Statistical estimation of delay fault detectabilities and fault grading

In this paper we present a technique to statistically estimate transition delay and path delay fault coverage. The basic method is an extension of STAFAN to include delay faults. By partitioning a combinational circuit into non-overlapping fanout free logic cones, we accurately calculate the transition sensitization controllabilities of 0 1 and 1 0 transitions of the lines within a fanout free logic cone to the output of the fanout free logic cone for each fanout free logic cone. A strategy to calculate the transition observabilities of fanout stems is proposed. The detectability of a path delay fault is evaluated as the product of the observabilities of the input line to its head gate within each fanout free logic cone on the path multiplied by the transition controllability of the path. When compared with the fault simulations, the estimations of transition delay fault coverage are within 2.3%. Also, the technique gives reasonably good path delay fault coverage estimation for large fault set of the ISCAS85 benchmark circuits.     

Field singularities at the tip of a metallic cone of arbitrary cross section

The "spherical-harmonics" problem is investigated for a cone of arbitrary cross section. The analysis shows that two basic singularities must be considered: 1) the electric singularity, in whichbar{e}becomes infinite likeR^{nu-1}near the tip of the cone, 2) the magnetic singularity, in whichbar{h}becomes infinite likeR^{tau-1}. Numerical results, in particular concerningnuandtau, are given for: 1) the elliptic cone and its limiting case the sector, 2) the pyramidal corner.     

Design and Optimization of a Broadband Waveguide Magic-T Using a Stepped Conducting Cone

The design of a broadband waveguide magic-T was accomplished using a genetical swarm optimization (GSO) technique. A multi-stepped, off-centered conducting cone was used to enhance the bandwidth performance of the conventional magic-Ts. The geometrical parameters of the stepped cone were optimized by GSO, and the optimized magic-T for X-band application was fabricated and tested. Measured scattering parameters are shown to be in good agreement with the computed results. The optimized design exhibits ${-}20$ dB reflection bandwidth over 20.0% at all waveguide ports.      

Electrostatic “fractional” image methods for perfectlyconducting wedges and cones

Engheta (1996) introduced a definition for the electric charge “fractional-order” multipoles using the concept of fractional derivatives and integrals. Here, we utilize that definition to introduce a detailed image theory for the two-dimensional (2-D) electrostatic potential distributions in front of a perfectly conducting wedge with arbitrary wedge angles, and for the three-dimensional potential in front of a perfectly conducting cone with arbitrary cone angles. We show that the potentials in the presence of these structures can be described equivalently as the electrostatic potentials of sets of equivalent “image” charge distributions that effectively behave as “fractional-order” multipoles; hence, the name “fractional” image methods. The fractional orders of these so-called fractional images depend on the wedge angle (for the wedge problem) and on the cone angle (for the cone problem). Special cases where these fractional images behave like the discrete images are discussed, and physical justification and insights into these results are given     

圆锥扫描光学系统成像特性研究

圆锥扫描光学系统与 \     

硅基有序截锥短纳米线的陷光特性

高效陷光是提高薄膜太阳电池效率的重要因素。本文利用周期性的截锥Si纳米线结构获得了宽光谱的高效陷光,其陷光机制借助FDTD solution软件进行了分析。利用图形衬底和选择性外延技术,先在硅衬底上生长出传统的周期性圆柱状硅纳米结构,长度为200nm,直径为80nm;之后利用热氧化技术,制备出可控的截锥纳米线结构,长度为140nm时,其在300-900nm的平均反射率低于5%。这表明有序截锥短纳米线具有良好的宽光谱减反特性,可应用于径向纳米线太阳电池的制备。     

Design of a small conformal array

The principal objective of this investigation was to determine how to efficiently excite a small conical body over a 2:1 frequency bandwidth such that a prescribed minimun value of gain is exceeded in a60degconical sector about the forward axis of the cone. To achieve the necessary bandwidth, two approaches have been considered. First, an electrically small moderately efficient tunable antenna can be employed to excite currents on the cone. Second, one can employ a wide-band antenna having at least a 2:1 bandwidth. This latter approach was investigated theoretically and found to be feasible but experimental confirmation was not attempted in deference to the first approach that has the potential of greater gain (efficiency). To demonstrate the validity of the first approach a four element conical array was constructed and is described in this paper. Experimental results agreed well with theoretical expectations.     

