Three-Dimensional Sound Source Location Algorithm for Subsea Leakage Using Hydrophone

Leakages from subsea oil and gas equipment cause substantial economic losses and damage to marine ecosystem,so it is essential to locate the source of the leak.However,due to the complexity and variability of the marine environment,the signals collected by hydrophone contain a variety of noises,which makes it challenging to extract useful signals for localization.To solve this problem,a hydrophone denoising algorithm is proposed based on variational modal decomposition(VMD)with grey wolf optimization.First,the average envelope entropy is used as the fitness function of the grey wolf optimizer to find the optimal solution for the parameters K andα.Afterward,the VMD algorithm decomposes the original signal parameters to obtain the intrinsic mode functions(IMFs).Subsequently,the number of interrelationships between each IMF and the original signal was calculated,the threshold value was set,and the noise signal was removed to calculate the time difference using the valid signal obtained by reconstruction.Finally,the arrival time difference is used to locate the origin of the leak.The localization accuracy of the method in finding leaks is investigated experimentally by constructing a simulated leak test rig,and the effectiveness and feasibility of the method are verified.

Remaining Useful Life Prediction Method for Multi-Component System Considering Maintenance:Subsea Christmas Tree System as A Case Study

Maintenance is an important technical measure to maintain and restore the performance status of equipment and ensure the safety of the production process in industrial production,and is an indispensable part of prediction and health management.However,most of the existing remaining useful life(RUL)prediction methods assume that there is no maintenance or only perfect maintenance during the whole life cycle;thus,the predicted RUL value of the system is obviously lower than its actual operating value.The complex environment of the system further increases the difficulty of maintenance,and its maintenance nodes and maintenance degree are limited by the construction period and working conditions,which increases the difficulty of RUL prediction.An RUL prediction method for a multi-omponent system based on the Wiener process considering maintenance is proposed.The performance degradation model of components is established by a dynamic Bayesian network as the initial model,which solves the uncertainty of insufficient data problems.Based on the experience of experts,the degree of degradation is divided according to Poisson process simulation random failure,and different maintenance strategies are used to estimate a variety of condition maintenance factors.An example of a subsea tree system is given to verify the effectiveness of the proposed method.

Effect of Artificial Electric Field Surface by Wave-Driven Triboelectricity on Anti-Bioadhesion for Riser Protection

Biofouling has been a persistent problem in marine riser system, resulting in energy waste and equipment damage. Inthis study, a kind of water wave-driven contact-mode flexible triboelectric nanogeneration has been prepared byusing graphene-doped PDMS as dielectric friction material. When the graphene content is 2%, the average outputvoltage can reach 46 V under the contact frequency 10 Hz. The flexible triboelectric nanogeneration encapsulationmodule is impinged by water waves to generate alternating microelectric field on the riser surface and destroy theadhesion conditions of microorganisms during the biofilm stage. In the biofouling experiments at different stages, thebiofouling area of the platymonas subcordiformis has been reduced by 53%, 62% and 61%. It provides a new ideafor effective treatment of biofouling of mussels, oysters and barnacles attached to risers.

一期行腹腔镜胆总管探查术加胆囊切除术与传统开放手术的临床疗效对比

目的本研究旨在比较腹腔镜胆总管探查(LCBDE)加腹腔镜胆囊切除术(LC)与开放胆总管探查术(OCBDE)加胆囊切除术(OC)治疗胆囊(GB)合并胆总管(CBD)结石患者的安全性和有效性。方法单中心回顾性研究了2022年5月至2023年3月期间50例诊断为胆总管合并胆囊结石患者的诊疗记录。在纳入本研究的50例患者中,25例接受了一期腹腔镜胆总管探查加腹腔镜胆囊切除术(LCBDE+LC),即微创组。25例接受开放胆总管探查术加胆囊切除术(OCBDE+OC),即传统组。结果两组患者性别、年龄等差异无统计学意义(P>0.05)。微创组与传统组患者术前的CBD直径(1.60cm vs 1.46 cm,P=0.093)、两组患者之间的手术出血量(29.68 mL vs 30.68 mL,P=0.072)、手术时间(129.64 min vs129.97 min,P<0.912)、结石复发率(8.0%vs 20.0%,P=0.415)、CBD完全清除率(96.0%vs 91.3%,P=0.941)差异均无统计学意义,两组患者在术后恢复时间的差异有统计学意义(5.40±1.00vs8.08±0.99,P<0.05)。另外,两组患者在胆漏(4.0%vs 8.0%,P=1.000),坠积性肺炎(0.0%vs 13.6%,P=0.190),肠梗阻(0.0%vs 8.0%,P=0.470)并发症的发生上无统计学差异,但两组患者的总并发症发生率差异存在统计学意义(4.0%vs 28%,P<0.05)。结论LCBDE+LC相较于OCBDE+OC术后总并发症的发生率较低,并且LCBDE+LC对患者术后早期恢复具有一定的优势,对患者有益,值得在临床中推广。

