Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Hottest Latest Alphabetical (A-Z) Alphabetical (Z-A)
Type:
All Topic Review Biography
Topic Review
Graphene-Based Membranes in Oil/Water Separation
Oily wastewaters, oil spills from the petroleum industry, and oil-shipping accidents have caused detrimental effects on aquatic ecosystems. Several methods were proposed by various number of studies to tackle oil spillage cleanups; these methods include absorption, dispersants, solidifiers, and controlled burning. Absorption is one of the most commonly used methods in the separation and recovery of spilled oil from water thanks to its good efficiency, simple operation, and flexibility to combine with other methods. Graphene has a large surface area, with a high chemical and thermal stability. It is an excellent adsorption material and has several applications in the field of oil spill cleanup and water purification processes.
  • 1.2K
  • 28 Feb 2022
Topic Review
Graphene-Coating for Efficient Electronics Cooling
Thermal management is essential in electronics, as it improves reliability and enhances performance by removing heat generated by the devices. Thermal management of handheld systems such as laptops is becoming increasingly challenging due to increasing power dissipation. The power dissipated per unit area on the laptop electronic chips is increasing while the area of the chips itself it decreasing, resulting a high heat flux that causes an increase in temperature. The increasing temperature adversely affects the performance of laptops and in many cases leads to failure through such modes as thermal fatigue and dielectric breakdown. In this work, three dimensional steady state CFD model of a laptop motherboard is presented. The model accounts for heat transfer for both natural convection and radiation to the ambient air temperature. The present CFD study allow accurate, rapid, physical modelling to make decisions on materials, components and layout beside power control feedback to achieve performance and target lifetime with reduced testing requirements. An alternative design for the cooling of laptop microprocessor using only passive cooling is proposed. The results showed that the assembled a thin plate of a copper material coated with graphene and use it as a heat sinks with the microprocessor of the laptop providing an efficient and economical solution in thermal management. Considerable drop in microprocessor temperature is obtained through the heat dissipation path suggested in the new design. The proposed passive cooling solution has the advantages of fanless operation compared to the existing active cooling solutions such as the noise-free operation, lower energy consumption and higher reliability. We hope this work may open the way for huge boost in the technology of electric cooling by innovative manufacturing techniques.
  • 2.9K
  • 28 Oct 2020
Topic Review
Graphene-Enabled Silicon-Based High-Speed Optoelectronic Devices
Silicon (Si) photonics has emerged as a prominent technology for meeting the escalating requirements of high-speed data transmission in optical communication systems. These systems need to be compact, energy-efficient, and capable of handling large amounts of data, driven by the advent of next-generation communication devices.
  • 433
  • 04 Dec 2023
Topic Review
Grasshopper (Rocket)
Grasshopper and the Falcon 9 Reusable Development Vehicles (F9R Dev) were experimental flight test reusable rockets that performed vertical takeoffs and landings. The project was privately funded by SpaceX, with no funds provided by any government until later on. Two prototypes were built, and both were launched from the ground. Grasshopper was announced in 2011 and began low-altitude, low-velocity hover/landing testing in 2012. The initial Grasshopper test vehicle was 106 ft (32 m) tall and made eight successful test flights in 2012 and 2013 before being retired. A second Grasshopper-class prototype was the larger and more capable Falcon 9 Reusable Development Vehicle (F9R Dev, also known as F9R Dev1) based on the Falcon 9 v1.1 launch vehicle. It was tested at higher altitudes and was capable of much higher velocity but was never tested at high velocity. The F9R Dev1 vehicle was built in 2013–2014 and made its first low-altitude flight test on 17 April 2014; it was lost during a three-engine test at the McGregor test site on 22 August 2014, which ended the low-velocity test program. Further expansion of the flight test envelope for the reusable rocket was moved to descending Falcon 9 boosters that had been used on orbital flight trajectories on commercial orbital flights of the Falcon 9. The Grasshopper and F9R Dev tests were fundamental to the development of the reusable Falcon 9 and Falcon Heavy rockets, which require vertical landings of the near-empty Falcon 9 and Falcon Heavy first-stage booster tanks and engine assemblies. The Grasshopper and the F9R Dev tests led into a series of high-altitude, high-speed controlled-descent tests of post-mission (spent) Falcon 9 booster stages that accompanied the commercial Falcon 9 missions since September 2013. The latter eventually resulted in the first successful booster landing on 21 December 2015.
  • 1.2K
  • 16 Nov 2022
Topic Review
Gravity Centre Watchdog Alarm
Gravity centre watchdog alarm, called a GC-WatchdogAlarm, monitors the condition of the press stamping and warns us when a pattern appears that we consider outside the correct working standards. To this end, two restrictions have been defined that must not be complied with: one is that there should be no deviation in the stamping and the second is that there should be no difference between each of the force values for each press position greater than usual. The GC-WatchdogAlarm tool runs every 24 h, analysing all the stamping parts made during a day of production. In the case of finding an anomaly, it generates an alarm that is sent to the maintenance team in order to perform a deep analysis of what happened. This is a good tool to take advantage of when making decisions.
