检索结果-内蒙古大学图书馆

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 2003年第594期129卷 2847-2866页

作者： Zhang, CD Mapes, BE Soden, BJ Univ Miami Rosenstiel Sch Marine & Atmospher Sci Miami FL 33149 USA NOAA CIRES Climate Diagnost Ctr Boulder CO 80303 USA NOAA Geophys Fluid Dynam Lab Princeton NJ USA

probability distribution functions of tropospheric water vapour in the tropics are shown to be commonly bimodal. This bimodality implies sharp gradients between dry and moist regimes in space and time. A method of testing for and quantifying bimodality is introduced. Using this method, the bimodality of water vapour is surveyed in satellite and in situ observations, as well as in global model re-analysis data and simulations. The bimodality suggests that the radiative drying time after an injection of moisture by convection is short (1-2 days) compared to a homogenizing time, whether physical (mixing) or mathematical (averaging). It is shown that the local bimodality found in cloud-model simulations and in situ point measurements disappears with modest time averaging (18 h and 200 km), but then reappears on the global-scale, where dry and moist regions are separated so widely that synoptic- and large-scale mixing times exceed the drying time-scale. Large discrepancies exist in the ability to reproduce the global-scale bimodality by global model re-analysis and simulations.

关键词： humidity mixing probability distribution function

来源：评论

学校读者我要写书评

暂无评论

DG integrated distribution system expansion planning with uncertainties

引用

JOURNAL OF INTELLIGENT & FUZZY SYSTEMS 2018年第5期35卷 4997-5006页

作者： Malee, Rahul Kumar Chundawat, Ashok Singh Maliwar, Niharika Sharma, Avadhesh Kumar Jaipur Engn Coll & Res Ctr Dept Elect Engn Jaipur Rajasthan India Dwarkadas J Sanghvi Coll Engn Dept Elect & Telecommun Engn Bombay Maharashtra India Swami Keshwanand Inst Technol Dept Elect Engn Jaipur Rajasthan India

Expansion planning of distribution system is the most significant tool which deal with the continuous increasing load demand. The main motive of the expansion planning is the minimization of the investment and operation cost of distribution network equipment which consider the installation/reinforcement cost of substation, feeders and distribution Generation. In this paper, price and load uncertainties are taken in to expansion planning which gives the robust and reliable expansion planning. These uncertainties are molded as Normal probability distribution function. By using Monte Carlo Simulation uncertainties are added in to planning. A 72 bus (Kian-pars Ahvaz 11 KV a practical distribution network in Iran) distribution network is used for case study of expansion planning. This multistage dynamic expansion planning problem is resolved by the Quantum Particle Swarm Optimization. The proposed algorithm is compared with the standard Particle Swarm Optimization and results shows the superiority of proposed algorithm over PSO.

关键词： probability distribution function distributed generation quantum PSO monte-carlo simulation

来源：评论

学校读者我要写书评

暂无评论

Risk assessment of power system oscillation instability based on geomagnetic storm events in the 24th solar cycle

引用

IET GENERATION TRANSMISSION & distribution 2022年第1期16卷 137-148页

作者： Wang, Zezhong Si, Yuan Liu, Lianguang North China Elect Power Univ Dept Elect & Elect Engn Beijing Peoples R China

When studying the harm of geomagnetic storms to the power system, the focus is often placed on the influence of transformers reactive power loss (GIC-Q) caused by geomagnetic induced current (GIC) on voltage fluctuation. GIC-Q, as a reactive load, can cause power flow changes, and the small disturbance stability is affected by the power flow distribution before disturbance, so GIC-Q connects geomagnetic storms with small disturbance stability. In this study, the probability distribution function of induced geoelectric fields is established, and the sample data is obtained by sampling. Combined with the GIC benchmark network model, multiple sets of GIC-Q in each substation are calculated and added to the system one by one to study the influence of geomagnetic storms on the oscillation characteristic parameters and establish the risk index of small disturbance instability. The result shows that the risk index value of oscillation instability in the occurrence of geomagnetic storms increases both in the AC system and the AC/DC hybrid system, but the increased range of risk value of local oscillation instability decreases with the addition of DC systems. The research results can provide a reference for evaluating the influence of geomagnetic storms on the stable operation of power systems.

关键词： disturbance instability power system stability local oscillation instability risk index value GIC-Q AC/DC hybrid system voltage fluctuation geomagnetic storm events substations statistical distributions risk management power system oscillation instability power loss AC-DC power convertors power flow distribution power flow changes power system faults magnetic storms GIC benchmark network model disturbance stability load flow probability distribution function reactive load

来源：评论

学校读者我要写书评

暂无评论

Behaviour of two-dimensional liquid dusty plasmas under perpendicular magnetic fields

引用

CONTRIBUTIONS TO PLASMA PHYSICS 2018年第4期58卷 269-275页

作者： Wang, Qiaoling Wang, Kang Feng, Yan Soochow Univ Coll Phys Optoelect & Energy Ctr Soft Condensed Matter Phys & Interdisciplinar Suzhou 215006 Peoples R China

The collective behaviour of two-dimensional (2D) liquid dusty plasmas under perpendicular magnetic fields is studied using Langevin dynamic simulations. Based on the positions and velocities of the simulated dust particles, the dynamic parameters of intermediate scattering functions and probability distribution functions are calculated. It is found that, under different 2D liquid dusty plasma conditions, the motion of individual dust particles tends to be more super-diffusive under stronger perpendicular magnetic fields, well consistent with the previous finding using a different diagnostic technique.

