Constant Expansion Rate Research Articles

Kinetics of thermal expansion of illite-based ceramics in the dehydroxylation region during heating

The kinetics of the illite dehydroxylation is investigated using data from non-isothermal thermodilatometric experiments. An illitic clay with more than 70 % of illite was thermally treated under several heating rates from 1 to 15 °C min−1 in the dehydroxylation region. Model-free and nonlinear model-fitting methods were used to analyze the data, and their results are discussed. The dehydroxylation of the trans-vacant and cis-vacant illite layers can be described by the Avrami–Erofeev model with the exponent values 1.010 and 2.1, respectively, and the apparent activation energies of 119 and 184 kJ mol−1, respectively. The obtained kinetic parameters were used for the calculation of an optimal heating regime in order to achieve a constant thermal expansion rate in the dehydroxylation region for an illite-based ceramic body.

Wind alters landing dynamics in bumblebees.

Landing is an important but understudied behavior that flying animals must perform constantly. In still air, insects decelerate smoothly prior to landing by employing the relatively simple strategy of maintaining a constant rate of image expansion during their approach. However, it is unclear whether insects employ this strategy when faced with challenging flight environments. Here, we tested the effects of wind on bumblebees (Bombus impatiens) landing on flowers. We find that bees' approach paths to flowers shift from multidirectional in still air to unidirectional in wind, regardless of flower orientation. In addition, bees landing in a 3.5 m s-1 headwind do not decelerate smoothly, but rather maintain a high flight speed until contact, resulting in higher peak decelerations upon impact. These findings suggest that wind has a strong influence on insect landing behavior and performance, with important implications for the design of micro aerial vehicles and the ecomechanics of insect flight.

Optimization of the workflow of multistage axial turbines with platforms

The turbine workflow is described by a large number of variables that often have contradictory impact on the turbine operating parameters. Hand-operated variation of these variables is a difficult time-consuming task. Application of mathematic optimization techniques could provide a solution of the problem. The paper outlines the basic principles of the method of mathematical optimization of an axial turbine based on the joint use of the NUMECA computational fluid dynamics software and the IOSO program optimizer. The procedure developed was implemented for a four-stage turbine developed and tested by NASA. Design models including one, two, three and four stages have been developed for the turbine under consideration. The results of calculations performed with their help showed good agreement with the experimental results. The settings of the numerical model that provide good agreement of design and experimental data but do not require large computational resource have been chosen according to the results of the research conducted. Low computational cost is very important because it allows significant reduction of the time spent to obtain the optimal solution with repeated reference to the design model. Automatic search of the turbine blade configuration allowing a 0.7 % increase of the turbine efficiency with constant mass flow and rate of expansion of gas (accuracy 0.5 %) was carried out with the help of the model created.&nbsp

STATE INTERVENTION AND MACROECONOMIC MANAGEMENT

The monetarists are opponents of government intervention and supporters of free market processes. Keynesians are, conversely, supporters and advocates of government intervention and opponents of uncontrolled operation of the market mechanism. As opponents of government intervention, the monetarists do not agree that it should take countercyclical fiscal policy which can cause greater increase in expenditures of the public sector during the recession, but spending cuts in the period of expansion and that, consequently, the public expenditures continue to increase. However, Tobin, indicating a negative attitude, claims that inflation cannot be used as a reason to reduce the budget, if fiscal policy has little or no effect on income. Undesirability of countercyclical fiscal policy is a logical consequence of the monetarist views on the stability of the sector and better performance of the free market of government intervention in social reproduction. Rule on a constant rate of monetary expansion eliminates the need for conducting discretionary policy, as the Phillips curve, previously defined, does not allow an optimal combination of inflation and unemployment. Therefore, the use of money (and interest rates and bank loans), as the goal of monetary policy provides economic policy makers to focus on managing variability (i.e. concentrate to money supply), which is beyond the scope of operation of the market, on the one hand, and to let determining the interest rates of bank loans and the free market, on the other hand. Finally, monetarists are extremely concerned about the multiple connections between inflation and expansion of the public sector, for three reasons: first, inflation increases the share of the public sector (and exacts an increase in public expenditure), if a progressive tax system is functioning; second, combating inflation can only indirectly limit the expenditure of the public sector, as the government expenditures partly increase by inflationary financing; and third, financing the budget deficit with the primary issues typically involves inflationary effect, which, if it continues, initiates the process prices and wages control. The paper is based on theoretical analysis of the impact of state intervention in the sphere of stimulating economic recovery, growth and development.

