An upper limit to the importance of local sources of radiation compared to the cosmic background in cosmological absorption systems is derived, as a simple consequence of the conservation of surface brightness. The limit depends only on the rate of incidence of the absorbers and the mean free path of the radiation. It is found that, on average, the ionizing radiation intensity from local source...

The growth of the Chinese district heating sector has been very rapid during recent years. No other country in the world can show the same rapid growth of district heating systems during the last decades. Heated building area increased six times between 1995 and 2008 according to the Chinese district heating statistics. China has also enjoyed strong growth of scientific articles and papers publ...