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Measurement Devices (measurement + device)
Selected AbstractsRestoration of PSD from Chord Length Distribution Data using the Method of Projections onto Convex SetsPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 2 2005Jörg Worlitschek Abstract The interpretation of chord length distributions (CLDs) is essential in many fields and has been discussed by various authors. Here, the technique of the Focused Beam Reflectance Measurement (FBRM) is considered as on-line and in-situ measurement device of the CLD of particle dispersions and emulsions. Though useful in general, this measurement cannot be converted directly into a particle size distribution (PSD), unless the physics of the measurement method is described and accounted for. In this work we present a new tool to carry out such a conversion once the particle shape is known a priori and can be fixed, which is based on a two step procedure: (1) the computation of a matrix that converts the PSD of a population of particles with given shape into the corresponding CLD using a 3-dimensional geometric model; (2) the calculation of the PSD from the resulting linear matrix equation for the measured CLD. Here, the method of Projections onto Convex Sets (POCS) is applied to solve the PSD restoration problem, which is a mathematically ill-posed inverse problem. We study the effect of particle shape and matrix dimension on the ill-posed character of the inverse problem. A detailed error analysis of the CLD allows for a predictive description of a posteriori constraints in the POCS framework. We discuss the application of this method to the characterization of simulated test cases and experimentally obtained data. [source] Impact of pinna compression on the RF absorption in the heads of adult and juvenile cell phone usersBIOELECTROMAGNETICS, Issue 5 2010Andreas Christ Abstract The electromagnetic exposure of cell phone users depends on several parameters. One of the most dominant of these is the distance between the cell phone and the head tissue. The pinna can be regarded as a spacer between the top of the phone and the head tissue. The size of this spacer has not yet been systematically studied. The objective of this article is to investigate the variations of distance as a function of age of the exposed person, and the mechanical force on the pinna and how it affects the peak spatial specific absorption rate (psSAR). The distances were measured for adults and children (6,8 years of age) while applying a well-defined force on the pinna using a custom-developed measurement device. The average distances of the pinnae to the heads and their standard deviations showed no major differences between the two age groups: 10.5,±,2.0,mm for children (6,8 years) and 9.5,±,2.0,mm for adults. The pinnae of our anatomical high-resolution head models of one adult and two children were transformed according to the measurement results. The numerical exposure analysis showed that the reduced distance due to the pinna compression can increase the maximum 10,g psSAR by approximately 2,dB for adults and children, if the exposure maximum is associated with the upper part of the phone. Bioelectromagnetics 31:406,412, 2010. © 2010 Wiley-Liss, Inc. [source] Respiratory Effect of Prolonged Electrical Weapon Application on Human VolunteersACADEMIC EMERGENCY MEDICINE, Issue 3 2007Jeffrey D. Ho MD Background: Conducted electrical weapons (CEWs) are used by law enforcement to subdue combative subjects. Occasionally, subjects will die after a CEW has been used on them. It is theorized that CEWs may contribute to these deaths by impairing respiration. Objectives: To examine the respiratory effects of CEWs. Methods: Human volunteers received a 15-second application of electrical current from a CEW while wearing a respiratory measurement device. Common respiratory parameters were collected before, during, and after exposure. Health histories and demographic information were also collected. Results: Fifty-two subjects were analyzed. Thirty-four underwent a 15-second continuous exposure, and 18 underwent three 5-second burst exposures. In the continuous application group, the baseline mean tidal volume of 1.1 L increased to 1.8 L during application, the baseline end-tidal CO2 level went from 40.5 mm Hg to 37.3 mm Hg after exposure, the baseline end-tidal oxygen level went from 118.7 mm Hg to 121.3 mm Hg after exposure, and the baseline respiratory rate went from 15.9 breaths/min to 16.4 breaths/min after exposure. In the 5-second burst group, the baseline mean tidal volume increased to 1.85 L during application, the baseline end-tidal CO2 level went from 40.9 mm Hg to 39.1 mm Hg after exposure, the baseline end-tidal oxygen level went from 123.1 mm Hg to 127.0 mm Hg after exposure, and the baseline respiratory rate went from 13.8 breaths/min to 14.6 breaths/min after exposure. Conclusions: Prolonged CEW application did not impair respiratory parameters in this population of volunteers. Further study is recommended to validate