Epi-Fluorescence Imaging of Colloid Transport in Porous Media at Decimeter Scales

A noninvasive epi-fluorescence imaging technique was developed for real-time observation of colloid transport in porous media at decimeter scales. Fluorescent latex microspheres and translucent quartz sand were used as a model colloid-porous medium system. Various calibrations were performed for accurate conversion of fluorescence intensities to microsphere concentrations. Fluorescence intensities were found to linearly increase with microsphere concentrations (5 × 105−5 × 108 spheres/mL in saturated sand) and with camera exposure time. Fluorescence intensities also increased with sand thickness (saturated with microsphere solution), indicating that the fluorescence signals detected by the imaging system were integrated signals from the entire thickness (10 mm) of the sand. A set of microsphere transport experiments was conducted to demonstrate the versatility of the imaging system. Excellent mass recoveries (93−103%) were achieved in all transport experiments, demonstrating the robustness of the imaging system for quantitative study of colloid transport. The system allowed the change of flow velocity, ionic strength, and flow direction within one transport experiment and the real-time, quantitative monitoring of the movement of microspheres in packed sand, greatly reducing the time and effort needed for similar work with traditional column experiments

A 30-year high resolution simulation of the ~1980-2010 climate over the Interior Western United States

A high-resolution (4 km) regional climate simulation is conducted in the Interior Western United States (IWUS) using the Weather Research and Forecasting (WRF) model. The IWUS simulation is convection permitting and uses the NoahMP land surface model. The model integration is conducted over a 30-year period from 1 October 1981 through 30 September 2011. This repository contains a 30-year gridded dataset of daily precipitation, and daily minimum and maximum surface (2 m) temperature from the IWUS simulation. Anyone interested in the full dataset of the IWUS simulation is encouraged to contact the lead author at [email protected].</p

Epi-Fluorescence Imaging of Colloid Transport in Porous Media at Decimeter Scales

A noninvasive epi-fluorescence imaging technique was developed for real-time observation of colloid transport in porous media at decimeter scales. Fluorescent latex microspheres and translucent quartz sand were used as a model colloid-porous medium system. Various calibrations were performed for accurate conversion of fluorescence intensities to microsphere concentrations. Fluorescence intensities were found to linearly increase with microsphere concentrations (5 × 105−5 × 108 spheres/mL in saturated sand) and with camera exposure time. Fluorescence intensities also increased with sand thickness (saturated with microsphere solution), indicating that the fluorescence signals detected by the imaging system were integrated signals from the entire thickness (10 mm) of the sand. A set of microsphere transport experiments was conducted to demonstrate the versatility of the imaging system. Excellent mass recoveries (93−103%) were achieved in all transport experiments, demonstrating the robustness of the imaging system for quantitative study of colloid transport. The system allowed the change of flow velocity, ionic strength, and flow direction within one transport experiment and the real-time, quantitative monitoring of the movement of microspheres in packed sand, greatly reducing the time and effort needed for similar work with traditional column experiments

Hansen Solubility Parameters of Coal Tar-Derived Typical PAHs Using Turbidimetric Titration and an Extended Hansen Approach

The advantage of selectivity for coal tar extraction can be obtained by using the solubility parameter of Hansen theory as a guide. However, most of the Hansen solubility parameters (dispersion contributions, δ_d; polarity contributions, δ_p; hydrogen bonding contributions, δ_hb) of coal tar components (e.g., polycyclic aromatic hydrocarbons, PAHs) were inadequate. This study estimated the Hansen solubility parameters of naphthalene, acenaphthene, anthracene, phenanthrene, pyrene, and fluoranthene from coal tar by applying a new approach regulated by turbidimetric titration and a calculating program based on the method of exhaustion. The extended Hansen approach was used to verify the new approach and evaluate the solubility of the six PAH components in different solvents. The results show that the new method can clearly identify the differences in Hansen solubility parameters caused by various combinations of benzene rings among some isomers (e.g., anthracene and phenanthrene). Among the six PAH compounds, high relativity between their Hansen solubility parameters and solubility data was revealed, indicating an excellent reliability of the new method. An extended Hansen approach is appropriate for the estimation of solubility for the six PAHs with acceptable deviations. Moreover, the relationship between the Hansen solubility sphere and the extended Hansen approach was successfully presented by regression analysis

Can variations in visual behavior measures be good predictors of driver sleepiness? A real driving test study

<p><b>Objective</b>: The primary purpose of this study was to examine the association between variations in visual behavior measures and subjective sleepiness levels across age groups over time to determine a quantitative method of measuring drivers' sleepiness levels.</p> <p><b>Method</b>: A total of 128 volunteer drivers in 4 age groups were asked to finish 2-, 3-, and 4-h continuous driving tasks on expressways, during which the driver's fixation, saccade, and blink measures were recorded by an eye-tracking system and the subjective sleepiness level was measured through the Stanford Sleepiness Scale. Two-way repeated measures analysis of variance was then used to examine the change in visual behavior measures across age groups over time and compare the interactive effects of these 2 factors on the dependent visual measures.</p> <p><b>Results</b>: Drivers' visual behavior measures and subjective sleepiness levels vary significantly over time but not across age groups. A statistically significant interaction between age group and driving duration was found in drivers' pupil diameter, deviation of search angle, saccade amplitude, blink frequency, blink duration, and closure duration. Additionally, change in a driver's subjective sleepiness level is positively or negatively associated with variation in visual behavior measures, and such relationships can be expressed in regression models for different period of driving duration.</p> <p><b>Conclusions</b>: Driving duration affects drivers' sleepiness significantly, so the amount of continuous driving time should be strictly controlled. Moreover, driving sleepiness can be quantified through the change rate of drivers' visual behavior measures to alert drivers of sleepiness risk and to encourage rest periods. These results provide insight into potential strategies for reducing and preventing traffic accidents and injuries.</p

