• Journal of Environmental Science International
• /
• v.16 no.10
• /
• pp.1119-1125
• /
• 2007

We examined the horizontal distribution of salinity and the concentrations of DIN and DIP after heavy rain-fall events in coastal areas of South Korea from Yeoja Bay to Narodo and from Gwangyang Bay to Geomodo to determine whether fresh water actually flows into areas of Cochlodinium polykrikoides red tides and to observe its effect on the growth of this organism after heavy rainfall. Following heavy rainfall (155 mm) in the Yeosu and Suncheon regions, the average salinity was 21 and 29 psu at Yeoja Bay and in the coastal waters of Narodo, respectively. After 126 mm of rainfall, the values were 19 and 25 psu in the coastal waters of Yeosu and Geomodo, respectively. This may have been caused by an influx of fresh water, after the rainfall event, into the open sea coastal areas around Narodo and Geomodo from the Dong and Seomjin Rivers, which are about 3540 km away. After the rainfall, the concentrations of $NH_4-N,\;NO_2-N$, and $PO_4-P$ were slightly increased; however, the concentration of $NO_3-N$ was greatly increased and diffused throughout the coastal areas of Narodo and Geomodo, which frequently experience C. polykrikoides blooms. The influence of $NH_4-N,\;NO_2-N$, and $PO_4-P$ on the occurrence of C. polykrikoidesred tides in coastal areas around Narodo and Geomodo after heavy rainfall does not appear to be great. Instead, the occurrence C. polykrikoides red tides in the coastal areas of Narodo and Geomodo seems to be facilitated by $NO_3-N$.

• Proceedings of the KIEE Conference
• /
• 2003.07a
• /
• pp.271-273
• /
• 2003

최근에 전력선통신(PLC: power line communication)에 관한 연구 및 개발이 활성화되고 있는 가운데, 정부에서는 전력선통신을 위한 전송채널의 주파수허용범위를 기존의 협대역인 450kHz에서 광대역인 30MHz로 확대할 계획이다. 현재, PLC 시스템에서는 대용량정보를 고속으로 전송하기 위한 고속 PLC기술의 개발이 활발히 진행되어지고 있으며, 이러한 통신시스템 기술의 구현을 위해서는 새롭게 확대될 30MHz대역에서의 전력선채널의 분석이 무엇보다도 중요한 해결 과제라고 할 수가 있을 것이다. 전력선은 각종 전기기기와 가전제품 및 사무기기로부터 발생되는 잡음들이 직접 유입되며, 또한 부하가 전력선에 연결되는 시간과 공간에 따라 전송 특성이 수시로 가변하는 특성을 가진다. 이와 같은 열악한 전력선통신채널 환경을 극복하고 통신의 에러극복능력을 향상시키기 위해서는 기존의 협대역 채널모델을 그대로 적용하기에는 부적합한 면이 많으므로, 새롭게 허용될 광대역 주파수를 갖는 전력선 채널에 대한 모델링기법이 요구된다. 따라서, 새롭게 인가될 광대역 채널을 위한 효율적인 전력선통신시스템을 개발하기 위해서는 전력선채널의 리모델링에 근거한 다양하고 실험적인 고찰이 수반되어야 하리라고 판단된다. 그러므로, 본 논문에서는 Mixture 잡음 모델링기법을 이용하여, 부하변동 및 가변적인 잡음 특성을 가진 전력선채널모델을 새롭게 분석하였다. 또한, 새롭게 분석한 전력선채널모델에 관한 수식을 직교 코드에 의한 다중접속 통신 기술인 CDMA 방식에 적용하여 비트 에러율을 유도해 봄으로써 그 유효성을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.12 no.5
• /
• pp.478-491
• /
• 1987

In this paper, an all Digital Phase-Locked Loop(DPLL) has been propoed, which has reduced the phase error by using a half period sampling in order to improve the performance of the conventional DPLL which tracks the phase of incoming sinusoidal signal once per cycle for the Positive Going Zero crossing(PGZC) of the signal. The proposed DPLL tracks the phase of input signal twice per cycle with two samplers for the PGZC. So the loop has a half reduction of the steady state phase error fluctuation ranges without decreasing the lock-range in a whole, comparing with that of the conventional DPLL. Also, it has been known that the proposed loop is rapidly locked to input signal for the same valves of phase differenc between sucessive samples and quantization level. The analytic results of the proposed loop have been verified by computer simulation for the practically requeired conditions.

