Research Progress on Flexibility Modification of Coal-Fired Generating Units

[Introduction] The strategic goal of "carbon peaking and carbon neutrality" has increased the demand for new energy power grid integration, so it is necessary to improve the flexible operation capacity of coal-fired generating units. [Method] This paper introduced the flexible transformation technology and common evaluation indicators of existing coal-fired units in detail. Flexibility transformation mainly included condensate throttling technology, coupled biomass co-combustion transformation technology of coal-fired units, flexibility technology of pulverizing system of coal-fired units, etc.; Common evaluation indicators for the flexibility of coal-fired generating units included: the power consumption rate of the generator set plant, the thermal efficiency of the boiler, the standard coal consumption rate of the generator set, etc. On this basis, this paper summarized and analyzed the flexibility transformation technology and evaluation indexes. [Result] Finally, the paper puts forward seven kinds of the technology development direction and relevant suggestions of coal-fired generating units. [Conclusion] The structural improvement of original generating units, the introduction of multi-form new energies and the coordinated regulation design of multi-heat storage will be the main direction of subsequent development. It is expected that paper can provide reference for subsequent coal-fired generating units to adapt to "dual carbon" energy planning

Polar-facing slopes showed stronger greening trend than equatorial-facing slopes in Tibetan plateau grasslands

The orientation of slopes in alpine zones creates microclimates, e.g. equatorial-facing slopes (EFSs) are generally drier and warmer than are polar-facing slopes (PFSs). The vegetation growing in these microhabitats responds divergently to climatic warming depending on the slope orientation. We proposed a spatial metric, the greenness asymmetric index (GAI), defined as the ratio between the average normalized difference vegetation index (NDVI) on PFSs and EFSs within a given spatial window, to quantify the asymmetry of greenness across aspects. We calculated GAI for each non-overlapping 3 × 3 km2 (100 × 100 Landsat pixels) grid, and seamlessly mapped it on Tibetan Plateau (TP) grassland using NDVI time series from the Landsat-5, -7 and -8 satellites. PFSs were greener than EFSs (GAI > 1) in warm and dry areas, and EFSs were greener than PFSs (GAI < 1) in cold and wet areas. We also detected a stronger greening trend (0.0040 vs 0.0034 y−1) and a higher sensitivity of NDVI to temperature (0.031 vs 0.026 °C−1) on PFSs than EFSs, leading to a significant positive trend in GAI (0.00065 y−1, P < 0.01) in the TP from 1991 to 2020. Our results suggest that global warming exacerbated the greenness asymmetry associated with the slope orientation: PFSs are more sensitive to warming and have been greening at a faster rate than EFSs. The gradient of EFSs and PFSs provided a “natural laboratory” to study interaction of water and temperature limitations on vegetation growth. Our study is the first to detect the effect of aspect on the greening trend in the TP. Future research needs to clarify the full biotic and abiotic determinants for this spatial and temporal asymmetry of greenness across aspects with the support of extensive field measurements and refined high-resolution NDVI products.This study was funded by the National Natural Science Foundation of China 42271323 and 41971282, the Sichuan Science and Technology Program 2021JDJQ0007, the Spanish Government project TED2021-132627B-I00 funded by the Spanish MCIN, AEI/10.13039/501100011033 and the European Union NextGenerationEU/PRTR, the Fundación Ramón Areces project CIVP20A6621 and the Catalan government project SGR2021-1333.N

A Linearly and Circularly Polarization-Reconfigurable Leaky Wave Antenna Based on SSPPs-HSIW

In this manuscript, a reconfigurable leaky wave antenna is proposed with linearly polarized and circularly polarized properties, which is composed of two layers with feeding waveguide and radiation elements. The bottom layer is a half-mode substrate integrated waveguide etched with a spoof surface plasmon polaritons structure as a high-dispersion feeding waveguide to excite 8 circular patches as radiation elements in the top layer. In a unit element, the horizontal linear polarization (HLP) and right-hand circular polarization (RHCP) radiation are switched using a p-i-n diode crossing a slot of a circular metal patch. HLP performance is achieved as the p-i-n diode is switched off, and RHCP is achieved as the p-i-n diode is switched on. The measured results verify the design theory and the simulated results. Over the working band of 10.4~12.8 GHz, the proposed antenna can radiate scanning beams covering about a 73° region, including the broadside direction with HLP and RHCP

A Sparse Shared Aperture Design for Simultaneous Transmit and Receive Arrays with Beam Constraints

The utilization of efficient digital self-interference cancellation technology enables the simultaneous transmit and receive (STAR) phased array system to meet most application requirements through STAR capabilities. However, the development of application scenario requirements makes array configuration technology for STAR phased arrays increasingly important. Thus, this paper proposes a sparse shared aperture STAR reconfigurable phased array design based on beam constraints which are achieved by a genetic algorithm. Firstly, a design scheme for transmit and receive arrays with symmetrical shared apertures is adopted to improve the aperture efficiency of both transmit and receive arrays. Then, on the basis of shared aperture, sparse array design is introduced to further reduce system complexity and hardware costs. Finally, the shape of the transmit and receive arrays is determined by constraining the side lobe level (SLL), main lobe gain, and beam width. The simulated results indicate that the SLL of the transmit and receive patterns under beam-constrained design have been reduced by 4.1 dBi and 7.1 dBi, respectively. The cost of SLL improvement is a reduction in transmit gain, receive gain, and EII of 1.9 dBi, 2.1 dBi, and 3.9 dB, respectively. When the sparsity ratio is greater than 0.78, the SLL suppression effect is also significant, and the attenuation of EII, transmit, and receive gains do not exceed 3 dB and 2 dB, respectively. Overall, the results demonstrate the effectiveness of a sparse shared aperture design based on beam constraints in producing high gain, low SLL, and low-cost transmit and receive arrays

