SPI

SPI
  • 文章类型: Journal Article
    本研究通过应用基于copula的双变量概率模型以及严重程度持续时间频率(SDF)曲线来分析Bal路支斯坦的干旱模式。标准化降水指数(SPI)的计算取决于六个月内从十个不同地点收集的每月总降水数据。在评估各种参数分布之后,对数正态分布适用于模拟干旱严重程度和持续时间。采用一系列双变量copulas来模拟干旱严重程度和持续时间的特征,然后将其与观察到的数据进行比较。值得注意的是,根据不同的统计基准,将Gumbelcopula分类为极值copula的表现优于其对应物。通过利用依赖函数,我们得出干旱变量的条件分布:严重程度和持续时间。这些条件分布随后为计算返回期提供信息,形成在整个研究区域以固定复发水平构建SDF图的基础。该研究的发现表明,在特定持续时间内,该地区可能会发生严重干旱,重现期较高。这项研究的意义重大,展示了基于copula的联合建模技术在生成干旱严重程度和持续时间的频率曲线方面的潜力。这一发展为有效的水资源管理和制定战略以减轻干旱对脆弱地区的影响提供了希望。
    This study delves into analyzing drought patterns in Baluchistan by applying copula-based bivariate probabilistic models complemented by Severity Duration Frequency (SDF) curves. The calculation of the Standardized Precipitation Index (SPI) hinges on monthly aggregate precipitation data from ten distinct sites compiled over six-month periods. After evaluating various parametric distributions, the Log-Normal distribution emerges as suitable for modeling drought severity and duration. A range of bivariate copulas is employed to simulate the characteristics of drought severity and duration, which are then compared against observed data. Remarkably, the Gumbel copula classified as an extreme value copula-outperforms its counterparts according to diverse statistical benchmarks. By utilizing the dependence function, we derive the conditional distribution of drought variables: severity and duration. These conditional distributions subsequently inform the calculation of return periods, forming the basis for constructing SDF diagrams at fixed recurrence levels across the study region. The study\'s finding indicates that a severe drought could occur over the region with higher return periods for a specific duration. The implications of this research are significant, showcasing the potential of copula-based joint modeling techniques to generate frequency curves for drought severity and duration. This development holds promise for effective water resource management and the formulation of strategies to mitigate the impact of drought in vulnerable regions.
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  • 文章类型: Journal Article
    在大多数干旱和半干旱环境中,地下水是受地下水位下降和干燥威胁的宝贵资源之一,因此必须不断监测。确定影响地下水位变化的原因,比如气象干旱,是监测这些波动的一种方法。在本研究中,评价了两个气象干旱指数SPI和SPEI对地下水位波动的影响,使用多元线性回归和M5决策树回归,以及它们与地下水水位干旱指数(SWI)的关系。在长期统计期(1989-2018年)的6个月时间窗口内计算气候和水文干旱指数后,Golestan省的半深含水层,位于伊朗北部,被认为是为此目的的研究地点。结果表明,气象干旱的影响并不能立即体现在地下水位和水文干旱指数的变化中。通过添加滞后6个月的气象干旱指数,平均气温,以及前6个月的总降雨量作为新的变量,与SWI指数的相关性增加,所以在最好的情况下,M5决策树模型在预测SWI指数方面提供了最好的结果。下半年,SPEI指数的确定系数为0.92,误差值为RMSE=0.27。在气象干旱指数中,SPEI指数,这是基于降水和蒸散,与SWI指数建立了更强的联系,这突出了潜在蒸散的重要性。这是一个警告,由于全球变暖,未来该地区的地下水位可能会下降。
    In most arid and semi-arid environments, groundwater is one of the precious resources threatened by water table decline and desiccation, thus it must be constantly monitored. Identifying the causes influencing the variations of the subsurface water level, such as meteorological drought, is one approach for monitoring these fluctuations. In the present study, the effect of two meteorological drought indices SPI and SPEI on the fluctuations of the underground water level was evaluated, as was their relationship with the drought index of the subsurface water level (SWI) using multivariate linear regression and M5 decision tree regression. After calculating climatic and hydrological drought indices in a 6-month time window for a long-term statistical period (1989-2018), the semi-deep aquifers of Golestan province, which is located in northern Iran, were considered as a research location for this purpose. The results demonstrated that the effect of meteorological drought does not immediately manifest in the changes of the subsurface water table and the hydrological drought index. By adding the meteorological drought index with a 6-month lag step, the average air temperature, and the total rainfall from the previous 6 months as new variables, the correlation with the SWI index increases, so that in the best-case scenario, the M5 decision tree model provides the best result in predicting the SWI index. The second half of the year yielded a coefficient of determination of 0.92 and an error value of RMSE = 0.27 for the SPEI index. Among the meteorological drought indices, the SPEI index, which is based on precipitation and evapotranspiration, created a stronger link with the SWI index, which highlights the significance of potential evapotranspiration. It is a warning that, as a result of global warming, subsurface water tables in this region may fall in the future.
