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Failure mechanisms and destruction characteristics of cemented coal gangue backfill under compression effect of non-uniform load
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作者 FENG Guo-rui GUO Wei +5 位作者 QI Ting-ye LI Zhu CUI Jia-qing WANG Hao-chen CUI Ye-kai MA Jing-kai 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第8期2676-2693,共18页
Backfill mining is one of the most important technical means for controlling strata movement and reducing surface subsidence and environmental damage during exploitation of underground coal resources. Ensuring the sta... Backfill mining is one of the most important technical means for controlling strata movement and reducing surface subsidence and environmental damage during exploitation of underground coal resources. Ensuring the stability of the backfill bodies is the primary prerequisite for maintaining the safety of the backfilling working face, and the loading characteristics of backfill are closely related to the deformation and subsidence of the roof. Elastic thin plate model was used to explore the non-uniform subsidence law of the roof, and then the non-uniform distribution characteristics of backfill bodies’ load were revealed. Through a self-developed non-uniform loading device combined with acoustic emission (AE) and digital image correlation (DIC) monitoring technology, the synergistic dynamic evolution law of the bearing capacity, apparent crack, and internal fracture of cemented coal gangue backfills (CCGBs) under loads with different degrees of non-uniformity was deeply explored. The results showed that: 1) The uniaxial compressive strength (UCS) of CCGB increased and then decreased with an increase in the degree of non-uniformity of load (DNL). About 40% of DNL was the inflection point of DNL-UCS curve and when DNL exceeded 40%, the strength decreased in a cliff-like manner;2) A positive correlation was observed between the AE ringing count and UCS during the loading process of the specimen, which was manifested by a higher AE ringing count of the high-strength specimen. 3) Shear cracks gradually increased and failure mode of specimens gradually changed from “X” type dominated by tension cracks to inverted “Y” type dominated by shear cracks with an increase in DNL, and the crack opening displacement at the peak stress decreased and then increased. The crack opening displacement at 40% of the DNL was the smallest. This was consistent with the judgment of crack size based on the AE b-value, i. e., it showed the typical characteristics of “small b-value-large crack and large b-value-small crack”. The research results are of significance for preventing the instability and failure of backfill. 展开更多
关键词 cemented coal gangue backfill non-uniform load degree of non-uniformity of load failure mode crack opening displacement
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Study of the pressure transient behavior of directional wells considering the effect of non-uniform flux distribution
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作者 Yan-Zhong Liang Bai-Lu Teng Wan-Jing Luo 《Petroleum Science》 SCIE EI CAS CSCD 2024年第3期1765-1779,共15页
During the production,the fluid in the vicinity of the directional well enters the wellbore with different rates,leading to non-uniform flux distribution along the directional well.However,in all existing studies,it i... During the production,the fluid in the vicinity of the directional well enters the wellbore with different rates,leading to non-uniform flux distribution along the directional well.However,in all existing studies,it is oversimplified to a uniform flux distribution,which can result in inaccurate results for field applications.Therefore,this paper proposes a semi-analytical model of a directional well based on the assumption of non-uniform flux distribution.Specifically,the direction well is discretized into a carefully chosen series of linear sources,such that the complex well trajectory can be captured and the nonuniform flux distribution along the wellbore can be considered to model the three-dimensional flow behavior.By using the finite difference method,we can obtain the numerical solutions of