This work extends the convolutional multiple whole profile (CMWP) line profile analysis (LPA) procedure to determine the total dislocation density and character of irradiation‐induced dislocation ...loops in commercial polycrystalline Zr specimens. Zr alloys are widely used in the nuclear industry as fuel cladding materials in which irradiation‐induced point defects evolve into dislocation loops. LPA has long been established as a powerful tool to determine the density and nature of lattice defects in plastically deformed materials. The CMWP LPA procedure is based on the Krivoglaz–Wilkens theory in which the dislocation structure is characterized by the total dislocation density ρ and the dislocation arrangement parameter M. In commercial Zr alloys irradiation‐induced dislocation loops broaden the peak profiles, mainly in the tail regions, and occasionally generate small satellites next to the Bragg peaks. In this work, two challenges in powder diffraction patterns of irradiated Zr alloys are solved: (i) determination of the M values from the long tail regions of peaks has been made unequivocal and (ii) satellites have been fitted separately, using physically well established principles, in order to exclude them from the dislocation determination process. Referring to the theory of heterogeneous dislocation distributions, determination of the total dislocation density from the main peaks free of satellites has been justified. The dislocation loop structure has been characterized by the total dislocation density of loops and the M parameter correlated to the dipole character of dislocation loops. The extended CMWP procedure is applied to determine the total dislocation density, the dipole character of dislocation loops, and the fractions of ⟨a⟩‐ and ⟨c⟩‐type loops in proton‐ or neutron‐irradiated polycrystalline Zr alloys used in the nuclear energy industry.
Satellites generated by small dislocation loops in polycrystalline proton‐ or neutron‐irradiated Zr alloys are characterized by X‐ray line profile analysis. The convolutional multiple whole‐profile procedure has been extended to characterize irradiation‐induced satellites around fundamental Bragg peaks.
Addressing DC Component in PLL and Notch Filter Algorithms Karimi-Ghartemani, M.; Khajehoddin, S. A.; Jain, P. K. ...
IEEE transactions on power electronics,
2012-Jan., 2012, 2012-01-00, 20120101, Letnik:
27, Številka:
1
Journal Article
Recenzirano
This paper presents a method for addressing the dc component in the input signal of the phase-locked loop (PLL) and notch filter algorithms applied to filtering and synchronization applications. The ...dc component may be intrinsically present in the input signal or may be generated due to temporary system faults or due to the structure and limitations of the measurement/conversion processes. Such a component creates low-frequency oscillations in the loop that cannot be removed using filters because such filters will significantly degrade the dynamic response of the system. The proposed method is based on adding a new loop inside the PLL structure. It is structurally simple and, unlike an existing method discussed in this paper, does not compromise the high-frequency filtering level of the concerned algorithm. The method is formulated for three-phase and single-phase systems, its design aspects are discussed, and simulations/experimental results are presented.
A continuous-rate digital clock and data recovery (CDR) with automatic frequency acquisition is presented. The proposed automatic frequency acquisition scheme implemented using a conventional ...bang-bang phase detector (BBPD) requires minimum additional hardware, is immune to input data transition density, and is applicable to subrate CDRs. A ring-oscillator-based two-stage fractional-N phase-locked loop (PLL) is used as a digitally controlled oscillator (DCO) to achieve wide frequency range, low noise, and to decouple the tradeoff between jitter transfer (JTRAN) bandwidth and ring oscillator noise suppression in conventional CDRs. The CDR is implemented using a digital D/PLL architecture to decouple JTRAN bandwidth from jitter tolerance (JTOL) corner frequency, eliminate jitter peaking, and remove JTRAN dependence on BBPD gain. Fabricated in a 65 nm CMOS process, the prototype CDR achieves error-free operation (BER <; 10 -12 ) from 4 to 10.5 Gb/s with pseudorandom binary sequence (PRBS) data sequences ranging from PRBS7 to PRBS31. The proposed automatic frequency acquisition scheme always locks the CDR loop within 1000 ppm residual frequency error in worst case. At 10 Gb/s, the CDR consumes 22.5 mW power and achieves a recovered clock long-term jitter of 2.2 ps rms /24.0 ps pp with PRBS31 input data. The measured JTRAN bandwidth and JTOL corner frequencies are 0.2 and 9 MHz, respectively.
