Sequential Components Research Articles

Health Monitoring and Structural Reliability as a Value Chain

A value chain is defined as an end‐to‐end solution to a problem, with the beneficiary constituting one end of the chain and the enabling technologies (or parties) making up the rest of the chain. In this context, enabling technologies such as health monitoring, damage detection, and reliability are viewed as sequential components in a chain, with each continuing the chain while adding value to it, so that the aggregate value of the chain can be delivered to the ownership. This holistic view is taken to expose a current imbalance in technology development, and the weak link corresponds to a lack of information that relates technology‐investment costs to financial benefits for the owner. Structural reliability, useful life expectancy, and other information of this genre are seen to be keeping the full value of the chain from being realized and appreciated by the ownership. An example of what the desired linkage may be comes from aerospace and mechanical engineering. In the form of so‐called symptom‐based reliability technology, reliability is quantified for existing structures based on actual usage instead of natural age and measured symptoms instead of idealized model prediction. Hence it is also compatible with current health‐monitoring and damage‐detection developments (enabling technologies of the value chain). Since the value of the chain is only as (in)effective as its weakest link, it is argued that future research effort should stress balanced development throughout the chain.

Synthesis of power-managed sequential components based on computational kernel extraction

This paper introduces a power optimization paradigm for sequential components based on the concept of computational kernel, a highly simplified logic block whose behavior mimics the steady-state behavior of the original specification. We present a flexible framework that supports a number of algorithmic options for carrying out kernel extraction. We first describe an exact symbolic procedure that is applicable to components for which only a functional specification (i.e., the state transition graph) is available. Due to its computational complexity, this procedure is mainly of theoretical interest and it is not usable for large circuits. We then propose two approximate algorithms that can be adopted in practical situations. The first one is simulation-based and it is suitable to cases where input data streams representing typical operation of the component are available. The second approach performs kernel extraction by iteratively refining a structural representation of the component obtained through synthesis. The impact of the power optimization paradigm based on kernel extraction is demonstrated by the results of extensive experimentation carried out on a number of benchmarks of different characteristics and nature.

Neural correlates of auditory stream segregation in primary auditory cortex of the awake monkey

An important feature of auditory scene analysis is the perceptual organization of sequential sound components, or ‘auditory stream segregation’. Auditory stream segregation can be demonstrated by presenting a sequence of high and low frequency tones in an alternating pattern, ABAB. When the tone presentation rate (PR) is slow or the frequency separation (ΔF) between the tones is small (<10%), a connected alternating sequence ABAB is perceived. When the PR is fast or the ΔF is large, however, the alternating sequence perceptually splits into two parallel auditory streams, one composed of interrupted ‘A’ tones, and the other of interrupted ‘B’ tones. The neurophysiological basis of this perceptual phenomenon is unknown. Neural correlates of auditory stream segregation were examined in A1 of the awake monkey using neuronal ensemble techniques (multiunit activity and current source density). Responses evoked by alternating frequency sequences of tones, ABAB, were studied as a function of PR (5, 10, 20 and 40 Hz). ‘A’ tones corresponded to the best frequency (BF) of the cortical site, while ‘B’ tones were situated away from the BF by an amount ΔF. At slow PRs, ‘A’ and ‘B’ tones evoked responses that generated an overall pattern of activity at the stimulus PR. In contrast, at fast PRs, ‘B’ tone responses were differentially suppressed, resulting in a pattern of activity consisting predominantly of ‘A’ tone responses at half the PR. The magnitude of ‘B’ tone response suppression increased with ΔF. Differential suppression of BF and non-BF tone responses at high PRs can be explained by physiological principles of forward masking. The effect of ΔF is explained by the hypothesis that responses to tones distant from the BF are more susceptible to suppression by BF tones than responses to tones near the BF. These results parallel human psychoacoustics of auditory stream segregation and suggest a cortical basis for the perceptual phenomenon.

