期刊文献+
共找到99,150篇文章
< 1 2 250 >
每页显示 20 50 100
浅谈“UNIT”在艺术体操中的运用
1
作者 肖琴 刁在箴 《湖北体育科技》 2004年第2期245-247,共3页
以文献资料、专家访谈法为主要研究手段 ,就 2 0 0 3年艺术体操新规则中新出现的“UNIT”难度进行了理论上的界定 ,在探讨“UNIT”与联合难度之间的本质区别的基础上 ,着重对“UNIT”的运用进行了研究。结果表明 :“UNIT”的出现使艺术... 以文献资料、专家访谈法为主要研究手段 ,就 2 0 0 3年艺术体操新规则中新出现的“UNIT”难度进行了理论上的界定 ,在探讨“UNIT”与联合难度之间的本质区别的基础上 ,着重对“UNIT”的运用进行了研究。结果表明 :“UNIT”的出现使艺术体操进一步向着竞技级别化的方向发展 ;“UNIT”的合理运用体现了教练员和运动员能力和水平。 展开更多
关键词 “unit” 艺术体操 联合难度 比赛规则 成套动作 难度价值 技术价值
下载PDF
从“UNIT”谈艺术体操身体难度的演变与前瞻态势 被引量:16
2
作者 胡凯 明洁 刁在箴 《体育与科学》 CSSCI 北大核心 2003年第1期56-58,共3页
以文献资料、录像解析、专家访谈为主要研究手段 ,循着艺术体操身体难度演变过程的走势 ,对世界艺术体操身体难度发展的趋势作了较深入的探寻。结果表明 ,“UNIT”难度的出现使得艺术体操向着量少质高的竞技级别化的方向发展 ;身体难度... 以文献资料、录像解析、专家访谈为主要研究手段 ,循着艺术体操身体难度演变过程的走势 ,对世界艺术体操身体难度发展的趋势作了较深入的探寻。结果表明 ,“UNIT”难度的出现使得艺术体操向着量少质高的竞技级别化的方向发展 ;身体难度将进入纵向发展时期 ;创新以及与器械的超难结合将成为身体难度的主流。 展开更多
关键词 艺术体操 身体难度 unit 竞技运动 身体技术 器械技术 艺术价值
下载PDF
基于Unity3D的油田抽油机三维可视化监控系统设计 被引量:6
3
作者 刘立强 孙文磊 +1 位作者 王一 王炳楷 《系统仿真学报》 CAS CSCD 北大核心 2024年第2期463-475,共13页
针对抽油机监测形式单一、三维可视化程度低和联动性差的缺陷,引入信息―物理实时映射思想,开发了油田抽油机三维可视化监控系统。设计了抽油机数字空间,搭建虚实交互层设计架构;搭建三维可视化系统数据组成及关系框架;结合逆运动学,构... 针对抽油机监测形式单一、三维可视化程度低和联动性差的缺陷,引入信息―物理实时映射思想,开发了油田抽油机三维可视化监控系统。设计了抽油机数字空间,搭建虚实交互层设计架构;搭建三维可视化系统数据组成及关系框架;结合逆运动学,构建数学模型,基于五维模型和Unity 3D平台设计抽油机三维可视化系统总体架构;以游梁式抽油机为对象进行实验验证,实现了实时动态监测、虚实混合控制、运动轨迹追踪和在线预警等服务功能。为三维可视化监控在石油机械领域的落地应用和数字孪生系统的开发提供借鉴。 展开更多
关键词 抽油机 三维可视化 实时动态监测 虚实混合控制 unitY3D
下载PDF
Nurse Stress Associated with Delirium Care in Intensive Care Units: A Cross-Sectional Study
4
作者 Tingting Xiao 《Open Journal of Nursing》 2024年第11期569-578,共10页
Background and Objectives: Delirium is highly prevalent in Intensive Care Units (ICUs). While prior studies have identified hyperactive and hyperalert behaviors as major stressors for nurses caring for delirious patie... Background and Objectives: Delirium is highly prevalent in Intensive Care Units (ICUs). While prior studies have identified hyperactive and hyperalert behaviors as major stressors for nurses caring for delirious patients, limited research exists on ICU nurses’ stress specifically related to delirium care. This study aims to investigate the stress experienced by ICU nurses in China when managing patients with delirium. Methods: This cross-sectional survey was conducted in China from January to February 2023. A total of 243 ICU nurses participated by completing an online survey that included the Personal Information Questionnaire and the Strain of Caring for Delirium Index (SCDI). Although 260 responses were initially collected, 29 invalid questionnaires were excluded, resulting in a final sample size of 243 valid responses. The SCDI scale demonstrated reliable internal consistency, with Cronbach’s α coefficients of 0.744, 0.812, 0.778, and 0.920 across its four subscales. Results: The survey results indicated that hypoactive delirium behaviors were perceived as the most significant stressors when caring for delirious patients. Among the behaviors, “noisy/yelling” was identified as the most challenging, whereas “pulling at tubes, dressings” was rated as the least challenging. No significant associations were found between demographic factors and stress levels. Conclusion: This study sheds light on the stress levels ICU nurses experience when caring for delirious patients, particularly in relation to hypoactive behaviors. Based on these findings, it is recommended that nurse managers implement stress management strategies and provide targeted delirium-related care training to better support ICU nurses and enhance the quality of delirium care. 展开更多
关键词 DELIRIUM STRESS Intensive Care units NURSE
下载PDF
A Retrospective Analysis of Intoxicated Patients Admitted to the Intensive Care Unit: A Single-Institution Assessment in the Post-Pandemic Period
5
作者 Müge Arikan Abdullah Yeşilkaya +1 位作者 Büşra Nur Taşdelen İbrahim Özyiğit 《Journal of Biosciences and Medicines》 2024年第3期159-167,共9页
