Dongseob Kim

Vision-based surface defect inspection for thick steel plates

Abstract. There are several types of steel products, such as wire rods, cold-rolled coils, hot-rolled coils, thick plates, and electrical sheets. Surface stains on cold-rolled coils are considered defects. However, surface stains on thick plates are not considered defects. A conventional optical structure is composed of a camera and lighting module. A defect inspection system that uses a dual lighting structure to distinguish uneven defects and color changes by surface noise is proposed. In addition, an image processing algorithm that can be used to detect defects is presented in this paper. The algorithm consists of a Gabor filter that detects the switching pattern and employs the binarization method to extract the shape of the defect. The optics module and detection algorithm optimized using a simulator were installed at a real plant, and the experimental results conducted on thick steel plate images obtained from the steel production line show the effectiveness of the proposed method.

Energy-loss return gate via liquid dielectric polarization

There has been much research on renewable energy-harvesting techniques. However, owing to increasing energy demands, significant energy-related issues remain to be solved. Efforts aimed at reducing the amount of energy loss in electric/electronic systems are essential for reducing energy consumption and protecting the environment. Here, we design an energy-loss return gate system that reduces energy loss from electric/electronic systems by utilizing the polarization of liquid dielectrics. The use of a liquid dielectric material in the energy-loss return gate generates electrostatic potential energy while reducing the dielectric loss of the electric/electronic system. Hence, an energy-loss return gate can make breakthrough impacts possible by amplifying energy-harvesting efficiency, lowering the power consumption of electronics, and storing the returned energy. Our study indicates the potential for enhancing energy-harvesting technologies for electric/electronics systems, while increasing the widespread development of these systems.One major energy loss in electronics is heat dissipation due to induced polarization in dielectric materials in the presence of electric fields. Kim et al. utilize large polarization in liquids to harvest dielectric loss via an energy-loss return gate design, which converts energy back to electricity.

Enhanced visible-light photocatalytic performance of Fe 3 O 4 nanopyramids for water splitting and dye degradation

Iron oxide (Fe3O4) pyramid nanostructures were synthesized via a co-precipitation method, without using surfactants or template, for photocatalytic and photoelectrocatalytic activities. The as-made Fe3O4 was characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), UV–vis spectroscopy, photoluminescence spectroscopy, N2 adsorption–desorption analysis, and X-ray photoelectron spectroscopy (XPS). The data clearly demonstrate that the Fe3O4 nanostructures display excellent crystallinity, uniform morphology with a Brunauer–Emmett–Teller (BET) surface area of 52.95xa0m2xa0g−1, and an optical bandgap of 2.17xa0eV, which allows them to serve as outstanding catalysts under visible irradiation. The highest photocatalytic activity of ~u200997% was achieved in the degradation of rhodamine B under visible irradiation, with a degradation rate constant of 0.0322xa0min−1 at room temperature. Further, electrochemical studies demonstrated that the Fe3O4 electrode possesses good electrocatalytic activity in 0.1xa0M KOH electrolyte. The highest photocurrent density of 1.2xa0×xa010−4xa0mAxa0cm−2 was observed in the water splitting reaction. The Fe3O4 nanostructures exhibited superior performance in terms of both dye degradation and photoelectrochemical activity.

Fire protection behavior of layer-by-layer assembled starch–clay multilayers on cotton fabric

UV–Vis spectrometry and quartz crystal microbalance were used to measure the growth of these films as a function of the number of bilayers deposited, while scanning electron microscopy and transmission electron microscopy were used to visualize the morphology of the thin film coatings on the cotton fabric. Nanocomposites formed of cationic starch (CS) and clay introduced fire protection properties into the pure cotton fabric by layer-by-layer (LbL) technique. The optical properties and mass of the films were precisely controlled by the number of bilayers. In this case, CS and clay multilayer thin films were used to increase the thermal stability of the fabrics and improve the anti-flammable properties through the formation of a ceramic char layer and thermally stable carbonaceous structure at a high temperature. This study demonstrates the ability of the LbL technique to produce anti-flammable starch–clay nanocomposite thin films. Cone calorimetry showed the lower total heat release and heat release capacity of the LbL-coated fabric. The LbL-coated cotton samples exhibited a reduced afterglow time in vertical flame tests. An increased amount of residue indicates that the LbL technique is a simple method which can be used to produce eco-friendly flame retardant thin film coatings.

Hand-Driven Gyroscopic Hybrid Nanogenerator for Recharging Portable Devices

Abstract With the rise of portable and wearable electronics, a fast‐charging, long‐lasting power solution is needed; thus, there are attempts to harvest energy from the ambient environment. Mechanical energy harvesting through piezoelectric and triboelectric nanogenerators (PENG and TENG) is a promising approach due to their light weight, low cost, and high‐power density in comparison to other technologies. Both types of generators are capable of charging portable and smart devices on their own by converting mechanical energy into electricity. However, most previous methods have excessive input conditions, such as high rpm and input frequency, that can be only applied with other actuators. Here, a hand‐held gyroscopic generator is presented that uses the gyroscopic principle to reach a rotation rate above 8000 rpm with only hand input. The generator comprises a rotating flywheel inside a casing. Both the flywheel and casing have a TENG, and with a hybrid generator, electrical power is produced from rotation, vibration, and centrifugal force during operation. The device shows a consistent open‐circuit voltage (V OC) of 90 V and a closed‐circuit current (I CC) of 11 µA with a frequency of 200 Hz. As a stand‐alone device, this generator can power portable sensors and smartphones through hand rotation.