• Journal of the Korean Society for Railway
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• 제19권6호
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• pp.833-843
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• 2016

Recently, in the field of rail freight transportation, the number of trains dedicated for shippers has been increasing. These dedicated trains, which run on the basis of a contract with shippers, had been restricted to the transportation of containers, or so called block trains. Nowadays, such commodities have extended to cement, hard coal, etc. Most full freight cars are transported by dedicated trains. But, for empty car distribution, the efficiency still remains questionable because the distribution plan is manually developed by dispatchers. In this study, we investigated distribution models delineated in the KTOCS system which was developed by KORAIL as well as mathematical models considered in the state-of-the-art. The models are based on optimization models, especially the network flow model. Here we suggest a new optimization model with a framework of the column generation approach. The master problem can be formulated into a transportation problem with additional constraints. The master problem is improved by adding a new edge between the supply node and the demand node; this edge can be found using a simple shorted path in the time-space network. Finally, we applied our algorithm to the Korean freight train network and were able to find the total number of empty car kilometers decreased.

• Archives of design research
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• 제19권6호
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• pp.27-32
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• 2006

TYME is an interactive typography program based on the ephemeral nature of time. It is a text based poetic tool, built with Processing. This project is presented as a performance that utilizes a computer with a display screen, a projector, and speakers. As the user types, white characters appear, flow on the score on the screen and trigger jazz sounds, then characters disappear into black space in several seconds on the screen like smoke. Typography from this invented instrument is evocative and wistful, and allows the user to associate with ephemeral time. While typing the characters as though playing an instrument at intervals of time, the user can freeze the motion and print out or save otherwise fleeting moment with a button. I intend to contain both characteristics: the amorphous shape of smoke and the elusive attribute of smoke for the expression of intangible and ephemeral time. Every alphabetic shape is derived from the video dips that I shot of smoke. The resulting alphabetic images are then programmed using the Processing scripting language and which can then be typed on the screen with a keyboard. TYME could be a model as a project that reflects the unfixed quality of digital typography, and as a design approach for interactive expressive typography by scripting code. This project also represents the characteristics of typographic play, which can be realized in an computational environment like this model.

• Geotechnical Engineering
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• 제13권1호
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• pp.35-46
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• 1997

The isotropic single-hardening constitutive model has been applied to predict the behavior of soils during reorientation of principal stresses in the field. The predicted response by the model agrees well with the measured behavior for a series of torsion shear tests performed on hollow cylinder specimens of Ko consoildated clay along various stress -paths. This indicates that the soil behavior during reorientation of principal stresses can be predicted by using the model with application of simple informations given by isotropic compression tests and conventional consolidated-undxained triaxial compression tests. Isotropic elasto-plastic soil behavior has been served during primary loading from both the torsion shear tests and the predictions by the model. However, the directions of maj or principal strain increment given by the model have not coincided with the directions for tests during stress reversal, such as unloading and reloading, within isotropic yield surface for Ko consolidated stress. This indicates that kinematic hardening model instead of isotropic hardening model should be developed to predict the soil behavior during stress reversal. The experimental strain increment vectors in the work-space have been compared with the directions expected for associated and nonassociated flow rules.

• Bulletin of the Korean Chemical Society
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• 제11권2호
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• pp.150-154
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• 1990