关键词： intermediate scattering function Langevin dynamical simulation magnetized dusty plasmas probability distribution function superdiffusion

来源：评论

学校读者我要写书评

暂无评论

Screening-level risk assessment of di(2-ethylhexyl) phthalate for aquatic organisms using monitoring data in Japan

引用

ENVIRONMENTAL MONITORING AND ASSESSMENT 2006年第1-3期115卷 451-471页

作者： Naito, Wataru Gamo, Yoshihiro Yoshida, Kikuo Natl Inst Adv Ind Sci Res Ctr Chem Risk Management Tsukuba Ibaraki Japan

Screening-level ecological risk assessments of di(2-ethylhexyl) phthalate ( DEHP) for aquatic organisms in Japan were conducted using estimated statistical values based on surface water and sediment monitoring data and effect threshold values based on a large aquatic toxicity database. An alternative method is proposed to handle monitoring data that contain nondetects including multiple detection limits and to determine the statistical values of DEHP concentrations in Japanese surface waters. The No-Observed-Effect-Concentration (NOECwater) of DEHP for aquatic life of 77 mu g/L was determined giving equal importance to both physical effects probably caused by undissolved DEHP and to the intrinsic toxicity potentially caused by DEHP. The NOECsediment of 615,000 mu g/kg was determined by the Equilibrium Partitioning (EqP) theory, conservatively assuming a threshold effect level in the water column as the water solubility of 3 mu g/L. The potential risks of DEHP in Japanese water environments were characterized simply by comparing the margin of exposure (MOE) with a specified uncertainty multiplier (UM). The MOE is expressed as the ratio of NOECwater or NOECsediment to the expected environmental concentrations such as the 95th percentiles of the estimated DEHP concentration distributions for surface water or sediment. The results of risk characterization show that all MOE values calculated using the statistical values of DEHP concentrations in Japanese surface waters and sediments are above 10, indicating minimal risk. Although the DEHP concentrations of some surface water samples showed MOE values of less than 10, considering environmental chemistry such as bioavailable fractions and the form of existence of DEHP in a water environment, we conclude that the current levels of DEHP are of little concern to aquatic life in the majority of Japanese surface waters and sediments.

关键词： DEHP (di(2ethylhexyl)phthalate) ecological risk assessment nondetects aquatic life monitoring data probability distribution function

来源：评论

学校读者我要写书评

暂无评论

The distribution of the local entropy in ultrasound images

引用

ULTRASOUND IN MEDICINE AND BIOLOGY 1996年第4期22卷 431-439页

作者： Zimmer, Y Akselrod, S Tepper, R TEL AVIV UNIV SCH PHYS & ASTRON DEPT MED PHYS IL-69978 TEL AVIV ISRAEL SAPIR MED CTR DEPT OBSTET & GYNECOL KEFAR SAVA ISRAEL

In this article, a model for the amplitude statistics of the backscattered ultrasonic signal is presented, We propose to view a tissue as being composed of a large number of small units, each having slightly different characteristics. This variability within the tissue is expressed by fluctuations in the parameters of the local probability distribution function (PDF), Based an analogous expressions derived for radio propagation and optical scintillations, the local PDF is modulated by a lognormal distribution of the local standard deviation, Integrating the local contributions yields the amplitude PDF for the entire tissue, We show that the local entropy is a normal variable, since for four different local PDFs it is linearly related to the logarithm of the local standard deviation, When the local entropy histogram exhibits distinct and multiple peaks, the local entropy distribution can be used for region segmentation, This fact is demonstrated for ultrasonic images of ovarian cysts.

关键词： ultrasonic backscatter speckle probability distribution function entropy segmentation ultrasound images ovarian cysts

来源：评论

学校读者我要写书评

暂无评论

Shape fabric development in rigid clast populations under pure shear: The influence of no-slip versus slip boundary conditions

引用

TECTONOPHYSICS 2015年 659卷 63-69页

作者： Mulchrone, Kieran F. Meere, Patrick A. Natl Univ Ireland Univ Coll Cork Sch Math Sci Dept Appl Math Cork Ireland Natl Univ Ireland Univ Coll Cork Dept Geol Sch Biol Earth & Environm Sci Cork Ireland

