Nghiên cứu điều chế alginate khối lượng phân tử thấp dùng làm thực phẩm chức năng hỗ trợ phòng chống đông máu tt tiếng anh

BỘ GIÁO DỤC VÀ ĐÀO TẠO

VIỆN HÀN LÂM KHOA HỌC
VÀ CÔNG NGHỆ VIỆT NAM

HỌC VIỆN KHOA HỌC VÀ CÔNG NGHỆ

-----------------------------

Phạm Minh Tiến

NGHIÊN CỨU PHÂN BỐ OZONE TRONG
KHÍ QUYỂN TẦNG THẤP VỚI ĐỘ PHÂN GIẢI CAO
TRÊN CƠ SỞ PHÁT TRIỂN VÀ ỨNG DỤNG
PHƯƠNG PHÁP LIDAR HẤP THỤ VI SAI

Chuyên ngành: Quang học
Mã số:
9 44 01 09

TÓM TẮT LUẬN ÁN TIẾN SĨ QUANG HỌC

Hà Nội, 2017


Công trình được hoàn thành tại Học Viện Khoa học và Công nghệ –
Viện Hàn lâm Khoa học và Công nghệ Việt Nam.

Người hướng dẫn Khoa học: PGS.TS. Đinh Văn Trung

Phản biện 1:.......................................................................

Phản biện 2:.......................................................................

Luận án sẽ được bảo vệ trước Hội đồng đánh giá luận án tiến sĩ cấp
Học Viện, họp tại Học Viện Khoa học và Công nghệ - Viện Hàn lâm
Khoa hoc và Công nghệ Việt Nam vào hồi …..giờ …, ngày … tháng…
năm 201…

Có thể tìm hiểu luận án tại :
- Thư viện Học Viện Khoa học và Công nghệ
- Thư viện Quốc Gia Việt Nam


TABLE OF CONTENTS
PREFACE ...................................................................................... 1
1. The necessary of the thesis ................................................. 1
2. Objectives of the thesis ....................................................... 1
3. The main research contents of the thesis .......................... 2
Chapter 1. INTRODUCTION ....................................................... 2
1.1 Ozone in the lower atmosphere .......................................... 2
1.1.1 Formation and distribution ........................................ 2
1.1.2 Ozone absorption cross section................................... 3
1.1.3 Role and impact of atmospheric ozone....................... 3
1.2 Measurement of atmospheric ozone .................................. 3
1.2.1 Overview ...................................................................... 3
1.2.2 Measuring ozone in the atmospher ............................ 3
1.2.2.1 Total ozone measurements .................................. 3
1.2.2.2 Measurement of the vertical profile of ozone...... 3
1.3 Differential Absorption LIDAR technique for measuring
atmospheric ozone dítribution ........................................................ 4
1.3.1 Physical principle of LIDAR and DIAL ..................... 4

1.3.2 LIDAR system and the LIDAR equation.................... 4
1.3.3 Differential Absorption LIDAR technique................. 5
1.3.4 Wavelength selection for ozone measuring DIAL ..... 6
1.3.5 DIAL measurement of ozone distribution in
the lower atmosphere .................................................. 6
1.3.6 Calculation of ozone concentration distribution ....... 7
1.3.7 Accuracy of ozone DIAL measurement ..................... 7


Chapter 2. DESIGN AND SIMULATION OF A DIAL SYSTEM
FOR MEASURING OZONE DISTRIBUTION IN THE
LOWER ATMOSPHERE ............................................................... 8
2.1 Design of a DIAL system for measuring ozone
distribution ....................................................................................... 8
2.1.1 Diagram of Differential Absorption LIDAR........... 8
2.1.2 Optical transmitter ................................................... 8
2.1.3 Optical receiver ........................................................ 8
2.1.4 Opto-electronic receiver........................................... 9
2.1.5 Processing and calculation program ...................... 9
2.2 Selection of pair of wavelength ......................................... 9
2.3 Simulation of received backscattered DIAL signal ....... 10
2.4 Simulation results and discussion ................................... 10
Chapter 3. DEVELOPMENT OF A DIFFERENTIAL
ABSORPTIN LIDAR SYSTEM TO MEASURE
ATMOSPHERIC OZONE DÍTRIBUTION ................................ 10
3.1 Configuration of DIAL system ......................................... 10
3.2 Development of two DFDL ............................................... 10
3.2.1 Oscillator ................................................................ 10
3.2.2 Optical pumping system ......................................... 11
3.2.3 Optical amplifier .................................................... 11

