Landau damping effect due to the trapped ions in a compact electron storage ring

Theoretical analysis and experimental results show that the Landau damping due to trapped ions is greatly enhanced in the low-energy beams in compact electron storage rings. This enhancement originates mainly from the decrease in beam size in the low-energy region. This effect must indeed be the main reason why the recently developed compact rings can store a large current even though they have a low injection energy. In the typical energy region of compact rings, more positive utilization of this effect could make the damping rate of a lower-energy beam far larger than that of a higher-energy one. Therefore, if we could control the effect of the trapped ions, we might prefer to adopt lower energy in order to inject a large current in a compact ring.     

Wake field analysis and modelling of microwave instability in the ILC damping ring

Wake field simulations are performed for given technical designs of the vacuum chamber components for the 6.4 km ILC damping ring, in order to calculate longitudinal wake functions. Modelling of the microwave instability based on multi-turn tracking with many particles is described. A comparison is presented between the potential well distortion found from solving the Haissinski equation and the results of tracking simulations. The threshold for the microwave instability is found for the given designs and lattice parameters.     

Equilibrium relationships in the system NiO-CoO-O2

As part of a programme to investigate the possibility of using conducting oxide electrodes in the fused carbonate fuel cell, equilibrium relationships in the system NiO-CoO-O₂ were investigated using a thermobalance. An isobaric ternary diagram of the system was constructed and it is shown that the variation in the temperature of the boundary between the single phase (NiO-CoO solid solution) and the two phase (Co₃O₄ + NiO-CoO solid solution) fields, with cationic composition, is consistent with approximately ideal behaviour. A mechanism based on the established phase relationships is also suggested to explain the observation that loss of oxygen from two-phase mixtures on heating results in the formation of NiO-CoO solid solution in the interior of the Co₃O₄ grains. Results are also presented to show the effects of composition and heat-treatment on the electrical conductivities at high temperatures of selected mixtures.     

Color image security system using double random-structured phase encoding in gyrator transform domain

A novel method for encoding color information based on a double random phase mask and a double structured phase mask in a gyrator transform domain is proposed. The amplitude transmittance of the Fresnel zone plate is used as structured phase-mask encoding. A color image is first segregated into red, green, and blue component images. Each of these component images are then independently encrypted using first a random phase mask placed at the image plane and transmitted through the first structured phase mask. They are then encoded by the first gyrator transform. The resulting information is again encrypted by a second random phase mask placed at the gyrator transform plane and transmitted through the second structured phase mask, and then encoded by the second gyrator transform. The system parameters of the structured phase mask and gyrator transform in each channel serve as additional encryption keys and enlarge the key space. The encryption process can be realized with an electro-optical hybrid system. The proposed system avoids problems arising from misalignment and benefits of a higher space-bandwidth product. Numerical simulations are presented to confirm the security, validity, and possibility of the proposed idea.     

Output signal and noise characteristics in RF pumped double SQUIDS

On the base of a rigorous theoretical model the output characteristics of a RF double SQUID for use as an instrument for delicate measurements are computed, and the two RF pump modes (external and autodyne) are optimized from the output signal level point of view. Then, a two-dimensional thermal activation model is applied for the analysis of the intrinsic noise influence on the output performances of such a device. A theoretical estimation for the flux noise spectral densities at low frequencies is given and an optimization from the signal-to-noise ratio and double SQUID flux coupling points of view is also made. Showing the superiority of this novel RF pumped SQUID configuration over the traditional one, both these theoretical approaches gave results that are in a very good agreement with the existed experimental data.     

爆炸冲击隔震系统实验研究

实验研究了由钢丝绳隔震器组成的爆炸冲击隔震系统在爆炸冲击下的响应及破坏机理，得到了爆炸冲击     

模态自适应相位调制的多压电元件压电分流系统

在含有多个压电元件的压电分流系统中,各压电元件的输出电压之间的相位关系会随着结构振动模态的变化而变化,导致诱发电荷中和抵消,降低了压电分流系统的抑振效果。由此,本文提出了几种典型的等效电压源网络拓扑结构,在分析各自优缺点的基础上,将并联连接确定为最佳组网方式。针对此组网方式,为了保证在不同阶次的模态响应下,各压电元件的输出电压均保持同相,提出了具有模态自适应能力的相位调制技术,并设计制作了相应的模拟电路。仿真结果表明,该系统能够可靠的完成自适应相位调制,避免了电荷中和现象的出现。     

Performance of the vacuum system for the PETRA III damping wiggler section

A record low horizontal emittance of 1 nm-rad was successfully obtained in PETRA III third generation synchrotron light source. A key system that allowed reaching such value includes 20 permanent magnet damping wigglers installed in two long straight sections. The wigglers radiate almost 1 MW at maximum current of hard X-ray radiation which issues a challenge for the design of SR absorbers and vacuum system components for the damping wiggler section. The paper describes in detail the design consideration, manufacturing and experimental performance of absorbers and vacuum system. The first experimental results of PETRA III damping wiggler section operation are presented.     

Effects of cavity damping on the entanglement for a three-level atomic system

Based on the master equation for the density matrix, the dynamics of the entanglement of the three-level atom interacting with single-mode field in a finite-Q cavity are studied. It was found that the cavity damping leads to growing entropy and a strong degradation of the entanglement, therefore the coherence loss and entanglement is very sensitive to any change in the cavity damping parameter.     

