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1.
ZnO nanorods were synthesized through a simple chemical method by reacting Zn(C2H3O2)2·2H2O and NaOH at low temperature and the effects of changing the order of addition of reactants on the morphological evolution of ZnO nanorods were investigated. The samples were characterized by using XRD, SEM, EDX, TEM, BET and Raman techniques. Optical properties of the ZnO nanostructures were too investigated by UV–Vis spectroscopy at room temperature.The hexagonal wurtzite phase of ZnO was confirmed by X-ray diffraction (XRD) for all the samples. SEM and TEM analysis indicated that different morphologies were obtained by changing the order of addition of reactants. 相似文献
2.
R. A. Vadov 《Acoustical Physics》2005,51(3):265-270
The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized. 相似文献
3.
We study the Cauchy problem for the Whitham modulation equations for increasing smooth initial data. The Whitham equations are a collection of one-dimensional quasi-linear hyperbolic systems. This collection of systems is enumerated by the genus g=0,1,2, ... of the corresponding hyperelliptic Riemann surface. Each of these systems can be integrated by the so-called hodograph transformation introduced by Tsarev. A key step in the integration process is the solution of the Tsarev linear overdetermined system. For each g>0, we construct the unique solution of the Tsarev system, which matches the genus g+1 and g–1 solutions on the transition boundaries. 相似文献
4.
It is shown that the relations generally used for interpreting the frequency dependence of complex susceptibility caused by magnetic after-effect differ from those obtained by consistent application of the Néel theory. These more exact expressions are derived and it is shown that they represent the measured dependence better. 相似文献
5.
We predict the trajectory of the center of a typhoon by using the coordinates of the first three positions of the center.
From this information, we obtain the initial distribution of the wind velocity using a neural network trained for solving
this inverse problem. We take the wind field at the initial time as the sum of a smooth part and a singular part, according
to the Maslov theory. This form of the field ensures the stability and self-similarity of the flow. The trajectory is found
by solving the shallow water equations numerically. In some cases, the resulting trajectory approximates the actual trajectory
fairly well.
This work has been supported by the project DSTN 521241 (Dep. Physics, Univ. La Sapienza, Italy, DSTN) 相似文献
6.
The probability distribution density of the deviation of the surface of liquid hydrogen from the equilibrium plane state in the system of capillary waves has been analyzed. It has been shown that this probability distribution density for the case of the excitation of the surface oscillations by low-frequency noise in the turbulent regime is well reproduced by a Gaussian. When the oscillations are excited by a low-frequency harmonic force, the stochastization of the waves occurs after several scattering events. 相似文献
7.
It is emphasized that any equation of state (EOS) based on the generalized Lennard-Jones potential or the Mie potential, suffers
from two main shortcomings as pointed out by Stacey and Davis [2]. One of the shortcomings viz. the problem related to imaginary numbers for the exponents in the potential function, has been removed recently by Jiuxun
[11] by using a relationship between the exponents. However, the modified EOS obtained by Jiuxun suffers from the second shortcoming
viz. it gives lower values for −B
0
B″0, an important equation of state parameter related to the second pressure derivative of the bulk modulus. Values of B
0
B″0 obtained by Jiuxun are not consistent with those reported by Stacey and Davis.
相似文献
8.
D. P. Bhattacharyya P. Pal B. Basu S. C. Mukherjee A. K. Ganguly M. Fujii 《Il Nuovo Cimento C》1991,14(1):35-40
Summary A stack of CR-39 (HCB 0.5%) passive solid-state nuclear track detectors were irradiated by primary cosmic rays near the top
of the atmosphere. The stack of detectors were flown by balloons launched from Alice Springs, Australia in 1983. After 16
h 41 min flight exposure at an atmospheric pressure of 9.5 mb the plates were collected and chemically etched in 6.7 N NaOH
aqueous solution at 70°C for 27 hours. The diameter distribution of the 1208 etch pits caused by the presence of heavy ions
in primary cosmic rays was measured by a transmitted light Leitz Ortholux microscope having an objective×10 and a×15 filar
micrometer eyepiece attachment. The diameter distribution was standardised and calibrated against the conventional cosmic-ray
results found by Tasakaet al. The estimated charge spectrum is in accord with the nuclear emulsion data of Daniel and Durgaprasad, Kristianssonet al., Saito and Chohanet al. 相似文献
9.
It is shown that the statistical properties of the magnitude of the magnetic field in turbulent electrically conducting media resemble, in the inertial range, those of passive scalars in fully developed three-dimensional fluid turbulence. This conclusion, suggested by the data from the Advanced Composition Explorer, is supported by a brief analysis of the appropriate magnetohydrodynamic equations. 相似文献
10.
V. V. Danilenko 《Physics of the Solid State》2004,46(4):595-599
The history of the discovery of nanodiamond synthesis, the investigation of nanodiamond properties, and the application and organization of their production in the second half of the 20th century is expounded. It is noted that this history is unique, since nanodiamond synthesis was discovered in the USSR three times over 19 years: first by K.V. Volkov, V.V. Danilenko, and V.I. Elin at the VNIITF (Snezhinsk) in 1963 and then, in 1982, by A.M. Staver and A.I. Lyamkin at the Institute of Hydrodynamics, Siberian Division, Academy of Sciences of the USSR (Novosibirsk), and by G.I. Savvakin at the Institute of Problems of Materials Science, Academy of Sciences of the UkSSR (Kiev). All of these researchers discovered nanodiamond synthesis accidentally while studying diamond synthesis by shock compression of nondiamond carbon modifications in blast chambers. The priority of work by Russian scientists in this field is demonstrated. 相似文献
11.