• The Journal of the Acoustical Society of Korea
• /
• v.37 no.3
• /
• pp.129-138
• /
• 2018

In port and coastal areas where ship traffic is frequent, ship noise dominantly influences underwater noise in low frequency band below 1 kHz. In this paper, we propose a modeling method to estimate the underwater shipping noise using the voyage information of ship observed in AIS (Automatic Identification System). For the purpose of ship noise modeling, the navigation information of the vessels operating in the southern part of Jeju was observed using AIS and underwater noise was measured by installing a hydrophone in the experimental area to verify the modeled ship noise. AIS data were used to model the noise level of ship and compared with measured underwater noise. The variation of noise level with time was found to be similar, and the cause of the error was discussed. Through this study, it was confirmed that the noise level of ship can be estimated within 5 dB error range using AIS data.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.10
• /
• pp.1075-1081
• /
• 2011

A leak-detection method has been developed by measuring the pressure variation between the inner and outer heattransfer tubes of a double-wall tube steam generator. An experiment was carried out to measure the leak rate in the gap between two surfaces pressed with a hydraulic press in order to simulate the phenomena, and a correlation was determined for the leak rate in a micro gap. However, in the correlation, the gap width and friction coefficient were coupled with the surface roughness, which affects the two parameters. The two parameters were separated using a surface-contact model to develop a correlation for the friction coefficient. The correlation was compared with the existing correlations used for crack analysis. Although the applied ranges of Reynolds numbers were different, the developed correlation for Reynolds numbers of 0.1.0.35 showed similar tendencies to existing correlations used for higher Reynolds numbers.

• Journal of the Korean Geophysical Society
• /
• v.2 no.4
• /
• pp.241-250
• /
• 1999

Reflection coefficients of the seafloor have been calculated from the amplitude ratio of secondary to primary water bottom reflection in seismic data obtained from Bransfield Strait, Antarctic Peninsula. Test processing for the coefficients shows that moving average is effective to reduce severe fluctuation of the coefficient measured at each point. Relationship between the coefficients and the properties of water bottom is analyzed to illuminate geological environment. In the central Bransfield Basin, the magnitude of reflection coefficients decreases as it is distant from the sedimentary sources. Reflection coefficients range from 0.12 to 0.2 near the continental slope of the basin, and from 0.1 to 0.12 in the basin floor. In the western Bransfield basin, reflection coefficients between 0.2 to 0.3 are obtained from the area eroded by glacial movement. On the volcanic structures near Deception Island, the coefficients show relatively high values more than 0.2. Paleo-geological structures uplifted by tectonic movement and outcropped by glacial erosion have relatively high coefficients.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2018.01a
• /
• pp.59-62
• /
• 2018

