Cycle Definition and 674 Threads

The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea (NH2)2CO from ammonia (NH3). This cycle occurs in ureotelic organisms. The urea cycle converts highly toxic ammonia to urea for excretion. This cycle was the first metabolic cycle to be discovered (Hans Krebs and Kurt Henseleit, 1932), five years before the discovery of the TCA cycle. This cycle was described in more detail later on by Ratner and Cohen. The urea cycle takes place primarily in the liver and, to a lesser extent, in the kidneys.

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  1. Islam Hassan

    Hydrogen Fusion Cycle in Stars: Storage/Transport/Consumption?

    I have always been wondering how in an active star the H/He fusion cycle is "managed" for lack of a better word, a little like a logistical analogy really. Specifically: i) Where in the star is the yet-to-be-fused H 'stored'? ii) Where in the star is the He result of fusion 'stored'...
  2. Q

    Battery Life Cycle: Explaining DoD vs Life Cycles

    Hello, I have seen graphs of Battery's DoD (depth of discharge) vs Life Cycles. But at the same time, "life cycle" is defined as the no. of COMPLETE charge-discharge cycles that a battery can perform before its nominal capacity falls below 80% of its initial rated capacity. Here's the...
  3. G

    Optimizing a Brayton Cycle to Produce Shaft Power

    I have a question about the minimum amount of heat required to operate a theoretical brayton cycle engine that is optimized for producing shaft power, not thrust (if that matters). What is the relationship between inlet compression ratio and other variables, turbine variables, and minimum...
  4. Jalo

    Thermodynamics - Cycle efficiency

    Homework Statement Consider the following reversible cycle: Where S2=S3=(S1+S4)/2 . Prove that the efficiency η is: η= 1 - 2*T6 / (T1+T3) Homework Equations The Attempt at a Solution I know that in a T-S diagram the heat received by the system is equal to the area...
  5. Jalo

    Thermodynamics - Cycle efficiency

    Homework Statement Compute the efficiency of the following cycle: Homework Equations The Attempt at a Solution I know there's an isothermic process between a and b, where heat comes into the system, let's call it Qh. I also know that between b and c heat will leave the...
  6. K

    Otto cycle mathematical model - Heat added by combustion?

    I am attempting to improve a spreadsheet I created back in uni some 5-6 years ago, which models all the velocities and accelerations of the pistons and rods, as well calculating pressure, temperature and resulting torque. It is only a simple model so far, originally it started simply by...
  7. S

    Find the average power over one cycle

    Homework Statement The problem and its solution are attached as TheProblemAndSolution.png. Homework Equations Integration P = VI V = RI The Attempt at a Solution I think Wolfram Alpha “says” ( http://www.wolframalpha.com/input/?i=integrate+900sin%5E2%28377t%29+dt+from+0+to+pi ) that...
  8. A

    How Does Increasing Compression Ratio Affect CO2 Emission in Otto Cycle Engines?

    Homework Statement Estimate the change in volume of carbon dioxide if 'r' is increased from 10 to 11 (10% increase). Assume 30 million cars, all use 1m^3 of fuel each year Homework Equations Efficiency of an Otto Cycle η=1-r^(1-gamma) The Attempt at a Solution Original...
  9. Gh778

    Thermodynamics cycle with liquid and gas

    I'm trying to find why this thermodynamics cycle is not possible but I don't find. The only problem for me is at step 3, the gas can't become a liquid but why ?
  10. D

    MHB SE Class 11 Physics Revision Notes Chapter 14 Oscillations

    $$ \begin{cases} x'=.05\left[y-\left(\frac{1}{3}x^3 - x\right)\right]\\ y'=-\frac{1}{.05}x \end{cases} $$ So this a Van de Pol equation where $\mu = .05$. It is basically a circle at the origin with radius 2. How do I find the period?
  11. D

    MHB Numerically Solving the Van de Pol Equation to Find Limit Cycle Periods

    s = NDSolve[{x'[t] == \[Mu]*(y[t] - (1/3*x[t]^3 - x[t])), y'[t] == -1/\[Mu]*x[t], x[0] == 8, y[0] == 2}, {x, y}, {t, 150}]; This code will show limit cycles when you parametric plot the Van de Pol Equation. However, I want to find the period T numerically. I need to add in a piece for mu...
  12. D

