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. E

    Checking my reasoning on a carnot cycle problem

    Homework Statement An approximate equation of state for a gas is P(v-b) = RT with b constant. The specific internal energy of the gas is u = c_vT + const . a) show that the specific heat at constant pressure of this gas is c_v +R and b) show that the equation of a reversible adabiatic...
  2. S

    ORC Setup in Garage - Advice Needed

    Hey I am new to this forum and I am looking for any pointers about my ORC before I start it up? I made an ORC in my garage with two Swep heat ex-changers, one B35 and one B10 (used but flushed). I have hooked up 3 (used) hot water heaters to the B35, 40 gal each with 4.4 kW elements in them, for...
  3. Adrian B

    Energy required to cycle a counter through its states.

    Greetings, While attempting to learn something about cryptography, I have repeatedly encountered a commonly quoted argument about the minimum energy required to cycle a 256 bit counter through all its states. It says that the absolute minimum energy required to change the state of a bit is...
  4. B

    Estimating The Mass Necessary For A Particular Rankine Cycle

    Calculating the Efficiency of A Rankine Cycle For Various Parameters Homework Statement Calculate the efficiency of a Rankine cycle that is modified from the parameters used in the text in each of the following three ways (one at a time), and comment briefly on the on the results: (a) reduce...
  5. Uriel

    Work done by a expanding and contracting wire over a Carnot cycle

    Homework Statement Basically I have the following problem. Given the equation of state \sigma = \frac{b}{T}\frac{L - L_0}{L_0} where b and L_0 are positive constants, calculate the work done over a Carnot cycle by a wire with this equation of state.Homework EquationsI already have the work...
  6. G

    Reversible Clapeyron cycle efficiency

    Homework Statement The Clapeyron cycle efficiency is similar to the Carnot cycle except that two adiabatic paths are replaced with isobaric processes a) based on the above information, draw a Clapeyron cycle. b)Derive the efficiency of the reversible Clapeyron cycle Homework...
  7. P

    Life Cycle Cost Analysis (LCCA)

    Hi all, for job reasons I have come across LCCA, and I have started documenting myself reading this ebook that I found googling: Fuller-Petersen, LCCA. Now, I'm new to the topic, and I have a few questions: 1) Is it just about calculating all the costs of two projects, maybe taking inflation...
  8. A

    Thermodynamics - Heat Engine Cycle

    Homework Statement n = 5 moles, monatomic, ideal gas p1 = 7280 Pa; v1 = 2 m3 p2 = 7280; v2 = 6 p3 = 6500; v3 = 6 What is the change in heat, from 2 to 3, and from 3 to 1? Homework Equations PV = nRT U = (3/2)nRT Q = du + dw The Attempt at a Solution PV = nRT (7280)(2) =...
  9. U

    Calculating work done in this thermodynamic cycle

    Homework Statement In the thermodynamic cycle as shown, a) What is the direction that the cycle is executed-clockwise or anticlockwise? b) What is the work done? Homework Equations First law of thermodynamics for a cycle E2-E1= Q-W= Tds-Pdv=0 The Attempt at a Solution a) I...
  10. L

    Prediction of reactor End of cycle

    There is a technical document in reactor operation which contains neutronic calculations to predict reactor situation in different power lever and effective power days. Operators use this document which usually called Album of Reactor Core Neutronic to operate the reactor based on that. This...
  11. Gh778

    Problem with energy in a cycle

    Hi, I compute sum of energy in a cycle and I don't find 0, could you help me to find the error ? I started an equivalent thread in another physics forum but nobody understand. I hope my english is clear enough for understand the problem. The system is under gravity and everywhere outside...
  12. MacLaddy

    Thermal Efficiency in an Ideal Diesel cycle.