Background: The aim of this study was to evaluate the clinical and epidemiological characteristics of patients with acute intoxication admitted to the Intensive Care Unit (ICU). Material and Methods: An observational ... Background: The aim of this study was to evaluate the clinical and epidemiological characteristics of patients with acute intoxication admitted to the Intensive Care Unit (ICU). Material and Methods: An observational retrospective study was conducted on intoxicated patients who admitted to ICU between January 2022 and January 2024. Data were collected from the patients medical records. The demographic characteristics, causes of intoxications, clinical parameters, the mean stay in the ICU, treatment modalities and prognosis were recorded. Results: A total of 2875 critically ill patients were admitted during the study period, and 109 (3.79%) of them were acute intoxications. Their mean of ages was 38.09 ± 12.29. The female-to-male ratio was 1.37/1. Drugs were found to be the primary cause (62.39%) of intoxications, and analgesics, antidepressants, and antibiotics were the most frequent agents. Suicidal attempts were present in 66 patients, most of them were female (62.13%) and between 17 - 24 years (40.91%). The other common causes of intoxications were carbon monoxide (CO) (22.02%), methyl/ethyl alcohol (8.26%) and mushroom (5.50%). The mean stay in the ICU was 2.69 ± 0.89 days. Mechanical ventilation was applied to 10 of our patients. Renal replacement therapy was required in 6 patients. Despite all treatments, 6 of our patients died, and we found the mortality rate to be 5.50%. Conclusion: Intoxications were more frequent in young female patients and drugs were the most common cause with suicidal intent. Unfortunately, CO poisoning continues to be a very important problem in our city. These findings provided significant information about the characteristics of intoxications in Karabuk. 展开更多
关键词 INTOXICATION Intensive Care unit SUICIDAL MORTALITY
下载PDF
Risk Factors for Mortality in Acute Kidney Injury in Intensive Care Units in Togo
6
作者 Eyram Makafui Yoan Yawo Amekoudi Kossi Akomola Sabi +3 位作者 Marcel David Keoula Badomta Dolaama Sarakawabalo Assenouwe Tabana Mouzou 《Open Journal of Nephrology》 2024年第1期37-47,共11页
Context: Acute kidney injury (AKI) in intensive care unit (ICU) is common and associated with very high mortality. In Togo, a tropical country with limited resources and only one nephrology department in the north, ac... Context: Acute kidney injury (AKI) in intensive care unit (ICU) is common and associated with very high mortality. In Togo, a tropical country with limited resources and only one nephrology department in the north, acute kidney injury seems to be a real tragedy with high mortality. Aims: to determine risk factors for mortality in acute kidney injury in the intensive care units. Methods and Material: We made a multicentric cross sectional study during 6 months in the four referral centers in northern Togo. Univariate and multivariate logistic regression was used to identify factors associated with mortality. Data were analyzed using RStudio 2023.04.1. Results: A total of 12.6% of patients admitted to intensive care had presented with AKI. The mean age was 49.6 ± 17.9. The sex ratio (M/F) was 2.1. Community-acquired AKI was in the majority (67.7%). Oligo anuria was the most frequent functional sign (38.4%). In our series, 81.6% of patients were in KDIGO stages 2 to 3. AKI was organic in 56.2% of cases. Mortality was 44.3%. In multivariate analysis, the main factors predictive of death were: respiratory distress (OR = 2.36;p Conclusions: Acute kidney injury in intensive care is common in northern Togo, and mortality is high. Identification of associated factors should help anticipate prognosis. 展开更多
关键词 AKI Intensive Care unit DIALYSIS EPIDEMIOLOGY TOGO
下载PDF
The Enforcement of Occupational Safety and Health Requirements in Public and Private Sectors in the Emirate of Abu Dhabi, the United Arab Emirates
7
作者 Alyazya Alhosani 《Occupational Diseases and Environmental Medicine》 2024年第2期78-114,共37页
