• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_2
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• pp.567-576
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• 2013

The determination of the geoid in South Korea is a national imperative for the modernization of height datums, specifically the orthometric height and the dynamic height, that are used to monitor hydrological systems and environments with accuracy and easy revision, if necessary. The geometric heights above a reference ellipsoid, routinely obtained by GPS, lead immediately to vertical control with respect to the geoid for hydrological purposes if the geoid height above the ellipsoid is known accurately. The geoid height is determined from gravimetric data, traditionally ground data, but in recent times also from airborne data. This paper illustrates the basic concepts for combining these two types of data and gives a preliminary performance assessment of either set or their combination for the determination of the geoid in South Korea. It is shown that the most critical aspect of the combination is the gravitational effect of the topographic masses above the geoid, which, if not properly taken into account, introduces a significant bias of about 8 mgal in the gravity anomalies, and which can lead to geoid height bias errors of up to 10 cm. It is further confirmed and concluded that achieving better than 5 cm precision in geoid heights from gravimetry remains a challenge that can be surmounted only with the proper combination of terrestrial and airborne data, thus realizing higher data resolution over most of South Korea than currently available solely from the airborne data.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.48-48
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• 2009

최근 빠른 동작속도와 고 집적도를 얻기 위해 metal oxide semiconductor field effect transistor (MOSFET) 의 크기는 계속 해서 줄어들고 있다. 동시에 게이트의 절연층도 얇아지게 된다. 절연층으로 사용되는 $SiO_2$ 의 두께가 2nm 이하로 얇아 지게 되면 터널링에 의해 누설 전류가 발생하게 된다. 이 문제를 해결하기 위해 $SiO_2$ 를 대체할 고유전체 물질의 연구가 활발하다. 고유전체 물질 중에는 $ZrO_2,\;Al_2O_3,\;HfO_2$ 등이 많이 연구 되어 왔다. 하지만 유전상수 이외에 band gap energy, thermodynamic stability, recrystallization temperature 등의 특성이 좋지 않아 대체 물질로 문제점이 있다. 이를 보안하기 위해 산화물을 합금과 결합시키면 서로의 장점들이 합쳐져 기준들을 만족하는 물질을 만들 수 있고 $HfAlO_3$가 그 중 하나이다. Al를 첨가하는 이유는 문턱전압을 낮추기 위해서다. $HfAlO_3$는 유전상수 18.2, band gap energy 6.5 eV, recrystallization temperature 800 $^{\circ}C$이고 열역학적 특성이 안정적이다. 게이트 절연층은 전극과 기판사이에 적층구조를 이루고 있어 이방성인 드라이 에칭이 필요하고 공정 중 마스크물질과의 선택비가 높아야한다. 본 연구는 $HfAlO_3$박막을 $BCl_3/Ar,\;N_2/BCl_3/Ar$ 유도결합 플라즈마를 이용해 식각했다. 베이스 조건은 RF Power 500 W, DC-bias -100 V, 공정압력 15 mTorr, 기판온도 40 $^{\circ}C$ 이다. 가스비율, RF Power, DC-bias, 공정 압력에 의한 마스크물질과 의 선택비를 알아보았다.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.322-327
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• 2012

Parallel-plate-type scanning sensors have been commercially used for X-ray imaging sensors. In this study, we manufactured the scan typed 1D X-ray image sensor that can be used to obtain scanning images, by using the plasma display panel (PDP) fabrication process. We fabricated drift and pixel electrodes in the glass chamber and injected Xe gas at atmospheric pressure. We evaluated the intensity of a pixel signal depending on the bias voltage on the drift electrode and investigated the characteristics of shielding effect on the single pixel using lead (Pb). The adsorption rate of X-ray photon is low (4%) on the soda lime glass (1.1mm) and the electrical signal detected on the X-ray sensor was increased in the high bias voltage. We acquired digital X-ray scanning image with our DAS (data acquisition system) and sensor scanning system.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.198-203
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• 2016

We investigate the effects of magnesium (Mg) suppressor layer on the electrical performances and stabilities of amorphous indium-zinc-tin-oxide (a-ITZO) thin-film transistors (TFTs). Compared to the ITZO TFT without a Mg suppressor layer, the ITZO:Mg TFT exhibits slightly smaller field-effect mobility and much reduced subthreshold slope. The ITZO:Mg TFT shows improved electrical stabilities compared to the ITZO TFT under both positive-bias and negative-bias-illumination stresses. From the X-ray photoelectron spectroscopy O1s spectra with fitted curves for ITZO and ITZO:Mg films, we observe that Mg doping contributes to an enhancement of the oxygen bond without oxygen vacancy and a reduction of the oxygen bonds with oxygen vacancies. This result shows that the Mg can be an effective suppressor in a-ITZO TFTs.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.1
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• pp.42-48
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• 2011

In this paper, a passive load-pull using a GaN HEMT (Gallium Nitride High Electron Mobility Transistor) bare-chip in X-band is presented. To obtain operation conditions that characteristic change by self-heating was minimized, pulsed drain bias voltage and pulsed-RF signal is employed. An accuracy impedance matching circuits considered parasitic components such as wire-bonding effect at the boundary of the drain is accomplished through the use of a electro-magnetic simulation and a circuit simulation. The microstrip line length-tunable matching circuit is employed to adjust the impedance. The measured maximum output power and drain efficiency of the pulsed load-pull are 42.46 dBm and 58.7%, respectively, across the 8.5-9.2 GHz band.

