共查询到19条相似文献，搜索用时 125 毫秒
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拉科斯特重力仪干扰因素分析 总被引：1，自引：0，他引：1
本文根据多年重力监测工作情况，结合拉科斯特重力仪的结构特点，对仪器在观测中的干扰因素进行分析，认为影响仪器观测精度的干扰因素有两类：一类是仪器本身产生的系统误差，如格值误差、零飘及弹性后效等；另一类是外界干扰因素，如振动、温度、人为观测方法不当等，如果在观测中能消除或减小这些干扰因素影响，拉科斯特重力仪就可能达到更高的观测精度。 相似文献
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本文对京西北1987年以来用拉科斯特重力仪复测的重力资料进行了分析,着重讨论了1990年9月22日小汤山4.0级地震前后的重力异常变化情况。 相似文献
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LCR—G／D重力仪静电反馈装置转换参数的确定 总被引：1，自引：0，他引：1
装配了静电反馈装置的ＬＣＲ－Ｇ／Ｄ型重力仪是目前世界上观测精度最好的相对重力仪，静电反馈装置的转换参数确定正得正确与否是影响观测精度的重要因素之一。本文在研究了转换参数数学模型及精度的基础上，介绍了它的标定方法和计算方法，并根据ＬＣＲ－Ｇ－７９３、Ｇ－８５４两台仪器的标定结果，分析了转换参数的变化特征及影响标定精度的诸多因素，最后提出了标定和使用转换参数的注意事项。 相似文献
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对拉科斯特重力仪稳定状态的分析 总被引：1，自引：0，他引：1
通过对闰科斯特重力仪稳定状态的分析,认为该仪器从断电至恢复供电后进入稳定状态的时间长短与断电,静置时间长短呈正相关。原因是重力仪核心部分的弹性材料的某些物理性质在不同温度下不尽相同。当工区转换时,仪器不能断电并尽量减少静置时间,以保证测量误差满足要求。 相似文献
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引言流动重力重复测量是我们长期以来一直在使用的一种地震前兆观测手段 ,由于这一手段采用在固定测网、测线、测点上 ,每年在相近的时间内多次重复测量的方法 ,所以具有监测面积较大、工作速度较快、监测地球重力场时间域中短期异常效果较好等特点。新疆地震局自 1 978年 4月开展此项工作以来 ,共使用过三种类型的重力仪 :1 978～ 1 980年使用国产 ZSM- 、ZSM- 型石英弹簧重力仪 ( 1 981年停测选埋点 ,验收仪器 ) ;1 982～ 1 988年使用美国产沃尔登( Wordern)石英弹簧重力仪 ;1 987年至今使用中国地震局局管共用的美国产拉科斯特 ( L… 相似文献
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一、序言我队从邢台地震后于1967年开始在北京、邢台等地区开展用流动重力复测的方法,来探索地震前后重力场的变化,十多年来积累了大量的、连续的、定期复测第一性资料。尽管使用的仪器为加拿大CG-2型重力仪,与目前国际上高精度的拉科斯特重力仪相比精度低,但在工作过程中和资料分析中,采取了各种措施和改正之后,观测精度已大大高于原仪器的观测精度,尤其在北京测区的复测资料,无论从资料的系统性、观测周期之密、连续时间之长在国内外也是罕见的。利用这些资料,探讨与地震有关的重力变化是本文的目的。 相似文献
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利用全球分布的精密重力场潮汐变化资料研究地球动力学问题 ,是重力学研究的重要组成部分。高精度和高灵敏度重力仪的出现和大量使用为此类研究提供了可靠保障。本文针对高精度重力仪的标定及数字化技术进行研究。重力仪的标定对重力潮汐观测异常重要。不同原理结构和不同型号的重力仪采用了不同的标定方法 ,到目前为止 ,这一问题还没有得到很好解决。本文讨论了目前国际国内重力仪已有标定方法并分析了这些方法的优缺点 ,具体针对国产 DZW型重力仪的摆系结构提出了更为合理的两种改进静电标定方法。一是摆系结构不变 ,将部分金属部件改为… 相似文献
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采用高精度拉科斯特重力仪在辽宁西部地区进行多期重力重复测量，获得了较为丰富的基础资料，通过对资料的分析与研究，进一步加深了辽宁西部地区重力场变化的认识。特别是１９９４年１０月和１９９６年７月，在测区内及其附近相继发生ＭＬ４．９级和ＭＬ５．０级地震。而这两次地震为１９８８年以来在辽宁西部地区发生的最大地震。通过对该区流动重力资料空间上和时间上的研究分析，从中获得了震前重力变化的某些前兆信息。通过对该 相似文献
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我们设计了一种便携式的宽频带反馈地震计,并与标准长周期地震计(763)及力平衡式宽频带反馈地震计(STS-1V,STS-1H)作了比较,并在不同干扰环境及工作条件下进行了考验.结果是令人满意的.地震计由一台垂直向和两台水平向组成.其惯性质量为0.8kg,自然机械振动周期为15s(秒),机械品质因素约为50.用一差动电容位移换能器将惯性质量的位移变化转变成电信号,而加于电磁系统的反馈使质量维持在它的平衡位置附近.该仪器在其通带范围内具有平坦的位移频响特性.这由反馈网络决定,它相当于一个具有30s 自然周期的位移传感长周期(LP)地震计加上截止频率为0.03s 的二阶低通滤波器系统.该仪器的动态范围为100dB,阻尼为0.8.设计中着重考虑便携性,安装方便以及对环境干扰的有效屏蔽及低功耗. 相似文献
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Impulse response functions derived from different types of flood wave equations (simplified shallow water equations) are continuously developed to conduct the linear channel routing (LCR), which is based on the linearized Saint Venant equation and has been widely applied to avoid any possibility of numerical instability. The impulse response function proposed by Dooge, Napiórkowski, and Strupczewski (1987) and derived from the dynamic wave equation with complete force terms has been acknowledged as a classic work to establish a good physical interpretation for the LCR model; however, the flexibility of altering the shape of impulse response still needs to be improved. Based on the concept of this work, this study intends to introduce the time-varying parameters in the model, so the values of parameters can be adjusted according to the inflow condition, flood stage, and the cross-sectional shape. Moreover, an integrated routing procedure is proposed to formulate the impulse response function for lateral-flow inputs and then to connect multiple inputs from subwatersheds or alongside the main channel with the impulse response function of each channel segment to reflect the spatial variation of hydraulic characteristics among different segments. In the discussion of this article, the impulse response function is analysed to show its sensitivity to hydraulic variables with spatial and temporary variations. Flood-event simulations of a studied watershed are also provided to verify the applicability of the proposed channel routing system. 相似文献
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Witold G. Strupczewski Vijay P. Singh Stanislaw Weglarczyk Krzysztof Kochanek Henryk T. Mitosek 《水文研究》2006,20(16):3535-3554
