共查询到14条相似文献,搜索用时 66 毫秒
1.
Carrier shock and frequency conversion of a few—cycle pulse laser propagating in a non—resonant two—level atom medium 下载免费PDF全文
We have studied the spectral behaviour of few-cycle soliton pulses in a non-resonant two-level atom medium by solving the full Maxwell-Bloch equations. It is demonstrated further that the carrier effects play an important role in the propagation of the few-cycle pulse laser. When the frequency detuning is not very large, both the population distribution and the refractive index of the medium follow the oscillatory carrier field instantaneously; in this case, carrier-wave compression or carrier shock occurs, and a supercontinuum broader than that in the resonant medium may be generated. When the frequency detuning is large, the carrier shock is weak and the spectrum is not continuous, only showing an odd harmonic radiation. 相似文献
2.
Anirban Bhaduri Susmita Bhaduri Dipak Ghosh 《Physics of Particles and Nuclei Letters》2017,14(4):576-583
Various works on multiplicity fluctuation have investigated the dynamics of particle production process and eventually have tried to reveal a signature of phase transition in ultra-relativistic nuclear collisions. Analysis of fluctuations of spatial patterns has been conducted in terms of conventional approach. However, analysis with fractal dynamics on the scaling behavior of the void has not been explored yet. In this work we have attempted to analyze pion fluctuation in terms of the scaling behavior of the void probability distribution in azimuthal space in ultra-relativistic nuclear collisions in the light of complex networks. A radically different and rigorous method viz. Visibility Graph was applied on the data of 32S-Ag/Br interaction at an incident energy of 200 GeV per nucleon. The analysis reveals strong scaling behavior of void probability distributions in azimuthal space and a strong centrality dependence. 相似文献
3.
Heat transfer analysis in the flow of Waiters' B fluid with a convective boundary condition 下载免费PDF全文
Radiative heat transfer in the steady two-dimensional flow of Walters' B fluid with a non-uniform heat source/sink is investigated. An incompressible fluid is bounded by a stretching porous surface. The convective boundary condition is used for the thermal boundary layer problem. The relevant equations are first simplified under usual boundary layer assumptions and then transformed into a similar form by suitable transformations. Explicit series solutions of velocity and temperature are derived by the homotopy analysis method (HAM). The dimensionless velocity and temperature gradients at the wall are calculated and discussed. 相似文献
4.
The scaling of the flowfield in a gas--gas combustion
chamber is investigated theoretically, numerically and
experimentally. To obtain the scaling criterion of the gas--gas
combustion flowfield, formulation analysis of the three-dimensional
(3D) Navier--Stokes equations for a gaseous multi-component mixing
reaction flow is conducted and dimensional analysis on the gas--gas
combustion phenomena is also carried out. The criterion implies that
the size and the pressure of the gas--gas combustion chamber can be
changed. Based on the criterion, multi-element injector chambers
with different geometric sizes and at different chamber pressures
ranging from 3~MPa to 20~MPa are numerically simulated. A
multi-element injector chamber is designed and hot-fire tested at
five chamber pressures from 1.64~MPa to 3.68~MPa. Wall temperature
measurements are used to understand the similarity of combustion
flowfields in the tests. The results have verified the similarities
between combustion flowfields under different chamber pressures and
geometries, with the criterion applied. 相似文献
5.
The recoilless absorption spectra of iron in the ternary alloys CoFeGe, CoFeSb and FeMnGe, which possess B82 type structure, reveal the existence of different ordering temperatures of moments at 2(a) and 2(d) sites. Using the Einstein model to describe the second order Doppler shift, it has been found thatΘ
E appropriate to the thermal motions of iron atoms at 2(a) and 2(d) sites in CoFeGe are different, which is also suggested by the temperature dependences of the relative areas of the corresponding
component spectra. In CoFeSb, on the other hand, relative areas of the component spectra are independent of temperature, and
give the relative distribution of iron at the inequivalent sites. A large difference in the isomer shifts of 2(a) and 2(d) site spectra indicates a larger number of d-electrons in the atomi configuration for 2(a) atoms. The isomer shift change is negative for 2(a) site nuclei and positive for 2(d) site nuclei with increase in temperature. The magnetic fields at 2(d) site nuclei in CoFeGe and CoFeSb alloys indicate that the moments of the parent atoms are not much different from the value
in iron metal. 相似文献
6.
