PHMayoi-chan
Eternal Poster
Pwede po ito ? salamat po
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3. Do you think that Earth can exist without human beings taking care of it ?
Yes, Earth exists without human beings taking care of it. The net impact is that its own civilization is destroying it extremely quickly.
No biodiversity does not need human beings for it to be in a continuous growing process
Cause: Intensification of agricultural practices (yielding pollution and disturbance) and disappearance of landscape elements that provide food and shelter that are exploitable by wildlife (such as hedges, trees, ponds, etc.
2. Main threat: Degradation, destruction and fragmentation of natural habitats
Cause: Spread of the urbanised areas, road network and industrial areas and associated problems (noise, pollution); abandon of former agricultural practices that were favourable to biodiversity
3. Main threat: Pollution of soils, air and water
Cause: Excess of heavy metals (industry, roads), manure and pesticides (agriculture) and other pollutants
.4. Main threat: Epidemics affecting wildlife
Cause: Arrivals of pathogens that are favoured by the introduction of exotic species, pollution and the destruction of habitats
5. Main threat: Climate change
Cause: Carbon emissions, deforestation and other land use changes due to human activities
6. Main threat: Dessication of soils and wetlands
Cause: Excess pumping of underground water tables
7. Main threat: Invasions by alien species
Cause: International trade and transport (roads, railways, rivers), gardening practices, exotic trees in forestry, exotic pests released in the wild, climate change, etc.
Cause: Industrial fishing, overexploitation of target species, by-catch species
2. Main threat: Degradation and destruction of the sea floor
Cause: Beam trawling, dredging, sand and gravel extraction
3. Main threat: Pollution and éùtrophication
Cause: Land-based activities (river run-off), atmospheric deposition, maritime traffic
4. Main threat: Alien species introductions
Cause: Maritime trade (ballast waters, fouling), leisure navigation, mariculture, climate change
5. Main threat: Leisure and tourism
Cause: Coastal development, water quality in summer (high population), mechanical beach cleaning, noise and other perturbations due to the high population.
9. What are nanomaterials ?
The mere presence of nanomaterials is not in itself a threat; as a matter of fact, nanoparticles exist in nature. It is only certain aspects that can make them risky, in particular their mobility and their increased reactivity. Only if certain properties of certain nanoparticles were proven harmful to living beings or the environment would we be faced with a genuine hazard.
1) Nanocomposites, nanostructured surfaces and nanocomponents (electronic, optical, sensors etc.), where nanoscale particles are incorporated into a substance, material or device ("fixed" nano-particles); and
2) "Free" nanoparticles, where at some stage in production or use individual nanoparticles of a substance are present. These free nanoparticles could be nanoscale species of elements, or simple compounds, but also complex compounds where for instance a nanoparticle of a particular element is coated with another substance.
There seems to be consensus that, although one should be aware of materials containing fixed nanoparticles, the immediate concern is with free nanoparticles.
11. What are the contributions of nanotechnology for the improvement and sustainability of our environment?
Nanotechnology could make battery recycling economically attractive
Before CO2 can be stored in Carbon dioxide Capture and Storage (CCS) schemes, it must be separated from the other waste gases resulting from combustion or industrial processes. Most current methods used for this type of filtration are expensive and require the use of chemicals. Nanotechnology techniques to fabricate nanoscale thin membranes could lead to new membrane technology that could change that.
13. Should gene therapy be limited to medical concerns only or could it be used for aesthetic purposes?
Climate change:
Individual action on climate change can include personal choices in many areas, such as diet, means of long- and short-distance travel, household energy use, consumption of goods and services, and family size. Individuals can also engage in local and political advocacy around issues of climate change.
There are many effective ways each one of us can make a difference:
1. Speak up
2. Power your home with renewable energy.
3. Invest in energy-efficient appliances.
4. Weatherize, weatherize, weatherize
5. Reduce water waste.
6. Actually eat the food you buy—and make less of it meat.
7. Buy better bulbs.
8. Drive a fuel-efficient vehicle
9. Rethink planes, trains, and automobiles.
10. Shrink your carbon profile.
Is climate change preventable?
Yes, it is.
It may not be too late to avoid or limit some of the worst effects of climate change.
15. What should be the significant contribution of the society as well as the government in mitigating the hazards caused by climate change?
Respect for nature is fundamental. Governments must protect ecosystems key to the fight against climate change: rivers, wetlands, oceans, forests and mangroves absorb large quantities of carbon, slowing warming. Mangroves also serve as a barrier against tropical storms, and wetlands absorb excess water from floods, both extreme weather events exacerbated by climate change.
