Tractable and Decidable Fragments of Conceptual Graphs

It is well-known that problems like validity and subsumption of general CGs are undecidable, whereas subsumption is NP-complete for simple conceptual graphs (SGs) and tractable for SGs that are trees. We will employ results on decidable fragments of rst-order logic to identify a natural and expressive fragment of CGs for which validity and subsumption is decidable in ExpTime. In addition, we will extend existing work on the connection between SGs and description logics (DLs) by identifying a DL that corresponds to the class of SGs that are trees. This yields a tractability result previously unknown in the DL community

H2-MHR Pre-Conceptual Design Report: SI-Based Plant; HTE-Based Plant

Hydrogen and electricity are expected to dominate the world energy system in the long term. The world currently consumes about 50 million metric tons of hydrogen per year, with the bulk of it being consumed by the chemical and refining industries. The demand for hydrogen is expected to increase, especially if the U.S. and other countries shift their energy usage towards a hydrogen economy, with hydrogen consumed as an energy commodity by the transportation, residential, and commercial sectors. However, there is strong motivation to not use fossil fuels in the future as a feedstock for hydrogen production, because the greenhouse gas carbon dioxide is a byproduct and fossil fuel prices are expected to increase significantly. For electricity and hydrogen production, an advanced reactor technology receiving considerable international interest is a modular, passively-safe version of the high-temperature, gas-cooled reactor (HTGR), known in the U.S. as the Modular Helium Reactor (MHR), which operates at a power level of 600 MW(t). For electricity production, the MHR operates with an outlet helium temperature of 850 C to drive a direct, Brayton-cycle power-conversion system (PCS) with a thermal-to-electrical conversion efficiency of 48 percent. This concept is referred to as the Gas Turbine MHR (GT-MHR). For hydrogen production, the process heat from the MHR is used to produce hydrogen. This concept is referred to as the H2-MHR

How to Maintain a Process Perspective on Retail Internationalization: The IKEA Case

The retail industry has witnessed fast international growth during the last couple of decades and various models and theories have been proposed for how to best explain the process and why some firms succeed while others fail. Recently researchers have argued that not only do we need more in-depth longitudinal case studies, and case studies from different sectors, but we also need to understand the core activity of internationalization, namely the learning processes of how to manage the complex process of entering and operating in different markets. While much research has focused on market and marketing aspects of internationalization, organizational aspects have received less attention. This article aims to fill that gap by focusing on the international home furnishings retail firm, IKEA, and their organizational routines for ensuring and managing a process perspective on their so-far-successful international expansion