IESL Part I flashcards

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

Field capacity

The water content a soil retains after excess water has drained away under gravity, typically one to three days after saturation. It sets the upper limit of readily available soil water for crops.

Permanent wilting point

The soil water content at which plants can no longer extract water and remain permanently wilted. The difference between field capacity and this point gives available water capacity.

Crop coefficient Kc

A dimensionless factor multiplying reference evapotranspiration to estimate a specific crop's water use. It changes with crop type and growth stage, peaking near full canopy cover.

Universal Soil Loss Equation

A = R × K × LS × C × P estimates average annual soil loss from water erosion, combining rainfall erosivity, soil erodibility, slope length and steepness, cover management and support practice.

Cation exchange capacity

The quantity of exchangeable cations a soil can hold, usually reported in cmol/kg. Higher values indicate greater nutrient retention and buffering against pH change.

Overall heat transfer coefficient

Symbol U, expressed in W/m²·K, combining conduction through construction layers and surface film resistances. Heat flow through an element equals U × area × temperature difference.

Utilization factor in lighting

The fraction of lamp luminous flux that reaches the working plane, accounting for room geometry, surface reflectances and luminaire distribution. Design illuminance equals flux × utilization × maintenance factor ÷ area.

Wet riser system

A vertical pipe network permanently charged with water and fitted with landing valves for firefighting. It is required where building height exceeds the reach of fire-service hose from ground level.

Five-minute handling capacity

The percentage of a building's population a lift group can transport in five minutes, derived from round-trip time, car capacity and expected stops. It is a standard lift design criterion.

Section modulus

The ratio I/y of second moment of area to distance from the neutral axis, giving bending stress as M/Z. For a rectangle of width b and depth d it equals bd²/6.

Balanced section in RC design

The reinforcement ratio at which concrete crushing and steel yielding occur simultaneously under bending. Higher ratios produce brittle compression failures; lower ratios give ductile tension failure.

Terzaghi bearing capacity

Ultimate bearing pressure for a shallow strip footing: qult = cNc + qNq + 0.5γBNγ, where c is cohesion, q surcharge, γ unit weight and B footing width.

Darcy's law

Seepage velocity through soil equals hydraulic conductivity times hydraulic gradient, v = k·i. Flow rate is obtained by multiplying velocity by the cross-sectional area normal to flow.

Log-mean temperature difference

The effective driving temperature for a heat exchanger, computed as (ΔT1 − ΔT2)/ln(ΔT1/ΔT2) from terminal differences. Counterflow gives the largest value for given terminal temperatures.

Relative volatility

The ratio of the vapour-liquid equilibrium ratios of two components, indicating ease of separation by distillation. Values near one mean many stages are needed; large values mean easy separation.

First-order reaction half-life

For a reaction with rate constant k, half-life equals ln2 divided by k. It is independent of initial concentration, which distinguishes first-order from higher-order kinetics.

Steady-state material balance

For a control volume at steady state, accumulation is zero, so total input plus generation equals total output plus consumption. Component balances are written for each chemical species.

Synchronous speed

The rotational speed of a rotating magnetic field in an AC machine, given by 120f/P rpm, where f is supply frequency and P the number of poles. Induction rotors run slightly slower.

Transformer EMF equation

The induced winding voltage is E = 4.44·f·N·Φm, where f is frequency, N turns and Φm peak core flux. It shows voltage per turn is set by frequency and flux.

Thevenin's theorem

Any linear two-terminal network can be replaced by an equivalent voltage source in series with a resistance. The source equals the open-circuit voltage and the resistance the input resistance with sources dead.

Shannon capacity theorem

Channel capacity in bits per second equals bandwidth times log2(1 + S/N), where S/N is the linear signal-to-noise power ratio. Capacity grows only logarithmically with power.

Nyquist sampling theorem

A band-limited signal must be sampled at more than twice its highest frequency to be reconstructed exactly. Sampling below that rate causes aliasing, where high frequencies appear as false low ones.

Usable hosts per subnet

For a subnet with h host bits, usable addresses equal 2^h − 2, because the all-zeros network address and all-ones broadcast address cannot be assigned to hosts.

OSI reference model

A seven-layer abstraction for network communication: physical, data link, network, transport, session, presentation and application. Each layer provides services to the layer above it.

Amdahl's law

Program speedup from parallelisation equals 1 divided by ((1 − p) + p/s), where p is the parallel fraction and s the speedup of that fraction. Serial portions cap achievable gain.

Carnot efficiency

The maximum possible efficiency of a heat engine between hot and cold reservoirs equals 1 − Tc/Th, with absolute temperatures. No real cycle between the same reservoirs can exceed it.

Reynolds number

A dimensionless ratio of inertial to viscous forces, Re = ρVD/μ. In pipes, flow is generally laminar below about 2000 and turbulent above about 4000.

Bernoulli's equation

For steady, incompressible, frictionless flow along a streamline, pressure head plus velocity head plus elevation head is constant. It is an energy statement per unit weight of fluid.

Otto cycle efficiency

For the ideal air-standard Otto cycle, efficiency equals 1 − 1/r^(γ−1), where r is compression ratio and γ the specific heat ratio. Higher compression ratio raises efficiency.

Critical path

The longest sequence of dependent activities through a project network, which sets the minimum project duration. Any delay on this path delays the whole project.

Newton-Raphson method

An iterative root-finding formula, x(n+1) = x(n) − f(xn)/f′(xn). It converges quadratically near a simple root but can fail if the derivative is near zero.

Cost variance in earned value

Cost variance equals earned value minus actual cost. A negative result means the work performed cost more than budgeted; a positive result indicates a saving.