• Atmosphere
• /
• v.29 no.3
• /
• pp.269-282
• /
• 2019

While it is important to obtain the accurate information on snowfall data due to the increase in damage caused by the heavy snowfall in the winter season, it is not easy to observe the snowfall quantitatively. Recently, snow measurements using a weighing precipitation gauge have been carried out, but there is a problem that high snowfall intensity results in low accuracy. Also, the observed snowfall data are sensitive depending on wind speed, temperature, and humidity. In this study, a new process of quality control for snow water equivalent (SWE) data of the weighing precipitation gauge were proposed to cover the low accuracy of snow data and maximize the data utilization. Snowfall data (SWE) observed by Pluvio, Parsivel, snow-depth meter using laser or ultrasonic, and rainfall gauge in Cloud Physics Observation Site (CPOS) were compared and analyzed. Applying the QC algorithm including the use of number of hydrometeor particles as reference, the increased SWE per the unit time was determined and the data noise was removed and marked by flag. The SWE data converted by the number concentration of hydrometeor particles are tested as a method to restore the QC-removed data, and show good agreement with those of the weighing precipitation gauge, though requiring more case studies. The three events data for heavy snowfall disaster in Pyeongchang area was analyzed. The SWE data with improved quality was showed a good correlation with the eye-measured data ($R^2$ > 0.73).

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.2
• /
• pp.317-325
• /
• 2019

A suction caisson has been widely used for anchor and foundation of offshore structures due to its broad application, simple installation, and rapid construction. In design of suction caisson foundation, the bearing capacity and the stability of soil are mainly dealt with and analysis methods for them are presented in design codes related to the foundation. On the other hand, the method for structural safety analysis of the suction caisson is not generalized, in particular for load modeling of the caisson under suction. Consequently, there are difficulties in design of the caisson cross section. For this reason, this study analyzed the magnitude and distribution of pore water pressure on inner and outer surface of the caisson using theoretical and numerical seepage analyse, and an approach to reasonably estimate the load applied to the structural analysis of the caisson was presented. Furthermore, effects of penetration depth, anisotropy of permeability, and suction pressure on the pore water pressure were analyzed.

• The Journal of the Acoustical Society of Korea
• /
• v.38 no.1
• /
• pp.82-95
• /
• 2019

In this study, we analyzed the beam time series of ocean reverberation which was conducted in the eastsouthern region of East Sea, Korea during the August, 2015. The reverberation data was gathered by moving research vessel towing LFM (Linear Frequency Modulation) source and triplet receiver array. After signal processing, we analyzed the variation of ocean reverberation level according to the seafloor bathymetry, source/receiver depth and sound speed profile. In addition, we used the normalized data by using cell averaging algorithm and identified the statistical characteristics of seafloor scatterer by using moment estimation method and estimated shape parameter. Also, we analyzed the coincidence of data with Rayleigh and K-distribution probability by Kolmogorov-Smirnov test. The results show that there is range dependency of reverberation according to the bathymetry and also that the time delay and the intensity level change depend on the depths of source and receiver. In addition, we observed that statistical characteristics of similar Rayleigh probability distribution in the ocean reverberation.

• Geomechanics and Engineering
• /
• v.24 no.2
• /
• pp.129-141
• /
• 2021

The vacuum preloading method has been used in many countries for soil improvement and land reclamation. However, the treatment time is long and the improvement effect is poor for the straight-line vacuum preloading method. To alleviate such problems, a novel combined air booster and straight-line vacuum preloading method for shallow ground treatment is proposed in this study. Two types of traditional vacuum preloading and combined air booster and straight-line vacuum preloading tests were conducted and monitored in the field. In both tests, the depth of prefabricated vertical drains (PVDs) is 4.5m, the distance between PVDs is 0.8m, and the vacuum preloading time is 60 days. The prominent difference between the two methods is when the preloading time is 45 days, the injection pressure of 250 kPa is adopted for combined air booster and straight-line vacuum preloading test to inject air into the ground. Based on the monitoring data, this paper systematically studied the mechanical parameters, hydraulic conductivity, pore water pressure, settlement and subsoil bearing capacity, as determined by the vane shear strength, to demonstrate that the air-pressurizing system can improve the consolidation. The consolidation time decreased by 15 days, the pore water pressure decreased to 60.49%, and the settlement and vane shear strengths increased by 45.31% and 6.29%, respectively, at the surface. These results demonstrate the validity of the combined air booster and straight-line vacuum preloading method. Compared with the traditional vacuum preloading, the combined air booster and straight-line vacuum preloading method has better reinforcement effect. In addition, an estimation method for evaluating the average degree of consolidation and an empirical formula for evaluating the subsoil bearing capacity are proposed to assist in engineering decision making.

