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1
Estimation of hydrodynamic coefficients from results of real ship sea trials
100%
Kim D.
Polish Maritime Research
|
2018
|
tom 25
|
nr 4
EN
This paper suggests an estimation method for ship’s hydrodynamic coefficients, which is based on the system identification method that calculates an optimum value in a mathematical way. For the purpose of modelling existing ships, this study collects real ship sea trial data as benchmarks. Prior to the optimization, a sensitivity analysis is carried out for easy and effective optimization. The simulation results using optimized coefficients agree well with corresponding benchmarks. Following this, with various trim and draught conditions, this study suggests new estimation formulas that concern all trim and draught conditions. Simulation results applying the estimation formulas are satisfactory in regard to a corresponding benchmark, compared to a result obtained by using an existing regression formula
2
Content available Estimation of hydrodynamic coefficients from results of real ship sea trials
100%
Kim D.
Polish Maritime Research
|
2018
|
tom nr 4
65--72
EN
This paper suggests an estimation method for ship’s hydrodynamic coefficients, which is based on the system identification method that calculates an optimum value in a mathematical way. For the purpose of modelling existing ships, this study collects real ship sea trial data as benchmarks. Prior to the optimization, a sensitivity analysis is carried out for easy and effective optimization. The simulation results using optimized coefficients agree well with corresponding benchmarks. Following this, with various trim and draught conditions, this study suggests new estimation formulas that concern all trim and draught conditions. Simulation results applying the estimation formulas are satisfactory in regard to a corresponding benchmark, compared to a result obtained by using an existing regression formula.
3
Content available remote Applicability of artificial intelligence to reservoir induced earthquakes
63%
Samui P. , Kim D.
Acta Geophysica
|
2014
|
tom Vol. 62, no. 3
608--619
EN
This paper proposes to use least square support vector machine (LSSVM) and relevance vector machine (RVM) for prediction of the magnitude (M) of induced earthquakes based on reservoir parameters. Comprehensive parameter (E) and maximum reservoir depth (H) are used as input variables of the LSSVM and RVM. The output of the LSSVM and RVM is M. Equations have been presented based on the developed LSSVM and RVM. The developed RVM also gives variance of the predicted M. A comparative study has been carried out between the developed LSSVM, RVM, artificial neural network (ANN), and linear regression models. Finally, the results demonstrate the effectiveness and efficiency of the LSSVM and RVM models.
4
Content available remote Weldability of pulse GMAW joints of 780 MPa dual-phase steel
51%
So W. , Kang M. , Kim D.
Archives of Materials Science and Engineering
|
2010
|
tom Vol. 41, nr 1
53-60
EN
Purpose: This paper assesses the gap bridgeability of pulse GMAW joints of DP 780 for automobile body. Design/methodology/approach: Wire melting was analyzed using a high-speed camera. The impact of EN ratio on the shape of the bead section was examined after analyzing the macrosection of welding which was obtained on a bead-on-plate-welding experiment. Welding conditions that are robust to the gap were suggested through an analysis on tensile strength, macrosection of the weld and fracture appearance of tensile strength testing at the lap joint welding of DP 780. Findings: A relation among the welding current (welding process parameter of AC pulse GMAW), EN ratio, welding speed and bead shape parameters which include bead width, bead height and penetration were computed. Research limitations/implications: The suitable welding conditions proposed in this paper can change because of types of welding joints thickness of base metal and other reasons. Practical implications: In this study, the suitable welding conditions were presented for securing a good weld quality of DP 780 for the automobile body. Originality/value: Through this study, the correlation between the weld bead geometry and the EN ratio in the AC pulse GMAW was confirmed. Though the weld quality assessment, suitable pulse GMAW conditions of DP 780 were suggested.
5
Content available Temperature Effect on the Growth Rate and Physical Characteristics of SnO2 Thin Films Grown by Atomic Layer Deposition
51%
Kim D. , Kim D. H. , Riu D.-H. , Choi B. J.
