Search

Nowadays, the BDS-3 satellites transmit new signals B1c and B2a that are compatible with GPS and Galileo, which is meaningful to fully take advantage of the BDS positioning capability. However, further research and analysis are needed to investigate the precise point positioning ambiguity resolution (PPP-AR) performance of the new BDS-3 signal combination. In this manuscript, the characteristics and quality of differential code bias (DCB), inter frequency clock bias (IFCB) and uncalibrated phase delay (UPD) of BDS-3 new signals are analyzed based on 30 days observation data from 70 multi GNSS experiment (MGEX) stations. The results show that the mean value of IFCB between B1I/B3I and B1C/B2a is 1.18 cm, which indicates that the IFCB can be ignored when performing the clock errors reference conversion of BDS-3 satellites. Besides, the DCB of the new BDS-3 signals varies within 0.2 ns over 30 days, and with a difference of 0.08 ns compared to the DCB product provided by chinese academy of science (CAS). The percentage of the estimated residuals less than 0.25 cycles for new signals WL UPD and less than 0.15 cycles for new signals NL UPD are 99.76% and 97.19%, respectively. The above results demonstrate the reliability of the DCB and UPD products, which can be used to estimate the carrier phase observable specific signal bias (OSB) product for the new signals. The average positioning errors of the BDS-3 new signals static PPP-AR in the N, E and U directions is 0.50 cm, 0.43 cm and 1.62 cm respectively, with an improvement of 18.3%, 28.3% and 11.5% compared to the ambiguity float static PPP. The average positioning errors of the kinematic PPP-AR are 2.09 cm, 2.67 cm and 4.79 cm in three directions, respectively, with an improvement of 17.1%, 23.9% and 15.7% compared to the ambiguity float PPP. The convergence time of the static and kinematic PPP-AR are 26.36 min and 29.12 min, respectively. [ABSTRACT FROM AUTHOR]

Global navigation satellite system (GNSS) precise point positioning (PPP) has potential as an alternative or replacement for real-time kinematic (RTK) processing. In this work, we reached for RTK levels of performance without the need for local information through PPP (i.e., centimeter-level positioning that was reached near-instantaneously). This work makes use of information currently available from processing signals from global positioning system (GPS), Galileo, BeiDou-2/3, and GLONASS by fixing ambiguities for the first three constellations on all available frequencies. This processing was done using a four-frequency, four-constellation uncombined decoupled clock model (DCM) that has been expanded as part of this work. The results were tested on 1448 global datasets and showed that instantaneous convergence on average to 2.5 cm error can be achieved for 81% of the stations. These findings were reinforced by the results of epoch-by-epoch processing, as an average of 80% of all single epochs converged below 2.5 cm error at 1σ, as opposed to less than the 0.5% typically observed for classic PPP. [ABSTRACT FROM AUTHOR]

As an endogenous time‐keeping mechanism, the circadian clock benefits plant fitness and adaptation to the rhythmically changed diel environments. The key components within the core oscillator of plant circadian clock have been extensively characterised, however, the fine‐tuning circadian regulators are still less identified. Here, we demonstrated that BBX28 and BBX29, the two B‐Box V subfamily members lacking DNA‐binding motifs, are involved in the regulation of Arabidopsis circadian clock. Over‐expressing either BBX28 or BBX29 significantly lengthened circadian period, whereas loss‐of‐function of BBX28 rather than BBX29 displayed a modestly long period in free‐running condition. Mechanistically, BBX28 and BBX29 interacted with core clock components PRR5, PRR7 and PRR9 in nucleus to augment their transcriptional repressive activities. RNA‐sequencing analysis further revealed that BBX28 and BBX29 shared 686 common differentially expressed genes (DEGs) including a subset of known direct transcriptional targets of PRR proteins within core oscillator, including CCA1, LHY, LNKs and RVE8 etc. Intriguingly, PRR proteins can feedback repress BBX28 and BBX29 transcription by associating with their promoters. Together, our findings unmasked an exquisite mechanism in which BBX28 and BBX29 interplay with PRR proteins to fine‐tune the circadian pace. Summary statement: BBX28/29 interact with PRR to augment their transcriptional repressive activity, while PRR proteins feedback inhibit the transcription of BBX28/29, which cooperatively orchestrates the circadian clock. [ABSTRACT FROM AUTHOR]

By keeping the very same transmission rate, a scheme is provided by DETFF (double-edge triggered flip-flops) for power dissipation reduction. As a result, they are suitable for use as shift registers. This investigation discussed various previous DETFF designs and demonstrated a new DETFF circuit applied to construct an 8-bit low-power shift register. This study makes a significant contribution by using two parallel data paths that operate in a single clock's opposing phases where an inverted input trigger is unnecessary. TSMC 90-nm complementary metal-oxide semiconductor (CMOS) technology was used to implement the proposed shift register. Comparing the proposed DETFF with prior works, it has fewer transistor counts since the negated input trigger and auxiliary devices were removed, resulting in lower area cost and lower power dissipation. At 100 MHz clock frequency and lower supply voltage of 1.0 V, it demonstrates a power consumption of 3.352 mW on silicon, making it suitable for low-power applications. Lastly, it has the best performance compared with prior works speaking of larger scale, as demonstrated by the chip's functionality and jitter measurement at the maximum frequency of 200 MHz. [ABSTRACT FROM AUTHOR]

A negative voltage generator was developed that can be used in the drivers of smart window films (SWF), which have typical operating voltages of ± 8 to ± 10 V. It consists of four Negative Charge Pump (NCP) stages and a 4-phase non-overlapping Clock Generator (CG), where the 4 NCP stages are configurable by external digital signals. This generates a wide output voltage range necessary to control different SWF modes, such as opaque, transparent, and tinted modes. TSMC 0.18- μ m HV BCD (High-Voltage Bipolar-CMOS-DMOS) process was used to fabricate the proposed negative voltage generator on silicon. Measurement results demonstrate that at switching frequency (fsw) = 20 MHz, supplied voltage (VDD) = 4.5 V and Vin = GND, it generates a wide output voltage range of −3.9 to −14.0 V, achieving the widest voltage range among the prior works, which covers the required negative voltage range for SWF usage. The peak efficiency is measured on silicon to be 58.08%. [ABSTRACT FROM AUTHOR]

