Evaluation of the Vulcanization Characteristics of Crude Rubber

1952 ◽  
Vol 25 (1) ◽  
pp. 99-106 ◽  
Author(s):  
Pierre Thirion
Keyword(s):  
Time Constant ◽  
Great Majority ◽  
Maximum Modulus ◽  
Present Form ◽  
Exponential Functions ◽  
Rubber Mixture ◽  
Order Of Magnitude ◽  
Experimental Values ◽  
General Specification ◽  
Source Of Information

Abstract Any vulcanization test of crude rubber which is based on a measurement of the strain modulus for only one time of vulcanization is insufficient as a source of information to the investigator of the rate of vulcanization and at the same time of the order of magnitude of the maximum modulus. It is proposed to complete this test by a second vulcanization for a different length of time and to correlate the complete vulcanization curves with the exponential functions of time. In this way it seems possible to derive two experimental values of the modulus: (1) A limiting modulus which characterizes the ultimate stiffness of the vulcanizate. (2) A vulcanization time constant which serves as an index of the rate of vulcanization of a rubber mixture. The more rapid the rate of vulcanization, the smaller is this constant. Application of this method to nine different lots of crude rubber proved that by this means it is possible to show well defined differences between various individual lots of crude rubber. Much more extensive studies will be necessary before it is known whether the method is applicable to the great majority of crude rubbers and whether it is adaptable in its present form to the formulation of a general specification for testing crude rubber. There is reason to believe that the use of the modulus value at 100 per cent elongation, already proposed by Gee, and his coworkers instead of 600 per cent elongation, would from this viewpoint offer numerous advantages.

Infrared spectra, rotational correlation functions, and intermolecular mean squared torques in compressed gaseous methane

1968 ◽  
Vol 46 (11) ◽  
pp. 1331-1340 ◽  
Author(s):  
R. L. Armstrong ◽  
S. M. Blumenfeld ◽  
C. G. Gray
Keyword(s):  
Correlation Functions ◽  
Theoretical Calculations ◽  
Dominant Contribution ◽  
Dispersion Interactions ◽  
Fundamental Vibration ◽  
Order Of Magnitude ◽  
The Mean ◽  
Vibration Rotation ◽  
Experimental Values ◽  
Rotational Correlation

Extensive measurements of the methane ν3 and ν4 fundamental vibration–rotation bands in CH4–He mixtures and the ν3 band in CH4–He, CH4–N2, and CD4–He mixtures have been carried out in infrared absorption at 295 °K to pressures of 3000 atm. Some profiles of the ν3 band in CH4–Ar mixtures and in pure CH4 have also been obtained. Rotational correlation functions, band moments, and intermolecular mean squared torques have been determined from the ν3 band profiles. Theoretical calculations of the mean squared torque due to anisotropic multipolar, induction and dispersion interactions have been carried out. The theoretical and experimental torques are in order-of-magnitude agreement for the CH4–N2 and CH4–CH4 systems; for CH4–He, CD4–He, and CH4–Ar the theoretical values are two to three orders of magnitude too small to account for the experimental values, indicating that in these cases the dominant contribution to the torques is given by the anisotropic overlap forces.

Determining the Role of Communication and Distribution Channels for Organic Foods

2017 ◽  
pp. 149-164
Author(s):  
V. Aslihan Nasir ◽  
Suphan Nasir
Keyword(s):  
Information And Communication Technologies ◽  
Online Social Networks ◽  
Organic Food ◽  
Great Majority ◽  
Distribution Channels ◽  
Organic Foods ◽  
Information And Communication ◽  
Organic Food Consumption ◽  
Source Of Information

While, the market for organic foods is growing; the proportion of consumers who buy organic foods is still considered low. The role of communication activities is very important for promoting the organic food consumption. In order to create awareness and generate demand for organic foods, companies need to use effective communication tools. Companies in the agribusiness sector try to take advantage of the information and communication technologies in the digital era with the purpose of communicating the value of their offer to consumers. Companies need to know which information sources (channels) are most influential in purchase decision while communicating with consumers. Thus, the aim of this study is to examine consumers' credibility perceptions of communication channels that are used to promote organic food. The great majority of the respondentsin this study mentioned that they had never seen organic food ads. However, a significant number of consumers who had seen organic food ads declared Internet as the medium they had exposed to organic food ads. Nevertheless, our study revealed that the respondents did not perceive Internet as a credible source of information about organic foods. Yet, online social networks were perceived as more reliable source of information about organic foods when compared to majority of traditional media such as radio and newspaper ads. The distribution channels that consumers prefer to purchase organic foods was also investigated; and it is found that a significant portion of the consumers choose supermarkets and neighborhood bazaars for their organic food shopping whereas Internet/online shops and pharmacy stores were shown as the least preferred shopping alternatives. Finally, a substantial majority of the consumers mentioned high prices and availability as the main barriers against buying organic foods.

