Values Of V0 Research Articles

Langley method applied in study of aerosol optical depth in the Brazilian semiarid region using 500, 670 and 870 nm bands for sun photometer calibration

Due to the high costs of commercial monitoring instruments, a portable sun photometer was developed at INPE/CRN laboratories, operating in four bands, with two bands in the visible spectrum and two in near infrared. The instrument calibration process is performed by applying the classical Langley method. Application of the Langley’s methodology requires a site with high optical stability during the measurements, which is usually found in high altitudes. However, far from being an ideal site, Harrison et al. (1994) report success with applying the Langley method to some data for a site in Boulder, Colorado. Recently, Liu et al. (2011) show that low elevation sites, far away from urban and industrial centers can provide a stable optical depth, similar to high altitudes. In this study we investigated the feasibility of applying the methodology in the semiarid region of northeastern Brazil, far away from pollution areas with low altitudes, for sun photometer calibration. We investigated optical depth stability using two periods of measurements in the year during dry season in austral summer. The first one was in December when the native vegetation naturally dries, losing all its leaves and the second one was in September in the middle of the dry season when the vegetation is still with leaves. The data were distributed during four days in December 2012 and four days in September 2013 totaling eleven half days of collections between mornings and afternoons and by means of fitted line to the data V0 values were found. Despite the high correlation between the collected data and the fitted line, the study showed a variation between the values of V0 greater than allowed for sun photometer calibration. The lowest V0 variation reached in this experiment with values lower than 3% for the bands 500, 670 and 870nm are displayed in tables. The results indicate that the site needs to be better characterized with studies in more favorable periods, soon after the rainy season.

Fabrication and high-power piezoelectric characteristics of textured (Sr0.7Ca0.3)2Bi4Ti5O18 ceramics

High-power piezoelectric characteristics under continuous driving were studied for lead-free piezoelectric ceramics of a textured bismuth layer-structured ferroelectric, (Sr0.7Ca0.3)2Bi4Ti5O18 + 0.2 wt % MnCO3 (abbreviated to HF-SCBT) and a non-oriented specimen (OF-SCBT). The orientation of the grains can improve their high-power piezoelectric properties such as the vibration velocity, v0–p. The value of v0–p for the HF-SCBT ceramic exceeded 2.0 m/s at an applied electric field of 3 V/mm under short- and long-time driving. We also observed that the change in resonance frequency under long-time driving for OF- and HF-SCBT was less than 0.15% at a v0–p of 2.0 m/s. Thus, the force factor, A, of HF-SCBT was superior to that of OF-SCBT. The reason for these results is considered to be that d33 for HF-SCBT was 1.5 times as large as that for OF-SCBT.

Spectral singularity in confined ${\cal {PT}}$PT symmetric optical potential

We present an analytical study for the scattering amplitudes (Reflection |R| and Transmission |T|), of the periodic ${\cal {PT}}$PT symmetric optical potential $V(x) = \displaystyle W_0 \left( \cos ^2 x + i V_0 \sin 2x \right)$V(x)=W0cos2x+iV0sin2x confined within the region 0 ⩽ x ⩽ L, embedded in a homogeneous medium having uniform potential W0. The confining length L is considered to be some integral multiple of the period π. We give some new and interesting results. Scattering is observed to be normal (|T|2 ⩽ 1, |R|2 ⩽ 1) for V0 ⩽ 0.5, when the above potential can be mapped to a Hermitian potential by a similarity transformation. Beyond this point (V0 > 0.5) scattering is found to be anomalous (|T|2, |R|2 not necessarily ⩽1). Additionally, in this parameter regime of V0, one observes infinite number of spectral singularities ESS at different values of V0. Furthermore, for L = 2nπ, the transition point V0 = 0.5 shows unidirectional invisibility with zero reflection when the beam is incident from the absorptive side (Im[V(x)] < 0) but with finite reflection when the beam is incident from the emissive side (Im[V(x)] > 0), transmission being identically unity in both cases. Finally, the scattering coefficients |R|2 and |T|2 always obey the generalized unitarity relation : $||T|^2 - 1| = \sqrt{|R_R|^2 |R_L|^2}$‖T|2−1|=|RR|2|RL|2, where subscripts R and L stand for right and left incidence, respectively.

