Physical Magnitude Research Articles

Comparative study on time-to-digital converters for low-power RFID tag sensors

This paper presents a comparative study on time-to-digital converters (TDC) for their use as part of an RFID tag sensor. TDCs can digitize any physical magnitude previously converted to time delay and exploit the benefits of time domain conversion: high resolution with reduced power consumption and low voltage operation. Three different TDC architectures are analyzed and a calibration strategy tailored for RFID sensing applications is proposed in order to account for process variations. Converters implemented using a 0.18μm CMOS standard process have been analyzed at transistor level for human body temperature sensing applications. An accuracy of 0.011°C is achieved in the range from 35°C to 43°C for the nonius TDC with a power consumption of only 4.1nW at 10 samples per second from a 1.8V voltage supply.

Viewing Tornado Impact as More Than Physical Magnitude

Ten years ago this fall, an F3 tornado tore a path straight through the heart of Ladysmith, a small Northern Wisconsintown. I grew up a few cities over, and spent many weekends at the Army Reserve ...

Residual vibration reduction in mechanical systems: A time-domain approach

This paper presents a time-domain technique to generate command inputs for the reduction of residual vibrations in mechanical systems. The technique is based on the generation of motion profiles with zero-crossing points in their frequency spectra at the system resonances in the same way as the zero-vibration (ZV) command generation methods. By including an appropriate negative exponential time function, which contains the system natural frequency and the damping ratio, the resultant input can be applied to damped systems with a result of zero residual vibration. The signals synthesized can be used as a generic physical magnitude in vibratory systems. However, they were particularized for mechanical systems and engineering metrics were used. Compared to other ZV methods, for a short duration input range, the signals obtained have better performance in terms of minimum-acceleration-switch shape which is translated to a smoother motion profile. The development includes the application to single-mode and multiple-mode mechanical systems and the possibility of handling two functional requirements or constraints in the desired application. The analyzed systems are those that can be modeled as discrete linear ones with several vibratory degrees of freedom and can be described with constant parameter motion equations. Experimental results show the efficacy of the method developed with its application to a damped pendulum test platform.

Correlation analysis for the incubation period of prion disease

Previous studies have shown that genetic quantitative trait loci (QTL), strain barriers, inoculation dose and inoculation method modulate the incubation period of prion diseases. We examined the relationship between a diverse set of physical, genetic and immunological characteristics and the incubation period of prion disease using correlation analyses. We found that incubation period was highly correlated with brain weight. In addition, mean corpuscular volume and cell size were strongly correlated with incubation period, indicating that the physical magnitude of prion-infected organs or individual cells may be important in determining the incubation period. Given the same prion inoculation dose, animals with a lower brain weight, mean corpuscular volume or cell size may experience more virulent disease, as the effective concentration of abnormal prion, which might regulate the attachment rate of prions to aggregates, is increased with smaller capacity of brains and cells. This is partly consistent with previous theoretical modeling. The strong correlations between incubation period and physical properties of the brain and cells in this study suggest that the mechanism underlying prion disease pathology may be physical, indicating that the incubation process is governed by simple chemical stoichiometry.

Implications of number-space synesthesia on the automaticity of numerical processing

Number-space synesthetes visualize numbers in specific spatial configurations. Their spatial-numerical perceptions are assumed to be automatic in nature and have been found to affect performance in various numerical tasks. The current study tested whether synesthetic number-space associations can modulate the well-established Size Congruency Effect (SiCE), which is considered to be an indication for the automaticity of numerical processing. Two groups, number-space synesthetes and matched controls, were tested on a numerical Stroop task (Henik and Tzelgov, 1982). In separate blocks, participants were presented with two digits and asked to make comparative judgments regarding either numerical values (numerical comparison) or physical size (physical comparison). Both dimensions were manipulated orthogonally, creating three congruency levels: congruent (e.g., 2 7), incongruent (e.g., 2 7) and neutral (e.g., 2 2 and 2 7 for physical and numerical blocks, respectively). For the numerical block, both synesthetes and controls showed the classic SiCE, indicating similar automatic processing of physical magnitude. However, in the physical block, synesthetes showed a lack of automatic numerical magnitude processing when the numbers to be compared were presented incompatibly with their relative position on the synesthetic number-form. This finding strongly suggests that synesthetes’ number-space perceptions affect their ability to automatically process the semantic meaning of numerals. The involvement of space in automatic magnitude processing for number-space synesthetes and non-synesthetes is discussed.