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  • 文章类型: Journal Article
    印度经常发生的干旱具有重要的社会性,经济,和环境影响。缺乏直接测量地下水的位置和时间阻碍了定量方法来分析地下水干旱的复杂性质。这项工作使用了重力和气候实验(GRACE和GRACE-FO)和全球土地数据同化系统(GLDAS)得出的数据集,使用独特的水文参数广泛分析了下恒河盆地(LGB)的地下水储量变化。2003年至2022年。分析结果表明,LGB中GRACE衍生的陆地储水异常显着下降(-12.12mm/yr),地下水存储异常(GWSA)的数量也类似地减少(-10.80毫米/年),而在GRACE-FO时期,TWSA(33.96mm/yr)和GWSA(64.8mm/yr)分别出现了积极趋势。已计算出整个LGB地区的干旱指标,称为GRACE衍生的地下水干旱指数(GGDI)。传统的干旱研究。在LGB上执行标准化的沉淀指数(SPI)以证明GGDI的结果。GGDI研究的结果有效地将重大干旱发生的时期与12个月的SPI时间序列相匹配。从GGDI,这项研究考察了地下水干旱的空间分布,时间演变,和趋势(修正曼恩·肯德尔趋势)方面。根据研究结果,LGB经历了2009-2010年、2019年的三个主要干旱时期(中度),2015-2016年(严重)。该研究提供了有关GRACE衍生的地下水干旱演变的可靠定量数据,这可能为人口稠密的研究区域的其他干旱研究增加新的视角,这主要取决于农业,在亚热带气候中,畜牧业和技术较低的水密集型产业,如皮革和纺织业。这种模式包含了人类活动和气候变化引起的地下水资源的变化,为衡量可持续利用和水安全方面的进展铺平道路。
    Droughts frequently occurring in India have significant societal, economic, and environmental effects. The lack of direct measurements of groundwater in location and time hinders quantitative methods to analyse the intricate nature of groundwater drought. This work used the datasets derived from the Gravity and Climate Experiment (GRACE and GRACE-FO) and Global Land Data Assimilation System (GLDAS) to extensively analyse Groundwater Storage changes in the Lower Gangetic Basin (LGB) using unique hydrological parameters between the years 2003 and 2022. The analysis highlights that the GRACE-derived terrestrial water storage anomaly in the LGB decreased significantly (-12.12 mm/yr), and the amount of Groundwater Storage Anomaly (GWSA) decreased similarly (-10.80 mm/yr), while in the GRACE-FO period, a positive trend has been noticed in TWSA (33.96 mm/yr) and GWSA (64.8 mm/yr) respectively. A drought indicator called the GRACE-derived groundwater drought index (GGDI) has been computed for the entire LGB region. A traditional drought study viz. Standardised Precipitation Index (SPI) was performed over LGB to justify the results of the GGDI. The results from GGDI study effectively matched the periods of significant drought occurrences with the 12-month SPI time series. From the GGDI, this study examined groundwater drought\'s spatial distribution, temporal evolution, and trend (Modified Mann Kendall trend) aspects. According to research findings, the LGB experienced three major drought periods between 2009-2010, 2019 (moderate), and 2015-2016 (severe). The study offers reliable quantitative data on the evolution of GRACE-derived groundwater drought, which may add a new perspective to additional drought research in the densely populated study area, which depends majorly on agriculture, livestock and less skilled water-intensive industries such as leather and textile industries in a sub-tropical climate. This paradigm incorporates changes in groundwater resources caused by human activities and climate change, paving the way for measuring progress towards sustainable use and water security.