these findings in other populations. [source] Screening the Hanford tanks for trapped gasENVIRONMETRICS, Issue 5-6 2002Paul Whitney Abstract The Hanford Site is home to 177 large, underground nuclear waste storage tanks. This article describes a screening study carried out in the mid 1990s that used the tank waste level measurements to assess the tanks for potential flammable gas hazards. At the time of the study, 25 of the 177 tanks were on the flammable gas watch list. The use of this monitoring data provided additional insight, resulting in operational changes on the Hanford site. The waste level measurements used in this study were made primarily to monitor the tanks for leaks and intrusions. Four measurement devices are widely used in these tanks. Three of these measure the level of the waste surface. The remaining device measures from within a well embedded in the waste, thereby monitoring the liquid level even if the liquid level is below a dry waste crust. The data from each of the four measurement devices were utilized in this investigation. The analytic method used for this screening was to look for an inverse correlation between waste level measurements and ambient atmospheric pressure. If the waste level in a tank decreases with an increase in ambient atmospheric pressure, then the compressibility may be attributed to gas trapped within the waste. In this article, this methodology is not used to estimate the volume of gas trapped in the waste. Copyright © 2002 John Wiley & Sons, Ltd. [source] Meta-Analysis of Genome-Wide Scans Provides Evidence for Sex- and Site-Specific Regulation of Bone Mass,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2007John PA Ioannidis Abstract Several genome-wide scans have been performed to detect loci that regulate BMD, but these have yielded inconsistent results, with limited replication of linkage peaks in different studies. In an effort to improve statistical power for detection of these loci, we performed a meta-analysis of genome-wide scans in which spine or hip BMD were studied. Evidence was gained to suggest that several chromosomal loci regulate BMD in a site-specific and sex-specific manner. Introduction: BMD is a heritable trait and an important predictor of osteoporotic fracture risk. Several genome-wide scans have been performed in an attempt to detect loci that regulate BMD, but there has been limited replication of linkage peaks between studies. In an attempt to resolve these inconsistencies, we conducted a collaborative meta-analysis of genome-wide linkage scans in which femoral neck BMD (FN-BMD) or lumbar spine BMD (LS-BMD) had been studied. Materials and Methods: Data were accumulated from nine genome-wide scans involving 11,842 subjects. Data were analyzed separately for LS-BMD and FN-BMD and by sex. For each study, genomic bins of 30 cM were defined and ranked according to the maximum LOD score they contained. While various densitometers were used in different studies, the ranking approach that we used means that the results are not confounded by the fact that different measurement devices were used. Significance for high average rank and heterogeneity was obtained through Monte Carlo testing. Results: For LS-BMD, the quantitative trait locus (QTL) with greatest significance was on chromosome 1p13.3-q23.3 (p = 0.004), but this exhibited high heterogeneity and the effect was specific for women. Other significant LS-BMD QTLs were on chromosomes 12q24.31-qter, 3p25.3-p22.1, 11p12-q13.3, and 1q32-q42.3, including one on 18p11-q12.3 that had not been detected by individual studies. For FN-BMD, the strongest QTL was on chromosome 9q31.1-q33.3 (p = 0.002). Other significant QTLs were identified on chromosomes 17p12-q21.33, 14q13.1-q24.1, 9q21.32-q31.1, and 5q14.3-q23.2. There was no correlation in average ranks of bins between men and women and the loci that regulated BMD in men and women and at different sites were largely distinct. Conclusions: This large-scale meta-analysis provided evidence for replication of several QTLs identified in previous studies and also identified a QTL on chromosome 18p11-q12.3, which had not been detected by individual studies. However, despite the large sample size, none of the individual loci identified reached genome-wide significance. [source] Feedback control design for an anaerobic digestion processJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2002Jose Alvarez-Ramirez Abstract An approach for the design of linear feedback controllers for anaerobic digestion systems is presented. The effluent chemical oxigen demand (COD) concentration and the dilution rate are taken respectively as the regulated and the manipulated variables. The control design is based on simple step-response models of the process endowed with an input delay to account for dead-times induced by measurement devices. The resulting feedback controller has a traditional proportional-integral (PI) control structure, so it can be easily implemented with conventional control technologies. Since the concentration of volatile