Multiple Redundancy Research Articles

Exploring fish community dynamics through size-dependent trophic interactions using a spatialized individual-based model

An individual-based model named OSMOSE (Object-oriented Simulator of Marine Ecosystems Exploitation) is used to investigate the dynamics of exploited marine fish communities. It allows the representation of age- and size-structured populations comprised of groups of individuals that interact within a spatialized food web. Within each group, which constitutes the basic interaction entity (the ‘super-individual’ in individual-based modelling terminology), fish belong to the same species, have similar biological parameters and behaviour rules. Somatic growth, reproduction, predation and starvation processes are modelled. Two rules apply for the predation process: for a given fish group, prey selection depends both on the spatial and temporal co-occurrence of the predator and its prey, and on the respective lengths of the prey versus the predator. Thus, fish feed regardless of the taxonomy of their prey. The strength of both predation and competition relationships therefore vary according to changes in relative species abundance. Preliminary investigations are conducted on a theoretical community comprising seven interacting species. The simulation results show how community stability can emerge from variability in species biomass. It is thus suggested that size-based trophic interactions, along with the existence of multiple weak links and species redundancy, favour community persistence and stability.

Optimal Sensor's Placement Under Constraints of Redundancy Degree and Cost

The quality of the state estimation of a process and consequently its safety and control are conditioned by the number and the distribution of its measurements. The availability and reliability of a process can be increased if the latter can work even during the failure of the sensors. In this paper, we present and we formalise the multiple redundancy notion which permits the toleration of sensor failure without harming the observability of a given variable. We shall propose a sensor placement to obtain a given redundancy degree at the lowest cost. So, we can analyse the influence of the redundancy degree of a variable on the reliability of the process.

A low-cost, full-function picture archiving and communication system using standard PC hardware and the traditional 4-over-4 display format.

With a 12-year background of our completely digital nuclear medicine picture archiving and communication system (PACS), we have recently implemented a novel PACS, OpenPACS, which can be used for interpretation and display of CT, MR imaging, sonography, nuclear medicine, and computed and digital radiography studies. OpenPACS uses low-cost standard PC hardware and software that is widely available and is readily serviced and maintained. The OpenPACS application program is available over the Internet. CT or MR imaging slices from one or multiple studies can be presented simultaneously or in cine mode on a wall-sized multimonitor display. The assembly, with a total resolution of 6400 x 4800 pixels, resembles a traditional array of eight standard X-ray viewboxes. A wireless mouse is used to vary attenuation and other display parameters. Multiple backup and redundancy are provided. Currently, six CT and six MR imaging scanners of different vendors are networked to OpenPACS, which is also networked to our nuclear medicine PACS. After only a brief introduction, radiologists rapidly become familiar with the system because it is based on the use of standard Windows icons and procedures and offers a display that resembles a standard X-ray film presentation.

Potassium iodide for thyroid blockade in a reactor accident: administrative policies that govern its use.

A marked increase in thyroid cancer among young children who were in the vicinity of the Chernobyl nuclear power plant at the time of the 1986 accident strongly suggests a possible causal relationship to the large amounts of radioactive iodine isotopes in the resulting fallout. Although remaining indoors, restricting consumption of locally produced milk and foodstuffs, and evacuation are important strategies in a major breach-of-containment accident, stable potassium iodide (KI) prophylaxis given shortly before or immediately after exposure can reduce greatly the thyroidal accumulation of radioiodines and the resulting radiation dose. Concerns about possible side effects of large-scale, medically unsupervised KI consumption largely have been allayed in light of the favorable experience in Poland following the Chernobyl accident; 16 million persons received single administrations of KI with only rare occurrence of side effects and with a probable 40% reduction in projected thyroid radiation dose. Despite the universal acceptance of KI as an effective thyroid protective agent, supplies of KI in the US are not available for public distribution in the event of a reactor accident largely because government agencies have argued that stockpiling and distribution of KI to other than emergency workers cannot be recommended in light of difficult distribution logistics, problematic administrative issue, and a calculated low cost-effectiveness. However, KI in tablet form is expensive and has a long shelf life, and many countries have largely stockpiles and distribution programs. The World Health Organization recognizes the benefits of stable KI and urges its general availability. At present there are 110 operating nuclear power plants in the US and more than 300 in the rest of the world. These reactors product 17% of the world's electricity and in some countries up to 60-70% of the total electrical energy. Almost all US nuclear power plants have multistage containment structures with large steel and concrete shells and multiple redundancy of core cooling mechanisms. These successfully prevented the release of major amounts of radionuclides in the Three Mile Island partial loss-of-primary coolant accident in 1979. The Chernobyl accident, in a different type of reactor that is common in Eastern Europe, did not have effective outer shell containment and released almost 50 MCi of 131I compared to the 20 Ci of 131I released at Three Mile Island. Such accidents have precipitated extensive re-evaluation of the design and safety devices of all operating reactors. However, a major contributing factor to the accidents was human error and considerable efforts must be made to train plant operators so they have a better understanding of reactor operation and use of safety mechanisms.

