Off-line Evaluation Research Articles

On Fast-Response Probes: Part 1—Technology, Calibration, and Application to Turbomachinery

A system for fast-response probe measurements in turbomachine flows has been developed and tested. The system has been designed for 40 kHz bandwidth and used with various in-house built probes accommodating up to four piezoresistive pressure transducers. The present generation of probes works accurately up to several bar pressure and 120°C temperature. The probes were found to be quite robust. The use of a miniature pressure transducer placed in the head of a probe showed that a precise packaging technique and a careful compensation of errors can considerably improve the accuracy of the pressure measurement. Methods for aerodynamic probe calibration and off-line data evaluation are briefly presented. These aimed, e.g., in the case of a four-hole probe, at measuring the velocity fluctuations as characterized by yaw, pitch, total pressure, and static pressure and at deriving mean values and spectral or turbulence parameters. Applications of the measuring system to turbomachinery flow in a radial compressor and to a turbulent pipe flow demonstrate the performance of the measuring system.

Computer-aided development of flexible batch production recipes

Abstract In this paper an approach to model-based batch process quality control and optimization using flexible production recipes is presented. Unlike the fixed recipes traditionally used in process industries, a flexible recipe depends on externally provided data from the process as well as the market. In order to manipulate a flexible recipe in a proper and convenient way, the information system FRIS—containing modules for experiment design, recipe initialization and correction, on-line process and off-line experiment evaluation, model development and recipe improvement—is being developed. Each of these functions will be discussed further.

A new model for “accept or reject” strategies in off-line and on-line megavoltage treatment evaluation

Purpose : With megavoltage on-line imaging, a temporal record of the treatment setup variation is made available during the course of radiotherapy. This work describes the theoretical framework where the imaging data is incorporated as feedback for deriving off-line and on-line “accept or reject” decisions to improve the quality of radiotherapy on an individual patient basis. Methods and Materials : A dynamic model of treatment setup variation is developed to describe: (a) the variations of multifraction treatment position and (b) the variation of measurement. Based on this model, a confidence region of subsequent treatment position is estimated from measurements of previous treatment position. The confidence region is compared with an allowance region of the treatment position, representing the acceptable margin of setup variation. The difference of the two regions are then evaluated to derive off-line and on-line “accept or reject” treatment decisions. Results : The model was simulated retrospectively using sequential daily images from different treatment sites. “Accept or reject” decisions were produced for on-line and off-line applications. The results also demonstrate the ability of the model to include the effects of setup variation that drifted during the course of treatment. Conclusion : The preliminary result demonstrates that “accept or reject” treatment decisions can be derived quantitatively from on-line imaging data. The model shows potential to guide the physician and therapist in implementing efficient and accurate treatment adjustments. Further work is required to test the model in the clinical setting.

Clinical monitoring with fuzzy automata

In this paper, a framework for an intelligent bedside monitor is presented. The monitor derives an abstraction of the current status of a patient by performing fuzzy state transitions on pre-processed input continuously supplied by clinical instrumentation. So far, an implementation called DiaMon-1 has been used for off-line evaluation of data of patients suffering from the adult respiratory distress syndrome (ARDS).

The development of “accept or reject” strategies in on-line and off-line treatment evaluation

We have developed and clinically tested a computer vision system capable of real time monitoring of the position of an oncology (cancer) patient undergoing radiation therapy. The system is able to report variations in patient setup from day to day, as well as patient motion during an individual treatment. The system consists of two CCD cameras mounted in the treatment room and focused on the treatment unit isocentre. The cameras are interfaced to a PC via a two channel video board. Special targets, placed on the patient surface are automatically recognized and extracted by our 3-D vision software. The three coordinates of each target are determined using a triangulation algorithm. System accuracy, stability and reproducibility were tested in the laboratory as well as in the radiation therapy room. Beside accuracy, the system must ensure the highest reliability and safety in the actual application environment. In this paper we also report on the results of clinical testing performed on a total of 23 patients having various treatment sites and techniques. The system in its present configuration is capable of measuring multiple targets placed on the patient surface during radiation therapy. In the clinical environment the system has an accuracy and repeatability of better than 0.5 mm in Cartesian space over extended periods (> 1 month). The system can measure and report patient position in less than 5 seconds. Clinically we have found that the system can easily and accurately detect patient motion during treatment as well as variations in patient setup from day to day. A brief description of the system and detailed analysis of its performance in the laboratory and in the clinic are presented.

