What is Cop: Definition and 43 Discussions

A community of practice (CoP) is a group of people who "share a concern or a passion for something they do and learn how to do it better as they interact regularly". The concept was first proposed by cognitive anthropologist Jean Lave and educational theorist Etienne Wenger in their 1991 book Situated Learning (Lave & Wenger 1991). Wenger then significantly expanded on the concept in his 1998 book Communities of Practice (Wenger 1998).
A CoP can evolve naturally because of the members' common interest in a particular domain or area, or it can be created deliberately with the goal of gaining knowledge related to a specific field. It is through the process of sharing information and experiences with the group that members learn from each other, and have an opportunity to develop personally and professionally (Lave & Wenger 1991).
CoPs can exist in physical settings, for example, a lunch room at work, a field setting, a factory floor, or elsewhere in the environment, but members of CoPs do not have to be co-located. They form a "virtual community of practice" (VCoP) (Dubé, Bourhis & Jacob 2005) when they collaborate online, such as within discussion boards, newsgroups, or the various chats on social media, such as #musochat centered on contemporary classical music performance (Sheridan 2015). A "mobile community of practice" (MCoP) (Kietzmann et al. 2013) is when members communicate with one another via mobile phones and participate in community work on the go.
Communities of practice are not new phenomena: this type of learning has existed for as long as people have been learning and sharing their experiences through storytelling. The idea is rooted in American pragmatism, especially C. S. Peirce's concept of the "community of inquiry" (Shields 2003), but also John Dewey's principle of learning through occupation (Wallace 2007).

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  1. S

    B Thermal physics, COP upper bound for heat driven heat pumps

    I made a presentation where I derived, or at least attempted to derive, the formulae for the upper bounds of the efficiency/cop (cop = coefficient of performance) for a heat engine, work driven heat pump, and a heat driven heat pump with 3 thermal reservoirs, hot, warm, and cold. There are many...
  2. KingMan

    Mastering Chiller COP: MCQ Answers and Tips

    Summary:: MCQ about COP of chiller The COP of a vapor compression chiller is characterized by its cooling capacity. At low cooling rates, the chiller COP is reduced by the effects of heat leaks to the environment. On the other hand, at high cooling rates, the chiller suffers from a) the high...
  3. D

    B Lorenz COP of a heat pump and the temperatures of the hot/cold reservoirs

    @Dale : “The COP of a heat pump and the efficiency of a heat engine both depend strongly on the temperatures of the hot and cold reservoirs. For this calculation you need to go back and check the sources for the temperatures corresponding to each of these numbers. You will find that the Stirling...
  4. 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.
  5. C

    Solve Heat Pump COP Equation with Q & T

    I have tried to solve this with these equations: COP=T(H)/( T(H)-T(L) ) and COP = Q(H)/ ( Q(H)-Q(L) ) But since I need both Q and T in the same equation, I can't find anything to solve it.
  6. S

    Refrigerant - mass flow, power, COP

    This is a past exam Q, I don't have the attached pressure enthalpy diagram. Q = 120kW Cp = Refrigerant enthalpy = I've looked this up, for ammonia enthalpy = 35.06 kJ / mol T2 = 5 degrees C = (5 deg C) (1100 kPa/300 kPa) = 18.33 deg C +273.15 K = 291.48 K T1 = 2 degrees C = (2 deg C)(1100...
  7. Screwed

    How to calculate a coefficient of performance (COP)

    Homework Statement Homework Equations [/B][/B] 3. The Attempt at a Solution Here's my solution attempt: NOTE: Evolution 2 to 3 is really an isothermic process, but in the diagram shows as an politropic process. 4. Further Questions But it isn't giving me logical values of COP...
  8. M

    When the COP of refrigerator is greater or less than 1?

    I still confuse about COP of refrigerator. When i read some journal, it is said that COP of VCRS can be greater than 1 (usually 2 - 4). But, why the COP other than VCRS usally lower than 1? like vortex tube, vapour absorption refrigeration system, etc. Actually, now i am doing a research about...
  9. L

    Does anybody know the sampling frequency of a cop radar?

    More specifically, does anybody know the sampling frequency of a mounted 360 degree cop radar? NOT a conical/directional hand-held radar gun.
  10. H

    Talked to my local cop about his sat phone comms

    Have always drooled over these awesome and mega priced babies until they started dissspearing. Cop says they are being replaced by sat phones which I thought were a nightmare to get a connection and crazy expensive. He would not discuss the performance. So awesome HF antenna versus sat phone...
  11. I

    Difference between the various COP formulae

    Homework Statement Homework Equations N/A The Attempt at a Solution My question is a simple one: how is the above equation for COPref different to the COPref equations I've already encountered (such as COPref = Qc/Win = (h1-h4)/(h2-h1). Is the above just a different form of these? Or is the...
  12. Rectifier

    How Long Does It Take for a Cop to Catch a Speeder?

