Seasonal Characteristics of Forecasting Uncertainties in Surface PM_(2.5)Concentration Associated with Forecast Lead Time over the Beijing-Tianjin-Hebei Region

Forecasting uncertainties among meteorological fields have long been recognized as the main limitation on the accuracy and predictability of air quality forecasts.However,the particular impact of meteorological forecasting uncertainties on air quality forecasts specific to different seasons is still not well known.In this study,a series of forecasts with different forecast lead times for January,April,July,and October of 2018 are conducted over the Beijing-Tianjin-Hebei(BTH)region and the impacts of meteorological forecasting uncertainties on surface PM_(2.5)concentration forecasts with each lead time are investigated.With increased lead time,the forecasted PM_(2.5)concentrations significantly change and demonstrate obvious seasonal variations.In general,the forecasting uncertainties in monthly mean surface PM_(2.5)concentrations in the BTH region due to lead time are the largest(80%)in spring,followed by autumn(~50%),summer(~40%),and winter(20%).In winter,the forecasting uncertainties in total surface PM_(2.5)mass due to lead time are mainly due to the uncertainties in PBL heights and hence the PBL mixing of anthropogenic primary particles.In spring,the forecasting uncertainties are mainly from the impacts of lead time on lower-tropospheric northwesterly winds,thereby further enhancing the condensation production of anthropogenic secondary particles by the long-range transport of natural dust.In summer,the forecasting uncertainties result mainly from the decrease in dry and wet deposition rates,which are associated with the reduction of near-surface wind speed and precipitation rate.In autumn,the forecasting uncertainties arise mainly from the change in the transport of remote natural dust and anthropogenic particles,which is associated with changes in the large-scale circulation.

Association of daily sitting time and leisure-time physical activity with body fat among U.S.adults

Background:Prolonged sitting and reduced physical activity lead to low energy expenditures.However,little is known about the joint impact of daily sitting time and physical activity on body fat distribution.We investigated the independent and joint associations of daily sitting time and physical activity with body fat among adults.Methods:This was a cross-sectional analysis of U.S.nationally representative data from the National Health and Nutrition Examination Survey2011-2018 among adults aged 20 years or older.Daily sitting time and leisure-time physical activity(LTPA)were self-reported using the Global Physical Activity Questionnaire.Body fat(total and trunk fat percentage)was determined via dual X-ray absorptiometry.Results:Among 10,808 adults,about 54.6%spent 6 h/day or more sitting;more than one-half reported no LTPA(inactive)or less than 150 min/week LTPA(insufficiently active)with only 43.3%reported 150 min/week or more LTPA(active)in the past week.After fully adjusting for sociodemographic data,lifestyle behaviors,and chronic conditions,prolonged sitting time and low levels of LTPA were associated with higher total and trunk fat percentages in both sexes.When stratifying by LTPA,the association between daily sitting time and body fat appeared to be stronger in those who were inactive/insuufficiently active.In the joint analyses,inactive/insuufficiently active adults who reported sitting more than 8 h/day had the highest total(female:3.99%(95%confidence interval(95%CI):3.09%-4.88%);male:3.79%(95%CI:2.75%-4.82%))and trunk body fat percentages(female:4.21%(95%CI:3.09%-5.32%);male:4.07%(95%CI:2.95%-5.19%))when compared with those who were active and sitting less than 4 h/day.Conclusion:Prolonged daily sitting time was associated with increased body fat among U.S.adults.The higher body fat associated with 6 h/day sitting may not be offset by achieving recommended levels of physical activity.