2. SUPPORT SMALL AGRICULTURAL PRODUCERS
According to the FAO, the meat industry is responsible for 15 to 18 percent of all greenhouse gas emissions, exceeding even those of the transportation sector. In addition, it is the most significant source of water use and contamination in the world. Today, 80 percent of all agricultural production goes toward feeding animals not people. The expansion of land for livestock, and the crops to feed them, is the most significant cause of deforestation in the Amazon.
Governments can make a difference by supporting small local producers who, unlike large factory farms, employ sustainable practices, care about land restoration, benefit nearby communities, and make animals and crops more resilient to climate change. It’s less about everybody becoming vegetarians, but more about supporting those who produce our food with a respect for nature.
3. PROMOTE GREEN ENERGY
Thirty-five percent of all global emissions come from energy production. But as countries bet on more development, they’re also betting on more energy production. But as countries bet on more development, they’re also betting on more energy.
While thermoelectric and hydroelectric energies were long considered the cheapest options, technological developments have allowed us to find better, cheaper, more efficient alternatives. With proper long-term planning, nations can avoid old climate-aggravating energy sources (hydropower is not green) and opt for small wind, solar, geothermal, oceanic and other projects that adapt to a place’s unique characteristics.
4. COMBAT SHORT-LIVED CLIMATE POLLUTANTS
Carbon dioxide (CO2) is the most infamous greenhouse gas. Since it remains in the atmosphere for centuries (even millennia), even if we stopped all its emissions sources today, the effects of climate change would continue. The good news is that other contaminants exist that contribute to climate change and only last a few days or years in the atmosphere. They’re known as short-lived climate pollutants, and they’re responsible for 30 to 45 percent of the emissions that cause global warming.
These pollutants include black carbon (soot), methane, ozone, and the hydro fluorocarbons found in refrigerants. Their effective control, through national policies and regulations, could accelerate the fight against climate change in the short term. In addition, because they cause serious air pollution, measures to mitigate them would directly benefit human health.
5. BET ON ADAPTATION, NOT JUST MITIGATION
In the fight against climate change, work aimed at reducing emissions, stopping their effects and diminishing future consequences is known as mitigation. It is important. However, some communities are already experiencing tragic consequences due to changes in climate over a short period of time. So we also must act to prevent catastrophes, increase resilience, and reduce vulnerability, which is known as adaptation.
Projects to mitigate emissions are more attractive financially than those designed for adaptation, which are generally focused on the most vulnerable communities. But it is important to give adaptation the significance it deserves in recognition of the fact that the impacts of climate change are already a grave reality for many.
Yes, Earth exists without human beings taking care of it. The net impact is that its own civilization is destroying it extremely quickly.
- Humans change ecosystems. As long as humans are on earth, changing ecosystems, then humans need to be aware of and try to mitigate their impacts.
- We are currently responsible for decreasing biodiversity on the planet. We are dependent on the ecosystems that we are changing, and if we are not careful, we will make the planet unlivable for ourselves, aside from dragging other species down with us.
- Once we are gone, it is likely that life will go on for surviving organisms, and evolutionary processes may lead to increases in biodiversity.
- Alternately, we can change our economies, our cultures, our habits, and start acting as caretakers for the ecosystems of earth, if only because it is the intelligent thing to do if we want to continue as a species beyong a few hundred or thousand more years.
No biodiversity does not need human beings for it to be in a continuous growing process
- Biodiversity creation is a natural process. Nature, doing its own thing, will become more and more complex. This is the process of evolution. As such, conservation is not necessary what people presume it is.
- However, if the human race decided to behave as guardians of our planets and the life on it. Instead of like assholes, then we no doubt would be able to achieve remarkable things for bio-diversity and its success if we wanted to.
- Due to human activities biodiversity is under serious threat. The main dangers worldwide are population growth and resource consumption, climate change and global warming, habitat conversion and urbanisation, invasive alien species, over-exploitation of natural resources and environmental degradation.
- Threats in terrestrial areas:
Cause: Intensification of agricultural practices (yielding pollution and disturbance) and disappearance of landscape elements that provide food and shelter that are exploitable by wildlife (such as hedges, trees, ponds, etc.
