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Groundwater nitrate-N contamination typically involves several natural and anthropogenic factors, such as hydrology, hydrogeology, topography, and land uses. DRASTIC-LU-based aquifer vulnerability can be adopted to explore pollution potentials of groundwater nitrate-N. Furthermore, groundwater nitrate-N pollution frequently has high levels of spatial variability because of various pollution sources and hydrogeological and hydrochemical conditions. Estimates are typically uncertain owing to limited in-situ data. Geostatistics is a commonly used technique of spatial estimates with limited data. To reduce the underestimation and overestimation of ordinary kriging (OK), this study employed regression kriging (RK) with environmental auxiliary information on DRASTIC-LU-based aquifer vulnerability to characterize groundwater nitrate-N pollution in the Pingtung Plain, Taiwan. First, the relationship between groundwater nitrate-N pollution and aquifer vulnerability assessment was determined using stepwise multivariate linear regression (MLR). Then, simple kriging was adopted to estimate residuals acquired from gaps between nitrate-N observations and MLR predictions. The sum of the estimated residuals and MLR predictions was the RK estimates for groundwater nitrate-N. Finally, groundwater nitrate-N distributions were spatially analyzed using RK, OK, and MLR. To reduce groundwater nitrate-N pollution, feasible environmental management strategies were discussed according to the study results. The study results revealed that the orchard land-use types and medium- and coarse-sand fractions of vadose zone were related to groundwater nitrate-N. Moreover, the fertilizer application in orchards was the major source of groundwater nitrate-N pollution. The RK estimates could characterize the characteristics of the pollution source of the orchard land uses, and exhibited higher spatial variability and accuracy via the correction of the residuals than MLR predictions and OK estimates. In addition, feasible management strategies of orchards at the eastern and western regions with high areal ratios of orchard land uses should be implemented to reduce nitrate-N leaching, such as organic fertilizer uses, ground covers, and irrigation with low intensity and high frequency.

Assessing aquifer vulnerability is crucial for preventing groundwater pollution. In this study, aquifer vulnerability to fecal coliform (FC) pollution was assessed using auxiliary environmental data in the Pingtung Plain, Taiwan. Moreover, key environmental factors inducing different fecal pollution levels were determined. First, 23 explanatory variables on land uses, population density, livestock and poultry densities, sanitary condition, antecedent precipitation, groundwater quality, aquifer characteristics, and subsurface hydrology were obtained using geographic information systems in 2014. As dependent variables, groundwater FCs were also simultaneously obtained. Then, multi-threshold logistic regression (LR) was adopted to model aquifer vulnerability assessment after cross validation. The thresholds of aquifer vulnerability causing risks of incidental ingestion were analyzed by risk assessment. Risks to human health were acceptable for a low-level threshold and exceeded the acceptable level for medium- and high-level thresholds when residents incidentally ingested FC-polluted groundwater. Finally, key environmental factors inducing low, medium, and high levels of groundwater FC pollution were characterized. The key environmental factors for the LR with low- and medium-level thresholds were sand and gravel soil textures of unsaturated aquifers and antecedent 3-day cumulative precipitation, and those for the LR with high-level thresholds were chicken farming, urban land use, and ratio of tap water use. Thus, the multi-threshold LR indicated that environmental factors must be ranked for assessing aquifer vulnerability.

sites_information.csv is the location, codename,land type of study sites. CCH_open_*_2018_2019_daily.csv are the daily Tmax/Tmin/DTR in the open field from 2018to 2019. CCH_forest_*_2018_2019_daily.csv are the daily Tmax/Tmin/DTR in the understory from 2018to 2019. CCH_forest_*_annual_avg.csvare themeandaily Tmax/Tmin/DTRin the understory from2018to 2019. CCH_open_*_annual_avg.csvare themeandaily Tmax/Tmin/DTRin the understory from2018to 2019. CCH_IOP_*.csv is the mean air temperature/visibilityevery 30/10 mins during IOP. 202001_05_CL*norain_temp.csvare themeanair temperature every 30 minsin fog/non-fog days. 2008_2011_CL*_radiation.csvare themean radiationevery 30 minsin fog/non-fog days. &nbsp

