Conservation Laws and Material Momentum in Thermoelasticity

1982 ◽  
Vol 49 (4) ◽  
pp. 710-714 ◽  
Author(s):  
G. Francfort ◽  
A. Golebiewska Herrmann
Keyword(s):  
Conservation Laws ◽  
Classical Mechanics ◽  
Scalar Function ◽  
Momentum Equation ◽  
Lagrangian Function ◽  
Time Interval ◽  
Material Particle ◽  
Material Conservation ◽  
Action Variables ◽  
Over Time

The main goal of this paper is to construct a Lagrangian function such that not only the well-known equations of thermoelasticity, but also material conservation laws can be derived. As action variables, the position x of a material particle and a scalar function η related to temperature are used. The material momentum for thermoelasticity is derived. Here, by contrast to the purely elastic case, the material momentum depends on a time interval rather than on an instant of time. The balance of material momentum is integrated over time to produce a relation reminiscent of the impulse-momentum equation in classical mechanics.

scholarly journals Significant increase in quantity and quality of knee arthroplasty related research in KSSTA over the past 15 years

2021 ◽  
Author(s):  
Stephanie Kirschbaum ◽  
Thilo Kakzhad ◽  
Fabian Granrath ◽  
Andrzej Jasina ◽  
Jakub Oronowicz ◽  
...  
Keyword(s):  
Knee Arthroplasty ◽  
Special Topic ◽  
Computer Assisted ◽  
Time Interval ◽  
Search Term ◽  
Level Of Evidence ◽  
The Past ◽  
Patient Reported ◽  
Over Time ◽  
Number Of Authors

Abstract Purpose This study aimed to evaluate both publication and authorship characteristics in Knee Surgery, Sports Traumatology, Arthroscopy journal (KSSTA) regarding knee arthroplasty over the past 15 years. Methods PubMed was searched for articles published in KSSTA between January 1, 2006, and December 31st, 2020, utilising the search term ‘knee arthroplasty’. 1288 articles met the inclusion criteria. The articles were evaluated using the following criteria: type of article, type of study, main topic and special topic, use of patient-reported outcome scores, number of references and citations, level of evidence (LOE), number of authors, gender of the first author and continent of origin. Three time intervals were compared: 2006–2010, 2011–2015 and 2016–2020. Results Between 2016 and 2020, publications peaked at 670 articles (52%) compared with 465 (36%) published between 2011 and 2016 and 153 articles (12%) between 2006 and 2010. While percentage of reviews (2006–2010: 0% vs. 2011–2015: 5% vs. 2016–2020: 5%) and meta-analyses (1% vs. 6% vs. 5%) increased, fewer case reports were published (13% vs. 3% vs. 1%) (p < 0.001). Interest in navigation and computer-assisted surgery decreased, whereas interest in perioperative management, robotic and individualized surgery increased over time (p < 0.001). There was an increasing number of references [26 (2–73) vs. 30 (2–158) vs. 31 (1–143), p < 0.001] while number of citations decreased [30 (0–188) vs. 22 (0–264) vs. 6 (0–106), p < 0.001]. LOE showed no significant changes (p = 0.439). The number of authors increased between each time interval (p < 0.001), while the percentage of female authors was comparable between first and last interval (p = 0.252). Europe published significantly fewer articles over time (56% vs. 47% vs. 52%), whereas the number of articles from Asia increased (35% vs. 45% vs. 37%, p = 0.005). Conclusion Increasing interest in the field of knee arthroplasty-related surgery arose within the last 15 years in KSSTA. The investigated topics showed a significant trend towards the latest techniques at each time interval. With rising number of authors, the part of female first authors also increased—but not significantly. Furthermore, publishing characteristics showed an increasing number of publications from Asia and a slightly decreasing number in Europe. Level of evidence IV.

scholarly journals Coupling Disease-Progress-Curve and Time-of-Infection Functions for Predicting Yield Loss of Crops