2. Main threat: Degradation, destruction and fragmentation of natural habitats
Cause: Spread of the urbanised areas, road network and industrial areas and associated problems (noise, pollution); abandon of former agricultural practices that were favourable to biodiversity
3. Main threat: Pollution of soils, air and water
Cause: Excess of heavy metals (industry, roads), manure and pesticides (agriculture) and other pollutants
.4. Main threat: Epidemics affecting wildlife
Cause: Arrivals of pathogens that are favoured by the introduction of exotic species, pollution and the destruction of habitats
5. Main threat: Climate change
Cause: Carbon emissions, deforestation and other land use changes due to human activities
6. Main threat: Dessication of soils and wetlands
Cause: Excess pumping of underground water tables
7. Main threat: Invasions by alien species
Cause: International trade and transport (roads, railways, rivers), gardening practices, exotic trees in forestry, exotic pests released in the wild, climate change, etc.
- Threats in marine areas:
Cause: Industrial fishing, overexploitation of target species, by-catch species
2. Main threat: Degradation and destruction of the sea floor
Cause: Beam trawling, dredging, sand and gravel extraction
3. Main threat: Pollution and éùtrophication
Cause: Land-based activities (river run-off), atmospheric deposition, maritime traffic
4. Main threat: Alien species introductions
Cause: Maritime trade (ballast waters, fouling), leisure navigation, mariculture, climate change
5. Main threat: Leisure and tourism
Cause: Coastal development, water quality in summer (high population), mechanical beach cleaning, noise and other perturbations due to the high population.
9. What are nanomaterials ?
- Nanomaterials are chemical substances or materials that are manufactured and used at a very small scale. Nanomaterials are developed to exhibit novel characteristics compared to the same material without nanoscale features, such as increased strength, chemical reactivity or conductivity.
- Nano materials are used in a variety of, manufacturing processes, products and healthcare including paints, filters, insulation and lubricant additives. In healthcare Nanozymes are nanomaterials with enzyme-like characteristics.
- Nanomaterials are made up of nano particles, which are extremely small particles measured on “nano-scale” units. They have been around for decades, produced for commercial purposes.
- Recently there has been a lot more attention given to nano particles; e.g., finding drugs that can be delivered directly into cancer cells via these particles.
- As for how they are made, you should refer to one of the numerous websites that diagram and explain the various technologies.
The mere presence of nanomaterials is not in itself a threat; as a matter of fact, nanoparticles exist in nature. It is only certain aspects that can make them risky, in particular their mobility and their increased reactivity. Only if certain properties of certain nanoparticles were proven harmful to living beings or the environment would we be faced with a genuine hazard.
- The environmental, health, and safety (EHS) risks of a nanomaterial may differ by characteristics such as size, shape, and surface chemistry, among others. 2) "Free" nanoparticles, where at some stage in production or use individual nanoparticles of a substance are present.
1) Nanocomposites, nanostructured surfaces and nanocomponents (electronic, optical, sensors etc.), where nanoscale particles are incorporated into a substance, material or device ("fixed" nano-particles); and
2) "Free" nanoparticles, where at some stage in production or use individual nanoparticles of a substance are present. These free nanoparticles could be nanoscale species of elements, or simple compounds, but also complex compounds where for instance a nanoparticle of a particular element is coated with another substance.
There seems to be consensus that, although one should be aware of materials containing fixed nanoparticles, the immediate concern is with free nanoparticles.
11. What are the contributions of nanotechnology for the improvement and sustainability of our environment?
- Nanotechnological products, processes and applications are expected to contribute significantly to environmental and climate protection by saving raw materials, energy and water as well as by reducing greenhouse gases and hazardous wastes. Using nanomaterials therefore promises certain environmental benefits and sustainability effects.
- However, that nanotechnology currently plays a rather subordinate role in environmental protection, whether it be in research or in practical applications. Environmental engineering companies themselves attach only limited importance to nanotechnology in their respective fields.
- Rising prices for raw materials and energy, coupled with the increasing environmental awareness of consumers, are responsible for a flood of products on the market that promise certain advantages for environmental and climate protection. Nanomaterials exhibit special physical and chemical properties that make them interesting for novel, environmentally friendly products.
- Examples include the increased durability of materials against mechanical stress or weathering, helping to increase the useful life of a product; nanotechnology-based dirt- and water-resistant coatings to reduce cleaning efforts; novel insulation materials to improve the energy efficiency of buildings; adding nanoparticles to a material to reduce weight and save energy during transport.
- In the chemical industry sector, nanomaterials are applied based on their special catalytic properties in order to boost energy and resource efficiency, and nanomaterials can replace environmentally problematic chemicals in certain fields of application.
