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Topic Review
Cigarette Filter
A cigarette filter is a component of a cigarette, along with cigarette paper, capsules and adhesives. It does not make cigarettes less unhealthy. The filter may be made from cellulose acetate fibre, paper or activated charcoal (either as a cavity filter or embedded into the cellulose acetate). Macroporous phenol-formaldehyde resins and asbestos have also been used in cigarette filters. The acetate and paper modify the particulate smoke phase by particle retention (filtration), and finely divided carbon modifies the gaseous phase (adsorption). Filters can reduce "tar" and nicotine smoke yields up to 50%, with a greater removal rate for other classes of compounds (e.g., phenols), but are ineffective in filtering toxins such as carbon monoxide. Most of these measured reductions occur only when the cigarette is smoked on a smoking machine; when a human smokes them, deliveries remain similar with or without a filter. Most factory-made cigarettes are equipped with a filter; those who roll their own can buy them from a tobacconist. The near-universal adoption of filters on cigarettes has not reduced harms to smokers; for instance, lung cancer rates have not declined. Filling a given length of cigarette with filter is cheaper than filling it with tobacco.
  • 3.1K
  • 10 Nov 2022
Topic Review
Architectural Perspective of Ant Nests
Ants are excellent architects in the animal kingdom. The activities of “design”, “material selection” and “construction” of their nests are full of magical secrets. After hundreds of millions of years of survival of the fittest, the nests of each species of ant are generally characterised by reasonable structure and good mechanical performance, and also reflect the law of “obtaining large and solid living space with the least amount of material”. The complex underground ant colony nest system is large in scale, stable in internal environmental characteristics, has excellent ventilation, appropriate humidity and temperature, and makes use of natural barriers, such as thin grasses, trees, sand and stone, around entrances and exits, as well as having good physical structure, resistant to pressure, water, heat and moisture. Ants have very strict requirements on the size, weight, lustre and colour of the building materials for the nest, such as soil particles. As social insects, ants are responsible for the site selection and materials selection of their nests, the design of the whole nest, organising and coordinating the grand construction process, and managing the nest. 
  • 3.1K
  • 26 Dec 2022
Topic Review
Chemical looping
Chemical looping technology in general, is the rising star in chemical technologies, which is capable of low CO2 emissions with applications in the production of heat, fuels, chemicals, and electricity. This entry discusses the technology in general, gives an overview of some pilot scale plants and the different chemical looping processes with focus on the production of heat and chemicals, highlights the importance of the development of oxygen carrier materials with suitable properties, 2.11.0.0 2.11.0.0
  • 3.1K
  • 02 Nov 2020
Topic Review
Direct Contact Condensers
Direct contact heat exchangers can be smaller, cheaper, and have simpler construction than the surface, shell, or tube heat exchangers of the same capacity and can operate in evaporation or condensation modes. For these reasons, they have many practical applications, such as water desalination, heat exchangers in power plants, or chemical engineering devices.
  • 3.1K
  • 23 Dec 2022
Topic Review
Application of Artificial Neural Networks in Construction Management
Artificial neural networks (ANN) exhibit excellent performance in complex problems and have been increasingly applied in the research field of construction management (CM) over the last few decades. This paper aims to provide a comprehensive understanding of the application of ANN in CM research and useful reference for the future.Content analysis is performed to comprehensively analyze 112 related bibliographic records retrieved from seven selected top journals published between 2000 and 2020. The results indicate that the applications of ANN of interest in CM research have been significantly increasing since 2015. Back-propagation was the most widely used algorithm in training ANN. Integrated ANN with fuzzy logic/genetic algorithm was the most commonly em-ployed way of addressing the CM problem. In addition, 11 application fields and 31 research topics were identified, with the primary research interests focusing on cost, performance, and safety.
  • 3.1K
  • 27 Oct 2021
Topic Review
Salinity and Turbidity in the Red Sea
Several industrial and scientific underwater applications require high-speed wireless connectivity. Acoustic communications have low data rates and high latency, whereas attenuation in seawater severely limits radio frequency communications. Optical wireless communication is a promising solution, with high transmission rates (up to Gb/s) and little attenuation in water at visible wavelengths.
  • 3.1K
  • 08 Oct 2022
Topic Review
Railway Nationalization
Railway nationalization is the act of taking rail transport assets into public ownership. Several countries have at different times nationalized part or all of their railway system. More recently, the international trend has been towards privatization. In some areas, notably Great Britain, resultant problems with track maintenance have led back to a more mixed solution, with a nationalised infrastructure operator but privately run train operating companies. National characteristics influenced the structures under which countries' rail networks developed. Some national railways were always under direct State management, some were State-planned but privately operated (as in France, others were wholly private enterprises lightly regulated (as in Great Britain, Ireland and Spain). Nationalization was therefore a bolder step to take in some countries than in others. While ideology has played a role, so too has the need for systematic reconstruction of vital infrastructure devastated by war, often following a period of State control over private companies initiated during the conflict.
