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The  Grashof number  is a dimensionless number, named after  Franz Grashof. The  Grashof number  is defined as the ratio of the buoyant to viscous force acting on a fluid in the velocity boundary layer. Its role in natural convection is much the same as that of the  Reynolds number  in forced convection. Natural convection is used if this motion and mixing is caused by  density  variations resulting from temperature differences within the fluid. Usually the density decreases due to an increase in  temperature  and causes the fluid to rise. This motion is caused by the buoyant force. The major force that resists the motion is the viscous force. The Grashof number is a way to quantify the opposing forces. The Grashof number is defined as: where: g is acceleration due to Earth’s gravity β is the coefficient of thermal expansion T wall  is the wall temperature T ∞  is the bulk temperature L is the vertical length ν is the kinematic viscosity. For gases β = 1/T where the temperature is in K

A VPN, or Virtual Private Network, allows you to create a secure connection to another network over the Internet. VPNs can be used to access region-restricted websites, shield your browsing activity from prying eyes on public Wi-Fi, and more. These days VPNs are really popular, but not for the reasons they were originally created. They originally were just a way to connect business networks together securely over the internet or allow you to access a business network from home. VPNs essentially forward all your network traffic to the network, which is where the benefits – like accessing local network resources remotely and bypassing Internet censorship – all come from. Most operating systems have integrated VPN support. What Is a VPN and How Does It Help Me? In very simple terms, a VPN connects your PC, smartphone, or tablet to another computer (called a server) somewhere on the internet, and allows you to browse the internet using that computer’s internet connection. So if that server

Pig iron is the crude form of iron and is used as a raw material for the production of various other ferrous metals, such as cast iron, wrought iron and steel. The pig iron is obtained by smelting iron ores in a blast furnace. The iron ores are found in various forms as shown below: The metallic contents of these iron ores are given in the following table: The haematite is widely used for the production of pig iron. Since pyrite contains only 30 to 40% iron, therefore it is not used for manufacturing pig iron. The pig iron is obtained from the iron ores in the following steps: 1. Concentration.   It is the process of removing the impurities like clay, sand etc. from the iron ore by washing with water. 2. Calcination or roasting.   It is the process of expelling moisture, carbon dioxide, sulphur and arsenic from the iron ore by heating in shallow kilns. 3. Smelting.   It is process of reducing the ore with carbon in the presence of a flux. The smelting is carried out in a large tower ca

Thermal imaging  is a technology that operates by capturing the upper portion of the infrared light spectrum, which is emitted as heat by objects instead of simply reflected as light. Hotter objects, such as warm bodies, emit more of this light than cooler objects like trees or buildings.  Thermal imaging working principle : A special lens focuses the infrared light emitted by all of the objects in view. The focused light is scanned by a  phased array  of infrared-detector elements. The detector elements create a very detailed temperature pattern called a  thermogram . It only takes about one-thirtieth of a second for the detector array to obtain the temperature information to make the thermogram. This information is obtained from several thousand points in the field of view of the detector array. The thermogram created by the detector elements is translated into electric impulses. The impulses are sent to a signal-processing unit, a circuit board with a dedicated chip that translates

  Q1) Which of the suggested answers best matches the relationship between the shapes in the image?   A, B, C, D         Answer:   The arrow changes direction and the shape on the right has 1 more side than its counterpart on the left.  Correct Answer; D           Q2) Which shape is the odd one out?   A, B, C, D     Answer   This question is asking you to identify a rule that applies to all but one shape. Things to consider include what shapes are present, how many shapes are present, relative position, colour. In this example, there are 2 consistent rules the largest shape is consistently the same colour and the shape closest to the bottom of each square is orange. There is only one square that the latter rule doesn’t apply to.  Correct Answer; C  Q3) Which domino comes next in the sequence?   A, B, C, D     Answer   This question is a bit trickier, as it is asking you to notice that there are two patterns appearing at the same time with alternating dominos. If you consider the 1st, 3

What are LEDs? LEDs are a type of semiconductor called "Light Emitting Diode". White LEDs, which have achieved practical realization through the use of high-brightness blue LEDs developed in 1993 based on Gallium Nitride, are attracting increased attention as a 4th type of light source. How do LEDs Emit Light? LEDs (Light Emitting Diodes) are semiconductor light sources that combine a P-type semiconductor (larger hole concentration) with an N-type semiconductor (larger electron concentration). Applying a sufficient forward voltage will cause the electrons and holes to recombine at the P-N junction, releasing energy in the form of light. Compared with conventional light sources that first convert electrical energy into heat, and then into light, LEDs (Light Emitting Diodes) convert electrical energy directly into light, delivering efficient light generation with little-wasted electricity. Types of LEDs Two types of LEDs are available, a lamp type (leaded) and a chip type (su

Einstein's mass-energy equivalence (1905): E = mc 2 , equation in German-born physicist Albert Einstein’s theory of  special relativity that expresses the fact that mass and energy are the same physical entity and can be changed into each other. In the equation, the increased relativistic mass ( m ) of a body times the speed of light squared ( c 2 ) is equal to the kinetic energy ( E ) of that body. What does it say? Energy equals mass multiplied by the speed of light squared. In other words ... Mass is really just a super-condensed form of energy. What did it teach us? Because of the size of the constant in the equation (the speed of light squared, an unimaginably huge number) a colossal amount of energy can be released through converting a tiny amount of mass. But was it practical? Einstein's most famous equation hinted at the potential for the huge amounts of energy released in nuclear fission, when a large unstable nucleus breaks into two smaller ones. This is because the m

Earth's atmosphere  has a series of layers, each with its own specific traits. Moving upward from ground level, these layers are named the troposphere, stratosphere, mesosphere, thermosphere and exosphere. The exosphere gradually fades away into the realm of interplanetary space. Troposphere The  troposphere  is the lowest layer of our atmosphere. Starting at ground level, it extends upward to about 10 km (6.2 miles or about 33,000 feet) above sea level. We humans live in the troposphere, and nearly all weather occurs in this lowest layer. Most clouds appear here, mainly because 99% of the water vapor in the atmosphere is found in the troposphere. Air pressure drops, and temperatures get colder, as you climb higher in the troposphere. Stratosphere The next layer up is called the  stratosphere . The stratosphere extends from the top of the troposphere to about 50 km (31 miles) above the ground. The infamous ozone layer is found within the stratosphere. Ozone molecules in this layer

Engineers are the inventors, designers, analysers and builders of our modern age. They create the machines, structures and systems we use on a daily basis, most of the time without thinking twice about the work that went into them. The constrains of physics, the confines of the manufacturing technology of the modern age, the limitations imposed by current material properties, requirements in terms of health and safety and cost: all of these are things that engineers must take into account when designing whatever it is they're working on. Luckily, engineers are trained to recognise and solve these problems; but in order to recognise and solve them, engineers have to have a very particular set of skills, skills acquired over a long career, skills that make engineers a nightmare for anything these problems might throw at them. Here are the Top 10 Characteristics of Great Engineers listed below. 1. Teamwork Teamwork drives the successful completion of a project. No one can complete a p