Models, Theoretical

模型, 理论
  • 文章类型: Journal Article
    提高初级卫生保健服务的效率对于像中国这样人口众多的发展中国家至关重要。本研究对中国初级卫生保健服务的效率和空间分布进行了系统分析。它阐明了效率的基本景观和区域差异,从而为提高服务效率和促进区域协调发展提供科学依据。
    采用三阶段DEA-Malmquist模型评估2012年至2020年中国大陆31个省级单位的基层医疗服务效率。此外,它使用Moran指数检验了效率分布的空间相关性。
    中国的初级卫生保健服务的效率总体上是次优的,并且有明显的下降趋势,突出了纯技术效率和规模效率的显著提高潜力。各省之间存在明显的效率差距,然而,正的空间相关性是明显的。区域,效率排序为东>中>西。人均GDP和人口密度等因素对效率提升有积极影响,而城市化水平和政府卫生支出似乎有不利影响。
    三阶段DEA-Malmquist模型和Moran指数的应用不仅扩展了研究初级卫生保健服务效率的方法框架,而且为提高初级卫生保健效率提供了科学有价值的见解。中国和其他发展中国家的服务。
    UNASSIGNED: Enhancing the efficiency of primary healthcare services is essential for a populous and developing nation like China. This study offers a systematic analysis of the efficiency and spatial distribution of primary healthcare services in China. It elucidates the fundamental landscape and regional variances in efficiency, thereby furnishing a scientific foundation for enhancing service efficiency and fostering coordinated regional development.
    UNASSIGNED: Employs a three-stage DEA-Malmquist model to assess the efficiency of primary healthcare services across 31 provincial units in mainland China from 2012 to 2020. Additionally, it examines the spatial correlation of efficiency distribution using the Moran Index.
    UNASSIGNED: The efficiency of primary healthcare services in China is generally suboptimal with a noticeable declining trend, highlighting significant potential for improvement in both pure technical efficiency and scale efficiency. There is a pronounced efficiency gap among provinces, yet a positive spatial correlation is evident. Regionally, efficiency ranks in the order of East > Central > West. Factors such as GDP per capita and population density positively influence efficiency enhancements, while urbanization levels and government health expenditures appear to have a detrimental impact.
    UNASSIGNED: The application of the three-stage DEA-Malmquist model and the Moran Index not only expands the methodological framework for researching primary healthcare service efficiency but also provides scientifically valuable insights for enhancing the efficiency of primary healthcare services in China and other developing nations.
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  • 文章类型: Journal Article
    磷(P)在调节生态系统对气候变化的响应中的重要性促进了地表模型中P循环的实施。但是他们的二氧化碳效应预测尚未根据测量结果进行评估。这里,我们进行了数据驱动的模型评估,其中八个广泛使用的P启用模型的模拟与来自成熟的长期自由空气CO2富集实验的观察。有限的桉树林。我们表明,大多数模型预测了CO2对生态系统碳(C)固存的影响的正确符号和大小,但是他们通常高估了对植物碳吸收和生长的影响。我们确定了光合作用的叶到冠层尺度,植物组织化学计量学,工厂地下C分配,以及植物-微生物相互作用的后续后果是可以改善生态系统C-P相互作用模型的关键领域。一起,这种数据模型相互比较揭示了数据驱动的对P启用模型的性能和功能的见解,并增加了现有证据,即模型高估了全球CO2驱动的碳汇。
    The importance of phosphorus (P) in regulating ecosystem responses to climate change has fostered P-cycle implementation in land surface models, but their CO2 effects predictions have not been evaluated against measurements. Here, we perform a data-driven model evaluation where simulations of eight widely used P-enabled models were confronted with observations from a long-term free-air CO2 enrichment experiment in a mature, P-limited Eucalyptus forest. We show that most models predicted the correct sign and magnitude of the CO2 effect on ecosystem carbon (C) sequestration, but they generally overestimated the effects on plant C uptake and growth. We identify leaf-to-canopy scaling of photosynthesis, plant tissue stoichiometry, plant belowground C allocation, and the subsequent consequences for plant-microbial interaction as key areas in which models of ecosystem C-P interaction can be improved. Together, this data-model intercomparison reveals data-driven insights into the performance and functionality of P-enabled models and adds to the existing evidence that the global CO2-driven carbon sink is overestimated by models.
