Further results on instability of the motion of a beam of periodically varying length

The paper is concerned with the parametric instability of the motion of a beam of periodically varying length. The instability regions are found and plotted. The study shows that the way in which the beam is driven has an essential effect on the stability of its motion.     

Comparison of Brueckner theory with “exact” results for H3 and He4 nuclei

The consistency of the second-order Brueckner-Baranger approximation to the ground-state energyE of H³ and He⁴ nuclei is confirmed by the agreement ofE with the recent Faddeev and Faddeev-Yakubovsky equation results for Reid local potential, by the dependence ofE on different phase-equivalent transforms (= off-shell changes) of the Reid potential which agrees with Faddeev equation and nuclear matter calculations, and by the Coester line well reproduced for a set of realistic potentials in He⁴. The influence of approximations in solving Bethe-Goldstone equation is also discussed.     

三镜波束波导在高功率微波天线中的应用

通过对波束波导馈电卡塞格仑天线工作原理的分析,论述了波束波导在高功率微波辐射天线中的应用及设计方法,重点介绍了一套利用波束波导馈电高功率微波辐射天线。该天线利用由三面反射镜组成的波束波导对一个由两个抛物面镜组成的双反射面天线进行馈电,实现了波束的快速扫描。该天线工作在X波段时,功率容量大于1 GW,天线增益大于50 dB。     

三镜波束波导在高功率微波天线中的应用

通过对波束波导馈电卡塞格仑天线工作原理的分析,论述了波束波导在高功率微波辐射天线中的应用及设计方法,重点介绍了一套利用波束波导馈电高功率微波辐射天线。该天线利用由三面反射镜组成的波束波导对一个由两个抛物面镜组成的双反射面天线进行馈电,实现了波束的快速扫描。该天线工作在X波段时,功率容量大于1GW,天线增益大于50dB。     

The quasicrystalline approximation: Comparison of the spectral density with exact results

The quasicrystalline approximation (QCA) for electronic excitations in a one-dimensional liquid metal is examined by comparing the spectral density A(k, E) to exact numerical results. The numerical method is briefly described and the limitations of teh QCA are indicated.     

有限长密绕圆柱形螺线管自感系数的精确表达式

对于有限长密绕圆柱形螺线管,首先用贝塞尔函数展开法推导出自感系数的积分形式的表达式,然后用直接积分的方法得出两个级数形式的自感系数表达式,最后对这两个表达式作了简要的分析与比较.     

Highly radiating hydrogen flames: Effect of toluene concentration and phase

Adapting hydrogen as a carbon-free fuel for industrial applications requires new, innovative approaches, especially when radiant heat transfer is required. One possible option is to dope hydrogen with bio-oils, containing aromatics that help produce highly sooting flames. This study investigates the potential doping effects of toluene on a hydrogen-nitrogen (1:1 vol) flames. Flames with 1–5% toluene, based on the mole concentration of hydrogen, are measured using a combination of techniques including: still photographs and laser-based techniques. Toluene was mixed with hydrogen-nitrogen fuel mixture as either a vapour carried by nitrogen, or as a dilute spray. Spray flames are found to produce substantially more polycylic aromatic hydrocarbons, with significantly more soot near the nozzle exit plane, than the prevaporised flames. Increasing the dopant concentration from 1 to 3% of the hydrogen has a marked effect on soot loading in the flame, although the further increasing the dopant concentration to 5% has a far smaller effect on the soot produced in the flame. Simulations of laminar flames using detailed chemical kinetics support the above findings and reveal details of the competition between soot precursor formation and hydrocarbon oxidation. Correlations of formation rates are non-linear with toluene concentration in cases where toluene represents less than 10% of the fuel, although expected linear relationships are noted beyond this regime up to 1:1 toluene/hydrogen blends. The study provides insight and explanation into effects of toluene as a dopant, comparison between flame doping in gaseous or liquid phases and suggests that flame doping and blending should be treated as different regimes for their global effect on flame sooting characteristics.     

