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1.
N. I. Shishkin 《Journal of Applied Mechanics and Technical Physics》2011,52(6):849-856
Formulas for the diameter and depth of an explosion crater are obtained which take into account the energy and impulse of
the explosion products, rock strength, burial depth of the explosive charge, and gravity. Using the explosive-shock analogy,
the obtained relations are extended to the case of meteorite (impactor) impact on the planet’s crust (target). It is shown
that in the gravity cratering regime, the influence of the impulse of the impactor is significant and increases with increasing
its size. In the strength cratering regime, the impulse has little effect on crater dimensions. It is established that crater
dimensions are determined mainly by the kinetic energy of the impactor and, to a lesser degree, by its impulse. 相似文献
2.
İbrahim Doymaz 《Heat and Mass Transfer》2011,47(3):277-285
The effect of blanching and drying temperature (50, 60 and 70°C) on drying kinetics and rehydration ratio of sweet potatoes
was investigated. It was observed that both the drying temperature and blanching affected the drying time and rehydration
ratio. The logarithmic model showed the best fit to experimental drying data. The values of effective moisture diffusivity
and activation energy ranged from 9.32 × 10−11 to 1.75 × 10−10 m2/s, and 22.7–23.2 kJ/mol, respectively. 相似文献
3.
Classical Darcy’s law assumes that the intrinsic permeability of porous media is only dependent on the micro-geometrical and
structural properties of the inner geometry of the medium. There are, however, numerous experimental evidences that intrinsic
permeability of shaly and clayey porous material is a function of the fluid phase used in the experiments. Several pore-scale
processes have been proposed to explain the observed behavior. In this study, we conduct a detailed investigation of one such
mechanism, namely the electrokinetic coupling. We have developed a numerical model to simulate this process at the pore-scale,
incorporating a refined model of the electrical double layer. The model is used to conduct a detailed sensitivity analysis
to elucidate the relative importance of several chemical–physical parameters on the intensity of the electrokinetic coupling.
We found that permeability reduction due to this mechanism is likely to occur only if the effective pore-radius is smaller
than 10−6 m. We also observed that electrokinetic coupling is strongly sensitive to electrophoretic mobility, which is normally reduced
in clays compared to free-water conditions. Based on these findings, we set up a suite of stochastic pore-network simulations
to quantify the extent of permeability reduction. We found that only if the effective pore-radius is ranging from 5 × 10−7 m to 5 × 10−8, electrokinetic coupling can be responsible for a 5–20% reduction of the intrinsic permeability, and, therefore, this mechanism
has a minor impact on situations of practical environmental or mining interest. 相似文献
4.
V. N. Snytnikov Vl. N. Snytnikov D. A. Dubov V. I. Zaikovskii A. S. Ivanova V. O. Stoyanovskii V. N. Parmon 《Journal of Applied Mechanics and Technical Physics》2007,48(2):292-302
The efficiency of utilization of CO
2 laser energy for vaporization of Al
2
O
3 ceramics is evaluated using a mathematical model for the interaction of laser radiation with materials. It is shown that
the calculated efficiency of radiation-energy utilization is not higher than 15% at a radiation power density of 105
W/cm
2 on the target. On the experimental facility designed for the synthesis of nanopowders, a vaporization rate of 1 g/h was achieved for Al
2
O
3, which corresponds to a 3% efficiency of radiation-energy utilization. The dependence of the characteristic particle size
of a zirconium oxide nanopowder on helium pressure in the range of 0.01–1.00 atm was studied. Results of experiments on vaporization
of multicomponent materials (LaNiO
3 and the Tsarev meteorite) are given.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 172–184, March–April, 2007. 相似文献
5.
MEMS and NEMS devices typically have a large surface area to volume ratio. As a result, a major concern in the development
of such devices is friction. Contact radii in MEMS and NEMS devices are expected to range from 10−8<a<10−5 m. This regime, which generally lies between the limits of single asperity and macroscopic contact, has yet to be explored
because the apparati used to characterize friction at these limits do not operate in the range of forces appropriate to these
length scales. A Mesoscale Friction Tester (MFT) with smooth probe tip radii from 50 nm to 50 μm and capable of applying forces
ranging from 10 nN to l mN over contact radii from 10 nm to 10 μm has been developed to address this need. With carefully
planned experiments, this device has the potential to help answer unresolved questions regarding friction mechanisms in the
mesoscale range. 相似文献
6.
