Off-line Verification Research Articles

Verification of Secure Network Protocols in Uncertain Environments

In this paper, we present a method for protocol checking and verification using discrete event control. By protocol checking and verification, we mean verifying that a protocol is logically correct, that it does not cause deadlocks, and that it has been defined to respond to uncontrollable events that may occur in a system implementing it. Our approach differs from those previously suggested in two key ways. We extend the elementary theory of discrete event control to allow us to model more complicated protocols, including protocols relying on arbitrary counting models. We then present a maximum probability method for analyzing a protocol’s ability to react to a priori unspecified events. Unlike current protocol modeling, we use a pushdown automata for modeling protocols. This allows us to model protocols with greater fidelity. Our methods are illustrated using a simple two-level hierarchical protocol that defines the behavior of ad hoc wireless network nodes as they attempt to establish a secure connection. As wireless networks become more prevalent throughout the world, the off-line verification of protocols before they are implemented will help ensure that wireless network protocols are robust to security intrusions before they are deployed into the field. This will save time and money in the long run.

Detector for measuring electrocardiogram, pulse and voice sound at the same time

The analyzing system of the present invention, taking electrocardiogram, pulse signals and sound voices from the outside of the body, is readily assessable and complete in function. The analyzing system of the present invention can provide physiological indexes for evaluating the functions of the heart, vocal chord, the respiration system and the autonomic nervous system. The measured signals and obtained data can be on-line analyzed or sent to computer systems for an off-line verification after the completion of the test. Through digital or wireless communications, a rapid on-line diagnosis can be achieved for mitigating potential consequences.

An Offline Verification Scheme of Skilled Handwritten Forgery Documents using Pressure Characteristics

We introduce an effective approach for offline verification of signatures where the forgeries are skillfully done, i.e., the true and forgery sample appearances are almost alike. Subtle details of temporal information used in online verification are not available offline and are also hard to recover robustly. Thus we take help of the spatial dynamic information like the pen-tip pressure characteristics and emphasize on the extraction of low pressure points. The points result from the ballistic rhythm of a genuine signature which a forgery, however skillful that may be, always lacks. Ten effective features along with low pressure points and pressure multiplication ratio are proposed to make the distinction between a true and a forgery sample. Three different threshold values are also derived for better verification judgements.

CONTROL SYSTEM VERIFICATION BY EMULATION: AN APPLICATION TO OFF-LINE PRESS LINE THROUGHPUT RATE OPTIMIZATION

This study is part of a research project aims at off-line programming and verification of industrial control systems. In this paper, an off-line method for press line throughput rate optimization and control system verification is proposed, implemented and evaluated. The main tool is a virtual press station, developed by the first author, consisting of an emulated control system for a feeder/extractor robot which communicates with 3D-simulated production equipment. Moreover, several virtual press stations have been coupled and synchronized in a virtual press line. An important feature of the system is that the virtual robot controller is emulated, yielding an exact representation of the control logic and the possibility to run the entire system in virtual real time. The application considered is a sheet metal forming process where it is difficult to achieve maximum capacity utilization. There is much to gain if the control logic is improved and the throughput rate is increased. For this purpose, an automated robot motion optimization method is implemented and evaluated, using the virtual press line.

Electronic portal image assisted reduction of systematic set-up errors in head and neck irradiation

Purpose: To quantify systematic and random patient set-up errors in head and neck irradiation and to investigate the impact of an off-line correction protocol on the systematic errors. Material and methods: Electronic portal images were obtained for 31 patients treated for primary supra-glottic larynx carcinoma who were immobilised using a polyvinyl chloride cast. The observed patient set-up errors were input to the shrinking action level (SAL) off-line decision protocol and appropriate set-up corrections were applied. To assess the impact of the protocol, the positioning accuracy without application of set-up corrections was reconstructed. Results: The set-up errors obtained without set-up corrections (1 standard deviation (SD)=1.5–2 mm for random and systematic errors) were comparable to those reported in other studies on similar fixation devices. On an average, six fractions per patient were imaged and the set-up of half the patients was changed due to the decision protocol. Most changes were detected during weekly check measurements, not during the first days of treatment. The application of the SAL protocol reduced the width of the distribution of systematic errors to 1 mm (1 SD), as expected from simulations. A retrospective analysis showed that this accuracy should be attainable with only two measurements per patient using a different off-line correction protocol, which does not apply action levels. Conclusions: Off-line verification protocols can be particularly effective in head and neck patients due to the smallness of the random set-up errors. The excellent set-up reproducibility that can be achieved with such protocols enables accurate dose delivery in conformal treatments.

