1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Ahat [919]
3 years ago
15

Create a Relational Schema for the following scenario. Include all primary and foreign keys and list any assumptions you make. 

A research facility has many chemists who work on one or more projects.  Attributes of chemists include a unique employee id, a name, rank and email.  Each project has one chemist who is given the title of project leader. A chemist may be the leader of several projects.  Attributes of a project include a unique project number, start date and description.  Each project is assigned to one or more laboratories but each laboratory can house at most one project at any time.  Attributes of a laboratory include a building name, room number, capacity and type. The combination of building name and room number is unique.  Chemists can borrow equipment from the stockroom. Each time a piece of equipment is borrowed the check-out date is recorded and when it is returned a return date is recorded. The return date is set to 00-00-0000 until the piece of equipment has been returned. Historical data on the equipment is maintained and a chemist can check out the same piece of equipment on multiple dates.  Attributes of equipment include a unique serial number, description and cost.

Engineering
1 answer:
NARA [144]3 years ago
4 0

Answer:

See explaination

Explanation:

Some of the Important Observation used in Entity Relational Diagram.

1. A Chemist can be involved one project or many projects

2. A project can hire just one or many chemists.

3. A chemist can lead over one or many projects

4. A project can have only one project leader chemist.

5. A project can be done in 1 or many laboratories.

6. A laboratory can host 0 or 1 projects.

7. A laboratory can have 1 or many equipments.

8. An Equipment can be in 1 or 0 laboratories.

9. A chemist can have 0 or many types of equipments.

10. An Equipment can have 0 or 1 chemist at a time

Notations:

PK=Primary Key:

A primary key, also called a primary keyword, is a key in a relational database that is unique for each record. It is a unique identifier, such as a driver license number, telephone number

FK=Foreign Key:

A foreign key is a column or group of columns in a relational database table that provides a link between data in two tables. It acts as a cross-reference between tables because it references the primary key of another table, thereby establishing a link between them

Composite key:

A composite key is a combination of two or more columns in a table that can be used to uniquely identify each row in the table when the columns are combined uniqueness is guaranteed, but when it is taken individually it does not guarantee uniqueness

You might be interested in
Determine the velocity of the 13-kgkg block BB in 4 ss . Express your answer to three significant figures and include the approp
Anvisha [2.4K]

Answer:

The question has some details missing : The 35-kg block A is released from rest. Determine the velocity of the 13-kgkg block BB in 4 ss . Express your answer to three significant figures and include the appropriate units. Enter positive value if the velocity is upward and negative value if the velocity is downward.

Explanation:

The detailed steps and appropriate calculation is as shown in the attached file.

6 0
3 years ago
Is an isothermal process necessarily internally reversible? Explain your answer with an example
torisob [31]

Answer:

please give me brainlist and follow

Explanation:

Example of an irreverseble isothermal process is mixing of two fluids on the same temperature - it requires a lot of energy to unmix Jack and coke. ... Example of an reversible process with changing temperature is isentropic expansion.

5 0
2 years ago
Air in a piston–cylinder assembly, initially at 3 bar, 142 K, and a volume of 2 m3. The air undergoes a process to a state where
Archy [21]

Answer:

mass of the air = 14.62kg

Workdone = 415.88 kJ

Heat transfer = 415.88 kJ

Explanation:

Please find the attached files for the solution

6 0
3 years ago
Read 2 more answers
H2O enters a conical nozzle, operates at a steady state, at 2 MPa, 300 oC, with the inlet velocity 30 m/s and the mass flow rate
Colt1911 [192]

Answer:

The flow velocity at outlet is approximately 37.823 meters per second.

The inlet radius of the nozzle is approximately 0.258 meters.

Explanation:

A conical nozzle is a steady state device used to increase the velocity of a fluid at the expense of pressure. By First Law of Thermodynamics, we have the energy balance of the nozzle:

Energy Balance

\dot m \cdot \left[\left(h_{in}+\frac{v_{in}^{2}}{2} \right)-\left(h_{out}+\frac{v_{out}^{2}}{2} \right)\right]= 0 (1)

Where:

\dot m - Mass flow, in kilograms per second.

h_{in}, h_{out} - Specific enthalpies at inlet and outlet, in kilojoules per second.

v_{in}, v_{out} - Flow speed at inlet and outlet, in meters per second.

