What is Cycle: Definition and 673 Discussions

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. Fisher

    Designing an ORC System for Ship's WHRS: A Process Engineer's Perspective

    Hello. Physics friends. I am Fisher. I am a process engineer in shipbuilding field. Now I am in a project to design ORC system for ship's WHRS. Let's make a lot of talk together. Thanks.
  2. F

    Admissions Profile evaluation for astronomy Phd applicant in the fall 2023 cycle

    I will apply for a Ph.D. in Astronomy in the fall of 2023. I want to have a realistic evaluation of my profile to see if I am over-ambitious or not. I think I am out of reach for the "big four" universities. I will donate money to two of them only and will be targeting other top schools...
  3. kornelthefirst

    Van der Pol Oscillator limit cycle

    First i looked at the case of ## \epsilon = 0## and came to the conclusion, that this oscillator has a circular limit cycle in a phase space trajectory, when plotted with the axes x and ##\dot{x}##. I have found that ##x_0^p (t) = a_1 \cos(t)## which implies that all other Fourier- coefficients...
  4. thomas_shvekher

    Newton's First Law to explain Washing Machine Spin Cycle

    I truly am not sure. I assume it is that because everything has inertia, an a tendency to remain in a constant state of motion, when the clothes are quickly spun around they cannot remain in a constant state of motion (of either rest or constant velocity), but the water is "pushed"/spun out of...
  5. S

    Calculate these 5 temperatures along this Thermodynamic cycle

    I only know T3 = 4•T1 I was able to calculate the T2 = Tb = T4 I built four equations: T2 = p2V1 / nR T4 = p1V2 / nR p1/T1 = p2/T2 V1/T2 = V2/4T1 I put them together and got T2 = 2T1 I can't figure out the temperatures of A and C. I tend to think Ta could equal Tc (then I would be able to...
  6. Astronuc

    NASA NASA - Bimodal NTP/NEP with a Wave Rotor Topping Cycle

    New Class of Bimodal NTP/NEP with a Wave Rotor Topping Cycle Enabling Fast Transit to Mars https://www.nasa.gov/directorates/spacetech/niac/2023/New_Class_of_Bimodal/ Ryan Gosse, University of Florida, Gainesville, FL...
  7. S

    I Expansion-Collapse cycle in cosmological structures?

    Concerning cosmological structures (like galaxies, clusters of galaxies, gas bodies, superclusters...etc) if the elements that make them are close enough they will be attracted towards each other by gravity. Contrarily, if they are sufficiently far apart they will get further away following the...
  8. Graeme M

    Is Reducing Livestock Herd Size the Key to Reducing Methane Emissions?

    I am aware that it is claimed that ruminant farming and animal agriculture more generally are significant contributors to anthropogenic emissions. Here in Australia, for example, about 80% of emissions from the ag sector are from methane and nitrous oxide. Various groups propose finding ways to...
  9. Z

    Angular deceleration of a washing machine spin cycle

    6.0 rev - 1 s 1 rev - 1/6 5.0 rev - (1/6) x 5 = (5/6) s = 0.833 s I do not know how to calculate the angular acceleration
  10. Tesla In Person

    Thermodynamic Cycle -- Work done as a function of Heat absorbed

    During a thermodynamic cycle, an ideal thermal machine absorbs heat Q2 > 0 from a hot source and uses it to perform Work W > 0, giving a cold source a heat Q1 < 0 with an efficiency of 20% . How much is the work done as a function of Q1 ?I have 2 question regarding this problem: 1) Why is Q1 the...
  11. dom_quixote

    Taurozzi's Oto Cycle Engine: A Notable Improvement

    Notable improvement on the Oto cycle engine, invented by Taurozzi in the early 1970s.
  12. L

    Change of entropy in the Universe in a thermodynamic cycle

    (a) We first find that: ##T_A=\frac{P_A V_A}{nR}=\frac{1\cdot 10^5 \cdot 4}{40\cdot 8.314}K\approx 1202.7904 K##, ##\frac{T_B}{T_A}=\frac{\frac{P_B V_B}{nR}}{\frac{P_A V_A}{nR}}=\frac{P_B V_B}{P_A V_A}=\frac{P_A \frac{V_A}{2}}{P_A V_A}=\frac{1}{2}##, ##\frac{T_C}{T_B}=\frac{P_C...
  13. Kamuna

    Engineering Regenerative Rankine cycle with one contact feedwater heater

    My question is how do i get : A. required steam generated from the boiler per hour B. extracted steam per hour for feedwater heater C. thermal efficiency of the cycle I can solve the thermal efficiency but A and B is giving me difficulties, i know when solving the extraction of steam needs mass...
  14. J

    I Is this water pumping device using the Rankine cycle?