Archives of Metallurgy and Materials
|
2018
|
tom Vol. 63, iss. 2
1061--1064
EN
Among the various thin film coating techniques, atomic layer deposition (ALD) has features of good controllability of the thickness, excellent step-coverage in 3-dimensional object even in the sub-nm thickness range at the relatively low deposition temperature. In this study, SnO2 thin films were grown by ALD in the variation of substrate temperatures from 150 to 250°C. Even such a low temperature may influence on the growth kinetics of the ALD reaction and thus the physical characteristics of thin films, such as crystallinity, film density and optical band gap, etc. We observed the decrease of the growth rate with increasing substrate temperature, at the same time, the density of the film was decreased with increasing temperature. Steric hindrance effect of the precursor molecule was attributed to the inverse relationship of the growth temperature and growth rate as well as the film density. Optical indirect band gap energy (~3.6 eV) of the ALD-grown amorphous SnO2 films grown at 150°C was similar with that of the literature value, while slightly lower band gap energy (~3.4 eV) was acquired at the films grown at higher temperature.
6
Content available remote A fast and robust level set motion-assisted deformable registration method for volumetric CT guided lung intervention
51%
Kim D. , Kim N. , Lee S. , Seo J. B.
Biocybernetics and Biomedical Engineering
|
2018
|
tom Vol. 38, no. 3
439--447
EN
This paper describes the accurate deformable registration method for image-guided lung interventions, including lung nodule biopsy and radiofrequency ablation of lung tumours. A level set motion assisted deformable registration method for computed tomography (CT) images was proposed and its accuracy and speed were compared with those of other conventional methods. Fifteen 3D CT images obtained from lung biopsy patients were scanned. Each scan consisted of diagnostic and preoperative CT images. Each deformable registration method was initially evaluated with a landmark-based affine registration algorithm. Various deformable registration methods such as level set motion, demons, diffeomorphic demons, and b-spline were compared. Visual assessment by two expert thoracic radiologists using five scales showed an average visual score of 3.2 for level set motion deformable registration, whereas scores were below 3 for other deformable registration methods. In the qualitative assessment, the level set motion algorithm showed better results than those obtained with other deformable registration methods. A level set motion based deformable registration algorithm was effective for registering diagnostic and preoperative volumetric CT images for image-guided lung intervention.
7
Content available remote Weldability of 440 MPa galvanized steel with inverter DC resistance spot welding process
51%
Hwang I. , Yoon H. , Kang M. , Kim D.
Archives of Materials Science and Engineering
|
2010
|
tom Vol. 42, nr 1
37-44
EN
Purpose: This paper comparatively analyzes resistance spot weldability depending on whether or not 440 MPa-grade steel is galvanized at inverter DC spot welding. Design/methodology/approach: To compare the resistance spot weldability depending on whether or not the steel is galvanized, an inverter DC welding system was designed. Then, using this system, both tensile strength testing and macro-section testing were conducted on SPRC440 (uncoated steel) and SGARC440 (galvanized steel), and weldability was evaluated. Suitable welding conditions were calculated using the resistance spot welding variables such as electrode force, welding time and lobe diagram on the welding current. The low limit of the lobe diagram was set to the low limit of the tensile strength of 440 MPa-grade steel while the high limit was set depending on whether or not expulsion was detected. Findings: Compared to uncoated steel, galvanized steel had lower suitable welding current conditions and a narrower lobe diagram. Research limitations/implications: This paper compared resistance spot weldability and lobe diagram depending on whether or not 440 MPa-grade steel is galvanized. Practical implications: This paper confirms the weldability of galvanized steel by comparing resistance spot weldability depending on whether or not steel is galvanized. Originality/value: For analysis of resistance spot weldability depending on whether or not steel is galvanized, weldability was compared between SPRC440 (uncoated steel) and SGARC440 (galvanized steel) under the same welding conditions. As a result, compared to uncoated steel, galvanized steel had lower suitable welding current conditions and a narrower lobe diagram.