2000 ◽  
Vol 90 (8) ◽  
pp. 788-800 ◽  
Author(s):  
L. V. Madden ◽  
G. Hughes ◽  
M. E. Irwin
Keyword(s):  
Yield Loss ◽  
Numerical Solutions ◽  
Disease Incidence ◽  
Time Interval ◽  
Short Time Interval ◽  
Time Duration ◽  
Plant Yield ◽  
Disease Progress ◽  
Time Of Infection ◽  
Over Time

A general approach was developed to predict the yield loss of crops in relation to infection by systemic diseases. The approach was based on two premises: (i) disease incidence in a population of plants over time can be described by a nonlinear disease progress model, such as the logistic or monomolecular; and (ii) yield of a plant is a function of time of infection (t) that can be represented by the (negative) exponential or similar model (ζ(t)). Yield loss of a population of plants on a proportional scale (L) can be written as the product of the proportion of the plant population newly infected during a very short time interval (X′(t)dt) and ζ(t), integrated over the time duration of the epidemic. L in the model can be expressed in relation to directly interpretable parameters: maximum per-plant yield loss (α, typically occurring at t = 0); the decline in per-plant loss as time of infection is delayed (γ; units of time-1); and the parameters that characterize disease progress over time, namely, initial disease incidence (X0), rate of disease increase (r; units of time-1), and maximum (or asymptotic) value of disease incidence (K). Based on the model formulation, L ranges from αX0 to αK and increases with increasing X0, r, K, α, and γ-1. The exact effects of these parameters on L were determined with numerical solutions of the model. The model was expanded to predict L when there was spatial heterogeneity in disease incidence among sites within a field and when maximum per-plant yield loss occurred at a time other than the beginning of the epidemic (t > 0). However, the latter two situations had a major impact on L only at high values of r. The modeling approach was demonstrated by analyzing data on soybean yield loss in relation to infection by Soybean mosaic virus, a member of the genus Potyvirus. Based on model solutions, strategies to reduce or minimize yield losses from a given disease can be evaluated.

scholarly journals Hubungan Perilaku Perdagangan Investor Dengan Volume Perdagangan Di Bursa Efek Indonesia

2009 ◽  
Vol 2 (1) ◽  
Author(s):  
Ghazali Syamni
Keyword(s):  
Trading Volume ◽  
Stock Exchange ◽  
Time Interval ◽  
Time Intervals ◽  
Using Data ◽  
Changes Over Time ◽  
Relationship Of ◽  
The Relationship ◽  
Order Pattern ◽  
Over Time

This paper examines the relationship of behavior trading investor using data detailed transaction history-corporate edition demand and order history in Indonesia Stock Exchange during period of March, April and May 2005. Peculiarly, behavior placing of investor order at trading volume. The result of this paper indicates that trading volume order pattern to have pattern U shape. The pattern happened that investors have strong desires to places order at the opening and close of compared to in trading periods. While the largest orders are of market at the opening indicates that investor is more conservatively when opening, where many orders when opening has not happened transaction to match. In placing order both of investor does similar strategy. By definition, informed investors’ orders more large than uninformed investors. If comparison of order examined hence both investors behavior relatively changes over time. But, statistically shows there is not ratio significant. This implies behavior trading of informed investors and uninformed investors stable relative over time. The result from regression analysis indicates that informed investors to correlate at trading volume in all time intervals, but not all uninformed investors correlates in every time interval. This imply investor order inform is more can explain trading volume pattern compared to uninformed investor order in Indonesia Stock Exchange. Finally, result of regression also finds that order status match has greater role determines trading volume pattern intraday especially informed buy match and informed sale match. While amend, open and withdraw unable to have role to determine intraday trading volume pattern.

