Self-Powered neutron detectors (SPND) detect current generated from interaction of neutron flux with emitter materials. They are inside a reactor in NPP (Nuclear Power Plant), and currently used to monitor the output and control the operation. Since the signal level of prompt-response SPND is very small (-nA), an analog circuit is necessary to amplify the current signal, and to convert it into voltage. This circuit needs to perform an anti-aliasing function to reduce distortion at the stage of digital conversion. In this paper, a systematic design process for high-gain amplification circuit is presented. Based on error analysis of the circuit, parameters are selected to satisfy design requirements. A third-order anti-aliasing filter is designed. A prototype circuit is built. Measured performance of the circuit confirms that the circuit satisfies all design requirements and validates the efficacy of the design to be used in practical environments.

Drone stations are increasingly being applied to enhance the mission capabilities of drones. The drone’s station landing occurs in a limited space. A relative position communication signal between the drone and the station is required. Strong, precise control over communication signal interference is required. In this paper, we describe a filter processing method for position signal processing. In consideration of the anchor position and installation angle of the UWB module of the drone station, nine performance test cases were proposed. As a result of the performance test, high position accuracy output was confirmed when considering the result of minimizing signal shading and beam pattern direction with excellent reception sensitivity. A performance test was conducted using the developed drone station, and the landing performance was confirmed with a precision of within 20 cm.

A linear motor is an actuator that has strong thrust and high controllability, and can perform linear motion without the use of a motion converter. In this study, we propose a new method to measure the position of the mover of a permanent magnet linear synchronous motor by measuring the magnetic flux density. To resolve the problem that existing methods have to spatially arrange multiple sensors, the proposed method uses a two-dimensional magnetic flux density measurement value at one point. In accordance with this, the estimation method was modified, the convergence condition of the estimation method was obtained, and the time required for the calculation was estimated. The validity of the proposed method was verified through comparative experiments with existing methods. As a result of the test, the proposed method had a small maximum absolute error compared to the existing methods, and was robust against sensor gain changes.

Recently, interest in Prognostics and Health management (PHM) has been increasing as an advanced technology of maintenance. PHM technology is a technology that allows equipment to check its condition and predict failures in advance. To realize PHM technology, it is important to implement artificial intelligence technology that diagnoses failures based on data. Vibration data is often used to diagnose the state of the rotating machine. Additionally, there have been many efforts to convert vibration data into 2D images to apply a convolutional neural network (CNN), which is emerging as a powerful algorithm in the image processing field, to vibration data. In this study, a series of PHM processes for acquiring data from a rotary machine and using it to check the condition of the machine were applied to the rotary table. Additionally, a study was conducted to introduce and compare two methodologies for converting vibration data into 2D images. Finally, a GUI program to implement the PHM process was developed.

The brake squeal noise is a high-frequency noise over 1 kHz range generated by the contact between the brake pad and the disk. The purpose of this paper was to investigate the behavior of the squeal noise characteristics of the brake system from an instability point of view, according to the variation of major parameters such as friction coefficient between the flexible pad and the disk, brake pressure, and Young’s modulus of disk. Full nonlinear perturbed modal analysis using commercial finite element analysis program was performed to derive complex eigenvalue results of the model. And the sensitivity behavior was observed. Increasing the coefficient of friction or Young’s modulus of disk tended to make the squeal mode of the model more unstable. However, the change in brake pressure has a complicated nonlinear relationship with the squeal mode of the model. The judgment technique conducted in this study should be considered to be used in the design of the vibration point of the disk and pad of railway vehicles in the future.

A novel method for the development of a highly sensitive triboelectric sensor based on porous PDMS matrix and carbon black (CB) particles is proposed. The porosity of the PDMS is controlled by using wet sugar particle sizes, and we fabricate a porous PDMS plate with a pore-to-volume ratio of 46%, which has a larger internal contact area compared to a non-pore one. To investigate the sensitive responses of the sensor, two key processes for the deposition of CB particles are conducted. One is the stirring process and another is ultrasonic vibration waving process. Based on the proposed method, a high-performance flat triboelectric sensor is fabricated. By a weight drop test of two different sensors, the amount of out-voltage is changed to approximately 29.1 and 95.1%, respectively. Through this study, we can evaluate that the sensitivity of triboelectric sensors is affected by the deposition method of the CB particles. The proposed flexible triboelectric sensor can be applied to analyze human physical behavior. Also, we believe that it can be applied to measure various physical signals such as contact force or gripping force with small values.

The main shaft of a mechanical press inevitably includes significant stress concentrations that can trigger severe mechanical damage and finally lead to failure under repetitive use. In this study, an efficient procedure to quantitatively evaluate the fatigue life of the shaft system including the main shaft and its support bearings, based on the macroscopic failure analysis of the main shaft broken during actual use, was investigated. For this purpose, the bearing support was modeled as an elastic foundation, and the elastic foundation stiffness value was varied to determine the optimal value that best simulates the failure behavior, especially with respect to the failure location and failure sequence, of an actual shaft. While the finite element mesh size was kept the same, only the effect of elastic foundation stiffness was investigated. The optimum value for the main shaft investigated in this study was approximately 60 N/mm³, and the fatigue life of the shaft was evaluated based on the conventional maximum principal stress theory. Based on this, two modified designs to enhance the fatigue life of the existing shaft are proposed.

The incremental sheet forming (ISF) process is a method of forming a metal sheet with a machine tool, such as a CNC or robot arm. In this study, the surface characteristics of the ISF process using the ball type tool and the conventional hemispherical tool were analyzed. Comparative experiments were conducted with the same size of the hemispherical tool and ball type tool. In experiments, the tool feed rate and spindle were fixed, and the step down was set up with seven levels. The surface profiles and roughness such as R_a and R_z after the ISF process with different values of the step down were compared. Additionally, the surface morphologies were analyzed through the scanning electron microscope. A ball type tool which can move and roll, can reduce the effect of friction effectively. As a result, the ISF process with a ball type tool can greatly reduce the damage of the surface of the product.

In this paper, we propose acoustophoretic microfluidic devices with an acoustic transparent polymer wall using a simple and low-cost fabrication method followed by MEMS (Micro-Electromechanical Systems) processes. Generally, due to the acoustic standing wave between two opposing walls in microfluidic channel, the particle focusing lines are fixed according to the applied frequency. In the proposed device, however, it is possible to place the particle focusing lines in the arbitrary position within the fluidic domain through the optimized width of polymer wall. The PDMS (Polydimethylsiloxane) mold with thin layer was used as the sealing layer between the Si substrate and cover glass, as well as the decoupling layer between the acoustic boundary and fluidic boundary. The thickness of PDMS mold needed to be minimized to decrease the heating by the acoustic energy absorption of PDMS layer, which was successfully made using the spin-coating of PDMS and the UV tape transfer method. The acoustophoretic device with thin PDMS layer and optimized width of PDMS wall can be applied, for biotechnological applications such as the separation of blood cells and micro-particles.