8
Improving the chromatographic analysis of N-nitrosamines in drinking water by completely drying the solid sorbent using dry air
51%
Jung S. , Kim D. , Kim H.
Polish Journal of Environmental Studies
|
2016
|
tom 25
|
nr 6
EN
The aim of this study was to develop a method for efficiently extracting eight N-nitrosamines (NAs) from chlorinated drinking water using a solid-phase extraction sorbent. This was achieved by completely drying the sorbent using dry air after passing the water through it and before eluting NAs from it. A 500 mL water sample containing NAs was passed through 2.0 g of Carboxen 572. The sorbent was dried by applying a vacuum (-34 kPa) to the sorbent cartridge for 1 h with a silica gel trap connected to the other end of the cartridge. The NAs were then eluted by passing 15 mL of dichloromethane through the cartridge. The dansyl derivatives of the NAs were analyzed by high-performance liquid chromatography with fluorescence detection using a Microsorb-MV Si column and a mixture of water (40%) and acetonitrile (60%) as stationary and mobile phases, respectively. The coefficients of determination (R2) for five-point linear calibration curves (2-80 ng/L) were 0.9968-0.9997. The relative standard deviations of repeated measurements were mostly less than 5.1%, but were higher for two NAs. The recoveries of all of the NAs when spiked samples were analyzed were > 95.1%, and the estimated method detection limits were 0.5-1.4 ng/L. The method showed much better performance than when the moisture trap was not applied to the cartridge, particularly when the laboratory air had a high level of humidity.
9
Content available remote Inverter DC resistance spot welding of magnesium alloy AZ31
51%
Hwang I. , Kim D. , Kang M.
Archives of Materials Science and Engineering
|
2011
|
tom Vol. 48, nr 2
112-117
EN
The welding lobes of AC resistance spot welding and inverter DC resistance spot welding for the magnesium alloy sheet AZ31 were compared and analyzed.
10
Content available Ship Collision Avoidance by Distributed Tabu Search
51%
Kim D. , Hirayama K. , Okimoto M.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
|
2015
|
tom Vol. 9, no. 1
23--29
EN
More than 90% of world trade is transported by sea. The size and speed of ships is rapidly increasing in order to boost economic efficiency. If ships collide, the damage and cost can be astronomical. It is very difficult for officers to ascertain routes that will avoid collisions, especially when multiple ships travel the same waters. There are several ways to prevent ship collisions, such as lookouts, radar, and VHF radio. More advanced methodologies, such as ship domain, fuzzy theory, and genetic algorithm, have been proposed. These methods work well in one-on-one situations, but are more difficult to apply in multiple-ship situations. Therefore, we proposed the Distributed Local Search Algorithm (DLSA) to avoid ship collisions as a precedent study. DLSA is a distributed algorithm in which multiple ships communicate with each other within a certain area. DLSA computes collision risk based on the information received from neighboring ships. However, DLSA suffers from Quasi-Local Minimum (QLM), which prevents a ship from changing course even when a collision risk arises. In our study, we developed the Distributed Tabu Search Algorithm (DTSA). DTSA uses a tabu list to escape from QLM that also exploits a modified cost function and enlarged domain of next-intended courses to increase its efficiency. We conducted experiments to compare the performance of DLSA and DTSA. The results showed that DTSA outperformed DLSA.
11
Content available Usefulness of the Internet-based (NTrip) RTK for Precise Navigation
51%
Uradziński M. , Kim D. , Langley R. B.
