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I

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then k minus nine eight seven six five

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four three two one solid rocket ignition

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and liftoff liftoff of Columbia on a

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the isothermal dendritic growth

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experiment or idge is a microgravity

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material science experiment plan to fly

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on board the space shuttle Columbia as

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part of the United States microgravity

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payload mission it is a fundamental

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materials research experiment to help

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better understand and correlate what

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parameters affect the size and shape of

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crystals which determine the final

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properties of materials idge was

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conceived at the Rensselaer Polytechnic

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Institute in Troy New York which is

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responsible for the science and

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dendritic growth chamber development dr.

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Martin a gliksin of rpi is the idge

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principal investigator well what we hope

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to accomplish in the idg experiment is

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to be able to observe the growth rates

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and

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krystal morphologies of dendritic

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crystals as they form and develop in the

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microgravity environment of low-earth

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orbit this experiment will constitute a

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basic check of the physics theories of

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dendritic growth and provide some

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critical data for the assessment of the

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scientific concepts that form the

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framework of our understanding of this

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rather important metallurgical

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phenomenon the experiment will take

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place inside this experiment apparatus

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container which will be mounted on the

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support structure inside the cargo bay

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of the spacecraft the experiment

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apparatus is a miniaturized automated

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space laboratory that was designed and

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built by a team of engineers at the NASA

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Lewis Research Center in Cleveland Ohio

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the specific objective of this space

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experiment is to improve the quality of

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metals through the study of sixy known

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nitrile this material was chosen because

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it mimics the behavior of iron in its

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melting and solidifying process with one

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additional advantage it is clear and

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transparent metals are not transparent

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we cannot see what is happening to their

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structure when they solidify if we were

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able to better understand what is

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occurring to the crystalline structure

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of the metal we would stand a much

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greater chance of improving its

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qualities that then is the objective of

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this space experiment this containment

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vessel houses the device through which

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we will attempt to learn and understand

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the internal changes taking place inside

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these solidifying materials inside the

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containment vessel of the automated

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space laboratory there is an isothermal

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bath it is a two gallon tank filled with

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a mixture of ethylene glycol and water

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in which the temperature can be

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maintained to within two thousandth of a

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degree it has a heater coil in it and a

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small impeller down at the

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to assure good mixing of the ethylene

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glycol and water so that there is an

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even temperature distribution within the

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vessel the isothermal tank also has four

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windows on it to accommodate the

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necessary photography mounted to the

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tank are 2 35 millimeter cameras which

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record the dendritic growth and to slow

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scan television cameras the television

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cameras monitor the dendritic growth and

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activate the 35 millimeter cameras when

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growth and the experiment begins the

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rack around the tank provides a place to

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mount the circuit boards the experiments

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will take place inside this growth

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chamber which was conceived and

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developed at Rensselaer Polytechnic

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Institute the chamber is constructed out

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of stainless steel and glass their

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misters extend from the bottom of the

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growth chamber up into the volume of 16

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Oh nitrile they measure the temperature

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of the dendritic growth with an accuracy

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of two thousandth of a degree Celsius

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sixy no nitrile or SCM is encapsulated

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in the volume of the growth chamber the

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scn is 99.9 percent pure and was chosen

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because it mimics the behavior of iron

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in its melting and solidifying process

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Sen is a solid at room temperature and

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melts at 58 degrees centigrade that's

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136 degrees Fahrenheit

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now let's take a closer look at what we

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expect to achieve and learn through

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these experiments during the

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solidification process dendrites are

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formed dendrites are branching tree like

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crystals that form during industrial

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metal production understanding and

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correlating what parameters affect the

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size and shape of this crystallization

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will help us to understand and

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subsequently be able to predict the

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final properties of many metals alloys

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and super alloys and how we propose

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gathering that information is through

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this isothermal dendritic growth

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experiment the growth chamber is filled

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with scn material and contains a stinger

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that is used to form the dendrites first

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the scn material is melted by raising

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the temperature of the isothermal bath

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the molten scn is then cooled to just

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below its freezing point by reducing the

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temperature of the isothermal bath the

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scn will not solidify at this

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temperature because it is such a pure

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material the stinger is a hollow shaft

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which is also filled with the polymer

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scn and extends right into the volume of

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this scn material in the growth chamber

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using thermal electric coolers

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additional chilling is started at the

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top of the stinger shaft which is

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located outside of the growth chamber

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as the Stinger cools too far below the

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freezing point the scn inside the shaft

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solidifies the solidification process

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moves down the shaft and pops out at the

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stinger tip which is being monitored by

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the slow scan television cameras when

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the SS TV and associated software spot a

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dendrite forming the 35 millimeter

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cameras are triggered the cameras are

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set to expose six pictures at regular

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intervals as the dendrite grows to fill

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the field of view this entire process is

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monitored in Huntsville Alabama at

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NASA's Marshall Space Flight Center to

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assure that the experiment is

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progressing as expected in the payload

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operations control center or POC the

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growth velocity of the dendrite is

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measured if necessary timing of the

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experiment can be adjusted and remelted

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to repeat the experiment as often as

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might be required after the flight the

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35 millimeter photos will be analyzed

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for size and shape information these are

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dendrites which were grown on earth you

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can see the effects of gravity in their

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formation there are no arms or branches

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on top of the stand right as this

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material solidifies it gives off the

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heat of fusion the heat works upward

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causing the top of the sample to stay a

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little bit hotter as a result the bottom

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solidifies a little sooner than the top

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as the bottom cools gravity is creating

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a force which speeds up the downward

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growth of the arms of the dendrite these

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convective forces confound the effect of

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dendritic growth and make it difficult

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to understand the formation of these

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dendrites the space environment will

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simplify this process and enable us to

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better understand the process of

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crystallization

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the dendrites will be more symmetrical

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because gravity will not be distorting

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the solidification process these

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experiments will be most beneficial to

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metal manufacturers they will provide a

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fundamental understanding of how

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dendrites grow so that we can better

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understand how to make predictions of

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the quality of an end product if we

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understand the process we can improve it

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if we can improve it we will be able to

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reduce scrap and produce stronger and

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more ductile materials it will be

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possible to achieve whatever kind of

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property may be needed to satisfy the

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consumer everyone making products out of

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any metal will benefit from what has

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learned from these experiments in the

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future automobiles airplanes ships and

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many other metal products will be a

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little better and somewhat less