Determination of Cyanuric Acid in Swimming Pool Water and Milk by Differential Pulse Polarography     

Ümmihan T. Yilmaz  Zehra Yazar 《洁净——土壤、空气、水》2010,38(9):816-821

Cyanuric acid is a suspected gastrointestinal or liver toxicant in humans. Therefore, determination of trace cyanuric acid is very important, in this work a novel, sensitive, and reliable method was developed using differential pulse polarography. Optimum conditions for analytical determination were found to be at a pH of 9.5, Britton–Robinson at a reduction potential of ?105 mV. Experimental results indicate an excellent linear correlation between the peak current and the concentration in the range of cyanuric acid from 0.5 to 27.0 µM (0.06–3.5 µg mL^?1) with a correlation coefficient of 0.997. The limit of detection and limit of quantification were obtained as 0.15 and 0.5 µM (0.02–0.06 µg mL^?1), respectively. The proposed method was successfully applied to the determination of cyanuric acid in pool water and in spiked milk. Cyanuric acid level in swimming pool water was found as 2.54 ± 0.47 µg mL^?1 (19.7 ± 2.29 µM) in swimming pool water for N = 4 and 95% confidence interval. The recoveries were found to be sufficient. Also, the standard deviation of the data was low which shows high accuracy and precision of proposed differential pulse polarographic method. The influences of some other commonly found inorganic salts on the determination of cyanuric acid were also examined. Some interfering species were eliminated using complexing agents, e.g., EDTA.  相似文献   

Near‐fault effects on residual displacements of RC structures          下载免费PDF全文

Eftychia Liossatou  Michael N. Fardis 《地震工程与结构动力学》2016,45(9):1391-1409

Residual displacements of single‐degree‐of‐freedom systems due to ground motions with velocity pulses or fling step displacements are presented as a function of period T and of its ratio to the pulse period T_p. Four hysteretic behaviors are considered: bilinear elastoplastic, stiffness‐degrading with cycling, stiffness‐cum‐strength degrading, with or without pinching. When expressed in terms of T/T_p, peak inelastic and residual displacements due to motions with a pulse or fling appear similar to those due to far‐fault motions, if the response to far‐field records are expressed in terms of the ratio of T to the record's characteristic period. However, as the latter is usually much shorter than the pulse period of motions with fling, the range of periods of interest for common structures becomes a short‐period range under fling motions and exhibits very large amplification of residual and peak inelastic displacements. Similar, but less acute, are the effects of motions with a velocity pulse. Wavelets of different complexity are studied as approximations to near‐fault records. Simple two‐parameter wavelets for fling motions overestimate peak inelastic displacements; those for pulse‐type motions overestimate residual displacements. A more complex four‐parameter wavelet for motions with a velocity pulse predicts overall well residual and peak displacements due to either pulse‐ or fling‐type motions; a hard‐to‐identify parameter of the wavelet impacts little computed residual displacements; another significantly affects them and should be carefully estimated from the record. Even this most successful of wavelets overpredicts residual displacements for the periods of engineering interest. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Dominant pulse simulation of near fault ground motions     

S.R. Hoseini Vaez  M.K. Sharbatdar  G. Ghodrati Amiri  H. Naderpour  A. Kheyroddin 《地震工程与工程振动(英文版)》2013,12(2):267-278

In this study, a new mathematical model is developed composed of two parts, including harmonic and polynomial expressions for simulating the dominant velocity pulse of near fault ground motions. Based on a proposed velocity function, the corresponding expressions for the ground acceleration and displacement time histories are also derived. The proposed model is then fitted using some selected pulse-like near fault ground motions in the Next Generation Attenuation (NGA) project library. The new model is not only simple in form but also simulates the long-period portion of actual velocity near fault records with a high level of precision. It is shown that the proposed model-based elastic response spectra are compatible with the near fault records in the neighborhood of the prevailing frequency of the pulse. The results indicate that the proposed model adequately simulates the components of the time histories. Finally, the energy of the proposed pulse was compared with the energy of the actual record to confirm the compatibility.  相似文献   

Research on the imaging of concrete defect based on the pulse compression technique     

Li Chang-Zheng  Zhang Bi-Xing  Shi Fang-Fang  Xie Fu-Li 《应用地球物理》2013,10(3):337-348

When the synthetic aperture focusing technology (SAFT) is used for the detection of the concrete, the signal-to-noise ratio (SNR) and detection depth are not satisfactory. Therefore, the application of SAFT is usually limited. In this paper, we propose an improved SAFT technique for the detection of concrete based on the pulse compression technique used in the Radar domain. The proposed method first transmits a linear frequency modulation (LFM) signal, and then compresses the echo signal using the matched filtering method, after which a compressed signal with a narrower main lobe and higher SNR is obtained. With our improved SAFT, the compressed signals are manipulated in the imaging process and the image contrast is improved. Results show that the SNR is improved and the imaging resolution is guaranteed compared with the conventional short-pulse method. From theoretical and experimental results, we show that the proposed method can suppress noise and improve imaging contrast, and can also be used to detect multiple defects in concrete.  相似文献   

Effects of pulse period of near‐field ground motions on the seismic demands of soil–MDOF structure systems using mathematical pulse models     

