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THE ARAL: A DYING SEA

       The Aral Sea was once the fourth biggest landlocked sea in the world – 66,100 square kilometers of surface. With abundant fishing resources, the Sea provided a healthy life for thousands of people.           

    The Aral receives its waters from two rivers – the Amu Dar’ya and the Syr Dar’ya. In 1918, the Soviet government decided to divert the two rivers and use their water to irrigate cotton plantations. These diversions dramatically reduced the volume of the Aral.

      As a result, the concentration of salt has doubled and important changes have taken place: fishing industry and other enterprises have ceased: salt concentration in the soil has reduced the area available for agriculture and pastures; unemployment has risen dramatically; quality of drinking water has been declining because of increasing salinity, and bacteriological contamination; the health of the people, animal and plant life have suffered as well.

      In the past few decades, the Aral Sea volume has decreased by 75 percent. This is a drastic change and it is human induced. During natural cycles, changes occur slowly, over hundreds of years.

      The United Nations Environment Program has recently created the International Fund for Saving the Aral Sea. Even if all steps are taken, a substantial recovery might be achieved only with 20 years.

(From: https://www.unenvironment.org/) 

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What is a Content Management System (CMS)?

July 19, 2018

      A content management system, often abbreviated as CMS, is software that helps users create, manage, and modify content on a website without the need for specialized technical knowledge. In simpler language, a content management system is a tool that helps you build a website without needing to write all the code from scratch (or even know how to code at all).

      Instead of building your own system for creating web pages, storing images, and other functions, the content management system handles all that basic infrastructure stuff for you so that you can focus on more forward-facing parts of your website. Beyond websites, you can also find content management systems for other functions – such as document management.

      The content management system is not just a backend management interface, though. It also makes all of the content that you create show up for your visitors exactly like you want it to.

(https://kinsta.com/knowledgebase/content-management-system. Adaptado) 

      Classes which are arranged in a circle make quite a strong statement about what the teacher and the students believe in. With all the people in the room sitting in a circle, there is a far greater feeling of equality than when the teacher stays out at the front. This may not be quite so true of the horseshoe shape, where the teacher is often located in a commanding position, but, even here, the rigidity that comes with orderly rows, for example, is lessened.

      With the horseshoe and circle seating, the classroom is a more intimate place and the potential for students to share feelings and information through talking, eye contact or expressive body movements (eyebrow-raising, shouldershrugging, etc.) is far greater than when they are sitting in rows.

                                      (Harmer, J. The practice of English language teaching. 2007)

1. What is an analog-digital converter?

An Analog-Digital Converter (ADC) is a widely used electronic component that converts an analog electric signal (usually a voltage) into a digital representation. The ADCs are at the front-end of any digital circuit that needs to process signals coming from the exterior world. Its schematic symbol is:

The output of a microphone, the voltage at a photodiode or the signal of an accelerometer are examples of analog values that need to be converted so that a microprocessor can work with them.

2. How does the ADC convert a signal?

Many ways have been developed to convert an analog signal, each with its strengths and weaknesses. The choice of the ADC for a given application is usually defined by the requirements you have: if you need speed, use a fast ADC; if you need precision, use an accurate ADC; if you are constrained in space, use a compact ADC.

All ADCs work under the same principle: they need to convert a signal to a certain number of bits N. The sequence of bits represents the number and each bit has the double of the weight of the next, starting from the Most Significant Bit (MSB) up to the Least Significant Bit (LSB). In a nutshell, we want to find the sequence of bits bN−1, bN−2, ..., b0 that represents the analog value Vin as Vin=∑n=0N−1bn2nVref2N.

                                (www.onmyphd.com/?p=analog.digital.converter. Adaptado)