    Pressure changes within a refrigeration cycle

    So I get that when the VP is equal to atmospheric pressure of 14.7 psia, if you will be at a saturated liquid and when more heat is added, it is latent head changing it to a gas. If however you are at a closed container where the can physically alter the "atmospheric pressure" in the container...
  13. G

    Cycle notation of permutations

    Homework Statement How many elements of each cycle-type are there in S5? The Attempt at a Solution One way of working this out would be to write out each permutation and see how many 2-cycles, 3-cycles ,4-cycles and 5-cycles there are but given that there are 5! permutations this would...
  14. E

    Determine the Main Cycle of a Counter (JK flip-flops)

    Homework Statement For the counter shown below, determine the main cycle, and for each of the unused states, show what happens if it starts up there. http://i45.tinypic.com/33l1lhc.jpg Homework Equations N/A The Attempt at a Solution I thought I knew how to do this, but after some...
  15. P

    Changing the duty cycle of a PWM signal

    I'm trying to control the speed of a computer fan using the radio input from an RC transmitter/ reciever. The PWM output of the reciever is 1ms to 2ms high and 20ms low, so 10%-20% duty cycle. The computer fan requires a 30% to 100% duty cycle, at 25khz (about a 40uS pulse) I was thinking of...
  16. T

    What is the efficiency of the cycle

    Question is attached Thanks!
  17. 1

    Life cycle of butterfly Differential equations

    Would someone be able to help me with the question Life cycle of butterfly is egg -> caterpillar -> butterfly. Each week 5% of the eggs will hatch and 2% of the caterpillars will turn to butterflies. You start with 100 eggs and 60 caterpillars. Using calculus to obtain an equation...
  18. T

    Heat engine- calculating minimum energy per cycle from hot reservoir

    Homework Statement A heat engine operating between freezing and boling points of water takes 20 cycles to raise a mass of 1000kg through a height of 3m. Calculate the minimum energy per cycle that must be extracted from the hot reservoir in order to achieve this. Homework Equations...
  19. C

    Is the Rotary Atkinson Cycle Engine Used in Production Vehicles?

    http://white-smoke.wetpaint.com/page/Rotary+Engine does anyone know of this engine being used in production?
  20. D

    Carnot Cycle and Reversibility

    I'm trying to resolve some of my conceptual sticking points with the Carnot cycle. For one thing, I'm reading Reiss's Methods of Thermodynamics, and he offers a proof that the Carnot cycle obtains maximum efficiency when conducted reversibly. How can the cycle be conducted reversibly? During...
  21. A

    Is the Phase Change Floatation Cycle a Theoretical Flaw in Thermodynamics?

    Consider the following theoretical cycle. There should be a flaw somewhere, but I could not find it yet and will appreciate it if someone can point it out to me. A lot of ideal assumptions are made, such as reversible heat transfer, but it is not intended to be practical, as long as it adheres...
  22. S

    Hitting the Cycle in Baseball: Maximizing Performance

    In baseball there's something called "the cycle". It means hitting a single, a double, a triple and a home run in one game. http://sports.yahoo.com/news/mets-hairston-hits-cycle-034749797--mlb.html If I had my way, any sportswriter or announcer who talked about "the cycle" would be...
  23. O

    Why Is My Calculation of Carnot Engine Efficiency Incorrect?

    Homework Statement A Carnot engine operates between 230°C and 120°C, absorbing 6.30*10^4 J per cycle at the higher temperature. What is the efficiency of the engine? Homework Equations eff = 1 - (Tcold/Thot) The Attempt at a Solution Using this equation, I get 47.83 percent...
  24. J

    Let σ a cycle of length s. Then σ^2 is a cycle iff s is odd.