3.2.4 Active medium ........................................................ 12
3.2.5 Dye transfer pump ................................................. 12
3.3 Development and evaluation of DIAL’s transmitter ...... 12
3.4 Development of UV telescope and optical receiver ......... 12
3.4.1 Development of UV telescope ................................ 12


3.4.2 Making a grinding and polishing machine .......... 13
3.4.3 Development of optical receiver ............................ 13
3.5 Development of electronic receiver .................................. 13
3.6 Programming for signal acquirement and data
processing ....................................................................................... 13
3.7 Testing of UV DIAL .......................................................... 14
Chapter 4. MEASUREMENT OFF OZONE DISTRIBUTION
IN THE LOWER ATMOSPHERE .............................................. 14
4.1 Data processing .................................................................. 14
4.2 Calculation of ozone concentration distribution............. 14
4.3 Results of vertical ozone distribution measurement....... 16
4.4 Error analysis .................................................................... 17
CONCLUSIONS ............................................................................ 19
NEW CONTRIBUTIONS OF THE THESIS .............................. 20
LIST OF PUBLISHED ARTICLES ............................................ 21


Preface
1. The necessary of the thesis
Ozone is of particular interest in the atmospheric composition
because of its presence, distribution, and properties that greatly affect
the life of our planet. With higher concentrations in the stratosphere,
ozone contributes greatly to protecting the earth by absorbing most of

the dangerous ultraviolet radiation from the sun in a wavelength range
of 200 to 300 nm. In the atmospheric layer close to the ground,
although only a small component (about several tens of billions - ppb),
but ozone is an important contributor to pollution smoke. It is one of
the main factors affecting human health, the life of organisms, and
contributing to the greenhouse effect. Therefore, the determination of
the concentration and distribution of ozone in the atmosphere is
essential, especially the atmosphere surrounding the ground.
According to the report of the National Hydro-Meteorological
Services of Vietnam (May, 2012), our country has about 20 AeroMeteorological Observatories. However, there are no annual
atmospheric ozone monitoring data.
The continuous monitoring of ozone concentration distribution
will help predict and warn the air pollution to protect human health,
increase our understanding of space weather and climate change, and
build future development plans.
2. Objectives of the thesis
Development of a UV Differential Absorption LIDAR ( DIAL)
system for high resolution study of the distribution of ozone in the
lower atmosphere.

1


3. The main research contents of the thesis
The main content of the thesis is to develop an DIAL system with
two UV pulses emitted at wavelengths on (282.9 nm) and off (286.4
nm) into the atmosphere. The elastic backscattering LIDAR signals of
these radiations are acquired and their intensity is used to calculate the
vertical ozone concentration. The DIAL system includes:
+ UV transmitter

+ UV receiver
+ Single photon counter, software program to process data and
calculate ozone concentration distribution.
Chapter 1. Introduction
1.1 Ozone in the lower atmosphere
Ozone (O3) is a pale blue gas and a powerful oxidant. It has a
distinctively pungent smell

and

strongly

absorbs

UV

light

[2,5]. There is very little ozone in the earth's atmosphere, with an
average of 10 million molecules of air per 3 molecules of ozone.
1.1.1 Formation and distribution
Tropospheric ozone is produced from photochemical reactions
with oxides of nitrogen (NOx) and volatile organic compound (VOC)
molecules, in the presence of sunlight. The highest ozone
concentration tends to be concentrated in and around urban areas,
where generate precursors necessary for ozone production, and often
have peaks at noon and lowest at night. Ozone concentration also vary
from day to day depending on weather conditions, temperature,
humidity, wind speed, etc.