Ambiguity resolution (AR) is critical for enhancing the orbit accuracy in precise orbit determination (POD) for low earth orbit (LEO) satellites. While orbit estimation using single-difference (SD) AR has been widely researched, the investigation of orbit estimation using undifferenced (UD) AR for LEO satellites is limited due to time-varying hardware biases at the LEO receiver end. To address this deficiency, we propose an improved UD AR method for LEO satellite orbit determination. The method employs the optimal integer datum ambiguity for a 1-day observation arc, and the random-walk clock model is utilized to transfer the integer ambiguity datum to the other epochs, which enables the arc-wise ambiguities to regain the integer property within the time frame. To validate the effectiveness of our improved method, numerical experiments are conducted. Moreover, we assess the performance of the random-walk clock model for a spaceborne ultra-stable oscillator (USO). The high frequency stability of the USO establishes the satisfactory requirements for this study. Both in the kinematic and dynamic modes, the AR success rates of our improved method are ∼ 2% higher than that of the current SD AR method, and the orbit results indicate a slight improvement. The 3-Dimensional (3D) root-mean-squares (RMS) of the orbit differences between JPL precise science orbits (PSO) and our orbits are reduced by up to 4% and 5% for kinematic and dynamic orbits, respectively. The subtle benefit is also proven by K-band ranging (KBR) system validations. In the case of the Gravity Recovery and Climate Experiment Follow-on (GFO) satellites, the results indicate that the effect of our improved UD AR can be equivalent to that of SD AR. Our improved UD AR method can be a good alternative for its superior ability to generate hardware delay at the LEO receiver end. [ABSTRACT FROM AUTHOR]

Recent studies suggest that epigenetic rejuvenation can be achieved using drugs that mimic calorie restriction and techniques such as reprogramming‐induced rejuvenation. To effectively test rejuvenation in vivo, mouse models are the safest alternative. However, we have found that the recent epigenetic clocks developed for mouse reduced‐representation bisulphite sequencing (RRBS) data have significantly poor performance when applied to external datasets. We show that the sites captured and the coverage of key CpGs required for age prediction vary greatly between datasets, which likely contributes to the lack of transferability in RRBS clocks. To mitigate these coverage issues in RRBS‐based age prediction, we present two novel design strategies that use average methylation over large regions rather than individual CpGs, whereby regions are defined by sliding windows (e.g. 5 kb), or density‐based clustering of CpGs. We observe improved correlation and error in our regional blood clocks (RegBCs) compared to published individual‐CpG‐based techniques when applied to external datasets. The RegBCs are also more robust when applied to low coverage data and detect a negative age acceleration in mice undergoing calorie restriction. Our RegBCs offer a proof of principle that age prediction of RRBS datasets can be improved by accounting for multiple CpGs over a region, which negates the lack of read depth currently hindering individual‐CpG‐based approaches. [ABSTRACT FROM AUTHOR]

Conventionally, a linear feedback shift register (LFSR) constitutes linear sets of sequences with predictable periods, which are considered vulnerable to intruders. Besides, an LFSR limits the sequences of scan-for-test patterns. This work introduces a private key, which is a collection of keywords, to program the feedback coefficients and initial states of the LFSR, where each keyword modulates the LFSR with a different polynomial of the same degree. That is, each polynomial generates a linear set of sequences. Consequently, the aggregate polynomial has a set of unpredictable and nonlinear sequences with high statistical randomness. The keyword, which holds the coefficients and initial states of the LFSR, can be managed in a few bits and stored in first-in first-out memory array. HSPICE simulations for 90 nm CMOS technology verify the functionality and speed of the proposed programmable feedback shift register (PFSR) of size 16-bit with 64 keywords. Results show a clock speed of 500 MHz with a power consumption of 73 µW and transistor count of 37,593, wherein the overall period has 4,194,240 unpredictable nonlinear sequences that surpass most LFSR structures. The PFSR can be suited for ASIC and reconfigurable HDL synthesis for efficient stream cipher and scan-for-test applications. [ABSTRACT FROM AUTHOR]

Epigenetic approaches for estimating the age of living organisms are revolutionizing studies of long‐lived species. Molecular biomarkers that allow age estimates from small tissue biopsies promise to enhance studies of long‐lived whales, addressing a fundamental and challenging parameter in wildlife management. DNA methylation (DNAm) can affect gene expression, and strong correlations between DNAm patterns and age have been documented in humans and nonhuman vertebrates and used to construct "epigenetic clocks". We present several epigenetic clocks for skin samples from two of the longest‐lived cetaceans, killer whales and bowhead whales. Applying the mammalian methylation array to genomic DNA from skin samples we validate four different clocks with median errors of 2.3–3.7 years. These epigenetic clocks demonstrate the validity of using cytosine methylation data to estimate the age of long‐lived cetaceans and have broad applications supporting the conservation and management of long‐lived cetaceans using genomic DNA from remote tissue biopsies. [ABSTRACT FROM AUTHOR]

JC polyomavirus (JCV) has an ethno-geographical distribution across human populations. Study the origins of the population of Misiones (Argentina) by using JCV as genetic marker. Viral detection and characterization was conducted by PCR amplification and evolutionary analysis of the intergenic region sequences. 22 out of 121 samples were positive for JCV, including 5 viral lineages: MY (n = 8), Eu-a (n = 7), B1-c (n = 4), B1-b (n = 2) and Af2 (n = 1). MY sequences clustered within a branch of Native American origin that diverged from its Asian counterpart about 21,914 years ago (HPD 95% interval 15,383–30,177), followed by a sustained demographic expansion around 5000 years ago. JCV in Misiones reflects the multiethnic origin of the current population, with an important Amerindian contribution. Analysis of the MY viral lineage shows a pattern consistent with the arrival of early human migrations to the Americas and a population expansion by the pre-Columbian native societies. • JCV classification was 36% American, 49.8% European, 9% Asian and 4.5% African. • American MY lineage was dated at 21,914 (15,383–30,177) years before present. • The demographic expansion of American MY began 5000 years before present. • The emergence of Amerindian complex societies may explain viral expansion. • Alternative models of virus evolution and TDR clocks were also explored. [ABSTRACT FROM AUTHOR]

Relaxed clock Bayesian evolutionary inference (BEI) enables the co‐estimation of phylogenetic trees and evolutionary parameters associated with models of character and lineage evolution. Fast advances in new model developments over the past decade have boosted BEI as a major macroevolutionary analytical framework using morphological and/or molecular data across vastly different study systems. However, there is limited availability of bioinformatic tools to pre‐ and postprocess data from BEI, such as identifying morphological data partitions, or statistically testing and creating publication quality plots of evolutionary hypotheses.Here, we introduce EvoPhylo, an r package to perform automated morphological character partitioning and analyse macroevolutionary parameter from relaxed clock (time‐calibrated) BEI outputted by the programs Mr.Bayes and BEAST2. These include rates of evolution and mode of selection for each character partition, diversification rate parameters, and handling fossil‐only posterior trees.We present the theoretical background behind EvoPhylo's functions and analytical tools for evolutionary hypothesis testing, its potential uses, and interpretation of its results with a series of vignettes and links to a step‐by‐step tutorial using examples from two empirical datasets.EvoPhylo will facilitate the use of Bayesian relaxed clocks as a tool for macroevolutionary inference across a wide range of users and fields of research, especially those that make usage of morphological datasets, from paleontological to total evidence dating analyses. [ABSTRACT FROM AUTHOR]