Research Problem: In Abu Dhabi, limited implementation of OSH Regulations contributes to the general unawareness among employees and workers about occupational hazards and safety measures, resulting in slow responsive... Research Problem: In Abu Dhabi, limited implementation of OSH Regulations contributes to the general unawareness among employees and workers about occupational hazards and safety measures, resulting in slow responsiveness toward enforcement measures and a lack of self-regulatory approaches within companies. Purpose: The purpose of this study is to examine the implementation methods practised in Abu Dhabi with those in developed countries with established OSH regulatory bodies. Methodology: Qualitative and quantitative research methods were employed to gather primary research data. Workers from various industries in Abu Dhabi were sampled on purpose and asked to respond to questionnaires and interviews on OSH protocol awareness and implementation, and circumstances of workplace incidence. Results: The findings of this study showed that the enforcement of OSH requirements in UAE positively correlated to a reduction in the rate of work-related injury and improved business performance. The quantitative research data showed that the energy sector had the highest score (15) while the tourism sector had the lowest score (5.3) in occupational health systems and improvements in business efficiency and productivity. Implications: The outcomes of this study shed light on the importance of implementing OSH Guidelines for companies to empower their safety managers to fully enforce OSH requirements in their organisations. In conclusion, effective OSH enforcement requires cooperation between general workers and OSH managers and facilitation from business owners. 展开更多
关键词 Occupational Health and Safety Abu Dhabi The united Arab Emirates IMPLEMENTATION
下载PDF
Maternal Mortality Rates among Im/Migrant Populations in the United States
8
作者 Tessa Peredy Mary Greenwald +4 位作者 Katy Doughty Fachon Fiona Danaher Rashmi Jasrasaria Samantha Truong Annekathryn Goodman 《Open Journal of Obstetrics and Gynecology》 2024年第8期1161-1175,共15页
Introduction: Maternal mortality rates have more than doubled in the U.S over the last two decades, making it one of the few places in the world where maternal mortality is increasing. Differences in maternal mortalit... Introduction: Maternal mortality rates have more than doubled in the U.S over the last two decades, making it one of the few places in the world where maternal mortality is increasing. Differences in maternal mortality among certain races and ethnicities are known but few studies examine maternal mortality among immigrants. Since immigrants represent 13.7% of the U.S. population, it is essential to examine immigrant subsets to understand maternal mortality among this vulnerable population. Methods: A literature search identified 318 articles on maternal mortality and immigrants, with 12 articles from the U.S. The keywords included maternal mortality, United States, migrants, asylum seekers, immigrants, and disparities. Maternal mortality statistics were obtained from the World Health Organization and Center for Disease Control. Results: Studies analyzed in this review found an overall lower maternal mortality rate among immigrant women compared to U.S.-born women, except for Hispanic immigrant women. Black women had the highest maternal mortality rate, regardless of immigration status. Conclusion: Although the literature points to lower maternal mortality among immigrants, the data is still somewhat mixed, making it challenging to draw comprehensive conclusions. Additional research examining maternal mortality among Im/migrants in the U.S. is needed to guide future training among healthcare professionals and policymakers. 展开更多
关键词 Maternal Mortality Im/Migrant Reproductive Health united States
下载PDF
Travel-Limiting Disabilities in the United States: Why Accessibility Matters?