It is recommended to use water in the form of superheated steam to avoid the appearing of corrosion issues on the nozzle. From Property Charts of water we find the missing specific enthalpies:

Inlet (Superheated steam)

p = 2000\,kPa

T = 300\,^{\circ}C

h_{in} = 3024.2\,\frac{kJ}{kg}

\nu_{in} = 0.12551\,\frac{m^{3}}{kg}

Where \nu_{in} is the specific volume of water at inlet, in cubic meters per kilogram.  

Outlet (Superheated steam)

p = 600\,kPa

T = 160\,^{\circ}C

h_{out} = 2758.9\,\frac{kJ}{kg}

If we know that \dot m = 50\,\frac{kJ}{kg}, h_{in} = 3024.2\,\frac{kJ}{kg}, h_{out} = 2758.9\,\frac{kJ}{kg} and v_{in} = 30\,\frac{m}{s}, then the flow speed at outlet is:

35765-25\cdot v_{out}^{2} = 0 (2)

v_{out} \approx 37.823\,\frac{m}{s}

The flow velocity at outlet is approximately 37.823 meters per second.

The mass flow is related to the inlet radius (r_{in}), in meters, by this expression:

\dot m = \frac{\pi \cdot v_{in}\cdot r_{in}^{2} }{\nu_{in}} (3)

If we know that \dot m = 50\,\frac{kJ}{kg}, v_{in} = 30\,\frac{m}{s} and \nu_{in} = 0.12551\,\frac{m^{3}}{kg}, then the inlet radius is:

r_{in} = \sqrt{\frac{\dot m\cdot \nu_{in}}{\pi\cdot v_{in}}}

r_{in}\approx 0.258\,m

The inlet radius of the nozzle is approximately 0.258 meters.  

7 0
2 years ago
A community plans to build a facility to convert solar radiation to electrical power. The community requires 2.80 MW of power, a
Greeley [361]

Given Information:  

Output power required = Pout = 2.80 MW

Efficiency = η = 30%

Intensity = I = 1180 W/m²

Required Information:  

Effective area = A = ?

Answer:  

Effective area = A = 7.907x10³ m²

Step-by-step explanation:  

A community plans to build a facility to convert solar power into electrical power and this facility has an efficiency of 30%

As we know efficiency is given by

η = Pout/Pin

Where Pout is the output power and Pin is the input power.

Pin = Pout/η

Pin = 2.80x10⁶/0.30

Pin = 9.33x10⁶ W

The effective area of a perfectly absorbing surface used in such an installation can be found using

A = Pin/I

Where I is the in Intensity of the sunlight in W/m²

A = 9.33x10⁶/1180

A = 7.907x10³ m²

Therefore, the effective area of the absorbing surface would be 7.907x10³ m².

6 0
3 years ago
Other questions:
  • Ion 2 23
    10·1 answer
  • 1. A glass window of width W = 1 m and height H = 2 m is 5 mm thick and has a thermal conductivity of kg = 1.4 W/m*K. If the inn
    8·1 answer
  • A saturated 1.5 ft3 clay sample has a natural water content of 25%, shrinkage limit (SL) of 12% and a specific gravity (GS) of 2
    11·1 answer
  • Scheduling can best be defined as the process used to determine:​
    8·1 answer
  • Define a separate subroutine for each of the following tasks respectively.
    6·2 answers
  • Two routes connect an origin and a destination. Routes 1 and 2 have performance functions t1 = 2 + X1 and t2 = 1 + X2, where the
    6·1 answer
  • The quantity of bricks required increases with the surface area of the wall, but the thickness of a masonry wall does not affect
    10·2 answers
  • How should you move your board through the planer? (Pick two choices.)
    8·1 answer
  • (CO 3) A nonrecursive filter may best be described as _____. Group of answer choices a filter whose current output depends on pa
    13·1 answer
  • What is the fastest plane in the world
    13·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!