Let R be an associative ring with unity. An element a in R is said to be r-clean if a = e+r, where e is an idempotent and r is a regular (von Neumann) element in R. If every element of R is r-clean, then R is called an r-clean ring. In this paper, we prove that the concepts of clean ring and r-clean ring are equivalent for abelian rings. Further we prove that if 0 and 1 are the only idempotents...

This thesis is a collection of three empirical essays on economic development and envronmental economics. Chapter 1 measures the response of U.S. based multinational firms to the Clean Air Act Amendments (CAAA), which dramatically strengthened U.S. environmental regulation. Using a panel of firm-level data over the period 1966-1999, I estimate the effect of regulation on a multinational's forei...

Air pollution has been one of the most critical urban problems. Urban energy networks are among major sources air pollution, particularly in highly populated areas. Residential heating, which is primary cause particulate matter (PM) emissions, contributes to problem through use low-quality fuels, such as coal. Natural gas, although a fossil fuel, modern, relatively clean, and more efficient alt...

many modern analytical methods deal with the trace-level determination of compounds of interest in highly complex environmental samples by means of chromatographic techniques. the introduction of a “clean” sample into an analytical instrument can make analyses easier and prolongs the equipment life. the use of solid-phase extraction (spe) has grown and is a fertile technique of sample preparati...

Today, greenhouse gas emissions and climate change stemming from the usage of fossil fuels are significant worldwide issues. Renewable energy, such as solar is an environmentally friendly non-polluting option. However, there numerous worries regarding possible influence renewable energy integration on power system stability. Therefore, research required to investigate assess this effect. This s...

Pet birds, being previously unexposed to the many dangers of our industrial world, are prime candidates for the ingestion/inhalation of toxins. What follows is a highlight of the most common toxins found in our homes. These will include "acute" fast acting fatal toxins and the "chronic" more long term, but still deadly types of toxins. REMEMBER: WHEN CONSIDERING IF A PRODUCT MIGHT BE TOXIC OR N...

In diesem Beitrag wird der Zusammenhang zwischen Code-Qualität und UMLModellen in einem Software-Entwicklungsprozess in der Informatik-Ausbildung vorgestellt. Es wird untersucht, welche der im Code sichtbar werdenden Mängel bereits im Modell erkannt werden können. Werkzeuge zur statischen Code-Analyse und Refactoring-Techniken unterstützen die Studierenden beim Entdecken und Beseitigen der Qual...