- High hopes are being placed in nanotechnologically optimized products and processes for energy production and storage; these are currently in the development phase and are slated to contribute significantly to climate protection and solving our energy problems in the future
- In most commercially available “nano-consumer products“, environmental protection is not the primary goal. Neither textiles with nanosilver to combat perspiration odor, nor especially stable golf clubs with carbon nanotubes, help protect the environment. Manufacturers often promise such advantages, typically without providing the relevant evidence. Examples include self-cleaning surface coatings or textiles with spot protection, with are advertized as reducing the cleaning effort and therefore saving energy, water and cleaning agents.
Nanotechnology could make battery recycling economically attractive
- Many batteries still contain heavy metals such as mercury, lead, cadmium, and nickel, which can contaminate the environment and pose a potential threat to human health when batteries are improperly disposed of. Not only do the billions upon billions of batteries in landfills pose an environmental problem, they also are a complete waste of a potential and cheap raw material.
- Conventional clean-up techniques are not adequate to solve the problem of massive oil s*****. In recent years, nanotechnology has emerged as a potential source of novel solutions to many of the world's outstanding problems. Although the application of nanotechnology for oil spill cleanup is still in its nascent stage, it offers great promise for the future. In the last couple of years, there has been particularly growing interest worldwide in exploring ways of finding suitable solutions to clean up oil s***** through use of nanomaterials.
- The potential impact areas for nanotechnology in water applications are divided into three categories – treatment and remediation, sensing and detection, and pollution prevention and the improvement of desalination technologies is one key area thereof.
- Nanotechnology-based water purification devices have the potential to transform the field of desalination, for instance by using the ion concentration polarization phenomenon.
Before CO2 can be stored in Carbon dioxide Capture and Storage (CCS) schemes, it must be separated from the other waste gases resulting from combustion or industrial processes. Most current methods used for this type of filtration are expensive and require the use of chemicals. Nanotechnology techniques to fabricate nanoscale thin membranes could lead to new membrane technology that could change that.
13. Should gene therapy be limited to medical concerns only or could it be used for aesthetic purposes?
- Gene therapy involves altering the genes inside your body's cells in an effort to treat or stop disease.
- Genes contain your DNA — the code that controls much of your body's form and function, from making you grow taller to regulating your body systems. Genes that don't work properly can cause disease.
- Gene therapy replaces a faulty gene or adds a new gene in an attempt to cure disease or improve your body's ability to fight disease.
- It holds promise for treating a wide range of diseases, such as cancer, cystic fibrosis, heart disease, diabetes, hemophilia and AIDS.
Climate change:
- The term climate refers to the general weather conditions of a place over many years.
- Climate change is a significant variation of average weather conditions means conditions becoming warmer, wetter, or drier over several decades or more. It’s that longer-term trend that differentiates climate change from natural weather variability.
- And while “climate change” and “global warming” are often used interchangeably, global warming is the recent rise in the global average temperature near the earth’s surface which is just one aspect of climate change.
Individual action on climate change can include personal choices in many areas, such as diet, means of long- and short-distance travel, household energy use, consumption of goods and services, and family size. Individuals can also engage in local and political advocacy around issues of climate change.
There are many effective ways each one of us can make a difference:
1. Speak up
2. Power your home with renewable energy.
3. Invest in energy-efficient appliances.
4. Weatherize, weatherize, weatherize
5. Reduce water waste.
6. Actually eat the food you buy—and make less of it meat.
7. Buy better bulbs.
8. Drive a fuel-efficient vehicle
9. Rethink planes, trains, and automobiles.
10. Shrink your carbon profile.
Is climate change preventable?
Yes, it is.
It may not be too late to avoid or limit some of the worst effects of climate change.
- Climate change mitigation is the act of decreasing the factors that contribute to climate change. One of the most significant contributors to climate change is the rise in greenhouse gases. Limiting greenhouse gas emissions is a common mitigation strategy. California's Assembly Bill 32, the Global Warming Solutions Act of 2006, mandated the reduction of greenhouse gas emissions in California to 1990 levels by 2020.
- Improving the energy efficiency of buildings to reduce emissions from heating/cooling
- Planting forests and tree to remove excess carbon dioxide from our atmosphere
- Invest in renewables and divest from fossil fuels
- Reducing fuel emissions associated with motor vehicles
- Consume less, waste less, enjoy life more
15. What should be the significant contribution of the society as well as the government in mitigating the hazards caused by climate change?
