• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2000.11a
• /
• pp.232-236
• /
• 2000

Multi-regression statistical analyses were applied for the water quality data of shallow alluvial ground water (n = 47) collected from the Youngdeok area, in order to quantitatively generalize the natural (non-anthropogenic) causes of regional water quality variation. Seven samples having the high contamination index ( $C_{a}$ > 3) reflect the striong effects by anthropogenic activity. Most of the alluvial groundwaters have acquired their quality primarily due to the dissolution of carbonate minerals. The results of multi-regression analysis show that chlorine is mainly derived from seawater effect. Sulfur isotopic compositions of dissolved sulfur and the S $O_4$/Cl ratio also enable us to discriminate the samples (n = 18) which are affected by atmospheric input of marine aerosol (sea-spray) and also by mixing between freshwater and seawater. Hydrogen and oxygen isotope data of the samples collected lie close to the local meteoric water line obtained from nearby Pohang city but has lower slope (5.45) on the $\delta$D-$^{18}$ O plot, indicating that alluvial groundwater was recharged from infiltrated meteoric water which has undergone some degree of kinetic evaporation. The estimated initial isotopic composition of the recharged water ($\delta$D = -74.8$^{0}$ /$_{00}$, $\delta$$^{18}$ O = -10.8$^{[-1000]}$ /$_{[-1000]}$ ) suggests that the alluvial ground water recharge largely occurs during summer storm events.s.s.

• Archives of design research
• /
• v.19 no.1 s.63
• /
• pp.69-78
• /
• 2006

Nowadays, the design and development of footwear are focused on not only to protect feet against some injuries also to satisfy its personality and high-quality based on customer' subjective sensibilities. Many image source based human sensibility is needed to establish concept of footwear by new idea in design process. For satisfying costumer's and designer's disires, this study is concerned to evaluate and analyze images using human sensibility and construct image source D/B according to the result. The image evaluation performed by internet is used 1,000 Images classified into four groups(structure or architecture, transportation device, natural articles and home appliance), and 300 subjects are participated. Finally, the web D/B is constructed by the result of image evaluation that is performed statistical analysis(basic statistic, factoranalysis and multi-scaled analysis).

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.12B no.1
• /
• pp.7-12
• /
• 2002

This paper presents a method to estimate an effective length of a 1000-kVA superconducting generator using three-dimensional FE analysis. Flux linkage of stator coil and the induced voltage are calculated with FEM program and Faraday's law. An effective length of the stator coil is estimated using the calculated voltage and geometric configurationn of the machine. In order to verify the estimation method, 30-kVA superconducting generator is built and tested. The test result agrees reasonably well with the estimation.

• Proceedings of the KIPE Conference
• /
• 2012.07a
• /
• pp.172-173
• /
• 2012

포항가속기 연구소에서는 4세대 가속기의 전자를 가속시키기 위해서 100ppm(0.01%) 이하의 고전압 안정도를 가진 200MW 펄스 모듈레이터가 요구된다. 그러므로 본 연구소에서는 고전압 안정도를 가진 고정밀 고전압 CCPS를 일반 CCPS와 병행하여 산업체와 함께 공동 개발을 진행하였다. 개발된 일반 CCPS의 사양은 50 kV, 30 kJ/sec, 600mA, 1000ppm이하이고, 고정밀 CCPS의 사양은 50 kV, 5 kJ/sec, 100mA, 100ppm이하이다. 본 논문에서는 CCPS의 개발 및 실제 모듈레이터에 설치하여 시험한 결과를 발표하고자 한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.977-980
• /
• 2004

본 논문에서는 저가 고효율 태양전지를 제작하기 위하여 p형 다결정 실리콘 기판을 사용하여 수산화 칼륨(KOH)이 포함된 용액에 Saw damage 과정 후 불산이 함유된 용액에 전기화학적 양극산화 과정으로 실리콘 웨이퍼 표면에 요철을 형성하여 다공성 실리콘을 형성 하였다. 본 논문은 전기화학적 에칭방법으로 기존의 진공장비로 제작된 반사방지막의 반사율만큼 감소된 다공성 실리콘 반사방지막을 형성하였다. 전자빔 증착기(e-beam evaporator)로 단층으로 형성된 $TiO_2$의 반사방지막은 400-1000 nm의 파장 범위에서 4.1 %의 평균 반사율을 가졌으며, 양극산화과정으로 형성된 다공성 실리콘은 400-1000 nm의 파장의 범위에서 4.4 %의 평균 반사율을 가졌다. 본 연구는 태양전지의 반사방지막 형성을 기존의 제작 방법보다 간단하고 저렴한 방법으로 접근하여 태양전지의 변환효율을 상승하는데 목적을 두었다.