Inferential quality assessment in breakfast cereal production

This paper describes the development of inferential models for the provision of real-time, on-line estimates of the quality of a breakfast cereal for production line operators. Five quality variables were selected and on-line measurements reflective of the key process conditions were identified. Following process data logging, a number of linear and non-linear data-based modelling methods were applied to identify relationships between the on-line measurements and the product quality. Off-line verification of the models indicated that the prediction accuracy achieved was sufficient to offer the opportunity for quality control improvements. The models were subsequently implemented on-line to provide the process operators with frequent estimates of product quality. Performance assessment has indicated a reduction in the variability of all five quality parameters. In addition to details of the modelling, the decisions relating to the development strategy and justification for implementation are considered.

M 2RT: A tool developed for predicting the mean message response time of communication channels in sizeable networks exemplified by the Internet

In this paper an algorithm M 2RT for predicting the mean message response time (MMRT) of a communication channel is proposed with emphasis on Internet applications. The M 2RT development went through four major phases. They include: (a) Formulating the theoretical foundation with the central limit theorem. (b) Determining the parameters of the algorithm by simulations. (c) Performing off-line verification tests for the algorithm with local Internet/Intranet nodes and well-known middleware (MPI and CORBA). (d) Performing on-line validation of the M 2RT over the Internet involving both local and international sites. The acceptance criteria for the algorithm include: (a) It must perform efficiently for different conditions of workload, geography, and traffic. (b) It must perform consistently with the same software entities (e.g., MPI) for similar operations. (c) It must be able to exist both as an off-line tool and an on-line program object (to be invoked on a real-time basis). (d) Its computation time should be sufficiently small so that the result actually reflects the current physical conditions. All the results from simulations, verification tests, and validation experiments have confirmed that the M 2RT algorithm indeed meets all the acceptance criteria. In these tests, we also discovered that the algorithm could be developed into a powerful tool for measuring the relative performance between firmware products. This development will be explored in the near future.

Reduction of irradiated small bowel volume and accurate patient positioning by use of a bellyboard device in pelvic radiotherapy of gynecological cancer patients

Purpose: To reduce the volume of small bowel within pelvic treatment fields for gynecological cancer using a bellyboard device and to determine the accuracy of the prone treatment position. Materials and methods: Fifteen consecutive patients with a gynecologic malignancy who were treated with postoperative pelvic radiotherapy were selected for this study. The volume of small bowel within the treatment fields was calculated for both the supine and prone treatment positions. The patients were treated in the prone position in a so-called bellyboard device. During treatment sessions electronic portal images were obtained. An off-line setup verification and correction protocol was used and the setup accuracy of the positioning in the bellyboard was determined. Results: The average volume of small bowel within the treatment fields was 229 cm 3 and 66 cm 3 in the supine and prone treatment, respectively, which means an average volume reduction in the prone position of 64% (95% CI 56–72%), as compared with the supine position. For the position of the patient in the field, the systematic error defined by the standard deviation (SD) of the mean difference per patient between simulation and treatment images was 1.7 mm in the lateral direction, 2.1 mm in the craniocaudal direction and 1.7 mm in the ventrodorsal direction. On average, only 0.4 setup correction per patient was required to achieve this accuracy. The random day-to-day variations were 1.9 (1SD), 2.6 and 2.3 mm, respectively. Standard deviations of the systematic differences between patient positioning relative to the bellyboard were 6.2 mm in lateral direction and 9.1 mm in craniocaudal direction. Conclusions: Treatment of gynecological cancer patients in the prone position using a bellyboard reduces the volume of irradiated small bowel. An off-line verification and correction protocol ensures accurate patient positioning. Daily setup variations using the bellyboard were small (1 SD<3 mm). Therefore for pelvic radiotherapy in patients with a gynecological malignancy, the use of a bellyboard is recommended.

