Test research on influence of draft on towing behaviors of 3-bucket foundation platform

To investigate the natural frequencies and towing behaviors of a 3-bucket foundation platform at different drafts, the decay and towing experiments were carried out in a towing tank on a scale of 1:20. The air pressure inside the bucket foundations, the water pressure at the bottom of the bucket foundations, the acceleration of the platform and the towing force were determined in the test process. The time-history curves of the measured parameters were obtained, and the frequency responses of the parameters at different drafts were analyzed by means of fast Fourier transform(FFT). The results showed that the platform natural frequency of heave decreased slightly with the rise of draft. The natural frequencies of roll and pitch are much lower than that of heave, and they increased slightly with the increase of draft. When towing in the following sea, the maximum acceleration of surge, sway and heave has downward trends with the increase of draft, but the change range decreased gradually with the increase of draft. When the draft is 5.0 m(the ratio of draft to bucket height is 0.56), the towing dynamic responses achieve the maximum, which is not conducive to the towing of the platform. When the draft is 6.0 m(the ratio of draft to bucket height is 0.67), the towing dynamic responses are the most stable.     

Investigation of a ship’s hydroelasticity and seakeeping performance by means of large-scale segmented self-propelling model sea trials

The traditional laboratory models for the hydroelasticity and seakeeping performance of ships are tested in calm water and in uni-directional, artificially generated waves. A new alternative to the tank model measurement methodology is to conduct experiments using large-scale models in actual sea conditions. To implement the tests, a large-scale segmented self-propelling model and testing system were designed and assembled. A buoy wave meter was adopted to record the coastal waves that the model encountered during the tests. The analysis of the results of waves in sheltered waters by the spectral method shows good agreement with ISSC spectra. To investigate the difference between this new methodology and the traditional towing tank tests, a small-scale model, whose type and configuration are the same as those of the large-scale model ship, was used and tests were conducted in a towing tank. Comparison of the two experimental results shows that there is a remarkable difference in the response characteristics between the large-scale model at sea and the small-scale model in the tank. Numerical simulations of the responses of the ship under equivalent sea states were also carried out. The influence of directional spreading functions on the results was analyzed by a numerical approach. The classical model tests under long-crested waves in the towing tank over-estimate the motion and wave load responses; however, large-scale model tests carried out at sea are more reasonable for ship design and scientific research.     

对自来水厂供水方案选择的分析

本文以普明水厂为例,说明将水泵变速运行以适应用水量的变化又保持恒定的扬程,是最优的一种供水方式。它革除了传统的水塔、水箱、气压罐等容器。因此,投资省、供水质量好,节能效果显著。近年来这一新技术已在水泵站、城市小区、高层建筑、工业及消防用水各领域逐步推广,均获得较好的经济效益。 当用多台泵并联供水时,可将台数控制与转速控制结合在一起,因此可靠性更高,节能效果更好。     

Motion information analysis system based on acceleration signals

A motion information analysis system based on the acceleration data is proposed in this paper,consisting of filtering,feature extraction and classification.The Kalman filter is adopted to eliminate the noise.With the time-domain and frequency-domain analysis,acceleration features like the amplitude,the period and the acceleration region values are obtained.Furthermore,the accuracy of the motion classification is improved by using the k-nearest neighbor （KNN） algorithm.     

建筑结构地震响应混沌特性及影响因素分析

采用混沌时间序列分析方法分别对以经典混沌信号和地震动为激励的结构响应进行混沌特性分析,从关联维数、Kolmogorov熵及最大Lyapunov指数等定量指标的角度,考察结构自振周期、地震动的类型和幅值等因素对结构地震响应的非线性特性的影响。研究结果表明:在经典混沌信号和地震动作用下,经过结构的放大和滤波作用,结构加速度响应仍然保留了混沌特性,且通过混沌参数的变化程度能够判断结构是否进入弹塑性状态。结构自振周期为结构加速度响应的混沌特性的主要影响因素;幅值对经典混沌信号作用结构下加速度响应的混沌特性影响较为显著;而地震动的类型、幅值等因素对地震动作用下响应的混沌特性影响更为显著。     