9
作者 Oluwaseun Ibukun Bhuiyan Alam 《Journal of Transportation Technologies》 2024年第3期336-357,共22页
This study evaluates the distribution of travel-limiting disabilities across genders and geographic locations in the United States. This study aims to describe and compare the socioeconomic and demographic variables o... This study evaluates the distribution of travel-limiting disabilities across genders and geographic locations in the United States. This study aims to describe and compare the socioeconomic and demographic variables of the people with and without travel-limiting disabilities across geographic locations and gender. The study further evaluates the trip purpose and impact of Covid-19 fourth wave pandemic on the use of public transit and travel to physical workplace for the people with and without travel-limiting disabilities across gender and geographic locations. The study uses the 2022 weighted National Household Travel Survey dataset and employs descriptive statistics. Results reaffirm the findings from previous literature that there are more people with travel-limiting disabilities in urban areas and among women. Over 50 percent of people aged 65 and above have a form of travel-limiting disabilities. The most trip for people with travel-limiting disabilities is made for shopping and medical purposes. Across all categories, rural areas, urban areas, male and female for the people without travel-limiting disabilities, COVID-19 fourth wave did not change the pattern of trips made to physical workplace as pre-COVID-19 era. This pattern is also observable for the people with travel-limiting disabilities in rural and urban areas. Females with travel-limiting disabilities reported making less trips to physical workplaces while male reported doing the same as before COVID-19 era. The study concludes that the quantification of travel-limiting disabilities across geographic location and gender is vital in disability study and could drive policy implementation for improved accessibility for the vulnerable population. 展开更多
关键词 National Household Travel Survey united States Travel-Limiting Disabilities Descriptive Statistics Covid-19 Disability Study
下载PDF
Coping with the Impact of Climate Change: A Dive into Precision Agriculture in the United States
10
作者 Oluwaseun Ibukun Kehinde Oke Olawale Oluwafemi 《Journal of Agricultural Chemistry and Environment》 2024年第2期208-222,共15页
With the continued increase in the number of people that are food insecure globally, which could be increasing because of the ongoing Ukraine-Russia war, leading to reduction in international agribusinesses, coupled w... With the continued increase in the number of people that are food insecure globally, which could be increasing because of the ongoing Ukraine-Russia war, leading to reduction in international agribusinesses, coupled with drastic climate change exacerbating the problem of food insecurity, there is a constant need to come up with innovative approaches to solve this global issue. In this article, we articulated how precision agriculture can be a tool for ensuring food security in the United States. This study aims to reiterate the significance of precision agriculture in solving global food insecurity. 展开更多
关键词 united States Food Insecurity Precision Agriculture Positioning Systems Climate Change
下载PDF
Improved Units of Measure in Rotational Mechanics