Some exact results on the ultrametric overlap distribution in mean field spin glass models (I)

The mean field spin glass model is analyzed by a combination of exact methods and a simple Ansatz. The method exploited is general, and can be applied to others disordered mean field models such as, e.g., neural networks. It is well known that the probability measure of overlaps among replicas carries the whole physical content of these models. A functional order parameter of Parisi type is introduced by rigorous methods, according to previous works by F. Guerra. By the Ansatz that the functional order parameter is the correct order parameter of the model, we explicitly find the full overlap distribution. The physical interpretation of the functional order parameter is obtained, and ultrametricity of overlaps is derived as a natural consequence of a branching diffusion process. It is shown by explicit construction that ultrametricity of the 3-replicas overlap distribution together with the Ghirlanda-Guerra relations determines the distribution of overlaps among s replicas, for any s, in terms of the one-overlap distribution. Received 14 February 2000     

Some exact results on the ultrametric overlap distribution in mean field spin glass models (I)

The mean field spin glass model is analyzed by a combination of exact methods and a powerful Ansatz. The method exploited is general, and can be applied to others disordered mean field models such as, e.g., neural networks.It is well known that the probability measure of overlaps among replicas carries the whole physical content of these models. A functional order parameter of Parisi type is introduced by rigorous methods, according to previous works by F. Guerra. By the Ansatz that the functional order parameter is the correct order parameter of the model, we explicitly find the full overlap distribution. The physical interpretation of the functional order parameter is obtained, and ultrametricity of overlaps is derived as a natural consequence of a branching diffusion process.It is shown by explicit construction that ultrametricity of the 3-replicas overlap distribution together with the Ghirlanda-Guerra relations determines the distribution of overlaps among s replicas, for any s, in terms of the one-overlap distribution.     

The theory of long waveguide structures radiating lower hybridwaves into a plasma

It is shown that the radiation into a plasma from the structures composed of many waveguides is well described by the theory of the infinite structures. This theory results in the efficient numerical code which is appropriate for the study of the nonlinear response of the plasma ill front of the grill. Both the infinite conventional grill and the structure built up from the infinite series of identical N-waveguide multijunction sections are investigated. It is proved that the spectrum of the last structure is the superposition of N spectra of the infinite conventional grills with the specially selected phase shifts. The theoretical results for three long structures (24-waveguide conventional grill on ASDEX and two multijunction arrays, namely a 32-waveguide grill on JET and a 30-waveguide grill proposed for T15) are compared with the predictions of the theory for the corresponding infinite structures. and the agreement is good     

Some exact results for the three-layer zamolodchikov model

In this talk, we present our recent results on the three-layer Zamolodchikov model. We discuss solutions to the Bethe ansatz equations following from functional relations. We consider two regimes I and II that differ by the signs of the spherical sides (a₁, a₂, a₃) → (?a₁, ?a₂, ?a₃). Also, we accept the two-line hypothesis for regime I and the one-line hypothesis for regime II. In the thermodynamic limit, we derive integral equations for distribution densities and solve them exactly. Using this solution, we calculate the partition function for the three-layer Zamolodchikov model and check the compatibility of this result with functional relations. We also discuss the reasons for the discrepancy with Baxter’s result of 1986.     

Effect of ion mean free path length on plasma polarization behind a dust particle in an external electric field

In this paper, a self‐consistent numerical model that describes the behavior of plasma around an isolated, highly charged dust particle is presented. Using the developed model, self‐consistent distributions of the space charge density and plasma potential in the presence of an external electric field are obtained. These distributions are thoroughly analysed though Legendre decomposition. For different dust plasma parameters, such as the radius of the dust particle, the amplitude of the external field, and the mean free path of ions, the dipole moment of the ion cloud surrounding the dust particle is calculated. It turns out that the dependencies of the dipole moment on the value of the external electric field obtained for different parameters are reduced to a single curve by simple scaling.     

Anomalous scattering of a relativistic electron beam in a beam created plasma

Measurements of the velocity angular distribution of a relativistic electron beam (0.8 MV, 6 kA, 150 ns) after propagation through hydrogen gas are presented. At a pressure of 25 Pa scattering of the beam electrons into a preferential angular interval is observed. At 190 Pa anomalously large scattering is observed, up to an angular width of 90°, during about 30 ns.     

Kodaira-Spencer theory of gravity and exact results for quantum string amplitudes

We develop techniques to compute higher loop string amplitudes for twistedN=2 theories with=3 (i.e. the critical case). An important ingredient is the discovery of an anomaly at every genus in decoupling of BRST trivial states, captured to all orders by a master anomaly equation. In a particular realization of theN=2 theories, the resulting string field theory is equivalent to a topological theory in six dimensions, the Kodaira-Spencer theory, which may be viewed as the closed string analog of the Chern-Simons theory. Using the mirror map this leads to computation of the number of holomorphic curves of higher genus curves in Calabi-Yau manifolds. It is shown that topological amplitudes can also be reinterpreted as computing corrections to superpotential terms appearing in the effective 4d theory resulting from compactification of standard 10d superstrings on the correspondingN=2 theory. Relations withc=1 strings are also pointed out.This article was processed by the author using the Springer-Verlag TEX CoMaPhy macro package 1991.