Online-data-based pattern recognition of transient responses and suboptimal iteration of control parameters

Technically, parametric performance evolution of control systems can be decomposed as two sequential components: online-data-based pattern recognition of transient responses and iteration of control parameters. This paper proposes a novel reactive knowledge-based method for parametric performance evolution of control systems. First, a novel knowledge-based system is developed for online-data-based pattern recognition of transient responses of control systems. Then, a quasistate equation, with features of transient responses as quasistates and forward increments of control parameters as quasicontrol variables, is proposed and structured, and the iteration of control parameters is formulated as and solved through a linear quadratic quasistate tracking problem. Moreover, a set of heuristic rules are designed to supervise the utilization of the rolling-optimization solution to the linear quadratic quasistate tracking problem. Finally, a variety of simulations were conducted to demonstrate the reasonableness of the proposed concept of parametric performance evolution of control systems, and the feasibility and effectiveness of the developed algorithms.

Effectiveness of ants as pollinators of Lobularia maritima: effects on main sequential fitness components of the host plant.

The effectiveness of ants as pollinators of Lobularia maritima (Cruciferae) was experimentally analyzed by assessing (1) their quantitative importance at flowers; (2) their effect on host plant seed production; (3) their effect on the performance of host plant progeny, estimated as seed germination, seedling emergence, seedling survival to flowering, and (4) the overall effect of ants on a cumulative, more realistic measure of plant fitness related to the recruitment probability. Flowers of L. maritima were visited during the 2 years of study (1996 and 1997) by more than 50 pollinator species belonging to about 30 families of disparate taxonomic affiliation, notably ants and flies. There was significant seasonal variability in insect abundance and type. Ants, especially Camponotus micans (Formicidae), visited the flowers of L. maritima in summer, representing 81.2% of the visits during this season. This ant species acted as a pollinator of L. maritima, with flowers visited exclusively by ants producing significantly more seeds than flowers from which all pollinators were excluded, whereas flowers visited by only winged insects did not differ from self-pollination. Ant-pollinated flowers produced seeds with a germination rate comparable to the other treatments. Moreover, seedlings from these seeds emerged as fast, and survived at the same rate as controls. Consequently, both ants and winged insects had similar overall effects on host plant recruitment probability (0.6 and 0.7% of initial ovules produced flowering offspring, respectively), a result similar to that of open-pollinated flowers (1.0%). This study demonstrated that the overall effectiveness of the ant C. micans as a summer pollinator of L. maritima was as high as that of other winged insects, contributing not only to the seed production of this crucifer but also to the recruitment of new flowering offspring.

PLL modeling and verification in a cycle-simulation environment

Recent advances in technology, computer architecture, and automated design environments have ushered in a new era of computer design in which large complex servers such as the S/390 G5 Parallel Enterprise Server™ can be delivered with times to market once reserved for low-end systems such as single-user workstations and personal computers. Yet, the time to market is inversely proportional to customer demand for reliable and continuously available systems. Therefore, the need exists to build and simulate a complete system which incorporates realistic and accurate behavioral representations for all design components. This paper describes a method for modeling an analog phase-locked loop, interfacing it with digital sequential logic components, and simulating the entire system in a high-performance two-cycle simulation environment. Further discussion demonstrates the role this verification has played in the deployment of an improved design point with a shorter time to market compared to previous genera tions of S/390® CMOS machines.

Pattern span: a tool for unwelding visuo–spatial memory

Evidence showing that non-verbal short-term memory has distinct visual and spatial/sequential components is reviewed. A new test, The Visual Patterns Test (VPT), which was designed to measure short-term visual memory largely shorn of its spatio–sequential component, is described. Correlational studies of the VPT and the Corsi Blocks Test with healthy subjects and brain-damaged patients indicate a separation between visual and sequential abilities. This separation of function is supported by double dissociations shown by patients. Moreover, in a selective interference experiment, the VPT and the Corsi tests were found to show a double dissociation pattern of interference from visual and spatio–sequential subsidiary tasks, respectively. The present results are discussed in relation to other findings in the literature, and it is concluded that non-verbal short-term memory can indeed be viewed as comprising distinct visual and spatio–sequential components. The VPT will be a useful neuropsychological instrument for measuring the visual component.

