W	Width of the spark image
H	Height and width of the spark image
qw	Heat flux of spark
q 0	Maximum heat flux q0 of spark
Rpc	Equivalent heat input radius
Fc	Fraction of total EDM spark power
V	Discharge voltage (V)
I	Discharge current (A)
S	Spark area (units)
Sup	Spark area above the workpiece (units)
Sdown	Spark area below the workpiece (units)
Ssum	Total area values of spark images (units)
E	Spark energy (units)
Eup	Spark energy above the workpiece (units)
Edown	Spark energy below the workpiece (units)
Esum	Total energy values (units)
ESR	Spark energy density (-)
SDk	Spark area distribution (units)
EDk	Spark energy distribution (units)
mpq	Classical geometric moments of an image
Ixy	Pixel value of spark image
SR	Surface roughness (µm)
SV	Spark gap voltage (V)
Ton	Pulse on time (µs)
Toff	Pulse off time (µs)
WF	Wire-speed feed (m/s)
MRR	Material removal rate (mm/s)
TWR	Tool electrode wear rate (-)
SR	Surface roughness (µm)
tanh	Hyperbolic tangent activation function
Conv	Convolutional layer
Maxpl	Max pooling layer
ReLU	ReLU active layer
BN	Batch normalization layer
WEDM	Wire electrical discharge machining
EDM	Electro/Electrical discharge machining
WEDT	Wire electrical discharge turning
CNN	Convolution neural network
RNN	Recurrent neural network
GRU	Gated recurrent unit
LSTM	Long short-term memory
DTW	Dynamic time warping
FEM	Finite element modeling
WEDT	Wire electrical discharge turning
GRP	Gaussian process regression
MOGA	Multi-objective genetic algorithm
ANN	Artificial neural network
ANFIS	Adaptive neuro-fuzzy inference system
ARAS	Additive ratio assessment
AHP	Analytical hierarchy process
BPNN	Neural network with back propagation algorithm
GA	Genetic algorithm
MSE	Mean-squared error
LWPA	Strategy of the leader
USV	Ultrasonic vibration
MF	Magnetic field
WMA	Wavelet moment analysis
HMA	Hu moment analysis
FDA	Fractal dimension analysis
GC	Local geometric characteristics
GGC	Global geometric characteristics
SVM	Support vector machine
ANOVA	Analysis of variance
NI	National Instruments