Moments Of Maximum Research Articles

Damage Accumulation in Cyclically‐Loaded Glass‐Ceramic Matrix Composites Monitored by Acoustic Emission

Barium osumilite (BMAS) ceramic matrix composites reinforced with SiC-Tyranno fibers are tested in a cyclic loading protocol. Broadband acoustic emission (AE) sensors are used for monitoring the occurrence of different possible damage mechanisms. Improved use of AE indices is proposed by excluding low-severity signals based on waveform parameters, rather than only threshold criteria. The application of such improvements enhances the accuracy of the indices as accumulated damage descriptors. RA-value, duration, and signal energy follow the extension cycles indicating moments of maximum or minimum strain, while the frequency content of the AE signals proves very sensitive to the pull-out mechanism.

Experimental study of heat generation at the vertex of a fatigue crack

The process of heat generation at the vertex of a fatigue crack in VT-6 titanium alloy under conditions of cyclic loading has been studied by infrared thermography. The spatial and temporal variations of temperature at the crack vertex have been measured, the shape of the zone of heat evolution has been determined, and the intensity of heat generation has been evaluated. Comparison of the obtained experimental data to the relations of the linear theory of elasticity shows that neither the observed shape of the plastic deformation zone nor the measured dynamics of heat evolution at the crack vertex is consistent with predictions of the linear theoretical models. The experimental results revealed a time delay between the moments of maximum applied stress and maximum intensity of heat evolution at the vertex of a fatigue crack.

A model for OFDM signals with applications

ABSTRACTA novel model for constant energy constellation (the data is drawn from equi‐energy symbols) discrete time orthogonal frequency‐division multiplexing (OFDM) signal is presented. On the basis of this model, the moments of the OFDM signal's envelope maximum and the moments of the energy of the clipped portion of the signal are computed. It is also shown that the rate at which the expected value of the maximum scales with the length of the signal coincides with Halasz's result. Simulations are presented, which show that this model gives much better results than the conventional Gaussian model in approximation of statistical properties of an OFDM signal. Copyright © 2012 John Wiley & Sons, Ltd.

On moments of the maximum of partial sums of moving average processes under dependence assumptions

Let {Y i ;−∞ < i < ∞} be a doubly infinite sequence of identically distributed φ-mixing random variables and let {a i ;−∞ < i < ∞} be an absolutely summable sequence of real numbers. In this paper we study the moments of $\mathop {\sup }\limits_{n \geqslant 1} \left| {\sum\limits_{k = 1 - \infty }^n {\sum\limits_{}^\infty {a_i Y_{i + k} /n^{1/r} } } } \right|^p (1 \leqslant r 0)$ under the conditions of some moments.

Influence de l’anesthésie locorégionale sur la récupération musculaire après ligamentoplastie du genou

Anesthetic agents used for motor blocks have local toxic effects, demonstrated in vitro and in animal models. Little work has been done on the clinical impact of this toxicity. In a context of physical medicine and sports medicine, we examined several patients who had undergone knee ligamentoplasty for tears of the anterior cruciate ligament (ACL). For these patients, functional recovery was correlated with recovery of quadriceps strength. The purpose of this study was to analyze the impact of peripheral nerve blocks on quadriceps recovery at 5.5 months after knee ligamentoplasty. Patients and methods We conducted a retrospective analysis of 69 patients divided into three groups: 33 who had had no locoregional anesthesia (NB), 24 had femoral nerve block (FNB) and 12 had an iliofascial block (IFB). Our main outcome criterion was relative loss of quadriceps muscle force compared with the healthy side using isokinetic measures five to six months after ligamentoplasty. Isokinetic parameters were concentric Moment of Force Maximum (MFM) measured at 60°/s and 240°/s. Results Loss of concentric force at 60°/s was, on average: 24.7 ± 14.8% in group NB, 17.2 ± 13.9% in group FNB, and 19.7 ± 10.7% in group IFB. The difference between the three groups was not significant ( P = 0.208). At rapid speed (240°/s) the deficit was on average: 23.111% in the group NB, 14.4 ± 10.5 in the group FNB and 13.4 ± 11% in the group FNB. The difference was significant only between NB and the two other groups, FNB and IFB. The quadriceps deficit was significantly greater in the patients who did not have a nerve block. Discussion Surprisingly, this study demonstrated result contradicting the initial hypothesis. Our finding showed that the local toxicity of anesthetic blocks did not have a negative clinical impact on muscle force, but that there was a positive effect on the quality of quadriceps recovery during the time studied. The conclusions of this retrospective preliminary study, with the resulting methodological limitations, must be re-evaluated with other work.

