মৃত্যু; এক অনিবার্য সত্য মানুষের জীবনে। শুধু কী মানুষের জীবনে? মৃত্যু তো সবারই হয়। হ্যা তা হয় কিন্তু শেষ নিঃশ্বাস পর্যন্ত বাঁচার আশা আর স্মৃতি ধরে রাখার গুণটি মানুষেরই আয়ত্তে। জহির রায়হান তার স্বল্প পরিসরের গল্পের মধ্যে জীবনের কঠোর সত্যগুলো তুলে ধরেন। তেমনি কয়েকটি মৃত্যু গল্পে মৃত্যুর আশংকায় শঙ্কিত কিছু মানুষের স্বার্থপর চেহারা তুলে ধরেছেন।

গল্পের পটভূমি বুড়োকর্তা আহমেদ আলী শেখের পরিবারকে নিয়ে। চার সন্তান ও নাতি নাতনীদেরকে নিয়ে বুড়োকর্তার সুখী পরিবার। কোন এক আনন্দঘন রাতে বুড়োকর্তার দেখা এক দুঃস্বপ্ন পারিবারিক সম্পর্কগুলোকে ওলটপালট করে দেয়। স্বপ্নটি সাধারণ কোন স্বপ্ন নয় বরং বুড়োকর্তার বাবা ও ভাইকে হারানোর অতীতের এক কালো সংকেত; পরিবারের কারো মৃত্যুর সংকেত!

পারিবারিক সম্প্রীতির আড়ালে স্বার্থপর চেহারা উন্মোচিত হয়। স্বামী-স্ত্রীর মাঝের দূরত্ব স্পষ্ট হয়ে ওঠে! সম্পত্তির নেশায় ভাইয়ে ভাইয়ের সম্পর্কে চিড় ধরে। সম্পর্কের এই পালাবদলে শুধু পালটায় না বাবা-মা এর সন্তানের প্রতি স্নেহ ভালোবাসা। বুড়োকর্তা ও স্ত্রী জোহরা তখনও প্রার্থনা করে নিজেদের জীবনের বিনিময়ে সন্তানের জীবন বাচানোর!!!

লেখক এই গল্পের ইতি টেনেছেন মৃত্যুর মধ্য দিয়ে নয় বরং সৃষ্টির মধ্য দিয়ে। বাড়ির পুরাতন চাকর আব্দুলের যমজ বাচ্চার জন্মের মধ্য দিয়ে গল্প শেষ হয়। কিন্তু আসলে এই সৃষ্টি নবজাতকের নয়। এ সৃষ্টি  বুড়োকর্তার পরিবারের সবার। মিথ্যে ও ঠুনকো পারিবারিক সম্পর্কের মৃত্যুর মধ্য দিয়ে প্রকৃত সম্পর্কের সৃষ্টির রূপক এই নবজাতক বলে আমি মনে করি। 

প্রিয় উক্তিঃ- 

 

"উত্তেজিত করছি কি আর সাধে! ঘরে ছেলেপেলেগুলো আছে তাদের কথা আমাকে ভাবতে হবেনা? খোদা না করুক আজকে যদি তোমার কিছু একটা হয় তাহলে ওদের নিয়ে আমি দাঁড়াবো কোথায়? "

"আশ্চর্য । আমি মরে গেলে আমার মৃত্যুটা তার কাছে বড় নয়। বড় হল কেমন করে সে খাবে। পড়বে। বাঁচবে।"

 

 

 

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Imagine a day without electricity! Irritating! disgusting!! and you feel so much helpless. Picking up your phone and gadgets and suddenly you remember "Oh! there is no electricity" It's disheartening right? We shout, blame the provider but don't try to understand why our loads are being shaded. To grab an idea, let's try to understand how the generated electricity is at our door; the concept of Grid System.

What is Grid?

You must have seen generators in shops, complexes, offices, markets, etc. When the electricity is out, they are used to provide a backup. But where is the generator that provides electricity to the whole country? Is there only one generator or several? The answer is, there are numerous generators connected together to serve the country. And the way they are connected to each other and to the users' end is known as grid. Therefore, grid is an interconnected network with different components working together.

How does grid works?

As we all know there are 3 blocks of operation generating station to users' end i.e. Generation, Transmission, Distribution. Let's discuss one by one.

