1On July 20th, 905, Li Da was born in Xinping Village, Pingjiang County, Hunan Province. Li Da is the second child in the family. His four brothers and sisters graduated from university, and his father Li is the headmaster of a primary school. When Li Da was a child, his family was very poor. "With the support of Mongolian President Jiang Jun and Mr. Wan Guojuner, he was admitted to Nanjing National Southeast University on 1923. He studied literature and history at first and then changed to mathematics." At that time, the Department of Mathematics of Southeast University was very strong, and it was a first-class position in China. The dean is Xiong Qinglai, and professors include He Lu and Duan Zixie. Among the students are Zhou Shaolian, Chen, Zhou Huaiheng, Hu Kunsheng, Tang Peijing and Zhou Hongjing, which can be described as talented people. Southeast University was later renamed the Fourth Sun Yat-sen University. At that time, people's livelihood was depressed and schools increased their fees. Many students can't afford tuition, so Li Da called on his classmates to do free sports. 1927 stayed in school as a teaching assistant after graduation.
Li Da's experience in Southeast University has laid a solid academic foundation for him. When German academic institutions recruited graduate students in China, they gave Hunan two places. Huang, then director of education, advocated fair competition and held public examinations. As a result, Li Da ranked first, and entered the University of Munich with another pilot, He Fengshan. Li studied under Peron (), former Greek mathematician Caratheodory (1873 ~ 1950), and studied under Csekovszky for a doctorate, specializing in real letter, reply, deviation, variational method and numerical calculation) and Hatogos lattice. This article comes from data management download. During Li Da's study abroad, he was supported by China Education and Culture Foundation for two consecutive years and published many papers in Swedish Journal of Mathematics.
Li Da is one of the earliest veterans in China who attended the International Congress of Mathematicians. The 9th International Congress of Mathematicians was held in Zurich, Switzerland from September 4th to June 2nd. At that time, chinese mathematical society had not been established. Only Li Da, Xiong Qinglai, Xu Guobao and Ceng Jiong signed up, but Ceng Jiong failed to qualify as a formal participant because of his lateness.
Li Da is the first mathematician who published a paper on the stability of difference equations in China. 1939, recommended by M. Frechet, a professor at the University of Paris, published The Solution of General Linear Differential Equations in the German magazine Commentarii Mathematici Helvetici. In the same year, the "Editor's Note" in the fourth issue of Buddhist Quarterly gave a high evaluation of this paper. Li Da also published "The Essence and Application of Mathematics", which was a rare reflection and discussion on the level of scientific philosophy in mathematics at that time. For the second time, it attracted attention in the history of mathematics and published the article "China's Arithmetic in Thirty Years". This article was published in the third issue of Science 1947, with more than 10,000 words. This is the first study of the history of modern Chinese mathematics, leaving some historical materials.
1934, Li da returned to the motherland and was hired as a professor of mathematics in Tsinghua University at the invitation of Xiong Qinglai. In August of the same year, Li Da resigned as Professor Tsinghua University and came to Shandong University as Professor and Acting Dean of the Department of Mathematics. He was a young man in his thirties when he was employed by Shandong University. As a professor in the Department of Mathematics, Li Da has a profound knowledge and a deep foundation in mathematics. In teaching, he not only insists on rigor and is strict with students, but also can explain things in simple terms. He combined practical and vivid examples to simplify the difficult and simplify the complex, inspiring students, enabling them to break the stereotype of mathematics being highly abstract and monotonous, consolidating professional ideas and improving their learning enthusiasm. He also spent a lot of energy and time translating Gu Long's calculus and Weatherburn's differential geometry as teaching materials, which broadened students' horizons and made them understand the new progress and improvement of mathematics in the world.