The twentieth century contiguous US temperature changes indicated by daily data and higher statistical moments

The daily surface air temperature data are used to assess the climate changes of the contiguous United States during the period of 1901 to 2000. The assessment is made through the first four statistical moments of the daily maximum, minimum, and mean temperature anomalies, the linear trends of the moments, and the changes of the anomalies’ probability density functions. The results on the first moment, i.e., the mean, are compared with the existing ones in terms of intra-annual means and their linear trends. Our first moment results agree with known ones and demonstrate a decrease from the 1930s to the 1960s and an increase from the 1970s to 2000. The temperature fluctuation is the smallest in the 1960s among the decades from 1931 to 2000. The trends of the higher (second-, third- and fourth-order) moments of the mean, maximum, and minimum surface air temperatures are calculated for the periods 1901–2000, 1910–1945, 1946–1975, and 1976–2000. The results show a decreasing trend of the second- and third-order moments of all the temperatures. The fourth-order moments of the mean and maximum surface air temperatures have increasing trends, but that of the minimum surface air temperature has a decreasing trend. The seasonal histograms of the mean, maximum, and minimum surface air temperatures are calculated for the three periods 1910–1945, 1946–1975, and 1976–2000 for the stations which have the largest trend of maximum daily surface air temperature. An obvious change has been identified in the probability density functions. Among the changes of statistical parameters, the ones for the minimum temperature are larger than those for the maximum and mean temperatures.

POLARIZATION SWINGS FROM CURVED TRAJECTORIES OF THE EMITTING REGIONS

We present a model of polarization swings in blazars from axially symmetric blobs propagating on curved trajectories. If the minimum inclination of the velocity vector to the line of sight is smaller than Γ-1, the polarization angle maximum rotation rate is simultaneous with the polarization degree minimum and a spike in the total flux. By measuring the maximum rotation rate and the moment of the polarization maximum, it is possible to estimate the distance covered by the blob and thus its approximate position. We apply this model to the recent polarization event in blazar 3C 279.

Carbon accumulation along a stand development sequence of Nothofagus antarctica forests across a gradient in site quality in Southern Patagonia

Above- and below-ground C pools were measured in pure even-aged stands of Nothofagus antarctica (Forster f.) Oersted at different ages (5–220 years), crown and site classes in the Patagonian region. Mean tissue C concentration varied from 46.3% in medium sized roots of dominant trees to 56.1% in rotten wood for trees grown in low quality sites. Total C concentration was in the order of: heartwood > rotten wood > sapwood > bark > small branches > coarse roots > leaves > medium roots > fine roots. Sigmoid functions were fitted for total C accumulation and C root/shoot ratio of individual trees against age. Total C accumulated by mature dominant trees was six times greater than suppressed trees in the same stands, and total C accumulated by mature dominant trees grown on the best site quality was doubled that of those on the lowest site quality. Crown classes and site quality also affected the moment of maximum C accumulation, e.g. dominant trees growing on the worse site quality sequestered 0.73 kg C tree −1 year −1 at 139 years compared to the best site where 1.44 kg C tree −1 year −1 at 116 years was sequestered. C root/shoot ratio decreased over time from a maximum value of 1.3–2.2 at 5 years to a steady-state asymptote of 0.3–0.7 beyond 60 years of age depending on site quality. Thus, root C accumulation was greater during the regeneration phase and for trees growing on the poorest sites. The equations developed for individual trees have been used to estimate stand C accumulation from forest inventory data. Total stand C content ranged from 128.0 to 350.9 Mg C ha −1, where the soil C pool represented 52–73% of total ecosystem C depending on age and site quality. Proposed equations can be used for practical purposes such as estimating the impact of silvicultural practices (e.g. thinning or silvopastoral systems) on forest C storage or evaluating the development of both above- and below-ground C over the forest life cycle for different site qualities for accurate quantification of C pools at regional scale.