the transient flow within the wellbore.With the aid of Green's function method,we can obtain the analytical solutions of the transient flow from the matrix to the wellbore.The complete flow behavior of a directional well is perfectly represented by coupling the above two types of transient flow.Subsequently,on the basis of the proposed model,we conduct a comprehensive analysis of the pressure transient behavior of a directional well.The computation results show that the flux variation along the direction well has a significant effect on pressure responses.In addition,the directional well in an infinite reservoir may exhibit the following flow regimes:wellbore afterflow,transition flow,inclined radial flow,elliptical flow,horizontal linear flow,and horizontal radial flow.The horizontal linear flow can be observed only if the formation thickness is much smaller than the well length.Furthermore,a dip region that appears on the pressure derivative curve indicates the three-dimensional flow behavior near the wellbore. 展开更多
关键词 Directional well Pressure transient behavior Semi-analytical model non-uniform flux
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Study on the influence of side-blown airflow velocities on plasma and combustion wave generated from fused silica induced by combined pulse laser
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作者 余昊 蔡继兴 +3 位作者 毛洪涛 王云鹏 李忆 李顺 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第7期165-176,共12页
This study examines the impact of variations in side-blowing airflow velocity on plasma generation,combustion wave propagation mechanisms,and surface damage in fused silica induced by a combined millisecond-nanosecond... This study examines the impact of variations in side-blowing airflow velocity on plasma generation,combustion wave propagation mechanisms,and surface damage in fused silica induced by a combined millisecond-nanosecond pulsed laser.The airflow rate and pulse delay are the main experimental variables.The evolution of plasma motion was recorded using ultrafast time-resolved optical shadowing.The experimental results demonstrate that the expansion velocities of the plasma and combustion wave are influenced differently by the sideblowing airflow at different airflow rates(0.2 Ma,0.4 Ma,and 0.6 Ma).As the flow rate of the sideblow air stream increases,the initial expansion velocities of the plasma and combustion wave gradually decrease,and the side-blow air stream increasingly suppresses the plasma.It is important to note that the target vapor is always formed and ionized into plasma during the combined pulse laser action.Therefore,the side-blown airflow alone cannot completely clear the plasma.Depending on the delay conditions,the pressure of the side-blowing airflow,the influence of inverse Bremsstrahlung radiation absorption and target surface absorption mechanisms can lead to a phenomenon known as the double combustion waves when using a nanosecond pulse laser.Both simulation and experimental results are consistent,indicating the potential for further exploration of fused silica targets in the laser field. 展开更多
关键词 different airflow speeds PLASMA combustion wave different pulse delay surface damage
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Effect of non-uniform swelling on coal multiphysics during gas injection: The triangle approach
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作者 Yifan Huang Jishan Liu +2 位作者 Yaoyao Zhao Derek Elsworth Yee-Kwong Leong 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第4期1362-1372,共11页
In current dual porosity/permeability models,there exists a fundamental assumption that the adsorption-induced swelling is distributed uniformly within the representative elementary volume (REV),irrespective of its in... In current dual porosity/permeability models,there exists a fundamental assumption that the adsorption-induced swelling is distributed uniformly within the representative elementary volume (REV),irrespective of its internal structures and transient processes.However,both internal structures and transient processes can lead to the non-uniform swelling.In this study,we hypothesize that the non-uniform swelling is responsible for why coal permeability