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速率相关混凝土模型中一个值得商榷的问题 被引量:5
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作者 方秦 钱七虎 《工程力学》 EI CSCD 北大核心 1998年第3期29-35,共7页
本文对一种广泛应用于钢筋混凝土结构动力分析的速率相关的混凝土模型进行讨论,该模型的基本特征是粘性参数与应变速率有关。为了比较和验证该模型的正确性,本文严格按照弹粘塑性理论并结合过应力概念,提出了一种应变速率相关模型。... 本文对一种广泛应用于钢筋混凝土结构动力分析的速率相关的混凝土模型进行讨论,该模型的基本特征是粘性参数与应变速率有关。为了比较和验证该模型的正确性,本文严格按照弹粘塑性理论并结合过应力概念,提出了一种应变速率相关模型。文中给出了在常应变速率、应力松弛和蠕变等加载情况下二种模型的分析解。理论和数值计算结果都表明,先前提出的应变速率相关模型不仅理论上有缺陷,而且在稳态响应阶段段值计算存在较大误差。 展开更多
关键词 速率相关 材料模型 混凝土 结构动力分析
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符号速率相关的带通采样速率选取及其仿真
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作者 万福 谢佑波 马锐 《信息化研究》 2009年第11期34-36,共3页
带通采样速率选取是软件无线电技术的关键问题之一。分析了常用带通采样速率选取方法的不足:采样速率一般不是符号速率的整数倍,后续基带数字信号处理需要进行复杂的小数内插或抽取算法运算,实现相当困难且运算量很大。为解决这一问题,... 带通采样速率选取是软件无线电技术的关键问题之一。分析了常用带通采样速率选取方法的不足:采样速率一般不是符号速率的整数倍,后续基带数字信号处理需要进行复杂的小数内插或抽取算法运算,实现相当困难且运算量很大。为解决这一问题,提出了一种实用的与符号速率相关的带通采样速率选取方法,在满足带通采样定理基础上,附加频谱间隔最大条件选取符号速率整数倍的采样速率,最后通过软件仿真验证了符号速率相关的带通采样速率选取方法的正确性和可行性。 展开更多
关键词 符号速率相关 中频数字化 带通采样
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地塞米松磷酸钠的粒度相关生长速率模型
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作者 郝红勋 王静康 《化工学报》 EI CAS CSCD 北大核心 2004年第1期143-146,共4页
The size-dependent growth of dexamethasone sodium phosphate was studied in a MSMPR crystallizer. The Bransom,CR,ASL,MJ2 and MJ3 size-dependent growth rate models were discussed in details. Using experimental steady st... The size-dependent growth of dexamethasone sodium phosphate was studied in a MSMPR crystallizer. The Bransom,CR,ASL,MJ2 and MJ3 size-dependent growth rate models were discussed in details. Using experimental steady state population density data of dexamethasone sodium phosphate, the parameters of five size-dependent growth rate models were determined by the non-linear least-squares method. By comparison of experimental population density data and linear growth rate data with those calculated from five size-dependent growth rate models, it was found that the MJ3 model was the best one for predicting the growth of dexamethasone sodium phosphate. 展开更多
关键词 地塞米松磷酸钠 粒度相关生长速率模型 MSMPR结晶器 晶体粒度分布(CSD)
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考虑加/卸载速率影响的Ti-Ni形状记忆合金简化本构模型 被引量:1
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作者 余滨杉 樊禹江 +1 位作者 王社良 杨涛 《材料导报》 EI CAS CSCD 北大核心 2017年第6期153-160,170,共9页
系统研究了Ti-Ni形状记忆合金丝(SMA)应力-应变曲线、特征点应力、耗能能力、等效阻尼比随材料直径、应变幅值、加载速率、加载循环次数的变化规律;针对SMA唯象Brinson本构模型无法描述SMA动态力学性能的缺点,结合前述试验结果,提出了... 系统研究了Ti-Ni形状记忆合金丝(SMA)应力-应变曲线、特征点应力、耗能能力、等效阻尼比随材料直径、应变幅值、加载速率、加载循环次数的变化规律;针对SMA唯象Brinson本构模型无法描述SMA动态力学性能的缺点,结合前述试验结果,提出了一种可考虑加/卸载速率影响的SMA简化本构模型。应用该模型对试验用SMA丝进行模拟,所得应力-应变曲线各特征点平均误差仅为3%,结果表明:所建立的速率相关SMA简化本构模型可较为精确地描述SMA在应力诱发相变过程中的超弹性力学行为,同时可反映加/卸载速率和应变幅值等主要因素对其动力本构模型的影响;该模型结构形式简单,具有较好的工程应用前景。 展开更多
关键词 形状记忆合金 Brinson本构模型 速率相关 动力本构模型
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TC21钛合金中应变速率拉伸力学行为实验研究 被引量:1
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作者 宫旭辉 王宇 薛钢 《材料开发与应用》 CAS 2013年第2期8-13,29,共7页
