Non-uniform Width Research Articles

Fabrication of Movable Mirror-Array Structure Using Hot-Embossing for Optical Switch Applications

A new micro hot-embossing process which combines the high accuracy of silicon micromachining process and low cost production of forming process was reported. A movable cantilever-array structure with vertical mirrors were designed under the limitation of hot-embossing fabrication and material properties of polymer. The cantilever has non-uniform width optimized for electrostatic actuation and high-density array configuration. Two metal molds were transferred by electroplating from silicon structures which is micromachined by DRIE and anisotropic wet etching. The polymer optical switch array chip was produced by hot-embossing between the two molds and laser cutting. Finally, the operation of the assembled 8 × 8 optical switch system was demonstrated.

Design and optimisation of impedance probes for void fraction measurements

The performance of impedance probes for measuring the conductance of gas–liquid mixtures in horizontal pipes is here studied by means of the numerical solution of Laplace problem. In particular the work is aimed at optimising the probe geometry in order to improve the probe response both in terms of linearity and in terms of spatial resolution to step changes in phase distribution. Starting from basic shapes employed in literature (ring and half-ring electrodes), the adopted approach allowed new probe geometries (characterised by non-uniform electrode distance and/or electrode width) to be found. The analysis is performed with reference to annular, stratified and dispersed distributions and the results are compared with available theoretical models. Measurements have been carried out to verify the predicted sensor response and to ascertain the effect of the particle size on the probe response under dispersed flow conditions. The analysis demonstrates the behaviour of different probe arrangements with respect to different flow patterns and shows the possibility to obtain optimised geometries matching the desired features of linear response and of enhanced spatial resolution.

The growth and collapse of a micro-bubble under pulse heating

The possibility of using a micro-thermal bubble, generated by a micro-heater under pulse heating, as an actuator for applications in micro-bio-analytical systems is investigated in this paper. The perturbation force, generated when the micro-thermal bubble is formed instantaneously, can be used to promote such actions as mixing in the solution of a micro-reactor. Under pulse heating, a specially designed non-uniform width micro-heater (10 × 3 μm 2) can induce highly localized near-homogeneous nucleation and results in periodic generation of stable single bubbles in DI water. The single bubble appears precisely on the narrow part of the micro-heater with size restricted within the superheated region in the fluid. The growth and collapse of the bubble, recorded by a high-speed CCD, is shown to be asymmetric with time if the pulse width is at milliseconds in time scale. This asymmetric behavior is very much different from those in thermal ink-jet printers. The bubble behavior under different heating duration, ranging from microseconds to milliseconds, is experimentally studied. A transient 3-D heat conduction numerical simulation is carried out to study the temperature field of the fluid before the nucleation process. To evaluate the perturbation area of the micro-bubble, submicron particles with diameter of 0.96 μm were placed in the fluid and their dynamic response during the transient bubble formation is recorded.

Experimental investigation of flux motion in exponentially shaped Josephson junctions

We report experimental and numerical analysis of expontentially shaped long Josephson junctions with lateral current injection. Quasi-linear flux flow branches are observed in the current-voltage characteristic of the junctions in the absence of magnetic field. A strongly asymmetric response to an applied magnetic field is also exhibited by the junctions. Experimental data are found in agreement with numerical predictions and demonstrate the existence of a geometry-induced potential experienced by the flux quanta in nonuniform width junctions.

Ising exchange interaction of two-level optical systems

It is shown that the indirect coupling between two-level optical systems through a radiation field has the form of the Ising exchange interaction if the coupling between atoms and the field is conducted through electric quadrupole interactions. The manifestation of the paired interaction between two-level systems in the form of a nonuniform optical transition width and in the kinetics of nonequilibrium optical processes is considered.

Concept of Shear Strength Measurement and Modification of Stability Analysis during Countermeasure Planning of Landslides

Two dimensional stability analysis along mid-section by limit equilibrium method with back analysis is popularly used in the world for stability analysis of landslides. However, the residual shear strength of the soil is mainly dominated by the clay mineralogy and may give the different shear strength than the calculated value by back analysis. The residual shear strength of 18 soil samples collected from shallow and deep sliding zone of Okimi landslide in Niigata prefecture, Japan have shown less than 15% variation in shear strength. The average of those shear strengths have been utilized to conduct the 3-D stability analysis of each landslide blocks. The sliding surface contour map has been prepared according to the check boring information to estimate the shearing surface depth. Likewise, available piezometer data and ground topography has been used to estimate the water level throughout the landslide area. New coefficient called stability correction factor (Cf) has been introduced to compare the ratio of calculated factor of safety with unit value by 2-D stability analysis along various sections and 3-D stability analysis. The value of Cf by all methods is found to be consistent when the sliding block has uniform width throughout and primary data are abundant. However, the value of Cf has considerably varied in the block having nonuniform width and less primary data. As the 3-D stabil-ity analysis proposed in this paper is simple 3-D form of simplified Bishop's 2-D method, the calculation process is very simple and can give better solution for the stability analysis of landslide than the method in common practice.

