Think you can multitask? Think again – Stanford's Clifford Nass and author Nicholas Carr argue that the internet is reprogramming our brains and shrinking our attention spans. 

Is technology distracting us from the real relationships in our lives? 
Friday, August 2, 2013
Myths of Multitasking
Monday, July 15, 2013
Links to my book & DVDs: Ancient Computers, Edition 2
Introduction
My first Abacus publication was The Roman Hand Abacus (2003). But then my studies continued.As an engineer and math teacher, my approach was to use historical clues to figure out the structure of an ancient counting board abacus and the way it was used. The clues were: The Salamis Tablet, the Roman Hand Abacus, and the Japanese Abacus (Soroban). The sources listed below this Introduction contain my analyses and conclusions.
Some surprising results:
 All four arithmetic operations are accomplished with surprising ease.
 Multiple number bases can be used (e.g., decimal, sexagesimal, or duodecimal).
 Numbers are held in exponential form; i.e., each number has two parts, a fraction and a radix shift (exponent),
 so no decimal point is needed, and no trailing zeros.
 Each number part can contain both positive and negative values.
 There's some builtin error checking in the number entry process.
 There is extreme pebble/token efficiency:
 Multiplication or division of two base10 numbers with 10 digits in their fraction part and 4 digits in their exponent part can be expressed with an average of about 1.9 x 14 x 4 ~= 100 pebbles or tokens. Just a small bag of pebbles for a Roman and two rolls of pennies for a modern user.
 The Ancient Babylonians using base60 numbers with 5 digit fractions and 2 digit exponents would only need on average about 2.9 x 7 x 4 ~= 80 pebbles or tokens.
 In the videos I use Heron's method to calculate the square root of 2 in sexagesimal to the precision on Yale tablet YBC 7289 in only 25 minutes; blindingly fast for that time (c. 18001600 BCE). Especially since the Babylonians wrote their numerals on clay tablets with reed styluses that they cut with bronze knives sharpened on stones  no paper or pencil.
Ancient Computers, Part I  Rediscovery, Edition 2:
Free online prepublish paper. (+ older version at http://arxiv.org/abs/1206.4349.) 

Paperback Book, ISBN 1490964371 Kindle eBook, ASIN: B00DVPPQ78 

Back and Front Covers 
Ancient Computers, Part II  Video Users' Manual:
DVD1. How To Use A Counting Board Abacus (First 12 of these free YouTube videos; but DVD has no ads.) 

DVD2. How Romans Used A Counting Board Abacus (Remainder of these free YouTube videos; but DVD has no ads.) 
Ancient Computers, Part III  You Do It:
Three Tablet Abacus on Paper, 36 in. x 24 in. You may have the file printed for your personal use. 
Ancient Computers, Part IV  You Do It, Advanced:
In video 9.2, position 2:20, I issue a challenge to historians. I ask them to calculate the square root of 2 in sexagesimal their way using clay and reeds and to record their entire process in a publicly viewable internet video; then to compare their time to my time of 25 minutes using a counting board abacus.I point out that I'm a rank beginner abacist and that speeds approaching a Soroban master may be possible.
I challenge you to use a counting board abacus to beat my time and publish your video on YouTube. Please leave a comment on video 9.2 with a URL link to your video so people can verify the correctness of your solution and your time.
Saying Thank You:
Click Thank You to send me a buck or two; as a retired teacher I could sure use it!Sunday, February 10, 2013
Questioning Performance Claims Made by Value Line
From http://www.vlfunds.com/funds/valueline on 2/9/2013:
Value Line Fund  VLIFX
Investment Objective
and Strategy (Condensed)
The Fund’s primary
investment objective is longterm growth of capital. Current income is a
secondary investment objective.
To achieve the Fund’s
investment objectives the Advisor invests substantially all of the Fund’s net
assets in common stocks. While the Fund is actively managed by the Adviser, the
Adviser relies primarily on the rankings of companies by the Value Line
Timeliness™ Ranking System (the “Ranking System”) in selecting securities for
purchase or sale. The Fund’s investments principally are selected from
common stocks ranked 1, 2 or 3 by the Ranking System at the time of purchase.
The Adviser will determine the percentage of the Fund’s assets invested in each
stock based on the stock’s relative attractiveness.
[Hmm ... Not showing 300% better than
S&P 500 here; why not?]
0.25% = 12b1 Fee, 0.69% = Max Mgmt Fee
Expense Ratios Before & After Waivers: 1.29%, 0.94%.
0.25% = 12b1 Fee, 0.69% = Max Mgmt Fee
Expense Ratios Before & After Waivers: 1.29%, 0.94%.
From https://personal.vanguard.com/us/funds/snapshot?FundId=0040&FundIntExt=INT:
Vanguard 500 Index Fund Investor Shares (VFINX)
As the industry’s first index fund for individual investors,
the 500 Index Fund is a low cost way to gain diversified exposure to the U.S.
equity market. The fund invests in 500 of the largest U.S. companies, which span
many different industries and account for about threefourths of the U.S. stock
market’s value. The key risk for the fund is the volatility that comes with its
full exposure to the stock market. Because the 500 Index Fund is broadly
diversified within the largecapitalization market, it may be considered a core
equity holding in a portfolio.
Expense ratio as of 04/26/2012: 0.17%;
This is 85% lower than the average expense ratio of funds with similar
holdings. [And 81.9% lower than VLIFX,
even after VLIFX’s “waivers.”]
Retrieved 2/10/2013 from http://finance.yahoo.com/echarts?s=%5EGSPC+Interactive#symbol=^gspc;range=19900102,20130210;compare=vfinx+vlifx;indicator=;charttype=area;crosshair=on;ohlcvalues=0;logscale=off;source=undefined;:
S&P 500 (blue mountain), Vanguard 500 (red), Value Line Fund
(green).
So a fund expertly managed by Value Line using their own
Value Line Ranking System LOST 40% over the last 23 years.
Value Line Ranking System LOST 40% over the last 23 years.
Closely tracking the S&P
500, the
Vanguard 500 fund GAINED 330% over the last 23 years.
Vanguard 500 fund GAINED 330% over the last 23 years.
How
can Value Line justify their envelope claim?
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