This research proposes a transmitting coil structure for wireless charging which has the constant efficiency regardless of the position of the receiving coil. The proposed transmitting coil is designed to operate at 140 kHz, and to improve the uniformity of the magnetic field intensity using a stepped helical coil and ferrite core. The measured results of the charging system with proposed transmitting coil show that it has low difference in rectifying voltage and efficiency within the charging area. Therefore, it has advantages in terms of wide charging area without the charging shadow area.

Many firms produce a variety of products that are subject to demand uncertainty and are substitutable by customers where the potential for product substitution affects the firm's pricing and production decisions. Two common reasons for product substitution are stockouts (or inventory‐driven substitution), when a customer will substitute a product that is out of stock with a similar product, and price‐driven substitution where customers respond to price differences by substituting a lower priced product for a similar but higher priced product. In this paper, we include the potential for demand to move from one product or market segment to another into the demand model of the firm and present a series of single‐period stochastic models for finding optimal solutions for production quantity and product prices separately, as well as investigating the joint pricing and production decision model. We derive the optimal solution with and without a total production capacity limit and consider both inventory‐driven and price‐driven substitutions. We investigate how the firm should modify pricing and production decisions to take into account both price‐driven and inventory‐driven substitution and examine changes in the optimal prices and supply quantities with and without an aggregate supply limit. Our results demonstrate that both forms of substitution provide a revenue or profit opportunity if the firm is able to recognize the potential for substitution and respond in advance using an optimal pricing and/or ordering strategy. The contribution of this research is to present theoretical results that demonstrate the value of more complex demand models that include the possibility of stockouts and customer “leakage” from higher priced market segments to lower priced segments. Insights derived from these models lead to modified pricing and ordering strategies that will increase firm revenues and/or profitability.

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The global oil market is experiencing a structural shift. Faced with a rapid price decline, large oil‐producing countries had decided to protect their market share, with the hopes of permanently removing expensive supply from the market. Meanwhile, the ability of the US shale oil producers to respond quickly to positive price signals puts downward pressure on prices. On the demand side, advances in renewable technology and the continued effort to curb consumption of fossil fuel conspire to inhibit long‐run growth.1 These factors suggest that the current down‐cycle may continue for an extended period of time or even invoke another down‐cycle.