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The human olfactory system remains one of the most challenging biological systems to replicate. Humans use it without thinking, where it can measure offer protection from harm and bring enjoyment in equal measure. It is the system’s real-time ability to detect and analyze complex odors that makes it difficult to replicate. The field of artificial olfaction has recruited and stimulated interdisciplinary research and commercial development for several applications that include malodor measurement, medical diagnostics, food and beverage quality, environment and security. Over the last century, innovative engineers and scientists have been focused on solving a range of problems associated with measurement and control of odor. The IEEE Sensors Journal has published Special Issues on olfaction in 2002 and 2012. Here we continue that coverage. In this article, we summarize early work in the 20th Century that served as the foundation upon which we have been building our odor-monitoring instrumental and measurement systems. We then examine the current state of the art that has been achieved over the last two decades as we have transitioned into the 21st Century. Much has been accomplished, but great progress is needed in sensor technology, system design, product manufacture and performance standards. In the final section, we predict levels of performance and ubiquitous applications that will be realized during in the mid to late 21st Century. [ABSTRACT FROM AUTHOR]

Signal and data processing are essential elements in electronic noses as well as in most chemical sensing instruments. The multivariate responses obtained by chemical sensor arrays require signal and data processing to carry out the fundamental tasks of odor identification (classification), concentration estimation (regression), and grouping of similar odors (clustering). In the last decade, important advances have shown that proper processing can improve the robustness of the instruments against diverse perturbations, namely, environmental variables, background changes, drift, etc. This article reviews the advances made in recent years in signal and data processing for machine olfaction and chemical sensing. [ABSTRACT FROM PUBLISHER]

An analysis of accuracy of time-constant spectrum extraction from thermal transients has been performed. Numerical calculations based on analytical models and finite element method simulations have been used in order to obtain the thermal transients. Simple geometries have been used such that analytical expressions for their time-constant spectrums are known. Results show that a large error in the time-constant spectrum is obtained for very small rms error (<1 mK) in the thermal transient. The estimation problem is ill-conditioned. Moreover, the differential structure function shows a low accuracy identifying stacked structures. The initial part of the differential structure function shows numerical oscillations and the final part has an asymptotic behavior to infinity that has been identified as an artifact related to errors in the time-constant spectrum estimation. Peak identification from the differential structure function heavily depends on an accurate determination of the time-constant spectrum. The limited spectral resolution and dynamic range of the differential structure function are a direct consequence of the time-constant spectrum imprecision. [ABSTRACT FROM AUTHOR]

The feasibility of a force-balance interface based on a second-order delta—sigma (ΔΣ) modulator for capacitive sensors has been analyzed in order to delimit the requirements to assure system stability for a given set of constraints related to the sensor-modulator system. A ΔΣ modulator based on a switched-capacitor architecture with floating MOSFET capacitors has been implemented using a 0.7-μm CMOS process. Nonlinear effects related to voltage dependence of the floating MOSFET capacitors have been avoided using a modulator architecture based on charge integrators. The behavior of the new proposed modulator has been measured experimentally and compared with an equivalent interface made with lineal capacitors. Similar results were obtained from both systems. In both circuits, the modulator resolution was better than 14 bits at a sample frequency of 250 kHz, and oversampling ratio of 256. [ABSTRACT FROM AUTHOR]

Whereas numerical modeling using finite-element methods (FEM) can provide transient temperature distribution in the component with enough accuracy, it is of the most importance the development of compact dynamic thermal models that can be used for electrothermal simulation. While in most cases single power sources are considered, here we focus on the simultaneous presence of multiple sources. The thermal model will be in the form of a thermal impedance matrix containing the thermal impedance transfer functions between two arbitrary ports. Each individual transfer function element Hij( s) is obtained from the analysis of the thermal temperature transient at node "i" after a power step at node "j." Different options for multiexponentiat transient analysis are detailed and compared. Among the options explored, small thermal models can be obtained by constrained nonlinear least squares (NLSQ) methods if the order is selected properly using validation signals. The methods are applied to the extraction of dynamic compact thermal models for a new ultrathin chip stack technology (UTCS). [ABSTRACT FROM AUTHOR]

Presents a thermal modeling for power management of a three-dimensional thinned dies stacking process. Description of the Ultra Thin Chip Stacking technology; Method for experimental characterization of packaging techniques; Global response of the expected thermal impedance for the stacked structure.

Presents a study which proposed a spectroscopic technique for the analysis of multiexponential signals. Theoretical noise analysis; Discrete time implementation and noise filtering; Alternative iterative deconvolution scheme; Conclusion.

Analyzes a nonlinear time scale transformation to reduce the total number of samples with minimum signal distortion for the analysis of multiexponential decays. Procedure; Heuristic method; Suboptimal method.

Presents information on a study that discussed the first-level ultrathin chip stacking structure and the thermomechanical stresses produced by the manufacturing process. Implications of the ultrathin chip stacking structure; Process simulation; Material models; Information on three-dimensional via structures.

Focuses on a study which examined the thermal behavior of complex packages as multichip modules by measuring the thermal impedance response preserving the convolution form. Methodology; Results and discussion; Conclusion.

Describes a nonlinear inverse dynamic model of gas sensing systems based on chemical sensor arrays. Components of the chemical sensor; Sensors and test equipment used; Results of inverse modelling.

Shows that the combination of a gas-sensor array together with self-organizing maps (SOMs) allow success in gas classification problems. Ability of the system to determine the gas present in an atmosphere with error rates lower than three percent; Investigation of a correction of the sensor's drift with an adaptive SOM; Details on low-cost tin oxide gas sensors.