Search Results (1,601)

In this study, we propose a digital domain TDI-CMOS dynamic imaging method based on minimum search domain alignment, which consists of five steps: image-motion vector computation, image jitter estimation, feature pair matching, global displacement estimation, and TDI accumulation. To solve the challenge of matching feature point pairs in dark and low-contrast images, our method first optimizes the size and position of the search box using an image motion compensation mathematical model and a satellite platform jitter model. Then, the feature point pairs that best match the extracted feature points of the reference frame are identified within the search box of the target frame. After that, a kernel density estimation algorithm is proposed for calculating the displacement probability density of each feature point pair to fit the actual displacement between two frames. Finally, we align and superimpose all the frames in the digital domain to generate a delayed integral image. Experimental results show that this method greatly improves the alignment speed and accuracy of dark and low-contrast images during dynamic imaging. It effectively mitigates the effects of image motion and jitter from the spatial camera, and the fitted global image motion error is kept below 0.01 pixels, which is compensated to improve the MTF coefficient of the image motion and jitter link to 0.68, thus improving the imaging quality of TDI. Full article

Developing control systems for high aspect ratio aircraft can be challenging due to the flexibility of the structure involved in the control loop design. A model-based approach can be straightforward to tune the control system parameters and, to this aim, a reliable aircraft flexible model is mandatory. This paper aims to present the approach pursued to design a control strategy considering the flexible aircraft simulator in the loop. Once the elastic model for the longitudinal dynamics has been set up, genetic algorithms are used to determine - together with a Linear Quadratic Regulator controller—a logic to improve the dynamic behaviour whilst encountering a gust. A relatively low order elastic model is developed for the dynamics in the longitudinal plane, including both rigid body and elastic degrees of freedom defined in a vehicle-fixed reference frame. The rigid body degrees of freedom and the associated states are the same as those of the rigid vehicle, whilst the additional states represent the elastic degrees of freedom. Modal characteristics are calculated from a finite element model of the aircraft using a commercial code, with the weight distribution added as lumped masses on grid points, while the aerodynamic rigid properties are described with a nonlinear database. Using the 2-D strip theory and neglecting the unsteady effects, the aeroelastic stability derivatives, i.e., elastic influence coefficients, are computed to superimpose the elastic effects on the rigid body degrees of freedom and vice versa. The flexible dynamics is compared to the rigid one in order to highlight the relevant changes in the aircraft modes. Following is herein proposed a control strategy combining genetic algorithms and Linear Quadratic Regulator controller to reduce the load factor, also considering the oscillation amplitude due to a deterministic gust encountered in a predefined flight condition. Full article

The internal growth patterns and surface micromorphology of diamonds provide a record of their multi-stage evolution, from initial formation within the mantle to their eventual ascent to the Earth’s surface via deeply derived kimberlite magmas. In this study, gemological microscopic examination, Diamond View^TM, Raman spectroscopy, and electron probe analysis were employed to analyze the surface features, internal patterns, and inclusions of the Tancheng alluvial diamonds in Shandong Province, China. The results show that surface features of octahedra with triangular and sharp edges, thick steps with irregular contours or rounded edges, and thin triangular or serrated layers are developed on diamonds during deep-mantle storage, as well as during the growth process of diamonds, when they are not subjected to intense dissolution. The rounding of octahedral and cubic diamond edges and their transformation into tetrahedral (THH) shapes are attributed to resorption in kimberlitic magma. These characteristics indicate that the Tancheng diamonds were commonly resorbed by carbonate–silicate melts during mantle storage. Abnormal birefringence phenomena, including irregular extinction patterns, petaloid and radial extinction patterns, and banded birefringence, were formed during the diamond growth stage. In contrast, fine grid extinction patterns and composite superimposed extinction patterns are related to later plastic deformation. The studied diamonds mainly contain P-type inclusions of olivine and graphite, with a minority of E-type inclusions, including coesite and omphacite. The pressure of entrapment of olivine inclusions within the Tancheng diamonds ranges from 4.3 to 5.9 GPa, which is consistent with that of coesite inclusions, which yield pressure ranging from 5.2 to 5.5 GPa, and a temperature range of 1083–1264 °C. Overall, the evidence suggests that Tancheng diamonds probably originated from hybrid mantle sources metasomatized by the subduction of ancient oceanic lithosphere. Full article