Projected Regional 1.50℃and 2.00℃Warming Threshold-crossing Time Worldwide Using the CMIP6 Models

The Paris Agreement aims to limit global warming to well below 2.00℃and pursue efforts to limit the temperature increase to 1.50℃.However,the response of climate change to unbalanced global warming is affected by spatial and temporal sensitivities.To better understand the regional warming response to global warming at 1.50℃and 2.00℃,we detected the 1.50℃and 2.00℃warming threshold-crossing time(WTT)above pre-industrial levels globally using the Coupled Model Intercomparison Project phase 6(CMIP6)models.Our findings indicate that the 1.50℃or 2.00℃WTT differs substantially worldwide.The warming rate of land would be approximately 1.35–1.46 times that of the ocean between 60°N–60°S in 2015–2100.Consequently,the land would experience a 1.50℃(2.00℃)warming at least 10–20 yr earlier than the time when the global mean near-surface air temperature reaches 1.50℃(2.00℃)WTT.Meanwhile,the Southern Ocean between 0°and 60°S considerably slows down the global 1.50℃and 2.00℃WTT.In 2040–2060,over 98.70%(77.50%),99.70%(89.30%),99.80%(93.40%),and 100.00%(98.00%)of the land will have warmed by over 1.50℃(2.00℃)under SSP(Shared Socioeconomic Pathway)1–2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5,respectively.We conclude that regional 1.50℃(2.00℃)WTT should be fully considered,especially in vulnerable high-latitude and high-altitude regions.

Effects of Spatial Row Arrangement and Time of Planting Intercrops on Performance of Groundnut (Arachis hypogaea L.) under Maize (Zea mays L.)—Groundnut Intercropping System in Ejura

In monoculture, crop failure due to biotic or abiotic causes can result in partial or total output failure. The yield, socio-economic, and environmental effects of intercropping on the farmer and the environment as a whole have not received much attention. There is a dearth of knowledge on the productivity of maize-groundnut intercrops in Ghana regarding the relative timing of planting and spatial arrangement of component crops. Therefore, the objective of the study was to determine the effects of spatial row arrangement and the time of planting intercrops on the productivity of groundnut under maize-groundnut intercropping. The 5 × 3 factorial field experiment was undertaken at the Miminaso community in the Ejura-Sekyedumase municipality of the Ashanti Region of Ghana during the 2020 cropping seasons. Treatments were evaluated in a Randomized Complete Block Design (RCBD) with three replicates. The levels of row arrangement of intercrops were: one row of maize and one row of groundnut (1M1G), one row of maize and two rows of groundnut (1M2G), two rows of maize and one row of groundnut (2M1G), two rows of maize and two rows of groundnut (2M2G), sole maize and sole groundnut (M/G). The levels of time of introducing groundnut included simultaneous planting of intercrops (0 WAP), planting groundnut one week after planting maize (1 WAP) and planting groundnut two weeks after planting maize (2 WAP). There were significant (P 0.05) treatment interactions for pod and seed yields of groundnut throughout the study. The highest groundnut pod yields of 1815.00 kg/ha and 2359.00 kg/ha were recorded by the 0WAP × 1M2G treatment in the major and minor seasons of 2020, respectively, while the highest groundnut seed yields of 741.00 kg/ha and 726.00 kg/ha were recorded in the major and minor rainy seasons of 2020 by 1WAP × G and 0WAP × G treatments, respectively. The highest seed yields of groundnut (404 kg/ha and 637 kg/ha for major and minor rainy seasons, respectively) were produced by 1WAP × 2M2G.

Dynamic Ensemble Multivariate Time Series Forecasting Model for PM2.5

In forecasting real time environmental factors,large data is needed to analyse the pattern behind the data values.Air pollution is a major threat towards developing countries and it is proliferating every year.Many methods in time ser-ies prediction and deep learning models to estimate the severity of air pollution.Each independent variable contributing towards pollution is necessary to analyse the trend behind the air pollution in that particular locality.This approach selects multivariate time series and coalesce a real time updatable autoregressive model to forecast Particulate matter(PM)PM2.5.To perform experimental analysis the data from the Central Pollution Control Board(CPCB)is used.Prediction is car-ried out for Chennai with seven locations and estimated PM’s using the weighted ensemble method.Proposed method for air pollution prediction unveiled effective and moored performance in long term prediction.Dynamic budge with high weighted k-models are used simultaneously and devising an ensemble helps to achieve stable forecasting.Computational time of ensemble decreases with paral-lel processing in each sub model.Weighted ensemble model shows high perfor-mance in long term prediction when compared to the traditional time series models like Vector Auto-Regression(VAR),Autoregressive Integrated with Mov-ing Average(ARIMA),Autoregressive Moving Average with Extended terms(ARMEX).Evaluation metrics like Root Mean Square Error(RMSE),Mean Absolute Error(MAE)and the time to achieve the time series are compared.