Shape fabrics of elliptical objects in rocks are usually assumed to develop by passive behavior of inclusions with respect to the surrounding material leading to shape-based strain analysis methods belonging to the R-f/phi:. family. A probability density function is derived for the orientational characteristics of populations of rigid ellipses deforming in a pure shear 2D deformation with both no-slip and slip boundary conditions. Using maximum likelihood a numerical method is developed for estimating finite strain in natural populations deforming for both mechanisms. Application to a natural example indicates the importance of the slip mechanism in explaining clast shape fabrics in deformed sediments. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Deformation Shape fabric Rigid object probability distribution function Stick Slip

来源：评论

学校读者我要写书评

暂无评论

Multiplatform Comparisons of Rain Intensity for Extreme Precipitation Events

引用

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2012年第3期50卷 675-686页

作者： Amitai, Eyal Petersen, Walter Llort, Xavier Vasiloff, Steve NASA Goddard Space Flight Ctr Greenbelt MD 20771 USA Chapman Univ Schmid Coll Sci & Technol Orange CA 92866 USA NASA Wallops Flight Facil Wallops Isl VA 23337 USA Hydrometeorol Innovate Solut HYDS Barcelona 08034 Spain NOAA Natl Severe Storms Lab Norman OK 73072 USA

Rainfall intensities during heavy rain events over the continental U. S. are compared for several advanced radar products. These products include the following: 1) Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) near-surface estimates;2) NOAA Quantitative Precipitation Estimation very high resolution (1 km, instantaneous) radar-only national mosaics (Q2);3) very high resolution gauge-adjusted radar national mosaics, which we have developed by applying a gauge correction on the Q2 products;and 4) several independent C-band dual-polarimetric radar-estimated rainfall samples collected with the Advanced C-band Radar for Meteorological and Operational Research (ARMOR) radar in Alabama. These instantaneous rainfall rate fields [i.e., 1)-3)] can be considered as radar products with the largest coverage currently available from space- and ground-based radar observations. Although accumulated rainfall amounts are often similar, we find the PR and Q2 rain-rate histograms quite different. PR rain-rate histograms are shifted toward lower rain rates, implying a much larger stratiform/convective rain ratio than do products such as Q2. The shift is more evident during strong continental convective storms and not as pronounced in tropical rain. A "continental/maritime regime" behavior is also observed upon adjusting the Q2 products to rain gauges, yet the rain amount more closely agrees with that of PR. The independent PR/ARMOR comparisons confirm this systematic regime behavior. In addition, comparisons are performed over central Florida where PR, Q2, and the NASA TRMM ground validation products are available. These comparisons show large discrepancies among all three products. Resolving the large discrepancies between the products presents an important set of challenges related to improving remote-sensing estimates of precipitation in general and during extreme events in particular.

关键词： Extreme precipitation events meteorological radar multi sensor quantitative precipitation estimation precipitation probability distribution function rainfall intensity spaceborne radar Tropical Rainfall Measuring Mission (TRMM)

来源：评论

学校读者我要写书评

暂无评论

Parameter analysis based on stochastic model for differential evolution algorithm

引用

APPLIED MATHEMATICS AND COMPUTATION 2010年第7期217卷 3263-3273页

作者： Wang, Ling Huang, Fu-zhuo Tsinghua Univ Dept Automat Tsinghua Natl Lab Informat Sci & Technol TNList Beijing 100084 Peoples R China

In this paper, a stochastic model is used to describe and analyze the evolution process of differential evolution (DE) for numerical optimization. With the model, it illustrates how the probability distribution of the whole population is changed by mutation, selection and crossover operations. Based on the theoretical analysis, some guidelines about the parameter setting for DE are provided. In addition, numerical simulations are carried out to verify the conclusions drawn from model analysis. (C) 2010 Elsevier Inc. All rights reserved.

关键词： Differential evolution Parameter analysis probability distribution function Stochastic model Numerical optimization

来源：评论

学校读者我要写书评

暂无评论

Application of multiscale finite element method in the uncertainty qualification of large-scale groundwater flow

引用

STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT 2012年第3期26卷 393-404页

作者： Shi, Liangsheng Yang, Jinzhong Zeng, Lingzao Wuhan Univ Natl Key Lab Water Resources & Hydropower Engn Sc Wuhan 430072 Peoples R China Zhejiang Univ Inst Soil & Water Resources & Environm Sci Hangzhou 310029 Zhejiang Peoples R China

In this article, we discuss the application of multiscale finite element method (MsFEM) to groundwater flow in heterogeneous porous media. We investigate the ability of MsFEM in qualifying the flow uncertainty. Monte Carlo simulation is employed to implement the stochastic analysis, and MsFEM is used to avoid a full resolution to the spatial variable conductivity field. Large-scale flow with high variability is investigated by inspecting the single realization as well as the probability distribution functions of head and velocity. The numerical results show that the performance of MsFEM depends on the ratio between the correlation length and the coarse element size. An accurate prediction to the velocity requires a much lower ratio than the head. The MsFEM has different convergence rates for the head and the velocity, while the convergence rates do not deteriorate as the variance grows.

关键词： Heterogeneous media Multiscale finite element probability distribution function

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：