共查询到20条相似文献,搜索用时 31 毫秒
1.
The molecular dynamics method is used to study the adsorption of ammonia on water clusters. The adsorption of ammonia is accompanied by a decrease in the ability of the cluster system to absorb infrared radiation, a significant decline in the thermal radiation power emitted by the system, and an almost double decrease in the frequency-averaged reflection coefficient. An increase in the concentration of ammonia in the clusters causes a slight change in IR absorption coefficient, but enhances the power of emission and reflection coefficient. 相似文献
2.
An expression is derived for the acoustic power emitted by a vertical compensated discrete linear array in a Pekeris waveguide. The sound field is represented by the sum of a discrete spectrum and a continuous one. We consider the dependence of the power emitted by the array on both the number of array elements and the array compensation angle. 相似文献
3.
This paper presents a robust control system design for suppressing the radiated acoustic power emitted from a vibrating planar structure, and spillover effect caused by neglected high-frequency modes. A state-space model of a simply supported panel structure is derived and an output equation is formed based on the one-dimensional PVDF film sensors. An output feedback H∞control is designed by introducing a multiplicative perturbation which represents unmodelled high-frequency dynamics in the control system. The simulation and experimental results demonstrated significant decrease in sound radiation for the considered structural power modes in control. 相似文献
4.
Miroslav Pardy 《General Relativity and Gravitation》1983,15(11):1027-1032
The power spectrum of radiation of gravitons which are emitted by the binary system represented by two point masses moving
around each other under their mutual gravitational interaction is calculated in the Schwinger source theory version of quantum
gravity. The calculation is applied to the zero eccentricity of the orbits but arbitrary orbital nonrelativistic velocity. 相似文献
5.
Röser F Schimpf D Schmidt O Ortaç B Rademaker K Limpert J Tünnermann A 《Optics letters》2007,32(15):2230-2232
We report on an ytterbium-doped fiber based chirped-pulse amplification system delivering 100 microJ pulse energy at a repetition rate of 900 kHz, corresponding to an average power of 90 W. The emitted pulses are as short as 500 fs. To the best of our knowledge, this is the highest average power ever reported for high-energy femtosecond solid-state laser systems. 相似文献
6.
We fabricated a highly efficient, broadband light emitting diode driven by an optical near field generated at the inhomogeneous
domain boundary of a dopant in a homojunction bulk Si crystal and evaluated its performance. To fabricate this device, a forward
current was made to flow through a Si p–n junction to anneal it. During this process, the device was irradiated with near-infrared
light, producing stimulated-emission light using a two-step phonon-assisted process triggered by the optical near field, and
the annealing rate was controlled in a self-organized manner. The device emitted light in a wide photon energy region of 0.73–1.24 eV
(wavelength 1.00–1.70 μm). The total power of the emitted light with 11 W of electrical input power was as high as 1.1 W.
The external power conversion efficiency of the emitted light was 1.3%, the differential external power conversion efficiency
was 5.0%, the external quantum efficiency was 15%, and the differential external quantum efficiency was 40%. The dependency
of the emitted light power density on the injected current density clearly showed a characteristic reflecting the two-step
phonon-assisted transition process. 相似文献
7.
An exclusive study of the characteristics of interactions accompanied by backward emission (θlab≥ 90°) of shower and grey particles in collisions of a 4.5 AGeV/c 16O beam with emulsion nuclei is carried out. The experimental multiplicity distributions of different particles emitted in the forward (θlab<90°) and backward hemispheres due to the interactions with the two emulsion components (CNO, AgBr) are presented and analyzed. The correlations between the different emitted particles are also investigated. The results indicate that there are signatures for a collective mechanism, which plays a role in the production of particles in the backward hemisphere. Hence, the backward multiplicity distribution of the emitted shower and grey particles at 4.5 AGeV/c incident momentum can be represented by a decay exponential law formula independent of the projectile size. The exponent of the power was found to increase with decreasing target size. The experimental data favor the idea that the backward particles were emitted due to the decay of the system in the latter stages of the reactions. 相似文献
8.