对网篮组织TC21钛合金进行了0.001 s-1~50 s-1的中应变速率室温拉伸试验。试验结果表明,TC21拉伸力学行为在试验应变速率范围内具有明显的应变速率强化效应、应变硬化效应和随应变速率升高而逐渐增大的温升软化效应;屈服应力的应变速... 对网篮组织TC21钛合金进行了0.001 s-1~50 s-1的中应变速率室温拉伸试验。试验结果表明,TC21拉伸力学行为在试验应变速率范围内具有明显的应变速率强化效应、应变硬化效应和随应变速率升高而逐渐增大的温升软化效应;屈服应力的应变速率相关性在6 s-1时发生转折;随应变率的升高,应变硬化效应减小,断裂应变和失稳应变增大;试验应变速率范围内TC21的变形机制为位错的热激活机制。SEM和金相观察结果表明,TC21的断裂方式均为韧性断裂,断裂机理为微孔洞的聚集和长大。 展开更多
关键词 TC21钛合金 中应变速率 应变速率相关 变形机制
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远场应变速率对非均质断层滑动成核影响研究 被引量:2
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作者 王威 任青文 张丽峰 《水电能源科学》 2008年第3期50-53,共4页
为进一步探讨断层滑动成核机理,以无限体弹性位错理论为基础,结合速率—状态相关摩擦准则,采用数值方法研究了远场应变加载率对非均质断层成核的影响及各物理量在断层失稳过程中的变化。结果表明,对于非均质断层,远场应变加载率对断层... 为进一步探讨断层滑动成核机理,以无限体弹性位错理论为基础,结合速率—状态相关摩擦准则,采用数值方法研究了远场应变加载率对非均质断层成核的影响及各物理量在断层失稳过程中的变化。结果表明,对于非均质断层,远场应变加载率对断层成核的时间和后期的速率、摩擦应力均有影响。远场应变加载率越高,断层成核时间越早,成核后期速率越高,应力降越小,成核区的尺寸略有增加。 展开更多
关键词 速率-状态相关摩擦准则 断层 成核 弹性位错 非均质
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A Hybrid Compensation Scheme for the Input Rate-Dependent Hysteresis of the Piezoelectric Ceramic Actuators
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作者 DONG Ruili TAN Yonghong +1 位作者 HOU Jiajia ZHENG Bangsheng 《Journal of Donghua University(English Edition)》 CAS 2024年第4期436-446,共11页
A hybrid compensation scheme for piezoelectric ceramic actuators(PEAs)is proposed.In the hybrid compensation scheme,the input rate-dependent hysteresis characteristics of the PEAs are compensated.The feedforward contr... A hybrid compensation scheme for piezoelectric ceramic actuators(PEAs)is proposed.In the hybrid compensation scheme,the input rate-dependent hysteresis characteristics of the PEAs are compensated.The feedforward controller is a novel input rate-dependent neural network hysteresis inverse model,while the feedback controller is a proportion integration differentiation(PID)controller.In the proposed inverse model,an input ratedependent auxiliary inverse operator(RAIO)and output of the hysteresis construct the expanded input space(EIS)of the inverse model which transforms the hysteresis inverse with multi-valued mapping into single-valued mapping,and the wiping-out,rate-dependent and continuous properties of the RAIO are analyzed in theories.Based on the EIS method,a hysteresis neural network inverse model,namely the dynamic back propagation neural network(DBPNN)model,is established.Moreover,a hybrid compensation scheme for the PEAs is designed to compensate for the hysteresis.Finally,the proposed method,the conventional PID controller and the hybrid controller with the modified input rate-dependent Prandtl-Ishlinskii(MRPI)model are all applied in the experimental platform.Experimental results show that the proposed method has obvious superiorities in the performance of the system. 展开更多
关键词 hybrid control input rate-dependent hysteresis inverse model neural network piezoelectric ceramic actuator
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基于扩展输入空间法的压电执行器迟滞特性动态建模 被引量:13
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作者 赵新龙 谭永红 董建萍 《机械工程学报》 EI CAS CSCD 北大核心 2010年第20期169-174,共6页
