Higher order modes in an RF deflecting structure

RF deflectors on the basis of a disk-loaded waveguide with different methods for stabilizing the polarization plane of an EH ₁₁ hybrid wave (with two holes in the diaphragm, with an oval-shaped coupling aperture, and with two grooves in a shell) were developed for the system of measuring the length and emittance of an electron bunch in a free electron laser. The electrodynamic characteristics of higher order modes were calculated and measured for the mentioned methods for specifying the wave polarization plane.     

A round-robin test of thermal desorption spectroscopy with quadrupole mass spectrometers calibrated by standard conductance element

The results of a round-robin test of thermal desorption spectroscopy (TDS) in which the quadrupole mass spectrometer of each participant was calibrated in-situ by a standard conductance element are reported. The desorption rate from three commercially available reference materials was quantified from the calibration results, and compared among the three participants. The total reported desorption amounts of hydrogen and argon molecules from the reference materials showed agreement within about 10%. The degree of equivalence of three TDS apparatuses was discussed. It is also shown that the quantification of the gas desorption amounts yields us the appropriate relative ratio between desorbed gas species.     

A pulse generator for feeding mass spectrometers

A small-size high-frequency rectangular alternating-voltage pulse generator is designed for energizing a cylindrical electrode of a monopole mass spectrometer. Amplitudes of positive and negative pulses linearly increase from zero to +150 V/?180 V for ～10 min and the frequency simultaneously linearly decreases from 2.0 to 1.4 MHz. A negative-polarity direct component, which is required for operation of the mass spectrometer, is formed due to unequal positive and negative amplitudes with respect to the ground. Spectra of residual gases with atomic mass numbers of 1–130 amu are obtained.     

Calibration of mass spectrometers for van der Waals dimers

A stream tube from a small supersonic free jet in vacuo is passed successively through the ion source of a quadrupole mass spectrometer and into an enclosed ionization gauge which indicates total mass flux. By simultaneous measurements of dimer and monomer ion currents as well as total mass flux we are able to arrive at absolute values of the relative concentration of neutral monomer and dimer in the free jet. Results obtained with argon, carbon dioxide, and oxygen indicate substantial fragmentation of dimers in the ion source. Consequently, populations of neutral dimers in supersonic free jets of the kind widely used as beam sources may be much larger than previous studies have indicated.     

Quartz tube orifice leaks for local, fast-response gas sampling to mass spectrometers

Simple and versatile quartz tube orifice leaks, suitable for sampling of gas mixtures to mass spectrometers, have been made by heating the tip of a quartz tube in a hydrogen-oxygen flame. With these leaks the requirement of expensive and clumsy differential pumping stages is removed. The quartz probes have been used in gas sampling from catalytic reaction cells at 1 atm to a mass spectrometer. The sampling position can be located within 0.1 mm from the catalyst. Continuous recording of the local gas composition is then achieved with a response time of about 0.05 s, and with a minimum perturbation of the gas flow. The probes have been used in ambient air and at temperatures around 1000 K for extended periods of time without deterioration or plugging. The high stability at elevated temperatures and chemical resistance seem to make these probes useful for various applications, e.g., in sampling from combustion flames. The gas flow through the leak is determined by a very short and narrow constriction at the tube tip. In a leak with a throughput of 1x10(-4) Torr l/s at 1 atm inlet pressure, the constriction has a diameter of 5-7x10(-4) cm and a length of about 0.015. cm.     

Secondary ion quadrupole mass spectrometer for depth profiling--design and performance evaluation

A quadrupole-based secondary ion mass spectrometer designed for depth profiling is described which combines ultrahigh vacuum construction with high sputtering rate, detection sensitivity, depth resolution, mass spectral purity, and abundance sensitivity. Impurities such as B and Al implanted in Si can be profiled to levels below one part per million atomic (ppma), at a depth resolution equal to that obtained by commercial ion microprobes. The primary beam consists of 5-keV, mass-analyzed (40)Ar(+) ions, focused to about 70 microm in diameter. Its high current density (>25mA/cm(2)) permits adequate beam rastering and electronic signal-gating to optimize depth resolution. A secondary ion extraction lens and spherical energy filter are responsible for achieving abundance sensitivities of five to six orders of magnitude on the low mass side of a matrix peak. The ultrahigh vacuum environment of the sample dramatically reduces molecular peaks containing H, C, and O, allowing even hydrogen to be profiled to concentrations below 10 ppma. Because large amounts of data are generated by multi-element depth profiling, means for automated instrument control and data acquisition have been developed.     

