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Topic Review
Tobacco Products
Tobacco is the agricultural product of the leaves of plants in the genus Nicotiana. All species of Nicotiana contain the addictive drug nicotine—a stimulant and sedative contained in all parts of the plants except the seeds—which occurs in varying amounts depending on the species and variety cultivated. See types of tobacco and curing of tobacco for more information. The vast majority of commercially available tobacco is derived from the species Nicotiana tabacum, although it is also produced from Nicotiana alata, and to a lesser extent Nicotiana clevelandii, Nicotiana longiflora, and Nicotiana rustica, among others. N. rustica in particular contains much more nicotine than N. tabacum and other species of Nicotiana, and forms the basis of a number of unique tobacco products, including several preparations used in Latin American shamanic ceremonies. Once tobacco has been grown, harvested, cured, and processed, it is used to produce a number of different products. These are most often consumable; however, tobacco and the nicotine derived from it are also used to create pesticides. Tobacco products can generally be divided into two types: smoked tobacco (see tobacco smoking) and smokeless tobacco. An expert in tobacco and tobacco products — especially pipes, pipe tobacco, and cigars—including their procurement and sale, is called a tobacconist. The health effects of tobacco consumption are discussed in health effects of tobacco.
  • 2.7K
  • 19 Oct 2022
Topic Review
Urban Wastewater Treatment in Greece
Although Greece has accomplished the wastewater infrastructure construction in a large extent, as 91% of the country’s population is already connected to urban wastewater treatment plants (WWTPs), many problems still need to be faced, such as the limited reuse of treated wastewater and of the surplus sludge (biosolids) produced, the relative higher energy consumption in the existing rather aged WWTPs infrastructure and the proper management of failing or inadequately designed septic tank/soil absorption systems, still in use in several (mostly rural) areas, lacking sewerage systems. Moreover, the wastewater treatment sector should be examined in the general framework of sustainable environmental development; therefore, Greece’s future challenges in this sector ought to be reconsidered. Thus, the review of Greece’s urban wastewater history, even from the ancient times, up to current developments and trends, will be shortly addressed. Noting also that the remaining challenges should be analyzed in respect to the country’s specific needs (e.g. interaction with the extensive tourism sector), as well as to the European Union’s relevant framework policies and to the respective international technological trends, aiming to consider the wastewater treatment plants (WWTPs) not only as sites for the treatment/removal of pollutants to prevent environmental pollution, but also as industrial places where energy is efficiently used (or even produced), resources’ content can be potentially recovered and reused (e.g. nutrients, treated water, biosolids) and the environmental sustainability is being overall practiced.
  • 2.7K
  • 04 Aug 2020
Topic Review
Gas Turbines with Water Injection and Full Evaporation
The concept behind humidifying gas turbines is that increasing the amount of water/steam injected into the turbine increases the amount of mass it moves. This results in a rise in the specific power output because the effort exerted by the compressor remains the same, and it takes far less effort to raise the pressure of a liquid than it does of a gas. The efficiency of the cycle may be improved by recovering the energy contained in the gas turbine’s exhaust and either preheating the injection water, making injection steam, or the recuperator’s preheating of the combustion oxidizer. The introduction of water prior to the combustor of a recuperated gas turbine lowers the compressed air’s temperature at the input of the recuperator. This results in an increase in the rate at which energy is recovered from the exhaust gas.
  • 2.7K
  • 27 Dec 2022
Topic Review
Metal Matrix Composites
Metal matrix composites (MMCs) present extraordinary characteristics, including high wear resistance, excellent operational properties at elevated temperature, and better chemical inertness as compared to traditional alloys. These properties make them prospective candidates in the fields of aerospace, automotive, heavy goods vehicles, electrical, and biomedical industries. MMCs are challenging to process via traditional manufacturing techniques, requiring high cost and energy. The laser-melting deposition (LMD) has recently been used to manufacture MMCs via rapid prototyping, thus, solving these drawbacks. Besides the benefits mentioned above, the issues such as lower ultimate tensile strength, yield strength, weak bonding between matrix and reinforcements, and cracking are still prevalent in parts produced by LMD. In this article, a detailed analysis is made on the MMCs manufactured via LMD. An illustration is presented on the LMD working principle, its classification, and dependent and independent process parameters. Moreover, a brief comparison between the wire and powder-based LMDs has been summarized. Ex- and in-situ MMCs and their preparation techniques are discussed. Besides this, various matrices available for MMCs manufacturing, properties of MMCs after printing, possible complications and future research directions are reviewed and summarized.
