Developing Intensity-Duration-Frequency Curves in Scarce Data Region: An Approach using Regional Analysis and Satellite Data

The availability of data is an important aspect in frequency analysis. This paper explores the joint use of lim- ited data from ground rainfall stations and TRMM data to develop Intensity Duration Frequency (IDF) curves, where very limited ground station rainfall records are available. Homogeneity of the means and variances are first checked for both types of data. The study zone is assumed to be belonging to the same region and checked using the Wiltshire test. An Index Flood procedure is adopted to generate the theoretical regional distribution equation. Rainfall depths at various return periods are calculated for all stations and plotted spatially. Regional patterns are identified and discussed. TRMM data are used to develop ratios between 24-hr rainfall depth and shorter duration depths. The regional patterns along with the developed ratios are used to develop regional IDF curves. The methodology is applied on a region in the North-West of Angola.

Frequency, Duration and Intensity of Dengue Fever Epidemic Risk in Townships in Pearl River Delta and Yunnan in China, 2013

Dengue fever （DF）, one of the neglected tropical diseases also known as breakbone fever, is a mosquito-borne disease common in the tropics and subtropics. Dengue fever is transmitted primarily by A.aegypti, resulting in infection with any of four distinct but closely related virus serotypes. The majority of infected people experience a self-limiting clinical course. A small proportion of cases develop into life-threatening Dengue Hemorrhagic Fever or Dengue Shock Syndrome.

Analysis of Rainfall Intensity-Duration-Frequency Relationship for Rwanda

Global atmospheric and oceanic perturbations and local weather variability induced factors highly alter the rainfall pattern of a region. Such factors result in extreme events of devastating nature to mankind. Rainfall Intensity Duration Frequency (IDF) is one of the most commonly used tools in water resources engineering particularly to identify design storm event of various magnitude, duration and return period simultaneously. In light of this, the present study is aimed at developing rainfall IDF relationship for entire Rwanda based on selected twenty six (26) rainfall gauging stations. The gauging stations have been selected based on reliable rainfall records representing the different geographical locations varying from 14 to 83 years of record length. Daily annual maximum rainfall data has been disaggregated into sub-daily values such as 0.5 hr, 1 hr, 3 hr, 6 hr and 12 hr and fitted to the probability distributions. Quantile estimation has been made for different return periods and best fit distribution is identified based on least square standard error of estimate. At-site and regional IDF parameters were computed and subsequent curves were established for different return period. The moment ratio diagram (MRD) and L-moment ratio diagram (LMRD) methods have been used to fit frequency distributions and identify homogeneous regions for observed 24-hr maximum annual rainfall. The rainfall stations have been divided into five homogeneous rainfall regions for all 26 stations. The results of present analysis can be used as useful information for future water resources development planning purposes.

Development of Rainfall Intensity Duration Frequency Curves for Mumbai City, India

The change in rainfall pattern and intensity is becoming a great concern for hydrologic engineers and planners. Many parts of the world are experiencing extreme rainfall events such as experienced on 26th July 2005 in Mumbai, India. For the appropriate design and planning of urban drainage system in an area, Intensity Duration Frequency (IDF) curves for given rainfall conditions are required. The aim of the present study is to derive the IDF curves for the rainfall in the Mumbai city, Maharashtra, India. Observed rainfall data from 1901 pertaining to Colaba and from 1951 of the Santacruz rain gauge stations in Mumbai are used in the present study to derive the IDF curves. Initially, the proposed IDF curves are derived using an empirical equation (Kothyari and Garde), by using probability distribution for annual maximum rainfall and then IDF curves are derived by modifying the equation. IDF curves developed by the modified equation gives good results in the changing hydrologic conditions and are compatible even with the extreme rainfall of 26th July 2005 in Mumbai.

Impact of Global Warming on Intensity-Duration-Frequency (IDF) Relationship of Precipitation: A Case Study of Toronto, Canada

Annual maximum rainfall intensity for several duration and return periods has been analyzed according to the Gumbel distribution. The Intensity-Duration-Frequency (IDF) curves before and after 1980 have been computed and compared. For the city of Toronto, it is shown that the rainfall intensities after 1980 are lower than those from before this date. This is especially clear for those of short duration. Comparing our results with those of other authors, it appears that, for the moment, no general law on the impact of global warming on the curves intensity duration frequency cannot be made. It appears that the impact of global warming on rainfall varies with geographic location and that it is not possible to draw some general conclusions across the planet.