Total lifetime distribution analysis was employed to obtain fluorescence lifetime profiles of the intrinsic fluorescence ofPseudomonas fluorescens, Escherichia coli, Bacillus subtilis, andStaphylococcus epidermidis. The lifetimes were measured using a multiharmonic Fourier transform phase-modulation fluorometer which can simultaneously
measure the phase shift and demodulation at many modulation frequencies. The 364-nm line from an argon-ion laser and the 325-
and 442-nm lines from a helium-cadmium laser were used for sample excitation. Broad emission windows were used to capture
as much of the bacterial emission as possible for the lifetime measurements. The maximum entropy method was used to recover
lifetime profiles from the multifrequency phasemodulation data. At all three excitation wavelengths, the bacteria exhibited
three lifetime components, in the ranges of 0.5-1, 2–3, and 4–8 ns. Using 325-nm excitation, a fourth component, in the range
of 9–14 ns, was recovered in all of the bacteria; using 364-nm excitation, the fourth component was resolved only in the two
Gram-negative bacteria (P. fluorescens andE. coli). Excitation at 364 nm provided the most reproducible lifetime profiles and showed some differences among the four bacteria. 相似文献
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We have analysed the small-amplitude non-linear electron acoustic shock waves by taking into account the effects of electron beam in magnetized plasma. Satellite observations in different regions of the Earth's magnetosphere have shown that the electrostatic solitary waves are generally associated with electron or/and ion beams. The nonlinear Korteweg-de-Vries Burgers (KdVB) equation has been derived by considering the basic fluid equations and dissipation effects. The nonlinear coefficient of KdVB equation comes out to be negative. Only dip-shaped potential structures are reported here. For the parameters discussed in this paper, we did not find positive polarity shocks. This could be due to the restrictions on the plasma parameters since we are using the fixed densities of the cold, hot, and beam electrons as observed by the Viking satellite in the auroral region. In this paper, the importance of the cold electron to hot electron temperature in conjunction with the beam speed is pointed out. Increase in beam density, kinematic viscosity, and magnetic field results in increase in the amplitude while the increase in hot electron concentration and superthermality leads to decrease in potential. The numerical analysis is presented for the parameters corresponding to the observation of burst b event by Viking satellite in the dayside auroral zone of the earth's magnetosphere. 相似文献
9.
A. C. Eapen S. M. Rao S. M. Agashe R. L. Ajmera V. N. Yelgaonkar 《Isotopes in environmental and health studies》2013,49(9):424-429
A variety of applications of radiotracers are in vogue in industries with significant economic advantage. Some of the applications in steel, petroleum and maritime industries provide interesting case studies. Different approaches are possible for arriving at the cost to benefit ratio. These include: (1) direct cost comparison with alternative technique, (2) savings due to increased production and reduction in interruption of process, (3) savings due to avoidance of infructuous expenditure. The case studies quoted based on experience in India include: (1) the monitoring of wear condition of refractory lining in blast furnaces. (2) location of leakages in a 140 km long underground crude petroleum pipeline, (3) study of sediment movement in sea bed for selecting the dumping ground for dredged spoils, in connection with harbour maintenance and expansion operations. Cost to benefit ratio is worked out in each case. The ratios range from 1:10 to 1:4500 depending on application and method of calculation of cost benefit ratio. 相似文献
10.