An Improved Method to Analyze the Stress Relaxation of Ligaments Following a Finite Ramp Time Based on the Quasi-Linear Viscoelastic Theory

2004 ◽  
Vol 126 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Steven D. Abramowitch ◽  
Savio L.-Y. Woo
Keyword(s):  
Stress Relaxation ◽  
Soft Tissues ◽  
Viscoelastic Behavior ◽  
Cyclic Stress ◽  
Elastic Response ◽  
Curve Fit ◽  
Order Of Magnitude ◽  
Linear Viscoelastic ◽  
Linear Viscoelastic Theory ◽  
Experimental Values

The quasi-linear viscoelastic (QLV) theory proposed by Fung (1972) has been frequently used to model the nonlinear time- and history-dependent viscoelastic behavior of many soft tissues. It is common to use five constants to describe the instantaneous elastic response (constants A and B) and reduced relaxation function (constants C, τ1, and τ2) on experiments with finite ramp times followed by stress relaxation to equilibrium. However, a limitation is that the theory is based on a step change in strain which is not possible to perform experimentally. Accounting for this limitation may result in regression algorithms that converge poorly and yield nonunique solutions with highly variable constants, especially for long ramp times (Kwan et al. 1993). The goal of the present study was to introduce an improved approach to obtain the constants for QLV theory that converges to a unique solution with minimal variability. Six goat femur-medial collateral ligament-tibia complexes were subjected to a uniaxial tension test (ramp time of 18.4 s) followed by one hour of stress relaxation. The convoluted QLV constitutive equation was simultaneously curve-fit to the ramping and relaxation portions of the data r2>0.99. Confidence intervals of the constants were generated from a bootstrapping analysis and revealed that constants were distributed within 1% of their median values. For validation, the determined constants were used to predict peak stresses from a separate cyclic stress relaxation test with averaged errors across all specimens measuring less than 6.3±6.0% of the experimental values. For comparison, an analysis that assumed an instantaneous ramp time was also performed and the constants obtained for the two approaches were compared. Significant differences were observed for constants B, C, τ1, and τ2, with τ1 differing by an order of magnitude. By taking into account the ramping phase of the experiment, the approach allows for viscoelastic properties to be determined independent of the strain rate applied. Thus, the results obtained from different laboratories and from different tissues may be compared.

Theory of spin-orbit coupling in atoms, II. Comparison of theory with experiment

1963 ◽  
Vol 271 (1347) ◽  
pp. 565-578 ◽  
Keyword(s):  
Wave Functions ◽  
Coupling Constants ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Outer Electron ◽  
Coupling Constant ◽  
Radial Wave ◽  
Order Of Magnitude ◽  
Experimental Values

Results of calculations of the spin-orbit coupling constant for 2 p , 3 p , 4 p , and 3 d shell ions and atoms are presented. The calculations are based on a theory developed in a previous paper. Excellent agreement of this theory with experiment is obtained for the 2 p and 3 d shell ions, while calculations using the familiar < ∂ V / r ∂ r > expression for the coupling constant lie 10 to 20 % too high. The exchange terms discussed in the earlier paper make a contribution to the coupling constant of the same sign and order of magnitude as the ordinary shielding terms. For the 3 p and 4 p shell atoms, the calculated coupling constants based on the exact theory and on the < ∂ V / r ∂ r > expression both tend to lie below the experimental values. An explanation for this disagreement is suggested, based on the noded nature of the outer-electron radial wave functions for these atoms. The importance of the residual-spin-other-orbit interaction is discussed, and it is shown that ignoring the form of this interaction may lead to a large variation in the coupling constant within a configuration.

scholarly journals Some remarks on integral equations with kernels: L (ξ 1 - x 1 ,..., ξ n - x n ; α)

1949 ◽  
Vol 197 (1049) ◽  
pp. 160-183 ◽  
Keyword(s):  
Integral Equations ◽  
Experimental Error ◽  
Normal Force ◽  
Partial Information ◽  
Maximum Modulus ◽  
Gravity Survey ◽  
Dispersive Media ◽  
Smoothing Functions ◽  
The Fourier Transform ◽  
Experimental Values

