Answer:
False.
Explanation:
Project management can be defined as the process of designing, planning, developing, leading and execution of a project plan or activities using a set of skills, tools, knowledge, techniques and experience to achieve the set goals and objectives of creating a unique product or service.
Generally, projects are considered to be temporary because they usually have a start-time and an end-time to complete, execute or implement the project plan.
The fundamentals of Project Management includes;
1. Project initiation.
2. Project planning.
3. Project execution.
4. Monitoring and controlling of the project.
5. Adapting and closure of project.
Basically, the specifications of a project or manufacturing process outlines the minimum requirements and quality that are acceptable. Thus, it must be adhered to strictly in order to achieve a successful and desired outcome.
As a rule, it is essential to check at every stage of a project if the sponsor or customer requirements and expectations have been met regarding the quality of the project deliverables.
For a sixth-order Butterworth high pass filter with cutoff frequency 3 rad/s, compute the following:
a. The locations of the poles.
b. The transfer function H(s).
c. The corresponding LCCDE description.
Solution :
Given :
A six order Butterworth high pass filter.
∴ n = 6, [tex]w_c=1 \ rad/s[/tex]
a). The location at poles :
[tex]$s^6-(w_c)^6=0$[/tex]
[tex]$s^6=(w_c)^6=1^6$[/tex]
∴ [tex]$s^6 = 1$[/tex]
Therefore, it has 6 repeated poles at s = 1.
b). The transfer function H(S) :
Transfer function H(S) [tex]$=\frac{1}{1+j\left(\frac{w_c}{s}\right)^6}$[/tex]
[tex]$=\frac{1}{1-\left(\frac{w_c}{s}\right)^6}$[/tex]
∴ H(S) [tex]$=\frac{s^6}{s^6-(w_c)^6}=\frac{s^6}{s^6-1}$[/tex]
H(S) [tex]$=\frac{Y(s)}{X(s)}=\frac{s^6}{s^6-1}$[/tex]
c). The corresponding LCCDE description :
[tex]$=\frac{Y(s)}{X(s)}=\frac{s^6}{s^6-1}$[/tex]
[tex]$Y(s)(s^6-1) = s^6 \times (s)$[/tex]
[tex]$Y(s)s^6-y(s).1 = s^6 \times (s)$[/tex]
By taking inverse Laplace transformation on BS
[tex]$L^{-1}[Y(s)s^6-Y(s)1]=L^{-1}[s^6 \times (s)]$[/tex]
[tex]$\frac{d^6y(t)}{dt^6}-y(t)=\frac{d^6 \times (t)}{dt^6}$[/tex]
Hence solved.
Just because I seen someone else ask but they didn't have enough information.
If a filesystem has a block size of 4096 bytes, this means that a file comprised of only one byte will still use 4096 bytes of storage. A file made up of 4097 bytes will use 4096*2=8192 bytes of storage. Knowing this, can you fill in the gaps in the calculate_storage function below, which calculates the total number of bytes needed to store a file of a given size?
Answer:
Following are the program to the given question:
def calculate_storage(filesize):#definging a method calculate_storage that takes filesize as a parameter
block_size = 4096#definging block_size that holds value
full_blocks = filesize//block_size#definging full_blocks that divides the value and hold integer part
partial_block_remainder = filesize%block_size#definging partial_block_remainder that holds remainder value
if partial_block_remainder > 0:#definging if that compare the value
return block_size*full_blocks+block_size#return value
return block_size*full_blocks#return value
print(calculate_storage(1)) # calling method by passing value
print(calculate_storage(4096)) # calling method by passing value
print(calculate_storage(4097)) # calling method by passing value
Output:
4096
4096
8192
Explanation:
In this code, a method "calculate_storage" is declared that holds a value "filesize" in its parameters, inside the method "block_size" is declared that holds an integer value, and defines "full_blocks and partial_block_remainder" variable that holds the quotient and remainder value and use it to check its value and return its calculated value. Outside the method, three print method is declared that calls the method and prints its return value.
thiết kế ic 555 và code để ic hoạt động
Answer:
here you go.
screenshot 2 should give you some basic idea
how Many years of college do you have To do in order To become a video game developer and designer
Answer:
Video game designers typically have a bachelor's degree in game design, computer engineering, or computer science which takes four to five years to complete. Courses in a game design degree program may include project management, integrated video design and technology, game prototyping and level design.