Javier Gamboa Félix Javier Jiménez-Jiménez Alberto Nieto Jose Montojo Miguel Ortí-Pareja José Antonio Molina Esteban García-Albea Ignacio Cobeta 《Journal of voice》1997,11(3):314-320
To quantify several acoustic features of the voice in patients withParkinson's disease (PD), 41 patients and 28 age and sex-matched controls were studied. PD severity was assessed with the Unified PD Rating Scale (UPDRS) and the Hoehn and Yahr staging. The Computerized Speech Lab 4300 program (Kay Elemetrics) was used. Two seconds of a sustained /a/ and a sentence were captured with a microphone and laryngograph equipment. Measures included fundamental frequency (FO), frequency perturbation (fitter), intensity perturbation (shimmer), and harmonic/noise ratio (H/N) of the vowel /a/, and frequency and intensity variability of a sentence, phonational range, dynamic range at the natural frequency, maximum phonational time and s/z ratio. All subjects underwent indirect laryngoscopy and/or laryngeal fibroscopy. When compared with controls, PD patients showed higher jitter, lower H/N ratio, lower frequency and intensity variability of the sentence, and lower phonational range and reported a higher frequency of the presence of low voice-intensity, monopitch, voice arrests, and struggle. These features seem to be unaffected by the duration and severity of the disease. 相似文献
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The spatial-temporal power-law distributions are found in many natural systems, which have self-similarity and fractal behavior. By analyzing the time series of such systems, we could expect to explore and understand the underlying mechanisms. In this paper, the Detrended fluctuation analysis (DFA) is used to analyze the long-range correlations of forest and urban fires in Japan and China. It is found that the interevent time series of both forest and urban fires have the persistent long-range power-law correlations, and they all have two scaling exponents, α1 and α2, which are both bigger than 0.5 and smaller than 1.0, despite the different regions and countries. For forest fires, 0.61<α1<0.73,0.87<α2<0.98 and for urban fires, 0.52<α1<0.61,0.59<α2<0.88. The result suggests that fires have self-similarity characteristics. The occurrence of forest fires may have connection with the weather fluctuations, which have significant effects on the ignition and have the similar temporal correlations. It is shown that the interval sequences of urban fires closely resemble that of white noise in small timescale, and the correlations are weaker than that of forest fires. Human behavior and human density may affect the long-range correlation in some way. This seems to be helpful to understand the complexity of fire system in temporal aspect. 相似文献
13.
Cailang Xie Ying Guo Qin Liao Wei Zhao Duan Huang Ling Zhang Guihua Zeng 《Physics letters. A》2018,382(12):811-817
How to narrow the gap of security between theory and practice has been a notoriously urgent problem in quantum cryptography. Here, we analyze and provide experimental evidence of the clock jitter effect on the practical continuous-variable quantum key distribution (CV-QKD) system. The clock jitter is a random noise which exists permanently in the clock synchronization in the practical CV-QKD system, it may compromise the system security because of its impact on data sampling and parameters estimation. In particular, the practical security of CV-QKD with different clock jitter against collective attack is analyzed theoretically based on different repetition frequencies, the numerical simulations indicate that the clock jitter has more impact on a high-speed scenario. Furthermore, a simplified experiment is designed to investigate the influence of the clock jitter. 相似文献
14.
The dispersion behavior of waves in multiferroic plates with imperfect interfacial bonding has been investigated via the method of reverberation-ray matrix, which is directly established from the three-dimensional equations of magneto-electro-elasticity in the form of state space formalism. A generalized spring-layer model is employed to characterize the interfacial imperfection. By introducing a dual system of local coordinates for each single layer, the numerical instability usually encountered in the state space method can be avoided. Based on the proposed method, a typical sandwich plate made of piezoelectric and piezomagnetic phases is considered in numerical examples to calculate the dispersion curves and mode shapes. It is demonstrated that the results obtained by the present method is unconditionally stable as compared to the traditional state space method. The influence of different interfacial bonding conditions on the dispersion characteristics and corresponding mode shapes is investigated. 相似文献