Optimal design for buckets layout based on muck removal analysis of TBM cutterhead

The layout of the buckets for tunnel boring machine(TBM)directly affects the muck removal efficiency of cutterhead during excavation.In order to improve the muck removal performance for TBM,the optimal design of bucket layout was investigated.The whole muck transfer process was simulated by discrete-element method(DEM),including the muck falling,colliding,pilling up,shoveling and transferring into the hopper.The muck model was established based on size distribution analysis of muck samples from the water-supply tunnel project in Jilin Province,China.Then,the influence of the bucket number and the interval angle between buckets on muck removal performance was investigated.The results indicated that,as the number of buckets increased from four to eight,the removed muck increased by 29%and the residual volume decreased by 40.5%,and the process became steadier.Different interval angles between buckets were corresponding to different removed muck irregularly,but the residual muck number increased generally with the angles.The optimal layout of buckets for the cutterhead in this tunnel project was obtained based on the simulation results,and the muck removal performance of the TBM was verified by the actual data in the engineering construction.

High-resolution Load Profile Clustering Approach Based on Dynamic Largest Triangle Three Buckets and Multiscale Dynamic Warping Path Under Limited Warping Path Length

With the popularity of smart meters and the growing availability of high-resolution load data, the research on the dynamics of electricity consumption at finely resolved timescales has become increasingly popular. Many existing algorithms underperform when clustering load profiles contain a large number of feature points. In addition, it is difficult to accurately describe the similarity of profile shapes when load sequences have large fluctuations, leading to inaccurate clustering results. To this end, this paper proposes a high-resolution load profile clustering approach based on dynamic largest triangle three buckets(LTTBs) and multiscale dynamic time warping under limited warping path length(LDTW). Dynamic LTTB is a novel dimensionality reduction algorithm based on LTTB. New sequences are constructed by dynamically dividing the intervals of significant feature points. The extraction of fluctuation characteristics is optimized. New curves with more concentrated features will be applied to the subsequent clustering. The proposed multiscale LDTW is used to generate a similarity matrix for spectral clustering, providing a more comprehensive and flexible matching method to characterize the similarity of load profiles. Thus, the clustering effect of a high-resolution load profile is improved. The proposed approach has been applied to multiple datasets. Experiment results demonstrate that the proposed approach significantly improves the Davies-Bouldin indicator(DBI) and validity index(VI). Therefore, better similarity and accuracy can be achieved using high-resolution load profile clustering.

Pelton turbine: Identifying the optimum number of buckets using CFD

A numerical case study on identifying the optimum number of buckets for a Pelton turbine is presented. Three parameters： number of buckets, bucket radial position and bucket angular position are grouped since they are found to be interrelated. By identifying the best combination of the radial and angular position for each number of buckets it is shown that reduction in the number of buckets beyond the limit suggested by the available literature can improve the efficiency and be beneficial with regard to the manufacturing complexity and cost perspective. The effect of this reduction in the number of buckets was confirmed experimentally.

Experimental Study on Towing Characteristics of Composite Bucket Wellhead Platform

With the rapid development of large-scale development of marginal oilfields in China,simple wellhead platforms that are simple in structure and easy to install have become an inevitable choice in the process of oilfield development.However,traditional simple wellhead platforms are often discarded after a single use.In pursuit of a more costeffective approach to developing marginal oilfields,this paper proposes a new offshore oil field development facility—an integrated bucket foundation for wellhead platform.To verify the safety of its towing behavior and obtain the dynamic response characteristics of the structure,this paper takes a bucket integrated bucket foundation for wellhead platform with a diameter of 40 m as the research object.By combining physical model tests and numerical simulations,it analyzes the static stability and dynamic response characteristics of the structure during towing,complete with the effects of the draft,wave height,wave period,and towing point height,which produce the dynamic responses of the structure under different influence factors,such as roll angle,pitch angle,heave acceleration and towing force as well as the sensibility to transport variables.The results show that the integrated bucket foundation for wellhead platform is capable of self-floating towing,and its movement is affected by the local environment,which will provide a reference for actual projects.