Mechanisms of flame stabilization and blowout in a reacting turbulent hydrogen jet in cross-flow

The mechanisms contributing to flame stabilization and blowout in a nitrogen-diluted hydrogen transverse jet in a turbulent boundary layer cross-flow (JICF) are investigated using three-dimensional direct numerical simulation (DNS) with detailed chemistry. Non-reacting JICF DNS were performed to understand the relative magnitude and physical location of low velocity regions on the leeward side of the fuel jet where a flame can potentially anchor. As the injection angle is reduced from 90° to 70°, the low velocity region was found to diminish significantly, both in terms of physical extent and magnitude, and hence, its ability to provide favorable conditions for flame anchoring and stabilization are greatly reduced. In the reacting JICF DNS a stable flame is observed for 90° injection angle and, on average, the flame root is in the vicinity of low velocity magnitude and stoichiometric mixture. When the injection angle is smoothly transitioned to 75° a transient flame blowout is observed. Ensemble averaged quantities on the flame base reveal two phases of the blowout characterized by a kinematic imbalance between flame propagation speed and flow normal velocity. In the first phase dominant flow structures repeatedly draw the flame base closer to the jet centerline resulting in richer-than-stoichiometric mixtures and high velocity magnitudes. In the second phase, in spite of low velocity magnitudes and a return to stoichiometry, due to jet bending and flame alignment normal to the cross-flow, the flow velocity normal to the flame base increases dramatically perpetuating the blowout.

Extended Stevens' power law

An extension of the Stevens' power law, widely used in psychophysics to relate a physical magnitude of a stimulus (e.g. taste, luminance, weight, sound pressure) with the corresponding experienced magnitude (saltiness, brightness, heaviness, loudness etc.) has been proposed. It takes into account the fact that psychophysical functions are basically of a sigmoid and not power-like type. To model the stimulus–response relationship the S-shaped Gompertz function converted to the power form by the mapping procedure is employed. It provides the extended Stevens' power law y(C) = k(C)Cn(C) with the scaling factor k(C) and exponent n(C) as function of the stimulus magnitude C. The model will be used in determination of the saltiness and brightness stimulus–response power function correctly reproducing the experimental psychophysical data in a wide range of the stimuli applied. It will be proven that the extended Stevens' power law belongs to the class of self-similar and allometric processes of the fractal nature.

Tethered Monte Carlo: Managing Rugged Free-Energy Landscapes with a Helmholtz-Potential Formalism

Tethering methods allow us to perform Monte Carlo simulations in ensembles with conserved quantities. Specifically, one couples a reservoir to the physical magnitude of interest, and studies the statistical ensemble where the total magnitude (system+reservoir) is conserved. The reservoir is actually integrated out, which leaves us with a fluctuation-dissipation formalism that allows us to recover the appropriate Helmholtz effective potential with great accuracy. These methods are demonstrating a remarkable flexibility. In fact, we illustrate two very different applications: hard spheres crystallization and the phase transition of the diluted antiferromagnet in a field (the physical realization of the random field Ising model). The tethered approach holds the promise to transform cartoon drawings of corrugated free-energy landscapes into real computations. Besides, it reduces the algorithmic dynamic slowing-down, probably because the conservation law holds non-locally.

Spatiotemporal scales and links between electrical neuroimaging modalities

Recordings of brain electrophysiological activity provide the most direct reflect of neural function. Information contained in these signals varies as a function of the spatial scale at which recordings are done: from single cell recording to large scale macroscopic fields, e.g., scalp EEG. Microscopic and macroscopic measurements and models in Neuroscience are often in conflict. Solving this conflict might require the developments of a sort of bio-statistical physics, a framework for relating the microscopic properties of individual cells to the macroscopic or bulk properties of neural circuits. Such a framework can only emerge in Neuroscience from the systematic analysis and modeling of the diverse recording scales from simultaneous measurements. In this article we briefly review the different measurement scales and models in modern neuroscience to try to identify the sources of conflict that might ultimately help to create a unified theory of brain electromagnetic fields. We argue that seen the different recording scales, from the single cell to the large scale fields measured by the scalp electroencephalogram, as derived from a unique physical magnitude--the electric potential that is measured in all cases--might help to conciliate microscopic and macroscopic models of neural function as well as the animal and human neuroscience literature.