Computing exponential moments of the discrete maximum of a Lévy process and lookback options

We present a fast and accurate method to compute exponential moments of the discretely observed maximum of a Levy process. The method involves a sequential evaluation of Hilbert transforms of expressions involving the characteristic function of the (Esscher-transformed) Levy process. It can be discretized with exponentially decaying errors of the form O(exp (−aM b )) for some a,b>0, where M is the number of discrete points used to compute the Hilbert transform. The discrete approximation can be efficiently implemented using the Toeplitz matrix–vector multiplication algorithm based on the fast Fourier transform, with total computational cost of O(NMlog (M)), where N is the number of observations of the maximum. The method is applied to the valuation of European-style discretely monitored floating strike, fixed strike, forward start and partial lookback options (both newly written and seasoned) in exponential Levy models.

Uniform bounds for exponential moment of maximum of a Dyck path

Let us consider the maximum $M(D)$ of a Dyck path $D$ chosen uniformly in the set of Dyck paths with $2n$ steps. We prove that the exponential moment of $M(D)$ normalized by the square root of $n$ is bounded in the limit of infinite $n$. This uniform bound justifies an assumption used in literature to prove certain estimates of high moments of large random matrices.

Relationship Between Anode Spots and Onset VoltageHash in Magnetoplasmadynamic Thrusters