Influence of Incomplete Soil Plugs on Bearing Capacities of Bucket Foundations in Clay

Due to the uneven seabed and heaving of soil during pumping,incomplete soil plugs may occur during the installation of bucket foundations,and the impacts on the bearing capacities of bucket foundations need to be evaluated.In this paper,the contact ratio(the ratio of the top diameter of the soil plug to the diameter of the bucket)and the soil plug ratio(the ratio of the soil heave height to the skirt height)are defined to describe the shape and size of the incomplete soil plug.Then,finite element models are established to investigate the bearing capacities of bucket foundations with incomplete soil plugs and the influences of the contact ratios,and the soil plug ratios on the bearing capacities are analyzed.The results show that the vertical bearing capacity of bucket foundations in homogeneous soil continuously improves with the increase of the contact ratio.However,in normally consolidated soil,the vertical bearing capacity barely changes when the contact ratio is smaller than 0.75,while the bearing capacity suddenly increases when the contact ratio increases to 1 due to the change of failure mode.The contact ratio hardly affects the horizontal bearing capacity of bucket foundations.Moreover,the moment bearing capacity improves with the increase of the contact ratio for small aspect ratios,but hardly varies with increasing contact ratio for aspect ratios larger than 0.5.Consequently,the reduction coefficient method is proposed based on this analysis to calculate the bearing capacities of bucket foundations considering the influence of incomplete soil plugs.The comparison results show that the proposed reduction coefficient method can be used to evaluate the influences of incomplete soil plug on the bearing capacities of bucket foundations.

Experimental Study on the Sinking and Leveling of A Large-Capacity Offshore Wind Turbine Five-Bucket Foundation in Sand

As offshore wind farms expand into deeper and farther ocean regions and the unit capacity of offshore wind turbines(OWTs)increases,there is a pressing need for a new foundation structure that can accommodate deep-sea conditions and support large capacities while maintaining economical and safe.To meet this goal of integrated transportation and one-step installation,a novel five-bucket jacket foundation(FBJF),with its suction installation and leveling methods in sand,has been proposed,analyzed and experimentally studied.First,seepage failure experiments of the FBJF at various depths were conducted,and a formula for calculating the critical suction of seepage failure suitable for the FBJF in sand was chosen and recommended for use with a range of values for the permeability coefficient ratio.Second,through leveling experiments of the FBJF at different depths,the maximum adjustable leveling angle during the sinking process was defined using seepage failure and the adjustable leveling angle of the foundation as control criteria.Various leveling control strategies were proposed and verified.Finally,an automatic sinking and leveling control system for the FBJF was developed and experimentally verified for feasibility.

砂土中长径比对三筒基础水平承载特性的影响

The tripod foundation(TF)is a prevalent foundation configuration in contemporary engineering practices.In comparison to a single pile,TF comprised interconnected individual piles,resulting in enhanced bearing capacity and stability.A physical model test was conducted within a sandy soil foundation,systematically varying the length-to-diameter ratio of the TF.The investigation aimed to comprehend the impact of altering the height of the central bucket on the historical horizontal bearing capacity of the foundation in saturated sand.Additionally,the study scrutinized the historical consequences of soil pressure and pore water pressure surrounding the bucket throughout the loading process.The historical findings revealed a significant enhancement in the horizontal bearing capacity of the TF under undrained conditions.When subjected to a historical horizontal loading angle of 0°for a single pile,the multi-bucket foundation exhibited superior historical bearing capacity compared to a single-pile foundation experiencing a historical loading angle of 180°under pulling conditions.With each historical increment in bucket height from 150 mm to 350 mm in 100 mm intervals,the historical horizontal bearing capacity of the TF exhibited an approximately 75%increase relative to the 150 mm bucket height,indicating a proportional relationship.Importantly,the historical internal pore water pressure within the bucket foundation remained unaffected by drainage conditions during loading.Conversely,undrained conditions led to a historical elevation in pore water pressure at the lower side of the pressure bucket.Consequently,in practical engineering applications,the optimization of the historical bearing efficacy of the TF necessitated the historical closure of the valve atop the foundation to sustain internal negative pressure within the bucket.This historical measure served to augment the historical horizontal bearing capacity.Simultaneously,historical external loads,such as wind,waves,and currents,were directed towards any individual bucket within the TF for optimal historical performance.

