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基于FDS的风扇舱双油池火温度变化特征
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作者 程关兵 叶豪辉 《中国安全科学学报》 CAS CSCD 北大核心 2024年第1期133-139,共7页
航空发动机燃油泄漏形成的油池火威胁发动机运行和飞机安全,为描述风扇舱内油池火复杂的物理传播过程,开展双油池火温度变化特征的研究。首先,基于火灾动力学模拟软件(FDS)建立CFM56-7B发动机风扇舱物理计算模型;然后,比较Trent 800发... 航空发动机燃油泄漏形成的油池火威胁发动机运行和飞机安全,为描述风扇舱内油池火复杂的物理传播过程,开展双油池火温度变化特征的研究。首先,基于火灾动力学模拟软件(FDS)建立CFM56-7B发动机风扇舱物理计算模型;然后,比较Trent 800发动机风扇舱单油池火温度计算值与试验值,验证网格独立性;最后,借助探测器和切片分析舱内双油池火的发展过程和温度变化特征。结果表明:双油池火温度在舱内环向上经历增加和振荡准稳态2个变化阶段,其变化幅度与探测器和油池的间距相关;油池火向左偏斜现象导致左半边温度较高;火焰在轴向上经历火羽流上浮、火焰开始融合、融合扩大和完全融合等阶段。 展开更多
关键词 火灾动力学模拟(fdS) 风扇舱 双油池火 温度变化特征 发动机
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基于FDS大型体育场馆火灾与疏散研究
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作者 倪燕翎 陈代杰 +1 位作者 杨毅 黄皓 《文体用品与科技》 2024年第1期130-132,共3页
大型体育场馆聚集人数多,人群密度高,一旦突发状况,大量人流的快速有效疏散成为首要安全问题。以某奥体中心项目为案例,分析大型体育场馆的平面布局、空间类型、功能分布特点、火灾防控的难点;利用FDS软件pyrosim,进行火灾动力学模拟,... 大型体育场馆聚集人数多,人群密度高,一旦突发状况,大量人流的快速有效疏散成为首要安全问题。以某奥体中心项目为案例,分析大型体育场馆的平面布局、空间类型、功能分布特点、火灾防控的难点;利用FDS软件pyrosim,进行火灾动力学模拟,研究火灾发生后场内烟气温度、CO浓度、烟气的空间数值变化;依托Pathfinder对大型体育场馆人群密集空间进行逃生实景演练,给出有针对性的、有效的疏散优化建议与解决方案。 展开更多
关键词 fdS PATHFINDER 火灾模拟 疏散演练 数字化
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基于FDS的管廊电缆火灾动态风险评估研究
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作者 苏峰 张钧 +5 位作者 朱晓平 刘坤琦 白一平 韩宇泽 张琛 吴建松 《中国安全生产科学技术》 CAS CSCD 北大核心 2024年第5期77-83,共7页
为解决管廊或管沟内的电缆敷设密度较大,发生火灾极易形成电力系统的连锁事故等问题,采用FDS仿真软件,综合考虑传感器、喷淋系统、通风系统和防火门等安全屏障不同响应情况构建管廊电缆火灾动态风险评估模型,并应用Arrhenius公式将数值... 为解决管廊或管沟内的电缆敷设密度较大,发生火灾极易形成电力系统的连锁事故等问题,采用FDS仿真软件,综合考虑传感器、喷淋系统、通风系统和防火门等安全屏障不同响应情况构建管廊电缆火灾动态风险评估模型,并应用Arrhenius公式将数值仿真结果指标映射为电缆火灾风险值,进而绘制时变的电缆火灾风险曲线,探究火灾情景下管廊电缆风险动态评估及应急决策优化方案。研究结果表明:喷淋系统是管廊电缆火灾风险的最关键影响因素,喷淋系统的安装位置以及动作状态在很大程度上影响管廊电缆火灾风险。研究结果可为地下管廊电缆线路典型事故的预防、处理和恢复提供应用价值。 展开更多
关键词 电缆火灾 动态风险评估 火灾模拟 风险量化 fdS
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基于DEM-FDM耦合的过渡段膨胀诱发钢轨上拱研究
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作者 汪优 高天涯 +4 位作者 闫斌 王瑞 陈子娟 张文旭 程建军 《铁道工程学报》 EI CSCD 北大核心 2024年第1期7-12,共6页
研究目的:为分析涵洞过渡段地基膨胀引起的钢轨上拱响应,基于现场测试、室内膨胀试验数据,开展DEM-FDM耦合数值模拟,分析某涵洞附近路基土在膨胀范围为16 m,膨胀中心距离涵洞中心分别为0 m、5 m、10 m这三种工况下,不同膨胀率时基床填... 研究目的:为分析涵洞过渡段地基膨胀引起的钢轨上拱响应,基于现场测试、室内膨胀试验数据,开展DEM-FDM耦合数值模拟,分析某涵洞附近路基土在膨胀范围为16 m,膨胀中心距离涵洞中心分别为0 m、5 m、10 m这三种工况下,不同膨胀率时基床填料的运动规律及钢轨的上拱响应。研究结论:(1)涵洞对于钢轨上拱位移的传递存在阻断作用,但会增大钢轨上拱的峰值,原位膨胀率下工况二的钢轨上拱峰值达到46 mm,当路基膨胀率为0.3%时钢轨上拱位移量达到无砟轨道钢轨可调节临界值(4mm);(2)过渡段钢轨上拱处同时产生轴向应力集中,其中原位膨胀率下工况二轴向应力峰值达到14.4 MPa;(3)对于膨胀区域位于涵洞下方的工况,钢轨轴向应力呈现出来的分布规律为钢轨上拱拱顶处为主拉应力状态,拱脚处为主压应力状态,因此一共包括三个压应力峰值点以及两个拉应力峰值点;(4)本文研究可为高铁涵洞过渡段路基膨胀病害解决方案的确定提供理论依据。 展开更多
关键词 过渡段 路基膨胀 无砟轨道 钢轨上拱 有限差分 离散元
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基于FDS准则的响应曲面设计预测能力比较
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作者 周祥 陈雪平 +1 位作者 严静 林金官 《统计与决策》 北大核心 2024年第2期41-45,共5页
预测能力是实际应用工作者评价设计优劣的重要准则之一,一般地,通过方差散布图可以对一个固定球面上的设计预测能力进行比较和选择,但无法获得对整个设计区域上的比较结果。文章介绍了基于正交表的响应曲面设计(OACD)以及基于极小极大... 预测能力是实际应用工作者评价设计优劣的重要准则之一,一般地,通过方差散布图可以对一个固定球面上的设计预测能力进行比较和选择,但无法获得对整个设计区域上的比较结果。文章介绍了基于正交表的响应曲面设计(OACD)以及基于极小极大准则的改进设计(OACM),并应用全区域预测方差占比准则——FDS准则对这两类中心组合设计进行预测能力的比较。结果表明,在一个较小方差范围内,OACD得到的FDS结果要优于OACM,而对于大部分给定方差值,OACM的FDS结果要优于OACD。 展开更多