With the aim of the limitations of the existing hydroelectric simulation experiment methods under non-homogeneous reservoir conditions, this paper investigates the seepage characteristics and production capacity laws of complex structural wells by designing hydroelectric simulation experiments of horizontal wells and planar multi-branch wells under non-homogeneous reservoir conditions, based on the hydroelectric similarity principle. The experiments use a CuSO₄ solution and gel to simulate homogeneous and non-homogeneous reservoirs, respectively, and combine with similarity theory to construct the correspondence between the seepage field and the electric field, and to analyze the pressure distribution and the change in production. The results show the following: non-homogeneity significantly alters seepage paths, leading to a reduction in the actual control area; the superimposed effects of branching interference of planar multi-branching wells, and the non-homogeneity of the reservoir, increase the effectiveness of mobilizing the low-permeability area between the branches; the daily gas production of the horizontal wells and the planar multi-branching wells under non-homogeneous conditions are 37.6 × 10⁴ m³/d and 70.9 × 10⁴ m³/d, respectively; and the production gap widened with the increase in the pressure function difference as compared to the homogeneous conditions. This study provides an experimental basis for the development of non-homogeneous gas reservoirs, and it has reference value for the study of seepage mechanism and optimization of well design. Full article

Asymmetric double-suction centrifugal fans are commonly employed in home kitchens to remove cooking pollutants, and their performance is critical to maintaining a healthy indoor environment. However, inlet condition variations significantly influence the aerodynamic efficiency and noise levels. This study utilizes a combination of performance testing and a large eddy simulation to analyze the impact of different inlet conditions on the performance curve, impeller outlet pressure pulsation, unsteady flow structures, and sound quality of an asymmetric double-suction centrifugal fan. A non-uniform air distribution at the inlet is proposed to enhance the fan’s aerodynamic and noise characteristics. The findings reveal that when the inlet area is reduced to less than 70% of its fully open state, the aerodynamic performance declines with decreasing intake area. The amplitude of the superimposed blade-passing frequency is minimized when only the left inlet is open; the pressure coefficient’s fluctuation amplitude in the time domain reaches 0.4, with sharpness peaking at 3.1. In the optimized design, the maximum deviation in total pressure efficiency is limited to 1.96%, with loudness reduced by four sones and improved sharpness and roughness. These results provide valuable insights into the design and noise reduction of asymmetric double-suction squirrel-cage fans. Full article

As an important component of sustainable development and energy transition, wind power is rapidly rising. This paper selects the time series of historical wind power as features and establishes a lightweight prediction model called a broad random forest model (BRF). The proposed model fully uses the feature representation ability of the broad learning system (BLS) and the fast computational speed of random forest (RF). To begin, the example sets are created with a sliding window for the wind power series. Then, the processed data are input into the BLS module. The feature-expansion function of BLS is fully utilized to generate mapped features and enhanced features. These two types of features are reconstructed to obtain a new sample set. Next, the RF model is established for the new sample set to make predictions. The prediction results of all decision trees are superimposed, and their average value is taken as the final prediction result. Finally, the predicted results of BRF are compared with other mainstream machine learning and deep learning methods. The experimental results show that the proposed model has the best predictive performance on the wind power datasets, with an improvement of 0.22% in R² at least. Full article