A heat pump heats the air in a rigid, insulated cuboid room of size 25m x 10m x 4m. The heat pump consumes 15 kW of power. The initial temperature and pressure in this room are 12°C and 1 bar, respectively. With an average coefficient of performance of COPHP= 3.0 over the range of air temperature in this room.
Requried:
How long will it take to raise the temperature in the room to 27 °C?
Answer:
Time required = 287.2 secs
Explanation:
Volume of room = 25 * 10 * 4 = 1000 m^3
power consumed by pump = 15 kW
T1 ( initial temperature ) = 12°C
P1 ( Initial pressure ) = 1 bar
COPhp = 3
Calculate time taken to raise room Temp to 27°C
average heat supplied ( ∅ ) = COPhp * power consumed by pump
= 3 * 15 = 45 kW
Time required can be calculated using the relation below
∅t = P*V*Cv ( T2 - T1 ) [ p = 1.2 kg/m^3 , Cv = 0.718 KJ/kg ( air properties ) ]
45 * 10^3 ( t ) = 1.2*1000* 718 ( 27 - 12 )
∴ solving for t
t = 287.2 secs ≈ 4.79 mins
Why is the newtons law of cooling and explain how to derive it/
Answer:
For small temperature difference between a body and its surrounding, the rate of cooling of the body is directly proportional to the temperature difference and the surface area exposed. qf = final temperature of object
Explanation:
hope this helps you sorry if it doesn’t help you
find the volume of the pond with the following dimension length 40m breadth 10m height 1.2m depth 0.9m express in both meters and feet
Answer:
The volume for this is 29.7
Explanation:
Trust me on this I'm an expert
8. The operation of a TXV is controlled by the
O A. thermostatic spring.
O B. temperature bulb.
O C. external pressure of the evaporator.
O D. modulating valve.
good housekeeping can increase production in a work place is it true or false
False, Good housekeeping eliminates accident and fire hazards. It also maintains safe, healthy work conditions; saves time, money, materials, space, and effort; improves productivity and quality; boosts morale; and reflects an image of a well-run, successful organization.
Hope it helps you❤️
What must you do when you reach a steady yellow traffic light?
Answer:
When you come up on a steady yellow traffic light you should always yield to cross traffic if you can yield safely. The flashing yellow light is there to inform drivers to be careful and to slow down.
Explanation:
hope it helped!
In a certain pressing operation, the metallic powder fed into the open die has a packing factor of 0.5. The pressing operation reduces the powders to 70% of their starting volume. In the subsequent sintering operation, shrinkage amounts to 10% on a volume basis. Given that these are the only factors that affect the structure of the finished part, determine its final porosity.
Answer:
0.2063
Explanation:
Given data:
packing factor = 0.5
percentage of reduction of powders = 70%
Calculate the final porosity
after sintering Bulk specific volume = 0.9 * 0.7 = 0.63
assuming true specific volume = 1
packing factor = 0.5 , bulk specific volume = 2
packing factor after pressing and sintering
= 1 / ( 2 * 0.63 ) = 0.7937
hence : porosity = 1 - packing factor
= 1 - 0.7937 = 0.2063
A 75- kw, 3-, Y- connected, 50-Hz 440- V cylindrical synchronous motor operates at rated condition with 0.8 p.f leading. the motor efficiency excluding field and stator losses, is 95%and X=2.5ohms. calculate the mechanical power developed, the Armature current, back e.m.f, power angle and maximum or pull out torque of the motor
78950W the answer
Explanation:
A 75- kw, 3-, Y- connected, 50-Hz 440- V cylindrical synchronous motor operates at rated condition with 0.8 p.f leading. the motor efficiency excluding field and stator losses, is 95%and X=2.5ohms. calculate the mechanical power developed, the Armature current, back e.m.f, power angle and maximum or pull out torque of the motor
A 75- kw, 3-, Y- connected, 50-Hz 440- V cylindrical synchronous motor operates at rated condition with 0.8 p.f leading. the motor efficiency excluding field and stator losses, is 95%and X=2.5ohms. calculate the mechanical power developed, the Armature current, back e.m.f, power angle and maximum or pull out torque of the motor
What is the differences between total revenue and total costs? Make
sure that your answer will cover all aspects related with two
mentioned concepts. With any supported simple example about
petroleum industrial?