in experimental measurements is not only controlled by the effective stress but also is affected by the adsorption-induced swelling.We propose a concept of the swelling triangle composed of swelling paths to characterize the evolution of the non-uniform swelling and serve as a core link in coupled multiphysics.A swelling path is determined by a dimensionless volumetric ratio and a dimensionless swelling ratio.Different swelling paths have the same start and end point,and each swelling path represents a unique swelling case.The swelling path as the diagonal of the triangle represents the case of the uniform swelling while that as the two perpendicular boundaries represents the case of the localized swelling.The paths of all intermediate cases populate inside the triangle.The corresponding relations between the swelling path and the response of coal multiphysics are established by a non-uniform swelling coefficient.We define this method as the triangle approach and corresponding models as swelling path-based ones.The proposed concept and models are verified against a long-term experimental measurement of permeability and strains under constant effective stress.Our results demonstrate that during gas injection,coal multiphysics responses have a close dependence on the swelling path,and that in both future experiments and field predictions,this dependence must be considered. 展开更多
关键词 Transient process HETEROGENEITY Swelling triangle Swelling path non-uniform swelling coefficient
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The Influence of Airflow Transport Pathways on Precipitation during the Rainy Season in the Liupan Mountains of Northwest China
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作者 Yujun QIU Chunsong LU +1 位作者 Zhiliang SHU Peiyun DENG 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2024年第11期2215-2229,共15页
This study investigates the influence of airflow transport pathways on seasonal rainfall in the mountainous region of the Liupan Mountains(LM) during the rainy seasons from 2020 to 2022, utilizing observational data f... This study investigates the influence of airflow transport pathways on seasonal rainfall in the mountainous region of the Liupan Mountains(LM) during the rainy seasons from 2020 to 2022, utilizing observational data from seven ground gradient stations located on the eastern slopes, western slopes, and mountaintops combined with backward trajectory cluster analysis. The results indicate 1) that the LM's rainy season, characterized by overcast and rainy days, is mainly influenced by cold and moist airflows(CMAs) from the westerly direction and warm and moist airflows(WMAs) from a slightly southern direction. The precipitation amounts under four airflow transport paths are ranked from largest to smallest as follows: WMAs, CMAs, warm dry airflows(WDAs), and cold dry airflows(CDAs). 2) WMAs contribute significantly more to the intensity of regional precipitation than the other three types of airflows. During localized precipitation events,warm airflows have higher precipitation intensities at night than cold airflows, while the opposite is true during the afternoon. 3) During regional precipitation events, water vapor content is the primary influencing factor. Precipitation characteristics under humid airflows are mainly affected by high water vapor content, whereas during dry airflow precipitation, dynamic and thermodynamic factors have a more pronounced impact. 4) During localized precipitation events, the influence of dynamic and thermodynamic factors is more complex than during regional precipitation, with the precipitation characteristics of the four airflows closely related to their water vapor content, air temperature and humidity attributes, and orographic lifting. 5) Compared to regional precipitation, the influence of topography is more prominent in localized precipitation processes. 展开更多
关键词 regional precipitation localized precipitation airflow transport water vapor flux instability energy topographic influence
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Pressure transient characteristics of non-uniform conductivity fractured wells in viscoelasticity polymer flooding based on oil-water two-phase flow
