X-ray Response Characteristic of Zn in the Polycrystalline Cd1-xZnxTe Detector for Digital Radiography

Sang-SikKang,Jae-HyungKim,Hyung-Won,Lee,Chi-WoongMun,Sang-HeeNam 한국전기전자재료학회 2002 Transactions on Electrical and Electronic Material Vol.3 No.2

The Cd1-xZnxTe film was fabricated by thermal evaporation for the flat-panel X-ray detector. The stoichimetric ratio and the crystal structure of a polycrystalline Cd1-xZnxTe film were investigated by EPMA and XRD, respectively. The leakage current and X-ray sensitivity of the fabricated films were measured to analyze the X-ray response characteristic of Zn in the polycrystalline CdZnTe thin film. The leakage current and the output charge density of Cd0.7Zn0.3Te thin film were measured to 0.37 nA/cm2 and 260 pC/cm2 at an applied voltage of 2.5 V/㎛, respectively. Experimental results showed that the increase of Zn doping rates in Cd1-xZnxTe detectors reduced the leakage current and improved the signal to noise ratio significantly.

Technologies for sleep monitoring at home: wearables and nearables

Heenam Yoon,Sang Ho Choi 대한의용생체공학회 2023 Biomedical Engineering Letters (BMEL) Vol.13 No.3

Sleep is an essential part of our lives and daily sleep monitoring is crucial for maintaining good health and well-being. Traditionally, the gold standard method for sleep monitoring is polysomnography using various sensors attached to thebody; however, it is limited with regards to long-term sleep monitoring in a home environment. Recent advancements inwearable and nearable technology have made it possible to monitor sleep at home. In this review paper, the technologiesthat are currently available for sleep stages and sleep disorder monitoring at home are reviewed using wearable and nearabledevices. Wearables are devices that are worn on the body, while nearables are placed near the body. These devicescan accurately monitor sleep stages and sleep disorder in a home environment. In this study, the benefits and limitationsof each technology are discussed, along with their potential to improve sleep quality.

소프트웨어 교육에서 학습자 주도 평가의 효과성 고찰

신희남 ( Heenam Shin ),안성훈 ( Sung Hun Ahn ) 한국창의정보문화학회 2020 창의정보문화연구 Vol.6 No.2

미래교육을 준비하면서 소프트웨어 교육은 그 필요성이 점점 증대되고 있다. 소프트웨어 교육에서 운영의 내용과 더불어 평가 부분도 중요한 영역으로 대두되고 있다. 이에 본 연구에서는 문헌 연구를 통해 소프트웨어 교육에서 학습자 주도 평가의 효과성을 살펴보고, 이것이 교육 현장에 시사하는 점에 대해 고찰해 보고자 하였다. 초등학생 대상으로 학습자 주도 평가 모형을 적용한 소프트웨어 교육을 실시한 연구에 따르면 학습자 주도 평가는 학생들의 창의력, 문제해결력, 정보 활용력 등의 향상에 유의미한 효과를 보였으며, 소프트웨어 교육에 대한 흥미 또한 높아지게 하였다. 앞으로 관련 연구를 통해 학교 현장이 학생주도의 소프트웨어 교육을 통해 미래교육을 준비해 나가는 데 도움이 될 수 있기를 기대한다. In preparing for future education, the need for software education is increasing. In addition to the content of operation, the assessment portion issues have emerged as an important area in software education. In this study, we wanted to look at the effectiveness of the learner-led assessment in software education through literature research and consider what this suggests to the schooling. According to a study conducted on software education for elementary school students, the student-led assessment showed significant effects on the improvement of students' creativity, problem solving, information literacy, and increased interests in software education. Further research efforts are requested to help the schooling prepare for future education through student-led software assessment.