Answer:
The basic difference between Total cost and total revenue is that the total cost includes the total expenditure incurred on the production of a commodity whereas total revenue refers to the money received from selling that commodity.
Explanation:
An assembly line has 3 fail safe sensors and one emergency shutdown switch.The line should keep moving unless any of the following conditions arise:
(1) If the emergency switch is pressed
(2) If the senor1 and sensor2 are activated at the same time.
(3) If sensor 2 and sensor3 are activated at the same time.
(4) If all the sensors are activated at the same time
Suppose a combinational circuit for above case is to be implemented only with NAND Gates. How many minimum number of 2 input NAND gates are required.
Answer:
1 NAND gate
Explanation:
The minimum number of 2 input NAND gates that can be used to implement the combinational circuit = 1
The only true combinations conditions that can produce a false result ( i.e. condition/result different from the expected result as stated in the question )
Sensor 2 activated + Emergency switch pressed = False ( Line will keep moving )
Your family has asked you to estimate the operating costs of your clothes dryer for the year. The clothes dryer in your home has a power rating of 2250 W. To dry one typical load of clothes the dryer will run for approximately 45 minutes. In Ontario, the cost of electricity is $0.11/kWh. Calculate the costs to run the dryer for your family for one year.
Answer:
The costs to run the dryer for one year are $ 9.03.
Explanation:
Given that the clothes dryer in my home has a power rating of 2250 Watts, and to dry one typical load of clothes the dryer will run for approximately 45 minutes, and in Ontario, the cost of electricity is $ 0.11 / kWh, to calculate the costs to run the dryer for one year the following calculation must be performed:
1 watt = 0.001 kilowatt
2250/45 = 50 watts per minute
45 x 365 = 16,425 / 60 = 273.75 hours of consumption
50 x 60 = 300 watt = 0.3 kw / h
0.3 x 273.75 = 82.125
82.125 x 0.11 = 9.03
Therefore, the costs to run the dryer for one year are $ 9.03.
A stream of ethylene glycol vapor at its normal boiling point and 1atm flowing at a rate of 175 kg/min is to be condensed at constant pressure. The product stream from the condenser is liquid g lycol at the condensation temperature.
a. Calculate the rate at which heat must be transferred from the condenser (kW).
b. If heat were transferred at a lower rate than that calculated in part (A), what would the state of the product stream be? (Dedu ce as much as you can about the phase and the temperature of the stream.)
c. If heat were transferred at a higher rate than that calculated in part (A), what could you deduce about the state of the product stream?
Answer: hello attached below is the question properly written
a) 2670 Kw
b) product will be made up of vapor and liquid
c) Product will be a super cooled liquid
Explanation:
mass Flow rate ( m ) = 175 kg/min
pressure = 1 atm
molecular weight of ethylene glycol ( mw ) = 62.07 g/mol
enthalpy of vaporization ( ΔHv ) = 56.9 KJ/mol
Using values from the table 8.1 related to the question
a) Determine the rate at which heat must be transferred from condenser
Using values from the table 8.1 related to the question
ΔH = 2670 Kw
b) If heat is transferred at a lower temperature the product will be made up of vapor and liquid
c) If heat was transferred at a higher temperature the product will be a super cooled liquid
If the two 304-stainless-steel carriage bolts of the clamp each have a diameter of 10 mmmm, and they hold the cylinder snug with negligible force against the rigid jaws, determine the temperature at which the average normal stress in either the magnesium or the steel first becomes 12.0 MPaMPa .
Answer: hello some data related to your question is missing attached below is the missing data
answer:
T2 = 265°C
Explanation:
First step : calculate sum of vertical forces
∑ y = 0
Fmg - 2(0.5 Fst ) = 0
∴Fmg = ( 12 * 10^6 ) ( 2 * π/4 (0.01)^2 )
= 1884.96 N
Also determine the Compatibility equation in order to determine the change in Temperature
ΔT = 250°C
therefore Temperature at which average normal stress becomes 12.0 MPa
ΔT = T2 - T1
250°C = T2 - 15°C
T2 = 250 + 15 = 265°C
attached below is the detailed solution
Một máy nghiền bi thùng ngắn đường kính D = 1.6m, dài L = 2m dùng để nghiền VL. Kích thước đầu vào D1 = 20mm, sản phẩm sau nghiền có kết quả phân tích rây sau:
