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Heterosis for water uptake by maize (Zea mays L.) roots under water deficit: responses at cellular, single-root and whole-root system levels

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Journal of Arid Land 2013年第2期5卷 255-265页

作者： XiaoFang liu SuiQi ZHANG lun SHAN State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau Institute of Soil and Water Conservation Chinese Academy of Sciences and Ministry of Water Resources Northwest A&F University Graduate University of Chinese Academy of Sciences

To examine the potential heterosis for water uptake by maize roots, the hydraulic properties of roots in the F1 hybrid （Hudan 4） were compared with those of its inbred parents （ 478 and Tian 4） at cellular, single-root and whole-root system levels under well-watered and water-deficit conditions. The cell hydraulic conductivity （Lpc） decreased under water deficit, but the Lpc of the F1 was higher than that of its inbred parents with or without stress from water deficit. Marked reductions in Lpc were observed following Hg2＋ treatment. The hydrostatic hydraulic conductivity of single roots （hydrostatic Lpsr） varied among genotypes under the two water treatments, with the highest in the F1 and the lowest in 478. Radial hydraulic conductivity （radial Lpsr） and axial hydraulic conductance （Lax） of the three genotypes varied similarly as Lpsr. The variations in hydraulic parameters were related to root anatomy. Radial Lpsr was negatively correlated with the ratio of cortex width to root diameter （R2=-0.77, P〈0.01）, whereas Lax was positively correlated with the diameter of the central xylem vessel （R2=0.75, P〈0.01） and the cross-sectional area of xylem vessels （R2=0.93, P〈0.01 ）. Hydraulic conductivity （Lpwr） and conductance （Lwr） of the whole-root system followed the same trend under the two water treatments, with the highest values in the F1. The results demonstrated that heterosis for water uptake by roots of the F1 occurred at cellular, single-root and whole-root system levels under well-watered and water-deficit conditions.

关键词： heterosis water uptake hydraulic conductivity water deficit maize

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Optimized beaconing rate control for vehicular Ad-hoc networks

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The Journal of China Universities of Posts and Telecommunications 2015年第6期22卷 10-17,50页

作者： Tang lun liu Yifu Chen Qianbin Key Laboratory of Mobile Communication Technology Chongqing University of Posts and Telecommunications

In vehicular Ad-hoc networks （VANETs）, beacon message is designed for the purpose of periodically broadcasting the status information （velocity, direction, etc.）, which enable neighbor awareness and support some safety applications. However, under high density scenarios, fixed rate beaconing can cause severe congestion and lower the deliver rate of beacons and other kinds of messages. In this paper, we describe beaconing rate control approach with an one-dimensional Markov model, and based on this, an optimized beacon rate control scheme is proposed which aims to mitigate the congestion and maximize the deliver efficiency of beaconing. Analytical and simulation results show that our proposed scheme can achieve higher adaptability and beaconing efficiency compared with other schemes in various environments.

关键词： VANETs IEEE 802.1 lp broadcast beacon rate control optimization model

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基础激励下裂纹梁结构疲劳寿命预测模型

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机械设计与制造 2024年第9期403卷 77-84页

作者：龙慧黄长征刘义伦李松柏韶关学院智能工程学院广东韶关512005 中南大学机电工程学院湖南长沙410083

为了发展基于模型的裂纹梁结构疲劳寿命预测方法,提出了一种新的三维裂纹梁单元刚度矩阵。基于该刚度矩阵,建立基础激励下裂纹梁结构的三维有限元模型。推导三维裂纹梁单元的应力强度因子,建立三维裂纹梁单元的疲劳裂纹扩展模型。采用... 详细信息

为了发展基于模型的裂纹梁结构疲劳寿命预测方法,提出了一种新的三维裂纹梁单元刚度矩阵。基于该刚度矩阵,建立基础激励下裂纹梁结构的三维有限元模型。推导三维裂纹梁单元的应力强度因子,建立三维裂纹梁单元的疲劳裂纹扩展模型。采用振动响应与裂纹扩展增量交互计算方法,计算循环载荷作用下裂纹梁结构的疲劳寿命。研究结果表明:裂纹梁结构寿命预测模型较好地体现了疲劳裂纹扩展寿命与基础激励参数、结构参数和裂纹参数之间的内在关系,反映了基础激励对裂纹梁结构疲劳寿命的影响。最后通过实验对模型进行了验证。