基于Bucket改进多箱体模型的降雨径流预报

洪涝灾害造成的淹没区覆盖范围广、影响严重,灾前进行洪水预警评估能够在洪灾发生时及时疏散人员和保护财产。针对易受洪水侵袭的美国密西西比河圣路易斯流域,对比了不同复杂度、不同结构特点的Bucket、Simhyd、Smar、Hycy降雨径流模型,并分析了复杂度和结构对流域拟合结果的影响。通过对初始Bucket模型的不断改进,利用Bucket_3改进多箱体模型拟合流域水文,以KGE为模型拟合评价标准,利用2014—2016年的气象径流数据进行模型参数率定,校准精度为0.82;预估2016—2018年的径流数据,精度可达0.79,能很好地识别异常径流的出现,达到洪水灾前预警的目的。

A multi-length bunch design for electron storage rings with odd buckets

A scheme with two superconducting RF cavities is designed to upgrade electron storage rings with odd buckets to multi-length bunches. In this paper, the Hefei Light Source（HLS） is given as an example for odd buckets. As it is designed for 45 buckets, which is a multiple of 3, simultaneous generation of three different lengths of bunches is proposed with the presently applied user optics. The final result, without low-α optics, is to fill HLS with long bunches of length 50 ps, medium bunches of 23 ps and short bunches of 6 ps. Every third bucket can be filled with short bunches, of which the current limit is up to 6.6 m A, more than 60 times the limit for low-α mode.Moreover, particle tracking simulations to examine the beam dynamics, performed by ELEGANT, and calculations of the beam instabilities are presented in this paper.

Energy dissipation of slot-type flip buckets

The energy dissipation is a key index in the evaluation of energy dissipation elements.In the present work,a flip bucket with a slot,called the slot-type flip bucket,is theoretically and experimentally investigated by the method of estimating the energy dissipation.The theoretical analysis shows that,in order to have the energy dissipation,it is necessary to determine the sequent flow depth h1 and the flow speed V1 at the corresponding position through the flow depth h2 after the hydraulic jump.The relative flow depth h2/ho is a function of the approach flow Froude numberFro,the relative slot widthb/Bo,and the relative slot angleθ/β.The expression for estimating the energy dissipation is developed,and the maximum error is not larger than 9.21%.

Flow choking over weir flow slit-type flip buckets

The flow choking may occur for weir flow slit-type flip buckets trader common operation conditions. An estimation method is developed through introducing a comprehensive coefficient to determine the approach flow Froude number for the flow choking to occur in those flip buckets. The error of the present method relative to the experimental data is less than 5%. The results show that, the Froude number for the flow choking to occur is related to the contraction ratio and the contraction angle of the flip buckets. When the flow choking occurs, the upper jet trajectory decreases and the lower one is almost not affected, and the dynamic pressures on the bottom and the sidewalls increase due to the flow profile rising on the flip buckets.

Flow regime and energy dissipation of SFS-type flip buckets

In the present work,a slot-type flip bucket with separated flows,called SFS-type flip bucket,is developed,and flow regime and energy dissipation are experimentally investigated.Comparing with the circular-shaped or slot-type flip bucket buckets,the present SFS-type flip bucket has better flow regime and larger energy dissipation since the three branches of the flows are separated through the outlet of the flip bucket.Meanwhile,the energy dissipation for this flip bucket is estimated.

