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. Saladsamurai

    I need some clarification Thermo Cycle

    I need some clarification! Thermo Cycle Homework Statement One kg of Refrigerant 22, initially at p1=.9MPa, u1=232.92 kJ/kG, is contained within a rigid closed tank. The tank is fitted with a paddle wheel that transfers energy to the refrigerant at a constant rate 0.1kW. Heat transfer from...
  2. Saladsamurai

    Thermodynamic Cycles: Understanding Energy Balance and Work-Energy Relations

    Homework Statement I have filled in a couple of spots as seen below, but I am a little confused as to how to proceed. If I get a good hint on one, I am sure the rest will follow. I think I am overlooking something obvious here. I know that in a cyclic process, all E (internal)...
  3. J

    Efficiency of an imaginary ideal-gas engine cycle

    Homework Statement The figure represents a simplified PV diagram of the Joule ideal-gas cycle. All processes are quasi-static, and C_P is constant. Prove that the thermal efficiency of an engine performing this cycle is \eta = 1 - \gamma \frac{\frac{V_{1}}{V_{2}} - 1}{\frac{P_{3}}{P_{2}}...
  4. J

    Efficiency of an engine performing the Joule ideal-gas cycle.

    Homework Statement The figure represents a simplified PV diagram of the Joule ideal-gas cycle. All processes are quasi-static, and C_P is constant. Prove that the thermal efficiency of an engine performing this cycle is 1 - \left(\frac{P_1}{P_2}\right)^\frac{\gamma - 1}{\gamma}...
  5. G

    How Is the Maximum Temperature of an Otto Cycle Engine Calculated?

    Homework Statement Gasoline engines operate approximately on the Otto cycle, consisting of two adiabatic and two constant-volume segments. The Otto cycle for a particular engine is shown in figure below. see atchmt 1. Find the maximum temperature in terms of the minimum temperature T_min...
  6. I

    Multipage Posters on Cellular Respiration, Photosynthesis (Calvin Cycle) etc

    Since I'm such a geeky person (trust me, my computer desktop background are digits of the pi), I'm looking for multipage posters (several A4 sheets of paper) in which I can just print out, tape them, and stick them on my wall. As said in the thread title I am looking for posters for the...
  7. T

    Existence of Singer Cycle in GL(n,q)

    Assume GL(n,q) is the general linear group of nxn matrices with entries in the finite field with q elements. Define a Singer Cycle to be an element of GL(n,q) of order (q^n)-1. How can we show that such an element always exists? That is, for all n and q. Thanx in advance.
  8. A

    Work and Heat Flow of a Heat Engine Cycle

    Homework Statement A heat engine follows the cycle shown in the figure. a) How much net work is done by the engine in one cycle? b) what is the heat flow into the engine per cycle? Diagram: http://farm4.static.flickr.com/3050/2703330973_26acb35c27.jpg?v=0 Homework Equations W =...
  9. B

    If we could see multiple octaves of light, would we perceive a cycle of colors?

    Similar to the cycle of notes we can hear? I read a similar question on another site about how we perceive red and violet as similar in nature even though they are far apart on the spectrum. I noticed that the frequency of violet light is almost double that of red light. Similarly, as you...
  10. B

    What Determines Earth's Yearly Cycle?

    1) the Earth moves around the sun. What is the force causing this movement around the sun? I know that there is a gravitational force pulling it inward, but what force keeps it from falling toward the sun? 2) The Earth is constantly spinning. This causes the day/night that we see. What is the...
  11. T

    Vapor Comression Refrigeration cycle

    I am doing a project for my thermodynamics class and we have to choose a compressor for a a vapor compression refrigeration cycle that has a heat transfer rate of 1500 btu/h and must maintain 0F in the freezer when the room temp is 90F. I have went through some calculations to find the mass flow...
  12. S

    Ideal Gas Carnot Cycle: Temperature and Entropy Analysis

    Homework Statement an ideal gas operates in a carnot cycle so that it produces a net positive work of 400 joules per cycle. the maximum temperature during the cycle is 300 deg celsius and the heat lost to a low temperature bath is 600 joules per cycle. a) what must be the temperature of the...
  13. I

    How do I calculate lines of constant pressure in a Brayton cycle diagram?