Effect of ageing time on corrosion behavior of Mg-10Gd-4.8Y-0.6Zr extruded-alloy

The corrosion behaviors of Mg-10Gd-4.8Y-0.6Zr extruded-alloys with various ageing time were investigated by immersion test and electrochemical measurements.The results show that the corrosion rate of the experimental alloy decreases with the increase of ageing time from 0 to 108 h.The corrosion resistance of the experimental alloy was found to increase with the increase of the size of the precipitate phases.The open circuit potential of the experimental alloy increases with the increase of the ageing time.The potentiodynamic polarization curves show that the cathodic over-potential increases with the increase of ageing time,leading to a decrease in the current density of anodic current plateau with the increase of ageing time.

Relationship between Storage Environment and Fruit Quality of a Pear Cultivar Xinli No.7 at Different Picking Time

[Objective] This study aimed to study the effects of different picking time and storage environment on fruit quality of a pear cultivar Xinlin No.7 and the relationship between storage environment and fruit quality, so as to provide a theoretical basis for storage and preservation of Xinli No.7. [Method] The fruits of Xinli NO.7 were picked up in August （optimal） and September respectively and then stored in room, cellar and freezer, respectively. The dynamics in temperature, humidity, CO2 concentration, fruit weight loss rate, pericarp chlorophyll content and fruit interior quality were determined. [Result] The environment differed significantly among different storage methods. In room and cellar, the temperature showed a downward trend, and the humidity decreased after early-mid October. The CO2 concentration changed steadily, and increased rapidly in cellar after December. In freezer, the temperature and humidity changed steadily, and the CO2 concentration increased after October. The changes in quality of the fruits harvested in August and September were similar. There was a certain correlation between storage environment and fruit quality of Xinli No.7. In room and cellar, the variation trends of tem- perature and humidity were consistent with those of chlorophyll content, fruit hardness and titratable acid content with positive correlations, but were opposite from those of fruit weight loss rate, soluble solids content and soluble sugar content with negative correlations. In freezer, the CO2 concentration was closely related to the changes in fruit quality. Its variation trend was consistent with those of fruit weight loss rate and soluble solids content, but was opposite from those of pericarp chlorophyll content, fruit firmness, soluble sugar content and titratable acid content. The differences in some of the traits reached significant levels （P〈0.05, P〈0.01）. [Conclusion] With the extension of storage time, the temperature, humidity and CO2 concentration changed according to different patterns among different storage methods. The changes in fruit quality of Xinli NO.7 were related to the storage environment, especially to the temperature, to a certain extent.

Effect of milling time on microstructure of Ti35Nb2.5Sn/10HA biocomposite fabricated by powder metallurgy and sintering

A new β-Ti based Ti35Nb2.5Sn/10 hydroxyapitite（HA） biocompatible composite was fabricated by mechanical milling and pulsed current activated sintering（PCAS）.The microstructures of Ti35Nb2.5Sn/10HA powder particles and composites sintered from the milled powders were studied.Results indicated that α-Ti phase began to transform into β-Ti phase after the powders were mechanically milled for 8 h.After mechanical milling for 12 h,α-Ti completely transformed into β-Ti phase,and the ultra fine Ti35Nb2.5Sn/10HA composite powders were obtained.And ultra fine grain sized Ti35Nb2.5Sn/10HA sintered composites were obtained by PCAS.The hardness and relative density of the sintered composites both increased with increasing the ball milling time.

