• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.199-203
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• 2004

In this paper, we only describe the digital block of two-channel 18-bit analog-to-digital (A/D) converter employing sigma-delta method and xl28 decimation. The device contains two fourth comb filters with 1-bit input from sigma­delta modulator. each followed by a digital half band FIR(Finite Impulse Response) filters. The external analog sigma-delta modulators are sampled at 6.144MHz and the digital words are output at 48kHz. The fourth-order comb filter has designed 3 types of ways for optimal power consumption and signal-to-noise ratio. The following 3 digital filters are designed with 12tap, 22tap and 116tap to meet the specification. These filters eliminate images of the base band audio signal that exist at multiples of the input sample rate. We also designed these filters with 8bit and 16bit filter coefficient to analysis signal-to-noise ratio and hardware complexity. It also included digital output interface block for I2S serial data protocol, test circuit and internal input vector generator. It is fabricated with 0.35um HYNIX standard CMOS cell library with 3.3V supply voltage and the chip size is 2000um by 2000um. The function and the performance have been verified using Verilog XL logic simulator and Matlab tool.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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• pp.203-206
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• 1996

During the electromyographic evaluation, the presence and site of lession may be predicted by a detection of denervation potentials such as fibrllation potentials or positive sharp waves in the group of muscles. Currently, clinicians diagnose the neuropathy by detecting fibrillation potentials during EMG tests, and sometimes it is not easy to distinguish between denervation potentials and endplate spikes. The purpose of this study was to find statistically significant parameters for the quantitative distinction between denervation potentials and endplate spikes. Endplate spikes and denervation potentials from the EDB muscle of 10 patients were extracted. Also, EMG signals were classified by experienced clinicians, and were collected using a 12 bit ADC with a sampling rate of 20KHz for the duration of 400msec. In order to find statistically significant parameters, positive and negative peaks were used for analysis. As a results, standard deviation of the endplate spikes and denervation potentials showed more significant difference than others specially for the positive sharp waves. It was concluded that the results of this study could be used to develope an automated system of a EMG analysis.

• 센서학회지
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• 제30권2호
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• pp.88-93
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• 2021

In this paper, a folding sensor based on capacitance is proposed. The sensor was developed to sense the length and angle data for the milli-scale actuators without causing any interference to the actuating joints. For the sensing and testing the robotic joint with reducing the cost and complexity aspects of manufacturing, a simple composition was adopted. The sensor comprises a pair of copper tapes, papers, and wires. The complete sensing unit is constructed by bonding the tapes with the papers and soldering the wire to the copper parts. For accuracy, a teensy 4.0 board, which has a 12-bit ADC resolution, is employed. Furthermore, the sensed analog data is not translated into the unit of capacitance for accuracy; however, it is filtered using a low-pass filter and subsequently, a Butter-worth filter. The data obtained demonstrate a periodic waveform, which implies that the data are in good agreement with the hypothesis set prior to the experiments. Compared to other milli-scale sensors, this could be a better option for sensing the length and angle data for milliscale actuators.

• 센서학회지
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• 제31권2호
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• pp.115-119
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• 2022

A readout circuit for a mercury-cadmium-telluride (MCT)-amplified mid-wave infrared (IR) photodetector was realized and applied to noncontact chemical agent detectors based on a quantum cascade laser (QCL). The QCL emitted 250 times for each wavelength in 0.2-㎛ steps from 8 to 12 ㎛ with a frequency of 100 kHz and duty ratio of 10%. Because of the nonconstant QCL emission power during on-duty, averaging the photodetector signals is essential. Averaging can be performed in digital back-end processing through a high-speed analog-to-digital converter (ADC) or in analog front-end processing through an integrator circuit. In addition, it should be considered that the 250 IR data points should be completely transferred to a PC during each wavelength tuning period of the QCL. To average and minimize the IR data, we designed a readout circuit using the analog front-end processing method. The proposed readout circuit consisted of a switched-capacitor integrator, voltage level shifter, relatively low-speed analog-to-digital converter, and micro-control unit. We confirmed that the MCT photodetector signal according to the QCL source can be accurately read and transferred to the PC without omissions.

