Peeling the Onion

As you can imagine, there is no way I can write about every conceivable problem that may arise. And for sure, I haven t seen all the possible problems either. That s what makes power so much fun. But maybe I can share a tip or two with you. Because even though we all learn a little more every day, all we are really destined to see eventually is a tip— the tip of the iceberg. Luckily, we do eventually develop a certain type of logic that can help us get through the next problem a little more easily. And that s what I am going to talk more about here. 

What do I mean by taking out everything superfluous That could mean any external circuitry not directly linked to the core functionality (such as current limits, OVPs, crowbars, OTPs, etc.). But it can mean much more. For example, a few days ago I walked into the lab to talk to a junior colleague of mine. He happened to be looking at some minor issue on a small DC-DC converter board in front of him. It was meant for a Li-ion cell input, and set for IV output. Suddenly, he started looking really puzzled. Why is the input 

8) Is there some strange interaction with the load  

11) Am I doing something known to be risky (to start with)  

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Now, where could the problem lie Is it within the power supply stage itself, or is it external If you have peeled the onion as I suggested previously, you are hopefully sure the efficiency is not being lost within the EMI filter of your AC-DC power supply. Bypass or disconnect everything external and confirm you have a problem. 

Put the diced tomatoes in a medium-size saucepan over medium heat. Peel the onion, slice it in half, and add one entire half to the pan along with the butter. Bring to a simmer, then reduce the heat to medium-low, and let the sauce simmer gently, stirring now and then, while you make the meatballs. Dice the rest of the onion finely and put it in a large mixing bowl. 

The reason why our eyes weep copiously when peeling an onion is because the onion contains minute pockets of sulphur trioxide, S03(g). Cutting the onion releases this gas. A mammalian eye is covered with a thin film of water-based liquid ( tears ) to minimize friction with the eyelid. The tears occur in response to SO3 dissolving in this layer of water to form sulphuric acid ... 

Fig. 7.28 Erosive dispersion of a carbon black agglomerate in butadiene rubber (BR) in simple shear flow, showing (a) the onion peeling mechanism, (b) a ribbon peeling mechanism and (c) both mechanisms. [Reprinted by permission from M. Astruc, Etude Rheo-optique des Mecanismes de Dispersion de Melanges sous Cisaillement Simple 1. Melanges concentres de polymeres immiscibles, 2. Melanges polymeres-charges poreuses, Doctoral Dissertation, Sophia Antipolis, Ecole des Mines de Paris, France (2001).]...

Trevor Kletz often described accident investigation with the story of peeling an onion. In the opening paragraph of Learning from Accidents in Industry, [6] Kletz states ... 

Accident Investigation is like peeling an onion or, if you prefer amove poetic metaphor, the dance of the seven veils. Beneath one layer ofcauses and recommendations there other less superficial, layers. The outer layers deal with the immediate technical causes while the inner layers are concerned with ways of avoiding the hazards and with the underlying causes such as weaknesses in the management system. Very often only the outer layers are considered and thus we fail to use all of the information for which we have paid the high price of an accident.. . . ... 

When we strip off as layers of convention all differences among ways of describing it what is left The onion is peeled down to its empty core, (ibid., 118)... 

Thus, the process-improvement approach to the safety of the medication-use cycle goes beyond the celebrated cases and first stories to scientifically investigate the system as a whole. Data on near-misses and uncelebrated errors should be analyzed to find hidden flaws and strengths, and to better understand the dynamics of our medication-use system. Scientific investigation of the whole cycle— peeling away the layers of the onion—will reveal latent points of failure and facilitate a redesign that substantially reduces the occurrence of harmful outcomes. 

The term mechanism has been Ifeely used in the foregoing sections, but without definition this is because it admits of no simple description, there being many formulations considered by their begetters to be adequate and satisfactory. Mechanistic discussion is like peeling an onion it is possible to go through a never-ending series of ever more profound analyses without ever reaching the end. 

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