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Topic Review
Grey Goo
Grey goo (also spelled gray goo) is a hypothetical end-of-the-world scenario involving molecular nanotechnology in which out-of-control self-replicating robots consume all biomass on Earth while building more of themselves, a scenario that has been called ecophagy ("eating the environment", more literally "eating the habitation"). The original idea assumed machines were designed to have this capability, while popularizations have assumed that machines might somehow gain this capability by accident. Self-replicating machines of the macroscopic variety were originally described by mathematician John von Neumann, and are sometimes referred to as von Neumann machines or clanking replicators. The term gray goo was coined by nanotechnology pioneer Eric Drexler in his 1986 book Engines of Creation. In 2004 he stated, "I wish I had never used the term 'gray goo'." Engines of Creation mentions "gray goo" in two paragraphs and a note, while the popularized idea of gray goo was first publicized in a mass-circulation magazine, Omni, in November 1986.
  • 893
  • 08 Oct 2022
Topic Review
WiMAX
Worldwide Interoperability for Microwave Access (WiMAX) is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide physical layer (PHY) and media access control (MAC) options. The WiMAX Forum was formed in June 2001 to promote conformity and interoperability, including the definition of system profiles for commercial vendors. The forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL". IEEE 802.16m or WirelessMAN-Advanced was a candidate for 4G, in competition with the LTE Advanced standard. WiMAX was initially designed to provide 30 to 40 megabit-per-second data rates, with the 2011 update providing up to 1 Gbit/s for fixed stations. WiMAX release 2.1, popularly branded as WiMAX 2+, is a backwards-compatible transition from previous WiMAX generations. It is compatible and interoperable with TD-LTE.
  • 891
  • 31 Oct 2022
Topic Review
Healthy Building in China
Healthy buildings are a deep-level development of green buildings, which can effectively help relieve stress and improve occupants’ physical and mental health. In addition, they are is likely to play an important role in preventing the spread of respiratory infectious diseases. Therefore, healthy buildings have attracted worldwide attention. The development of healthy buildings in China is quite different from that of other countries and has its own characteristics with many factors, such as project implementation, environmental pollution, and social issues affecting healthy buildings development in China. 
  • 890
  • 28 Mar 2022
Topic Review Video
3D Visualisation in Railway Tunnel SubSurface Inspection
Railway Tunnel SubSurface Inspection (RTSSI) is essential for targeted structural maintenance. ‘Effective’ detection, localisation and characterisation of fully concealed features (i.e., assets, defects) is the primary challenge faced by RTSSI engineers, particularly in historic masonry tunnels. Clear conveyance and communication of gathered information to end-users poses the less frequently considered secondary challenge.
  • 890
  • 22 Nov 2022
Topic Review
Piezoelectric MEMS Laterally Vibrating Resonators
Piezoelectric MEMS Laterally Vibrating Resonators (LVRs), which belong to one type of micromachined resonators that uses piezoelectric transduction, are characterized by dominant mechanical vibration in the lateral direction (within the plane of the device). In piezoelectric MEMS LVRs, the electric field is mainly applied across the thickness of the piezoelectric film to generate a lateral strain within the plane of the device with suspended free edges. Due to the lithographically definable resonant frequency, piezoelectric LVRs feature wide operation frequency coverage (from tens of MHz to several GHz) and provide a pathway towards realizing a multi-frequency integrated solution on a single chip. Depending on the structure of resonators, piezoelectric MEMS LVRs can be categorized into two types. The first type of LVRs consists of a piezoelectric film, both as the transducer and acoustic cavity. The second type of LVRs uses the thin piezoelectric film as a transducer only while having most of the acoustic energy propagating in the underlying thicker substrate. Such resonators are usually referred to as thin-film piezoelectric-on-substrate (TPoS) resonators. Typical applications of piezoelectric MEMS LVRs include resonant sensors, oscillators and RF filters.
  • 890
  • 14 Sep 2020
Topic Review
Microfluidic Systems and Breast Cancer Metastasis
Microfluidic devices are useful tools in studying biological phenomena involving fluid flow, thin tissue culture, and cell mobility; each of these aspects make microfluidic techniques attractive for studying human breast cancer, which is the most commonly occurring cancer in women and the second most common cancer overall worldwide.
  • 890
  • 15 Feb 2022
Topic Review
Billing (Performing Arts)
Billing is a performing arts term used in referring to the order and other aspects of how credits are presented for plays, films, television, or other creative works. Information given in billing usually consists of the companies, actors, directors, producers, and other crew members.
  • 890
  • 14 Oct 2022
Topic Review
Viewing Angle Switchable Liquid Crystal Devices
For pure liquid crystals (LCs) system, methods for switchable viewing angle devices are divided into hybrid aligned nematic (HAN) LC cells, double cells, pixel division and three-electrode structure. Utilizing 3M light-control film and PDLC film together to create switchable anti-peeping film, PDLC is a voltage-controlled LC film that can switch between transparent and scattering, light scattering intensity of PDLC film is dependent on electric field, switchable voltage between light scattering (share mode) and transparent state (privacy mode) is approximately 5.0 V.
  • 890
  • 10 Oct 2022
Topic Review
MIMO Radars
This entry reports a thorough overview on the last developments concerning the vital sign detection and the human localization employing the multiple-input-multiple-output (MIMO) technology. The wireless motion and vital sign detection represents an outstanding research area aimed at monitoring the health conditions of human subjects and at detecting their presence in different environments with minimal concern. MIMO radars exhibit several interesting advantages over conventional single-input-single-output architectures mainly related to their angle detection capabilities and enhanced signal-to-noise ratio. This paper describes the main features and details the operating principles of MIMO technology. Thereafter, it summarizes the state-of-the-art of the available solutions with the purpose of fueling the research activities on this hot topic.
  • 889
  • 17 Sep 2020
Topic Review
Experimental Techniques for Chatter Avoidance
The general trend towards lightweight components and stronger but difficult to machine materials leads to a higher probability of vibrations in machining systems. Amongst them, chatter vibrations are an old enemy for machinists with the most dramatic cases resulting in machine-tool failure, accelerated tool wear and tool breakage or part rejection due to unacceptable surface finish. To avoid vibrations, process designers tend to command conservative parameters limiting productivity. Among the different machining processes, turning is responsible of a great amount of the chip volume removed worldwide.
  • 889
  • 27 Oct 2020
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