  • 3.1K
  • 01 Dec 2022
Topic Review
Earthquake Early Warning Systems
An Earthquake Early Warning Systems (EEWS) is the combination of different elements, such as seismometers, sensors, communication appliances, computers, and alarm systems, able to detect and warm of the arrival of seismic waves. It serves to mitigate damages and losses , to be used primarily in moderate and high seismically active regions.  
  • 3.1K
  • 25 Feb 2021
Topic Review
Probabilistic Slope Stability Evaluation
Evaluating the stability of slopes in soil is an important, interesting, and challenging aspect of civil engineering. Despite the advances that have been made, evaluating the stability of slopes remains a challenge. Slope failures are often caused by processes that increase shear stresses or decrease shear strengths of the soil mass [4, 9]. Water plays a role in many of the processes that reduce strength; water is also involved in many types of loads on slopes that increase shear stresses. Another factor involved in most slope failures is the presence of soils that contain clay minerals. In concept, any slope with a factor of safety above 1.0 should be stable [6, 10]. In practice, however, the level of stability is seldom considered acceptable unless the factor of safety is significantly greater than 1.0. In this study an attempt has been done to perform stability analyses corresponding to several different conditions, reflecting different stages in the life of the new railway embankment found in Ethiopia. As various parameters are involved and determined based on correlations, the probabilistic approach was employed to scrutinize the effects of uncertainty on the likelihood of failure. There is no problem with performing a single analysis in which the embankment is considered to be drained and is treated in terms of effective stresses, and in which the clay foundation material is considered to be undrained and is treated in terms of total stresses (during end-of-construction analysis). This is because equilibrium in terms of total stresses must be satisfied for both total and effective stress analyses [2]. The inertia slope stability analysis was used. Since the foundation materials are overconsolidated cohesive soils such as stiff to very stiff clays that tend to dilate during the seismic shaking. The embankment is also expected to be well graded compacted granular material [12]. The critical factor of safety for the railway embankment during short term analysis was found to be 2.199. However, it has increased by 17.6% during the long term analysis (i.e., 2.585). Typical minimum factor of safety used in slope design are about 1.5 for normal long-term loading conditions and about 1.3 for end-of- construction conditions.  Apart from that, the minimum short term and long term factor of safety were reduced by 44.5% and 35.9% respectively, due to the introduction of the horizontal seismic load in the limit equilibrium analysis. According to Hynes-Griffin and Franklin (1984) criteria [8] the minimum factor of safety for ~1m tolerable displacement is 1. However, the minimum factor of safety during the pseudostatic analysis (i.e., 1.221) was found to be 22% higher than the required minimum factor of safety. Beside, Newmark’s deformation analysis has been done to predict slope displacement. However, the analysis predicted zero permanent slope displacement. Since; the Newmark (1965) method assumes no deformation of the slope during the earthquake if the pseudostatic factor of safety is greater than 1.0. The more realistic probability of failure is likely in between of 0% and 6.9 %. The sensitivity analysis showed that, the cohesion of the clay layer (i.e., layer II) governs the stability of the railway embankment.
  • 3.1K
  • 30 Oct 2020
Topic Review
Thorium-Based Nuclear Power
Thorium-based nuclear power generation is fueled primarily by the nuclear fission of the isotope uranium-233 produced from the fertile element thorium. A thorium fuel cycle can offer several potential advantages over a uranium fuel cycle [Note 1] —including much greater abundance of thorium found on Earth, superior physical and nuclear fuel properties, and reduced nuclear waste production. One advantage of thorium fuel is its low weaponization potential; it is difficult to weaponize the uranium-233/232 and plutonium-238 isotopes largely consumed in thorium reactors. Between 1999 and , the number of operational thorium reactors in the world has risen from zero, to a handful of research reactors, to commercial plans for producing full-scale thorium-based reactors for use as power plants on a national scale. Some believe thorium is key to developing a new generation of cleaner, safer nuclear power. In 2011 a group of scientists at the Georgia Institute of Technology assessed thorium-based power as "a 1000+ year solution or a quality low-carbon bridge to truly sustainable energy sources solving a huge portion of mankind’s negative environmental impact." However, development of thorium power has significant start-up costs. Development of breeder reactors in general (including thorium reactors, which are breeders by nature) will increase proliferation concerns. After studying the feasibility of using thorium, nuclear scientists Ralph W. Moir and Edward Teller suggested that thorium nuclear research should be restarted after a three-decade shutdown and that a small prototype plant should be built.
  • 3.1K
  • 18 Oct 2022
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