2


1.1.2 Ozone absorption cross section
The absorption cross section of ozone in the wavelength range
from 200 to 1100 nm includes four absorption bands: Hartley,
Huggins, Chappuis and Wulf. Hartley và Huggins are intense bands
in UV region. They are particularly important in atmospheric ozone
monitoring using remote sensing techniques (Differential Optical
Absorption Spectroscopy and Differential Absorption LIDAR).
1.1.3 Role and impact of atmospheric ozone
Stratospheric ozone filters out sunlight harmful UV wavelegths
and protects the life on Earth. In contrast, ozone in the lower
atmosphere is a major component of photochemical smog in urban
environments, an atmospheric pollutant, harmful to human health and
a greenhouse gas.
1.2 Measurement of atmospheric ozone
1.2.1 Overview
Ozone measuring devices can be placed on the ground or flying
objects. Atmospheric ozone is measured both by remote sensing and
by in situ techniques.
1.2.2 Measuring ozone in the atmosphere
1.2.2.1 Total ozone measurements
Total ozone is measured by remote‑sensing techniques using
ground‑based and satellite instruments that measure irradiances in the
UV absorption spectrum of ozone between 300 and 340 nm.
1.2.2.2 Measurement of the vertical profile of ozone
The vertical profile of ozone expresses ozone concentration as a
function of height or ambient pressure. It is measured with

3


ozonesondes, LIDARs, Umkehr technique with ground-based
spectrometers and various satellite-borne instruments [19].
1.3 Differential Absorption LIDAR technique for measuring
atmospheric ozone dítribution
1.3.1 Physical principle of LIDAR and DIAL
The main components of a LIDAR system consists of laser
transmitter, optical receiver, electronic controller and software for
processing and analyzing data.
In LIDAR technique, laser radiation will interact with
atmospheric components including molecules, atoms, aerosols and
steam. Then, the range of physical processes amenable to laser remote
sensing includes Rayleigh scattering, Mie scattering, Raman
scattering, resonance scattering, fluorescence, absorption, and
differential absorption and scattering (DAS). These processes are
responsible for the extenction of laser radiation beams emitted by
LIDAR system.
The absorbtion cross section of ozone in the ultraviolet region is
much larger than the fluorescent cross section and Raman scattering
cross section. Therefore, the extinction of an appropriate laser beam
caused by ozone will be a highly sensitive method to determine the
concentration of ozone in the atmosphere.
1.3.2 LIDAR system and the LIDAR equation
The functional elements and manner of operation of most lidar
systems are schematically illustrated in Fig. 1.17. An intense pulse of
optical energy emitted by a laser is directed through some appropriate
output optics toward the target of interest. A small fraction of this
pulse is sampled to provide a zero-time marker (trigger). The radiation

4


gathered by the optical receiver and the photodetection system. The
spectrum analyzer serves to select the observation wavelength interval
and thereby discriminate against background ratiation at other
wavelengths. The Newtonian and Cassegrainian telescope are the
main components in the optical receiver.

Fig 1.17. The essential elements of a LIDAR system [3]
The detected LIDAR signal received from a distance R can be
written as an equation, called the LIDAR equation:
𝑃(𝑅, 𝜆) = 𝑃0

𝑅
𝑐𝜏
𝑂(𝑅)
𝐴𝜂
𝛽(𝑅,
𝜆)
𝑒𝑥𝑝
𝛼(𝑟, 𝜆)𝑑𝑟]
[−2
∫
2
0
2
𝑅

(1.21)