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作者 Yang Wang Jia Zhang +2 位作者 Shi-Long Yang Ze-Xuan Xu Shi-Qing Cheng 《Petroleum Science》 SCIE EI CAS CSCD 2024年第1期343-351,共9页
Polymer flooding in fractured wells has been extensively applied in oilfields to enhance oil recovery.In contrast to water,polymer solution exhibits non-Newtonian and nonlinear behavior such as effects of shear thinni... Polymer flooding in fractured wells has been extensively applied in oilfields to enhance oil recovery.In contrast to water,polymer solution exhibits non-Newtonian and nonlinear behavior such as effects of shear thinning and shear thickening,polymer convection,diffusion,adsorption retention,inaccessible pore volume and reduced effective permeability.Meanwhile,the flux density and fracture conductivity along the hydraulic fracture are generally non-uniform due to the effects of pressure distribution,formation damage,and proppant breakage.In this paper,we present an oil-water two-phase flow model that captures these complex non-Newtonian and nonlinear behavior,and non-uniform fracture characteristics in fractured polymer flooding.The hydraulic fracture is firstly divided into two parts:high-conductivity fracture near the wellbore and low-conductivity fracture in the far-wellbore section.A hybrid grid system,including perpendicular bisection(PEBI)and Cartesian grid,is applied to discrete the partial differential flow equations,and the local grid refinement method is applied in the near-wellbore region to accurately calculate the pressure distribution and shear rate of polymer solution.The combination of polymer behavior characterizations and numerical flow simulations are applied,resulting in the calculation for the distribution of water saturation,polymer concentration and reservoir pressure.Compared with the polymer flooding well with uniform fracture conductivity,this non-uniform fracture conductivity model exhibits the larger pressure difference,and the shorter bilinear flow period due to the decrease of fracture flow ability in the far-wellbore section.The field case of the fall-off test demonstrates that the proposed method characterizes fracture characteristics more accurately,and yields fracture half-lengths that better match engineering reality,enabling a quantitative segmented characterization of the near-wellbore section with high fracture conductivity and the far-wellbore section with low fracture conductivity.The novelty of this paper is the analysis of pressure performances caused by the fracture dynamics and polymer rheology,as well as an analysis method that derives formation and fracture parameters based on the pressure and its derivative curves. 展开更多
关键词 Polymer flooding Non-Newtonian fluid non-uniform fracture conductivity Two-phase flow Pressure transient analysis
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An improved non-uniform fast Fourier transform method for radio imaging of coronal mass ejections
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作者 Weidan Zhang Bing Wang +3 位作者 Zhao Wu Shuwang Chang Yao Chen Fabao Yan 《Astronomical Techniques and Instruments》 CSCD 2024年第2期117-127,共11页
Radioheliographs can obtain solar images at high temporal and spatial resolution,with a high dynamic range.These are among the most important instruments for studying solar radio bursts,understanding solar eruption ev... Radioheliographs can obtain solar images at high temporal and spatial resolution,with a high dynamic range.These are among the most important instruments for studying solar radio bursts,understanding solar eruption events,and conducting space weather forecasting.This study aims to explore the effective use of radioheliographs for solar observations,specifically for imaging coronal mass ejections(CME),to track their evolution and provide space weather warnings.We have developed an imaging simulation program based on the principle of aperture synthesis imaging,covering the entire data processing flow from antenna configuration to dirty map generation.For grid processing,we propose an improved non-uniform fast Fourier transform(NUFFT)method to provide superior image quality.Using simulated imaging of radio coronal mass ejections,we provide practical recommendations for the performance of radioheliographs.This study provides important support for the validation and calibration of radioheliograph data processing,and is expected to profoundly enhance our understanding of solar activities. 展开更多
