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Now showing 1 - 10 of 17

Online video streaming for human tracking based on weighted resampling particle filter
(2018-01-01)
Prasad, Mukesh
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Chang, Liang-Cheng
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Gupta, Deepak
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Pratama, Mahardhika
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Sundaram, Suresh
This paper proposes a weighted resampling method for particle filter which is applied for human tracking on active camera. The proposed system consists of three major parts which are human detection, human tracking, and camera control. The codebook matching algorithm is used for extracting human region in human detection system, and the particle filter algorithm estimates the position of the human in every input image. The proposed system in this paper selects the particles with highly weighted value in resampling, because it provides higher accurate tracking features. Moreover, a proportional integral derivative controller (PID controller) controls the active camera by minimizing difference between center of image and the position of object obtained from particle filter. The proposed system also converts the position difference into pan-tilt speed to drive the active camera and keep the human in the field of view (FOV) camera. The intensity of image changes overtime while tracking human therefore the proposed system uses the Gaussian mixture model (GM,M) to update the human feature model. As regards, the temporal occlusion problem is solved by feature similarity and the resampling particles. Also, the particle filter estimates the position of human in every input frames, thus the active camera drives smoothly. The robustness of the accurate tracking of the proposed system can be seen in the experimental results. (C) 2018 The Authors. Published by Elsevier Ltd.
Constructing the Apparent Geological Model by Fusing Surface Resistivity Survey and Borehole Records
(2019-07-01)
Tsai, Jui-Pin
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Chang, Ping-Yu
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Yeh, Tian-Chyi J.
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Chang, Liang-Cheng
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Hsiao, Chin-Tsai
We constructed an apparent geological model with resistivity data from surface resistivity surveys. We developed a data fusion approach by integrating dense electrical resistivity measurements collected with Schlumberger arrays and wellbore logs. This approach includes an optimization algorithm and a geostatistic interpolation method. We first generated an apparent formation factor model from the surface resistivity measurements and groundwater resistivity records with an inverse distance method. We then converted the model into a geology model with the optimized judgment criteria from the algorithms relating the apparent formation factors to the borehole geology. We also employed a non-parametric bootstrap method to analyze the uncertainty of the predicted sediment types, and the predictive uncertainties of clay, gravel, and sand were less than 5%. Overall, our model is capable of capturing the spatial features of the sediment types. More importantly, this approach can be arranged in a self-updated sequence to enable adjustments to the model to accommodate newly collected core records or geophysical data. This approach yields a more detailed apparent geological model for use in future groundwater simulations, which is of benefit to multi-discipline studies.
River Width Measurement Using Sentinel-1 Satellite Data
(2018-01-01)
Hsu, Wei-Ling
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Chang, Kuan-Tsung
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Chang, Liang-Cheng
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Wang, Chih-Tien
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土木工程學系
The sentinel-1 Synthetic Aperture Radar image analysis technology is conducted to measure river width in a multitemporal change in this study. With the field surveying work, two Sentinel-1A images taken on March 14 and May 24, 2018, have been obtained. Next the SNAP data processing software can be used to produce backscattering coefficient, and the values can be converted into intensity image. Low intensity features related with water body will be helpful for river width measurement. Moreover, an UAS flight also arranged on May 24 to take 525 photos with a DJI Phantom 4 Pro UAS under flying altitude of 120 meters. The Agisoft Photoscan Professional software used to produce an ortho-mosaic image in a spatial resolution of 3.39 cm for the comparison of geometrical differences in river width measurement. According to the comparison results with manual measurement, the derived difference of river width is 1.2 meters at the Zhongtou bridge in the Wuxi river.