P0 is the average power of a single laser pulse, τ is the temporal pulse
length. The factor 1/2 appears because of an apparent “folding” of the
laser pulse through the backscatter process, c is the speed of light. A
is the area of the primary receiver optics responsible for the collection
of backscattered light, and η is the overall system efficiency . O(R) is
the laser-beam receiver-field-of-view overlap function. β(R,λ) is
backscatter coefficient and α(R,λ) is the extinction coefficient. The
factor 2 stands for the two-way transmission path.
1.3.3 Differential Absorption LIDAR technique
Differential Absorption LIDAR technique allows the detection of
atmospheric gases with high sensitivity. With this technique, two
5


frequencies are used, one at the center of the absorption band (λon) and
the other at the edge of the absorption band (λoff). By taking the ratio
of intensity Pon of lidar signal at wavelength λon and Poff signal at λoff,
the concentration of interested gas is deduced from LIDAR equation.
1.3.4 Wavelength selection for ozone measuring DIAL
In order to measure tropospheric ozone distribution where the
ozone concentration is small, the wavelengths of laser transmitter
must be selected in the strong absorption region of ozone, between
266 nm and 320 nm, to increase detection sensitivity.
In addition, the selection of wavelengths results from the balance
of the following considerations: diferential absorption cross sections
for optimizing the altitude range to make retrievals and the spatial
resolution; reducing the impact of aerosol interference upon the ozone
retrieval.
1.3.5 DIAL measurement of ozone distribution in the lower

atmosphere
The DIAL measurements of ozone distribution in the lower
atmosphere or the troposphere have used wavelength pairs in the
range of 266 nm to 320 nm. The DIAL systems have used the
radiations emitted from a Q-switched frequency-quadruped Nd:YAG
laser (266 nm); H2, D2, He Raman cells (Stokes lines: 289 nm, 299
nm, 316 nm) [48,49] or CO2 Raman cell (276.2 nm, 287.2 nm, 299.1)
[50,51] pumped by a frequency-quadruped Nd:YAG at 266 nm; H2
Raman cell pumped by krypton–fluoride excimer laser at 248 nm
(stimulated Raman shifting lines at 277 and 313 nm) [52]; or dye
lasers [39,53,54]. The altitude of measured ozone distribution in the
troposphere of these DIAL systems depends on the pair of
6


wavelengths used, the intensity of the transmitter laser and the
weather conditions.
1.3.6 Calculation of ozone concentration distribution
LIDAR equation (1.22) of a elastic scattering differential
absorption LIDAR system is written for two wavelengths on and off.
After taking the ratio of two intensities at two wavelengths, the
concentration of N (R) between the height R and R+R can be
expressed as the sum of the measured signal term Ns(R), the
differential backscattering term Nb(R) and the differential
attenuation term Ne(R) caused by atmospheric molecules, aerosols
and interference gases are as follows [3,39,58]:
𝑁𝑂3 (𝑅) = 𝑁 𝑠 (𝑅) + 𝛿𝑁 𝑏 (𝑅) + 𝛿𝑁 𝑒 (𝑅)

(1.31)

NS(R) is the basic term in (1.31), determined directly from the ratio of
the signals. The terms 𝛿𝑁 𝑏 (𝑅) và 𝛿𝑁 𝑒 (𝑅) are considered as
correction terms, which must in some way be determined to determine
a more accurate ozone concentration. The iterative method has been
used to simultaneously determine the aerosol backscattering
coefficient

𝛽𝑎𝑒𝑟 (𝜆𝑜𝑓𝑓 , 𝑅),

the

aerosol

𝛼𝑎𝑒𝑟 (𝜆𝑜𝑓𝑓 , 𝑅), thereby determining 𝛿𝑁
concentration 𝑁𝑂3 (𝑅) [39].

extinction

𝑏 (𝑅),

𝛿𝑁

𝑒 (𝑅)

coefficient
and ozone

1.3.7 Accuracy of ozone DIAL measurement
The accuracy of a Differential Absorption LIDAR measurement
is determined by statistical errors. Due to the random character of the

signal detection process, the Poisson distribution has been assumed
for the photon counting [37]. The accuracy of the measurement
depends on the approximations used to deduce the concentration of
ozone and the linearity of the lidar signal.
7