关键词 Radio interference GRIDDING IMAGING non-uniform fast Fourier transform
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Dynamic behavior of outburst two-phase flow in a coal mine T-shaped roadway:The formation of impact airflow and its disaster-causing effect
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作者 Liang Cheng Jiang Xu +4 位作者 Shoujian Peng Hailin Yang Feng Jiao Bin Zhou Fazhi Yan 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2023年第8期1001-1017,共17页
The study of the dynamic disaster mechanism of coal and gas outburst two-phase flow is crucial for improving disaster reduction and rescue ability of coal mine outburst accidents.An outburst test in a T-shaped roadway... The study of the dynamic disaster mechanism of coal and gas outburst two-phase flow is crucial for improving disaster reduction and rescue ability of coal mine outburst accidents.An outburst test in a T-shaped roadway was conducted using a self-developed large-scale outburst dynamic disaster test system.We investigated the release characteristics of main energy sources in coal seam,and obtained the dynamic characteristics of outburst two-phase flow in a roadway.Additionally,we established a formation model for outburst impact flow and a model for its flow in a bifurcated structure.The results indicate that the outburst process exhibits pulse characteristics,and the rapid destruction process of coal seam and the blocking state of gas flow are the main causes of the pulse phenomenon.The outburst energy is released in stages,and the elastic potential energy is released in the vertical direction before the horizontal direction.In a straight roadway,the impact force oscillates along the roadway.With an increase in the solid–gas ratio,the two-phase flow impact force gradually increases,and the disaster range extends from the middle of the roadway to the coal seam.In the area near the coal seam,the disaster caused by the two-phase flow impact is characterized by intermittent recovery.In a bifurcated roadway,the effect of impact airflow on impact dynamic disaster is much higher than that of two-phase flow,and the impact force tends to weaken with increasing solid-gas ratio.The impact force is asymmetrically distributed;it is higher on the left of the bifurcated roadway.With an increase in the solid-gas ratio,the static pressure rapidly decreases,and the bifurcated structure accelerates the attenuation of static pressure.Moreover,secondary acceleration is observed when the shock wave moves along the T-shaped roadway,indicating that the bifurcated structure increases the shock wave velocity. 展开更多
关键词 Multiphase flow Coal and gas outburst Dynamic disaster Impact airflow T-shaped bifurcated roadway Coal seam
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Robust and Reusable Fuzzy Extractors from Non-Uniform Learning with Errors Problem
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作者 Joo Woo Jonghyun Kim Jong Hwan Park 《Computers, Materials & Continua》 SCIE EI 2023年第1期1985-2003,共19页
Afuzzy extractor can extract an almost uniformrandom string from a noisy source with enough entropy such as biometric data.To reproduce an identical key from repeated readings of biometric data,the fuzzy extractor gen... Afuzzy extractor can extract an almost uniformrandom string from a noisy source with enough entropy such as biometric data.To reproduce an identical key from repeated readings of biometric data,the fuzzy extractor generates a helper data and a random string from biometric data and uses the helper data to reproduce the random string from the second reading.In 2013,Fuller et al.proposed a computational fuzzy extractor based on the learning with errors problem.Their construction,however,can tolerate a sub-linear fraction of errors and has an inefficient decoding algorithm,which causes the reproducing time to increase significantly.In 2016,Canetti et al.proposed a fuzzy extractor with inputs from low-entropy distributions