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2 years ago

Select the correct statement(s) regarding antenna and RF wave polarization.

Computers and Technology

1 answer:

Serggg [28]2 years ago

8 0

Answer:

Explanation:

A. Polarization is simple for most antennas to determine. It is only on the same level as the antenna components. A vertically polarised antenna (that is one with vertical elements) is better received and a horizontal antenna is equally provided with horizontally polarised signals.

B. The left-hand circular polarization is named if the electric chambers vector rotates counter-clockwise as far as they are from the antenna.

The right-hand circular polarisation is named as the electric field vector rotates counter-clockwise as far as it gets from the antenna.

It then goes without stating the polarisation on the right hand is orthogonal to the left.

C. signals of the same frequency can be transmitted together in an non-interfering manner as long as their polarizations are orthogonal to one another. This too a correct statement.

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[1] Please find all the candidate keys and the primary key (or composite primary key) Candidate Key: _______________________ Pri

AVprozaik [17]

Answer:

Check the explanation

Explanation:

1. The atomic attributes can't be a primary key because the values in the respective attributes should be unique.

So, the size of the primary key should be more than one.

In order to find the candidate key, let the functional dependencies be obtained.

The functional dependencies are :

Emp_ID -> Name, DeptID, Marketing, Salary

Name -> Emp_ID

DeptID -> Emp_ID

Marketing -> Emp_ID

Course_ID -> Course Name

Course_Name -> Course_ID

Date_Completed -> Course_Name

Closure of attribute { Emp_ID, Date_Completed } is { Emp_ID, Date_Completed , Name, DeptID, Marketing, Salary, Course_Name, Course_ID}

Closure of attribute { Name , Date_Completed } is { Name, Date_Completed , Emp_ID , DeptID, Marketing, Salary, Course_Name, Course_ID}

Closure of attribute { DeptID, Date_Completed } is { DeptID, Date_Completed , Emp_ID,, Name, , Marketing, Salary, Course_Name, Course_ID}

Closure of attribute { Marketing, Date_Completed } is { Marketing, Date_Completed , Emp_ID,, Name, DeptID , Salary, Course_Name, Course_ID}.

So, the candidate keys are :

{ Emp_ID, Date_Completed }

{ Name , Date_Completed }

{ DeptID, Date_Completed }

{ Marketing, Date_Completed }

Only one candidate key can be a primary key.

So, the primary key chosen be { Emp_ID, Date_Completed }..

The functional dependencies are :

Emp_ID -> Name, DeptID, Marketing, Salary

Name -> Emp_ID

DeptID -> Emp_ID

Marketing -> Emp_ID

Course_ID -> Course Name

Course_Name -> Course_ID

Date_Completed -> Course_Name

For a relation to be in 2NF, there should be no partial dependencies in the set of functional dependencies.

The first F.D. is

Emp_ID -> Name, DeptID, Marketing, Salary

Here, Emp_ID -> Salary ( decomposition rule ). So, a prime key determining a non-prime key is a partial dependency.

So, a separate table should be made for Emp_ID -> Salary.

The tables are R1(Emp_ID, Name, DeptID, Marketing, Course_ID, Course_Name, Date_Completed)

and R2( Emp_ID , Salary)

The following dependencies violate partial dependency as a prime attribute -> prime attribute :

Name -> Emp_ID

DeptID -> Emp_ID

Marketing -> Emp_ID

The following dependencies violate partial dependency as a non-prime attribute -> non-prime attribute :

Course_ID -> Course Name

Course_Name -> Course_ID

So, no separate tables should be made.

The functional dependency Date_Completed -> Course_Name has a partial dependency as a prime attribute determines a non-prime attribute.

So, a separate table is made.

The final relational schemas that follows 2NF are :

R1(Emp_ID, Name, DeptID, Marketing, Course_ID, Course_Name, Date_Completed)

R2( Emp_ID , Salary)

R3 (Date_Completed, Course_Name, Course_ID)

For a relation to be in 3NF, the functional dependencies should not have any transitive dependencies.

The functional dependencies in R1(Emp_ID, Name, DeptID, Marketing, Date_Completed) is :

Emp_ID -> Name, DeptID, Marketing

This violates the transitive property. So, no table is created.

The functional dependencies in R2 ( Emp_ID , Salary) is :

Emp_ID -> Salary

The functional dependencies in R3 (Date_Completed, Course_Name, Course_ID) are :

Date_Completed -> Course_Name

Course_Name -> Course_ID

Here there is a transitive dependency as a non- prime attribute ( Course_Name ) is determining a non-attribute ( Course_ID ).

So, a separate table is made with the concerned attributes.

The relational schemas which support 3NF re :

R1(Emp_ID, Name, DeptID, Course_ID, Marketing, Date_Completed) with candidate key as Emp_ID.

R2 ( Emp_ID , Salary) with candidate key Emp_ID.

R3 (Date_Completed, Course_Name ) with candidate key Date_Completed.

R4 ( Course_Name, Course_ID ). with candidate keys Course_Name and Course_ID.

6 0

3 years ago

(tco 8) when a file is opened in the append mode, the file pointer is positioned

Artyom0805 [142]

At the end of the file, so that additional data is appended while the existing data stays intact.

6 0

3 years ago

What is computer hacking? describe some examples

Naily [24]

Computer hacking refers to the practice of modifying or altering computer software and hardware to accomplish a goal that is considered to be outside of the creator's original objective.

“bot,” is a computer under the control of a hacker without the knowledge of the computer user.

3 0

3 years ago

A customer reports that recently several files cannot be accessed. The service technician decides to check the hard disk status

Lyrx [107]

Answer:

Back up the user data to removable disk

Explanation:

Before you work on a computer, especially anything that has to do with files not accessible, this might need to format the system because it might either be a virus or other forms of malware. Since backup was done to a different logical partition on the disk, the first thing to do before performing any diagnostic procedures on the disk is to back up the user data to a removable disk in order not to lose the information in the system.

8 0

2 years ago

ARP only permits address resolution to occur on a single network.could ARP send a request to a remote server in an IP datagram?w

romanna [79]

Answer:

The answer to this question is Yes it is possible

Explanation:

It can be done In the case where a special server is required in each network that would forward the request to the remote ARP(Address Resolution Protocol) server and will receive the response from the server and send it to the requesting host.So we conclude that we can do that hence the answer is Yes.

5 0

3 years ago