☛ Generation: Electrical energies are generated, actually not generated but transformed from other sources (water, coal, gas, nuclear, etc.) by mechanical means.

Hydro-electric Power Plant

There are numerous power plants all over the country like this. The output from these stations are connected to different nodes create a common energy bus. The transmission system starts from here.

☛ Transmission: The generated electricity is stepped up to a higher potential of about 33 KV through transformers for transmitting to a long-distance without a severe drop in the transmission line.

Transmission

☛ Distribution: These high voltage transmission wires end in substations outside the towns. There, with the help of step down transformers, the potential is stepped down to 11 KV Again they are stretched to the substations inside the town and stepped down to 220 V (3 phase 4 wire), and then single-phase supply is provided to the houses. The three-phase supply (11 KV) is given to the industries on demand. 

Power system 

This diagram shows the entire system from producer to consumer. And the entire network with all these components is called Grid. All the generating stations contribute to the grid and also work as a backup for other stations. Many interesting topics are related to this grid. Or do you think it's so simple as stated above! 

When I studied Grid System, a number of questions came in my mind that why it is necessary to interconnect so many generators together? Can't a single generator serve the purpose? And why different countries have separate grids? Why not a single grid is created all over the world that connects all the countries?

Do you also have these questions in your mind? If so,  stay with us and find your answers. Visit the next article to know about a great scientist and his unfinished inventions! Readout Tesla Vs Tesla.

Image Source:

* Circuit Globe

* Giphy

In the previous articles, we've discussed different features and UI of COMSOL. There's a lot yet to be discussed but it is a better idea to learn them through designing a structure. What do you think? But before jumping directly into the process, we first need to know which phases we need to follow.

Now have you ever tried to design a structure? Maybe no. But those who have tried to learn SOLIDWORKS or similar software, you may know the fundamental blocks are;

1) Designing blocks:

▣ Selecting the Material

▣ Specifying the Parameters 

▣ Selecting the Components

2) Simulation blocks:

▣ Defining the Mesh

▣ Selecting the Solver Type

▣ Creating the Simulation profile

▣ Defining the Boundary Conditions

From the previous article, we know that the necessary information regarding a model is concerned with the Model Builder Window (Model Tree). Let us explore this section a bit more deeply.

** We will be using Electromagnetic Heating > Joule Heating as Physics & Stationary as Study. **

Model Tree

This is the resulting Model Builder Window. Here we can see a Root Node which is initially, set as Untitled.mph. This is named under the model file. Two subnodes, Global Definitions & Results are the basic ones. Under Globar Definition, we have the subnode of Material, which represents the material of the model. We can set up the material from the material library. Also, we can have the parameters here.

Parameters

Again the materials of the design can be selected from the Material Library. This library offers a vast option to choose the proper material even it offers user-defined materials!!!

Material Library

And under the Result subnode, we have,

1	Datasets	List of solutions
2	Derived Values	Defines values to be derived from the solution using post-processing tools
3	Tables	Stores the real-time simulation solution
4	Export	Defines numerical data, images & animations to be exported to files
5	Reports	Contains automatically generated reports about the model in HTML/MSW

Results (Datasets)

Results (Table)

As we can see there are additional subnodes in the result node which are not mentioned in the table, i.e. Views, 1D Plot Group 2, etc. These results are added during the simulation process. 

The reminder is that you can always edit the associated settings of each component of the model tree in the Settings Window.

Visit the next article COMSOL Multiphysics Part - 04: What It Takes To Design A Structure - II for Component & Study discussion.

Image Source:

* Freelancer

So, we're talking about the steps to form a design in COMSOL. And after a hazy discussion, we were left with 2 subnodes; Component & Study in the Model Tree. The immense significance of these 2 nodes calls for a separate discussion. Don't you think so? Let's first talk about the Study!

According to our early discussion, we know that the Study sets up the solver type (i.e. Stationary, Time-dependent, Frequency-dependent, etc.).

Model Wizard automatically creates the nodes under Study while simulation. Additional studies can be added from the study tab from the Ribbon.

So, we can switch between different studies and compute. Each study has a Compute button to run simulation for the selected study. The settings & boundary mode operations and configurations can be set here. It is very much important to simulate the model with the correct study. The result nodes will be added as per the selected study.