应急封井装置二次密封盖疲劳寿命分析

本文介绍了材料疲劳寿命的Miner理论,并根据南海载荷参数估算出二次密封盖的疲劳累计损伤。对二次密封盖进行有限元静载分析,运用名义应力法,通过nCode软件得到二次密封盖的疲劳损伤云图和疲劳寿命云图,找出二次密封盖的危险部位,为以后的优化设计和无损检测提供参照。

A Dynamic-Bayesian-Networks-Based Resilience Assessment Approach of Structure Systems: Subsea Oil and Gas Pipelines as A Case Study

Under unanticipated natural disasters, any failure of structure components may cause the crash of an entire structure system. Resilience is an important metric for the structure system. Although many resilience metrics and assessment approaches are proposed for engineering system, they are not suitable for complex structure systems, since the failure mechanisms of them are different under the influences of natural disasters. This paper proposes a novel resilience assessment metric for structure system from a macroscopic perspective, named structure resilience, and develops a corresponding assessment approach based on remaining useful life of key components. Dynamic Bayesian networks(DBNs) and Markov are applied to establish the resilience assessment model. In the degradation process, natural degradation and accelerated degradation are modelled by using Bayesian networks, and then coupled by using DBNs. In the recovery process, the model is established by combining Markov and DBNs. Subsea oil and gas pipelines are adopted to demonstrate the application of the proposed structure metric and assessment approach.

A data-driven early micro-leakage detection and localization approach of hydraulic systems

Leakage is one of the most important reasons for failure of hydraulic systems.The accurate positioning of leakage is of great significance to ensure the safe and reliable operation of hydraulic systems.For early stage of leakage,the pressure of the hydraulic circuit does not change obviously and therefore cannot be monitored by pressure sensors.Meanwhile,the pressure of the hydraulic circuit changes frequently due to the influence of load and state of the switch,which further reduces the accuracy of leakage localization.In the work,a novel Bayesian networks(BNs)-based data-driven early leakage localization approach for multi-valve systems is proposed.Wavelet transform is used for signal noise reduction and BNs-based leak localization model is used to identify the location of leakage.A normalization model is developed to improve the robustness of the leakage localization model.A hydraulic system with eight valves is used to demonstrate the application of the proposed early micro-leakage detection and localization approach.

Bionic Flexible Texture Design Based on Bio-Fouling Suppression Effect for Protection of Marine Structures

Marine equipments such as marine risers and oil pipelines operate in complex underwater environments and are usually attached by animals,plants and microorganisms.The attachment of marine fouling organisms will accelerate the corrosion damage of offshore structure and greatly reduce the service life.Studies have shown that non-smooth bionic surfaces with specific microstructures can inhibit fouling formation.Based on the idea of bionics,this paper proposes a new type of underwater flexible fretting texture,which is a composite material prepared by mixing graphene and silicone rubber,and modified by pulsed laser to construct a hexagonal bionic surface texture.Under the impact of specific water flow,the flexible texture can produce an angular displacement around 8°and a linear displacement in the amplitude range of 165μm,and the inhibition rate of fouling biological diatoms up to 97.5%,which can effectively avoid the occurrence of marine biological fouling.The results provide a new idea for the surface protection of marine structures,which is of great significance for the development of marine industry.