Abstract: Disclosed are a method and a system for measuring a displacement of a structure based on fusion of asynchronous vision measurement data of natural target and acceleration data of the structure. A scale factor, which is a conversion factor between a pixel resolution of the image frame data and a distance resolution of real space, is calculated using image frame data taken at a predetermined first sample frequency of a stationary target outside the structure by a camera installed on the structure, and acceleration data measured at a predetermined second sample frequency by an accelerometer installed on the structure, over time. A vision-based displacement value of the structure is estimated using a feature point matching algorithm and the scale factor.

Abstract: Disclosed are method and system of estimating an absolute strain of a structure under tensile force in a reference-free manner using ultrasonic wave velocity. Ultrasonic vibrations are generated by a vibration exciting element attached to the structure, and first and second ultrasonic vibrations propagating in a tensile force direction and a direction orthogonal to the tensile force direction in the structure are detected using first and second vibration detection elements, respectively. The detected first and second ultrasonic vibration signals are converted into first and second digital signals. Then, a computing unit calculates propagation velocities of the first and second ultrasonic vibrations, and applies them to an equation of relationship between propagation velocities of ultrasonic vibrations and a strain of the structure to obtain an absolute strain of the structure in the x-direction due to the tensile force. The calculated absolute strain can be used to evaluate stability of the structure.

Abstract: An embodiment antioxidant liquid for a fuel cell is provided. The antioxidant liquid is to be charged in a gas diffusion layer of a fuel cell stack, and the antioxidant liquid includes a solvent, an oxide as a first antioxidant dispersed in the solvent, and a salt as a second antioxidant dissolved in the solvent.

Abstract: A power supply includes an inverter configured to direct current (DC) power into alternating current (AC) power, an impedance matching circuit configured to supply the AC power to a load; and a controller configured to adjust disposition of a powering period, in which the AC power is output, and a freewheeling period, in which the AC power is not output, to adjust a power amount of the power supplied to the load through the impedance matching circuit by the inverter.

Abstract: A power supply includes an inverter configured to direct current (DC) power into alternating current (AC) power, an impedance matching circuit configured to supply the AC power to a load; and a controller configured to adjust disposition of a powering period, in which the AC power is output, and a freewheeling period, in which the AC power is not output, to adjust a power amount of the power supplied to the load through the impedance matching circuit by the inverter.

Abstract: A plasma generating apparatus according to an embodiment of the present invention comprises: a pair of electrodes arranged in a dielectric discharge tube; an initial discharge induction coil module; and a main discharge induction coil module. The initial discharge induction coil module and the main discharge induction coil module are connected to an RF power source, and the RF power source provides RF power having different resonance frequencies to the initial discharge induction coil module and the main discharge induction coil module, respectively.

Abstract: Disclosed are a method of inspecting a printing quality of a 3D printing object using a femtosecond laser beam during a 3D printing process, and an apparatus and a 3D printing system for the same. A laser beam is irradiated from a femtosecond laser source disposed coaxially with a 3D printing laser source to inspect a state of the printing object. The laser beam generated by the femtosecond laser source is separated into a pump laser beam and a probe laser beam. The printing laser beam irradiated from a 3D printing laser source or the pump laser beam is irradiated onto a printing object to generate ultrasonic waves. To measure the ultrasonic waves, a probe laser beam is irradiated onto the printing object. The probe laser beam reflected by the printing object is detected. The quality of the printing object is inspected by analyzing the reflected probe laser beam.

Abstract: A method for detecting fatigue cracks in a structure and a system therefore are disclosed. A vibration detection element detects vibration of the structure generated when the structure is excited at low and high frequencies and generates a measurement signal in the time domain. Based on a trained long short-term memory (LSTM) network, a signal of the next time step is predicted from the measurement signal of the current time step measured by the vibration detection element. The measurement signal and the prediction signal are combined to create a new combined signal with an increased length in the time domain. The combined signal is Fourier transformed to reduce noise and enhance the information of the measured signal in the frequency domain, and the Fourier transformed signal is used to obtain a spectral density function and to detect cracks in the structure.

Abstract: Disclosed are a femtosecond laser-based ultrasonic measuring apparatus for a 3D printing process, and a 3D printing system including the apparatus. The apparatus includes a femtosecond laser source for generating a femtosecond laser beam irradiated to inspect a state of a printing object formed by melting a base material by a printing laser beam irradiated from the laser source for 3D printing, a beam splitter for separating the femtosecond laser beam generated by the femtosecond laser source into a pump laser beam and a probe laser beam, an electric/acoustic optical modulator for modulating the pump laser beam, a time delay unit for delaying the probe laser beam, a photo detector for detecting the probe laser beam reflected by the printing object, and a lock-in amplifier for detect an amplitude and a phase of the output signal from the photo detector. The femtosecond laser source is disposed coaxially with a laser source for 3D printing.