Modeling Rainfall Intensity-Duration-Frequency (IDF) and Establishing Climate Change Existence in Uyo-Nigeria Using Non-Stationary Approach

This study aims at establishing if climate change exists in the Niger Delta environment using non-stationary rainfall Intensity-Duration-Frequency (IDF) modelling incorporating time-variant parameters. To compute the intensity levels, the open-access R-studio software was used based on the General Extreme Value (GEV) distribution function. Among the four linear parameter models adopted for integrating time as a covariate, the fourth linear model incorporating scale and location with the shape function constant produced the least corrected Akaike Information Criteria (AICc), varying between 306.191 to 101.497 for 15 and 1440 minutes, respectively, selected for calibration of the GEV distribution equation. The non-stationary intensities yielded higher values above those of stationary models, proving that the assumption of stationary IDF models underestimated extreme events. The difference of 13.71 mm/hr (22.71%) to 14.26 mm/hr (17.0%) intensities implies an underestimation of the peak flood from a stationary IDF curve. The statistical difference at a 95% confidence level between stationary and non-stationary models was significant, confirming evidence of climatic change influenced by time-variant parameters. Consequently, emphasis should be on applying shorter-duration storms for design purposes occurring with higher intensities to help reduce the flood risk and resultant infrastructural failures.

Therapeutic effects of different durations of acupuncture on rats with middle cerebral artery occlusion

Acupuncture is regarded as an effective therapy for cerebral ischemia. Different acupuncture ma- nipulations and durations may result in different therapeutic effects. In the present study, the Neig uan （PC6） acupoint of rats with occluded middle cerebral arteries was needled at a fixed frequency （3 Hz） with different durations, i.e., 5, 60 and 180 seconds under a twisting-rotating acupuncture method. Results showed that different durations of acupuncture had different therapeutic effects, with 60 seconds yielding a better therapeutic effect than the other two groups. This duration of treatment demonstrated rapid cerebral blood flow, encouraging recovery of neurological function, and small cerebral infarct volume. Experimental findings indicated that under 3 Hz frequency, the treatment of needling Neiguan for 60 seconds is effective for ischemic stroke.

Parametric study of high-frequency characteristics of plasma synthetic jet actuator

A major issue of plasma synthetic jet actuator(PSJA)is the severe performance deterioration at high working frequency.In this study,experiments and numerical simulation are combined together to investigate the influence of thermal conductivity,throat length(Lth)and discharge duration(Td)on the high-frequency characteristics of PSJA.Results show that the variation of the actuator thermal conductivity and discharge duration will not alter the saturation frequency of the actuator,whereas decreasing the throat length results in an increase of the saturation frequency.For a short-duration capacitive discharge of 1.7μs,a clear shock wave is issued from the orifice,followed by a weak jet.As a comparison,when the discharge duration is increased up to 202.6μs,a strong jet column is formed and no obvious shock wave can be visualized.Based on numerical simulation results,it becomes clear that the long-duration pulse-DC discharge is able to heat the cavity gas to a much higher temperature(3141 K)than capacitive discharge,greatly improving the conversion efficiency of the arc discharge energy to the internal energy of the cavity gas.In addition,high-speed Schlieren imaging is deployed to study the performance degradation mechanism of PSJA at high working frequency.Monitor of the exit jet grayscale indicates that as long as the saturation frequency is exceeded,the actuator becomes unstable due to insufficient refresh time.The higher the discharge frequency,the more frequently the phenomenon of‘misfires’will occur,which explains well the decaying jet total pressure at above saturation frequency.

Rainfall Infiltration Return Frequency Estimates

Depth-duration analysis, such as accomplished for rainfall, can be useful in the analysis of infiltration of rainfall. The assessment of infiltration depth-duration in terms of return frequency is of interest. In this paper, depth-duration values of daily rainfall infiltration are estimated using the National Resources Conservation Service (NRCS) Curve Number (CN) approach for estimating daily runoff. The CN methods may be generally applicable to soils that are free draining. From the estimated history of daily infiltration, a depth-duration analysis is accomplished for all duration sizes from 1 day to 365 days. These annual outcomes are then analyzed as to a possible underlying probability distribution. For the rain gages considered, the depth-duration infiltration estimates (using the CN approach) appear to be normally distributed. From the fitted distribution, estimates of rare events of rainfall infiltration may be made, and possible linkage to earth movement events accomplished with respect to return frequency of infiltration, which in turn can aid in the design and risk assessment of fixed works involving soil water accumulation.

