• Journal of Korean Society of Transportation
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• v.29 no.1
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• pp.71-79
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• 2011

Traditionally, a dynamic network model is considered as a tool for solving real-time traffic problems. One of useful and practical ways of using such models is to use it to produce and disseminate forecast travel time information so that the travelers can switch their routes from congested to less-congested or uncongested, which can enhance the performance of the network. This approach seems to be promising when the traffic congestion is severe, especially when sudden incidents happen. A consideration that should be given in implementing this method is that travel time information may affect the future traffic condition itself, creating undesirable side effects such as the over-reaction problem. Furthermore incorrect forecast travel time can make the information unreliable. In this paper, a network-wide travel time prediction model under incidents is developed. The model assumes that all drivers have access to detailed traffic information through personalized in-vehicle devices such as car navigation systems. Drivers are assumed to make their own travel choice based on the travel time information provided. A route-based stochastic variational inequality is formulated, which is used as a basic model for the travel time prediction. A diversion function is introduced to account for the motorists' willingness to divert. An inverse function of the diversion curve is derived to develop a variational inequality formulation for the travel time prediction model. Computational results illustrate the characteristics of the proposed model.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.4
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• pp.43-54
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• 2007

Silicone hydrogel contact lenses developed as a continuous-wear modality are now used as a daily-wear contact lenses. The purpose of this study was to investigate the clinical performance in a group of successful long-term wearers of conventional hydrogel contact lenses when refitted with daily wear $O_2OPTIX$ silicone hydrogel lenses. Sixty-two wearers ($30.7{\pm}19.9$ months of prior lens wear) among sixty-five soft lens wearers refitted with $O_2OPTIX$ silicone hydrogel lenses were participated in this study finally. Subjective symptoms were scored and objective signs were graded using CCLRU scales during the study period. 98% of subjects were successfully refitted with the one base curve of $O_2OPTIX$, and 33.9% of subjects were needed more or less lens powers compared with their habitual lenses. Subjects reported a concurrent reduction in dryness, redness and tiredness compared with their habitual lenses and both subjective and objective evaluations showed that dryness, tiredness, itchiness, bulbar and limbal hyperemia were decreased and significantly decreased particularly for those subjects with greater baseline symptoms (p<0.0001). But corneal staining was increased and was seen in many subjects during the study (p<0.0001). Refitting existing soft contact lens wearers with silicone hydrogel contact lens could result in a decreased in dryness, redness and tiredness, particularly more effective for those subjects with greater baseline of those symptoms. When patients using conventional hydrogel materials switch to a silicone hydrogel material, the potential for increased corneal staining should be considered and over-refraction should be needed to give a best vision.