为辨识压电执行器中的速率相关迟滞特性,基于扩展输入空间法建立迟滞的神经网络动态模型。提出动态迟滞算子来描述速率相关迟滞的变化趋势和动态特性并基于该动态迟滞算子构建扩展输入空间。在这个扩展输入空间上,迟滞的多值映射能够转... 为辨识压电执行器中的速率相关迟滞特性,基于扩展输入空间法建立迟滞的神经网络动态模型。提出动态迟滞算子来描述速率相关迟滞的变化趋势和动态特性并基于该动态迟滞算子构建扩展输入空间。在这个扩展输入空间上,迟滞的多值映射能够转化成一一映射,同时可以利用动态迟滞算子来提取迟滞的速率相关性。用神经网络来逼近这个一一映射实现速率相关迟滞的动态建模。所提出的神经网络动态模型可以描述迟滞的速率相关性,结构简单,打破了常规迟滞模型基于算子加权叠加的建模框架,并且能够在线调整参数以适应不同条件下的迟滞建模。最后应用该方法对压电执行器中的迟滞特性进行动态建模,试验结果证明了这种建模方法的有效性。 展开更多
关键词 速率相关迟滞 动态迟滞算子 建模 扩展输入空间法
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几种材料的等效粘性系数、初始可动位错密度和拖曳应力 被引量:3
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作者 张万甲 刘仓理 《高压物理学报》 EI CAS CSCD 北大核心 2006年第4期345-352,共8页
基于LY12铝、MB2镁、铅、2#铁和不锈钢等几种材料的弹性前驱波幅度随传播距离衰减的实验结果,应用含位错参量的速率相关本构方程,按照Gilman提议的位错运动速度的热激活模型,得出了LY12铝、MB2镁、铅的可动位错密度N0和拖曳应力0τ的下... 基于LY12铝、MB2镁、铅、2#铁和不锈钢等几种材料的弹性前驱波幅度随传播距离衰减的实验结果,应用含位错参量的速率相关本构方程,按照Gilman提议的位错运动速度的热激活模型,得出了LY12铝、MB2镁、铅的可动位错密度N0和拖曳应力0τ的下限值分别为106cm-2和0.1GPa量级,不锈钢的N0和0τ为108cm-2和1.5 GPa量级。根据弹性前驱波幅度衰减曲线,还得出了2#铁、不锈钢的有效粘性系数μ的上限值为104Pa.s量级。LY12铝、MB2镁的有效粘性系数μ的上限值为103Pa.s量级。 展开更多
关键词 等效粘性系数 可动位错密度 拖曳应力 速率相关本构方程
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适用于小型岩石试件的三轴压缩试验技术与设备的开发及其应用 被引量:2
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作者 高秀君 羽柴公博 +1 位作者 大久保诚介 福井胜则 《岩石力学与工程学报》 EI CAS CSCD 北大核心 2006年第10期1960-1968,共9页
为了用有限的岩石试样在室内进行大量的岩石力学试验测试,对直径10 mm、长度20 mm的小型岩石试件进行开发、制作。同时对S.Okubo等(2002)开发的透明围压容器进行改进,其围压可达10 MPa左右。用此改进的试验设备对小型岩石试件进行三轴... 为了用有限的岩石试样在室内进行大量的岩石力学试验测试,对直径10 mm、长度20 mm的小型岩石试件进行开发、制作。同时对S.Okubo等(2002)开发的透明围压容器进行改进,其围压可达10 MPa左右。用此改进的试验设备对小型岩石试件进行三轴压缩试验。通过对田下凝灰岩的试验,由小型试件得到的力学参数——黏聚力和内摩擦角,与用常规试件获得的试验结果相一致。而且在载荷速率交替变换的试验中,用一个小型试件就可获得应力–应变曲线的载荷速率相关性。通过对三峡库区周边滑坡地带采集的岩石试样的测试,成功获得不同岩石的强度特性曲线及表示载荷速率相关性的参数。 展开更多
关键词 岩石力学 小型试件 田下凝灰岩 三轴压缩试验 载荷速率相关 三峡库区
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关于三峡库区周边坡体岩石特性的考察
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作者 高秀君 大久保誠介 福井勝則 《地下空间与工程学报》 CSCD 2006年第6期975-978,981,共5页
岩石强度的载荷速率相关性与岩石的时间相关性特性及粘弹性性质密切相关,而且强度的载荷速率相关性越大,越容易发生蠕变破坏。对于坡体来说,如果构成坡体的岩石的时间相关性很显著,那么即使在比较低的应力下仅施加一点载荷,也容易发生... 岩石强度的载荷速率相关性与岩石的时间相关性特性及粘弹性性质密切相关,而且强度的载荷速率相关性越大,越容易发生蠕变破坏。对于坡体来说,如果构成坡体的岩石的时间相关性很显著,那么即使在比较低的应力下仅施加一点载荷,也容易发生变形。针对三峡库区周边滑坡多发,采集了组成滑坡坡体的4类主要岩石-泥岩、灰岩、泥质砂岩及砂岩。通过室内岩石力学强度试验,获得了不同岩石的强度特性曲线及表示载荷速率相关性的参数n。利用一个试件通过载荷速率交替变换获得了不同应变速率下的应力-应变曲线,从而根据强度的变化率不仅获得了峰值强度的载荷速率相关性,而且还求得了残余强度的载荷速率相关性。在单轴压缩试验中,残余强度的n值与峰值强度的n值有较大的差异,但在三轴压缩试验中两者的差异却不太明显。而且在气干状态下,不管是峰值强度还是残余强度的n值均随着围压的增加而增加。 展开更多
关键词 三峡库区 三轴压缩试验 峰值强度 残余强度 载荷速率相关
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自保护隔震支座力学性能试验研究
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作者 滕晓飞 谭平 +1 位作者 周林丽 贺辉 《振动工程学报》 EI CSCD 北大核心 2020年第3期477-484,共8页
为解决传统隔震支座不具备自保护能力的问题,研发了一种自保护隔震支座,并对其工作机理进行了阐述。据该隔震支座在不同侧向荷载作用下的工作特点可将其分为两个工作阶段。根据隔震支座的自保护能力要求对支座滑移材料进行了摩擦性能测... 为解决传统隔震支座不具备自保护能力的问题,研发了一种自保护隔震支座,并对其工作机理进行了阐述。据该隔震支座在不同侧向荷载作用下的工作特点可将其分为两个工作阶段。根据隔震支座的自保护能力要求对支座滑移材料进行了摩擦性能测试及择优分析,并对本次设计的自保护隔震支座及传统隔震支座进行了力学性能试验,结果表明:自保护隔震支座比传统隔震支座的竖向刚度最大降低幅值为21.91%,但仍具有足够的竖向刚度承受上部荷载,且这种差异随着竖向面压的增大而逐渐减小;支座在第一工作阶段的水平剪切变形加载下未滑动,发挥与传统隔震支座相同的功效,其滞回特性表现为典型的双线性特点;在第二工作阶段的水平剪切变形加载下支座开始滑动并摩擦耗能,其滞回曲线呈现为三线型特征,虽然有一定的捏拢,但滞回曲线的包络面积仍比传统隔震支座增加约86%;自保护隔震支座在第一工作阶段随加载速率的增加,屈服力和屈服后刚度均有增加,对应包络曲线的面积也呈增大趋势,整体的滞回曲线仍和传统铅芯橡胶支座相似,呈现出典型的双线性特性;在"第二工作阶段"启动后随着加载速率的变大,自保护隔震支座在复位段的捏拢现象逐渐减轻且支座在滑移状态下的性能逐渐趋于稳定。通过对试验曲线进行参数识别发现自保护隔震支座的恢复力模型可以采用呈捏拢效应的Bonc-Wen模型进行模拟,且拟合曲线与试验曲线吻合较好。 展开更多