The paper discusses integral equations of the type k (ξ 1 ... ξ n ) = ∫ -∞ ∞ ... ∫ -∞ ∞ ψ ( x 1 ... x n ) L (ξ 1 -x 1 ... ξ n -x n ;α) d x 1 ... d x n , where L is L -integrable, and ψ and k are bounded. Since rapidly oscillating ψ have a small k , and since measurements of k are necessarily uncertain within non-zero limits of experimental error, very different ψ are consistent with any given set of measurements of k . Thus ψ is not determined by measurements of k . Instead of ψ, partial information about ψ that is not sensitive to rapid oscillations of ψ, can be obtained from k . In the present paper we consider smoothed versions of ψ, and their applications to gravity survey and the theory of surface waves. (1) For given L we construct normalized smoothing functions μ( x 1 ... x n ), so that ψ( x 1 ... x n ) = ∫ -∞ ∞ ... ∫ -∞ ∞ ψ( u 1 ... u n )μ (x 1 - u 1 ... x n - u n ) d u 1 .... d u n can be calculated from measurements of k( (ξ 1 ... ξ n ). The method is applied to gravity survey, where the distribution ψ of masses on a plane ∑' is to be calculated from the normal force k on another (parallel) plane∑. (2) By studying suitable smoothing functions we get a lower bound for the maximum modulus of the functions ψ which are consistent with given experimental values of k . The bound is large if k is known to vary rapidly. The bound is also large if α is large and if the Fourier transform of L tends to 0 when α→∞. The results are applied to gravity survey where now we consider the normal force on ∑ due to masses of bounded density distributed in the space below ∑', where ∑' is itself below ∑. If the normal force is not uniform the distance between ∑ and ∑' must not be too large, the estimate depending on the bound for the density. Also fairly general conditions are imposed on ψ so that ψ that is approximately determined by measurements of k , and an example from the theory of propagation in dispersive media is given where such conditions may be justified. The gist of the paper is contained in theorems A and B.

The Measurement of Oil-Film Thickness in Gear Teeth

1960 ◽  
Vol 82 (1) ◽  
pp. 29-34 ◽  
Author(s):  
I. O. MacConochie ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Voltage Drop ◽  
Theoretical Work ◽  
Discharge Voltage ◽  
Constant Current ◽  
Oil Film ◽  
Gear Teeth ◽  
Order Of Magnitude ◽  
The Difference ◽  
Experimental Values

The voltage drop across thin oil films when a constant current of 1 amp is passed, i.e., the discharge voltage, is used to measure the oil-film thickness between loaded gear teeth while running. It is found that the thickness at the pitch line is between 1 and 4 × 10−4 in., which varies slightly with the viscosity and rather more strongly with load. The thickness at the tips and roots is very dependent on the tip relief. The conditions here may explain the difference between disk and gear tests. These experimental values are compared with theoretical work and are shown to be of the same order of magnitude.

scholarly journals POTASSIUM MOVEMENT IN RELATION TO NERVE ACTIVITY

1951 ◽  
Vol 34 (6) ◽  
pp. 795-807 ◽  
Author(s):  
Abraham M. Shanes
Keyword(s):  
Time Constant ◽  
Calcium Concentration ◽  
Sea Water ◽  
Calcium Content ◽  
Squid Axon ◽  
Nerve Activity ◽  
Potassium Accumulation ◽  
Low Concentrations ◽  
Order Of Magnitude ◽  
Wet Weight

The depolarization of crab nerve during repetitive stimulation is unaffected by the presence of glucose or by an increase in the calcium content of the medium. It is increased in both amplitude and rate by veratrine; in the presence of this alkaloid mixture the rate but not the magnitude of the depolarization is increased by an elevation in the calcium concentration. Repolarization following stimulation is unaltered by glucose and accelerated by a greater calcium concentration. Veratrine increases both the amplitude and the time constant of repolarization; its effect on the time constant is counteracted by an elevation of the calcium in the medium. Potassium released during stimulation and its reabsorption following activity have been observed by analyses of small volumes of sea water in contact with crab nerve. Under the conditions employed 3 x 10–8 µM potassium is liberated per impulse per gm. wet weight of nerve. This loss is increased by low concentrations of veratrine, which also increase the amount reabsorbed during recovery. The depletion of potassium from the medium is appreciably less if the potassium previously released during activity has not been removed. Inexcitability resulting from anoxia can be washed away with oxygen-free solution—rapidly and completely in the case of the squid axon, slowly and incompletely in crab nerve. The potassium shifts are in the proper direction and of the correct order of magnitude to account for the negative and positive after-potentials in terms of potassium accumulation or depletion in the extracellular space.

scholarly journals Creep of model piles in frozen soil

1979 ◽  
Vol 16 (1) ◽  
pp. 69-77 ◽  
Author(s):  
V. R. Parameswaran
Keyword(s):  
Frozen Soil ◽  
Displacement Rate ◽  
Laboratory Studies ◽  
Creep Equation ◽  
Pull Out ◽  
Surface Finishes ◽  
Frozen Sand ◽  
Theoretical Predictions ◽  
Order Of Magnitude ◽  
Experimental Values

