What is Cycles: Definition and 168 Discussions

In ecology and Earth science, a biogeochemical cycle is a pathway by which a chemical substance is turned over or moves through the biotic (biosphere) and the abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. There are biogeochemical cycles for the chemical elements calcium, carbon, hydrogen, mercury, nitrogen, oxygen, phosphorus, selenium, iron and sulfur; molecular cycles for water and silica; macroscopic cycles such as the rock cycle; as well as human-induced cycles for synthetic compounds such as polychlorinated biphenyls (PCBs). In some cycles there are reservoirs where a substance remains or is sequestered for a long period of time.

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  1. T

    A Why is the concept of cycles overlooked in causation models?

    The online Stanford Encyclopedia of Philosophy has a lengthy article on Causal Models. https://plato.stanford.edu/entries/causal-models/ In this article the word 'cycle' appears twice in non-substantive fashion. Given the prevalence of cycles in many kinds of dynamics, I am curious why it does...
  2. nomadreid

    I Cycles from patterns in a permutation matrix

    In a permutation matrix (the identity matrix with rows possibly rearranged), it is easy to spot those rows which will indicate a fixed point -- the one on the diagonal -- and to spot the pairs of rows that will indicate a transposition: a pair of ones on a backward diagonal, i.e., where the...
  3. V

    Comp Sci How Do Pipeline Stages Affect Clock Cycles in CPU Processing?

    I think I am having trouble visualizing the count for the clock cycle. Would this just be the clock cycles divided by the instructions of the pipeline? I'm confused about how each stage of the pipeline takes three clock cycles to complete when there are five stages? The consequence of improving...
  4. G

    I Could Passing Asteroids Alter Milanković Cycles and Trigger Climate Change?

    Our planet being smacked by a huge asteroid is a common doomsday trope. But what if our planet didn't actually get smacked but came close to getting smacked? Could a sufficiently large body, or perhaps a group of several large bodies, pass close enough to alter the workings of the Milanković...
  5. V

    I Limit cycles, differential equations and Bendixson's criterion

    I have a few questions about the negative Bendixon criterion. In order to present my doubts, I organize this post as follows. First, I present the theorem and its interpretation. Second, I present a worked example and my doubts. The Bendixson criterion is a theorem that permits one to establish...
  6. L

    Engineering Reviewing Efficiency of Otto & Diesel Cycle Heat Engines

    Hi, i have this question and don't understand it. can somebody explain what i have to do. i know a ideal engine is a engine running on carnot cycle i what the cycles are i don't know what relative efficiency is and what there looking for (Q) Review the relative efficiency of ideal heat engines...
  7. A

    Distinction between circadian cycles and sleep?

    Is, in biology, the notion of the circadian cycle (or rhythm) that one finds also in elementary forms of life (say a paramecium) the same notion of "sleep"? If not what is its technically difference? If it is, why are then biologist surprised to observed sleep-like states in organism with...
  8. L

    Engineering Otto and Diesel cycles: Which PV diagram is for SI and CI?

    Writing about Engines and just muddled up diagrams and confused now. Which PV diagrams is for Compression Ignition and which one for Compression Ignition. I think one on left is CI and right SI. Cheers
  9. S

    I Exploring Saros Cycles & Eclipse Differences

    Is the difference in the eclipses of a Saros cycle (i.e., other than the longitude) due to the fact that a Saros cycle is exactly 223 synodic months but 241.999 draconic months and 238.992 anomalistic months, with the 0.001 & 0.008 month differences causing the slight differences in the eclipses...
  10. R

    Expansion in non-adiabatic Otto / Diesel cycles

    Hello! I have a question that has been bothering me for a while now. If we look at the expansion step of a real otto or diesel cycle we see that while the pressure drops to near surrounding levels the temperature remains relatively high ( high T of the exhaust gas). How is that possible? How...
  11. R

    I Non-adiabatic expansion in Diesel and Otto cycles

    Hello! I have a question that has been bothering me for a while now. If we look at the expansion step of a real otto or diesel cycle, we see that while the pressure drops to near surrounding levels, the temperature remains relatively high ( high T of the exhaust gas). How is that possible? How...
  12. G

    Eccentric winter and summer cycles

    I think about Three Body Problem and Game of Thrones. Both show erratic, unpredictable shifting of summer and winter times. Of course, GoT don't bother with physical explanation, but could this behavior occur in a binary star system, or with other conditions, like stellar clouds? Three Body...
  13. Uchida