Competition between Redlich–Kister and adapted Herráez equations of correlation conductivities in isobutyric acid + water binary mixtures near and far away from the critical temperature

Electrical conductivity deviation Δσ has been investigated by using electrical conductivity (σ) measurements for isobutyric acid + water (IBA + W) mixtures over the entire range of mole fractions at six different temperatures, both near and close to the critical temperature (0.055 < (T − T c)/K < 16.055). Knowledge of the conductivity of binary mixtures is of great importance in many industrial processes. Rarely can the conductivity of mixtures be obtained from the sum of the conductivities of the pure components. The theoretical study of the conductivity of mixtures is generally complicated. Numerous empirical correlation models have been proposed. The present study proposes a new empirical correlation equation, based on lineal behaviour. The results were also fitted with the Redlich–Kister polynomial equations and the recently proposed Herráez equation for viscosity correlation which is adapted for electrical conductivity in this work. The investigation of the Herráez equation shows that it exhibits a universal exponent as a physical magnitude feature. Competition between the two models at different temperatures and parameter numbers is discussed.

Robust determination of effective atomic numbers for electron interactions with TLD-100 and TLD-100H thermoluminescent dosimeters

Lithium fluoride thermoluminescent dosimeters (TLD) are the most commonly implemented for clinical dosimetry. The small physical magnitude of TLDs makes them attractive for applications such as small field measurement, in vivo dosimetry and measurement of out-of-field doses to critical structures. The most broadly used TLD is TLD-100 (LiF:Mg,Ti) and, for applications requiring higher sensitivity to low-doses, TLD-100H (LiF:Mg,Cu,P) is frequently employed. The radiological properties of these TLDs are therefore of significant interest. For the first time, in this study effective atomic numbers for radiative, collisional and total electron interaction processes are calculated for TLD-100 and TLD-100H dosimeters over the energy range 1 keV–100 MeV. This is undertaken using a robust, energy-dependent method of calculation rather than typical power-law approximations. The influence of dopant concentrations and unwanted impurities is also investigated. The two TLDs exhibit similar effective atomic numbers, ranging from approximately 5.77–6.51. Differences arising from the different dopants are most pronounced in low-energy radiative effects. The TLDs have atomic numbers approximately 1.48–2.06 times that of water. The effective atomic number of TLD-100H is consistently higher than that of TLD-100 over a broad energy range, due to the greater influence of the higher- Z dopants on the electron interaction cross sections. Typical variation in dopant concentration does not significantly influence the effective atomic number. The influence on TLD-100H is comparatively more pronounced than that on TLD-100. Contrariwise, unwanted hydroxide impurities influence TLD-100 more than TLD-100H. The effective atomic number is a key parameter that influences the radiological properties and energy response of TLDs. Although many properties of these TLDs have been studied rigorously, as yet there has been no investigation of their effective atomic numbers for electron interactions. The discrepancy between the effective atomic numbers of the TLDs and water is significantly higher than would be indicated by comparing effective atomic numbers calculated via the common – but dubious – power-law method. The mean effective numbers over the full energy range are 6.06, 6.09, 3.34 and 3.37 for TLD-100, TLD-100H, soft tissue and water respectively.

Discomfort of vertical whole-body shock-type vibration in the frequency range of 0.5 to 16 Hz

Shock-type vibrations are frequently experienced in vehicles excited by impulsive input, such as bumps in the road, and cause discomfort. Current national and international standard weightings were primarily developed for assessing exposure to sinusoidal or random vibrations and not impulsive excitations or shocks. In this experimental study, various shock signals were systematically produced using the response of a one degree-of-freedom vibration model to hanning-windowed half-sine force input. The fundamental frequency of the shock was varied from 0.5 to 16 Hz at a step of 1/3 of an octave. The magnitude estimation method was used for fifteen subjects to compare the discomfort of shocks with various unweighted vibration dose values between 0.35 ms−1.75 and 2.89 ms−1.75 at each frequency. The equivalent comfort magnitude of shock showed greater sensitivity at frequencies less than 0.63 Hz and at the resonance frequency of the human body between 5.0 Hz and 6.3 Hz. The frequency weighting constructed by using both the equivalent comfort magnitude and the growth rate of discomfort obtained in this study was compared with the current standard weightings, Wb of BS 6841 and Wk of ISO 2631. The derived weightings for shock were applied to the acceleration of the shocks, and an enhanced correlation was proved between the magnitude estimations and the weighted physical magnitude of shock.

