检索结果-南通市图书馆

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

基于神经网络的电网连锁跳闸评估方法研究

基于神经网络的电网连锁跳闸评估方法研究

作者： Abdalalziz altayeb Ibrahim Omer（德拉杰）福建工程学院

学位级别：硕士

对于当今的电网,其安全水平与以往相比大大提升。但这并不意味着当今的电网就不存在安全问题,放眼全世界,可以看到全世界每年都会有各类的停电事故发生,似乎停电事故已经成了电力系统的一种顽疾。而从各种停电事故的具体发展情形来看,... 详细信息

对于当今的电网,其安全水平与以往相比大大提升。但这并不意味着当今的电网就不存在安全问题,放眼全世界,可以看到全世界每年都会有各类的停电事故发生,似乎停电事故已经成了电力系统的一种顽疾。而从各种停电事故的具体发展情形来看,这些停电事故往往是由连锁故障引起,连锁故障通常都是由简单的初始故障经由连锁跳闸形成的,而且,在那些连锁跳闸事件发生时,电网往往对其缺乏预见性,不能及早地发现并阻止这些连锁跳闸事件的发生。所以,为了避免大停电事故的发生,在电网运行中尽早地评估电网是否会发生连锁跳闸是非常重要的,这可为电网的安全决策,及早地采取阻断电网连锁故障的措施提供重要的依据。本论文针对电网的连锁跳闸问题,根据基于神经网络实现模式识别具有快速、准确的优点,提出一种基于神经网络的连锁跳闸评估方法,主要研究内容如下:首先,根据电网连锁跳闸通常经由后备保护动作引起的事实,并结合实际电网中参与连锁跳闸的后备保护通常为距离III段和具有电流整定值的过负荷保护的情况,根据电网连锁跳闸的表达方程,深入地探讨了引起连锁跳闸的电网主要参数,即电网的节点注入功率。然后据此将电网节点注入功率向量视作输入,将电网连锁跳闸的是否发生看作输出,给出了表征此输入、输出变量之间一般映射关系的描述,以此为基础,提出了基于神经网络技术,利用样本数据,通过训练和测试神经网络来形成反映此输入、输出变量间映射关系的思路,并进一步提出了根据形成的神经网络来评估电网在任一的节点注入功率状态下是否发生连锁跳闸的思路。其次,分别针对单一初始故障场景和多初始故障的场景,并结合电网后备保护为距离III段和过负荷保护这两类常见情形,提出了利用神经网络技术评估电网在某一运行状态下是否因初始故障的冲击而发生连锁跳闸的操作方法及详细流程,然后以IEEE39节点系统和IEEE14节点系统为例,进行了详尽的算例分析,验证了所提方法的有效性。最后,将前述评估电网连锁跳闸的方法与初始故障的筛选相结合,形成了一种减少考虑初始故障数量的综合评估方法,使得所提出的连锁跳闸评估方法能够面向应用场景,并通过IEEE39节点系统上的算例分析进一步验证了所提评估方法的合理性和有效性。总之,本文提出的基于神经网络的电网连锁跳闸评估方法是在建立较完整的理论分析基础上的,其合理性和有效性通过算例分析得到了一定的验证,可为电网连锁跳闸的评估以及进一步研究提供有益的借鉴。

关键词：连锁跳闸 BP神经网络电力系统保护复杂网络理论模式识别

影响三大洲的北非强沙尘暴动力机制WRF-chem模拟与分析

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

气象科学 2022年第6期42卷 769-780页

作者： altayeb Ragab 王坚红 Abdoul Aziz Saidou Chaibou Muhammad Arshad Mohammed AbdAllah Birhanu Asmerom Habtemicheal 南京信息工程大学大气科学学院南京210044 苏丹气象局苏丹南京信息工程大学气象灾害预报预警与评估协同创新中心南京210044 南京信息工程大学海洋科学学院南京210044 南京信大气象科学技术研究院南京210044 南京信息工程大学大气物理学院南京210044 尼日尔—尼亚美国家气象局尼日尔—尼亚美巴基斯坦国家气象部伊斯兰堡44000 南京信息工程大学地理科学学院南京210044

基于WRF-chem模式对北非2018年3月下旬的典型强沙尘暴过程进行模拟,分析了此次强沙尘发生季节、持续时间、局地特征以及传输路径的关键动力系统与动力机制。鉴于起沙是沙尘暴发生的关键点之一,并且起沙主要取决于风力和下垫面沙源性质,... 详细信息

