This study proposes a fast and precise voltage feedback-based islanding detection method (IDM) for grid-connected photovoltaic systems (GCPVSs) based microgrid. In this algorithm, a disturbance ...containing the absolute deviation of the output voltage is injected into the inverter's d-axis reference current which tunes the active power output. In islanded mode, the applied disturbance reduces the active power output and consequently point of common coupling voltage beyond the standard setting while its effect at the presence of the grid is negligible. The assessment of the proposed IDM has been conducted in the MATLAB/Simulink platform under extensive scenarios defined by IEEE 1547-2008 and UL 1741 standards for a case study system with two large-scale GCPVSs. The provided outputs remark accurate islanding classification in all cases within 810 ms, much lower than the maximum permissible time postulated in islanding standards. This time is short enough to restore GCPVS for autonomous operation of microgrid as well. The comparative analysis of the proposed strategy with a few existing IDMs confirmed its overall superiorities in the terms of non-detection zone, detection time, being applicable into the microgrid, simple threshold determination, and straightforward and cost-effective implementation.
Purpose The purpose of this paper is to evaluate the efficiency of a series network system with undesirable and unreturnable simultaneously. Design/methodology/approach The research was conducted by ...applying data envelopment analysis (DEA) approach to measure the efficiency score of a system and substages with an undesirable output of the second and third stages separately. For each case, new production technology was introduced, and based on them, novel DEA models were proposed. Findings One of the most important issues in the development of a country is the banking industry. In this study, 51 branches of commercial banks as a three-stage system with undesirable and unreturnable outputs in the second stage are considered. Then, the efficiency of each branch and substages is measured by using proposed models. Originality/value The efficiency of a three-stage network in the presence of undesirable and unreturnable outputs was assessed. In this model, Kousmanen’s technology was used.
In view of some applications for red green blue (RGB) light‐emitting diodes (LEDs), a modular multi‐channel constant‐current LED driver is getting more important to obtain desirable colour and ...brightness. A multi‐channel constant‐current LED driver is proposed according to the constant‐current characteristics of the passive LCL‐T resonant network, which is composed of one high‐frequency half‐bridge inverter and as many passive LCL‐T resonant rectifiers as the number of output channels. Only one passive resonant rectifier is added to increase a constant‐current output channel, thus, it is easy to achieve multi‐channel constant‐current output as needed. In practical applications, the control can be simplified and the reliability can be improved in the open‐loop mode. However, any change of input and output voltage would cause a certain fluctuation in the output current considering the high‐order harmonic components in the open‐loop mode. To this end, the precise solution of the actual output current is obtained in the paper. The quantitative parameter design has been completed according to the desirable current to meet the output constant‐current accuracy within the given input and output. Finally, a 120‐W prototype with three different constant‐current outputs is built to verify the correctness of theoretical analysis.
Today, in the face of ever increasing communication traffic, minimizing power consumption in data communication systems has become a challenge. Direct modulation of lasers, a technique as old as ...lasers themselves, is known for its high energy efficiency and low cost. However, the modulation bandwidth of directly modulated lasers has fallen behind those of external modulators. In this Article, we report wide bandwidths of 65–75 GHz for three directly modulated laser design implementations, by exploiting three bandwidth enhancement effects: detuned loading, photon–photon resonance and in-cavity frequency modulation–amplitude modulation conversion. Substantial reduction of chirp (α < 1.0) as well as isolator-free operation under a reflection of up to 40% are also realized. A fast data transmission of 294.7 Gb s−1 over 15 km of a standard single-mode fibre in the O-band is demonstrated. This was achieved without an optical fibre amplifier due to a high laser output power of 13.6 dBm.Directly modulated semiconductor lasers are shown to be able to operate with bandwidths exceeding 65 GHz thanks to a cavity design that harnesses photon–photon resonances.