关键词 隔震支座 力学性能 自保护 速率相关
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WAVELET BASED SPECTRAL CORRELATION METHOD FOR DPSK CHIP RATE ESTIMATION 被引量:3
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作者 LiYingxiang XiaoXianci TaiHengming 《Journal of Electronics(China)》 2004年第5期353-358,共6页
A wavelet-based spectral correlation algorithm to detect and estimate BPSK signal chip rate is proposed. Simulation results show that the proposed method can correctly estimate the BPSK signal chip rate, which may be ... A wavelet-based spectral correlation algorithm to detect and estimate BPSK signal chip rate is proposed. Simulation results show that the proposed method can correctly estimate the BPSK signal chip rate, which may be corrupted by the quadratic characteristics of the spectral correlation function, in a low SNR environment. 展开更多
关键词 Spectral correlation BPSK signal CYCLOSTATIONARITY Wavelet transform
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Study Rheological Behavior for Rapeseed Oils 被引量:1
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作者 Ioana Stanciu 《Journal of Chemistry and Chemical Engineering》 2013年第2期184-186,共3页
Rheological behavior of this article presents rapeseed oil. Dynamic viscosity of rapeseed oil was determined at temperatures between 40 ℃-90 ℃ and shear rates ranging from 3.3-120 s1. All types of oils studied Bingh... Rheological behavior of this article presents rapeseed oil. Dynamic viscosity of rapeseed oil was determined at temperatures between 40 ℃-90 ℃ and shear rates ranging from 3.3-120 s1. All types of oils studied Bingham fluid behavior in the temperature range from 313-363 K. Correlation coefficients have similar values to one for all oils studied. 展开更多
关键词 Rheological behaviour rapeseed oil degummed rapeseed oil.
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Three vertex degree correlations of fixed act-size collaboration networks
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作者 雷敏 赵清贵 侯振挺 《Journal of Central South University》 SCIE EI CAS 2011年第3期830-833,共4页
A rate equation approach was presented for the exact computation of the three vertex degree correlations of the fixed act-size collaboration networks.Measurements of the three vertex degree correlations were based on ... A rate equation approach was presented for the exact computation of the three vertex degree correlations of the fixed act-size collaboration networks.Measurements of the three vertex degree correlations were based on a rate equation in the continuous degree and time approximation for the average degree of the nearest neighbors of vertices of degree k,with an appropriate boundary condition.The rate equation proposed can be generalized in more sophisticated growing network models,and also extended to deal with related correlation measurements.Finally,in order to check the theoretical prediction,a numerical example was solved to demonstrate the performance of the degree correlation function. 展开更多
