期刊文献+
共找到5,422篇文章
< 1 2 250 >
每页显示 20 50 100
基于DDS的数字脉冲电火花沉积电源研究 被引量:1
1
作者 刘宇 高洋 +3 位作者 张诗奇 杜姗 张生芳 王紫光 《电加工与模具》 北大核心 2024年第1期26-30,51,共6页
在电火花沉积加工中,脉冲电源的放电参数对沉积效果和加工效率有重要影响。针对传统电火花沉积电源放电参数可控性差的问题,基于直接数字频率合成(DDS)技术全数字化调制、输出稳定的特性,设计了一种数字脉冲电火花沉积电源。以单片机和... 在电火花沉积加工中,脉冲电源的放电参数对沉积效果和加工效率有重要影响。针对传统电火花沉积电源放电参数可控性差的问题,基于直接数字频率合成(DDS)技术全数字化调制、输出稳定的特性,设计了一种数字脉冲电火花沉积电源。以单片机和DDS芯片为核心来控制斩波电路输出加工脉冲,可实现放电电压、频率等参数的较精确控制以及宽范围内的无极调节。经测试,控制及驱动模块输出信号稳定、准确且频率误差在1 Hz以内,放电电压波形可控性好,满足电火花沉积加工的要求,可用于电火花沉积加工基础研究。 展开更多
关键词 电火花沉积 ddS技术 脉冲电源 可控性
下载PDF
包裹有CTA1-DD蛋白的OCS-DS纳米颗粒的制备及佐剂活性
2
作者 秦竹 陈瑾 +7 位作者 侯立婷 乔绪稳 李兰 杨利 杜露平 于晓明 张元鹏 郑其升 《江苏农业学报》 CSCD 北大核心 2024年第1期141-148,共8页
重组CTA1-DD蛋白具有与完整CT分子相当的全身性和黏膜佐剂功能,但在复杂的生理环境中易被酶或酸降解。本研究以同样具有佐剂活性的O-羧甲基壳聚糖(OCS)和硫酸葡聚糖(DS)为载体,通过离子交联形成纳米颗粒,将CTA1-DD蛋白嵌入其中,使其得... 重组CTA1-DD蛋白具有与完整CT分子相当的全身性和黏膜佐剂功能,但在复杂的生理环境中易被酶或酸降解。本研究以同样具有佐剂活性的O-羧甲基壳聚糖(OCS)和硫酸葡聚糖(DS)为载体,通过离子交联形成纳米颗粒,将CTA1-DD蛋白嵌入其中,使其得到稳定保护。包裹有CTA1-DD蛋白的OCS-DS纳米颗粒的粒径为50~150 nm,Zeta电位约-50 mV,质量浓度1.0 mg/ml的CTA1-DD蛋白投入制备的包裹有CTA1-DD蛋白的OCS-DS纳米颗粒载药率25.33%,包封率86.56%。体外模拟释放试验结果显示CTA1-DD蛋白可在7 d内缓慢释放。将CTA1-DD蛋白与PRV灭活抗原混合后,接种至小鼠鼻腔,结果表明,包裹有CTA1-DD蛋白的OCS-DS纳米颗粒能够同时诱导更高的血清IgG抗体和黏膜IgA抗体表达,证明了其作为黏膜佐剂的高效性。 展开更多
关键词 CTA1-dd蛋白 O-羧甲基壳聚糖 硫酸葡聚糖 纳米颗粒 佐剂活性
下载PDF
基于改进DDS的应答器动态检测系统2FSK调制器设计
3
作者 朱明勋 吕旌阳 许庆阳 《中国铁路》 北大核心 2024年第4期85-91,共7页
基于高速综合检测列车平台的应答器动态检测系统可实现对应答器相关设备性能的实时检测。为测试车载应答器动态检测系统的性能,需产生高精度可控波特率和载频的调制信号(2FSK)作为上行链路信号。基于直接数字频率合成器(DDS)技术,通过... 基于高速综合检测列车平台的应答器动态检测系统可实现对应答器相关设备性能的实时检测。为测试车载应答器动态检测系统的性能,需产生高精度可控波特率和载频的调制信号(2FSK)作为上行链路信号。基于直接数字频率合成器(DDS)技术,通过对相位累加模块和相幅转换模块进行设计,提出分段相位累加算法,计算同周期内相位增量和码元跳变处的相位增量;通过改进的坐标旋转数字计算方法(CORDIC)实时计算对应的信号幅值,用数字模拟转换器(DAC)将离散信号转换为模拟信号,从而实现频偏和数据速率可变且相位连续的信号调制。在相幅转换模块设计中,采用改进CORDIC算法替代传统的查表法,将相位增量转换成信号幅度,有效减少了现场可编程逻辑门阵列(FPGA)存储资源的开销。基于改进DDS的2FSK调制器设计方法,可为应答器动态检测系统提供高精度可控波特率和载频的2FSK调制信号,保证了应答器动态检测系统校准的准确性。 展开更多
关键词 应答器动态检测系统 2FSK ddS 分段相位累加 CORDIC FPGA
下载PDF
DD6合金组织退化表征及与疲劳寿命的量化映射关系
4
作者 崔文明 李铸铁 +4 位作者 张晓辰 王巍 张瑞 张凯 臧昊良 《有色金属工程》 CAS 北大核心 2024年第9期32-38,共7页
以DD6镍基单晶高温合金为研究对象,通过高温长时或热力耦合热暴露模拟其高温服役环境获得退化组织,研究组织退化机理以及对应的剩余疲劳寿命,并探讨合适的组织定量表征方法建立组织退化损伤程度与疲劳寿命映射关系。结果表明,在热环境... 以DD6镍基单晶高温合金为研究对象,通过高温长时或热力耦合热暴露模拟其高温服役环境获得退化组织,研究组织退化机理以及对应的剩余疲劳寿命,并探讨合适的组织定量表征方法建立组织退化损伤程度与疲劳寿命映射关系。结果表明,在热环境服役过程中,DD6合金中γ′相发生了粗化和筏化退化,降低了980℃、应力比为0.1条件下的疲劳寿命。采用当下组织状态的γ相和γ′相尺寸参量可将DD6合金高温粗化和筏化组织与合金疲劳寿命建立相关系数较高的统一的量化映射关系式,且该表征方式无需获取初始的组织尺寸,更具有工程应用意义。 展开更多
关键词 dd6合金 组织退化 疲劳寿命 量化表征
下载PDF
热障涂层对DD6单晶燃气热腐蚀及力学性能的影响
5
作者 王玉锋 付前刚 +2 位作者 杨俊 张华 杨岩 《材料导报》 EI CAS CSCD 北大核心 2024年第18期142-147,共6页
DD6单晶高温合金材料以其优异的高温服役性能,在我国多型航空发动机制造领域拥有十分广阔的应用前景。随着我国航空发动机技术的不断发展,燃烧室涡轮前服役温度不断提升,DD6单晶高温合金无法完全满足高温、高压、高转速的服役环境,急需... DD6单晶高温合金材料以其优异的高温服役性能,在我国多型航空发动机制造领域拥有十分广阔的应用前景。随着我国航空发动机技术的不断发展,燃烧室涡轮前服役温度不断提升,DD6单晶高温合金无法完全满足高温、高压、高转速的服役环境,急需开展DD6单晶表面热障涂层技术研究。鉴于此,本工作采用多弧离子镀技术在DD6单晶高温合金上制备了NiCoCrAlY金属粘结层(BC),然后采用电子束物理气相沉积技术制备了Y_(2)O_(3)·ZrO_(2)(YSZ)陶瓷面层,研究热障涂层对DD6单晶抗燃气热腐蚀及力学性能的影响。结果表明:在900℃条件下,燃气热腐蚀性能测试100 h后,DD6合金表面形成了厚度约100μm的腐蚀疏松结构、孔洞及横向裂纹,DD6合金抗燃气热腐蚀性能较差;BC涂层或YSZ涂层内部未出现Na、K、Ca、Cl、S等腐蚀性元素,BC涂层表面形成了均匀连续的Al_(2)O_(3)层,在其表面粘附的Na_(2)SO_(4)未出现高温分解,腐蚀介质未对BC涂层产生侵蚀;YSZ涂层柱状晶组织具有较好的应变容限,高温时柱状晶膨胀引起柱晶间隙缩小,外部的腐蚀介质无法有效渗入YSZ涂层内部,从而避免了腐蚀介质对涂层或基体的侵蚀破坏。热障涂层对DD6单晶合金980℃条件下的抗拉强度σb、屈服强度σ_(0.2)、延伸率δ和断面收缩率ψ无不良影响,断裂模式与未涂覆涂层试样一致,均呈典型的韧性断裂。在980℃、250 MPa条件下,涂覆与未涂覆涂层的DD6试样高温持久时间和延伸率δ无明显差异,呈典型的塑性变形和蠕变变形韧性断裂机制。本工作的研究结果为DD6单晶高温合金热障涂层技术的开发与工程化应用奠定了技术支撑。 展开更多