Effects of dwell time during sintering on electrical properties of 0.98(K_(0.5)Na_(0.5))NbO_3-0.02LaFeO_3 ceramics

The effects of dwell time on the phase structure, microstructure, and electrical properties were investigated for the 0.98（K0.sNa0.5）NbO3-0.02LaFeO3 ceramics （abbreviated as 0.98KNN-0.02LF）. All the ceramics sintered for different dwell time are of pure phase and the peak intensity of the 0.98KNN-0.02LF ceramics becomes stronger with a longer dwell time. Denser microstructures with larger grain size are developed for the sample with a longer dwell time. The maximum dielectric permittivity decreases with increasing the dwell time, and the deteriorative dielectric properties are due to the increasing grain size and the domain wall motion. Ferroelectric properties results indicate that 2Pr value slightly decreases with increasing the dwell time, while the 2Ec value increases. Consequently, the 0.98KNN-0.02LF ceramic sintered at 1150 ℃ for 2 h shows optimum dielectric properties （er=2253 and tan fi〈5%） and ferroelectric properties （2Pr=34.51 gC/cm2 and 2Ec=5.07 kV/mm）.

Diversity of Flower Opening Time and Duration in Rice (Oryza sativa ssp. indica) Landraces of South and Southeast Asia in Different Cultivation Seasons

Different cultivars of rice(Oryza sativa)open at different times of the day,and the overlap of anthesis time in rice between the neighbouring cultivars is of crucial importance to the degree of cross pollination in rice.Nevertheless,none of the past experiments with cross pollination between different rice cultivars ever reported the respective flower opening time(FOT)and flower exposure duration(FED)of the parent cultivars,until recently.The authors present here the first record of FOT and FED of 1114 indica rice landraces of South and Southeast Asia,growing during sum-mer and winter seasons in three consecutive years.The authors also present an analysis of the influences of the grow-ing season on the anthesis behaviour,and present the first records of the FOT and FED variability on sunny and cloudy days of a large number of landraces.The data show that rice florets tend to open later in the morning(that is,take longer time to anthesis after sunrise)on sunny days than on cloudy days,and also significantly later during long day seasons(spring and summer)than during short day season(winter);and that FED is inversely related to both FOT and the length of duration from sunrise to first flower opening.The wide ranges of FOT(8:50 a.m.to 12:40 p.m.)and FED(15 to 194 minutes)also suggest the ample time window for receiving pollen from neighbouring cultivars with differ-ent FOT,enhancing the chances of cross pollination between hundreds of rice landraces with FOT and FED overlaps.

Time Delay Characteristic of Industrial Wireless Networks Based on IEEE 802.15.4a

The IEEE 802.15.4a standard provides a framework for low-data-rate communication systems,typically sensor networks.In this paper,we established a realistic environment for the time delay characteristic of industrial network based on IEEE 802.15.4a.Several sets of practical experiments are conducted to study its various features,including the effects of 1） numeral wireless nodes,2） numeral data packets,3） data transmissions with different upper-layer protocols,4） physical distance between nodes,and 5） adding and reducing the number of the wireless nodes.The results show that IEEE 802.15.4a is suitable for some industrial applications that have more relaxed throughput requirements and time-delay.Some issues that could degrade the network performance are also discussed.

基于2.4 GHz无线技术的RTK定位系统

利用2.4 GHz无线技术,设计RTK(real time kinematic)定位系统.在两种实验场景下,进行对比实验,比较RTK定位系统和传统PVT(position velocity time)定位系统的定位误差.实验结果表明:两种实验场景下,相对于传统PVT定位系统,该文设计的RTK定位系统均有更小的定位误差.该文定位系统可应用于无人机、精准农业等领域.