  • 249
  • 26 Oct 2023
Topic Review
Gravity Concentration Techniques in Urban Mining Applications
Urban mining has emerged as a concept that goes beyond conventional recycling, as it aims to tackle both the challenges of solid waste generation and management, as well as the scarcity of primary resources. Gravity concentration has gained increasing attention as a promising method for addressing crucial challenges in urban mining applications. Gravity concentration has a long history, dating back to ancient times. During this time, numerous methods have been developed, and for each method, various equipment has been manufactured and commercialized. Therefore, categorizing gravity concentration techniques is not an easy task, and it ultimately depends on the criteria that one relies upon. Such criteria may include whether the operation is dry or wet, the capacity of the equipment, the typical efficiency (the efficiency of gravity concentration equipment can be evaluated using the partition or Tromp curve method. In this, the separation is assessed by examining the fraction of material in each density fraction that ends up in the product, and how this relates to the original fraction present in the feed. More details can be found in mineral processing textbooks), the process target (yield or content), the costs involved, and others. Of these criteria, the operating size range is the most critical factor that should be considered when selecting appropriate gravity concentration techniques for a given application.
  • 682
  • 08 Nov 2023
Topic Review
Gravity Field and Steady-State Ocean Circulation Explorer
The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) was the first of ESA's Living Planet Programme satellites intended to map in unprecedented detail the Earth's gravity field. The spacecraft's primary instrumentation was a highly sensitive gravity gradiometer consisting of three pairs of accelerometers which measured gravitational gradients along three orthogonal axes. Launched on 17 March 2009, GOCE mapped the deep structure of the Earth's mantle and probed hazardous volcanic regions. It brought new insight into ocean behaviour; this in particular, was a major driver for the mission. By combining the gravity data with information about sea surface height gathered by other satellite altimeters, scientists were able to track the direction and speed of geostrophic ocean currents. The low orbit and high accuracy of the system greatly improved the known accuracy and spatial resolution of the geoid (the theoretical surface of equal gravitational potential on the Earth). The satellite's unique arrow shape and fins helped keep GOCE stable as it flew through the thermosphere at a comparatively low altitude of 255 kilometres (158 mi). Additionally, an ion propulsion system continuously compensated for the variable deceleration due to air drag without the vibration of a conventional chemically powered rocket engine, thus limiting the errors in gravity gradient measurements caused by non-gravitational forces and restoring the path of the craft as closely as possible to a purely inertial trajectory. After running out of propellant, the satellite began dropping out of orbit and made an uncontrolled reentry on 11 November 2013.
  • 1.0K
  • 02 Nov 2022
Topic Review
Gravity Recovery and Climate Experiment
File:15 Years of Freshwater Trends Seen by GRACE.webm The Gravity Recovery and Climate Experiment (GRACE) was a joint mission of NASA and the German Aerospace Center. Twin satellites took detailed measurements of Earth's gravity field anomalies from its launch in March 2002 to the end of its science mission in October 2017. By measuring gravity anomalies, GRACE showed how mass is distributed around the planet and how it varies over time. Data from the GRACE satellites is an important tool for studying Earth's ocean, geology, and climate. GRACE was a collaborative endeavor involving the Center for Space Research at the University of Texas at Austin, NASA's Jet Propulsion Laboratory, the German Aerospace Center and Germany's National Research Center for Geosciences, Potsdam. The Jet Propulsion Laboratory was responsible for the overall mission management under the NASA ESSP (Earth System Science Pathfinder) program. The principal investigator is Byron Tapley of the University of Texas Center for Space Research, and the co-principal investigator is Christoph Reigber of the GeoForschungsZentrum (GFZ) Potsdam. The two GRACE satellites (GRACE-1 and GRACE-2) were launched from Plesetsk Cosmodrome, Russia, on a Rockot (SS-19 + Breeze upper stage) launch vehicle on 17 March 2002. The spacecraft were launched to an initial altitude of approximately 500 km at a near-polar inclination of 89°. During normal operations, the satellites were separated by 220 km along their orbit track. This system was able to gather global coverage every 30 days. GRACE far exceeded its 5-year design lifespan, operating for 15 years until the decommissioning of GRACE-2 on 27 October 2017. Its successor, GRACE-FO, was successfully launched on 22 May 2018.
  • 1.4K
  • 06 Oct 2022
Topic Review
Great Republic
Launched on October 4, 1853 Great Republic is noteworthy as the largest wooden clipper ship ever constructed.
  • 868
  • 01 Nov 2022
Topic Review
Green and Blue Hydrogen Production in Colombia
Hydrogen is the most abundant element in nature, but it cannot be considered an energy source by itself because it is impossible to find it in its elemental form in nature. Colombia, a privileged country in terms of diversity, availability of natural resources, and geographical location, has set a roadmap for hydrogen as part of the energy transition plan proposed in 2021. To reduce its emissions in the mid-term and foster its economy, hydrogen production should be green and blue, with specific targets set for 2030 for the hydrogen costs and produced quantities. A comparison is made concerning the state-of-the-art production of blue and green hydrogen and how Colombia performs in each pathway.
  • 929
  • 30 Nov 2022
  • Page
  • of
  • 678
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
ScholarVision Creations
Feedback