Stability Study on the Bucket Foundation with Multi-Compartment During the Floating-up Process Considering Air Compressibility

In the process of developing offshore wind power towards deeper waters,the advantages of the bucket foundation in terms of integrated construction and economy are becoming increasingly evident.In contrast to conventional floating bodies,the air-floating bucket foundations can achieve self-floating with the help of the air in the compartment and adjust its buoyancy and stability by controlling the air volume in the compartment.The construction process of the bucket foundation involves the control of air in the compartment,thus making it more difficult to construct.Especially after the prefabrication of the bucket foundation,the stability of the bucket foundation at the floating-up stage is particularly critical.The stability of a multi-compartment bucket foundation during the floating-up process cannot be accurately evaluated as the existing theoretical method of air-floating structures does not adequately consider air compressibility.To ensure the safety of the floating-up process,a theoretical method based on the idea of intact stability has been developed to analyze the stability of the air-floating bucket foundations,which will allow accurate calculation of the righting arm for different tilt states and critical air leakage angle.At the same time,accuracy and feasibility of the proposed theoretical method are verified through indoor model tests and practical operation of the prototype structure during the floating-up process.In addition,measures to enhance the stability of the bucket foundation are proposed through sensitivity analysis of influencing factors.

Research on the Critical Buckling Pressure of Bucket Foundations with Inner Compartments for Offshore Wind Turbines

In the process of suction penetration of bucket foundations with inner compartments for offshore wind turbines,most researches focus on soil seepage failure and soil plugs,while the buckling of foundations is rarely investigated.Therefore,theoretical calculation methods for critical buckling pressures of the skirt and bulkheads of the bucket foundation are first presented according to the stability theory of a cylindrical shell and the small deflection theory of a thin plate,respectively.Furthermore,two types of models with and without considering the skirt-soil interaction are developed for the calculation of critical buckling pressure of the bucket foundation.Taking a practical project as an example,theoretical and numerical methods are used to obtain the critical buckling pressures of a bucket foundation.In this work,the theoretical method and the finite element model considering the skirt-soil interaction for calculating the critical buckling pressure of bucket foundations are firstly proposed.The results can help to optimize the design process of offshore wind turbine foundations and improve the safety of offshore wind power systems.

Failure rate,return-to-sports and magnetic resonance imaging after meniscal repair:119 patients with 7 years mean follow up

BACKGROUND One of the most important factors to consider in relation to meniscal repair is the high failure rate reported in the existing literature.AIM To evaluate failure rates,return to sports(RTS)rate,clinical outcomes and magnetic resonance image(MRI)evaluation after meniscus suture repair for longitudinal tears at a minimum 2-year-follow-up.METHODS We conducted a retrospective review of meniscal repairs between January 2004 and December 2018.All patients treated for longitudinal tears associated or not with an anterior cruciate ligament reconstruction(ACL-R)were included.Meniscal ramp lesions,radial and root tears,associated with multiligament injuries,tibial fracture and meniscal allograft transplants were excluded.Surgical details and failure rate,defined as symptomatic patients who underwent a revision surgery,were analyzed.As isolated bucket handle tears(BHTs)were usually associated with higher failure rates,we compared BHTs and not BHTs associated or not with an ACL-R.Since 2014,the inside-out technique using cannulas and suture needles with 2-0 Tycron began to predominate.In addition,the number of stitches per repair was increased.In view of differences in surgical technique,we compared two different cohorts:before and after 2014.We recorded the RTS according to the level achieved and the time to RTS.Lysholm and IKDC scores were recorded.Patients were studied with x-rays and MRI as standard postoperative control.RESULTS One hundred and nineteen patients were included with a mean follow up of 7 years(SD:4.08).Overall failure rate was 20.3%at a mean 20.1 mo.No statistically significant differences were found when comparing failure for medial and lateral meniscal repair(22.7%and 15.3%,P=0.36),BHTs and not BHTs(26%and 17.6%,P=0.27),isolated or associated with an ACL-R(22.9%and 18%,P=0.47),or when comparing only BHTs associated with an ACL-R(23%and 27.7%,P=0.9)or not.When comparing cohorts before and after 2014,we found a significant decrease in the overall failure rate from 26%to 11%(P<0.03).Isolated lesions presented a decrease from 28%to 6.6%(P=0.02),BHTs from 34%to 8%(P=0.09)and those associated with an ACL-R from 25%to 10%(P=0.09).Mean RTS time was 6.5 mo in isolated lesions and 8.64 mo when associated with an ACL-R.Overall,56%of patients returned to the same sport activity level.Mean pre and postoperative Lysholm scores were 64 and 85(P=0.02),and IKDC 58 and 70(P=0.03).Out of 84 asymptomatic patients evaluated with MRI,39%were classified as“not healed”and 61%as“healed”.CONCLUSION Even though the overall failure rate of our series was 20.3%,we found a statistically significant decrease from 26%to 11%,not only for isolated lesions,but also for BHT’s and those associated with an ACL-R when comparing our series in two different cohorts,most probably due to improvements in surgical technique.

