• The Transactions of the Korean Institute of Power Electronics
• /
• v.3 no.3
• /
• pp.263-272
• /
• 1998

This paper presents the new control strategy that can minimizes the torque ripple by considering the magnetic nonlinearity and phase torque averlapping intervals, and describes the whole SRM drive system using proposed control method implemented by DSP(Digital Signal Processor). To do this, inductance and torque are, at first, measured according to the variation of rotor position angle while current is kept constant at predetermined several values. From these measured values, the entire inductance and torque for any current and rotor position are inferred by using neural network. And the waveform of the reference phase torque is determined for the torque ripple to be minimized considering the torque overlap between phases. The controller is designed for the actual torque obtained by the inferred torque look-up table using measured current and rotor position angle to track the predetermined reference phase torque by delta modulation technique. To perform a real time processing and ensure the reliability of the controller, DSP is implemented.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.3 no.1
• /
• pp.18-23
• /
• 1966

An experimental study of a steel plate thickness gauge by means of the measurements of backscatered gamma-rays has been carried out. The difference between this and other methods is that this method does not include any shilding matterials in the detecting probe, because the primary radiations and the backscattered radiations are detected simultaneously by an NaI (TI) scintillating crystal, and the activity of the Co-60 source used is low enough. In this thickness gauge, the thickness of the steel plates can be read directly on the counting ratemeter scale. The optimum conditions in the source-to-detector distance, window width of the analyzer, energy and strength of the gamma-ray source were found experimentally. The results have shown that the accuracy of the gauge was about $\pm$3% in the range of 3 to 8mm thickness. This gauge can be used to detect the pits or corrosions on the inner walls of the steel pipes.

• Journal of Korean Society for Geospatial Information Science
• /
• v.20 no.1
• /
• pp.109-116
• /
• 2012

The effect of the grid resolution on the hydrodynamic simulation has been investigated by using CCHE2D and EFDC. Since a high resolution of the grid results in the increase of computation time, an appropriate grid resolution should be selected by considering the efficiency of simulation according to the objectives of projects. In order to understand the effect of grid resolution and determine the optimal grid resolution, several cases with different lateral grid resolutions have been simulated for the reach of Nakdong river at the confluence of Kumho river for the floods in 2006. Orthogonal curvilinear grids for the domain have been constructed from the survey products at the sections with the longitudinal interval of 20 m. Area-elevation curve and the comparison of simulated results with measured stage at the specific station have been used to check the effect of grid resolution. From the results, the existence of optimal grid resolution has been observed, which ensure both efficiency of computation and certainty of results.

• Journal of Korean Society of Forest Science
• /
• v.88 no.2
• /
• pp.142-148
• /
• 1999

This research describes the construction of a site index equation and curves for Douglas-fir plantation (Pseudotsuga menziesii Mirb. Franco) in Nelson, New Zealand. The data sets of 146 Permanent Sample Plots (PSP) were used to build the model, and it was developed using the difference equation method. Parameter estimates were obtained using the non-linear routine of the SAS, PROC NLIN procedure. Of the models tested, a variant of the Schumacher polymorphic yield function showed the higher precision of fitting. About 95% of the observations used to fit the model could be predicted within ${\pm}1.2m$ of the actual values. Therefore, polymorphic family of site index curves, which reflect different shapes for the different site index classes, were derived from the Schumacher equation. It was found that the polymorphic site index equation was more accurate than the anamorphic equation in this study.

• Journal of Navigation and Port Research
• /
• v.28 no.5
• /
• pp.365-372
• /
• 2004

LNGC suffers a great heat inflow during navigation and this heat inflow inevitably boils off the LNG. The boiled off gas(BOG) is normally consumed as a fuel for ship's engine. The boiled off LNG means a loss of cargo during transportation in the viewpoint of shipper. Therefore, a contract between shipper and ship operator is made for the limitation of BOR under 0.15 ％/day based on laden voyage. This contract on BOR limit requires that ship's officer has a correct knowledge on BOR for his ship. nut, in most cases ship IS operated based on only officer's experiences. In this study, author presented a simple model to predict the BOG during navigation based on the existing precision heat exchange design technology about the heat distribution on the hull and heat inflow from outside through the hull. The BOG is calculated for ballast and laden voyage based on the actual weather conditions and verified by comparing with the measured BOG for the study ship. The study ship is a membrane type LNGC which is now servicing in Middle east route. Thus, the BOG prediction method which is presented in this study is expected to be used for an useful tool to manage the BOG in now servicing LNGC.

