Detection of intensity changes with subpixel accuracy using laplacian-gaussian masks

We present a system that takes a gray level image as input, locates edges with subpixel accuracy, and links them into lines. Edges are detected by finding zero-crossings in the convolution of the image with Laplacian-of-Gaussian (LoG) masks. The implementation differs markedly from M.I.T.'s as we decompose our masks exactly into a sum of two separable filters instead of the usual approximation by a difference of two Gaussians (DOG). Subpixel accuracy is obtained through the use of the facet model [1]. We also note that the zero-crossings obtained from the full resolution image using a space constant ? for the Gaussian, and those obtained from the 1/n resolution image with 1/n pixel accuracy and a space constant of ?/n for the Gaussian, are very similar, but the processing times are very different. Finally, these edges are grouped into lines using the technique described in [2].     

Microfabrication of thick tungsten films for use as absorbers of deep X-ray lithography masks

 We fabricated thick (5 μm) tungsten (W) film patterns by sputtering and dry etching, and realized a new deep X-ray lithography mask. The X-ray mask with 5-μm-thick W absorbers could expose about 1-mm-thick resist structures. In the deposition process of W films, the column structure of about 0.2 μm grain size, from which pattern edge roughness originates, disappeared by adding nitrogen into the sputtering gas. W film etching was carried out by reducing gas pressure and cooling the substrate (−40 °C), and a side etch width of below 0.2 μm was obtained. From the results of the pattern edge roughness and the side etch width, a pattern fabrication accuracy below ±0.5 μm was achieved. Furthermore, film stress, which induces pattern distortion, was reduced to below 50 MPa by controlling the sputtering gas pressure. The obtained mask achieved a pattern distortion below ±0.3 μm. Received: 7 July 1999/Accepted: 29 May 2000     

Fast prototyping of high-aspect ratio, high-resolution X-ray masks by gas-assisted focused ion beam

The capacity of chemically-assisted focused ion beam (FIB) etching systems to undertake direct and highly anisotropic erosion of thin and thick gold (or other high atomic number {Z}) coatings on X-ray mask membranes/substrates provides new levels of precision, flexibility, simplification and rapidity in the manufacture of mask absorber patterns, allowing for fast prototyping of high-aspect ratio, high-resolution masks for deep X-ray lithography for the LIGA process. In preliminary demonstrations, an automated FIB system operating at 30 keV with a gallium liquid metal source and an iodine gas injection system was used for direct milling into a few micrometer thick gold of microstructures into the sub-hundred nanometer regime. Three-dimensional micromachining in bulk diamond is also reported to illustrate the capability of the technique.This work was made possible under funding for California Institute of Technology from NASA general contract (# NAS7-1407), the partial funding for CAMD from the DARPA grant HI-MEMS Development and Manufacturing (contract # N66001-98-1-8926). Patrick Deshaye (Norsam) microsculpting work is also gratefully acknowledged.This paper was presented at the Fourth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2001 in June 2001.     

Issues of numerical accuracy and stability in inverse simulation

Inverse simulation algorithms based on integration have been widely applied to predict the control input time histories required for aircraft to follow ideally defined manoeuvres. Several different inverse simulation algorithms are available but these different methods are all subject to a number of numerical and stability problems, such as high frequency oscillation effects and also lower frequency oscillatory phenomena termed “constraint oscillations”. Difficulties can also arise in applications involving discontinuous manoeuvres, discontinuities within the model or input constraints involving actuator saturation. This paper has shown that the dynamic response properties of the internal system are the cause of the so-called “constraint oscillation” phenomenon. In addition, a new inverse simulation approach based on the constrained derivative-free Nelder–Mead search-based optimisation method has been developed to eliminate problems of discontinuities and saturation. Simulation studies involving nonlinear ship models suggest that this new approach leads to improved properties in terms of convergence and numerical stability.     

Development of SAW based gyroscope with high shock and thermal stability

A novel surface acoustic wave (SAW)-based gyroscope with an 80 MHz central frequency was developed on a 128° YX LiNbO₃ piezoelectric substrate. The developed sensor was composed of a SAW resonator, metallic dots, and two SAW delay lines. A SAW resonator was employed to generate a stable standing wave with a large amplitude, metallic dots were used to induce a Coriolis force and to form a secondary SAW, and two delay lines were formed to extract the Coriolis effect by comparing the resonance frequencies between these two delay lines. Coupling of modes (COM) modeling was conducted to determine the optimal device parameters prior to fabrication. According to the simulation results, the device was fabricated and then measured on a rate table. When the device was subjected to an angular rotation, resonant frequency differences between the two oscillators were observed because of the secondary wave, generated by the Coriolis force, perturbed the propagation of the SAW in the sense element. Depending on the angular velocity, the difference of the resonance frequency was linearly modulated. The obtained sensitivity was approximately 172 Hz deg^?1 s^?1 at an angular rate range of 0–500 deg/s. Device performances depending on different mass weights and temperatures were also characterized. Good thermal and shock stabilities were observed during the evaluation process.     