关键词 试验设计 最优设计 正交设计 fdS准则
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山东省双向FDI协调发展对实体经济高质量发展的影响研究
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作者 王长义 马永兴 陈利霞 《聊城大学学报(社会科学版)》 2024年第1期60-73,共14页
理论剖析双向FDI协调发展对实体经济高质量发展的影响机理,测度和统计分析山东省双向FDI协调发展和实体经济高质量发展的实践现状,实证检验双向FDI协调发展对实体经济高质量发展的影响。研究发现:双向FDI协调发展与实体经济高质量发展... 理论剖析双向FDI协调发展对实体经济高质量发展的影响机理,测度和统计分析山东省双向FDI协调发展和实体经济高质量发展的实践现状,实证检验双向FDI协调发展对实体经济高质量发展的影响。研究发现:双向FDI协调发展与实体经济高质量发展均呈现出逐步增长的态势,但在胶东经济圈、省会经济圈和鲁南经济圈间存在明显差异。双向FDI协调发展有效推动了实体经济高质量发展,科技投入是重要促进因素;双向FDI协调发展对实体经济高质量发展的促进作用具有明显区域差异性特征:对鲁南经济圈促进作用最大,其次是胶东经济圈,对省会经济圈影响较弱。 展开更多
关键词 双向fdI协调发展 实体经济高质量发展 区域差异
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基于FDS的飞机客舱内饰材料的参数优化研究
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作者 陈莹隆 伍毅 《科技与创新》 2024年第8期101-103,共3页
为了优化飞机客舱火灾数值模型并提高其模拟的精确度,采用火灾动力学三维模拟软件FDS(Fire Dynamics Simulator)建立全尺寸A320客舱火灾模型,通过对飞机客舱典型内饰材料热物理性参数的敏感性分析,探究这些参数对飞机客舱火灾动态模拟... 为了优化飞机客舱火灾数值模型并提高其模拟的精确度,采用火灾动力学三维模拟软件FDS(Fire Dynamics Simulator)建立全尺寸A320客舱火灾模型,通过对飞机客舱典型内饰材料热物理性参数的敏感性分析,探究这些参数对飞机客舱火灾动态模拟结果的影响程度。结果表明,飞机内饰材料的密度、比热系数、参考温度等参数都会对火灾的热释放速率(Heat Release Rate,HRR)和燃烧过程产生影响,在不同误差范围内的变化会导致热释放速率的增加或减少,其中参考温度的变化会导致热释放速率的峰值提前90 s到达。 展开更多
关键词 fdS 飞机客舱火灾 数值模拟 参数分析
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AZ31B镁合金FDS连接工艺与性能分析
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作者 吴磊 唐伟能 黄昌军 《现代交通与冶金材料》 CAS 2024年第3期91-94,共4页
镁合金材料是密排六方结构,常温下可开动的滑移系较少,加工性能较低,容易产生脆性断裂。以AZ31B镁合金挤压板材为例,采用FDS连接工艺进行连接实验,通过优化关键工艺参数如转速、压力、扭矩等,改善连接成形性。参数优化后,连接成形性得... 镁合金材料是密排六方结构,常温下可开动的滑移系较少,加工性能较低,容易产生脆性断裂。以AZ31B镁合金挤压板材为例,采用FDS连接工艺进行连接实验,通过优化关键工艺参数如转速、压力、扭矩等,改善连接成形性。参数优化后,连接成形性得到了显著改善,包络面无裂纹,连接剪切强度达到4.9 kN以上。研究了镁合金AZ31B材料FDS连接剪切拉伸过程,分析了两次峰值力的形成原因。 展开更多
关键词 镁合金 连接 fdS工艺 力学性能
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基于FDS的甲醇罐区池火灾事故后果模拟研究
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作者 陈虹燕 徐昕 王浩 《化工管理》 2024年第9期91-96,共6页
大容量的甲醇罐区在化工生产项目中往往以危险化学品重大危险源的形式存在,是防灭火的重点目标。为了有效选取最佳灭火位置、科学应急处置,通过池火灾模型分析与计算,确定在常年风向一定时,无风、平均风速、中等风速和最大风速四种情况... 大容量的甲醇罐区在化工生产项目中往往以危险化学品重大危险源的形式存在,是防灭火的重点目标。为了有效选取最佳灭火位置、科学应急处置,通过池火灾模型分析与计算,确定在常年风向一定时,无风、平均风速、中等风速和最大风速四种情况下甲醇储罐区池火灾热辐射强度和范围。文章以徐州某化工厂甲醇罐区为例,利用FDS软件构建火灾模型,分析不同热辐射强度对周围设施的破坏情况,完成热辐射演化三维仿真效果,为最佳灭火位置设置提供建议。 展开更多
关键词 池火灾 fdS 甲醇罐区 数值模拟 火灾风险分析
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Age-specific differences in the association between prediabetes and cardiovascular diseases in China:A national cross-sectional study
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作者 Shuo Xie Li-Ping Yu +4 位作者 Fei Chen Yao Wang Rui-Fen Deng Xue-Lian Zhang Bo Zhang 《World Journal of Diabetes》 SCIE 2024年第2期240-250,共11页
