Clock Monitoring Research Articles

A Metastability Risk Prediction and Mitigation Technique for Clock-Domain Crossing With Single-Stage Synchronizer in Near-Threshold-Voltage Multivoltage/ Frequency-Domain Network-on-Chip

For a network-on-chip (NoC) with multiple voltage/frequency domains, metastability hurts the reliability during the clock-domain crossing, especially in the near-threshold-voltage (NTV) region. Conventional multistage synchronizers reduce the probability of metastability but have a high latency penalty. This article presents a technique titled metastability risk prediction and mitigation (MPAM) that predicts the near-future metastability risks by a triple-phase clock monitoring circuitry and mitigates them by a metastability-free clock scheme. Therefore, the MPAM enables only one flip-flop for data synchronization without degrading the reliability against metastability, thus improving the latency and throughput of NoC. We prototyped a 2-by-2 NoC test chip with four independent voltage/frequency domains in a 40-nm low-power (LP) process, featuring the MPAM technique. The measurement shows that the MPAM significantly reduces the metastability condition rate by 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{10}$</tex-math> </inline-formula> times under different clock frequency ratios. Moreover, by enabling only one flip-flop for synchronization, the MPAM-based NoC achieves packet latency reduction, throughput improvement, and energy efficiency gain by 58%, 13.4%, and 8.6%, respectively.

A sub-picosecond digital clock monitoring system

We describe a low-cost system designed to monitor wander in digital clocks with a precision of ≤ 1 ps. With this system we have shown that it is possible to track phase variations at the sub-picosecond level by adding noise to a reference clock. As in many cases where a clock is part of a complex distribution network small changes in temperature and other effects can lead to small changes in the clock's phase. As a further demonstration of the system, we have used it to measure the phase changes induced in optical signals in fibers.

Clock monitoring is associated with age-related decline in time-based prospective memory

In laboratory time-based prospective memory tasks, older adults typically perform worse than younger adults do. It has been suggested that less frequent clock checking due to problems with executive functions may be responsible. We aimed to investigate the role of clock checking in older adults’ time-based prospective memory and to clarify whether executive functions would be associated with clock checking and consequently, with time-based prospective memory. We included 62 healthy older adults (62-85 years of age) and applied tasks of time-based prospective memory as well as of executive functions (i.e., inhibition, fluency, and working memory). We used mediation analysis to test whether time-based prospective memory declined with advancing age due to less frequent clock checking. In addition, we tested whether there would be an association between executive functions and clock checking or time-based prospective memory. Time-based prospective memory declined with advancing age due to less frequent clock checking within 30s prior to intention completion. We only found a link between executive functions and clock checking (or time-based prospective memory) when not controlling for age. Our results support the importance of clock checking for time-based prospective memory and add to the current literature that older adults’ prospective memory declines because they are less able to adapt their clock checking. Yet, the reason why older adults are less able to adapt their clock checking still remains open. Our results do not indicate that executive function deficits play a central role.

Real-time clock comparison and monitoring with multi-GNSS precise point positioning: GPS, GLONASS and Galileo

The precise point positioning (PPP) technique is widely used in time and frequency applications. Because of the real-time service (RTS) project of the International GNSS Service, we can use the PPP technique for real-time clock comparison and monitoring. As a participant in the RTS, the Centre National d’Etudes Spatiales (CNES) implements the PPPWIZARD (Precise Point Positioning with Integer and Zero-difference Ambiguity Resolution Demonstrator) project to validate carrier phase ambiguity resolution. Unlike the Integer-PPP (IPPP) of the CNES, fixing ambiguities in the post-processing mode, the PPPWIZARD operates in the real-time mode, which is also called real-time IPPP (RT-IPPP). This paper focuses on applying the RT-IPPP for real-time clock comparison and monitoring. We review the principle of real-time clock comparison and monitoring, and introduce the methodology of the RT-IPPP technique. The observations of GPS, GLONASS and Galileo were processed for the experiments. Five processing modes were provided in the experiment to analyze the benefits of ambiguity resolution and multi-GNSS. In the clock comparison experiment, the average reduction ratios of standard deviations with respect to the G PPP mode range from 9.7% to 35.0%. In the clock monitoring experiment, G PPP mode can detect clock jumps whose magnitudes are larger than 0.9 ns. The RT-IPPP technique with GRE PPP AR (G) mode allows for the detection of any clock jumps larger than 0.6 ns. For frequency monitoring, G PPP mode allows detection of frequency changes larger than 1.1 × 10−14. When the RT-IPPP technique is applied, monitoring with GRE PPP AR (G) mode can detect frequency changes larger than 6.1 × 10−15.

