空间有源消声的声能量流研究

本文从理论和实验两个方面对平面噪声场中单极子次级源、偶极子次级源最小辐射声功率时的空间产能量流作了研究,从而直观、清晰地描述了一种消声机理:有源声吸收。并指出:尽管此时次级声源是\     

新型能源技术与未来武器装备的变革

本文介绍了电磁能、太阳能、核能等在军事领域的研究现状，预测未来军事能源技术的发展趋势，从而说明新型能源技术对武器装备发展的影响。     

The effect of anomalous transparency of the water-air interface for a volumetric sound source

Anomalous transparency consists in the passage at certain frequencies of the majority of a source’s radiated energy through an interface, which usually gives strong reflection. Earlier, this effect was established for low-frequency point sources located in a fluid bounded by an air medium. In the case of volumetric sources, additional scattering of waves occurs between the interface of the media and the emitter surface; and the character of the manifestation of this effect is unclear. This work, using the solution to the integral equation corresponding to a boundary value problem, examines the emission of wave energy by spherical sources of different radius and its distribution between the energy flow passing through the water-air interface into the upper half-space and the energy flow going to infinity in the lower half-space. It has been established that the size of the source has virtually no effect on the energy distribution in the low-frequency range, i.e., on the anomalous transparency effect. We also analyze how the relative dimensions of spherical sources affect the energy characteristics in the mid- and high-frequency range.     

噪声源非均匀分布海洋环境噪声水平声能流理论分析

研究水平非均匀分布噪声源所产生的各向异性海洋环境噪声场声能流。提出一种混合型非均匀分布噪声源模型,理论分析并数值计算了此模型情况下的环境噪声场水平声能流。结果表明:非均匀分布噪声源引起的海洋环境噪声场具有显著非零平均水平声能流;不同接收点的水平声能流明显不同;其幅度和方向取决于各个局部海域不等强度声源产生的合成噪声声能流矢量和。研究了两接收点间噪声的声压和振速水平分量、振速水平分量归一化相关系数随两接收点间距的关系,各量之间表现出较强相关性,为分析水下矢量声场目标探测技术性能提供理论依据。     

Broad Beam Gas Ion Source with Hollow Cathode Discharge and Four-grid Accelerator System

1 Introduction Ion sources with wide energy and current ranges are used extensively in industrial applications such as ion implantation, etching, and deposition. Broad beam ion sources with a uniform current distributions are needed for many industrial applications and development of commercial ion bean technologies for surface modification of materials is impossible without highly efficient, simple, and dependable ion sources. These and other needs have spurred the development of high efficiency ion sources that can produce ion beams with high energy and current and require low or no maintenance.     

On Chu's disturbance energy

Chu [On the energy transfer to small disturbances in fluid flow (part I), Acta Mechanica 1 (1965) 215-234] proposed a positive definite energy norm for characterizing the level of fluctuation in a disturbance. In the absence of heat transfer at the boundaries, work done by boundary or body forces, heat and material sources of energy, this norm is a monotone, non-increasing function of time. In this paper, we show that Chu's disturbance energy defines an inner product, with respect to which the conservation equations of fluid motion linearized about a uniform base flow are self-adjoint. This ensures that the eigenvectors of the linearized operator are orthogonal to each other, and the property that the energy norm is a non-increasing function of time in the absence of physical sources of energy follows as an immediate consequence. Examples from numerical simulations of Euler equations are presented to highlight the importance of choosing an energy norm that is consistent with the underlying physics. We demonstrate that the disturbance energy as measured by Chu's norm does not exhibit spurious transient growth in the absence of physical sources of energy and hence is suitable for analyzing thermoacoustic instability.     