Chapter 2. Design and simulation of a DIAL system for
measuring ozone distribution in the lower atmosphere
2.1 Design of a DIAL system for measuring ozone distribution
2.1.1 Diagram of Differential Absorption LIDAR

Fig 2.1. Diagram of Differential Absorption LIDAR system
2.1.2 Optical transmitter
Distributed Feedback Dye Laser (DFDL) was successfully
developed at the Institute of Physics [67 – 72]. With emitted power
strong enough to be able to acquire LIDAR signals, DFDLs have a
number of advantages: simple structure; large range of wavelength
corrections (10-20 nm depending on the dye) and linewidth of ~ps. So
DFDL is convenient to select the pairs of wavelengths for the DIAL
system, reduce the effect of interfering gas on the measurement results
and give a high frequency doubling performance. Therefore, the
DFDL has been selected to develop DIAL’s transmitter.
2.1.3 Optical receiver
The main part of the DIAL’s receiver is a telescope. The telescope
is designed and developed with a minimum diameter of 40 cm to
increase the gain of LIDAR signals. In addition, the aluminum must
be deposited on the surface of the telescope’s primary mirror so that
the receiver has a high performance in the ultraviolet region.
8

2.1.4 Opto-electronic receiver
Opto-electronic receiver of DIAL system consists of three parts:
photomultiplier tube (PMT), preamplifier and single photon counter.
The quantum efficiency of PMT must be high in UV region. Because
the LIDAR signal is low intensity signals and the elastic backscattered
photons are discrete pulses, single photon counting method will be
used in receiver. In addition, the photon counting method is more
advantageous than the analog method because of stability, high
detection efficiency and high signal to noise ratio (SNR) [73]. The
electronic receiver is designed with fast-responding electronic
components.
2.1.5 Processing and calculation program
The function of the designed software is LIDAR signal
acquisition, data storage, data processing and calculation of vertical
ozone distribution.
2. 2 Selection of pair of wavelength
The differential pair of wavelengths selected for the DIAL system
are two UV wavelengths 282.9 nm (λon) and 286.4 nm (λoff). The
absorption cross section of ozone at λon is of 29.7.10-23 m2 and the
differential absorption cross section 𝜎(𝜆𝑜𝑛 ) − 𝜎(𝜆𝑜𝑓𝑓 ) is of 8,9.10-23
m2 [3]. The selection of these wavelengths results from the balance of
the following the considerations: fluorescence efficiency of laser
dyes, altitude range to make retrievals, reducing the impact of the
solar background, reducing the impact of aerosol and SO2 interference
upon the ozone retrieval [3].

9

2.3 Simulation of received backscattered DIAL signal
The return LIDAR signals are simulated as a function of range by
to estimate the expected LIDAR signals of the designed DIAL system
(altitude and counting duration). In the simulation, the number of
backscattered photons is calculated by the LIDAR equation (1.21).
2.4 Simulation results and discussion
In this simulation, the LIDAR equation has been computed with
the change of the laser pulse energy emitted, the diameter of telescope
(40 cm and 60 cm), the photon counting duration. Our simulations of
backscattered signals indicate that transmitter is appropriate to a
DIAL system which can be used to measure the vertical ozone
distribution to an altitude of over 5000 m, counting duration of 10
minutes.
Chapter 3. Development of a Differential Absortion LIDAR
system to measure atmospheric ozone distribution
3.1 Configuration of DIAL system
The configuration of DIAL system is developed according to the
selections described in Chapter 2.
3.2 Development of two DFDL
DFDLs have been developed for the DIAL’s transmitter and their
laser radiation is emitted at 565.8 nm and 572.8 nm (Fig 3.2).
3.2.1 Oscillator
In the DFDL’s oscilator, a double-faced aluminum mirror CM
plays the role of a beam splitter, which divides the pumping beam into
two parts. After the pumping beam propagates through a cylindrical
quartz lens, both parts of the beam are reflected by two rotating

10

dielectric mirrors m1 and m2. The beam is then focused onto the dye
cell C1 that contains the sample, and forms an interference pattern.