High-pressure elastic behavior of Ca4La6(SiO4)6(OH)2 a synthetic rare-earth silicate apatite: a powder X-ray diffraction study up to 9.33 GPa

The compression behavior of a synthetic Ca4La6(SiO4)6(OH)2 has been investigated to about 9.33 GPa at 300 K using in situ angle-dispersive X-ray diffraction and a diamond anvil cell. No phase transition has been observed within the pressure range investigated. The values of zero-pressure volume V0, K0, and \(K_{0}^{'}\) refined with a third-order Birch–Murnaghan equation of state are V0 = 579.2 ± 0.1 A3, K0 = 89 ± 2 GPa, and \(K_{0}^{'} = 10.9 \pm 0.8\). If \(K_{0}^{'}\) is fixed at 4, K0 is obtained as 110 ± 2 GPa. Analysis of axial compressible modulus shows that the a-axis (Ka0 = 79 ± 2 GPa) is more compressible than the c-axis (Kc0 = 121 ± 7 GPa). A comparison between the high-pressure elastic response of Ca4La6(SiO4)6(OH)2 and the iso-structural calcium apatites is made. The possible reasons of the different elastic behavior between Ca4La6(SiO4)6(OH)2 and calcium apatites are discussed.

Real-Time Colorimetric Assay of Inorganic Pyrophosphatase Activity Based on Reversibly Competitive Coordination of Cu2+ between Cysteine and Pyrophosphate Ion

In this study we demonstrate a new colorimetric method for real-time pyrophosphatase (PPase) activity assay based on reversible tuning of the dispersion/aggregation states of gold nanoparticles (Au-NPs) by controlling the coordination of Cu(2+) between cysteine and pyrophosphate ion (PPi) with PPase. The addition of Cu(2+) to the cysteine-stabilized Au-NP dispersion results in the aggregation of Au-NPs, while the further addition of PPi to this aggregation turns the aggregated Au-NPs into their dispersed state because of the higher coordination reactivity between Cu(2+) and PPi than that between Cu(2+) and cysteine. The subsequent addition of PPase to the PPi-triggered dispersed Au-NPs restores the aggregation state of Au-NPs because PPase catalyzes the hydrolysis of PPi into orthophosphate and thus consumes PPi in the reaction system. In this study, we utilize this reversibility of the change between the aggregation/dispersion states of Au-NPs for real-time colorimetric monitoring of PPase activity by continuously measuring the ratio of absorbance at the wavelength of 650 nm (A650) to that at 522 nm (A522) in the time-dependent UV-vis spectra of Au-NP dispersions containing different activities of PPase. To calculate the kinetics of the PPase-catalyzed hydrolysis of PPi, the A650/A522 values are converted into PPi concentrations to obtain the time-dependent changes of PPi concentrations in the dispersions containing different activities of PPase. The initial reaction rates (v0) are thus achieved from the time-dependent logarithm of PPi concentrations with the presence of different PPase activities. Under the experimental conditions employed here, the v0 values are linear with the PPase activity within a range from 0.025 to 0.4 U with a detection limit down to 0.010 U (S/N = 3). Moreover, the colorimetric method developed here is also employed for PPase inhibitor evaluation. This study offers a simple yet effective method for real-time PPase activity assay.

Apparent Molal Volumes of Aqueous Rare Earth Salts Fit to the Pitzer Equation

The apparent molal volumes (Vϕ) of the trivalent rare earth (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) chlorides, nitrates and perchlorates have been calculated from the density measurements at 25 °C and (5 to 80) °C and 0.02 – 4 m. The values of Vϕ have been fitted to the Pitzer equations, Vϕ = V0 + (AvI/(1.2m) ln(1 + 1.2I0.5) + 2RTm(βV(0) + βV(1) g(y) + mCV), where V0 is the infinite dilution partial molal volume, Av is the Debye- Huckel slope, I is the ionic strength, and g(y) = (2/y2)·[1 – (1 + y) exp(−y)] where y = 2(I0.5). The Pitzer volume parameters βV(0), βV(1) and CV are functions of temperature. The values of V0, βV(0), βV(1), and CV for most of the rare earth chlorides are similar orders of magnitude. These results should be useful in estimating the effect of pressure on the equilibria of rare earths in natural waters over a wide range of temperature.

An in situ high-pressure X-ray diffraction experiment on hydroxyapophyllite

The compression behavior of a natural hydroxyapophyllite is investigated up to about 10.01 GPa at 300 K using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at the High Pressure Experiment Station, Beijing Synchrotron Radiation Facility (BSRF). Over this pressure range, no phase change or disproportionation is observed. The isothermal equation of state is determined for the first time. The values of zero-pressure volume V0, isothermal bulk modulus K0, and K′0 refined with a third-order Birch—Murnaghan equation of state are V0 = 1276.3±0.9 Å3, K0 = 71±3 GPa, and K′0 = 8±1. Furthermore, we confirm that the values of linear compressibility β along the a and c directions of hydroxyapophyllite are elastically anisotropic.