关键词：基础激励裂纹梁结构有限单元法疲劳寿命动力学模型裂纹扩展

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白鹤滩百万千瓦水轮发电机组转轮动应力特性研究

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水电能源科学 2024年第9期42卷 166-170页

作者：乔鹏董钟明周玉国张双全刘伦洪陈喜阳白鹤滩水力发电厂四川凉山615000 华中科技大学能源与动力工程学院湖北武汉430074 华中科技大学机械科学与工程学院湖北武汉430074

转轮是白鹤滩水电站百万千瓦水轮发电机组研发难度最大和制造难题最多的核心部件,为有效预防转轮裂纹,选择白鹤滩水电站右岸#12机组作为研究对象,探索百万千瓦水轮机转轮动应力测量方法,研究运行稳定性和转轮动应力特性,揭示机组转轮动... 详细信息

转轮是白鹤滩水电站百万千瓦水轮发电机组研发难度最大和制造难题最多的核心部件,为有效预防转轮裂纹,选择白鹤滩水电站右岸#12机组作为研究对象,探索百万千瓦水轮机转轮动应力测量方法,研究运行稳定性和转轮动应力特性,揭示机组转轮动应力真实分布规律,用于指导机组在合理运行区运行,延长叶片使用寿命,提高机组运行可靠性。白鹤滩水电站#12机组稳定性和动应力测试分析表明,机组机械部分制造和安装质量优良,运行稳定性表现优秀;转轮叶片动应力在全负荷范围内保持在较低状态,远低于材料的许用应力值,甩负荷等过渡过程产生的动应力幅值大于稳定工况动应力幅值;稳定工况下,转轮叶片动应力典型频率成分为1.785、42.84、0.45 Hz,这分别是机组转频、24倍转频和涡带频率,对应的动应力分量由蜗壳内非轴对称速度干扰叶片进口流动、活动导叶出口的不均匀流场干扰叶片进口流动和涡带尾水压力脉动引起。

关键词：百万千瓦水轮发电机组转轮动应力裂纹

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GENERATION METHOD FOR FIVE-AXIS NC SPIRAL TOOL PATH BASED ON PARAMETRIC SURFACE MAPPING

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Journal of Systems Science & Complexity 2013年第5期26卷 676-694页

作者： ZHOU Bo ZHAO Jibin liu Weijun LI lun Graduate University of the Chinese Academy of Sciences Shenyang Institute of Automation Shenyang Institute of Automation

A new spiral tool path generation algorithm for 5-axis high speed machining is proposed in this ***,the voltage contours are calculated to satisfy the machining parameters in the mapping parametric domain by means of the electrostatic field model of partial differential ***,the mapping rules are constructed and the machining trajectory is planned out in the standard parametric domain in order to map and generate the spiral trajectory in the corresponding parametric ***,this trajectory is mapped onto the parametric surface for the obtainment of the spiral tool *** spiral tool path can realize the machining of complicated parametric surface and trimmed surface without tool *** above-mentioned algorithm has been implemented in several simulations and validated successfully through the actual machining of a complicated *** results indicate that this method is superior to the existing machining methods to realize the high speed machining of the complicate-shaped cavity based on parametric surface and trimmed surface.

关键词： 5-axis NC machining mapping rule partial differential equations spiral tool path.

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Neutrophil-to-lymphocyte ratio compared to N-terminal pro-brain natriuretic peptide as a prognostic marker of adverse events in elderly patients with chronic heart failure

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Journal of Geriatric Cardiology 2017年第2期14卷 127-134页

作者： Wei YAN Rui-Jun LI Qian JIA yang MU Chun-Lei liu Kun-lun HE Department of Cardiology Chinese PLA General Hospital Beijing China School of Medicine Nankai University Tianjin China