This article presents an iterative frequency lock loop (FLL)-assisted-phase lock loop (PLL) (FPLL) design in state space according to the minimum mean square error criterion. This is achieved by ...constructing a high fidelity carrier signal model with the consideration of the non-Gaussian nonwhite measurement noise characteristics. Two popular arctangent discriminators, e.g., two-quadrant (Atan) and four-quadrant (Atan2) are used to produce the PLL and FLL measurements for FPLL, respectively. The filter gain is selected to minimize the trace of the error covariance matrix and an iteration approach to quickly compute the steady-state filter gain is introduced. The nonlinearity in the discriminator and filter behaviors in FPLL at low C/N_0 and high dynamic conditions are investigated. The closed-form expressions of the closed-loop transfer function as well as error transfer function are clarified. The thermal noise induced tracking jitters on each carrier state, e.g., phase, doppler, and doppler rate, are derived, analyzed, and verified via Monte Carlo simulation, accordingly. The theoretical properties show that the iterative FPLL achieves the following. 1) The comparable tracking performance to the well-designed PLL-only. 2) The enhanced tracking accuracy over the well-designed FLL-only. 3) The improved tracking sensitivity over the conventional Kalman filter-based FPLL (KF-FPLL), at low C/N_0 condition and high dynamic conditions.
•How the circular economy framework can manifest in agricultural systems is analysed.•A novel definition for circular agriculture production systems is provided.•The scope of circularity indicators ...with application in agriculture is evaluated.•The challenges of adopting circular economy models in agriculture is discussed.•Future lines of research and institutional changes are provided.
In the current context of resource scarcity, global climate change, environmental degradation, and increasing food demand, the circular economy (CE) represents a promising strategy for supporting sustainable, restorative, and regenerative agriculture. A review of the literature on CE confirms the initial hypothesis that the theoretical CE framework has not yet been adapted to the field of agriculture. Therefore, this paper overcomes this gap in two ways: i) by adjusting the general CE framework to the agricultural sector's specificities, and ii) by analyzing the scope of the indicators available for measuring agricultural production systems’ circularity performance in supporting decision-making processes. Accordingly, the different elements in the theoretical CE framework are adapted to agricultural production systems. One major contribution of this paper is the definition of CE applied to agriculture. In addition, the principles of CE are adapted to the field, and CE strategies for agricultural activity are defined. Forty-one circularity indicators for application in agricultural systems were also comprehensively assessed to determine their strengths and weaknesses. Building on the key findings, future research paths and changes at the institutional and normative levels are proposed to facilitate CE implementation in agricultural production systems. For example, internationally recognized standards and adequate units of measurement must be defined, to develop meaningful studies and determine agricultural activities’ circularity performance.
Power converters may lose synchronization with the remaining network when integrated in a weak power grid. Such an instability phenomenon known as grid-synchronization instability (GSI) features the ...frequency divergence of phase-locked loop (PLL) and oscillations of the converter's power output. In this paper, we focus on the influences of reactive power control (RPC) methods on GSI. We develop a single-input-single-output model to explicitly reveal how the PLL interacts with the other parts of the converter system in terms of grid synchronization. Then, after deriving the open-loop transfer function and sensitivity function of the entire converter system, we compare the stability margins for different RPC methods. Furthermore, we elaborate on the interactions among RPC, PLL, and voltage feedforward (VFF), and then demonstrate that different design methods of RPC and VFF will lead to different stability margins. The subsequent stability analysis provides insightful guidelines for coordinating the design of multiple control loops, i.e., RPC, VFF, and PLL. In particular, we demonstrate how the loop shaping of PLL takes effect in increasing the stability margin and eventually preventing the converter from GSI. The validity of the stability analysis is verified through simulations in MATLAB/Simulink.