高速铁路0.01~1 m波段高低轨道不平顺特性分析

随着我国高速铁路发展规模的不断扩大及运营速度的不断提升,轨道短波不平顺引起的振动与噪声问题日益严重。深入研究高速铁路短波不平顺的时域、频域与时频域特征,对精准掌握高速铁路轨道短波平顺状态及其引起的车-轨系统振动、伤损等一系列问题具有重要的参考价值。以某高速铁路实测0.01~1 m波段轨面高低不平顺数据为研究对象,经过数据预处理剔除异常值并消除趋势项后,对实测不平顺数据进行时域分析,得到该高铁线路短波不平顺数据的统计与分布特性。采用平均周期图法计算该高铁线路轨道短波不平顺功率谱密度,应用非线性最小二乘拟合优化算法进行拟合,提出高速铁路轨道短波不平顺谱。从时频域角度对该段数据进行经验模态分解与希尔伯特变换,分析该高铁线路短波不平顺的希尔伯特谱与边际谱。研究结果表明:该高铁线路轨道短波不平顺数据各统计量幅值都较小,且近似服从正态分布;该高铁线路轨道短波不平顺功率谱密度存在与钢轨波磨有关的多个周期性成分,提出的高速铁路短波不平顺谱函数能够很好地对实测功率谱密度进行拟合,且拟合效果优于经典的SATO建议的短波谱与50 kg/m钢轨的短波谱;对该高铁线路轨道可能存在的短波病害进行识别与定位,时频域分析的方法可以较好地应用于高速铁路轨道平顺性的分析与日常的管理维护。

新疆乌什7.1级地震前GNSS变形特征分析

2024年1月23日新疆乌什发生7.1级地震。为了研究震前GNSS变形特征,通过对比分析GNSS基线时间序列结果和区域应变结果,发现迈丹断裂带东西两段的地壳运动有所差异,东段的运动较强,乌什地震即发生在断裂带东段;利用4期速度场结果,计算得到动态应变场变化,从NS向应变场结果可以看出该区域的应变量值持续增加,应变持续在积累状态,从长期背景场可以看出7.1级地震发生在应变高值区的边缘;发震断层东西两侧的挤压滑动速率存在明显差异,西侧为(1.0±0.35)mm/a,东侧为(4.1±0.51)mm/a,且东侧的闭锁程度较高。研究认为迈丹断裂带两侧运动差异明显,乌什7.1级地震发生在滑动速率较高的东段,且该区域处于应变高值区的边缘。

基于CEEMDAN的多时间尺度的北京市PM_(2.5)浓度影响因素研究

研究PM_(2.5)浓度的主要影响因素,对提升北京市空气质量具有重要意义。与以往仅限于原始时间尺度的研究不同,本文基于CEEMDAN方法考察了多时间尺度下年平均风速、城市绿化、人口密度、产业结构和能源强度对北京市PM_(2.5)浓度波动的影响,并与原始时间尺度的主导因素进行对比。研究发现:原始尺度的北京市PM_(2.5)浓度影响因素是不同时间尺度内影响因素合力作用结果,不同时间尺度下影响因素不同。城市绿化、人口密度、产业结构和能源强度在多时间尺度中起到短期增强波动的作用,城市绿化和产业结构是贯穿于各个时间尺度的具有趋势性,决定北京市PM_(2.5)浓度基本走势的影响因素。

模拟启动时间和双台风对“21.7”河南极端暴雨事件的影响研究

对发生在2021年7月18日至21日的河南极端暴雨事件(“21.7”河南暴雨)进行集合模拟数值试验,旨在探究模拟启动时间以及台风“烟花”和“查帕卡”对此次暴雨事件的影响.不同模拟启动时间的试验组分析表明,在降水峰值发生前24 h启动的一组试验能够最准确地模拟双台风的路径和强度演变特征,其再现了“21.7”河南暴雨中心位置、强度及时间演变特征,这主要是由于该试验很好地再现了低层东南风急流及其动力辐合特征,基于此最优试验移除台风环流后,副热带高压西伸南压且水汽输送路径随之发生调整.通过定量分析降水关键区的整层水汽通量发现,在降水最大峰值出现的时段内,台风“烟花”和“查帕卡”分别削弱了东南风和偏南风的水汽输送,表明台风的存在对降水的影响存在不确定性,某些时段内反而减缓了河南地区的极端降水.