• Journal of Korean Society for Geospatial Information Science
• /
• v.4 no.2 s.8
• /
• pp.23-33
• /
• 1996

The conventional monitoring of water quality constrained by time and equipment produce neither complete nor synoptic geographic coverage of pollutant distribution, transport, and water quality. To circumvent these limitations in temporal and spatial measurements, the use of remote sensing is increasingly being involved in the lacustrine environmental research. Consequently, satellite remote sensing, with its synoptic coverage, is used to obtain the eutrophication-related water quality parameters in Daecheong reservoir in this study. The approach involved acquisition of water quality samples from boats of 15 sites on 20 June 1995 and 30 sites on 18 March 1996, simultaneous with Landsat-5 satellite overpass. Regression models have been developed between the water quality parameters and Landsat Thematic Mapper(TM) digital data. The best regression model was determined based on the correlation coefficient which was higher than 0.6. As a result, satellite remote sensing can provide meaningful information on water quality parameters. The regression models developed in this study show good relationship for transparency, turbidity, SS, and chlorophyll, but not for TN and TP because their spectral characteristics are not well defined.

• Journal of Korean Society of Steel Construction
• /
• v.26 no.4
• /
• pp.251-262
• /
• 2014

It has been considered that factors affecting accuracy of the estimated weight of moving vehicle by BWIM system are vehicle and bridge characteristics, and measurement conditions which is related to the strain curve. In this study, theoretical review and field test were performed to evaluate effect of these factors in BWIM system. From these evaluations, we proposed a way to improve accuracy of the estimated vehicle information in BWIM system. As the results, it was known that girder type and continuity of spans in bridge are not governing factor, but its plane shape gives large influence on accuracy of the estimated vehicle information. In addition, running speed of vehicle has also large effect on the estimated accuracy of axle distance if the distance between second and third axles is short. However, weight sum of the two axles can be estimated reasonably by assuming them as one axle.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.27 no.5
• /
• pp.585-597
• /
• 2009

This research aims to develop a registration method to remove the geometric inconsistency between aerial images and LIDAR data acquired from an airborne multi-sensor system. The proposed method mainly includes registration primitives extraction, correspondence establishment, and EOP(Exterior Orientation Parameters) adjustment. As the registration primitives, we extracts planar patches and intersection edges from the LIDAR data and object points and linking edges from the aerial images. The extracted primitives are then categorized into horizontal and vertical ones; and their correspondences are established. These correspondent pairs are incorporated as stochastic constraints into the bundle block adjustment, which finally precisely adjusts the exterior orientation parameters of the images. According to the experimental results from the application of the proposed method to real data, we found that the attitude parameters of EOPs were meaningfully adjusted and the geometric inconsistency of the primitives used for the adjustment is reduced from 2 m to 2 cm before and after the registration. Hence, the results of this research can contribute to data fusion for the high quality 3D spatial information.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.17 no.2
• /
• pp.89-96
• /
• 2011

A three dimensional ecological model(EMT-3D) was applied to Ulsan Bay for the simulation of Dioxins. The simulated results of dissolved Dioxins were in agreement with the observed values, with a correlation coefficient(R) of 0.7951 and a coefficient of determination($R^2$) of 0.6265. The results of sensitivity analysis showed that partition rate, adsorption rate and bioconcentration factor were important factors. Therefore, the parameters must be carefully considered in the modeling. In the case of 50% and 80% total loads reduction, concentration of dissolved Dioxins was shown to be lower than 0.150 and 0.250 pg WHD-TEQ/L, respectively.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.2 no.1
• /
• pp.54-64
• /
• 1984

This paper is a study on structural measurement by using a terrestrial camera. The aim of this paper is to understand the method of a composition by analyzing the geometrical compositive ratio of threestoried pagodas at Gamun-Sa, Gosun-Sa, Bulguk-Sa, Seated iron Buddha in Kwang-Jn, and Main-Seat Buddha at Sukkuram Cave-temple. Measured data and contour maps are accurately obtained by means of photogrammetry, and the following points are able to he found by analyzing them. At first, for Stone Pagodas. the breaths of the Okgesuks are made to the ratio, 8 : 7 : 6. And when an equililateral triangle and an 45$^{\circ}$ isosceles triangle are drawn of which the bases are the length of the upper Gabsuk, and then a circle is drawn whose radius is the length between the vertexes of the two triangles and its center is the vertex of the former the circle passes the upper line of the third Oksin. Also it can be found that an $70^{\circ}$ isosceles triangle being drawn at base line, the triangle passes the edge point of the upper Gabsuk and the center of the third Okgesuk. Also for Budha statues, it can be found that circles whose center is that of eyes can be drawn, and if 2 lines which pass the shoulder and the center of Buddha's body are extended, they intersect the knees.