Liu Gang

Liu Gang (born 30 January 1961, Liaoyuan, Jilin) is a Chinese scientist whose fields of study include mathematical modeling, computer science, and theoretical physics. He was a prominent student leader at the Tiananmen Square protests of 1989. Liu holds a M.A. in physics from Peking University and a M.A. in computer science from Columbia University. After his exile to the United States in 1996, Liu studied technology and physics at Bell Labs in New Jersey. Liu is currently employed at Morgan Stanley as a Wall Street IT analyst.^[1]

As a major leader of the Chinese democracy movement, Liu is a friend of fellow activists Wang Dan and Wuer Kaixi.^[2]

Student activist

As an undergraduate student at University of Science and Technology of China in Hefei, Liu met Fang Lizhi, a pro-democracy activist.^[3] Then, at Peking University, Liu organized "Democracy Salons". Wang Dan later held a position there.

Liu was a 28-year-old graduate when the 1989 demonstrations began. He organized the Beijing Students' Autonomous Federation and joined the movement's organizing body. As a result, he was sixth on a list of twenty-one activists whose arrests were ordered by the government. Liu went into hiding as a fugitive, but on 15 June 1989, Liu was arrested and charged with attempted subversion of the Communist Party of China.^[4] In 1991, he was convicted and sentenced to six years imprisonment at Qincheng Prison.^{[5][6][7][8][9][10]}

After his release from prison in 1996, Liu continued to advocate for human rights in China and organized an underground democracy movement. ^[11][12] After moving to the United States, Liu continued his studies at Columbia University in New York City. ^[13][14][15] From there, he continued to support the Chinese democracy movement and in 2011, initiated further pro-democracy protests.^[16]

Scientific research

China

In 1982, Liu received a bachelor's degree in modern mechanics from the University of Science and Technology of China. He was employed by the Aviation Industry Corporation of China in Shenyang in the field of aerodynamics. He worked in partnership with Luo Yang, and was promoted to head of aircraft design. Liu's field of research was the theory of air resistance, and he worked on problems of double-sided entry and radar technology.

In 1984, Liu received a master's degree in optics from the Department of Physics at Peking University in Beijing. While there, he was an assistant teacher.^[17] Liu returned to work at the China Soft Science Research Institute but was also acting assistant director at the University of Science and Technology of China.

In 1988, Liu became an assistant and associate researcher at the Wear-Resistant Materials Development Company of the National Ministry of Higher Education & the Dalian Institute of Technology. He was then transferred to research in the Department of Physics at the Chinese Academy of Sciences.

United States

In 1996, Liu received a master's degree in computer science from Columbia University. He was invited to speak at the New York Academy of Sciences.^[18] Liu gained employment as a technician at the Mathematics of Networks and Systems Research Department at Bell Laboratories in Murray Hill, New Jersey. There he worked on Optical telecommunication network design and planning, routing algorithms, optimization techniques, and economic models and strategy analysis.^[19]

Liu's areas of research included: SPIDER, a design tool for fast-restoration in all-optical networks; VPNStar, a system for provisioning multi-service VPNs with Quality of service guarantees over Internet Protocol; in software design, a management system for Lambda Router in all-optical networks; and analysis of Internet pricing.^[20]

During his days at Bell Laboratories, Liu introduced the A*Prune (1999, ISSN 0743-166X) with K. G. Ramakrishnan, to describe a new class of Algorithm. This opened a new research direction in theoretical science. He found that A*Prune is comparable to the current best known-approximate algorithms for most randomly generated graphs. The algorithm constructs paths, starting at the source and going towards the destination. But, at each iteration, the algorithm is rid of all paths that are guaranteed to violate the constraints, thereby keeping only those partial paths that have the potential to be turned into feasible paths, from which the optimal paths are drawn.^[21]

Liu also proposed a special class of Optical devices called SPIDER (2001, ISSN 1089-7089); optical routers, dense wavelength division multiplexing (DWDM) systems, and cross-connects of unprecedented capacities. Liu and his colleagues are developing techniques for efficient and reliable optical network design, covering decentralized dedicated protection to shared path-based mesh restoration.^[22]

Articles

• Liu G. T-Forward Method: a Closed-Form Solution and Strongly Polynomial Time Approach for Convex Nonlinear Programming. Algorithms Research, Elmhurst, New York 2014 3(1):1-25.
• Liu G. A Mathematic Model for Supply-Demand Equilibrium and the Optimal Solution for Labor Assignment American Journal of Economics, Elmhurst, New York, 2014 4(2):83-98 doi 10.5923/j.economics.20140402.01
• Liu G. et al. SPIDER: A Simple and Flexible Tool for Design and Provisioning of Protected Lightpaths in Optical Networks Bell Laboratories Technical Memorandum, Murray Hill, New Jersey, 2001.
• Liu G. and Ramakrishnan K. G. A*Prune: an Algorithm for Finding K Shortest Paths Subject to Multiple Constraints. Bell Laboratories Technical Memorandum 10009626-000302-04TM, Murray Hill, New Jersey, 1999. CiteSeerX: 10.1.1.20.8011
• Liu G. et al. Algorithms for DWDM Mesh Network Design: Routing and Wavelength Assignment for Dedicated Protection, Ring Auto-Recovery and Optical Cross-Connect Restoration in Core Optical Networks. Bell Laboratories Technical Memorandum 10009626-000126-01TM, Murray Hill, New Jersey, 1999.
• Liu G. and Stern T. E. An Algorithm for Optimal Routing and Wavelength Assignment on a Bi-directional Ring Bell Laboratories Technical Memorandum BL0112120-990610-10TM, Murray Hill, New Jersey, 1999.

References

External links

• Quatratic.com — A website solver for Convex Nonlinear Programming

Optimization: Algorithms, methods, and heuristics
Unconstrained nonlinear: Methods calling … … functions Golden section search Interpolation methods Line search Nelder–Mead method Successive parabolic interpolation … and gradients Convergence Trust region Wolfe conditions Quasi–Newton BFGS and L-BFGS DFP Symmetric rank-one (SR1) Other methods Gauss–Newton Gradient Levenberg–Marquardt Conjugate gradient Truncated Newton … and Hessians Newton's method
Constrained nonlinear General Barrier methods Penalty methods Differentiable Augmented Lagrangian methods Sequential quadratic programming Successive linear programming
Convex optimization Convex minimization Cutting-plane method Reduced gradient (Frank–Wolfe) Subgradient method Linear and quadratic Interior point Affine scaling Ellipsoid algorithm of Khachiyan Projective algorithm of Karmarkar Basis-Exchange Simplex algorithm of Dantzig Revised simplex algorithm Criss-cross algorithm Principal pivoting algorithm of Lemke
Combinatorial Paradigms Approximation algorithm Dynamic programming Greedy algorithm Integer programming Branch & bound or cut Graph algorithms Minimum spanning tree Bellman–Ford Borůvka Dijkstra Floyd–Warshall Johnson Kruskal Network flows Dinic Edmonds–Karp Ford–Fulkerson Push–relabel maximum flow
Metaheuristics Evolutionary algorithm Hill climbing Local search Simulated annealing Tabu search
Categories Algorithms and methods Heuristics Software