Wednesday, January 21, 2009
How many pats of butter per day is "optimal"?
After reading Michael Trick's Operations Research blog post, "A Sheriff Goes to Jail for Not Using Operations Research" I followed the link he provided to the Menu Optimizer he cited. I've been interested in such models for many, many years.
My first professional assignment was to help food scientists doing product development use such models. In so doing, and reading an article or two in the ORSA (now INFORMS) journal, I came to appreciate their limitations and consider alternative ways to address the question possibly better. The major limitation was, and probably still is, palatability. Another challenge, also very hard to regulate, which jam-makers and wine-makers will understand, is the variability of the attributes of the raw materials; sugar content of grapes depends on the weather, where they were grown, and when they were picked, for a simple example.
The palatability challenge comes down to something like this: if all your meals of the week (which are the same as the meals of all other weeks) are put in the blender, would you be able to swallow one day's worth each day? Astronauts said "no" to the first "blends" and provoked the follow-up research on how many different tubes of paste were necessary and what combinations they could contain (if I am not mistaken [reference needed]). The opinions of cats, dogs and other "dumb" animals is harder to obtain, but there are industries trying to provide foods these animals will eat day after day, and which will keep the animals healthy.
One approach to the "palatability" constraint was researched and the results were published over thirty years ago. The first phase of the research was to gather "how often would you like to eat..." ratings. The second phase was the linear programming optimization with the results of the first phase as constraints (salmon not more than three times a week, coffee not more than once an hour except before 9:00 a.m., etc.). The cost of "minimum decent subsistance" with the variety constraints was nearly double the cost of just plain (water torture?) "minimum subsistance" without.
Consequently, and with all the disclaimers ("your doctor may not approve") as well, not to mention price-per-serving assumptions which may not be "current" where I live, I didn't expect an "optimal menu" I would want to eat every day in every season. But I didn't expect to be told a lot of popcorn and a baked potato with a fair amount of butter, and a little egg and broccoli and a few glasses of milk, would be my sentence.
The Solution and Cost Breakdown by Food
|3.3% Fat,Whole Milk||3.09||0.49|
- In an earlier trial, I had excluded "whole" milk and my diet included ten pats of butter per day.
- I did not tick "yes" to all the foods proposed.
- I haven't checked whether or not they have a constraint for the share (per cent) of calories from fats and greases.
Tags: diet, linear programming, operations research
Sunday, January 18, 2009
Times-ly RSS Feeds: Why Don't They Stay Fresh?
For quite some time, my browser "start page" has been Netvibes. I don't claim to make full use of it, but I find it a very convenient way to scan and dig-down into selected RSS feeds. I have a tab for personal and otherwise hard to categorize boxes, lists and widgets (weather, TV programs, Facebook, my own blog, delicious bookmarks, and so on), tabs grouping rss feeds from "UK Media", "US Media", "French Media", one for "opinion" and one for "econ" (including business), plus one for Meebo.
In my UK media tab, I have feeds from the Independent, The Guardian, and the Times Online, plus a couple of others. At the moment, of the fifteen headlines from the Independent, only one is over a day old. The Guardian list shows none older than today (Sunday!). The Times (UK) Online is usually pretty fresh, I thought, but right now their "World" headlines are all five (V) days old.
The French publishers (le Parisien, le Monde, le Figaro, Libé) are all full of stories from today. The seven French-language feeds from the Russian agency, RIA Novosti (which I included on this tab because it was French-language news) are all less than three (III) hours old.
I could skip the "econ" tab because I don't expect much fresh business news over the week-end, but the stories from the Financial Times and NYT are all from yesterday and today; I think that is worth noting.
Nevermind the "opinion" tab; its contents are such a mixed bag, and uncadenced, that there is not much to notice about freshness.
Let's go back to the US media tab, now. At one point, I had a selection of feeds from the New York Times, the Los Angeles Times, and the Christian Science Monitor. The selection did not include "sections" I would expect to be rarely published. For the LATimes, I follow the National News, World News, and Local. For the NYTimes, I've given up and removed their feeds; I'll explain below. From the Christian Science Monitor, I follow "top" stories--now two days old, so I guess they respect the Sabbath and don't write on Saturday or Sunday.
