DLN燃烧室的燃料-空气预混均匀性研究

参照国产燃机DLN燃烧室的燃料-空气预混机构,模化设计了相应的试验装置,并在冷态条件下,测量了燃料-空气的预混预均匀性,发现无论在径向还是周向的燃料分空间布都极不均匀,这对控制燃烧时的NOx排放显然是十分不利的。为此,本文进一步分析了影响预混均匀性的各种因素,指出该燃烧室的预混不均的主要原因是燃料-空气射流动量比偏小,预混长度短和燃料径向喷射不匀,并通过实验验证了上述分析,提出了改进的措施和方向。     

用推广的Viola-Seaborg公式计算α衰变寿命

根据Audi等编评的最新核数据表, 对Z≥84, N≥128的核的α衰变实验寿命用Viola-Seaborg公式进行最小方差拟合, 得到一套新参数. 用新拟合参数计算的偶偶核的衰变寿命与实验寿命很好地符合, 平均偏差1.3倍.而对奇A和奇奇核理论寿命与实验寿命相差较远. 考虑到处于基态时奇A和奇奇核与偶偶核的主要区别在于自旋和宇称, 对Viola-Seaborg公式做了推广. 在公式中引入了离心势垒(即α粒子轨道角动量)对衰变寿命的影响. 由推广公式计算的奇A和奇奇核的寿命与实验寿命平均偏差2.5倍,最大偏差5—6倍.     

Pion electroproduction in parity violating elastic ep scattering experiment

This study has been developed for electron-proton scattering experiments when only the scattered electrons are detected. Pion electroproduction on the proton including the cascade π⁰→ 2γ decay and the QED radiative corrections to elastic ep scattering are investigated. Our results are shown in the kinematical configuration of the parity violating electron scattering experiment planned at the Mainz Microtron (MAMI). Received: 20 April 1999 / Revised version: 4 June 1999     

Total photon cross sections for low energy photons in light elements

A large amount of compiled data on total photon cross sections is available in the literature. However, for some elements, in the low Z region data is sparse, although new theoretical data have become available. In the present study, transmission experiments in the low photon energy region 5–60 keV were carried out for four low Z elements using a Freolectric cooled Si(Li) detector attached to a System-100 multichannel analyser. Results are presented in the light of present theory.     

Manipulating the phase of a single-mode micromaser by polarized three-level atoms

We investigate the phase probability distribution (PPD) of a single-mode micromaser pumped by atoms injected in the most general case, i.e. in the superposition of the upper, intermediate and lower states by the Monte Carlo wave function approach. The phase properties of the cavity mode are greatly influenced by the relative phases and the amplitudes of the polarized atoms, and the detunings between the atom and cavity. The cavity field has a single preferred phase if the cavity is pumped by the atoms in the superposition of the upper and intermediate states or of the intermediate and lower states. However, a double-peak feature appears in the PPD of the cavity field when the cavity is pumped by the atoms in the superposition of the upper and lower states. With appropriate detunings, the double peaks become narrower and more remarkable, which shows the better defined phase of the cavity field, as compared to the resonant case. The PPD displays complicated characteristics when the cavity is pumped by the atoms in the superposition of the upper, intermediate and lower states. The phase distribution changes from a single peak to double peaks and to another single peak when we modulate the phase of the intermediate state, which has been explained in the semi-classical radiation theory.     

A zero-point energy approach for estimating the photon mass

An upper bound for the photon rest-mass is calculated on the basis of zero-point energy considerations within the context of fluctuations in the quantum foam, our results being compared with experimental data. Furthermore, some aspects related to energy spectrum are discussed.     

φ-meson photoproduction from nuclei

We study coherent and incoherent φ-meson photoproduction from nuclei. The available data are analyzed in terms of single- and coupled-channel photoproduction. It is found that the data on coherent photoproduction can be well reproduced within a single-channel optical model and show only little room for ω-φ mixing. These data indicate a normal distortion of the φ-meson in nuclei, which is compatible with the results obtained through the vector meson dominance model. The data on incoherent φ-meson photoproduction show an anomalous A-dependence resulting in a very strong φ-meson distortion. These data can be explained by a coupled-channel effect through the dominant contribution from the ω↦φ or the π↦φ transition or, more speculative, through the excitation of a cryptoexotic B _φ-baryon.     

Dynamics of two quantum entangled particles interacting with a potential barrier in an EPR experiment

The effect of a position measurement on one component of a two-particle wave packet in a regularized space-momentum entangled state is analyzed. The wave packet interacts in the physical space with a potential barrier. When a position or momentum measurement is performed on one particle, a consequent strong modification of the dynamics of the other particle occurs.     

The gravitational field of photons

The gravitational field of a photon on an infinite straight path is a single sheet of plane-fronted gravitational wave accompanying the photon and perpendicular to its track. This field cannot arise from a retarded potential generated by the photon, and I suggest that it arises in the process of emission. The near-field depends on the energy of the photon, but the far-field does not. The field of a steady beam of photons is compared with that of a static material rod, and the differences discussed.     

Squeezed two-mode lasers without and with inversion

On the basis of the nondegenerate quantum-beat laser model, we introduce a coherent field which drives the transition between the upper lasing level and an auxiliary level. We demonstrate that such a four-level system can produce squeezed two-mode laser without and with inversion. When the laser is operated well above threshold, the intensity fluctuation in the average mode is reduced below the shot noise with an optimum Mandel parameter Q=- 1/2. At the same time, the noises in the relative amplitude and the relative phase drop to their vaccum noise levels. Furthermore, regardless of inversion, noninversion, and transition between inversion and noninversion, the optimum Mandel Q parameter of Q=- 1/2 is retained when the system operates well above threshold. A simple physical explanation of the squeezing mechanism for two-mode squeezing is given. Received: 22 December 1997 / Revised: 25 March 1998 / Accepted: 9 September 1998