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  • 文章类型: Journal Article
    干旱作为一种自然现象,一直是炎热和干燥气候地区的严重威胁。干旱的主要影响之一是地下水位的下降。本文重点研究了SPI(标准化降水指数)和SWI(标准化水位指数)来评估气象和水文干旱,分别。在第一部分,我们使用不同的SPI时间框架(3、6、12和24个月)来调查亚兹德的干旱,伊朗中部的干旱省份已有29年(1990-2018年)。然后,在第二部分,通过一些雨量计站和最接近它们的观测井,在亚兹德的三个含水层中研究了SPI和SWI之间的关系。除了使用SPI和SWI,我们还使用不同的机器学习(ML)算法来预测干旱条件,包括K_Nearest_Neighbors的线性模型和六个非线性模型,梯度_提升,决策树,XGBoost,Random_Forest,和神经网络。为了评估上述模型的准确性,包括得分在内的三个统计指标,RMSE,使用MAE。根据第一部分的结果,亚兹德省在气象干旱(根据SPI的降雨量)方面由轻度湿润转为轻度干旱,由于气候变化,这种情况可能会恶化。ML中使用的模型显示SPI-6(得分为ave=0.977),SPI-3(评分ave=0.936),SPI-24(评分ave=0.571),SPI-12(得分为ave=0.413)指数的准确性最高,分别。Neural_Net(评分ave=0.964-RMSEave=0.020-MAEave=0.077)和Gradient_Boosting(评分ave=0.551-RMSEave=0.124-MAEave=0.248)的模型在所有四个时间尺度上的SPI预测精度最高和最低。根据第二部分的结果,关于SWI,随机森林模型(得分=0.929-RMSE=0.052-MAE=0.150)和神经网络模型(得分=0.755-RMSE=0.235-MAE=0.456)的准确度最高和最低,分别。此外,该地区的水文干旱(地下水位下降)要严重得多,根据平均SPI和SWI的低相关系数(R2=0.14),我们发现不受控制的抽水井,作为降雨不足的主要因素,加剧了水文干旱,该地区将来有可能成为更干旱的地区。
    Drought as a natural phenomenon has always been a serious threat to regions with hot and dry climates. One of the major effects of drought is the drop in groundwater level. This paper focused on the SPI (Standardized Precipitation Index) and SWI (Standardized Water-Level Index) to assess meteorological and hydrological drought, respectively. In the first part, we used different time frames of SPI (3, 6, 12, and 24 months) to investigate drought in Yazd, a dry province in the center of Iran for 29 years (1990-2018). Then, in the second part, the relationship between SPI and SWI was investigated in the three aquifers of Yazd by some rain gauge stations and the closest observation wells to them. In addition to using SPI and SWI, we also used different machine learning (ML) algorithms to predict drought conditions including linear model and six non-linear models of K_Nearest_Neighbors, Gradient_Boosting, Decision_Tree, XGBoost, Random_Forest, and Neural_Net. To evaluate the accuracy of the mentioned models, three statistical indicators including Score, RMSE, and MAE were used. Based on the results of the first part, Yazd province has changed from mild wet to mild drought in terms of meteorological drought (the amount of rainfall according to SPI), and this condition can worsen due to climate change. The models used in ML showed that SPI-6 (score ave = 0.977), SPI-3 (score ave = 0.936), SPI-24 (score ave = 0.571), and SPI-12 (score ave = 0.413) indices had the highest accuracy, respectively. The models of Neural_Net (score ave = 0.964-RMSE ave = 0.020-MAE ave = 0.077) and Gradient_Boosting (score ave = 0.551-RMSE ave = 0.124-MAE ave = 0.248) had the highest and lowest accuracy in prediction of the SPI in all four-time scales. Based on the results of the second part, about the SWI, Random_Forest model (score = 0.929-RMSE = 0.052-MAE = 0.150) and model of Neural_Net (score = 0.755-RMSE = 0.235-MAE = 0.456) had the highest and lowest accuracy, respectively. Also, hydrological drought (reduction of the groundwater level) of the region has been much more severe, and according to the low correlation coefficient of average SPI and SWI (R2 = 0.14), we found that the uncontrolled pumping wells, as a main factor than a shortage of rainfall, have aggravated the hydrological drought, and this region is at risk of becoming a more arid region in the future.