- Large-scale measures that are vital to ensuring a better future for all:
Respect for nature is fundamental. Governments must protect ecosystems key to the fight against climate change: rivers, wetlands, oceans, forests and mangroves absorb large quantities of carbon, slowing warming. Mangroves also serve as a barrier against tropical storms, and wetlands absorb excess water from floods, both extreme weather events exacerbated by climate change.
2. SUPPORT SMALL AGRICULTURAL PRODUCERS
According to the FAO, the meat industry is responsible for 15 to 18 percent of all greenhouse gas emissions, exceeding even those of the transportation sector. In addition, it is the most significant source of water use and contamination in the world. Today, 80 percent of all agricultural production goes toward feeding animals not people. The expansion of land for livestock, and the crops to feed them, is the most significant cause of deforestation in the Amazon.
Governments can make a difference by supporting small local producers who, unlike large factory farms, employ sustainable practices, care about land restoration, benefit nearby communities, and make animals and crops more resilient to climate change. It’s less about everybody becoming vegetarians, but more about supporting those who produce our food with a respect for nature.
3. PROMOTE GREEN ENERGY
Thirty-five percent of all global emissions come from energy production. But as countries bet on more development, they’re also betting on more energy production. But as countries bet on more development, they’re also betting on more energy.
While thermoelectric and hydroelectric energies were long considered the cheapest options, technological developments have allowed us to find better, cheaper, more efficient alternatives. With proper long-term planning, nations can avoid old climate-aggravating energy sources (hydropower is not green) and opt for small wind, solar, geothermal, oceanic and other projects that adapt to a place’s unique characteristics.
4. COMBAT SHORT-LIVED CLIMATE POLLUTANTS
Carbon dioxide (CO2) is the most infamous greenhouse gas. Since it remains in the atmosphere for centuries (even millennia), even if we stopped all its emissions sources today, the effects of climate change would continue. The good news is that other contaminants exist that contribute to climate change and only last a few days or years in the atmosphere. They’re known as short-lived climate pollutants, and they’re responsible for 30 to 45 percent of the emissions that cause global warming.
These pollutants include black carbon (soot), methane, ozone, and the hydro fluorocarbons found in refrigerants. Their effective control, through national policies and regulations, could accelerate the fight against climate change in the short term. In addition, because they cause serious air pollution, measures to mitigate them would directly benefit human health.
5. BET ON ADAPTATION, NOT JUST MITIGATION
In the fight against climate change, work aimed at reducing emissions, stopping their effects and diminishing future consequences is known as mitigation. It is important. However, some communities are already experiencing tragic consequences due to changes in climate over a short period of time. So we also must act to prevent catastrophes, increase resilience, and reduce vulnerability, which is known as adaptation.
Projects to mitigate emissions are more attractive financially than those designed for adaptation, which are generally focused on the most vulnerable communities. But it is important to give adaptation the significance it deserves in recognition of the fact that the impacts of climate change are already a grave reality for many.
Mayoi-chan
Eternal Poster
Salamat po dito <3
romomi00003
Honorary Poster
Pa unlock po TS. Tignan ko lang po kung paanong approach masolve yung problem. Maraming salamat po.
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romomi00003
Honorary Poster
Maraming salamat po TS.
tukmol202020
Grasshopper
Lods patulong https://www.Çℎḙḡḡ.com/homework-help...inged-held-together-cable-bc-top-an-q58332000
ThePinoy23
Leecher
[XX='CarisGrace, c: 445369, m: 1485280'][/XX]
To CarisGrace,
https://www.Çℎḙḡḡ.com/homework-help...er-10-problem-20qp-solution-9781118214220-exc
Thanks po.
To CarisGrace,
https://www.Çℎḙḡḡ.com/homework-help...er-10-problem-20qp-solution-9781118214220-exc
Thanks po.
A)
i)
In presence of gate pulse, the SCR is turned ON and is in forward blocking state till the current through it exceeds the latching current. Once it is turned ON it stays in the same state till the current id reduced below the holding current.
ii)
In absence of triggering pulse the SCR , will not turn ON . There will be an open circuit, no current will flow (except leakage current, it may flow).
B)
i)
One of the commonly used SCR Turn On methods is by increasing the forward anode to cathode voltage. By doing this, the depletion layer width is also increasing at junction J2. This also increases the minority charge carriers accelerating voltage at junction J2. This further leads to an avalanche breakdown of the junction J2 at a forward breakover voltage VBO.
