Magnetostatic simulation . . . GPS satellite orbits . . . Materials for dental diagnosis . . .
Dear Search Engineer: We know of a few software programs for permanent magnet calculation (COSMOSEMS and Integrated Engineering). Can you suggest some more programs for magnetostatic, low-frequency simulations?—G.R., Troy, MI
Dear G.R.: One reader replied that while modeling magnetic gauss fields for medical and research MRI (magnetic resonance imaging), he used a software package called Vector Fields. "The software was very flexible and, from what I understand, more user-friendly now than when I used it," he reports. Check it out at http://rbi.ims.ca/4392-524.
Dear Search Engineer: I'm looking for a tool that will mark each bolt/screw with a color dot and will allow me to know where I left the last bolt/screw I torque after a break or the following day. Any suggestions? —D.C., Netherlands
Dear D.C.: Among other options, you may try an Avery label with an adhesive-backed foil sticker (#6007) and stick it on or next to the last fastener that was torqued at the end of the day. A Markal Paint Marker is also available in different point sizes and colors, including yellow, red, white, silver, etc. It will mark on a variety of materials and the marks are visible and durable.
Dear Search Engineer: How high are the orbits for GPS satellites? —E. H.,
Dear E.H.: GPS consists of three segments: space, control, and user. The Space Segment consists of a minimum of 24 operational satellites in six circular orbits 20,200 km (10,900 NM) above the earth at an inclination angle of 55 degrees with a 12 hr period. The satellites are spaced in orbit so that at any time a minimum of six satellites will be in view to users anywhere in the world. The satellites continuously broadcast position and time data to users throughout the world. See http://rbi.ims.ca/4392-525.
Dear Search Engineer: I am developing an instrument with a peltier cooler for diagnosing teeth requiring root canal therapy (so the dentist gets the right tooth). I need to get rid of the heat quickly and want 99.99 percent pure aluminum as its thermal conductivity is much higher than 6061-grade alloy (230 vs. 160 approximately). Do you know where I could get this material? Also, I need thermally conductive rubber to apply the heat to the tooth. I am mixing aluminum powder with polyvinyl siloxane 50/50. Any better ideas?—C. S.,
Dear C.S.: Depending on the mechanical constraints of your product, you might be able to use a heat pipe, which is particularly good for small diameter long paths as might be used in instruments. Many times that container is stainless, which will hold up better than aluminum. The heat transfer is substantially higher than aluminum. For more information, go to http://rbi.ims.ca/4392-526. Otherwise, consider 6063T5 grade aluminum, which one reader uses for all of his heat exchangers. Pure aluminum is too difficult to machine by comparison, he insists.