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Topic Review
PEC Reactors for Water/Wastewater Treatment
Now and in the coming years, how we use and treat water, greywater and wastewater will become more important. A suitably designed photoelectrocatalytic (PEC) reactor is one potential solution. The photoexcitation of suitable semiconducting materials in aqueous environments can lead to the production of reactive oxygen species (ROS). ROS can inactivate microorganisms and degrade a range of chemical compounds. In the case of heterogeneous photocatalysis, semiconducting materials may suffer from fast recombination of electron–hole pairs and require post-treatment to separate the photocatalyst when a suspension system is used. To reduce recombination and improve the rate of degradation, an externally applied electrical bias can be used where the semiconducting material is immobilised onto an electrically conducive support and connected to a counter electrode. These electrochemically assisted photocatalytic systems have been termed “photoelectrocatalytic” (PEC). The term is stated in the IUPAC Recommendations 2011 as “electrochemically assisted photocatalysis. The role of the photocatalyst is played by a photoelectrode, often a semiconductor”. A short description of photocatalysis is included as it can be beneficial for those unfamiliar with the topic, before moving onto PEC. This entry is adapted from https://doi.org/10.3390/w13091198
  • 1.9K
  • 20 Oct 2021
Topic Review
Fruit and Smart Packaging
Smart packaging of fresh produce is an emerging technology targeting the reduction of waste and the preservation of consumer health and safety. Smart packaging systems also help to prolong the shelf life of perishable foods during transport and mass storage, which are difficult to regulate. The use of these ever-progressing technologies in the packaging of fruits has the potential to result in many positive consequences, including improved fruit quality, reduced waste, higher consumer confidence and associated improved public health. 
  • 1.9K
  • 28 Sep 2021
Topic Review
Digital Twins for Additive Manufacturing
A brief state-of-the-art  introduction of digital twins for additive manufacturing.
  • 1.9K
  • 17 Feb 2021
Topic Review
Fuzzy Logic Control for Refrigeration Systems
Logic fuzzy systems are based on the human ability to think, which has allowed controllers to adapt better to systems by finding an approximation to their real behavior.
  • 1.9K
  • 14 Mar 2022
Topic Review
Reversible Hydrogen Storage
In the field of energy storage, recently investigated nanocomposites show promise in terms of high hydrogen uptake and release with enhancement in the reaction kinetics. Among several, carbonaceous nanovariants like carbon nanotubes (CNTs), fullerenes, and graphitic nanofibers reveal reversible hydrogen sorption characteristics at 77 K, due to their van der Waals interaction. The spillover mechanism combining Pd nanoparticles on the host metal-organic framework (MOF) show at room temperature uptake of hydrogen. Metal or complex hydrides either in the nanocomposite form and its subset, nanocatalyst dispersed alloy phases illustrate the concept of nanoengineering and nanoconfinement of particles with tailor-made properties for reversible hydrogen storage. Another class of materials comprising polymeric nanostructures such as conducting polyaniline and their functionalized nanocomposites are versatile hydrogen storage materials because of their unique size, high specific surface-area, pore-volume, and bulk properties. The salient features of nanocomposite materials for reversible hydrogen storage are reviewed and discussed.
  • 1.9K
  • 22 Jul 2020
Topic Review
Biomass Pyrolysis
Pyrolysis process has been considered to be an efficient approach for valorization of lignocellulosic biomass into bio-oil and value-added chemicals. Bio-oil refers to biomass pyrolysis liquid, which contains alkanes, aromatic compounds, phenol derivatives, and small amounts of ketone, ester, ether, amine, and alcohol. Lignocellulosic biomass is a renewable and sustainable energy resource for carbon that is readily available in the environment. This review article provides an outline of the pyrolysis process including pretreatment of biomass, pyrolysis mechanism, and process products upgrading. The pretreatment processes for biomass are reviewed including physical and chemical processes. In addition, the gaps in research and recommendations for improving the pretreatment processes are highlighted. Furthermore, the effect of feedstock characterization, operating parameters, and types of biomass on the performance of the pyrolysis process are explained. Recent progress in the identification of the mechanism of the pyrolysis process is addressed with some recommendations for future work. In addition, the article critically provides insight into process upgrading via several approaches specifically using catalytic upgrading. In spite of the current catalytic achievements of catalytic pyrolysis for providing high-quality bio-oil, the production yield has simultaneously dropped. This article explains the current drawbacks of catalytic approaches while suggesting alternative methodologies that could possibly improve the deoxygenation of bio-oil while maintaining high production yield.
