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The penetration of new energy sources such as wind power is increasing, which consequently increases the occurrence rate of subsynchronous oscillation events. However, existing subsynchronous oscillation source-identification methods primarily analyze fixed-mode oscillations and rarely consider time-varying features, such as frequency drift, caused by the random volatility of wind farms when oscillations occur. This paper proposes a subsynchronous oscillation sourcelocalization method that involves an enhanced short-time Fourier transform and a convolutional neural network (CNN). First, an enhanced STFT is performed to secure high-resolution time-frequency distribution (TFD) images from the measured data of the generation unit ports. Next, these TFD images are amalgamated to form a subsynchronous oscillation feature map that serves as input to the CNN to train the localization model. Ultimately, the trained CNN model realizes the online localization of subsynchronous oscillation sources. The effectiveness and accuracy of the proposed method are validated via multimachine system models simulating forced and natural oscillation events using the Power Systems Computer Aided Design platform. Test results show that the proposed method can localize subsynchronous oscillation sources online while considering unpredictable fluctuations in wind farms, thus providing a foundation for oscillation suppression in practical engineering scenarios. [ABSTRACT FROM AUTHOR]

Wheat production is seriously influenced by extreme hot weather, which has attracted increasing attention. It is important to compare wheat responses to heat at seedling and reproductive stages, to explore the potential relationship between the performances at different growing stages and the possibility of early selection to accelerate heat tolerance breeding. In this study, forty wheat genotypes were screened under heat stress at both seedling and adult stages. It was found that root lengths at seedling stage were severely reduced by heat stress with significant variations among wheat genotypes. Heat-tolerant genotypes at seedling stage showed less root length decrease than susceptible ones. Wheat genotypes tolerant at seedling stage showed higher yield at adult stage after heat treatment. The performances of wheat genotypes screened under heat stress at seedling and adult stages were ranked by seedling damage index and adult damage index. A significant positive relationship was found between heat tolerance at seedling stage and at adult stage (r = 0.6930), suggesting a similar tolerant/susceptible mechanism at different plant growth stages and the possibility of early selection at seedling stage for breeding heat tolerance. Extremely tolerant and susceptible genotypes with consistent performances at seedling and adult stages were genetically compared and associated SNP markers and linked candidate genes were identified. [ABSTRACT FROM AUTHOR]

The multiphase flow characteristic is one of the most concerning problems during solid fluidization exploitation of marine natural gas hydrate reservoirs. In this research, a new transient gas--liquid--solid multiphase flow model with hydrate phase transition was developed. Meanwhile, this model considered the coupling relationship among convective heat transfer, hydrate dynamic decomposition, and multiphase flow. The model can simulate the change of flow pattern from solid--liquid to gas--liquid--solid flow, and describe the distribution character of volume fraction of phase, wellbore temperature and pressure, and hydrate decomposition rate during transportation. The simulation results indicate that the hydrate decomposition region in the wellbore gradually expands, but the hydrate decomposition rate gradually decreases during the solid fluidization exploitation of hydrate. When mining time lasts for 4 h, and the bottom hole pressure decreases by about 0.4 MPa. Increasing NaCl concentration in seawater helps expand hydrate decomposition regions and improves the wellbore hydrate decomposition rate. When the NaCl mass fraction in seawater reaches 15%, it will raise the hydrate decomposition regions to the whole wellbore. In addition, the higher the wellhead backpressure, the lower the decomposition area and decomposition rate of hydrate in the wellbore. When wellhead backpressure reaches 2 MPa, the volume fraction of gas near the wellhead will reduce to about 12%. This work is expected to provide a theoretical basis for the development of marine hydrate reservoirs. [ABSTRACT FROM AUTHOR]

The southern Ordos Basin has excellent petroleum exploration prospects. However, the tectono-thermal history and the controls on petroleum generation, accumulation and preservation conditions in southern basin are unclear. In this study, we analyzed the present geothermal field, paleo-geothermal gradient, maturity of the hydrocarbon source rocks, uplift and cooling process and tectono-thermal evolution history. In the study area, for the Ordovician, Permain and the Triassic strata, the present temperature is low (30-70 °C) in the southeastern area but high (80-140 °C) in the northwestern area. The paleogeothermal gradient varied from 24 °C/km to 30 °C/km with a heat flow of 58e69 mW/m2 (i.e., a medium-temperature basin). The paleo-temperatures are higher than the present temperatures and the maximum paleo-temperatures controlled the thermal maturity of the source rocks. The vitrinite reflectance (Ro) values of the Triassic strata are >0.7% and the thermal maturity reached the middlemature oil generation stage. The Ro values of the Permian-Ordovician strata are >1.8% and the thermal maturity reached the over-mature gas generation stage. The southern Ordos Basin has experienced the multiple tectonic events at the Late Ordovician Caledonian (452 Ma), Late Triassic (215 Ma), Late Jurassic (165-160 Ma), End-Early Cretaceous (110-100 Ma) and Cenozoic (since 40 Ma). A large-scale tectonothermal event occurred at the End-Early Cretaceous (110-100 Ma), which was controlled by lithospheric extension, destruction and thinning. This event led to the highest paleo-temperatures and thermal maturities and coeval with the peak period of petroleum generation and accumulation. The southern Ordos Basin has undergone rapid and large-scale uplift since the Late Cretaceous due to expansion of the northeastern margin of the Tibetan Plateau, uplift of the Qinling orogenic belt and thrust faulting in the Liupanshan tectonic belt. The southern Ordos Basin experienced tectonic overprinting that was strong in the south and weak in the north. The strongest overprinting occurred in the southwestern part of the basin. The large-scale uplift, denudation and faulting led to oil and gas loss from reservoirs. The petroleum generation, accumulation and preservation in the southern Ordos Basin were affected by deep lithospheric structures and the tectono-thermal evolution. This work provides a novel tectono-thermal perspective on the petroleum generation, accumulation and preservation condition of the southern Ordos Basin. [ABSTRACT FROM AUTHOR]