    A while back a was messing around in the shop, and ended up making this water pump that uses only heat to pump. The two check valves are the only moving parts. Here is a drawing of what it looks like inside. Here is another drawing of what I believe it is doing in its cycle. The system...
  15. Kamuna

    Engineering Understanding Rankine Cycle Pressures: Should P2 Equal P3?

    Is this the right path in solving this problem? Am i finding the correct enthalpies? I am also having difficulty understanding so what I've understood is that in a rankine cycle P2=P3 but here P2 is given and P3 has a given variable which is T=25 C too so should I neglect P2=P3? Heres my...
  16. Kamuna

    Engineering How Does Efficiency Impact Calculations in a Regenerative Rankine Cycle?

    I tried to solve and get the answer but i know this is wrong since i didnt use the efficiencies. If you can help me pls indicate where did you use the given efficiency so that i can learn and understand from it. I am still new to this topic. Thank you In a steam power plant operating on...
  17. Kamuna

    What Are High and Low Turbine Stages in a Regenerative Rankine Cycle?

    In this cycle/ schematics I'm a bit confused what are the high turbine stage low turbine stage. Does high turbine occur in state 2? and low on state 345? I am still having difficulties in determining what state is the high turbine or low turbine stage occur please enlighten me I'm just new...
  18. Kamuna

    Thermodynamics Regenerative Rankine Cycle

    Summary:: regenerative rankine cycle Im a bit troubled by my home activity recently and maybe i could use some help this is the problem : In a steam power plant operating on regenerative Rankine cycle with one contact feedwater heater, steam enters the turbine at 8.0 MPa, 350 C and condensed...
  19. D

    Specific heat in for the Otto cycle

    A class project requires us to model the Otto cycle using ideal gas properties. We are not given the value for qin (specific heat in) and are told to make an intelligent approximation. My approach to this has been to find the calorific value of petrol, multiplying this by the density of petrol...
  20. guyvsdcsniper

    Evaluating a cycle [Thermodynamics]

    Since this is a cycle, there should leave the system unchanged, hence Q+W = 0. I wrote evaluated the heat and work done on/by the system at each cycle as shown in my work. The first question ask is work done at the fourth stage. Since this a cycle and again the system she remain unchanged...
  21. B

    Vapour Absorption Cycle Questions

    Hi all, I'm doing some research on vapour absorption cycle machines, mainly water ammonia refrigerators. I've got a few questions. 1. What is the role of the water absorber? ie why do we need the water? 2. In the absorber we have a water ammonia solution. Is the ammonia a gas in the solution...
  22. berkeman

    GE initiates testing on second XA100 "adaptive cycle" fighter jet engine

    This is pretty interesting. It sounds like GE and the Air Force have been able to make some good improvements recently...
  23. bardia sepehrnia

    Engineering Carnot Cycle and Coefficient of Performance

    I think I calculated part a correctly by extracting the cp (specific heat) of water from the table which is 4.188 Then calculated Q_dot by simply using the equation Q=m*c*deltaT=10.47kW But I am stuck at part b, I know that the heat extracted from the water is the same as Q_L (rate of heat...
  24. S

    Engineering Entropy of Otto Cycle: Deriving s1=s2

    Hello, just wanted to ask regarding the otto cycle; if we were to find the entropy at the phase of isentropic compression and I was already able to derive the temperature 1 and 2 and the pressures at 1 and 2 and I also have the compression ratio of 10. How do I derive the entropy (s1 and s2)...
  25. Benjies

    The vacuum optimized Raptor: No attempt at an expander-bleed cycle

    Hello all, The merits of the full-flow cycle are without question and have been fielded with Starship tests to the point of my complete buy-in into Raptor's capability as a launch engine. Elon Musk loosely discusses further refinement of their vacuum-optimized engine that they have created...
  26. Delta2

    I Cycle of an air conditioner and power consumed

    I have an air condition that is 9.000 BTU and it states at the external unit that its Power is 1.2KW. However because I know that an air condition has inductive loads (motors) its power factor is not 1 so I am not sure 1.2KW is the real power consumed. I am thinking to calculate the power...
  27. M

    How to calculate the electrical power output using the Organic Rankine Cycle?

