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1.
Assessing the dynamics of heart rate fluctuations can provide valuable information about heart status. In this study, regularity of heart rate variability （HRV） of heart failure patients and healthy persons using the concept of singular value decomposition entropy （SvdEn） is analyzed. SvdEn is calculated from the time series using normalized singular values. The advantage of this method is its simplicity and fast computation. It enables analysis of very short and non-stationary data sets. The results show that SvdEn of patients with congestive heart failure （CHF） shows a low value （SvdEn： 0.056±0.006, p 〈 0.01） which can be completely separated from healthy subjects. In addition, differences of SvdEn values between day and night are found for the healthy groups. SvdEn decreases with age. The lower the SvdEn values, the higher the risk of heart disease. Moreover, SvdEn is associated with the energy of heart rhythm. The results show that using SvdEn for discriminating HRV in different physiological states for clinical applications is feasible and simple. 相似文献
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文中探讨了模拟偏差对自助法均值估计的影响.首先,从分布N（1,12）中产生样本数据,利用自助法,得到自助法均值的估计.然后讨论了样本数据均值和总体分布均值的偏差对自助法估计的影响.结果表明,当偏差的绝对值小于等于0.54时,模拟结果较好,当偏差的绝对值大于等于0.56时,模拟结果很差. 相似文献
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Characterizations of PSD Fractal of Porous Medium 总被引：1，自引：0，他引：1
Fractalisatermusedtodescribegeometricalobjectsthatareinvariantuponthechangeoflengthscale .Manyfrac talcharactersofscaleinvarianceonporousmediumshavebeeninvestigatedduringthepastdecades[1] .Particle sizedistribution (PSD)isafundamentalpropertyofporousmedi ums.PSDofporousmediumsiscommonlyreportedintermsofthepercentagesofvariousparticle sizeintervalsandhasusuallybeenfoundtoobeypowerscalingofthetype[2 ] N(≥d)∝d-Dp (1)whereN(≥d)isthenumberofparticlediameterlargerthanorequaltod ,andthepow… 相似文献
5.
杨学锋 《实验室研究与探索》2010,29(1)
提出一种利用基于声卡的虚拟仪器研究声拍和和测量拍频的方法,仪器由装有V0.94软件的PC、扬声器和话筒组成;计算机的虚拟信号发生器产生2路频率相近的信号,通过Lineout接口输出,并分别连接至2个扬声器作为声源;驻极体式话筒作为声音传感器通过M ic接口,输入到计算机,通过虚拟示波器观察两声源叠加后产生的拍波形;根据每格采样时间,从拍波形图测量2个同一侧相邻峰值点对应的时间,从而得到振声信号的拍频;虚拟仪器的FET功能用来对拍信号进行频谱分析。实验现象形象、直观、清晰,操作简便,既可作为演示性实验,又可定量测定拍频,改变了传统实验无法定量分析的缺陷,同时还可对声拍信号逆向进行FET频谱分析。1台计算机同时实现了2台信号发生器、1台数字存储示波器和1台频谱分析仪的功能。 相似文献
6.