Similarity and differences between linear flood routing modelling (LFRM) and flood frequency analysis (FFA) techniques are presented. The moment matching used in LFRM to approximate the impulse response function (IRF) was applied in FFA to derive the asymptotic bias caused by the false distribution assumption. Proceeding in this way, other estimation methods were used as approximation methods in FFA to derive the asymptotic bias. Using simulation experiments, the above investigation was extended to evaluate the sampling bias. As a feedback, the maximum likelihood method (MLM) can be used for approximating linear channel response (LCR) by the IRFs of conceptual models. Impulse responses of the convective diffusion and kinematic diffusion models were applied and developed as FFA models. Based on kinematic diffusion LFRM, the equivalence of estimation problems of discrete‐continuous distribution and single‐censored sample are shown both for the method of moments (MOM) and the MLM. Hence, the applicability of MOM is extended for the case of censored samples. Owing to the complexity and non‐linearity of hydrological systems and resulting processes, the use of simple models is often questionable. The rationale of simple models is discussed. The problems of model choice and overparameterization are common in mathematical modelling and FF modelling. Some results for the use of simple models in the stationary FFA are presented. The problems of model discrimination are then discussed. Finally, a conjunction of linear stochastic processes and LFRM is presented. The influence of river courses on stochastic properties of the runoff process is shown by combining Gaussian input with the LCR of the simplified Saint Venant model. It is shown that, from the classification of the ways of their development, both LFRM and FFA can benefit. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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E. Groten 《Journal of Geodynamics》1987,7(3-4)
High precision relative gravimetry can play a dual role in the study of vertical recent crustal movemen: exploring and monitoring. A number of G-meters of LCR type have been calibrated over the full measurement range so that they can be used in almost any part of African. Recent high precision measurements in desert, tropical and subtropical zones reveal clearly that even under unfavorable climatical and transportation conditions precise gravity is available within ± 10 to 20 microgal accuracy. 相似文献
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Time delay problem and its compensation in active control of civil engineering structures were studied. It has been shown by stability analysis of a SDOF system with time delayed feedback that the maximum allowable time delay depends not only on the natural period of the structure but also on feedback gains. We have demonstrated by numerical simulation that the performance of the control system degrades significantly when the time delay is close to this value and it even becomes unstable when time delay is greater than or equal to this value. The maximum allowable time delay decreases with decrease in natural period of the structure as well as with increase in active damping. The paper presents a technique for compensation by modelling time delay as transportation lag. This method ensures the stability of the controlled system as well as the desired response reduction. 相似文献
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Recently, several hybrid protective systems have been explored for applications to seismic-excited bridge structures. In particular, two types of aseismic hybrid protective systems have been shown to be quite effective: (i) rubber bearings and variable dampers (or actuators), and (ii) sliding bearings and actuators. In this paper, control methods are presented for these hybrid protective systems. The control methods are based on the theory of variable structure system (VSS) or sliding mode control (SMC). Emphasis is placed on the static (direct) output feedback controllers using only the information measured from a few sensors without an observer. Simulation results demonstrate that the control methods presented are robust with respect to system parametric uncertainties and the performance is quite remarkable. Sensitivity studies are conducted to evaluate the effectiveness of hybrid protective systems and passive sliding isolators for reducing the response of seismic-excited bridge structures. The advantages of each protective system are demonstrated by simulation results for a wide range of earthquake intensities. 相似文献
