Change In Strength Distribution Research Articles

β− decay of Tz=+112 isotopes Al37 and Si39 : Understanding Gamow-Teller strength distribution in neutron-rich nuclei

${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of ${T}_{z}=+\frac{11}{2}$ nuclei $^{37}\mathrm{Al}$ and $^{39}\mathrm{Si}$ was studied to obtain information about excited states in the daughter and granddaughter nuclei. New information on excited states has been obtained for $^{37,39}\mathrm{P}$, whereas level schemes for $^{37}\mathrm{Si}$ and $^{37,39}\mathrm{S}$ were confirmed and expanded on as compared to the most recent investigations. For the nuclei studied, the valence proton and neutron occupy different major shells with opposite parities, hence, the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay preferentially and primarily populates core-excited $1p1h$ intruder states with a parity opposite to the ground state of the daughter nucleus. These low-lying intruder states shed light on the $N=20$ shell gap and its evolution with neutron number. The ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of very neutron-rich nuclei also illustrates how the Gamow-Teller (GT) strength distribution changes with neutron excess. Comparing ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{37,39}\mathrm{Si}$ presented here with $^{38,40}\mathrm{Si}$ from a previous study, we clearly see an even-odd effect in the GT strength distribution with the decay from even-even nuclei showing strong low-lying strength whereas for the odd $A$ being very fragmented. Configuration interaction shell-model calculations with the state-of-art SDPFSDG-MU effective interaction were performed to understand the structure of the $1p1h$ states and explore the GT strength distribution.

Unthrottled Flows with Complex Background Waves in Curved Isolators

The unthrottled flows in curved isolators are studied experimentally and numerically. Wind-tunnel tests are conducted at a freestream Mach number of 4.92. The internal flowfield is visualized and measured. Large-scale separation bubbles in the inlet are observed, and the downstream duct curvature is found to be able to decrease the separation bubble size via lowering the local pressure downstream of the separation bubble. Complex background waves appear in these isolators, and the increase of duct curvature tends to intensify the reflected shocks. Particularly, the strength distributions along the shock direction of the background shocks behave differently under the influence of duct curvature. For the right-running shocks, the strength distribution changes from a descending trend to an ascending trend with the increase of duct curvature, whereas the strength of left-running shocks always descends with an increasing speed. The strength of background shocks is particularly related to the left-running expansion waves, which get intensified and become the dominant expansion waves in the isolators as the duct curvature increases. The schlieren images indicate a significant transverse density gradient and pressure gradient in the curved isolators. The wall pressure distributions further show that the radial pressure gradient in small curvature isolators switches between centripetal and centrifugal repeatedly; whereas it remains centripetal consistently in large curvature isolators, which is also determined by the left-running expansion waves. As a result, the secondary flow gets stronger as the duct curvature increases, resulting in a larger low-momentum flow region near the bottom wall. In general, the compression capability of the isolator gets attenuated with the increase of the duct curvature.

Simulated Total Wrist Fusion and its Influence on Hand Grip Function

Wrist fusion is still a common treatment for patients with advanced stage arthritis. Since patients are often intimidated by the functional limitations, we intended to evaluate the influence of the lack of wrist motion in different positions on the dynamic grip function and the grip strength of the hand. We simulated wrist fusion in 20° extension and 20° flexion and evaluated the following grip types: fist closure, 2 different power grips, pinch grip and precision grip. A TUB sensor glove was used, which allowed us to dynamically record the range of motion (ROM) of the finger joints as well as grip strength. Nineteen healthy subjects participated and all types of grips were performed using a standardised protocol with and without simulated wrist fusion. Lack of wrist motion in 20° extension had no relevant effect on the fingers' ROM, grip speed or strength. Simulated fusion in 20° flexion also had no influence on ROM or grip speed, rejecting our hypothesis that a tenodesis effect of the extensors in flexion would decrease ROM in the finger joints and grip speed. However, we were able to show a significant decrease of grip strength in flexion compared with extension or healthy wrists. The decrease averaged between 23 and 42% of healthy values, depending on the grip type. There was no change in strength distribution among the fingers. We didn't find any impact of lack of wrist motion on finger movement during forceful hand grip at normal speed. However, a significant loss of grip strength in flexed position of the wrist joint should be considered in patients with an indication for bilateral wrist fusion.