    Homework Statement Helium in an ideal Diesel cycle is compressed from 4 L to 0.25 L, and then it expands during the constant pressure heat addition process to 0.50 L. Under air standard conditions, the thermal efficiency of this cycle is: a) 79.5% b) 20.5% c) 61.4% d) 67.4% e) 84.3%...
  13. A

    Refrigeration Cycle: Understanding qL/wc & qH

    I'm trying to get a good understanding of the two images attached. So when calculating the coefficient of performance, I will need to use qL/wc. This is something that I've read in my textbook. Now when I was working with another student on this he told me that the work of the compressor...
  14. R

    Otto Cycle Engine Homework: Total Work & Efficiency Calculation

    Homework Statement "A car has a six-cylinder Otto-cycle engine with compression ratio r = 10.6. The diameter of each cylinder is 82.5 mm. The distance that the piston moves during the compression stroke (see fig. 1) is 86.4 mm. The initial pressure of the air-fuel mixture (at point a in...
  15. S

    Modelling Diesel Cycle in Excel.

    Homework Statement Construct a Microsoft Excel® spreadsheet that models an internal combustion engine based on the ideal air-standard Diesel cycle. Given the minimum temperature (##T_1##) and pressure (##P_1##) in the cycle, the engine size (##V_1##), the compression ratio (##r_v##), the...
  16. Kelsi_Jade

    Carnot Cycle Refrigerator - Thermal Battery Problem

    The question is: Consider a thermal battery - a device for storing mechanical energy. Use two large containers as heat reservoirs where one contains ice and water in equilibrium and the other contains steam and water in equilibrium. Both are held at pressure=1atm. Energy is stored by using a...
  17. Kelsi_Jade

    Find the work and heat transferred in a carnot cycle.

    I'm having some difficulty understanding how to find the work and heat transferred in a carnot cycle. Problem: One mole of ideal gas (cV=1.5 R) perform a Carnot cycle between the temperature 400 K and 300 K. On the upper isothermal transformation, the initial volume is 1 liter and the final...
  18. N

    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 Relevant equations N/AThe attempt at a solution Based on the diagram in the link I provided, I know that...
  19. E

    Does the temperature return to its initial value in an adiabatic cycle?

    In an adiabatic compression/expansion cycle of an ideal gas, does the temperature return to its initial value after the cycle has completed? Or does it increase as the cycles continue?
  20. R

    Finding Temperature at stage four, Refrigeration Cycle

    Dear all, This is for a theoretical system, which is trying to represent an 'actual' vapour compression cycle. I have the pressure, temperature, enthalpy and entropy at stage four of a single stage cycle. Stage four is the stage where refrigerant leaves expansion valve and enters...
  21. L

    Time Period of Limit Cycle numerically

    Homework Statement Consider the system of equations : x' = x-y-x^3 and y'=x+y-y^3 a) Draw a phase plot ( Done numericlly program listed here in matlab) b) Prove analytically that at-least one stable cycle exists ( Used Poincare Bendixon theorem to prove done) c) Compute the period of...
  22. T

    Question regarding rankine cycle

    On what factors does the pressure in condenser of a rankine cycle depend? The lesser the pressure in the condenser, the more expansion work will be done by the steam turbine. And depending on the pressure in the condenser, the temperature of the steam entering the condenser will depend...
  23. T

    Randomness and the life cycle of events of our Universe

    This is a very important question for me which has bothered me greatly. I started talking about it in the Smolin cosmic natural selection thread. What I would like to know is, if the Universe started over a very large number of times (n) from t=0, the start of the big bang, In how many of these...
  24. S

    Cno cycle dense plasma focus fusion

    hello, new to site. This is my first post. I just was wondering what any ones thoughts were on using the carbon, nitrogen, oxygen cycle in a dense plasma focus device to produce aneutronic fusion power.
  25. D

    Stages of life cycle of mammals

    Dear experts, please help me with this debate between my buddy and I. I'm on the side that most mammals, like cats, dogs, humans and monkeys have 2 stage life cycle. Young --> adult and back. My buddy says it should be 3 stage egg--> young--> adult and back. We are both rather weak on...
  26. S

