Re: General semantics
Date: Thu, 20 May 2010 14:31:31 -0700
Message-ID: <kdabv5l26gvl5jrbai7jqcuun7tmv49l98_at_4ax.com>
On Thu, 20 May 2010 13:52:24 -0700 (PDT), Tegiri Nenashi <tegirinenashi_at_gmail.com> wrote:
>On May 20, 9:24 am, Gene Wirchenko <ge..._at_ocis.net> wrote:
>> On Wed, 19 May 2010 18:54:45 -0700 (PDT), Tegiri Nenashi
>>
>> <tegirinena..._at_gmail.com> wrote:
>> >On May 19, 5:22 pm, paul c <toledobythe..._at_oohay.ac> wrote:
>> >> ... The message I got from the book, at least the practical conclusion, is
>> >> that we must always think separately about a system and reality, ...
>>
>> >This is a recurring theme in many science endeavors. I remember a
>> >story told by prof Mark Krasnoselski (RIP). "Here is a linear dynamic
>> >system with a simple positive lookback. It converts an input x(t)
^^^^
An input on x at time t?
>> >into x(t-T). Think about it: it predicts the future! When this has
^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^
An input on x at time t-T?
What is T?
How does this follow?
>> >been discovered many "hands-on" people rushed to make actual
>> >implementations! Than he paused.... Do you understand the difference
>> >between the model and reality?"
>>
>> Could you please unpack this? I do not have the background to
>> follow the story, but I understand the conclusion.
>
>Not sure what you are asking. The background
>http://www.stanford.edu/class/ee102a/lecture4x4.pdf
>It studies systems assembled out of well defined primitive blocks such
>as delay, integrator, differentiator, etc. I don't remember the detail
>of the system in question, other than it contained a no more than two
>elements arranged in a simple feedback loop and one of them was delay.
>One reason why it doesn't work as intended is because it is unstable.
Sincerely,
Gene Wirchenko Received on Thu May 20 2010 - 23:31:31 CEST