Background: The circadian clock is an evolutionarily conserved mechanism that exerts pervasive temporal control in stem cell behavior. This time-keeping machinery is required for orchestrating myogenic progenitor properties in regenerative myogenesis that ameliorates muscular dystrophy. Here we report a screening platform to discover circadian clock modulators that promote myogenesis and identify chlorhexidine (CHX) as a clock-activating molecule with pro-myogenic activities. Methods: A high-throughput molecular docking pipeline was applied to identify compounds with a structural fit for a hydrophobic pocket within the key circadian transcription factor protein, Circadian Locomotor Output Cycles Kaput (CLOCK). These identified molecules were further screened for clock-modulatory activities and functional validations for pro-myogenic properties. Results: CHX was identified as a clock activator that promotes distinct aspects of myogenesis. CHX activated circadian clock that reduced cycling period length and augmented amplitude. This action was mediated by the targeted CLOCK structure via augmented interaction with heterodimer partner Bmal1, leading to enhanced CLOCK/Bmal1-controlled transcription with upregulation of core clock genes. Consistent with its clock-activating function, CHX displayed robust effects on stimulating myogenic differentiation in a clock-dependent manner. In addition, CHX augmented the proliferative and migratory activities of myoblasts. Conclusion: Our findings demonstrate the feasibility of a screening platform to discover clock modulators with myogenic regulatory activities. Discovery of CHX as a pro-myogenic molecule could be applicable to promote regenerative capacities in ameliorating dystrophic or degenerative muscle diseases. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Precise timing plays a key role in the time‐sensitive industrial Internet of Things (IIoT). However, precise time synchronization requires more frequent packet exchange, which consumes more communication bandwidth and energy. This is a particular challenge in battery‐powered wireless nodes, and low communication costs have become an important factor in clock synchronization. To address the challenge of achieving low communication cost clock synchronization in distributed wireless sensor networks, this paper proposes an improved event‐triggered control and synchronization scheme with a novel asynchronous broadcast packet exchange protocol. Unlike the traditional event‐triggered control scheme which is based on synchronous polling packet exchange, this proposed asynchronous broadcast packet exchange is more communication efficient and requires fewer number of packet exchanges. And it is worth noting that the proposed algorithm in this paper is a distributed algorithm and does not require real‐time acquisition of information from neighbouring nodes. Finally, a numerical example is given to illustrate the effectiveness of the proposed event‐triggered control strategy. The efficiency and precision of the proposed clock synchronization method is evaluated by intensive simulations, which show that the number of packet exchange is reduced by 60% for a moderate IIoT network and is particularly useful for large scale network. [ABSTRACT FROM AUTHOR]

Background: DNA methylation (DNAm) is robustly associated with chronological age in children and adults, and gestational age (GA) in newborns. This property has enabled the development of several epigenetic clocks that can accurately predict chronological age and GA. However, the lack of overlap in predictive CpGs across different epigenetic clocks remains elusive. Our main aim was therefore to identify and characterize CpGs that are stably predictive of GA. Results: We applied a statistical approach called 'stability selection' to DNAm data from 2138 newborns in the Norwegian Mother, Father, and Child Cohort study. Stability selection combines subsampling with variable selection to restrict the number of false discoveries in the set of selected variables. Twenty-four CpGs were identified as being stably predictive of GA. Intriguingly, only up to 10% of the CpGs in previous GA clocks were found to be stably selected. Based on these results, we used generalized additive model regression to develop a new GA clock consisting of only five CpGs, which showed a similar predictive performance as previous GA clocks (R2 = 0.674, median absolute deviation = 4.4 days). These CpGs were in or near genes and regulatory regions involved in immune responses, metabolism, and developmental processes. Furthermore, accounting for nonlinear associations improved prediction performance in preterm newborns. Conclusion: We present a methodological framework for feature selection that is broadly applicable to any trait that can be predicted from DNAm data. We demonstrate its utility by identifying CpGs that are highly predictive of GA and present a new and highly performant GA clock based on only five CpGs that is more amenable to a clinical setting. [ABSTRACT FROM AUTHOR]

Artificial light at night (ALAN) is a pervasive pollutant that alters physiology and behavior. However, the underlying mechanisms triggering these alterations are unknown, as previous work shows that dim levels of ALAN may have a masking effect, bypassing the central clock. Light stimulates neuronal activity in numerous brain regions which could in turn activate downstream effectors regulating physiological response. In the present study, taking advantage of immediate early gene (IEG) expression as a proxy for neuronal activity, we determined the brain regions activated in response to ALAN. We exposed zebra finches to dim ALAN (1.5 lux) and analyzed 24 regions throughout the brain. We found that the overall expression of two different IEGs, cFos and ZENK, in birds exposed to ALAN were significantly different from birds inactive at night. Additionally, we found that ALAN-exposed birds had significantly different IEG expression from birds inactive at night and active during the day in several brain areas associated with vision, movement, learning and memory, pain processing, and hormone regulation. These results give insight into the mechanistic pathways responding to ALAN that underlie downstream, well-documented behavioral and physiological changes. [ABSTRACT FROM AUTHOR]

Processing physical quantities into an indirect signal is a standard method of transferring information about the measured quantity to the master system, which analyzes the data obtained from the acquisition system. The intermediate signal is very often the voltage, but another transmission medium can be the frequency of the output signal of the "physical quantity-to-frequency" converter. The article presents the implementation of the adaptive method of selecting the clock signal frequency of the counter working in the converter. The issue of selecting the clock signal frequency for the required processing range of the transducer is discussed in detail. The application of the method using the STM32L476RG microcontroller is presented. The principle of checking the processing range of the developed transducer model is discussed. The algorithms of transducer operation in basic and adaptive modes of measuring the period of the variable frequency signal are proposed. The results of operation, in both modes, of the transducer model of frequency processing are presented, along with the metrological analysis of the results. The influence of selected approximations used to reconstruct the measured quantity on the final presentation of the measurement result is discussed. [ABSTRACT FROM AUTHOR]