    Open loop rankine cycle with no condenser

    Hello, I'm working on a small scale parabolic trough concentrator project to generate electricity. This electricity is used for pumping water for irrigation,and I want to use an open loop Rankine cycle with no condenser(if it is applicable),to reduce cost,with the steam exhausting directly...
  27. M

    Costs of some components of combined cycle power plants

    hello all I want to find costs of some components of a combined cycle power plants.like turbine.generator and ... how can I find them?
  28. M

    What are the costs associated with a combined cycle power plant?

    hello all I have a project about a combined cycle power plant costs from first to the end of the project. I just need the prices of componets of it. I need a guide to find them.
  29. E

    Ultra high stretch cycle elastics?

    Hi all. I'm trying to find a durable elastic material for a project of mine but I can't seem to find the needed information. Basicly what I need is a elastic/rubber band that can withstand at least 100 000 (or preferably over 1 million) stretch cycles without its resting length increasing more...
  30. R

    Finding the times when one cycle occurs for FM wave

    Hello everyone, I'm trying to find the times when one cycle occurs for a FM wave. For instance, given y(t) = sin(2∏f_{c}*t_{1} + sin(2∏f_{m}*t_{1})) at an arbitrary time t_{1}, I wish to find the time t_{2} such that (f_{c}* t_{2} + sin(2∏f_{m}* t_{2}) – (f_{c}*t_{1} +...
  31. J

    Find Area Enclosed by Thermodynamic Cycle

    Homework Statement The question is pretty much explained in the picture. The area ABCD is enclosed, i need to find that area. The equation for AB is P=0.8+8.6e^(-0.3V) and the equation for CD is P=1.2+9.6e^-(0.1V) What I did was find the area enclosed by the rectangular shape (C-B)*9. From...
  32. S

    Open loop rankine cycle with no condenser

    Hello, I'm working on a small scale parabolic trough concentrator project to generate electricity. This electricity is used for pumping water for irrigation,and I want to use an open loop Rankine cycle with no condenser(if it is applicable),to reduce cost,with the steam exhausting directly...
  33. T

    Heat (Energy) distribution during day-night cycle

    Hello everyone, This is my first post on PhysicsForums (although not my first encounter) which I would like to start with asking a question. How does heat from the sun get distributed on Earth so that we have temperature variations between day and night? In other words, if an...
  34. L

    Energy generated by proton-proton cycle

    [b] My attempt [b] Q Reaction 1: Q1 = 2(1.007825) - (2.014102 + 0.000549) = 9.99E-4 u Q Reaction 2: Q2 = 1.007825 + 2.014102 - 4.002603 = -0.980676 u Q Reaction 3: Q3 = 3.016030 - (4.002603 + 2(1.007825)) = 0.013807 u --------- 2(Q1) + 2(Q2) + Q3 = -1.945547 u (-1.945547...
  35. X

    How Is the Efficiency of the Diesel Cycle Derived Using Compression Ratios?

    Homework Statement Derive a formula for the efficiency of the Diesel cycle, in terms of the compression ratio V1/V2 Homework Equations e=\frac{W}{Q_{h}} w= ∫pdV The Attempt at a Solution Now I know I should have used e=1-\frac{Q_{c}}{Q_{h}} to get it but he said it is...
  36. B

    Carnot Cycle Graphs: Understand Work and Temperature

    Hello, In the Volume vs. pressure graph I understand the area under the curve is work. However, I have a hard time reconciling this graph with a pressure vs. temperature or a temperature vs. volume graph. What does the area inside the box represent? Work? Like which parts on the P vs. V graph...
  37. E

    Fractional energy loss per cycle in a heavy damped oscillator

    http://www1.gantep.edu.tr/~physics/media/kunena/attachments/382/chapter2.pdf On page 9 and 10 of the above PDF the method for deriving the fractional energy loss per cycle in a lightly damped oscillator is described. I understand and follow this derivation. What would the derivation...
  38. S

    How does the pressure ratio affect the efficiency of a gas turbine?

