兰州重离子加速器深层治癌扫描电源研究与设计

This paper describes the technique targets and operation principle of the scanning power supply for the deep tumor therapy facility with heavy ions in Cooler-Storage-Ring of the Heavy Ion Research Facility in Lanzhou(HIRFL-CSR).To ensure the specified accuracy of the current,the hysteresis loop control strategy was adopted,and tracking error was constrained in the specified tolerance.One prototype was designed and installed.And the simulation results and test results were listed in the paper.The results sho...中文摘要：阐述了用于兰州重离子深层治癌装置的扫描电源的技术指标和工作原理,为保证该电源输出电流的精度,采用滞环控制策略,将跟踪误差限制在设计要求的误差范围内。研制了1台扫描电源样机,并给出了电路仿真和测试结果。测试结果显示各项指标均达到了设计要求,表明所选电路结构和滞环控制方案是切实可行的。

SSC新高频腔设计与分析

Beam matching relationship between the two cyclotrons(SFC and SSC) of HIRFL is briefly discussed, and the frequency band of the new RF cavity is obtained. The new cavity is simulated with the three-dimensional electromagnetic calculation code MAFIA, and the parameters of it such as frequency, Q value, shunt impedance and voltage distribution are worked out and discussed. The simulation results show that the new RF cavity can fully meet the requirements of physics design and space configuration.中文摘要：简要分析了HIRFL SFC与SSC之间的束流匹配关系,给出了新高频腔的频率范围。利用经典三维电磁场数值模拟软件MAFIA对SSC新高频腔体进行了模拟计算,得出了SSC新高频腔体的相关物理参数,并对频率范围、Q值、并联阻抗和电压分布等参数进行了分析。高频腔体的模拟计算结果完全符合SSC回旋加速器改造的物理设计及空间结构要求。

Study of buncher efficiency in axial injection system of SFC

In order to reduce the influence of the stray electric field of the buncher in the axial injection system of SFC and to improve the injection efficiency of SFC, the existing buncher electrode is investigated and a new electrode is designed. The influences of the electric field to the beams for the both cases are simulated. The simulation results show that the bunching efficiency is improved from 55% to 74% with the new electrode. At the same time, the influence of the space charge is computed and according to the results, the location of the buncher is readjusted too.

Design studies on the 4 pi gamma-ray calorimeter for the ETF experiment at HIRFL-CSR

A high detection efficiency calorimeter which is used to detect gamma-rays with energies from 1 MeV up to 10 MeV as well as light charged particles has been proposed. Design of the geometry, results of the crystal tests and Monte Carlo simulations are presented in this paper. The simulation results confirm that the calorimeter can obtain high detection efficiency and good energy resolution with the current designed geometry. And the calorimeter is competent for the future External Target Facility (ETIF) experiments.

A Particle-in-cell scheme of the RFQ in the SSC-Linac

A 52 MHz Radio Frequency Quadrupole (RFQ) linear accelerator (linac) is designed to serve as an initial structure for the SSC-Linac system (injector into Separated Sector Cyclotron). The designed injection and output energy are 3.5 keV/u and 143 keV/u, respectively. The beam dynamics in this RFQ have been studied using a three-dimensional Particle-In-Cell (PIC) code BEAMPATH. Simulation results show that this R,FQ structure is characterized by stable values of beam transmission efficiency (at least 95%) for both zero-current mode and the space charge dominated regime. The beam accelerated in the RFQ has good quality in both transverse and longitudinal directions, and could easily be accepted by Drift Tube Linac (DTL). The effect of the vane error and that of the space charge on the beam parameters have been studied as well to define the engineering tolerance for RFQ vane machining and alignment.

Promotion of cooperation in the form C0C1D classified by 'degree grads' in a scale-free network

In this paper, we revisit the issue of the public goods game (PGG) on a heterogeneous graph. By introducing a new effective topology parameter, 'degree grads' phi, we clearly classify the agents into three kinds, namely, C-0, C-1, and D. The mechanism for the heterogeneous topology promoting cooperation is discussed in detail from the perspective of C0C1D, which reflects the fact that the unreasoning imitation behaviour of C-1 agents, who are 'cheated' by the well-paid C-0 agents inhabiting special positions, stabilizes the formation of the cooperation community. The analytical and simulation results for certain parameters are found to coincide well with each other. The C0C1D case provides a picture of the actual behaviours in real society and thus is potentially of interest.

An integrated aurora image retrieval system: AuroraEye

With the digital all-sky imager (ASI) emergence in aurora research, millions of images are captured annually. However, only a fraction of which can be actually used. To address the problem incurred by low efficient manual processing, an integrated image analysis and retrieval system is developed. For precisely representing aurora image, macroscopic and microscopic features are combined to describe aurora texture. To reduce the feature dimensionality of the huge dataset, a modified local binary pattern (LBP) called ALBP is proposed to depict the microscopic texture, and scale-invariant Gabor and orientation-invariant Gabor are employed to extract the macroscopic texture. A physical property of aurora is inducted as region features to bridge the gap between the low-level visual features and high-level semantic description. The experiments results demonstrate that the ALBP method achieves high classification rate and low computational complexity. The retrieval simulation results show that the developed retrieval system is efficient for huge dataset. (c) 2010 Elsevier Inc. All rights reserved.

Lattice Boltzmann study of hydrodynamic effects in lamellar ordering process of two-dimensional quenched block copolymers

By incorporating self-consistent field theory with lattice Boltzmann method, a model for polymer melts is proposed. Compared with models based on Ginzburg-Landau free energy, our model does not employ phenomenological free energies to describe systems and can consider the chain topological details of polymers. We use this model to study the effects of hydrodynamic interactions on the dynamics of microphase separation for block copolymers. In the early stage of phase separation, an exponential growth predicted by Cahn-Hilliard treatment is found. Simulation results also show that the effect of hydrodynamic interactions can be neglected in the early stage.