Schottky direct-current (DC) generators can convert ambient mechanical energy into DC power, showing potential in portable electronics, wireless networks, and the Internet of Things. However, most ...Schottky DC generators generate a voltage output below 1 volt. Increasing the voltage output would considerably broaden their applications but remains challenging to achieve. In this study, we developed a novel DC generator that shows increased and tunable voltage outputs by combing the Schottky DC generator with triboelectric components. Using polyaniline-coated fabric and metal aluminum to prepare Schottky DC devices, we showed that the device voltage outputs were increased largely when a scatting layer of polyvinylidene fluoride (PVDF) powder covered the surface of either the metal Al or the polyaniline-coated fabric between them. Under compression impact, the PVDF-involved device (areal coverage 46.26 ± 0.60% on the Al surface) generated a peak open-circuit voltage of 3.2 ± 0.10 V and a short-circuit current of 15.06 ± 0.3 μA (current density 3.77 ± 0.08 μA cm−2), with a power of 12.32 ± 0.45 μW (measured by an external resistor method). The open-circuit voltage and power were 3.7 times and 1.5 times higher when compared with the same DC generator without PVDF. By changing the PVDF powder coverage area, the DC output voltage can be tuned linearly in the range of 0.86–3.20 V. However, when the coverage was above 50%, the outputs turned from DC to AC. We also simulated the electrical outputs using a circuit simulation program (LTspice XVII). The simulation results agreed well with the experimental findings, suggesting the improvement of the electrical output follows the classic electrical principle. Such Schottky diode-triboelectric hybrid may form a novel approach for developing DC energy harvesters and self-powered sensors with adjustable voltage output for various applications.
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•DC Schottky-triboelectric hybrid generators were prepared by incorporating PVDF particles into the Schottky devices.•The modified devices showed an increase in voltage outputs up to 3.2 V.•The PVDF particles introduce triboelectric charges into the device.•The circuit simulation results indicate that the triboelectric units are connected in parallel with the Schottky device.
Circadian clock in plants: Linking timing to fitness Xu, Xiaodong; Yuan, Li; Yang, Xin ...
Journal of integrative plant biology,
April 2022, 2022-Apr, 2022-04-00, 20220401, Letnik:
64, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Endogenous circadian clock integrates cyclic signals of environment and daily and seasonal behaviors of organisms to achieve spatiotemporal synchronization, which greatly improves genetic diversity ...and fitness of species. This review addresses recent studies on the plant circadian system in the field of chronobiology, covering topics on molecular mechanisms, internal and external Zeitgebers, and hierarchical regulation of physiological outputs. The architecture of the circadian clock involves the autoregulatory transcriptional feedback loops, post‐translational modifications of core oscillators, and epigenetic modifications of DNA and histones. Here, light, temperature, humidity, and internal elemental nutrients are summarized to illustrate the sensitivity of the circadian clock to timing cues. In addition, the circadian clock runs cell‐autonomously, driving independent circadian rhythms in various tissues. The core oscillators responds to each other with biochemical factors including calcium ions, mineral nutrients, photosynthetic products, and hormones. We describe clock components sequentially expressed during a 24‐h day that regulate rhythmic growth, aging, immune response, and resistance to biotic and abiotic stresses. Notably, more data have suggested the circadian clock links chrono‐culture to key agronomic traits in crops.
This review summarizes recent research on the circadian clock, an endogenous time‐keeping mechanism, covering how the circadian clock anticipates environmental and internal timing cues (Zeitgebers), the molecular architecture of core oscillators, the synchronization of cell‐autonomous clocks with circadian rhythm in whole plants, and circadian outputs including agronomic traits.