Hydro-climate in the montane cloud forest (MCF) regions is unique for its frequent fog occurrence and abundant water interception by tree canopies. Latent heat (LH) flux, the energy flux associated with evapotranspiration (ET), plays an essential role in modulating energy and hydrological cycles. However, how LH flux is partitioned between transpiration (stomatal evaporation) and evaporation (non-stomatal evaporation), and how it impacts local hydro-climate remain unclear. In this study, we investigate how fog modulates the energy and hydrological cycles of MCF by using a combination of in-situ observations and model simulations. We compare LH flux and associated micrometeorological conditions at two eddy-covariance sites—Chi-Lan (CL), a MCF, and Lien-Hua-Chih (LHC), a non-cloud forest in Taiwan. The comparison between the two sites reveals an asymmetric LH flux with an early peak at 9:00 in CL as opposed to LHC, where LH flux peaks at noon. The early peak of LH flux and its evaporative cooling dampen the increase in near-surface temperature during the morning hours in CL. The relatively small diurnal temperature range, abundant moisture brought by the valley wind, and local ET result in frequent afternoon fog formation. Fog water is then intercepted by the canopy, sustaining moist conditions throughout the night. To further illustrate this hydrological feedback, we used a land surface model to simulate how varying canopy water interception can affect surface energy and moisture budgets. Our study highlights the unique hydro-climatological cycle in MCF and, specifically, the inseparable relationship between the canopy and near-surface meteorology during the diurnal cycle.

Crack extensions in small side-grooved arc-shaped tension specimens of uncharged and hydrogen-charged conventionally forged 21-6-9 stainless steels are simulated using two-dimensional plane strain finite element analyses with the nodal release method. The finite element analyses are conducted with the input crack extension-displacement curves from the experiments. The crack extensions are simulated by releasing the nodal points ahead of the initial crack tips. The crack extensions follow the experimental results based on the electric potential drop method. The maximum opening stresses and the separation work rates as functions of the crack extension are then determined for determination of the cohesive strength and cohesive energy for a two-dimensional cohesive zone modeling approach. With the nodal release method for crack extensions, the experimental J-R curves are shown to be significantly higher than the separation work rates and therefore the use of the experimental J-integral values as guides for the selections of the cohesive energies should be careful for small fracture specimens. The computational results are useful for identification of the varying cohesive strengths and cohesive energies for the two-dimensional cohesive zone modeling of crack extensions in small fracture specimens.

In this study, the effects of various fabrication parameters on the electrical performance of an electrospun nanofiber-based triboelectric nanogenerator (EN-TENG) are systematically investigated through the design of experiments. We selected four fabrication parameters to examine, namely: (i) working distance (needle to collector distance), (ii) needle gauge, (iii) electrospinning time, and (iv) counter materials. A mixed orthogonal array of L18 experiments was designed with respect to the one factor having two level values and three factors having three level values. The open circuit voltage of the EN-TENG was varied from 86.1 to 576.7 V with the aforementioned fabrication parameters. A longer working distance, a larger needle gauge, and a longer electrospinning time increased the open circuit voltage. The power density of the optimized EN-TENG was approximately 2.39 W/m2 at a 100 MΩ load resistance and was sufficient to illuminate a total of 200 LEDs.

The effects of curvature on K, J, plastic zone, near-tip stress and fracture initiation in curved compact tension (CCT) specimens of unhydrided and hydrided irradiated Zr-2.5Nb materials are determined by three-dimensional finite element analyses. Based on a strain-based failure criterion, the fracture initiation load for unhydrided CCT specimens is slightly lower than those for unhydrided compact tension (CT) and pressure tube (PT) specimens. For hydrided specimens, the reductions of fracture initiation loads for CT, CCT and PT specimens are similar. The fractions of fracture initiation loads for hydrided specimens are about 60–70% of those for unhydrided specimens.