Experimental results are presented which indicate a direct relationship between voltage transients in magnetoplasmadynamicthrustersoperatingaboveonsetandthetime-resolvedappearanceofdestructivelyreleased anode material in the thruster plume. Such a relationship gives support to previously discussed anode spotting theories. Langmuir probe measurements of plasma density fluctuations and measurements of argon and copper (anodematerial)ionluminosityarecomparedwiththevoltagetransients.Theonsetofspikesinthethrustervoltageis directly correlated with the onset of similar spikes in the plasma density at the probe location, and with a rise in the copper luminosity, but a fall in that of argon, in the plume. The voltage hash is categorized into two types: largeamplitudespikesatcurrentswell abovetheonsetcurrent, andlower-amplitude random fluctuations atcurrentsjust abovethe onsetcurrent. Itisshownthatthetwocategoriesofvoltagehashcan berelated totwoclasses ofdamageon the anode surface: pitlike damage of 10 to 100 � m extent, caused by explosive emission due to voltage spikes, and shallow surface melting due to the lower-amplitude random fluctuations, which may be responsible for observed density and luminosity oscillations at 600 kHz, and a dip in the voltage power spectrum at the same frequency. I. Introduction O NSET in a magnetoplasmadynamic thruster (MPDT) is a condition encountered in high-current operation, in which the thruster voltage (quiescent at lower currents) fluctuates with an amplitude that can be large compared with the mean voltage, and in which the anode sustains significant damage. Onset is a lifetimelimiting factor in the operation of the MPDT, and so must be understood and overcome to improve the performance of MPDTs as primary propulsion systems for long-duration space missions. The nature of the voltage fluctuations (“hash”) and the associated anode damage has been the subject of many studies, many of which pointoutarelationship between thepresence ofa fluctuating voltage and fluctuationsinotherthrusterparameters,suchasopticalemission [1], electric and magnetic fields [2], and plasma density [3]. Kuriki and Iida [1] measured the fluctuation of the total light output from a quasi-steady MPDT, observing, in particular, similarities in the power spectra of both the voltage and the luminosityatabout500kHz,showingarelationshipbetweenthetwo quantities. Ho [4] and Rudolph [5] measured the time-integrated optical spectrum of a quasi-steady MPDT, and discovered an increase in the luminosity of anode material in the thruster plume as the current rose above onset. However, Kuriki and Iida’s data [1] cannot identify which atomic species in the plume was responsible for the luminosity fluctuation, nor could Ho’s and Rudolph’s measurements[4,5]provideinformationconcerningwhenduringthe thruster pulse anode material appeared in the plume; therefore, the connection between hash and anode erosion was not completely elucidated. Hugel [6] has suggested that the presence of anode material in the plume can be attributed to the formation of anode spots, which he observed to form on his MPDT anode in high-speed photographs at the moments of maxima in the voltage hash. At high currents, the plasma density near the anode is small enough that the anode is starved of the charge carriers needed to conduct the current. Hugel suggests that the anode spots form in response to this starvation. Diamant et al. [3] have further demonstrated that spot damage on the anodesurfaceismuchgreateratcurrentsaboveonsetthanbelow,and that the plasma density, averaged over a quasi-steady firing, increases above onset. What Hugel’s [6] and Diamant’s [3] data togethercannotconclusivelydemonstrate,however,isthattheanode spots are the source of additional plasma density above onset, and that their density contribution is correlated with the voltage hash fluctuations. Previous modeling work [7], however, has suggested this relationship between anode damage and voltage hash. In this paper, we address key questions that remain from these studies; namely, we search out the time-resolved correlations between voltage hash and anode erosion lacking in the previous work. We do this using time- and wavelength-resolved plume luminosity measurements and time-resolved plasma density measurements. We correlate the measurements made by these two diagnosticswiththevoltagehash fluctuations,andshowthatallthree arecorrelatedinamannerconsistentwithwhatistobeexpectedfrom transient damage to the anode surface. Briefly, the paper is organized as follows. In Sec. II, we give relevantdetailsoftheexperimentalsetupusedtotakethedata,which we present in Sec. III. We defer major interpretation of the results to Sec.IV,wherewerelatetheexperimentalresultstothehypothesisof anode damage at high currents.

Distributions of Additive Functionals of Brownian Motion Stopped at Moments of Maxima and Minima of Random Times

We study distributions of additive functionals of a Brownian motion stopped at moments constructed by maxima and minima operations from the inverse range time, moments inverse to some additive functionals, and the first exit time. Some interesting examples of application are considered. Bibliography: 6 titles.

Observations of the type IIn supernova 1999EL in the near infrared

Abstract We present the preliminary results of near-infrared photometric observations of the type IIn SN1999EL covering the period between 5 to 80 days after discovery. These infrared data represeat the second time that such extensive time and wavelength coverage has been achieved for a type IIn SN event. We estimate the absolute magnitudes of the SN at the moment of brightness maximum in J, H and K bands. If the luminosity of the SN event in the K band is powered mostly by the deposition of redioactive decay energy, the mass of radioactive 56Ni is estimated as 0.2M[odot]. The effect of blueing of the J, H, K light curves is discovered and explained by the interaction of the explosion shock and UV/optical flash with pre-existing dust in the circumstellar medium of the progenitor.

