Spatio-temporal Characteristics of Area Coverage and Observation Geometry of the MISR Land-surface BRF Product: A Case Study of the Central Part of Northeast Asia

The Multi-angle imaging spectroradiometer(MISR) land-surface(LS) bidirectional reflectance factor(BRF) product(MILS_BRF) has unique semi-simultaneous multi-angle sampling and global coverage. However, unlike on-satellite observations, the spatio-temporal characteristics of MILS_BRF data have rarely been explicitly and comprehensively analysed. Results from 5-yr(2011–2015) of MILS_BRF dataset from a typical region in central Northeast Asia as the study area showed that the monthly area coverage as well as MILS_BRF data quantity varies significantly, from the highest in October(99.05%) through median in June/July(78.09%/75.21%) to lowest in January(18.97%), and a large data-vacant area exists in the study area during four consecutive winter months(December through March). The data-vacant area is mainly composed of crop lands and cropland/natural vegetation mosaic. The amount of data within the principal plane(PP)±30°(nPP) or cross PP ±30°(nCP), varies intra-annually with significant differences from different view zeniths or forward/backward scattering directions. For example, multiple off-nadir cameras have nPP but no nCP data for up to six months(September through February), with the opposite occurring in June and July. This study provides explicit and comprehensive information about the spatio-temporal characteristics of product coverage and observation geometry of MILS_BRF in the study area. Results provide required user reference information for MILS_BRF to evaluate performance of BRDF models or to compare with other satellite-derived BRF or albedo products. Comparing this final product to on-satellite observations, what was found here reveals a new perspective on product spatial coverage and observation geometry for multi-angle remote sensing.

Spatio-Temporal Characteristics of Winter Cold Events in China from 1960 to 2020

Under the background of global warming, extreme cold events occur frequently. It is important to enhance the understanding of cold air patterns for forecasting cold air and reducing cold air-induced meteorological disasters. The study used the daily minimum temperatures from the National Climate Centre to classify the cold events affecting China into five different grades and the characteristics of different intensity cold events in China during the winter from 1960 to 2020 were analyzed. The results showed that there is little difference in the distribution of the frequency of general cold events from north to south, with duration longer in the north than in the south and an increase in frequency in the north in the last 60 years. The frequency of strong cold events is more in the north of China than in the south of China, and the duration is longer in the south than in the north China, with the frequency decreasing in most parts of the country. In addition to latitude, cold events frequency is closely linked to topography, with basins surrounded by high mountains being difficult to be affected by cold events, especially extreme cold events. In terms of month distribution, December was subject to the highest frequency of cold events and the longest duration of a single cold events process.

Spatio-Temporal Analysis of Drought in the North-Eastern Coastal Region of Vietnam Using the Standardized Precipitation Index (SPI)

Spatio-temporal analysis of drought provides valuable information for drought management and damage mitigation. In this study, the Standardized Precipitation Index at the time scale of 6 months (SPI-6) is selected to reflect drought conditions in the North-Eastern coastal region of Vietnam. The drought events and their characteristics from 1981 to 2019 are detected at 9 meteorological stations and 10 Chirps rainfall stations. The spatio-temporal variation of drought in the study region is analyzed on the basis of the number, duration, severity, intensity, and peak of the detected drought events at the 19 stations. The results show that from 1981 to 2019 the drought events mainly occurred with 1-season duration and moderate intensity and peak. The number, duration, severity, and peak of the drought events were the greatest in the period 2001-2010 and were the smallest in the period 2011-2019. Among the 19 stations, the drought duration tends to decrease at 11 stations, increase at 7 stations, and has a slight variant at 1 station;the drought severity tends to decrease at 14 stations, increase at 4 stations, and has not a significant trend at 1 station;the drought intensity tends to decrease at 17 stations, increase at 1 station, and has a slight variant at 1 station;and the drought peak tends to decrease at 18 stations and increase at 1 station.

