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Social media plays an important role in the era of e-government. Facebook and Twitter are now widely used by law enforcement agencies to inform the public, communicate and establish partnerships. In this paper, we present a multiplatform investigation of law enforcement agencies on Facebook and Twitter. More specifically, we collected 26,490 Facebook posts and 41,277 Twitter tweets made by 40 U.S. municipal police agencies in 2015. We classified these posts and tweets according to topics related to three social media strategies, i.e., Push, Pull and Networking. We applied quantitative methods to examine the patterns of agencies' posting behavior and user interactions both within and across the two platforms. Our findings provide empirical evidence of how police agencies applied different social media strategies on Facebook and Twitter in their daily practice. We also contribute new knowledge of different public interactions with these agencies on the two platforms and discuss the practical implications.

One three-transistor push-pull (TTPP) converter is proposed in this study. In this TTPP converter, an extra transistor is inserted between the input power supply and midpoint of two primary windings. On the secondary side, a saturable inductor and an extra freewheeling diode are employed. Adopting the proposed pulse-width modulation method for three power switches, two original transistors can achieve zero-voltage-switching (ZVS) easily in a wide range of load current, the extra transistor can also realise ZVS assisted by the saturable inductor. Each operation mode of the proposed TTPP converters is discussed in detail. The soft-switching conditions are explained. One 83.3 kHz, 800 W prototype has been built. Its peak efficiency reaches 94.87%. The experimental result is provided to verify the analysis.

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