GGRA03H3 Lecture 8: lecture 8

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aquamarineminnow819

25 Feb 2012

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During the last 15 years new understanding of cities as complex ecosystems. Cities are now seen as complex organisms with their own metabolic processes. They have huge inputs and outputs, that are structured by metabolic processes of production, delivery, consumption, and waste emission. Inputs and outputs can be measured and where necessary can be influenced by public policy. It is critical to understand the nature of the inputs and outputs. Water is one of the most important urban inputs. Ensuring quality water supply is important for health. Polluted water is one of main urban outputs. One of the key achievements of the 19th century sanitary revolution was the development of public water supply and wastewater removal infrastructure. Initially just pipes to dump the water downstream, later primary treatment, secondary treatment [-50 and 60 s water system put bacteria to clean water and filter non-dissolve-(biological waste)] , tertiary treatment systems were added [-deal with toxic-]

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Tiny solid and liquid particles suspended in the atmosphere are called aerosols. Windblown dust, sea salts, volcanic ash, smoke from wildfires, and pollution from factories are all examples of aerosols. Depending upon their size, type, and location, aerosols can either cool the surface, or warm it. They can help clouds to form, or they can inhibit cloud formation. And if inhaled, some aerosols can be harmful to people's health.

These maps show average monthly aerosol amounts around the world based on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite. Satellite measurements of aerosols, called aerosol optical thickness, are based on the fact that the particles change the way the atmosphere reflects and absorbs visible and infrared light. An optical thickness of less than 0.1 (palest yellow) indicates a crystal clear sky with maximum visibility, whereas a value of 1 (reddish brown) indicates very hazy conditions.

High aerosol amounts are linked to different process in different places and times of year. High aerosol amounts occur over South America from July through September. This pattern is due to land clearing and agricultural fires that are widespread across the Amazon Basin and Cerrado regions during the dry season. Aerosols have a similar seasonal pattern in Central America (March-May), central and southern Africa (June-September, and Southeast Asia (January-April).

In other cases, however, aerosol concentrations are not related to fires. For example, from May through August each year, aerosol amounts rise dramatically around the Arabian Peninsula and nearby oceans due to dust storms. Elevated aerosol amounts nestle at the foothills of the Himalaya Mountains in northern India in some months, and linger over eastern China for much of the year. These elevated aerosol amounts are due to human-produced air pollution.

What is the most likely source of the high concentration of particulates that appear off the coast of northwestern Africa?

What is the most likely source of the high concentrations of particulates over central Africa and central South America?

What is the most likely source of the high concentrations of particulates over eastern China?

apricottermite85

Vapor cycles
5EM - Thermodynamics
September 2010
1 The T-S diagram
The temperature-entropy diagram is an alternative to the well knownpressure-
volume diagram. Before using it to analyze different vapor cycles,we need
to understand it properly.
1. Plot the following transformations for ideal gases in a T-Sdiagram
(a) Isothermal expansion
(b) Isobaric expansion
(c) Isometric heating
(d) Reversible adiabatic expansion
(e) Irreversible adiabatic expansion
2. Repeat the last question, but this time do it for a realsubstance,
starting in the compressed liquid1 region and ending in thesuperheated
region, when possible. Indicate the boundaries of eachregion.
3. We know that under certain circumstances the area under theplot
in a P-V diagram represents the work performed during theprocess.
What does it represent in this case? Under what assumptions isyour
answer true? Compare examples 6.1 and 6.2.
2 Thermal machines
We understand by thermal machine a device capable of transformingther-
mal energy (heat) into mechanical energy (work). We already knowthat
these machines have a limited efficiency which, in the two-sourcesmodel, is
obtained by Carnotâs cycle.
(Compressed liquid is sometimes also called subcooled liquid)
2.1 Carnot cycle
This cycle, although efficient, is impractical. To begin with, theextreme
temperatures of the cycle should be within the sources temperaturesfor a
finite heat flow to exist.
1. Given the temperature of the sources, draw the cycle accordingto the
named limitation.
2. Show that this leads to lower efficiency than the theoreticallimit.
3. Assume that heat flow from/to the sources is proportional to thetem-
perature difference between them and the working fluid, anddemon-
strate that a higher power output is related to a decreasedefficiency.
2.2 Rankine cycle
Out of the several practical possibilities, Rankine cycle and itsvariations is
widely used, especially for electric power generation.
1. Draw the basic cycle in a T-S diagram and explain it.
2. What does the efficiency of the cycle depend on? Comparewith
Carnotâs.
3. What are the differences between the ideal cycle and the realone?
4. Describe how it is modified by superheating and/or reheating.Explain
te benefits.
2.3 Problems
After answering the previous questions solve the followingexercises from the
book: 8.2, 8.4, 8.5, 8.13, 8.19, 8.20
3 Frigorific machines
3.1 Reverse Carnot cycle
We have already studied Carnot cycle in detail as the ideal thermalmachine.
Now we will take is as the starting point to understand thecharacteristics
of frigorific machines.
1. Draw the ideal cycle in a T-S diagram and explain it.
2. Show that this cycle has a theoretical efficiency Ã =Tcold/Thot-Tcold
3. What are the difficulties in implementing such cycle in actualdevices?
3.2 Actual refrigerators
1. Why is the turbine replaced by an expansion valve in mostcases?
2. Plot the actual cycle and explain the differences with the idealcase.
3. How do cascade and multistage systems improve the performanceof
the refrigerator?
4. What aspects are important in the choice of a refrigerant fluid?Justify
3.3 Problems
After answering the previous questions solve the followingexercises from the
book: 10.2 10.7, 10.8, 10.9, 10.22, 10.23 10.1D

