Fluctuation In Strength Research Articles

Effects of the concentrated NH4NO3 solution on mechanical properties and structure of the fly ash based geopolymers

Abstract The geopolymers based on fly ash were exposed to the concentrated (6 M) NH4NO3 solution for 540 days. The highest compressive strength decrease occurred in the initial 28 days testing period. Study of the effects of the NH4NO3 solution on the geopolymer structure indicated leaching of alkali and alkaline earth cations and breaking of –Si–O–Al– bonds in aluminosilicate gel. The reduction of compressive strength of the geopolymers was associated with the structural defects in the aluminosilicate gel created by breaking of –Si–O–Al– bonds. Subsequent fluctuation in compressive strength was a result of the structural defects reparation by silicon.

Effect of weld tip geometry on ultrasonic welding of A6061 aluminium alloy

The authors ultrasonically welded A6061 aluminium alloy sheet using two types of weld tips with different contact face geometries, and investigated the effect of the weld tip on the performance and interface structure of the welds. One type of tip has a cylindrical contact face without knurl, which is called a C-tip in this study. The other type of tip has a flat contact face with knurl, which is a called K-tip in this study. The following main results were obtained. The strength of the joints welded using the C-tip was higher than that welded using the K-tip and the fluctuation in joint strength with the C-tip was smaller. The C-tip could stably produce the higher strength joint. Using the K-tip, the knurl indentations were made on the workpiece surface due to the pyramidal projections on the weld tip, and the indentation size expanded with welding time, resulting in the deterioration of the joint property. On the other hand, the indentation made on a workpiece surface by using the C-tip showed a distinctive shape like an ellipse, elongated perpendicular to the ultrasonic vibration, and the indentation grew with welding time. Using the K-tip, unbonded regions remained at the weld interface due to the concavity on the weld tip face. In the cross-sectional structure parallel to the workpiece width of the joint welded using the C-type tip, a distinctive feature was observed that the faying surface of the anvil workpiece was mixed with that of the sonotrode workpiece by intense plastic deformation and a horn-like protuberance intruding into the sonotrode workpiece was formed at the periphery of the welded area.

Dynamics of 2-D one electron quantum dots in time-dependent magnetic field: Influence of size

We explore the dynamics of harmonically confined single electron quantum dots as a function of dot size under time-dependent magnetic field. The system of interest is a 2-D system in the presence of a perpendicular magnetic field. We show that for given strengths of the confinement potential and effective mass; periodic, as well as exponential variation in the strength of the magnetic field could invite interesting features in the dynamics of the system. Also, the pattern of time evolution of eigenstates of the unperturbed system reveals significant size-dependence. The fluctuation in the magnetic field strength from its initial value is found to modulate the dynamical aspects in a prominent way.

Ａ６０６１アルミニウム合金の超音波接合における接合チップ形状の効果

Authors ultrasonically welded A6061 aluminum alloy sheet using two types of weld tips with the different contact face geometry, and investigated the effect of the weld tip on the performance and interface structure of the welds. One type of tip has a cylindrical contact face without knurl, which is called C-tip in this study. The other type of tip has flat contact face with knurl, which is called K-tip in this study. The following main results were obtained.The strength of the joints welded using C-tip was higher than that welded using K-tip and the fluctuation in joint strength with C-tip was smaller. The C-tip could stably produce the higher strength joint. Using K-tip, the knurl indentations were made on the workpiece surface due to the pyramidal projections on the weld tip, and the indentation size expanded with welding time, resulted in the deterioration of the joint property. On the other hand, the indentation made on a workpiece surface by using C-tip showed a distinctive shape like an ellipse elongated perpendicular to the ultrasonic vibration, and the indentation grew with welding time.Using K-tip, unbonded regions remained at the weld interface due to the concave on the weld tip face. In the cross-sectional structure parallel to the workpiece width of the joint welded using C-type of tip, the distinctive feature was observed that the faying surface of the anvil workpiece was mixed with that of the sonotrode workpiece by intense plastic deformation and a horn-like protuberance intruding into the sonotrode workpiece was formed at the periphery of the welded area.