BACKGROUND Cardiovascular disease(CVD)is a leading cause of morbidity and mortality worldwide,the global burden of which is rising.It is still unclear the extent to which prediabetes contributes to the risk of CVD in ... BACKGROUND Cardiovascular disease(CVD)is a leading cause of morbidity and mortality worldwide,the global burden of which is rising.It is still unclear the extent to which prediabetes contributes to the risk of CVD in various age brackets among adults.To develop a focused screening plan and treatment for Chinese adults with prediabetes,it is crucial to identify variations in the connection between prediabetes and the risk of CVD based on age.AIM To examine the clinical features of prediabetes and identify risk factors for CVD in different age groups in China.METHODS The cross-sectional study involved a total of 46239 participants from June 2007 through May 2008.A thorough evaluation was conducted.Individuals with prediabetes were categorized into two groups based on age.Chinese atherosclerotic CVD risk prediction model was employed to evaluate the risk of developing CVD over 10 years.Random forest was established in both age groups.SHapley Additive exPlanation method prioritized the importance of features from the perspective of assessment contribution.RESULTS In total,6948 people were diagnosed with prediabetes in this study.In prediabetes,prevalences of CVD were 5(0.29%)in the younger group and 148(2.85%)in the older group.Overall,11.11%of the younger group and 29.59% of the older group were intermediate/high-risk of CVD for prediabetes without CVD based on the Prediction for ASCVD Risk in China equation in ten years.In the younger age group,the 10-year risk of CVD was found to be more closely linked to family history of CVD rather than lifestyle,whereas in the older age group,resident status was more closely linked.CONCLUSION The susceptibility to CVD is age-specific in newly diagnosed prediabetes.It is necessary to develop targeted approaches for the prevention and management of CVD in adults across various age brackets. 展开更多
关键词 Age Cardiovascular diseases PREDIABETES Risk factors differenceS
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Differential pressure difference based altitude control of a stratospheric satellite
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作者 陈丽 WANG Xiaoliang 《High Technology Letters》 EI CAS 2024年第1期1-12,共12页
An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to bal... An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to balance the platform gravity.The two-way blower inflates and deflates the ballonet to regulate the buoyancy.Altitude adjustment is achieved by tracking the differential pressure difference(DPD),and a threshold switching strategy is used to achieve blower flow control.The vertical acceleration regulation ability is decided not only by the blower flow rate,but also by the designed margin of pressure difference(MPD).Pressure difference is a slow-varying variable compared with altitude,and it is adopted as the control variable.The response speed of the actuator to disturbance can be delayed,and the overshoot caused by the large inertia of the platform is inhibited.This method can maintain a high tracking accuracy and reduce the complexity of model calculation,thus improving the robustness of controller design. 展开更多
关键词 stratospheric satellite(StratoSat) differential pressure difference(DPD) altitude adjustment threshold switching strategy margin of pressure difference(MPD)
