Natural frequency: 
The frequency at which an underdamped second order
system subject to a forcing function of sine wave of
that frequency oscillates with amplitude greater
than the input. For a third order system there are
two natural frequency values while for a fourth
order system there are three. 
Network: 
(1) Any system of connected computers and
peripherals. (2) In an electrical or hydraulic
circuit, a combination of circuit elements. (3) A
representation of interconnected nodes or locations
with suppliers and customers and a set of
connections such as a road or the flow of
information or materials. 
Networked organization: 
A
company organized in the form of a group of peers
rather than a hierarchy or a system of departments. 
Numerical control (NC): 
A
technique of operating machine tools or similar
equipment in which motion is generated in response
to numerically ordered commands generated by CAD
systems, punched tapes or other communication media. 
Nyquist frequency 
Digital signal processing requires analog to digital
conversion of the input signal. The first step in
AtoD conversion is to sample the instantaneous
amplitude of the signal at specific times determined
by the sampling rate. If the signal contains changes
in information at frequencies more than half the
sampling rate, the signal will be sampled
incorrectly, and the samples will contain spurious
components know as Aliasing. The theoretical maximum
frequency that can be correctly sampled is half the
sampling rate and is called the Nyquist frequency.
To avoid aliasing, the sampling rate must be
significantly greater than twice the highest
frequency present in the signal. 
Nyquist plot: 
A
method used to assess system stability in which
a plot of the real part versus the imaginary
part of the frequency response function is made. For
a singledegreeoffreedom system, the Nyquist plot
is a circle. The Nyquist plot represents a frequency
response function by graphing the "real" part versus
the "imaginary" part. In the Nyquist plot, a
resonance shows up as a circle, but there is no
indication what its frequency is  the Nyquist plot
is like sighting down the frequency axis at the real
and imaginary parts of the function. 
Objectoriented database: 
A
database used to store objects that are the basis of
objectoriented computing in which data as well as
references to the procedures used to perform data
operations are combined. 
Objectoriented software: 
Results from modular programming in which each
object is a software package containing a collection
of related procedures and data that can be reused to
shorten application development time. Objects make
it easier to customize software systems to mirror
actual business processes without negatively
impacting the ability to migrate to later software
releases. 
Offset: 
A
property of a proportional control system in which
the final steady state value is "offset" from the
desired value. 
Onoff control: 
A
control system in which the final control element
has only two positions  fully open or fully closed.
It is also known as twoposition control. 
Output variable: 
(1) The end result of a process or system. (2)
Information leaving a device; data resulting from
processing. (3) An audio, electric or mechanical
signal delivered by an instrument. 
Overdamped system: 
A
system is said to be overdamped when it shows a
cyclic response and the oscillations decrease in
amplitude over time. 
Overshoot: 
In
a second order system, overshoot is the amount by
which the amplitude of the first cycle exceeds the
final steady state value. 
Pade approximation: 
To
linearize the delay time in a system, a Taylor
Series Expansion is performed on the exponential
function and only the first order terms are
retained. The technique permits the mathematical
analysis of such a system. 
Perfect load compensator: 
A
Feedforward controller system in which the
controlled variable produces a response exactly
opposite to that of the load change resulting in an
overall response that is zero. 
PID 
Acronym used to describe a control philosophy based
on related the error signal to the controller output
according to proportional, integral and derivative
relationships, each of which are additive. 
P
& ID 
Acronym used to describe diagrams that show process
and instrumentation layouts for a plant. 
Planning and scheduling systems: 
A
new generation of planning and scheduling tools
that, unlike MRP II, includes constraint models that
deal with both materials and capacity. These
technologies can be applied along a continuum
extending from shortterm, plantfloor scheduling to
strategic planning of supply chains. 
Phase lag: 
The time lag of a system expressed as an angular
definition to reflect the frequency of a forcing
function applied to the system. 
Process: 
A
natural phenomenon marked by gradual changes that
lead toward a particular result; a series of actions
or operations leading to an end; a continuous
operation or treatment in manufacturing; a
continuous and regular production executed in a
definite, uninterrupted manner. 
Process control: 
Automatic process monitoring and control by an
instrument or computer programmed to respond
appropriately to feedback. 
Process identification: 
A
method by which a mathematical model of a process is
identified and proven. Changes in the model can also
be IDed. 
Process load: 
Any variable not controlled directly by an existing
system but which has a role in determining system
output. A load change causes the system to attempt
to "regulate" system output. 
Process simulation: 
Use of a mathematical model by a computer program to
envision process design scenarios with realtime
visual and numerical feedback. Process optimization
and the ability to forecast potential problems are
the results. 
Process time constant: 
This term describes the distribution over time of a
system response. For a first order system, it
represents that time at which 63.2% of the total
response occurs. 
Productivity: 
A
measurement of output for a given amount of input(s).
In this document, labour productivity (valueadded
per employee) is used as the measure of
productivity. Increases in productivity are
considered critical to raising living standards.

Program: 
(1) A complete structured sequence of program
statements directing a computer to implement an
algorithm. (2) All software programming necessary to
solve a problem. 
Programmable logic controller (PLC):

A
system that controls large numbers of discrete
elements using very fast I/O scan times. Today, even
the smallest PLCs may be equipped with serial
communication and analog control capabilities, and
perform arithmetic functions. 
Proportional control: 
A
controller relationship or transformation in which
the controller output changes in proportion to the
error signal. The error is multiplied by a term
called the Controller Gain. 
Protocol: 
A
standard set of procedures to allow data to be
transferred among systems. 