Automatic multi-image stitching for concrete bridge inspection by combining point and line features

Most of the current techniques for concrete bridge inspection are based on human visual interpretation, which often is dangerous and time-consuming. To address this problem, we introduce in this paper a newly developed vehicle-based robot inspection system that can automatically capture thousands of bottom surface images with a group of high-resolution industrial cameras, which are then stitched into a single composite image. However, traditional image stitching methods generally fail with large drift due to the great number (more than 2000) and sparse texture of linearly distributed images in sequence. Therefore, a novel image stitching method was developed for our robot inspection system, which combines both the 2D image point features and the 3D line features to reduce the drift. First, the bottom surface images are arranged into different strips based on their acquisition order and rough poses, and images in a single strip are divided into several groups. Then, the proposed image stitching method is performed in a bottom-up way, as follows: 1) the images within a single group initially are aligned via their point and line features; 2) the groups within a single strip are then stitched together via a homographic refinement procedure; 3) the strips are aligned into a single composite image that completely covers the bottom surface of the bridge; and 4) after all the stitching procedure are complete, a multi-band blending algorithm is applied to generate the mosaicked panorama as seamlessly as possible. The experimental results on a set of representative images acquired from the bottom surfaces of a real bridge demonstrate the capabilities and the limitations of the proposed approach.     

电解液成分对等离子体电解氧化TC4合金腐蚀行为和摩擦学性能的影响（英文）

在TC4合金表面制备4种典型等离子体电解氧化(PEO)涂层,研究电解质组成对PEO涂层腐蚀行为和摩擦学性能的影响。结果表明,PEO涂层的腐蚀行为和摩擦学性能与电解质成分密切相关。在含NaH₂PO₂的电解液中制备的PEO涂层由于内氧化膜较致密而具有最好的耐蚀性能,而在含NaAlO₂的电解液中制备的PEO涂层由于含有Al₂O₃而具有最好的摩擦学性能。为制备具有良好耐蚀性和耐磨性的PEO涂层,以NaH₂PO₂和NaAlO₂为电解液主要成分制备了复合PEO涂层。     

Responses of calcareous sand foundations to variations of groundwater table and applied loads

The long-term settlement of calcareous sand foundations caused by daily periodic fluctuations has become a significant geological hazard, but effective monitoring tools to capture the deformation profiles are still rarely reported. In this study, a laboratory model test and an in situ monitoring test were conducted. An optical frequency domain reflectometer (OFDR) with high spatial resolution (1 mm) and high accuracy (±10^-6) was used to record the soil strain responses to groundwater table and varied loads. The results indicated that the fiber-optic measurements can accurately locate the swelling and compressive zones. During the loading process, the interlock between calcareous sand particles was detected, which increased the internal friction angle of soil. The foundation deformation above the sliding surface was dominated by compression, and the soil was continuously compressed beneath the sliding surface. After 26–48 h, calcareous sand swelling occurred gradually above the water table, which was primarily dependent on capillary water. The swelling of the soil beneath the groundwater table was completed rapidly within less than 2 h. When the groundwater table and load remain constant, the compression creep behavior can be described by the Yasong-Wang model with R² = 0.993. The daily periodically varying in situ deformation of calcareous sand primarily occurs between the highest and lowest groundwater tables, i.e. 4.2–6.2 m deep. The tuff interlayers with poor water absorption capacity do not swell or compress, but they produce compressive strain under the influence of deformed calcareous sand layers.     

Are forecast updates progressive?

Many macroeconomic forecasts and forecast updates like those from IMF and OECD typically involve both a model component, which is replicable, as well as intuition, which is non-replicable. Intuition is expert knowledge possessed by a forecaster. If forecast updates are progressive, forecast updates should become more accurate, on average, as the actual value is approached. Otherwise, forecast updates would be neutral. The paper proposes a methodology to test whether macroeconomic forecast updates are progressive, where the interaction between model and intuition is explicitly taken into account. The data set for the empirical analysis is for Taiwan, where we have three decades of quarterly data available of forecasts and their updates of the inflation rate and real GDP growth rate. Our empirical results suggest that the forecast updates for Taiwan are progressive, and that progress can be explained predominantly by improved intuition.     