11
作者 Richard James Petti 《World Journal of Mechanics》 2024年第1期1-7,共7页
The SI system of units in rotational mechanics yields correct numerical results, but it produces physically incorrect units of measure in many cases. SI units also violate the principle of general covariance—the gene... The SI system of units in rotational mechanics yields correct numerical results, but it produces physically incorrect units of measure in many cases. SI units also violate the principle of general covariance—the general rule for defining continuous coordinates and units in mathematics and mathematical physics. After 30+ years of wrestling with these problems, the ultimate authority on units of measure has declared that Newton–meter and Joule are not equivalent in rotational mechanics, as they are in the rest of physics. This article proposes a simple modification to SI units called “Nonstandard International units” (“NI units”) until a better name is agreed upon. NI units yield correct numerical results and physically correct units of measure, and they satisfy the principle of general covariance. The main obstacle to the adoption of NI units is the consensus among users that the radius of rotation should have the unit meter because the radius can be measured with a ruler. NI units assigned to radius should have units meter/radian because the radius is a conversion factor between angular size and circumferential length, as in arclength = rθ. To manage the social consensus behind SI units, the author recommends retaining SI units as they are, and informing users who want correct units that NI units solve the technical problems of SI units. 展开更多
关键词 Rotational Mechanics Angular unit TORQUE Moment of Inertia Angular Momentum General Covariance
下载PDF
Delayed Grafting as a Valid Technique in Burn Management: Experience from a Burn Unit in Oman
12
作者 Taif Alsafy Joe Jacob +10 位作者 Anish Thadathil Elias Ahmed Salah El Din Salim Mohammed Ghawas Majid Tariq Saud Albusaidi Ahmed Al Jabri Al Anood Al Hadhrami Mutazz Obeid Al Khaldi Moath Abdelhamid Shummo Karim Mohamed Haridi Aml Eid Saleh Said Al-Busaidi 《Modern Plastic Surgery》 2024年第1期9-14,共6页
Background: Early excision and grafting has been the preferred method of managing major burns around the world since 1970. Considering the advances in health care and the development of new antibiotics over the past 5... Background: Early excision and grafting has been the preferred method of managing major burns around the world since 1970. Considering the advances in health care and the development of new antibiotics over the past 50 years, delayed grafting as a technique for the management of burns over 15%-20% of total body surface area (TBSA) could have comparable results to that of early excision. This study aims to highlight the outcomes of practicing delayed grafting in burn patients. Methods: A case series analysis was performed of 51 patients who were admitted to the burns unit in Sultan Qaboos Hospital Salalah with over 20% TBSA between January 2014 and December 2019. The patients received prophylactic antibiotics and silver sulphadiazine dressing until the burn eschar had completely separated, followed by grafting. Results: Two patients were lost during the entire duration of the study. The mortality rate was comparable to that of early excision, while the rate of hypertrophic scarring was lower than the range reported by other studies. Conclusion: In the management of patients with over 20% TBSA, delayed grafting after complete separation of eschar is still a valid technique. 展开更多