Operational monitoring in German nuclear power plants

The Atomic Energy Act requires that measures made feasible by state of the art technology be adopted to avoid damage that could be caused as the result of the construction and operation of a nuclear plant. This stipulation constitutes the basis for deriving requirements for planning, design, construction, operation and decommissioning. Ensuring the function and integrity of those components and systems that are relevant to plant safety is of major significance with regard to operation of a nuclear power plant. The basis for ensuring these features is laid in planning, design and construction. Important as these foundations may be, it is absolutely essential to monitor the quality originally planned and achieved in an object as undeniably complex as a nuclear power plant. The RSK-Leitlinien für Druckwasserreaktoren (Reactor Safety Commission Guidelines for Pressurized Water Reactors) incorporate fundamental requirements for design, mechanical design, materials, manufacturing, testing and examination, and operation. Meeting these requirements makes it possible to exclude a catastrophic rupture of the components in the reactor cooling system pressure boundary (primary system), as has been demonstrated in detailed research and development work. The term basic safety was defined for this concept. Basic safety coupled with multiple redundancy suffices to exclude the possibility of large ruptures (rupture preclusion). The principle of plant monitoring and documentation (operational monitoring) implements redundancy in a significant manner within this concept. The monitoring techniques used in Germany have reached an advanced state of development and are still being optimized. Thus, operational monitoring is a major contributory factor in the safety and high availability of nuclear power plants. It also provides a means of expanding our knowledge of life time expectation.

Fault Tolerance with Multiple Task Modular Redundancy

The redundant units in a classic N Modular Redundancy (NMR) system are employed solely for fault tolerance, making this technique inefficient. This paper introduces Multiple Task Modular Redundancy that allows an NMR system to have a higher throughput by exploiting, when no faults have occurred, the system’s redundancy. More than one group of replicated tasks are optimistically executed. This method has a 50-100% better throughput over NMR but does not jeopardize the fault tolerance of the basic NMR system. Unlike other methods, this technique applies to systems as small as three processors (TMR). Variations on the granularity and dependencies of tasks are considered.

Bit-serial VLSI sorter with high reliability specifications

This paper presents the design, operation and fault-tolerance enhancements of a parallel VLSI sorting architecture for bit-serial input which operates as a single pipelined comparator module. The basis design is enriched with a novel multiple redundancy fault-tolerance scheme so that the sorter meets high reliability specifications. Fault management operates locally at the most basic level of functionality. Hierarchical reconfiguration is supported by the fact that only data (no control) signals flow throughout the system. Reconfiguration is in real-time and automatic. The proposed sorter is a completely modular system having three levels of modularity, all exhibiting high regularity throughout. The sorting time is completely overlapped with the i/o time making the overall sorting process very fast. The sorter can sort N numbers of any length k without any modification.

Computational arrays with flexible redundancy

Different multiple redundancy schemes for fault detection and correction in computational arrays are proposed and analyzed. The basic idea is to embed a logical array of nodes onto a processor/switch array such that d processors, 1/spl les/d/spl les/4, are dedicated to the computation associated with each node. The input to a node is directed to the d processors constituting that node, and the output of the node is computed by taking a majority vote among the outputs of the d processors. The proposed processor/switch array (PSVA) is versatile in the sense that it may be configured as a nonredundant system or as a system which supports double, triple or quadruple redundancy. It also allows for spares to be distributed in the PSVA in a way that permits spare sharing among nodes, thus enhancing the overall system reliability. In addition to choosing the required degree of redundancy, the flexibility of the PSVA architecture allows for the embedding of redundant arrays onto defective PSVA's and for run-time reconfiguration to avoid faulty processors and switches. Different embedding and reconfiguration algorithms are presented and analyzed using Markov chain techniques, using probability arguments, and via simulation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Signal transduction through gp130 that is shared among the receptors for the interleukin 6 related cytokine subfamily.