离心式压缩机转子系统稳定性控制方法研究

针对离心压缩机转子失稳已成高效长周期运转主要障碍问题,通过分析失稳机理及影响因素,研究压缩机转子系统稳定性控制方法。结合工程案例,采用有限元方法对转子进行瞬态动力学分析,研究转速及因密封等部件交叉刚度对转子稳定性影响。研究转子振动位移反馈与速度反馈方法对转子失稳振动的控制效果。结果表明,两种方法均能有效提高转子系统稳定性。对比在达到相同控制效果时执行机构能量消耗表明,通过位移反馈方式能以更低能耗达到控制效果。该结果可为离心压缩机转子稳定性控制与提高提供新的思路及可行性。     

基于目标模拟器的测量雷达相位一致性测试方法

相位一致性直接影响测量雷达的测角精度,因此在重大任务前必须对一致性进行测试,而常用测试方法如注入法安装架设复杂、使用条件要求高,标定法又过度依赖于标校塔或标校架,在地形受限时无法使用。该文中提出一种利用雷达自带的目标模拟器进行"注入式"相位一致性测试的方法,可对除馈源和天线以外的部分进行相位一致性测试,并在某型精密跟踪测量雷达上进行验证。结果表明:该方法操作简便,精度与常规注入法相当,可应用于基层雷达站进行相位一致性自检及野外临时阵地等不具备常规测试方法的场合。     

Condensed phase diagram for the In-As-O system

An estimate of the condensed phase portion of the equilibrium In-As-O ternary diagram has been constructed from thermodynamic calculations and checked against binary mixture reaction experiments. Utilization of the diagram to explain the phase composition of thin films associated with thermal oxidation and native oxide-substrate reaction processes on InAs and In_xGa_1-xAs are presented in a companion paper.     

Frost heave and phase front instability in freezing soils

The main equations and conditions at the phase transition front are presented for a generalized model of secondary frost heave in freezing fine-grained soils. The analytical criterion for the stability/instability of the freezing phase front in porous media is derived. This criterion is obtained for the occurrence of the frost heave process by using the perturbation method in a two-dimensional, coupled heat and mass transfer model. This model assumes that the non-instantaneous crystallization process takes place in the kinetic zone, and that the rate of crystallization is a function of supercooling. This corresponds to the Arrhenius form equation and agrees with experimental investigations. The perturbation analysis of the freezing front shows that the stability criterion depends upon 1) the Stefan and Peclet numbers, 2) a parameter describing the phase transition kinetics and also 3) dimensionless parameters which characterize the frost heave process. Employing Fourier synthesis, actual front shape evolution is calculated. It is seen that the front displays a periodic morphology whose scale is essentially unrelated to that of the initial (starting) perturbation. The effect of the non-instantaneous kinetics on the front shape evolution is described. As is shown in results, the kinetics has a stabilizing effect and, in this case, the perturbations grow more slowly. The theoretical stability/instability conditions as predicted from the derived criterion were found to be in agreement with experimental investigations of the formation of soil cryogenic structure in the freezing process. On the basis of the asymptotic solution the engineering approach for the calculation of the heave rate and maximal frost penetration depth values — main characteristics for design and construction in cold regions, is presented. The good agreement between calculated values and experimental data is observed.     

Rapid phase transformations caused by thermodynamic instability in cryogens

The cause of rapid phase transformations observed by several investigators can be explained by the phenomenon of thermodynamic metastability and incipient instability. A liquid cryogen coming into intimate, sudden contact with a substantially warmer host liquid is heated and forms a thin layer of metastable, superheated liquid at the interface between the two. A shock wave is initiated in the metastable layer when the interface temperature is approximately 0.84 times the critical temperature of the cryogen. A heat transfer and thermodynamic model is given that enables us to predict the necessary host liquid temperature that will cause a shock wave for a given cryogen. Experimental results are presented that support the analytical contention, that for several water-cryogen combinations the water temperature necessary to produce a shock wave is about 1.10 times the critical temperature of the cryogen.     

耗能增效惯容系统的自适应权重粒子群优化

耗能增效是惯容减震系统的典型特征。为充分发挥此特性并同时满足减震性能需求,提出将惯容减震结构耗能增效程度最大化作为目标,并以性能需求作为约束条件进行减震参数寻优。基于随机振动理论推导惯容减震单自由度结构在白噪声激励下的解析解;建立最大耗能增效设计所对应等效约束优化问题的数学表达式。鉴于表达式的复杂性,采用鲁棒性好且便于实现的粒子群算法对问题进行求解。在粒子群算法中引入自适应惩罚权重考虑约束条件,并采用自适应调整的惯性权重提高求解效率。基于Python语言编制了自适应权重粒子群算法程序对惯容减震结构最大耗能增效设计问题进行求解。设计实例的求解过程体现了自适应权重粒子群算法对求解惯容减震结构优化设计问题的有效性,动力时程分析结果表明设计参数实现了预设的减震性能需求。     

Role of phase key in the double random phase encoding technique: an error analysis

We perform a numerical analysis of the double random phase encryption-decryption technique to determine how, in the case of both amplitude and phase encoding, the two decryption keys (the image- and Fourier-plane keys) affect the output gray-scale image when they are in error. We perform perfect encryption and imperfect decryption. We introduce errors into the decrypting keys that correspond to the use of random distributions of incorrect pixel values. We quantify the effects that increasing amounts of error in the image-plane key, the Fourier-plane key, and both keys simultaneously have on the decrypted image. Quantization effects are also examined.