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TSCND:Temporal Subsequence-Based Convolutional Network with Difference for Time Series Forecasting
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作者 Haoran Huang Weiting Chen Zheming Fan 《Computers, Materials & Continua》 SCIE EI 2024年第3期3665-3681,共17页
Time series forecasting plays an important role in various fields, such as energy, finance, transport, and weather. Temporal convolutional networks (TCNs) based on dilated causal convolution have been widely used in t... Time series forecasting plays an important role in various fields, such as energy, finance, transport, and weather. Temporal convolutional networks (TCNs) based on dilated causal convolution have been widely used in time series forecasting. However, two problems weaken the performance of TCNs. One is that in dilated casual convolution, causal convolution leads to the receptive fields of outputs being concentrated in the earlier part of the input sequence, whereas the recent input information will be severely lost. The other is that the distribution shift problem in time series has not been adequately solved. To address the first problem, we propose a subsequence-based dilated convolution method (SDC). By using multiple convolutional filters to convolve elements of neighboring subsequences, the method extracts temporal features from a growing receptive field via a growing subsequence rather than a single element. Ultimately, the receptive field of each output element can cover the whole input sequence. To address the second problem, we propose a difference and compensation method (DCM). The method reduces the discrepancies between and within the input sequences by difference operations and then compensates the outputs for the information lost due to difference operations. Based on SDC and DCM, we further construct a temporal subsequence-based convolutional network with difference (TSCND) for time series forecasting. The experimental results show that TSCND can reduce prediction mean squared error by 7.3% and save runtime, compared with state-of-the-art models and vanilla TCN. 展开更多
关键词 difference data prediction time series temporal convolutional network dilated convolution
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Study on sex differences and potential clinical value of threedimensional computerized tomography pelvimetry in rectal cancer patients
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作者 Xiao-Cong Zhou Fei-Yue Ke +2 位作者 Gaurav Dhamija Hao Chen Qiang Wang 《World Journal of Gastrointestinal Oncology》 SCIE 2024年第3期773-786,共14页
BACKGROUND Laparoscopic rectal cancer radical surgery is a complex procedure affected by various factors.However,the existing literature lacks standardized parameters for the pelvic region and soft tissues,which hampe... BACKGROUND Laparoscopic rectal cancer radical surgery is a complex procedure affected by various factors.However,the existing literature lacks standardized parameters for the pelvic region and soft tissues,which hampers the establishment of consistent conclusions.AIM To comprehensively assess 16 pelvic and 7 