Spatio-temporal Variability of Northern Hemipheric Sea Level Pressure(SLP)and Precipitation over the Mid-to-Low Reaches of the Yangtze River

The spatio-temporal variability of Northern Hemisphere Sea Level Pressure （SLP） and precipitation over the mid-to-low reaches of the Yangtze River （PMLY） is analyzed jointly using the multi-taper/singular value decomposition method （MTM-SVD）. Statistically significant narrow frequency bands are obtained from the local fractional variance （LFV） spectrum. Significant interdecadal （i.e., 16-to-18-year periods） and interannual （i.e., 3-to-6-year periods） signals are identified. Moreover, a significant quasi-biennial signal is identified but only for PMLY data. The spatial joint evolution of patterns obtained for peaks in the LFV spectrum sheds light on relationships between SLP and PMLY： the Arctic Oscillation （AO） modulates the variability of the PMLY while the interannual variability of PMLY is in phase with the Northern Atlantic Oscillation （NAO） and the Northern Pacific Oscillation （NPO）.

Spatio-temporal Variability of Disastrous Convective Weather in China from 1961 to 2016

Based on the data of hail,gale,thunderstorm and lightning days in 2 481 stations in China from 1961 to 2016,the spatial and temporal distribution characteristics,periodicity and climate abruption characteristics of four kinds of disastrous convective weather in China were analyzed by various mathematical statistics methods. The results showed that in time,the days of four kinds of disastrous convective weather in China decreased,and the hail and thunderstorm days were characterized by " increasing firstly and then decreasing" from 1961 to 2016. The hail,gale,thunderstorm and lightning days in China had oscillation cycles of 3-5,2-3,1-2 and 1-4 a respectively,and the hail and thunderstorm days changed suddenly in 2002 and 1992 respectively. In space,the Qinghai-Tibet Plateau and western Sichuan were the highvalue distribution areas of hail,gale and thunderstorm days. The high-value distribution areas of thunderstorm days were also distributed to the south of the Yangtze River. South China and its southwestern regions at the same latitude were the high-value distribution areas of lightning days. In terms of trend,the hail days in China showed a decreasing trend mainly in the Qinghai-Tibet Plateau. The gale days in China decreased in the east,was unchanged in the central region,and increased and decreased alternately in the west. The thunderstorm days in China increased in Tibet,North China,Chongqing,Zhejiang and northwestern Heilongjiang. The lightning days in China decreased obviously to the south of the Yangtze River. In terms of the fluctuation,the hail days fluctuated greatly in the southeast. The gale days fluctuated greatly to the east of Hu Huanyong line. The thunderstorms days in China fluctuated greatly in the northwest and slightly in the southeast. In addition to the small fluctuation in northern Xinjiang and South China,the lightning days fluctuated greatly in other regions of China.

鄂尔多斯盆地南梁地区延长组长6沉积特征

为了研究南梁地区延长组重力流沉积特征,利用钻井岩芯、轻重矿物和测井解释等对鄂尔多斯盆地南梁地区三叠系延长组长6沉积体系特征与沉积模式进行分析。结果表明:鄂尔多斯盆地长6以K2、K3、K4这3套泥岩作为标志层,根据测井分析方法将延长组长6划分为3个小层;依据轻、重矿物数据资料分析,明确了南梁地区延长组长6发育有东北、西南2个物源,主要受东北物源的控制,东北部母源来自于大青山、阴山一带的太古界高级变质岩和火山岩;南梁地区延长组长6主要以陆源湖泊、三角洲沉积为主,不同的沉积相的类型控制着砂体的展布形状,长6期发育的砂体自北东向西南方向呈现出条带状展布;延长组在长6期湖盆面积逐渐减小盆地边缘的三角洲沉积范围向湖盆中心收缩。长6期自北东向西南发育了三角洲前缘亚相、深湖亚相、浅湖亚相,由于三角洲前缘斜坡地带沉积物发生了滑塌,在重力作用下形成了浊流沉积。

Adaptation analysis and fusion correction method of CMIP6 precipitation simulation data on the Qinghai-Tibetan Plateau

