determining the orientation of in-situ stresses is crucial for various geoscience and engineering applications. Conventional methods for estimating these stress orientations often depend on focal mechanism solutions(F...
详细信息
determining the orientation of in-situ stresses is crucial for various geoscience and engineering applications. Conventional methods for estimating these stress orientations often depend on focal mechanism solutions(FMSs) derived from earthquake data and formation micro-imager(FMI) data from well ***, these techniques can be costly, depth-inaccurate, and may lack spatial coverage. To address this issue, we introduce the use of three-dimensional(3d) seismic data(active sources) as a lateral constraint to approximate the 3d stress orientation field. recognizing that both stress and fracture patterns are closely related to seismic velocity anisotropy, we derive the orientation of azimuthal anisotropy from multi-azimuth 3d seismic data to compensate for the lack of spatial stress orientation information. We apply our proposed workflow to a case study in the Weiyuan area of the Sichuan Basin, china, a region targeted for shale gas production. By integrating diverse datasets, including 3d seismic, earthquakes, and well logs, we develop a comprehensive 3d model of in-situ stress(orientations and magnitudes). Ourresults demonstrate that the estimated anisotropy orientations from 3d seismic data are consistent with the direction of maximum horizontal principal stress(SHmax) obtained from FMIs. We analyzed 12earthquakes(magnitude > 3) recorded between 2016 and 2020 for their FMSs and compressional axis(Paxis) orientations. The derived SHmax direction from our 3d stress model is 110°ES(East-South), which shows excellent agreement with the FMSs(within 3.96°). This close alignment validates the reliability and precision of our integrated method for predicting 3d SHmax orientations.
With photovoltaic(PV)sources becoming more prevalent in the energy generation mix,transitioning grid-connected PV systems from grid-following(GFL)mode to gridforming(GFM)mode becomes essential for offering self-synchr...
详细信息
With photovoltaic(PV)sources becoming more prevalent in the energy generation mix,transitioning grid-connected PV systems from grid-following(GFL)mode to gridforming(GFM)mode becomes essential for offering self-synchronization and active support *** numerous GFM methods have been proposed,the potential of dC voltage control malfunction during the provision of the primary and inertia support in a GFM PV system remains insufficiently *** fill the gap,some main GFM methods have been integrated into PV systems featuring detaileddC source *** conduct a comparative analysis of their performance in active support anddC voltage *** GFM methods such as virtual synchronous machine(VSM)face a significant risk of dC voltage failure in situations like alterations in solarradiation,leading to PV system tripping and jeopardizing local system *** the case of dC GFM methods such as matching control(MC),the active support falls short due to the absence of an accurate anddispatchable droop *** address the issue,a matching synchronous machine(MSM)control method is developed to provide dispatchable active support and enhance the dC voltage dynamics by integrating the MC and VSM control *** active support capability of the PV systems with the proposed method is quantified analytically and verified by numerical simulations and field tests.
1 Introduction Microbial infections represent significant global health challenges with far-reaching *** contemporary medical practice,quantitative polymerase chain reaction(qPCr)stands as an important technique for p...
详细信息
1 Introduction Microbial infections represent significant global health challenges with far-reaching *** contemporary medical practice,quantitative polymerase chain reaction(qPCr)stands as an important technique for pathogen detection,and the success of qPCr-baseddiagnosis fundamentally depends on the precision of the qPCr primers employed[1].However,to our knowledge,no easy-to-use qPCr primerdesign tool with flexible,customized options is *** most clinical contexts,detecting the presence of a pathogen within a given clinical sample is the primary ***,well-designed primers should achieve dual objectives:high sensitivity and specificity fordetecting target pathogens,while avoiding false positives,even when testing evolutionarily closely related ***,a constellation of software andprogram packages towards qPCr primerdesign is available(for example,ssPrimer).However,these tools typically operate on a single gene orregion,necessitating user-driven selection of the region or gene[2,3].In this context,we introduce the first one-step solution,to our knowledge,for scanning entire genomes to identify the best candidate primer *** addition,our framework allows users to efficiently search against a large number of genomes(over 1,800 genomes in our test case)to identify specific primers.
real-worldrobots will face a wide variety of complex environments when performing navigation or exploration tasks, especially in situations where the robots have never been seen before. Usually, robots need to establ...
