• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.1
• /
• pp.68-78
• /
• 2006

In the past few years, considerable efforts have been directed towards the further development of Urea-SCR(selective catalytic reduction) technique for diesel-driven vehicle. Although urea possesses considerable advantages over Ammonia$(NH_3)$ in terms of toxicity and handling, its necessary decomposition into Ammonia and carbon dioxide complicates the DeNOx process. Moreover, a mobile SCR system has only a short distance between engine exhaust and the catalyst entrance. Hence, this leads to not enough residence times of urea, and therefore evaporation and thermolysis cannot be completed at the catalyst entrance. This may cause high secondary emissions of Ammonia and isocyanic acid from the reducing agent and also leads to the fact that a considerable section of the catalyst may be misused for the purely thermal steps of water evaporation and thermolysis of urea. Hence the key factor to implementation of SCR technology on automobile is fast thermolysis, good mixing of Ammonia and gas, and reducing Ammonia slip. In this context, this study performs three-dimensional numerical simulation of urea injection of heavy-duty diesel engine under various injection pressure, injector locations and number of injector hole. This study employs Eulerian-Lagrangian approach to consider break-up, evaporation and heat and mass-transfer between droplet and exhaust gas with considering thermolysis and the turbulence dispersion effect of droplet. The SCR-monolith brick has been treated as porous medium. The effect of location and number of hole of urea injector on the uniformity of Ammonia concentration distribution and the amount of water at the entrance of SCR-monolith has been examined in detail under various injection pressures. The present results show useful guidelines for the optimum design of urea injector for reducing Ammonia slip and improving DeNOx performance.

• Computational Structural Engineering
• /
• v.10 no.4
• /
• pp.303-313
• /
• 1997

Though many techniques for the damage assessment of structures have been studied recently, most of them can be only applied to simple structures. Therefore, practical damage assessment techniques that evaluate the damage location and the damage state for large structures need to be developed. In this study, a damage assessment technique using a neural network is developed, in which the bilevel damage assessment procedure is proposed to evaluate the damage of a large structure from the limited monitoring data. The procedure is as follows ; first, for the rational selection of damage critical members, the members that affect the probability of failure or unusual structural behavior are selected by sensitivity analysis. Secondly, the monitoring points and the number of sensors that are sensitive to the damage severity of the selected members are also selected through the sensitivity analysis with a proposed sensitivity measurement format. The validity and applicability of the developed technique are demonstrated by various examples, and it has been shown that the practical information on the damage state of the selected critical members can be assessed even though the limited monitoring data have been used.

• Geotechnical Engineering
• /
• v.13 no.1
• /
• pp.59-74
• /
• 1997

This paper presents the results of the geotechnical investigation and settlement analysis of a finished waste landfill to find the possibility of the site as a construction area. Also, the variations of the strength of the municipal waste after mixing with the several types of the particulate grouts are investigated. The materials of the grouts used in the experiment are Quick Lime, Portland Cement, Slag Cement and Geocrete Cement. The results of the geotechnical investigation show that the maximum dry unit weight of the waste becomes lower and optimum moisture content higher as the age of the disposed waste is younger and the organic content is higher. The thickness of the predicted differential settlements of the waste fill has large difference from location to location and the unconfined compression strength of the grout mixed waste from the experiment was higher in the order of Geocrete Cement, Slag Cement, Portland Cement and Quick Lime.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.6A
• /
• pp.550-557
• /
• 2007

We predict a context of various structures by using Bayesian Networks Algorithms, Three-Dimensional Structures Algorithms and Genetic Algorithms. However, these algorithms have unavoidable problems when providing a context-aware service in reality due to a lack of practicality and the delay of process time in real-time environment. As far as context-aware system for specific purpose is concerned, it is very hard to be sure about the accuracy and reliability of prediction. This paper focuses on reasoning and prediction technology which provides a stochastic mechanism for context information by incorporating various context information data. The objective of this paper is to provide optimum services to users by suggesting an intellectual reasoning and prediction based on hierarchical context information. Thus, we propose a design of user location prediction algorithm using sequential matching with n-size flexible window scheme by taking user's habit or behavior into consideration. This algorithm improves average 5.10% than traditional algorithms in the accuracy and reliability of prediction using the Flexible Window Scheme.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.9
• /
• pp.1069-1080
• /
• 2016

TDOA(Time Difference Of Arrival)-based localization system such as the passive surveillance system performs the time synchronization between the receivers after separated installing multiple receivers to set the same clock for all receivers. And it estimates 2D(or 3D) location of the target by solving intersection of the multiple hyperbola(or hyperboloid) using TDOA. To perform time synchronization, one receiver must be set to the master, and it provide the reference data to compensate the clock of the rest of the slaves. The positioning accuracy of TDOA-based localization system is changed in accordance with the master that is selected among multiple receivers. So, the optimum receiver which is selected among multiple receivers must be set to master to get best performance in the considered deployment of receivers. In this paper, we propose a selection scheme of master receiver for time synchronization using DOP(Dilution Of Precision) which is based on location of the target and the multiple receivers. The proposed scheme has low complexity and short processing time, and it is easy to automate in the TDOA-based localization systems.