    This problem was translated from Swedish, sorry for any grammatical errors present. 1. The problem A cop sets up a radar trap. A speeder passes the policeman and continues going at ##60km/h## even though the maximal allowed speed is ##50km/h##. The cop starts accelerating at ##5 m/s^2##...
  13. 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...
  14. R

    Speeder and Cop Meeting Time Calculation

    Homework Statement Problem: A police car traveling at 80km/h is passed by speeder traveling at 145km/h. 3 seconds after the speeder passes, the police car starts accelerating at 2.5m/s2. How much time passes before the police overtakes the speeder (moving at a constant speed)? Variables...
  15. A

    How Do Collisions Affect the Moment of Inertia and Angular Momentum of a Rod?

    I am trying to learn to calculate collisions on the center of percussion of a rod. Can you tell me how to find the moment of inertia? Suppose we have a rod of length 1m and mass M = 12 kg., we know that ##I = 12 * 1^2 / 3 = 4## , if a collision takes place at the CoP ( at 0.166666 m from the...
  16. C

    Why Does COP in Heat Pumps Depend on Time?

    Hi experts... I'm new to this forum and want to know that why does COP(Coefficient of Performance) in heat pumps depend on time?
  17. E

    Heat Pump Power and COP: How Does Temperature Affect Efficiency?

    So if we start with question a) to calculate P = Q/t we can use that Q=m*c*ΔT so for for the 10 liters of water in the hot reservoir we get P=10*4186*25.8/1616=668 W. However it says the answer for a) is 667 W. Any idea why the difference? For question b) we have Vf = Pout / Pin where Pout =...
  18. Q

    How to increase COP and SCP of the absorption chiller

    Dear all, I would to like to ask do anyone have any idea on how to increase the COP and SCP(Specific Cooling Power) of a silica gel absorption chiller? COP= Heat removed by evaporator/ Heat supplied to system( normally is the hot water supplied to the absorption bed) SCP= heat removed at...
  19. J

    I feel like the term fundamental fields is a cop out

    Whenever I ask someone what an electromagnetic field is exactly, they say that science does how questions, not why questions (which doesn't really make sense in this context, maybe i worded my question differently). We say that there are four fundamental forces that create the universe we live...
  20. T

    Heat Pump COP: Air-to-Water Explained

    The COP of a heat pump can be expressed as COP_{heating}=\frac{T_{hot}}{T_{hot}-{T_{cold}}} As higher is better, the value of this can be improved by reducing the temperature gap at which the system works. I'm just a little unsure about which temperatures are being talked about. The heat pump...
  21. T

    Heat pump COP theoretical maximum

    Hello everybody. I have trouble of proving the theoretical maximum of heat pump Coefficent of Performance. The thing I'm trying to calculate is for heat pump pumping heat from colder reservoir to the hotter reservoir: COP=Qh/W Qh - heat supplied to the hot reservoir(output) W - mechanical...
  22. C

    Speeding Driver & Cop Car Velocity/Time/Acceleration Q

    So I'm new here, and I apologize if I've posted in the wrong format/place/etc., but this is a makeup exam question, and I (think) I've finished it, but I want a second opinion on the correctness if you guys wouldn't mind. :smile: Homework Statement A speeding driver passes a hidden police...
  23. L

    Is the Heat Pump and Motor Setup Efficient?

    Not sure if I am doing this correct and do not have answer available... A heat pump takes on 30,000BTU/hr of heat and uses 5030 watts. However its COP as an air conditioner is 2.19. How efficient is the pump and motor setup? I am assuming the following: Qh=30000 BTU/hr=11.79 hp WKin=5030...
  24. Low-Q

    How Do You Calculate the Inverse COP of a Heat Exchanger?

    Hi, I wonder how you calculate the "inverse COP" of a heat exchanger. Say a heat exchanger has a COP 4 at 0 degrees C. Under that condition the heat exchanger consumes 1kW, and deliver 4kW heat. So if you now turn it off, and instead heat one side and cool the other side with external heat...
  25. C

    COP refrigerator vs COP Heat Pump

    Homework Statement I just want to know when do I use the formula for COP refrigerator vs COP Heat pump. If the heat is absorbing something then what formula do I use Homework Equations [b]3. The Attempt at a Solution [/b} Uh I just trying 2 figure out the concept so Idk how 2...
  26. S

    Calculating COP of a Heat Pump in an Experiment

    Homework Statement I am trying to work out the Cop of a heat pump in an experiment, I recorded the temperatures before and after the Condenser, but am unsure of how to calculate the work input to the condenser Homework Equations cop= heat gained at the condenser/ work input to the...
  27. P

    COP refrigerator/freezer problem

    Homework Statement Compare a refrigerator set at +2 oC and a freezer set at -18 oC, both of which are operating in the room with temperature of +20 oC. What is relative amount of electric energy that will need to be used in both cases to cool a cup of water (250 ml) from room temperature to +5...
  28. I

    Got caught at 150, cop put 110++ with the mnath HELPPPP

    I need to know what distance a crown vic police car covers from 0-110mph It was a CHP in san diego and I'm pretty sure they drive the crown vic? Help
  29. A

    News The Shooting Of J T Williams - Murder by Cop ?