based on a strong primitive,which is called digital locker.However,their construction necessitates an excessive amount of storage space for the helper data,which is stored in authentication server.Based on these observations,we propose a new efficient computational fuzzy extractorwith small size of helper data.Our scheme supports reusability and robustness,which are security notions that must be satisfied in order to use a fuzzy extractor as a secure authentication method in real life.Also,it conceals no information about the biometric data and thanks to the new decoding algorithm can tolerate linear errors.Based on the non-uniform learning with errors problem,we present a formal security proof for the proposed fuzzy extractor.Furthermore,we analyze the performance of our fuzzy extractor scheme and provide parameter sets that meet the security requirements.As a result of our implementation and analysis,we show that our scheme outperforms previous fuzzy extractor schemes in terms of the efficiency of the generation and reproduction algorithms,as well as the size of helper data. 展开更多
关键词 Fuzzy extractor REUSABILITY robustness biometric authentication non-uniform learning with errors
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Radial Basis Approximations Based BEMD for Enhancement of Non-Uniform Illumination Images
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作者 Anchal Tyagi Salem Alelyani +3 位作者 Sapna Katiyar Mohammad Rashid Hussain Rijwan Khan Mohammed Saleh Alsaqer 《Computer Systems Science & Engineering》 SCIE EI 2023年第5期1423-1438,共16页
An image can be degraded due to many environmental factors like foggy or hazy weather,low light conditions,extra light conditions etc.Image captured under the poor light conditions is generally known as non-uniform il... An image can be degraded due to many environmental factors like foggy or hazy weather,low light conditions,extra light conditions etc.Image captured under the poor light conditions is generally known as non-uniform illumination image.Non-uniform illumination hides some important information present in an image during the image capture Also,it degrades the visual quality of image which generates the need for enhancement of such images.Various techniques have been present in literature for the enhancement of such type of images.In this paper,a novel architecture has been proposed for enhancement of poor illumination images which uses radial basis approximations based BEMD(Bi-dimensional Empirical Mode Decomposition).The enhancement algorithm is applied on intensity and saturation components of image.Firstly,intensity component has been decomposed into various bi-dimensional intrinsic mode function and residue by using sifting algorithm.Secondly,some linear transformations techniques have been applied on various bidimensional intrinsic modes obtained and residue and further on joining the transformed modes with residue,enhanced intensity component is obtained.Saturation part of an image is then enhanced in accordance to the enhanced intensity component.Final enhanced image can be obtained by joining the hue,enhanced intensity and enhanced saturation parts of the given image.The proposed algorithm will not only give the visual pleasant image but maintains the naturalness of image also. 展开更多
关键词 non-uniform illumination BEMD intrinsic modes radial basis approximation linear transformation
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微米级类球形介孔材料用于乙烯聚合催化剂 被引量:1
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作者 亢宇 吕新平 刘红梅 《石油化工》 CAS CSCD 北大核心 2024年第3期339-346,共8页
采用2-(4-氯磺酰苯基)乙基三甲氧基硅烷对类球形介孔材料进行疏水处理,制备了疏水性类球形介孔材料,将其作为载体,通过气流式喷雾干燥技术制备了聚乙烯催化剂。对疏水处理前后的类球形介孔材料进行了XRD、N2吸附-脱附、TEM、SEM表征,考... 采用2-(4-氯磺酰苯基)乙基三甲氧基硅烷对类球形介孔材料进行疏水处理,制备了疏水性类球形介孔材料,将其作为载体,通过气流式喷雾干燥技术制备了聚乙烯催化剂。对疏水处理前后的类球形介孔材料进行了XRD、N2吸附-脱附、TEM、SEM表征,考察了气流式喷雾干燥过程中载气流量和浆料浓度对聚乙烯催化剂的影响,并评价了催化剂的乙烯聚合性能。实验结果表明,类球形介孔材料在疏水处理后孔结构和微观结构稳定;最佳喷雾干燥条件为喷雾干燥器进、出风口温度分别为140,105℃,载气流量为30 L/s,浆料浓度为30%(w);在最佳喷雾干燥条件下制备的催化剂用于乙烯聚合时,催化活性为28000 g/g,远高于工业用TS-610硅胶制备的催化剂的活性(9000 g/g),反应得到的聚合物性能也优于TS-610硅胶制备的催化剂得到的聚乙烯粉料。 展开更多
关键词 类球形介孔材料 疏水改性 气流式喷雾干燥 乙烯聚合
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Image Non-Uniformity Correction in 3T Gd-EOB-DTPA-Enhanced Magnetic Resonance Imaging: Comparison among Different Software Versions
