Real-time Computer Model Research Articles

Case Studies of SST Variability Derived from AQUA/AMSR-E Satellite Data Near the Sumatra Region Frequently Affected by Under-Sea Earthquakes

A real-time computer model has been developed to monitor Sea Surface Temperature (SST) focussing on specific latitude-longitude grids of interest. The model uses the daily binary file data from AQUA/AMSRE satellite sensors made available through website. The main purpose of the case studies is to explore and demonstrate possibility of any SST anomalies before, during and after the two great earthquakes of 26 December 2004 and 28 March 2005 that occurred near the western coast of Sumatra. The code is used to analyse and plot SST contour maps and time sequence of average SST deviations from the long-term means pertaining to grid sizes of 2° x 2° and 6° x 6° sea surface areas around the epicentres of these two earthquakes. The results indicate a small but significant warming of 0.2-0.3 °C in the 2° x 2° grid area starting a week earlier to a week later for the event date of 26 December 2004. Similarly the 28 March 2005 earthquake shows temporal changes in the mean SST anomalies but with reduced clarity due to limitation of data. Wavelet analysis brings out more details of the time sequence of the inherent power spectra. Such computer aided analysis and approach may be useful in other fields like El Nino induced monsoon rainfall, patterns of climate change, distribution of atmospheric pollutants and aerosols over oceans

Fractional Multi-models of the Frog Gastrocnemius Muscle

In this article, frog gastrocnemius muscles are studied, and a multi-model identification presented. A transfer function is defined with few parameters to simulate striated muscle (Gastroctnemius) behaviour, for inclusion in a future real-time salamander computer model. A two-model structure permits description of both contraction and relaxation properties. Here, two physiological influences, fatigue and fibre types, are taken into account. A multi-model structure for each fibre type (fast (IIB), intermediate (IIA) and slow (I) fibres) is also used for inclusion in a future agonist-antagonist structure computer model.

Growth and developmentThe diversity of plant development

www.sciencedirect.com The reviews on plant development presented here cover a wide range of subjects that seem only loosely connected. In a sense, this is a departure from the direction of the field over the past 15 years with its increasing focus on Arabidopsis as a model system. It is legitimate to ask whether we have lost something by narrowing our attention on a single species. Will Arabidopsis be like the Escherichia coli of the 1980s? Is it a powerful model system soon to be abandoned because it has made more complex systems accessible? Or to put it positively: does the remarkable progress made in Arabidopsis, combined with the ever increasing power of brute-force genomics, allow us to broaden our horizons again, revisit classical problems and perhaps identify novel avenues for research? While there is no sign at all of Arabidopsis losing its attractiveness, it is also true that alternative model species and comparative analyses are beginning to regain popularity. In this issue of Current Opinion in Plant Biology, we have attempted to provide examples of this new trend. In plant developmental biology, progress has been made on three fronts: comparative studies at the molecular and genetic level are illuminating the history of morphogenesis in plants; the evolution of key molecular players in developmental regulation is also being elucidated; and finally, developmental principles are being elucidated in the context of the whole organ or organism by utilizing real-time analyses and computer modeling.

An online virtual acoustic guitar laboratory

We present a ‘‘virtual acoustic guitar laboratory’’ in which students can bring in their own acoustic guitars, record several notes, and follow a step-by-step procedure to create their own real-time computational model, suitable for use in a synth plugin in an electronic music studio. The guitar synthesis model is based on the commuted waveguide synthesis technique (http://ccrma.stanford.edu/∼jos/cs.html). Online laboratory materials are presently available at (http://ccrma.stanford.edu/∼jos), the project website (http://ccrma.stanford.edu/realsimple/), and are also being ported to Connexions (http://www.cnx.org/), an online repository of educational materials freely distributable under a Creative Commons license. Connexion’s ‘‘modules’’ and ‘‘courses’’ (which are simply module sequences) are readily and freely accessible and modifiable to allow instructors to adapt the materials as appropriate for their own classroom needs. The online lab materials contain Web pointers to relevant portions of online textbooks covering theoretical aspects of the analysis and synthesis methods used, thereby offering the student a demand-driven deeper understanding within a motivating context. [This work was supported by the Wallenberg Global Learning Network.]

FRACTIONAL MULTI-MODELS OF THE GASTROCNEMIUS FROG MUSCLE

Frog gastrocnemius muscles are studied, and a multi-model identification presented. A transfer function is here defined with few parameters to simulate striated muscle (Gastroctnemius) behaviour, for inclusion in a future real-time salamander computer model. A two-model structure permits description of both contraction and relaxation properties. Here, two physiological influences, fatigue and fibre types, are taken into account. A multi-model structure for each fibre type (Fast (IIB), Intermediate (IIA) and Slow (I) fibres) is also used for inclusion in a future agonist-antagonist structure computer model.

