An accurate experimental method for characterizing transmission lines embedded in multilayer printed circuit boards

We have developed an accurate method for measuring the complex propagation constant and characteristic impedance of transmission lines embedded in multilayer printed circuit boards. It is based on mathematical error-removal schemes using two different length transmission lines and an advanced via-hole structure that minimizes coupling. Consequently, associated errors, due to discontinuities and interference can be effectively eliminated, and the frequency dependencies of the transmission line parameters can be clarified in wide frequency bandwidths. We verified the validity of this method in frequency ranges up to at least 18 GHz, by comparing the determined values with the theory derived from transverse electromagnetic (TEM) approximations.     

Sandia National Laboratories Validation Workshop: Structural dynamics application

This article specifies a virtual structural dynamic subsystem and some systems, as well as mathematical models that approximately simulate them. The purpose is to define a setting for model validations conceived by participants in the Sandia National Laboratories Validation Workshop. Some broad guidelines for the model validations are set, as well as a regulatory requirement to be satisfied by the target system. Participants are directed to present techniques for subsystem model validation, to analytically predict whether or not the regulatory requirement will be met, and to estimate the likelihood of accuracy of the prediction.     

Thomson scattering diagnostic systems in the ITER divertor

A diagnostic array has been developed for studying the operating modes of the divertor in the ITER tokamak-reactor using the Thomson scattering technique. The aim of this study is to measure the spatial profiles of the electron temperature and density. The structure of the diagnostic setup was selected on the basis of a classical diagnostic geometry and the high-resolution LIDAR system, which provide access to different regions of the divertor plasma. A severe radiation environment, limited access to the plasma in the ITER divertor, and a high-dust environment (the divertor plate erosion material) in the divertor volume pose many problems for performing diagnostics under unique conditions having no analogs in the tokamaks that are now in operation. Different methods for protecting optical surfaces from plasma-enriched deposition are proposed and analyzed. The efficiency of these methods has been demonstrated in bench tests. The concept of laser and detector systems and diffraction polychromators capable of operating at different electron temperatures with a lower limit of 1 eV, has been justified and approved.     

An efficient electron-beam-pumped semiconductor laser for the green spectral range based on II–VI multilayer nanostructures

Emission characteristics of an electron-beam-pumped Cd(Zn)Se/ZnMgSSe semiconductor laser are studied. The laser’s active region consists of a set of ten equidistant ZnSe quantum wells containing fractional-monolayer CdSe quantum-dot inserts and a waveguide formed by a short-period superlattice with the net thickness of ～0.65 μm. Lasing occurs at room temperature at a wavelength of 542 nm. Pulsed power as high as 12 W per cavity face and an unprecedentedly high efficiency of ～8.5% are attained for the electron-beam energy of 23 keV.     

Total classes of composition systems of discrete signals in isomorphous Galois fields

It is proposed a rule of total classes of composition systems of discrete frequency signals (CDF-signals) construction in extended Galois fields. It is carried out modeling and research a correlation properties of CDF-signals, and determined their practical attraction.     

运用现代CFD方法设计高效率的汽轮机(续前期)

论述了运用现代计算流体动力学(ComputationalFluidDynamics,CFD)技术设计高效率汽轮机的方法,典型应用的实例有全三维叶片级流场、叶片汽封和排汽蜗壳计算。计算结果和实际是相符的。进一步对结构性单元和非结构单元程序的计算结果进行了比较,已证明,非结构单元CFD程序用于复杂形状的流场计算时,结果与实际相当一致,并具有独特的功能。     

Solution of the general moment problem via a one-parameter imbedding

This paper presents a computational theory for the general scalar moment problem. The formalism is sufficiently general to encompass problems in sensor arrays with arbitrary geometry and dynamics, and in nonuniform multidimensional sampling. Given a finite set of moments, the theory provides a test for the existence of a positive measure which is consistent with such data. At the same time, the theory also provides a characterization of all such consistent positive measures. It should be noted that classical results (e.g., in the theory of the trigonometric moment problem, Hamburger, Stieljes, Nevanlinna-Pick interpolation, etc.) are not applicable to the general setting sought herein where there is no natural shift operator in the space spanned by the integration kernels. The centerpiece of the theory is a differential equation which depends on the given finite set of moments and on an arbitrary positive function /spl Psi/-which plays the role of a "free parameter." The differential equation has an exponentially attractive point of equilibrium if and only if there exists a consistent positive measure. For each /spl Psi/, the fixed point determines a corresponding measure. Suitable choice of /spl Psi/ allows recovering any measure which is consistent with the data. The fixed point of the differential equation corresponds to an extremum of an entropy-like functional, and the differential equation is constructed via an appropriate homotopy that follows changes in the Lagrange multipliers from a convenient starting value to a value for the multipliers that corresponds to the given moments.     

Clay compaction modelling by homogenization theory

The modelling of hydromechanical behavior of clayey sediments by homogenization theory is described. The rheological model of clays buried in depth requires a three-dimensional approach and laboratory experiments to quantify the model parameters. An iterative process which can be coupled to any homogenization method is used to model the porous media behavior. Hydromechanical compaction results from oedometric experiments are simulated with the proposed model.     

Modelling the FEBEX THM experiment using a state surface approach

Buffer materials being considered as engineered barriers in nuclear fuel waste (NFW) disposal systems possess a pronounced nonlinear behaviour in the unsaturated state. In order to simulate such non-linear responses,the authors adopted an incrementally nonlinear poro-elastic approach where the coefficients of the governing equations are assumed to be functions of suction and the void ratio. These functions are in turn developed from a state-surface equation obtained from suction-controlled oedometric tests. In this paper we show the derivation of the governing equations of the poro-elastic model. A finite element computer code, FRACON, was developed by the authors to numerically solve the above equations. We first use the code to simulate laboratory tests to characterize the swelling properties of a typical bentonite. That same bentonite was used in the FEBEX in-situ heater experiment, conducted at the Grimsel site, Switzerland. The FRACON code was also used to perform blind predictions of the FEBEX heater experiment. It is shown that the model correctly predicts drying of the bentonite near the heaters and re-saturation near the rock interface. The evolution of temperature and the heater thermal output were also reasonably well predicted by the model. The trends in the total stresses developed in the bentonite were correctly predicted; the absolute values however were underestimated probably due to the omission of pore pressure build-up in the rock mass.