Preliminary results of laboratory studies on the behaviour of model piles of wood, concrete, and steel, having different surface finishes, embedded in artificially frozen sand and subject to constant loads, are reported in this paper. The displacement rate [Formula: see text], was found to vary with the applied stress [Formula: see text]f, according to a steady state creep equation of the type [Formula: see text], as found for other viscoelastic materials such as metals at high temperature. The value of the exponent n varied between 6.7 and 9.1 for various types of piles.The results agreed favourably with field data obtained from pile pull-out tests carried out at Gillam and Thompson, Manitoba. The value of n from Gillam and Thompson tests, 8.05 and 7.5, respectively, were within the range of the present experimental values. Comparison with pile pull-out tests carried out in ice, and theoretical predictions for ice showed that the value of the exponent n was much larger for frozen soil than for ice. The bearing capacity at a particular displacement rate was also found to be almost an order of magnitude larger in frozen soil than in ice.

scholarly journals On the scale sizes of magnetosheath jets

2020 ◽  
Author(s):  
Ferdinand Plaschke ◽  
Heli Hietala
Keyword(s):  
Large Scale ◽  
Dynamic Pressure ◽  
Large Population ◽  
Small Scale ◽  
Size Distributions ◽  
Exponential Functions ◽  
Scale Size ◽  
Order Of Magnitude ◽  
Log Normal ◽  
Spacecraft Data

&lt;p&gt;The subsolar magnetosheath is oftentimes permeated by jets. These are localized entities of enhanced dynamic pressure with respect to the ambient plasma. Magnetosheath jets are thought to arise from bow shock ripples and/or foreshock structures. They can easily propagate through the entire magnetosheath and impact on the magnetopause, where they can cause large amplitude indentations, launch magnetopause surface waves, or modulate magnetopause reconnection. The scale size distributions of magnetosheath jets observed by single spacecraft are relatively well modeled by exponential functions with characteristic scales of 0.71 Earth radii (RE) and 1.34 RE in the directions parallel and perpendicular to the jet propagation direction, respectively. However, these functions do not represent the actual, true jet scale size distributions, because of two reasons: (1) Spacecraft are much more likely to observe large scale jets rather than small scale jets. Hence, the observed scale size distributions are biased towards larger scales. (2) The distributions modeled by exponential functions highly overestimate observation probabilities of jets of smallest scales (on the order of 0.1 RE). We overcome both shortcomings by replacing the exponential functions by log-normal functions, which can be corrected for the bias. By re-analyzing THEMIS multi-spacecraft data, we obtain, for the first time, unbiased, i.e., actual jet scale size distributions. Our results reveal a large population of jets of smallest scales that have not been accounted for, so far. Consequently, we find median scale sizes of jets to be about an order of magnitude smaller than previously thought: 0.15 and 0.12 RE in the parallel and perpendicular directions, respectively.&lt;/p&gt;

scholarly journals Experimental Study of Collection Efficiencies between Submicron Aerosols and Cloud Droplets

2011 ◽  
Vol 68 (9) ◽  
pp. 1853-1864 ◽  
Author(s):  
Luis Ladino ◽  
Olaf Stetzer ◽  
Bodo Hattendorf ◽  
Detlef Günther ◽  
Betty Croft ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Collection Efficiency ◽  
Pure Water ◽  
Cloud Droplet ◽  
Cloud Droplets ◽  
Inductively Coupled ◽  
Aerosol Mass ◽  
Order Of Magnitude ◽  
Plasma Mass Spectrometry ◽  
Experimental Values

Abstract Collection efficiency E experiments for aerosol particles scavenged by cloud droplets were carried out in the newly built Collision Ice Nucleation Chamber (CLINCH). Pure water droplets having radii between 12.8 and 20.0 μm were allowed to fall freely and to collide in a laminar flow with lithium metaborate particles having radii between 0.05 and 0.33 μm. At the bottom of the chamber, the droplets and the particles captured were collected using a cup impactor. The collected solution was analyzed for the scavenged aerosol mass by inductively coupled plasma mass spectrometry. Evaporation of droplets was taken into account since the relative humidity inside the chamber was below 100%, resulting in final theoretical droplet sizes between 4.2 and 17.6 μm. The resulting experimental measurements were compared with theoretical values to see their correlation. The authors found an experimental trend similar to theory, as well as the “Greenfield gap” at the particle radius of 0.24 μm (E = 0.038) for the smallest cloud droplet size investigated in this study. The experimental values of collection efficiency found herein agree with those from theory within one order of magnitude, similar to previous studies reported in the literature.

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