Biuletyn Wojskowej Akademii Technicznej
|
2010
|
tom Vol. 59, nr 2
197-209
EN
One of the topics that has long been a subject of research is improving the safety and efficiency of automobile transportation. Because GNSS/RTK techniques have great potential (enabling positioning to centimeter accuracy), researchers are developing tools to put them to practical use for controlling vehicle motion for driver assistance. The combination of high-accuracy positioning information obtained from NTrip/RTK with high-precision INS sensors can support the latest concepts in vehicle-control systems (detection of relative vehicle position on a highway or collision avoidance). In this paper, we focus on evaluating the performance of NTrip/RTK solutions for accurate and precise car navigation. Our approach is based on field experiments and the analysis of both the accuracy and availability of RTK data using mobile wireless transmissions. We investigate the advantages and disadvantages of each component in the navigation system. Car experiments were conducted on test routes under different driving conditions. To demonstrate the versatility of mixed-receiver systems, both NovAtel and Trimble mobile receivers were connected via a CDMA network to an Ntrip broadcaster hosted by a Trimble NetR5 reference station receiver. Additional tests were performed using an NTrip stream delivered by a free-standing mount point obtaining data from the same reference receiver acting as an NTrip server.
PL
Jednym z szybko rozwijających się i budzących szerokie zainteresowanie wśród naukowców problemów jest zwiększenie bezpieczeństwa i wydajności transportu samochodowego. Ze względu na ogromny potencjał jaki posiada technika GNSS/RTK (dokładności centymetrowe), rozwijane są różnego rodzaju narzędzia, które pozwolą na jej praktyczne wykorzystanie do badań nad kontrolą ruchu pojazdów, głównie w celu zwiększenia bezpieczeństwa uczestników ruchu drogowego. Połączenie dokładnej informacji o pozycji uzyskanej z systemu NTrip/RTK z precyzyjnymi sensorami INS może w znacznym stopniu wspierać systemy kontrolujące ruch pojazdów (unikanie kolizji). W artykule przedstawiono wykorzystanie protokołu NTrip/RTK w precyzyjnej nawigacji. Omówiono wyniki eksperymentów polowych mających na celu analizę dokładności oraz dostępności danych RTK przy wykorzystaniu bezprzewodowej transmisji danych. Autorzy przedstawili wady i zalety każdego z komponentów skompletowanego systemu nawigacyjnego. Eksperymenty wykonano z wykorzystaniem pojazdu na przygotowanych trasach doświadczalnych, przebiegających w urozmaiconych warunkach. Wysokiej klasy odbiorniki NovAtel Propak OEMV3 oraz Trimble R7 zostały podłączone do NTrip castera (Trimble NetR5) przy wykorzystaniu bezprzewodowej transmisji danych (technologia CDMA). Dodatkowo przeprowadzono badania z wykorzystaniem tego samego odbiornika (Trimble NetR5), pełniącego funkcję wolnostojącego serwera dla systemu Ntrip.
12
Content available remote Effect of flash butt welding parameters on weld quality of mooring chain
51%
Kim D. , So W. , Kang M.
Archives of Materials Science and Engineering
|
2009
|
tom Vol. 38, nr 2
112-117
EN
Purpose: The effects of flash butt welding parameters on mechanical properties were explored for mooring chain for offshore structure. Design/methodology/approach: Through the tensile strength, impact energy, hardness of weld, macrosection, microstructure and waveform analysis of the flash butt weld, following the change of the flash mode, flash length, upset mode, and upset length which are the parameters of the flash butt welding, the weld quality has been assessed. Findings: It is confirmed that even if the mechanical properties of the weld are satisfied through experiments, a weld defect may exist, and in case of using force mode in upset process, the mechanical characteristics of the weld is superior to position mode. Research limitations/implications: The optimal welding condition presented in this study may be changed in accordance with the chemical composition of the material, size of mooring chain. Practical implications: In this study, the suitable welding conditions were presented for securing a good weld quality of the high strength steel mooring chain for the offshore structure. Originality/value: Through this study, the correlation between the weld parameters and the weld quality in the flash butt welding was confirmed. Though the weld quality assessment, flash butt welding condition of the ř84 mm mooring chain for the offshore structure was presented.
13
Content available remote Resistance spot welding of aluminium alloy sheet 5J32 using SCR type and inverter type power supplies
51%
Kim D. , Park H. , Hwang I. , Kang M.