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作者 Hirofumi Hata Yusuke Inoue +5 位作者 Keiji Matsunaga Kaoru Fujii Toshio Tamiya Ai Nakajima Yuki Takato Kazuki Hashizume 《Open Journal of Medical Imaging》 2023年第3期114-126,共13页
Background: Non-uniformity in signal intensity occurs commonly in magnetic resonance (MR) imaging, which may pose substantial problems when using a 3T scanner. Therefore, image non-uniformity correction is usually app... Background: Non-uniformity in signal intensity occurs commonly in magnetic resonance (MR) imaging, which may pose substantial problems when using a 3T scanner. Therefore, image non-uniformity correction is usually applied. Purpose: To compare the correction effects of the phased-array uniformity enhancement (PURE), a calibration-based image non-uniformity correction method, among three different software versions in 3T Gd-EOB-DTPA-enhanced MR imaging. Material and Methods: Hepatobiliary-phase images of a total of 120 patients who underwent Gd-EOB-DTPA-enhanced MR imaging on the same 3T scanner were analyzed retrospectively. Forty patients each were examined using three software versions (DV25, DV25.1, and DV26). The effects of PURE were compared by visual assessment, histogram analysis of liver signal intensity, evaluation of the spatial distribution of correction effects, and evaluation of quantitative indices of liver parenchymal enhancement. Results: The visual assessment indicated the highest uniformity of PURE-corrected images for DV26, followed by DV25 and DV25.1. Histogram analysis of corrected images demonstrated significantly larger variations in liver signal for DV25.1 than for the other two versions. Although PURE caused a relative increase in pixel values for central and lateral regions, such effects were weaker for DV25.1 than for the other two versions. In the evaluation of quantitative indices of liver parenchymal enhancement, the liver-to-muscle ratio (LMR) was significantly higher for the corrected images than for the uncorrected images, but the liver-to-spleen ratio (LSR) showed no significant differences. For corrected images, the LMR was significantly higher for DV25 and DV26 than for DV25.1, but the LSR showed no significant differences among the three versions. Conclusion: There were differences in the effects of PURE among the three software versions in 3T Gd-EOB-DTPA-enhanced MR imaging. Even if the non-uniformity correction method has the same brand name, correction effects may differ depending on the software version, and these differences may affect visual and quantitative evaluations. 展开更多
关键词 GD-EOB-DTPA non-uniformity Correction 3 Tesla Software Version Image Contrast
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综掘面风流调控下的瓦斯与粉尘浓度双目标预测模型研究 被引量:1
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作者 龚晓燕 程傲 +5 位作者 邹浩 孙育恒 杨富强 张红兵 李昊 孙康 《煤炭技术》 CAS 2024年第1期153-157,共5页
针对综掘面瓦斯和粉尘浓度预测能力不足,导致瓦斯粉尘积聚难以提前解决,造成风筒出风口风流调控降尘排瓦效果不佳的问题,采用层次分析法确定了瓦斯和粉尘浓度分布的关键影响因素,建立了7-11-3结构的双目标预测神经网络模型,并进行出风... 针对综掘面瓦斯和粉尘浓度预测能力不足,导致瓦斯粉尘积聚难以提前解决,造成风筒出风口风流调控降尘排瓦效果不佳的问题,采用层次分析法确定了瓦斯和粉尘浓度分布的关键影响因素,建立了7-11-3结构的双目标预测神经网络模型,并进行出风口距端头5 m和10 m工况下的应用测试,结果表明:模型误差率最大9.85%,最小0.27%。瓦斯浓度最高降低了45%,粉尘浓度最高降低了40%,有效预防了瓦斯和粉尘浓度的积聚问题。 展开更多
关键词 综掘面 风流调控 BP神经网络 瓦斯及粉尘浓度 双目标预测模型
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西安市一次雷暴过程的闪电活动特征
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作者 黄勤 龙亚星 +1 位作者 黄鑫 高亮书 《气象与环境科学》 2024年第4期88-97,共10页
利用陕西省闪电定位数据、多普勒天气雷达资料及逐小时降水资料,分析2018年8月9日西安市一次雷暴过程中闪电与降水、雷达回波和气流切变的关系特征,并进行特征对比分析。结果表明:15:00左右初始闪电发生后,闪电频次逐渐增加,17:54达到... 利用陕西省闪电定位数据、多普勒天气雷达资料及逐小时降水资料,分析2018年8月9日西安市一次雷暴过程中闪电与降水、雷达回波和气流切变的关系特征,并进行特征对比分析。结果表明:15:00左右初始闪电发生后,闪电频次逐渐增加,17:54达到最大峰值后,闪电频次逐渐减少。整个雷暴过程中,正地闪占比较高,为23.8%;闪电频次出现了2次明显峰值,最大闪电频次为124次/6min,出现时段为17:48-17:54。闪电主要集中在强降水发生区域和时段,且先有闪电活动后有降水发生,正地闪活动与降水有密切关系。60 dBZ以上反射率面积与闪电频次随时间变化趋势一致,65 dBZ强反射率的出现和消失伴随着闪电频次的增加和减少。闪电频次与50 dBZ和40 dBZ的反射率等值线变化有较好的对应关系。正、负地闪在不同反射率范围集中程度不同,正地闪主要活动在强回波区前部和后部,且主要发生在雷暴云发展成熟后,负地闪则集中在强回波区中部和后部。地闪发生区域与上升气流和风切变区域有密切关系,但并不完全发生在上升气流区,负地闪在上升气流和下沉气流区的占比,对对流系统发展阶段有一定指示作用。经过特征对比分析,3次雷暴过程中降水量与正地闪的相关性、闪电与雷达反射率的关系均与西安市雷暴过程有相似特征。 展开更多
关键词 闪电 降水 雷达反射率 气流与切变
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气流与激光联合作用铝合金板热响应研究