Characterization and friction performances of Co–Al-layered double-metal hydroxides synthesized in the presence of dodecylsulfate

In this paper, Co–Al-layered double-metal hydroxides (CAD-LDHs) were synthesized by co-precipitation in the presence of dodecylsulfate (DDS) and characterized by XRD, FT-IR, TG–DSC, SEM. In addition, their frictional features were evaluated by four-ball friction tester, gear tester and air compressor. The results showed that synthesized CAD-LDHs have a hexagonal platelet morphology. Most crystallites have a disk diameter of around 150–250 nm and a thickness of about 20 nm, with a₀ = b₀ = 0.31 nm, c₀ = 8.33 nm, d-spacing = 2.78 nm and gallery height = 2.30 nm. The specific surface area is 78 m²/g. DDS anions entered the interlayer of LDHs and were perpendicular to the LDH layer in a monolayer array. As a lubricant, CAD-LDH powder has excellent dispersability and suspension stability in the lubrication oil, and can significantly reduce friction coefficient (50.7%) and wear of friction pairs (17.9%). At the same time, they can reduce the temperature of lubrication oil (6.1%) and power consumption of driving motor (2.6–6.8%). Accordingly, CAD-LDHs may broadly be used as lubrication and anti-frictional materials.     

Selective pyrolysis of paper mill sludge by using pretreatment processes to enhance the quality of bio-oil and biochar products

Paper mill sludge (PMS) is a residual biomass that is generated at paper mills in large quantities. Currently, PMS is commonly disposed in landfills, which causes environmental issues through chemical leaching and greenhouse gas production. In this research, we are exploring the potential of fast pyrolysis process for converting PMS into useful bio-oil and biochar products. We demonstrate that by subjecting PMS to a combination of acid hydrolysis and torrefaction pre-treatment processes it is possible to alter the physicochemical properties and composition of the feedstock material. Fast pyrolysis of pretreated PMS produced bio-oil with significantly higher selectivity to levoglucosenone and significantly reduced the amount of ketone, aldehyde, and organic acid components. Pretreatment of PMS with combined 4% mass fraction phosphoric acid hydrolysis and 220 °C torrefaction processed prior to fast pyrolysis resulted in a 17 times increase of relative selectivity towards levoglucosenone in bio-oil product along with a reduction of acids, ketones, and aldehydes combined from 21 % to 11 %. Biochar, produced in higher yield, has characteristics that potentially make the solid byproduct ideal for soil amendment agent or sorbent material. This work reveals a promising process system to convert PMS waste into useful bio-based products. More in-depth research is required to gather more data information for assessing the economic and sustainability aspects of the process.     

Quantification of singlet oxygen generation from photodynamic hydrogels

Recently, we described a series of novel porphyrin-impregnated hydrogels capable of producing microbicidal singlet oxygen (¹O₂) on photoactivation. Indirect assessment of the efficacy of ¹O₂ production from such hydrogels has been previously described using microbiological techniques, but here we report a novel, direct method of quantification. Anthracene-9,10-dipropionic acid (ADPA) is known to irreversibly form an endoperoxide on reaction with ¹O₂, causing photobleaching of its absorbance band at approximately 378 nm. Here, the reaction of this probe is exploited in a novel way to provide a simple, inexpensive, and convenient measurement of ¹O₂ generation from the surface of porphyrin-incorporated photosensitising hydrogels, with the ability to account for effects due to hydrogel porosity. Ingress of the probe into the materials was observed, with rates of up to 3.83 × 10³ s⁻¹. This varied by up to 200-fold with material composition and surface modification. Rates of ¹O₂ generation in these porphyrin-incorporated hydrogels, after compensating for ADPA ingress, ranged from 1.86 × 10³ to 5.86 × 10³ s⁻¹. This work demonstrates a simple and straightforward method for direct ¹O₂ quantification from porous materials, with general utility.     

深海浅层非成岩天然气水合物喷射破碎压控滑套的研制

为了解决海洋天然气水合物固态流化开采过程中射流喷头作业过程不可控、不可重复使用且需要多次起下钻柱等问题，基于节流压降原理与天然气水合物固态流化开采工艺，针对深海浅层非成岩天然气水合物的特点，设计出了一种可控制射流喷头开启与关闭且作业过程不受水深和井深影响的压控滑套，并对其进行了仿真分析与室内实验评价。研究结果表明：①所研制的压控滑套入口处锥面角度越大，滑套所产生的压降与轴向力越大，但钻井液对锥面的冲蚀越严重，因此综合考虑上述因素，滑套锥部角度选择30°为最佳；②钻井液通过滑套的流量越大，滑套内部产生的压降与滑套轴向力越大；③验证实验表明，在钻井液的作用下滑套能够滑动并开启射流喷头，喷头的全开启流量为833 L/min，与设计流量的误差值为4.13%；④试压实验表明，压力滑套内部压力的变化不能驱使滑套运动，有效地验证了其工作状态不受环境压力的影响。结论认为，该工具的研制和应用将有助于促进海洋天然气水合物固态流化开采技术的进步。