Hyungjun Lim

Fabrication of cylindrical micropins with various diameters using DC current density control

Abstract An electrochemical method is shown to fabricate extremely thin cylindrical tungsten micropins. The cylindrical micropin is obtained by regulating the current density. The current profile for the current density control is obtained with a mathematical model based on the relationship between an electric charge and a surface area.

A Symmetric Motion Estimation Method for Motion-Compensated Frame Interpolation

This paper proposes a new motion-compensated frame interpolation (MCFI) method. The proposed method utilizes a symmetric motion estimation (SME) method, which is a new pixel-wise motion estimation method for intermediate frame interpolation. By using an adaptive search range for the motion estimation, the proposed method can obtain a more reliable motion vector for each pixel than previous MCFI methods that use a conventional block matching algorithm (BMA). In addition, we propose a combined method of the SME and BMA to reduce the computation time of the pixel-wise motion estimation method. The experimental results show that the proposed method outperforms other MCFI methods in terms of generating objectively and subjectively better interpolated frames.

Iterative True Motion Estimation for Motion-Compensated Frame Interpolation

This paper proposes a new motion-compensated frame interpolation (MCFI) method. The performance of MCFI is highly dependent on the accuracy of the estimated motion vectors (MVs). The proposed iterative motion estimation (ME) method estimates reliable MVs using linearity checking and restricted search areas. An adaptive interpolation method is also proposed to obtain MVs for blocks that do not have reliable MVs in the iterative ME process. The experimental results show that the proposed method outperforms the conventional MCFI methods in terms of the quality of the interpolated frames. Furthermore, the MVs from the proposed method are more accurate than those from the conventional methods.

A Ringing-Artifact Reduction Method for Block-DCT-Based Image Resizing

This paper proposes a new ringing-artifact reduction method for image resizing in a block discrete cosine transform (DCT) domain. The proposed method reduces ringing artifacts without further blurring, whereas previous approaches must find a compromise between blurring and ringing artifacts. The proposed method consists of DCT-domain filtering and image-domain post-processing, which reduces ripples on smooth regions as well as overshoot near strong edges. By generating a mask map of the overshoot regions, we combine a ripple-reduced image and an overshoot-reduced image according to the mask map in the image domain to obtain a ringing-artifact reduced image. The experimental results show that the proposed method is computationally faster and produces visually finer images than previous ringing-artifact reduction approaches.

Fabrication of Arbitrarily Shaped Microelectrodes by Electrochemical Etching.

Some conventional machining methods have been developed to machine microelectrodes. However, these methods still require too much time and too many resources. This paper uses electrochemical etching as an alternative method for the simple and cheap fabrication of microelectrodes. Electrochemical etching is usually considered an appropriate method of producing sharp probes. However, it is possible for the entire shape of an electrode to be controlled under certain conditions such as the immersed length, the applied current, and the etching time. After developing a method to estimate the electrode shape, we produced some electrodes by generating etching conditions. Stepped and punch shapes were fabricated. These have applications in the manufacturing of operation utensils, measurement tips, and machining tools.

Motion estimation with adaptive block size for motion-compensated frame interpolation

This paper proposes a new frame rate up-conversion (FRUC) method. In the paper, we propose an overlap ratio between motion vectors, with which we determine adaptive block size for the motion estimation. In addition, the proposed method estimates the region of repeated patterns and treats them in a special manner. Conventional motion estimation methods usually produce wrong motion vectors for the repeated patterns. The experimental results show that the proposed method outperforms other FRUC methods in terms of generating better interpolated frames.

Cross-acoustic transfer learning for sound event classification

A well-trained acoustic model that effectively captures the characteristics of sound events is a critical factor to develop more reliable system for sound event classification. Deep neural network (DNN) which has an ability to extract discriminative representation of features can be a good candidate for acoustic model of sound events. Compared to other data such as speech or image, the amount of sound database is often insufficient for learning the DNN properly, resulting in overfitting problems. In this paper, we propose a cross-acoustic transfer learning framework that can effectively train the DNN even with insufficient sound data by employing rich speech data. Three datasets are used to evaluate our proposed method; one sound dataset is from Real World Computing Partnership (RWCP) DB and two speech datasets are from Resource Management (RM) and Wall Street Journal (WSJ) DBs. A series of experimental results verify that cross-acoustic transfer learning performs significantly better than the baseline DNN which was trained only from sound data, achieving 26.24% relative classification error rate (CER) improvement over the DNN baseline system.

A new impact actuator using linear momentum exchange of inertia mass

For self-controlled endoscopes, many kinds of systems have been proposed. Among these, pneumatic actuators show significant potential. However, existing actuators, such as those used in endoscopes, have many weak points. In particular, free movement inside the human intestine is difficult because the diameter of the intestine varies dramatically along its length. We design and test a new method of locomotion of robotic endoscopes which allows safe manoeuverability in the human intestine. The actuating mechanism is composed of a solenoid at each end of the actuator and a single permanent magnet in the centre guide. If current is supplied to the two solenoids, attractive and repulsive forces occur between the permanent magnet and solenoid at each end. The permanent magnet moves by controlling the current supply period. When the current direction for operation is reversed, repulsive and attractive forces at each side are changed and the permanent magnet moves in the opposite direction. The collision at each period transfers momentum from the moving magnet to the actuator body. Furthermore, the moving speed of the actuator can be changed by the control of the impact force. Modelling and simulation are carried out to predict the performance of the actuator. The results of simulations are verified by comparison with experimental results. Finally, the momentum is measured by attaching an accelerometer to the solenoid head to define moving characteristics.

An optimal motion vector regularization method using variance-distortion curve

This paper proposes a new motion vector (MV) regularization method. We present an optimization method of the tradeoff between motion accuracy and regularity. The proposed method adopts Lagrangian multiplier and greedy algorithm for optimization. By smoothing MVs while preserving motion accuracy, the proposed method can more efficiently regularize MVs than previous regularization methods. The experimental results show that the proposed method outperforms previous regularization methods by generating objectively and subjectively better results.

Fabrication of tungsten micro-punch for micro-nozzles

A very thin electrode with a tapered shape and a cylindrical tip, named ultrathin punch, is fabricated by electrochemical etching and by controlling the vertical position of the electrode during etching. We used electrochemical etching by which we obtain punches quickly and simply. The fabrication procedure and its results are presented in this article. With this punch, we can get holes or nozzles for ink-jet printers, textile machines, and other uses. Various angles of the taper can be obtained by adjusting the immersion depth. The tip diameter also can be controlled by adjusting current density and etching time.