Magnitude and rupture duration from high frequency teleseismic P wave with projected landweber deconvolution

Earthquake magnitude and rupture duration are among the most important parameters characterizing an earthquake for the purpose of early tsunami warning. While they can be routinely determined from broadband P waveforms with iterative inver- sion procedures, the inversion procedures may fail when the rupture either lasts longer than the interval between P and later ar- rivals or requires too much time or human intervention. Little contaminated by later arrivals, high frequency P waves are useful for modeling earthquake source processes, though the envelope waveform is affected by strong scattering in lithosphere. With high frequency envelopes from aftershocks as Empirical Green＇s Function （EGF）, the coda effects can be removed and more accurate relative source time function （RSTF） of the main shock can be obtained. Assuming that RSTFs cannot be negative, we use the projected Landweber deconvolution method （PLD） to obtain high frequency RSTFs because PLD method has the ad- vantage of non-negativity, causality, and compactness （finite duration）. We are able to determine rupture durations of four large earthquakes： the 2004 Sumatra-Andaman earthquake, the 2005 Nias event, the 2006 Java event, and the 2011 Tokuko earthquake. The rupture durations of the Sumatra-Andaman, Nias, and Tohuko events are found to be around 550, 1 i0, and 120 s respectively, consistent with previous studies. The rupture duration of the Java event is about 130 s, supporting that the Java event is a tsunami earthquake. The magnitudes of these earthquakes are found to depend on both the amplitude and the duration of the deconvolved waveforms, and can be approximated by integrating these waveforms.

Climatological relationships among the tropical cyclone frequency,duration,intensity and activity regions over the Western Pacific

Climatological relationships among the tropical cyclone(TC)frequency,duration,intensity and activity regions over the Western Pacific are explored based on long-term best track data.Frequent TC occurrence does not necessarily imply a long duration of TCs in the same periods.Three types of relationship between TC number and duration in the period 1945-2007 were identified in this study:low frequency and short duration during 1945-1955(Period I);high frequency and short duration in the 1960s(Period II);and high frequency and long duration in the 1990s(Period III).TC activity regions differed among the three periods.During Period I,the main activity regions were over the ocean east of the Philippines(120°-140°E).During period II,two prevailing storm tracks extended west-northwest between 110° and 147°E.During period III,TCs had an extensive activity region from 110° to 160°E.TC intensity is related closely to activity regions.Most strong TCs developed over the ocean far from the Philippines,and had a northwestward track.Our results also show that the relationships between TC frequency,duration and their active regions are modulated strongly by broad-scale vertical motion,geopotential height and horizontal wind anomalies.

学校体育改善负性情绪的剂量特征:锻炼频率与时长维度

为了明确青少年在学校体育情境下改善负性情绪的锻炼剂量特征,探索从学校体育角度解决青少年心理行为问题的规律,本研究利用中国教育追踪调查(CEPS)2014—2015年的追访数据,采用多元回归、U检验和非线性关系的调节效应分析法,对8984名初中生进行实证分析。结果显示,每周锻炼频率与负性情绪并非U型关系,而是呈单调下降趋势,即1周内锻炼次数越多越好;锻炼时长与负性情绪呈U型关系,即负性情绪随着锻炼时长的增加先减少后增加,最优时长为40~60 min;学习压力在调节锻炼时长与负性情绪之间的U型关系中起到削弱和平缓的作用。综合效应方面,每周锻炼3次、每次持续50~60 min,或者每周锻炼6次、每次持续50~120 min,都能够获得改善负性情绪的良好效果。为了促进青少年心理健康,学校体育应保证学生每天有大约1 h的锻炼时间,并引导学生合理安排学习与锻炼时间,以防范过长锻炼时间在高学习压力下导致负性情绪增加的风险。