    Proposition: Suppose σ is a cycle of length s. Then σ2 is a cycle if and only if s is odd. Quick remark... The following "proof" seems more like an explanation. This is for a self-study and I am looking back through my notes to refine/correct/improve. If you were correcting this, say out of...
  25. H

    Heat Engine Cycle: Answers to (i), (ii) & (iii)

    Does anyone can help me in this question? Two reversible heat engines operate in series between a source at 600C and a sink at 30C. If the engines have equal efficiencies and the first rejects 400 kJ to the second, calculate: (i) the temperature at which heat is supplied to the second...
  26. L

    Z diagram and Q cycle ? (Bad teacher)

    Z diagram and Q cycle ?? (Bad teacher) Hey guys, my teacher told me to review the Z diagram + Q cycle. I'm pretty sure that this means I'm to study Light reactions of Photo synthesis and The Fluid mosiac model. Sound Right? Also this is my first post, so hi :D
  27. F

    Otto cycle exhaust heat rejection

    Hello All! I am new to the forum and need help. I have looked at multiple sites an looked at 328 threads titles and about 20 actual threads today to find the info I was looking for...no luck. Here is my question: I have a 12.5KW natural gas generator and want to know much heat and I can...
  28. L

    Question regarding carnot cycle

    In Carnot cycle we assume that heat addition takes place at constant temperature(temperature of system and source being same) and same is the case for Heat rejection. But as we know that for heat flow (ie heat addition and heat rejection), temperature difference has to be there between system...
  29. M

    Could a Black Hole be the cycle of Dark Matter powered by Dar Energy:?

    Could a "Black Hole" be the cycle of "Dark Matter" powered by "Dar Energy:? Could the "black hole" be like a cycle for "dark matter". So let's say "Dark Energy" is what transports "Dark Matter". So all a black whole is, is a huge amount of energy pulling in "Dark Matter" and pushing it out to...
  30. T

    Find the order of a k cycle in group Sn

    Homework Statement Prove that a k-cycle in the group Sn has order k. Homework Equations The Attempt at a Solution I'm mostly confused on how to write this in math notation. I know it will have order k because a1 → a2 → a3 ... ak-1 → ak → a1 if we do the compositions K times. and so...
  31. J

    Gas turbine brayton cycle thermodynamic mass flow rate of air

    Homework Statement a gas turbine is designed to produce 3000hp when using air at a maximum inlet temperature of 650k and assuming a heat loss of 70 kj/s. if the exhaust temperature is desired to be no greater than 200 degrees celsius, determine the mass flow rate of air required. Homework...
  32. fluidistic

    Carnot cycle, fundamental equation of ideal gas

    Homework Statement Assuming that the auxiliary system in the Carnot cycle is a monoatomic ideal gas whose fundamental equation is S=\frac{NS_0}{N_0} +NR \ln \left [ \left ( \frac{U}{U_0} \right ) ^{3/2} \left ( \frac{V}{V_0} \right ) \left ( \frac{N}{N_0} \right ) ^{-5/2} \right ]. 1)Find...
  33. fluidistic

    Efficiency of a cycle from a diagram

    Homework Statement Calculate the efficiency of the heat machine that is shown in the figure. Draw the corresponding Carnot cycle diagram in the S-T plane. Homework Equations \varepsilon = \frac{ \Delta W}{\Delta Q}. \Delta Q = T \Delta S The Attempt at a Solution My problem lies in...
  34. N

    Calculating Efficiency of Diesel Cycle

    1. Homework Statement given: diesel cycle, P1V1 P2V2 P3V3 P4V4 - all known T1 = 20°c specific heat capacity constant pressure = 1000j/kgk specific gas constant = 287j/kgk compression index = 1.4 2. Homework Equations heres where i am stuck! 3. The Attempt at a Solution Hi...
  35. N

    Calculating diesel cycle efficiency

    Homework Statement given: diesel cycle, P1V1 P2V2 P3V3 P4V4 - all known T1 = 20°c specific heat capacity constant pressure = 1000j/kgk specific gas constant = 287j/kgk compression index = 1.4 Homework Equations heres where i am stuck! The Attempt at a Solution Hi all, I am...
  36. B

    Is cycle the same as wavelength?