Số mesh
60/80
80/100
100/150
150/200
Khối lượng VL trên rây
0.1
0.3
2.5
0.1
Hỏi
1. Tính kích thước bi nghiền bi.
2. Tính số vòng quay tối ưu.
3. Tính năng suất (biết K1 = 1.01).
4. Tính số lượng bi cần nạp vào thùng. Biết hệ số chứa đầy φ = 0.25, hệ số rỗng = 0.65, ⍴bi = 8000 kg/m3
Answer:
bood ekogcd gcaerh is an American fbnuxc
In the figure below, this “double” nozzle discharges water (at 10°C, density= 1000 kg/m3) into the atmosphere at a rate of 0.50 m3/s. The pressure at the inlet is to be 315612 Pa. If the nozzle is lying in a horizontal plane. Jet A is 10 cm in diameter, jet B is 12 cm in diameter, and the pipe (1) is 30 cm in diameter. The x-component of force (Rx) acting through the flange bolts is required to hold the nozzle in place is:
Solution :
Given data :
p = 315612 Pa
[tex]$V_1=7.07 \ m/sec$[/tex]
At exit of B,
p = [tex]$P_{atm}$[/tex]
[tex]$V_B = 26.1 \ m/sec$[/tex]
At exit of A,
[tex]p=P_{atm}[/tex]
[tex]$V_{A} = 26.1 \ m/s$[/tex]
We need to determine X component of force ([tex]$R_x$[/tex]) to hold in its place.
From figure,
[tex]$\sum F_x = m_0'V_{0x} - m_iV_{ix} $[/tex]
[tex]$=F_x+P_1A_1\sin 30=-mVA-mV_1 \sin 30$[/tex]
[tex]$=F_x=-pA_1\sin 30-m_AV_AA-m_B \sin30$[/tex]
Substitute all the values,
[tex]$=F_x=[-315612 \times \frac{\pi}{4}(0.3)^2 \sin 30]-[26.1 \times 1000 \times 26.1 \frac{\pi}{4}(0.1)^2]-[7.07 \times 1000\times 0.5 \sin 30]$[/tex][tex]$=F_x = -11154.64-5350.21-1767.28$[/tex]
[tex]$F_x = -18.2733 \ kN$[/tex]
Therefore, the force required to hold the nozzle in its place along horizontal direction.
[tex]$F_x = -18.2733 \ kN$[/tex]
To convert from the U.S. Customary (FPS) system of units to the SI system of units. A first-year engineering student records three separate measurements as 653 lb, 69.0 mi/h, and 297(106)ft2. Suppose this engineering student has to turn in the results, but the professor only accepts results given in SI units.
Required:
What is the area measurement, 293 (106) ft^2, in SI units?
This question is incomplete, the complete question is;
To convert from the U.S. Customary (FPS) system of units to the SI system of units. A first-year engineering student records three separate measurements as 653 lb, 69.0 mi/h, and 293 × 10⁶ ft². Suppose this engineering student has to turn in the results, but the professor only accepts results given in SI units.
Required:
What is the area measurement, 293 × 10⁶ ft², in SI units?
293 × 10⁶ ft² = ?km²
Answer:
the area measurement is 27.221 km²
Explanation:
Given the data in the question;
What is the area measurement, 293 × 10⁶ ft², in SI units
we are to the result of the measured area from ft² to km²
we know that;
1 meter = 3.2808 ft
1 km = 1000 m
1 ft = (1 / 3.2808)m
1 m = ( 1/1000 ) km
since our measured are is 293 × 10⁶ ft²
hence
A = 293 × 10⁶ × [ (1 / 3.2808)m ]²
A = 27221252.74 m²
A = 27221252.74 × [ ( 1/1000 ) km ]²
A = 27.221 km²
Therefore, the area measurement is 27.221 km²
A uniform plane electromagnetic wave propagates in a lossless dielectric medium of infinite extent. The electric field in the wave has the instantaneous expression
E(r,t) = (ix √3 - iz) 2 sin(2π.10^8t + 2πx/3 + 2nz/√3 + 30 ), V/m.