In order to obtain more accurate precipitation data and better simulate the precipitation on the Tibetan Plateau,the simulation capability of 14 Coupled Model Intercomparison Project Phase 6(CMIP6)models of historical precipitation(1982-2014)on the Qinghai-Tibetan Plateau was evaluated in this study.Results indicate that all models exhibit an overestimation of precipitation through the analysis of the Taylor index,temporal and spatial statistical parameters.To correct the overestimation,a fusion correction method combining the Backpropagation Neural Network Correction(BP)and Quantum Mapping(QM)correction,named BQ method,was proposed.With this method,the historical precipitation of each model was corrected in space and time,respectively.The correction results were then analyzed in time,space,and analysis of variance(ANOVA)with those corrected by the BP and QM methods,respectively.Finally,the fusion correction method results for each model were compared with the Climatic Research Unit(CRU)data for significance analysis to obtain the trends of precipitation increase and decrease for each model.The results show that the IPSL-CM6A-LR model is relatively good in simulating historical precipitation on the Qinghai-Tibetan Plateau(R=0.7,RSME=0.15)among the uncorrected data.In terms of time,the total precipitation corrected by the fusion method has the same interannual trend and the closest precipitation values to the CRU data;In terms of space,the annual average precipitation corrected by the fusion method has the smallest difference with the CRU data,and the total historical annual average precipitation is not significantly different from the CRU data,which is better than BP and QM.Therefore,the correction effect of the fusion method on the historical precipitation of each model is better than that of the QM and BP methods.The precipitation in the central and northeastern parts of the plateau shows a significant increasing trend.The correlation coefficients between monthly precipitation and site-detected precipitation for all models after BQ correction exceed 0.8.

South China Sea Typhoon Hagibis enhanced Xinfengjiang Reservoir seismicity

There was an evident increase in the number of earthquakes in the Xinfengjiang Reservoir from June to July 2014 after the landing of Typhoon Hagibis.To understand the spatial and temporal evolution of this microseismicity,we built a high-precision earthquake catalog for 2014 and relocated 2275 events using recently developed methods for event picking and catalog construction.Seismicity occurred in the southeastern part of the reservoir,with the preferred fault plane orientation aligned along the Heyuan Fault.The total seismic energy peaked when the typhoon passed through the reservoir,and seismicity correlated with typhoon energy.In contrast,a limited seismic response was observed during the later Typhoon Rammasun.Combining data regarding the water level in the Xinfengjiang Reservoir and seismicity frequency changes in the Taiwan region during these two typhoon events,we suggest that typhoon activity may increase microseism energy by impacting fault stability around the Xinfengjiang Reservoir.Whether a fault can be activated also depends on how close the stress accumulation is to its failure point.

姬塬油田马家山地区长4+5_(1)亚段油藏特征及主控因素

为了加深对姬塬油田马家山地区长4+5_(1)亚段油藏特征及其主控因素的认识,从烃源岩构造、优势砂体及物性特征等方面对其作了对比分析。分析认为:研究区位于长7段烃源岩生烃中心,具有成藏的有利基础;叠置的优势砂体,促成了长7段烃源岩向长4+5_(1)亚段排出油气运移的主要通道;分流河道交汇处高渗砂体与近东西向排状鼻隆构造的匹配形成了石油聚集的有利场所;长4+5_(1)亚段油藏在多因素的共同控制下主要发育岩性油藏,其纵向上的砂体结构决定了石油富集于长4+5^(2)_(1)小层。

跨内支撑杆及阶梯杆屈曲的一种解析法分析

针对跨内含支撑的杆和变截面阶梯杆的弹性屈曲问题,提出一种分段作屈曲分析再叠加重组的分析方法.首先在杆两端引入横向和旋转弹簧,用以模拟弹性边界条件.其次建立两端弹性约束杆屈曲方程的通用形式,并通过屈曲方程求得几种边界约束杆端部弹性刚度因子的解析表达式.最后,建立拆分杆段连接处的平衡方程和协调条件,综合杆段的屈曲方程和节点的补充刚度条件得到整个杆件的屈曲方程,从而求得临界力.本文还提出一种基于泰勒展开求解屈曲特征方程近似根的方法.算例中将本方法所得结果与既有文献和有限元软件计算结果对比,验证本方法的适用性和准确度.所提方法属于解析方法,得到简洁、严密和易用的解析公式,可为多跨结构和变截面杆件的屈曲分析提供新参考.

