NLPCA as a diagnostic tool for control valve stiction

A significant number of control loops in process plants perform poorly due to control valve stiction. Developing a method to detect valve stiction in the early phase is imperative to avoid major disruptions to the plant operations. Nonlinear principal component analysis (NLPCA), widely known for its capability in unravelling nonlinear correlations in process data, is extended in this paper to diagnose control valve stiction problems. The present work is based on distinguishing the difference between the shapes of the signals caused by stiction and other sources, and utilizes the operating data of controlled variable-controller output (pv–op). The structure of pv–op data used in this work is of sufficiently low dimension such that the NLPCA’s output allows the usage of simple mathematical tests in quantifying the nonlinear behavior of the loop. It is shown that if the underlying structure of pv–op data is linear, the NLPCA output generally approximates to a straight line with a regression coefficient (R²) greater than 0.8, otherwise there is a possibility of presence of nonlinearity or non-Gaussianity. The presence of stiction is then detected via a new and simple NLPCA curvature index, I_NC. Results from simulated and real industrial case studies show that NLPCA is a very promising tool for detecting valve stiction.     

Performance of a diagnostic system (Iliad) as a tool for quality assurance.

Quality assurance improves health care through detection of quality problems and feedback to the care giver. Current review procedures employed by the Peer Review Organizations (PROs), however, appear to underdetect quality problems, particularly those arising from diagnostic errors. We studied the use of an expert diagnostic system, Iliad, to detect quality problems arising from diagnostic errors. One hundred cases were selected from among those Medicare cases reviewed by the Utah PRO (UPRO) and which contained diagnoses recognized by Iliad. Iliad flagged 28 cases out of the 100 as containing diagnostic errors, and a gold standard physician review confirmed quality problems in 17 cases (60.7%). The UPRO review found 28 cases with quality problems, mostly treatment and documentation errors. The quality problems detected by Iliad appeared to be more serious than those detected by the UPRO review. Among the six cases with quality problems detected by both the UPRO and the Iliad review, there was none for which the same quality problem was detected by the two procedures. The two review procedures were therefore complementary.     

Identifying and re-meshing contact interfaces in a polyhedral assembly for digital mock-up

Polyhedral models are widely used for applications such as manufacturing, digital simulation or visualization. They are discrete models; easy to store, to manipulate, allowing levels of resolution for visualization. They can be easily exchanged between CAD systems without loss of data. Previous works (Comput Aided Des 29(4):287–298, 1997, Comput Graphics 22(5):565–585, 1998) have focused on simplification process applied to polyhedral part models. The goal of the proposed approach is to extend these processes to polyhedral assembly models, describing the digital mock-up of a future manufacturing product. To apply simplification techniques or other processes on polyhedral assemblies, contact surfaces between interacting objects have to be identified and specific constraints must be applied for processing. The approach proposed allows checking and maintaining a global consistency of the assembly model to ensure the reliability of the future processes. Thus, contacts between objects are detected using an approach that works for a static configuration of the assembly. Finally, a precise detection of the faces involved in each contact area is made and the resulting input domains identified are processed using a local Frontal Delaunay re-meshing technique to produce an identical tessellation on both objects involved in the processed contact. The quality of the triangulation produced is also checked.     

Implementation of a situation awareness assessment tool for evaluation of human-robot interfaces

In this paper, we outline a methodology for evaluating the situation awareness (SA) provided by a supervisory interface for an autonomous on-road vehicle. Our goal is to be able to use the evaluations to compare interface designs with respect to how well each facilitates the users' acquisition of SA. We used Endsely's Situation Awareness Global Assessment Technique (SAGAT) (Endsely, 1988) and developed scenarios and assessment questions appropriate for supervisors of autonomous on-road driving vehicles. We describe the results of two experiments used to refine our SA assessment implementation. In a third experiment, we applied the refined implementation to a graphical user interface we developed to test the sensitivity of our SAGAT implementation. We discuss the results of this experiment and implications for applying the SAGAT methodology to supervisory user interfaces for autonomous vehicles.     

