DPEE flashcards

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

Ohm's law and power

V = I·R relates voltage, current, and resistance. Power dissipated is P = V·I = I²R = V²/R. For balanced three-phase loads, total real power is √3·V_L·I_L·cos φ.

Hooke's law

In the linear-elastic region, stress is proportional to strain: σ = E·ε, where E is Young's modulus. Beyond yield, the relationship is nonlinear and permanent deformation occurs.

Reynolds number

Re = ρvD/μ = vD/ν compares inertial to viscous forces. Pipe flow is typically laminar below about 2,300, transitional to 4,000, and turbulent above 4,000.

Bernoulli equation

For steady, incompressible, frictionless flow along a streamline: p/γ + v²/2g + z = constant. Real systems add a head-loss term for friction and fittings.

Thermal expansion stress

Free expansion gives ΔL = α·L·ΔT. If the member is fully restrained, the induced stress is σ = E·α·ΔT, independent of length.

Von Mises stress

A scalar equivalent stress for ductile materials under multiaxial loading. For plane stress, σ_vm = √(σx² − σxσy + σy² + 3τxy²); yielding is predicted when it reaches yield strength.

Euler buckling load

Critical load for a slender column: P_cr = π²EI/(K·L)². The effective-length factor K is 1.0 pinned-pinned, 0.5 fixed-fixed, 0.7 fixed-pinned, and 2.0 fixed-free.

Goodman fatigue criterion

Fatigue failure is predicted when σ_a/S_e + σ_m/S_ut = 1, where S_e is the endurance limit and S_ut the ultimate strength. Mean stress reduces the allowable alternating stress.

Tolerance stack-up methods

Worst-case stack-up sums all tolerances, guaranteeing assembly. Statistical (root-sum-square) stack-up uses √(Σt_i²), assuming independent, centered distributions, and yields tighter but probabilistic limits.

FMEA risk priority number

RPN = Severity × Occurrence × Detection, each scored on a 1–10 scale. Higher RPN indicates higher priority for corrective action; severity alone can override the ranking.

Net present value rule

NPV discounts all cash flows at the hurdle rate. Accept independent projects with NPV > 0. Among mutually exclusive alternatives, choose the one with the highest positive NPV.

Internal rate of return

IRR is the discount rate at which NPV equals zero. It can mislead when comparing projects of different scale or timing, so use incremental IRR or NPV for mutually exclusive choices.

Critical path float

Total float = LS − ES = LF − EF. Activities on the critical path have zero total float, and the longest path through the network sets the minimum project duration.

Earned value indices

CPI = EV/AC measures cost efficiency; SPI = EV/PV measures schedule efficiency. Values below 1.0 indicate overrun or slippage. EAC is often estimated as BAC/CPI.

Order of precedence for engineers

Licensed engineers hold public health, safety, and welfare paramount, followed by client and employer obligations, then the profession's integrity, then their own interests.

Conflict of interest

A situation where a secondary interest could improperly influence professional judgment. The engineer must disclose it in writing and, where required, withdraw from the decision.

Regulatory hierarchy

Statutes are enacted by legislatures; regulations are issued by agencies under statutory authority; standards and codes become enforceable when incorporated by reference into a regulation.

Hierarchy of controls

Ranked from most to least effective: elimination, substitution, engineering controls, administrative controls, and personal protective equipment. PPE is the last line of defense.

ALARP principle

Risk should be reduced as low as reasonably practicable. Further reduction is required until its cost is grossly disproportionate to the safety benefit gained.

Confined space oxygen limits

Atmospheric testing precedes entry. Oxygen below 19.5% is deficient and above 23.5% is enriched and a fire hazard. Entry requires continuous monitoring and an attendant.

Lockout/tagout purpose

Isolates and renders safe all hazardous energy sources - electrical, mechanical, pneumatic, hydraulic, thermal, and stored - before work, then verifies a zero-energy state.

PDCA cycle

Plan defines the problem and countermeasure, Do pilots it, Check measures results, and Act standardizes the change or adjusts. It underpins ISO management system improvement.

Process capability Cpk

Cpk = min[(USL − μ), (μ − LSL)]/(3σ). It accounts for centering; values below 1.0 mean the process produces nonconforming output. It is valid only for stable processes.

Control vs specification limits

Control limits (μ ± 3σ) come from the process's own variation and detect special causes. Specification limits come from the customer or design and define acceptability.

Pareto principle

Roughly 80% of effects arise from 20% of causes. A Pareto chart ranks causes by frequency or cost so improvement effort targets the vital few.

Tuckman team stages

Forming, storming, norming, performing, and adjourning. Conflict typically peaks during storming and subsides as roles, goals, and working norms are clarified.

RACI matrix roles

Responsible performs the work; Accountable owns the outcome and is assigned exactly one per task; Consulted provides input; Informed is kept updated.

Thomas-Kilmann conflict modes

Five modes based on assertiveness and cooperativeness: competing, collaborating, compromising, avoiding, and accommodating. Collaborating requires time and trust.

Digital twin definition

A virtual model synchronized with a physical asset through sensor data. It supports simulation, condition monitoring, predictive maintenance, and optimization across the asset lifecycle.

Nyquist sampling rule

To reconstruct a signal without aliasing, sample at more than twice its highest frequency component. Anti-aliasing filters are applied before sampling.

BIM maturity levels

Level 0 is paper; Level 1 uses 2D and 3D CAD; Level 2 uses federated discipline models with separate files; Level 3 uses an integrated shared model.

OT cybersecurity segmentation

Operational technology networks should be separated from IT by firewalls and zones, with least-privilege access, validated patching, and monitoring for anomalous control traffic.