K. N. Jonnalagadda I. Chasiotis S. Yagnamurthy J. Lambros J. Pulskamp R. Polcawich M. Dubey 《Experimental Mechanics》2010,50(1):25-35
A new microscale uniaxial tension experimental method was developed to investigate the strain rate dependent mechanical behavior
of freestanding metallic thin films for MEMS. The method allows for highly repeatable mechanical testing of thin films for
over eight orders of magnitude of strain rate. Its repeatability stems from the direct and full-field displacement measurements
obtained from optical images with at least 25 nm displacement resolution. The method is demonstrated with micron-scale, 400-nm
thick, freestanding nanocrystalline Pt specimens, with 25 nm grain size. The experiments were conducted in situ under an optical
microscope, equipped with a digital high-speed camera, in the nominal strain rate range 10−6–101 s−1. Full field displacements were computed by digital image correlation using a random speckle pattern generated onto the freestanding
specimens. The elastic modulus of Pt, E = 182 ± 8 GPa, derived from uniaxial stress vs. strain curves, was independent of
strain rate, while its Poisson’s ratio was v = 0.41 ± 0.01. Although the nanocrystalline Pt films had the elastic properties
of bulk Pt, their inelastic property values were much higher than bulk and were rate-sensitive over the range of loading rates.
For example, the elastic limit increased by more than 110% with increasing strain rate, and was 2–5 times higher than bulk
Pt reaching 1.37 GPa at 101 s−1. 相似文献
7.
The passage of solid spheres through a liquid–liquid interface was experimentally investigated using a high-speed video and
PIV (particle image velocimetry) system. Experiments were conducted in a square Plexiglas column of 0.1 m. The Newtonian Emkarox
(HV45 50 and 65% wt) aqueous solutions were employed for the dense phase, while different silicone oils of different viscosity
ranging from 10 to 100 mPa s were used as light phase. Experimental results quantitatively reveal the effect of the sphere’s
size, interfacial tension and viscosity of both phases on the retaining time and the height of the liquid entrained behind
the sphere. These data were combined with our previous results concerning the passage of a rising bubble through a liquid–liquid
interface in order to propose a general relationship for the interface breakthrough for the wide range of Mo
1/Mo
2 ∈ [2 × 10−5–5 × 104] and Re
1/Re
2 ∈ [2 × 10−3–5 × 102]. 相似文献
8.
Damped inertial water flow in a cylindrical vessel is investigated. A return effect or "recoil" as the shear strain rate falks
to a value of the order of 10−3s−1 is observed. Over the range of low strain rates the water behaves like a medium with very low shear strength and a shear
modulus of the order of 10−6 Pa.
Ekaterinburg. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 3–7, January–February,
1997. 相似文献
9.
Measurement of drainage relative permeability by the centrifuge method was first introduced by Hagoort (SPE J. 29(3):139–150,
1980). It has been shown that capillary end effects can cause error in the measurement of relative permeability if a minimum
rotational speed is not honoured. To determine the minimum rotational speed that makes the capillary end effect negligible,
ω
min, we propose that the value of capillary-gravity number, N
cg, should be of the order of 10−2 or smaller. This conclusion is based on the use a Forward–backward scheme consisting of a forward numerical simulator developed
for centrifuge experiments and applying Hagoort’s method as a backward model. The article presents the use of this Forward–backward
scheme as a powerful tool for error analysis such as determining the impact of capillary end effects. By using this loop,
we first determine ω
min for specific core and fluid properties. Later, we generalize the ω
min calculations by using the definition of N
cg as a “rule of thumb” for designing relative permeability experiments by centrifuge method. We also demonstrate another use
of this loop for controlling the quality of the experimental data. 相似文献
10.
