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.

新型半潜式浮式风机在不同流速下的动力响应特性研究

本文提出一种适用于50~120 m水深的新型半潜式浮式风机,用频域法研究浮式平台的水动力特性,通过建立风机-塔筒-浮式平台-系泊系统全耦合分析模型,考虑二阶差频波浪力作用,对其开展风、浪、流联合作用下的时域分析,重点分析不同流速条件下新型半潜式浮式风机耦合动力响应特性。分析结果表明:新型半潜式浮式风机结构设计合理,其固有周期能较好地避开波浪能量密集的周期范围,有效避免了共振发生;风浪条件一定的情况下,流速增大将使新型半潜式浮式风机的最大纵荡响应和锚链拉力显著增大,但对纵摇和艏摇响应有一定程度的抑制作用。流速变化对基础垂荡运动和发电功率影响较小。

慢加急性肝衰竭预后研究及新评分的建立分析

目的研究慢加急性肝衰竭(acute-on-chronic liver failure,ACLF)预后相关因素及国内外常用预后评分模型效能,并分析纳入甲胎蛋白及乳酸脱氢酶指标单指标及联合评分模型对ACLF患者预后评估效果。方法收集2010-2021年青岛大学附属医院及青岛市第六人民医院收治的ACLF的临床资料,使用统计学方法分析可能影响预后的因素,并使用评估ACLF常用的评估模型并分析甲胎蛋白/乳酸脱氢酶单指标及新评分模型对ACLF患者预后的预测力。结果共纳入159例ACLF患者,28 d内有存活与死亡之比为129∶30,90 d内存活与死亡之比为111∶48。其中根据疾病严重程度分为早期48例、中期58例、晚期53例。根据90 d内患者预后情况分为存活组及死亡/肝移植组,两组入院基线指标中:ALT(410比204)、AST(296比211)、ALT/AST(1.27比0.88)、总胆红素(271比349)、胆固醇(2.7比2.2)、甘油三酯(1.07比0.81)、中性粒细胞数(6.35比6.21)、尿素氮(3.7比6.0)、淋巴细胞数(1.45比0.69)、中性粒细胞数/淋巴细胞数(2.38比7.04)、红细胞计数(4.19比3.60)、血红蛋白(132比119)、血小板计数(90比74)、HBV DNA载量(104比103)、PTA(37.1比30.3)、INR(2.09比2.56)、MLR(0.37比0.61)、血肌酐(59比64)、乳酸脱氢酶(221.0比279.5)、甲胎蛋白(82.30比7.66)、肝性脑病情况、合并腹水情况、MELD得分(20.57比26.34)、COSSH得分(5.05比6.08)相比较差异具有统计学意义(P<0.05)。而年龄、性别、白蛋白、前白蛋白、血尿酸、直接胆红素、间接胆红素、胆碱酯酶、血钠、血氨、γ-谷氨酰转肽酶、ALBI、ALT、AST两组相比差异无统计学意义(P>0.05),甲胎蛋白,乳酸脱氢酶,总胆红素、甘油三酯、红细胞、血红蛋白、ALT/AST、尿素氮/肌酐及纳入甲胎蛋白及乳酸脱氢酶的新评分,是预测ACLF 90 d预后的独立影响因素。新评分模型(AUC=0.87,敏感度89.6%,特异度75.7%,cutoff值-0.9909)较传统的NLR(AUC=0.72,敏感度68.9%,特异度75.2%,cutoff值3.86),MELD(AUC=0.67,敏感度69.6%,特异度67%,cutoff值14.64),COSSH(AUC=0.76,敏感度75%,特异度76%,cutoff值5.37)在预测ACLF患者预后方面具有更准确的预测性。结论在ACLF患者预后相关因素研究中,乳酸脱氢酶、总胆红素、尿素氮/肌酐、ALT/AST、红细胞为预测ACLF患者90 d预后的独立危险因素,甘油三酯、甲胎蛋白、血红蛋白为独立保护性因素。本研究中由以上8项指标组成的新评分系统在所有ACLF患者人群中较MELD及NLR评分能够更准确预测预后,在本研究乙型肝炎患者人群中新评分较MELD及NLR评分预测力高,但较COSSH评分相比差异并无统计学意义,但总体来讲新评分仍具有很高的预测力,从而节约临床器官的使用,提供最优治疗方案。

Hydrodynamic Characteristics of Three-Bucket Jacket Foundation for Offshore Wind Turbines During the Lowering Process