Improved Multi-GNSS PPP Software for Upgrading the DEMETRA Project Time Monitoring Service

The H2020 DEMETRA project provides short latency clock monitoring services to the time users using the Atomium precise point positioning (PPP) software developed by the Royal Observatory of Belgium. In this paper, three recent updates of the current Atomium software are introduced: adding Galileo signals in the PPP computation; the option to constrain the receiver clock; PPP with integer ambiguity resolution. The advantages of these updates are demonstrated: Combining the Galileo and global positioning system (GPS) signals for PPP time transfer will further improve the frequency stability inside the computation batch; PPP with receiver clock constraint is not only used to reduce the short-term noise of the clock measurements but can also be used for some specific applications to a keep continuous clock solution in the computation batch or retrieve correct clock measurements from extremely noisy environments; the integer PPP allows a continuous clock solution, and improves the mid-term and long-term stability of the frequency transfer compared to the current PPP frequency transfer techniques.

An Application-Level Method of Arbitrary Synchronization Failure Detection in TTEthernet Networks

Precise distributed clock synchronization is important for Time-Triggered Ethernet (TTEthernet) in which fail-arbitrary synchronization failure cannot be treated by existed protocols unless every synchronization node is equipped with a dedicated clock monitoring. A novel method was presented to detect arbitrary synchronization failure by some application-level routines which make distributed decisions mainly by monitoring the protocol control frames (PCFs). An arbitrary failure node can be exactly detected and located by the routine resided on each of the Compression Masters based on the concerned accusation messages sent from Synchronization Masters or Synchronization Clients. The proposed method can make up the weak points on the detection of the arbitrary failure node of the existed fault-tolerant synchronization mechanism and enhance the synchronization node to resist the arbitrary failure for TTEthernet. By our SAL-based model checking, this method had been formally verified to have a fail-arbitrary detection capacity even in a standard integration configuration. Simulations imply that the quality of the whole clock synchronization is effectively improved after the failure node has been isolated.

Identifying behavioural changes for health monitoring applications using the advanced metering infrastructure

ABSTRACTThe rising demand for health and social care, and around the clock monitoring services, is increasing and are unsustainable under current care provisions. Consequently, a safe and independent living environment is hard to achieve; yet the detection of sudden or worsening changes in a patient’s condition is vital for early intervention. The use of smart technologies in primary care delivery is increasing significantly. However, substantial research gaps remain in non-invasive and cost effective monitoring technologies. The inability to learn the unique characteristics of patients and their conditions seriously limits the effectiveness of most current solutions. The smart metering infrastructure provides new possibilities for a variety of applications that are unachievable using the traditional energy grid. By 2020, UK energy suppliers will install 50 million smart meters, therefore, providing access to a highly accurate sensing network. Each smart meter records the electrical load for a given property at 30 minute intervals. This granular data captures detailed habits and routines through the occupant’s interactions with electrical devices, enabling the detection and identification of alterations in behaviour. The research presented in this paper explores how this data could be used to achieve a safe living environment for people living with progressive neurodegenerative disorders.

Data Timing, Time Transfer and On-board Clock Monitoring for Space Astrometry with Gaia

The paper discusses the problematic of data timing in the framework of the space astrometry mission Gaia. For various reasons related both to astrometry and to the measuring principles of the Gaia instrument it is mandatory to assign a highly stable and accurate time tag for each observational point. For this purpose Gaia has a Rb clock on board. That on-board clock is a free-running oscillator and must be regularly synchronized with TCB which is used as the underlying relativistic coordinate time scale in the whole Gaia data processing. To monitor the reading of the on-board clock with respect to TCB (or any other timescale) a one-way clock synchronization scheme is implemented. This scheme takes into account all known theoretical effects (e.g., relativity, tropospheric delay, etc.) and allows one both to monitor the health of the on-board clock and to create a clock model at the accuracy of better than 1 microsecond.