Yi Wu Hangfeng Wang Zhaohui Liu Jing Li Liqi Zhang Chuguang Zheng 《Acta Mechanica Sinica》2006,22(2):99-108
Particle-laden flows in a horizontal channel were investigated by means of a two-phase particle image velocimetry (PIV) technique.
Experiments were performed at a Reynolds number of 6 826 and the flow is seeded with polythene beads of two sizes, 60 μm and 110 μm. One was slightly smaller than and the other was larger than the Kolmogorov length scale. The particle loadings were relatively
low, with mass loading ratio ranging from 5×10−4 to 4×10−2 and volume fractions from 6×10−7 to 4.8×10−5, respectively. The results show that the presence of particles can dramatically modify the turbulence even under the lowest
mass loading ratio of 5×10−4. The mean flow is attenuated and decreased with increasing particle size and mass loading. The turbulence intensities are
enhanced in all the cases concerned. With the increase of the mass loading, the intensities vary in a complicated manner in
the case of small particles, indicating complicated particle-turbulence interactions; whereas they increase monotonously in
the case of large particles. The particle velocities and concentrations are also given. The particles lag behind the fluid
in the center region but lead in the wall region, and this trend is more prominent for the large particles. The streamwise
particle fluctuations are larger than the gas fluctuations for both sizes of particles, however their varying trend with the
mass loadings is not so clear. The wall-normal fluctuations increase with increasing mass loadings. They are smaller in the
60 μm particle case but larger in the 110 μm particle case than those of the gas phase. It seems that the small particles follow the fluid motion to certain extent while
the larger particles are more likely dominated by their own inertia. Finally, remarkable non-uniform distributions of particle
concentration are observed, especially for the large particles. The inertia of particles is proved to be very important for
the turbulence modification and particles behaviors and thus should be considered in horizontal channels.
The project supported by the National Natural Science Foundation of China (50276021), and Program for New Century Excellent
Talents in University, Ministry of Education (NCET-04-0708) The English text was polished by Yunming Chen. 相似文献
11.
Natural convection in a partially filled porous square cavity is numerically investigated using SIMPLEC method. The Brinkman-Forchheimer
extended model was used to govern the flow in the porous medium region. At the porous-fluid interface, the flow boundary condition
imposed is a shear stress jump, which includes both the viscous and inertial effects, together with a continuity of normal
stress. The thermal boundary condition is continuity of temperature and heat flux. The results are presented with flow configurations
and isotherms, local and average Nusselt number along the cold wall for different Darcy numbers from 10−1 to 10−6, porosity values from 0.2 to 0.8, Rayleigh numbers from 103 to 107, and the ratio of porous layer thickness to cavity height from 0 to 0.50. The flow pattern inside the cavity is affected
with these parameters and hence the local and global heat transfer. A modified Darcy–Rayleigh number is proposed for the heat
convection intensity in porous/fluid filled domains. When its value is less than unit, global heat transfer keeps unchanged.
The interfacial stress jump coefficients β
1 and β
2 were varied from −1 to +1, and their effects on the local and average Nusselt numbers, velocity and temperature profiles
in the mid-width of the cavity are investigated. 相似文献
12.
Sayed Z. Mohammady 《Rheologica Acta》2007,46(8):1109-1119
To determine the impact of molecular architecture on the molecular dynamics of the glass relaxation processes of soft blocks
in different types of block copolymers, model block copolymers with a variation in both molecular architecture and chemical
composition were studied. Four block copolymer models, namely, two styrene–butadiene–styrene (S-B-S) block copolymers and
two styrene–styrene butadiene–styrene (S-SB-S) were chosen. In each pair of block copolymers, one is linear triblock and the
other is star asymmetric. For the sake of comparison, two polybutadiene (PB) homopolymer samples, having similar chain lengths
of the PB blocks present in the S-B-S block copolymers, have been investigated. Dynamic mechanical measurements have been
carried out for the real and imaginary parts of the complex shear modulus (G′, G”) in the temperature and frequency ranges from −110 to 30 °C and from 10−2 to 15.9 Hz, respectively. Complete master curves have been constructed for all samples investigated. Moreover, broadband
dielectric spectroscopy has been carried out to cover wide temperature and frequency windows, −120 to 0 °C and 10−1 to 107 Hz, respectively. The results showed that the molecular dynamics of the glass relaxation process of the PB or statistical
PSB soft phases in the block copolymers is dramatically changed when compared to the PB homopolymer. In addition, the molecular
architecture is found to be an important factor in determining the molecular mobility of the soft blocks. The results are
discussed in terms of the applied confinement of the counter PS hard phase, block lengths, domain thicknesses and the type
of end-to-end junctions between the different polymeric blocks.
