Google's Equiano Subsea Cable

Google announced the construction about their third third subsea cable. Called "Equiano". The cable start in Lisbon, Portugal and go along Cape Town, South Africa, It boosts is cloud, browsing and searching infrastructure. Google said it completely privet and international cable funded by them connecting Europe and Africa is the first phase of the whole project which is expected to be completed in 2021.

Equiano Cable is named after "Olaudah Equiano", an African poet who lead anti-slave trading movement. The other two Cables are also named after historical persons : "Curie" - connects Chile and Los Angeles,"Dunant" - connects Us and French Coast. 

Equiano is the first subsea cable which incorporate optical switching at fiber-pair level. Google said "Previous cables has 4-6 pair of cables, each pair can transfer data on 60 different wavelength channels where this cable has 12 pairs or more of fiber-optic lines. These cables are more cost-effective and power-effective switching solution."  

These cables will be able to transmit 12 terabits/second, which is 1000 times faster than newer PCs. It can send continuous data instead of bursting it, which makes them more faster. These cables are design to lasted at least 25 years said Alcatel Submarine Network, who also  finished the installation of Google's first subsea cable Curie in this April.

All 14 subsea cables that connects the world :

Operating Systems - Memory Allocation Method

The main memory must be accommodate both Operating System and various user processes. The Operating System place in either low memory or high memory. There are so many method available for memory allocation like : 

• Single Partition Allocation
• Fixed Equal Multiple Partition Allocation
• Fixed Variable Partition Allocation
• Dynamic Partition Allocation

1. Single Partition Allocation :  

In this memory allocation method the Operating System reside in low memory and the remain memory is treated as single partition which only available for user space. The short term or CPU scheduler selects a job from ready queue the departure loads that job into main memory and connect CPU to that job.

Advantages :  

1. The main Advantage of this scheme is its simplicity.

Disadvantages : 

1. Poor utilization of the processor. 
2. Poor utilization of memory. 

2. Fixed Equal Multiple Partition Allocation :

In this scheme the OS occupies the low memory and rest of main memory is available for user space. The user space is divided into fixed partition depending on OS. For example, total main memory size is 6MB, 1MB occupied by OS and remaining 5MB partitioned into  equal fixed Partitions.

Advantages:

1. It supports multi-programming.
2. It require most special costly hardware.

Disadvantages :

1. This scheme suffers from internal as well as external fragmentation.  
2. It does more memory then a single partition method. 

3. Fixed Variable Partition Allocation :

In this  scheme the user space divide into number of fixed  partitions, but the partition size are different length. Operating System keep a table indicating which partition of memory are occupied or which are available. When a process is arrive and need memory, it search for partition large enough for this process. There are 3-types of algorithm available to build this.

•  First Fit :   Allocate the partition that is big enough. Searching can start either from low memory or high memory, we can stop searching as we find a free partition that is large enough.

• Best Fit :  Allocate the smallest partition that big enough which having least internal fragmentation.

• Worst Fit :  Search entire partition and select a partition which is largest of all or select a partition which having maximum internal fragmentation.

Advantages :

1.  this scheme  support multi-programming.
2. Efficient processor utilization and memory utilization is possible.

Disadvantages :

1.  It suffers from internal and external fragmentation.

4. Dynamic Partition Allocation :

To eliminate all disadvantages of fixed Partition, a new approach is introduce known as Dynamic Partition. In this method, partitions are created dynamically so that each process is loaded into partition of exactly the same size at that process. In this scheme boundary partition are dynamically changed and the boundaries are depend on size of processes. 

Advantages :

1.  Though the partition are changed dynamically does not suffer from internal fragmentation.
2. Efficient memory and processor utilization.

Disadvantages :

1.   This scheme suffering from external fragmentation.

Physics - Maxwell's Electrodynamical Equations

 

In 1859, James Clerk Maxwell introduced  mathematical form of  four fundamental laws of electricity and magnetism. The laws are :

1. Gauss's law of Electricity
2. Gauss's law of Magnetism
3. Faraday's law of Electromagnetic Induction  
4. Ampere's Circuital Law

Gauss's Law of Electricity :

He expressed first law as,

which states that the total normal electronic introduction / flux coming out from a close surface is equal to the ration of amount of charge enclosed by the surface and the permittivity of the vacuum. 

Gauss's Law of Magnetism :

 The second law which states that, the total magnetic flux coming out from any closed surface is always zero, can be written as, 

Faraday's Law of Electromagnetic Induction :

Faraday's law states that Emf induced in a loop is equal to rate of change of magnetic flux in it.

Ampere's Circuital Law :

4th law states that, the closed integration of ∮B ᐧ dl over any loop is equal the current enclosed by the loop is expressed as 

These are the integral form of these laws.