A Mathematical Approach Using Thermoporoelastic Model for Reamer While Drilling Efficiency Analysis and Closeness

The main objective of this research is to predict the proper bit/reamer size ratio based on the rock strength weakening zone around the wellbore. Nowadays, the Reaming While Drilling (RWD) technology is gaining more and more acceptance in the petroleum industry by means of reducing drilling time and Non-Productive Time (NPT), which results in significant cost saving. The importance of this research is analyzing scenarios in which RWD would add benefit to the operation, given that the reaming process is often fraught with much inefficiency. Thus, through the process of estimation optimum reamer/size ratio, by coupling three key parameters in geo mechanics: thermo-poro-elastic, a model of rock strength is developed to analytically assess how rock strength distribution changes around the wellbores and in particular below the reamer in drilling environments. An analytical model of thermoporoelastic is used with published data (for rock properties usage purposes) in order to develop a model of rock strength below the reamer to show in how far some specific rock could be a good candidate for reamer usage. This in turn allows finding proper candidates for effective RWD applications and also can assist to determine the maximum reamer/bit size ratio for certain rock characteristics in order to optimize the drilling system. From the analysis performed, which was carried considering two different groups in terms of formation permeability, it is be conclusive that for low-permeable formation the size of reamer is function of exposure time of wellbore after making pilot hole while the reamer size for enlargement operation through the permeable formation due to fast diffusion rate is not a time dependent parameter.

Monte Carlo Simulation of the Torsional Strength due to Concrete Compression of Reinforced Concrete Element

The aim of the work was to assess the safety margin of reinforced concrete element of rectangular cross-sections subjected to torsion. In the performed analyses two models of torsional resistance based on concrete compressive strength was taken into account. Assessment was performed with use of Monte Carlo method. Utilized models of shear resistance were taken from formerly used Polish standards: PN-84/B-03264, PN-B-03264:2002 and the actual Polish standard EN-1992-1-1:2004. From the same standards necessary assumptions related with the models were taken. The safety margin and influence of the differences in assumptions on the obtained results were analyzed. The selected models was also evaluated in terms of their “sensitivity” to changes of basic parameters of distribution functions of selected random variables. Results showed that average torsional resistance differs of about 50% times depending of assumed model. The reliability level, measured with the partial reliability exponent ΔR, differs of 10% if different models are concerned but the differences are much higher (up to 5 times, when the standard deviation of concrete compressive strength distribution changes).

Modification of the performance of WO3-ZrO2 catalysts by metal addition in hydrocarbon reactions

A study of the different hydrocarbon reactions over Ni doped WO3-ZrO2 catalysts was performed. Ni was found as NiO at low Ni concentration while at high Ni concentrations a small fraction was present as a metal. For both cases, Ni strongly modified total acidity and concentration of strong acid sites. In the cyclohexane dehydrogenation reaction, Ni addition promotes both benzene and methyl cyclopentane production. The hydroconversion activity (n-butane and n-octane) increases with the augment of total acidity produced by Ni. The selectivity to reaction products is modified according to the acid strength distribution changes produced by Ni addition.

The influence of the symmetry energy on the giant monopole resonance of neutron-rich nuclei analyzed in Thomas–Fermi theory

We analyze the influence of the density dependence of the symmetry energy on the average excitation energy of the isoscalar giant monopole resonance (GMR) in stable and exotic neutron-rich nuclei by applying the relativistic extended Thomas–Fermi method in scaling and constrained calculations. For the effective nuclear interaction, we employ the relativistic mean field model supplemented by an isoscalar–isovector meson coupling that allows one to modify the density dependence of the symmetry energy without compromising the success of the model for binding energies and charge radii. The semiclassical estimates of the average energy of the GMR are known to be in good agreement with the results obtained in full RPA calculations. The present analysis is performed along the Pb and Zr isotopic chains. In the scaling calculations, the excitation energy is larger when the symmetry energy is softer. The same happens in the constrained calculations for nuclei with small and moderate neutron excess. However, for nuclei of large isospin the constrained excitation energy becomes smaller in models having a soft symmetry energy. This effect is mainly due to the presence of loosely bound outer neutrons in these isotopes. A sharp increase of the estimated width of the resonance is found in largely neutron-rich isotopes, even for heavy nuclei, which is enhanced when the symmetry energy of the model is soft. The results indicate that at large neutron numbers the structure of the low-energy region of the GMR strength distribution changes considerably with the density dependence of the nuclear symmetry energy, which may be worthy of further characterization in RPA calculations of the response function.

Delayed Fatigue of Hydroxy- and Fluorhydroxyapatite Ceramics in Simulated Body Fluid

Ultrafine hydroxyapatite (HA) and fluorhydroxyapatite (FHA) powders were synthesized and dense bioceramic samples were fabricated thereof. The samples were treepoint bend tested in different environments, i.e. in ambient air, distilled water and simulated human saliva, in the wide deformation rate range. Weibull’ statistics test was performed under standard testing conditions but in different media. The stress velocity exponent was evaluated from the dynamic fatigue testing data. The mean strength is shown to decrease when both ceramics are exposed to water or to simulated saliva. HA ceramics is more susceptible to the environment compared to FHA ceramics, due to the later is less subjected to the stress corrosion. Fracture surface observations revealed the crack propagation is of mixed trans- and intergranular mode. Strength distribution changes from uni-modal in air environment to bimodal in harsh conditions of water and saliva, indicating slow increment of flaw size in ceramics. Crack velocity exponent values correspond to transient region from dissociative chemisorption to ion solvation mechanisms of stress corrosion in both HA and FHA ceramics. Generally, FHA ceramics is considered to be much more reliable for application in bone defects replacement or dental reconstruction.

