The JKind Model Checker

JKind is an open-source industrial model checker developed by Rockwell Collins and the University of Minnesota. JKind uses multiple parallel engines to prove or falsify safety properties of infinite state models. It is portable, easy to install, performance competitive with other state-of-the-art model checkers, and has features designed to improve the results presented to users: inductive validity cores for proofs and counterexample smoothing for test-case generation. It serves as the back-end for various industrial applications.Comment: CAV 201

The Internationalization of Industry Supply Chains and the Location of Innovation Activities

Current policy discussions on offshoring mostly focus on its impact on lower skilled manufacturing and services jobs, assuming that higher-value-added jobs and, especially, the location of innovation activities are not affected by offshoring. Contrary to this view, we suggest that innovation mainly driven by R&D activities can also move abroad as a result of offshoring. We suggest that the movement of innovation abroad will be conditioned by the nature of technology innovation processes, in particular knowledge spillovers, causing some innovation activities to remain in the United States while driving other activities away. To explore this idea we conduct an in-depth study of the rare earth industry which provides critical raw materials for numerous technology based applications. This industry is pertinent because it has experienced significant supply chain relocation away from the United States and to developing countries. Using industry accounts and patent information, we examine the impact of the movement of rare earth production from the United States to China on the location of rare earth innovation over the past two decades. We find that, while supply chain offshoring has caused rare earth magnet innovation activities to move away from the United States, innovation activities in rare earth catalysts remains in the country. Direct observations and industry reports suggest this dichotomous response to supply chain internationalization is driven by the role of knowledge spillovers across value chain actors and the changing nature of technology innovation processes. We employ rare earth technology patents to perform regression analyses and develop a model that empirically validates these critical drivers in the co-location of production and innovation activities

Examination of Gain Scheduling and Fuzzy Controllers with Hybrid Reachability

Modern aircraft with nonlinear flight envelopes predominately utilize gain scheduled controllers to provide stability of flight. Using gain scheduled control techniques, nonlinear envelopes can be linearized into collections of linear systems that operate under various system dynamics. Linear controllers approximate the nonlinear response over setpoints of operating conditions which allow traditional linear theory to be applied to maintain stability. Techniques to prove linear stability are well understood and realized in control systems, but when controllers are switched, interpolation methods must be used. Interpolation is necessary as gain scheduled systems do not have foundational switching paradigms as part of their realization and therefore can not naturally guarantee smooth (or stable) transitions. To ensure stability between linear controllers, empirical data must be obtained through test and simulation which adds significant time and fiscal cost to development. This work examines if fuzzy controllers can provide similar response to that of gain scheduled controllers. By representing controllers as fuzzy representations, transitions between the designed linear setpoints can be smoothed by adding membership functions between defined linear controllers. However, fuzzy control lacks analytical tools to find the stability margins to test the stability of fuzzy systems. In order to provide assurance of stability and performance concerns, fuzzy controllers are translated into hybrid automata representations. Hybrid Automata (HA) theory, which is gaining popularity to represent cyber-physical systems (CPS), is an extension of finite state machines (finite automata) which blends continuous dynamics with discrete switching conditions. The hybrid representation of the fuzzy system allows reachability tools and formal methods to examine stability and desired performance characteristics. This provides evidence that a fuzzy controller can produce, at a minimum, an equally effective controller. The goal of this effort is to establish a process to use fuzzy controller design and reachability tools to provide evidence of control system key attributes. The work primarily focuses on using two reachability tools which capture flow-pipe construction in linear models. The first, SpaceEx, uses representations of continuous sets to compute an overapproximation of the reachable states. The second, HyLAA, provides a simulation-equivalent reachability representation. Through reachability evidence generated by these tools, the tested fuzzy systems show that they maintain stability over the entire range of normalized input signal

President's Column: Reflections on LITA's Past and Future

President's Column: Reflections on LITA's Past and Futur

Stable-isotope geochemistry of the Pierina high-sulfidation Au–Ag deposit, Peru: influence of hydrodynamics on SO\u3csub\u3e4\u3c/sub\u3e\u3csup\u3e2-\u3c/sup\u3e–H\u3csub\u3e2\u3c/sub\u3eS sulfur isotopic exchange in magmatic-steam and steam-heated environments

The Pierina high-sulfidation Au–Ag deposit formed 14.5 my ago in rhyolite ash flow tuffs that overlie porphyritic andesite and dacite lavas and are adjacent to a crosscutting and interfingering dacite flow dome complex. The distribution of alteration zones indicates that fluid flow in the lavas was largely confined to structures but was dispersed laterally in the tuffs because of a high primary and alteration-induced permeability. The lithologically controlled hydrodynamics created unusual fluid, temperature, and pH conditions that led to complete SO4 2‒–H2S isotopic equilibration during the formation of some magmatic-steam and steam-heated alunite, a phenomenon not previously recognized in similar deposits. Isotopic data for early magmatic hydrothermal and main-stage alunite (δ34S=8.5%◦ to 31.7%◦; δ18OSO4 =4.9%◦ to 16.5%◦; δ18OOH=2.2%◦ to 14.4%◦ ; δD=‒97%◦ to ‒39%◦), sulfides (δ34S=‒3.0%◦ to 4.3%◦), sulfur (δ34S=‒1.0%◦ to 1.1%◦), and clay minerals (δ18O=4.3%◦ to 12.5%◦; δD=‒126%◦ to ‒81%◦) are typical of high-sulfidation epithermal deposits. The data imply the following genetic elements for Pierina alteration–mineralization: (1) fluid and vapor exsolution from an I-type magma, (2) wallrock buffering and cooling of slowing rising vapors to generate a reduced (H2S/SO4≈6) highly acidic condensate that mixed with meteoric water but retained a magmatic δ34SΣS signature of ~1%◦, (3) SO2 disproportionation to HSO‒4and H2S between 320 and 180 °C, and (4) progressive neutralization of laterally migrating acid fluids to form a vuggy quartz→alunite– quartz±clay→intermediate argillic→propylitic alteration zoning. Magmatic-steam alunite has higher δ34S (8.5%◦ to 23.2%◦) and generally lower δ18OSO4 (1.0 to 11.5%◦), δ18OOH (‒3.4 to 5.9%◦), and δD (‒93 to ‒77%◦) values than predicted on the basis of data from similar occurrences. These data and supporting fluid-inclusion gas chemistry imply that the rate of vapor ascent for this environment was unusually slow, which provided sufficient time for the uptake of groundwater and partial to complete SO4 2‒–H2S isotopic exchange. The slow steam velocities were likely related to the dispersal of the steam column as it entered the tuffs and possibly to intermediate exsolution rates from magmatic brine. The low δD values may also partly reflect continuous degassing of the mineralizing magma. Similarly, data fo

President's Message: Focus on Information Ethics

President's Message: Focus on Information Ethic

President's Column: For The Record

President's Column: For The Recor