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  • 文章类型: Journal Article
    固体氧化物燃料电池(SOFC)对于替代能源至关重要,有效地为电机供电。它们提供燃料的多功能性和废热回收,使它们成为各种应用的理想选择。优化互连器结构对于SOFC的进步至关重要。本文介绍了一种新颖的互连SOFC二维仿真模型,旨在提高他们的表现。我们最初为常规互连器SOFC构建了单个半电池模型,确保模型准确性。随后,我们提出了一种创新的互连SOFC模型,在各个方面都优于常规对应物。
    Solid oxide fuel cells (SOFCs) are vital for alternative energy, powering motors effi-ciently. They offer fuel versatility and waste heat recovery, making them ideal for various applications. Optimizing interconnector structures is crucial for SOFC advancement. This paper introduces a novel 2D simulation model for interconnector SOFCs, aiming to enhance their performance. We initially construct a single half-cell model for a conventional interconnector SOFC, ensuring model accuracy. Subsequently, we propose an innovative interconnector SOFC model, which outperforms the conventional counterpart in various aspects.
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  • 文章类型: Journal Article
    人为磷(P)的过量排放给水生生态系统带来了持续的压力。通过将P排放联系起来,可以将该压力量化为淡水富营养化潜力(FEP)。环境隔室中的P命运,以及由于淡水中P浓度增加而可能消失的物种部分。然而,先前在全球和区域尺度上的命运建模主要基于八方向算法,而不区分污染源。该算法无法表征通过地下管道和废水处理基础设施的点源排放的命运路径,并且在考虑由河流分叉引起的多向路径方面表现出次优的性能,尤其是在平坦的地形。在这里,我们旨在通过结合各种命运路径和解决多方向场景来改善命运建模。我们还通过补充潜在的未经处理的点源排放(PSu)来更新P估计值。在太湖流域快速城市化地区研究了改进的方法,中国2017年的空间分辨率为100m×100m。结果表明,PSu对FEP的贡献(62.6%)大于对P排放的贡献(58.5%)。通过改进的命运建模,FEP在空间上分布更广泛,促进根据当地情况制定有针对性的监管策略。
    Excessive anthropogenic phosphorus (P) emissions put constant pressure on aquatic ecosystems. This pressure can be quantified as the freshwater eutrophication potential (FEP) by linking P emissions, P fate in environmental compartments, and the potentially disappeared fraction of species due to increase of P concentrations in freshwater. However, previous fate modeling on global and regional scales is mainly based on the eight-direction algorithm without distinguishing pollution sources. The algorithm fails to characterize the fate paths of point-source emissions via subsurface pipelines and wastewater treatment infrastructure, and exhibits suboptimal performance in accounting for multidirectional paths caused by river bifurcations, especially in flat terrains. Here we aim to improve the fate modeling by incorporating various fate paths and addressing multidirectional scenarios. We also update the P estimates by complementing potential untreated point-source emissions (PSu). The improved method is examined in a rapidly urbanizing area in Taihu Lake Basin, China in 2017 at a spatial resolution of 100 m × 100 m. Results show that the contribution of PSu on FEP (62.6%) is greater than that on P emissions (58.5%). The FEP is more spatially widely distributed with the improved fate modeling, facilitating targeted regulatory strategies tailored to local conditions.
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  • 文章类型: Journal Article
    本研究手稿旨在研究非奇异分数阶导数意义上的新型隐式微分方程,即Atangana-Baleanu-Caputo([公式:参见文本])属于区间(2,3]的任意阶,相对于另一个正函数和递增函数。利用Banach定理和拓扑度定理研究了存在性和唯一性的主要结果。通过采用非线性分析的主题来分析Ulam-Hyers([公式:见正文])类型的稳定性。最后,用一些特殊情况构建和增强了两个示例,以及用于检查主要结果影响的说明性图形。
    This research manuscript aims to study a novel implicit differential equation in the non-singular fractional derivatives sense, namely Atangana-Baleanu-Caputo ([Formula: see text]) of arbitrary orders belonging to the interval (2, 3] with respect to another positive and increasing function. The major results of the existence and uniqueness are investigated by utilizing the Banach and topology degree theorems. The stability of the Ulam-Hyers ([Formula: see text]) type is analyzed by employing the topics of nonlinear analysis. Finally, two examples are constructed and enhanced with some special cases as well as illustrative graphics for checking the influence of major outcomes.