Real-Time Sensor-Actuator Networks

Emerging technologies offer new paradigms for computation, control, collaboration, and communication. To realize the full potential of these technologies in industry, defense, and homeland security applications, it is necessary to exploit the real-time distributed computing capabilities of sensor-actuator networks. To reliably design and develop such networks, it is necessary to develop deeper insight into the underlying model for real-time computation and the infrastructure at the node level that supports this model. In this paper, we discuss a new node-level operating system and mechanisms necessary to deploy reliable applications. The overriding issue that guides the design of this operating system is quality of service metric called predictability.A sensor-actuator network is a distributed platform for integrated computation and control in real-time environments. The nodes in such a network are distinguished by being resource constrained. The power of the network arises from the interactions between simple nodes. Such a network extends the popular distributed sensor networks in several dimensions. After identifying a real-time model, we develop a notion of predictability for a sensor-actuator network. We discuss how the node-level operating system is designed in the resource-constrained environment. An efficient multithreading mechanism and scheduling strategy are required to ensure that local tasks are executed within jitter bounds and that end-to-end delays do not violate application constraints. Mechanisms to support communication, monitoring, safety, fault tolerance, programming, diagnosability, reconfiguration, composability, interoperability, and security are discussed.

Imaging of near-Earth space plasma.

This paper describes the technique of imaging the ionosphere using tomographic principles. It reports on current developments and speculates on the future of this research area. Recent developments in computing and ionospheric measurement, together with the sharing of data via the internet, now allow us to envisage a time when high-resolution, real-time images and 'movies' of the ionosphere will be possible for radio communications planning. There is great potential to use such images for improving our understanding of the physical processes controlling the behaviour of the ionosphere. While real-time images and movies of the electron concentration are now almost possible, forecasting of ionospheric morphology is still in its early stages. It has become clear that the ionosphere cannot be considered as a system in isolation, and consequently new research projects to link together models of the solar-terrestrial system, including the Sun, solar wind, magnetosphere, ionosphere and thermosphere, are now being proposed. The prospect is now on the horizon of assimilating data from the entire solar-terrestrial system to produce a real-time computer model and 'space weather' forecast. The role of tomography in imaging beyond the ionosphere to include the whole near-Earth space-plasma realm is yet to be realized, and provides a challenging prospect for the future. Finally, exciting possibilities exist in applying such methods to image the atmospheres and ionospheres of other planets.

Brushless exciter modeling for small salient pole alternators using finite elements

In this paper, the self and mutual inductances of an exciter for a genset alternator are estimated for different rotor angular positions by the use of finite-element (FE) techniques. These inductances, which are described by complex functions, are measured using a stationary test and compared with calculated values. A real-time computer model for the exciter, the load and the diode bridge mounted on the rotor is then proposed, and a sample of performance prediction and measurement for a specific transient condition of the exciter is presented here as confirmation of the method. The model thus validated is ultimately to be included in the evolving total system model used for simulation of genset transient and steady-state performance.

A real-time computer model to assess resident work-hours scenarios.