Presupplementary Motor Area Activation during Sequence Learning Reflects Visuo-Motor Association

In preceding studies (Hikosaka et al., 1996; Sakai et al., 1998) we have shown that the presupplementary motor area (pre-SMA), an anterior part of the medial premotor cortex, is active during visuo-motor sequence learning. However, the paradigm required the subjects first to acquire correct visuo-motor association and then to acquire correct sequence, and it was still unknown which of the two processes the pre-SMA is involved in. To further characterize the role of pre-SMA, we have conducted another series of functional magnetic resonance imaging experiments using three learning paradigms. The three were the same in that they involved a visuo-motor association component, but they differed in terms of the involvement of sequential components; one involved no sequence learning, whereas the other two involved learning of motor sequence or perceptual sequence. Comparison of the learning conditions with the any-order button press condition revealed pre-SMA activation in all three paradigms. The pre-SMA activation remained unchanged during learning of visuo-motor associations but decreased during learning of sequences, suggesting that the pre-SMA is related to visuo-motor association rather than sequence. The decrease of pre-SMA activation in the sequential paradigms may reflect the process by which individual visuo-motor associations were replaced by the formation of sequential procedural memory, which occurs outside the pre-SMA. Thus activation of the pre-SMA was related to the extent to which the task performance depended on conscious visuo-motor associations.

On the Semantic Foundations of Probabilistic Synchronous Reactive Programs

In this paper we consider synchronous parallel programs ▪ that are composed by sequential randomized processes ▪1,…, ▪k which communicate via shared variables. First, we give an operational semantics for the sequential components ▪i on the basis of a transition relation defined in the classical SOS-style à la Plotkin [Plo81] which we use to specify the behaviour of ▪ by a Markov chain whose transitions stand for the cumulative effect of the activities of the components ▪1,…▪k within one time step. Second, we provide a denotational semantics for ▪ that also models ▪ by a Markov chain. It is based on a (denotational) least fixed point semantics for the sequential components which formalizes the input/output behaviour of the sequential components within one time step. While the operational (declarative) semantics might be the one that a designer (who provides the input for the tool) has in mind, the denotational (procedural) semantics is the one that a compiler might use. We establish a consistency result stating that the Markov chains induced by the operational and denotational semantics are bisimilar in the sense of [LS91].

Automatic Generation of Invariants

When proving invariance properties of programs, one is faced with two problems. The first problem is related to the necessity of proving tautologies of the considered assertion language, whereas the second manifests itself in the need of finding sufficiently strong invariants. This paper focuses on the second problem and describes techniques for the automatic generation of invariants. The first set of these techniques is applicable to sequential transition systems and allows deriving so-called local invariants, i.e., predicates which are invariant at some control location. The second is applicable on networks of transition systems and allows combining local invariants of the sequential components to obtain local invariants of the global system.

Verbal Prompting, Hand-over-Hand Instruction, and Passive Observation in Teaching Children with Developmental Disabilities

In hand-over-hand modeling with response-contingent verbal prompts, tasks are divided into identifiable sequential components, and the achievement of each component is marked by the delivery of some form of verbal prompt. In a within-subjects design, children were trained in one skill with response-contingent verbal prompts and in a second skill with simple passive observation. A separate group of children were trained with less rigorous verbal prompting in one skill and with passive observation in a second. Consistent with previous research, we found that passive modeling was overall significantly more effective than hand-over-hand modeling and that passive modeling was significantly more effective than hand-over-hand modeling with response-contingent prompting. Our evidence therefore indicates that current methods for teaching basic skills to children with severe developmental delays may require reassessment because simple observation of modeled skills appears to be more effective than more labor-intensive instruction.