    Is cycle the same as wavelength? Thanks!
  37. D

    Solving Otto Cycle Problem: Find p2, p3, p4, T2, T3, T4, V2, V3, V4

    Homework Statement p1, V1, T1 and ε (compression ratio) are known I need to find: p2, p3, p4 T2, T3, T4 V2, V3, V4 but I don't know how to find p3, p4, T3, T4 Homework Equations ε = V1 / V2 V1 = V4 V2 = V3 T1 * V1^(k - 1) = T2 * V2^(k - 1) T3 * V3^(k - 1) = T4 *...
  38. H

    Adiabat Process - with pV cycle

    Homework Statement A heat engine uses 2 mole of a diatomic gas that follows the pV cycle shown, how much work is done, over the cycle if P=100kPa, T1=207K * P is suppose to be 0.5P this was a typo on the graph This is what I've figured out so far: (if i am incorrect on anything...
  39. R

    (Water Heater)Geyser Heating Cycle

    Ok, I know there is the argument about switching off/on a geyser versus the leaving it on all day argument, let's argue that for specific set of circumstance I have found out that the turn off method is saving me money. This choice now seems to have me in two minds. 1 is to keep the geyser on...
  40. A

    Carnot Cycle: Exploring Heat Efficiency and Adiabatic Processes

    I have some trouble understanding the carnot cycle and why you have to make it so complicated, i.e. this process involves 2 isothermal and 2 adiabatic processes. If you want an engine with maximum efficiency why can't you just have a system whose temperature is just a tiny inch above your hot...
  41. J

    MHB ODE system. Limit cycle; Hopf bifurcation.

    Problem: The following two-dimensional system of ODEs possesses a limit-cycle solution for certain values of the parameter$a$. What is the nature of the Hopf bifurcation that occurs at the critical value of $a$ and state what the critical value is. $\dot{x}=-y+x(a+x^2+(3/2)y^2)$...
  42. S

    ODE system. Limit cycle; Hopf bifurcation.

    Homework Statement The following two-dimensional system of ODEs possesses a limit-cycle solution for certain values of the parameter a. What is the nature of the Hopf bifurcation that occurs at the critical value of a and state what the critical value is. Homework Equations...
  43. M

    Analyzing a partially reversible cycle

    Thermodynamic: Analyzing a partially reversible cycle Homework Statement A cycle (which at first appears to be a Carnot cycle) consists of a reversible isothermal process (with reversible heat exchange with a reservoir at 500 C), followed by an adiabatic process, which is followed by...
  44. teroenza

    Damped oscillator energy dissipated per cycle.

    Homework Statement Sinusoidal driving force driving a damped oscillator (mass = m). Natural frequency is assumed to equal the drive frequency = w Time has elapsed to the point any transients have dissipated. Show that the energy dissipated by the damping force [F=-bv] during one cycle is...
  45. O

    What's special about the Carnot Cycle?

    Why do we always talk about the Carnot cycle as being the most efficient, ideal engine? Doesn't the same equation hold for any reversible heat engine operating between two thermal reservoirs? Couldn't you prove e = 1-T_{L}/T_{H} for any reversible cycle? And then you can apply the usual "no...
  46. R

    Modifying Program to Control Current at Maximum Duty Cycle

    Hi, I want to modify a program that was written long ago. I would like to give the output from hardware as user input. Here, user input deals with current at maximum duty cycle allways. My task is to control the current according to the user input. Let say, if user wants 2kA as O/P and i...
  47. L

    Reverse Carnot - Refrigeration Cycle problem

    Hi guys, I have difficulties understanding the what I need to do in this problem. I have a ideal refrigeration cycle. first part is standard calculations, work of compressor and such. Results are Temperature range between -23 and 60 degrees C. Second part is the one that i do not understand. it...
  48. K

    Calculating Efficiency of an Ottos Cycle: I Need Help!

    I have made an Ottos Cycle graph and found the area Wnet and W12. I now have to find the efficiency η = Wnet/W12 I have found that to be 0,20 but I have no idea what this tells me about the work or anything. I need help.
  49. R

    Is It Possible to Extend Flame Duration Beyond 100% Duty Cycle?

    Hello, I am making some modifications in my programm that had written by someone. it is about a flame machine and AC mains frequency is 50Hz. Now, the program is working for outputting a 20ms continuous flame that means it is quiet clear that it was working at 100% duty cyle(not...
  50. J

    Finding Qdot for a Thermodynamic Rankine Cycle

    Homework Statement Water is the working fluid in a Rankine cycle. Superheated vapor enters the turbine at 10 MPa, 480 °C condenser pressure = 6 kPa ηturbine = 80% ηpump = 70% determine a.) Qdot of the steam generator. b.) ηth c.) Qdot from the condenser to the cooling water. Homework...
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