关键词 dd6单晶 热障涂层 燃气热腐蚀 高温持久性能 EB-PVD 金属粘结层
下载PDF
保温时长对DD5/FGH98扩散焊接头组织及力学性能的影响
6
作者 张鑫 钟陈康 +2 位作者 田富强 石俊秒 孙现军 《精密成形工程》 北大核心 2024年第10期139-146,共8页
目的为优化焊接工艺参数,探究不同保温时长对DD5/FGH98固相扩散焊接头组织和性能的影响。方法采用高熵合金和镍箔作为复合中间层,通过固相扩散焊方式连接DD5单晶高温合金和FGH98粉末高温合金。在1130℃、4 MPa的压力条件下,进行不同保... 目的为优化焊接工艺参数,探究不同保温时长对DD5/FGH98固相扩散焊接头组织和性能的影响。方法采用高熵合金和镍箔作为复合中间层,通过固相扩散焊方式连接DD5单晶高温合金和FGH98粉末高温合金。在1130℃、4 MPa的压力条件下,进行不同保温时长的焊接。焊接完成后,通过多种表征手段观察接头的微观组织,并通过剪切实验确定接头的性能。结果从微观组织上看,随着保温时间的延长,中间层中高熵合金晶粒长大,FGH98和DD5近焊缝处的γ′相溶解变小,DD5侧母材在高温高压下发生严重的筏化。母材与中间层的元素扩散更加充分。在力学性能方面,保温时间的延长导致中间层硬度降低,与基材硬度差距增加,接头剪切强度逐渐降低。在1130℃、4 MPa条件下,保温1 h的接头强度最高,达到650 MPa。保温1~4 h试样的剪切断裂位置在高熵中间层;保温6 h试样的断裂位置在镍箔区域。结论保温时长影响接头的微观结构和力学性能。在一定焊接温度下,实现完全键合的接头的剪切强度会随着保温时长的延长而降低。 展开更多
关键词 扩散连接 保温时长 dd5 FGH98 高熵合金中间层
下载PDF
DD5缓进磨削表面粗糙度和硬化率对疲劳性能影响研究
7
作者 靳淇超 包虎子 +4 位作者 李良万 汪文虎 张锦淇 叶子银 郭磊 《中国机械工程》 EI CAS CSCD 北大核心 2024年第8期1472-1479,共8页
为研究DD5镍基单晶高温合金缓进磨削表面粗糙度和硬化率对疲劳性能的影响规律及机理,设计实验并进行了试件磨削与疲劳性能测试。结果表明:表面粗糙度的增大引起应力集中加剧,导致疲劳性能降低,不同磨削工艺下表面粗糙度由0.347μm增大到... 为研究DD5镍基单晶高温合金缓进磨削表面粗糙度和硬化率对疲劳性能的影响规律及机理,设计实验并进行了试件磨削与疲劳性能测试。结果表明:表面粗糙度的增大引起应力集中加剧,导致疲劳性能降低,不同磨削工艺下表面粗糙度由0.347μm增大到0.687μm,其疲劳寿命由5.51×10^(5)降至3.38×10^(5),下降率约38.66%;表面粗糙度小于0.4μm时表面硬化可提高试件疲劳寿命,表面粗糙度超过0.4μm时表面硬化对疲劳性能的影响不显著;形貌测试结果表明,随着表面粗糙度的提高,磨削表面耕犁产生的沟壑数量和深度均增大,疲劳载荷作用下磨削表面裂纹源数量增加、应力集中加剧,从而导致疲劳寿命降低。较小的表面粗糙度与较大的表面硬化率均可提高DD5缓进磨削疲劳性能。 展开更多
关键词 dd5高温合金 缓进磨削 表面粗糙度 表面硬化率 疲劳性能 断裂机理
下载PDF
梅山钢铁焦炉煤气DDS生物脱硫技术的应用研究
8
作者 王军 《低碳世界》 2024年第5期10-12,共3页
2022年,上海梅山钢铁股份有限公司焦炉煤气脱硫脱氰(desulfurization and decyanation sorbent,DDS)生物脱硫技术项目成功建设并投入运行。基于此,概述DDS生物脱硫技术的技术核心、技术原理、工艺流程及现场布置,深入分析DDS生物脱硫技... 2022年,上海梅山钢铁股份有限公司焦炉煤气脱硫脱氰(desulfurization and decyanation sorbent,DDS)生物脱硫技术项目成功建设并投入运行。基于此,概述DDS生物脱硫技术的技术核心、技术原理、工艺流程及现场布置,深入分析DDS生物脱硫技术的实际应用与优化、应用效果及应用前景,对项目建设及运行过程中出现的问题进行分析、总结与完善,以期提高企业自身的技术水平,并为其他企业选择煤气脱硫工艺提供了参考。 展开更多
关键词 焦炉煤气 ddS 生物脱硫
下载PDF
Impact of D-dimer on in-hospital mortality following aortic dissection:A systematic review and meta-analysis
9
作者 Sashwath Srikanth Shabnam Abrishami +6 位作者 Lakshmi Subramanian Ashwini Mahadevaiah Ankit Vyas Akhil Jain Sangeetha Nathaniel Subramanian Gnanaguruparan Rupak Desai 《World Journal of Cardiology》 2024年第6期355-362,共8页
BACKGROUND The utility of D-dimer(DD)as a biomarker for acute aortic dissection(AD)is recognized.Yet,its predictive value for in-hospital mortality remains uncertain and subject to conflicting evidence.AIM To conduct ... BACKGROUND The utility of D-dimer(DD)as a biomarker for acute aortic dissection(AD)is recognized.Yet,its predictive value for in-hospital mortality remains uncertain and subject to conflicting evidence.AIM To conduct a meta-analysis of AD-related