THz频段粗糙导体圆锥的极化成像特性

太赫兹频段下粗糙导体表面会对电磁散射回波的幅度、相位、极化状态产生影响,为分析这一影响,以导体圆锥为例,研究了不同粗糙参数表面电磁散射在雷达图像中的表现规律。基于谱方法和坐标变换对粗糙圆锥面进行建模,利用高频电磁计算方法获得不同粗糙度导体圆锥样本多角度、多频点、全极化的单站散射场,基于转台模型,利用二重积分法获得目标二维像。从仿真结果可以看出,粗糙与理想光滑导体的圆锥图像存在明显差异,粗糙圆锥图像中能量分布偏离理想光滑情况下的强散射区域;随着粗糙度的增加,图像能量分布愈加均匀;相比于同极化图像,交叉极化图像更具反映目标轮廓信息的潜力。     

Image reconstruction based on human and monkey cone mosaics

The image reconstruction capacity of the actual foveal cone sampling mosaics of an adult monkey and human is investigated through computer simulations. A retinocortical mapping model in which positions are known and disorder is compensated (DC) has been implemented using classical Whittaker-Kotelnikov-Shannon (WKS) reconstruction theory and a two-dimensional hexagonal tessellation technique that maps the cone lattice onto a perfectly hexagonal grid. The DC model has been compared with a retinocortical mapping model in which cone positions are also known but position disorder is uncompensated (DU) in the reconstruction process. A control model has also been implemented using WKS reconstruction based on sampled data obtained with simulated perfectly hexagonal lattices whose Nyquist limits are equivalent to those of the human and monkey lattices. Quantitative comparisons of these models are based on the RMS error per pixel between the original and reconstructed images. Results of these simulations demonstrate a pronounced superiority of the DC over the DU model. The results of these simulations, which use “biologically correct” sampling lattices, document a potential image reconstruction advantage when foveal cone positions are known.     

The biconical antenna in a radially stratified medium

The theory of a transmitting biconical antenna in a radially and continuously stratified medium is developed; its input impedance is computed and plotted vs. its length for various media and cone angles. The medium extends to infinity and is characterized by a complex dielectric factorxi=epsilon-isigma/omega=epsilon_{0}f(r), whereris the radial distance from the center of the antenna. For the "stratification function" the formf(r)= (kr+a)/(kr+b)is considered, whereaandbare constant parameters, in general complex. The plots clearly exhibit all effects of dissipation and stratification expected on physical grounds and observed experimentally for dipole antennas.     

Wide-angle scanning of linear arrays located on cones

The characteristics of an 8-element linear array located along the generatrix of a cone with a20degfull cone angle is described. The array is scanned from broadside to a direction parallel to the cone axis. Radiation patterns and admittances are measured over wide scan angles. Theoretical calculations are performed for a similar array located on an infinite groundplane. The agreement between theory and measurement is very good.     

