Research

Below you can see some of our students research projects.

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Underwater electrical wire explosion and its applications

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Alex Fedotov Gefen

 

 

Results of an investigation of underwater electrical wire explosions using high-power microsecond and nanosecond generators will be reported. Different diagnostics, including electrical, optical, and spectroscopic, together with hydrodynamic and magnetohydrodynamic simulations, were used to characterize parameters of the discharge channel and generated strong shock waves.

The estimated energy deposition into Cu and Al wire material of up to 200 eV/atom was achieved. Analysis of the generated shock waves shows that 15% of the deposited energy is transferred into the mechanical energy of the water flow.

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Who said size doesn't matter? The mystery of Quantum Mechanics.

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Humans intuitively understand a world defined by relatively large scales (km, m and cm), on which the “regular” forces, described by Newton's laws, work properly and succeed to describe various phenomena that occur in nature. But when we look at molecules and atoms, we enter into a world with very small scales; there the particle behavior is not compatible with the regular forces, the intuitive ones. Quantum mechanics describe phenomena that occur in the small scales.

 

First, in order to understand quantum mechanics we need to understand the building blocks of classical mechanics, which divide our world into two types of effects: effects of particles and effects of waves. Particle is characterized by mass or energy, the particle occupies a finite volume (defined borders) and is described by its location and time. Wave is disturbance that travels through space and matter according to the waves’ equation and described by wave length (which determines the frequency) and wave amplitude (the wave height).

 

Laws of classical mechanics, used to describe many phenomena until the early 20th century, for example, one of those phenomena is when shooting particles through a single crack, we get a typical particles’ pattern, a mark for places where particles pass through the crack and hit the wall (single stripe); therefore we respectively guess that when we will shot particles through two cracks we need to see two stripes. But in the 60s, scientists conducted an experiment in which electrons, which until then were defined as pure particles, were shoot through one and two cracks. Through the single crack, they saw a single stripe as expected, but in the case of two cracks, they saw interference and diffraction phenomena, fitting to behavior of waves. From the experiments they concluded that particles can also have wave’s features.

 

Large objects, like humans also have wave’s features, however since this is a large scale (macroscopic) the waves are not distinguishable. Quantum mechanics explain that, you can refer to any object of any size, like a wave under certain conditions and like a particle on other terms; this is called wave - particle duality.

 

Another confusing phenomenon was observed in the experiment with two cracks: when they added a measuring device to check from which crack the particle passed through, instead of receiving interference and diffraction pattern of a wave as before, they got two stripes, which corresponds to particle behavior. You can think the electron was aware of the measurement device and subsequently returns to behave as a particle. But basically, in order to perform the measurement, the measuring instruments performed with the electron interaction and thus affect the experiment and caused to the collapse of the interference pattern.

 

This experiment, together with additional experiments led to the development of quantum mechanics theory. In order to develop this theory scientists have to put away a fundamental principle in physics, determinism, which means, repeating the same experiment several times under the same conditions would lead to the same result. Quantum mechanics discard this view, if you perform the same experiment again, there is a chance to get a different result, and nature, like throwing dice, draw the experimental results. If it comes to draw the results, it means that every result has a certain probability to be accepted in the experiment. So quantum mechanics deals with predicting the distribution of results.

 

As physicists have learned, scale size is very important when we examine phenomena in our world. Theories describing phenomena that occur at larger scale in a good way, fall when examining smaller scales, forcing physicists to rethink about the importance of the concept of size.

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The world does not revolve around you, the idea that led to a different view of our world.

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Nicolaus Copernicus was the first to claim that, the sun stand in the middle of the solar system, and around the sun orbits planet Earth. Furthermore he claimed that Earth is an ordinary planet under specific conditions that led to the origin of life. This idea, 500 years ago, wasn’t warmly accepted.

The sun is a star producing effectively for over 5 billion years, nuclear energy in the process of turning hydrogen into helium, and will continue to do so until hydrogen will run out, then the sun will turn off. Shortly before that moment, the sun will expand 200 times her current size and swallow nearby planets including the earth. Before this dramatic end, humanity has long time for exploring the environment we live in.

If you ask yourself why life evolved in the solar system on planet Earth, the answer is, because of the mediocrity. Earth is a middle size planet in specified distance from the sun that allows the existence of liquid water, which led to the origin of life. The sun is a medium-sized star relative to over 500 billion other stars in the galaxy.Contrary to light star which don’t produce sufficient energy to allow life, heavier stars than the sun explode too early to allow the creation of life. So, the demand for life is a medium condition - neither too hot nor too cold. Our galaxy is a medium one, out of billions of galaxies in the universe that allowed vast production of stars and planets, including our solar system planets and sun.