Alpha Cygnids - a possible July minor meteor shower

We present a comprehensive study of a possible $\alpha$-Cygnid meteor shower. Based on visual and telescopic observations made by Polish observers we estimate basic parameters of the stream. Activity of $\alpha$-Cygnids lasts from around June 30 to July 31 with clear maximum near July 18 (solar longitude $\lambda_\odot=116.5^\circ$). Maximal Zenithal Hourly Rates (ZHRs) are equal to $3.6\pm1.2$. The structure of the radiant analyzed by {\sc radiant} software is most compact for geocentric velocity of the events equal to 41 km/s, and for the drift of the radiant (in units $^\circ$/day) equal to $\Delta\alpha=+0.6$ $\Delta\delta=+0.2$. Center of the radiant for the moment of maximum is $\alpha=302.5^\circ$ $\delta=+46.3^\circ$.We derive population index $r$ equal to $2.55\pm0.14$ from magnitude distribution of 738 possible members of the stream. Comparing the velocity distributions of 754 possible $\alpha$-Cygnids and 4339 sporadic events by $\chi^2$ and Kolmogorov-Smirnov tests we conclude that both distributions are different with probability very close to 1.0. Telescopic observations strictly confirm the results obtained from visual observations. The smallest values of $\chi^2$ parameter we obtained for the geocentric velocity equal to 40 km/s and for the drift of the radiant (in units $^\circ$/day) equal to $\Delta\alpha=+0.6$ $\Delta\delta=+0.2$. The center of the radiant for moment of maximum is $\alpha=304.9^\circ$ $\delta=+46.2^\circ$. In spite of making many photographic exposures we still have no photographic or video confirmation of the existence of this stream.

TT Arietis: Photometric variability from 1985 to 1994

Results of photoelectric observations of TT Ari during the 1985{1994 interval are presented. Observations were carried out at the Rozhen and Belogradchik observatories as part of our programme for the study of anti-dwarf novae. The long-term light curve in the standard UBV system is constructed and peculiar- ities of the long-term behaviour of the star in this time interval are discussed. 21 moments of maxima and 14 mo- ments of minima are added to the list of known maxima and minima of 3.2-hour modulations. The period of 3.2- hour modulations during the 1987/1988, 1989/1990 and 1990/1991 seasons is determined. In our 29 observing runs we searched for 20-min quasi-periodic variations, which were detected in 25 of them. Our results show that in 1989, the 20-min modulation mean period reached a lo- cal maximum of 19.45 min and declined afterwards. The mean brightness variability analysis during the aforemen- tioned seasons conrmed the reliability of the 3: d 8p eriod suspected by Semeniuk et al. (1987).

Principles, Mediations, and the "Good" as Synthesis

In 1973, Karl-Otto Apel published in Frankfurt his work Transformation of Philosophy.' The same year, in Buenos Aires, appeared the first two volumes of my work Toward an Ethics of Latin American Liberation. Two weeks after the "fall of the Berlin Wall," on November 24th, 1989, we met in Freiburg. I immediately understood the importance and creative potential of Apel's thought for the project of an ethics of liberation. At the same time, however, I realized the insufficiency of an intersubjective formal morality that could not integrate the material moment of practical truth. At first, it was Marx's work that motivated me to reach this conclusion. Through six dialogues with Apel, I was able to express in a clearer fashion my original intuitions.3 Now, after our 1997 colloquium in Mexico, I believe to have advanced to a new level of architectonic distinctions. These new distinctions are what I wish to elucidate in this short work, which nevertheless presupposes all that has already been articulated in the prior works that emerged from our encounters. I will divide the presentation in two parts: fundamental ethics and critical ethics or ethics of liberation. In both parts I will consider three levels: A, B, and C, in counter position to Apel's distinctions between Parts A and B of his discourse ethics. 1. First Part: Fundamental Ethics As indicated by its name, the "fundamental" (or foundational) part analyzes the problematic of ethics in its basic structure, which was inevitably studied by all schools of ethics, in some fashion or another, whether by articulating aspects, parts or specifications of it. A reconstruction from the perspective of an ethics of liberation articulates its own theses, which will not escape the reader. 1.1 Level A: Abstract "Universality"4 To begin, and accepting partly this distinction, although giving it another sense, this level concerns the moment of maximum abstraction or "universality" (Allgemenheit) of every possible ethics, which is arrived at through use of the Hegelian distinction between levels of generality. 1.1.1 The Principle of Discursive Validity or of Formal Morality Without question, one of the irreversible contributions of modernity to ethics has been the thematization of the moral "validity" (Gultigkeit) of the human act. To achieve this decisive level it was necessary to go through the linguistic turn, and in particular, the form it assumed under discursive pragmatics. It is thus that an act is "valid" (Gultig) if it is intersubjectively "accepted" by a community of communication, whatever its reach. It is in this way that the first version of the Kantian categorical imperative is re-interpreted, which now speaks of "validity," and not directly of "goodness" or the "good" (Das Gute): So act that the maxim of your will could always hold at the same time as the principle of a universal legislation.5 The condition of possibility of the "validity" of a maxim of action consists in its "acceptability" by the other members of an affected community with respect to that which is under discussion, for which linguistic communication is necessary. The "affected community" includes those who will suffer the consequences of the action were it to be realized. A "valid" act is that which has received the rational and symmetrical assent of all the affected in actu, under equal conditions and rights, and not by the mere fact that someone "has assumed the place" of others, as Kant suggests.6 There can not exist a "good" act which is not first "valid." Validity is one of its conditions of possibility. But the "good" act, as we will see below, is so not only because it can be "valid." It also depends on other conditions. Herein resides the error of discursive formalism, namely on subordinating goodness solely to validity. The discursive principle of validity could approximately be formulated in the following manner: one who acts morally ought to arrive at a valid decision through a community of communication with the symmetrical participation of all the affected through the medium of rational argumentation, without coercion of any sort whatsoever. …