顶/底部变频交替进水的厌氧氨氧化系统特性

针对厌氧氨氧化污泥颗粒化过程较慢且易受水力剪切力和基质浓度波动的影响,颗粒污泥的传质性能随着粒径的增长逐渐恶化,进而导致系统脱氮性能受限问题,提出一种顶/底部变频交替进水运行模式,通过延长进水时间,并增设回流提供充足水力剪切力,改变顶/底部交替进水位置及频次,有效降低了基质浓度对厌氧氨氧化菌的冲击负荷,强化了系统脱氮性能.探究了系统运行期间污泥浓度、颗粒性能、EPS分泌和脱氮稳定性等变化情况.结果表明,该进水模式下总氮去除率达84.80%,颗粒平均粒径为783.67μm,EPS含量为169.13mg/gVSS.增加进水负荷后,游离氨最高浓度为9.70mg/L,未对系统造成抑制作用.显微镜结果显示,该进水模式下系统内颗粒颜色较深,血红素c含量较高,AnAOB活性较佳.高通量测序结果表明,顶/底部变频交替进水模式能够大幅提高系统内厌氧氨氧化菌属Candidatus_Brocadia的丰度,当交替频次为3次时达43.59%的最高占比.该进水方式加快了污泥与底物的混合,缩短了颗粒化进程,同时提升了污泥活性和抗冲击负荷能力,实现了厌氧氨氧化系统的稳定运行.

非Ⅲ级胎监胎心率基线变异消失时长与频率变化规律

目的探索非Ⅲ级胎监胎心率基线变异消失时长与频率变化规律。方法随机选取2020年1月至2023年5月规律产检并住院分娩的宫内单活胎孕妇2000例,依孕期是否有高危因素,分为高危组与低危组。孕28周开始行胎心监护,每天一次直至分娩,观察其基线变异消失时长与频率变化。结果孕28~40^(+6)周胎心率基线变异消失时长中位数:低危组为5.45~12.40 s/次、高危组为5.95~12.00 s/次;频率中位数:低危组为2.00~3.00次/20 min、高危组为2.00~3.00次/20 min。重复测量方差分析示:两组间胎心率基线变异消失时长与频率:时间效应、组间效应、交互效应差异均有统计学意义(P<0.05)。胎心率基线变异消失事件前12 h内:胎心率基线变异消失时长[M(P_(25),P_(75))]低危组为12.40(11.80,13.50)s/次,高危组为12.70(11.80,13.50)s/次;低危组与高危组胎心率基线变异消失频率[M(P_(25),P_(75))]均为4.00(3.00,5.00)次/20 min;重复测量方差分析示:两组间胎心率基线变异消失时长时间效应有统计学意义(P<0.05)。结论非Ⅲ级胎监胎心率基线变异消失是胎儿心率生理不成熟的表现,也受监测临床环境影响,胎儿越危险,其变异消失持续时间越长,当变异消失时长≥10 s/次,频率≥3次/20 min提示胎心率基线变异消失事件,需及时干预。

DoS攻击下抛物型多智能体系统的输出反馈领导-跟随一致性

为了解决抛物型多智能体系统(MASs)在拒绝服务(DoS)攻击下的一致性问题,提出了一种基于输出反馈方法的MASs领导-跟随一致性控制协议来应对恶意攻击者发起的DoS攻击,从而实现智能体在无向通信拓扑图上的领导-跟随一致性。对DoS攻击的频率和持续时间进行了分析,利用Lyapunov稳定性定理推导了抛物型偏微分系统的稳定条件,证明了触发时间间隔不为零,避免了芝诺行为的发生,并通过仿真算例验证了理论结果的有效性。

南京市老年人日常休闲性步行的时频规律及影响因素

以生态模型视角下影响老年人日常休闲性步行时频规律为研究框架,基于1285份南京市老年人休闲性步行调查数据,运用多元Logistic回归等方法,探讨南京市老年人日常休闲性步行时频规律及其影响因素。研究发现:1)南京市老年人日常休闲性步行时频规律总体呈现“中时长和高频次”居多的特征,步行中高时长占75.02%,中高频次占89.96%,且老年人休闲性步行时频规律表现出较大的群体差异性;2)性别、家庭结构和居住年限等个人社会因素;步行偏好、步行动机、个人制约和步行时段意向等个人心理因素是南京市老年人日常休闲性步行时频规律的共同影响因素;3)健康状况、协商效能和建成环境制约感知是南京市老年人日常休闲性步行时长差异的主要影响因素;而年龄和个人月收入是影响老年人日常休闲性步行频次差异的主要因素。