基于WRF-chem模式对北非2018年3月下旬的典型强沙尘暴过程进行模拟,分析了此次强沙尘发生季节、持续时间、局地特征以及传输路径的关键动力系统与动力机制。鉴于起沙是沙尘暴发生的关键点之一,并且起沙主要取决于风力和下垫面沙源性质,本文测试了三种起沙参数化方案的影响,并将模拟结果与卫星MODIS监测及其再分析资料MERRA-2进行了对比,又经系列统计方法检验。结果显示,宏观思路的起沙方案GOCART比AFWA和UoC两种起沙方案更适合此次大尺度强沙尘暴数值模拟(锋面跨度接近60个经度)。综合沙尘暴关键系统的动力机制分析和数值模拟结果显示,强沙尘暴关键系统为深厚的西风槽、沙尘冷锋锋面和锋后的地面高压反气旋。北非中部深厚的西风槽为后倾槽,该系统稳定,造成沙尘暴持续时间长。沙尘暴锋后反气旋中的下沉气流抑制了扬沙向高层扩散,造成低层能见度恶劣。沙尘锋区结合了动力、热动力以及湿热动力不稳定,因此锋区风力大,地面沙尘驱动力强。而西风槽和强大反气旋依托环流形势,提供了沙尘传输到三大洲的长途输送力。

关键词：北非强沙尘暴影响三大洲的传输路径 WRF-chem模式模式起沙方案检测对比沙尘暴关键天气系统北非沙尘过程湿热动力机制

The Role of Kappa and Lambda in Subclassification of B Cell Lymphoblastic Leukemia in Sudanese Patients Using Flow Cytometry

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Open Journal of Blood Diseases 2016年第3期6卷 44-52页

作者： Hameeda Abd Eladeem Abdalla Amira Ahmed Khalid Humeida Eman Abbass Osama A. altayeb Ghada M. Marghani Faculty of Medical Laboratory Sciences Al Neelain University Khartoum Sudan Faculty of Medicine Al Neelain University Khartoum Sudan Flow Cytometry Laboratory for Leukemia & Lymphoma Diagnosis Khartoum Sudan Medical Laboratory Flow Cytometry Laboratory for Leukemia & Lymphoma Diagnosis Khartoum Sudan

Background: B-cell Acute lymphoblastic leukemia (B-ALL) is a neoplasm of lymphoblasts which are of B-cell lineage typically composed of small to medium sized blast cells, moderately condensed to dispersed chromatin with scanty cytoplasm and inconspicuous nucleoli, involving the bone marrow and/or blood. Methods and materials: This is a prospective cross-sectional study in which 50 blood and/or bone marrow samples of newly diagnosed patients (B-ALL) were tested for immunophenotyping. All samples were prepared for surface and cytoplasmic markers including kappa and lambda human antibody for 10 minutes in dark place and then run by the Flow Cytometer. Results: 64% of the study populations were males and 36% were females. Cases were classified according to immunophenotype and the age into different subtypes and showed the following frequencies: Pro B-ALL (8%), early pre B-ALL (56%), common B-ALL (16%), Pre-B-ALL (14%) and Mature B-ALL (only 6%). Surface immunoglobulin was positive in 10% and negative in 90% of all patients, showing 100% positivity in mature B-ALL and totally negative in other subtypes. While cytoplasmic immunoglobulin was positive in 16% and negative in 84% of all patients and was positive in 100% of Pre-B-ALL and in 50% of mature B-ALL. Surface kappa was more expressed in mature B-ALL than lambda giving a ratio of 2:1, while cytoplasmic kappa:lambda was 6:1 in Pre-B-ALL. Conclusion: Kappa and lambda have important role in B-ALL classification which necessitates their presence in immunophenotyping of B-ALL.

关键词： B Cell Acute Lymphoblastic Leukemia Immunoglobulin Kappa Lambda Flow Cytometer

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

采用先进超滤系统提高电泳漆清洗质量

电镀与环保 1993年第3期13卷 15-17页

作者： alsh.,J 吕国超 KOCH膜系统公司

对能达到最大电沉积漆清洗效率的超滤设计和清洗系统作了综述。

关键词：超滤系统电泳漆清洗

Rapid Detection of Accelerants in Fire Debris Using a Field Portable Mid-Infrared Quantum Cascade Laser Based Analyzer

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Applied Sciences 2023年第5期13卷 746-757页

作者： Hao Huang Yongfeng Zhang Fuqiang Dai Xiaobo Yan altayeb Hamdalnile Liyun Wu Tingting Zhang Haowen Li Frank Inscore Shanghai Fire Research Institute of MEM Shanghai China Micro Optical Instruments Shenzhen China Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences Hefei China University of Science and Technology of China Hefei China

Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.

关键词： Quantum Cascade Laser (QCL) Mid-Infrared Spectroscopy Fire Debris Analysis Gasoline Vapor Detection Ignitable Liquids

Synthesis and Characterization of SnO<SUB>2</SUB>Flower-Shaped by Hydrothermal Route for Formaldehyde Sensing Properties

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Advances in Materials Physics and Chemistry 2021年第4期11卷 67-77页

作者： Abeer Alhadi Shuyi Ma Shitu Pei Tingting Yang Pengdou Yun Qianqian Zhang Hamouda Adam Hamouda Li Wang Omer Almamoun altayeb alsh.ply Pengfei Cao Manahil H. Balal Khalid Ahmed Abbakar Key Laboratory of Atomic and Molecular Physics & Functional Materials of Gansu Province College of Physics and Electronic Engineering Northwest Normal University Lanzhou China College of Chemistry and Chemical Engineering Northwest Normal University Lanzhou China Department of Chemistry Faculty of Science University of Kordofan El Obeid Sudan Faculty of Petroleum and Hydrology Engineering West Kordofan Peace University Almugled Sudan Department of Physics Faculty of Education University of Khartoum Khartoum Sudan Physics Department Faculty of Science and Art Al Baha University Gilwah KSA Department of Mathematics and Physics Faculty of Education University of Gadarif Gadarif Sudan College of Mathematics and Statistics Northwest Normal University Lanzhou China