 

So from where all this mediocrity has started? The idea for the beginning of the universe is described best by the big bang theory which confirmed each time by measurements and observations. The theory claims that the universe began 13.7 billion years ago, from a very hot area, containing only elementary particles. After the ‘initial expansion’ process that shaped our current universe, the first elements created were hydrogen and helium, which after billion years formed the first stars which produced the heavier elements, among them oxygen, nitrogen and carbon necessary for life.

 

The universe continues to expand until eventually stars will cease to be formed. The stars that exist will stop producing energy and then it will be impossible to sustain life. Not only that the universe is expanding, but it’s also accelerating his movement For the measuring of the accelerating movement of the universe three researchers won the Nobel prize.

 

The Earth, the Sun and our galaxy are all relative medium size and were created from the big bang. The question we should ask is: whether the big bang is relative medium bang of a series of big bangs? If the answer is yes, that mean multiple universes each with different physics laws, exists parallel to each other. This idea derived from Copernicus who said there's nothing special on Earth, the sun and the galaxy. Idea of ​​multiple universes also comes from theorists trying to explain the basic forces in nature. From developing models, a huge collection of solution is obtained, so for each solution there is an appropriate universe, but we still don’t know which solution fits our universe. In different universes, different physics laws are applied, and therefore we can’t measure physical phenomena with the tools we have developed in our universe. Furthermore each universe has its own individual expanding space and time field.

 

Our universe as Earth, the sun and our galaxy is also Medium universe, that hasn’t spread to fast nor collapsed too quickly, to give enough time for the creation of life. The obvious conclusion, in the search for other life forms we need to search the mediocrity that lead for them.  

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Much more than small size, nanotechnology - a new territory

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Nanotechnology is going to take a place in our lives for decades to come. Part of this development already existed in miniaturization in microelectronics, optoelectronics, medical diagnostics, and more. And some part obtained unique features in the nano-scale systems. But the touchstone is to what extent nanotechnology will break the conceptual limits of current engineering.

 

Intuitively nano is linked to the word minimizing, to illustrate the concept of miniaturization. Let’s look at one cube made of one nanometer edge length. This cube can contain 125 atoms. One nanometer is also the size of the DNA, containing our genetic information. In DNA, the information is coded by four nucleic acids like a digital storage based on four bits of memory. that’s the reason why in Biology, the size of one bit is 1 nm.

 

So we can conclude that miniaturization is especially effective for storing information. If we take all the information gathered during mankind history (text, images, architecture, etc.), we can save all the information in 2*10^21 bits. For keeping it, we need thousands of miles of hard-disk with a base of 10 cm, however storing the information in nanometers bits, as happens in the DNA, requires the volume of a sugar cube.  The required question- is there a limit to the miniaturization where we can store information?

 

To answer this question we must look at another aspect: complexity. The hard part is not writing at small scales but how to manipulate the data at those scales. In ten nanometers thirty bases of DNA can be seen and thus can encode meaningful information, but once we pass tenth nm and reach sizes of atoms, we have no information and all the complexity is lost. Therefore nanometer is the building block for storing information, and includes some degree of complexity that allows some function. So it’s not likely that we will able to build technology based on smaller sizes than nano scale.

 

In order to understand the nanotechnology we need to understand what is happening in reducing dimensions. One of the changes is the change in geometry. If we look at a cube with a certain ratio between the volume and the surface area, when we reduce this cube, the volume is considerably get smaller compared to the surface area, so the ratio between the volume and the surface area is decreasing, meaning that in nanometer, atoms are placed on the surface area, and this is the reason why those small particles are more chemically active. In addition, the microscopic world is an isothermal one (the temperature remains the same all over the space) because the heat conductivity is greater than the heat production capacity.Nanotechnology is  mainly made in solutions which mean that particles constantly collide with each other, so they need to overcome forces of friction considerably more stronger than in the macroscopic world. We can conclude that the small dimensions bring a different expression to the laws of nature we  know in large objects, so a main part in nanotechnology is to understand how the rules of chemistry are changing.

 

One of the biggest market of chemical engineering is enzymes. Enzymes are proteins that can catalyze a certain chemical reaction. Enzyme is a complex protein, and therefore we have limited understanding of how it works. This poses a problem for us in planning new enzyme as we wish. However in order to produce a new enzyme we imitate nature by choosing an existing enzyme produced by translation of genes, and we do a process similar to evolution to get an enzymes that work effectively better and suited to the industry. We solve a difficult problem that is hard to solve with our existing knowledge by the strategy of evolution and relying on something that works without knowing how it works completely.

 

Directed evolution strategy cannot be applied to any process because evolution requires high availability of the building blocks and short production time, which did not exist, for example, in a conventional car manufacturing industry. Unlike today conventional engineering, nanotechnology  has cheap building blocks that can be mass produced in a short time.

 

Nanotechnology is more than minimized technology and even closer to biology than conventional engineering. Therefore nanotechnology is a new chapter in science we are just beginning to explore.

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