Random Ruminations: Engineering

MacGyver Engineering

Posted Sat Oct 15, 2011 in Engineering

While I’m waiting for my coffee to finish brewing, I’m cleaning out my email inbox. It got away from me the last couple of days, as did my recording of time for my weekly timecard. I’ll probably tackle that a little later this morning.

My graduate-school advisor sent this image the other evening. It probably sums up what most folks think about engineering and certainly represents the bulk of tools needed by MacGyver to extract himself from almost any situation. [grinning]

WD-40 really isn’t a lubricant; it’s a water-displacement material intended for use on objects that need chemical assistance to be loosened. It has a light penetrating solvent to penetrate small openings. As far as lubrication is concerned, it contain a light mineral oil, and that might be sufficient for some assembly lubrication (think door hinges).

The classic urban legend is of the police officer who used WD-40 to clean and lubricate his service revolver once each week. When the unfortunate time came for use of his sidearm in the line of duty, it failed to fire and he was killed. His choice of lubricants deactivated the cartridge primers, resulting in a failure to fire.

Regardless of the veracity of the oft-cited story or the ability of MacGyver to use anything at hand to accomplish the mission, the point is clear — use appropriate cleaners and lubricants for the job at hand, not a dose of “man-in-a-can.”

Comment [2]

Marketing

Posted Sun Oct 9, 2011 in Engineering

I’m on the email list for The Domino Project. A few days ago, this essay (very brief) crossed my desk via email. I read it, then set it aside.

While reviewing my email Friday (purging the inbox is a good thing) I returned to the email. Although I hate to admit it, I am a marketer. I market my services. I develop contacts and work toward developing new projects. It’s part of what I do. It’s been a part of what I do for a very long time now.

I never thought of myself as a salesman. I never thought I was in sales.

But I am. Moreover, I have been for a very long time. Without articulating it, I follow Godin’s thesis. I don’t market to strangers. I build relationships with people who need what I do and then work develops.

It takes time and energy to build those relationships. But it’s the only way I know to get work. Most people are reluctant to hire people they don’t know (at least not without a strong referral). They hire people they know.

It’s one reason it is so difficult to break into some markets. No one knows me.

Comment

Climate Change

Posted Tue Jun 7, 2011 in Engineering

I had just a couple of thoughts about climate change and renewable energy I thought I should get down. These topics deserve a lot more time and thought than I can give them at the moment.

My first thought is that climate has never been and never will be static. Earth’s systems are dynamic in nature and driven by many processes. These systems include the climate of the earth.

The prime driver of climate is solar output. I haven’t done detailed research, but I do know the solar constant is not so constant. It would be interesting to understand the variability of the solar constant and the sensitivity of the climate to that value. I’d like to do some research here, but don’t have time for it now.

I remain unconvinced that anthropogenic activity is the prime reason for recently-observed changes in global temperature. There is too much uncertainty associated with the measurement of global average temperature.

That said, I think one of the most important things we can do is to invest the resources necessary to determine how to move our energy supply from fossil fuels to renewable resources. The supply of fossil fuel is not infinite and our reliance on that resource will come to an end. I would prefer to see that occur not as a catastrophic event but as a planned shift from fossil fuels to other sources of energy.

This will require a reasoned investment of resources to determine how to make it efficient and effective. I agree with a lot of folks on the other side of the climate change issue that it is time to act in this regard.

Comment

Tired…

Posted Thu Mar 17, 2011 in Engineering

Maybe I’ll find a lead-in image for this entry later.

I woke early this morning, listening to my iPod and thinking about finishing up this project. I believe I finally understand and can execute all of the computations required. I have a meeting at 0800, then I will sit down at the computer, make my final decision on parameter values for the flow-duration and flood-frequency curves and finalize my estimates. I can then take those numbers and build the balanced hydrographs the prime contractor requires.

I should have that work done this afternoon. Then I can take an hour or so to review it. I’ll write up a brief draft report in the morning and deliver the materials tomorrow afternoon.

The analysis remains somewhat incomplete. I think the flood frequency curve derives from a mixed distribution of spring snowmelt events and rain or rain-on-snow flooding events. The two distributions are quite different with the snowmelt being left-skewed and the rain events having about zero skew (log-normal). A reasonable upper limit for spring snowmelt events appears to be about 10,000 cfs. There is no upper limit for the rain floods.

A combination of the two distributions is possible. (It’s a conditional probability problem.) However, that approach is inconsistent with the balanced hydrograph approach used to derive approximate hydrograph shapes for large events. Although I censored the daily discharges from the study streamgages, there are many years in which no substantial rain-flood event occurs. Therein lies the inconsistency.