in-hospital mortality(ADIM)with elevated DD levels.METHODS We searched PubMed,Scopus,Embase,and Google Scholar for AD and ADIM literature through May 2022.Heterogeneity was assessed using I2 statistics and effect size(hazard or odds ratio)analysis with random-effects models.Sample size,study type,and patients’mean age were used for subgroup analysis.The significance threshold was P<0.05.RESULTS Thirteen studies(3628 patients)were included in our study.The pooled prevalence of ADIM was 20%(95%CI:15%-25%).Despite comparable demographic characteristics and comorbidities,elevated DD values were associated with higher ADIM risk(unadjusted effect size:1.94,95%CI:1.34-2.8;adjusted effect size:1.12,95%CI:1.05-1.19,P<0.01).Studies involving patients with a mean age of<60 years exhibited an increased mortality risk(effect size:1.43,95%CI:1.23-1.67,P<0.01),whereas no significant difference was observed in studies with a mean age>60 years.Prospective and larger sample size studies(n>250)demonstrated a heightened likelihood of ADIM associated with elevated DD levels(effect size:2.57,95%CI:1.30-5.08,P<0.01 vs effect size:1.05,95%CI:1.00-1.11,P=0.05,respectively).CONCLUSION Our meta-analysis shows elevated DD increases in-hospital mortality risk in AD patients,highlighting the need for larger,prospective studies to improve risk prediction models. 展开更多
关键词 d-dimer Aortic dissection MORTALITY BIOMARKER Systematic review META-ANALYSIS
下载PDF
Utility of plasma D-dimer for diagnosis of venous thromboembolism after hepatectomy
10
作者 Taiichiro Miyake Hiroaki Yanagimoto +16 位作者 Daisuke Tsugawa Masayuki Akita Riki Asakura Keisuke Arai Toshihiko Yoshida Shinichi So Jun Ishida Takeshi Urade Yoshihide Nanno Kenji Fukushima Hidetoshi Gon Shohei Komatsu Sadaki Asari Hirochika Toyama Masahiro Kido Tetsuo Ajiki Takumi Fukumoto 《World Journal of Clinical Cases》 SCIE 2024年第2期276-284,共9页
BACKGROUND Venous thromboembolism(VTE)is a potentially fatal complication of hepatectomy.The use of postoperative prophylactic anticoagulation in patients who have undergone hepatectomy is controversial because of the... BACKGROUND Venous thromboembolism(VTE)is a potentially fatal complication of hepatectomy.The use of postoperative prophylactic anticoagulation in patients who have undergone hepatectomy is controversial because of the risk of postoperative bleeding.Therefore,we hypothesized that monitoring plasma D-dimer could be useful in the early diagnosis of VTE after hepatectomy.AIM To evaluate the utility of monitoring plasma D-dimer levels in the early diagnosis of VTE after hepatectomy.METHODS The medical records of patients who underwent hepatectomy at our institution between January 2017 and December 2020 were retrospectively analyzed.Patients were divided into two groups according to whether or not they developed VTE after hepatectomy,as diagnosed by contrast-enhanced computed tomography and/or ultrasonography of the lower