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  • 文章类型: Journal Article
    阿尔及利亚撒哈拉牧场是一个干旱的生态系统,其特征是土壤有限,水,和植被资源,这使得它很容易退化。本研究主要利用遥感数据(MSAVI指数),对1987-2019年期间比斯克拉南部草原植被退化的历时评估和多时态制图,提取时空数据,监测草地植被动态。我们研究了人口结构的演变,牲畜数量,和土地利用来自定量数据。结果表明,在此期间,该地区的景观发生了很大变化。牧场面积从19,939公顷(1987年)减少到3605公顷(2019年),其中58%的先前存在的植被转化为裸露的土壤。本研究证实,草地植被健康与气候密切相关,它的退化主要是由于复发,持续时间,严重程度,以及干旱事件的严重程度。人造活动也是牧场长期退化的决定因素,例如扩大新的土地开发面积,从3754公顷(1987年)增加到24,410公顷(2019年)。这种趋势在整个地区都有,包括Oumache和ElHaouch等主要牧区,导致过度放牧,损失约2%的植被覆盖。所有这些因素导致了在脆弱环境中牧区资源的严重和持续退化。保护这些有限的资源需要对生态系统进行适当的管理和对其植被进行合理的开发,土壤,和水资源。
    The Algerian Saharan rangelands are an arid ecosystem characterized by limited soil, water, and vegetation resources, which make it very susceptible to degradation. This research focuses on the diachronic assessment and multi-temporal mapping of the degradation of steppe vegetation in the south of Biskra during the period 1987-2019, using remote sensing data (MSAVI index), for extracting spatiotemporal data to monitor the rangeland vegetation dynamics. We examined demographic evolution, number of livestock, and land use from quantitative data. The results show that during this period, the landscape of the region changed considerably. The area of rangelands decreased from 19,939 ha (1987) to 3605 ha (2019), where 58% of the pre-existing vegetation was transformed into bare soil. This study confirmed that the rangeland vegetation health is closely related to climate, and its degradation is mainly due to the recurrence, duration, severity, and magnitude of drought events. Manmade activities were also a determinant factor of long-term degradation of the rangeland, such as the expansion of new land development areas that increased from 3754 ha (1987) to 24,410 ha (2019). This trend was found throughout the region, including predominantly pastoral regions such as Oumache and El Haouch, leading to overgrazing with a loss of about 2% of vegetation cover. All these factors have led to a severe and continuous degradation of pastoral resources in a vulnerable environment. The preservation of these limited resources requires appropriate management of the ecosystem and a rational exploitation of its vegetation, soil, and water resources.
