New answers tagged

2

Comparison of fabrication techniques for hollow retroreflectors describes, in great detail, the two obvious methods: The use of a precision solid prism corner cube as a mandrel to hold the glass plates prior to gluing of the edges. An adjustable set of precision mirror mounts, designed to hold the three plates In both cases interferometric techniques ...


1

For the equation $\epsilon_{ss} = Ce^{\frac{-Q}{RT}}$ it appears that you know $Q, R$ and you have some experimental values (well at least two!) for $\epsilon_{ss}$ and $T$. The usual way to determine the constant $C$ is to take logarithms of both sides giving (as you have noted) $\ln(\epsilon_{ss}) = \ln(C) - \frac{Q/R}{T}$ and to plot $\ln(\epsilon_{ss})$ ...


-1

But by combination of electrons with holes there will be increase in repulsion forces of electrons this will create more resistance. so currrent should not increase exponentially with voltage


0

To briefly summarize the whole physics: P-n diode has excessive holes in one side of the junction and excess free electrones on the other but both sides are electrically neutral. Initially they diffuse to create an equilibrium of numbers of electron and hole , but in this way They create electric potential on the opposite side Off the flow. This Presents ...


1

Take a piece of string (I just use cheap yard twine) and soak it im rubbing alcohol. Then wrap the soaked string around the glass tube along/in the score mark you made. Then light the alcohol soaked string on fire. let it burn for a few seconds then dip the gloss tube in cold water and it will break along you score line.. I personally use this method in ...


0

The deformation of a material and the corresponding mode of failure depends on many conditions in addition to crystal structure such as stress state, rate of loading and ambient temperature among other things.


1

The brittleness is caused primarily by interstitial impurities. That's the case of chromium as well as all Group VI A metals. For chromium, the nitrogen atoms are the main impurities.


1

In general your relation is $$ \vec{B}(\omega) = (1 + \chi_m(\omega))\vec{B}_0(\omega) $$ or in the time domain $$ \vec{B}(t) =\vec{B}_0(t) + \int\limits_{-\infty}^\infty \chi_m(t,t') \vec{B}_0(t') \;\rm{d}t' $$ Only in the case of instantanous material response, i.e. $\chi_m(t,t') = \chi_{m,0} \cdot \delta(t-t') $, your equation is correct. This already ...


0

Yes of course, the materials that are used for thermal insulation applications,like polystyrene, mineral wool and polyurethane have such characteristics.


1

First of all let me make a correction in your given value of flexural strength of concrete. The value of $16 Mpa$ or $16 N/mm^2$ is about the compressive strength of a typical concrete cube with an edge of 15cm under clear compression. It's tensile strength is about 1/10 of its compressive strength ,so it's about $1.6 Mpa.$ Like concrete ,most materials ...


2

From what I've learnt, this relative strengthening,of cloth when wet, and weakening of paper is due to two factors. First up:The cloth - google fibre structures of cloth, and you will notice that cloth fibers are uniformly but relatively less interlocked, and addition of water causes further attraction via hydrogen bonding. For the paper, it has relatively ...


0

The stone when hits the glass( like wind shield, or a window pane) the impulse is small as the time of contact to the force applied is more. But for the bullet the time of contact to the force applied to the glass is small so the impulse of the bullet is large. The glass is not a solid or liquid entirely. the glass is a semi solid or amorphous solid. So it ...


2

Agarose is a polysaccharide, and like all polysaccharides it is bristling with polar hydroxyl groups. This means the agarose chains interact very strongly with each other by hydrogen bonding. If the solution is heated to a high enough temperature to break the hydrogen bonds (around 90-100ºC) then the agarose molecules behave pretty much like any other ...


0

One would expect that a positively charged sphere could hold a different amount of charge than a negatively charged one, one reason being that the tunneling probability for electrons to escape would tend to be different than for ions. There may be other effects as well that could cause a difference. If I were to venture a guess I would suppose that more ...