soft tissue parameters through computerized tomography(CT)-based three-dimensional(3D)reconstruction,providing a strong theoretical basis to address challenges in laparoscopic rectal cancer radical surgery.METHODS We analyzed data from 218 patients who underwent radical laparoscopic surgery for rectal cancer,and utilized CT data for 3D pelvic reconstruction.Specific anatomical points were carefully marked and measured using advanced 3D modeling software.To analyze the pelvic and soft tissue parameters,we emp-loyed statistical methods including paired sample t-tests,Wilcoxon rank-sum tests,and correlation analysis.RESULTS The investigation highlighted significant sex disparities in 14 pelvic bone parameters and 3 soft tissue parameters.Males demonstrated larger measurements in pelvic depth and overall curvature,smaller measurements in pelvic width,a larger mesorectal fat area,and a larger anterior-posterior abdominal diameter.By contrast,females exhibited wider pelvises,shallower depth,smaller overall curvature,and an increased amount of subcutaneous fat tissue.However,there were no significant sex differences observed in certain parameters such as sacral curvature height,superior pubococcygeal diameter,rectal area,visceral fat area,waist circumference,and transverse abdominal diameter.CONCLUSION The reconstruction of 3D CT data enabled accurate pelvic measurements,revealing significant sex differences in both pelvic and soft tissue parameters.This study design offer potential in predicting surgical difficulties and creating personalized surgical plans for male rectal cancer patients with a potentially“difficult pelvis”,ultimately improving surgical outcomes.Further research and utilization of these parameters could lead to enhanced surgical methods and patient care in laparoscopic rectal cancer radical surgery. 展开更多
关键词 Computerized tomography Rectal cancer Three-dimensional reconstruction PELVIMETRY Sex differences
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Keep in mind sex differences when prescribing psychotropic drugs
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作者 Marianna Mazza Domenico De Berardis Giuseppe Marano 《World Journal of Psychiatry》 SCIE 2024年第2期194-198,共5页
Women represent the majority of patients with psychiatric diagnoses and also the largest users of psychotropic drugs.There are inevitable differences in efficacy,side effects and long-term treatment response between m... Women represent the majority of patients with psychiatric diagnoses and also the largest users of psychotropic drugs.There are inevitable differences in efficacy,side effects and long-term treatment response between men and women.Psychopharmacological research needs to develop adequately powered animal and human trials aimed to consider pharmacokinetics and pharmacodynamics of central nervous system drugs in both male and female subjects.Healthcare professionals have the responsibility to prescribe sex-specific psychopharmacotherapies with a priority to differentiate between men and women in order to minimize adverse drugs reactions,to maximize therapeutic effectiveness and to provide personalized management of care. 展开更多