京津冀地区倒春寒时空特征及风险概率统计分析

利用京津冀99个国家气象站1961-2020年3-5月日气温数据,应用MK趋势检验等方法,分析倒春寒发生频次、持续天数和站次比时空分布规律,基于信息扩散理论评估不同等级倒春寒风险概率。结果表明:近30年99个国家气象站共发生2570次倒春寒,轻度最多,重度最少。发生频次上,轻度和中度由北向南递减,重度自东北向西南递减,4月轻度、中-重度和发生总次数均最多,年际变化呈下降趋势,其中3-5月和5月显著下降。总持续天数上,轻度和重度由东北向西南递减,中度呈南北高、中间低的格局。各站轻度平均持续天数相差不大,中度和重度则差异明显,平均持续天数随着等级的增大而跃增。年均倒春寒持续天数为6.9 d·a^(-1),呈下降趋势,降幅为1.5 d·(10a)^(-1)。88.9%的站点持续天数呈年际下降趋势,35个站显著下降,南部比北部降幅更大。3-5月和5月站次比年际下降趋势显著,4月轻度和中-重度站次比均最高,各月轻度站次比均远高于中-重度。倒春寒风险随着等级升高呈阶梯式降低,轻度2年一遇以下约占34.3%的站点,主要在北京、石家庄、邢台和邯郸等地;中度5~10年一遇和10年一遇以下的站点约占90%,前者集中在京津冀南北两端,后者大多位于京津冀中部。研究区重度倒春寒风险均较低,高达97.0%的站点为25年一遇以下。

基于CMIP6模式数据的京津冀山区未来极端降水频率的变化

基于偏差校正后的第六次国际耦合模式比较计划(CMIP6)中多个全球气候模式数据,选取三种气候变化情景下3 h降水数据,探究京津冀山区未来极端降水频率值及其相对变化速率的时空分布规律。结果显示:校正后的模式模拟降水与观测数据差异较小,能很好地模拟出未来降水的时空分布变化。相对于历史,多个模式未来不同情景下降水频率值的增速明显,极端降水增多,且超半数模式各情景的增长率处于0%~15%。其中,I区的降水频率值最高,可达162.53 mm,增长率最大约为37%,Ⅱ区和Ⅳ区的降水频率值接近,Ⅲ区的降水频率变化缓慢。空间上,研究区西部、西南部及东北部等地区的增长率较大。

浙江省台风暴雨强度-历时-频率关系分析

基于1971—2018年浙江省62个气象站点降水和台风路径数据,识别台风降水场次与强度。采用基于Hill估计的分位数图法(Q-Q图)的超门限阈值模型法(POT法),获取合适的台风暴雨事件样本。利用广义帕累托分布(GPD分布)分别开展最大1、2、3d台风暴雨频率特征分析,揭示台风暴雨强度-历时-频率关系。总体上,浙江省年均台风发生频次与台风降水量指标均呈现由东南向西部递减的空间分布格局;通过Kolmogorov-Smirnov(K-S)检验、理论与经验频率曲线的拟合程度可以看出,GPD分布能够很好地拟合浙江省极端台风降水的频率特征;不同重现期条件下的最大1、2和3d台风暴雨量也呈现由东部沿海向西部内陆递减的空间分布格局。

元胡止痛滴丸联合氟桂利嗪胶囊治疗偏头痛患者的疗效研究

目的:探讨元胡止痛滴丸联合氟桂利嗪胶囊治疗偏头痛患者的疗效研究。方法:选取临沂市中医医院脑病科2023年1月至2023年5月偏头痛患者116例为对象,随机数字表法分为两组,各58例。对照组采用氟桂利嗪胶囊治疗,观察组联合元胡止痛滴丸治疗,两组均完成4周治疗,并完成6个月门诊随访,比较两组视觉模拟疼痛(VAS)评分、疼痛频次、疼痛持续时间、脑血流动力学水平、药物安全性及复发率。结果:两组干预4周后疼痛减轻,疼痛持续时间缩短;观察组VAS评分、疼痛频次及疼痛持续时间低于对照组(P<0.05);两组干预4周后脑血流动力学水平得到降低;观察组大脑中动脉(MCA)、基底动脉(BA)、椎动脉(VA)、大脑后动脉(PCA)及大脑前动脉(ACA)水平低于对照组(P<0.05);两组用药期间腹泻便秘、血压波动、皮疹过敏发生率无统计差异(P>0.05);观察组6个月复发率低于对照组(P<0.05)。结论:元胡止痛滴丸联合氟桂利嗪胶囊用于偏头痛患者中,能减轻患者疼痛,降低疼痛频次,缩短疼痛持续时间,有助于改善脑血流动力学水平,药物安全性较高,能降低6个月复发率。