At this stage SCR turns into conduction mode and thus a large current flow through it with a low voltage drop across it.
In practice this method is not employed because it needs a very large anode to cathode voltage. And also once the voltage is more than the VBO, it generates very high currents which may cause damage to the SCR. Therefore, most of the cases this type of triggering is avoided.
2) dv/dt Triggering
In forward blocking state junctions J1 and J3 are forward biased and J2 is reverse biased. Thus the junction J2 behaves as a capacitor due to the space charges in the depletion region. The charging current of the capacitor is given as
where dv/dt is the rate of change of applied voltage and C is the junction capacitance of the SCR.
From the above equation, if the rate of change of the applied voltage is large that leads to increase the charging current. So the SCR becomes turned ON without a gate signal.
However, this method is also practically avoided because it is a false turn ON process and also this can also produce very high voltage spikes across the SCR so there will be considerable damage to it.
3) Gate Triggering
This is most common and efficient method to turn ON the SCR. When the SCR is forward biased, a sufficient voltage applied at the gate terminal injects some electrons into the junction J2. This result to increase reverse leakage current and hence causes the breakdown of junction J2 even at the voltage lower than the VBO.
In gate triggering method, a positive voltage applied between the gate and the cathode terminals. We can use three types of gate signals to turn On the SCR namely DC signal, AC signal and pulse signal.
ii)
There are two methods by which a thyristor can be turned OFF( also called as Commutation):
In AC circuit, the current always passes through zero for every half cycle.As the current passes through natural zero, a reverse voltage will simultaneously appear across the device.This will turn OFF the device immediately on it's own.
This process is called as natural commutation, as no external circuit is required for this purpose. This is also known as line commutation.
b) Forced Commutation:
To turn OFF a thyristor, the forward anode current should be brought to zero(less than the holding current) for sufficient time to allow the removal of charged carriers.
In case of DC circuits the forward current should be forced to zero by means of some external circuits.
This process is called as forced commutation.
The forced commutation is further classified as
(1) Voltage Commutation (charge stored in the capacitor with opposite polarity will be applied to the SCR to turn it off)
(2) Current Commutation (field stored in the inductor will be applied to the SCR to turn it off or the current will be diverted through some other path for sufficient time)
i)
In presence of gate pulse, the SCR is turned ON and is in forward blocking state till the current through it exceeds the latching current. Once it is turned ON it stays in the same state till the current id reduced below the holding current.
ii)
In absence of triggering pulse the SCR , will not turn ON . There will be an open circuit, no current will flow (except leakage current, it may flow).
B)
i)
- Forward voltage triggering
- Temperature triggering
- dv/dt triggering
- Light triggering
- Gate triggering
One of the commonly used SCR Turn On methods is by increasing the forward anode to cathode voltage. By doing this, the depletion layer width is also increasing at junction J2. This also increases the minority charge carriers accelerating voltage at junction J2. This further leads to an avalanche breakdown of the junction J2 at a forward breakover voltage VBO.
At this stage SCR turns into conduction mode and thus a large current flow through it with a low voltage drop across it.
In practice this method is not employed because it needs a very large anode to cathode voltage. And also once the voltage is more than the VBO, it generates very high currents which may cause damage to the SCR. Therefore, most of the cases this type of triggering is avoided.
2) dv/dt Triggering
In forward blocking state junctions J1 and J3 are forward biased and J2 is reverse biased. Thus the junction J2 behaves as a capacitor due to the space charges in the depletion region. The charging current of the capacitor is given as
where dv/dt is the rate of change of applied voltage and C is the junction capacitance of the SCR.
From the above equation, if the rate of change of the applied voltage is large that leads to increase the charging current. So the SCR becomes turned ON without a gate signal.
However, this method is also practically avoided because it is a false turn ON process and also this can also produce very high voltage spikes across the SCR so there will be considerable damage to it.
3) Gate Triggering
This is most common and efficient method to turn ON the SCR. When the SCR is forward biased, a sufficient voltage applied at the gate terminal injects some electrons into the junction J2. This result to increase reverse leakage current and hence causes the breakdown of junction J2 even at the voltage lower than the VBO.
In gate triggering method, a positive voltage applied between the gate and the cathode terminals. We can use three types of gate signals to turn On the SCR namely DC signal, AC signal and pulse signal.
ii)
There are two methods by which a thyristor can be turned OFF( also called as Commutation):
- Natural Commutation
- Forced Commutation
In AC circuit, the current always passes through zero for every half cycle.As the current passes through natural zero, a reverse voltage will simultaneously appear across the device.This will turn OFF the device immediately on it's own.