大批量定制服装裁剪分床计划的两阶段优化方法

为解决大批量定制服装生产中裁剪分床计划尺码较多且各尺码数量不规则的问题,建立了裁剪分床计划的数学模型;提出基于概率搜索和遗传算法的两阶段优化方法进行求解,第一阶段随机生成若干满足生产约束的初始裁床铺料层数方案,利用搜索算法结合概率,按投入裁床数量最少的原则得到最优尺码组合方案和相应初始裁床铺料层数方案,第二阶段基于前一阶段得到的最优尺码组合方案,按照满足订单情况下生产多余服装的比例不超过企业允许的最大值原则,利用遗传算法再次优化得到最优裁床铺料层数方案。针对实际生产案例,分别利用本算法和人工经验算法求解并进行比较,结果表明在相同的生产条件下,两阶段优化方法能快速求解出服装裁剪分床方案,减少铺床数、节省面料并降低成本。     

大规模定制中客户订单解耦点定位的专家系统

针对大规模定制中多个客户订单解耦点确定的复杂情况,提出了多客户订单解耦点的定位方法与思路,构建了多客户订单解耦点定位的智能决策专家系统.把多客户订单解耦点定位的影响因素、确定方法与规则等以知识库的形式保存起来,利用专家系统推理机进行解释执行,以协助多客户订单解耦点的定位决策.通过JESS编程实现了多客户订单解耦点定位专家系统,并在汽轮机生产案例中验证了该系统的可行性.     

Higher modes contribution for estimating the inelastic deformation ratios and seismic demands of structures

Journal of Mechanical Science and Technology - In order to estimate the seismic demand by using the nonlinear static procedure, different approximate methods have been developed. One of the most...     

大批量定制下供应链节点企业间的订单处理过程

在大批量定制环境分析和订单驱动原理基础上,针对订单处理特征,提出批量生产与定制生产在时间和空间上的两结合方式,并根据订单处理分离点的推移,分别对按订单销售、设计、制造、装配和采购的供应链节点间生产方式和订单处理流程进行描述,最后详细阐述制造节点基于智能体的订单处理流程。     

Higher order explicit solutions for nonlinear dynamic model of column buckling using variational approach and variational iteration algorithm-II

This paper deals with the determination of approximate solutions for a model of column buckling using two efficient and powerful methods called He’s variational approach and variational iteration algorithm-II. These methods are used to find analytical approximate solution of nonlinear dynamic equation of a model for the column buckling. First and second order approximate solutions of the equation of the system are achieved. To validate the solutions, the analytical results have been compared with those resulted from Runge-Kutta 4th order method. A good agreement of the approximate frequencies and periodic solutions with the numerical results and the exact solution shows that the present methods can be easily extended to other nonlinear oscillation problems in engineering. The accuracy and convenience of the proposed methods are also revealed in comparisons with the other solution techniques.     

A finite element model for the analysis of flexible tube Coriolis mass flow meter using first order shear deformation shell theory

The numerical modelling of Coriolis Mass flow Meter (CFM) is essential for predicting its outcomes accurately in terms of sensitivity as well as exact mass flow rates. In the majority of mathematical and numerical modelling concerning the flexible structures, the authors neglect the dimensional and shape variation of the structure due to self-weight. The shell based on the First-order shear deformation shell theory (FSDST) is preferred in modelling shells compared to the beam model. The current work includes numerical modelling of CFM using eight noded isoparametric shell elements and twenty noded Acoustic fluid elements. The fluid energy describes as the potential, and the dynamic boundary condition is assumed utilising the displacement of structure and potential of the fluid. The fluid dynamic equation combining suitable numerical model, fluid-structure interaction module and cross-correlation technique helps to achieve the numerical modelling of CFM. The numerical model of CFM utilises the Newmark Beta method of numerical integration, and the response of two equidistant locations from the point of tube excitation is acquired. For the flexible tube conveying fluid, there exists sagging of tube due to the weight of tube and fluid. The Coriolis force and the external excitation force cause the fluid conveying tube to bend and twist, and as a result, the velocity responses picked from two equidistant points shows a difference in phase. The effect of sagging leads to a lower phase shift and time decay, and hence the sensitivity of the CFM is low for low pre-stretched flexible tubes. The pre-stretching of flexible tubes reduces the effect of sagging, facilitates to regain the cylindrical shape of the tube and increases the sensitivity of CFM. The result reveals that the shell element along with the three-dimensional acoustic fluid element provides the most accurate numerical model for the CFM and the change in sensitivity, as well as the change in mass flow measurements, can appropriately be analysed with the help of this numerical model. The amplitude of the velocity of the structure, measured from the two equidistant points, shows a difference. The severe variation in amplitude of velocity measured from two points is an implication of the out of plane deflection of the tube. For a CFM made up of metal tubes, the amplitude of velocity variation is minimal and ignored by the authors.     

Use of internally resonant energy transfer from the symmetrical to anti-symmetrical modes of a curved beam isolator for enhancing the isolation performance and reducing the source mass translation vibration: Theory and experiment

This study aims to use the internally resonant energy transfer from the symmetrical to anti-symmetrical modes of a simply supported curved beam isolator to enhance the isolation performance and reduce the source mass vibration. The model is setup and based on the differential equation of the Euler-Bernoulli beam. The dynamic modal displacements and forces are then obtained from the model using a numerical integration method. The numerical and experimental results indicate that when the ratio of the resonant frequencies of the first bending symmetric and anti-symmetric modes is close to 2 and the excitation frequency is equal to the resonant frequency of the first symmetric mode, the contribution of the first anti-symmetric mode is significant, even though the curved beam and excitation are symmetrical. The net modal force induced by the first anti-symmetric mode acting on the ground is much smaller than that of the first symmetric mode because the two reaction forces at the beam ends induced by the first anti-symmetric mode are equal but opposite. Further, the source mass translational vibration is significantly reduced because it is placed on the node of the anti-symmetric mode.