A Model for the Fragility of Metallic Glass Forming Liquids

An expression for the temperature dependence of the viscosity and fragility is derived based on a simple model of the melt. According to the model, the fragility is determined by the relaxation of structural units that form the melt, and is described in terms of the bond strength, coordination number, and their fluctuations of the structural units. It is shown that the fragility of some metallic glass forming liquids such as Pd40Ni40P20 ,L a 55Al25Ni20 and Zr65Al10Ni10Cu15 are quite well reproduced by the model. The application of the theory to La55Al25Ni20 has revealed that the fluctuation in the bond strength between the structural units is about 6% and that the viscous flow occurs when the bonds in about 8 adjoining structural units are broken. [doi:10.2320/matertrans.MJ200737]

Homogenous alumina tube with controlled pore morphology

Porous alumina tubes with homogenous microstructures were prepared from commercial alumina and polymethylmethacrylate (PMMA) powders with two kinds of particle sizes using a centrifugal molding technology. PMMA powders were used as the pore-forming agent and the proportion of fine to coarse particles was adjusted to control the pore morphology of the alumina tubes. The open porosity and air permeability was optimized with respect to the proportion of PMMA powders. The fracture strength decreased with increasing porosity and was insensitive to the proportion of fine to coarse PMMA powders despite the changing pore morphology. Analysis of the Weibull statistics showed that specimens with higher porosity exhibit a narrower scatter in fracture strength. A 50:50 mixture (v/v) of fine and coarse PMMA particles showed the lowest fluctuation in fracture strength. The present study paves the way to more reliable material design using porous materials.

Miocene climate change recorded in the chemical and isotopic (Pb, Nd, Hf) signature of Southern Ocean sediments

The Middle Miocene transition from carbonate to biosilica sedimentation at DSDP site 266 (Australian‐Antarctic basin) reflects a global transition toward a colder climate. The 143Nd/144Nd, 176Hf/177Hf, and Al/Ti of bulk sediments display systematic, coupled variations through time, which have been attributed to a change of the detrital source. This change could correspond to a reduction of input from the Antarctic continent, an increase of input from the Kerguelen volcanic province, or both. Mixing models based on Nd isotopes and Al/Ti suggest a 30–40% reduction of Antarctic input and an equivalent increase of Kerguelen input during the Miocene. Reduction of Antarctic input may result from the formation of a stable East Antarctic ice sheet. Consistently, Pb isotopes and trace element systematics suggest a change of weathering style during the Miocene, with an increase in physical weathering, or a reduction of chemical weathering, after 15 Ma. Increase of Kerguelen input may reflect the initiation, or enhancement, of the Antarctic Circumpolar Current (ACC), thus raising the possibility of a simultaneous onset of North Atlantic Deep Water production and the ACC during the Middle Miocene. In addition, large geochemical oscillations occurred during the Pliocene, possibly reflecting fluctuation in strength of the ACC or, alternatively, periods of instability of the Antarctic ice sheet.

Diurnal Variation in Grip Strength and Hand Dexterity in Healthy Adults

Handgrip and dexterity are integral to hand function and both are used to assess functional status in clinical practice. Many studies have examined the daily fluctuation in handgrip strength with differing conclusions, but none to date have looked at variation in dexterity. This study recruited 30 healthy volunteers and measured their handgrip strength and dexterity using the Nine Hole Peg Test at three-hourly intervals between 9.00am and 4.00pm, over one day. There were statistically significant differences in hand dexterity over the day but not in handgrip strength. Although a possible learning effect from practising a task-specific dexterity assessment such as the Nine Hole Peg Test may explain these findings, the difference was inconsistent and differed between the dominant and non-dominant hand. This study highlights the need for parallel forms of testing hand function to help control for any learning effects and also for therapists to be as constant as possible in the time of day when using functional hand assessments.

Breakup in stochastic Stokes flows: sub-Kolmogorov drops in isotropic turbulence

Deformation and breakup of drops in an isotropic turbulent flow has been studied by numerical simulation. The numerical method involves a pseudospectral representation of the turbulent outer flow field coupled to three-dimensional boundary integral simulations of the local drop dynamics. A statistical analysis based on an ensemble of drop trajectories is presented; results include breakup rates, the distribution of primary daughter drops produced by breakup events, and stationary distributions for drop deformation and orientation. Depending on the local flow history, drops may break at modest length or become highly elongated and relax without breaking. Drop deformation is the dominant mechanism of drop reorientation. The volume of the primary daughter drops, produced by a given fluctuation in flow strength, scales with the volume of the corresponding critical drop size for the fluctuation. A simplified description for the evolution of the drop size distribution, based on this scaling, is presented.