The Operational Elements of Developing a Congestive Heart Failure Clinic

Congestive heart failure (CHF) is a common and chronic form of heart disease. Disease management offers a new model for more effectively managing patient health care over a continuum. One increasingly popular tool is a dedicated CHF clinic program. Implementation of new programs represents new organizational challenges for health-care providers. Operational planning is a component of the larger strategic planning process. Chances for realizing enhanced operational effectiveness are increased by adhering to a focused developmental process. We review the sequential components of operational planning including directional vision, feasibility studies, pilot studies, and final implementation. This is followed by a case study of a large cardiology group as they went from a developmental concept to a fully implemented clinic.

Teaching basic skills to children with Down syndrome and developmental delays: the relative efficacy of interactive modeling with social rewards for benchmark achievements and passive observation.

In interventions attempting to remediate deficiencies in the skills repertoire of developmentally delayed children, no less than in medical interventions, it may be fairly said that less is more. That is, the instructor should intervene as little as possible both from the perspective of efficient instructional practice and from time allotment concerns which modern classrooms face. Evidence from this laboratory has indicated that in skills training for children with severe developmental delays the passive observation of a model demonstrating the target skill is more effective than interactive modeling involving hand-over-hand instruction with verbal prompting. We have considered the role of verbal prompting in interactive modeling and have found that prompts intended to provide typical social reinforcers are counterproductive (e.g., Biederman, Davey, Ryder, & Franchi, 1994). The present study examines the efficacy of hand-over-hand modeling with response-contingent verbal prompts. In such instruction, tasks are divided into identifiable sequential components, and the achievement of each component is marked by the delivery of some form of verbal prompt. In a within-subjects design, children were trained in one skill with response-contingent verbal prompts and in a second skill with simple passive observation. A separate group of children were trained with less rigorous verbal prompting in one skill and with passive observation in a second. Consistent with previous research, we found that passive modeling was overall significantly more effective than hand-over-hand modeling and moreover that passive modeling was significantly more effective than hand-over-hand modeling with response-contingent prompting. Our evidence therefore indicates that current classroom practice in training basic skills to children with severe developmental delays may require reassessment in that simple observation of modeled skills appears to be more effective than more labor-intensive instruction.

Cluster analysis: A new technology for the evaluation of oximetry and airflow waveforms in obstructive sleep apnea

A new diagnostic method is described which identifies the presence of waveform clusters indicative of OSA, and an illustrative OSA screening system is presented which applies the new cluster analysis method to the oximetry waveform. Rather than using the conventional identification of an excess average number of isolated events to infer the presence of upper airway instability, cluster analysis identifies a prolonged spatial pattern of clustered waveforms derived from the underlying mechanism of OSA. The illustrative screening system includes a microprocessor which divides the basic timed oxygen saturation waveform into slope defined dipoles and then further classifies sequential components of the waveform as slope and interval derived "objects" for microprocessor analysis. The microprocessor then performs an analysis of the objects to further derive more complex objects called coupled oscillations and slope clusters. Each new sequential object is added if it has suitable spatial relationships, and occurs in acceptable order and time interval. The building of complex objects from the repetitive derivation of basic objects along a timed waveform exploits the unique self perpetuating physiological events which underlie the propagation of OSA. The identification and comparison of these objects are then used to determine the presence of sleep apnea. The method can also be applied to a secondary plot of a flow signal parameter such as the maximum exhaled CO(2) or the mean attenuation of the inspiratory loop as a function of time. The utilization of cluster based recognition of events to improve the conventional AHI and DI averaging methods of diagnosis is also discussed. In addition, the differentiation of three basic oxygen saturation cluster types and their potential relevance to the induction of sustained ischemia and cardiovascular morbidity are discussed.

Working memory impairment in early multiple sclerosis. Evidence from an event-related potential study of patients with clinically isolated myelopathy.

