Velma Dinkley

Velma Dinkley is a fictional character in the Scooby-Doo franchise. She is prone to losing her glasses. She is usually seen wearing a baggy orange turtleneck, short pleated skirt (or in later episodes an A-line skirt, or sometimes shorts), knee socks, and Mary Janes. She is seen as the brain of the group.

Character description

Throughout her various incarnations, Velma is usually portrayed as a highly intelligent young woman with highly specific interests in science (which in the Scooby and Scrappy Doo series leads her to pursue a career as a NASA research scientist) or merely being very well read on obscure fields, such as Viking writing (as in the third Scooby-Doo series The New Scooby-Doo Mysteries). In Scooby-Doo! Abracadabra-Doo, Velma is described by her younger sister Madelyn as being "born with a mystery book in her hand". Consequently, Velma is usually the one to figure out the mystery, sometimes with the help of Fred and Daphne. The Velma character was inspired by the brainy tomboy Zelda Gilroy, as played by Sheila James, from the late 1950s/early 1960s American sitcom The Many Loves of Dobie Gillis.

Lead

Lead (/lɛd/) is a chemical element in the carbon group with symbol Pb (from Latin: plumbum) and atomic number 82. It is a soft, malleable and heavy post-transition metal. Freshly cut, solid lead has a bluish-white color that soon tarnishes to a dull grayish color when exposed to air; the liquid metal has shiny chrome-silver luster. Lead is the heaviest (has the highest atomic number) non-radioactive element (two radioactive elements, namely technetium and promethium, are lighter), although the next higher element, bismuth, has one isotope with a half-life that is so long (over one billion times the estimated age of the universe) that it can be considered stable. Lead's four stable isotopes each have 82 protons, a magic number in the nuclear shell model of atomic nuclei. The isotope lead-208 also has 126 neutrons, another magic number, and is hence double magic, a property that grants it enhanced stability: lead-208 is the heaviest known stable nuclide.

Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield.

Cutoff (steam engine)

In a steam engine, cutoff is the point in the piston stroke at which the inlet valve is closed. On a steam locomotive, the cutoff is controlled by the reversing gear.

The point at which the inlet valve closes and stops the entry of steam into the cylinder from the boiler plays a crucial role in the control of a steam engine. Once the valve has closed, steam trapped in the cylinder expands adiabatically. The steam pressure drops as it expands. A late cutoff delivers full steam pressure to move the piston through its entire stroke, for maximum start-up forces. But, since there will still be unexploited pressure in the cylinder at the end of the stroke, this is achieved at the expense of engine efficiency. In this situation the steam will still have considerable pressure remaining when it is exhausted resulting in the characteristic “chuff chuff” sound of a steam engine. An early cutoff has greater thermodynamic efficiency but results in a lower Mean effective pressure so less average force on the piston and is used for running the engine at higher speeds. The steam engine is the only thermodynamic engine design that can provide its maximum torque at zero revolutions per minute.

Lead (electronics)

In electronics, a lead is an electrical connection consisting of a length of wire or metal pad (SMD) that comes from a device. Leads are used for physical support, to transfer power, to probe circuits (see multimeter), to transmit information, and sometimes as a heatsink. The tiny leads coming off through-hole components are also often called pins.

Many electrical components such as capacitors, resistors, and inductors have only two leads where some integrated circuits (ICs) can have several hundred leads to more than a thousand for the largest BGA devices. IC pins often either bend under the package body like a letter "J" (J-lead) or come out, down, and form a flat foot for securing to the board (S-lead or gull-lead).

Most kinds of integrated circuit packaging are made by placing the silicon chip on a lead frame, wire bonding the chip to the metal leads of that lead frame, and covering the chip with plastic. The metal leads protruding from the plastic are then either "cut long" and bent to form through-hole pins, or "cut short" and bent to form surface-mount leads. Such lead frames are used for surface mount packages with leads—such as small-outline integrated circuit (SOIC), Quad Flat Package (QFP), etc. -- and for through-hole packages such as dual in-line package (DIP) etc. -- and even for so-called "leadless" or "no-lead" packages—such as quad-flat no-leads package (QFN), etc.