Hui-Chul Yang

Void fraction measurement using impedance method

Abstract To investigate the relationship between void fraction and volume-averaged impedance in water–air mixtures, a Styrofoam simulator was designed and manufactured. Because the relative permittivity of Styrofoam is negligible compared to that of water, Styrofoam spheres immersed in water act like air bubbles. Three kinds of rectangular conductance electrode were examined to verify the performance of the Styrofoam simulator and to choose the optimum electrode shape. In addition, a water–air level swell facility was designed and constructed to verify the performance of recommended electrode shape developed using the Styrofoam simulator. Three circular conductance probes were designed and their impedance data in the water–air level swell facility were compared. Two-probe designs, characterized by probe-I and probe-II, were shown to be the best candidates for the measurement of volume-averaged void fraction. The impedances of the water–air mixtures with void fractions of 0.0−0.1 were similar to theoretical predictions, with a maximum error of 0.5%. Therefore, the Styrofoam simulator and circular conductance probes should prove useful for the measurement of volume-averaged void fraction in pool conditions.

A framework for evaluating the usability of spoken language dialog systems (SLDSs)

Usability evaluation is now considered an essential procedure in developing a spoken language dialogue system (SLDS). This paper proposes a systematic framework for evaluating the usability of SLDSs. The framework consists of what to evaluate and how to evaluate. What to evaluate includes components, evaluation criteria, and usability measures to evaluate various aspects of SLDSs. With respect to how to evaluate, a procedure for developing scenarios and scenario-based evaluation methods are introduced. In addition, a case study, in which the usability an SLDS was evaluated, was conducted to validate the proposed framework. The results of the case study showed successfully the usability level, usability problems, and design implications for further development. The framework proposed in the study can be practically applied to usability evaluation of SLDSs.

Cursor Capturing Functions as an Aid for Target Selection in Mouse Operation

This study proposed two cursor capturing functions in mouse operation. One is to move the cursor over a target instantaneously (jumping function) when the cursor reaches around the target, and the other is to move the cursor over the target gradually (gravity function). The effects of cursor capturing functions were examined and compared with the normal condition (i.e., without the functions). Task completion times, number of errors, and subjective preferences were evaluated. The results showed that the gravity function had faster movement times and fewer errors than the normal condition. The gravity function was more preferred than the jumping and the normal condition.