extremities.Clinicopathological factors,including demographic data and perioperative D-dimer values,were compared between the two groups.Receiver operating characteristic curve analysis was performed to determine the D-dimer cutoff value.Univariate and multivariate analyses were performed using logistic regression analysis to identify significant predictors.RESULTS In total,234 patients who underwent hepatectomy were,of whom(5.6%)were diagnosed with VTE following hepatectomy.A comparison between the two groups showed significant differences in operative time(529 vs 403 min,P=0.0274)and blood loss(530 vs 138 mL,P=0.0067).The D-dimer levels on postoperative days(POD)1,3,5,7 were significantly higher in the VTE group than in the non-VTE group.In the multivariate analysis,intraoperative blood loss of>275 mL[odds ratio(OR)=5.32,95%confidence interval(CI):1.05-27.0,P=0.044]and plasma D-dimer levels on POD 5≥21μg/mL(OR=10.1,95%CI:2.04-50.1,P=0.0046)were independent risk factors for VTE after hepatectomy.CONCLUSION Monitoring of plasma D-dimer levels after hepatectomy is useful for early diagnosis of VTE and may avoid routine prophylactic anticoagulation in the postoperative period. 展开更多
关键词 HEPATECTOMY Malignant tumor Postoperative complication d-dimer Early diagnosis Venous thromboembolism
下载PDF
基于DDS+PLL的频率合成方法研究
11
作者 王锋 郭中会 +2 位作者 庞洋 张一萌 陈鹏 《环境技术》 2024年第4期155-159,共5页
针对传统的PLL在小数分频时引起的边界杂散问题,采用DDS作为PLL的参考时钟,通过动态调整DDS的输出频率及PLL的整数分频比,使PLL在整数分频模式下仍具有小步进的合成频率精度。经过理论分析和实测实验验证了方案的可行性,实测实验表明,采... 针对传统的PLL在小数分频时引起的边界杂散问题,采用DDS作为PLL的参考时钟,通过动态调整DDS的输出频率及PLL的整数分频比,使PLL在整数分频模式下仍具有小步进的合成频率精度。经过理论分析和实测实验验证了方案的可行性,实测实验表明,采用DDS+PLL方案合成频率可以有效解决整数边界杂散,并实现了最大9.31 Hz的频率步进精度。 展开更多
关键词 小数分频 边界杂散 ddS激励PLL 小步进 频率精度
下载PDF
基于DDS的分布式仿真平台接口设计
12
作者 张同 陈聪 惠慧 《机电工程技术》 2024年第6期156-161,共6页
为了充分利用MATLAB/Simulink仿真软件的建模功能并与其他仿真软件建立的机电系统模型进行数据交互,从而实现对分布在不同仿真节点的多电飞机各机电系统进行分布式协同仿真。详细介绍了分布式仿真平台的运行管理机制与DDS数学通信模型,... 为了充分利用MATLAB/Simulink仿真软件的建模功能并与其他仿真软件建立的机电系统模型进行数据交互,从而实现对分布在不同仿真节点的多电飞机各机电系统进行分布式协同仿真。详细介绍了分布式仿真平台的运行管理机制与DDS数学通信模型,建立了MATLAB/Simulink仿真软件接口架构,通过编程设计将MATLAB/Simulink软件集成于基于DDS的分布式仿真平台上,并利用该仿真软件对其他机电系统仿真模型进行算法控制建模,从而实现多电飞机各机电系统的联合仿真。验证结果表明,该数据接口能够实现MATLAB/Simulink仿真模型与分布式仿真平台上其他仿真模型的数据交互与指令调控,进一步拓宽了分布式仿真平台的规模,完善了多电飞机的系统功能,为接下来实现对多电飞机机电系统分布式协同仿真虚拟监控打下坚实基础。 展开更多
关键词 分布式协同仿真 ddS MATLAB/SIMULINK 接口设计
下载PDF
Associations of serum D-dimer and glycosylated hemoglobin levels with third-trimester fetal growth restriction in gestational diabetes mellitus
13
作者 Ying Zhang Teng Li +1 位作者 Chao-Yan Yue Yun Liu 《World Journal of Diabetes》 SCIE 2024年第5期914-922,共9页