Fracture tests of uncharged and hydrogen-charged single edge bend specimens of additively manufactured 304 stainless steels are simulated using the cohesive zone modeling (CZM) approach. Two-dimensional plane strain finite element analyses without cohesive elements are conducted to identify the values of cohesive energy. Similar analyses using CZM with the trapezoidal traction-separation laws are then conducted. The best-fit cohesive parameters show the values of cohesive strength for the uncharged specimens are higher than those for the hydrogen-charged ones whereas the value of cohesive energy for the uncharged specimens can be either slightly lower or higher than that for the hydrogen-charged ones.

Oxidative steam reforming of methanol (OSRM) is autothermal and therefore well suited for hydrogen production. The exothermic part of OSRM generates heat at the reactor inlet to be used as the reaction heat for the endothermic methanol steam reforming in the rest of the reactor. With conventional particle catalysts, a hot spot is formed at the reactor inlet because of the poor thermal conductivity in the catalyst bed. The catalyst at the hot spot is deactivated by thermal sintering. Side reactions such as the reverse water gas shift reaction and methanol decomposition reaction become active at the hot spot. We developed a high-thermal-conductivity Al plate catalyst to suppress the formation of the hot spot in the catalyst bed during OSRM. In particular, a strongly bonded layer of anodic aluminum oxide as a catalyst support was grown on the Al plate surface via anodic oxidation in oxalic acid solution, and the internal surface area of the support was increased by pore widening and hot water treatments. To obtain a catalyst with high activity, multiple impregnations (>three times) and an anodization time of 24 h was needed. The catalyst was deactivated when operated at an elevated temperature of 623 K, but the activity was completely restored by a simple oxidation. Notably, OSRM was proven to be a combination of methanol combustion and methanol steam reforming reactions, and the kinetics of these two reactions were studied in detail.

Due to fast industrialization and urbanization, air pollution is more and more serious in Taiwan. Generally, many anthropogenic factors can affect air quality; for example, exhaust gas from automobiles and motorcycles, factory emissions, fossil fuels, burning straw, incinerators, etc. The factors are highly associated with land use. Previous studies typically used multiple linear regression model to analyze the relationships between air quality and land use. This study adopts multi-threshold land use logistic regression (LULR) models with several continuous and categorical variables to assess different levels of fine particulate matters (PM2.5) in Taiwan and to determine key land-use factors controlling various levels of air PM2.5 pollution. First, data on annual air PM2.5 pollution in the Taiwan Island are collected in 2017. Four thresholds of 16.37, 18.68, 21.83, 25.83 µg/m3 are determined based on the 20th, 40th, 60th, and 80th percentiles, respectively, of observed data. Geographical information system is then adopted to analyze data on 29 environmental variables obtained from the three main dimensions–information of land-use categories, amounts of specified pollution sources in townships, and geographical locations adjacent to monitoring stations of air quality. Finally, data in 2017 are employed to establish the LULR model and significant land-use factors causing air PM2.5 pollution are determined using stepwise LULR models for various levels of air PM2.5 pollution. Moreover, data in 2018 are used to verify the established LULR models. The analyzed results reveal that correct responses of the LULR models range from 83.6% to 100%. For the 20th-percentile threshold, locations and the industry land-use area are positively contributed to air pollution, while tempt densities and building, agriculture, forest land-use areas are negatively contributed to air pollution. For the 40th-percentile threshold, locations, plains with an elevation of less than 150 m, and agriculture land-use areas are related to air pollution. For the 60th-percentile threshold, locations are positively related to air pollution, while forest land-use areas are negatively related to air pollution. For the 80th-percentile threshold, locations and industry park areas associated with air pollution. According to the research results, a feasible strategy of environmental management and outdoor activities is proposed.

Rivers are an important urban water resource. This study adopted multivariate linear regression (MLR) and logistic regression (LR) with multiple thresholds to assess river fecal pollution in the Tamsui River watershed using auxiliary environmental data. First, environmental data between 2015 and 2017 on land use, antecedent precipitation, population density, sewerage infrastructure, and river water quality were obtained using geographic information systems and served as explanatory variables. River fecal coliforms (FC), the dependent variable, were also collected for the same period. Then, MLR was used to establish an overall prediction model after validation, and to determine significant factors influencing the level of river fecal pollution. Finally, after stratifying the fecal pollution as low, medium, and high levels, LR with multiple thresholds was employed to explore key factors affecting different FC pollution levels. The study results revealed that land use type and river water quality (other than FC) strongly affected river FC pollution. The discharge of household sewage and wastewater from urban areas was a major source of river FC pollution, particularly for low and medium pollution levels, while farmland land use was negatively correlated with the medium and high levels of river FC pollution in the highly urbanized watershed. Biochemical oxygen demand and suspended solids were highly correlated with medium and high pollution levels in river water.

