[en] When charged particles pass through a metal pipe, they are accompanied by an image current on the metal surface. With intense short bunches passing near the metal surface, the peak image current density can be very high. This current may result in substantial temperature rise on the surface, especially in multi-bunch operation. In this paper, the authors derive an explicit formula for the surface temperature rise due to this previously unrecognized effect, and show that it should be taken into account in structure and collimator design for future accelerators

[en] This paper reports the development of an object-oriented programming methodology for particle simulations. It is established on the [m reductionist] view that many physical phenomena cana be reduced to many-body problems. By doing the reduction, many seemly unrelated physical phenomena can be simulated in a systematic way and a high-level programming system can be constructed to facilitate the programming and the solution of the simulations. In the object-oriented particle simulation methodology, a hierarchy of abstract particles is defined to represent a variety of characteristics in physical system simulations. A simulation program is constructed from particles derived from the abstract particles. The object- oriented particle simulation methodology provides a unifying modeling and simulation framework for a variety of simulation applications with the use of particle methods. It allows easy composition of simulation programs from predefined software modules and facilitates software reusability. It greatly increase the productivity of simulation program constructions. Boltzmann (after Ludwig Boltzmann, 1844-1906) is a prototype programming system in the object-oriented particle simulation methodology. Boltzmann is implemented in C++ and the X Window System. It contains a library of data types and functions that support simulations in particle methods. Moreover, it provides a visualization window to support friendly user-computer interaction. Examples of the application of the Boltzmann programming system are presented. The effectiveness of the object-oriented particle simulation methodology is demonstrated. A user's manual is included in the appendix

[en] Macroscopic response and microscopic dislocation structures of Zr-4 subjected to biaxial fatigue under different phase angles of 30 degree, 60 degree, 90 degree, and different equivalent strain ranges of 0.8%, 0.6%, 0.4% were studied. The testing results show that the delay angle between the stress deviators and strain increment tensors is strongly dependent on phase angle and the equivalent strain range. When phase angle equals 60degree, the delay angle has the minimum variation range for all specimens. The mean value of the delay angle decreases with increasing phase angle or the equivalent strain range. The variation range and average value of the Mises equivalent stress have the maximum in S3 with the phase angle of 90degree. They decrease as the equivalent strain range decreases. Zr-4 displays a pronounced initial hardening followed by a continuous softening for all specimens during out-of-phase cycling. The stabilized saturation stresses of Zr-4 under out-of-phase cycling are much higher than that under uniaxial cycling. It indicates that Zr-4 displays an obvious additional hardening. As the phase angle increases, the typical dislocation structure changes from dislocation cells to tangles. The dislocation-dislocation interactions increase resulting in an additional hardening. In essence, the degree of additional hardening depends, among other factors, on the maximum shear stress ratio of resolved shear stresses and critical resolved shear stresses (RSS/CRSS)

[en] In the design of new high energy particle colliders with higher luminosity one is naturally led to consider multi-bunch operation. However, the passage of a leading bunch through an accelerator cavity Generates a wakefield that may have a deleterious effect on the motion of the subsequent bunches. Therefore, the suppression of the wakefield is an essential requirement for beam stability. One solution to this problem, which has been studied extensively is to drain the wakefield energy out of the cavity by means of waveguides coupled with the cavity and fed into matched terminations. Waveguide dimensions are chosen to yield a cutoff frequency well above the frequency of the accelerating mode so that the latter is undamped. This paper presents a thorough investigation of the wakefield for this configuration. The effectiveness of waveguide damping has typically been assessed by evaluating the resultant Q_ext of higher order cavity modes to determine their exponential damping rate. We have developed an efficient method to calculate Q_ext of the damped modes from popular computer simulation codes such as MAFIA. This method has been successively applied to the B-factory RF cavity We have also found another type of wakefield, associated with waveguide cut-off, which decays as t^-3/2 rather than in the well-known exponentially damped manner. Accordingly, we called it the persistent Wakefield. A similar phenomenon with essentially the same physical origin but occurring in the decay of unstable quantum states, has received extensive study. Then we have developed various methods of calculating this persistent wakefield, including mode matching and computer simulation. Based on a circuit model we estimate the limit that waveguide damping can reach to reduce the wakefield

