IESL Part III flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

FAO Penman-Monteith ET₀

Reference evapotranspiration formula combining radiation, temperature, wind speed and humidity: ET₀ = [0.408Δ(Rn−G) + γ(900/(T+273))u₂(es−ea)] / [Δ + γ(1+0.34u₂)].

Crop coefficient Kc

Ratio of actual crop evapotranspiration to reference ET₀; varies across initial, mid-season and late-season stages and is used as ETc = Kc × ET₀.

Universal soil loss equation

A = R·K·LS·C·P predicts average annual soil loss from sheet and rill erosion; R is rainfall erosivity, K soil erodibility, LS slope factor, C cover, P support practice.

Drip emission uniformity

EU = 100 × (1 − 1.27 CV/√n), where CV is emitter coefficient of variation and n is emitters per plant; higher EU indicates more uniform water application.

Cooling coil sensible heat

Sensible heat load for air is Qs = 1.23 × airflow in L/s × temperature difference in K, giving watts; latent heat uses 3010 × L/s × humidity ratio difference.

Fan affinity laws

For a fan or pump, flow varies linearly with speed, pressure with speed squared, and shaft power with speed cubed; used to predict performance at changed speed.

Illuminance lumen method

Maintained illuminance E = (N·Φ·UF·MF)/A, where N is number of luminaires, Φ flux per luminaire, UF utilisation factor, MF maintenance factor, and A area.

Lift handling capacity

Percentage of building population served in five minutes: HC = (300 × P × 100)/T, where P is passengers per car and T round-trip time in seconds.

Terzaghi bearing capacity

Ultimate bearing capacity qu = cNc + qNq + 0.5γBNγ for a strip footing; allowable bearing pressure is qu divided by a factor of safety of about 2.5 to 3.

Reinforced concrete stress block

At ultimate limit state, concrete compression is idealised as a rectangular block of 0.36 fck over depth 0.42x, with steel force 0.87 fy As; used to compute Mu.

Hazen-Williams head loss

Friction head loss hf = 10.67·L·Q^1.852/(C^1.852·d^4.87) for water in pipes, with C the roughness coefficient, Q flow and d internal diameter.

Levelling height of instrument

HI = backsight reading + reduced level of benchmark; reduced level of a point = HI − foresight or intermediate sight reading, giving rise and fall.

Log mean temperature difference

ΔTlm = (ΔT1 − ΔT2)/ln(ΔT1/ΔT2) for heat exchanger ends; used in Q = U·A·ΔTlm with correction factor F for non-counter-current arrangements.

Fenske minimum stages

Nmin = ln[(xD/(1−xD))·((1−xB)/xB)]/ln α gives minimum theoretical stages at total reflux for constant relative volatility α in distillation.

CSTR design equation

For steady-state continuous stirred tank reactor, volume V = FA0·X/(−rA), where FA0 is feed molar flow, X conversion and −rA rate of reaction at outlet conditions.

Arrhenius equation

Rate constant k = A·exp(−Ea/RT), where A is pre-exponential factor, Ea activation energy, R gas constant and T absolute temperature; reaction rate rises with temperature.

Transformer EMF equation

Induced EMF per winding E = 4.44·f·N·Φm, where f is frequency, N turns and Φm peak flux; relates voltage to core flux and turns ratio.

Induction motor slip

Slip s = (Ns − Nr)/Ns, where Ns = 120f/P synchronous speed and Nr rotor speed; rotor frequency equals s·f and slip rises with load.

Surge impedance loading

Surge impedance Zc = √(L/C) and SIL = V²/Zc for a transmission line; at SIL the line reactive generation balances absorption and voltage stays flat.

Shannon capacity theorem

Channel capacity C = B·log₂(1 + SNR) bits per second for bandwidth B and signal-to-noise ratio; sets the maximum error-free data rate.

Carson's rule FM bandwidth

Approximate FM bandwidth BW ≈ 2(Δf + fm), where Δf is peak frequency deviation and fm highest modulating frequency; used for link and filter design.

Subnet usable hosts

For a subnet with h host bits, usable addresses = 2^h − 2, excluding network and broadcast addresses; a /24 prefix gives 254 usable IPv4 hosts.

Free-space path loss

Lfs = 32.45 + 20log10(fMHz) + 20log10(dkm) dB; subtracted in the link budget Pr = Pt + Gt + Gr − Lfs − Lmisc.

Cellular frequency reuse ratio

For cluster size N = i² + ij + j², co-channel reuse ratio Q = D/R = √(3N), where D is reuse distance and R cell radius; larger Q reduces interference.

TCP three-way handshake

Connection setup exchanges SYN, then SYN-ACK, then ACK, synchronising sequence numbers before data transfer; TCP also provides congestion control and reliable delivery.

Database ACID properties

Atomicity, Consistency, Isolation and Durability guarantee reliable transactions; third normal form additionally removes transitive dependencies from relational schemas.

Otto cycle efficiency

Air-standard efficiency η = 1 − 1/r^(γ−1), where r is compression ratio and γ specific heat ratio; efficiency rises with compression ratio and γ.

Diesel cycle efficiency

η = 1 − (1/r^(γ−1))·[(ρ^γ − 1)/(γ(ρ − 1))], with r compression ratio and ρ cut-off ratio; lower cut-off gives higher efficiency at fixed r.

Cylindrical conduction resistance

Heat flow through a pipe wall Q = 2πkLΔT/ln(r2/r1); thermal resistance is ln(r2/r1)/(2πkL), used to add insulation layers in series.

Taylor tool life equation

VT^n = C relates cutting speed V and tool life T; exponent n is about 0.1 for high-speed steel and 0.25 for carbide, C a constant for the tool-work pair.

Sommerfeld number

S = (r/c)²·(μN/P) for a journal bearing, where r radius, c clearance, μ viscosity, N rotational speed and P unit load; indicates lubrication regime.

Gear module and pitch

Module m = d/N relates pitch diameter d to tooth number N; circular pitch p = πm, and velocity ratio equals N2/N1 or d2/d1 for meshing gears.