-2

Inflating a Rubber Balloon www.engr.uvic.ca/~struchtr/2002balloons.pdf University of Victoria by A DUVTCEV - ‎Cited by 26 - ‎Related articles


2

Dielectric implies nonmagnetic, so the best example of an insulator that isn't a dielectric I can think of is ferrite crystals like yttrium iron garnet, that show a magnetic response while having low or zero conductivity. There are also ferroelectric materials that show a permanent polarization in response to an electric field, and these aren't considered ...


1

There are often several different methods of synthesizing materials, and in lots of cases they arrive at the same result. Sometimes the experiments you want to do will depend on your growth method, though: for instance, the polycrystalline samples you get from solid state reactions can be good for x-ray or neutron diffraction studies. If you want to ...


1

The presence of a ductile to brittle transition temperature implies there are insufficient (ductile) deformation modes at low temperatures to support plastic deformation and therefore fracture occurs to release energy/load. In FCC materials, dislocation slip of both edge and screw dislocations is relatively athermal and due to the number of active slip ...


0

It is by simply erosion. The higher the water velocity impacts the surface, the faster the erosion or, if by drips, the longer time span it will require. High pressure water jets will erode rock very quickly while drips of water can take eons. But the process is the same. By erosion.


3

If the parts are perfectly solid and they are at equilibrium, then the pressure is constant (ideally). $$q(x,y) = \frac{\int p(x,y)\,{\rm d}A}{\int \,{\rm d}A} =\frac{\text{applied force}}{\text{area}}$$ But if either the floor or the body are ever so slightly elastic then the pressure distribution is given by a non-hertzian contact which concentrates all ...


11

Damping implies a loss mechanism. In liquids, where molecules move freely in close proximity, this loss mechanism is a transfer of momentum from one molecule to another. In pure crystalline metals, the position of atoms in the lattice is fixed, and the forces between them are elastic. That is, if an atom is displaced, it will experience a force that puts it ...


9

I'd like to point out the example of cast iron. It is renowned for its excellent vibration-damping properties. It is wrong to reach a blanket conclusion saying that metals are bad for vibration damping. The properties of any solid depends part on the material it is made up of and part on the micro-structure of the material. By micro-structure, I mean the ...


1

Metals are not liquids (I am referring to metals which are in solid phase in standard conditions of pressure and temperature) and have no viscous mechanical dissipation on time scales associated with most mechanical vibrations. This implies that they can transmit transverse waves contrary to fluids. How efficiently they can do so is related to the details of ...


0

Although the average force applied during a collision might be small enough that an object can take it, the peak force applied can be much higher. In physics this is called impulse. Calculating the impulse for real world collisions (like a car crash) is very complicated. This is because cars have many structural members and the materials are not uniform. ...


2

To understand this, use the definition of force $\frac{d{\bf p}}{dt} = {\bf F}$, namely the force is equal to the rate of change of momentum. Something like a collision can be very complicated to model, but the average force is approximately given by ${\bf F}_{average} = \frac{\text{change in momentum}}{\text{time taken}}$. Typically, in a collision, the ...


1

An empirical answer: Metals (often copper) can be used as insulating support structures in superconducting magnets. Compared to ~0 resistivity of the coil, the resistivity of metals makes for very good insulating properties! Or, going in the other direction, a 50-watt VandeGraaff-type power supply may output 500KV at 100uA. Such a supply has an internal ...


0

As is often the case, the answer to this is actually slightly context-dependent. For many everyday purposes, the answer of Cort Ammon that it is all a matter of degree is correct. However, one other context worth mentioning is when condensed matter physicists speak of whether a particular state of matter is a "conducting" (or "metallic") state or an ...


2

I have no experience with either CVD or PLD, but it was interesting to think about this question. In a humble attempt to build on Peter Diehr's answer, here is some theory (at a very heuristic and simplified level). The deposition of each new layer can be thought of as being governed at large scales by some mixture of Laplacian and Eden growth in two ...



Top 50 recent answers are included