The structures of $Tl_{12-2x}Zn_x-A$ (x = 4.3 and 3.25), vacuum dehydrated zeolite A with all $Na^+$ ions replaced by $Tl^+$ and $Zn^{2+}$ as indicated, have been determined by single-crystal X-ray diffraction techniques in cubic space group Pm3m at 21(1) $^{\circ}C$ (a=12.100(2) ${\AA}$ for $Tl_{3.4}Zn_{4.3}-A$ and a=12.092(2) ${\AA}$ for $Tl_{5.5}Zn_{3.25}-A$). The crystals of $Tl_{3.4}Zn_{4.3}-A$ and $Tl_{5.5}Zn_{3.25}-A$ were prepared by flow method using exchange solutions in which mole ratios of $TlNO_3$,/TEX> and $Zn(NO_3)_2$ were 1:50 and 1:1, respectively, with total concentration of 0.05 M. The structures of the dehydrated $Tl_{3.4}Zn_{4.3}-A$ and $Tl_{5.5}Zn_{3.25}-A$ were refined to yield the final error indices $R_1$ = 0.075 and $R_2$ = 0.075 with 236 reflections, and $R_1$ = 0.057 and $R_2$ = 0.064 with 202 reflections, respectively, for which I > 3$\sigma$(I). Both structures indicate that Zn(II) ions are coordinated by three framework oxygens: the Zn(II) to O(3) distances are 2.08(1) ${\AA}$ for $Tl_{3.4}Zn_{4.3}-A$ and 2.07(1) ${\AA}$ for $Tl_{5.5}Zn_{3.25}-A$, respectively. In each structure, the angle subtended at Zn(II), O(3)-Zn(II)-O(3) is 119.9(3)$^{\circ}$ for $Tl_{3.4}Zn_{4.3}-A$, and 120.0(3)$^{\circ}$ for $Tl_{5.5}Zn_{3.25}-A$, respectively, close to the idealized trigonal-planar value. Zn(II) ions prefer to 6-ring sites. $Tl^+$ ions do not have any preference to a particular site but occupy simultaneously both at the 6-ring sites and 8-ring sites.

• Journal of Aerospace System Engineering
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• 제18권1호
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• pp.53-63
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• 2024

Adopting an engine igniter with high efficiency and ignition performance is essential for reliable operation of liquid rocket engines. In this study, we developed a spark torch igniter for a 450 N-scale methane-oxygen liquid rocket engine by conducting numerical analyses, igniter manufacturing and validation. Specifically, we conducted a parametric study for maximizing the enthalpy at the igniter exit, specifically by adjusting the mass flow rate, nozzle area ratio, fuel-oxidizer mixture ratio, and the igniter length-to-diameter. The heat transferred via the igniter nozzle exit was computed using 3-dimensional numerical simulations. We also manufactured and tested the igniter based on a deduced design to confirm ignition performance of the designed spark torch igniter. The igniter developed through this study could contribute to the development of practical propulsion systems such as upper-stage engines of small launch vehicles.

• Journal of Korea Water Resources Association
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• 제53권3호
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• pp.155-166
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• 2020

In this study, we applied the Radar-AWS Rainrates (RAR), weather radar-based quantitative precipitation estimations (QPEs), to the Yongdam study watershed in order to perform the flood runoff simulation and calculate the inflow of the dam during flood events using hydrologic model. Since the Yongdam study watershed is a representative area of the mountainous terrain in South Korea and has a relatively large number of monitoring stations (water level/flow) and data compared to other dam watershed, an accurate analysis of the time and space variability of radar rainfall in the mountainous dam watershed can be examined in the flood modeling. HEC-HMS, which is a relatively simple model for adopting spatially distributed rainfall, was applied to the hydrological simulations using HEC-GeoHMS and ModClark method with a total of eight independent flood events that occurred during the last five years (2014 to 2018). In addition, two NCL and Python script programs are developed to process the radar-based precipitation data for the use of hydrological modeling. The results demonstrate that the RAR QPEs shows rather underestimate trends in larger values for validation against gauged observations (R² 0.86), but is an adequate input to apply flood runoff simulation efficiently for a dam watershed, showing relatively good model performance (E_NS 0.86, R² 0.87, and PBIAS 7.49%) with less requirements for the calibration of transform and routing parameters than the spatially averaged model simulations in HEC-HMS.

