The contact force between lunar-based equipment and lunar soil.

Lunar-based equipment plays a vital role in the exploration of the moon because it undertakes the tasks of moving, transporting, digging, and so on. In order to control the gait of lunar-based equipment more precisely and guarantee mobile stability, the contact mechanism between its foot and lunar soil is worthy of in-depth study. In this paper, a contact model is proposed to predict the stress, strain, and displacement both on the contact surface and in the lunar soil when the foot is under vertical load. The axial stress in the proposed contact model is verified through the experiment and its accuracy in the lunar equipment is verified through simulation. The error is in a reasonable range and the influence depth of load conforms to the experiment results. This paper provides a relatively accurate model to describe the contact force between the lunar-based equipment's foot and the lunar soil and will promote the research of lunar exploration.

Single-Frequency GNSS Integer Ambiguity Solving Based on Adaptive Genetic Particle Swarm Optimization Algorithm.

Carrier phase measurements currently play a crucial role in achieving rapid and highly accurate positioning of global navigation satellite systems (GNSS). Resolving the integer ambiguity correctly is one of the key steps in this process. To address the inefficiency and slow search problem during ambiguity solving, we propose a single-frequency GNSS integer ambiguity solving based on an adaptive genetic particle swarm optimization (AGPSO) algorithm. Initially, we solve for the floating-point solution and its corresponding covariance matrix using the carrier-phase double difference equation. Subsequently, we decorrelate it using the inverse integer Cholesky algorithm. Furthermore, we introduce an improved fitness function to enhance convergence and search performance. Finally, we combine a particle swarm optimization algorithm with adaptive weights to conduct an integer ambiguity search, where each generation selectively undergoes half-random crossover and mutation operations to facilitate escaping local optima. Comparative studies against traditional algorithms and other intelligent algorithms demonstrate that the AGPSO algorithm exhibits faster convergence rates, improved stability in integer ambiguity search results, and in practical experiments the baseline accuracy of the solution is within 0.02 m, which has some application value in the practical situation of short baselines.

Research on the Improvement of Semi-Global Matching Algorithm for Binocular Vision Based on Lunar Surface Environment.

The low light conditions, abundant dust, and rocky terrain on the lunar surface pose challenges for scientific research. To effectively perceive the surrounding environment, lunar rovers are equipped with binocular cameras. In this paper, with the aim of accurately detect obstacles on the lunar surface under complex conditions, an Improved Semi-Global Matching (I-SGM) algorithm for the binocular cameras is proposed. The proposed method first carries out a cost calculation based on the improved Census transform and an adaptive window based on a connected component. Then, cost aggregation is performed using cross-based cost aggregation in the AD-Census algorithm and the initial disparity of the image is calculated via the Winner-Takes-All (WTA) strategy. Finally, disparity optimization is performed using left-right consistency detection and disparity padding. Utilizing standard test image pairs provided by the Middleburry website, the results of the test reveal that the algorithm can effectively improve the matching accuracy of the SGM algorithm, while reducing the running time of the program and enhancing noise immunity. Furthermore, when applying the I-SGM algorithm to the simulated lunar environment, the results show that the I-SGM algorithm is applicable in dim conditions on the lunar surface and can better help a lunar rover to detect obstacles during its travel.

Greenhouse gas emissions from U.S. crude oil pipeline accidents: 1968 to 2020.

Crude oil pipelines are considered as the lifelines of energy industry. However, accidents of the pipelines can lead to severe public health and environmental concerns, in which greenhouse gas (GHG) emissions, primarily methane, are frequently overlooked. While previous studies examined fugitive emissions in normal operation of crude oil pipelines, emissions resulting from accidents were typically managed separately and were therefore not included in the emission account of oil systems. To bridge this knowledge gap, we employed a bottom-up approach to conducted the first-ever inventory of GHG emissions resulting from crude oil pipeline accidents in the United States at the state level from 1968 to 2020, and leveraged Monte Carlo simulation to estimate the associated uncertainties. Our results reveal that GHG emissions from accidents in gathering pipelines (~720,000 tCO2e) exceed those from transmission pipelines (~290,000 tCO2e), although significantly more accidents have occurred in transmission pipelines (6883 cases) than gathering pipelines (773 cases). Texas accounted for over 40% of total accident-related GHG emissions nationwide. Our study contributes to enhanced accuracy of the GHG account associated with crude oil transport and implementing the data-driven climate mitigation strategies.