Age- and sex-related differences in force-velocity characteristics of upper and lower limbs of competitive adolescent swimmers.

While there is a direct relationship between maximal anaerobic power (Pmax) and swimming performance, the relationship between upper and lower limbs with regard to Pmax and force-velocity (F-v) characteristics is not clear. The aim of the present study was to examine the effect of age and sex on the ratios of mechanical characteristics between upper and lower extremities of adolescent swimmers. Seventeen girls (aged 14.7±1.8 yr) (mean±standard deviation) and 28 boys (14.6±1.4 yr), all members of competitive swimming clubs, performed a F-v test for both legs and arms. In legs, boys had higher values of Pmax (t43=2.4, p<0.05), Pmax expressed in relative to body mass values (rPmax, t43=3.4, p<0.01) and v0 (t43=4.3, p<0.001), while no differences were found for F0 (t43=1.0, p=0.31) and v0/F0 (t43=0.55, p=0.59). In arms, boys had higher values of Pmax (t43=3.2, p<0.01), rPmax (t43=3.9, p<0.001) and v0 (t43=3.4, p<0.01), while no differences were found for F0 (t43=1.9, p=0.06) and v0/F0 (t43=0.16, p=0.87). However, no sex difference was found with regard to the ratios of Pmax (t43=1.9, p=0.06), F0 (t43=1.2, p=0.23) and v0 (t43=1.3, p=0.20) between upper and lower extremities. There was direct relationship between age and Pmax of legs (r=0.64, p<0.01 in girls; r=0.43, p<0.05 in boys) and arms (r=0.56, p<0.05; r=0.57, p<0.01 respectively), while there was not any significant association between age and the ratios of mechanical characteristics of upper and lower limbs. These findings emphasize the need for separate evaluation of arms’ and legs’ force-velocity characteristics on a regular basis and the consideration of these measures in training design.

Synchrotron X-ray diffraction study of phenacite at high pressure

We report the results of a natural phenacite from 0 to 30.9 GPa using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at the National Synchrotron Light Source, Brookhaven National Laboratory. Over this pressure range, no phase change or disproportionation has been observed. The isothermal equation of state was determined. The values of V0, K0, and K′0 refined with a third-order Birch-Murnaghan equation of state are V0=1116.1±1.2 Å3, K0=223±9 GPa, and K′0=5.5±0.8. Furthermore, we confirm that the linear compressibilities (β) along a and c directions of phenacite are elastically isotropic (βa=1.50×10−3 and βc=1.34×10−3 GPa−1). Consequently, it can be concluded that the compressibility of phenacite under high pressures has been accurately constrained.

Study on the dynamics of an inelastic bouncing ball

Considering the case of air damping, we use the method of numerical simulation to study dynamic behavior of inelastic bouncing ball. By changing the value of control parameter V0, the motion of the bouncing ball exhibits nonlinear phenomena of period doubling bifurcation, chaos, etc. These phenomena are confirmed by both 0-1 test and maximal Lyapunov exponent.

In Situ High-Pressure Synchrotron X-Ray Diffraction Study of Clinozoisite

We investigate the elastic behavior of a natural clinozoisite under about 20.4 GPa at 300 K using in situ angle-dispersive x-ray diffraction and a diamond anvil cell at the National Synchrotron Light Source, Brookhaven National Laboratory. Over this pressure range, no phase change or disproportionation has been observed. The isothermal equation of state is determined. The values of V0 and K0 refined by the Murnaghan equation of state are V0 = 460.0 ± 0.2 Å3, K0 = 138 ± 3 GPa. Consequently, it can be concluded that the compressibility of clinozoisite under high pressures is accurately constrained.

Synchrotron X-ray diffraction study of haüyne at high pressure

The compression behavior of a natural haüyne has been investigated to about 8.1GPa at 300K using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at High Pressure Experiment Station, Beijing Synchrotron Radiation Facility (BSRF). Over this pressure range, no phase change or disproportionation has been observed. The isothermal equation of state was determined for the first time. The values of V0, K0, and K′0 refined with a third-order Birch–Murnaghan equation of state are V0=751.6±0.4Å3, K0=49±1GPa, and K′0=3.3±0.3, respectively.

