Elastic Waves in Solids

1983 ◽  
Vol 50 (4b) ◽  
pp. 1152-1164 ◽  
Author(s):  
Yih-Hsing Pao
Keyword(s):  
Steady State ◽  
Inverse Problems ◽  
Elastic Waves ◽  
Layered Media ◽  
Two Dimensional ◽  
Transient Waves ◽  
Direct And Inverse Problems ◽  
The Past ◽  
Elastic Bodies

Research contributions over the past 50 years on the theory and analysis of elastodynamics are reviewed in this paper. Major topics reviewed are: general theories, steady-state waves in waveguides, transient waves in layered media, diffraction and scattering, and one and two-dimensional theories of elastic bodies. A brief discussion on the direct and inverse problems of elastic waves completes this review.

scholarly journals Southern hemispheric halon trends and global halon emissions, 1978–2011

2013 ◽  
Vol 13 (11) ◽  
pp. 5551-5565 ◽  
Author(s):  
M. J. Newland ◽  
C. E. Reeves ◽  
D. E. Oram ◽  
J. C. Laube ◽  
W. T. Sturges ◽  
...  
Keyword(s):  
Steady State ◽  
Atmospheric Model ◽  
Production Data ◽  
Two Dimensional ◽  
Top Down ◽  
East Anglia ◽  
Mixing Ratios ◽  
The Past ◽  
Alternative Set ◽  
Cape Grim

Abstract. The atmospheric records of four halons, H-1211 (CBrClF2), H-1301 (CBrF3), H-2402 (CBrF2CBrF2) and H-1202 (CBr2F2), measured from air collected at Cape Grim, Tasmania, between 1978 and 2011, are reported. Mixing ratios of H-1211, H-2402 and H-1202 began to decline in the early to mid-2000s, but those of H-1301 continue to increase up to mid-2011. These trends are compared to those reported by NOAA (National Oceanic and Atmospheric Administration) and AGAGE (Advanced Global Atmospheric Experiment). The observations suggest that the contribution of the halons to total tropospheric bromine at Cape Grim has begun to decline from a peak in 2008 of about 8.1 ppt. An extrapolation of halon mixing ratios to 2060, based on reported banks and predicted release factors, shows this decline becoming more rapid in the coming decades, with a contribution to total tropospheric bromine of about 3 ppt in 2060. Top-down global annual emissions of the halons were derived using a two-dimensional atmospheric model. The emissions of all four have decreased since peaking in the late 1980s–mid-1990s, but this decline has slowed recently, particularly for H-1301 and H-2402 which have shown no decrease in emissions over the past five years. The UEA (University of East Anglia) top-down model-derived emissions are compared to those reported using a top-down approach by NOAA and AGAGE and the bottom-up estimates of HTOC (Halons Technical Options Committee). The implications of an alternative set of steady-state atmospheric lifetimes are discussed. Using a lifetime of 14 yr or less for H-1211 to calculate top-down emissions estimates would lead to small, or even negative, estimated banks given reported production data. Finally emissions of H-1202, a product of over-bromination during the production process of H-1211, have continued despite reported production of H-1211 ceasing in 2010. This raises questions as to the source of these H-1202 emissions.

scholarly journals Southern hemispheric halon trends and global halon emissions, 1978–2011

2012 ◽  
Vol 12 (11) ◽  
pp. 29289-29324 ◽  
Author(s):  
M. J. Newland ◽  
C. E. Reeves ◽  
D. E. Oram ◽  
J. C. Laube ◽  
W. T. Sturges ◽  
...  
Keyword(s):  
Steady State ◽  
Atmospheric Model ◽  
Two Dimensional ◽  
Top Down ◽  
Bottom Up ◽  
Mixing Ratios ◽  
The Past ◽  
Cape Grim

Abstract. The atmospheric records of four halons, H-1211 (CBrClF2), H-1301 (CBrF3), H-2402 (CBrF2CBrF2) and H-1202 (CBr2F2), measured from air collected at Cape Grim, Tasmania between 1978 and 2011, are reported. Mixing ratios of H-1211, H-2402 and H-1202 began to decline in the early to mid-2000s but those of H-1301 continue to increase throughout the record. These trends are compared to those reported by NOAA (National Oceanic and Atmospheric Administration) and AGAGE (Advanced Global Atmospheric Experiment). The continued increase of H-1301 mixing ratios means that the contribution of the halons to total tropospheric bromine is not declining. Top-down global annual emissions of the halons were derived using a two-dimensional atmospheric model. The emissions of all four have decreased since peaking in the late 1980s–mid 1990s but this decline has slowed recently, particularly for H-1301 and H-2402 which have shown no decrease in emissions over the past five years. The UEA top-down model derived emissions are compared to those reported using a top-down approach by NOAA and AGAGE and the bottom-up estimates of HTOC (Halons Technical Options Committee). Additionally results are presented that suggest that H-1202 emissions are linked to H-1211 emissions rather than H-1211 production. Finally revised steady state atmospheric lifetimes are reported as 14 yr for H-1211, 75 yr for H-1301, 17 yr for H-2402 and 2.6 yr for H-1202. These revised lifetimes would reduce the estimated existing bank of H-1211 by over 80% to 10 Gg while increasing the H-1301 bank by 15% to 49 Gg.

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