Shaping a VLSI wire to minimize Elmore delay with consideration of coupling capacitance

In this paper, by using calculus of variations, we determine the optimal shape for a wire under the Elmore delay model. Coupling capacitance has been taken into consideration explicitly by treating it as another source of grounded capacitance. Given two wires in parallel, one has uniform width and the other has non-uniform width whose shape is described by a function f (x) . Let T D be the delay through the non-uniform wire. We determine f (x) such that T D is minimized. We also extend our study to the case where a non-uniform wire has two neighboring wires. Our study shows that the optimal shape function satisfies an integral equation. Numerical methods are employed to solve the corresponding differential equation and carry out the integration. We provide an efficient algorithm to find the optimal solution. Experiments show that it only takes several iterations to get the optimal results by using our algorithm. Our experiments also show that the wire delay T D is a convex function of the wire width at the driver end.

Skeletonization of binary images with nonuniform width via block decomposition and contour vector matching

Thinning is a very important preprocessing step for many image analysis operations, such as optical character recognition and fingerprint recognition. The main drawbacks of traditional thinning algorithms are low speed and serious deformation. To remedy these problems, a novel approach which generates the skeletons of binary patterns via block decomposition and contour vector matching is proposed in this paper. The proposed skeletonization mechanism not only skeletonizes binary patterns but also vectorizes the generated skeletons simultaneously. In our approach, the considered binary image is first decomposed into several smaller blocks. Then, the block skeleton is generated for each decomposed block. The generated block skeletons are gathered to form the skeleton of the considered image. Last, the gaps inside or between block skeletons are filled based on the block connectivity information to form the final intact skeleton. The performance of the proposed algorithm is compared with existing algorithms. Experimental results confirm the superiority of our proposed approach.

Design of pseudo-QMF banks with rational sampling factors using several prototype filters

A method is presented for designing filter banks that allow the spectrum of a signal to be split into nonuniform width subbands. The filters of the banks are obtained by the cosine modulation of more than one prototype. The method uses the cancellation of the main aliasing component of the reconstructed signal. This imposes constraints on the prototypes that become dependent on each other. The procedure can be applied to banks with both integer and rational decimation factors. Numerical examples are presented to show the effectiveness of the design procedure.

Spiral junction termination

A new junction termination structure composed of a decreasing width spiral diffused resistor connecting anode and cathode region is presented. Leakage current through the spiral resistor results in optimized voltage distribution between the spiral turns which effectively reduces high electric field at the anode junction curvature. By circuit mode device modeling approach, the influence of several design parameters of importance on the breakdown properties were investigated. A major concern was shown to be the possibility of a premature reach-through between the spiral turns, resulting in increased leakage current and soft breakdown characteristics. A design with nonuniform spiral width and optimized spacing between the spiral turns is proposed, enabling almost ideal breakdown voltages with reduced spiral leakage current and eliminated reach-through between the spiral turns. Low susceptibility to oxide charges is confirmed by irradiation test, showing improvement of breakdown properties after irradiation. Further improvement in operation is obtained by a floating spiral structure due to spiral resistance limiting the increase of the multiplication induced current through the spiral. In comparison with common termination structures the spiral junction termination offers simple design and processing, close to ideal breakdown voltages and high reliability of operation.

Structure and Chemistry of Interfaces in Si<sub>3</sub>N<sub>4</sub> Ceramics Studied by Transmission Electron Microscopy