Estimation of velocity function parameters in unconsolidated sands using semblance velocity analysis

To properly understand seismic wave propagation in unconsolidated sand layers, it is important to estimate the parameters of their continuous velocity–depth functions. This study proposes a procedure to estimate the V0 and k parameters of a specific velocity function, where V0 is the direct P-wave velocity at the ground surface and k is the velocity gradient. The V0 and k parameters are generally independent of each other. However, it is possible to relate them numerically because both depend strongly on the porosity (ϕ) and water saturation (Sw). The proposed procedure starts by tabulating V0 and k for 0.05 ≤ ϕ ≤ 0.5 sampled at Δϕ = 0.05 and Sw = 0.6, so that only V0 is needed for fitting. Then, time–distance (T-X) type curves of the direct arrival are calculated for the corresponding values of V0 and k parameters values. The type curves are fitted then to the observed shot gather through a modification of the classic semblance velocity analysis method. Once the best-fit V0 value is found, the corresponding k, ϕ, and Sw values are picked from a V0–k–ϕ lookup table. The procedure is applied on synthetic shot gathers with various amounts of additive Gaussian random noise. Results show that the method is robust and tolerant to low to moderate amounts of noise.

Propagator and multiple scattering approach to the time of arrival problem

The propagator approach combined with the multiple-scattering theory is applied to the particle time of arrival (TOA) problem. This approach allows us to naturally include in the consideration the components of the particle initial wavefunction (defined at t = t0) corresponding to the positive (forward-moving term) and negative (backward-moving term) momenta. For a freely moving particle it is shown that the Allcock definition of the ideal total TOA probability disregards the backward-moving and interference terms entirely. In the presence of a measuring apparatus modeled by an imaginary step potential with the amplitude V0, the general expression for the TOA rate is obtained, the forward-moving component of which coincides with that obtained by Allcock. It is shown that when the initial particle wavefunction is well separated from the point of arrival and has a well-defined average momentum, the contribution of the backward-moving and interference terms are small and can be neglected. For a small V0, except the well-known convolution result by Allcock–Kijowski, the exponential form of the TOA rate follows at the double limit condition V0 → 0, t − t0 ∼ ℏ/2V0 → ∞ (2V0(t − t0)/ℏ is finite) while the backward-moving and interference terms vanish. We show that the Allcock result for the TOA rate is valid in the entire range of V0 including the Zeno case (V0 → ∞) and the normalized TOA rate can be introduced for all values of V0 as a probability distribution. The latter is illustrated for the Gaussian wave packet.

Halogen‐free intumescent flame retardant acrylonitrile‐butadiene‐styrene/poly(ethylene terephthalate) blends

AbstractThe influence of ammonium polyphosphate (APP) with and without synergistic agents — aluminum hypophosphite (Al(H2PO2)3), epoxy resin (E‐44), and Zeolite 4A — in acrylonitrile‐butadiene‐styrene/poly(ethylene terephthalate) (ABS/PET) blends was investigated. The limiting oxygen index (LOI) and UL94 tests were used to investigate flame properties. The results showed that APP with and without synergistic agents all improved the flame retardancy of ABS/PET systems. The ABS/PET/APP + 2 wt % Al(H2PO2)3, ABS/PET/APP + 2 wt % E‐44, and ABS/PET/APP + 3 wt % Zeolite 4A systems achieved the best flame retardancy rating of V0 and LOI values were 32, 34, and 30.5, respectively. The thermal degradation behaviors analyzed by thermogravimetric analysis (TGA) indicated APP mainly accelerated the degradation of PET and led to the increase of charring residues. Al(H2PO2)3 and E‐44 resulted in synergistic effects on the charring process of ABS/PET/APP. SEM revealed that the intact, dense, and strong char layer formed on the surface of the ABS/PET/APP/ Al(H2PO2)3 (or E‐44) system, which was significantly different from the loose and porous char layer of ABS/PET and ABS/PET/APP systems. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Mechanism of Interior Ballistic Peak Phenomenon of Guns and Its Effects