To accurately model residents' work hours and assess options to forthrightly meet Residency Review Committee-Internal Medicine (RRC-IM) requirements. The requirements limiting residents' work hours are clearly defined by the Accreditation Council for Graduate Medical Education (ACGME) and the RRC-IM: "When averaged over any four-week rotation or assignment, residents must not spend more than 80 hours per week in patient care duties."(1) The call for the profession to realistically address work-hours violations is of paramount importance.(2) Unfortunately, work hours are hard to calculate. We developed an electronic model of residents' work-hours scenarios using Microsoft Excel 97. This model allows the input of multiple parameters (i.e., call frequency, call position, days off, short-call, weeks per rotation, outpatient weeks, clinic day of the week, additional time due to clinic) and start and stop times for post-call, non-call, short-call, and weekend days. For each resident on a rotation, the model graphically demonstrates call schedules, plots clinic days, and portrays all possible and preferred days off. We tested the model for accuracy in several scenarios. For example, the model predicted average work hours of 85.1 hours per week for fourth-night-call rotations. This was compared with logs of actual work hours of 84.6 hours per week. Model accuracy for this scenario was 99.4% (95% CI 96.2%-100%). The model prospectively predicted work hours of 89.9 hours/week in the cardiac intensive care unit (CCU). Subsequent surveys found mean CCU work hours of 88, 1 hours per week. Model accuracy for this scenario was 98% (95% CI 93.2-100%). Thus validated, we then used the model to test proposed scenarios for complying with RRC-IM limits. The flexibility of the model allowed demonstration of the full range of work-hours scenarios in every rotation of our 36-month program. Demonstrations of status-quo work-hours scenarios were presented to faculty as well as real-time demonstrations of the feasibility, or unfeasibility, of their proposed solutions. The model clearly demonstrated that non-call (i.e., short-call) admissions without concomitant decreases in overnight call frequency resulted in substantial increases in total work hours. Attempts to "get the resident out" an hour or two earlier each day had negligible effects on total hours and were unrealistic paper solutions. For fourth-night-call rotations, the addition of a "golden weekend" (i.e., a fifth day off per month) was found to significantly reduce work hours. The electronic model allowed the development of creative schedules for previously third-night-call rotations that limit resident work hours without decreasing continuity of care by scheduling overnight call every sixth night alternating with sixth-night-short-call rotations. Our electronic model is sufficiently robust to accurately estimate work hours on multiple and varied rotations. This model clearly demonstrates that it is very difficult to meet the RRC-IM work-hours limitations under standard fourth-night-call schedules with only four days off per month. We are successfully using our model to test proposed alternative scenarios, to overcome faculty misconceptions about resident work-hours "solutions," and to make changes to our call schedules that both are realistic for residents to accomplish and truly diminish total resident work hours toward the requirements of the RRC-IM.

Brushless Exciter Modeling for Small Salient Pole Alternators Using Finite Elements

The self and mutual inductances of an exciter for a genset altemator are estimated for different rotor angular positions by the use of finite element (FE) techniques. These inductances, which are described by complex functions, are measured using a stationary test and compared with calculated values. A real-time computer model for the exciter, the load, and the diode bridge mounted on the rotor is proposed, and a sample of performance prediction and measurement for a specific transient condition of the exciter is presented as confirmation of the method. The model thus validated is ultimately to be included in the evolving total system model used for simulation of genset transient and steady-state performance.

On the Necessity of Formal Models for Real-Time Parallel Computations

We assume the multitape real-time Turing machine as a formal model for parallel real-time computation. Then, we show that, for any positive integer k, there is at least one language Lk which is accepted by a k-tape real-Turing machine, but cannot be accepted by a (k - 1)-tape real-time Turing machine. It follows therefore that the languages accepted by real-time Turing machines form an infinite hierarchy with respect to the number of tapes used. Although this result was previously obtained elsewhere, our proof is considerably shorter, and explicitly builds the languages Lk. The ability of the real-time Turing machine to model practical real-time and/or parallel computations is open to debate. Nevertheless, our result shows how a complexity theory based on a formal model can draw interesting results that are of more general nature than those derived from examples. Thus, we hope to offer a motivation for looking into realistic parallel real-time models of computation.

ON THE NECESSITY OF FORMAL MODELS FOR REAL-TIME PARALLEL COMPUTATIONS

We assume the multitape real-time Turing machine as a formal model for parallel real-time computation. Then, we show that, for any positive integer k, there is at least one language Lk which is accepted by a k-tape real-Turing machine, but cannot be accepted by a (k - 1)-tape real-time Turing machine. It follows therefore that the languages accepted by real-time Turing machines form an infinite hierarchy with respect to the number of tapes used. Although this result was previously obtained elsewhere, our proof is considerably shorter, and explicitly builds the languages Lk. The ability of the real-time Turing machine to model practical real-time and/or parallel computations is open to debate. Nevertheless, our result shows how a complexity theory based on a formal model can draw interesting results that are of more general nature than those derived from examples. Thus, we hope to offer a motivation for looking into realistic parallel real-time models of computation.

Tokamak fusion reactor plant assembly, logistics and critical issues

A tokamak fusion reactor will be an installation with linear sizes of a single assembly element of ∼10–20 m and a weight >1000 t. Similar weights can be handled at a construction site by commercially available equipment. But a problem is created by the combination of high weights and large dimensions of the components with tight installation tolerances driven by plasma physics requirements. To overcome this problem, the best available metrology techniques with 3-D real time computer modeling and specially selected assembly procedures are needed at all stages of production and assembly. Some of the biggest components i.e. poloidal coils must be produced at the construction site. Some smaller components must be preassembled at the site to accelerate construction. Adequate space with proper environmental control must be provided for these operations. These and other considerations determine the logistics of a fusion plant assembly.