Fig 3.2: Diagram of DFDL system
3.2.2 Optical pumping system
Two DFDLs is pumped by a frequency-doubled Nd:YAG laser
(5ns, 10 Hz, 532 nm). The optical pumping system consists of mirrors
M1, M2, M3 and M7; two beam splitter Rm1, Rm2; two prisms P2
and P3 to project the pumping beam to the dye cells of the oscillator
and amplifier. The optical pumping system extends the journey of the
pumping pulse to the power amplifier in order to ensure the amplifier
performance when the DFDL’s laser pulse passes through the cuvette
C3.
3.2.3 Optical amplifier
The optical amplifier consists of a 6-pass amplifier (lens L2,
mirrors from m3 to m14 and cuvette C2) and output power amplifier
(cylindrical quartz lens L3, cuvette C3).
11


3.2.4 Active medium
The dye of Rhodamine 6G dissolved in ethanol is the active
medium for each DFDL.
3.2.5 Dye transfer pump
The dye transfer pumps have been designed and manufactured
with glass material. The transfer pump use the magnetic paddle to
push the dye through the cuvettes.
3.3 Development and evaluation of DIAL’s transmitter
The two DFDLs have the same design. There is only one

difference in the incident angle of the pumping laser beam to the
cuvette C1. The energy of DFDL and UV pulses are measured and
presented in Table 3.2.
Table 3.2: The energy of DFDL and UV pulses
Laser beam
Wavelength (nm)
Energy
DFDL
565,8
0,62 mJ/pulse
572,8
1,8 mJ/ pulse
UV
282,9
30 J/ pulse
286,4
60 J/ pulse
3.4 Development of UV telescope and optical receiver
3.4.1 Development of UV telescope
The configuration of the telescope is Newtonian. It is possible to
install spherical mirrors with a maximum diameter of 40 cm and a
maximum focal length of 210 cm. The telescope frame will be
covered with a thick black fabric to prevent near-field scattered
radiation. The optical axis of the system is calibrated with a
semiconductor laser.

12


3.4.2 Making a grinding and polishing machine

A grinding and polishing machine has been designed to make
spherical mirrors (primary mirrors of telescope) with a diameter from
20 cm to 80 cm.
The optical spherical mirrors were examined and evaluated by the
combination of Ronchi and Foucault methods [80]. The results show
that the optical mirror has a regular spherical concave and a focal
length of 1.8 m after grinding and polishing process..
3.4.3 Development of optical receiver
The optical receiver of Differential absorption LIDAR system
includes a telescope, a wavelength filter (F), two lenses L1 and L2.
3.5 Development of electronic receiver
The electronic receiver of UV DIAL system is developed from
the one of multi-wavelength LIDAR system developed at the Institute
of Physics. This receiver consists of a signal amplifier, a PC
oscilloscope Picoscope 5204 with a diagram as shown in Figure 3.22.
Amplifier
PMT

Digital
Oscilloscope

PC: program of
photon counting
(Labview)

Fig 3.22: Diagram of electronic receiver
3.6 Programming for signal acquirement and data processing
A software has been written using Labview programming to
control Picoscope oscilloscope, acquire LIDAR signals, save data,
and display measurement results. This software was developed at the

Institute of Physics for the study of atmospheric aerosols.
The signal processing software was built using Matlab code to
smooth the measured data, remove the dark and offset curent of the
13