The erosion and wear in the gun barrel will get worse with an increase in the number of projectiles fired. Generally speaking, the ballistic performance of the gun, measured through indicators such as the maximum pressure pm and the muzzle velocity v0, will decrease gradually due to gun barrel erosion. However, the above analysis does not agree with the firing test data of certain types of guns, especially of some small-caliber guns. The ballistic performance of such guns will exhibit an increase to their peak values followed by a gradual decrease with the number of rounds fired. This is the so-called interior ballistic peak phenomenon, also named as the hump effect. Taking several kinds of guns as examples, such as a 76 mm gun and a 100 mm gun, we calculated the engraving pressure p0 of the guns by an approximate method and built a lumped-parameter interior ballistic model of the guns that exhibits the effect, according to the interior ballistics theory of guns with erosion and wear. The results of the modeling of the guns under different wear conditions are close to the test data, showing the existence of the peak values of pm and v0. The simulation results of some of the other guns that exhibit this phenomenon also show good agreement. Furthermore, it can explain the double-peak phenomenon for some types of guns with double driving bands. It was proven that the mismatch of the structure and the dimensions of the gun bore with those of the projectile driving band is the fundamental cause of this effect. Due to the mismatch, the engraving pressure will first increase and then decrease with the enlargement of the bore dimensions caused by barrel erosion and wear. The variation in the engraving pressure p0 will inevitably lead to the variation in interior ballistic performance in the life cycle of the gun. This observed process appears to explain the interior ballistic peak phenomenon.

Numerical simulation of the shape of charged drops over a solid surface

In this work we study the static shape of charged drops of a conducting fluid placed over a solid substrate, surrounded by a gas, and in absence of gravitational forces. The problem can be posed, since Gauss, in a variational setting consisting of obtaining the configurations of a given mass of fluid that minimize (or in general make extremal) a certain energy involving the areas of the solid-liquid interface and of the liquid-gas interface, as well as the electric capacity of the drop. In [6] we have found, as a function of two parameters, Young's angle θY and the potential at the drop's surface V0, the axisymmetric minimizers of the energy. In the same article we have also described their shape and showed the existence of symmetry-breaking bifurcations such that, for given values of θY and V0, configurations for which the axial symmetry is lost are energetically more favorable than axially symmetric configurations. We have proved the existence of such bifurcations in the limits of very flat and almost spherical equilibrium shapes. In this work we study all other cases numerically. When dealing with radially perturbed equilibrium shapes we lose the axially symmetric properties and need to do a full three-dimensional approximation in order to compute area and capacity and hence the energy. We use a boundary element method that we have already implemented in [3] to compute the surface charge density. From the surface charge density we can obtain the capacity of the body. One conclusion of this study is that axisymmetric drops cannot spread indefinitely by introducing sufficient amount of electric charges, but can reach only a limiting (saturation) size, after which the axial symmetry would be lost and finger-like shapes energetically preferred.

Formation and decay of coherent structures in pipe flow

Experimental investigation of the generation and decay of coherent structures, namely, streaks (accompanied by a counter-rotating vortex pair) and hairpin vortices in pipe flow, is carried out by artificial injection of continuous disturbances. Flow visualization and velocity measurements show that for small amplitudes of disturbances (v0) streaks are produced, and increasing v0 produces instability waves on the streaks, which further break down into an array of hairpin vortices. However, the streaks and hairpins decay along the downstream direction (X). In fact, the critical value of v0 required for the initiation of hairpins at a given Re (Reynolds number) varies with the streamwise distance (in contrast to the previously found scaling of v0 ~ Re−1, valid only close to the location of injection, i.e. smaller X). This is a consequence of the decay of the coherent structures in the pipe. Moreover, the hairpins have been found to decay more slowly with increasing Re. Measurements of energy in the cross-sectional plane of the pipe, and maps of disturbance velocity at various X-locations show the transient growth and decay of energy for relatively low v0. For higher v0 and Re the energy has been seen to increase continuously along the length of the pipe under observation. Owing to the increase in the cross-sectional area occupied by the disturbance along the X-direction, it is observed that energy can transiently increase even when the total disturbance magnitude is decreasing. Observing the similarity of the present work and other investigations wherein decay of turbulence in pipe flow is found, a schematic illustration of the transition surface for pipe flow on a v0−Re−X, three-dimensional coordinate system is presented.

Studying the scattering length by varying the depth of the potential well

Discussions of the scattering length frequently focus on the special case of the deuteron, and sometimes statements that are not true in general are made. To obtain a deeper understanding, we study the scattering length as a function of the depth V0 of a square well and an exponential well and show how the scattering length becomes infinite at values of V0 for which new bound states appear at zero energy.

10.1007/s11445-008-2004-4

The atomic scattering factors of fast electrons at zero angle of incidence of an electron beam, f el(0), are calculated for neutral atoms with Z = 1−54, using the mean-square radii of electron-density distributions in atoms and ions, derived on the basis of the Hartree-Fock wave functions. The values of f el(0) have been calculated for the first time for some positive and negative ions. The obtained values of f el(0) were used to determine the mean inner potentials V0 of metallic, covalent, and ionic crystals. The calculated values of V0 are compared with the experimental data in the literature. The values of V0 calculated for III–V and II–VI compounds are reported.