A Thawing Earth

This chapter examines the warming of permafrost found in the Earth’s coldest regions. It relates how this warming results in the release of large amounts of methane gas from gas hydrates buried in frozen grounds and discusses the implications for climate change of this release. The chapter outlines the categories of permafrost and the role that thawing and freezing cycles play in the local environment. It also describes how to use online GIS tools to locate permafrost regions on the Earth. Finally, the chapter reviews the common impacts of melting permafrost such as subsidence, sinkholes, destruction of infrastructure, as well as the possible release of human and animal disease agents.

Analysis of shear behavior between old concrete and fiber concrete

Concrete structures that are influenced by degradation, overloading, the thawing, and freezing cycles, corrosion of reinforced bars, should be repaired or strengthened. Each of the mentioned influences lead to decreased load-carrying capacity of the structure or its member. Exceeding the load-carrying capacity leads to mechanical damage of members or excessive deformation. The damaged member has to be strengthened to the required level of reliability and load-carrying capacity. There exist many types and methods of strengthening the columns. This research work deals with strengthening of columns by concreting a new layer of fiber concrete. When applying that type of strengthening, it is necessary to assure the contact between the old layer and the new one. The paper deals with analysis of different types of contacts and determination of their parametric values.

FACTORS AFFECTING THE COLD SURVIVAL OF WINTER CEREALS

Several parameters affecting cold tolerance of winter cereals in artificial freeze tests were examined. Supercooling followed by freezing resulted in death occurring at a higher temperature than when freezing was initiated just below 0 C. The cold tolerance of fully acclimated crowns of winter wheat and a winter rye were reduced an average of 5 C after two thawing and freezing cycles. The duration of freezing in artificial freeze tests has a significant effect on the LD50 of winter cereals. Rapid thawing (2–4 C/min) resulted in death occurring at a higher temperature than slow thawing (0.5–2 C/h).