    Did you guys hear about this ? Saw it on one of our news channels today. I generally am the first to support police and armed services, rule of law, etc, but this, IMO, is plain murder. The cop is a psycho - should never be allowed near a gun ever again.
  30. J

    Refrigerator COP to Efficiency

    Homework Statement The question is simply: A reversible refrigerator has a coefficient of performance equal to 13.8. What is its efficiency? Homework Equations COPrefrigerator = Tc/(Th - Tc) Efficiency = (Th - Tc) / Th The Attempt at a Solution I'm assuming I need to use these equations to...
  31. bearcharge

    COP in vapor compression refrigeration analysis

    Hi, has anybody worked with heat pumps? I'm recently confused about how the heat pump compressor operates. Does it have a fixed pressure or it actually adjust its pressure automatically to outdoor temperature variation? All my confusion originate from the following problem: Now we have a heat...
  32. R

    Can Outside Temperature Affect the COP of Air-Conditioning Systems?

    Hi All, I'm doing a study on effects of outside temperature on the energy efficiency of air-conditioning systems in computer server farms/data centers. It will be a simulated study so I cannot use the standard definition of COP; COP = heat removed / work At the same time I also want...
  33. A

    Calculate COP & VCC for Refrigerant - Urgent Help Needed

    COP of a Refrigerant...Urgent Please Help! How do you find the COP ( Coefficient of Performance ) of a Refrigerant if you know the basic details of the refrigerant such as: Critical tempertaure Critical Pressure w Cp Also I am trying to calculate the VCC as well!? Any advice would be...
  34. L

    Police Officer Catches Car After 1.72 Seconds

    Homework Statement A motorcycle officer hidden at an intersection observes a car driven by an oblivious driver who ignores a stop sign and continues through the intersection at constant speed. The police officer takes off in pursuit 1.72 s after the car has passed the stop sign. She...
  35. N

    How Far Does the Trooper Travel to Catch the Speeder?

    Homework Statement A state trooper sets up a radar trap. A speeder passes the trooper and continues going at a constant speed of 40 m/s. The instant the speeder passes the trooper, the trooper accelerates at 5.0 m/s/s for 10 seconds and then continues at a constant speed. How far will the...
  36. P

    Why do they call a police officer a cop?

    Hi all, Why do they call a police officer a cop? (My first language is not English).
  37. Jeebus

    Cop car and opposing directions

    This is not a homework problem, I just want to know if this is possible. The cop is traveling in the opposite direction of me. Let's say I'm going 60mph and am speeding. He turns around, catches up to me, and clocks me going 15mph over the speed limit. Is this even possible? I found this...
  38. S

    Calculating COP of a Refrigerator

    Hi, I think I have confused myself over the COP of a refrigerator. I have refrigeration system and a certain set of values which enable me to plot a P-s diagram. The refrigerant is R-12. I also have another set of 4 results for varying evaporator pressures, and I have drawn all these...
  39. wolram

    Aircraft Crash at London Airport: Ice in Fuel or Cop Out?

    Heard on the radio that the aircraft that crash landed at London airport crashed because of ice in the fuel (or that is the best guess) surly this is a cop out.
  40. G

    Heat Pumps & COP: How Do They Work?

    I was reading on the Clausius statement and heat pumps. Apparently, the COP (coefficient of performance) for heat pumps can be greater than unity (1), and it usually is for several systems (depending on the conditions). So the energy transfer due to work done on the system results in a greater...
  41. W

    Help Needed: Calculating Acceleration over 185 Meters

    Hi, I'm after some help because my intelligence doesn't stretch as far as you guys! I am being taken to court for speeding, the police officer has stated in her evidence that she saw me traveling at 80 mph, that at that time she was traveling at 70 mph. She then states that both she and I were...
  42. J

    Calculating COP of Refrigerator: Solve with W=P(delta)t

    A vessel containing 8.43 kg of water at 21.1C is put into a refrigerator. The 0.1655 hp motor runs for 9 min to cool the liquid to the refrigerator's low temperature 4C. What is the COP of the refrigerator? W=P(delta)t = 123.463Wx540s = 66670.02 J COP = Qc/W Please Help. Thank...
  43. R

    Expansion of the Universe, cop this

    Hi! I am doing year eleven physics and love it, I am a teachers pet and all. Anyway, I have this theroy with my physics teacher, we came up with it together its really cool. So anyway, the expansion of the universe is accelerating, "defying gravity". Anyway, let's assume that it keeps...