详细信息
real-worldrobots will face a wide variety of complex environments when performing navigation or exploration tasks, especially in situations where the robots have never been seen before. Usually, robots need to establish local or global maps and then use path planning algorithms to determine theirroutes. However, in some environments, such as a wild grassy path or pavement on either side of a road, it is difficult forrobots to plan routes through navigation maps. To address this, we propose a robust framework forrobot navigation using contrastive learning called Contrastive Observation-Action in Latent (COAL) space. To extract features from the action space and observation space, respectively, COAL uses two different encoders. At the training stage, COAL does not require any data annotation and a mask approach is employed to keep features with significant differences away from each other in latent space. Similar to multimodal contrastive learning, we maximize bidirectional mutual information to align the features of observations and action sequences in latent space, which can enhance the generalization of the model. At the deployment stage, robots only need the current image as observation to complete exploration tasks. The most suitable action sequence is selected from the sampleddata for generating control signals. We evaluate the robustness of COAL in both simulation andreal environments. Only 41 min of unlabeled training data is required to allow COAL to explore environments that have never been seen before, even at night. Compared with state-of-the-art methods, COAL has the strongest robustness and generalization ability. More importantly, the robustness of COAL is further improved by augmenting our training data using other open-source data sets, which indicates that our framework has great potential to extract deep features of observations and action sequences. Our code and trained models are available at .
Homochiral coordination polymers(HCPs) represent a class of structurally ordered crystalline materials assembled by the coordination of metal ions or metal clusters with chiral ligands, holding great promise for appli...
详细信息
Homochiral coordination polymers(HCPs) represent a class of structurally ordered crystalline materials assembled by the coordination of metal ions or metal clusters with chiral ligands, holding great promise for applications in catalysis,separation, sensing, and other fields [1–9]. Chiral ligands play a central role in the construction of HCPs. Proline and its derivatives have been extensively studied as homogeneous catalysts in a wide range of asymmetric organic reactions, where the pyrrolidine-NH functionality stands out as a pivotal catalytic site [10,11].
With a broadrange of application prospects,hydrogen fuel cell technology is regarded as a clean and efficient energy conversion ***,challenges exist in terms of the safe storage and transportation of *** proposed sol...
详细信息
With a broadrange of application prospects,hydrogen fuel cell technology is regarded as a clean and efficient energy conversion ***,challenges exist in terms of the safe storage and transportation of *** proposed solution to this problem is the utilization of methanol on-line steam reforming technology for hydrogen *** this paper,an integrated system for in-situ steam reforming of fuel coupled with proton exchange membrane fuel cells(PEMFC)power generation is proposed,and sensitivity analysis and exergy sensitivity analysis are *** the gradual utilization of waste heat and the integration of the system,fuel consumption is reduced and the power generation efficiency of the system is *** the design operating conditions,the power generation efficiency and exergy efficiency of the system are achieved at 44.59%and 39.70%,*** study presents a proven method for the efficient integration of fuel thermochemical conversion for hydrogen production with fuel cells for power generation,highlighting the advantages of complementary utilization of methanol steam reforming and PEMFC.
Ongoing climate change has a considerable influence on the seasonality,timing,and intensity of rainfall worldwide,and is also predicted to decrease snow cover in cold *** is a widely distributed tree species in boreal...
