Toward Sensor to Reproduce Human Sense - The Electronic Nose Artificial Olfaction Technology - page 129

olfactory and gustatory receptor cells. After about 10 days, taste receptor cells die
and are substitute by cells that distinguish from a sort of stem cell in the taste bud.
Unexpected is the story of olfactory sensory cells. These are not epithelial cells as
are taste cells, but neurons, which until recently were not known to be generated in
adults. The olfactory sensory neurons are not only replaced every 60 days or so,
but each must also grow an axon to the correct place in the brain. Researchers are
investigating how taste perception and odor recognition are maintained in the face
of this turnover and new axon growth.
5.8 Signal Analysis Techniques
Human body is made up of many systems i.e., nervous system, olfactory system,
cardiovascular system. Each system is made up of subsystem which sum up many
physiological processes. Biomedical signal analysis is the process to deal with the
signal produced by these physiological processes. These signals could be electri-
cal, chemical or acoustic in origin and an analysis of these signals are often useful
in explaining or identifying conditions of the human body. These signals are in
their rawest forms do not provide much information and therefore, inspiration
behind biological signal analysis is to extract the relevant information. This
analysis has become more important to provide cost effective point of care diag-
nosis and fast treatments.
The analysis of electrical signals is a basic problem as the essential parameters
of significance are frequently changed into electrical signals by means of trans-
ducers. A signal is basically the record of a process that occurs in relation to an
independent variable. This independent variable can be any of a number of things,
but in most cases it is time, in which case the signal is actually called a ''time-
series''. Bio-signal contains a Physical, chemical, mechanical, thermal, electrical
and magnetic quantities that provide information of health condition in physiology
and psychophysiology. Transduction is a procedure by which the quantity that
characterizes the property or state of an object was sensed or transduces and
conditioning analogically and digitally is a procedure of obtaining wanted infor-
mation or signal components from the above object quantity.
Signal and information processing/analysis technology plays an essential role in
current research. Recent data acquisition equipments provide a huge amount of
raw data but the valuable information is embedded within high energy noise and
irrelevant surroundings activity. Therefore, advanced signal processing/analysis
methods are needed to process/analyze that information before using it by the
clinicians for diagnosis or therapy.
Many instruments are available for the analysis of electrical signals in the time,
frequency and model domains. Any signal transducing from a biological or
medical source can be called a bio-signal. The signal source could be at the
molecular level, cell level, or a systemic or organ level.