Spatio-temporal disparities of Clonorchis sinensis infection in animal hosts in China:a systematic review and meta-analysis

Background Clonorchis sinensis,one of the most important food-borne zoonotic trematodes,remains prevalent in China.Understanding its infection status in animals is crucial for controlling human clonorchiasis.Here we conducted a systematic review and meta-analysis to focus on the spatio-temporal disparities ofC.sinensis infection in animals in China.Methods Data onC.sinensis prevalence in snails,the second intermediate hosts,or animal reservoirs in China were extracted from electronic databases including PubMed,Embase,Web of Science,Chinese Wanfang database,CNKI,VIP,and China Biomedical Literature database.A random-effects meta-analysis model was utilized to estimate the pooled prevalence in each of the above animal hosts.Subgroup analysis and multivariable meta-regression were performed to explore potential sources of heterogeneity across studies and compare the temporal disparity of infection rates between high and low epidemic areas.Scatter plots were used to depict the biogeographical characteristics of regions reportingC.sinensis infection in animals.Results The overall pooled prevalence ofC.sinensis was 0.9%(95%CI:0.6-1.2%)in snails,14.2%(12.7-15.7%)in the second intermediate host,and 14.3%(11.4-17.6%)in animal reservoirs.Prevalence in low epidemic areas(with human prevalence<1%)decreased from 0.6%(0.2-1.2%)before 1990 to 0.0%(0.0-3.6%)after 2010 in snails(P=0.0499),from 20.3%(15.6-25.3%)to 8.8%(5.6-12.6%)in the second intermediate hosts(P=0.0002),and from 18.3%(12.7-24.7%)to 4.7%(1.0-10.4%)in animal reservoirs.However,no similar decrease in prevalence was observed in high epidemic areas(with human prevalence≥1.0%).C.sinensis infections were predominantly reported in areas with altitudes below 2346 m and annual cumulative precipitation above 345 mm and were mostly concentrated in eastern China.Conclusions There are spatio-temporal disparities in the animal infections ofC.sinensis in different areas of China.Animal infections are primarily concentrated in regions with low altitude and high precipitation.The results suggest that implementing One Health-based comprehensive measures targeting both humans and animals,especially in high epidemic areas,is essential for successful eradication ofC.sinensis in China.

永磁接触器位移分段PWM控制及吸合过程动态特性分析

在分析永磁接触器吸合特性的基础上,提出位移分段的控制策略,实时检测接触器动铁心位移,并据此调整控制电压脉宽调制(pulse width modulation,PWM)占空比,使接触器的动态吸力和反力特性达到良好的配合,实现最优运动特性下的吸合控制。建立在位移分段PWM智能化控制下吸合过程的动态特性方程,耦合电压平衡方程和机械运动方程,采用4阶龙格-库塔算法仿真永磁接触器整个吸合动态过程。仿真结果与实验测量较吻合,验证了动态特性方程和仿真方法的正确性。最后,针对提出的控制策略,通过实验比较了4种不同分段的PWM控制方案,选出了最佳,可显著降低永磁接触器动触头及动铁心的闭合速度,并减少由其碰撞带来的触头一、二次弹跳。

考虑土结构性影响的砂井地基固结度计算

基于软土结构性分析 ,提出了固结系数分段模型 ,同时给出了考虑土结构性影响的瞬时加载砂井地基固结度的计算方法 ,使计算分析趋于合理。算例表明 ,土结构性对砂井地基固结性状影响明显。

山西断裂带跨断层形变观测资料动态特征分析

利用多种分析方法对山西断裂带跨断层形变观测资料进行了分析。长趋势分析结果表明,山西断裂带南北两段以拉张变形为主,中段以剪切变形为主。时间分段结果表明,1989—2000年间,位于山西断裂带中部的下达枝、代县、广胜寺3个测点出现断层逆继承性转折变化,断层垂直运动速率绝对值明显减小,反映下达枝、代县和广胜寺地区断层活动呈闭锁状态。另外,跨断层形变观测资料和GPS应变率场结果均表明山西断裂带以近NW向拉张变形为主,但由于观测尺度不同,在量值上二者不具有可比性。

