Eigenmodes and growth rates of relativistic current filamentation instability in a collisional plasma

I theoretically found eigenmodes and growth rates of relativistic current filamentation instability in collisional regimes, deriving a generalized dispersion relation from self-consistent beam-Maxwell equations. For symmetrically counterstreaming, fully relativistic electron currents, the collisional coupling between electrons and ions creates the unstable modes of growing oscillation and wave, which stand out for long-wavelength perturbations. In the stronger collisional regime, the growing oscillatory mode tends to be dominant for all wavelengths. In the collisionless limit, those modes vanish, while maintaining another purely growing mode that exactly coincides with a standard relativistic Weibel mode. It is also shown that the effects of electron-electron collisions and thermal spread lower the growth rate of the relativistic Weibel instability. The present mechanisms of filamentation dynamics are essential for transport of homogeneous electron beam produced by the interaction of high power laser pulses with plasma.Comment: 44 pages, 12 figures. Accepted for publication in Phys. Rev.

Plasma Dynamics

Contains table of contents for Section 2 and reports on three research projects.U.S. Navy - Office of Naval Research Grant N00014-90-J-4130Princeton University/Tokamak Physics Experiment Grant S-03688-GU.S. Department of Energy Grant DE-FG02-91-ER-54109National Science Foundation Grant ATM 94-2428

Bi-Abductive Resource Invariant Synthesis

Abstract. We describe an algorithm for synthesizing resource invariants that are used in the verification of concurrent programs. This synthesis employs bi-abductive inference to identify the footprints of different parts of the program and decide what invariant each lock protects. We demonstrate our algorithm on several small (yet intricate) examples which are out of the reach of other automatic analyses in the literature.

Economic progress and international mobility of human resources: Chinese immigrants in the United States labor market

In the past several decades, the United States has experienced major shifts in the source of immigration due to the amendment of the Immigration and Nationality Act in 1965. The shifts in the countries of origin raise concerns as to their effects on the U.S. labor market and welfare system. These concerns rekindle interest in questions such as how immigrants are selected from their original populations and what skills they bring with them.This thesis investigates Chinese immigrants in the United States. The purposes are twofold. First, most researchers have usually treated Chinese immigrants in the United States as a homogeneous group regardless of their country of origin--mainland China, Taiwan or Hong Kong. Because of different levels of economic development and different kinds of political systems in the three areas, the Chinese immigrants are likely to be at differing quality levels, and to experience different assimilation rates. The first part of this thesis examines differences in the quality and assimilation of Chinese immigrants in relation to their points of origin.Second, this thesis investigates how Taiwanese immigrants in the United States are selected from Taiwan's population to examine the observed (skills or levels of education) and unobserved (motivation or ability) characteristics of Taiwanese immigrants and non-emigrants. Previous researchers provide less insight regarding differences between emigrants and non-emigrants in the context of their countries of origin. The thesis takes a direct approach to compare Taiwanese immigrants and non-emigrants in Taiwan.The results indicate great differences among Chinese immigrants from the three areas in age, wage rates, years of schooling and industrial and occupational distributions. Immigrants from China tend to be older and less educated (less skilled) than immigrants from Hong Kong and Taiwan. In addition, the thesis finds that the three Chinese immigrant groups experienced substantial assimilation into the U.S. labor market during the 1980s.When Taiwanese emigrants and Taiwanese non-emigrants are compared, there is positive selection on unobserved and observed characteristics for both emigrants and non-emigrants. Taiwanese emigrants in the United States are more skilled and educated than non-emigrants because the wage distribution in Taiwan is more compressed than that in the United states and because a more egalitarian wage distribution rewards lower-income (lower-skill) people relative more and encourages higher-income (higher-skill) people to emigrate.U of I OnlyETDs are only available to UIUC Users without author permissio

RGSep Action Inference

Abstract. We present an automatic verification procedure based on RGSep that is suitable for reasoning about fine-grained concurrent heapmanipulating programs. The procedure computes a set of RGSep actions overapproximating the interference that each thread causes to its concurrent environment. These inferred actions allow us to verify safety, liveness, and functional correctness properties of a collection of practical concurrent algorithms from the literature.

A.: An integrated specification and verification technique for highly concurrent data structures

Abstract. We present a technique for automatically verifying safety properties of concurrent programs, in particular programs which rely on subtle dependencies of local states of different threads, such as lock-free implementations of stacks and queues in an environment without garbage collection. Our technique addresses the joint challenges of infinite-state specifications, an unbounded number of threads, and an unbounded heap managed by explicit memory allocation. Our technique builds on the automata-theoretic approach to model checking, in which a specification is given by an automaton that observes the execution of a program and accepts executions that violate the intended specification. We extend this approach by allowing specifications to be given by a class of infinite-state automata. We show how such automata can be used to specify queues, stacks, and other data structures, by extending a data-independence argument. For verification, we develop a shape analysis, which tracks correlations between pairs of threads, and a novel abstraction to make the analysis practical. We have implemented our method and used it to verify programs, some of which have not been verified by any other automatic method before.