BACKGROUND Gestational diabetes mellitus(GDM)is a special type of diabetes that commonly occurs in women during pregnancy and involves impaired glucose tolerance and abnormal glucose metabolism;GDM is diagnosed for th... BACKGROUND Gestational diabetes mellitus(GDM)is a special type of diabetes that commonly occurs in women during pregnancy and involves impaired glucose tolerance and abnormal glucose metabolism;GDM is diagnosed for the first time during pregnancy and can affect fetal growth and development.AIM To investigate the associations of serum D-dimer(D-D)and glycosylated hemoglobin(HbA1c)levels with third-trimester fetal growth restriction(FGR)in GDM patients.METHODS The clinical data of 164 pregnant women who were diagnosed with GDM and delivered at the Obstetrics and Gynecology Hospital of Fudan University from January 2021 to January 2023 were analyzed retrospectively.Among these women,63 whose fetuses had FGR were included in the FGR group,and 101 women whose fetuses had normal body weights were included in the normal body weight group(normal group).Fasting venous blood samples were collected from the elbow at 28-30 wk gestation and 1-3 d before delivery to measure serum D-D and HbA1c levels for comparative analysis.The diagnostic value of serum D-D and HbA1c levels for FGR was evaluated by receiver operating characteristic analysis,and the influencing factors of third-trimester FGR in GDM patients were analyzed by logistic regression.RESULTS Serum fasting blood glucose,fasting insulin,D-D and HbA1c levels were significantly greater in the FGR group than in the normal group,while the homeostasis model assessment of insulin resistance values were lower(P<0.05).Regarding the diagnosis of FGR based on serum D-D and HbA1c levels,the areas under the curves(AUCs)were 0.826 and 0.848,the cutoff values were 3.04 mg/L and 5.80%,the sensitivities were 81.0%and 79.4%,and the specificities were 88.1%and 87.1%,respectively.The AUC of serum D-D plus HbA1c levels for diagnosing FGR was 0.928,and the sensitivity and specificity were 84.1%and 91.1%,respectively.High D-D and HbA1c levels were risk factors for third-trimester FGR in GDM patients(P<0.05).CONCLUSION D-D and HbA1c levels can indicate the occurrence of FGR in GDM patients in the third trimester of pregnancy to some extent,and their combination can be used as an important index for the early prediction of FGR. 展开更多
关键词 Gestational diabetes mellitus d-dimer HEMOGLOBIN Fetal growth restriction Fasting blood glucose
下载PDF
Method for detector description conversion from DD4hep to Filmbox
14
作者 Zhao-Yang Yuan Tian-Zi Song +3 位作者 Yu-Jie Zeng Kai-Xuan Huang Yu-Mei Zhang Zheng-Yun You 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2024年第9期115-126,共12页
DD4hep serves as a generic detector description toolkit recommended for offline software development in next-generation high-energy physics(HEP)experiments.Conversely,Filmbox(FBX)stands out as a widely used 3D modelin... DD4hep serves as a generic detector description toolkit recommended for offline software development in next-generation high-energy physics(HEP)experiments.Conversely,Filmbox(FBX)stands out as a widely used 3D modeling file format within the 3D software industry.In this paper,we introduce a novel method that can automatically convert complex HEP