    I Minimum number of cycles in a short pulse laser

    Hello to all, In a short pulse laser emission setup, can a pulse be emmited with beam length shorter than one wavelenght? (can a pulse have a duration shorter than its period?) Lets say a laser emmiter shoots a quarter cycle pulse, what would happen to this short beam? (lets supose the...
  14. F

    Irreversible cycles, Carnot's Principle and volume-pressure diagrams

    Hi all, this question is related to a similar one I posted a couple of weeks back. Please keep in mind that the level here is high school. I'm looking for a way of describing the concepts in the title that is not overly technical. I keep circling back to these concepts because it seems to me...
  15. F

    How many reversible thermodynamic cycles are there between two heat reservoirs?

    Hi, I was revisiting my (high school level) understanding of thermodynamic cycles and I think I still have some doubts. Last year and more recently I posted a few questions which surely helped me, but I think I need more clarifications. In a nutshell, what I'd like to know is the following...
  16. G

    B Milankovitch Cycles: Find the 53,300,000 Year Cycle

    I wanted to look at Milankovitch cycles and each cycle like a clock and that would mean we have 3 clocks each one moving at a different speed. We have a 100,000 year clock (Eccentricity), a 41,000 year clock (Obliquity), a 26,000 year clock (Procession). I want to start all the clocks at the...
  17. S

    Prove using induction that if a graph has no odd cycles it is bipartite

    We learned in class how to do this problem the more traditional way, but we are required to reprove this using induction, which I'm not too sure how to do. My Attempt: For the base case I had three vertices connected by three edges, with the last one looping back to the first to create a cycle...
  18. mfb

    I Disappearing lakes on Titan - seasonal cycles

    Earth and Titan are the only objects in the Solar System with stable liquids on its surface. Earth has water oceans, lakes, rivers and rain, Titan has methane/ethane oceans, lakes, rivers and rain. Earth has seasons, and so does Titan. They are just much longer as Saturn's orbital period is 29.5...
  19. V

    Amplification Cycles and Cycles of PCR

    Homework Statement A sample undergoes 35 amplification cycles. How many copies of the target sequence has been produced after 30 cycles of PCR? Homework EquationsThe Attempt at a Solution 2n=230=1073741824 Is this correct? Im just a little confused as to what the difference is between...
  20. S

    B How hard is it to track moon cycles

    I know this may be extremely basic to almost everyone on the forums, but I really can't tell if moon cycles are predictable or not ! like can we tell in advance when is the full moon ? I feel like the answer sould be a definite YES, but my confusion is based on what I see each year. I live in an...
  21. Mr Davis 97

    I Order of a permutation is the lcm of the orders of cycles

    Let ##\sigma \in S_n##, and ##|\sigma| = r##. Then, we'll assume that ##\sigma## can be decomposed into a product of disjoint cycles, which commute with each other. So ##\sigma = c_1c_2 \dots c_k##. Then ##\sigma^r = (c_1c_2 \dots c_k)^r## = 1. Since the cycles commute, we have ##c_1^rc_2^r...
  22. physea

    I Are Qin and W equivalent in the Rankine and Otto cycles?

    Hello! In ideal Rankine cycle, we say that during the isobaric expansion, the heat provided to the system is Qin = h3 - h2 However, in my opinion, it is Qin - W = Δh -> Qin - PΔV = Δh. Which is correct? Secondly, In Otto cycle, let's say you have calculated Wnet in kJ/kg. In order to be able...
  23. physea

    B Laws in Otto, Diesel, etc. cycles

    Hello guys, I am a bit confused. Is it that PV/T=constant for ALL the processes of ALL cycles, like Otto, Diesel, Rankine? I know that PV=mRT, so does that mean that PV/T=constant all the time? Secondly, I am a bit confused as I read that PV^γ=constant. What is that exactly? Where does it come...
  24. Z

    Setting Up a 12V DC Test Stand w/ Controller & Cycle Count

    Setting up a test stand that will need a controller to cycles a device ON and OFF at an adjustable time interval (allows me to make the ON duration and OFF duration whatever I want). It will also need to keep a count, so I can track the cycles count and also set a limit on cycles so it will stop...
  25. caters

    A Milancovitch cycles and how they relate to seasons

    There are 3 cycles important for determining seasons, extreme temperatures, and length for any given planet in any given orbit as long as it isn't too elliptical. Those are: Orbital precession(this is what causes supermoons(when perigee lines up with a full moon)) Axial tilt(this determines...
  26. F