Background The neutrophil-to-lymphocyte （N/L） ratio has been associated with poor prognosis in patients with heart failure, but it has not been compared with N-terminal pro-brain natriuretic peptide （NT-proBNP） in elderly patients with chronic heart failure （CHF）. We sought to make this comparison. Methods A total of 1355 elderly patients with CHF were analyzed. A multivariate logistic regression model was used to analyze the variables associated with atrial fibrillation （AF）. Cox regression analysis was used to assess the multivariable rela- tionship between the N/L ratio, NT-proBNP level, and subsequent major cardiovascular events （MCE）. Results In the multiple logistic regression analysis, the N/L ratio was demonstrated as a risk factor for AF in elderly patients with CHF [odds ratio （OR）： 1.079, 95% confi- dence interval （CI）： 1.027-1.134, P = 0.003]. The median follow-up period was 18 months. In a multivariable model using tertiles of both variables, the highest tertile of the N/L ratio was significantly associated with MCE [hazard ratio （HR）： 1.407, 95% CI： 1.098-1.802, P = 0.007] compared with the lowest tertile. Similarly, the highest NT-proBNP tertile was also significantly associated with MCE （HR： 1.461, 95% CI： 1.104-1.934, P- 0.008）. Conclusions In elderly patients with CHF, the N/L ratio is one of the important risk factors for AF and it is an inexpensive and readily available marker with similar independent prognostic power to NT-proBNP. The risk of MCE increases 1.407-fold when the N/L ratio is elevated to the highest tertile.

关键词： Atrial fibrillation Chronic heart failure Elderly patients Neutrophil-to-lymphocyte ratio N-terminal pro-brain natriureticpeptide

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An Error Equivalent Model of Revolute Joints with Clearances for Antenna Pointing Mechanisms

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Chinese Journal of Mechanical Engineering 2018年第2期31卷 97-105页

作者： Quan liu Sheng-Nan Lu Xi-lun Ding School of Mechanical Engineering and Automation Beihang University

Joint clearances in antenna pointing mechanisms lead to uncertainty in function deviation. Current studies mainly focus on radial clearance of revolute joints, while axial clearance has rarely been taken into consideration. In fact, own?ing to errors from machining and assembly, thermal deformation and so forth, practically, axial clearance is inevitable in the joint. In this study, an error equivalent model(EEM) of revolute joints is proposed with considering both radial and axial clearances. Compared to the planar model of revolute joints only considering radial clearance, the journal motion inside the bearing is more abundant and matches the reality better in the EEM. The model is also extended for analyzing the error distribution of a spatial dual?axis("X–Y" type) antenna pointing mechanism of Spot?beam antennas which especially demand a high pointing accuracy. Three case studies are performed which illustrates the internal relation between radial clearance and axial clearance. It is found that when the axial clearance is big enough, the physical journal can freely realize both translational motion and rotational motion. While if the axial clearance is limited, the motion of the physical journal will be restricted. Analysis results indicate that the consideration of both radial and axial clearances in the revolute joint describes the journal motion inside the bearing more precise. To further validate the proposed model, a model of the EEM is designed and fabricated. Some suggestions on the design of revolute joints are also provided.

关键词： Error modeling Joint clearances Antenna pointing mechanism Radial clearance Axial clearance

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Influences of the diameter of the balance hole on the flow characteristics in the hub cavity of the centrifugal pump

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Journal of Hydrodynamics 2019年第5期31卷 1060-1068页

作者： Wei Dong Wu-li Chu Zai-lun liu College of Water Resources and Architectural Engineering Northwest A&F UniversityYangling 712100China School of Power and Energy Northwestern Polytechnical UniversityXi'an 710129China College of Energy and Power Engineering Lanzhou University of TechnologyLanzhou 730050China

The diameter of the impeller balance hole in a centrifugal pump is closely related to axial ***,to select the appropriate diameter of a balance hole is crucial for balancing the axial force of the centrifugal *** the validation of the CFD method and the grids independence study,the characteristics of flow in the hub cavity have been analyzed in 4 cases with different diameters of balance *** leakage rate of the liquid in the hub cavity of the centrifugal pump is calculated and compared with the test *** to the research,when no balance hole exists,the distribution of liquid velocity in the core area of the hub cavity exhibits axial symmetry,and the circumferential velocity component is approximately 0.4 times of the impeller's rotational *** the balance hole exists,the distribution of liquid velocity in the hub cavity does not exhibit axial symmetry,and the circumferential velocity component is larger than 0.4 times of the impeller's rotational *** radial leakage velocity on the turbulent boundary layer of the pump cover will increase with the increasing diameter of the balance hole.