Interleukin 6 (IL-6) and related cytokines, such as leukemia inhibitory factor (LIF), oncostatin M (OSM), ciliary neurotrophic factor (CNTF) and IL-11 exhibit multiple functions and redundancy in biological activities and play important roles in the immune response, hematopoiesis, the nervous system and acute phase reactions. These IL-6 family cytokines exhibit a similar helical structure, and their receptors are structurally similar and constitute a cytokine receptor super family. In addition, a receptor subunit is shared among these IL-6 related cytokine subfamily receptors, contributing to one of the mechanisms of functional redundancy of cytokine activities and suggesting the presence of a common signal transduction pathway among these receptors. In this review, we describe the structure of the receptors for IL-6 and its related cytokine subfamily members. Furthermore, we propose a novel mechanism for the generation of cytokine diversity, i.e. the complex of a cytokine and one of its receptor subunits act as a novel cytokine on the cells that express the other receptor subunit(s) capable of acting as a receptor for the complex. Finally, we describe a Ras-independent novel signal transduction pathway that utilizes Jak tyrosine kinase family, Stat protein family and yet unidentified H-7-sensitive pathway. This signal transduction pathway is commonly generated through the receptors for a wide range of cytokines and growth factors.

Real-time collision avoidance of manipulators with multiple redundancy

A method is presented for the control of robot manipulators with multiple redundancies, using a technique based on Laplacian potential fields. Obstacles and a goal point are modelled as points of fixed potential within a continuous, closed region. All obstacles are modelled as having the same high potential and the goal point is defined as having some lower potential. From the field calculated, a method based on gradient descent is used to control the motion of the robot joints in an optimal manner, which will automatically avoid collisions between any of the links and any of the obstacles. The proposed field representation is compared with other potential field methods and in particular, the method is shown to be appropriate for fixed base, non-point robots. Four simulated case studies are presented which illustrate the technique in two-dimensional space. The studies consider the problems of: insertion of a robot into an annulus; negotiation of a high aspect-ratio corridor; a randomly cluttered field; and a symmetrical trap.

Self-compensating carrier aircraft recovery system

Major improvements and expansion of the capabilities of the aircraft recovery systems that are now in service on our aircraft carriers are feasible with existing technology, without any major hardware design change and without jeopardizing the high reliability of the current hydraulic-mechanical arresting gear that was designed in the 1950s. A self-compensat ing (model-reference adaptive) control system with multiple redundancy and majority voting logic can be developed and installed on our aircraft carriers at a cost less than that of the first aircraft saved by such a system. Feasibility of a Closed-Loop Control System that eliminates the risk of aircraft losses due to an erroneous weight preset has been demonstrated by computer simulation. The installation of cable-payout transducers (encoders), of a signal processor, and a servo-actuator that can correct the mis-set of a weight adjustment lever can solve this problem. In addition, an expansion of the current design limits for off-center engagement and for weight and speed of the landing aircraft, as well as a reduction in stress levels and a corresponding increase in service life for aircraft (such as the A-6) and arresting systems, can be achieved by modifications of the cable damper subsystems that are now in service.

Multicriteria redundancy optimization using an efficient search procedure

An efficient approach to multiple criteria redundancy optimization problem, often encountered in reliability design of engineering systems, is presented. A search technique introduced earlier (Misra 1991) in combination with multicriteria optimization methods, based on the min-max concept for finding the Pareto optimal solution of multicriteria optimization problems, provides an efficient and excellent approach for solving redundancy optimization problems. The approach is illustrated through several numerical examples. Based on this approach, a very general computer code called efficient search multi-objective programming (ESMOP) has also been developed. It is capable of considering any type of redundancy, constraint or individual cost function and thus offers a solution to many reliability design problems.

An efficient approach for multiple criteria redundancy optimization problems

The present paper provides an efficient approach to multiple criteria redundancy optimization problems, often encountered in reliability design of engineering systems. A search technique introduced earlier [10,11] in combination with the multicriteria optimization methods, based on min-max concept for finding Pareto optimal solution of multicriteria optimization problems, provides an efficient and excellent approach for solving redundancy optimization problems. The approach is illustrated through several numerical examples. Further, based on this approach, a very general computer code called ESMOP (Efficient Search Multi-Objective Programming) has also been developed. It is capable of considering any type of redundancy, constraint or individual cost function and thus offers to solve many reliability design problems.

Continous monitoring of copper and cadmium in zinc plat electrolyte usinga microprocessor-based batter-operated data acquisition system, multiple ion-selective electrodes and redundancy principles

Monitoring of both copper and cadmium is essential in the electrolytic production of zinc because these elemetns must be removed in order to improve the efficiency of the zinc electro-refining process. A new high-volume flow-through cell with an assembly of four ion-selective electrodes (four copper, four cadmium or two copper and two cadmium electrodes), reference electrode and temperature probe coupled with microprocessor-based instrumentattion can be used for this purpose. Determinations can be done continuously for 72-h periods without maintenance in an on-line mode. when multiple electrode determinations and redundncy principles are implemented. A microcomputer system incorporating low-power CMOS technology with multichannel and multiplexing capabilities is used for data acquisition. The use of the battery-powered data acquisition system provides excellent signal-to-noise ratios, meets the special demands of the harsh industrial environment, and is preferable to conventional mains-powered monitoring systems based on ion-selective electodes.

