Li, an expert in underwater acoustic signal processing and sonar design. People from Wenzhou, Zhejiang. 1963 graduated from the Department of Mathematical Mechanics of Peking University. Researcher and former director of Institute of Acoustics, Chinese Academy of Sciences. Chief scientist of the national "863" plan marine monitoring technology expert group.
Long-term engaged in signal processing theory and sonar design and development. According to the characteristics of shallow water acoustic propagation in China, a series of problems in underwater acoustic signal processing are solved by using information theory, digital signal processing and underwater acoustic engineering. The steady-state characteristics of adaptive beamforming are studied, and the expression of solving beam directivity by using frequency domain optimal transfer function is given. The gain calculation method of detecting weak signal under the background of ocean noise is given. It solves the problem that the classical theory should be corrected by the noise field which is unstable in time and uneven in space.
1997 was elected as an academician of China Academy of Sciences.
Chinese name: Li
Nationality: China.
Ethnic group: Han nationality
Place of birth: Wenzhou, Zhejiang
Date of birth: July 1939
Occupation: scientist
Graduate school: Peking University.
Main achievements: mathematical mechanics
1997 was elected as an academician of China Academy of Sciences.
Masterpiece: The paper "Research on Cancellation Capability of Adaptive Noise Cancellation Filter"
Gender: male
outline
Li is an outstanding expert in underwater acoustic signal processing and sonar design in China. He is currently an academician of China Academy of Sciences, a researcher at Institute of Acoustics, Chinese Academy of Sciences, a professor at the Department of Communication Engineering, and a doctoral supervisor. Academician Li has long been engaged in signal processing theory and sonar design and development. Former director of Institute of Acoustics, Chinese Academy of Sciences.
Academician Li creatively applied information theory, digital signal processing and underwater acoustic engineering to solve a series of problems in underwater acoustic signal processing, and made important contributions to the modernization of China's naval sonar equipment. In this paper, the steady-state characteristics of adaptive beamforming are studied, and the expression of solving beam directivity by using the optimal transfer function in frequency domain is given. The gain calculation method of detecting weak signals under the background of marine noise is given, which solves the problem that the classical theory needs to be corrected by the non-stationary noise field in time and the non-uniform noise field in space, and puts forward a new sonar equation expression, which is an important basis for guiding sonar design.
In the passive detection of underwater targets, a new method of estimating the target azimuth by using the phase information of acoustic signals and a new algorithm of completely separating multiple non-overlapping point source signals in space by using adaptive array processing method are proposed. In the design of digital sonar, technologies such as dynamic beamforming, programmable digital filtering, variable sampling rate operation, Kalman-like filtering, and gray scale transformation are put forward for the first time, and a simple underwater target recognition expert system is designed through cluster analysis, which has played a very good role in promoting the development of digital sonar in China.
1997 was elected as an academician of China Academy of Sciences. From 1984 to 1986, I worked in the United States for nearly two years at the invitation of Princeton University. 1976 participated in adaptive filtering research and won the first prize of major scientific and technological achievements of Chinese Academy of Sciences; 1978 participated in the research of 00 1 shore-based sonar station and won the first prize of the National Science Conference; 1984 was responsible for the development of 262 sonar, and won the scientific and technological progress award of the Sixth Machinery Division.
He has published dozens of papers, including Computer Simulation Technology in Sonar Design and Adaptive Array Signal Separation Theory. Monographs include Design Principle of Digital Sonar, Introduction to Sonar Signal Processing and Computer Graphics (co-edited).
On April 26th, 2007, the reporter of Science and Atheism interviewed Li, an academician of China Academy of Sciences. Academician Li is an expert in underwater acoustic signal processing and sonar design. He has been engaged in signal processing and sonar design and development for many years, and was the director of Institute of Acoustics, Chinese Academy of Sciences. In the long-term scientific research work, Academician Li deeply realized that scientific research should first have a scientific attitude, and only with a scientific attitude can research be carried out. Secondly, science needs truth, and science cannot be adulterated. Because what is truly scientific needs to be tested by practice.
life experience
Be admitted to Peking University.
Li Zu was born in Shuomen, Wenzhou. He studied at Wenyi Primary School (the predecessor of Mo Chi Primary School), which is a missionary primary school. In order to enter Wenzhou Middle School smoothly, when Li was in the fifth grade, his considerate mother specially transferred him to Wenzhou No.1 Primary School (the predecessor of Square Road Primary School) with strong teachers and high enrollment rate.
A year later, Li lived up to his mother's expectations and was admitted to Wenzhou Middle School with excellent results. After entering middle school, Li was lucky enough to meet many good teachers, such as Zou Yihao and Pan Zhipei, the head teachers. In particular, the math teacher Yang is particularly concerned about Li, who is smart and eager to learn, and often takes him home to "cook a small stove", which makes Li have a strong interest in science.