This process is called as natural commutation, as no external circuit is required for this purpose. This is also known as line commutation.
b) Forced Commutation:
To turn OFF a thyristor, the forward anode current should be brought to zero(less than the holding current) for sufficient time to allow the removal of charged carriers.
In case of DC circuits the forward current should be forced to zero by means of some external circuits.
This process is called as forced commutation.
The forced commutation is further classified as
(1) Voltage Commutation (charge stored in the capacitor with opposite polarity will be applied to the SCR to turn it off)
(2) Current Commutation (field stored in the inductor will be applied to the SCR to turn it off or the current will be diverted through some other path for sufficient time)
ThePinoy23
Leecher
[XX='CarisGrace, c: 445792, m: 1485280'][/XX]
Hi po, Sorry po sa daming request. Nalilito lang po talaga ako eh and Çℎḙḡḡ usually explains it better. THANKS Po!!!
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And
https://www.Çℎḙḡḡ.com/homework-help...-mg-figure-4-composition-pb-10-20-3-q42434605
Hi po, Sorry po sa daming request. Nalilito lang po talaga ako eh and Çℎḙḡḡ usually explains it better. THANKS Po!!!
https://www.Çℎḙḡḡ.com/homework-help...8-heated-250-c-temperature-entirely--q5351320
And
https://www.Çℎḙḡḡ.com/homework-help...-mg-figure-4-composition-pb-10-20-3-q42434605
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self.size=-1
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self.items.append(value)
self.size+=1
def pop(self):
if self.isempty():
return 0
else:
self.size-=1
return self.items.pop()
def isempty(self):
if(self.size==-1):
return True
else:
return False
def seek(self):
if self.isempty():
return False
else:
return self.items[self.size]
def is0perand(self,i):
if i.isalpha() or i in '1234567890':
return True
else:
return False
def reverse(self,expr):
rev=""
for i in expr:
if i is '(':
i=')'
elif i is ')':
i='('
rev=i+rev
return rev
def infixtoprefix (self,expr):
prefix=""
for i in expr:
if(len(expr)%2==0):
print("Incorrect infix expr")
return False
elif(self.is0perand(i)):
prefix +=i
elif(i in '+-*/^'):
while(len(self.items)and self.precedence < self.precedence[self.seek()]):
prefix+=self.pop()
self.push(i)
elif i is '(':
self.push(i)
elif i is ')':
o=self.pop()
while o!='(':
prefix +=o
o=self.pop()
#end of for
while len(self.items):
if(self.seek()=='('):
self.pop()
else:
prefix+=self.pop()
#print(prefix)
return prefix
# Python program to convert infix E×ρréššion to postfix
# Class to convert the E×ρréššion
class Conversion:
# Constructor to initialize the class variables
def init(self, capacity):
self.top = -1
self.capacity = capacity
# This array is used a stack
self.array = []
# Precedence setting
self.output = []
self.precedence = {'+':1, '-':1, '*':2, '/':2, '^':3}
# check if the stack is empty
def isEmpty(self):
return True if self.top == -1 else False
# Return the value of the top of the stack
def peek(self):
return self.array[-1]
# Pop the element from the stack
def pop(self):
if not self.isEmpty():
self.top -= 1
return self.array.pop()
else:
return "$"
# Push the element to the stack
def push(self, op):
self.top += 1
self.array.append(op)
# A utility function to check is the given character
# is operand
def isOperand(self, ch):
return ch.isalpha()
# Check if the precedence of operator is strictly
# less than top of stack or not
def notGreater(self, i):
try:
a = self.precedence
b = self.precedence[self.peek()]
return True if a <= b else False
except KeyError:
return False
# The main function that converts given infix E×ρréššion
# to postfix E×ρréššion
def infixToPostfix(self, exp):
# Iterate over the E×ρréššion for conversion
for i in exp:
# If the character is an operand,
# add it to output
if self.isOperand(i):
self.output.append(i)
# If the character is an '(', push it to stack
elif i == '(':
self.push(i)
# If the scanned character is an ')', pop and
# output from the stack until and '(' is found
elif i == ')':
while( (not self.isEmpty()) and self.peek() != '('):
a = self.pop()
self.output.append(a)