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  • 文章类型: Journal Article
    众所周知,定位蝙蝠会在搜索阶段改变其波形,接近,捕获猎物。估计蝙蝠物种识别的呼吁参数和合成系统的技术改进是有意义的,比如雷达和声纳。蝙蝠叫声的类型与物种有关,并且许多呼叫可以被建模为双曲调频(HFM)信号。要获得HFM建模的蝙蝠呼叫的参数,可逆积分变换,即,双曲尺度变换(HST),建议将呼叫转换为“延迟标度”域中的二维峰值,在此基础上实现了谐波分离和参数估计。与基于时频分析的方法相比,基于HST的方法不需要提取蝙蝠叫声的瞬时频率,只寻找山峰。验证结果表明,HST适用于分析HFM建模的蝙蝠叫声包含多个谐波,具有较大的能量差,和估计的参数意味着使用从搜索阶段到捕获阶段的波形有利于减少测距偏差,参数的趋势可能对蝙蝠物种识别有用。
    Echolocating bats are known to vary their waveforms at the phases of searching, approaching, and capturing the prey. It is meaningful to estimate the parameters of the calls for bat species identification and the technological improvements of the synthetic systems, such as radar and sonar. The type of bat calls is species-related, and many calls can be modeled as hyperbolic frequency- modulated (HFM) signals. To obtain the parameters of the HFM-modeled bat calls, a reversible integral transform, i.e., hyperbolic scale transform (HST), is proposed to transform a call into two-dimensional peaks in the \"delay-scale\" domain, based on which harmonic separation and parameter estimation are realized. Compared with the methods based on time-frequency analysis, the HST-based method does not need to extract the instantaneous frequency of the bat calls, only searching for peaks. The verification results show that the HST is suitable for analyzing the HFM-modeled bat calls containing multiple harmonics with a large energy difference, and the estimated parameters imply that the use of the waveforms from the searching phase to the capturing phase is beneficial to reduce the ranging bias, and the trends in parameters may be useful for bat species identification.
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  • 文章类型: Journal Article
    土壤有机碳(SOC)分解释放的热量(以下称为微生物热)可以改变土壤的热和水文条件,随后调节SOC分解及其与气候的反馈。虽然理解这些反馈对于制定政策以实现特定的气候目标至关重要,尚未全面评估。本研究采用ORCHIDEE-MICT模型来研究微生物热的影响,称为加热效应,关注它们对SOC积累的影响,土壤温度和净初级生产力(NPP),以及两种二氧化碳排放情景(RCP2.6和RCP8.5)下对陆地气候反馈的影响。研究结果表明,微生物热量减少了土壤碳储量,主要在上层,并提高土壤温度,尤其是在更深的层次。由于加速的SOC分解,这导致全球SOC存量的边际减少。模拟了SOC分解和土壤温度的季节性周期变化,每单位微生物热量(0.31KJ-1)的温度增加最显著,发生在273.15K左右(空气温度约为273.15K的所有网格单元的中值)。热效应导致RCP8.5下多年冻土面积的早期损失,并阻碍了峰值变暖后RCP2.6下多年冻土面积的恢复。尽管气候变暖下土壤温度升高符合预期,没有观察到预期的加速SOC分解和对气候变暖的大的放大反馈,主要是因为减少了建模的初始SOC库存和有限的NPP与热效应。这些强调了微生物热的多方面影响。全面了解这些影响对于在变暖的世界中制定有效的缓解气候变化战略至关重要。
    Heat released from soil organic carbon (SOC) decomposition (referred to as microbial heat hereafter) could alter the soil\'s thermal and hydrological conditions, subsequently modulate SOC decomposition and its feedback with climate. While understanding this feedback is crucial for shaping policy to achieve specific climate goal, it has not been comprehensively assessed. This study employs the ORCHIDEE-MICT model to investigate the effects of microbial heat, referred to as heating effect, focusing on their impacts on SOC accumulation, soil temperature and net primary productivity (NPP), as well as implication on land-climate feedback under two CO2 emissions scenarios (RCP2.6 and RCP8.5). The findings reveal that the microbial heat decreases soil carbon stock, predominantly in upper layers, and elevates soil temperatures, especially in deeper layers. This results in a marginal reduction in global SOC stocks due to accelerated SOC decomposition. Altered seasonal cycles of SOC decomposition and soil temperature are simulated, with the most significant temperature increase per unit of microbial heat (0.31 K J-1) occurring at around 273.15 K (median value of all grid cells where air temperature is around 273.15 K). The heating effect leads to the earlier loss of permafrost area under RCP8.5 and hinders its restoration under RCP2.6 after peak warming. Although elevated soil temperature under climate warming aligns with expectation, the anticipated accelerated SOC decomposition and large amplifying feedback on climate warming were not observed, mainly because of reduced modeled initial SOC stock and limited NPP with heating effect. These underscores the multifaceted impacts of microbial heat. Comprehensive understanding of these effects would be vital for devising effective climate change mitigation strategies in a warming world.