When I was in Li middle school, I dabbled in extracurricular knowledge. At that time, extracurricular books were very scarce, and students were not allowed to enter the library without permission, so they could only get them through teachers. Jenny Yang happens to be the curator of the school library, which provides great convenience for Li to borrow books casually. Because of the "special pass", Li almost read all the books he was interested in in in the school library, just like a sapling after a long drought, greedily sucking the nectar of knowledge.
"At that time, if I didn't go to college, my personal situation would be very bad. Unlike now, I can go out and look for a job, so even if my parents don't give us pressure, we will work hard. " Recalling this past many years later, Li still remembers it vividly.
1956 The CPC Central Committee issued the call of "marching into science". The following year, after graduating from high school, Li actively responded to the call and applied for the Department of Mathematical Mechanics in Peking University. 1959 Peking University set up the major of information theory and cybernetics, and he was transferred to this new major.
1963, after graduating from Peking University, Li was assigned to the seventh laboratory of Institute of Electronics, Chinese Academy of Sciences. He studied under Mr. Wang Dezhao, a famous scientist in China and an academician of Chinese Academy of Sciences, and started the research journey of national defense hydroacoustics.
Li has made outstanding contributions to underwater acoustic signal processing and sonar design in China. Little known is that He, who is now famous at home and abroad, returned to Wenzhou almost as an ordinary teacher.
1969, Li got married, and his wife worked in Wenzhou Mechanical Instrument Bureau. After a long separation, he had the idea of returning to work. Li's brothers and sisters are all working in other places, and the mother also hopes that her youngest son can return to her side. At that time, the Institute of Acoustics was led by the Commission of Science, Technology and Industry for National Defense and compiled by the army, so he found the Wenzhou Military Management Committee and asked for a transfer. At that time, it coincided with the "Cultural Revolution", and all units were revolting. It is difficult to find a suitable job. Finally, the relevant departments went through a lot of difficulties and finally arranged for Li to teach at Sanxi Middle School in Ouhai, which was also a kind of care. "At that time, the city was more than ten kilometers away from Sanxi, and the road was muddy and difficult to walk. Even if you ride a bike every day, you may not be able to eat it. " I hesitated at the news of Li.
"In the end, I didn't go back to be a teacher, thanks to my teacher Wang Dezhao." Li said that when I called Wenzhou, Mr. Wang had been sitting next to me, and he tried to dissuade me from going back. After the downfall of the Gang of Four, the Institute of Acoustics returned to China Academy of Sciences. 1977, Comrade Deng Xiaoping instructed the relevant state departments to grant 400 places to the Chinese Academy of Sciences in Beijing. Mr. Wang, then director of the Institute of Acoustics, won a place for Li, which finally reunited the couple.
There is joy in suffering.
Acoustics is an experimental science, and many studies need to be verified, so researchers often do experiments at sea. Li has been engaged in hydroacoustics research for more than 40 years. Because of his work, he traveled to almost every port city in China and reached the Xisha Islands as far as possible.
Whether it is cold or hot, whether it is windy or rainy, it is extremely hard to go out to sea to do experiments. An experiment can be as short as several weeks and as long as several months. There is no fixed commuting time, so it is necessary to overcome the difficulties of seasickness and inability to eat. "Every time I go out to sea, I bring seasickness medicine. It will be better if you eat it, but you won't get used to seasickness at sea. "
From 65438 to 0993, Li became the director of the Institute of Acoustics. "Being a director is more of a responsibility. In addition to leading scientific research, we must also provide logistics services. " There are about 800 people in the Institute of Acoustics, with workstations in Qingdao, Shanghai, Hainan and other places. The team is huge and the affairs are trivial. At that time, Li's wife had to retire early to support her work.
Old but full of energy.
"Academicians don't retire." Li 200 1 has been very busy since he retired as the director of the Institute of Acoustics. Even on Saturday and Sunday, Li's figure often appears in the office. The so-called words and deeds, Li's serious persistence in his work, also exerts a subtle influence on children. Today, both his children have achieved success. One graduated from the University of Science and Technology of China and now works in Canada. One graduated from Shanghai Jiaotong University and is now studying for a doctorate in the United States.
In 2009, Academician Li became the chairman of Ningbo Park in Ningbo National High-tech Zone.
At present, Li is also the head of the expert group of national defense system-related research projects, and has served in domestic signal processing associations, acoustic associations and some foreign conference organizations. In addition, he also participated in some scientific research projects.
What makes Li proud is that apart from national defense security, sonar is also widely used in national economic development, and it is indispensable in shipwreck detection, underwater treasure exploration, underwater oil and gas resources exploration, shipwreck rescue and so on. "Even the Olympic Games has a place to play the role of underwater acoustic science." In 2008, in the Olympic windsurfing competition held in Qingdao, underwater anti-terrorism sonar detection equipment must be installed as required to prevent the destruction and terrorist activities in the form of underwater frogmen. "This technology was developed by our Institute of Acoustics, which lasted for more than a year and was delivered to the relevant departments not long ago." Li said to him.