Predicting condition monitoring signals has become a critical task for health status assessment and monitoring of industrial systems. It is crucial to incorporate correlated historical data when ...making predictions for the target signal. As a flexible nonparametric approach, the multi-output Gaussian process (MOGP) model can be employed for this nonlinear regression problem. One effective way to construct MOGP is through convolving a latent function drawn from a Gaussian process. While leveraging the convolution process makes MOGP expressive, there are several challenges that remain to be addressed. First, the scalability of MOGP is always an important issue since the computational demands would increase drastically as the dimension of output variables grows. Besides, the negative transfer should be mitigated when the target variable and the source variable share little commonality. In this study, a pairwise structure is adopted by decomposing the full multivariate model into a group of bi-output models. Furthermore, a Bayesian model averaging approach is utilized to combine the prediction results of the bi-output models. A model selection scheme based on Bayes factor is employed to alleviate negative transfer and facilitate model scalability further by discarding the weakly correlated outputs. The key advantage of the proposed model lies in the improved prediction and uncertainty quantification performance compared with traditional MOGP models. The superiority of the proposed method is validated by numerical studies and a case study. Note to Practitioners -This study addresses the challenge of predicting condition monitoring signals in a high-dimensional setting. Existing nonparametric approaches suffer from high computation complexity or ineffective information integration from different signals. We propose a novel approach using a scalable pairwise MOGP model based on Bayesian model averaging. Our method decomposes the full model into bi-output submodels and averages them in a Bayesian way. We also employ a model selection scheme based on the Bayes factor to alleviate negative transfer by discarding weakly correlated outputs. Numerical experiments suggest that this approach can improve prediction accuracy and uncertainty quantification performance for the prediction of condition monitoring signals. Our approach offers a promising solution for condition monitoring signal prediction in automatic and industrial systems where condition monitoring data are readily available.
This article proposes a scan driver circuit based on indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) for multiple output signals. The proposed circuit could generate two overlapped ...output signals using a separate driving structure. The separate driving structure enabled the control nodes of each output signal to have a sufficiently high voltage during the output period. Consequently, the proposed circuit stably operated with the threshold voltage (<inline-formula> <tex-math notation="LaTeX">{V}_{\text {TH}}{)} </tex-math></inline-formula> varying from −3 to 4 V in the circuit simulation. The proposed scan driver circuit could reduce the circuit area because a single stage could output two output signals for two adjacent scan lines. Furthermore, the fabricated scan driver circuit exhibited a stable operation with multiple overlapped signals. Consequently, the proposed IGZO TFT-based scan driver circuit showed a stable circuit operation with multiple output signals through the separate driving structure.
This study deepens our knowledge of critical success factors in the innovation process of low- and medium-technology (LMT) industries. To accomplish this, it explores how the innovation process in ...LMT firms may depend on non-formal R&D activities and the use of external sources. The empirical analysis is based on a representative panel of Spanish manufacturing firms. The results strongly support the view that non-R&D activities such as design, the use of advanced machinery and training are crucial to understanding the innovation process of any firm. The study finds, however, that the impact of these activities is especially important in LMT industries, particularly for the achievement of product innovations. The empirical evidence also reveals the importance of external sources such as the use of consultants, the hiring of personnel, collaboration agreements and external R&D, with the greatest differences between LMT and high-technology (HT) firms being observed in process innovations.
Data envelopment analysis (DEA) has recently become a popular method in measuring energy efficiency at the macro-economy level. However, previous studies are limited in that they failed to consider ...the issues of undesirable outputs and minimisation of energy consumption. Thus, this study considers both factors in measuring Chinese industrial energy efficiency and investigates the maximum energy-saving potential in 28 administrative regions in China. The results show that industries in the east area have the best average energy efficiency for the period 2000–2006, followed by the central area. Further, after comparing the industrial energy overall efficiency, pure technical efficiency (IEPTE), and scale efficiency of the 28 administrative regions examined, the study finds that in most regions of this study, the two main reasons causing the wastage of a large amount of energy during the industrial production process are that the industrial structure of most regions still relies on the massive use of energy in order to support the industrial-based economy and the IEPTE is too low. Based on these findings, this paper correspondingly proposes some policies to improve regional industrial energy efficiency.
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