Find:
a. iE, the unit vector in the direction of the wave electric field
b. the amplitude Eo of the wave
c. the wavelength of the wave
d. ik, the unit vector in the direction of propagation
Answer:
Explanation:
From the information given:
The instantaneous expression of the electric field in the wave is:
[tex]E(r,t)= (i_x \sqrt{3} -i_z) 2 \ sin (2 \pi*10^8t + 2 \pi x/3+2 \pi z /\sqrt{3} + 30 ^0) , \ V/m[/tex]
To determine the unit vector in line with the wave electric field, we take the first term in E(r,t) for [tex]I_E^\to[/tex] as:
[tex]I_E^\to = i_x \sqrt{3}-i_z \\ \\ I_E^\to = \dfrac{i_x \sqrt{3}-i_z}{\sqrt{3 +1}} \\ \\ \mathbf{ I_E = \dfrac{i_x\sqrt{3} -i_z}{2}}[/tex]
The amplitude is denoted by the numerical value after the first term, which is:
[tex]\mathbf{E_o = 2}[/tex]
The wavelength can be determined by using the expression:
[tex]\beta =\dfrac{2 \pi}{\lambda }[/tex]
from the given instantaneous expression:
[tex]\beta = \dfrac{2 \pi}{3}x+\dfrac{2 \pi}{\sqrt{3}}z[/tex]
[tex]\beta = \sqrt{\dfrac{2 \pi}{(3)^2}+\dfrac{(2 \pi}{(\sqrt{3})^2}}[/tex]
[tex]\beta = \sqrt{\dfrac{2 \pi}{9}+\dfrac{2 \pi}{{3}}}[/tex]
Factorizing 2π
[tex]\beta =2 \pi \sqrt{\dfrac{1}{9}+\dfrac{1}{{3}}}[/tex]
[tex]\beta =2 \pi \sqrt{\dfrac{9+3}{9*3}}}[/tex]
[tex]\beta =2 \pi \sqrt{\dfrac{12}{27}}}[/tex]
[tex]\beta =2 \pi \sqrt{\dfrac{4*3}{9*3}}}[/tex]
[tex]\beta =2 \pi \sqrt{\dfrac{4}{9}}}[/tex]
[tex]\beta =2 \pi\times {\dfrac{2}{3}}}[/tex]
recall from the expression using in calculating wavelength:
[tex]\beta =\dfrac{2 \pi}{\lambda }[/tex]
∴
equating both together, we have:
[tex]\dfrac{2 \pi}{\lambda }= 2 \pi\times {\dfrac{2}{3}}}[/tex]
[tex]\lambda = \dfrac{3}{2}[/tex]
λ = 1.5 m
In line with the wave direction; unit vector [tex]i_k[/tex] can be computed as follows:
[tex]i_k = - [ \beta_1x +\beta_2z]/\beta[/tex]
where;
[tex]\beta_1 = \dfrac{2 \pi }{3} \ ; \ \beta_2 = \dfrac{2 \pi }{\sqrt{3}} \ ; \ \beta = \dfrac{2 \pi \times 2}{3} ;[/tex]
∴
[tex]i_k = - \Big[\dfrac{2 \pi}{3}x + \dfrac{2 \pi}{\sqrt{3}} z\Big]\times \dfrac{1}{\dfrac{2 \pi *2}{3}}[/tex]
[tex]i_k = - \Big[\dfrac{x}{2} + \sqrt\dfrac{{3}}{4}} z\Big][/tex]
[tex]i_k = - \Big[\dfrac{1}{2}x + \sqrt{\dfrac{3}{4} }z\Big][/tex]
[tex]\mathbf{i_k = - \Big[0.5x +0.86 z\Big]}[/tex]
A masonry chimney should be braced with horizontal metal straps every few feet against the structure and into reinforced points such as wall studs to stabilize the chimney from the shaking force of an earthquake.
a. True
b. False
Answer: True
Explanation:
The statement that "a masonry chimney should be braced with horizontal metal straps every few feet against the structure and into reinforced points such as wall studs to stabilize the chimney from the shaking force of an earthquake" is true.
In a scenario whereby the chimney isn't braced with the horizontal metal straps every few feet, this can lead to its collapse in case of an earthquake. Therefore, the correct option is "true".
convert 25 inches / min to mm/hour
Answer:
25 mins into hours = 0.416667 hours
25 inches as mm = 635
Explanation:
Consider a venturi with a throat-to-inlet area ratio of 0.75, mounted on the side of an airplane fuselage. The airplane is in flight at standard sea level. If the static pressure at the throat is 2050 lb/ft2 , calculate the velocity of the airplane.