关键词 fixed act-size collaboration networks degree correlation function clustering coefficient Markov chain
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A GENERAL APPROACH BASED ON AUTOCORRELATION TO DETERMINE INPUT VARIABLES OF NEURAL NETWORKS FOR TIME SERIES FORECASTING 被引量:10
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作者 HUANGWei NAKAMORIYoshiteru WANGShouyang 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2004年第3期297-305,共9页
Input selection is probably one of the most critical decision issues in neural network designing, because it has a great impact on forecasting performance. Among the many applications of artificial neural networks to ... Input selection is probably one of the most critical decision issues in neural network designing, because it has a great impact on forecasting performance. Among the many applications of artificial neural networks to finance, time series forecasting is perhaps one of the most challenging issues. Considering the features of neural networks, we propose a general approach called Autocorrelation Criterion (AC) to determine the inputs variables for a neural network. The purpose is to seek optimal lag periods, which are more predictive and less correlated. AC is a data-driven approach in that there is no prior assumptiona bout the models for time series under study. So it has extensive applications and avoids a lengthy experimentation and tinkering in input selection. We apply the approach to the determination of input variables for foreign exchange rate forecasting and conductcomparisons between AC and information-based in-sample model selection criterion. The experiment results show that AC outperforms information-based in-sample model selection criterion. 展开更多
关键词 input variables foreign exchange rate neural networks time seriesforecasting
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Precise simulation of surface acoustic wave devices using frequency-dependent coupling-of-modes parameters 被引量:1
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作者 WANG Hao WANG WeiBiao +2 位作者 WU HaoDong SU Bo SHUI YongAn 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2013年第7期1263-1268,共6页
Herein we extract all the frequency-dependent coupling-of-modes (COM) parameters, which will be used to the rapid simulation and optimal design of surface acoustic wave (SAW) devices. FEM/BEM is used to calculate ... Herein we extract all the frequency-dependent coupling-of-modes (COM) parameters, which will be used to the rapid simulation and optimal design of surface acoustic wave (SAW) devices. FEM/BEM is used to calculate the exact field distributions of forward and backward surface acoustic waves within a finite-length periodic grating at every frequency. The middle compo- nent of the grating, regarded as a periodic structure, is selected to be investigated which can satisfy the