Modern shopping centres are undoubtedly a beehive of intense shopping activities. However, customers are often plagued by salient challenges, which may include fatigue derived from pushing trolleys around the mall and prolonged sorting of bills by the cashier. These shopping challenges could be daunting for the elderly, disabled, pregnant and nursing mothers. In this paper, we addressed these shopping challenges by developing an autonomous shopping cart with the following characteristics; (1) it follows the customer’s movement relieving the need to push a cart, (2) it bills automatically all stock placed in the cart, (3) it prompts the customer to make payment and updates each stock via a local database. Our design adopts a Raspberry Pi, a camera and a few direct current motors programmed to achieve autonomy. We used an open-source cross platform software called XAMPP to create the database and used RFID tags to bill the items placed in the cart automatically. The system updates payments and communicates these transactions to a local database via nRF24 wireless transceivers. The experimental tests conducted demonstrate that our system successfully followed customers accurately within the mall. We consider our design a major contribution to the vision of automated shopping systems for the near future.

A <span>graphene-polyvinyl alcohol (PVA) composite saturable absorption is demonstrated at 2000 nm region. Graphene suspension is produced using low-cost electrochemical exfoliation process. The suspension is mixed with PVA host polymer in 1:1 ratio and left evaporated at room temperature which finally produced graphene-PVA thin film. Thulium doped fiber (TDF) gain medium has been shown to produce a stable Q-switched pulse with a highest repetition rate of 54 kHz, a short pulse duration of 2.89 µs, a maximum peak power of 16 mW, and an estimated maximum pulse energy of 49 nJ. Apparently, at 2000 nm region, superior performances of graphene-PVA composite have been recorded which was largely contributed by meticulous composite preparation and homogenous mixture with PVA host</span>.

<span>Ozone gas is a greenhouse gas. Accurate measurement of its concentration is dependent on the right value of the ozone gas absorption cross-section. In the literature, discrepancies and inconsistencies have been however linked with ozone gas absorption cross-section. In the literature, information on the pressure effect on pressures less than 100 mbar and greater than 100 but less than 1000 mbar is not available for the visible spectrum. Thus, creating an information gap which this manuscript is intended to fill up. This is the problem that has been addressed in this present work. The method of simulation with SpectralCalc is the method adopted for the present work. HITRAN 2012 simulator, available on spectralcalc.com, was used in simulating the ozone gas absorption cross-section to determine the simultaneous effect of optical path length and pressure at two peak wavelengths in the visible spectrum. Simulation outcomes were obtained for an optical path length of 10 cm to 120 cm shows that the optimum absorption cross-section value of 5.1084×10-25 m²/molecule at 603 nm and 4.7182×10-25 m²/molecule at 575 nm for gas cells length between 10 cm and 120 cm are obtained at peak points. Pressure values at which ozone gas absorption cross-section becomes a constant value of 5.1058×10-25 m²/molecule at 603 nm and 4.7158×10-25 m²/molecule at 575 nm is optical path length dependent. The percentage difference between 5.1084×10-25 m²/molecule and 5.1058×10-25 m²/molecule is 0.05% for all lengths of gas cells considered. Similarly, the percentage difference between 4.7182×10-25 m²/molecule and 4.7158×10-25 m²/molecule is also 0.05% for all lengths of gas cells considered. These results are relevant for high accuracy and high precision ozone gas measurements. Furthermore, efficient measurement of ozone gas is a direct enhancement of green communication.</span>

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