Key supplier-side factors that affect the usage level of mobile Internet were identified and the procedural mechanism among the independent and dependent variables was investigated. For this, a research model was introduced to describe associations among four external variables (access quality, service variety, cost rationality, and ease of use), an intermediate variable (usefulness) and a dependent variable (the usage level of mobile Internet). Through the on-line survey, data were gathered from actual mobile Internet users. Confirmatory factor analysis and path analysis were applied to test the overall integrity of the research model and of proposed hypotheses. All four external variables affected user perceptions on the usefulness of mobile Internet. Among them, service variety and cost rationality had a relatively larger influence on perceived usefulness. Perceived usefulness of the mobile Internet had a positive effect on its usage, confirming the important role of usefulness as a significant mediator between the four external variables and the dependent variable. Meanwhile, the cost rationality was the only external variable with direct influence on the MI usage. Theoretical and practical implications of the study results are discussed.

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A pn junction consisting of n-type ZnO nanowires (NWs) on p-type Si substrate exhibits analog resistive switching dependent on the polarity of applied voltage before forming operation for the bipolar switching. The current-voltage curves of Ti/ZnO-NWs/ZnO-seed-layer/p+-Si substrate show diode characteristics with hysteresis in the reverse bias condition, presenting a gradually increasing and then saturated current with repeated voltage sweeps. The current is then further increased with sweeping –V and decreased during the subsequent +V sweep. This polarity-dependent analog switching remains the same during pulse measurement. The analog switching is thought to originate from gradual redistribution of oxygen vacancies, trapping and detrapping of charges in the ZnO NWs, which modulate the depletion width and space charge density. Consequently, the resistance of the pn junction is changed in an analog fashion. After the forming operation, bipolar switching is observed with a transition from high to low resistance states (SET) at +V and reverse transition (RESET) at –V, originating from the formation and rupture of filaments. These results demonstrate multiple features of the ZnO NWs based pn junction, including diode characteristics, analog-type resistive switching before forming operation, and digital-type bipolar switching after forming.

This paper presents the flexural capacities of one-way hollow slab with donut type hollow sphere. Recently, various types of slab systems which can reduce self-weight of slabs have been studied as the height and width of building structures rapidly increase. A biaxial hollow slab system is widely known as one of the effective slab system which can reduce self-weight of slab. A biaxial hollow slab has hollow spheres within slabs in order to reduce self-weight of slabs. The capacities of biaxial hollow slab are influenced by the shapes, volume and materials of hollow spheres. According to analytical studies, the hollow slab with donut type hollow sphere had good flexural capacities such as strength, stiffness and deflection. To verify the flexural capacities of this hollow slab, flexural tests were performed on the one-way hollow slabs. Five test specimens were used for test parameters. One was conventional RC slab and others were hollow slabs. The test parameters included two different shapes and materials of plastic balls. The shape parameters were donut and non-donut forms. And the material parameters were general plastic and glass fiber plastic.

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