Neogene contourites, Miura-Boso forearc basin, SE Japan

Abstract The mid to late Miocene Misaki Formation sediments of the Miura and Boso peninsulas, south central Japan, were deposited in the Pacific-facing forearc region of the proto Izu-Bonin arc at bathyal depths. The hemipelagic background facies, composed mainly of calcareous biogenic and pumiceous voicaniclastic material, are interbedded with thin to thick scoriaceous beds of turbiditic and pyroclastic fall origin. Careful study in the field and in the laboratory of these fine-grained background sediments has revealed the marked influence of bottom currents at certain horizons in producing intervals with distinct muddy contourite characteristics. These include: a general absence of primary structures due to intense bioturbation, some diffuse layering, irregular concentrations of coarser-grained material, sharp and erosive top and bottom lamina contacts, rare micro-cross-lamination disrupted by bioturbation that was continuous with deposition, and a mixed pelagic biogenic (commonly fragmented), volcaniclastic and terrigenous composition. Small-scale cyclicity of variations in grain-size and structural features can be related in part to episodic volcaniclastic input and in part to fluctuation in bottom current strength. Evidence for bottom current reworking of the tops of thin-bedded sandy turbidites is equivocal, and further work is required to resolve this debate. The recognition of Miocene-age contourites from the NW Pacific provides further evidence for the existence of active deep-ocean circulation in the Pacific at this time. However, it is not possible to determine which current system, Antarctic Bottom Water or deep Kuroshio Current, was responsible for these outcrop examples of fossil contourites.

Excess partial molar enthalpy of 1-propanol in 1-propanol–acetone (or tetramethyl urea)–H 2O at 25°C: effect of acetone (or tetramethyl urea) on H 2O

Excess partial molar enthalpies of 1-propanol, H 1P E, were measured at 25°C in ternary 1-propanol–acetone (or tetramethyl urea)–H 2O, with various initial compositions of acetone (or tetramethyl urea). They were determined accurately and in small increments in mole fraction of 1-propanol. It was therefore, possible to take a derivative of H 1P E with respect to the amount of 1-propanol, n 1P, H 1P–1P E≡ N( ∂H 1P E/ ∂n 1P). The changes in the mole fraction dependence of H 1P E and hence, H 1P–1P E caused by adding a third component, acetone or tetramethyl urea, were compared with the results of analogous earlier studies with urea and 2-propanol as a third component. The effects of acetone and tetramethyl urea were found qualitatively the same. The CH 3 group in each compound works as a typical hydrophobic moiety and enhances the hydrogen bond network of H 2O in the immediate vicinity of solute molecule (“iceberg formation”) with concomitant reduction of the hydrogen bond probability of H 2O. The CO group on the other hand, seems to reduce the degree of fluctuation in the hydrogen bond strength in the bulk H 2O away from the solute.

各種粉末の製造技術，製造方法 噴霧乾燥式流動層によるアルミナ粒子の造粒とコーティングへの応用

In the present study, the novel granulation method, spray fluidized bed granulation method was used to produce the granules. Subsequently compacts of the granules were produced through a series of process of dry compaction and sintering under atmospheric pressure. The effects of the properties of granules on compacts and sintered compacts were investigated.First, the granules with target size and good flowability could be produced by using the granulator. The granules were found to have spherical shapes and smooth surfaces. Second, compaction of the granules with sharp size distribution and good flowability showed low fluctuation in flexural strength. Third, granules with low strength were useful for the production of sintered compacts with highly density and flexural strength.In addition to granulation, the granulator has ability to perform the coating of the granules. For pharmaceutical materials, coating of granules and subsequent compaction was performed. The results showed coating operation enhanced the strength of compacts. For ceramic materials, similar achievement is expected.

Grain size distribution along the Msasani Beach, north of Dar es Salaam Harbour

Beach sediments collected from the tidal flat and beach slope at the Msasani Beach, about 15 km north of the Dar es Salaam Harbour, are used to (1) establish the grain size distribution pattern, (2) assess the effect of man-made and natural structures (rivers, creeks, sea wall and groynes) on the grain size distribution, and (3) assess whether sediments are preferentially transported northward by longshore currents. Generally, the Msasani Beach slope sediments have an average mean diameter of 1.55φ while those from the tidal flat average at 1.87φ. There is a general trend of decreasing grain size from south to north that is associated with improvement in sorting, particularly in the tidal flat. The northward fining of the sediment suggests that the sediment in the study area is transported from south to north. The trend of northward decrease in the mean grain size is locally distorted at the river mouths, creeks and man-made structures. The contribution of the man-made structures to the observed distortion can not be separated from that of natural structures owing to the fact that these man-made structures were placed next to the natural features. The data collected from the Msasani Beach were subjected to factor analysis. Four factors account for more than 95% of the observed variations in the grain size distribution in the study area. These factors are: medium energy environments (66.5% of total variance) common at the beach slope; low energy environments found in micro-bays (16%); high energy environment found at the tidal creeks and river entrance (7.8%); and intermediate (between medium and low) energy environments common in the tidal flat (5.6%).Most of the beach slope samples are unimodal (87%), while a significant number of the tidal flat samples (46%) are bimodal, with the most common mode being 2.25φ. The bimodality observed in this study can be attributed to the presence of shell fragments that were not removed during sieving, to sudden fluctuation in the energy strength at the beach, and to mixing of different grain populations.