Dynamic Simulation on Collision Between Ship and Offshore Wind Turbine简

By using ABAQUS/Explicit, the dynamic process of an offshore wind turbine（OWT） stricken by a ship of 5000DWT in the front direction is simulated. The OWT is located on a large-scale prestressing bucket foundation constructed by an integrated installation technique. According to the simulation results, under the ship collision, a cer-tain range of plastic zone appears within a local area of arc transition structure of the bucket foundation, and the con-crete plastic zone is seriously damaged. As the stress level of OWT tower is relatively low, the OWT tower is less af-fected. A great inertial force is generated at the top of the OWT tower as the mass of nacelle and blades is up to 400 t. The displacement of the tower is in the opposite direction of the ship collision at the end of 1 s under the action of iner-tial force. There is only a minor damage in the ship bow. Most of the kinetic energy is transformed into the plastic dissipation and absorbed by the arc transition structure of bucket foundation.     

One-step-installation of offshore wind turbine on large-scale bucket-top-bearing bucket foundation

In 2010,the first offshore wind turbine with integrated installation was established in Qidong sea area of Jiangsu Province,China,which led to the implementation phase of one-step-installation technique based on the design and construction of large-scale bucket-top-bearing (LSBTB) bucket foundation.The critical technique of LSBTB bucket foundation included self-floating towing,penetration with adjustment of horizontal levelness,removability and one-step-installation.The process of one-step-installation included the prefabrication of LSBTB bucket foundation in onshore construction base,installation and debugging of wind power,overall water transportation of foundation and wind power system,and installation of foundation and offshore wind turbine on the appointed sea area.The cost of one-step-installation technique was about 5 000 Yuan/kW,which was 30%-50% lower than that of the existing technique.The prefabrication of LSBTB bucket foundation took about two months.During the one-step-installation process,the installation and debugging of wind power and overall water transportation need about one to two days in sea area within 35 m depth.After the proposed technique is industrialized,the cost will be further reduced,and the installation capacity is expected to be up to 500 wind turbines per year.     

强震作用下独塔斜拉桥抗震性能分析

以某跨径为110 m的独塔异形斜拉桥为工程背景,通过非线性有限元分析对斜拉桥在强震作用下的地震响应特性及减震措施进行了研究,得出如下结论:相比Lander-amboy波,卓越周期与桥梁固有周期较为接近的Cerro Prieto波能够引起结构较大的地震响应。行波效应能够显著增大工程背景斜拉桥的地震响应,且随着视波速的增大,桥梁的加速度响应明显增大。阻尼系数25 000 kN·s/m为工程背景斜拉桥的最优粘滞阻尼器设计参数,且在塔梁连接处安装该参数粘滞阻尼器后,斜拉桥减震效果显著,尤其能明显减小结构的位移响应。     

讨论Hanoi塔问题

从Hanoi塔不变的塔座位置入手,用静态的塔座位置对应在圆盘的移动过程中不断变化的形式参数,很直观地讨论了Hanoi塔的递推和回推过程。     

土钉墙优化设计及稳定性分析

建立一种土钉墙的优化设计模型,并编制优化设计程序;同时提出土钉长度和直径变化与最危险滑移面位置改变的动态关联思想,程序模拟动态变化自动搜索最不利滑移面位置;并且模拟土钉墙开挖施工过程,分级验算基坑稳定性,避免因设计过程中只验算基坑最终开挖深度稳定性而忽略开挖过程中的稳定性验算导致的施工过程失稳破坏。     

并接两个电光偏转器的激光脉冲稳定性实验研究

介绍用两个相同的电光偏转器相应的电极并联连接后,激光脉冲光束依次通过它们进行偏转扫描的削波整形原理.由实验测出用两个电光偏转器并联比用单个对激光脉冲扫描光线更长,在同样的狭缝宽度下削出更窄的激光脉冲,提高了输出激光脉冲幅度的稳定性,幅度起伏RMS的精度提高了约33.3%,实验结果与理论基本一致.虽还没有达到理论分析预期的效果,但也说明电光偏转器偏转能力还有进一步挖掘的潜力,用电光偏转器进行激光脉冲稳定性的实验研究,在惯性约束核聚变、激光脉冲削波、整形等方面有广泛的应用前景.     