20 15, Li attended the second national academic conference on marine technology.
Devotion to science
Hydroacoustics, as its name implies, is a subject that studies acoustics in water, especially in the ocean, that is, the generation, propagation, reception, measurement and application of sound waves in water. Sound wave is the only form known to man that can transmit energy in seawater for a long distance. Sonar is widely used in ocean utilization and development, such as shipwreck detection, underwater treasure exploration, underwater oil and gas resources exploration, shipwreck rescue and other national economic and national defense security. The biggest application in economic construction is to find oil offshore. Underwater acoustic science has opened a door to treasure hunting under the sea.
Since 1996, China has brought the marine field into the national 863 plan and actively promoted the development of high-tech marine monitoring, among which the underwater acoustic monitoring technology has made great progress. Li worked in the ocean field of the National 863 Project for 8 years.
Li said to:
"Science is science, science cannot be adulterated, nor can it be made out of nothing. You can't claim that the research has achieved anything, so you can be recognized by others. That won't do. It needs to be proved by experiments. Science respects practice. The practice of natural science is a scientific experiment, and others can do it under the same conditions.
Science not only respects practice, but also has to be tested by practice. What is real science needs to be tested by practice, and so does any discipline.
We study sonar in order to serve the national economic development and national defense security. This is an experimental science, and many studies need to be verified, so we often do experiments at sea. Scientific experiments have proved new discoveries under water. If there is an oil and gas field underwater, it must be found.
In 2008, China will host the Olympic Games, which is a great event for our people and the people of the world. The Olympic Games will also give full play to our underwater acoustic science. For example, in the water windsurfing competition held in Qingdao, it is necessary to install underwater anti-terrorism sonar detection equipment to prevent the destruction and terrorist activities in the form of underwater frogman. "
The latest research
The 1st International Conference on Underwater Acoustic Survey (UAM) was held in Greece. Li, an academician of China Academy of Sciences and a researcher at the Institute of Acoustics, was invited to attend the meeting and gave a report entitled "Application of Underwater Acoustic Technology in Ocean Monitoring". In the report, Li expounded the important role of underwater acoustic measurement technology in marine monitoring, and introduced the research results of underwater acoustic monitoring technology in the marine field of China's "863" plan, which aroused great interest and concern of experts and scholars from all over the world.
Li pointed out the importance of underwater acoustic measurement technology in ocean monitoring for the first time in his report. Li said that ocean monitoring is one of the important tasks of ocean development and utilization. It includes marine environmental protection, marine disaster early warning, national security and marine resources development. The main means of ocean monitoring are based on mechanics, electromagnetism, chemistry, acoustics, optics and other research fields. Because sound wave is the only medium that can propagate in seawater at present, the attenuation of sound wave signal with distance in the ocean is much less than that of light wave and electromagnetic wave, so underwater acoustic technology plays a vital role in marine environmental monitoring, especially in the monitoring of sea body and seabed.
Since 1996, the Ministry of Science and Technology has brought the marine field into the "863" plan, actively promoting the development of high-tech marine monitoring, in which the underwater acoustic monitoring technology has made great progress. In the report, Li introduced these achievements to his international counterparts. One is multifunctional acoustic Doppler current profiler (MADCP). Current profile is an important parameter to be considered in marine development activities. The traditional acoustic Doppler current profiler (ADCP) can only give the current profile with a depth of several hundred meters. Now, with MADCP, suspended substances can be detected in addition to the current configuration file. This equipment has "China characteristics"-the seawater in China is usually turbid and full of sediment, and the detection of suspended solids is very necessary in marine monitoring, so the appearance and application of MADCP is of great significance. The second is Acoustic Correlation Current Profiler (ACCP) technology. Working depth is the limitation of traditional ADCP, so it is difficult to work at a depth of more than 460 meters. At present, the current measured by ACCP is much deeper than ADCP, and the measuring depth can exceed 3000 meters. ACCP instrument is small in size and has a good application prospect in the military. At present, only China and the United States have mastered ACCP technology, and China completed the prototype construction of ACCP two years ago. Thirdly, Synthetic Aperture Sonar (SAS) technology. This is a major technological innovation in the field of ocean engineering. SAS technology is a high-resolution underwater image sonar, which can be used to detect seabed topography. At present, China, the United States and some western European countries are studying SAS.
In the report, Li also introduced the application of underwater acoustic technology in military oceanography. Include underwater target recognition, underwater communication, ocean surveillance and anti-submarine warfare. In fact, since the 1950s, due to the appearance of nuclear submarines that can dive underwater for a long time, especially the appearance of low-noise stealth submarines, major maritime countries have paid special attention to sonar research. However, after the "9. 1 1" incident in the United States, the role of underwater acoustic technology in protecting national security has been paid more attention by the whole world, and its military functions are mainly manifested in harbor defense, unknown underwater traffic monitoring, network-centric operations and so on.