关键词 WOMEN PSYCHOPHARMACOLOGY Psychotropic drugs Sex differences
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A High Order Accurate Bound-Preserving Compact Finite Difference Scheme for Two-Dimensional Incompressible Flow
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作者 Hao Li Xiangxiong Zhang 《Communications on Applied Mathematics and Computation》 EI 2024年第1期113-141,共29页
For solving two-dimensional incompressible flow in the vorticity form by the fourth-order compact finite difference scheme and explicit strong stability preserving temporal discretizations,we show that the simple boun... For solving two-dimensional incompressible flow in the vorticity form by the fourth-order compact finite difference scheme and explicit strong stability preserving temporal discretizations,we show that the simple bound-preserving limiter in Li et al.(SIAM J Numer Anal 56:3308–3345,2018)can enforce the strict bounds of the vorticity,if the velocity field satisfies a discrete divergence free constraint.For reducing oscillations,a modified TVB limiter adapted from Cockburn and Shu(SIAM J Numer Anal 31:607–627,1994)is constructed without affecting the bound-preserving property.This bound-preserving finite difference method can be used for any passive convection equation with a divergence free velocity field. 展开更多
关键词 Finite difference MONOTONICITY Bound-preserving Discrete maximum principle Passive convection Incompressible flow Total variation bounded limiter
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Fuzzy Difference Equations in Diagnoses of Glaucoma from Retinal Images Using Deep Learning
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作者 D.Dorathy Prema Kavitha L.Francis Raj +3 位作者 Sandeep Kautish Abdulaziz S.Almazyad Karam M.Sallam Ali Wagdy Mohamed 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第4期801-816,共16页
The intuitive fuzzy set has found important application in decision-making and machine learning.To enrich and utilize the intuitive fuzzy set,this study designed and developed a deep neural network-based glaucoma eye ... The intuitive fuzzy set has found important application in decision-making and machine learning.To enrich and utilize the intuitive fuzzy set,this study designed and developed a deep neural network-based glaucoma eye detection using fuzzy difference equations in the domain where the retinal images converge.Retinal image detections are categorized as normal eye recognition,suspected glaucomatous eye recognition,and glaucomatous eye recognition.Fuzzy degrees associated with weighted values are calculated to determine the level of concentration between the fuzzy partition and the retinal images.The proposed model was used to diagnose glaucoma using retinal images and involved utilizing the Convolutional Neural Network(CNN)and deep learning to identify the fuzzy weighted regularization between images.This methodology was used to clarify the input images and make them adequate for the process of glaucoma detection.The objective of