Structural behavior and performance of water pipes rehabilitated with a fast-setting polyurea–urethane lining

This paper presents the structural behavior and performance of a fast-setting polyurea–urethane (PUU) lining as a structural lining material for rehabilitating water pipes. To this end, a series of experimental tests were carried out to assess the following: (1) bond strength; (2) hole and gap spanning capabilities; (3) angular displacement ability; (4) transverse shear resistance; and (5) fatigue cyclic loading resistance. First, pull-off bond tests were conducted to evaluate the bond characteristics of a fast-setting PUU lining bonded to steel specimens. Surfaces were dried to ensure adequate bond strength. Second, hole and gap spanning tests were carried out to investigate the spanning capability of the lining on the water pipes. From these tests, the hole spanning capability of water pipe with 5 mm hole was observed to be 11 MPa. Then, angular displacement and transverse shear tests on fast-setting PUU lined water pipes were also carried out to evaluate the behavior and performance in bending and shear of this material. Peel off failure of PUU occurred at an angular displacement capacity of 6.74° and no failure of PUU was observed at a transverse shear capacity of 25% of the diameter. Finally, fatigue cyclic loading test was conducted to investigate the fatigue behavior and performance of the water pipe lined with this PUU material. The fatigue resistance of PUU in the range of 10⁵ cyclic loadings was achieved.     

Online monitoring of wire breaks in prestressed concrete cylinder pipe utilising fibre Bragg grating sensors

With steel prestressing wires tensioned around core, Prestressed Concrete Cylinder Pipe (PCCP) is a high-strength composite pipe designed for large-diameter water propagation and distribution. However, some PCCPs may fail after a certain time of service due to corrosion and deterioration. Real-time health monitoring of wire breaks is essential to assess the condition and avoid catastrophic failures of PCCPs. In this paper, a novel approach based on Fibre Bragg Grating (FBG) sensing technology, is presented to monitor and locate wire breaks in PCCP lines. FBG vibration sensors are utilised to capture the signals of wire break activities in the pipeline and obtain their locations. The online monitoring system and localization principle of wire break activities are described. Preliminary experiments were carried out on PCCPs with an inner diameter of 2 m, which were filled with pressurized water. Experimental results indicate that the wire break activity can be detected and located effectively by FBG sensors. The detection error of wire break locations is analysed. With unique features, the proposed non-destructive method is expected to be used for the online monitoring of wire break activities in long term for the condition assessment and performance prediction of PCCP lines.     

Validation of a simple gravimetric method for measuring biogas production in laboratory experiments

This work presents a gravimetric method for measuring biogas or methane production from anaerobic reactors, based on measurement of reactor mass loss. Results are most sensitive to error in biogas methane content, and less so to temperature and pressure. To evaluate the method, we applied it and volumetric methods to 133 laboratory-scale batch and semi-continuous reactors, ranging in size from 37 g to 8.0 kg of reacting mass. For most observations, the relative difference between the two methods was <10% when the “true” biogas composition was used in calculations. Small systematic differences observed in some cases were probably due to error in estimates of biogas pressure, temperature, and composition, as well as biogas leakage. Based on theory and observation, it is reasonable to expect relative accuracy better than 15% of the true value.     

Metakaolin-based inorganic polymer composite: Effects of fine aggregate composition and structure on porosity evolution,microstructure and mechanical properties

This paper examines the phase transformation, pore evolution, microstructural and mechanical changes that occur in inorganic polymer cement (IPC) in the presence of three different grade of fine aggregates (ф < 100 μm) of ladle slag, nepheline syenite and quartz sand. Experimental results indicate that polycondensation was enhanced in nepheline syenite based specimens, compared to quartz sand, due to the increase in HMAS phases in relation to the dissolution and interaction of amorphous/disordered fraction of aggregates. HCS and HCAS with HMAS phases were identified in the ladle slag based specimens. The formation of these new phases reduced both the cumulative pore volume and pores size. The apparent increase in volume of capillary pores in ladle slag based specimens was explained by the residual bubbles from the carbonates included in raw slag. The flexural strength of the inorganic polymer cement increases from 4 MPa to 4.2, 4.8 and 6.8 MPa with the addition of 20 wt% of quartz sand, nepheline syenite and ladle slag respectively. These values increase significantly between 28 and 180 days of curing (9.1 MPa for ladle slag and 10.0 MPa for nepheline syenite). It was concluded that fines can be used to remove the HM and poorly bounded alumina oligomers in metakaolin based inorganic polymer matrices and improve the interfacial zone for the design of an optimum grade and high-performance composites.     

千瓦级小型液压式波浪能装置能量转换系统研究

针对小型海洋观测仪器用电需求,研究高效、可靠的小型液压式波浪能装置能量转换系统。在实验室建立一套3 kW的液压式波浪能能量转换系统,进行不同电阻负载、不同蓄能体积以及不同控制策略的液压系统试验,获得PTO效率曲线及各发电过程的特性曲线,详细分析不同控制策略的能量转换特性,得到PTO效率随阻值的增大趋于平稳、蓄能体积基本不影响PTO转换效率的结论,验证有蓄能器无控制器型直冲式能量转换系统的可行性。     

自航气动式振荡水柱波浪能发电船技术

介绍中国自主发展的自航气动式振荡水柱波浪能发电船技术。发电船由一个船型浮力舱、一个水平管、一个垂直管、空气透平和发电机组成。在长1.2 m、宽0.51 m的模型进行水槽实验,结果表明在规则波下俘获宽度比最高可达104.07%,在随机波下最高俘获宽度比为82.4%。基于该模型按相似原则设计多种型号的发电船,其中一艘样机装机功率1 kW,主体长5.2 m、宽2.3 m,质量4.5 t,在深圳大亚湾海域进行试验,可实现装置的波浪发电和航行。     

Outlier Detection of Mixed Data Based on Neighborhood Combinatorial Entropy

Outlier detection is a key research area in data mining technologies, as outlier detection can identify data inconsistent within a data set. Outlier detection aims to find an abnormal data size from a large data size and has been applied in many fields including fraud detection, network intrusion detection, disaster prediction, medical diagnosis, public security, and image processing. While outlier detection has been widely applied in real systems, its effectiveness is challenged by higher dimensions and redundant data attributes, leading to detection errors and complicated calculations. The prevalence of mixed data is a current issue for outlier detection algorithms. An outlier detection method of mixed data based on neighborhood combinatorial entropy is studied to improve outlier detection performance by reducing data dimension using an attribute reduction algorithm. The significance of attributes is determined, and fewer influencing attributes are removed based on neighborhood combinatorial entropy. Outlier detection is conducted using the algorithm of local outlier factor. The proposed outlier detection method can be applied effectively in numerical and mixed multidimensional data using neighborhood combinatorial entropy. In the experimental part of this paper, we give a comparison on outlier detection before and after attribute reduction. In a comparative analysis, we give results of the enhanced outlier detection accuracy by removing the fewer influencing attributes in numerical and mixed multidimensional data.     

One-dimensional compression feature and particle crushability behavior of dry calcareous sand considering fine-grained soil content and relative compaction

Bulletin of Engineering Geology and the Environment - The particle breakage of porous and angular calcareous sand (CS) at the high-stress level is essential on compression feature but less...