This work proposes a precise temperature measurement method based on wavelength modulation heterodyne phase-sensitive dispersion spectroscopy (WM-HPSDS). Before the light intensity of the laser was modulated by an electro-optic modulator to generate a three-tone beam, the laser produced additional wavelength modulation by superimposing a high-frequency sinusoidal waveform on a slow sawtooth wave. The second harmonic peak value of the H₂O dispersion phase at 7185.59 cm⁻¹ and 7182.94 cm⁻¹ was used to extract temperature through two-line thermometry. The experiment was carried out on a water-based thermostat and an acoustically excited Bunsen burner. The extracted temperatures of the thermostat agreed well with the reference temperature, and the deviation was within 1.5 °C. The measurement stability of the Bunsen burner flame was approximately 10.4 dB higher than that of direct HPSDS. Furthermore, measuring the peak values under varying laser powers demonstrated that WM-HPSDS was immune to optical power fluctuations. Therefore, this method has potential for measuring temperature in harsh environments. Full article

The Yanbian area of Jilin Province is situated in the eastern segment of the southern margin of the Xing-Meng Orogenic Belt, representing a region that has been superimposed and reworked by the Paleo-Asian Ocean and Circum-Pacific tectonic event. To determine the emplacement age and petrogenesis of the quartz diorite in the Fudong area of Yanbian, Jilin Province, and to investigate its tectonic setting, petrographic studies, zircon U-Pb geochronology, whole-rock Sr-Nd isotopic analysis, zircon Hf isotopic analysis, and detailed geochemical investigations of this intrusion were carried out. The results indicate that the Fudong quartz diorite has: (1) A weighted mean zircon U-Pb age of 186 ± 1.7 Ma, corresponding to the Late Early Jurassic; (2) geochemically high concentrations of Sr (average: 1146 ppm) and Ba (average: 1213 ppm), and enrichment of light rare earth elements (LREE), along with notably high Th/Yb and Rb/Y ratios; (3) geochemically, the quartz diorite is enriched in large-ion lithophile elements (LILEs; e.g., Ba, K) and light rare earth elements (LREEs), while being depleted in high-field-strength elements (HFSEs; e.g., Ta, Ti). These features are consistent with magma formed in a subduction-related setting. In summary, the Fudong quartz diorite formed within an active continental margin tectonic environment associated with the subduction of the Paleo-Pacific Plate. Its primary magma likely originated from an enriched lithospheric mantle that had been metasomatized by fluids released from the subducted slab. Full article

The erosion of Pelton turbine components in mountainous areas with high sediment input is a major challenge for energy- and cost-efficient operation. Quantitative data on possible efficiency losses associated with local damage are needed. A systematic experimental study was carried out on a model turbine to determine the efficiency losses caused by damaged needles and seat rings. For this purpose, artificial patterns of erosion-like damage were generated on the surfaces of needles and seat rings. These patterns were gradually deepened, and hill charts were measured repeatedly. The combination of needle and seat ring defects was also studied, and the finding is that superimposing the individual efficiency losses of the needle and seat ring resulted in the same efficiency loss measured for both damaged parts. The results of the measurement campaign show that damaged needles should be replaced at an early stage of deterioration, as efficiency losses can quickly add up to several percent and become unacceptable at partial load operations of the turbines. Full article

Pelton turbines are susceptible to hydro-abrasive erosion from sediment-laden flows, resulting in a progressive loss of efficiency. Typical defect classes can be derived from the analysis of such damage observed in hydropower plants. A systematic strategy was developed to investigate the effect of locally damaged Pelton runners on the efficiency in laboratory tests using a model turbine. For this purpose, nine identical runners were fabricated and machined with an increasing size, depth, or number of different artificial defect types, such as splitter, rounded or sharp-edged, defects at the cutout, defects in the bucket base, and added ripples on the bucket sides. The processing steps, the efficiency measurement, and the extracted slopes of the efficiency drops are discussed in detail. The main findings are that the efficiency losses due to the various defects increase in a good approximation linearly with the machining depth and that the individual defect types can be superimposed. Defects at the splitter, bucket base, and bucket side dominate the losses at partial load of the turbine, while those at the cutout dominate at full load. Based on the results of this measurement campaign, power plant operators can estimate the magnitude of efficiency losses in their plant. Full article