Auditory and visual event-related potentials were recorded during a short-term memory task in 24 patients who had recently presented with symptomatically and clinically isolated spinal cord syndromes suspected to be due to multiple sclerosis, and in 24 matched control subjects. Event-related potentials (ERPs) were recorded during two sequential components of the working memory task, first the temporary active memorizing of sets of digits and secondly, their subsequent manipulation, namely digit-probe recognition and matching. The patients' reaction times were slower and showed larger increments than those of the control subjects as the number of items to be memorized was increased. The patients' ERPs during both memorizing and probe matching/recognition phases differed significantly from control subjects for both auditory and visual presentations. The more marked changes were seen in a subgroup of eight patients who had the lowest levels of performance on a battery of general tests of memory and who also made significantly more errors in the working memory task as the memory load increased. In this subgroup, the abnormalities of the ERPs during recognition and matching tests occurred in the component of the response that has been shown to be sensitive to memory loading in healthy control subjects. This study provides objective evidence of subclinical working memory dysfunction in patients at an early stage of demyelinating disease, i.e. when they first present with clinically isolated spinal cord lesions and before they have developed symptoms of cognitive or memory dysfunction. The defect at this early stage is either restricted to processes involved in the formation of a memory trace or, more probably, involves both trace formation and the mechanisms that underly recognition ('retrieval') and matching of memory traces in working memory.

Sequential Patterns of Sex Allocation in Simultaneous Hermaphrodites: Do We Need Models That Specifically Incorporate This Complexity?

Theoretical and empirical studies of sex allocation usually treat sequential and simultaneous hermaphroditism as distinct and disparate forms of allocation. However, the sexual patterns of numerous species have both sequential (e.g., size-based) and simultaneous components. In most cases, we have drawn from sex allocation theory developed for sequential hermaphrodites to explain ontogenetic changes in allocation and from theory developed for simultaneous hermaphrodites to explain the remaining aspects of these sexual patterns rather than develop a more integrated theory. Here I present the evolutionary stable solution (ESS) to a dynamic statevariable model that explicitly combines the effects of size and simultaneous allocation to male and female function in a dynamic game. The model structure and initial parameter values are based on the sexual pattern of the blue-banded goby, Lythrypnus dalli, a simultaneous hermaphrodite. I then compare the natural patterns of sex allocation in L. dalli with the predictions of the model and with those of a dynamic version of the size advantage model. The integrated model predicted variation in allocation, sex-specific size distributions, and seasonal sex ratio better than the sequential hermaphroditism model did. Indeed, the sequential model, using L. dalli parameter values, predicts a dioecious rather than sequentially hermaphroditic allocation pattern. The comparison of these two models illustrates the disadvantage of drawing from two bodies of theory without a formal integrated framework. Furthermore, the comparison focuses attention on the role of costs of reallocation in the evolution of mixed (or intermediate) sexual patterns.

Structure of the mouse behaviour on the elevated plus-maze test of anxiety

The elevated-plus maze is an animal model where the behavioural repertoire of rodents is used to detect effects on anxiety. However, the structure of behaviour has not been duly discerned. The objective was to perform descriptive, sequential and principal components analyses to discern the overall structure of the mouse behaviour on the elevated plus-maze test. Behaviour was videotaped and later analyzed. Behavioural elements were encoded from an ethological point of view, being employed an 8-pattern ethogram. Stretched attend posture (SAP) and head-dippings (Dip) were split into protected (pSAP, pDip) and unprotected (uSAP, uDip) behaviours. Markovian sequential analysis revealed that sniffing is the main pattern, pSAP and pDip are highly linked `anxiety-related' responses, and uSAP is an `approach-avoid conflict' response usually followed by either sniffing on an open arm or closed arm entry. Principal component analysis allowed obtaining four components: (i) anxiolysis—open arm entry, pSAP, pDip and uDip; open arm entry and uDip were positively loaded, in contrast to pSAP and pDip, which were oppositely related to them; (ii) motor activity—closed arm entry, sniffing, rearing, and total arm entries; (iii) approach-avoid conflict—uSAP and negatively loaded, closed arm return; and (iv) displacement—grooming and rearing. Results suggested that open arm entry, pSAP, pDip, and uDip are the best indicators of anxiety on the elevated plus-maze. Closed arm return and uSAP are independent anxiety-related patterns, reflecting an approach-avoid conflict dimension. Results should be taken into account if the effects of drugs or CNS manipulations on Swiss mouse behaviour on the elevated plus-maze are analyzed.