超导技术在未来电网中的应用

大力发展可再生能源并实现清洁能源变革,是当今能源领域的大趋势。随着可再生能源越来越多地接入电网,将对直流输电和大规模储能技术提出愈加迫切的需求。在此背景下,超导直流输电技术、超导直流限流器以及基于超导电性的电力储能技术等具有潜在的应用前景。文章较为系统地介绍上述直流超导电力装置的原理、优势以及近些年国内外的进展等。     

Processes of energy exchange in systems of nonidentical particles with inhomogeneous sources of heat

Processes of energy exchange in dissipative systems of nonidentical interacting particles (having different sizes, charges, etc.) with an inhomogeneous distribution of sources of heat and/or any other sources of stochastic kinetic energy are considered. A theoretical model is proposed for analyzing the energy balance in such systems. Analytical relations describing the redistribution of the “kinetic temperature” between interacting particles of the system are obtained within this model. These relations are tested by the numerical simulation of the problem for Yukawa systems.     

Multiparticle azimuthal correlations in central nucleus-nucleus collisions at high energy

Multiparticle azimuthal correlations in central nucleus-nucleus collisions at high energy are described by a simple formula.The calculated results are in agreement with the experimental data of carbon and oxygen induced interactions at Dubna energy.The comparison between the calculated results and experimental data shows that particles are emitted isotropically in the rest frame of the emission sources,and the emission sources have movements in momentum space.     

关于单极子次级声源管道有源降噪能量机制的理论分析

本文通过对单极子次级声源管道有源降噪中声场能量的再分布与初、次级声源的工作情况的定量分析与讨论,说明了有源降噪的三种能量机制中的多极子能量存贮机制,总是同能量转移或吸收机制中的一种同时存在的,哪一种机制起主导作用取决于初、次级声源之间的距离.     

Multiparticle azimuthal correlations in central nucleus-nucleus collisions at high energy

Multiparticle azimuthal correlations in central nucleus-nucleus collisions at high energy are described by a simple formula. The calculated results are in agreement with the experimental data of carbon and oxygen induced interactions at Dubna energy. The comparison between the calculated results and experimental data shows that particles are emitted isotropically in the rest frame of the emission sources, and the emission sources have movements in momentum space.     

The 21st century power: Tendencies and prospects

Any increase of the energy potential is survival, independence, and prosperity of each nation (community) in the system of chaotic globalization, but the Mantra of global cooperation not always is the Mantra of a separate nation. India uses all possibilities for obtaining additional energy sources. This was demonstrated at the recent conference and exhibition “Petrotech-2009.” India assumes to increase power consumption to 400,000 MW in 2030 against 130,000 MW in 2008 at the expense of all sources. Great attention is given to renewable and alternative sources.     

A future project at tibet: the large high altitude air shower observatory (LHAASO)

Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray sources. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100 GeV. In order to target those goals, a large air shower particle detector array of 1 km~2 (the LHAASO project) at 4300 m a.s.l, is proposed. By adding two MagicII-type telescopes in the array as proposed, LHAASO will be enhanced in source morphologic investigation power. The proposed array will be utilized also for energy spectrum measurement for individual cosmic ray species above 30 TeV. By re-configuring the wide field of view telescopes into fluorescence light detector array, the aperture of the detector array can be enlarged to cover an energy region above 100 PeV where the second knee is located. Cosmic ray spectrum and composition will be measured in order to transfer an energy scale to ultra high energy cosmic ray experiments.     

Specular and diffuse reflections of rays in coupled thin plates at high frequencies

The flexural energy distribution in two right-angled point-excited thin plates at high frequencies is investigated by means of an integral energy flow approach. The fields of energy averaged over time and frequency are described by the superposition of uncorrelated cylindrical waves stemming from both boundaries and direct sources. Specular and diffuse laws are considered for the reflection and transmission of rays, giving rise to two kinds of energy equations. The diffuse law leads to a Fredholm integral equation over the boundary sources while the specular law is shown to allow an image source solution when the plates have identical propagation properties. The algorithm for computing the image position, magnitude and directivities is described. Then, some comparisons between the results from the both energy formulations and also from the statistical energy analysis and the numerical solution of the equations of motion are performed with two damped plates at high frequency. The non-diffuse pattern of the averaged flexural energy fields is well described by the energy flow approaches.     