electronic receiver module, and change the LIDAR signal depending
to the distance P(R,) into undepending R2P(R,). The software for
calculating atmospheric ozone concentration distribution is also built
using Matlab code.
3.7 Testing of UV DIAL
The Differential Absorption LIDAR system is calibrated to
acquire the LIDAR signal from the highest altitude possible.
After calibration, the DIAL system has been tested and it can
acquire the LIDAR signals to a height of over 4 km at both on and off
wavelengths. With the sampling rate of 125 MSamples/s and using
data filtering technique by averaging on some measurement points,
the spatial resolution of DIAL measurements is 480 m with a
statistical error of ~ 18% at the altitude of 4 km. The spatial resolution
may be smaller, but the statistical errors will be high. The DIAL
system does not acquire LIDAR signals from the height above 5 km
as the simulation calculation, this can be explained by the average
thickness of aerosols of 5 km over Hanoi [81]. This aerosol scatters
the radiations emitted by the laser transmitter, reducing of
backscattering signals and limiting of measurement height.
Chapter 4. Measurement of ozone distribution
in the lower atmosphere
4.1 Data processing
In order to improve the accuracy, the data (in the * .txt file) will
be calibrated over time, adjusted the background and averaged.

4.2 Calculation of ozone concentration distribution
The concentration of ozone 𝑁𝑂3 (𝑅) between the height R and

R+R is calculated according to the expression (1.34), and it is the
14


sum of three terms: Ns(R) : signal term (s – signal), Nb(R) : correction
term of differential backscattering (b – backscattering), Ne(R) :
correction term of differential attenuation (e – extinction).
Ns(R) is calculated directly from the measured data, the correction
terms Nb(R) và Ne(R) are calculated using the expressions (1.41)
and

(1.42)

correspondingly.

The

backscattering

coefficients

𝛽𝑎𝑒𝑟 (𝜆𝑜𝑓𝑓 , 𝑅), the aerosol extinction coefficient 𝛼𝑎𝑒𝑟 (𝜆𝑜𝑓𝑓 , 𝑅) and
the ozone concentration 𝑁𝑂3 (𝑅) are determined by the iterative
method presented in Section 1.3.6.
Based on aerosol studies in Hanoi [81], in urban and polluted
environments [63,76], the LIDAR ratio S was assumed to be 30 sr-1.
The Ångström exponent η is often seen as an indicator of aerosol

particle size. The Ångström exponent was investigated in many
published reports [82,83], its value for the troposphere aerosol varies
from 0 to 2 around the wavelength of 300 nm. Considering that η
could be relatively small when it is applied in the UV region, we
assume that η =0 .5 at our DIAL wavelengths for urban aerosols [39].
The iterative procedure can be summarized as follows:
 Step 1: Calculate the first ozone concentration from [1.35].
 Step 2: Substitute the first ozone concentration into (1.46) to derive
the aerosol backscatter profile 𝛽𝑎𝑒𝑟 (𝜆𝑜𝑓𝑓 , 𝑅) for the off wavelength,
and iterate to obtain a stable solution with (1.48).
 Step 3: Calculate the differential aerosol backscatter and extinction
corrections Nb(R) và Ne(R) to obtain a second ozone
concentration from (1.34).
 Step 4: With the second ozone concentration, go back to step 2. This
loop ends when the condition 𝜉𝑂𝑘3 < 0,001 is satisfied.
15


This program is written in Matlab code..
4.3 Results of vertical ozone distribution measurement
The UV DIAL, with two DFDL installed in the transmitter, has
been used to measure the ozone concentration profile on cloudless
nights. Figure 4.2 presents the results of continuous ozone
concentration distribution in January 2017, from about 1.2 km to a
height of over 4 km, with a spatial resolution of 480 m and an counting
duảtion of 10 minutes. The LIDAR signals at a height of less than 1.2
km are removed due to the small overlap between emitted laser beam
and the field of view of the telescope receiver.

Fig 4.2: Distribution of ozone concentration measured in Jan.