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  • 文章类型: Journal Article
    这是对木材粘合剂最初应用的概念的研究,该粘合剂完全来自大豆分离蛋白(SPI)和商业类黄酮单宁之间的共价反应,即quebrachotannin。该粘合剂仅由上述两种植物生物材料组成,因此是完全生物来源且无毒的,因为单宁被欧盟委员会REACH计划归类为根本没有毒性。当温度限制在40°C时,两者之间的预反应产生了最佳的胶合板粘合结果,在胶合板高温热压过程中实现的最终交联,至于任何其他热固性粘合剂。在较高温度下预反应,即60°C和80°C,实现了广泛的过早交联,当热压制备胶合板时,该交联失去了任何进一步交联的活性。反应后进行热机械分析,通过基质辅助激光解吸电离飞行时间(MALDIToF)质谱,并通过干燥测试胶合板的剪切强度,冷水浸泡24小时后,在沸水中浸泡1小时。这种方法的粘合剂本身可以通过其他几个研究小组已经开发的多种大豆树脂方法进一步增强。
    This is a study of concept on the initial application for wood adhesives totally biosourced from the covalent reaction between soy protein isolate (SPI) and a commercial flavonoid tannin, namely quebracho tannin. The adhesive is composed exclusively of the two vegetable biomaterials mentioned and thus is totally biosourced and non-toxic, as tannin has been classified as being not at all toxic by the European Commission REACH program. The pre-reaction between the two yielded the best plywood bonding results when limited to a temperature of 40 °C, final cross-linking being achieved during the plywood higher temperature hot pressing procedure, as for any other thermosetting adhesive. Pre-reaction at higher temperatures, namely 60 °C and 80 °C, achieved extensive premature cross-linking that lost any activity to cross-link further when hot pressed for preparing plywood. The reaction was followed by thermomechanical analysis, by matrix assisted laser desorption ionization time of flight (MALDI ToF) mass spectrometry, and by plywood shear strength tested dry, after a 24 h cold water soak and 1 h in boiling water. The adhesive of this approach lends itself to be further reinforced by the multitude of approaches on soy resins already developed by several other research groups.
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  • 文章类型: Journal Article
    这项研究的目的是确定使用单扫描斜坡混合编码(RHE)方法对人体膝关节进行快速双组分T2*分析的可行性。所提出的方法利用RHE在单次扫描中以40μs和30ms之间的16个不同回波时间采集超短回波时间(UTE)和随后的梯度回波图像。在提出的RHE技术中,UTE成像后采集14张梯度回波图像,其中通过过采样单点成像(SPI)编码在第一读出内获得额外的UTE图像。在3T下对来自六个供体的人尸体膝关节和来自四个健康志愿者的体内膝关节进行9分钟扫描时间的单扫描RHE方法。使用双组分信号模型来表征短T2*和长T2*水成分。髌腱的平均双组分T2*参数,前交叉韧带(ACL),计算后交叉韧带(PCL)和半月板。在实验结果中,RHE技术提供了肌腱的双组分T2*参数估计,ACL,PCL和弯月面,与文献中先前报道的值相似。总之,提出的单扫描RHE技术提供了人膝关节的快速双组分T2*分析,总扫描时间少于9分钟。
    The purpose of this study is to determine the feasibility of using a single scan ramped hybrid-encoding (RHE) method for rapid bicomponent T2* analysis of the human knee joint. The proposed method utilizes RHE to acquire ultrashort echo time (UTE) and subsequent gradient echo images at 16 different echo times ranging between 40 μs and 30 ms in a single scan. In the proposed RHE technique, UTE imaging was followed by acquisition of 14 gradient recalled echo images, where an additional UTE image was obtained within the first readout by oversampling single point imaging (SPI) encoding. The single scan RHE method with a 9-minute scan time was performed on human cadaveric knee joints from six donors and in vivo knee joints from four healthy volunteers at 3 T. A bicomponent signal model was used to characterize the short T2* and long T2* water components. Mean bicomponent T2* parameters for patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL) and meniscus were calculated. In the experimental results, the RHE technique provided bicomponent T2* parameter estimations of tendon, ACL, PCL and meniscus, which were similar to previously reported values in the literature. In conclusion, the proposed single scan RHE technique provides rapid bicomponent T2* analysis of the human knee joint with a total scan time of less than 9 minutes.
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  • 文章类型: Journal Article
    In this study, we explore the feasibility of a new imaging scheme for quantitative susceptibility mapping (QSM): continuous single-point imaging (CSPI), which uses a pure phase encoding strategy to achieve true phase imaging and improve QSM accuracy.
    The proposed CSPI is a modification of conventional SPI to allow acquisition of multiple echoes in a single scan. Immediately following a phase encoding gradient, the free induction decay is continuously sampled with extremely high temporal resolution to obtain k-space data at a fixed spatial frequency (i.e., at a fixed k-space coordinate). By having near-0 readout duration, CSPI results in a true snapshot of the transverse magnetization at each TE. Additionally, parallel imaging with autocalibration is utilized to reduce scan time, and an optional temporal averaging strategy is presented to improve signal-to-noise ratio for objects with low proton density or short T2* decay. The reconstructed CSPI images were input to a QSM framework based on morphology enabled dipole inversion.
