Constant Total Time Research Articles

High efficient preparation of low molecular weight galactomannan from Leucaena leucocephala galactomannan through the combination of hydrogen peroxide and oxalic acid

Researchers have always been interested in polysaccharide degradation because of the increased biological activity and usability following degradation. In this work, low molecular weight galactomannan (LMW-GM) was produced through the degradation of galactomannan by H2O2 and oxalic acid (OA). The optimal reaction conditions were found by conducting the response surface optimization experiment based on single-factor experiment and kinetics analysis. Under these conditions, the LMW-GM yield was 69.48 ± 1.02 %. Ultimately, an analysis of the degradation process revealed that OA attacked GM indiscriminately, and H2O2 has a stronger effect on the removal of branched chains while degrading GM. Hence, the degradation steps were rearranged as H2O2 was added 20 min before OA at a constant total time. The LMW-GM yield was successfully increased to 76.49 ± 1.27 %. The goal of this work is hopefully to give a theoretical foundation for the low-cost preparation and industrial production of the degradation of galactomannan.

Performing linear regression with responses calculated using Monte Carlo transport codes

In many of the complex systems modeled in the field of nuclear engineering, it is often useful to use linear regression-based analyses to analyze relationships between model parameters and responses of interests. In cases where the response of interest is calculated by a simulation which uses Monte Carlo methods, there will be some uncertainty in the responses. Further, the reduction of this uncertainty increases the time necessary to run each calculation. This paper presents some discussion on how the Monte Carlo error in the response of interest influences the error in computed linear regression coefficients. A mathematical justification is given that shows that when performing linear regression in these scenarios, the error in regression coefficients can be largely independent of the Monte Carlo error in each individual calculation. This condition is only true if the total number of calculations are scaled to have a constant total time, or amount of work, for all calculations. An application with a simple pin cell model is used to demonstrate these observations in a practical problem.

Predicted rates of merging neutron stars in galaxies

ABSTRACT We compute rates of merging neutron stars (MNS) in different galaxies, as well as the cosmic MNS rate in different cosmological scenarios. Our aim is to provide predictions of kilonova rates for future observations both at low and high redshift. In the adopted galaxy models, the production of r-process elements either by MNS or core-collapse supernovae is taken into account. To compute the MNS rates, we adopt either a constant total time delay for merging (10 Myr) or a distribution function of such delays. We conclude (i) the observed present time MNS rate in our Galaxy is well reproduced either with a constant time delay or a distribution function ∝t−1. (ii) The [Eu/Fe] versus [Fe/H] relation can be well reproduced with only MNS, if the time delay is short and constant. If a distribution function of delays is adopted, core-collapse supernovae are also required. (iii) The present time cosmic MNS rate can be well reproduced in several cosmological scenarios. (iv) Spiral galaxies are the major contributors to the cosmic MNS at all redshifts in hierarchical scenarios. In the pure luminosity evolution scenario, the spirals are the major contributors locally, whereas at high redshift ellipticals dominate. (v) The predicted cosmic MNS rate well agrees with the cosmic rate of short gamma-ray bursts, if the distribution function of delays is adopted in a cosmological hierarchical scenario observationally derived. (vi) Future observations of kilonovae in ellipticals will allow us to disentangle among constant or a distribution of time delays and among different cosmological scenarios.

スタティックストレッチングが腓腹筋筋腱複合体の筋力及びスティフネスに及ぼす影響の検討：異なるストレッチング時間と反復回数を用いた検討

Many previous studies have reported that static stretching (SS) may decrease muscle stiffness and compromise muscles’ ability to produce maximal strength. However, the effects of SS at different repetition durations and numbers within a constant total time remain unclear. Therefore, the purpose of this study was to examine whether SS for a constant total time (2 min) with different repetition durations and numbers (e.g., 60 s × 2 times, 30 s × 4 times, and 10 s × 12 times) produces different changes in muscle stiffness and strength. Fifteen healthy males (mean age: 23.3 ± 1.0 years) participated in this study. Muscle stiffness was measured during passive ankle dorsiflexion using dynamometer and ultrasonography. In addition, muscle strength of the plantar flexors was measured using a dynamometer at 0° of plantarflexion with the hip and knee joints fully extended. Muscle stiffness and strength were measured before and immediately after SS. Each experimental protocol was conducted in random order with at least a 1-week interval but no longer than a 2-week interval between testing sessions. The results showed that there were no significant interaction effects on muscle stiffness and strength. However, in all experimental protocols, muscle stiffness and strength immediately decreased after SS. In conclusion, SS for a constant total of 2 min decreases muscle stiffness and strength regardless of repetition durations and numbers of each individual SS.