It might be possible to resolve the apparent inconsistency, but there is no time available to complete the research and analysis necessary. That process will have to wait for the next project, or for additional time and funding to become available.

I think I’ll take off after I send my materials and do something else for the rest of the day. I’d like to get some range time in — the weather has not been cooperative lately and I’ve been too busy and too focused on this project to tear myself away anyway.

Comment

Risk of Complexity

Posted Wed Feb 9, 2011 in Engineering

I suspect there is a bit of mathematics that deals with this issue, but I haven’t tried to track it down.

I’m finishing up a highly-complex technical report. The source was generated by several individuals, jointly and independently. It is hosted on my Dropbox, but in a shared directory. Several of us edited the text, and then rendered it using the LaTeX typesetting system.

It was handed off to me today to complete a few minor changes and add a few things to the bibliography. I made the changes and then attempted to set the report.

Crash…

I spent the next three hours trying to figure out the problem. I haven’t gotten there yet.

When I look at the number of packages used by this LaTeX report, it’s no wonder there is a problem. No doubt it’s confounded by different installations of the software we use as well. I guess things are not perfectly compatible.

I count 23 packages included in the preamble of the source. If just one of them is interacting with a single package and causing the problem, then I think the number of possibilities is 23 taken two at a time. That’s 253 possibilities if I calculate correctly.

I’m not prepared to go through that systematically. I’ll spend a little more time trying to figure out where the specific issue lies. Hopefully that won’t take too long. Otherwise I’ll have to go through the laborious process of removing a package, setting the source, and checking the log.

Urgh…

Later: I finally had to comment out all of the package installs and the re-enable them one at a time. I never found out what the problem was, but I think it was loading order. Sometimes LaTeX is picky about how things are loaded.

At least my report is setting. I have a few more edits to make, but then will be done with my part — once again.

Comment

Expected Probability

Posted Tue Feb 8, 2011 in Engineering

Some years ago I came across the concept of expected probability. The context was a flood frequency analysis I was doing in the Denver area. After reviewing the data and running a fit of the Pearson Type III distribution to the logarithms of the annual peak series, I compared my results to those published for the stream.

They were different. They were a lot different at the one percent annual exceedance frequency. I was stymied.

I asked one of the senior engineers and his response was that it was probably based on the expected probability for the particular return interval. However, I couldn’t find the definition of expected probability.

Here it is.

It is an adjustment that attempts to consider sampling error, if I read the text correctly. In that context, the concept is useful in assessing the potential error in the estimate¹. However, it should not be used as an estimate of the n-year event. I believe that is what happened and that is the explanation of the difference between my estimate and the published estimate.

¹ Rare flood events have enormous uncertainty associated with them. The 50-percent confidence interval can easily be an order of magnitude (factor of ten). In addition, there is additional uncertainty associated with the use of logarithms as a skew-reducing transformation and identification of the appropriate probability distribution (probably not a Pearson Type III). If your take-home message is that this is messed up, you are correct.

Comment

Freaky Friday

Posted Fri Aug 27, 2010 in Engineering

This might be a running entry, or it might not. I’m starting early — it’s about 0600 as I write. I’m also starting tired. The last couple of weeks are beginning to tell.

There won’t be enough coffee to get me through the day, because caffeine will only be a support. Like the last few repetitions in a strength-training session, getting through the day will require just gutting-it-out. I love how Bill Phillips describes the last few repetitions in his book. He talks about how he stops focusing on training the muscle group and focuses on inner strength. It’s about disciplining oneself through the discomfort of the lactic-acid burn and the muscle fatigue to reach the goal — momentary muscle fatigue where the muscle refuses to contract one more time.

This is where I am mentally. I started really pushing on this project about ten days ago. The software didn’t work as it was supposed to. I wasted a few days trying to resolve the issue, but it would not resolve and had to be tabled in favor of a work-around. At least I can generate a HEC-RAS project, run the model, and return the inundation zone to the mapping software. But, the delay was costly and now it’s pay day.

So, today will be the day to grind through the last structure. I started a few minutes ago and am working on laying out the first hydraulic model prototype. I’ll be able to reuse a good part of my work yesterday, which means I only have to create a subset of the entire reach. This should speed up things a bit… or at least take a little of the mental load off. My little pea-brain is tired. I’m not whining (yet); just stating a fact.

Now I’m off to get another cup of coffee and turn my attention to the problem at hand. There will be more as I track progress through the day.

Oh yeah, I almost forgot to mention the image. That’s the draft zone of inundation for one of the structures. There are no details on the map (which is appropriate), but it’s a graphical depiction of what I do. The results will be used to assist development of an emergency action plan for the structure, which is used to guide parties responsible for emergency management in the (unlikely) event the integrity of the structure should be compromised.

Comment

| Next Page