Variation in the accuracy of thermal remote sensing

Thermal infrared (TIR) remote-sensing techniques have been used to estimate land surface temperatures (LSTs) and to study the relationship between land uses and LSTs. Remotely sensed thermal data provide a time-synchronized dense grid of temperature data, and there has been a growing interest on LSTs in various fields, such as urban climatology and global environmental change. It is also important for urban planning and management practices to maintain thermally efficient urban structures. This article focuses on differences between the estimated LSTs and the measured temperatures. Three different methods, the Black Body method, the normalized difference vegetation index (NDVI) Threshold method, and the US Geological Survey (USGS) method, are used to retrieve LSTs; how various land uses affect the accuracy of LSTs is also discussed. Landsat-5 data sets covering the Columbus Metropolitan Area (CMA) are used to obtain LSTs for six different dates between January 2005 and February 2006. The land-use map is derived from Landsat-5 data, dated 1 August 2005. Measured temperatures derived from the five measuring stations, located in or near the CMA, are used to compare with LSTs. The USGS method has the estimated temperatures that are close to the measured temperatures for most cases, and the LSTs in homogeneous areas, including green and agricultural areas, have temperatures closer to the measured temperatures. Statistical results of LSTs in six land uses for seven different dates are also displayed.     

Enhancement of photochromic hologram thermal stability

Significant enhancement of the thermal stability of the hologram recorded on photochromic materials had been achieved via covalent bonding of the photochromic dye to the polymer matrix as compared to the host-guest systems. One time partial reduction of the hologram’s initial diffraction efficiency due to thermal exposure was observed for both—polymers with attached dye as well as hostguest materials. Such one time reduction is interpreted to be due to the thermal relaxation of the polymer network induced with photochromic transition in the dye molecule. A gradual hologram erasure at elevated temperatures was observed for the host-guest system, which is assumed to be due to dye’s diffusion between highly lit and dark areas. For the photochromic materials with covalent boding of the dye to the polymer matrix the level of thermal stability is demonstrated such that at temperatures ca. 100C there was no detectable diffusion type degradation of the hologram after 6 hours of exposure to elevated temperature. Same heating of the hologram in photochromic host-guest polymer led to a full hologram erasure within 40 minutes. In both cases the one time initial DE reduction due to polymer matrix relaxation at elevated temperatures had comparable value of about 0.5 of hologram’s initial DE. The article is published in the original.     

High performance medical robot requirements and accuracy analysis

The treatment of disease using particle beams requires highly accurate patient positioning. Patients must be well immobilized and precisely aligned with the treatment beam to take full advantage of the dose localization potential. Robots can be used as high accuracy patient positioning systems. In this paper, the first such implementation using robotics techniques for patient positioning will be discussed. This robot is being developed for the Northeast Proton Therapy Center at the Massachusetts General Hospital. The unique requirements and design characteristics of the patient positioning system are presented. Of special interest is the system's patient positioning accuracy. A systematic methodology to perform the error analysis of serial link manipulators and its application to the PPS is described. Experimental measurements that verified the validity of the method are shown.     

Synthesis of opaque systems with static and dynamic masks

Opacity is a security property formalizing the absence of secret information leakage and we address in this paper the problem of synthesizing opaque systems. A secret predicate S over the runs of a system G is opaque to an external user having partial observability over G, if s/he can never infer from the observation of a run of G that the run belongs to S. We choose to control the observability of events by adding a device, called a mask, between the system G and the users. We first investigate the case of static partial observability where the set of events the user can observe is fixed a priori by a static mask. In this context, we show that checking whether a system is opaque is PSPACE-complete, which implies that computing an optimal static mask ensuring opacity is also a PSPACE-complete problem. Next, we introduce dynamic partial observability where the set of events the user can observe changes over time and is chosen by a dynamic mask. We show how to check that a system is opaque w.r.t. to a dynamic mask and also address the corresponding synthesis problem: given a system G and secret states S, compute the set of dynamic masks under which S is opaque. Our main result is that the set of such masks can be finitely represented and can be computed in EXPTIME and this is a lower bound. Finally we also address the problem of computing an optimal mask.     

One step integration methods of third-fourth order accuracy with large hyperbolic stability limits

One step integration methods of third and fourth order accuracy that use K function evaluations to solve the system of differential equations $\text{d}\text{y}\text{d}\text{t}\text{= A · y}$ are proposed. These methods are shown to have a hyperbolic stability limit of y (K ? 1)² ? 1 which approaches the theoretical maximum limit of K ? 1 at large K obtained for methods of lower order accuracy.     