The validity of clerkship performance evaluations.

The validity of narrative evaluations of clinical performance in medical school was investigated for three successive classes of medical school graduates. The criteria were ratings obtained from residency supervisors one year after entering the programme. Bivariate correlational analysis, multiple regression analysis and canonical redundancy analysis were performed to examine the associations between the evaluations by teachers of competence in medical school clerkships and the subsequent ratings by residency supervisors. The results, best summarized in the canonical analysis, showed two relationships between the two sets of measures (lambda 1 = 0.54 and lambda 2 = 0.47). The first relationship revealed an overall-competence-in-medicine dimension; the second suggested an interpersonal-skills/professional-maturity dimension. Overall, knowledge of clerkship performance accounted for 15% of the variance in residency ratings. The findings suggest the need to improve the assessment of professional maturity and behaviour during medical school.

Dynamic fault recovery in mesh‐connected parallel computers

AbstractA trend in computer development aiming at high‐speed processing is high‐level parallel processing using a large number of processing elements. This scheme is becoming more realistic with the recent progress of VLSI technology. On the other hand, there arises a problem of how to cope with the generation of faults with the increased number of processing elements. A faulttolerant computer with multiple redundancy has been developed, but no method has been presented in the parallel computer environment whereby sufficient redundancy against fault can be provided, to recover from fault and to continue the computation without a system down. In general, completeness of data is lost by a fault. In the field of numerical computation, however, there are problems with less stringent requirement for completeness of data (e.g., in iterative solution of a system of equations). This paper discusses the case where such a problem is solved by a parallel computer with lattice topology. Three structural types are proposed for dynamic fault recovery during execution, mutual connection and the method of recovery. The result of evaluation by simulation is shown.

A relational database for non-manipulative representation of solid objects

As the heart of any solid modelling system, much effort has been spent on formulating the data models which represent the shape of a polyhedral solid object within the computer in an accurate, unique and complete manner. Most of this effort has been devoted to make the models manipulateable in terms of computational efficiency, and preserve their semantic integrity. The price paid for achieving these goals is a proliferation of cross-reference data links which, coupled with multiple redundancy, renders the models inefficient for storage or transmission over communication channels. Moreover, the interrogation of these models by non-manipulative applications is usually unsupported functionally, requiring direct accesses to the data, which involves extensive pointer chasing and therefore high familiarity with the manipulative data structure. This paper presents an example relational model as a complementary logical scheme for viewing the shape database that facilitates compact storage and supports non-manipulative query operations through the projection, selection and join operators defined for the relational model, without requiring expert knowledge of the manipulative structure. The flexibility of the relational model, compared with that of the hierarchical, manipulative one, allows easy extensibility and the association of non-geometric attributes with each data item.

A method for evaluating the reliability of complex multiple redundant systems

Analysis of petrochemical and nuclear power plants increasingly requires complex, interconnected systems with multiple redundancy to be evaluated not in isolation, but rather interactively with other sustems. A current limitation of most computer codes to evaluate the reliability of such plants is the high computing costs. The technique described in this paper shows how it is possible to evaluate the reliability of large systems in a cost-effective manner. A typical problem is 30 subsystems each with 30 components.

User's Vs. Systems Analyst's Point of View in the Definition Phase of Industrial DCCS

Publisher Summary This chapter describes the users versus systems analyst's point of view in the definition phase of industrial DCCS. Insufficiency of configuration management tools often caused large-scale centralized CCS to go wrong. DCCS projects are less sensitive to specification errors as a result of flexible modular design and implementation. The DCCS designer, however, tackles with additional degrees of freedom of functional distribution, interconnection, and coordination of multiple information processing entities, redundancy, software distribution, and control equipment allocation. At the same time, the users' position has little changed and therefore, adequate and timely DCCS definition remains a bottleneck. Answers to this problem are plant-oriented system analysis, and simulation, design of DCCS as an embedded modifiable computer system and computer-aided specification, and prototyping support systems to ease user participation in the design process. DCCS is considered solely as a functional entity of the entire production plant, indifferent to its architecture.

On-Board Computers for Control

Spacecraft computers have evolved over the last decade from simple, hard-wired sequencers to complex, general purpose machines with large memories and redundant processors. Manned spacecraft during the 1960's were the first to use general purpose architectures, but were limited by their excessive weight and enormous power requirements. The invention of Large Scale Integrated circuits (LSI) in the early 1970's permitted unmanned spacecraft computers to use architectures which were capable of in-flight reprogramrning. Recent developments, including microprocessors and large memories on a single chip, have permitted the development of distributed processors and the application of multiple redundancy for long life, high reliability missions.