Graceful exit and energy conditions in string cosmology

String cosmology solutions are examined in a generalized phase-space including sources representing arbitrary corrections to lowest order string-dilaton-gravity effective action. We find a set of necessary conditions for a graceful exit transition from a dilaton-driven inflationary phase to a radiation dominated era. We show that sources allowing such a transition have to violate energy conditions similar to those appearing in singularity theorems of general relativity. Since familiar classical sources, excepting spatial curvature, obey these energy conditions we conclude that a generic graceful exit in string cosmology requires a new effective phase of matter. Our results clarify and generalize previous analyses and enable us to critically reexamine proposed non-singular cosmologies.     

Statistics of clustering of ultrahigh energy cosmic rays and the number of their sources

Observation of clustering of ultrahigh energy cosmic rays (UHECR) suggests that they are emitted by compact sources. Assuming small ( <3 degrees ) deflection of UHECR during the propagation, the statistical analysis of clustering allows an estimate of the spatial density of the sources h(*), including those not yet observed. When applied to astrophysical models involving extragalactic sources, the estimate based on 14 events with energy E>10(20) eV gives h(*) approximately 6x10(-3) Mpc(-3). With increasing statistics, this estimate may lead to exclusion of some models.     

Methods and approaches of high resolution spectroscopy for analytical applications

Application of high resolution spectroscopy methods for analyzing vapors and decomposition products of high energy substances is considered. The approaches currently used for detecting such substances are analyzed. Terahertz sources and receivers promising for constructing high resolution spectrometers are identified. A new approach to developing a terahertz spectroscopy technique using phase-diffusion noise radiation sources is proposed. The results of using the high resolution spectroscopy method for analyzing high energy substances vapors are presented.     

Astrophysical neutrinos: flavor ratios depend on energy

Electromagnetic (and adiabatic) energy losses of pi's and mu's modify the flavor ratio (measured at Earth) of neutrinos produced by pi decay in astrophysical sources, Phi v: phi v mu: phi v tau, from 1:1:1 at low energy to 1:1.8:1.8 at high energy. The transition occurs over 1-2 decades of v energy, and is correlated with a modification of the neutrino spectrum. For gamma-ray bursts, e.g., the transition is expected at approximately 100 TeV and may be detected by km-scale v telescopes. Measurements of the transition energy and energy width will provide unique probes of the physics of the sources. Pi and mu energy losses also affect the ratio of ve flux to total v flux, which may be measured at the resonance (6.3 PeV): It is modified from 1/6(1/15) at low energy to 1/9 (practically 0) at high energy for neutrinos produced in p p (p gamma) interactions.     

关于我国核能发展技术路线之我见

简要地阐述了核能在当前世界和我国能源发展中的地位和作用,提出了在近１０～２０年内我国核能发展应遵循的原则和技术路线的建议.The position and role of nuclear energy in china’s energy sources development is briefly outlined and a proposal about strategic principles and technology line of china’s nuclear energy development in recent 10～20 years is put forward.     

The effects of shielding around the source on neutron energy spectra

The knowledge of neutron energy spectra contributes to unambiguous identification of neutron sources in the fields of nuclear safeguards and nuclear non-proliferation. Since a real scenario situation includes the presence of shielding around the source, we have investigated the influence of the potential shielding surrounding the source on the shape of energy spectra for a few neutron sources. We have applied the maximum-likelihood, expectation–maximisation (MLEM) method with one-step-late (OSL) algorithm for neutron spectra unfolding. The pulse height distributions used in the unfolding procedures were simulated with the high accuracy by using the MCNP-PoliMi code based on the Monte Carlo method. A possibility to identify the shielded neutron sources by using the unfolding method was examined with two continuous-in-energy sources, such as ²⁵²Cf and ²⁴¹Am–Be in source-shielding configurations with lead (Pb) and polyethylene (PE) blocks. The results of calculations have shown that the identification of ²⁵²Cf and ²⁴¹Am–Be sources with 2.5 cm of Pb and PE shield can be achieved successfully by using the MLEM method with the OSL algorithm. However, the unfolded results for ²⁵²Cf and ²⁴¹Am–Be sources with 10 cm of PE shield significantly deviate from the reference spectra and the sources cannot be correctly identified on the basis of their unfolded energy spectra.