Ice core records of monoterpene- and isoprene-SOA tracers from Aurora Peak in Alaska since 1660s: Implication for climate change variability in the North Pacific Rim

Monoterpene and isoprene secondary organic aerosol (SOA) tracers are reported for the first time in an Alaskan ice core to better understand the biological source strength before and after the industrial revolution in the Northern Hemisphere. We found significantly high concentrations of monoterpene- and isoprene-SOA tracers (e.g., pinic, pinonic, and 2-methylglyceric acids, 2-methylthreitol and 2-methylerythritol) in the ice core, which show historical trends with good correlation to each other since 1660s. They show positive correlations with sugar compounds (e.g., mannitol, fructose, glucose, inositol and sucrose), and anti-correlations with alpha-dicarbonyls (glyoxal and methylglyoxal) and fatty acids (e.g., C-18:1) in the same ice core. These results suggest similar sources and transport pathways for monoterpene- and isoprene-SOA tracers. In addition, we found that concentrations of C-5-alkene triols (e.g., 3-methyl-2,3,4-trihydroxy-1-butene, cis-2-methyl 1,3,4-trihydroxy-1-butene and trans-2-methyl-1,3,4-trihydroxy-1-butene) in the ice core have increased after the Great Pacific Climate Shift (late 1970s). They show positive correlations with a-dicarbonyls and fatty acids (e.g., C-18:1) in the ice core, suggesting that enhanced oceanic emissions of biogenic organic compounds through the marine boundary layer are recorded in the ice core from Alaska. Photochemical oxidation process for these monoterpene- and isoprene-/sesquiterpene-SOA tracers are suggested to be linked with the periodicity of multi-decadal climate oscillations and retreat of sea ice in the Northern Hemisphere. (C) 2015 Elsevier Ltd. All rights reserved

振動測定からみた鉄塔の問題点

The vibrations of steel towers under the action of wind have not yet been clarifiedcompletely. This paper sets forth the problems of wind forces acting on the steel towers thatare vibrating. Usually, we assume that the design wind load on steel towers is the staticpressure and the structure of tower is perfectly rigid. However, the deformations of structuremay induce additional aerodynamic forces, and the vibrations have a significant effect upon thestress distributions in the structure.The vibration tests on the actual transmission towers are reviewed and as the results, the dynamic force of wind acting on the structure is introduced under the simple assumption.In conclusion, the mathematical analysis on a simple model is made.The vibrations of steel towers under the action of wind have not yet been clarifiedcompletely. This paper sets forth the problems of wind forces acting on the steel towers thatare vibrating. Usually, we assume that the design wind load on steel towers is the staticpressure and the structure of tower is perfectly rigid. However, the deformations of structuremay induce additional aerodynamic forces, and the vibrations have a significant effect upon thestress distributions in the structure.The vibration tests on the actual transmission towers are reviewed and as the results,the dynamic force of wind acting on the structure is introduced under the simple assumption.In conclusion, the mathematical analysis on a simple model is made

振動する円筒の周りの流れについて(その2)

For several years we have been studying about the vibration of an elastically restrained circularcylinder in wind. To control the oscillation of smoke stacks induced by wind, this kind of theproblem is very important and in these years some papers on it have been published but theproblem is complicated and the limited data can be obtained at present.Although the oscillation of stacks in wind is on the problem in the range of supercriticalReynolds' number, it is interesting also to carry Out the tests in the subcritical range if the ex-citing force is only due to the alternative vortex shedding. So in this range we have investigatedthe alternative lift forces to the circular cylinders which would be affected by the amplitudes andthe frequencies of the vrbration.From the experiment we got the results as follows;1. Through the all range of wind speed 7 in/sec to 20 in/sec. The vibration of the cylinderwas caused by the natural frequency.2. We found one peak point of the amplitude in the range of the wind speed, though theremight be more than one over this range. The Strouhal number was about 0.15.3. The amlitude was nearly sinusoidal and stationary.4. In the low damping system as in our tests (logarithmic decrement a-0001-003), smallchange of wind speed near ｶhe critical speed influenced is amplitudes sensitively.We can see that the alternative lift force is approximately sincsoidal from the time variationof the amplhude and if the vibration of the cylinder is ~I linear sysem, it is regarded as like asthe resonant vibration, because the fre uency of external force always coincides with the naturalfrequency. On the detail of these phenomena we s':ill develoj further experiments in near future.For several years we have been studying about the vibration of an elastically restrained circularcylinder in wind. To control the oscillation of smoke stacks induced by wind, this kind of theproblem is very important and in these years some papers on it have been published but theproblem is complicated and the limited data can be obtained at present.Although the oscillation of stacks in wind is on the problem in the range of supercriticalReynolds' number, it is interesting also to carry Out the tests in the subcritical range if the ex-citing force is only due to the alternative vortex shedding. So in this range we have investigatedthe alternative lift forces to the circular cylinders which would be affected by the amplitudes andthe frequencies of the vrbration.From the experiment we got the results as follows;1. Through the all range of wind speed 7 in/sec to 20 in/sec. The vibration of the cylinderwas caused by the natural frequency.2. We found one peak point of the amplitude in the range of the wind speed, though theremight be more than one over this range. The Strouhal number was about 0.15.3. The amlitude was nearly sinusoidal and stationary.4. In the low damping system as in our tests (logarithmic decrement a-0001-003), smallchange of wind speed near ｶhe critical speed influenced is amplitudes sensitively.We can see that the alternative lift force is approximately sincsoidal from the time variationof the amplhude and if the vibration of the cylinder is ~I linear sysem, it is regarded as like asthe resonant vibration, because the fre uency of external force always coincides with the naturalfrequency. On the detail of these phenomena we s':ill develoj further experiments in near future