Multilevel simulation for advanced manufacturing systems

This paper focuses on the techniques used to generate a multilevel simulation system that can optimise the design, layout, control and performance of a flexible manufacturing system (FMS). It discusses the software structures used to design and implement the simulator, which operates in the following modes: Off-line system-layout optimisation Off-line part-schedule evaluation Off-line control-algorithm evaluation/optimisation On-line state extrapolation and “what if?” testing All of these modes of operation are essential to the efficient running of a complex FMS. The techniques described have been applied and tested on an FMS at the Key Centre for Computer Integrated Manufacture at Swinburne Institute of Technology in Melbourne, Australia.

Microcomputer based digital differential relaying for generator protection: Real time test results

The paper presents the development of a digital differential relaying scheme around a 16-bit microprocessor for generator winding protection. It uses a simple filter algorithm which is based on cross-correlation with a heptagonal wave for the extraction of fundamental frequency components of differential and sum currents. Application of this filter and use of the real parts alone, instead of both the real and imaginary parts, of the fundamental frequency components for the relaying reduces the computation requirement drastically, thus enabling implementation of a complete three-phase differential relay on a single microprocessor without requiring a coprocessor or multiplier. The relay has been tested in real time on simulated generator currents representing internal-, external- and no-fault conditions separately. The test results agree well with the results of off-line evaluation reported earlier and point to a successful implementation of the differential relaying algorithm on a microprocessor in real time.

Digital differential relaying for generator protection: Development of algorithm and off-line evaluation

Abstract The paper proposes the use of real parts, instead of the RMS values, of the fundamental frequency components of the differential and sum currents for the purpose of digital differential relaying for generator protection. For the extraction of the real parts of the fundamental frequency components of current signals, a simple filter based on cross-correlation of the distorted signal with an even heptagonal wave is suggested. The frequency response of this filter is almost identical to that of the filter based on the discrete Fourier transform, while its computational requirement is far less. The paper also examines filters based on cross-correlation with square and trapezoidal waves and discards them on the grounds of poor rejection of odd harmonics. The suggested use of real parts in place of RMS values and a heptagonal wave correlation filter instead of a Fourier transform based filter for extracting them reduce the computational needs of the differential relaying algorithm so drastically that a complete three-phase differential relay can be implemented on a 16-bit microprocessor without supplementing it with a coprocessor or multiplier. The efficacy of these measures has been evaluated off-line on a mainframe computer and the test results are presented in the paper.

Charge coupled devices (CCDs) — A detector system for particles with time resolution and local assignment with particle trajectories

The properties of Charge Coupled Devices (CCDs) have been investigated with respect to the detection of charged particles. Using standard TV-techniques for reading the particle induced charge distribution in the pixel elements, these devices yield the local information of the trajectory of particles with an resolution of 10 x 15 μm and information on the linear energy transfer (LET) of the particle. A linear response is expected for particles with LET between that of relativistic protons and relativistic iron ions. For particles with higher LET irreversible damage of single pixel elements have been observed. In the low LET region the CCD elements can be used as local and time resolving active detector with a fast continuous electronic read out, whereas in the high LET region permanent damage is accumulated like as in an usual passive particle track detector for off-line evaluation. Examples for the advancement of experiments with CCDs in the field of radiobiology is discussed.

Acute negative intracranial pressure effects on the auditory evoked response in rabbits.