新型装配式屈曲约束支撑试验研究

为了克服普通灌浆型屈曲约束支撑加工周期较长、钢结构加工和填充料加工交叉作业等缺点,提出了一种新型装配式屈曲约束支撑;该支撑采用填充料分段预制,然后与支撑芯板及外套筒组合拼装的加工方式,使得钢结构部分和灌浆料部分同时进行加工,简化了支撑加工工序,缩短了加工周期,降低了支撑制造过程中的人工费用。并对该新型屈曲约束支撑进行了往复加载试验,对试验数据进行分析处理。结果表明:此新型装配式屈曲约束支撑具有很好的滞回特征和耗能性能,各项指标均符合《建筑抗震设计规范》对位移相关型消能器的性能指标要求,是一种十分有效的耗能构件。

分段线性弹簧振动系统的非线性分析

应用非线性谱分析法对分段线性弹簧系统在随机载荷作用下的动力响应进行分析。在假设系统的运动响应是平稳的高斯过程的条件下,导出响应谱密度与激励谱密度之间的关系,并应用数值计算方法,求得系统的响应谱密度,进而对系统幅频特性进行分析。研究表明,响应谱密度随激励强度的增加而增加,幅频特性在固有频率附近随阻尼比的减小变化显著,随弹簧间隙的增加而增加,随固有频率的增加而减小。

试验研究VFTO作用下层式绕组暂态特性

为了研究特快速暂态过电压(VFTO)对层式绕组绝缘的影响,设计制作了分段层式绕组试验模型,该模型分为4段,每段5层,以每1层为1个单元,共分20个单元。试验过程分别对该分段层式绕组模型中有铁心和无铁心注入VFTO脉冲电压信号,并采集记录了入波后分段层式绕组模型各个单元节点电压信息,通过各节点电压信息分析了分段层式绕组模型暂态电位分布情况,并根据入波电压和响应电压求出分段层式绕组电压传输函数的幅频特性,分析了分段层式绕组中谐振频率情况。试验研究结果为层式绕组的绝缘结构设计提供了理论依据。

基于激光诱导击穿光谱的水稻品种鉴别研究

采用激光诱导击穿光谱技术,结合BP神经网络技术对5种水稻种子进行了品种鉴别研究。讨论了两种用于水稻品种鉴别的方法,第一种是"特征谱法",从样品的全谱光谱图中选取Mg、Si、Ca、Na、K等5种元素的谱线构成特征谱,再将此特征谱输入BP神经网络对水稻种子进行识别;第二种是"分段特征谱法",将样品的全谱分为12段光谱,在每一段光谱中,利用自动选谱法选择一些峰构成特征谱,将其输入BP神经网络对水稻种子进行识别。实验结果表明:利用BP神经网络进行水稻种子的品种鉴别时,"分段特征谱法"比"特征谱法"更加适用,且前者的BP神经网络识别率最高可达100%。

一种高精度低温漂带隙基准电路的设计与实现

针对带隙基准电路对集成电路精度的影响,提出了一种新的低温漂带隙基准电路。通过分段温度补偿,补偿了带隙基准电路,减小了温度漂移,优化了基准的温度性能。基于西岳公司3μm18V双极工艺,设计了基准电路和版图,并进行流片。仿真和流片结果表明:在典型工艺角下,基准在-55℃～125℃内,温度系数为1.7×10-6～6.0×10-6/℃;在2.2V的电源幅度范围下,具有0.03mV/V的电源抑制特性。该电路已成功应用于一款线性稳压电源中。

恒温和分段式降温热风干制技术对黑枣干制特性及品质的影响

为提高黑枣在热风干制技术下的品质和干制速率,比较了恒温和分段降温热风干制工艺对其干制特性及热敏性营养物质、感官品质和复水性的影响。结果表明:分段降温较恒温热风干制可将黑枣的干制时间缩短1/4,成品品质显著提升。适宜黑枣干制的分段式降温热风干制工艺为:(40±1)℃预热15 min,(68±1)℃干制至含水量41.0%±0.5%,再(63±1)℃干制至含水量37.0%±0.5%,最后在(55±1)℃干制至35.0%±0.5%含水量,所得黑枣干中总糖、总酚和V_(C)含量分别为49.53%±0.31%、(0.94±0.01)mg/g和(16.41±0.28)mg/100 g,较恒温热风干制成品营养保留率分别提高了11.47%、10.01%和47.91%,干制速率提高了18.75%,感官品质和复水性更好,产品被消费者广泛接受,研究结果可为黑枣的工业化干制提供理论依据和技术参考。