    Multiplying permutation cycles

    Homework Statement Compute each of the following products in ##S_9## (Write your answer as a single permutation). a) (145)(37)(682) Homework Equations Theorem: Every permutation is either the identity, a single cycle, or the product of disjoint cycles. The Attempt at a Solution I start with...
  27. bradk2fan

    Confused on a few things for a beam and cycles to failure

    I have a problem which is a beam with 2 machines on the beam and one of them has an operating frequency between 200 and 600 rad/s that transmits a force to the beam. I have to determine the number of cycles to failure of the beam. It's stated in the problem statement to account for the mean...
  28. Mr Davis 97

    Write (13257)(23)(47512) as a product of disjoint cycles

    Homework Statement Write (13257)(23)(47512) as a product of disjoint cycles. Each bracket is a permutation of seven elements written in cycle notation. Homework EquationsThe Attempt at a Solution This isn't too hard of a problem. One easy way would be to evaluate the entire product, and then...
  29. W

    I Solar physics: coronal holes & sunspot cycles

    Does anyone know if there is a relationship between corneal holes and the sunspot cycle? As we move in now towards solar minimum should we expect to see a big decline in corona holes? I have noticed a lot less sun spots over the last few months but the frequency of coronal holes seems to be...
  30. RJLiberator

    Disjoint cycles in permutations

    Homework Statement Homework EquationsThe Attempt at a SolutionMy answers for the disjoint cycles of f,g,h,k are as follows. My question concerns my disjoint cycles for g. Are we allowed to have 3 cycles? I would think "yes" because that just makes sense to me. for f: ( 1 3 8 4 6) (2 5) g: (2...
  31. Marcin H

    Heat Cycles, Work, and Efficiency

    Homework Statement Homework Equations W=-∫PdV ε=W/Q PV=nRT COP=Q/W The Attempt at a Solution Using the first equation for work, I got W=-nrT*ln(3V1/V1) but I don't think that is right. Is this the wrong formula to use for this problem? My answer should be in terms of P1 and V1.
  32. wololo

    Efficiently Finding Cycles in a Graph: A Scientific Exploration

    Homework Statement Homework Equations Recursion, graphs, DFS The Attempt at a Solution To try to solve this algorithm, I first need to find all the basic cycles in the Graph G. When I have these cycles, I can simply pick the smallest edge in each of them and add them to the set F, while...
  33. J

    Altering the Milankovitch Cycles

    As I understand it, the Pleistocene ice ages were dictated by three major factors suggested by the Serbian geophysicist Milutin Milankovitch--eccentricity (orbital shape), obliquity (axial tilt) and precession (direction of rotation in relation to fixed stars). The one identical factor between...
  34. T

    Find Nice Numbers: A Program to Count Divisible Digits in Range [0,1000]

    Hello, My task is to write a program that after reading a positive integer i (from 0 to 1000) will write how many "nice numbers" are in the interval [0..i]. "Nice numbers" are numbers that are divisible by their every digit. For example 612 is a nice number becasuse it is divisible by 6,1 and 2...
  35. B

    Vapor power cycles help please

    Hey guys, I've been given this mini project for my thermodynamics2 class. It's supposed to be a really good example of how the upcoming exam will be. The downside is i don't really know what values I should pick. I really need help with strictly the analysis part of this project. If anyone could...
  36. Soumalya

    COP of Reversible Refrigeration Cycles

    Considering two thermal energy reservoirs, one at a higher temperature of TH compared to the other at TL, if we operate a reversible refrigeration cycle between the reservoirs then its coefficient of performance is given by, COPR,rev=TL/TH-TL This is the basically the maximum COP a...
  37. DavideGenoa

    Reversible cycle approximated by Carnot cycles

    My textbook gives the definition of a reversible transformation as a transformation that can be inverted by effectuating only infinitesimal changes in the surroundings. I admit that I have no idea of what infinitesimal means in a rigourous mathematical language, therefore the definition is quite...
  38. S

    Otto & Diesel Cycles: Heat Addition/Rejection Processes

    why are heat addition and rejection processes in an otto cycle constant volume processes?similarily why does heat addition occurs at constant pressure in a diesel cycle?
  39. C

    How Is Heat Calculated in a Diesel Cycle Using Volumes and Temperatures?