Vanadium-bearing beryl is a vanadium-bearing variety of green beryl (distinct from emerald) that exhibits an “electro-optical” green (blue-green) color, which has led to its commercial popularity. However, the underlying coloration mechanism remains unclear. The present study adopted standard gemological tests and non-destructive spectroscopic tests, such as X-ray fluorescence, UV-visible-near infrared (UV-Vis-NIR), infrared and Raman spectroscopy, to analyze the vanadium-bearing beryl from Nigeria. The results of these tests indicated the presence of Fe as the predominant chromogenic element of vanadium-bearing beryl, followed by V, at a level exceeding that of Cr. Furthermore, the samples displayed lower levels of alkali and magnesium when compared to other beryls, accompanied by lower refractive indices and specific gravities. Spectroscopic analysis indicates that the structural channels are dominated by type I H₂O, with CO₂, HDO, and D₂O molecules also present. The inclusions observed in vanadium-bearing beryl bear a resemblance to those found in typical aquamarines, which are raindrop-shaped inclusions, and to those found in emeralds of various origins, which are irregular, jagged, gas–liquid two-phase/three-phase inclusions. The broad UV-Vis-NIR absorption bands at 427 and 610 nm are characteristic of V³⁺ (and a minor amount of Cr³⁺). Charge transfer between Fe²⁺ and Fe³⁺ may also contribute to the 610 nm band, which is superimposed on the absorption bands of V³⁺ and Cr³⁺. These factors primarily contribute to the blue-green coloration of beryl. The absorption induced by V³⁺ in the visible violet-blue region exhibits stronger intensity and a greater tendency towards the blue region compared to Cr³⁺. Consequently, the resultant vanadium-bearing beryl acquires the yellow-green hue (induced by V) overlaid with the light blue (induced by charge transfer between Fe²⁺-Fe³⁺ pairs), resulting in the so-called “electro-optical” green (blue-green) beryl. Full article

Precipitation cyclicity plays a crucial role in regional water supply and climate predictions. In this study, we used observational data from 34 representative meteorological stations in the Xinjiang region, a major part of inland arid China, to characterize the interannual cyclicity of regional precipitation from 1951 to 2021 and analyze its contributing factors. The results indicated that the mean annual precipitation in Xinjiang (MAP_XJ) was dominated by a remarkably increasing trend over the past 70 years, which was superimposed by two bands of interannual cycles of approximately 3 years with explanatory variance of 56.57% (Band I) and 6–7 years with explanatory variance of 23.38% (Band II). This is generally consistent with previous studies on the cyclicity of precipitation in Xinjiang for both seasonal and annual precipitation. We analyzed the North Tropical Atlantic sea-surface temperature (NTA_SST), El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Arctic Oscillation (AO), and Indian Summer Monsoon (ISM) as potential forcing factors that show similar interannual cycles and may contribute to the identified precipitation variability. Two approaches, multivariate linear regression and the Random Forest model, were employed to ascertain the relative significance of each factor influencing Bands I and II, respectively. The multivariate linear regression analysis revealed that the AO index contributed the most to Band I, with a significance score of −0.656, whereas the ENSO index with a one-year lead (ENSO_−1yr) played a dominant role in Band II (significance score = 0.457). The Random Forest model also suggested that the AO index exhibited the highest significance score (0.859) for Band I, whereas the AO index with a one-year lead (AO_−1yr) had the highest significance score (0.876) for Band II. Overall, our findings highlight the necessity of employing different methods that consider both the linear and non-linear response of climate variability to driving factors crucial for future climate prediction. Full article

