Threshold Definition and 120 Threads

Hello, I want to ask about neutron contamination threshold. Is there a threshold for neutron contamination in tissue used LINAC that is safe and has been regulated by an international organization? thanks for your help.

Hello, A classifier is a ML model that can classify between 2 or more classes. Some classifiers are called probabilistic in the sense that they output a probability score that is then compared against a threshold value (usually 0.5) to make the class decision. Other classifiers are not...

One of the strange features of Quantum Mechanics is that for his formulation one needs the classical physics that actually should emerge as its macroscopic limit. All experiences with quantum objects have to be analyzed through classical "glasses". Naturally, then the question arises: where...

Hello there, i wanted to ask if anyone knows a process or mechanism, that reduces the electric field that is requiered to tunnel an electron. When i use the work function of 4 eV (Aluminum) i get with Schottky-Nordheim approach a field of 870 kV/mm to tunnel an electron. Measurements tho just...

Is this a 'big deal' ? https://www.llnl.gov/news/national-ignition-facility-experiment-puts-researchers-threshold-fusion-ignition

I've attached pictures with the circuit and part of the attempted solution. I've replaced the diode with its offset model and obtained the equivalent circuit in the 2nd picture. After applying KVL, I've obtained that u_l=−u_D−i_D*R. Since U_D0 is greater than 0, I've deduced that the diode must...

What is the threshold energy (or frequency) required for an electromagnetic field to transition from a near field to become self propagating (EMR), far field? (If I'm using the right definitions to ask the question correctly). Is this constant or are there other details needed to calculate this?

Physics is not my area of expertise. That being said, philosophy of science is, but I'm not here to discuss philosophy. I recently found myself trying to imagine how light behaves once it crosses the event horizon of a black hole. Presumably, between the event horizon and the singularity...

Just wondering, what is the general consensus on the undifferentiable point in a graph of static friction and kinetic friction values regarding whether the object moves or doesn't move? Also wondering what the space between that point and where kinetic friction straightens out is called?

Hello, A femtosecond optical pulse is characterized by a maximum peak intensity ##I(W/m^2)##, a pulse duration ##\Delta {t}## and a repetition rate ##R (Hz)##. The damage threshold of an optical material is often expressed using either the maximum fluence ##(J/cm^2)## or the maximum intensity...

In a field effect transistor, does the threshold voltage decrease with increasing temperature? Imagine that there would be an increase in thermally generated carriers and thus the device would reach saturation faster? I realize the mobility would decrease, but the increase of thermal carriers...

I'm getting 2119.36 for the concentration of mg/cubic meter of this substance...it just feels wrong though. Steps I followed: First, I figured out how many grams of the substance there were using the density formula, then saw how many were present per cubic meter after calculating the volume...

The existence of a frequency threshold in the photoelectric effect is often regarded as the strongest objection to the wave theory. Because?

I’m only an interested layman and my math is pretty basic so please excuse my lack expertise in this subject but I was wondering how to calculate the threshold distance an object of mass m would have to be to a system of mass M to overcome the effects of dark energy and not be receding?

Hi, Wikipedia in its article on 'Glycosuria' says that the renal threshold for glucose (RTG) reabsorption in the kidney is around 160-180 mg/dL. Beyond which the glucose starts to excrete in the urine. But in diabetic people blood glucose exceeds in range of 300-400 mg/dL is prevalent. How this...

Homework Statement Mass of neutrino = 0 Mass of proton/neutron = 1 GeV Mass of tau = 2 GeV Homework Equations Energy of neutrino in lab = e Energy of neutrino in CM = e0 The Attempt at a Solution In the centre of mass frame, we will take the momentum of the neutron to be e0/c, c = speed of...

I've been reading about the photoelectric effect, and something got me thinking. If the frequency of light shone onto the metal is below the threshold frequency, no electrons are liberated from the surface of the metal, since electrons absorb quanta of energy, so if that light is shone for a...

Hello all, I want to know a suitable way to calculate VTL and VTH of a gate having the gate schematic and constituent transistors SPICE model (NMOS/PMOS models). Is there an easier than doing hand calculations ?

In order to calculate the energy of a reaction's ejectile, we make use of the concepts of the conservation of energy and momentum along with the reaction Q energy. However, if there is a threshold energy with above zero, meaning Q value is negative, do we have to consider the threshold energy as...

So I've read this "article"[ http://afiodorov.github.io/2015/12/04/terry-replies/ ] that really depressed me especially because I'm young. Apparently the threshold IQ is around 150, so does that mean someone has no chance?

For example a metal atom have 3 electrons which occupies 2 energy level. Is the threshold frequency = the energy needed to bring an electron in E2 to E(infinity) / h?

Homework Statement The binding energy of an electron to a metal surface is (3.90x10^2) kJ/mol. What is the threshold wavelength (in nm)for the onset of the photoelectric effect? Homework EquationsThe Attempt at a Solution work function= 3.9*10^2 kj/mol=6.476103179*10^-19j I know I have to...

Hi, up to this day I thought that endothermic and threshold reactions are equivalent. I mean each endothermic reaction must be threshold and each threshold reactions must be endothermic. But I think I was wrong. Here is example (from this source Q-value): 10B(n,2*alpha)T This threshold...

Hi, I need to calculate the threshold voltage for an op amp circuit. I am given "The maximum output voltage swing of the op-amp is ± 3 V for when the supply is ± 5 V." Would this mean that I should calculate the upper threshold voltage as 8V and the lower threshold at 2V? I have added an...

Please can someone tell me if this calculation is correct? Please see attached question. I have used the +/-3V as the saturation voltage and multiplied it by R2/R2+R3 to give me +/-1.5V.