fatty acids can be easily and quickly measured as compared with COD concentration, it is used as a secondary measurement that is incorporated into the feedback loop scheme to enhance the robustness of the control scheme with respect of influent disturbances. The performance of the proposed control scheme is illustrated via numerical simulations and experimental work. © 2002 Society of Chemical Industry [source] Fast principal component analysis of large data sets based on information extractionJOURNAL OF CHEMOMETRICS, Issue 11 2002F. Vogt Abstract Principal component analysis (PCA) and principal component regression (PCR) are routinely used for calibration of measurement devices and for data evaluation. However, their use is hindered in some applications, e.g. hyperspectral imaging, by excessive data sets that imply unacceptable calculation time. This paper discusses a fast PCA achieved by a combination of data compression based on a wavelet transformation and a spectrum selection method prior to the PCA itself. The spectrum selection step can also be applied without previous data compression. The calculation speed increase is investigated based on original and compressed data sets, both simulated and measured. Two different data sets are used for assessment of the new approach. One set contains 65,536 synthetically generated spectra at four different noise levels with 256 measurement points each. Compared with the conventional PCA approach, these examples can be accelerated 20 times. Evaluation errors of the fast method were calculated and found to be comparable with those of the conventional approach. Four experimental spectra sets of similar size are also investigated. The novel method outperforms PCA in speed by factors of up to 12, depending on the data set. The principal components obtained by the novel algorithm show the same ability to model the measured spectra as the conventional time-consuming method. The acceleration factors also depend on the possible compression; in particular, if only a small compression is feasible, the acceleration lies purely with the novel spectrum selection step proposed in this paper. Copyright © 2002 John Wiley & Sons, Ltd. [source] Use of Shade Guides for Color Measurement in Tooth-Bleaching StudiesJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 2003WILLIAM D. BROWNING DDS ABSTRACT Several different methods are used to measure tooth color in bleaching studies. The ADA Acceptance Program Guidelines for Home Use Tooth Whitening Products specify the use of a value-oriented shade guide and/or electronic color measurement devices. Since people perceive color differently, shade guides are a subjective measure. Differences between raters and by the same rater are well documented in the dental literature. The purposes of this article will be to discuss the advantages and disadvantages using shade guides to measure color change related to tooth whitening, and to evaluate the correlation of data gathered from the use of shade guides to electronic color measurement devices. Using an order published by the manufacturer, both the TRUBYTE® Bioform and Vita Classical guides can be arranged by value. A study by O'Brien demonstrated however, that the order is flawed and the change in brightness from tab to tab varies greatly. Despite these disadvantages, a review of data from several clinical trials demonstrates that Vita Classical shade guide data is consistent with data gathered using electronic color measurements. Furthermore, the O'Brien data can be used to make both these guides better measurement systems. The ADA Certification program standards define the degree of overall color change that should be considered clinically important. This issue is as critical as the measurement system used. Reporting color changes that are neither detectable to the human eye nor considered by the public to be important offers the profession little usable information. Given that any standard for color change during bleaching must relate to the abilities of the human eye, it is the conclusion of the author that shade guides should remain a critical element of any bleaching study. CLINICAL SIGNIFICANCE Clinicians are frequently exposed to reports of bleaching agents that have been shown to result in a change of 6, 7, 8, etc., tabs. Without understanding the limitations of the shade guide used, reports of a specific shade tab change are of little use and may actually be misleading. [source] Biomarkers of ovulation, endometrial receptivity, fertilisation, implantation and early pregnancy progressionPAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 2006Kenneth L. Campbell Summary Increasing interest in early preconception and periconception exposures and human developmental outcomes has led to studies that monitor subjects from before conception to gestation, birth and childhood. Monitoring ovulation, endometrial receptivity, fertilisation, implantation and gestation requires the non-invasive collection of biological information and samples, and the measurement of