Photons, thermodynamics, and expanding universe

The total number of blackbody photons of cosmic background radiation after decoupling from matter is independent of time,but the cosmic redshift effect lets the radiation tempreture decrease with the universe scale increasing,then the total energy of cosmic background radiation decreases as the universe expands,which is contrary to the first law of thermodynamics. The density of dark energy corresponding to the cosmological constant is independent of time,which means that matter is continuously created in an expanding universe,then the total energy of the universe will reach to infinity. The paradoxes in the standard model of cosmology indicate that the foundation of cosmic dynamics needs to be carefuly inspected. We propose an alternative model of cosmology with energy conservation giving an evolution picture of universe completely different with the standard model. In our model the state of equilibrium between matter and dark energy with a constant expansion rate is ordinary for universe,acceleration or deceleration is just temporary deviation from the equilibrium state by a phase transition with transformation between balanced matter and dark energy. It is expected that cosmological observations will judge the two kinds of cosmological model.

A TEST OF COSMOLOGICAL MODELS USING HIGH-zMEASUREMENTS OFH(z)

The recently constructed Hubble diagram using a combined sample of SNLS and SDSS-II Type Ia SNe, and an application of the Alcock-Paczynski (AP) test using model-independent Baryon Acoustic Oscillation data, have suggested that the principal constraint underlying the cosmic expansion is the total equation-of-state of the cosmic fluid, rather than that of its dark energy. These studies have focused on the critical redshift range (0 < z < 2) within which the transition from decelerated to accelerated expansion is thought to have occurred, and they suggest that the cosmic fluid has zero active mass, consistent with a constant expansion rate. The evident impact of this conclusion on cosmological theory calls for an independent confirmation. In this paper, we carry out this crucial one-on-one comparison between the R_h=ct Universe (an FRW cosmology with zero active mass) and wCDM/LCDM, using the latest high-z measurements of H(z). Whereas the Type Ia SNe yield the integrated luminosity distance, while the AP diagnostic tests the geometry of the Universe, the Hubble parameter directly samples the expansion rate itself. We find that the model-independent cosmic chronometer data prefer R_h}=ct over wCDM/LCDM with a BIC likelihood of ~95% versus only ~5%, in strong support of the earlier SNeIa and AP results. This contrasts with a recent analysis of H(z) data based solely on BAO measurements which, however, strongly depend on the assumed cosmology. We discuss why the latter approach is inappropriate for model comparisons, and emphasize again the need for truly model-independent observations to be used in cosmological tests.

Robust model comparison disfavors power law cosmology

Late-time power law expansion has been proposed as an alternative to the standard cosmological model and shown to be consistent with some low-redshift data. We test power law expansion against the standard flat $\Lambda$CDM cosmology using goodness-of-fit and model comparison criteria. We consider Type Ia supernova (SN Ia) data from two current compilations (JLA and Union2.1) along with a current set of baryon acoustic oscillation (BAO) measurements that includes the high-redshift Lyman-$\alpha$ forest measurements from BOSS quasars. We find that neither power law expansion nor $\Lambda$CDM is strongly preferred over the other when the SN Ia and BAO data are analyzed separately but that power law expansion is strongly disfavored by the combination. We treat the $R_\text{h} = ct$ cosmology (a constant rate of expansion) separately and find that it is conclusively disfavored by all combinations of data that include SN Ia observations and a poor overall fit when systematic errors in the SN Ia measurements are ignored, despite a recent claim to the contrary. We discuss this claim and some concerns regarding hidden model dependence in the SN Ia data.