The feeds from the NYTimes I followed were much the same categories as those from the LATimes: major, standard categories suitable for the top stories. But for some reason, the lists often got stale. Perhaps they forgot to put stories in the standard categories, just kept inventing newer and better categories/feed-names, then changing their collective mind and going back...it was hard to tell. I was not willing to subscribe to fifty (L) from each paper and scan all of them trying to spot the fresh stories: that is what RSS is supposed to do for me! Now, here is the current status (extracts of a screen-cap from a few minutes ago) of the LATimes feeds. "1 mois" means the local stories are a month old; "1 semaine" means the world news is a week old.
The feeds are not always this stale. There is not a systematic lag of a week in the world news. These stories were "fresh" and appeared as "1 hour" old when they were one (I) hour old; but curiously, they have not been replaced by newer stories. Or, even more curiously, they may have been succeded by newer stories, but then the newer stories vanished from the list allowing these stale ones to reappear.
Why is it that British, French and Russian news agencies and papers master the administration of rss feeds and major American papers don't? A variety of possibilities come to mind:
- Too high-tech, can't find competent rss-feed managers in America.
- The problem is not in America, but in India: poor choice of outsourced administrators.
- Nobody notices. Americans don't consume rss feeds, so administration quality doesn't matter.
- Twitter has replaced rss.
- Americans consume the feeds provided by Yahoo!, Windows Live, AOL without supplementing their information diet with Times-ly titles.
- All of the above.
In any case, the Timeses get a much smaller share of my attention than European media do, simply because they make it too hard to find fresh content on breaking stories.
Tags: LATimes, rss feed freshness, Netvibes, NYTimes
Better Bremner: on airmanship and Airbus
In his blog post from last Friday, Airmanship, not miracle, saved US Airways jet in New York, Charles Bremner demonstrates that he is much more knowledgeable (perhaps because more interested--quote I can imagine the picture well because I used to pilot light aircraft along the same low path over the George Washington Bridge and down the Hudson beside Manhattan.) about planes and flying than the place of China in the global supply chains. I recommend this piece, as well as two ( In case you were wondering, about that airplane in the Hudson and Two quick followups about the airplane in the Hudson) by James Fallows, another experienced pilot.
Since Bremner is sometimes accused of French-bashing (by SuperFrenchie, for one: "Bremner: Maybe We Can No Longer Say We’re So Superior But That Ain’t Gonna Prevent Us From Bashing You Anyway!") I'd like to highlight his inclusion of this paragraph:
Praise is also going to the three cabin crew who organised the evacuation of the 150 passengers. And there is credit for the French-based European Airbus firm for building a tough airliner. Among other things, unlike Boeings, the Airbus has an emergency "Ditch button", which closes vents and makes the fuselage more watertight. Airbus pilots have always been sceptical about the button, on the overhead panel. Today, they are saying today "Oh, so that's what it's for."
[UPDATE] In The Guardian story "Pilot tells of crash-landing as plane pulled from Hudson river" it is noted that (emphasis mine):
The co-pilot kept trying to restart the engines, while checking off emergency landing procedures that the crew normally begins at 35,000 feet, rather than their altitude of 3,000ft (900 metres).
After guiding the gliding jet over the George Washington Bridge, Sullenberger picked a stretch of water near Manhattan's commuter ferry terminals to land. Rescuers were able to arrive within minutes.
The descent happened so fast the crew never threw the aircraft's "ditch switch," which seals off vents and holes in the fuselage to make it more seaworthy.
Nevertheless, I'm glad to know Airbus has this feature.
Postscipt: I had happened to catch the television coverage, live, as the passengers and crew were pulled on to the boats which had quickly clustered around the floating plane. I try to believe I would have turned it off if things had gone badly. I almost turned it off very quickly because one of the French "journalists" providing commentary on i-télé kept talking about the plane which had gone down in Hudson's Bay! French can be geographically challenged, too, evidently.
Identificateurs Technorati : Bremner, Airbus, Hudson River, Fallows, pilots