Empirical evaluation of performance models of pointing accuracy and speed with a PC mouse

This study looks at the performance model of mouse movement from the following three viewpoints: (a) effects of the direction of movement on the performance model, (b) optimal formula to define the size of targets in the performance model, and (c) comparison of fit to the pointing time among five performance models. As a result, it was shown that the fit to the experimental data did not differ among four conditions of direction of movement The contribution of the performance model was found to be the highest when the square of the area of a target is used as the size of a target. Moreover, the performance model based on the multiple‐regression analysis was better than that based on Fitts's law.     

Economic performance assessment of advanced process control with LQG benchmarking

Economic performance assessment of advanced process control is conducted to investigate performance potentials that can be obtained by control system improvement. An optimization-based approach for economic performance assessment of the constrained process control is integrated with the LQG benchmark in this paper. By explicitly incorporating uncertainty into the performance assessment problem, economic performance evaluation can be formulated as a stochastic optimization problem, which helps to identify the opportunity to improve profitability of the process by taking appropriate risk levels. Using the LQG benchmark to estimate achievable variability reduction through control system improvement, the proposed method provides an estimate of both the performance that can be expected from the improved control system and the operating condition that delivers the improved performance. The results obtained can serve as a tool for control engineers to make decisions on control system tuning and/or upgrading. The proposed algorithm is illustrated via simulation examples as well as an industrial example.     

Some statistical bounds for the accuracy of distance-based pattern classification

Before implementing a pattern recognition algorithm, a rational step is to estimate its validity by bounding the probability of error. The ability to make such an estimate impacts crucially on the satisfactoriness of the particular features used, on the number of samples required to train and test the system and on the overall paradigm. This study develops statistical upper and lower bounds for estimating the probability of error, in the one-dimensional case. The bounds are distribution-free except for requiring the existence of the relevant statistics and can be evaluated easily by hand or by computer. Many of the results are also applicable to other problems involving the estimation of an arbitrary distribution of a random variable. Some multidimensional generalizations may be feasible.     

Analysis of tradeoff between data accuracy and performance of databases

Databases in large organizations are used for supporting the storage and manipulation of both operational and aggregate data. The operational data is characterized by frequent updates based on changes to values of items in the real world. Aggregate data is used in statistical analysis for decision making, forcasting and formulation of business strategies. The accuracy of the results of statistical processing depends on the processing resources allocated to the update transactions relative to the query and statistical reporting requests. Different types of statistical processing may require varying degress of data accuracy. For example, long range planning decisions may require less accurate data than those needed for tactical decisions. In this paper we propose a model for estimating the accuracy of a database and for the planning of computing resources based on database system performance and accuracy requirements of various groups of users.     

基于双金属元件的物体内部温度X光测量研究

针对密封结构体的温度测量,提出一种基于对螺旋形双金属感温元件X光成像的物体内部温度测量方法;首先,利用X射线成像设备获取物体内部双金属元件图像,再对其采用区域生长法进行图像分割以及边缘检测,得到双金属元件的图像特征;基于Hu不变矩在图像旋转平移的稳定性,通过构造温度测量模型和实验研究,第一个Hu不变矩与温度值之间呈现良好的线性关系;实验结果表明,所给出的方法准确可靠,为物体内部温度测量提供了一条新途径。     

Utility and accuracy of smell-driven performance analysis for end-user programmers

This paper proposes a technique, called smell-driven performance analysis (SDPA), which automatically provides situated explanations within a visual dataflow language IDE to help end-user programmers to overcome performance problems without leaving the visual dataflow paradigm. An experiment showed SDPA increased end-user programmers’ success rates at finding performance problems and decreased the time required for finding solutions. Another study, based on using SDPA to analyze a corpus of example end-user programs, revealed that it is usually accurate at identifying performance problems. Based on these results, we conclude that SDPA provides a reliable basis for helping end-user programmers to troubleshoot performance problems, as well as a potential foundation for future work aimed at training users and at aiding code reuse.     

Optimal annular plates with respect to their stability under thermal loadings

In the paper the uni- and multimodal optimization problems of elastic annular plates with respect to their stability under thermal loading are investigated. We look for such a distribution of a thickness of a plate (circularly symmetric), which leads to the maximum increment |ΔT| of temperature, causing buckling of the optimal structure under the equality constraint of a constant volume of the material and under inequality constraints imposed on the minimal and maximal values of a plate thickness. The optimal solutions for different modes of supports and different ratio of the inner and outer radius are looked for using the method of moving asymptotes and the simulated annealing.A short version of the paper was presented at WCSMO-6