學術出版;;Publications

Permanent URI for this communityhdl:11536/1

收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

Browse

🏛️國立陽明交通大學機構典藏

Search Results

Now showing 1 - 10 of 41

Online video streaming for human tracking based on weighted resampling particle filter
(2018-01-01)
Prasad, Mukesh
;
Chang, Liang-Cheng
;
Gupta, Deepak
;
Pratama, Mahardhika
;
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
;
Chang, Ping-Yu
;
Yeh, Tian-Chyi J.
;
Chang, Liang-Cheng
;
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.
Developing a Conjunctive Use Optimization Model for Allocating Surface and Subsurface Water in an Off-Stream Artificial Lake System
(2016-08-01)
Pan, Chen-Che
;
Chen, Yu-Wen
;
Chang, Liang-Cheng
;
Huang, Chun-Wei
;
土木工程學系
This work develops a rule curve-based conjunctive use management model for optimizing the operating rules for a lake-groundwater system with off-stream storage lakes. The proposed procedure is a simulation-optimization approach that embeds an Artificial Neural Network ( ANN) instead of a groundwater numerical model into a genetic algorithm ( GA). The direct physical exchange between lake water with groundwater is simulated using the ANN model, which is a reduced version of a full numerical model, MODFLOW with an LAK3 module. By applying the ANN model, the proposed procedure can reduce the computational burden that is induced by the nonlinear exchange. An operating rule-based optimal conjunctive use management model for the Gaopin Artificial lakes system in Taiwan was thus developed using the proposed framework. A set of optimal solutions involves rule curves and a discount ratio. Simulation results demonstrate that the embedded ANN model can accurately simulate the nonlinear exchange of a lake with groundwater. The embedded ANN model is less computationally complex than the numerical model. This work demonstrates a methodology for reducing the computational burden of the optimal conjunctive use management model that is associated with an internal nonlinear system by using the ANN reduced model. Specifically, the concept of, and results obtained using the developed operating rule-based model incorporating five artificial lakes and considering the nonlinear exchange of those lakes with the groundwater system provides a valuable practical reference for solving related conjunctive use problems.
High Recharge Areas in the Choushui River Alluvial Fan (Taiwan) Assessed from Recharge Potential Analysis and Average Storage Variation Indexes
(2015-04-01)
Tsai, Jui-Pin
;
Chen, Yu-Wen
;
Chang, Liang-Cheng
;
Kuo, Yi-Ming
;
Tu, Yu-Hsuan
High recharge areas significantly influence the groundwater quality and quantity in regional groundwater systems. Many studies have applied recharge potential analysis (RPA) to estimate groundwater recharge potential (GRP) and have delineated high recharge areas based on the estimated GRP. However, most of these studies define the RPA parameters with supposition, and this represents a major source of uncertainty for applying RPA. To objectively define the RPA parameter values without supposition, this study proposes a systematic method based on the theory of parameter identification. A surrogate variable, namely the average storage variation (ASV) index, is developed to calibrate the RPA parameters, because of the lack of direct GRP observations. The study results show that the correlations between the ASV indexes and computed GRP values improved from 0.67 before calibration to 0.85 after calibration, thus indicating that the calibrated RPA parameters represent the recharge characteristics of the study area well; these data also highlight how defining the RPA parameters with ASV indexes can help to improve the accuracy. The calibrated RPA parameters were used to estimate the GRP distribution of the study area, and the GRP values were graded into five levels. High and excellent level areas are defined as high recharge areas, which composed 7.92% of the study area. Overall, this study demonstrates that the developed approach can objectively define the RPA parameters and high recharge areas of the Choushui River alluvial fan, and the results should serve as valuable references for the Taiwanese government in their efforts to conserve the groundwater quality and quantity of the study area.
Groundwater Simulations and Uncertainty Analysis Using MODFLOW and Geostatistical Approach with Conditioning Multi-Aquifer Spatial Covariance
(2017-03-01)
Lin, Yu-Pin
;
Chen, Yu-Wen
;
Chang, Liang-Cheng
;
Yeh, Ming-Sheng
;
Huang, Guo-Hao