In this work, we’ve made SnO2 flower formed with the aid of using easy test steps, and without cost, which is the hydrothermal approach and without a template. We have used a variety of techniques to characterize SnO2 flower-shaped by (SEM, TEM, XRD, BET and XPS) instruments. Confirmatory tests carried out have proven that the surface of the tetragonal structure of SnO2 has a rough surface which makes it excellent for its gas-sensing properties. The gas detection test of SnO2 flower-shaped proved that it possesses the selectivity of formaldehyde gas (about 30), the optimum operating temperature of the sensor is 220°C, and also the sensor has a high response time and recovery time is (5 s and 22 s) to 100 ppm, respectively. Particularly, the sensor has an obvious response value (2) when exposed to 5 ppm formaldehyde. As well, the mechanism of gas-sensing was also discussed.

关键词： SnO2 Flower-Shaped Hydrothermal Method Formaldehyde Semiconductor Gas Sensor

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

计及网损的电网连锁故障预防方法

福建工程学院学报 2022年第4期20卷 369-372,396页

作者：邓慧琼王晓铭 ABDALAZIZ altayeb IBRAHIM OMER 陈世举钟运恒智能电网仿真分析与综合控制福建省高校工程研究中心(福建工程学院) 福州350118 福建工程学院电子电气与物理学院福州350118

针对电网连锁跳闸引起的停电事故以及降低电力系统的有功功率损耗,提出了一种计及网损的电网连锁故障预防方法。该方法综合考虑网损指标和衡量电网安全稳定运行指标,构建了多目标优化模型。该模型的优化目的在于确保均衡权重下安全裕度... 详细信息

针对电网连锁跳闸引起的停电事故以及降低电力系统的有功功率损耗,提出了一种计及网损的电网连锁故障预防方法。该方法综合考虑网损指标和衡量电网安全稳定运行指标,构建了多目标优化模型。该模型的优化目的在于确保均衡权重下安全裕度尽可能大,同时使网损尽可能小。通过粒子群优化算法求解,在IEEE-39节点系统上进行了算例分析。仿真结果表明该优化模型不仅提高了电网安全运行的界限,也实现了降损节能。

关键词：电力系统网损连锁故障连锁跳闸安全裕度

Outcomes of Pregnancy with Group B Streptococcal Infections in Najran, Saudi Arabia

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Open Journal of Obstetrics and Gynecology 2023年第3期13卷 395-402页

作者： Majed Saeed alshahrani Ali H. Alhajri Fahad Thamer Almutairi Ashwag Hassan Abdelmajed Fatima Ibrahim Abdalla Yousra Bala Babkir Abdullah Mosab Mohamedelamineltaib Ahmed Faroug Ahmed Abdelaal Mohamed Ahmed Mukhtar Mowafag Bushra Galaleldin Elsayed Marwa Mohamed Ahmed Elkhidir Babikir Nihal altayeb Abdallah Selma Mohammed Abdelgadir Elhabeeb Department of Obstetrics and Gynecology College of Medicine Najran University Najran Saudi Arabia Najran Armed Forces Hospital Najran Saudi Arabia

Background: The gram-positive, beta-hemolytic, and chain-forming Group B Streptococcus (GBS), commonly known as Streptococcus agalactiae, may asymptomatically invade the human gastrointestinal and vaginal tracts. However, GBS may become very invasive and pathogenic to the mother and baby during pregnancy, having negative effects. Study Aim: This study aims to investigate the pregnancy outcomes of women who tested positive for genitourinary GBS infection during pregnancy in Najran, Saudi Arabia. Methods: Data was collected retrospectively from patient files in Armed Forces Hospital, Najran, Saudi Arabia. Data collected were entered to a Microsoft Excel sheet, then imported and analysed using the Statistical Package for Social Sciences. Results: The study included 272 women of whom 66.5% were 31 to 45 years old. Gestational diabetes was diagnosed in 8.5% of the sample, 71.7% had a normal spontaneous vaginal delivery (NSVD), 1.8% had previous abortions, and 27.2% of new-borns were admitted to the NICU after delivery. There was a significant association between NICU admissions and women employment status (p = 0.001), gravidity (p = 0.001), parity (p = 0.001), history of abortions (p = 0.001), medical conditions (p = 0.049), and mode of delivery (p = 0.049). Conclusion: According to the findings of our study, GBS infection during pregnancy is associated to more NICU admissions. NICU admissions were significantly correlated with gestational diabetes, hypertension, and hypothyroidism in mothers but not with intrapartum antibiotic use.

关键词： Pregnancy Group B Streptococcal Outcomes