突合せおよび重ね合せ接着継手の強度分布特性

Since adhesive bonded joints generally possess a considerable scatter in their strength, elucidation of the strength distribuion properties of these joints is important for better utilization of these joints.In this study, to investigate the change in strength distribution of adhesive joints due to the size effect, tensile and tensile shear strengths of adhesive bonded butt and lap joints were statistically evaluated. The probability of failure was calculated for butt joints with a different diameter and for lap joints with a different lap length. Each data set was then plotted using normal, Weibull and doubly exponential functions. Furthermore, the effect of adhesive area on the mean and coefficient of variation of the joint strength was investigated. First, the strength distributions of butt and lap joints were simulated by the weakest link model based on the strength distribution of the butt joint having the smallest diameter and stress distribution of the adhesive layer obtained by FEM analysis. Then, the mean and coefficient of variation of these joints were compared with the simulation results. The main results obtained are summarized as follows;(1) The strength distribution of adhesive bonded butt joint was nearly approximated by a normal distribution. However, for lap joint the strength distribution was fitted for an extreme distribution rather than a normal ditribution.(2) The relationship between the mean strength and adhesive area plotted on a logarithmic graph paper showed experimental curves of butt and lap joints with a convex shape. However, the mean strength of the butt joint simulated by the weakest link model decreased linearly with increasing adhesive area, while the shape of the simulated curve of the lap joint was concave.(3) The coefficient of variation of the butt joint was independent of the adhesive area, as predicted from the model, whereas the coefficient of variation of the lap joint decreased with increasing adhesive area contrary to the prediction of the model. This discrepacy may have been caused by a variation in shear strength due to a measurement error in the lap length.

計算機実験によるセラミックスの強度分布と寸法効果 続報： 強度に下限値が存在する場合

Following the previous report, the strength distribution of ceramics was simulated by the Monte-Carlo method for the case in which the lower limit existed in the strength of ceramics. In this study, the tensile strength, 3-point and 4-point bending strengths of specimens of four different sizes were calculated, by using the model specimens with a number of penny-shaped inner cracks. In order to investigate the change of strength distribution of ceramics due to the size effect, the strength obtained was plotted on the Weibull probability paper. It was found that the shape of strength distribution was convex for the specimens of large effective volume, while it was concave for those of small effective volume. The strength distribution function for this model was also expressed and compared with the simulation results. As a result, both distributions showed good agreement in the range of fracture probability greater than a few percents.Furthermore, the relation between the mean strength and the effective volume was discussed. As the strength of the specimens varied between the lower and upper limits, its relation was represented by a inverse S-shape curve on the logarithmic graph paper.

Shape fluctuations and damping of the giant dipole resonance in a hot spherical nucleus

The strength functions for the giant dipole resonance in heated 90Zr are calculated within the framework of the finite temperature quasiparticle-phonon nuclear model. For the strength functions a Lorentzian factor of width dependent upon state energies and temperature T is adopted. Shape fluctuations are taken into account at the excitation energy corresponding to T=1.5 MeV and I=7.5 h(cross). While the effect of the Landau zero sound damping on the broadening of the dipole strength distribution changes weakly with T, shape fluctuations increase remarkably the width of the giant dipole resonance. They influence profoundly the structural modifications of the dipole strength distribution at finite temperature.

ガラス繊維の強度 ＩＩ ガラス繊維の強度分布に及ぼす試験片長の影響について

The change in strength distribution of glass fibers with varying specimen length was investigated. When the fiber length decreased, the mean value of fracture stress increased remarkably, but the coefficient of variation decreased.The effect of specimen length on the strength distribution was analysed by using the weakest link model. The strength distribution of links was assumed to be exppressible by Weibull distribution function. In this case, the shape parameter (corresponding to the coefficient of variation) was found to include the variation in sectional area of glass fibers when obtained from the fracture load data. The correlation coefficient for the fracture load and the sectional area was about unity and the coefficient of variation in fracture stress of glass fibers was 15-20%, which is lower than those estimated previously by several researchers.

Static Fatigue Limit with Particular Reference to Glass

After a review of the literature on the static fatigue limit, it was concluded that the normal method for its determination, using time‐to‐rupture data, is inadequate. There are very few experimental demonstrations of the existence of a true fatigue limit, and it is difficult to measure its value with any statistical confidence. An alternative experimental approach is suggested which is based on measuring the change in strength distribution of a representative sample after a high‐temperature anneal under a fixed tensile stress. This stress weakens weak specimens in the as‐received distribution, whereas strong specimens gain in strength. Those specimens whose strength remains constant demonstrate the existence of a fatigue limit and can be used to calculate a numerical value. The results are analyzed on the basis of the Charles‐Hillig stress corrosion theory, which has been slightly modified to facilitate the examination of the parameters associated with the fatigue limit. This analysis relates the static fatigue limit to the effective surface energy appropriate to the fatigue mechanism, i.e. corrosion caused by water vapor. Some implications of the modified model are discussed.