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  • 文章类型: Journal Article
    热源的热损伤严重影响深部矿井生产的安全。热源和气流之间的传热和传质导致气流温度(AFT)升高,气流含水量(AFMC)和气流相对湿度(AFRH)。本研究旨在量化工作面参数对AFT的不确定性贡献,AFMC和AFRH并找到它们的主要贡献者。流动,选择几何和物理参数作为不确定性来源。随后,Sobol指数是使用点搭配非侵入式多项式混沌方法获得的,表示每个输入参数的灵敏度。发现流入风温度和风速是影响AFT和AFMC的两个主要因素,流入风的相对湿度和风速是影响AFRH的两个主要因素。在单因素分析中,流入风温度对AFT和AFMC的不确定性贡献,AFRH上的入流风相对湿度可超过0.7,高于风速。工作面的几何参数,即长度,宽度和高度,通风时间也是影响AFT的重要量,AFMC和AFRH。与AFT和AFMC相比,影响AFRH的另外两个重要量是煤的热导率和岩石的原始温度。
    Thermal damage from heat sources severely affects the safety of deep mine production. Heat and mass transfer between heat sources and airflow leads to the increase of the airflow temperature (AFT), moisture content of airflow (AFMC) and relative humidity of airflow (AFRH). This study aims to quantify uncertainty contributions of the working face parameters on AFT, AFMC and AFRH and find their main contributors. The flow, geometric and physical parameters are chosen as uncertainty sources. Subsequently, Sobol indices are obtained using the point-collocation non-intrusive polynomial chaos method, denoting the sensitivity of each input parameter. It was found that the inflow wind temperature and the wind velocity are two top factors influencing AFT and AFMC, while relative humidity of inflow wind and the wind velocity are two top factors influencing AFRH. In the single factor analysis, the uncertainty contributions of the inflow wind temperature on AFT and AFMC, and relative humidity of inflow wind on AFRH can exceed 0.7, which is higher than those of the wind velocity. The geometric parameters of the working face, namely the length, width and height, and ventilation time are also significant quantities influencing AFT, AFMC and AFRH. Compared to AFT and AFMC, two other significant quantities influencing AFRH are the thermal conductivity of coal and the original temperature of the rock.
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  • 文章类型: Journal Article
    反应堆冷却剂泵是核电站的关键设备。如果泄漏超过某一阈值,它可能导致反应堆过热和停机。反应堆冷却剂泵泄漏故障通常存在两个问题:腐蚀和结垢。尽早准确有效地诊断泄漏故障模式并预测其剩余使用寿命(RUL)对于及时采取维护措施非常重要。在本文中,提出了一种综合方法。首先,提取第一密封件的横截面面积作为故障指示器。动机是腐蚀可能会扩大横截面积,和缩放可以减小横截面积。基于流体力学理论,在横截面积之间建立了具有多个不确定参数的集成模型,温度,以及在第一密封件的入口和出口处的泄漏。在诊断过程中,提出了一种改进的变化检测方法来检测退化的起点。然后,估计先前关系中的未知参数,并且在退化开始点之前的退化数据用于诊断泄漏故障模式。第二,建立了自回归综合移动平均(ARIMA)时间序列模型,根据退化起点后的退化数据预测剩余使用寿命。最后,利用某核电厂六个反应堆冷却剂泵的泄漏退化数据进行泄漏故障模式诊断和寿命预测,退化点检测误差率不超过4%,故障模式诊断修正率100%和实用的RUL预测结果,证明了所提出的集成方法的准确性和高效性。所提出的集成方法结合了物理模型诊断和数据驱动模型诊断的优点,创新性地利用主泵输出侧的流量作为监测指标,横截面积作为特征指标一起诊断密封发生的泄漏故障模式并预测其RUL。能满足实际运行和维护的需要,确保泵的健康稳定运行,防止核电站意外停机和严重事故的发生。
    The reactor coolant pump is a key equipment in a nuclear power plant. If the leakage exceeds a certain threshold, it may cause reactor overheating and shutdown. The reactor coolant pump leakage fault usually has two problems: corrosion and scaling. Accurately and efficiently diagnosing the leakage fault mode as early as possible and predicting its remaining useful life (RUL) are important for taking timely maintenance measures. In this paper, an integrated method is proposed. First, the cross-sectional area of the first seal is extracted as a fault indicator. The motivation is that corrosion may enlarge the cross-sectional area, and scaling may reduce the cross-sectional area. Based on the fluid mechanics theory, an integrated model with several uncertain parameters is established among the cross-sectional area, temperature, and leakage at the inlet and outlet of the first seal. In the diagnosing process, a modified change-detection method is proposed to detect the starting point of