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作者 陶彦辉 张家雷 张旭平 《激光技术》 CAS CSCD 北大核心 2024年第4期603-607,共5页
为了获得激光加工等应用中气流环境激光辐照材料的热响应特性和熔穿规律,采用面热源近似和不定常热传导分析方法构建了包括热传导、对流换热、熔化烧蚀等主要机制的物理模型,并通过实验校核后进行了气流环境激光辐照铝合金热学响应定量... 为了获得激光加工等应用中气流环境激光辐照材料的热响应特性和熔穿规律,采用面热源近似和不定常热传导分析方法构建了包括热传导、对流换热、熔化烧蚀等主要机制的物理模型,并通过实验校核后进行了气流环境激光辐照铝合金热学响应定量评估,获得气流环境不同激光功率密度下铝合金靶板温升和烧蚀熔穿规律。结果表明,相同靶参数下,熔穿时间随着激光功率密度增加而急剧减小,并且熔穿时间变化规律与热平衡积分方法气化烧蚀模型结果一致;不同条件下熔穿时间显示,在激光功率密度较小(500 W/cm^(2)附近)时,气流引起对流换热因素对激光烧蚀熔穿影响较大,而在激光功率密度较高(1500 W/cm^(2)以上)时,气流引起对流换热因素对激光烧蚀熔穿影响较小。建立的气流条件下激光辐照热响应模型与实际物理过程更接近,计算获得的熔穿规律为激光辐照模型合理简化提供了定量的参考依据。 展开更多
关键词 激光技术 激光辐照 气流环境 热响应 激光烧蚀
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湿热地区室内气流调控对人群健康的影响
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作者 刘倩妮 郭倩 +7 位作者 孟庆林 汪俊松 张仲军 翟永超 金玲 王小蕊 康瑞祥 张宇峰 《暖通空调》 2024年第7期25-33,共9页
气流调控在改善湿热地区夏季热环境质量方面发挥着关键作用。然而,多数研究主要关注气流对人体全身热舒适的积极作用,而忽略了气流作用于身体局部时对人体健康的潜在影响。本研究采用随机抽样方法,于2023年8—10月在广东省21个地级市开... 气流调控在改善湿热地区夏季热环境质量方面发挥着关键作用。然而,多数研究主要关注气流对人体全身热舒适的积极作用,而忽略了气流作用于身体局部时对人体健康的潜在影响。本研究采用随机抽样方法,于2023年8—10月在广东省21个地级市开展了问卷调研,共收集1 349份有效问卷。统计分析结果显示:当气流温度过低或气流主要作用于人体额头、腹部、太阳穴等敏感部位时,最易引发头疼、流涕、面瘫等症状;在年龄与性别差异上,青年人群相较于其他年龄段人群更容易因气流影响而出现此类症状,女性相比男性更排斥被气流直吹身体。这些发现可为制定湿热地区不同人群的健康气流调控策略提供支撑,有利于提升城市居民的生活质量和健康水平。 展开更多
关键词 气流调控 健康风险 体表骤冷 吹风感 热舒适
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煤气化渣气流分级提炭分质试验
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作者 杨凯 张乾 +2 位作者 栾春晖 彭泽宇 黄伟 《洁净煤技术》 CAS CSCD 北大核心 2024年第7期30-38,共9页
煤气化渣提炭分质是实现其减量化、资源化、高值化利用的关键。基于此,提出研磨破碎-气流分级的干法提炭工艺,利用研磨使气化渣中炭灰结合物解离,再利用气流分级机内离心力和气体曳力作用,将解离所得的细颗粒进行高效分离。通过设计均... 煤气化渣提炭分质是实现其减量化、资源化、高值化利用的关键。基于此,提出研磨破碎-气流分级的干法提炭工艺,利用研磨使气化渣中炭灰结合物解离,再利用气流分级机内离心力和气体曳力作用,将解离所得的细颗粒进行高效分离。通过设计均匀试验并对各影响因素进行回归分析,获取优选试验条件并对该试验条件下的提炭效果进行验证。结果表明,气流分级提炭受多因素耦合作用影响,其中分级机频率和引风机频率是影响提炭效果的关键。均匀试验优选条件为分级机频率175 Hz、引风机频率5 Hz,喂料螺旋频率5 Hz,二次风口全开;该条件下所得富炭产品的收率为25.86%,烧失量49.76%,较原气化渣烧失量提高了26.91%,与试验预测值(49.64%)较一致,且试验效果明显优于未研磨破碎直接气流分级的气化渣。优选条件下气流分级得到的富炭产品的平均粒径(Dav)为5.95μm,满足橡胶补强填充料的粒度要求,其热值为16.73 MJ/kg,亦可作为细粉燃料等使用。同时,气流分级可实现较好的气化渣脱炭效果,所得脱炭渣烧失量低于10%,有利于其在建材等领域应用。研磨破碎-气流分级方法可实现气化渣的提炭分质,有利于其下游利用。 展开更多
关键词 煤气化渣 破碎 气流分级 分离 均匀试验 废物处理
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果蔬隧道式气流冲击干燥流场模拟及其设备结构优化
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作者 袁越锦 史韵 +2 位作者 聂皓 王栋 徐英英 《包装与食品机械》 CAS 北大核心 2024年第5期70-81,共12页
为解决隧道式气流冲击干燥设备中风速流场不均匀的问题,利用计算流体动力学对气流冲击干燥过程的流场进行模拟分析,提出2种改进方案,并且每种方案选择9组模型,通过对比分析每组模型的速度均匀性和流场分布情况,以速度不均匀性为指标,得... 为解决隧道式气流冲击干燥设备中风速流场不均匀的问题,利用计算流体动力学对气流冲击干燥过程的流场进行模拟分析,提出2种改进方案,并且每种方案选择9组模型,通过对比分析每组模型的速度均匀性和流场分布情况,以速度不均匀性为指标,得到结构参数为高度H=630 mm、半径R=60 mm圆柱扰流装置,并在此基础上,进行气流分配口大小调整,将上层和下层气流分配口调整为25 mm,中层气流分配口调整为20 mm的模型为最优结构。最优结构气流分配口速度不均匀系数减小到20.4%,物料层截面速度不均匀系数减小到16.89%,极大地改善气流冲击干燥的均匀性。对改进的模型进行试验验证,模拟值与试验测量值的相对误差均在11%以内。研究为相关干燥设备的结构优化提供参考。 展开更多
关键词 果蔬 气流冲击干燥 流场模拟 结构优化
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六盘山区地面碘化银发生器催化作业条件分析
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作者 田磊 穆建华 +3 位作者 常倬林 左河疆 曹宁 林彤 《气象与环境学报》 2024年第1期88-96,共9页
利用数值模式模拟的1 km×1 km六盘山区2009年6月至2010年5月的垂直速度资料、宁夏173个加密自动气象站数据、云高观测资料等开展了六盘山区碘化银发生器催化作业条件研究。结果表明:有降水过程时,六盘山区2.0 km、2.5 km、3.0 km、... 利用数值模式模拟的1 km×1 km六盘山区2009年6月至2010年5月的垂直速度资料、宁夏173个加密自动气象站数据、云高观测资料等开展了六盘山区碘化银发生器催化作业条件研究。结果表明:有降水过程时,六盘山区2.0 km、2.5 km、3.0 km、3.5 km高度层均有明显上升气流;地面发生器释放的碘化银催化剂的有效扩散高度可达3000 m;降雪开始前6 h至降雪开始后12 h内,发生器作业点有明显上升气流,80%以上时间内上升气流速度分钟平均值大于0.3 m·s~(-1)。结合六盘山区云底、0℃层等特征层高度,综合分析得出了六盘山东西两侧及六盘山顶一年中不同时期开展碘化银发生器催化作业的适宜程度。 展开更多
关键词 地面碘化银发生器 垂直气流 扩散
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气流对飞秒激光加工炸药装药过程的热安全性影响分析
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作者 伍俊英 郑富德 +2 位作者 姚雨乐 刘嘉锡 陈朗 《强激光与粒子束》 CAS CSCD 北大核心 2024年第1期103-111,共9页
由于炸药具有热传导系数小、对温度极其敏感的特点,在使用多脉冲飞秒激光对其进行持续加工时,极有可能在炸药内形成热累积,从而导致点火、燃烧等危险事件的发生。为了降低激光加工材料过程中的热效应,人们普遍采取在材料加工表面施加气... 由于炸药具有热传导系数小、对温度极其敏感的特点,在使用多脉冲飞秒激光对其进行持续加工时,极有可能在炸药内形成热累积,从而导致点火、燃烧等危险事件的发生。为了降低激光加工材料过程中的热效应,人们普遍采取在材料加工表面施加气流的方法。为了研究加载气流条件下,炸药装药在飞秒激光作用下产生的烧蚀产物的运动规律以及炸药装药内部的温度变化,建立了加载气流条件下飞秒激光加工炸药装药过程的二维流固耦合计算模型,对在单侧、双侧不同入射角度的亚音速气流作用下,飞秒激光加工奥克托今(HMX)炸药装药的过程进行了数值模拟计算。计算结果表明:单侧气流会在炸药加工表面形成漩涡流,导致烧蚀气体产物在炸药表面做旋转运动,加重了烧蚀产物对炸药的热影响;双侧气流会在远离炸药加工表面的地方形成较大的漩涡流,从而使烧蚀气体产物迅速离开炸药加工表面,有效降低了炸药的温度,提高了飞秒激光加工炸药装药过程的安全性。 展开更多
关键词 飞秒激光 炸药 数值模拟 气流 热安全性
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