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In most of the research work on structural vibration control only two‐dimensional plane structural modelling has been considered, although only a few practical building structures can be modelled as planar structures. Therefore, these methods are not directly applicable to the majority of the practical building structures. This paper discusses the design of a multiobjective optimal fuzzy logic controller (FLC) driven hybrid mass damper (HMD) system for seismically excited torsionally coupled building structures. Floor acceleration and velocity information have been used as feedback to the fuzzy logic controller. A three branch tournament Genetic Algorithm has been used for the multiobjective optimal design of the FLC driven HMD system, where the minimization of the non‐dimensionalized peak displacement, acceleration and rotation of the structure about its vertical axis, have been as the three objective functions. The proposed multiobjective optimal fuzzy logic controller has been verified for an example problem reported in the literature. This HMD system consists of four HMDs arranged in such a way that the system can control the torsional mode of vibration effectively in addition to the flexure modes of vibration. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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短周期地震计主要用于观测地方性的微小地震,用速度传感器设计的反馈式短周期的地震计的工作参数稳定性不好,是国内外观测实践都证实了的问题。借鉴位移传感反馈地震计工作参数偏差较低的思路,介绍了通过采用函数变换方法设计速度传感反馈地震计的解决方案。用函数变换方法设计的速度传感反馈地震计,既实现了加大负反馈深度又不降低噪声指标的双重目标,有加深负反馈和由闭环反馈生成的闭环周期位于通带外的优点。即便是机械摆受到环境变化的影响或随时间推移而出现了漂移或老化,其对通带内的幅频特性的影响亦较小。由函数变换电路生成摆函数的工作周期及工作阻尼与机械摆的参数完全无关,仅取决于变换电路中的两个电阻和两个电容的精度。 相似文献
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Chunxiang Li 《地震工程与结构动力学》2003,32(6):949-964
An Erratum has been published for this article in Earthquake Engineering and Structural Dynamics 2003; 32(15):2451. Multiple active–passive tuned mass dampers (MAPTMD) consisting of many active–passive tuned mass dampers (APTMDs) with a uniform distribution of natural frequencies have been, for the first time here, proposed for attenuating undesirable oscillations of structures under the ground acceleration. The MAPTMD is manufactured by keeping the stiffness and damping coefficient constant and varying the mass. The control forces in the MAPTMD are generated through keeping the identical displacement and velocity feedback gain and varying the acceleration feedback gain. The structure is represented by the mode‐generalized system corresponding to the specific vibration mode that needs to be controlled. Through minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure with the MAPTMD (i.e. through implementation of Min.Min.Max.DMF), the optimum parameters of the MAPTMD are investigated to delineate the influence of the important parameters such as mass ratio, total number, normalized acceleration feedback gain coefficient and system parameter ratio on the effectiveness (i.e. Min.Min.Max.DMF) and robustness of the MAPTMD. The optimum parameters of the MAPTMD include the optimum frequency spacing, average damping ratio and tuning frequency ratio. Additionally, for the sake of comparison, the results for a single APTMD are also taken into account in the present paper. It is demonstrated that the proposed MAPTMD can be employed to significantly reduce the oscillations of structures under the ground acceleration. Also, it is shown that the MAPTMD can render high robustness and has better effectiveness than a single APTMD. In particularly, if and when requiring a large active control force, MAPTMD is more promising for practical implementations on seismically excited structures with respect to a single APTMD. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献