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Mingyu Kang Team Korea Hearing Light Problem Statement Connected to AC Drilled hole Layer of soot.

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Presentation on theme: "Mingyu Kang Team Korea Hearing Light Problem Statement Connected to AC Drilled hole Layer of soot."— Presentation transcript:

1

2 Mingyu Kang Team Korea Hearing Light

3 Problem Statement Connected to AC Drilled hole Layer of soot

4

5 Soot absorbs light Absolutely opaque: ALL light is absorbed

6 Explanation #1: Thermal Vibration Allan Rosencwaig and Allen Gersho, Theory of the photoacoustic effect with solids, Journal of Applied Physics (Jan. 1976), vol. 47, No. 1

7 Explanation #2: Mechanical Vibration Soot itself expands and contracts! F. Alan McDonald, Photoacoustic effect and the physics of waves, American Journal of Physics (Jul. 1979), vol. 48

8 What is the frequency? Manfred Euler, Hands-On Resonance-Enhanced Photoacoustic Detection, Physics Teacher (Oct. 2011), vol. 39 “Blink” twice at each AC wave!

9 AC Bulb Experiment Setting Power- controllable Lightbulb Microphone Jar + Soot Empty Jar

10 Recorded Sound Sample rate: /s

11 Frequency-Domain Graph : Jar with soot : Empty jar (noise)

12 Frequency-Domain Graph 120hz 240hz 360hz Harmonics!

13 Light intensity – 120hz peak intensity Graph

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15 Helmholtz Resonance Resonance frequency of AIR inside the jar

16 Various jars

17 Parameter control for various jars Slide-glass covered with soot

18 Helmholtz Frequencies of jars RESONANCE!

19 Sound produced in various jars

20 Another method to change Helmholtz Frequency: Neck Length

21 Sound produced by jars of different neck length

22 1.Frequency Control 2.Extract only the sound produced by light  New Experiment Setting!

23 Preliminary Experiment Setting

24 Stroboscope Experiment Setting Stroboscope

25 Flash frequency – Fundamental sound frequency graph

26 Limits of Stroboscope Setting Glass blocks ultraviolet rays Noise caused by jar itself

27 Revised Experiment Setting

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29 Recorded Sound : Slide glass with soot : Empty slide glass (noise)

30 Zoom-in! silence IMPACT! stroboscope noise 5~7 small vibrations damping silence

31 Sound caused by only light

32 Speed Camera Resolution 32×32 Sample rate /s Duration of Stroboscope Flash

33 Flash at what point? stroboscope noise

34 Experiment on Flash Time Light sensor Sound sensor

35 Time gap between sound and light Sound sensor Light sensor

36 So the flash is at….. stroboscope noise s

37 Shockwave?

38 Similar waveform! Sharp pencil broken Flash - soot

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40 Samples of various powders SootActivated Carbon Graphite (Grained pencil lead) Charcoa l Iron

41 Sound from various powders Soot 3.8 Activated Carbon 0.90 Graphite 0.86 Charcoal 0.76 Iron 0.40

42 Sample of powder and chunk Charcoal powder Charcoal chunk

43 Powder VS Chunk Powder 0.76 Chunk 0.34

44 Sample of powder and lubricant Graphite powder Graphite lubricant

45 Powder VS Lubricant Graphite Powder 0.86 Graphite Lubricant ?

46 Samples of various surfaces PaperMarker Vinyl Plastic

47 Sound from various surfaces Paper 0.1 Marker 0.1 Vinyl 0.1 Plastic ?

48 Mechanism of heat conduction Something special about C

49 Hypothesis for Photoacoustic Mechanism Mechanical Vibration (sample) Thermal Vibration (air)

50 Thermal conductivity

51 Thermal expansion coefficient

52 Porous Structure of Soot SEM

53 Porous Structure of Soot LARGE Sound!

54 Plane Structure of Graphite Lubricant

55 NO Sound!

56 Conclusion Absorption Mechanical Vibration Thermal Vibration Helmholtz Frequency } Pores !

57 Thank You

58 [nSamples, nChannels]=size(data); data=data*20; waveFileLength=nSamples/fs; N=2^(nextpow2(nSamples)); Y=fft(data(:,1),N); NumbUniquePts=ceil((N+1)/2); Y=Y(1:NumbUniquePts); P=abs(Y)/waveFileLength; f=(0:NumbUniquePts-1)*fs/N; plot (f,P) xlabel('Frequency (Hz)') ylabel('Sound Intensity (Arbitrary Unit)') axis([0, 400, 0, 10000]) MATLAB FFT Code FFT Number determined!

59 Heat vibration caused by lightbulb offon

60 Microphone inside the jar

61 Microphone position and Resonance effect

62 Stroboscope sound has not arrived Fast reaction!

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64 FFT: Sound caused by only light

65 Depth of soot is not important Soot is opaque -> All light is absorbed!

66 Effect of heat from lightbulb (justification) Sound absorption due to thermal conduction (fundamentals of acoustics)


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