Electric singularity near the tip of a sharp cone

The singularity of the electric fields, proportional to the radial coordinate value R^ν-1, is investigated for a very sharp, perfectly conducting cone of arbitrary cross section. It is shown that, in the limit of a very small cone, the exponent ν tends to zero in proportion with the inverse of the logarithm of the maximum opening angle. Results are shown for the circular and elliptic cone, with the flat sector as a special case, and for the pyramid with n equal faces. An expression, valid for arbitrary opening angles, is presented in the case of a flat sector     

Adhesion improvement of Cu-based substrate and epoxy molding compound interface by hierarchical structure preparation

For microelectronic industry, Cu-based substrate and epoxy molding compound (EMC) interface is inherently weak and most likely to delaminate, well-known as a major threat for integrated circuits (ICs) reliability. In this paper, hierarchical whisker-like oxide/Cu cone structure was for the first time to be fabricated by combining electroless plating with heat treatment methods to enhance the interface adhesion between Cu-based substrate and EMC. The surface morphology was characterized by scanning electron microscope (SEM). Result shows that the hierarchical whisker-like oxide/Cu cone film is fine, dense and uniform; Single Cu cone structure is about 3–5 μm in height and 1 μm in root diameter; a layer of whisker-like oxide grows perpendicularly to circular surface of Cu cone, with length ranging from tens to hundreds of nanometers. Adhesion strength between the as-prepared substrates and EMC were measured by button shear test. With consideration of oxidation caused by practical processes (e.g. wire bonding), the interface of EMC and porous oxide formed at 260 °C for 5 min was taken as standard sample, representative of practical interface. To further study the effect of whisker-like oxide and Cu cone solely on adhesion performance, whisker-like oxide, porous oxide/Cu cone were investigated as well. Button shear test results reveal that interfacial adhesion strength of EMC and whisker-like oxide, porous oxide/Cu cone, hierarchical whisker-like oxide/Cu cone are 85%, 110% and 162% higher than that of standard interface. Moreover, the mechanism for adhesion improvement was discussed by facture surface observation, failure path assumption and force–displacement curve analysis. Results show that interface of EMC and hierarchical whisker-like oxide/Cu cone exhibits brittle/ductile property with about 3–5 μm thick EMC left on the fracture surface, indicating cohesive failure caused by remarkable mechanical interlocking effect.     

Radiation field consideration of biconical horn antenna withdifferent flare angles

The radiation fields of a biconical horn antenna with different flare angles are computed from both the fields of an equivalent Huygens source on the spherical-surface aperture and the infinite biconical horn antenna with spherical transverse electromagnetic wave. Numerical data and experimental results are first presented for the symmetrical biconical horn antenna ka=1.57 and 3.14 (where k is the propagation constant and a=cone length) with equal flare angle. Curves of the beamwidth versus cone length are then given for various flare angles. At flare angles above 75°, the beamwidth increases with the cone length, while at flare angles below about 75°, the beamwidth decreases with the cone length in this region of ka. For the asymmetrical biconical horn antenna, with two different flare angles (including a conical coaxial type and a discone type), the numerical and the experimental patterns are both presented. For the asymmetrical biconical horn antenna, the pattern main lobe direction, with respect to the antenna axis, may be adjusted by using suitable flare angles     

一种新型高峰值功率激光注入光纤耦合技术

分析了导光锥的导光原理和激光注入光纤耦合原理,通过射线理论分析并提出了导光锥的设计方法。通过对实验用导光锥进行导光率测试和耦合传输特性实验研究得到:导光锥的导光率为99%,导光锥与光纤耦合效率大于73%;导光锥端面的激光诱导损伤阈值能量密度为56 J/cm2,阈值功率密度为2.25 GW/cm2;在光纤发生端面损伤前其输出端输出激光能量达到50 mJ。采用导光锥实现高峰值功率脉冲激光注入光纤耦合可以有效地提高光纤传输激光容量。     

Growth,Cathodoluminescence and Field Emission of ZnS Tetrapod Tree‐like Heterostructures