Three-dimensional measurement of underwater work sites using structured laser light

Some current operations with remotely operated vehicle (ROVs) require the vehicle to fix itself onto an underwater work site and carry out robotic tasks. For this to occur, a real-time computer model of the work site and its relationship to the vehicle must be determined, especially if the work site has not been designed for such interventions and no fixed docking structure is available. We described a laser-based system that can be used from an ROV to scan the underwater work site and translate the information into a CAD or virtual reality (VR) model. A single stripe is projected onto the work site and an image acquired by the ROV. An image-processing routine is used to optimize object range and shape information obtainable from this stripe and, when several such stripe positions have been determined, the information is combined. This paper concentrates on the image-processing techniques needed to isolate information from underwater images and the results obtained in trials of the system in a laboratory tank. The methodology is able to accommodate differing turbidities and the limitations of the system in terms of accuracy are discussed.

A large-scale transputer network application: the aero-mechanical simulation of a single-rotor helicopter for control system design

The proposed role for future advanced rotorcraft requires superior agility and enhanced safety, coupled with a reduced pilot workload. More elaborate flight control systems will therefore be required which will have to be digitally implemented. New design methodologies will be required, in turn necessitating the development of new tools. One such tool will be a more complex real-time simulation of helicopter dynamics. This paper describes a generic real-time computer model of helicopter dynamics that eliminates the need for simplifying assumptions to enable real-time operation. A concurrent approach is used that exploits the natural parallelism of the helicopter dynamics. Implemented on a transputer network, the model exhibits ideal qualities as a development tool for advanced helicopters and their systems.

Utilizing A Field Computer System During Cementing To Help Avoid Costly Workovers

Abstract The need for costly workover operations can be reduced by accurately monitoring and modelling cementing operations with a field computer system. This paper shows how realtime computer monitoring is used to detect downhole problems prior to and during cementing, increase quality control, maintain proper flow regimes and present downhole equivalent circulating densities to assist in avoiding lost circulation and/or influx. A description of the application of A.P.I. Specification 10 (Appendix J)(1) by this realtime model is presented. Introduction A great deal of work has been done by the industry to increase our ability to model a cementing operation. The value of realtime job monitoring has been presented(2). Methods for on-site diagnosis(3), and post-job analysis(4) have been presented. With the recent advances in personal computer technology it is now possible and more economically feasible to apply a realtime computer model to cementing treatments. This technology has been applied on a large number of treatments and has helped improve the probability of success. By monitoring and analyzing the rate of pumping, slurry density, and well head pressure with a computer system, the quality control of a cementing operation is greatly enhanced. The rate of returns and return density are monitored when possible. This allows the actual downhole conditions to be more accurately modelled and potential problems detected. The flow regime of mud, spacer and cement are calculated by tracking the slurry density, rheology and velocity throughout the annulus. Surface adjustments have then been made to keep the respective fluids in a flow regime that will be most beneficial for mud removal and cement placement. Pore and fracture pressures throughout the open hole region are convened to equivalent densities. By overlaying a graphic representation of these parameters vs depth with the calculated equivalent circulating density, an equivalent density window is presented. This information can be used to adjust the rate to help avoid influx from the formation or lost circulation. The procedure for calculating frictional pressure outlined in the American Petroleum Institute Specification 10 Appendix J(1) was followed in the program development. Description of Computer Monitoring System The computer monitoring system used consists of transducers on the pumping and return lines, a data acquisition system and an MS-DOS-based computer with various peripherals (Fig. 1). This system is described in the Appendix. The computer uses information from the transducers to calculate several screens of information. These screens are described below. Wellbore and Data Display The wellbore diagram and monitored data displayed across the top of Figure 2 are the same for each of the screens. The wellbore diagram displays the respective position of each fluid in the wellbore. This is updated continuously as a function of the profile calculations. The data display is updated every one to two seconds. Flow Regime This screen displays a continuously updated plot of equivalent Reynold's Number vs depth (Fig. 2). The line marked ‘laminar’ represents the maximum Reynold's Number for the fluid to be in laminar flow.

Simulation of cardiac arrhythmia haemodynamics with a real-time computer model.

A simplified real-time computer model of the cardiovascular system was developed to simulate the haemodynamic waveforms of pressure, volume and flow that occur in cardiac arrhythmias. The cardiovascular system was viewed as a sixcompartment model in which the heart chambers are geometric objects and the pulmonary and systemic circulations are electrical circuit analogues that represent simplified ‘Windkessel’ models. With the use of a surface electrocardiogram (ECG) as input, this closed-loop model can show the haemodynamics of cardiac arrhythmias in real time. The model has been used to construct a simulator which has proved to be useful as a teaching tool and shows great potential for applications in research and in clinical medicine.