2017 over Hanoi.
16


From the ozone profiles shown in Figure 4.2, we find that average
ozone concentrations over Hanoi from a height of about 1200 m to
4,000 m varies from 2.1012 to 5,1011 molecules/cm3, respectively from
80 to 20 ppbv. This trend is consistent with characteristic ozone
distribution in the troposphere. Because there is no data of
ozonesonde at the same time, Figure 4.2 shows an ozone profile over
Hanoi, measured by balloon ozonesonde with the spatial resolution of
1 km (published at the meteorological conference in South Korea in
2007 [4]) to illustrate the trend of reduction of ozone concentration in
the lower atmosphere and the equivalence of the data.
4.4 Error analysis
The error of DIAL measurement of ozone concentration is devide
into the following four categories:
1. Statistical uncertainties 1 arising from signal and background
noise fluctuations
2. Errors 2 associated with differential backscatter and
extinction of otherwise gases (O2, NO2, SO2, etc) and aerosols
3. Errors 3 due to uncertainties in the ozone absorption cross
section
4. Errors 4 related to instrumentation and electronics.
1 is a random error. 2, 3 and 4 are systematic errors. With the
assumption of a Poisson distribution governing the photon counting,
1 is calculated by the expression (1.51) [66]. A summary of the errors
in the DIAL measurements is shown in Table 4.2 with vertical
resolution of 480 m, altitudes below 4km and counting duration of 10
min.

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Table 4.2: Summary of the errors in the DIAL measurements.
TT

Error

%

1

1 – Statistical error

2

2 – interference by non-ozone species

3

< 18

Aerosol

< 20

Non-ozone absorption gases

< 0,3

Rayleigh

< 0,6

3 due to uncertainty in differential cross

< 2,5

section of ozone
4

4 due to SIB and dead-time

<5

Total RMS error

< 27

Currently, the global ozone maps are provided by NASA Aura
satellite data. The global ozone distribution in the troposphere is
synthesized from the total column ozone measurements OMI (Ozone
Monitoring Instrument) and the stratosphere ozone measurements
MLS (Microwave Limb Sounder) with a resolution of 36 km x 48 km.
[86]. According to Aura data, the average ozone density / month in
the troposphere in January 2013, 2014 and 2015 is 40 ppbv, January
2016 is 55 ppbv over Hanoi. Figure 4.4 shows this average ozone
density / month and the average data of ozone density measured by
UV DIAL system on days in January 2017. The average ozone

density/day measured by the Differential Absorption LIDAR system
is averaged from ozone concentration in the height range from 1.2 km
to 4 km. We find that the values measured by UV DIAL system are
the same level, within the error range and quite similar to the
measurements from Aura satellite (Figure 4.4).
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Fig 4.4: Average ozone density/month over Hanoi area in Jan. of
2013, 2014, 2015 and 2016 (Aura satellite data - NASA [70]) and
measurement data from the UV DIAL system on Jan. 2017 in Hanoi
CONCLUSIONS
With the aim of studying and developing a high-resolution
Differential Absorption LIDAR system to measure the distribution of
ozone

concentration

in

the

lower

atmosphere,

several

accomplishments of this research include:
1. A new UV laser transmitter consisting of two Distributed

Feedback Dye Lasers (DFDLs) has been developed and used
for a DIAL system. Using the DFDLs with the active medium
of Rhodamine 6G, we can easily control the emitted
wavelengths in order to have a pair of suitable wavelengths
for the DIAL measurements of atmospheric ozone
concentrations.
2. A new receiver of the DIAL system has been built to acquire
elastic backscattering signals. A primary mirror of the
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receiver's telescope has been made with the diameter of 40
cm and the aluminum deposited on its surface so that the
receiver has a high optical gain and a high performance in the
ultraviolet region.
3. A simulation program for estimating the expected LIDAR
signals of the designed DIAL system is developed.
4. A software program to process data and calculate ozone
concentration distribution is developed.
5. The UV DIAL system has been used to measure atmospheric
ozone distribution over Hanoi and it is able to monitor ozone
concentration continuously.

With the results and experience gained from the completing of
thesis, it is realized that we can develop the Differential Absorption
LIDAR systems multi-channel, multi-wavelength, to study the other
components of the atmosphere of the atmosphere. In the future, we
can continue to improve the transmitter and receiver of UV DIAL
system to continuously measure the ozone concentration during
daytime condition and increase the height of monitoring.

20