首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 393 毫秒
1.
In this paper, a semi-analytical method for the analysis of pile-supported embankments is proposed. The mathematic model describes the cooperative behavior of pile, pile cap, foundation soil, and embankment fills. Based on Terzaghi??s 1D consolidation theory of saturated soil, the consolidation of foundation soil is calculated. The embankments with two different types of piles: floating piles and end-bearing piles are investigated and discussed. The results of axial force and skin friction distributions along the pile and the settlements of pile-supported embankments are presented. It is found that it takes a longer time for soil consolidation in the embankment with floating piles, compared with the case using end-bearing piles. The differential settlement between the pile and surrounding soil at the pile top is larger for the embankment with end-bearing piles, compared with the case of floating piles.  相似文献   

2.
以振动压路机为例,对振动压路机压实过程建立了三自由度线性动力学方程,分别运用欧拉数值积分法和频域分析法进行了仿真.仿真结果显示,两种方法计算出的压路机系统响应结果一致.数值积分法所得的系统响应包含瞬态响应和稳态响应,计算时间长,对初始条件要求严格;而频域分析法得到的系统响应只有稳态响应,计算时间短,但对采样频率有一定的要求.  相似文献   

3.
The intact stability and damage stability of a model of an anemometer tower with buoyancy tank foundation are computed by the finite element software MOSES in this paper. The natural period of the anemometer tower is discussed through frequency domain analysis. The influence of a single factor, such as towing point position, wave height, wave direction and wave period, on towing stability is discussed through time domain analysis. At the same time, the towing stability under the condition of various combinations of many factors is analyzed based on the meas- ured data of the target area. Computer simulation results show that the intact stability is preferable and the damage stability is sufficient under the condition of plenty of subdivisions. Within the scope of the buoyancy tank foundation, the higher the towing point position is, the better the stability is. Wave height has a great impact on the motion amplitude of buoyancy tank foundation, but the effect on the acceleration is not obvious; wave period has a great impact on the acceleration, while the effect on the motion amplitude is not obvious; following-waves towing is more conducive to safety than atry.  相似文献   

4.
Numerical simulation and experimental tests were carried out to examine the hydrodynamic behaviors of a double-column floating system of gravity cage under wave conditions. A floating system of gravity cage can be treated as a small-sized floating structure when compared with the wavelengths. The main problem in calculating the wave loads on the small-sized floating structure is to obtain the reasonable force coefficients, which may differ from a submerged structure. In this paper, the floating system of gravity cage is simplified to a 2D problem, where the floating system is set symmetrically under wave conditions. The motion equations were deduced under wave conditions and a specific method was proposed to resolve the problem of wave forces acting on a small-sized floating system of gravity cage at water surface. Results of the numerical method were compared with those from model tests and the hydrodynamic coefficients Cn and Cr were studied. It is found that Cn ranges from 0.6 to 1.0 while Cr is between 0.4 and 0.6 in this study. The results are useful for research on the hydrodynamic behavior of the deep-water gravity sea cages.  相似文献   

5.
INTRODUCTION There is obvious demand for oil exploitation in deep water. Increasing water depth will make the environment more severe and so some innovative structures are required for economic production of gas and petroleum in deep water. An engineering idea is the minimization of the structure resistance to en-vironmental loads by making the structure flexible. This structural flexibility causes nonlinearity in the structural stiffness matrix because of large deforma-tions. Wave loadi…  相似文献   

6.
基于ANSYS的高速包装机的椭圆齿轮模态分析   总被引：1，自引：1，他引：0  
采用有限元法,建立了椭圆齿轮的动力学模型,通过有限元分析软件ANSYS对椭圆齿轮进行模态分析,得到了椭圆齿轮的前六阶固有频率和对应振型。该方法和所得结果为动态设计提供了参考,同时也为椭圆齿轮系统的动态响应计算和分析奠定了基础。  相似文献   

7.
The singularities and oscillatory performance of translating-pulsating source Green＇s function in Bessho form were analyzed. Relative numerical integration methods such as Gaussian quadrature rule, variable substitution method （VSM）, and steepest descent integration method （SDIM） were used to evaluate this type of Green＇s function. For SDIM, the complex domain was restricted only on the 0-plane. Meanwhile, the integral along the real axis was computed by use of the VSM to avoid the complication of a numerical search of the steepest descent line. Furthermore, the steepest descent line was represented by the B-spline function. Based on this representation, a new self-compatible integration method corresponding to parametric t was established. The numerical method was validated through comparison with other existing results, and was shown to be efficient and reliable in the calculation of the velocity potentials for the 3D seakeeping and hydrodynamic performance of floating struc- tures moving in waves.  相似文献   