Saccades compress space, time and number

It has been suggested that space, time and number are represented on a common subjective scale. Saccadic eye movements provide a fascinating test. Saccades compress the perceived magnitude of spatial separations and temporal intervals to approximately half of their true value. The question arises as to whether saccades also compress number. They do, and compression follows a very similar time course for all three attributes: it is maximal at saccadic onset and decreases to veridicality within a window of approximately 50ms. These results reinforce the suggestion of a common perceptual metric, which is probably mediated by the intraparietal cortex; they further suggest that before each saccade the common metric for all three is reset, possibly to pave the way for a fresh analysis of the post-saccadic situation.

Haptic perception of gravitational and inertial mass

Mass can be perceived in different ways: statically, through gravitational cues; dynamically, through inertial cues; or a combination of both. This article investigates the relationship between these modes of perception. In three different experiments, subjects matched masses that were held statically in the hand to masses that were either accelerated or decelerated. Accelerated masses were perceived to be smaller than masses of equal physical magnitude held statically by a factor of 2. However, decelerated masses were matched veridically to masses held statically. This difference remained present when contact duration was made very short. This shows that the shift in perceived mass is not the result of differences in the information available, but of differences in the mode of perception (active acceleration vs. passive deceleration). It is hypothesized that this is due to a suppression of the perception of applied force in active touch.

When is a Physical Concept born? The Emergence of ‘Work’ as a Magnitude of Mechanics

The physical magnitude ‘work’ has a long history. It emerged when two different practices, performed during the whole eighteenth century, met each other. The first was theoretical, practiced by philosophers and mathematicians, and was related mainly to the ‘living forces’ (vires vivae). The second was empirical, practiced by engineers, and was related to the work and the effectiveness of the motor engines. In both activities, the products ‘weight (or force) multiplied by height (or displacement)’ were used for calculations. Can we regard that these products constitute a well defined physical magnitude and are anticipations of the magnitude ‘work’? Modern historians of science assert that ‘work’, as a magnitude of mechanics, was created in France, at the beginning of the nineteenth century. Why? In order to examine these issues, a brief survey into the history of the relevant ideas will be done, and a number of characteristics, acquired by the magnitude of ‘work’ through the historical process of its construction, will be presented. These characteristics may help to depict a magnitude, in general, which is autonomous and embedded in a physical theory. Finally, from the historical data concerning the history of ‘work’, some educational implications will be considered.

Electric current density distribution in planar solid tumor and its surrounding healthy tissue generated by an electrode elliptic array used in electrotherapy

The knowledge of the electric current density distribution generated by an electrode array is very useful in electrotherapy for tumor treatment. We propose an innovative mathematical approach that takes into account planar solid tumor elliptic geometry, electrical differences between it and its surrounding healthy tissue, and positioning of the electrodes with respect to tumor-surrounding healthy tissue interface. We show the distributions of the electric current density in leading order and first correction terms in a heterogeneous planar medium formed by two regions (tumor and its surrounding healthy tissue) in function of these parameters. The results show that when electrodes are completely inserted in tumor and/or its conductivity is higher than that of its surrounding healthy tissue, the electric current density lines concentrate more in tumor and its tumor-surrounding healthy tissue interface. No significant differences are reported between the electric current density distributions in leading-order and first-order correction for each parameter investigated. However, norm of this physical magnitude reveals that these distributions are different when the ratio between radius of the electrodes and radius of the tumor is less than 0.8. We conclude that the analytical modeling presented in this study is of practical interest because it provides a convenient way to visualize the electric current density distributions generated by an electrode elliptic array in order to efficiently destroy the localized planar tumors with the minimum damage to organism, through an increase of the potential applied to the electrodes, the tumor conductivity with respect to its surrounding healthy tissue and insertion of all electrodes into tumor.

Fechner's Law: Where Does the Log Transform Come From?

This paper looks at Fechner's law in the light of 150 years of subsequent study. In combination with the normal, equal variance, signal-detection model, Fechner's law provides a numerically accurate account of discriminations between two separate stimuli, essentially because the logarithmic transform delivers a model for Weber's law. But it cannot be taken to be a measure of internal sensation because an equally accurate account is provided by a chi(2) model in which stimuli are scaled by their physical magnitude. The logarithmic transform of Fechner's law arises because, for the number of degrees of freedom typically required in the chi(2) model, the logarithm of a chi(2) variable is, to a good approximation, normal. This argument is set within a general theory of sensory discrimination.