detector geometries from DD4hep description into 3D models in the FBX format.The feasibility of this method was dem-onstrated by its application to the DD4hep description of the Compact Linear Collider detector and several sub-detectors of the super Tau-Charm facility and circular electron-positron collider experiments.The automatic DD4hep–FBX detector conversion interface provides convenience for further development of applications,such as detector design,simulation,visualization,data monitoring,and outreach,in HEP experiments. 展开更多
关键词 Detector description dd4hep FBX GEOMETRY Offline software
下载PDF
D-Dimer: Predictor of Postpartum Hemorrhage among Pre-Eclampsia at Kilimanjaro Christian Medical Centre
15
作者 Husna Silim Ally Nyasatu G. Chamba +12 位作者 Raziya Gaffur Nasra Batchu Glory Mangi Pendo S. Mlay Bariki Mchome Mtoro J. Mtoro Thomas J. Kakumbi Rafiki N. Mjema Doris Rwenyagila Eusebius Maro Fredrick Mbise Gilleard Masenga Patricia S. Swai 《Open Journal of Obstetrics and Gynecology》 2024年第6期923-937,共15页
Background: Postpartum hemorrhage (PPH) is the major contributor to maternal mortality and morbidity worldwide as well as in Tanzania. Studies have shown Pre-eclampsia as a risk indicator for Postpartum hemorrhage and... Background: Postpartum hemorrhage (PPH) is the major contributor to maternal mortality and morbidity worldwide as well as in Tanzania. Studies have shown Pre-eclampsia as a risk indicator for Postpartum hemorrhage and D-dimer tends to rise in women with pre-eclampsia. Few studies that have shown the association between D-dimer and PPH have been controversial and differ according to ethnicity and lifestyle. Hence there is no suitable reference interval for D-dimer in predicting Postpartum hemorrhage among women with pre-eclampsia. Broad Objective: This study aimed to assess the association, sensitivity, and specificity of D-dimer as a laboratory predictor of postpartum hemorrhage among women with pre-eclampsia at KCMC hospital. Methodology: This was a hospital-based analytical cross-sectional study conducted at KCMC Hospital in Northern Tanzania from September 2022 to March 2023. A total of 195 women with pre-eclampsia were included in this study. Plasma D-dimer levels were taken from women with pre-eclampsia pre-delivery. Haematocrit was compared before and after delivery, and a fall of 10% was considered as Postpartum hemorrhage together with clinical assessment of the patient. Participants were divided among those who had severe features and those who did not have severe features and were further categorized into those who had PPH and those who did not have PPH. Logistic regression was used to determine the association between D-dimer and PPH adjusting for other factors. The Receiver Operating Curve (ROC) was used to evaluate the predictive value. Results: Higher median D-dimer levels were seen among women who had PPH compared to those who had no PPH. D-dimer was seen to