关键词： Centrifugal pump balance hole hub cavity circumferential velocity component radial velocity component

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CH_4 emission and conversion from A^2O and SBR processes in full-scale wastewater treatment plants

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Journal of Environmental Sciences 2014年第1期26卷 224-230页

作者： Yan liu Xiang Cheng Xiaoxiu lun Dezhi Sun College of Environmental Science and Engineering Beijing Forestry University

Wastewater treatment systems are important anthropogenic sources of CH4 emission. A full-scale experiment was carried out to monitor the CH4 emission from anoxic/anaerobic/oxic process （A2O） and sequencing batch reactor （SBR） wastewater treatment plants （WWTPs） for one year from May 2011 to April 2012. The main emission unit of the A2O process was an oxic tank, accounting for 76.2% of CH4 emissions; the main emission unit of the SBR process was the feeding and aeration phase, accounting for 99.5% of CH4 emissions. CH4 can be produced in the anaerobic condition, such as in the primary settling tank and anaerobic tank of the A2O process. While CH4 can be consumed in anoxic denitrification or the aeration condition, such as in the anoxic tank and oxic tank of the A2O process and the feeding and aeration phase of the SBR process. The CH4 emission flux and the dissolved CH4 concentration rapidly decreased in the oxic tank of the A2O process. These metrics increased during the first half of the phase and then decreased during the latter half of the phase in the feeding and aeration phase of the SBR process. The CH4 oxidation rate ranged from 32.47% to 89.52% （mean： 67.96%） in the A2O process and from 12.65% to 88.31% （mean： 47.62%） in the SBR process. The mean CH4 emission factors were 0.182 g/ton of wastewater and 24.75 g CH4/（***） for the A2O process, and 0.457 g/ton of wastewater and 36.55 g CH4/（***） for the SBR process.

关键词： CH4 emission production and consumption wastewater treatment plant A2O SBR

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股骨颈固定系统固定与空心螺钉内固定治疗股骨颈骨折的疗效观察

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临床和实验医学杂志 2024年第8期23卷 838-841页

作者：吴聪刘伦贾全忠四川绵阳四0四医院骨科四川绵阳621000

目的观察股骨颈固定系统(FNS)固定与空心螺钉(CCS)内固定治疗股骨颈骨折的疗效。方法回顾性分析2020年2月至2023年1月四川绵阳四0四医院骨伤外科收治的股骨颈骨折患者的临床资料,按照内固定方式的不同分为FNS组(n=40)和CCS组(n=40)。... 详细信息

目的观察股骨颈固定系统(FNS)固定与空心螺钉(CCS)内固定治疗股骨颈骨折的疗效。方法回顾性分析2020年2月至2023年1月四川绵阳四0四医院骨伤外科收治的股骨颈骨折患者的临床资料,按照内固定方式的不同分为FNS组(n=40)和CCS组(n=40)。两组术前常规治疗及术后处理相同,FNS组实施FNS内固定治疗,CCS组实施CCS内固定治疗。两组均随访至术后6个月,比较两组手术相关指标(手术时间、术中出血量、切口长度、术中透视次数、术后完全负重时间及住院时间)、骨折复位质量(Garden对线指数)、骨折愈合时间、髋关节功能恢复(Harris量表),并记录治疗及随访期间并发症发生情况。结果 FNS组的手术时间、切口长度及术后完全负重时间分别为(47.52±9.43) min、(4.33±0.41) cm、(11.13±1.88)周,均短于CCS组[(67.45±12.84) min、(3.42±0.38) cm、(14.67±1.74)周],术中出血量及术中透视次数分别为(26.47±7.56) mL、(12.72±1.83)次,均少于CCS组[(43.58±10.62) mL、(17.41±2.64)次],差异均有统计学意义(P0.05)。术后6个月,FNS组Garden对线指数分型优于CCS组,差异有统计学意义(P0.05)。术后6个月,FNS组股骨颈缩短程度优于CCS组,差异有统计学意义(P0.05)。结论 FNS与CCS均对股骨颈骨折有较好的疗效,但与CCS相比,FNS可进一步缩短手术时间,减少术中出血量,使患者尽快完全负重,并能明显改善骨折复位质量及髋关节功能。

关键词：股骨颈骨折内固定术股骨颈内固定系统空心螺钉髋关节功能

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