基于参数激励法的MEMS陀螺电馈通抑制方法

针对微机电系统(MEMS)陀螺驱动电极和感应电极之间存在寄生电容,导致驱动信号的电馈通,限制了陀螺仪的灵敏度的问题,采用一种新型驱动方式—参数激励法,可以有效改变陀螺的刚度。仿真测试表明,通过调节激励信号的参数(频率、幅度和相位),可以以可控的方式显著地减少电馈通。     

GCI—A tool for developing interactive cad user interfaces

GCI is a Unix-based tool for developing interactive CAD programs. By separating command/ menu definitions from the progam, GCI makes it easier to change and extend the user interface. The language provided by GCI is used to define the syntax of commands, menus, messages, and help text. Generally, GCI supports a static hierarchical structure of commands and menus. However, through a program interface, an application program has the freedom to change environments, commands and menus. This flexibility of run-time control of the user interface is essential for developing highly responsive interfaces in a CAD environment. This paper presents the main concepts and definition language of GCI. It then discusses architectural and implementation issues, and finally presents a typical application's view of using the tool.     

Review of phenotypic diversity formulations for diagnostic tool

Practitioners often rely on search results to learn about the performance of a particular optimizer as applied to a real-world problem. However, even the best fitness measure is often not precise enough to reveal the behavior of the optimizer's added features or the nature of the interactions among its parameters. This makes customization of an efficient search method a rather difficult task.The aim of this paper is to propose a diagnostic tool to help determine the impact of parameter setting by monitoring the exploration/exploitation balance (EEB) of the search process, as this constitutes a key characteristic of any population-based optimizer. It is common practice to evaluate the EEB through a diversity measure. For any diagnostic tool developed to perform this function, it will be critical to be able to certify its reliability. To achieve this, the performance of the selected measure needs to be assessed, and the EEB framework must be able to accommodate any landscape structure. We show that to devise a diagnostic tool, the EEB must be viewed from an orthogonal perspective, which means that two diversity measures need to be involved: one for the exploration axis, and one for the exploitation axis. Exploration is best described by a genotypic diversity measure (GDM), while exploitation is better represented by a phenotypic convergence measure (PCM). Our paper includes a complete review of PCM formulations, and compares nearly all the published PCMs over a validation framework involving six test cases that offer controlled fitness distribution. This simple framework makes it possible to portray the underlying behavior of phenotypic formulations based on three established requirements: monotonicity in fitness varieties, twinning, and monotonicity in distance. We prove that these requirements are sufficient to identify phenotypic formulation weaknesses, and, from this conclusion, we propose a new PCM, which, once validated, is shown to comply with all the above-mentioned requirements. We then compare these phenotypic formulations over three specially designed fitness landscapes, and, finally, the new phenotypic formulation is combined with a genotypic formulation to form the foundation of the EEB diagnostic tool. The value of such a tool is substantiated through a comparison of the behaviors of various genetic operators and parameters.     

MEMS陀螺振动特性试验技术

对于MEMS振动陀螺来说,找到一个快速有效的方法来评估其结构参数是非常重要的,比如谐振频率和阻尼系数,应根据微机械陀螺设计和制作的不同阶段,从测试精度、测试速度和试验方便程度等方面考虑,采用不同的方法进行动态试验。本文给出了一种能够判断MEMS器件振动特性的可靠的电测试系统,并通过分析和实验比较了几种微机械陀螺振动系统传递函数的快速测定方法,分析讨论了微机械陀螺振动系统测试方法和数据处理等问题。     

A neuro-fuzzy tool for CT-PT contact detection in a pressurized heavy water reactor

In a pressurized heavy water reactor (PHWR), contact between the calandria tube (CT) and the pressure tube (PT) makes them susceptible to delayed hydrogen cracking. Periodic inspection of the channels must be carried out to detect such contacts. As the number of channels in a PHWR is very large (306 in a 230 MW plant) periodic in-service inspection of all the channels leads to an unacceptable downtime. A non-intrusive technique that employs a system-identification method is presently used for contact detection. Attempts to identify all the contacting channels, without missing any, lead to overprediction of the number of channels in contact; i.e., many channels are diagnosed as contacting, while those channels are actually not in contact. This puts a large number of healthy channels in the at-risk list, reducing the efficacy of the method. Previously, the authors demonstrated the power of a neural post-processor in improving the strike rate of the system-identification tool. This paper demonstrates a stand-alone neuro-fuzzy tool for the detection of CT–PT contact. The network consists of a cascade of self-organizing artificial neural networks (ANNs), along with fuzzy processors. The performance of the network has been compared with that of the system-identification techniques. The noise tolerance of the network is also demonstrated.     