• Journal of Ocean Engineering and Technology
• /
• v.23 no.1
• /
• pp.140-145
• /
• 2009

This paper deals with a stability evaluation of a butterfly valve using the body and disc of a valve seat. The experimental results of a strength evaluation are shown using STS316 stainless steel and spheroidal graphite cast iron (GCD450). The disc material was made from GCD450. The results of the strength analysis are as follows: Ultimate tensile strength 485MPa, Yield strength 370 MPa, Young's modulus $1.1{\times}10^5$, and Poisson's ratio v = 0.28. For the results of the disc analysis, the safety factor was about 4. This shows that a design was derived that satisfied the requirements of structural safety. However, some problems, such as the deflection and deformation of the disc, may occur when the sea water has back flow with a high pressure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.318-321
• /
• 2002

This paper presents a proper condition to achieve high conversion efficiency using PC1D simulator on sri-crystalline Si solar cells. Various efficiency influencing parameters such as rear surface recombination velocity and minority carrier diffusion length in the base region, front surface recombination velocity, junction depth and doping concentration in the Emitter layer, BSF thickness and doping concentration were investigated. Optimized cell parameters were given as rear surface recombination of 1000 cm/s, minority carrier diffusion length in the base region 200 $\mu\textrm{m}$, front surface recombination velocity 100 cm/s, sheet resistivity of emitter layer 100 Ω/$\square$, BSF thickness 5 $\mu\textrm{m}$, doping concentration 5${\times}$10$\^$19/ cm$\^$-3/. Among the investigated variables, we learn that a diffusion length of base layer acts as a key factor to achieve conversion efficiency higher than 19 %.

• ETRI Journal
• /
• v.19 no.2
• /
• pp.35-47
• /
• 1997

A power amplifier operating at 3.3 V has been developed for CDMA/AMPS dual-mode cellular phones. It consists of linear GaAs power MESFET's, a new gate bias control circuit, and an output matching circuit which prevents the drain terminal of the second MESF from generating the harmonics. The relationship between the intermodulation distortion and the spectral regrowth of the power amplifier has been investigated with gate bias by using the two-tone test method and the adjacent channel leakage power ratio (ACPR) method of CDMA signals. The dissipation power of the power amplifier with a gate bias control circuit is minimized to below 1000 mW in the range of the low power levels while satisfying the ACPR of less than -26 dBc for CDMA mode. The ACPR of the power amplifier is measured to be -33 dBc at a high output power of 26 dBm.

• Phonetics and Speech Sciences
• /
• v.2 no.3
• /
• pp.151-156
• /
• 2010

The purpose of this study was to develop a computer-animated pure tone audiometry for screening (CAPTAS) for toddler and to determine its validity and reliability. The CAPTAS utilizes an animated cartoon story producing visual and auditory stimuli. The intensities were 40 dB, 60 dB, 80 dB. The frequencies were 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz. The subjects were 20 (9 males and 11 females) severely hearing impaired children. As a result, The correlation coefficient between mean hearing threshold of children who were able to perform PTA and average hearing threshold of CAPTAS was performed and it revealed CAPTAS's high validity. And to verify the reliability of the re-test, all children had the CAPTAS and repeated it periodically. The result confirmed the reliability.

• Journal of Nutrition and Health
• /
• v.29 no.2
• /
• pp.153-158
• /
• 1996

Polyethylene glycols(PEGs)are hydrophilic molecules that have been used to characterize intestinal permeability via the paracellular pathway. Using a mixture of PEGs(400, 600 and 1000), containing oligomers in the molecular weight range 330 to 1122 D, the molecular weight permeability dependence in the jejunum of the rat small intestine was examined, employing an in situ recirculation perfusion technique. Individual oligomers were determined by HPLC with refractive detection. In the range studied, a distinct molecular weight cut-off was not apparent. Corrected for the length of jejunum used in the study, over the molecular weight range 330 to 1122D, the apparent permeability(Papp) of PEG ranged from 4.92$\pm$0.02$\times$10-5cm/sec(mean$\pm$SEM, n=5) to 0.28$\times$10-5cm/sec. Also, it was observed that the apparent permeability was inversely proportional to approximately MW2. The results in this study suggest that molecular weight is an important factor in determining the intestinal permeability.