Active Optimum Control of Orthotropic Plates Using Piezoelectric Stiffeners

1993 ◽  
Author(s):  
Victor Birman ◽  
Sarp Adali
Keyword(s):  
Time Interval ◽  
Short Time Interval ◽  
Bending Moments ◽  
Optimum Control ◽  
Orthotropic Plates ◽  
Time Intervals ◽  
Control Forces ◽  
Short Time ◽  
Alternating Voltage ◽  
Over Time

Abstract Active control of orthotropic plates subjected to an impulse loading is considered. The dynamic response is minimized using in-plane forces or bending moments induced by piezoelectric stiffeners bonded to the opposite surfaces of the plate and placed symmetrically with respect to the middle plane. The control forces and moments are activated by a piece-wise constant alternating voltage with varying switch-over time intervals. The magnitude of voltage is bounded while the switch-over time intervals are constantly adjusted to achieve an optimum control. Numerical examples presented in the paper demonstrate the effectiveness of the method and the possibility of reducing the vibrations to very small amplitudes within a short time interval which is in the order of a second.

Fibrinolysis after an Elective Caesarean Section without Postpartum Hemorrhage: Pilot Study for Reference Values from the Simultaneous Thrombin and Plasmin Generation Assays

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Ducloy-Bouthors A S ◽  
◽  
Lassalle F ◽  
Gilliot S ◽  
Kyheng M ◽  
...  
Keyword(s):  
Blood Loss ◽  
Postpartum Hemorrhage ◽  
Mixed Model ◽  
Elective Caesarean Section ◽  
Individual Variability ◽  
Elective Cesarean Section ◽  
Time Interval ◽  
Simultaneous Generation ◽  
D Dimer ◽  
Over Time

ntroduction: Postpartum Hemorrhage (PPH)-induced coagulopathy should be better explored. An innovative Simultaneous Generation of Thrombin and Plasmin Assay (SGTPA) was developed. Objective: To establish postpartum SGTPA references. Methods: Blood samples collected immediately after delivery (T0) and then 30, 60, 120 and 360 minutes later. Thrombin Generation (TG) and Plasmin Generation (PG) changes over time analyzed in 51 women after elective cesarean section without PPH and compared with Non-Pregnant (NP) women. The SGTPA variables’ correlations with fibrinogen levels, D-dimer levels and physiological blood loss were assessed in a mixed model. Results: 37 women were included. TG and PG were higher in the postpartum group than in the NP group. TG increased early and then remained stable (baseline TG Area Under the Curve (AUC) [95% Confidence Interval (CI)] = 41037 [36850-43537] nM.min). The fibrinogen level varied over time, along with TG (p<0.001). Plasmin generation increased from 30 to 120 minutes (AUC [95% CI]: 2104 [1437; 2613] nM.min), along with a change in the D-dimer level (p=0.018). The time to the plasmin peak and the time interval between the TG and PG peaks showed the greatest inter-individual variability at T0 and were associated with physiological volumes of blood loss during cesarean delivery. Conclusion: Reference SGTPA postpartum range was established. The SGTPA appears to be valuable for measuring TG and PG. TG and coagulation activation increased immediately after delivery, whereas PG and fibrinolysis increased later.

scholarly journals Roughening in Nonlinear Surface Growth Model

2020 ◽  
Vol 10 (4) ◽  
pp. 1422 ◽  
Author(s):  
Gabriella Bognár
Keyword(s):  
Molecular Beam Epitaxy ◽  
Surface Morphology ◽  
Molecular Beam ◽  
Film Growth ◽  
Nonlinear Differential Equations ◽  
Numerical Approach ◽  
Surface Roughening ◽  
Time Interval ◽  
Nonlinear Surface ◽  
Over Time

The aim of this paper is to examine the coarsening process in the evolution of the surface morphology during molecular beam epitaxy (MBE). A numerical approach for modeling the evolution of surface roughening in film growth by MBE is proposed. The model is based on the nonlinear differential equations by Kuramoto–Sivashinsky (KS) namely, KS and CKS (conserved KS). In particular, we propose a “combined version” of KS and CKS equations, which is solved as a function of a parameter r for the 1 + 1 dimensional case. The computation provides film height as a function of space and time. From this quantity the change of the width of the film over time has numerically been studied as a function of r. The main result of the research is that the surface width is exponentially increasing with increasing time and the change in surface width for smaller r values is significantly greater over longer time interval.