This study presents an approach for obtaining limited sets of realizations of hydraulic conductivity (K) of multiple aquifers using simulated annealing (SA) simulation and spatial correlations among aquifers to simulate realizations of hydraulic heads and quantify their uncertainty in the Pingtung Plain, Taiwan. The proposed approach used the SA algorithm to generate large sets of natural logarithm hydraulic conductivity (ln(K)) realizations in each aquifer based on spatial correlations among aquifers. Moreover, small sets of ln(K) realizations were obtained from large sets of realizations by ranking the differences among cross-variograms derived from the measured ln(K) and the simulated ln(K) realizations between the aquifer pair Aquifer 1 and Aquifer 2 (hereafter referred to as Aquifers 1-2) and the aquifer pair Aquifer 2 and Aquifer 3 (hereafter referred to as Aquifers 2-3), respectively. Additionally, the small sets of realizations of the hydraulic conductivities honored the horizontal spatial variability and distributions of the hydraulic conductivities among aquifers to model groundwater precisely. The uncertainty analysis of the 100 combinations of simulated realizations of hydraulic conductivity was successfully conducted with generalized likelihood uncertainty estimation (GLUE). The GLUE results indicated that the proposed approach could minimize simulation iterations and uncertainty, successfully achieve behavioral simulations when reduced between calibration and evaluation runs, and could be effectively applied to evaluate uncertainty in hydrogeological properties and groundwater modeling, particularly in those cases which lack three-dimensional data sets yet have high heterogeneity in vertical hydraulic conductivities.
River Width Measurement Using Sentinel-1 Satellite Data
(2018-01-01)
Hsu, Wei-Ling
;
Chang, Kuan-Tsung
;
Chang, Liang-Cheng
;
Wang, Chih-Tien
;
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
;
Hwang, Cheinway
;
Chang, Liang-Cheng
;
Ke, Chien-Chung
;
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.
Estimating Hydraulic Conductivity Fields in Composite Fan Delta Using Vertical Electrical Sounding
(2018-11-01)
Chen, You-Cheng
;
Tsai, Jui-Pin
;
Chang, Liang-Cheng
;
Chang, Ping-Yu
;
Lin, Helen
Hydraulic conductivity (K) is crucial for groundwater studies and is conventionally obtained through pumping tests, which are costly due to well installation, resulting in a limited amount of data. Recent studies have addressed this limitation by estimating K through the integration of a pumping-test K and electrical resistivity measurements. While this approach is suitable for local areas, it cannot readily be applied to determine K fields for the composite fan delta. This study proposes and demonstrates an advanced method to estimate the K's spatial distribution of a composite fan delta. The proposed method included data classification, linear regression, and kriging interpolation. Data classification was conducted using a physical-based zonation method. The K and formation factor (F) data pairs were classified into several groups. Linear regression was used to develop K-F mapping for each group. The regression results showed a good correlation between K and F in each group. These K-F mappings were verified by additional pumping tests. These results indicate that estimation errors were between 7 m/day and 58 m/day, and the correlation coefficient of each data group was greater than 0.8. Based on these regression equations and ordinary kriging method, the detailed K spatial distribution of the study area was derived. According to these results, the proposed method is efficient and economical to delineate K's spatial features for regional groundwater systems and can benefit groundwater-related studies.
Effects of the Grain Size on Dynamic Capillary Pressure and the Modified Green-Ampt Model for Infiltration
(2018-01-01)
Tsai, Yi-Zhih
;
Liu, Yu-Tung
;
Wang, Yung-Li
;
Chang, Liang-Cheng
;
Hsu, Shao-Yiu
Darcy-scale capillary pressure is traditionally assumed to be constant. By contrast, a considerable gap exists between the measured and equilibrium capillary pressures when the same moisture saturation is considered with a high flow rate, and this gap is called the dynamic effect on the capillary pressure. In this study, downward infiltration experiments of sand columns are performed to measure cumulative infiltration and to calculate the wetting front depth and wetting front velocity in sands with different grain sizes. We estimate the equilibrium capillary pressure head or suction head at the wetting front using both the classical Green-Ampt (GAM) and modified Green-Ampt (MGAM) models. The results show that the performance of MGAM in simulating downward infiltration is superior to that of GAM. Moreover, because GAM neglects the dynamic effect, it systematically underestimates the equilibrium suction head in our experiments. We also find that the model parameters (alpha) over cap and beta of MGAM are affected by the grain size of sands and porosity, and the dynamic effect of the capillary pressure increases with decreasing grain size and increasing porosity.
Spatial-temporal pattern recognition of groundwater head variations for recharge zone identification
(2017-06-01)
Tsai, Jui-Pin
;
Chang, Liang-Cheng
;
Chang, Ping-Yu
;
Lin, Yuan-Chien
;
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.

學術出版;;Publications

Browse

Filters

Settings

Sort By

Results per page

🏛️國立陽明交通大學機構典藏

Search Results