[en] Ground level O₃ in urban and regional air pollution represents one of the most pervasive and stubborn environmental problems. In this study, The authors used a comprehensive regional air quality modeling system to investigate the role played by fossil-fueled power plant's NO_x emissions in regional O₃ formation. The modeling system consists of two models, MC2 (Mesoscale Compressible Community Model) and ADOM (Acid Deposition and Oxidant Model). While the first model generates meteorological fields, the second one calculates the chemical transformation, transport and deposition. The modeling system features a nesting scheme to zoom into a small region with high resolution. The authors applied the system to a series of emissions scenarios under regional O₃ episodic conditions. From the analysis of modeling results, it is found that the addition of a power plant's NO_x emissions initially induces a significant O₃ depression in a short range. As the power plant plumes move farther, O₃ in the plumes could either be kept below or elevated above its background level depending on the NO_x amount existing in the background air mass. The study revealed that a drastic O₃ enhancement in the plumes could occur after 50 km downwind in a clean environment. The O₃ enhancement could remain at a noticeable level until 350 km. On the contrary, in a dirty environment, O₃ in power plant plumes could be suppressed continuously below its background level by the NO_x associated with the plumes. The different responses of the regional O₃ level to the power plant NO_x emissions are discussed from the aspect of non-linear photochemistry

[en] Field studies have confirmed O₃ depletion inside power plant plumes, due to the rate-limited cycle between NO₂ and O₃. A reactive power plant plume model has been developed that includes a description of the complex photochemical system and a dispersion mechanism for mass transfer in the horizontal cross-wind direction. In addition, the model uses a one dimensional diffusion module to simulate the vertical transport of chemical species based on diffusivity profiles which are dependent on meteorological conditions. The model was applied to the plume from Nanticoke thermal generating station (TGS) in Ontario, released at 7:00 am and travelling for 12 hours towards the north-north-east at 5 m/s. The preliminary results suggest that under the emission conditions that were obtained, O₃ in the plume centre is reduced compared to the case in which the plume is absent. The O₃ reduction within the plume increases as the NOx emission from Nanticoke TGS increases. The general conclusion is confirmed by relaxing the local emissions and the dispersion parameter σ_y over a reasonable range. Further investigation shows that the O₃ reduction is consistent with current knowledge of nonlinear photochemical systems. 32 refs., 22 figs

No abstract available

[en] The higher-order-mode (HOM) heating of the central beryllium beam pipe in the PEP-II B-Factory interaction region is evaluated. Both single and multi-bunch effects are considered. While single-bunch heating is not an issue, resonant heating due to multiple bunch passages is found to be unacceptable. Modifying the IR configuration around the central pipe has been shown to alleviate this problem. Simulation results indicate that the new design is sufficiently effective in reducing possible resonant heating down to a level that is within existing cooling requirements

[en] To study the relationship between dopamine (DA) D₂ receptors and cerebral blood flow in hemiparkinsonism rats. Hemi-parkinsonism rats were made by stereotaxic 6-hydroxy dopamine (6-OH-DA) lesions in substantia nigra and ventral tegmental area, apomorphine (Apo) which could induce the successful model rat rotates toward the intact side was used to screen that rats, ¹²⁵I-IBZM in vivo autoradiography and ^99mTc-HM-PAO regional brain biodistribution were used to study D₂ receptors and cerebral blood flow. The HPLC-ECD were used to measure the concentration of DA and it metabolites homovanillic acid (HVA), 3,4-dehydroxyphenyl acetic acid (DOPAC) in bilateral striatum (ST). The lesioned side ST DA and its metabolites HVA DOPAC reduced significantly than that of the intact side and pseudo-operated control group, ST/cerebellum (CB) ¹²⁵I-IBZM uptake ratio was 8.04 ±0.71 in lesioned side of hemi-parkinsonism rats, significantly increased compared with the intact side and the pseudo-operated group (p<0.05), 30^99mTc 30.1±4.53% enhancement as compared to the intact side, and also show good correlation with 30 min Apo induced rotation numbers (r=0.98), the regional cerebral blood flow study didn't show significant difference between bilateral brain cortex area (p>0.05). The DA content decreased significantly and induced an up-regulation of ST D₂ receptor binding sites in 6-OH-DA lesioned side in hemi-parkinsonism rats, the increased percentage of lesioned-intact side ST/CB ¹²⁵I-IBZM uptake ratio showed good correlation with rotation behavior induced by Apo. Compare with cerebral blood flow, D₂ receptor reflected by IBZM seems to be more specific and earlier to detect the cerebral functional impairment in experimental hemi-parkinsonism

[en] A large sample INAA (LS-INAA) was conducted based on available experimental conditions. Four different materials, e.g., a quartz-sand and three wastes from an incineration plant were analyzed on sample size of 1 kg. The neutron flux spatial distribution was determined by irradiation of flux monitors in the sample. The gamma-ray apparent counting efficiency was evaluated based on the effective-solid angle concept, using linear attenuation coefficients calculated from an iteration process. The k₀- and the modified monostandard methods were modified for the LS-INAA. To check the LS-INAA performance, a conventional small sample INAA was carried out for the quartz sand and a waste. All detected elements in the LS-INAA are presented and the discussion is conducted to explore the sources of errors in the LS-INAA. As a pilot experiment, the information from this work will be used in constructing irradiation and counting devices for the new FRM-II neutron source in Garching, Germany. (author)