加工中心MTBF值的点估计与区间估计 总被引：2，自引：0，他引：2
应用基于截尾数据的似然函数理论和Weibull分布下的似然比方法,对加工中心有替换定时截尾试验数据分别进行了加工中心平均故障时间间隔(MTBF)值的点估计与区间估计。根据似然函数的重要引理,用迭代方法进行了Weibull模型两个参数的区间估计,并进行了MTBF值的区间估计。本研究解决了加工中心可靠性评估工作中的难题。 相似文献
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针对许多设计者存在错误使用快速傅里叶变换计算△Σ调制器输出信号信噪比的问题,在分析△Σ调制器工作原理和推导计算△Σ调制器信噪比理论模型的基础之上,详细地阐述了使用快速傅里叶变换计算△Σ调制器信噪比和绘制其功率谱密度的过程。以二阶△Σ调制器为例,在MATLAB和Simulink环境中完成了信噪比的计算和功率谱密度的绘制,实验结果证明了所述方法的正确性,对正确设计△Σ调制器具有重要的实际应用价值。 相似文献
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高速磁浮轨道不平顺测试及分析 总被引：2，自引：0，他引：2
研究目的：提出高速磁浮轨道不平顺处理方法,分析不平顺特征,拟合形成轨道谱,为线路卒问维护提供参考。创新要点：实现了对高速磁浮轨道不平顺的提取,确定了轨道谱参数。研究方法：基于惯性基准法,运用数字信号处理方法实现对轨道不平顺的提取,采用最小二乘法拟合得剑定子向和导向面七参数轨道谱。重要结论：定子面和导向面分别在5-100m和10-100m波长范围内平顺性状态较好,由功能件安装等引起的1-5m和1—10m波长范围内的偏差应严格控制。 相似文献
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脉冲形状甄别技术（PSD）已经广泛应用于粒子与核物理、核医学等许多领域。传统 PSD 技术有死区时间长和甄别效率低等缺点，数字 PSD 技术直接使用波形原始信息，并采用先进的数字信号处理技术，可避免传统 PSD 的缺点，同时具有灵活、高效的特点。介绍几种脉冲甄别方法的原理及典型应用，总结不同方法的优缺点并展望未来数字 PSD 技术的发展方向。 相似文献
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李晓莉 《荆门职业技术学院学报》2010,25(9):38-40
目的：探讨卒中后抑郁的临床特征、相关因素与治疗。方法：对40例卒中后抑郁患者的临床资料、相关检查及治疗方法进行回顾性分析、总结。结果：卒中后抑郁发病率高,尤其是首发卒中患者,早期给予心理干预及药物治疗,抑郁症状明显改善,HAMD评分降低,神经功能恢复好,并发症少。结论：对卒中患者应早期行抑郁评价,降低其发病率;对卒中后抑郁患者应采取综合治疗,特别是早期心理干预尤为重要。 相似文献
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Ingrid Vilà-Giménez Natalie Dowling Ö. Ece Demir-Lira Pilar Prieto Susan Goldin-Meadow 《Child development》2021,92(6):2335-2355
A longitudinal study with 45 children (Hispanic, 13%; non-Hispanic, 87%) investigated whether the early production of non-referential beat and flip gestures, as opposed to referential iconic gestures, in parent–child naturalistic interactions from 14 to 58 months old predicts narrative abilities at age 5. Results revealed that only non-referential beats significantly (p < .01) predicted later narrative productions. The pragmatic functions of the children’s speech that accompany these gestures were also analyzed in a representative sample of 18 parent-child dyads, revealing that beats were typically associated with biased assertions or questions. These findings show that the early use of beats predicts narrative abilities later in development, and suggest that this relation is likely due to the pragmatic–structuring function that beats reflect in early discourse. 相似文献
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用水平旋转的方法模拟微重力环境来处理正萌发的玉米种子,探讨微重力条件对玉米根尖细胞核结构的影响．结果表明,在微重力的作用下,根尖分生区细胞出现较多的异形核及微核,同时还发现大量的异位核;在36h内,随着处理时间的增长,出现异形核、微核、异位核的频率增高,当处理时间进一步增长时,异形核、微核、异位核的出现频率有下降趋势．结论：模拟微重力对植物细胞核的形态、结构具有明显的诱变作用． 相似文献
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采用溶胶凝胶法合成纳米二氧化钛光催化剂,X衍射及红外表征显示银已进入催化剂晶胞中.以汞灯模拟紫外光,氙灯模拟自然条件下太阳光催化降解酸性红B染料,结果表明1%和2%银掺入提高了纳米二氧化钛的可见光催化效能,使得催化剂的吸光波长范围红移,X衍射表征及催化剂筛选实验表明2%Ag-TiO2为锐钛矿晶型,具有较高催化活性,常温常压500 w氙灯照射下,催化剂用量为1.5 g/L、模拟废水pH=4、光照150 min、模拟废水浓度为50 mg/L时,酸性红B染料模拟废水的脱色率达90%,矿化率达60%. 相似文献
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This study explores classification consistency and accuracy for mixed-format tests using real and simulated data. In particular, the current study compares six methods of estimating classification consistency and accuracy for seven mixed-format tests. The relative performance of the estimation methods is evaluated using simulated data. Study results from real data analysis showed that the procedures exhibited similar patterns across various exams, but some tended to produce lower estimates of classification consistency and accuracy than others. As data became more multidimensional, unidimensional and multidimensional item response theory (IRT) methods tended to produce different results, with the unidimensional approach yielding lower estimates than the multidimensional approach. Results from simulated data analysis demonstrated smaller estimation error for the multidimensional IRT methods than for the unidimensional IRT method. The unidimensional approach yielded larger error as tests became more multidimensional, whereas a reverse relationship was observed for the multidimensional IRT approach. Among the non-IRT approaches, the normal approximation and Livingston-Lewis methods performed well, whereas the compound multinomial method tended to produce relatively larger error. 相似文献