Behaviour of sonogels under isotropic pressure

The aim of this article is to present a method that simplifies the standard procedure to determine the yield point providing complementary information about changes in the behaviour of the materials under study. It is generally accepted that the yield point is determined by the inflection point of the curve of pressure versus apparent volume of the sample, P(V), from Hg porosimetry runs. Although compressible materials present an easily identifiable neat inflection point, in resilient materials, the inflection point is not easy to identify by simple visual inspection of the curve. A physical magnitude (K’) is introduced to characterise the evolution of the material's compliance under isotropic pressure. The physical meaning of K’ is the variation in the resistance to uniform compression with the pressure applied, helping to identify the yield point and the plastic mechanism beyond the yield point in a single run.

Rating a New Hedonic Scale: A Commentary on "Derivation and Evaluation of a Labeled Hedonic Scale" by Lim, Wood and Green

To the extent that our experiences of tastes and odors haveunderlyingdimensions, onecanmountastrongcase thattheexpression of those dimensions is via hedonics (Scott andMark1987;Khanetal.2007).Thehedonicdimensioniscru-cialin defining responses in the chemical senses in awaythatis not true for other senses, in that all chemosensory stimuliare intrinsically valenced, either at birth (e.g., in the case ofsweetness and bitterness) or as a result of our subsequent ex-perienceswiththem(arguablythecaseforallodorqualities).Traditional psychophysics, developed primarily for studiesin vision, audition or touch, asks questions about stimulusintensity, but this may be of less importance for taste orsmell, which derive much of their meaning from theirhedonic properties. Moreover, certainly in the case of tastequalities, our hedonic responses may provide crucial cluesregarding the adaptive significance of those qualities. Assuch, the overall paucity of attempts to ‘‘fine tune’’ our psy-chophysical methods in relation to chemosensory hedonicsis all the more puzzling.Even in the tortoise world of psychophysics, the develop-mentofhedonicmeasurementhasbeenstartlinglyslow.Thismay be because much of the interest in psychophysical mea-surement has been centered on addressing the question ofhow best to directly access perceptual processes, that is, tocharacterize sensory systems in psychological terms, whichcouldthenbeusefullylinkedtounderlyingphysiologicalpro-cesses. The importance of the development of the LabeledMagnitude Scale (LMS), first published in 1993 (Green et al.1993), and later modified as the general (g)LMS (Bartoshuket al. 2002), lies in the attempt to provide a means of scalingconsistent with S.S. Steven’s psychophysical model, whichspecified a relationship between physical stimulus magni-tude and sensation in ratio terms. Magnitude estimation(ME), derived from the same theoretical base, enjoyed a pe-riod of application that has waned in recent decades. It hasbeen suggested that the primary reasons for ME falling outof favor was both that people do not themselves consis-tently use numbers in a ratio fashion and also that the mea-surement process itself was unwieldy because of the priortraining that was deemed necessary. Thus, the introductionof the LMS was timely, quickly being adopted by manypsychophysical researchers, especially those hoping fora measurement free of the context of the stimuli under mea-surement (Bartoshuk 2000).Accessing ‘‘secondary states,’’ including the hedonic eval-uationofsensorystimuli,hasbeenregardedaslessimportantbecauseithasbeenfeltthatthestimulus-affectiverelationshipis less direct (although there is evidence that affective statesmight occur in the absence of perceptual awareness—seeKunst-Wilson and Zajonc 1980), has less to tell us aboutperception per se, and is further from being ‘‘objective,’’ inthataffectivestatesclearlyshowconsiderableindividualvar-iability(often,oforiginunknown).Ironically,todate,oneofthemostcommon applicationsofthe gLMShasbeeninthestudyofindividualdifferencesinperception,particularlyinrelationtooralirritationand6-n-propylthiouracilbitterness(Bartoshuk 2000; Prescott et al. 2001; Green and Hayes2003). One of the benefits of the gLMS is that, via the useofasupposed(andperhaps,inpractice,actual)frameofref-erence external to the stimuli themselves, generated by thetop-end label ‘‘Strongest Imaginable Sensation of AnyKind,’’wecanminimizethegenerallyuninterestingvariabil-ityassociatedwithscaleusageandmaximizethequiteinter-esting variability associated with individual perceptual orphysiological differences. Affective states and responsesare, of course, expected to show considerable individual

Plantar pressure distribution character in the Latin dance

The Latin dance is full of social, entertainment, arts, sports and exercise. It shows both physical and natural beauty of the sport through the physical intensity, magnitude, velocity and shape cha...