3D Printed Double Roller-Based Triboelectric Nanogenerator for Blue Energy Harvesting

The ocean covers 70% of the earth’s surface and is one of the largest uncultivated resources still available for harvesting energy. The triboelectric energy harvesting technology has the potential to effectively convert the ocean’s “blue energy” into electricity. A half-cylinder structure including rollers floating on the water has already been used, in which the pendulum motion of the rollers is driven by the waveform. For the stable motion of the rollers, the printed surface of the device was treated with acetone for attaining hydrophilicity. The electrical outputs with the proposed device were enhanced by increasing the contact surface area by simply implementing the double roller structure with double side-covered electrodes. With the optimized structure, the maximum power density reached a value of 69.34 µW m−2 at a load resistance of 200 MΩ with the device’s high output durability. Finally, the fabricated device was also applied to the artificial water waves to demonstrate the possibility of using this device in the ocean. By simply modifying the electrode structure and adding a roller, this device demonstrated the ability to generate over 160% of electrical output with the same covered area of the ocean by the triboelectric nanogenerators (TENGs) and potential ocean application.

Detecting Effects of Low Levels of FCCP on Stem Cell Micromotion and Wound-Healing Migration by Time-Series Capacitance Measurement

Electric cell–substrate impedance sensing (ECIS) has been used as a real-time impedance-based method to quantify cell behavior in tissue culture. The method is capable of measuring both the resistance and capacitance of a cell-covered microelectrode at various AC frequencies. In this study, we demonstrate the application of high-frequency capacitance measurement (f = 40 or 64 kHz) for the sensitive detection of both the micromotion and wound-healing migration of human mesenchymal stem cells (hMSCs). Impedance measurements of cell-covered electrodes upon the challenge of various concentrations of carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), from 0.1 to 30 μM, were conducted using ECIS. FCCP is an uncoupler of mitochondrial oxidative phosphorylation (OXPHOS), thereby reducing mitochondrial ATP production. By numerically analyzing the time-series capacitance data, a dose-dependent decrease in hMSC micromotion and wound-healing migration was observed, and the effect was significantly detected at levels as low as 0.1 μM. While most reported works with ECIS use the resistance/impedance time series, our results suggest the potential use of high-frequency capacitance time series for assessing migratory cell behavior such as micromotion and wound-healing migration.

A Comparison Between Air and In-Service Welding on Oxygen Concentration and Microinclusions in E7018-1 Weld Metal

In the maintenance of in-service pipelines, the use of covered electrodes is usual due to several factors such as the flexibility of welding in hard-to-reach places and its low cost. During in-service welding of pipelines, the line remains in operation, which implies more rigorous temperature gradients that can result in microstructures more susceptible to failure. The objective of this work is to relate the welding current and cooling conditions, commonly used in-service welding, with the oxygen content and the volumetric fraction of microinclusions. In this step, the effect on the oxygen content and the volumetric fraction of microinclusions are analyzed based on experimental results using the technique of factorial experiments. Bead-on-plate samples were welded under two cooling conditions, air and cooling with water, and two nominal welding currents, 86 A and 98 A. The increase in oxygen content was observed with increasing welding current and with the cooling rate. In addition, the more rigorous cooling rate reduced the mean microinclusions size, which can suppress the formation of acicular ferrite and, consequently, reduce the toughness and the ultimate stress limit of weld metal.

Effect of Electrode Waterproof Coating on Quality of Underwater Wet Welded Joints

In this paper, the effects of different hydrophobic coatings on the surface of covered electrodes on the quality of wet welded carbon steel joints were discussed. Commonly available hydrophobic substances used in industrial applications were selected for the research. The aim of using waterproof coatings was to check the possibility to decreasing the susceptibility of high-strength low-alloy S460N steel to cold cracking. During experiments diffusible hydrogen content in deposited metal determination by mercury method, metallographic macro- and microscopic testing and hardness measurements were performed. Investigations showed that waterproof coatings laid on covered electrodes can improve the quality of wet welded joints, by decreasing the Vickers HV10 hardness in heat-affected zone and decreasing the diffusible hydrogen content in deposited metal, which minimalize possibility of cold cracking.

Underwater “Wet Welding & Cutting” with NAUTICA Stick Electrodes for Marine and Offshore Applications

The basics of diving and working under water have been highlighted and explained as such, while these circumstances have also great influence on the welding behavior of the consumables applied. The challenge is in the execution of the welds and repairs. The paper covers the diving, welding and metallurgical aspects of underwater „wet” welding & cutting using covered electrodes based on industrial examples and applications for joining and repair welding. Shielded Metal Arc Welding (SMAW) and covered stick electrodes are a very versatile, flexible, simple and practical welding process, for this reason often used for underwater maintenance and repairs.

The Abrasive Wear Resistance of Coatings Manufactured on High-Strength Low-Alloy (HSLA) Offshore Steel in Wet Welding Conditions

Some marine and offshore structure elements exploited in the water cannot be brought to the surface of the water as this will generate high costs, and for this reason, they require in-situ repairs. One of the repair techniques used in underwater pad welding conditions is a wet welding method. This paper presents an investigation of the abrasive wear resistance of coatings made in wet welding conditions with the use of two grades of covered electrodes—an electrode for underwater welding and a commercial general use electrode. Both electrodes were also used for manufacturing coatings in the air, which has been also tested. The Vickers HV10 hardness measurements are performed to demonstrate the correlation in abrasive wear resistance and the hardness of each specimen. The microscopic testing was performed. For both filler materials, the coatings prepared in a water environment are characterized by higher resistance to metal–mineral abrasion than coatings prepared in an air environment—0.61 vs. 0.44 for commercial usage electrode and 0.67 vs. 0.60 for underwater welding. We also proved that in the water, the abrasive wear was greater for specimens welded by the general use electrode, which results in a higher hardness of the layer surface. In the air welding conditions, the layer welded by the electrode for use in the water was characterized by a lower hardness and higher resistance to metal–mineral abrasion. The microstructure of the prepared layers is different for both the environment and both electrodes, which results in abrasive wear resistance.