• Journal of Ocean Engineering and Technology
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• v.17 no.4
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• pp.73-80
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• 2003

This paper presents considerations on the results of the rotating arm test, which was carried out for assessment of an 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. A navigational systemmodel is derived to include the scale effect and bias errors of the DVL, of which the state equation composed of the navigation states and sensor parameters are 25 in the order. The extended Kalman filter was used to propagate the error covariance, The rotating arm tests were carried out in the Ocean Engineering Basin of KRISO, to generate circular motion. 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.5
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• pp.594-604
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• 2017

The Korean National Institute of Fisheries Science (NIFS) has biannually (spring and fall, respectively) deployed a bottom trawl survey along the coastal areas for last decade, taking samples on a regular basis (i.e., a systematic sampling). Despite the availability of the survey data, NIFS has not yet officially reported the estimates of the groundfish population sizes as well as has not evaluated uncertainty of the estimates. The objectives of our study were to infer the relative size of a fish population, applying two different sampling techniques (namely simple and stratified sampling) with different observation units to the NIFS survey data, and to compare those two techniques in bias and precision. For demonstration purposes, we used data on Pacific cod (Gadus macrocephalus) collected by the 2011-2015 surveys, and the results of simple and stratified sampling showed that the point estimates and precision varied by observation unit as well as the sampling technique.

• Journal of Korean Society of Transportation
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• v.4 no.2
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• pp.37-58
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• 1986

Since 1960's there have been conducted quite numbers of origin and destination (0-D) surveys in Korea, Most of them, however, were to be said not so successful. In this paper, it was investigated that why the previous 0-D surveys were failed, and that how it could be improved. The findings of this study are: 1. The collection of sample data itself was performed relatively well, but the problem was in the improper expansion methods which were applied. 2. To improve the expansion methods, it should be performed not only the dwelling unit-based sample surveys but also commercial vehicle survey, cordon line survey, screen line counts and other auxiliary travel surveys like transit patronage survey, vehicle miles survey etc. at the same time. 3. To expand the sample surveyed data in a proper way, the adjustment factors should take a disaggregate form and also should be applied not to the specific trips, but to the specific trip makers to avoid the bias which could be caused by the application of adjustment factors in a way that has been used previously. 4. If there is no considerable change in travel patterns, we can synthesize the present 0-D data with past surveyed sample data, using present statistic data in the same way which was developed in this paper when expanding and adjusting sample data.

• Communications for Statistical Applications and Methods
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• v.27 no.3
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• pp.349-363
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• 2020

Penalized spline is a suitable nonparametric approach in estimating mean model in small area. However, application of the approach in informative sampling in a published article is uncommon. We propose a semiparametric mixed-model using penalized spline under informative sampling to estimate mean of small area. The response variable is explained in terms of mean model, informative sample effect, area random effect and unit error. We approach the mean model by penalized spline and utilize a penalized spline function of the inclusion probability to account for the informative sample effect. We determine the best and unbiased estimators for coefficient model and derive the restricted maximum likelihood estimators for the variance components. A simulation study shows a decrease in the average absolute bias produced by the proposed model. A decrease in the root mean square error also occurred except in some quadratic cases. The use of linear and quadratic penalized spline to approach the function of the inclusion probability provides no significant difference distribution of root mean square error, except for few smaller samples.

• BMB Reports
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• v.34 no.4
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• pp.347-354
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• 2001

$\alpha$-Glucosidase of an extreme thermophile, Thermus caldophilus GK24 (TcaAG), was purified 80-fold from cells to a homogeneous state and characterized. The enzyme exhibited optimum activity at pH 6.5 and $90^{\circ}C$, and was stable from pH 6.0 to 85 and up to $90^{\circ}C$. The enzyme had a half-life of 85 minutes at $90^{\circ}C$. An analysis of the substrate specificity showed that the enzyme hydrolyzed the non-reducing terminal unit of $\alpha$-1,6-glucosidic linkages of isomaltosaccharides and panose, $\alpha$-1,3-glycosidic bond of nigerose and turanose, and $\alpha$-1,2-glycosidic bond of sucrose. The gene encoding the TcaAG was cloned, sequenced, and sequenced in E. coli. The nucleotide sequence of the gene encoded a 530 amino acid polypeptide and had a G+C content of 68.4% with a strong bias for G or C in the third position of the codons (93.6%). A sequence analysis revealed that TcaAG belonged to the $\alpha$-amylase family. We suggest that this monomeric, thermostable, and broad-acting $\alpha$-glucosidase is a departure from previously exhibited specificities. It is, therefore, a novel $\alpha$-glucosidase.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.707-710
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• 2002