    1. Ideal gas cycle - diesel engine cycle. You begin at some volume V1. Perform an adiabatic compression to V2. Perform an expansion to V3 at constant pressure. Next, perform an adiabatic expansion to V4, Last, it moves back to V1 at a fixed volume, while decreasing temperature back to...
  40. GiantSheeps

    Wavelength given time, velocity, and cycles

    Homework Statement As your hand moves back and forth to generate longitudinal pulses in a spiral spring, your hand completes 2.88 back-and-forth cycles every 6.98 s. The velocity of the pulse in the spring is 0.581 cm/s. What is the wavelength? Answer in units of m. Homework Equations v=λf...
  41. A

    Python checking numbers in a given name

    Homework Statement I need to write a Python program, which would: 1) Ask for a name (input function) 2) Keep asking for the name if it is not entered correctly(if it has a digit in it) 3) If the name is entered correctly it will print the name Homework Equations How should I continue the...
  42. I

    No cycles in permutation N how to calculate sgn(N^2)?

    N is a 2 x n matrix: N = 1 2 3 4 ... n-1 n n n-1 ... 4 3 2 1 then N^2 = 1 2 3 4 ... n-1 n 1 2 3 4 ... n-1 nYou COULD use the theorem: sgn(N^2) = sgn(N)sgn(N) however, I am asked to find sgn(N^2) by the traditional method: sgn(N^2) = (-1)^([L1 - 1] + [L2 - 1]...) where L represents the...
  43. J

    Thermodynamics cycles quick question

    I'm unsure of part b of the question 7 below; My attempt: I'm confused as to what direction the arrows are meant to go. If heat transfer occurs to the gas, and the piston rises, the volume must have decreased in the cylinder. So from state 1 - 2, the gas is cooling or heating up? This is a...
  44. J

    Thermodynamics problem over cycles

    Homework Statement The filament is 30 cm long and has a diameter of 1.5mm. The filament is drawing 15 watts and has an emissivitity of 0.9. The surroundings are at 283 k. Estimate the surface temp of the filament in K. Homework Equations N = Wcycle/Qin, W cycle = Qhot - Q cold. The Attempt at...
  45. K

    MHB Proof of Conjugate Cycles Property of Permutations

    Prove: Let \alpha = (a_1,...,a_s) be a cycle and let \pi be a permutation in Sn. Then \pi \alpha \pi ^{-1} is the cycle (\pi(a_1), ... \pi(a_s)) My attempt. (\pi \alpha \pi ^{-1})^s = (\pi \alpha^s \pi ^{-1})=e so if this thing is a cycle and its length divides s. Assume \pi (a_1) is a...
  46. R

    Calculating energy left in oscillator after 3 cycles

    Homework Statement Calculate how much original energy the oscillator in will have left after three cycles. Using Q= (ω/Δω) I have calculated the Q factor to be 4 Homework Equations The answer can be obtained by using the equation Q=2π(E/ΔE) Where ΔE/E is the fractional energy loss per...
  47. C

    Solving Computations w/ Cycles: Permutations, Inverses, Orders

    So I've been sitting here for a while looking at my study guide and I am not sure how to find the product (or even the inverse) of this permutation in S9: (2 5 1 3 6 4) (8 5 6)(1 9) = (1 3 8 5 9)(2 6 4) (Correct answer) I know it starts off with 1 --> 3, then you get (1 3 and then after you...
  48. M

    How many cycles of time should be measured for the most accurate T?

    Homework Statement Measuring the period of a sine wave using oscilloscope, for the best accuracy, is it better to measure only one cycle? Homework Equations The Attempt at a Solution Let t=T_{1}+T_{2}+\cdots + T_{n} (Measuring n cycle) From error propagation formula...
  49. M

    Throttling in Refrigeration Cycles

    Hi all, The process of throttling in refrigeration is taken to be isenthalpic. And as enthalpy remains constant then so should the temperature. But in the TS diag of the process it shows a drop of temperature from Thigher to Tlower. Please help me regarding this. Thanks!
  50. PsychonautQQ

    Understanding Disjoint Cycles and Commutativity in Sn

    Homework Statement I'm taking an online class this summer and the notes gave the proposition that Disjoint Cycles Commute with the following proof. Proof. Let σ and τ represent two disjoint cycles in Sn and choose some arbitrary j ∈ {1,2, . . . , n}. Since σ and τ are disjoint, at most one...
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