Off-Line Verification for Chinese Signatures

Signature verification is one of the important methodologies for personnel identification. Because of its wide applications to security practices quite a number of signature verification techniques associated with various features have been proposed. The features utilized in a signature verification system directly affect the performance of the system. In this paper, we review a variety of recently proposed features of signatures and present two new features. Each of these features is examined to evaluate its performance for Chinese signature verification. Then we choose and combine the features that establish good verification rates. As a result, we propose an off-line Chinese signature verification system based on this combination of features. The experimental results show that the proposed system achieves a good performance in term of verification rate.

Efficient recurrent neural network training incorporating a priori knowledge

A new technique for efficient training of Hopfield network models using iterative training algorithms is described and demonstrated. This technique is useful for producing stable Hopfield networks, using recently derived results concerning stability conditions for the Hopfield network. Since the modified training algorithm ensures the stability of the network, no off-line verification of stability is required. This technique can be applied to Hopfield networks of any size, and therefore is tested for three different randomly selected sizes. Additionally, the advantage of utilising a priori information about the plant is also tested and the results are compared with those cases where no such information is available. This information is used to determine critical dynamic properties of the network model, necessary for the network’s ability to generalise. In all tests, the networks are trained with modified genetic algorithms, using different initial starting points for the algorithm.

Verification of dynamic multileaf collimation using an electronic portal imaging device

High standards of treatment verification are necessary where complex new delivery techniques, such as intensity modulated radiation therapy using dynamic multileaf collimation, are being developed. This paper describes the use of a fluoroscopic electronic portal imaging device (EPID) to provide real-time qualitative verification of leaf position during delivery of a dynamic MLC prescription in addition to off-line quantitative verification. A custom-built circuit triggers the EPID to capture a series of snap-shot images at equally spaced dose points during a dynamic MLC prescription. Real-time verification is achieved by overlaying a template of expected leaf positions onto the images as they are acquired. Quantitative off-line verification is achieved using a maximum gradient edge detection algorithm to measure individual leaf positions for comparison with required leaf positions. Investigations have been undertaken to optimize image acquisition and assess the edge detection algorithm for variations in machine dose rate, leaf velocity and beam attenuation. On-line verification enables the operator to monitor the progress of a dynamic delivery and has been used for independent confirmation of accurate dynamic delivery during intensity modulated treatments. Off-line verification allows measurement of leaf position with a precision of 1 mm although image acquisition times must be less than or equal to 140 ms to ensure coincidence of the maximum gradient in the image with the 50% dose level.

Observation study of electronic portal images for off-line verification

Purpose: The goals of this study were to evaluate the use of electronic portal imaging device (EPID) paper images as off-line verification tools and to assess the feasibility of replacing portal films by EPID printed images. Materials and methods: Electronic portal images were acquired using a video-based imaging system. After contrast enhancement, these images were printed and compared to portal films when prescribed, and judged about their usefulness for off-line verification. A total of 2025 images were acquired from 322 fields on 137 patients. The images were shown to eight radiation oncologists and two senior residents in radiation oncology, each one of them judging fields relevant to his (her) daily practice. The questions asked were related to the choice of important anatomical structures and the visibility of such structures, the usefulness of the printed images, the comparison with portal films and the possible replacement of such films by paper images. Results: Answers to the different questions were treated as quantitative scores. For the visibility question, means and standard deviations were calculated for each individual structure, then a global score was obtained for a given treatment site. Means and standard deviations were also computed for the comparison question. Proportions and confidence intervals were used for the other questions. The results show that EPID paper images are useful for some treatment sites such as breast, thorax, prostate, abdomen, pelvis (other than rectum) and axilla. The image quality remains insufficient for some other sites such as head and neck and spine. Conclusion: Although global anatomical landmarks scores are good, the usefulness score is not always as high because some essential anatomical structures scores must be taken into account. There is also a strong habit factor related to acceptance of EPID printed images as verification tools. As long as they see more and more images, radiation oncologists can more easily visualize anatomical structures and are less stringent when evaluating the efficiency of EPID paper images as off-line verification tools.