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Cong-jing REN Jing-dai WANG Di SONG Bin-bo JIANG Zu-wei LIAO Yong-rong YANG 《浙江大学学报(A卷英文版)》2011,12(4):260-267
Particle size distribution (PSD) is an important parameter in the process of fluidization, and it always plays a crucial role
in a gas-solid fluidized system. A PSD model for on-line PSD determination based on acoustic emission (AE) measurement was
developed according to the mechanism of particle collision with the inner wall of the cylinder and multi-scale wavelet decomposition
analysis. This PSD model illuminates the quantitative relationship between the energy percentage of AE signals for different
scales and the PSD, which indicates the feasibility of the application of the PSD model. Experiments were undertaken both
in lab and plant gas-solid fluidized setup with polyethylene particles, and the parameters of the PSD model were calibrated
and revised. The experimental conditions and results proved that the PSD model was suitable for on-line measurement and was
sufficiently sensible and accurate. Concerning agglomeration, the PSD model also showed exact serviceability on detecting
the onset of agglomeration by abnormal PSD, and the result agreed with that from the radiation method. Ultimately, AE measurement
was found to be a reliable and credible means for understanding the PSD information that affects the behavior of a system,
which can provide valuable guidance for practical applications. 相似文献
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应用人工神经网络（Artificial Neural Network，ANN）算法对MIT-BIH心电数据库中的数据进行检测，对波形辨识算法做初步研究。设计三层神经网络结构：输入层、隐含层和输出层。从心电信号中提取4项特征参数作为输入层的输入量，并对MIT-BIH心电数据库中的15例心电数据进行了检测。表明该算法对QRS波总体检测灵敏度为98．96％，检测真阳性率为99．93％，对室性异位博动检测灵敏度为94．97％，检测真阳性率为98．72％。实验证实该神经几乎络算法对心电波形辨识非常有效。 相似文献
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介绍了采用先进的科学计算软件MATLAB对含噪信号进行分解 ,并通过软件波波重构出消噪后的信号 ,计算机仿真结果表明 ,利用MATLAB语言可以方便的得到信号含噪前后的频谱 ,并有效的波除噪声 相似文献
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ABSTRACTThe emerging paradigm of responsible research and innovation (RRI) in the European Commission policy discourse identifies science education as a key agenda for better equipping students with skills and knowledge to tackle complex societal challenges and foster active citizenship in democratic societies. The operationalisation of this broad approach in science education demands, however, the identification of assessment frameworks able to grasp the complexity of RRI process requirements and learning outcomes within science education practice. This article aims to shed light over the application of the RRI approach in science education by proposing a RRI-based analytical framework for science education assessment. We use such framework to review a sample of empirical studies of science education assessments and critically analyse it under the lenses of RRI criteria. As a result, we identify a set of 86 key RRI assessment indicators in science education related to RRI values, transversal competences and experiential and cognitive aspects of learning. We argue that looking at science education through the lenses of RRI can potentially contribute to the integration of metacognitive skills, emotional aspects and procedural dimensions within impact assessments so as to address the complexity of learning. 相似文献
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在无线网络控制系统中,多传感器之间通过信道传输数据时可能会产生时延以及丢包等现象,这种传输误差以指数级增长,造成在某个时刻之后中心处传感器估计值与真实值相差过大。为降低估计误差,通过分析信道参数特征计算出信道临界丢包率,并且给出在信道质量下降时进行切换的判断条件,再利用卡尔曼滤波计算中心处传感器的估计值,在传输出现丢包时进行信道切换。仿真结果表明,通过给出的信道切换方法和切换条件,在同等传输条件下,双信道传输情况下某时刻中心处传感器的估计误差比单信道传输平均下降了23.8%。 相似文献
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文章给出了一种测量RC积分电路时间常数的实验方法。利用信号源幅值与电容两端电压之间的比例关系,解决了不能在RC积分电路响应波形图中利用常规方法测量时间常数的问题。 相似文献