Weighted Performance Metrics for Automatic Neonatal Seizure Detection Using Multiscored EEG Data.

In neonatal intensive care units, there is a need for around the clock monitoring of electroencephalogram (EEG), especially for recognizing seizures. An automated seizure detector with an acceptable performance can partly fill this need. In order to develop a detector, an extensive dataset labeled by experts is needed. However, accurately defining neonatal seizures on EEG is a challenge, especially when seizure discharges do not meet exact definitions of repetitiveness or evolution in amplitude and frequency. When several readers score seizures independently, disagreement can be high. Commonly used metrics such as good detection rate (GDR) and false alarm rate (FAR) derived from data scored by multiple raters have their limitations. Therefore, new metrics are needed to measure the performance with respect to the different labels. In this paper, instead of defining the labels by consensus or majority voting, popular metrics including GDR, FAR, positive predictive value, sensitivity, specificity, and selectivity are modified such that they can take different scores into account. To this end, 353 hours of EEG data containing seizures from 81 neonates were visually scored by a clinical neurophysiologist, and then processed by an automated seizure detector. The scored seizures were mixed with false detections of an automated seizure detector and were relabeled by three independent EEG readers. Then, all labels were used in the proposed performance metrics and the result was compared with the majority voting technique and showed higher accuracy and robustness for the proposed metrics. Results were confirmed using a bootstrapping test.

The daily life of people with disabilities: experience of Lappeenranta

The article is devoted to the experience of social services in South Karelia (region of Finland) in respect of different types of urban support for disabled people in the areas of employment, housing and hobbies. The article describes the work of institutions providing assistance to people with disabilities and the services which are being provided by social service Eksote in Lappeenranta, Imatra and Parikkale. The article describes the work of centers round the clock monitoring and employment for the day, as well as the daily lives of people with Down syndrome, severe autism, intellectual disabilities. The attention is focused on the best practices in Finland, enabling the disabled child to engage in open employment. The article informs about the kinds of financial support for disabled people in Finland and assistance from the National Insurance Institute Kela, including the payment of rental housing. This article describes the features and differences of the centers around the clock care for people with disabilities in South Karelia: Houses “Petyayamyaki” and Private accommodation center “Villa of Karelia “for people requiring intensive care. The article describes the features of the day centers of employment for people with disabilities in Finland: the Center for Independent Living Support “Arttu” and Center “Valtsy.” According to the official position of the Government of Finland, persons with disabilities have the same rights as all other citizens of the country, and they have possibility to make decisions about their own lives. The Finnish system of medical and social rehabilitation of people with disabilities deserves the attention and replication in Russia.

Предупреждение пенитенциарной преступности: проблемы и пути решения

As a result of convicts employees’ poll, study of judicial practice and analysis of statistical data the author revealed the main problems preventing penitentiary prison crime. Bare stuff, insufficient qualifications of employees, employee turnover, crime liaison officer with the criminal world, lack of work organization convicted — these problems are causality reduction for convicts, increase the feeling of permissiveness supervision density from convicts, increase the number of complaints and appeals on the work of correctional institutions, a possible deterioration of the operating environment, reducing the output level of the convicts in paid work and as a consequence of the impossibility of the convicted have the funds to account. The author proposes measures of warning penal crime by improving the implementation of innovative safety systems which can reduce the burden on the staff of the correctional facility, arrange round the clock monitoring of prisoners, as well as the employment of convicts by attracting outside organizations on ways to use the best practices of some of territorial bodies.