초등 소프트웨어 교육에서 AI기반의 학습자 주도 평가의 효과성 고찰

신희남 ( Heenam Shin ),안성훈 ( Sung Hun Ahn ) 한국창의정보문화학회 2021 창의정보문화연구 Vol.7 No.3

미래교육에서는 학습자 주도의 교육방식과 평가방식의 변화로 교육의 패러다임이 바뀌고 있다. 또한 AI 기반의 학습 인프라와 소프트웨어 교육은 그 역할와 필요성이 점점 확대되고 있다. 이에 본 연구에서는 미래교육에서 추구하는 AI 기반의 평가를 학습자 주도 평가에 접목시켜 그 효과성을 고찰해 보고자 하였다. AI 교육 및 평가 관련 문헌 연구와 학습자 주도형의 소프트웨어 평가 방법 7단계를 인용하여 초등학교 수준에 맞는 평가요소를 2015 개정 초등 실과교육과정 내용 요소인 소프트웨어의 이해, 절차적 문제해결, 프로그래밍 요소와 구조 평가요소와 연계하여 추출하고자 하였다. 앞으로 관련 연구를 통해 소프트웨어 교육에서 AI 기반의 학습자 주도 평가 요소를 적용한 채점 시스템을 개발하여 그 효과성을 지속적으로 입증한 후 학교 현장이 소프트웨어 교육에서 AI 기반의 학습자 주도 평가를 통해 미래교육을 주체적으로 준비해 나가는 데 도움이 되고자 한다. In future education, the paradigm of education is changing due to changes in learner-led and assessment methods. In addition, AI-based learning infrastructure and software education are increasingly needed. Thus, this study aims to examine the effectiveness of AI-based evaluation in future education by combining it with learner-led assessment. Using AI education and evaluation literature and Step 7 of the Learner-Driven Software Assessment Method, we sought to extract evaluation elements tailored to elementary school level in conjunction with the 2015 revised elementary practical course content elements, software understanding, procedural problem solving, and structural evaluation elements. In the future, we will develop a grading system that applies AI-based learner-led evaluation elements in software education and continuously demonstrate its effectiveness, and help the school site prepare for future education independently through AI-based learner-led assessment in software education.

Real-time apnea-hypopnea event detection during sleep by convolutional neural networks

Choi, Sang Ho,Yoon, Heenam,Kim, Hyun Seok,Kim, Han Byul,Kwon, Hyun Bin,Oh, Sung Min,Lee, Yu Jin,Park, Kwang Suk Elsevier 2018 Computers in biology and medicine Vol.100 No.-

<P><B>Abstract</B></P> <P>Sleep apnea-hypopnea event detection has been widely studied using various biosignals and algorithms. However, most minute-by-minute analysis techniques have difficulty detecting accurate event start/end positions. Furthermore, they require hand-engineered feature extraction and selection processes. In this paper, we propose a new approach for real-time apnea-hypopnea event detection using convolutional neural networks and a single-channel nasal pressure signal. From 179 polysomnographic recordings, 50 were used for training, 25 for validation, and 104 for testing. Nasal pressure signals were adaptively normalized, and then segmented by sliding a 10-s window at 1-s intervals. The convolutional neural networks were trained with the data, which consisted of class-balanced segments, and were then tested to evaluate their event detection performance. According to a segment-by-segment analysis, the proposed method exhibited performance results with a Cohen's kappa coefficient of 0.82, a sensitivity of 81.1%, a specificity of 98.5%, and an accuracy of 96.6%. In addition, the Pearson's correlation coefficient between estimated apnea-hypopnea index (AHI) and reference AHI was 0.99, and the average accuracy of sleep apnea and hypopnea syndrome (SAHS) diagnosis was 94.9% for AHI cutoff values of ≥5, 15, and 30 events/h. Our approach could potentially be used as a supportive method to reduce event detection time in sleep laboratories. In addition, it can be applied to screen SAHS severity before polysomnography.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We propose an automated apnea-hypopnea (AH) event detection model, based on Convolutional Neural Network (CNN). </LI> <LI> Overlapping nasal pressure signal segments are used to precisely detect AH events. </LI> <LI> Event detection performance was evaluated via segment analysis and apnea-hypopnea index (AHI) estimation analysis. </LI> <LI> The proposed model exhibited a kappa of 0.82 in event detection and an average accuracy of 94.9% in SAHS severity diagnosis. </LI> </UL> </P>

Sleep-Dependent Directional Coupling of Cardiorespiratory System in Patients With Obstructive Sleep Apnea

Yoon, Heenam,Park, Kwang Suk,Choi, Sang Ho,Kwon, Hyun Bin,Kim, Sang Kyong,Hwang, Su Hwan,Oh, Sung Min,Choi, Jae-Won,Lee, Yu Jin,Jeong, Do-Un IEEE 2018 IEEE Transactions on Biomedical Engineering Vol.65 No.12

<P>Objective: Cardiorespiratory interactions have been widely investigated in different physiological states and conditions. Various types of coupling characteristics have been observed in the cardiorespiratory system; however, it is difficult to identify and quantify details of their interaction. In this study, we investigate directional coupling of the cardiorespiratory system in different physiological states (sleep stages) and conditions, i.e., severity of obstructive sleep apnea (OSA). Methods: Directionality analysis is performed using the evolution map approach with heartbeats acquired from electrocardiogram and abdominal respiratory effort measured from the polysomnographic data of 39 healthy individuals and 24 mild, 21 moderate, and 23 severe patients with OSA. The mean phase coherence is used to confirm the weak and strong coupling of cardiorespiratory system. Results: We find that unidirectional coupling from the respiratory to the cardiac system increases during wakefulness (average value of -0.61) and rapid eye movement sleep (-0.55). Furthermore, unidirectional coupling between the two systems significantly decreases during light (-0.52) and deep sleep, which is further decreased in deep sleep (-0.46), approaching bidirectional coupling. In addition, unidirectional coupling from the respiratory to the cardiac system also significantly increases according to the severity of OSA. Conclusion: These coupling characteristics in different states and conditions are believed to be linked with autonomic nervous modulation. Significance: Our approach could provide an opportunity to understand how integrated systems cooperate for physiological functions under internal and external environmental changes, and how abnormality in one physiological system could develop to increase the risk of other systemic dysfunctions and/or disorders.</P>