关键词 BURNS Burn units Burn Management Delayed Grafting Major Burns Treatment Efficacy
下载PDF
Temperature Trends and Accumulation of Chill Hours, Chill Units, and Chill Portions in South Carolina
13
作者 José O. Payero 《Atmospheric and Climate Sciences》 2024年第2期173-190,共18页
There is considerable concern about the potential impact of climate change on agriculture, such as the accumulation of chilling hours needed to break the dormancy of many perennial plants, like fruit trees. Therefore,... There is considerable concern about the potential impact of climate change on agriculture, such as the accumulation of chilling hours needed to break the dormancy of many perennial plants, like fruit trees. Therefore, this study aimed to determine if there had been a significant change in air temperatures and chill hours, chill units, and chill portion accumulation in South Carolina over the last two decades. Two decades of daily maximum (T<sub>max</sub>) and minimum (T<sub>min</sub>) air temperature records were obtained from weather stations in thirty-one counties in South Carolina. Hourly temperature data, reconstructed from the daily data, were used to calculate the daily and annual chill hours, chill units, and chill portions accumulation using four different chill models for each location and year. The chill models included the T(t) °C model, the 0°C °C model, the Utah model, and the Dynamic model. For each county, regression analyses were conducted to evaluate the historical trends. Despite year-to-year variability, the tendency was a statistically significant (α = 0.05) increase in air temperature, averaging 0.089°C per year for 20 out of 31 counties in South Carolina. The other 11 counties had no significant change in temperature. The average temperature increase in the 31 counties was 0.072°C per year. The temperature increase resulted in a decrease in annual chill accumulation during the fall to spring, averaging 17.7 chill hours, 8.6 chill hours, 17.0 chill units, and 0.40 chill portions per year calculated with the T(t) °C, 0°C °C, Utah, and Dynamic models, respectively. However, whether this decrease in chill values was statistically significant or not depended on the chill model used. This study did not investigate the cause of the observed historical trends in temperature and chill accumulation. Still, if the trends continue, they could significantly impact the future of the temperate fruit tree industry in the state. 展开更多
关键词 Chill Hours Chill units Chill Portions TEMPERATURE Fruit Trees Climate Change DORMANCY
下载PDF
有效避免ABB UNITROL 6800励磁系统故障导致机组跳闸的方案
14
作者 王赟 《上海节能》 2024年第7期1187-1195,共9页
ABB UNITROL 6800拥有多重冗余和多CPU配置,通道最大可达三通道。整个控制系统配有两套恒机端电压控制(AVR)、两套恒励磁电流控制(FCR)和一套备用恒励磁电流控制(BFCR),高冗余度的设计和彼此间的合理切换大大地提高了机组运行的安全性... ABB UNITROL 6800拥有多重冗余和多CPU配置,通道最大可达三通道。整个控制系统配有两套恒机端电压控制(AVR)、两套恒励磁电流控制(FCR)和一套备用恒励磁电流控制(BFCR),高冗余度的设计和彼此间的合理切换大大地提高了机组运行的安全性和可靠性,但ABB UNITROL 6800励磁系统测量板(CCM)本身存在一个概率极小的故障,且动作权限最高,一旦发生,将直接导致机组跳闸。介绍了一种有效避免因CCM板故障导致机组跳闸的优化方案。 展开更多
关键词 励磁系统 测量板(CCM) 极小概率故障 机组跳闸
下载PDF
南海主要断裂(带)与构造分区
15
作者 邱燕 杜文波 +3 位作者 鞠东 韩冰 马浩明 胡小三 《海洋地质与第四纪地质》 北大核心 2025年第1期136-153,共18页
