There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Odors are sensations that occur when compounds (called odorants) stimulate receptors located in the olfactory epithelium at the roof of the nasal cavity. Odorants are hydrophobic, volatile compounds with a molecular weight of less than 300 daltons. Humans can recognize and distinguish up to 10 000 different substances on the basis of their odor quality. Odorant receptors (ORs) in the nasal cavity detect and discriminate among these thousands of diverse chemical ligands. An individual odorant can bind to multiple receptor types, and structurally different odorants can bind to a single receptor. Specific patterns of activation generate signals that allow us to discriminate between the vast number of distinct smells. The physicochemical attributes of odorants that induce specific odor sensations are not well understood. The genes that code for ORs have been cloned, and results from cloning studies indicate that ORs are members of a superfamily of hundreds of different G-protein-coupled receptors that possess seven transmembrane domains. A complete knowledge of structureodor relationships in olfaction awaits the three-dimensional analysis of this large family of ORs. Ultimately, simultaneous knowledge of the three-dimensional structure of ORs as well as odorants will allow us to develop a pattern recognition paradigm that can predict odor quality.

/pdf/handbook-of-machine-olfaction-4sqbr5ud63.pdf

Handbook of Machine Olfaction

The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily ...

/pdf/discrimination-of-complex-mixtures-by-a-colorimetric-sensor-54qaau0fnw.pdf

Discrimination of complex mixtures by a colorimetric sensor array: coffee aromas.

The influence of the thickness of SnO2 films deposited by a spray pyrolysis method on the operating characteristics of gas sensors is analyzed in this paper. It outlines how the thickness of metal oxides is an important parameter for gas sensors in determining the main operating parameters, such as the magnitude and rate of the sensor response and the optimal operating temperature. It is also shown that the optimal film thickness of a gas sensing layer depends on the required sensor parameters.

Thin film SnO2-based gas sensors: Film thickness influence

The effect of electrode geometry on the gas sensitivity of lead phthalocyanine (PbPc) thin films has been studied. The material PbPc has been chosen for this study because it has a high sensitivity (∼ppm) to oxidizing gases and may be suitable for use in a commercial solid-state chemical sensor. PbPc films of varying thickness (up to 1.5 μm) are vacuum sublimed across ultrathin (0.1 μm) coplanar pairs of gold electrodes lying on a sapphire substrate. The change of the electrical conductance of these devices in atmospheric nitrogen dioxide (NO 2 ) is measured, over a range of electrode separations for several film thicknesses and temperatures, by a computer-controlled automated system. The temperatures are chosen around 160 °C, at which a peak sensitivity of PbPc to nitrogen dioxide has been observed. The transient and steady-state responses of these devices are analysed in terms of diffusion-rate limited and reaction-rate limited models modified from previous work on thick porous metal oxide semiconducting films. Experimental results show that the response time of the device at temperatures from 130 to 190 °C is insensitive to both the electrode separation and film thickness. Furthermore, the response time, typically 120 s, decreases with increasing nitrogen dioxide concentration (1–9 ppm). These observations are consistent with the reaction-rate limited rather than the diffusion-rate limited model of mass transport in thin PbPc films. The activation energy of the PbPc films is determined from the temperature dependence of the device conductance, and found to be (0.15 ± 0.1) eV; as expected, it is independent of electrode separation and film thickness. The film conductance in air increases with increasing reciprocal electrode separation, but does not follow the linear relationship predicted from the model. Furthermore, the steady-state response (defined as the fractional change in conductance) of the PbPc films to atmospheric nitrogen dioxide shows a gradual but systematic increase with electrode separation, whereas the model predicts a constant value. The deviation of the experimental results from theory suggests the presence of considerable film inhomogeneity. The nature of this deviation is consistent with a film in which both the electrical conductivity and density of adsorption sites are considerably lower near the substrate surface than elsewhere. This observed heterogeneity in the gas sensitivity of thin sublimed PbPc films makes it more difficult to characterize their behaviour and may reduce their commercial viability as chemical sensors.

Effect of electrode geometry on gas sensitivity of lead phthalocyanine thin films

An electronic nose system for quality control of coffee is designed and tested. The system uses the Figaro TGS800 series sensors with an integrated heating element. The testing of the system is carried out using different types of coffee where it is proved successful in classifying the tested coffees and actual discrimination of ingredients into different classes[10]. Database based software is designed to interface the built hardware and to process the electronic nose signals before being classified.

/pdf/quality-control-of-coffee-using-an-electronic-nose-system-4fvznrpgg4.pdf

Quality Control of Coffee Using an Electronic Nose System

The influence of information and communication technology on the collective activities and interests of a broad range of people was discussed and analyzed. The important consequence of ICT called digital divide was mathematically modeled and the results analyzed. The closed loop feedback model proved the need for a society to be educationally, culturally, economically and politically ready to integrate and implement new technologies into its infrastructure.

/pdf/effect-of-information-and-communication-technologies-ict-on-18o8r01kw9.pdf

Effect of Information and Communication Technologies (ICT) on Non-Industrial Countries-Digital Divide Model

An electronic nose system for multi application purposes is designed and tested. Our
hardware design allows various types of sensors to be used for different applications. The system is
capable of being interfaced to both analog and digital instruments with special filtering devices that
isolate the system from surrounding signals. The design of the system is distinguished through the use
of two logic controlled micro fans that stabilize the system atmosphere, which surrounds the smelling
sensor and also serves an important function of removing any adsorbed odors on the surface of the
sensor. Comprehensive mathematics are used to design and describe each part of the presented system,
which allows methodical development and changes of the system parameters for future advances.
Testing of the hardware was carried out under computer control using various TGS sensors such as
TGS822, and TGS824 and TGS30. Database based software with neural network facility was designed
to interface the built hardware and to process the electronic nose signals before being classified.

/pdf/design-and-analysis-of-a-smart-multi-purpose-electronic-nose-2gstxaa1ii.pdf

Design and Analysis of a Smart Multi Purpose Electronic Nose System

A novel security technique for network and data communication applications that makes use of odors as password generators is developed and tested. The developed system employs odor keys derived from an original key together with the original key to allow access to systems and networks. The used key combinations are initially unknown to the user, and if detected while in the transmission process, there is no way of being able to be emulated. The uniqueness of the developed system is that it is not necessary for an odor key to be an exact replica of the original, but to be derived from the original. This is a chemical encryption and encoding as the right key will not be detected by anyone since it is a derived version and not a match. Genetic Algorithm is used to emulate the chemical derivation and to make up for any margin of odor detection error and sensors tolerances.

/pdf/a-novel-approach-to-system-security-using-derived-odor-keys-329tyujzo0.pdf

Mahmoud Zaki Iskandarani

Papers

Effect of electrode geometry on gas sensitivity of lead phthalocyanine thin films

Quality Control of Coffee Using an Electronic Nose System

Effect of Information and Communication Technologies (ICT) on Non-Industrial Countries-Digital Divide Model

Design and Analysis of a Smart Multi Purpose Electronic Nose System

A novel Approach to System Security using Derived Odor Keys with Weight Elimination Neural Algorithm (DOK-WENA)