• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2068-2072
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• 1997

Acoustic noise has become an increasingly important issue, especially in the industrial environment. Nowadays home and office are not exceptional, mainly due to the increase in the usage of machinery. Active Noise Control(ANC) becomes efficiently an available tool for the noise suppression with rapid advances of solid state electronics. In this study an ANC system is developed for audio headphone to work as a noise protector, so called an ear-muff. The system is developed to kill a certain frequency band noises selectively which is purposed to suppress only the dominant ambient noise such that normal numan conversation is not disturbed with wearing the ear-muff. For the purpose, an ANC design strategy is suggested and implemented with an analogue control circuit. The performance is evaluated by frequency response test, which shows well consistence with theoretical one. The results are so satisfactory that noise of 640 Hz, which is aimed to suppress, is reduced by 20db without significant distortion in other frequency band.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.447-452
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• 2001

An automated system is developed to perform fatigue crack growth tests under constant effective stress intensity factor range ${\Delta}K_{eff}$. In the system, crack length and crack opening load are measured in real-time by using the unloading elastic compliance method. The system consists of two personal computers, an analogue electrical subtraction circuit, a stepping motor, a stepping motor driver, a PIO board, and the application software used to integrate the whole system. The performance of the developed system was tested and discussed performing constant ${\Delta}K_{eff}$ crack growth tests on a CT specimen of 7075-T6 aluminum alloy. The performance of the system is found to be strongly dependent on the accuracy of measurements of crack opening load. Besides constant ${\Delta}K_{eff}$ testing, the system is expected to be successfully applied for automation of various fatigue tests.

• Journal of the Korean Institute of Navigation
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• v.10 no.1
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• pp.81-100
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• 1986

Self-contained portable remote-indicating magnetic compass was designed and tested. Its sensing part consists of main scale disk of rotary encoder with photo-etched 180, oopaque slits and three pairs of light sources and detectors seperated by a transparent index scale, so that any angular deflection of main scale disk against the bowl may be detected optically. The outputs from the sensing part are transformed into digital ship's course indication by electronics unit which consists of operational amplifier, phase discriminator, up-down counter and counting starter circuit. The results from testign the above compass with turntable at variable rate of turn are as following : 1) The main scale disk deflection against the bowl can be detected without any disturbing influence to the freedom of its north-seeking function. 2) The digital indication resolution is found to be $\circ \pm$1 degree. 3) Misrepresenting indication can be avoided by ensuring dimension uniformity and arrangement accuracy of slits on main and index scale disks and by centering pivot in the encoder disk. 4) Indication resolution should be improved by modifying the signal processing and by doubling the number of slits on compass card. 5) Further study should be made on developing non-conductive compass liquid, analogue repeater driving system and more compact processing element.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.6
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• pp.504-513
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• 2009

This paper proposes the new type LED driver modularization for illumination LED driver. The proposed LED driver circuit insulates a hot GND of AC input power and a cold GND of LED driver part by using a fly-back converter. In order to control easily the current of the LED, the fly-back converter is operated in the discontinuous mode with excellent dynamic characteristics, and the characteristics of the LED are verified after the closed loop control is performed using a KIA2431. The LED driver module allows the wide AC power input ranges and realizes the burst dimming function which directly regulates a PWM control IC. This paper describes the operation principle of the LED driver module and it is proved the usefulness through the real model with experimentation. Besides, this paper proposes the multi-channel LED driver which the miniaturized and modularized LED driver module are connected by parallel, and verified its propriety by experiments.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.5 s.347
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• pp.34-47
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• 2006

In this paper, a new testing technique for core components of wireless transceiver was proposed. That was, band fault models (including the information of specifications in the analogue and RF IC) and methods which can test specifications in the time domain easily by observing a variation of band fault models in the circuit output were proposed and developed. This technique had an advantage over testing technique in frequency domain because it didn't need expensive test equipments and could reduce the time required. Test technique proposed in this paper was adapted to the test of 5.25 GHz low noise amplifier and proved that this testing technique was efficient in RF IC including low noise amplifier.

• Journal of Chest Surgery
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• v.39 no.8 s.265
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• pp.579-587
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• 2006

Background: Preoperative risk analysis for Fontan candidates is still less than optimal in that patients with apparently low risks may have poor surgical outcome; prolonged pleural drainage, protein losing enteropathy, pulmonary thromboembolism and death. We hypothesized that low pulmonary vascular compliance (PVC) is a risk factor for prolonged pleural effusion drainage after the Fontan operation. Material and Method: A retrospective review of 96 consecutive patients who underwent the Extracardiac Fontan procedures (median age: 3.9 years) was performed. Fontan risk score (FRS) was calculated from 12 categorized preoperative anatomic and physiologic variables. PVC $(mm^2/m^2{\cdot}mmHg)$ was defined as pulmonary artery index $(mm^2/m^2)$ divided by total pulmonary resistance $(W.U{\cdot}/m^2)$ and pulmonary blood flow $(L/min/m^2)$ based on the electrical circuit analogue of the pulmonary circulation. Chest tube indwelling time was log-transformed (log indwelling time, LIT) to fit normal distribution, and the relationship between preoperative predictors and LIT was analyzed by multiple linear regression. Result: Preoperative PVC, chest tube indwelling time and LIT ranged from 6 to 94.8 $mm^2/mmHg/m^2$ (median: 24.8), 3 to 268 days (median: 20 days), and 1.1 to 5.6 (mean: 2.9, standard deviation: 0.8), respectively. FRS, PVC, cardiopulmonary bypass time (CPB) and central venous pressure at postoperative 12 hours were correlated with LIT by univariable analyses. By multiple linear regression, PVC (p=0.0018) and CPB (p=0.0024) independently predicted LIT, explaining 21.7% of the variation. The regression equation was LIT=2.74-0.0158 PVC+0.00658 CPB. Conclusion: Low pulmonary vascular compliance is an important risk factor for prolonged pleural effusion drainage after the extracardiac Fontan procedure.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.39-46
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• 2016

This paper describes the third order feedforward delta-sigma modulator with inverter-based integrators and a 1.5bit comparator for the application of audio signal processing. The proposed 3rd-order delta-sigma modulator is multi-bit structure using 1.5 bit comparator instead of operational amplifier. This delta-sigma modulator has high SNR compared with single-bit 4th-order delta-sigma modulator in a low OSR. And it minimizes power consumes and simplified circuit structure using inverter-based integrator and using inverter-based integrator as analogue adder. The modulator was designed with 0.18um CMOS standard process and total chip area is $0.36mm^2$. The measured power cosumption is 28.8uW in a 0.8V analog supply and 66.6uW in a 1.8V digital supply. The measurement result shows that the peak SNDR of 80.7 dB, the ENOB of 13.1bit and the dynamic range of 86.1 dB with an input signal frequency of 2.5kHz, a sampling frequency of 2.56MHz and an oversampling rate of 64. The FOM (Walden) from the measurement result is 269 fJ/step, FOM (Schreier) was calculated as 169.3 dB.