The coupling of water level fluctuations and heavy rainfall in the Three Gorges reservoir area poses a significant threat to the stability of bank slopes, especially in landslide areas with complex geological conditions. In this study, the Huasushu slope in Fengjie County, Chongqing, was taken as the research object and, based on a field investigation and monitoring data, two- and three-dimensional numerical models were constructed to analyze the response mechanism of the slope under the combined effects of different reservoir water level decreases and rainfall. In addition, the safety coefficients under each working condition were calculated using the Morgenstern–Price method. The results show that it is difficult to trigger significant deformation with a single water level drop or rainfall. However, when the reservoir water level drops more than 10 m within a short period of time and is superimposed with strong rainfall, the landslide body is prone to plastic zone extension and significant displacement, showing typical strain localization characteristics. The three-dimensional model further reveals the spatial distribution characteristics of the landslide deformation area, which helps to accurately identify potential destabilization locations. The research results provide theoretical support for the construction of early warning systems for reservoir bank slopes and have reference value for the development of disaster mitigation engineering measures based on the coupling mechanism of rainwater and reservoir water. Full article

Background/Objectives: Migraines contain neurological and gastrointestinal manifestations. The first specific migraine preventive drugs, CGRP monoclonal antibodies (mAbs), though efficacious and very well-tolerated in general, induce constipation as their main adverse event. Our goal was to analyze the role of the two isoforms of CGRP in the development of constipation in patients treated with mABs. Methods: We prospectively measured by ELISA circulating alpha- and beta-CGRP levels in 133 high-frequency episodic/chronic migraine patients before and three months after mAbs treatment and correlated these levels with a number of clinical variables, including the development of constipation during this treatment. Results: Twelve patients (9.0%) noticed de novo constipation with mAbs. Demographics, efficacy end-points, profile of preventive treatment, and comorbidities, with the exception of anxiety/depression, were superimposable between patients with or without emergent constipation. Basal alpha-CGRP levels (49.5 [29.2–73.8] pg/mL) significantly decreased at month three of treatment (40.5 [20.4–61.0] pg/mL; p < 0.0001), both in patients with and without emergent constipation. Pre-treatment circulating beta-CGRP levels (4.0 [2.1–6.2] pg/mL) remained unchanged after three months of treatment (4.3 [2.5–6.0] pg/mL; p = 0.574) in the whole series but were selectively reduced in patients with emergent constipation (p = 0.034). Conclusions: This is the first work exploring the role of the two isoforms of CGRP in the pathophysiology of constipation with mAbs. Our results suggest that the antagonism on the alpha-CGRP isoform plays a relevant role in the antimigraine action of mABs but not in the development of constipation. By contrast, the specific reduction in beta-CGRP levels in patients with emergent constipation supports the role of beta-CGRP antagonism in the development of this adverse event. Full article

To address roof overhang hazards (e.g., rock bursts and gas accumulation) in high-gas coal mines, this study proposes a static stress intervention method for controlled directional roof collapse. Using the 150110 fully mechanized face at Yiyuan Coal Mine as a case study, we investigate the mechanical mechanism of static stress intervention-induced roof collapse through theoretical modeling and FLAC3D simulations in the absence of pre-cracks. The study reveals that advanced boreholes filled with static expansion agents generate stress concentration zones along the drilling array. When superimposed with mining-induced stresses, this configuration induces tensile failure preferentially at borehole locations, thereby achieving controlled directional roof collapse. Theoretical calculations indicate that roof fracturing occurs at predetermined locations when expansion pressure reaches ≥9.11 MPa. FLAC3D simulations analyzed stress redistribution and plastic zone evolution under combined static and mining-induced stresses, demonstrating the method’s efficacy in optimizing roadway stability. Field trials implement spaced boreholes (65 mm diameter, 16 m depth, 1 m spacing) with alternating expansion agent charging, achieving a 6 m reduction in roof collapse intervals, effectively mitigating overhang hazards. Results confirm that static stress intervention reshapes the roof stress field, inducing tensile failure along predetermined paths without relying on pre-cracks. The findings provide theoretical and technical insights for roof stability control in high-gas coal mines. Full article