A Novel Analytical Model of Solute Transport in an Aquifer-Aquitard System with Mixing Processes in the Reservoirs

Analytical models have been widely used to aid understanding the physical and chemical processes of tracer (or chemicals) in an aquifer-aquitard system in the laboratory-controlled experiment, when the observation data is few or not available during the experiment. When injecting tracer into (or extracting them from) the aquifer-aquitard system during experiments, the pre-inlet and after-outlet reservoirs are indispensable. However, the concentration variation in the reservoirs was not treated properly in previous analytical models, resulting in poor performance in interpreting experimental data. In this study, new mathematical models describing the concentration variation in the pre-inlet and the after-outlet reservoirs are proposed, and they are integrated into the novel analytical model. The novel analytical model is developed under the mobile-immobile (MIM) framework in the aquifer-aquitard system, considering the longitudinal and vertical dispersion, the advection, and the first-order chemical reaction in both aquifer and aquitard. A finite-difference solution is developed and the experimental data are employed to test the new analytical model. Results indicate that the concentration variation in the reservoirs is important to solute transport in the aquifer-aquitard system in the laboratory-controlled experiment, and the new analytical model outperforms the previous models in interpreting experimental data. The global sensitivity analysis demonstrates that the output concentration of solute transport in the aquifer-aquitard system is most sensitive to the volume of water in the pre-inlet reservoir. The contribution of the diffusion effect to the total mass flux of tracer crossing the aquifer-aquitard interface is much smaller than the contribution of the dispersive and advective effects.

Maximizing Coverage, Reducing Time: A Usability Evaluation Method for Web-Based Library Systems

Usability of a Web Based Library Systems (WBLS) is a major quality attribute. Checklists have become common and easy method to evaluate the usability of these WBLS; however the available checklists support evaluation of general usability aspects of WBLS only. The domain specific usability aspects are required to maximize the usability for such systems. This research proposes and validates a checklist based usability evaluation method that supports the evaluation of general as well as specific usability aspects of WBLS. The usability evaluation checklist is proposed based on analysis of literature and data of a controlled experiment. The checklist is validated in comparison to the “Academic Library Website Evaluation Checklist” via another controlled experiment. The proposed checklist is applied to the WBLS of universities in Pakistan. The manual and statistical result shows that, the proposed usability evaluation checklist identifies more general and specific usability aspects. It is found that both the checklists are equally efficient while identifying the usability errors. The proposed checklist is beneficial for the academia as well as industry to evaluate the usability of WBLS to an optimal level.

Multi-channel Tactile Feedback Based on User Finger Speed

Alongside vision and sound, hardware systems can be readily designed to support various forms of tactile feedback; however, while a significant body of work has explored enriching visual and auditory communication with interactive systems, tactile information has not received the same level of attention. In this work, we explore increasing the expressivity of tactile feedback by allowing the user to dynamically select between several channels of tactile feedback using variations in finger speed. In a controlled experiment, we show that a user can learn the dynamics of eyes-free tactile channel selection among different channels, and can reliable discriminate between different tactile patterns during multi-channel selection with an accuracy up to 90% when using two finger speed levels. We discuss the implications of this work for richer, more interactive tactile interfaces.

HybridPointing for Touch

We propose CursorTap, an extension of Forlines et al.'s mixed, absolute and relative "HybridPointing" to large wall-sized multitouch displays. Our technique uses a relative pointing quasimode activated with one hand, while the other hand controls a distant cursor similar to a large touchpad. A controlled experiment compares the technique to standard absolute touch input as a baseline and a whole-display "Drag" technique representing a common alternate approach. Results show CursorTap is fastest for the common usage scenario of reaching distant targets and then returning to nearby targets. Overall, median selection times across distances are similar with CursorTap, but linearly increase with the other techniques. As further validation, a second study explore show people use CursorTap in a two-person game. The results found just over half of the participants choose to use CursorTap for half of the primary interactions where "enemies" are eliminated using a tap, drag, or lasso "tool".

Controlled experiment of underwater vision-based mapping: A preliminary evaluation

Underwater vision-based mapping (VbM) constructs three-dimensional (3D) map and robot position simultaneously out of a quasi-continuous structure from motion (SfM) method. It is the so-called simultaneous localization and mapping (SLAM), which might be beneficial for mapping of shallow seabed features as it is free from unnecessary parasitic returns which is found in sonar survey. This paper presents a discussion resulted from a small-scale testing of 3D underwater positioning task. We analyse the setting and performance of a standard web-camera, used for such a task, while fully submerged underwater. SLAM estimates the robot (i.e. camera) position from the constructed 3D map by reprojecting the detected features (points) to the camera scene. A marker-based camera calibration is used to eliminate refractions effect due to light propagation in water column. To analyse the positioning accuracy, a fiducial marker-based system –with millimetres accuracy of reprojection error– is used as a trajectory’s true value (ground truth). Controlled experiment with a standard web-camera running with 30 fps (frame per-second) shows that such a system is capable to robustly performing underwater navigation task. Sub-metre accuracy is achieved utilizing at least 1 pose (1 Hz) every second.