Let us take the example of 89Y(n,n')89mY reaction. In the calculation of Q value we require mass of reactants and products. Both are same here. Then how to calculate the Q value of this reaction or how to calculate the threshold energy of this type of reactions?

I know the definition of photoelectric effect : the release of electrons from a metal when it is in contact with electromagnetic waves.. However, my question is.. If a light wave hits a metal and that photon has freq = threshold frequency of that metal, does this mean that the energy of the...

What is pain threshold? Can pain be measured? If so, how? What are the units? Thx :-p

hi im supposed to simulate a vcsel laser for my thesis i got problem in selecting physics.. i should check its heat transfer and threshold current but i don't know which physics should i choose ! does anyone know about vcsel's physical structure in Comsol ? by the way does anyone know that how...

Do you guys know a low-cost low-threshold optical beam limiter, with cost somewhere ~$100. Or if you know certain method to fabricate such. I would be greatful if you could include links and/or references. I am still noob in photonics so I am only familiar with a beam limiter that blocks the...

A (k,n) quantum threshold scheme (QTS) as a method to split up an unknown secret quantum state | S > into n pieces (shares) with the restriction that k > n / 2 (for if this inequality were violated, two disjoint sets of players can reconstruct the secret, in violation of the quantum no-cloning...

Homework Statement Determine at what energy, in electron volts, the Nonrelativistic expression for the de Broglie wavelength will be in error of 1% for an electron. 2. The attempt at a solution For the error to be 1%, that means that the classical wavelength/relativistic wavelength will be...

I've been reading up on lasers recently and learned that within the cavity while the laser light is amplified by the gain coefficient, it loses power due to transmission and absorption. Suppose the pumping radiation comes from a monochromatic source whose energy is not exactly equal to the...

I mean the photoelectric effect of the hydrogen atom. It is weird. By the Fermi golden rule, the transition or absorption rate is proportional to the density of the final states. At threshold, the electron has zero momentum and thus zero density of state. Therefore, the absorption coefficient...

Homework Statement A thin target of lithium is bombarded by helium nuclei of energy E0. The lithium nuclei are initially at rest in the target but are essentially unbound. When a Helium nucleus enters a lithium nucleus, a nuclear reaction can occur in which the compound nucleus splits apart...

For example, when you have a photon interacting with a bound electron, there is a work function relating the minimum energy photon capable of interaction (given by hf). My question is, what exactly is going on in this situation if the work function is exactly equivalent or less than the energy...

This question is easier to explain with an example. A silicon microprocessor consumes 100W of real power. If the surrounding air has a temperature of 22°C, and the temperature of the microprocessor must stay below 60°C, how much heat must the microprocessor dissipate? This isn’t a homework or...

I would like to know why the threshold voltage increases for an NMOS transistor when the voltage difference between the source and the body terminals is greater than 0. If, for example, the body terminal is connected to -1V and the source to 0V, holes from the p-substrate are attracted to this...

I'm a first year physics student, and one of my assignment for my programming class is about percolation. I need to create some disks randomly distributed in an area (this is a 2-D), and then by varying the density of the disk, I need to figure out the percolation threshold such that the two...

When a cm thick surface is illuminated with light of wavelength lambda,the stopping potential is V. When the same surface is illuminated by light of wavelength 2lambda , the stopping potential is V/3.The threshold wavelength for the surface is ? Homework EquationsThe Attempt at a Solution

Why is that large neurons have smaller threshold potentials than small neurons during external stimulation? My confusion is because the time constant should be larger, right? tau = (r_m) * (c_m). where r_m is membrane resistance and c_m is membrane capacitance Capacitance increases...

Can we define a threshold velocity V for an object with mass(rest) M which the object at motion need to attain so that its center of mass accelerates faster than the Dimensional object?

Hi, I recently conducted a lab experiment involving several mosfets of varying channel length and width and have plotted Ids against Vds for different values of Vgs (below is one of the graphs). I am now trying to find the threshold voltage of each mosfet using their graphs although I am...

In Padmanabhan's Theoretical Astrophysics by defining a ratio for comparing gravitational potential energy with rest-mass energy it is shown that if massive objects with M=10^33 gm are confined to small regions with R= 1km then we cannot use Newtonian gravity because the system has general...

Hi there, When it sounds like I am hearing the world from underwater for a few hours/few days after a very loud music concert, is that what is called temporary threshold shift? Or is TTS something that occurs only during the exposure to high dB? (Eg. at the loud concert itself). Thank...

Dear Forum: I would like to know where could I find charged particle interaction cross section for oxygen-18? I know I can get some of it from ENDF. https://www-nds.iaea.org/exfor/endf.htm Where can I get reference,like the threshold energy for 18O(p,n)18F is 2.5MeV and its cross...

Homework Statement I am trying to find the minimum energy for a proton beam to make pions that have 100Gev of momentum. The proton beam is hitting a fixed target. Homework Equations p + n -> n + n + ##π^{+}## The Attempt at a Solution In the centre of mass frame, there is zero...

Homework Statement Two photons collide and create an electron-positron pair: y1+y2 -> e-+e+ If the wavelength of y1 is 1 mm calculate the energy threshold for photon y1 to produce the electron-positron pair. Suppose E(y1)=hc/\lambda2 where \lambda2 =1.1 mm Hints: In the center of...

Could anyone guide me through this problem? https://www.physicsforums.com/showthread.php?t=348863 Just need to get started. Note that this would need to be solved in the proton rest frame.

Hello all, This is probably a simple question, but for some reason no matter how much I fight these figures I can't seem to make it work out correctly. $$y' = -r(1-\frac{y}{T})y$$ $$y' = -ry + \frac{ry^2}{T}$$ $$y'' = -ryy' + \frac{2ryy'}{T}$$ $$0 = -ryy' + \frac{2ryy'}{T}$$ $$ryy' =...