On Thermal Gravitational Contribution to Particle Production and Dark Matter

We investigate the particle production from thermal gravitational annihilation in the very early universe, which is an important contribution for particles that might not be in thermal equilibrium or/and only have gravitational interaction, such as dark matter (DM). For particles with spin 0, 1/2 and 1 we calculate the relevant cross sections through gravitational annihilation and give the analytic formulas with full mass-dependent terms. We find that DM with mass between TeV and $10^{16}$GeV could have the relic abundance that fits the observation, with small dependence on its spin. We also discuss the effects of gravitational annihilation from inflatons. Interestingly, contributions from inflatons could be dominant and have the same power dependence on Hubble parameter of inflation as that from vacuum fluctuation. Also, fermion production from inflatons, in comparison to boson, is suppressed by its mass due to helicity selection.Comment: 10 pages, 3 figures and 2 tables, published versio

Pure Gravitational Dark Matter, Its Mass and Signatures

In this study, we investigate a scenario that dark matter (DM) has only gravitational interaction. In the framework of effective field theory of gravity, we find that DM is still stable at tree level even if there is no symmetry to protect its longevity, but could decay into standard model particles due to gravitational loop corrections. The radiative corrections can lead to both higher- and lower-dimensional effective operators. We also first explore how DM can be produced in the early universe. Through gravitational interaction at high temperature, DM is then found to have mass around TeV $\lesssim m_X \lesssim 10^{11}$GeV to get the right relic abundance. When DM decays, it mostly decays into gravitons, which could be tested by current and future CMB experiments. We also estimate the resulting fluxes for cosmic rays, gamma-ray and neutrino.Comment: 6 pages, 3 figure

Analysis of thermal field in 110 kV cable systems

The paper presents the distribution of temperature field in high voltage cables, 64/110 kV, (2XS (FL)) with copper conductor, depending on the depth of their arrangement in the soil and the soil thermal conductivity. Used to simulate the professional program NISA / Heat Transfer in the calculation using the finite element method (FEM)

Reliability, availability and security of wireless networks in the community

Wireless networking increases the flexibility in the home, work place and community to connect to the Internet without being tied to a single location. Wireless networking has rapidly increased in popularity over recent years. There has also been a change in the use of the internet by users. Home users have embraced wireless technology and businesses see it as having a great impact on their operational efficiency. Both home users and industry are sending increasingly sensitive information through these wireless networks as online delivery of banking, commercial and governmental services becomes more widespread. However undeniable the benefits of wireless networking are, there are additional risks that do not exist in wired networks. It is imperative that adequate assessment and management of risk is undertaken by businesses and home users. This paper reviews wireless network protocols, investigates issues of reliability, availability and security when using wireless networks. The paper, by use of a case study, illustrates the issues and importance of implementing secured wireless networks, and shows the significance of the issue. The paper presents a discussion of the case study and a set of recommendations to mitigate the threat