• Journal of Korean Society of Transportation
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• 제25권6호
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• pp.185-196
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• 2007

The aim of this research is to develop a signal control algorithm using internal metering to minimize total delay that vehicles go through, in case a network is oversaturated. To calculate total delay on the network, the authors first detect vehicles' arrivals and departures in the network through the detecting system, and chase the vehicles' flow in the links with a platoon dispersion model. Following these, the authors calculate the queue length in all the inks of the network through the chase of vehicles, deduce the stopped time delay, and finally convert the stopped time delay to the approach delay with a time-space diagram. Based on this calculated delay, an algorithm that calculates the level of the internal metering necessary to minimize the deduced approach delay is suggested. To verify effectiveness of this suggested algorithm, the authors also conduct simulation with the micro-simulator VISSIM. The result of the simulation shows that the average delay per vehicle is 82.3 sec/veh and this delay is lower than COSMOS (89.9sec/veh) and TOD (99.1sec/veh). It is concluded that this new signal control algorithm suggested in this paper is more effective in controlling an oversaturated network.

• Journal of the Korean earth science society
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• 제29권7호
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• pp.579-585
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• 2008

The time-dependent evolution of disk mass for outburst limit cycle in a black hole microquasar is calculated based on the non-linear hydrodynamic model of thermally unstable accretion disk. The physical parameters such as black hole mass, disk size and mass transfer rate are adopted to reproduce the historical 1975 outburst observed in a prototype black hole X-ray nova A0620-00. The time-dependent effect of irradiation from the central hot region to the disk is considered in two ways: direct irradiation and indirect irradiation reflected from hot accretion flow above the disk. The accretion disk thermal instability model can account for the bolometric luminosity appropriate to typical characteristics of system luminosity observed in X-ray transients during the whole cycle of the outburst evolution. The maximum mass of the accretion disk, ${\sim}4.03{\times}10^{24}g$, is achieved at the ignition of an outburst, and the minimum value, ${\sim}8.54{\times}10^{23}g$, is reached during the cooling decay to quiescence. The disk mass varies ${\sim}5$ times during outburst limit cycle.

• Tunnel and Underground Space
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• 제21권5호
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• pp.394-405
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• 2011

In this paper, we applied coupled non-isothermal, multiphase fluid flow and geomechanical numerical modeling using TOUGH-FLAC coupled analysis to study the complex thermodynamic and geomechanical performance of underground lined rock caverns (LRC) for compressed air energy storage (CAES). Mechanical stress in concrete linings as well as pressure and temperature within a storage cavern were examined during initial and long-term operation of the storage cavern for CAES. Our geomechanical analysis showed that effective stresses could decrease due to air penetration pressure, and tangential tensile stress could develop in the linings as a result of the air pressure exerted on the inner surface of the lining, which would result in tensile fracturing. According to the simulation in which the tensile tangential stresses resulted in radial cracks, increment of linings' permeability and air leakage though the linings, tensile fracturing occurred at the top and at the side wall of the cavern, and the permeability could increase to $5.0{\times}10^{-13}m^2$ from initially prescribed $10{\times}10^{-20}m^2$. However, this air leakage was minor (about 0.02% of the daily air injection rate) and did not significantly impact the overall storage pressure that was kept constant thanks to sufficiently air tight surrounding rocks, which supports the validity of the concrete-lined underground caverns for CAES.

• Tunnel and Underground Space
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• 제31권3호
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• pp.167-183
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• 2021

It is essential to understand the complex thermo-hydro-mechanical-chemical (THMC) coupled behavior in the engineered barrier system and natural barrier system to secure the high-level radioactive waste repository's long-term safety. The heat from the high-level radioactive waste induces thermal pressurization and vaporization of groundwater in the repository system. Groundwater inflow affects the saturation variation in the engineered barrier system, and the saturation change influences the heat transfer and multi-phase flow characteristics in the buffer. Due to the complexity of the coupled behavior, a numerical simulation is a valuable tool to predict and evaluate the THMC interaction effect on the disposal system and safety assessment. To enhance the knowledge of THMC coupled interaction and validate modeling techniques in geological systems. DECOVALEX, an international cooperation project, was initiated in 1992, and KAERI has participated in the projects since 2008 in Korea. In this study, we introduced the main contents of all tasks in the DECOVALEX-2023, the current DECOVALEX phase, to the rock mechanics and geotechnical researchers in Korea.