Gye Rok Jeon

Dual Domain Effects on a Homogeneously Aligned Nematic Liquid Crystal Cell Driven by a Fringe-Field

The fringe-field switching (FFS) mode is known to exhibit both a wide viewing angle and high transmittance, owing to the approximated in-plane rotation of the liquid crystal (LC) director. However, in the bright state, the device shows bluish and yellowish color parallel and perpendicular to the LC director at off-normal directions since the LC director rotates only in one direction. The degree of color shift becomes even stronger when the retardation value of the cell is high. This problem was greatly improved using a wedge shape of only pixel electrodes. These wedged shaped pixel electrodes allow two different field directions to exist in a pixel, enabling the LC director to rotate in two opposite directions. Consequently, owing to the dual domain effect with unidirectional rubbing, the color shift dependence on the viewing angle is greatly reduced.

The Development of Integrated Sensor System for Measuring Simultaneously ECG, PPG and PPW

The pulse transit time(PTT), which is determined by measuring the electrocardiogram(ECG) and pulse wave, gives comprehensive information about the cardiovascular system. However, a little movement of body and/or inaccurate pressure applied to skin during the measurement of pulse wave leads to acquire incorrect results. To overcome such problem, we developed an integrated sensor system which makes it possible to measure ECG, pressure pulse wave(PPW) and photoplethysmograph(PPG) at the same time. Futhermore, we implemented a new metal electrode which enables to continuously measure ECG. We verified that both integrated sensor system and new electrode provide useful effect.

Surface Characteristics of Nanostructure Formed on Sand Blasted with Large Grit and Acid Etched Dental Implant

The purpose of this study was to apply nanotechnology to dental implant for improved osseointegration. Titania nanostructures were fabricated on the sand blasted with large grit and acid etched (SA) titanium (ASTM grade 4) implants (TSIII SA®, Osstem, 3.5 x 5 mm) using potentiostatic anodic oxidation in HF. The nanostructures were uniformly formed on the SA surface. The mean pore size of nanostructure was about 30 nm. In the result of torque test, the nanostructure formed on SA surface was preserved from the torque, even after the loading of 40Ncm. An amorphous titania nanostructure was annealed at 400 °C. Through heat treatment, the amorphous titania nanostructure was turned into anatase phase. Hydrofluoric acid was used as the electrolyte to form nanostructure. In the result of ion release test, however, fluoride ions were not detected at the heat treated group. Therefore, such nanostructured SA implant (Nano-SA) will be suitable for dental implant.

Evaluation of an Experimentally Designed Stereotactic Guidance System for Determining Needle Entry Point during Uniplanar Fluoroscopy-guided Intervention

Background In discography performed during percutaneous endoscopic lumbar discectomy (PELD) via the posterolateral approach, it is difficult to create a fluoroscopic tunnel view because a long needle is required for discography and the guide-wire used for consecutive PELD interrupts rotation of fluoroscope. A stereotactic system was designed to facilitate the determination of the needle entry point, and the feasibility of this system was evaluated during interventional spine procedures. Methods A newly designed stereotactic guidance system underwent a field test application for PELD. Sixty patients who underwent single-level PELD at L4-L5 were randomly divided into conventional or stereotactic groups. PELD was performed via the posterolateral approach using the entry point on the skin determined by premeasured distance from the midline and angles according to preoperative magnetic resonance imaging (MRI) findings. Needle entry accuracy provided by the two groups was determined by comparing the distance and angle measured by postoperative computed tomography with those measured by preoperative MRI. The duration and radiation exposure for determining the entry point were measured in the groups. Results The new stereotactic guidance system and the conventional method provided similarly accurate entry points for discography and consecutive PELD. However, the new stereotactic guidance system lowered the duration and radiation exposure for determining the entry point. Conclusions The new stereotactic guidance system under fluoroscopy provided a reliable needle entry point for discography and consecutive PELD. Furthermore, it reduced the duration and radiation exposure associated with determining needle entry.

A Evaluation Parameter Development of Anesthesia Depth in Each Anesthesia Steps by the Wavelet Transform of the Heart Rate Variability Signal

Abstract In this study, the parameter extraction for evaluation of the anesthesia depth in each anesthesiastages was conducted. An object of the this experiment study has studied 5 adult patients (mean ± SD age:42 ± 9.13), ASA classification I and Ⅱ , undergoing surgery of obstetrics and gynecology. Anaesthesia was maintained with Enflurane. HRV signal was created by R-peak detection algorithm form ECG signal. The HRV data were preprocessing algorithm. It has tried find out the anesthesia parameter which responds the anesthesia events and shows objective anesthesia depth according to anesthesia stage including pre-anesthesia, induction, maintenance, awake and post-anesthesia. In this study, proposed algorithm to analysis the HRV(heart rate variability) signal using wavelet transform in anesthesia stage. Three sorts of wavelet functions applied to PSD. In the result, all of the results were showed similarly. But experiment results of Daubeches 10 is better. Therefore, this parameter is the best parameter in the evaluation of anesthesia stage.Key Words : HRV, Depth of anesthesia, Wavelet transform,

Basis research of nail style photoplethysmogram measurement system for motion artifact reduction

Pulse wave is basic and, important living body signal for vital sign of measurement target or patient’s disease diagnosis. Reflection style of existent pulse wave measurement system is system that receipt light element, emitting light element hangs on palm part of finger or receipt light element, emitting light element hangs on finger lower and upper parts of permeation style. Such existent pulse wave measurement system is sensitive to motion artifact. In this study, it is going to reduce motion artifact irritableness that existent pulse wave measurement sensor has comparative rigidity degree sensor that receipt light element, emitting light element is situated on nail latitude reveal and do basic research that do example addition. This is considered to become reduction of motion artifact of other pulse wave sensor.