  • 2.7K
  • 18 May 2021
Topic Review
Woodward Effect
The Woodward effect, also referred to as a Mach effect, is part of a hypothesis proposed by James F. Woodward in 1990. The hypothesis states that transient mass fluctuations arise in any object that absorbs internal energy while undergoing a proper acceleration. Harnessing this effect could generate a reactionless thrust, which Woodward and others claim to measure in various experiments. Hypothetically, the Woodward effect would allow for field propulsion spacecraft engines that would not have to expel matter. Such a proposed engine is sometimes called a Mach effect thruster (MET) or a Mach Effect Gravitational Assist (MEGA) drive. So far, experimental results have not strongly supported this hypothesis, but experimental research on this effect, and its potential applications, continues. The Space Studies Institute was selected as part of NASA's Innovative Advanced Concepts program as a Phase I proposal in April 2017 for Mach Effect research. The year after, NASA awarded a NIAC Phase II grant to the SSI to further develop these propellantless thrusters. The effect is controversial within mainstream physics because the underlying model proposed for it appears to be faulty, resulting in violations of energy conservation as well as momentum conservation.
  • 2.7K
  • 16 Nov 2022
Topic Review
Wave Energy Marine Buoys
The power supply is usually the bottleneck for marine distributed systems such as buoys. Wave energy technologies are especially useful in this sense, as they can capture and convert the promising “native” renewable energy in the ocean (i.e., wave energy) into electricity.
  • 2.7K
  • 08 Jul 2022
Topic Review
LAN Switching
LAN switching is a form of packet switching used in local area networks (LAN). Switching technologies are crucial to network design, as they allow traffic to be sent only where it is needed in most cases, using fast, hardware-based methods. LAN switching uses different kinds of network switches. A standard switch is known as a layer 2 switch and is commonly found in nearly any LAN. Layer 3 or layer 4 switches require advanced technology (see managed switch) and are more expensive, and thus are usually only found in larger LANs or in special network environments.
  • 2.7K
  • 15 Nov 2022
Biography
Firouz Naderi
Firouz Michael Naderi (Persian: فیروز نادری‎: Fīrouz Nāderi; born 1946) is an Iranian scientist who spent more than 30 years in various technical and executive positions at NASA's Jet Propulsion Laboratory (JPL) where he contributed to some of America's most iconic robotic space missions. He retired from NASA in 2016 and currently is a management consultant, an advisor to early-st
  • 2.7K
  • 15 Nov 2022
Topic Review
Single-Zone HVAC Systems
Single-zone HVAC systems are installed in most residential buildings, which implies regulating all the rooms of the house with a single thermostat and with static ventilation registers.
  • 2.7K
  • 27 Oct 2020
Topic Review Video
Direct Carbon Fuel Cells
Most fuel cells invariably use gaseous or liquid fuels. A fuel cell technology that has attracted attention only recently, the direct carbon fuel cell (DCFC) uses solid fuel (carbon) and converts the chemical energy in the carbon to electricity through its direct participation in the fuel cell reactions and electrochemical oxidation. The fuel use can be almost 100% compared with about 85% for most other fuel cells. The electrical efficiency is expected to be above 70% - almost twice those of current generation coal-fired plants leading to 50% reduction in greenhouse gas emissions. The amount of CO2 for storage/sequestration is also halved. Moreover, the exit gas is almost pure carbon dioxide stream, requiring no or minimal gas separation and processing for sequestration. Therefore, the energy and cost penalties to capture the CO2 will be significantly less than for other technologies. However, the technology is at an early stage of development requiring many complex challenges to be overcome, related to materials and corrosion, fuel delivery mechanism, and system development, before it can be commercialized. Section 19.4 of a recent book by the author gives an overview of this technology focusing on its main issues (Sequeira, 2019.). Two of the main DCFCs, the direct carbon molten carbonate fuel cell (DC-MCFC) and the direct carbon solid oxide fuel cell (DC-SOFC) are described in this topic review. 
  • 2.7K
  • 04 Aug 2021
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