be associated with PPH, thus for every unit increase of µg/ml of D-dimer among women who had pre-eclampsia without severe features there was a 14% significant increase in the odds of having postpartum hemorrhage and a 45% significant increase of having postpartum hemorrhage among those who had pre-eclampsia with severe features. Furthermore, the cut-off point of a D-dimer level of 0.66 µg/ml significantly predicts postpartum hemorrhage with a sensitivity of 75% and specificity of 55%. For those who had no severe features the cut-off point was 0.53 µg/ml with a sensitivity of 95% and specificity of 53%, and for those who had severe features the cut-off point was 3.58 µg/ml with a sensitivity of 50% and specificity of 96%. Conclusion: D-dimer can be used to predict postpartum hemorrhage among pre-eclampsia, especially among those who have severe features. This shows that D-dimer has specificity in predicting PPH in women with pre-eclampsia and can be applied in clinical services to save women from maternal morbidity and mortality. Blood products such as fresh frozen plasma, platelets, and whole blood together with tranexamic acid should be readily available in women with pre-eclampsia especially those with severe features with a D-dimer level of 3.58 µg/ml and above during delivery as they are at high risk of developing PPH. 展开更多
关键词 d-dimer PREECLAMPSIA Postpartum Hemorrhage Tanzania
下载PDF
DD26单晶高温合金钎焊接头微观组织与力学性能研究
16
作者 贺文燮 张元伟 +2 位作者 任海水 任新宇 毛唯 《航空制造技术》 CSCD 北大核心 2024年第10期102-106,114,共6页
采用NiNbCoWCrAlSiMo钎料,在1225℃/30 min钎焊条件下开展了DD26单晶高温合金的钎焊试验,分析了0.05 mm、0.20 mm两种钎焊间隙对应接头的微观组织和性能。研究发现,接头组织主要由颗粒状的γ+γ′双相组织,以及分布在颗粒相之间的富W相... 采用NiNbCoWCrAlSiMo钎料,在1225℃/30 min钎焊条件下开展了DD26单晶高温合金的钎焊试验,分析了0.05 mm、0.20 mm两种钎焊间隙对应接头的微观组织和性能。研究发现,接头组织主要由颗粒状的γ+γ′双相组织,以及分布在颗粒相之间的富W相和Ni–Nb(Si)相构成。当钎焊间隙为0.05 mm时,接头室温抗拉强度为614 MPa,达到DD26单晶合金的75.9%;1000℃抗拉强度为466 MPa,达到DD26单晶合金的78.8%;1000℃/75MPa条件下的持久寿命最高可达44.6 h。当钎焊间隙为0.20 mm时,接头室温抗拉强度为686 MPa,达到DD26单晶合金的84.8%;1000℃抗拉强度为479 MPa,达到DD26单晶合金的81.0%;1000℃/75 MPa条件下的持久寿命最高可达17.5 h。焊后热处理对间隙0.05 mm的接头持久性能影响不明显,间隙0.20 mm的接头持久性能在热处理后有所提升。断口分析发现,接头断裂表现出裂纹沿颗粒状的γ+γ'双相组织边缘扩展的特征。 展开更多
关键词 dd26单晶高温合金 镍基钎料 钎焊间隙 焊缝组织 接头性能
下载PDF
基于自适应VMD和DD-cCycleGAN的滚动轴承剩余寿命预测
17
作者 于军 赵坤 +1 位作者 张帅 邓四二 《振动与冲击》 EI CSCD 北大核心 2024年第13期45-52,共8页
为准确预测强噪声干扰小样本情况下的滚动轴承剩余寿命(remaining useful life, RUL),提出一种基于自适应变分模态分解(variational mode decomposition, VMD)和双判别器条件循环一致对抗网络(double-discriminator conditional CycleGA... 为准确预测强噪声干扰小样本情况下的滚动轴承剩余寿命(remaining useful life, RUL),提出一种基于自适应变分模态分解(variational mode decomposition, VMD)和双判别器条件循环一致对抗网络(double-discriminator conditional CycleGAN, DD-cCycleGAN)的滚动轴承RUL预测方法。将黑猩猩优化算法(chimp optimization algorithm, ChOA)与VMD相结合,给出一种基于ChOA的自适应VMD算法,选取有效模态分量进行重构,降低强背景噪声的干扰;开发一种DD-cCycleGAN生成新样本,这些生成的新样本不但保留了源域的样本信息,还与目标域的样本相似;将训练样本的重构样本和生成的新样本作为输入,训练长短时记忆(long short-term memory, LSTM)网络,用训练后的LSTM网络预测测试样本中滚动轴承的RUL。通过采用XJTU-SY滚动轴承加速寿命试验数据集验证该方法的有效性,试验结果表明该方法具有较强的抗噪能力和较高的轴承RUL预测精度。 展开更多