A COMPARATIVE ANALYSIS OF THE SUPERNOVA LEGACY SURVEY SAMPLE WITH ΛCDM AND THERh=ctUNIVERSE

The use of Type~Ia SNe has thus far produced the most reliable measurement of the expansion history of the Universe, suggesting that $\Lambda$CDM offers the best explanation for the redshift--luminosity distribution observed in these events. But the analysis of other kinds of source, such as cosmic chronometers, gamma ray bursts, and high-$z$ quasars, conflicts with this conclusion, indicating instead that the constant expansion rate implied by the $R_{\rm h}=ct$ Universe is a better fit to the data. The central difficulty with the use of Type~Ia SNe as standard candles is that one must optimize three or four nuisance parameters characterizing supernova luminosities simultaneously with the parameters of an expansion model. Hence in comparing competing models, one must reduce the data independently for each. We carry~out such a comparison of $\Lambda$CDM and the $R_{\rm h}=ct$ Universe, using the Supernova Legacy Survey (SNLS) sample of 252 SN~events, and show that each model fits its individually reduced data very well. But since $R_{\rm h}=ct$ has only one free parameter (the Hubble constant), it follows from a standard model selection technique that it is to be preferred over $\Lambda$CDM, the minimalist version of which has three (the Hubble constant, the scaled matter density and either the spatial curvature constant or the dark-energy equation-of-state parameter). We estimate by the Bayes Information Criterion that in a pairwise comparison, the likelihood of $R_{\rm h}=ct$ is $\sim 90\%$, compared with only $\sim 10\%$ for a minimalist form of $\Lambda$CDM, in which dark energy is simply a cosmological constant. Compared to $R_{\rm h}=ct$, versions of the standard model with more elaborate parametrizations of dark energy are judged to be even less likely.

Optimization of the workflow of multistage axial turbines with platforms

The turbine workflow is described by a large number of variables that often have contradictory impact on the turbine operating parameters. Hand-operated variation of these variables is a difficult time-consuming task. Application of mathematic optimization techniques could provide a solution of the problem. The paper outlines the basic principles of the method of mathematical optimization of an axial turbine based on the joint use of the NUMECA computational fluid dynamics software and the IOSO program optimizer. The procedure developed was implemented for a four-stage turbine developed and tested by NASA. Design models including one, two, three and four stages have been developed for the turbine under consideration. The results of calculations performed with their help showed good agreement with the experimental results. The settings of the numerical model that provide good agreement of design and experimental data but do not require large computational resource have been chosen according to the results of the research conducted. Low computational cost is very important because it allows significant reduction of the time spent to obtain the optimal solution with repeated reference to the design model. Automatic search of the turbine blade configuration allowing a 0.7 % increase of the turbine efficiency with constant mass flow and rate of expansion of gas (accuracy 0.5 %) was carried out with the help of the model created.

Study of instability formation and EUV emission in thin liners driven with a compact 250 kA, 150 ns linear transformer driver

A compact linear transformer driver, capable of producing 250 kA in 150 ns, was used to study instability formation on the surface of thin liners. In the experiments, two different materials, Cu and Ni, were used to study the effect of the liner's resistivity on formation and evolution of the instabilities. The dimensions of the liners used were 7 mm height, 1 mm radius, and 3 μm thickness. Laser probing and time resolved extreme ultraviolet (EUV) imaging were implemented to diagnose instability formation and growth. Time-integrated EUV spectroscopy was used to study plasma temperature and density. A constant expansion rate for the liners was observed, with similar values for both materials. Noticeable differences were found between the Cu and Ni instability growth rates. The most significant perturbation in Cu rapidly grows and saturates reaching a limiting wavelength of the order of the liner radius, while the most significant wavelength in Ni increases slowly before saturating, also at a wavelength close to the liner radius. Evidence suggests that the instability observed is the well-known m = 0 MHD instability. However, upon comparing the instability evolution of Cu and Ni, the importance of the resistivity on the seeding mechanism becomes evident. A comparison of end-on and side-on EUV emission possible indicates the formation of precursor plasma, where it has been estimated using EUV spectroscopy that the precursor plasma temperature is approximately 40 eV with ion density of order 1019 cm−3, for both materials.