  • 1.9K
  • 21 Jul 2020
Topic Review
Active Pixel Sensor
An active-pixel sensor (APS) is an image sensor where each picture element ("pixel") has a photodetector and an active amplifier. There are many types of integrated circuit active pixel sensors including the complementary metal–oxide–semiconductor (CMOS) APS used most commonly in cell phone cameras, web cameras, most digital pocket cameras since 2010, in most digital single-lens reflex cameras (DSLRs) and Mirrorless interchangeable-lens cameras (MILCs). Such an image sensor is produced using CMOS technology (and is hence also known as a CMOS sensor), and has emerged as an alternative to charge-coupled device (CCD) image sensors. The term 'active pixel sensor' is also used to refer to the individual pixel sensor itself, as opposed to the image sensor; in that case the image sensor is sometimes called an active pixel sensor imager, or active-pixel image sensor.
  • 1.9K
  • 23 Nov 2022
Topic Review
Transmission (Mechanics)
A transmission is a machine in a power transmission system, which provides controlled application of power. Often the term 5-speed transmission refers simply to the gearbox, that uses gears and gear trains to provide speed and torque block conversions from a rotating power source to another device. The term transmission properly refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive vehicles), differential, and final drive shafts. In the United States the term is sometimes used in casual speech to refer more specifically to the gearbox alone, and detailed usage differs. The most common use is in motor vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a relatively high rotational speed, which is inappropriate for starting, stopping, and slower travel. The transmission reduces the higher engine speed to the slower wheel speed, increasing torque in the process. Transmissions are also used on pedal bicycles, fixed machines, and where different rotational speeds and torques are adapted. Often, a transmission has multiple gear ratios (or simply "gears") with the ability to switch between them as the speed varies. This switching may be done manually (by the operator) or automatically (by a control unit). Directional (forward and reverse) control may also be provided. Single-ratio transmissions also exist, which simply change the speed and torque (and sometimes direction) of motor output. In motor vehicles, the transmission generally is connected to the engine crankshaft via a flywheel or clutch or fluid coupling, partly because internal combustion engines cannot run below a particular speed. The output of the transmission is transmitted via the driveshaft to one or more differentials, which drive the wheels. While a differential may also provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds (essential to avoid wheel slippage on turns) as it changes the direction of rotation. Conventional gear/belt transmissions are not the only mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformation (e.g. diesel-electric transmission and hydraulic drive system). Hybrid configurations also exist. Automatic transmissions use a valve body to shift gears using fluid pressures in response to engine RPM, speed, and throttle input.
  • 1.9K
  • 01 Nov 2022
Topic Review
Desalination in Mexico
Since the sixteenth century, water desalination systems have been developed. Mexico is a country that faces a severe water shortage, mainly due to its territorial extension, because the concentration of water resources is located in the southern zone of the country, while the main industrial activity is carried out in the north (which presents scarcity conditions). The distance and the technical limitations of transporting water between the northern and southern zones make water desalination the main tool to combat water stress in Mexico.
  • 1.9K
  • 16 Nov 2022
Topic Review
TiO2
TiO2 probably plays the most important role in photocatalysis due to its excellent chemical and physical properties. However, the band gap of TiO2 corresponds to the Ultraviolet (UV) region, which is inactive under visible irradiation. At present, TiO2 has become activated in the visible light region by metal and nonmetal doping and the fabrication of composites. Recently, nano-TiO2 has attracted much attention due to its characteristics of larger specific surface area and more exposed surface active sites. nano-TiO2 has been obtained in many morphologies such as ultrathin nanosheets, nanotubes, and hollow nanospheres.
  • 1.9K
  • 29 Oct 2020
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