in the Taiwan metamorphic belt     

Chih‐Tung Chen  Yu‐Chang Chan  Chia‐Yu Lu  Martine Simoes  Olivier Beyssac 《地学学报》2011,23(2):85-91

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A general solution for groundwater flow in an estuarine's leaky aquifer system after considering aquifer anisotropy          下载免费PDF全文

Po‐Chia Chen  Mo‐Hsiung Chuang  Yih‐Chi Tan  Kuo‐Chen Ma 《水文研究》2016,30(12):1862-1871

This paper presents an analytical model for describing the tidal effects in a two‐dimensional leaky confined aquifer system in an estuarine delta where ocean and river meet. This system has an unconfined aquifer on top and a confined aquifer on the bottom with an aquitard in between the two. The unconfined and confined aquifers interact with each other through leakage. It was assumed that the aquitard storage was negligible and that the leakage was linearly proportional to the head difference between the unconfined and confined aquifers. This model's solution was based on the separation of variables method. Two existing solutions that deal with the head fluctuation in one‐dimensional or two‐dimensional leaky confined aquifers are shown as special cases in the present solution. Based on this new solution, the dynamic effect of the water table's fluctuations can be clearly explored, as well as the influence of leakage on the behaviour of fluctuations in groundwater levels in the leaky aquifer system. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Using Chlorine Dioxide to Remove the Fouling of Ultrafiltration Membrane and Control Disinfection By‐Products     

Shu‐Hai You  Chia‐Yu Tsai 《洁净——土壤、空气、水》2011,39(4):351-355

Ultrafiltration (UF) can remove natural organic matter (NOM) effectively. Moreover, chlorine dioxide (ClO₂) has been an alternative disinfectant as it forms fewer disinfection by‐products with NOM than chlorination does. Therefore, combining ClO₂ with UF may improve conventional purification processes. In this study, feed water containing humic acid with 4.07 mg/L total organic carbon (TOC) was dosed directly with various amounts of ClO₂ (0, 2, 5, 10, and 15 mg/L) before being filtered through a 5‐kDa UF membrane. With a low dose (2 mg/L ClO₂), UF removed humic acid effectively, as TOC was not detected in the permeate, and the permeate flux increased to about 80% of the initial permeate flux by cross flow. Moreover, the concentrations of ClO, ClO, and trihalomethanes in the permeate were below the United States Environmental Protection Agency guidelines.  相似文献