Blood flow and pressure in a brachial artery under cuff pressure

In the present work, we investigate the artery pressure across a brachial artery under the cuff pressure. Deformation of the arm tissue is numerically simulated with the finite element method. The artery pressure is analyzed based on hemodynamics of blood circulation. From the analysis, it is found that the cuff pressure deforms the arm tissue significantly, but not the artery wall. Deformation of the artery wall is not significantly affected by the artery pressure. The artery pressure is found not to decrease significantly across a part of the arm pressurized by the cuff.

Study on the Development of Sensors for Distance Measure Using Ultrasonic

Abstract In this paper, we report a novel algorithm based on phase displacement, which supplements conventional TOF methods for distancemeasurement using an ultrasonic wave. The proposed algorithm roughly measures the distance between the transmission part and thereceiving part by using the initial TOF. Thereafter, the precise distance is determined by measuring the phase displacement valuebetween the synchronizing transmission signal and the signal obtained at the receiving end. A distance measurement experiment usinga micrometer was performed to verify the accuracy of the ultrasonic wave sensor system. We found that the mean errors from the oneadopting the distance measurement algorithm based on phase displacement varied from a minimum of 0.03 mm to a maximum of 0.09mm. In addition, the standard deviation varied from a minimum of 0.04 mm to a maximum of 0.07 mm, thus giving a precision of0.1 mm. Keywords : Ultrasonic, Distance measure 1. 서론 초음파는 주파수가 20 kHz 이상으로 사람의 귀로 들을 수 없는 음파이다. 초음파의 고유한 성질은 가청 범위의 음파와 같다.그러나 주파수가 높고 파장이 짧기 때문에 상당히 강한 진동이발생되는 특징을 지니고 있다. 초음파는 물체 인식[1,2], 거리 측정[3,4], 질병 진단과 치료[5] 등 거리 정보에 기반한 응용에 많이 이용되고 있다.초음파를 이용해서 거리 정보를 알아내기 위해서는 초음파를발생 시켜 송신하는 부분과 송신된 초음파를 수신하는 부분으로 구성하고 펄스파 또는 연속파를 사용한다. 연속파를 사용한거리 측정은 송신부에서 초음파를 전송한 순간부터 수신부에 그파가 도착한 순간의 시간 경과를 계산하여 수행한다[6-8]. 이 거리 측정 방법을 일반적으로 TOF(Time-of-Flight)법이라고 한다.TOF를 측정하는 방법은 임계값 검출 기법[9], 포락선 추정 기법[10], 주파수 인식 기법[11] 등이 적용되고 있다. 임계값 검출기법은 초음파 신호의 세기가 주위 환경에 의해 발생되는 소음보다 높아야 한다는 전제 조건을 만족해야 한다. 포락선 추정기법은 포락선이 측정 거리에 따라 감쇠되는 단점이 존재한다.주파수 인식 기법에서는 수신되는 초음파 신호에 잡음과 여러주파수들이 혼합되어 수신된다. 따라서 잡음 제거를 위한 필터와 추가적인 신호처리 기법을 적용해야 하는 단점이 있다. TOF방법의 단점을 제거하기 위해 초음파 신호를 진폭 변조하여 송수신하고, 송신부와 수신부 사이의 위상 차이를 이용하여 거리를 측정하는 방법이 소개 되었다[12]. 이 방법은 변조를 위해 송신부에 변조기, 수신부에 복조기와 증폭기를 추가해야 하는 단점이 있다.본 논문에서는 TOF 방법의 단점을 배제시킬 수 있고 간단하게 구성할 수 있는 위상 변위 기반+ 거리 측정 알고리즘을 제안한다. 제안하는 위상 변위 기반 거리 측정 알고리즘은 초기 TOF를 사용하여 송신부와 수신부의 거리를 개략적으로 측정한 후,송신 동기 신호와 초음파 센서의 수신부에서 얻은 신호 사이의위상 변위 값을 측정하여 정밀하게 거리를 측정한다. 그리고 본논문에서 제안하는 알고리즘을 기반으로 거리를 측정할 수 있

Effective Falls Detection Method Using Two Tri-Axial Accelerometers

Falls detection systems have been developed in recent years because falls are detrimental events that can have a devastating effect on health of the elderly population. Current fall detecting methods mainly employ accelerometer to discriminate falls from activities of daily living (ADL). However, this makes it difficult to distinguish real falls from certain fall-like activities such as jogging and jumping. In this paper, an accurate fall detection system was implemented using two tri-axial accelerometers. By attaching the accelerometers on the chest and the abdomen, our system can effectively differentiate between falls and non-fall events.The Diff_Z and Sum_diff_Z parameter resulted in falls detection rate of 100%, respectively.

Support of Automatic Calibration for Computerized Puretone Audiometer Using Linux Real-time Spectrum Analyzer

Compared to conventional pure-tone audiometer(PTA), the computerized one has several advantages such as relatively lower price, better flexibility, and easy operation. In addition, the computerized PTA can be easily extended to support automatic calibration. In this study, the support of automatic calibration in the computerized PTA has been addressed using the Linux realtime spectrum analyzer and network. In terms of accuracy, the new automatic calibration machine was compared to the existing manually operated one. According to the comparison, normal operation and high accuracy were observed within the scope of the international standard.