this study was to propose a novel approach to the early diagnosis of glaucoma using the Fuzzy Expert System(FES)and Fuzzy differential equation(FDE).The intensities of the different regions in the images and their respective peak levels were determined.Once the peak regions were identified,the recurrence relationships among those peaks were then measured.Image partitioning was done due to varying degrees of similar and dissimilar concentrations in the image.Similar and dissimilar concentration levels and spatial frequency generated a threshold image from the combined fuzzy matrix and FDE.This distinguished between a normal and abnormal eye condition,thus detecting patients with glaucomatous eyes. 展开更多
关键词 Convolutional Neural Network(CNN) glaucomatous eyes fuzzy difference equation intuitive fuzzy sets image segmentation retinal images
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基于FDS的双洞单向隧道火灾温度变化及烟气扩散分析
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作者 黄海涛 余陶 《宿州学院学报》 2024年第3期51-56,共6页
为应对隧道火情的发生,避免不必要的人员伤亡和财产损失,分析隧道内温度变化和烟气蔓延特性,选择合适纵向风速和烟气蔓延控制方案具有重要的研究价值。为此,采用PyroSim软件,建立公路隧道模型进行FDS数值模拟。模拟最大热释放功率为20 M... 为应对隧道火情的发生,避免不必要的人员伤亡和财产损失,分析隧道内温度变化和烟气蔓延特性,选择合适纵向风速和烟气蔓延控制方案具有重要的研究价值。为此,采用PyroSim软件,建立公路隧道模型进行FDS数值模拟。模拟最大热释放功率为20 MW的火灾,在三种不同的纵向通风强度下,观测烟气的逆流长度,确定3.5 m/s为此次模拟的临界风速;在三种不同的纵向风下,依据发生火灾时隧道内温度场变化和烟气的扩散蔓延特点,以及人员的疏散和火灾救援影响;模拟隧道烟气控制方案时,为不让烟气通过横通道蔓延至辅隧道中影响人员疏散,确定合适的主辅隧道的纵向通风强度起着十分重要的作用。 展开更多
关键词 安全工程 双洞单向隧道 fdS 火灾通风 烟气蔓延
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基于FD6288设计的经济型无刷电机驱动器
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作者 姚愉彬 吕艳蕊 +3 位作者 李虹 周宏甫 黄德铭 刘创宇 《机电工程技术》 2024年第2期243-247,266,共6页
无刷电机是大多数机器人主要动力来源,而配套的无刷电机驱动器也成为决定机器人成本的关键部件。市面上应用于机器人无刷电机驱动器的主流硬件方案为德州仪器的DRV8301驱动方案,该器件由于庞大的需求量而一直处于高昂的价格,针对此问题... 无刷电机是大多数机器人主要动力来源,而配套的无刷电机驱动器也成为决定机器人成本的关键部件。市面上应用于机器人无刷电机驱动器的主流硬件方案为德州仪器的DRV8301驱动方案,该器件由于庞大的需求量而一直处于高昂的价格,针对此问题,基于STM32嵌入式控制系统,采用国产FD6288驱动IC配合INA240电流采样芯片低成本硬件驱动方案。电机的控制方式采用场定向控制(FOC)算法。通过AD (Altium Design)对选定的器件设计原理图和PCB,并焊接元器件,通过示波器检测功能板输出波形的稳定性。驱动软件使用Keil IDE编写,通过串口将代码无刷电机驱动驱动电机过程中的各相关键数据打印到上位机,通过数据分析驱动器控制及电机的响应能力,进而调整对应的参数。驱动器电路板调试结果证明提出的驱动方案能使无刷电机稳定运行,为机器人无刷电机驱动器提供一个可行的方案。 展开更多
关键词 FOC STM32 fd6288 INA240 无刷电机驱动
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高阶SF-SFDTD方法在含时薛定谔方程求解中的应用研究
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作者 谢国大 潘攀 +4 位作者 任信钢 冯乃星 方明 李迎松 黄志祥 《物理学报》 SCIE EI CAS CSCD 北大核心 2024年第3期72-81,共10页
时域有限差分方法(finite-difference time-domain,FDTD(2,2))被广泛用于量子力学中薛定谔方程的求解,然而受Courant-Friedrichs-Lewy(CFL)条件的影响,计算空间中的网格尺寸会限制时间步长的取值范围,极大降低了FDTD(2,2)方法的数值计... 时域有限差分方法(finite-difference time-domain,FDTD(2,2))被广泛用于量子力学中薛定谔方程的求解,然而受Courant-Friedrichs-Lewy(CFL)条件的影响,计算空间中的网格尺寸会限制时间步长的取值范围,极大降低了FDTD(2,2)方法的数值计算效率.另外,FDTD(2,2)方法在时间域和空间域只具有二阶数值精度,在计算中往往会导致较大的误差累计,影响仿真结果的正确性.为了克服这些问题,结合空间滤波方法(spatial filtering,SF)和高阶辛时域有限差分(symplectic finite-difference time-domain,SFDTD(3,4))方法(3和4分别表示时间和空间数值精度),提出了一种时间稳定性条件可扩展的SF-SFDTD(3,4)方法用于求解含时薛定谔方程.SF-SFDTD(3,4)方法无需对传统SFDTD(3,4)方法的迭代公式进行进一步的推导,只需要在每一次的数值迭代过程中加入空间滤波操作,滤除因采用不满足CFL条件的时间步长而产生的不稳定空间域高频分量,保证数值方法的稳定性,因此所提方法与传统SFDTD(3,4)方法具有较高的兼容性.同时,理论分析了SF-SFDTD(3,4)方法的数值色散误差.最后,通过数值算例验证了本文所提方法的正确性和有效性. 展开更多
