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Topic Review
Resonant Vibration Energy Harvesters
An increasing number of practical applications (e.g. medical implants, embedded sensors in buildings and bridges, industrial applications) are based on the use of Wireless Sensor Nodes (WSNs), which are small computing devices capable of collecting and transmitting data to a base station. In order to limit or to avoid the drawbacks associated to the use of primary batteries (expensive maintenance/replacement, insufficient or unpredictable duration of operational life, not eco-friendly disposal due to their hazardous chemical content), the required energy can be delivered to the WSNs by energy harvesting. Energy harvesting is the conversion of otherwise wasted energy into electrical energy. Since vibrations can be found almost everywhere, an interesting possibility is represented by the use of vibration energy harvesters.  Here the attention is focused on Resonant Vibration Energy Harvesters (RVEHs) and in particular on Piezoelectric RVEHs and Electromagnetic RVEHs. A brief description of their operating principles is provided and their equivalent electric circuits are analyzed in order to identify the operating conditions able to maximize the extracted electrical power. This is a crucial aspect in applications involving energy harvesting systems. Moreover a brief introduction to the concepts of Electrical and Mechanical Tuning Techniques is also provided.
  • 1.3K
  • 18 Sep 2021
Topic Review Peer Reviewed
Sustainable Architecture–What’s Next?
Sustainable architecture encompasses more than energy efficiency, zero carbon dioxide (CO2) emission or renewable energy use in the built environment. It also needs to alleviate overall impacts on the natural environment or ecosystem that surrounds it. It may be argued that primitive vernacular architecture (architecture without architects) built and operated using local techniques and resources alone can be considered to be sustainable. Yet later, after the 1992 Rio Conference and its declarations, more specific definitions emerged putting weight on the rational use of land area, materials and energy, preferably local, as well as area efficient planning, economy and recyclability. The advantage of this is to reduce the ecological footprint of buildings and the climate gas emissions from a sector that represents 35–50 percent of global climate gas emissions, depending on how one counts. This paper clarifies concepts, questions cemented truths and points a way forward by asking; what’s next?
  • 1.3K
  • 13 Apr 2022
Topic Review
Annealing (Metallurgy)
In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature, maintaining a suitable temperature for an appropriate amount of time and then cooling. In annealing, atoms migrate in the crystal lattice and the number of dislocations decreases, leading to a change in ductility and hardness. As the material cools it recrystallizes. For many alloys, including carbon steel, the crystal grain size and phase composition, which ultimately determine the material properties, are dependent on the heating rate and cooling rate. Hot working or cold working after the annealing process alters the metal structure, so further heat treatments may be used to achieve the properties required. With knowledge of the composition and phase diagram, heat treatment can be used to adjust from harder and more brittle to softer and more ductile. In the case of ferrous metals, such as steel, annealing is performed by heating the material (generally until glowing) for a while and then slowly letting it cool to room temperature in still air. Copper, silver and brass can be either cooled slowly in air, or quickly by quenching in water. In this fashion, the metal is softened and prepared for further work such as shaping, stamping, or forming.
  • 1.3K
  • 09 Oct 2022
Topic Review
GNSS Positioning Calculation
The global navigation satellite system (GNSS) positioning for receiver's position is derived through the calculation steps, or algorithm, given below. In essence, a GNSS receiver measures the transmitting time of GNSS signals emitted from four or more GNSS satellites (giving the pseudorange) and these measurements are used to obtain its position (i.e., spatial coordinates) and reception time.
  • 1.3K
  • 05 Dec 2022
Topic Review
British Airways Ethnic Liveries
In 1997 British Airways (BA) adopted a new livery. One part of this was a newly stylised version of the British Airways "Speedbird" logo, the "Speedmarque", but the major change was the introduction of tail-fin art. Also known as the Utopia or world image tailfins, they used art and designs from international artists and other sources to represent countries on BA's route network. The signature of the artist was carried near the design on the tail. The new corporate logo was created by the London-based design agency Newell & Sorrell, who also oversaw the implementation of the tailfin designs. The German designs refer to the BA subsidiary Deutsche BA, the French designs refer to the BA subsidiary Air Liberté, and the Australian designs refer to BA's alliance with Qantas.
