• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.27 no.3
• /
• pp.70-81
• /
• 2019

The effects of weather on aircraft operations are predominant. In particular, severe weather, such as fog, strong winds, rainfall and snow, can cause delays, diversion or cancellation of operations. Of these, fog is considered the main reason for restricting aircraft operations. Meanwhile, Precision instrument approach using instrument landing system(ILS) has allowed aircraft to land safely even in situations where visibility is limited. However, the precision instrument approach require not only the performance of the aircraft but also the enhancement of the runway. In November 2018, Gimpo international Airport raised the category of the runway 14R from CAT-IIIa to CAT-IIIb to improve aviation safety and operational efficiency. Based on this, the research presented a methodology for estimating benefits according to the category upgrade of the precision approach runway, and estimated the benefits to Gimpo International Airport based on the methodology presented.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.61 no.3
• /
• pp.43-53
• /
• 2019

It is well-known fact that the stone-mastic asphalt (SMA) mixture has shown superior rut resistance, compared with the dense-graded asphalt (DGA) mixture in highway pavements. However, the SMA is measured to be inferior to DGA mixes when tested by well-known high-temperature test methods, such as the wheel tracking (WT), asphalt pavement analyzer, the Marshall Stability and Kim Test. Therefore, this study examined the reasons why it was measured to be inferior, and devised a potential procedure by which the superiority of SMA could be measured at $60^{\circ}C$. The strength against deformation ($S_D$), which was known to show very high correlation with WT results for DGA mixes, was measured by the Kim Test on the specimen confined in the compacted mold. In standard Kim Test, which used the specimen without confinement, the DGA was measured to show higher $S_D$ than the SMA. But by confining specimen, it was found that the $S_D$ of SMA was measured to be higher than that of DGA. Therefore, the confined static test protocol devised in this study was found to be feasible for evaluating rut resistance of SMA mix.

• Journal of IKEEE
• /
• v.25 no.1
• /
• pp.83-87
• /
• 2021

In harsh environments such as fog or fine dust, the cameras' detection ability for object recognition may significantly decrease. In order to accurately obtain important information even in bad weather, fog removal algorithms are necessarily required. Research has been conducted in various ways, such as computer vision/data-based fog removal technology. In those techniques, estimating the amount of fog through the input image's depth information is an important procedure. In this paper, a linear model is presented under the assumption that the image dark channel dictionary, saturation ∗ value, and sharpness characteristics are linearly related to depth information. The proposed method of haze removal through a linear model shows the superiority of algorithm performance in quantitative numerical evaluation.

• Earthquakes and Structures
• /
• v.20 no.3
• /
• pp.337-351
• /
• 2021

On September 12, 2016, the Gyeongju earthquake occurred in the south-eastern region of the Korean peninsula. The event was ranked as the largest magnitude earthquake (=5.8) since instrumental recording was started by the Korean Metrological Administration (KMA) in 1978. The objective of this study is to provide information obtained from the 2016 Gyeongju earthquake and to propose a procedure estimating seismic risk of a typical old RC building for past and potential earthquakes. Ground motions are simulated using the point source model at 4941 grid locations in the Korean peninsula that resulted from the Gyeongju earthquake and from potential future earthquakes with the same hypocenter considering different soil conditions. Nonlinear response history analyses are conducted for each grid location using a three-story gravity-designed reinforced concrete (RC) frame that most closely represents conventional old school and public buildings. Then, contour maps are constructed to present the seismic risk associated with this building for the Gyeongju earthquake and potential future scenario earthquakes. These contour maps can be useful in the development of a mitigation plan for potential earthquake damage to school and public buildings at all grid locations on the Korean peninsula.