Blue 465-nm radiation is generated by frequency doubling of the output of an InGaAs diode-laser oscillator-amplifier system in critically phase-matched LiB(3)O(5) (LBO). The diode-laser system emitted 4 W of single-frequency 930-nm radiation in a near-diffraction-limited beam (M(2)<1.2) . The laser power is enhanced to values of up to 150 W in a resonant external ring cavity. The LBO crystal is placed at a resonator internal focus. The frequency doubling in the LBO crystal generates blue radiation at 465 nm with a power of 1 W. The spectral width of the blue radiation is less than 3 MHz, and the value of the M(2) beam parameter is less than 1.2. 相似文献
9.
The synergic synchrotron-Cerenkov (SC) radiation emitted by a relativistic charged particle under the combined effect of the constant external magnetic field and the collective interactions in the ambient plasma (medium) is given in the framework of the non-equilibrium statistical mechanics developed by Prigogine and his co-workers. Starting from the formal solution of the Liouville equation, the one-particle distribution function is calculated. Restricting the motion of the test particle to a circular orbit in the plane normal to the magnetic field, we use the above distribution function to calculate the power emitted per unit solid angle by the test particle as a function of time. We have thus obtained the time evolution of the synergic SC radiation which in the asymptotic limit reproduces the results of Schwinger and his co-workers. It is also shown that the collective interactions within the system produces a shift in the frequency of the outcoming radiation. 相似文献
10.
11.
A pulsed master-oscillator power fiber amplifier (MOPFA) system based on Yb3+-doped large mode area (LMA) double-clad optical fiber was developed. The system generated pulses of changeable duration ranging from about 8.5 to 250.0 ns at the repetition rate of up to 500 kHz. The laser system emitted up to 22 W of average output power at the wavelength of 1064 nm. 相似文献
12.
13.
In this paper, the concept of directivity is generalised to acoustic sources radiating transients or signals evolutive with time. (These are the most common cases in the power or reinforcement electroacoustic systems.) The generalisation proposed is based upon the anamorphism relating the signal levels emitted into the free space in different directions. The relationship between the signals observed in two arbitrary directions is essentially independent of time. Therefore, the anamorphical relationship offers the possibility of obtaining the directivity patterns simply by using as a test signal that signal commonly emitted by the system (i.e. speech in a reinforcement system for a conference room). This principle and method can be applied without major restrictions to any other system, or piece or part of machinery emitting acoustic energy in discontinuous form.Concerning electroacoustic sources, it appears advantageous to replace the usual test signal consisting of pure tones by the signal proper to the system (music, speech, etc.) filtered into the standardised frequency bands. The complete signal (not filtered) can also give significant results. As a simplifying and reasonable compromise regarding the directivity for speech and music, bands of white noise are proposed as test signals. 相似文献
14.
The field lines of energy flow of the radiation emitted by a linear dipole in free space are straight lines, running radially outward from the source. When the dipole is embedded in a medium, the field lines are curves when the imaginary part of the relative permittivity is finite. It is shown that due to the damping in the material all radiation is emitted in directions perpendicular to the dipole axis, whereas for a dipole in free space the radiation is emitted in all directions except along the dipole axis. It is also shown that some field lines in the near field form semiloops. Energy flowing along these semiloops is absorbed by the material and does not contribute to the radiative power in the far field. 相似文献
15.
The paper reports on a study to investigate the influence of load intensity and material structure on statistical regularities of fragmentation in ZrO2-based ceramics differing in porosity. The study was performed on a modified split Hopkinson pressure bar system and allowed a comparative analysis of dynamic stress-strain curves and statistical characteristics of fragmentation such as distributions of emitted light pulses (fractoluminescence) and fragment sizes. It is shown that increasing the ceramic porosity changes both the form of stress-strain curves and the pulse distribution. In ceramic specimens with up to 45% porosity, the pulse distribution is described by a bimodal power law; in ceramic specimens with 60% porosity, by a power law. The fragment size distribution in the material corresponds to a power law with the exponent dependent on porosity and load intensity. 相似文献
16.
