Assignments for this tutorial
1. 03:15: In Scilab, enter the following Matrices:
A = ⌊ ⌋ 1 1∕2 ⌈1∕3 1∕4⌉ 1∕5 1∕6
B = [ ] 5 - 2, C = [4 5∕4 9∕4] 1 2 3
Using Scilab commands, compute each of the following, if possible.
1. A * C
2. A * B
3. A + C′
4. B * A - C′* A
5. (2 * C - 6 * A′) * B′
6. A * C - C * A
7. A * A′ + C′* C
Explain the errors, if any.
2. 04:15: From the video:
1. Find E(:, :)
2. Extract the second column of E
3. 05:46: If A = ⌊ ⌋ ⌈1 - 1 0⌉ 2 3 1 4 1 5
Use a suitable sequence of row operations on A to bring A to upper triangular form.1
4. 07:28: Represent the following linear system as a matrix equation. Solve the system using the inverse method:
x + y + 2z - w = 3
2x + 5y - z - 9w = -3
2x + y - z + 3w = -11
x - 3y + 2z + 7w = -5
5. 08:01: Try solving the above system using the backslash method.
6. 08:38: Verify the solution from the previous question.
7. 09:38: Try det(A), A2, A3 and Eigenvalues of A (from the previous question).
Also multiply A by an identity matrix of the same size.
Every time a car brakes, energy is generated. At present this energy is not used, but new research shows that it is perfectly possible to save it for later use in the form of compressed air. It can then provide extra power to the engine when the car is started and save fuel by avoiding idle operation when the car is at a standstill
Air hybrids, or pneumatic hybrids as they are also known, are not yet in production. Nonetheless, electric cars and electric hybrid cars already make use of the brake energy, to power a generator that charges the batteries. However, according to Per Tunestål, a researcher in Combustion Engines at Lund University in Sweden, air hybrids would be much cheaper to manufacture. The step to commercialisation does not have to be a large one.
"The technology is fully realistic. I was recently contacted by a vehicle manufacturer in India which wanted to start making air hybrids," he says.
The technology is particularly attractive for jerky and slow driving, for example for buses in urban traffic.
"My simulations show that buses in cities could reduce their fuel consumption by 60 per cent," says Sasa Trajkovic, a doctoral student in Combustion Engines at Lund University who recently defended a thesis on the subject.
Sasa Trajkovic also calculated that 48 per cent of the brake energy, which is compressed and saved in a small air tank connected to the engine, could be reused later. This means that the degree of reuse for air hybrids could match that of today's electric hybrids. The engine does not require any expensive materials and is therefore cheap to manufacture. What is more, it takes up much less space than an electric hybrid engine. The method works with petrol, natural gas and diesel.
For this research the Lund researchers have worked with the Swedish company Cargine, which supplies valve control systems.
The idea of air hybrids was initially hit upon by Ford in the 1990s, but the American car company quickly shelved the plans because it lacked the necessary technology to move forward with the project. Today, research on air hybrids is conducted at ETH in Switzerland, Orléans in France and Lund University in Sweden. One company that intends to invest in engines with air hybrid technology is the American Scuderi. However, their only results so far have been from simulations, not from experiments.
"This is the first time anyone has done experiments in an actual engine. The research so far has only been theoretical. In addition, we have used data that means we get credible driving cycle results, for example data from the driving patterns of buses in New York," says Sasa Trajkovic.
The researchers in Lund hope that the next step will be to convert their research results from a single cylinder to a complete, multi-cylinder engine. They would thus be able to move the concept one step closer to a real vehicle.
A milestone in the history of renewable energy occurred in the year 2008 when more new wind-turbine power generation capacity was added in the U.S. than new coal-fired power generation. The costs of producing power with wind turbines continues to drop, but many engineers feel that the overall design of turbines is still far from optimal.
New ideas for enhancing the efficiency of wind turbines are being presented this week at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, CA.
One issue confronting the efficiency of wind energy is the wind itself -- specifically, its changeability. The aerodynamic performance of a wind turbine is best under steady wind flow, and the efficiency of the blades degrades when exposed to conditions such as wind gusts, turbulent flow, upstream turbine wakes, and wind shear.
Now a new type of air-flow technology may soon increase the efficiency of large wind turbines under many different wind conditions.