Archives of Materials Science and Engineering
|
2009
|
tom Vol. 38, nr 1
55-59
EN
Purpose: A characteristic was compared and analyzed between the lobe diagram of SCR type resistance spot welding and that of inverter type resistance spot welding of the aluminum alloy sheet 5J32 for the car body. Design/methodology/approach: Using the lobe diagram on the electrode force, weld time, and weld current which are process variables of the resistance spot welding, the range of optimal welding condition was determined. The low limit of the range of the optimal welding condition was decided by the lower limit of the tensile strength of the aluminum alloy sheet 5J32, and the upper limit was decided by whether an expulsion occurs or not. Findings: It was found that the range of the optimal welding condition of the inverter type resistance spot welding was larger than the SCR type resistance welding and that the nugget size of inverter type resistance spot welding was larger in the same welding condition. Research limitations/implications: A comparison was between the lobe diagram at the SCR type on the aluminum alloy sheet 5J32 and the lobe diagram at the inverter type resistance spot welding. Practical implications: In this study, by comparing the range of the appropriate welding condition of the resistance spot welding between SCR type and inverter type power supplies, the characteristic of the appropriate welding range by the power supply characteristic could be confirmed. Originality/value: This study compared the characteristic of the resistance spot welding between the SCR type and inverter type power supply using lobe diagram. It was confirmed that the range of appropriate welding conditions of the inverter type resistance spot welding was large.
14
Content available remote Inverter DC resistance spot weldability of 590 MPa galvannealed steel for automotive applications
51%
Yoon H. , Kim D. , Kang M.
Archives of Materials Science and Engineering
|
2011
|
tom Vol. 49, nr 2
112-117
EN
Purpose: This study analyzes resistance spot weldability of coated and uncoated DP 590 steels. Design/methodology/approach: To compare the resistance spot weldability of coated (GAFC590, galvannealed) and uncoated (SPFC590) steels, tensile strength test and macro-section test were conducted for the resistance spot welds. Acceptable welding conditions were determined as a function of the resistance spot welding process parameters such as electrode force, welding time, and welding current. The lower limit of the welding lobe was the minimum shear tension strength for 590 MPa-grade steel while the upper limit was determined whether or not expulsion was detected. Findings: Galvannealed steel required more welding current than uncoated steel. Acceptable welding current condition and welding lobe were changed depending on whether steel is coated or not. Research limitations/implications: This study is forced on inverter DC resistance spot weldability of 590Mpa-grade steels for automotive application. Practical implications: This study confirms the weldability of galvannealed steel by comparing resistance spot weldability depending on whether or not the steels is coated. Originality/value: This study analysed resistance spot weldability depending on whether or not steel sheets are coated, where SPFC590 uncoated steel) and GAFC590 (galvannealed steel) were used. The required spot welding current for galvannealed steels was higher than the uncoated steel and welding lobes for coated and uncoated steels were determined.
15
The influence of energy recovery from waste on landfill gas: A case study from Korea
51%
Kim D. , Pak D. , Chun S.-K.
Polish Journal of Environmental Studies
|
2018
|
tom 27
|
nr 6
EN
In order to conceive of an efficient way to manage a landfill, we conducted an exemplary study of the Sudokwon Landfill Site in South Korea, with particular regard to the influence of energy recovery from waste. As a result of the BMP test, biogas production of demolition waste was much lower than household waste even in the same waste type. Gas production from the residual substance of energy recovery from waste (ash), waste soil, and the sludge landfill cover material was almost zero, but the solidified sludge showed 4.1 times greater than digested sludge due to the fewer pozzolanic reactions. Lysimeter test results show that the total amount of landfill gas was reduced to about 1/27 when combustible waste is buried after the recovery of energy, but, in order to be able to completely eliminate the landfill gas collecting system in a newly managed landfill, solidified sludge should not be disposed of in the landfill site. In addition, the maximum concentration of hydrogen sulfide was 60.9×10³ ppm, when total waste was mixed and landfilled. However, the concentration of hydrogen sulfide decreased to about 1/6 and the total load largely decreased to about 0.9% when applied to landfill waste after energy recovery.