Interfaces in liquid-phase sintered Si3N4 materials were investigated employing both analytical and high-resolution transmission electron microscopy techniques (AEM, HREM). Owing to the sintering process that involves the addition of metal oxides to the Si3N4-starting powder, densified materials are composed of Si3N4-grains and amorphous as well as partly crystalline secondary phases. Most Si3N4 ceramics contain continuous, thin interlayers of residual glass along grain boundaries. HREM studies in conjunction with electron energy-loss spectroscopy (EELS) focused on the characterization of these grain-boundary films. A comparison between the diffuse dark field, the Fresnel fringe and the high-resolution lattice imaging technique revealed the latter technique to be most accurate in order to determine intergranular film width quantitatively. Depending on the interface composition, HREM imaging revealed conspicuous differences in film thickness. However, with a given batch composition each as sintered material is characterized by a constant film width within ±0.1nm. Crystallization of secondary phases can alter the interface chemistry and thus change intergranular film thickness. The latter result is in line with the variation of interfacial film widths before and after oxidation. Owing to cation outward diffusion, a thinning of the interlayer was observed. In contrast, with increasing impurity-cation concentration at the interface, first a thinning and furtheron a widening of the intergranular film was observed. Si3N4 materials with only SiO2 present at interfaces showed a film thickness of 1.0nm, independent of glass volume fraction. Apart from cations, the influence of anion segregation at Si3N4-grain boundaries was studied. Fluorine was found to markedly affect the mechanical response of the material. Owing to a lowered cohesive interface strength, as a consequence of F-segregation at grain boundaries, intergranular fracture was predominantly monitored. Moreover, in comparison to undoped specimens, anion-doped samples revealed markedly higher creep rates, which are related to a decrease in the apparent grain-boundary viscosity, as elaborated from internal friction measurements.In addition to the characterization of internal interfaces at room temperature, microstructures at high service temperatures were studied by rapid cooling Si3N4 materials from high temperatures. Quenching a MgO-doped Si3N4 from 1350°C produced no observable variation in the grain-boundary film thickness. A substantial increase and a non-uniform width of the amorphous films was, however, observed when rapidly cooling from temperatures of about 1420°C. Specimens quenched from higher temperatures or longer residence times above the eutectic temperature again revealed an equilibrium thickness that was slightly wider compared to the film widths observed in the material slowly cooled down to room temperature.By studying a MgO-doped Si3N4 that was exposed for about 14, 000h to 1100°C, the question was addressed as to whether internal grain-boundary films are actually stable and can sustain a long-term exposure to high testing temperatures. It is shown that, apart from other microstructural changes induced during high-temperature exposure, the grain-boundary structure was fundamentally altered and depleted grain boundaries were formed. Moreover, the characteristics of interfaces, observed in Si3N4/SiC microstructures obtained by the pyrolysis and subsequent crystallization of organometallic precursors, are briefly discussed. Here, similar to the long-term exposure experiment, complex interface structures without the presence of continuous grain-boundary films were observed. In brief, the content of this

A family of large eddy simulation (LES) filters with nonuniform filter widths

In this Brief Communication a family of filters for large eddy simulation (LES) with nonuniform filter widths is constructed that commute with differentiation up to any given order.

Quantitative analysis of gel electrophoretograms by image analysis and least squares modeling.

A computer-aided quantitative method for a complex analysis of gel electrophoretograms is presented. The analysis consists of several steps: (i) determination of the background image by methods of mathematical morphology and its subtraction from the gel image, (ii) selection of an appropriate part of the gel lane including curved lanes and lanes with a nonuniform width, (iii) computation of the lane densitogram by averaging several lane-parallel scans, (iv) decomposition of the lane densitogram into component bands using a data selecting algorithm and Marquardt's minimizer. Several different functions for component bands are utilized. It is shown that the densitogram can be decomposed into component bands with reasonable accuracy only if an appropriate model function is chosen. The algorithms are tested on several different gel electrophoretograms which show typical features as a nonuniform background, curved lanes, an asymmetrical band shape and a superposition of small bands on the shoulders of big ones. It is shown that overlapped bands are best approximated by an asymmetrical Gausian curve and an asymmetrical Gauss-Cauchy function. Linear response to the serial dilution of the protein sample is tested.

Effects of nonuniform well width on compressively strained multiple quantum well lasers

We theoretically investigate the effects of nonuniform well widths on compressively strained In0.2Ga0.8As/GaAs multiple quantum well lasers using multiband effective mass theory and density matrix formalism. We find that the well width fluctuations do not degrade the transparency current, differential gain, and linewidth broadening factor. Besides, lasers with intentionally designed chirped well width have much broader gain profiles compared to uniform well lasers. This feature is attractive for applications requiring large gain bandwidth such as tunable lasers, mode-locked lasers, and wavelength division multiplexed laser arrays.

Geometry of melt-spun ribbons

The geometry (thickness t, width w and maximum fragmentation length L), of AlCu (0, 5.23, 13.36 and 33 wt.% Cu) ribbons cast by chill-block melt-spinning (wheel diameter 200 mm) is investigated as a function of the substrate velocity V, injection pressure P, substrate material (different thermal conductivity K), melt superheat ΔT, nozzle/substrate height H and nozzle diameter d. A critical V of 5–6 m s −1 is defined, so that varying V up to this value causes an increase in w and L and a decrease in t, but increasing V beyond this value causes a decrease in w, L and a further decrease in t. The influence of the other parameters is such that using higher P, ΔT, or H is important for achieving a larger L. A critical P value is defined beyond which a nonuniform width with feather defect is obtained. Similarly, above a critical ΔT or H, a fragmented ribbon is obtained. d is found to affect the width and uniformity of the ribbon width.