• The Journal of Industrial Distribution & Business
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• v.11 no.1
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• pp.39-47
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• 2020

Purpose: This study investigated the effects of valuation errors on the capital market through the earnings forecasting errors of financial analysts. As a follow-up to Jensen (2005)'s study, which argued of agency cost of overvaluation, it was intended to analyze the effect of valuation errors on the earnings forecasting behavior of financial analysts. We hypothesized that if the manager tried to explain to the market that their firms are overvalued, the analysts' earnings forecasting errors would decrease. Research design, data and methodology: To this end, the analysis period was set from 2011 to 2018 of KOSPI and KOSDAQ-listed markets. For overvaluation, the study methodology of Rhodes-Kropf, Robinson, and Viswanathan (2005) was measured. The earnings forecasting errors of the financial analyst was measured by the accuracy and bias. Results: Empirical analysis shows that the accuracy and bias of analysts' forecasting errors decrease as overvaluation increase. Second, the negative relationship showed no difference, depending on the size of the auditor. Third, the results have not changed sensitively according to the listed market. Conclusions: Our results indicated that the valuation error lowered the financial analyst earnings forecasting errors. Considering that the greater overvaluation, the higher the compensation and reputation of the manager, it can be interpreted that an active explanation of the market can promote the accuracy of the financial analyst's earnings forecasts. This study has the following contributions when compared to prior research. First, the impact of valuation errors on the capital market was analyzed for the domestic capital market. Second, while there has been no research between valuation error and earnings forecasting by financial analysts, the results of the study suggested that valuation errors reduce financial analyst's earnings forecasting errors. Third, valuation error induced lower the earnings forecasting error of the financial analyst. The greater the valuation error, the greater the management's effort to explain the market more actively. Considering that the greater the error in valuation, the higher the compensation and reputation of the manager, it can be interpreted that an active explanation of the market can promote the accuracy of the financial analyst's earnings forecasts.

• Journal of Korea Water Resources Association
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• v.39 no.8 s.169
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• pp.659-668
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• 2006

The uncertainty of the risk of failure of hydraulic structures can be determined by estimating the variance of the risk of failure based on the methods of moments, probability weighted moments, and maximum likelihood assuming that the underlying model is the Gumbel distribution. In this paper, the variance of the risk of failure was derived. Monte Carlo simulation was peformed to verify the characteristics of the derived formulas for various sample size, design life, nonexceedance probability, and variation coefficient. As the results, PWM showed the smallest relative bias and root mean square error than the others while ML showed the smallest ones for relatively large sample siBes regardless of design life and nonexceedance probability. Also, it was found that variation coefficient does not effect on the relative bias and relative root mean square error.

• Journal of the Korean Vacuum Society
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• v.16 no.2
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• pp.122-127
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• 2007

In this research, amophous carbon films (a-C, a-C:H, a-C:N) were synthesized by closed-field unbalanced magnetron (CFUBM) sputtering using graphite target. We also fabricated amorphous carbon films with applying negative DC bias voltage of 200 V in during the deposition in working pressure. Also, a-C:H and a-C:N films was synthesized by adding acethylene($C_{2}H_{2}$) and nitrogen(N) gases of 4 and 3 sccm into Ar pressure. The a-C:H film synthesized at -200 V exhibited the maxumum hardness of 26.3 GPa, the smooth surface of 0.1 nm and the good adhesion of 30.5 N. And a-C:N film synthesized at -200 V exhibited at -200 V exhibited the best adhesion of 32 N. This paper examined the effect of $C_{2}H_{2}$ gas, $N_{2}$ gas and negative DC bias voltage as the parameter for improving the physical properties and the relation between structral and physical properties of carbon films.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.1
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• pp.46-52
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• 2010

A compact circular microstrip patch antenna with a switchable circular polarization(CP) is proposed at 2.4 GHz. An unequal cross-shaped slot on a ground plane is utilized as a perturbation. By switching pin diodes mounted on the slot, the CP sense of each antenna can be simply switched from left-handed(LH) CP to right-handed(RH) CP vice versa. Since the perturbation can be made on the ground plane and no bias circuit is required on the patch side, the bias circuit has not effect on the main beam radiation. From the experimental results, the impedance bandwidth and CP bandwidth of the proposed antenna have shown up to 150 MHz and 35 MHz, respectively. The peak gain of the proposed antenna is 1.7 dBi for both CP senses.

• The Journal of Korean Medicine
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• v.40 no.4
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• pp.16-28
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• 2019

Objectives: The purpose of this meta-analysis was to evaluate the effects of Yukgunja-tang(YGJT, Rikkunshito, Liujunzi) on Gastroesophageal Reflux Disease(GERD). Methods: Sixteen electronic databases were used to search for studies published through March 2019, and a randomized controlled study was conducted to study the effects of YGJT or modified YGJT on GERD. Study quality was assessed using the risk bias tool provided by Cochran, and data analysis was performed using Review Manager 5.3.0 software Results: Two-hundred and forty articles were initially searched, and 13 studies that satisfied the study criteria were evaluated qualitatively; 11 of the 13 were included in the meta-analysis. In the two studies, the effects of YGJT and a placebo were compared. Meta-analysis showed that YGJT significantly improved FSSG (Frequency Scale for the Symptoms of GERD) scores, but not GSRS (Gastrointestinal Symptom Rating Scale) scores (FSSG: MD -2.40, 95% CI [-5.31, 0.51], p=0.11, GSRS: MD 0.05, 95% CI [-0.12, 0.22], p=0.55). Meta-analysis of nine studies comparing the efficacies of YGJT and conventional medicine showed that YGJT had a significant clinical effect (OR 5.72; 95% CI [3.41, 9.61]; I2 p<0.00001). Conclusion: This study suggests that YGJT effectively relieves the symptoms of GERD. Unfortunately, owing to the small sample sizes, limitations of several methodological qualities, we believe large-scale clinical studies with less bias will provide evidence of qualitative improvement.