An inventory of greenhouse gas emissions due to natural gas pipeline incidents in the United States and Canada from 1980s to 2021.

Natural gas is believed to be a critical transitional energy source. However, natural gas pipelines, once failed, will contribute to a large amount of greenhouse gas (GHG) emissions, including methane from uncontrolled natural gas venting and carbon dioxide from flared natural gas. However, the GHG emissions caused by pipeline incidents are not included in the regular inventories, making the counted GHG amount deviate from the reality. This study, for the first time, establishes an inventory framework for GHG emissions including all natural gas pipeline incidents in the two of the largest gas producers and consumers in North America (United States and Canada) from 1980s to 2021. The inventory comprises GHG emissions resulting from gathering and transmission pipeline incidents in a total of 24 states or regions in the United States between 1970 and 2021, local distribution pipeline incidents in 22 states or regions between 1970 and 2021, as well as natural gas pipeline incidents in a total of 7 provinces or regions in Canada between 1979 and 2021. These datasets can improve the accuracy of regular emission inventories by covering more emission sources in the United States and Canada and provide essential information for climate-oriented pipeline integrity management.

An Adaptive and Robust Control Strategy for Real-Time Hybrid Simulation.

A real-time hybrid simulation (RTHS) is a promising technique to investigate a complicated or large-scale structure by dividing it into numerical and physical substructures and conducting cyber-physical tests on it. The control system design of an RTHS is a challenging topic due to the additional feedback between the physical and numerical substructures, and the complexity of the physical control plant. This paper proposes a novel RTHS control strategy by combining the theories of adaptive control and robust control, where a reformed plant which is highly simplified compared to the physical plant can be used to design the control system without compromising the control performance. The adaptation and robustness features of the control system are realized by the bounded-gain forgetting least-squares estimator and the sliding mode controller, respectively. The control strategy is validated by investigating an RTHS benchmark problem of a nonlinear three-story steel frame The proposed control strategy could simplify the control system design and does not require a precise physical plant; thus, it is an efficient and practical option for an RTHS.

Improvement of AD-Census Algorithm Based on Stereo Vision.

Problems such as low light, similar background colors, and noisy image acquisition often occur when collecting images of lunar surface obstacles. Given these problems, this study focuses on the AD-Census algorithm. In the original Census algorithm, in the bit string calculated with the central pixel point, the bit string will be affected by the noise that the central point is subjected to. The effect of noise results in errors and mismatching. We introduce an improved algorithm to calculate the average window pixel for solving the problem of being susceptible to the central pixel value and improve the accuracy of the algorithm. Experiments have proven that the object contour in the grayscale map of disparity obtained by the improved algorithm is more apparent, and the edge part of the image is significantly improved, which is more in line with the real scene. In addition, because the traditional Census algorithm matches the window size in a fixed rectangle, it is difficult to obtain a suitable window in the image range of different textures, affecting the timeliness of the algorithm. An improvement idea of area growth adaptive window matching is proposed. The improved Census algorithm is applied to the AD-Census algorithm. The results show that the improved AD-Census algorithm has been shown to have an average run time of 5.3% and better matching compared to the traditional AD-Census algorithm for all tested image sets. Finally, the improved algorithm is applied to the simulation environment, and the experimental results show that the obstacles in the image can be effectively detected. The improved algorithm has important practical application value and is important to improve the feasibility and reliability of obstacle detection in lunar exploration projects.

Characteristics of macrofaunal assemblages and their relationships with environmental factors in a semi-enclosed bay.

Characteristics of macrofaunal assemblages and their relationships with environmental factors in a semi-enclosed bay were studied seasonally in China. A total of 251 species were identified, including polychaetes (104 species), crustaceans (73 species), mollusks (51 species), and other phyla (23 species). Mean values of macrofaunal abundance were 1210, 2483, 3209, 3600 ind./m2 while those of biomass were 56.88, 176.15, 136.28, 265.55 g/m2, respectively. Ranges of species richness index, evenness index, Shannon-Wiener index were 1.54-8.16, 0.17-0.90, 0.69-4.78, respectively. The diversity indices were affected by bottom water salinity and pH. BIOENV analysis showed that water depth, phaeophorbide, and silt-clay proportion had important impacts on macrofaunal assemblages while abundance and biomass were affected by bottom water temperature, salinity, and water depth. Compared with historical data, macrofaunal species number, abundance and biomass showed a slight increasing trend, which may be due to the water quality improvement of this bay.