Four-gated transcranial Doppler ultrasound in the detection of circulating microemboli

Objective: Embolus detection by transcranial Doppler ultrasound is very time consuming and semi-automated detection is mandatory. The device studied, a TC4040, Nicolet-EME, uses the four-gate technique and allows for audiovisual off-line verification of the recorded events. Methods: Twenty controls, 10 patients with mechanical prosthetic heart valves and 12 patients with occlusive carotid artery disease were investigated by transcranial colour-coded duplex sonography and, subsequently, underwent a 1-h unilateral embolus detection from the middle cerebral artery using four-gate TCD. We investigated the Doppler spectrum background, microembolic signals (MES) and artefacts produced. A detection threshold of 5 dB or more was defined taking into account natural fluctuations of the Doppler spectrum. Results: Sensitivity of the software was 91.9% and observer–software agreement on MES was 7.8% in the valve patients, and 77.7% and 7.5% in the carotid artery disease patients, respectively. Weaker MES were more likely not to be detected in all four channels. The artefact signal rejection rate was 62%. MES produced either positive or zero time delays in adjacent channels. Artefact signals produced either no delay, or a positive or a negative time delay. Duration of MES ranged from 1–88 ms. Conclusions: Besides refined recognition of MES using the time delay, four gates give faint MES no less than four opportunities to overcome the detection threshold. With this device’s satisfying sensitivity, regions of interest in a 1-h recording can audiovisually be evaluated off-line in a few minutes by an investigator.

Off-line verification of the day-to-day three-dimensional table position variation for radiation treatments of the head and neck region using an immobilization mask

Variation in the table height position for 175 treatments of 167 patients was calculated as a measure for day-to-day set-up precision in 2063 treatment sessions and resulted in a median standard deviation of 1 mm. The median standard deviations of table longitudinal and lateral position were 3 and 5 mm, respectively.

Off-line writer verification utilizing multiple neural networks

A writer verification system based on multiple neural network classifiers is described, aimed to be easily extendable. Each writer reg- isters with the system by writing a set of discrete Chinese characters. One neural network is constructed for each enrolled character class on a per-person or a per-subgroup basis. The decisions from individual net- work classifiers are combined by voting. The method has been verified to work reliably on our testing database: a verification rate above 96% is achieved on short-term data. © 1997 Society of Photo-Optical Instrumentation En- gineers. (S0091-3286(97)01211-7)

Dose quality assurance for industrial irradiation with an electron linac

In the development of the IMPELA family of electron linacs for industrial radiation processing, the needs for on-line monitoring of exposure dose have been recognized. The diverse applications under consideration demand a broad range of control-system performance and delivered-dose assurance measures appropriate to the sensitivities of the processes. The AAMI Guideline for Electron Beam Radiation Sterilization of Medical Devices points to a probable upper bound to the complexity of such requirements. ASTM and IAEA standards and guidelines for radiation dosimetry define the methods available for off-line verification of absorbed dose. The impact of the requirements for on-line measurements and the limitations inherent to the IMPELA design, are reviewed. The interdependencies of off-line product dosimetry and analyses with the on-line monitoring of process parameters are explored in search of criteria for optimization of cost-effective, flexible industrial irradiators.

CONTROLLED ANAESTHESIA: AN APPROACH USING PATIENT CHARACTERISTICS IDENTIFIED DURING UPTAKE

A system to control the alveolar anaesthetic concentration of patients undergoing halothane anaesthesia with controlled ventilation is described. Parameters characterizing the alveolar concentration response are determined on-line from breath-by-breath measurement of the inspired and end-tidal concentrations and the mixed venous anaesthetic partial pressure is estimated throughout the procedure. The method does not depend on the use of reference models or pre-programming and the inspired concentration required to control the alveolar concentration is determined as induction proceeds. Results using both computer simulations and data from patients undergoing routine clinical anaesthesia are analysed. Off-line verification results illustrate the operation of the technique and in 20 cases the inspired concentration, as controlled by the anaesthetist, was compared with that predicted by the automated system. These results indicate the feasibility of the system as a method for the control of anaesthesia.