• Geomechanics and Engineering
• /
• v.34 no.1
• /
• pp.29-41
• /
• 2023

The 3D geospatial modeling of geotechnical information can aid in understanding the geotechnical characteristic values of the continuous subsurface at construction sites. In this study, a geostatistical optimization model for the three-dimensional (3D) mapping of subsurface stratification and the SPT-N value based on a trial-and-error rule was developed and applied to a dam emergency spillway site in South Korea. Geospatial database development for a geotechnical investigation, reconstitution of the target grid volume, and detection of outliers in the borehole dataset were implemented prior to the 3D modeling. For the site-specific subsurface stratification of the engineering geo-layer, we developed an integration method for the borehole and geophysical survey datasets based on the geostatistical optimization procedure of ordinary kriging and sequential Gaussian simulation (SGS) by comparing their cross-validation-based prediction residuals. We also developed an optimization technique based on SGS for estimating the 3D geometry of the SPT-N value. This method involves quantitatively testing the reliability of SGS and selecting the realizations with a high estimation accuracy. Boring tests were performed for validation, and the proposed method yielded more accurate prediction results and reproduced the spatial distribution of geotechnical information more effectively than the conventional geostatistical approach.

• Journal of Ocean Engineering and Technology
• /
• v.37 no.3
• /
• pp.81-88
• /
• 2023

Maneuverability is a crucial factor for the safety and success of submarine missions. This paper introduces a mathematical model that considers the large drift and angle of attack motions of submarines. Various computational fluid dynamics (CFD) simulations were performed to adapt Karasuno's fishery vessel maneuvering mathematical model to submarines. The study also presents the procedure for obtaining the physics-based hydrodynamic coefficients proposed by Karasuno through CFD calculations. Based on these coefficients, the reconstructed forces and moments were compared with those obtained from CFD and to the hydrodynamic derivatives expressed by a Taylor expansion. The study also discusses the mathematical maneuvering model that accounts for the large drift angles and angles of attack of submarines. The comparison results showed that the proposed maneuvering mathematical model based on modified Karasno's model could cover a large range of motions, including horizontal motion and vertical motions. In particular, the results show that the physics-based mathematical maneuvering model can represent the forces and moments acting on the submarine hull during large drift and angle of attack motions. The proposed mathematical model based on the Karasuno model could obtain more accurate results than the Taylor third-order approximation-based mathematical model in estimating the hydrodynamic forces acting on submarines during large drift and angle of attack motions.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.21 no.4
• /
• pp.481-487
• /
• 2023

Concerning the apprehensions about naturally occurring radioactive materials (NORM) residues, the International Atomic Energy Agency (IAEA) and its member nations have acknowledged the imperative to ensure the radiation safety of NORM industries. Residues with elevated radioactivity concentrations are predominantly produced during NORM processing, in the form of scale and sludge, referred to as technically enhanced NORM (TENORM). Substantial quantities of TENORM residues have been released externally due to the dismantling of NORM processing factories. These residues become concentrated and fixed in scale inside scrap pipes. To assess the radioactivity of scales in pipes of various shapes, a Monte Carlo simulation was employed to determine dose rates corresponding to the action level in TENORM regulations for different pipe diameters and thicknesses. Onsite gamma spectrometry was conducted on a scrap iron pipe from the titanium dioxide manufacturing factory. The measured dose rate on the pipe enabled the estimation of NORM concentration in the pipe scale onsite. The derived action level in dose rate can be applied in the NORM regulation procedure for on-site judgments.

