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1.
针对自制垂直引入式飞行时间质谱仪(orthogonal extraction time-of-flight mass spectrometer, O-TOFMS)的需要,运用直接数字频率合成 (direct digital frequency synthesis,DDS)技术,研制了射频四极杆的高压射频驱动电路装置。该驱动器频率可调范围为0.5~2 MHz,幅度最高达到1 000 Vp-p。该射频四极杆驱动器(radio frequency quadrupole driver,RFQ Driver)可用于分子离子反应器(molecule ion reactor,MIR)和RFQ驱动,其结构简洁、成本低、性能稳定可靠。 相似文献
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光电容积描记图(PPG)是一种利用光学技术无创检测人体心血管脉搏波的方法。PPG信号来源于MIMIC数据库,它含有许多生理信息。本文提出了将集合经验模态分解(EEMD)、倒谱、快速傅里叶变化和过零点检测相结合的方法,从PPG中可靠地估算脉搏率(PR)、心率(HR)和呼吸频率(RR)。首先,将PPG信号通过EEMD分解为有限个固有模态函数(IMF)。因为EEMD有自适应滤波特性,所以估算不同的生理参数时,可以用不同的IMF分量来重构信号。其次,估算脉搏率时,舍去低频含有伪迹的IMF,再通过过零点检测可以得到瞬时脉搏率。然后,估算心率时,用1 Hz~1.67 Hz(60次/分钟~100次/分钟)的IMF来重构信号,再求倒谱,选取反映心脏活动的频带来得到心率。最后,估算呼吸率时,用0.05 Hz~0.75 Hz(3次/分钟~45次/分钟)的IMF来重构信号,然后对呼吸信号求快速傅里叶变化得到频谱图,寻找频谱图中的峰值得到呼吸率。对来自MIMIC数据库的53个成人PPG信号进行了仿真。仿真结果表明使用该综合信号处理方法提取的生理参数与实际生理参数一致,且该方法有运算量小,精确度高的优点(误差不超过1.17%)。 相似文献
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建立了二苯甲烷二异氰酸酯(MDI)的超高效液相色谱-串联质谱(UPLC-MS/MS)联用的分析方法。实验用甲醇作衍生试剂,将二苯甲烷二异氰酸酯衍生成二苯甲烷二氨基甲酸甲酯(MDC),通过测定二苯甲烷二氨基甲酸甲酯来确定二苯甲烷二异氰酸酯的含量。实验采用Waters Acquity BEH C18超高效液相色谱柱,甲醇-0.1%甲酸作为梯度洗脱液,二苯甲烷二氨基甲酸甲酯在1.5 min内与其他化合物进行完全分离,经四极杆质谱选择离子监测模式检测。线性范围为2~100 μg/L,检出限为1 μg/L,相关系数0.999 4。考察了水、甲酸、甲酸铵流动相体系,以及进样量大小对样品的分离效果,发现甲酸流动相体系的分离效果优于其他两种流动相体系,同时发现在进样量大时出现平头峰。并且在优化条件下,对实际样品中游离的二苯甲烷二异氰酸酯进行了测定。 相似文献
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Y.L. Tu S.Q. Xie J.J. Kam 《The International Journal of Advanced Manufacturing Technology》2006,29(5):499-510
To shorten the product development cycle time and reduce the cost at the same time, which is very critical for the survival
of those small and mid-sized one-of-a-kind production (SMOKP) companies, various computer communication, simulation and computer
aided engineering and management techniques have been widely used in these SMOKP companies. However, according to our study,
the applications of these advanced computer technologies in these SMOKP companies are lack of system integration and synergy,
which result in communication errors, reworks, duplications and hence a longer product development lead time and a higher
cost. To solve this problem, an inter/intranet based computer aided rapid product development system is presented in this
paper. This system consists of a number of inter/intranet based computer models or sub-systems for supporting rapid development
of a one-of-a-kind product. It also employs a novel concurrent product development strategy called “prototype based incremental
product development strategy” and an integrated product data structure called “product production structure”. Some industrial
implementations of the proposed system, product development strategy and product data structure are also reported in the paper. 相似文献
5.