Coming to the Components node, it comprises of multiple sections as;

✦ Definitions: Defines the variables, boundaries, system selections, and their modifications.

✦ View: It gives the axes settings.

✦ Geometry: Gives the necessary options to build the model.

✦ Materials: Materials property like refractive index and others can be specified here. You can also add material in this node.

✦ Mesh: The whole model is divided into numerous small nonoverlapping elements. The behavior model is approximated by assembling all the elements' behavior. As COMSOL is based on the Finite Element Method (FEM), it is highly dependent on meshing. Here we can select the mesh type (rectangular, triangular, square, etc.), their size, and the relative setups.

✦ Physics: Gives selection options based on the selected Physics.

✦ Variables: Numbers, parameters, built-in constants, unary and binary operators can be set as Global or Local variable. Variables are listed under the Definition tab. Too many variables can be grouped together using the Node Group feature.

In the next segment, we will try to design a model. Till then explore & learn. Keep in mind, software can't be taught by articles. These articles are to provide a guide. One has to learn the software by exploring it.

And be with us for the next article and yes obviously for the video tutorial !!! 

Image Source:

* COMSOL Multiphysics

As we talked earlier, we have different kinds of Arduino boards with different specifications. These boards extend the area of working with Arduino. For different purposes, different boards are preferred over others and more compatible. We now want to talk about them. In this part, we'll be demonstrating;

-- Arduino Uno

-- Arduino Mega

-- Arduino Due

-- LilyPad Arduino

-- Arduino Leonardo

-- Arduino Nano

-- Arduino Micro

But before that, we need to have some ideas on some terms;

⌕ Flash Memory: It is the program memory of the Arduino where the Arduino sketch is stored.

⌕ SRAM: It stands for Static Random Access Memory. The sketch creates and manipulates variables here when the programs run.

⌕ EEPROM: It is the memory where the programmers store their long-term information.

Now the fact to notice is that, Flash memory & EEPROM are non-volatile memories that persists for a long time after the power being off. But the SRAM data is lost when the power is cycled.

▶ Arduino Uno R3 (Revolution 3): 

Arduino uno is the best tool for small projects. It provides a moderate number of input & output pins with compatible specifications. It uses the ATmega 328P on-board chip.

1	Microcontroller	ATmega328P
2	Operating Voltage	5V
3	Input Voltage (recommended)	7-12V
4	Input Voltage (Limit)	6-20V
5	Digital I/O Pins	14
6	PWM Pins	6
7	Analog Input Pins	6
8	DC Current per I/O Pin	20mA
9	DC Current for 3.3V Pin	50mA
10	Flash Memory	32 KB
11	SRAM	2 KB
12	EEPROM	1 KB
13	Clock Speed	16 MHz
14	LED Built in Pin	13

 

0.5 KB of the Flash Memory is used by bootloader. We'll get to know more about this board later on. 

▶ Arduino Mega: 

Mega is called the 'Big Brother' of Uno! Mega offers more input & output pins than Uno and also larger memory components. Usually Mega is preferred for large projects where many components are needed to be connected with Arduino that Uno can't supply.

1	Microcontroller	ATmega2560
2	Operating Voltage	5V
3	Input Voltage (recommended)	7-12V
4	Input Voltage (Limit)	6-20V
5	Digital I/O Pins	54
6	PWM Pins	15
7	Analog Input Pins	16
8	DC Current per I/O Pin	20mA
9	DC Current for 3.3V Pin	50mA
10	Flash Memory	256 KB
11	SRAM	8 KB
12	EEPROM	4 KB
13	Clock Speed	16 MHz

 

8 KB of the Flash Mmeory is used by the bootloader. Get to know more by clicking here.

▶ Arduino Due:

Due resembles to Mega in appearance but along with memory upgradaiton, Due is the first Arduino with 32 bit ARM core microcontroller. Thus Due is able to provide more power to larger projects. But a major fact to notice, it supports 3.3 V input voltage.