E. Lifshitz 《General Relativity and Gravitation》2017,49(2):18
This is the republished English edition of a paper by E. Lifshitz, first published in 1946, in which the author investigates the gravitational stability of the non–stationary isotropic models of the universe. The paper has been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by George F. R. Ellis, and by a brief biography of Evgenii Mikhailovich Lifshitz, written by Andrzej Krasiński. 相似文献
12.
Jean-Marc Richard 《Few-Body Systems》2009,45(1):65-70
A new investigation is done of the possibility of binding the “dodecatoplet”, a system of six top quarks and six top antiquarks,
(t
6
t̄
6), using the Yukawa potential mediated by Higgs exchange. A simple variational method gives a upper bound close to that recently
estimated in a mean-field calculation. It is supplemented by a lower bound provided by identities among the Hamiltonians describing the system and its subsystems. 相似文献
13.
The Coulomb correction to the rate of multiphoton ionization of atoms and ions by intense laser radiation is derived for large Keldysh adiabaticity parameters using the imaginary time method. This correction increases the ionization rate by several orders of magnitude. 相似文献
14.
15.
16.
D. Kropman S. Dolgov T. Karner 《Applied Physics A: Materials Science & Processing》1996,62(5):469-472
The results of studies of the point-defect generation kinetics in the Si-SiO2 system by means of Electron Spin Resonance (ESR) and InfraRed (IR) absorption spectroscopy are presented. The influence of oxidation conditions (oxidation temperature and time, cooling rate) on the defect structure of the Si-SiO2 interface has been studied. It is shown that this influence can be explained by the model of point-defect generation proposed by Tan and Gösele, and the structural properties of the Si-SiO2 system can be improved by an appropriate choice of the oxidation conditions. 相似文献
17.
The anomalous fading (AF) of thermoluminescence (TL) and optically stimulated luminescence (OSL) signals in Durango apatite is attributed to tunnelling effects. Electrons from the TL and OSL traps in this material are transferred, via a tunnelling effect, to the recombination sites. The availability of recombination sites for tunnelled electrons is of major importance for the degree of AF rate observed in this material. It is expected that a variation of the number of the electron recombination sites will be reflected in the experimentally measured AF rate. In the present work an investigation of the recombination sites for the tunnelled electrons is attempted by studying the AF effect using a special technique, in which the anomalously faded TL (OSL) is replaced by an equal amount of TL (OSL) induced by a beta dose. 相似文献
18.
以平面波为例,分别针对较弱和较强的湍流模型,通过计算到达角起伏讨论了高空光学遥感系统由大气湍流引起的地面图像分辨力问题。结果表明,对于给定的遥感系统口径和高度,较强湍流引起的图像分辨力的1cm左右;而较强湍流引起的图像分辨力则可达10cm量级。对于自身的地面分辨力具有m的量级的传统光学遥感系统,上述影响并不明显。对于现代高辨力光学遥感系统,这种影响便不容忽略,特别是对较强的湍流,往往需要用自适应光学等方法加以补偿。 相似文献
19.
R. Brout 《Foundations of Physics》1987,17(6):603-619
Time arises in the theory of gravity through the semiclassical approximation of the gravitational part of the solution of the Wheeler-De Witt equation in the manner shown by Banks (SCAG). We generalize Banks' procedure by grafting a Born-Oppenheimer type approximation onto SCAG. This allows for the feedback of matter onto gravity, wherein the latter is driven by the (quantum) mean energy-momentum tensor of matter. The wave function is nonvanishing in classically forbidden configurations of gravity. In SCAG this is described by the evolution of matter in imaginary time. This is interpreted as an inverse temperature, and the norm of the matter wave function, no longer conserved for these gravitational configurations, is a partition function. A simple cosmological model is worked out to illustrate these ideas. In this model it is shown that the temperature of the matter which emerges into the classically permitted region is the inverse bounce time of the bounce executed by the system in the forbidden region (behind the horizon).Time present and time past are both perhaps present in time future. And time future contained in time past. If all time is eternally present All time is unredeemable.—T. S. Eliot, Burnt Norton,Four Quartets, 1943.In honor of Ilya Prigogine on the occasion of his 70th birthday. 相似文献
20.
彭宁阱是用于直接测量原子核质量的精确设备。为了保证彭宁阱的测量精度,需在阱中心产生精准的四极静电场,而四极静电场是通过对彭宁阱的核心电极施加合适的电压产生的。采用公式推导法和最小二乘法两种方法计算得到了LPT核心电极需加电压幅值。对于公式推导法,电压值完全从理论出发,经公式推导后计算得到;最小二乘法的出发点是使取样偏差的平方和最小,且通过仿真模拟考虑了电极的实际几何形状。由这两种方法得到的非四极项系数C4 和C6,可用于估算因偏离理想四极电场所产生的实验误差。虽然这两种方法的出发点不同,但都可以在阱中心产生需要的四极电场。Penning trap mass spectrometry is one of the direct methods and maybe the most accurate tool for atomic mass measurements. The quadrupole electric eld produced in the trap should be very accurate in order to ensure the precision of measurements. The optimal amplitudes for the key electrodes of the Lanzhou Penning Trap(LPT) have been calculated by two methods|formula derivation and least-squares tting. For formula derivation method, the optimal values are based on the theory and deduced from the formulas. Least-squares tting method is to minimize the quadratic sum of sampling deviations, where the actual geometry of the electrodes has been considered by the simulation. The obtained C4 and C6 values can be used to estimate the experimental error produced by the deviation from the ideal quadrupole electric eld. The expected quadrupole electric led could be gotten by both methods. 相似文献