全面准确地标定与测试是开发车辆电子稳定控制(electronic stability control,ESC)系统的关键环节。车辆控制过程是典型的强非线性系统,建立精确的车辆模型比较困难,驾驶员模型也很难准确模拟紧急工况下驾驶员的真实反应。在仿真系统中将难以精确建模的液压制动系统、ESC压力调节单元、转向及电子节气门装置采用真实硬件,并在试验平台中嵌入真实驾驶员,基于Matlab/Simulink/dSPACE环境和车辆动力学软件veDYNA,开发硬件在环(hardware-in-the-loop,HIL)和驾驶员在环(driver-in-the-loop,DIL)的仿真试验平台,并在此平台上对所设计的ESC系统进行仿真试验研究。试验结果表明,所设计的DIL/HIL仿真平台可以大幅提高ESC系统的开发效率和测试准确性。 相似文献
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Yang Sun Yongda Yan Yingchun Liang Zhenjiang Hu Xuesen Zhao Tao Sun Shen Dong 《Scanning》2013,35(5):308-315
Nanobundles patterns can be formed on the surface of most thermoplastic polymers when the atomic force microscope (AFM)‐based nanomechanical machining method is employed to scratch their surfaces. Such patterns are reviewed as three‐dimensional sine‐wave structures. In the present study, the single‐line scratch test is used firstly to study different removal states of the polystyrene (PS) polymer with different molecular weights (MWs). Effects of the scratching direction and the scratching velocity on deformation of the PS film and the state of the removed materials are also investigated. Single‐wear box test is then employed to study the possibility of forming bundle structures on PS films with different MWs. The experimental results show that the state between the tip and the sample plays a key role in the nano machining process. If the contact radius between the AFM tip and the polymer surface is larger than the chain end‐to‐end distance, it is designated as the “cutting” state that means the area of both side ridges is less than the area of the groove and materials are removed. If the contact radius is less than the chain end‐to‐end distance, it is designated as the “plowing” state that means the area of both side ridges is larger than the area of the groove and no materials are removed at all. For the perfect bundles formation on the PS film, the plowing state is ideal condition for the larger MW polymers because of the chains’ entanglement. SCANNING 35:308‐315, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
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Y. L. Tu S. Q. Xie J. J. Kam 《The International Journal of Advanced Manufacturing Technology》2006,29(5-6):499-510
To shorten the product development cycle time and reduce the cost at the same time, which is very critical for the survival
of those small and mid-sized one-of-a-kind production (SMOKP) companies, various computer communication, simulation and computer
aided engineering and management techniques have been widely used in these SMOKP companies. However, according to our study,
the applications of these advanced computer technologies in these SMOKP companies are lack of system integration and synergy,
which result in communication errors, reworks, duplications and hence a longer product development lead time and a higher
cost. To solve this problem, an inter/intranet based computer aided rapid product development system is presented in this
paper. This system consists of a number of inter/intranet based computer models or subsystems for supporting rapid development
of a one-of-a-kind product. It also employs a novel concurrent product development strategy called “prototype based incremental
product development strategy” and an integrated product data structure called “product production structure”. Some industrial
implementations of the proposed system, product development strategy and product data structure are also reported in the paper. 相似文献
8.
R. K. Dutta S. Paul A. B. Chattopadhyay 《The International Journal of Advanced Manufacturing Technology》2006,31(5-6):434-442
Face milling is a process predominantly affected by dynamic variation of cutting forces, thermo-mechanical shocks and vibration leading to catastrophic tool failure along with gradual wear of the inserts. Keeping in view the industrial importance of this process, it is necessary to devise suitable methods to predict in advance the onset of tool failure without grossly impairing the machining set-up and the job. Hence, the applicability of back propagation neural network with delta bar delta learning rule for faster convergence has been studied with the above objective. The multi sensor based tool condition monitoring strategy shows that the learning rate adaptation scheme combined with the selection of suitable process parameters drastically reduces the training time of the artificial neural network without dispensing with the prediction accuracy. 相似文献
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A method developed to participate the pilot study of international comparison CCQM-P67 was introduced. Isotope dilution mass spectrometry (IDMS) was used in the detection of five PCB congeners in freeze-dried muscle tissue. Soxhlet Extraction is used for extraction of mussel, duplicate clean-up of GPS and SPE column were used, C-13 labeled PCB congeners were added as internal standard to avoid the error from sample preparation and diction. High resolution Mass spectrometer was used to give good result of detection. 相似文献
11.
自主致密局部特征尺度分解方法通过确定待分解信号的最小信号极值尺度以度量其信号尺度的方式,采用新增伪极值点均匀化信号尺度的方法,可有效抑制局部特征尺度分解的模态混叠。在广义局部频率解调的基础上,基于强局部加权回归和伪端点方法的原理,提出了改进的广义局部频率解调方法。该方法通过分析广义局部频率和广义局部幅值突变情况,在广义局部频率和广义局部幅值中插入伪端点,并采用强局部加权回归对新增伪端点后的广义局部频率和广义局部幅值进行分段平滑处理,可有效改进广义局部频率和广义局部幅值曲线的平滑效果。采用仿真信号将自主致密局部特征尺度分解与局部特征尺度分解、经验模态分解进行对比,同时将改进的广义局部频率解调与希尔伯特变换、广义局部频率解调进行对比,结果证实了自主致密局部特征尺度分解和改进的广义局部频率解调方法的有效性。对转子碰摩故障实验数据的对比分析结果,进一步验证了该方法的有效性和实用性。 相似文献
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在设计优化中,确定性优化由于没有考虑输入量的不确定性,其优化结果可能不可靠(不安全),因此基于可靠性的设计优化(reliability-based design optimization,RBDO)得到关注.然而可靠性设计优化计算量大,尤其对于高维问题.基于此,提出一种新方法--改进拉丁超立方体取样(Latin hyp... 相似文献
13.