A routine procedure for measurement of calcium carbonate activity in gypsum rich soils

Abstract Techniques developed to measure soil CaCO3 activities are not suited for routine measurement in gypsum rich soils. The procedure presented here is a modification of earlier work using stochastic model for dissolution of mixed particle size calcite in conjunction with pH‐stat titration. Its main features is to record the time needed for one gram of standard CaCO3 (semi‐pure CaCO3 in separate size fraction ranging from fine clay to coarse sand) or soil consignment containing one gram CaCO3 (based on calcimeter estimation) to raise the pH of 0.005M H2SO4 acid from 3.0 to 6.0. The procedure includes means to minimize the fluctuation in suspension ionic strength and pCO2 levels. The procedure was tested on calcareous soil (20% CaCO3) undergone limited acidification. Using the activity of the CaCO3 standard, the activity of the soils CaCO3 was stipulated and the effective CaCO3 size distribution was determined.

Gyne development in the Argentine ant Iridomyrmex humilis: role of overwintering and queen control

Abstract A possible stimulatory effect of overwintering on gyne development in Iridomyrmex humilis (Mayr) was investigated. Although gyne‐potent larvae are present in the nest throughout the year, small queenless colony fragments composed of freshly overwintered ants (collected in late winter or early spring) produced 3–8 times more gynes than comparable fragments made up of non‐freshly overwintered ants (collected at other times of the year). Apparently, this stimulatory effect of overwintering acts on both the developmental potential of larvae and the tendency of workers to rear sexually competent larvae as gynes; queenless colony fragments in which either the brood or workers were freshly overwintered produced more gynes than fragments composed of non‐freshly overwintered workers or brood but fewer than fragments containing both brood and workers freshly overwintered. This increased sexualization potential of larvae due to overwintering is enough to overcome weak pheromonal inhibition of queens associated with low queen number; a single queen in a large freshly overwintered colony fragment is insufficient to inhibit gyne development, whereas ten queens are totally inhibitory. In non‐freshly overwintered colony fragments one queen is completely inhibitory. Variability in egg developmental potential according to queen age does not appear to play a major role in the seasonal production of gynes, because at least some eggs of very young queens (less than 3 weeks old) are capable of gyne development. In the field this stimulatory effect of overwintering is superimposed on a seasonal fluctuation in the combined strength of pheromonal queen control. In southern France, gynes are produced only in spring where they arise primarily from overwintered larvae just after a sharp drop in queen number, and presumably the total level of inhibitory queen pheromone, due to the massive execution of queens by workers.

Reproducibility across Experiments of Behavioral Results Obtained under Strictly Standardized Conditions: Another View of the Results of the Collaborative Behavioral Teratology Study

The data of the Collaborative Behavioral Teratology Study were reanalyzed. The degree of reproducibility of the treatment effect across experiments was assessed as the magnitude of fluctuation in strength of association (η2) for the replication experiment. There was no evidence that fluctuation of treatment effects across experiments was greater for behavioral measures than for nonbehavioral ones, suggesting the conventional belief that low reproducibility of results in behavioral teratology reflects the low reliability of the behavior test per se is unwarranted. Although the distributions of obtained treatment effects were almost symmetric and unimodal for most measures, the ranges were considerable. Considering that experiments were conducted under strictly standardized conditions across experiments, finding of the considerable ranges indicates that inconsistency in results across experiments cannot be remedied adequately by employing solely a standardized method. Basing in the main their results in terms of conventional significance tests, research workers in the collaborative study concluded that excellent reproducibility of behavioral data was demonstrated. The logic underlying the statistically nonsignificant interaction used in the original work was examined critically. A serious limitation upon the significance test for assessing the reproducibility of results was pointed out, and a warning issued about customary reliance only on a significance test.