With the emerging of Internet of Things (IoT) industry, applications like smart power plugs, security ID tags, home automation and wearable electronic devices all make the demand for low-power WiFi chips impendency. In this paper, a low-power 2.4 GHz 802.11b/g/n WiFi system-on-chip (SoC) is designed and implemented with 40-nm CMOS process, with area of 8.1 mm2. The low-power SoC integrates 32-bit microcontroller, 802.11b/g/n WiFi baseband, 2.4 GHz RF transceiver, ample memory space, ADC, 6-channel PWM, flexible I/O interfaces, multi-stage power management module, etc. It has several sleep modes with extremely low leakage current as 0.8 mA/12 µA in light/deep sleep mode and 0.4 µA in shutdown mode to reduce the power consumption. High performance is demonstrated, including Pout (−28 dB/-30 dB EVM) of 20.1 dBm/19.1 dBm and RX sensitivity of −76 dBm/-74 dBm meanwhile the total current of 148.5 mA/146.5 mA (TX) for 54 Mbps OFDM/HT20 MCS7. [ABSTRACT FROM AUTHOR]

In this article, we present a new numerical approach for solving a class of systems of fractional initial value problems based on the operational matrix method. We derive the method and provide a convergence analysis. To reduce computational cost, we transform the algebraic problem produced by this approach into a set of 2 × 2 nonlinear equations, instead of solving a system of 2 m × 2 m equations. We apply our approach to three main applications in science: optimal control problems, Riccati equations, and clock reactions. We compare our results with those of other researchers, considering computational time, cost, and absolute errors. Additionally, we validate our numerical method by comparing our results with the integer model when the fractional order approaches one. We present numerous figures and tables to illustrate our findings. The results demonstrate the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Quantum networks provide the framework for quantum communication, clock synchronization, distributed quantum computing, and sensing. Implementing large-scale and practical quantum networks relies on the development of scalable architecture and integrated hardware that can coherently interconnect many remote quantum nodes by sharing multidimensional entanglement through complex-medium quantum channels. We demonstrate a multichip multidimensional quantum entanglement network based on mass-manufacturable integrated-nanophotonic quantum node chips fabricated on a silicon wafer by means of complementary metal-oxide-semiconductor processes. Using hybrid multiplexing, we show that multiple multidimensional entangled states can be distributed across multiple chips connected by few-mode fibers. We developed a technique that can efficiently retrieve multidimensional entanglement in complex-medium quantum channels, which is important for practical uses. Our work demonstrates the enabling capabilities of realizing large-scale practical chip-based quantum entanglement networks. [ABSTRACT FROM AUTHOR]

In addition to the legacy B1I and B3I signals, the BeiDou global navigation satellite system (Beidou-3) are capable of transmitting B1C/B2a/B2b/B2 several new navigation signals. The multi-frequency signals of Beidou-3 are expected to benefit precise point positioning with ambiguity resolution (PPP AR). Currently, most international GNSS service (IGS) analysis center adopt the Beidou-3 B1I/B3I ionosphere-free (IF) combination to estimate the satellite orbit and clock products, the Beidou-3 B1C/B2a/B2b/B2 phase biases should be aligned with satellite B1I/B3I clocks. Therefore, in this paper, the multi-frequency phase observable-specific phase biases (OSB) estimation method is developed for Beidou-3 system, which is compatible with satellite B1I/B3I legacy clock. Experimenting on the Beidou-3 multi-frequency observations over 30 days from the globally distributed stations, the characteristics of the estimated Beidou-3 multi-frequency phase OSB and the positioning performance of the IF kinematic PPP AR with different frequency combination are assessed. After the OSB are used in the raw observations, the results demonstrate that the wide-lane ambiguities residuals within ± 0.25 cycle are approximately 97%, 94%, 97% and 93% for Beidou-3 B1I/B3I, B1C/B2b, B1C/B3I and B1C/B2a combinations, respectively. When the OSB and satellite B1I/B3I legacy clock are used in different dual-frequency combination PPP AR tests, over 94% of the corresponding narrow-lane ambiguities are within ± 0.25 cycle. In addition, owing to the low noise of the B1C/B2a combination, the positioning performance of B1C/B2a PPP AR outperforms that of the other frequency combinations. More specifically, in case of B1I/B3I PPP AR, almost 22.7 min is required to successfully achieve 10 cm for east, north and up components, while only 18.8 min is needed for B1C/B2a PPP AR. The results show that such phase OSB, along with Beidou-3 satellite B1I/B3I legacy clock, can fully recover the PPP ambiguities based on all available frequency choices and observable combinations. [ABSTRACT FROM AUTHOR]

This paper presents a charge-pump phase-locked loop (PLL) frequency-synthesizer-based low-jitter wideband clock generator for multi-protocol data communications applications. Automatic frequency calibration (AFC) using linear variable time window technology and modified multi-modulus dividers (MMD) based on sub-multi-modulus dividers (SMMD) are developed for faster locking, lower jitter, and implementation of multi-protocol data communications applications. The clock generator is fabricated in 0.18 μm CMOS technology. The measured division ratio of the multi-modulus divider ranges from 1.875 to 25, and the output frequency is 46.875~625 MHz. The lock time does not exceed 30 μs, while jitter is less than 500 fs. [ABSTRACT FROM AUTHOR]

As the PCIe 6.0 specification places higher requirements on signal integrity and transmission latency, it becomes especially important to improve signal transmission performance at the physical layer of the transceiver interface. Retimer circuits are a key component of high-speed serial interfaces, and their delay and jitter size directly affect the overall performance of PCIe. For the typical retimer circuit with large-latency and low-jitter performance, this paper proposes a low-latency and low-jitter Retimer circuit based on CDR + PLL architecture for PCIe 6.0, using a jitter-canceling filter circuit to eliminate the frequency difference between the retiming clock and data, reduce the retiming clock jitter, and improve the quality of Retimer output data. The data are sampled using the retiming clock and then output, avoiding the problem of large penetration latency of typical retimer circuits. The circuit is designed using the CMOS 28 nm process. Simulation results show that when 112 Gbps PAM4 data are input to the retimer circuit, the Retimer penetration latency is 27.3 ps, which is 83.5% lower than the typical Retimer structure; the output jitter data are 741 fs, a 31.4% reduction compared to the typical retimer structure. [ABSTRACT FROM AUTHOR]

One-time readout temporal ghost imaging is a viable time-analog of single pixel imaging using a sluggish light receiver haunted by memory effects, which can be utilized to eliminate the need for steady watch and as such save computer clocks for data capturing and processing. Although the as-retrieved ghost image of a temporal object is modulated in proportion to the time-reversed impulse response function of the light receiver, it can be easily corrected by division. Nevertheless, inhomogeneously distributed noise plagues the images wildly, depending on the transmittance profile of an intensity-only object, which puzzles us. A coherent explanation is attempted for such apparently inconsistent behavior of the biased noise that develops even in simulation. [ABSTRACT FROM AUTHOR]