Short-Time Geodetic Determination of Aquifer Storage Coefficient in Taiwan
(2018-12-01)
Chen, Kuan-Hung
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Hwang, Cheinway
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Chang, Liang-Cheng
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Ke, Chien-Chung
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土木工程學系
Specific yield (S-y) and specific storage (S-s) are two hydrogeological parameters often estimated in a costly pumping test (hydraulic method). Pumping or a natural aquifer recession can cause gravity change and surface deformation, useful for S-y and S-s determination by the more economic geodetic method. From 2013 to 2017, over a few days we measured gravity changes at four sites and subsidence at one site in Taiwan by a FG5 gravimeter and a precision level to estimate S-y and S-s. Using short-time gravity and level records avoids complicated logistic supports and temporal effects. The measured gravity changes are associated with the MODFLOW-modeled groundwater depletion. We succeeded in estimating S-y at two sites and failed at the other two. One successful case uses rapid postrain declines of gravity and groundwater level. We did leveling only at one site, but here the 500-min, continuous, submillimeter subsidence records result in a S-s consistent with the hydraulic result. Lessons on the failed cases of S-y are suggested to avoid disrupting factors in gravity surveys. A semiautomatic leveling procedure is proposed to maximize the chance for S-s determination. Our simulations show that gravity changes increase with S-y and decrease with initial hydraulic head and horizontal gravimeter-pumping well distance, helping to predict if the gravity-based method works at a site and to best plan a gravity survey. Drilling data show that the S-y values from the hydraulic and geodetic methods represent aquifer storage coefficients over different aquifer layers. Plain Language Summary A pumping test extracts groundwater from a well to estimate an aquifers storage coefficients, based on measurements of the groundwater lowering rate during pumping. But pumping can also lower gravity values and deform the surface. After a heavy rain stops, the aquifer level can rapidly decline to lower gravity values. We measure such gravity changes and surface deformations to determine hydrogeological parameters critical to understanding aquifer storage capacity and managing groundwater resource.
Spatial-temporal pattern recognition of groundwater head variations for recharge zone identification
(2017-06-01)
Tsai, Jui-Pin
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Chang, Liang-Cheng
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Chang, Ping-Yu
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Lin, Yuan-Chien
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Chen, You-Cheng
The delineation of groundwater recharge zones is crucial for the conservation of groundwater quality and quantity. To objectively estimate groundwater recharge zones, many field surveys are required that are costly in both time and money. To facilitate the assessment of recharge zones with high efficiency and low expense, this study proposes a 'fast-filter' approach based on empirical orthogonal function analysis and applies it in a synthetic case study and to Taiwan's Yilan Plain. In the synthetic case study, we demonstrate that the proposed method can effectively identify the recharge area by considering the head variations driven by rainfall recharge. For the case of Yilan Plain application, the field investigations (i.e., collected wellbore logs and electrical resistivity tomography [ERT] surveys) and a groundwater simulation model support the recharge zones estimated by the proposed method. The study results show that within the estimated recharge zone, all of the collected wellbore logs consist of coarse grains, and thick and continuous high resistivity zones were shown in the ERT profile images. Moreover, the groundwater model indicates that the recharge within the estimated recharge zone is 57.6% of the total recharge despite that the area of the estimated zone is only 26.8% of the study area. Therefore, the proposed method is shown to delineate recharge zones at low cost. (C) 2017 Elsevier B.V. All rights reserved.
Determining an Optimal Action Portfolio for Water Resource Management by Using Stochastic Programming
(2017-07-01)
Ho, Chih-Chao
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Pan, Chen-Che
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Chang, Liang-Cheng
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土木工程學系
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Department of Civil Engineering
A regional water management system always contains long-term and short-term actions in practice. The uncertainty of short-term actions increases great complexity for evaluating the performance of action portfolio comprised with long-term and short-term actions. Developing an efficient methodology to define a cost-effective action portfolio is an important task. Hence, this study develops a novel decision model, the Stochastic Programming with Recourse Decision Model (SPRDM), to compute a cost-effective action portfolio. The effectiveness of SPRDM is verified by address a problem of water shortage and financial cost in Taoyuan City, Northern Taiwan. The results shown adding Kaotai Reservoir alone can fulfill the Taoyuan demand most of the time, and the remaining extreme water shortage events can be addressed by short-term and irrigation management actions additionally. When drought duration of water shortage event is longer than 200 days, using irrigation management action to address water deficit has lower expected costs than other short-term actions do. Although the study focuses on Northern Taiwan, the proposed model is applicable to other areas with an integrated water resources management framework.
Features of spatiotemporal groundwater head variation using independent component analysis
(2017-04-01)
Hsiao, Chin-Tsai
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Chang, Liang-Cheng
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Tsai, Jui-Pin
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Chen, You-Cheng
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土木工程學系
The effect of external stimuli on a groundwater system can be understood by examining the features of spatiotemporal head variations. However, the head variations caused by various external stimuli are mixed signals. To identify the stimuli features of head variations, we propose a systematic approach based on independent component analysis (ICA), frequency analysis, cross-correlation analysis, well selection strategy, and hourly average head analysis. We also removed the head variations caused by regional stimuli (e.g., rainfall and river stage) from the original head variations of all the wells to better characterize the local stimuli features (e.g., pumping and tide). In the synthetic case study, the derived independent component (IC) features are more consistent with the features of the given recharge and pumping than the features derived from principle component analysis. In a real case study, the ICs associated with regional stimuli highly correlated with field observations, and the effect of regional stimuli on the head variation of all the wells was quantified. In addition, the tide, agricultural, industrial, and spring pumping features were characterized. Therefore, the developed method can facilitate understanding of the features of the spatiotemporal head variation and quantification of the effects of external stimuli on a groundwater system. (C) 2017 Elsevier B.V. All rights reserved.