A 120kV/70A high voltage switch has been installed at Korea Atomic Energy Research Institute in Taejon to supply power with Korea Superconducting Tokamak Advanced Research (KSTAR) Neutral Beam Injection (NBI) system. NBI system requires fast cutoff of the power supply voltage for protection of the grid when arc detected and fast turn-on the voltage for sustaining the beam current. Therefore the high voltage switch and arc current detection circuit are important part of the NBI power supply and there are much need for high voltage solid state switches in NBI system and a broad area of applications. This switch consisted of 100 series connected MOSFETs and adopted the proposed simple and reliable gate drive circuit without bias supply, Various results taken during the commissioning phase with a 100kW resistive load and NBI source are shown. This paper presents the detailed design of 120kV/70A high voltage MOSFETs switch and simple gate drive circuit. Problems with the high voltage switch and gate driver and solutions are also presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.164-167
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• 2003

Carbon nitride films with ${\beta}-C_3N_4$ crystals were grown by rf reactive magnetron sputtering system with negative DC bias. Chamber baking system to supply whole chamber with activation energy was used to reduce the contamination of H and O atoms. XRD peaks showed the existence of crystalline ${\beta}-C_3N_4$(200) and lonsdaleite structures. FTIR spectroscopy studies revealed that the film contain ${\alpha}-C_3N_4$ and ${\beta}-C_3N_4$ with $1011\;cm^{-1},\;1257\;cm^{-1}\;and\;1529\;cm^{-1}$ peaks. We could also find the grain growth of hexagonal structure from SEM photograph, which is coincident with the theoretical carbon nitride unit cell. ${\alpha}$-step was used to make the thickness profile of the grown films.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.293-294
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• 1998

In this paper, the electric properties of amorphous selenium specimen has been investigated. Amorphous selenium was thermally evaporated on the glass plate which had been deposited onto the interface by aluminium as an electrode. On the surface of the amorphous selenium, the aluminium electrode was deposited again in order to make an unit cell for dark current measurement. The dark current was measured while applying the bias voltage across the selenium layer in the range of 0V-2500 Volts. The leakage property of the amorphous selenium was significantly low at even high voltage range so it has good advantage as a X-ray receptor for digital radiography. For further study, the C-V curves measurement according to thicker amorphous selenium layer.

• The Journal of Korea Robotics Society
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• v.9 no.1
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• pp.28-38
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• 2014

This paper verifies the performance of Extended Kalman Filter(EKF) and MCL(Monte Carlo Localization) approach to localization of an underwater vehicle through experiments. Especially, the experiments use acoustic range sensor whose measurement accuracy and uncertainty is not yet proved. Along with localization, the experiment also discloses the uncertainty features of the range measurement such as bias and variance. The proposed localization method rejects outlier range data and the experiment shows that outlier rejection improves localization performance. It is as expected that the proposed method doesn't yield as precise location as those methods which use high priced DVL(Doppler Velocity Log), IMU(Inertial Measurement Unit), and high accuracy range sensors. However, it is noticeable that the proposed method can achieve the accuracy which is affordable for correction of accumulated dead reckoning error, even though it uses only range data of low reliability and accuracy.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.152-161
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• 1996

In tis work, a three-stage pipelined A/D converter (ADC) was implemented to obtain 10-bit resolution at a conversion rate of 20 msamples/s for video applications. The ADC consists of three identical stages employing a mid-rise coding technique. The interstage errors such as offsets and clock feedthrough are digitally corrected in digitral logic by one overlapped bit between stages. The proposed ADC is optimized by adopting a unit-capacitor array architecture in the MDAC to improve the differential nonlinearity and the yield. Reduced power dissipation has been achieve dby using low-power latched comparators. The prototype was fabricated in a 0.8$\mu$m p-well CMOS technology. The ADC dissipates 160 mW at a 20 MHz clock rate with a 5 V single supply voltage and occupies a die area of 7 mm$^{2}$(2.7 mm $\times$ 2.6mm) including bonding pads and stand-alone internal bias circuit. The typical differential and integral nonlinarities of the prototype are less than $\pm$ 0.6 LSB and $\pm$ 1 LSB, respectively.