presupposition of the COM model. From these field distributions, the values of P-matrix elements of one cell are calculated. The COM parameters taken as functions of frequency are accurately obtained. Specifically, the frequency-dependent relationships of reflection coefficient and propagation velocity are obtained independently. Using the resultant COM parameters, a one-port resonator on the substrate of 128°YX-LiNbO3 is simulated and the admittance curve shows good agreement with the simulating results using FEM/BEM. These results verify the validity and accuracy of this method. 展开更多
关键词 surface acoustic wave devices coupling-of-modes model frequency-dependent parameters
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Gross Nitrification Rates and Nitrous Oxide Emissions in an Apple Orchard Soil in Northeast China 被引量:1
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作者 GE Shunfeng JIANG Yuanmao WEI Shaochong 《Pedosphere》 SCIE CAS CSCD 2015年第4期622-630,共9页
A better understanding of nitrogen (N) transformation in agricultural soils is crucial for the development of sustainable and environmental-friendly N fertilizer management and the proposal of effective N20 mitigati... A better understanding of nitrogen (N) transformation in agricultural soils is crucial for the development of sustainable and environmental-friendly N fertilizer management and the proposal of effective N20 mitigation strategies. This study aimed: i) to elucidate the seasonal dynamic of gross nitrification rate and N20 emission, ii) to determine the influence of soil conditions on the gross nitrification, and iii) to confirm the relationship between gross nitrification and N20 emissions in the soil of an apple orchard in Yantai, Northeast China. The gross nitrification rates and N20 fluxes were examined from March to October in 2009, 2010, and 2011 using the barometric process separation (BaPS) technique and the static chamber method. During the wet seasons gross nitrification rates were 1.64 times higher than those under dry season conditions. Multiple regression analysis revealed that gross nitrification rates were significantly correlated with soil temperature and soil water-filled pore space (WFPS). The relationship between gross nitrification rates and soil WFPS followed an optimum curve peaking at 60% WFPS. Nitrous oxide fluxes varied widely from March to October and were stimulated by N fertilizer application. Statistically significant positive correlations were found between gross nitrification rates and soil N20 emissions. Further evaluation indicated that gross nitrification contributed significantly to N20 formation during the dry season (about 86%) but to a lesser degree during the wet season (about 51%). Therefore, gross nitrification is a key process for the formation of N20 in soils of apple orchard ecosystems of the geographical region. 展开更多
关键词 barometric process separation system mineral N N transformation soil water-filled pore space static chamber
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