Syracuse University researchers Guannan Wang, Basman El Hadidi, Jakub Walczak, Mark Glauser and Hiroshi Higuchi are testing new intelligent-systems-based active flow control methods with support from the U.S. Department of Energy through the University of Minnesota Wind Energy Consortium. The approach estimates the flow conditions over the blade surfaces from surface measurements and then feeds this information to an intelligent controller to implement real-time actuation on the blades to control the airflow and increase the overall efficiency of the wind turbine system. The work may also reduce excessive noise and vibration due to flow separation.
Initial simulation results suggest that flow control applied on the outboard side of the blade beyond the half radius could significantly enlarge the overall operational range of the wind turbine with the same rated power output or considerably increase the rated output power for the same level of operational range. The team is also investigating a characteristic airfoil in a new anechoic wind tunnel facility at Syracuse University to determine the airfoil lift and drag characteristics with appropriate flow control while exposed to large-scale flow unsteadiness. In addition, the effects of flow control on the noise spectrum of the wind turbine will be also assessed and measured in the anechoic chamber.
Another problem with wind energy is drag, the resistance felt by the turbine blades as they beat the air. Scientists at the University of Minnesota have been looking at the drag-reduction effect of placing tiny grooves on turbine blades. The grooves are in the form of triangular riblets scored into a coating on the blade surface. They are so shallow (between 40 and 225 microns) that they can't be seen by the human eye -- leaving the blades looking perfectly smooth.
Using wind-tunnel tests of 2.5 megawatt turbine airfoil surfaces (becoming one of the popular industry standards) and computer simulations, they are looking at the efficacies of various groove geometries and angles of attack (how the blades are positioned relative to the air stream).
Riblets like these have been used before, in the sails on sailboats taking part in the last America's Cup regatta and on the Airbus airliner, where they produced a drag reduction of about 6 percent. The design of wind turbine blades was, at first, closely analogous to that of airplane wings. But owing to different engineering concerns, such as turbine blades having a much thicker cross section close to the hub and wind turbines having to cope with peculiar turbulence near the ground, drag reduction won't be quite the same for wind turbines.
University of Minnesota researchers Roger Arndt, Leonardo P. Chamorro and Fotis Sotiropoulos believe that riblets will increase wind turbine efficiency by about 3 percent.
Wind turbines have a problem: Depending on the wind's force, the rotational speed of the turbine and thus of the generator changes. However, alternating current must be fed into the grid with precisely 50 (or 60) hertz. Typically the generated alternating current is first rectified and then transformed back to alternating current of the required frequency. Scientists have now developed an active transmission that makes this double transformation superfluous.
Most large wind turbines currently operate at variable speeds. When the wind is strong, the rotor turns fast; when it slows down, the rotor speed drops. Typically rotors complete 12 to 16 revolutions per minute. The generator is connected to the rotor via a gearbox. Here too, the speed of rotation varies with the speed of the wind.
Yet, a wind turbine may only feed alternating current with exactly the frequency of the electric grid. That is why the alternating current from generators is today transformed into direct current by way of giant rectifiers. In a second step the direct current is then transformed back into alternating current of the right frequency. This twofold conversion takes a loss of close to 5 percent.
In their research, scientists from the Chair of Machine Elements at the TU Muenchen took a closer look at the gears and generator system. To attain the grid frequency of 50 hertz, a generator with the usual two poles pairs must operate at a synchronous speed of exactly 1500 revolutions per minute. To fulfill this requirement in spite of the variable input rotational speed, the researchers developed a novel active torque-vectoring gear analogous to a controlled differential in motor vehicles.
As in conventional designs, planetary gears generate most of the transmission required. These are supplemented by a torque-vectoring gear with a supplemental electric motor that can be used as both as a drive and as a generator. This allows the power from the rotor to be either be boosted or diverted, leading to a constant rotational speed of the generator. Applying this concept to a 1.5 MW wind turbine, an electric motor of only about 80 KW is sufficient.
The advantage of this concept is a lighter power train that requires a much smaller nacelle for the wind turbine. Additionally a robust, low-maintenance synchronous generator can be used, which dispenses with the need for power electronics for frequency adjustment, thereby increasing the overall facility efficiency.
Originally this development, patented under the name of Torque Vectoring, was developed for cars. Within the Science Center for Electrical Mobility at the Technische Universitaet Muenchen the chair develops a torque-vectoring gear box for the electric vehicle concept "MUTE" which will be presented at the IAA 2011. Here the active control of force distribution improves driving safety, traction and provides for dynamic handling characteristics in curves.