Homologous recombination (HR) repairs DNA double-strand breaks (DSBs) in the S and G2 phases of the cell cycle
. Several HR proteins are preferentially recruited to DSBs at transcriptionally active ...loci
, but how transcription promotes HR is poorly understood. Here we develop an assay to assess the effect of local transcription on HR. Using this assay, we find that transcription stimulates HR to a substantial extent. Tethering RNA transcripts to the vicinity of DSBs recapitulates the effects of local transcription, which suggests that transcription enhances HR through RNA transcripts. Tethered RNA transcripts stimulate HR in a sequence- and orientation-dependent manner, indicating that they function by forming DNA-RNA hybrids. In contrast to most HR proteins, RAD51-associated protein 1 (RAD51AP1) only promotes HR when local transcription is active. RAD51AP1 drives the formation of R-loops in vitro and is required for tethered RNAs to stimulate HR in cells. Notably, RAD51AP1 is necessary for the DSB-induced formation of DNA-RNA hybrids in donor DNA, linking R-loops to D-loops. In vitro, RAD51AP1-generated R-loops enhance the RAD51-mediated formation of D-loops locally and give rise to intermediates that we term 'DR-loops', which contain both DNA-DNA and DNA-RNA hybrids and favour RAD51 function. Thus, at DSBs in transcribed regions, RAD51AP1 promotes the invasion of RNA transcripts into donor DNA, and stimulates HR through the formation of DR-loops.
This paper presents a generalized theoretical framework for carrier tracking of global navigation satellite systems signals by constructing a state space representation for the carrier tracking loop ...and applying control system design techniques to derive state feedback and state estimator gain matrices. Both phase-locked loop and frequency-locked loop are studied using this approach. Their performances are evaluated using the closed-form expressions in the presence of thermal noise, oscillator noise, and receiver platform dynamics. The proposed approach unified the phase tracking and frequency tracking within the same theoretical framework, thereby facilitating a systematic analysis of the effects of tracking loop design parameters under weak signal and highly dynamic signal environments.
Phase-locked loop (PLL) is commonly used for the grid-connected voltage-source converter (VSC) to synchronize with the grid. Under weak grid conditions, it has been found that the frequency-dependent ...characteristic of the network impedance inherently introduces a positive feedback loop into PLL. Previous studies focused on the PLL analysis intuitively believe that the positive feedback loop will deteriorate the dynamic performance of the PLL. However, this conclusion is not rigorous since only the dynamic of the PLL is considered and the theoretical analysis is insufficiency to reveal the influence of the positive feedback loop on system stability. In this paper, the impact of the frequency-dependent network on VSC stability is quantified in terms of the overall system based on the damping torque analysis. It is found that the influence of the positive feedback loop on stability depends on the parameters of the PLL and the damping of the dominant eigenvalues. Besides, an angular frequency feedback scheme is proposed to eliminate the adverse effect of the frequency-dependent network and enhance the stability of the VSC under weak grid conditions. Time-domain numerical simulations and reduced-scale experiments are performed to validate the effectiveness of the proposed scheme.
This article presents a 2-GHz dual-path subsampling phase-locked loop (SSPLL) with ring voltage-controlled oscillator (VCO) phase noise suppression (PNS). In addition to the conventional subsampling ...charge pump (SSCP), a high-pass path from the subsampling phase detector (SSPD) to the low-pass filter (LPF) is implemented in the proposed SSPLL. Due to this dual-path architecture, a new in-band zero and pole are introduced into the open-loop transfer function (zero frequency is smaller than the pole frequency), which extends the open-loop unit-gain bandwidth without sacrificing the phase margin. Consequently, the phase noise contribution of the ring VCO is suppressed while the loop stability is ensured. Meanwhile, the phase noise contribution of the high-pass path is negligible compared to the reference and ring VCO's contribution. Measurement results show that the SSPLL's closed-loop bandwidth is extended to around 6 MHz with a reference of 20 MHz and the jitter is reduced by 1.34<inline-formula> <tex-math notation="LaTeX">\times</tex-math> </inline-formula> (from 3.52 to 2.63 ps) with a maximum noise suppression of 6.5 dB at the 1.1-MHz offset. The PNS path consumes 0.16 mW and no delay line or calibration is needed, which results in a relatively high FoM<inline-formula> <tex-math notation="LaTeX">_{\mathrm{PNC}}</tex-math> </inline-formula> value of 40.5 dB.
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