Multibody dynamics as a tool for historical research

Ancient musical instruments can tell us much about the way composers of the past centuries wrote their music. Indeed, the sound and playing characteristics of historical instruments are often very different from those of the instruments we are used to. For example, in the case of the Viennese piano actions used by Mozart and his contemporaries, the so-called “escapement height” largely conditions the response of the instrument to the pianist’s touch. In this contribution, we aim to define how the Viennese action behaves when the escapement height, usually tuned by piano technicians, is changed.To do this, a multibody model containing the frame, the key, the hammer, the pawl, and the string has been developed. This paper describes how the model has been carried out; a special focus is put on the detection of the intermittent contacts between bodies, which may look easy in the real action, but is rather complex to model. The model is compared with high-speed imaging data and a parametric study of the escapement height is performed by adjusting the rest position of the pawl. The high sensitivity of this regulation is revealed as a shift of 1 mm of the pawl seems to induce a displacement of the escapement height of 20 mm. It is also shown that a strong but linear decrease of the maximal force between the hammer and the string appears when the escapement height increases.     

YUTPA as a design tool for public participation

Engaging the public in decision-making processes is commonly accepted as an effective strategy for a better policy making, a better policy support and for narrowing the gap between government and the public. In today’s digitised society, participation via online media is becoming more important. But is this so-called e-participation being used optimally? Or is a better design possible? In my opinion, the answer to these questions is a ‘yes’. Despite numerous efforts in engaging the public with policy deliberation, the actual amount of participants remains low. In this article, I have used the YUTPA model (Nevejan 2009) to analyse some existing e-participation projects. Additionally, I derived ten characteristics of ‘play’ to make proposals for a more designerly e-participation approach.     

Electromagnetic signatures as a tool for connectionless test

When we test boards, we usually think in terms of traditional electrical test (in-circuit, flying probe) and nonelectrical test (optical, x-ray). This Orebro University article develops an alternative, connectionless technique based on scanning the electromagnetic field generated by active on-board devices. Could this make it into industry as an additional diagnostic tool?.     

Simulation models as a tool for urban planning

Computer-simulation models are a useful tool in planning in general. They can be of particular use in the areas of urban planning such as land use, choice of residential locations, problems of transport, etc. A general utility simulation system (GUSS) has been developed that can be applied in a multitude of problems. This system, GUSS, a module of UPFAR (Utility Program for the Analysis of Risk), has been applied successfully for the evaluation of risk in investment alternatives. An effort is made in this paper to illustrate how GUSS can be used in simulating urban planning problems. The preliminary model presented in the paper combines different factors of importance to the urban planning decisions.     

Pattern analysis as a tool for inventing algorithms

A method for inventing algorithms and several examples are presented. The Julian conversion is useful for all date calculations and for switching to daylight saving time. The algorithm rotates the calendar by 2 months and performs a few straightforward calculations on the new month-day-year to produce the Julian date (and back again). The butterfly sort is based on the work on Woodrum. The algorithm repeatedly delivers two linked lists to a merge machine that produces a single linked list for further use. The length of the two lists going into the merge machine never differs by more than one. This accounts for the theoretical minimal number of comparisons⁵. The algorithm uses patterns within a simple binary counter to schedule the delivery of these lists. This accounts for the minimal number of steps between each comparison³.     

Dynamic 3-D computer graphics for designing a diagnostic tool for patients with schizophrenia

We introduce a novel procedure that uses dynamic 3-D computer graphics as a diagnostic tool for assessing disease severity in schizophrenia patients, based on their reduced influence of top-down cognitive processes in interpreting bottom-up sensory input. Our procedure uses the hollow-mask illusion, in which the concave side of the mask is misperceived as convex, because familiarity with convex faces dominates sensory cues signaling a concave mask. It is known that schizophrenia patients resist this illusion and their resistance increases with illness severity. Our method uses virtual masks rendered with two competing textures: (a) realistic features that enhance the illusion; (b) random-dot visual noise that reduces the illusion. We control the relative weights of the two textures to obtain psychometric functions for controls and patients and assess illness severity. The primary novelty is the use of a rotating mask that is easy to implement on a wide variety of portable devices and avoids the use of elaborate stereoscopic devices that have been used in the past. Thus our method, which can also be used to assess the efficacy of treatments, provides clinicians the advantage to bring the test to the patient’s own environment, instead of having to bring patients to the clinic.     

GIS as a visualization tool for economic development

GIS technology is now being applied to the economic development process at local, regional, and state levels of government. Most of the existing systems have utilized the analytical capabilities of GIS to locate suitable sites for various types of development. A computer system recently developed by Georgia Tech and Georgia Power uses GIS technology in a new way: as an interactive-visualization and decision-support tool designed to directly support business location decision-makers. The development of such presentation systems, along with the more traditional analytical systems, raises important policy implications of concept transferability, appropriate organizational structures, and the potential savings to be achieved by the rational targeting of future infrastructure finance.