“Ask the Experts" is moderated by Béla Lipták, process control consultant and editor of the Instrument Engineer's Handbook (IEH). He is recruiting a team of co-authors to work on the 5th edition and welcomes contribution offers from qualified colleagues. If you have questions for our team of experts, please send them to: [email protected].
Q: My measurement question has to do with archeology. King Attila died in 453 CE and according to legend, was buried in three metallic caskets, one inside the other (made of gold, silver and copper). Also according to legend, a river was rerouted over the grave to protect it from being robbed. This grave is likely to contain valuable information concerning the 5th century and the Hun culture. Are there metal sensors that could scan a riverbed to find these caskets?
Nicholas Wagoner
[email protected]
A: Put on a diver suit and walk the river bed. If you can find a group of archeology students who are willing to spend their summer vacation walking the riverbed, using equipment such as a high-end metal detector, you could try doing it. Naturally, you would need sponsors to cover the expenses of renting tents, diver suits, metal detectors, etc. The principles of detection are covered in my handbook, and suppliers are listed at http://tinyurl.com/35bhfqy and www.hotektech.com/Tinsley5916.htm
Béla Lipták
[email protected]
A: Detecting gravitational anomalies might be the only way to do it. The question is will the size of the burial be large enough to create an anomaly large enough to be seen through the water. The paper referenced below is a good introduction to the measurement and detection of gravitational anomalies and refers to oilfield practices too.
The author of the question is certainly correct. The finding of the burial of Attila would be an archaeological coup of major proportions, second only to the discovery of the tomb of Temujin, a.k.a. Genghis Khan (1162?–1227?). And Attila should finally get some good press. He appears to have been a rather sophisticated Roman-educated leader—not a filthy barbarian, as he is often portrayed.
Start your search here: www.au.af.mil/au/awc/awcgate/awc/streland.pdf.
Walt Boyes
[email protected]
A: Fluid Kinetics used to sell a device which was used to detect the presence of communication cables in the ocean. I do not know if this device is still on the market, but it might be able to help find these legendary caskets. [Editor's note: This product line has been acquired by Subsea Systems of Ventura, Calif., www.subsea-usa.com.]
Steve Freitas, CCI
[email protected]
Q: You wrote about the potentials of process control in modeling and predicting the performance of non-industrial processes such as the economy. Could the laws of process control be also used to estimate the rate and consequences of global warming?
Harold Crowney
[email protected]
A: I did discuss some aspects of global warming when I wrote about the process dynamics of the Gulf Current (www.controlglobal.com/articles/2006/002.html) and also wrote a book titled The Post-Oil Energy Technology, (http://tinyurl.com/38o2yy7), which also included a discussion of the rates and time constants of global warming.
One can look at this process as one which started about 2 billion years ago when the atmosphere began to change from a reducing (CO2) to an oxidizing one (O2). This is the time when climate evolution started and life appeared on the planet. The atmospheric concentration of O2 stabilized at around 21% and its CO2 content never increased over 280 ppm during the last couple of million years, but during the industrial age greenhouse gases were admitted into the atmosphere, causing the CO2 content to rise to 360 ppm to 380 ppm, and this concentration is projected to reach 510 ppm by the turn of the 21st century (Figure 1).
Figure 1. The changing content of the Earth's atmosphere
It seems that life depends on the presence of liquid water (which can exist only between 0˚C and 100˚C) and on an atmosphere that protects life from both ultraviolet radiation and extreme temperatures. Weather is the state of the atmosphere that results from a number of processes. One of these processes is the heat balance of the planet.
Global temperature is a somewhat self-regulating process because, as the heat input of the planet increases, the excess heat is removed by increased vaporization of the oceans and increased melting of the polar ice caps and glaciers. Melting and vaporization both increase the overall water circulation on the planet (storms, rain, floods), while increased vaporization also dries land areas, increasing the frequency of forest fires, water shortages and desertification.
While the melting of the ice requires heat, and therefore temporarily cools the planet, it has the reverse effect in the long run, because ice and snow reflect more radiation back to space than does water. The reflection coefficient, the Bond albedo, says 29% of solar radiation received is scattered back into space, but as ice melts, that number drops.
Water serves as the natural temperature controller of the planet, but this thermostat can only increase its cooling effect so long as there is ice at the glaciers and the poles. Once the ice is gone, the temperature will jump because incoming solar energy will be absorbed by the melting ice, and therefore, besides providing the energy needed to support life on Earth, the excess heat coming from the sun has to increase the temperature of the planet itself. While the overall planet warms, there will also be localized cooling caused by the stopping of ocean currents, such as the Gulf Current, which is a gigantic heat conveyor, moving the heat from the Equator to Europe and the east coast of the United States.
The heat input of the planet is received from the sun and is a variable. Over the past few hundred years, there has been a steady increase in the numbers of sunspots and the Earth's temperature has also increased in proportion to them by about 0.2˚C. On the other hand, as shown by the figure to the right, during the last half century this process reversed, solar activity was dropping while the temperature of the planet increased (Figure 2).
For the dynamics of the atmospheric heat balance process, we have fairly good historical data concerning the dynamics and effects of hurricanes, wind, rain, clouds, CO2 content, smoke, etc. The energy content of a larger hurricane approaches the energy consumption of the United States for about a year and serves to equalize the air temperature in the stratosphere. As far as the dynamics of the thermal processes on the continents and in the oceans goes, the inertia and time constants of the process are much greater and take much more energy to move or reverse.
So what are the variables (the control valves if you wish) that can influence the operation of this heat transfer control loop? What can humans manipulate (accidentally or intentionally) to lower and stabilize the global temperature?
- Lower the amount of the incoming solar heat by introducing large quantities of solids into the atmosphere to block the sun's radiation. This can occur due to natural causes such as nuclear wars, large fires or volcanic activity.
- Change the reflectivity of the planet's surface by making roofs and road surfaces more reflective (lighter in color).
- Rebalance animal and plant life by the introduction of gigantic algae farms in the oceans or by other means.
• Lower the CO2 concentration of the atmosphere by gradually replacing fossil fuels with solar-hydrogen and other renewable energy sources.
It seems that the simplest variable to manipulate is to gradually stop the burning of fossil fuels. This we can do voluntarily and in a planned manner on the time frame dictated by the process control model, or we can let nature do it for us as fossil fuels are exhausted. The consequences of the second can be drastic and can possibly cause the collapse of human civilization (turn the process into a batch one).
Béla Lipták
[email protected]
