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| In the next experiment, red ink was diluted to different concentration to study the effect of absorption coefficient upon photoacoustic spectrum. The ink provides viscosity as small as water, when diluted with water, a remarkable decrease in the absorption coefficient can be observed, but there is scarcely any change in the viscosity. The time-domain results of red ink with various absorption coefficients are given in Fig. 3(a), and the corresponding frequency spectrum is shown in Fig. 3(b). As shown in the figure, the photoacoustic amplitude increases linearly with the absorption coefficients, whereas the dominant frequency and the bandwidth of the frequency spectrum has no change. Some papers have indicated that the bandwidth increases with absorption coefficient,16 but it is only obvious when the absorption coefficient had a difference of almost one order of magnitude. In the experiment, the maximum absorption difference is 40%, while the spectrum has no change and the main frequency of photoacoustic signals has no shift, which indicating that the frequency shift of Fig. 2(b) is not induced by the variations of absorption but attributed to the effect of viscosity. |
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clearsky7228
½ð³æ (ÕýʽдÊÖ)
·ÒëÁªÃË
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¡ï
sirljz(½ð±Ò+1):лл½»Á÷ 2010-04-08 10:01
loulou85(½ð±Ò+8, ·ÒëEPI+1): 2010-04-08 11:17
sirljz(½ð±Ò+1):лл½»Á÷ 2010-04-08 10:01
loulou85(½ð±Ò+8, ·ÒëEPI+1): 2010-04-08 11:17
|
1 different concentrations 2 ¸ù¾ÝÒâ˼¿É¸ÄΪThe ink diluted by water possesses a viscosity which is scarcely any change comparing with water, but a remarkable decrease on the absorption coefficient can be observed. 3 various absorption coefficients are given in Fig. 3(a), and the corresponding frequency spectrum is shown in Fig. 3(b). ǰºóÓ¦¸ÃÒ»Ö£¬is £¬are¸ÄÒ»¸ö¾ÍÐÐ 4 As shown in the figure3£¬ÐèҪдÉÏͼÃû 5 has no change¸ÄΪkeep constant 6Some papers have indicated ¸ÄΪreported 7but it is only obvious ¸ÄΪ7but it is obvious only 8photoacoustic signals has no shift¸ÄΪphotoacoustic signals don't shift 9which indicating that the frequency shift of Fig. 2(b) of ¸ÄΪin 10attributed to the effect of viscosity attributed to¸ÄΪdue to |

2Â¥2010-04-07 20:14:40
¡ï
sirljz(½ð±Ò+1):лл½»Á÷ 2010-04-08 10:01
loulou85(½ð±Ò+8): 2010-04-08 11:17
sirljz(½ð±Ò+1):лл½»Á÷ 2010-04-08 10:01
loulou85(½ð±Ò+8): 2010-04-08 11:17
|
In the SECOND STUDY, red ink was diluted to different concentration to INVESTIGATE the PHOTOACOUSTIC absorption coefficient. The ink HAS SIMILAR viscosity as water. when diluted BY water, a remarkable decrease in the absorption coefficient IS EXPECTED WITH MINIMAL change OF the viscosity. FIG. 3(B) ILLUSTRATED The time-domain results of red ink with various absorption coefficients AS WELL AS the corresponding frequency spectrum. As shown in the figure, the photoacoustic amplitude HAD A LINEAR RELATIONSHIP with the absorption coefficients, WHILE the dominant frequency and the bandwidth of the frequency spectrum WERE NOT AFFECTED. OTHER RESEARCHES have indicated that the bandwidth increases with absorption coefficient ONLY WHEN the absorption coefficient had a difference of almost 10 TIMES.16 In CURRENT experiment, the maximum absorption difference is ONLY 40%. THEREFORE, IT WAS NOT SURPRISING THAT the spectrum KEPT SAME WITH NO OBVIOUS SHIFT OF the main frequency of photoacoustic signals. THE RESULT INDICATED that the frequency shift IN Fig. 2(b) MIGHT BE the effect of viscosity RATHER THAN the CHANGE of absorption. ²»ÖªµÀviscosity as small as waterÊÇʲôÒâ˼£¬Áô¸öÖÐÎİæÒªºÃЩ¡£ |
3Â¥2010-04-08 06:52:50
shirongjiu
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¡ï
sirljz(½ð±Ò+1):лл½»Á÷ 2010-04-08 10:02
loulou85(½ð±Ò+6): 2010-04-08 11:18
sirljz(½ð±Ò+1):лл½»Á÷ 2010-04-08 10:02
loulou85(½ð±Ò+6): 2010-04-08 11:18
| In the subsequent experiment, red ink was diluted with water to different concentrations to investigate the effect of absorption coefficient upon photoacoustic spectrum. A remarkable decrease in the absorption coefficient is expected due to similar viscosity of red ink compared with water. however, there is scarcely any change in the viscosity. As shown in Figure 3, the photoacoustic amplitude increased linearly with the absorption coefficients, whereas the dominant frequency and the bandwidth of the frequency spectrum remained constant. Some papers have indicated that the bandwidth increase with absorption coefficient,16 but it is not obvious until the absorption coefficient was one order of magnitude higher. In this experiment, the maximum absorption difference was 40%, while the spectrum did not change and the main frequency of photoacoustic signals has no shift, indicating that the frequency shift of Fig. 2(b) is rather induced by the variations of absorption than viscosity. |
4Â¥2010-04-08 09:18:40
5Â¥2010-04-08 09:55:05
6Â¥2010-04-08 09:55:17
7Â¥2010-04-08 09:55:31














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