• Steel and Composite Structures
• /
• v.50 no.4
• /
• pp.443-458
• /
• 2024

The construction industry, one of the biggest producers of greenhouse emissions, is under a lot of pressure as a result of growing worries about how climate change may affect local communities. Geopolymer concrete (GPC) has emerged as a feasible choice for construction materials as a result of the environmental issues connected to the manufacture of cement. The findings of this study contribute to the development of machine learning methods for estimating the properties of eco-friendly concrete, which might be used in lieu of traditional concrete to reduce CO₂ emissions in the building industry. In the present work, the compressive strength (f_c) of GPC is calculated using random forests regression (RFR) methodology where natural zeolite (NZ) and silica fume (SF) replace ground granulated blast-furnace slag (GGBFS). From the literature, a thorough set of experimental experiments on GPC samples were compiled, totaling 254 data rows. The considered RFR integrated with artificial hummingbird optimization (AHA), black widow optimization algorithm (BWOA), and chimp optimization algorithm (ChOA), abbreviated as ARFR, BRFR, and CRFR. The outcomes obtained for RFR models demonstrated satisfactory performance across all evaluation metrics in the prediction procedure. For R² metric, the CRFR model gained 0.9988 and 0.9981 in the train and test data set higher than those for BRFR (0.9982 and 0.9969), followed by ARFR (0.9971 and 0.9956). Some other error and distribution metrics depicted a roughly 50% improvement for CRFR respect to ARFR.

• Journal of Soil and Groundwater Environment
• /
• v.12 no.5
• /
• pp.19-32
• /
• 2007

In Korea, there have been various methods of estimating groundwater recharge which generally can be subdivided into three types: baseflow separation method by means of groundwater recession curve, water budget analysis based on lumped conceptual model in watershed, and water table fluctuation method (WTF) by using the data from groundwater monitoring wells. However, groundwater recharge rate shows the spatial-temporal variability due to climatic condition, land use and hydrogeological heterogeneity, so these methods have various limits to deal with these characteristics. To overcome these limitations, we present a new method of estimating recharge based on water balance components from the SWAT-MODFLOW which is an integrated surface-ground water model. Groundwater levels in the interest area close to the stream have dynamics similar to stream flow, whereas levels further upslope respond to precipitation with a delay. As these behaviours are related to the physical process of recharge, it is needed to account for the time delay in aquifer recharge once the water exits the soil profile to represent these features. In SWAT, a single linear reservoir storage module with an exponential decay weighting function is used to compute the recharge from soil to aquifer on a given day. However, this module has some limitations expressing recharge variation when the delay time is too long and transient recharge trend does not match to the groundwater table time series, the multi-reservoir storage routing module which represents more realistic time delay through vadose zone is newly suggested in this study. In this module, the parameter related to the delay time should be optimized by checking the correlation between simulated recharge and observed groundwater levels. The final step of this procedure is to compare simulated groundwater table with observed one as well as to compare simulated watershed runoff with observed one. This method is applied to Mihocheon watershed in Korea for the purpose of testing the procedure of proper estimation of spatio-temporal groundwater recharge distribution. As the newly suggested method of estimating recharge has the advantages of effectiveness of watershed model as well as the accuracy of WTF method, the estimated daily recharge rate would be an advanced quantity reflecting the heterogeneity of hydrogeology, climatic condition, land use as well as physical behaviour of water in soil layers and aquifers.

• Journal of the military operations research society of Korea
• /
• v.36 no.1
• /
• pp.77-90
• /
• 2010

Adapting commercial equipments to military operations may provide the advantage of low cost, reduced acquisition time, and technology advancement. On the other hand, it may also offer the opportunity for a reliability and logistics risk because commercial products, standards, and practices may not meet military requirements. In addition to this, commercial vendors have little experience in providing the technical data required to support military deployment logistics. As more companies are equipped with data aquisition systems for their products, considerable amount of field warranty data has been accumulated. Typically, the field data for a given product comprise with the sales volume and the number of the claims for each period. Three types of product data are considered in this study: military designed equipment operating in a military environment, commercial equipment operating in a military environment, and commercial equipment operating in a commercial environment. We construct a estimation model for each type of data and propose an reliability transform method from a commercial environment to a military environment. Parametric methods for estimating the product reliability are proposed based on maximum likelihood criteria and least square criteria. Then a reliability transform procedure for handling different types of data is proposed in a consistent fashion. A case study is investigated to characterize our model based on a real field warranty data set.