Single receiver positioning has been widely used as a standard and standalone positioning technique for about 25 years. To detect the slowly growing faults caused by satellite and receiver clocks in single receiver positioning, the Autonomous Integrity Monitoring with an Extrapolation method (AIME) was proposed based on the Kalman filter measurement domain. However, AIME was designed with the assumption of there is the same number of visible satellites at each epoch, which limits its application. To address this issue, this paper proposes a state-domain Robust Autonomous Integrity Monitoring with the Extrapolation Method (SRAIME). The slowly growing fault detection statistics is established based on the difference between the estimates of the state propagator and the posterior state estimation in Kalman filtering. Meanwhile, singular value decomposition is adopted to factor the covariance matrix of the difference to increase computational robustness. Besides, the relevant formulas of the proposed method are theoretically derived, and it is proven that the proposed method is suitable for any positioning model based on the Kalman filter. Additionally, the results of two experiments indicate that SRAIME can detect slowly growing faults in single receiver positioning earlier than AIME. [ABSTRACT FROM AUTHOR]

Atomic clocks are highly precise timing devices used in numerous Positioning, Navigation, and Timing (PNT) applications on the ground and in outer space. In recent years, however, more precise timing solutions based on optical technology have been introduced as current technology capabilities advance. State-of-the-art optical clocks—predicted to be the next level of their predecessor atomic clocks—have achieved ultimate uncertainty of 1 × 10−18 and beyond, which exceeds the best atomic clock's performance by two orders of magnitude. Hence, the successful development of optical clocks has drawn significant attention in academia and industry to exploit many more opportunities. This paper first provides an overview of the emerging optical clock technology, its current development, and characteristics, followed by a clock stability analysis of some of the successfully developed optical clocks against current Global Navigation Satellite System (GNSS) satellite clocks to discuss the optical clock potentiality in GNSS positioning. The overlapping Allan Deviation (ADEV) method is applied to estimate the satellite clock stability from International GNSS Service (IGS) clock products, whereas the optical clock details are sourced from the existing literature. The findings are (a) the optical clocks are more stable than that of atomic clocks onboard GNSS satellites, though they may require further technological maturity to meet spacecraft payload requirements, and (b) in GNSS positioning, optical clocks could potentially offer less than a 1 mm range error (clock-related) in 30 s and at least 10 times better timing performance after 900 s in contrast to the Galileo satellite atomic clocks—which is determined in this study as the most stable GNSS atomic clock type used in satellite positioning. [ABSTRACT FROM AUTHOR]

This paper presents the developments that have been carried out in Uruguayan institutions regarding standards of the quantities of time and frequency. The period analyzed covers about 80 years. Therefore, the technologies were very diverse, from oscillators based on quartz crystals and vacuum tube electronics, to modern cesium clocks, based on the transition of their electronic levels. The relative stabilities, then, cover several orders of magnitude, from 10-7 to 10-13, which demonstrates the great progress that the development of this physical quantity has had in Uruguay. The current state of the National Standard of Uruguay, based on cesium clocks, has reached uncertainties that are low enough to be admitted as part of the international system that defines the time, UTC (Coordinated Universal Time). [ABSTRACT FROM AUTHOR]

Objectives: Although the precise point positioning (PPP) can provide global cm-level positioning, it takes tens of minutes to converge. While PPP-RTK (real-time kinematic) relies on regional reference stations to provide atmospheric delay corrections to accelerate the convergency, however, only the regional service can be provided. Methods: PPP with multi-frequency and multi-GNSS observations is presented, and only the satellite orbit, clock and observable-specific signal bias (OSB) are needed to achieve instantaneous cm-level positioning. This approach solves the problems of slow convergence of PPP as well as the limited-service scope of PPP-RTK. Furthermore, a wide-area instantaneous cm-level service system com ‐ patible with BDS （BeiDou satellite navigation system） PPP-B2b service is proposed, and the performance of real-time orbit, clock and OSB is evaluated. Results: The results of static and in-vehicle kinematic data in China confirm that the system can provide cm-level precision positioning within 1 min. Conclu⁃ sions: It's implied that our system bears the ability to meet the needs of fast, high-precision and high-confidence positioning in autonomous driving and other fields around the world. [ABSTRACT FROM AUTHOR]

Objectives: In October 2019, the International GNSS Service(IGS) began the third data reprocessing campaign(repro3). To enable more robust ambiguity resolution(AR) in precise point positioning (PPP), one of IGS important tasks is to combine satellite clock and code/phase bias products. Methods: We elaborated the precise satellite clock product model, code/phase bias product model, as well as prior corrections and specific processes for the combination of global navigation satellite system(GNSS) satellite clock and code/phase bias products. What􀆳s more, entrusted by the IGS Analysis Center Coordinator, we combined the clock/bias products of repro3 from 2000 to 2020 successfully. Results: Through the statistics of the combination, it is concluded that the integrity rate of combined clock can reach more than 95% after stabilization, which is superior to most of the products of IGS Analysis Centers. The average root mean square error of GPS and Galileo satellite navigation system satellite clock reach 6.13 ps and 5.63 ps respectively, which prove that the correction models in the combination can significantly improve the consistency. The average weight of Graz University of Technology participating in the combination reaches 21.83%, which has better precision than that of other analysis centers. The weight of phase/integer clock is higher than that of legacy clock, with better stability and precision. Furthermore, 103 stations with uniform global distribution were selected for the static PPP-AR solution to validate the positioning precision of the combined products. The results showed that the average fixed rates of GPS wide and narrow-lane ambiguity based on combined products are 90.16% and 86.72% respectively, and those of Galileo are 97.11% and 93.77% respectively, which are about 1-5 percentage points higher than those based on Center for Orbit Determination in Europe (COD) repro3 products. The average positioning precision based on combined products in the east, north and high directions is 0.154, 0.178 and 0.542 centimeters respectively, which is 20% to 30% higher than COD. Conclusions: The multi-GNSS satellite clock and code/phase combination method can effectively solve the problems of the consistency among products of analysis centers,and enable more robust ambiguity resolution in PPP-AR. Moreover, the combined products have been officially downloaded (IGSMAIL-8248:https://cddis.nasa.gov/archive/gnss/products/repro3/). [ABSTRACT FROM AUTHOR]

