Electrocaloric Effect (ECE) in Ferroelectric Polymer Films

Abstract

(1) Red Lake Peatland in northern Minnesota covers an area of about 80 x 15 km which is uninterrupted by streams or uplands and consists of a vast patterned complex of raised bogs and water tracks. Infra-red photography and LANDSAT imagery have been used to examine their interrelationships. (2) To the west, a large water track up to 5 km broad carries minerotrophic water from uplands adjacent to the peatland. This western water track is differentiated into a series of transverse ridges (strings) and linear pools (flarks), among which are much larger teardrop-shaped islands consisting of a forested head and a long tail of dwarf birch (Betula pumila var. glandulifera) leading downslope. (3) Raised bogs with radiating lines of spruce trees and 'bog drains' form the watershed divedes to the east. The bogs are fringed downslope by non-patterned Sphagnum lawns on which incipient water tracks arise. These incipient tracks lead downslope into well-drained water tracks that flow between other raised bogs, apparently shaping these bogs into ovoid islands several kilometers long. (4) The major tupes of vegetation of the Red Lake Peatland were determined subjectively by the Braun-Blanquet method and are characterized by different water chemistry. (5) Two types of bog vegetation occur on the raised bogs and ovoid islands. They have waters of low pH (range 3.8-4.1), low Ca^2+ concentration (range 0.5-2.1 mg l^-1) and low conductivity, Kcorr (range 12-50 uS cm^-1). (6) Three types of fen vegetation occur on strings, flarks and teardrop islands in the water tracks; these fens are characterized by high pH (range 23-128 uS cm^-1). (7) Poor fens closely resemble bog or fen vegetation, but they may be distinguished by their location, water chemistry an the presence or absence of certain indicator species. Poor fens occur on the broad Sphagnum lawns, within ovoid islands that have been altered by fire, and wherever minrotophic water tracks border ombrotrophic landforms. The poor fens have intermediate ranges in pH (4.0-5.1), Ca^2+ concentration (2.2-4.3 mg l^-1) and Kcorr (22-50 uS cm^-1). (8) The importance of surface drainage in the maintenance of mire patterns is suggested by the localized effects of drainage ditches on the vegetation and landforms. (9) Infra-red aerial photographs and LANDSAT imagery indicate that water flow is channelled across broad surfaces of peat to initiate the development of water tracks, bog drains, and islands that have an ovoid, horseshoe or teardrop shape.