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Search Results: 1 - 10 of 33399 matches for " 江志农 "
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内燃机工况对气缸敲击振动的影响探究
任中睿,宋力喆,志农
- , 2018, DOI: 10.13543/j.bhxbzr.2018.01.010
Abstract: 为了更深入地了解内燃机工况与敲缸振动的关系,通过建立数学模型和仿真计算验证了内燃机气缸敲击振动峰峰值与发动机转速的非线性关系及与发动机负载的线性关系。内燃机扭矩平衡方程包含了发动机转速、负载和动力扭矩等信息,通过动力扭矩与活塞所受侧推力之间的几何关系将活塞径向加速度引入扭矩平衡方程,以活塞径向加速度在燃烧膨胀冲程上止点处的冲击信号峰峰值来表征敲缸振动的剧烈程度,整理后的数学模型显示加速度振动与内燃机转速为非线性关系、与负载为线性关系,经AVL-EXCITE仿真计算验证了数学模型的正确性。研究结果可以帮助在线监测系统和故障诊断人员根据敲缸振动对转速和负载的敏感性判断是否发生敲缸,为敲缸故障预警提供参考依据。
Abstract:The nonlinearity of piston-slap vibration peak-to-peak values as a function of engine speed as well as their linearity as a function of load have been verified using mathematical modeling and simulations. Engine speed, load and power torque were included in the balanced equation for internal combustion engine torque, in which piston radial acceleration refers to the geometrical relationship between power torque and piston side thrust. The severity of vibrations was formulated using the peak-to-peak values of the impulse signal of the radial acceleration around the fire phase. An integrated mathematical model confirmed both the nonlinearity between speed and vibration, and the linearity between load and vibration, and these results were verified using simulations with AVL-EXCITE. Given the dependence of piston-slap vibration on engine speed and load, an on-line monitoring system and on-site staff are able to diagnose piston-slap faults more accurately, allowing a piston-slap alarm to be implemented.
人工自愈与动力机械振动故障靶向抑制
高金吉,王维民,何立东,志农
- , 2018, DOI: 10.13543/j.bhxbzr.2018.05.016
Abstract: 人工自愈是在故障机理和风险分析的基础上,通过仿生设计赋予机器自发作用的维持健康状态的能力,从而使机器储存、补充和调动自愈力以维持机体的健康状态。透平压缩机、发电机组和航空发动机等动力机械是工业和国防的心脏设备,一旦发生故障将导致事故和巨大损失,在运行中通过自监测、自诊断和主动控制来抑制故障的发生以实现自愈化,是机器向高级智能阶段发展研究中的一个重要方向。本文总结了北京化工大学诊断与自愈工程(DSE)研究中心在人工自愈与动力机械振动故障靶向抑制方面的主要研究工作及成果,并以转子轴系不平衡和压缩机转子失稳振动为例,证明了靶向抑制方法的有效性。以上成果可为自主开发具有自愈功能的智能动力机械提供科学依据。
Abstract:Based on the mechanism of fault and risk analysis as well as bionics design, artificial self-recovery is designed to provide a machine with the ability to maintain a healthy state spontaneously. In this way, the machine can store, replenish and mobilize self-recovery power to maintain its healthly state. Power machines such as turbo-compressors, generators, and aero-engines are key equipment in industry and defense. Faults in these machines, which may even lead to accidents can result in significant losses. Therefore, developing machines with advanced intelligence involving self-monitoring, self-diagnosis and active control to suppress faults, resulting in self-recovery during operation, has become an important research direction. The paper summarizes the research on artificial self-recovery and target suppression of power machine vibration faults carried out in the Diagnosis and Self-recovery Engineering Research Center (DSE) at Beijing University of Chemical Technology (BUCT). The experimental results cover the unbalance of a multi-rotor shafting system, the mechanism of instability, and the effectiveness of the targeted suppression method. These achievements can provide a scientific basis for the development of intelligent turbomachinery with self-recovery functionality.
基于CART决策树的柴油机故障诊断方法研究
志农,魏东海,王磊,赵志超,茆志伟,张进杰
- , 2018, DOI: 10.13543/j.bhxbzr.2018.04.013
Abstract: 采用一种自适应局部有效值(RMS)计算方法提取柴油机缸盖振动信号时域特征,结合分类回归树(CART)算法建立故障分类模型并进行柴油机的状态识别。通过实验获取柴油机失火和撞缸两种故障工况及正常工况下的振动数据,计算出原始信号的局部RMS后,根据自适应阈值确定点火冲击区域和非点火上止点冲击区域提取局部特征,最后将特征输入CART算法中构建分类模型来验证所提取特征的有效性。结果表明:柴油机在3种状态下的识别率均达到100%,基于CART算法和局部特征提取的方法能够有效诊断柴油机故障。
Abstract:An adaptive local root mean square (RMS) calculation method has been used to extract the time-domain characteristics of a diesel engine cylinder head vibration signal. The classification model of the diesel engine was established based on the classification and regression tree (CART) algorithm. The vibration data for diesel engine misfiring, crashing cylinders and the normal operating conditions were obtained through experiments. After calculating the local RMS of the original signal, the local characteristics were extracted based on the self-adaptive thresholds to determine the ignition impact area and non-ignition top dead center impact area. Finally, these features were input into the CART algorithm to build a classification model in order to verify the validity of the extracted features. The results show that the recognition rate of the diesel engine reaches 100% in all three states. Thus the CART algorithm and local feature extraction method can effectively diagnose diesel engine faults.