Extending Required Navigation Performance to Include Time Based Operations and the Vertical Dimension

Extending Required Navigation Performance to Include Time Based Operations and the Vertical Dimension

High-rate clock variations of the Galileo IOV-1/2 satellites and their impact on carrier tracking by geodetic receivers

The carrier signals of the first two Galileo satellites, IOV-1 and IOV-2, exhibit subtle phase variations, which may cause high-rate oscillations in carrier phase measurements of geodetic-grade receivers as well as associated Doppler measurement errors. The carrier phase oscillations slightly exceed the noise level of the measurements and have been attributed to a subtle cross talk of signals from two active atomic frequency standards in the clock monitoring and control unit (CMCU). This cross talk is only present in the first two IOV satellites, and its practical implications have partly been compensated by now through a suitable configuration of the CMCU. Nevertheless, a proper understanding of the phenomenon is deemed relevant to the interpretation of Galileo IOV measurements collected with global ground networks in the 2012 to early 2015 time frame. Also, the data collected so far offer valuable insight into the tracking of high-frequency signal variation of geodetic receivers that are of interest for applications such as structural monitoring or earthquake research. We present practical measurements from zero-baseline tests of common geodetic receivers with data rates of 1/30---1 Hz as well as dedicated tests with high-rate (50---100 Hz) receivers to evidence the phenomenon. Efforts are made to understand the different response of specific receivers based on generic receiver tracking and measurement generation concepts.

Terrestrial Trunked Radio (TETRA) exposure and its impact on slow cortical potentials

BackgroundStudies have shown that exposure to radiofrequency electromagnetic fields (RF-EMF) in the mobile communication frequency range may induce physiological modifications of both spontaneous as well as event-related human electroencephalogram. So far, there are very few peer-reviewed studies on effects of Terrestrial Trunked Radio (TETRA), which is a digital radio communication standard used by security authorities and organizations in several European countries, on the central nervous system. ObjectivesTo analyze the impact of simulated TETRA handset signals at 385MHz on slow cortical potentials (SCPs). Methods30 young healthy males (25.2±2.7 years) were exposed in a double-blind, counterbalanced, cross-over design to one of three exposure levels (TETRA with 10g averaged peak spatial SAR: 1.5W/kg, 6.0W/kg and sham). Exposure was conducted with a body worn antenna (especially designed for this study), positioned at the left side of the head. Subjects had 9 test sessions (three per exposure condition) in which three SCPs were assessed: SCP related to a clock monitoring task (CMT), Contingent negative variation (CNV) and Bereitschaftspotential (BP). ResultsNeither behavioral measures nor the electrophysiological activity was significantly affected by exposure in the three investigated SCP paradigms. Independent of exposure, significant amplitude differences between scalp regions could be observed for the CMT-related SCP and for the CNV. ConclusionsThe present results reveal no evidence of RF-EMF exposure-dependent brain activity modifications investigated at the behavioral and the physiological level.

Age-related differences in time-based prospective memory: The role of time estimation in the clock monitoring strategy

Time-based prospective memory (TBPM) is required when it is necessary to remember to perform an action at a specific future point in time. This type of memory has been found to be particularly sensitive to ageing, probably because it requires a self-initiated response at a specific time. In this study, we sought to examine the involvement of temporal processes in the time monitoring strategy, which has been demonstrated to be a decisive factor in TBPM efficiency. We compared the performance of young and older adults in a TBPM task in which they had to press a response button every minute while categorising words. The design allowed participants to monitor time by checking a clock whenever they decided. Participants also completed a classic time-production task and several executive tasks assessing inhibition, updating and shifting processes. Our results confirm an age-related lack of accuracy in prospective memory performance, which seems to be related to a deficient strategic use of time monitoring. This could in turn be partially explained by age-related temporal deficits, as evidenced in the duration production task. These findings suggest that studies designed to investigate the age effect in TBPM tasks should consider the contribution of temporal mechanisms.

Marine systems biology.

EDITORIAL article Front. Genet., 13 May 2015Sec. Systems Biology Archive Volume 6 - 2015 | https://doi.org/10.3389/fgene.2015.00181

Notes from the Underground: The Rise of Nouri Al-Maliki and the New Islamists

Notes from the Underground: The Rise of Nouri Al-Maliki and the New Islamists

Real-Time GPS Clock Monitoring with IGS Ultra-Rapid Products

The objective of this study is to develop a real-time strategy that results in higher precision than any real-time solutions currently available for GPS satellite clock monitoring. A real-time time transfer methodology was employed for satellite clock monitoring, composed of carrier phase smoothed code measurements and IGS ultra-rapid products to obtain precise satellite positions. The performance of the time transfer method was assessed by comparison with the results based on the all-in-view method using the broadcasting ephemeredes. The results showed that the stability of satellite clock monitoring for a short-term period was improved by the proposed method.