This question is incomplete, the complete question is;
Consider a venturi with a throat-to-inlet area ratio of 0.75, mounted on the side of an airplane fuselage. The airplane is in flight at standard sea level. If the static pressure at the throat is 2050 lb/ft2 , calculate the velocity of the airplane.
Note that standard sea level density and pressure are 1.23 kg/m3 (0.002377 slug/ft3) and 1.01 x 105 N/m2 (2116lb/ft3), respectively.
Answer:
the velocity of the airplane is 267.2 ft/s
Explanation:
Given the data in the question;
throat-to-inlet area ratio A₂/A₁ = 0.75
density of air ρ = 0.002377 slug/ft³
the pressure at inlet p₁ = 2116 lb/ft³
the pressure at the throat p₂ = 2050 lb/ft³
Now, for a venturi duct, the velocity of the airplane V is given as;
V = √[ (2( p₁ - p₂ )) / (ρ( [A₁/A₂]² - 1 )) ]
so we substitute in our values
V = √[ (2( 2116 - 2050 )) / (0.002377 ( [1/0.75]² - 1 )) ]
V = √[ ( 2 × 66 ) / (0.002377 ( 1.7778 - 1 )) ]
V = √[ ( 2 × 66 ) / (0.002377 × 0.7778 ) ]
V = √[ 132 / 0.0018488 ]
V = √[ 71397.663349 ]
V = 267.2 ft/s
Therefore, the velocity of the airplane is 267.2 ft/s
nơi nào có điện tích thì xung quanh điện tích đó có :
Explanation:
sory sorry sorry sorrysorrysorry
A confined aquifer with a transmissivity of 300 m2/day and a storativity of 0.0005 and a well radius of 0.3 m. Find the drawdown in the well at 100 days if the following pumping schedule is followed after a long period of time of no pumping.
Period
1 2 3 4
Time (days) 0-20 20-50 50-90 90-100
Q (m3/day) 500 300 800 0
Answer:
8.4627 m
Explanation:
Transmissivity( T ) = 300 m^2/day
Storativity( S ) = 0.0005
well radius ( r ) = 0.3m
Determine the drawdown in well at 100 days
Drawdown at 100 days = ∑ Drawdown at various period
We will use the equation : S = Q / U*π*T [ -0.5772 - In U ] ----- ( 1 )
where : Q = discharge , T = transmissivity
S = drawdown ,
U = r^2*s / 4*T*t --- ( 2 )
r = well radius , S = Storativity, t = time period
i) During 0-20
U1 = r^2*s / u*π*t = 1.875 * 10^-9
Input values into equation 1
S1 = 2.5885
ii) During 20-50
U2 = r^2*s / 4*π*t = 0.3^2 * 30 / u * 300 * 30 = 1.25 * 10^-9
input values into equation 1
S2 = 1.5854 m
iii) During 50 -90
U3 = r^2*s / 4*π*t = 9.375 * 10^-10
input values into equation 1
S3 = 4.2888 m
iv) During 90-100
U4 = 0
s4 = 0
Drawdown at 100 days = ∑ Drawdowns at various period
= s1 + s2 + s3 + s4 = 2.5885 + 1.5854 + 4.2888 + 0
= 8.4627 m
Please label the following statements as either True (T) or False (F).
(a) The true stress is higher than the engineering stress for a sample under tension.
(b) Creep test is carried out with a dynamic stress under elevated temperature.
Answer:
a. True
b. False
Explanation:
a. Since true stress, σ' = σ(1 + ε) where σ = engineering stress and ε = engineering strain.
Also under tension ε > 0, so, (1 + ε) > 1
Since (1 + ε) = σ'/σ > 1, ⇒ σ' > σ
So, the true stress is greater than the engineering stress.
So, the statement is true
b. Creep is a time-dependent deformation under certain applied load.
Creep occurs at high temperatures under different types of stress.
But, Creep test is carried out at constant high temperature and constant stress.
This statement is false.
Các đặc điểm chính của đường dây dài siêu cao áp .