Abstract: A plasma generating apparatus according to an embodiment of the present invention comprises: a pair of electrodes arranged in a dielectric discharge tube; an initial discharge induction coil module; and a main discharge induction coil module. The initial discharge induction coil module and the main discharge induction coil module are connected to an RF power source, and the RF power source provides RF power having different resonance frequencies to the initial discharge induction coil module and the main discharge induction coil module, respectively.

Abstract: A power supply includes an inverter configured to convert direct current (DC) power into alternating current (AC) power, an impedance matching circuit configured to supply the AC power to a load, and a controller configured to detect a delay time of an output voltage and an output current output to the impedance matching circuit and the load and to adjust a frequency of the output voltage according to the detected delay time.

Abstract: A power supply includes an inverter configured to direct current (DC) power into alternating current (AC) power, an impedance matching circuit configured to supply the AC power to a load; and a controller configured to adjust disposition of a powering period, in which the AC power is output, and a freewheeling period, in which the AC power is not output, to adjust a power amount of the power supplied to the load through the impedance matching circuit by the inverter.

Abstract: According to one embodiment of the present specification, there can be provided an apparatus for generating plasma, comprising: a chamber configured to provide a generating space for the plasma; an antenna module placed adjacent to the chamber and configured to be connected to a first power source and generate induced electric field in the chamber; an electrode placed adjacent to the chamber and configured to be connected to a second power source and assist in a generation of the plasma; a sensor configured to obtain sensing information related to a status of the plasma; and a controller configured to control the first power source and the second power source.

Abstract: According to one embodiment of the present disclosure, there can be provided a plasma generating device for performing plasma discharge, the plasma generating device having multiple operation modes including a first mode and a second mode, and including: a first power supply capable of changing a frequency within a first frequency range; a second power supply capable of changing a frequency within a second frequency range that is at least partially different from the first frequency range; a dielectric tube; and an antenna module including a first unit coil wound around the dielectric tube at least one time, a second unit coil wound around the dielectric tube at least one time, and a first capacitor connected in series between the first unit coil and the second unit coil.

Abstract: This invention is an antenna structure inducing plasma in a chamber with applied alternative power, comprising: a first antenna segment and a second antenna segment arranged based on a virtual central axis to have a first curvature radius and a second curvature radius respectively, the central axis crossing a first plane, and a first capacitive load electrically connecting the first antenna segment and the second antenna segment, wherein the first antenna segment extends from one end of the first capacitive load with the first curvature radius having a first length and the second antenna segment extends from other end of the first capacitive load with the second curvature radius having a second length, and wherein a sum of the first length and the second length is shorter than a circumference of the first curvature radius or the second curvature radius.

Abstract: A method of feedback controlling a 3D printing process in real time, and a system therefor are disclosed. The method includes collecting big data, generated through 3D printing experiments, related to process variables of 3D printing, measurement signals, and 3D printing quality of the 3D printing object; building an artificial neural network model by performing machine-learning based on the collected big data; evaluating whether or not a 3D printing quality of the 3D printing object is abnormal in real time based on an actual measurement signal of the 3D printing object and the artificial neural network model; and feedback controlling printing quality of the 3D printing object in real time based on the evaluation result of whether or not the 3D printing quality of the 3D printing object is abnormal.

Abstract: A power supply includes an inverter configured to direct current (DC) power into alternating current (AC) power, an impedance matching circuit configured to supply the AC power to a load; and a controller configured to adjust disposition of a powering period, in which the AC power is output, and a freewheeling period, in which the AC power is not output, to adjust a power amount of the power supplied to the load through the impedance matching circuit by the inverter.

Abstract: In a method of estimating displacement of a bridge, a first displacement including a low frequency component and a first high frequency component is generated based on a strain that is measured by a plurality of pairs of strain gauges installed at positions in a first direction from a reference point, in a bridge, a second displacement including a second high frequency component is generated based on an acceleration that is measured by an accelerometer installed at a first position spaced apart from the reference point by a first distance in the first direction, in the bridge, and a final displacement of the bride is generated based on an unknown parameter associated with the displacement, the low frequency component and the second high frequency component. The unknown parameter is generated by applying a recursive least square algorithm to the first high frequency component and the second high frequency component.

Abstract: A plasma generating apparatus according to an embodiment of the present invention comprises: a pair of electrodes arranged in a dielectric discharge tube; an initial discharge induction coil module; and a main discharge induction coil module. The initial discharge induction coil module and the main discharge induction coil module are connected to an RF power source, and the RF power source provides RF power having different resonance frequencies to the initial discharge induction coil module and the main discharge induction coil module, respectively.

Abstract: Disclosed are a method and apparatus of estimating a depth of a molten pool formed during a 3D printing process, and a 3D printing system. A surface temperature of the molten pool is measure by taking a thermal image of a laminated printing object during the 3D printing process with a thermal imaging camera. The measured surface temperature is compared with a melting point of the base material to determine a surface boundary of the molten pool. The maximum lengths in x-axis and y-axis directions of a surface region of the molten pool defined by the surface boundary of the molten pool are determined as a length and a width of the surface of the molten pool, respectively. A maximum depth in the z-axis direction of the molten pool is determined in real time based on the length and width of the surface region of the molten pool.