### sepdek

#### Determine the date of a webpage

October 21, 2017

There is often a need to use a webpage as a reference. So how is it possible to get the most recent date that webpage was updated? There have been people suggesting that one might exploit the power of google and execute a specific kind of search that might reveal the date of a webpage. […]

#### AppleScript control of login items

October 7, 2017

Everyone loves automation. Automation is conservation of energy; its like the habits we people are into, the habits that seem to be there for all living entities. One great automation option we may enjoy in our everyday work is that provided by the operating systems on our computers to perform tasks for us. One such […]

#### A basic step-by-step Linux shell-based web server installation

July 4, 2017

The following set of shell commands are among the basic steps to setup a Linux-based web server (LAMP=Linux Apache MySQL PHP). The procedure has been tested on an Ubuntu 14.04.05 Trusty Tahr (LTS) installation. Most steps and procedures are based on the tutorial found in DigitalOcean and in the linked pages. In the commands that […]

#### Imagine

November 11, 2016

imagine
you exit to where there is no exit
just to look at what’s inside
and build more bubbles out in the nowhere
not to feel alone in the dark,
but this transforms nothing to something
by this simple given thought
and then you run back into symmetries
for a meaning all in all,
on a stage of equal weights
on which singulars are stars

#### Differentiation cheat sheet

October 13, 2016

This post serves as a cheat sheet for differentiation. It just includes the most basic of the rules to be remembered when computing derivatives. First a little reminder on the notation being used in differentiation. Leibniz’s notation for the first derivative of a function f(x) is Newton’s notation for the first derivative of a function […]

#### On critical points of functions

October 12, 2016

There is a really large number of applications in engineering, in which the identification of critical points of a function is crucial for the analysis and modeling of a process or a system. Generally, one may identify three kinds of critical points, that is (a) maxima, (b) minima and (c) saddle or stationary inflection points. […]

#### Functions and graphs primer

October 9, 2016

A function is a rule that maps each of the elements in a domain to one and only one element in a range. The set of all possible elements in the input is the domain D of a function; the set of all possible elements in the output is the range R of a function. […]

#### Handy & powerful differentiation method

October 8, 2016

Formally stated, the derivative of a function of the form with k a constant and with respect to an independent variable x, is simply, I find this to be extremely handy in all cases. Consider the simple case in which, In the same way, In a more complex example, In an even more complex example, […]

#### A short note on functionals, conservation, invariance and symmetry

October 8, 2016

The thing starts with invariance, conservation and symmetry… Invariant is something that is unchanged by a coordinate transformation. Conserved is something that is unchanged by a process within a given coordinate system. Symmetry could be considered a broader property of some ‘universe’ in which some entity of interest remains the same under a specific operation. […]

#### Measure and Metric cheat sheet

October 8, 2016

In order to be a measure (distance) d must:   In order to be a metric (distance) d has to be a measure and:   …and here is the cheat sheet:

#### Remove from a Twitter list

June 2, 2016

Strangely, although anyone can add somebody in a Twitter list, Twitter does not offer a simple “Remove me from list X” option. Adding somebody to a list is not controlled by the person being added, at least in the default Twitter setting. Nevertheless there is a way, rather awkward way that is, to remove oneself […]

#### JSON data on the Android mobile with App Inventor 2

June 20, 2015

Recently I have been experimenting with MIT app inventor 2 on the Web to check the development cycle and production time. It turns out that the platform is extremely productive and offers numerous features for Android app development. In a day I have been able to develop a relatively simple app and in two hours […]