scholarly journals Exact Averaging of Atmospheric State and Flow Variables

2012 ◽  
Vol 69 (5) ◽  
pp. 1750-1757 ◽  
Author(s):  
Andrew S. Kowalski
Keyword(s):  
Conservation Laws ◽  
Gas Phase ◽  
Air Temperature ◽  
Classical Mechanics ◽  
Mixing Ratio ◽  
Momentum Exchange ◽  
Weighting Factors ◽  
Eddy Transport ◽  
Atmospheric State ◽  
Flow Variables

Abstract A new set of averaging rules is put forward that exactly determines the means of air temperature, mixing ratio, and velocity by incorporating weighting factors in accordance with physical conservation laws. For the temperature and velocity, respectively, the means calculated according to these rules are shown to be in accordance with the gas law and the most fundamental definition from classical mechanics. By contrast, those reckoned according to traditional arithmetic averaging rules are found to be incorrect. For studies of eddy transport, and micrometeorology in particular, such imprecisely determined averages of state and flow variables bias the perturbation variables over the entire averaging domain and thereby skew estimates of mass, heat, and momentum exchange unless appropriate adjustments (such as density corrections) are applied. The exact calculation of gas-phase averages amends this problem and is equally applicable to planetary-, synoptic-, and mesoscale averaging, as well as to climatology.

Material conservation laws in higher-order shell theories

1985 ◽  
Vol 21 (10) ◽  
pp. 1035-1045 ◽  
Author(s):  
R. Kienzler ◽  
A. Golebiewska-Herrmann
Keyword(s):  
Conservation Laws ◽  
Higher Order ◽  
Material Conservation

The Imposition of Empirical Acceptability Conditions on Sequences of Single Measurements

1969 ◽  
Vol 24 (1) ◽  
pp. 86-96 ◽  
Author(s):  
Paul A. Benioff
Keyword(s):  
Quantum Mechanics ◽  
Classical Mechanics ◽  
Physical Principle ◽  
Small Time ◽  
Time Interval ◽  
Single Measurement ◽  
Time Intervals ◽  
Regression Problem ◽  
Expectation Value ◽  
Almost All

AbstractHere, some difficulties resulting from the application of any empirical acceptability conditions on sequences of single measurements are investigated. In particular, the often used acceptability requirement that each single measurement be made under the "same conditions" is discussed. In quantum mechanics, this means that each single measurement is made of the same physical quantity on a system in a ensemble of identically prepared systems. One of the resultant difficulties is that such an application leads to an infinite regression of sequences of single measurements. That is, it does not account for the fact that an observer must start the process of measurement or knowledge acquisition. Furthermore, it is seen that there are some basic sequences of single measurements for which an observer can not possibly know at the outset that the "same condition" requirements are satisfied. These include those measurements by which the homogeneity of space-time is tested. The possible relevance of these difficulties to physics is shown by first considering two possi­bilities of avoiding these difficulties. One is that the "same condition" requirements can be given the weaker interpretation that there be no physical principle forbidding an observer from knowing in terms of limit empirical means, that they are satisfied at the outset of any sequence. This gets rid of the infinite regression problem as it does not mean that an observer must know in fact that these requirements are satisfied. The other possibility is that if physics does not forbid one in principle from measuring an expectation value in an arbitrarily small time interval then both the basic sequence as well as those by which one knows the "same" requirements are satisfied can be relegated to arbitrarily small time intervals. As far as physics is concerned, then the epistemological difficulties while existing in these small intervals, do not exist for other times, or almost all time. It is then shown that quantum mechanics, as distinct from classical mechanics, and the special relativity require that an infinite time interval is necessary to measure, as a limit mean, any expectation value. Thus physics denies both the above possibilities as it forbids an observer from knowing even in principle, by any finite time that the "same" requirements are satisfied. Also, physics forbids the relegation of the epistemological problems to arbitrarily small time intervals.

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