Zinc Sulfide selenium X-ray Detector for Digital Reaiography

ji-KoonPark,Sang-SikKang,Jae-HyungKim,Chi-WoongMun,Sang-HeeNam 한국전기전자재료학회 2002 Transactions on Electrical and Electronic Material Vol.3 No.4

The high bias voltage associated with the thick layer (typically 500-1000 ㎛) of selenium required to have an acceptable x-ray absorption in radiography and fluoroscopy applications may have some practical inconvenience. A hybrid x-ray detector with zinc sulfide-amorphous selenium structure has been developed to improve the x-ray sensitivity of a a-Se based flat-panel digital imaging detector. Photoluminescence(PL) characteristic of a ZnS:Ag phosphor layer showed a light emission peak centered at about 450 nm, which matches the sensitivity spectrum of selenium. The dark current of the hybrid detector showed similar characteristics with that of a a-Se detector. The x-ray sensitivity of hybrid and a-Se x-ray detector was 345 pC/cm2/mR and 295 pC/cm2/mR at an applied voltage of 10 V/㎛, respectively. The purpose of this study was to evaluate the pertinence of a solution using a thin selenium layer, as a photosensitive converter, with a thick coating of silver doped zinc sulfide phosphor.

Study on Electrical Properties of X-ray Sensor Based on ScI:Na-Selenium Film

Ji-KoonPark,Sang-SikKang,Dong-GilLee,Jang-YongChoi,Jae-HyungKim,Sang-HeeNam 한국전기전자재료학회 2003 Transactions on Electrical and Electronic Material Vol.4 No.3

In this paper, we have introduced the x-ray detector built with a CsI:Na scintillation layer deposited on amorphous selenium. To determine the thickness of the CsI:Na layer, we have estimated the transmission spectra and the absorption of continuous x-rays in diagnostic range by using computer simulation (MCNP 4C). A x-ray detector with 65㎛-CsI:Na/30㎛-Se layer has been fabricated by a thermal evaporation technique. SEM and PL measurements have been performed. The dark current and x-ray sensitivity of the fabricated detector has been compared with that of the conventional a-Se detector with 100 ㎛ thickness. Experimental results show that both detectors exhibit a similar dark current, which was of a low value below 400 pA/cm2 at 10 V/㎛. However, the CsI:Na-Se detector indicates high x-ray sensitivity, roughly 1.3 times that of a conventional a-Se detector. Furthermore, a CsI:Na-Se detector with an aluminium reflective layer shows a 1.8 times higher x-ray sensitivity than an a-Se detector. The hybrid type detector proposed in this work exhibits a low dark current and high x-ray sensitivity, and, in particular, excellent linearity to the x-ray exposure dose.

Modulation of sleep using noninvasive stimulations during sleep

Kwang Suk Park,Sang Ho Choi,Heenam Yoon 대한의용생체공학회 2023 Biomedical Engineering Letters (BMEL) Vol.13 No.3

Among the various sleep modulation methods for improving sleep, three methods using noninvasive stimulation during sleephave been reviewed and summarized. The first method involves noninvasive direct brain stimulation to induce a currentdirectly in the brain cortex. Electrically or magnetically applied stimulations trigger electrical events such as slow oscillationsor sleep spindles, which can also be recorded by an electroencephalogram. The second method involves sensory stimulationduring sleep, which provides stimulation through the sensory pathway to invoke equivalent brain activity like direct brainstimulation. Olfactory, vestibular, and auditory stimulation methods have been used, resulting in several sleep-modulatingeffects, which are characteristic and depend on the experimental paradigm. The third method is to modulate sleep by shiftingthe autonomic balance affecting sleep homeostasis. To strengthen parasympathetic dominance, stimulation was appliedto decrease heart rate by synchronizing the heart rhythm. These noninvasive stimulation methods can strengthen slow-wavesleep, consolidate declarative or procedural memory, and modify sleep macrostructure. These stimulation methods provideevidence and possibility for sleep modulation in our daily life as an alternative method for the treatment of disturbed sleepand enhancing sleep quality and performance beyond the average level.