An Experimental Battery Providing Electrical Power From Living Processes of the Fermentation Bacteria.
Very easy to be made of plastic PVC pipe pieces 50 mm in internal diameter and about 100 - 110 mm long.
Seal one end of 12 plastic pipes with the same plastic sheet material cutting round pieces corresponding with an outside pipe diameter. Finish the seal gluing with acetone-based glue or pure acetone. Form this way 12 battery cells. Each cell ought to produce about 0.5 Volt of direct current. Make am appropriate in size box to hold tightly whole the dozen of your battery cells. Form and fit into each cell two electrodes, cathode and anode. Best use old batteries’ carbon cores, zinc or copper rods or make them from thick wire. Connect these cells in sequential order to receive current of about 6 V / 40mA. To increase your power to 12 V/ 80mA make one more set. Connect it with the previous one in parallel. Finally, fill all cells with rice husks or crushed rice and top all this up with water to provide food for the bacteria that gives off power as the result of its living processes. It is totally harmless kind of bacteria, found in our food, especially marinated by natural processes, like marinated cucumbers, souerkraut, etc.
You can use also rye or its husks, wheat or other grains to experiment with. Biological battery cells with a food consisting of inorganic salts with bananas feeds for 24 hours electric appliances with a current of 3.7W (0.76V/4.92A).
Instead of bananas, vine grapes or some other sort of grapes, cucumbers, pumpkin, or other produce and fruits, can be used.
In just eight years, self-driving cars may be hitting the highways, allowing commuters to work, read, watch TV, nap -- or do just about anything else they can manage within the confines of a moving vehicle. Google has tested several such cars in California, and the only mishap that occurred in 140,000 miles was one of the self-driving cars being rear-ended at a stoplight.
While it has been rumored for some time, Google (Nasdaq: GOOG) announced Sunday is has been testing self-driving cars. The company equipped six Toyota Priuses and an Audi TT with technology that enabled a vehicle to drive from Google's Mountain View, Calif., campus to its Santa Monica office. It then moved on to Hollywood Boulevard. In all, Google has sent its auto-cars more than 140,000 miles -- including along the Pacific Coast Highway and across the Golden Gate Bridge.
Google notified local police of its testing program and insisted there was a clean-record driver in each vehicle ready to take over if the robot technology decided to go rogue. That may not always have been the case, though. At least one driver claims to have caught a Google car driving unmanned and posted a video on YouTube to prove it.
The Google cars use video cameras, radar sensors and a laser range finder to "see" other traffic. The cars also utilize detailed maps, which Google has gathered using manned cars. Fifteen engineers worked on the project, including some from DARPA Challenges, a group that runs a series of autonomous-vehicle races organized by the U.S. government.
Safety and Energy Efficiency:
The goal of the project is driver safety and energy efficiency.
More than 1.2 million lives are lost every year in traffic accidents, according to the World Health Organization. That number could be cut by as much as half through the use of self-driving cars, suggested Google.
Productivity is another issue. The average daily commute is 52 minutes, noted Google -- time that could be spend doing other things once operating a vehicle is taken out of the equation.
Furthermore, a car run by robotics would not be subject to dangerous driving behavior such as distracted driving, the company pointed out. So far, the only mishap the self-driving car has encountered was getting rear-ended at a traffic light.
The impact of creating a safer car could trump all other concerns in self-driving technology.
How Do You Monetize It?
There is no obvious profit in Google's investment in self-driving cars, but the technology could potentially be licensed to the automotive industry.
Even an optimistic view puts the technology eight years away from deployment, though.
"Monetizing it is the trouble," said Enderle. "Google is having trouble spelling the word 'focus.' They could use these self-driving cars to help them keep their location-based technology up to date, but that's a real stretch in monetizing it."
Robot at the Wheel
At the heart of the self-driving technology is robotics, and advances in robotics could be a road to profit, observed Laura DiDio, principal analyst at ITIC.
Robotics are beginning to appear in a wide range of applications, from helping to plug the Gulf of Mexico oil leak to highly delicate surgery, to drones flying over Afghanistan.
"Robotics are all over land, sea and air," said DiDio. "Microsoft has a large robotics research program. Now Google is dipping its toes into robotics. That's the takeaway here.
Tips for usind Google: Dictionary Definitions:
To see a definition for a word or phrase, simply type the word "define" then a space, then the word(s) you want defined. To see a list of different definitions from various online sources, you can type "define:" followed by a word or phrase. Note that the results will define the entire phrase.