Illustration of some moment identities for order statistics

This paper discusses some identities for the marginal distribution functions and marginal moments of the order statistics X (1) ⩽ … ⩽ X ( n) of n random variables X 1, …, X n . These identities express the distribution function or moments of X (1) as linear combinations of the distribution functions or moments of minima or maxima of subsets of the X i . Two applications to waiting time problems in urn sampling illustrate the value of the moment identities. These applications rely on embedding the urn models in Poisson and uniform stochastic processes.

Electron and population temperatures in a non-LTE optically thick plasma

The distribution temperature between excited atomic states in an arc plasma can be determined using self-reversed lines. This technique was applied to a high-pressure mercury arc. The electron temperature was deduced from the distribution temperature between the 63P2,0 metastable levels. The population temperatures of the 63P1, 73S1 and 63D3 levels were also determined as well as the lowering of the population of the 63P1 resonance level caused by resonance radiation. The electron density was deduced from the Saha law, the known electron temperature and the measurement of the density of the 63D2 level. At the arc axis the difference between the electron temperature and the 'equilibrium temperature' deduced from the optically thin line technique assuming local thermodynamic equilibrium (LTE), is of the order of 1000 K and 450 K at the moments of maximum and minimum current phase, respectively. The difference found between the population temperatures of the different levels indicates that collisionally dominated plasma is not a sufficient condition for the presence of LTE in the central region of an inhomogeneous arc where the diffusion of charged particles can disturb the Saha balance.

Alternating cycle durations in dwarf novae

The cycle durationC in some dwarf novae underwent abrupt significant changes, as was found by using our own photometric data and the published moments of maxima. For the analysis, the DMRT method (Dumontet al., 1978) as well as least-squares (LS) routine were used. The DMRT method is more appropriate for a search for ‘mean period’, if the cycle numeration is unknown. Such changes may be possibly explained by a solar-type activity of convective secondary stars in cataclysmic binaries. However, the ‘abrupt’ character of the changes ofC (i.e., the time of ‘switchings’ from one cycle to another is sufficiently small as compared with the ‘lifetime’ of a given cycle) is an observational puzzle which is to be interpreted theoretically.

Moments of a filtered binary process (Corresp.)

The problem of determining the moments of the output of a resistance-capacitance (RC) filter driven by a random binary process is considered. It is assumed that the driving process is governed by an alternating renewal process. A method is given for computing the moments of any order, as well as the conditional moments and moments of the local maxima and minima. Explicit formulas are given for the second moment in the asymmetric case and second and fourth moments in the symmetric case.