Introspecting a conscious decision or the consciousness of a decision?

Introspection is a highly elusive, and thus recurrently debated, topic in consciousness studies. On one hand introspection can be meant as the direct account of what happens in one’s mind. On the other hand it is argued that what is reported through introspection is not a reliable description of what occurred in one’s mind but it is a reconstruction, often invalidated by beliefs and inferences about how the mind works. Indeed introspection may be both things. It depends on what and how the subject is asked to introspect. Thus, the thorough analysis of the setting and of the instructions given to the participants is crucial to highlight what is actually investigated in the experiments. Little changes in the experimental conditions and in the wording can in fact alter deeply the introspective act. Let us consider the setting devised by Guggisberg, Dalal, Schnider, and Nagarajan (2011). Participants knew that, in the free choice condition (the most relevant to the aims of the study), they had to choose to move either the right or left finger approximately the same number of times. So, (1) they had to keep in mind at least a part of the sequence of their previous choices in order to check whether they were not privileging a finger over the other. Then they had (2a) to decide which finger they would move and, concurrently, (2b) look at the clock and (2c) detect the position of the clock hand when they decided to move the finger. They had (3) to memorize the position of the clock hand. Afterword, they had (4) to decide to move the finger and (5) operate accordingly. The core of this process is the second phase. It is worth noting that during such a phase three acts have to be performed simultaneously by the participant. Moreover, such a phase may be affected by the need to activate the memory of the previous choices (phase 1) and to remind what has to be performed successively (phase 3). Each act can have its own cerebral counterpart. For instance, it has been showed recently that clock monitoring (phase 2b) in a Libet-like experiment is associated to a distinct EEG activity in the brain (Miller, Shepherdson, & Trevena, 2011). Guggisberg et al. argued that also the introspective act in itself has a specific neural counterpart. Even though Guggisberg et al.’s study shows apparent similarities with other Libet-like experiments, it is deeply different. Firstly, contrary to usual experiments, the cerebral counterpart identified by the authors is not intended to correspond to one of the phases of the decision process but rather to an act (introspection) which covers all the central phases. In Guggisberg et al.’s experiment participants were asked to identify when they ‘‘decided which finger to move’’. In order to identify such a moment participants had to be aware that they had made the choice. Presumably the choice was preceded by a sort of planning or pre-programming process (even though participants were asked to avoid predefined response patterns; however, the procedure fails to ensure that participants were prevented to do so: for instance, they might have thought to move the right finger the next time the phoneme corresponding to the free choice condition would appear), but in this case it is irrelevant if such process was conscious or unconscious since the focus was on the awareness of having decided but not on the alleged precursors of the decision. This sweeps away the criticisms usually addressed to the experiments aimed at showing that an unconscious mechanism preceded the awareness of the decision. The second difference concerns the fact that the kind of introspection investigated by Guggisberg et al. implies a lowerorder level of consciousness than introspection investigated by other Libet-like experiments where participants were asked to report, for instance, ‘‘when they made the conscious decision which finger to move’’ (Soon, Brass, Heinze, & Haynes, 2008). The difference is subtle but important since two different kinds of introspection are underlying. Conscious decision and con-

Effects of Clock Monitoring on Electroencephalographic Activity

Electroencephalographic (EEG) activity was recorded while participants waited to make spontaneous key-press movements (Experiment 1) or waited for tones in a pitch judgment task (Experiment 2). In one condition of each experiment, participants also had to report the position of a spot traveling on a clock at the crucial time point (i.e., when they decided to move or when the tone was presented), mimicking a procedure used to assess the time of conscious awareness of an event of interest. In a second condition, there was no clock or temporal judgment. Average EEG activity preceding key presses was substantially different when participants had to monitor the clock than when they did not. Smaller clock-related differences in average EEG activity were also present preceding tone onsets. The effects of clock monitoring on EEG activity could be responsible for previous reports that movement-related brain activity begins before participants have consciously decided to move (e.g., Libet, Gleason, Wright, & Pearl, 1983).