1	Microcontroller	AT91SAM3X8E
2	Operating Voltage	3.3V
3	Input Voltage (recommended)	7-12V
4	Input Voltage (Limit)	6-16V
5	Digital I/O Pins	54
6	PWM Pins	12
7	Analog Input Pins	12
8	Analog Output Pins	2 (DAC)
9	DC Current for 5V/3.3V Pin	800mA
10	Flash Memory	512 KB
11	SRAM	96 KB (two banks: 64 KB & 32 KB
12	EEPROM	4 KB
13	Clock Speed	84 MHz
14	Total DC Output Current on all I/O lines	130 mA

 

Get to know more by clicking here.

▶ Arduino Leonardo:

Leonardo is the first development board of Arduino. It differs from other boards to has a built-in usb communication that don't require a secondary processor. Another thing is that the libraries allows the board to act as a keyboard or mouse while connecting to a computer!

1	Microcontroller	ATmega 32u4
2	Operating Voltage	5V
3	Input Voltage (recommended)	7-12V
4	Input Voltage (Limit)	6-20V
5	Digital I/O Pins	20
6	PWM Pins	12
7	Analog Input Pins	12
8	DC Current per I/O pin	40 mA
9	DC Current for 3.3V Pin	50 mA
10	Flash Memory	32 KB (4KB used by bootloader)
11	SRAM	2.5KB
12	EEPROM	1 KB
13	Clock Speed	16 MHz

Get to know more by clicking here.

▶ LilyPad Arduino: 

This is the most good looking and tiny sized arduino board. This board is specially modified for e-textile. The purpose of this one is to use in wearable clothes. Along with I/O pins, there are board sensors, especially built for e-textiles. The board provides large pin-out holes that made it easy to sew and connect through conductuve threads. And will you believe if I say this Arduino is washable !!!

1	Microcontroller	ATmega 168
2	Operating Voltage	2.7-5.5 V
3	Input Voltage (recommended)	2.7-5.5 V
4	Input Voltage (Limit)	-
5	Digital I/O Pins	14
6	PWM Pins	6
7	Analog Input Pins	6
8	DC Current per I/O pin	40 mA
9	DC Current for 3.3V Pin	-
10	Flash Memory	16 KB (2KB used by bootloader)
11	SRAM	1 KB
12	EEPROM	512  KB
13	Clock Speed	8 MHz

Therefore, this Arduino is useful for wearable projects like Gesture Controlled Robot. Get to know more by clicking here.

▶ Arduino Nano:

Nano is the smallest member of Arduino family to make projects with. The main feature of it is, it is breadboard friendly, light with mostly resembles to the functionalities of  Dueemilanove. It lacks the power jack. A mini- B USB cable is used instead the standard ones.

1	Microcontroller	ATmega 328
2	Operating Voltage	5 V
3	Input Voltage (recommended)	7-12 V
4	Input Voltage (Limit)	-
5	Digital I/O Pins	22
6	PWM Pins	6
7	Analog Input Pins	6
8	DC Current per I/O pin	-
9	DC Current for 3.3V Pin	-
10	Flash Memory	32 KB (2 KB used by bootloader)
11	SRAM	2 KB
12	EEPROM	1 KB
13	Clock Speed	16 MHz

Get to know more by clicking here.

▶ Arduino Micro:

The Micro has an appearance just like Nano but if we talk about features, it can be said as a mini version of Arduino Leonardo with the additional feature of breadboard friendly. Using ATmega 32U4 like  the Leonardo, it allows the Micro to appeas as a mouse or keyboard to a connected computer in addition to a virtual (CDC) serial/ COM port.

1	Microcontroller	ATmega 32U4
2	Operating Voltage	5 V
3	Input Voltage (recommended)	7-12 V
4	Input Voltage (Limit)	6-20
5	Digital I/O Pins	20
6	PWM Pins	7
7	Analog Input Pins	12
8	DC Current per I/O pin	20 mA
9	DC Current for 3.3V Pin	50 mA
10	Flash Memory	32 KB (4 KB used by bootloader)
11	SRAM	2.5 KB
12	EEPROM	1 KB
13	Clock Speed	16 MHz

Get to know more by clicking here.

Checkout the next article to know about the other members of Arduino in Arduino Family: Part-02

Reference Articles:

* What are the different types of arduino boards

* Different types of Arduino boards & their uses

*https://www.arduino.cc/

Image sources:

* EIProcus

* circuito.io

* classes.engineering.wsutl.edu

* Wiring Library

* Arduino for Projects

* Pininterest

* ChillRain

* Flickr