Browsing University of Alaska Fairbanks by Subject "Propagation"
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Investigation of strongly ducted infrasonic dispersion using a vertical eigenfunction expansion of the Helmholtz equation in a modal broad band acoustic propagation codeThis study investigates an infrasound propagation model created by the National Center for Physical Acoustics (NCPA) which is applied to atmospheric data with a strong temperature inversion in the lower atmosphere. This temperature inversion is believed to be the primary cause of a dispersed infrasonic signal recorded by an infrasound sensor array located on the Southern California coast in August, 2012. The received signal is characterized by initial low frequency content followed by a high frequency content tail. It is shown the NCPA model is hindered by limited atmospheric data and no ground truth for the source function which generated the received signal. The results of the NCPA model are shown to not reproduce the recorded signal and provide inconclusive evidence for infrasonic dispersion.
NCPA propagation code users manualThis manual was written for University of Alaska Fairbanks infrasound group to assist researchers in using the National Center for Physical Acoustics (NCPA) code suite to further investigate observed infrasonic phenomena. The NCPA code suite is designed to simulate various aspects of infrasound propagation through a model atmosphere. This suite was developed and tested by the University of Mississippi National Center for Physical Acoustics infrasound group. Included are raytrace routines to initially establish signal paths, both single frequency and broadband modal routines to calculate pressure fields and transmission losses, and a parabolic method to calculate pressure fields and transmission losses in model atmospheres.
Propagation of Woody Plants by SeedA majority of the plants discussed in his publication are usually propagated by seed sown in the fall, or stratified in preparation for spring sowing. However, the seed of some may be planted without special treatment and still others are normally propagated by vegetative means. Table 1 indicates the general methods by which the species of each genera may be propagated. No attempt has been made to make this table all-inclusive. Some genera are of limited usefulness in Alaska. The table actually represents material acquired by the Alaska Agricultural Experiment Station, or sent sent to the Station for evaluation during the past eight years.