Objectives: Real time precise point positioning(RT-PPP) technology can realize one-way timing with sub-nanosecond precision and daily stability of 1×10-14 level. Clock steering affects the stability of the receiver's output time-frequency signal, however, inappropriate clock steering parameters can degrade the short-term stability of the receiver's oscillator. Methods: To combine the short-term stability of the oscillator and the long-term stability of the RT-PPP, we propose a phase-locked loop clock steering model for the RT-PPP time-frequency receiver. The noises of the system are analyzed. And the parameter design method of the second-order phase-locked loop is proposed. Experiments were carried out with the clock steering model and designed parameters used in the RT-PPP time-frequency receiver. Results: Experimental results show that the frequency stability of the RT-PPP time-frequency receiver is 4.344 4×10-12 at 1 s, 1.102 9×10-14 at 1 d, the frequency stability of the time intervals shorter than 300 s can get close to the free-running Rubidium clock, the frequency stability of the time intervals longer than 300 s can get close to the RT-PPP. Conclusions: The proposed clock steering model and parameter design method can well realize the combination of the oscillator's short-term stability and the RT-PPP's long-term stability. [ABSTRACT FROM AUTHOR]

Objectives: Global navigation satellite system (GNSS) satellite chip shape distortions lead to individual biases in the pseudorange measurements. These biases are the results of the correlator's tracking response and thus depend on the correlator and front-end design of the receiver. As a result, different receivers are likely to exhibit inconsistent biases, called receiver-related pseudorange biases. The researches show that the receiver-related pseudorange biases cannot be absorbed by clock offset, which will affect GNSS precision applications. Methods: We estimate the receiver-related pseudorange biases of global positioning system (GPS)/BeiDou satellite navigation system (BDS) /Galileo satellite navigation system (Galileo) from 9 short/zero-baselines stations from the multi-GNSS experiment network using double difference method. The baselines are divided into three groups according to the combinations of two receivers of one baseline. Results: The results indicate that the receiver-related pseudorange biases of receivers with different manufacturers even the same manufacturers with different models cannot be neglected. For base‐lines with receivers from different manufacturers,the inconsistences of pseudorange biases can reach up to 160 cm. Conclusions: Among GPS, Galileo and BDS, Galileo shows the smallest pseudorange biases, while BDS in general is the largest. Furthermore, the stability of pseudorange biases is analyzed, the results suggest that estimated receiver-related pseudorange biases are quite stable with the standard deviation less than 12 cm for the three systems. We investigate the effect of receiver-related pseudorange biases on integer ambiguity resolution and pseudorange relative positioning, with the pseudorange biases correction, the root mean squares of fractional parts of double difference Melbourne ‐Wübbena combination are decreased by 17%, 22%, and 14% for GPS, BDS, Galileo, respectively. An improvement of pseudorange relative positioning accuracy is also confirmed, the 3D positioning errors of GPS, BDS, Galileo are reduced from 84.4, 77.3 and 60.0 to 80.1, 72.1 and 57.0 cm, respectively. [ABSTRACT FROM AUTHOR]

Objectives: The rapid development of unmanned aerial vehicles (UAV), autonomous driving and other fields have put forward higher accuracy requirements for global navigation satellite system realtime kinematic positioning. However, the traditional filtering model with constant velocities based on the Doppler measurements, or the filtering model with position variations based on the time-differenced carrier phase measurements, is difficult to describe the accurate state of the moving targets, and thus cannot acquire their real-time, accurate, and stable location information, especially when the receiver can only observe a single system. To solve this issue, we propose a novel filtering model for real-time kinematic positioning, and its performance is compared with the above two filtering models. Methods: The time-variable parameters, including the coordinates and the receiver clock error, are eliminated according to the equivalent elimination principle.The integer ambiguities are removed and the atmospheric delays are reduced using the time-differenced observations. The quasi-static Kalman filtering model is constructed by considering the impact of the model residuals, and the described state in the filtering model becomes much more consistent with the reality. The estimated model residuals are used to correct the position information of moving targets. In this way, the accumulation of the model residuals when directly using the time-differenced phase observables to obtain the position variations are greatly alleviated. The kinematic positioning experiments were carried out using the single-frequency GPS and BeiDou satellite navigation system(BDS) data collected by the UAV and the vehicle platforms, respectively, and the obtained results from three different filtering models are compared with the referenced results from real-time kinematic positioning. Results: Experimental results show that: (1) The filtering model based on the equivalent elimination principle can achieve positioning convergence better than 30 s. Compared with the filtering model based on time-differenced phase observables, the convergence time of the proposed method is improved by about 50%. (2) The standard deviations of the three-dimensional relative positioning errors with respect to the position at the initial epoch are generally within 10 cm, and the horizontal accuracy can reach 3 cm. In addition, the positioning accuracy of UAV in open environment is better than that of vehicle. (3) The number of observed BDS satellites is obviously more than that of the GPS satellites, whether on the UAV platform or on the vehicle platform. This makes a great contribution to a faster convergence speed and better stability of kinematic positioning for the BDS than those for the GPS. Conclusions: The filtering model based on the equivalent elimination principle can achieve shorter convergence time and more accurate positioning results relative to the position at the initial epoch. But it is still susceptible to cycle slips, and cannot obtain accurate absolute positions. In the future work, the approach to accurate absolute position determination at the initial epoch will be investigated, and the real trajectory of the moving target will be achieved thereby. [ABSTRACT FROM AUTHOR]

At present, most of the space-borne atomic clocks used by the major global navigation satellite systems include rubidium atomic clocks, passive hydrogen master (PHM) clocks and cesium atomic clocks. The new independently developed space-borne rubidium atomic clocks and PHM clocks on BeiDou Global Navigation Satellite System (BDS-3) are important hardware improvements. In this paper, performances of new Beidou domestic atomic clocks are evaluated using precise clock offset data from September 2019 to September 2021 and compared with the mainstream space-borne atomic clocks of other satellite navigation systems. The results show that the BDS-3 space-borne PHM clocks have low drift rate and high stability at 86400s interval, which respectively reaches 8.26 × 10−16 and 5.13 × 10−15. These performances are only slightly lower than Galileo PHM clocks. The frequency stability at 86400s interval of BDS-3 rubidium clock is up to 9.03 × 10−15, which is 27.76% higher than GPS rubidium clocks. [ABSTRACT FROM AUTHOR]