关键词 辛时域有限差分方法 空间滤波方法 时间稳定性条件 薛定谔方程
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Assessment of vegetation cover changes and the contributing factors in the Al-Ahsa Oasis using Normalized Difference Vegetation Index(NDVI)
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作者 Walid CHOUARI 《Regional Sustainability》 2024年第1期42-53,共12页
The abandonment of date palm grove of the former Al-Ahsa Oasis in the eastern region of Saudi Arabia has resulted in the conversion of delicate agricultural area into urban area.The current state of the oasis is influ... The abandonment of date palm grove of the former Al-Ahsa Oasis in the eastern region of Saudi Arabia has resulted in the conversion of delicate agricultural area into urban area.The current state of the oasis is influenced by both expansion and degradation factors.Therefore,it is important to study the spatiotemporal variation of vegetation cover for the sustainable management of oasis resources.This study used Landsat satellite images in 1987,2002,and 2021 to monitor the spatiotemporal variation of vegetation cover in the Al-Ahsa Oasis,applied multi-temporal Normalized Difference Vegetation Index(NDVI)data spanning from 1987 to 2021 to assess environmental and spatiotemporal variations that have occurred in the Al-Ahsa Oasis,and investigated the factors influencing these variation.This study reveals that there is a significant improvement in the ecological environment of the oasis during 1987–2021,with increase of NDVI values being higher than 0.10.In 2021,the highest NDVI value is generally above 0.70,while the lowest value remains largely unchanged.However,there is a remarkable increase in NDVI values between 0.20 and 0.30.The area of low NDVI values(0.00–0.20)has remained almost stable,but the region with high NDVI values(above 0.70)expands during 1987–2021.Furthermore,this study finds that in 1987–2002,the increase of vegetation cover is most notable in the northern region of the study area,whereas from 2002 to 2021,the increase of vegetation cover is mainly concentrated in the northern and southern regions of the study area.From 1987 to 2021,NDVI values exhibit the most pronounced variation,with a significant increase in the“green”zone(characterized by NDVI values exceeding 0.40),indicating a substantial enhancement in the ecological environment of the oasis.The NDVI classification is validated through 50 ground validation points in the study area,demonstrating a mean accuracy of 92.00%in the detection of vegetation cover.In general,both the user’s and producer’s accuracies of NDVI classification are extremely high in 1987,2002,and 2021.Finally,this study suggests that environmental authorities should strengthen their overall forestry project arrangements to combat sand encroachment and enhance the ecological environment of the Al-Ahsa Oasis. 展开更多
关键词 Normalized difference Vegetation Index(NDVI) Vegetation cover Ecological environment Land use and land cover(LULC) Urban expansion Al-Ahsa Oasis
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