• 전자공학회논문지
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• 제50권10호
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• pp.91-97
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• 2013

본 논문에서는 NTSC/PAL 아날로그 TV를 구동하기 위한 10-bit current steering D/A 변환기를 제안하였다. 제안하는 D/A 변환기는 50MS/s 의 동작속도를 가지며, 6+4 분할 구조로 설계되었다. 또한 새로운 개념의 자가보정 바이어스 기법을 적용하여 칩 내부의 종단저항을 사용하고도 공정오차를 최소화 하였다. 제안하는 D/A 변환기는 3.3V 0.11um 1-poly 6-metal CMOS 공정을 사용하여 제작되었다. 제작된 칩의 유효 면적은 $0.35mm^2$, 3.3V 전원전압 상에서 약 88mW의 전력소모를 나타내었다. 실험 결과는 변환 속도 50MS/s, 입력 주파수 1MHz에서 SFDR 63.1dB의 특성을 나타내었다.

• 한국조사연구학회지:조사연구
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• 제5권1호
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• pp.27-49
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• 2004

최근 한국을 포함한 여러 국가들에 있어 이동전화가 빠르게 보급되면서 유선전화가구보유율이 감소하고 있다. 이러한 유선전화 보유율의 감소로 인하여 표집틀의 중요한 비포함문제가 발생되고 결국 조사 추정치의 편향이 커질 수 있다. 본 논문에서는 먼저 국내에서의 유선전화 가구보유율과 이동전화 가구보유율의 변화를 살펴보고, 사회인구학적 가구 특성에 따른 이들 전화 가구보유율의 변화도 알아본다. 아울러 이로 인한 국내에서의 유선전화 표집틀 비포함 수준의 변화와 문제점들을 언급한다. 다음 유럽연합의 일부 국가들과 미국, 캐나다 등의 최근 유선전화 가구보유율을 비교한다. 마지막으로 국내의 이동전화 증가에 따른 전화조사환경의 변화에 대응하기 위한 앞으로의 연구방향을 제시한다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.141-148
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• 2003

This paper presents a rotating ann test for assessment of an underwater hybrid navigation system for a semi-autonomous underwater vehicle. The navigation system consists of an inertial measurement unit (IMU), an ultra-short baseline (USBL) acoustic navigation sensor and a doppler velocity log (DVL) accompanying a magnetic compass. The errors of inertial measurement units increase with time due to the bias errors of gyros and accelerometers. A navigational system model is derived to include the error model of the USBL acoustic navigation sensor and the scale effect and bias errors of the DVL, of which the state equation composed of the navigation states and sensor parameters is 25 in the order. The conventional extended Kalman filter was used to propagate the error covariance, update the measurement errors and correct the state equation when the measurements are available. The rotating ann tests are conducted in the Ocean Engineering Basin of KRISO, KORDI to generate circular motion in laboratory, where the USBL system was absent in the basin. The hybrid underwater navigation system shows good tracking performance against the circular planar motion. Additionally this paper checked the effects of the sampling ratio of the navigation system and the possibility of the dead reckoning with the DVL and the magnetic compass to estimate the position of the vehicle.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.533-536
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• 2016

본 논문에서는 진동 에너지를 이용한 MPPT 제어기능을 갖는 에너지 하베스팅 회로를 설계하였다. Body-bias technique과 bulk-driven technique을 이용하여 저전압에서도 높은 효율특성을 갖는 고성능 AC-DC 변환기를 제안하고 진동에너지 하베스팅 회로 설계에 적용하였다. MPPT (Maximum Power Point Tracking) 제어는 진동소자의 개방회로전압과 MPP 전압간의 관계를 이용하였으며, 진동소자의 개방회로전압을 주기적으로 샘플링 함으로써 이를 이용해 MPPT 기준전압을 생성하고, 이를 기준으로 부하로의 에너지 공급을 제어한다. $0.35{\mu}m$ CMOS 공정으로 설계된 회로의 칩 면적은 $1.21mm{\times}0.98mm$이다.