Paper presented 3rd Annual European Rheology Conference (AERC 2006) April 27–29, 2006, Crete, Greece. 相似文献
13.
This paper concerns the regularity of a capillary graph (the meniscus profile of liquid in a cylindrical tube) over a corner
domain of angle α. By giving an explicit construction of minimal surface solutions previously shown to exist (Indiana Univ. Math. J. 50 (2001), no. 1, 411–441) we clarify two outstanding questions.
Solutions are constructed in the case α = π/2 for contact angle data (γ1, γ2) = (γ, π − γ) with 0 < γ < π. The solutions given with |γ − π/2| < π/4 are the first known solutions that are not C2 up to the corner. This shows that the best known regularity (C1, ∈) is the best possible in some cases. Specific dependence of the H?lder exponent on the contact angle for our examples is
given.
Solutions with γ = π/4 have continuous, but horizontal, normal vector at the corners in accordance with results of Tam (Pacific J. Math. 124 (1986), 469–482). It is shown that our examples are C0, β up to and including the corner for any β < 1.
Solutions with |γ − π/2| > π/4 have a jump discontinuity at the corner. This kind of behavior was suggested by numerical work
of Concus and Finn (Microgravity sci. technol. VII/2 (1994), 152–155) and Mittelmann and Zhu (Microgravity sci. technol. IX/1 (1996), 22–27). Our explicit construction, however, allows us to investigate the solutions quantitatively. For example,
the trace of these solutions, excluding the jump discontinuity, is C2/3. 相似文献
14.
An Australian hard wheat flour–water dough has been characterised using parallel plate and capillary rheometers over an extensive
range of apparent shear rates (10 − 3–103 s − 1) relevant to process conditions. Torsional measurements showed that the shear viscosity of the dough increased with strain
to a maximum value and then decreased, suggesting a breakdown of the dough structure. Both torsional and capillary experiments
revealed the shear-thinning behaviour of the dough. The wall slip phenomenon in capillary rheometry was investigated and found
to be diameter dependent and occurred at a critical shear stress of approximately 5–10 kPa. A two-regime power law behaviour
was observed, with the power law index approximately 0.3 in the low shear rate range increasing to 0.67 in the high shear
rate range. Pressure fluctuation was observed in the capillary data and increased with shear rate, in particular, at shear
rates approaching 104 s − 1. The results demonstrate that capillary rheometry is a viable means of rheologically testing dough at high shear rates provided
pressure fluctuation is carefully monitored and capillary rheometry corrections, including wall slip, are accounted for. 相似文献
15.
V. A. Simonenko N. I. Shishkin G. A. Shishkina 《Journal of Applied Mechanics and Technical Physics》2006,47(4):461-471
Analytic representations are obtained for the displacement and stress fields in the Rayleigh surface wave (R-wave) generated
in an elastic half-space by an internal source that produces the same seismic P-wave as an underground explosion. Oscillograms,
particle trajectories, and stresses in the half-space and on its surface are calculated. Relations for the energy flux in
the R-wave are obtained. For rock salt, the fraction of the explosion energy transferred to the R-wave is estimated. It is
established that this fraction can reach values of about 1% of the total explosion energy if the explosion is a contained
one. As the charge depth is increased, the energy of the R-wave decreases in approximately inverse proportion to the depth.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 4, pp. 3–14, July–August, 2006. 相似文献
16.