碳减排“时-空-效-益”统筹理论:I.时间统筹

在气候变化应对过程中,面临一种纵向的代际统筹,即当前人类应当或者愿意付出多大代价来避免未来可能发生的气候变化损失。对这一问题的回答关乎当代人与后代人的利益,需要权衡当前减缓气候变化的成本和未来气候变化带来的损失。然而,当前国际上对贴现率和跨期均衡路径的探讨暂未得出明确方案,亟需形成统筹长期与短期的碳减排理论,以指导相关减排路径设计。作为碳减排“时-空-效-益”统筹理论系列论文的组成部分,聚焦于碳减排的时间统筹,构建了跨期均衡路径,并设置了积极但不激进的贴现率,从而统筹当前减缓气候变化的成本和未来气候变化带来的损失,回答碳减排的跨期责任分担与成本分配等问题,应用于CEEP-BIT自主开发的中国气候变化综合评估模型(C3IAM)等气候环境治理与碳减排路径的研究中,为统筹长期减排与短期减排提供方法基础。

第二相体积分数对Mg-13Gd-4Y-2Zn-0.5Zr合金力学性能的影响

采用万能拉伸试验机、SEM、EDS及XRD对固溶处理后的Mg-13Gd-4Y-2Zn-0.5Zr合金力学性能、第二相形态、化学成分进行了分析,并利用Image-Pro-Plus软件对第二相体积分数进行了统计。结果表明:固溶处理后,合金中仍有大量不同形态、成分的第二相,主要是灰色块状LPSO相、灰色棒状LPSO相和白色点状富稀土相。随着固溶时间的增加,Mg-13Gd-4Y-2Zn-0.5Zr合金的抗拉强度与伸长率表现出先降低后升高的变化规律。在510℃固溶16 h,合金的抗拉强度与伸长率达到最小值,分别为196.77 MPa、3.8%。510℃固溶10~16 h,LPSO相体积分数不变,富稀土相体积分数增加,富稀土相质地较脆,受力时容易破碎,成为裂纹萌发和扩展的源头,使合金抗拉强度、伸长率均降低。510℃固溶16~19 h,富稀土相体积分数减少,合金的力学性能增加。

转基因番茄植株Mi1.2表达水平的Real Time PCR检测体系的建立

[目的]为转基因番茄植株的高通量筛选奠定基础。[方法]利用CTAB法提取番茄叶片总RNA进行Real Time PCR扩增，分析转MI1、2基因的番茄植株表达水平的检测体系。[结果]提取RNA的A260／A280为1．78～1．88，RNA无明显降解。在严谨扩增条件下，引物SYBR2的扩增效率高于SYBR1。Mg^2＋的适宜浓度为2．0mg／L。Real Time PCR扩增产物具有良好的特异性，熔解曲线特异峰出现在84．5℃附近，在熔解曲线略低于83℃附近有极微弱的非特异峰。因此在定量反应中信号检测步骤应放在84℃。以4种不同模板分子数条件下扩增曲线Ct值得到的回归方程为Y=-3．78×log（copynumber）＋39．50，相关系数为0．998。[结论]该试验获得的Real Time PCR体系可用于转基因植株表达水平的检测。

武钢7.63 m焦炉上升管荒煤气温度变化规律研究

为研究武钢7.63 m焦炉上升管余热利用工程实施的可行性,对2#炭化室上升管根部和桥管处荒煤气温度进行连续在线检测。分析发现:上升管根部荒煤气温度在整个结焦过程呈现类似Z字型周期变化规律,最高温度发生在推焦前烧石墨阶段,达1300℃~1400℃,整个结焦周期的平均温度约为771℃;桥管处荒煤气温度仍保持较完整的周期性规律;7.63 m焦炉单孔炭化室荒煤气产量为1156.42 m^(3)/h,一个结焦周期内单孔炭化室荒煤气可利用理论热量约13.76 GJ,工程理论吨焦产汽量(1.6 MPa低压饱和蒸汽)为108 kg。