• 대기
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• 제25권1호
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• pp.19-30
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• 2015

The Ka-band cloud radar (KCR) has been operated by the National Institute of Meteorological Research (NIMR) of Korea Meteorological Administration (KMA) at Boseong National Center for Intensive Observation of severe weather since 2013. Evaluation of data quality is an essential process to further analyze cloud information. In this study, we estimate the measurement error and the sampling uncertainty to evaluate data quality. By using vertically pointing data, the statistical uncertainty is obtained by calculating the standard deviation of each radar parameter. The statistical uncertainties decrease as functions of sampling number. The statistical uncertainties of horizontal and vertical reflectivities are identical (0.28 dB). On the other hand, the statistical uncertainties of Doppler velocity (spectrum width) are 2.2 times (1.6 times) larger at the vertical channel. The reflectivity calibration of KCR is also performed using X-band vertically pointing radar (VertiX) and 2-dimensional video disdrometer (2DVD). Since the monitoring of calibration values is useful to evaluate radar condition, the variation of calibration is monitored for five rain events. The average of calibration bias is 10.77 dBZ and standard deviation is 3.69 dB. Finally, the statistical characteristics of cloud properties have been investigated during two months in autumn using calibrated reflectivity. The percentage of clouds is about 26% and 16% on September to October. However, further analyses are required to derive general characteristics of autumn cloud in Korea.

• 산학경영연구
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• 제21권2호
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• pp.111-136
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• 2008

균형성과표(BSC) 모형은 기업의 경영성과를 비재무적 지표로서 학습 및 성장성과, 내부 경영프로세스 성과, 고객성과, 재무적 지표로서 재무적 성과를 중심으로 측정하고 평가하는 통합적 성과 측정 시스템이다. 이러한 균형성과표(BSC) 모형은 재무적 성과 지표를 중심으로 기업의 경영성과를 측정하고 평가하는데 있어서 나타나는 한계를 보완하고 종합적으로 측정하고 평가함으로써 합리적인 기업의 성과를 예측하고 측정하는 평가시스템이다. 본 연구에서는 기업이 균형성과표(BSC) 모형을 도입하여 활용하는 경우 도입전과 후의 성과에서 유의미한 차이가 있는지를 구명하고, 비재무적 성과 지표와 재무적 성과 지표, 그리고 전반적인 경영성과 간의 영향관계를 분석하였다. 분석결과 균형성과표(BSC) 모형을 도입하여 활용하는 경우 기업의 학습 및 성장성과에 유의미한 차이가 분석되었으며, 비재무적 성과 지표들은 재무적 성과를 개선하여 전반적인 기업의 경영성과를 향상시키는 것으로 분석되었다.

• 한국대기환경학회지
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• 제25권3호
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• pp.219-236
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• 2009

Particle-phase organic tracers (molecular markers) have been shown to be an effective method to assess and quantify the impact of sources of carbonaceous aerosols. These molecular markers have been used in chemical mass balance (CMB) models to apportion primary sources of organic aerosols in regions where the major organic aerosol source categories have been identified. As in the case of all CMB models, all important sources of the tracer compounds must be included in a Molecular Marker CMB (MM-CMB) model or the MMCMB model can be subject to biases. To this end, the application of the MM-CMB models to locations where reasonably accurate emissions inventory of organic aerosols are not available, should be performed with extreme caution. Of great concern is the potential presence of industrial point sources that emit carbonaceous aerosols and have not been well characterized or inventoried. The current study demonstrates that emissions from industrial point sources in the St. Louis, Missouri area can greatly bias molecular marker CMB models if their emissions are not correctly addressed. At a sampling site in the greater St. Louis Area, carbonaceous aerosols from industrial point sources were found to be important source of carbonaceous aerosols during specific time periods in addition to common urban sources (i.e. mobile sources, wood burning, and road dust). Since source profiles for these industrial sources have not been properly characterized, method to identify time periods when point sources are impacting a sampling site, needs to avoid obtaining biases source apportionment results. The use of real time air pollution measurements, along with molecular marker measurements, as a screening tool to identify when point sources are impacting a receptor site is presented.