    Basically this would be a closed loop geothermal system for electrical power generation. The system would consist of 2 Horizontal Wells connected creating a U-shaped closed loop cycle using thermosiphon effect, with constant recirculation. It's not really a conventional geothermal power...
  28. S

    I Why can a person cycle more in a day than they can walk or run?

    Hello All Numbers vary, but the consensus is that an average person can cycle much further in a given time than they can walk or run. The world record for running is about 300km in 24 hours, whereas the cycling record is about 900km. A more typical comparison might be that a fit athlete could...
  29. S

    Designing an Actual Vapor-Compression Refrigeration Cycle

    Greetings! I'm a recent ME grad and I'm trying to design a refrigeration system for the first time. I understand most of the theory and calculations (I guess not, cause I wouldn't be here otherwise), but I'm having difficulty applying it to the real world. Homework problems in college often...
  30. S

    I The stellar system genesis & supernova cycle

    AIUI, the early universe, after the Great Recombination, was a fairly, but not absolute, isotropic cloud of mostly H, with some He. Eventually regions of the cloud coalesced into stars, and if the mass was big enough, the temperature & pressure in the star core was sufficient enough for H in...
  31. PhysicsTest

    Calculating Average Power and Energy Consumption for a Heater

    The v(t) = 120##\sqrt(2)\sin(2\pi 60t)##. Let the resistance of the heater be "R", then the rated power = 1500W. The rated power is the average power 1500 = ##\frac{120^2 *5 * 60} {12*60 * R} ## ->eq1 R = 4 Ohm. a. Instantaneous power is ##P = \frac{v^2} R ## -> eq2 ##P =...
  32. DanjoJojo

    Is My Clock Cycle Calculation Accurate for a 2.5 GHz CPU?

    So far I have come to the understanding that a nanosecond is one billionth of a second or 10-9 seconds. So I found this formula to calculate the clock cycle in nanoseconds, for a CPU running at 2.5 GHz. 10^-9 x 2.5 x 10^9 = 2.5 nanoseconds Am I missing any important steps with my calculation...
  33. Kaguro

    Net heat in a thermodynamic cycle

    In AB, dU=0 (Isothermal) Hence dQ=dW W1= RT ln(2V/V) = RT ln(2) = 800R*ln(2) Q1=W1 = 800R*ln(2) Q2= Cp(300-800)=-500Cp = -500*2.5R Q3 = Cv(800-300) = 500Cv = 500*1.5R So Q= 800R*ln(2) -500*2.5R + 500*1.5R = 800R*ln(2) -500R Hence net heat absorbed is 800R*ln(2) -500R But. Suppose I find...
  34. theycallmevirgo

    Servo duty cycle and overdriving

    What kind of service life can I expect from small hobby servomotors? Can I exceed current rating for increased power? How will that affect duty cycle? Thanks so much in advance Joe
  35. R

    I Irreversible Isochoric Process in a Cycle

    Consider a reversible ideal gas cycle consisting of: 1. An isochoric heat addition, 2. An isothermal expansion to the initial pressure, and 3. An isobaric compression to the initial volume. What, if any, is the difference in net work done by the gas in the cycle if the isochoric heat addition...
  36. yecko

    Revisiting Refrigeration Efficiency: Impact of Potential Typo on Calculations

    Can efficiency be larger than 100%? I have double checked the values of enthalpy of point 1,2,3 from R-22 tables. And I obtained enthalpy of point 4 from the work done given. Thank you.
  37. J

    Validating "NET Power's" use of the Allam-Fetvedt cycle

    The Allam-Fedvedt cycle is a method to burn natural gas without releasing Carbon to the atmosphere. www.netpower.com claims they have a 50 Mw commercial grade power plant using this innovation and I hope that is the case. Netpower states they are building a 300 Mw plant. This NEEDS TO BE...
  38. Ntip