Axial and torsional impact drilling technology is used to improve the drilling efficiency of hard rock formation in the deep underground. Still, the corresponding theory is not mature, and there are few correlative research reports on the rock-breaking mechanism of axial and torsional coupled impact drilling tools. Considering the influence of the impact hammer geometry and movement on the dynamic load parameters (i.e., wavelength, amplitude, frequency, and phase difference), a numerical model that includes a hard formation and single polycrystalline diamond compact cutter was established. The Riedel-Hiermaier-Thoma model, which considers the dynamic damage and strength behavior of rocks, was adopted to analyze the rock damage under axial and torsional impact loads. The numerical simulation results were verified by the experimental results. It was found that compared with conventional drilling, the penetration depths of axial, torsional, and axial-torsional coupled impact drilling increased by 31.3%, 5.6%, and 34.7%, respectively. Increasing the wavelength and amplitude of the axial impact stress wave improved the penetration depth. When the bit rotation speed remained unchanged, increasing the frequency in the axial and circumferential directions had little effect on the penetration depth. However, as the frequency increased, the cutting surface became increasingly smooth, which reduced the occurrence of bit vibration. When the phase difference between the axial and circumferential stress waves was 25%, the penetration depth significantly increased. In addition, the bit vibration problem can be effectively reduced. Finally, the adjustment of engineering and tool structure parameters is proposed to optimize the efficiency of the axial-torsional coupled impact drilling tool. [ABSTRACT FROM AUTHOR]

Herein, we designed and constructed a mesoporous LaAlOx via a solvent evaporation induced selfassembly protocol. The structure and physicochemical property of the corresponding NiMo supported catalyst was analyzed by a set of characterizations, and its catalytic activity was investigated for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene. It has confirmed that the incorporation of La profoundly facilitate the generation of "Type II" NiMoS phase by weakening the interaction of MoeO eAl leakage and promoting the sulfidation of both Ni and Mo oxides as well as changing the morphology of Ni promoted MoS2 slabs, thereafter boosting the HDS performance substantially. The finding here may contribute to the fundamental understanding of structure-activity in ultra-deep desulfurization and inspire the advancement of highly-efficient HDS catalyst in future. [ABSTRACT FROM AUTHOR]

Common wheat (Triticum aestivum L.) is the most important crop in the world and a typical allopolyploid with a large and complex genome. Pre-harvest sprouting (PHS) leads to a significant reduction in grain quality worldwide. PHS is a complex trait with related QTL located on different chromosomes. However, the study of markers and genes related to PHS resistance is limited especially for whitegrained wheat. Four pairs of near isogenic lines (NILs) from a white-grained wheat cross of Chara x DM5637B*8 targeting a major QTL for PHS resistance (Qphs.ccsu-3A.1) on wheat chromosme 3AL were genotyped using the 90K SNP Illumina iSelect array. Ten SNPs were identified, with a 75%-100% consistency between genotype and phenotype in the resistant or susceptible isolines. The 10 SNPs were converted to cost-effective kompetitive allele-specific PCR (KASP) markers. Screening of 48 wheat cultivars with different phenotypes of PHS identified four KASP markers with 81.3%-85.4% conformity between genotype and phenotype. Further investigation revealed that the four SNPs (BS00022245_51, Kukri_c49927_151, BS00022884_51 and BS00110550_51) corresponding to the four validated KASP markers are residing in three independent genes (TraesCS3A03G1072800, TraesCS3A03G1072400, TraesCS3A03G1071800) close to each other with a distance of 4.28-4.48 Mb to the targeted QTL. These three annotated genes have potential functions related to PHS resistance. Our study revealed that combined use of NILs and the 90K SNP chip is a powerful approach for developing KASP markers and mining functional genes in wheat. The KASP markers for PHS resistance on chromosome 3AL are useful for high-throughput evaluation and marker-assisted selection, and the three identified genes could lead to a better understanding of the genetic pathways controlling PHS. [ABSTRACT FROM AUTHOR]