Chronic Non-Specific Low Back Pain (cNSLBP) has been identified as one of the leading global causes of disability and is characterized by symptoms without clear patho-anatomical origin. The majority of clinical trials assess cNSLBP using scales or questionnaires, reporting an influence of cognitive, emotional and behavioral factors. However, few studies have explored the effect of chronic pain in daily life tasks such as walking and avoiding obstacles, which involves perceptual-motor processes to interact with the environment. Are action strategies in a horizontal aperture crossing paradigm affected by cNSLBP and which factors influence these decisions ? 15 asymptomatic adults (AA) and 15 cNSLBP participants walked along a 14 m long path, crossing through apertures ranging from 0.9 to 1.8 times their shoulder width. Their movement was measured using the Qualisys system, and pain perception was evaluated by self-administered questionnaires. The cNSLBP participants stopped rotating their shoulders for a smaller aperture relative to their shoulder width (1.18) than the AA participants (1.33). In addition, these participants walked slower, which gave them more time to make the movement adaptations necessary to cross the aperture. No correlation was found between the variables related to pain perception and the critical point but the levels of pain were low with a small variability. This study shows that during a horizontal aperture crossing task requiring shoulder rotation to pass through small apertures, cNSLBP participants appear to exhibit a riskier adaptive strategy than AA participants by minimizing rotations that could induce pain. This task thus makes it possible to discriminate between cNSLBP participants and pain-free participants without measuring the level of pain. The identification number registered in the clinical trials is NCT05337995. • Investigation of cNSLBP movement strategies in an ecological context. • Horizontal aperture crossing paradigm discriminated the influence of cNSLBP. • cNSLBP participants stopped turning their shoulder at a smaller opening. • Pain perception scores were not correlated with the critical point but were low. [ABSTRACT FROM AUTHOR]

Thirty percent of adults in the United States use wearable fitness devices as of 2020 [1], such as fitness watches, to monitor and track health and physical activity parameters. Physical changes during pregnancy may impact wrist worn device accuracy. The arms may be needed as compensation during walking because thorax axial rotation may be inhibited by pelvic tilt during pregnancy [2]. To examine arm motion changes, twenty-three pregnant women (28 ± 4 y) were tested in four-week intervals (± 2 weeks) at 18-, 22-, 26-, 30- and 34-weeks' gestation. Kinematic data were measured during self-selected speed walking. Segment angles and angular velocities were analyzed over time. Linear regressions were used to analyze the correlations between arm motion and the other kinematic variables. Arm range of motion significantly increased (p = 0.006) over gestation, but leg, thorax, and pelvis range of motions did not significantly change. Arm range of motion was correlated with pelvis (r2 =0.311, p = 0.001, β = 1.724) and leg (r2 = 0.285, p = 0.004, β = 1.520) range of motion and gait velocity (r2 =0.566, p = 0.001, β = 39.110). Arm velocities significantly increased (p < 0.012), as did leg velocities (p < 0.022) over gestation time, but thorax and pelvis rotational velocities did not significantly change over time. Arm velocity was correlated with leg velocity in both flexion (r2 =0.598, p = 0.001, β = 1.61) and extension (r2 =0.568, p = 0.001, β = 1.35). Arm swing increases over the course of gestation during walking, which does not follow the exact pattern of changes seen in the legs, thorax, and pelvis. These results show that a typical gait analysis of lower body motions may miss important biomechanical changes or compensations at different points over pregnancy. Future studies should examine why these changes may occur. Studies should also be conducted to see if arm changes impact outcome parameters from fitness watches and affect their validity as an exercise tracker during pregnancy. • Arm swing increases over the course of pregnancy. • Changes in arm swing may impact the reported parameters of wearable fitness devices. • The arms should be considered when examining full body changes during pregnancy. [ABSTRACT FROM AUTHOR]

In order to improve clock synchronization precision of the power distribution field network, a power distribution field network with high‐speed power line broadband carrier communication is designed, and a step‐by‐step precision clock synchronization strategy is developed based on modified timing‐sync protocol for sensor networks. In the strategy, the clock of the central node is calibrated in real‐time as the master clock of the field network by the communication master station through the long‐distance communication network, the time and frequency deviations of the clocks of each node in the network are accurately monitored using the broadcast mechanism and the network time base of the carrier communication, and the clock frequency is gradually amended by re‐calibrating the clock temperature compensation coefficient of the node so that the clock of the node is synchronized step‐by‐step within a clock synchronization cycle. The clock synchronization performances of the field network are tested in the laboratory and jobsite, and test results show that the clock synchronization accuracy of the field network is within ± 0.23 s/24 h, which is 28% higher than that of the power distribution field network based on narrowband power line carrier, and these phenomena of time gap or time repetition are avoided in the clock synchronization process. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This study proposes a method for analyzing sampling jitter in audio equipment based on the time-domain analysis, considering the temporal fluctuations of the zero-crossing points in the recorded sinusoidal waves to characterize the jitter. This method enabled the separate evaluation of jitter in an audio player from those in audio recorders when the same playback signal is simultaneously fed into two audio recorders. The experiments were conducted using commercially available portable devices with a maximum sampling rate of 192 000 samples per second. The results demonstrated that jitter values on the order of a few tens of picoseconds can be identified in an audio player. Moreover, the proposed method enabled the separation of jitter from phase-independent noise utilizing the left and right channels of the audio equipment. As such, this method is applicable for performance evaluation of audio equipment, signal generators, and clock sources. [ABSTRACT FROM AUTHOR]

The subject of this paper is the analysis of the stability of BeiDou system clocks; currently only signals from two blocks, BSD-2 and BDS-3, are available. For elaboration, 30 s clock corrections from the 2014 to 2020 period for 37 satellites were used (9 IGSO, 28 MEO). Four different Allan variances were used to determine stability, and additionally, the type of noise characteristic for each satellite was also determined. Based on the calculations, it was shown that the BDS-2 segment has a significantly lower stability than BDS-3. Moreover, it was possible to notice a difference in the course of the graphs of the same satellites using different variances. BDS-2 satellites were mostly characterised by the presence of WFM noise, while BDS-3 satellites were characterised by WFM noise for the shortest averaging times and RWFM for the other intervals. Accuracy varies between 10−10 s to 10−6 s for a rubidium clocks in general, in case of the hydrogen masers in is between 10−14 s to 10−10 s. [ABSTRACT FROM AUTHOR]