A Robust Design for Aperture-Level Simultaneous Transmit and Receive with Digital Phased Array

Aperture-level simultaneous transmit and receive (ALSTAR) attempts to utilize adaptive digital transmit and receive beamforming and digital self-interference cancellation methods to establish isolation between the transmit and receive apertures of the single-phase array. However, the existing methods only discuss the isolation of ALSTAR and ignore the radiation efficiency of the transmitter and the sensitivity of the receiver. The ALSTAR array design lacks perfect theoretical support and simplified engineering implementation. This paper proposes an adaptive random group quantum brainstorming optimization (ARGQBSO) algorithm to simplify the array design and improve the overall performance. ARGQBSO is derived from BSO and has been ameliorated in four aspects of the ALSTAR array, including random grouping, initial value presets, dynamic probability functions, and quantum computing. The transmit and receive beamforming carried out by ARGQBSO is robust to all elevation angles, which reduces complexity and is conducive to engineering applications. The simulated results indicate that the ARGQBSO algorithm has an excellent performance, and achieves 166.8 dB of peak EII, 47.1 dBW of peak EIRP, and &minus;94.6 dBm of peak EIS with 1000 W of transmit power in the scenario of an 8-element array

A Tunable Constant-Absolute-Bandwidth Bandpass Filter with Switchable Ability

This paper presents a tunable bandpass filter (BPF) with constant absolute bandwidth (CABW) and switchable properties. The BPF is performed by using a tri-mode cross-shape resonator (CSR) loaded with varactors. The CABW and switchable ability are achieved by adjusting the resonant frequencies. Meanwhile, the two transmission zeros (TZs) produced by center-loaded stubs strengthen the skirt selectivity in the on-state and the isolation in the off-state. For demonstration, a tri-pole switchable BPF with three control voltages is implemented and verified, and the control mechanism is simple. In the on-state, it exhibits a 120 MHz, 3 dB CABW with the measured insertion loss (IL) of 2.2–2.5 dB in the tuning range of 0.816–1.188 GHz. In the off-state, the measured isolation is better than 27 dB

A Sparse Design for Aperture-Level Simultaneous Transmit and Receive Arrays

The aperture-level simultaneous transmit and receive (ALSTAR) system uses full digital architecture with an observation channel to achieve remarkably effective isotropic isolation (EII). However, the number of observation channels must be the same as the number of transmit channels, which increases the system’s complexity. To balance the system cost and performance of the ALSTAR, this paper proposes a joint design of sparse arrays and beamforming, which are achieved by a genetic algorithm and an alternating optimization algorithm, respectively. In the sparse design, we introduce beamforming technology to guarantee the EII while decreasing the corresponding elements of observation channel that contribute slightly to the EII. The simulation results are presented for a 32-element array that achieves 185.87 dB of the EII with 1000 W of transmit power. In the cases of sparsity rates at 0.875 and 0.75 (≥0.6), i.e., the number of observation channels decreases by 12.5% (2/16) and 25% (4/16), the reductions in EII do not exceed 1 dB and 3 dB, respectively. However, the EII decreases rapidly with a sparsity rate less than 0.25. Results demonstrate that our proposed joint design of sparse arrays and beamforming can reduce the system cost with little performance loss of EII

Does Innovation Climate Help to Effectiveness of Green Finance Product R&amp;D Team? The Mediating Role of Knowledge Sharing and Moderating Effect of Knowledge Heterogeneity

Green finance innovation has received emerging attention from the finance industry in recent years; however, few studies have explored the internal mechanisms that link innovation climate to a green finance R&amp;D team&rsquo;s effectiveness. Using data from 65 teams that belong to green finance industries, collected via the questionnaire survey, we explore how innovation climate positively affects knowledge sharing, and both innovation climate and knowledge sharing can improve the effectiveness of the green finance R&amp;D team. We also find that knowledge sharing mediates the relationship between innovation climate and a green finance R&amp;D team&rsquo;s effectiveness and that knowledge heterogeneity moderates the relationship between knowledge sharing and team effectiveness. Based on these findings, this study contributes to providing useful recommendations for professional managers and policymakers to effectively promote the development of the green finance industry

Breaking the constraints to a high performance metacomputing system : a system approach

The Theory of Constraints (TOC) maintains that every system has its goal. There are necessary conditions that must be satisfied in order to achieve the goal. A constraint is a condition that prevents a system from satisfying a necessary condition or reaching the goal. This paper, by using a system approach, starts by identifying users' requirements, presents a discussion on system goal and necessary conditions for a metacomputing system on the Internet. Constraints that prevent a system from achieving applicability, efficiency, scalability and reliability are particularly exploited. Corresponding injections to break and/or balance the constraints are presented