Quantifying growth and development of bulb turnips

Bulb brassicas are used as supplementary feed in intensive pastures systems. However, there is a lack of quantitative data to define their growth and development. This has limited the creation and use of prediction models and decision support systems. Thus a field experiment measured growth and development of ‘Barkant’ and ‘Green Globe’ turnips sown on five dates from November 2008 to March 2009. In a second field experiment ‘Green Globe’ turnips were sown on four dates from December 2009 to March 2010, under two ground cover treatments that changed mean soil temperature by ∼2°C. Bulb initiation was defined botanically as when the hypocotyl was 10mm thick, at 360°Cd (±13.0) for ‘Barkant’ and 420°Cd (±13.7) (Tb=3.6°C) for ‘Green Globe’. However, the bulb participation in dry matter production occurs after an 18mm hypocotyl thickness, which occurred at ∼500°Cd for both turnip cultivars. A single base parameter of 0.995 described the exponential decline of the leaf:bulb ratio. Relationships also described how leaf production and total leaf area expansion changed up until bulb initiation. Radiation use efficiency (RUE) ranged from 1.13 to 1.33g DM/MJ total. A constant rate of total leaf area expansion (0.015m2/m2/°Cd) was obtained up to LAIc for ‘Green Globe’ turnips. A third pot experiment confirmed the thermal time requirement to bulb initiation based on direct assessment of the hypocotyl thickening of ‘Barkant’ and ‘Green Globe’ turnips. Temperature was shown as the main driver of bulb development and growth. The relationships provided could be used to improve the performance of prediction models.

Deformed Lorentz symmetry and relative locality in a curved/expanding spacetime

The interest of part of the quantum-gravity community in the possibility of Planck-scale-deformed Lorentz symmetry is also fueled by the opportunities for testing the relevant scenarios with analyses, from a signal-propagation perspective, of observations of bursts of particles from cosmological distances. In this respect the fact that so far the implications of deformed Lorentz symmetry have been investigated only for flat (Minkowskian) spacetimes represents a very significant limitation, since for propagation over cosmological distances the curvature/expansion of spacetime is evidently tangible. We here provide a significant step toward filling this gap by exhibiting an explicit example of Planck-scale-deformed relativistic symmetries of a spacetime with constant rate of expansion (de Sitterian). Technically, we obtain the first ever example of a relativistic theory of worldlines of particles with 3 nontrivial relativistic invariants: a large speed scale (``speed-of-light scale''), a large distance scale (inverse of the ``expansion-rate scale''), and a large momentum scale (``Planck scale''). We address some of the challenges that had obstructed success for previous attempts by exploiting the recent understanding of the connection between deformed Lorentz symmetry and relativity of spacetime locality. We also offer a preliminary analysis of the differences between the scenario we here propose and the most studied scenario for broken (rather than deformed) Lorentz symmetry in expanding spacetimes.

Faster than expected escape for a class of fully chaotic maps

We investigate the dependence of the escape rate on the position of a hole placed in uniformly hyperbolic systems admitting a finite Markov partition. We derive an exact periodic orbit formula for finite size Markov holes which differs from other periodic expansions in the literature and can account for additional distortion to maps with piecewise constant expansion rate. Using asymptotic expansions in powers of hole size we show that for systems conjugate to the binary shift, the average escape rate is always larger than the expectation based on the hole size. Moreover, we show that in the small hole limit the difference between the two decays like a known constant times the square of the hole size. Finally, we relate this problem to the random choice of hole positions and we discuss possible extensions of our results to non-Markov holes as well as applications to leaky dynamical networks.