8.
针对感烟、感温等火灾探测器探测距离短,响应速度慢,易受到外界信号干扰导致误判和漏判等问题,提出了一种基于热释电火焰传感器和数字信号处理实现方案．系统以dsPlC33FJ64GP802处理器作为核心构建信号处理平台,信号先通过预处理电路隔直,滤波,放大处理之后通过数字信号处理系统,采用IIR数字滤波器滤除干扰信号,再进行FFT运算,将信号由时域转换到频域,计算出信号在各个频段的能量值,通过分析火焰信号的时域与频域,实现对火焰信号的准确判断．基于本设计方案的火焰探测器,可以通过适当增加光学组件改变探测距离,并能实现远距离火焰探测．这在大空间自动消防水炮设计、森林防火等领域具有广阔的应用前景．试验证明,本系统达到了预期的效果．  相似文献   

9.
在考虑坝水耦合振动影响下,对拱坝边坡在地震作用下承受的动水压力进行了理论分析和数值计算。对正常蓄水位时、枯水位时边坡地震响应进行了分析。包括边坡的损伤演化、应力、位移的分析。在水坝地震动力分析中,应当将边坡、库水和地基三者作为一个综合的振动系统进行动力分析,考虑它们之间的相互作用,为类似库区边坡稳定性评价和边坡加固提供理论依据。  相似文献   

10.
在一般的信道预测方案中,对于信道脉冲响应的预测问题,有些是没有考虑到信道传输函数的相关性,一些预测方案则是实现复杂度较高。针对这些问题,首先实现时域的信道预测方法,再用根据信道传输函数的自相关函数设计出来的滤波器对预测后信道的频率响应进行滤波,可使预测后的信道频域相关性与观测的信道频域相关性一致。这样,时间上的相关性可确保信道预测的可行性,而频域相关性保证了预测前后的空间相关性不变,从而时频联合信道预测方案与其他方案相比具有更可靠的信道预测效果。  相似文献   

11.
The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are utilized to examine the time dependent flow field and pressure field inside the proposed flowmeter. The effect of varying structural parameters on flow characteristics of the proposed fluidic flowmeter is investigated by computational simulations for the optimization. Both the simulation and experimental results disclose that the hydrodynamic vibration,with the same intensity,frequency and 180° phase shift,occurs at axisymmetric points in the feedback channel of the fluidic flowmeter. Using the structural combination of impinged concave wall and bistable fluid amplifier and differential signal processing technique,a novel fluidic flowmeter with excellent immunity and improved sensibility is developed.  相似文献   

12.
In this paper, the effects of second-order difference-frequency wave forces on the global motion of an offshore wind turbine system with a large displacement under the survival condition are studied. In this case, the hydrodynamic force is the main force because the blades are feathered to reduce the lifting force. The first-order hydrodynamic forces are calculated by WADAM, while the second-order wave forces are calculated by a customized MATLAB module. Then the hydrodynamic coefficients are transferred to the wind turbine analytical code FAST. Through the comparisons of dynamic responses between the first- and second-order numerical models, it is found that the second-order wave forces significantly influence the motion of floating wind turbine under the survival condition. Moreover, neglecting the second-order force significantly underestimates the tension forces in the mooring lines.  相似文献   

13.
提出一种以空间换取时间的方案,能有效提高分数域时频分析的运算效率。鉴于该算法对时间域进行切割,将导致时频分布在衔接处出现边界效应,文章还提出错位平滑技术,有效将各时间段的时频分布进行无缝拼接。  相似文献   

14.
随着WTO后过渡期内人口流动特别是农村相对剩余劳动力的跨地区流动大量增加,公安机关的流动人口管理形势日趋严峻。本文在对现行的以暂住证为核心的流动人口管理模式进行分析的基础上,提出了一种基于居民身份证的流动人口登记制度管理模式。  相似文献   

