A mobile ad hoc network is a new type of wireless networking paradigm which, in general, consists of solely mobile hosts and dispenses with infrastructure. One main challenge in design of mobile ad hoc networks is the vulnerability to security attacks. Without physical boundaries, a mobile ad hoc network faces many more security threats than a wired network does. Therefore the security of mobile ad hoc networks is one of the major research interests in wireless communications. In contrast with conventional networks, public key management protocols of mobile ad hoc networks do not based on infrastructures, where we can use trusted third parties or centralized servers for key management. This is because that the topology of mobile ad hoc networks is unknown due to link and node failures and to node mobility. For these factors, traditional key management solutions which require on-line trusted authorities or certificate authorities are not suitable for securing mobile ad hoc networks. In this report, we first review some existed public-key management protocols for mobile ad hoc networks and after that we propose a fully distributed public –key management model which does not need the third trusted authority.
Pine wood nematode disease, namely pine wilt disease, is caused by the invasion of Bursaphelenchus xylophilus (Bx)
into pines. Once susceptible pines are infected by the nematode, the disease develops rapidly, the infected pines cease to
exude oleoresin and die quickly. Hence it is called pine cancer. Given the fact that there are still no good methods in
diagnosing the disease, here we propose to study the spectroscopic characteristics of pine wood nematode and diseased pine wood in the THz regime in order to look for a rapid spectroscopic discrimination method for the disease. Firstly, we measure the transmittances of a Bx sample, a B. mucronatus (Bm) sample, a healthy Pinus massoniana wood sample and a diseased P. massoniana wood sample by a superconducting heterodyne mixer at 500 GHz. And their characteristics are compared. Secondly, we measure the transmission characteristics of a Bx sample and a Bm sample by terahertz time domain spectroscopy (THz-TDS). The measured time domain spectrums and corresponding frequency domain spectrums are compared to distinguish them from their absorption characteristics. Thirdly, we measure the transmission characteristics of a healthy P. massoniana wood sample and a diseased P. massoniana wood sample by THz TDS and compare their difference in THz absorption spectrum and diffraction dispersive spectrum to confirm the effect of Bx on P. massoniana by the absorption coefficient and refractive index. Some discussions are given for future development of the diagnostic technique of pine wood nematode disease based on THz spectrum.
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