    Hey guys (and girls?) I'm new here, just registered, because I have a problem that my textbooks or google can't help me with: I am making "Brayton cycle diagrams" for a study in jet engine efficiency. It's basically a Temperature - Entropy diagram for those of you who are unfamiliar with...
  14. D

    Path of shear stress over one load cycle

    Homework Statement normal tension [MPa], shear tension [MPa], equivalent tension [MPa], deformation [%], number of cycles until failure all this are given for a lot of specimen of the same material Homework Equations \sigma_\theta, \tau_\theta The Attempt at a Solution Find...
  15. I

    Charging a deep cycle battery from cigarette lighter socket

    hi, I'd just like some advice on how best to charge a 70 amp hour deep cycle battery from a cigarette lighter socket. I use the battery to run my 35 litre waeco fridge when I'm camping for a couple of days, but would then like to charge the battery while travelling. I'm guessing a flat 70AHr...
  16. A

    Work and Heat in Gas Cycle (formatted: may load slowly)

    Problem: One (1.00) mole of an ideal diatomic gas (with = 1.40) initially at 20.6°C and 1.00 atm pressure is taken around the following cycle: Path (1): an isochoric increase in pressure until the temperature of the gas is 159°C and the pressure is P; Path (2): an adiabatic expansion until...
  17. A

    Refrigeration Cycle temperatures

    Please look at the picture on this link of a refrigeration cycle: http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Dane_Lenaker/img/pics/frigcycle.gif Would the temperature at position 1 be the temperature leaving the evaporator or the temperature entering the compressor? or should they in...
  18. Zenparticle

    Motor Cycle from UK, help w/measurements

    Hello, My boyfriend is working on his dirt bike, it's a Husqvarna and he is having trouble converting liquid(I assume its gas/oil or something to that effect)to American standards. The problem is: 450cm^3=? in cc's? so, that's 450cm's to the third power equals what in liquid volume cc's...
  19. E

    Why the Carnot cycle is not used with real engines?

    I have a question on Why the Carnot cycle is not used with real engines? I need to refer to real cycles in my explanation.
  20. H

    Heat Engines and the Carnot Cycle

    [SOLVED] Heat Engines and the Carnot Cycle Homework Statement The operating temperatures for a Carnot engine are Tc and Th= Tc + 55K. The efficiency of the engine is 15%. How do i find Tc?
  21. M

    Understanding the FETCH-EXECUTE Overlap Cycle

    What does the FETCH EXECUTE OVERLAP instruction mean ?
  22. V

    Period and cycle of a function .is the same thing, no?

    [SOLVED] period and cycle of a function...is the same thing, no? it essentially is right? but can be further defined as a)cycle...-can start at any x point b)period...-the unit measure of the cycle correct?
  23. M

    Product Life Cycle: What Shortens It?

    Hey all, I am in the process of starting up a herb business. It is very small and I will only be selling to one or two local restaurants. Funnily enough I phoned them up and they gave me the all clear. My question is, even though it is not a factor in this case, why would a products life...
  24. S

    How Do Steam Temperature and Exhaust Temperature Affect Steam Engine Efficiency?

    Homework Statement Homework Equations You are designing a steam engine and you want to make it as efficient as possible in terms of the energy used to run it and the useful energy it can produce. What do you want to maximize and minimize in terms of the steam temperature and the...
  25. S

    Diesel Cycle Help: P,T @ Start & End Head Addition

    Homework Statement The pressure and temperature at the beginning of compression in an air-standard Diesel cycle are 95 kPa and 300K. At the end of the head addition process, the pressure is 7.2 MPa and 2150 K. Assume variable specific heats. I'm not going to list the parts because all...
  26. M

    Work by an ideal gas in a thermodynamic cycle

    1. Homework Statement Two moles of an ideal gas are carried around the thermodynamic cycle shown in Fig. 18-29. The cycle consists of (1) an isothermal expansion A to B at a temperature of 700 K, with the pressure at A given by pA = 9 atm; (2) an isobaric compression B to C at PC = 4 atm...
  27. M

    Volume of gas in a thermdynamic cycle

    1. Homework Statement A 1 mol sample of an ideal gas for which c'V = 3R/2 follows the closed thermodynamic cycle shown in Fig. 18-36. There are three legs in the cycle: an isothermal expansion, A B; an isobaric compression, B C; and a constant-volume increase in pressure, C A. The...
  28. M

    Volume of gas in a thermodynamic cycle.

