Jungjoon Kim

Design and Analysis of Sub-10 nm Junctionless Fin-Shaped Field-Effect Transistors

We design and analyze the n-channel junctionless fin-shaped field-effect transistor (JL FinFET) with 10-nm gate length and compare its performances with those of the conventional bulktype fin-shaped FET (conventional bulk FinFET). A three-dimensional (3-D) device simulations were performed to optimize the device design parameters including the width (Wfin) and height (Hfin) of the fin as well as the channel doping concentration (Nch). Based on the design optimization, the two devices were compared in terms of direct-current (DC) and radio-frequency (RF) characteristics. The results reveal that the JL FinFET has better subthreshold swing, and more effectively suppresses short-channel effects (SCEs) than the conventional bulk FinFET.

R-wave Detection Algorithm in ECG Signal Using Adaptive Refractory Period

In this paper, R-wave detection algorithm using refractory period to reflect the depolarization and repolarization of the myocardial cells of the heart is proposed. The proposed algorithm detects R-peaks using the features of R-wave and variable refractory period. First, the proposed algorithm extracts candidate R-peaks that have a relatively high potential and calculates the refractory period based on the kurtosis and potential for candidate R-peaks. Next, R-peak is determined by morphological features of the R-wave within the refractory period. In addition, due to less computation in the proposed algorithm, real-time processing is possible. The algorithm is applied to all records of the MIT-BIH arrhythmia database and the obtained results show a competitive detection rate of over 99.7%.

Rotationally reconfigurable metamaterials based on moiré phenomenon

Exploiting moiré interference, we make a new type of reconfigurable metamaterials and study their transmission tunability for incident electromagnetic waves. The moiré pattern is formed by overlapping two transparent layers, each of which has a periodic metallic pattern, and the cluster size of the resulting moiré pattern can be varied by changing the relative superposition angle of the two layers. In our reconfigurable metamaterials, both the size and structural shape of the unit cell can be varied simultaneously through moiré interference. We show that the transmission of electromagnetic waves can be controlled from 90% to 10% at 11 GHz by experiments and numerical simulation. The reconfigurable metamaterial proposed here can be applied in bandpass filters and tunable modulation devices.

Microstructure Evolution and Electrical Properties of Ba2NaNb5O15 and Pb(Mg1/3Nb2/3)O3 Composites

Phase development, sintering behaviors and dielectric characteristics of the composites between tungsten bronze structured Ba2NaNb 5 O 15 (BNN) and perovskite structured Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) were examined as a function of molar ratio x in (1− x) BNN-xPMN. The lattice constant of BNN and PMN continuously changed throughout the entire composition change, which signifies that BNN and PMN have a wide range of solid solution with each other. The Curie temperature (T C ) and the maximum dielectric constant of BNN decreased as the content of PMN increased. Besides, when BNN is added to PMN, the T C also decreased and more dispersive dielectric relaxation was observed due to the incorporation of Na in PMN. The pyrochlore phase was formed in PMN rich compositions, which deteriorated the dielectric characteristics.

Investigation of InAs/InGaAs/InP Heterojunction Tunneling Field-Effect Transistors

Tunneling field-effect transistors (TFETs) are very applicable to low standby-power application by their virtues of low off-current (Ioff) and small subthreshold swing (S). However, low on-current (Ion) of silicon-based TFETs has been pointed out as a drawback. To improve Ion of TFET, a gate-all-around (GAA) TFET based on III-V compound semiconductor with InAs/InGaAs/InP multiple-heterojunction structure is proposed and investigated. Its performances have been evaluated with the gallium (Ga) composition (x) for In1-xGaxAs in the channel region. According to the simulation results for Ion, Ioff, S, and on/off current ratio (Ion/Ioff), the device adopting In0.53Ga0.47As channel showed the optimum direct-current (DC) performance, as a result of controlling the Ga fraction. By introducing an n-type InGaAs thin layer near the source end, improved DC characteristics and radio-frequency (RF) performances were obtained due to boosted band-to-band (BTB) tunneling efficiency.

Electrocardiogram Signal Compression with Reconstruction via Radial Basis Function Interpolation Based on the Vertex

Patients with heart disease need long-term monitoring of the electrocardiogram (ECG) signal using a portable electrocardiograph. This trend requires the miniaturization of data storage and faster transmission to medical doctors for diagnosis. The ECG signal needs to be utilized for efficient storage, processing and transmission, and its data must contain the important components for diagnosis, such as the P wave, QRS-complex, and T wave. In this study, we select the vertex which has a larger curvature value than the threshold value for compression. Then, we reconstruct the compressed signal using by radial basis function interpolation. This technique guarantees a lower percentage of root mean square difference with respect to the extracted sample points and preserves all the important features of the ECG signal. Its effectiveness has been demonstrated in the experiment using the Massachusetts Institute of Technology and Boston’s Beth Israel Hospital arrhythmia database.

Ventricular Arrhythmia Classification Based on High-Order Statistical Features of ECG Signals

One class SVM classification model based on high-order statistical features of ECG signals is proposed. This utilizes distinct features of variance, skewness and kurtosis between normal signals and ventricular arrhythmia ECG signals. The model based on a few simple features motivates immediate treatment for sudden cardiac event and wearable technology in practice. The classification algorithm shows significantly improved performance of 98.9% accuracy in correct classification in the experiment using the MIT-BIH Malignant Ventricular Arrhythmia Database (VFDB). It is expected to be used in real-time electrocardiogram monitoring system in conjunction with ECG measurement part and application part.

Fabrication and Characterization of GaN-based Light-emitting Diode (LED) with Triangle-type Structure

This study investigated characteristics of the fabricated triangle-type light-emitting diode (T-LED), conventional triangular LED (CT-LED), and conventional square LED (CS-LED). The T-LED is expected to provide uniform current spreading that leads to high output power, low current crowding, and high light extraction in the lateral direction of the LED device, compared to CT-LED and CS-LED. The light extraction of the T-LED in the lateral direction is much higher than that of the CT-LED and the CS-LED due to enhancement of light emission from the sidewalls of the T-LED.

Hierarchical Neural Network for Real-time Medicine-bottle Classification

In The matching algorithm for automatic packaging of drugs is essential to determine whether the canister can exactly refill the suitable medicine. In this paper, we propose a hierarchical neural network with the upper and lower layers which can perform real-time processing and classification of many types of medicine bottles to prevent accidental medicine disaster. A few number of low-dimensional feature vector are extracted from the label images presenting medicine-bottle information. By using the extracted feature vectors, the lower layer of MLP(Multi-layer Perceptron) neural networks is learned. Then, the output of the learned middle layer of the MLP is used as the input to the upper layer of the MLP learning. The proposed hierarchical neural network shows good classification performance and real- time operation in the test of up to 30 degrees rotated to the left and right images of 100 different medicine bottles.