受约束的广义Birkhoff系统的平衡稳定性

建立了受约束的广义Birkhoff系统的运动方程,求出系统的平衡位置,并在平衡位置处建立受约束的广义Birkhoff系统的受扰运动方程,根据Lyapnnov一次近似理论和直接法来判定受约束的广义Birkhoff系统的平衡稳定性。举例说明它的应用。     

Seismic response of offshore wind structure supported by bucket foundation

An integrated finite element model(FEM)of offshore wind tower-foundation-soil is established by ABAQUS, where a large-scale composite bucket foundation with seven compartments inside is applied to supporting the upper wind tower. The dynamic response of the structure-foundation system is studied under three seismic waves with the same peak ground acceleration of 0.035g. It can be seen that the dynamic response increases at the beginning with the structure height, then it decreases because the structural damping increases due to the mass effect of the upper wind turbine generator system. It is shown that the anti-liquefaction capacity of the soil inside and underneath the foundation is improved owing to the high overburden pressure of the upper structure and the constraint effect of the bucket skirt and subdivisions. Moreover, the liquefaction resistance of the soil inside the middle compartment is improved to a higher degree than that inside the side compartments.     

Optimal Skirt Spacing for Subsea Skirted Foundation Considering Floating Stability

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.     

自由来流中展向速度对流动稳定性的影响

采用线性稳定性理论研究了三维平板边界层中展向来流速度对流动稳定性的影响。在基本流中给出了展向速度的大小,从特征值、特征函数和扰动波的增长幅值上显示不同展向来流速度的计算结果,并和无展向来流速度的二维边界层进行比较,结果表明,展向速度对边界层内的扰动起着不稳定的作用,且展向速度越大稳定性越差。     

Design of large-scale prestressing bucket foundation for offshore wind turbines

The key in the force transmission between the tower and the foundation for offshore wind turbines is to transfer the large moment and horizontal loads.The finite element model of a large-scale prestres...     

电子镇流器中半桥逆变电路负载特性分析

为了电子镇流器电路的准确分析和设计,对半桥逆变电路的稳态工作状态进行了时域分析,把工作在高频状态下的灯管近似等效为一个电阻,运用分阶段时域分析法推导大功率细灯管节能灯的灯管电压表达式,并用示波器测量出灯管两端电压波形,结果显示,实测波形与理论波形基本一致,为电子镇流器的设计工作提供了依据和便利,具有较大的应用价值。     

Floating-roof steel tanks under harmonic settlement：FE parametric study and design criterion

INTRODUCTION Vertical cylindrical steel tanks widely used for fluid storage generally consist of a thin bottom plate, a cylindrical shell, and a fixed or floating roof. Large tanks constructed on soft foundations are susceptible to various types of settlement deflections. The set-tlement components are: uniform settlement, planar tilt and differential settlement. The uniform settle-ment and planar tilt cause rigid-body deflection or rotation of the tank, and so, are of relatively little i…     

基于电容倍增器的超低频正弦信号发生器的研究

为了改善超低频正弦信号发生器对电容大容量、无极性的要求,介绍了一种基于电容倍增原理的超低频正弦波振荡电路。利用电容倍增器的原理,选择电容接地的RC移相选频网络,设计一个三节相位滞后式RC正弦波振荡器。通过硬件电路实验和仿真分析,此电路能够实现以无极性、小容量等高性能参数电容获得频率很低、幅值大的正弦信号输出。此振荡电路调节方便,输出稳定,可满足实验教学对超低频信号源的要求。     

Reduction of Vibration Noise for Amorphous Metal Alloy Core Distribution Transformer

To understand the vibration noise behaviors of amorphous metal alloy core distribution transformer(AMACDT), a 10 k VA prototype was tested under no-load and short-circuit conditions, respectively. The vibration characteristics were described when rated voltage was applied to the secondary side, and the primary side was connected with different load resistances. The largest amplitude positions on the upper bracket and tank surfaces were recorded by vibration sensors arranged on the surface. A data-acquisition platform was set up for signal measurement. The vibration amplitude related to frequency was discussed, and experimental results indicated that the position with the largest amplitude accrued in the middle of the upper bracket and tank surface, at phases a and c, respectively. The experimental results suggest that magnetostrictive and electrodynamic forces play a major role in exciting the vibration noise. At the same time, some rib-reinforcements were welded on the upper bracket and tank surfaces to lessen the vibration energy, which reduced the noise.