• Korean Journal of Heritage: History & Science
• /
• v.47 no.4
• /
• pp.120-135
• /
• 2014

There is a necessity of re-research about Geumgangsaji temple site as reviewed recently confirmed typical temple arrangement of Baekje. The purposes of this study are, determine that building remains and layout patterns using Ground Penetrating Radar, and identify that the location and terrain changes of Geumgangsaji using aerial photographs and a numerical map by GIS. In the GPR result, it was confirmed that new building sites in the west and the north area which in Geumgangsaji is more wide. In addition, it was found that the temple is located on stable river terrace with low soil loss. And this site has spontaneous drainage system for the optimum position.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.28 no.3
• /
• pp.211-215
• /
• 2022

Air distribution occupies an important position in the smart unit load container design process for agricultural products. Inner air may be uncomfortable because of its temperature, speed, direction, and volume flow rate. It doesn't matter how efficient the ventilation equipment is if the air is not distributed well. The main aim of this study was to design the inlet and outlet fan locations of smart unit load container for agricultural products. A numerical study was performed on the effects of the location of inlet air and outlet air in relation to the container cooling sources on air distribution and thermal comfort. A concept of combining inner container cooling sources with the exhaust outlet was employed in this investigation. Also, in this research, the developed CFD (Computational Fluid Dynamics) models were thoroughly validated. This system was adopted for use in container spaces, where the exhaust outlet was located. In this study, the location of the inlet was derived through CFD for a container with a size of 1,100×1,100×1,700 mm, and it was derived that the inlet was located at the center of the lower part of the container for efficient air flow. It was efficient to position the outlet through the air inlet in the center of the lower part of the container at the top of the same side.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.3D
• /
• pp.307-315
• /
• 2008

The aim of this study is to develop travel time estimation model by using Self-Organized Neural network(in brief, SON) algorithm. Travel time data based on vehicles equipped with GPS and number-plate matching collected from National road number 3 (between Jangji-IC and Gonjiam-IC), which is pilot section of National Highway Traffic Management System were employed. We found that the accuracies of travel time are related to location of detector, the length of road section and land-use properties. In this paper, we try to develop travel time estimation using SON to remedy defects of existing neural network method, which could not additional learning and efficient structure modification. Furthermore, we knew that the estimation accuracy of travel time is superior to optimum located detectors than based on existing located detectors. We can expect the results of this study will make use of location allocation of detectors in highway.

• Geomechanics and Engineering
• /
• v.31 no.1
• /
• pp.1-14
• /
• 2022

Urban deep excavation will affect greatly on the deformation of adjacent existing buildings, especially those with shallow foundations. Isolation piles has been widely used in engineering to control the deformation of buildings adjacent to the excavation, but its applicability is still controversial. Based on a typical engineering, numerical calculation models were established and verified through monitoring data to study the influence characteristics of isolation piles on the deformation of existing shallow foundation buildings. Results reveal that adjacent buildings will increase building settlement δ_v and the deformation of diaphragm walls δ_h, while the isolation piles can effectively decrease these. The surface settlement curve is changed from "groove" type to "double groove" type. Sufficiently long isolation pile can effectively decrease δ_v, while short isolation piles will lead to a negative effect. When the building is within the range of the maximum settlement location P, maximum building rotation θ_m will increase with the pile length L and the relative position between isolation pile and building d/D increase (d is the distance between piles and diaphragm walls, D is the distance between buildings and diaphragm walls), instead, θ_m will decrease for buildings outside the location P, and the optimum was obtained when d/D=0.7.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.3
• /
• pp.243-248
• /
• 2013

Internal combustion engines typically expel 30%-40% of the energy supplied by fuel to the environment through their exhaust system. Therefore, further significant improvements in the thermal efficiency of IC engines are possible by recovering the waste heat from the engine exhaust gas. With this fact in mind, a numerical simulation was carried out to investigate the potential of using thermoelectric generation with an internal combustion engine for waste heat recovery. Physical parameters such as the exhaust temperature and mass flow rate were evaluated in the exhaust system, and the optimum location for inserting a thermoelectric generator (TEG) into the system was determined. The TEG will be located in the exhaust system and will use the energy flow between the warmer exhaust gas and the external environment. The optimum position of the temperature distribution and the TEG performance were predicted through numerical analysis. The experimental results obtained showed that the power output significantly increases with the temperature difference between the cold and hot sides of the TEG.