构造分区是区域构造演化研究的基础。由于区域性构造分区的界线基本上都以深大断裂(带)为依据,因此在划分构造单元之前,研究区域内规模较大的主要断裂(带)是必不可少的。本文在分析南海主要断裂(带)的基础上,以板块构造理论为指导,完善... 构造分区是区域构造演化研究的基础。由于区域性构造分区的界线基本上都以深大断裂(带)为依据,因此在划分构造单元之前,研究区域内规模较大的主要断裂(带)是必不可少的。本文在分析南海主要断裂(带)的基础上,以板块构造理论为指导,完善了南海的构造分区。南海主要断裂(带)分为以俯冲带、碰撞带、大型逆冲带、大型走滑带为特征的一级断裂带;切穿沉积基底与上地壳、延伸至下地壳的二级断裂带;错断沉积基底的三级断裂。本区一级构造单元为“南海次板块”,其边界基本以一级断裂带,个别以二级断裂带为界;二级构造单元有微板块、断阶带、隆起区、深坳带、深坳区、碰撞带等;三级构造单元在微板块之内划分为隆坳带和微地块。 展开更多
关键词 主要断裂(带) 构造活动 构造分区 南海
下载PDF
基于纵轴流开式玉米脱粒装置的优化设计与试验
16
作者 张红梅 胡经营 +5 位作者 何勋 屈哲 杨立权 李世龙 刘冰杰 张静 《河南农业大学学报》 北大核心 2025年第1期122-135,共14页
【目的】解决现阶段玉米籽粒收获过程中籽粒破碎率和未脱净率高的问题,满足黄淮海地区玉米籽粒收获的要求。【方法】设计了纵轴流开式玉米脱粒装置,搭配钉齿式脱粒元件,将其按螺旋等间距排列的方式分布在辐条上。通过EDEM软件对脱粒装... 【目的】解决现阶段玉米籽粒收获过程中籽粒破碎率和未脱净率高的问题,满足黄淮海地区玉米籽粒收获的要求。【方法】设计了纵轴流开式玉米脱粒装置,搭配钉齿式脱粒元件,将其按螺旋等间距排列的方式分布在辐条上。通过EDEM软件对脱粒装置进行仿真分析,确定较佳的滚筒转速参数。以滚筒转速、喂入量、含水率为试验因素对脱粒装置进行单因素试验,得到较优的参数组合:滚筒转速为350.00 r⋅min^(-1)、喂入量为8.00 kg⋅s^(-1)、含水率为25.90%±1%。【结果】正交试验确定了影响的主次因素,先后依次为含水率、滚筒转速、喂入量。当滚筒转速为400 r⋅min^(-1)、喂入量为8.66 kg⋅s^(-1)、含水率为15.90%时,破碎率为3.99%、未脱净率为0.39%,脱粒装置台架验证试验得出该参数组合下破碎率和未脱净率分别为4.27%和0.51%,其中破碎率与理论优化值相差0.28%、未脱净率与理论优化值相差0.12%,试验结果与理论优化值非常接近。【结论】符合国家玉米籽粒直收的标准要求,为玉米籽粒收获机的研制提供了理论依据和新的研究思路。 展开更多
关键词 玉米脱粒 开式 脱粒装置 钉齿结构
下载PDF
Designing a Protection Scheme in Micro-Grid Systems with DG Using Central Protection Unite and Multiple Setting Group Protection Relays
17
作者 Mostafa I. Saleh Gaber El-Saady +1 位作者 Ali M. Yousef El-Noby A. Ibrahim 《Journal of Power and Energy Engineering》 2024年第9期37-49,共13页
Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this... Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains. 展开更多
关键词 Directional Overcurrent Relay Protection Coordination Distributed Generators Central Protection unite Multiple Setting Group Protection Relay
下载PDF
乌兰煤生物产气过程中大分子结构的变化特征
18
作者 夏大平 秦旭 +4 位作者 邓泽 石尚威 李银川 薛培 张亚伟 《煤炭转化》 北大核心 2025年第1期55-66,共12页
为阐明煤的大分子结构特征及其在生物产气过程中的变化,选择内蒙古锡林郭勒盟乌兰图噶矿区的褐煤进行生物产气实验,通过^(13)C-NMR测试、元素分析、X射线光电子能谱测试研究其结构变化特征。结果表明:原始乌兰煤样的芳香结构基本单元由... 为阐明煤的大分子结构特征及其在生物产气过程中的变化,选择内蒙古锡林郭勒盟乌兰图噶矿区的褐煤进行生物产气实验,通过^(13)C-NMR测试、元素分析、X射线光电子能谱测试研究其结构变化特征。结果表明:原始乌兰煤样的芳香结构基本单元由3个苯环、3个萘环、1个蒽环和3个吡咯组成,碳原子总数为129个。经过微生物的生物产气作用,碳原子总数减少了21个,其中芳香族碳减少了4个,脂肪族碳减少了17个。原始乌兰煤样大分子结构中的脂肪碳原子为55个,生物产气结束后,脂肪碳数量减少了21.8%,亚甲基碳数量减少了25%,次甲基碳和季碳数量减少了16.7%,氧接脂碳和甲基碳数量分别减少了14.3%和33.3%。煤大分子的芳香结构基本单元和侧链脱落主要发生在水解阶段,在后期产甲烷阶段,煤的结构改造基本停止,仅依靠已脱落于反应液中的物质参与生化反应,这证实了在生物产气过程中,煤大分子结构向更高芳构化程度转化是一个显著的趋势。 展开更多
关键词 大分子结构 褐煤 生物产气 芳香结构基本单元 脂肪碳
下载PDF
耦合蒸汽压缩与储热的燃煤热电联产机组调峰性能研究
19
作者 周霞 李建锋 +1 位作者 周宏 高云鹏 《中国电机工程学报》 北大核心 2025年第1期194-205,I0016,共13页
为降低调峰期间的能耗水平,该文提出热电联产机组与蒸汽压缩储热系统耦合的技术方案,该方案是从汽轮机中压缸排汽中抽出部分蒸汽,利用多级压缩机对抽汽进行压缩,利用储热装置对压缩过程中蒸汽进行冷却,储热装置所储存的热量可用于加热... 为降低调峰期间的能耗水平,该文提出热电联产机组与蒸汽压缩储热系统耦合的技术方案,该方案是从汽轮机中压缸排汽中抽出部分蒸汽,利用多级压缩机对抽汽进行压缩,利用储热装置对压缩过程中蒸汽进行冷却,储热装置所储存的热量可用于加热再热蒸汽或锅炉给水。该文建立热电联产机组耦合蒸汽压缩储热系统以及耦合电锅炉储热系统的调峰性能计算模型,并以某350 MW超临界燃煤热电联产机组为例进行性能计算。结果表明:在机组本身负荷保持在50%额定负荷甚至更高情况下,耦合两种系统的机组供电功率均可大幅降低,能够低于35%额定负荷;在机组耦合蒸汽压缩储热系统后,相比较机组50%额定负荷的能效指标,综合热效率提高7.38%。 展开更多
关键词 燃煤机组 热电联产 蒸汽压缩 灵活性改造 深度调峰 储热
下载PDF
混合动力驱动单元技术发展与展望
20
作者 张国耕 史训亮 王全任 《汽车文摘》 2025年第1期14-22,共9页
随着新能源汽车发展走向深入,混合动力汽车成为增速较快的细分市场,各汽车制造商加大对混合动力车型及混合动力驱动单元的研发投入。为了更高效地开发混合动力驱动单元,从零部件组成、结构型式、电机位置等维度介绍混动车辆及混动驱动... 随着新能源汽车发展走向深入,混合动力汽车成为增速较快的细分市场,各汽车制造商加大对混合动力车型及混合动力驱动单元的研发投入。为了更高效地开发混合动力驱动单元,从零部件组成、结构型式、电机位置等维度介绍混动车辆及混动驱动系统的主要概念及分类,结合2024年度中国市场混动车型的驱动系统型式,详细阐述不同构型混动驱动系统的应用现状,并以丰田、本田、通用、上汽、比亚迪等汽车公司混合动力驱动单元发展历程为依托,梳理混动驱动单元的迭代过程,最后对混动驱动单元未来的发展趋势进行展望,以期为各企业开发具有自主知识产权的混合动力驱动单元提供参考。 展开更多
关键词 混合动力 驱动单元 机电耦合 电机 逆变器
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部