16
Content available In vitro antibacterial effects of non-thermal atmospheric plasma irradiation on Staphylococcus pseudintermedius and Pseudomonas aeruginosa
45%
Bae S. , Lim D. , Kim D. , Jeon J. , Oh T.
Polish Journal of Veterinary Sciences
|
2020
|
tom 23
|
nr 1
17
Content available Fabrication of Mo-Si-B Intermetallic Compound Powders Under Different Heat Treatment Conditions
38%
Park J. H. , Lee S. , Kim D. , Kim Y. , Yang S. H. , Lee S. H.
Archives of Metallurgy and Materials
|
2018
|
tom Vol. 63, iss. 3
1509--1512
EN
In this research, we investigated the effects of reduction atmospheres on the creation of the Mo-Si-B intermetallic compounds (IMC) during the heat treatments. For outstanding anti-oxidation and elevated mechanical strength at the ultrahigh temperature, we fabricated the uniformly dispersed IMC powders such as Mo5SiB2 (T2) and Mo3Si (A15) phases using the two steps of chemical reactions. Especially, in the second procedure, we studied the influence of the atmospheres (e.g. vacuum, argon, and hydrogen) on the synthesis of IMCs during the reduction. Furthermore, the newly produced IMCs were observed by SEM, XRD, and EDS to identify the phase of the compounds. We also calculated an amount of IMCs in the reduced powders depending on the atmosphere using the Reitveld refinement method. Consequently, it is found that hydrogen atmosphere was suitable for fabrication of IMC without other IMC phases.
18
Content available remote Development of single-filter Doppler signal discrimination method for incoherent Doppler lidar system
38%
Choi S. , Baik S. , Park S. , Song I. , Kim D. , Jung J.
Optica Applicata
|
2012
|
tom Vol. 42, nr 3
545-553
EN
In this paper, we present a single-filter Doppler signal discrimination method for an incoherent Doppler lidar system that has been developed by the Korea Atomic Energy Research Institute. For the incoherent Doppler system, we use an injection-seeded pulsed Nd:YAG laser as a transmitter and an iodine filter as a Doppler frequency discriminator. To reduce the temperature-dependence error, a single iodine filter is used to lock the laser frequency and to detect the Doppler frequency shift. The mean squared error of the frequency locking process is 3.87 MHz, which corresponds to a wind velocity detection limit of approximately 1.04 m/s. The range and velocity measurements are performed using a tunable rotating disc. The results are consistent with those of previous studies in terms of the correlation between the signal ratio (signal/reference) and the actual speed of the rotating disc.
19
Possible lattice constribution to the mwchanism of the verwey transition of magnetite
38%
Kąkol Z. , Kozłowski A. , Zalecki R. , Knight K. , Kim D. , Honig J. M.
Electron Technology
|
1998
|
tom Vol. 31, No. 1
22-28
EN
We report on systematic neutron differaction measurments of the crystal structure and lattice parameters as a function of tenperature for the Fe3-yZnyO4 series. The time-ofiflight data were collected in ISIS Rutheford Appleton Laboratory in a temperature range 4.2 K to 270 K for samples showing different orders of the Veswey transition. The change of transition order, resulting from doping, is accompanied by the clear difference in the characteristic, low temperature rhombohedral distortion. For samples exhibiting first-order transitions this distortion is nearly constant and much bigger than for samples showing second-order transitions where distortion diminishes with increasing doping levels. These observations, consistent with our recent heat capacity results, suggests that the lattice contribution should be considered in the analysis of possible interactions leading to the Verwey transition and to the change of its character with doping.
20
Fluctuating membrane pores - a possible mechanism for the action of the antibiotic peptide KLA1
38%
Kim D. , Dathe M. , Bezrukov S. , Hauss T. , Dante S. , Klosgen B.
Cellular and Molecular Biology Letters
|
2005
|
tom 10
|
nr Suppl.
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