    In an experiment performed using iron phantoms, susceptibility estimated using CSPI showed high linearity (R2 = 0.9948) with iron concentration. Additionally, reconstructed CSPI phase images showed much reduced ringing artifact compared with phase images obtained using a frequency encoding strategy. In an ex vivo experiment performed using human tibia samples, estimated susceptibilities ranged from -1.6 to -2.1 ppm, in agreement with values reported in the literature (ranging from -1.2 to -2.2 ppm).
    We have demonstrated the feasibility of using CSPI to obtain true phase images for QSM.
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  • 文章类型: Comparative Study
    Robotic thyroid surgery using the da Vinci surgical system has certain cosmetic advantages; however, the invasiveness of robotic thyroid surgery is still a concern to many surgeons. Previous research has not directly compared the surgical stress of robotic thyroidectomy with that of conventional open surgery. The aim of the present study was to evaluate surgical stress using postsurgical measurements of several clinical markers.
    A pilot study was performed to evaluate surgical stress following robotic and open thyroid surgery. A total of 29 papillary thyroid cancer patients from July to November 2014 were enrolled. Fourteen patients underwent conventional open surgery, and fifteen underwent robotic thyroidectomy. IL-6 levels, serum WBC counts, CRP levels, surgical plethysmographic index (SPI), and visual analogue scale (VAS) score were measured to compare surgical stress between the robotic and the open surgery groups.
    No significant differences were seen between the two groups in IL-6 level, WBC count or CRP level (p = 0.380, 0.374, 0.360, respectively). Mean SPI level during the surgery was 41.9 ± 4.7 in open group compared to 39.5 ± 2.2 in robotic group, though this finding showed borderline significance (p = 0.095). VAS score after open surgery was significantly higher than after robotic operation (p = 0.048).
    The results of this study suggest that robotic thyroidectomy can result in a less than equivocal systemic stress response than is seen in open thyroidectomy. However, further investigation including large-scale, prospective, multicenter studies is warranted for non-inferiority trials.
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  • 文章类型: Journal Article
    大豆分离蛋白(SPI)纳米颗粒(28-179nm)是通过采用冷凝胶法进行轻微修饰而制备的。所获得的纳米颗粒具有均匀的尺寸分布和球形,具有独特的蜂窝状核结构。纳米粒子的特征,包括尺寸,表面电荷和疏水性可以通过改变钙浓度和环境pH来调节。一般来说,较高的钙浓度和较低的pH导致形成具有较大尺寸的纳米颗粒,较低的表面电荷和疏水性。蛋白质构象和纳米颗粒解离研究都表明钙可能屏蔽SPI多肽链上的负电荷,并充当盐桥以允许多肽链相互接近。在这个过程中,钙有利于β-折叠结构的发展,以形成通过氢键稳定的SPI聚集体。然后将这些聚集体结合以通过疏水相互作用构建SPI纳米网络。体外研究表明,SPI纳米颗粒无毒,摄入Caco-2细胞后主要位于细胞质中。
    Soy protein isolate (SPI) nanoparticles (28-179 nm) were prepared by employing a cold gelation method with a slight modification. The obtained nanoparticles exhibited uniform size distribution and spherical shape with a unique honeycomb-like core structure. Nanoparticle characteristics including size, surface charge and hydrophobicity could be adjustable by changing calcium concentration and environmental pH. Generally, higher calcium concentration and lower pH led to formation of nanoparticles with larger size, lower surface charge and hydrophobicity. Both protein conformation and nanoparticle dissociation studies indicated that calcium likely shielded negative charges on the SPI polypeptide chains, and functioned as a salt-bridge to permit polypeptide chains to approach one another. In this process, calcium favoured the development of β-sheet structures to form SPI aggregates stabilised by hydrogen bonding. These aggregates were then associated to build SPI nano-networks through hydrophobic interactions. In vitro study indicated that the SPI nanoparticles were non-toxic and mainly located in the cytoplasm when uptaken into Caco-2 cells.
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