基于瞬时转速信号的柴油机角域转换方法
范正天,尚彦龙,张译丹,茆志伟,志农
- , 2017, DOI: 10.13543/j.bhxbzr.2017.06.011
Abstract: 针对往复机械故障分析诊断中通过平均转速等间隔划分角度的方法诊断效果不精确的问题,提出了一种利用瞬时转速对柴油机时域信号进行角域转换的方法。分析了转速波动较大工况下平均转速等角度划分方法中影响相位偏差产生的主要因素,根据转速波动量的大小以及预期的角域精度范围设定阈值参数,再通过该阈值实现角域转换方法的自动选择。研究结果表明,在转速波动工况下采用瞬时转速对时域信号进行角域转换能够有效避免相位偏差,为基于角域的柴油机故障诊断奠定基础。
Abstract:In the fault diagnosis of reciprocating machinery, the traditional fault diagnosis method involving dividing the angle into equal intervals using the average rotational speed is inaccurate. A method of using the instantaneous rotational speed to transform the time-domain signal of a diesel engine into the angle-domain has been developed in this work. The main factors influencing the phase deviation in the method of the angular division of the average rotational speed under the condition of large rotational speed fluctuation are discussed, and the threshold parameter set according to the magnitude of the speed fluctuation rate and the expected angle-domain accuracy range. It is possible to automatically determine which method should be selected to perform the angle-domain conversion based on the threshold parameter. The results showed that phase deviation can be avoided by using the instantaneous rotation speed to transform the time-domain signal into the angle-domain under the conditions of speed fluctuation, which provides a basis for the fault diagnosis of diesel engines based on the angle-domain.
单侧完全性唇裂鼻底修复的临床研究进展
Clinical research progress on nasal floor repair of unilateral complete cleft lip

李海鹏,王予,宁文杰,志农,郭美玲
- , 2016, DOI: 10.7518/gjkq.2016.01.023
Abstract: 摘要:
单侧完全性唇裂裂隙侧上颌骨与前颌骨分离,健侧前颌骨前端向健侧旋转,患侧上颌骨发育不足和外移,加重了患侧鼻孔扁平、鼻底过宽、鼻翼塌陷、鼻翼基部外旋和下沉畸形。大部分单侧完全性唇裂皆伴牙槽突裂及腭裂,鼻底完全消失。单侧完全性唇裂鼻底修复有单侧完全性唇裂术前正畸治疗和单侧完全性唇裂鼻底修复的手术治疗。术前正畸可缩小鼻底裂隙间隙,缩短手术时间,手术方法简单。后者有旋转推进法:手术操作简单,术中、术后出血少,术后早期渡过平稳;唇裂裂缘黏膜瓣修复:在修复鼻底和恢复鼻底形态的同时,消灭了所有裸露创面,保留了所有可利用的组织,操作进一步简化,手术时间短,术中、术后出血少。下鼻甲黏膜瓣修复完全性唇裂鼻底裂隙:可有效地增加组织量、减少术区张力、保证伤口愈合、减少并发症,安全的闭合鼻底。术前的正畸治疗在中国还处于积累和总结经验的阶段,治疗效果还不稳定;因此,需要人们不断去探索寻找新的突破口,以弥补传统整复方法的不足。
Abstract:
中图分类号
杨树人工林生态系统立地质量因子的定量排序与评价
志农
应用生态学报 , 1992,
Abstract: 从系统论的观点出发,运用多元数理统计法,系统地辩识和评价了长江中游平原地区黑杨派南方型无性系(ⅰ-69杨,ⅰ-72杨)主要立地因子。结果表明,土壤有效水分是主要的综合立地因子,其对林分优势高生长的贡献率为44.56%(ⅰ-69杨)和34.09%(ⅰ-72杨);其次是物理性状和通气条件,各占24%左右;土壤养分贡献率最低,仅10%左右。主要立地子因子包括水淹程度、微地形、地下水位、经营程度、土壤质地、土壤结构和ph值,累积贡献率达到90%以上。文中最后编制了具有数量化立地指数表和地位级表双重功能的立地因子贡献值表。
新疆典型土类路基干压实试验
志农, 金昌宁
中国公路学报 , 2007,
Abstract: ?针对新疆很多地区干旱缺水、路基压实困难的现状,选择了3种典型土类(砾石土、风积沙、粉土)系统地进行了粒度分析、击实特性、动态特性、沉降特性等试验;在此基础上修筑了相应的试验路段,进行了3种典型土类的路基干压实施工工艺及路用性能试验研究。试验研究及工程实践结果表明:对于砾石土及风积沙,采用干压实施工工艺修筑路基是完全可行的;对于粉土,在采取隔断措施后,可在较低含水量条件下进行路基压实。
婺源黄喉噪鹛(Garrulaxgalbanuscourtoisi)
何芬奇,志农
动物学杂志 , 2002,
Abstract:
电力负荷特性的在线测辨——模型及辨识
鞠平卫志农
电力系统自动化 , 1992,
Abstract: 利用变电站可测到的波动信息在线辨识负荷特性是一种可取的办法,这可以从根本上解决负荷特性的时变性问题。本文提出了一种新的在线测辨原理:先根据在线采集的数据辨识得到动态模型,然后再由动态模型获取静态特性参数。文中提出了新的PQ耦合动态模型,然后简单介绍并比较了三种参数辨识方法;最小二乘法、辅助变量法及卡尔曼滤波法。
电力负荷特性在线测辨——硬件、软件及功能
志农,鞠平
电力系统自动化 , 1993,
Abstract: 文献[1]中提出了负荷特性在线测辨的新方法,文献[2]中给出了各种动态模型之间的转换关系及由动态模型获取静态模型的公式,本文介绍了电力负荷特性在线测辨装置的硬件、软件及功能,数据采集应用了直接交流采样的处理方法。试验表明该装置性能良好。
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