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Machining optimization has been studied for low machining cost, high production rate, and energy saving. Nevertheless, most of the studies did not consider the part geometry. The complex part geometry results in varying contact conditions between the cutting tool and the workpiece. Therefore, the conventional tool life equation may not be applicable, and it is impossible to expect the same performance of machining different parts even with the same cutting parameters. In addition, the amount of material removal is different from part to part. Either the underuse or overuse of the tool is considered production loss in machining process. As a result, it is better for the cutting tool to be utilized until it reaches the end of its life when the operation is completed. Taking the conditions above into considerations, an objective function including the machining cost and the loss of tool usage is proposed in this study. Three turning operations, one straight turning and two profiling, were investigated to show the effect of part geometry on the machining optimization and tool wear. The results showed the different optimization processes and tool wear patterns although the initial cutting parameters and the amount of material removal were identical. The optimization processes were converged in 5 iterations. The cost of three cases reduced 34%, 33%, and 19%, respectively, with different optimized cutting parameters, and the tool approached the end of its life when the operation was done. [ABSTRACT FROM AUTHOR]

• Travel-irrelevant mobile service affects how bus passengers perceive waiting time. • Smartphone usage is frequently associated with longer waiting time. • Unexpected longer waiting time may further increase the perceived waiting time. • Bus passengers show heterogeneous responses to travel-irrelevant mobile service. • Young passengers are more likely to benefit from travel-irrelevant mobile service. Smartphones and relevant mobile service have greatly influenced people's daily lives, and intense smartphone users can be commonly seen at transit stops/stations, playing with their smartphones while waiting for buses/trains. This research presents a holistic perspective for analyzing the effects of smartphone usage on transit passengers, which also considers the effects at a psychological level. Such effects may be manifested as the reduction of perceived waiting time at stops/stations against the negative emotionality induced by long waiting, such as boredom and tediousness, so as to result in improved travel experience. An on-site survey is designed and implemented over the bus system in Taipei, Taiwan, to collect the revealed responses of bus passengers in regard to waiting time perception and smartphone usage, particularly for travel-irrelevant mobile service. The survey data are modeled and analyzed in both numerical and verbal representation of perceived waiting time by using a multiple linear regression model and a cumulative proportional odds logistic model, respectively. A finite mixture model is further employed to investigate the potential heterogeneity of waiting time perception related to using smartphones for travel-irrelevant mobile service. The analysis results highlight that travel-irrelevant smartphone usage may lead to the reduction of perceived waiting, and the effect can be more significant for young passengers and those without receiving bus arrival information, especially when waiting time is prolonged. Such findings can contribute to the comprehensive consideration of passenger behavior in transit system planning and associated information/service provision strategies. [ABSTRACT FROM AUTHOR]