    Boost converter duty cycle in DCM

    Hi, This is not a homework problem, I am trying to analyze how various parameters affect a boost converter operating in DCM most of the time. The input and output voltage is fixed so I will eventually like to sweep parameters for D, L, T, Vi, and R. R is less important though. Here I am using...
  39. A

    Thermal Machine: Solving for Q23 to Complete the Otto Cycle

    1-->2 (adiabatic) $$P_1V_1^γ=P_2V_2^γ$$ $$P_2=18,4.10^5Pa$$ $$T_1V_1^{1-\gamma}=T_2V_2^{1-\gamma}$$ $$T_2=429,32K$$ 2-->3 (isochoric) $$\frac{P_2}{T_2}=\frac{P_3}{T_3}$$ $$\frac{18,4.10^5}{429,32}=\frac{P_3}{T_3}$$ 3--> 4 (adiabatic) $$P_3V_3^{\gamma}=P_4V_4^{\gamma}$$...
  40. J

    Understanding the effect of duty cycle on the brightness of LEDs

    The brightness of an LED is a result of the current passing through it. The current is a function of the voltage across the LED. The duty cycle represents the percentage of the time period that the signal is in the ON state ( which means that the voltage is at max value as compared to 0 V for...
  41. J

    Reversible Otto Cycle Efficiency: Investigating the Difference from Carnot's

    So we know that every reversible engine working between the same temperatures will have the same efficiency(the same as Carnot engine). So let's consider for example reversible Otto cycle. So as you can see on the picture it is operating between ##T_1## and ##T_3##, so I was thinking that it...
  42. A

    Conceptual thermodynamics problem about ammonia executing a Carnot cycle

    Is there a mathematical explanation for why the work done in the condenser (in process 2 to 3) is zero? I am aware that ammonia does not expand or compress in the condenser, only changes phase, but without knowing that the process takes place in a condenser and only considering the graph...
  43. K

    I The life cycle of a star and the bell shaped energy emission curve

    Do all stars in their life cycle (t) emit energy (E) that follow a bell shape curve? If yes, is the curve symmetrical always? How is this related to nuclear and thermal time scale?
  44. VictorMedvil

    A What is the energy release of the CNO cycle in carbon fusion?

    I would like details on CNO Cycle Carbon Fusion about the exact energy release of an entire cycle through the reaction and other details you would think would be important about the CNO cycle.
  45. B

    Ammonia Rankine cycle heat engine calculation

    A Rankine Cycle heat engine uses ammonia as a working fluid, turbine entry temperature is 25 Bar at 60 degrees Celsius. The turbine outlet pressure is 4 Bar, the question is: what is the outlet temperature? and if the output power is 6 Gigawatt (6x10^9 watt) what would the mass flow rate of the...
  46. M

    MHB Determine the cycle decomposition of the permutations

    Hey! :o We have the following permutations in $\text{Sym}(14)$ : - $\pi_1=(1 \ 2\ 4 \ 9)\circ(1 \ 3)\circ (6 \ 8\ 12)$ - $\pi_2=(2 \ 4\ 5 \ 8\ 7)\circ (1 \ 12 \ 6)\circ \ (13 \ 14)$ - $\pi_3=(1 \ 4 \ 5\ 8 \ 11)\circ (2 \ 4\ 6 \ 5 \ 1)$ 1. Determine the cycle decomposition of $\pi_1...
  47. F

    Temperatures of the hot source and cold sink in a heat engine

    Hi, I was just wondering about the efficiency of a cycle that is not Carnot cycle. In that case one should use \eta = 1-\left|\frac{Q_{\rm out}}{Q_{\rm in}}\right|, where Q_{\rm in} and Q_{\rm out} are the amounts of heat absorbed and released during the cycle. For instance, I guess that in...
  48. alexmahone

    Textbook containing the Rankine cycle (Thermodynamics)

    I'm taking an online course that covers the Rankine power cycle, that, unfortunately, isn't mentioned in any of my textbooks. Do you guys have a textbook that covers this cycle? Thanks
  49. Genava

    I Variations in Sun-Earth distance with a 2000-year cycle?

    Hi, I see that a newspaper is making a claim that Zharkova identified a 2000-year cycle causing some significant variations in Sun-Earth distance with a cycle of 2000 years, seemingly because of the perturbations caused by Jupiter making the Sun orbiting a barycentre slightly eccentric. This...