Faramarz Khoshnoudian  Ehsan Ahmadi 《地震工程与结构动力学》2013,42(11):1565-1582

In this paper, the effects of pulse period associated with near‐field ground motions on the seismic demands of soil–MDOF structure systems are investigated by using mathematical pulse models. Three non‐dimensional parameters are employed as the crucial parameters, which govern the responses of soil–structure systems: (1) non‐dimensional frequency as the structure‐to‐soil stiffness ratio; (2) aspect ratio of the superstructure; and (3) structural target ductility ratio. The soil beneath the superstructure is simulated on the basis of the Cone model concept. The superstructure is modeled as a nonlinear shear building. Interstory drift ratio is selected as the main engineering demand parameter for soil–structure systems. It is demonstrated that the contribution of higher modes to the response of soil–structure system depends on the pulse‐to‐interacting system period ratio instead of pulse‐to‐fixed‐base structure period ratio. Furthermore, results of the MDOF superstructures demonstrate that increasing structural target ductility ratio results in the first‐mode domination for both fixed‐base structure and soil–structure system. Additionally, increasing non‐dimensional frequency and aspect ratio of the superstructure respectively decrease and increase the structural responses. Moreover, comparison of the equivalent soil–SDOF structure system and the soil–MDOF structure system elucidates that higher‐mode effects are more significant, when soil–structure interaction is taken into account. In general, the effects of fling step and forward directivity pulses on activating higher modes of the superstructure are more sever in soil–structure systems, and in addition, the influences of forward directivity pulses are more considerable than fling step ones. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

核脉冲信号数字高斯成形模型的建立与仿真     

周伟  周建斌  方方  朱星  刘易  李扬红 《物探与化探》2012,(2):260-262

详细阐述了一种以Sallen—Key滤波器为基础的新型数字高斯成形的方法。运用二阶微分方程建立高斯成形数学模型,在模型解算过程中利用数值微分算法得到一个通用的输入信号与输出信号的数值递推解,从而实现了核脉冲信号的数字高斯成形。通过标准指数信号的模拟以及实际测量信号的模拟,确定了数字高斯成形的参数。  相似文献   

Effect of near-fault earthquakes with forward directivity on telecommunication towers     

M.Yahyai  B.Rezayibana  E.Mohammadrezapour 《地震工程与工程振动(英文版)》2011,10(2):211-218

In this paper, the effect of pulse-type motions caused by forward directivity that can release huge amounts of energy in a short time period is studied on a telecommunication tower. Since telecommunication towers have longer periods, they are not as affected by seismic forces. Nevertheless, near source earthquakes characterized by high velocity and velocity pulses can change the behavior of these structures. For this reason, a telecommunication tower located near active faults was selected in this study. Considering the probable earthquake magnitude at the site and the distance of the tower from adjacent faults, nine simulated pulses and three near-fault earthquake records with forward directivity are selected and applied to a 3D fi nite element model of the tower. The results of nonlinear dynamic analysis, i.e., displacements and damage in the tower, indicate that the maximum displacement and drift ratio of the tower under the pulses are obviously affected by the ratio of the structure period to pulse period. When this ratio is decreased and close to 1.0, the maximum displacement and drift ratio are sharply increased and cause large displacements in the tower.  相似文献   

Modeling of electromagnetic waves in axisymmetric geometry using a Laguerre spectral method     

A.F. Mastryukov 《Russian Geology and Geophysics》2011,52(9):1035-1042

A spectral method for modeling high-frequency electromagnetic waves in axisymmetric geometry is proposed.The method is based on the expansion of the solutions of Maxwell’s equations in Laguerre functions in the time region.The spectral method is used to solve Maxwell’s equations for both 2D media and stratified media. In the case of stratified media, a Fourier–Bessel expansion in the radial variable is used. The effectiveness of the spectral and finite-difference methods is compared. Harmonic solutions and solitary solutions by the Laguerre method are considered, and the dynamics of monochromatic and broadband electromagnetic pulses are examined.  相似文献   

黑河流域荒漠区土壤水分对降水脉动响应   总被引：16，自引：5，他引：11  

刘冰  赵文智  常学向  李守波 《中国沙漠》2011,30(3):716-722

 利用气象站资料,对黑河流域荒漠区降水特征及其土壤水分对降水脉动响应进行了系统研究。结果表明,荒漠区降水属于降水脉动事件,降水前后土壤水分特征存在显著差异,且随土层增加差异逐渐变小。土壤水分在降水量、土壤深度和降水前后的差异极显著,交互效应也极显著(P<0.0001),表明荒漠区土壤水分对降水脉动具有显著的响应现象。土壤水分的降水脉动响应表现为降水后土壤含水量激增,在蒸散作用下缓慢减小。降水前后土壤含水量的时间序列变异规律均能较好地拟合成变异函数的理论模型。降水前后土壤含水量随机变异均小于结构性变异,反映出荒漠区土壤水分在时间尺度上具有较强的自相关性格局。降水使土壤水分空间结构差异呈现下降趋势,在时间序列上异质性降低。  相似文献   

脉冲压缩方法检测岩石弹性波速度     

李长征  张碧星  师芳芳 《岩土力学》2013,34(6):1815-1821

针对岩石弹性波速度检测信噪比低、回波信号初至时间不易判读,以及较长岩石（或混凝土）超声检测难以穿透问题,提出用脉冲压缩方法检测弹性波速度。该方法与超声脉冲法检测的不同之处是在发射端采用编码信号激励,在接收端进行匹配滤波,得到高信噪比的压缩信号。介绍线性调频信号的宽时宽带特性,分析了脉冲压缩的基本原理和数字实现过程。试验研究了换能器带宽对激发信号的影响。用常规的单脉冲法和脉冲压缩方法检测了多个岩样的弹性波速度,试验结果表明,两种检测结果差异较小。给出了脉冲压缩方法用于岩石弹性波速度检测的具体步骤和计算过程。综合分析,脉冲压缩方法检测岩石弹性波速度是可行的,能够用于岩土工程的质量评价。  相似文献