Online fault diagnosis techniques are a key enabler of effective failure mitigation. For real-time systems, the problem of identifying faults is aggravated by timing imprecisions such as varying latency between events and their observation. This paper tackles the challenge of diagnosing faults based on partial observations which are subject to timing imprecisions and potentially made out-of-order due to latency. In this paper, we develop a theory of robust real-time diagnosis importing well-established notions from timed automata theory and the diagnosis of discrete event systems. The theory itself enables a foundational understanding and investigation of the problem and its intricacies. Based on this theory, we further devise an online diagnosis algorithm consuming observations incrementally as they are made and enabling diagnosis, whenever possible, within a bounded worst-case delay. We prove the correctness of the algorithm and its properties with respect to the theory. Aiming at practical feasibility, we also show how to obtain sound but not necessarily complete diagnosis results with space and time requirements bounded by the size of the system model and independent of the number of observations. Finally, using a prototypical implementation, we report on first empirical results obtained by simulation of a small excerpt of an industrial automation example. [ABSTRACT FROM AUTHOR]

This article proposes a novel approach for the generation of memory-efficient table-based function approximation circuits for edge devices in general and FPGAs in particular. Given a function f (x) to be approximated in a given interval [x0, x0 +a) and a maximum approximation error Ea, the goal is to determine a function table implementation with a minimized memory footprint, i.e., number of entries that need to be stored. Rather than state-of-the-art work performing an equidistant sampling of the given interval by so-called breakpoints and using linear interpolation between two adjacent breakpoints to determine f (x) at the maximum error bound, we propose and compare three algorithms for splitting the given interval into sub-intervals to reduce the required memory footprint drastically based on the observation that in sub-intervals of low gradient, a coarser sampling grid may be assumed while guaranteeing the maximum interpolation error bound Ea. Experiments on elementary mathematical functions show that a large fraction in memory footprint may be saved. Second, a hardware architecture implementing the sub-interval selection, breakpoint lookup, and interpolation at a latency of just 9 clock cycles is introduced. Third, for each generated circuit design, BRAMs are automatically instantiated rather than synthesizing the reduced footprint function table using LUT primitives, providing an additional degree of resource efficiency. The approach presented here for FPGAs can equally be applied to other circuit technologies for fast and, at the same time, memory-optimized function approximation at the edge. [ABSTRACT FROM AUTHOR]

For the realization of an optical nuclear clock, the first isomeric excited state of thorium-229 (229mTh) is currently the only candidate due to its exceptionally low-lying excitation energy ( 8.338 ± 0.024 eV). Such a nuclear clock holds promise not only to be a very precise metrological device but also to extend the knowledge of fundamental physics studies, such as dark matter research or variations in fundamental constants. Considerable progress was achieved in recent years in characterizing 229mTh from its first direct identification in 2016 to the only recent observation of the long-sought-after radiative decay channel. So far, nuclear resonance as the crucial parameter of a nuclear frequency standard has not yet been determined with laser-spectroscopic precision. To determine another yet unknown basic property of the thorium isomer and to further specify the linewidth of its ground-state transition, a measurement of the ionic lifetime of the isomer is in preparation. Theory and experimental investigations predict the lifetime to be 103–104 s. To precisely target this property using hyperfine structure spectroscopy, an experimental setup is currently being commissioned at LMU Munich. It is based on a cryogenic Paul trap providing long-enough storage times for 229mTh ions, that will be sympathetically cooled with 88Sr+. This article presents a concept for an ionic lifetime measurement and discusses the laser-optical part of a setup specifically developed for this purpose. [ABSTRACT FROM AUTHOR]

In this paper, we study mathematical models of three dimensional competitive systems originated from the represillator and their variants. There are two parts for the mathematical results. In part I, we first prove the uniqueness of the positive equilibrium $ (x^{*}, y^{*}, z^{*}) $. Then we present necessary and sufficient conditions for their local asymptotic stability and instability. In part II, we present sufficient conditions for the global asymptotic stability of $ (x^{*}, y^{*}, z^{*}) $ provided $ (x^{*}, y^{*}, z^{*}) $ is locally asymptotic stable. [ABSTRACT FROM AUTHOR]

In this paper, for the wireless network, wearable device, and Internet of Things (IoT) markets, a delay-locked loop (DLL) is used to implement accurate multiplication for a reference clock and the frequency of various applications through an edge combiner (EC). A simpler structure is more sensitive to process, voltage, and temperature (PVT), so DLL complements itself quickly in the feedback system and improves the stability of the final output. The proposed DLL-based multiplier can prevent harmonic lock generation using a first phase canceller (FPC), thus compensating for faster lock time. The circuit is built with a 55 nm CMOS process and has a chip area of 0.0225 mm2. The proposed design achieves a total power consumption of 0.48 mW at the 30.72 MHz operating clock frequency, and the clock duty can also operate stably from 15 to 75%. [ABSTRACT FROM AUTHOR]

Maintaining the accuracy of a sensor system across various operating conditions has always been a challenge, especially for those operating in harsh surroundings such as a radiation environment. Concerning frequency-based sensor interfaces, supply voltage drifts and gain shift of the voltage-to-frequency converter (VFC) are critical design issues. These manifest as gain, offset, and linearity errors at the system level and therefore require continuous correction mechanisms. In this paper, dynamic gain and offset error-compensated open-loop frequency-based sensor interface architectures with adaptive clock frequency are proposed, which result in a ratiometric digital output. To address the mismatch issue, two architectures, one with periodic swapping of the VFCs' inputs and outputs, and the other with the use of a single analog-to-digital converter (ADC) as an analog front end, are developed. The concepts were demonstrated with implementations on a Zynq board (ZYBO). The results of the first architecture showed that for a 25% gain mismatch between the VFCs, the output gain error was reduced from around 7.4% to 0.79% and the offset error was reduced from around 11.8% to 0.01%. Additionally, for the second architecture, a maximum of 0.11% gain error and 0.1% offset error were recorded for an emulated ± 25% supply drift. [ABSTRACT FROM AUTHOR]

The article focuses on the development of nuclear clocks, a new type of timekeeping device that could surpass current atomic clocks in precision. Topics include recent advancements in nuclear clock research, such as achieving simultaneous operation of all necessary components, the potential for these clocks to explore fundamental physics questions, and the use of precise measurements of thorium-229's excitation energy to improve clock accuracy.

Ultimate bounds on the maximum operating frequency of networks of Quantum-dot Cellular Automata (QCA) devices have yet to be established. We consider the adiabaticity of such networks in the two-state approximation where clocking is achieved via modulation of the interdot tunneling barriers. Estimates of the maximum operating frequency that would allow a 99% probability of observing the correct logical output are presented for a subset of the basic components used in QCA network design. Simulations are performed both in the coherent limit and for a simple dissipative model. We approach the problem of tunnel-based clocking from the perspective of quantum annealing and present an improved clocking schedule allowing for faster operation. Using an analytical solution for driven QCA wires, we show that the maximum operating frequency in the coherent limit falls off with the square of the wire length, potentially limiting the size of clocked regions. [ABSTRACT FROM AUTHOR]