Mesoporous Carbon Nanofibers for Supercapacitor Application

Mesoporous carbon nanofibers have been prepared by a confined self-assembly of triblock copolymers with soluble low molecular weight phenolic resol within the channels of anodic alumina membranes. SEM and TEM observations showed that hexagonally arranged mesoporous channels were coiled concentrically around the longitudinal axis of the carbon nanofibers. These carbon nanofibers with BET surface area over 1424 m2 g−1 have been used as electrode materials for electrochemical capacitors tested in KOH and EC/DEC electrolyte solutions. Compared to mesoporous carbon prepared from the same precursor sol, these one-dimensional nanofibers could provide a shortened diffusion distance for electrolyte ions. The better performance of these mesoporous nanofibers greatly benefited from their high specific surface area, shortened diffusion distance, mesoporous openings on the outer surface, and well-controlled pore size. These mesoporous carbon nanofibers have been proved to be promising electrode materials for electrochemical supercapacitors in high-rate charge/discharge operations

Self-reports of workloads and aberrant driving behaviors as predictors of crash rate among taxi drivers: A cross-sectional study in China

Objective: Taxis provide an important mode of public transport in China, but there has been very little in-depth research on the crash involvement propensity of taxi drivers. Thus, this study was conducted to develop a quantitative model for predicting the crash rate of taxi drivers. Methods: A total of 2,391 taxi drivers from 29 companies in 4 Chinese cities completed a structured and anonymous face-to-face questionnaire reporting their demographic information, workload conditions, aberrant driving behaviors, and crash history within the 2 years prior to the survey. Using the self-reported variables, a negative binomial model was implemented to predict taxi drivers’ property damage only (PDO) and personal injury (PI) crash rates and identify the factors contributing to this risk. Results: Descriptive analysis of the survey data revealed that the workload of taxi drivers in China is relatively heavy. Seven significant predictors of PDO and PI crash rates were identified, including crossing red lights, dangerous overtaking, honking at a slow driver, failure to use an indicator lamp, driving while fatigued, stopping in forbidden areas to pick up or drop off a passenger, and driving with one hand. Taxi drivers’ average off-duty days per week, aggressive driving behaviors, and preventing another driver from merging had significant effects only on PDO crash rate, and sleep problems were found to be significantly correlated with PI crash rate. Conclusions: To improve the safety of taxi drivers, considerable measures should be strictly implemented, ranging from periodic driver training and safety education to workload reduction, with the cooperation of government agencies and taxi companies. The findings of this study contribute to the design of potentially useful policy initiatives as well as targeted safety promotion programs.</p

Comparison of the endometrial thickness between groups (±s).

<p>Note: ^*PP^☆P<0.01, ^○P>0.05. There is significant difference between the groups when P<0.05.</p

Aqueous Lithium-Ion Batteries Using Polyimide-Activated Carbon Composites Anode and Spinel LiMn₂O₄ Cathode

Polyimide/activated carbon (PI/AC) composites were prepared by in situ polymerization of 1,4,5,8-naphthalenete-tracarboxylic dianhydride (NTCDA) and ethylene diamine (EDA) on activated carbon with various mass ratios varying from 50:50 to 70:30. These composites were examined as anode materials in 5 M LiNO3 solution in the potential window from −0.75 to 0 V vs Ag/AgCl. With an optimal composition PI/AC 50:50 in mass ratio, the composite delivers a specific capacity of 87 mAh g–1 at a current density of 0.2 A g–1, and it also shows excellent cycling stability and rate capability. A sealed full cell containing a PI/AC composite anode and LiMn2O4 cathode delivers a specific capacity of 42 mAh g–1 and energy density of 51Wh kg1– (based on the total weight of both active materials) at a current density of 0.2 A g–1. The full cell exhibits good cycling stability with a specific capacity of 35 mAh g–1 after 450 cycles, corresponding to a capacity retention of 89%

In Situ One-Step Synthesis of a Ge/Zn₂GeO₄/N-Doped Carbon Composite as an Anode Material for Lithium-Ion Batteries

Zinc orthogermanate (Zn2GeO4) is an attractive anode material for lithium-ion rechargeable batteries. Nevertheless, owing to its disadvantages of low electrical conductivity and large volume change in cycles, it is subjected to poor cycling stability and rate capability, which restrict its rapid development. Herein, an in situ one-step synthetic route is presented for preparing Ge/Zn2GeO4/N-doped carbon composite by direct carbonization of a mixture of Zn-based metal–organic framework (MET-6) and commercial GeO2 under N2 atmosphere. The composite prepared at 800 °C exhibits a uniform spherical morphology comprising Ge/Zn2GeO4 crystals that are tightly covered by thin layers of nitrogen-doped carbon. The Ge/Zn2GeO4/N-doped carbon anode displays a large charge capacity of 901.9 mAh g–1 over 100 cycles at 0.1 A g–1, long-term stability over 1000 cycles at 1.0 A g–1, as well as good rate capability. Additionally, the assembled full cell with a LiNi0.8Co0.1Mn0.1O2 cathode and Ge/Zn2GeO4/N-doped carbon composite anode also shows good electrochemical performance