The three-bucket jacket foundation is a new type of foundation for offshore wind turbine that has the advantages of fast construction speed and suitability for deep water. The study of the hoisting and launching process is of great significance to ensure construction safety in actual projects. In this paper, a new launching technology is proposed that is based on the foundation of the three-bucket jacket for offshore wind turbine. A complete time domain simulation of the launching process of three-bucket jacket foundation is carried out by a theoretical analysis combined with hydrodynamic software Moses. At the same time, the effects of different initial air storage and sea conditions on the motion response of the structure and the hoisting cable tension are studied. The results show that the motion response of the structure is the highest when it is lowered to 1.5 times the bucket height. The natural period of each degree of freedom of the structure increases with the increase of the lowering depth. The structural motion response and the hoisting cable tension vary greatly in the early phases of Stages Ⅰ and Ⅲ, smaller in Stage Ⅱ, and gradually stabilize in the middle and late phases of Stage Ⅲ.

MOOC理念下的地方财经类院校“计算机导论”课程教学改革探究——以山西财经大学为例

地方财经类院校计算机专业在“计算机导论”课程教学中存在教学内容覆盖面宽广,引导主线种类繁多,缺乏财经类特色需求的引导;教学模式陈旧,导思维、导意识的教学手段不突出;教学效果的评价指标相对传统且流于表面形式等实际问题。基于MOOC理念的地方财经类院校“计算机导论”课程教学改革的思路是:引入MOOC资源,结合实际情况重新规划教学内容,并添加体现财经特色的相关内容;基于网络建设实行线上线下的混合教学模式,并采取突出培养计算思维能力和创新意识的教学手段;突破传统考核指标,实施多方位教学评价体系。

地方院校“计算机导论”一流课程建设的问题与对策

随着2019年一流本科课程建设“双万计划”的启动,各大高校着手开始了一流课程即“金课”的积极建设。对标“两性一度”一流课程的建设标准,地方院校“计算机导论”课程主要存在的差距是:课堂教学引导仍属于低阶层次的认知阶段,课程教学“三基”创新性和挑战度远远不够。在一流课程“双万计划”的引领下,以学生学为中心的“计算机导论”课程建设,应注重引导和培养学生认知的高阶性;改革教学“三基”,以学生为中心增强课程的创新性;引发学生深入思考,提高课程的挑战度。

预制管混凝土柱粘结性能试验研究及数值分析

为了研究新型预制管混凝土柱界面之间的粘结性能,利用ABAQUS内聚力模型,建立了新型预制管混凝土柱轴心推出的非线性有限元分析模型,并基于推出试验实测结果对模型进行了修正,继而研究了外壳预制管、核心混凝土、两者交界面的应力、粘结及相对滑移沿加载方向的变化规律。研究结果表明:经过试验修正的数值模型能够较好的反应出预制管混凝土柱的受力特性,试验及数值分析结果对进一步研究新型预制管混凝土柱粘结性能有一定的参考价值。

Study on Seepage Characteristics of Composite Bucket Foundation Under Eccentric Load

Under the effect of eccentric loads,when the suction pressure of the composite bucket foundation is leveled,the seepage failure is very easy to occur.The seepage failure occurrence causes the foundation to settle unevenly and impairs the bearing performance.This study uses ABAQUS finite element software to establish a composite bucket foundation model for finite element analysis.The model simulates the seepage of the foundation penetrating process under eccentric load to reveal the induced seepage characteristics of the bucket foundation.The most vulnerable position of seepage failure under the eccentric loading is elucidated.Critical suction formulas for different offset eccentric moment strategies are derived and compared with existing literature formulas.Then the derived formula is supplemented and corrected according to the pressure difference between adjacent cabins.Conclusions can be drawn:(1)Under eccentric loads,the critical suction decreases about 7%−10%.(2)The pressure difference between adjacent cabins impacts significantly on the seepage field,and the critical suction,at most,can be reduced by 17.56%.(3)the offset strategies have little effect on the seepage field.Efficient and appropriate strategies can be selected to meet the requirement of leveling in engineering project.

Integrated Towing Transportation Technique for Offshore Wind Turbine with Composite Bucket Foundation

Composite bucket foundation and one-step installation technology for offshore wind turbine are the integration of foundation construction,transportation and whole installation at sea.The cost of offshore wind turbine construction and installation has been largely reduced.Foundation stability is the key technology in the process of towing transportation.Field observation data can reflect the real state of the foundation.In this paper,the influence of water depth and towing speed on liquid level,the compartment pressure,and the pitch angles during towing of composite bucket foundation are studied.These data are analyzed based on the field measurements data from a 3.3 MW offshore wind power project in China.The results show that with varied water depths and towing speeds,the compartment pressure changes are small during the bucket foundation towing process.The offshore wind turbine composite bucket foundation is stable while being towed in the ocean.