In the oxidative steam reforming of methanol (OSRM), the partial oxidation of methanol (POM) is commonly assumed to be the main reaction between oxygen and methanol. This assumption was experimentally tested with a commercial Cu/ZnO/Al2O3 catalyst, and it was found that, in fact, the combustion of methanol (COM) was the main reaction between oxygen and methanol in the OSRM. Furthermore, POM was not an independent reaction but a series of COM and steam reforming of methanol (SRM) reactions. In the presence of oxygen, COM was the main reaction, and, as oxygen was depleted, SRM started and produced hydrogen. Multiple steady states were observed during the temperature cycling of the reactor between 453 and 583 K. The multiplicity was caused by COM and was analyzed in terms of the mass and heat transfer between the catalyst particle and the surrounding gas phase. Although the reactor temperature was kept below 573 K, the upper steady state of the catalyst particle (of the two steady states) was estimated to occur at temperatures above 880 K because of the high heat of combustion and the heat transfer resistance between the catalyst and the surrounding gas phase. When the catalyst was in the upper steady state, the combustion rate was so fast that COM was completed at the reactor inlet and SRM was the main reaction in the reactor. In the lower steady state, on the other hand, the combustion rate was low, and COM was the main reaction in the reactor.

Groundwater contamination with high arsenic (As) levels has caused serious health problem in Jianghan Plain. This study presents a framework to evaluate the results and their probable influencing factors of non-carcinogenic risk and carcinogenic risk in Shahu Village. An appropriate health risk assessment for residents exposing to As through ingestion and dermal contact pathways is also discussed in the paper. Hazard quotient (HQ) and target cancer risk (TR) are adopted to compute the non-carcinogenic and carcinogenic effects for residents, respectively. Monte Carlo simulation technique is used to quantify the uncertainty of the risk assessment. The assessment results show that the HQs and TRs of 10-m-deep and 25-m-deep wells exhibit seasonal variations with higher values in rainy season and lower values in dry season. The HQ values exceeding 1 at the depths of 10 (from 0.09 to 23.21 m) and 25 m (from 0.29 to 130.55 m) account for 61 and 94%, respectively, which associate with the As contents distribution in the aquifer sediments. The estimated TR values at the depths of 10 (from 3.86E−05 to 1.04E−02) and 25 m (from 1.32E−04 to 5.87E−02) exceeding the highest acceptable standard (10−4) account for 95 and 100%, respectively. Comparison of the two exposure pathways, the ingestion exposure contributes much more than the dermal contact exposure for both non-carcinogenic risk and carcinogenic risk. The results of sensitivity analysis indicate that a more accurate measurement and better definition of probability distributions for As concentration in the groundwater can increase the accuracy of health risk assessment in Jianghan Plain. The findings demonstrate the importance of the drinking water safety, and the government should take measures to ensure the drinking water safety.

Ductile fracture initiation with consideration of strain concentration and stress triaxiality near crack fronts in compact tension specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides is investigated by three-dimensional finite element analyses. The results indicate that plastic strain concentration is observed in the middle of the ligaments ahead of the crack front. A strain-based failure criterion with consideration of stress triaxiality is developed from the Gurson yield model. With the failure criterion, the necessary fraction of the load for crack initiation is about 0.60–0.70 to fracture the ligaments when compared to that for a CT specimen without split circumferential hydrides.

Ductile fracture initiation with consideration of strain concentration and stress triaxiality near axial crack fronts in pressure tube (PT) specimens of hydrided irradiated Zr-2.5Nb materials with split circumferential hydrides is examined by three-dimensional finite element analyses with submodeling. For a PT specimen with split circumferential hydrides, strain concentration occurs in the middle of the ligaments ahead of the crack front. The computational results suggest that only 60–70% of the internal pressure for fracture initiation of an unhydrided irradiated PT specimen is needed to fracture a hydrided irradiated PT specimen with many split circumferential hydrides along the crack front.

