A simple temperature sensor based on a bent singlemode–multimode–singlemode (SMS) fiber structure fastened on
a polymer base plate is proposed and experimentally investigated. The surrounding refractive index (RI) is higher than
that of the silica fiber and RI changes with temperature will not lead to wavelength shift. This SMS fiber structure
utilizes changing of temperature to control the curvature of SMS fiber which is induced by expanding of polymer base
plate. The shifts of central wavelength are measured at temperature range from 59 to 82 °C. The proposed temperature
sensor offers sensitivity of 3.9 nm/°C, which is significantly higher than that of a normal straight SMS structure or a
grating-based fiber structure.
We propose a way to enhance the temperature sensitivity of single-mode-multimode-single-mode (SMS) fiber structure,
by replacing the cladding of silica multimode fiber with a polymer coating. Based on the mode expansion method, we
analyze transmission characteristics of the polymer-coated SMS fiber structure and optimize design parameters for
sensing. Then we do experiments and verify theoretical analysis. By using the optimized parameters in sample
fabrication, a temperature sensor is obtained with an easily detected and demodulated transmission spectrum; and then
by monitoring valley wavelength shifts, a measuring sensitivity of about 706 pm/°C is achieved.
A co-axial transmission elastic-backscattered lidar aiming to detect the optical properties of the clouds is presented in
this paper. The modular co-axial design can guarantee the consistency of the transmitting part and the receiving part. In
practice a specific diaphragm is used to suppress the stray light of the primary mirror and background light to improve
SNR of the backscattered signal in the daytime. So the near ground signal must be corrected with the appropriate overlap
factor. A Licel transient recorder is used for data acquisition in analog and photon counting combined in one acquisition
system. With the 15 MHz sampling rate, the spatial resolution of 10 m can be attained. The control over the transient
recorder and the treatment of the data is performed on a PC. After getting the correctional backscattered signal, retrieving
and analyzing the extinction coefficient profile, the cloud base, cloud peak and related optical parameters of the clouds
can be confirmed. In order to testify the feasibility of our lidar, it was implemented with a Finland ceilometer Vaisala
simultaneously in May in 2008 in Hefei. Results show the lidar system is stable and the data is reliable.
Medical image processing has been investigated for more than three decades. It is clear that medical imaging will still
play a very dominant role in clinical research as well as in the daily routine practice in the coming decade. For a number
of reasons the images obtained by the medical instruments itself, such as CT, MRI are insufficient for the efficient
performance of a surgical intervention and various image processing techniques are necessary in order to make the most
important features more easily visible. Owing to its rapidly increasing popularity over last few decades, the wavelet
transform has become quite a standard tool in numerous image research and application domains. Wavelet thresholding
has been a popular technique for image denoising. The basic principle of wavelet thresholding is to identify and zero out
wavelet coefficients of a signal which are likely to contain mostly noise. By preserving the most significant coefficients,
wavelet thresholding preserves important highpass features of a signal such as discontinuities. Here we used this
technology in medicine image denoising and resulted in quite satisfying result. The goal of the medical image denoising
in a broad sense is the research, implementation, and validation of image processing approaches. Research is carried out
among others medical application areas.
Knowing the quantity of pollutants that the vehicle fleet is emitting to the air has become a vital question in almost every major city in China. Finding and fixing gross polluters is therefore very important to control the urban air quality and protect the human health and the environment. Remote sensing is an important advance in the technology of on-road vehicle emissions testing because it is fast, mobile, and unobtrusive. This on-road vehicle emissions remote system is designed to measure the carbon monoxide, carbon dioxide and opacity from the vehicles's tailpipe based on the Tuneable Diode Laser Absorption Spectroscopy (TDLAS). There are several advantages of this system such as compact design and ease of use. The measurement principle and optical layout of the instrument has been described in this paper. Field testing at Beijing and Hefei were conducted over one year, more than 6000 vehicles were tested. This vehicle emissions remote system has been shown to be able to measure CO,CO2 and opacity from individual at highway speeds. In parallel, the plate license, speed, acceleration and length of vehicle are recognised by computer so that the owners of vehicles exceeding the permissible level of emissions can be identified.
The field experiment of Dongpu reservoir has been carried out from April 11 to 20 in 2005, and the concentrations of dissolved organic matter (DOM) are measured and analyzed in combination with laser-induced fluorescence (LIF) measurements. The aim of the field investigations was to determine the concentration of DOM in water and evaluate the performance of fluorescence remote sensing system. In experiment, we obtained interesting data of DOM at 49.35m distance by changing the angle of excitation laser incidence to water. The concentration of the DOM is 3.325mg/l and the relative standard deviation is 2.65%. It has been shown that the measurement of water quality in real time and on line can be done using LIF technique with high sensitivity and high precision.
In the past decade interest has focused on the remote analysis of emissions from motor vehicle using spectrometric techniques driven by recognition of the fact that a very proportion of the environmental damage done in this way originates with a small percentage of vehicles. In this paper a remote sensing system designed to measure air-pollutant emission from on-road motor vehicles is described. The system uses a tunable infrared laser differential absorption spectrometer and a technique of UV DOAS. It has been shown to be able to measure CO, C02 NO, HC and the dust emissions from on-road individual vehicles. Excellent detection sensitivity is obtained with measure precision.
On-road motor vehicle emissions have been estimated being the single largest contributor of major atmospheric pollutants worldwide. The amount of motor vehicles in Beijing has rapidly grown in the past few years and will increase even more noticeably in the near future. It is therefore clearly required that a targeted approach to identifying the grossly polluting vehicles will have maximum impact on reducing the detrimental effects of the emissions. In this paper we will introduce an on-road motor vehicle exhaust emission monitor built by our group. This monitor was fabricated with tunable diode laser absorption spectroscopy (TDLAS) technique. On-road remote sensing of CO and CO2 of the motor vehicle exhaust emissions on Xueyuan road and at Dayangfang motorway toll station in Beijing were performed with this monitor. Analysis of the results shows that only 73.4% on-road motor vehicles are clean. Among the rest more than 15% are heavy gross polluters which should be warn for repair or removed from service.
In the past decade interest has focused on the remote analysis of emissions from motor vehicles using spectrometric techniques, driven by recognition of the fact that a very large proportion of the environmental damage done in this way originates with a small percentage of vehicles. Several instrumentation manufacturers now market such devices, and others are developing new technologies that will offer opportunities for enhanced performance and lower cost.
In this paper we demonstrate the prototype design of vehicle emission remote sensing system by differential optical absorption spectroscopy (DOAS) and tunable diode laser absorption spectroscopy (TDLAS). In this design, vehicle emissions will be measured when they past a on road remote sensing station while driving along a road. The concentrations of hydrocarbons (HC) and Oxides of Nitrogen (NOx) are measured by DOAS, and the concentrations of Carbon Monoxide (CO) and Carbon Dioxide (CO2) are measured by TDLAS. The measurement precisions for CO and CO2 are ±0.25%, and the detection limits for HC and NO are ±250ppm.
Photodiode Array (PDA) detector is a key component of Optical Multiple Analyzer (OMA). The present paper reported the design of low-noise thermoelectrically-cooled Photodiode Array detector and its performance test and analysis in practice. It shows that our designed PDA detector has the advantages of small size low noise and constant temperature etc. and settles for the demands of high precision spectrum analysis.
The DOAS system is a synthetical system that combines optics mechanics electricity and computer technologies in it. The Multi-Path DOAS system that we developed is of great sensibility and lower measure limits. Advanced controlling and signal detection technology are applied in the system. This paper briefly summarizes the principle and the realization ofthe electrical control and signal detection in DOAS system
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