if (not self.isEmpty() and self.peek() != '('):
return -1
else:
self.pop()
# An operator is encountered
else:
while(not self.isEmpty() and self.notGreater(i)):
self.output.append(self.pop())
self.push(i)
# pop all the operator from the stack
while not self.isEmpty():
self.output.append(self.pop())
print ("".join(self.output))
exp = input("enter the E×ρréššion: ")
p = int(input("enter \n1. to convert to postfix \n2. to convert to prefix"))
# Driver program to test above function
if(p==1):
obj = Conversion(len(exp))
obj.infixToPostfix(exp)
if(p==2):
s=infix_to_prefix()
rev=""
rev=s.reverse(exp)
#print(rev)
result=s.infixtoprefix(rev)
if (result!=False):
prefix=s.reverse(result)
print("the prefix exp of :",exp,"is",prefix)
precedence={'^':5,'*':4,'/':4,'+':3,'-':3,'(':2,')':1}
def init(self):
self.items=[]
self.size=-1
def push(self,value):
self.items.append(value)
self.size+=1
def pop(self):
if self.isempty():
return 0
else:
self.size-=1
return self.items.pop()
def isempty(self):
if(self.size==-1):
return True
else:
return False
def seek(self):
if self.isempty():
return False
else:
return self.items[self.size]
def is0perand(self,i):
if i.isalpha() or i in '1234567890':
return True
else:
return False
def reverse(self,expr):
rev=""
for i in expr:
if i is '(':
i=')'
elif i is ')':
i='('
rev=i+rev
return rev
def infixtoprefix (self,expr):
prefix=""
for i in expr:
if(len(expr)%2==0):
print("Incorrect infix expr")
return False
elif(self.is0perand(i)):
prefix +=i
elif(i in '+-*/^'):
while(len(self.items)and self.precedence < self.precedence[self.seek()]):
prefix+=self.pop()
self.push(i)
elif i is '(':
self.push(i)
elif i is ')':
o=self.pop()
while o!='(':
prefix +=o
o=self.pop()
#end of for
while len(self.items):
if(self.seek()=='('):
self.pop()
else:
prefix+=self.pop()
#print(prefix)
return prefix
# Python program to convert infix E×ρréššion to postfix
# Class to convert the E×ρréššion
class Conversion:
# Constructor to initialize the class variables
def init(self, capacity):
self.top = -1
self.capacity = capacity
# This array is used a stack
self.array = []
# Precedence setting
self.output = []
self.precedence = {'+':1, '-':1, '*':2, '/':2, '^':3}
# check if the stack is empty
def isEmpty(self):
return True if self.top == -1 else False
# Return the value of the top of the stack
def peek(self):
return self.array[-1]
# Pop the element from the stack
def pop(self):
if not self.isEmpty():
self.top -= 1
return self.array.pop()
else:
return "$"
# Push the element to the stack
def push(self, op):
self.top += 1
self.array.append(op)
# A utility function to check is the given character
# is operand
def isOperand(self, ch):
return ch.isalpha()
# Check if the precedence of operator is strictly
# less than top of stack or not
def notGreater(self, i):
try:
a = self.precedence
b = self.precedence[self.peek()]
return True if a <= b else False
except KeyError:
return False
# The main function that converts given infix E×ρréššion
# to postfix E×ρréššion
def infixToPostfix(self, exp):
# Iterate over the E×ρréššion for conversion
for i in exp:
# If the character is an operand,
# add it to output
if self.isOperand(i):
self.output.append(i)
# If the character is an '(', push it to stack
elif i == '(':
self.push(i)
# If the scanned character is an ')', pop and
# output from the stack until and '(' is found
elif i == ')':
while( (not self.isEmpty()) and self.peek() != '('):
a = self.pop()
self.output.append(a)
if (not self.isEmpty() and self.peek() != '('):
return -1
else:
self.pop()
# An operator is encountered
else:
while(not self.isEmpty() and self.notGreater(i)):
self.output.append(self.pop())
self.push(i)
# pop all the operator from the stack
while not self.isEmpty():
self.output.append(self.pop())
print ("".join(self.output))
exp = input("enter the E×ρréššion: ")
p = int(input("enter \n1. to convert to postfix \n2. to convert to prefix"))
# Driver program to test above function
if(p==1):
obj = Conversion(len(exp))
obj.infixToPostfix(exp)
if(p==2):
s=infix_to_prefix()
rev=""
rev=s.reverse(exp)
#print(rev)
result=s.infixtoprefix(rev)
if (result!=False):
prefix=s.reverse(result)
print("the prefix exp of :",exp,"is",prefix)
- Status