• Asian Pacific Journal of Cancer Prevention
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• 제16권15호
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• pp.6469-6475
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• 2015

Background: Diffusion-weighted magnetic resonance imaging (DWI) makes it possible to detect malignant tumors based on the diffusion of water molecules. It is uncertain whether DWI is more useful than positron emission tomography-computed tomography (PET-CT) for distinguishing benign from malignant mediastinal tumors and mass lesions. Materials and Methods: Sixteen malignant mediastinal tumors (thymomas 7, thymic cancers 3, malignant lymphomas 3, malignant germ cell tumors 2, and thymic carcinoid 1) and 12 benign mediastinal tumors or mass lesions were assessed in this study. DWI and PET-CT were performed before biopsy or surgery. Results: The apparent diffusion coefficient (ADC) value ($1.51{\pm}0.46{\times}10^{-3}mm^2/sec$) of malignant mediastinal tumors was significantly lower than that ($2.96{\pm}0.86{\times}10^{-3}mm^2/sec$) of benign mediastinal tumors and mass lesions (P<0.0001). Maximum standardized uptake value (SUVmax) ($11.30{\pm}11.22$) of malignant mediastinal tumors was significantly higher than that ($2.53{\pm}3.92$) of benign mediastinal tumors and mass lesions (P=0.0159). Using the optimal cutoff value (OCV) $2.21{\times}10^{-3}mm^2/sec$ for ADC and 2.93 for SUVmax, the sensitivity (100%) by DWI was not significantly higher than that (93.8%) by PET-CT for malignant mediastinal tumors. The specificity (83.3%) by DWI was not significantly higher than that (66.7%) for benign mediastinal tumors and mass lesions. The accuracy (92.9%) by DWI was not significantly higher than that (82.1%) by PET-CT for mediastinal tumors and mass lesions. Conclusions: There was no significant difference between diagnostic capability of DWI and that of PET-CT for distinguishing mediastinal tumors and mass lesions. DWI is useful in distinguishing benign from malignant mediastinal tumors and mass lesions.

• Korean Journal of Radiology
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• 제24권2호
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• pp.133-144
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• 2023

Objective: Cyclin-dependent kinase inhibitor (CDKN)2A/B homozygous deletion is a key molecular marker of isocitrate dehydrogenase (IDH)-mutant astrocytomas in the 2021 World Health Organization. We aimed to investigate whether qualitative and quantitative MRI parameters can predict CDKN2A/B homozygous deletion status in IDH-mutant astrocytomas. Materials and Methods: Preoperative MRI data of 88 patients (mean age ± standard deviation, 42.0 ± 11.9 years; 40 females and 48 males) with IDH-mutant astrocytomas (76 without and 12 with CDKN2A/B homozygous deletion) from two institutions were included. A qualitative imaging assessment was performed. Mean apparent diffusion coefficient (ADC), 5th percentile of ADC, mean normalized cerebral blood volume (nCBV), and 95th percentile of nCBV were assessed via automatic tumor segmentation. Logistic regression was performed to determine the factors associated with CDKN2A/B homozygous deletion in all 88 patients and a subgroup of 47 patients with histological grades 3 and 4. The discrimination performance of the logistic regression models was evaluated using the area under the receiver operating characteristic curve (AUC). Results: In multivariable analysis of all patients, infiltrative pattern (odds ratio [OR] = 4.25, p = 0.034), maximal diameter (OR = 1.07, p = 0.013), and 95th percentile of nCBV (OR = 1.34, p = 0.049) were independent predictors of CDKN2A/B homozygous deletion. The AUC, accuracy, sensitivity, and specificity of the corresponding model were 0.83 (95% confidence interval [CI], 0.72-0.91), 90.4%, 83.3%, and 75.0%, respectively. On multivariable analysis of the subgroup with histological grades 3 and 4, infiltrative pattern (OR = 10.39, p = 0.012) and 95th percentile of nCBV (OR = 1.24, p = 0.047) were independent predictors of CDKN2A/B homozygous deletion, with an AUC accuracy, sensitivity, and specificity of the corresponding model of 0.76 (95% CI, 0.60-0.88), 87.8%, 80.0%, and 58.1%, respectively. Conclusion: The presence of an infiltrative pattern, larger maximal diameter, and higher 95th percentile of the nCBV may be useful MRI biomarkers for CDKN2A/B homozygous deletion in IDH-mutant astrocytomas.