Numerical simulation of pressure-controlled cavity expansion process in clay at constant volumetric expansion rate

The cavity expansion theory is being applied to describe many geotechnical engineering processes. Many of these processes are controlled by the cavity volumetric expansion rate in practice. As soil is not an elastic material, the injection pressure is a non-linear function of the cavity volume, rendering it very difficult to produce the appropriate time history of injection pressure so that the controlled cavity volumetric expansion rate can be simulated. In this technical note, an algorithm to develop the time history of injection pressure using appropriate soil properties to generate the required cavity volumetric expansion rate in clay is presented. The simulation and experimental results of a series of laboratory-scale compaction grouting experiments are presented as an example to demonstrate the validity of the approach.

Influence of Cathode Diameter on the Operation of a Planar Diode with an Explosive Emission Cathode

This paper presents the results of experimental investigations into the current-voltage characteristics of a planar diode with an explosive emission cathode made from graphite. Studies were performed using a TEU-500 pulsed electron accelerator (350–500 keV, 100 ns, 250 J per pulse). Duration of diode operation, in a mode when electron current is limited by the emissive ability of the graphite cathode, is 15–20 ns. The contribution of the cathode periphery to total electron current appears only as an increase in the emissive surface area due to an expansion of explosive plasma. Investigations of an ion diode with a graphite cathode (plane and focusing geometry) were also carried out. Experiments were performed using a TEMP-4M ion accelerator, which forms two nanosecond pulses: the first negative pulse (150–200 kV, 300–600 ns) followed by the second positive (250–300 kV, 150 ns). Total diode current in the first pulse is well described by the Child-Langmuir law for electron current at a constant rate of plasma expansion, equal to 1.3 cm/μs. It is shown that for an area of flat cathode over 25 cm2, the influence of edge contribution does not exceed measurement error of total diode electron current (10%).

Assessment of Bread Dough Expansion during Fermentation

The aim of this work was to investigate different methods of measuring the expansion of bread dough during fermentation and to develop a mathematical model to describe the variation of dough volume. Dough was prepared with wheat flour, salt, yeast, and selected amount of water (56%, 58%, and 60% w/w flour basis). Proving time was 1 h and proving temperature investigated were 25, 30, and 35°C. Dough volume was measured with three methods: (1) vertical expansion in a flask, (2) horizontal expansion between two plates, and (3) free expansion method. Volume was measured either using displacement transducer or from image analysis of pictures taken during expansion. All the methods allowed monitoring the increase in dough volume as a function of proving time. Small differences were observed between the three methods. Free expansion shows a faster start of expansion in comparison with the two other methods. Expansion curves have been fitted with a modified Gompertz model (Romano et al., J Food Eng 83:142–148, 2007). They exhibited three phases: a lag phase, followed by a linear phase (constant expansion rate), and finally a phase with a decreasing expansion rate. Statistical analysis of the set of data showed that the proving temperature had a significant effect on the different parameters calculated (volume expansion ratio, expansion rate), while the water content had no significant effect.

Numerical analysis for the coating thickness prediction in continuous hot-dip galvanizing

Gas wiping is a decisive operation in the hot-dip galvanizing process. Especially, it has a crucial influence on the thickness and uniformity of coating film, but may be subsequently responsible for splashing. To date, the number of fundamental studies on the jet structure impinging on a vertical moving strip for various nozzle systems has not been sufficient to draw any meaningful conclusion. In this connection, at first, to confirm the validation of numerical analysis, the impinging jet pressure on the surface of a vertical strip by experiment is compared with the results by numerical analysis. Next, after confirming for the superiority of a constant expansion rate nozzle in splashing, the relationship between the stagnation pressure and the impinging jet pressure distribution issuing from the nozzle system of constant expansion rate is investigated. Finally, by using the calculated wall shear stress, the relationships among the coating thickness, strip speed and nozzle stagnation pressures are clarified. It is found that the impinging wall pressure for the case of constant expansion rate nozzle is more favorable for the problem of splashing to the case of the conventional one. Furthermore, from the point of view of energy conservation, it is advisable to use a constant expansion rate nozzle as a gas-wiping nozzle.