Taiwan is surrounded by oceans, and therefore numerous pleasure beaches attract millions of tourists annually to participate in recreational swimming activities. However, impaired water quality because of fecal pollution poses a potential threat to the tourists' health. This study probabilistically characterized the health risks associated with recreational swimming engendered by waterborne enterococci at 13 Taiwanese beaches by using quantitative microbial risk assessment. First, data on enterococci concentrations at coastal beaches monitored by the Taiwan Environmental Protection Administration were reproduced using nonparametric Monte Carlo simulation (MCS). The ingestion volumes of recreational swimming based on uniform and gamma distributions were subsequently determined using MCS. Finally, after the distribution combination of the two parameters, the beta-Poisson dose–response function was employed to quantitatively estimate health risks to recreational swimmers. Moreover, various levels of risk to recreational swimmers were classified and spatially mapped to explore feasible recreational and environmental management strategies at the beaches. The study results revealed that although the health risks associated with recreational swimming did not exceed an acceptable benchmark of 0.019 illnesses daily at all beaches, they approached to this benchmark at certain beaches. Beaches with relatively high risks are located in Northwestern Taiwan owing to the current movements.

New analytical closed-form structural stress solutions for a rigid inclusion in a finite square thin plate under counter bending, central bending, in-plane shear and tension are developed. The new solutions are used to derive new analytical structural stress and stress intensity factor solutions for similar and dissimilar spot welds in lap-shear specimens. The new analytical solutions can predict the stress intensity factor solutions for similar and dissimilar magnesium/steel spot welds in lap-shear specimens of equal thickness under pinned loading conditions with less than 6% differences when compared with the results of three-dimensional finite element analyses.

In this paper, analytical stress intensity factor solutions for similar and dissimilar spot welds in lap-shear specimens under pinned and clamped loading conditions are derived. Closed-form solutions for similar welds in lap-shear specimens of equal thickness under pinned and clamped loading conditions are derived to show explicitly the effects of the clamped edges on the stress intensity factor solutions. Finite element analyses are also employed to obtain the stress intensity factor solutions for similar and dissimilar spot welds in lap-shear specimens under pinned and clamped loading conditions. Both computational and analytical solutions indicate that the clamped loading reduces the stress intensity factor solutions for the given specimen geometries by up to 7% for similar welds and by about 20% for dissimilar magnesium/steel welds.

Eutrophication has become a crucial issue for water resource management in recent years. In addition, reservoir trophic states are varied with environmental and water quality variables. The objectives of this study were to apply the DFA model to examine which water quality variables significantly affect variations of trophic state index (TSI) factors (i.e. total phosphorus (TP), chlorophyll-a (Chl-a), and Secchi disk transparency (SD)) and use classification and regression tree (CART) to determine the trophic states of the Shinmen Reservoir based on the levels of TSI factors during spring 2001–winter 2009. Results showed that the optimal DFA model contained one common trend (the underlying processes influencing trophic states, which can be rainfall intensity or runoff volume) and 7 explanatory variables. Turbidity (TB), pH, and dissolved oxygen (DO) influence concentrations of TP, while ammonium nitrogen (NH3-N), organic nitrogen (O-N), and nitrate nitrogen (NO3-N) control variations of Chl-a, and TB is related to SD. The CART model can specify trophic states only using two dominant driving factors, i.e. TP and Chl-a. The results of the CART illustrated that eutrophication could be occurred in the Shihmen Reservoir if TP is greater than 31.65 μg/L or if Chl-a is greater than 5.95 μg/L while TP concentration is less than 31.65 μg/L. Runoff nonpoint source pollution resulted from heavy storms may be the important factor affecting reservoir trophic states. Establishing vegetative filter strips along the riparian zone may able to effectively reduce this pollution in a reservoir. The integrated DFA and CART serves as good-fit relationships among trophic states, TSI factors, and water quality variables and provide control strategies for managing water quality in the Shihmen Reservoir.