Fluctuation in grip and pinch strength among normal subjects

Grip and pinch strength testing are commonly used to evaluate hand strength for disability ratings and to assess responses to various forms of therapy. This study determined the variations in grip and pinch strength in normal individuals. Ninety-five healthy subjects—61 women and 34 men—were examined prospectively by use of a Jamar dynamometer and a Preston pinch gauge. Grip and pinch were measured in the morning and afternoon twice a week for 3 weeks, giving a total of 12 testing periods. Mean grip strength fluctuated between 5.1 and 8.4 kg, or between 19.2% and 23.7%. Mean Lateral pinch strength fluctuated between 2.6 and 3.8 pounds, or between 13.8% and 17.6%. There were no differences between the morning and afternoon values. Grip and pinch strength fluctuate over time. Repeat testing is necessary to accurately assess hand strength. Grip and pinch strength do not vary from morning to afternoon.

Stability of grip strength during the menstrual cycle.

Early studies of strength fluctuations, using the cable tensiometer and dynamometric instrumentation for grip strength, show premenstrual and menstrual decreases in strength (Dawson, 1935). Although these studies were completed over 40 years ago, they apparently have not been replicated. Mood swings paralleling the menstrual cycle have been documented (Bardwick, 1971 ) , with the premenstrual and menstrual phases associated with negative moods, e.g., depression, irritability, but ability and achievement test performance swings have not been found (Golub, 1976). It is possible that fluctuation in grip strength, if it exists, may be more related to motivational factors than ability. Two groups of women college studencs volunteered. A motivated group (n = 12) were told that we believe observed changes In physical strength during the menstrual cycle are associated with motivational faaors we urge them to overcome; a control group (n = 10) were given standard instructions for grip strength. Subjects came in for testing four times during their menstrual cycles: premenstrually, menstrually, postmenstrually, and in midcycle. Menstrual phases were determined by self-report. For each woman a Lafayette Instrument Co. hand dynamometer (Model No. 78010) was adjusted to a comfortable grip size. Each subject, while standing with her arms at her side and the dynamometer in the self-reported dominant hand, was told to squeeze as hard as possible. Her score was the highest recorded on three consecutive trials. Mean performances during the four phases (premenstrual, menstrual, postmenstrual, and midcycle) were 35.3, 34.7, 33.2, and 34.8 for the motivated group and 34.5, 35.0, 34.2, and 35.0 for the uninformed group, with SDs of 7.1, 6.1, 6.8, 5.5 for the motivated group and 6.3, 5.3, 7.1, and 8.2 for the uninformed group, respectively. A two-way mixed-design analysis of variance (group x menstrual phase) was applied. There was no evidence for fluctuation in grip strength during the menstrual cycle among either group of subjects (P1.20 = .005 for group; P3.60 = 1.52 for phase). Dawson's original findings were not replicated. Since no physiological measures (such as basal body temperature) were obtained, a replication with more careful determination of menstrual phase would be highly desirable. REFERENCES

Reproductive Uncertainty and the Evolution of Iteroparity: Why Don't Flatfish Put All Their Eggs in One Basket?

Murphy's hypothesis that variation in reproductive life span is an adaptive response to variation in the predictability of reproductive success is examined. Murphy's contention that this hypothesis explains the variation in reproductive life span within the clupeids is reexamined incorporating further data on the Peruvian anchovy (Engraulis ringens). A nonsignificant correlation is now obtained between reproductive life span and brood strength variation; thus, the hypothesis is called into question. An alternative explanation is presented that considers the interaction between life history parameters: because it is necessary for the intrinsic rate of increase to exceed zero, variation in one parameter must be associated with variation in at least one other parameter. In the clupeids it is noted that the age of maturity and reproductive life span vary in concert and it is suggested that this provides an explanation of variation in reproductive life span. These two hypotheses are examined using data on the family Pleuronectidae, the flatfish. No correlation exists between reproductive life span and the degree of fluctuation in brood strength but there is a significant correlation between reproductive life span and age of maturity. It is concluded that variation in reproductive life span within the flatfish group is not a response to variation in reproductive success but rather a correlate of variation in age of maturity.Key words: flatfish, Pleuronectidae, iteroparity, natural selection, reproduction, clupeids

Some Factors Associated with Fluctuation in Year-class Strength of Sauger, Lewis and Clark Lake, South Dakota

Abstract The strength of sauger, Stizostedion canadense (Smith), year classes in Lewis and Clark Lake has fluctuated widely since formation of the reservoir in 1956. Our studies suggest that more than 80% of the variability in year-class strength measured from the catch of fish older than age 0 can be predicted from knowledge of water level change over the spawning ground, June reservoir water temperature, and reservoir water exchange rate. These factors were measured and probably function during the first 2 months of fish life. Sauger year classes of better than average strength can be expected in most years if both power-peaking operations at Fort Randall Dam during the fish spawning and incubation period, and the reservoir water exchange rate during June are minimized.