근저당권(根抵當權)은 지속적(持續的)인 거래관계(去來關係)에서 생겨나는 많은 채권(債權)을 거래(未來)의 결산기(決算期)에 일정(一定) 한도(限度)까지 확보(確保)하기 위해 부동산(不動産)에 담보물권(擔保物權)을 설정(設定)하는 저당권(抵當權)을 말한다. 저당권(抵當權)과는 다르게 담보(擔保) 채권(債權)은 거래(未來)에 증감(增減) 등(等)으로 달라지는 불특정(不特定) 채권(債權)이므로 당장(當場) 채무(債務)가 없어도 담보물권(擔保物權)인 저당권(抵當權)이 성립(成立)하게 되고, 일단(一旦) 성립(成立)한 채권(債權)이 이행(履行)되어도 후(後) 순위(順位)의 저당권(抵當權) 순위(順位)가 승진(昇進)하지 않는 점(點)이 일반적(一般的)인 저당권(抵當權)과 다르다. 근저당권(根抵當權)과 저당권(抵當權)의 제(第)일 큰 차이점(差異點)은 근저당권(根抵當權)은 채권최고(債權最高) 금액(金額)의 범위(範圍) 내(內)에서 지속적(持續的)인 거래(去來)로 인한 채권(債權)이 증감(增減) 변동(變動)할 수 있다는 것인데 반해(半解) 저당권(抵當權)은 앞서 확정(確定)된 채권(債券)을 담보(擔保)하는 것이다. 따라서 근저당권(根抵當權)을 설정(設定)하고자 할 때에는 채권(債權)의 최고금액(最高金額)을 등기(登記)하여야 한다. 이처럼 오늘날 근저당권(根抵當權)이 실질적(實質的)으로 신용거래(信用去來)에서 있어서 많이 이용(利用)되고 있으나, 우리민법(民法) 제(第)357조(條) 하나만으로 규율(規律)하고 있어 이와 관련(關聯)하여 발생(發生)하는 다양(多樣)한 법률분쟁(法律紛爭)을 해결(解決)하지 못하고 이 모든 부분(部分)을 학설(學說)과 판례(判例)에 의존(依存)하고 있는 실정(實情)이다. 따라서 본(本) 연구(硏究)에서는 외국입법례(外國立法例)를 통(通)하여 우리나라의 근저당권(根抵當權)의 문제점(問題點)이 무엇인지 살펴본 후(後) 바람직한 근저당권(根抵當權)의 해결방안(解決方案)을 제시(提示)하고자 한다.

• Journal of IKEEE
• /
• v.15 no.4
• /
• pp.319-323
• /
• 2011

In this paper presents a new model of dual-mode synchronous buck converter with dynamic control for mobile applications was proposed. The proposed circuit can operate at 2.5MHz with supply voltage 2.5V to 5V for low ripple and minimum inductor and capacitor size, which is suitable for single-cell lithium-ion battery supply mobile applications. For high efficiency, the proposed circuit adopts synchronous type and dynamic control. The proposed circuit is designed by using the device parameter of TSMC 0.18um BCD process and the performance is evaluated by Cadence spectre. Experimental board level results show the maximum conversion efficiency is 96% at 100mA load current.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.6
• /
• pp.11-19
• /
• 2013

An experimental study was conducted to investigate fuel injection characteristics through swirl injectors when the fuel was heated to very high temperature conditions. Three swirl injectors with different orifice diameters and swirler geometries were used to measure the flow coefficient (${\alpha}$) for the injection pressure ranges between 3 and 10 bar and the fuel temperature from 50 to $270^{\circ}C$. The results showed that the variation characteristics of ${\alpha}$ with respect to cavitation number ($K_c$) were highly dependent on both the orifice diameter and the swirler geometry. In addition, the characteristics of ${\alpha}$ variation with respect to AR, the area ratio of the flow through the swirler and the orifice, has revealed that the effect of boiling is retarded but the slope of decreasing ${\alpha}$ after the boiling effect is present tumbles as AR increases.

• Geotechnical Engineering
• /
• v.6 no.2
• /
• pp.5-20
• /
• 1990

In the seismic analysis of structures, where the dynamic soil-structure interaction (DSSI) is considred, earthquake input motions as well as dynamic soil properties are random in nature. To take into account the random nature of both the input motions and the dynamic soil properties systematically, a probabilistic analysis of the DSSI subjected to seismic loading is proposed in this paper, The complex response method formulized by the elastic half space theory, the random vibration theory, and the Rosenblueth's two-point estimate method are combined for the proposed probabilistic analysis. The conclusions drawn from this study are as follows ' 1) The uncertainty bands of the earthquake input motions proposed by Kanai-Tajimi as well as those of the dynamic properties are large the coefecients of variation of those parameters tinge from 0.4 to 0.6. 2) The uncertainties of the dynamic soil properties are more sensitive to the structural responses than those of the input motion parameters. 3) The effect of correlations between the input motion parameters and the dynamic soil properties is negligible.