The study of banded spherulite patterns by coupled logistic map lattice model

Banded spherulite patterns are simulated in two dimensions by means of a coupled logistic map lattice model. Both target pattern and spiral pattern which have been proved to be existent experimentally in banded spherulite are obtained by choosing suitable parameters in the model. The simulation results also indicate that the band spacing is decreased with the increase of parameter mu in the logistic map and increased with the increase of the coupling parameter epsilon, which is quite similar to the results in some experiments. Moreover, the relationship between the parameters and the corresponding patterns is obtained, and the target patterns and spiral patterns are distinguished for a given group of initial values, which may guide the study of banded spherulite.

Effect of polydispersity on the self-assembly structure of diblock copolymers under various confined states: A Monte Carlo study

We studied the self-assembly of polydisperse diblock copolymers under various confined states by Monte Carlo simulation. When the copolymers were confined within two parallel walls, it was found that the ordered strip structures appeared alternately with the increase in wall width. Moreover, the wall width at which the ordered structure appeared tended to increase with an increase in the polydispersity index (PDI). On the other hand, the simulation results showed that the copolymers were likely to form ordered concentric strip structures when they were confined within a circle wall.

Defect evolution and hydrodynamic effects in lamellar ordering process of two-dimensional quenched block copolymers

The effects of hydrodynamic interactions on the lamellar ordering process for two-dimensional quenched block copolymers in the presence of extended defects and the topological defect evolutions in lamellar ordering process are numerically investigated by means of a model based on lattice Boltzmann method and self-consistent field theory. By observing the evolution of the average size of domains, it is found that the domain growth is faster with stronger hydrodynamic effects. The morphological patterns formed also appear different. To study the defect evolution, a defect density is defined and is used to explore the defect evolutions in lamellar ordering process. Our simulation results show that the hydrodynamics effects can reduce the density of defects. With our model, the relations between the Flory-Huggins interaction parameter chi, the length of the polymer chains N, and the defect evolutions are studied.

STUDY OF COARSENING OF MICRODOMAINS IN BLOCK COPOLYMERS BY LATTICE BOLTZMANN METHODS

In order to understand the coarsening of microdomains in symmetric diblock copolymers at the late stage, a model for block copolymers is proposed. By incorporating the self consistent field theory with the free energy approach Lattice Boltzmann model, hydrodynamic interactions can be considered. Compared with models based on Ginzburg-Landau free energy, this model does not employ phenomenological free energies to describe systems. The model is verified by comparing the simulation results obtained using this method with those of a dynamical version of the self consistent mean field theory. After that,the growth exponents of the characteristic domain size for symmetric block copolymers at late stage are studied. It is found that the viscosity of the system affects the growth exponents greatly, although the growth exponents are all less than 1/3 Furthermore, the relations between the growth exponent, the interaction parameter and the chain length are studied.

The time delay in electrochemical measurements of a finite-volume system

For a sphere electrode enclosed in finite-volume electrolyte, the measured current will deviate from the result predicted by the semi-infinite diffusion theory after some time. By random-walk simulation, we compared this time to the one needed for diffusion layer to reach electrolyte boundary, and revealed a clear signal delay of electrochemical current. Further we presented a quantitative description of this delay time. The simulation results suggested that the semi-infinite diffusion theory can even be applied when the theoretical diffusion layer grows to 1.28 electrolyte thicknesses, with an accuracy better than 0.5%. We attributed this time delay to the molecules' finite propagation velocity. Finally, we discussed how this delay can influence and facilitate the following electrochemical detection towards the nanometer and single-cell scale.

Grafting of maleic anhydride onto linear polyethylene: A Monte Carlo study

Monte Carlo simulation was used to study the graft of maleic anhydride (MAH) onto linear polyethylene (PE-g-MAH) initiated by dicumyl peroxide (DCP). Simulation results revealed that major MAH monomers attached onto PE chains as branched graft at higher MAH content. However, at extremely low MAH content, the fraction of bridged graft was very close to that of branched graft. This conclusion was somewhat different from the conventional viewpoint, namely, the fraction of bridged graft was always much lower than that of branched graft under any condition. Moreover, the results indicated that the grafting degree increased almost linearly to MAH and DCP concentrations. On the other hand, it was found that the amount of grafted MAH dropped sharply with increasing the length of grafted MAH, indicating that MAH monomers were mainly attached onto the PE chain as single MAH groups or very short oligomers. With respect to the crosslink of PE, the results showed that the fraction of PE-(MAH)(n)-PE crosslink structure increased continuously, and hence the fraction of PE-PE crosslink decreased with increasing MAH concentration.

Near-Space Wide-Swath Radar Imaging With Multiaperture Antenna

Near-space, defined as the altitude region between 20 and 100 km, offers many capabilities that are not accessible for low Earth-orbit (LEO) satellites or airplanes because it is above storm and not constrained by orbital mechanics and high fuel consumption. Hence, a high flying speed can be obtained for the maneuvering vehicles operating in near-space. This offers a promising solution to simultaneous high-resolution and wide-swath synthetic aperture radar (SAR) imaging. As such, one near-space wide-swath SAR imaging technique is presented in this letter. The system configuration, signal model, and imaging scheme are described. An example near-space SAR system is designed, and its imaging performance is analyzed. Simulation results show that near-space maneuvering vehicle SAR indeed seems to be a promising solution to wide-swath SAR imaging.