《Measurement》2016
To investigate on the crystalline structure of AISI M2 steel by using tungsten–thorium electrode in electrical discharge machining (EDM) process was studied. Furthermore, the investigation were carried out for finding the value of material removal rate (MRR), electrode wear rate (EWR) and surface roughness (SR) of tool steel material depending upon three variable input process parameters. On the basis of weight loss, the value of MRR and EWR were calculated at optimized process parameter. Subsequently, surface topography of the processed material were examined through different characterization techniques like scanning electron microscopy (SEM), Optical surface profiler (OSP) and Atomic force microscopy (AFM), respectively. In XRD study, broadening of the peak was observed which confirmed the change in material properties due to the homogeneous dispersion of the particles inside the matrix. Lowest surface roughness and MRR of 0.001208 mg/min was obtained. Minimum surface roughness was obtained 1.12 μm and 2.18427 nm by OSP and AFM study, respectively. Also, minimum EWR was found as 0.013986 mg/min. 相似文献
14.
目的:探讨甲胎蛋白(AFP)、糖类抗原199(CA199)、谷氨酰转肽酶(GGT)和碱性磷酸酶(ALP)单独或联合检测对原发性肝癌(PHC)的早期诊断价值。方法:本研究为回顾性研究,筛选2016年-2019年本院87例原发性肝癌(PHC)患者、105例慢性乙肝患者及104例健康志愿者,收集不同组首次入院和体检外周血检测数据和其他临床资料。比较各血清指标在组间差异性,分析了血清学指标与入组PHC临床分期和病理分型的相关性,进一步利用ROC曲线法分析血清指标单项与联合诊断的灵敏度、特异度。结果:AFP、CA199、GGT、ALP检测均值在PHC组均明显高于慢乙肝组和健康体检组。AFP阳性检测值与PHC临床分期(r=0.9536)和病理分型(r=0.525)呈正相关性。AFP诊断PHC灵敏度和特异性分别为60.87%和77.97%、精准度AUC为0.726。联合四项指标检测灵敏度、特异度和AUC分别为75.36%、65.64%、0.806。结论:AFP、CA199、GGT、ALP四项指标联合检测可提高原发性肝癌早期诊断的准确率,操作性强且易于推广。 相似文献
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文章首先分析了移动智能体的主要特点,简要介绍了UML定义,分析UML建模的基本思想,利用UML描述和分析了基于移动智能体的入侵检测系统。 相似文献
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介绍了网络虚拟现实建模语言(VRML),VRML具有动态对象描述和超链接、通用性、扩展性、易实现性等特点。VRML浏览器和生成VRML文件的工具广泛使用于多种平台的计算机,是虚拟制造VM与虚拟设计中的网络虚拟现实技术的基础。 相似文献
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Nowadays validation of anti-lock braking systems(ABS) relies mainly on a large amount of road tests.An alternative means with higher efficiency is employing the hardware-in-the-loop simulation(HILS) system to substitute part of road tests for designing,testing,and tuning electronic control units(ECUs) of ABS.Most HILS systems for ABS use expensive digital signal processor hardware and special purpose software,and some fail-safe functions with regard to wheel speeds cannot be evaluated since artificial wheel speed signals are usually provided.In this paper,a low-cost ABS HILS test bench is developed and used for validating the anti-lock braking performance and tuning control parameters of ABS controllers.Another important merit of the proposed test bench is that it can comprehensively evaluate the fail-safe functions with regard to wheel speed signals since real tone rings and sensors are integrated in the bench.A 5-DOF vehicle model with consideration of longitudinal load transfer is used to calculate tire forces,wheel speeds and vehicle speed.Each of the four real-time wheel speed signal generators consists of a servo motor plus a ring gear,which has sufficient dynamic response ability to emulate the rapid changes of the wheel speeds under strict braking conditions of very slippery roads.The simulation of braking tests under different road adhesion coefficients using the HILS test bench is run,and results show that it can evaluate the anti-lock braking performance of ABS and partly the fail-safe functions.This HILS system can also be used in such applications as durability test,benchmarking and comparison between different ECUs.The test bench developed not only has a relatively low cost,but also can be used to validate the wheel speed-related ECU design and all its fail-safe functions,and a rapid testing and proving platform with a high efficiency for research and development of the automotive ABS is therefore provided. 相似文献