Theoretical-molar Fe3+ recovering lithium from spent LiFePO4 batteries: an acid-free, efficient, and selective process.

In spent lithium iron phosphate batteries, lithium has a considerable recovery value but its content is quite low, thus a low-cost and efficient recycling process has become a challenging research topic. In this paper, two methods about using the non-oxidizing inorganic iron salt - Fe2(SO4)3 to recover lithium from LiFePO4 are proposed. The method-1 is theoretical-molar Fe2(SO4)3 (Fe2(SO4)3 : LiFePO4 =1:2) dosage is added and more than 97% of lithium can be leached in just 30 min even under a pretty high solid-liquid ratio of 500 g/L. Spectrophotometry provides the evidence of Fe2+/Fe3+ substitution in the leaching process. In the method-2, the generated Fe2+ originating from LiFePO4 is fully utilized with the addition of H2O2, and the dosage of Fe2(SO4)3 is decreased by two thirds (Fe2(SO4)3 : LiFePO4 =1:6). Several sulphates (CuSO4, NiSO4, MgSO4) are employed to explore the leaching mechanism. All the results reveal that the reaction of Fe3+ substituting Fe2+ has a powerful driving force. In addition, these two leaching processes simultaneously present superior selectivity for the impurities. The Fe2(SO4)3 in two methods does not cause pollution and is easily regenerated by adding H2SO4. The proposed rapid, efficient and selective leaching thought would be a competitive candidate for recycling spent LiFePO4 batteries.

Frequent interferon regulatory factor 1 (IRF1) binding at remote elements without histone modification.

Transcriptional activators bind DNA and recruit cofactors to modify chromatin. The extent to which these two events are separable is unclear. Here, using a custom ChIP tiling array to map chromatin modifications, we show that interferon-γ-induced DNA binding of signal transducer and activator of transcription 1 (STAT1), typically associated with the transcription factor interferon regulatory factor 1 (IRF1), causes histone acetylation (H3ac, H4ac). In contrast, among IRF1 sites lacking concomitant STAT1 recruitment, only 25% underwent inducible histone acetylation, 31% exhibited constitutive histone acetylation, and 44% had no histone acetylation. These latter "orphan sites" also lacked other activating modifications (e.g. H3K4me1, H3K4me2) and were typically remote from transcription start sites. In these cases the closest gene was typically an IFNγ-inducible locus that did not respond to IFNγ in this setting. Orphan sites were detected in different cell types, suggesting broad relevance. Despite an atypical downstream response (i.e. no histone modifications), IRF1 binding depended on SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4 (SMARCA4 or BRG1), as is typical of active IRF1 enhancers. Although SMARCA4 permitted IRF1 access to the orphan sites, there was no corecruitment of the histone acetyltransferases CREB-binding protein (CBP) and p300. Orphan sites were constitutively unacetylated, and several were marked with repressive chromatin modifications (e.g. H3K27me3). In conclusion, although IRF1 can trigger enhanceosome formation independently of STAT1, its ability to do so depends on local chromatin cues.

Properties of STAT1 and IRF1 enhancers and the influence of SNPs.

BACKGROUND: STAT1 and IRF1 collaborate to induce interferon-γ (IFNγ) stimulated genes (ISGs), but the extent to which they act alone or together is unclear. The effect of single nucleotide polymorphisms (SNPs) on in vivo binding is also largely unknown. RESULTS: We show that IRF1 binds at proximal or distant ISG sites twice as often as STAT1, increasing to sixfold at the MHC class I locus. STAT1 almost always bound with IRF1, while most IRF1 binding events were isolated. Dual binding sites at remote or proximal enhancers distinguished ISGs that were responsive to IFNγ versus cell-specific resistant ISGs, which showed fewer and mainly single binding events. Surprisingly, inducibility in one cell type predicted ISG-responsiveness in other cells. Several dbSNPs overlapped with STAT1 and IRF1 binding motifs, and we developed methodology to rapidly assess their effects. We show that in silico prediction of SNP effects accurately reflects altered binding both in vitro and in vivo. CONCLUSIONS: These data reveal broad cooperation between STAT1 and IRF1, explain cell type specific differences in ISG-responsiveness, and identify genetic variants that may participate in the pathogenesis of immune disorders.