Fusion of Time-Lapse Gravity Survey and Hydraulic Tomography for Estimating Spatially Varying Hydraulic Conductivity and Specific Yield Fields
(2017-10-01)
Tsai, Jui-Pin
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Yeh, Tian-Chyi Jim
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Cheng, Ching-Chung
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Zha, Yuanyuan
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Chang, Liang-Cheng
Hydraulic conductivity (K) and specific yield (S-y) are important aquifer parameters, pertinent to groundwater resources management and protection. These parameters are commonly estimated through a traditional cross-well pumping test. Employing the traditional approach to obtain detailed spatial distributions of the parameters over a large area is generally formidable. For this reason, this study proposes a stochastic method that integrates hydraulic head and time-lapse gravity based on hydraulic tomography (HT) to efficiently derive the spatial distribution of K and Sy over a large area. This method is demonstrated using several synthetic experiments. Results of these experiments show that the K and Sy fields estimated by joint inversion of the gravity and head data set from sequential injection tests in unconfined aquifers are superior to those from the HT based on head data alone. We attribute this advantage to the mass constraint imposed on HT by gravity measurements. Besides, we find that gravity measurement can detect the change of aquifer's groundwater storage at kilometer scale, as such they can extend HT's effectiveness over greater volumes of the aquifer. Furthermore, we find that the accuracy of the estimated fields is improved as the number of the gravity stations is increased. The gravity station's location, however, has minor effects on the estimates if its effective gravity integration radius covers the well field.
Effects of liquid layers and distribution patterns on three-phase saturation and relative permeability relationships: a micromodel study
(2017-12-01)
Tsai, Jui-Pin
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Chang, Liang-Cheng
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Hsu, Shao-Yiu
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Shan, Hsin-Yu
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土木工程學系
In the current study, we used micromodel experiments to study three-phase fluid flow in porous media. In contrast to previous studies, we simultaneously observed and measured pore-scale fluid behavior and three-phase constitutive relationships with digital image acquisition/analysis, fluid pressure control, and permeability assays. Our results showed that the fluid layers significantly influenced pore-scale, three-phase fluid displacement as well as water relative permeability. At low water saturation, water relative permeability not only depended on water saturation but also on the distributions of air and diesel. The results also indicate that the relative permeability-saturation model proposed by Parker et al. (1987) could not completely describe the experimental data from our three-phase flow experiments because these models ignore the effects of phase distribution. A simple bundle-of-tubes model shows that the water relative permeability was proportional to the number of apparently continuous water paths before the critical stage in which no apparently continuous water flow path could be found. Our findings constitute additional information about the essential constitutive relationships involved in both the understanding and the modeling of three-phase flows in porous media.
Using the Resistivity Imaging Method to Monitor the Dynamic Effects on the Vadose Zone During Pumping Tests at the Pengtsuo Site in Pingtung, Taiwan
(2016-02)
Chang, Ping-Yu
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Hsu, Shao-Yiu
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Chang, Liang-Cheng
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Chen, Wen-Fu
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Chen, Yu-Wen
We conducted a time-lapse monitoring study during a well-pumping test at the Pengtsuo site in Pingtung, Taiwan. Water-level gauges were installed in four wells (P1, W1, O1, and O2) at the Pengtsuo site with different screen depths for the observation. We designed the pumping test to be executed in three phases: the background, the stepwise-pumping, and the continuous-pumping phases. The survey line crossed the four wells so that a comparison would be possible between the resistivity measurements and the water-level records. The resistivity differences relative to the pre-pumping background show that electrical resistivity imaging (ERI) can resolve changes due to dewatering from pumping activity. The time-lapse resistivity images reveal that the maximum resistivity increase took place at the locations in the vadose zone instead of at the ground-water surface. The variation in the resistivity differences in the vadose zone correlated to the change in groundwater level in the stepwise phase. On the other hand, the resistivity-difference change was not fully consistent with the groundwater-level change in the continuous-pumping phase. We attribute the abnormal ERI signals to the dynamic non-equilibrium of the water movement in the vadose zone. The findings suggest that pumping designs can affect the changing resistivity differences and water-content distribution patterns. We show the potential of the ER method to reveal both the water flow and water-content changes in the vadose zone with different transient boundary conditions.

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