A wide dynamic range (WDR) CMOS image sensor (CIS) was developed with a specialized readout architecture for realizing highsensitivity (HS) and low-sensitivity (LS) reading modes. The proposed pixel is basically a three-transistor (3T) active pixel sensor (APS) structure with an additional transistor. In the developed WDR CIS, only one mode between the HS mode for relatively weak light intensity and the LS mode for the strong light intensity is activated by an external controlling signal, and then the selected signal is read through each column-parallel readout circuit. The LS mode is implemented with the column capacitors and a feedback structure for adjusting column capacitor size. In particular, the feedback circuit makes it possible to change the column node capacitance automatically by using the incident light intensity. As a result, the proposed CIS achieved a wide dynamic range of 94 dB by synthesizing output signals from both modes. The prototype CIS is implemented with 0.18-μm 1-poly 6-metal (1P6M) standard CMOS technology, and the number of effective pixels is 176 (H) × 144 (V).

Recreational fishing is a popular activity in many urbanized watersheds. When river water is incidentally ingested during fishing sessions, substantial waterborne fecal contamination can cause adverse health effects. This study aims to spatially map health risks for recreational fishers caused by waterborne Escherichia coli (E. coli) in the highly urbanized Tamsui River watershed. First, indicator kriging was used to probabilistically estimate the distributions of waterborne E. coli and determine the conditional cumulative distribution function (CCDF). Subsequently, to propagate the parameter variability, Monte Carlo simulation was adopted to characterize the ingestion rate and exposure duration for recreational fishers and E. coli realizations were generated using random fields on the basis of the estimated CCDF. Finally, after the three parameters were combined, the approximate beta-Poisson dose–response function was employed to quantitatively determine potential risks to recreational fishers in the Tamsui River and its tributaries. The analysis results revealed that the risks of recreational fishing exceed an acceptable level of 8 infections per 1000 fishers per day at several urban river courses. Therefore, recreational fishing activities in urban riverbanks pose a substantial health threat. Recreational fishing in urban riverbanks should be limited before the construction of complete sanitary sewer systems. The river mouth and certain upstream river sections are suitable for the development of recreational fishing.

Because of the limited surface water on the Pingtung Plain, Taiwan, the plain’s residents frequently extract groundwater to meet their daily household water demands. The residents may experience gastrointestinal infections due to incidental ingestion of groundwater with fecal pollution. This study used indicator kriging (IK) and quantitative microbial risk analysis (QMRA) to assess the health risks of using groundwater for household cleaning and horticultural irrigation on the Pingtung Plain. First, IK was employed to determine the conditional cumulative distribution function (CCDF) of groundwater Escherichia coli (E. coli). Nonparametric Monte Carlo simulation based on established CCDF was then adopted to characterize the distributions and uncertainty of groundwater E. coli. Finally, QMRA was employed to determine health risks of groundwater use for household cleaning and horticultural irrigation, and the 95th percentiles of the risk distributions were calculated to obtain a representative risk. The study results indicated that the health risks of groundwater use ranged from 3.95 × 10−5 to 2.49 × 10−2 infections/user/year and exceeded the acceptable level, 1 × 10−4 infections/user/year, in most of the aquifers. Accordingly, residents of this plain should not directly extract groundwater for use in daily life.

The crack tip opening displacements (CTODs) and the effective plastic strains ahead of the crack front in a hydrided irradiated Zr-2.5Nb pressure tube specimen with an axial crack are investigated using two 3-D finite element models in this paper. The first model is a pressure tube with 80 split circumferential hydrides distributed through the thickness ahead of the crack front. The second model is a large thin plate with a central crack with four split circumferential hydrides under symmetry/symmetry, free/symmetry and free/free constraint conditions. The results for CTOD indicate that the CTOD of the pressure tube specimen with 80 hydrides is slightly smaller than that for the large thin plate with the free/symmetry constraint condition and larger than that for the large thin plate with the symmetry/symmetry constraint condition. The effective plastic strain of the pressure tube specimen with 80 hydrides is smaller than that for the large thin plate with the free/symmetry constraint condition and larger than that for the large thin plate with the symmetry/symmetry constraint condition at large normalized loads. The computational results show that instead of modeling a full 3-D pressure tube with a larger number of hydrides, a large thin plate model with a limited number of hydrides can be used to efficiently determine the upper and lower bounds of the CTODs and the effective plastic strains ahead of the crack front in a pressure tube specimen.