degradation. Then, the unknown parameters in the previous relation are estimated, and the degrading data before the starting point of degradation are used to diagnose the leakage fault mode. Second, a time-series model of the autoregressive integrated moving average (ARIMA) is established to predict the remaining useful life based on the degrading data after the starting point of degradation. Finally, the leakage degrading data from six reactor coolant pumps of a nuclear power plant is used to perform the leakage fault mode diagnosis and life prediction with degradation point detection error rates not exceeding 4%, fault mode diagnosis correction rates 100% and practical RUL predicting results, which proves that the proposed integrated method is accurate and efficient. The proposed integrated method combines the advantages of both the physical model diagnosis and the data-driven model diagnosis and innovatively make use of the quantity of flow from the output side of the primary pump as the monitoring indicator and the cross-sectional area as the characteristic index together to diagnose the leakage fault mode happened to the seal and predict its RUL, which can meet the needs of actual operation and maintenance to ensure a healthy and stable operation of the pump and prevent unexpected shutdowns of nuclear power plants and serious accidents.
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  • 文章类型: Journal Article
    为了提高基于集中质量分析法的带有平衡盘的四级离心泵转子系统的模态分析精度,建立了简化的集中质量数学模型和ANSYS仿真模型。比较这两个模型的结果,以确定导致模式形状显着差异的因素。随后,提出了一种基于惯性矩阵修正质量矩和刚度修正系数的优化数学模型,并利用后叶片型四级离心泵验证了该优化数学模型的有效性。结果表明,从ANSYS模拟获得的固有频率始终高于使用分析方法获得的固有频率。叶轮和平衡盘的转动惯量的简化主要导致计算误差。优化后的数学模型将固有频率的误差从12.96%降低,12.13%,9.96%,5.85%,和8.74%至2.45%,1.56%,0.65%,5.34%,和2.28%,分别。固有频率的优化在低阶模式下提供了更好的性能,而其对高阶模式的影响则不太显著。该优化方法适用于带有后叶片的离心泵,减少了理论计算中的误差,基于浓缩质量从13.11%的减少,12.85%,9.91%,7.2%至3.7%,3.86%,0.57%,和2.87%,分别,从而进一步证实了优化模型设计的可行性。
    To improve the accuracy of modal analysis for a four-stage centrifugal-pump rotor system with a balancing disc based on the concentrated-mass analytical method, a simplified concentrated mass mathematical model and an ANSYS simulation model are established. The results from these two models are compared to determine factors that cause significant differences in the mode shapes. Subsequently, an optimized mathematical model based on the corrected mass moment of an inertia matrix and stiffness correction coefficients is proposed, and the effectiveness of this optimized mathematical model is validated using a four-stage centrifugal pump with back blades. The results show that the natural frequencies obtained from the ANSYS simulations are consistently higher than those obtained using the analytical method. The simplification of the moment of inertia at the impeller and balancing disc contributes primarily to the calculated errors. The optimized mathematical model reduces the errors in the natural frequencies from 12.96%, 12.13%, 9.96%, 5.85%, and 8.74% to 2.45%, 1.56%, 0.65%, 5.34%, and 2.28%, respectively. The optimization of natural frequencies offers better performance at lower-order modes, whereas its effects on higher-order modes are less significant. The optimization method is applicable to centrifugal pumps with back blades and reduces the error in theoretical calculations, based on reductions in the concentrated mass from 13.11%, 12.85%, 9.91%, and 7.2% to 3.7%, 3.86%, 0.57%, and 2.87%, respectively, thus further confirming the feasibility of the optimized model design.
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