详细信息
Ongoing climate change has a considerable influence on the seasonality,timing,and intensity of rainfall worldwide,and is also predicted to decrease snow cover in cold *** is a widely distributed tree species in boreal Eurasia,calling for a comprehensive understanding of how larch adapts to changes in both rainfall and snowfall by adjusting carbon-water ***,we conducted a short-term rainfall(−60% ambient rainfall;three-year)and snowfall(−73% ambient snowfall;two-year)exclusions experiment in Larix gmelinii forest in northeastern china,and aimed to explore the responses of hydraulic(leaf pressure-volume traits,leaf and branch hydraulic conductivity and embolism resistance),stomatal(stomatal closure point and stomatal safety margin),and economic(photosynthetic rate,nutrient and non-structural carbohydrates contents)traits to rainfall and snowfall *** the weak alternation of leaf and branch hydraulic traits,both rainfall and snowfall reductions significantly led to early stomatal closure and increased stomatal safety margins(the difference between stomatal closure point and xylem embolism threshold,describing drought resistance by merging both hydraulic and stomatal strategies).reductions in rainfall and snowfall induced water or/and low-temperature stress,resulting in more conservative leaf economic traits,including a reduced photosynthetic rate,lower leaf nitrogen concentration,and higher leaf *** addition,larch responded to reductions in rainfall and snowfall by up-regulating non-structural carbohydrates in the xylem,which helps repair embolism or lower the freezing point acting as ***,our findings reveal that larch could adapt to the drought and snowpack reduction by strict stomatal regulation and investing non-structural carbohydrates in embolism repairing,at the cost of carbon assimilation.
Nonlinear oscillators with multiple potential wells are widely used in practical structures such as vibration absorbers and energy harvesters due to their lower energy thresholds. The study of the chaotic characterist...
详细信息
Nonlinear oscillators with multiple potential wells are widely used in practical structures such as vibration absorbers and energy harvesters due to their lower energy thresholds. The study of the chaotic characteristics of various homoclinic oscillators is of great significance for further understanding multi-stable systems, since homoclinic orbits characterize the boundary between different types of motion. The properdesign of triple smooth-discontinuous (Sd) oscillators can achieve four-well characteristics, and the elastic restoring force of the system can be approximated as a piecewise linear function. Unlike bistable and tri-stable oscillators, this oscillator exhibits multiple types of homoclinic orbits, and analytical expressions for these types of orbits are derived by analyzing the geometric structure of phase space. By utilizing the energy relationships of the Hamiltonian system and extending the Melnikov method, the threshold curves of these three types of homoclinic orbits are derived. Finally, the relationship between these threshold curves and the chaotic characteristics of the system is investigated through numerical simulations.
Germanium,a critical yet often overlooked metal,has experienced significant shifts in its global market,largely driven by china’s dominant ***,concerns are growing over the sustainability of germanium supply in china...
详细信息
Germanium,a critical yet often overlooked metal,has experienced significant shifts in its global market,largely driven by china’s dominant ***,concerns are growing over the sustainability of germanium supply in chinadue to imbalances in mining,manufacturing,recycling,andrising *** this study,we employ substance flow analysis to provide a quantitative assessment of china’s germanium flow system in 2019,and we project future demand and anthropogenic mineral generation up to 2050 using stock-driven *** results indicate that by 2050,domestic demand for germanium will increase to 164–187 t—double the demand in 2019—with infrared optics and solar cells being the primary drivers.A supply shortage is anticipated before 2040,although recycling through urban mining could meet around 30%of the *** findings underscore the urgent need to address emerging supply challenges and offer critical insights for policymakers and stakeholders to inform strategic decision-making.
As a cluster overlap amplitude,the reduced-width amplitude is an important physical quantity for analyzing clustering in the nucleus depending on specified channels and has been calculated and widely applied in nuclea...
详细信息
As a cluster overlap amplitude,the reduced-width amplitude is an important physical quantity for analyzing clustering in the nucleus depending on specified channels and has been calculated and widely applied in nuclear cluster *** this review,we briefly revisit the theoretical framework for calculating the reduced-width amplitude,as well as the outlines of cluster models to obtain microscopic or semi-microscopic cluster wave *** also introduce the recent progress related to cluster overlap amplitudes,including the implementation of cross-section estimation and extension to three-body clustering *** examples are provided to demonstrate the application of the reduced-width amplitude in analyzing clustering structures.
暂无评论