• Journal of Environmental Impact Assessment
• /
• v.31 no.6
• /
• pp.438-448
• /
• 2022

This study is to improve the quantitative estimation index of biotop area ratio, which is an environmental planning index and environmental ecological planning technique, as a planning means that can induce the improvement of ecological soundness in the spatial planning stage. It is intended to identify the relative importance of space types and calculation indicators currently in operation, and to find alternatives through opinion analysis on improvement of space types and weights. As the method of this study, AHP analysis was performed to evaluate the relative importance of spatial types for in-depth analysis of spatial types and calculation indicators. In order to secure the reliability and objectivity of the study, 50 experts participated. Through this study, it can be linked with the improvement of technologies and construction methods, maintenance efficiency, economic feasibility, and construction technology, which are developed through analysis on the limitations and improvements by type of biotop area ratio. And it is expected to contribute to the improvement of the urban environment and vitalization of the biotop area ratio through the application of the biotop area ratio.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.4
• /
• pp.687-694
• /
• 2022

In this paper, we proposed an autonomous vehicle platform that delivers goods to a designated destination based on the SLAM (Simultaneous Localization and Mapping) map generated indoors by applying the Visual SLAM technology. To generate a SLAM map indoors, a depth camera for SLAM map generation was installed on the top of a small autonomous vehicle platform, and a tracking camera was installed for accurate location estimation in the SLAM map. In addition, a convolutional neural network (CNN) was used to recognize the label of the destination, and the driving algorithm was applied to accurately arrive at the destination. A prototype of an indoor delivery autonomous vehicle was manufactured, and the accuracy of the SLAM map was verified and a destination label recognition experiment was performed through CNN. As a result, the suitability of the autonomous driving vehicle implemented by increasing the label recognition success rate for indoor delivery purposes was verified.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.33 no.3
• /
• pp.254-261
• /
• 1988

Lysimeter and field experiments were conducted in Sandy Loam to establish a simple estimation model for evapotranspiration (ET) of soybean for three years (l984-1986). Potential ET (PET) could be estimated by the eq.1 using Pan-evaporation (Eo) and was ranged from 1.1 to 4.6 mm/day during the experiments. PET (mm/day)=1.348＋0.573 Eo …(1) Crop coefficient (Kc=maximum ET/PET) could be estimated by the eq.2 using Growth degree (G=days after planting/total growing days) and was ranged from 0.2 to 1.1 and from 0.6 to 1.4 for monoculture cropping and double cropping followed by barley, respectively, during the experiments. Monoculture : Kc=0.016＋3.719 G-3.224 G$^2$…(2), Double cropping : Kc=0.609＋2.014 G-2.120 G$^2$…(2). However, the maximum Kc was shown when G was about 50% and 40% for the monoculture and the double cropping, respectively. Soil water coefficient (f=AET/maximum ET) could be estimated by the eq.3 using soil water tension (Ψ) in 15cm depth. and it was decleased to 0.2 when Ψ was 10 bar. f=0.755-0.537 log │Ψ│…(3) Consequentially, the model to estimate the Actual ET (AET) of soybean was determined as eq.4 with the correction coefficient of -0.380. AET(mm/day)=PETㆍKcㆍf -0.380 …(4) The estimated AET were compared with the measured AET to verify the model established above. The average deviation of the estimated ET(AET) was 0.5782$\pm$0.338 (mm/day), and it would be within reasonable confidence range.

• Journal of the Korea Society of Computer and Information
• /
• v.28 no.8
• /
• pp.95-101
• /
• 2023

Colmap is one of the innovative artificial intelligence technologies, highly effective as a tool in 3D reconstruction tasks. Moreover, it excels at constructing intricate 3D models by utilizing images and corresponding metadata. Colmap generates 3D models by merging 2D images, camera position data, depth information, and so on. Through this, it achieves detailed and precise 3D reconstructions, inclusive of objects from the real world. Additionally, Colmap provides rapid processing by leveraging GPUs, allowing for efficient operation even within large data sets. In this paper, we have presented a method of collecting 2D images of traditional Korean towers and reconstructing them into 3D models using Colmap. This study applied this technology in the restoration process of traditional stone towers in South Korea. As a result, we confirmed the potential applicability of Colmap in the field of cultural heritage restoration.

• Journal of the Korean Society for Precision Engineering
• /
• v.13 no.10
• /
• pp.154-160
• /
• 1996

The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surfice. However, as the accuracy requirement gets tighter and desired surface cnotours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function to result in the estimated dapth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in additn to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using the precision dynamoneter. Based on the parameter estimation of cutting dynamics and the admitance model-based nanodynamic control scheme, simulation results are shown.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.27 no.3
• /
• pp.147-155
• /
• 2023

This study aims to present a method to evaluate the relative risk of failure due to liquefaction of domestic small to medium-sized earthfill dams with a height of less than 15 m, which has little information on geotechnical properties. Based on the results of previous researches, a series of methods and procedures for estimating the probability of dam failure due to liquefaction, which calculates the probability of liquefaction occurrence of the dam body, the amount of settlement at the dam crest according to the estimation of the residual strength of the dam after liquefaction, the overtopping depth determined from the amount of settlement at the dam crest, and the probability of failure of the dam due to overtopping was explicitly presented. To this end, representative properties essential for estimating the probability of failure due to the liquefaction of small to medium-sized earthfill dams were presented. Since it is almost impossible to directly determine these representative properties for each of the target dams because it is almost impossible to obtain geotechnical property information, they were estimated and determined from the results of field and laboratory tests conducted on existing small to medium-sized earthfill dams in previous researches. The method and procedure presented in this study were applied to 12 earthfill dams on a trial basis, and the liquefaction failure probability was calculated. The analysis of the calculation results confirmed that the representative properties were reasonable and that the overall evaluation procedure and method were effective.