Answer:
Đường dây siêu cao áp 500kV: Những chuyện giờ mới kể ... Ngày 27/5/1994, hệ thống đường dây điện siêu cao áp 500kV Bắc - Nam chính thức đưa ... Tại thời điểm đó, các nước như Pháp, Úc, Mỹ khi xây dựng đường dây dài nhất ... và chế ra các máy kéo dây theo đặc thù công việc của từng đơn vị.
Explanation:
R-134a is throttled in a line flowing at 25oC, 750 kPa with negligible kinetic energy to a pressure of 165 kPa. Find the exit temperature and the ratio of the exit pipe diameter to that of the inlet pipe (Dex/Din) so that the velocity stays constant.
Solution :
For R-134a, we are given :
[tex]$T_i = 25^\circ C$[/tex]
[tex]$P_i=750 \ kPa$[/tex]
[tex]$P_e=165 \ kPa$[/tex]
Now we have one inlet and one exit flow, no work and no heat transfer. The energy equation is :
[tex]$h_e+\frac{1}{2}.v_e^2= h_i+\frac{1}{2}.v_i^2 $[/tex]
We also know that the gas is throttled and there is no change in the kinetic energy.
So, [tex]$v_e=v_i$[/tex]
Now from the energy equation above, we can see that the inlet and the exit enthalpies are also the same. Therefore,
[tex]$h_i=h_e$[/tex]
From the saturated R-134a table, corresponding to [tex]P_e = 165 \ kPa[/tex], we can find the exit saturation temperature.
[tex]$T_e=-15^\circ C$[/tex]
From the saturated R-134a table, corresponding to [tex]P_e = 165 \ kPa[/tex], we can find the specific enthalpies :
[tex]$h_f = 180.19 \ kJ/kg$[/tex]
[tex]$h_{fg} = 209 \ kJ/kg$[/tex]
Calculating the exit flow quality factor,
[tex]$x_e=\frac{h_e-h_f}{h_{fg}}$[/tex]
[tex]$=\frac{234.59-180.19}{209}$[/tex]
= 0.26
From the saturated R-134a table, corresponding to [tex]P_e = 165 \ kPa[/tex], we can find the specific volumes :
[tex]$v_f = 0.00746 \ m^3/kg$[/tex]
[tex]$v_{fg} = 0.11932 \ m^3/kg$[/tex]
Calculating the exit specific volume :
[tex]$v_e=v_f+x_e(v_{fg})$[/tex]
= 0.000746 + 0.26 (0.11932)
= 0.0318 [tex]m^3/kg[/tex]
The mass flow is equal to :
[tex]$\dot{m} = A_i . \frac{v}{v_i}$[/tex]
[tex]$=A_e . \frac{v}{v_e}$[/tex]
So, [tex]$\frac{A_e}{A_i}=\frac{v_e}{v_i}$[/tex]
Therefore, the ratio of the exit pipe and the inlet pipe diameter is equal to
[tex]$\frac{D_e}{D_i}=\sqrt{\frac{A_e}{A_i}}$[/tex]
[tex]$\frac{D_e}{D_i}=\sqrt{\frac{v_e}{v_i}}$[/tex]
[tex]$\frac{D_e}{D_i}=\sqrt{\frac{0.0318}{0.000829}}$[/tex]
[tex]$\frac{D_e}{D_i}=6.19$[/tex]
An electron is traveling with initial kinetic energy K in a uniform electric field. The electron comes to rest momentarily after traveling a distance d.
a. What is the magnitude of the electric field?
b. What is the direction of the electric field?
1. in the direction of the electron's motion
2. opposite to the direction of the electron's motion
3. perpendicular to the direction of the electron's motion
Answer:
The answer is below
Explanation:
a) The work done is equal to the loss in kinetic energy (KE)
Change in kinetic energy (ΔKE) = Final kinetic energy - initial kinetic energy
Final KE = [tex]\frac{1}{2}mv_f^2[/tex]
But the final velocity is 0 (at rest). Hence:
Final KE = [tex]\frac{1}{2}mv_f^2=\frac{1}{2}m(0)^2=0[/tex]
ΔKE = 0 - K = -K
W = ΔKE = -K
Also, the work done (W) = charge (q) * distance (d) * electric field intensity (E)
W = qEd
but q = -e, hence:
W = -e * E * d
Using:
W = ΔKE
-e * E * d = -K
E= K / (e * d)
b) The electric field is in the direction of the electrons motion