We report the growth mechanism, cathodoluminescence and field emission of dual phase ZnS tetrapod tree‐like heterostructures. This novel heterostructures consist of two phases: zinc blende for the trunk and hexagonal wurtzite for the branch. Direct evidence is presented for the polarity induced growth of tetrapod ZnS trees through high‐resolution electron microscopy study, demonstrating that Zn‐terminated ZnS (111)/(0001) polar surface is chemically active and S‐terminated ( )/(000 ) polar surface is inert in the growth of tetrapod ZnS trees. Two strong UV emissions centered at 3.68 and 3.83 eV have been observed at room temperature, which are attributed to the bandgap emissions from the zinc blende trunk and hexagonal wurtzite branch, indicating that such structures can be used as unique electromechanical and optoelectronic components in potential light sources, laser and light emitting display devices. In addition, the low turn‐on field (2.66 Vµm⁻¹), high field‐enhancement factor (over 2600), large current density (over 30 mAcm⁻² at a macroscopic field of 4.33 Vµm⁻¹) and small fluctuation (∼1%) further indicate the availability of ZnS tetrapod tree‐like heterostructures for field emission panel display. This excellent field‐emission property is attributed to the specific crystallographic feature with high crystallinity and cone‐shape patterned branch with nanometer‐sized tips. Such a structure may optimize the FE properties and make a promising field emitter.     

Geometric-Optical Bidirectional Reflectance Modeling of a Conifer Forest Canopy

A geometric-optical forest canopy model that treats conifers as cones casting shadows on a contrasting background explains the major anisotropies in bidirectional reflectance measurements of a conifer forest canopy taken from the literature. The model uses parallelray geometry to describe the illumination and viewing of conifers as three-dimensional cones. Cones are randomly placed and overlap freely. Cone size (height) is distributed lognormally, and cone form, described by the apex angle of the cone, is a negative exponential function of height. The cones are first presumed to be solid dark gray Lambertian objects, located on a lighter gray Lambertian background. To add realism, "translucence" is added and light is allowed to pass through cones with negative exponential attenuation. Both computer simulation and analytical closed-form expressions are implemented. The results show a good qualitative agreement with the directional reflectance measurements of the conifer stand, indicating that the three-dimensional nature of the canopy is a key factor in determining its directional reflectance.     

Electrostatic charge distribution and capacitance of isolatedcylinders and truncated cones in free space

The capacitance and charge distribution of an isolated hollow conducting cylinder of finite length are evaluated. The analysis is based on replacing the charged cylinder by a charged filament along its axis and on the moment method formulation. The numerical results are compared with those determined from the evaluation of the integral for the potential and data of R.F. Harrington (see Field Computation by Moment Method, Krieger Publishing Company, 1985). The method is used to evaluate the variation of capacitance and charge distribution of a hollow conducting truncated cone with its smaller radius. The validity of the analysis is established from a comparison of data for the smaller radius approaching the large radius when the truncated cone becomes a cylinder     

Small-angle scattering by a finite cone

High-frequency scattering by a finite perfectly conducting right-circular cone is analyzed by modifying geometrical diffraction theory for application at and near nose-on aspects. Formulas appropriate for predicting principal-polarization radar cross sections as functions of frequency and aspect angle are presented. Calculations on a cone are in very good agreement with monostatic measurement data in the limited aspect interval0 leq phi leq gamma, wheregamma, is the half-angle of the cone.     

Attenuation compensation of cone beam SPECT images using maximum likelihood reconstruction

Attenuation compensation for cone beam single-photon emission computed tomography (SPECT) imaging is performed by cone beam maximum likelihood reconstruction with attenuation included in the transition matrix. Since the transition matrix is too large to be stored in conventional computers, the E-M maximum likelihood estimator is implemented with a ray-tracing algorithm, efficiently recalculating each matrix element as needed. The method was applied and tested in both uniform and nonuniform density phantoms. Test projections sets were obtained from Monte Carlo simulations and experiments using a commercially available cone beam collimator. For representative regions of interest. reconstruction of a uniform sphere is accurate to within 3% throughout, in comparison to a reference image simulated and reconstructed without attenuation. High- and low-activity regions in a uniform density are reconstructed accurately, except that low-activity regions in a more active background have a small error. This error is explainable by the nonnegativity constraints of the E-M estimator and the image statistical noise