Effect of steam curing cycles on strength and durability of SCC: A case study in precast concrete

Use of Self-Compacting Concrete (SCC) in pre-cast concrete plants is growing rapidly due to its benefits such as reduction in labor and equipment costs, increasing productivity, providing flexibility in filling highly reinforced sections and complex formworks, lowering the noise on job site and having superior surface quality. Also, considering the critical importance of “production time” in precast plants, accelerated curing is considered as an inevitable part of precast concrete elements production.In this study the effects of thirty-six different steam-curing regimes on the compressive strength and permeability of a self-compacting concrete mixture, used in precast concrete elements of Sadr elevated highway was investigated. Compressive strength measurements indicated that in a constant total time, increase in precuring period leads to lower immediate compressive strength. On the other hand, increase in treatment temperature and total cycle time (which means higher energy and time consumption) led to higher immediate compressive strength. Furthermore, durability tests results demonstrated that application of cycles with maximum temperature of 70°C imposes negative effect on durability properties of reference SCC, such as surface resistivity and capillary absorption. Finally, on the basis of three criteria (compressive strength, permeability and energy consumption by steam curing cycle), an optimum steam curing cycle was introduced and utilized in the precast concrete plant.

Hamstring flexibility increases the same with 3 or 9 repetitions of stretching held for a total time of 90 s

ObjectiveTo determine if stretching for a constant total time with differing repetition durations and number of repetitions over a 6-week period produced different changes in hamstring flexibility measured by knee extension range of motion (ROM). DesignRandomized Control Trial. SettingUniversity laboratory. Subjects34 volunteers, 18–25 years old with tight hamstrings as determined by a greater than 30° loss of knee extension with hip flexed to 90° participated in the study. Main outcome measuresChange in knee extension ROM was assessed in participants who were randomly assigned to a control, or to a stretching group of either 10 s for 9 repetitions or 30 s for 3 repetitions, for a total stretch time of 90 s. Each group stretched 6 days a week for 6 weeks. ResultsPre to post stretch comparison indicated both stretching groups were successful in increasing joint ROM (11.6 ± 5.25°–13.4 ± 5.36°) over the control (F = 19.77, p < 0.003). However, there was no significant difference between the stretching groups (p = 0.9). ConclusionStretching for 6 weeks for total of 90 s showed increased joint ROM regardless of the number of repetitions or the duration of each individual stretch.

Order Learning and Item Presentation Method

Summary Experiment 1 (N = 60) and Experiment 2 (N = 60) examined the learning of item and order information in serial learning (SL) with constant total time, under the study-test, anticipation, and modified anticipation methods with study (S) and test (T) events of an anticipation exposure operationally separated. Both acquisition and serial position effects based only on item learning differed little among the methods. However, both effects based on the combined learning of both item and order (ordered recall) were significantly superior with the two types of the anticipation method vis-à-vis the study-test method. The primacy effects occurred for all methods, but the recency effects were limited to the anticipation methods, with no tangible trace thereof for the study-test method. The latter serial position curve may pose difficulties for most extant theories, but this may be accounted for by interferences from intervening Ts, stronger than those of Ss in the retention interval. Order learning may be greater with the anticipation method than with the study-test method because of facilitating factors, uniquely present for the former, including (a) the external cue during the test phase, (b) responsegenerated effects during both study and test phases, and (c) immediate feedback. Spaced practice effects in SL were large under the study-test method, but small under the anticipation method.

L'hypothèse de la capacité limitée des processus de traitement de l'information. L'apprentissage distribué et le rappel libre

Summary The hypothesis of limitations on information processing capacity permits one to predict : a) that the recall will be a constant when the total time accorded to learning is itself a constant ; b) that this relationship will be produced within certain limits of fractionation of the total time as a resuit of the number of presentations. The purpose of this study is to verify if the recall tallies with these predictions when learning is distri-buted, that is, when the total constant time is mode up in variable proportions of presentation times and temporal intervals. In the first experiment, the time of presentation represents 25, 50, 75 and 100 % (relations TE/TT) of the total time of the learning process of a series of 8 consonnant trigrams. This variable does not constitute a source of significant variation, in conformance with what the hypothesis of limited capacity leads one to expect. On the other hand, when the distributed learning process is realized in four presentations instead of one, a significant improvement is noted. A second experiment demonstrates that this improvement is not more significant under a massed learning situation. The discussion leads to the conclusion that within a constant total time, learning distributed over one presentation is more difficult than learning distributed over four presentations : in this case, the hypothesis of limited capacity predicts that the recall constants will not have the same importance in the two situations. The results obtained from the first experiment and notably, the absence of interaction between the number of presentations and the TE/TT relation, are in accordance with this prediction.

A steering law satisfying the constant total time of flight constraint.

The problem considered in this paper is that of steering a rocket vehicle so as to achieve a ballistic trajectory that arrives at a specified position at a specified time. An exoatmospheric steering equation, which is only a function of the current state of the booster, is derived from the dynamic equation of velocity-to-be-gained, and its accuracy is shown to be relatively insensitive to variations in booster characteristics and to the coordinate system with respect to which steering is done. Moreover, steering can easily be done so as to satisfy such additional constraints and boundary conditions as near optimality with respect to fuel consumption for nonthrottleable, continuous-burn engines, low turning rates, and a roll-axis attitude constraint at thrust termination. Simulation results show that since the steering equation is sufficiently accurate, no trajectory-de pendent preflight calculations need be done when a simple in-flight choice of certain constants is made.