In this paper, finite element analyses are employed to obtain the stress intensity factor solutions for similar and dissimilar welds in lap-shear specimens under pinned and clamped loading conditions. Analytical solutions for welds in lap-shear specimens under clamped loading conditions are then derived based on the energy release rate and the structural stress approaches. Both computational and analytical solutions indicate that the clamped loading reduces the stress intensity factor solutions for a given specimen geometry by about 7% for similar welds and by about 20% for dissimilar aluminum/steel and magnesium/steel welds, and results in higher fatigue lives of the welds.

This paper presents an average current mode buck dimmable light-emitting diode (LED) driver for large-scale single-string LED backlighting applications. The proposed integrated current control technique can provide exact current control signals by using an autozeroed integrator to enhance the accuracy of the average current of LEDs while driving a large number of LEDs. Adoption of discontinuous low-side current sensing leads to power loss reduction. Adoption of a fast-settling technique allows the LED driver to enter into the steady state within three switching cycles after the dimming signal is triggered. Implemented in a 0.35-μm HV CMOS process, the proposed LED driver achieves 1.7% LED current error and 98.16% peak efficiency over an input voltage range of 110 to 200 V while driving 30 to 50 LEDs.

Accurately estimating a spatial pattern of low permeability topsoil materials, such as clay, silt, and mud, is critical because these materials are a natural barrier to groundwater recharge and flow in subsurface engineering applications. This study determined the spatial distributions and thicknesses of low permeability topsoil materials in the Choushui River alluvial fan, Taiwan by using a combined ordinary–indicator kriging (OIK) approach with multiple thresholds. The thicknesses were first estimated using ordinary kriging (OK). To reduce the overestimation of low values and underestimation of high values, indicator kriging (IK) was then adopted to probabilistically categorize the thickness of the materials. The maximum occurrence probability among the categories was selected for determining the most suitable thickness category of low permeability topsoil materials. Finally, the thicknesses of the materials estimated using OK were amended according to the upper and lower limits of the most suitable category determined using multi-threshold IK. The research results reveal that the combined OIK approach with multiple thresholds can reduce the overestimation of low values and underestimation of high values for various topsoil thicknesses and characterize a reliable hydrogeological pattern in topsoil. The approach facilitates evaluating groundwater recharge and constructing a numerical model of coupled surface water and groundwater flow.

Summary Overexploitation of groundwater is a common problem in the Pingtung Plain area of Taiwan, resulting in substantial drawdown of groundwater levels as well as the occurrence of severe seawater intrusion and land subsidence. Measures need to be taken to preserve these valuable groundwater resources. This study seeks to spatially determine the most suitable locations for the use of surface water on this plain instead of extracting groundwater for drinking, irrigation, and aquaculture purposes based on information obtained by combining groundwater quality analysis and a numerical flow simulation assuming the planning of manmade lakes and reservoirs to the increase of water supply. The multivariate indicator kriging method is first used to estimate occurrence probabilities, and to rank townships as suitable or unsuitable for groundwater utilization according to water quality standards for drinking, irrigation, and aquaculture. A numerical model of groundwater flow (MODFLOW) is adopted to quantify the recovery of groundwater levels in townships after model calibration when groundwater for drinking and agricultural demands has been replaced by surface water. Finally, townships with poor groundwater quality and significant increases in groundwater levels in the Pingtung Plain are prioritized for the groundwater conservation planning based on the combined assessment of groundwater quality and quantity. The results of this study indicate that the integration of groundwater quality analysis and the numerical flow simulation is capable of establishing sound strategies for joint groundwater and surface water use. Six southeastern townships are found to be suitable locations for replacing groundwater with surface water from manmade lakes or reservoirs to meet drinking, irrigation, and aquaculture demands.