A study of the influence of air-knife tilting on coating thickness in hot-dip galvanizing

Gas wiping is a decisive operation in hot-dip galvanizing process. In special, it has a crucial influence on the thickness and uniformity in coating film, but may be subsequently responsible for the problem of splashing. The progress of industry demands continuously the reduction of production costs which may relate directly with the increase of coating speed, and the speed up of coating results in the increase of stagnation pressure in gas wiping system in final. It is known that the increase of stagnation pressure may accompany a harmful problem of splashing in general. Together with these, also, from the view point of energy consumption, it is necessary to design a nozzle optimally. And there is known that the downward tilting of nozzle using in air knife system is effective to prevent in somewhat the harmful problem of splashing. In these connections, first, we design a nozzle with constant expansion rate. Next, for the case of actual coating conditions in field, the effects of tilting of the constant expansion rate nozzle are investigated by numerical analysis. Under the present numerical conditions, it was turned out that the nozzle of constant expansion rate of p = having a downward jet angle of 5° is the most effective to diminish the onset of splashing, while the influence of small tilting of the nozzle on impinging wall pressure itself is not so large.

Comment on “Can infrared gravitons screenΛ?”

We reply to the recent criticism by Garriga and Tanaka of our proposal that quantum gravitational loop corrections may lead to a secular screening of the effective cosmological constant. Their argument rests upon a renormalization scheme in which the composite operator $(R\sqrt{\ensuremath{-}g}\ensuremath{-}4\ensuremath{\Lambda}\sqrt{\ensuremath{-}g}{)}_{\mathrm{ren}}$ is defined to be the trace of the renormalized field equations. Although this is a peculiar prescription, we show that it does not preclude secular screening. Moreover, we show that a constant Ricci scalar does not even classically imply a constant expansion rate. Other important points are: (1) the quantity ${R}_{\mathrm{ren}}$ of Garriga and Tanaka is neither a properly defined composite operator, nor is it constant; (2) gauge dependence does not render a Green's function devoid of physical content; (3) scalar models on a nondynamical de Sitter background (for which there is no gauge issue) can induce arbitrarily large secular contributions to the stress tensor; (4) the same secular corrections appear in observable quantities in quantum gravity; and (5) the prospects seem good for deriving a simple stochastic formulation of quantum gravity in which the leading secular effects can be summed and for which the expectation values of even complicated, gauge invariant operators can be computed at leading order.

Cosmology from string theory

We explore the cosmological content of Salam-Sezgin six dimensional supergravity, and find a solution to the field equations in qualitative agreement with observation of distant supernovae, primordial nucleosynthesis abundances, and recent measurements of the cosmic microwave background. The carrier of the acceleration in the present de Sitter epoch is a quintessence field slowly rolling down its exponential potential. Intrinsic to this model is a second modulus which is automatically stabilized and acts as a source of cold dark matter, with a mass proportional to an exponential function of the quintessence field (hence realizing VAMP models within a String context). However, any attempt to saturate the present cold dark matter component in this manner leads to unacceptable deviations from cosmological data – a numerical study reveals that this source can account for up to about 7% of the total cold dark matter budget. We also show that (1) the model will support a de Sitter energy in agreement with observation at the expense of a miniscule breaking of supersymmetry in the compact space; (2) variations in the fine structure constant are controlled by the stabilized modulus and are negligible; (3) “fifth” forces are carried by the stabilized modulus and are short range; (4) the long time behavior of the model in four dimensions is that of a Robertson-Walker universe with a constant expansion rate (w = −1/3). Finally, we present a String theory background by lifting our six dimensional cosmological solution to ten dimensions.