    Homework Statement A 1 mol sample of an ideal gas for which c'V = 3R/2 follows the closed thermodynamic cycle shown in Fig. 18-36. There are three legs in the cycle: an isothermal expansion, A B; an isobaric compression, B C; and a constant-volume increase in pressure, C A. The...
  29. M

    Work by an ideal gas in a thermodynamic cycle

    Homework Statement Two moles of an ideal gas are carried around the thermodynamic cycle shown in Fig. 18-29. The cycle consists of (1) an isothermal expansion A to B at a temperature of 700 K, with the pressure at A given by pA = 9 atm; (2) an isobaric compression B to C at PC = 4 atm; and...
  30. C

    Complete cycle of a trig function.

    Hi, I have an assignment where I must graph various trig functions and the instructions say to graph each for a complete cycle. Does a complete cycle mean until the graph begins to repeat so for instance a complete cycle for a sin graph would be from the range 0 to 2 pi? Thanks for any help.
  31. B

    Find Thermal Efficiency & Mean Effective Pressure in Dual Cycle Engine

    ice as in internal combustion engine, sorry for confusion Homework Statement I'm given an engine operating on the dual cycle and asked to find the thermal efficiency and the mean effective pressure. the compression ratio is 18:1, the temperature at the start of the compression 300K and the...
  32. G

    Working fluid for a thermodynamic cycle.

    I am looking for a liquid with a high thermal expansion coefficient. This liquid should act as a working fluid in an thermodynamic cycle based on a system where the working fluid act in the same phase (liquid phase) throughout the cycle. So far I have found pentane as one of the most...
  33. R

    Calculate Theoratical Machining Cycle Time

    Please help me to calculate theoratical machining cycle time for the below mentioned operations: 1. Hobbing 2. Shaping 3. Shaving I need variious calculations involed in determining the theoratical cycle time. Please refer any website, if it can help me. Thanks, Rishi
  34. L

    Reversibility and Carnot cycle

    I have two short questions: 1) Is the Carnot cycle completely reversible? 2) \Delta S = 0 for a reversible process, right?
  35. S

    Find the time required to complete each cycle

    Homework Statement A particular engine has a power output of 6.00 kW and an efficiency of 26.0%. Assume the engine expels 6000 J of energy in each cycle. (a) Find the energy absorbed in each cycle. (b) Find the time required to complete each cycle. P=W/delta t e=W/Q...
  36. X

    Carnot Cycle, how ideal is it?

    Homework Statement We have stressed that the Carnot engine does not exist in real life: It is a purely theoretical device, useful for understanding the limitations of heat engines. Real engines never operate on the Carnot cycle; their efficiency is hence lower than that of the Carnot engine...
  37. L

    Glycolysis & Creb Cycle Biochemistry

    Can someone help me out?? 1. The synthesis of glucose from smaller precursors is called: a) gluconeogenesis. b) glycogenolysis. c) glucosynthesis. d) glycolysis. e) none of the above I think the answer is A. gluconeogenesis...because gluconeogenesis is from puruvate back to...
  38. F

    How to increase max frequency due to half cycle constraints

    I'm trying to design a synchronous logic that uses a negative edge flop to shift data out of a chip (as part of the IEEE1149.1 standard). The input to this negedge flop is muxed from a whole bunch of shift registers within the chip, and these registers are all on posedges. Ideally, if...
  39. L

