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Topic Review
Virtual Water Trade
As a semi-arid/arid country located in the northwest of Africa, Morocco is facing serious water scarcity driven by the dual stresses of decreasing availability of water resources and increasing water demands. Virtual water trade could be an effective tool to alleviate water scarcity.
  • 376
  • 24 Oct 2023
Topic Review
Virtual Volunteering
Virtual volunteering refers to volunteer activities completed, in whole or in part, using the Internet and a home, school, telecenter, or work computer or other Internet-connected device, such as a smart-phone (a cell phone with Internet functions) or personal digital assistant (PDA). Virtual volunteering is also known as online volunteering, remote volunteering or e-volunteering.
  • 340
  • 14 Nov 2022
Topic Review Video
Virtual Travel
Virtual experience in tourism and hospitality can be broadly described as the totality of tourists’ affective, cognitive, and sensorial responses before, during, and after interaction with the virtual environment (VR). VR is traditionally defined as a computer-generated environment where the user has an opportunity to immerse, look around, and control the experience. Technologies represented in virtual reality range from 360° videos, VR, AR, and virtual meetings to the digital world as a persistent virtual environment, which can be broadly classified based on the levels of immersion, presence, and complexity. The levels of immersion can be defined as non-immersive (e.g., computer, display, mice), semi-immersive (e.g., high-resolution displays, projectors, hard simulators), and fully immersive (e.g., VR glasses, head mount display), based on the type of simulation and degree of user’s abstraction from the real world.
  • 1.1K
  • 11 Mar 2023
Topic Review
Virtual Synchrony
Virtual synchrony is an interprocess message passing (sometimes called ordered, reliable multicast) technology. Virtual synchrony systems allow programs running in a network to organize themselves into process groups, and to send messages to groups (as opposed to sending them to specific processes). Each message is delivered to all the group members, in the identical order, and this is true even when two messages are transmitted simultaneously by different senders. Application design and implementation is greatly simplified by this property: every group member sees the same events (group membership changes and incoming messages) in the same order. A virtually synchronous service is typically implemented using a style of programming called state machine replication, in which a service is first implemented using a single program that receives inputs from clients through some form of remote message passing infrastructure, then enters a new state and responds in a deterministic manner. The initial implementation is then transformed so that multiple instances of the program can be launched on different machines, using a virtually synchronous message passing system to replicate the incoming messages over the members. The replicas will see the same events in the same order, and are in the same states, hence they will make the same state transitions and remain in a consistent state. The replication of the service provides a form of fault-tolerance: if a replica fails (by crashing), the others remain and can continue to provide responses. Different members of the replica group can also be programmed to subdivide the workload, typically by using the group membership to determine their respective roles. This permits a group of N members to run as much as N times faster than a single member, or to handle N times as many requests, while continuing to offer fault-tolerance in the event of a crash. Virtual synchrony is distinguished from classical state machine replication because the model includes features whereby a programmer can request early (optimistic) delivery of messages, or relaxed forms of ordering. When used appropriately, these features can enable substantial speedup. However, the programmer needs to be sure that the relaxation of guarantees will not compromise correctness. For example, in a service that uses locking to protect concurrently updated data, the messaging system can be instructed to use an inexpensive form of message ordering, in which the messaging system respects the ordering in which individual senders send messages (FIFO guarantee) but does not attempt to impose an agreed order if messages are sent concurrently by different senders. Provided that the sender indeed held locks on the data, it can be shown that FIFO ordering suffices for correctness. The benefit is that FIFO ordering is much less costly to implement than total ordering for concurrent messages. To give another example, by delivering messages optimistically, virtual synchrony systems can outperform the Paxos that is normally required for implementation of state machine replication: Paxos normally requires a 2-phase protocol, whereas optimistic virtual synchrony protocols can deliver messages immediately upon their arrival. However, this could result in a violation of the safety property of the state machine replication model. To prevent such problems, the programmer who uses this feature is required to invoke a primitive called flush, which delays the caller until any optimistically delivered messages have reached all of the group members. Provided that the programmer understands this behavior and is careful to call flush before interacting with external clients or persistent storage, higher performance can be achieved without loss of safety. The flexibility associated with these limited forms of event reordering and optimistic early delivery permit virtual synchrony platforms to achieve extremely high data rates while still preserving very strong fault-tolerance and consistency guarantees.
  • 1.2K
  • 01 Dec 2022
Topic Review
Virtual Screening Algorithms in Drug Discovery
Virtual screening (VS) is an in silico technique used in the drug discovery process. During VS, large databases of molecular structures are automatically evaluated using computational methods. With the use of VS, it is expected to identify molecules more susceptible to binding to the molecular target, typically a protein or enzyme receptor.
  • 710
  • 29 May 2023
Topic Review
Virtual Restaurants in COVID-19 Pandemic
Due to COVID-19 restrictions, many restaurants were forced to discontinue in-person service, either by locking down or finding alternative methods of operation. Despite the fact that, in the United States of America, digital restaurants have already been established for many years, in Greece, this phenomenon became popular during the pandemic. These delivery-only companies operate exclusively online, allowing customers to place orders from restaurants without a physical location.
  • 341
  • 28 Jul 2023
Topic Review
Virtual Reality-Assisted Language Learning
Virtual Reality (VR) refers to a three-dimensional (3D) environment generated by computer technology, which can provide a context similar to visual simulation and other senses. It allows users to communicate with people, machines, and other entities in the virtual environment by using computers and various devices. The dramatic reduction in the cost of devices and technology has driven a rapid growth of VR applications in educational fields such as medicine, science, and mathematics in recent years that has been proven to be positive. Learners feel the actual situation through sensory organs, which can help them improve their motivation, participation, and learning ability. Moreover, VR has also been applied to language learning and has shown the importance and potential of applications to support language learning.
  • 805
  • 22 Mar 2022
Topic Review
Virtual Reality Therapy for Social Anxiety Disorder Treatment
Virtual reality (VR) is a three-dimensional environment generated by the computer, in which subjects interact with the environment as if they were really inside it. The most used VR tools are the so-called HMD (head-mounted display) which make it possible to achieve what theorists define “direct mediated action”. The most common treatment for social anxiety disorder is represented by “in vivo exposure therapy” (iVET). Virtual reality therapies proved to be a valid alternative to the acquisition of social skills suitable for improving the symptoms of SAD. Although there has not been a significant difference between VRET and iVET, the low costs and flexibility of VRET open up new scenarios for achieving greater psychophysical well-being. 
  • 763
  • 16 Dec 2021
Topic Review
Virtual Reality Therapy for Depression
Virtual reality (VR) describes a family of technologies which immerse users in sensorily-stimulating virtual environments. Such technologies have increasingly found applications in the treatment of neurological and mental health disorders. Depression, anxiety, and other mood abnormalities are of concern in the growing older population—especially those who reside in long-term care facilities (LTCFs).
  • 742
  • 11 Jun 2021
Topic Review
Virtual Reality Technologies Supporting Screening Oculomotor Problems
Oculomotor dysfunctions (OMDs) are problems relating to coordination and accuracy of eye movements for processing visual information. Eye-tracking (ET) technologies show great promise in the identification of OMDs. Virtual Reality (VR) and ET technologies emerged in the field of vision science, integrating built-in eye trackers into head-mounted displays (HMDs). Therefore, today, VR has the potential to be an effective tool in complementing the treatment of a variety of vision disorders requiring ET technologies for identification or treatment, e.g., treating amblyopia and convergence insufficiency.
  • 323
  • 25 Jul 2023
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