15.
ABSTRACT

Distance education (DE) is a constantly evolving and advancing field, and as such, its intellectual network and dynamics need to be investigated and explored. In this regard, this study reviewed a total of 1685 articles and 51,940 references through social network analysis for a bibliometric examination of the DE field. The findings indicate that DE is an interdisciplinary field and part of mainstream education. The progressive knowledge domain analysis revealed that the intellectual roots of DE stem from generic social learning theories, after which DE-related theories began to emerge following the foundation of open universities. The research concludes that there was a paradigm shift that resulted from developments in online networked technologies in the 2000s, at which time DE started to gradually evolve into sixth generation ubiquitous DE.  相似文献   

16.
A hydraulics model is built in Moses to find the optimal internal skirt spacing for the maximum floating stability of the skirted foundation. The results show that the increase in the internal skirts' number can help improve the floating stability of the skirted foundation. However, with the increase in the internal skirts' number, the improvement of floating stability becomes more and more weak. In this study, an optimal number of four are found for the internal skirt spacing. Moreover, to testify the feasibility of internal skirt spacing, a practical project is modeled, which indicates that the optimal internal skirt spacing can satisfy the requirements of towing.  相似文献   

17.
通过拟合实用自动交流调压器的传递函数,在频域和时域两方面对其进行稳定性分析及PID校正理论设计,并据此设计了新的自动控制研究性自主性实验。根据自控理论对调压器在适当校正环节下的动态曲线进行二阶近似拟合,求出其无阻尼自然频率和阻尼比,进而求出调压器在无校正环节时的近似闭环传递函数。故可在调压器系统中加入各种校正环节,在频域中根据bode图分析调压器的稳定性和进行PID校正理论设计,还可在时域中直观地表现出频域的分析结果,并加以实验验证。该方法对于实用自控装置的工程设计有所裨益;作为研究性实验也较为理想。  相似文献   

18.
大城市农民工中青年人所占的比例较大,这部分流动人口有其自身的特点,在以往的调查研究中大多没有通过对比其他年龄人群的方法对此加以总结.上海市闵行区的流动人口抽样调查数据显示,青年农民工在职业结构特征、寻找工作途径、工作时间与工资报酬、更换工作的频率与原因等方面与其他年龄人群的流动人口相比具有明显的差异;由此可以发现青年农民工就业中存在的主要问题,即受教育程度偏低,相互关联的就业隔离与社会隔离,针对流动人口中青年人的就业扶助政策还不够等.因此,有关部门应从发展职业教育、培育劳动力市场、完善制度和法规以及促进青年流动人口的社会整合等方面着手解决上述问题.  相似文献   

19.
The vertical vibration of a large diameter pile embedded in inhomogeneous soil with hysteretic type damping is investigated based on the 3D axisymmetric model. Firstly, the pile is assumed to be a Rayleigh-Love rod with the consideration of its transverse inertia effect. Following this assumption, the pile-soil system is divided into several segments according to the stratification of the surrounding soil, and the dynamic interactions of the adjacent soil layers are simulated using the distributed Voigt model. Meanwhile, the surrounding soil is discretized into finite annular vertical zones to consider its radial inhomogeneity, and the force equilibrium and displacement coordination are satisfied at the interfaces of the adjacent soil zones and the interface of the pile-soil. Then, the analytical solution in the frequency domain and the semi-analytical solution in the time domain are obtained by solving the vibration governing equations of pile-soil system. Based on the solutions, a parametric analysis is conducted to investigate the influence of the transverse inertia effect on the dynamic response of the large diameter pile and its relationship with the pile parameters and the radial inhomogeneity of the surrounding soil. Finally, a comparison with the measured result and two other calculated results is presented to verify the effectiveness of the present solution.  相似文献   

20.
系统采用ARM920T作为核心处理器,以低频信号作为信号源,采用DDS技术,从而实现相频,幅度,频率特性的分析仪器,能够简单的实现信号源的时域和具体参数的波形。本系统主要由ARM920T控制处理器,DDS扫频模块,ADC采样模块,DAC输出模块,检波滤波器模块,扫频信号源幅度模块组成。其中处理器采样ARM920T,扫频信号源采样DDS芯片AD9851,检波模块以AD637JQ芯片构成,相位检测模块由AD8302芯片构成,通过DAC芯片TLV5618控制扫频信号的幅度。通过实验本仪器可以检测20Hz到1MH  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号