    Maximum efficiency = Carnot cycle

    Is it possible to show that the maximum efficiency for a heat engine is given by \eta = 1 - \frac{T_c}{T_h} where T_c is the temperature of the cold sink and T_c is the temperature of the warm sink? In other words: How do I prove that a engine run by a Carnot cycle is the most efficient engine?
  40. T

    Formula for otto cycle ang carnot engine

    hi i just want to know the formula of the otto cycle for the folowwing parameter: compression ratio,cycle work,heat added,heat rejection,thermal efficiency and mean effective pressure. and also may i know the formula for getting the pressure (bar) and the volume(m3/kg) temperature(K) for...
  41. C

    Centripetal Acceleration of washer spin cycle

    Homework Statement On your first day at work for an appliance manufacturer, you are told to figure out what to do to the period of rotation during a washer spin cycle to triple the centripetal acceleration. You impress your boss by answering immediately. Express your answer in terms of T...
  42. B

    Carnot Cycle help - Engine temp reservoirs

    Hi, I need some help concerning the Carnot cycle [i've searched, but what i needed didn't come up]. I am trying to work out the efficiency of a 4 or 2 stroke motorcyle engine. [car engine, it doesn't matter really]. But I'm having some difficulty finding temperatures for the hot and cold...
  43. W

    Mechanical energy required each cycle to operate the refrigerator

    MODS close this thread down i figured out the answer myselfHomework Statement A refrigerator has a coefficient of performance of 2.16. Each cycle it absorbs an amount of heat equal to 3.435×104 J from the cold reservoir. i need to find a) the mechanical energy required each cycle to operate...
  44. S

    Calculating Net Work, Heat Transfers in a Thermodynamic Cycle

    Homework Statement A gas within a piston-cylinder assembly undergoes a thermodynamic cycle consisting of three processes: Process 1-2: Constant volume, V_1=0.028m^3, U_2-U_1=26.4kJ Process 2-3: Expansion with pV=constant, U_3=U_2 Process 3-1: Constant pressure, p_2=1.4 bar, W_{31}=-10.5kJ...
  45. B

    The order of a permutation cycle

    Homework Statement what is the order of k-cycle (a(1),a(2),...,a(k)) Homework Equations The Attempt at a Solution According to the theorem of the order of a permutation: the order of a permutation set written in disjoint cycle form is the least common multiple of the lengths...
  46. kach22i

    Magnesium Injection Cycle (MAGIC) engine

    MAGIC engine http://www.mitsubishi.com/mpac/e/monitor/back/0608/green.html The exciting thing about the MAGIC engine is that it introduces competition to the market, the first time since the demise of the steam and electric motor cars. Just watch oil prices drop like a brick striving...
  47. C

    Need help regarding finding out the max pressure in a isothermal cycle.

    A volume of 1.5 m3 of air initially at 1.31 bar and 293k undergoes three processes in order to complete a cycle: Process 1 to 2 Isothermal compression from state 1 through a volumetric compression ratio of Rv to state 2 2 to 3 Isobaric heating back to the original volume. 3 to 1...
  48. A

    Drip Disposal in Gas Power Cycle (Rankine Cycle): Help Needed!

    i need some link or help or maybe some comments on different methods of drip disposal in a gas power cycle(rankine cycle).:confused::confused:quite honestly , i was sleeping:zzz::zzz: in the class, so i didnt get anything:shy::shy:. geez i don't even know what drip disposal is?? can anyone...
  49. M

    Ideal Diesel Cycle Calculations

    Ideal Diesel Cycle Help?? Homework Statement A 5-liter 10 cylinder, 4 stroke engine to produce 550kw at 12000rpm. Compression ratio 18, cut-off ratio 2.5. Air enters with 280K and 170Kpa, after passing two-stage turbo charger and intercooler. Using variable specific heats. (a) find gas...
  50. J

    Proton affinity via. Born Haber cycle

    I'm baaaaack... Is this the correct way to procede [b]1. The problem statement, all variables and given/known d The Born Haber cycle for the process was given as follows: ........U ......NH4Cl(s) → NH4+ + Cl- ......↑......↓.....P(NH3) ......↑......NH3 + H+ + Cl-...
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