No evidence for mesothelial cell contact across the costal pleural space of sheep

Pleural space width was measured by four morphological approaches using either frozen hydrated or freeze-substituted blocks of chest wall and lung. Anesthetized sheep were held in the lateral (n = 2), sternal recumbent (n = 2), or vertical (head-up; n = 2) position for 30 min. The ribs and intercostal muscles were excised along a 20-cm vertical distance of the chest wall region, which was sprayed with liquid Freon 22, cooled with liquid nitrogen, to facilitate the fastest possible freezing of the visceral and parietal pleura. We measured pleural space width in frozen hydrated blocks by reflected-light and low-temperature scanning electron microscopy and in freeze-substituted, fixed, and embedded tissue blocks by light and transmission electron microscopy. We combined the data from the two groups of sheep held sternally recumbent and vertical because the results were comparable. The average arithmetic mean data for pleural space width determined by reflected-light analysis for samples near the top (18.5 microns) and bottom (20.3 microns) of the chest, separated by 15 cm of lung height, varied inversely with lung height (n = 4; P less than 0.009). The average harmonic mean data demonstrated a similar gravity-dependent gradient (17.3 and 18.8 microns, respectively; P less than 0.02). Therefore a slight vertical gradient of approximately -0.10 micron/cm of lung height was found for costal pleural space width. Pleural space width in the most dependent recesses, such as the costodiaphragmatic recess, reached 1-2 mm. We never found any contacts between the visceral and parietal pleura with either of the frozen hydrated preparations. No points of mesothelial cell contact were revealed in the light- and transmission electron microscopic views of the freeze-substituted tissue, despite an apparent narrower pleural space associated with the tissue-processing steps. We conclude that the pleural space has a slightly nonuniform width, contacts if they occur must be very infrequent, and pleural liquid clearance is probably facilitated by liquid accumulation in dependent regions where lymphatic pathways exist.

Application of multiresolution spatial filters to long-axis tracking

A method was developed for automatically tracking the long axis of thin objects which have nonuniform width and arbitrary orientation in a two-dimensional image space. This method is used to determine the length of isolated contractile smooth muscle cells, but has applications in other medical areas such as angiographic imaging. Pattern recognition techniques that determine object size and orientation are used to identify the long axis of an imaged object from its responses to difference of Gaussian and orientation filters. This method needs no a priori knowledge of object location, adapts to varying image magnification, requires little human interaction, and yields reproducible results.

Five-wavelength integrated DFB laser arrays with quarter-wave-shifted structures

Five-wavelength integrated DFB laser arrays with quarter-wave-shifted structures, using nonuniform stripe width, have been developed for high-density WDM systems around the 1.3 μm wavelength region for the first time. Each DFB laser of the five-wavelength integrated DFB laser array oscillated at the Bragg wavelength with a side mode suppression ratio of more than 30 dB. Good reproducibility of 50 ± 5 A lasing wavelength separations has been obtained.

A router for channels of nonuniform width containing preplaced wiring and obstacles

This paper presents a routing algorithm capable of dealing with channels of nonuniform width and with channels containing preplaced wiring or obstacles along the. borders. The new router is an extension of Rivest and Fiduccia's ‘greedy’ channel router. It is based on a left-to-right column-by-column scan of the channel, whereby wiring is completed for each column before proceeding to the next. To each column, a set of rules is applied to control the placement of wires on the two routing layers. In the simplest case of an empty rectangular channel, these rules are basically reduced to those of the ‘greedy’ router. The main features of the ‘greedy’ router, namely speed, simplicity, effectiveness and the ability to always succeed, are preserved by the extended set of routing rules. There already exists a number of channel routing systems that handle obstacles. Our router's main novel aspect is its ability to both avoid obstacles and adopt partially routed nets by incorporating them properly into the final result.

Oxygen Segregation and Microscopic Inhomogeneity in Czochralski Silicon

In this paper, the origins of the microscopic impurity inhomogeneity in Czochralski (CZ) silicon are reviewed. The relevance of impurity segregation behavior and microscopic growth rate variations to the impurity microfluctuations are analyzed and discussed. The nature of the oxygen microfluctuations is studied in terms of its segregation behavior and its effects on precipitation. Spatially resolved infrared absorption and spreading resistance are used to study the oxygen microfluctuations induced by the melt thermal asymmetry, isolated by a manually controlled crystal growth. It is shown that oxygen segregates microscopically in the same manner as arsenic in silicon, that is, for oxygen. A quantitative analysis yields a value in the neighborhood of 0.3 for oxygen, which agrees well with the previous result based on a macroscopic analysis. Heat‐treatment experiments have shown that when CZ silicon exhibits microfluctuations in oxygen concentration the precipitation is not uniform; rather, the precipitation is enhanced in the high oxygen regions of the fluctuations. Such behavior can impede the formation of the denuded zone where the high oxygen regions meet the wafer surface, resulting in nonuniform denuded zone width across the wafer.