• Journal of Biosystems Engineering
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• 제27권3호
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• pp.259-266
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• 2002

It is crucial to know spatial soil variability for precision farming. However, it is time-consuming, and difficult to measure spatial soil properties. Therefore, there are needs fur sensing technology to estimate spatial soil variability, and for electronic mapping technology to store, manipulate and process the sampled data. This research was conducted to develop a real-time soil organic matter sensor and an electronic mapping system. A soil organic matter sensor was developed with a spectrophotometer in the 900∼1,700 nm range. It was designed in a penetrator type to measure reflectance of soil at 15cm depth. The signal was calibrated with organic matter content (OMC) of the soil which was sampled in the field. The OMC was measured by the Walkeley-Black method. The soil OMCs were ranged from 0.07 to 7.96%. Statistical partial least square and principle component regression analyses were used as calibration methods. Coefficient of determination, standard error prediction and bias were 0.85 0.72 and -0.13, respectively. The electronic mapping system was consisted of the soil OMC sensor, a DGPS, a database and a makeshift vehicle. An algorithm was developed to acquire data on sampling position and its OMC and to store the data in the database. Fifty samples in fields were taken to make an N-fertilizer dosage map. Mean absolute error of these data was 0.59. The Kring method was used to interpolate data between sampling nodes. The interpolated data was used to make a soil OMC map. Also an N-fertilizer dosage map was drawn using the soil OMC map. The N-fertilizer dosage was determined by the fertilizing equation recommended by National Institute of Agricultural Science and Technology in Korea. Use of the N-fertilizer dosage map would increase precision fertilization up to 91% compared with conventional fertilization. Therefore, the developed electronic mapping system was feasible to not only precision determination of N-fertilizer dosage, but also reduction of environmental pollution.

• Child Health Nursing Research
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• 제22권2호
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• pp.153-162
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• 2016

Purpose: It is critical that evidence from research is applied to everyday nursing practice to improve the quality of care and health outcomes. Aims of this study were to review high-risk infant related studies published in major nursing and non-nursing journals in Korea and to assess the quality of intervention studies. Methods: Through the Korean literature search engine of RISS.KR the authors identified 132 studies, and two researchers evaluated each of these studies using the analysis criteria. The quality of intervention studies was assessed using the van Tulder Scale. Results: Among the studies, 40.2% were either thesis or dissertation and 86.4% were quantitative studies. Convenience sampling was the most commonly used sampling method. All experimental studies were quasi-experiment except one pre-experiment study. Sensory stimulation and kangaroo care were the most common interventions for high-risk infants. Over half of the intervention studies were assessed to be "low risk of bias" but both randomization and blinding processes were not adequately satisfied in most of the studies. Conclusion: Findings of this study suggest that high-risk infants are more likely to be recruited for experimental studies but types of interventions were very limited. To provide evidence-based care for high-risk infants, rigorously conducted experimental studies should be encouraged.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 추계학술대회
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• pp.221-224
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• 2012

본 논문에서는 MEMS 가속도센서를 위한 CMOS 인터페이스 회로를 설계하였다. 설계된 CMOS 인터페이스 회로는 CVC(Capacitance to Voltage Converter), 그리고 SC-Integrator와 Comparator를 포함하는 ${\Sigma}{\Delta}$ Modulator로 구성되어 있다. 회로에 일정한 Bias를 공급할 수 있도록 Bandgap Reference를 이용하였으며, 저주파 잡음과 offset을 감소시키기 위하여 ${\Sigma}{\Delta}$ Modulator에 CHS(Chopper-Stabilization) 기법을 사용하였다. 그 결과 설계된 ${\Sigma}{\Delta}$ Modulator의 출력은 입력 전압 진폭이 100mV가 증가할 때 duty cycle은 10%의 비율로 증가하고, 전체 회로의 Sensitivity는 x, y축은 0.45V/g, z축은 0.28V/g의 결과를 얻을 수 있었다. 제안된 CMOS 인터페이스 회로는 CMOS 0.35um공정을 이용하여 설계되었다. 입력 전압은 3.3V이며, 샘플링 주파수는 2MHz이다. 설계된 칩의 크기는 PAD를 포함하여 $0.96mm{\times}0.85mm$이다.