关键词 滚动轴承 剩余寿命(RUL)预测 自适应变分模态分解(VMD) 双判别器条件循环一致对抗网络 黑猩猩优化算法(ChOA)
下载PDF
制孔工艺对DD6镍基单晶高温合金低周疲劳性能的影响
18
作者 张志金 张明岐 潘志福 《电加工与模具》 北大核心 2024年第1期31-34,共4页
在900℃、540 MPa条件下,研究了电液束加工、电火花成形加工、电火花小孔加工三种制孔工艺对DD6单晶高温合金试验件低周疲劳性能的影响,并对孔微观形貌和断口形貌进行了对比分析。结果表明,在相同试验条件下,电液束加工得到的气膜孔具... 在900℃、540 MPa条件下,研究了电液束加工、电火花成形加工、电火花小孔加工三种制孔工艺对DD6单晶高温合金试验件低周疲劳性能的影响,并对孔微观形貌和断口形貌进行了对比分析。结果表明,在相同试验条件下,电液束加工得到的气膜孔具有最佳的疲劳寿命。疲劳源位于气膜孔周边,不同制孔工艺的断口特征相似,均为多源断裂,而断口主要包括疲劳裂纹源区、扩展区和瞬断区三个区域。 展开更多
关键词 dd6单晶 镍基单晶高温合金 低周疲劳
下载PDF
基于DDS中间件实现分布式系统的热备份技术
19
作者 郭建忠 赵昶宇 《科技与创新》 2024年第14期130-132,共3页
为实现分布式系统中多个设备的热备份,提出了一种分布式系统的热备份方法。通过以太网和DDS(Data Distribution Service,数据分发服务)中间件技术,使得分布式系统中所有设备节点能够动态地发现彼此,根据主题、数据类型及服务质量策略进... 为实现分布式系统中多个设备的热备份,提出了一种分布式系统的热备份方法。通过以太网和DDS(Data Distribution Service,数据分发服务)中间件技术,使得分布式系统中所有设备节点能够动态地发现彼此,根据主题、数据类型及服务质量策略进行匹配,只有匹配成功后才会建立通信连接。一旦检测到系统中某个设备节点不可用时,用其他设备节点替换当前故障的设备节点,重新匹配和建立通信连接,从而实现设备节点的热备份。此方法不需要采用仲裁机构,易于实现,具有成本低、可靠性高、多机间相互热备份等优点,降低了分布式系统的冗余度,最大限度保证了分布式系统网络的实时性、可用性和可靠性。 展开更多
关键词 ddS中间件 动态发现 分布式系统 热备份
下载PDF
Analysis of the Role of D-Dimer,Interleukin-6,and Interleukin-18 in Differential Diagnosis of Pediatric Refractory Mycoplasma pneumoniae Pneumonia
20
作者 Yong Peng Aimin Li 《Journal of Clinical and Nursing Research》 2024年第7期118-122,共5页
Objective:To analyze the value of D-dimer(D-D),interleukin-6(IL-6),and IL-18 in the differential diagnosis of children with refractory Mycoplasma pneumoniae pneumonia(RMPP).Methods:The medical records of 92 children w... Objective:To analyze the value of D-dimer(D-D),interleukin-6(IL-6),and IL-18 in the differential diagnosis of children with refractory Mycoplasma pneumoniae pneumonia(RMPP).Methods:The medical records of 92 children with Mycoplasma pneumoniae pneumonia(MPP)treated in the hospital were selected for retrospective analysis from January 2023 to January 2024.After comprehensive examinations such as computed tomography examination of the chest,48 children with general Mycoplasma pneumoniae pneumonia(GMPP)were put in the GMPP group and 44 children with RMPP were grouped in the RMPP group.The IL-6,IL-18,and D-D levels were compared between the two groups,and the receiver operating characteristic(ROC)curves were plotted to analyze their value for differential diagnosis of RMPP.Results:The levels of IL-6,IL-18,and D-D in the RMPP group were higher than those in the GMPP group(P<0.05);the ROC curves showed that the specificity of the differential diagnosis of IL-6,IL-18,and D-D was higher,and their diagnostic value was significant.Conclusion:Determination of IL-6,IL-18,and D-D levels in children with MPP can further diagnose the children’s condition,which can help physicians formulate targeted treatment plans,and is of great significance to the improvement of the children’s condition,which is worthy of attention. 展开更多
关键词 Refractory Mycoplasma pneumoniae pneumonia d-dimer INTERLEUKIN-6 INTERLEUKIN-18 Differential diagnosis
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部