  • 1.3K
  • 11 Nov 2022
Topic Review
Tin-Based Perovskite Solar Cells
Since its invention in 2009, Perovskite solar cell (PSC) has attracted great attention because of its low cost, numerous options of efficiency enhancement, ease of manufacturing and high-performance. Within a short span of time, the PSC has already outperformed thin-film and multicrystalline silicon solar cells. A current certified efficiency of 25.2% demonstrates that it has the potential to replace its forerunner generations. However, to commercialize PSCs, some problems need to be addressed. The toxic nature of lead which is the major component of light absorbing layer, and inherited stability issues of fabricated devices are the major hurdles in the industrialization of this technology. Therefore, new researching areas focus on the lead-free metal halide perovskites with analogous optical and photovoltaic performances. Tin being nontoxic and as one of group IV(A) elements, is considered as the most suitable alternate for lead because of their similarities in chemical properties. Efficiencies exceeding 13% have been recorded using Tin halide perovskite based devices. This review summarizes progress made so far in this field, mainly focusing on the stability and photovoltaic performances. Role of different cations and their composition on device performances and stability have been involved and discussed. With a considerable room for enhancement of both efficiency and device stability, different optimized strategies reported so far have also been presented. Finally, the future developing trends and prospects of the PSCs are analyzed and forecasted.
  • 1.3K
  • 14 Oct 2020
Topic Review
Cryotropic Gelation and Macroporous Scaffolds
Cryogels obtained by the cryotropic gelation process are macroporous hydrogels with a well-developed system of interconnected pores and shape memory. Biodegradable cryogels have been prepared from natural polymers (biopolymers) and synthetic polymers with biodegradable/bioresponsive bonds containing bio-resembling or artificial units. The cryogels could be composed of one type of polymer or a combination of different materials. Polymers from natural origins (plants or animals) attract considerable attention for their intrinsic biocompatibility and potential ability to mimic ECM, favoring cell-matrix interactions for tissue-engineering and regeneration.
  • 1.3K
  • 12 Jul 2021
Topic Review
Wave-Structure-Seabed Interactions and Scour
Sediment transport has been the subject of extensive research over recent decades, particularly wave–structure interactions and, more importantly, their effects on the seabed. It includes mechanical models, analytical solutions of wave–structure–seabed interactions, and their verification with numerical models and experimental tests. Experimentally, both field and laboratory measurements focus on the structure foundation. Moreover, given the great progress in numerical modelling in the last decade, there is a need to put into context and focus the most widely used numerical approaches for modelling the wave-structure-seabed interaction. The numerical model selected and the resolution method depend mainly on the coastal study area, the importance and dependence of the processes involved, the temporal-spatial scale of the problem and the computational time.
  • 1.3K
  • 16 Jun 2021
Topic Review
Additive Manufacturing Processes
Additive manufacturing (AM, 3D printing) is used in many fields and different industries. In the medical and dental field, every patient is unique and, therefore, AM has significant potential in personalized and customized solutions. This text explores what additive manufacturing processes and materials are utilized in medical and dental applications, especially focusing on processes that are less commonly used. The processes are categorized in ISO/ASTM process classes: powder bed fusion, material extrusion, VAT photopolymerization, material jetting, binder jetting, sheet lamination and directed energy deposition combined with classification of medical applications of AM. Based on the findings, it seems that directed energy deposition is utilized rarely only in implants and sheet lamination rarely for medical models or phantoms. Powder bed fusion, material extrusion and VAT photopolymerization are utilized in all categories. Material jetting is not used for implants and biomanufacturing, and binder jetting is not utilized for tools, instruments and parts for medical devices. The most common materials are thermoplastics, photopolymers and metals such as titanium alloys. If standard terminology of AM would be followed, this would allow a more systematic review of the utilization of different AM processes.
  • 1.3K
  • 09 Apr 2021
Topic Review
Freight Bicycle
Freight bicycles, carrier cycles, freight tricycles, cargo bikes, box bikes, or cycletrucks are human powered vehicles designed and constructed specifically for transporting loads. Vehicle designs include a cargo area consisting of an open or enclosed box, a flat platform, or a wire basket, usually mounted over one or both wheels, low behind the front wheel, or between parallel wheels at either the front or rear of the vehicle. The frame and drivetrain must be constructed to handle loads larger than those on an ordinary bicycle.
  • 1.3K
  • 03 Jan 2023
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