17.
Raman lasing of a two-phonon Raman band in the anti-Stokes side is demonstrated. Two femtosecond light pulses with identical wavelengths are irradiated onto a SrTiO3 crystal in a cross-beam configuration. Under low excitation power, several wave-mixing signals with identical wavelengths are emitted. When the power exceeds a critical value, cascaded coherent anti-Stokes Raman scattering (CARS) signals are emitted, the frequency step of which is coincident with that of the strongest two-phonon Raman band of 2TO2. 相似文献
18.
设计了工作在太赫兹频段的无线通信系统,基带部分采用16QAM调制体制,射频部分采用混频器实现两级上下变频,功放部分采用固态功率放大+电真空器件放大级联的功率放大技术,实现了0.14 THz频段W量级的功率输出。接收端采用全固态常温接收技术,接收机等效噪声温度为1100 K,接收灵敏度达到-57 dBm。采用两个增益50 dBi的卡塞格伦天线,在成都市双流区与新津县之间开展了距离21 km的无线通信试验,单路实时通信速率达到5 Gbps,误码率低于10-6。并成功同时实时传输了两路符合HD-SDI标准的无压缩高清视频数据流,每一路的标准有效速率达到1.485 Gbps。 相似文献
19.
The evolution of effective force chains percolating through a compressed granular system is investigated. We compressed an ensemble of spherical particles monitoring the macroscopic constitutive behavior and the acoustic signals emitted by microscopic rearrangements of particles. We applied the continuous damage model of fiber bundles to describe the evolution of the array of force chains. The model provides a nonlinear constitutive behavior in good quantitative agreement with the experimental results. The amplitude distribution of acoustic signals was found experimentally to follow a power law of an exponent delta=1.15+/-0.05, which is in good agreement with the analytic solution of the model. 相似文献
20.
N. Toyosugi H. Yamada D. Minkov M. Morita S. Imai T. Yamaguchi 《Journal of synchrotron radiation》2007,14(2):212-218
The tabletop synchrotron light sources MIRRORCLE‐6X and MIRRORCLE‐20SX, operating at electron energies Eel = 6 MeV and Eel = 20 MeV, respectively, can emit powerful transition radiation (TR) in the extreme ultraviolet (EUV) and the soft X‐ray regions. To clarify the applicability of these soft X‐ray and EUV sources, the total TR power has been determined. A TR experiment was performed using a 385 nm‐thick Al foil target in MIRRORCLE‐6X. The angular distribution of the emitted power was measured using a detector assembly based on an NE102 scintillator, an optical bundle and a photomultiplier. The maximal measured total TR power for MIRRORCLE‐6X is Pmax? 2.95 mW at full power operation. Introduction of an analytical expression for the lifetime of the electron beam allows calculation of the emitted TR power by a tabletop synchrotron light source. Using the above measurement result, and the theoretically determined ratio between the TR power for MIRRORCLE‐6X and MIRRORCLE‐20SX, the total TR power for MIRRORCLE‐20SX can be obtained. The one‐foil TR target thickness is optimized for the 20 MeV electron energy. Pmax? 810 mW for MIRRORCLE‐20SX is obtained with a single foil of 240 nm‐thick Be target. The emitted bremsstrahlung is negligible with respect to the emitted TR for optimized TR targets. From a theoretically known TR spectrum it is concluded that MIRRORCLE‐20SX can emit 150 mW of photons with E > 500 eV, which makes it applicable as a source for performing X‐ray lithography. The average wavelength, = 13.6 nm, of the TR emission of MIRRORCLE‐20SX, with a 200 nm Al target, could provide of the order of 1 W EUV. 相似文献