Rate encoding of binaurally alternating low-frequency tone bursts in macaque A1

Integration of sequential components is an essential feature of auditory scene analysis. Humans consistently underestimate by 35–50% the frequency (F) of click trains, when the component clicks alternate between ears, and F exceeds 10 Hz [Axelrod et al., J. Acoust. Soc. Am. 43, 51–55 (1968)]. This suggests a boundary for integration of sequential components. Multiunit Activity (MUA) and current source density (CSD) in A1 of the awake monkey were used to explore neural correlates of this illusion. Phase-locked responses of cortical neuronal ensembles correlate with the perceptions of human listeners [Soc. Neurosci. Abstr. 22:637.18 (1996)]. Above 10 Hz, inhibition in thalamorecipient layers suppressed the response to each ipsilateral click in the train, in regions of high best frequency (BF). Here these observations are extended to low BF sites, which respond poorly to clicks. Responses to 25-ms low-frequency alternating tone bursts exhibit a boundary above 10 Hz, in agreement with click train data. The consistency of this physiologic boundary across the tonotopic map of A1 may represent an important neural substrate for assigning individual components to perceptual streams. [Work supported by DC00657 and the Institute for Music and Neurologic Function of Beth Abraham Hospital.]

A framework for parallel processing in multiblock flow computations

The past several years have witnessed an ever-increasing acceptance and adoption of parallel processing, both for high performance scientific computing as well as for more general purpose applications. Furthermore with increasing needs to perform the complex flow calculations in an efficient manner, the use of the message passing model on distributed networks has emerged as an important alternative to the expensive supercomputers. This work attempts to provide a generic framework to enable the parallelization of all CFD-related works using the master-slave model. This framework consists of (1) input geometry, (2) domain decomposition, (3) grid generation, (4) flow computations, (5) flow visualization, and (6) output display as the sequential components, but performs computations for (2) to (5) in parallel on the workstation clustering. The flow computations are parallized by having multiple copies of the flow-code to solve a PDE on different spatial regions on different processors, while their flow data are exchanged across the region boundaries, and the solution is time-stepped. The Parallel Virtual Machine (PVM) is used for distributed communication in this work.

Initial pursuit responses using a fixation-gapramp paradigm

Pursuit eye movements keep the image of a small moving target near the fovea with an admixture of smooth pursuit and saccades. To probe the initiation of pursuit, four humans and one monkey attended a bright laser spot that was rear-projected on a diffusely illuminated (1 cd/m2) tangent screen. Movement of the viewing eye was recorded with a magnetic search coil. After presenting a stationary target for a random time (1–3 sec), the computer extinguished the target in separate trial blocks for 40, 100, 200, or 500 ms. At the end of this gap period, the target reappeared on the fovea, moving centrifugally at 10°/sec in a random direction before decelerating to a stop.The predominate initial response (< 90%) to unpredictable changes in target motions had four sequential components: a latent period, a primary smooth movement, a small saccade, and then a secondary smooth movement. None of five measured variables depended systematically on the gap duration: the latency to primary smooth pursuit (range of means 144–217 ms), average eye velocity in the first 50 msec of primary smooth pursuit (0.7–3.6°/s), latency to the first saccade (207–319 ms), amplitude of the first saccade (1.6–2.7°), or average eye velocity in the first 100 ms of the secondary smooth pursuit (7.4–11–4°/s). Our data do not support the hypothesis that a separate fixation system has to be disengaged before smooth pursuit can begin, as has been suggested for the saccadic system.