Professor Li Da also pays special attention to cultivating students' independent thinking ability and encourages them to think bravely and innovate constantly. Wang Xiqiang is a student of the Second Mathematics Department of Shandong University. Please keep this mark after graduation. ) and stay in school to teach. In an article recalling his teacher Li Da, he wrote: "My thesis" The Net Distribution of bernhard and Euler Polynomials "was written after careful consideration and reasoning under his guidance. This paper won the first prize in the national mathematics selection, and was well received by the mathematics community after the publication of Ta Kung Pao. The results also laid the foundation for my research in mathematical science and formed an indissoluble bond with mathematical science. "
From 65438 to 0946, Li Da was sent to the United States for further study by the Ministry of Education. Teaching at Drake University in Iowa. 1948, by Berman (Dr.? Richard bellman, 1920 ~ 1984, the founder of the branch of dynamic programming mathematics, and the differential method and variational method also made important contributions) was introduced to Chance Vought Company to study aircraft manufacturing. From 65438 to 0950, Li Da transferred to Genetic Dynamics and Canvair Division to study the dynamics of rockets and objects without suction field. 1962, Li arrived in North America (now Rockwell International Company, Space) to participate in the work of the moon landing spacecraft Apo 1lo.
When studying in Germany, Li Da had to complete several physics research projects under the guidance of Professor Amold Sommerfeld of Munich as part of the doctoral program in mathematics. The stability criterion he discussed is widely used in stability control, and the "integral transformation" he developed to solve aerodynamic problems has been continuously used by pure mathematics and applied mathematics researchers at home and abroad.
Li Da summed up his experience and academic achievements in six aspects in a resume: (1) stability control-stability criterion; (2) Aeroelastic deformation-Mach element method for supersonic aircraft design: (3) Shell theory-frequency of polar-orbiting geophysical observation satellites; (4) fluid mechanics-the performance of fluid under zero gravity; (5) heat conduction-temperature prediction of Saturn II liquid fuel tank under adiabatic failure, (6) integration of fluid dynamics-Neville-Stokes equation.
From Li Da's own summary, we can see that he is not only a famous mathematician, but also has made great achievements in aerospace. In addition to being a member of the American Mathematical Society, he is also a communication researcher at the American Institute of Aeronautics and Astronautics. He published a large number of papers in world-famous science and engineering magazines, and was included in the who's who of science in the United States. His most important contribution to aerospace lies in the following aspects: the basic method of wing design of supersonic aircraft; Singular integral transformation; Improvement of fuel nozzle position of space shuttle under zero gravity and low gravity conditions.
One of Li Da's important contributions in aerospace is Mach box method for supersonic aircraft design. Li Da himself called this method "matrix method", which is to plan the wing shape according to the highest speed of the aircraft to avoid the damage caused by the earthquake. The Mach element method for flutter prediction only takes ten months from the beginning to the numerical verification. Supersonic aircraft designers often use this method.
Li Da is also very good at studying the performance of fluid under zero gravity, and his principle of minimum energy can be used to predict the fuel position under various gravity levels. This theory applies to every spacecraft with fluid. His theory has been verified by falling tower and free fall experiments in the United States and Russia, and several Russian papers affirming this theory have also been translated into English by NASA.
Lida's theory of heat conduction-temperature prediction of Saturn II liquid fuel tank under adiabatic failure has solved the problem of solving thermodynamic boundary layer equation in closed state for the first time. He pointed out that the theory of how to control liquid and the influence of gravity on human body has also been adopted by various countries.
1974, Li Da retired, and Pamona made an evaluation report for him. The evaluation host is Emil R.Herzog (Amy? r？ Hertzog). According to the report, "Mr. Li is the most valuable member of our department." This article comes from data management download. He is not only an extremely active researcher (as evidenced by the fact that the number of his publications exceeds that of all his colleagues), but also a teacher deeply loved by students.
Li Da has been very concerned about the motherland all his life. He wrote in his family letter: "Vice Premier Deng is very popular in the United States and has gained a lot ... To build a socialist country, we must first destroy the old society and then build a new society with science and technology. Science and technology is knowledge, and knowledge is very important in modern countries. China must catch up and improve its life. You can't work on an empty stomach. ..... Everyone should work hard and make progress. "