Hi everyone,
I'm International Students and I have difficault to understand someproblems in physics. I want to do extra work to be ready forMidtearm.
Please if there is any one can help me by showing me how to solveit.
and if u can show me the steps because I will use it asnotes.

1-What are the metric prefixes for ten and tenth?

2-If you multiplied 7774 m by 36 m, how many significant figuresshould you report in your answer?

3-A ball is dropped:
What is its initial speed?
What is the magnitude of its initial acceleration?

4-A jogger jogs two blocks directly north.
(a) How do the jogger's average speed and the magnitude of theaverage velocity compare?
average speed ( ) magnitude of average velocity
(b) If the jogger's return trip follows the same path, how doaverage speed and magnitude of the average velocity compare for thetotal trip?
average speed ( ) magnitude of average velocity

5-A child's cubic play block has a mass of 115 g and sides of 5.2cm. When placed in a bath tub full of water, will the cube sink orfloat?
(sink) or (float)

6-A ball with a radius of 8 cm and a mass of 550 g is thrown into alake. Will the ball sink or float?
(sink) or (float)

7-Persons A and B do the same job, but B takes longer
Who does the greater amount of work?
person A, person B, Or all the same
Who is more "powerful"?
Person A or Person B

8- Which two renewable energy sources depend on the weather?(Select all that apply.)
geothermal
biomass
tidal
solar
wind

9- The two common liquids used in liquid-in-glass thermometers arealcohol (ethanol) and mercury, which have melting points andboiling points of -114Â°C, 79Â°C and -39Â°C, 357Â°C,respectively.
Which one of these thermometers would be better for low temperaturemeasurements?
(alcohol or mercury)
Which one of these thermometers would be better for hightemperature measurements?
(alcohol or mercury)

10-What determines the phase of a substance? (Select all thatapply.)
humidity
temperature
amount of the substance
pressure

11-What is the difference between a longitudinal wave and atransverse wave?

Longitudinal wave: particle displacement is (---) parallelperpendicular to wave velocity.
Transverse wave: particle displacement is ( ------) perpendicularparallel to wave velocity.

Give an example of a longitudinal wave.
(sound wave in air OR
light wave)
Give an example of a transverse wave.
(sound wave in air Or
light wave)

12-Which end (blue or red) of the visible spectrum has the shorterwavelength?
Which has the lower frequency?

13- How long does the image of a 18-in ruler appear in a planemirror?
Does this depend on the distance the ruler is from themirror?
(Yes OR
No)

14-What optical phenomenon causes soap bubbles and oil slicks toshow colorful displays?

15- Which two particles that make up atoms have about the samemass? (Select all that apply.)
protons
electrons
neutrons

16- Which two have the same magnitude of electric charge? (Selectall that apply.)
neutrons
electrons
protons

17- Name one phenomenon that can only be explained by light havinga wave nature.
polarization
photoelectric effect
acceleration
displacement

18- How are frequency and wavelength of an electromagnetic waverelated?
higher the frequency, longer the wavelength
higher the frequency, shorter the wavelength
the frequency and wavelength are not direclty related

19- What other name is often used to refer to the electron cloudmodel of the atom?
plum pudding model
billiard ball model
quantum model
nuclear model
planetary model

20- What are the names of the elements with the followingsymbols?
(a) Ne
(b) Li
(c) He

21- After 4 half-lives have gone by, what fraction of a sample of aradioactive isotope remains? (Write your answer in fractionform.)

22- What are the most common names for these compounds andions?
(a) N2O
(b) HCl
(c) C2H3O2 ?
(d) PO43-

23- What is the formula for the common household compound known astable salt? (Type your answer using the format CO2 for CO2.)

24- What element has the lowest electronegativity?
What element has the second highest electronegativity?

Give the Stock system name for the following.
(a) Cr(OH)2
(b) CuCl2
(c) AuBr3

GGRA03H3 Lecture 8: lecture 8

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