Shaking Table Tests of Four-Bucket Jacket Foundation for Offshore Wind Turbines

As the offshore wind turbine foundation,the four-bucket jacket foundation has a large stiffness and the structure is difficult to be damaged under seismic load.Nevertheless,the saturated subsoil of the four-bucket jacket foundation tends to be liquefied under earthquake,which greatly affects the safety of offshore wind turbine.Therefore,the seismic performance of four-bucket jacket foundation is mainly reflected in the anti-liquefaction capacity of foundation soil.In this paper,the liquefaction resistance of sandy soil of four-bucket jacket foundation for offshore wind turbine is studied.The liquefaction and dynamic response of sandy soil foundation of four-bucket jacket foundation under seismic load are obtained by carrying out the shaking table test,and the influence mechanism of four-bucket jacket foundation on the liquefaction resistance of sandy soil foundation is analyzed.

Experimental Study on Influencing Factors of Motion Responses for Air-Floating Tetrapod Bucket Foundation

Air floating transport is one of the key construction technologies of bucket foundation.The influences of draft,water depth and bucket spacing on the motion response characteristics of tetrapod bucket foundation(TBF)during air-floating transportation were studied by models tests.The results showed that with the increase of draft,the natural periods of heave motion increased,while the maximum amplitudes of oscillating motion decreased.The maximum amplitudes of heave motion decreased while pitch motion increased with the increasing of water depth;further,the period range of oscillating amplitude close to the maximum amplitude was expanded due to shallow water effect.With increasing bucket spacing,the maximum amplitudes of heave motion first increase and then decreased,whereas the maximum amplitudes of pitch motion decreased.Therefore,the favorable air-floating transportation performance can be achieved by choosing a larger bucket spacing under the condition of meeting the design requirements and reducing the draft under shallower water.

Model Tests Research on A Float-Over Barge in Shallow Water Under the Undocking Conditions

In this study,the Jinzhou 9-3 CEPD float-over installation project was investigated.During the undocking condition,the water depth of the motion path of the working barge gradually changed from 10.31 m to 9.41 m.The undocking clearance of the HYSY 228 is smaller than 1 m;therefore,the barge shows highly nonlinear hydrodynamic characteristics,and it is difficult to be accurately simulated by numerical analysis.Thus,it is necessary to obtain the hydrodynamic characteristics and laws of the float-over barge at different water depths by using tank model test,to provide some reference and guidance for float-over operations in shallow water.

Collision Analysis Between Spudcan and Seabed During the Process of Jack-up Platform Lowering Jack-up Legs

In the leg-lowering process,the offshore jack-up platform is in a floating state,and the spudcan may collide with the seabed due to the platform motion in waves,thereby threatening the safety and stability of the platform.This paper first analyzed the hydrodynamic response of a jack-up platform under different sea states.Then a finite-element model was established which considered the material and geometrical nonlinearity in the structure and the nonlinear interaction between soil and structure to investigate the collision response between the spudcan and seabed during lowering jack-up legs.The results show that the dynamic response of the platform decreases and gradually tends to be stable as the wave period increases.The motion response of the platform reach the largest value when the wave period is 8 s and the wave direction is 0°.The collision angle between the spudcan and seabed has a large influence on the collision response,while the velocity of leg-lowering has little influence on the collision response.The collision response is also significantly affected by soil conditions.For clay,the increase in undrained shear strength and Young’s modulus will increase the impact force.

Stochastic Analysis of Short-Term Structural Responses and Fatigue Damages of A Submerged Tension Leg Platform Wind Turbine in Wind and Waves

In connection with the design of floating wind turbines,stochastic dynamic analysis is a critical task considering nonlinear wind and wave forces.To study the random structural responses of a newly designed submerged tension leg platform(STLP)wind turbine,a set of dynamic simulations and comparison analysis with the MIT/NREL TLP wind turbine are carried out.The signal filter method is used to evaluate the mean and standard deviations of the structural response.Furthermore,the extreme responses are estimated by using the mean upcrossing rate method.The fatigue damages for blade root,tower,and mooring line are also studied according to the simulated time-series.The results and comparison analysis show that the STLP gives small surge and pitch motions and mooring line tensions in operational sea states due to the small water-plane area.Additionally,in severe sea states,the STLP gives lower extreme values of platform pitch,slightly larger surge and heave motions and better towerbase and mooring line fatigue performances than those of the MIT/NREL TLP.It is found that the STLP wind turbine has good performances in structural responses and could be a potential type for exploiting the wind resources located in deep waters.