An approach to design an invisible cloak with controlled constitutive parameters and arbitrary shaped boundaries is presented. Helmholtz's equation is adopted to establish a mapping between original and transformed coordinates inside the cloak. Then the constitutive parameters are obtained by the established mapping. The analytical solution of a regular cloak and the numerical solution of an irregular cloak both verify that that our method will guide electromagnetic wave efficiently and control the constitutive parameters of the cloak conveniently. It has great significance in realizing a cloak practically.
Unmanned aerial vehicles (UAVs), also known as drones, are expected to play an essential role in future life. However, if drone technology is misused, it will bring unpredictable harm. For example, the use of drones to engage in illegal, criminal, and terrorist activities has brought new challenges to confidentiality, security, and counter-terrorism. The demand for anti-drone systems from all walks of life is rising. These systems can detect and prevent the activities of illegal drones, so that the technology of drones can be used well. This article introduces the current mainstream methods of UAV detection, and then uses the radio frequency (RF) control and map transmission signal exchanged between the drone and its remote controller to achieve a way of passive radio detection of drones.
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