Online journals, also known as e-journals, and electronic serials, are scholarly journals or intellectual magazines that can be accessed via electronic transmission. In practice, this means that they are usually published on the Web. They are a specialized form of electronic document: they have the purpose of providing material for academic research and study, and they are formatted approximately like journal articles in traditional printed journals. Many electronic journals are listed in directories such as the Directory of Open Access Journals, and the articles indexed in bibliographic databases and search engines for the academic discipline concerned.
Pollution control, in environmental engineering, any of a variety of means employed to limit damage done to the environment by the discharge of harmful substances and energies. Specific means of pollution control might include refuse disposal systems such as sanitary landfills, emission control systems for automobiles, sedimentation tanks in sewerage systems, the electrostatic precipitation of impurities from industrial gas, or the practice of recycling. For full treatment of major areas of pollution control, see air pollution control, wastewater treatment, solid-waste management, and hazardous-waste management.
Pollution controls divert economic resources from other economic activities, thereby reducing the potential size of measured national output. As long as the increase in the value of the environment is at least one dollar for each additional dollar spent on controls, the total value of goods, services, and environmental amenities is not reduced. Unfortunately, that seldom happens, for at least three reasons.
One of the oldest and most efficient methods of particulate control, however, is filtration. The most commonlyused filtration device is known as a baghouse and consists of fabric bags through which the air stream is directed. Particles become trapped in the fiber mesh on the fabric bags, as well as the filter cake which is subsequently formed.