    Hello, In http://www.aerostudents.com/files/gasTurbines/gasTurbinesFullVersion.pdf it is shown that the efficiency of a gas turbine is determined by the Brayton cycle and it depends on the pressure ratio ε. ε is the compression ratio before fossil fuel burning invests further energy into...
  39. J

    Comp. Physics: Finite time Carnot cycle

    Hi, For my Bachelor's thesis I've been working on a finite time Carnot cycle. I've finished my numerical analysis using the differential equations governing the time evolution. My next step should be a simulation. First I should stick to a 1 dimensional system. This system consists of a...
  40. A

    Calculating Work in Isothermal Processes of Carnot Cycle

    Hallo, I read about thr Carnot-Cycle and got a problem. A->B: isothermal B->C: adiabatic C->D: isothermal D->A: adiabatic I want to understand how to calculate the work done in the isothermal processes. I have read: W_{AB}= T_{H}Nk\ln{(\frac{V_{A}}{V_{\text{B}}})}\\...
  41. H

    MHB Scaling of throughput over renewal cycle

    the system alternates between ON and OFF states. Whenever the system is in ON state, packet transmission mechanism happens. whenever OFF state comes in between the system is frozen and resumes from the point where it left at the end of ON state. Now the packet transmissions are renewals...
  42. D

    Irreversible Carnot Vapor Power Cycle

    Two questions: 1. What does the T-s diagram look like for the irreversible cycle? 2. Do the isentropic efficiency equations that you apply to turbines and compressors (especially in the Rankine cycle) apply to the theoretical "turbines" and "pumps" in the Carnot cycle?
  43. A

    Generating a pulse of high frequency and very small duty cycle

    Hey, I wanted to generate a pulse of ON time of about 10-50 ns and time period of around 1us. Don't know how to get such precision ? Thanks
  44. G

    Is the Straight Line in a Carnot Cycle Graph Isobaric or Isothermal?

    Homework Statement Consider the gas do the themodynamics process. If the process graph is one line with constant gradient, Homework Equations What process was happened? How to calculate its amount of heat which absorbed or liberated? The Attempt at a Solution I really need your...
  45. Z

    Vapor-compression refrigeration cycle

    Homework Statement A conventional vapor-compression refrigeration cycle uses ammonia as the refrigerant. Evaporation and condensation are at -4°C and 34°C respectively and the refrigeration rate is 5kW. The compressor efficiency is 0.75. Assume that the throttle process is isenthalpic...
  46. D

    Thorium Fuel Cycle Reaction Initiation

    In an liquid fluoride thorium reactor, how is the reaction started? My assumption would be a piece of fissile material would be somehow inserted into the fuel to introduce neutrons to the solution, but I have not found any information to show if this is how the reaction is started. If this is...
  47. A

    Maximum thermal cycle range to avoid onset of plasticity

    Homework Statement The linear thermal expansion coefficient of aluminum is 22.2x10-6 m/m K and that of alumina is 5.4x10-6 m/m K. If the criterion for onset of dislocation plasticity is related to thermal mismatch exceeding Burgers vector for aluminum, which is 2.8x10-10 m. What is the...
  48. G

    About nuclear fuel cycle simulation software

    Hello ,everybody I plan to develop a nuclear fuel cycle simulation software . Is there any body interesting it. I think this is a very complex project. :)
  49. A

    Question on Vapor Compression Cycle.

    For convenience, let's assume the following process to be ideal. Process 1-2 Isenthalpic compression Process 2-3 Condensation Process 3-4 Throttling Process 4-1 Evaporation The refrigerant is dry-saturated at the end of compression. Here's what I don't understand: During process 2-3, if we...
  50. 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'...
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