Recent clinical experience has shown that significant neurological symptoms and deficits occur in patients who have been shunted for hydrocephalus when "overshunting" produces unusual negative intracranial pressure (ICP). Therefore, the effect of acute negative ICP .on the early auditory evoked response (AER) was studied in the normal New Zealand rabbit. ICP was reduced to -50, -100, and -150 mm H2O below base line pressure. The AER after rarefaction auditory stimulation was obtained from ongoing electroencephalographic activity at the base line ICP and at each of the three negative ICP levels. Off-line statistical evaluation of the AER showed minimal changes in the absolute and interpeak latencies of N-0 to P-5 at some negative pressures. However, no statistically significant changes were observed for any of the measures for grouped data. At the negative ICP levels studied, the cerebrospinal fluid (CSF) pulse pressure was considerably augmented over base line measures. Such augmentation of the CSF pulse pressure may be the cause of the minimal effects observed on the AER, which may be due to a neuropraxic effect rather than ischemia from cerebral perfusion pressure changes.

Microphotometric determination of hematocrit in small vessels.

Evaluation and calibration of a microphotometric method for hematocrit determination in microvessels of transilluminated tissues is described. This method is based on the relation of the optical density (OD) of a microvessel to its hematocrit (Hct). The following requirements of the microphotometric system appear essential: narrow-band monochromatic light source with efficient false light suppression, high numerical aperture of the objective and low numerical aperture of the condensor. We used a video system to measure the intensities of incident (Io) and transmitted (I) light. For converting of Io and I into OD values, correcting procedures were evaluated to eliminate the influence of glare, shading, and fading. The calibration procedure was performed with glass tubes of inner diameter (ID) between 13 and 68 microns perfused with red cell suspensions. A function was fitted to the data, correlating OD to ID and Hct. The standard deviation of the original data from this function is +/- 0.02 units of fractional hematocrit. The presented method allows the continuous determination of the hematocrit in a microvessel as well as the off-line evaluation of the hematocrit distribution within a microvessel network.

Acoustic-Emission-Monitored Tests for TAB Inner Lead Bond Quality

An introduction to acoustic-emission (AE)-based tests applied to quality control in the electronics industry is given. Bond integrity tests for tape automated bonding (TAB) devices using AE monitoring are described. These include a pull tester and a microfatigue tester for off-line evaluation of bond quality and metallurgical system reliability as well as a prototype of an automatic on-line production bond quality tester. The microfatigue tester for TAB leads can apply a small oscillatory (up to 80 Hz) force on top of a constant force bias of a few grams. A major result was that the most common metallurgical system (tin-plated copper leads bonded to gold bumps) results in the formation of brittle intermetailic compounds which crack relatively easily. The cracks propagate under cyclic stress and result in a very low fatigue life, compared to another TAB metallurgical system. The inner lead bond integrity tester and lead-forming system is designed to be used on-line. Precision tools apply a predetermined force to the leads, which nondestructively tests the bonds and forms the leads. The AE monitor can indicate any failures and the device can be rejected.

Eeg Alpha Activity Processing and Modelling

On-line as well as off-line EEG alpha activity evaluation is described. The methods of detection of EEG alpha activity and its scoring are mentioned. A filtered EEG activity is fed into a computer where by sequential approach the value of median of probability distribution of their local extremes has been estimated. This value serves as a threshold for the threshold detection itself. Integral detection method is based on the computation of the area under this filtered signal. Model of alpha and non-alpha alternation based upon the analogy with the queueing process is suggested.

A Unit Task Simulator for Off-Line Evaluation of Man/Computer Interfaces

A method is shown for simulating individual operator man/computer tasks and collecting performance statistics. This method employs a minicomputer with structured software that receives user-written programs for the specific processes and for display formatting. Users can easily try out and evaluate alternative interface designs, different combinations of task assignments, or various formatting dialogues. Job and task performance characteristics are directly obtained. An illustration is given. These performance characteristics may be used comparatively or as inputs to a total system simulation for the design of large man/machine systems.