Based on the mass transfer theory, a new mass transfer model of ion-exchange process on zeolite under liquid film diffusion
control is established, and the kinetic curves and the mass transfer coefficients of –K+ ion-exchange under different conditions were systemically determined using the shallow-bed experimental method. The results
showed that the –K+ ion-exchange rates and transfer coefficients are directly proportional to solution flow rate and temperature, and inversely
proportional to solution viscosity and the size of zeolite granules. It also showed that the transfer coefficient is not influenced
by the ion concentrations. For a large ranges of operational conditions including temperatures (10 − 75°C), flow rates (0.031 m s−1 −0.26 m s−1), liquid viscosities (1.002 × 10−3 N s m−2 − 4.44 × 10−3 N s m−2), and zeolite granular sizes (0.2 − 1.45 mm), the average mass transfer coefficients calculated by the model agree with the
experimental results very well. 相似文献
17.
The dynamic yield strengths of three steels were determined at strain rates of about 103 s−1 and 106 s−1. The measurements at 103 s−1 were obtained by a new technique based on measurements of large amplitude elastic waves in long bars struck by rigid flyer
plates. Embedded manganin gages were used to measure stress, and the gage records were long enough to observe subsequent reverberations
between the bar free end and the plastically deformed impact end. The measurements at 106 s−1 were made with a slightly modified version of a conventional flyer-plate impact configuration. The data are combined with
static results to show the behavior of these steels at strain rates of 10−3 s−1 to 106 s−1. 相似文献
18.
G. I. Rastorguev S. I. Snisarenko 《Journal of Applied Mechanics and Technical Physics》2009,50(1):155-162
A problem of determining elastic and viscous characteristics of composite materials, necessary and sufficient for choosing
physical relations in solving problems of impact loading with low impact velocities (up to 200 m/sec) and unsteady deformation in the range of strain rates within 10
2
sec−1
for multilayer beams, plates, and shells, is considered.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 1, pp. 187–196, January–February, 2009. 相似文献
19.
This paper presents an experimental and theoretical investigation of drying of moist slab, cylinder and spherical products
to study dimensionless moisture content distributions and their comparisons. Experimental study includes the measurement of
the moisture content distributions of slab and cylindrical carrot, slab and cylindrical pumpkin and spherical blueberry during
drying at various temperatures (e.g., 30, 40, 50 and 60°C) at specific constant velocity (U = 1 m/s) and the relative humidity φ = 30%. In theoretical analysis, two moisture transfer models are used to determine drying process parameters (e.g., drying
coefficient and lag factor) and moisture transfer parameters (e.g., moisture diffusivity and moisture transfer coefficient),
and to calculate the dimensionless moisture content distributions. The calculated results are then compared with the experimental
moisture data. A considerably high agreement is obtained between the calculations and experimental measurements for the cases
considered. The effective diffusivity values were evaluated between 0.741 × 10−5 and 5.981 × 10−5 m2/h for slab products, 0.818 × 10−5 and 6.287 × 10−5 m2/h for cylindrical products and 1.213 × 10−7 and 7.589 × 10−7 m2/h spherical products using the Model-I and 0.316 × 10−5–5.072 × 10−5 m2/h for slab products, 0.580 × 10−5–9.587 × 10−5 m2/h for cylindrical products and 1.408 × 10−7–13.913 × 10−7 m2/h spherical products using the Model-II. 相似文献
20.
Understanding the radiation embrittlement of reactor pressure vessel (RPV) steels is required to be able to operate safely
a nuclear power plant or to extend its lifetime. The mechanical properties degradation is partly due to the clustering of
solute under irradiation. To gain knowledge about the clustering process, a Fe−1.1 Mn−0.7 Ni (at.%) alloy was irradiated in
a test reactor at two fluxes of 0.15 and 9 ×1017 n
E > 1MeV
.m − 2.s − 1 and at increasing doses from 0.18 to 1.3 ×1024 n
E > 1MeV
.m − 2 at 300°C. Atom probe tomography (APT) experiments revealed that the irradiation promotes the formation in the α iron matrix of Mn/Mn and/or Ni/Ni pair correlations at low dose and Mn–Ni enriched clusters at high dose. These clusters
dissolve partially after a thermal treatment at 400°C. Based on a comparison with thermodynamic calculations, we show that
the solute clustering under irradiation can just result from an induced mechanism. 相似文献