Planning Approaches of Sustainable Agricultural Village

The concept of sustainable agricultural village was proposed in this study,and its major economic pattern was summarized as:with the sustainable agriculture,grain production and processing as core contents,to enhance the attraction of agricultural regions and establish more effective connections between rural and urban areas by properly developing eco-agricultural sightseeing and organizing satellite sustainable agricultural villages into an urban peripheral network.Dajidian Sustainable Agricultural Village in Baoding City,Hebei Province was taken for an example to elaborate the overall design concepts,and analyze the strategies for planning the village as an integrated system,including social,ecological and economic dimensions,which are specifically demonstrated as:the development of sustainable agriculture,the establishment of diversified circulation system,the independence of energy utilization,the soundness of public service system,the improvement of agricultural villages as communities.Through studying the planning of sustainable agricultural villages,this research aimed at realizing the sustainable development of overall environment system in both cities and rural areas,and guiding the improvement of the new countryside construction.

Towing characteristics of large-scale composite bucket foundation for offshore wind turbines

In order to study the towing dynamic properties of the large-scale composite bucket foundation the hydrodynamic software MOSES is used to simulate the dynamic motion of the foundation towed to the construction site.The MOSES model with the prototype size is established as the water draft of 5 and 6 m under the environmental conditions on site.The related factors such as towing force displacement towing accelerations in six degrees of freedom of the bucket foundation and air pressures inside the bucket are analyzed in detail.In addition the towing point and wave conditions are set as the critical factors to simulate the limit conditions of the stable dynamic characteristics.The results show that the large-scale composite bucket foundation with reasonable subdivisions inside the bucket has the satisfying floating stability.During the towing process the air pressures inside the bucket obviously change little and it is found that the towing point at the waterline is the most optimal choice.The characteristics of the foundation with the self-floating towing technique are competitive for saving lots of cost with few of the expensive types of equipment required during the towing transportation.

BEPCII事件定时系统

北京正负电子对撞机重大改造工程(BEPCII)的定时系统主要包括用于产生各种触发信号和时钟信号的事件定时部分,以及储存环主频和注入器主频的锁相部分,其中前者的研制基于事件系统模块。本文介绍BEPCII事件定时系统的结构和基本功能、任意Bucket选择的设计和实现、以及定时系统的总体性能。

基于LQS的基本矩阵计算方法

基本矩阵作为分析两视图对极几何的有力工具,在视觉领域中占用重要的地位。分析了传统鲁棒方法在基本矩阵的求解问题中存在的不足,引入了稳健回归分析中的LQS方法,并结合Bucket分割技术,提出一种鲁棒估计基本矩阵的新方法,克服了RANSAC方法和LMedS方法的缺陷。模拟数据和真实图像实验结果表明,本文方法具有更高的鲁棒性和精确度。

频谱分析仪全数字中频设计研究与实现

介绍了频谱分析仪的全数字中频的设计方案和工作原理,重点讨论了数据抽取造成的频谱扩散在设计中的考虑、CIC滤波器的截短误差与传递、数字滤波器的响应时延与扫描Bucket的修正等设计技术,这对实现接收机全数字中频设计具有重要意义。给出了数字中频设计的细节和实现方法,采用所述技术方案和设计方法,实现了1 Hz^3 MHz分辨率带宽(RBW);带宽准确度±2%;RBW转换误差0.05 dB;矩形系数优于1/4;全跨度扫频时间为50 ms等性能指标。并且,还节省了FPGA资源、提高了扫频精度,设计结果满足高性能频谱分析仪的设计需求。