• 전자공학회논문지 IE
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• 제43권1호
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• pp.16-24
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• 2006

본 논문에서는 생체신호의 발생을 자유롭게 조절 할 수 있는 전정기관으로부터 생성된 전기신호를 추출하여 window discriminator로 필요한 신호를 선택한 후, BCI 시스템을 적용하여 정밀하고 정확한 제어가 가능하고 멀티채널을 이용하여 데이터를 처리할 수 있는 통합 시스템을 구현하였다. 전정신경세포의 흥분신호를 검출하는 전치증폭기는 측정된 이득이 47.6dB, 왜율은 100 Hz에서 측정 시 0.005%이었으며, 입력임피던스 특성은 12M$\Omega$이었다. Window discriminator는 2개의 CPU를 사용하여 역할을 분담함으로써 처리 속도를 증가시켰고, ADC 샘플링 주파수는 87kHz이었으며, 기존 시스템보다 분해능이 2배, 변별 오차는 10배가 향상되었음을 알 수 있었다. 제안된 방법이 뇌파분석법 보다 100ms동안 축적된 데이터양이 약 100배 정도 감소되었음을 입증하였다.

• 한국식품과학회지
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• 제37권3호
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• pp.334-338
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• 2005

본 연구는 식품병마개 PVC 가스켓과 식품에 함유된 SEM을 효과적으로 분석하기 위해 연구했다. SEM은 발포제로 사용되는 ADC의 열분해산물로 알려졌다. 그러나 SEM은 분자량이 낮으며 ultraviolet light나 fluorescence에 활성을 갖지 않는다. 따라서 2-NBA-SEM으로 유도체화하여 HPLC triple column system으로 분석했을 때 상관관계는 0.9997이상이며 검출한계는 0.48ng/g으로 나타났다. 식품병마개 PVC 가스켓에서 SEM의 검출율은 77.08%로 나타났으며, 유통중인 병마개 PVC 가스켓에서 SEM은 812.20-5771.30ng/g 수준이였다. 그리고 회수율은 PVC 가스켓과 식품에서 각각 92.12-98.71%와 83.45-97.33%로 측정되었다.

• 대한의용생체공학회:의공학회지
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• 제22권6호
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• pp.503-510
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• 2001

인체의 각 조직은 서로 다른 저항률(resistivity)을 가지고 있고. 심장의 박동이나 호흡과 같은 생리현상은 해당 생체조직의 임피던스를 변화시킨다. 본 논문에서는 인체 내부에 존재하는 비정상 조직의 크기와 위치를 검출하기 위한 32-채널 생체 임피던스 측정 시스템에 대하여 기술한다. 이러한 기술은 유방암 조직의 경우와 같이 배경 조직과는 저항률이 다른 비정상 조직을 검출하는 경우에 응용할 수 있을 것으로 기대한다. 32-채널 생체 임피던스 측정 시스템을 위하여 32개의 복합형 전극과 32 채널의 정전류원을 사용하였다. 임피던스의 측정을 위해 50kHz의 정현파 전류를 주입하고. 유기되는 전압을 가변 이득 협대역 계측용 증폭기로 측정하고, 그 크기를 위상감응복조기로 검출하였다. 검출된 임피던스 신호는 A/D 변환하여 PC에 입력하였다. 전해질 팬텀을 이용한 실험에서 전체 시스템의 정확도는 2.42%이며, 직경 270mm인 팬텀 내부에 존재하는 직경 8mm 이상인 물체의 크기와 위치를 검출할 수 있었다. 본 연구의 결과를 기초로 다채널 생체 임피던스 측정 시스템의 정확도를 개선하여. 직경 lmm 이내의 물체를 검출하는 것이 향후의 연구 목표이다 이러한 정확도를 가지는 생체 임피던스 계측 시스템을 개발하면. 인체 내부의 임피던스 분포를 측정하는 EIT(electrical impedance tomography) 시스템과, 최근에 연구되고 있는 자기공명 임피던스 단층촬영(MREIT, magnetic resonance electrical impedance tomography)에도 응용이 가능할 것이다.

• 한국정보통신학회논문지
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• 제12권2호
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• pp.309-314
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• 2008

계측 및 측정분야에 사용되는 아날로그-디지털 변환기는 우수한 선형성과 무시할 만큼 적은 dc 오프셋 특성을 갖으면서 높은 정밀도를 요구한다. 증분형(적분형) 데이터 변환기는 $\Delta{\Sigma}$ 변환기의 대부분의 장점을 보유하면서, 측정 응용분야에 적합한 해법을 제공한다. 또한 이러한 형태의 변환기는 오프셋 조정이 필요 없이 정확한 변환을 할 수 있다. 본 논문에서는 멀티채널을 통한 협대역 AC 신호를 변환시켜 주는 다중화 증분형 데이터 변환기의 구현 기술을 제안한다. 또한 동작 원리, 토폴로지, 그리고 디지털 decimation 필터 설계에 대해 논의한다. 마지막으로 시뮬레이션 결과를 통해 제안한 이론에 대한 타당성을 검증한다.