biochemical and biological markers (biomarkers) that are associated with the aforementioned physiological events. This paper describes some of the key features of biomarkers needed for epidemiological studies, identifies some existing and potential biomarkers and available measurement devices, and suggests some directions for identification and development of new biomarkers that might be employed in longitudinal studies involving the analysis of female reproductive function and of embryonic development. [source] Interval techniques for enclosures of regions of reachability and controllability and for guaranteed state and parameter estimation of dynamical systemsPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2007Andreas Rauh Interval techniques are a powerful means for calculation of enclosures of the regions of reachability and controllability of dynamical systems with uncertainties during analysis and design of controllers. In this contribution, both discrete-time and continuous-time dynamical systems are considered. Using suitable algorithms, guaranteed state enclosures can be determined for systems with uncertain parameters, uncertain initial conditions, nonlinearities, and time-varying characteristics. Although both uncertain system parameters and bounded control variables are assumed to be represented by interval boxes in the following, they have to be distinguished in reachability and controllability analysis. Typically, robustness specifications for controllers of dynamical systems are given in terms of bounds on the system's time response which must not be violated for any possible operating condition. Hence, reachability as well as controllability of states have to be proven for all possible parameter values but for at least one admissible control sequence. Robust control strategies for nonlinear systems usually rely on knowledge of all current states. However, the complete state vector is not always directly accessible for measurement. In this case, observers are applicable to reconstruct non-measurable state variables. Furthermore, they can reduce the uncertainties of the measured quantities by model-based recursive computation of estimates and fusion of information gathered by different measurement devices. If guaranteed bounds of all uncertain parameters of a dynamical system (including the sensor characteristics) and conservative bounds of all disturbances can be specified, the presented interval observer provides guaranteed enclosures of all reachable states. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Bestimmung der Tunnelinnenschalendicke mit zerstörungsfreien PrüfverfahrenBETON- UND STAHLBETONBAU, Issue 8 2006Dietmar Mähner Prof. Dr.-Ing. Der vorliegende Beitrag befaßt sich mit dem Einfluß von zerstörungsfreien Prüfmethoden zur Bestimmung der Tunnelinnenschalendicke und der Auswertung eines auf einer Baustelle durchgeführten Untersuchungsprogramms. Die Bandbreite der Untersuchungen bilden dabei an drei Tunnelblöcken unterschiedlich eingesetzte Meßverfahren und ihre jeweilige spezifische Eignung, verschiedene Meßteams sowie unterschiedliche Meßraster, die jeweils vor und nach der Firstspaltverpressung zum Einsatz kamen und analysiert wurden. Als wichtiger Parameter zum Einfluß der Meßqualität ist hierbei die durchzuführende Kalibrierung der Meßgeräte am Einsatzort zu nennen, die die Grundlage der Meßgenauigkeit bildet. Weiterhin konnte die Qualität bzw. der Erfolg der durchgeführten Firstspaltverpressung mittels eines Injektionsgutes in den Messungen nicht zweifelsfrei bestätigt werden und wurde daher zusätzlich durch Kernbohrungen und endoskopische Aufnahmen überprüft. Mit den daraus gewonnen Erkenntnissen werden wesentliche Aspekte und Empfehlungen aufgeführt, die im Umgang mit den zerstörungsfreien Prüfmethoden zur Dickenbestimmung einer Tunnelschale zu beachten sind und in zukünftige Projekte einfließen sollten. Determining the thickness of tunnel internal shell with non-destructive testing methods This report deals with the influence of non-destructive testing methods for determining the thickness of internal tunnel shells and evaluates the results of examinations performed on a construction site. The investigations cover different measurement techniques performed on three tunnel blocks; also analyzed were the specific advantages of these techniques, the employment measurement personnel and different measurement grids used before and after ridge-gap grouting. An essential parameter influencing the measurement accuracy is the calibration needed by the measurement devices at the site of deployment. Because the measurements were not able to unmistakably confirm the quality or success of ridge-gap grouting through injection, these results had to be examined additionally using drill cores and endoscopy. Permitting a crystallization of essential aspects and recommendations as regards the conduction of non-destructive tests for determining the thickness of tunnel shells, the obtained findings are to be incorporated into future projects. [source] | ||||||||||||||||